JP2012004564A - Exposure method, exposure apparatus and method of manufacturing device - Google Patents

Abstract

An overlay error between superimposed patterns is reduced.
An exposure method of the present invention is an exposure method in which an image of a pattern is projected onto a substrate and the pattern is exposed on the substrate, and exposure light is irradiated onto a first substrate on which the image of the underlying pattern is projected. Projecting a first pattern image over a plurality of irradiation areas, obtaining an overlay error of the first pattern image with respect to the base pattern image for each irradiation area, The projection conditions in the first and second irradiation areas are set so that the overlapping error in the first and second irradiation areas adjacent to each other among the irradiation areas is distributed to the first and second irradiation areas. Adjusting.
[Selection] Figure 4

Description

  The present invention relates to an exposure method, an exposure apparatus, and a device manufacturing method.

  When forming a film pattern on a large substrate, a multi-lens scan exposure apparatus may be used (for example, see Patent Document 1). This type of exposure apparatus projects an image of a mask pattern onto a substrate by a projection optical system while synchronously scanning the mask and the substrate in a predetermined scanning direction. The projection optical system includes a plurality of projection modules arranged in a direction intersecting the scanning direction, and an adjustment unit that adjusts projection conditions such as the position, shape, and dimensions of the projection image on the substrate. The light that becomes the projection image scans the substrate while adjusting the projection conditions by the adjusting means, and the pattern is exposed by the plurality of projection images.

  In the device manufacturing process, device components may be formed by stacking, and a plurality of patterns may be superimposed and exposed in the process. When a plurality of patterns are overlaid and exposed, the accuracy of the relative position between the plurality of patterns may be required. As a method for aligning a plurality of patterns, a method is known in which the position of a pattern to be exposed is aligned with the position of an exposed pattern.

JP 2001-215718 A

  When a plurality of patterns are overlaid and exposed, if the position of each projection image is adjusted to the position of the exposed pattern for each projection module, the splicing accuracy between the plurality of projection images may be reduced. On the other hand, if it is attempted to ensure the joint accuracy of a plurality of projection images, it may be difficult to reduce the overlay error.

  The present invention has been made in view of the above circumstances, and an object thereof is to reduce an overlay error between superimposed patterns.

  An exposure method according to a first aspect of the present invention is an exposure method in which an image of a pattern is projected onto a substrate and the pattern is exposed on the substrate, and exposure light is emitted from the first substrate on which the image of the underlying pattern is projected. Projecting the image of the first pattern across the plurality of irradiation areas and applying the overlay error of the image of the first pattern to the image of the base pattern to the irradiation areas. Each of the first and second irradiation regions so as to distribute the overlap error in the first and second irradiation regions adjacent to each other among the plurality of irradiation regions. And adjusting the projection condition in the second irradiation region.

  In the exposure method according to the second aspect of the present invention, an image of a pattern included in a mask is divided into first and second projection regions adjacent to each other in the first direction and projected onto the substrate, and the pattern is projected onto the substrate. An exposure method for exposing, wherein an image of a first pattern of a first mask is projected onto a first substrate on which a base pattern has been exposed, divided into the first and second projection regions, and projected onto the first substrate. Exposing the first pattern; a first irradiation area where the first pattern is exposed by the first projection area; and a second irradiation area where the first pattern is exposed by the second projection area. Determining the overlay error between the base pattern and the first pattern in each of the first and second irradiation regions based on the overlay error in each of the first and second irradiation regions. Territory Adjusting the projection condition of the image of the pattern in the first and second projection areas so that the overlay error is distributed to the second mask, and adjusting the projection condition and adjusting the projection condition. Dividing an image of two patterns into the first and second projection regions, projecting the image onto a second substrate, and exposing the second pattern onto the second substrate.

  A device manufacturing method according to a third aspect of the present invention includes exposing a substrate using the exposure method according to the aspect of the present invention, and developing the exposed substrate.

  An exposure apparatus according to a fourth aspect of the present invention includes a projection optical system that projects an image across a plurality of irradiation areas irradiated with exposure light, and an area in which the projection optical system projects the first image. When projecting the second image in an overlapping manner, an overlay error of the second image with respect to the first image is caused in the first and second irradiation regions adjacent to each other in the plurality of irradiation regions. A control device that controls the projection conditions of the projection optical system for each of the irradiation areas so as to be distributed.

  A device manufacturing method according to a fifth aspect of the present invention includes exposing a substrate using the exposure apparatus according to the aspect of the present invention, and developing the exposed substrate.

  According to the present invention, it is possible to reduce the overlay error between the superimposed patterns while ensuring the joint accuracy in a plurality of projection images.

It is a perspective view which shows one Embodiment of exposure apparatus. It is a perspective view which shows the structural example of a projection module. It is a conceptual diagram which shows the projection area | region on a board | substrate. It is a figure which shows one Embodiment of the exposure method. It is a top view which shows an example of the positional relationship of an irradiation area | region and a measurement point. It is a conceptual diagram which shows an example of the overlap error vector in each measurement point. (A), (b) is a figure which shows the example of the overlay error in each irradiation area | region, a correction amount, and a residual error. (A) is a graph which shows an example of the appearance frequency with respect to the value of the X-axis direction component of an overlay error, (b) is a graph which shows an example of the appearance frequency with respect to the value of the Y-axis direction component of an overlay error. It is a figure which shows one Embodiment of a device manufacturing method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the scope of the present invention is not limited to the following embodiments. In the following description, an XYZ orthogonal coordinate system is set, and the positional relationship of each part will be described based on the XYZ orthogonal coordinate system. A predetermined direction in the horizontal plane is defined as an X-axis direction, a direction orthogonal to the X-axis direction in the horizontal plane is defined as a Y-axis direction, and a direction orthogonal to each of the X-axis direction and the Y-axis direction (that is, a vertical direction) is defined as a Z-axis direction. Further, the rotation (inclination) directions around the X axis, Y axis, and Z axis are the θX, θY, and θZ directions, respectively.

