Chemical mapping of patterned polymer photoresists by near-field infrared microscopy

Latent images obtained by deep-ultraviolet (DUV) patterning and post-exposu re bake in the polymer system poly(t-butylmethacrylate) (PTBMA) resist/trip henyl sulfonium photoacid generator are characterized by infrared near-fiel d microscopy (IR-NSOM). Chemical sub-group specificity is achieved in the i nfrared near-field images by using wavelengths tuned on the OH absorption b and of the poly(methacrylate acid) (PMAA) resulting from the photoacid-cata lyzed decomposition of t-butoxycarbonyl groups. The experimental images of the patterned thin polymer film are compared with predictions based on scal ar diffraction theory calculations for the initial light illumination step through the mask. Partial disagreement between the theory and the experimen t is observed, but only for certain line/space dimensions of the pattern. T he results suggest a structure-dependent chemistry during the latent image development. (C) 2001 Elsevier Science B.V. All rights reserved.