Moisture Effects on the 1/F Noise Of Mos Devices

We have exposed MOS gate and field oxide transistors to moisture treatments with all pins grounded for up to three weeks. Irradiated field oxide structures showed a significant decrease in low frequency noise with moisture treatment, due to the passivation of Si dangling bonds at or near the Si/SiO2 interface. With moisture exposure, pMOS gate oxide transistors showed significant increases in pre-irradiation 1/f noise and post-irradiation oxide- and interface-trap charge densities. The 1/f noise of nMOS gate oxide transistors shows much less sensitivity to moisture exposure than pMOS transistors, before and after irradiation. We attribute these differences in sensitivities to moisture treatment to the enhancement of water diffusion in SiO2 by B atoms in the oxides that overlie the source/drain junctions of the pMOS transistors, in contrast to the retardation of moisture diffusion by P atoms in the corresponding regions of the nMOS devices.