Preparation method of orthogonal grating

Abstract

The invention belongs to the technical field of nano processing, and particularly discloses a preparation method of an orthogonal grating, which comprises the following steps: coating a negative electronic resist on a substrate and curing to obtain a substrate with an anti-corrosion glue layer; performing electron beam exposure on the anti-corrosion adhesive layer by using a scanning electron microscope, wherein the magnification factor of the scanning electron microscope is 2700-6700; and developing and fixing the substrate subjected to electron beam exposure to obtain the orthogonal grating with the frequency of 10000 lines / mm to 25000 lines / mm. According to the method, the scanning electron microscope is used for preparing the high-frequency orthogonal grating, a pattern generator and a mask plate are not needed, a professional electron beam photoetching system is also not needed, and the preparation means of the high-frequency orthogonal grating is more universal, convenient and low in cost.

Description

Technical Field

[0001] The invention discloses a method for preparing an orthogonal grating, and belongs to the technical field of nano-processing. Background Art

[0002] Orthogonal gratings are effective carriers for measuring deformation in electron beam moiré method, grid method and geometric phase analysis method. Their frequency and quality directly affect the sensitivity and accuracy of the test results.

[0003] There are four main methods for manufacturing orthogonal gratings on sample surfaces: extreme ultraviolet lithography, focused ion beam lithography, nanoimprint lithography, and electron beam lithography. All of these methods have their own advantages and disadvantages and are suitable for different processing needs and scenarios. Extreme ultraviolet lithography can provide high-energy light to achieve fine pattern transfer, but it is limited by factors such as the stability of the light source, the sensitivity of the photoresist, and the cost of the equipment. Focused ion beam lithography has extremely high resolution and precision and can achieve nanometer-level pattern preparation. However, its equipment cost is high and its production efficiency is relatively low. It is usually only used for specific high-precision processing needs. The advantages of nanoimprint lithography are simple process, low cost, high production efficiency, and high-resolution pattern replication. However, the production cost of its template is high and it is easily damaged during use, which limits the application potential of this method for imprinting gratings on sample surfaces. The advantages of electron beam lithography are fast pattern generation, high resolution, and mask-free exposure, but the equipment used for electron beam lithography is an electron beam lithography system, which leads to a high cost for preparing orthogonal gratings. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing an orthogonal grating to solve the technical problem of high cost in the existing process of preparing an orthogonal grating using an electron beam lithography machine.

[0005] The present invention provides a method for preparing an orthogonal grating, comprising:

[0006] Applying a negative electron resist on the substrate and curing the substrate to obtain a substrate with an anti-corrosion layer;

[0007] Performing electron beam exposure on the resist layer using a scanning electron microscope, wherein the magnification of the scanning electron microscope is 2700 to 6700;

[0008] The substrate after electron beam exposure is developed and fixed to obtain an orthogonal grating with a frequency of 10,000 lines / mm to 25,000 lines / mm.

[0009] Preferably, the scanning electron microscope has a scanning resolution of 1,536×1,024 and an acceleration voltage of 18 kV to 22 kV.

[0010] Preferably, the spot size of the electron beam in the scanning electron microscope is 4 to 6.

[0011] Preferably, the residence time of the electron beam in the scanning electron microscope is 60 μs to 140 μs.

[0012] Preferably, a negative electron resist is coated on the substrate, specifically comprising:

[0013] A coating machine is used to coat 5% to 7% of a negative electron resist by mass on the substrate; the rotation speed of the coating machine is 800 to 1200 rpm, and the coating time is 50 to 70 seconds.

[0014] Preferably, the curing temperature is 85° C. to 95° C., and the curing time is 3 minutes to 5 minutes.

[0015] Preferably, developing and fixing the substrate after electron beam exposure specifically includes:

[0016] Placing the electron beam exposed substrate in a 2% to 3% tetramethylammonium hydroxide developer for 10 to 15 seconds;

[0017] The developed substrate is placed in deionized water for fixing.

[0018] Preferably, the component of the negative electron resist is hydrogen silsesquioxane.

[0019] Preferably, before applying the negative electron resist on the substrate and curing it, the method further comprises:

[0020] preparing a substrate having a roughness of 15 nm to 25 nm;

[0021] A first conductive film layer is disposed on the substrate.

