CN111211049B - Silicon wafer alkali corrosion process and application thereof - Google Patents
Silicon wafer alkali corrosion process and application thereof Download PDFInfo
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- CN111211049B CN111211049B CN201811393404.6A CN201811393404A CN111211049B CN 111211049 B CN111211049 B CN 111211049B CN 201811393404 A CN201811393404 A CN 201811393404A CN 111211049 B CN111211049 B CN 111211049B
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 217
- 239000003513 alkali Substances 0.000 title claims abstract description 215
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 215
- 239000010703 silicon Substances 0.000 title claims abstract description 215
- 238000000034 method Methods 0.000 title claims abstract description 140
- 238000005260 corrosion Methods 0.000 title claims abstract description 53
- 230000007797 corrosion Effects 0.000 title claims abstract description 53
- 239000007864 aqueous solution Substances 0.000 claims abstract description 109
- 238000009418 renovation Methods 0.000 claims abstract description 38
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 claims abstract description 30
- 238000006243 chemical reaction Methods 0.000 claims abstract description 29
- 238000000926 separation method Methods 0.000 claims abstract description 24
- 238000004519 manufacturing process Methods 0.000 claims abstract description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 20
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 19
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 19
- 230000002035 prolonged effect Effects 0.000 claims abstract description 7
- 235000012431 wafers Nutrition 0.000 claims description 181
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 104
- 238000005530 etching Methods 0.000 claims description 86
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims description 53
- 239000000292 calcium oxide Substances 0.000 claims description 31
- 239000000843 powder Substances 0.000 claims description 25
- 238000012545 processing Methods 0.000 claims description 22
- 239000011550 stock solution Substances 0.000 claims description 20
- QVQLCTNNEUAWMS-UHFFFAOYSA-N barium oxide Chemical compound [Ba]=O QVQLCTNNEUAWMS-UHFFFAOYSA-N 0.000 claims description 17
- 239000002585 base Substances 0.000 claims description 15
- 239000003638 chemical reducing agent Substances 0.000 claims description 15
- 239000002826 coolant Substances 0.000 claims description 15
- 239000007800 oxidant agent Substances 0.000 claims description 15
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 14
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 12
- 239000013078 crystal Substances 0.000 claims description 12
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 claims description 9
- 239000000446 fuel Substances 0.000 claims description 9
- 239000000395 magnesium oxide Substances 0.000 claims description 9
- WGTYBPLFGIVFAS-UHFFFAOYSA-M tetramethylammonium hydroxide Chemical compound [OH-].C[N+](C)(C)C WGTYBPLFGIVFAS-UHFFFAOYSA-M 0.000 claims description 8
- 239000004020 conductor Substances 0.000 claims description 7
- 238000009419 refurbishment Methods 0.000 claims description 7
- 239000002131 composite material Substances 0.000 claims description 6
- 230000007423 decrease Effects 0.000 claims description 4
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 claims description 4
- 150000007529 inorganic bases Chemical class 0.000 claims description 2
- 150000007530 organic bases Chemical class 0.000 claims description 2
- 239000007788 liquid Substances 0.000 abstract description 17
- 239000002699 waste material Substances 0.000 abstract description 14
- 239000012670 alkaline solution Substances 0.000 abstract description 13
- 230000007613 environmental effect Effects 0.000 abstract description 5
- 239000000463 material Substances 0.000 abstract description 2
- 239000000243 solution Substances 0.000 description 35
- 235000012255 calcium oxide Nutrition 0.000 description 30
- OYACROKNLOSFPA-UHFFFAOYSA-N calcium;dioxido(oxo)silane Chemical class [Ca+2].[O-][Si]([O-])=O OYACROKNLOSFPA-UHFFFAOYSA-N 0.000 description 20
- 239000011575 calcium Substances 0.000 description 12
- 230000000694 effects Effects 0.000 description 11
- 239000002994 raw material Substances 0.000 description 10
- 238000005516 engineering process Methods 0.000 description 9
- 239000002351 wastewater Substances 0.000 description 9
- 229910052910 alkali metal silicate Inorganic materials 0.000 description 6
- 238000005406 washing Methods 0.000 description 6
- 238000001556 precipitation Methods 0.000 description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 239000002253 acid Substances 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 238000005189 flocculation Methods 0.000 description 4
- 230000016615 flocculation Effects 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 239000002244 precipitate Substances 0.000 description 4
- 238000003303 reheating Methods 0.000 description 4
- 238000007792 addition Methods 0.000 description 3
- 238000004134 energy conservation Methods 0.000 description 3
- 229910021645 metal ion Inorganic materials 0.000 description 3
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 3
- 229940095676 wafer product Drugs 0.000 description 3
- 238000004065 wastewater treatment Methods 0.000 description 3
- 229910019440 Mg(OH) Inorganic materials 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 229910052581 Si3N4 Inorganic materials 0.000 description 2
- HMOQPOVBDRFNIU-UHFFFAOYSA-N barium(2+);dioxido(oxo)silane Chemical class [Ba+2].[O-][Si]([O-])=O HMOQPOVBDRFNIU-UHFFFAOYSA-N 0.000 description 2
- 239000000378 calcium silicate Substances 0.000 description 2
- 229910052918 calcium silicate Inorganic materials 0.000 description 2
- 239000003518 caustics Substances 0.000 description 2
- 239000000701 coagulant Substances 0.000 description 2
- 230000001112 coagulating effect Effects 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000000706 filtrate Substances 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- ZADYMNAVLSWLEQ-UHFFFAOYSA-N magnesium;oxygen(2-);silicon(4+) Chemical class [O-2].[O-2].[O-2].[Mg+2].[Si+4] ZADYMNAVLSWLEQ-UHFFFAOYSA-N 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000003908 quality control method Methods 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- 239000004115 Sodium Silicate Substances 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 239000000920 calcium hydroxide Substances 0.000 description 1
- 235000011116 calcium hydroxide Nutrition 0.000 description 1
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 1
- LUMVCLJFHCTMCV-UHFFFAOYSA-M potassium;hydroxide;hydrate Chemical compound O.[OH-].[K+] LUMVCLJFHCTMCV-UHFFFAOYSA-M 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000011085 pressure filtration Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000007650 screen-printing Methods 0.000 description 1
- 229910052911 sodium silicate Inorganic materials 0.000 description 1
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000000967 suction filtration Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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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
- H01L21/18—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 elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
- H01L21/30604—Chemical etching
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00436—Shaping materials, i.e. techniques for structuring the substrate or the layers on the substrate
- B81C1/00523—Etching material
- B81C1/00539—Wet etching
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0236—Special surface textures
- H01L31/02363—Special surface textures of the semiconductor body itself, e.g. textured active layers
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/0258—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C2201/00—Manufacture or treatment of microstructural devices or systems
- B81C2201/01—Manufacture or treatment of microstructural devices or systems in or on a substrate
- B81C2201/0101—Shaping material; Structuring the bulk substrate or layers on the substrate; Film patterning
- B81C2201/0128—Processes for removing material
- B81C2201/013—Etching
- B81C2201/0133—Wet etching
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Abstract
The invention discloses a silicon wafer alkali corrosion process and application thereof, wherein a metal oxide capable of reacting with water to generate renovating alkali is adopted, and the renovating alkali can react with SiO 3 2‑ The reaction is carried out to generate water-insoluble silicate which can be removed by adopting a separation method and is used for realizing the renovation of the alkaline aqueous solution, and the alkaline concentration of the alkaline aqueous solution is maintained to be not lower than the preset lowest value or the time for maintaining the alkaline concentration to be not lower than the preset lowest value of the alkaline concentration is prolonged through the renovation; and simultaneously the SiO of the alkaline aqueous solution is realized by renovation 3 2‑ Reaction into water-insoluble silicate to make SiO 3 2‑ The concentration of (2) is reduced; the invention can obviously improve the operation environment of the strong alkaline solution for a long time, reduce the generation of waste liquid, further obviously reduce the material and environmental cost of the process and obviously improve the operation environment of the process; meanwhile, the process quality of the silicon wafer alkali corrosion can be obviously improved, the downtime of a production line can be effectively reduced, and the production capacity and the production efficiency are improved.
