EP0078681A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Method for producing single crystal semiconductor areas
Assignee: Xerox Corp
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Filing: 1982-10-29
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Granted: —
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Expires: 2002-10-29
Abstract
Abstract A method for laser induced conversion of large predefined areas (10) of amorphous or polycrystalline semiconductor material, upon a substrate (12), into single crystal areas by using an infrared laser energy source to cause the bulk of heating to occur in the substrate and not In the predefined areas to that the areas are heated to melting by the substrate. The substrate comprises a material which is highly absorptive of the laser wavelength and the predefined areas comprise a material substantially transparent to the laser wavelength. The substrate and the predefined areas have different refractive indexes, and are arranged so that more of the laser energy (16) is reflected from the substrate directly below the predefined areas than from the surrounding areas, whereby a thermal gradient exists across said areas during cooling, with the centers of the areas being cooler than their edges. This promotes the formation of single crystals in said areas.
Inventors
- 👤 William G. Hawkins
- 👤 Jerry G. Black
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 04:02
CPC Classifications
H; H10; H10P; H10P34/00; H10P34/40; H10P34/42; Y; Y10; Y10S; Y10S117/00; Y10S117/901; Y10S117/902; Y10S117/903; Y10S117/904
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
232 words
A method for converting predefined areas of semiconductor material into single crystal areas, characterised by including the steps of: providing support means in the form of a material being highly absorptive of the wavelength of electromagnetic radiation from a predetermined source and having a first refractive index; providing an array of crystallizable semiconductor areas upon said support means, said areas being in the form of a material substantially transparent to the wavelength of radiation from said source and having a second refractive index; projecting radiation from said source upon each semiconductor area and a portion of the support surrounding each area, so as to heat said substrate, the thicknesses and refractive indices of said support means and said areas being such that more incident energy is reflected from the region of said substrate directly beneath said areas than in the region of said substrate surrounding said areas whereby the region of said substrate surrounding said areas is made hotter than the region of said substrate directly beneath said areas; ceasing the projection of said radiation; and allowing the melting of said areas by heat from said heated substrate, and the cooling of said melted areas and said substrate such that during cooling a concave thermal gradient exists across said areas with the center of each of said areas being cooler than ' its edges so that said areas recrystallize as single crystals.
Claim 2
Independent Claim
232 words
A method for converting predefined areas of semiconductor material into single crystal areas, characterised by including the steps of: providing support means in the form of a material being highly absorptive of the wavelength of electromagnetic radiation from a predetermined source and having a first refractive index; providing an array of crystallizable semiconductor areas upon said support means, said areas being in the form of a material substantially transparent to the wavelength of radiation from said source and having a second refractive index; projecting radiation from said source upon each semiconductor area and a portion of the support surrounding each area, so as to heat said substrate, the thicknesses and refractive indices of said support means and said areas being such that more incident energy is reflected from the region of said substrate directly beneath said areas than in the region of said substrate surrounding said areas whereby the region of said substrate surrounding said areas is made hotter than the region of said substrate directly beneath said areas; ceasing the projection of said radiation; and allowing the melting of said areas by heat from said heated substrate, and the cooling of said melted areas and said substrate such that during cooling a concave thermal gradient exists across said areas with the center of each of said areas being cooler than ' its edges so that said areas recrystallize as single crystals.
Claim 3
Dependent Claim
27 words
The method of claim 1 wherein said first refractive index and said second refractive index are different from one another by at least a factor of two.
Claim 4
Dependent Claim
27 words
The method of claim 1 or claim 2, including the step of confining said areas to maintain the shape of said areas when in their molten state.
Claim 5
Dependent Claim
27 words
The method of claim 3 wherein said step of confining is carried out by providing an encapsulating layer over said areas and a portion of said substrate.
Claim 6
Dependent Claim
18 words
The method of claim 4 wherein said encapsulating layer comprises Si0 2 or Si 3 N 4 .
Claim 7
Dependent Claim
24 words
The method of claim 3 wherein said step of confining is carried out by providing cavities in said substrate for receiving said semiconductor areas.
Claim 8
Independent Claim
27 words
The method of any one of claims 1 to 6 including projecting a laser spot and imparting relative motion between said spot and said array of areas.
Claim 9
Independent Claim
39 words
The method of any one of claims 1 to 7 including projecting a laser spot onto said areas for a predetermined time for producing (100) oriented single crystal areas and that said (100) plane is parallel to said substrate.
Claim 10
Dependent Claim
36 words
The method of claim 7 including projecting said laser spot onto said areas for a predetermined time for producing (100) oriented single crystal areas and that said (100) plane is in the direction of relative motion.
Claim 11
Independent Claim
35 words
The method of any one of claims 1 to 9 wherein said projected optical energy source is a C0 2 laser, said semiconductor areas are islands of silicon, and said substrate is Si0 2 .
References Cited (Backward Citations)
No citation records indexed.
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