Y. Kitagawara et al., ACCURATE EVALUATION TECHNIQUES OF INTERSTITIAL OXYGEN CONCENTRATIONS IN MEDIUM-RESISTIVITY SI CRYSTALS, Journal of the Electrochemical Society, 141(5), 1994, pp. 1362-1364
Accurate evaluation methods for interstitial oxygen concentrations ([O
(i)]) by infrared absorptiometry at 1107 cm-1 are investigated for med
ium resistivity Si crystals with carrier concentrations betwee 3 x 10(
15) and 5 x 10(16) cm-3, which correspond to resistivities between 5 a
nd 0.5 OMEGA-cm for p-type crystals. Difficulty of accurate [O(i)] mea
surements for these crystals originates from the strong dependence of
the internal multiple reflection effect inside the sample crystal on t
he free-carrier absorption intensity. Neglect of this effect introduce
s an error as large as 1 ppma for a p-type approximately 1 OMEGA-cm cr
ystal. Two reliable methods to overcome this difficulty are presented.
One is to eliminate the multiple reflection effect physically by appl
ying the p-polarized light incident on the sample surface at Brewster'
s angle. The other is to eliminate the effect mathematically by a mult
iple reflection correction carefully taking account of the free-carrie
r absorption. Results obtained by the two reliable infrared absorption
methods are consistent with a result by a high precision oxygen evalu
ation using secondary ion mass spectrometry.