Grating manufacturing method

Abstract

The invention relates to a grating manufacturing method which comprises the following steps: providing a wafer which comprises a substrate, a lower waveguide layer, a multi-layer quantum well layer, an upper waveguide layer, a grating layer and a coating layer; forming a sacrificial layer on one side of the coating layer, wherein the material of the sacrificial layer is a III-V group material; forming a self-assembled single-layer film with the surface roughness of 0.1 nm to 0.3 nm on one side of the sacrificial layer; a grating pattern with the line width smaller than 10 nm is formed on the self-assembled single-layer film; etching the sacrificial layer through a first wet etching process, and transferring the grating pattern to the sacrificial layer; heating to remove the self-assembled single-layer film; etching the coating layer through a second wet etching process, and transferring the grating pattern to the coating layer; and etching the grating layer and removing the sacrificial layer through a third wet etching process, and transferring the grating pattern to the grating layer. According to the grating manufacturing method provided by the invention, the uniformity and consistency of grating patterns can be ensured, so that the optical loss of the grating is reduced, and the optical performance of the grating is improved.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor manufacturing, and in particular to a grating manufacturing method. Background Art

[0002] High-speed optical chips usually need to integrate complex gratings of different sizes and functions on a single chip. The production precision of these complex gratings is very high, usually on the order of tens of nanometers. Holographic exposure technology can only produce uniform gratings with a period of more than 200 nanometers. Therefore, the industry usually uses electron beam lithography (EBL) technology to produce complex gratings.

[0003] Electron beam lithography is a high-precision pattern making technology that uses a focused electron beam (Ebeam) to draw patterns directly on a photoresist (also called an resist). Since the electron beam used has an extremely short wavelength, it can be used to make extreme graphics as low as 10nm in size. And because electron beam lithography uses a direct write exposure method, it does not require a mask, making it very suitable for making customized complex gratings.

[0004] At present, the common practice in the industry is to dilute ordinary photoresist and use it as photoresist for electron beam lithography. Since photoresist itself is a relatively viscous and complex compound, the uniformity and repeatability of the diluted glue cannot be guaranteed. Even if a relatively thin glue film can be formed by spin coating, its resolution is still low, and the line width of the grating cannot be accurately controlled (the line width refers to the width of the light-transmitting gap of the grating). At the same time, the adhesion and surface roughness cannot meet the requirements, which greatly limits the production of complex gratings and the improvement of the corresponding optical chip performance.

[0005] Therefore, a grating production method is needed to select a photolithography material with higher resolution and sensitivity, lower roughness, higher contrast and adhesion, to achieve good grating line width control, ensure the uniformity and consistency of the grating pattern, form a clear and complete grating pattern, and thus reduce the optical loss of the grating and improve the optical performance of the grating. Summary of the invention

[0006] Therefore, the present invention provides a grating production method to solve the problems in the prior art of low line width accuracy of the prepared grating, unclear and incomplete edges of the grating pattern, and high optical loss of the grating due to factors such as poor uniformity and repeatability of the photoresist, low resolution, poor adhesion, and high surface roughness.

[0007] The present invention provides a grating manufacturing method, comprising:

[0008] Providing a wafer on which a grating is to be formed, the wafer sequentially comprising a substrate, a lower waveguide layer, a multi-layer quantum well layer, an upper waveguide layer, a grating layer and a cladding layer;

[0009] A sacrificial layer is formed on a surface of the cladding layer facing away from the grating layer, wherein the material of the sacrificial layer is a III-V group material;

[0010] A self-assembled monolayer film is formed on the surface of the sacrificial layer facing away from the coating layer, and the surface roughness of the self-assembled monolayer film is 0.1nm to 0.3nm;

[0011] A grating pattern is formed on the self-assembled monolayer film to form a patterned self-assembled monolayer film, wherein the line width of the grating pattern is less than 10 nm;

[0012] Using the patterned self-assembled monolayer as a mask, etching the sacrificial layer through a first wet etching process to transfer the grating pattern to the sacrificial layer;

[0013] Heating to remove the patterned self-assembled monolayer;

[0014] etching the cladding layer by a second wet etching process to transfer the grating pattern to the cladding layer;

[0015] The grating layer is etched and the sacrificial layer is removed by a third wet etching process, and the grating pattern is transferred to the grating layer to form a grating.

[0016] Optionally, the step of forming a grating pattern on the self-assembled monolayer film includes:

[0017] The grating pattern is formed on the self-assembled monolayer film by electron beam direct writing process.

[0018] Optionally, in the first wet etching process, selective etching is performed using a first wet etching solution;

[0019] The first wet etching solution reacts with the material of the sacrificial layer but does not react with the material of the coating layer.

[0020] Optionally, in the second wet etching process, selective etching is performed using a second wet etching solution;

[0021] The second wet etching solution reacts with the material of the cladding layer, does not react with the material of the sacrificial layer, and does not react with the material of the grating layer.

[0022] Optionally, in the third wet etching process, selective etching is performed using a third wet etching solution;

[0023] The third wet etching solution reacts with the material of the grating layer and the material of the sacrificial layer, but does not react with the material of the cladding layer and does not react with the material of the upper waveguide layer.

[0024] Optionally, the etching selectivity ratio of the second wet etching solution to the sacrificial layer and the cladding layer is the same as the etching selectivity ratio of the second wet etching solution to the grating layer and the cladding layer;

[0025] The etching selectivity of the third wet etching solution to the sacrificial layer and the cladding layer, the etching selectivity of the third wet etching solution to the grating layer and the cladding layer, and the etching selectivity of the third wet etching solution to the sacrificial layer and the upper waveguide layer are the same as the etching selectivity of the third wet etching solution to the grating layer and the upper waveguide layer;

[0026] The thickness of the sacrificial layer is smaller than the thickness of the grating layer.

[0027] Optionally, the material of the substrate, the material of the cladding layer, and the material of the grating layer are III-V compound materials;

[0028] The material of the grating layer is the same as that of the sacrificial layer;

[0029] The material of the upper waveguide layer is the same as that of the cladding layer;

[0030] The material of the cladding layer is different from that of the grating layer;

[0031] The material of the self-assembled monolayer is an organic compound containing a thiol group.

