Incorporation of Fractal Geometry into Surface Reflection and Sputtering Monte Carlo Codes
D. N. Ruzic,* J. P. Allain
National Science Foundation, DMR-9201689

Sea coasts, clouds, mountains, and the microstructure of surfaces can all be described by fractal geometry-a geometry not limited to integer dimensions. Present surface analysis computer models such as TRIM and the "embedded atom method" treat surfaces as flat. They calculate the reflection coefficient and sputtering coefficients as a function of energy, angle of incidence, and material composition. This study introduces realistic surface roughness and more complete interaction physics into those codes by incorporating the fractal geometry concept.

Ionized Magnetron Sputtering
D. N. Ruzic,* D. Hayden, D. Juliano, M. Allain
Materials Research Corp.

The next generation of microelectronic integrated circuits will have submicron features whose depths are much greater than their width. To fill such features with metal (which creates the "wires" which connect various parts of the microchip), a new technology is needed. Standard magnetron sputtering fails because the top closes over before the trench (or via) is filled. By ionizing the metal atoms before they reach the substrate, the ions can be drawn to the bottom of the trenches filling the features. We are developing and testing novel ionization techniques in a commercial-scale system.

Measurements of Ion-induced Electron Emission, Reflection, and Sputtering
D. N. Ruzic,* J. P. Allain, D. Alman
Tosoh SMD Inc.; National Science Foundation, DMR 9201689

When ions strike materials, electrons may be emitted, the ion reflected or the material removed (sputtered). Magnetron sputtering is used in all microelectronics and the production of video cassette tapes. In a magnetron, plasma ions fall through the plasma sheath and impact the target. The emitted electrons are accelerated away from the target and sustain the plasma discharge, the sputtered material deposits on the microelectronic device being fabricated. To understand this system in detail, the emission coefficients for low-ion energy must be known. These measurements are complicated by the presence of real-life adsorbates and surface defects. Measurements of these phenomena are under way in a UHV ion-surface interaction facility. Modeling efforts are also underway.

Time-varying Electron Energy Distributions in Plasmas
D. N. Ruzic,* D. Juliano
Intel Foundation

Radio frequency power is used to heat and drive many industrial plasma applications. The rf waves interact with the edge plasma of the device and effect the waves' propagation. The details of this physical process are poorly understood. The electron energy distribution has not been measured and modeling of the system cannot be done without knowing it. An experiment to measure this distribution and the time-varying plasma potential using new electric and magnetic probe techniques in an actual industrial application is underway.

Modeling of Atomic Transport in an Ionized Magnetron Reactor
D. N. Ruzic,* D. Juliano, M. Allain
Materials Research Corp.

The wires that connect the tiny transistors together in a computer chip are produced using a magnetron sputtering plasma-processing reactor. As chips have gotten smaller and smaller, the techniques for making these wires have needed improvement and modification. Ionized sputtering is the latest of these and we are producing an accurate model of the metal atoms from their "creations" all the way to their deposition site. This model includes the critical step of turning the atoms into ions en route to the target.