阅读说明：本技术 光波模式转换装置及其制造方法 (Light wave mode conversion device and manufacturing method thereof ) 是由 王庆 方青 汪巍 涂芝娟 曾友宏 蔡艳 王书晓 余明斌 于 2018-07-23 设计创作，主要内容包括：本发明涉及半导体技术领域,尤其涉及一种光波模式转换装置及其制造方法。所述光波模式转换装置,包括同层设置的第一波导和第二波导,且所述第一波导的折射率大于所述第二波导；所述第二波导朝向所述第一波导的端部具有开口,所述开口的直径沿所述第二波导指向所述第一波导的方向逐渐增大,且所述第一波导的光耦合端面与所述开口对齐设置。本发明不仅降低了光学器件的工艺复杂度,而且提高了两种波导之间的耦合效率,实现了两种波导之间的低损耗互连。(The present invention relates to the field of semiconductor technology, and more particularly, to a light wave mode conversion device and a method for manufacturing the same. The optical wave mode conversion device comprises a first waveguide and a second waveguide which are arranged on the same layer, and the refractive index of the first waveguide is larger than that of the second waveguide; the end part of the second waveguide, which faces the first waveguide, is provided with an opening, the diameter of the opening is gradually increased along the direction that the second waveguide points to the first waveguide, and the optical coupling end surface of the first waveguide is aligned with the opening. The invention not only reduces the process complexity of the optical device, but also improves the coupling efficiency between the two waveguides, and realizes the low-loss interconnection between the two waveguides.)

1. A light wave mode conversion device is characterized by comprising a first waveguide and a second waveguide which are arranged in the same layer, wherein the refractive index of the first waveguide is larger than that of the second waveguide; the second waveguide is provided with an opening towards the end part of the first waveguide, the width of the opening is gradually increased along the direction that the second waveguide points to the first waveguide, and the optical coupling end surface of the first waveguide is aligned with the opening.

2. The device according to claim 1, wherein the first waveguide is a silicon waveguide, the second waveguide is a silicon nitride waveguide, the opening is filled with a silicon tapered structure, and a bottom surface of the silicon tapered structure is aligned with and connected to the optical coupling end surface of the first waveguide.

3. The device according to claim 2, further comprising an SOI substrate, wherein the first waveguide and the silicon tapered structure are fabricated from top silicon of the SOI substrate, and wherein the second waveguide is located on a buried oxide surface of the SOI substrate.

4. The device according to any of claims 1 to 3, wherein the first waveguide and the second waveguide are the same thickness.

5. The device according to any of claims 1 to 3, further comprising an upper cladding layer covering the surfaces of the first waveguide and the second waveguide.

6. The device according to claim 5, wherein the material of the upper cladding layer is silica.

7. A method of manufacturing a lightwave mode conversion device, comprising the steps of:

providing a substrate;

forming a first waveguide on the surface of the substrate;

and forming a second waveguide on the surface of the substrate, wherein the refractive index of the second waveguide is smaller than that of the first waveguide, the end part of the second waveguide facing the first waveguide is provided with an opening, the width of the opening is gradually increased along the direction from the second waveguide to the first waveguide, and the light coupling end face of the first waveguide is aligned with the opening.

8. The method for manufacturing a lightwave mode conversion device according to claim 7, wherein the substrate is an SOI substrate; the specific steps of forming the first waveguide on the surface of the substrate include:

etching the top silicon layer of the SOI substrate, simultaneously forming a first waveguide and a silicon conical structure, and defining a second waveguide area; the bottom surface of the silicon conical structure is aligned with the optical coupling end surface of the first waveguide.

9. The method according to claim 8, wherein the second waveguide region has an opening, the width of the opening gradually increases along a direction in which the second waveguide region is directed toward the first waveguide, and the silicon taper structure is located in the opening; the specific steps of forming the second waveguide on the surface of the substrate include:

etching the top silicon layer of the second waveguide region to expose the buried oxide layer of the SOI substrate;

and depositing a second waveguide material on the surface of the buried oxide layer of the second waveguide region to form the second waveguide layer.

10. The method of manufacturing a lightwave mode conversion device according to claim 9, further comprising the steps of:

and depositing silicon dioxide on the surfaces of the first waveguide and the second waveguide to form an upper cladding.

