Electron beam neutralization in ICP RIE with auxiliary cold cathode e-beam

Abstract

Summary form only given. A cold cathode electron beam (e-beam) source has been developed to operate in the plasma environment of reactive ion beam etching (RIE). The e-beam was generated by the secondary electron emitted from an aluminum-oxide coldcathode in a RF plasma sheath. It employs a separate RF biased, electrically insulating cathode with high secondary electron emission. This electron source produced electron flux up to I mA/cm/sup 2/ with electron energy up to 1 keV. The electron beam can be independently controlled to irradiate the etch workpiece. The measured electron beam energy spectra agreed with a simple model comparing the RF waveform applied to the cathode. The inductively coupled plasma (ICP) system, desired for oxide etching, was set its 13.56 MHz RF power up to 500 W with CF/sub 4/:H/sub 2/ of 6 mTorr. Experimental study of oxide films on silicon substrate with 0.45 /spl mu/m feature size of patterns had shown the neutralization effect of e-beam, to eliminate the undesired micro-trench feature, which was caused by nonuniform charge buildup. That effect was predicted by G. Hwang and K. Giapias in previous theoretical studies for sub-micron IC-device oxide-etching process. A two-dimensional charged particle flux simulation, based on Arnold & Sawin's work, verified the reduction of micro-trench by irradiating the feature bottom with an energetic electron beam to neutralize the positive charge buildup on oxide island. This cold cathode e-beam source is compatible with several varieties of RIE plasma environment with high reliability, and works in concert with the 13.56 MHz RF system. It is one candidate for the neutralization source in plasma etch processing systems that suffer from undesired charge build-up.