Method for improving etching of thin film lithium niobate

Abstract

The invention relates to a method for improving etching of thin-film lithium niobate. The method comprises the following steps: carrying out dry etching and wet cleaning on thin-film lithium niobate provided with a mask pattern; etching gas used in the dry etching comprises argon or mixed gas of argon and fluorine-based gas; a cleaning solution used in wet cleaning comprises an alkaline peroxide mixed solution. According to the method provided by the invention, the TFLN ridge-shaped structure with a neat edge and a complete structure can be obtained, and the TFLN ridge-shaped structure has good anisotropy, low surface residue and a morphology basis for subsequent device integration; and the method has the characteristics of high universality, high equipment compatibility degree and mild cleaning, and is suitable for batch preparation of high-quality TFLN.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor processing, and relates to a method for improving etching of a thin-film lithium niobate. BACKGROUND

[0002] Thin-film lithium niobate (TFLN) is a functional material with wide application prospects in the field of optoelectronics, and has excellent electro-optic, piezoelectric, nonlinear optical and acousto-optic properties. In particular, in the fields of optical modulation, optical switching, integrated optical waveguide, quantum optics and frequency conversion, TFLN gradually replaces traditional materials and becomes a core material for constructing the next generation of high-performance photonic chips due to its high electro-optic coefficient, wide transparent window (about 0.35 μm~5.2 μm), low loss and high intrinsic bandwidth.

[0003] With the rapid development of optoelectronic integration technology, the use of thin-film lithium niobate to prepare a ridge waveguide has become one of the current mainstream schemes. Compared with a diffusive optical waveguide structure, the ridge waveguide structure has the advantages of smaller size, higher integration density, stronger light field restriction, etc., and shows important practical value in modulators, miniaturized optical switches and other devices.

[0004] The ridge waveguide structure of TFLN is usually realized by a dry etching process, and the current mainstream method is a physical etching method based on inert gas (such as Ar + ). This method has the advantages of stable etching rate and strong directionality, but since it mainly relies on kinetic bombardment for material removal, it lacks effective chemical reaction assistance, so that in the etching process, the sidewall is easy to accumulate non-volatile by-products rich in niobium elements. Such by-products are difficult to remove by conventional wet processing, not only affecting the etching profile accuracy, but also being not conducive to the subsequent device integration and optical performance maintenance.

[0005] Although Ar + plasma etching is essentially a physical sputtering process, in actual process, due to the presence of fluorine (F) and chlorine (Cl) containing elements in the photoresist or substrate residues, lithium elements exposed in the etching process may still react with them to form high-boiling-point difficult-to-volatilize by-products such as LiF and LiCl. These by-products are easy to remain on the surface and sidewall of TFLN, and are difficult to be removed by the conventional wet method, so that the accumulation of by-products is intensified, affecting the structure quality after etching.

[0006] Therefore, how to effectively reduce the accumulation of sidewall byproducts while retaining high anisotropic etching characteristics and improve the cleaning efficiency of post-processing has become one of the key problems to be solved for the current TFLN dry etching process. There is still a lack of an optimized process flow that can balance etching quality and cleaning efficiency in the prior art, which limits the large-scale integration and application development of TFLN devices. SUMMARY

[0007] In view of the deficiencies in the prior art, the purpose of the present application is to provide a method for improving thin film lithium niobate etching, which can obtain a TFLN ridge structure with clean edges and complete structure, good anisotropy, low surface residue, and a morphology foundation for subsequent device integration. The method has the characteristics of strong universality, high equipment compatibility, and mild cleaning, and is suitable for batch production of high-quality TFLN.

[0008] To achieve this application purpose, the following technical solutions are adopted:

[0009] The present application provides a method for improving thin film lithium niobate etching, which comprises the following steps:

[0010] Dry etching and wet cleaning are performed on the thin film lithium niobate with a mask pattern;

[0011] The etching gas used in the dry etching includes argon, or a mixture of argon and fluorine-based gas;

[0012] The cleaning liquid used in the wet cleaning includes an alkaline peroxide mixture.

[0013] The method provided by the present application can obtain a TFLN ridge structure with clean edges and complete structure, good anisotropy, low surface residue, and a morphology foundation for subsequent device integration. The method has the characteristics of strong universality, high equipment compatibility, and mild cleaning, and is suitable for batch production of high-quality TFLN.

