The Development Of Wafer Prealigner

The Wafer Prealigner for integrate circuit(IC) manufacturing, used for compensating the location error of wafer handling robot in wafer handling system, is a sort of high-precision alignment device integrated with the subjects of mechanics, electronics, optics and computer science, which can detect and locate automatically the geometrical center and the notch or flat of the wafer accurately.With respect to the Wafer Prealigner, based on the survey of current status, a kind of optical Wafer Prealigner with the characteristics of the simple structure, low cost, upper alignment precision, practicality is developed, which can accomplish the high-precision alignment of wafer with the dimension of 300mm. Firstly, the general design scheme and the performance indexes of the Wafer Prealigner are presented. Then, according to the design requirements, mechanical noumenon, driving and pneumatic system design, vision system design as well as the control system design of the Wafer Prealigner are introduced respectively. Finally, the error analysis of the Wafer Prealigner is performed.The ball screw spline is used in the mechanical noumenon design and this structure can realize the moments of two degree of freedom in one axis, which makes the structure of the Wafer Prealigner more compact and increases the transmission precision of the system. In the sections of the driving and pneumatic system design, step motor and micro step driver are selected, which not only satisfy the precision request, but also increase the performance of the system and reduce the cost. Linear step motor is used to drive the horizontal alignment cell, which makes the structure more simply. In the part of vision system design, the hardware platform is composed of linear array light, cylindrical lens and linear array image sensor, then the algorithm of circle fitting method is carried on. In the section of the control system design, PC+MPC07 is used and the location is informed to the PC according to the vision system and control the step motor to accomplish the accurate location. In the section of the error analysis, machining error, drive error, pneumatic exchange error and vision detecting error are calculated, and the results prove that all the indexes satisfy the design requirement of the Wafer Prealigner.Along with the accretion of wafer diameter, the error of linearity and angle location increases continually due to the handling process. It is hard to satisfy the increase of manufacture precision, especially under the circumstance that our country so far has no such kind of production. So it is significant to manufacture a kind of Wafer Prealigner with the...