JP2010135479A - Scanning projection exposure apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problems: the size of a scanning projection exposure apparatus for a large liquid crystal display panel is increased for an expansion of productivity to cause a focus distribution in an exposure area owing to the deformation under mask's own weight associated with the growth in its size, and a surface error and a strain error of an optical component in an imaging system causes a focus distribution in the exposure area. <P>SOLUTION: The optical component in an imaging system of the scanning projection exposure apparatus imaging a circular-arc-shaped illumination area is decentered in response to the deformation under mask's own weight, or the mask or a plate is inclined in the scanning direction to compensate an essential part of the focus distribution caused by the deformation under mask's own weight. Further, illuminating to projection-expose the uniform-focused area compensates the focus distribution in the direction orthogonal to the scanning. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exposure apparatus and an exposure method, and more particularly to a scanning exposure apparatus that accurately projects and exposes a mask pattern onto a photosensitive substrate by controlling an illumination area.

  The liquid crystal display panel is manufactured by a photolithography technique by transferring a mask pattern onto a photosensitive substrate. In the process of transferring the mask pattern, a high-precision scanning projection exposure apparatus is used to form a fine pattern image.

  FIG. 2 is a diagram schematically showing a scanning projection exposure apparatus.

  The coordinate system of this schematic diagram is as indicated by 16.

  This projection exposure apparatus is mainly composed of two units. (1) to (7) indicate an illumination system, and (9) to (14) indicate an imaging system.

  A mercury lamp is used for the light source (1), and the light beam emitted from the light source is collimated by the elliptical mirror (2) and enters the optical integrator (3). The optical integrator is used to control the illuminance uniformity and NA of illumination light in the irradiation area. The light beam emitted from the optical integrator irradiates the slit (5) that defines the irradiation region through the lens and the mirror (4).

  The slit is in a conjugate position with the mask (8). This schematic diagram shows a typical liquid crystal scanning projection exposure apparatus. Since the good image area of the image forming system (shown in FIGS. 9 to 14) of the exposure apparatus is an arc, the shape of the slit opening is YX. It is arcuate (17) on the surface.

  The light beam collimated by the slit irradiates a mask (8) on which a pattern for a liquid crystal panel is drawn through a lens (6) and a mirror (7). The irradiation area is circular, and the mask is projected and exposed while scanning in the Y direction in synchronization with the plate (15).

  The light transmitted through the pattern on the mask forms an image on the plate (15) through the imaging system (9 to 14). The imaging system is characterized by an optical optical system that is symmetric with respect to the convex mirror (13) in order to prevent distortion and coma.

  FIG. 3 is a diagram showing the relationship between the good image area and the illumination range of the imaging system. FIG. 3A is a diagram illustrating aberrations of the imaging system. The horizontal axis represents the focus position, and the vertical axis represents the image height. The solid line represents the focus position of the sagittal ray, and the dotted line represents the focus position of the meridional ray. In the region from image height A to B, the focus of the sagittal ray and the focus of the meridional ray coincide with each other, and a good image without blurring is obtained in this region.

  FIG. 3-2 shows an illumination range on the mask surface in the imaging system. A dotted line portion indicates a region (good image region) where blurring does not occur as illustrated in FIG. 3A, and is a region surrounded by an arc of radius A and an arc of radius B at the same center. The illumination range is an area within the good image area and surrounded by an arc having the same radius. In the example shown in the drawing, the radius of the arc is A, and in order to improve productivity, it is a region sandwiched between arcs having a high image height radius in a good image area. The scanning direction is the Y direction in the illustrated coordinate system. In order to make the illuminance in the direction orthogonal to the scanning direction (X direction) uniform, the length of the illumination area in the scanning direction (FIG. 3-2, length C) needs to be equal. Therefore, the area surrounded by the solid line surrounded by the same radius is the illumination range.

This imaging system schematically shows the imaging optical system described in Patent Document 1.
JP 60-93410 A

  In order to project and expose a liquid crystal display panel with a scanning projection exposure apparatus as shown in the conventional example, it is necessary to adjust the focus of the mask and the plate with high accuracy within the range of the exposure area.

