US 4,379,020 A · Polycrystalline semiconductor processing

Abstract

A process for forming large-grain polycrystalline films from amorphous films for use as photovoltaic devices. The process operates on the amorphous film and uses the driving force inherent to the transition from the amorphous state to the crystalline state as the force which drives the grain growth process. The resultant polycrystalline film is characterized by a grain size that is greater than the thickness of the film. A thin amorphous film is deposited on a substrate. The formation of a plurality of crystalline embryos is induced in the amorphous film at predetermined spaced apart locations and nucleation is inhibited elsewhere in the film. The crystalline embryos are caused to grow in the amorphous film, without further nucleation occurring in the film, until the growth of the embryos is halted by imgingement on adjacently growing embryos. The process is applicable to both batch and continuous processing techniques. In either type of process, the thin amorphous film is sequentially doped with p and n type dopants. Doping is effected either before or after the formation and growth of the crystalline embryos in the amorphous film, or during a continuously proceeding crystallization step.

Claims12

Dependent claims

A process for forming large grain polycrystalline films of random crystallographic orientation from amorphous films comprising:

(a) depositing a thin amorphous film on a substrate in a controlled atmosphere;
(b) inducing the formation of crystalline embryos at predetermined spaced apart locations in the free upper surface of said amorphous film by localized surface treatment thereat and inhibiting nucleation elsewhere in said film;
and
(c) allowing said crystalline embryos to grow in a controlled atmosphere and at a temperature below the melting point of said amorphous film with random crystallographic orientation by the excess free energy of said amorphous film, without further nucleation occurring in said amorphous film, until the growth of said embryos is halted by impingement on adjacently growing embryos, with the resultant grain size of said polycrystalline film being determined by the distances between said spaced apart locations and being greater than the thickness of said film, with transformation from said amorphous films to said large grain polycrystalline films being effected in a solid phase transition from the amorphous to the crystalline state.

1 more element

A continuous process for forming doped large-grain polycrystalline films from amorphous films for use as photovoltaic devices comprising:

(a) forming in a first controlled atmosphere a first thin doped amorphous film on a moving substrate;
(b) forming in a second controlled atmosphere a second thin oppositely doped amorphous film on said first doped amorphous film;
(c) inducing in a third controlled atmosphere the formation of crystalline embryos at predetermined spaced apart locations in said combined doped amorphous film and inhibiting nucleation elsewhere in said film;
and
(d) causing, in a fourth controlled atmosphere and at a temperature below the melting point of said combined doped amorphous film, said crystalline embryos to grow, without further nucleation occurring in said amorphous film, until the growth of said embryos is halted by impingement on adjacently growing embryos.

2 more elements

Dependencies are inferred from the claim text.

Polycrystalline semiconductor processing

Life of this patent

Polycrystalline semiconductor processing

Life of this patent

Abstract

Claims12