  FIG. 1 is a perspective view showing an embodiment of an exposure apparatus. The exposure apparatus EX of the present embodiment is a multi-lens scan exposure apparatus that performs exposure by projecting an image of the pattern of the mask M onto the substrate P while moving the mask M and the substrate P synchronously in a predetermined scanning direction. is there.

  The exposure apparatus EX shown in FIG. 1 includes a mask stage 1, a substrate stage 2, an interferometer system 3, an illumination system IS, a projection system PS as a projection optical system, and a control apparatus 4. The mask stage 1 is movable while holding the mask M. The substrate stage 2 is movable while holding the substrate P. The interferometer system 3 measures the position of the mask stage 1 and the position of the substrate stage 2. The illumination system IS illuminates the mask M with the exposure light EL. The projection system PS projects an image of the pattern of the mask M illuminated with the exposure light EL onto the substrate P. The control device 4 controls the overall operation of the exposure apparatus EX.

  The mask stage 1 includes a mask holding unit 10 that can hold the mask M. The mask M includes a reticle on which a pattern is formed. The mask holding unit 10 of this embodiment holds the mask M so that the pattern formation surface of the mask M is substantially parallel to the XY plane. The mask stage 1 is movable with respect to the first to seventh illumination regions IR1 to IR7 by a driving force of a driving system including a linear motor, for example. The mask stage 1 of the present embodiment can be moved in three directions of the X axis, the Y axis, and the θZ direction with the mask M held by the mask holding unit 10 by the above drive system.

  The substrate stage 2 includes a substrate holder 11 that can hold the substrate P. The substrate P is used for manufacturing a liquid crystal panel, for example, and has a rectangular shape in plan view with a side size of, for example, 500 mm or more. The substrate holding part 11 of this embodiment holds the substrate P so that the surface (exposure surface) of the substrate P and the XY plane are substantially parallel. The substrate P is a photosensitive substrate and includes, for example, a base material such as a glass plate and a photosensitive film such as a photoresist film provided on the base material. The surface layer of the substrate may be, for example, a film that forms a part of various functional films such as an antireflection film, a film that forms a part of a thin film transistor, or a film that becomes a wiring or an electrode. This film may be an insulating film, a conductive film, or a semiconductor film. The substrate stage 2 is movable with respect to the first to seventh projection regions PR1 to PR7 by a driving force of a driving system including a linear motor, for example. The substrate stage 2 of the present embodiment has six directions of the X-axis, Y-axis, Z-axis, θX, θY, and θZ directions in a state where the substrate P is held by the substrate holder 11 by the operation of the drive system described above. Can be moved to.

  The interferometer system 3 includes a first interferometer unit 3A and a second interferometer unit 3B. The first interferometer unit 3A can optically measure the position of the mask stage 1 (mask M) in the XY plane. The second interferometer unit 3B can optically measure the position of the substrate stage 2 (substrate P) in the XY plane. When executing the exposure process of the substrate P or when performing a predetermined measurement process, the control device 4 controls the relative position between the mask stage 1 and the substrate stage 2 based on the measurement result of the interferometer system 3. .

  The controller 4 controls the mask stage 1 and the substrate stage 2 when exposing the substrate P, and moves the mask M and the substrate P in a predetermined scanning direction in the XY plane. In the present embodiment, it is assumed that the scanning direction (synchronous movement direction) of the substrate P is the X-axis direction, and the scanning direction (synchronous movement direction) of the mask M is also the X-axis direction. That is, the control device 4 moves the substrate P in the X axis direction with respect to the projection area of the projection system PS, and in synchronization with the movement of the substrate P, moves the mask M with respect to the illumination area of the illumination system IS in the X axis direction. Move to. During synchronous movement of the mask M and the substrate P, the illumination system IS illuminates the mask M with the exposure light EL, and the projection system PS projects the exposure light EL that has passed through the mask M onto the substrate P.

  The illumination system IS of this embodiment includes a mercury lamp 5, an elliptical mirror 6, a dichroic mirror 7, a relay optical system 8, a light guide unit 9, and a plurality (seven in the figure) of illumination modules IL1 to IL7. In the following description, each of the illumination modules IL1 to IL7 will be appropriately referred to as first to seventh illumination modules IL1 to IL7. In the present embodiment, light having a predetermined wavelength among the light emitted from the mercury lamp 5, here, one or more of g-line, h-line, and i-line are separated by the dichroic mirror 7 and used as the exposure light EL.

  The light emitted from the mercury lamp 5 is reflected by the elliptical mirror 6 and then enters the dichroic mirror 7. The dichroic mirror 7 has a characteristic of selectively reflecting a predetermined wavelength component in incident light. The exposure light EL (separated bright line) reflected by the dichroic mirror 7 enters the relay optical system 8. The relay optical system 8 includes a collimating lens and a condenser lens. The exposure light EL that has passed through the relay optical system 8 enters the light guide unit 9. The light guide unit 9 branches the exposure light EL from the relay optical system 8 and guides it to each of the first to seventh illumination modules IL1 to IL7.

