Abstract
The next generation of microelectromechanical systems (MEMS) requires new materials and platforms that can exploit the intrinsic properties of advanced materials and structures, such as materials with high thermal conductivity, broad optical transmission spectra, piezoelectric properties, and miniaturization potential. Therefore, we need to look beyond standard SiO2-based silicon-on-insulator (SOI) structures to realize ubiquitous MEMS. This work proposes using AlN as an alternative SOI structure due to several inherent material property advantages as well as functional advantages. This work presents the results of reactively sputtered AlN films on a Si handle wafer bonded with a mirror-polished Si device wafer. Wafer bonding was achieved by using hydrophilic wafer bonding processes, which was realized by appropriate polymerization of the prebonding surfaces. Plasma activation of the AlN surface included O2, Ar, SF6, SF6 + Ar, and/or SF6 + O2, which resulted in a change in the chemical and topography state of the surface. Changes in the AlN surface properties included enhanced hydrophilicity, reduced surface roughness, and low nanotopography, components essential for successful hydrophilic direct wafer bonding. Wafer bonding experiments were carried out using promising surface activation methods. The results showed a multilayered bonding interface of Si(Device)/SiO2/ALON/AlN/Si(Handle) with fluorine in the aluminum oxynitride layer from the proceeding AlN surface activation process. More notably, this work provided wafer bonding tensile strength results of the AlN alternative SOI structure that compares with the traditional SiO2 SOI counterpart, making AlN to Si direct bonding an attractive alternative SOI platform.
Highlights
The silicon-on-insulator (SOI) platform based on silicon dioxide has been an enabler of CMOS-based technologies through to silicon-based microelectromechanical systems (MEMS)
The bonding process would develop at room temperature (RT) within the chamber for the duration t21, the temperature was raised to 80 °C for the duration t80, and the temperature was raised to 300 °C for the duration t300
Four wafer-level bonding experiments were undertaken: a nonactivated bond made in the wafer bonder with progressive annealing stages (NA), a room temperature bond made in ambient air outside of the wafer bonder (RT), a vacuum bond made in the wafer bonder with progressive annealing stages (V), and a combined bond made in the activation process in ambient air but carried out in the wafer bonder with progressive annealing stages (C)
Summary
The silicon-on-insulator (SOI) platform based on silicon dioxide has been an enabler of CMOS-based technologies through to silicon-based microelectromechanical systems (MEMS). SOI has helped realize partially and fully depleted CMOS transistor technology, giving superior transistor electrostatic control and reduced parasitic capacitances. As MEMS technologies move beyond the consumer-driven boom of the last decade, new materials and platforms are required to realize the generation of ubiquitous MEMS.[1−5]. New materials and platforms are required to achieve technological developments in all subfields of MEMS, such as micro-opto-electromechanical systems (MOEMS), radiofrequency-MEMS(RF-MEMS), and BioMEMS. This becomes a significant disadvantage as thermal designs are becoming increasingly challenging due to miniaturization, density, and the increasing number of thermal interfaces
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