Description
Technical Field
The invention belongs to the field of silicon wafer processing, and particularly relates to a silicon wafer alkali corrosion process and application thereof.
Background
The silicon wafer is widely applied to the photovoltaic field, the electronic chip field (mainly adopting MEMS processing technology) and other fields after being processed due to the characteristics of the silicon wafer. The alkali corrosion process has the advantages of low cost and mature process, so that the alkali corrosion process becomes a common silicon wafer processing process, and can be particularly used for completing a silicon wafer texturing process in the photovoltaic field and manufacturing a silicon wafer microstructure in the MEMS processing technology.
Specifically, the conventional silicon wafer alkaline etching process mainly etches a silicon wafer with a strongly alkaline solution (mainly, an inorganic alkaline solution such as sodium hydroxide or potassium hydroxide, or an organic alkaline solution such as tetramethylammonium hydroxide), and in order to obtain a desired silicon wafer processing microstructure, silicon is often subjected to alkaline etchingThe surface of the wafer is pre-provided with a silicon dioxide or silicon nitride mask. However, in the silicon wafer alkali corrosion process, as the strong alkaline solution continuously participates in the reaction, the alkali concentration in the alkaline solution is gradually reduced, and SiO 3 2- The concentration is gradually increased, when the alkali concentration is reduced to a certain value, the alkali corrosion reaction tends to stop (namely, under the alkali concentration, the alkali corrosion speed of the silicon wafer is very slow and is not accepted by practical application), at the moment, the alkali solution is required to be replaced, the former alkali solution is changed into waste liquid, and not only is the waste liquid subjected to pH value neutralization by adopting various treatment methods, but also the final waste water discharge can be completed by adopting precipitation flocculation desliming treatment. Because the strongly alkaline solution needs to be replaced continuously, the operation environment under the strongly alkaline solution for a long time is also relatively severe, and the treatment cost of waste liquid is high.
It should be noted that, because the existing silicon wafer alkali etching process needs to be changed with strongly alkaline solution continuously, and because the process is usually performed under heating conditions (the temperature is generally set above 70 ℃, the silicon wafer alkali etching reaction can reach the speed acceptable for practical application), a new alkali stock solution needs to be added after the waste liquid is discharged every time, and then the alkali etching process needs to be restarted after reheating is completed, obviously, the process is embodied in the practical industrialization: the addition of new liquid requires a production line shutdown, and obviously the productivity and efficiency are negatively affected.
However, after searching the prior publications, the applicant found that the alkali etching process for silicon wafers has been applied industrially for decades, but there are only a few published techniques to improve the waste liquid treatment after the silicon wafers are subjected to alkali etching:
for example, a chinese patent with an issued publication number of CN104230049B discloses a wastewater treatment method in photovoltaic industry, comprising the steps of: respectively collecting alkali washing wastewater and acid washing wastewater; adding metal ions required for generating silicate into the alkaline washing wastewater, reacting the metal ions with sodium silicate in the alkaline washing wastewater to generate silicate precipitate, and filtering the silicate precipitate to obtain filtrate; adding the obtained filtrate into the acid washing wastewater to adjust the pH value to 7.5-8.5; adding a coagulant and a coagulant aid into the acid pickling wastewater to obtain a coagulating sedimentation product; and (4) concentrating the coagulating sedimentation, and then performing pressure filtration. By adopting the technology, colloidal particles in the wastewater in the photovoltaic industry can be destabilized, so that the subsequent wastewater treatment is easier to carry out; however, the generated alkaline washing wastewater amount is large, the wastewater treatment process is very complicated, and the adopted corrosion process is still to continuously replace strong alkaline aqueous solution for silicon wafer alkaline corrosion, and the process requires operators to be in a strong alkaline and severe operating environment for a long time.
As described above, the applicant has found that the above-mentioned technical problems of the silicon wafer alkali etching process have not been substantially improved so far.
Disclosure of Invention
In view of the above, the present invention is to provide an alkali etching process for silicon wafers and an application thereof, which can significantly reduce the usage amount of alkali solution, significantly improve the operating environment of the alkali solution for a long time, and significantly reduce the generation of alkali silicate waste liquid, thereby significantly reducing the material and environmental costs of the process and significantly improving the operating environment of the process.
The invention also aims to provide a silicon wafer alkali corrosion process and application thereof, which can maintain the alkali concentration of an alkaline aqueous solution to be not lower than the preset minimum value or prolong the time for maintaining the alkali concentration to be not lower than the preset minimum value, thereby not only obviously improving the process quality of the silicon wafer alkali corrosion, but also effectively reducing the downtime of a production line and improving the production capacity and the production efficiency.