[0014] In one embodiment of the present application, the etching gas includes argon (Ar), CHF3 and CF4.

[0015] In one embodiment of the present application, the volume ratio of argon to CHF3 is 2:1 to 10:1.

[0016] In one embodiment of the present application, the volume ratio of CHF3 to CF4 is 1:1 to 1:10.

[0017] In one embodiment of the present application, the etching power of the dry etching is 200W to 1000W.

[0018] In one embodiment of the present application, the bias power of the dry etching is 100-500 W.

[0019] In one embodiment of the present application, the etching depth of the dry etching is 300-500 nm.

[0020] In one embodiment of the present application, the composition of the alkaline peroxide mixture comprises ammonia (NH4OH), hydrogen peroxide (H2O2) and deionized water (H2O).

[0021] In one embodiment of the present application, the volume ratio of the ammonia, hydrogen peroxide and deionized water is (1-5):(1-5):(1-2).

[0022] In one embodiment of the present application, the concentration of the ammonia is 10-50 wt%.

[0023] In one embodiment of the present application, the concentration of the hydrogen peroxide is 15-35 wt%.

[0024] In one embodiment of the present application, the temperature of the wet cleaning is 30-70 °C.

[0025] In one embodiment of the present application, the time of the wet cleaning is 5-30 min.

[0026] In one embodiment of the present application, the method comprises the following steps:

[0027] (1) setting a mask pattern on the surface of the thin film lithium niobate;

[0028] (2) dry etching the thin film lithium niobate with the mask pattern by inductively coupled plasma method;

[0029] The etching gas used in the dry etching is argon, CHF3 and CF4, and the volume ratio of argon, CHF3 and CF4 is (2-10):1:(1-10);

[0030] The etching power of the dry etching is 200-1000 W, the bias power is 100-500 W, and the etching depth is 300-500 nm;

[0031] (3) wet cleaning the thin film lithium niobate after the dry etching by alkaline peroxide mixture;

[0032] The composition of the alkaline peroxide mixture is ammonia, hydrogen peroxide and deionized water with a volume ratio of (1-5):(1-5):(1-2); the concentration of the ammonia is 10-50 wt%, and the concentration of the hydrogen peroxide is 15-35 wt%.

[0033] The wet cleaning temperature is 30℃~70℃, and the time is 5min~30min.

[0034] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The method provided by this invention can obtain TFLN ridge structures with clean edges and complete structure, which have good anisotropy, low surface residue and morphological basis for subsequent device integration; and the method has the characteristics of strong versatility, high equipment compatibility and gentle cleaning, and is suitable for the mass production of high-quality TFLNs. Attached Figure Description

[0037] Figure 1 SEM images of the TFLN structure after method processing are provided for Example 7;

[0038] Figure 2 The method provided in Example 7, after wet cleaning, is shown in the SEM image of the TFLN structure;

[0039] Figure 3 The method provided in Example 1, SEM image of TFLN structure after dry etching;

[0040] Figure 4 The method provided in Example 1 includes a SEM image of the TFLN structure after wet cleaning;

[0041] Figure 5 The method provided in Example 4, SEM image of the TFLN structure after dry etching;

[0042] Figure 6 The method provided in Example 5 includes a SEM image of the TFLN structure after wet cleaning;

[0043] Figure 7 The method provided in Example 6 is a SEM image of the TFLN structure after wet cleaning.

[0044] HSQ Mask refers to hydrogen silsesquioxane mask, i.e., the mask pattern in this invention; TFLN refers to thin-film lithium niobate. Detailed Implementation

[0045] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0046] Compared to common semiconductor or glass materials (such as GeSbSe, Si, or SiO2), TFLN presents several significant technological challenges during dry etching and cleaning, primarily in the following aspects: First, lithium in lithium niobate readily reacts with fluorine to form lithium fluoride (LiF) byproducts during etching. This substance has a boiling point as high as 1676℃, exhibits extremely high thermal stability, and is a typical non-volatile residue. It easily deposits on the etched sidewalls and bottom, making it difficult to remove using conventional evacuation or inert gas etching. Second, TFLN structures are extremely sensitive to etching morphology and edge cleanliness. While common inert gas physical etching methods offer good directionality, the lack of effective chemical reaction assistance leads to significant byproduct accumulation after etching, affecting the preservation of the structural contour.

