Langasite and langatate nonuniform material properties correlated to the performance of SAW devices

Proceedings of the 2001 IEEE International Frequncy Control Symposium and PDA Exhibition (Cat. No.01CH37218) Pub Date : 2001-06-06 DOI:10.1109/FREQ.2001.956194

R. Fachberger, T. Holzheu, E. Riha, E. Born, P. Pongratz, H. Cerva

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引用次数: 7

Abstract

Material properties of Langasite (LGS) and its homologous compounds, e.g., Langatate (LGT) have been investigated employing lattice constants measurements revealing that the micro structured growth striations affect the a and c-parameter of the unit cell. Thus deviations off the congruent melt composition of the crystal are assumed. Transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDX) exhibit amorphous inclusions having a nearly identical chemical composition as the surrounding crystal. X-ray topography (XRT) has been applied to correlate the crystal quality of 3" LGS and LGT wafers including defects and transverse growth banding (TGB) with SAW frequency shifts. Evaluation of the RF-signal of SAW test devices showed frequency deviations of about 1000 ppm even within one wafer. The pattern of the frequency shifts is related to the orientation of the TGB. Local accumulations of defects, e.g., dislocations, however, did not cause observable interference with the SAW frequency.

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Langasite和langatate非均匀材料的性质与SAW器件的性能相关

利用晶格常数测量研究了Langasite (LGS)及其同类化合物Langatate (LGT)的材料性质，揭示了微结构生长条纹影响单元胞的a和c参数。因此，假定晶体的熔体组成偏离一致。透射电子显微镜(TEM)结合能量色散x射线光谱(EDX)显示出与周围晶体具有几乎相同化学成分的非晶夹杂物。利用x射线形貌(XRT)分析了3" LGS和LGT晶圆的晶体质量，包括缺陷和横向生长带(TGB)与SAW频移之间的关系。对声表面波测试设备的射频信号的评估显示，即使在一个晶圆内，频率偏差也约为1000ppm。频移的模式与TGB的方向有关。然而，缺陷的局部累积，例如位错，不会对声表面波频率造成可观察到的干扰。

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Proceedings of the 2001 IEEE International Frequncy Control Symposium and PDA Exhibition (Cat. No.01CH37218)

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