Photonic device and method of forming a photonic device
阅读说明：本技术 光子器件和形成光子器件方法 (Photonic device and method of forming a photonic device ) 是由 余振华 夏兴国 丁国强 林品佐 黄松辉 侯上勇 吴集锡 于 2019-06-27 设计创作，主要内容包括：方法包括在衬底上方的第一氧化物层中形成硅波导段,第一氧化物层设置在衬底上,在第一氧化物层上方形成布线结构,该布线结构包括一个或多个绝缘层以及位于一个或多个绝缘层中的一个或多个导电部件,使布线结构的区域凹进,在布线结构的凹进区域中形成氮化物波导段,其中,氮化物波导段在硅波导段上方延伸,在氮化物波导段上方形成第二氧化物层,以及将半导体管芯附接至布线结构,管芯电连接至导电部件。本发明的实施例还涉及光子器件和形成光子器件方法。(The method includes forming a silicon waveguide segment in a first oxide layer over a substrate, the first oxide layer disposed on the substrate, forming a routing structure over the first oxide layer, the routing structure including one or more insulating layers and one or more conductive components located in the one or more insulating layers, recessing a region of the routing structure, forming a nitride waveguide segment in the recessed region of the routing structure, wherein the nitride waveguide segment extends over the silicon waveguide segment, forming a second oxide layer over the nitride waveguide segment, and attaching a semiconductor die to the routing structure, the die electrically connected to the conductive components. Embodiments of the invention also relate to photonic devices and methods of forming photonic devices.)
1. A method of forming a photonic device, comprising:
forming a silicon waveguide segment in a first oxide layer over a substrate, the first oxide layer disposed on the substrate;
forming a wiring structure over the first oxide layer, the wiring structure comprising one or more insulating layers and one or more conductive features in the one or more insulating layers;
recessing a region of the wiring structure;
forming a nitride waveguide segment in the recessed region of the wiring structure, wherein the nitride waveguide segment extends over the silicon waveguide segment;
forming a second oxide layer over the nitride waveguide segment; and
attaching the semiconductor die to the routing structure, the die being electrically connected to the conductive member.
2. The method of claim 1, further comprising patterning the first oxide layer and the second oxide layer to form a cladding structure surrounding the silicon waveguide segment and the nitride waveguide segment, the cladding structure having exposed sidewalls.
3. The method of claim 1, wherein the nitride waveguide segment is straight.
4. The method of claim 1, further comprising forming a photonic device over the first oxide layer, wherein the photonic device comprises silicon, and wherein the photonic device is optically coupled to at least one first waveguide segment.
5. The method of claim 4, wherein the photonic device comprises a modulator.
6. The method of claim 1, further comprising forming a via extending through the substrate, wherein the conductive member is electrically coupled to the via.
7. The method of claim 1, wherein at least one semiconductor die is an integrated photonics die.
8. The method of claim 1, wherein at least one nitride waveguide segment extends over an end of the silicon waveguide, the end having a tapered shape.
9. A method of forming a photonic device, comprising:
forming a first photonic structure comprising:
patterning a silicon layer on a first substrate to form a first set of waveguides, wherein the silicon layer is disposed on a first oxide layer;
forming a conductive member over the first set of waveguides; and
removing the first substrate to expose the first oxide layer;
forming a second photonic structure comprising:
depositing a silicon nitride layer on the second substrate;
patterning the silicon nitride layer to form a second set of waveguides; and
forming a second oxide layer over the second set of waveguides; and
bonding the first photonic structure to the second photonic structure, wherein the first oxide layer is bonded to the second oxide layer, wherein the first set of waveguides is laterally aligned with the second set of waveguides.
10. A photonic device comprising:
an integrated photonic structure comprising:
a plurality of oxide layers over the substrate;
a plurality of first waveguides and a plurality of second waveguides within the plurality of oxide layers, wherein the plurality of first waveguides are optically coupled to the plurality of second waveguides, wherein the plurality of first waveguides comprise silicon and the plurality of second waveguides comprise silicon nitride; and
a wiring structure over at least a portion of a first waveguide of the plurality of first waveguides, the wiring structure comprising a plurality of insulating layers and a plurality of conductive members in the plurality of insulating layers; and
a plurality of semiconductor dies attached to the routing structure, wherein the plurality of semiconductor dies are electrically coupled to the plurality of conductive members.
Technical Field
Embodiments of the invention relate to photonic devices and methods of forming photonic devices.
Background
Electrical signals and processing are one technique used for signal transmission and processing. In recent years, optical signals and processing have been used in an increasing number of applications, particularly due to the use of optical fiber related applications for signal transmission.
Optical signals and processing are often combined with electrical signals and processing to provide fully developed applications. For example, optical fibers may be used for long-range signal transmission, and electrical signals may be used for short-range signal transmission as well as processing and control. Thus, a device integrating an optical component and an electronic component is formed for conversion between optical signals and electrical signals, and processing of optical signals and electrical signals. Thus, a package may include an optical (photonic) die containing an optical device and an electronic die containing an electronic device.
Disclosure of Invention
Some embodiments of the present invention provide a method of forming a photonic device, comprising: forming a silicon waveguide segment in a first oxide layer over a substrate, the first oxide layer disposed on the substrate; forming a wiring structure over the first oxide layer, the wiring structure comprising one or more insulating layers and one or more conductive features in the one or more insulating layers; recessing a region of the wiring structure; forming a nitride waveguide segment in the recessed region of the wiring structure, wherein the nitride waveguide segment extends over the silicon waveguide segment; forming a second oxide layer over the nitride waveguide segment; and attaching the semiconductor die to the routing structure, the die being electrically connected to the conductive member.
Another embodiment of the present invention provides a method of forming a photonic device, comprising: forming a first photonic structure comprising: patterning a silicon layer on a first substrate to form a first set of waveguides, wherein the silicon layer is disposed on a first oxide layer; forming a conductive member over the first set of waveguides; and removing the first substrate to expose the first oxide layer; forming a second photonic structure comprising: depositing a silicon nitride layer on the second substrate; patterning the silicon nitride layer to form a second set of waveguides; and forming a second oxide layer over the second set of waveguides; and joining the first photonic structure to the second photonic structure, wherein the first oxide layer is joined to the second oxide layer, wherein the first set of waveguides is laterally aligned with the second set of waveguides.
Yet another embodiment of the present invention provides a photonic device including: an integrated photonic structure comprising: a plurality of oxide layers over the substrate; a plurality of first waveguides and a plurality of second waveguides within the plurality of oxide layers, wherein the plurality of first waveguides are optically coupled to the plurality of second waveguides, wherein the plurality of first waveguides comprise silicon and the plurality of second waveguides comprise silicon nitride; and a wiring structure over at least a portion of a first waveguide of the plurality of first waveguides, the wiring structure comprising a plurality of insulating layers and a plurality of conductive members in the plurality of insulating layers; and a plurality of semiconductor dies attached to the routing structure, wherein the plurality of semiconductor dies are electrically coupled to the plurality of conductive members.
Drawings
Various aspects of the invention are best understood from the following detailed description when read with the accompanying drawing figures. It should be noted that, in accordance with standard practice in the industry, various components are not drawn to scale. In fact, the dimensions of the various elements may be arbitrarily increased or decreased for clarity of discussion.
Fig. 1A-1C and 2 illustrate plan and cross-sectional views of a photonic system according to some embodiments.
Fig. 3A-3C illustrate schematic diagrams of an optical network and photonic devices of a hybrid light subsystem according to some embodiments.
Fig. 4A-4C and 5 illustrate plan and cross-sectional views of a photonic system according to some embodiments.
Fig. 6A-6H illustrate cross-sectional views of intermediate steps during a process for forming an integrated photonic structure, in accordance with some embodiments.
Fig. 7A-7C-10A-10D illustrate cross-sectional and plan views of intermediate stages during a process for forming a hybrid optical network of an integrated photonic structure, in accordance with some embodiments.
