Rapid stripping of thick negative-tone acrylic photoresists for semiconductor BEOL applications

摘要

Many BEOL semiconductor applications require vertical wall patterns to produce thick metallic structures. To achieve these plated or etched topographies, the resist must endure severe chemical and thermal exposures. Negative-tone resists of the acrylic and acrylic-styrene resin varieties are common choices. One spin-on applied product includes Shipley BPR~(TM)100 photoresist, manufactured by Rohm and Haas Electronic Materials, L.L.C. Successful integration requires an aggressive stripper to rapidly dissolve the resin, yet protect the metal. GenSolve~(TM) 475, produced by General Chemical, achieves these goals, cycle after cycle, in a closed-loop spray system that filters and delivers the stripper back onto the wafer. The resist is dissolved in minutes, even at moderate temperatures, as demonstrated in Semitool''s spray solvent platform, Scepter~(TM). Using GenSolve~(TM)475, the Scepter™ dissolves away cured Shipley BPR~(TM)100 resist from >50um in-via or mushroom copper studs, water rinses, and spin-dries wafers in a nitrogen environment. The Semitool platform can process 300mm wafers with a total dry-to-dry process time of <30 min, corresponding to >100 wph throughput in single or >200wph with dual chambers. Metal safety is proven by SEM, profilometry, and ESCA, by observing Cu etch rates of <30 A/min and conversion of surface Cu(Ⅱ) to Cu(Ⅰ).