Patent Number: 
Section: description

FIG. 1 schematically shows the arrangement of one embodiment of the proximity exposure device in accordance with the invention in which a workpiece W, for example, a liquid crystal display element substrate or the like, is placed on a workpiece carrier WS. Furthermore, a mask M is located spaced above the workpiece W with a predefined gap G between them (in the drawing, the size of the gap is shown exaggerated). On the mask M and the workpiece W, mask alignment marks (hereinafter called xe2x80x9cmask marks MAMxe2x80x9d) and workpiece alignment marks (hereinafter called xe2x80x9cworkpiece marks WAMxe2x80x9d) are recorded for positioning and are viewed using an alignment microscope 7 which is described below. In this way, positioning of the mask M relative to the workpiece W is performed. The workpiece carrier WS is driven by means of an X-Y-"THgr" drive device 1 in the X-Y-"THgr" directions (for example, X: to the right and left in FIG. 1; Y: in and out of the plane of the drawing, "THgr": in a direction of rotation around an axis perpendicular to the X-Y plane, i.e., an axis extending in a Z-direction, up and down in the drawings) and by means of a Z-drive device 2 is driven in the Z-direction (up and down in the drawings). A lamp housing 3 in which a lamp L for emitting light which contains UV radiation, and an oval reflector R and the like are located. Parallel exposure light is emitted from an exit opening 3a of the lamp housing 3. The lamp housing 3 is furthermore supported by an arc-shaped guide 4, as is shown in the drawings. The lamp housing 3 is arranged to be able to move along the guide 4. Therefore, the angle of incidence xcex4 of the exposure light can be changed with respect to the mask M and the workpiece W by the lamp housing 3 being moved along the guide 4 by means of a lamp housing drive device 5. The lamp housing 3, the guide 4 and the lamp housing drive device 5 are made such that they can be turned as a whole around an axis T. The irradiation direction of the exposure light can be changed with respect to the mask M and workpiece W by turning the lamp housing 3 around the axis T by means of the lamp housing drive device 5 (hereinafter the angle of rotation around the axis T is called the xe2x80x9cirradiation angle "PHgr"xe2x80x9d). By moving the lamp housing 3 along the guide 4, the angle of incidence 6 can be changed in the range 0 less than xcex4 less than 90xc2x0. Furthermore, the irradiation angle "PHgr" can be changed in the range from 0xe2x89xa6"PHgr"xe2x89xa6360xc2x0 by the lamp housing 3 being turned around the axis T. For the above described lamp housing, the lamp housing already proposed by in published Japanese patent application HEI-10-154658 can be used. Above the mask M, there are a gap measuring device 6 for measuring the gap size G between the mask M and the workpiece W and an alignment microscope 7 for positioning of the mask M relative to the workpiece W. The measuring device already proposed in published Japanese patent application HEI 10-268525 (EP 0 867 775 A2) can be used as the gap measuring device. Furthermore, a control element 10 controls driving of the X-Y-"THgr" drive device 1 and the Z-drive device 2 based on the outputs of the gap measuring device 6 and the alignment microscope 7 and moves the workpiece carrier WS in the X-Y-"THgr"-Z directions. The control element 10 has a storage part 10a which stores an adjustment value Go of the gap size G as the light irradiation gap between the mask M and the workpiece W and the adjustment values xcex4o, "PHgr"o of the angle of the light which is incident on the workpiece W. These adjustment values which are input by an input part 11 are adjusted in the storage part 10a.  In the following, the process for positioning of the mask relative to the workpiece in accordance with the invention is described. Here, an example in described in which the mask pattern shown in FIG. 2 is formed on the mask M (a mask pattern which corresponds to a pixel), the mask M is attached and the workpiece is moved. Using the mask M, the mask M and the workpiece W are arranged with a predefined gap G between them, as is illustrated in FIG. 3, and using the alignment microscope 7, the coordinates of the mask marks MAM and of the workpiece marks WAM are determined. In FIG. 3, the alignment microscope 7 has a CCD camera 7a and a light source 7b for emitting alignment light. The alignment light emitted from the light source 7b is emitted onto the mask marks MAM and the workpiece marks WAM. By means of the CCD camera 7a of the alignment microscope 7, the mask marks MAM and the workpiece marks WAM are recorded. The recorded video signals are sent to the above described control element 10. Before positioning, in the