Research On Design And Dynamic Characteristics Of Motion Stage For Wafer Inspection

The high-precision motion stage as positioning carrier is the key equipment in wafer surface quality inspection. With the feature size continuously reducing and the wafer dimensions ever growing, it brings a severe challenge to structure design and dynamic characteristic of precision motion stage and its key components. How to improve the motion accuracy and detection efficiency of the precision motion stage becomes the choke point which we need to conquer. In order to fulfill the urgent requirements of state key scientific research and engineering projects, motion stage the overall scheme and structure design, modeling of the key unit and the characteristics analysis of motion stage, motion performance of motion stage prototype are studied in this dissertation to provide theoretical basis and technical support for the dynamic design of the high-precision motion stage.According to the special requirements of wafer exchange in a vacuum absorption way, a new method of wafer auto-exchange is proposed, when the vacuum chuck without grooves moves relative to intermediate support. The spiral scanning paths is realized by motions of precise aerostatic spindle and direct drive feed in horizontal direction. Sub-micron positioning in the phase of scanning motion and long traval in the phase of wafer change is realized by the parallel drive of voice coil motor and gravity balance cylinders in vertical direction. A new multi-freedom precision wafer stage with floating bearing and linear guide, the electromagnetic drive and cylinder balancing mechanism is designed for wafer detection based on the above technologies and methods.In the structure design of aerostatic bearing spindles, the dynamic balance question are analyzed by theoretical derivation, experimental verification and simulation analysis to overcome the dynamic balance question, which provide some theoretical guidance to structural design of aerostatic bearing spindles. The dynamic models of thrust bearings and journal bearings are established by dynamic grid method, respectively. A new mesh updating method used in transient flow numerical simulations of the journal bearings is proposed according to the distortion causes of the elements. The aerostatic thrust bearings and journal bearings under different working parameters and structure parameters were studied in order to investigate the influence of dynamic characteristics. Theoretical analysis indicates that the change of the disturbance frequency and rotational speed have the most obvious impact on the dynamic characteristic. An experimental instrument is set up to investigate the dynamic characteristics of the aerostatic bearing spindle with aerostatic thrust bearings and journal bearings. Theoretical results and experimental results are basically coincident.According to sub-structure method, a dynamic modeling method on multibody systems is put forward for complicated motion characteristics of the motion stage with gas-solid-electromagnetic interactions. It is studied that dynamic unbalance and rotation speed influence on the axis orbit of aerostatic bearing spindle. The experimental stage is set up to identify the key dynamics parameters of the key components.The the natural vibration characteristic of the key components and system are studied by the combination method of theoretical analysis and simulation. The modal test of the precision motion stage is carried out. The results demonstrate that the dynamic modeling method and dynamics model is verified by modal experiment and errors of modal frequencies in the operating frequency domain is less than 10%. This study provides a basis for the subsequent structure optimization and the motion control design.The hardware system and the co-simulation of the electro-mechanical system of the principle prototype are designed and implemented. After a compound control method with feedforward compensation, the position tracking errors of R-stage, the position tracking errors of Theta-stage and the position errors of Z-stage are less than ±2?m, ±2arcsec and ±0.4?m, respectively. The maximal rotation speed is raised from 300rpm to 900rpm by optimized structural design to raise dynamic stiffness characteristic.Test results show that the motion stage not only achieve the desired technical requirements, but also the inspection efficiency of the motionstage advance 2 times.Structure dynamic design is the critical technology to realize the performance of motion stage. The research results conclusions are instructive and meaningful to structure design of the multi freedom mechanical motion stage and precision aerostatic bearing spidle.