應用磁力組裝與封裝之可調品質因子射頻微機電電感元件技術開發

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

黃煜哲(Yu-Che Huang)

指導教授 ： 方維倫

國立清華大學/工學院/動力機械工程學系/博士(2011年)

摘要

本論文提出創新性微機電製程技術於射頻微機電感元件之應用，針對電感元件設計分別以提升元件之品質因子與電感值進行探討。為了降低基材損耗提升品質因子，本研究提出應用磁力組裝與封裝之可調品質因子電感元件設計，利用磁場抬升懸浮電感結構於基材以降低基材損耗，並藉由磁場自對準特性以達到抬升角度的控制，進而可調整電感之品質因子，同時抬升之電感結構以電磁感應加熱方式針對元件所需接合部分產生渦電流做局部加熱組裝，加熱過程不會影響元件基本操作特性，此局部感應加熱方式並可同時應用於元件封裝之機制，因此可完成電感元件之自組裝與封裝的目的。
本研究設計並製作以鎳銅鎳為結構、厚度為20 μm之四匣折曲型(4-turn meander strip)電感，並使其結構分別以0o、45o及90o組立於基材表面，利用向量網路分析儀(vector network analyzer, VNA)，針對電感元件高頻特性進行量測。根據量測結果，直立電感結構抬升由0o至90o，其品質因子可由4.2(Qmax@0.64 GHz)有效提高至7.9(Qmax@1.24 GHz)，完成電感之品質因子的調整及特性提升。封裝強度測試經剪力與拉伸試驗，其剪應力達23.5 MPa、拉伸應力達40.4 MPa，初步驗證局部加熱之封裝可達有效的封裝保護。
電感值提升方面，本研究提出整合鈷鐵硼(CoFeB)鐵磁薄膜圖案化設計之電感元件製程開發，透過磁性膜圖樣化設計以探討對於電感元件特性所產生的影響，電感元件分別以折曲型與螺旋型之電鍍銅結構作為設計，同時整合高分子Parylene-C及蒸鍍氮化矽薄膜作為介電層材料，完成整合圖樣化鐵磁薄膜之電感元件設計、製作及量測，整合磁性膜之折曲型電感元件量測結果，其電感值能在頻率2 GHz時提升12.6 %。

關鍵字

射頻微機電電感 ； 局部焊接技術 ； 自組裝

並列摘要

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.

並列關鍵字

RF-MEMS Inductor ； localize welding ； self-assembly

參考文獻

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