JP2002022609A - Projection aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a projection aligner in which the wave front aberration of a projection optical system can be measured easily with high accuracy under a state where the projection optical system is mounted on the projection aligner. SOLUTION: A pattern to be inspected sufficiently larger than the resolution limit pattern of a projection optical system is placed in the vicinity of the focus position thereof and the amount of image shift in the focus image of a light beam passed through a sufficiently small region in the aperture of the projection optical system, among focus light beams of the pattern, is measured at a plurality of sufficiently small regions in order to calculate the wave front aberration of the projection optical system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a projection exposure apparatus for transferring a pattern on a mask to a photosensitive substrate via a projection optical system, which is used in a lithography process for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art In a photolithography process in the manufacture of semiconductor devices, a projection type exposure apparatus for transferring a circuit pattern formed on a reticle or a photomask (hereinafter collectively referred to as a reticle) onto a semiconductor wafer coated with a photosensitive agent. Is used. In this type of exposure apparatus, in order to transfer a pattern on a reticle onto a wafer with high accuracy at a predetermined magnification (reduction ratio), it is important to use a projection optical system with good imaging performance and reduced aberration. . In recent years, with the demand for further miniaturization of semiconductor devices, there has been an increasing demand for transferring a finer pattern than the imaging performance expected of conventional optical systems. In forming a finer pattern than ever before, the sensitivity of the optical system to aberrations is high. On the other hand, the projection optical system is required to have a large exposure area and a high NA, which makes aberration correction more difficult.

In a situation where the requirements for aberrations are becoming severe, there is a demand for measuring the aberrations of the projection optical system, particularly the wavefront aberration, in a state where the projection optical system is mounted on the exposure apparatus, that is, in a state where the projection optical system is actually used for exposure. Has arisen. This is because the measurement of the wavefront aberration makes it possible to precisely adjust a lens in accordance with a use state and to design a device that is hardly affected by aberration.

As a manual projection for determining the imaging performance of the projection optical system in a state of being mounted on an exposure apparatus, a pattern is actually exposed / exposed.
There is a method of developing and estimating the amount of aberration from a pattern shift or shape, or a method of obtaining the contrast of a pattern having a specific shape such as a bar chart. However,
No attempt has been made to determine the wavefront aberration using these methods. The method of obtaining wavefront aberration using an interferometer is generally used as an inspection device at the stage of manufacturing a projection optical system, and has a technically and costly wall to be mounted on an exposure device, and is not practical. .

[0005]

In the method of estimating the amount of aberration from the pattern shift and the shape by actually exposing and developing a pattern, the time and cost required for the measurement are long, and the process for resist and development is difficult. Difficult to separate from factors. In addition, the obtained result only estimates a specific aberration, and cannot obtain total aberration information of the projection optical system. On the other hand, in the method of obtaining the wavefront aberration in a manner of obtaining the contrast using a bar chart, it is necessary to obtain the contrast in a very large number of bar charts from a coarse pitch to a pitch exceeding the resolution limit, on the production of the bar chart, and Not practical in terms of measurement effort.

In order to mount an interferometer on a projection exposure apparatus, an interferometer including a prism, a mirror, a lens, and the like, and an illumination system with good coherence for the interferometer must be arranged near the reticle stage or wafer stage. Not be. In general, the space near the wafer stage or reticle stage is often limited, and the size of the interferometer and the illumination system for the interferometer is limited. High difficulty. Furthermore, due to the recent shortening of the exposure wavelength, a light source with good coherence that can be used for an interferometer in the exposure wavelength region does not exist or is very expensive. For this reason, mounting the interferometer type aberration measuring apparatus on a projection exposure apparatus is not practical either technically or cost-effectively.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a projection exposure apparatus having a function of directly measuring the wavefront aberration of a projection optical system on an apparatus.

[0008]

According to a first aspect of the present invention, there is provided a projection exposure apparatus for projecting and exposing a circuit pattern on a reticle or a photomask onto a substrate via a projection optical system. When arranging a pattern on an object plane or an imaging plane and forming an image of the pattern via the projection optical system, a partial area is formed in an opening of the projection optical system, and the position of the partial area is variable. Means to do
The method is characterized in that wave shifts of the projection optical system are calculated by measuring image shift amounts caused by the image formation of the light beam passing through the partial area with respect to a plurality of positions in the aperture.

According to a second aspect of the present invention, in the first aspect of the present invention, an illumination aperture variable hand throw that allows a sufficiently small area within the aperture of the projection optical system to pass through an illumination system for making illumination light incident on the projection optical system. And a light receiving system that detects the position of the image formed through the projection optical system after passing through the illumination aperture variable unit, and the image shift formed according to the change of the illumination aperture variable unit. The amount is measured, and the wavefront aberration amount of the projection optical system is calculated from the image shift amount information of the plurality of illumination apertures.

