Lithium niobate with sub-10 nanometer resolution and method of processing the same

Abstract

The application provides a processing method of lithium niobate with sub-10-nanometer resolution. The application combines and synergistically optimizes focused inert gas ion beam direct writing, heat treatment and wet chemical etching process, and finally realizes the etching processing of lithium niobate. The method has high manufacturing precision and can realize sub-10-nanometer resolution; the side wall appearance can be controlled in the range of 90° (vertical side wall) to 120° (inscribed side wall), and the depth-width ratio can be realized from 1:20 to 15:1. Compared with the common lithium niobate processing technology at present, the method can realize high-precision processing only by three steps (one ion irradiation, one heat treatment and one chemical wet etching), and has the advantages of simple manufacturing process, high efficiency, no need to prepare a mask, high flexibility, no introduction of metal pollution, strong matching adaptability with other processes and device design.

Description

Technical Field

[0001] This invention belongs to the field of lithium niobate nanofabrication technology, specifically relating to a lithium niobate with sub-ten nanometer resolution and its processing method. Background Technology

[0002] Lithium niobate (LiNbO3), hailed as "optical silicon," possesses exceptional electro-optic, acousto-optic, and nonlinear optical properties. These properties make it a key functional material for a range of advanced optical applications. In recent years, emerging research on metasurfaces and high-density integrated photonic chips has placed increasingly stringent demands on the nanoscale fabrication of lithium niobate, particularly requiring high-quality patterning with resolutions below 30 nm. However, the inherent hardness and chemical inertness of lithium niobate severely hinder the realization of its high-precision nanostructures. Currently, typical fabrication techniques for high-precision LiNbO3 micro / nanostructures include electron beam lithography (EBL) combined with dry etching, gallium (Ga) ion-based focused ion beam (FIB) etching, and femtosecond laser ablation, but these techniques present significant challenges in terms of processing accuracy and sidewall morphology. Regarding processing accuracy, even the most advanced Ga-FIB etching process can only achieve a minimum linewidth of approximately 30 nm and introduces metal ion contamination, affecting the electrical and optical performance of the device. The widely used EBL combined with dry etching (such as ICP / RIE) technology can only achieve a final precision of about 30-50 nm on lithium niobate. Therefore, existing methods cannot meet the processing requirements of sub-30 nm feature structures for advanced applications. Furthermore, traditional manufacturing methods often produce structures with non-vertical sidewalls (sidewall inclination angles typically in the range of 60°–80°) and low aspect ratios (typically about 1:1–3:1), mainly due to the redeposition of etching byproducts and the limited etching selectivity between the mask material and lithium niobate. These problems significantly reduce the optical propagation loss and mode manipulation efficiency of lithium niobate devices. These manufacturing challenges hinder the development of lithium niobate-based nanodevices and limit their high-end photonics applications, thus urgently requiring innovative processing technologies. Summary of the Invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide a processing method for lithium niobate with sub-ten nanometer resolution. The processing method provided by the present invention has high manufacturing precision, the etching structure can achieve sub-ten nanometer resolution, the sidewall morphology can be controlled within the range of 90° vertical sidewall to 120° internal sidewall, and the depth-to-width ratio can be 1:20 to 15:1.

[0004] This invention provides a method for processing lithium niobate with sub-10 nanometer resolution, comprising the following steps:

[0005] A) Ionize a patterned area on the surface of a single-crystal lithium niobate using a focused inert gas ion beam to obtain the ion-irradiated product.

[0006] B) The product irradiated with ions is subjected to heat treatment to obtain a heat-treated product;

[0007] C) Etch the heat-treated product to obtain a product with an etched structure;

[0008] D) The product with the etched structure is cleaned and dried to obtain lithium niobate with sub-10 nanometer resolution.

[0009] Preferably, the inert gas ions are selected from He ions or Ne ions.

[0010] Preferably, the ion energy of the ion irradiation is 1~100 keV, and the surface dose of the irradiation is 1E14 ions / cm. 2 ~1E18ions / cm 2 Or the linear dose of irradiation is 0.1 nC / μm to 100 nC / μm;

[0011] The surface size of the irradiated area of ​​the product after ion irradiation is 1 nm to 500 μm.

[0012] The depth of the irradiated area is 5~500 nm.

