A Study Of Key Technologies Of Precise Control Of Prober

Integrated circuit automation equipment-prober has been a hot spot of the wafer test field. Because of the small size of the die on the wafer, which can reach micron, the prober should keep a high positioning accuracy and movement accuracy in order to guarantee the accurate needle of die and probe and the accurate test. Thus, the key problem of this thesis is how to guarantee the high-precision control of prober, then to meet the requirement of micron position.The thesis comes from national 02 special-the key technology research of automatic prober about 12" wafer. Firstly, the thesis introduces the key structure and movement process of the prober s two main parts:Loader and Prober; then, the thesis researches precise control of three key components:the pre-alignment, the lifting mechanism of Z-axis and X-Y module, analyzes the multi-dimensional factors that influence the control precision and puts forward the corresponding technical scheme and algorithms; lastly, from the perspective of system implementation, the thesis achieves the real-time and accurate control of prober by CAN technology.Chapter 1 illustrates the development of IC industry, introduces the research status of Prober, refines the key technologies of Prober about precise control and describes research frame.Chapter 2 summarizes the structure and control process of Prober, illustrates the work process of pre-alignment, Z axis lifting and X-Y table and gives the control requirement and parameter index.Chapter 3 puts forward stepping motor subdivision drive uniformization technology and unbiased fitting circle algorithm on accurate pre-alignment. It adopts the constant amplitude uniform rotation drive technology of current vector and modifies and compensates the motor drive current with Newton interpolation to export uniform stepping value. On the other hand, the thesis adopts least square fitting circle matching the circular linear unbiased estimation and calculates the center coordinates and gap position. Compared to other methods, the algorithm provides more reliable data support for precise pre-alignment. Finally, the thesis puts forward the concept of offset angle, and lists formula in different situations to meet the requirements of pre-alignment.Chapter 4 analyzes the relationship of deformation, top force and drive voltage and researches the reason for repeatable positioning error in the technical level of accurate micro contact control between wafer and probe. It concludes the curve between z axis displacement and the force and fits the relational model between drive voltage and top force by the experiment so as to implement the precise micron control of the stepping motor. Finally for the actual working condition of the Z axis lifting, the thesis puts forward the concept of repeatable positioning accuracy and determines the displacement and velocity of z axis lifting.Chapter 5 adopts the grating ruler and MAP to form a dual-loop feedback on the technical level of precise control of the X-Y module. First of all, it introduces the X-Y platform system in brief; Secondly, Analyzes the edge scanning method which improves efficiency and accuracy greatly. Compared to traditional grid generation algorithm, the MAP algorithm based on the dynamic threshold ensures the uniqueness and comprehensiveness of map and provides data support for the X-Y module. Finally, the thesis demonstrates the superiority of dual-loop control.Chapter 6 solves the question of high precision control based on CAN bus on the level of system implementation. It represents a Prober system framework based on CAN control, designs hardware and software structure of the CAN node; mainly for the pre-alignment key module and Z axis lifting module, analyzes the advantages of CAN compared with the centralized control from the aspects of communication response time, step motor motion precision and driving voltage output discrete degree。Chapter 7 is the summary of the research point and the gives an outlook on future research directions.