Novel chlorine-enriched SiO2/Si3N4 bilayers to downscale gate dielectrics toward sub-45nm and beyond

We have developed a low leakage and highly reliable SiON gate dielectrics by using novel low temperature deposition of chlorine-enriched silicon nitride upon a thin oxide. This method can achieve higher top-to-bottom nitrogen concentration ratio and keep nitrogen peak toward top surface. It was found that the low temperature Si3N4 deposition technique can form a high nitrogen percentage SiON (> 40%), compared to DPN (decoupled plasma nitridation) nitrided films (< 20%). The gate leakage of the novel bilayers SiON dielectric was 3.3 times lower than DPN nitrided SiON at the same EOT. This result showed that no significant interface trap existed between SiO2/Si3N4. The proposed scheme demonstrated a superior interface state density with excellent resistance to boron penetration without mobility degradation giving very promising features for gate oxynitride scaling toward 45nm and beyond high performance CMOS applications.