Correlation between Plasma Damage and Dielectric Reliability for Ultra-Porous Low-k Materials

摘要

The effects of plasma damage on dielectric reliability were studied using voltage ramp stress experiments. Altering ramp rates allowed us to identify the main mechanisms for failure, namely intrinsic and metal catalyzed failure. Failure mechanisms are identified using In (t_(B D)) / In(R) trends for pristine and plasma damaged SiCOH films. Failure dynamics are discussed for 7% and 25% porous SiCOH films. O_2 plasma treatment was found to lower the breakdown strength of 7% SiCOH from 79.5 V to 67.1 V at low ramp rates (0.01 V/s), and from 135.7 V to 109.3 V at fast ramp rates (20 V/s). The breakdown strength of 25% SiCOH films was enhanced from 41.0 V to 55.4 V after plasma treatment at slow ramp rates. However, at fast ramp rates, the plasma treatment lowered the breakdown voltage from 112.0 V to 99.7 V. The enhancement in breakdown strength for highly porous samples under slow ramp rates is attributed to film densification upon plasma treatment, while the deterioration at fast ramp rates is associated with the generation of defects catalyzing dielectric failure.