US4292093A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method using laser irradiation for the production of atomically clean crystalline silicon and germanium surfaces
Assignee: United States Department of Energy
•
Filing: 1979-12-28
•
Granted: 1981-09-29
•
Expires: 1999-12-28
Abstract
Abstract This invention relates to a new method for removing surface impurities from crystalline silicon or germanium articles, such as off-the-shelf p- or n-type wafers to be doped for use as junction devices. The principal contaminants on such wafers are oxygen and carbon. The new method comprises laser-irradiating the contaminated surface in a non-reactive atmosphere, using one or more of Q-switched laser pulses whose parameters are selected to effect melting of the surface without substantial vaporization thereof. In a typical application, a plurality of pulses is used to convert a surface region of an off-the-shelf silicon wafer to an automatically clean region. This can be accomplished in a system at a pressure below 10 -8 Torr, using Q-switched ruby-laser pulses having an energy density in the range of from about 60 to 190 MW/cm 2 .
Inventors
- 👤 Gary W. Ownby
- 👤 Clark W. White
- 👤 David M. Zehner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 17:08
CPC Classifications
H; H10; H10P; H10P34/00; H10P34/40; H10P34/42; B; B08; B08B; B08B7/00; B08B7/0035; B08B7/0042; H10D; H10D62/00; H10D62/80; H10D62/83; H10D62/834; Y; Y10; Y10S; Y10S117/00; Y10S117/903; Y10S117/904; Y10S148/00; Y10S148/092; Y10S148/093; Y10S438/00; Y10S438/974
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
67 words
A method for treating a body of crystalline silicon having a surface region which is contaminated with a macro amount of oxygen, to render said region atomically clean with respect to said oxygen, said method comprising: in an evacuated zone, irradiating said region with a plurality of Q-switched laser pulses characterized by a peak-power density in the range of from about 70 to 190 MW/cm 2 .
Claim 2
Independent Claim
67 words
A method for treating a body of crystalline silicon having a surface region which is contaminated with a macro amount of oxygen, to render said region atomically clean with respect to said oxygen, said method comprising: in an evacuated zone, irradiating said region with a plurality of Q-switched laser pulses characterized by a peak-power density in the range of from about 70 to 190 MW/cm 2 .
Claim 3
Dependent Claim
16 words
The method of claim 1 wherein said zone is at a pressure below about 10-8 Torr.
Claim 4
Independent Claim
84 words
A method for treating a crystalline silicon body, a surface layer of which is contaminated with macro amounts of oxygen as SiO 2 and carbon to render said layer atomically clean with respect to said oxygen and carbon while avoiding damage to said layer, said method comprising: in a zone at a pressure below about 10 -8 Torr, irradiating said layer with a plurality of Q-switched laser pulses having a peak-power density in the range of from about 70 to 190 MW/cm 2 .
Claim 5
Independent Claim
84 words
A method for treating a crystalline silicon body, a surface layer of which is contaminated with macro amounts of oxygen as SiO 2 and carbon to render said layer atomically clean with respect to said oxygen and carbon while avoiding damage to said layer, said method comprising: in a zone at a pressure below about 10 -8 Torr, irradiating said layer with a plurality of Q-switched laser pulses having a peak-power density in the range of from about 70 to 190 MW/cm 2 .
Claim 6
Independent Claim
94 words
A method for decreasing macro concentrations of oxygen and carbon present as contaminants in a surface layer of a crystalline silicon body while avoiding alteration of the crystal structure of the contaminated layer, said method comprising: in an evacuated zone, irradiating said layer with at least one Q-switched laser pulse characterized by a peak-power density in the range of from about 70 to 190 MW/cm 2 to generate a melt front which moves (a) through said layer, (b) into a portion of said body immediately underlying said layer, and (c) back to said surface.
Claim 7
Independent Claim
94 words
A method for decreasing macro concentrations of oxygen and carbon present as contaminants in a surface layer of a crystalline silicon body while avoiding alteration of the crystal structure of the contaminated layer, said method comprising: in an evacuated zone, irradiating said layer with at least one Q-switched laser pulse characterized by a peak-power density in the range of from about 70 to 190 MW/cm 2 to generate a melt front which moves (a) through said layer, (b) into a portion of said body immediately underlying said layer, and (c) back to said surface.
Claim 8
Independent Claim
82 words
A method for treating a crystalline germanium body having a surface region which is contaminated with a macro amount of oxygen to render said region atomically clean with respect to said oxygen, said method comprising: in vacuum, irradiating said region with at least one laser pulse characterized by a peak-power density in the range of from about 11 to 135 MW/cm 2 to effect (a) melting of said region, and (b) melting of a layer of said body immediately underlying said region.
Claim 9
Independent Claim
82 words
A method for treating a crystalline germanium body having a surface region which is contaminated with a macro amount of oxygen to render said region atomically clean with respect to said oxygen, said method comprising: in vacuum, irradiating said region with at least one laser pulse characterized by a peak-power density in the range of from about 11 to 135 MW/cm 2 to effect (a) melting of said region, and (b) melting of a layer of said body immediately underlying said region.
Claim 10
Independent Claim
82 words
A method for treating a crystalline germanium body, a surface layer of which is contaminated with macro amounts of oxygen and carbon, to render said layer atomically clean with respect to said oxygen and carbon, said method comprising: in a zone at a pressure below about 10 -8 Torr, irradiating said layer and a contiguous layer of said body with a plurality of Q-switched laser pulses having a peak-power density in the range of from about 11 to 135 MW/cm 2 .
Claim 11
Independent Claim
82 words
A method for treating a crystalline germanium body, a surface layer of which is contaminated with macro amounts of oxygen and carbon, to render said layer atomically clean with respect to said oxygen and carbon, said method comprising: in a zone at a pressure below about 10 -8 Torr, irradiating said layer and a contiguous layer of said body with a plurality of Q-switched laser pulses having a peak-power density in the range of from about 11 to 135 MW/cm 2 .
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-09-28 | 1985-03-30 | 1985-09-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-09-28 | 1989-03-30 | 1989-09-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-09-28 | 1993-03-30 | 1993-09-29 | $7700.00 | Window Closed / Lapsed |