[0032] Optionally, the material of the substrate is GaAs, InP, InAs, InGaAs or GaN;

[0033] The material of the sacrificial layer and the material of the grating layer are InGaAsP, InAlGaAs, AlGaAs, InGaAs or GaAsP;

[0034] The material of the cladding layer and the material of the upper waveguide layer are InP, GaAs or InGaP;

[0035] The material of the self-assembled monolayer film is mercapto organic alcohol or 3-mercaptopropyltrimethoxysilane.

[0036] Optionally, the material of the substrate and the material of the lower waveguide layer are n-type doped InP;

[0037] The material of the multi-layer quantum well layer is InGaAsP;

[0038] The material of the upper waveguide layer and the material of the cladding layer are p-type doped InP;

[0039] The material of the grating layer and the material of the sacrificial layer are InGaAsP;

[0040] The ratio of the first wet etching solution is H2SO4:H2O2:H2O=1:1:10-1:1:25;

[0041] The ratio of the second wet etching solution is HCl:H3PO4=1:3-1:5;

[0042] The ratio of the third wet etching solution is H2SO4:H2O2:H2O=1:1:10-1:1:25;

[0043] The material of the self-assembled monolayer is mercapto organic alcohol.

[0044] Optionally, the thickness of the multi-layer quantum well layer is 100nm to 500nm;

[0045] The thickness of the grating layer is 25nm to 100nm;

[0046] The thickness of the sacrificial layer is 15nm to 80nm;

[0047] The thickness of the coating layer is 20nm to 100nm;

[0048] The thickness of the self-assembled monolayer is 2nm to 3nm.

[0049] Optionally, the step of removing the patterned self-assembled monolayer by heating includes:

[0050] In a mixed gas atmosphere of hydrogen and argon, heating the wafer to a first temperature and for a first time to remove the patterned self-assembled monolayer film; the first temperature is a decomposition temperature of the self-assembled monolayer film;

[0051] The first temperature is 150° C. to 300° C., and the first time period is 10 minutes to 20 minutes.

[0052] Optionally, the step of forming a self-assembled monolayer on the surface of the sacrificial layer facing away from the coating layer includes:

[0053] preparing a self-assembling organic solution;

[0054] The wafer is placed in a self-assembling organic solution, and the self-assembling organic solution forms a self-assembling monolayer film on the surface of the sacrificial layer facing away from the coating layer.

[0055] Optionally, the material of the self-assembled monolayer is mercapto organic alcohol; the self-assembled organic solution is mercapto organic alcohol solution;

[0056] The steps of preparing a self-assembling organic solution include:

[0057] Evenly mixing anhydrous ethanol and mercapto organic alcohol to obtain a first solution;

[0058] Adding a second ammonia solution with a concentration of 30% into the first solution to obtain a mercapto organic alcohol solution, wherein the volume ratio of the second ammonia solution to the first solution in the mercapto organic alcohol solution is 2% to 10%;

[0059] Degassing is performed to remove oxygen from the mercapto organic alcohol solution.

[0060] The technical solution of the present invention has the following advantages:

[0061] (1) The grating manufacturing method provided by the present invention uses a self-assembled monolayer film as a photolithography material for etching a grating sacrificial layer. First, since the material of the sacrificial layer is a III-V material, the self-assembled monolayer film and the sacrificial layer are connected by chemical coordination bonds, so that the self-assembled monolayer film has good adhesion and stability, and is firmly bonded to the sacrificial layer and is not easy to fall off. When the sacrificial layer is etched by the first wet etching process, the grating pattern can be completely transferred to the sacrificial layer; secondly, since the thickness of the self-assembled monolayer film is only a few nanometers, the line width of the formed grating pattern is less than 10nm, so the self-assembled monolayer film has extremely high resolution and can achieve good grating line width control, which is very suitable for manufacturing complex gratings with a period of tens of nanometers; finally, the surface roughness of the self-assembled monolayer film is 0.1nm~0.3nm, the surface is relatively smooth, which can ensure the uniformity and consistency of the grating pattern and reduce the optical loss of the grating device. Therefore, the grating manufacturing method provided by the present invention uses a self-assembled monolayer film as the photolithography material for etching the grating sacrificial layer, which can form a clear and complete grating pattern on the sacrificial layer, achieve good grating line width control, and at the same time ensure the uniformity and consistency of the grating pattern, thereby reducing the optical loss of the grating and improving the optical performance of the grating.

[0062] (2) The grating manufacturing method provided by the present invention forms a grating pattern on a self-assembled monolayer film through an electron beam direct writing process. On the one hand, since the self-assembled monolayer film has a high sensitivity and responds quickly to electron beam irradiation, it can complete exposure in a very short time, which can improve the manufacturing efficiency of the grating and is conducive to large-scale mass production; on the other hand, the byproducts generated by the self-assembled monolayer film during the electron beam irradiation process can be directly taken away by the vacuum pump, and no subsequent development process is required, which greatly simplifies the grating manufacturing process. Therefore, the grating manufacturing method provided by the present invention can simplify the grating manufacturing process and improve the grating manufacturing efficiency.

[0063] (3) In the grating manufacturing method provided by the present invention, the first wet etching process is selective etching, and the etching selectivity ratio of the first wet etching solution to the sacrificial layer and the self-assembled monolayer film is at least 10:1, which can ensure that the first wet etching solution reacts with the material of the sacrificial layer but does not react with the material of the coating layer, thereby achieving selective etching of the sacrificial layer, and can achieve precise pattern replication and structural control, thereby clearly and completely transferring the grating pattern to the sacrificial layer.

[0064] (4) In the grating manufacturing method provided by the present invention, the second wet etching process is selective etching, and the etching selectivity ratio of the second wet etching solution to the sacrificial layer and the cladding layer is the same as the etching selectivity ratio of the second wet etching solution to the grating layer and the cladding layer and is greater than or equal to 10:1. This can ensure that the second wet etching solution reacts with the material of the cladding layer, does not react with the material of the sacrificial layer, and does not react with the material of the grating layer, thereby achieving selective etching of the cladding layer, and can achieve precise pattern replication and structural control, thereby clearly and completely transferring the grating pattern to the cladding layer.

