压电晶圆厚度对声表面波器件性能的影响及改进方法研究

Research on the Influence of Piezoelectric Substrate Thickness on Surface Acoustic Wave Filters Performance and It’s Improvement Method

摘要:

钽酸锂（LiTaO₃，LT）为目前声表面波（SAW）滤波器普遍采用的压电晶圆之一。为控制 SAW 滤波器的制造成本和体积，制造时通常会采用更薄、价格更低的 0. 25 mm 厚的 LT 替代原来 0. 35 mm 厚的晶圆。然而，在滤波器设计结构相同的情况下，相较于 0. 35 mm 厚的 LT，采用 0. 25 mm 厚 LT 的 SAW 滤波器性能有所降低。针对该问题，首先建立了含封装粘片胶的电磁仿真模型，分别仿真了两种厚度（0. 35 mm、0. 25 mm）的压电基底在不同粘片胶厚度条件下的电磁特性；然后结合电磁、声学联合仿真优化了粘片胶的厚度，进而提升了 SAW 滤波器的仿真性能。实验结果表明，通过优化粘片胶厚度，可使 0. 25 mm 厚 LT 滤波器的性能优于 0. 35 mm 厚 LT 滤波器， 满足器件指标要求，该方案可推广至其他压电晶圆的 SAW 器件。

Abstract:

LiTaO₃（LT） is an excellent candidate for piezoelectric substrates in surface acoustic wave （SAW） filters. To reduce the manufacturing cost and size of SAW filters， a 0. 35 mm thick LT piezoelectric substrate needs to be replaced with one that is 0. 25 mm thick. However， using the same design structure deteriorates the performance of the device. To address this issue， this article establishes an electromagnetic simulation model that includes chip bonding adhesive and simulates the electromagnetic characteristics of two different piezoelectric substrate thicknesses （0. 25 mm and 0. 35 mm） with varying adhesive thicknesses. The adhesive thickness is then optimized by combining electromagnetic and acoustic simulations to improve SAW filter performance. Finally， experiments show that by optimizing the adhesive thickness， the performance of the filter using the 0. 25 mm piezoelectric substrate surpasses that of the original filter using the 0. 35 mm substrate， thus meeting device specification requirements. This technical solution can be further extended to SAW devices using other piezoelectric substrates.