Semiconductor device manufacturing: process – Introduction of conductivity modifying dopant into... – Ion implantation of dopant into semiconductor region
Reexamination Certificate
1999-03-29
2001-05-22
Picardat, Kevin M. (Department: 2823)
Semiconductor device manufacturing: process
Introduction of conductivity modifying dopant into...
Ion implantation of dopant into semiconductor region
C438S510000, C438S514000
Reexamination Certificate
active
06235616
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to acceptor atom introduction that is performed in fabricating SiC semiconductor devices. More particularly, the invention performs ion implantation of C atoms in addition to acceptor atoms, thereby forming p-type SiC of better quality in local areas and contributing to the fabrication of SiC integrated circuits.
As is well known, p-type conduction characteristics are attained by ion implantation of Al, B and other acceptor impurities into SiC. Problems with this conventional approach are that the introduced acceptor atoms are poorly activated electrically and that they tend to diffuse outwardly as the result of a heat treatment conducted after the ion implantation. No technology has not yet been established in forming p-type SiC of better quality that is suitable for device fabrication.
SUMMARY OF THE INVENTION
The present invention has been accomplished under these circumstances and has as an object enhancing the electrical activation of acceptor atoms introduced into SiC while controlling their thermal diffusion, thereby forming p-type SiC of better quality that is suitable for device fabrication.
This object of the invention can be attained by a process for producing p-type SiC semiconductor of better quality which comprises the step of introducing acceptor atoms such as aluminum (Al) and boron (B) into a silicon carbide semiconductor (SiC) by ion implantation together with the additional ion implantation of carbon (C) atoms, thereby enhancing the electrical activation of the implanted acceptor atoms while controlling their diffusion due to a thermal treatment.
The acceptor atoms such as Al and B that have been introduced into SiC are electrically activated after they occupy substitutional positions in the Si lattice of the SiC crystal. If C atoms are additionally introduced according to the present invention, more vacancies form in the Si lattice to accelerate the process of substitution of the acceptor atoms for the Si atoms, thereby increasing the concentration of effective, carrier generating acceptors.
The acceptor atoms occupying substitutional position in the Si lattice diffuse at a slower speed than when they are at interstitial sites, and this explains why the additional C ion implantation is effective in controlling the diffusion of acceptor atoms during a subsequent heat treatment. Thus, satisfactory p-type SiC can be formed in local areas by the additional C ion implantation.
REFERENCES:
patent: 5604135 (1997-02-01), Edmond et al.
Hisayoshi Itoh et al.; “Effects of C or Si Co-Implantation on the Electrical Activation of B Atoms Implanted in 4H-SiC”; Applied Physic Letters, vol. 73. No. 10; Sep. 7, 1998; pp 1427-1429.
Banner & Witcoff , Ltd.
Collins D. M.
Japan Atomic Energy Research Institute
Picardat Kevin M.
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