JP2012059733A - Exposure device and device manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exposure device advantageous for controlling both distortion aberration and astigmatism of a projection optical system to be within a target range.SOLUTION: The exposure device has a projection optical system for projecting a pattern of an original plate onto a substrate and exposes the substrate. The projection optical system includes a first parallel flat plate at a front side of a pupil thereof and a second parallel flat plate at a rear side of the pupil. Two shapes, which are obtained by bending points on the first parallel flat plate and the second parallel flat plate corresponding to each other so that each of the points moves to the same direction, are defined as a first shape and a second shape. And two shapes, which are obtained by bending points on the first parallel flat plate and the second parallel flat plate corresponding to each other so that each of the points moves to an opposite direction, are defined as a third shape and a fourth shape. Then, the distortion aberration and the astigmatism of the projection optical system are adjusted by deforming the first parallel flat plate so as to become a fifth shape obtained by synthesizing the first shape and the third shape, and by deforming the second parallel flat plate so as to become a sixth shape obtained by synthesizing the second shape and the fourth shape.

Description

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

  Semiconductors, liquid crystal panels, and the like are manufactured by a photolithography process. In the photolithography process, an exposure apparatus that projects a pattern on an original plate called a mask or a reticle onto a glass substrate or wafer coated with a photosensitive agent called a resist via a projection optical system is used. In recent years, with the miniaturization of the pattern line width, the performance of the exposure apparatus has been improved. Therefore, it is necessary to correct distortion (distortion aberration) and astigmatism in order to satisfy strict apparatus specifications. Distortion refers to deviation of the exposure pattern on the substrate from the ideal lattice position when a mask having an ideal lattice is exposed. Regarding the correction of magnification, as shown in Patent Document 1, a parallel plate having a thickness that does not affect the imaging performance is arranged in the optical path of the imaging optical system, and the shape of the parallel plate is changed. The magnification is corrected by curving. As for distortion correction, as disclosed in Patent Document 2, correction is performed by partially deforming a parallel plate in the optical path of the imaging optical system. Regarding correction of astigmatism, position adjustment and aspherical processing of a refractive optical element constituting the projection optical system are performed. The aspherical surface processing means that at least one surface of the optical element is processed into an aspherical shape having a characteristic of canceling out aberration.

Japanese Patent Laid-Open No. 08-306618 JP 2000-195784 A

  At present, distortion and astigmatism are corrected separately. If the target component is corrected, another aberration is generated, and the image performance deteriorates due to the generated aberration, and it takes time to correct it due to the processing of the optical element and reassembly of the exposure device. To do.

  An object of the present invention is to provide an exposure apparatus that is advantageous for keeping both distortion and astigmatism of a projection optical system within a target range.

  The present invention is an exposure apparatus that has a projection optical system that projects an original pattern onto a substrate, and that exposes the substrate, the projection optical system including a first parallel plate on the front side of the pupil, and The first shape has two shapes obtained by including a second parallel plate behind the pupil and bending the corresponding points of the first parallel plate and the second parallel plate so as to move in the same direction. The two shapes obtained by bending the shape corresponding to the shape and the second shape and moving the corresponding points of the first parallel plate and the second parallel plate so as to move in opposite directions are the third shape and the fourth shape. Then, the first parallel plate is deformed so as to be a fifth shape obtained by combining the first shape and the third shape, and the sixth shape is formed by combining the second shape and the fourth shape. The second parallel plate is deformed so that Adjusting the distortion and the astigmatism of the projection optical system, characterized in that.

  According to the present invention, for example, it is possible to provide an exposure apparatus that is advantageous for keeping both distortion and astigmatism of a projection optical system within a target range.

It is a figure which shows a part of exposure apparatus in one Embodiment of this invention. It is a flowchart of the procedure which correct | amends distortion and astigmatism in one Embodiment of this invention. It is a figure which shows the effect | action which corrects the distortion or astigmatism in Example 1,2. It is a figure which shows the effect | action which corrects the distortion and astigmatism in Example 3. FIG. It is a figure which shows the exposure apparatus in one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[Exposure equipment]
An exposure apparatus for exposing a substrate according to the present invention will be described with reference to FIGS. First, the optical system of the exposure apparatus will be described, and then the parallel plate portion of the exposure apparatus will be described. FIG. 5 is a diagram showing an optical system in the scanning exposure method used in this embodiment. As shown in FIG. 5, the exposure apparatus includes an illumination system 11, an alignment scope 10 that detects alignment marks on the original 1 and the substrate 7, and a projection optical system 12 that projects a pattern on the original 1 onto the substrate 7. Although not shown in FIG. 5, the illumination system 11 may include, for example, a light source, a first condenser lens, a fly-eye lens, a second condenser lens, a slit defining member, an imaging optical system, and a plane mirror. The light source can include, for example, a mercury lamp and an elliptical mirror. The slit defining member defines the illumination range of the original 1 (that is, the cross-sectional shape of the slit-shaped light that illuminates the original 1). The imaging optical system is arranged so as to image the slit defined by the slit defining member on the object plane. The plane mirror bends the optical path in the illumination system 11.

