Browse Prior Art Database

Method for Laser Annealing of Polysilicon with Reduced Damage

IP.com Disclosure Number: IPCOM000051573D
Original Publication Date: 1981-Feb-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Leas, JM: AUTHOR [+2]

Abstract

A major problem in the use of laser energy for processing polycrystall silicon films on silicon wafers is that the underlying silicon wafer can be damaged.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 1

Method for Laser Annealing of Polysilicon with Reduced Damage

A major problem in the use of laser energy for processing polycrystall silicon films on silicon wafers is that the underlying silicon wafer can be damaged.

Intrinsic silicon, however, is transparent to certain wavelengths of laser energy, such as infrared. The reason that it is transparent is that there are no free electrons to absorb the laser energy, so the laser beam passes through with little or no attenuation. In contrast, heavily doped silicon has a high concentration of free electrons (n type) or holes (p type) that can absorb the laser energy.

Considering the foregoing properties of intrinsic silicon and heavily doped silicon, the following method can be used to process thin films of polycrystalline silicon with laser energy: (1) the polycrystalline silicon is deposited onto very lightly doped or intrinsic silicon wafers, (2) the polycrystalline silicon is heavily doped to a predetermined level by diffusion or ion implantation to provide a structure of opaque highly doped polycrystalline silicon on a transparent silicon base, and (3) the structure is laser annealed using radiation with a wavelength that will be absorbed in the doped region and not absorbed in the intrinsic region. A CO(2) laser, which works in infrared wavelengths, could be used. Tunable lasers which work at a variety of wavelengths have been developed, so that this procedure could be used regardless of the desired wavelength....