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°C), the noise increase is very small in the frequency range of interest. However, at room temperature, the noise increase is large