Electrical damage in MOS devices by RF diode sputtered aluminum metallization

Electrical damage induced by RF diode sputtered aluminum metallization has been investigated in n-channel silicon gate MOS transistors and capacitors. The following results were obtained: 1) Positive fixed oxide charge Qoxand surface state Nssare created near Si-SiO2interface. 2) A majority of Nssact as acceptor-type surface state. Then, threshold voltages of transistors shift toward positive voltage, due to the acceptor,type surface state, in spite of creation of Qox. 3) Dependences of threshold voltage on substrate voltage in the as-deposited sample become greater due to the metallization. 4) Electrical damage for both devices Can be effectively reduced by annealing them in forming gas at 450°C for 20 min.