6.1.3 Oxidation with Orientation effects

The rate of silicon oxidation depends in part to the orientation of the silicon crystals, as previously discussed in Section 2.2.1 and Section 2.3. Orientation effects can be observed, when oxidizing a trench in a (100) silicon surface. A thicker oxide is expected on the sidewalls since their orientation is (110). This effect is implemented in the presented LS model framework.

Figure 6.3: Results of the oxidation of a trench etched into (100) oriented silicon with (110) oriented sidewalls. 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 Si-SiO$_2$ interface. The volumes shown is the original location of the silicon trench.

(a) Initial Si(100) trench	(b) Trench after oxidation
(c) Slice of the trench after oxidation. Some two-dimensional features of oxide growth are visible.

The effects of silicon orientation are visible in Figure 6.3 where the (110) sidewalls are seen as having a thickness greater than that of the (100) surfaces. The corners also experience pinching due to the amorphous nature of the oxidant diffusion through the oxide.