Method for selectively etching lithium niobate by ion implantation assisted wet process
By using an ion implantation-assisted wet process to prepare a metal adhesion layer and a photoresist layer on the surface of lithium niobate, selective etching is performed, which solves the problems of surface roughness and lateral etching in the etching of lithium niobate micro-nano structures, and realizes efficient and precise lithium niobate microstructure processing.
Patent Information
- Application Number
- CN202511414416.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-29
- Publication Date
- 2026-01-16
AI Technical Summary
Existing technologies for etching lithium niobate micro/nano structures suffer from problems such as secondary deposition of byproducts during dry etching leading to surface roughness and low verticality, and lateral etching under the mask caused by liquid flowability and crystal anisotropy during wet etching, resulting in a reduced aspect ratio.
An ion implantation-assisted wet process was employed to prepare a metal adhesion layer and a photoresist layer on the surface of lithium niobate. A mask layer was then prepared by development and wet etching. The etched areas were modified by multiple ion implantations, and the damaged areas were removed by wet etching. Finally, the mask layer was removed to form a high-quality lithium niobate microstructure.
It significantly improves the etching rate, ensures smooth sidewalls and high aspect ratio, expands the application range, overcomes the limitations of traditional etching methods, and meets the etching needs of complex structures.
Smart Images
Figure CN121344529A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and more specifically to a method for selectively etching lithium niobate using an ion implantation-assisted wet process. Background Technology
[0002] As a multifunctional crystalline material possessing a variety of excellent properties, lithium niobate (LiNbO3) has shown great application potential in many fields, including optoelectronic devices, surface acoustic wave devices, and pyroelectric infrared detectors, thanks to its outstanding photoelectric, piezoelectric, and pyroelectric effects. However, lithium niobate has encountered numerous challenges in micro- and nano-structure etching, which has kept the development and research of surface microfabrication processes for it at the micrometer and sub-micrometer scale in a continuous exploratory stage. In the past decade or so of exploration, although many microstructure etching techniques have been proposed, each technique inevitably has some inherent limitations.
[0003] Taking the commonly used dry etching technology as an example, some non-volatile byproducts are often generated during the etching process, such as lithium fluoride (LiF) and niobium fluorides. These byproducts undergo secondary deposition in the etched area, forming a passivation layer. The presence of this passivation layer not only hinders further etching and reduces the subsequent etching rate, but also causes the surface of the lithium niobate sidewalls to become rough, and the perpendicularity is difficult to guarantee. When this rough-surfaced and poorly perpendicular lithium niobate is used in related devices, it will cause significant optical scattering loss, which will have a very adverse effect on the overall performance of the device and seriously restrict the improvement of device performance.
[0004] While wet etching technology is relatively simple in its process and produces relatively smooth sidewall surfaces, it also has significant limitations. In wet etching, chromium (Cr) metal is typically used as a hard mask, followed by etching with a mixture of hydrofluoric acid (HF) and nitric acid (HNO3). However, due to the fluidity of the etching liquid and the anisotropic nature of the crystal, lateral etching occurs beneath the mask. This lateral etching significantly reduces the aspect ratio of the etched structure, affecting the structural accuracy and performance of the device, thus limiting the application of wet etching technology in the fabrication of high-performance lithium niobate micro / nanostructures.
[0005] Based on the current state of technological development, this invention provides a novel method for selectively etching lithium niobate using an ion implantation-assisted wet process. Summary of the Invention
[0006] Based on the above description, the present invention provides a method for selective etching of lithium niobate using an ion implantation-assisted wet process, in order to solve the technical problems faced by existing lithium niobate micro-nano structure etching, such as surface roughness and low verticality caused by secondary deposition of byproducts in dry etching, and the reduction of aspect ratio caused by lateral etching under the mask due to liquid flowability and crystal anisotropy in wet etching.
