Temperature compensation of liquid FBAR sensors
Temperature compensation of liquid FBAR sensors
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DOI：
10.1088/0960-1317/17/3/030
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发表时间：
2007-03-01
影响因子：
2.3
通讯作者：
Katardjiev, I.
中科院分区：
文献类型：
--
作者：
Bjurstrom, J.;Wingqvist, G.;Katardjiev, I.
在这项工作中，我们展示了在温度范围为25℃-95℃的复合Al/AlN/Al/SiO2薄膜体声谐振器（FBAR）中几乎完全的二次谐波剪切模式的温度补偿。该模式的主要优点是在液体中具有更高的Q值以及更高的频率，因此对于传感器应用具有更高的分辨率。出于比较的原因，这些研究中也包括了非补偿基剪模式。当在空气和纯水中工作时，这两种模式都具有特征。研究了Q值、机电耦合、耗散和灵敏度等特性。对于由2 μ m厚AlN和200 nm厚Al电极组成的氧化层厚度为1.22 μ m的FBAR，可以观察到二次谐波剪切模几乎完全的温度补偿。因此，在上述温度范围内，非补偿基频剪切模式（1.25 GHz）的测量频率温度系数（TCF）在-31和-36 ppm°C-1之间变化，而补偿二次谐波剪切模式（1.32 GHz）的温度系数在+2 ppm°C-1和-2 ppm°C-1之间变化。当在纯水中运行时，前一种类型的Q值和耦合系数k(t)(2)分别约为180和2%，而对于二次谐波，这些值分别为230和1.4%。
In this work we demonstrate a practically complete temperature compensation of the second harmonic shear mode in a composite Al/AlN/Al/SiO2 thin film bulk acoustic resonator (FBAR) in the temperature range 25 degrees C-95 degrees C. The main advantages of this mode are its higher Q value in liquids as well as its higher frequency and hence higher resolution for sensor applications. For comparative reasons the non-compensated fundamental shear mode is also included in these studies. Both modes have been characterized when operated both in air and in pure water. Properties such as Q value, electromechanical coupling, dissipation and sensitivity are studied. An almost complete temperature compensation of the second harmonic shear mode was observed for an oxide thickness of 1.22 mu m for an FBAR consisting of 2 mu m thick AlN and 200 nm thick Al electrodes. Thus, the measured temperature coefficient of frequency (TCF) in air for the non-compensated fundamental shear mode (1.25 GHz) varied between -31 and -36 ppm degrees C-1 over the above temperature range while that of the compensated second harmonic shear mode (1.32 GHz) varied between +2 ppm degrees C-1 and -2 ppm degrees C- 1 over the same temperature interval. When operated in pure water the former type shows a Q value and coupling coefficient, k(t)(2), around 180 and 2%, respectively, whereas for the second harmonic these are 230 and 1.4%, respectively.