Shallow Trench Isolation Stress Effect on 45 Degree Rotated MOSFET Layout

摘要

This paper describes the Shallow Trench Isolation (STI) stress effect on 45 degree rotated MOSFET layouts. 45 degree rotated PMOS layout with large Sa (active space) shows 15% increase in saturation drain current (Idsat)as compared to the non-rotated ones. On the other hand, PMOS layout with minimum Sa and same rotation show 3.8% Idsatenhancement only. This is because when rotated 45 degree, the channel orientation changes from <110> to <100> axis. This enhances the PMOS Idsatwith large Sa. At minimum Sa, the Idsatenhancement is small because the PMOS is at high STI stress. For <110> or non-rotated layouts, the STI stress is observed to increase the Idsatby 14 %. The impact of STI stress effect on PMOS with minimum Sa is negligible at <100> or rotated. For NMOS, no Idsat enhancement or degradation is observed on 45 degree rotated layouts. Finally, we have studied the effect of using 45 degree rotated PMOS in ring oscillator circuit.