An electron-beam plasma source and geometry for plasma processing

Abstract

The operation of an electron-beam plasma source and its application as a secondary source of ionization in a radio frequency- (RF) powered reactive-ion-etching (RIE) reactor is investigated. RF-powered RIE is an important tool in the manufacture of semiconductor devices. One aspect of RF RIE is its ability to produce a DC substrate potential on insulating as well as conducting substrates. Substrate potential is an important determinant of etch anisotropy. However, traditional RF RIE reactors can only be operated over a limited range of parameter space. Ion flux, neutral radical flux and ion energy must all be controlled with only two independent variables: RF power and pressure. Expanded and precise control over process parameters is becoming more important as device structures are made smaller and less damage tolerant. Process control may be enhanced by the addition of an alternative source of power. The experimental arrangement is designed to investigate these possibilities. As a test case, the system is utilized to etch patterned silicon wafers with SF6 gas. Etch rate, etch uniformity and DC bias potential versus RF power and beam current are presented. Electron-gun generated contamination is addressed and several solutions are reported.