Screen printed Ag contacts for n-type polysilicon passivated contacts

Abstract

We have printed firing through silver paste on n+ polysilicon passivated layer structures deposited by Low Pressure Chemical Vapor Deposition (LPCVD). We analysed recombination at the metal contacts by photoluminescence imaging of metallised lifetime samples and found for the best paste, metal semiconductor recombination current density values (J0met) below 100 fA/cm². To our knowledge, these are among the lowest values reported so far for full size M2 wafers with 150 nm thin polysilicon layer. On samples metallised with standard commercial pastes for diffused emitters, we observed higher J0met values, while contact resistivity was acceptable for all samples. We also studied the effect of the peak firing temperature on the J0met and contact resistivity in this work. Further, we compared the impact of deep and shallow doping profiles on the passivation and the J0met values.