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 [micro]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-/[micro]m technology compared to 1.2-/[micro]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./[micro]m technology. We find that the radiation hardness improves with a scaling of better than [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] ([t.sub.ox]: oxide thickness). Basic parameters of MOSFETs are also studied to understand the mechanism of radiation damage in the VA1. Index Terms--Integrated circuit radiation effects, MOS analog integrated circuits, radiation detector circuits, radiation hardening, silicon radiation detectors.