S波段温度补偿型FBAR窄带滤波器的研制

Development of S-Band Temperature-Compensated Narrow-Band FBAR Filter

研制了一种以SiO_2材料作为温度补偿层的S波段温度补偿型薄膜体声波谐振器(FBAR)窄带滤波器。研究了SiO_2层厚度对FBAR温度漂移特性的影响,对不同厚度SiO_2层时的温度补偿特性进行了仿真。仿真结果表明,当Mo/Al N/Mo的厚度为0.15,1.35和0.15μm,SiO_2层的厚度为10 nm时,FBAR的频率温度系数(TCF)约为3×10^(-6)/℃。采用MEMS工艺制备了温度补偿型FBAR滤波器芯片并进行了测试。测试结果表明,滤波器的中心频率为2 492 MHz,中心插损为3.74 dB,3 dB带宽为17 MHz,相对带宽为0.68%,在2 477和2 507 MHz处阻带抑制分别为27.44和33.81 dBc。在三温(常温25℃、高温85℃、低温-55℃)对该滤波器的S参数进行了测试,计算得出频率温度系数为5×10^(-6)/℃。与未加入温度补偿层的传统滤波器相比,频率温度系数改善明显。

A narrow-band temperature-compensated film bulk acoustic resonator（ FBAR） filter for S band with the SiO2 material as the temperature-compensated layer was developed. The effects of the SiO2 thickness on the temperature drift characteristics of the FBAR were studied. The temperature-compensated characteristics at different thicknesses of the SiO2 layer were simulated. The simulation results show that when the thicknesses of the Mo/Al N/Mo are 0. 15,1. 35 and 0. 15 μm,respectively,and the thickness of the SiO2 layer is 10 nm,the temperature coefficient of frequency（ TCF） of the FBAR is about 3 × 10^-6/℃. Then the temperature-compensated FBAR filter chip was fabricated through MEMS process and was tested. The test results show that the center frequency of the filter is 2 492 MHz,the center insertion loss is 3. 74 dB,the 3 dB bandwidth is 17 MHz,the relative bandwidth is 0. 68%,and the stopband rejection at 2 477 and 2 507 MHz are 27. 44 and 33. 81 dBc respectively. The S parameters of the filter were measured at three different temperatures（ the room temperature of 25 ℃,the high temperature of 85 ℃ and the low temperature of-55 ℃）,and the calculated TFC is 5×10^（-6）/℃. The TFC is significantly improved compared with that of the conventional filter without the temperature-compensated layer.