A method for producing a planar single crystal silicon with reduced mid-frequency error and high-frequency roughness

Abstract

The application relates to the technical field of optical processing, in particular to a plane monocrystalline silicon processing method capable of reducing medium-frequency error and high-frequency roughness. The plane monocrystalline silicon blank processed and formed is sequentially subjected to grinding treatment, rough polishing treatment and twice fine polishing treatment, so that the preparation of the plane monocrystalline silicon capable of reducing medium-frequency error and high-frequency roughness is completed. The application also detects the medium-frequency error of the monocrystalline silicon surface through an interferometer and detects the roughness of the monocrystalline silicon surface through an atomic force microscope; it is found through detection that the preparation method can effectively reduce the medium-frequency error and high-frequency roughness of the plane monocrystalline silicon.

Description

Technical Field

[0001] This invention relates to the field of optical processing technology, and in particular to a method for preparing planar single-crystal silicon that reduces mid-frequency error and high-frequency roughness. Background Technology

[0002] In high-energy laser systems, single-crystal silicon mirrors are widely used. These mirrors need to achieve high-precision and high-stability beam transmission under prolonged irradiation by high-power-density lasers, placing extremely high demands on component precision and laser load capacity.

[0003] However, the intermediate frequency error on the surface of monocrystalline silicon can cause instability in laser systems, seriously affecting their safe operation. Therefore, it is essential to control the intermediate frequency error on the monocrystalline silicon surface. This intermediate frequency error is caused by regular, periodic removal processes. Current processing methods include magnetorheological polishing, ion beam polishing, and gasbag polishing, but these methods have varying capabilities in removing intermediate frequency errors.

[0004] At the same time, higher surface roughness will cause greater surface scattering, resulting in a loss of laser energy.

[0005] Therefore, it is crucial to provide a method for fabricating planar single-crystal silicon that reduces mid-frequency error and high-frequency roughness. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a method for preparing planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness. The present invention involves sequentially grinding, coarse polishing, and two fine polishing processes on a pre-formed planar single-crystal silicon blank to achieve the preparation of planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness. The present invention also uses an interferometer to detect the mid-frequency error of the single-crystal silicon surface and an atomic force microscope to detect the surface roughness; the tests revealed that the preparation method of the present invention can effectively reduce the mid-frequency error and high-frequency roughness of planar single-crystal silicon.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] This invention provides a method for preparing planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness, specifically including the following steps:

[0009] (S1) Grind the planar single-crystal silicon blanks that have been processed to reduce mid-frequency error and high-frequency roughness.

[0010] (S2) After step (S1) is completed, perform rough polishing to remove pinholes;

[0011] (S3) After step (S2) is completed, perform a first fine polishing to reduce mid-frequency error and roughness;

[0012] (S4) After step (S3) is completed, a second fine polishing is performed to further reduce the roughness, thus completing the preparation of planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness.

[0013] In one embodiment of the present invention, step (S1) of the grinding process specifically includes the following steps:

[0014] One surface of the machined planar single-crystal silicon blank with reduced mid-frequency error and high-frequency roughness is sequentially subjected to W40 diamond grinding, W28 diamond grinding, and W14 diamond grinding.

[0015] In one embodiment of the present invention, W40 diamond abrasive is used for grinding 20-25 microns, W28 diamond abrasive for grinding 10-15 microns, and W14 diamond abrasive for grinding 7-10 microns.

[0016] In one embodiment of the present invention, W40 diamond abrasive is used for grinding 20 filaments, W28 diamond abrasive for grinding 10 filaments, and W14 diamond abrasive for grinding 7 filaments.

[0017] In one embodiment of the present invention, step (S2) of the rough polishing process specifically includes the following steps:

[0018] A surface of a planar single-crystal silicon wafer, after grinding treatment to reduce mid-frequency error and high-frequency roughness, is rough polished using a silica polishing slurry.

[0019] In one embodiment of the present invention, a coarse polishing process of 5-8 filaments is performed using a silica polishing slurry.

