Characterizing edge profiles of photomask structures with complementary information from SEM and AFM

Wolfgang Häßler-Grohne; Dorothee Hüser

doi:10.1117/12.2014417

10 April 2013 Characterizing edge profiles of photomask structures with complementary information from SEM and AFM

Wolfgang Häßler-Grohne, Dorothee Hüser

Proceedings Volume 8681, Metrology, Inspection, and Process Control for Microlithography XXVII; 868133 (2013) https://doi.org/10.1117/12.2014417
Event: SPIE Advanced Lithography, 2013, San Jose, California, United States

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.

Citation Download Citation

Wolfgang Häßler-Grohne and Dorothee Hüser "Characterizing edge profiles of photomask structures with complementary information from SEM and AFM", Proc. SPIE 8681, Metrology, Inspection, and Process Control for Microlithography XXVII, 868133 (10 April 2013); https://doi.org/10.1117/12.2014417

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KEYWORDS

Atomic force microscopy

Scanning electron microscopy

Convolution

Critical dimension metrology

Line width roughness

Photomasks

Metrology

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