CN116153778A - Method for removing metal on surface of silicon carbide wafer - Google Patents
Method for removing metal on surface of silicon carbide wafer Download PDFInfo
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- CN116153778A CN116153778A CN202211613743.7A CN202211613743A CN116153778A CN 116153778 A CN116153778 A CN 116153778A CN 202211613743 A CN202211613743 A CN 202211613743A CN 116153778 A CN116153778 A CN 116153778A
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- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 126
- 229910010271 silicon carbide Inorganic materials 0.000 title claims abstract description 125
- 238000000034 method Methods 0.000 title claims abstract description 63
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 30
- 239000002184 metal Substances 0.000 title claims abstract description 30
- 238000004140 cleaning Methods 0.000 claims abstract description 159
- 239000000126 substance Substances 0.000 claims abstract description 19
- 229910021642 ultra pure water Inorganic materials 0.000 claims description 101
- 239000012498 ultrapure water Substances 0.000 claims description 101
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 100
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 94
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 40
- 239000011259 mixed solution Substances 0.000 claims description 38
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 32
- 239000000243 solution Substances 0.000 claims description 32
- 230000005587 bubbling Effects 0.000 claims description 18
- 238000005507 spraying Methods 0.000 claims description 18
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 16
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 16
- 239000007789 gas Substances 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 8
- 238000001020 plasma etching Methods 0.000 claims description 7
- 239000000463 material Substances 0.000 claims description 5
- 229910052731 fluorine Inorganic materials 0.000 claims description 3
- 239000011737 fluorine Substances 0.000 claims description 3
- -1 fluorine ions Chemical class 0.000 claims description 3
- 238000005530 etching Methods 0.000 claims description 2
- 150000002739 metals Chemical class 0.000 abstract description 9
- 230000000694 effects Effects 0.000 abstract description 4
- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 abstract description 2
- 235000012431 wafers Nutrition 0.000 description 78
- 230000008878 coupling Effects 0.000 description 5
- 238000010168 coupling process Methods 0.000 description 5
- 238000005859 coupling reaction Methods 0.000 description 5
- 230000001939 inductive effect Effects 0.000 description 5
- 238000005498 polishing Methods 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 4
- 239000002245 particle Substances 0.000 description 3
- 239000004065 semiconductor Substances 0.000 description 3
- 230000007547 defect Effects 0.000 description 2
- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 description 1
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/0445—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising crystalline silicon carbide
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
- B08B3/04—Cleaning involving contact with liquid
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
- B08B3/04—Cleaning involving contact with liquid
- B08B3/08—Cleaning involving contact with liquid the liquid having chemical or dissolving effect
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B7/00—Cleaning by methods not provided for in a single other subclass or a single group in this subclass
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02041—Cleaning
- H01L21/02057—Cleaning during device manufacture
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Crystallography & Structural Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Cleaning Or Drying Semiconductors (AREA)
Abstract
The invention relates to a method for removing metal on the surface of a silicon carbide wafer, which is a silicon carbide wafer cleaning process comprising wet chemical cleaning, dry plasma cleaning and wet chemical cleaning; the effect of removing the metal on the surface of the silicon carbide is obviously improved, and the content of the metals which are difficult to remove, such as Ca, fe, na, mg, al on the surface of the silicon carbide, and the like, is tested by ICP-MS<5E10atoms/cm 2 The working efficiency is greatly improved.
Description
Technical Field
The invention belongs to the technical field of silicon carbide processing, and particularly relates to a method for removing metal on the surface of a silicon carbide wafer.
Technical Field
Silicon carbide (SiC) is a typical third-generation semiconductor material, and has excellent physical properties such as large forbidden bandwidth, high electron mobility, high critical breakdown field strength, high thermal conductivity, and the like, compared with conventional semiconductor materials such as silicon, gallium arsenide, and the like, and thus is widely used in the fields of high-power and high-temperature electronic devices, and the like. During the processing of silicon carbide wafers, various organic matters, particles, metals and other impurities are inevitably introduced, and the silicon carbide wafers used for manufacturing the devices must ensure high cleanliness, otherwise, the devices are irreversibly seriously damaged, so that a cleaning step after Chemical Mechanical Polishing (CMP) is of great importance.