The technical scheme adopted by the invention is as follows:
an alkali corrosion process for silicon chip, which adopts alkali aqueous solution stock solution to carry out alkali corrosion on the silicon chip and generate SiO 3 2- The alkali concentration of the alkaline aqueous solution decreases with the corrosion of silicon, siO 3 2- The concentration increases with the etching of silicon, and the alkaline etching process comprises the following refurbishment steps:
a metal oxide is employed that reacts with water and produces a refurbishing base, and the refurbishing base can react with the SiO 3 2- React to generate recoverableThe water-insoluble silicate removed by the separation method is used for realizing the renovation of the alkaline aqueous solution, wherein,
the alkali concentration of the alkaline aqueous solution is increased through the renovation, so that the alkali concentration of the alkaline aqueous solution is maintained not lower than the preset lowest value of the alkali concentration or the time for maintaining not lower than the preset lowest value of the alkali concentration is prolonged;
and simultaneously the SiO of the alkaline aqueous solution is realized by the renovation 3 2- Reaction-converting into the water-insoluble silicate to make SiO of the alkaline aqueous solution 3 2- The concentration of (c) is decreased.
Preferably, the alkali etching process further comprises: removing water-insoluble silicate in the alkaline aqueous solution by a separation method; further preferably, the operation time of the separation method can be performed simultaneously when the renovation of the alkaline aqueous solution is completed, or the operation time of the separation method can be set in other ways according to actual needs, for example, the separation can be performed once every fixed period of time (because the amount of silicate precipitation can be expected), or other conditions can be used to set the operation time, such as measuring the deposition thickness of silicate precipitation, etc.; the applicants believe that these choices are conventional choices made by those skilled in the art based on the disclosure herein, and that the present invention is not expanded upon.
Preferably, the raw material of the metal oxide is calcium oxide powder or magnesium oxide powder or barium oxide powder.
Preferably, the alkali concentration of the basic aqueous solution stock solution ranges from 10% to 45%; the preset minimum range of the alkali concentration of the alkaline aqueous solution is 6-30%.
Preferably, the temperature range of the alkali etching process is set to 70-120 ℃.
Preferably, the crystal orientation of the silicon wafer is a non <111> crystal orientation; the original thickness range of the silicon wafer is 0.05-5mm; the thickness range of the silicon slice corroded by the silicon slice alkali corrosion process is 2-300 microns.
It should be noted that the original thickness range data of the preferred silicon wafer proposed by the present invention is a preferred selection made based on the thickness range obtained by the current silicon wafer cutting processing technology, and certainly, with the development of the silicon wafer cutting processing technology, the present invention can completely perform the alkali etching process on the silicon wafer with a thinner thickness, and completely perform the alkali etching process on the silicon wafer with a thicker thickness according to the actual needs, and the present invention has no particular limitation thereto.
Preferably, the stock basic aqueous solution is an aqueous inorganic base solution comprising sodium hydroxide or potassium hydroxide or an aqueous organic base solution comprising tetramethylammonium hydroxide.
Preferably, the metal oxide is added during the alkaline etching process, or the metal oxide is reacted with water to form a refurbished base in advance and then the refurbished base is added during the alkaline etching process.
Further preferably, the number of additions of the metal oxide or the renovating base does not exceed 20. Of course, if the amount per addition is small, the number of times the refreshing alkali is added may be increased.
Preferably, the application of the silicon wafer alkali etching process is applied to a silicon wafer texturing process in the photovoltaic field.
Preferably, the application of the silicon wafer alkali corrosion process is applied to a silicon wafer microstructure processing process in the field of MEMS.
Preferably, the application of the silicon wafer alkali corrosion process is applied to a silicon wafer flow channel processing process in the field of fuel cells.
Preferably, the silicon wafer is a doped silicon wafer, and the resistivity of the doped silicon wafer is not higher than 0.1 ohm.cm; the silicon wafer is used for manufacturing a silicon electrode plate of the fuel cell; the silicon electrode plate is provided with an internal cooling medium flow passage, a front reducing agent flow passage and/or a back oxidizing agent flow passage, and the internal cooling medium flow passage, the front reducing agent flow passage and/or the back oxidizing agent flow passage are respectively provided with a silicon electrode plate inlet and outlet combination communicated with the internal cooling medium flow passage, the front reducing agent flow passage and/or the back oxidizing agent flow passage.
Preferably, the silicon plate comprises 2 or more than 2 silicon wafers, wherein the silicon wafers are provided with single-sided or double-sided flow channels; the surface areas of the silicon wafers, which do not cover the flow channels, are connected and stacked into a whole by adopting a conductive material in a composite mode, an internal flow channel located in the silicon polar plate is formed through the composite connection, and the internal flow channel is used as the internal cooling medium flow channel; and the flow channel positioned on the non-stacking surface of the silicon wafer is used as a reducing agent flow channel or an oxidizing agent flow channel.
It should be noted that the data of the alkali concentration mentioned throughout the present invention all represent the mass concentration of the alkali concentration.
It should be noted that the concentration of the alkaline aqueous solution described throughout the present invention can be set based on the expected alkali etching rate of the silicon wafer, wherein the preset minimum concentration of the alkaline aqueous solution can also be specifically set based on the alkali etching rate of the silicon wafer acceptable to the actual user, and the setting of the concentration of the alkaline aqueous solution based on the alkali etching rate of the silicon wafer is routine technical choice and common knowledge of the silicon wafer alkali etching process of the skilled person, and is not an innovative content of the present invention, therefore, the present invention is not particularly described.