According to a third aspect of the present invention, in the first aspect of the present invention, the illumination light incident on the projection optical system is illuminated so as to have a greater extent than a pupil of the projection optical system, and is formed through the projection optical system. Light-receiving aperture variable means for allowing a light-receiving system for detecting the position of the image to pass through a sufficiently small area within the aperture of the projection optical system, and an image formed in response to a change in the light-receiving aperture means The shift amount is measured, and the wavefront aberration amount of the projection optical system is calculated from the image shift amount information of the plurality of light receiving apertures.

According to a fourth aspect of the present invention, in the second or third aspect, the projection optical system is arranged on a wafer stage of the projection lens as a pattern arranged on an image plane of the projection optical system for observing the image shift amount. It is characterized in that a measurement pattern sufficiently larger than the resolution limit pattern of the projection optical system is arranged near the image forming position of the system.

According to a fifth aspect of the present invention, in the second, third or fourth aspect, the illumination system has a dedicated illumination system for measuring aberration.

According to a sixth aspect of the present invention, in the fifth aspect, the illumination system is configured as a TTR alignment scope.

The invention of claim 7 is characterized in that, in the invention of claim 5, the illumination system illuminates the measurement pattern from the wafer stage side.

The invention of claim 8 is characterized in that, in the invention of any one of claims 2 to 7, the light receiving system is configured in common with a TTR alignment scope.

According to a ninth aspect of the present invention, in the first aspect of the present invention, a reference mark is provided at a position on a reticle corresponding to the measurement pattern when the image shift amount is measured. The image shift amount is measured from a relative distance between a mark and the measurement pattern.

According to a tenth aspect of the present invention, in the ninth aspect, the reference mark is formed of a single edge pattern.

An eleventh aspect of the present invention is characterized in that, in the ninth or tenth aspect of the present invention, the position of the reference mark on the reticle is detected in the light receiving system without passing through the projection optical system.

According to a twelfth aspect of the present invention, in any one of the first to eighth aspects, the position of the image of the measurement pattern is measured as a reference position by imaging using the entire aperture of the projection optical system, Measuring the image shift amount caused by the imaging of the light beam that has passed through a sufficiently small area in the opening of the projection optical system based on the reference position, and calculating the wavefront aberration amount of the projection optical system. I have.

According to a thirteenth aspect of the present invention, in the invention according to any one of the first to twelfth aspects, the size of the aperture by the illumination aperture variable means or the light reception aperture variable means is optically the diameter of the pupil of the projection optical system. It is characterized by having a diameter of about 1/10 of the size of.

According to a fourteenth aspect of the present invention, there is provided a projection exposure apparatus for projecting and exposing a circuit pattern on a reticle or a photomask onto a substrate via a projection optical system. And a mechanism for photoelectrically detecting the position of the image of the first pattern via the projection optical system when the first pattern is arranged, the second pattern being disposed on a wafer stage, and Means for forming a partial area in the opening of the lens and changing the position of the partial area, wherein the image shift of the first pattern with respect to the second pattern caused by the imaging of the light beam passing through the partial area The amount is measured for a plurality of positions in the opening to calculate a wavefront aberration of the projection optical system.

A fifteenth aspect of the present invention is characterized in that, in the fourteenth aspect, the photoelectric detection mechanism is mounted on a wafer stage.

The invention of claim 16 is characterized in that, in the invention of claim 14 or 15, the ratio of the pitch of the first pattern to the pitch of the second pattern is equal to the magnification of the projection optical system.

According to a seventeenth aspect of the present invention, there is provided the illumination system according to the fourteenth, fifteenth, or sixteenth aspect, wherein the illumination system allows illumination light to enter the projection optical system, so that the illumination system can pass through a sufficiently small area within the opening of the projection optical system. It has a variable aperture hand throw, and has a light receiving system that detects the position of the image formed through the projection optical system through the illumination aperture variable means, and forms the light in response to a change in the illumination aperture variable means. The amount of image shift to be performed is measured, and the amount of wavefront aberration of the projection optical system is calculated from the information of the amount of image shift of a plurality of illumination apertures.

According to an eighteenth aspect of the present invention, in the invention of the seventeenth aspect, the pattern arranged on the reticle surface for observing the image shift amount is a measurement pattern sufficiently larger than a pattern corresponding to the resolution limit of the projection optical system. Is arranged.

