The Harp
ECE 449
Adil Ahmed
Sadeddin Lambaz
King Moy
Outline
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Why we did the Harp
Application
Marketing
Fabrication Process
Design Problems
Design Solutions
Conclusion
Harp:
Why we did it
• Multiple Reasons
– Sole Purpose: out-of-plane device and learn
fabrication techniques
– First Time Done
– Possibility of out-of-plane free moving
structures, true three dimensional device
– Introducing clamps at the micro scale level
to facilitate free movement
Harp:
Applications
• Entertainment
– Micromachined guitar
– Orchestra
• As A Result of Out-of-plane Application
– Fan
• Used for cooling microchips
• Sensor
– Heat
– Flow
Marketing our Harp device
• MMB: Micromachined Music Box
– A complete Orchestra-on-a-Chip
• Micromachined Wings
– By utilizing such fine strings, implementing a
matrix as “WINGS”
• Sensor
– Cheaper
– Convenient
– Efficient
Fabrication Process I
Cu
•0.6µm SiO2
•200 A Ta
•1 µm Cu
Ta
SiO2
Si
Mask # 3
P.R.
Copper Etch
•Wet Etching
Tantalum Etch
•Plasma Etch : CF4 plasma
Fabrication Process II
Photoresist
•1000 rpm, 30 s
4.36um
Mask # 4
•Prebake: 5 min at 115 C
•Develop for 2 min in 1:4 developer
•Postbake:30 min at 115 C
•Etch SiO2
Fabrication ProcessIII
Deposit Cr/Cu
•1 µm Cr/Cu
Mask # 5
•Etch Cr/Cu
Fabrication Process IV
Etch SiO2
Final Product
Final Harp
Side View of Base of Harp
Bottom View of Base of Harp
Harp Design Problems
• Angle Problem at
the connection of
strings and harp
frame
• Not enough
clearance for
clamps when harp
folds (“lifted”) up
• Damage to base
or/and clamp
– Harp Base Width
• 10 µm -15 µm
– Clamp
Clearance
• 3.5 µm
10 µm-15µm
Harp Design Problems
• No dimples for base of
harp
– Stiction Problem
• Harp strings may “sag”
when SiO2 is etched
• Switched from
Polysilicon to Copper
– Poor polysilicon
quality
• Lift Off of Harp and Harp
Holder
– Suction
– Magnets
– Tweezers
Harp
Dimples
String
Harp
Harp Design Problems
•Result of first problem
•Even after
redesigning of Mask,
problem still exists
Solutions
• Redesign the harp mask
– From acute to obtuse
• Ensure proper clearance of harp base
Clamp
Harp’s Base
Conclusion
• Testing
– Using Laser-beams, the strings can be
plucked
– Frequency of mini-strings can be compared
with ideal frequency
– Amplify sound by using an amplifier