Aging and Irradiation Response of 1/f Noise in Metal Oxide Semiconductor Devices

Abstract

Defects that lie at or near the semiconductor-oxide interface of MOS transistors were characterized using 1/f noise and charge pumping measurements. The frequency, gate-voltage, and temperature dependence of the noise were investigated for moisture-exposed and control Si nMOS and pMOS transistors before and after irradiation. Moisture exposure did not significantly change nMOS device noise after irradiation compared to control devices. For the exposed pMOS parts, significant changes in the noise with irradiation occurred, which reflect changes in the trap density and energy distributions. Three-level charge pumping measurements, in conjunction with noise measurements, were used to probe the trap densities of these pMOS devices before and after irradiation. For the exposed device, enhanced radiation-induced border trap densities were observed through an increase in the charge recombined charge per cycle, consistent with the increase in noise and the change in gate-voltage dependence of the noise. The techniques described above were applied to Ge pMOS transistors to gain insight into the properties of the semiconductor/gate-dielectric interface, and to determine the effects of processing on the defects within that region. The number of silicon monolayers and the halo implantation dose strongly affect the radiation response and 1/f noise levels of these devices. In addition, significantly different border trap and interface trap energy distributions were estimated via 1/f noise and charge pumping measurements, strongly suggesting that the noise in these devices is dominated by bulk oxide traps in the dielectric layer.