Development of adaptive alignment system for spectroscopic ellipsometers

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Kökényesi Tamás
Department of Automation and Applied Informatics

My thesis is related to ellipsometry which is an optical metrology often used for material testing in semiconductor technology. With this methodology thickness and optical properties of thin layers can be measured. It is based on the fact that light's polarization state will change after reflection from a thin layer and this change depends on some properties of the reflective material.

The position of the measured sample can be adjusted manually or automatically. In the first case the user has to tune the sample holder so that the reflected light's intensity shall be maximal while it's symmetry error is minimal. In the case of automatic tilting systems this is done by a module without human interaction. The value of the product is increased when the sample alignment is done automatically.

During my thesis project I was committed to design an adaptive system which optimizes the position of the sample on the basis of the measured signal. My main tasks were to choose proper actuators for moving the sample holder, to construct a controller circuit which drives the actuators, to write a software which allows communication between the controller circuit and a PC, and to work out the concept of optimization of the sample's alignment.


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