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US5462898A
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Methods for passivating silicon devices at low temperature to achieve low interface state density and low recombination velocity while preserving carrier lifetime
Assignee: Georgia Tech Research Corp
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Filing: 1994-05-25
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Granted: 1995-10-31
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Expires: 2014-05-25
Abstract
Abstract A new process has been developed to achieve a very low SiOx/Si interface state density Dit, low recombination velocity S (<2 cm/s), and high effective carrier lifetime Teff (>5 ms) for oxides deposited on silicon substrates at low temperature. The technique involves direct plasma-enhanced chemical vapor deposition (PECVD), with appropriate growth conditions, followed by a photo-assisted rapid thermal annealing (RTA) process. Approximately 500-A-thick SiOx layers are deposited on Si by PECVD at 250 DEG C. with 0.02 W/cm-2 rf power, then covered with SiN or an evaporated thin aluminum layer, and subjected to a photo-assisted anneal in forming gas ambient at 350 DEG C., resulting in an interface state density Dit in the range of about 1-4x1010 cm-2 eV-1, which sets a record for the lowest interface state density Dit for PECVD oxides fabricated to date. Detailed analysis shows that the PECVD deposition conditions, photo-assisted anneal, forming gas ambient, and the presence of an aluminum layer on top of the oxides during the anneal, all contributed to this low value of interface state density Dit. Detailed metal-oxide semiconductor analysis and model calculations show that such a low recombination velocity S is the result of moderately high positive oxide charge (5x1011-1x1012 cm-2) and relatively low midgap interface state density (1x1010-4x1010 cm-2eV-1). Photo-assisted anneal was found to be superior to furnace annealing, and a forming gas ambient was better than a nitrogen ambient for achieving a very low surface recombination velocity S.
Inventors
- 👤 Zhizhang Chen
- 👤 Ajeet Rohatgi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 09:14
CPC Classifications
H; H10; H10P; H10P14/00; H10P14/60; H10P14/69; H10P14/692; H10P14/6921; H10P14/69215; H10P14/63; H10P14/6326; H10P14/6328; H10P14/6334; H10P14/6336; H10P14/65; H10P14/6502; H10P14/6508; H10P14/6516; H10P14/6529; H10P14/6536; H10P14/6548; H10P14/66; H10P14/668; H10P14/6681; H10P14/6682; H10P95/00; H10W; H10W74/00; H10W74/10; H10W74/131; H10W74/137; Y; Y10; Y10S; Y10S438/00; Y10S438/958
Claims Analysis
Total Claims: 33
Claim 1
Independent Claim
60 words
A method for passivating a surface of crystalline silicon, comprising the steps of: forming an oxide layer over said crystalline silicon using a plasma enhanced chemical vapor deposition process; and lowering an interface state density associated with said silicon by heating said oxide layer and said silicon with a light radiating source after said plasma enhanced chemical vapor deposition process.
Claim 2
Independent Claim
60 words
A method for passivating a surface of crystalline silicon, comprising the steps of: forming an oxide layer over said crystalline silicon using a plasma enhanced chemical vapor deposition process; and lowering an interface state density associated with said silicon by heating said oxide layer and said silicon with a light radiating source after said plasma enhanced chemical vapor deposition process.
Claim 3
Dependent Claim
11 words
The method of claim 1, wherein said silicon is n-type silicon.
Claim 4
Dependent Claim
11 words
The method of claim 1, wherein said silicon is p-type silicon.
Claim 5
Dependent Claim
16 words
The method of claim 1, wherein said oxide layer is formed below about 250 degrees Celsius.
Claim 6
Dependent Claim
17 words
The method of claim 1, wherein said heating step is performed at between 300° and 450° C.
Claim 7
Dependent Claim
30 words
The method of claim 1, wherein said heating step includes the step of utilizing a forming gas having hydrogen so that hydrogen migrates to and passivates defects within said silicon.
Claim 8
Dependent Claim
18 words
The method of claim 1, further comprising the step of forming a nitride layer over said oxide layer.
Claim 9
Dependent Claim
27 words
The method of claim 1, wherein said plasma enhanced chemical vapor deposition process uses a plasma containing silane (SiH 4 ) and nitrous oxide (N 2 O).
Claim 10
Dependent Claim
18 words
The method of claim 1, further comprising the step of forming an aluminum layer over said oxide layer.
Claim 11
Dependent Claim
14 words
The method of claim 1, further comprising the step of producing an integrated circuit.
Claim 12
Dependent Claim
20 words
The method of claim 6, wherein said forming gas comprises about 90 percent nitrogen gas and 10 percent hydrogen gas.
Claim 13
Independent Claim
94 words
A method for passivating surface and bulk defects in crystalline silicon, comprising the steps of: forming an oxide passivating layer over said crystalline silicon using a plasma enhanced chemical vapor deposition process; lowering an interface state density associated with said silicon by heating said passivating layer and said silicon with a light radiating source after said plasma enhanced chemical vapor deposition process; and exposing said passivating layer to a hydrogen-containing forming gas while said passivating layer is being heated so that hydrogen migrates to and passivates said surface and bulk defects within said silicon.
