1. Layer Transfer Technology for Micro-System Integration
SFR Workshop
May 24, 2001
Changhan Yun, Yonah Cho, Adam Wengrow,
and Nathan Cheung
Berkeley, CA
2001 GOAL: To establish low-temperature micro-system assembly process for sensor integration by 9/30/2001.
5/24/2001

2. Motivation Low-Temp assembly process enables integration of dissimilar
Detector
Sensor array
Electronics
Interconnects
Battery
Resonators
Photon emitters
Low-Temp assembly process enables integration of dissimilar
microsystems (embedded photon emitter, energy source, sensors, and electronics)
5/24/2001

3. LED Array Transfer with Laser Liftoff
1. Bond receptor onto GaN sapphire
2. Laser Liftoff (LLO)
3. Acetone bath
4. Bond to any substrate
Interfacial decomposition
Thermal
detachment (~40°C)
receptor
wafer
adhesive
adhesive
LED
handle
substrate
Sapphire
Laser beam
Transfer of LED layers from sapphire to silicon or plastic substrate
5/24/2001

4. LEDs from Sapphire to Silicon Substrates
LED’s grown on sapphire
Laser-detached GaN surface
(bottom surface)
LED’s transferred on silicon
contact pads
Ga residues
rough In surface underneath
receptor
wafer
LED
LED
Indium
Silicon
Al2O3
epoxy
LED
* LED’s provided by Oriol Inc., Santa Clara, CA
5/24/2001

5. Blue LED Transferred on Silicon Substrate
From a distance
Under a microscope
probe tip
probe tip
No performance degradation after layer transfer!
5/24/2001

6. Low-Temperature Silicon Device Layer Transfer
1. H+ Implantation
through MOS devices
2. Wafer Bonding
at low temperature
3. Mechanical bending
for layer transfer
Device
Region
Si donor wafer
Hydrogen
peak H+
Glued metal pad
SiO2
Si handle wafer
~10 lb·ft
Demonstrates low-temperature mechanical cleavage of Si layer
5/24/2001

7. Surface Roughness of Mechanically Transferred Silicon Layer
RMS roughness ~ 5nm
5/24/2001

8. Concerns : Gate Oxide Degradation due to Hydrogen Implantation
Leakage current measurement through W=10mm, L=1.5mm gate oxide
1. Dose Dependence
2. Antenna Ratio (AR) Dependence
18Å
50Å
SILC
For 50Å Gox, SILC increases with Hydrogen dose and AR
For 18Å Gox, No SILC was detected.
5/24/2001

9. 2002 and 2003 Goals
By 9/30/2002
Incorporate light emitting devices on sensor wafers
Demonstrate silicon layer transfer for subsystem encapsulation (e.g. batteries)
By 9/30/2003
Design interconnection schemes between the dissimilar microsystems
Demonstrate integration of signal and data processing systems with photonics and MEMS
5/24/2001