CAPACITANCE AND DOPING PROFILES OF ION-IMPLANTED, BURIED-CHANNEL MOSFETS

Detailed capacitance measurements are presented of large-area, ion-implanted, buried-channel MOSFETs. The gate capacitance was measured as a function of gate-substrate voltage with drain (source)-substrate voltage as parameter. The MOSFETs were prepared on 10 Ω-cm, n-type, 〈111〉 Si. Boron ions with doses of 4 × 1011 and 8 × 1011/cm2 were implanted through the gate oxide to a depth of 0.30-0.35 μ m in the Si. The devices were subjected to heat treatments of 900-1100°C. Calculated capacitances based on a one-dimensional, partial-ionization model are in good agreement with experiment. The model is used to assess the validity of C-V profiling technique based on the abrupt space-charge approximation. It is concluded that the impurity distribution can be measured quite accurately near the peak of the profile, for ion-implantation and heat-treatment conditions examined in this paper. However, the tails" of the distribution cannot be measured with this technique. The limitations of the C-V profiling method are discussed quantitatively for a stepped profile. © 1979."