CN114290132A - Surface treatment method for silicon carbide wafer - Google Patents
Surface treatment method for silicon carbide wafer Download PDFInfo
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- CN114290132A CN114290132A CN202111660362.XA CN202111660362A CN114290132A CN 114290132 A CN114290132 A CN 114290132A CN 202111660362 A CN202111660362 A CN 202111660362A CN 114290132 A CN114290132 A CN 114290132A
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- 229910010271 silicon carbide Inorganic materials 0.000 title claims abstract description 115
- 238000000034 method Methods 0.000 title claims abstract description 65
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- 238000005498 polishing Methods 0.000 claims abstract description 74
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- 239000004744 fabric Substances 0.000 claims description 13
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 10
- 230000003197 catalytic effect Effects 0.000 claims description 10
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 9
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 9
- 239000002738 chelating agent Substances 0.000 claims description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 7
- 230000001678 irradiating effect Effects 0.000 claims description 7
- LLYCMZGLHLKPPU-UHFFFAOYSA-M perbromate Chemical compound [O-]Br(=O)(=O)=O LLYCMZGLHLKPPU-UHFFFAOYSA-M 0.000 claims description 6
- 239000012286 potassium permanganate Substances 0.000 claims description 6
- LSGOVYNHVSXFFJ-UHFFFAOYSA-N vanadate(3-) Chemical compound [O-][V]([O-])([O-])=O LSGOVYNHVSXFFJ-UHFFFAOYSA-N 0.000 claims description 6
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 5
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- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 4
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 claims description 4
- UIIMBOGNXHQVGW-DEQYMQKBSA-M Sodium bicarbonate-14C Chemical compound [Na+].O[14C]([O-])=O UIIMBOGNXHQVGW-DEQYMQKBSA-M 0.000 claims description 3
- ALTWGIIQPLQAAM-UHFFFAOYSA-N metavanadate Chemical compound [O-][V](=O)=O ALTWGIIQPLQAAM-UHFFFAOYSA-N 0.000 claims description 3
- -1 metavanadate ions Chemical class 0.000 claims description 3
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- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 claims description 3
- VLTRZXGMWDSKGL-UHFFFAOYSA-M perchlorate Inorganic materials [O-]Cl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-M 0.000 claims description 3
- VLTRZXGMWDSKGL-UHFFFAOYSA-N perchloric acid Chemical compound OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 claims description 3
- KHIWWQKSHDUIBK-UHFFFAOYSA-N periodic acid Chemical compound OI(=O)(=O)=O KHIWWQKSHDUIBK-UHFFFAOYSA-N 0.000 claims description 3
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- 229910052814 silicon oxide Inorganic materials 0.000 claims description 3
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- CMZUMMUJMWNLFH-UHFFFAOYSA-N sodium metavanadate Chemical compound [Na+].[O-][V](=O)=O CMZUMMUJMWNLFH-UHFFFAOYSA-N 0.000 description 2
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Abstract
The invention provides a surface treatment method of a silicon carbide wafer, the silicon carbide wafer comprises an A surface and a B surface; the surface treatment method comprises the following steps: A) coating a resin film on the surface of the silicon carbide A to obtain the smooth silicon carbide on the surface A; B) fixing the surface A, and polishing the surface B; C) removing the resin film on the surface of the silicon carbide A, fixing the polished surface B, and polishing the surface A to obtain a silicon carbide wafer with two polished surfaces; D) and polishing the silicon carbide wafer with two polished surfaces to obtain the silicon carbide wafer. The silicon carbide single crystal polished wafer prepared by the method has the surface warping degree smaller than 20 mu m, the bending degree smaller than 10 mu m, the flatness smaller than 4 mu m, the local flatness smaller than 1.5 mu m and the surface roughness smaller than 0.2 nm.
Description
Technical Field
The invention relates to the technical field of semiconductor materials, in particular to a surface treatment method of a silicon carbide wafer.
Background
Silicon carbide has a wide forbidden band width, high thermal conductivity and high breakdown voltage, so that the silicon carbide can be widely applied to devices which work under high frequency, high power, radiation resistance and extreme conditions. Is a semiconductor material with great potential.
