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

准分子激光处于紫外区，与碳酸气体、YAG等激光相比，其光子能量高，加工材料时不发生热反应。准分子激光发生光化学反应的过程称为烧蚀。准分子激光可以使孔的角形明显。但由于气体和电极的锈蚀，KrF准分子激光器的能量不稳定。能量值随时间的变化而降低，加工形状的可重复性也不期望使用该工艺。在能量控制稳定的情况下，利用准分子激光建立微过程是可能的。为了稳定激光的能量值，本研究构建了一种能够进行原位能量测量的反馈系统。通过衰减器调节能量值，激光束直径在能表处变为1mm。激光加工单晶硅，因为本研究的目的是建立制造微机电系统的工艺方法。激光束经过透镜聚焦，在硅表面达到120μm。首先，我们尝试使用光束轮廓仪来稳定能量分布。其次，利用步进电机内的电能表和衰减器组成的反馈控制系统，将能量相对于时间控制为定值。采用该反馈控制系统后，激光能量趋于稳定。最后，通过使用该控制系统，可以获得加工形状的重复性。

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.