1/f noise and oxide traps in MOSFETs

摘要

MOSFETs historically have exhibited large 1/f noise magnitudes because of carrier-defect interactions that cause the number of channel carriers and their mobility to fluctuate. Uncertainty in the type and location of defects that lead to the observed noise have made it difficult to optimize MOSFET processing to reduce the level of 1/f noise. This has limited one's options when designing devices or circuits (high-precision analog electronics, preamplifiers, etc.) for low-noise applications at frequencies below (approximately)10--100 kHz. We have performed detailed comparisons of the low-frequency 1/f noise of MOSFETs manufactured with radiation-hardened and non-radiation-hardened processing. We find that the same techniques which reduce the amount of MOSFET radiation-induced oxide-trap charge can also proportionally reduce the magnitude of the low-frequency 1/f noise of both unirradiated and irradiated devices. MOSFETs built in radiation-hardened device technologies show noise levels up to a factor of 10 or more lower than standard commercial MOSFETs of comparable dimensions, and our quietest MOSFETs show noise magnitudes that approach the low noise levels of JFETS.