  The first illumination module IL1 includes a collimating lens, a fly eye integrator, and a condenser lens. The exposure light EL from the light guide unit 9 enters the fly eye integrator through the collimator lens, and enters the condenser lens through the fly eye integrator. The exposure light EL emitted from the condenser lens illuminates the first illumination area IR1. The configurations of the second to seventh illumination modules IL2 to IL7 are the same as those of the first illumination module IL1.

  The illumination system IS can irradiate the exposure light EL to each of a plurality (seven in the drawing) of illumination areas IR1 to IR7. The illumination area IR1 is illuminated by the exposure light EL emitted from the first illumination module IL1. Similarly, the illumination areas IR2 to IR7 are illuminated by the second to seventh illumination modules IL2 to IL7. In the following description, the illumination areas IR1 to IR7 are appropriately referred to as first to seventh illumination areas IR1 to IR7.

  The positional relationship of each illumination area with respect to the pattern formation surface of the mask M changes with time as the mask stage 1 moves. The illumination system IS illuminates a part of the mask M corresponding to the first to seventh illumination regions IR1 to IR7 at each time with the exposure light EL having a uniform illuminance distribution.

  The projection system PS has the same number (seven in the drawing) of projection modules PL1 to PL7 as the illumination modules IL1 to IL7. In the following description, each of the projection modules PL1 to PL7 is appropriately referred to as first to seventh projection modules PL1 to PL7. The number of projection modules (the same number as the illumination modules) is not limited to 7. For example, the projection system PS may have 11 projection modules, and the illumination system IS may have 11 illumination modules. The projection system PS can project the exposure light EL onto a plurality (seven in the drawing) of projection regions PR1 to PR7. In the following description, the projection areas PR1 to PR7 are appropriately referred to as first to seventh projection areas PR1 to PR7.

  Each projection module of the projection system PS has a one-to-one correspondence with each illumination module of the illumination system IS. For example, the exposure light EL emitted from the first illumination module IL1 illuminates the first illumination region IR1 on the mask M, passes through the mask M, and then the first projection region on the substrate P by the first projection module PL1. Projected to PR1. Similarly, the exposure light EL emitted from the second to seventh illumination modules IL2 to IL7 is projected by the second to seventh projection modules PL2 to PL7 via the second to seventh illumination regions IR2 to IR7. Projected to regions PR2 to PR7.

  The positional relationship of each projection area with respect to the exposure surface of the substrate P changes with time as the substrate stage 2 moves. The projection system PS displays the pattern image of the mask M corresponding to the first to seventh illumination regions IR1 to IR7 at each time on the substrate P corresponding to the first to seventh projection regions PR1 to PR7 at this time. A portion is projected at a predetermined projection magnification.

  FIG. 2 is a perspective view showing a configuration example of the projection module. The first to seventh projection modules PL1 to PL7 have the same configuration, and here, the configuration of the first projection module PL1 will be described as a representative.

  The first projection module PL1 shown in FIG. 2 includes a first Dyson optical system 21, a second Dyson optical system 22, a field stop 23, a shift mechanism 24, a rotation correction mechanism 25, a magnification correction mechanism 26, and a compensation optical system 27. The field stop 23 is disposed in the optical path between the first Dyson optical system 21 and the second Dyson optical system 22. The shift mechanism 24 is disposed in the optical path between the mask stage 1 (mask M) and the first Dyson optical system 21.

  The emission optical axis of the first illumination module IL1 is parallel to the Z-axis direction, and the exposure light EL that has passed through the mask M enters the first Dyson optical system 21 through the shift mechanism 24. The exposure light EL emitted from the first Dyson optical system 21 travels in the Z-axis direction and enters the field stop 23, and the exposure light EL that passes through the field stop 23 enters the second Dyson optical system 22. The exposure light EL emitted from the second Dyson optical system 22 travels in the Z-axis direction and forms a projection image on the substrate P.

  The first Dyson optical system 21 includes a right-angle prism 31, a lens 32, and a concave mirror 33. The right-angle prism 31 has two reflecting surfaces. One of the two reflecting surfaces forms an angle of 45 ° with respect to the pattern forming surface of the mask M, and the other forms an angle of −45 ° with respect to the pattern forming surface of the mask M. The optical axis of the lens 32 and the optical axis of the concave mirror 33 are parallel to the in-plane direction of the mask M. The second Dyson optical system 22 has the same configuration as the first Dyson optical system 21 and includes a right-angle prism 34, a lens 35, and a concave mirror 36.

  The shift mechanism 24, the rotation correction mechanism 25, and the magnification correction mechanism 26 constitute an imaging characteristic adjustment mechanism of the first projection module PL1. By controlling the imaging characteristic adjusting mechanism, the projection condition of the projected image on the substrate P can be adjusted for each projection module. The projection conditions here include one or more items of the translation position, rotation position, shape, and size of the projection area on the substrate P. The projection condition can be determined for each position of the projection area with respect to the substrate P at the time of synchronous scanning. By adjusting the projection condition of the projection image, it is possible to correct the distortion of the projection image when compared with the pattern of the mask M.

