Theoretical investigation of crystallographic orientation effect on the chemical etching rate

The chemical etching of boron-doped p-Si(100) and p-Si(111) substrates in Br2+Ar mixture is considered. The experimentally measured dependences of silicon etching rate on partial pressure of Br2 molecules are compared with those theoretically calculated. It is found that at the same temperature desorption rate constant for SiBr2 molecules on p-Si(100) substrates is more than twice higher than on p-Si(111) substrates. The difference in desorption rate constants is caused by higher concentration of dangling bonds on Si(100) surface. The averaged desorption activation energy of SiBr2 molecules is equal to Ed±ΔEd=(2.02±0.11)eV. The influence of crystallographic orientation on the rate constant for Si+Br2→SiBr2 reaction is negligible.