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Electrostatic chucking of EUVL masks: Coefficients of friction

: Kalkowski, G.; Semmler, C.; Risse, S.; Peschel, T.; Damm, C.; Müller, S.; Bauer, R.


Fontaine, B.M. la ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Extreme Ultraviolet (EUV) Lithography : 22-25 February 2010, San Jose, California
Bellingham, WA: SPIE, 2010 (Proceedings of SPIE 7636)
ISBN: 978-0-8194-8050-7
Art. 76362J
Conference "Extreme Ultraviolet (EUV) Lithography" <2010, San Jose/Calif.>
Conference Paper
Fraunhofer IOF ()
EUVL mask; electrostatic chuck; coefficient of friction; low thermal expansion material

In extreme ultraviolet lithography (EUVL), the mask hangs on an electrostatic chuck and is moved laterally during exposition. For proper control of the chucked mask under corresponding inertial forces, static friction of the mask on the chuck is critical and an important input parameter for reliable theoretical modelling. To determine static and dynamic friction values, measurements were performed in vacuum on a mask blank with a test chuck, smaller than a real EUVL mask chuck, but otherwise nearly identical in its characteristics. Experimental results were obtained at various voltages for a materials combination of Low Thermal Expansion Glass (LTEM) for the pin chuck surface and a mask blank with a chromium metal backside metallisation, respectively. Dynamic friction was found to be only marginally smaller than static friction and values in the range from 0.27 to 0.33 were determined for the static friction coefficient under vacuum conditions.