The invention of claim 19 is characterized in that, in the invention of claim 17 or 18, the illumination system has a dedicated illumination system for measuring aberration.

The invention of claim 20 is characterized in that, in the invention of claim 17 or 18, the illumination system is shared with an illumination system for projection exposure.

According to a twenty-first aspect of the present invention, the size of the aperture in the pupil of the projection optical system formed by the illumination aperture variable means is the same as that of the pupil of the projection optical system. It is characterized by having a diameter of about 1/10 of the diameter.

According to a twenty-second aspect of the present invention, in any one of the first to twenty-first aspects, the ray aberration of the projection optical system is obtained from the measured image shift amount, and the wavefront aberration amount is calculated from the ray aberration amount. It is characterized by doing.

A projection exposure apparatus according to a twenty-third aspect of the present invention is a projection exposure apparatus for projecting and exposing a circuit pattern on a reticle or a photomask illuminated by an illumination optical system onto a substrate via the projection optical system. The illumination optical system is characterized in that an illumination aperture varying means for measuring the wavefront aberration of the projection optical system is provided therein.

A projection exposure apparatus according to a twenty-fourth aspect of the present invention is a projection exposure apparatus for projecting and exposing a circuit pattern on a reticle or a photomask onto a substrate via a projection optical system. A variable aperture for measuring wavefront aberration is provided at the conjugate position.

According to a twenty-fifth aspect of the present invention, there is provided a method for measuring a wavefront aberration of a projection optical system of a projection exposure apparatus for projecting and exposing a circuit pattern on a reticle or a photomask onto a substrate via a projection optical system. A partial area is set within the aperture of the projection optical system from the pupil conjugate position of the projection optical meter outside the projection optical system, and an image shift amount caused by imaging of a light beam passing through the partial area is determined by the aperture. And measuring the wavefront aberration of the projection optical system.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiments described below, the ray aberration of the projection optical system is obtained from the image shift amount information of a plurality of areas within the aperture of the projection optical system. can do.

An image forming beam which passes through a sufficiently small area in the aperture of the projection optical system is generated by illuminating a variable aperture aperture in the illumination system or illuminating so as to cover the entire pupil of the projection optical system. This is realized later by using a light-receiving aperture variable means arranged in the light-receiving system.

That is, first, an arbitrary position within the opening of the projection optical system is illuminated under illumination conditions of a sufficiently small area, and a measurement width and a pitch having a line width and a pitch at which the diffracted light distribution within the opening of the projection optical system is sufficiently small. The reflection and diffraction patterns of the pattern to be inspected are observed by the detection optical system via the projection optical system. Subsequently, the amount of shift of the image of the pattern to be inspected is detected to measure the amount of lateral aberration. The measurement is performed for a plurality of sufficiently small illumination conditions, and the wavefront aberration of the projection optical system is calculated based on the position information in the opening of the projection optical system and the shift information of the pattern to be inspected.

The pattern 11 to be inspected is a pattern having a size that falls within the isoplanatic area in the image forming area of the projection optical system, and the distribution of the diffracted light of the pattern, that is, the Fourier transform is small in the pupil space. It is a pattern having a shape having only expansion. When the illumination light beam for illuminating the pattern 11 is also narrowed down so as to be limited in the pupil space, the light beam in the pupil space for forming an image of the pattern can be reduced,
Local ray aberration information (ε, η) in the pupil can be obtained. Here, (ε, η) indicates a ray aberration on the connection surface of the projection optical system, that is, a so-called lateral aberration.

In general, the wavefront aberration φ and the ray aberration (ε,
During η), if R ′ is the optical path length between the position where the imaging light beam intersects the reference spherical surface and the position where it intersects on the imaging surface, ε (x, y) = R′∂φ / ∂x ... <1) η (x, y) = R′∂φ / ∂y (2) Therefore, the wavefront aberration φ can be obtained from the equations (1) and (2). Here, (x, y) is the position coordinates of the pattern to be inspected on the imaging plane (on the measurement plane) and the coordinates of the exit pupil plane of the projection optical system. The derivation of this relational expression is based on Max Born, Emil
Wolf, "Principlesof Optics 6 ^th Edition", Chapter
V, 1993, Pergamon Press.

In general, R ′ is an amount dependent on aberration, and is expressed by the following equation (1),
(2) It is customary to obtain a wavefront aberration from a complicated process. The purpose of this patent is to obtain the wavefront aberration φ in a practical form by using equations (1) and (2).

