Total-dose effects of gamma-ray irradiation on CMOS/SIMOX devices

Radiation-hardened CMOS/SIMOX (separation by implanted oxygen) devices have been developed using a combination of vertical isolation structures obtained by SIMOX technology and recently developed lateral isolation structures. The n-channel MOSFET is vertically isolated by multilayers of highly-oxygen-doped polysilicon and buried SiO
₂
; it is laterally isolated by multilayers of thin sidewall SiO
₂
, sidewall polysilicon, and thick field SiO
₂
. The p-channel MOSFET has the same vertical isolation structure as that of the n-channel MOSFET, but has no sidewall polysilicon layer and uses a thick field SiO
₂
layer for lateral isolation. Highly-oxygen-doped polysilicon and sidewall polysilicon layers act to shield radiation-induced positive charges trapped in the buried SiO
₂
and field SiO
₂
layers, respectively.