[0022] Preferably, after obtaining an orthogonal grating with a frequency of 10000 lines / mm to 25000 lines / mm, the method further comprises:

[0023] A second conductive film layer is disposed on the orthogonal grating.

[0024] Compared with the prior art, the method for preparing the orthogonal grating of the present invention has the following beneficial effects:

[0025] The present invention utilizes a scanning electron microscope to prepare a high-frequency orthogonal grating, does not require a pattern generator and a mask plate, and does not require a professional electron beam lithography system, making the preparation method of the high-frequency orthogonal grating more universal and convenient.

[0026] In the process of exposure using a scanning electron microscope, the present invention sets fewer variable parameters and has a wide range of electron beam residence time, that is, the low sensitivity of HSQ to exposure dose makes the instrument easy to operate, has low technical requirements, and facilitates the precise positioning of high-quality orthogonal gratings on the material surface.

[0027] The present invention prepares high-frequency and ultra-high-frequency orthogonal gratings of different frequencies by setting the magnification of the scanning electron microscope and the electron beam spot size during exposure, which can meet the multi-scale requirements in the characterization of material deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the process of preparing an orthogonal grating in an embodiment of the present invention.

[0029] Figure 2 The topography of the orthogonal grating with a frequency of 5191 lines / mm prepared in an embodiment of the present invention.

[0030] Figure 3 The topography of the orthogonal grating with a frequency of 7416 lines / mm prepared in the embodiment of the present invention.

[0031] Figure 4 The topography of the orthogonal grating with a frequency of 10011 lines / mm prepared in the embodiment of the present invention.

[0032] Figure 5 The topography of the orthogonal grating with a frequency of 12496 lines / mm prepared in the embodiment of the present invention.

[0033] Figure 6 The topography of the orthogonal grating with a frequency of 14832 lines / mm prepared in the embodiment of the present invention.

[0034] Figure 7 The topography of the orthogonal grating with a frequency of 17427 lines / mm prepared in the embodiment of the present invention.

[0035] Figure 8 This is a topographical image of an orthogonal grating having a frequency of 20023 lines / mm prepared in an embodiment of the present invention.

[0036] Fig. 9 The topography of the orthogonal grating with a frequency of 24843 lines / mm prepared in the embodiment of the present invention.

[0037] Fig.10 This is a 3D topography image of an orthogonal grating with a frequency of 10011 lines / mm according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0039] The embodiment of the present invention provides a method for preparing an orthogonal grating, such as Figure 1 As shown, the present invention provides a method for preparing an orthogonal grating, comprising:

[0040] Step 1: coating a negative electron resist on a substrate and curing the substrate to obtain a substrate with an anti-corrosion adhesive layer.

[0041] In the embodiment of the present invention, the substrate needs to be pre-processed before step 1 to reduce the device performance fluctuation caused by pollutants or interface defects and improve the processing accuracy and yield of the grating structure. The pre-processing specifically includes grinding, polishing and cleaning.

[0042] The roughness of the substrate surface has a great influence on the quality of the orthogonal grating, so the embodiment of the present invention grinds and polishes the substrate surface to a roughness of 15nm to 25nm, illustratively, 15nm, 18nm, 20nm, 22nm or 25nm, etc., preferably 20nm. Within this roughness range, a high-frequency orthogonal grating with stable performance can be obtained. The substrate used in the embodiment of the present invention is a silicon wafer.

[0043] The cleaning method of the substrate in the embodiment of the present invention is specifically as follows: placing the substrate in a mixed solution of acetone and alcohol for ultrasonic cleaning for 10 to 20 minutes to remove pollutants on the surface of the substrate, and then drying the substrate to keep the substrate dry.

[0044] In order to increase the conductivity of the substrate surface and reduce the proximity effect caused by charge accumulation when preparing the orthogonal grating, the embodiment of the present invention also sets a first conductive film layer on the cleaned substrate surface, and the first conductive film layer can be prepared by sputtering gold or platinum.

