Gas-Phase Chemical Etching

The etching behaviour of Si in HCI-H2 mixtures at low-pressure CVD conditions shows (85) that, at constant HCI concentration and total pressure, the polishing effect improves with an increase in temperature. With an increase in the concentrations of HCI and H2 or with an increase in the total pressure, a roughening of the surface takes place. The effect of temperature observed in this case is similar to that described above in Fig. 17. 

Depending on experimental conditions, which ultimately determine the concentration of adsorbed hydrogen and chlorine on the surface, the number of HCI molecules reacting with a silicon atom may be different, forming different species containing Si-CI bonds (86). The stable species forming at high and low temperatures are SiClj and SiCI, respectively, but 

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