  In particular, countermeasures have been studied for the focus distribution generated by the self-weight deformation of the mask.

  For example, Japanese Patent Laid-Open No. 2004-39697 proposes a method of correcting a focus distribution generated by the deformation of a mask by tilting a plate stage or a mask stage.

  However, with the recent increase in the size of liquid crystal display panels, the size of masks has increased, and the amount of deformation of the mask itself has increased. As a result, sufficient focus correction cannot be performed by the above method.

  FIG. 4A is a schematic diagram illustrating deformation of the mask by its own weight. The coordinate system is as shown, and the Y direction is the scanning direction of the mask. (1) is a mask, and (2) and (3) are holding parts for supporting the mask. The holding part supports only two sides parallel to the scanning direction.

  FIG. 4B is a diagram illustrating the deformation of the mask by its own weight from the Y direction. It bends in the z direction under the influence of gravity.

  FIG. 5 is a diagram simulating the self-weight deformation shape of the mask (the free end is held). The vertical axis represents the self-weight deformation amount (um) of the mask, and the horizontal axis represents the length (mm) in the direction orthogonal to the scanning direction (X direction in FIG. 4). The calculation was performed when the length of the current mask in the X direction was 800 mm and the length of the next generation mask in the X direction was 1000 mm. It can be seen that when the length of the mask in the X direction is extended by 20%, the amount of deformation of the mask's own weight is more than twice. Since the focus distribution is generated according to the amount of deformation of its own weight, the focus distribution increases as the mask size increases.

  FIG. 6 shows the shape of the focus distribution that can be corrected by tilting the mask stage or plate stage. Since the illumination area of the present optical system is arcuate, the focus distribution that can be corrected by tilting the stage is arcuate.

  FIG. 7 shows the residue when the focus distribution generated by the self-weight deformation of the mask is corrected by the tilt of the stage. According to the inventor's calculations, the correction residue when the length of the mask in the X direction is 1000 mm is more than double that of the correction residue when the length of the mask in the X direction is 800 mm, and a liquid crystal display panel is manufactured. Therefore, the performance of the exposure apparatus is insufficient.

  Japanese Patent Laid-Open No. 10-214780 has also been disclosed as a countermeasure against the focus distribution due to the deformation of the mask by its own weight. Japanese Patent Laid-Open No. 10-214780 proposes a method of controlling the amount of deformation of the mask by sucking the mask by disposing a transmissive glass on the top of the mask and reducing the pressure between the mask and the transmissive glass. However, this method requires an expensive transmissive glass and a mechanism for controlling the atmospheric pressure with high accuracy.

  In addition to the deformation of the mask due to its own weight, factors that cause the focus distribution between the mask and the plate include surface errors and surface distortions of optical components in the imaging system. Compared to conventional liquid crystal display panels, production of higher-definition liquid crystal display panels has been demanded, and it has become necessary to accurately correct the focus distribution due to surface errors and surface distortions of optical components.

  The invention of claim 1 is characterized in that the scanning projection exposure apparatus for forming an image of an arcuate illumination area includes first means for deforming the illumination area in accordance with the focus distribution.

  According to a second aspect of the present invention, in the scanning projection exposure apparatus according to the first aspect, the second means for generating a focus change in the circumferential direction (radial direction) of the arc is provided.

  The invention of claim 3 is characterized in that, as the first means of claim 1, there is provided means for changing the shape of the slit at a position conjugate with the illumination region.

  According to a fourth aspect of the invention, as the second means of the second aspect, there is provided a means for inclining a reflecting optical member in the imaging optical system.

  The invention of claim 5 is characterized in that, as the second means of claim 2, there is provided means for inclining the plate stage.

  The invention of claim 6 is characterized in that as the second means of claim 2, means for inclining the mask stage is provided.

  The invention of claim 7 is characterized in that the scanning exposure apparatus of claim 2 is provided with a third means for generating a focus change (field curvature) in the radial direction of the arc.

  The invention of claim 8 is characterized in that the scanning exposure apparatus of claims 1 to 7 is provided with fifth means for correcting the telecentricity.