Technical Field

The present invention relates to the field of semiconductor technology, and more particularly, to a light wave mode conversion device and a method for manufacturing the same.

Background

With the updating of network products, the size and power consumption of modules used in the network are becoming smaller and smaller, so as to meet the requirements of reducing the cost and improving the performance. Silicon-based photonic devices have recently received extensive attention from the industry due to their unique characteristics of low cost, ultra-small size, low power consumption, etc., and have become one of the major considerations in the network product upgrading.

Disclosure of Invention

The invention provides a light wave mode conversion device and a manufacturing method thereof, which are used for solving the problem of low optical coupling efficiency between the existing optical waveguides with different mode fields.

In order to solve the above problems, the present invention provides a light wave mode conversion device, including a first waveguide and a second waveguide which are disposed in the same layer, and the refractive index of the first waveguide is greater than that of the second waveguide; the end part of the second waveguide, which faces the first waveguide, is provided with an opening, the diameter of the opening is gradually increased along the direction that the second waveguide points to the first waveguide, and the optical coupling end surface of the first waveguide is aligned with the opening.

Preferably, the first waveguide is a silicon waveguide, the second waveguide is a silicon nitride waveguide, the opening is filled with a silicon tapered structure, and the bottom surface of the silicon tapered structure is aligned and connected with the optical coupling end surface of the first waveguide.

Preferably, the optical waveguide further comprises an SOI substrate, the first waveguide and the silicon taper structure are made of top silicon of the SOI substrate, and the second waveguide is located on a surface of a buried oxide layer of the SOI substrate.

Preferably, the first waveguide and the second waveguide are the same thickness.

Preferably, the waveguide further comprises an upper cladding layer covering the surfaces of the first waveguide and the second waveguide.

Preferably, the material of the upper cladding is silica.

In order to solve the above problems, the present invention further provides a method for manufacturing a light wave mode conversion device, comprising the steps of:

providing a substrate;

forming a first waveguide on the surface of the substrate;

and forming a second waveguide on the surface of the substrate, wherein the refractive index of the second waveguide is smaller than that of the first waveguide, the end part of the second waveguide facing the first waveguide is provided with an opening, the width of the opening is gradually increased along the direction from the second waveguide to the first waveguide, and the light coupling end face of the first waveguide is aligned with the opening.

Preferably, the substrate is an SOI substrate; the specific steps of forming the first waveguide on the surface of the substrate include:

etching the top silicon layer of the SOI substrate, simultaneously forming a first waveguide and a silicon conical structure, and defining a second waveguide area; the bottom surface of the silicon conical structure is aligned with the optical coupling end surface of the first waveguide.

Preferably, the second waveguide region has an opening, the width of the opening gradually increases along the direction from the second waveguide region to the first waveguide, and the silicon conical structure is located in the opening; the specific steps of forming the second waveguide on the surface of the substrate include:

etching the top silicon layer of the second waveguide region to expose the buried oxide layer of the SOI substrate;

and depositing a second waveguide material on the surface of the buried oxide layer of the second waveguide region to form the second waveguide layer.

Preferably, the method further comprises the following steps:

and depositing silicon dioxide on the surfaces of the first waveguide and the second waveguide to form an upper cladding.

According to the light wave mode conversion device and the manufacturing method thereof, the two waveguides with different refractive indexes are arranged on the same layer, the tapered opening is arranged in the waveguide with the low refractive index, the high refractive index waveguide and the waveguide with the low refractive index are subjected to light wave coupling through the tapered opening, so that the conversion of a light wave mode is realized, the process complexity of an optical device is reduced, the coupling efficiency between the two waveguides is improved, and the low-loss interconnection between the two waveguides is realized.

Drawings

FIG. 1 is a schematic top view of a light wave mode conversion device according to an embodiment of the present invention;

FIG. 2 is a schematic cross-sectional view of a light wave mode conversion device according to an embodiment of the present invention;

fig. 3 is a flowchart of a method of manufacturing a light wave mode conversion device according to an embodiment of the present invention.

Detailed Description

The following describes in detail embodiments of the optical wave mode conversion device and the method for manufacturing the same according to the present invention with reference to the accompanying drawings.

