WO2011152973A1 - Texturing of multi-crystalline silicon substrates - Google Patents
Texturing of multi-crystalline silicon substrates Download PDFInfo
- Publication number
- WO2011152973A1 WO2011152973A1 PCT/US2011/036163 US2011036163W WO2011152973A1 WO 2011152973 A1 WO2011152973 A1 WO 2011152973A1 US 2011036163 W US2011036163 W US 2011036163W WO 2011152973 A1 WO2011152973 A1 WO 2011152973A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- etching
- texturing
- crystalline silicon
- silicon
- solution
- Prior art date
Links
- 239000000758 substrate Substances 0.000 title claims abstract description 25
- 229910021420 polycrystalline silicon Inorganic materials 0.000 title claims abstract description 18
- 238000005530 etching Methods 0.000 claims abstract description 34
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 22
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 21
- 239000010703 silicon Substances 0.000 claims abstract description 21
- 238000000034 method Methods 0.000 claims description 8
- 239000000126 substance Substances 0.000 claims description 7
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 5
- 229910017604 nitric acid Inorganic materials 0.000 claims description 5
- 239000002253 acid Substances 0.000 claims description 4
- 150000004761 hexafluorosilicates Chemical class 0.000 claims description 4
- 235000012431 wafers Nutrition 0.000 abstract description 8
- 239000000243 solution Substances 0.000 description 29
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 3
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 229910001868 water Inorganic materials 0.000 description 3
- 229910004014 SiF4 Inorganic materials 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- 239000006117 anti-reflective coating Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- ABTOQLMXBSRXSM-UHFFFAOYSA-N silicon tetrafluoride Chemical compound F[Si](F)(F)F ABTOQLMXBSRXSM-UHFFFAOYSA-N 0.000 description 2
- 229910003638 H2SiF6 Inorganic materials 0.000 description 1
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 1
- 229910018557 Si O Inorganic materials 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- 229910004074 SiF6 Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 230000003466 anti-cipated effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000003776 cleavage reaction Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 1
- QPJSUIGXIBEQAC-UHFFFAOYSA-N n-(2,4-dichloro-5-propan-2-yloxyphenyl)acetamide Chemical compound CC(C)OC1=CC(NC(C)=O)=C(Cl)C=C1Cl QPJSUIGXIBEQAC-UHFFFAOYSA-N 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000007017 scission Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Inorganic materials [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- ZEFWRWWINDLIIV-UHFFFAOYSA-N tetrafluorosilane;dihydrofluoride Chemical compound F.F.F[Si](F)(F)F ZEFWRWWINDLIIV-UHFFFAOYSA-N 0.000 description 1
- 239000004408 titanium dioxide Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
-
- 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
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
Definitions
- the present invention relates to improves chemistries and methods for texturing of multi-crystalline silicon substrates, particularly for use as solar cells or photovoltaic cells.
- ARC anti-reflective coating
- silicon oxide silicon oxide
- silicon nitride silicon dioxide
- titanium dioxide an anti-reflective coating
- Another method of reducing reflectance and improving device efficiency is to texture the silicon wafer surface using a wet-chemical etch to from small structures, often having a pyramidal shape. These structures provide higher levels of light trapping due to multiple scattering. Based on geometrical optics, the texturing should be on a scale equal to or greater than optical wavelengths of the incident light to cause the incident light to reflect multiple times and thereby enhance the amount of absorption.
- the texturing process is generally carried out using a mixture of potassium hydroxide (KOH) or sodium hydroxide (NaOH) and isopropyl alcohol (IP A) in deionized (DI) water as the etchant.
- KOH potassium hydroxide
- NaOH sodium hydroxide
- IP A isopropyl alcohol
- DI deionized
- alkaline etch solutions are not generally useful for the etching of multi-crystalline silicon substrates. This is because the etch rate for silicon using alkaline solutions depends strongly on the orientation of the crystal faces exposed to the etching solution. For example, the alkaline etch rate of a Si (111) orientation is one to two orders of magnitude smaller than that of other orientations, so that when the substrate is a (100) single crystalline wafer, the resulting structures appear as four- sided pyramids having (111) orientation sidewalls. This is not true for multi- crystalline silicon substrates because the orientation varies from grain to grain within the substrate and adequate reduction of reflectance can not be easily obtained with alkaline etching.
