a new remover chemistry based on a choline compound , such as choline hydroxide , is provided in order to address problems related to removal of residues , modified photoresists , photoresists , and polymers such as organic anti - reflective coatings and gap - fill and sacrificial polymers from surfaces involved in dual damascene structures without damaging the dielectrics and substrates involved therein . an etch stop inorganic layer at the bottom of a dual damascene structure may or may not be used to cover the underlying interconnect of copper . if not used , a process step of removing that protective layer can be avoided through a timed etch of the via in trench - first dual damascene processes .