[0065] (5) In the grating manufacturing method provided by the present invention, the third wet etching process is selective etching, and the etching selectivity ratio of the third wet etching solution to the sacrificial layer and the cladding layer, the etching selectivity ratio of the third wet etching solution to the grating layer and the cladding layer, and the etching selectivity ratio of the third wet etching solution to the sacrificial layer and the upper waveguide layer are the same as the etching selectivity ratio of the third wet etching solution to the grating layer and the upper waveguide layer and are all greater than or equal to 10:1, which can ensure that the third wet etching solution reacts with the material of the grating layer and the material of the sacrificial layer, does not react with the material of the cladding layer and does not react with the material of the upper waveguide layer, and selective etching of the grating layer is achieved, which can achieve accurate pattern replication and structural control, so as to transfer the grating pattern clearly and completely to the grating layer. At the same time, since the thickness of the sacrificial layer is less than the thickness of the grating layer, the sacrificial layer can be completely removed during the etching of the grating layer.

[0066] (6) In the grating production method provided by the present invention, when heating to remove the graphic self-assembled monolayer film, a mixed gas of hydrogen and argon is introduced, which can easily remove the by-products of the decomposition process of the self-assembled monolayer film, so that the self-assembled monolayer film is completely removed without any residue on the semiconductor surface, and will not cause any impact on the sacrificial layer and the coating layer. In addition, the products after the decomposition of the self-assembled monolayer film will not cause any pollution to the wafer and the equipment.

[0067] (7) The grating manufacturing method provided by the present invention does not require special equipment for the growth of the self-organized monolayer film, and only a simple wet process machine is required. The growth process of the self-organized monolayer film only requires placing the wafer into the self-assembled organic solution, and the self-assembled organic solution forms a self-assembled monolayer film on the surface of the sacrificial layer facing away from the coating layer. This manufacturing method is simple and efficient, and has extremely high stability and repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0069] Figure 1 A schematic flow chart of a grating manufacturing method according to an embodiment of the present invention;

[0070] Figure 2 to Figure 7 It is a structural schematic diagram of each process of a grating manufacturing method according to an embodiment of the present invention;

[0071] Figure 8 The figure is a schematic diagram of a specific process of a grating manufacturing method according to an embodiment of the present invention.

[0072] Description of reference numerals:

[0073] 1-substrate; 2-lower waveguide layer; 3-multi-layer quantum well layer; 4-upper waveguide layer; 5-grating layer; 6-cladding layer; 7-sacrificial layer; 8-self-assembled monolayer film; 100-electron beam. DETAILED DESCRIPTION

[0074] The ideal photoresist in electron beam lithography technology should have the following characteristics: 1) high resolution, capable of achieving pattern feature sizes as small as a few nanometers; 2) high sensitivity, with a quick response to electron beam irradiation to reduce exposure time and increase yield; 3) good line width control to ensure pattern uniformity and consistency; 4) low roughness and smooth surface to reduce optical loss of the grating; 5) high contrast to provide clear pattern edges during development; 6) good adhesion, firmly bonded to the substrate material to prevent the pattern from falling off during subsequent processing; 7) good chemical stability: remain stable during development and etching.

[0075] Self-assembled monolayers (SAMs) are thermodynamically stable, highly oriented, tightly packed single-layer ordered molecular films formed by spontaneous adsorption of organic functional molecules on the liquid-solid or gas-solid interface through chemical bonds. They are usually only a few nanometers thick and are therefore particularly suitable for making ultra-fine structures, such as complex grating structures with a period of tens of nanometers.

[0076] In order to solve the problems in the prior art that the grating line width precision is low, the edge of the grating pattern is unclear and incomplete, and the grating optical loss is high due to factors such as poor uniformity and repeatability of the photoresist, low resolution, poor adhesion, and high surface roughness, the present invention provides a grating manufacturing method, comprising: providing a wafer to be formed with a grating, the wafer sequentially comprising a substrate, a lower waveguide layer, a multi-layer quantum well layer, an upper waveguide layer, a grating layer, and a cladding layer; forming a sacrificial layer on a surface of the cladding layer facing away from the grating layer, the material of the sacrificial layer being a III-V group material; forming a self-assembly layer on a surface of the sacrificial layer facing away from the cladding layer The invention discloses a monolayer film, wherein the surface roughness of the self-assembled monolayer film is 0.1nm to 0.3nm; a grating pattern is formed on the self-assembled monolayer film to form a patterned self-assembled monolayer film, wherein the line width of the grating pattern is less than 10nm; the patterned self-assembled monolayer film is used as a mask, and a sacrificial layer is etched through a first wet etching process to transfer the grating pattern to the sacrificial layer; the patterned self-assembled monolayer film is removed by heating; the coating layer is etched through a second wet etching process to transfer the grating pattern to the coating layer; the grating layer is etched through a third wet etching process to remove the sacrificial layer, and the grating pattern is transferred to the grating layer to form a grating.

[0077] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In the description of the present invention, it should be noted that the terms "first", "second" and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0078] Example 1

[0079] like Figure 1 to Figure 7 As shown, this embodiment provides a grating manufacturing method, including S101-S108.

[0080] S101 , providing a wafer on which a grating is to be formed, wherein the wafer sequentially comprises a substrate 1 , a lower waveguide layer 2 , a multi-layer quantum well layer 3 , an upper waveguide layer 4 , a grating layer 5 and a cladding layer 6 .

[0081] S102 , forming a sacrificial layer 7 on a surface of the cladding layer 6 facing away from the grating layer 5 , wherein the material of the sacrificial layer 7 is a III-V group material.

[0082] S103, forming a self-assembled monolayer film 8 on the surface of the sacrificial layer 7 facing away from the coating layer 6, the surface roughness of the self-assembled monolayer film 8 is 0.1nm-0.3nm, such as Figure 2 shown.