11A-11C-14A-14D illustrate cross-sectional views of intermediate steps during a process for forming an edge coupler of an integrated photonic structure, in accordance with some embodiments.
Figures 15A-15C illustrate cross-sectional views of intermediate steps during a process for forming a first integrated photonic structure, in accordance with some embodiments.
Figures 16A-16G illustrate cross-sectional views of intermediate steps during a process for forming a second integrated photonic structure, in accordance with some embodiments.
Figures 17-19 illustrate cross-sectional views of intermediate steps during a process for forming an integrated photonic structure, in accordance with some embodiments.
Detailed Description
The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to limit the invention. For example, in the following description, forming a first feature over or on a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. Further, the present invention may repeat reference numerals and/or characters in the various embodiments. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Also, spatially relative terms, such as "below …," "below …," "lower," "above …," "upper," and the like, may be used herein for ease of description to describe one element or component's relationship to another element (or other) component as illustrated. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
According to some embodiments, a photonic system including an optical device and an electronic device and a method of forming the same are provided. In particular, a photonic system is formed having an optical network that includes a silicon waveguide coupled to a silicon nitride waveguide. Silicon nitride waveguides have lower signal propagation losses than silicon waveguides and are therefore used to transmit optical signals over relatively long distances. A cladding layer may be formed over the waveguide to reduce leakage of the optical signal into the substrate. In some embodiments, the silicon nitride waveguide is formed in a layer above the silicon waveguide. In some embodiments, the silicon waveguide is formed as a first structure and the silicon nitride waveguide is formed as a second structure, and the structures are then bonded together. By forming the silicon nitride waveguide in a different structure than the silicon waveguide, the silicon nitride waveguide may be formed using techniques that improve the performance of the silicon nitride waveguide. According to some embodiments, intermediate stages of forming a photonic system are shown. Some variations of some embodiments are discussed. Like reference numerals are used to refer to like elements throughout the various views and illustrative embodiments.
Fig. 1A-1C illustrate a photonic system 100 according to some embodiments. The photonic system 100 may be, for example, a High Performance Computing (HPC) system and includes a plurality of sites 10, each site 10 may be a separate computing system. Fig. 1A shows a plan view of a photonic system 100 including a plurality of sites 10. Fig. 1B shows a close-up view of two adjacent sites 10 as shown in fig. 1A, and fig. 1C shows a cross-sectional view through section C-C' as shown in fig. 1B. Each site 10 includes one or more dies (e.g., dies 210, 212, 214, or 216, described in more detail below) coupled to an Integrated Photonic Structure (IPS) 20. The IPS20 may be attached to the interconnect substrate 30 as shown in fig. 1A to 1C.
Each site 10 communicates with other sites 10 using one or more optical networks 40 formed in IPS 20. The optical network 40 formed in the IPS20 may include waveguides and other photonic components. In some embodiments, optical network 40 may include silicon (Si) waveguides and silicon nitride (SiN) waveguides, such as silicon waveguide 50 or nitride waveguide 60, described in more detail below in fig. 5. In some embodiments, optical network 40 is a closed loop (or ring) connected to each site 10 of photonic system 100, as shown in fig. 1A. In some embodiments, optical network 40 may not be a closed loop, may have branched segments, or may include split segments. In an embodiment, optical network 40 includes a plurality of waveguides connected to site 10 in a point-to-point fashion. Optical network 40 may convey optical signals and/or optical power between sites 10. In some embodiments, optical network 40 may also communicate optical signals and/or optical power between IPS20 and external components. For example, optical network 40 may be coupled to external components via one or more optical fibers.
Each site 10 of photonic system 100 may include one or more dies, which may include a processor die 210, a memory die 212, an Electronic Integrated Circuit (EIC)214, a Photonic Integrated Circuit (PIC)216, or the like, or combinations thereof. For example, each site 10 shown in fig. 1A-1C includes a processor die 210, a memory die 212, an EIC 214, and a PIC216, but the site 10 may include more than one of each type of die or other types of die. The processor die 210 may include, for example, a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), an Application Specific Integrated Circuit (ASIC), and so forth. The memory die 212 may include, for example, volatile memory, Dynamic Random Access Memory (DRAM), Static Random Access Memory (SRAM), and the like. In some cases, site 10 may include a processor die 210 that also includes memory. In this case, a separate memory die 212 may not be present within site 10.
In some embodiments, EIC die 214 may include control circuitry for controlling the operation of photonic devices associated with site 10. The photonic device may be, for example, a photonic device formed in PIC216 and/or a photonic device formed in IPS20 (see fig. 6B-6C). In some embodiments, the EIC die 214 may also include a CPU. EIC die 214 may communicate with PIC216 or the photonic device of IPS20 using electrical signals. In some embodiments, EIC 214 includes circuitry for processing electrical signals received from photonic devices, such as electrical signals received from a photodetector of PIC216 or a photodetector within IPS 20. For example, the EIC 214 may include a controller, a transimpedance amplifier, and the like. The EIC 214 may be communicatively coupled to one or more processor dies 210. In some cases, the EIC 214 controls the high frequency signal of the photonic device according to an electrical signal (digital or analog) received from the processor die 210. In some embodiments. The functionality of EIC 214 may be part of processor die 210, or the functionality of processor die 210 may be part of EIC 214, or processor die 210 and EIC 214 may be combined together into a single die.
PIC216 includes photonic devices (not separately shown in fig. 1A-1C) that interact with, control, or sense optical signals transmitted over optical network 40. These photonic devices may include devices such as light modulators, photodetectors, grating couplers, light emitting diodes or lasers, or the like, or combinations thereof. For example, the PIC216 may include a grating coupler that couples optical signals from the optical network 40 to a photodetector within the PIC 216. Additionally, integrated electronic devices such as transistors, diodes, capacitors, resistors, metal wiring, etc. may also be formed within the PIC216 and may be coupled to photonic devices within the PIC 216.
In some embodiments, the interconnect substrate 30 may be, for example, a glass substrate, a ceramic, a dielectric substrate, an organic substrate (e.g., organic core), a semiconductor substrate (e.g., semiconductor wafer), or the like. The interconnect substrate 30 may be electrically connected to the IPS20 by electrical connections (e.g., solder bumps, etc.). The interconnect substrate 30 may include Through Substrate Vias (TSVs), metallization layers, passive or active devices, and the like. In some embodiments, the interconnect substrate 30 may not be present. In this manner, the photonic system 100 may be a system on a wafer (SoW), a chip on system on a wafer (CoWOS), or the like. In some embodiments, the interconnect substrate 30 may be another type of structure, such as an integrated fan-out structure, a redistribution structure, or the like.
Turning to fig. 2, a cross-sectional view of a portion of a photonic system 101 is shown in accordance with an embodiment. The photonic system 101 shown in fig. 2 may be similar to the photonic system 100 shown in fig. 1A through 1C. For example, photonic system 101 includes an IPS20, which may be similar to IPS20 shown in fig. 1A-1C. The photonic system 101 comprises a plurality of sites 10 comprising one or more dies. Site 10 shown in fig. 2 includes EIC 214 and PIC216, but site 10 of photonic system 101 may include other dies, as described above with reference to fig. 1A-1C. The die is electrically connected to IPS20 by conductive connections 220 (e.g., solder bumps, etc.). In some embodiments, underfill 322 may extend between a die (e.g., 214/216) and IPS 20. The underfill 322 may be transparent or relatively transparent to optical wavelengths associated with the photonic components of the photonic system 101 and/or the optical network 40. IPS20 is electrically connected to interconnect substrate 30 through vias 122 or electrical connections 224 (e.g., solder bumps, etc.). In some embodiments, underfill 226 may extend between IPS20 and interconnect substrate 30.
