Effect of quartz window temperature on plasma composition during STI etch

An etch-stop phenomenon taking place in Cl2/O2/N2 plasma was investigated by means of the actinometry technique as well as using PlasmaVolt and PlasmaTemp in-situ sensor wafers from K-T promesys of KLA Tencor. The temperature of TCP quartz window was determined to increase from 50°C to more than 100°C during sequential plasma processing that in turn induces a plasma composition change. Based on the optical spectra a 20% increase in both atomic [O] and [Cl] concentrations was determined to take place in Cl2/O2/N2 plasma used for STI etching. Performing experiments on the blanket wafers the dependence of the etch-stop on O2-flow, pressure, TCP power, wafer temperature and quartz window temperature was determined. The values of RF voltage and temperature were measured locally at different positions on the wafer surface providing additional information about plasma homogeneity. Finally, the results are discussed in terms of the well-known recombination model considering the increase of [O] concentration results in the etch stop in the middle of the wafer.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.