Copper dry etching by sub-atmospheric-pressure pure hydrogen glow plasma

Copper(Cu) dryetching is demonstrated using a narrow-gap hydrogenplasma generated at 13.3  kPa (100 Torr) for applications in theCu wiring technology of integrated circuits. A localized hydrogenplasma is generated around the apex of a fine pipeelectrode. TheCuetching can be observed only when the process gas contains hydrogen, and theetching rates decrease with decreased hydrogen concentration. Theplasma heating effect owing toplasma localization is negligible for theCuetching because noetching occurs in the presence of pure N2plasma whose volume is almost equal to that of the pure H2plasma. Furthermore, the influences of physicalsputtering and vacuum ultraviolet irradiation on theCuetching are confirmed to be insignificant by exposing the samples to rare-gasplasma. The maximumCuetching rate of 500  nm/min can be achieved at a stagetemperature of 0  °C. However, theCuetching rate has no obvious dependence on the stagetemperature in a range from −20 to 330 °C. In contrast, theetching rates for Si and SiO2 at a stagetemperature of 0  °C are 100 μm/min and 50  nm/min, respectively. TheCuetching rate is 10 times higher than that of SiO2, which implies that thisetching technique has potential applications forCu wiring on an SiO2 layer. TheCu surfaceetched by the hydrogenplasma is roughened and exhibits many round pits and bumps, which seems to be owing to excessive incorporation of the diffused hydrogen in theCu bulk.

Source: Applied Physics Letters - November 23, 2016 Category: Physics Authors: Hiromasa Ohmi, Jumpei Sato, Tatsuya Hirano, Yusuke Kubota, Hiroaki Kakiuchi and Kiyoshi Yasutake Source Type: research