  According to a ninth aspect of the present invention, in the scanning exposure apparatus according to any one of the first to eighth aspects, the scanning projection exposure apparatus further comprises fifth means for adjusting the position / tilt of the optical component of the imaging system.

  The present invention can provide a high-performance scanning projection exposure apparatus by correcting the focus distribution between a mask and a plate with high accuracy in a scanning projection exposure apparatus that forms an image of an arcuate illumination area. As a result, the contrast uniformity within the screen is improved and a uniform image can be obtained.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  Embodiment 1 of the present invention will be described with reference to FIG.

  FIG. 1 is a diagram of a projection optical system of a scanning projection exposure apparatus for a large liquid crystal display panel in which the present invention is mounted.

  The coordinate system of this schematic diagram is as shown in (16).

  A mercury lamp is used for the light source (1), and the light beam emitted from the light source is collimated by the elliptical mirror (2) and enters the optical integrator (3). The optical integrator is used to control the illuminance uniformity and NA of illumination light in the irradiation area. The light beam emitted from the optical integrator irradiates the slit (5) that defines the irradiation region through the lens and the mirror (4).

  The slit is in a conjugate position with the mask (8). This schematic diagram shows a typical liquid crystal scanning projection exposure apparatus. As shown in the conventional example (FIGS. 3-1, -2), the imaging system (9 to 14 in the figure) of this exposure apparatus is good. The image area is arcuate.

  In the present invention, the focus change caused by the deformation of the self-weight of the mask is controlled by inclining a mirror or the like in the imaging system and illuminating the focused part in the good image area of the imaging system. The shape of the slit opening will be described below.

  The solid line portion (17) shows the shape of the opening of the slit in the ZY plane. A dotted line portion (17) indicates a good image area of the present imaging system, and the slit is inscribed in the good image area. The slit has a structure that can be freely set within the good image area.

  FIG. 8 shows the shape of a typical slit opening. FIG. 8A shows the shape of the opening of the slit suitable when the mask causes its own weight deformation at the free end. In the coordinate system, the longitudinal direction of the slit is the X axis, and the short direction is the Y direction. If the slit central part is X = 0, the shape is symmetrical. FIG. 8-2 has a slit shape suitable when the mask causes its own weight deformation at the fixed end. Compared with FIG. 8-1, a higher-order slit shape is suitable at the peripheral portion. FIG. 8-3 shows a slit shape that is asymmetrical. Used to correct a focus distribution that is asymmetric left and right.

  The light beam collimated by the slit irradiates a mask (8) on which a pattern for a liquid crystal panel is drawn through a lens (6) and a mirror (7). The irradiation area of the mask has a shape similar to the slit opening. The mask is scanned in the Y direction in synchronization with the plate (15).

  As the liquid crystal panel becomes larger, the mask is expected to bend more than before. (18) is a diagram schematically showing the self-weight deformation shape of the mask as seen from the Y direction. Since the mask center part is bent with respect to the mask peripheral part, the focus positions of the mask central part and the mask peripheral part are shifted.

  As shown in the conventional example (FIG. 5), when the length of the mask in the X direction is increased by 20%, the amount of deformation of the mask's own weight becomes twice or more. As the mask becomes larger, the focus distribution increases.

  The light beam that has passed through the mask forms an image on the plate (15) through the imaging system (9 to 14). (11) and (13) are reflection-type optical members that have power for condensing and diverging light rays. (9), (12), and (14) are transmissive optical members that have a function of improving the imaging performance. (10) and (19) are reflection-type optical members that have a function of bending light rays.

  The feature of the present embodiment is that the irradiation area can be arbitrarily adjusted and the mirror (19) having the function of bending the light beam is inclined. The mirror (19) is rotatable around the X axis and can be adjusted according to the amount of focus distribution on the plate surface.

