Research And Implementation By Circuit Of Positioning Algorithm For Wafer Pre-align System

IC industry is booming nowadays,which drive the IC manufacturing process to update continuously.To meet the requirements of high efficiency and high precision,IC manufacturing process is also constantly to change to be more and more mechanical, automatic and intelligent.At the request of the enterprise, a set of positioning device is designed, which is applied to the enterprise’s wafer processing equipment.I studied the relevant literatures about the wafer pre-focus at home and abroad,and determined the overall scheme of the system in the second chapter according to the actual situation of chamfering machine. This design includes three aspects:embedded hardware circuit design,software design and algorithm design.The information of wafer’s edge points includes two aspects:the distance from the edge point to the center of the wafer and the angle. The detection of the distance is completed by linear CCD, and the detection of angle is completed by the photoelectric encoder.Hardware’s part is based on an ARM chip as the core,which completed sensor signal’s acquisition and storage by FPGA and high-speed AD,and completed the wafer’s edge detection by the linear CCD.It is based on static storage chip-IS61WV25616BLL as storage devices,and completed the signal subdivision by HCTL2020,and completed the communication with PLC through RS485 serial port.Software’s part, VHDL language was used to program on the FPGA in QuartusII9.0, and the C language was used to program on the microcontroller in the Keil4,to achieve the various functions with the hardware circuit.Algorithm’s part,the position of the circle’s center and the calculation of the wafer’s radius is conpleted by the least square circle method, and the position of the cutting edge is conpleted by equation of linear regression.Meantime,the calculation of the cutting edge length and other parameters of the wafer is finished.First of all,the functional testing was finished in the laboratory,then a lot of repetitive tests had been done at the scene. The performance of the positioning circuit,the change of the scene’s electric environment and the algorithm of the positioning accuracy had been improved constantly.The final positioning results basically meet the production requirements.