A two-dimensional array of planar Langmuir probes built on a 200 mm diam silicon wafer was used to measure the radial and azimuthal variation of ion flux impinging on the wafer surface in Ar/SF6 and Ar/Cl2 discharges maintained in an inductively coupled plasma etching reactor. The spatial variation of ion flux in a pure Ar discharge is approximately radially symmetric and peaks at the center of the wafer for pressures between 10 and 60 mTorr. The spatially averaged ion flux in a pure Ar discharge increases with increasing pressure and the corresponding uniformity degrades with increasing pressure within the pressure range studied. Addition of small amounts of electronegative gases to an Ar discharge flattens the radial and azimuthal ion flux distribution and accentuates azimuthal variations 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.

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