Still referring to fig. 2, IPS20 includes a wiring structure 120 formed on substrate 104. The wiring structure 120 includes one or more layers and includes components of the optical network 40 (e.g., waveguides or other photonic components as described below), and may include electrical wiring (e.g., the conductive members 113, see fig. 6G-6H) or other electronic components. Electrical routing provides electrical connections between components of the optical subsystem 101 (e.g., sites 10, die 214/216, etc., interconnect substrate 30, etc.), and may transport electrical signals or electrical power between the components. As previously described, optical network 40 allows sites 10 to communicate using optical signals. Optical network 40 may include one or more edge couplers 90 that couple optical signals between optical network 40 and optical fiber 140. In this manner, the optical network 40 may communicate with external components via one or more optical fibers 140.
Still referring to fig. 2, the optical network 40 may communicate with the PIC216 using optical signals. For example, the optical network 40 may include a grating coupler 152 that directs the optical signal to the PIC 216. The PIC216 may include a coupler 352 (e.g., a grating coupler) that receives optical signals from an optical network and couples the optical signals into a photonic component of the PIC216, such as a photodetector 354. In some embodiments, the PIC216 may direct the optical signal to the grating coupler 152 of the optical network 40. The PIC216 may provide an optical signal using, for example, a modulated LED or laser signal.
In some embodiments, the optical network 40 within the routing structure 120 may include waveguides formed of different materials. For example, optical network 40 may include a waveguide formed of silicon (silicon waveguide 50) and a waveguide formed of silicon nitride (nitride waveguide 60). In this manner, optical network 40 may be considered a "hybrid waveguide" network. The use of a hybrid waveguide network (e.g., optical network 40) as described herein may allow for more efficient transmission of optical signals between sites 10, as will be described in more detail below. The silicon waveguide 50 or the nitride waveguide 60 may be, for example, a slab waveguide.
Turning to fig. 3A-3C, schematic diagrams of an optical network 40 including a silicon waveguide 50 and a nitride waveguide 60 are shown, according to some embodiments. Fig. 3A shows the optical network 40 in plan view, and some components are omitted or shown as transparent for clarity. Fig. 3B-3C illustrate photonic components that may be integrated with silicon waveguide 50 of optical network 40. In optical network 40, in some embodiments, silicon waveguide 50 or nitride waveguide 60 may be covered in cladding layer 70, which may reduce propagation loss or light leakage. The cladding 70 may be formed of, for example, silicon dioxide (SiO)2) And may have a surface exposed to air (see fig. 10A to 10D). The cladding 70 may not cover portions of the optical network 40. For example, a die is placed over optical network 40 (e.g.210, 212, 214, 216), the dielectric material may not be formed as the cladding 70. An exemplary region of cladding 70 that does not surround site 10 is shown in fig. 3A. The optical network 40 shown in fig. 3A is an illustrative example, and optical networks may have different configurations in other embodiments.
In some cases, a waveguide formed from silicon nitride (e.g., nitride waveguide 60) may have advantages over a waveguide formed from Si (e.g., silicon waveguide 50). For example, silicon nitride has a higher dielectric constant than silicon, and thus nitride waveguide 60 may have a greater internal optical confinement than silicon waveguide 50. This may also allow the performance or leakage of nitride waveguide 60 to be insensitive to process variations, to dimensional uniformity, and to surface roughness (e.g., edge roughness or line width roughness). In some cases, the reduced process sensitivity may allow nitride waveguide 60 to be processed more easily or less expensively than silicon waveguide 50. These characteristics may allow nitride waveguide 60 to have lower propagation losses than silicon waveguide 50. In some cases, the propagation loss (dB/cm) of nitride waveguide 60 may be between about 0.1% and about 50% of silicon waveguide 50. In some cases, nitride waveguide 60 may also be less sensitive to ambient temperature than silicon waveguide 50. For example, the nitride waveguide 60 may be as sensitive to temperature as little as about 1% of the silicon waveguide 50.
The optical network 40 shown in fig. 3A utilizes a nitride waveguide 60 and a silicon waveguide 50 coupled together at a mode converter 80. Mode converter 80 allows an optical signal traveling in silicon waveguide 50 to couple into nitride waveguide 60 and vice versa. Optical network 40 uses nitride waveguide 60 to transmit signals over a relatively long distance due to the small propagation loss of nitride waveguide 60. In this way, more optical signal strength can be preserved during transmission. In some embodiments, nitride waveguide 60 may have a length between about 50 μm and about 1000 μm. For some curved segments of optical network 40, optical network 40 uses silicon waveguide 50 because silicon waveguide 50 may have a smaller bend radius than nitride waveguide 60 (due to the difference in dielectric constant between silicon and silicon nitride).
As shown in fig. 3A-3C, optical network 40 may include photonic components such as a photodetector 154, modulator 156, grating coupler 152, or other components. An exemplary site 10 is shown in fig. 3A, which may include a die (e.g., 210, 212, 214, 216) electrically connected to or optically coupled to a photonic component. Fig. 3A shows a single site 10, but multiple dies or sites 10 may be coupled to multiple groups of photonic components of the optical network 40. Fig. 3B shows a plan view of the grating coupler 152, photodetector 154, and modulator 156 optically coupled to the silicon waveguide 50, and fig. 3C shows a perspective view of the grating coupler 152, photodetector 154, and modulator 156 optically coupled to the silicon waveguide 50. The photonic component may be integrated with the silicon waveguide 50 and may be formed with the silicon waveguide 50. Fig. 6A to 6D show cross-sectional views of the photodetector 154 and the modulator 156. The photonic component may be optically coupled to the silicon waveguide 50 to interact with the optical signal within the silicon waveguide 50. For example, a grating coupler may be optically coupled to the silicon waveguide 50 to transmit an optical signal out within the silicon waveguide, and a photodetector 152 may be physically coupled to the silicon waveguide 50 to detect an optical signal within the silicon waveguide 50, and a modulator 156 may be optically coupled to the silicon waveguide 50 to generate an optical signal within the silicon waveguide 50. In this manner, the use of a hybrid optical network, such as optical network 40, may improve the transmission of optical signals over the longer distances allowed by nitride waveguide 60, while also having a smaller bend radius and integrated photonic components allowed by silicon waveguide 50.
Turning to fig. 4A-4C, a photonic system 102 is shown in accordance with some embodiments. The photonic system 102 may be, for example, a High Performance Computing (HPC) system and includes a plurality of sites 10, each site 10 may be a separate computing system. Fig. 4A shows a plan view of a photonic system 102 including multiple sites 10. Fig. 4B shows a close-up view of two adjacent sites 10 as shown in fig. 4A, and fig. 4C shows a cross-sectional view through section C-C' as shown in fig. 4B. Each site 10 includes one or more dies (e.g., dies 210, 212, or 214, described in more detail below) coupled to an Integrated Photonic Structure (IPS) 20. The IPS20 may be attached to the interconnect substrate 30 as shown in fig. 4A to 4C.
The photonic system 102 is similar to the photonic system 100 shown in fig. 1A through 1C, except that the photonic system 102 of fig. 4A through 4C does not include the PIC 216. In photonic system 102, the photonic components (e.g., photodetectors, modulators, etc.) associated with each site 10 are formed in IPS20 and electrically connected to die 212/214. (according to some embodiments, the process flow for forming a photonic component in IPS20 is described below in FIGS. 6A-6E.) the photonic component may be electrically connected to and controlled by, for example, EIC 214. By forming photonic components in IPS20, fewer dies are used in each site 10, which may reduce cost, the number of components, and the size of the photonic system. In addition, less optical signal strength due to transmission between the optical network 40 and the PIC216 may be lost, which may reduce the power used by the photonic system.
Turning to fig. 5, a cross-sectional view of a portion of a photonic system 103 is shown, in accordance with some embodiments. The photonic system 103 shown in fig. 5 may be similar to the photonic system 102 shown in fig. 4A through 4C. For example, photonic system 103 does not include PIC 216. The photonic system 103 includes a plurality of sites 10 comprising one or more dies. Site 10 shown in fig. 5 includes two EICs 214, but site 10 may include other dies, as described above with reference to fig. 1A-4C. The die is electrically connected to IPS20 by conductive connections 220 (e.g., solder bumps, etc.). In some embodiments, underfill 322 may extend between a die (e.g., 214/216) and IPS 20. Underfill 322 may be transparent or relatively transparent to optical wavelengths associated with photonic components of photonic system 103 and/or optical network 40. IPS20 is electrically connected to interconnect substrate 30 through vias 122 or electrical connections 224 (e.g., solder bumps, etc.). In some embodiments, underfill 226 may extend between IPS20 and interconnect substrate 30.
