Investigation of “fur-like” residues post dry etching of polyimide using aluminum hard etch mask

The authors found that oxygen plasma etching of polyimide (PI) with aluminum (Al) as a hard-etch mask results in lightly textured arbitrary shaped “fur-like” residues. Upon investigation, the presence of Al was detected in these residues. Ruling out several causes of metal contamination that were already reported in literature, a new theory for the presence of the metal containing residues is described. Furthermore, different methods for the residue free etching of PI using an Al hard-etch by using different metal deposition and patterning methods are explored. A fur-free procedure for the etching of PI using a one step-reactive ion etch of the metal hard-etch mask is presented.