Semiconductor device and method of forming the same
阅读说明:本技术 半导体器件及其形成方法 (Semiconductor device and method of forming the same ) 是由 林孟汉 吴伟成 于 2019-08-27 设计创作,主要内容包括:提供一种用于制造集成半导体器件的方法,该集成半导体器件包括形成在半导体衬底的凹进区域中的嵌入式闪存阵列,该方法包括:在形成存储器阵列的浮置和控制栅极堆叠件之前,在栅极材料层上方沉积保护层,并且在保护层上方沉积自流平牺牲层,以产生基本平坦的上表面。然后将牺牲层蚀刻到去除牺牲层并在保护层上留下基本平坦的面的深度。然后在保护层上沉积光掩模,并且从栅极材料层蚀刻栅极堆叠件。本发明的实施例还涉及半导体器件及其形成方法。(There is provided a method for manufacturing an integrated semiconductor device including an embedded flash memory array formed in a recessed region of a semiconductor substrate, the method comprising: prior to forming the floating and control gate stacks of the memory array, a protective layer is deposited over the gate material layer, and a self-leveling sacrificial layer is deposited over the protective layer to create a substantially planar upper surface. The sacrificial layer is then etched to a depth that removes the sacrificial layer and leaves a substantially planar face on the protective layer. A photomask is then deposited on the protective layer and the gate stack is etched from the gate material layer. Embodiments of the invention also relate to semiconductor devices and methods of forming the same.)
1. A method of forming a semiconductor device, comprising:
forming a protective layer over a non-planar surface of a semiconductor substrate (102);
forming a sacrificial layer over the protective layer;
forming a surface on the sacrificial layer; and
planarizing the surface of the sacrificial layer to a depth sufficient to remove the sacrificial layer and remove portions of the protective layer.
2. The method of claim 1, wherein planarizing the surface of the sacrificial layer to a depth sufficient to remove the sacrificial layer and remove portions of the protective layer comprises: etching the surface of the sacrificial layer to completely remove the sacrificial layer and partially remove the protective layer.
3. The method of claim 1, wherein the sacrificial layer comprises a photoresist material, and wherein forming the sacrificial layer over the protective layer and forming the surface on the sacrificial layer together comprise: spin coating a self-leveling material on the semiconductor substrate.
4. The method of claim 1, wherein forming the protective layer over the non-planar surface of the semiconductor substrate comprises: the protective layer is formed over a recessed region of the semiconductor substrate.
5. The method of claim 4, comprising:
forming a material for a plurality of floating gates and control gates of a memory array in a layer above the recessed region prior to forming the protective layer; and
forming a material for the plurality of floating gates in a layer above the recessed region.
6. The method of claim 5, wherein forming material for the plurality of floating gates in a layer above the recessed region comprises:
forming a first dielectric layer over the semiconductor substrate;
forming a first polysilicon layer over the first dielectric layer;
forming a second dielectric layer over the first polysilicon layer; and
a second polysilicon layer is formed over the second dielectric layer.
7. A method of forming a semiconductor device, comprising:
forming a recess region in a semiconductor substrate;
forming gate material for a plurality of floating gates and control gates of a memory array in a layer above the recessed region;
forming a protective layer over the gate material in the recessed region;
planarizing the protective layer;
forming an etching mask layer over the planarized protection layer; and
forming a plurality of gate stacks in the recessed regions by etching the gate material.
8. The method of claim 7, wherein planarizing the protective layer comprises:
forming a sacrificial layer over the protective layer;
planarizing the sacrificial layer; and
after planarizing the sacrificial layer, a planarized surface of the sacrificial layer is etched at a uniform rate across the recessed region to a depth sufficient to leave a planarized surface on the protective layer.
9. A method of forming a semiconductor device, comprising:
forming a protective layer over the stack of gate material layers in the recessed region of the semiconductor substrate;
depositing a sacrificial layer over the protective layer, the sacrificial layer having a depth sufficient to create a planarized surface on the semiconductor substrate; and
the sacrificial layer is removed to a depth sufficient to create a planar surface on the protective layer.
