The lifetime and the efficiency of EUV source collector optics will have direct impact on the cost effectiveness of
the EUV lithography semiconductor production. Therefore the collector optics was identified as a critical issue
in EUVL. To continually improve and optimize the source collector optics precise measurements of the optics
characteristics are required as well as life time studies.
Adequate measuring equipment must be designed to perform these measurements on-site, at-wavelength and
under realistic conditions. Moreover, the measurement accuracy must be sufficient to allow the detection of small
changes in reflectivity and homogeneity of the EUV source collector optics. This makes it possible to predict
the lifetime of an EUV source collector operated with a high power EUV source after a fraction of the specified
pulse number, e.g. after a couple of hours.
A reflectometer for the investigation of full EUV source collectors was developed, designed and set up. As an
EUV source a commercial microfocus EUV tube was used. This source is particularly suitable for application in
metrology, as it is very stable in its output parameters (namely power, spectrum, spot size, spot position), and
it does not emit debris.
The radiation cone emitted by the EUV source is tailored with a Schwarzschild objective to the spectral and
geometrical requirements of the Wolter-shell EUV source collector optics
At the time of this contribution the measurement system presented here is in operation since 18 months,
and a large number of collector measurements was performed. It is used for the quality control of factory-new
EUV source collectors as well as for repeated measurements within the context of lifetime tests. With this
device the efficiency of debris filters, which prevent the EUV source collector optics from contamination, could
be determined and improved.
The concept of the device and the implementation together with measurement results are described.