Magnetized Surface-Wave Discharges for Submicrometer Pattern Transfer

Abstract

Most dry etching techniques used for fabricating integrated structures with controlled profiles utilize the capacitively-coupled discharge, in the so-called reactive ion etching (RIE) configuration. To achieve submicrometer patterning, several requirements must be met which include strict observance of dimensions, perfect anisotropy, high microscopic uniformity (no influence of the size and shape of patterns on the etch rate), low substrate damage, high etching selectivity and an acceptable etch rate. Filling all these requirements at the same time implies a perfect control of plasma parameters, in particular, of ion energy. RIE discharges are routinely used on production lines in microcircuit fabrication, among other reasons because they allow for the simultaneous treatment of several substrates, but they suffer from serious limitations. First, charged particle density is weak (typically 10⁸ to 10¹⁰ ions/cm³), yielding an ionization degree below 0.1% due to a relatively high operating pressure (typically 0.02–0.5 torr). Another important drawback is certainly the high sheath potential (typically 100 V), which reduces the ability to control the ion bombardment energy. In the coming generation of integrated circuits, pattern dimensions will be reduced to typically 0.25 µm, which requires the ion flux towards the surface to be perfectly perpendicular to it. At the same time, these new devices will be less tolerant to substrate surface damaging, which requires lower energy ions impinging on the surface than with RIE systems.