FIG. 2A is a diagram illustrating the relationship between the light rays and the wavefronts at the exit pupil, the image plane, and the light intensity distribution measurement plane of the projection optical system. The symbols in the figure are as follows. XYZ: a coordinate system in which the center of the exit pupil of the projection optical system 10 is the origin and the optical axis direction is the Z axis. W: Wavefront of an image forming light beam emitted from the pattern to be inspected 11 and formed by the projection optical system 10 and passing through the center of the exit pupil. G: Reference spherical surface. C: imaging plane of the projection optical system 10. D: Intensity distribution measuring surface of light intensity distribution measuring device 18. O1: the center of the exit pupil of the projection optical system 10. O2: center of reference sphere. P1: A point at which the image forming light flux of the pattern 11 to be inspected crosses the exit pupil plane. P2: The imaging light flux of the pattern 11 to be inspected is the intensity distribution measurement surface D
Intersection with (imaging plane C). Q0: A point at which the maximum NA light flux of the imaging light flux of the pattern 11 to be inspected crosses the reference spherical surface. Q1: The point where the imaged light flux of the pattern 11 to be inspected crosses the wavefront W. Q2: The point at which the imaging light flux of the pattern 11 to be inspected intersects the reference spherical surface. R: radius of reference sphere. R ': distance Q2P2. φ: wavefront aberration of the projection optical system 10 (optical path length Q1Q2). (Ε, η): Ray aberration (line segment O2P2). H0: maximum radius of the exit pupil of the projection optical system 10. NA0: numerical aperture corresponding to the maximum radius of the exit pupil of the projection optical system 10. NA0 = H0 / R xy coordinates: XY standardized by the maximum radius of the exit pupil of the projection optical system 10.
Coordinate.

X = H0.x, Y = H0.y H0 ': The maximum radius of the area where the total luminous flux from the exit pupil of the projection optical system 10 crosses on the intensity distribution measurement plane without aberration.

H0 ′ = NA0 · (L−R) As described above, ε = R ′ ∂φ / ∂X = R (1 + △ R / R) ∂φ / ∂X η = R '∂φ / ∂Y = R (1 + △ R / R) ∂φ / ∂Y where ΔR = R'-R.

When the above equation is represented by coordinates normalized by the maximum radius H0 of the pupil, ε = (1 + △ R / R) ・ R / H0∂∂ / ∂x = (1 + △ R / R) ・1 / NA0 ・ ∂φ / ∂x …… (3) η = (1 + △ R / R) ・ R / H0∂∂ / ∂y = (1 + △ R / R) ・ 1 / NA0 ・ ∂φ /∂y...(4)

From the above relationships (3) and (4), if the region can be regarded as ΔR / R≪1 (5), the relationship between the wavefront aberration and the ray aberration is ε in normalized coordinates (x, y). (x, y) = 1 / NA0∂φ / ∂x (6) η (x, y) = 1 / NA0∂∂ / ∂y (7) In the above equations (6) and (7), NA0
Is a fixed value that does not depend on the aberration, so that the wavefront aberration can be obtained by ordinary numerical integration.

The details will be described below with reference to the drawings.

FIG. 1 shows Embodiment 1 of the present invention.

Reference numeral 10 denotes a projection optical system, 80 and 81 denote illumination systems for ordinary projection exposure, 80 denotes a laser light source, and 81 denotes an illumination optical system. The light beam emitted from the illumination optical system 81 transmits and illuminates the reticle 12, is diffracted and scattered by a fine circuit pattern formed on the lower surface of the reticle 12, and is staged by the projection optical system 10.
An image is formed in the vicinity of the surface of the wafer arranged on 14.

Reference numeral 100 denotes an aberration measuring optical system unit constituting the present invention. In the aberration measurement according to the present embodiment, a pattern on a wafer is observed through a reticle with light having the same exposure wavelength as that of the projection optical system, and a shift amount of an imaging pattern corresponding to a lateral aberration in imaging is detected by a TTR alignment scope. It is characterized by.

The light split from the exposure illumination system 81 is led by an optical fiber 90 or a lens or a mirror, and is guided to a measurement illumination system 91 in the aberration measurement optical system unit 100. It is desirable that the spread of the light emitted from the measurement illumination system 91 be large enough to cover all the openings of the projection optical system.

The light emitted from the measurement illumination system 91 is supplied to a variable aperture stop unit 10 provided at a position almost conjugate with the aperture stop surface of the projection optical system, that is, the so-called pupil surface 20.
The light flux is restricted at 1, 102. Reference numeral 101 denotes a turret-shaped aperture plate on which various aperture stops are formed. Reference numeral 102 denotes an actuator and a control device for rotating the turret aperture. FIG. 6 is an example showing the aperture area of the projection optical system 10 as the optical system to be inspected, that is, the sampling aperture area when measuring the ray aberration over the entire area of the pupil plane. Measurement is performed at 33 measurement points in 8 directions. The case is illustrated.

