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一、引言 众所周知,在硅片上能否生长“洁净”的介电膜是成功地制作MOS电路的关键,而膜的厚度、组分及均匀性决定了MOS器件的性能和参数。业已有许多方法可以测定介电膜的厚度。如比色法、腐蚀台阶干涉法及电容法等等。但是这些方法都有一些缺点,无论在精度和操作方便性方面都远不能满足日益发展的大规模集成电路工艺控制的需要。自从椭圆仪问世以来,由于其固有的光学精度及操作方便性,一直受到工业界的重视。椭圆仪的组成如图1所示,它有一个平行校正单色光源(或激光源),需要一个可转动的起偏器、四分之一波长片和检偏器,一个能在x和y方向平移和上下移动的样品台、一个光电检测器和消光计。初期的椭圆仪采用汞光源,因而需要滤
I. INTRODUCTION As we all know, the ability to grow a “clean” dielectric film on a silicon wafer is the key to successfully fabricating a MOS circuit. The thickness, composition, and uniformity of the film determine the performance and parameters of the MOS device. There are many ways to determine the thickness of the dielectric film. Such as colorimetric, corrosion step interference and capacitance method and so on. However, these methods have some shortcomings, which are far from being able to meet the needs of increasingly large-scale integrated circuit process control in terms of accuracy and convenience of operation. Since the advent of elliptical instruments, due to its inherent optical accuracy and ease of operation, has been the industry’s attention. The ellipse consists of a single, parallel-corrected monochromatic source (or laser source) as shown in Figure 1. It requires a rotatable polarizer, a quarter-wave plate and an analyzer. A sample stage that is translated in direction and up and down, a photodetector, and an extinction meter. The initial ellipsometer used mercury light sources, which required filtration