[0083] S104, forming a grating pattern on the self-assembled monolayer film 8 to form a patterned self-assembled monolayer film 8, wherein the line width of the grating pattern is less than 10 nm, such as Figure 3 shown.

[0084] S105, using the patterned self-assembled monolayer film 8 as a mask, etching the sacrificial layer 7 through a first wet etching process, and transferring the grating pattern to the sacrificial layer 7, such as Figure 4 shown.

[0085] S106, removing the patterned self-assembled monolayer film 8 by heating, such as Figure 5 shown.

[0086] S107, etching the cladding layer 6 by a second wet etching process to transfer the grating pattern to the cladding layer 6, such as Figure 6 shown.

[0087] S108, etching the grating layer 5 and removing the sacrificial layer 7 through a third wet etching process, transferring the grating pattern to the grating layer 5, and forming a grating, such as Figure 7 shown.

[0088] The grating manufacturing method provided in this embodiment uses a self-assembled monolayer film as a photolithography material for etching a grating sacrificial layer. First, since the material of the sacrificial layer is a III-V material, the self-assembled monolayer film and the sacrificial layer are connected by chemical coordination bonds, so that the self-assembled monolayer film has good adhesion and stability, and is firmly bonded to the sacrificial layer and is not easy to fall off. When the sacrificial layer is etched by the first wet etching process, the grating pattern can be completely transferred to the sacrificial layer; secondly, since the thickness of the self-assembled monolayer film is only a few nanometers, the line width of the formed grating pattern is less than 10nm, so the self-assembled monolayer film has extremely high resolution and can achieve good grating line width control, which is very suitable for manufacturing complex gratings with a period of tens of nanometers; finally, the surface roughness of the self-assembled monolayer film is 0.1nm~0.3nm, the surface is relatively smooth, which can ensure the uniformity and consistency of the grating pattern and reduce the optical loss of the grating device. Therefore, the grating manufacturing method provided by the present invention uses a self-assembled monolayer film as the photolithography material for etching the grating sacrificial layer, which can form a clear and complete grating pattern on the sacrificial layer, achieve good grating line width control, and at the same time ensure the uniformity and consistency of the grating pattern, thereby reducing the optical loss of the grating and improving the optical performance of the grating.

[0089] Further, in some embodiments, the step of forming a grating pattern on the self-assembled monolayer film includes:

[0090] The grating pattern is formed on the self-assembled monolayer film by electron beam direct writing process.

[0091] When implementing it, Figure 3As shown, the CC bonds in the self-assembled monolayer can be destroyed by the electron beam 100 to form a grating pattern. The byproducts of the destroyed self-assembled monolayer can be easily taken away by the vacuum pump without causing pollution to the equipment and the wafer.

[0092] The grating manufacturing method provided in this embodiment forms a grating pattern on a self-assembled monolayer film through an electron beam direct writing process. On the one hand, since the self-assembled monolayer film has a high sensitivity and responds quickly to electron beam irradiation, it can complete exposure in a very short time, which can improve the manufacturing efficiency of the grating and is conducive to large-scale mass production; on the other hand, the byproducts generated by the self-assembled monolayer film during the electron beam irradiation process can be directly taken away by the vacuum pump, and no subsequent development process is required, which greatly simplifies the grating manufacturing process. Therefore, the grating manufacturing method provided by the present invention can simplify the grating manufacturing process and improve the grating manufacturing efficiency.

[0093] Further, in some embodiments, in the first wet etching process, a first wet etching solution is used for selective etching;

[0094] The first wet etching solution reacts with the material of the sacrificial layer but does not react with the material of the coating layer.

[0095] In a specific implementation, the etching selectivity ratio of the first wet etching solution to the sacrificial layer and the self-assembled monolayer film is at least 10:1, such as 10:1, 20:1, 50:1 or 100:1. The etching selectivity ratio is selected as large as possible, and this embodiment does not limit this, so as to ensure that the first wet etching solution reacts with the material of the sacrificial layer but does not react with the material of the coating layer.

[0096] The grating manufacturing method provided by the present invention comprises a first wet etching process which is selective etching, and an etching selectivity ratio of the first wet etching solution to the sacrificial layer and the self-assembled monolayer film is at least 10:1, which can ensure that the first wet etching solution reacts with the material of the sacrificial layer but does not react with the material of the coating layer, thereby achieving selective etching of the sacrificial layer, and realizing precise pattern replication and structural control, thereby clearly and completely transferring the grating pattern to the sacrificial layer.

[0097] Further, in some embodiments, in the second wet etching process, a second wet etching solution is used for selective etching;

[0098] The second wet etching solution reacts with the material of the cladding layer, does not react with the material of the sacrificial layer, and does not react with the material of the grating layer.

[0099] In a specific implementation, the etching selectivity of the second wet etching solution to the sacrificial layer and the cladding layer is at least 10:1, such as 10:1, 20:1, 50:1 or 100:1; the etching selectivity of the second wet etching solution to the grating layer and the cladding layer is at least 10:1, such as 10:1, 20:1, 50:1 or 100:1. The etching selectivity is selected as large as possible, and this embodiment does not limit this, so as to ensure that the second wet etching solution reacts with the material of the cladding layer, does not react with the material of the sacrificial layer, and does not react with the material of the grating layer, so as to achieve selective etching of the cladding layer.

[0100] Further, in some embodiments, in the third wet etching process, a third wet etching solution is used for selective etching;

[0101] The third wet etching solution reacts with the material of the grating layer and the material of the sacrificial layer, but does not react with the material of the cladding layer and does not react with the material of the upper waveguide layer.

[0102] In a specific implementation, the etching selectivity of the third wet etching solution to the sacrificial layer and the cladding layer is at least 10:1, for example, 10:1, 20:1, 50:1 or 100:1; the etching selectivity of the third wet etching solution to the grating layer and the cladding layer is at least 10:1, for example, 10:1, 20:1, 50:1 or 100:1; the etching selectivity of the third wet etching solution to the sacrificial layer and the upper waveguide layer is at least 10:1, for example, 10:1, 20:1, 50:1 or 100:1; the etching selectivity of the third wet etching solution to the grating layer and the upper waveguide layer is at least 10:1, for example, 10:1, 20:1, 50:1 or 100:1. The etching selectivity is as large as possible, and this embodiment does not limit this, so as to ensure that the third wet etching solution reacts with the material of the grating layer and the material of the sacrificial layer, does not react with the material of the cladding layer and does not react with the material of the upper waveguide layer, thereby achieving selective etching of the grating layer.

