Wet cleaning remains the most applied process step in semiconductor device manufacturing to achieve acceptable yield during continuous downscaling. Traditionally, cleaning process challenges are focused on the removal of particulate, metallic and organic contamination and the removal or growth of thin passivating films. These processes are typically based on the know-how of classical silicon processes, from which a large portion was transferred over the last years from batch to single wafer process tools. This transfer was also driven by the transition to larger wafer sizes, demanding additional efforts regarding uniform wafer processing and effective substrate wetting and drying. Furthermore, the downscaling introduces new device geometries and materials different from silicon.
This introduction requires the development of new critical and selective cleans tackling galvanic corrosion, pattern collapse both in FEOL and BEOL process steps. An additional challenge is that the reduction in device size and an increase in device topography makes the removal of small particles even more challenging.