Most of the methods currently used in the industry are RCA cleaning processes or are partly detailed adjustments based on RCA cleaning processes. For example, chinese patent document CN201910824773.4 discloses a final cleaning method of a silicon carbide single crystal polished wafer substrate, which first uses the generated O under ultraviolet light irradiation 3 And (3) cleaning the silicon carbide polished wafer, rinsing with ultrapure water, and performing a conventional RCA process. Chinese patent document CN109585268A (201811302593.1) discloses a cleaning method of a silicon carbide wafer, which firstly uses hydrogen gas to perform ion cleaning on the silicon carbide wafer, and then performs a conventional RCA process. Although the two methods are improved to a certain extent compared with the traditional RCA cleaning process, the number of particles on the surface of the cleaned silicon carbide monocrystal polished wafer is still more, and the number of particles needs to be reduced, and importantly, the cleaning method for Ca, fe, na, mg, al and other metals which are difficult to remove is lacking in the field at present.
Disclosure of Invention
Aiming at the defects of the prior art, particularly the defects of a cleaning method for Ca, fe, na, mg, al and the like which is difficult to remove metals, the invention provides a method for removing metals on the surface of silicon carbide, and the method can effectively remove metals on the surface of silicon carbide, such as Ca, fe, na, mg, al and the like.
The invention is realized by the following technical scheme:
a method for removing metal from the surface of a silicon carbide wafer comprising the steps of:
1) Immersing the silicon carbide wafer into hydrofluoric acid solution for cleaning;
2) Cleaning the silicon carbide wafer by using ultrapure water, and spin-drying after cleaning;
3) Performing dry plasma etching on the surface of the silicon carbide wafer treated in the step (2) to remove a damaged layer and an oxide layer on the surface of the silicon carbide wafer;
4) The silicon carbide wafer is rinsed with ultra-pure water and then rinsed using a modified RCA rinsing process.
According to the invention, the hydrofluoric acid solution in the step 1) is hydrofluoric acid and ultrapure water according to the volume ratio of 1: 25-100, the cleaning temperature is normal temperature, and the cleaning time is 15-25 min.
According to the invention, in the step 2), the silicon carbide wafer is cleaned by ultrapure water by adopting a process of combining overflow, bubbling and spraying, the cleaning temperature is normal temperature, and the cleaning time is 8-12 min.
According to the preferred embodiment of the present invention, in step 3), SF is used for dry plasma etching 6 Gas, generating fluorine ions (F) - ) The chemical damage layer and the oxide layer after the silicon carbide wafer CMP are effectively removed, the rate is 100-800 w, the pressure is 5-20 mTorr, the temperature is 10-30 ℃, and the SF is the SF 6 The gas flow is 10-50 sccm, and the etching time is 10-25 min.
According to a preferred embodiment of the invention, in step 3), the dry plasma etching is carried out in an ICP device which generates a gaseous plasma by means of inductive coupling, using the generated F with energy - And removing the damaged layer and the oxide layer on the surface of the silicon carbide.
According to the invention, in the step 4), the etched silicon carbide wafer is cleaned by ultrapure water by a process of combining overflow, bubbling and spraying, the cleaning temperature is normal temperature, and the cleaning time is 8-12 min.
