Sandra Müller

Electrostatic chucking of EUVL masks: coefficients of friction

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.

DESIS - DLR earth sensing imaging spectrometer for the International Space Station ISS

The DLR Earth Sensing Imaging Spectrometer (DESIS) is a new space-based hyperspectral sensor developed and operated by a collaboration between the German Aerospace Center (DLR) and Teledyne Brown Engineering (TBE). DESIS will provide hyperspectral data in the visible to near-infrared range with high resolution and near-global coverage. TBE provides the platform and infrastructure for the operation on the International Space Station (ISS), DLR has developed the instrument. This paper gives an overview of the design of the DESIS instrument together with results from the optical on-ground calibration. In-flight calibration, stability of dark signal and rolling vs. global shutter analysis will be presented.

Ultra-precise Optical Components with Machinable Silicon Layer

Several micron thick silicon films deposited by magnetron sputtering have a nearly amorphous structure. Optical elements coated with theses films can be machined, polished, and structured in order to achieve ultra-precise optical components.