PLASMA-ETCHING PROCESS-DEVELOPMENT USING IN-SITU OPTICAL-EMISSION ANDELLIPSOMETRY

In situ optical emission and ellipsometry are used to control the etch ing of titanium nitride/polysilicon gate stacks deposited on 70 Angstr om gate oxide patterned with 0.25-0.35 mu m design rules. Multistep re cipes using various chemistries are developed and optimized with a low pressure, high plasma density helicon source in which the goal is to obtain stringent profile control, and high selectivity to the gate oxi de. The characteristic real-time optical emission and ellipsometry tra ces are used as a reference to evaluate reproducibility and to compare the etching rates as a function of the different processing condition s. Optical emission and ellipsometry appear crucial for the rapid deve lopment of a multistep etching sequence using various chemistries. Com plementary post-process diagnostics using a spectral reflectometer for film thickness measurements and scanning electron microscopy for quan tification of profile control are also presented. (C) 1996 American Va cuum Society.