[0013] Preferably, the heat treatment temperature is 100~1000℃, the time is 1min~8h, and the gas environment is vacuum, inert gas atmosphere, air or oxygen-containing atmosphere.

[0014] Preferably, the heat treatment refers to the use of heat treatment equipment such as an annealing furnace, a rapid hot annealing machine, an oxidation furnace, LPCVD, or a hot plate.

[0015] Preferably, the etching is selected from chemical etching, and the chemical etching is selected from wet etching.

[0016] Preferably, the etchant used in the wet etching is a mixed solution of 40% HF and deionized water, wherein the volume ratio of 40% HF to deionized water is 100:1 to 1:100.

[0017] Preferably, the wet etching temperature is room temperature to 90°C, and the time is 0.1 to 60 minutes.

[0018] Preferably, the cleaning method is to soak in pure water, isopropanol, or alcohol in sequence.

[0019] The drying method is either nitrogen blowing or natural air drying.

[0020] The present invention also provides a lithium niobate processed by the above processing method, wherein the surface pattern of the etched structure of the lithium niobate with sub-ten nanometer resolution reaches the sub-ten nanometer level, the sidewall morphology can be controlled within the range of 90° vertical sidewall to 120° incised sidewall, and the aspect ratio can be achieved from 1:20 to 15:1.

[0021] Compared with existing technologies, this invention provides a processing method for lithium niobate with sub-10 nanometer resolution, comprising the following steps: A) irradiating a patterned region on the surface of a single-crystal lithium niobate using a focused inert gas ion beam to obtain an ion-irradiated product; B) heat-treating the ion-irradiated product to obtain a heat-treated product; C) etching the heat-treated product to obtain a product with an etched structure; D) cleaning and drying the product with the etched structure to obtain lithium niobate with sub-10 nanometer resolution. This invention combines and synergistically optimizes focused inert gas ion beam direct writing, heat treatment, and wet chemical etching processes to ultimately achieve the etching processing of lithium niobate. This method offers high manufacturing precision, achieving sub-10 nanometer resolution; the sidewall morphology can be controlled within the range of 90° (vertical sidewall) to 120° (inward-cut sidewall), and the aspect ratio can be achieved from 1:20 to 15:1. Compared with the current common lithium niobate processing technology, this method can achieve high-precision processing with only three steps (one ion irradiation, one heat treatment and one chemical wet etching). Its manufacturing process is simple and efficient, does not require the preparation of a mask, is highly flexible, does not introduce metal contamination, and has strong compatibility with other processes and device designs. Attached Figure Description

[0022] Figure 1 This is a flowchart of the lithium niobate processing method provided by the present invention;

[0023] Figure 2 This is a schematic diagram of the process steps of the present invention;

[0024] Figure 3 This is a comparison of etching results (cross-sectional SEM images) with and without heat treatment in the technical route of this invention, and simulated etching thresholds;

[0025] Figure 4 This is a SEM image of the linear trench structure of lithium niobate obtained by this invention (taken at a tilt angle of 53°).

[0026] Figure 5 This is a SEM image (top view) of the linear trench structure obtained by this invention.

[0027] Figure 6 This is a SEM image of the lithium niobate nanopore array structure obtained by this invention;

[0028] Figure 7This is a SEM image of the lithium niobate checkerboard array structure obtained by this invention;

[0029] Figure 8 This is a SEM image of the rectangular structure of lithium niobate obtained by this invention;

[0030] Figure 9 This is a SEM image (taken at a 53° angle) of the circular lithium niobate structure obtained by this invention. Detailed Implementation

[0031] This invention provides a method for processing lithium niobate with sub-10 nanometer resolution, comprising the following steps:

[0032] A) Ionize a patterned area on the surface of a single-crystal lithium niobate using a focused inert gas ion beam to obtain the ion-irradiated product.

[0033] B) The product irradiated with ions is subjected to heat treatment to obtain a heat-treated product;

[0034] C) Etch the heat-treated product to obtain a product with an etched structure;

[0035] D) The product with the etched structure is cleaned and dried to obtain lithium niobate with sub-10 nanometer resolution.

[0036] See Figure 1 , Figure 1 A flowchart of the lithium niobate processing method provided by the present invention.

