2.3.2 Limitations of the Deal-Grove Model

It should be noted that the Deal-Grove model, although good in many aspects when attempting to model the thermal oxidation of silicon, has several limitations. Mainly, the model does not describe several observed phenomena:

- The surface reaction, which converts Si and O$ _2$ or H$ _2$O into SiO$ _2$, is influenced by pressure and the silicon surface doping concentration. This is dealt with in ways which go beyond the Deal-Grove model, such as introducing an additional expression for the effects of the atmospheric pressure on the linear and parabolic rate constants. This is implementable as an additional feature to the Deal-Grove model.
- The Deal-Grove model does not include the influence of treatment prior to oxidation, which is standard for any silicon processing, such as wafer cleaning or UV treatment, which was found to cause an oxide growth of up to 1.5 nm, reduce the carbon content in the subsequent thermal oxide growth, and improve the dielectric strength in gate oxides [181].
- In a dry ambient, ultra-thin oxides (10 - 30nm) experience accelerated growth. The Deal-Grove model does not deal with this phenomenon, but it will be addressed within Section 2.3.3.
- Two-dimensional effects are also not a part of the Deal-Grove model. These effects cause oxide thinning at trench corners and steps. Although not covered by Deal-Grove, some effects can be added to a Deal-Grove model.
- The growth of a thin later ($ \sim $1nm) of native oxide even at room temperature is not described or explained by the model.

L. Filipovic: Topography Simulation of Novel Processing Techniques