Abstract:
Scanning type exposure device that includes a projection optical system having a plurality of projection optical system modules configured to facilitate projection exposure of a pattern onto a photosensitive substrate based on a mask. The projection optical system modules are configured to be individually adjusted based on a displacement characteristic related to the mask. Also disclosed are methods of manufacturing and using the scanning type exposure device.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to exposure devices such as those used to manufacture liquid crystal display panels. 
     2. Description of the Related Art 
     For many years, liquid crystal display (LCD) panels have been used in word processors, personal computers, televisions, and other display-oriented devices. To manufacture such liquid crystal display panels, it is necessary to produce patterns on transparent conductive films, amorphous silicon films, or the like disposed on glass or similar substrates by means of photolithography. 
     To facilitate such photolithography, step and repeat type exposure devices often are used. Such devices typically perform exposure projection of an original picture pattern formed on a mask onto a resist film disposed on a glass substrate via a projection optical system. Such exposure devices have become quite reliable in terms of facilitating manufacture of LCD panels. Unfortunately, however, as LCD “picture” sizes have increased, so too have the sizes of glass plates, masks, and exposure regions. Such increased sizes have led to several problems which have not heretofore been effectively addressed and solved. 
     For example, to design an enlarged projection optical system to produce relatively large LCD panels, it has become necessary to produce large optical elements that can support very high accuracy and the like. Such accuracy comes at a high price. For example, manufacturing costs are increased whenever greater device accuracy is required. Furthermore, larger optical systems require larger device infrastructures which causes increases in costs associated with device manufacture, transportation, and installation. And, to exacerbate such problems, increased exposure device size often results in poorer image projections and the like. 
     To address such problems, various exposure devices have been proposed. For example, as shown in U.S. Pat. No. 5,625,436, the inventors thereof proposed using a projection optical system unit consisting of plural projection optical system modules. More particularly, the inventors proposed using a scanning type exposure device of a multi-lens projection optical system which performs equal and multiple exposures while simultaneously causing a mask and substrate to move. Scanning is done while fixing in place an illuminating optical system and a projection optical system unit. By simultaneously moving the mask and a substrate, an exposure pattern (e.g., a rectangular pattern) formed on a surface of the substrate moves and, as a result, a whole exposure is achieved. When using such a projection optical system which is not very large in comparison with the size of the mask and substrate, exposure becomes possible in a region of a comparatively large image plane. 
     The device shown and described in the &#39;436 patent incorporates a single projection optical system. As such, after plural projection optical system modules were assembled into the exposure device, the same were inspected by inspection devices for accuracy. Then, after an accuracy inspection, the single-part projection optical system was loaded into the exposure device. In such an inspection device, as a mask used for inspection, in at least one scan direction and a direction about at right angles, using a large mask to about the same degree as a mask used in practice, the projection optical system unit was inspected and adjusted. As such, the adjustment of the projection optical system unit was time-consuming and, in addition, the inspection device became large. 
     Together with larger substrates, it was necessary to make masks larger. As masks became larger, the same were recognized to bend under their own weight and size. As a result, the bending amount was large at a center portion of a mask, and became small at side portions thereof. For example, in order to perform exposure of a large substrate of say about 500 mm×650 mm, it was not uncommon to realize up to 40 μm in bending. As such, even when correctly positioned in accordance with an exposure pattern formed on a surface of a substrate there was concern that bending would cause distorted projections, etc. 
     Thus, there exists a need to provide new and improved scanning type exposure devices which may be used to manufacture LCD panels and the like having relatively large dimensions and surface areas. To be viable, such devices must effectively address the problems stated above and, in particular, those related to mask bending. 
     SUMMARY OF THE INVENTION 
     The present invention solves the aforementioned problems associated with prior scanning type exposure devices. In so doing, the present invention provides a new and improved scanning type exposure device and methods of manufacturing and using the same which can perform high accuracy exposures without regard for displacement of a mask such as realized by masks that bend under their own weight, size, etc. As a result, the present invention achieves lower device adjustment times, reduce inspection device sizes, and lower manufacturing costs. 