[0103] Further, in some embodiments, the etching selectivity of the second wet etching solution to the sacrificial layer and the cladding layer is the same as the etching selectivity of the second wet etching solution to the grating layer and the cladding layer;

[0104] The etching selectivity of the third wet etching solution to the sacrificial layer and the cladding layer, the etching selectivity of the third wet etching solution to the grating layer and the cladding layer, and the etching selectivity of the third wet etching solution to the sacrificial layer and the upper waveguide layer are the same as the etching selectivity of the third wet etching solution to the grating layer and the upper waveguide layer;

[0105] The thickness of the sacrificial layer is smaller than the thickness of the grating layer.

[0106] In the grating manufacturing method provided in this embodiment, the second wet etching process is selective etching, and the etching selectivity ratio of the second wet etching solution to the sacrificial layer and the cladding layer is the same as the etching selectivity ratio of the second wet etching solution to the grating layer and the cladding layer, and both are greater than or equal to 10:1, which can ensure that the second wet etching solution reacts with the material of the cladding layer, does not react with the material of the sacrificial layer, and does not react with the material of the grating layer, thereby achieving selective etching of the cladding layer, and can achieve precise pattern replication and structural control, so as to clearly and completely transfer the grating pattern to the cladding layer.

[0107] In the grating manufacturing method provided in this embodiment, the third wet etching process is selective etching, and the etching selectivity ratio of the third wet etching solution to the sacrificial layer and the cladding layer, the etching selectivity ratio of the third wet etching solution to the grating layer and the cladding layer, and the etching selectivity ratio of the third wet etching solution to the sacrificial layer and the upper waveguide layer are the same as the etching selectivity ratio of the third wet etching solution to the grating layer and the upper waveguide layer and are all greater than or equal to 10:1, which can ensure that the third wet etching solution reacts with the material of the grating layer and the material of the sacrificial layer, does not react with the material of the cladding layer and does not react with the material of the upper waveguide layer, and selective etching of the grating layer is achieved, which can achieve accurate pattern replication and structural control, so as to transfer the grating pattern clearly and completely to the grating layer. At the same time, since the thickness of the sacrificial layer is less than the thickness of the grating layer, the sacrificial layer can be completely removed during the etching of the grating layer.

[0108] Further, in some embodiments, the material of the substrate, the material of the cladding layer, and the material of the grating layer are III-V compound materials;

[0109] The material of the grating layer is the same as that of the sacrificial layer;

[0110] The material of the upper waveguide layer is the same as that of the cladding layer;

[0111] The material of the cladding layer is different from that of the grating layer;

[0112] The material of the self-assembled monolayer is an organic compound containing a thiol group.

[0113] In a specific implementation, the III-V compound atoms (such as Ga or In) in the sacrificial layer of the present invention can form coordination bonds with the sulfur atoms in the organic compound containing a mercapto group to generate a stable surface complex.

[0114] Further, in some embodiments, the material of the substrate is GaAs, InP, InAs, InGaAs or GaN;

[0115] The material of the sacrificial layer and the material of the grating layer are InGaAsP, InAlGaAs, AlGaAs, InGaAs or GaAsP;

[0116] The material of the cladding layer and the material of the upper waveguide layer are InP, GaAs or InGaP;

[0117] The material of the self-assembled monolayer film is mercapto organic alcohol or 3-mercaptopropyltrimethoxysilane.

[0118] Further, in some embodiments, the material of the substrate and the material of the lower waveguide layer are n-type doped InP;

[0119] The material of the multi-layer quantum well layer is InGaAsP;

[0120] The material of the upper waveguide layer and the material of the cladding layer are p-type doped InP;

[0121] The material of the grating layer and the material of the sacrificial layer are InGaAsP;

[0122] The ratio of the first wet etching solution is H2SO4:H2O2:H2O=1:1:10 to 1:1:25, for example, 1:1:10, 1:1:15, 1:1:18 or 1:1:25;

[0123] The ratio of the second wet etching solution is HCl:H3PO4=1:3-1:5, for example, 1:3, 1:4 or 1:5;

[0124] The ratio of the third wet etching solution is H2SO4:H2O2:H2O=1:1:10 to 1:1:25, for example, 1:1:10, 1:1:15, 1:1:18 or 1:1:25;

[0125] The material of the self-assembled monolayer is mercapto organic alcohol.

[0126] Further, in some embodiments, the thickness of the multi-layer quantum well layer is 100 nm to 500 nm;

[0127] The thickness of the grating layer is 25 nm to 100 nm, for example, 25 nm, 50 nm, 70 nm, 90 nm or 100 nm;

[0128] The thickness of the sacrificial layer is 15 nm to 80 nm, for example, 15 nm, 30 nm, 50 nm, 60 nm or 80 nm;

[0129] The coating layer has a thickness of 20 nm to 100 nm, for example, 20 nm, 50 nm, 70 nm, 90 nm or 100 nm;

[0130] The thickness of the self-assembled monolayer is 2 nm to 3 nm, for example, 2 nm, 2.3 nm, 2.5 nm, 2.8 nm or 3 nm.

[0131] Further, in some embodiments, the step of removing the patterned self-assembled monolayer by heating includes:

[0132] A mixed gas of hydrogen and argon is introduced to heat the wafer to a first temperature for a first time to remove the patterned self-assembled monolayer film; the first temperature is the decomposition temperature of the self-assembled monolayer film;

[0133] The first temperature is 150° C. to 300° C., and the first time period is 10 minutes to 20 minutes.

