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US4556524A
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Method for preparing digital storage device by laser application
Assignee: Qinetiq Ltd
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Filing: 1982-09-30
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Granted: 1985-12-03
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Expires: 2002-09-30
Abstract
Abstract A digital storage device comprises a crystalline substrate such as silicon in which pockets of amorphous substrate material represent one of the binary logic states; the absence of amorphous material represents the other logic state. The amorphous material is formed by irradiation with a laser beam. Typically the radiation for silicon is at 347 nanometers, 2.5 nanosecond pulse length. The power density varies with crystalline orientation; for (001) silicon it is typically 0.3 J/cm 2 and for (111) silicon it is 0.3 to 0.6 J/cm 2 . Erasure of the information is achieved by laser annealing the amorphous material back to its crystalline form.
Inventors
- 👤 Anthony G. Cullis
- 👤 Hugh C. Webber
- 👤 Nigel G. Chew
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 21:20
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/24; G11B7/2407; G11B7/24085; G11B7/004; G11B7/0045; G11B7/00454
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
97 words
A method of making a digital storage device by selectively irradiating a crystalline or polycrystalline silicon substrate with laser radiation to form uniform amorphous regions in the surface of the substrate representing logic one and zero states, the laser radiation being of a wavelength less than 400 nanometers, applied for a time between 0.1 and 10 nanoseconds, with an energy density in the range of 0.1 to 0.8 J/cm 2 so that most of the radiation is absorbed in the top approximately 3000 Å of the substrate which rapidly melts and rapidly freezes into an amorphous state.
Claim 2
Independent Claim
97 words
A method of making a digital storage device by selectively irradiating a crystalline or polycrystalline silicon substrate with laser radiation to form uniform amorphous regions in the surface of the substrate representing logic one and zero states, the laser radiation being of a wavelength less than 400 nanometers, applied for a time between 0.1 and 10 nanoseconds, with an energy density in the range of 0.1 to 0.8 J/cm 2 so that most of the radiation is absorbed in the top approximately 3000 Å of the substrate which rapidly melts and rapidly freezes into an amorphous state.
Claim 3
Dependent Claim
22 words
The method of claim 1 wherein the laser radiation is directed through a transparent material forming a support fixed to the substrates.
Claim 4
Dependent Claim
14 words
The method of claim 1 wherein the (111) surface of the substrate is irradiated.
Claim 5
Dependent Claim
14 words
The method of claim 1 wherein the (001) surface of the substrate is irradiated.
Claim 6
Dependent Claim
13 words
The method of claim 1 wherein the substrate is cooled prior to irradiation.
Claim 7
Dependent Claim
14 words
The method of claim 1 wherein the substrate is cooled down to 77° K.
Claim 8
Dependent Claim
24 words
The method of claim 1 wherein amorphous regions are annealed to crystalline or polycrystalline regions by heating by laser irradiation and a slower cooling.
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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) | 1988-12-02 | 1989-06-03 | 1989-12-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-12-02 | 1993-06-03 | 1993-12-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-12-02 | 1997-06-03 | 1997-12-03 | $7700.00 | Window Closed / Lapsed |