[0037] Specifically, the focused inert gas ion beam irradiation method of this invention refers to using a device capable of generating focused He / Ne ion beams, such as a helium ion microscope (HIM), to focus He / Ne inert gas ions with a certain energy into a beam spot with a diameter of nanometers to sub-nanometers, and then scanning and irradiating a specific patterned area of ​​a single-crystal lithium niobate sample. The sample material is single-crystal lithium niobate. The irradiated ions are inert gas ions, such as He ions and Ne ions. This invention does not impose any special restrictions on the shape of the specific patterned area; scanning and irradiation can be performed as needed. The shape of the irradiated area after irradiation can be a straight line, curve, rectangle, circle, ring, polygon, or irregular shape. The surface size of the irradiated area of ​​the product after ion irradiation is 1 nm to 500 μm, and can be any value between 1 nm, 5 nm, 10 nm, 50 nm, 100 nm, 200 nm, 500 nm, 1 μm, 5 μm, 10 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, or 1 nm to 500 μm.

[0038] The depth of the irradiated area is 5~500 nm, and can be any value between 5, 10, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, or 5~500 nm.

[0039] The ion energy of the ion irradiation is 1~100 keV, and can be 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or any value between 1~100 keV. The surface dose of the irradiation is 1E14 ions / cm². 2 ~1E18ions / cm 2 It can be 1E14 ions / cm 2 5E14ions / cm 2 1E15ions / cm 2 5E15ions / cm 2 1E16ions / cm 2 5E16ions / cm 2 1E17ions / cm 2 5E17ions / cm 2 1E18ions / cm 2 , or 1E14 ions / cm 2 ~1E18ions / cm 2 Any value between 0.1 nC / μm and 100 nC / μm; or the linear dose of irradiation is 0.1 nC / μm to 100 nC / μm, which can be 0.1, 0.5, 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or any value between 0.1 nC / μm and 100 nC / μm.

[0040] Next, the ion-irradiated product is subjected to heat treatment to obtain a heat-treated product. The heat treatment temperature is 100~1000℃, which can be 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, or any value between 100~1000℃. The time is 1min~8h, which can be 1min, 10min, 30min, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, or any value between 1min~8h. The gas environment is a vacuum, an inert gas atmosphere, air, or an oxygen-containing atmosphere. The heat treatment refers to the use of heat treatment equipment such as an annealing furnace, a rapid thermal annealing machine, an oxidation furnace, LPCVD, or a hot plate.

[0041] Then, the heat-treated product is etched to obtain a product with an etched structure. The etching is selected from chemical etching, preferably from wet etching.

[0042] The etchant used in the wet etching process is a mixed solution of 40% HF and deionized water. The volume ratio of 40% HF to deionized water is 100:1 to 1:100, and can be any value between 100:1, 100:10, 100:30, 100:50, 100:70, 100:100, 70:100, 50:100, 30:100, 10:100, 1:100, or 100:1 to 1:100, preferably 10:1 to 1:50. The wet etching temperature is between room temperature and 90°C, and can be any value between room temperature, 40, 50, 60, 70, 80, 90°C, or room temperature and 90°C. The etching time is between 0.1 and 60 minutes, and can be any value between 0.1, 1, 5, 10, 20, 30, 40, 50, 60 minutes, or 0.1 to 60 minutes, preferably 2 to 20 minutes. In this invention, the room temperature is defined as 23±5°C.

[0043] Finally, the product with the etched structure is cleaned and dried to obtain lithium niobate with sub-10 nanometer resolution. This invention does not impose any particular limitation on the cleaning and drying methods; any cleaning and drying method known to those skilled in the art is acceptable. Specifically, the cleaning method involves sequentially immersing in pure water, isopropanol, or alcohol; the drying method involves nitrogen blowing or natural air drying.

[0044] See Figure 2 , Figure 2 This is a schematic diagram of the process steps of the present invention. 1 represents a single-crystal lithium niobate substrate, 2 represents a focused inert gas ion beam, 3 represents an amorphous region generated after ion beam irradiation of the substrate, 4 represents an amorphous region after partial lattice repair following heat treatment, and 5 represents an etched region formed after being removed by wet chemical etching, cleaning, and drying.