     The present invention solves the aforementioned problems and achieves the above-described benefits by providing a scanning type exposure device that includes a projection optical system having a plurality of projection optical system modules configured to facilitate projection exposure of a pattern onto a photosensitive substrate based on a mask. The projection optical system modules are configured to be individually adjusted based on a displacement characteristic related to the mask. Additionally, the present invention provides corresponding methods of manufacturing and using the scanning type exposure device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     The present invention is described below with reference to the following drawing figures, of which: 
     FIG. 1 is a schematic diagram of an exposure device provided in accordance with a preferred embodiment of the present invention; 
     FIG. 2 is an oblique diagram of the exposure device shown in FIG. 1; 
     FIG. 3 is a plan view that illustrates the positional relationship of the exposure regions formed on the surface of a substrate; 
     FIG. 4 is a plan view that illustrates the scanning movement of the exposure regions formed on the surface of a substrate; 
     FIG. 5 is a schematic diagram that illustrates the relationship of the bending of a mask and the projection optical system modules; 
     FIG. 6 is a schematic diagram of an inspection device projection optical system module provided in accordance with a preferred embodiment of the present invention; and 
     FIG. 7 is a plan view that illustrates the positional relationship of exposure regions formed by means of a projection optical system unit of an exposure device according to another preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is now discussed with reference to the drawing figures that were briefly described above. A discussion of each preferred embodiment of the present invention is followed by a corresponding discussion of its operation. Unless otherwise specified, like parts and processes are referred to with like reference numerals. 
     A First Preferred Embodiment 
     Referring now to FIG. 1, depicted therein is a schematic diagram of a scanning type exposure device provided in accordance with a preferred embodiment of the present invention. In particular, an exposure device  10  has an illumination optical system unit  4 , a mask stage (not shown) which supports a mask  1 , a projection optical system unit  2 , and a substrate stage  6  which supports a substrate  3 . There is no particular limitation on the substrate  3 , but in the present preferred embodiment, a glass substrate is used in order to manufacture a liquid crystal display panel (LCD). 
     A control device  100  controls the operations of scanning type exposure control device  10  and, in particular, the component parts thereof including, but not limited to, projection optical system unit  2 , drive systems (described below), etc. Control device  100  may include data processing structures to allow intelligent control including control operations based on data analysis and the like. 
     In the present preferred embodiment, in order to manufacture a comparatively large picture LCD, a glass substrate is used having a height of 500 mm or more and a width of 650 mm or more. Polysilicon film, colorant film, transparent electrically conductive film, and other various kinds of functional thin films are laminated on the surface of substrate  3 . Substrate  3  is thereafter etched with desired patterns. Accordingly, during an etching process, a film of a resist and the like photosensitive thin film is formed so that substrate  3  becomes a photosensitive substrate and so that an exposure process may be performed by scanning type exposure device  10  in accordance with the present preferred embodiment. 
     In scanning type exposure device  10  and, in particular, with respect to illumination optical system unit  4  and projection optical system  2  thereof, mask  1  and substrate  3 , as shown in FIGS. 1 and 2, simultaneously move in a scan direction X. The direction approximately at right angles to the scan direction X is taken as the Y direction, and the direction approximately at right angles to both the X and Y directions is taken as the Z direction. 
     Substrate stage  6  supports substrate  3  and is driven in the X direction by means of a scan direction drive device  8 . The amount of movement, for example, is detected with high accuracy by means of a laser interferometer and the like position measurement device  9  so that accurate movement of substrate stage  6  is performed. A Y direction drive device  12  causes movement of substrate stage  6  in the Y direction and is mounted in the substrate stage  6 . 
     In cases in which substrate  3  is large in comparison to mask  1 , the amount of movement of substrate stage  6  in the Y direction becomes large. 
     A scan direction drive device, a Y direction drive device, and a position measurement device also are provided in the mask stage (not shown) which supports mask  1 . Position matching of mask  1  and substrate  3  is performed by an alignment sensor  14  which detects an alignment mark M 1  formed in mask  1 , and an alignment sensor  16  which detects an alignment mark M 2  formed in substrate  3 . The present invention is not limited to utilizing alignment sensors  14  and  16 . 
     Illumination optical system unit  4  has a structure suitable for forming on mask  1  plural (e.g., five, etc.) rectangular illumination regions  11  which are located in two (2) rows in the Y direction and which are mutually and alternately located in the X direction. Namely, illumination optical system unit  4  of the present preferred embodiment has plural light exit modules  18  which are used to supply illumination light for exposures. For example, g light (436 nm) or i light (365 nm) may be illuminated from each light exit module  18 . Light exit modules  18  have respective single light sources, or secondary light sources from a single light source, and via built-in condensing lenses, uniformly illuminate field stops which have rectangular apertures. Illuminating light for exposure has its light path rotated 90° by mirror  20  and reaches the surface of mask  1  to form plural rectangular illumination regions  11  which are images of the rectangular apertures of the field stops. 
