REAL-TIME MONITORING OF SILICON-NITRIDE COMPOSITION DURING PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION

The study of bulk and interfacial material properties during thin film deposition or growth is important for learning how to optimize and co ntrol processing conditions. Unfortunately, there have been no techniq ues available that offer simultaneously non-intrusive in situ, monitor ing, sufficient sensitivity to permit real-time data acquisition, and chemical specificity to determine how process parameters affect compos ition, In this work, we demonstrate that attenuated total reflection F ourier transform infrared (ATR-FTIR) spectroscopy can be used to provi de all these capabilities for the study of plasma enhanced chemical va por deposition of amorphous, hydrogenated silicon nitride (a-SiN:H). W e use this technique to develop a low temperature deposition process w here bulk H concentrations are low enough that the material could be u seful as a thin him transistor gate dielectric. At the interface betwe en the single crystallne Si substrate and the a-SiN:H layer, we observ e a thin layer where the concentration of -Si-H is enriched. The appea rance of two distinct absorption bands at 2190 cm(-1) and 2050 cm(-1) suggests that this interfacial layer is formed by amorphisation and hy drogenation of the single crystalline Si substrate. At the interface b etween the deposited nitride and the reactive plasma, there is an enri ched layer of -N-Si-H that appears to act as an intermediate to a-SiN: H growth.