Effect of hydrogen-argon mixing for sputtered aluminum metallization on MOS devices

Effects of aluminum films deposited by RF diode sputtering in hydrogen and argon mixed gases have been investigated in n-channel silicon-gate MOS transistors and capacitors. Positive fixed oxide charge Qoxand acceptor-type surface states Nsscreated by the sputter metallization process have been confirmed experimentally. The threshold voltage Vthof a transistor metallized with aluminum sputtered in pure argon was found to be shifted toward positive voltages and its transconductance was markedly lowered due to acceptor-type surface states. Hydrogen mixing in the sputtering argon gas minimizes Qoxand Nss, resulting in small Vthand gmchanges.