10. A semiconductor device, comprising:
a semiconductor substrate including a recessed region having a central portion and an outer peripheral portion; and
a flash memory array in the recessed region, the flash memory array including a plurality of gate stacks, and each of the gate stacks having a width, the width of the gate stacks being uniform for the gate stacks in the central portion of the recessed region and the gate stacks in the peripheral portion of the recessed region.
Technical Field
Embodiments of the invention relate to semiconductor devices and methods of forming the same.
Background
Flash memory has certain advantages and benefits over other types of solid state non-volatile memory structures. Many of these advantages and benefits are associated with, for example, improved read, write and/or erase speeds, power consumption, compactness, cost, and the like. Flash memory is commonly used in high density data storage devices configured for use with cameras, cell phones, voice recorders, portable USB data storage devices (commonly referred to as thumb drives or flash drives, etc.). Typically, in such applications, the flash memory is fabricated on a dedicated microchip and then coupled in a single package with another chip or chips containing appropriate processor circuitry, or in separate packages configured to be electrically coupled.
Processors with embedded flash memory are a recent development. In such devices, the flash array is fabricated on a single chip along with logic and control circuitry. Such arrangements are typically used in microcontroller units (MCUs) (i.e., small computer devices integrated on a single chip), which are typically designed to repeatedly perform a limited number of specific tasks. MCUs are often used in smart cards, wireless communication devices, automotive control units, etc. Integration of memory with associated processing circuitry may increase processing speed while reducing package size, power consumption, and cost.
Disclosure of Invention
An embodiment of the present invention provides a method of forming a semiconductor device, including: forming a protective layer over a non-planar surface of a semiconductor substrate (102); forming a sacrificial layer over the protective layer; forming a surface on the sacrificial layer; and planarizing the surface of the sacrificial layer to a depth sufficient to remove the sacrificial layer and remove portions of the protective layer.
Another embodiment of the present invention provides a method of forming a semiconductor device, including: forming a recess region in a semiconductor substrate; forming gate material for a plurality of floating gates and control gates of a memory array in a layer above the recessed region; forming a protective layer over the gate material in the recessed region; planarizing the protective layer; forming an etching mask layer over the planarized protection layer; and forming a plurality of gate stacks in the recessed regions by etching the gate material.
Yet another embodiment of the present invention provides a method of forming a semiconductor device, including: forming a protective layer over the stack of gate material layers in the recessed region of the semiconductor substrate; depositing a sacrificial layer over the protective layer, the sacrificial layer having a depth sufficient to create a planarized surface on the semiconductor substrate; and removing the sacrificial layer to a depth sufficient to create a planar surface on the protective layer.
Still another embodiment of the present invention provides a semiconductor device including: a semiconductor substrate including a recessed region having a central portion and an outer peripheral portion; and a flash memory array in the recessed region, the flash memory array including a plurality of gate stacks, and each of the gate stacks having a width, the width of the gate stacks being uniform for the gate stacks in the central portion of the recessed region and the gate stacks in the peripheral portion of the recessed region.
Drawings
Various aspects of the invention are best understood from the following detailed description when read with the accompanying drawing figures. It should be emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale and are used for illustration purposes only. In fact, the dimensions of the various elements may be arbitrarily increased or decreased for clarity of discussion.
Fig. 1 is a schematic side cross-sectional view of a portion of a semiconductor device having an embedded flash memory (e.g., a microcontroller unit) during fabrication according to an embodiment.
Fig. 2A-2D are schematic side cross-sectional views of the semiconductor device of fig. 1 at respective stages of the fabrication process, particularly illustrating recessed regions during control of the embedded memory array and formation of the floating gates, and illustrating the source of problems addressed by the various disclosed embodiments.
