AVS 46th International Symposium
    Plasma Science and Technology Division Wednesday Sessions
       Session PS+SS-WeA

Paper PS+SS-WeA9
Surface Interactions of Plasma-Generated NH@sub 2@ Radicals

Wednesday, October 27, 1999, 4:40 pm, Room 612

Session: Ion-Surface Interactions II
Presenter: J.R.D. Peers, Colorado State University
Authors: E.R. Fisher, Colorado State University
J.R.D. Peers, Colorado State University
M.L. Steen, Colorado State University
Correspondent: Click to Email
Ammonia plasmas are used in the microelectronics industry to deposit amorphous hydrogenated silicon nitride (a-SiN@sub x@:H) films. Thin films of a-SiN@sub x@:H are used as gate dielectrics and barrier coatings in microelectronic devices, capacitors in dynamic random access memory (DRAM) cells, and microfabrication of sensors and actuators. Using the imaging of radicals interacting with surfaces (IRIS) technique, we have performed a comprehensive study of the interactions of NH@sub 2@ with a variety of surfaces during NH@sub 3@ plasma processing. The substrates examined were Si(100), Pt, polyimide, polyethylene, and Teflon. In most cases, NH@sub 2@ scattering from the surface was greater than unity, indicating a production of NH@sub 2@ through surface reaction. Removal of charged species from the plasma molecular beam results in a decrease in the scattered NH@sub 2@ signal, indicating that the presence of ions in the plasma is responsible in large part for radical production at the surface. We have examined the dependence of the scattering signal intensity on applied rf plasma power and substrate temperature for all species. In addition, velocity distributions for NH@sub 2@ radicals scattering off the surfaces were measured. Using Monte Carlo simulation methods and assuming a Maxwell-Boltzmann distribution, we determine the translational temperatures of the scattered species. Species scattering off 300 K Si and Pt substrates have a translational temperature of 400±30 K, significantly higher than the substrate temperature, while the translational temperature of species scattering off the polymeric substrates tends to be closer to the substrate temperature. This suggests that the NH@sub 2@ radicals are coming to equilibrium with the polymeric substrates and not with Si or Pt. The temperature of the radicals in the plasma molecular beam itself is 512±8 K at 25 W applied plasma power, indicating that the radicals are cooling by collisions with the substrate surface.