Phosphorous silicate glass (PSG) was formed at the temperature range 800-900degreesC during diffusion of phosphorous (P) into Si wafers from liquid POCl3 source in ambient atmosphere of N-2 and O-2. The thickness and refractive indices were measured by an ellipsometer. The refractive index increased with the temperature of formation upto 875degreesC and then became constant at which point PSG is saturated with P. From the growth rate data at different temperatures, the linear and parabolic activation energies were determined as 0.79 and 1.43 eV for parabolic and linear rate constants, respectively. Therefore, growth rate of PSG is higher than thermal SiO2. The PSG films were found to have refractive indices 1.85, 1.78, 1.74 and 1.71 for forming temperature 800degreesC, 825degreesC, 850degreesC and 875degreesC, respectively. Reflectivity varied from 2.5 to 7.5 in the wavelength range 450-700 nm. SIMS depth profiling suggests that there has been a pile up of P on the Si side at the Si/SiO2 (PSG) interface. (C) 2002 Elsevier Science B.V. All rights reserved. References: 12
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