Transient plasma-induced emission analysis of laser-desorbed species during Cl-2 plasma etching of Si

The surface during the etching of Si in a Cl-2 inductively-coupled plasma ( ICP) was analyzed by laser desorption (LD), followed by detection of the de sorbed species by monitoring the transient changes by plasma-induced emissi on (PIE). Optical emission from Si, SiCl, SiCl2, and possibly other species was detected in situ using this LD-PIE method as a function of rf power, s ubstrate bias, and pressure. The surface coverage of chlorine was determine d by normalizing the LD-PIE signal by either of two ways: by the electron d ensity, as measured by microwave interferometry, or by using the background PIE signal. Little change in surface coverage was observed as the ion dens ity was changed by varying the rf power supplied to the ICP, confirming the observation made using laser-induced fluorescence (LIF) detection (LD-LIF) . The LD-PIE signal is related to the density of species desorbed from the surface and subsequently excited by electrons. LD-PIE analysis of the surfa ce is more versatile than LD-LIF-sometimes it can detect the desorbed speci es while LD-LIF cannot. Still, it requires calibration to account for the e lectron collision-induced excitation of the laser-desorbed species. (C) 200 0 American Vacuum Society. [S0734-2101(00)00506-6].