The design of a ceramic chuck with integrated mirrors
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Abstract
With electron beam lithography, a cutting edge technology has been developed that might introduce new possibilities in the design of chips. The word "might" has been used here because e-beam lithography is not yet available for the mass production market. One of the bottlenecks in the development of e-beam lithography is the positioning uncertainty of wafers with respect to the electron beams. A wafer positioning system is used to position wafers. The accuracy of the system is highly determined by a component, that mechanically couples the wafer with the position actuators and the mirrors that are used by the interferometers. This component is called the chuck. Topic of this project is the redesign of the chuck. The aim of this redesign is to reduce the position uncertainty caused by the chuck. In order to get to this result, a problem analysis has been performed that summarizes the bottlenecks in the positioning accuracy of a chuck. With respect to these bottlenecks, the performance of the present chuck has been analysed. The most critical bottlenecks in the present chuck turns out to be the optical quality and dynamic behaviour. This gives rise to the redesign of the chuck. In the concept development phase, 9 concepts have been created that promise to have a better overall performance. The most promising concept is a monolithic ceramic chuck with mirrors polished into 2 edges. Next to a great overall score on the estimated performance, the chuck design becomes simple which is a big benefit. A wafer table is mounted to the chuck with a kinematic mount. Expectations arise that stick slip might occur on the interface of the kinematic mount due to expansion if the grooves are integrated in the ceramic. An analytic model has been derived that theoretically assists the expectation. Two experiments have been performed, both suffer from measurement disturbances. Although these measurements were subject to errors, the data seems to confirm stick slip behaviour. Because of this, a third experiment is proposed. As a verification method, a set-up has been proposed to measure the actual performance of the present chuck and that of a ceramic chuck. This makes it possible to do a comparison of both concepts and select the best option.