alignment microscope 7, the mask mark MAM and the workpiece mark WAM are viewed, as is shown in FIG. 4. The mask M and the workpiece W can be positioned in the vertical direction when the workpiece is moved in the X-Y-"THgr" directions such that the mask mark MAM and the workpiece mark WAM are aligned with one another (such that the workpiece mark WAM is located at the site shown in the mask mark MAM in FIG. 4 using the broken line). FIG. 3 shows this state. Specifically, the correlation is determined between the amount of movement of the workpiece carrier WS and the amount of movement in the video processing coordinates of the workpiece mark WAM which corresponds to the movement of the workpiece carrier WS, beforehand. The positional information about the alignment marks obtained by the alignment microscope 7 according to FIG. 3 is subjected to video processing in the control element 10 and the position coordinates for the video processing coordinates of the respective alignment mark are computed. The above described processing makes it possible to compute the amount of displacement (xcex94X, xcex94Y, xcex94"THgr") in the X-Y-"THgr" directions with which the workpiece mark WAM which is originally located at coordinates (Xn, Yn) moves to the coordinates in which it is aligned with the mask mark MAM. The amount of displacement in the X-Y-"THgr" directions (xcex94X, xcex94Y, xcex94"THgr") is computed as the amount of movement of the workpiece carrier WS in the X-Y directions and as the amount of rotation "THgr" of the workpiece carrier WS in which the positions of the two mask marks MAM shown in FIG. 5 and the workpiece marks WAM are aligned with one another. When based on the above described computation, the workpiece carrier WS moves and positioning of the mask M relative to the workpiece W is performed in the vertical direction, the workpiece mark WAM has position coordinates of (Xn+xcex94X, Yn+xcex94Y). In the case of oblique light irradiation of the mask M, the position at which the mask pattern is projected on the workpiece W is shifted, depending on the xe2x80x9cangle (angle of incidence) xcex4 with which the irradiation light is incident in the mask M,xe2x80x9d the xe2x80x9cangle (irradiation angle) with which the irradiation light is incident with respect to the X-direction of the mask patternxe2x80x9d and xe2x80x9cthe size of the gap G between the mask M and the workpiece Wxe2x80x9d because the irradiation light is parallel light as is shown in FIGS. 6(a) and 6(b). Within the mask pattern surface, the X-Y coordinate axes are defined. The angle of the light incident with respect to the X-axis is called the irradiation angle "THgr". The direction of the X-Y coordinate axes of the mask pattern and the direction of the X-Y coordinate axes of the workpiece carrier are brought into alignment with one another. In this way, the movement of the workpiece carrier is regulated. Therefore, by moving the workpiece W by the amount of displacement described above, the mask pattern can be projected onto a predetermined area and a desired area can be irradiated with light, as is shown in FIG. 6(c). The above described amount of displacement is computed as follows: With reference to the positions (X, Y) to which the mask pattern is shifted as shown in FIG. 6(b), these positions are described with the following formulas where (Xo, Yo) are the position coordinates at which any mask pattern MAM is projected onto the workpiece W when light is incident vertically on the mask M, G is the size of the gap between the mask M and the workpiece W, xcex4 is the angle of incidence of the irradiation light with respect to the mask, and "PHgr" is the irradiation angle with which the irradiation light is incident with respect to the X-direction of the mask pattern: X=Xoxe2x88x92Gxc2x7tan xcex4xc2x7cos "PHgr" Y=Yoxe2x88x92Gxc2x7tan xcex4xc2x7sin "PHgr" Here, it can be imagined that the coordinates (Xo, Yo) are the position coordinates of the workpiece mark when the mask M is positioned relative to the workpiece W in the vertical direction. Therefore, the following applies: (Xo, Yo)=(Xn+xcex94X, Yn+xcex94Y) Therefore, for oblique light irradiation, only a desired area can be irradiated with light when the workpiece carrier is subjected to movement control in the X-Y-"THgr" directions such that the workpiece mark WAM is moved from the coordinates (Xn, Yn) to the coordinates (X, Y). In the following, the processes of positioning and exposure using the above described process are described using the exposure device which is shown above in FIG. 1. (1) The adjustment value Go of the size of the light irradiation gap between the mask M and the workpiece W, the adjustment value xcex4o of the angle of incidence with respect to the workpiece W