Comparison of micromachined FBAR band pass filters with different structural geometry

• Main Authors: Park, J.Y., Lee, H.M., Lee, H.C., Lee, K.H., Ko, Y.J., Shin, J.H., Moon, S.H., Bu, J.U.
• Format: Conference Proceeding
• Language: English
• Subjects: Acoustic waves; Band pass filters; Electrodes; Film bulk acoustic resonators; Geometry; Insertion loss; Micromachining; Semiconductor films; Silicon; Wireless communication
• ISSN: 0149-645X; 2576-7216
• DOI: 10.1109/MWSYM.2003.1210553

In this paper, fully integrated FBARs (Film Bulk Acoustic Wave Resonators) and FBAR band pass filters have been designed, fabricated, and characterized for advanced mobile/wireless communication systems by using silicon bulk micromachining technology. Two different band pass filters are fabricated and compared with 7 bulk acoustic resonators in series and shunt connection. Various structures are also investigated for finding the better geometry of the FBAR BPF. In addition, dependency of the quality of AlN film on Mo bottom electrode is also presented. The developed AlN film has 1.9/spl deg/ of FWHM (full width half maximum) of rocking curve and approximately 70 MPa in tensile stress on top of the Mo electrode layer. The measured effective coupling coefficient, K/sup 2//sub effective/ is ranged from 6.8 to 7.3. The fabricated resonator has a quality factor of 1530, insertion loss of -0.45 dB, and return loss of -28 dB, respectively. Fabricated two different (Type-A and Type-B) band pass filters have insertion loss of -1.5 dB and -1.578 dB, return loss of -6 dB and -10 dB, stop band notch of -50 dB and -52 dB, bandwidth of 75 MHz and 70 MHz, 18 MHz and 32 MHz in separation between lower stop band notch and left edge of pass band, and chip size of 1.3 mm /spl times/ 1.5 mm, respectively.