Fig. 3A-3F are schematic side cross-sectional views of the semiconductor device of fig. 1 at various stages of the fabrication process and illustrate the control and floating gate formation of the
Fig. 4 and 5 are flow charts summarizing methods of manufacturing according to respective embodiments, consistent with the process described with reference to fig. 2A-2B and 3A-3F.
Detailed Description
The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific embodiments or examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. 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. As used herein, forming a first feature over a second feature refers to forming the first feature in direct contact with the second feature. Moreover, the present disclosure may repeat reference numerals and/or letters in the various examples. 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.
Furthermore, spatial relationship terms such as "below …," "below …," "lower," "above …," "upper," and the like may be used herein to describe one element or component's relationship to another element or component as illustrated in the figures for ease of description. Spatial relationship 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 spatial relationship descriptors used herein interpreted accordingly as such.
In the drawings, some elements are indicated by reference numerals followed by letters, such as "704 a, 704 b". In this case, letter designations are used in the respective description to refer to or distinguish particular elements or differences between particular elements among a number of other similar or identical elements. If the specification omits letters from the reference and refers to these elements only by number, it is to be understood that a general reference to any or all of the elements identified by the reference number, unless other distinguishing language is used.
Unless the context clearly further limits the scope, reference to a semiconductor substrate may include within its scope any element formed or deposited on the substrate. For example, reference to planarizing a surface of a semiconductor substrate may refer to planarizing one or more layers of material deposited or otherwise formed over the actual base material of the substrate, including, for example, polysilicon layers, metal layers, dielectric layers, or combinations of materials, layers, and/or elements.
A microcontroller unit (MCU) typically includes a number of discrete devices such as a Central Processing Unit (CPU) core, a Static Random Access Memory (SRAM) array (or module), a flash memory module, a system integration module, a timer, an analog-to-digital converter (ADC), a communication and networking module, a power management module, and the like. Each of these devices, in turn, includes a number of passive and active electronic components, such as resistors, capacitors, transistors, and diodes. A large number of these components, in particular active components, are based on various types of Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) or variants thereof. In a MOSFET, the conductivity in the channel region extending between the source and drain terminals is controlled by the electric field in the channel region, which is generated by the voltage difference between the control gate and the body of the device.
Fig. 1 is a schematic side cross-sectional view of a portion of a device 100 (e.g., MCU) during fabrication on a
The
Due to the similarity in structure of the
One solution is to form the
According to an alternative embodiment, a layer of semiconductor material is deposited or grown on the surface of
As described above, the
In
As technology advances, components are smaller and more compact, reducing power consumption and voltage requirements while increasing memory density and speed. However, a problem that arises with decreasing size is that very small changes in gate size can have a progressively increasing effect on performance, since such changes represent larger changes relative to a proportionally smaller nominal gate size. This becomes a greater problem as technology nodes fall below 65nm, 40nm and 28 nm.
Fig. 2A-2D are schematic side cross-sectional views of the
Initially, as shown in fig. 2A, a
Entering the stage shown in fig. 2B, a
In fig. 2C, a bottom antireflective coating (BARC)164 is applied over the
Turning finally to fig. 2D, after the patterning of the patterned film layer 166, an etching process is performed, resulting in a plurality of gate stacks 168, each
As shown in fig. 2D,
To utilize
The inventors have also recognized that this problem can be eliminated if the BARC is deposited on a substantially planar surface. However, planarizing the surface at the stage of the process shown in fig. 2B is problematic. The CMP process will have a tendency to recess over the recessed
The embodiments described below with reference to FIGS. 3A-3F reduce or eliminate the BARC layer thickness variation and associated gate uniformity variation described above. Fig. 3A-3F are schematic side cross-sectional views of the
As shown in fig. 3B, a non-selective etching process is performed to etch back the surface of the substrate into the
Other processes may be utilized to remove
According to an embodiment, the etching of the
Proceeding to fig. 3C, the patterned film layer 188 is patterned to form an etch mask, and the
Fig. 3D-3E are schematic side cross-sectional views of
Fig. 4 and 5 are flow diagrams summarizing methods of manufacture according to various embodiments, consistent with the processes described above with reference to fig. 2A-2B and 3A-3F.
