Direct detection of H atoms in the catalytic chemical vapor deposition of the SiH4/H2 system

The absolute densities of H atoms produced in catalytic chemical vapor deposition (Cat-CVD or hot-wire CVD) processes were determined by employing two-photon laser-induced fluorescence and vacuum ultraviolet absorption techniques. The H-atom density in the gas phase increases exponentially with increases in the catalyzer temperature in the presence of pure H-2. When the catalyzer temperature was 2200 K, the absolute density in the presence of 5.6 Pa of H-2 (150 sccm in flow rate) was as high as 1.5x10(14) cm(-3) at a point 10 cm from the catalyzer. This density is one or two orders of magnitude higher than those observed in typical plasma-enhanced chemical vapor-deposition processes. The H-atom density decreases sharply with the addition of SiH4. When 0.1 Pa of SiH4 was added, the steady-state density decreased to 7x10(12) cm(-3). This sharp decrease can primarily be ascribed to the loss processes on chamber walls. (C) 2002 American Institute of Physics.