Still referring to fig. 5, IPS20 includes a wiring structure 120 formed on substrate 104. The wiring structure 120 includes one or more layers and includes components of the optical network 40 (e.g., waveguides or other photonic components as described below), and may include electrical wiring (e.g., the conductive members 113, see fig. 6G-6H) or other electronic components. The electrical wiring provides electrical connections between the components of the optical subsystem 103 (e.g., sites 10, die 214/216, etc., interconnect substrate 30, etc.) and may transport electrical signals or electrical power between the components. Optical network 40 allows site 10 to communicate using optical signals. For example, the EIC 214 may be electrically connected to a photodetector 154 formed in the wiring structure 120 that detects optical signals in the optical network 40. EICs 214 may also be electrically connected to modulators 156 within wiring structure 120 that generate optical signals by modulating light within optical network 40. Optical network 40 may include waveguides formed of silicon (silicon waveguides 50) and waveguides formed of silicon nitride (nitride waveguides 60). Optical network 40 may include one or more edge couplers 90 that couple optical signals between optical network 40 and optical fiber 140. In this manner, the optical network 40 may communicate with external components via one or more optical fibers 140.
Turning to fig. 6A-14D, intermediate steps in the formation of an IPS20 according to some embodiments are shown. The processes shown in fig. 6A-14D may be used to form photonic structures, such as those shown in fig. 1A-1C-5, but other processes may be used in other embodiments. Fig. 6A-6H illustrate cross-sectional views of a silicon waveguide 50 forming an IPS20 according to some embodiments. In some embodiments, the formation of the components shown in fig. 6A-6H may be part of a back end of line (BEOL) process. Fig. 7A-10D illustrate plan or cross-sectional views of intermediate steps in forming nitride waveguide 60 and mode converter 80 according to some embodiments. The process illustrated in fig. 7A-10D may be implemented as part of the photonic system formation after the process illustrated in fig. 6A-6H. Fig. 11A-14D illustrate plan or cross-sectional views of intermediate steps in forming nitride waveguide 60 and edge coupler 90, according to some embodiments. The process illustrated in fig. 11A-14D may be implemented as part of the photonic system formation after the process illustrated in fig. 6A-6H. In some embodiments, the processes shown in fig. 7A-10D and the processes shown in fig. 11A-14D may be performed simultaneously.
Fig. 6A-6H illustrate a process for forming a silicon waveguide 50 in an IPS20, according to some embodiments. Turning first to fig. 6A, an oxide layer 106 is formed over a substrate 104, and a silicon layer 108 is formed over the oxide layer 106. The substrate 104 may be a material such as glass, ceramic, dielectric, or a semiconductor substrate. For example, the substrate 104 may comprise a bulk semiconductor or the like that may be doped (e.g., with p-type or n-type dopants) or undoped. In some embodiments, the substrate 104 is a wafer, such as a silicon wafer or other type of semiconductor wafer. Other substrate materials such as multilayer or gradient substrates may also be used. In some embodiments, the material of the substrate 104 may include silicon; germanium; a compound semiconductor including silicon carbide, gallium arsenide, gallium phosphide, indium arsenide, and/or indium antimonide; alloy semiconductors including SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP, or the like, or combinations thereof. Oxide layer 106 may be, for example, silicon oxide or the like. In some embodiments, oxide layer 106 may have a thickness between about 0.5 μm and about 4 μm. Silicon layer 108 may comprise doped silicon or undoped silicon and may have a thickness between about 0.1 μm and about 1.5 μm. In some embodiments, substrate 104, oxide layer 106, and silicon layer 108 may be formed as a buried oxide ("BOX") substrate, shown in fig. 6A as BOX substrate 105.
In fig. 6B, the silicon layer 108 is patterned to form silicon regions for the silicon waveguide 50 and other photonic components. For example, as shown in fig. 6B, a patterned region 154 'of silicon layer 108 may be used to form photodetector 154, and a patterned region 156' of silicon layer 108 may be used to form modulator 156. The silicon layer 108 may be patterned using photolithography and etching techniques. For example, a hard mask layer (e.g., a nitride layer or other dielectric material, not shown in fig. 6B) may be formed over the silicon layer 108 and patterned. The pattern of the hard mask layer may then be transferred to the silicon layer 108 using one or more etching techniques, such as dry and/or wet etching techniques. In some embodiments, more than one lithography and etch sequence may be used to pattern silicon layer 108 into patterned regions 154 'or 156'. For illustrative purposes, the photonic component (e.g., 154, 156, etc.) and the silicon waveguide 50 are shown disconnected, but the photonic component and/or the silicon waveguide 50 may be connected or arranged as desired for a particular design, such as those shown in fig. 3A-3C.
In fig. 6C, an oxide layer 112 is formed over the oxide layer 106 and the patterned silicon layer 108. Oxide layer 112 may be formed by high density plasma chemical vapor deposition (HDP-CVD), flowable CVD (fcvd) (e.g., CVD-based material deposition and post-cure in a remote plasma system to convert it to another material, such as an oxide), the like, or combinations thereof. Other insulating materials formed by any acceptable process may be used. In some embodiments, a planarization process (e.g., a chemical mechanical polishing process) is performed such that the patterned portions of the oxide layer 112 and the silicon layer 108 are coplanar. Thus, oxide layer 112 may have approximately the same thickness as silicon waveguide 50, which may be between about 100nm and about 600nm, such as about
Still referring to fig. 6C, in some embodiments, an optional Etch Stop Layer (ESL)114 may be formed over silicon regions 154 'and 156' and over silicon waveguide 50. The ESL114 may be a material such as silicon carbide (SiC), silicon carbonitride (SiCN), silicon oxycarbonitride (SiOCN), and the like, and may have a thickness of between about
Turning to fig. 6D, according to some embodiments, a via 122 and a conductive feature 113 are formed. The via 122 may be, for example, a Through Substrate Via (TSV), or the like. The conductive features 113 may include contacts, vias, metallization layers, electrical wiring, and the like, or combinations thereof. For example, the conductive member 113 shown in fig. 6D may include contacts to the photodetector 154 or modulator 156. In some embodiments, a dielectric layer 118 is formed over the dielectric layer 116 prior to forming the vias 122 or the conductive features 113. Dielectric layer 118 may be a similar material as dielectric layer 116 and may be formed using similar techniques. After formation, dielectric layer 118 may be planarized using, for example, a CMP process.
In some embodiments, an opening for via 122 is formed through oxide layers 106 and 112 and dielectric layers 116 and 118, partially into substrate 104, using acceptable photolithography and etching techniques. A conductive material may then be formed in the openings to form vias 122. A liner (not shown) such as a diffusion barrier layer, an adhesion layer, or the like may be formed in the opening from a material such as TaN, Ta, TiN, Ti, CoW, or the like, and may be formed in the opening by a deposition process such as ALD or the like. In some embodiments, a seed layer (not shown) comprising copper and copper alloys may be deposited in the opening. The conductive material of the via 122 may be formed in the opening using, for example, ECP, electroless plating, or the like. The conductive material may be a metallic material, including a metal or metal alloy, such as copper, silver, gold, tungsten, cobalt, aluminum, or the like, or alloys thereof. A planarization process, such as a CMP process, may be performed to remove excess conductive material along the top surface of oxide layer 118 so that via 122 is flush with the top surface of oxide layer 118. In some embodiments, the backside of substrate 104 may be thinned to expose vias 122 to form electrical connections to vias 122.