Fig. 4 outlines a
Fig. 5 is a flow chart summarizing a
The embodiments shown and described herein provide improvements in processes for fabricating microelectronic devices that include embedded flash memory arrays. According to various embodiments, prior to defining the control and floating gate stacks of the memory array in recessed regions on a semiconductor substrate, a planar surface is provided on the substrate over the material layers that will form the gate stacks for depositing an antireflective coating and patterning film of uniform thickness. This is beneficial because the anti-reflective coating has a tendency to vary in thickness, particularly when it is deposited on non-planar surfaces, which in turn can lead to non-uniformity in the dimensions of the control gate and the floating gate. The dimensions of the control gate and floating gate directly affect key operating characteristics of the memory device, such as read, write and erase speeds, program and erase state voltage and current levels, power consumption, and the like. If the gate dimensions vary within the memory array, it is typical to operate the entire array based on the operating characteristics of the weakest cell. Thus, significant variations in size are a problem because even if a small fraction of the cells in the array require higher voltages and/or longer read and write times, the entire array operates at the same level, resulting in a loss of efficiency and speed for the entire array. By providing a planar surface, non-uniformity in the gate dimensions of the memory array is reduced or eliminated. This in turn results in an array with higher overall speed and efficiency.
According to an embodiment, the improvement comprises forming a protective layer over a non-planar surface of a semiconductor substrate, particularly, for example, over a recessed region of the semiconductor substrate in which an embedded memory array is to be formed. A sacrificial layer is then deposited over the protective layer, the sacrificial layer having a depth sufficient to allow a substantially planar surface to be formed on the sacrificial layer. The sacrificial layer is then etched to a depth that removes the sacrificial layer and leaves a planar surface formed in the protective layer.
According to another embodiment, the method includes forming a recessed region in a semiconductor substrate, and forming a gate material for a plurality of floating gates and control gates of a memory array in a layer above the recessed region. A protective layer is then formed over the gate material in the recessed region and planarized to improve gate dimension uniformity. An etch mask is formed over the planarized protective layer and a gate stack of the memory array is formed in the recessed region by etching the gate material. According to an embodiment, planarizing the protective layer includes depositing a self-leveling sacrificial layer over the protective layer to create a substantially planar surface, then etching the surface at a uniform rate and to a depth sufficient to remove the sacrificial layer, which creates a planar surface on the protective layer.
According to another embodiment, the method includes forming a protective layer over the stack of gate material layers in the recessed region of the semiconductor substrate. A self-leveling sacrificial layer is then deposited over the protective layer, the self-leveling sacrificial layer having a depth sufficient to produce a planarized surface of the semiconductor substrate, and the sacrificial layer is etched back at a uniform rate to a depth sufficient to produce a substantially planar surface on the protective layer.
An embodiment of the present invention provides a method of forming a semiconductor device, including: forming a protective layer over a non-planar surface of a semiconductor substrate (102); forming a sacrificial layer over the protective layer; forming a surface on the sacrificial layer; and planarizing the surface of the sacrificial layer to a depth sufficient to remove the sacrificial layer and remove portions of the protective layer.
In the above method, wherein planarizing the surface of the sacrificial layer to a depth sufficient to remove the sacrificial layer and remove portions of the protective layer comprises: etching the surface of the sacrificial layer to completely remove the sacrificial layer and partially remove the protective layer.
In the above method, wherein the sacrificial layer comprises a photoresist material, and wherein forming the sacrificial layer over the protective layer and forming the surface on the sacrificial layer together comprise: spin coating a self-leveling material on the semiconductor substrate.