[0047] Fluorine-based gases such as CHF3 and CF4 can be used for dry etching of lithium-free materials such as glass or semiconductors, and the resulting byproducts are easily volatile. However, they are not suitable for treating LiF residues formed after etching lithium niobate materials. Wet cleaning using a combination of NH4OH and H2O2 is mostly used in Si-based device structures. It has a shallow etching depth and less particulate contamination, but it is not capable of treating the sidewall structures of TFLN.

[0048] An embodiment of the present invention provides a method for improving the etching of thin-film lithium niobate, the method comprising the following steps:

[0049] Dry etching and wet cleaning were performed on thin film lithium niobate with mask pattern.

[0050] The etching gas used in the dry etching process includes argon, or a mixture of argon and fluorine-based gas.

[0051] The cleaning solution used in the wet cleaning process includes an alkaline peroxide mixture.

[0052] The method provided by this invention can obtain TFLN ridge structures with clean edges and complete structure, which have good anisotropy, low surface residue and morphological basis for subsequent device integration; and the method has the characteristics of strong versatility, high equipment compatibility and gentle cleaning, and is suitable for the mass production of high-quality TFLNs.

[0053] Specifically, the method provided by this invention aims to solve the problems of etching profile deterioration and difficulty in cleaning caused by by-product accumulation in the dry etching process of TFLN ridge structures. Specifically, based on dry etching using inert gas ions, the method reduces the generation of by-products during etching by adjusting the etching gas and parameters; and by introducing a more controllable and milder alkaline wet cleaning process to replace the traditional hydrofluoric acid treatment method, effectively removing etching residues. Therefore, the method provided by this invention can obtain TFLN ridge structures with fewer sidewall by-products and better morphology retention, thereby improving the consistency and reliability of device fabrication.

[0054] The method provided by this invention mainly includes two main steps: dry etching and wet cleaning. This combination can effectively reduce the accumulation of high-boiling-point byproducts during the etching process and achieve efficient cleaning of sidewall residues, thereby obtaining a ridge-shaped thin film lithium niobate structure with clear morphology and complete structure.

[0055] Existing technologies require a complex wet cleaning process after dry etching with argon. This invention, however, utilizes an alkaline peroxide mixture to achieve efficient cleaning of sidewall residues, resulting in a clean, structurally intact polar thin-film lithium niobate structure. Furthermore, as a further preferred solution, the use of a mixture of argon and fluorine-based gases effectively reduces the accumulation of high-boiling-point byproducts during etching, further facilitating efficient wet cleaning in this invention.

[0056] In some embodiments, the etching gas includes argon (Ar), CHF3, and CF4.

[0057] CHF3 and CF4 can generate -HF and -H radicals under plasma irradiation. Utilizing a surface reaction process helps to regulate the chemical environment of the etching reaction, thereby suppressing the deposition of high-boiling-point LiF byproducts on the etching sidewalls or the bottom of the grooves, and improving the cleanliness and morphology control precision of the etched surface. Simultaneously, the addition of CHF3 has a passivation effect on the etching profile morphology, suppressing surface roughening while maintaining good anisotropy.

[0058] In some embodiments, the volume ratio of argon to CHF3 is 2:1 to 10:1, for example, it can be 2:1, 4:1, 5:1, 6:1, 8:1 or 10:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0059] In some embodiments, the volume ratio of CHF3 to CF4 is 1:1 to 1:10, for example, it can be 1:1, 1:3, 1:5, 1:6, 1:8 or 1:10, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0060] In some embodiments, the etching power of the dry etching is 200W to 1000W, for example, it can be 200W, 400W, 500W, 600W, 800W or 1000W, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0061] In some embodiments, the bias power of the dry etching is 100W to 500W, for example, it can be 100W, 200W, 300W, 400W or 500W, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0062] The time for dry etching is related to the etching depth. This invention does not impose a specific time limit, as long as the expected etching depth can be achieved.

[0063] In some embodiments, the etching depth of the dry etching is 300nm~500nm, for example, it can be 300nm, 350nm, 400nm, 450nm or 500nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0064] In some embodiments, the alkaline peroxide mixture comprises ammonia, hydrogen peroxide, and deionized water.