According to a preferred embodiment of the invention, in step 4), the improved RCA cleaning process comprises in particular the following steps:
a) Placing the cleaned silicon carbide wafer into a mixed solution of sulfuric acid and hydrogen peroxide, cleaning for 15-25 min at 110-130 ℃, and then cleaning the surface of the silicon carbide wafer by using ultrapure water, wherein the volume ratio of the sulfuric acid to the hydrogen peroxide is 1-3.5:1;
b) Taking out the silicon carbide wafer in the step a), placing the silicon carbide wafer in a hydrofluoric acid solution, cleaning for 15-25 min at normal temperature, and cleaning the surface of the silicon carbide wafer by using ultrapure water, wherein the hydrofluoric acid solution is prepared by mixing hydrofluoric acid and ultrapure water according to a volume ratio of 1: 25-100 parts of mixed solution;
c) Taking out the silicon carbide wafer in the step b), placing the silicon carbide wafer in a mixed solution composed of ammonia water, hydrogen peroxide and ultrapure water, cleaning for 15-25 min at 50-70 ℃, and then cleaning the surface of the silicon carbide wafer by using the ultrapure water, wherein the volume ratio of the ammonia water to the hydrogen peroxide to the ultrapure water is 0.5-1.5:0.5-1.5:5;
d) Taking out the silicon carbide wafer in the step c), placing the silicon carbide wafer in a mixed solution consisting of hydrochloric acid, hydrogen peroxide and ultrapure water, cleaning for 15-25 min at 60-80 ℃, and cleaning the surface of the silicon carbide wafer by using the ultrapure water, wherein the volume ratio of the hydrochloric acid to the hydrogen peroxide to the ultrapure water is 0.5-1.5: 0.5 to 1.5:6, preparing a base material;
e) Taking out the silicon carbide wafer in the step c), placing the silicon carbide wafer in hydrofluoric acid solution, cleaning the silicon carbide wafer at normal temperature for 15-25 min, cleaning the surface of the silicon carbide wafer by using ultrapure water, and spin-drying; the hydrofluoric acid solution is hydrofluoric acid and ultrapure water according to the volume ratio of 1:25 to 100 percent of mixed solution.
According to the present invention, the ultrapure water cleaning in steps a) to e) is preferably performed as: the silicon carbide wafer is cleaned by ultrapure water by adopting a process combining overflow, bubbling and spraying, the cleaning temperature is normal temperature, and the cleaning time is 8-12 min.
The invention has the beneficial effects that:
1. according to the method for removing the metal on the surface of the silicon carbide, the silicon carbide wafer cleaning process of wet chemical cleaning, dry plasma cleaning and wet chemical cleaning is adopted; can obviously improve the effect of removing the metal on the surface of the silicon carbide, and the content of the metals which are difficult to remove, such as Ca, fe, na, mg, al on the surface of the silicon carbide, and the like, is tested by ICP-MS<5E10 atoms/cm 2 The working efficiency is improved.
2. The method adopts wet chemical cleaning-dry plasmaA method combining sub-body cleaning and wet chemical cleaning. Wet chemical cleaning is to pretreat the silicon carbide wafer by utilizing the special effect of hydrofluoric acid on removing metal; dry plasma etching is performed using SF 6 The gas generates a large amount of fluorine ions (F) - ) Further reflect F - +SiO 2 →SiF 4 +O 2 The chemical damage layer and the oxidation layer of the silicon carbide wafer after CMP are effectively removed by combining wet chemical pretreatment; the subsequent wet chemical cleaning is to clean the silicon carbide wafer by adopting an improved RCA process, and finally the effect of removing the metal on the surface of the silicon carbide wafer is achieved.
Detailed Description
The method for removing metal on the surface of silicon carbide according to the present invention is further described below with reference to examples, but is not limited thereto.
The silicon carbide wafer in the examples is a four inch or six inch diameter post CMP wafer, of N-type or semi-insulating conductivity type, offered by the new generation semiconductor materials institute of university in the Shandong.
Example 1
A method for removing metal on the surface of a silicon carbide wafer comprises the following steps:
step (1): immersing the silicon carbide wafer subjected to chemical mechanical polishing CMP into hydrofluoric acid solution for cleaning, wherein the hydrofluoric acid solution is prepared from hydrofluoric acid and ultrapure water according to a volume ratio of 1:100, cleaning the mixed solution at normal temperature for 20min;
step (2): immersing the silicon carbide wafer subjected to the step (1) into ultrapure water, cleaning by adopting overflow, bubbling and spraying processes, wherein the cleaning temperature is normal temperature, the cleaning time is 10min, and spin-drying is carried out after the cleaning is finished.
Step (3): placing the silicon carbide wafer subjected to the step (2) in an ICP device, and generating gaseous SF by means of inductive coupling 6 Plasma, F with energy generated - Removing a damaged layer and an oxide layer on the surface of silicon carbide, wherein the power of ICP equipment is 600w, the pressure is 10mTorr, the temperature is 20 ℃, and SF is the same 6 The gas flow was 20sccm and the purge time was 18 minutes.