[0020] In one embodiment of the present invention, a coarse polishing process of 5 filaments is performed using a silicon dioxide polishing slurry.

[0021] In one embodiment of the present invention, the mass fraction of the silica polishing slurry is 30-40%.

[0022] In one embodiment of the present invention, the mass fraction of the silica polishing slurry is 30%.

[0023] In one embodiment of the present invention, step (S3) specifically includes the following steps:

[0024] The coarsely polished planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness is placed in a special tooling fixture, which is placed on the surface of an asphalt disc and polished using a silica polishing slurry.

[0025] In one embodiment of the present invention, the dedicated tooling fixture is circular in shape, and the inner diameter of the circle is slightly larger than the size of the planar single crystal silicon.

[0026] In one embodiment of the present invention, a silica polishing slurry is used to polish 3-4 filaments.

[0027] In one embodiment of the present invention, a silica polishing slurry is used to polish 3 wires.

[0028] In one embodiment of the present invention, the mass fraction of the silica polishing slurry is 20-30%.

[0029] In one embodiment of the present invention, the mass fraction of the silicon dioxide polishing slurry is 20%.

[0030] In one embodiment of the present invention, step (S4) specifically includes the following steps:

[0031] The planar single-crystal silicon, after the first fine polishing treatment to reduce mid-frequency error and high-frequency roughness, is placed in a special tooling fixture. The special tooling fixture is placed on a soft cloth surface that is tightly attached to the workpiece tray. Polishing is then performed using silica polishing slurry.

[0032] In one embodiment of the present invention, a silica polishing slurry is used to polish 1-2 filaments.

[0033] In one embodiment of the present invention, a silicon dioxide polishing slurry is used to polish a wire.

[0034] In one embodiment of the present invention, the mass fraction of the silica polishing slurry is 20-30%.

[0035] In one embodiment of the present invention, the mass fraction of the silicon dioxide polishing slurry is 20%.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) A method for preparing planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness, which can effectively reduce the mid-frequency error of planar single-crystal silicon.

[0038] (2) A method for preparing planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness, which can effectively reduce the high-frequency roughness of planar single-crystal silicon. Detailed Implementation

[0039] This invention provides a method for preparing planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness, specifically including the following steps:

[0040] (S1) Grind the planar single-crystal silicon blanks that have been processed to reduce mid-frequency error and high-frequency roughness.

[0041] (S2) After step (S1) is completed, perform rough polishing to remove pinholes;

[0042] (S3) After step (S2) is completed, perform a first fine polishing to reduce mid-frequency error and roughness;

[0043] (S4) After step (S3) is completed, a second fine polishing is performed to further reduce the roughness, thus completing the preparation of planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness.

[0044] In one embodiment of the present invention, step (S1) of the grinding process specifically includes the following steps:

[0045] One surface of the machined planar single-crystal silicon blank with reduced mid-frequency error and high-frequency roughness is sequentially subjected to W40 diamond grinding, W28 diamond grinding, and W14 diamond grinding.

[0046] In one embodiment of the present invention, W40 diamond abrasive is used for grinding 20-25 microns, W28 diamond abrasive for grinding 10-15 microns, and W14 diamond abrasive for grinding 7-10 microns.

[0047] In one embodiment of the present invention, W40 diamond abrasive is used for grinding 20 filaments, W28 diamond abrasive for grinding 10 filaments, and W14 diamond abrasive for grinding 7 filaments.

[0048] In one embodiment of the present invention, step (S2) of the rough polishing process specifically includes the following steps:

[0049] A surface of a planar monocrystalline silicon wafer, after grinding treatment, is rough polished using a silica polishing slurry to reduce mid-frequency error and high-frequency roughness.

[0050] In one embodiment of the present invention, a coarse polishing process of 5-8 filaments is performed using a silica polishing slurry.

[0051] In one embodiment of the present invention, a coarse polishing process of 5 filaments is performed using a silicon dioxide polishing slurry.

