High temperature platinum etching using Ti mask layer

Platinum is a strong candidate for an electrode material of the high dielectric capacitors in highly integrated dynamic random access memory devices. However, it is extremely difficult to etch the fine patterns of Pt due to an inherently low etch slope. This characteristic comes from the physical sputtering nature of the Pt etching process. This article reveals that the Pt etching profile depends on the change of the Ti mask layer caused by the increase of wafer temperature during etching. The Pt etching slope of 80° in 0.40 μm pitch was attained by heating the wafer substrate up to 220° with plasma-on. From the transmission electron microscopy analysis the Ti mask is considered to be deformed to TiOx layer in oxygen plasma at high wafer temperature, elevated either by high electrode temperature or plasma irradiation.