  The shift mechanism 24 can shift the projection image independently in the X-axis direction and the Y-axis direction. The rotation correction mechanism 25 can rotate the projection image in the θZ direction. The magnification correction mechanism 26 can adjust the magnification of the projected image. The shift mechanism 24, the rotation correction mechanism 25, and the magnification correction mechanism 26 are individually controlled by the control device 4 for each projection module.

  The shift mechanism 24 includes parallel flat plates 41 and 42 having translucency. The shift mechanism 24 shifts (translates) the projected image in the X-axis direction by rotating the X-shift parallel plate 41 in the θY direction. Similarly, the shift mechanism shifts the projection image in the Y-axis direction by the parallel plate 42 for Y shift.

  The rotation correction mechanism 25 includes a prism base 43 and actuators 44 and 45. The right-angle prism 31 is attached to the prism base 43 via actuators 44 and 45. The actuators 44 and 45 are constituted by piezoelectric elements, for example. The actuators 44 and 45 change the interval between the right-angle prism 31 and the prism base 43 at the attachment position of each piezoelectric element.

When the expansion / contraction amount of the piezo element is made different between the actuator 44 and the actuator 45, the right-angle prism 31 rotates around the emission optical axis (Z axis) of the first illumination module IL1, and the projection image formed on the substrate P is in the θZ direction. Rotate to.
When the actuator 44 and the actuator 45 have the same amount of expansion and contraction of the piezo elements and the distance between the right-angle prism 31 and the prism base 43 is changed, the right-angle prism 31 moves in the X-axis direction.
In this way, the imaging position of the exposure light EL can be changed, and the focus can be adjusted by the rotation correction mechanism 25. In FIG. 2, the actuators are arranged at two locations, but the right-angle prism 31 may be supported at three or more points by using three or more piezoelectric elements.

  The magnification correction mechanism 26 is configured by, for example, a zoom optical system disposed in the optical path between the right-angle prism 31 and the lens 32. The zoom optical system has, for example, a plurality of lenses and actuators. The focal distance of the zoom optical system can be variably controlled by changing the lens interval of the plurality of lenses with an actuator. The compensation optical system 27 is disposed in the optical path between the lens 35 of the second Dyson optical system 22 and the right-angle prism 34. The compensation optical system 27 is configured by, for example, a plurality of lenses so as to cancel out the influence of aberration and the like caused by the magnification correction mechanism 26.

FIG. 3 is a conceptual diagram showing a projection area on the substrate.
In the present embodiment, the planar shapes of the first to seventh projection regions PR1 to PR7 on the substrate P are all trapezoids. The first, third, fifth, and seventh projection regions PR1, PR3, PR5, and PR7 (hereinafter collectively referred to as the first group) are arranged side by side at substantially equal intervals in the Y-axis direction. The second, fourth, and sixth projection regions PR2, PR4, and PR6 (hereinafter collectively referred to as the second group) are arranged side by side at substantially equal intervals in the Y-axis direction.

  The projection area belonging to the first group is arranged on the negative side in the X-axis direction with respect to the projection area belonging to the second group. With respect to the Y-axis direction, projection areas belonging to the first group and projection areas belonging to the second group are alternately arranged. For example, the second projection region PR2 is disposed between the first and third projection regions PR1 and PR3. The first to seventh projection regions PR1 to PR7 are arranged such that the end in the Y-axis direction of the projection region belonging to the first group overlaps with the end in the Y-axis direction of the projection region belonging to the second group with respect to the Y-axis direction. Is placed.

  When the substrate P is moved in the scanning direction during exposure, the exposure light EL incident on the first projection region PR1 scans the substrate P in the scanning direction, and the first irradiation region PA1 that is the scanning range of the exposure light EL is set. Exposed. Similarly, the second to seventh irradiation areas PA2 to PA7 are exposed by the exposure light EL irradiated to the second to seventh projection areas PR1, respectively. The first to seventh irradiation areas PA1 to PA7 have overlapping areas where a pair of irradiation areas adjacent to each other overlap. For example, in the first irradiation area PA1, the first overlapping area PB1 overlaps with the second irradiation area PA2, and the second irradiation area and the sum area are configured using the first overlapping area PB1 as a joint. Similarly, the second to seventh irradiation areas PA2 to PA7 form a sum area and an irradiation area adjacent to each other in the Y direction with the second to sixth overlapping areas PB2 to PB6 as joints. Each of the first to seventh projection areas PR1 to PR7 is arranged such that the integrated exposure amounts of the respective irradiation areas when the substrate P is moved in the scanning direction during exposure are equal.

  By the way, in the manufacturing process of a device, the component of a device may be laminated and formed, and in the process, a plurality of patterns corresponding to various components may be superimposed on a substrate and exposed. The projection condition of the projected image may change for each projection module depending on each layer constituting the laminated structure. In the present embodiment, when the projection system PS projects an image of the pattern to be exposed on the exposed pattern, the control device 4 controls the projection conditions by the projection system PS.

  Specifically, the control device 4 controls each imaging characteristic adjustment mechanism so as to distribute the overlapping error between the exposed pattern and the pattern to be exposed to a pair of irradiation areas adjacent to each other. Control projection conditions. The overlay error is a value corresponding to the relative position between the substrate P and the projection area at the time of exposure, and is measured in advance by test exposure described later. The correction amount used for adjusting the projection condition of the projection image is obtained based on the measurement result in the test exposure. This correction amount is set as a value associated with the relative position of the projection region with respect to the substrate P. This correction amount is stored in a storage device provided as an internal device or an external device of the control device 4, for example, in a table format.