High quality silicon carbide wafer surfaces are critical to the fabrication of high quality epitaxial wafers, which in turn determine the performance of semiconductor devices. The Mohs of the silicon carbide single crystal is 9.2, which is second to diamond in nature, and the difficulty of physical processing is very high; moreover, silicon carbide has high chemical stability, such as acid and alkali resistance and oxidation resistance, which greatly increases the difficulty of removing surface particles and metals during Chemical Mechanical Polishing (CMP) and cleaning.
In view of the processing difficulty of silicon carbide materials, the currently common silicon carbide wafer processing and cleaning methods mainly comprise double-sided or single-sided grinding, polishing, chemical mechanical polishing and standard RCA cleaning, and have the main problems that: the warping degree (Warp), Bow (Bow) and surface type (TTV and LTV) of a processed wafer are poor, and surface particles and metal pollutants cannot be well removed; the method has no capability of repairing larger deformation generated in the previous cutting process; the processing steps are complicated, the automation degree is low, and the surface quality and the stability of the wafer are difficult to ensure. The defects on the surface of the wafer can be amplified in the processes of epitaxial growth and device preparation, so that the yield of the chip is greatly reduced, and the defects are the primary factors influencing the yield of the chip.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide a method for treating the surface of a silicon carbide wafer, wherein the silicon carbide wafer treated by the method of the present invention has low surface roughness, high flatness and low surface warpage.
The invention provides a surface treatment method of a silicon carbide wafer, the silicon carbide wafer comprises an A surface and a B surface; the surface treatment method comprises the following steps:
A) coating a resin film on the surface of the silicon carbide A to obtain the smooth silicon carbide on the surface A;
B) fixing the surface A, and polishing the surface B;
C) removing the resin film on the surface of the silicon carbide A, fixing the polished surface B, and polishing the surface A to obtain a silicon carbide wafer with two polished surfaces;
D) and polishing the silicon carbide wafer with two polished surfaces to obtain the silicon carbide wafer.
Preferably, the resin film of step a) has a hardness of 50 to 70 HRD; the resin film is formed by filling a curved or convex-concave fluctuating silicon carbide A surface to be flat.
Preferably, the polishing in the step B) is specifically performed by using one or two of a resin grinding wheel or a metal bond grinding wheel; the mesh number of the grinding wheel is 500-50000 meshes;
c), polishing specifically by adopting one or two of a resin grinding wheel or a metal bond grinding wheel; the mesh number of the grinding wheel is 500-50000 meshes.
Preferably, the fixing in the step B) is to fix the surface a of the silicon carbide on an adsorption device by a vacuum adsorption method; the adsorption device drives the silicon carbide wafer to rotate, and the silicon carbide wafer rubs against the grinding wheel to remove the surface damage layer of the silicon carbide wafer.
Preferably, the rotating speed of the adsorption head is 200-600 rpm; the rotating speed of the grinding wheel is 500-3600 rpm.
Preferably, the method for removing the resin film on the surface of the silicon carbide a in the step C) specifically comprises the following steps: irradiating or baking with ultraviolet lamp; the parameters of the ultraviolet lamp irradiation are as follows: irradiating the sample for 10-120 s by using ultraviolet light with the wavelength of 100-350 nm; the baking temperature is 60-90 ℃.
Preferably, the polishing in the step D) is specifically performed by polishing in a polishing solution by using a polishing cloth; the polishing cloth is a polishing cloth containing fixed abrasive; the fixed abrasive comprises one or more of silicon oxide, aluminum oxide, cerium oxide and zirconium oxide.
Preferably, the polishing solution comprises a catalytic oxidizer complex and a pH adjuster; a complex of the catalytic oxidant complex vanadate or metavanadate ion and an oxidant, or a complex of a metal, a chelating agent and an oxidant; the oxidant comprises one or more of hydrogen peroxide, potassium permanganate, perchlorate, periodate and perbromate; the pH regulator comprises one or more of sodium carbonate, sodium bicarbonate, sodium dihydrogen phosphate, potassium hydroxide, sodium hydroxide, organic acid or organic base.