Fig. 1 is a schematic top view structure diagram of a light wave mode conversion device in an embodiment of the present invention, and fig. 2 is a schematic cross-sectional structure diagram of the light wave mode conversion device in the embodiment of the present invention.

As shown in fig. 1 and fig. 2, the optical wave mode conversion apparatus provided in this embodiment includes a first waveguide 11 and a second waveguide 12 that are disposed in the same layer, and a refractive index of the first waveguide 11 is greater than that of the second waveguide 12; the second waveguide 12 has an opening 13 towards the end of the first waveguide 11, the width of the opening 13 gradually increases along the direction in which the second waveguide 12 points to the first waveguide 11, and the optical coupling end face of the first waveguide 11 is aligned with the opening 13.

In the present embodiment, the first waveguide 11 and the second waveguide 12 are provided in the same layer, and thus the complexity of the manufacturing process of the optical waveguide and the optical device can be reduced to a large extent. Meanwhile, by providing the opening 13 at the end of the second waveguide 12 facing the first waveguide 11, the diameter of the opening 13 gradually increases along the direction in which the second waveguide 12 points to the first waveguide 11, that is, a tapered slit is formed at the end of the second waveguide 12, and the bottom surface of the tapered slit is disposed facing the first waveguide 11, so that the end of the second waveguide 12 has an inverted cone-shaped structure. The optical coupling end face of the first waveguide 11 is aligned with the bottom face of the tapered opening 13, so that light can be mode-converted between the first waveguide 11 and the second waveguide 12 through the tapered opening 13, for example, when the light is transmitted from the first waveguide 11 to the second waveguide 12, the light is converted from a smaller optical mode to a larger optical mode. Meanwhile, the coupling of light is limited in the area of the conical opening 13, so that the light loss can be effectively reduced, and the light coupling efficiency is improved.

In the present embodiment, the width of the opening 13 can be selected by a person skilled in the art according to actual needs, for example, according to the wavelength band of the light to be converted. In this embodiment, the width of the end of the opening 13 connected to the first waveguide 11 (i.e., the bottom surface of the tapered opening 13) is preferably equal to the width of the first waveguide 11, for example, 400nm to 600nm, and more preferably 500 nm. The cross section of the opening 13 along the direction parallel to the substrate may be triangular or trapezoidal.

Preferably, the first waveguide 11 is a silicon waveguide, the second waveguide 12 is a silicon nitride waveguide, the opening 13 is filled with a silicon tapered structure, and a bottom surface of the silicon tapered structure is aligned with the optical coupling end surface of the first waveguide 11. The silicon conical structure comprises a bottom surface and a top surface which are oppositely arranged, the top surface is arranged towards the second waveguide 12, the bottom surface is arranged towards the first waveguide 11, and the width of the silicon conical structure is gradually increased along the direction of the top surface towards the bottom surface. Silicon nitride materials have the advantages of lower non-linearity, low loss, and allowing greater energy input, and thus have natural advantages in applications where greater energy input is required. However, the properties of silicon nitride materials determine that they are not suitable for the fabrication of active devices. The specific implementation mode realizes mode conversion between the silicon waveguide and the silicon nitride waveguide, can realize connection between a passive structure and an active structure in the application field requiring high energy input, realizes integration of various materials, and improves the application range of the silicon optical integration process.

Preferably, the optical wave mode conversion device according to the present embodiment further includes an SOI substrate, the first waveguide 11 and the silicon tapered structure are made of top silicon of the SOI substrate, and the second waveguide 12 is located on a surface of a buried oxide layer of the SOI substrate. Specifically, as shown in fig. 2, the optical mode conversion device includes a bottom layer silicon 20, a buried oxide layer 21, and a waveguide layer including the first waveguide 11, the silicon taper structure, and the second waveguide 12, which are sequentially stacked in the axial direction thereof.

In order to further improve the light coupling efficiency, it is preferable that the first waveguide 11 and the second waveguide 12 have the same thickness. The specific thicknesses of the first waveguide 11 and the second waveguide 12 may be selected by those skilled in the art according to actual needs, for example, according to the wavelength band of light to be converted, and in this embodiment, the specific thicknesses are preferably 100nm to 300nm, and more preferably 220 nm.

