New observance and analysis of various guard-ring structures on latch-up hardness by backside photo emission image

In this paper, the influence of different guard-ring structures on latch-up susceptibility has been studied on four standard test structures fabricated on a standard twin well CMOS process. The test structures include the non-, single, double, and multi-double guard-rings. Based on hold I-V characteristics test results, the latch-up hardness of the P+ guard-ring structure is much greater than that of the N+ guard-ring. Because the shunting resistances of N-well and P-well are significantly reduced by multi-double guard-rings, the latchup immunities of multi-double guard-ring structures are better than those of double guard-ring structures.