Lifting, Welding, and Packaging of a Quality-Factor-Controllable Micromachined Inductor Using Magnetic Fields

• Main Authors: Huang, Yu-Che, 黃煜哲
• Other Authors: Fang, Weileun
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/10195492477164076978

博士 === 國立清華大學 === 動力機械工程學系 === 99 === In order to reduce inductor’s substrate loss, this study demonstrates a novel approach to lift the RF-MEMS inductor from the lossy substrate by static magnetic field to improve the quality factor of the inductor. 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 alternating magnetic field. Thus, the heating-induced thermal problem is prevented. In addition, the inductor is also simultaneously packaged inside silicon capping by the alternating magnetic field. To demonstrate the feasibility of the proposed concept, the 4-turn meander inductor was fabricated and tested using the three-layer Ni/Cu/Ni sandwich structure. The radio frequency (RF) performance of the inductor at various tilting angles away from the substrate (0o, 45o and 90o) was characterized by using a two-port vector network analyzer. The quality factor has been improved from 4.2 to 7.9, as the lift angle increased from 0o to 90o. Moreover, the central frequency of the inductor can also be varied from 0.64 GHz to 1.24 GHz. Measurement results also indicate that the bonded silicon capping has a good shear strength of 23.5 MPa and a tensile strength of 40.4 MPa. In order to enhance inductor’s inductance, the inductor integrated with the patterned ferromagnetic film (CoFeB) was fabricated and tested. The meander and spiral type inductor were fabrication by copper electroplating. This study demonstrates a novel approach to deposit the dielectric layer using Parylene-C and nitride film, respectively. As a result, the influence of the ferromagnetic film contributes to 12.6 % increase of the inductance of the inductor at 2 GHz.