ALD of Silicon-Based Materials

Silicon Nitride, Silicon Carbide and Silicon Oxide

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.