6.2 Nitric Acid Oxidation

Section 3.3.1 explains the NAOS model and suggests that the main use for this processing technology is for the manufacture of TFT for LCD. For this technology, the oxide must grow evenly across polycrystalline or doped silicon, which is possible with NAOS and is the main reason for the continuing interest in this technology [111], [112], [147]. Using the azeotropic NAOS model, after four hours of immersion in a 61wt% HNO$ _3$ concentration of a (100) oriented silicon wafer at 60 $ ^{\textrm {o}}$C temperature, an oxide with a thickness of 1.18nm is grown, depicted in Figure 6.7.

Figure 6.7: Results of the oxidation of (100) oriented silicon during immersion in a 61wt% HNO$ _3$ concentration at a temperature of 60 $ ^{\textrm {o}}$C. The top surface (red) depicts the SiO$ _2$-ambient interface, while the lower surface (blue) depicts the location of the Si-SiO$ _2$ interface. The volume shown is the original location of the silicon substrate.
\includegraphics[width=0.481\linewidth]{chapter_applications/figures/NAOS_initial.eps} \includegraphics[width=0.481\linewidth]{chapter_applications/figures/NAOS_final.eps}
(a) Silicon wafer before NAOS. (b) Topographies after NAOS.

L. Filipovic: Topography Simulation of Novel Processing Techniques