     The shape of the respective illumination regions need not be rectangular. Furthermore, the number of illumination regions  11  located alternately at a predetermined pitch in two rows along the Y direction on mask  1  is not limited to five (5), and may be four (4) or less, or six (6) or more. The number of illumination regions  11  corresponds to the number of illumination regions used to illuminate the substrate. 
     Next, a description is given of projection optical system unit  2  as shown in FIGS. 1 and 2. Projection optical system unit  2  has a support base  2   b  which has a comparatively high rigidity and which remains relatively stiff. A number of projection optical system modules  2   a  (e.g., five modules, etc.) are mounted on support base  2   b  and correspond to the number of illumination regions  11  formed by illumination optical system unit  4 . The respective projection optical system modules  2   a , in the present preferred embodiment, are optical systems with uniform magnification to produce erect normal images. 
     Projection optical system modules  2   a  all have the same structure, and are optical systems which perform projection exposure causing imaging on the surface of the substrate  3  for the respective exposure regions  21  of patterns on mask  1  which correspond to the respective illumination regions  11  which are illuminated with respect to mask  1 . Accordingly, the structure of (e.g., shape, dimensions, etc.) of projection optical system modules  2   a  is not limited to that shown in FIGS. 1 and 2. The respective projection optical system modules  2   a  of projection optical system unit  2  have field stop regions of the prescribed rectangular shape by means of field stops within the respective projection optical system modules  2   a ; images of such field regions are formed as erect images of equal magnification on substrate  3 , and become two rows of exposure regions  21  located alternately as shown in FIG.  3 . That is, on the substrate  3 , by means of the respective projection optical system modules  2   a  located in the projection optical system unit  2 , five (5) rectangular exposure regions  21  are formed arrayed alternately in 2 rows by projection optical system unit  2 . The Y-direction end portions of the respective exposure regions  21  formed on substrate  3 , between the adjacent exposure regions  21 , are separated at a predetermined pitch in the X direction. In the Y direction, the end portions thereof overlap. 
     Mask  1  and substrate  3  as shown in FIGS. 1 and 2 are in a state which they do not move simultaneously in scan direction X. The exposure region  21  formed by means of illumination optical system  4  and projection optical system unit  2 , as shown in FIG. 3, is only a partial region in the scan direction X. However, by means of simultaneously moving mask  1  and substrate  3  in scan direction X, as shown in FIG. 4, the respective exposure regions  21  correspondingly move in scan direction X on the surface of the substrate  3  and the whole surface of substrate  3  can be exposed. 
     With scan type exposure device  10 , as shown in FIG. 5, for example, mask  1  deforms due to bending as a result of its own weight, size, etc. As a result, a position deviation ΔY results between the position of Y 1  along mask  1  from the scan center line S 1  of the Y direction of the mask  1  and substrate  3 , and the position of Y 1  along the substrate  3 . When substrate  3  is large and mask  1  is correspondingly large, ΔY causes a large distortion effect on the exposure. Moreover, due to the bending deformation of mask  1 , the change of the distance between foci Z 1  also cannot be neglected. 
     Consequently, the deviation amounts ΔY corresponding to the optical center axes of the respective projection optical system modules  2   a , and the distance between foci Z 1 , taking into account the bending deviation of the mask  1  due to its own weight, size, etc. are found prior to exposure operations based on estimation and calculation techniques (i.e., a distortion simulation result is determined). Such evaluations may be carried out by control device  100  using programmatic control logic that includes mathematical operations to take differences between relative positional placements, etc. Thereafter, during inspection of projection optical system unit  2  and before mounting the respective projection optical system modules  2   a  shown in FIG. 2 on support base  2   b , each of the respective projection optical system modules  2   a  is individually adjusted using the inspection device shown in FIG.  6 . 
     The inspection device  30  shown in FIG. 6 has a temporary support base (not shown) which temporarily supports projection optical system unit  2 , a mask stage (not shown) which supports mask  5 , and a substrate holder (not shown) which supports substrate  7 . The inspection mask stage which supports mask  5  for inspection use is movable in six degrees of freedom. 
     In adjusting a respective projection optical system module  2   a  using inspection device  30 , the projection optical system module  2   a  is temporarily supported on the temporary support base. Thereafter, the center  5   a  of mask  5  is caused to move based on the aforementioned simulation result such that the Y direction position deviation amount ΔY and the distance between foci Z 1  correspond to the respective projection optical system module  2   a . Accordingly, the tilt angle of lenses and the interval between lenses and the like which constitute the respective projection optical system module  2   a  are adjusted so as to position the image of the center  5   a  of the mask  5  with respect to the center of substrate  7 . 
