Laser-induced etching of Si with chlorine

Photo-induced dry etching of silicon with chlorine is studied by measuring mass spectra and time-of-flight (TOF) distributions of the particles desorbed from a chlorinated target during irradiation with 308- and 248-nm photons. The detected masses are Si, SiCl, SiCl2, and SiCl3. The measured TOF spectra can be fitted with Maxwell–Boltzmann-like distributions. The temperatures obtained by these fits depend on laser power and chlorine pressure. A higher laser power or gas pressure results in a higher temperature. Activation energies for desorbing Cl, SiCl, and SiCl2 are obtained. Possible mechanisms to explain the results will be discussed. Etching of rough silicon is much more efficient than the etching of polished silicon. The maximum etch rate obtained is 30 Å per laser pulse. No difference is found between p- and n-type silicon.