  The projection optical system 12 projects an image of the pattern on the original 1 illuminated by the illumination system 11 onto the substrate 7. The original 1 is disposed on the object plane of the projection optical system 12, and the substrate 7 is disposed on the image plane of the projection optical system 12. Although the projection optical system 12 can be configured as any one of an equal magnification imaging optical system, an enlarged imaging optical system, and a reduced imaging optical system, in the present embodiment, it is configured as an equal magnification optical system. In the projection optical system 12, the first parallel plate 2a, the first plane mirror 14, the first concave mirror, the convex mirror 17, the second concave mirror, and the second parallel plate 2b are arranged in the optical path from the object plane to the image plane in order from the object plane. Has been placed. In FIG. 5, the first concave mirror and the second concave mirror are constituted by one concave mirror 16. The plane including the mirror surface of the first plane mirror 14 and the plane including the mirror surface of the second plane mirror 15 form an angle of 90 degrees with each other. The first plane mirror 14 and the second plane mirror 15 may be integrally formed. The first parallel plate 2a and the second parallel plate 2b have the same thickness. The pattern image on the original 1 illuminated by the illumination system 11 passes through the first parallel plate 2a, the first plane mirror 14, the concave mirror 16, the convex mirror 17, the concave mirror 16, the second plane mirror 15 and the second parallel plate 2b again. An image is formed on the substrate 7. In this state, the substrate 7 is scanned along the y direction (scanning direction), and all the patterns on the original 1 are exposed. In the projection optical system 12, the convex mirror 17 is at the pupil position of the projection optical system 12. Therefore, the projection optical system 12 includes the first parallel flat plate 2a on the front side of the pupil and the second parallel flat plate 2b on the rear side of the pupil.

  FIG. 1 is a schematic view showing a portion excluding the illumination system in the scanning exposure apparatus according to the present embodiment. In the figure, reference numeral 6 denotes an optical system including a first plane mirror 14, a concave mirror 16, a convex mirror 17, a concave mirror 16, and a second plane mirror 15 excluding the first parallel plate 2 a and the second parallel plate 2 b from the projection optical system 12. . In the drawing, the z-axis of the xyz coordinate system is taken in parallel to the optical axis of the projection optical system 12, and the right-handed coordinate is taken in the plane perpendicular to the z-axis in the scanning direction of the exposure apparatus. The first parallel plate 2a and the second parallel plate 2b are respectively deformed by the deformation mechanisms 3a and 3b. The parallel plates 2a and 2b have an optical thickness that does not substantially affect the imaging performance other than the shift of the imaging position. In the case of an i-line exposure apparatus, for example, synthetic quartz may be used as the material of the parallel plates 2a and 2b. For example, if the plate thickness is uniform, an arc shape or a rectangle may be used in accordance with the shape of the exposure light beam. The deformation mechanisms 3a and 3b have a pair of drive units and holding units facing each other across the parallel plates 2a and 2b in a direction parallel to the scanning direction (y direction) of the parallel plates 2a and 2b. The drive unit can be driven in the normal direction (z direction) of the plane of the parallel plates 2a and 2b to be deformed, and deforms the surface shape of the parallel plates 2a and 2b. The holding interval of the driving unit is arranged according to the period of the nonlinear distortion to be corrected. For example, the holding interval of the drive unit can be narrow when correcting nonlinear distortion more precisely, and can be wide when the operation does not require precision. The measurement systems 5a and 5b measure the substrate position of each of the parallel plates 2a and 2b. The measuring systems 5a and 5b are composed of a movable displacement meter or a plurality of fixed displacement meters that measure the displacement of the parallel plates 2a and 2b or the deformation mechanisms 3a and 3b, and can be configured as a contact type or a non-contact type. is there. The measurement systems 5 a and 5 b are arranged on the drive mechanism 9 of the substrate 7 or the drive mechanism 8 of the original 1. The measurement systems 5 a and 5 b may be held by a mechanism other than the substrate drive mechanism 9 and the original plate drive mechanism 8.

