REACTIVE ION ETCHING OF MULTI-LAYER RESIST.

Multi-layer resist has been utilized commonly in optical and E-beam lithography for its ability to resolve submicron features over topography. In addition, the use of a low-Z (atomic number) material as the intermediate layer reduces the proximity effect. This paper describes the development of etching process used to pattern a tri-level resist based on polyimide, an inorganic intermediate layer, and positive resist as top image layer. A high-aspect-ratio image can be anisotropically transferred from the inorganic intermediate layer into the polyimide planarizing layer by oxygen RIE. Directionality, profile control, and backsputtering residue are the primary considerations during the pattern transfer etching.