Instability trade-off of inter-layer or inter-metal dielectrics formation with low-k dielectrics on active and field device's characteristics

Abstract

The effects of back end of line (BEOL) processing with low dielectric constant (low-k) materials on active and field devices' performances have been studied. The study reveals: 1) There is SPICE model uncertainty because Idsat increases as more metal layers are added; 2) Low-k dielectrics can enhance this Idsat increase; and 3) NMOSFETs hot carrier lifetime and PMOSFETs Vt stability are degraded. These effects are attributed to the BEOL-induced hydrogen generation and passivation with gate oxide dangling bonds, which are primarily created in the contact etching process. The modified process involves pure hydrogen alloy after metal-1 formation, which ensures the same device performance at metal-1 and at the final metal layer. In addition, the alloy can reduce the inverse narrow width effect and field isolation leakage currents.

Etching characteristics of thin SiON films using a liquefied perfluorocarbon precursor of C6F12O with a low global warming potential

“…Silicon oxynitride (SiON) thin films, which have low leakage current and excellent thermal stability, have been used, instead of silicon dioxide and silicon nitride, as IMD thin films, final passivation and protective layers, spacer dielectrics, insulators, and diffusion barriers [27,28] in the semiconductor industry. Accordingly, we investigated the etching characteristics of SiON films in CF 4 +X+O 2 plasmas (X=CHF 3 and C 6 F 12 O) with various gas-mixing ratios of CF 4 and X at a fixed O 2 gas flow rate.…”