Wafer level vacuum packaging of mems sensors and resonators

Torunbalcı, Mustafa Mert
This thesis presents the development of wafer level vacuum packaging processes using Au-Si eutectic and glass frit bonding contributing to the improvement of packaging concepts for a variety of MEMS devices. In the first phase of this research, micromachined resonators and pirani vacuum gauges are designed for the evaluation of the vacuum package performance. These designs are verified using MATLAB and Coventorware finite element modeling tool. Designed resonators and pirani vacuum gauges and previously developed gyroscopes with lateral feedthroughs are fabricated with a newly developed Silicon-On-Glass (SOG) process. In addition to these, a process for the fabrication of similar devices with vertical feedthroughs is initiated for achieving simplified packaging process and lower parasitic capacitances. Cap wafers for both types of devices with lateral and vertical feedthroughs are designed and fabricated. The optimization of Au-Si eutectic bonding is carried out on both planar and non-planar surfaces. The bonding quality is evaluated using the deflection test, which is based on the deflection of a thinned diaphragm due to the pressure difference between inside and outside the package. A 100% yield bonding on planar surfaces is achieved at 390ºC with a v holding time and bond force of 60 min and 1500 N, respectively. On the other hand, bonding on surfaces where 0.15μm feedthrough lines exist can be done at 420ºC with a 100% yield using same holding time and bond force. Furthermore, glass frit bonding on glass wafers with lateral feedthroughs is performed at temperatures between 435-450ºC using different holding periods and bond forces. The yield is varied from %33 to %99.4 depending on the process parameters. The fabricated devices are wafer level vacuum packaged using the optimized glass frit and Au-Si eutectic bonding recipes. The performances of wafer level packages are evaluated using the integrated gyroscopes, resonators, and pirani vacuum gauges. Pressures ranging from 10 mTorr to 60 mTorr and 0.1 Torr to 0.7 Torr are observed in the glass frit packages, satisfying the requirements of various MEMS devices in the literature. It is also optically verified that Au-Si eutectic packages result in vacuum cavities, and further study is needed to quantify the vacuum level with vacuum sensors based on the resonating structures and pirani vacuum gauges.


Wafer level hermetic sealing of MEMS devices with vertical feedthroughs using anodic bonding
Torunbalci, Mustafa Mert; Alper, Said Emre; Akın, Tayfun (2015-04-01)
This paper presents a new method for wafer-level hermetic packaging of MEMS devices using a relatively low temperature anodic bonding technique applied to the recently developed advanced MEMS (aMEMS) process. The aMEMS process uses vertical feedthroughs formed on an SOI cap wafer, eliminating the need for any complex via-refill or trench-refill steps while forming the vertical feedthroughs. The hermetic sealing process is achieved at 350 degrees C by using an anodic bonding potential of 600 V. The bonding p...
Wafer-Level Low-Temperature Solid-Liquid Inter-Diffusion Bonding With Thin Au-Sn Layers for MEMS Encapsulation
Temel, Oguzhan; Kalay, Yunus Eren; Akın, Tayfun (Institute of Electrical and Electronics Engineers (IEEE), 2020-01-01)
IEEEA novel solid-liquid inter-diffusion (SLID) bonding process is developed allowing to use thin layers of the Au-Sn material in wafer-level microelectromechanical systems (MEMS) packaging while providing a good bonding strength. The bond material layers are designed to have a robust bond material configuration and a metallic bond with a high re-melting temperature, which is an important advantage of SLID bonding or with its alternative name, transient liquid phase (TLP) bonding. The liquid phase in SLID b...
Microwave Characterization of a Wafer-Level Packaging Approach for RF MEMS Devices Using Glass Frit Bonding
Comart, Ilker; Topalli, Kagan; Demir, Şimşek; Akın, Tayfun (Institute of Electrical and Electronics Engineers (IEEE), 2014-06-01)
This paper presents the microwave characterization of a wafer level packaging approach for RF MEMS devices, using glass frit as the bonding material. Coplanar waveguide transmission lines are packaged by silicon caps to carry out the RF characterization of the package structure. Prior to bonding of the cap on the transmission lines, cap wafers are bulk micromachined to form the cavities for housing the device to be packaged and pad windows to access the RF ports of the devices. Lateral feedthroughs are desi...
Multi-Band Metamaterial Absorber: Design, Experiment and Physical Interpretation
Dincer, F.; KARAASLAN, MUHARREM; ÜNAL, EKİN ANIL; Akgol, O.; Sabah, C. (2014-03-01)
This paper presents the design, fabrication, characterization and experimental verification of a perfect Multi-Band Metamaterial (MTM) absorber (MA) based on a simple configuration of a rectangular resonator and strips operating in microwave frequency regime. The proposed multi-band MA provides perfect absorption with TE-incident angle independency. Maximum absorption rate is achieved as 99.43% at 5.19 GHz for simulation and 98.67% at 5.19 GHz for experiment, respectively. The measurement results of the fab...
Wafer level hermetic encapsulation of MEMS inertial sensors using SOI cap wafers with vertical feedthroughs
Mert Torunbalci, Mustafa; Alper, Said Emre; Akın, Tayfun (2014-02-26)
This paper reports a new, inherently simple, and high-yield wafer-level hermetic encapsulation method developed for MEMS inertial sensors, enabling lead transfer using vertical feedthroughs that do not require any complex via-refill or trench-refill processes. The process requires only seven masks to complete both the sensor and cap wafers, whereas the combined yield for the sealing and lead transfer is experimentally verified to be above 90%. Hermetic encapsulation is achieved by Au-Si eutectic bonding, an...
Citation Formats
M. M. Torunbalcı, “Wafer level vacuum packaging of mems sensors and resonators,” M.S. - Master of Science, Middle East Technical University, 2011.