Research On Wafer Pre-Alignment System

In the 20th 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. The wafer processing system is an important subsystem of the lithography, which consists of a wafer transmission system and a wafer pre-alignment system.This work is partially supported by the High Technology Research and Development Programme of China. The main content of the research is to design and manufacture a system that is fit for 12-inch wafer pre-aligning.In the function decision and structure design, the function and the flow of the wafer pre-alignment system are analyzed,the system architecture is selected and the precision of this system is analyzed, the driving mode and the system structure are fixed, and then the motor and raster are selected. At the same time,the structure of parts is designed on consideration of the request and the function of the vacuum grasping of wafer.In the wafer-cycle fitting algorithm, comparing with Circumgyration Radius approach, Track Fitting approach, and Least Square Circle Fitting approach. In the wafer pre-alignment system, the wafer square fitting algorithm-Least Square Circle Fitting approach, based on optical linear CCD sensor, as well as the theoretical error analyze of this algorithm. In the wafer notch detecting part, edge flexion method is adopted to find the notch range, then calculating the notch center by means of arc fitting.In the system controlling, GALIL DMC2143 motion control card is selected in the system, then adjust the piezoelectricity motors PID parameters and control them. and AD-LINK ACL-8112HG data acquisition card is used in gas road exchanging controlling to make this exchange reposefullyIn the system experiments, tests are given by system control programme. Scale the error of center and notch in the system. Calculate the last precision of...