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Fabrication of Large Grain Columnar Polycrystalline Thin Films

IP.com Disclosure Number: IPCOM000085127D
Original Publication Date: 1976-Feb-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Cuomo, JJ: AUTHOR [+3]

Abstract

Thin films comprising grains with a large width-to-height ratio are desirable for many applications such as polycrystalline solar cells. In particular, the efficiency of a polycrystalline silicon solar cell is reduced by grain boundary recombination of the charge pairs which are generated. Therefore, larger grains and fewer grain boundaries in the film will provide a higher efficiency yield. A method is described for fabricating thin films with very large columnar grains in a filamentary structure, which is applied to a silicon thin film.

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Fabrication of Large Grain Columnar Polycrystalline Thin Films

Thin films comprising grains with a large width-to-height ratio are desirable for many applications such as polycrystalline solar cells. In particular, the efficiency of a polycrystalline silicon solar cell is reduced by grain boundary recombination of the charge pairs which are generated. Therefore, larger grains and fewer grain boundaries in the film will provide a higher efficiency yield. A method is described for fabricating thin films with very large columnar grains in a filamentary structure, which is applied to a silicon thin film.

The nucleation of the film takes place from a saturated thin-liquid film of an alloy near the eutectic point. A thin film of metal or compound A is deposited onto an inert substrate. Next, the substrate and film A are heated to a temperature T above the eutectic point of materials A and B. Then, the material B is deposited onto film A, resulting in a structure consisting of a substrate, a solid film of A, a liquid layer of A + B at a composition near the eutectic.

As the deposition of B continues, the liquid layer of A + B extends through the film, leaving no undissolved A behind. When the liquid becomes saturated, component B will precipitate out of the thin-film melt to form a large grain polycrystalline film of B.

Illustratively, material A is platinum and B is silicon. Initially, there was 1000 Angstroms of Pt on SiO(2) or Al(2)O(3). The substrate and Pt film wer...