The working principle and the advantages of the invention are as follows: the invention breaks through the conventional inherent thinking of the existing silicon wafer alkali corrosion process for the first time, and creatively provides the method for keeping the alkali concentration of the alkaline aqueous solution within a certain range all the time and effectively removing SiO of the alkaline aqueous solution 3 2- The renovation core solution idea specifically means that in the silicon wafer alkali corrosion process, a strong alkali solution with high solubility is firstly adopted for silicon wafer dissolution corrosion, when the alkali concentration is reduced to a certain value, a metal oxide which can react with water and generate renovation alkali is adopted, and the renovation alkali can also react with SiO of an alkaline aqueous solution 3 2- The reaction is carried out to generate water-insoluble silicate which can be removed by adopting a separation method, so as to realize the renovation of the alkaline aqueous solution, and the renovation has the working principle that:
the renovation alkali is ionized in the alkaline water solution to generate OH - The alkali concentration of the alkaline aqueous solution can be effectively increased: meanwhile, metal ions of the renovating alkali can be mixed with SiO of the alkaline aqueous solution 3 2- Reacting to generate water-insoluble silicate;
the significance of refurbishment as described above can be simultaneously reflected in the following aspects:
on the one hand, the alkali concentration for the alkaline aqueous solution can be maintained in a state of not lower than the preset minimum value thereof or the time for which it is maintained in a state of not lower than the preset minimum value of the alkali concentration can be extended by the refreshing; and SiO of an alkaline aqueous solution 3 2- The reaction is converted into water-insoluble silicate which can be removed by a separation method, so that the SiO of the alkaline aqueous solution 3 2- The concentration of the alkali silicate solution is reduced, so that the using amount of the alkali solution and the time of an operator contacting the alkali solution can be obviously reduced, the operating environment of the alkali solution for a long time can be obviously improved, the generation of alkali silicate waste liquid can be obviously reduced, the process cost is effectively reduced, and the process operating environment is obviously improved;
on the other hand, as described above, the alkali concentration of the alkaline aqueous solution can be maintained at a state not lower than the preset minimum value or the time for maintaining the alkali concentration at a state not lower than the preset minimum value is prolonged through the renovation, which means that in the silicon wafer alkali etching process of the present invention, the alkali concentration of the alkaline aqueous solution can be maintained within a certain numerical range for a long time, which is obviously beneficial to the process integrity and consistency of the silicon wafer in the alkali etching process, so that the silicon wafer product subjected to alkali etching with more consistent quality and convenient quality control can be obtained, and the present invention does not need to shut down a production line with higher frequency to replace waste liquid to add new liquid and restart the alkali etching process after reheating as in the existing silicon wafer alkali etching process, so in conclusion, the present invention not only can significantly improve the process quality of the silicon wafer alkali etching, but also can effectively reduce the downtime of the production line, and improve the production capacity and the production efficiency;
the silicon wafer alkali corrosion process provided by the invention can be directly applied to a silicon wafer texturing process in the photovoltaic field, a silicon wafer microstructure processing process in the MEMS field, a silicon wafer runner processing process in the fuel cell field and other related fields needing the silicon wafer alkali corrosion process, has a wide application range, and has great significance in energy conservation, environmental protection and efficiency improvement;
the invention further most preferably provides that calcium oxide powder (commonly known as quicklime) is directly used as a raw material of the metal oxide, on one hand, the quicklime is wide in source, low in cost and very easy to obtain; on the other hand, since calcium lime reacts with water to form Ca (OH) 2 ，Ca(OH) 2 Will be due to OH - The concentration (namely, the alkali concentration) is increased and reduced, so that the generation of a high alkali solution environment is avoided, and the time for maintaining the alkali concentration of the alkaline aqueous solution within a certain numerical range is facilitated; in addition, the invention adopts calcium oxide to renew the alkaline aqueous solution by Ca (OH) 2 Due to the solubility characteristic, the alkali concentration of the alkaline aqueous solution in which the silicon wafer is located is always in a relatively stable range, so that the quality consistency of the silicon wafer after the alkali corrosion is finished is facilitated, and a preset mask structure of the silicon wafer cannot be damaged due to the continuous change of the alkali concentration (the mask structure is usually required to be preset in the silicon wafer microstructure processing or silicon wafer runner processing technology);
the invention further preferably provides a separation method for removing water-insoluble silicate in the alkaline aqueous solution, which can effectively avoid the problem that when the silicate is deposited to a certain amount, the silicate can be retained in the alkaline aqueous solution in a flocculated form to further cause possible negative influence on the alkaline corrosion reaction of the silicon wafer; the invention further provides a preferable separation method which is simple and effective, and the silicate obtained by the separation method has good performance, can be directly used as a silicate raw material to be applied to related fields, and realizes zero waste output.
Drawings
FIG. 1 is a block diagram of the operation steps of the caustic etching process for silicon wafer in example 1 according to the embodiment of the present invention;
FIG. 2 is a block diagram of the operation steps of the method for separating calcium silicate salt in the wafer caustic etching process of example 1 according to the embodiment of the present invention.
Detailed Description
Examples of the inventionDiscloses a silicon wafer alkali corrosion process, which adopts alkali aqueous solution stock solution to carry out alkali corrosion on a silicon wafer and generate SiO 3 2- The alkali concentration of the alkaline aqueous solution decreases with the corrosion of silicon, siO 3 2- The concentration increases with the etching of silicon, and the alkaline etching process comprises the following refurbishment steps: using a metal oxide which reacts with water and forms a refurbishing base, and the refurbishing base can react with SiO 3 2- The reaction is carried out to generate water-insoluble silicate which can be removed by adopting a separation method and is used for realizing the renovation of the alkaline aqueous solution, wherein the alkali concentration of the alkaline aqueous solution is increased by renovation, so that the alkali concentration of the alkaline aqueous solution is maintained not lower than the preset lowest value of the alkali concentration or the time for maintaining the alkali concentration not lower than the preset lowest value of the alkali concentration is prolonged; and simultaneously the SiO of the alkaline aqueous solution is realized by renovation 3 2- Reaction of the SiO in the alkali aqueous solution to form a water-insoluble silicate 3 2- The concentration of (c) is decreased.
The embodiment of the invention breaks through the conventional inherent thinking of the existing silicon wafer alkali corrosion process for the first time, and creatively provides the method for effectively removing SiO in the alkaline aqueous solution while keeping the alkali concentration of the alkaline aqueous solution in a certain range all the time 3 2- The renovation core solution idea specifically means that in the silicon wafer alkali corrosion process, a strong alkali solution with high solubility is firstly adopted for silicon wafer dissolution corrosion, when the alkali concentration is reduced to a certain value, a metal oxide which can react with water and generate renovation alkali is adopted, and the renovation alkali can also react with SiO of an alkaline aqueous solution 3 2- The reaction is carried out to generate water-insoluble silicate which can be removed by a separation method, so as to realize the renovation of the alkaline aqueous solution, and the significance of the renovation can be simultaneously embodied in the following aspects:
on the one hand, the alkali concentration for the alkaline aqueous solution can be maintained at not less than its preset minimum value or the time for which it is maintained at not less than its preset minimum value can be extended by the refreshing; and SiO of an alkaline aqueous solution 3 2- The reaction is converted into water-insoluble silicate which can be removed by a separation method, so that the SiO of the alkaline aqueous solution 3 2- The concentration of the alkali silicate solution is reduced, so that the using amount of the alkali solution and the time of an operator contacting the alkali solution can be obviously reduced, the embodiment of the invention can obviously improve the operating environment of the alkali solution for a long time, can also obviously reduce the generation of alkali silicate waste liquid, effectively reduce the process cost and obviously improve the process operating environment; on the other hand, as described above, the alkali concentration of the alkaline aqueous solution can be maintained at a state not lower than the preset minimum value or the time for maintaining the alkali concentration at the preset minimum value is prolonged through the renovation, which means that in the silicon wafer alkali etching process of the embodiment of the present invention, the alkali concentration of the alkaline aqueous solution can be maintained within a certain numerical range for a long time, which is obviously beneficial to the process integrity and consistency of the silicon wafer in the alkali etching process, so that the silicon wafer product subjected to alkali etching, which is convenient for quality control and more consistent in quality, can be obtained, and the embodiment of the present invention does not need to shut down a production line at a higher frequency to replace waste liquid to add new liquid and restart the alkali etching process after reheating, so in conclusion, the embodiment of the present invention can not only obviously enhance the process quality of alkali etching of the silicon wafer of the embodiment of the present invention, but also can effectively reduce the downtime of the production line, and improve the production capacity and the production efficiency;
the silicon wafer alkali corrosion process provided by the embodiment of the invention can be directly applied to a silicon wafer texturing process in the photovoltaic field, a silicon wafer microstructure processing process in the MEMS field, a silicon wafer runner processing process in the fuel cell field and other related fields needing the silicon wafer alkali corrosion process, has a wide application range, and has great significance in energy conservation, environmental protection and efficiency improvement.
