For EUV-lithography, reliable measurements of the radiant power throughout the optical chain are an essential requirement for the optimization of the lithographic production process as well as for the development of new applications like EUV-based metrology tools. From dose control to aerial imaging, specialized detectors are required - ranging from simple diodes to sophisticated imaging detectors like CCD or CMOS systems. For all these applications, sensitivity, homogeneity and lifetime are crucial parameters. While extended lifetime and sub percent homogeneity requirements are common among all detector uses, sensitivity targets range from single photon sensitivity for spectroscopy detectors to deliberately reduced sensitivity for dose control at high-power sources. Photon detector calibration in the EUV spectral range is therefore a prerequisite for new detector developments and a basis for the introduction of EUV-lithography into volume manufacturing. PTB employs two dedicated and complimentary EUV beamlines for radiometric characterizations of photon detectors. The wavelength range covered reaches from below 1 nm to 45 nm for the two EUV beamlines. Longer wavelengths coverage in the VUV range (out-of-band) is provided at PTB’s VUV radiometry beamline. The standard spot size is 1 mm by 1 mm with an option to go as low as 0.1 mm by 0.1 mm. For lifetime testing, a dedicated exposure setup with power densities of up to 20 W/cm2 is operated. It enables exposures in the range of 100 kJ/cm2 within a reasonably short time. Lower fluence levels are available by attenuation or exposure farther out of focus. We will explain calibration basics, describe PTB's calibration capabilities in the EUV spectral range and show exemplary data for the respective detector types.
The introduction of EUV lithography into high volume manufacturing poses new challenges to any optical component in the lithography machines. Particularly the homogeneity of the optical properties is of importance. The present measurement capabilities of PTB using synchrotron radiation are based on a monochromatized, focused beam with a typical footprint on the sample in the order of 1 mm2. This, however, is not sufficient to detect small defects of optical coatings, local effects of irradiation and lifetime experiments or the like. We present our new set-ups for the spatially resolved measurement of reflectance and transmittance of optical elements. For the transmittance measurement we prepare a homogeneous almost parallel beam and place a CCD detector close behind the sample. For a sufficiently parallel beam and short enough distance, the resulting resolution is defined by the CCD pixel size, 13.5 μm square. For the spatial resolved reflectance measurement, the illuminated spot on the mirror under investigation is imaged with 10x magnification using a Wolter-type optic onto a CCD. The grazing incidence Wolter optic provides a broad-band transmittance for the optics starting from about 6 nm to longer wavelengths and thus allows measuring spectrally resolved the full reflectance curve of Mo/Si mirrors.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.