Investigation of Al-PMA Effect on Al2O3/GeOX/Ge Gate Stack

Abstract

We investigated the Al post metallization annealing (PMA) effect on Al2O3/GeOX/Ge gate stacks. The Al-PMA is effective for Al2O3/GeOX/Ge gate stacks, similar to the case of SiO2/GeO2 gate stack. It was found that interface states density in the lower half of the band gap and slow trap density can be reduced by Al-PMA at 400°C. However, a serious problem occurred in the metal source/drain (S/D) MOSFET fabricated using the gate stack with Al-PMA, which was poor electrical isolation between gate and S/D. It was found that Al-PMA at 400°C caused the reaction of Al with Al2O3 film on the S/D side wall, resulting in a decrease in insulating quality of Al2O3 film. To solve this problem, we demonstrated a method for depositing a thin SiO2 film on the S/D side wall.