- the present invention provides chemicals and methods for texturing of multi- crystalline silicon substrates, particularly for use as solar cells or photovoltaic devices.
- the solutions of the present invention provide more consistent and uniform texturing over the entire life of the solution, with a resultant decrease in the number of discarded wafers and therefore increased reliability and yield at lower cost.
- the present invention relates to improved chemical solutions for texturing of multi-crystalline silicon substrates, particularly for use as solar cells or photovoltaic devices.
- the solutions of the present invention provide more consistent and uniform texturing over the entire life of the solution.
- Si containing ions are made part of the etching solution prior to first use to improve the isotropic etch that creates the texturing of multi-crystalline silicon.
- the present invention provides a higher concentration of Si containing ions in the fresh etching solution by dissolving silicon in HF/HN0 3 .
- hexafluorosilicate acid may be added to the HF/HNO3 to increase stability and consistency.
- the concentration of silicon is maintained within a range of 4 to 30 g 1 of etch solution.
- the effects of dissolving silicon into the etching solution for multi- crystalline silicon substrates according to the present invention are improved uniformity and consistency. In particular, superior results are achieved over the use of etching solutions that do not have the dissolved silicon.
- the etching solutions of the present invention provide more consistent and uniform texturing of multi - crystalline silicon substrates over the entire life of the etching solution, resulting in fewer discarded wafers. Therefore, increases in reliability and yield and a lower cost are obtained by the present invention.
- the structures formed using the etching solutions of the present invention are uniform and consistent with the textured substrates formed being particularly useful for solar cells and photovoltaic devices.
Abstract
Etching solutions for etching and texturing of multi-crystalline silicon substrates, particularly for use as solar cells or photovoltaic devices are described. The solutions of the present invention provide more consistent and uniform texturing over the entire life of the solution, resulting in fewer discarded wafers, increased reliability and yield and lower costs. The etching solutions HF/HN03/H20 solutions having silicon dissolved therein.
Description
TEXTURING OF MULTI-CRYSTALLINE SILICON SUBSTRATES
FIELD OF THE INVENTION
(001) The present invention relates to improves chemistries and methods for texturing of multi-crystalline silicon substrates, particularly for use as solar cells or photovoltaic cells.
BACKGROUND OF THE INVENTION
(002) It is known that the efficiency of solar cells and photovoltaic devices can be improved by reducing the reflectance of incident solar light on the device.
(003) One common method of reducing reflectance is to coat the silicon substrate with an anti-reflective coating (ARC), such as silicon oxide, silicon nitride or titanium dioxide. However, these films exhibit resonance structures that limit their effectiveness to a small range of angles and wavelengths, such that reflectance becomes highly dependent on the angle of incidence and wavelength of the light.
(004) Another method of reducing reflectance and improving device efficiency is to texture the silicon wafer surface using a wet-chemical etch to from small structures, often having a pyramidal shape. These structures provide higher levels of light trapping due to multiple scattering. Based on geometrical optics, the texturing should be on a scale equal to or greater than optical wavelengths of the incident light to cause the incident light to reflect multiple times and thereby enhance the amount of absorption.
(005) For single crystal silicon substrates, the texturing process is generally carried out using a mixture of potassium hydroxide (KOH) or sodium hydroxide (NaOH) and isopropyl alcohol (IP A) in deionized (DI) water as the etchant. The addition of IP A
serves to mask specific silicon sites, preventing etching by the solution, to thereby form the pyramidal structures. It has also been reported that a combination of IP A and aqueous alkaline ethylene glycol resulted in more uniform pyramidal texturing on highly polished silicon (100) for use in semiconductor electronic applications.
(006) However, alkaline etch solutions are not generally useful for the etching of multi-crystalline silicon substrates. This is because the etch rate for silicon using alkaline solutions depends strongly on the orientation of the crystal faces exposed to the etching solution. For example, the alkaline etch rate of a Si (111) orientation is one to two orders of magnitude smaller than that of other orientations, so that when the substrate is a (100) single crystalline wafer, the resulting structures appear as four- sided pyramids having (111) orientation sidewalls. This is not true for multi- crystalline silicon substrates because the orientation varies from grain to grain within the substrate and adequate reduction of reflectance can not be easily obtained with alkaline etching. Therefore, acidic texturing using a mixture of hydrofluoric and nitric acid, .e.g. HF/HNO3/H2O has been used to etch multi-crystalline silicon substrates. Isotropic etching does not rely on crystal orientation but rather removes silicon almost independently of the different orientations of the multi -crystalline silicon substrates.
