Small signal analysis of source vapor control requirements for APCVD

A method for small signal operating point analysis of the stability of chemical source vapor flow from liquid source vapor generators (bubblers) is presented. The analytical technique allow´s quantification of the relative effect of changes in the flow, pressure, and temperature operating conditions of the vapor generator on the vapor output of the generator. Application of the analysis to ({tetraethylorthosilicate≡TEOS)+{trimethylphosphite ≡TMPi}+({trimethyl borate≡TMB}+{O₃≡ozone) based atmospheric pressure chemical vapor deposition (APCVD) processes yields example stability criteria for the bubbler control parameters. Examination of 5-wt%-B/4-wt%-P BPSG pre-metal dielectric (PMD), and SiO ₂ intermetal dielectric (IMD) processes show that variances in the bubbler temperature, ΔT, bubbler head space pressure, ΔP_HS, and carrier nitrogen flow, ΔQ_N2 affect the source vapor flow variance, ΔQ_ν, in the ratio of about 4.3:2.8:1 respectively. Film-doping and film-depth range-method uniformity specifications of ±0.1 wt% and ±2% require bubbler parameter control limits of: ΔT<0.25°C, ΔP_HS⩽6 torr, and ΔQ_N2⩽0.3% of operating point flow