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Proceedings Paper

Characterizing edge profiles of photomask structures with complementary information from SEM and AFM
Author(s): Wolfgang Häßler-Grohne; Dorothee Hüser
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Paper Abstract

The demand for growing precision of shrinking structures on photolithographic masks makes fast, reliable, and robust testing tools necessary. Scanning electron microscopes (SEM) therefore are standard metrology tools for critical dimension (CD) measurements. An algorithm that is independent of `a priory knowledge of material parameters of the nanostructure is employed to determine CD. The analysis procedure is optimized in particular for fast scanning and small current probing beams to measure line structures on photolithographic masks. The edge characterization with SEM has been complemented with AFM measurements. In particular, the width of the edge transition estimated from height and slope of AFM topography information has been compared to that obtained from SEM scans. Height and slope are unidirectional parameters, so their determination does not need tip deconvolution. To characterize corner roundings the convolution process has to be understood. Therefore, simulations of physical processes of atomic force microscopy have been carried out to understand the influence of force gradients on the probing process causing a double convolution of tip and sample geometry, firstly of the geometries directly and secondly because of the changing interaction due to changing geometries. The analysis method to estimate edge parameters from SEM images works stable for line widths down to 50 nm. A long term stability down to ±0.6 nm has been observed.

Paper Details

Date Published: 10 April 2013
PDF: 11 pages
Proc. SPIE 8681, Metrology, Inspection, and Process Control for Microlithography XXVII, 868133 (10 April 2013); doi: 10.1117/12.2014417
Show Author Affiliations
Wolfgang Häßler-Grohne, Physikalisch-Technische Bundesanstalt (Germany)
Dorothee Hüser, Physikalisch-Technische Bundesanstalt (Germany)


Published in SPIE Proceedings Vol. 8681:
Metrology, Inspection, and Process Control for Microlithography XXVII
Alexander Starikov; Jason P. Cain, Editor(s)

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