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Example 1:
a silicon wafer alkali corrosion process is applied to a silicon wafer runner processing process in the field of fuel cells; alkali corrosion is carried out on the silicon chip by adopting alkaline aqueous solution stock solution to generate SiO 3 2- The alkali concentration of the alkaline aqueous solution decreases with the corrosion of silicon, siO 3 2- The concentration increases with the etching of silicon, and the alkaline etching process comprises the following refurbishment steps: using a metal oxide which reacts with water and forms a refurbishing base, and the refurbishing base can react with SiO 3 2- The reaction is carried out to generate water-insoluble silicate which can be removed by adopting a separation method and is used for realizing the renovation of the alkaline aqueous solution, wherein the alkali concentration of the alkaline aqueous solution is increased by renovation, so that the alkali concentration of the alkaline aqueous solution is maintained not lower than the preset lowest value of the alkali concentration or the time for maintaining the alkali concentration not lower than the preset lowest value of the alkali concentration is prolonged; and simultaneously the SiO of the alkaline aqueous solution is realized by renovation 3 2- Reaction into water-insoluble silicate to make SiO of alkaline aqueous solution 3 2- The concentration of (2) is reduced;
wherein, preferably, in the embodiment, the silicon wafer is a doped silicon wafer, and the resistivity of the doped silicon wafer is not higher than 0.1 Ω · cm; the crystal orientation of the silicon wafer is not a <111> crystal orientation; the original thickness range of the silicon wafer is 0.05-5mm; particularly preferably, in this embodiment, the silicon wafers used are all N-type single crystal silicon wafers, which are square, and the crystal orientation is not the <111> crystal orientation, and specifically may be the <100> crystal orientation or the <110> crystal orientation or another crystal orientation having an obvious angle with the <111> crystal orientation, which is beneficial to the subsequent use of the silicon wafer alkali etching process in this embodiment; the resistivity of the N-type single crystal silicon wafer is about 0.01 omega cm; the thickness of the silicon chip is 0.5mm, and the size is about 150mm; in the embodiment, conductive material layers with the thickness of 1-15 micrometers are respectively manufactured on the two sides of a silicon wafer through a screen printing process, and the conductive material adopts nickel; the conductive material layer is simultaneously used as a mask layer of the silicon wafer, and the silicon wafer alkali corrosion process in the embodiment is started;
preferably, in this embodiment, referring to fig. 1, the alkali etching process of the silicon wafer specifically includes the following steps:
a10 Preparing a stock solution of an aqueous solution of potassium hydroxide having an alkali concentration in the range of 10 to 45% in advance in an alkali etching apparatus, specifically, in the present embodiment, the stock solution of an aqueous solution of potassium hydroxide has an alkali concentration of 30%;
a20 Silicon chip is put into the stock solution of the potassium hydroxide aqueous solution; wherein the quantity of the silicon chips is determined by calculation according to the following reaction formula of the silicon chips and the potassium hydroxide aqueous solution;
Si+2KOH+H 2 O＝K 2 SiO 3 +2H 2 × (heating condition);
of course, in other embodiments of the present invention, a stock solution of sodium hydroxide aqueous solution or a stock solution of tetramethylammonium hydroxide organic alkali may be used, and other alkaline aqueous solutions used in the prior art for alkaline etching of silicon wafers may also be used as the stock solution of the alkaline aqueous solution in the examples of the present invention, and the technical solutions disclosed in the prior art for adding related additives to the stock solution of the alkaline aqueous solution to improve the alkaline etching effect of the silicon wafers may also be used, and the alternative combination applications of these prior arts do not affect the specific implementation of the present invention, and the present invention is not particularly limited thereto;
a30 Heating the silicon wafer to 70-120 deg.c, and making the stock solution of potassium hydroxide solution produce alkali corrosion reaction on the silicon wafer to produce SiO 3 2- (ii) a Meanwhile, as the reaction proceeds, the alkali concentration of the potassium hydroxide aqueous solution is reduced along with the corrosion of silicon, and SiO 3 2- The concentration is increased along with the corrosion of the silicon until the alkali concentration of the potassium hydroxide aqueous solution is monitored to be reduced to a critical preset minimum value; wherein the preset lowest value range of the alkali concentration of the potassium hydroxide aqueous solution is 6-30%; specifically, in this embodiment, the alkali etching apparatus is heated to 80 ℃, the preset minimum value of the alkali concentration of the aqueous solution of potassium hydroxide is set to 10%, which is set based on the minimum acceptable alkali etching speed of the silicon wafer based on the thickness of the silicon wafer to be etched and the common knowledge in the present embodiment, and in other embodiments of the present invention, the minimum acceptable alkali etching speed of the silicon wafer can be combined with the required etching speed of the silicon waferThe thickness is used to finally set the preset minimum value of the alkali concentration; in other embodiments, other heating conditions in the temperature range of 70 ℃ to 120 ℃ are adopted, the implementation effect is not obvious, and the technical effect emphasized by the invention can be obtained;
a40 ) adding a metal oxide which can react with water to form a renovating base, and the renovating base can react with SiO to form a renovating base, to an aqueous solution of potassium hydroxide with a base concentration at a critical preset minimum value 3 2- The reaction to produce water insoluble silicate which can be removed by separation method for renewing the alkaline aqueous solution of potassium hydroxide, preferably, in the present embodiment, the raw material of metal oxide is directly used to react with water and produce renewing alkali Ca (OH) 2 The CaO of the quicklime is low in price and easy to obtain; the alkali concentration of the potassium hydroxide alkaline aqueous solution is increased through the renovation, so that the alkali concentration of the potassium hydroxide alkaline aqueous solution is maintained to be not lower than 10% of the preset minimum value; and simultaneously by renewing the alkali Ca (OH) 2 With SiO 3 2- The reaction is carried out to generate water-insoluble calcium silicate salt, thus realizing the reaction of SiO in the potassium hydroxide alkaline aqueous solution 3 2- Reaction of SiO with water-insoluble calcium silicate salt to give an aqueous alkaline solution of potassium hydroxide 3 2- The concentration of (2) is reduced; in other embodiments of the present invention, calcium oxide and water may be fully stirred to react to form Ca (OH) 2 Then adding the potassium hydroxide solution with the alkali concentration at the preset lowest value, wherein the implementation of the invention is not influenced by the sequential conventional technical selection and replacement, and the skilled person can select the potassium hydroxide solution according to the specific practical implementation environment during the practical operation;
