Characterization of phosphosilicate glass films obtained using plasma-enhanced chemical vapor deposition from tetraethylorthosilicate and trimethylphosphite

Abstract

We examine the deposition rate, step coverage and film thickness uniformity of 2 μm (8.4 wt.% P) phosphosilicate glass (PSG) films obtained using plasma-enhanced chemical vapor deposition (PECVD) from tetraethylorthosilicate (TEOS), trimethylphosphite and O 2 as reactants in an Ar diluent. A 2 6-2 fractional factorial screening equipment was performed to evaluate the effects of r.f. power, pressure, temperature, O 2-to-TEOS feed ratio, plasma duty cycle and Ar flow in a batch PECVD reactor. Factor effects are considered to have a significant influence at an 85% confidence level. The deposition rate increases with increasing duty cycle, power and pressure and decreasing Ar flow. Step coverage is characterized for rectangular trenches with two initial aspect ratios, 0.64 and 2.5, by three ratios; (1) the film thickness S 1 in the plane of the original trench mouth to the thickness T on the wafer surface, (2) the film thickness S 2 where it is the thinnest at the base of the side wall to T and (3) the thickness B at the center of the base to T. S 1/ T increases with increasing duty cycle, pressure and temperature for an aspect ration of 0.64. For feature with an aspect ratio of 2.5; (1) S 1/ T increases with increasing temperature and decreasing Ar flow, (2) S 2/ T increases slightly with increasing temperature and (3) B/T increases with increasing temperature and Ar flow and decreasing O 2-to-TEOS ratio and power. Step coverages are superior to those of low pressure chemical vapor deposited PSG films from SiH 4, O 2 and PH 3. The inter-wafer film thickness uniformity is independent of the factor level settings in this experiment. The intra-wafer film thickness variability increases with increasing temperature and O 2-to-TEOS ratios.