FIG. 7 shows a one-letter stop for switching the illumination aperture corresponding to FIG. On the turret aperture, apertures formed with pinholes corresponding to the area of the illumination aperture to be sampled are arranged by the number of sampling points, and the turret is rotated by 102 in order to perform switching.

Although the turret-shaped variable aperture device as described above has a simple structure, the size of the sampling aperture and the sampling position are fixed. In order to perform more accurate measurement, the number of sampling points may need to be set densely. FIG. 8 shows an embodiment in which a diaphragm is constituted by four movable plates capable of forming an opening of an arbitrary size at an arbitrary position, such as a masking blade used for an illumination system of a projection exposure apparatus. If an aperture stop whose aperture position and size can be freely controlled as shown in FIG. 8 is used, the number of sampling points can be increased or superimposed sampling can be performed, so that highly accurate measurement can be performed.

The illumination light beam whose illumination opening position is limited is transmitted through the half mirror 103, the detection objective lens 104 and the mirror 105 through the reticle through the half mirror 103, the light path similar to the projection exposure light beam, and the wafer stage 14. The reference pattern 11 arranged above is illuminated.

The illuminated light is specularly reflected and diffracted by the reference pattern 11 on the reference plate, which is the pattern to be inspected for measurement, and passes through the optical path symmetrical with respect to the principal ray PL1 of the light beam of the projection optical system. Aberration measurement optical system unit 10 that constitutes the system
Come back to 0 again. The returned light passes through the half mirror 103 via the mirror 105 and the objective lens 104,
After passing through 106, CC with a re-imaging lens 107 that enlarges the image
An image is formed on the photoelectric detection sensor 108 such as D. 109 is a signal processing device from the detection sensor.

The aberration measurement optical system unit 100 is set to be movable in the XY plane so that an arbitrary point in the image forming area of the projection optical system can be measured. Although not shown, another aberration measurement optical system unit 100 may be disposed at a symmetrical position.

The reference pattern 11 arranged on the stage is also
It can move in XYZ directions. The aberration measurement optical system unit 100 is moved to the position of the corresponding point on the reticle in accordance with the movement of the reference pattern 11, and the imaging performance is measured, thereby forming an image at a plurality of image points in the imaging area of the projection optical system 10. Image performance can be measured.

What is detected by the photoelectric detection sensor 108 is the amount of lateral aberration, that is, the shift information of the image from the point O2 in FIG. The image shift information is measured in accordance with the illumination aperture position (x, y), that is, the coordinates of the exit pupil plane of the projection optical system, and stored in the signal processing device 109, where the ray aberration (ε (x, y), η (x ,
y)) is required.

From the ray aberration obtained in this manner, the above-mentioned relational expression ε (x, y) = 1 / NA0 · ∂φ / ∂x (6) η (x, y) = 1 / NA0 · If ∂φ / ∂y (7) is used, the wavefront aberration φ (x, y) is obtained by the signal processing device 109.

FIG. 2 is a diagram showing the relationship between ray aberration and wavefront aberration. As shown in the equations (6) and (7), the ray aberration (lateral aberration) is obtained as a derivative of the wavefront aberration. Accordingly, the value of the ray aberration is large in a region where the wavefront aberration locally changes in the aperture. Conversely, the ray aberration that can be obtained locally can be measured over the entire aperture area and converted into wavefront aberration by performing integration processing. In order to obtain local ray aberration information in the pupil space of the projection optical system, it is preferable that the sampling area is sufficiently small. When calculating the wavefront aberration from the relations of equations (6) and (7), if the image shift amount can be measured with an extremely small light flux, the measured value can be used as it is as the ray aberration amount. However, in practice, from the viewpoint of the S / N ratio associated with the detected light amount, it is necessary to measure a light beam having a certain finite size spread and a finite size pattern. The spread of the luminous flux from the illumination system of the aberration measurement optical system unit depends on the accuracy of the calculated wavefront aberration, but needs to be 1/10 or less of the diameter of the aperture of the projection optical system.

The reference pattern 11, which is the pattern to be inspected for measurement in the present invention, has a relatively large line width and space to make the diffracted light dense, so that it does not spread within the aperture of the projection optical system, and has an illumination. It is characterized in that the light beam is made as narrow as possible so that a small light beam passes only through a predetermined portion within the projection lens aperture. For example, if the numerical aperture of the projection optical system is 0.75 at an exposure wavelength of 248 nm, and the measurement pattern is a repetitive pattern having a line width and space of about 5 μm or more, the spread of the diffracted light will be one of the aperture of the projection optical system. / 10 or less.