Step (4): immersing the silicon carbide wafer subjected to the step (3) into ultrapure water for cleaning, and adopting overflow, bubbling and spraying processes, wherein the cleaning time is 10min, and the cleaning temperature is normal temperature;
step (5): and (3) carrying out an improved RCA cleaning process on the silicon carbide wafer subjected to the step (4), wherein the improved RCA cleaning process is to sequentially immerse the silicon carbide wafer in a mixed solution of sulfuric acid and hydrogen peroxide, ultrapure water, a hydrofluoric acid solution, ultrapure water, a mixed solution of ammonia water and hydrogen peroxide and ultrapure water, a mixed solution of hydrochloric acid and hydrogen peroxide and ultrapure water, and finally clean the silicon carbide wafer in the ultrapure water, the hydrofluoric acid solution and the ultrapure water, and spin-dry the silicon carbide wafer.
The volume ratio of sulfuric acid to hydrogen peroxide in the sulfuric acid and hydrogen peroxide mixed solution is 1.5:1, the cleaning temperature is 115 ℃, and the cleaning time is 20min.
The hydrofluoric acid solution is prepared from hydrofluoric acid and ultrapure water according to a volume ratio of 1:100, the cleaning temperature is normal temperature, and the cleaning time is 20min;
the volume ratio of the ammonia water, the hydrogen peroxide and the ultrapure water in the mixed solution of the ammonia water, the hydrogen peroxide and the ultrapure water is 0.6:0.6:5, the cleaning temperature is 50 ℃, and the cleaning time is 23min.
The ratio of hydrochloric acid, hydrogen peroxide and ultrapure water in the mixed solution of hydrochloric acid, hydrogen peroxide and ultrapure water is 1:1:6, the cleaning temperature is 80 ℃ and the cleaning time is 20min.
The ultra-pure water technology adopts overflow, bubbling and spraying, the cleaning temperature is normal temperature, and the cleaning time is 10min. In particular, the ultra-pure water cleaning temperature after sulfuric acid+hydrogen peroxide solution is 65 ℃.
Step (6): the silicon carbide wafer subjected to the step (5) was subjected to a surface metal test, and the results are recorded in table 1.
Example 2
A method for removing metal on the surface of silicon carbide comprises the following steps:
step (1): immersing the silicon carbide wafer subjected to chemical mechanical polishing CMP into hydrofluoric acid solution for cleaning, wherein the hydrofluoric acid solution is prepared from hydrofluoric acid and ultrapure water according to a volume ratio of 1:75, cleaning the mixed solution at normal temperature for 15min;
step (2): immersing the silicon carbide wafer subjected to the step (1) into ultrapure water, and cleaning by adopting overflow, bubbling and spraying processes, wherein the cleaning temperature is normal temperature, and the cleaning time is 10min. And spin-drying the product after the cleaning is finished.
Step (3): placing the silicon carbide wafer subjected to the step (2) in an ICP device, and generating gaseous SF by means of inductive coupling 6 Plasma, F with energy generated - Removing the damaged layer and the oxide layer on the surface of the silicon carbide, wherein the power of ICP equipment is 500w, the pressure is 15mTorr, the temperature is 25 ℃, and SF is the same 6 The gas flow rate was 30sccm and the cleaning time was 22min.
Step (4): immersing the silicon carbide wafer subjected to the step (3) into ultrapure water for cleaning, and adopting overflow, bubbling and spraying processes, wherein the cleaning time is 10min, and the cleaning temperature is normal temperature;
step (5): and (3) carrying out an improved RCA cleaning process on the silicon carbide wafer subjected to the step (4), wherein the improved RCA cleaning process is to sequentially immerse the silicon carbide wafer in a mixed solution of sulfuric acid and hydrogen peroxide, ultrapure water, a hydrofluoric acid solution, ultrapure water, a mixed solution of ammonia water and hydrogen peroxide and ultrapure water, a mixed solution of hydrochloric acid and hydrogen peroxide and ultrapure water, and finally clean the silicon carbide wafer in the ultrapure water, the hydrofluoric acid solution and the ultrapure water, and spin-dry the silicon carbide wafer.
