Development of Line-Focus-Beam Acoustic Microscopy System for Evaluation of Electronic Device Materials

研制了一种适用于电子器件材料定量表征的线聚焦光束声学显微镜系统。从测量精度的角度出发，对机械精度和温度等重要问题进行了实验和理论探讨。研究表明，稳定LFB系统中水耦合液的温度对精确测量至关重要，而精确测量是通过测定泄漏表面声波（LSAWs）在水/样品边界的传播特性来实现的。本系统已安装在温度控制在23<正负>0.1^ C左右的室内。据估计，LSAW速度测量的相对精度在某一点优于<±>0.005%，在直径3英寸的扫描区域优于<±>0.02%。该系统已用于研究LiNbO_3和LiTaO_3压电晶体的弹性性能。研究了128^ YX LiNbO_3晶圆中Li/Nb的化学组成比与漏声表面波速度之间的关系。LSAW的速度测量已经对从一系列晶体生长中获得的商业晶圆进行了测量。由于成分的变化，检测到0.092%的微小变化。经计算，该生产线的“有效”同分成分为48.440 Li_2O mol%，密度为4647.4 kg/m^3。用该体系考察了工业制备过程中存在的X-112.2^ Y LiTaO_3的弹性性能问题。各种类型的弹性不均匀性已被定量地检测为LSAW速度的显著变化。在一些晶圆中，观察到LSAW速度的大变化，约为2.5%，这对应于单域和多域速度之间的差异。其中一个原因是晶圆制造过程中的极化过程。其中一个潜在的应用是薄膜表征。本文提出了一种利用泄漏Sezawa波和伪Sezawa波在截止区域附近的传播特性以及泄漏瑞利波的传播特性来确定薄膜材料弹性常数、密度和厚度的新方法。在熔融石英上制备的金膜样品，其硬度常数C_<44>，密度比多晶块金的硬度常数C_<44>，分别小11%和5.5%，厚度为6370A。少

A system of the line-focus-beam (LFB) acoustic microscope applicable to quantitative characterization of electronic device materials has been developed. Some serious problems, such as mechanical precision and temperature, has been experimentally and theoretically discussed from the point of view of measurement accuracy. It has been shown that stabilization of the temperature of coupling liquid of water in the LFB system is most important for accurate measurements, which are carried out by determining propagation characteristics of leaky surface acoustic waves (LSAWs) on the water/sample boundary. The system has been installed in a temperature controlled room around 23<plus-minus>0.1^ﾟC. The relative accuracy of LSAW velocity measurements has been estimated to be better than <plus-minus>0.005% at a point and <plus-minus>0.02% over a scanning area of 3-inch diameter.The system has been applied to investigate the elastic properties of piezoelectric LiNbO_3 and LiTaO_3 crystals. Experiment … More al relations between chemical composition ratios of Li/Nb and leaky surface acoustic wave (LSAW) velocities for 128^ﾟYX LiNbO_3 wafers have been determined. LSAW velocity measurements have been carried out for commercial wafers obtained from a series of crystal growths. Small changes of 0.092% have been detected due to the compositional variation. It has been estimated that the "effective" congruent composition in the production line is 48.440 Li_2O mol% with the density of 4647.4 kg/m^3. A serious problem regarding the elastic properties of X-112.2^ﾟY LiTaO_3 during industrial preparation has been examined with the system. Various types of elastic inhomogeneities have been detected quantitatively as a significant variation of LSAW velocities. In some wafers, large changes, about 2.5%, in LSAW velocities have been observed, which have corresponded to a difference between the velocities for single- and multi-domains. One of the causes has been found to be in the poling process during wafer fabrication.One of the potential applications is thin-film characterization. A new method of determining the elastic constants, density, and thickness of thin-film materials has been developed using propagation characteristics of leaky Sezawa and pseudo-Sezawa waves in the neighborhood of the cut-off region, in addition to those of leaky Rayleigh waves. It has been demonstrated for a sample of gold film on fused quartz that the values of the stiffness constant, C_<44>, and density have been, respectively, about 11% and 5.5% less than those for polycrystalline bulk gold, and the thickness has been determined as 6370A. Less