FIG. 3A shows the state of diffracted light of a pattern having a line width and a space of 5 μm in a pupil space of a projection optical system having a numerical aperture of 0.75, and FIG. Is schematically represented. It can be seen that the spread of the illumination light beam effective for detecting the diffraction light distribution of the original pattern is about NA 0.1. When it is desired to view a finer area in the aperture, it can be seen that the effective light flux is reduced by illuminating with a pattern having a larger line width pitch and a smaller σ.

If the intensity distribution of the effective luminous flux of the illumination optical system of the aberration measuring optical system unit is measured or calculated in advance, and deconvolution is performed when converting the ray aberration into the wavefront aberration, a higher level is obtained. Accurate conversion can be performed.

FIG. 5A shows an example of a pattern to be inspected for measurement. By arranging such repetitive patterns in the X and Y directions, it is possible to separately measure the aberration in the XY direction or sagittal / meridional.

FIG. 5B shows a reference mark formed on the reticle so as to sandwich the pattern to be inspected. Since it is formed on the reticle, the reflected light can be guided directly to the detection optical system without using a projection lens to detect the position, so it can be used as the reference position of the pattern to be inspected without being affected by the aberration of the projection optical system. You can do it.

FIG. 4 shows the state of the image shift signal of the pattern to be inspected 11 obtained by the aberration measuring optical system unit 100 in the present embodiment and the signal when the reference mark is observed at the same time. If the center position of the reference mark is used as a reference, the shift amount ΔL of the pattern to be measured for measurement can be obtained.

In the present embodiment, a method has been described in which a reference mark is provided on a reticle as a reference for measuring an image shift of a pattern to be inspected. In the case of the present embodiment, a dedicated reticle provided with a reference mark for each image height to be measured is required.

If the reference position can be determined by using the signal of the pattern to be inspected instead of forming a reference mark on the reticle, there is no need to prepare a dedicated reticle, and the apparatus itself measures the aberration of the projection optical system. It can be performed.

For determining the reference position from the pattern to be inspected, for example, there is a method using the average aberration of the entire pupil plane of the projection optical system. In this case, the diameter of the switching illumination system is illuminated as an illumination condition of σ1.0 that is the entire aperture of the projection optical system,
The light receiving side also receives light under the condition of full aperture. Since the amount of image shift of the pattern due to the aberration is averaged, the deviation of the pattern from the reference position is small enough that the influence of the aberration can be ignored, and can be used as a reference.

FIG. 9 is a flowchart for measuring ray aberration and wavefront aberration when the reference position is measured based on the average aberration of the entire pupil in the first embodiment.

As another method, a pattern to be inspected for measurement is
A pattern of a single edge may be arranged on the outer periphery of 11 and the single edge may be used as a reference. Since the single edge has comparatively broad spread of the diffracted light in the pupil plane of the projection optical system, it has an effect of averaging aberrations in the pupil plane. Therefore, the aberration amount may be calculated from the shift amount of the pattern to be inspected with respect to the reference position determined from the outer edge information.

FIG. 10 shows a second embodiment of the present invention. Members that are the same as those in the first embodiment with the numbers in the figure are indicated by the same numbers as in FIG.

In this embodiment, the first pattern 150 is arranged on the reticle, and at the same time, the second pattern 151 is formed on the image forming surface of the first pattern 150 via the projection optical system.
Light receiving means 111 for receiving light transmitted through second pattern 151
Is arranged inside the stage 14. When the stage 14 is scanned, the first
This means that the image of the pattern 150 is slit-scanned, and the position of the image of the first pattern 150 is detected.

For illumination of the first pattern, a dedicated illumination system similar to that of Embodiment 1 having an opening position and opening shape variable mechanism is used, and the first pattern 150 on the mask is transmitted and illuminated.

The luminous flux whose aperture position and aperture size are restricted by the dedicated illumination system 160 illuminates a pattern 150 which is sufficiently larger than the resolution limit of the projection optical system formed on the reticle.
The pattern 150 generates only a sufficiently small diffraction angle as in the first embodiment, and the diffracted light beam passes through a local and sufficiently small area in the opening of the projection optical system and is formed on the wafer stage side for image shift measurement. An image is formed on the second pattern 151.

FIG. 11 shows an example of the first pattern 150 on the reticle and the slit pattern 151 for image shift measurement on the stage on the wafer side. The second pattern 151 on the wafer side is
The slits are formed with slits that are sufficiently thinner than the pattern 150, and the pitch and number of the slits are converted to the first by converting the magnification of the projection optical system.
It matches with the pattern of.

