微纳电子技术

为满足快速准确测量分子束外延(MBE)生长的GaAs表面椭圆缺陷,提出了基于表面颗粒度扫描仪(Surfscan)测量椭圆缺陷的方法。根据理论计算,将Surfscan的测试模型由球形优化为更适用于椭圆缺陷的椭球形测试模型。由于椭圆缺陷的长轴基本都沿[1 ■0]方向,通过旋转晶片,分别沿着外延片的[1 ■0]和[110]晶向上进行激光扫描,测量外延片表面缺陷的尺寸、位置和数量,并通过Surfscan的数据分析系统读取选取椭圆缺陷的长轴和短轴尺寸,然后利用椭球形测试模型计算出所选取椭圆缺陷的长轴和短轴尺寸,与光学显微镜测试结果比较发现,Surfscan测试的原始数据与光学显微镜测试结果差别较大,而经椭球测试模型优化后的结果与光学显微镜测试结果一致;利用两次扫描的缺陷尺寸和数量的变化以及椭圆缺陷的长短轴比,能够计算出椭圆缺陷的数量和占总缺陷的比例,与光学显微镜测试结果较为一致。相比于光学显微镜测试外延片缺陷用时几十分钟,Surfscan测试只需要10 min左右就可完成,缩短了测试时间,并且可以扫描样品的整个表面,减少了人为因素的影响,重复性更好,满足生产需要。

In order to quickly and accurately measure the oval defects on the surface of the GaAs wafer grown by the molecular beam epitaxy(MBE),a method of measuring the oval defects based on Surfscan was proposed.According to the theoretical calculation,the test model of Surfscan was optimized from sphere to ellipsoid,which was more suitable for oval defects.Because the long axis of the oval defect is basically along the[1 ■0]direction of GaAs wafers,by rotating the wafer,the size,poisition and quantity of the defects on the surface of the epitaxial wafer were measured through the laser scanning along the crystal orientations of[1 ■0]and[110],respectively.And the sizes of the long axis and short axis of the selected oval defects were read through the data analysis system of Surfscan,and then the spheroidicity test model was used to calculate the sizes of the long axis and short axis of the selected oval defects.Compared with the test results of the optical microscope,it is found that the original data of Surfscan is quite different from those of the optical microscope,while the optimized results of the spheroidicity test model are consistent with the test results of the optical microscope.The number of oval defects and the proportion of which to the total defects can be calculated from the changes of the size and number of defects in two scans and the ratio of the long axis to short axis of the oval defects,and the result is very consistent with that of the optical microscope.Compared with tens of minutes to test the oval defects of the epitaxial wafer by the optical microscope,it takes about ten minutes to complete the test by using Surfscan.The test time is shortened and the whole wafer is scanned,which reduces the influence of human factors,improves the repeatability and meets the production requirement.