Radiation hardness of VA1 with submicron process technology

We have studied the radiation hardness of the VA1, a Viking-architecture preamplifier VLSI chip. Large-scale integrated (LSI) samples are fabricated in 0.8 and 0.35 /spl mu/m process technologies to improve the 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 compared to 1.2-/spl mu/m technology. Little degradation of noise and gain is observed up to a total dose of 20 Mrd for the VA1 fabricated in the 0.35-/spl mu/m technology. We find that the radiation hardness improves with a scaling of better than t/sub ox//sup -6/ (t/sub ox/: oxide thickness). Basic parameters of MOSFETs are also studied to understand the mechanism of radiation damage in the VA1.