(007) It has been found that as etching solutions age, the uniformity and consistency of textured wafers improves. Because fresh etching solution does not provide uniform and consistent texturing, a significant amount of wafers may need to be discarded before the etching solution is broken in and starts to provide acceptable uniformity and consistency.
(008) Therefore, there remains a need in the art for further improvements to texturing multi-crystalline silicon substrates, particularly for use in solar cells and photovoltaic devices. In particular, there remains a need in the art for improvements to the consistence and uniformity of production throughout the life of the etching solution.
SUMMARY OF THE PRESENT INVENTION
(009) The present invention provides chemicals and methods for texturing of multi- crystalline silicon substrates, particularly for use as solar cells or photovoltaic devices. The solutions of the present invention provide more consistent and uniform texturing over the entire life of the solution, with a resultant decrease in the number of discarded wafers and therefore increased reliability and yield at lower cost.
DETAILED DESCRIPTION OF THE INVENTION
(010) The present invention relates to improved chemical solutions for texturing of multi-crystalline silicon substrates, particularly for use as solar cells or photovoltaic devices. The solutions of the present invention provide more consistent and uniform texturing over the entire life of the solution.
(011) Poor uniformity of surface structures when using fresh etching solutions can be attributed at least in part to a relatively low concentration of dissolved Si in the solution. As the etching solutions are re-used (or aged), subsequently treated wafers show more consistent reflectance, leading to the belief that the difference in results between fresh and aged solutions is caused by the amount of dissolved silicon in the etching solution.
(012) Chemical reactions for achieving uniform and consistent texturing in accordance with the present invention are summarized below. In particular, isotropic etching and texturing using HF/HN03/H20 as the etching solution proceeds in accordance with the following chemical sequence.
3Si + 4HN03 +12HF→ 3SiF4 + 4NO + 8H20
This can be differentiated into two separate reactions as follows.
First the oxidation of silicon
3Si + 4HN03→ 3Si02 + 4HO + 2H20
followed by the cleavage of the Si-O bond
S1O2 + 4HF→ SiF4 + 2H20
coupled with the formation of a water-soluble complex [SiF6]2" according to SiF4 + 2HF→ H2SiF6.
(013) In order to maintain consistency and uniformity throughout the life of the etching solution, it is necessary to have adequate Si containing ions in the solution at the beginning or when the etching solution is fresh. Therefore, in accordance with the present invention, Si containing ions are made part of the etching solution prior to first use to improve the isotropic etch that creates the texturing of multi-crystalline silicon.
(014) The present invention provides a higher concentration of Si containing ions in the fresh etching solution by dissolving silicon in HF/HN03. Alternatively, hexafluorosilicate acid may be added to the HF/HNO3 to increase stability and consistency. However, the amount of excess dissolved silicon should be carefully monitored as too much dissolved silicon may adversely affect the texturing rate and quality. Therefore, in accordance with the present invention, the concentration of silicon is maintained within a range of 4 to 30 g 1 of etch solution.
(015) The effects of dissolving silicon into the etching solution for multi- crystalline silicon substrates according to the present invention are improved uniformity and consistency. In particular, superior results are achieved over the use of etching solutions that do not have the dissolved silicon. In particular, the etching solutions of the present invention provide more consistent and uniform texturing of multi - crystalline silicon substrates over the entire life of the etching solution, resulting in fewer discarded wafers. Therefore, increases in reliability and yield and a lower cost are obtained by the present invention. The structures formed using the etching solutions of the present invention are uniform and consistent with the textured substrates formed being particularly useful for solar cells and photovoltaic devices.
(016) It is anticipated that other embodiments and variations of the present invention will become readily apparent to the skilled artisan in the light of the foregoing
description, and it is intended that such embodiments and variations likewise be included within the scope of the invention as set out in the appended claims.
Claims
1. A wet chemical solution for etching multi-crystalline silicon substrates comprising an HF/HNO3 solution with dissolved silicon.
2. The wet chemical solution of claim 1 , wherein the dissolved silicon has a concentration of between 4 and 30 g 1.
3. The wet chemical solution of claim 1, further including hexafluorosilicate acid.
4. A method of etching multi- crystalline silicon substrates comprising:
etching the substrate using an etching solution of HF/HN03 with dissolved silicon.
