Mechanism and Principles of Post Etch Al Cleaning With Inorganic Acids

摘要

In the metallurgical industry, Al cleaning has been carried out traditionally with inorganic acids, such as sulfuric acid and phosphoric acid, quite often with an oxidizer added such as sodium or potassium dichromate [1], e.g. before bonding aluminum surfaces. In the semiconductor industry, the use of inorganic acids for cleaning aluminum with mixtures such as phosphoric/chromic and fuming nitric acid was used since the early 1980's. However, it was rather the use of hydroxylamine (NH_2OH) for cleaning aluminum that found widespread use, since it could be used for both post-aluminum etch and post via-etch cleaning processes. In 1998, David Rath and Ravikumar Ramachandran patented a formulation using the traditional sulfuric acid and an oxidizer for aluminum cleaning as a basis, but they added a very small amount of HF (0-100ppm) [2]. This together with other work reinvigorated the interest in using inorganic chemicals for aluminum cleaning.