T. Itoga et al., New technique to determine gettering efficiency of heavy metals and its application to carbon-ion-implanted Si epitaxial wafers, JPN J A P 1, 40(4A), 2001, pp. 2105-2109
Using a newly developed method to evaluate the gettering efficiency of Si w
afers, we found that C-ion implantation prior to epitaxial growth greatly i
mproves the gettering efficiency of heavy metals in epitaxial Si wafers. Th
e gettering efficiency was evaluated through direct observation by total X-
ray reflection fluorescence (TXRF) by counting the number of heavy metal at
oms that diffused from the back to the front surface of wafers. Heavy metal
s were deposited on the backside surface of Si wafers from metal-dissolved
aqua solution. Two-step annealing was carried out after the deposition. The
first step caused metal diffusion and the second produced precipitation fr
om the front surface of the wafers. The effectiveness of the method was con
firmed by comparing the results obtained from as-received and intrinsic (or
internal) gettering (IG)-processed Czochralski-grown Si wafers. The method
was applied to C-ion-implanted epitaxial Si wafers to confirm the improvem
ent in gettering efficiency in accordance with the implanted C dose. The ef
fectiveness of the C-ion implantation was also confirmed by evaluating the
electrical characteristics of the oxide grown on the Si wafers.