FIG. 4 is a diagram showing an embodiment of an exposure method. Here, an embodiment of an exposure method will be described based on the configuration of the above-described exposure apparatus EX.
In the exposure method of this embodiment, first, test exposure is performed in steps S1 and S2. In step S3, an overlay error during test exposure is obtained, and in step S4, correction information for each projection module is obtained. Then, in step S5, using the correction information obtained in step S4, the main exposure for manufacturing the device is performed while correcting the projection image by each projection module. Hereinafter, processing in each step will be described.

  In step S1, a ground pattern is exposed on a test substrate as a first substrate, and position information of the ground pattern on the test substrate is obtained. This position information includes the coordinates of a plurality of positions on the base pattern. In the test substrate of this embodiment, one or more items among the material, size, and shape are the same as the substrate P (second substrate) that is the subject of the main exposure. For example, a test substrate having the same lot as the substrate P is used. The shape of the base pattern is not particularly limited. For example, a shape including a cross hatch or the like used for an alignment mark or the like, a shape capable of detecting the position of the exposed base pattern by pattern recognition, or the like is manufactured. Is appropriately selected from the shape and the like of the film pattern constituting the film. The base pattern of the present embodiment has the same shape as the film pattern of the layer corresponding to the base pattern in the device to be manufactured.

  As a method for obtaining the position of the ground pattern, for example, a method of optically detecting each projection area when exposing the ground pattern, a method of developing and detecting the exposed ground pattern, and a method of developing the ground pattern For example, a reflective film pattern such as a metal wiring is formed and a method of optically detecting the reflective film pattern, a surface pattern of the test substrate is detected to detect unevenness or deformation amount, and a simulation of the position of the base pattern image The method of estimating by is mentioned. It is also possible to obtain coordinates of three or more positions of the base pattern by obtaining coordinates on the test substrate for two or more points on the base pattern and performing interpolation processing or the like.

  In the present embodiment, after laminating one or more layers on the layer on which the ground pattern is exposed, in step S2, an image of the first pattern is projected on the ground pattern that has been exposed. For example, by using the projection system PS described above, the image of the first pattern is projected onto the sum area of the first to seventh irradiation areas PA1 to PA7. The shape of the first pattern is appropriately selected similarly to the base pattern, and may be the same shape as the base pattern or a shape different from the base pattern. The first pattern of this embodiment has the same shape as the film pattern of the layer corresponding to the first pattern in the device to be manufactured.

  In step S3, for example, the position of the first pattern on the test substrate is measured, and the overlay error of the first pattern with respect to the base pattern is determined for each of the first to seventh irradiation areas PA1 to PA7 based on the coordinates on the test substrate. Ask. As a method for measuring the position of the first pattern, a method similar to the measurement of the position of the base pattern can be used. The overlay error of the first pattern with respect to the base pattern is, for example, the position of the first pattern and the reference position in the test exposure with the position of the first pattern when the first pattern is superimposed on the base pattern in design as a reference position. Are represented by vectors (hereinafter referred to as error vectors).

  FIG. 5 is a plan view showing an example of the positional relationship between the irradiation region and the measurement point, and FIG. 6 is a conceptual diagram showing an example of the overlap error vector at each measurement point. Reference numeral M1 in FIG. 5 indicates a boundary line corresponding to the first projection module PL1 when the center line in the Y direction of the overlapping area of the first irradiation area PA1 and the second irradiation area PA2 is used as the boundary line. 2 shows a region (hereinafter referred to as a first module region) located closer to the first irradiation region PA1. Similarly, reference numerals M2 to M4 indicate second to fourth module areas corresponding to the second to fourth projection modules PL2 to P4, respectively.

  In the present embodiment, a plurality of measurement points are set in an area excluding the overlapping area in each irradiation area, and an overlay error of the first pattern at each measurement point is obtained. For example, measurement points MP1 to MP3 are set in the first irradiation area PA1 excluding the first overlapping area PB1 shown in FIG. 3 and in the vicinity of the first overlapping area PB1. The number of measurement points is not particularly limited, and the number of measurement points can be increased from the viewpoint of obtaining a high-definition distribution of overlay errors, or the number of measurement points can be reduced from the viewpoint of reducing the load of measurement. You can also reduce the number.

  In the present embodiment, the positions of the measurement points MP1 to MP3 are set so that the measurement points MP1 to MP3 are arranged in a direction (X-axis direction) in which the relative position between the projection region and the substrate changes during exposure. Further, in the second irradiation area PA2 constituting the sum area with the first irradiation area PA1, the measurement points are set at positions symmetrical to the measurement points MP1 to MP3 with respect to the boundary line.

  In the example shown in FIG. 6, the direction and magnitude (absolute value) of the error vector at each measurement point changes nonlinearly depending on the position of the measurement point in the X-axis direction or the position in the Y-axis direction. One cause of the overlay error of the first pattern with respect to the base pattern is, for example, deformation of the substrate in the manufacturing process and transport process of the substrate, the manufacturing process of the device using the substrate, and the like. When a substrate of the same lot as the substrate used for device manufacture is used as a test substrate, correction information to be described later can be obtained in consideration of the deformation amount of the substrate for each lot. For example, correction information can be obtained by obtaining an overlay error every time a lot of substrates used for manufacturing a device changes.

  In step S4, correction information indicating a correction amount in each irradiation region is obtained, for example, as will be described below, so that the overlapping error in a pair of irradiation regions adjacent to each other is distributed to the pair of irradiation regions.

