Lecture 6 - ME 601: Manufacturing in Micro- and Nanosystems...

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ME 601: Manufacturing in Micro- and Nanosystems Lecture 6: X-ray Lithography
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X-ray Lithography Earliest developed “next generation lithography” (NGL), promising alternative to photolithography, developed by Hank Smith at MIT in early 1970s Small wavelength of x-ray radiation allows investigation of materials properties at molecular and even atomic scale, ie. XRD, DNA structure Achieved 85 nm structures in 1994! (laboratory), production VLSI at 250 nm ready in 1995 In spite of these advantages, did not succeed as next logical technology evolution. Why?
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X-ray Lithography X-rays penetrate most materials, excepting those with very high atomic number (Au, W, Ta, Pb) X-rays cannot be focused: refractive index of all materials at such low wavelengths is n ~ 1 XRL is 1:1 proximity only, resolution also depends on gap height (remember ) z k w λ =
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X-ray Lithography Fresnel (near-field) diffraction still a problem, causes line- edge blurring (recall optical proximity) Advantage: exposed features can be narrower than features on mask (demagnification)
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X-ray Lithography Sources Types of X-ray sources: – Electron impact X-ray source (point source) – Plasma heated X-ray source: laser or e-beam (point source)
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Lecture 6 - ME 601: Manufacturing in Micro- and Nanosystems...

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