Actuation System Design for a 3 DoF Contactless Wafer Stage

Silicon wafers are getting bigger and bigger in the production line, aiming for faster manufacturing, lower cost and higher yield. The handling/transportation technique is becoming more and more critical during the production. As the wafer is being handled with physical contact there is always risk of damage and contemination coming from the contact surface. Contactless wafer stage utilizes a thin film of pressurized air to support the wafer, provides wafer handling without physical contact, hence reducing the risk of damage and contamination. A special contactless 3DoF wafer stage called "the Flowerbed" is developed by H.P.Vuong during his PhD research. This flowerbed has a creative mechanical design to combine the wafer support and driving function, so that the wafer can be supported and driven by pressurized air with 3 degrees of freedom (x-y-theta). The goal of this MSc research is to design an actuation system for the Flowerbed, and design a special pneumatic actuator specific for this application. Two actuation configurations are discussed and the concept of 3-RPR parallel manipulator is chosen. Pneumatic actuator is chosen to be the type of actuator in this research. This pneumatic actuator has to be specially made, because the requirement of the actuators is, that it should have a stroke of 80 micro meters, with a maximum force of higher than 140N, and the required bandwidth is 150Hz. Such pneumatic actuator is rarely seen and is not available. A model is developed for this special pneumatic actuator, and is validated by test setups. Further development is made by a design with piezo buzzer. This piezo buzzer is implemented as a low cost valve with high performance, and the use of piezo buzzer makes it possible to integrate the valve into the actuator housing, hence further reduce the cost and improve the performance. A prototype is made to demonstrate the feasibility of such kind of pneumatic actuator. This prototype meets the requirement of the actuator and has very good performance for small range of stroke. However due to the weakness of the pneumatic actuator, the performance of large stroke must be improved. The knowledge developed in this research is summarised as a design method, and a GUI toolbox is made using MATLAB. This toolbox can be used to assist the design of such actuator, reducing the difficulty and provides assist for further research.

Subject

pneumatic
actuator
contactless
wafer
stage
piezo
low cost
RPR
valve
orifice
compressed air

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master thesis

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