Preferably, the polishing time is 10 min-10 h; the mass ratio of the vanadate or metavanadate ions to the oxidant is 1: 1-1: 30; the mass ratio of the metal to the chelating agent to the oxidant is 1:1: 20-1: 10: 100; the pH value of the polishing solution is 2-11.
The invention provides a silicon carbide wafer which is obtained by the surface treatment method in any one of the technical schemes.
Compared with the prior art, the invention provides a surface treatment method of a silicon carbide wafer, the silicon carbide wafer comprises an A surface and a B surface; the surface treatment method comprises the following steps: A) coating a resin film on the surface of the silicon carbide A to obtain the smooth silicon carbide on the surface A; B) fixing the surface A, and polishing the surface B; C) removing the resin film on the surface of the silicon carbide A, fixing the polished surface B, and polishing the surface A to obtain a silicon carbide wafer with two polished surfaces; D) and polishing the silicon carbide wafer with two polished surfaces to obtain the silicon carbide wafer. The silicon carbide single crystal polished wafer prepared by the method has the surface warping degree smaller than 20 mu m, the bending degree smaller than 10 mu m, the flatness smaller than 4 mu m, the local flatness smaller than 1.5 mu m and the surface roughness smaller than 0.2 nm.
Drawings
FIG. 1 is a schematic flow chart of a surface treatment method according to a preferred embodiment of the present invention;
fig. 2(a) is a graph of Warp (Warp), Bow (Bow), and profile (TTV and LTV) of a dicing sheet, and fig. 2(b) is a graph of Warp (Warp), Bow (Bow), and profile (TTV and LTV) of a wafer processed by one of the preferred embodiments of the present invention;
FIG. 3 is a graph showing the results of the roughness of the wafer surface in example 3 of the present invention;
FIG. 4 is a diagram showing the results of the wafer surface in example 1 of the present invention;
FIG. 5 is a graph of Warp (Warp), Bow (Bow), and areal (TTV and LTV) of a wafer processed according to comparative example 1 of the present invention;
FIG. 6 is a graph showing the results of the roughness of the wafer surface after the method of comparative example 1 according to the present invention.
Detailed Description
The invention provides a surface treatment method of a silicon carbide wafer, and the method can be realized by appropriately improving process parameters by one skilled in the art with reference to the content in the text. It is expressly intended that all such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the scope of the invention. While the methods and applications of this invention have been described in terms of preferred embodiments, it will be apparent to those of ordinary skill in the art that variations and modifications in the methods and applications described herein, as well as other suitable variations and combinations, may be made to implement and use the techniques of this invention without departing from the spirit and scope of the invention.
The invention provides a surface treatment method of a silicon carbide wafer, the silicon carbide wafer comprises an A surface and a B surface; the surface treatment method comprises the following steps:
A) coating a resin film on the surface of the silicon carbide A to obtain the smooth silicon carbide on the surface A;
B) fixing the surface A, and polishing the surface B;
C) removing the resin film on the surface of the silicon carbide A, fixing the polished surface B, and polishing the surface A to obtain a silicon carbide wafer with two polished surfaces;
D) and polishing the silicon carbide wafer with two polished surfaces to obtain the silicon carbide wafer.
The silicon carbide wafer provided by the invention comprises an A surface and a B surface; the above definitions are merely for distinguishing the two surfaces, and the two surfaces may be replaced with each other without limitation.
The surface treatment method of the silicon carbide wafer provided by the invention firstly coats the resin film on the surface A of the silicon carbide to obtain the silicon carbide with a flat surface A.
Resin films of the present invention include, but are not limited to, HT-140H-UA40-PC2, SB-145HM-NB-PL 2A; the hardness of the resin film is 50-70 HRD; the resin film is formed by filling a curved or convex-concave fluctuating silicon carbide A surface to be flat.
The strength of the resin film is greater than the suction force of the adsorption head, and the bonding force with the surface of the silicon carbide is greater than the transverse force generated by the relative friction between the silicon carbide and the diamond grinding wheel, so that the resin film is not deformed and moved in the processing process.
And fixing the surface A, and polishing the surface B.
The fixing method specifically comprises the step of fixing the silicon carbide A surface on an adsorption device by adopting a vacuum adsorption method. The adsorption device of the present invention is not limited, and an adsorption head known to those skilled in the art may be used.
