INTEGRATED PLASMA EQUIPMENT MODEL FOR POLYSILICON ETCH PROFILES IN ANINDUCTIVELY-COUPLED PLASMA REACTOR WITH SUBWAFER AND SUPERWAFER TOPOGRAPHY

Above wafer topography of the substrate, such as wafer clamps, is know n to impact adjacent feature profiles during plasma etching of microel ectronic devices. The consequences of subwafer topography, such as ele ctrostatic chucks and cooling channels, on feature profiles is less we ll characterized. To investigate these issues we have developed and in tegrated a plasma equipment model and a Monte Carlo feature profile mo del, and applied the integrated model to investigate polysilicon etchi ng in an inductively coupled plasma reactor. We find that, when using low conductivity wafers, subwafer topography reduces the sheath potent ials above the wafer which results in lower ion energies incident on t he wafer. Etch rates sensitive to ion power are therefore also reduced . Due to the perturbation of the presheath and sheath, subwafer topogr aphy can also affect the angular distribution of the ion flux incident on the wafer which then results in asymmetric etch profiles. Superwaf er structures perturb both the magnitude and angular distribution of t he ion flux due to shadowing at the edge of the wafer. This leads to l ower etch rates and asymmetric etch profiles. Inhibitor fluxes can be used to control the etch profile shape but only at relatively low magn itudes of those fluxes. (C) 1997 American Vacuum Society.