[0052] In one embodiment of the present invention, the mass fraction of the silica polishing slurry is 30-40%.

[0053] In one embodiment of the present invention, the mass fraction of the silica polishing slurry is 30%.

[0054] In one embodiment of the present invention, step (S3) specifically includes the following steps:

[0055] The planar single-crystal silicon, after being rough polished to reduce mid-frequency error and high-frequency roughness, is placed in a special tooling fixture. The special tooling fixture is placed on the surface of an asphalt disc and polished using a silica polishing slurry.

[0056] In one embodiment of the present invention, the dedicated tooling fixture is circular in shape, and the inner diameter of the circle is slightly larger than the size of the planar single crystal silicon.

[0057] In one embodiment of the present invention, a silica polishing slurry is used to polish 3-4 filaments.

[0058] In one embodiment of the present invention, a silica polishing slurry is used to polish 3 wires.

[0059] In one embodiment of the present invention, the mass fraction of the silica polishing slurry is 20-30%.

[0060] In one embodiment of the present invention, the mass fraction of the silicon dioxide polishing slurry is 20%.

[0061] In one embodiment of the present invention, step (S4) specifically includes the following steps:

[0062] The planar single-crystal silicon, after the first fine polishing treatment to reduce mid-frequency error and high-frequency roughness, is placed in a special tooling fixture. The special tooling fixture is placed on a soft cloth surface that is tightly attached to the workpiece tray. Polishing is then performed using silica polishing slurry.

[0063] In one embodiment of the present invention, a silica polishing slurry is used to polish 1-2 filaments.

[0064] In one embodiment of the present invention, a silicon dioxide polishing slurry is used to polish a wire.

[0065] In one embodiment of the present invention, the mass fraction of the silica polishing slurry is 20-30%.

[0066] In one embodiment of the present invention, the mass fraction of the silicon dioxide polishing slurry is 20%.

[0067] The present invention will now be described in detail with reference to specific embodiments.

[0068] Unless otherwise specified, all reagents used in the following embodiments are commercially available reagents, and all detection methods and techniques used are conventional detection methods and techniques in the art.

[0069] Example 1

[0070] A method for preparing planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness mainly includes the following:

[0071] (1) Select a single crystal silicon blank lens with dimensions of 200mm (length) * 50mm (width) * 30mm (thickness). For one side of the 200mm * 50mm (hereinafter referred to as side A), use W40 diamond abrasive to grind 20 mils, W28 diamond abrasive to grind 10 mils, and W14 diamond abrasive to grind 7 mils.

[0072] (2) Rough polishing of surface A after grinding, using silica polishing slurry with a concentration of 30% to rough polish 5 filaments.

[0073] (3) Perform the first fine polishing on surface A. Place a special tooling fixture on the surface of the asphalt disc. The fixture is circular with an inner diameter of 201 mm, slightly larger than the length of the monocrystalline silicon, and a thickness of 5 mm. Use a silica polishing slurry with a concentration of 20% to perform fine polishing on surface A.

[0074] (4) Perform a second fine polishing on surface A. Place a special fixture on the surface of the felt cloth, with the cloth tightly against the workpiece tray. The special fixture is circular in shape, with an inner diameter of 201mm, slightly larger than the length of the single crystal silicon, and a thickness of 5mm. Use a silicon dioxide polishing slurry with a concentration of 20% to perform a fine polishing of 1 filament.

[0075] (5) Clean the polished single-crystal silicon and use an interferometer to test the mid-frequency error of the A-side of the single-crystal silicon. The result is 1.23urad. Use atomic force to test the high-frequency roughness of the A-side of the single-crystal silicon. The result is 0.31nm.

[0076] Example 2

[0077] A method for preparing planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness mainly includes the following:

[0078] (1) Select a single crystal silicon blank lens with dimensions of 240mm (length) * 60mm (width) * 30mm (thickness). For one side of the 240mm * 60mm (hereinafter referred to as side A), use W40 diamond abrasive to grind 25 mils, W28 diamond abrasive to grind 15 mils, and W14 diamond abrasive to grind 10 mils.

