Research On Wafer Pre-alignment Control System

Integrated circuit (IC) manufacturing is a high-tech information industry, and its rapid development has changed people’s lives. IC manufacturing involves lithography, etching, oxidation, diffusion, CMP and other processes, each process requires different devices, lithography is one of the essential manufacturing equipment. Wafer pre-alignment is an integral part of the lithographic machine, which for the first time the precise positioning of the wafer, the positioning accuracy has a direct impact on the production line.Based on the fully research at home and abroad on the basis of all kinds of wafer alignment system, this paper developed an optical wafer alignment device cooperationed with the mechanics, it has the characteristics of miniaturization, integration, high precision, high efficiency, and able to complete the precise localization of8inch and12inch wafer. At the same time, the device can also automatically handle issues beyond the scope of the wafer eccentric, eccentric wafer can be done automatically adjust the positioning continues.Firstly, the design of work processes and the pre-alignment device wafer; then according to the functional requirements for the various subsystems of the selection and design of the device to determine the combination of the mechanical structure. Motion positioning system device uses a stepper motor with ball screw drive plus subdivision completed precise control; simultaneously, including the level of X, Y-axis, vertical axis and the axis of rotation axis control system, not only simplify the algorithm, but also to ensure safe working of the system. Stepper motor control using programmable multi-axis motion controller (Turbo PMAC Clipper) to perform control functions, complete the precise positioning of the wafer. In the design of the detection system, using high-precision laser displacement sensors to detect light barrier the length of the wafer rotation, and analyzed circle fitting algorithm. Error analysis and experiments validate the design of the device to achieve the goal.