6.1.1 Oxide Growth without Native Oxide

When no native oxide is present, a flat interface representing a Si-ambient interface is grown into SiO$_2$ with a thickness dependent on the oxidation time, temperature, ambient (wet-H$_2$O or dry-O$_2$), pressure, and the crystal orientation of the underlying silicon. The modifications and requirements of the LS method to include oxidation are presented in Section 3.2.1.

When no native oxide is present, the oxidation process begins with $x_o=0$, as shown in Figure 6.1a, where the surfaces representing the Si-SiO$_2$ interface and SiO$_2$-ambient interface are overlapping. As the oxidation process begins, the Si-SiO$_2$ interface goes deeper into the initial Si wafer, while the SiO$_2$-ambient interface moves towards the ambient.

Figure 6.1: Results of the oxidation of (100) oriented silicon in a dry ambient at 1atm pressure and 1000 $^{\textrm {o}}$C temperature for 100 minutes. The top surface (red) depicts the SiO$_2$-ambient interface, while the lower surface (blue) depicts the location of the $\textrm {Si-SiO}_{2}$ interface. The volume shown is the original location of the silicon substrate.

(a) Initial state of the processing environment before oxidation.

(b) State of the processing environment after oxidation.

Using the Massoud model, after 100 minutes of oxidation of a (100) oriented silicon wafer in a dry ambient at 1atm pressure and 1000 $^{\textrm {o}}$C temperature, an oxide with a thickness of 66.5nm is grown, depicted in Figure 6.1.