FIG. 11b shows the first image formed through the projection optical system.
FIG. 5 shows a state in which light passing through the slit on the wafer side is guided to the photoelectric sensor in the image intensity distribution of the pattern of FIG. FIG. 11c shows a signal obtained when the second slit pattern is scanned in one direction. The position of the average image pattern of the entire first pattern is measured, and the image is formed as shown by signals 161 and 162. It can be seen that the shift amount can be detected.

The first pattern is a pattern sufficiently larger than the resolution limit, for example, the line width and the pitch are each 5 μm or the like. On the other hand, if the second pattern disposed on the wafer side is provided with a slit having an opening of about 0.5 μm, a sufficiently high-accuracy image profile can be obtained. The arrangement of the slit having an opening of about 0.5 μm can be easily configured.

As another method, the second pattern may be a single edge having a sufficiently large aperture, knife edge scan may be performed, and an image profile may be measured by differentiating a signal intensity obtained according to the scan position. The knife edge method requires a high signal-to-noise ratio and a wide dynamic range because the signal variation is small.

From the obtained image shift information and information on the aperture position, size, intensity distribution, and image shift amount, the signal processing device 10
The process in which the ray aberration amount is calculated in 9 and converted into the wavefront aberration amount is the same as in the first embodiment.

FIG. 12 shows a third embodiment of the present invention in which the illumination system for measuring aberration used in the second embodiment shown in FIG. 10 has the same configuration as the illumination system for the projection exposure system. Therefore, the lighting system 300
Has both functions of ordinary projection exposure and local illumination at the time of aberration measurement. In the drawings, the same members as those in the previous embodiment are denoted by the same reference numerals.

A light beam emitted from a monochromatic light source 80 such as a laser is shaped by a beam shape converter 201 or the like, and then enters a uniformizing element 203 such as a fly-eye optical system. The exit surface of the homogenizing element 203 is almost co-projected with the pupil plane of the projection optical system, and switches light beams in the vicinity thereof, and forms control means 101 and 102. The fly-eye optics consists of a series of small optical elements that cover the pupil plane.
Light flux control for turning ON / OFF may be performed.

Although the configuration of the illumination system is different, the method of image measurement is the same as that of the second embodiment.

In the present embodiment, the local illumination function at the time of aberration measurement is shared by providing the illumination system for normal projection exposure, so that a compact device configuration is possible.
Furthermore, since light from an illumination system used for actual projection exposure is used, there is an advantage that aberration measurement can be performed under conditions close to actual exposure.

FIG. 13 shows a fourth embodiment of the present invention, in which the same members as those in the previous embodiment are denoted by the same reference numerals.

This embodiment is similar to the configuration of the first embodiment, but is characterized in that a detection aperture control means 130 is provided inside the light receiving means instead of providing the light beam varying means in the illumination system. The illumination system illuminates with a large opening that covers the entire opening of the projection optical system.

In the figure, a dedicated illumination system 91 is provided with an aperture 20 of the projection optical system.
The reticle is illuminated under conditions of so-called σ1.0 or more covering the entire surface of the reticle. The reflected diffraction light from the pattern to be inspected having a relatively large line width for measurement also returns to the measurement optical system 180 as a light receiving system through the entire surface of the projection optical system. The aperture position and size of the light beam are limited by the light receiving aperture control hand throw 130 provided at a position approximately conjugate with the aperture 20 of the projection optical system 10, and C
An image is formed on the image measurement sensor 108 such as a CD, and the image shift amount is detected.

FIG. 14 shows a fifth embodiment of the present invention.
The same members as those in the previous embodiment have the same numbers.

The present embodiment is characterized in that the illuminated light beam transmits and illuminates the reference pattern 11 from the stage side. As in the fourth embodiment, there is no aperture changing means on the side to be illuminated, and the illumination system illuminates with a large opening that covers the entire opening of the projection optical system. The designation of the position of the light beam at the opening of the projection optical system is performed by a control aperture control inside the light receiving means which is detected through the reticle.

[0088]

As described above, the projection exposure apparatus of the present invention makes it possible to directly measure the wavefront aberration of the projection optical system on the main body of the projection exposure apparatus while actually exposing. As a result, the state of the projection optical system can be accurately evaluated, and the projection optical system can be adjusted more precisely on the apparatus. Further, since the influence of the aberration can be grasped in advance, it is possible to select in advance whether the device can be applied to the projection exposure apparatus according to the state of the aberration.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of the present invention;

FIG. 2 is a diagram illustrating a state of ray aberration near an imaging point of a projection optical system, and a diagram illustrating a relationship between wavefront aberration and ray aberration.

