Shapes of agglomerates in plasma etching reactors
Dust particle contamination of wafers in reactive ion etching (RIE) plasma tools is a continuing concern in the microelectronics industry. It is common to find that particles collected on surfaces or downstream of the etch chamber are agglomerates of smaller monodisperse spherical particles. The shapes of the agglomerates vary from compact, high fractal dimension structures to filamentary, low fractal dimension structures. These shapes are important with respect to the transport of particles in RIE tools under the influence electrostatic and ion drag forces, and the possible generation of polarization forces. A molecular dynamics simulation has been developed to investigate the shapes of agglomerates in plasma etching reactors. We find that filamentary, low fractal dimension structures are generally produced by smaller (<100s nm) particles in low powered plasmas where the kinetic energy of primary particles is insufficient to overcome the larger Coulomb repulsion of a compact agglomerate. This is analogou...
A model for transport and agglomeration of particles in reactive ion etching plasma reactors
Dust particle contamination of wafers in reactive ion etching (RIE) plasma tools is a continuing concern in the microelectronics industry. It is common to find that particles collected on surfaces or downstream of the etch chamber are agglomerates of smaller monodisperse spherical particles. These observations, and the fact that the forces which govern the transport and trapping of particles are partly determined by their size, place importance on understanding particle growth and agglomeration mechanisms. Since individual particles in plasma etching tools are negatively charged, their agglomeration is problematic since the particles must obtain sufficient kinetic energy to overcome their mutual electrostatic repulsion. In this article, we discuss results from a model for particle agglomeration in RIE plasma tools with which we address the transport of particles and interparticle collisions resulting in agglomeration. These results indicate that the rate and extent of particle agglomeration depend on the particle density, plasma power deposition, and, to a lesser degree, gas flow. The dependence of agglomeration on rf power results from the fact that the kinetic energy of a dust particle is largely determined by its acceleration by ion drag forces. Significant agglomeration may occur in particle traps where the particle density is large.
Continuous calibration of a vacuum ultraviolet system from 65 to 125 nm by a cascade arc and comparison with the calibrated line radiation of a hollow cathode.
A high-power stationary helium cascade arc has been developed as a standard source for continuum radiation in the VUV spectral range from 65 to 125 nm. The calibration of the VUV system response was based on the calculated and measured continuum radiation of a 2-mmphi pure He arc. Diagnostics of the arc plasma in partial thermal equilibrium yielded the electron density and the temperature that were inserted in the calculations of the continuous radiation. The results were compared with the helium, argon, and krypton radiation lines of a high-current hollow cathode lamp. This lamp was built according to the construction drawings of a hollow cathode, which was calibrated by means of the electron synchrotron radiation at the Physikalisch Technische Bundesanstalt Berlin.