  The exposure apparatus includes a control unit 4 that controls deformation of the first parallel plate 2a and the second parallel plate 2b via the deformation mechanisms 3a and 3b. The control unit 4 includes calculation units 4a and 4b that calculate the driving amounts of the deformation mechanisms 3a and 3b, respectively. The control unit 4 has an input unit 4c for distortion (distortion aberration) and astigmatism measurement values measured from the pattern on the substrate after projection exposure. The calculation units 4a and 4b calculate the difference between the distortion and astigmatism measurement results and the desired distortion and astigmatism state, or the difference between the distortion and astigmatism-free state. The calculation units 4a and 4b determine the surface deformation shape of the parallel plates 2a and 2b for eliminating the difference between the measurement result and a desired state, and calculate the driving amounts of the deformation mechanisms 3a and 3b necessary for the surface deformation. . The control unit 4 outputs a drive signal for driving the deformation mechanisms 3a and 3b. Further, the arithmetic units 4a and 4b input displacement amounts of the parallel flat plates 2a and 2b or the deformation mechanisms 3a and 3b after the surface deformation measured by the measurement systems 5a and 5b. Then, the calculation units 4a and 4b calculate the difference between the drive amount calculated for the surface deformation and the measured displacement amount, and calculate the drive amount of the deformation mechanisms 3a and 3b that minimize the drive error. The arithmetic units 4a and 4b can easily automate a series of calculations by using, for example, a computer.

  Next, a procedure for correcting distortion and astigmatism will be described with reference to FIG. The distortion and astigmatism of the pattern of the original 1 projected onto the substrate 7 by test exposure are measured. If the distortion and astigmatism measurement values are acceptable for the tolerance, the exposure apparatus continues to be used as it is. When the measured value is not negligible with respect to the allowable value, the surface deformation shapes of the parallel plates 2a and 2b necessary for correction are calculated by the calculation units 4a and 4b, and the driving amounts of the respective deformation mechanisms 3a and 3b are determined. The control unit 4 drives the deformation mechanisms 3a and 3b to perform surface deformation of the parallel plates 2a and 2b. The parallel plates 2a and 2b are deformed by the deformation mechanisms 3a and 3b in a plane (in the xz plane) including at least the direction orthogonal to the scanning direction and the optical axis of the projection optical system 12, and in the scanning direction and the projection optical system 12. And at least one of in-plane including the optical axis (in the yz plane). The displacements of the parallel plates 2a, 2b or the deformation mechanisms 3a, 3b are measured by the measurement systems 5a, 5b, and the deformation amount of the surface shape of the parallel plates 2a, 2b calculated by the calculation units 4a, 4b or the driving of the deformation mechanisms 3a, 3b. The control unit 4 determines whether the calculated error is within an allowable range. If the drive error is within the allowable range, the control unit 4 ends the correction and starts using the exposure apparatus. When the drive error cannot be ignored with respect to the allowable value, the control unit 4 calculates the drive amounts of the deformation mechanisms 3a and 3b that minimize the drive error by the calculation units 4a and 4b, and again the parallel by the deformation mechanisms 3a and 3b. Surface deformation of the flat plates 2a and 2b is performed.