5. The method of claim 4, wherein the dissolved silicon has a concentration of between 4 and 30 g 1.
6. The method of claim 4, wherein the etching solution further includes hexafluorosilicate acid.
7. A textured multi-crystalline silicon substrate formed by etching a multi- crystalline silicon substrate using an etching solution comprising an HF/HNO3 solution with dissolved silicon.
8. The substrate of claim 7, wherein the dissolved silicon has a concentration of between 4 and 30 g/1.
9. The substrate of claim 7, wherein the etching solution further includes hexafluorosilicate acid.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US35012510P | 2010-06-01 | 2010-06-01 | |
| US61/350,125 | 2010-06-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2011152973A1 true WO2011152973A1 (en) | 2011-12-08 |
Family
ID=45067023
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/US2011/036163 WO2011152973A1 (en) | 2010-06-01 | 2011-05-12 | Texturing of multi-crystalline silicon substrates |
Country Status (2)
| Country | Link |
|---|---|
| TW (1) | TW201214548A (en) |
| WO (1) | WO2011152973A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20130078750A1 (en) * | 2010-08-02 | 2013-03-28 | Gwangju Institute Of Science And Technology | Fabricating method of nano structure for antireflection and fabricating method of photo device integrated with antireflection nano structure |
| CN109853036A (en) * | 2019-03-05 | 2019-06-07 | 常州工程职业技术学院 | A kind of etching method of Buddha's warrior attendant wire cutting polysilicon chip |
| CN114267751A (en) * | 2021-12-22 | 2022-04-01 | 晋能清洁能源科技股份公司 | Polycrystalline silicon wafer wet-method texturing method for solar cell |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20060138539A1 (en) * | 2004-12-23 | 2006-06-29 | Siltronic Ag | Process for treating a semiconductor wafer with a gaseous medium, and semiconductor wafer treated by this process |
| US20080053815A1 (en) * | 2006-08-31 | 2008-03-06 | Wacker Chemie Ag | Method for processing an etching mixture which is formed during the production of highly pure silicon |
-
2011
- 2011-05-12 WO PCT/US2011/036163 patent/WO2011152973A1/en active Application Filing
- 2011-05-24 TW TW100118182A patent/TW201214548A/en unknown
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20060138539A1 (en) * | 2004-12-23 | 2006-06-29 | Siltronic Ag | Process for treating a semiconductor wafer with a gaseous medium, and semiconductor wafer treated by this process |
| US20080053815A1 (en) * | 2006-08-31 | 2008-03-06 | Wacker Chemie Ag | Method for processing an etching mixture which is formed during the production of highly pure silicon |
Non-Patent Citations (2)
| Title |
|---|
| STEINERT ET AL.: "Study on the Mechanism of Silicon Etching in HN03-Rich HF/HNO3 Mixtures.", JOURNAL OF PHYSICAL CHEMISTRY, C, vol. 111, no. 5, 12 January 2007 (2007-01-12), pages 2133 - 2140 * |
| WEINREICH ET AL.: "The effect of H2SiF6 on the surface morphology of textured multi-crystalline silicon.", SEMICONDUCTOR SCIENCE AND TECHNOLOGY, vol. 21, 24 July 2006 (2006-07-24), pages 1278 - 1286 * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20130078750A1 (en) * | 2010-08-02 | 2013-03-28 | Gwangju Institute Of Science And Technology | Fabricating method of nano structure for antireflection and fabricating method of photo device integrated with antireflection nano structure |
| US9123832B2 (en) * | 2010-08-02 | 2015-09-01 | Gwangju Institute Of Science And Technology | Fabricating method of nano structure for antireflection and fabricating method of photo device integrated with antireflection nano structure |
| CN109853036A (en) * | 2019-03-05 | 2019-06-07 | 常州工程职业技术学院 | A kind of etching method of Buddha's warrior attendant wire cutting polysilicon chip |
| CN114267751A (en) * | 2021-12-22 | 2022-04-01 | 晋能清洁能源科技股份公司 | Polycrystalline silicon wafer wet-method texturing method for solar cell |
Also Published As
| Publication number | Publication date |
|---|---|
| TW201214548A (en) | 2012-04-01 |
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