Zaven Kalfayan

Lindsay Hunting

Phyllis Xu

Joy Perkinson

Presentation Outline

Motivation of project

Project goals

Processing and materials

Results

Cost analysis

TechWatch and future work

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”

Project Motivation

Developing field of research

Applications in wide range of sectors, such as communications, optics, energy

Currently used for wave manipulation

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

Process Design

2-D photoresist

pattern

Phase mask

Sol-gel infiltration

3-D pattern

Titania structure

Interference lithography

2D Structure Fabrication

Coat

Exposure

Develop

plain Si wafer

coat with HMDS to promote adhesion

coat with SU-8 20xx photoresist using spin coater

soft bake @95° to evaporate solvent and cut into pieces

UV exposure for xx seconds

flip 90° and expose again

post bake at first 65° then 95° to promote crosslink formation

submerge in PM acetate to dissolve unexposed photoresist (20 min）

submerge in isopropanol to wash away all remnants—final structure

Phase Mask Fabrication

Step 1

Step 2

Step 3

Vacuum sample with open bottle of fluorosilane so that it evaporates onto sample.

Layer with PDMS and heat at 65°to 75°for at least three hours.

Gently peel off PDMS layer as phase mask.

3D Structure Fabrication

Coat

Exposure

Develop

plain glass slide

coat with HMDS to promote adhesion

coat with SU-8 2005 photoresist using spin coater

soft bake @95° to evaporate solvent and cut into pieces

Place phase mask on top of slide

Expose for xx seconds and remove phase mask

post bake at first 65° then 95° to promote crosslink formation

submerge in PM acetate to dissolve unexposed photoresist (5-10 min)

submerge in isopropanol to wash away all remnants—final structure

Process Tuning

Exposure times (contact lithography):SU8-2002: 0.5-25 secondsSU8-2005: 5-40 secondsSU8-2015: 1-45 seconds

Exposure times (interference lithography):3-20 seconds for all samples

Prototype FunctionalityProblems for 2D & 3D patterns

1. Overexposure

2. Unwashed monomer

3. Adhesion problems

4. Inconsistent results

15s SU-8 2015 Top

15s SU-8 2015 Cross

Design Functionality2-D Patterns

5s SU-8 2015 Cross 5s SU-8 2015 Top

• 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

Design FunctionalityPhase mask

PM of 10s SU-8 2015 PDMS on 10s SU-8 2015

•PDMS on SU-8 2015 2D pattern

•Coated with flourosilane

•Baked overnight 65C

•Column

•Spacing ~ 4 um

•Height ~15 um

Design Functionality3-D Patterns

3s SU-8 2005Top

•3s exposure of SU-8 2005

•Coated with HMDS

•Thickness ~ 5um

•355 YAG pulse laser

•Used in continues mode

2-D Pattern Phase Mask 3-D Pattern

CAD Model

3-D Printing Model

Actual Sample

Cost Analysis Fixed cost:

Spin coater, lasers, SEMGeneral 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

Future Work

Optimize process

Explore new thicknesses and exposure

times

Adhesion promoters

Create more complicated 3D structures

Characterize 3D structure properties

TechWatch2004:• 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

Questions?

Design Functionality Thick Film Photoresist

Sin (70) = 58 / t

Calculation:

Thickness (t) ~ 61 microns

Success!

45s SU-8 2050

Design FunctionalityProblems in 2-D patterns

1. Un-washed monomer

2. Over exposure

3. Non-uniform columns

Width of top ~ 1.81 um

Width of bottom ~ 1.00 um

15s SU-8 2015 Top

15s SU-8 2015 Cross

TiO2 Sol Gel Infiltration

Step 1

Step 2

Step 3

Dip sample in TiO2 solution (trifluoroacetic acid, titanium oxide, and deionized water) for about 30 seconds.

Dry the sample for at least 2 hours.

Heat sample up to 600°C in 8 hours and cool down to room temperature in 6 hours to evaporate photoresist.