Investigation of a rf inductively coupled plasma ion source capable of highly uniform and collimated ion-beam generation

Abstract

In accordance with advanced data storage device fabrication requirements, we have evaluated a new broad-beam rf ion source for ion beam etching and deposition application. This source utilizes a novel reentrant shaped plasma inductively coupled plasma generator for improved radial plasma density uniformity and a dynamic magnetic field for improved static etch uniformity. It has the capability of reproducibly generating extremely uniform ion beams from 500to1500eV with divergence angle <3° and high directionality [Kanarov et al. (patent pending)]. For a 150mm diameter wafer, an etch uniformity of <1% σ/mean in static condition or <0.5% with wafer rotation is obtained over an ion incident angle range of 0°–65°. Recently, we have investigated extending the operation of this source to the critical low energy range, 100–500eV, required for fabricating thin film magnetic head sensors. It was found that, under optimum operating conditions, excellent static etch uniformity (1%–1.5% σ/mean) could be obtained at high ion beam current densities, up to 0.5mA∕cm2, over the entire low-energy range while still achieving low divergence angles (<5°) and high beam directionality. The ion beam performance was consistent with results obtained by simulation and by experiment using a 19-hole array ion optic test stand with scanning ion probe [E. Wåhlin (unpublished)]. In this article we will describe the design of the ion source and then present the experimental performance data including plasma density distribution measured by an array of flat Langmuir probes, beam divergence distribution obtained by a “pepper-pot” etch measurement technique, and etching rate distributions.