Single Wafer Tool Cleaning for Bi-layer Photoresist Rework - Stripper Development and Evaluation

A wet-cleaning solution for bi-layer photoresist rework using single-wafer tool process has been developed and proved to be successful. The chemical design of stripper related to cleaning mechanism was investigated. The cleaning performance of two types of strippers were evaluated and compared between beaker and single-wafer tool process. The results indicated that chemical design of stripper is the key to determine cleaning mechanism for bi-layer photoresist. It is demonstrated that removal of bi-layer photoresist through lift-off is not acceptable in single-wafer tool process; dissolution proved to be the key mechanism for successful removal of bi-layer photoresist in a single wafer tool. For single-wafer tool evaluation, the influence of process parameters such as wafer spin speed, process time, medium temperature and chemical dispense characteristics were evaluated and are discussed.