Theoretical and Experimental Studies of Flip-Chip Assembled High- Q Suspended MEMS Inductors

• Published in: IEEE transactions on microwave theory and techniques Vol. 55; no. 6; pp. 1171 - 1181
• Main Authors: Jun Zeng, Changhai Wang, Sangster, A.J.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.06.2007; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Assembly; Computer simulation; Design. Technologies. Operation analysis. Testing; Devices; Electromagnetic fields; Electronics; Exact sciences and technology; Flip-chip assembly; high Q; Inductors; Integrated circuits; Magnetic devices; Mathematical models; Meanders; Micro- and nanoelectromechanical devices (mems/nems); microelectromechanical systems (MEMS); Micromechanical devices; modeling; Numerical simulation; Packaging; passive inductor; polyimide film; Q factor; Q factors; Radio frequency; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; silicon RF integrated circuit (RFIC); Spirals; Studies; Substrates; Thin film inductors; Suspended structure; Inductor; Modeling; Thin film; Integrated circuit bonding; polyimide film; Flip-chip assembly; Electronic packaging; Air gap; Electromagnetic field; Cost lowering; Microelectromechanical device; Wafer; Flip chip bonding; high Q; High Q factor; Q factor; microelectromechanical systems (MEMS); Flip-chip; Theoretical study; passive inductor; silicon RF integrated circuit (RFIC); Interconnection; Integrated circuit; Numerical simulation; Radiofrequency integrated circuits; High frequency; Simulator
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2007.897716

This paper reports the theoretical and experimental studies of high-Q suspended microinductors produced by flip-chip assembly for multigigahertz RF integrated-circuit applications. The effects of device and substrate parameters on the Q factor of the inductor devices are studied by numerical simulation using Ansoft's high frequency structure simulator electromagnetic field simulation package. Suspended inductor devices are realized using a flip-chip assembly method in which the inductor structures with the supporting pillars are fabricated on a low-cost polyimide thin-film carrier and then assembled onto a low resistivity (3-4 Omegaldrcm) silicon substrate by flip-chip bonding. Individual and 2times2 arrays of meander and spiral inductor designs have been successfully fabricated with air gap heights ranging from 15 to 31 mum. Maximum Q factors of ~15 and ~13 at ~1 GHz have been achieved for meander and spiral suspended inductor devices before pad deembedding. It is shown that the optimal air gap between the inductor and substrate surface is ~15 mum beyond which no further enhancement in the Q factor can be obtained for devices on low-resistivity substrates. The experimental results are in excellent agreement with that of theoretical simulation. The inductor assembly method requires minimal chip/wafer processing for integration of high-Q inductors.