Research on technique of grating nanometer-subdivision

摘要

In this paper, a new system and method of grating nanometer metrology are introduced. The system is made up of light resource, metrological grating, object lens of microscope, electronic-ocular based on CMOS image sensor, and personal computer. Firstly, metrological grating were irradiated by light resource. Secondly, the grating images on electronic-ocular based on CMOS image sensor. Thirdly, electronic-ocular gained the image and trans to the PC by USB. After gained the image, computer converts it to bitmap and processing. There are three steps of the grating subdivision.Firstly, digital image processing is used to set a soft-reticle over the bitmap. Position of the origin in a period is the result we want, and system resolution depends on pixels in a period. Secondly, pixels on gratings border will be calculated, analyzing any pixel coordinate and value, and using statistics and linear function to calculate more precision of the position of border. And thirdly, multi-origins and average effect of grating are used. In this system, higher measuring resolution based on higher quality gratings and clearer imaging system are obtained, and more pixels are processed in arithmetic. In the experiment system, period of grating is 0.02mm, object lens 40～60X, CMOS image sensor 352 X 288 pixels,and the resolution of subdivision 80nm. Many experiment data have been gained by using this system, and all measuring data are displayed on the screen, in real-time, and automatically recorded in disk. At last, analyzing these data, conclusion of the measuring resolution and precision accuracy is drawn.