Cl etching of silicon surfaces assisted with short pulsed laser irradiation is analyzed to find out chloride removal processes without using thermal reaction. When a Cl-saturated Si(111) surface was irradiated by a picosecond pulsed laser at 400 nm, desorptions of SiCl and $\mathrm{Si}{\mathrm{Cl}}_2$ molecules were observed with a quadrupole mass spectrometer with a pulse-counting system. The presence of the SiCl desorption shows previously unfound etching process without thermally induced recombinative reaction. Time-of-flight and signal-ratio of the SiCl and $\mathrm{Si}{\mathrm{Cl}}_2$ molecules indicated that they were assigned to products from restatom monochlorides and adatom polychlorides, respectively. High desorption rates of the chlorides which depend on laser fluence nonlinearly suggest that multiple excitation by substrate hot carriers is essential to the etching.

• Received 11 August 2005

DOI:https://doi.org/10.1103/PhysRevB.73.085309