[0065] Unlike other materials that are easily etched and cleaned using dry etching and wet cleaning methods, lithium niobate readily generates non-volatile byproducts such as LiF during dry etching. These substances are difficult to remove using conventional organic solvents, and highly corrosive cleaning solutions such as HF pose a risk of damaging the ridge structure. This invention employs an alkaline peroxide mixture composed of ammonia, hydrogen peroxide, and deionized water for wet cleaning, replacing the traditional HF cleaning method. This method effectively removes non-volatile byproducts adhering to the etched area under gentle conditions, reducing the risk of structural corrosion and uncontrollable dimensional changes. This alkaline peroxide mixture exhibits high selectivity and cleaning efficiency, improving the integrity and morphological quality of the etched structure.

[0066] In some embodiments, the volume ratio of ammonia, hydrogen peroxide and deionized water is (1~5):(1~5):(1~2).

[0067] Specifically, the volume ratio of ammonia to hydrogen peroxide is (1~5):(1~5), for example, it can be 1:5, 1:1 or 5:1, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0068] The volume ratio of hydrogen peroxide to deionized water is (1~5):(1~2), for example, it can be 1:2, 1:1 or 5:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0069] In some embodiments, the concentration of the ammonia water is 10wt% to 50wt%, for example, it can be 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt% or 50wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0070] In some embodiments, the concentration of hydrogen peroxide is 15wt% to 35wt%, for example, it can be 15wt%, 20wt%, 25wt%, 30wt% or 35wt%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0071] In some embodiments, the temperature of the wet cleaning is 30°C to 70°C, for example, it can be 30°C, 40°C, 50°C, 60°C or 70°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0072] In some embodiments, the wet cleaning time is 5 min to 30 min, for example, it can be 5 min, 10 min, 15 min, 20 min, 25 min or 30 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0073] In some embodiments, the method includes the following steps:

[0074] (1) A mask pattern is set on the surface of thin-film lithium niobate;

[0075] (2) Dry etching of thin film lithium niobate with mask pattern is performed by inductively coupled plasma method;

[0076] The etching gas used in the dry etching process is argon, or a mixture of argon, CHF3 and CF4, and the volume ratio of argon, CHF3 and CF4 is (2~10):1:(1~10).

[0077] The dry etching process has an etching power of 200W~1000W, a bias power of 100W~500W, and an etching depth of 300nm~500nm.

[0078] (3) The thin film lithium niobate after dry etching was wet-cleaned using an alkaline peroxide mixture;

[0079] The alkaline peroxide mixture is composed of ammonia, hydrogen peroxide, and deionized water in a volume ratio of (1~5):(1~5):(1~2); the concentration of the ammonia is 10wt%~50wt%, and the concentration of the hydrogen peroxide is 15wt%~35wt%.

[0080] The wet cleaning temperature is 30℃~70℃, and the time is 5min~30min.

[0081] Example 1

[0082] This embodiment provides a method for improving the etching of thin-film lithium niobate, the method comprising the following steps:

[0083] (1) Thin film lithium niobate based on SiO2 insulating layer is selected as etching material, and HSQ mask pattern is prepared on the surface by electron beam exposure to define the ridge waveguide structure of the area to be etched;

[0084] (2) Dry etching of thin film lithium niobate with mask pattern is performed by inductively coupled plasma method;

[0085] The etching gases used in the dry etching process are argon, CHF3 and CF4, and the volume ratio of argon, CHF3 and CF4 is 5:1:5.

[0086] The dry etching process has an etching power of 500W, a bias power of 300W, and an etching depth of 400nm.

[0087] The effect of dry etching in this embodiment is as follows: Figure 3 As shown, the edges of the TFLN ridge structure are neat and there are no obvious by-product residues on the sidewalls;

[0088] (3) The thin film lithium niobate after dry etching was wet-cleaned using an alkaline peroxide mixture;

[0089] The alkaline peroxide mixture is composed of ammonia, hydrogen peroxide, and deionized water in a volume ratio of 3:3:1, with the ammonia concentration being 30 wt% and the hydrogen peroxide concentration being 25 wt%.

[0090] The wet cleaning process is carried out at a temperature of 50°C for 20 minutes.

[0091] like Figure 4 As shown, after wet cleaning in this embodiment, there are no obvious byproduct residues in the etched area, the sidewall edges are clear, and particle contamination is greatly reduced.

