MECHANISMS OF DEHYDROGENATION DURING ARF EXCIMER LASER PATTERNING OF PLASMA-DEPOSITED SILICON-NITRIDE FILMS

Using Fourier-transformed infrared spectroscopy, we show that pulsed ArF excimer laser irradiation of plasma-deposited silicon nitride films causes a large reduction in NH (∼100%) and SiH (∼50%) in the top ∼500 Å, and further show that this is responsible for the large suppression of the etch rate in buffered HF solution. Temperature rise calculations qualitatively predict the observed maximum falloff in etch rate and in SiH and NH concentration at the surface of the film. The observed reduction of the effect in thin films, which is due to the heat-sink effect of the underlying substrate, is also predicted. Both are strong indications that NH and SiH bonds are broken in a laser heating process. H2 has been detected as a product evolved during laser irradiation; however, most H2 remains trapped in the film.