[0134] During specific implementation, the first temperature is the decomposition temperature of the self-assembled monolayer. Since the self-assembled monolayer is very thin, only 2-3 nm, the decomposition products are easily carried away by the gas and will not cause any pollution to the wafer and equipment. When the temperature of the self-assembled monolayer is greater than the first temperature (150°C to 300°C), the self-assembled monolayer will begin to decompose, and after the first period of time, the self-assembled monolayer will be completely decomposed. At the same time, a mixed gas of hydrogen and argon is used to take away the by-products in the decomposition process of the self-assembled monolayer, so that the self-assembled monolayer is completely removed, and it will not cause any impact on the sacrificial layer and the coating layer, and the products after the decomposition of the self-assembled monolayer will not cause any pollution to the wafer and equipment.

[0135] Furthermore, in some embodiments, the step of forming a self-assembled monolayer on the surface of the sacrificial layer facing away from the coating layer includes:

[0136] preparing a self-assembling organic solution;

[0137] The wafer is placed in a self-assembling organic solution, and the self-assembling organic solution forms a self-assembling monolayer film on the surface of the sacrificial layer facing away from the coating layer.

[0138] In practice, the growth of the self-organized monolayer does not require any special equipment, but only a simple wet process machine. This production method is simple and efficient, and has extremely high stability and repeatability.

[0139] Furthermore, in some embodiments, before the step of placing the wafer into the self-assembling organic solution, the step further includes:

[0140] Cleaning the wafer, and temporarily storing the cleaned wafer in a first ammonia solution (NH4OH solution);

[0141] The volume ratio of the 30% ammonia solution and H2O in the first ammonia solution is: 30% ammonia solution: H2O = 1:9 to 1:25;

[0142] The temporary storage time is less than 10 minutes.

[0143] In the specific implementation, the wafer is first cleaned, and then the cleaned wafer is placed in the first ammonia solution for temporary storage without drying, ensuring that the surface of the sacrificial layer does not directly contact the air. Among them, the volume ratio of the first ammonia solution is: 30% ammonia solution: H2O = 1:9 ~ 1:25; the NH4OH solution in this concentration range can effectively inhibit oxidation, and at the same time has almost no etching or impact on the wafer. In addition, the temporary storage time is less than 10 minutes, which will not affect the production capacity, and can also provide sufficient time to prepare the self-assembled organic solution. Therefore, it can be ensured that the sacrificial layer is always not exposed to the air from the etching to the formation of the self-assembled monolayer film, effectively inhibiting the occurrence of oxidation, and at the same time, it will not have any impact on the wafer, nor will it affect the production capacity.

[0144] Further, in some embodiments, the step of placing the wafer into the self-assembling organic solution includes:

[0145] In a nitrogen atmosphere, the wafer was taken out from the first ammonia aqueous solution and placed in the self-assembling organic solution in less than 10 seconds.

[0146] In the specific implementation, a small amount of NH4OH solution residue will drip into the mercapto organic alcohol solution during this process. As long as the overall NH4OH ratio is controlled within 10%, it will not affect the film formation. The growth process can be carried out in a glove box with N2 to prevent the dissolution of oxygen, which can ensure that the self-assembled monolayer film on the surface of the sacrificial layer is not exposed to air during the formation process, which can effectively inhibit the occurrence of oxidation and have no effect on the wafer.

[0147] Furthermore, in some embodiments, after the step of forming a self-assembled monolayer on the surface of the sacrificial layer facing away from the coating layer, the method further comprises:

[0148] The wafer is removed from the nitrogen atmosphere and dried.

[0149] In specific implementation, after the self-assembled monolayer film is grown, the wafer is removed from the nitrogen atmosphere and dried. The drying method may be to put it into a spin dryer or blow it dry with nitrogen. Other drying methods may be selected as needed, which is not limited in this embodiment.

[0150] Further, in some embodiments, the material of the self-assembled monolayer is mercapto organic alcohol; the self-assembled organic solution is mercapto organic alcohol solution;

[0151] The steps of preparing a self-assembling organic solution include:

[0152] Evenly mixing anhydrous ethanol and mercapto organic alcohol to obtain a first solution;

[0153] Adding a second ammonia solution with a concentration of 30% to the first solution to obtain a mercapto organic alcohol solution, wherein the volume ratio of the second ammonia solution to the first solution in the mercapto organic alcohol solution is 2% to 10%, for example, 2%, 4%, 7% or 10%;

[0154] Degassing is performed to remove oxygen from the mercapto organic alcohol solution.

[0155] In specific implementation, when preparing the first solution, different thiol organic alcohols have different solubility in anhydrous ethanol. For example, each 100 mL of anhydrous ethanol can only dissolve 500 mg of thiol organic alcohol at most. When preparing the thiol organic alcohol solution, the volume ratio of the second ammonia solution to the first solution is the second ammonia solution: the first solution = 2% to 10%. The volume ratio of the second ammonia solution to the first solution is controlled at 2% to 10%, which is conducive to forming a self-assembled monolayer film with full coverage and good quality.

[0156] In one example, 100 mg to 400 mg of mercapto organic alcohol is added to every 100 mL of anhydrous ethanol to obtain a first solution; a second ammonia solution having a concentration of 30% is added to the first solution at a volume ratio of 2% to 10%, and the mixture is mixed evenly to obtain a final mercapto organic alcohol solution.

[0157] In this embodiment, the obtained mercapto organic alcohol solution is subjected to degassing treatment in order to remove oxygen dissolved in the mercapto organic alcohol solution. In specific implementation, the solution can be placed in a sealed container for vacuuming by reducing pressure, or ultrasonic degassing can be performed using an ultrasonic cleaner.

[0158] In one example, a container containing the mercapto organic alcohol solution is placed in an ultrasonic cleaning machine and operated without load for 20 minutes to complete the degassing process.

[0159] Furthermore, in some embodiments, after the step of performing a degassing treatment to remove oxygen from the mercapto organic alcohol solution, the method further includes: heating the degassed mercapto organic alcohol solution to a second temperature and maintaining the temperature at a constant temperature to prepare for the subsequent growth of a self-assembled monolayer film.

