Transformer coupled plasma etch technology for the fabrication of subhalf micron structures

Abstract

A transformer coupled plasma (TCP) source has been integrated into a production tool and characterized for subhalf micron etching of thin films. A planar 13.56 MHz plasma is produced over a wide pressure range of 1–500 mTorr. Langmuir probe measurements below 10 mTorr show ion densities ≳1012 cm−3 and low plasma potentials. These properties are favorable for high etch rates and low damage to device structures. Radio-frequency power is also supplied to the wafer electrode for dc bias control. Separation of the plasma generation and dc bias functions allows the control of microloading effects upon the etch profiles of dense and isolated lines. Performance of the tool is described for the etching of polysilicon and tungsten polycide films on substrates up to 200 mm in size. The evaluated characteristics include etch rate, selectivity, and microloading. The TCP is shown to be an advanced source with the capability for meeting 64 megabit device requirements.