The Visible Tunable Filter (VTF) is a diffraction-limited narrowband tunable instrument for imaging spectropolarimetry in the wavelength range between 520 and 860 nm. It is based on large-format Fabry Perot. The instrument will be one of the first-light instruments of the 4m aperture Daniel K. Inoue Solar Telescope (DKIST). To provide a field of view of 1 arcmin and a spectral resolution λ/Δλ of about 100.000, the required free aperture of the Fabry Perot is 250mm. The high reflectivity coatings for the Etalon plates need to meet the specifications for the reflectivity over the entire wavelength range and preserve the plate figure specifications of better λ/300, and a micro roughness of < 0.4 nm rms. Coated surfaces with similar specifications have successfully been made for reflecting mirrors on thick substrates but not for larger format Fabry-Perot systems. Ion Beam Sputtering (IBS) based coatings provide stable, homogeneous, and smooth coatings. But IBS coatings also introduce stresses to the substrate that influence the plate figure in our case at the nm level. In a joint effort with an industry partner and a French CNRS research laboratory, we developed and tested processes on small and full size substrates, to provide coated Etalon plates to the required specifications. Zygo Extreme Precision Optics, Richmond, CA, USA, is polishing and figuring the substrates, doing the metrology and FE analysis. LMA (Laboratoire Matériaux Avancés, Lyon, France) is designing and making the IBS coatings and investigating the detailed behavior of the coatings and related processes. Both partners provide experience from manufacturing coated plane optics for gravitational wave detection experiments and EUV optics. The Kiepenheuer-Institut für Sonnenphysik, Freiburg, Germany is designing and building the VTF instrument and is leading the coating development. We present the characteristics of the coatings and the substrate processing concept, as well as results from tests on sample size and from full size substrate processing. We demonstrate that the tight specifications for a single Etalon can be reached.
The Hubble Space Telescope 1st Servicing Mission carried with it a total of 14 corrective mirrors, four in wide field (WF) 2 and the planetary (PC) 2 (three WF and one PC), two each for the three axial SIs (FOS red and blue), faint object camera (f48 and f/96), and Goddard high resolution spectrograph, which were packaged in a single module, corrective optics space telescope axial replacement (COSTAR). This paper presents the fabrication and validation of these mirrors that were the cornerstone of strategy to recover the telescope performance. The COSTAR optics were particularly challenging and represented one of the earliest examples of anamorphic aspheric mirrors fabricated to <0.005 waves RMS of surface figure residual. Other firsts included one of the earliest applications of phase stepping interferometry, now an industry standard. Insights into the corrective designs, the mirror figure shapes, and the technology used in the validation of the mirrors are presented.
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 .
A hardware demonstration has been performed in which a nominally flat, complex aspheric mirror is used to correct the high-order aberrated wavefront error of an off-axis parabolic mirror to 0.5 nm rms. The purpose of the project is to demonstrate the viability of using a static, aspheric optic to correct a telescope wavefront to the degree needed for detection of extra-solar Jovian planets. The demonstration procedure and test results are presented.
Computer generated holograms (CGHs) are an alternative to refractive or reflective null optics when testing spheric optic components. A key attraction is that the difficulty of designing and fabricating a CGH null is largely independent of the detailed shape of the test asphere. CGH nulls have been used quite successfully in a number of high profile programs, but certification issues have limited their more widespread acceptance as a primary testing means. This is due largely to unfamiliarity with appropriate verification and certification methods. We here discuss specification and tolerancing of CGH nulls and present a comprehensive methodology for verification and certification.