Calibration and validation of projection lithography focusing by fluorescence detection of latent photoacid images in chemically amplified resist

Abstract

Articles you may be interested inResolution blur of latent acid image and acid generation efficiency of chemically amplified resists for electron beam lithography J. Appl. Phys. 99, 054509 (2006); 10.1063/1.2173689On-wafer spectrofluorometric evaluation of the response of photoacid generator compounds in chemically amplified photoresistsWe dope the commercial resist UVIII with the pH sensitive dye coumarin 6 ͑C6͒ to demonstrate a fluorescence microscopy technique for detecting latent photoacid images in exposed chemically amplified resist films. The spectroscopic properties of C6 in the resist matrix are investigated in order to select spectroscopic filters which optimize the fluorescence image contrast of exposed patterns. We apply this technique to focus calibration of a projection lithography system and show a significant correlation of the results to scanning electron microscope analysis of developed features. Hence, we demonstrate the utility of this technique as a fabrication line diagnostic for focus calibration and validation ͑i.e., proof of focus͒ prior to postexposure processing of the resist film.

Mapping Acid‐Catalyzed Deprotection in Thin Polymer Films: Fluorescence Imaging Using Prefluorescent 7‐Hydroxycoumarin Probes

“…Fluorescence imaging in thin polymer films is of interest both as a tool for the study of processes relevant to lithographic imaging [1][2][3][4][5][6] and for the preparation of potentially functional materials. [7][8][9][10][11][12][13] Formation of an image can be achieved by irradiating through a mask a thin film of polymer containing a photoinitiator and a dye, the fluorescence properties of which are altered by interaction with the initiator.…”

“…[11,12] The most commonly employed strategy for imaging of this type involves the protonation of pH-sensitive dyes by photogenerated acid. [1,2,[4][5][6][10][11][12]14] The pH-sensitive dyes provide a means to generate fluorescent images which are maps of the spatial distribution of acid in a polymer film. This type of information is of value in studies of the lithographic process because it is the acid-catalyzed deprotection of polymers that is responsible for the photoinduced changes in dissolution rates that allow lithographic imaging.…”