[0045] The specific process is as follows: First, a focused inert gas ion beam 2 is used to scan and irradiate the desired position and pattern on the surface of a single-crystal lithium niobate substrate 1. Due to the interaction between the inert gas ions and lithium niobate, the single-crystal lithium niobate directly below the incident point undergoes amorphization, forming a teardrop-shaped amorphous region 3. Then, a heat treatment process is used to controllably repair the damaged lattice of region 3, resulting in a corrected amorphous region 4. Finally, a wet etchant is used to selectively etch region 4, and the sample is cleaned and dried to remove residual wet etchant, ultimately obtaining the etched structure 5. Figure 3It is evident that the etch boundary shrinks significantly after heat treatment. This is because heat treatment intensifies atomic thermal motion, repairs some lattice defects, and reduces the overall equivalent displacement per atom (DPA, a quantitative indicator of lattice damage), thereby shrinking the area above the reaction threshold. The synergistic effect of DPA spatial distribution and etching threshold determines the final etch cross-sectional morphology (etch linewidth, sidewall angle, and aspect ratio). DPA is determined by ion type, dosage, energy, heat treatment time, and temperature, while the etching threshold is determined by etchant, etching temperature, and time.

[0046] The lithium niobate processing method provided in this application has the following beneficial effects:

[0047] (1) Preliminary definition of target pattern by focusing He / Ne ion beam irradiation: This method utilizes the advantage that He / Ne ion beam can be focused into a nanometer to sub-nanometer beam spot for scanning direct writing pattern definition, without the need for a mask. It is more flexible, simpler and has higher resolution than the traditional method of making a patterned mask and then transferring the pattern to lithium niobate. At the same time, He / Ne ions are light ions. Compared with Ga ions used in traditional FIB, they have better controllability and linewidth compression potential for the modulation of lattice damage spatial distribution and final etching morphology in lithium niobate, and also have higher resolution. In addition, He / Ne ions are inert gas ions, which will not introduce metal ion contamination, are more friendly to device performance and have higher process adaptability.

[0048] (2) Combining focused He / Ne ion beam irradiation with wet etching process can make full use of the sub-nanometer beam diameter and positioning accuracy of focused He / Ne ion beam, and can also achieve lithium niobate etching at a relatively low dose. This overcomes the problems of low sputtering efficiency, lattice distortion / expansion leading to pattern deformation and sharp decrease in resolution when directly using focused He / Ne ion beam to process lithium niobate, thus enabling high-precision processing.

[0049] (3) By using heat treatment to controllably and finitely repair the lattice damage of lithium niobate in the irradiated area, the degree of damage in different regions within the nanometer range can be precisely controlled, maximizing the spatial contrast of the etching rate and achieving sub-ten nanometer etching precision. Simultaneously, this controllable lattice repair can precisely control the sidewall morphology, achieving a range from 120° incised sidewalls to 90° vertical sidewalls. This is one of the key process control methods of this invention.

[0050] (4) By combining heat treatment with chemical etching, the etching threshold is artificially controlled and optimized to match the spatial distribution of etching rate, thereby improving etching selectivity and ultimately achieving etching precision down to the sub-10 nanometer level. This is another key process control method of the present invention.

[0051] To further understand the present invention, the following description, in conjunction with embodiments, illustrates the lithium niobate with sub-10 nanometer resolution and its processing method provided by the present invention. The scope of protection of the present invention is not limited by the following embodiments.

[0052] Example 1:

[0053] Step 1: Ionize a specific patterned region on the surface of a single-crystal lithium niobate using a focused He / Ne ion beam.

[0054] Step 2: Perform heat treatment on the sample obtained in Step 1.

[0055] Step 3: Use a wet etching agent to chemically etch the sample obtained in Step 2 to form an etched structure corresponding to the shape of the ion irradiation region.

[0056] Step 4: Clean and dry the sample obtained in Step 3 to remove residual wet etching agent.

[0057] The focused He / Ne ion beam irradiation method described in step 1 involves using a helium ion microscope to focus high-energy He ions and scan to irradiate a specific region of the sample. The ion energy is 30 keV, the substrate material is single-crystal lithium niobate, and the irradiation region on the two-dimensional plane is a rectangular slit with a width of 5 nm and a length of 5 μm. The irradiation dose is 5E15 ions / cm. 2 .

[0058] In step 2, the heat treatment method is to anneal the sample using a rapid thermal annealing machine at a temperature of 500°C for 4 minutes in an air atmosphere.

[0059] In step 3, the wet etching agent is a mixture of 40% HF and deionized water at a volume ratio of 1:10. The etching time is 10 min, and the temperature is 40℃. The resulting etched structure is shown below. Figure 4 As shown in (a).

