Non-Aqueous/Dry Cleaning Technology without Causing Damage to Fragile Nano-Structures

With semiconductor-device geometry shrinking and becoming more complex, conventional aqueous cleaning/drying tends to collapse free-standing MEMS and high-aspect-ratio fragile LSI structures due to the high surface tension of aqueous chemicals and water. The use of physical cleaning aids such as megasonics with dilute chemistry or high-pressure atomizing jet sprays can also cause damage to nano-structures. The process window for damage-free cleaning is also becoming narrower as device geometry shrinks. This makes the development of new damage-free cleaning methods a high priority. In this paper, various alternative damage-free non-aqueous/dry cleaning techniques are described and discussed including low pressure, elevated temperature HF vapor cleaning, cryogenic aerosol cleaning, supercritical CO2 cleaning, and pinpoint dry cleaning that employs lasers, nano-probes, or nano-tweezers. There will be more research challenges and opportunities in these environmentally-benign damage-free cleaning technologies in the future.