The Method for Integrating FBAR with Circuitry on CMOS Chip Po-Hsun Sung Electronics Research & Service Organization, Industrial Technology Research Institute No.31, Gongye 2 nd Rd., 709, Tainan City, Taiwan, R.O.C, phsung@itri.org.tw Chi-Ming Fang and Pei-Zen Chang Institute of Applied Mechanics, National Taiwan University, Taipei, Taiwan, R.O.C Yung-Chung Chin and Pei-Yen Chen Chung-Shan Institute of Science and Technology, Taoyuan, Taiwan, R.O.C Abstract— The method is described to integrate the 3x2 ladder type film bulk acoustic wave (FBAR) filter on CMOS chip. The modified Mason equivalent circuit model is used to simulate the characteristics of FBAR. The filter is designed by insertion loss method to meet the requirements. Low noise amplifier (LNA) has been designed and manufactured by the UMC 0.18um process. By the use of post CMOS process, the FBAR filter structure can be realized on CMOS chip. Finally, the mass loading frequency trimming method can adjust the center frequency of FBAR. The feasibility of integration can be proved by this method. Keywords-Film Bulk Acoustic wave Resonator (FBAR), CMOS MEMS, Filter, LNA, Integration I. INTRODUCTION With the development of the wireless communication, many discrete components have been integrated by advanced RF technology. System-on-chip (SOC) and system-in-package (SIP) are also the solutions to resolve these problems. The integration method by the use of LTCC [1] and above IC integration [2] is also described in paper. In this paper, the modeling method of FBAR with the consideration of loss effect is introduced. By the use of this modified model, the performance of FBAR can be simulated exactly in design. In the RF front end, the FBAR is still a discrete component on the circuit board. The parasitic effect from bonding pad and package is still a problem in circuitry design. In order to demonstrate the feasibility of SOC concept, the FBAR filter integrated with LNA circuit has been designed and made. By the use of modified Mason equivalent model, the mechanical FBAR structure can be transformed into a circuitry block in RF circuit design software. So, we can simulate the performance of integration and tune the parameter of FBAR and LNA circuitry. The LNA circuit has been manufactured by UMC 0.18um 1p6M process. This process is suitable for RF circuit owing to the MIM capacitor and top metal layer inductor. The post CMOS MEMS process is introduced for realizing the FBAR on CMOS chip. The difficulties of post CMOS MEMS process are hard to alignment the die and the etching selectivity between piezoelectric layer and sacrificial layer. However, the frequency trimming is still a problem in manufacturing FBAR. Here, the mass loading of nano particles is taken for solving this problem. II. MODELING AND CIRCUIT DESIGN A. Modeling of Resonator A basic FBAR structure formed on a structure layer includes a piezoelectric layer sandwiched between bottom electrode layer and top electrode layer and loading layer as shown in Fig. 1. To solve the equation about acoustic wave propagating in bulk acoustic wave resonator with multilayer, there were many methods presented in the past. Among them, the exact solution of equivalent circuit model had been presented by Mason in 1948 [3]. However, the inclusion of transformer and a negative capacitance in Mason model imposes difficulties in circuit simulation software. Besides, the acoustic losses and electric losses of piezoelectric thin film, metal layers and structure layer are not also considered in conventional Mason equivalent circuit model. Figure 1. The schematic of basic multilayer FBAR structure In order to model the layered FBAR structure exactly, this paper adopts the concept of Mason model and KLM model [4] to build up FBAR equivalent circuit model shown in Fig. 2. By the use of network analytical method, the characterization of FBAR can be simulated by Matlab program. In order to modify the idea Mason equivalent circuit model, the loss and parasitic effect has been substituted into programmable simulation. Firstly, the imaginary part is added in the mechanical impedance (Z 0 ) of each layer and wave number (k). It is modified by the acoustic loss term which is related with quality factor Q and attenuation factor. Secondly, the 276 2004 IEEE International Ultrasonics, Ferroelectrics, and Frequency Control Joint 50th Anniversary Conference 562 0-7803-8414-8/04/$20.00 (c)2004 IEEE.