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Proceedings Paper

Calibration and validation of projection lithography in chemically amplified resist systems using fluorescence imaging
Author(s): Michael D. Mason; Krishanu Ray; Gilbert D. Feke; Robert D. Grober; Gerd Pohlers; James F. Cameron
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Paper Abstract

Coumarin 6 (C6), a pH sensitive fluorescent molecule were doped into commercial resist systems to demonstrate a cost-effective fluorescence microscopy technique for detecting latent photoacid images in exposed chemically amplified resist films. The fluorescenec image contrast is optimized by carefully selecting optical filters to match the spectroscopic properties of C6 in the resist matrices. We demonstrate the potential of this technique for two sepcific non-invasive applications. First, a fast, conventient, fluorescence technique is demonstrated for determination of quantum yeidsl of photo-acid generation. Since the Ka of C6 in the 193nm resist system lies wihtin the range of acid concentrations that can be photogenerated, we have used this technique to evaluate the acid generation efficiency of various photo-acid generators (PAGs). The technique is based on doping the resist formulations containing the candidate PAGs with C6, coating one wafer per PAG, patterning the wafer with a dose ramp and spectroscopically imaging the wafers. The fluorescence of each pattern in the dose ramp is measured as a single image and analyzed with the optical titration model. Second, a nondestructive in-line diagnostic technique is developed for the focus calibration and validation of a projection lithography system. Our experimental results show excellent correlation between the fluorescence images and scanning electron microscope analysis of developed features. This technique has successfully been applied in both deep UV resists e.g., Shipley UVIIHS resist and 193 nm resists e.g., Shipley Vema-type resist. This method of focus calibration has also been extended to samples with feature sizes below the diffraction limit where the pitch between adjacent features is on the order of 300 nm. Image capture, data analysis, and focus latitude verification are all computer controlled from a single hardware/software platform. Typical focus calibration curves can be obtained within several minutes.

Paper Details

Date Published: 2 June 2003
PDF: 10 pages
Proc. SPIE 5038, Metrology, Inspection, and Process Control for Microlithography XVII, (2 June 2003);
Show Author Affiliations
Michael D. Mason, Yale Univ. (United States)
Krishanu Ray, Yale Univ. (United States)
Gilbert D. Feke, Yale Univ. (United States)
Robert D. Grober, Yale Univ. (United States)
Gerd Pohlers, Shipley Co. LLC (United States)
James F. Cameron, Shipley Co. LLC (United States)

Published in SPIE Proceedings Vol. 5038:
Metrology, Inspection, and Process Control for Microlithography XVII
Daniel J. Herr, Editor(s)

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