1. Metamaterials
Zaven Kalfayan
Lindsay Hunting
Phyllis Xu
Joy Perkinson

2. Presentation Outline Motivation of project Project goals
Processing and materials
Results
Cost analysis
TechWatch and future work

3. What is a Metamaterial?
A periodic material that derives its properties from its structure rather than its components.
*Taken From handout & Physics Worlds 2005 “Sound Ideas”

4. Project Motivation Developing field of research
Applications in wide range of sectors, such as communications, optics, energy
Currently used for wave manipulation

5. Project Goals
Design a process using lithography to fabricate a 3D structure
Create macroscale models of 2D structure, phase mask, and 3D structure
Create a 3D metamaterial and image using SEM

6. Process Design Phase mask 3-D pattern Titania structure 2-D
Interference lithography
2-D
photoresist pattern
Phase mask
3-D pattern
Titania structure
Sol-gel infiltration

7. 2D Structure Fabrication
Coat
plain Si wafer
coat with HMDS to promote adhesion
coat with SU-8 20xx photoresist using spin coater
soft to evaporate solvent and cut into pieces
Exposure
post bake at first 65° then 95° to promote crosslink formation
UV exposure for xx seconds
flip 90° and expose again
submerge in PM acetate to dissolve unexposed photoresist (20 min）
submerge in isopropanol to wash away all remnants—final structure
Develop

8. Phase Mask Fabrication
Vacuum sample with open bottle of fluorosilane so that it evaporates onto sample.
Step 1
Step 2
Layer with PDMS and heat at 65°to 75°for at least three hours.
Step 3
Gently peel off PDMS layer as phase mask.

9. 3D Structure Fabrication
Coat
plain glass slide
coat with HMDS to promote adhesion
coat with SU photoresist using spin coater
soft to evaporate solvent and cut into pieces
Exposure
post bake at first 65° then 95° to promote crosslink formation
Place phase mask on top of slide
Expose for xx seconds and remove phase mask
submerge in PM acetate to dissolve unexposed photoresist (5-10 min)
submerge in isopropanol to wash away all remnants—final structure
Develop

10. Process Tuning Exposure times (contact lithography):
SU8-2002: seconds
SU8-2005: 5-40 seconds
SU8-2015: 1-45 seconds
Exposure times (interference lithography):
3-20 seconds for all samples

11. Prototype Functionality
Problems for 2D & 3D patterns
15s SU Top
Overexposure
Unwashed monomer
Adhesion problems
Inconsistent results
15s SU Cross

12. Design Functionality 2-D Patterns Coated with HMDS
5s exposure of SU
Coated with HMDS
Broadband laser filtered at 365nm
Top down
Hole spacing um
Hole length ~1.5um
5s SU Cross
5s SU Top

13. Design Functionality Phase mask PDMS on SU-8 2015 2D pattern
Coated with flourosilane
Baked overnight 65C
Column
Spacing ~ 4 um
Height ~15 um
PM of 10s SU
PDMS on 10s SU

14. Design Functionality 3-D Patterns 3s exposure of SU-8 2005
3s SU Top
3s exposure of SU
Coated with HMDS
Thickness ~ 5um
355 YAG pulse laser
Used in continues mode

15. 2-D Pattern
Phase Mask
3-D Pattern
CAD Model
3-D Printing Model
Actual Sample

16. Cost Analysis Fixed cost: Spin coater, lasers, SEM
General lab equipment, facilities
Variable cost:
SU-8 20xx and HMDS ($300/1L $30/500mL )
Trifluoroacetic acid and TiO2 ($60/100mL, $117/50mL)
Si wafers ($15/piece)
Glass wafers ($240/2500 slides)
Total costs/sample: $6/sample

17. Future Work Optimize process
Explore new thicknesses and exposure times
Adhesion promoters
Create more complicated 3D structures
Characterize 3D structure properties

18. TechWatch
2004:
Miniaturized antennas based on negative permittivity materials—Lucent Technologies
Metamaterial scanning lens antenna systems and methods—The Boeing Company
2003:
Metamaterials employing photonic crystal—MIT
Methods of fabricating electromagnetic metamaterials—The Boeing Company
2002:
Resonant antennas—Lucent Technologies

19. Questions?

20. Design Functionality Thick Film Photoresist Calculation:
Sin (70) = 58 / t
Thickness (t) ~ 61 microns
Success!
45s SU

21. Design Functionality Problems in 2-D patterns Un-washed monomer
Over exposure
Non-uniform columns
15s SU Top
Width of top ~ 1.81 um
Width of bottom ~ 1.00 um
15s SU Cross

22. TiO2 Sol Gel Infiltration
Dip sample in TiO2 solution (trifluoroacetic acid, titanium oxide, and deionized water) for about 30 seconds.
Step 1
Step 2
Dry the sample for at least 2 hours.
Step 3
Heat sample up to 600°C in 8 hours and cool down to room temperature in 6 hours to evaporate photoresist.