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US5565377A
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Process for forming retrograde profiles in silicon
Assignee: University of California
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Filing: 1994-10-27
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Granted: 1996-10-15
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Expires: 2014-10-27
Abstract
Abstract A process for forming retrograde and oscillatory profiles in crystalline and polycrystalline silicon. The process consisting of introducing an n- or p-type dopant into the silicon, or using prior doped silicon, then exposing the silicon to multiple pulses of a high-intensity laser or other appropriate energy source that melts the silicon for short time duration. Depending on the number of laser pulses directed at the silicon, retrograde profiles with peak/surface dopant concentrations which vary from 1-1e4 are produced. The laser treatment can be performed in air or in vacuum, with the silicon at room temperature or heated to a selected temperature.
Inventors
- 👤 Kurt H. Weiner
- 👤 Thomas W. Sigmon
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 15:33
CPC Classifications
H; H10; H10D; H10D84/00; H10D84/01; H10D84/0123; H10D84/0126; H10D84/0165; H10D84/0191; H10D84/02; H10D84/03; H10D84/038; H10P; H10P32/00; H10P32/10; H10P32/12; H10P32/14; H10P32/1404; H10P32/17; H10P32/171; Y; Y10; Y10S; Y10S438/00; Y10S438/914
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
69 words
A process for forming at least one retrograde impurity profile in silicon, comprising: directing pulsed energy onto a surface of the silicon having impurities and causing melting of an area of the surface onto which the pulsed energy is applied; and controlling the pulsed energy applied to the silicon to produce a recrystallization rate in the range of 0.5-15 meters per second, whereby the impurity concentration increases with depth.
Claim 2
Dependent Claim
69 words
A process for forming at least one retrograde impurity profile in silicon, comprising: directing pulsed energy onto a surface of the silicon having impurities and causing melting of an area of the surface onto which the pulsed energy is applied; and controlling the pulsed energy applied to the silicon to produce a recrystallization rate in the range of 0.5-15 meters per second, whereby the impurity concentration increases with depth.
Claim 3
Dependent Claim
16 words
The process of claim 1, wherein the impurities constitute at least one dopant in the silicon.
Claim 4
Dependent Claim
26 words
The process of claim 2, additionally including incorporating the at least one dopant into the silicon prior to directing the pulsed energy onto the surface thereof.
Claim 5
Dependent Claim
23 words
The process of claim 2, additionally including incorporating the at least one dopant into the silicon during melting thereof by the pulsed energy.
Claim 6
Dependent Claim
25 words
The process of claim 1, wherein the pulsed energy is produced from the group consisting of a pulsed excimer laser and a pulsed x-ray source.
Claim 7
Dependent Claim
26 words
The process of claim 1, additionally including controlling peak to surface concentration of the impurity profile in the range of 1 to 1e4 atoms/cm 3 .
Claim 8
Dependent Claim
22 words
The process of claim 1, additionally including controlling the width of different concentration regions of the at least one retrograde impurity profile.
Claim 9
Dependent Claim
15 words
The process of claim 1, wherein impurities in the silicon comprises n-type and p-type dopants.
Claim 10
Dependent Claim
19 words
The process of claim 8, wherein the dopants are selected from the group consisting of phosphorus, boron, and arsenic.
Claim 11
Dependent Claim
26 words
The process of claim 7, wherein the pulsed energy is produced by a source selected from the group of pulsed excimer lasers and pulsed x-ray sources.
Claim 12
Dependent Claim
55 words
The process of claim 9, additionally including controlling physical characteristics of the at least one retrograde impurity profile by controlling the amount of dopant in the silicon, controlling the number of times the silicon is melted and recrystallized, controlling the rapidity of the recrystallization rate, and controlling the depth to which the silicon is melted.
Claim 13
Dependent Claim
34 words
The process of claim 11, wherein the rapidity of the recrystallization rate is controlled by the deposition rate of the dopant, deviation of the energy used to melt the silicon, and the silicon temperature.
Claim 14
Dependent Claim
32 words
The process of claim 10, additionally including a peak to surface concentration of the at least one retrograde impurity profile in the range of about 1 to about 1e4 atoms/cm 3 .
Claim 15
Dependent Claim
76 words
A process for forming at least one retrograde profile of at least one dopant in silicon, comprising: providing silicon with at least one dopant incorporated therein; melting areas of silicon by directing pulsed energy onto the areas of the silicon for a time duration, controlling the melting of the silicon such that a recrystallization rate thereof exceeds 0.5 meters per second and is lower than 15 meters per second, whereby the impurity concentration increases with depth.
Claim 16
Dependent Claim
76 words
A process for forming at least one retrograde profile of at least one dopant in silicon, comprising: providing silicon with at least one dopant incorporated therein; melting areas of silicon by directing pulsed energy onto the areas of the silicon for a time duration, controlling the melting of the silicon such that a recrystallization rate thereof exceeds 0.5 meters per second and is lower than 15 meters per second, whereby the impurity concentration increases with depth.
Claim 17
Dependent Claim
15 words
The process of claim 14, additionally including providing the silicon with n-type and p-type dopants.
Claim 18
Dependent Claim
26 words
The process of claim 14, additionally including providing the pulsed energy from a source selected from the group of pulsed excimer lasers and pulsed x-ray sources.
Claim 19
Dependent Claim
85 words
A process for forming at least one retrograde profile of at least one dopant to be incorporated into silicon, comprising: providing silicon to be doped, incorporating said at least one dopant into the silicon by either ion implantation or vapor-phase diffusion, and forming said at least one retrograde profile of the dopant by melting the previously doped silicon with an excimer laser beam such that a recrystallization rate in the range of 0.5-15 meters per second is achieved, whereby the impurity concentration increases with depth.
Claim 20
Dependent Claim
85 words
A process for forming at least one retrograde profile of at least one dopant to be incorporated into silicon, comprising: providing silicon to be doped, incorporating said at least one dopant into the silicon by either ion implantation or vapor-phase diffusion, and forming said at least one retrograde profile of the dopant by melting the previously doped silicon with an excimer laser beam such that a recrystallization rate in the range of 0.5-15 meters per second is achieved, whereby the impurity concentration increases with depth.
Claim 21
Dependent Claim
15 words
The process of claim 17, additionally including providing the silicon with n-type and p-type dopants.
Claim 22
Dependent Claim
39 words
The process of claim 17, additionally including controlling physical characteristics of the at least one retrograde profile so that a greater concentration of the dopant is in the bulk of the silicon compared to the surface of the silicon.
Claim 23
Dependent Claim
35 words
The process of claim 18, wherein the at least one retrograde profile of the dopant consists of a plurality of peaks which are formed by utilizing a lesser laser energy for producing each subsequent peak.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1999-10-15 | 2000-04-15 | 2000-10-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-10-15 | 2004-04-15 | 2004-10-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-10-15 | 2008-04-15 | 2008-10-15 | $7700.00 | Window Closed / Lapsed |