and the adjustment value "PHgr"o of the irradiation angle are input by the input part 11. These values are all stored in the storage part 10a of the control element 10. (2) The control element 10, based on the input information about the angle of incidence xcex4o and the irradiation angle "PHgr"o, drives the lamp housing drive device 5 and moves the lamp housing 3 which emits the light. (3) The output of an encoder which is located in the device 5 is input into the control element 10. The control element 10 determines the amount of movement of the lamp housing 3 and computes the actual angles xcex4, "PHgr" of the light which is incident in the actual workpiece. These values are stored in the storage part 10a of the control element 10. (4) On the other hand, the workpiece carrier Ws is lifted by the Z-drive device 2. The locations of the mask marks MAM and the workpiece marks WAM are determined by the alignment microscope 7 at the alignment gap position. The determined signals are subjected to video processing. Based on this information, in the control element 10, the position coordinates of the workpiece carrier WS (Xn+xcex94X, Yn+xcex94Y)=(Xo, Yo) are determined in which positioning of the mask relative to the workpiece in the X-Y-"THgr" directions is to be produced in the vertical direction. (5) Then, the workpiece carrier WS is lifted according to the adjustment gap size Go as far as the position of the adjustment gap size G. After movement, the gap measuring device 6 measures the gap size G between mask M and the workpiece W at several locations. These values are returned to the control element 10. The position of the workpiece carrier WS in the Z-direction is moved back and forth by means of an adjustment device (not shown) for movement back and forth such that it is in a predetermined area with respect to the adjusted gap size GO. The substrate of the LCD element is large, as described above. The mask M used for this purpose is also large. In the mask M, sagging occurs due to its weight. Therefore, it is necessary to measure again whether the gap size G with respect to the adjustment value Go lies in an allowable range in order to regulate the sagging of the mask M when necessary. (6) The actual gap size at the conclusion of adjustment is G. This gap size G is stored in the storage part 10a of the control element 10. (7) Based on the actual values xcex4 and "PHgr" of the light angle and of the gap size G stored in the storage part 10a, i.e., the values stored in the storage part 10a, the control element 10 computes the position coordinates (X, Y) to which the workpiece carrier should move using the formulas described above. Based on this computation result, the control element 10 moves the workpiece W by means of the X-Y-"THgr" drive device 1 such that the workpiece mark WAM is moved to coordinates (X, Y). (8) After completion of the movement of the workpiece carrier WS, light is emitted from the lamp housing 3 and the mask pattern is exposed onto the workpiece W. In the case of a device in which the lamp housing 3 is manually moved, the movement position of the workpiece W is determined by the fact that the adjustment values xcex4o and "PHgr"o of the angle of the light which is incident in the workpiece W is used unchanged. (9) After completion of exposure of the first zones of the pixel on the substrate of the LCD element in the above described manner, the workpiece is turned, for example, by 180xc2x0, as was described above. The mask M and the workpiece W are positioned relative to one another in the above described manner. Then, the third zones which are located point-symmetrically with respect to the first zones around the pixel center are irradiated with light with a predetermined angle of incidence and a preset irradiation angle. The mask M is replaced. The second and fourth zones of the pixel on the substrate of the LCD element are exposed in the above described manner. As was described above, in accordance with the invention, in a proximity exposure device in which a mask and a workpiece are arranged with a predetermined gap between them and the workpiece is irradiated obliquely with light via the mask, based on the gap size G between the mask and the workpiece, on the angle of incidence xcex4 of the irradiation light with respect to the mask and based on the irradiation angle "PHgr" with which the irradiation light is incident with respect to the X-direction of the mask pattern, the displacement position of the mask pattern to be projected is computed, and according to the result of this computation, the workpiece is moved and the light is emitted. In this way, the mask pattern can be projected onto the predetermined position of the workpiece and the desired area can be irradiated with light.