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Quantitative Boron Doping of Polycrystalline Silicon

IP.com Disclosure Number: IPCOM000048367D
Original Publication Date: 1982-Jan-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Malin, K: AUTHOR [+2]

Abstract

Enriching of boron atoms at the grain boundaries in highly doped polysilicon is prevented by converting the polycrystalline into monocrystalline silicon by means of epitaxial re-crystallization. This conversion is effected through an implantation of atoms of a higher mass into the polysilicon layer and the interface area between polycrystalline and monocrystalline silicon, and through a subsequent annealing to effect the epitaxial re-crystallization.

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Quantitative Boron Doping of Polycrystalline Silicon

Enriching of boron atoms at the grain boundaries in highly doped polysilicon is prevented by converting the polycrystalline into monocrystalline silicon by means of epitaxial re-crystallization. This conversion is effected through an implantation of atoms of a higher mass into the polysilicon layer and the interface area between polycrystalline and monocrystalline silicon, and through a subsequent annealing to effect the epitaxial re-crystallization.

In bipolar semiconductor elements, highly conductive, p doped zones with a sheet resistivity of less than 100 ohms per square are preferably made in polysilicon technology. First, a polycrystalline silicon layer is deposited on the silicon substrate, with boron atoms of high dose being subsequently implanted therein. A disadvantage of this method is that a large part of the implanted boron atoms concentrates at the grain boundaries of the polycrystalline silicon, and thus does not contribute to the p-doping.

Enriching at the grain boundaries is prevented when the polysilicon layer is converted after boron implantation into monocrystalline silicon through epitaxial re-crystallization. The polysilicon layer and the interface between monocrystalline and polycrystalline silicon is homogenized through the implantation of ions of higher mass and high solubility, e.g., through the implantation of tin or gallium. Subsequently, during an annealing at temperatures higher than 600 degrees C, which is required in the process, there follows an epitaxial...