[Example 1]
FIG. 3A shows the measurement results of the distortion of the substrate pattern and the astigmatism measured after the test exposure in Example 1. 3A, 3B, and 3C, the vertical axis of the left graph indicates distortion, and the vertical axis of the right graph indicates astigmatism. The horizontal axis indicates the position in the x direction in FIG. 1 of the exposure region of the substrate to be exposed. With respect to the deformation mechanisms 3a and 3b, the calculation unit is configured to calculate the drive amount at each location so that the x-direction surface shape of the driven parallel plates 2a and 2b is a shape represented by z = ax ³ (a <0). Calculated by 4a and 4b. The control unit 4 drives the deforming mechanisms 3a and 3b at each location according to the calculated driving amount. After driving, the driving error is measured by the measuring systems 5a and 5b. When the drive error cannot be ignored, the control unit 4 calculates the drive amounts of the deformation mechanisms 3a and 3b that minimize the drive error by the calculation units 4a and 4b, and again the surfaces of the parallel plates 2a and 2b by the deformation mechanisms 3a and 3b. Perform deformation. When the distortion and astigmatism of the pattern of the substrate exposed by the apparatus after the plane deformation of the parallel plates 2a and 2b are measured, the measurement results of distortion and astigmatism as shown in FIG. 3B are obtained. When both the first parallel plate 2a and the second parallel plate 2b have the same surface deformation shape, the second parallel plate 2b and the first parallel plate 2a generate astigmatism that occurs in the first parallel plate 2a. Astigmatism that cancels astigmatism occurs. On the other hand, the same amount of distortion occurs in each parallel plate 2a, 2b. As a result, the astigmatism of the exposure image that has passed through the first parallel plate 2a, the optical system 6, and the second parallel plate 2b does not change, and only the distortion changes. Thus, by giving the same plane shape to the parallel plates 2a and 2b, it is possible to independently correct only the distortion without affecting the astigmatism.

[Example 2]
FIG. 3A shows the measurement results of the distortion and astigmatism of the substrate pattern measured after the test exposure. The first parallel flat plate 2a is deformed into a surface shape represented by z ₁ = −ax ³ (a <0) in the x direction, and the second parallel flat plate 2b is deformed into z ₂ = ax ³ (a <0) in the x direction. In such a case, a result as shown in FIG. 3C is obtained. When a surface shape represented by z ₁ = −h (x) is given to the first parallel plate 2a and a surface shape represented by z ₂ = h (x) is given to the second parallel plate 2b, each surface Cause the same astigmatism. Here, h (x) is not a constant. On the other hand, with respect to the distortion, a distortion that cancels the distortion generated in the first parallel flat plate 2a is generated in the second parallel flat plate 2b with respect to the distortion generated in the first parallel flat plate 2a. As a result, the distortion of the exposure image that has passed through the first parallel plate 2a, the optical system 6, and the second parallel plate 2b does not change, and only astigmatism changes. Thereby, the deformation amount in the z direction represented by z ₁ = −h (x) is applied to the first parallel plate 2a, and the z direction in the z direction represented by z ₂ = h (x) is applied to the second parallel plate 2b. By providing the deformation amount, it is possible to independently correct only astigmatism without affecting the distortion.

[Example 3]
FIG. 4A shows the measurement results of the distortion of the substrate pattern and the astigmatism measured in Example 3 after the test exposure. The first parallel plate 2a is represented by z ₁ = bx ⁴ -cx ³ (b <0, c <0) in the x direction, and the second parallel plate 2b is represented by z ₂ = bx ⁴ + cx ³ in the x direction. When the shape is deformed, a result as shown in FIG. 4B is obtained.

Let g (x) be the amount of deformation in the z direction to be applied to the first parallel plate 2a and the second parallel plate 2b in order to correct the distortion in the x direction. Further, the deformation amount in the z direction to be applied to the first parallel plate 2a and the second parallel plate 2b in order to correct the astigmatism in the x direction is h (x). At least one of g (x) and h (x) is not a constant. The position z _{1 in} the z direction of the cross-sectional shape when the first parallel flat plate 2a is cut along a plane parallel to the xz plane is z ₁ = g (x) −h (x) + k ₁ (where k ₁ is a constant) ) So that the first parallel flat plate 2a is deformed in the z direction. At the same time, the position _{z 2} in the z-direction cross-sectional shape obtained by cutting the second parallel plate 2b in xz plane parallel to the _{plane, z 2 = g (x)} + h (x) + k 2 ( provided that _{k 2} is a constant) The second parallel flat plate 2b is deformed in the z direction so as to satisfy the above. As a result, distortion occurs when the parallel plate 2a, 2b is given a surface shape represented by z = g (x). On the other hand, astigmatism, astigmatism generated when a surface shape represented by z = −h (x) is given to the first parallel plate 2a and z = h (x) is given to the second parallel plate 2b, is astigmatism. appear. Thus, distortion in the x direction and astigmatism can be corrected independently.