[0045] The embodiment of the present invention coats a negative electron resist on a substrate, specifically coats a negative electron resist on a first conductive film layer of the substrate after thermal baking, specifically comprising: coating a negative electron resist with a mass fraction of 5% to 7% on the substrate using a coating machine; the rotation speed of the coating machine is 800 to 1200 rpm, preferably 1000 rpm; the coating time is 50 to 70 seconds, preferably 60 seconds. Exemplarily, the coating machine is a coating machine of model KW-4A of the Institute of Microelectronics of the Chinese Academy of Sciences.

[0046] The mass fraction of the negative electron resist in the embodiment of the present invention can be 5%, 6% or 7%, etc., preferably 6%. The negative electron resist within this mass fraction range can ensure the formation of high-resolution graphics by subsequent exposure, and will not cause excessive reaction due to excessive mass fraction, resulting in line expansion or blurring.

[0047] The above-mentioned negative electronic resist is preferably HSQ (hydrogen silsesquioxane polymers), whose main component is hydrogen silsesquioxane. As a negative resist, HSQ has the advantages of high resolution, low line edge roughness, good corrosion resistance and stability. Exemplarily, the HSQ powder of the embodiment of the present invention is produced by AQM Company of Canada, and the model is H-SiOx-15.

[0048] In the embodiment of the present invention, the substrate coated with the negative electron resist is cured by placing the substrate coated with HSQ in an oven for curing at a curing temperature of 85° C. to 95° C., preferably 90° C., and a curing time of 3 minutes to 5 minutes, preferably 4 minutes. After curing, a substrate with an anti-corrosion adhesive layer is obtained.

[0049] Step 2: Perform electron beam exposure on the resist layer using a scanning electron microscope, wherein the magnification of the scanning electron microscope is 2700 to 6700.

[0050] The scanning resolution of the scanning electron microscope of the embodiment of the present invention is 1,536×1,024, the acceleration voltage is 18 kV to 22 kV, preferably 20 kV; the residence time of the electron beam is 60 μs to 140 μs; the working distance is 7 mm to 9 mm, preferably 8 mm.

[0051] Since the negative electron resist used in the embodiment of the present invention is HSQ, the present application limits the acceleration voltage of the scanning electron microscope to 18 kV to 22 kV, and the residence time of the electron beam to 60 μs to 140 μs, so as to avoid excessive acceleration voltage and excessive residence time of the electron beam, which may cause the electron beam to penetrate too deeply into the HSQ resist layer, thereby expanding the forward scattering range, blurring the edge of the graphic after development, and reducing the line width control accuracy; further, it can also avoid excessive electron beam energy aggravating the internal scattering of the HSQ resist layer, resulting in increased line edge roughness after development.

[0052] In order to avoid the proximity effect caused by charge accumulation when preparing the orthogonal grating, the spot size of the electron beam in the scanning electron microscope of the embodiment of the present invention is 4 to 6.

[0053] The frequency of the orthogonal grating is determined by the magnification of the scanning electron microscope. The embodiment of the present invention uses a scanning electron microscope with a scanning resolution of 1,536×1,024, so the relationship between the frequency f (unit: line / mm) of the orthogonal grating and the magnification M of the electron microscope is: f=3.708*M.

[0054] Step 3: Develop and fix the substrate after electron beam exposure to obtain an orthogonal grating with a frequency of 10,000 lines / mm to 25,000 lines / mm.

[0055] The developing and fixing of the substrate after electron beam exposure specifically includes:

[0056] Step 3.1, placing the electron beam exposed substrate in a tetramethylammonium hydroxide developer having a concentration of 2% to 3% and a temperature of 15° C. to 25° C. for development for 10 seconds to 15 seconds, preferably 12 seconds.

[0057] Exemplarily, the concentration of the tetramethylammonium hydroxide developer can be 2%, 2.38%, 2.5%, 3%, etc., preferably 2.38%; the temperature of the tetramethylammonium hydroxide developer can be 15°C, 20°C, 25°C, etc., preferably 20°C.

[0058] Step 3.2, the developed substrate is quickly placed in deionized water for fixing, and after fixing in deionized water for 5 minutes, the substrate is taken out and dried to obtain a high-frequency orthogonal grating with a frequency of 10,000 lines / mm to 25,000 lines / mm.

[0059] In order to further increase the conductivity of the obtained orthogonal grating and facilitate observation of the orthogonal grating morphology under a scanning electron microscope, a second conductive film layer is provided on the surface of the orthogonal grating in an embodiment of the present invention. The second conductive film layer is prepared by sputtering gold or platinum.

