A new compact inductively-coupled plasma (ICP) source will be presented. The source is designed to extract either a monochromatic ion beam or a neutral beam out of the plasma, to achieve highly selective etching of silicon, silicon nitride, or silicon dioxide. Two identical plasma sources were fabricated and installed on a processing chamber, with their axes perpendicular to one another. This setup offers flexibility in bombarding a substrate with neutrals and energetic ions either simultaneously, at a 450 angle of incidence, or sequentially at 900. Ion and neutral beams can be extracted in continuous or pulsed plasma modes. The sources can be characterized with line-of-sight mass spectroscopy, while etched surfaces can be examined by vacuum-transferred x-ray photon spectroscopy (XPS). A Langmuir probe was employed to measure spatially- and temporally- resolved plasma parameters as a function of pressure and power. At the center of the plasma, an electron density of 9.5× 1011 cm-3 was reached for 500 W input power at a pressure of 50 mTorr Ar. A retarding field ion energy analyzer was employed to measure the ion energy distributions (IEDs) on a grounded substrate. In a pulsed mode, when the electron temperature decreased to a low value late in the afterglow, a synchronous pulsed DC bias was applied to a boundary electrode, creating a monoenergetic ion beam at a peak energy that was nearly equal to the bias voltage. The IEDs showed a single peak with or without bias. Initial characterization of the neutral beam composition and etching of silicon will also be presented.

 

*Work supported by Lam Research Corp.