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 Q
ox
and acceptor-type surface states N
ss
created by the sputter metallization process have been confirmed experimentally. The threshold voltage V
th
of 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 Q
ox
and N
ss
, resulting in small V
th
and g
m
changes.