[0092] Example 2

[0093] This embodiment provides a method for improving the etching of thin-film lithium niobate, the method comprising the following steps:

[0094] (1) Thin film lithium niobate based on SiO2 insulating layer is selected as etching material, and HSQ mask pattern is prepared on the surface by electron beam exposure to define the ridge waveguide structure of the area to be etched;

[0095] (2) Dry etching of thin film lithium niobate with mask pattern is performed by inductively coupled plasma method;

[0096] The etching gases used in the dry etching process are argon, CHF3 and CF4, and the volume ratio of argon, CHF3 and CF4 is 2:1:1.

[0097] The dry etching method has an etching power of 200W, a bias power of 100W, and an etching depth of 300nm.

[0098] After dry etching in this embodiment, the edges of the TFLN ridge structure are neat and there are no obvious by-product residues on the sidewalls.

[0099] (3) The thin film lithium niobate after dry etching was wet-cleaned using an alkaline peroxide mixture;

[0100] The alkaline peroxide mixture is composed of ammonia, hydrogen peroxide, and deionized water in a volume ratio of 1:1:1, with the ammonia concentration being 10 wt% and the hydrogen peroxide concentration being 35 wt%.

[0101] The wet cleaning process is carried out at a temperature of 30°C for 30 minutes.

[0102] After wet cleaning in this embodiment, there were no obvious byproducts remaining in the etched area, the sidewall edges were clear, and particulate contamination was greatly reduced.

[0103] Example 3

[0104] This embodiment provides a method for improving the etching of thin-film lithium niobate, the method comprising the following steps:

[0105] (1) Thin film lithium niobate based on SiO2 insulating layer is selected as etching material, and HSQ mask pattern is prepared on the surface by electron beam exposure to define the ridge waveguide structure of the area to be etched;

[0106] (2) Dry etching of thin film lithium niobate with mask pattern is performed by inductively coupled plasma method;

[0107] The etching gases used in the dry etching process are argon, CHF3 and CF4, and the volume ratio of argon, CHF3 and CF4 is 10:1:10.

[0108] The dry etching process has an etching power of 1000W, a bias power of 500W, and an etching depth of 500nm.

[0109] After dry etching in this embodiment, the edges of the TFLN ridge structure are neat and there are no obvious by-product residues on the sidewalls.

[0110] (3) The thin film lithium niobate after dry etching was wet-cleaned using an alkaline peroxide mixture;

[0111] The alkaline peroxide mixture is composed of ammonia, hydrogen peroxide, and deionized water in a volume ratio of 5:5:2; the concentration of ammonia is 50 wt%, and the concentration of hydrogen peroxide is 15 wt%.

[0112] The wet cleaning process is carried out at a temperature of 70°C for 5 minutes.

[0113] After wet cleaning in this embodiment, there were no obvious byproducts remaining in the etched area, the sidewall edges were clear, and particulate contamination was greatly reduced.

[0114] Example 4

[0115] This embodiment provides a method for improving the etching of thin-film lithium niobate. Except for the volume ratio of argon, CHF3 and CF4 being 1:1:5, everything else is the same as in Example 1.

[0116] In the method provided in this embodiment, the effect of dry etching is as follows: Figure 5 As shown. By Figure 5 It can be seen that the relatively large amount of CHF3 and CF4 used in dry etching leads to the large consumption and retreat of the HSQ mask, resulting in the TFLN sidewalls not being effectively protected, and producing etching results with low angle, high roughness and more particulate byproducts.

[0117] However, wet cleaning can also achieve the technical effect of no obvious by-product residue in the etched area, clear sidewall edges, and a significant reduction in particulate contamination.

[0118] Example 5

[0119] This embodiment provides a method for improving the etching of thin-film lithium niobate. Except for the volume ratio of argon, CHF3 and CF4 being 12:1:5, everything else is the same as in Example 1.

[0120] In the method provided in this embodiment, the effect of wet cleaning is as follows: Figure 6 As shown. By Figure 6 It can be seen that when the amount of Ar used in dry etching is relatively large, the top of the TFLN will have arc-shaped damage after wet cleaning.

[0121] Example 6

[0122] This embodiment provides a method for improving the etching of thin-film lithium niobate. Except for the volume ratio of ammonia, hydrogen peroxide and deionized water being 6:6:1, everything else is the same as in Example 1.

[0123] In the method provided in this embodiment, the effect of wet cleaning is as follows: Figure 7 As shown. By Figure 7It is known that when a large amount of ammonia and hydrogen peroxide are used during dry etching, TFLN will experience sidewall corrosion and lose its original design shape.