In the above method, wherein forming the protective layer over the non-planar surface of the semiconductor substrate comprises: the protective layer is formed over a recessed region of the semiconductor substrate.
In the above method, wherein forming the protective layer over the non-planar surface of the semiconductor substrate comprises: forming the protective layer over the recessed region of the semiconductor substrate, comprising: forming a material for a plurality of floating gates and control gates of a memory array in a layer above the recessed region prior to forming the protective layer; and forming a material for the plurality of floating gates in a layer above the recessed region.
In the above method, wherein forming the protective layer over the non-planar surface of the semiconductor substrate comprises: forming the protective layer over the recessed region of the semiconductor substrate, comprising: forming a material for a plurality of floating gates and control gates of a memory array in a layer above the recessed region prior to forming the protective layer; and forming a material for the plurality of floating gates in the layer above the recessed region, wherein forming the material for the plurality of floating gates in the layer above the recessed region comprises: forming a first dielectric layer over the semiconductor substrate; forming a first polysilicon layer over the first dielectric layer; forming a second dielectric layer over the first polysilicon layer; and forming a second polysilicon layer over the second dielectric layer.
Yet another embodiment of the present invention provides a method of forming a semiconductor device, including: forming a recess region in a semiconductor substrate; forming gate material for a plurality of floating gates and control gates of a memory array in a layer above the recessed region; forming a protective layer over the gate material in the recessed region; planarizing the protective layer; forming an etching mask layer over the planarized protection layer; and forming a plurality of gate stacks in the recessed regions by etching the gate material.
In the above method, wherein planarizing the protective layer comprises: forming a sacrificial layer over the protective layer; planarizing the sacrificial layer; and after planarizing the sacrificial layer, etching the planarized surface of the sacrificial layer at a uniform rate across the recessed region to a depth sufficient to leave a planarized surface on the protective layer.
In the above method, wherein planarizing the protective layer comprises: forming a sacrificial layer over the protective layer; planarizing the sacrificial layer; and after planarizing the sacrificial layer, etching the planarized surface of the sacrificial layer at a uniform rate across the recessed region to a depth sufficient to leave a planarized surface on the protective layer, wherein etching the planarized surface of the sacrificial layer to a depth sufficient to leave a planarized surface on the protective layer comprises: the planarized surface of the sacrificial layer is etched to a depth sufficient to completely remove the sacrificial layer.
In the above method, wherein planarizing the protective layer comprises: forming a sacrificial layer over the protective layer; planarizing the sacrificial layer; and after planarizing the sacrificial layer, etching a planarized surface of the sacrificial layer at a uniform rate across the recessed region to a depth sufficient to leave a planarized surface on the protective layer, wherein forming the sacrificial layer over the protective layer and planarizing the sacrificial layer together comprise: depositing a self-leveling sacrificial layer over the protective layer.
In the above method, wherein planarizing the protective layer comprises: forming a sacrificial layer over the protective layer; planarizing the sacrificial layer; and after planarizing the sacrificial layer, etching a planarized surface of the sacrificial layer at a uniform rate across the recessed region to a depth sufficient to leave a planarized surface on the protective layer, wherein forming the sacrificial layer over the protective layer and planarizing the sacrificial layer together comprise: depositing a self-leveling sacrificial layer over the protective layer, wherein depositing the self-leveling sacrificial layer over the protective layer comprises: the self-leveling sacrificial layer is deposited using a spin-on process.
In the above method, wherein planarizing the protective layer comprises: forming a sacrificial layer over the protective layer; planarizing the sacrificial layer; and after planarizing the sacrificial layer, etching the planarized surface of the sacrificial layer at a uniform rate across the recessed region to a depth sufficient to leave a planarized surface on the protective layer, wherein etching the planarized surface of the sacrificial layer comprises: the planarized surface of the sacrificial layer is etched directly after deposition and planarization of the sacrificial layer without intermediate process steps.