The adsorption device drives the silicon carbide wafer to rotate, and the silicon carbide wafer rubs against the grinding wheel to remove the surface damage layer of the silicon carbide wafer.
The grinding is preferably to a flat.
The polishing is specifically performed by adopting one or two of a resin grinding wheel or a metal bond grinding wheel; the mesh number of the grinding wheel is preferably 500-50000 meshes; more preferably 500 to 30000 meshes; most preferably 2000 to 20000 mesh.
The rotating speed of the adsorption head is preferably 200-600 rpm; more preferably 300 to 500 rpm; the rotating speed of the grinding wheel is preferably 500-3600 rpm; more preferably 1000-3500 rpm;
and removing the resin film on the surface of the silicon carbide A.
The method for removing the resin film on the surface of the silicon carbide A specifically comprises the following steps: irradiating or baking with ultraviolet lamp.
Wherein the parameters of the ultraviolet lamp irradiation are that the sample is irradiated by ultraviolet light with the wavelength of 100-350 nm for 10-120 s; and removing the adhesive of the resin film to separate the resin film from the surface of the wafer.
The baking parameters are 60-90 ℃. The film paste is softened, after which the resin film is separated from the wafer surface.
The invention adopts one or two combined methods of ultraviolet lamp irradiation and baking to remove the resin film from the surface of the wafer.
Fixing the polished surface B, and polishing the surface A to obtain a silicon carbide wafer with polished two surfaces;
the polishing is specifically performed by adopting one or two of a resin grinding wheel or a metal bond grinding wheel; the mesh number of the grinding wheel is preferably 500-50000 meshes; more preferably 500 to 30000 meshes; most preferably 2000 to 20000 mesh.
And polishing the silicon carbide wafer with two polished surfaces to obtain the silicon carbide wafer.
Conveying the wafer with two flat surfaces to a chemical mechanical polishing station, and polishing the C surface and the Si surface of the silicon carbide respectively by using polishing cloth containing fixed abrasive and polishing solution containing catalytic oxidizer complex;
the polishing of the invention is specifically to polish in polishing solution by adopting polishing cloth.
Wherein the polishing cloth is a polishing cloth containing fixed abrasive; the fixed abrasive comprises one or more of silicon oxide, aluminum oxide, cerium oxide and zirconium oxide.
The polishing solution comprises a catalytic oxidizer complex and a pH regulator; a complex of the catalytic oxidant complex vanadate or metavanadate ion and an oxidant, or a complex of a metal, a chelating agent and an oxidant; the oxidant comprises one or more of hydrogen peroxide, potassium permanganate, perchlorate, periodate and perbromate; the pH regulator comprises one or more of sodium carbonate, sodium bicarbonate, sodium dihydrogen phosphate, potassium hydroxide, sodium hydroxide, organic acid or organic base.
The polishing time is 10 min-10 h; the mass ratio of the vanadate or metavanadate ions to the oxidant is 1: 1-1: 30; preferably 1: 5-1: 20. the mass ratio of the metal to the chelating agent to the oxidant is preferably 1:1: 20-1: 10: 100; more preferably 1: 2: 30-1: 5: 50. the pH value of the polishing solution is 2-11;
fig. 1 is a schematic flow chart of a surface treatment method according to a preferred embodiment of the present invention.
The invention provides a silicon carbide wafer which is obtained by the surface treatment method in any one of the technical schemes.
The processing method of the present invention has been described clearly, and is not described herein again.
The invention provides a surface treatment method of a silicon carbide wafer, the silicon carbide wafer comprises an A surface and a B surface; the surface treatment method comprises the following steps: A) coating a resin film on the surface of the silicon carbide A to obtain the smooth silicon carbide on the surface A; B) fixing the surface A, and polishing the surface B; C) removing the resin film on the surface of the silicon carbide A, fixing the polished surface B, and polishing the surface A to obtain a silicon carbide wafer with two polished surfaces; D) and polishing the silicon carbide wafer with two polished surfaces to obtain the silicon carbide wafer. The silicon carbide single crystal polished wafer prepared by the method has the surface warping degree smaller than 20 mu m, the bending degree smaller than 10 mu m, the flatness smaller than 4 mu m, the local flatness smaller than 1.5 mu m and the surface roughness smaller than 0.2 nm.