[0160] The second temperature is 30° C. to 50° C. The degassed mercapto organic alcohol solution is kept at a constant temperature of 30° C. to 50° C., so that in the subsequent process of forming a self-assembled monolayer on the surface of the sacrificial layer facing away from the coating layer, the temperature of the mercapto organic alcohol solution is maintained at 30° C. to 50° C., which can prepare for the subsequent growth of the self-assembled monolayer, so that when the wafer is directly placed in the mercapto organic alcohol solution, the self-assembled monolayer starts to grow immediately without the need for reheating, shortening the growth time of the self-assembled monolayer, and ensuring that a self-assembled monolayer with full coverage and good quality can be generated in the shortest time.

[0161] Furthermore, in some embodiments, during the process of forming the self-assembled monolayer on the surface of the sacrificial layer facing away from the coating layer, the temperature of the self-assembled organic solution is 30° C. to 50° C., and the formation time of the self-assembled monolayer is 30 mins to 50 mins.

[0162] In the specific implementation, during the process of forming a self-assembled monolayer on the surface of the sacrificial layer facing away from the coating layer, the temperature of the self-assembled organic solution is 30°C to 50°C, and the formation time of the self-assembled monolayer is 30 minutes to 50 minutes, which can ensure that a self-assembled monolayer that completely covers the entire sacrificial layer can be generated on the surface of the sacrificial layer in the shortest time. If the growth time is too short, it is not enough to form a completely covered self-assembled monolayer, and the passivation effect is not good; if the growth time is too long, the polymer chains of the formed self-assembled monolayer will have lateral connections, increasing the difficulty of the subsequent in-situ removal process.

[0163] Example 2

[0164] refer to Figure 8 This embodiment provides a specific process of a grating manufacturing method, including steps S201-S215.

[0165] S201, providing a wafer on which a grating is to be formed, the wafer sequentially comprising a substrate, a lower waveguide layer, a multi-layer quantum well layer, an upper waveguide layer, a grating layer and a cladding layer; the material of the substrate and the material of the lower waveguide layer are n-type doped InP; the material of the multi-layer quantum well layer is InGaAsP; the material of the upper waveguide layer and the material of the cladding layer are p-type doped InP; the material of the grating layer is InGaAsP.

[0166] S202, forming a sacrificial layer on a surface of the cladding layer facing away from the grating layer by MOCVD (metal organic chemical vapor deposition) epitaxial technology, wherein the material of the sacrificial layer is InGaAsP.

[0167] S203, adding 100 mg to 400 mg of mercapto organic alcohol to every 100 mL of anhydrous ethanol to obtain a first solution.

[0168] S204, adding a second ammonia solution with a concentration of 30% into the first solution at a volume ratio of 2% to 10%, and mixing them evenly to obtain a final mercapto organic alcohol solution.

[0169] S205, placing the container containing the mercapto organic alcohol solution into an ultrasonic cleaning machine and running it at no load for 20 minutes to complete degassing treatment and remove oxygen in the mercapto organic alcohol solution.

[0170] S206, heating the degassed mercapto organic alcohol solution to 30° C. to 50° C. and maintaining the solution at a constant temperature.

[0171] S207, cleaning the wafer to remove oxide on the surface of the sacrificial layer.

[0172] S208, temporarily storing the cleaned wafer in a first ammonia solution; wherein the volume ratio of the first ammonia solution is: 30% ammonia solution: H2O=1:20; the temporary storage time is less than 10 minutes.

[0173] S209, in a nitrogen atmosphere, taking the wafer out of the first ammonia solution, and placing it in a mercapto organic alcohol solution within less than 10 seconds to form a self-assembled monolayer film on the surface of the sacrificial layer facing away from the coating layer; wherein the temperature of the mercapto organic alcohol solution is 30°C to 50°C, and the formation time of the self-assembled monolayer film is 30 minutes to 50 minutes.

[0174] S210, the wafer having the self-assembled monolayer film formed thereon is removed from the nitrogen atmosphere and subjected to a drying process.

[0175] S211, placing the wafer into an Ebeam vacuum chamber for Ebeam direct writing, forming a grating pattern on the self-assembled monolayer film, and forming a patterned self-assembled monolayer film, wherein the line width of the grating pattern is less than 10 nm.

[0176] S212, using the patterned self-assembled monolayer film as a mask, etching the sacrificial layer through a first wet etching process, and transferring the grating pattern to the sacrificial layer; the ratio of the first wet etching solution is H2SO4:H2O2:H2O=1:1:10~1:1:25.

[0177] The first wet etching solution only etches the InGaAsP of the sacrificial layer, but does not etch the InP of the cladding layer. Since the self-assembled monolayer film has good chemical stability, it can be used as a mask to transfer the grating pattern to the sacrificial layer.

[0178] S213 , in a mixed gas atmosphere of hydrogen and argon, heating the wafer to 150° C. to 300° C. for 10 minutes to 20 minutes to remove the patterned self-assembled monolayer film.

[0179] S214, etching the cladding layer through a second wet etching process to transfer the grating pattern to the cladding layer; the ratio of the second wet etching solution is HCl:H3PO4=1:3~1:5.

[0180] The second wet etching solution only etches the InP of the cladding layer, but does not etch the InGaAsP of the sacrificial layer or the grating layer. Here, the sacrificial layer is used as a mask to transfer the grating pattern to the cladding layer.

[0181] S215, etching the grating layer and removing the sacrificial layer through a third wet etching process, transferring the grating pattern to the grating layer to form a grating; the ratio of the third wet etching solution is H2SO4:H2O2:H2O=1:1:10~1:1:25.

[0182] The third wet etching solution only etches the InGaAsP of the grating layer, but not the InP of the cladding layer or the upper waveguide layer. Here, the cladding layer is used as a mask and the upper waveguide layer is used as an etching stop layer, and the grating pattern is successfully transferred to the grating layer.

[0183] Furthermore, in some embodiments, after step S215, a new InP device coating layer can be covered on the surface by MOCVD epitaxial regrowth, and the thickness of the device coating layer is 5 to 10 times the thickness of the coating layer, and the production of the entire optical device is completed.

