RF IPDs (Integrated Passive Devices) and WLAN FEM (Front End Module) on the SAAO (Selectively Anodized Aluminum Oxide)

Abstract

This thesis describes the design and fabrication of IPDs (Integrated Passive Devices) and FEMs (Front-end Modules) for 2.45 GHz WLAN applications on the SAAO (Selectively Anodized Aluminum Oxide). The proposed FEM involves not only various passive devices such as LPF, BPF, and Balun but also active devices such as a PA, LNA, and SPDT switch in a single package. In the first chapter, we study various RF package technologies and trends to realize small and complex modules. MCM-L, MCM-C and MCM-D technologies were briefly summarized as the recent and widely used packages. IPD technology was introduced to make small package and integrated inductors and capacitors, key elements of IPDs, were compared for various package substrates. IPD realized by MCM-D technology has the highest wiring density and also it was possible to realize accurate MIM capacitors using thin film process. However, the cost of the substrates (HRS, GaAs, or Glass) was too high and it was hard to make large size to compensate expensive semiconductor process. So, a low-cost anodized aluminum was proposed as the package substrate to realize WLAN FEM. In the chapter 2, I have studied how to realize high Q inductor to make good IPDs. It was required to make high Q inductor that the inductor had to be realized on high resistivity substrates with low signal ohmic loss. In addition, the inductor had to be fabricated on the low k material to improve SRF (Self-resonance Frequency). First, high Q inductor was fabricated on anodized aluminum substrate which had high resistivity. The fabricated inductor had high Q more than 20 at 2 GHz. Second, to improve the performances of the inductors, the inductors were realized on alumina membrane or as suspending structure using selective etching of alumina and aluminum. The fabricated inductor had large increment of inductance and the Q peak was increased comparing to normal spiral inductors in high frequency range. Third, thick inductor was fabricated using poly...