[0060] Figure 4 This is a SEM image of the linear trench structure of lithium niobate obtained by the present invention (taken at a tilt angle of 53°). Figure 4 (a) The trench linewidth is 13nm, the trench depth is 130nm, the depth-to-width ratio is approximately 10:1, and the sidewall inclination angle is 90°.

[0061] In step 4, the cleaning method involves immersing the item in pure water followed by isopropanol. The drying method involves blowing the item with nitrogen gas.

[0062] Example 2:

[0063] Step 1: Ionize a specific patterned region on the surface of a single-crystal lithium niobate using a focused He / Ne ion beam.

[0064] Step 2: Perform heat treatment on the sample obtained in Step 1.

[0065] Step 3: Use a wet etching agent to chemically etch the sample obtained in Step 2 to form an etched structure corresponding to the shape of the ion irradiation region.

[0066] Step 4: Clean and dry the sample obtained in Step 3 to remove residual wet etching agent.

[0067] The focused He / Ne ion beam irradiation method described in step 1 involves using a helium ion microscope to focus high-energy He ions and scan to irradiate a specific region of the sample. The ion energy is 30 keV, the substrate material is single-crystal lithium niobate, and the irradiation region on the two-dimensional plane is a rectangular slit with a width of 1 nm and a length of 5 μm. The irradiation dose is 1E18 ions / cm². 2 .

[0068] In step 2, the heat treatment method involves annealing the sample using a rapid thermal annealing machine at a temperature of 800°C for 4 minutes in a nitrogen atmosphere.

[0069] In step 3, the wet etching agent is a mixture of 40% HF and deionized water at a volume ratio of 100:1. The etching time is 2 minutes, and the temperature is room temperature. The resulting etched structure is shown below. Figure 4 As shown in (b). Figure 4 This is a SEM image of the linear trench structure of lithium niobate obtained by the present invention (taken at a tilt angle of 53°). Figure 4 (b) The trench linewidth is 160 nm, the trench depth is 210 nm, the depth-to-width ratio is approximately 1.3:1, and the sidewall inclination angle is 90°.

[0070] In step 4, the cleaning method involves immersing the item in pure water followed by isopropanol. The drying method involves blowing the item with nitrogen gas.

[0071] Example 3:

[0072] Step 1: Ionize a specific patterned region on the surface of a single-crystal lithium niobate using a focused He / Ne ion beam.

[0073] Step 2: Perform heat treatment on the sample obtained in Step 1.

[0074] Step 3: Use a wet etching agent to chemically etch the sample obtained in Step 2 to form an etched structure corresponding to the shape of the ion irradiation region.

[0075] Step 4: Clean and dry the sample obtained in Step 3 to remove residual wet etching agent.

[0076] In step 1, the focused He / Ne ion beam irradiation method involves using a helium ion microscope to focus high-energy He ions and scan to irradiate a specific region of the sample. The ion energy is 30 keV, the substrate material is single-crystal lithium niobate, the irradiation region is a one-dimensional straight line with a length of 10 μm, and the irradiation dose is 10 nC / μm.

[0077] In step 2, the heat treatment method is to anneal the sample using a rapid thermal annealing machine at a temperature of 500°C for 10 minutes in a vacuum atmosphere.

[0078] In step 3, the wet etching agent is a mixture of 40% HF and deionized water at a volume ratio of 1:10. The etching time is 10 min, and the temperature is 40℃. The resulting etched structure is shown below. Figure 4 As shown in (c). Figure 4 This is a SEM image of the linear trench structure of lithium niobate obtained by the present invention (taken at a tilt angle of 53°). Figure 4 (c) The trench linewidth is 60nm, the trench depth is 180nm, the depth-to-width ratio is about 3:1, and the sidewall inclination angle is 120°.

[0079] In step 4, the cleaning method involves immersing the item in pure water followed by isopropanol. The drying method involves blowing the item with nitrogen gas.

[0080] Example 4:

[0081] Step 1: Ionize a specific patterned region on the surface of a single-crystal lithium niobate using a focused He / Ne ion beam.

[0082] Step 2: Perform heat treatment on the sample obtained in Step 1.

[0083] Step 3: Use a wet etching agent to chemically etch the sample obtained in Step 2 to form an etched structure corresponding to the shape of the ion irradiation region.

