In EIDEC, a micro extreme UV (EUV) exposure tool for next-generation lithography has been developed, referred to as a High NA Small Field Exposure Tool (HSFET), and its basic configuration is as follows: Xe DPP source, critical illumination configuration, a rotationally moving turret with several sigma apertures, a larger than 30 × 200 μm field size, and variable NA mechanics to cover from 0.3 to 0.5 NA and beyond. The PO optical performance is well suited to our required 11 nm half-pitch patterning. The transmitted optical wavefront error (WFE) was measured and confirmed to be 0.29 nm RMS, which is far less than the required value of 0.6 nm RMS, and the tool was successfully installed in August 2015. Here we show the exposure results using a newly designed reticle for HSFET patterning. We report the basic printing performance and consideration for high-NA effects as know n polarization effects.
In support of the Extreme Ultraviolet Lithography (EUV, EUVL) roadmap, a joint program between Zygo Corporation and SEMATECH is under way to develop 13.5 nm, 0.5NA R&D photolithography tools with small fields. Those tools are referenced as micro-field exposure tools, or <i>METs</i>. Previous papers<sup>1,2,3</sup> have focused on the design and theoretical performance and the fabrication and testing of the optical components. <p> </p>In this paper, results from the completed projection optic box (PO, POB) systems are presented. The achieved single pass transmitted wavefront (CA – 30 cycles/aperture) on the first two systems was better than 0.25nm RMS at the center of the field and < 0.48nm RMS over the 30um x 200um field, less than half of the original specification. The flare, as calculated from the component roughness data, is less than the 5% specification. <p> </p>The paper includes a presentation of results from the component mirror metrology, the multilayer coatings, and the system metrology. To support the tight specifications, the component and system metrology tests required test reproducibility on the order of <50pm. To achieve the high quality wavefront, the optic mounts had to produce very small surface deformation. Also, the precision and stability of the alignment had to be controlled to a few tens of nanometer. The mirror motion is controlled by a hexapod system and the processes and mechanics that were used to align the POB will be described. Results of alignment convergence, wavefront error at the center of the field and over the field, as well as reproducibility are presented.
In last year’s report, we discussed the design and requirements of the optical projection module (Projection Optics Box [POB]) for the 0.5-NA Micro-field Exposure Tool (MET5) and the resulting challenges. Over the course of this past year, we have completed and fully qualified the metrology of individual mirrors. All surface figure errors have been measured over seven orders of magnitude with spatial periods ranging from the full clear aperture down to 10 nm. The reproducibility of the full aperture tests measures 16 pm RMS for the M1 test and 17 pm for the M2 test with a target of 30 pm for both tests. Furthermore, we achieved excellent results on scatter and flare: For scatter, both mirrors perform about a factor of two below specification. For flare, the larger M2 mirror performs well within and the smaller M1 mirror about a factor of two below specification. In addition, we have developed processes for correcting surface figure errors for both mirrors and have successfully demonstrated high-reflectivity coatings on pathfinder mirrors. Further, we have achieved significant goals with respect to the design, assembly, metrology and alignment of the projection module. This paper reviews this progress and describes the next step in the ambitious MET5 POB development program.
In support of the Extreme Ultraviolet Lithography (EUVL) roadmap, a SEMATECH/CNSE joint program is underway to produce multiple EUVL (wavelength of 13.5 nm) R&D photolithography tools. The 0.5 NA projection optic magnification (5X), track length and mechanical interfaces match the currently installed 0.3 NA micro-field exposure tools (MET) projection optic   . Therefore, significant changes to the current tool platforms and other adjacent modules are not necessary. However, many of the existing systems do need upgrades to achieve the anticipated smaller exposure feature sizes . To date we have made considerable progress in the production of the first of the two-mirror 0.5 NA projection optics for EUVL . With a measured transmitted wave front error of less than 1 nm root mean square (RMS) over its 30 μm × 200 μm image field, lithography modeling shows that a predicted resolution of ≤12 nm and an ultimate resolution of 8 nm (with extreme dipole illumination) will be possible.<p> </p>
This paper will present an update from the 0.5 NA EUVL program. We will detail the more significant activities that
are being undertaken to upgrade the MET and discuss expected performance.
In support of the Extreme Ultraviolet Lithography (EUVL) roadmap, a SEMATECH/CNSE joint program is under way to develop 13.5 mn R and D photolithography tools with small fields (micro-field exposure tools [METs]) and numerical apertures (NAs) of 0.5. The transmitted wavefront error of the two-mirror optical projection module (projection optics box [FOB]) is specified to less than 1 mn root mean square (RMS) over its 30 μm x 200 μm image field. Not accounting for scatter and flare losses, its Strehl ratio computes to 82%. Previously reported lithography modeling on this system  predicted a resolution of 11 mn with a k-factor of 0.41 and a resolution of 8 mn with extreme dipole illumination. The FOB's magnification (5X), track length, and mechanical interfaces match the currently installed 0.3 NA FOBs   , so that significant changes to the current tool platforms and other adjacent modules will not be necessary. The distance between the reticle stage and the secondary mirror had to be significantly increased to make space available for the upgraded 0.5 NA illumination modules .
We review the present status of liquid mirror telescopes. Interferometric tests of liquid mirrors (the largest one having a diameter of 2.5 meters) show excellent optical qualities. The basic technology is now sufficiently reliable that it can be put to work. Indeed, a handful of liquid mirrors have now been built that are used for scientific work. A 3.7-m diameter LMT is presently being built in the new Laval upgraded testing facilities. Construction of the mirror can be followed on the Web site: http://astrosun.phy.ulaval.ca/lmt/lmt-home.html. Finally we address the issue of the field accessible to LMTs equipped with novel optical correctors. Optical design work, and some exploratory laboratory work, indicate that a single LMT should be able to access, with excellent images, small regions anywhere inside fields as large as 45 degrees.
We review the status of the liquid mirror project. Interferometric tests of a f/1.2 2.5-m diameter liquid mirror carried out with a scatterplate interferometer show Strehl ratios of order 0.6, close to the value of 0.8 usually taken to signify that diffraction limit has been reached. The mirror is certainly better than implied by the data because the interferograms were taken with 1/500 second exposures and the wavefronts therefore include the effects of seeing in the testing tower. Correctable small variations of the rotational velocity account for another substantial fraction of the deviations from a parabola. We have videotaped hours of interferogram and PSF observations that show that those we analyze are representative.
Since liquid mirrors are potentially useful in science (e.g., astronomy, atmospheric sciences, and optical testing), work has been undertaken to determine whether they are technologically feasible. A testing tower has been equipped with a scatterplate interferometer interfaced with a CCD for data acquisition and a microcomputer for data analysis. This equipment was used to test a 1.5-m-diameter f/2 liquid mirror, showing that it is diffraction limited; interferometric measurements give Strehl ratios of order 0.8. A 2.7-m-diameter liquid mirror and astronomical observatory presently under construction is briefly described.