Research On The Embedded Control System Of Wafer Pre-Alignment

In the 21st century,the microelectronics is still one of the basic technical for the information industry. The lithography is an important device for the microelectronics manufacturing. It is one of the key technologies to drive the IC manufacturing forward and it is widely used in the fields such as electronic encapsulation, photo-electricity equipment, detector, MEMS equipment, display and so on.This work is partially supported by the High Technology Research and Development Programme of China. The main content of the research is to design an embedded control system for 12-inch wafer pre-alignment.The wafer processing system is an important subsystem of the lithography, the wafer pre-alignment system is the most important subsystem of the wafer processing system, and the precision of the pre-alignment will directly affect the precision of the wafer's exposal. So, the requirement of the wafer pre-alignment system's movement and control precision is very rigorous, that will make the cost of the system very high. Therefore, it is meaningful to design a wafer pre-alignment system with the characteristic such as miniaturization and integration.Firstly,the structure of the wafer pre-alignment system is ascertained based on the analysis of the function and flow of the system. After that, the detected algorithm were selected, the Least Square Circle fitting approach was used for calculating the center and radius of the wafer, the edge flexion method was used for detecting the range of wafer notch, the arc fitting approach was used for calculating the notch's center. At last, the tasks of the embedded control system were obtained.Next, the digital signal processor chip TMS320LF2407A of TI was selected to use as the MCU in the embedded control system. Then, the functions of the embedded control system were fixed based on the tasks of the system, and the analysis of the control system's functions was present. After that, the hardware circuit of the control system was designed. At last, the software of the control system was designed, which was based on the detected algorithm. The designed embedded control system can be used to control the wafer pre-align even it is divorced from the PC, which is very helpful for the wafer pre-alignment system developed to miniaturization and integration.At last, the precision analysis of the wafer pre-alignment system was done, which confirmed that the request precision of the system was satisfied by the design. Then, the embedded control system was used to control the wafer pre-alignment system, and the experiment of wafer pre-align was done。The experiment results show that the repeatability of the orientation is 6.46μm, and the average time of the pre-alignment is 28s. So the experiment validated the design of the embedded control system of wafer pre-alignment system.