Research On The Measurment Of Diameter Of Crystal Based On Image Processing Technology

Silicon single-crystal is the vital material of manufacturing integrated circuits and solar batteries.As the semiconductor industry in China develops rapidly, the consumption of Silicon single-crystal in China will be the world's second largest behind US. Currently the production of Silicon single-crystal in China meets only 6% demands of China's consumption, and it accounts for mere 1% of world's production. The crystal furnace is the main equipment manufacturing Silicon single-crystal. Nowadays large diameter Silicon single-crystal which is highly needed in China is manufactured all by the foreign automatic crystal furnaces. The technology of diameter measurement based on CCD is the core technology of automatic crystal furnace which is monopolied by several foreign companies. The homemade semi-automatic crystal furnaces using the technology of infrared measurement indirectly are unable to obtain the authentic diameter of Silicon single-crystal, which results to the low efficiency and the poor quality.As the consequences, the production of large diameter Silicon single-crystal can't meet the great needs in China which is growing fast. This paper focuses on the technology of diameter measurement based on image processing, which will improve the technology of manufacturing Silicon single-crystal, especially the Silicon single-crystal of large diameter. As a result,the domestic consumption of semiconductor industry which growing fast could be fulfilled completely. This technology breaks the monopoly of technology by foreign companies.The diameter measurement system uses the structures of two CCD cameras. The images of Silicon single-crystal are captured by two CCD cameras with different focuses through the equipment of heat isolation, one of which is the seeding step of the growing of single-crystal, and the other is the constant diameter step.The digital signals are transfered from the analog image signals by the image capture card, which are filtered by intermediate filter to reduce the fuzzy edge information. The image edge of the crystal is detected by the Sobel edge detection algorithm and automatic tracking algorithm rapidly and then apply the subpixel edge detection technology acquiring the precise location of single-crystal edge. Two functions are realized through the development of the algorithm, one of which is the achievement of the automatic track of Silicon single-crystral image in seeding step and the other is the measurement of the diameter of the partial circle in constant diameter step.The algorithm can obtain the authentic diameter of Silicon single-crystral so as to realize the automatic control of the crystal growing.This paper has five chapters. Chapter 1 is introduction, which concludes the purpose of the research and the basic knowledge. Chapter 2 is the hardwares of the image measurement system, which concludes the principles of the operation and the adoption of the CCD, lens and image collect card. Chapter 3 is the image analysis and calculation. CCD cameras capture the image signals of the growing process of Silicon single-crystal and the digital signals are transfered from the analog image signals by the image capture card. The digital signals are analyzed and calculated by the technology of image processing. The images of the Silicon single-crytal in seeding step are tracked by the technology of image automatic track. The diameter of the partial circle in constant diameter step is measured by the partical circle algorithm. Chapter 4 is the development of the software of image measurement system. Under the circumstance of Visual C++ 6.0, the software is developed by the function library MIL8 attached to Matrox-meteor2. Chapter 5 is summary, which gives an expection of the further research.