Patent Number: 050013513
Section: description

An object holder as shown in the FIG. 1 comprises a supporting plate 2 on which an X-guide 6 is mounted, preferably by way of a bracket 4 connected to the rear side. An X-transporter 8 is displaceable along the X-guide, for example in known manner by means of rollers 9, over a distance of up to, for example 50 mm or more. The X-transporter 8 is driven by a motor 10 via a transmission 12. In order to save space, the motor 10 is arranged parallel to the X-guide, but this is irrelevant for the invention. On a side which faces the supporting plate 2, FIG. 1A the X-transporter 8 is provided with preferably three magnets 16 (for kinematic reasons), which magnets bear on the supporting plate via intermediate spacers 18 and are pressed against the supporting plate by the magnetic force produced by the magnets. It is thus achieved that the X-transporter always moves exactly parallel to the supporting face 14. The flatness of the supporting plate 2 at the area of the supporting face determines the accuracy of displacement. Such a plate, being made of a magnetic material in order to realize the magnetic pressing force, can be worked so as to be flat in an extremely accurate as well as comparatively inexpensive manner. A layer against corrosion of notably the supporting face can be locally provided. If desirable, in order to achieve an adjustable pressing force use can also be made of magnets to be energized by coils, a minimum energization being substained in order to prevent the transporter from coming loose from the supporting plate; this can alternatively be ensured by a permanent sub-magnet. The X-transporter supports an Y-guide 20 for guiding an Y-transporter 22 which is displaceable along the Y-guide, via wheels (not shown), in exactly the same way as the X-transporter. The Y-transporter is also pressed against the supporting face 14 of the supporting plate 2 by way of magnets 16 and spacers 18 (not separately shown). Therefore, also the Y-transporter will always move parallel to the supporting face 14 and rotation or tilting errors will not be summed. Rotations about an axis transversely of the supporting plate are determined as a function of the degree of straightness of the guides; such straightness can also be comparatively simply realized. The Y-transporter is driven by a motor 24 which drives a spindle 28 via a transmission 26. The Y-transporter supports an object table 30 on which an object, for example a wafer can be mounted, for example on supporting points 32. In the embodiment shown the object table 30 is rotatable about an axis 36 extending transversely of the supporting face 14. To this end, the supporting plate supports a gearwheel 38 which is driven by a motor 40, via a spindle 42 which is supported by a holder 44 and which realizes a rotation of, for example up to 360.degree.. As a result of this construction, an object arranged on the object table can be rotated into any desirable X-Y position in the radiation beam path. To this end, the rotary shaft 34 of the supporting plate is connected to a support 46 for the object holder. Via this support, the object holder can be mounted on or in an apparatus, for example an X-ray analysis apparatus, a wafer inspection apparatus and the like. When the object table is mounted so as to be tiltable about an axis 48 parallel to the supporting face as shown, the rotary shaft 34 is coupled via a bracket 50. Using a drive motor not shown, the bracket 50 is tiltable, together with the supporting table and the X-Y translation mechanism, through an angle of, for example plus and minus 10.degree. with respect to a vertical zero position of the supporting plate. In order to offer free passage to a radiation beam, bushes 52 for tilting are provided with lateral apertures 54. An object carrier in accordance with the invention can be successively used in X-ray analysis apparatus, in wafer inspection apparatus and the like where an object carrier of the described kind can be mounted on or in such an apparatus by means of the support 46. An object to be examined may then also be accommodated in a space to be evacuated.