In order to further illustrate the present invention, the following describes in detail a surface treatment method for a silicon carbide wafer according to the present invention with reference to examples.
Example 1
A production method of a high-quality polished silicon carbide single crystal wafer having a diameter of 150mm, comprising:
step 1, uniformly coating a resin film HT-140H-UA40-PC2 with a UV type adhesive produced by Mitsui corporation on the surface A of a silicon carbide cutting slice;
step 2, fixing the flat wafer A surface on an adsorption head of grinding equipment by using a vacuum adsorption method, and grinding the B surface to be flat by using a diamond grinding wheel of No. 2000 metal bond, wherein the specific processing parameters are as follows: the rotating speed of the adsorption head is 300rpm, the feeding speed is 0.25 mu m/s, the rotating speed of the grinding wheel is 3000rpm, and the removal amount is 30 mu m; and then, continuously removing the damaged layer on the surface B to the lowest by using a diamond grinding wheel with 20000-grade metal bond, wherein the specific processing parameters are as follows: the rotation speed of the adsorption head is 150rpm, the feed speed is 0.2 mu m/s, the rotation speed of the grinding wheel is 2500rpm, and the removal amount is 10 mu m;
step 3, irradiating the resin film on the A surface of the silicon carbide wafer by using ultraviolet rays, and then removing the resin film by using a mechanical stripping method;
step 4, turning the wafer, adsorbing and fixing the flat wafer B surface, and polishing the A surface to be flat in the same processing mode as the step 2;
step 5, polishing cloth containing silicon dioxide abrasive materials, and polishing solution containing sodium metavanadate, hydrogen peroxide and sodium carbonate as catalytic oxidant complexes are selected to polish the C surface and the Si surface of the silicon carbide respectively; the concentration of sodium metavanadate is 3g/L, and the concentration of 30% UP-grade hydrogen peroxide is 30% by volume; the concentrations of sodium carbonate in polishing solutions of a C surface and a Si surface of the silicon carbide are 1.5g/L and 0.5g/L respectively; the removal amount of the C-plane and the Si-plane was 5um, respectively.
The silicon carbide single crystal polished wafer processed by the method can achieve the following indexes: the surface warping degree is less than 20 μm, the bending degree is less than 10 μm, the flatness is less than 4 μm, the local flatness is less than 1.5 μm, the surface roughness is less than 0.2nm, the number of defects larger than 0.1 μm is less than 200 per sheet,
example 2
A production method of a high-quality polished silicon carbide single crystal wafer having a diameter of 150mm, comprising:
step 1, uniformly coating a resin film SB-145HM-NB-PL2A with a non-UV adhesive, which is produced by Mitsui corporation, on the surface A of a silicon carbide cutting blade;
step 2, fixing the flat wafer A surface on an adsorption head of grinding equipment by using a vacuum adsorption method, and grinding the B surface to be flat by using a diamond grinding wheel of No. 1500 metal bond, wherein the specific processing parameters are as follows: the rotating speed of the adsorption head is 400rpm, the feeding speed is 0.3 mu m/s, the rotating speed of the grinding wheel is 3000rpm, and the removal amount is 20 mu m; and then, continuously removing the damaged layer on the surface B to the lowest by using a diamond grinding wheel of No. 30000 resin binder, wherein the specific processing parameters are as follows: the rotating speed of the adsorption head is 150rpm, the feeding speed is 0.25 mu m/s, the rotating speed of the grinding wheel is 2000rpm, and the removal amount is 5 mu m;
step 3, heating the resin film on the surface A of the wafer, and then removing the resin film by using a mechanical stripping method;
step 4, turning the wafer, adsorbing and fixing the flat wafer B surface, and polishing the A surface to be flat in the same processing mode as the step 2;
step 5, polishing cloth containing cerium oxide abrasive, and polishing solution containing iron, chelating agent and hydrogen peroxide as catalytic oxidant complex are selected to polish the C surface and the Si surface of the silicon carbide respectively; the concentration of iron is 0.5g/L, and the volume concentration of 30% UP-grade hydrogen peroxide is 20%; the removal amounts of the C-plane and the Si-plane were 3um, respectively.