[0124] Example 7

[0125] This embodiment provides a method for improving the etching of thin-film lithium niobate, the method comprising the following steps:

[0126] (1) Thin film lithium niobate based on SiO2 insulating layer is selected as etching material, and HSQ mask pattern is prepared on the surface by electron beam exposure to define the ridge waveguide structure of the area to be etched;

[0127] (2) Dry etching of thin film lithium niobate with mask pattern is performed by inductively coupled plasma method;

[0128] The etching gas used in the dry etching process is argon.

[0129] The dry etching process has an etching power of 500W, a bias power of 300W, and an etching depth of 400nm.

[0130] The effect of dry etching in this embodiment is as follows: Figure 1 As shown, the TFLN ridge structure has severe surface contamination, blurred sidewall structure, and obvious accumulation of deposits on both sides. It is also heavily covered by byproducts, and the sidewall morphology is blurred, which affects the implementation of conventional wet cleaning.

[0131] However, after wet cleaning in this embodiment, the technical effect of no obvious by-product residue in the etched area, clear sidewall edges, and significantly reduced particulate contamination can also be achieved (see [reference]). Figure 2 ).

[0132] In summary, the method provided by this invention aims to solve the problems of etching profile deterioration and difficulty in cleaning caused by by-product accumulation in the dry etching process of TFLN ridge structures. Specifically, based on dry etching using an inert gas as an example, the method reduces the generation of by-products during the etching process by adjusting the etching gas and parameters. Furthermore, it effectively removes etching residues by introducing a more controllable and milder alkaline wet cleaning process to replace the traditional hydrofluoric acid treatment method. Therefore, the method provided by this invention can obtain TFLN ridge structures with fewer sidewall by-products and better morphology retention, thereby improving the consistency and reliability of device fabrication.

[0133] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for improving the etching of thin-film lithium niobate, characterized in that, The method includes the following steps: Dry etching and wet cleaning were performed on thin film lithium niobate with mask pattern. The etching gas used in the dry etching process includes argon, or a mixture of argon and fluorine-based gas. The cleaning solution used in the wet cleaning process includes an alkaline peroxide mixture.

2. The method according to claim 1, characterized in that, The etching gases include argon, CHF3, and CF4.

3. The method according to claim 2, characterized in that, The volume ratio of argon to CHF3 is 2:1 to 10:1; And / or, the volume ratio of CHF3 to CF4 is 1:1 to 1:

10.

4. The method according to claim 1, characterized in that, The etching power of the dry etching method is 200W~1000W; And / or, the bias power of the dry etching is 100W~500W.

5. The method according to any one of claims 1 to 4, characterized in that, The etching depth of the dry etching method is 300nm~500nm.

6. The method according to claim 1, characterized in that, The alkaline peroxide mixture consists of ammonia, hydrogen peroxide, and deionized water.

7. The method according to claim 6, characterized in that, The volume ratio of ammonia, hydrogen peroxide and deionized water is (1~5):(1~5):(1~2); And / or, the concentration of the ammonia solution is 10wt%~50wt%; And / or, the concentration of the hydrogen peroxide is 15wt% to 35wt%.

8. The method according to claim 1, characterized in that, The temperature for wet cleaning is 30℃~70℃.

9. The method according to any one of claims 6 to 8, characterized in that, The wet cleaning time is 5 min to 30 min.

10. The method according to claim 1, characterized in that, The method includes the following steps: (1) A mask pattern is set on the surface of thin-film lithium niobate; (2) Dry etching of thin film lithium niobate with mask pattern is performed by inductively coupled plasma method; The etching gas used in the dry etching process is argon, or a mixture of argon, CHF3 and CF4, and the volume ratio of argon, CHF3 and CF4 is (2~10):1:(1~10). The dry etching process has an etching power of 200W~1000W, a bias power of 100W~500W, and an etching depth of 300nm~500nm. (3) The thin film lithium niobate after dry etching was wet-cleaned using an alkaline peroxide mixture; The alkaline peroxide mixture is composed of ammonia, hydrogen peroxide, and deionized water in a volume ratio of (1~5):(1~5):(1~2); the concentration of the ammonia is 10wt%~50wt%, and the concentration of the hydrogen peroxide is 15wt%~35wt%. The wet cleaning temperature is 30℃~70℃, and the time is 5min~30min.

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