The volume ratio of sulfuric acid to hydrogen peroxide in the sulfuric acid and hydrogen peroxide mixed solution is 2.8:1, the cleaning temperature is 120 ℃, and the cleaning time is 18min.
The hydrofluoric acid solution is prepared from hydrofluoric acid and ultrapure water according to a volume ratio of 1:75, wherein the cleaning temperature is normal temperature, and the cleaning time is 15min;
the volume ratio of the ammonia water, the hydrogen peroxide and the ultrapure water in the mixed solution of the ammonia water, the hydrogen peroxide and the ultrapure water is 0.8:0.8:5, the cleaning temperature is 65 ℃ and the cleaning time is 20min.
The ratio of hydrochloric acid, hydrogen peroxide and ultrapure water in the mixed solution of hydrochloric acid, hydrogen peroxide and ultrapure water is 1.2:1.2:6, the cleaning temperature is 65 ℃ and the cleaning time is 18min.
The ultra-pure water technology adopts overflow, bubbling and spraying, the cleaning temperature is normal temperature, and the cleaning time is 10min. In particular, the ultra-pure water cleaning temperature after sulfuric acid+hydrogen peroxide solution is 65 ℃.
Step (6): the silicon carbide wafer subjected to the step (5) was subjected to a surface metal test, and the results are recorded in table 1.
Example 3
A method for removing metal on the surface of silicon carbide comprises the following steps:
step (1): immersing the silicon carbide wafer subjected to chemical mechanical polishing CMP into hydrofluoric acid solution for cleaning, wherein the hydrofluoric acid solution is prepared from hydrofluoric acid and ultrapure water according to a volume ratio of 1:50, cleaning the mixed solution at normal temperature for 15min;
step (2): immersing the silicon carbide wafer subjected to the step (1) into ultrapure water, and cleaning by adopting overflow, bubbling and spraying processes, wherein the cleaning temperature is normal temperature, and the cleaning time is 10min. And spin-drying the product after the cleaning is finished.
Step (3): placing the silicon carbide wafer subjected to the step (2) in an ICP device, and generating gaseous SF by means of inductive coupling 6 Plasma, F with energy generated - And removing the damaged layer and the oxide layer on the surface of the silicon carbide. The ICP device has a power of 400w, a pressure of 15mTorr, a temperature of 25 ℃, and SF 6 The gas flow is 20sccm, and the cleaning time is 15min;
step (4): immersing the silicon carbide wafer subjected to the step (3) into ultrapure water for cleaning, and adopting overflow, bubbling and spraying processes, wherein the cleaning time is 10min, and the cleaning temperature is normal temperature;
step (5): and (3) carrying out an improved RCA cleaning process on the silicon carbide wafer subjected to the step (4), wherein the improved RCA cleaning process is to sequentially immerse the silicon carbide wafer in a mixed solution of sulfuric acid and hydrogen peroxide, ultrapure water, a hydrofluoric acid solution, ultrapure water, a mixed solution of ammonia water and hydrogen peroxide and ultrapure water, a mixed solution of hydrochloric acid and hydrogen peroxide and ultrapure water, and finally clean the silicon carbide wafer in the ultrapure water, the hydrofluoric acid solution and the ultrapure water, and spin-dry the silicon carbide wafer.
The volume ratio of sulfuric acid to hydrogen peroxide in the sulfuric acid and hydrogen peroxide mixed solution is 3.5:1, the cleaning temperature is 125 ℃, and the cleaning time is 22min;
the hydrofluoric acid solution is prepared from hydrofluoric acid and ultrapure water according to a volume ratio of 1:50, the cleaning temperature is normal temperature, and the cleaning time is 15min;
the volume ratio of the ammonia water, the hydrogen peroxide and the ultrapure water in the mixed solution of the ammonia water, the hydrogen peroxide and the ultrapure water is 1.2:1.2:5, the cleaning temperature is 52 ℃, and the cleaning time is 17min.
The ratio of hydrochloric acid, hydrogen peroxide and ultrapure water in the mixed solution of hydrochloric acid, hydrogen peroxide and ultrapure water is 0.7:0.7:6, the cleaning temperature is 70 ℃, and the cleaning time is 22min.