The silicon carbide single crystal polished wafer processed by the method can achieve the following indexes: the surface warping degree is less than 20 μm, the bending degree is less than 10 μm, the flatness is less than 4 μm, the local flatness is less than 1.5 μm, the surface roughness is less than 0.2nm, the number of defects larger than 0.1 μm is less than 200 per sheet,
example 3
A production method of a high-quality polished silicon carbide single crystal wafer having a diameter of 200mm, comprising:
step 1, uniformly coating a resin film HT-140H-UA40-PC2 with a UV type adhesive produced by Mitsui corporation on the surface A of a silicon carbide cutting slice;
step 2, fixing the flat wafer A surface on an adsorption head of grinding equipment by using a vacuum adsorption method, and grinding the B surface to be flat by using a No. 1000 metal bond diamond grinding wheel, wherein the specific processing parameters are as follows: the rotating speed of the adsorption head is 200rpm, the feeding speed is 0.2 mu m/s, the rotating speed of the grinding wheel is 2000rpm, and the removal amount is 50 mu m; and then, continuously removing the damaged layer on the surface B to the lowest by using a diamond grinding wheel with 20000-grade metal bond, wherein the specific processing parameters are as follows: the rotating speed of the adsorption head is 100rpm, the feeding speed is 0.2 mu m/s, the rotating speed of the grinding wheel is 1500rpm, and the removal amount is 10 mu m;
step 3, irradiating the resin film on the A surface of the silicon carbide wafer by using ultraviolet rays, and then removing the resin film by using a mechanical stripping method;
step 4, turning the wafer, adsorbing and fixing the flat wafer B surface, and polishing the A surface to be flat in the same processing mode as the step 2;
step 5, polishing cloth containing aluminum oxide abrasive materials, and polishing solution containing iron, chelating agent and potassium permanganate serving as catalytic oxidant complex are selected to polish the C surface and the Si surface of the silicon carbide respectively; the concentration of iron is 0.3g/L, and the concentration of potassium permanganate is 4 g/L; the removal amounts of the C-plane and the Si-plane were 10um, respectively.
The silicon carbide single crystal polished wafer processed by the method can achieve the following indexes: the surface warping degree is less than 20 mu m, the bending degree is less than 10 mu m, the flatness is less than 4 mu m, the local flatness is less than 1.5 mu m, the surface roughness is less than 0.2nm, the number of defects larger than 0.1 mu m is less than 200 defects per wafer, and typical test results are shown in figures 2-4. Wherein fig. 2(a) is a graph of Warp (Warp), Bow (Bow), and profile (TTV and LTV) of the dicing sheet, and fig. 2(b) is a graph of Warp (Warp), Bow (Bow), and profile (TTV and LTV) of the wafer processed by one of the preferred embodiments of the present invention. FIG. 3 is a graph showing the results of the roughness of the wafer surface in example 3 of the present invention; FIG. 4 is a diagram of the wafer surface result of example 1 of the present invention. It can be seen from the figure that the wafer processed by the invention has good improvement of surface warping (Warp), Bow (Bow), surface profile (TTV and LTV), and good quality of surface roughness, scratches and the like.
Comparative example 1
Step 1, directly adsorbing the surface A of a silicon carbide cutting disc with the diameter of 150mm by using a vacuum adsorption method, and polishing the surface B by using the same parameters in the embodiment 1: selecting a diamond grinding wheel of No. 2000 metal bond to grind the surface of the wafer, wherein the rotating speed of an adsorption head is 300rpm, the feeding speed is 0.25 mu m/s, the rotating speed of the grinding wheel is 3000rpm, and the removal amount is 30 mu m; then, using a diamond grinding wheel with 20000-grade metal bond to continuously remove the damaged layer on the surface B to the lowest, wherein the rotating speed of an adsorption head is 150rpm, the feeding speed is 0.2 mu m/s, the rotating speed of the grinding wheel is 2500rpm, and the removal amount is 10 mu m;
step 2, turning over the wafer, adsorbing and fixing the surface B of the wafer, and polishing the surface A to be flat in the same processing mode as the step 1;
and 3, selecting a polyurethane polishing pad, selecting silicon dioxide particles with the solid content of 20% as an abrasive and 4 g/L potassium permanganate as a polishing solution of an oxidant, and polishing the C surface and the Si surface of the silicon carbide respectively, wherein the removal amount of the C surface and the removal amount of the Si surface are respectively 5 um.
