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 Q
ox
and surface state N
ss
are created near Si-SiO
2
interface. 2) A majority of N
ss
act 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 Q
ox
. 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.