Patent Number: 051503913
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 2 and 3 are a sectional view and a plan view, showing the structure of a portion around an aperture in an X-ray aligner according to a fourth embodiment of the present invention. Denoted in the drawings at 1 is a mask having a circuit pattern (exposure region) 2 to be transferred; at 3 is a wafer onto which the circuit pattern of the mask is to be transferred; at 4 is a base on which the mask is held fixed; at 5 is a wafer chuck with which the wafer is held fixed on a wafer stage (not shown); at 6a-6d are pickups each comprising a semiconductor laser for projecting light onto alignment marks AM formed on the mask and the wafer, a CCD line sensor for detecting diffraction light or the like from the alignment marks, which contains positional deviation information and the like; and at La-Ld are paths for the alignment lights. In this X-ray aligner as the wafer 3 is brought to the exposure position, a positional deviation between the mask 1 and the wafer 3 with reference to a predetermined standard positional relationship is detected on the basis of the outputs from the pickups 6a-6d. Then, on the basis of results of positional deviation detection, the wafer stage is driven to correct a positional deviation (gap, parallelism and the like) of the mask 1 and the wafer 3 in the Z-axis direction as well as a positional deviation of them in respect to the X, Y and .theta. directions. After such positional deviation correction, exposure light such as X-rays emitted from a SOR (synchrotron orbit radiation) source, for example, is projected from the above to the below in the Z direction in FIG. 2, namely, in a direction perpendicular to the sheet of the drawing of FIG. 11, whereby an image of the pattern of the mask is printed on the wafer. Denoted at 7a-7d are light blocking plates for defining the exposure region 2. Each of these light blocking plates 7a-7d is made of a material having a sufficient thickness such that, while the laser light projected from the pickup can path therethrough, almost all the X-rays (exposure light) are blocked thereby. Usable examples are X-ray resistive glasss such as BK-7R available from OHARA Inc. Japan and BK-7G25 available from JENAer GLASWERK SCHOTT & GEN. Denoted at 8a-8d are first stages for carrying thereon the pickups 6a-6d , respectively, each of which comprises a single-axis stage movable in a plane parallel to the exposure plane (X--Y plane) and in a direction parallel to corresponding one of the sides 2a-2d of the exposure region 2. The first movable stages 8a and 8c are movable in the Y direction, while the first movable stages 8b and 8d are movable in the X direction. Denoted at 9a-9d are second movable stages for carrying thereon the first movable stages 8a-8d , respectively, each of which comprises a single-axis stage movable in a plane parallel to the X--Y plane and in a direction perpendicular to corresponding one of the sides 2a-2d of the exposure region 2. The second movable stages 9a-9c are movable in the X direction, while the second movable stages 9b and 9d are movable in the Y direction. The first movable stage 8a and the second movable stage 9a cooperate and constitute a dual-axis stage for moving the pickup 6a in the X and Y directions. Similarly, the pair of single-axis stages 8b and 9b, the pair of the single-axis stages 8c and 9c and the pair of single-axis stages 8d and 9d, provide dual-axis stages, respectively, for moving the pickups 6b, 6c and 6d, respectively. The light blocking plates 7a-7d are mounted on the second movable stages 9a-9d , respectively, and they are set at those positions defining the aperture 10 corresponding to the exposure region 2, prior to the X-ray exposure. Alignment marks are formed at such positions that, when the blocking plates 7a-7d are aligned with respect to the exposure region 2, the alignment marks can be detected by the pickups 6a-6d , respectively. In this X-ray aligner, each dual-axis stage for moving corresponding one of the pickups 6a-6d , is provided by a combination of corresponding one of the single-axis stages 8a-8d each being movable in a direction (lateral direction) parallel to corresponding one of the four sides 2a-2d of the exposure region 2, with corresponding one of the single-axis stages 9a-9d each being movable in a direction (longitudinal direction) perpendicular to the corresponding one of the sides 2a-2d of the exposure region 2. Each of the single-axis stages 8a-8d is mounted on corresponding one of the single-axis stages 9a-9d , with the moving direction of each of the single-axis stages 9a-9d being confined only to the longitudinal direction. Additionally, the light blocking plates 7a-7d for defining the exposure region are mounted on the single-axis stages 9a-9d , respectively. In this manner, the stages for moving the pickups 6a-6d , respectively, are used also as the stages for moving the light blocking plates 7a-7d , respectively. This makes it possible to eliminate the necessity of using specific stage means exclusively for changing the aperture size. Also, the light blocking plates 7a-7d are mounted on the stages 9a-9d each being movable only in the longitudinal direction. This avoids the necessity of moving the stages 9a-9d and the blocking plates 9a-9d in their lateral directions even in such occasion where, as shown in FIG. 4, each alignment mark is formed at an end portion of corresponding one of the sides 2a-2d of the exposure region 2 and thus the pickups 6a-6d have to be moved laterally to the end portions. Therefore, as compared with a structure wherein each light blocking plate moves laterally, the aperture device comprising the light blocking plates 7a-7d and the like can be made compact. Further, by using, as the light blocking plates 7a-7d , such a material effective to block X-rays for the exposure but effective to transmit alignment laser light, it is possible to dispose the aperture member (blocking plates 7a-7d ) between the mask 1 and the pickups 6a-6d since the alignment light can pass through the light blocking plate. By disposing the aperture member close to the mask 1, as above, it is possible to prevent deterioration of the precision of controlling the exposure region limitation attributable to a change in the angle of incidence of the exposure X-rays or diffraction at the edges of the light blocking plates 7a-7d . Further, when the exposure X-rays are projected, the light blocking plates 7a-7d can serve to prevent impingement of scattered X-rays from the mask 1 upon the pickups 6a-6d . Therefore, it is possible to protect the alignment system against the scattered X-rays. As a matter of course, each light blocking plate has a sufficient size so as to prevent impingement of the scattered X-rays from the mask 1 upon the pickup. As described hereinbefore, an important feature of this embodiment resides in that the light blocking member for blocking the illumination light for the exposure, itself, dose allow passage of the illumination light for the positional deviation detection. Where the illumination light for the exposure comprises X-rays and the illumination light for the positional deviation detection comprises light such as a laser light, for example, having a wavelength longer than near-ultraviolet light, the light blocking member may be made of a material such as light transmissive ceramics such as PLZT or MgO, Y.sub.2 O.sub.3, Gd.sub.2 O.sub.3, etc. FIG. 5 shows the structure of a portion, around an aperture, of an X-ray aligner according to another embodiment of the present invention. As compared with the FIG. 2 embodiment, in the X-ray aligner of this embodiment the position of the light blocking plates 7a-7d and the pickups 6a-6d with respect to the mask 1 and the wafer 3, are interchanged. In the aligner of FIG. 5, the light blocking plates 7a-7d do not block the alignment light paths La-Ld and, therefore, higher freedom is attainable with regard to the material of the light blocking plates 7a-7d , as compared with the FIG. 2 aligner. In FIG. 5, reference numeral 11 denotes a base of the alignment optical system. While in the foregoing description the invention has been explained with reference to examples wherein the invention is applied to an X-ray exposure apparatus, the invention is applicable also to a case wherein ultraviolet light or the like is used as the exposure illumination light. While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.