Michael Hopkins

Ion Energy Distribution Skew Control Using Phase-Locked Harmonic RF Bias Drive

The energy distribution of ions accelerated through a radio frequency sheath and incident on a plasma-facing material significantly influences material interaction with the plasma and can impact manufacturing at the nanoscale. Ion energy distributions are controlled through appropriate mixing of drive frequencies, which has been shown to control distribution width. This paper presents a modification to multifrequency drive for ion energy control by exploiting a digital frequency and phase controller that enables modification of the higher order moments of the distribution, specifically, controlling the skew of the distribution. By modulating the sheath with two frequencies where one frequency is the harmonic of the other and controlling the relative phase of these two waveforms incident on the plasma-facing surface, skew control is achieved. A simple empirical model is presented to describe this method, as well as experimental validation of the model and demonstration of skew control in a parallel plate capacitively coupled reactor.

Formation of a Double Layer in Electronegative

A double layer (DL) was observed at the boundary between the source region and expansion region of an inductively coupled, radio frequency, plasma reactor when an oxygen discharge was ignited at low pressure. A DL is a narrow localized region with relatively large potential difference and electric field, which can be formed in electropositive as well as electronegative plasmas. In an inductively coupled plasma reactor of this type, it seems to be formed at the interface between the smaller source region and the larger expansion chamber and acts as an internal boundary separating two plasma regions of significantly different compositions, density, and plasma potentials.

{\rm O}_{2}

We propose to use infrared light coupled with a near field scanning optical microscope (NSOM) to probe organic materials. The initial emphasis will be on the 2.8 – 3.25 µm range, which contains bands from both C - H and O - H stretching vibrations. This provides great sensitivity to specific chemical alterations as induced, e.g., in a photoresist by exposure and/or development. We have attempted to make IR NSOM probes by the fabrication of versatile coaxial nanostructures for their distinct use as waveguides supporting TEM modes free of frequency cut-off. We have modeled a conical coaxial structure for its losses at target areas with 2.8µm wavelength. Preliminary results indicate their potential as efficient and reproducible probes.