Modification of Photoresist by UV for Post-Etch Wet Strip Applications

In Back-End-of-Line processing, the remaining photoresist layer after plasma etch is traditionally removed using a plasma process. Plasma process was reported to induce damage to porous dielectric [1-3]. To minimize damage to low-k material, wet alternative methods of removal of photoresist layer on porous low-k dielectrics are gaining a renewed interest [4]. However, the presence of a “crust” generated by etch plasma at the photoresist surface makes it impossible to completely remove by a pure organic solvent. Indeed, the crust, most likely composed of crosslinked polymer, is not soluble in organic solvents [5]. For this reason, a UV pre-treatment is investigated to break cross-links in the crust or to modify the crust to enhance removal efficiency with solvent stripping in more advanced generations.