[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: This invention provides a method for selectively etching lithium niobate using an ion implantation-assisted wet process, comprising the following steps: S1. Prepare a metal adhesion layer on the surface of lithium niobate; S2. Spin-coat a photoresist layer onto the surface of the metal adhesion layer; S3. A mask layer patterned from the metal adhesion layer and the photoresist layer is prepared by development exposure and wet etching. S4. Prepare a charge absorption layer on the surface of the mask layer and the surface of the lithium niobate to be etched; S5. Lithium niobate in the etchable region is modified by multiple ion implantations; wherein the ion implantation energy ranges from 0.5 to 20 MeV, and the implantation dose ranges from 1 × 10⁻⁶. 13 ~1×10 16 ions / cm 2 The pattern depth of lithium niobate etching increases with the number of ion implantation repetitions until the desired lithium niobate etched structure is obtained. S6. Remove the surface charge absorption layer and use a wet etching process to remove the damaged area after implantation; S7. After etching, the mask layer on the surface is removed to obtain the etched lithium niobate structure.
[0008] Based on the above technical solution, the present invention can be further improved as follows.
[0009] Furthermore, step S1 specifically includes: preparing a metal adhesion layer on the lithium niobate surface by one of the following methods: magnetron sputtering, thermal evaporation, atomic layer deposition, and molecular beam epitaxy; The metal material of the metal adhesion layer is one or a combination of several of the following: Cr, Ni, Cu, Fe, Co, Ir, Pt, Au, Ag, Ti, and Zr.
[0010] Furthermore, the types of photoresist mentioned in step S2 include PMMA, SU-8, HSN, HSQ, CARs, PSPI, DNQ-Novolac-based positive photoresist, metal oxide photoresist, or molecular glass photoresist.
[0011] Furthermore, the method for preparing the charge absorption layer in step S4 is one of vapor deposition, magnetron sputtering, thermal evaporation, atomic layer deposition, and molecular beam epitaxy.
[0012] Furthermore, in step S5, the injected ions are one or a combination of several of the following: H, He, Ar, B, P, O, C, As, Sb, Si, Cu, Ti, Al, and Ge.
[0013] Furthermore, the etching in step S6 is one of full etching, deep etching, and shallow etching.
[0014] Furthermore, in the case of full etching or deep etching, high-energy implantation is performed first, and then the implantation energy is gradually reduced to achieve implantation from deep to shallow. Furthermore, in the case of shallow etching, the corresponding area with fewer surface defects is removed by grinding after adjusting the energy, and then wet etching is performed.
[0015] Furthermore, in step S6, the etching solution used in the wet etching process is an acidic solution or an alkaline solution.
[0016] Furthermore, the thickness of the metal adhesion layer is 1~500 nm; and / or, The photoresist is prepared with a thickness of 1~2000 nm; and / or, The thickness of the charge absorption layer is 50~100nm.
[0017] Compared with the prior art, the technical solution of this application has the following beneficial technical effects: The method for selective etching of lithium niobate using an ion implantation-assisted wet process and its preparation method provided by this invention have the following advantages compared to existing technologies: 1. By modifying the etched area through ion implantation, the etching rate of lithium niobate during the etching process was significantly improved, laying the foundation for efficient processing.
[0018] 2. The introduction of a metal adhesion layer and photoresist can effectively protect non-etched areas from damage caused by ion implantation, while meeting the etching requirements of complex structures such as large-scale waveguide structures or integrated domain wall memory arrays on lithium niobate wafers, thus expanding the application range.
[0019] 3. The repeated ion implantation and etching process enables the high aspect ratio of the lithium niobate etching region, ensuring smooth sidewalls and low surface roughness, thus significantly improving the etching quality.
[0020] The technology provided by this invention utilizes a hard mask composed of metal and photoresist for selective ion implantation to form a predetermined damage region inside lithium niobate. During subsequent wet etching, the extremely high etching selectivity between the damaged and undamaged areas enables the process to precisely fabricate high-quality lithium niobate microstructures with smooth sidewalls, high aspect ratio, and excellent optical quality, effectively overcoming the limitations of traditional etching methods. Attached Figure Description
[0021] Figure 1 This is a schematic flowchart of a method for selectively etching lithium niobate using an ion implantation-assisted wet process, as provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the actual operation process of the method for selective etching of lithium niobate using an ion implantation-assisted wet process provided in an embodiment of the present invention. Detailed Implementation
[0022] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.
[0023] Ion implantation technology uses high-energy particles to bombard the surface of materials, enabling precise control of doping and alteration of the physicochemical properties of localized areas. For lithium niobate, ion implantation can introduce high-density defects or even form amorphous layers in specific regions within the material, significantly enhancing the selectivity of those regions during subsequent etching.
