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 500 to 1500 eV with divergence angle Ͻ3°and high directionality ͓Kanarov et al. ͑patent pending͔͒. For a 150 mm diameter wafer, an etch uniformity of Ͻ1% /mean in static condition or Ͻ0.5% 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, 100-500 eV, required for fabricating thin film magnetic head sensors. It was found that, under optimum operating conditions, excellent static etch uniformity ͑1%-1.5% /mean͒ could be obtained at high ion beam current densities, up to 0.5 mA/ cm 2 , over the entire low-energy range while still achieving low divergence angles ͑Ͻ5°͒ 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obtained by simulation and by experiment using a 19-hole array ion optic test stand with scanning ion probe ͓E. Wåhlin ͑unpublished͔͒. 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.

Modeling and Simulation of Fast Neutral Beam Sources for Materials Processing

“…Should this reactor be used as a plasma source for an ion gun, the extracted ion flux would be maximum on axis, resulting in non‐uniform etch or deposition rate. Kanarov et al52 proposed a modification to the plasma source design to correct this problem. They used a re‐entrant vessel design to suppress the ion flux maximum at the center of the reactor.…”

Fast (tens to hundreds of eV) neutral beams for materials processing

“…Being a 'gentler' process (no charging, very little VUV/UV radiation) compared with RIE, NBE may also be superior in the etching of ultra thin (∼tens of nm) films, for which the possibly lower etch rate of NBE has no significant throughput consequences. Large area (300 mm diameter or more) neutral beam processing has not been demonstrated yet, but appears feasible given the viability of large area ion beam sources [78]. From the practical point of view, pumping requirements are expected to be demanding for large wafer processing.…”

“…This implies that the parent ion beam must also be uniform. Uniform ion beams over large area substrates have been demonstrated [78]. Ways to control the ion (and thus neutral) beam energy are also available (see [79] and references therein).…”