The ultra-pure water technology adopts overflow, bubbling and spraying, the cleaning temperature is normal temperature, and the cleaning time is 10min. In particular, the ultra-pure water cleaning temperature after sulfuric acid+hydrogen peroxide solution is 65 ℃.
Step (6): the silicon carbide wafer subjected to the step (5) was subjected to a surface metal test, and the results are recorded in table 1.
Example 4
A method for removing metal on the surface of silicon carbide comprises the following steps:
step (1): immersing the silicon carbide wafer subjected to chemical mechanical polishing CMP into hydrofluoric acid solution for cleaning, wherein the hydrofluoric acid solution is prepared from hydrofluoric acid and ultrapure water according to a volume ratio of 1:50, cleaning the mixed solution at normal temperature for 20min;
step (2): immersing the silicon carbide wafer subjected to the step (1) into ultrapure water, and cleaning by adopting overflow, bubbling and spraying processes, wherein the cleaning temperature is normal temperature, and the cleaning time is 10min. And spin-drying the product after the cleaning is finished.
Step (3): placing the silicon carbide wafer subjected to the step (2) in an ICP device, and generating gaseous SF by means of inductive coupling 6 Plasma, F with energy generated - Removing a damaged layer and an oxide layer on the surface of silicon carbide, wherein the power of ICP equipment is 300w, the pressure is 10mTorr, the temperature is 20 ℃, and SF is the same 6 The gas flow rate was 25sccm and the cleaning time was 20min.
Step (4): immersing the silicon carbide wafer subjected to the step (3) into ultrapure water for cleaning. The overflow, bubbling and spraying processes are adopted, the cleaning time is 10min, and the cleaning temperature is normal temperature.
Step (5): and (3) carrying out an improved RCA cleaning process on the silicon carbide wafer subjected to the step (4), wherein the improved RCA cleaning process is to sequentially immerse the silicon carbide wafer in a mixed solution of sulfuric acid and hydrogen peroxide, ultrapure water, a hydrofluoric acid solution, ultrapure water, a mixed solution of ammonia water and hydrogen peroxide and ultrapure water, a mixed solution of hydrochloric acid and hydrogen peroxide and ultrapure water, and finally clean the silicon carbide wafer in the ultrapure water, the hydrofluoric acid solution and the ultrapure water, and spin-dry the silicon carbide wafer.
The volume ratio of sulfuric acid to hydrogen peroxide in the sulfuric acid and hydrogen peroxide mixed solution is 3:1, the cleaning temperature is 120 ℃, and the cleaning time is 20min;
the hydrofluoric acid solution is prepared from hydrofluoric acid and ultrapure water according to a volume ratio of 1:50, the cleaning temperature is normal temperature, and the cleaning time is 20min;
the volume ratio of the ammonia water, the hydrogen peroxide and the ultrapure water in the mixed solution of the ammonia water, the hydrogen peroxide and the ultrapure water is 1:1:5, cleaning at 60 ℃ for 20min;
the ratio of hydrochloric acid, hydrogen peroxide and ultrapure water in the mixed solution of hydrochloric acid, hydrogen peroxide and ultrapure water is 1:1:6, cleaning at 75 ℃ for 20min;
the ultra-pure water technology adopts overflow, bubbling and spraying, the cleaning temperature is normal temperature, and the cleaning time is 10min. In particular, the ultra-pure water cleaning temperature after sulfuric acid+hydrogen peroxide solution is 65 ℃.
Step (6): the silicon carbide wafer subjected to the step (5) was subjected to a surface metal test, and the results are recorded in table 1.
TABLE 1 silicon carbide surface Metal detection results
As can be seen from Table 1, the wet chemical cleaning, dry plasma etching and wet chemical cleaning process provided by the present inventionThe content of metals on the surface of the silicon carbide can be obviously reduced, and the content of metals which are difficult to remove, such as Ca, fe, na, mg, al on the surface of the silicon carbide, and the like can be obviously reduced<5E10 atoms/cm 2 。
It should be noted that the above-described embodiments are only examples of some of the embodiments of the present invention. It will be apparent to those skilled in the art that equivalent changes and modifications can be made to the present invention without departing from the spirit and scope of the invention, which is defined in the appended claims.
