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Photonic Band-gap Masks to Enhance Resolution and Depth of Focus

Photonic Band-gap Masks to Enhance Resolution and Depth of Focus. John Nistler, Koby Duckworth, Jiri Chaloupka, and Matt Brock Proc. SPIE Vol. 6517, 65171F (Mar. 19, 2007). By Marshal Miller 4/18/2007. Outline. Background Phase Shift Mask (PSM) Finite Difference Time Domain (FDTD)

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Photonic Band-gap Masks to Enhance Resolution and Depth of Focus

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  1. Photonic Band-gap Masks to Enhance Resolution and Depth of Focus John Nistler, Koby Duckworth, Jiri Chaloupka, and Matt BrockProc. SPIE Vol. 6517, 65171F (Mar. 19, 2007) By Marshal Miller 4/18/2007

  2. Outline • Background • Phase Shift Mask (PSM) • Finite Difference Time Domain (FDTD) • Photonic Crystals • Simulation data • Comparison of Photonic Bandgap Enhanced (PBE) masks to current PSM technology

  3. Phase Shift Mask • Alternating Aperture Phase Shift Mask (AAPSM) • Uses etch into quartz of mask to produce 180o phase difference • Destructive interference allows printing of sub wavelength features • Features of 65nm can be printed with 193nm illumination Out of phase by 180 degrees

  4. Finite Difference Time Domain • Grid-based differential time-domain numerical method • Maxwell’s differential equations converted to difference equations and discretized • Simulation domain broken up into fixed size cells • Equations solved in leapfrog manner

  5. Photonic Crystals • Block of transparent material with tiny holes or nanotubes arranged in a lattice pattern, abruptly changing permitivity and permeability • Ex: Silicon with tiny air holes • Creates confinement in one of the materials, allowing only certain energy states, separated by a forbidden region, the band-gap • By adjusting the size of holes and contrast in refractive index can tune properties of photonic crystals

  6. Negative Refraction [ Veselago, 1968 negative e, m ] opposite of ordinary lens: only images close objects does not require curved lens can exceed classical diffraction limit Slide from SPIE short course on photonic crystals

  7. Basic Simulation Geometry • Quartz/glass opening on left etched to make the phase difference between the two openings 180 degrees • Undercut and non-undercut etch tested • For 248nm phase trench: .2439um • For 193nm phase trench: .1721um

  8. Simulation Results: All TE AAPSM 248nm: 180nm line space pattern PBE 248nm: 80nm line space pattern PBE 248nm: 180nm line space pattern PBE 193nm 30nm line space pattern

  9. Final Comparison • Using 193nm TE illumination • Photonic Band Gap enhanced reticles show capability of producing near field image with 25 nm features • Existing Phase Shift Technology can only produce near field images down to 65nm • Authors claim manufacturable approach for validating results is indicated, but not explained due to proprietary information about Photonic Bandgap materials • Paper not specific about materials used or geometries simulated for PBE masks, only simulation results given

  10. The End Questions?

  11. Extra

  12. backwards slope: negative refraction dw/dk 0: slow light (e.g. DFB lasers) synthetic medium for propagation strong curvature: super-prisms, … (+ negative refraction) Properties of Bulk Crystals by Bloch’s theorem band diagram (dispersion relation) (cartoon) photonic band gap conserved frequencyw conserved wavevectork Slide from SPIE short course on photonic crystals http://ab-initio.mit.edu/photons/tutorial/

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