Impact of etching on doping profiles in CZ silicon photo-diodes

The technique of differential voltage contrast (DVC) measurement was developed in our laboratory several years ago. The viability of DVC measurement for determining parameters such as doping profiles has been clearly demonstrated. In this paper, we use DVC to study differences in doping profiles on CZ silicon photo-diodes using two well known surface processing methods. KOH etched wafers showed almost square pits, 100 μm in length. The presence of these etch pits caused, in spin on glass technology, a graded doping profile. On the other hand, samples etched in 5:3:1 solution (HF:HNO3:CH3COOH) had steep doping gradients. The distribution of spin on glass diffusant, deposited after the above processing, for the two groups of samples seems to be responsible for the variation in the diffusion profile.