Development of stage temperature control for vacuum lithography tool - Two approaches of fine temperature control

It has become a recent trend to apply a special environment into a lithography tool, for instance, immersion, EPL (Electron beam Projection Lithography) and EUVL (Extreme Ultra Violet Lithography) in order to exposure less than 22nm line and space at semiconductor industry field. For a cooling system that a heater is surrounded by metal can and a coolant is supplied into the can by using movable tubes, not only flexibility, damping, durability, particle protection and anti-liquid, etc, but also pressure-resistance, low outgasing and low leak from connections, etc might be strongly taken into account for vacuum lithography. Especially, because a coolant leak is very critical for EUVL in which a partial pressure of several molecular is strictly restricted, a special tube and joint have to be required in the case of liquid cooling system. On the other hand, a gas cooling can be one candidate because of a lower leak damage, however it is necessary to compensate its low cooling efficiency of gas system by using temperature feedback control. In this paper, two guide lines of a cooling mechanism for wafer and mask stage of vacuum compatible tool, a liquid cooling and gas cooling system are introduced.