Activation of the Si(100)/Cl2 Etching Reaction at High Cl2 Translational Energies

Exposing a Si(100) surface to a pulsed beam of neutral Cl2 with high translational energy results in etching at a rate faster than that seen with chlorine at thermal energies. The Cl2 beam used in these experiments is produced by laser vaporization of cryogenic films. It has a broad energy distribution which can be varied by changing laser energy and film thickness. Beams with mean energies as low as 0.4 eV result in etching =10 times faster than etching by thermal Cl2. When Cl2 beams are used which have considerable flux above 3 eV, the etching rate increases by a further factor of 3.6 ± 0.6. This rate increase, which occurs at energies just above the Si-Si bond energy, suggests that kinetic energy can be efficiently utilized to break surface bonds.