The device comprises an object table (3) mounted on an adjustable support (2) inside the X-ray vacuum chamber (1). The movable support is linked to the chamber and to the support structure (7) by a first rubber membrane (9). The adjustable supporting structure is terminated by a vacuum wall (11) at the bottom, spaced from a second vacuum wall (12) to form a secondary vacuum chamber. The two walls are separated by a second rubber membrane (10). The secondary vacuum chamber is linked to the main vacuum chamber by a vacuum line (15) to equalise the pressures. The object, comprising a resistible covered substrate and a mask is held on the object table via a support layer and a pressure ring which prevents rotation. The adjustment comprises fine and coarse adjusting supports.
