Search

Thin oxide property in a metal–oxide–semiconductor structure subjected to substrate injection from semiconductor into oxide is investigated by means of ramp-up and ramp-down current–voltage (I–V) measurements. Generally, gate injection causes catastrophic dielectric breakdown, and the damaged oxide suffers from permanent destruction which exhibits resistorlike behavior in the I–V curve. For substrate injection, however, there are three distinct modes existing in I–V characteristics. They are resistorlike, hysteresislike, and saturation, i.e., no breakdown. Their occurrence frequencies are dependent on the oxide thickness. For oxides thinner than 2.4 nm, in general, the gate current nearly saturates due to the limitation of minority carriers. For 3.9 nm oxide, the minority carrier generation rate increases due to trap generation near the Si surface. Thus the oxide sustains higher field and larger carrier injection causing destructive damage, i.e., resistorlike mode. For 3 nm oxide, sometimes a hysteresislike mode appears due to light damage in the oxide. The related characteristics of these three modes are studied and exhibit oxide thickness dependence. These phenomena are important to recent studies on devices with ultrathin gate oxides.