Y. Hayamizu et al., NOVEL EVALUATION METHODS OF SILICON EPITAXIAL LAYER LIFETIMES BY PHOTOLUMINESCENCE TECHNIQUE AND SURFACE-CHARGE ANALYSIS, Denki Kagaku Oyobi Kogyo Butsuri Kagaku, 63(6), 1995, pp. 505-512
A novel method, the short wavelength laser excited photoluminescence (
PL) technique at room temperature, was applied to evaluate carrier lif
etime characteristics of silicon epitaxial (epi) layers which are grow
n on heavily doped p(+) substrates with similar to 10(19) cm(-3) of bo
ron. The carrier excitation at 488 nm enables one to evaluate the life
time characteristics of epi-layers thicker than 3 mu m. Method of surf
ace charge analysis (SCA) was also applied to the epi-layer lifetime e
valuation. Applying these methods to silicon epitaxial wafers with the
p/p(+) structure, a trace metallic contamination in the epi-layers in
troduced during the epi-growth processes has been evaluated successful
ly by the PL method and the SCA method. In case of the PL method, it h
as been found that no heat treatment for surface passivation is requir
ed for the epi-layer evaluation. This implies a great advantage of the
method which enables evaluation of the ''as-grown'' epi-qualities. We
have observed that degraded epi-layer lifetimes by iron contamination
in the as-grown p/p(+) wafers recover remarkably even by a slight sur
face passivation heat treatment. This indicates a strong iron getterin
g capability of the heavily boron doped substrates.