Etching Characteristics of WSi2 with Pulsed-Electron Cyclotron Resonance Plasma

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Abstract
Etching properties of WSi2 are investigated with pulsed-electron cyclotron resonance (ECR) plasma. A new type of charge-induced notch, which appears at an inside line, has been discovered in polycide etching. By comparing the notch properties to reactive ion etch (RIE) lag characteristics, the deposition of a conductive film on the sidewall is suggested as the origin of the electrons. The RIE-lag is improved with pulse plasma due to a reduced dissociation of reaction byproducts. The dissociation of byproducts produces a large amount of tungsten. The actual quantity depends on the duty ratio of the pulse modulation, and continuous discharge is the worst case. The formation of volatile byproducts with pulse plasma also effectively reduces RIE-lag. The volatile byproducts are formed during afterglow, which produces an electron temperature lower than the W–Cl bond strength.