As the text discussion continues, a more predictive measure is whether the etch

Question

As the text discussion continues, a more predictive measure is whether the etch product is volatile or decomposes. The lower the boiling point (liquid vapor) temperature, sublimation (solid vapor) temperature, or decomposition temperature, the more readily removed the etch product, i.e, the better for etchability. If the etch product does not evaporate or further decompose, it will form a protective residue on the surface of the material to be etched and hinder the etching reaction. Based on this criteria, rank which compounds (fluorides, chlorides, or bromides) would better etch silicon. Why might you be skeptical fluorides and chlorides were good candidates to etch copper?

Explanation / Answer

Based on the properties of the halogens, fluorides would better etch silicon. Fluoride being the lowest boiling point compound would be far better choice than the chlorides and bromides. Bromide being the least selective of all having highest boiling point among the three compounds listed here. Fluorides and chlorides are having lower reactivity as compared to copper (when compared to silicon), therefore making them a bit skeptical of etching agent for copper.   

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