AVS 49th International Symposium
    Plasma Science Tuesday Sessions
       Session PS+MS-TuM

Paper PS+MS-TuM4
Two-Dimensional Ion Flux Distributions on the Wafer Surface in Inductively Coupled Plasma Reactors

Tuesday, November 5, 2002, 9:20 am, Room C-105

Session: Plasma Diagnostics and Sensors
Presenter: E.S. Aydil, University of California, Santa Barbara
Authors: E.S. Aydil, University of California, Santa Barbara
T.W. Kim, University of California, Santa Barbara
Correspondent: Click to Email
A two-dimensional array of planar Langmuir probes manufactured on a 200 mm diameter silicon wafer was used to measure the radial and azimuthal variation of ion flux impinging on the wafer surface in various mixtures of electropositive and electronegative gases maintained in an inductively coupled plasma etching reactor. The spatial variation of ion flux in a pure Ar discharge is radially symmetric and peaks at the center of the wafer for pressures between 10 and 60 mTorr. Addition of small amounts of electronegative gases to an Ar discharge flattens the radial and azimuthal ion flux distribution and accentuates azimuthal variation due to subtle asymmetries in the reactor geometry such as pumping ports. At fixed power, pressure, and flow rate, the spatially averaged ion current density decreases with increasing mole fraction of the electronegative gases in the feed gas. In conjunction with experimental data, we developed a simple theoretical framework within which the spatial variation of ion flux in gas mixtures can be understood. Ion Flux uniformity in various binary mixtures of Cl2, He, Ar, HBr, O2, and SF6 will be discussed. Spatiotemporal variation of ion flux in presence of instabilities in SF6 discharges will be presented.