Pattern collapse phenomenon was first time observed in BEOL application with the integration of ultra low-k film scheme. With the dimension and pitch shrinkage, the pattern collapse defects are getting worse during wet clean process. In this study, the line collapse defects can be significantly reduced by adding surfactant solution to the rinse liquid. Moreover, higher aspect ratio (>4) will also deteriorate the collapse window. In addition, the kink or bowing trench profile will induce localized stress at the interface. Accordingly, optimization of both wet clean and dry etch process are the successful keys to solve line collapse issue toward future generation and beyond.