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SOLID PHASE REGROWTH OF AMORPHOUS DEPOSITED LAYERS ON PREAMORPHIZED SUBSTRATES

IP.com Disclosure Number: IPCOM000039680D
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Iyer, SS: AUTHOR [+2]

Abstract

Solid phase epitaxial regrowth of films offers the possibility of attaining sharp doping profiles in films for various device applications. As shown in [*], one can grow amorphous films in UHV and, simultaneously, incorporate dopant atoms in any desired profile and subsequently regrow the amorphous film epitaxially with minimal alteration of the doping profile, at temperatures of about 600oC. Experience shows that this process has a very narrow process window. The hazard is that if the film is thick or if for some reason (impurity incorporation, improper substrate preparation, etc.) regrowth is slow, nucleation of crystallites which is not in phase may also take place.

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SOLID PHASE REGROWTH OF AMORPHOUS DEPOSITED LAYERS ON PREAMORPHIZED SUBSTRATES

Solid phase epitaxial regrowth of films offers the possibility of attaining sharp doping profiles in films for various device applications. As shown in [*], one can grow amorphous films in UHV and, simultaneously, incorporate dopant atoms in any desired profile and subsequently regrow the amorphous film epitaxially with minimal alteration of the doping profile, at temperatures of about 600oC. Experience shows that this process has a very narrow process window. The hazard is that if the film is thick or if for some reason (impurity incorporation, improper substrate preparation, etc.) regrowth is slow, nucleation of crystallites which is not in phase may also take place. This competes with the growth front proceeding from the amorphous/single crystal interface and leads to twinning and other defects included in the worst-case polysilicon films. Samples amorphized with ion implantation at high doses, however, do not show this effect to such a great extent possibly because amorphization is not complete and there is some "memory" of the original crystal.

Thus, even if spontaneous random nucleation of crystallites occurs, it is in phase with the growth front. There is, however, one drawback in this scheme. The tail end of the implant which does not cause amorphization, upon annealing, results in the nucleation of extended defects. These extended defects may grow into the active area of the a...