Claim 14
Independent Claim
94 words
A method for passivating surface and bulk defects in crystalline silicon, comprising the steps of: forming an oxide passivating layer over said crystalline silicon using a plasma enhanced chemical vapor deposition process; lowering an interface state density associated with said silicon by heating said passivating layer and said silicon with a light radiating source after said plasma enhanced chemical vapor deposition process; and exposing said passivating layer to a hydrogen-containing forming gas while said passivating layer is being heated so that hydrogen migrates to and passivates said surface and bulk defects within said silicon.
Claim 15
Dependent Claim
10 words
The method of claim 12, wherein said defects comprise dislocations.
Claim 16
Dependent Claim
11 words
The method of claim 12, wherein said defects comprise grain boundaries.
Claim 17
Dependent Claim
10 words
The method of claim 12, wherein said defects comprise vacancies.
Claim 18
Dependent Claim
11 words
The method of claim 12, wherein said silicon is n-type silicon.
Claim 19
Dependent Claim
11 words
The method of claim 12, wherein said silicon is p-type silicon.
Claim 20
Dependent Claim
16 words
The method of claim 12, wherein said passivating layer is formed below about 250 degrees Celsius.
Claim 21
Dependent Claim
16 words
The method of claim 12, wherein said heating step is performed at about 350 degrees Celsius.
Claim 22
Dependent Claim
26 words
The method of claim 12, wherein said plasma enhanced chemical vapor deposition process employs an electromagnetic plasma excitation signal having a frequency of about 13.7 megahertz.
Claim 23
Dependent Claim
33 words
The method of claim 12, wherein said plasma enhanced chemical vapor deposition process uses a plasma containing silane (SiH 4 ) and ammonia (NH 3 ) to produce atomic hydrogen during film deposition.
Claim 24
Dependent Claim
34 words
The method of claim 12, wherein said plasma enhanced chemical vapor deposition process uses a plasma containing silane (SiH 4 ) and nitrous oxide (N 2 O) for producing atomic hydrogen to passivate defects.
Claim 25
Dependent Claim
14 words
The method of claim 12, further comprising the step of producing a solar cell.
Claim 26
Dependent Claim
14 words
The method of claim 12, further comprising the step of producing an integrated circuit.
Claim 27
Dependent Claim
20 words
The method of claim 12, wherein said forming gas comprises about 90 percent nitrogen gas and 10 percent hydrogen gas.
Claim 28
Independent Claim
69 words
A method for passivating a surface of crystalline silicon, comprising the steps of: forming an oxide layer over said crystalline silicon using a plasma enhanced chemical vapor deposition process; and heating said oxide layer and said silicon to a temperature of about 350° C. with a light radiating source after said plasma enhanced chemical vapor deposition process so that an interface state density associated with said silicon is lowered.
Claim 29
Independent Claim
69 words
A method for passivating a surface of crystalline silicon, comprising the steps of: forming an oxide layer over said crystalline silicon using a plasma enhanced chemical vapor deposition process; and heating said oxide layer and said silicon to a temperature of about 350° C. with a light radiating source after said plasma enhanced chemical vapor deposition process so that an interface state density associated with said silicon is lowered.
Claim 30
Independent Claim
71 words
A method for passivating a surface of crystalline silicon, comprising the steps of: forming an oxide layer over said crystalline silicon using a plasma enhanced chemical vapor deposition process; and heating said oxide layer and said silicon to a temperature approximately between 300° and 450° C. with a light radiating source after said plasma enhanced chemical vapor deposition process so that an interface state density associated with said silicon is lowered.
Claim 31
Independent Claim
71 words
A method for passivating a surface of crystalline silicon, comprising the steps of: forming an oxide layer over said crystalline silicon using a plasma enhanced chemical vapor deposition process; and heating said oxide layer and said silicon to a temperature approximately between 300° and 450° C. with a light radiating source after said plasma enhanced chemical vapor deposition process so that an interface state density associated with said silicon is lowered.
Claim 32
Independent Claim
79 words
A method for passivating a surface of crystalline silicon, comprising the steps of: forming an oxide layer over said crystalline silicon using a plasma enhanced chemical vapor deposition process; forming an aluminum layer over said oxide layer; and achieving an interface state density associated with said silicon at least as low as 1.1×10 10 cm -2 eV -1 by heating said oxide layer and said silicon with a light radiating source after said plasma enhanced chemical vapor deposition process.
Claim 33
Independent Claim
79 words
A method for passivating a surface of crystalline silicon, comprising the steps of: forming an oxide layer over said crystalline silicon using a plasma enhanced chemical vapor deposition process; forming an aluminum layer over said oxide layer; and achieving an interface state density associated with said silicon at least as low as 1.1×10 10 cm -2 eV -1 by heating said oxide layer and said silicon with a light radiating source after said plasma enhanced chemical vapor deposition process.
References Cited (Backward Citations)
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