In the above method, wherein forming the etch mask layer over the planarized protection layer comprises: forming an anti-reflective coating over the planarized protective layer; and forming the etch mask layer over the antireflective coating.
In the above method, wherein forming the gate material for the plurality of floating gates and control gates comprises: forming a gate dielectric layer over the recessed region; forming a first polysilicon layer over the gate dielectric layer; forming an inter-gate dielectric layer over the first polysilicon layer; and depositing a second polysilicon layer on the inter-gate dielectric layer.
In the above method, wherein forming the gate material for the plurality of floating gates and control gates comprises: forming a gate dielectric layer over the recessed region; forming a first polysilicon layer over the gate dielectric layer; forming an inter-gate dielectric layer over the first polysilicon layer; and depositing a second polysilicon layer on the inter-gate dielectric layer, wherein forming the plurality of gate stacks in the recessed region comprises: providing the etching mask layer having a pattern corresponding to a gate pattern; and etching the inter-gate dielectric layer and the second polysilicon layer using the patterned etch mask layer.
Yet another embodiment of the present invention provides a method of forming a semiconductor device, including: forming a protective layer over the stack of gate material layers in the recessed region of the semiconductor substrate; depositing a sacrificial layer over the protective layer, the sacrificial layer having a depth sufficient to create a planarized surface on the semiconductor substrate; and removing the sacrificial layer to a depth sufficient to create a planar surface on the protective layer.
In the above method, wherein forming the protective layer comprises: forming the protective layer comprising one or more of amorphous silicon, oxide, and nitride.
In the above method, wherein depositing the sacrificial layer comprises: and spin-coating a photoresist material layer on the semiconductor substrate.
In the above method, wherein forming the protective layer over the stack of gate material layers in the recessed region of the semiconductor substrate comprises: forming the protective layer comprising a first dielectric layer, a first polysilicon layer, a second dielectric layer, and a second polysilicon layer over the stack of gate material layers.
In the above method, further comprising: after removing the sacrificial layer, a plurality of gate stacks are formed from the stack of gate material layers and the protective layer.
An embodiment of the present invention provides a semiconductor device including: a semiconductor substrate including a recessed region having a central portion and an outer peripheral portion; and a flash memory array in the recessed region, the flash memory array including a plurality of gate stacks, and each of the gate stacks having a width, the width of the gate stacks being uniform for the gate stacks in the central portion of the recessed region and the gate stacks in the peripheral portion of the recessed region.
In the above semiconductor device, wherein each of the gate stacks includes: a floating gate on the recessed region of the semiconductor substrate; the control grid is positioned on the floating grid; and the protective cap layer is positioned on the floating gate.
In the above semiconductor device, wherein each of the gate stacks includes: a floating gate on the recessed region of the semiconductor substrate; the control grid is positioned on the floating grid; and the protective cap layer is positioned on the floating gate, wherein the protective cap layer has the depth of 1500-2000 angstroms.
In accordance with conventional claim practice, ordinal numbers are used in the claims, e.g., first, second, third, etc., i.e., to clearly distinguish between claimed elements or features thereof. Ordinal numbers may be arbitrarily assigned or simply assigned in the order in which the elements are introduced. The use of such numbers does not indicate any other relationship, such as order of operation, relative position of the elements, etc. Furthermore, ordinal numbers used to refer to elements in the claims should not be assumed to be associated with numerals used in the specification to refer to elements of the disclosed embodiments that are read by the claims, nor are numerals used to refer to similar elements or features in unrelated claims.
Although the method and process steps recited in the claims may be presented in an order corresponding to the steps disclosed and described in the specification, unless explicitly stated otherwise, the order in which the steps are presented in the specification or claims is not limited to the order in which the steps may be performed.
The abstract of the invention is provided as a brief summary of some principles of the invention according to embodiments, and is not intended as a complete or definitive description of any embodiment thereof, nor should it be relied upon to define terms used in the specification or claims. The abstract does not limit the scope of the claims.
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 invention 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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