Absolute intensities of the vacuum ultraviolet spectra in a metal-etch plasma processing discharge

In this article we report absolute intensities of vacuum ultraviolet (VUV) and near ultraviolet emission lines (4.8-18 eV) for discharges used to etch aluminum in a commercial inductively coupled plasma reactor. We report lin e intensities as functions of wafer type, pressure, gas mixture, and radio frequency excitation level. In a standard aluminum etching mixture containi ng Cl-2 and BCl3 almost all the light emitted at energies exceeding 8.8 eV was due to neutral atomic chlorine. Optical trapping of the VUV radiation i n the discharge complicates calculations of VUV fluxes to the wafer. Howeve r, we measured total photon fluxes to the wafer at energies above 8.8 eV on the order of 4 x 10(14) photons/cm(2)s with a nonreactive wafer and 0.7 X 10(14) photons/cm(2)s with a reactive wafer. The majority of the radiation was between 8.9 and 9.3 eV. At these energies, the photons have enough ener gy to create electron-hole pairs in SiO2 and may penetrate up to a micron i nto the SiO2 before being absorbed. Relevance of these measurements to VUV photon-induced damage of SiO2 during etching is discussed. (C) 1999 America n Vacuum Society. [S0734-2101(99)05306-3].