Photonic Band-gap Masks to Enhance Resolution and Depth of FocusOutlinePhase Shift MaskFinite Difference Time DomainPhotonic CrystalsSlide 6Basic Simulation GeometrySimulation Results: All TEFinal ComparisonThe EndSlide 11ExtraSlide 13Photonic Band-gap Masks to Enhance Resolution and Depth of FocusJohn Nistler, Koby Duckworth, Jiri Chaloupka, and Matt BrockProc. SPIE Vol. 6517, 65171F (Mar. 19, 2007) By Marshal Miller4/18/2007Outline•Background–Phase Shift Mask (PSM)–Finite Difference Time Domain (FDTD)–Photonic Crystals•Simulation data•Comparison of Photonic Bandgap Enhanced (PBE) masks to current PSM technologyPhase 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 illuminationOut of phase by 180 degreesFinite 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 mannerPhotonic 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 crystals2-Dperiodic intwo directions3-Dperiodic inthree directions1-Dperiodic inone directionNegative Refraction[ Veselago, 1968negative , ]opposite of ordinary lens:only images close objectsdoes not requirecurved lens can exceed classicaldiffraction limitSlide from SPIE short course on photonic crystalsBasic 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: .1721umSimulation Results: All TEAAPSM 248nm: 180nm line space patternPBE 248nm: 180nm line space pattern PBE 193nm 30nm line space patternPBE 248nm: 80nm line space patternFinal 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 givenThe EndQuestions?ExtraProperties of Bulk Crystalsby Bloch’s theoremQuickTime™ and aGraphics decompressorare needed to see this picture. (cartoon)conserved frequency conserved wavevector kphotonic band gapband diagram (dispersion relation)d/dk 0: slow light(e.g. DFB lasers)backwards slope:negative refractionstrong curvature:super-prisms, …(+ negative refraction)synthetic mediumfor propagationSlide from SPIE short course on photonic crystals
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