In the present invention, the deformation direction of the surface shapes of the first parallel plate 2a and the second parallel plate 2b is not limited to the x direction, but also holds in the y direction. Now, let the deformation amount in the z direction to be applied to the first parallel plate 2a and the second parallel plate 2b in order to correct the distortion in the y direction be m (y). Further, the deformation amount in the z direction to be applied to the first parallel plate 2a and the second parallel plate 2b in order to correct the astigmatism in the y direction is n (y). Here, it is assumed that at least one of m (y) and n (y) is not a constant. At that time, the position z _{3 in} the z direction of the cross-sectional shape when the first parallel flat plate 2a is cut along a plane parallel to the yz plane is z ₃ = m (y) −n (y) + k ₃ (where k ₃ is The first parallel plate 2a is deformed in the z direction so as to satisfy (constant). At the same time, the position z _{4 in} the z direction of the cross-sectional shape when the second parallel flat plate 2b is cut along a plane parallel to the yz plane is z ₄ = m (y) + n (y) + k ₄ (where k ₄ is a constant). The second parallel flat plate 2b is deformed in the z direction so as to satisfy the above. Then, y-direction distortion and astigmatism can be corrected independently.

  The mechanism for changing the surface shapes of the first parallel plate 2a and the second parallel plate 2b in the y direction is the same as the mechanism for changing the surface shapes of the first and second parallel plates 2a, 2b in the x direction. Can be used. By simultaneously performing surface deformation in the x direction and y direction of the first and second parallel plates 2a and 2b, distortion and astigmatism in the x direction and y direction can be corrected simultaneously.

  The present invention is not limited to the equal-magnification imaging optical system, and can be configured in any of an enlargement imaging optical system and a reduction imaging optical system. Now, two shapes obtained by bending the corresponding points of the first parallel plate 2a and the second parallel plate 2b so as to move in the same direction are defined as a first shape and a second shape. Two shapes obtained by bending the corresponding points of the first parallel plate 2a and the second parallel plate 2b so as to move in opposite directions are defined as a third shape and a fourth shape. At that time, the first parallel flat plate 2a is deformed so as to be a fifth shape obtained by synthesizing the first shape and the third shape, and a sixth shape obtained by synthesizing the second shape and the fourth shape is obtained. The second parallel plate 2b is deformed. Then, even if the projection optical system 12 is an enlargement imaging optical system or a reduction imaging optical system, the distortion aberration and astigmatism of the projection optical system 12 can be adjusted.

[Device manufacturing method]
The device manufacturing method according to a preferred embodiment of the present invention is suitable for manufacturing a semiconductor device or an FPD device, for example. The method may include a step of exposing a substrate coated with a photosensitive agent using the above exposure apparatus, and a step of developing the exposed substrate. Furthermore, the device manufacturing method may include other well-known steps (oxidation, film formation, vapor deposition, doping, planarization, etching, resist stripping, dicing, bonding, packaging, and the like).

Claims (5)

An exposure apparatus having a projection optical system for projecting a pattern of an original onto a substrate, and exposing the substrate,
The projection optical system includes a first parallel plate on the front side of the pupil, and a second parallel plate on the rear side of the pupil,
Two shapes obtained by bending the corresponding points of the first parallel plate and the second parallel plate so as to move in the same direction are defined as a first shape and a second shape, and the first parallel plate When the two shapes obtained by bending the corresponding points of the second parallel flat plate so as to move in opposite directions are the third shape and the fourth shape, the first shape and the third shape are The first parallel flat plate is deformed to be a combined fifth shape, and the second parallel flat plate is deformed to be a sixth shape obtained by combining the second shape and the fourth shape, Adjusting distortion and astigmatism of the projection optical system;
An exposure apparatus characterized by that.   The projection optical system is an equal-magnification optical system, and in the optical path from the object plane to the image plane, the first parallel plate, the first plane mirror, the first concave mirror, the convex mirror, the second concave mirror, the second plane mirror, and The exposure apparatus according to claim 1, wherein the exposure apparatus includes the second parallel plates in order, and the convex mirror is located at the position of the pupil. The exposure is performed while scanning the original and the substrate along a scanning direction,
The first parallel plate and the second parallel plate have an in-plane including a direction orthogonal to the scanning direction and the optical axis of the projection optical system, and the scanning direction and the optical axis of the projection optical system. Deflected in at least one of the containing planes,
The exposure apparatus according to claim 1 or 2, wherein A drive unit for deforming the first parallel plate and the second parallel plate;
A control unit that controls the drive unit based on the distortion and the astigmatism;
The exposure apparatus according to any one of claims 1 to 3, further comprising:
A step of exposing the substrate using the exposure apparatus according to any one of claims 1 to 4,
Developing the substrate exposed in the step;
A device manufacturing method comprising:

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