Zygo Interferometry of Echelle Gratings

This deck illustrates the need to deproject interferometry of echelle gratings to understand the origin of instrumental artifacts in the device development process.

Transcript

1. zygo interferometry of gratings
   michael gully-santiago | grad student
   UT Austin Silicon Diffractive Optics Group
   

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2. who
   michael gully-santiago
   astronomer, engineer,
   bicycle rider
   amanda turbyfill
   astrophysicist,
   basketball enthusiast
   

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3. Interferometry tells us two things
   Where did we go wrong?
   Is it good enough?
   

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4. Interferometry tells us two things
   Where did we go wrong?
   Is it good enough?
   Astronomers care about this
   Engineers care about this
   

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5. There are two data products
   Where did we go wrong?
   Is it good enough?
   Astronomers care about this
   Engineers care about this
   PSF
   FULL
   MAP
   

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6. PSF
   FULL
   MAP
   The two data products are
   related to each other
   

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7. PSF
   FULL
   MAP
   The two data products are
   related to each other
   Sub
   aperture
   FFT
   €
   ∫∫
   

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8. Let’s talk about the full map.
   Since we’re engineers
   

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9. You have to de-project
   the full map.
   

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10. de-project
    

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11. We didn’t used to
    de-project
    

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12. We didn’t used to
    probably because astronomers don’t care.
    de-project
    

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13. We didn’t used to
    probably because astronomers don’t care.
    but now we’re learning something,
    because de-projected images look like
    what engineers see.
    shadow of
    grating holder
    Shadow
    of
    grating holder
    Photoresist thickening at edge
    Periodic
    structures
    resembling
    Newton’s fringes
    Comets from photoresist spin
    Photoresist
    thickening at edge
    de-project
    

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14. We can do even better with
    shadow of
    grating holder
    Shadow
    of
    grating holder
    Photoresist thickening at edge
    Periodic
    structures
    resembling
    Newton’s fringes
    Comets from photoresist spin
    Photoresist
    thickening at edge
    

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15. high pass*
    .
    We can do even better with
    shadow of
    grating holder
    Shadow
    of
    grating holder
    Photoresist thickening at edge
    Periodic
    structures
    resembling
    Newton’s fringes
    Comets from photoresist spin
    Horizontal artifact,
    probably from using the cart and slit.
    high pass filtering* is:
    way faster than fitting Zernike polynomials.
    k ~ 51 pixels is the median smoothing kernel
    d = d - median( d, k )
    

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16. But since we are astronomers and engineers, we want
    the best of both worlds™, so:
    We are proud to introduce…
    ZIGZAG:
    Zygo Interferometry of
    Gratings with Zernike
    Analysis by Gully
    

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20. H!
    L!
    !"
    Silicon!
    Desired line
    edge position!
    Realized line
    edge position!
    Value measured by Zygo!
    

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21. I’m having a hard time getting the PSF
    to work. This is either hard or I am
    not smart enough to figure it out.
    Help!
    
    

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22. In summary: gully@astro.as.utexas.edu |
    astronomer and engineer
    You have to de-project
    the full map.
    and high pass filter
    and ZIGZAG™ does it all
    except PSFs… for now.
    

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