The Research Of Vision System Based On Wafer Pre-aligner Robot

The vision system used for collection, detection and processing of wafer information is an important compoment of wafer pre-alignment robot, based on which the eccentric wafer can be located by alignment motion. The working ability of vision system is the key point for pre-alignment robot to achieve high-precision positioning and alignment.Based on the basic machine of robot, the research in this paper has established a vision system responsible for 300mm (i. e.12 inch) wafer information detection and processing using linear CCD as the main image sensor. Because of the new kind of image sensor and alignment method being used instead of CCD camera, the system gets rid of the complicated algorithm and the weakness of hard promotion. At the same, a new way has been explored to make the vision system more simple and robust than systems before.In this paper, firstly the working principle of vision system is proposed according to the analysis of existent wafer pre-alignment robot products and the technology of vision system applied in other industrial systems, which conclude two parts named light information collection principle and wafer edge identification principle.Then, based on the working principle, the general solution scheme of vision system is put forward, and the structure and application program of system has been designed. The whole scheme is consist of background light projection part, information collection part, procession part and motion control part. The background light projection part is made up of LED array and light divergent materials. The information collection part is made up of linear CCD sencor and complex programmable logic device (i. e. CPLD) to design the circuit of signal driver and detected. The A/D card is used for collection of edge angle information and convention of data. The motion part has taken the PCI motion control card and step motors as the main execution tools to realize the pre-alignment of wafer.At last, it is explored a new idea of vision information processing in the paper, which can be used in the vision system of wafer pre-aligner to obtain the special area of wafer edge, and then concentrate them to some feature points by which the wafer can be located.The research of vision system based on wafer pre-aligner robot also make a conclusion about the problem and deficiency durning the period of R&D, and give the prospect of further work as well as finishing most of the expected target about whole system.