Indium-silver as solder materials for low temperature bonding had been introduced earlier. In theory the final bonding
interface composition is determined by the overall materials composition. Wafer bonding based multiple intermediate
layers facilitates precise control of the formed alloy composition and the joint thickness. Thus the bonding temperature
and post-bonding re-melting temperature could be easily designed by controlling the multilayer materials. In this paper, a
more fundamental study of In-Ag solder materials is carried out in chip-to-chip level by using flip-chip based
thermocompression bonding. Bonding at 180°C for various time duration under various bonding pressure is studied.
Approaches of forming Ag2In with re-melting temperature higher than 400°C at the bonding interface are proposed and
discussed. Knowledge learned in this process technology can support us to develop sophisticated wafer level packaging
process based wafer bonding for applications of MEMS and IC packages.
This paper presents design, simulation and fabrication of a wafer level packaged Microelectromechanical Systems
(MEMS) scanning mirror. In particular we emphasize on the process development and materials characterization of In-
Ag solder for a new wafer level hermetic/vacuum package using low temperature wafer bonding technology. The
micromirror is actuated with an electrostatic comb actuator and operates in resonant torsional mode. The mirror plate
size is 1.0 mm × 1.0 mm. The dynamic vibration characteristics have been analyzed by using FEM tools. With a single
rectangular torsion bar, the scanning frequency is 20 KHz. Besides, the hermetically sealed packaged is favored by
commercial applications. The wafer level package is successfully carried out at process temperature of 180°C. With
proper process design, we may lead the form a single phase of Ag2In at the bonding interface, in which it is an
intermetallic compound of high melting temperature. This new wafer level packaging approach allows us to have high
temperature stability of wafer level packaged scanning mirror devices. The wafer level packaged devices are able to
withstand the peak temperature in SMT (surface mount technology) manufacturing lines. It is a promising technology for
commercializing MEMS devices.
Silicon photonic crystal (PhC) waveguide based resonator is designed by introducing a micro-cavity within the line
defect so as to form the resonant band gap structure for PhC. Free-standing silicon beam comprising this nanophotonic
resonator structure is investigated. The output resonant wavelength is sensitive to the shape of air holes and defect length
of the micro-cavity. The resonant wavelength shift in the output spectrum is a function of force loading at the center of a
suspended beam with PhC waveguide resonator. The sensing capability of this new nanomechanical sensor is derived as
that vertical deformation is about 20nm at center and the smallest strain is 0.005% for defect length.