  FIG. 9 is a diagram showing the amount of focus distribution generated when the mirror (19) is tilted. The vertical axis represents the focus change amount, and the horizontal axis represents the direction orthogonal to the scanning direction. When the shape of the opening of the slit is shown in FIG. 8A, the amount of change in focus when the mirror is tilted is represented by A in FIG. When the slit shape is as shown in FIG. 8B, the amount of change in focus when the mirror is tilted is represented by B in FIG. Compared with the focus shape A, it can be seen that a higher-order focus change amount occurs in the peripheral portion. When the slit shape is shown in FIG. 8C, the focus change amount when the mirror is tilted is represented by C in FIG. It can be seen that the amount of change in focus occurs asymmetrically on the left and right. It is also possible to change the focus amount while maintaining the shape of the focus change that occurs when the tilt amount of the mirror is adjusted. FIG. 9 shows a focus change amount when the shape of the slit opening is A and the tilt amount of the mirror is halved.

  As described above, according to the present invention, it is possible to arbitrarily control the amount of focus change perpendicular to the scanning direction by adjusting the shape of the slit opening and the amount of tilt of the mirror. is there.

  In addition, surface error and surface distortion generate an asymmetric focus distribution in the direction orthogonal to the scanning direction, but as in this embodiment, by adjusting the mirror tilt amount and slit opening according to the focus distribution, The mask pattern can be favorably imaged on the plate surface.

  In this embodiment, an example of focus adjustment is shown by the mirror (17) in the imaging system. In this case, as shown in FIG. 1, the light ray incident on the plate surface (15) has an inclination. Therefore, there is a concern about the influence of distortion due to defocusing.

  FIG. 10 shows an embodiment for correcting the influence of distortion caused by defocusing. The telecentricity correction plate (20) corrects the inclination of light incident on the mask from the illumination system. The telecentricity correction plate is a wedge-shaped or aspherical transmissive optical member, and can tilt a predetermined amount of light from the illumination system. The light beam that has passed through the mask pattern illuminated by the illumination light tilted by a predetermined amount enters the plate vertically, and the influence of distortion due to defocusing can be reduced.

  In this embodiment, the focus change is generated by tilting the reflection mirror in the imaging system. As a method of generating a similar focus change, there is a method of tilting the mask (8) or the plate (15) as shown in FIG. By performing scanning exposure with the mask or plate tilted, the same focus change as when the reflecting mirror is tilted can be generated, and the same effect as in the first embodiment can be obtained.

  Further, the minute performance change caused by the tilt error of the mirror surface and the tilt error of the mask / plate surface is an optical component that is less sensitive to the drive amount (FIGS. 2-9, 10, 12, 14). It may be corrected by position adjustment or angle adjustment of

  In Japanese Patent Laid-Open No. 10-214780, the influence of the focus distribution due to the self-weight deformation of the mask is reduced by correcting the deflection of the mask by controlling the pressure of the mask and the space above the mask. However, it is expected that the deflection error will increase as the mask size increases. The present invention is also effective as a method for correcting a focus distribution due to a deflection error caused by atmospheric pressure control.

  In the first embodiment, a correction method of the focus distribution in the circumferential direction (radial radius direction—the longitudinal method in FIG. 1-17) when performing scanning exposure is shown. On the other hand, in order to manufacture a good liquid crystal display panel, it is necessary to control the focus distribution in the scanning direction (short method in FIGS. 1-17).

  When the performance of the imaging system is shown in FIG. 13-1 (the same aberration diagram as in FIG. 3-1), when the folding mirror or the plate surface in the imaging system is tilted, the plate surface is shown by a thick solid line. Thus, a focus difference occurs between the image height A and the image height B.

  In the scanning projection exposure apparatus, defocused images from image height A to image height B are integrated, which affects the pattern image formed on the plate. In a projection exposure apparatus, an exposure method for adding defocused images is used as a method for improving the depth of an image with respect to a specific circuit pattern. However, if the defocus amount of an integrated image is large, the image contrast is increased. There is also a concern of lowering.

  In particular, in order to produce a high-definition liquid crystal display panel, it is necessary to control the contrast of the image.

  FIG. 12 shows a second embodiment of the projection optical system that adjusts the focus difference in the scanning direction and controls the focus distribution orthogonal to the scanning direction. The difference from the first embodiment is that the radius of curvature of the convex mirror (FIG. 12-13) in the imaging system is different.

