No abstract

In a chemically amplified (CA) resist process, photochemically generated acid can diffuse in the resist matrix, inducing the de-protection reactions. The concentration of acid in resist matrix should be constant during the post-exposure-bake (PEB) treatment.In the practical resist processes, bottom anti-reflective coating (BARC) is essentially important to provide reflectivity control for resist patterning.In some cases, however, the photochemically generated acid in resist layer can diffuse into BARC layer, which causes the footing for resist patterns. In this work, we have studied the diffusion of acid from CA resist layer to Si-hardmask (Si-HM) layer. The Si-HM is essential for the multi-layer patterning process. The acid concentration in the resist layer was estimated based on the de-protection reaction kinetics for the CA resist using rapid scan FT-IR spectroscopy. It was found that the acid in resist layer diffused into the Si-HM layer. The diffusion efficiency of the acid was dependent on the crosslinking density of the Si-HM and the chemical structure of the resist.