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 3.042 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
7. 2D Structure Fabrication
Coat
plain Si coat with HMDS to coat with SU-8 20xx soft bake @95°
wafer promote adhesion photoresist using to evaporate
spin coater solvent and cut
into pieces
post bake at first
Exposure 65° then 95° to
promote crosslink
UV exposure for flip 90° and formation
xx seconds expose again
submerge in PM submerge in
Develop acetate to dissolve isopropanol to
unexposed wash away all
photoresist (20 remnants—final
min ） structure
8. Phase Mask Fabrication
Step 1 Vacuum sample with open bottle of
fluorosilane so that it evaporates onto
sample.
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 coat with HMDS to coat with SU-8 2005 soft bake @95°
slide promote adhesion photoresist using to evaporate
spin coater solvent and cut
into pieces
post bake at first
Exposure 65° then 95° to
promote crosslink
Place phase
Expose for xx formation
mask on top of
seconds and
slide
remove phase mask
submerge in PM submerge in
Develop acetate to dissolve isopropanol to
unexposed wash away all
photoresist (5-10 min) remnants—final
structure
10. Process Tuning
Exposure times (contact lithography):
SU8-2002: 0.5-25 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-8 2015 Top
1. Overexposure
2. Unwashed monomer
3. Adhesion problems 15s SU-8 2015 Cross
4. Inconsistent results
12. Design Functionality
2-D Patterns • 5s exposure of SU-8 2015
• Coated with HMDS
•Broadband laser filtered at 365nm
•Top down
•Hole spacing - 3.38 um
•Hole length ~1.5um
5s SU-8 2015 Cross 5s SU-8 2015 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-8 2015 PDMS on 10s SU-8 2015
14. Design Functionality
3-D Patterns
3s SU-8 2005Top
•3s exposure of SU-8 2005 •355 YAG pulse laser
•Coated with HMDS •Used in continues mode
•Thickness ~ 5um
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
20. Design Functionality
Thick Film Photoresist
Calculation:
Sin (70) = 58 / t
Thickness (t) ~ 61 microns
Success!
45s SU-8 2050
21. Design Functionality
Problems in 2-D patterns
1. Un-washed monomer
2. Over exposure
15s SU-8 2015 Top
3. Non-uniform columns
Width of top ~ 1.81 um
Width of bottom ~ 1.00 um
15s SU-8 2015 Cross
22. TiO2 Sol Gel Infiltration
Step 1 Dip sample in TiO2 solution (trifluoroacetic
acid, titanium oxide, and deionized water) for
about 30 seconds.
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.
