Elimination of gate oxide damage during electron cyclotron resonance plasma etching of the tungsten polycide gate structure (WSi/poly-Si)

Abstract

Oxide damage during the over etch step of a polycide gate structure is studied. Seven process parameters of the electron cyclotron resonance (ECR) plasma etching system are systematically investigated. These parameters include: rf power, microwave power, main coil and subcoil currents, Cl2 and O2 gas flow rate, and pressure. The results show that damage depends strongly on only three parameters: rf power, subcoil current, and O2 flow rate. As a result, a highly anisotropic, damage and poly-Si residue free etch of the polycide gate structure, with a high etch rate, has been achieved. These etch characteristics are critical for manufacturing the next generation of IC products.