Preferably, the light wave mode conversion device provided in the present embodiment further includes an upper cladding layer 22 covering the surfaces of the first waveguide 11 and the second waveguide 12. More preferably, the material of the upper cladding layer 22 is silica. Specifically, the upper cladding layer covers the surfaces of the first waveguide 11 and the second waveguide 12, and the opening 13 is filled with a silicon tapered structure, so as to further reduce optical loss.

In order to solve the above problems, the present embodiment further provides a method for manufacturing a light wave mode conversion device, fig. 3 is a flowchart of a method for manufacturing a light wave mode conversion device according to an embodiment of the present invention, and fig. 1 and 2 show a structure of a light wave mode conversion device manufactured by the method for manufacturing a light wave mode conversion device according to the present embodiment. As shown in fig. 1 to 3, the method for manufacturing a light wave mode conversion device according to the present embodiment includes the following steps:

step S31, a substrate is provided. In this embodiment, the substrate may be a Silicon substrate, an SOI (Silicon On Insulator) substrate, a GOI (Germanium On Insulator) substrate, or the like.

Step S32, forming a first waveguide 11 on the surface of the substrate.

Preferably, the substrate is an SOI substrate; the specific steps of forming the first waveguide 11 on the surface of the substrate include:

etching the top silicon layer of the SOI substrate, simultaneously forming a first waveguide 11 and a silicon conical structure, and defining a second waveguide region; the bottom surface of the silicon cone structure is arranged in alignment with the optical coupling end-face of the first waveguide 11.

Specifically, the SOI substrate includes a bottom layer silicon 20, a buried oxide layer 21, and a top layer silicon, which are stacked in sequence, and the top layer silicon is etched to form the first waveguide 11 and a silicon tapered structure, which are connected to each other, and a second waveguide region for forming a second waveguide is defined in the top layer silicon by using a photolithography process. Wherein, the cross section of the first waveguide 11 along the direction parallel to the bottom layer silicon 20 can be a rectangular shape with a length of 500nm and a width of 220 nm.

Step S33, forming a second waveguide 12 on the surface of the substrate, where the refractive index of the second waveguide 12 is smaller than that of the first waveguide 11, and an end of the second waveguide 12 facing the first waveguide 11 has an opening 13, the width of the opening 13 gradually increases along a direction in which the second waveguide 12 points to the first waveguide 11, and the optical coupling end face of the first waveguide 11 is aligned with the opening 13.

Preferably, the second waveguide region has an opening 13, the width of the opening 13 gradually increases along the direction of the second waveguide region toward the first waveguide 11, and the silicon conical structure is located in the opening 13; the specific steps of forming the second waveguide 12 on the surface of the substrate include:

(S33-1) etching the top silicon of the second waveguide region to expose the buried oxide layer 21 of the SOI substrate.

(S33-2) depositing a second waveguide material on the surface of the buried oxide layer 21 in the second waveguide region to form the second waveguide layer 12. Wherein the second waveguide material is preferably silicon nitride. The specific method for depositing the second waveguide material on the surface of the buried oxide layer 21 in the second waveguide region is preferably LPCVD (Low Pressure Chemical vapor deposition). The second waveguide layer 12, the first waveguide layer 11 and the silicon taper structure are all equal in thickness, for example, 220 nm.

Preferably, the method for manufacturing a light wave mode conversion device according to the embodiment further includes the steps of: and depositing silicon dioxide on the surfaces of the first waveguide 11 and the second waveguide 12 to form an upper cladding layer 22. Among them, a specific method of depositing silicon dioxide is preferably a PECVD (Plasma Enhanced Chemical Vapor Deposition) process.

In the light wave mode conversion device and the manufacturing method thereof provided by the present embodiment, two waveguides having different refractive indexes are disposed on the same layer, and a tapered opening is disposed in the waveguide having a low refractive index, and the waveguide having a high refractive index and the waveguide having a low refractive index are subjected to light wave coupling through the tapered opening, so that conversion of a light wave mode is realized, which not only reduces the process complexity of an optical device, but also improves the coupling efficiency between the two waveguides, and realizes low-loss interconnection between the two waveguides.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.