Surface modification of EUVL mask blanks by e-beam

Arun John Kadaksham; Thomas Laursen; Timothy Owen; Jon Underwood; Abbas Rastegar

doi:10.1117/12.879452

20 April 2011 Surface modification of EUVL mask blanks by e-beam

Arun John Kadaksham, Thomas Laursen, Timothy Owen, Jon Underwood, Abbas Rastegar

Proceedings Volume 7971, Metrology, Inspection, and Process Control for Microlithography XXV; 79710X (2011) https://doi.org/10.1117/12.879452
Event: SPIE Advanced Lithography, 2011, San Jose, California, United States

Abstract

Mask inspection review of pattern features and defects is normally carried out using a secondary electron microscopy (SEM) technique. Ideally, such mask inspections reviews should be non-destructive; nonetheless, as reported in this paper, high-dose exposures of EUVL mask surfaces have resulted in significant topographical changes, which were revealed by topographical mapping of reviewed masks using atomic force microscopy (AFM). Exposures with current densities of 1 mA/cm² and higher resulted in the formation of topographical features in and around the scanned region on mask surfaces. On the Ru-capped multilayer blanks, the topographies consisted of small or absent depressions surrounded by ridges, which were attributed to secondary-electron-emission induced hydrocarbon deposition. On the chromium-nitride backsides, the topographies were usually simple depressions - although sometimes ridges were observed. The depressions were attributed to volume compaction in the substrate. The depressions were attributed to volume compaction in the substrate, and were observed for all for mask surfaces studied - substrate compaction took place with both quartz and LTEM substrates. The height range of the topography extended up to 25 nm, whereas the lateral dimensions often exceeded the scanned area by about a micron. While these lateral extensions could not be explained by either beam-induced heating or stress relief, Monte-Carlo simulations showed that it could be explained qualitatively by the size of the region within which the energy deposition had taken place. This interpretation suggests that the current understanding as described by Hau- Riege qualitatively describe our observations related to depression topography.

Citation Download Citation

Arun John Kadaksham, Thomas Laursen, Timothy Owen, Jon Underwood, and Abbas Rastegar "Surface modification of EUVL mask blanks by e-beam", Proc. SPIE 7971, Metrology, Inspection, and Process Control for Microlithography XXV, 79710X (20 April 2011); https://doi.org/10.1117/12.879452

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KEYWORDS

Monte Carlo methods

Quartz

Scanning electron microscopy

Multilayers

Atomic force microscopy

Inspection

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