Radiation-hardness of VA1 with sub-micron process technology

We have studied the radiation hardness of the VA1, a Viking-architecture preamplifier VLSI chip. LSI samples are fabricated by 0.8 /spl mu/m and 0.35 /spl mu/m process technology to improve radiation hardness of the LSI for the Belle silicon vertex detector upgrade. We have observed significant improvement of the radiation hardness with 0.8 /spl mu/m technology. Little degradation of noise and gain is observed to total dose of 20 Mrad for the VA1 fabricated by the 0.35 /spl mu/m technology. We find that the radiation hardness improves at a scaling of better than t/sub ox//sup -6/ (t/sub ox/: oxide thickness). Basic parameters of MOSFETs are also studied to understand a mechanism of the radiation damage in the VA1.