A typical example of the conventional art is disclosed in U.S. Pat. No. 4,726,689, in which a plurality of exhaust grooves are provided on a housing for a direct air bearing disclosed therein, with several of the grooves nearest a vacuum chamber being exhausted by the vacuum pump and the groove furthest from the vacuum chamber being opened to the atmosphere.
However, the conventional art described above has several disadvantages.
The exhaust system of the conventional art requires a large number of pumps in order to operate properly, which increases the size and weight of the bearing. Moreover, the exhaust system is located outside the vacuum chamber, which is unsuitable for use with a stage capable of two-dimensional movement like the XY stage.