  FIG. 7A is a diagram illustrating an example of an overlay error, a correction amount, and a residual error in each irradiation region. Reference sign MP in FIG. 7A indicates a point near the boundary between the first module region M1 and the second module region M2. The vector a represents an error vector corresponding to the overlay error at the point MP of the first irradiation area PA1, and the vector b represents an error vector corresponding to the overlay error at the point MP of the second irradiation area PA2. Show. The vector c indicates a correction amount vector corresponding to the position correction amount at the point MP.

  Here, a method for correcting the first and second irradiation areas PA1 and PA2 so that the overlay error is substantially zero will be considered. In this method, the first irradiation area PA1 is such that the position where the point MP is projected by the first projection module PL1 corresponding to the first projection area PR1 is shifted by the same magnitude as the error vector a and in the opposite direction. Correct. Further, the second irradiation area PA1 is corrected so that the position at which the point MP is projected by the second projection module PL2 corresponding to the second projection area PR2 is shifted by the opposite direction and the same magnitude as the error vector b. To do. In general, since the error vectors a and b are not the same, the correction amount differs between the first irradiation area PA1 and the second irradiation area PA2, and the first irradiation area PA1 and the second irradiation area PA2 are different. Misalignment occurs.

  In the present embodiment, the average vector of the error vectors a and b is the correction amount vector c. The correction amount vector c is expressed by the following equation (1) using the error vectors a and b. The error vectors a and b are obtained from the measurement result in step S3.

  As shown in FIG. 7A, in the present embodiment, the first projection module PL1 corresponding to the first projection region PR1 shifts the position at which the point MP is projected by the correction amount vector c. The irradiation area PA1 is corrected. Further, the second irradiation region PA2 is corrected so that the position where the point MP is projected by the second projection module PL2 corresponding to the second projection region PR2 is shifted by the correction amount vector c. Since the correction amount of the position of the projected point MP is the same in the first irradiation area PA1 and the second irradiation area PA2, the overlap between the corrected first irradiation area PA1 and second irradiation area PA2 The joint accuracy in the area can be made equal to that before correction.

  A vector d in FIG. 7A indicates a residual error vector corresponding to an overlay error at the point MP of the first irradiation area PA1 when the first irradiation area PA1 is corrected by the correction amount vector c. The vector e indicates a residual error vector corresponding to the overlay error at the point MP of the second irradiation area PA2 when the second irradiation area PA2 is corrected by the correction amount vector c. The residual error vector d is expressed by the following formula (2), and the residual error vector e is expressed by the following formula (3).

  As can be seen from the equations (2) and (3), the residual error vector d has the same absolute value (magnitude) as the residual error vector e and is a vector having the opposite direction. That is, by correcting by the above correction amount, the overlay error distribution becomes symmetric. The absolute value of the residual error vectors d and e is equal to or smaller than the larger absolute value of the error vectors a and b. In other words, the maximum value of the overlay error can be reduced by correcting by the above correction amount.

  FIG. 7B is a diagram illustrating another example of an error, a correction amount, and a residual error in each irradiation region. In the example shown in FIG. 7B, the magnitudes of the error vectors a and b are substantially the same, and the error vectors a and b are symmetric with respect to the boundary line between the first and second module regions M1 and M2. ing. As can be seen from the equations (2) and (3), as the absolute value of the difference between the error vectors a and b becomes smaller, the absolute values of the residual error vectors d and e become smaller. In the example shown in FIG. 7B, among the d and e components of the residual error vector, the component parallel to the boundary line is almost zero. As described above, the absolute values of d and e of the residual error vector may be smaller than both the absolute value of the error vector a and the absolute value of the error vector b.

  In the above example, the correction amount vector c is set so that the overlap error in the first and second irradiation areas PA1 and PA2 is equally divided into the first and second irradiation areas PA1 and PA2. However, the ratio for distributing the overlay error can be changed as appropriate. For example, as shown in the following equation (4), the correction amount vector c may be set according to the distribution ratio t. The ratio t in Equation (4) is a real number that satisfies 0 <t <1. When correction is performed based on the correction amount vector c shown in Expression (4), the residual error vector d is expressed by the following Expression (5), and the residual error vector e is expressed by the following Expression (6). The above example corresponds to the case where t = 1/2. In principle, the closer the value of t is to ½, the higher the symmetry of the overlay error distribution.

  By using the above-described correction amount calculation method or the like, by calculating correction amount vectors for a plurality of points in the X-axis direction where the relative positions of the projection region and the substrate change during exposure, the projection region and substrate during exposure are obtained. The correction information indicating the correction amount according to the relative position of is obtained. The obtained correction information is stored in, for example, the storage device described above, and is read out to the control device 4 at the time of exposure. In order to adjust the projection condition of the projected image, for example, an adjustment amount by the imaging characteristic adjustment mechanism is set. Specifically, one or more of the shift amount of the projection image in the X-axis direction or Y-axis direction by the shift mechanism, the rotation angle of the projection image around the optical axis of the projection module by the rotation correction mechanism, and the magnification of the projection image by the magnification correction mechanism By setting, it is possible to adjust the projection condition of the projection image so as to satisfy the above correction amount. In the present embodiment, the second pattern is exposed on the substrate P using the correction information obtained in step S4. The second pattern has the same shape as the film pattern of the layer corresponding to the second pattern in the device to be manufactured. That is, in the present embodiment, the first pattern and the second pattern are the same. Further, the first mask used for the exposure of the first pattern and the mask used for the exposure of the second pattern are the same.