wherein, the quicklime in the step A40) reacts with water to generate renovating alkali, thereby realizing renovation of the potassium hydroxide water solution, and the reaction formula in the renovation process is as follows:
(1)CaO+H 2 O＝Ca(OH) 2
(2)Ca(OH) 2 +SiO 3 2- ＝Ca SiO 3 +2OH -
in the step A40), the stirring function in the alkali corrosion equipment is started to ensure the reaction to be complete;
a50 Adopting a separation method to remove water-insoluble calcium silicate salt in the potassium hydroxide alkaline aqueous solution, and continuously using the potassium hydroxide alkaline aqueous solution for the silicon wafer alkaline corrosion process in the embodiment, namely entering the step A20), so as to facilitate the next silicon wafer alkaline corrosion; in this embodiment, a certain amount of water may be supplemented to the potassium hydroxide alkaline aqueous solution from which the water-insoluble calcium silicate salt is removed, and in other embodiments, a small amount of potassium hydroxide may be simultaneously supplemented when the alkali concentration value to be maintained is high;
the applicant also believes after many experiments that it is preferable that the number of adding quicklime CaO is not higher than 20, and after more than 20, the calcium silicate salt is difficult to separate, the impurity content of the potassium hydroxide aqueous solution is high, and the final alkali etching process effect of the silicon wafer is poor, so although theoretically, in this embodiment, the alkali concentration of the potassium hydroxide alkaline aqueous solution can be always maintained at a state not lower than the preset minimum value thereof by adding quicklime at intervals, after actual operation, it is found that, since the quality of the potassium hydroxide aqueous solution is obviously deteriorated when the number of adding reaches a certain number, as a whole, the embodiment can at least prolong the time for maintaining the preset minimum value not lower than the alkali concentration by renewing; more specifically, in the present embodiment, the number of times of adding quicklime CaO is 8, and in the specific implementation, a person skilled in the art can use OH consumed based on the reaction rate of silicon wafer alkaline corrosion - Setting the interval time of adding the CaO every time and the adding amount of the CaO by the speed; in other embodiments, the specific times of adding the quicklime CaO are specifically selected according to the number of silicon wafers needing to be treated and the capacity of the alkali corrosion equipment, and the adding times are not recommended to exceed 20 times;
the thickness range of the silicon wafer etched by the silicon wafer alkali etching process provided by the embodiment of the invention is 50-300 microns, specifically, in the embodiment, the thickness of the etched silicon wafer is 100 +/-10 microns, through detection, the mask structure of the silicon wafer after the alkali etching is completed is complete and is not damaged, and the consistency of the etching thickness and the flow channel flatness of the silicon wafer after each round of alkali etching is good.
When the embodiment of the invention is applied to a silicon wafer microstructure processing technology in the field of MEMS or a silicon wafer runner processing technology in the field of fuel cells, the thickness range of a silicon wafer corroded by a silicon wafer alkali corrosion technology is usually 50-300 micrometers.
This example also specifically proposes a preferable method for separating calcium silicate salt, and of course, in other embodiments, the operation time of the separation method may be set by using other conditions mentioned in the technical solution of the present application, or may be set by using other feasible conditions, which is not particularly limited by the examples of the present invention.
Referring further to fig. 2, the operation steps include:
s10), standing the flocculated precipitate of the water-insoluble calcium silicate salt, and layering the flocculated precipitate with an alkaline aqueous solution, wherein the alkaline aqueous solution is positioned at the upper layer, and the water-insoluble silicate is positioned at the lower layer;
s20), quicklime is used as a filter layer, so that the flocculation separation effect of calcium silicate salt can be obviously improved; filtering to separate water insoluble calcium silicate salt, and continuing to use the alkaline aqueous solution for silicon wafer alkaline corrosion, wherein the filtering can be filter pressing or high pressure suction filtration; further preferably, after tests, the flocculation separation effect is better when quicklime and hydrated lime are used as the filter layer at the same time, and the specific expression is that the filtration separation degree of calcium silicate salt can reach more than 95%; preferably, in the embodiment, a small amount of precipitation aid can be mixed in the quicklime, so that the quick flocculation precipitation of the calcium silicate salt is facilitated, and the separation in the embodiment is facilitated;
s30), drying the water-insoluble calcium silicate salt separated in the step S20) at high temperature to obtain silicate powder; preferably, the calcium silicate salt is neutralized with an acid solution prior to high temperature drying to ensure that the calcium silicate salt is in a neutral state.
The embodiment also provides a calcium silicate salt which is prepared by adopting the method for separating the calcium silicate salt in the silicon wafer alkali corrosion process; the calcium silicate salt is in the form of a particulate powder having an average particle size in the range of 8-50 microns; the calcium silicate provided in this example can be directly applied to the related industries, and can also be pressed into calcium silicate boards, and these applications are routine technical choices for those skilled in the art.