Still referring to fig. 6D, the conductive features 113 may be formed by a damascene process, such as dual damascene, single damascene, etc. For example, in some embodiments, openings for conductive features 113 are first formed in oxide layers 118 and 116 using acceptable photolithography and etching techniques. A conductive material may then be formed in the opening, thereby forming the conductive member 113. The conductive material of the conductive member 113 may be formed of a metal or a metal alloy including aluminum, copper, tungsten, or the like. In other embodiments, other techniques or materials may be used to form the conductive features 113.
Turning to fig. 6E-6F, additional dielectric layers and conductive features 113 are formed over the dielectric layer 118, forming wiring regions 121. Fig. 6F shows a cross-sectional view along section F-F' shown in fig. 6E. The routing region 121 includes the dielectric layer, the conductive member 113, the photonic component, the silicon waveguide 50, and other components present in the final routing structure 120 (see fig. 2 or 5). Additional dielectric layers are not separately labeled for clarity, and there may be more or less dielectric layers in the routing region 121 than shown. The additional dielectric layers may be of similar materials to dielectric layers 114 or 116 or oxide layers 106 or 112 and may be formed using similar techniques. The additional conductive features 113 may include vias or metal lines, and may be formed in a similar manner as the conductive features 113 of fig. 6D. In some embodiments, one or more conductive pads 115 may be formed on the conductive member 113. Conductive connections 220 are then formed on the conductive pads 115 (see fig. 2 and 5). Conductive pad 115 may be a conductive material including aluminum, copper, tungsten, and the like. In some embodiments, a passivation layer 117 is then formed over the wire region 121. The passivation layer 117 may be a material such as SiN, and may have a thickness between about 1 μm and about 3 μm. The passivation layer 117 may be formed using acceptable deposition techniques such as those previously described.
Turning to fig. 6G to 6H, the wiring region 121 above the region of the silicon waveguide 50 is recessed, thereby forming a recessed region 121'. Wire regions 121 may be recessed using acceptable photolithography and etching techniques. The etching technique may include a dry etching process and/or a wet etching process, and the recess may include a plurality of etching steps. In some embodiments, the wiring region 121 is recessed using an etching process such that a portion of the ESL114 remains, the remaining portion being denoted as ESL 114' in fig. 6G-6H. In some embodiments, the remainder of the ESL 114' has a thickness of between about
Turning to fig. 7A-7C-10A-10D, intermediate stages of forming nitride waveguide 60 (see, e.g., fig. 10B-10C) and mode converter 80 (see, e.g., fig. 10A) are illustrated, according to some embodiments. In some embodiments, the processes illustrated in fig. 7A-10D may be performed on the structures illustrated in fig. 6G-6H. Mode converter 80 couples silicon waveguide 50 and nitride waveguide 60 allowing optical signals to be transmitted between silicon waveguide 50 and nitride waveguide 60. Fig. 7A, 8A, 9A, and 10A show plan views, and fig. 7B to 7C, 8B to 8C, 9B to 9C, and 10B to 10D show sectional views indicated on each plan view. For example, FIG. 7B shows a cross-sectional view through section B-B' shown in FIG. 7A.
In fig. 7A to 7C, a recessed region 121 'of the wiring region 121 is illustrated, similar to the recessed region 121' illustrated in fig. 6G to 6H. In the recessed region 121' shown in fig. 7A, the silicon layer 108 (see fig. 6A-6B) has been patterned to form a silicon waveguide 50 having tapered ends. In some embodiments, silicon waveguide 50 has a width W1 of between about 250nm and about 1000nm or a thickness T1 of between about 100nm and about 600 nm. In some embodiments, the tapered end of silicon waveguide 50 has a length L1 of between about 10 μm and about 500 μm. In some embodiments, the tapered end of the silicon waveguide 50 may have a taper angle between about 0.7 degrees and about 1.4 degrees with respect to the longitudinal direction of the silicon waveguide 50. In other embodiments, the end of the silicon waveguide 50 may have a shape other than a taper, such as a circular or flat shape.
Turning to fig. 8A-8C, a nitride waveguide 60 is formed over the silicon waveguide 50 shown in the structure of fig. 7A-7C. Nitride waveguide 60 may be formed by, for example, depositing a silicon nitride layer (not shown) over oxide layer 112 and silicon waveguide 50, and then patterning the silicon nitride layer using acceptable photolithography and etching techniques. A silicon nitride layer may also be formed over the entire structure, such as over wiring regions 121 and over recessed regions 121'. In some embodiments, a photoresist structure may be formed and patterned over the silicon nitride layer, and then the pattern is transferred to the silicon nitride layer using an etching process to form nitride waveguide 60. In some embodiments, the etching process may include a dry etching process and/or a wet etching process, and the etching process may be selective to silicon nitride relative to silicon oxide or other materials (e.g., the material of the passivation layer 117). For example, the etching process may remove silicon nitride from over the wiring region 121 or from over portions of the recessed region 121'. The silicon nitride may be formed using a suitable deposition technique such as CVD, LPCVD, PVD, and the like. In some embodiments, nitride waveguide 60 may have a width W2 of between about 200nm and about 1000nm, and a thickness T3 of between about 200nm and about 500 nm. The end of the nitride waveguide 60 is shown as being flat, but in other embodiments the end of the nitride waveguide 60 may have other shapes (e.g., tapered, rounded, etc.).
As shown in fig. 8A-8C, nitride waveguide 60 is formed over silicon waveguide 50 and oxide layer 112, and nitride waveguide 60 extends over the tapered end of silicon waveguide 50. In some embodiments, nitride waveguide 60 extends a length L2 of between about 20 μm and about 500 μm from the end of silicon waveguide 50 over silicon waveguide 50. The taper of the end of the silicon waveguide 60 causes the optical signal within the silicon waveguide 50 to extinguish and a portion of the energy of the optical signal to be coupled into the nitride waveguide 60. Similarly, optical signals within the nitride waveguide may be coupled to the silicon waveguide 50. In this way, mode converter 80 is formed to couple the optical mode of silicon waveguide 50 and the optical mode of nitride waveguide 60.
Fig. 9A to 9C and fig. 10A to 10D show the formation of a cladding layer 70 (see fig. 10A to 10D) surrounding the silicon waveguide 50 and the nitride waveguide 60. In some embodiments, the cladding layer 70 is formed by patterning an oxide layer 124 (see fig. 9A-9C) formed over the silicon waveguide 50 and the nitride waveguide 60. The oxide layer 124 is patterned such that the sidewall surfaces and/or the top surface of the cladding layer 70 are exposed to air (e.g., an atmospheric environment). The interface between the higher dielectric constant of the cladding 70 and the lower dielectric constant of air may reduce light leakage from within the cladding 70. By forming the cladding layer 70 such that regions of the silicon waveguide 50 and the nitride waveguide 60 are covered by the cladding layer 70 and laterally separated by air, confinement of optical signals within the silicon waveguide 50 and the nitride waveguide 60 can be improved. In some cases, forming the cladding layer 70 surrounded by air as described above may reduce the amount of optical signal loss due to optical coupling between the silicon waveguide 50 and the substrate 104. In this manner, cladding layer 70 may be considered a second mode converter operating with mode converter 80 to improve the coupling efficiency between silicon waveguide 50 and nitride waveguide 60.
Turning to fig. 9A-9C, an oxide layer 124 is formed over oxide layer 112, exposed silicon waveguides 50, and nitride waveguides 60. Oxide layer 124 may be a similar material as oxide layer 112 and may be formed using similar techniques. In some embodiments, oxide layer 124 may be formed to have a thickness T4 between about 4 μm and about 8 μm over oxide 112. In fig. 10A-10D, oxide layer 124 is patterned to form cladding layer 70. Oxide layer 124 may be patterned using acceptable photolithography and etching techniques. For example, a photoresist structure may be formed and patterned over oxide layer 124, and then the pattern is transferred to oxide layer 124 using an etching process to form cladding layer 70. In some embodiments, the etching process may include a dry etching process and/or a wet etching process, and the etching process may be selective to silicon oxide relative to silicon. In some embodiments, the region of the cladding layer 70 surrounding the nitride waveguide 60 may have a width W3 of between about 1.0 μm and about 2.5 μm, and the region of the cladding layer 70 surrounding the silicon waveguide 50 may have a width W4 of between about 6 μm and about 10 μm. In some embodiments, the cladding 70 may have a thickness T5 of between about 8 μm and about 10 μm.