  FIG. 8A is a graph showing an example of the appearance frequency of the overlay error with respect to the value of the X-axis direction component, and FIG. 8B is a graph of an example of the appearance frequency of the overlay error with respect to the value of the Y-axis direction component. Comparative example 1 in FIG. 8A and FIG. 8B shows a plot based on a measurement value obtained by performing a test exposure using three substrates in the same lot and measuring an overlay error. Comparative Example 2 shows a plot based on data after linear correction by EGA (enhancement global alignment) with respect to the measurement value of the overlay error of Comparative Example 1. The example shows a plot based on data when the projection condition of the projection image is adjusted according to the exposure method of the present embodiment using the measurement value of the overlay error of the comparative example 1. In the example, the correction amount was calculated by setting the distribution ratio t to ½. As can be seen from FIG. 9A and FIG. 9B, in the example compared to Comparative Example 1, both the X-axis direction component and the Y-axis direction component are around the axis where the overlap error is zero. And the appearance frequency of a superposition error having a large absolute value is reduced. Further, in the example, the appearance frequency of the overlay error near 0 is higher than that of the comparative example 2, and the appearance frequency of the overlay error having a large absolute value is decreased. From this, it can be seen that the overlay error can be reduced according to the exposure method of the present embodiment. In addition, since the symmetry around the axis where the overlay error is 0 is improved, it can be expected that characteristic variations in the manufactured device are reduced.

As described above, according to the exposure method of the present embodiment, it is possible to reduce the maximum value of the overlay error between the superimposed patterns while ensuring the joint accuracy in a plurality of projection images.
Further, if the measurement points are set in the area excluding the overlapping area as described above, it becomes easy to separate the influence of each projection module on the projection image from the influence of other projection modules on the projection image. . On the other hand, if measurement points are set in the overlapping area, it is possible to obtain an overlap error in two irradiation areas at one measurement point, and to reduce the number of measurement points.

  Also, correction information corresponding to the relative position between the projection region and the substrate is obtained by obtaining an overlay error at a plurality of points in the scanning direction (X-axis direction) where the relative position between the projection region and the substrate changes during exposure. Is possible. By adjusting the projection condition of the projection image according to the relative position using the correction information, the overlay error can be reduced even when the overlay error distribution in the scanning direction is nonlinear, for example.

  As the substrate P, not only a glass substrate for a display device but also a semiconductor wafer for manufacturing a semiconductor device, a ceramic wafer for a thin film magnetic head, or a mask or reticle used in an exposure apparatus (synthetic quartz, silicon wafer) ) Etc. apply.

  As the exposure apparatus EX, a scanning exposure apparatus (scanning stepper) of a step-and-scan method in which the mask M and the substrate P are moved synchronously and the substrate P is scanned and exposed with the exposure light EL via the pattern of the mask M. In addition, the present invention can also be applied to a step-and-repeat projection exposure apparatus (stepper) that collectively exposes the pattern of the mask M while the mask M and the substrate P are stationary, and sequentially moves the substrate P stepwise. . The present invention is not limited to an exposure apparatus for manufacturing a liquid crystal display element or a display, but an exposure apparatus for manufacturing a semiconductor element, a thin film magnetic head, an image sensor (CCD), a micromachine, a MEMS, a DNA chip, a reticle or a mask, etc. Can be widely applied to an exposure apparatus for manufacturing.

  The present invention relates to a twin-stage type exposure apparatus having a plurality of substrate stages as disclosed in US Pat. No. 6,341,007, US Pat. No. 6,208,407, US Pat. No. 6,262,796, and the like. Is also applicable. In addition, as disclosed in US Pat. No. 6,897,963, European Patent Application No. 1713113, etc., a substrate stage for holding a substrate, and a reference in which a reference mark is formed without holding the substrate. The present invention can also be applied to an exposure apparatus including a member and a measurement stage on which at least one of various photoelectric sensors is mounted. An exposure apparatus including a plurality of substrate stages and measurement stages can be employed.

  In the above embodiment, the position information of each stage is measured using an interferometer system including a laser interferometer. However, the present invention is not limited to this, and for example, a scale (diffraction grating) provided in each stage is detected. An encoder system may be used.

  In the above embodiment, a light transmissive mask is assumed in which a predetermined light shielding pattern (or phase pattern / dimming pattern) is formed on a light transmissive substrate. For example, US Pat. As disclosed in US Pat. No. 6,778,257, a variable shaped mask (also called an electronic mask, an active mask, or an image generator) that forms a transmission pattern, a reflection pattern, or a light emission pattern based on electronic data of a pattern to be exposed. ) May be used. Further, a pattern forming apparatus including a self-luminous image display element may be provided instead of the variable molding mask including the non-luminous image display element.