The embodiment can obviously reduce the using amount of the strong alkaline solution and the time of contacting the strong alkaline solution by operators, so the embodiment can obviously improve the operating environment of the strong alkaline solution for a long time, can also obviously reduce the generation of alkali silicate waste liquid, obviously and effectively reduce the process cost, obviously improve the process operating environment and greatly improve the severe operating environment of the conventional silicon wafer alkali corrosion process; it should be noted that, since the alkali concentration of the alkaline aqueous solution of potassium hydroxide in this embodiment can be maintained within a certain numerical range for a long time, this is obviously beneficial to the process integrity and consistency of the silicon wafer in the process of alkali etching, so that the silicon wafer product after alkali etching with more consistent quality can be obtained, and the invention does not need to shut down the production line with higher frequency to replace the waste liquid and add new liquid, and then restart the process of alkali etching process after reheating, as a result, in conclusion, this embodiment can not only obviously improve the process quality of alkali etching of silicon wafer, but also effectively reduce the downtime of the production line, and improve the production capacity and production efficiency; has great significance in energy conservation, environmental protection and efficiency improvement.
The silicon wafer of the embodiment is used for manufacturing a silicon electrode plate of a fuel cell, wherein the silicon electrode plate is provided with an internal cooling medium flow passage, a front reducing agent flow passage and/or a back oxidizing agent flow passage, and the internal cooling medium flow passage, the front reducing agent flow passage and/or the back oxidizing agent flow passage are respectively provided with a silicon electrode plate inlet and outlet combination communicated with the internal cooling medium flow passage, the front reducing agent flow passage and/or the back oxidizing agent flow passage; the silicon polar plate comprises 2 or more than 2 silicon wafers, wherein each silicon wafer is provided with a single-sided or double-sided flow channel; the surface areas of the silicon wafers, which do not cover the flow channels, are compositely connected and stacked into a whole by adopting a conductive material, and an internal flow channel positioned in the silicon pole plate is formed by composite connection and is used as an internal cooling medium flow channel; the flow channel positioned on the non-stacking surface of the silicon wafer is used as a reducing agent flow channel or an oxidizing agent flow channel; specifically, in the present embodiment, the silicon electrode plate is formed by composite processing of two silicon wafers, and has an internal cooling medium flow passage, a front-side reducing agent flow passage, and a back-side oxidizing agent flow passage; and the internal cooling medium flow passage, the front reducing agent flow passage and the back oxidant flow passage are respectively provided with silicon polar plate inlet and outlet combinations communicated with the internal cooling medium flow passage, the front reducing agent flow passage and the back oxidant flow passage;
the specific technical solutions of the silicon wafer of this embodiment and the silicon plate manufactured by using the silicon wafer of this embodiment can be directly referred to the technical solution of embodiment 1 of the prior patent application cn201810577211.X of this application; moreover, the silicon wafer subjected to the alkali etching process proposed in the cn201810577211.X can also adopt the alkali etching process for the silicon wafer according to the embodiment of the present invention, and these combined applications are all conventional technical means of those skilled in the art, and no creative work is required, and the embodiments are not described one by one.
Example 2:
the rest of the technical solutions in this embodiment 2 are the same as those in embodiment 1, except that: in this example 2, magnesia powder was used as a raw material of the metal oxide; wherein, the magnesium oxide powder in the step A40) reacts with water to generate renovating alkali, so as to realize renovation of the alkaline aqueous solution of the potassium hydroxide aqueous solution; simultaneous refurbishment of alkali and SiO 3 2- The reaction generates water-insoluble magnesium silicate salt, and the reaction formula is as follows:
(1)MgO+H 2 O＝Mg(OH) 2
(2)Mg(OH) 2 +SiO 3 2- ＝Mg SiO 3 +2OH -
in step S20) of the method for separating magnesium silicate salt in embodiment 2, magnesia powder is used as a filter layer;
since the raw material cost of the magnesium oxide powder of example 2 is higher than that of calcium oxide powder, and the renovating alkali Mg (OH) 2 The solubility of (2) is inferior to that of Ca (OH) 2 To achieve the same renovation effect, a larger amount of magnesia powder raw material needs to be added, so the renovation effect by using magnesia powder is not as good as that by using calcium oxide powder.
Example 3:
the rest of the technical solutions in this embodiment 3 are the same as those in embodiment 1, except that: in the bookIn example 3, barium oxide powder was used as a raw material of the metal oxide; wherein, the barium oxide powder in the step A40) reacts with water to generate renovating alkali, so as to realize renovation of the alkaline aqueous solution of the potassium hydroxide aqueous solution; simultaneous refurbishment of alkali and SiO 3 2- The reaction generates water-insoluble barium silicate salt, and the reaction formula is as follows:
(1)BaO+H 2 O＝Ba(OH) 2
(2)Ba(OH) 2 +SiO 3 2- ＝Ba SiO 3 +2OH -
in step S20) of the method for separating a barium silicate salt in embodiment 3, barium oxide powder is used as a filter layer;
since the raw material cost of barium oxide powder of example 3 is significantly higher than that of calcium oxide powder, and the renovating alkali Ba (OH) 2 The solubility of (2) is inferior to that of Ca (OH) 2 To achieve the same renovation effect, a larger amount of barium oxide powder raw material needs to be added, so the renovation effect of the barium oxide powder is not as good as that of the calcium oxide powder.
Example 4:
the rest of the technical solutions of this embodiment 4 are the same as those of embodiment 1, embodiment 2 or embodiment 3, except that: in this example 4, the alkali concentration of the stock solution of potassium hydroxide aqueous solution was 35%, the thickness of the etched silicon wafer was 200 ± 10 μm, the alkali etching apparatus was heated to 95 ℃, the preset minimum value of the alkali concentration of the potassium hydroxide aqueous solution was set to 15%, and the number of times of adding quicklime was 10.
Example 5:
the remaining technical solutions of this embodiment 5 are the same as those of embodiment 1, embodiment 2 or embodiment 3, except that: in this example 5, the alkali concentration of the stock solution of potassium hydroxide aqueous solution was 45%, the thickness of the etched silicon wafer was 300 ± 10 μm, the alkali etching apparatus was heated to 115 to 120 ℃, the preset minimum value of the alkali concentration of the potassium hydroxide aqueous solution was set to 30%, and the number of times of adding quicklime was 10 times.
Example 6:
the remaining technical solutions of this embodiment 6 are the same as those of embodiment 1, embodiment 2 or embodiment 3, and the differences are as follows: in this example 6, the alkali concentration of the stock solution of potassium hydroxide aqueous solution was 10%, the thickness of the etched silicon wafer was 50 ± 10 μm, the alkali etching apparatus was heated to 70 ℃, the preset minimum value of the alkali concentration of the potassium hydroxide aqueous solution was set to 6%, and the number of times of adding quicklime was 15.
