Ion Velocity Distributions Functions in an Inductively Coupled Plasma's Meniscus

By increasing aspect ratios and fitting more features onto chips, semiconductors have continued to increase the processing power of modern electronics. This requires a great amount of precision in the processing techniques as the features are only a few dozen silicon atoms in size and are more prone to defects. To better understand the ion dynamics for etching and doping, we used laser induced fluorescence (LIF) to obtain ion velocity distribution functions inside an inductively coupled plasma (ICP) source. The ICP was fitted with graphite extraction optics that allowed for beam formation through a 5 mm aperture. A wafer was placed 12 mm away and biased so that a plasma meniscus was formed on the inside of the extraction optics. This meniscus boundary acts as an electrostatic lens and affects ion trajectories. Therefore, the focal spot of the beam is dependent on the meniscus’s spatial structure. This boundary can be affected by changing source parameters such as applied extraction bias and rf antenna power. A confocal LIF system was used to investigate this boundary and the background plasma. We report non-perturbative, localized measurements up to 25 mm into an ICP for ion velocity and temperature. We also measured the meniscus extraction region in order to characterize the extracted ion properties’ relation to controllable source parameters.