[0084] Step 4: Clean and dry the sample obtained in Step 3 to remove residual wet etching agent.

[0085] In step 1, the focused He / Ne ion beam irradiation method involves using a helium ion microscope to focus high-energy He ions and scan to irradiate a specific region of the sample. The ion energy is 30 keV, the substrate material is single-crystal lithium niobate, the irradiation region is a one-dimensional straight line with a length of 5 μm, and the irradiation dose is 0.1 nC / μm.

[0086] In step 2, the heat treatment method is to anneal the sample using a rapid thermal annealing machine at a temperature of 400°C for 5 minutes in an N2 atmosphere.

[0087] In step 3, the wet etching agent is a mixture of 40% HF and deionized water at a volume ratio of 1:20. The etching time is 10 min, and the temperature is 40℃. The resulting etched structure is shown below. Figure 5 As shown. Figure 5 This is a SEM image (top view) of the linear trench structure obtained by this invention. The trench linewidth is 9 nm.

[0088] Figure 4 and Figure 5 This invention demonstrates that it has a sub-10 nanometer processing resolution and can achieve sidewalls with tilt angles of 90° to 120°.

[0089] In step 4, the cleaning method involves immersing the item in pure water followed by isopropanol. The drying method involves blowing the item with nitrogen gas.

[0090] Example 5:

[0091] Step 1: Ionize a specific patterned region on the surface of a single-crystal lithium niobate using a focused He / Ne ion beam.

[0092] Step 2: Perform heat treatment on the sample obtained in Step 1.

[0093] Step 3: Use a wet etching agent to chemically etch the sample obtained in Step 2 to form an etched structure corresponding to the shape of the ion irradiation region.

[0094] Step 4: Clean and dry the sample obtained in Step 3 to remove residual wet etching agent.

[0095] In step 1, the focused He / Ne ion beam irradiation method involves using a helium ion microscope to focus high-energy He ions and scan and irradiate a specific region of the sample. The ion energy is 35 keV, the substrate material is single-crystal lithium niobate, the irradiation region is an orthogonally arranged circular array with a diameter of 15 nm and a period of 50 nm, and the irradiation dose is 1E17 ions / cm². 2 .

[0096] In step 2, the heat treatment method is to use an annealing furnace to heat treat the sample. The heat treatment temperature is 200℃, the heat treatment time is 2h, and the ambient atmosphere is O2.

[0097] In step 3, the wet etching agent is a mixture of 40% HF and deionized water at a volume ratio of 1:5. The etching time is 5 minutes, and the temperature is 60°C. The resulting etched structure is shown below. Figure 6 As shown. Figure 6 This is a SEM image of the lithium niobate nanopore array structure obtained by this invention. The diameter of the circular pores is 18±2 nm.

[0098] In step 4, the cleaning method involves soaking in pure water and then washing with isopropanol in sequence. The drying method is natural air drying.

[0099] Example 6:

[0100] Step 1: Ionize a specific patterned region on the surface of a single-crystal lithium niobate using a focused He / Ne ion beam.

[0101] Step 2: Perform heat treatment on the sample obtained in Step 1.

[0102] Step 3: Use a wet etching agent to chemically etch the sample obtained in Step 2 to form an etched structure corresponding to the shape of the ion irradiation region.

[0103] Step 4: Clean and dry the sample obtained in Step 3 to remove residual wet etching agent.

[0104] The focused He / Ne ion beam irradiation method described in step 1 involves using a helium ion microscope to focus high-energy He ions and scan and irradiate a specific region of the sample. The ion energy is 40 keV, the substrate material is single-crystal lithium niobate, the irradiation region is a checkerboard-patterned square hollow two-dimensional rectangular array with a side length of 150 nm, and the irradiation dose is 1E17 ions / cm². 2 .

[0105] In step 2, the heat treatment method is to anneal the sample using a rapid thermal annealing machine at a temperature of 300°C for 10 minutes in an N2 atmosphere.

[0106] In step 3, the wet etching agent is a mixture of 40% HF and deionized water at a volume ratio of 1:50. The etching time is 30 min, and the temperature is 80℃. The resulting etched structure is shown below. Figure 7 As shown. Figure 7 This is a SEM image of the lithium niobate checkerboard array structure obtained by this invention. The checkerboard square has a side length of 160 nm.