Example 7:
the rest of the technical solutions of this embodiment 7 are the same as those of embodiment 1, embodiment 2 or embodiment 3, except that: in this example 7, the alkali concentration of the stock solution of the aqueous potassium hydroxide solution was 20%, the thickness of the etched silicon wafer was 80 ± 10 μm, the alkali etching apparatus was heated to 90 ℃, the preset minimum value of the alkali concentration of the aqueous potassium hydroxide solution was set to 9%, and the number of times of adding quicklime was 12.
The above embodiments 4 to 7 can bring about the technical effects which are not different from the corresponding embodiments 1 to 3, and all can solve the technical problems to be solved by the present invention.
Example 8:
the remaining technical solutions of this embodiment 8 are the same as any one of embodiments 1 to 7, except that: in this embodiment 8, a silicon wafer alkali etching process is applied to a silicon wafer texturing process in the photovoltaic field, where the silicon wafer may be a monocrystalline silicon wafer or a polycrystalline silicon wafer, and the embodiment of the present invention is not limited thereto, where two sides of the silicon wafer are not provided with a conductive material layer, the silicon wafer is subjected to a silicon wafer alkali etching process after being cleaned, and the silicon wafer texturing process is completed after removing residual damaged layers on the upper and lower surfaces of the silicon wafer by the silicon wafer alkali etching process, and the silicon wafer texturing process in the photovoltaic field described in the embodiment of the present invention is finally completed, specifically, in this embodiment, a total thickness range of the residual damaged layers on the upper and lower surfaces of the silicon wafer removed by the alkali etching process is 9 to 15 micrometers, and certainly, in other embodiments, the residual damaged layers on the upper and lower surfaces of the silicon wafer having a thicker thickness, such as 15 to 50 micrometers, may also be completely etched as needed; the thickness range of the silicon wafer texturing process itself removed by the alkali etching process in the embodiment is 2-5 microns.
Example 9:
the remaining technical solutions of this embodiment 9 are the same as any one of embodiments 1 to 7, except that: in this embodiment 9, an application of a silicon wafer alkali etching process is applied to a silicon wafer microstructure processing process in the field of MEMS, where silicon dioxide or silicon nitride mask layers are disposed on both sides of a silicon wafer, and a method for disposing the mask layers is any one of the methods in the prior art, and this embodiment is not particularly limited.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (12)
1. An alkali etching process for silicon wafer, which adopts alkaline aqueous solution stock solution to carry out alkali etching on the silicon wafer and generate SiO 3 2- The alkali concentration of the alkaline aqueous solution decreases with the corrosion of silicon, siO 3 2- The concentration increases with the etching of silicon, characterized in that the alkaline etching process comprises the following refurbishment steps:
a metal oxide is employed that reacts with water and produces a refurbishing base, and the refurbishing base can react with the SiO 3 2- The reaction is carried out to generate water-insoluble silicate which can be removed by a separation method and is used for realizing the renovation of alkaline aqueous solution, wherein,
the alkali concentration of the alkaline aqueous solution is increased through the renovation, so that the alkali concentration of the alkaline aqueous solution is maintained not lower than the preset lowest value of the alkali concentration or the time for maintaining not lower than the preset lowest value of the alkali concentration is prolonged;
and simultaneously the SiO of the alkaline aqueous solution is realized by the renovation 3 2- Reaction-converting into the water-insoluble silicate to make SiO of the alkaline aqueous solution 3 2- The concentration of (2) is reduced;
the metal oxide is added in the alkali etching process, or the metal oxide is reacted with water to generate the renovated alkali in advance, and then the renovated alkali is added in the alkali etching process.
2. The silicon wafer alkaline etching process of claim 1, further comprising: and removing water-insoluble silicate in the alkaline aqueous solution by a separation method.
3. The silicon wafer alkali etching process according to claim 1 or 2, wherein the metal oxide is prepared from calcium oxide powder, magnesium oxide powder or barium oxide powder.
4. The silicon wafer alkali etching process according to claim 1 or 2, wherein the alkali concentration of the stock solution of the alkali aqueous solution is in the range of 10 to 45%; the preset minimum range of the alkali concentration of the alkaline aqueous solution is 6-30%.
5. The alkali etching process for silicon wafers according to claim 1 or 2, wherein the temperature of the alkali etching process is set in the range of 70 ℃ to 120 ℃.
6. The alkali etching process for silicon wafers according to claim 1 or 2, wherein the crystal orientation of the silicon wafer is a non <111> crystal orientation; the original thickness range of the silicon wafer is 0.05-5mm; the thickness range of the silicon wafer corroded by the silicon wafer alkali corrosion process is 2-300 micrometers.
7. The silicon wafer alkaline etching process according to claim 1 or 2, wherein the stock solution of the alkaline aqueous solution is an aqueous solution of an inorganic base comprising sodium hydroxide or potassium hydroxide or an aqueous solution of an organic base comprising tetramethylammonium hydroxide.
8. Use of the alkaline etching process for silicon wafers according to any of claims 1 to 7 in texturing silicon wafers in the photovoltaic field.
9. Use of the silicon wafer alkaline etching process according to any one of claims 1 to 7 in a process for processing a silicon wafer microstructure in the field of MEMS.
10. The application of the silicon wafer alkali etching process as claimed in any one of claims 1 to 7, which is applied to a silicon wafer flow channel processing process in the field of fuel cells.
11. The use of the alkali etching process for silicon wafers according to claim 10 wherein the silicon wafers are doped silicon wafers having a resistivity of not more than 0.1 Ω. Cm; the silicon wafer is used for manufacturing a silicon electrode plate of the fuel cell; the silicon electrode plate is provided with an internal cooling medium flow passage, a front reducing agent flow passage and/or a back oxidizing agent flow passage, and the internal cooling medium flow passage, the front reducing agent flow passage and/or the back oxidizing agent flow passage are respectively provided with a silicon electrode plate inlet and outlet combination communicated with the internal cooling medium flow passage, the front reducing agent flow passage and/or the back oxidizing agent flow passage.
12. The use of the wafer alkaline etching process of claim 11, wherein the silicon plate comprises 2 or more than 2 wafers, wherein the wafers have single-sided or double-sided flow channels;
the surface areas of the silicon wafers, which do not cover the flow channels, are connected and stacked into a whole by adopting a conductive material in a composite mode, an internal flow channel located in the silicon polar plate is formed through the composite connection, and the internal flow channel is used as the internal cooling medium flow channel; and the flow channel positioned on the non-stacking surface of the silicon wafer is used as a reducing agent flow channel or an oxidizing agent flow channel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN201811393404.6A CN111211049B (en) | 2018-11-21 | 2018-11-21 | Silicon wafer alkali corrosion process and application thereof |
Applications Claiming Priority (1)
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