Performance Improvement Induced by Metal Gate Undercut for Ring Oscillator

The performance of 101-stage ring oscillator is effectively improved by the undercut process of metal gate for 28 nm high-k first metal gate-last planar CMOS technology. Using a simple over-etch process after dummy poly-Si gate formation, the undercut metal gate can be fabricated. The metal gate undercut is demonstrated to be able to effectively reduce the overlap capacitance between gate and drain, which further results in over 3.7% improvement of the maximum oscillating frequency at the same integrated circuit active current. While the comparable alternating current performance with reduced power consumption can be obtained.