Vacuum packaged MEMS scanning mirrors

Vacuum packaged MEMS scanning mirrors
Ulrich Hofmann
Outline
Fraunhofer ISIT 09
•
•
•
•
•
Introduction
MEMS mirror fabrication
Hermetic wafer level packaging
Two applications
Conclusion
Seite 2
Fraunhofer ISIT 09
Silicon MEMS scanning mirrors
Seite 3
Silicon MEMS scanning mirrors
Fraunhofer ISIT 09
• laser scanning microscopes
Seite 4
Silicon MEMS scanning mirrors
Fraunhofer ISIT 09
• laser scanning microscopes
• barcode-readers
Seite 5
Silicon MEMS scanning mirrors
Fraunhofer ISIT 09
• laser scanning microscopes
• barcode-readers
• laser projection displays
Seite 6
Silicon MEMS scanning mirrors
Fraunhofer ISIT 09
•
•
•
•
laser scanning microscopes
barcode-readers
laser projection displays
LIDAR sensors
Seite 7
Silicon MEMS scanning mirrors
Fraunhofer ISIT 09
•
•
•
•
•
laser scanning microscopes
barcode-readers
laser projection displays
LIDAR sensors
endoscopes etc.
Seite 8
Single axis MEMS scanning mirror
Fraunhofer ISIT 09
mirror
Seite 9
Single axis MEMS scanning mirror
mirror
Fraunhofer ISIT 09
torsion springs
Seite 10
Single axis MEMS scanning mirror
mirror
torsion springs
Fraunhofer ISIT 09
silicon chip
Seite 11
Two-axis MEMS scanning mirror
Mirror
torsional springs
stacked
vertical
comb electrodes
Fraunhofer ISIT 09
Gimbal
Seite 12
MEMS mirror based laser projection display
projection screen
2D-MEMS mirror
Fraunhofer ISIT 09
beam combiner
rgb laser diodes
Seite 13
Target applications of laser projection displays
Fraunhofer ISIT 09
embedded pico-projectors
Automotive head up & dashboard displays
Seite 14
fabrication process
oxide
silicon substrate
Fraunhofer ISIT 09
oxide
Seite 15
fabrication process
polysilicon 30µm
oxide
silicon substrate
Fraunhofer ISIT 09
oxide
Seite 16
fabrication process
poly
oxide
polysilicon 30µm
oxide
silicon substrate
Fraunhofer ISIT 09
oxide
Seite 17
fabrication process
silver
polysilicon 30µm
poly
oxide
polysilicon 30µm
oxide
silicon substrate
Fraunhofer ISIT 09
oxide
Seite 18
Fraunhofer ISIT 09
frontside etch (DRIE)
Seite 19
Fraunhofer ISIT 09
backside etch (DRIE)
Seite 20
Fraunhofer ISIT 09
First testing of a MEMS mirror in a vacuum chamber
Seite 21
Investigating the impact of gas damping
Optical Scan Angle [deg]
120
108kHz-scanner
100
32 kHz-scanner
80
24kHz-scanner
U = 15 Volts
60
40
20
0
Fraunhofer ISIT 09
0,01
0,1
1
10
100
1000
Pressure [mbar]
Seite 22
vacuum encapsulation of 2D-MEMS mirrors on wafer-level
Fraunhofer ISIT 09
MEMS wafer
Seite 23
vacuum encapsulation of 2D-MEMS mirrors on wafer-level
Glass wafer
glassfrit bonding
Fraunhofer ISIT 09
MEMS wafer
Seite 24
vacuum encapsulation of 2D-MEMS mirrors on wafer-level
Glass wafer
glassfrit bonding
MEMS wafer
bottom wafer
Fraunhofer ISIT 09
Au / Si
eutectic bonding
Seite 25
MEMS scanning mirrors
vacuum packaged on wafer level
© Fraunhofer ISIT July 11
final dice after MEMS wafer
level testing
benefit of vacuum encapsulation
Fraunhofer ISIT 09
atmosphere
vacuum
Seite 28
high Q-factor (energy conservation)
slow axis (gimbal)
Fraunhofer ISIT 09
Q-factor > 140,000
Seite 29
Fraunhofer ISIT 09
phase controlled high-Q laser projection
Seite 30
Fraunhofer ISIT 09
Demonstrator
resolution
1024 x 512
scan frequencies
18 kHz / 520 Hz
max. FOV
60 deg x 70 deg
Seite 31
Fraunhofer ISIT 09
Solving the reflex problem of packaged MEMS mirrors
Seite 32
FP7-ICT-2009-4_248123 (MiniFaros)
MEMS scanning mirror for TOF-LIDAR sensor application
target specifications:
Fraunhofer ISIT 09
omnidirectional lens
range
cost
compact size
80 m
< 40 €
6 x 6 x 6 cm3
2D-MEMS mirror
Seite 33
fabricated tripod scanning mirror
comb drive
electrodes
mirror
circular
suspension
7mm
Fraunhofer ISIT 09
1.7mm
mirror aperture size
scan frequency
optical scan angle
scan concept
7 mm
550Hz
60 degrees
circular scanning
Seite 34
first functional test of tripod mirror test structure
Fraunhofer ISIT 09
single axis excitation
dual axis excitation
Seite 35
Conclusion
Vacuum packaging of MEMS mirrors is the key to enable
Fraunhofer ISIT 09
•
•
•
•
much larger deflection angles
much higher scan frequencies
larger aperture size
lower power consumption
Seite 36
Acknowledgement
This work has been supported by the EC within the 7th framework programme
Fraunhofer ISIT 09
under grant agreement no. FP7-ICT-2009-4_248123 (MiniFaros)
Seite 37
Fraunhofer ISIT 09
Thank you for your attention !
Seite 38