The polished silicon carbide single crystal wafer processed by the method of comparative example 1 had no effect on improvement of the cut profile, surface warpage of 39.877 μm, bow of 7.371 μm, flatness of 5.284 μm, local flatness of 4.273 μm, and cut kerfs of the surface were reproduced on the wafer surface during processing, as shown in fig. 5. The surface roughness of the wafer is less than 0.2nm, but dark cracks exist on the surface, namely, a damage layer is newly added in the polishing process, as shown in FIG. 6.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A surface treatment method of a silicon carbide wafer is characterized in that the silicon carbide wafer comprises an A surface and a B surface; the surface treatment method comprises the following steps:
A) coating a resin film on the surface of the silicon carbide A to obtain the smooth silicon carbide on the surface A;
B) fixing the surface A, and polishing the surface B;
C) removing the resin film on the surface of the silicon carbide A, fixing the polished surface B, and polishing the surface A to obtain a silicon carbide wafer with two polished surfaces;
D) and polishing the silicon carbide wafer with two polished surfaces to obtain the silicon carbide wafer.
2. The method according to claim 1, wherein the resin film of step a) has a hardness of 50 to 70 HRD; the resin film is formed by filling a curved or convex-concave fluctuating silicon carbide A surface to be flat.
3. The method as claimed in claim 1, wherein the grinding in step B) is specifically grinding with one or both of a resin grinding wheel or a metal bond grinding wheel; the mesh number of the grinding wheel is 500-50000 meshes;
c), polishing specifically by adopting one or two of a resin grinding wheel or a metal bond grinding wheel; the mesh number of the grinding wheel is 500-50000 meshes.
4. The method as claimed in claim 3, wherein the fixing in step B) is carried out by fixing the silicon carbide A surface on a suction device by a vacuum suction method; the adsorption device drives the silicon carbide wafer to rotate, and the silicon carbide wafer rubs against the grinding wheel to remove the surface damage layer of the silicon carbide wafer.
5. The method according to claim 4, wherein the rotation speed of the adsorption head is 200-600 rpm; the rotating speed of the grinding wheel is 500-3600 rpm.
6. The method according to claim 1, wherein the method for removing the resin film on the surface of the silicon carbide A in the step C) is specifically as follows: irradiating or baking with ultraviolet lamp; the parameters of the ultraviolet lamp irradiation are as follows: irradiating the sample for 10-120 s by using ultraviolet light with the wavelength of 100-350 nm; the baking temperature is 60-90 ℃.
7. The method as claimed in claim 1, wherein the polishing in step D) is carried out by polishing in a polishing solution by using a polishing cloth; the polishing cloth is a polishing cloth containing fixed abrasive; the fixed abrasive comprises one or more of silicon oxide, aluminum oxide, cerium oxide and zirconium oxide.
8. The method of claim 7, wherein the polishing slurry comprises a catalytic oxidizer complex and a pH adjuster; a complex of the catalytic oxidant complex vanadate or metavanadate ion and an oxidant, or a complex of a metal, a chelating agent and an oxidant; the oxidant comprises one or more of hydrogen peroxide, potassium permanganate, perchlorate, periodate and perbromate; the pH regulator comprises one or more of sodium carbonate, sodium bicarbonate, sodium dihydrogen phosphate, potassium hydroxide, sodium hydroxide, organic acid or organic base.
9. The method according to claim 1, wherein the polishing time is 10min to 10 h; the mass ratio of the vanadate or metavanadate ions to the oxidant is 1: 1-1: 30; the mass ratio of the metal to the chelating agent to the oxidant is 1:1: 20-1: 10: 100; the pH value of the polishing solution is 2-11.
10. A silicon carbide wafer treated by the surface treatment method according to any one of claims 1 to 9.
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