Proceedings Article | 16 October 2019
KEYWORDS: Extreme ultraviolet, Extreme ultraviolet lithography, Metrology, Control systems, Pellicles, Optical components, Reflectivity, Defect inspection, Semiconductors, Photomasks
With EUV lithography inserted into the semiconductor production the characterization and control of critical components like blanks, masks, pellicles, optical elements, thin film windows and photoresist is required. Needed for the supply and process chains are on one hand “traditional”, e.g. mechanical, thermal or chemical tests with extended capabilities as well as “actinic” ones, which are directly linked to the interaction of EUV radiation with the sample. Actinic tests are needed to
• measure optical properties in the spectral range which is relevant when the components are used, like reflectance, transmission, scatter
• determine or apply modifications of material when irradiated with EUV, e. g. resist exposures, degradation tests for components
• find or inspect defects and structures on optical components used in EUVL
• Mimic processes in the EUV scanner for off-line optimization.
For such actinic qualification in the individual industrial or research lab with 13.5 nm radiation only few metrology tools are readily available off-the-shelf. The industrial infrastructure for EUVL lab tools suffer from the fact that most of such tools are such specialized that only – at best – few of a kind are needed in the world, which does not deserve a classical product development.
This analysis has driven our strategy for supporting our customers mainly with tailored “one of a kind” solutions, while still reaching product like reliability by frequent reusing of already existing building blocks, tested subunits and components and general approaches and architectures.
The basis of this approach is on one hand our experience to serve our customers from “big science” worldwide with RI-engineered research installations since more than 30 year. On the other hand our EUV application experience is based on a broad source portfolio with stand-alone DPP and LPP sources for XUV together with an established supply chain in advanced EUV optics, detectors and spectral filtering.
This allows us to use long experience in design, machining and assembly of ultra-clean components in ultra-high vacuum and cleanroom applications, including ultra-clean sample handling, loading and manipulation. Our stand-alone tools offer fully automated, fail safe electronic control including custom tailored data evaluation and reporting solutions. With the special demand from each new project, we are consolidating and expanding the knowledge base.
Examples of such actinic tools for the EUVL infrastructure will be presented, as e.g. spectral reflectometers, full area inband EUV property mapping, EUV pellicle transmission and reflectance tools, microscope, defect inspection, nano-printing tools and sensitivity calibrated stand-alone resist exposers.
