Photoresist Characterization and Wet Strip after Low-k Dry Etch

摘要

In new semiconductor technology generations, with BEOL feature sizes shrinking to 65 nm and below, the amount of damage induced by plasma etch and ash processes to porous low-k materials is becoming an issue [1]. The k-value degradation from densification and chemical modification of the low-k is generally unacceptable, while the removal of the damaged layer may affect critical dimension (CD) control too severely to be taken into account in the design. Consequently, all-wet processes are gaining renewed interest for the removal of post-etch photoresist (PR). However, specifications on material loss and k-value integrity considerably reduce the operating space for a purely wet-chemical clean. The composition of post-etch PR is strongly dependent on integration scheme, etch plasma chemistry and materials used. PR composition in turn determines its cleanability. Hence, the identification of a chemical solution that is capable of removing modified PR layers greatly benefits from a thorough chemical characterization of these layers.