A Top Surface Imaging Method Using Area Selective ALD on Chemically Amplified Polymer Photoresist Films

Abstract

A method for performing top surface imaging (TSI) on a single polymeric photoresist film using area selective atomic layer deposition (ALD) is presented. In this method, exposure of the polymer thin film creates reactive hydroxyl sites on the film surface in the exposed areas that subsequently act as nucleation and growth sites for deposition of metal oxide features using a chemically selective atomic layer deposition process. Specifically, it is shown that titanium isopropoxide and water can be used as ALD precursors in conjunction with a chemically amplified photoresist film, formulated using a protected polymer [poly(tert-butyl methacrylate)] and a photoacid generator [triphenylsulfonium tris(perfluoromethanesulfonyl)methide], to successfully perform such an area selective ALD TSI process. Using this material set and methodology, micrometer-scale photoresist features are defined, metal oxide patterns are produced, and these patterns have been transferred through the polymer film via plasma etching. One unique feature of this TSI process is that it has been achieved without requiring a descum etch, which is commonly needed with other TSI methods, due to the highly selective nature of the ALD process.