FIG. 9 is a diagram showing an example of a device manufacturing method according to the present invention.
In the device manufacturing method shown in FIG. 9, first, the function / performance design of a device such as a liquid crystal panel is performed (step 201). Next, a mask (reticle) is manufactured based on the device design (step 202). Further, a substrate such as a glass wafer, which is a base material of the device, is prepared by purchase, manufacture, or the like (step 203). Next, a film pattern such as an electrode, wiring, insulating film, or semiconductor film constituting the device is formed on the substrate (step 204). Step 204 includes forming a film on the substrate, forming a resist pattern on the film, and etching the film using the resist pattern as a mask. In order to form a resist pattern, a resist film is formed, and the substrate is exposed with exposure light passing through a mask according to the above embodiment, so that an image of the pattern corresponding to the film pattern to be formed is formed on the substrate Projecting onto the resist film and developing the exposed resist film. Next, depending on the device to be manufactured, for example, the substrate is diced, a pair of substrates are bonded together, a liquid crystal layer is formed between the pair of substrates, and the device is assembled (step 205). Next, post-processing such as inspection is performed on the device (step 206). A device can be manufactured as described above.

  DESCRIPTION OF SYMBOLS 1 ... Mask stage, 2 ... Substrate stage, 4 ... Control apparatus, M ... Mask, P ... Substrate, Pt ... Test substrate, PL1-PL7 ... Projection module, PR1-PR7 ... Projection area

Claims (16)

An exposure method for projecting an image of a pattern onto a substrate and exposing the pattern onto the substrate,
Projecting an image of the first pattern across the plurality of irradiation regions to a plurality of irradiation regions irradiated with the exposure light on the first substrate on which the image of the base pattern is projected;
Obtaining an overlay error of the image of the first pattern with respect to the image of the base pattern for each irradiation region;
The first and second irradiation regions so as to distribute the overlap error in the first and second irradiation regions adjacent to each other among the plurality of irradiation regions to the first and second irradiation regions. Adjusting a projection condition in the exposure method.   The exposure method according to claim 1, wherein the projection condition is adjusted such that the magnitude of the overlay error in the first irradiation area and the magnitude of the overlay error in the second irradiation area are close to each other.   The exposure method according to claim 1, further comprising exposing a second pattern to a second substrate different from the first substrate in a state where the projection conditions are adjusted. An exposure method in which an image of a pattern included in a mask is divided into first and second projection regions adjacent to each other in a first direction, projected onto a substrate, and the pattern is exposed on the substrate.
Projecting an image of the first pattern of the first mask divided into the first and second projection areas onto the first substrate on which the base pattern has been exposed, and exposing the first pattern to the first substrate. When,
The ground pattern and the first pattern in each of the first irradiation area where the first pattern is exposed by the first projection area and the second irradiation area where the first pattern is exposed by the second projection area Obtaining an overlay error with one pattern;
The first and second projection regions are arranged such that the overlap error is distributed to the first and second irradiation regions based on the overlap error in each of the first and second irradiation regions. Adjusting the projection condition of the image of the pattern in
With the projection conditions adjusted, the image of the second pattern of the second mask is divided into the first and second projection regions and projected onto the second substrate, and the second pattern is projected onto the second substrate. Exposure method including exposing.   The projection condition is that the magnitude of the overlay error in each of the first and second irradiation areas is greater than the magnitude of the overlay error in at least one of the first and second irradiation areas. The exposure method according to claim 4, wherein the exposure method is adjusted to be small.   The exposure method according to claim 3, wherein the first pattern and the second pattern are the same.   The exposure method according to claim 4 or 5, wherein the first mask and the second mask are the same. An image of the pattern is projected by exposure light that scans the first substrate,
2. The projection condition is adjusted according to the position in the scanning direction based on the overlay error at a plurality of positions in the scanning direction of the exposure light when the image of the first pattern is projected. The exposure method as described in any one of -7. Each of the first and second irradiation areas includes overlapping areas that overlap each other,
The projection condition is adjusted according to any one of claims 1 to 8, wherein a relative positional relationship between the overlapping region in the first irradiation region and the overlapping region in the second irradiation region is not changed. Exposure method. Each of the first and second irradiation areas includes overlapping areas that overlap each other,
The exposure method according to any one of claims 1 to 9, wherein, in each of the first and second irradiation regions, the overlap error is obtained in a region excluding the overlap region.   The projection condition is adjusted according to any one of claims 1 to 10, wherein the projection condition is adjusted so as to average the overlap error in the first irradiation region and the overlap error in the second irradiation region. Exposure method.   The first irradiation so as to reduce the overlapping error in the first irradiation region by half of the sum of the overlapping error in the first irradiation region and the overlapping error in the second irradiation region. The projection condition in the second irradiation region is adjusted so as to adjust the projection condition in the region and reduce the overlap error in the second irradiation region by half of the sum. The exposure method according to any one of the above. The plurality of irradiation areas include a third irradiation area,
The second irradiation region is disposed between the first irradiation region and the third irradiation region, overlaps with the first irradiation region on one end side, and the third irradiation region. And the other end overlaps,
The overlap error in the first irradiation region and the overlap error in the second irradiation region are distributed, and the overlap error in the second irradiation region and the overlap error in the third irradiation region are divided. The exposure method according to any one of claims 1 to 12, wherein the projection condition in the second irradiation region is adjusted so as to be distributed. Exposing the substrate using the exposure method according to any one of claims 1 to 3,
And developing the exposed substrate. A projection optical system that projects an image across a plurality of irradiation regions irradiated with exposure light; and
When the projection optical system projects the second image superimposed on the region where the first image is projected, the overlay error of the second image with respect to the first image is determined by the plurality of irradiation regions. An exposure apparatus comprising: a control device that controls a projection condition by the projection optical system for each of the irradiation areas so as to distribute the first and second irradiation areas adjacent to each other. Exposing the substrate using the exposure apparatus according to claim 15;
And developing the exposed substrate.

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