Nondestructive characterization of residual strain in large-diameter semiconductor crystal ingot using three-dimensional infrared photoelastic CT method

本工作的目的是开发一种新技术，通过该技术可以无损地表征大直径半导体晶锭（如硅和砷化镓）中残余应变的e维分布，然后将其用于实际应用。为此，我们研制了一种三维红外光弹性CT设备，在该设备中，沿z轴方向将直线偏振光光束引入圆柱形半导体晶锭中，并分析了透射光束的偏振特性，然后实际表征了lec生长的GaAs单晶锭、fz生长的无位错Si单晶锭和cz生长的Si单晶锭中的残余应变。由于原位生长的LEC-GaAs铸锭的圆柱形表面存在许多凹或凸沟槽，给红外光弹性测量带来了困难。然而，我们设计了一种新技术，可以在粗糙表面而非抛光镜面条件下对圆柱磨锭进行更多的光弹性测量。利用这一新技术，我们可以表征LEC-GaAs单晶锭中残余应变的拟三维分布。另一方面，我们可以在无位错的FZ-Si单晶锭上进行红外光弹性测量。结果表明，由于FZ-Si锭中的残余应变非常小，光学各向异性诱导的双折射比残余应变诱导的光弹性多。虽然在cz生长的Si锭中光学各向异性也占主导地位，但我们已经证明了残余应变诱导的双折射是可以测量的。红色通过引入沿[100]晶体学方向的探测红外光束。根据我们的工作，红外光弹性技术在研究大直径硅单晶的位错方面是非常有用的。少

The purpose of this work is to develop a new technique by which there e-dimensional distribution of residual strain in large-diameter semiconductor crystal ingots such as silicon and GaAs can be characterized nondestructively as standard ingot form and then for it to be intended for practical use. To do so, we have developed a three-dimensional infrared photoelastic CT equipment, in which a linearly-polarized light beam is introduced both along to the z-axis into a cylindrical semiconductor crystal ingot and the polarization of the transmitted light beam is analyzed, and then pratically characterized the residual strain in LEC-grown GaAs single crystal ingots, FZ-grown dislocation-free Si single crystal ingots, and CZ-grown Si single crystal ingots.It was difficult for us to make the infrared photoelastic measurement in as-grown LEC-GaAs ingots, because there were many concave or convex ditches on their cylindrical surface. However, we have designed a new technique by which we can make … More the photoelastic measurement in cylindrically-grinded ingots under the condition of rough surfaces, not polished mirror surfaces. With this new technique, we become able to characterize pseudo-three-dimensional distribution of residual strain in LEC-GaAs single crystal ingots. On the other hand, it was possible for us to make the infrared photoelstic measurement in dislocation-free FZ-Si single crystal ingots. It was found that the birefringence induced due to optical anisotropy was dominated over that photoelastically induced by residual strain, since the residual strain was extremely small in the FZ-Si ingots. Although the optical anisotropy was also dominated in CZ-grown Si ingots, we have demonstrated that the residual-strain-induced birefringence can be measu.Red by introducing the probing infrared light beam along the [100] crystallographic directions. According to our work, the infrared photoelastic technique developed here is very useful in investigating dislocations in large-diameter Si single crystals. Less