On the chemistry of a-SiO2 deposition by plasma enhanced CVD

The chemistry in depositing a-SiO2 using tetraethoxysilane, Si(OC2H5)4, (TEOS) and tetraisocyanatesilane, Si(NCO)4, (TICS) with an oxidant is comparatively studied. In both cases, absorption and desorption reactions of intermediate precursors are seen to be dominant. TEOSO2 chemistry, where there is no N atom in the source gas, yields conformal step coverage over patterned surfaces. The precursor or precursors generated in TICSO2 chemistry are expected to contain N atom or atoms and have no surface migration property. The N atom in the precursor is believed to limit the surface migration property. This results in an uneven step coverage over patterned surfaces similar to that of SiH4O2 chemistry.