Realization of virtual sub chamber on active controlled pneumatic isolation table with pressure differentiator

Pneumatic isolation tables are widely used in semiconductor production processes. Softer air-springs for the table are now needed because the semiconductor line width continues to decrease. In this paper, a new method for developing a soft air-spring virtually is proposed through feedback control of the differentiated pressure. Since the pressure change in the chamber is very small, it is difficult to obtain the differentiated pressure by discrete simultaneous differentiation of the pressure. Instead, this value is obtained through direct measurements by a newly developed pressure differentiator. The effectiveness of the proposed method is demonstrated experimentally.