Acoustic Characterization of Patterning Degradation during Wet Etching
Résumé
Photoresist degradation can occur during wet etching processes due to chemicals diffusion through the polymer. The adhesion of the resist is not guaranteed anymore and damage on the resist / material interface appears. This phenomenon is usually monitored by optical methods. However, invisible resist degradation cannot be detected and the physical nature of the resist / material modification remains unknown. A high-frequency acoustic echography method has been developed to overcome these problems and has been performed to study the apparition of blisters in a deep UV photoresist exposed to a Standard Clean 1 solution. This technique allows the quantitative detection of resist degradation even if blisters cannot be seen in the resist. It has also been found that gas pockets appear during blisters formation.