AVS 52nd International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS-MoP

Paper PS-MoP4
The Effect of Oxide Thickness on Photoemission and Photoconduction Currents during VUV Irradiation

Monday, October 31, 2005, 5:00 pm, Room Exhibit Hall C&D

Session: Plasma Science and Technology Poster Session
Presenter: J.L. Lauer, University of Wisconsin-Madison
Authors: J.L. Lauer, University of Wisconsin-Madison
J.L. Shohet, University of Wisconsin-Madison
G.S. Upadhyaya, University of Wisconsin-Madison
Correspondent: Click to Email
Vacuum ultraviolet (VUV) radiation with photons in the energy range of 5 to 20 eV produced by high-density plasmas in plasma-processing systems can cause degradation to devices by changing the optical, mechanical, chemical and electrical properties of dielectrics. This is particularly important for thin films used in intermetal dielectric layers, because VUV is absorbed by the dielectric layer. Radiation charging of Si wafers coated with SiO@sub 2@ of different thicknesses in the range of 3000Å to 200Å was made by exposing them to synchrotron VUV radiation with photon fluxes in the range of 10@super 10@ -10@super 11@ photons/sec cm@super -2@ and photon energies of 7, 10, and 13 eV. The photoemission current and the current drawn by the substrate were monitored during each exposure. The tunneling and/or photoconduction current drawn through the oxide layer can be found by subtracting the photoemission current from the current drawn by the substrate. The total charge induced on the dielectric during VUV exposure consists of charge due to photoemission and electron-hole-pair creation, the net amount of which can be measured with a Kelvin Probe. The tunneling current (electrons injected from the silicon substrate into the oxide layer) causes a decrease in the charge produced by photoemission and electron-hole-pair creation. For most dielectrics, the threshold photon energy for photoemission is higher than that for electron-hole-pair production. The photoemission current can be minimized while the tunneling/photoconduction current increases, if the photon energies are below the threshold energy for photoemission but larger then the bandgap energy. VUV-exposed SiO@sub 2@ of various thicknesses shows the photon penetration depth as a function of energy and allows a quantitative description of the mechanisms that are involved in the photoconduction/tunneling processes taking place. @FootnoteText@ Work supported by NSF under Grants DMR-0306582.and DMR-0084402. .