[0024] Based on the above principles, this invention proposes a novel method for selective etching of lithium niobate using an ion implantation-assisted wet process—the "ion implantation-assisted wet etching" technique for lithium niobate. This technique utilizes a hard mask composed of metal and photoresist for selective ion implantation, forming predetermined damage regions within the lithium niobate. During subsequent wet etching, the extremely high etching selectivity between the damaged and undamaged regions enables the precise fabrication of high-quality lithium niobate microstructures with smooth sidewalls, high aspect ratio, and excellent optical quality, effectively overcoming the limitations of traditional etching methods.
[0025] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention, but should not be used to limit the scope of the present invention.
[0026] like Figure 1 As shown, this embodiment of the invention provides a method for selectively etching lithium niobate using an ion implantation-assisted wet process, comprising the following steps: Step S1: Prepare a metal adhesion layer on the surface of lithium niobate.
[0027] This step specifically includes: preparing a metal adhesion layer on the surface of lithium niobate by one of the following methods: magnetron sputtering, thermal evaporation, atomic layer deposition, and molecular beam epitaxy; magnetron sputtering is the preferred method in this embodiment.
[0028] The metal material of the metal adhesion layer is one or a combination of several of the following: Cr, Ni, Cu, Fe, Co, Ir, Pt, Au, Ag, Ti, and Zr.
[0029] Step S2: Spin-coat a photoresist layer onto the surface of the metal adhesion layer.
[0030] In this step, the types of photoresist include PMMA, SU-8, HSN, HSQ, CARs, PSPI, DNQ-Novolac-based positive photoresist, metal oxide photoresist, or molecular glass photoresist. The specific type can be selected based on actual needs; no further limitations are specified here.
[0031] Step S3: Prepare a mask layer for the patterned metal adhesion layer and the photoresist layer by developing exposure and wet etching.
[0032] In particular, the mask layer (metal + photoresist) in the embodiments of the present invention requires that the energy and dosage of the ions be such that the mask layer is not damaged during repeated implantation.
[0033] Step S4: Prepare a charge absorption layer on the surface of the mask layer and the surface of the lithium niobate to be etched.
[0034] In this step, the charge absorption layer is prepared by one of the following methods: magnetron sputtering, thermal evaporation, atomic layer deposition, and molecular beam epitaxy.
[0035] Step S5: Modify the lithium niobate in the etchable region through multiple ion implantations; wherein the implantation energy ranges from 0.5 to 20 MeV, and the implantation dose ranges from 1 × 10⁻⁶. 13 ~1×10 16 ions / cm 2 The pattern depth of lithium niobate etching increases with the number of ion implantation repetitions until the desired lithium niobate etched structure is obtained.
[0036] The implanted ions are one or a combination of several of the following: H, He, Ar, B, P, O, C, As, Sb, Si, Cu, Ti, Al, and Ge.
[0037] In optional embodiments, other methods such as femtosecond laser irradiation or electron beam irradiation are also used to modify the lithium niobate in the area to be etched.
[0038] Step S6: Remove the surface charge absorption layer and use a wet etching process to remove the damaged area after implantation. The etching solution used in the wet etching process can be an acidic solution (hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid) or an alkaline solution (ammonia, potassium hydroxide, sodium hydroxide).
[0039] Furthermore, the etching in step S6 is one of full etching, deep etching, and shallow etching.
[0040] In the case of full etching or deep etching, high-energy implantation is performed first, and then the implantation energy is gradually reduced to achieve implantation from deep to shallow. When the etching is shallow, the energy is adjusted first, and then the corresponding area with fewer surface defects is removed by grinding before proceeding to the next step of wet etching.
[0041] Step S7: After etching, the mask layer on the surface is removed to obtain the etched lithium niobate structure.
[0042] Furthermore, in step S6, the thickness of the metal adhesion layer is 1~500 nm; and / or the thickness of the photoresist is 1~2000 nm; and / or the thickness of the charge absorption layer is 50~100 nm. Specific dimensions are selected according to actual needs and are not specifically limited here.