Turning to fig. 11A-11C-16A-16C, intermediate stages in the formation of an edge coupler 90 according to some embodiments are illustrated. In some embodiments, the process illustrated in fig. 11A-16C may be performed on the structures illustrated in fig. 6G-6H. The process shown in fig. 11A to 16C may be performed simultaneously with the process shown in fig. 7A to 10D. Edge coupler 90 couples silicon waveguide 50 to optical fiber 140 (see, e.g., fig. 2, 3A, or 5), thereby allowing optical signals to be transmitted between silicon waveguide 50 and an external component (not shown). Fig. 11A, 12A, 13A, 14A, 15A, and 16A show plan views, and fig. 11B to 11C, 12B to 12C, 13B to 13C, 14B to 14D, 15B to 15C, and 16B to 16C show sectional views indicated on each plan view. For example, FIG. 11B shows a cross-sectional view through section B-B' shown in FIG. 11A.
In fig. 11A to 11C, a recessed region 121 'of the wiring region 121 is illustrated, similar to the recessed region 121' illustrated in fig. 6G to 6H. The recessed region 121 ' shown in fig. 11A to 11C and the recessed region 121 ' shown in fig. 7A to 7C may be different recessed regions 121 ' of the same structure as shown in fig. 6G to 6H, for example. In the recessed region 121' shown in fig. 11A, the silicon layer 108 (see fig. 6A-6B) has been patterned to form a silicon waveguide 50 having a tapered end. The patterned silicon waveguide 50 shown in fig. 11A-11C may have the same shape or a different shape than the patterned silicon waveguide 50 shown in fig. 7A-7C. In some embodiments, the tapered end of silicon waveguide 50 has a length L3 of between about 50 μm and about 500 μm. The end of the silicon waveguide 50 may taper to a point or may taper to a blunt end as shown in fig. 11A. In some embodiments, the tapered end of the silicon waveguide 50 may have a taper angle between about 0.1 degrees and about 0.6 degrees with respect to the longitudinal direction of the silicon waveguide 50. In other embodiments, the end of the silicon waveguide 50 may have a shape other than a taper, such as a circular shape, a flat shape, or other shapes.
Turning to fig. 12A-12C, a nitride coupler 92 is formed over the end of the silicon waveguide 50 shown in the structure of fig. 11A-11C. The optical signal is coupled from the tapered end of the silicon waveguide 50 into the nitride coupler 92. Nitride coupler 92 then couples the optical signal into optical fiber 140. As described above, coupling an optical signal from silicon waveguide 50 to optical fiber 140 using nitride coupler 92 in edge coupler 90 may increase the optical confinement of the coupled optical signal, and thus reduce losses and improve coupling efficiency. Nitride coupler 92 may be formed of silicon nitride in a similar manner to nitride waveguide 60 described previously, and may be formed simultaneously with nitride waveguide 60. The nitride coupler 92 may be formed by, for example, depositing a silicon nitride layer (not shown) and then patterning the silicon nitride layer using acceptable photolithography and etching techniques. The nitride coupler 92 shown in fig. 12A is an illustrative example, and the nitride coupler 92 may have a different size or a different shape from that shown in fig. 12A. For example, in other embodiments, the nitride coupler 92 may have a tapered shape, a polygonal shape, a rectangular shape, a circular shape, an irregular shape, or other shapes. In some embodiments, the nitride coupler 92 may have a width W5 of between about 0.5 μm and about 5 μm, and a thickness T6 of between about 100nm and about 500 nm. In some embodiments, nitride coupler 92 may have approximately the same thickness as nitride waveguide 60. The nitride coupler 92 may have a length L3 of between about 400 μm and about 1600 μm. Nitride coupler 92 may extend from the end of silicon waveguide 50 over the silicon waveguide a length L4 of between about 100 μm and about 500 μm.
Fig. 13A-13E illustrate the formation of cladding layer 70 around nitride coupler 92 and silicon waveguide 50, thereby forming edge coupler 90. The cladding 70 surrounding the edge coupler 90 may be formed with the cladding 70 (see fig. 10A-10D) described previously. By forming the cladding 70 such that the edge coupler 90 is covered by the cladding 70 and laterally isolated by air, loss of optical signals can be reduced. As previously described, the cladding layer 70 may be formed by forming the oxide layer 124 over the nitride coupler 92 and then performing an etching process using a patterned mask. In some embodiments, the etching process also etches portions of the nitride couplers 92 such that the sidewalls of the nitride couplers 92 are exposed after the etching process, as shown in fig. 13A, 13C, and 13D. In some embodiments, the width of the exposed sidewalls of the nitride couplers 92 may be between about 100nm and about 500 nm.
Turning to fig. 14A-14D, fiber trenches 134 are etched in the substrate 104. The fiber grooves 134 serve to support the optical fibers 140 (shown schematically in fig. 14C) and facilitate alignment of the optical fibers 140 with the edge coupler 90. The fiber trench 134 may be formed by suitable photolithography and etching techniques. For example, a photoresist structure may be formed and patterned over the substrate 104, and then the pattern is transferred to the substrate 104 using an etching process to form the fiber trenches 134. In some embodiments, the etching process may include a dry etching process and/or a wet etching process, and the etching process may be selective to silicon relative to silicon oxide or silicon nitride. The fiber grooves 134 may have vertical or angled sidewalls, a flat bottom, or a V-shaped bottom, or may have a different shape than these examples. In some cases, the shape and size of the fiber trench 134 can be controlled by controlling the characteristics of the etching process (e.g., etching time, choice of etchant, etc.). In some embodiments, the edge of the fiber groove 134 may be separated from the edge coupler 90 by a distance W6 of between about 5 μm and about 50 μm. The fiber grooves 134 may extend from the edge of the substrate 104 a distance W6 of between about 0 μm and about 50 μm. The fiber trench 134 may have a depth D1 of between about 0 μm and about 50 μm into the substrate 104. In some embodiments, the optical fiber 140 may be secured within the fiber channel 134 by an optical glue (not shown). In some embodiments, more than one fiber trench 134 may be formed in the substrate 104. In this manner, fig. 6A-6C-14A-14D depict embodiments of photonic systems that include an optical network 40, the optical network 40 having a silicon waveguide 50 and a nitride waveguide 60. In these embodiments, nitride waveguide 60 is formed over silicon waveguide 50, and air isolation cladding 70 is formed over silicon waveguide 50 and nitride waveguide 60 to reduce light leakage from silicon waveguide 50 to substrate 104.
Turning now to fig. 15A-19, an embodiment is shown in which silicon waveguide 50 and nitride waveguide 60 (including mode converter 80 or edge coupler 90) are formed in first IPS structure 240 (see fig. 15C) and second IPS structure 250 (see fig. 16G), respectively, and then bonded together to form IPS20 (see fig. 17). In these embodiments, nitride waveguide 60 may be located between silicon waveguide 50 and silicon substrate 104 in IPS 20. As the distance between silicon waveguide 50 and substrate 104 increases, leakage between silicon waveguide 50 and silicon substrate 104 may decrease. In this manner, an optical network 40 can be formed having the above-described advantages of nitride waveguide 60 while also having reduced optical signal loss without the formation of cladding layer 70. The IPS20 shown in fig. 17 may be used in a photonic system, such as photonic system 101 shown in fig. 2, photonic system 103 shown in fig. 5, or other embodiments photonic systems described herein.
Fig. 15A-15B illustrate cross-sectional views of forming a first IPS structure 240, according to some embodiments. In some embodiments, the formation of the components shown in fig. 15A-15B may be part of a back end of line (BEOL) process. Fig. 16A-16G illustrate cross-sectional views of forming a second IPS structure 250, according to some embodiments. Fig. 16B, 16D, and 16F to 16G show sectional views of the section B-B' shown in fig. 16A. Fig. 17-19 illustrate cross-sectional views of forming IPS20, according to some embodiments.
