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.
During 2009, Tinsley finished most of the Configuration 1 pre-cryo test Computer Controlled Optical Surfacing (CCOS)
operations on the James Webb Space Telescope primary mirror segments and in mid-2009 we began the Configuration 2
post-cryo test CCOS operations. After completing the grinding and polishing operations, including final figuring to a
cryo-null target, we delivered the finished Engineering Development Unit (EDU) to Ball Aerospace Technology
Corporation on 4 December 2009. Achieving fabrication and metrology conditions to meet the specifications for this off-axis
~1.5 m hexagonal point-to-point segmented mirror required special methods. Achieving repeatable and accurate
interferometric alignment of the off-axis aspherical mirror surface and stable thermal gradient control of the beryllium
substructure during tests required rigorous component and system-level validation. Final optical wavefront
measurements over the various spatial frequency ranges have demonstrated that all of the requirements are met. This
success has validated our processes of fabrication and metrology and allows us to proceed with the production of the 18
flight mirror segments. The first finished flight mirror, the Tertiary Mirror, was shipped to BATC on 24 February, 2010.
Performance of that mirror is reported here also.
Tinsley, under JWST funding, has led the team that has developed a novel and highly versatile piece of ground support equipment for optical surface testing of JWST beryllium mirror segments during optical fabrication. The infrared Scanning Shack Hartmann System (SSHS) offers the advantage of being able to characterize mid-to-high spatial frequency structure on a mirror from early stages of fabrication when slopes may be high and surface irregular, eliminating the need for an extra polishing step before metrology. Working at 9.3μm, the system will accept and measure a wide dynamic range of surface characteristics, including roll-off near the edge of the segment. Knowledge of these surface features at the early grinding stage is imperative if characteristics such as mirror edge roll-off are to be minimized. WaveFront Sciences, producer of commercial COAS and Columbus Shack Hartmann systems, has provided systems engineering and component support for the SSHS system.
The SSHS system is based around a special Long Wave Infrared (LWIR) wavefront sensor developed by WaveFront Sciences that is scanned over the mirror surface, making sub-aperture measurements. The smaller, high-resolution measurements are then stitched together to provide high-resolution measurement of the entire mirror surface, even though the surface is in a rough ground state.
The system leverages technology from smaller visible instrumentation produced by Wavefront Sciences, especially those for surface sub-aperture measurements of semiconductor wafers. This paper will describe the implementation of the first infrared scanning Shack Hartmann system at Tinsley to address optical fabrication optimization of the JWST Primary Mirror Segments.
The context, preparation, and facilitization of Tinsley to produce the 18 JWST primary mirror segments are described,
and an overview of the Project at Tinsley is presented. The mirror segments are aggressively lightweighted,
approximately hexagonal, and approximately 1.32m flat-to-flat. While the optical finishing approach is strongly seated
in Tinsley's Computer Controlled Optical Surfacing (CCOSTM) technology, extensions have been implemented to
address safe and efficient nearly simultaneous flow of the high value mirror segments through numerous cycles of
optical finishing, processing and metrology steps. JWST will operate at cryogenic temperatures, and Tinsley will do
final figuring from a "hit map" made during cryogenic testing at the NASA MSFC X-Ray Calibration Facility (XRCF).
A formal beryllium safety protocol has been established throughout. Extensive handling fixtures assure that the mirrors
are moved from station to station experiencing low accelerations. A rigorous qualification process is applied to each
new fixture, machine and instrument. Special problems of cryo figuring, and co-finishing the segments to stringent
specifications are described.
The optical design, test, and fabrication of a large ultra lightweight flat beryllium scan mirror is reported. The mirror is a key component for the (TIR) thermal infrared radiometer instrument which is scheduled to compliment the (EOS) Earth observation satellite program. The unique optical design properties of the mirror provide state of the art performance for scan operations and thermal imaging of the earth's surface in the 8.0 to 12.0 micron wavelength range. The mirror's opto-mechanical design provides a very stable non-deformed platform for the scan drive system. The mirror's optical figure, surface characteristics and protected gold coating have been tested and are well within the flight specifications.
A 50 cm diameter, beryllium mirror was fabricated and cryogenically tested as a joint project between NASA-Ames Research Center and Jet Propulsion Laboratory. The purpose of this project was to determine the cryogenic distortion and hysteresis of a large, state-of-the-art beryllium mirror when cooled to liquid helium temperatures. The mirror blank was HIPed from I-70 special beryllium and machined to a plano-concave sphere with a 200 cm radius of curvature. The blank was annealed, acid etched, and thermally cycled may times during machining, figuring, and polishing to reduce stress. The mirror was tested twice to liquid helium temperature using the Ames Research Center Cryogenic Test Facility. No hysteresis or temporal instability was measured in the two tests. The cryogenic distortion was 0.5 p-v. This distortion is comparable to fused silica and is the lowest for any beryllium mirror tested by this facility.
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