Balun is a key component in radio frequency (RF) circuits. The conventional Si-based planar spiral balun presented a high insertion loss. To solve this problem, this thesis firstly develops a Si-based suspending spiral balun using electrochemical deposition and surface micromachining technology for the fourth generation of wireless communication system. To reduce the power dissipation of the conventional Si-based planar spiral balun, thesis utilized a suspending structure to reduce the power loss through the substrate and dielectric layer. The fabricated suspending spiral balun are constructed by three bottom GSG electrodes, thirty three supporting copper vias and a suspending spiral copper conducting layer. The main fabrication processes in this research including: (1) four thin-film deposition processes, (2) four photolithography processes, (3) two etching processes and (4) two copper electroplating processes. In addition, this thesis used the commercial software (Ansoft HFSS) to analysis the high frequency characteristic of Si-based suspending spiral balun. The finished Si-based suspending spiral balun were measured by a commercial network analyzer under 2~8 GHz testing frequency range. Based on the measurement results, the value of insertion loss is 1.26 dB at 5.2 GHz, magnitude imbalanced is lower than 0.86 dB, phase imbalanced is less than 3.4 degree and CMRR is more than 30 dB. Finally, this thesis successfully develops a Si-based suspending spiral balun using MEMS technology for the fourth generation wireless communication system.

The conventional planar micro transformers presented very low quality-factor (Q<10) and very high insertion loss (-6 ~ -10 dB) at high operation frequency since most of the microwave power is dissipated through the silicon substrate. To increase the quality-factor and reduce the insertion loss of silicon-based transformers, this dissertation presents a two-port and three-port micro transformers with suspending structure utilizing the micro-electro-mechanical systems (MEMS) technology. The proposed silicon-based transformers are constructed by two winding and suspending micro inductors. Each suspending micro inductor consists of a 0.32 &#x00B5;m-thick TaN/Ta/Cu bottom electrode, a 10 &#x00B5;m-height supporting copper vias and a 6 &#x00B5;m-thick spiral copper conducting layer. This research adopts the Taguchi method and commercial electromagnetic simulation software (Ansoft-HFSS) to optimize the dimensional specifications of the copper conducting layer. Many high frequency characteristics of the suspending micro transformers are simulated, including the inductance, the magnetic coupling factor, the quality-factor, the magnitude imbalance, the phase imbalance, the common mode rejection ratio (CMRR) and the insertion loss. In this research, the surface micromachining and electrochemical deposition techniques are used to implement the suspending micro transformers. The main fabrication steps include five photolithography and eight thin-film deposition processes. According to the simulation and measurement results from the commercial network analyzer (Agilent-E8364B) and software (Agilent-ADS), the implemented two-port transformer demonstrates a high magnetic coupling factor (0.78) and a very high quality-factor (Q=17.20) at 5.2 GHz. On the other hand, the proposed three-port transformer presents a low magnitude imbalance (-0.02 dB), a low phase imbalance (1.65¢X), a high CMRR (36.78 dB) and a very low insertion loss (-4.52 dB) under the same operation frequency. In this dissertation, a novel suspending micro transformer has been developed and characterized. The proposed micro transformer is very suitable for being used in the portable microwave communication system due to its small chip size (0.7 mm¡Ñ0.7 mm¡Ñ0.5 mm) and excellent high-frequency characterization.