[0184] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A grating manufacturing method, characterized in that: include: Providing a wafer on which a grating is to be formed, the wafer sequentially comprising a substrate, a lower waveguide layer, a multi-layer quantum well layer, an upper waveguide layer, a grating layer and a cladding layer; Forming a sacrificial layer on a surface of the cladding layer facing away from the grating layer, wherein the material of the sacrificial layer is a III-V group material; Forming a self-assembled monolayer film on the surface of the sacrificial layer facing away from the coating layer, wherein the surface roughness of the self-assembled monolayer film is 0.1 nm to 0.3 nm; Forming a grating pattern on the self-assembled monolayer film to form a patterned self-assembled monolayer film, wherein the line width of the grating pattern is less than 10 nm; Using the patterned self-assembled monolayer as a mask, etching the sacrificial layer through a first wet etching process to transfer the grating pattern to the sacrificial layer; removing the patterned self-assembled monolayer by heating; Etching the cladding layer by a second wet etching process to transfer the grating pattern to the cladding layer; The grating layer is etched and the sacrificial layer is removed by a third wet etching process, and the grating pattern is transferred to the grating layer to form a grating.

2. The grating manufacturing method according to claim 1, characterized in that: The step of forming a grating pattern on the self-assembled monolayer film comprises: A grating pattern is formed on the self-assembled monolayer film by an electron beam direct writing process.

3. The grating manufacturing method according to claim 2, characterized in that: In the first wet etching process, selective etching is performed using a first wet etching solution; The first wet etching solution reacts with the material of the sacrificial layer but does not react with the material of the coating layer.

4. The grating manufacturing method according to claim 3, characterized in that: In the second wet etching process, selective etching is performed using a second wet etching solution; The second wet etching solution reacts with the material of the cladding layer, does not react with the material of the sacrificial layer, and does not react with the material of the grating layer.

5. The grating manufacturing method according to claim 4, characterized in that: In the third wet etching process, selective etching is performed using a third wet etching solution; The third wet etching solution reacts with the material of the grating layer and the material of the sacrificial layer, but does not react with the material of the cladding layer and does not react with the material of the upper waveguide layer.

6. The grating manufacturing method according to claim 5, characterized in that: The etching selectivity of the second wet etching solution to the sacrificial layer and the cladding layer is the same as the etching selectivity of the second wet etching solution to the grating layer and the cladding layer; The etching selectivity of the third wet etching solution to the sacrificial layer and the cladding layer, the etching selectivity of the third wet etching solution to the grating layer and the cladding layer, the etching selectivity of the third wet etching solution to the sacrificial layer and the upper waveguide layer is the same as the etching selectivity of the third wet etching solution to the grating layer and the upper waveguide layer; The thickness of the sacrificial layer is smaller than the thickness of the grating layer.

7. The grating manufacturing method according to claim 6, characterized in that: The material of the substrate, the material of the cladding layer, and the material of the grating layer are III-V compound materials; The material of the grating layer is the same as that of the sacrificial layer; The material of the upper waveguide layer is the same as that of the cladding layer; The material of the cladding layer is different from the material of the grating layer; The material of the self-assembled monolayer film is an organic compound containing thiol groups.

8. The grating manufacturing method according to claim 7, characterized in that: The material of the substrate is GaAs, InP, InAs, InGaAs or GaN; The material of the sacrificial layer and the material of the grating layer are InGaAsP, InAlGaAs, AlGaAs, InGaAs or GaAsP; The material of the cladding layer and the material of the upper waveguide layer are InP, GaAs or InGaP; The material of the self-assembled monolayer film is mercapto organic alcohol or 3-mercaptopropyltrimethoxysilane.

9. The grating manufacturing method according to claim 8, characterized in that: The material of the substrate and the material of the lower waveguide layer are n-type doped InP; The material of the multi-layer quantum well layer is InGaAsP; The material of the upper waveguide layer and the material of the cladding layer are p-type doped InP; The material of the grating layer and the material of the sacrificial layer are InGaAsP; The ratio of the first wet etching solution is H2SO4:H2O2:H2O=1:1:10-1:1:25; The ratio of the second wet etching solution is HCl:H3PO4=1:3-1:5; The ratio of the third wet etching solution is H2SO4:H2O2:H2O=1:1:10-1:1:25; The material of the self-assembled monolayer film is mercapto organic alcohol.

10. The grating manufacturing method according to claim 1, characterized in that: The thickness of the multi-layer quantum well layer is 100nm to 500nm; The thickness of the grating layer is 25nm to 100nm; The thickness of the sacrificial layer is 15nm to 80nm; The coating layer has a thickness of 20 nm to 100 nm; The thickness of the self-assembled monolayer film is 2nm-3nm.

11. The grating manufacturing method according to claim 1, characterized in that: The step of removing the patterned self-assembled monolayer film by heating includes: In a mixed gas atmosphere of hydrogen and argon, heating the wafer to a first temperature for a first time to remove the patterned self-assembled monolayer film; the first temperature is the decomposition temperature of the self-assembled monolayer film; The first temperature is 150° C. to 300° C., and the first time period is 10 minutes to 20 minutes.

12. The grating manufacturing method according to claim 1, characterized in that: The step of forming a self-assembled monolayer film on the surface of the sacrificial layer facing away from the coating layer comprises: preparing a self-assembling organic solution; The wafer is placed in the self-assembled organic solution, and the self-assembled organic solution forms a self-assembled monolayer film on the surface of the sacrificial layer facing away from the coating layer.

13. The grating manufacturing method according to claim 12, characterized in that: The material of the self-assembled monolayer is mercapto organic alcohol; the self-assembled organic solution is mercapto organic alcohol solution; The step of preparing the self-assembling organic solution comprises: Evenly mixing anhydrous ethanol and mercapto organic alcohol to obtain a first solution; Adding a second ammonia solution with a concentration of 30% into the first solution to obtain the mercapto organic alcohol solution, wherein the volume ratio of the second ammonia solution to the first solution is 2% to 10%; Degassing is performed to remove oxygen in the mercapto organic alcohol solution.

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