[0079] (2) Rough polishing of surface A after grinding, using silica polishing slurry with a concentration of 40% to rough polish 8 filaments.

[0080] (3) Perform the first fine polishing on surface A. Place a special tooling fixture on the surface of the asphalt disc. The fixture is circular with an inner diameter of 241 mm, slightly larger than the length of the single crystal silicon, and a thickness of 5 mm. Use a silica polishing slurry with a concentration of 30% to perform fine polishing on surface A.

[0081] (4) Perform a second fine polishing on surface A. Place a special tooling fixture on the velvet cloth surface. The velvet cloth and the special tooling fixture are circular in shape, with an inner diameter of 241mm, slightly larger than the length of the single crystal silicon, and a thickness of 5mm. Use a silicon dioxide polishing slurry with a concentration of 30% to perform a fine polishing of 2 filaments.

[0082] (5) Clean the polished single-crystal silicon and use an interferometer to test the mid-frequency error of the A-side of the single-crystal silicon. The result is 1.12urad. Use atomic force to test the high-frequency roughness of the A-side of the single-crystal silicon. The result is 0.29nm.

[0083] Comparative Example 1

[0084] A method for preparing planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness mainly includes the following:

[0085] (1) Select a single crystal silicon blank lens with dimensions of 200mm (length) * 50mm (width) * 30mm (thickness). For one side of the 200mm * 50mm (hereinafter referred to as side A), use W40 diamond abrasive to grind 20 mils, W28 diamond abrasive to grind 10 mils, and W14 diamond abrasive to grind 7 mils.

[0086] (2) Rough polishing of surface A after grinding, using silica polishing slurry with a concentration of 30% to rough polish 5 filaments.

[0087] (3) Polish surface A. Place a square fixture on the surface of the asphalt disc. The dimensions of the square fixture are 201mm (length) * 51mm (width) * 5mm (thickness). Polish with 3-micron silica polishing slurry with a silica concentration of 20%.

[0088] (4) Clean the polished single-crystal silicon and use an interferometer to test the mid-frequency error of the A-side of the single-crystal silicon. The result is 5.67 μrad. Use atomic force to test the high-frequency roughness of the A-side of the single-crystal silicon. The result is 0.64 nm.

[0089] Comparative Example 2

[0090] (1) Select a single crystal silicon blank lens with dimensions of 240mm (length) * 60mm (width) * 30mm (thickness). For one side of the 200mm * 50mm lens (hereinafter referred to as surface A), use W40 diamond abrasive to grind 25 mils, W28 diamond abrasive to grind 15 mils, and W14 diamond abrasive to grind 10 mils.

[0091] (2) Rough polishing of surface A after grinding, using silica polishing slurry with a concentration of 40% to rough polish 8 filaments.

[0092] (5) Polish surface A. Place a square fixture on the surface of the asphalt disc. The dimensions of the square fixture are 241mm (length) * 61mm (width) * 5mm (thickness). Polish with 4-filament silica polishing slurry with a silica concentration of 30%.

[0093] (6) Clean the polished single-crystal silicon and use an interferometer to test the mid-frequency error of the A-side of the single-crystal silicon. The result is 6.26 urad. Use atomic force to test the high-frequency roughness of the A-side of the single-crystal silicon. The result is 0.59 nm.

[0094] Comparative Example 3

[0095] A method for preparing planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness mainly includes the following:

[0096] (1) Select a single crystal silicon blank lens with dimensions of 200mm (length) * 50mm (width) * 30mm (thickness). For one side of the 200mm * 50mm (hereinafter referred to as side A), use W40 diamond abrasive to grind 30 mils, W28 diamond abrasive to grind 20 mils, and W14 diamond abrasive to grind 10 mils.

[0097] (2) Rough polishing of surface A after grinding, using silica polishing slurry with a concentration of 15%.

