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US5348627A
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Process and system for the photoelectrochemical etching of silicon in an anhydrous environment
Assignee: Georgia Tech Research Corp
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Filing: 1993-05-12
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Granted: 1994-09-20
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Expires: 2013-05-12
Abstract
Abstract The photoelectrochemical oxidation and dissolution of silicon (Si) is performed in the absence of water and oxygen. Etch rates and photocurrents in an anhydrous HF-acetonitrile (MeCN) solution are directly proportional to light intensity up to at least 600 mW/cm 2 , producing a spatially selective etch rate of greater than 4 μm/min. Four electron transfer reactions per silicon molecule occur with a quantum yield greater than 3.3 due to electron injection from high energy reaction intermediates. Further, the electrochemical oxidation of p-doped silicon in HF-MeCN results in the formation of porous silicon which electroluminescence in an aqueous solution. In an aprotic electrolyte, where tetrabutylammonium tetrafluoroborate (TBAFB) is used as both the supporting electrolyte and source of fluoride in MeCN, photo-induced etching of n-doped silicon occurs at quantum efficiency of 1.9. This indicates that the oxidation and dissolution mechanism of Si in MeCN can occur without protons.
Inventors
- 👤 Eric K. Propst
- 👤 Paul A. Kohl
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 18:11
CPC Classifications
H; H10; H10P; H10P50/00; H10P50/60; H10P50/61; H10P50/613; C; C25; C25F; C25F3/00; C25F3/02; C25F3/12; C25F3/14
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
101 words
A photoelectric etching process for high speed etching of silicon which is proportional to light intensity, comprising the steps of: placing a silicon semiconductor in an electrolytic solution having fluoride, said electrolytic solution being substantially devoid of oxygen-containing species that react with said silicon semiconductor to form oxide compounds; applying a potential to said semiconductor which is between the maximum potential of the valence band of said semiconductor and the minimum potential of the conductor band of said semiconductor; illuminating a surface part of said semiconductor to be etched with radiation of sufficient energy to produce holes in said valence band.
Claim 2
Dependent Claim
101 words
A photoelectric etching process for high speed etching of silicon which is proportional to light intensity, comprising the steps of: placing a silicon semiconductor in an electrolytic solution having fluoride, said electrolytic solution being substantially devoid of oxygen-containing species that react with said silicon semiconductor to form oxide compounds; applying a potential to said semiconductor which is between the maximum potential of the valence band of said semiconductor and the minimum potential of the conductor band of said semiconductor; illuminating a surface part of said semiconductor to be etched with radiation of sufficient energy to produce holes in said valence band.
Claim 3
Dependent Claim
10 words
The process of claim 1, wherein said silicon is p-doped.
Claim 4
Dependent Claim
10 words
The process of claim 1, wherein said silicon is n-doped.
Claim 5
Dependent Claim
11 words
The process of claim 1, wherein said silicon semiconductor is amorphous.
Claim 6
Dependent Claim
11 words
The process of claim 1, wherein said silicon semiconductor is crystalline.
Claim 7
Dependent Claim
11 words
The process of claim 1, wherein said silicon semiconductor is polycrystalline.
Claim 8
Dependent Claim
17 words
The process of claim 1, wherein said electrolytic solution has less than about 50 ppm of water.
Claim 9
Dependent Claim
18 words
The process of claim 1, further comprising the step of creating a porous surface in said silicon semiconductor.
Claim 10
Dependent Claim
30 words
The process of claim 1, wherein said silicon semiconductor comprises a silicon oxide (SiO x ) layer exposed to said electrolytic solution prior to said illuminating of said surface part.
Claim 11
Dependent Claim
15 words
The process of claim 1, wherein said fluoride comprises free-flowing ions within said electrolytic solution.
Claim 12
Dependent Claim
18 words
The process of claim 1, wherein said fluoride is a complexed material which decomposes within said electrolytic solution.
