US5346850A
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US
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Crystallization and doping of amorphous silicon on low temperature plastic
Assignee: University of California
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Filing: 1992-10-29
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Granted: 1994-09-13
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Expires: 2012-10-29
Abstract
Abstract A method or process of crystallizing and doping amorphous silicon (a-Si) on a low-temperature plastic substrate using a short pulsed high energy source in a selected environment, without heat propagation and build-up in the substrate. The pulsed energy processing of the a-Si in a selected environment, such as BF3 and PF5, will form a doped micro-crystalline or poly-crystalline silicon (pc-Si) region or junction point with improved mobilities, lifetimes and drift and diffusion lengths and with reduced resistivity. The advantage of this method or process is that it provides for high energy materials processing on low cost, low temperature, transparent plastic substrates. Using pulsed laser processing a high (>900° C.), localized processing temperature can be achieved in thin films, with little accompanying temperature rise in the substrate, since substrate temperatures do not exceed 180° C. for more than a few microseconds. This method enables use of plastics incapable of withstanding sustained processing temperatures (higher than 180° C.) but which are much lower cost, have high tolerance to ultraviolet light, have high strength and good transparency, compared to higher temperature plastics such as polyimide.
Inventors
- 👤 James L. Kaschmitter
- 👤 Joel B. Truher
- 👤 Kurt H. Weiner
- 👤 Thomas W. Sigmon
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 19:25
CPC Classifications
H; H10; H10P; H10P14/00; H10P14/20; H10P14/38; H10P14/3802; C; C30; C30B; C30B1/00; C30B1/02; C30B1/023; C30B29/00; C30B29/02; C30B29/06; H10D; H10D30/00; H10D30/60; H10D30/67; H10D30/6758; H10P14/29; H10P14/2901; H10P14/2922; H10P14/32; H10P14/3202; H10P14/3238; H10P14/34; H10P14/3402; H10P14/3404; H10P14/3411; H10P14/3451; H10P14/3452; H10P14/3456; H10P14/3808; H10P14/3816; H10P14/3818; H10P32/00; H10P32/30; H10P32/302
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
103 words
A method for improving the crystallinity of a thin film of amorphous silicon directly deposited on a low temperature plastic substrate incapable of withstanding sustained processing temperatures higher than about 180° C. and sustained processing time periods longer than about 10 5 nanoseconds, comprising the steps of: positioning the deposited thin film in a controlled atmosphere; and applying at least one pulse from a pulsed high energy source onto the thin film for a time period sufficient to change the crystallinity of the thin film without heating the substrate above a temperature of about 180° C. for more than about 10 5 nanoseconds.
Claim 2
Independent Claim
103 words
A method for improving the crystallinity of a thin film of amorphous silicon directly deposited on a low temperature plastic substrate incapable of withstanding sustained processing temperatures higher than about 180° C. and sustained processing time periods longer than about 10 5 nanoseconds, comprising the steps of: positioning the deposited thin film in a controlled atmosphere; and applying at least one pulse from a pulsed high energy source onto the thin film for a time period sufficient to change the crystallinity of the thin film without heating the substrate above a temperature of about 180° C. for more than about 10 5 nanoseconds.
Claim 3
Dependent Claim
31 words
The method of claim 1, additionally including the step of forming the low-temperature plastic substrate from material selected from the group consisting of E-CTFE, E-TFE, PES, PVDF, PTFE, FEP and HDPE.
Claim 4
Dependent Claim
22 words
The method of claim 2, additionally including the steps of depositing a thin film of amorphous silicon on the low-temperature plastic substrate.
Claim 5
Dependent Claim
31 words
The method of claim 3, wherein the step of depositing the thin film is carried by a process selected from the group of evaporation, sputtering, electro-deposition, solvent-deposition, spin-on coating and PECVD.
Claim 6
Dependent Claim
38 words
The method of claim 2, additionally including the steps of depositing a layer of thermal barrier material on the low-temperature plastic substrate, and then depositing a thin film of amorphous silicon on the layer of thermal barrier material.
Claim 7
Dependent Claim
46 words
The method of claim 5, wherein the step of depositing the layer of thermal barrier material is carried out by depositing a layer of SiO 2 onto the low-temperature plastic substrate by a process selected from the group of sputtering, electro-deposition, solvent-deposition, spin-on coating and PECVD.
Claim 8
Dependent Claim
31 words
The method of claim 6, wherein the step of depositing the thin film of amorphous silicon is carried out by a technique selected from evaporation, electro-deposition, solvent-deposition, spin-on coating and sputtering.
Claim 9
Dependent Claim
35 words
The method of claim 6, wherein the layer of SiO 2 is deposited to a thickness of 0.5 μm, and wherein the thin film of amorphous silicon is deposited to a thickness of 0.5 μm.
Claim 10
Dependent Claim
16 words
The method of claim 8, wherein the low-temperature substrate is formed from 0.13 mm thick E-CTFE.
