AVS 49th International Symposium
    Plasma Science Monday Sessions
       Session PS2-MoA

Paper PS2-MoA3
Optimization of Source Modules in ICP-Helicon Multi-Element Arrays for Large Area Plasma Processing

Monday, November 4, 2002, 2:40 pm, Room C-105

Session: Plasma Processing for Large Area Substrates
Presenter: J.D. Evans, University of California, Los Angeles
Authors: J.D. Evans, University of California, Los Angeles
F.F. Chen, University of California, Los Angeles
Correspondent: Click to Email
Optimization studies of compact inductive rf-source modules for use as individual elements of a multi-element ICP-helicon source array, with sufficient density N and spatial N(R) profile uniformity for plasma processing of arbitrarily large substrates, is described. Attention is restricted to a low-magnetic-field (low-B) regime (B < 250G), within which a local maximum (low-B peak) in N vs B is routinely observed and exploited for optimum plasma production efficiency. Proof of principle experiments that exploit this low-B peak have been successfully performed [PSST 10, 236 (2001)] in Ar and Cl. Arrays consisted of 7 cylindrical Pyrex tubes (o.d. = 5cm) plus antennas, with center-to-center spacing = 2d, mounted in a honeycomb pattern on top of a magnetic bucket. Optimization of individual modules of various aspect ratios and sizes are the focus of the present work. Static Bo is provided by a combination of coils and ring-shaped permanent magnets in close proximity to each module, designed such that they can fit in a usable multi-element source of arbitrarily large area. Measurements of N(R) vs B, at RF powers Prf < 1.6kW and neutral pressures Po = 1-25 mTorr, as well as radial N(R) profiles obtained from Langmuir probes vs axial distance are obtained. Anomalous enhancement of N(R) uniformity is observed when the low-field peak condition is met, with "flat" density profiles extending 5 tube radii, at axial distances < 2 tube diameters below the mouth. The implications for large area plasma processing applications are discussed.