[0060] The preparation parameters of the embodiment of the present invention and the frequency of the obtained orthogonal grating are shown in Table 1.

[0061] Table 1 Preparation parameters and corresponding orthogonal grating frequencies

[0062]

[0063] As can be seen from Table 1, the present invention can prepare high-frequency orthogonal gratings with a frequency exceeding 10,000 lines / mm using a common scanning electron microscope, and the preparation method is simple and low in cost.

[0064] Figures 2 to 10 From the morphology images of orthogonal gratings of different frequencies prepared in the embodiments of the present invention, it can be seen that the grating points are clear and uniform, the grating pitch is consistent, the contrast is high, the grating quality is high, and it can be used for material deformation characterization.

[0065] The present invention utilizes a scanning electron microscope to prepare a high-frequency orthogonal grating, does not require a pattern generator and a mask plate, and does not require a professional electron beam lithography system, making the preparation method of the high-frequency orthogonal grating more universal and convenient.

[0066] In the process of exposure using a scanning electron microscope, the present invention sets fewer variable parameters and has a wide range of electron beam residence time, that is, the low sensitivity of HSQ to exposure dose makes the instrument easy to operate, has low technical requirements, and facilitates the precise positioning of high-quality orthogonal gratings on the material surface.

[0067] The present invention prepares high-frequency and ultra-high-frequency orthogonal gratings of different frequencies by setting the magnification of the scanning electron microscope and the electron beam spot size during exposure, which can meet the multi-scale requirements in the characterization of material deformation.

[0068] The above are only several embodiments of the present invention and are not intended to limit the present invention in any form. Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the profession, without departing from the scope of the technical solution of the present invention, using the above disclosed technical content to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing an orthogonal grating, characterized in that: include: Applying a negative electron resist on the substrate and curing the substrate to obtain a substrate with an anti-corrosion layer; Performing electron beam exposure on the resist layer using a scanning electron microscope, wherein the magnification of the scanning electron microscope is 2700 to 6700; The substrate after electron beam exposure is developed and fixed to obtain an orthogonal grating with a frequency of 10,000 lines / mm to 25,000 lines / mm.

2. The method for preparing an orthogonal grating according to claim 1, characterized in that: The scanning electron microscope has a scanning resolution of 1,536×1,024 and an accelerating voltage of 18 kV to 22 kV.

3. The method for preparing an orthogonal grating according to claim 2, characterized in that: The spot size of the electron beam in the scanning electron microscope is 4 to 6.

4. The method for preparing an orthogonal grating according to claim 3, characterized in that: The dwell time of the electron beam in the scanning electron microscope is 60 μs to 140 μs.

5. The method for preparing an orthogonal grating according to claim 1, characterized in that: Applying a negative electron resist on a substrate specifically comprises: A coating machine is used to coat 5% to 7% of a negative electron resist by mass on the substrate; the rotation speed of the coating machine is 800 to 1200 rpm, and the coating time is 50 to 70 seconds.

6. The method for preparing an orthogonal grating according to claim 1, characterized in that: The curing temperature is 85° C. to 95° C., and the curing time is 3 minutes to 5 minutes.

7. The method for preparing an orthogonal grating according to claim 1, characterized in that: Developing and fixing the substrate after electron beam exposure, specifically including: Placing the electron beam exposed substrate in a 2% to 3% tetramethylammonium hydroxide developer for 10 to 15 seconds; The developed substrate is placed in deionized water for fixing.

8. The method for preparing an orthogonal grating according to claim 1, characterized in that: The component of the negative electron resist is hydrogen silsesquioxane.

9. The method for preparing an orthogonal grating according to claim 1, characterized in that: Before coating a negative electronic resist on a substrate and curing it, the method further comprises: preparing a substrate having a roughness of 15 nm to 25 nm; A first conductive film layer is disposed on the substrate.

10. The method for preparing an orthogonal grating according to claim 1, characterized in that: After obtaining an orthogonal grating with a frequency of 10000 lines / mm to 25000 lines / mm, the method further includes: A second conductive film layer is disposed on the orthogonal grating.

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