Nitriding process for next-generation semiconductor devices by VHF (162 MHz) multi-tile push-pull plasma source

For the low power and high-performance semiconductor devices, a silicon oxynitride (SiO_xN_y) layer is required as the gate sidewall spacer material by replacing oxygen of the silicon oxide (SiO₂) sidewall layer with nitrogen through a plasma nitriding process. In this study, as a plasma nitriding process, instead of conventional radio frequency plasma nitriding utilizing high frequency (HF; 13.56 MHz, etc.) plasmas, a very high frequency (VHF) plasma operated at 162 MHz with a multi-tile push-pull plasma source has been used in nitriding the SiO₂ layer at room temperature and the effects of the VHF (162 MHz) plasma on SiO_xN_y formation from a SiO₂ layer and electrical characteristics of the SiO_xN_y formed by the plasma nitridation were investigated. The use of the VHF (162 MHz) multi-tile push-pull plasma formed ∼10 nm thick SiO_xN_y with a very high nitrogen percentage of ∼24% on the SiO₂ layer surface. Also, when the surface roughness of the SiO_xN_y and electrical characteristic of MOS capacitors fabricated with the SiO_xN_y formed by the VHF (162 MHz) plasma were compared with those formed by a capacitively coupled plasma at 60 MHz, a lower surface roughness and much lower leakage current of MOS capacitor could be obtained.