Desorption Activation Energy of $SiBr_2$ Molecules according to Steady-State Approximation

The chemical etching of intrinsic and n-type polycrystalline silicon in $Br_2$ ambient is considered. The theoretically calculated dependences of silicon etching rates on pressure of $Br_2$ molecules at different temperatures are compared with experimentally measured ones. The reaction and desorption activation energies are evaluated. It is found that activation energy of Si + $Br_2$ → $SiBr_2$ reaction for intrinsic silicon is equal to (1.82 ± 0.24) eV, and decreases to (1.45 ± 0.24) eV when n-type silicon films are used. Desorption activation energy of $SiBr_2$ molecules for intrinsic silicon is equal to (1.94 ± 0.17) eV, and decreases to (1.51 ± 0.17) eV when n-type silicon films are used. Desorption of $SiBr_2$ molecules is an etching-rate limiting process at high pressure of $Br_2$ molecules.