Abstract

We have demonstrated sensitive resonance-enhanced multiphoton ionization detection (REMPI) of silicon monofluoride radicals, SiF, using light from a Nd:YAG pumped dye laser tuned between 430 and 490 nm. This SiF radical is of interest to the semiconductor industry since it is one of the products observed during chemical etching reactions at silicon surfaces. SiF radicals were generated by the reaction of fluorine atoms with silane in a low pressure flow reactor. The laser-ionized radicals were detected in a quadrupole mass spectrometer with a sensitivity of better than 10¹⁰/cm³. Two laser excitation schemes were used: (1) simultaneous two-photon absorption through C'²∏_r ← X²∏ and C″²∑⁺ ← X²∏_r transitions and (2) sequential one-photon absorption through the (0,0) A²∑⁺ ← X²∏½ and (1,0)C″²∑⁺ ← A²∑⁺ transitions. In both schemes SiF radicals absorbed at least three photons before ionizing. An attractive feature of SiF REMPI detection is that the ion signal is concentrated exclusively into m/z 47.

© 1985 Optical Society of America