AVS 45th International Symposium
    Plasma Science and Technology Division Wednesday Sessions
       Session PS-WeM

Paper PS-WeM10
Spatial Characterization of Plasma VUV Emission in an ECR Etcher

Wednesday, November 4, 1998, 11:20 am, Room 318/319/320

Session: Plasma Damage
Presenter: C. Cismaru, University of Wisconsin, Madison
Authors: C. Cismaru, University of Wisconsin, Madison
J.L. Shohet, University of Wisconsin, Madison
Correspondent: Click to Email
In MOS (Metal-Oxide-Semiconductor) device fabrication, plasma processing plays an important role since it has many advantages in terms of process convenience, directionality and high resolution. However, because of the existence of charged particles, together with x-ray and vacuum ultraviolet emission, plasma processing enhances the possibility of damage of the processed materials. The damage potential of vacuum ultraviolet emission of processing plasmas on MOS devices is investigated. High energy photons, with energies higher than the energy band gap of SiO@sub 2@ (~9 eV) can be generated from recombination and relaxation processes in the plasma. It has been established that electron-hole pairs generated in the oxide by these photons@footnote 1@ will increase the SiO@sub 2@ bulk and Si/SiO@sub 2@ interface trapped-charge density, which will affect the device quality accordingly.@footnote 2@ In this work, emission spectra of various plasmas have been recorded in an ECR (Electron Cyclotron Resonance) etcher, at pressures ranging between 0.5 mTorr and 5 mTorr, and microwave powers between 700 W and 1000 W. The measurements were taken in the range of 20 Å to 3000 Å (600 eV to 4 eV), with a one-meter normal incidence vacuum monochromator, with a resolution of 0.2 Å. By use of a special reflection probe, the spectra were also recorded as a function of position across the wafer stage. The measurements show that most of the VUV emission of processing plasmas ranges above 9 eV, which may result in a potentially damaging effect on MOS devices. Also, a nonuniformity of the VUV photon flux impinging on the wafer surface as a function of position across the wafer has been found. This nonuniformity should be considered as having the potential for another MOS processing damaging factor. This work was supported in part by the National Science Foundation under Grant No. EEC 8721545. @FootnoteText@ @footnote 1@ R. A. Gdula, IEEE Transaction on Electron Devices 26(4), 644 (1979). @footnote 2@ R.J. Powell and G.F. Derbenwick, IEEE Transactions on Nuclear Science 18(6), 99 (1971).