  FIG. 12 shows the second embodiment, and the radius of curvature of the convex mirror (13) in the imaging system is different from that of the first embodiment. Compared to the radius of curvature of the convex mirror of Example 1, the radius of curvature of the convex mirror differs by 10 to 100 Newtons. When the radius of curvature of the convex surface changes, the imaging performance changes. However, in this optical system, the curvature of field particularly in the good image area changes. The field curvature is the distribution of the focal position in the optical axis direction with respect to the image height.

  FIG. 13 shows the performance of the imaging system when the curvature radii of the convex surfaces are different. FIG. 13-1 is a performance diagram in a state where there is no field curvature, and FIG. 13-2 is a performance diagram when the convex curvature radius of the imaging system of FIG. 13-1 is changed.

  In FIG. 13, the imaging surface when the folding mirror or the plate surface in the imaging system is tilted is indicated by a thick solid line. In the case of FIG. 13A, the image plane and the field curvature when the folding mirror and the plate surface in the image forming system are tilted do not match. Therefore, when scanning exposure is performed, the defocused images from the image height A to the image height B are integrated, and there is a concern that the contrast of the image is lowered.

  In 13-2, the image forming surface and the field curvature when the folding mirror and the plate surface in the image forming system are tilted coincide with each other to the extent that the contrast of the image is not deteriorated. Therefore, in the central portion of the arc-shaped slit (the region shown in FIG. 12-17 (1)), an image is added that does not deteriorate the contrast of the image even if scanning exposure is performed, and the exposure that does not decrease the contrast of the image. An apparatus can be realized.

  Example 2 will be specifically described in more detail.

  In the present invention, the tilt amount of the reflection mirror in the imaging system is determined according to the mask bend amount. This will be described with reference to FIG. The coordinate system is as shown. The scanning direction during scanning exposure is the Y direction.

  For example, assuming an exposure system using a ± 45 degree tension angle in an imaging system with an image height in the good image area of 400 mm to 500 mm, the longitudinal direction of the exposure area is 500 / √2 = ± 353 mm. The depth of the arc is 500 x (1-1 / √2) = 146mm. If the mask self-weight deformation amount is 146 μm, the focus difference between X = 0 and X = 353 is adjusted, so that the mirror is tilted to generate a focus change of 146 μm / 146 mm = 100 μm / 100 mm on the plate surface.

  In Example 2, the curvature of field is adjusted in order to reduce the decrease in image contrast. When the curvature of field is generated by changing the power in the imaging system (in the embodiment, the curvature radius of the convex surface is changed), a uniform focus change occurs in the circumferential direction.

  FIG. 14 shows the focus distribution on the plate surface when the curvature of field is generated. In addition, the amount of curvature of field was set to 100 μm from an image height of 400 mm to 500 mm, and a dotted line indicated a place where the focus in the circumferential direction was uniform. The pitch of the focus contour lines was 25um.

  From the above, it is assumed that the exposure width in the scanning direction at X = 0 (the width in the Y direction) is 100 mm, and focus correction of 100 μm / 100 mm is performed by tilting the mirror in the imaging system. In FIG. 14, when a field curvature of −100 μm / 100 mm is generated at X = 0, the focus distribution in the short direction of the slit generated by the mirror tilt and the focus distribution generated by the field curvature cancel each other. An image without the influence of direction defocusing is obtained.

  However, when X = ± 343 mm, the direction of occurrence of field curvature is not the scanning direction, and the amount of focus distribution due to field curvature is −100 μm / 157 mm.

  In order to control the image contrast in a well-balanced manner in the exposure region orthogonal to the scanning direction, it is necessary to generate a well-balanced field curvature at X = 0 mm and X = ± 353 mm.

  FIG. 14B shows the shape of the focus distribution in FIG. 14A with a YZ cross section with X = 0 and a YZ cross section with X = 353 mm. The vertical axis represents the focus distribution (um), and the horizontal axis represents the Y axis (mm) of each sectional view.

  When a 100um field curvature is generated at an image height of 400mm to 500mm, X = 0 has an inclination of 100um / 100mm and cancels the 100um / 100mm defocus caused by mirror tilt. However, when X = 353 mm, the inclination is 64 μm / 100 mm, and a residue of 36 μm / 100 mm remains with respect to the defocus of 100 μm / 100 mm generated by the mirror tilt.