     After each projection optical system module has been adjusted, the group is mounted in the support base as shown in FIG. 2, and the projection optical system unit  2  is thereby assembled. Furthermore, on support base  2   b , plural projection optical system modules  2   a  are also mounted, and it is necessary for it to be of high rigidity to the extent that problems during exposure such as bending deformation and the like do not arise. Moreover, during inspection support base  2   b  may be used instead of the temporary arrangement shown in FIG.  6 . 
     When an exposure operation is performed on substrate  3  of comparatively large size, the deformation of mask  1  due to bending of mask  1  is simulated prior to exposure operations, and based on the deformation of mask  1 . In particular, a position deviation ΔY and distance between foci Z 1  and the like values of change are evaluated beforehand. Such values and the location of the respective projection optical system modules  2   a  with respect to the support base  2   b  of the projection optical system unit  2  are evaluated using inspection device  30  to individually adjust projection optical system modules  2   a . As such, adjusted projection optical system modules  2   a  are inserted into support base  2   b  to assemble projection optical system unit  2 . 
     In the present preferred embodiment, exposures of substrates of relatively large size can be performed with high accuracy, without regard for deformation of a mask due to bending of the same under its own weight, size, etc. Moreover, because each projection optical system module  2   a  is individually inspected and adjusted, inspection device  30  is of reduced size relative to other adjustment devices. And, when a non-conformity (e.g., malfunction, etc.) arises in one of the projection optical system modules  2   a  of projection optical system unit  2 , the same may now be easily exchanged. 
     A Second Preferred Embodiment 
     Next described is a second preferred embodiment of the present invention. The structure of the second preferred embodiment is the same as that discussed above with regard to the first described preferred embodiment. Here, each projection optical system module  2   a  is individually adjusted by means of inspection device  30  as shown in FIG. 6 based on its position within support base  2   b . That is, in contrast to using a temporary support base as described above with regard to FIG. 6, the present preferred embodiment uses support base  2   b . In particular, the bend deformation of mask  1  as shown in FIG. 5 is evaluated prior to exposure, and based on the result of such an evaluation and according to the position of each projection optical system module within base  2   b  so that each projection optical system module is separately configured and adjusted. 
     With the present preferred embodiment, because the optical system modules  2   a  are configured based, in part, on their position within support base  2   b , inspection time using inspection device  30  as shown in FIG. 6 is shortened especially since removal and placement of the same into a temporary support member is not needed. 
     A Third Preferred Embodiment 
     Next described is a third preferred embodiment of the present invention. With the first and second preferred embodiments described above, individual adjustment of a particular optical system module  2   a  is performed with respect to its position within a support member such as support base  2   b  or other temporary structure. In contrast, the present preferred embodiment utilizes scanning traits to achieve adjustment. That is, as the scan movement directions X and Y are approximately at right angles relative to each other, by linearly and symmetrically inserting the center line S 1  (see FIG. 5) of scan movement will causes projection optical system modules  2   a  to be in a linear, symmetric relationship. As such, projection optical system modules  2   a  may be adjusted in similar fashion if the center line of mask  1  and the center line S 1  of the scan direction are in agreement. Because mask  1  deforms (e.g., bends, etc.) symmetrically with respect to the center line S 1  of scan movement, the position deviation amount ΔY and the distance between foci Z of mask  1  with respect to a projection optical system module  2   a  is linear and symmetric, and can be considered to be approximately the same for all projection optical system modules. 
     Accordingly, in the context of the present preferred embodiment, it is not necessary to individually adjust all of the projection optical system modules  2   a  which are mounted with respect to support base  2   b . Instead, each projection optical system module  2   a  may be adjusted based on certain assumptions derived from scanning traits. 
     It should be noted that in the case that mask  1  is quartz or low expansion glass, the amount of bending that will be realized is different than as described above. Also, in cases in which a mask is used whose size or thickness differs from those described above, the amount of bending of that mask will be different. In such cases, information (material, size, etc.) relating to mask  1  may be input to control device  100 , and the focus adjustment lens in each projection module  2   a  may be adjusted. Furthermore, the information relating to mask  1  may be read out from the bar code formed in the mask  1 , or may be input manually to a controller such as control device  100 . 
