Improvement of Isolated table Using Auxiliary Tank

Abstract

Semi-conductor lithograph machine have to be kept away from many kind of vibration, one of which is floor vibration, the isolation performance from floor to body vibrations is particularly called the transmissibility. Isolation vibration system is very important unit of lithograph machine for semi-conductor manufacturing. In recent years, the progress of semi-conductor is remarkable development, therefore outside vibration isolation performance became more important factor than current machine for total machine accuracy. Isolation vibration system is generally supported by air-spring, and isolated the main body from unnecessary vibration from outside, mainly from floor vibration. There is one of mechanical method in order to increase vibration rejection ratio, which is reduced the stiffness of air-spring by using auxiliary tank. Helmholtz resonance is caused by using auxiliary tank, and vibration rejection ratio become worse. In usual, as introduced in the Handbook, we can reduce the peak of Helmholtz-resonance by adjusting the aperture with the built-in the connected pipe. Furthermore, there is the best aperture as introduced in the Handbook. However there is no reference regarding the relationship between Helmholtz frequency and vibration rejection ratio. This paper firstly explains by analysis that there is no effect of auxiliary tank over Helmholtz frequency and over-damping for Helmholtz lead to no effect, it will prove there exist the optimization of damping in the end. Next, this shows experimental result, such as pressure response in the air-tank and vibration rejection ratio by using sintered metal as damping device.