  This is because when the field curvature is generated under this condition and scanning exposure is performed, the defocused image of 36um is added at X = 353mm, and the line width variation of the image exposed in the direction orthogonal to the scanning direction is increased. growing.

  As a method for obtaining an image having a small line width variation in a direction orthogonal to the scanning direction, a method of distributing residues can be mentioned.

  If an image surface curvature of 112 um is generated from an image height of 400 mm to 500 mm, an Xum has an inclination of 118 um / 100 mm at X = 0, and an 18 um residue remains with respect to 100 um / 100 mm generated by mirror tilt. Further, when X = 353 mm, the inclination is 82 μm / 100 mm, and a residue of 18 μm / 100 mm remains with respect to the defocus of 100 μm / 100 mm generated by the mirror tilt.

  This is because when scanning exposure is performed with the field curvature generated under these conditions, even if X = 0 mm or X = 353 mm, 18um defocused images are added together, and the line width variation is perpendicular to the scanning direction. A small image can be obtained.

  In this embodiment, the curvature of field is generated by changing the radius of curvature of the convex mirror. In order to obtain the same effect, the Y-direction positions of the convex mirror (13) and the meniscus lens (12) in FIG. 12 may be moved.

  As described above, when the field curvature is generated according to the amount of inclination of the folding mirror or the plate surface in the imaging system, an exposure apparatus capable of adjusting the focus distribution while controlling the contrast of the image can be realized.

The figure which showed Example 1 of this invention. The figure which showed the prior art example. (3-1) Aberration diagram showing performance of imaging system, (3-2) Diagram showing good image area of imaging system. (4-1) A diagram showing a mask holding portion and a scanning direction, and (4-2) a diagram showing a self-weight deformation of the mask. The figure which showed the weight deformation amount of the mask when the magnitude | size of a mask changed. The conceptual diagram of the amount of focus correction when tilting the stage. The correction residue figure at the time of tilting the stage and correcting the focus change due to the self-weight deformation of the mask. (8-1) Slit shape 1 of Example 1, (8-2) Slit shape 2 of Example 1, and (8-3) Slit shape 3 of Example 1. FIG. 3 is a focus distribution diagram that is generated when the mirror is tilted in the slit shape of the first embodiment. The conceptual diagram when the telecentricity is correct | amended in Example 1. FIG. FIG. 3 is a conceptual diagram when the mask stage or the plate stage is tilted in the first embodiment. The figure which showed Example 2 of this invention. (13-1) Diagram showing the relationship between defocusing of the image plane and good image area when no curvature of field occurs, (13-2) Image plane and good image when curvature of field occurs The figure which showed the relationship of area | region defocusing. (14-1) Contour drawing of the focus distribution of the imaging system when the field curvature occurs, (14-2) The focus distribution of the imaging system when the field curvature occurs Figure.

Claims (9)

  A scanning projection exposure apparatus for imaging an arcuate illumination area, comprising: a first means for deforming the illumination area in accordance with a focus distribution of a projection optical system.   2. The scanning projection exposure apparatus according to claim 1, further comprising second means for generating a focus change in a circumferential direction (radial direction) of the arc.   2. The scanning projection exposure apparatus according to claim 1, further comprising means for deforming a shape of an opening of a slit at a position conjugate with an illumination area as the first means.   3. The scanning projection exposure apparatus according to claim 2, wherein the second means includes means for inclining a reflecting optical member in the imaging optical system.   The scanning projection exposure apparatus according to claim 2, further comprising means for inclining a plate stage as the second means.   The scanning projection exposure apparatus according to claim 2, further comprising means for inclining a mask stage as the second means.   3. The scanning projection exposure apparatus according to claim 2, further comprising third means for generating a focus change (curvature of field) in the radial direction of the arc.   8. The scanning projection exposure apparatus according to claim 1, further comprising a fourth means for correcting the telecentricity.   9. The scanning projection exposure apparatus according to claim 1, further comprising fifth means for adjusting the position and inclination of the optical component of the imaging system.

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