     Other Embodiments 
     The present invention is not limited to the above-described preferred embodiments. For example, the exposure regions formed by the respective projection optical system modules  2   a  need not necessarily be formed as rectangular regions  21 . As shown in FIG. 7, projection optical system modules  2   a  may be designed so as to form trapezoidal exposure regions  21   a . Additionally, as shown in FIG. 7, a positional relationship of  2  rows of trapezoidal exposure regions along the Y direction may be separated at a predetermined pitch in the scan direction X and caused to overlap as seen in the scan direction X. By forming exposure regions  21   a  by the respective projection optical system modules  2   a  in such a way, the pattern located in the joint portion of the respective exposure region  21   a  does not leave any unexposed area on the surface of substrate  3 . 
     Moreover, In the above-mentioned embodiments, the respective projection optical system modules  2   a  of the projection optical system unit  2  are an optical system of equal magnification to produce erect images. The present invention, however, is so limited. To the contrary, the present invention may incorporate optical systems that provide reduction optical effects, enlargement optical effects, inverted images, etc. 
     Also, illumination optical system unit  4  includes plural lenses to perform optical adjustment of the projection optical system unit containing a focusing lens which is inserted in the exposure device housing. Additionally, substrate stage  6  includes many mechanical components and is mounted in the housing of scanning type exposure device  10 . Such structures are assembled to connect to a wiring system (now shown). Furthermore, scanning type exposure device  10  can be manufactured by means of performing coordination adjustment (electrical adjustment, operational confirmation, and the like). It is desirable to manufacture scanning type exposure device  10  in a clean room with controlled temperature and cleanliness. 
     Based on the foregoing discussion, when performing exposure of photosensitive substrates of comparatively large size, it is possible to perform exposures with high accuracy, without effects due to the deformation of a mask resulting from bending under its own weight, size, etc. Moreover, because projection optical system modules may be individually inspected and adjusted, in accordance with the present invention, an inspection device can be designed in a smaller form, the adjustment time can be shortened, and cost reductions can be achieved. 
     Moreover, when a non-conformity arises (e.g., a mal-function, etc.) in one of the projection optical system modules occurs, only the effected projection optical system module need be exchanged, repaired, etc. 
     The present invention is not limited as to individual adjustment of the respective projection optical system modules  2   a . Instead, the present invention contemplates adjustment of the tilt angle of the lenses which are included within a respective projection optical system module  2   a , intervals between lenses, rotation angles of lenses (rotation around an optical axis), eccentricity of the lenses, and the like, to perform exposure at an optimal focus state in relation to a photosensitive substrate. Moreover, individual adjustment of the respective photosensitive substrates means that by specially designing the kind of lenses included within the respective projection optical system modules, tilt angle, interval between lenses, lens thickness, lens surface curvature and the like for each respective projection optical system module, is such as to perform exposure at an optimal focus state in relation to a photosensitive substrate. 
     With an exposure device provided in accordance with the present invention, when performing exposure of photosensitive substrates of a relatively large size, performing a simulation/evaluation of the deformation of a mask due to the mask bending under its own weight, size, etc., the values of the change of the positional deviation amount and distance between foci and the like are estimated prior to exposure. Taking such values and the locations of the respective projection optical system modules of a projection optical system unit, the projection optical system modules may be individually adjusted. Accordingly, the projection optical system modules whose adjustment is completed are assembled in the projection optical system. 
     As such, when performing exposures of photosensitive substrates of comparatively large sizes, exposures can be performed with high accuracy, without displacement of a mask due to bending under its own weight, size, etc. Moreover, in contrast to the prior art, there is no single inspection for a whole projection optical system unit because the respective projection optical system modules may be individually inspected and adjusted, providing for a reduced size of inspection device, shortening of the adjustment time and a reduction in manufacturing costs. 
     Furthermore, in the context of the present invention, mask  1  is generally considered to be one containing a reticle. Moreover, in the present invention, the light source of the exposure device  10  is not limited. In fact, light sources such as those that produce g light (436 nm), i light (365 nm), and that light produced by KrF excimer lasers (248 nm), ArF excimer lasers (193 nm), F 2  lasers (157 nm) or YAG lasers and other high frequency light sources may be used. 
     Thus, having fully described the present invention by way of example with reference to the attached drawing figures, it will be readily appreciated that many changes and modifications may be made to the invention and to the embodiments shown and/or described herein without departing from the spirit or scope of the present invention which is defined in and covered by the appended claims.