[0107] In step 4, the cleaning method involves immersing the item in pure water followed by isopropanol. The drying method involves blowing the item with nitrogen gas.

[0108] Example 7:

[0109] Step 1: Ionize a specific patterned region on the surface of a single-crystal lithium niobate using a focused He / Ne ion beam.

[0110] Step 2: Perform heat treatment on the sample obtained in Step 1.

[0111] Step 3: Use a wet etching agent to chemically etch the sample obtained in Step 2 to form an etched structure corresponding to the shape of the ion irradiation region.

[0112] Step 4: Clean and dry the sample obtained in Step 3 to remove residual wet etching agent.

[0113] In step 1, the focused He / Ne ion beam irradiation method involves using a helium ion microscope to focus high-energy Ne ions and scan and irradiate a specific region of the sample. The ion energy is 38 keV, the substrate material is single-crystal lithium niobate, and the irradiation region is a rectangle of different sizes, with dimensions of 1×1 μm and 2×2 μm. The irradiation dose is 1E15 ions / cm². 2 .

[0114] In step 2, the heat treatment method is to use a vacuum annealing furnace to heat the sample at a temperature of 100°C for 0.5 hours, with a chamber vacuum degree of 1E-5 Torr.

[0115] In step 3, the wet etching agent is a mixture of 40% HF and deionized water at a volume ratio of 50:1. The etching time is 60 minutes, and the temperature is 85℃. The resulting etched structure is shown below. Figure 8 As shown. Figure 8 This is a SEM image of the rectangular lithium niobate structure obtained by this invention. The side lengths of the rectangles are 1×1μm and 2×2μm, respectively.

[0116] In step 4, the cleaning method involves immersing the item in pure water followed by isopropanol. The drying method involves blowing the item with nitrogen gas.

[0117] Example 8:

[0118] Step 1: Ionize a specific patterned region on the surface of a single-crystal lithium niobate using a focused He / Ne ion beam.

[0119] Step 2: Perform heat treatment on the sample obtained in Step 1.

[0120] Step 3: Use a wet etching agent to chemically etch the sample obtained in Step 2 to form an etched structure corresponding to the shape of the ion irradiation region.

[0121] Step 4: Clean and dry the sample obtained in Step 3 to remove residual wet etching agent.

[0122] In step 1, the focused He / Ne ion beam irradiation method involves using a helium ion microscope to focus high-energy He ions and scan and irradiate a specific region of the sample. The ion energies are 10 keV and 20 keV, the substrate material is single-crystal lithium niobate, and the irradiation region is a circle with a diameter of 700 nm. The irradiation dose is 5E16 ions / cm². 2 .

[0123] In step 2, the heat treatment method is to use a rapid thermal annealing machine to perform heat treatment on the sample at a temperature of 100°C for 3 minutes, with an air atmosphere for annealing.

[0124] In step 3, the wet etching agent is a mixture of 40% HF and deionized water at a volume ratio of 5:1. The etching time is 3 minutes, and the temperature is 50°C. The resulting etched structure is shown below. Figure 9 As shown. Figure 9 This is a SEM image of the rectangular lithium niobate structure obtained by this invention. The diameter of the circle is 750 nm, and the depths are 75 nm and 150 nm, with aspect ratios of 1:10 and 1:5, respectively.

[0125] In step 4, the cleaning method involves immersing the item in pure water followed by isopropanol. The drying method involves blowing the item with nitrogen gas.

[0126] Example 9:

[0127] Step 1: Ionize a specific patterned region on the surface of a single-crystal lithium niobate using a focused He / Ne ion beam.

[0128] Step 2: Perform heat treatment on the sample obtained in Step 1.

[0129] Step 3: Use a wet etching agent to chemically etch the sample obtained in Step 2 to form an etched structure corresponding to the shape of the ion irradiation region.

[0130] Step 4: Clean and dry the sample obtained in Step 3 to remove residual wet etching agent.

[0131] The focused He / Ne ion beam irradiation method described in step 1 involves using a helium ion microscope to focus high-energy He ions and scan to irradiate a specific region of the sample. The ion energy is 30 keV, the substrate material is single-crystal lithium niobate, and the irradiation region on the two-dimensional plane is a rectangular slit with a width of 5 nm and a length of 10 μm. The irradiation dose is 6E17 ions / cm². 2

[0132] In step 2, the heat treatment method is to use a rapid thermal annealing machine to perform heat treatment on the sample at a temperature of 350°C for 3.5 minutes, with a nitrogen atmosphere.

