Exposure of silicon nitride to above-bandgap 6.5-eV photons from an ArF excimer laser drives both the dissociation of silicon-nitrogen bonds and the desorption of nitrogen atoms and/or molecules over a wide fluence range. Crystalline silicon precipitates are also generated on laser exposed surfaces, however, only for fluences exceeding 0.2 J/cm². The rates of nitrogen desorption and the concentration of silicon precipitation were found to depend strongly on laser fluence, rising rapidly above 0.2 J/cm², and saturating at approximately 0.5 J/cm². This saturation was also observed in the thickness of the silicon precipitate layer, which peaked at 35 nm depth for fluences greater than 0.5 J/cm². Such saturation phenomena can be explained by the onset of laser ablation at approximately 0.5 J/cm² fluence which removes material in the laser affected zone. The formation of silicon precipitates is discussed in the context of photochemical reactions that follow band-to-band electronic transitions.

Date Published: 9 May 1997
PDF: 7 pages
Proc. SPIE 2991, Laser Applications in Microelectronic and Optoelectronic Manufacturing II, (9 May 1997); doi: 10.1117/12.273742

Published in SPIE Proceedings Vol. 2991:
Laser Applications in Microelectronic and Optoelectronic Manufacturing II
Jan J. Dubowski, Editor(s)