Comparison of arsenic diffusion in Si and Si/sub 1-x/Ge/sub x/ epilayers

Abstract

Rapid thermal annealing of ion implanted arsenic in relaxed Si/sub 1-x/Ge/sub x/ (x=0.90/spl sim/0.43) epilayers was studied and compared to diffusion in Si. Sample analysis included depth profiling by secondary-ion-mass spectroscopy, and electrical characterization employing spreading resistance probe measurement. Arsenic chemical concentration profiles indicated that the behavior of implanted As in Si/sub 1-x/Ge/sub x/ after RTA was different from that in Si, and the Si/sub 1-x/Ge/sub x/ samples with the higher x exhibited box-shaped, concentration-dependent diffusion profiles. The maximum concentrations of electrically active arsenic in Si/sub 0.57/Ge/sub 0.43/ were found to be 3.0/spl times/10/sup 19/ and 4.2/spl times/10/sup 19/ cm/sup -3/ for 18 second anneals at 950/spl deg/C and 1050/spl deg/C, respectively, which is about one order of magnitude lower than the arsenic equilibrium solubility limit for arsenic-implanted Si.