The interaction of extreme ultraviolet (EUV) light with matter is a critical step in EUV lithographic processes, and optimization of the optical material properties of all elements in the lithographic chain (from optical coatings and pellicles to photoresists) is crucial to harnessing the full power of EUV lithography. To optimize these materials, accurate measurements of EUV absorption and reflection are needed to extract the corresponding actinic optical properties and structural parameters. Here, we report on actinic EUV metrology-based absorption and reflection measurements enabled by coherent table-top EUV sources based on high-harmonic generation. We demonstrate the capabilities and flexibility of our setup with measurements on crystalline films, photoresist systems, and carbon nanotube membranes and provide extracted optical parameters, absorption kinetics, and 2D transmission maps, respectively. These results showcase the power of lab-based actinic inspection methods based on compact, coherent EUV sources for providing crucial data for material optimization and lithographic simulation.
The interaction of EUV light with matter is a critical step in EUV lithographic processes and optimization of the optical material parameters of photoresists and reflector/absorber stacks is crucial to harness the full power of EUV lithography. To optimize these materials, accurate measurements of EUV absorption and reflection are needed to extract the corresponding actinic optical properties and structural parameters. Here, we report on two endstations within imec’s AttoLab that enable actinic EUV absorption and reflection measurements. We commission these tools with measurements on model thin film and photoresist systems and provide extracted optical parameters as well as absorption kinetics, respectively. These results showcase the power of these tools for providing crucial data for material optimization and lithographic simulation.
Imec’s AttoLab is the first industrial laboratory capable of watching the ultrafast dynamics of photoresists following 13.5 nm, EUV exposure, and for emulating high-numerical-aperture (high-NA) exposure on 300-mm wafers using two-beam EUV interference. The two respective beamlines are powered by a laser-based high-harmonic generation EUV source. Its capabilities have recently been proven by imaging 20 nm pitch lines and spaces using Lloyd’s Mirror interference lithography. In parallel, time-averaged and time-resolved techniques for studying the ultrafast dynamics of photoresists after EUV exposure, coherent diffractive imaging to study resist interfaces, and more sophisticated interference lithography techniques for printing sub-22 nm pitches on full 300-mm wafers are being developed. Taking advantage of the bright and short EUV pulses now available at imec, we will be able to contribute to a smooth transition towards next generation high-NA lithography.
Recently, imec has installed and commissioned an industrial, ultrafast EUV materials characterization and lithography lab, imec’s AttoLab, with a primary aim to explore limits of photoresist performance and their associated ultrafast chemistries. Here, we demonstrate, for the first time, the use of a table-top, high-harmonic EUV system (KM Labs, XUUS4) to perform interference lithography of sub-22-nm pitch patterns in an Inpria MOx resist via a Lloyd’s mirror interference lithography (IL) tool. Analysis of SEM images enables us to identify potential sources of image blur, which we attribute to out-of-sync vibrations, flare, spectral purity, and laser stability. Nevertheless, these results confirm the ability of table-top, high-harmonic EUV sources to print lithographic patterns below a 22-nm pitch. In future work, we plan to investigate sub-20-nm patterning in different resist formulations, as well as expand the lithographic capabilities in AttoLab to perform IL on full 300-mm wafers.
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