In fig. 15A, an upper wiring structure 123 is formed over a substrate 230. The upper wiring structure 123 is a part of the wiring structure 120 (see fig. 17, and fig. 2 or 5) which is formed later. In some embodiments, the upper wiring structure 123 may be similar to the wiring region 121 shown in fig. 6E, and may be formed in a similar manner. For example, in some embodiments, upper wiring structure 123 shown in fig. 15A may be formed over a BOX substrate similar to BOX substrate 105 shown in fig. 6A. The silicon layer (e.g., silicon layer 108, see fig. 6A) may be patterned to form silicon waveguides 50 and integrated optical components, such as photodetectors 154, modulators 156, grating couplers 152 (not shown in fig. 15A-19), or other components. Conductive features 113 may then be formed over silicon waveguide 50 and integrated optical subassembly 154/156, and conductive pads 115 may be formed over conductive features 113.
In fig. 15B, conductive connections 220 are formed over conductive pads 115 and upper routing structures 123 are attached to carrier 232 (e.g., by an adhesive). In some embodiments, one or more dielectric layers 222 may be formed over conductive pads 115, and then openings are formed in dielectric layers 222 to expose conductive pads 115. The dielectric layer 222 may include one or more oxide layers, nitride layers, etch stop layers, passivation layers, the like, or combinations thereof. The dielectric layer 222 may be patterned using suitable photolithography and etching techniques.
In some embodiments, an Under Bump Metal (UBM)221 is formed on the conductive pad and the dielectric layer 222. UBM 221 may be formed by forming one or more conductive layers on dielectric layer 222 and conductive pad 115. The conductive layer may be formed using a suitable process such as a plating process. The conductive layer may be formed of copper, copper alloy, silver, titanium, gold, aluminum, nickel, or the like, or a combination thereof. The conductive layer may then be patterned to form UBM 221.
Conductive connection 220 is then formed on UBM 221. The conductive connections 220 may be Ball Grid Array (BGA) connections, solder balls, metal posts, controlled collapse chip connection (C4) bumps, micro bumps, bumps formed by Electroless Nickel Electroless Palladium Immersion Gold (ENEPIG), and the like. The conductive connection 220 may include a conductive material such as solder, copper, aluminum, gold, nickel, silver, palladium, tin, or the like, or a combination thereof. In some embodiments, the conductive connection 220 is formed by first forming a solder layer by common methods such as evaporation, plating, printing, solder transfer, ball placement, and the like. Once the solder layer is formed on the structure, reflow can be performed to shape the material into the desired bump shape. In another embodiment, the conductive connection 220 is a metal pillar (such as a copper pillar) formed by sputtering, printing, electroplating, electroless plating, CVD, or the like. The metal pillars may be solder-free and have substantially vertical sidewalls. In some embodiments, a metal cap layer (not shown) is formed on top of the conductive connection 220. The metal capping layer may include nickel, tin-lead, gold, silver, palladium, indium, nickel-palladium-gold, nickel-gold, or the like, or a combination thereof, and may be formed by a plating process.
In fig. 15C, the substrate 104 is removed and the oxide layer 106 is thinned, forming a first IPS structure 240. The substrate 104 may be removed using a planarization process (e.g., a CMP or grinding process), an etching process, or a combination thereof. A planarization process may be used to thin oxide layer 106, forming a thinned oxide layer 106'. In some embodiments, the thinned oxide layer 106' can have a thickness between about 400nm and about 600 nm.
Turning to fig. 16A-16G, formation of a second IPS structure 250 is shown, according to some embodiments. In fig. 16A-16B, an oxide layer 254 is formed over a substrate 252. The substrate 252 may be a material such as a glass, ceramic, dielectric, or semiconductor substrate. For example, the substrate 252 may comprise a bulk semiconductor or the like, which may be doped (e.g., with p-type or n-type dopants) or undoped. In some embodiments, substrate 252 is a wafer, such as a silicon wafer or other type of semiconductor wafer. Other substrate materials such as multilayer or gradient substrates may also be used. In some embodiments, the material of the substrate 252 may include silicon; germanium; a compound semiconductor including silicon carbide, gallium arsenide, gallium phosphide, indium arsenide, and/or indium antimonide; alloy semiconductors including SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP, or the like, or combinations thereof. The oxide layer 254 may be, for example, silicon oxide or the like. In some embodiments, oxide layer 254 can be formed by high density plasma chemical vapor deposition (HDP-CVD), flowable CVD (fcvd) (e.g., CVD-based material deposition and post-cure in a remote plasma system to convert it to another material, such as an oxide), or the like, or combinations thereof. In some embodiments, a planarization process (e.g., a CMP process) is performed on oxide layer 254 after formation. In some embodiments, oxide layer 254 may have a thickness between about 500nm and about 2500 nm.
Still referring to fig. 16A-16B, a silicon nitride layer (not shown) is formed and patterned over the oxide layer 254 to form the nitride waveguide 60 and the nitride coupler 92, wherein fig. 16B is a cross-sectional view along line B-B' of fig. 16A. The silicon nitride layer may be patterned using acceptable photolithography and etching techniques. For example, a photoresist structure may be formed and patterned over a silicon nitride layer, and then the pattern is transferred to the silicon nitride layer using an etching process to form nitride waveguide 60 and nitride coupler 92 (hereinafter sometimes referred to as "nitride component 60/92"). In some embodiments, the etching process may include a dry etching process and/or a wet etching process, and the etching process may be selective to silicon nitride relative to silicon oxide. The silicon nitride may be formed using a suitable deposition technique, such as CVD, LPCVD, PVD, or the like. In some embodiments, a nitride layer may be formed having a thickness between about 50nm and about 500 nm.
In some cases, depositing silicon nitride of nitride member 60/92 using LPCVD techniques may reduce propagation loss of nitride member 60/92 (e.g., as compared to other deposition techniques such as PECVD). In some cases, propagation loss of nitride feature 60/92 may be reduced by forming silicon nitride using LPCVD techniques at process temperatures between about 600 ℃ and about 800 ℃. However, in some cases, temperatures in excess of about 400 ℃ can damage silicon photonic components, such as silicon waveguide 50, photodetector 154, modulator 156, and the like (see fig. 15A-15C). Thus, by forming nitride component 60/92 and the silicon photonic component on separate substrates, nitride component 60/92 may be formed using deposition techniques that improve the performance of nitride component 60/92 without the risk of damaging the silicon photonic component.
Turning to fig. 16C-16D, an oxide layer 256 is formed over the oxide layer 254 and the nitride features 60/92, where fig. 16D is a cross-sectional view along line B-B' of fig. 16C. Oxide layer 256 may be formed of a similar material as oxide layer 254 and may be formed in a similar manner. Oxide layer 256 may be planarized using a CMP process or the like. In some embodiments, oxide layer 256 may be formed to have a thickness between about 55nm and about 550 nm. In some embodiments, the thickness of the oxide layer 256 above the nitride feature 60/92 may be between about 5nm and about 50 nm.
Turning to fig. 16E-16G, a via 258 and a fiber trench 134 are formed in the substrate 252, thereby forming the second IPS structure 250. The via 258 may be, for example, a via (TV), etc., in which fig. 16F to 16G are sectional views along the line B-B' of fig. 16E. When the first IPS structure 240 is bonded to the second IPS structure 250 (see fig. 17), the via 258 may be formed to make electrical connection with the via 122. Via 258 may be formed using a similar material or similar process as via 122. For example, an opening for via 258 is formed through oxide layers 256 and 254 and into substrate 252 using acceptable photolithography and etching techniques. A conductive material may then be formed in the opening to form via 258. A planarization process, such as a CMP process, may be performed so that the top surfaces of the via 258 and the oxide layer 256 are flush.
