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22 March 2010 Characterization of the clamp pressure of electrostatic chucks
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Abstract
Berliner Glas KGaA is specialized on the manufacturing of high performance wafer and reticle chucks. Electrostatic chucks (ESC) are especially used in vacuum environments e.g. during lithographic processing, coating and etching. The main task of the chuck is to provide a well defined positioning and thermal stabilization of the wafer or reticle. Typical wafer materials are semiconductors like silicon and in some special cases dielectrics like magnesia, alumina or glass. For a functional characterization of the ESC clamps Berliner Glas has developed a measurement method to determine the clamp pressure with a Fizeau interferometer. The setup utilizes the local bending of clamped wafers to determine the effective clamp pressure. The clamp pressure is measured in the range of 20...500 mbar. This new method allows for a lateral resolution of the clamp pressure measurement. It can be calibrated by various methods. Direct computation of the clamp pressure based on the bending height or comparative measurements with vacuum chucking by the same chuck gives evidence for the quantitative results. Transient clamp pressure variation can be measured with a resolution of 2 mbar. The results can be used to qualify and optimize ESC´s and even for a local correction of the clamp force.
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M. Ziemann, S. Voss, O. Baldus, and V. Schmidt "Characterization of the clamp pressure of electrostatic chucks", Proc. SPIE 7636, Extreme Ultraviolet (EUV) Lithography, 76362F (22 March 2010); https://doi.org/10.1117/12.839840
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