method of dark field

A dark field alignment system using optical dark field technique and reflecting the dark field wafer information toward the photomultipler tube is presented.

暗场对准技术是利用光学暗场成像原理和微光真空光电探测技术，使投影光刻硅片上的标记获得大幅值、高信噪比的对准信号通过双池偏差优化软件，借助计算机进行采样控制和数据处理，从而获得很高的对准精度。

From the experiment,it is shown that intensity of the pixel in dark frame follows the normal distribution.

其中热噪声Hn与读出噪声Rn最为核心,采用拍摄暗场帧的方法对其进行实验研究。