ANALYSIS OF DELAY-TIME INSTABILITY ACCORDING TO THE OPERATING FREQUENCY IN-FIELD SHIELD ISOLATED SOI CIRCUITS

It has been demonstrated that field shield (FS) isolation technology c an suppress the delay time instability according to the operating freq uency. The FS isolation technology has been proposed to fix the body p otential without any area penalty in a gate array, In this technology, an FS plate, which is an additional polysilicon gate, is introduced t o electrically isolate active regions. The body potential of the SOI M OSFET can be fixed through the so. layer under the FS plate. The effec t of body resistance on the delay time instability was also investigat ed using device simulation. The simulation showed that although the bo dy potential momentarily falls to a nonsteady level due to capacitive coupling during switching operation, the body potential recovers to a steady level, following the RC law. From the simulation result, a help ful design guideline concerning the body resistance was deduced. This guideline showed that the FS isolation has a superior capability to su ppress the frequency-dependent instability for practical deep submicro n SOI circuits.