Development of a Hydrostatic Bearing in High Vacuum Using an Ionic Liquid for a Semiconductor Fabrication Device

A hydrostatic bearing using ionic liquid (IL) has been developed to float semiconductor wafers in a high vacuum chamber. In semiconductor manufacturing, it is important to suppress overheating of wafers and maintain a constant temperature distribution. This method aims to achieve uniform temperature distribution by supplying IL from the backside of the wafer to float it, thereby without mechanical contact. However, since there are no examples of wafers levitated by hydrostatic bearings using IL in a high-vacuum environment, the effect of circulating IL to the vacuum conditions such as vacuum pressure and outgassing were investigated in this study. Experimental results showed that the developed prototype machine was capable of maintaining a stable ultrahigh-vacuum of 10 -5 Pa and supplying sufficient pressure to levitate wafers even when 100 ml of IL was circulated.