Claims (7)
1. A method for removing metal from the surface of a silicon carbide wafer comprising the steps of:
1) Immersing the silicon carbide wafer into hydrofluoric acid solution for cleaning;
2) Cleaning the silicon carbide wafer by using ultrapure water, and spin-drying after cleaning;
3) Performing dry plasma etching on the surface of the silicon carbide wafer treated in the step (2) to remove a damaged layer and an oxide layer on the surface of the silicon carbide wafer;
4) The silicon carbide wafer is rinsed with ultra-pure water and then rinsed using a modified RCA rinsing process.
2. The method according to claim 1, wherein the hydrofluoric acid solution in step 1) is hydrofluoric acid and ultrapure water in a volume ratio of 1: 25-100, the cleaning temperature is normal temperature, and the cleaning time is 15-25 min.
3. The method according to claim 1, wherein in step 2), the silicon carbide wafer is cleaned with ultrapure water by a process of combining overflow, bubbling and spraying, the cleaning temperature is normal temperature, and the cleaning time is 8-12 min.
4. The method of claim 1, wherein in step 3), the dry plasma etching uses SF 6 Gas, generating fluorine ions (F) - ) The chemical damage layer and the oxide layer after the silicon carbide wafer CMP are effectively removed, the rate is 100-800 w, the pressure is 5-20 mTorr, and the temperature is 10-30 DEG C，SF 6 The gas flow is 10-50 sccm, and the etching time is 10-25 min.
5. The method according to claim 1, wherein in step 4), the etched silicon carbide wafer is cleaned with ultrapure water by a process of combining overflow, bubbling and spraying, the cleaning temperature is normal temperature, and the cleaning time is 8 to 12 minutes.
6. The method of claim 1, wherein in step 4), the improved RCA cleaning process comprises the steps of:
a) Placing the cleaned silicon carbide wafer into a mixed solution of sulfuric acid and hydrogen peroxide, cleaning for 15-25 min at 110-130 ℃, and then cleaning the surface of the silicon carbide wafer by using ultrapure water, wherein the volume ratio of the sulfuric acid to the hydrogen peroxide is 1-3.5:1;
b) Taking out the silicon carbide wafer in the step a), placing the silicon carbide wafer in a hydrofluoric acid solution, cleaning for 15-25 min at normal temperature, and cleaning the surface of the silicon carbide wafer by using ultrapure water, wherein the hydrofluoric acid solution is prepared by mixing hydrofluoric acid and ultrapure water according to a volume ratio of 1: 25-100 parts of mixed solution;
c) Taking out the silicon carbide wafer in the step b), placing the silicon carbide wafer in a mixed solution composed of ammonia water, hydrogen peroxide and ultrapure water, cleaning for 15-25 min at 50-70 ℃, and then cleaning the surface of the silicon carbide wafer by using the ultrapure water, wherein the volume ratio of the ammonia water to the hydrogen peroxide to the ultrapure water is 0.5-1.5:0.5-1.5:5;
d) Taking out the silicon carbide wafer in the step c), placing the silicon carbide wafer in a mixed solution consisting of hydrochloric acid, hydrogen peroxide and ultrapure water, cleaning for 15-25 min at 60-80 ℃, and cleaning the surface of the silicon carbide wafer by using the ultrapure water, wherein the volume ratio of the hydrochloric acid to the hydrogen peroxide to the ultrapure water is 0.5-1.5: 0.5 to 1.5:6, preparing a base material;
e) Taking out the silicon carbide wafer in the step c), placing the silicon carbide wafer in hydrofluoric acid solution, cleaning the silicon carbide wafer at normal temperature for 15-25 min, cleaning the surface of the silicon carbide wafer by using ultrapure water, and spin-drying; the hydrofluoric acid solution is hydrofluoric acid and ultrapure water according to the volume ratio of 1:25 to 100 percent of mixed solution.
7. The method according to claim 1, wherein the ultrapure water cleaning in steps a) -e) is: the silicon carbide wafer is cleaned by ultrapure water by adopting a process combining overflow, bubbling and spraying, the cleaning temperature is normal temperature, and the cleaning time is 8-12 min.
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