AVS 59th Annual International Symposium and Exhibition
    Plasma Science and Technology Tuesday Sessions
       Session PS1-TuM

Paper PS1-TuM11
Single and Multi-Point Ion Energy Distributions in a VHF+RF Commercial Reactor Measured by Novel In-Wafer Ion Energy Analyzer

Tuesday, October 30, 2012, 11:20 am, Room 24

Session: Plasma Diagnostics, Sensors and Control 1
Presenter: B.G. Lane, Tokyo Electron America
Authors: B.G. Lane, Tokyo Electron America
M. Funk, Tokyo Electron America
L. Chen, Tokyo Electron America
R. Sundararajan, Tokyo Electron America
J. Zhao, Tokyo Electron America
Correspondent: Click to Email
The energy distribution of the ions impacting the wafer is a key determinant of process results. A novel, all silicon, minimally perturbing, non-contaminating, in-wafer, 2 and 3 layer ion energy analyzer described elsewhere in this conference is used to measure ion energy distributions for a variety of realistic processing conditions in a commercial VHF + 13.56 MHZ RF reactor with no modifications to its basic geometry or RF delivery system. Spectra with energies as high 1 keV are measured with resolution on the order of 1%. Total ion transmitted flux as well as the floating potential of the plasma exposed 1st grid relative to ground are measured in addition allowing estimates of the plasma potential at the sheath edge. Measured energy spectra are compared to particle simulations aiding in the interpretation of the spectral features. We show data and discuss the splitting of the high energy peaks due to finite ion sheath crossing time effects and how this splitting scales with frequency, power and pressure. We discuss how such splitting can be used to estimate the ion density at the sheath edge. We discuss the origin and scaling of charge exchange peaks. We use the identification of atomic and molecular oxygen ion peaks to estimate the resolution of the diagnostic . The use of VHF to obtain narrow ion energy distributions at moderate ion energies will be highlighted. Spectra using a multi-point, 2 layer variant of the ion energy analyzer design were obtained at 4 radial locations for a variety of conditions in argon and oxygen plasmas. These spectra quantify center to edge variations and reveal unique spectral features due to pre-existing modifications to the test reactor's upper counter electrode surface. We believe that these may be the first reported measurements of ion energy distribution functions for some of the more extreme conditions investigated and some of the first reported multi-point ion energy spectra for a commercial plasma reactor.