Kenneth Goldberg is seen in the reflective coating of a photolithography mask, contained in the clear plastic box, which he’s about to measure at the Advanced Light Source’s beamline 11.3.2. Inset at lower right shows a mask’s extreme-ultraviolet (EUV) absorbing layer, printed on a six-inch square of glass coated with multiple layers of molybdenum and silicon only billionths of a meter thick to reflect unwanted EUV. The patterned layer represents one level of a working microprocessor or memory chip, which may have 20 or more such levels. Its structures are less than one ten-millionth of a meter across and diffract visible light in rainbow patterns.
SHARP is called an “actinic” microscope because it uses the same EUV wavelengths used in production. Thus the new EUV microscope will enable semiconductor company researchers to better evaluate defects and repair strategies, mask materials and architectures, and advanced pattern features.
Like its predecessor, the SHARP microscope will also feature an array of lenses, side by side, so users can select the different imaging properties they need, much as a common lab microscope mounts different lenses on a rotating turret.
The high-magnification objective lenses for the new microscope are holographic Fresnel zoneplate lenses, microscopic objects produced by CXRO’s Nanowriter. The Nanowriter, under the direction of Erik Anderson, holds the world record for creating the highest resolution zoneplates for many synchrotron and other short-wavelength applications. The lenses are only slightly wider than a single human hair, yet they project high-quality images of the mask surface with up to 2,000 times magnification.
A special feature of the new microscope will be illumination coherence control. The ALS produces an EUV beam with laser-like coherence, ideal for many experiments. For microscopy, however, the image resolution can be improved by a factor of two by carefully re-engineering the illumination into a state called partial coherence. Microscopists have recognized the importance of partial coherence for years, and the synchrotron community is now catching up.
An angle-scanning mirror in the new microscope’s beamline illuminator will take the highly-coherent ALS light and steer it into patterns, like a mini-laser-light show, breaking and re-shaping the coherence properties. In this way, the SHARP microscope will replicate the properties of current and future tools for lithography production and research, giving researchers the most advanced look at what’s to come.
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