1. 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

2. Outline Background Simulation data
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 only images close objects does not require
[ 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?

12. Extra

13. Properties of Bulk Crystals
by Bloch’s theorem
band diagram (dispersion relation)
(cartoon)
backwards slope:
negative refraction
photonic band gap
dw/dk  0: slow light
(e.g. DFB lasers)
conserved frequency w
strong curvature:
super-prisms, …
(+ negative refraction)
synthetic medium
for propagation
conserved wavevector k
Slide from SPIE short course on photonic crystals