[0098] (3) Perform the first fine polishing on surface A. Place a special tooling fixture on the surface of the asphalt disc. The fixture is circular with an inner diameter of 201 mm, slightly larger than the length of the single crystal silicon, and a thickness of 5 mm. Use a silica polishing slurry with a concentration of 10% to perform the fine polishing on surface A.

[0099] (4) Perform a second fine polishing on surface A. Place a special fixture on the surface of the felt cloth, with the cloth tightly against the workpiece tray. The special fixture is circular in shape, with an inner diameter of 201mm, slightly larger than the length of the single crystal silicon, and a thickness of 5mm. Use a silicon dioxide polishing slurry with a concentration of 10% to perform a fine polishing of 1 filament.

[0100] (5) Clean the polished single-crystal silicon and use an interferometer to test the mid-frequency error of the A-side of the single-crystal silicon. The result is 2.79 μrad. Use atomic force to test the high-frequency roughness of the A-side of the single-crystal silicon. The result is 0.44 nm.

[0101] As can be seen from Examples 1 and 2, and Comparative Examples 1, 2, and 3, the method for preparing planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness of the present invention can effectively reduce the mid-frequency error and high-frequency roughness of planar single-crystal silicon.

[0102] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the interpretation of the present invention, without departing from the scope of the invention, should be within the protection scope of the present invention.

Claims

1. A method for preparing planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness, characterized in that, Specifically, the following steps are included: (S1) Grind the planar single-crystal silicon blanks that have been processed to reduce mid-frequency error and high-frequency roughness. (S2) After step (S1) is completed, perform rough polishing to remove pinholes; (S3) After step (S2) is completed, perform a first fine polishing to reduce mid-frequency error and roughness; (S4) After step (S3) is completed, a second fine polishing is performed to further reduce the roughness, thus completing the preparation of planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness. In step (S1), the grinding process specifically includes the following steps: One side of the flat single-crystal silicon blank, which has been processed to reduce mid-frequency error and high-frequency roughness, is successively subjected to W40 diamond grinding, W28 diamond grinding, and W14 diamond grinding. W40 diamond grinding produces 20-25 microns, W28 diamond grinding produces 10-15 microns, and W14 diamond grinding produces 7-10 microns. In step (S2), the rough polishing process specifically includes the following steps: The planar single-crystal silicon surface after grinding treatment is rough polished using a silica polishing slurry to reduce mid-frequency error and high-frequency roughness; the silica polishing slurry is used to rough polish 5-8 filaments; the mass fraction of the silica polishing slurry is 30-40%; In step (S3), the first fine polishing process specifically includes the following steps: The coarsely polished planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness is placed in a special tooling fixture, which is placed on the surface of an asphalt disc and polished using a silica polishing slurry; the silica polishing slurry has a mass fraction of 20-30%, and the silica polishing slurry is used for fine polishing with 3-4 filaments at a polishing speed of 2-3 revolutions per minute; In step (S4), the secondary fine polishing process specifically includes the following steps: After the first fine polishing treatment to reduce mid-frequency error and high-frequency roughness, the planar single-crystal silicon is placed in a special tooling fixture. The special tooling fixture is placed on a velvet surface and polished using a silica polishing slurry. The silica polishing slurry has a mass fraction of 20-30%, and the silica polishing slurry is used for fine polishing 1-2 filaments at a polishing speed of 2-3 revolutions per minute.

2. The method for preparing planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness according to claim 1, characterized in that, The special tooling fixture is circular in shape, with an inner diameter slightly larger than that of single-crystal silicon.

3. The method for preparing planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness according to claim 1, characterized in that, The special tooling fixture is circular in shape, with an inner diameter slightly larger than that of single-crystal silicon.

4. The method for preparing planar single-crystal silicon with reduced mid-frequency error and high-frequency roughness according to claim 1, characterized in that, The velvet material used is very soft and adheres tightly to the workpiece tray.