Lifting, welding, and packaging of a quality-factor-controllable micromachined inductor using magnetic fields

Abstract

This study demonstrates a novel approach to lift the inductor from the lossy substrate by static magnetic field. The lift angle of the inductor, which tuned by a position stage, is employed to control the quality factor of the inductor. The lifted inductor is then welded by localized induction heating using the ac magnetic field. Thus, the heating-induced thermal problem is prevented. In addition, the inductor is also simultaneously packaged inside a Si capping by the alternating magnetic field. To demonstrate the feasibility of the proposed concept, the meander strip inductor was fabricated and tested. The radio frequency performance of the inductor at various tilting angles away from the substrate (0, 45, and 90 deg) was characterized by using a two-port vector network analyzer. The quality factor has been improved from 4.2 (at the central frequency of 0.64 GHz) to 7.9 (at the central frequency of 0.74 GHz), as the lift angle increased from 0 to 90 deg. In other words, the central frequency of the inductor can also be varied from 0.64 to 0.74 GHz. Measurement results also indicate that the bonded Si capping has a good shear strength of 23.5 MPa. C 2010 Society of Photo-Optical Instrumentation Engineers.