[0043] The core process of this invention is to modify the interior of the lithium niobate in the etched portion using ion implantation. Unlike the implantation stripping and conventional implantation doping in the Smart-Cut process, the ion implantation involved in this invention tends to be over-implantation. By injecting a large number of external ions, the original crystal structure is forced to change from ordered to disordered, making it tend to be amorphous. This results in a high etching rate in the subsequent wet etching process. In areas that do not need to be etched, the influence of ion implantation on the non-etched areas is avoided by using hard masks of metal and photoresist. This allows for differentiated etching rates in different regions of the same matrix during the subsequent wet etching process, improving the sidewall smoothness and aspect ratio of the lithium niobate device after etching.
[0044] The following is for reference Figure 2 The specific operating procedures will be described accordingly: 1. A metal adhesion layer (11) is prepared on the surface of lithium niobate (10). Physical and chemical methods such as magnetron sputtering, thermal evaporation, atomic layer deposition, and molecular beam epitaxy can be used. The preferred method for preparing the metal adhesion layer is magnetron sputtering. The types of metal materials include, but are not limited to, one or more of Cr, Ni, Cu, Fe, Co, Ir, Pt, Au, Ag, Ti, and Zr. The thickness of the selected adhesion layer is 1 to 500 nm. In particular, if the etching target depth is shallow, the metal adhesion layer may not be deposited.
[0045] 2. Spin-coat a layer of photoresist (12) onto the surface of the metal adhesion layer. The types of photoresist include, but are not limited to, PMMA, SU-8, HSN, HSQ, CARs, PSPI, DNQ-Novolac positive resist, metal oxide resist, and molecular glass resist; wherein the thickness of the photoresist is 1-2000nm.
[0046] 3. A mask layer of patterned metal adhesion layer (11) and photoresist (12) is prepared by development exposure and wet etching.
[0047] 4. A charge absorption layer (13) is prepared on the surface of the mask layer and the surface of the lithium niobate wafer to be etched. Physical and chemical methods such as magnetron sputtering, thermal evaporation, atomic layer deposition, molecular beam epitaxy, etc. can be used. The preferred method for preparing the charge absorption layer is magnetron sputtering. The material of the charge absorption layer includes, but is not limited to, Au, Al, etc., and the thickness of the selected charge absorption layer is 50~100nm.
[0048] 5. Modify the lithium niobate in the etchable region (14) by ion implantation. The types of implanted ions include, but are not limited to, one or a combination of several of H, He, Ar, B, P, O, C, As, Sb, Si, Cu, Ti, Al, and Ge; the preferred implantation energy range is 0.5~20 MeV, and the implantation dose range is 1×10⁻⁶. 13 ~1×10 16 ions / cm 2 .
[0049] 6. Ion implantation varies depending on the etching depth, such as full etching, deep etching, or shallow etching. For full etching and deep etching, high-energy implantation can be performed first, and then the implantation energy can be gradually reduced to achieve implantation from deep to shallow. For shallow etching, the energy can be adjusted to low or high, and then the areas with fewer surface defects can be ground away before proceeding to the next step of wet etching. In particular, when considering multiple implantations, the mask layer (metal + photoresist) in the invention must ensure that the ion energy and dosage are not damaged during repeated implantation. 7. Remove the surface charge absorption layer (13) and use a wet etching process to remove the damaged area after injection (14). The etching solution can be an acidic (hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid) or alkaline (ammonia, potassium hydroxide, sodium hydroxide) solution.
[0050] 8. After etching, remove the mask layer formed by the surface metal adhesion layer (11) and the photoresist (12).
[0051] Steps 5 and 6 can be repeated multiple times. The depth of the lithium niobate etching pattern can be gradually increased with the number of repetitions until the requirements are met, and finally the desired lithium niobate etched structure (15) is obtained.
[0052] In summary, the method for selective etching of lithium niobate using an ion implantation-assisted wet process and the corresponding preparation method provided in the above embodiments have the following technical advantages: 1. By modifying the etched area through ion implantation, the etching rate of lithium niobate during the etching process was significantly improved, laying the foundation for efficient processing.
[0053] 2. The introduction of a metal adhesion layer and photoresist can effectively protect non-etched areas from damage caused by ion implantation, while meeting the etching requirements of complex structures such as large-scale waveguide structures or integrated domain wall memory arrays on lithium niobate wafers, thus expanding the application range.
[0054] 3. The repeated ion implantation and etching process enables the high aspect ratio of the lithium niobate etching region, ensuring smooth sidewalls and low surface roughness, thus significantly improving the etching quality.
