氮化鋁薄膜體聲波元件分析與研製

氮化鋁膜由於具有高效能的壓電特性，已經廣泛的應用在高頻率的薄膜體聲波元件上。本研究討論分析與研製薄膜體聲波元件，所採用的製造技術是微機電矽微細加工技術，另外，本研究發展了一套方法，能將網路分析儀所測得的薄膜體聲波諧振器的S參數，轉換成阻抗的特性，諧振器的阻抗特性對諧振器的應用電路如濾波器，振盪器與相位控制電路而言非常重要。由諧振器的阻抗分析，我們可以精確的知道其非負載品質因數（Q值），諧振頻率與機電耦合係數等參數，為了驗證我們所提的方法，我們製造了雙埠型的薄膜體聲波諧振器，包含了諧振器兩邊的傳輸線，傳輸線會造成整體元件的能量損耗，我們提出一套數學公式能將傳輸線對整體諧振器的影響排除，回歸真正諧振器的特性。在本研究中，我們也提出了一個針對薄膜體聲波諧振器品質因數計算的改良公式，通常，串聯諧振腔與並聯諧振腔品質因數的計算是互相獨立，但當薄膜體聲波諧振器的機電耦合係數過低時，造成串並聯頻率太靠近，此時品質因數值過低時，傳統的品質因數計算公式就會有誤差，因此，本研究提出一套新的公式能更準確的計算品質因數。另外，本論文也發展出一套薄膜體聲波濾波器設計的方法，使用的方法是傳統濾波器設計的方法。利用薄膜體聲波諧振腔同時具有串聯與並聯諧振的特性，我們提出一套簡易的設計方法，有系統地應用它於傳統帶通濾波器所慣用的串聯與並聯諧振腔，經由其元件厚度與面積的設計，來滿足帶通濾波器的阻抗、中心頻率、頻寬……等規格。傳統帶通濾波器的使用已具有相當久遠歷史，各種設計理論也非常成熟，不妨根據現有的設計加以修改，使其能適應於新的元件。藉由巴特沃斯（Butter worth）最平緩的階梯式帶通濾波器為實例，說明所提設計方法的適用性，當設計頻寬小於薄膜體聲波諧振腔零點與極點距離的1.2倍時，設計頻寬與實際頻寬相當一致，當設計頻寬再提高時，實際頻寬的縮減效應會越來越明顯，且不會超過薄膜體聲波諧振腔零點與極點距離的2倍。同時本方法亦可運用到其它要採用薄膜體聲波諧振腔元件的帶通濾波器上。利用這個設計方法，可以有系統地應用薄膜體聲波諧振腔於傳統帶通濾波器的串聯與並聯諧振腔。

關鍵字

諧振器； S參數；體聲波

並列摘要

A high performance piezoelectric film, such as aluminum nitride (AlN), is promising for applications as high frequency film bulk acoustic devices. This study presents the analysis and fabrication of thin film bulk acoustic devices using MEMS technology. This study also develops a method for determining the impedance of a film bulk acoustic wave resonator (FBAR) using scattering (S) parameters, those data are readily available from network analyzer measurements. Moreover determining the impedance of a resonator is very important for describing the frequency-selective performance of filters, oscillators and phase control circuits. The impedances associated with FBAR contain the information requirement for the accurate determination of unloaded quality factor, resonance frequency and effective coupling coefficient. A FBAR with a two-port configuration is fabricated using silicon bulk micromachining technology including the transmission lines. FBAR is analyzed to determine its characteristics using a network analyzer. The signal power loss of the transmission lines is modeled and isolated to recover the characteristics of FBAR itself. In this study, we also describe an improved formula that accurately determine the quality factor of FBAR with close series and parallel resonance frequencies. Conventionally, the series and parallel resonance behaviors are treated independently. The FBAR piezoelectric coupling coefficient is low such that the series and parallel frequencies are sufficiently close to influence each other. An example is given for calculating the quality factor of FBAR, in which the new method is compared to the conventional method. Moreover, this research also investigates a systematic method of FBAR band pass filter design using conventional series and parallel resonators. Band pass filter impedance, frequency, bandwidth , etc. can be specified according to the design of the device area and thickness. This method can also be used with other filter design theories using film bulk acoustic resonators. We propose a systematic method to design band-pass filters composed of FBARs for wireless communication. FBARs have demonstrated excellent performance due to their compact size, low loss, power endurance and IC compatibility. Modifying the traditional Butterworth theory, the ladder-type band-pass filters can be composed of FBARs to satisfy various filter specifications including impedance, center frequency and bandwidth. The filter design parameters are considered using the thickness and area of the composed FBARs, which are used to replace the conventional series and parallel LC resonators. When the design bandwidth is smaller than 1.2 times the distance between zero to pole, the design bandwidth is identical to the real bandwidth. When the design bandwidth is increased, the effect on bandwidth reduction will also rise. But it will never exceed twice the frequency distance between zero to pole. This method can also be used with other filter design theories using film bulk acoustic resonators.

並列關鍵字

resonator ； S-parameter ； bulk acoustic

參考文獻

[52] D. E. Johnson, Introduction to Filter Theory, Prentice Hall, New Jersey, (1976). pp.40-50

[1] J.F. Carpentier et al., “BiCMOS WCDMA Zero-IF RF Front-End Using an Above-IC BAW Filter ”, IEEE International Solid-State Circuits Conference pp.21.3 , 2005

[2] K.M. Lakin, “Thin Film Resonator Technology,” Proc. 2003 IEEE International Frequency Control Symposium and PDA Exhibition Jointly with the 17th European Frequency and Time Forum, pp. 765-778, 2003.

[3] Jae Y. Park et al., “Micromachined FBAR RF Filters for Advanced Handset Application,” IEEE the 12th International Conference on Solid State Sensors, Actuators and Microsystems, pp. 911-914, 2003.

[6] T. Nishihara, T. Yokoyama, T. Miyashita, and Y. Satoh, “High Performance and Miniature Thin Film Bulk Acoustic Wave Filters for 5 GHz,” Proc. 2002 IEEE Ultrasonics Symposium, pp.969-972, 2002.

國際替代計量

氮化鋁薄膜體聲波元件分析與研製

全文下載

主題瀏覽