Device quality MOS Gate insulators: Sputter deposition and low temperature processing

A series of n-channel, Al-gate MOS transistors were fabricated using reactively sputtered SiO
2
as the gate insulator. The SiO
2
was deposited at low temperatures and low RF powers, and during subsequent processing was not subjected to temperatures in excess of 465°C. Test results showed that for gate oxides deposited at 20 W, the measured breakdown strength was 3-4 MV/cm with interface trapped charge density of 4-8 × 10
¹⁰
cm
^-2
and that the resulting electron mobility of the transistor was 470 cm
²
/V.s. After annealing in nitrogen at 1000°C, the deposited oxides exhibited electrical properties which are very similar to those of thermally grown SiO
2
.