[0133] In step 3, the wet etching agent is a mixture of 40% HF and deionized water at a volume ratio of 1:10. The etching time is 5 minutes, and the temperature is 40°C. The resulting etched structure is shown in [reference needed]. Figure 3 , Figure 3 The etching results (cross-sectional SEM images) with and without heat treatment in Example 9 and Comparative Example 1 are compared with the simulated etching threshold. Figure 3As shown in the lower left SEM image, the etched trench has a linewidth of 15 nm, a depth of 100 nm, and a sidewall inclination of 90°.

[0134] In step 4, the cleaning method involves immersing the item in pure water followed by isopropanol. The drying method involves blowing the item with nitrogen gas.

[0135] Comparative Example 1

[0136] Based on Example 9, step 2 is omitted, i.e., heat treatment is not performed.

[0137] See Figure 3 , Figure 3 The etching results (cross-sectional SEM images) with and without heat treatment in Example 9 and Comparative Example 1 are compared with the simulated etching threshold. Figure 3 As shown in the two figures above, the cross-sectional shape of the etched structure is similar to that of a water droplet. The width of the etched structure surface pattern is 55nm, the widest point in the depth direction is 180nm, the depth is 250nm, and the sidewall of the etched structure is incised at an angle of 110°.

[0138] The above experimental results demonstrate that by precisely controlling the heat treatment process parameters, the present invention can controllably and finitely repair the lattice damage of lithium niobate in the irradiated area, thereby precisely controlling the degree of damage in different areas within the nanometer range and precisely controlling the sidewall morphology, achieving sub-ten nanometer etching accuracy and a sidewall tilt angle of 90°~120°.

[0139] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for processing lithium niobate with sub-10 nanometer resolution, characterized in that, Includes the following steps: A) Ionize a patterned area on the surface of a single-crystal lithium niobate using a focused inert gas ion beam to obtain the ion-irradiated product. B) The product irradiated with ions is subjected to heat treatment to obtain a heat-treated product; C) Etch the heat-treated product to obtain a product with an etched structure; D) The product with the etched structure is cleaned and dried to obtain lithium niobate with sub-10 nanometer resolution.

2. The processing method according to claim 1, characterized in that, The inert gas ions are selected from He ions or Ne ions.

3. The processing method according to claim 1, characterized in that, The ion energy of the ion irradiation is 1~100 keV, and the surface dose of the irradiation is 1E14 ions / cm. 2 ~1E18ions / cm 2 Or the linear dose of irradiation is 0.1 nC / μm to 100 nC / μm; The surface size of the irradiated area of ​​the product after ion irradiation is 1 nm to 500 μm. The depth of the irradiated area is 5~500 nm.

4. The processing method according to claim 1, characterized in that, The heat treatment temperature is 100~1000℃, the time is 1min~8h, and the gas environment is vacuum, inert gas atmosphere, air or oxygen-containing atmosphere.

5. The processing method according to claim 1, characterized in that, The heat treatment refers to the use of heat treatment equipment such as annealing furnace, rapid thermal annealing machine, oxidation furnace, LPCVD or hot plate.

6. The processing method according to claim 1, characterized in that, The etching is selected from chemical etching, and the chemical etching is selected from wet etching.

7. The processing method according to claim 6, characterized in that, The etching agent used in the wet etching process is a mixed solution of 40% HF and deionized water, wherein the volume ratio of 40% HF to deionized water is 100:1 to 1:

100.

8. The processing method according to claim 6, characterized in that, The wet etching temperature is room temperature to 90°C, and the time is 0.1 to 60 minutes.

9. The processing method according to claim 1, characterized in that, The cleaning method involves sequentially soaking in pure water, isopropanol, or alcohol. The drying method is either nitrogen blowing or natural air drying.

10. Lithium niobate processed by the processing method according to any one of claims 1 to 9, characterized in that, The surface pattern of the etched structure of lithium niobate with sub-10 nanometer resolution reaches the sub-10 nanometer level, and the sidewall morphology can be controlled within the range of 90° vertical sidewall to 120° incised sidewall, with an aspect ratio of 1:20 to 15:1.

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