A novel top surface imaging approach utilizing direct-area selective atomic layer deposition of hardmasks

Abstract

A novel 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 ALD process. It is demonstrated 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-tertbutylmethacrylate (PtBMA)) and a photoacid generator (triphenylsulfonium tris(perfluoromethanesulfonyl) methide), to successfully perform such an area selective ALD TSI process. Using this material set and methodology, micron scale photoresist features are defined, metal oxide patterns are produced, and these patterns have been transferred through the polymer film via plasma etching. A comparison is also made between the silylation chemical contrast obtained from earlier TSI methods and the metal oxide deposition contrast obtained using the ALD TSI method. It is shown that the ALD TSI chemical contrast for metal oxide deposition can be much higher than the corresponding silylation-based silicon incorporation contrast This result translates into a unique feature of the ALD TSI process which is it can be achieved without requiring the descum etch that is commonly needed with other TSI methods based on silylation.