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US 4,330,363 AGranted
Thermal gradient control for enhanced laser induced crystallization of predefined semiconductor areas
AssigneeXerox Corporation
InventorsDavid K. Biegesen, Noble M. Johnson, Dirk J. Bartlelink, Marvin D. Moyer
Life of this patent
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Abstract
A method for laser induced conversion of large predefined areas of amorphous or polycrystalline semiconductor material, disposed nonepitaxially upon a substrate, into large single crystal areas, by controlling the lateral heat flow out of the melted regions of the areas for causing their recrystallization from a single nucleation site and for suppressing the formation of competitive nucleation sites at their edges.
Claims22
A method of converting predefined areas of semiconductor material into single crystal areas comprising the steps of:
- providing support means,
- providing an array of optical energy absorbing crystallizable semiconductor areas upon said support means,
- providing optical energy absorbing means upon said support means in the region adjacent to and around each of said areas,
- providing thermal control means, associated with said optical energy absorbing means, in the region adjacent to and around each of said areas, for effecting the amount of thermal energy absorbed in the region immediately adjacent to and around each area to compensate for perferential heat loss at the edges of each of said areas.
- projecting an optical energy source wherein said source is a shaped laser spot upon and to expose a portion of each of said areas and that portion of said optical energy absorbing means and said thermal control means immediately adjacent and around each of said areas, and imparting relative motion between said spot and said substrate, said spot being of elongated shape such that its short dimension is less than the dimension of each of said areas in the direction of relative movement and its long dimension is greater than the dimension of each of said areas normal to the direction of relative movement,
- melting the exposed portion of each of said areas with said optical energy source,
- elevating the temperature of the exposed portion of said optical energy absorbing means with said optical energy source,
- removing said optical energy source,
- cooling said optical energy absorbing means by drawing heat stored therein into said support means,
- cooling said melted areas by drawing heat stored therein into said support means, and
- establishing a differential thermal gradient between the central portion of each of said areas and the edges of each of said areas for slowing the rate of cooling at said edges such that as said melted areas cool, each will crystallize from a single nucleation location and competitive nucleation locations at said edges will be suppressed, whereby each of said areas will be converted to a single crystal when cooled.
8 more elements
A method of converting predefined areas of semiconductor material into single crystal areas comprising the steps of:
- providing support means,
- providing an array of optical energy absorbing crystallizable semiconductor areas upon said support means,
- providing optical energy absorbing means upon said support means in the region adjacent to and around each of said areas,
- providing thermal control means, associated with said optical energy absorbing means, in the region adjacent to and around each of said areas, for affecting the amount of thermal energy absorbed in the region immediately adjacent to and around each of said areas to compensate for preferential heat loss at the edges of each of said areas,
- encapsulating each of said areas by providing a layer of material over each of said areas,
- projecting an optical energy source, upon and to expose a portion of each of said areas, and its encapsulating layer, and that portion of said optical energy absorbing means and said thermal control means immediately adjacent to and around each of said areas,
- melting the exposed portion of each of said areas with said optical energy source,
- elevating the temperature of the exposed portion of said optical energy absorbing means with said optical energy source,
- removing said optical energy source,
- cooling said optical energy absorbing means by drawing heat stored therein into said support means,
- cooling said melted areas by drawing heat stored therein into said support means, and
- establishing a differential thermal gradient between the central portion of each of said areas and the edges of each of said areas for slowing the rate of cooling at said edges such that as said melted areas cool, each will crystallize from a single nucleation location and competitive nucleation locations at said edges will be suppressed, whereby each of said areas will be converted to a single crystal when cooled.
9 more elements
Dependencies are inferred from the claim text.