Low-frequency noise in proton damaged LDD MOSFET's

One of the concerns in the design of a guide camera for a satellite astronomy mission was an increase in the low-frequency noise in the output amplifier of the charge-coupled device (CCD) image sensor due to the radiation environment of the satellite. We investigated this potential problem by measuring the noise in several MOSFET's which had been subjected to varying amounts of high-energy proton radiation. These MOSFET's were typical of those used in the output stage of a CCD. They were lightly-doped drain (LDD) n-type buried-channel devices with aspect ratios between 4 and 6. We found a significant increase in the low-frequency noise of our devices after radiation. The frequency and temperature dependence of the noise indicates that it is generation-recombination noise due to the introduction of bulk trapping states. Fortunately, at the operating temperature of the CCD in the guide camera (-50/spl deg/C), the noise increase is very small in the frequency range of interest. However, at room temperature, the noise increase is large.