STABILIZATION ON PROCESS OF EXIMER LASER BY IN SITU MEASUREMENT OF ENERGY

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Eximer laser that is in ultraviolet region processes materials without thermal reaction since photon energy is high in comparison with other laser such as carbonic acid gas and YAG.The process of eximer laser with optical-chemical reaction is referred to ablation. The eximer laser can sharply shape corner of hole. However energy of KrF eximer laser is unstable because of rust of gas and electrode. The energy value with respect to time has decreased and repeatability of processed shape has not been expected by using this process. It is possible to establish the micro process using eximer laser when the energy is controlled to be stable.In order to stabilize the energy value of laser, a feed back system that can perform in-situ measurement of energy is constructed in this study. Laser beam diameter becomes 1mm at energy meter through attenuator, which adjusts the energy value. Laser processes single crystal silicon because the purpose of this study is to establish method of process to fabricate micro-electro-mechanical systems. The laser beam is focused by a lens to becomes 120μm at the surface of silicon. Firstly we tried to stabilize the energy distribution using beam profiler. Secondly the energy with respect to time is controlled to be constant value using feedback control system consists of the energy meter and the attenuator built in a stepping motor. The laser energy can becomes stable when this feedback control system is used. Finally repeatability in terms of processed shape can be obtained through use of this control system.