Wafer and reticle positioning system for the Extreme Ultraviolet Lithography Engineering Test Stand Page: 2 of 13
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Deep-UV step-and-scan systems and shunts stage control forces directly to ground. Shunting the control forces to ground
prevents internal vibrations of the PO box and other sensitive structures.
The in-vacuum components of the positioning system are the wafer and reticle stages, interferometers, stage support
structures, X and Y position reference mirrors, stage position initialization sensors, focus sensors, the isolators and isolated
frame, and electrical cables. These components are located in the main chamber of the ETS. The in-vacuum components and
a cut-away view of the ETS are shown in Figure 1.
Figure 1: ETS In-vacuum stage components.
The stage supporting structures are the main chamber pedestal and the bridge. The wafer stage is mounted on the pedestal
and the reticle stage is mounted to the bridge structure, which also mounts to the pedestal. The pedestal provides a stabilizing
mass for the machine and rests on the laboratory floor. The bridge is sufficiently stiff to reduce relative motion between the
wafer and reticle stages. The interferometers, beam optics, stage initialization sensors, and focus sensors, are mounted on the
wafer and reticle metrology trays. Mirrors are attached to the PO box to provide X, Y, and 6z position referencing for each
the wafer and reticle stages. The metrology trays, PO box, and connecting structures are isolated from ground vibration by
three isolators that are mounted to the pedestal by the isolator support structure.
3. MAGLEV STAGES
The need to perform EUVL in a vacuum environment places unique requirements on the scanning stages for the ETS.
Particle generation must be minimized to eliminate possible contamination of the object reticle, target wafer, and machine
optics. A magnetically levitated fine position stage has successfully performed under similar requirements and is in use in
the 1oX Microstepper'. This success combined with the availability of concept maglev scanning stage designs 2 3 led to the
inclusion of 1D-long-travel maglev stages for both reticle and wafer positioning.
The wafer stage (Figure 2) consists of the stage base, off-axis coarse stage (the beam of the maglev stage), levitated platen,
cable stage, and wafer chuck. The reticle stage (Figure 3) is identical to the wafer stage without the off-axis coarse stage and
7 7 - 7 uL
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WRONOSKY,JOHN B.; SMITH,TONY G.; CRAIG,MARCUS J.; STURGIS,BEVERLY R.; DARNOLD,JOEL R.; WERLING,DAVID K. et al. Wafer and reticle positioning system for the Extreme Ultraviolet Lithography Engineering Test Stand, article, January 27, 2000; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc702960/m1/2/: accessed October 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.