Semiconductor device manufacturing: process – Introduction of conductivity modifying dopant into...
Reexamination Certificate
1999-01-19
2001-03-27
Bowers, Charles (Department: 2813)
Semiconductor device manufacturing: process
Introduction of conductivity modifying dopant into...
Reexamination Certificate
active
06207537
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for formation of an impurity region in a semiconductor layer by introduction of a dopant impurity as a donor or an acceptor, and to an apparatus for introducing an impurity into a semiconductor layer.
2. Description of the Prior Art
Methods for formation of an impurity region in a semiconductor substrate include heat diffusion, epitaxial growth, ion implantation, and plasma doping.
These methods require heating at a high temperature (approximately 800-1300° C.) for diffusion of impurities and electric activation of the diffused impurities.
However, such heating of the semiconductor substrate at a high temperature causes problems such as crystal defects in the semiconductor substrate, a penetration of atoms other than a dopant impurity into the semiconductor substrate, or decrease in life time of a minority carrier.
In addition, there are the problems: the depth of the impurity region is as deep as several micrometers or more; and the concentration at the surface of the impurity region cannot be controlled to make a proper concentration of 10
22
atms/cm
3
or lower.
SUMMARY OF THE INVENTION
It is the purpose of the invention to provide a method for formation of an impurity region in a semiconductor layer, wherein the impurity region can be formed without heating of the semiconductor layer at a high temperature so that crystal defects in the semiconductor layer and the penetration of a substance other than a dopant impurity into the semiconductor layer can be prevented, and the impurity concentration at the surface of the impurity region can be controlled uniformly to a proper concentration of 10
22
atms/cm
3
or lower, and the depth of the impurity region can be controlled to 1 &mgr;m or lower.
According to the invention, an impurity gas is mixed with a gas containing any one of H
2
and inert gases, and the mixed gas is electrically discharged.
Electric discharge of the impurity gas generates ions and radicals of the impurity gas. These ions and radicals attach to the surface of a semiconductor layer.
At the same time, the impurity gas is ionized, the gas containing any one of H
2
and inert gases is also almost simultaneously ionized. Thus the ions of the gas containing any one of H
2
and inert gases are accelerated to collide with the semiconductor layer, resulting in a rise of temperature of the target site. Therefore, thermal energy is given to the impurities on the surface of the semiconductor layer, so that these impurities are diffused into the semiconductor layer, and the impurities are electrically activated. Namely, the surface impurities can be activated simultaneously with the introduction thereof into the semiconductor layer.
These steps allow the impurity region to be formed in the semiconductor layer.
Further, according to the method the present invention for formation of an impurity region in a semiconductor layer, lack of heating the semiconductor layer at a high temperature can reduce thermal stress in the semiconductor layer and crystal defects. The deep penetration of impurities into the semiconductor layer can be also prevented.
Furthermore, the adjustment of the mixing ratio of the impurity gas with the gas containing any one of H
2
and inert gases allows adjusting the quantity of impurity activated electrically.
REFERENCES:
patent: 4618381 (1986-10-01), Sato et al.
Matsui Bunya
Satoh Noritada
Bowers Charles
Christianson Keith
Lorusso & Loud
Semiconductor Process Laboratory Co. Ltd.
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