Still referring to fig. 16E-16G, fiber trenches 134 are etched in the substrate 252. Prior to etching the fiber trenches 134, the oxide layer 254/256 and the nitride coupler 92 may be patterned and etched (e.g., using suitable photolithography and etching techniques) so that the sidewalls of the nitride coupler 92 are exposed. The fiber trench 134 may be formed by suitable photolithography and etching techniques. In some embodiments, the etching process may include a dry etching process and/or a wet etching process, and the etching process may be selective to silicon with respect to oxide or silicon nitride. The fiber grooves 134 may have vertical or angled sidewalls, a flat bottom, or a V-shaped bottom, or may have a different shape than these examples. In some embodiments, the etching process undercuts oxide layer 254, as shown in fig. 16F. The fiber trench 134 may undercut the oxide layer 254 a distance between about 40 μm and about 100 μm. In other embodiments, the etching process does not undercut the oxide layer 254, as shown in fig. 16G. In some embodiments, more than one fiber trench 134 may be formed in the substrate 252.
Turning to fig. 17, a first IPS structure 240 (see fig. 15C) is bonded to a second IPS structure 250 (see fig. 16E) to form an IPS20 with a hybrid optical network, according to some embodiments. The IPS20 shown in fig. 17 may be used in an optical subsystem, such as the photonic system 101 shown in fig. 2, the photonic system 103 shown in fig. 5, or other embodiments photonic systems described herein. The first IPS structure 240 may be bonded to the second IPS structure 250 using suitable bonding techniques, such as hybrid bonding, fusion bonding, direct bonding, dielectric bonding, metal bonding, and the like. For example, the thinned oxide layer 106' of the first IPS structure 240 may be bonded to the oxide layer 256 of the second IPS structure 250. In addition, the via 122 of the first IPS structure 240 may be joined to the via 258 of the second IPS structure 240 to form an electrical connection between the first IPS structure 240 and the second IPS structure 250. The silicon waveguides 50 of the first IPS structure 240 may be aligned over the corresponding nitride features 60/92 of the second IPS structure 250 to form the optical network 40 of the IPS 20. For example, an end of nitride waveguide 60 (e.g., similar to the end shown in fig. 8A) may be aligned over an end of silicon waveguide 50 (e.g., similar to the end shown in fig. 7A) to form mode converter 80 within IPS20 after bonding. In this way, the wiring structure 120 of the IPS20 is also formed. After bonding, the carrier 232 may be removed from the first IPS structure 240.
In some embodiments, multiple IPS20 may be formed and then split into multiple IPS20, as shown in fig. 18. In some embodiments, a plurality of first IPS structures 240 may be bonded to a plurality of second IPS structures 250, and then a singulation process 260 is performed to singulate individual IPS 20. The singulation process 260 may include a suitable singulation process using a saw blade, laser, or other technique or combination of techniques. After cleaving, the fiber 140 may be mounted in the trench 134 and aligned with the nitride coupler 92, as shown in FIG. 19. The optical fibers 140 may be secured in place using optical glue (not shown) or other suitable adhesive material.
In some cases, many advantages may be realized using an integrated optical network that includes silicon and silicon nitride components. For example, silicon nitride waveguides may have lower propagation losses than silicon waveguides, and thus transmitting optical signals between sites using silicon nitride waveguides may improve signal strength and reduce power consumption to compensate for signal losses. The silicon waveguide and the silicon nitride waveguide may be coupled by forming a coupling structure. A silicon nitride waveguide may be formed on a layer above the silicon waveguide, and a silicon oxide cladding may be formed surrounding the silicon nitride waveguide and the silicon waveguide. By exposing the sides and top surface of the cladding to the atmosphere, signal loss due to optical coupling with the substrate can be reduced. The silicon nitride waveguide may be formed on a different substrate than the silicon waveguide, and the silicon nitride waveguide structure and the silicon waveguide structure may then be bonded together. In this manner, a silicon nitride waveguide may be formed between the silicon waveguide and the substrate, which reduces coupling between the silicon waveguide and the substrate. Photonic systems using these techniques may be formed with photonic components integrated in a separate die or may be formed with photonic components integrated with silicon waveguides.
In an embodiment, a method includes forming a silicon waveguide segment in a first oxide layer over a substrate, the first oxide layer disposed on the substrate, forming a routing structure over the first oxide layer, the routing structure including one or more insulating layers and one or more conductive components located in the one or more insulating layers, recessing a region of the routing structure, forming a nitride waveguide segment in the recessed region of the routing structure, wherein the nitride waveguide segment extends over the silicon waveguide segment, forming a second oxide layer over the nitride waveguide segment, and attaching a semiconductor die to the routing structure, the die electrically connected to the conductive components. In an embodiment, the method further includes patterning the first oxide layer and the second oxide layer to form a cladding structure surrounding the silicon waveguide segment and the nitride waveguide segment, the cladding structure having exposed sidewalls. In an embodiment, the nitride waveguide segment is straight. In an embodiment, the method further comprises forming a photonic device over the first oxide layer, wherein the photonic device comprises silicon, and wherein the photonic device is optically coupled to the at least one first waveguide segment. In an embodiment, the photonic device comprises a modulator. In an embodiment, the method further includes forming a via extending through the substrate, wherein the conductive feature is electrically coupled to the via. In an embodiment, at least one of the semiconductor dies is an integrated photonics die. In an embodiment, the at least one nitride waveguide segment extends over an end of the silicon waveguide, the end having a tapered shape. In an embodiment, the method further includes forming an edge coupler over the first oxide layer, the edge coupler comprising silicon nitride, wherein a portion of the edge coupler extends over one of the silicon waveguide segments.
In an embodiment, a method includes forming a first photonic structure, including patterning a silicon layer on a first substrate to form a first set of waveguides, wherein the silicon layer is disposed on a first oxide layer, forming conductive features over the first set of waveguides, and removing the first substrate to expose the first oxide layer. The method also includes forming a second photonic structure including depositing a silicon nitride layer on a second substrate, patterning the silicon nitride layer to form a second set of waveguides, and forming a second oxide layer over the second set of waveguides. The method also includes bonding the first photonic structure to a second photonic structure, wherein the first oxide layer is bonded to the second oxide layer, wherein the first set of waveguides is laterally aligned with the second set of waveguides. In an embodiment, the method further comprises connecting the semiconductor die to the conductive member. In an embodiment, the method further includes patterning the silicon nitride layer to form an edge coupler and recessing the second oxide layer to expose sidewalls of the edge coupler. In an embodiment, the method further includes etching a trench in the second substrate adjacent the edge coupler, wherein the trench is configured to align the optical fiber with the edge coupler. In an embodiment, the method includes attaching a second photonic structure to the interconnect structure. In an embodiment, the method includes patterning the silicon layer to form a photonic device, the photonic device optically coupled to the first set of waveguides. In an embodiment, the silicon nitride layer is deposited using a low pressure chemical vapor deposition process comprising a process temperature of 700 ℃ to 850 ℃.
In an embodiment, a photonic device includes an integrated photonic structure including a plurality of oxide layers over a substrate, a plurality of first waveguides and a plurality of second waveguides within the plurality of oxide layers, wherein the plurality of first waveguides are optically coupled to the plurality of second waveguides, wherein the plurality of first waveguides includes silicon and the plurality of second waveguides includes silicon nitride, and a routing structure over at least a portion of the first waveguides of the plurality of first waveguides, the routing structure including a plurality of insulating layers and conductive features in the plurality of insulating layers, and a plurality of semiconductor dies attached to the routing structure, wherein the plurality of semiconductor dies are electrically coupled to the plurality of conductive features. In an embodiment, the plurality of first waveguides is closer to the substrate than the plurality of second waveguides. In an embodiment, the photonic device includes a photodetector within the plurality of oxide layers, the photodetector optically coupled to the first waveguide and electrically coupled to the plurality of conductive members. In an embodiment, the photonic device includes a grating coupler within the plurality of oxide layers, the grating coupler optically coupled to the first waveguide, and further includes a photodetector within the semiconductor die, the photodetector configured to receive an optical signal from the grating coupler.
The foregoing has outlined features of several embodiments so that those skilled in the art may better understand the aspects of the present invention. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.
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