Claim 11
Dependent Claim
32 words
The method of claim 8, wherein said at least one pulse from a pulsed high energy source is provided by a pulsed ultra-violet laser producing 30 ns pulses of 308 nm light.
Claim 12
Dependent Claim
43 words
The method of claim 1, wherein the step of applying at least one pulse from a pulsed high energy source is provided from a group of high energy sources composed of XeCl, KrF and ArF excimer lasers, electron-beams, dye lasers, flashlamps, YAG lasers.
Claim 13
Dependent Claim
42 words
The method of claim 11, wherein the at least one pulse from a pulsed energy high energy source is provided by an XeCl excimer laser operating at energy levels of about 150 mJ cm -2 to about 800 mJ cm -2 .
Claim 14
Dependent Claim
31 words
The method of claim 12, additionally including the step of providing the at least one pulse from the XeCl eximer laser for a time period of about 5 to 60 ns.
Claim 15
Dependent Claim
25 words
The method of claim 11, additionally including the step of providing the at least one pulse for a time period less than 10 5 ns.
Claim 16
Dependent Claim
34 words
The method of claim 1, wherein the controlled atmosphere is provided by the step of selecting an environment from the group of air, hydrogen, oxygen, BF 3 , AsF 5 and PF 5 .
Claim 17
Dependent Claim
39 words
The method of claim 2, wherein the controlled atmosphere is provided by the step of selecting an environment from the group consisting of a vacuum at <1 mT, 50 torr BF 3 , and 50 torr PF 5 .
Claim 18
Dependent Claim
36 words
The method of claim 16, wherein the at least one pulse is provided by a XeCl excimer laser producing irradiation in the range of about 150 mJ cm -2 to about 800 mJ cm -2 .
Claim 19
Dependent Claim
46 words
The method of claim 1, additionally including the step of providing the controlled atmosphere with a dopant selected from the group of BF3, and PF5 such that the changed crystallinity of the amorphous silicon is composed of polycrystalline or micro-crystalline silicon doped with boron or phosphorous.
Claim 20
Dependent Claim
19 words
The method of claim 17, wherein the XeCl excimer laser produced 30 ns (FFWHM) pulses of 308 nm light.
Claim 21
Dependent Claim
146 words
A process for producing at least one region of doped polycrystalline or micro-crystalline silicon in a thin film of amorphous silicon deposited on a substrate composed of commercial-grade plastic incapable of withstanding processing; temperatures of higher than 180° C. for longer than about 35 nanoseconds, comprising the steps of: forming the substrate from material selected from the group of E-CTFE, E-TFE, PES, PVDF, PTFE, FEP, and HDPE; depositing a thin film of amorphous silicon on the substrate; positioning the thus formed structure in a controlled environment selected from the group of vacuum (<1 mT), 50 torr BF 3 , and 50 torr PF 5 ; and directing at least one pulse of 308 nm light from a XeCl laser onto the thin film of amorphous silicon for providing irradiation energy in the range of about 150 mJ cm -2 to about 800 mJ cm -2 .
Claim 22
Dependent Claim
146 words
A process for producing at least one region of doped polycrystalline or micro-crystalline silicon in a thin film of amorphous silicon deposited on a substrate composed of commercial-grade plastic incapable of withstanding processing; temperatures of higher than 180° C. for longer than about 35 nanoseconds, comprising the steps of: forming the substrate from material selected from the group of E-CTFE, E-TFE, PES, PVDF, PTFE, FEP, and HDPE; depositing a thin film of amorphous silicon on the substrate; positioning the thus formed structure in a controlled environment selected from the group of vacuum (<1 mT), 50 torr BF 3 , and 50 torr PF 5 ; and directing at least one pulse of 308 nm light from a XeCl laser onto the thin film of amorphous silicon for providing irradiation energy in the range of about 150 mJ cm -2 to about 800 mJ cm -2 .
Claim 23
Dependent Claim
23 words
The process of claim 20, wherein a pulse of 308 nm light is provided for a time period of 5 to 60 nanoseconds.
Claim 24
Dependent Claim
28 words
The process of claim 21, additionally including the step of depositing a buffer layer of SiO2 on the substrate prior to depositing the thin film of amorphous silicon.
Claim 25
Dependent Claim
22 words
The process of claim 21, wherein the formed structure is produced from 0.13 mm thick E-CTFE, and 0.5 μm thick amorphous silicon.
Claim 26
Dependent Claim
28 words
The process of claim 23, wherein the formed structure is produced to include a 0.5 μm thick layer of SiO 2 between the substrate and the amorphous silicon.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-09-12 | 1998-03-14 | 1998-09-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-09-12 | 2002-03-14 | 2002-09-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-09-12 | 2006-03-14 | 2006-09-13 | $7700.00 | Window Closed / Lapsed |