sticking probability of etch products

Although the sticking coefficient of SiCl4 on Si surfaces is known to be small, Sp < 0.002[45], the unsaturated SiClx species are expected to have much larger sticking coefficients of Sp〜0.1. In effect, the deposition yields of low-energy (Ei = 30 eV) SiCl+ and SiCl2+ ions on Si and SiO2 substrates have been measured to be in the range 0.1-0.5.[46] Thus, if SiCl4 is the dominant product species desorbed from the surface, the redeposition of etch products is negligible during etching as shown in Fig. 6a. However, the redissociation of SiCl4 into unsaturated species SiClx in plasmas may result in the deposition of product species on the surface.
Tuda, JVST B 14(1996)

The initial sticking coefficient is expected to be about order of 10^-3 if the SiO is a stable gas. Otherwise, it is expected to be about order of 10^-1. Therefore we varied the sticking coefficient SSiO from 0.001 to 0.5 to estimate the effect of etch products on the Si etch rate.

気相中のSiCl2/SiCl4 比について：
In our etching model, we assumed that SiCl2 was a dissociative species from SiCl4 and its dissociation degree was 3%, because the dissociation degree of Cl2 molecules was 1% - 3% in the downstream region of ECR discharges. [7,27]

Nishikawa, JVST B, 1999