薄膜體聲波濾波器於無線通訊應用之研發

Abstract

隨著無線通訊的蓬勃發展，其已成為人類生活中不可或缺的一部份，但由於人的需求隨著科技日新月異而不斷提高，優良的通訊品質與多媒體的大量傳輸支援變成顧客之首選，其取決於系統中的關鍵零組件。在新一代無線射頻前端模組中，薄膜體聲波濾波器將會是最具優勢之帶通濾波器組件，因為其具有高操作頻率、高品質因子、高負載功率，且可與積體電路整合等優點。基於此緣故，本論文以薄膜體聲波濾波器應用於無線射頻為研究主軸，文中完整涵蓋薄膜體聲波濾波器之設計、製作與量測分析。 薄膜體聲波濾波器係由數個薄膜體聲波共振器串並聯而成，故論文一開始推導出薄膜體聲共振器之電性阻抗特徵，接著將前者應用在傳統階梯式濾波器之理論中，作為薄膜體聲波濾波器之設計架構，此過程中提出一套完整清晰的標準設計流程。為提供與積體電路設計之共同模擬平台，本研究將薄膜體聲波元件之等效電路模型建立於電子設計自動化之模擬軟體中，以提供研究者準確且迅速的設計參考。經過實驗結果與模擬相互驗證，證明此模型不論是在元件本身特性或與積體電路整合之模擬及製程變化所造成元件特性影響之推估，皆具有極佳的精準度與可信度。同時，為了追求高良率之薄膜體聲波濾波器製作，本論文中先描述出利用微機電製程製作元件時之關鍵要素與結構中各層薄膜製程，最後以實際圖例說明來展示薄膜體聲波濾波器之製作流程。 優異的薄膜體聲波濾波器仰賴於具備高品質因子與充足機電耦合係數的共振器單元，本論文先以薄膜體聲波共振器研發為基礎，量測相關特徵參數作為薄膜體聲波濾波器設計模擬時之參考。接下來，論文中依據前述設計製作方法研發適用於目前無線通訊頻段之薄膜體聲波濾波器，考量目前無線通訊頻段需求之潛力後，研究中選用2.4-GHz及5.4-GHz之無線通訊標準作為目標，並依據規格需求研製出2.4-GHz及5.4-GHz頻段之薄膜體聲波濾波器，主要可應用於802.11b/g/n、藍芽、4G-WiMAX 無線通訊系統中。 最後，本論文將研究專注在關於薄膜體聲波濾波器與積體電路整合之課題，其中包含薄膜體聲波濾波器與低雜訊放大器電路整合之研究與薄膜體聲波濾波器整合於高阻抗開關鍵移式射頻接受器之研究。研究過程中，利用前述之共同模擬平台，將所設計的薄膜體聲波濾波器與電路同時模擬，並利用0.18微米CMOS標準製程進行電路製作，最後由後製程來實現薄膜體聲波濾波器。研究中已研製出薄膜體聲波濾波器整合低雜訊放大器之元件，同時，研製出匹配此接受器之薄膜體聲波濾波器。本研究成果證實了薄膜體聲波濾波器與積體電路於單晶片整合之可行性。

With the rapid development of wireless communication field, the potential advantages of Film bulk acoustic wave resonator (FBAR) are attractive to microelectronics researchers for bandpass filters. The advantages of FBAR include microminiaturization, high quality (Q) factor, high frequency operation, great power handling, and compatibility of complementary metal oxide semiconductor (CMOS) etc. Based on the trend, this research proposes to develop film bulk acoustic wave (FBAW) filters for radio frequency (RF) front-end modules. This thesis completely includes design, simulation, fabrication, measurement, and analysis of the FBAW filters. A FBAW filter cnsists of several FBAR components. Therefore, the electrical impedance characteristic of the FBAR is derived first. Then, a complete design methed of FBAW filters utilizing traditional ladder type filters concept is proposed in this study. Furthermore, this research demonstrates the equivalent circuit model of FBAW devices in electronic design automation (EDA) simulation software to rapidly design and simulate the FBAW device with circuitry on a single platform. This simulation model is verified through comparison with experiments. It can be used of simulating accurately the characteristics of FBAW devices with/without circuit components and predicting the influence of process variation on the devices. Meanwhile, to enhance the yield of FBAW devices, the fabricated process and key factor of the FBAW devices are described clearly through micro-electro-mechanical systems (MEMS) technique. An excellent FBAW filter is dependent on the high quality factor and electromechanical coupling coefficient of the FBAR components. First, FBAR are designed and fabricated to investigate the significant parameters of the various FBARs. Next, the FBAW filters for wireless communications are developed, which includes the 2.4-GHz and 5.4-GHz FBAW filters, individually. The above FBAW filters can be applied to 802.11b/g/n, Bluetooth, and 4G-WiMAX wireless communication systems. These studies confirm FBAW filters are a great potential solution for providing the high performance bandpass filters. Finally, the integration of FBAW filters with circuitry using 0.18μm CMOS technology and post-COMS MEMS process are investigated in the thesis. The study of the FBAW filter integrated with low noise amplifier is achieved. In addition, the specific FBAW filters based on an on-off keying RF receiver are accomplished. These studies are promising that FBAW devices integrated with the RF front-end system on a chip (SOC) are feasible.