Berkeley Sensor Actuator Center Latest Result Multiple Wafer
Berkeley Sensor & Actuator Center Latest Result Multiple Wafer Bonding Process Lixia Zhou, Matt Last Joseph M. Kahn Kristofer S. J. Pister October 16, 2002
Berkeley Sensor & Actuator Center Spontaneous hydrophilic Si bonding • Infrared picture of spontaneous wafer bonding. a) Start of bonding by applying a slight pressure, b) Extension after 2 sec, c) Complete bonding after about 5 sec. • Maximum bonding wave velocity observed: 2 cm/s.
Berkeley Sensor & Actuator Center Why bonding? Scanning Mirror Veljko Milanovic, Matt Last, Kris Pister
Berkeley Sensor & Actuator Center Patterned SOI alignment bonding to realize multi-layer devices
Berkeley Sensor & Actuator Center Process flow I: SCS Wet Oxide PR
Berkeley Sensor & Actuator Center Process flow II: SCS Wet Oxide PR
Berkeley Sensor & Actuator Center Process flow III: SCS Wet Oxide PR
Berkeley Sensor & Actuator Center Problems coming across bonding • Ksaligner Si/Si bonding alignment accuracy is within +/- 30 um. Design rule has to take care of this. • Bow/warpage of SOI wafer is preventing a secure bonding. Retaining an oxide layer on the back of handle wafer helps to reduce the bow. • Thermal stress from oxide membrane causes cracks and even breaks off part of the membrane during and after STS handle wafer etch. Having a thinner oxide membrane helps to reduce the stress.
Berkeley Sensor & Actuator Center Stress from thermal oxide membrane
Berkeley Sensor & Actuator Center Stress from thermal oxide membrane
Berkeley Sensor & Actuator Center Working 1 D scanning mirror realized by bonding
Berkeley Sensor & Actuator Center * 1 D scanning mirror: DC actuation Comb drive pull_in * Compared with Veljko and Matt’s timed etch mirror: 20 degrees at 90 V or 6 degrees at 56 V.
Berkeley Sensor & Actuator Center 2 D scanning mirror realized by bonding
Berkeley Sensor & Actuator Center Testing structures pressure sensor pillar and roof bond strength measurement
Berkeley Sensor & Actuator Center Process works great! • High yield. • Need a more powerful simulation tool. • Problems associated with comb drive pull_in and 2 D scanning mirror coupling can be solved with better design. • New design ideas are welcome. Microrobots? And what’s more?
- Slides: 15