Claim 13
Dependent Claim
42 words
The process of claim 1, wherein said electrolytic solution comprises any fluoride source in the group consisting of hydrofluoric acid (HF), fluoroborate (BF 4 - ), tetrabutylammonium tetrafluoroborate (TBAFB), aluminum hexaflouride (AlF 6 3- ), and hydrogen difluoride (HF 2 - ).
Claim 14
Dependent Claim
37 words
The process of claim 1, wherein said electrolytic solution comprises any supporting electrolyte in the group consisting of tetrabutylammonium perchlorate (C 16 H 36 NClO 4 ) and tetramethylammonium perchlorate (C 4 H 12 NClO 4 ).
Claim 15
Dependent Claim
45 words
The process of claim 1, wherein said electrolytic solution comprises any anhydrous solvent in the group consisting of acetonitrile (CH 3 CN), dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), propylene carbonate (C 3 O 3 H 6 ), and methylene chloride (CH 2 Cl 2 ).
Claim 16
Dependent Claim
16 words
The process of claim 1, wherein said radiation comprises photon energy greater than 1.12 electron volts.
Claim 17
Dependent Claim
27 words
The process of claim 1, further comprising the steps of selectively etching a particular position on said semiconductor by selectively applying said radiation to said particular position.
Claim 18
Dependent Claim
22 words
The process of claim 1, further comprising the step of varying the rate of etching by varying the intensity of said radiation.
Claim 19
Dependent Claim
68 words
A photoelectrochemical etching process, comprising the steps of: placing a silicon semiconductor in an electrolytic solution, and having fluoride, said electrolytic solution being substantially devoid of oxygen-containing species that react with said silicon semiconductor to form oxide compounds; applying a potential to said semiconductor which is between the maximum potential of the valence band of said semiconductor and the minimum potential of the conduction band of said semiconductor.
Claim 20
Dependent Claim
68 words
A photoelectrochemical etching process, comprising the steps of: placing a silicon semiconductor in an electrolytic solution, and having fluoride, said electrolytic solution being substantially devoid of oxygen-containing species that react with said silicon semiconductor to form oxide compounds; applying a potential to said semiconductor which is between the maximum potential of the valence band of said semiconductor and the minimum potential of the conduction band of said semiconductor.
Claim 21
Dependent Claim
11 words
The process of claim 18, wherein said silicon semiconductor is p-doped.
Claim 22
Dependent Claim
39 words
The process of claim 18, wherein said silicon semiconductor is n-doped and further comprising the step of illuminating a surface part of said semiconductor to be etched with radiation of sufficient energy to produce holes in said valence band.
Claim 23
Dependent Claim
121 words
A photoelectrochemical etching process for high speed etching of silicon which is proportional to light intensity, comprising the steps of: placing a silicon semiconductor in an electrolytic solution having fluoride, said electrolytic solution being substantially devoid of oxygen-containing species that react with said silicon semiconductor to form oxide compounds; applying a potential to said semiconductor which is between the maximum potential of the valence band of said semiconductor and the minimum potential of the conduction band of said semiconductor; illuminating a surface part of said semiconductor to be etched with radiation of sufficient energy to produce holes in said valence band; and preventing oxidation of said silicon semiconductor within said electrolytic solution during production of said holes in said valence band.
Claim 24
Dependent Claim
121 words
A photoelectrochemical etching process for high speed etching of silicon which is proportional to light intensity, comprising the steps of: placing a silicon semiconductor in an electrolytic solution having fluoride, said electrolytic solution being substantially devoid of oxygen-containing species that react with said silicon semiconductor to form oxide compounds; applying a potential to said semiconductor which is between the maximum potential of the valence band of said semiconductor and the minimum potential of the conduction band of said semiconductor; illuminating a surface part of said semiconductor to be etched with radiation of sufficient energy to produce holes in said valence band; and preventing oxidation of said silicon semiconductor within said electrolytic solution during production of said holes in said valence band.
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