Effective reduction of fixed charge densities in germanium based metal-oxide-semiconductor devices

Abstract

Metal-oxide-semiconductor capacitor was fabricated using in situ O2 plasma passivation and subsequent deposition of a HfO2 high-k gate stack on Ge. By extracting flat band voltages from capacitors with different equivalent oxide thicknesses (EOT), the effect of forming gas annealing (FGA) and O2 ambient annealing on the fixed charge was systematically investigated. The O2 ambient annealing is more effective than FGA as it reduced fixed charge density to 8.3 × 1011 cm−2 compared to 4.5 × 1012 cm−2 for at the same thermal budget and showed no degradation of EOT. Further, the distribution of fixed charges in gate stack was discussed in detail.