[0055] The technology provided by this invention utilizes a hard mask composed of metal and photoresist for selective ion implantation to form a predetermined damage region inside lithium niobate. During subsequent wet etching, the extremely high etching selectivity between the damaged and undamaged areas enables the process to precisely fabricate high-quality lithium niobate microstructures with smooth sidewalls, high aspect ratio, and excellent optical quality, effectively overcoming the limitations of traditional etching methods.
[0056] In the description of this specification, references to terms such as "specific example" or "some examples" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.
[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method of selectively etching lithium niobate using an ion implantation assisted wet process, characterized in that, The method comprises the following steps: S1, preparing a metal adhesion layer on the surface of lithium niobate; S2, spin-coating a photoresist layer on the surface of the metal adhesion layer; S3, preparing a mask layer of the patterned metal adhesion layer and the photoresist layer by developing, exposing and wet etching; S4, preparing a charge absorption layer on the surface of the mask layer and the surface of the lithium niobate to be etched; S5, modifying the lithium niobate in the area to be etched by multiple ion implantations; wherein the ion implantation has an implantation energy ranging from 0.5 to 20 MeV and an implantation dose ranging from 1×1010 to 1×1014 ions / cm2; the depth of the etched pattern of the lithium niobate increases with the number of ion implantations until the desired etched structure of the lithium niobate is obtained. 13 ~1×10 16 ions / cm 2 2; the depth of the etched pattern of the lithium niobate increases with the number of ion implantations until the desired etched structure of the lithium niobate is obtained. S6, removing the surface charge absorption layer and removing the damaged area after ion implantation by using a wet etching process; S7, removing the mask layer on the surface after etching to obtain the etched lithium niobate structure.
2. The method for selectively etching lithium niobate using an ion implantation-assisted wet process according to claim 1, characterized in that, Step S1 specifically comprises: preparing a metal adhesion layer on the surface of the lithium niobate by one of the following methods: magnetron sputtering, thermal evaporation, atomic layer deposition and molecular beam epitaxy; The metal material of the metal adhesion layer is one or a combination of several of Cr, Ni, Cu, Fe, Co, Ir, Pt, Au, Ag, Ti and Zr.
3. The method of claim 1, wherein the method is a method of selectively etching lithium niobate using an ion implantation assisted wet process. The type of photoresist in step S2 includes PMMA, SU-8, HSN, HSQ, CARs, PSPI, DNQ-Novolac positive glue, metal oxide glue or molecular glass glue.
4. The method of claim 1, wherein the method is a method of selectively etching lithium niobate using an ion implantation assisted wet process. The preparation method of the charge absorption layer in step S4 is one of magnetron sputtering, thermal evaporation, atomic layer deposition and molecular beam epitaxy.
5. The method of claim 1, wherein the method is a method of selectively etching lithium niobate using an ion implantation assisted wet process. In step S5, the implanted ion species is one or a combination of several of H, He, Ar, B, P, O, C, As, Sb, Si, Cu, Ti, Al and Ge.
6. The method of claim 1, wherein the method is a method of selectively etching lithium niobate using an ion implantation assisted wet process. The etching in step S6 is one of full etching, deep etching and shallow etching.
7. The method for selectively etching lithium niobate using an ion implantation-assisted wet process according to claim 6, characterized in that, In the case of full etching or deep etching, high-energy implantation is performed first, and then the implantation energy is gradually reduced to achieve implantation from deep to shallow.
8. The method of claim 6, wherein the method is a method of selectively etching lithium niobate in an ion implantation assisted wet process, and wherein the method comprises: providing a substrate comprising lithium niobate; and exposing the substrate to a solution comprising a mixture of hydrogen peroxide and water, wherein the solution has a pH of about 2 to about 5. In the case of shallow etching, the energy is adjusted first, then the corresponding area with less surface defects is ground off, and then wet etching is performed.
9. The method of claim 1, wherein the method is a method of selectively etching lithium niobate using an ion implantation assisted wet process. In step S6, the etching solution used in the wet etching process is an acidic or alkaline solution.
10. The method of claim 1, wherein the method is a method of selectively etching lithium niobate using an ion implantation assisted wet process. The prepared thickness of the metal adhesion layer is 1-500 nm; and / or, The prepared thickness of the photoresist is 1-2000 nm; and / or, The thickness of the charge absorption layer is 50-100 nm.