Novel Non-Oxidative Aqueous Cleaning Solutions for Tungsten Layers

Abstract

As memory devices shrink, the introductions of new processes and materials have been prerequisite for high speed and reliability of semiconductors. Particularly, enlargement of processes using metal layers in fabricating devices led to many cleaning problems like metal corrosion, particle adsorption, and polymer remnants after stripping process. On account of the absence of an effective cleaning solution for metal layers, major semiconductor manufacturing companies have been experienced yield drops and endurance fails. In this study, we will report the development of novel cleaning solution for tungsten layers and its application of mass production line. New cleaning chemical is composed of tetramethylammonium hydroxide (TMAH), hydrofluoric acid (HF), and two additives. It could remove polymers formed by RIE (reactive ion etching) without corrosion of metal layers and prevent the adsorption of particles and metal ions accumulated from consecutive cleaning processes. Compared with APM (ammonia peroxide mixture) used as the standard cleaning, this cleaning solution showed the same particle removal efficiency but didn't absorb metal ions on the silicon wafer surface. Furthermore, sidewall and bottoms polymers could be removed effectively in cleaning process of tungsten bit line and various contact holes. In addition, we could obtain the lower resistance of line and contact patterns, and enhancement of yield in memory production line, applying this novel solution to the corresponding cleaning processes instead of amine-based organic stripper.