Edward P. Hammond

Measured radial dependence of the peak sheath voltages present in very high frequency capacitive discharges

The radial distribution of the measured voltage drop across a sheath formed between a 300mm electrode and an argon plasma discharge is shown to depend on the excitation radio frequency, under constant power and pressure conditions. At a lower frequency of 13.56MHz, the voltage drop across the sheath is uniform across the 300mm electrode, while at higher frequencies of 60 and 162MHz the voltage drop becomes radially nonuniform. The magnitude and spatial extent of the nonuniformity become greater with increasing frequency.

Electric fields in the sheath formed in a 300 mm, dual frequency capacitive argon discharge

The spatial structure and temporal evolution of the electric fields in a sheath formed in a dual frequency, 300 mm capacitive argon discharge are measured as functions of relative mixing between a low frequency current and a high frequency current. It is found that the overall structure of the sheath (potential across the sheath and the thickness of the sheath) are dominated by the lower frequency component while (smaller) oscillations in these quantities are dictated by the higher frequency component. Comparisons of the measured spatial and temporal profiles are made for Liebermans and Robiche et al sheath model and with a particle in a cell calculation.

Plasma and flow modeling of photomask etch chambers

The uniformity of critical dimensions is an important aspect of photomask fabrication, and the etch process can be improved by optimizing the geometry of the focus ring that surrounds the mask. Previous experimental results have shown that the focus ring can have a dramatic impact on the variability of critical dimensions on the photomask. Simulations were performed with the Hybrid Plasma Equipment Model (HPEM) software to examine the impact of different focus ring geometries on the plasma characteristics and improve the understanding of the experimental data.