The electrically insulating, dielectric materials silicon oxide (SiO2) and silicon nitride (Si3N4) are used for liner and spacer applications in semiconductor wafer processing. Due the continuing decrease of feature size in microelectronic devices, atomic layer deposition (ALD) of silicon-based dielectric has become necessary. Unfortunately, lab-based studies have found the ALD of these materials to be problematic, limiting their application and therefore require theoretical methods in order to resolve the experimental problems.
In collaboration with Lam Research Corporation, we have developed theoretical models for the ALD of SiO2 and Si3N4 films and compared the results to experiments. We found that both gas phase and surface models can successfully explain the experimental observations, in particular the significantly longer silicon precursor exposure times for Si3N4 compared to SiO2. Working together with Lam, these theoretical results are used to improve experimental conditions and thus allow the ALD of SiO2 and Si3N4 to be applied in industry. The development of successful ALD methods for SiO2 and Si3N4 will also enable additional applications such as FinFET conformal doping, double patterning, and through-Si-via (TSV) 3D integration.
The next phase of the collaboration with Lam is an exploration of suitable chemistries for the ALD of silicon carbide, which is another important material in electronic chips.