An Ultra-precision Measurement System for Next Generation 400 mm Silicon Wafers

本研究的目的是开发一种精确的平面度测量系统，用于直径高达400 mm的大型硅片。该系统由二维（2D）斜率传感器单元，晶圆主轴，和传感器托架。晶片样品垂直安装在真空吸盘上，并可通过主轴旋转。2D斜率传感器单元由两个2D斜率传感器组成。2D斜率传感器单元放置在传感器托架上。它检测晶片表面上一点的2D局部斜率（X和Y方向局部斜率）。当晶片旋转时，2D斜率传感器由传感器托架沿沿着X方向移动以扫描晶片表面。在这种基于角度的测量系统中，传感器滑架的跨国误差运动（直线度误差运动）和晶片主轴的跨国误差运动（轴向误差运动）将不会影响传感器输出。基于误差分离的概念，可以从角度误差模型中分离出晶片表面的二维局部斜率， ...更多信息 使用斜率传感器的2D输出来测量传感器滑架（偏航、滚动）和晶圆主轴（角误差运动）的运动。通过对晶片表面的X方向局部斜率进行积分，可以得到晶片表面沿着径向的截面高度轮廓，通过对Y方向局部斜率进行积分，可以得到晶片表面沿着同心圆的截面高度轮廓。因此，整个晶片表面的高度轮廓可以通过组合这两个方向上的截面轮廓来评估。利用自准直原理研制了二维倾角传感器，实现了测量系统。利用位置传感器检测反射光斑在物镜透镜焦平面上的二维位置，得到二维局部斜率（角度）。为了使传感器尺寸紧凑，通过选择适当的位置感测器件来提高角度检测的灵敏度比使用具有较大焦距的物镜透镜更有效。结果表明，四分之一光电二极管是最好的高灵敏度的二维斜率检测。紧凑型原型斜率传感器被证实具有约0.01弧秒的分辨率。大尺寸硅片的平面度测量实验表明了该系统的可行性。少

The purpose of this study is to develop an accurate flatness measuring system for large silicon wafers with diameters of up to 400 mm. The system consists of two-dimensional (2D) slope sensor unit, a wafer spindle, and a sensor carriage. The wafer sample is mounted on a vacuum chuck vertically and can be rotated by the spindle. The 2D slope sensor unit consists of two 2D slope sensors. The 2D slope sensor unit is placed on the sensor carriage. It detects the 2D local slopes (X-and Y-directional local slopes) at a point on the wafer surface. The 2D slope sensor is moved by the sensor carriage along X-direction to scan the wafer surface while the wafer is rotating. In this angle-based measuring system the transnational error motions of the sensor carriage (straightness error motions) and the wafer spindle (axial error motion) will not affect in the sensor outputs. Based on the concept of error separation, the 2D local slopes of the wafer surface can be separated from the angular error mo … More tions of the sensor carriage (yaw, roll) and the wafer spindle (angular error motion) using the 2D outputs of the slope sensors. The cross-sectional height profiles of the wafer surface along radial directions can be obtained through integrating the X-directional local slopes of the wafer surface, and the cross-sectional height profiles along concentric circles can be obtained through integrating the Y-directional local slopes. The height profile of the entire wafer surface can thus be evaluated from combining the sectional profiles in these two directions. Two-dimensional slope sensors, which utilizes the principle of autocollimation, were developed to realize the measuring system. The two-dimensional local slopes (angles) are obtained through detecting the corresponding two-dimensional positions of the reflected light spot on the focal plane of the object lens using position-sensing devices. To make the sensor compact in size, it is more effective to improve the sensitivity of angle detection by selecting proper position-sensing devices than using an objective lens with a larger focal distance. It was shown that a quadrant photodiode is the best for highly sensitive two-dimensional slope detection. The compact prototype slope sensors were confirmed to have a resolution of approximately 0.01 arc-seconds. Flatness measurement experiments of large silicon wafers have been conducted to indicate the feasibility of the developed system. Less