FIG. 3 is a diagram (σ = 0) showing a diffracted light intensity distribution of a pattern having a relatively large line width pitch in the projection optical system opening, and FIG. Diagram showing intensity distribution of diffracted light (σ = 0.1)

FIG. 4 is a diagram of an image profile obtained by a measurement optical system.

FIG. 5 is a diagram illustrating a first pattern for measurement and a diagram illustrating a battery for reference.

FIG. 6 is a diagram showing an aperture of an optical system to be inspected and a measurement sampling aperture.

FIG. 7 is a view showing an opening switching mechanism formed in a turret shape;

FIG. 8 shows an example of a mechanism capable of switching an opening to an arbitrary position and an arbitrary size.

FIG. 9 is a diagram showing a measurement flow in the present embodiment.

FIG. 10 is a diagram illustrating a configuration of a projection exposure apparatus according to a second embodiment of the present invention.

FIG. 11 is a diagram illustrating a pattern used for signal measurement according to the second embodiment, a diagram illustrating a relationship between a measurement signal according to the second embodiment and an intensity distribution near an image plane, and a diagram illustrating a signal intensity obtained by measurement according to the second embodiment.

FIG. 12 is a diagram illustrating a schematic configuration of a projection exposure apparatus according to a third embodiment.

FIG. 13 is a diagram schematically illustrating a configuration of a projection exposure apparatus according to a fourth embodiment.

FIG. 14 is a diagram illustrating a schematic configuration of a projection exposure apparatus according to a fifth embodiment.

[Explanation of symbols]

10 Projection optical system 11 Pattern to be inspected for measurement (reference pattern) 12 Reticle 13 Wafer 14 Wafer stage 16 Wafer chuck 20 Aperture stop of projection optical system 50 Surface position detector 80 Laser light source 81 Illumination system 91 Measurement illumination system 100 Measurement Optical system unit 101 Variable illumination aperture 102 Illumination aperture control means 103 Half mirror 104 Measurement objective lens 105 Mirror 108 Image detection element 109 Signal processing device 110 Photoelectric sensor 130 Reception aperture control means 150 First pattern on reticle side 151 Wafer stage side Second pattern 160 Dedicated illumination system 190,195 Illumination beam 191 Measurement beam 201 Beam shape converter 203 Uniformizing element AX: Optical axis of projection optical system XYZ: Center of exit pupil of projection optical system A coordinate system with the Z axis W: a wavefront of an imaging light beam emitted from the pattern 11 to be inspected and formed by the projection optical system 10 and passing through the center of the exit pupil G Reference spherical surface C: Image forming surface of projection optical system 10 D: Intensity distribution measuring surface of light intensity distribution measuring device O1: Center of exit pupil of projection optical system 10 O2: Center of reference spherical surface P1: Image of pattern 11 to be inspected Point P2 where the image light beam intersects the exit pupil plane: The image light beam of the pattern 11 to be inspected is the intensity distribution measurement surface D
Q0: Point at which the maximum NA beam of the imaging light beam of the pattern 11 to be inspected intersects the reference spherical surface Q1: Point at which the imaged light beam of the pattern 11 to be inspected intersects the wavefront W Q2: Pattern to be inspected The point at which the 11 imaging light beams intersect the reference spherical surface R: radius of the reference spherical surface R ': distance Q2P2 φ: wavefront aberration of the projection optical system 10 (optical path length Q1Q2) (ε, η): ray aberration (line segment O2P2) 0 : Maximum radius of exit pupil of projection optical system 10 A0: Numerical aperture corresponding to maximum radius of exit pupil of projection optical system 10
NA0 = H0 / R y coordinate: XY standardized by the maximum radius of the exit pupil of the projection optical system 10.
Coordinates X = H0.x, Y = H0.y0 ': Maximum radius of a region where all luminous fluxes from the exit pupil of the projection optical system 10 intersect on the intensity distribution measurement surface H0' = NA0. (LR) )

Claims (25)

[Claims] 1. A projection exposure apparatus for projecting and exposing a circuit pattern on a reticle or a photomask onto a substrate via a projection optical system, wherein a pattern is arranged on an object plane or an image forming plane of the projection optical system, and When an image of the pattern is formed via an optical system, a means for forming a partial area in the opening of the projection optical system and changing the position of the partial area is provided. A projection exposure apparatus, wherein an amount of image shift caused by image formation is measured for a plurality of positions in the aperture, and a wavefront aberration of the projection optical system is calculated. 2. An illumination system for allowing illumination light to enter the projection optical system, the illumination system having an illumination aperture variable hand throw capable of passing a sufficiently small area in an opening of the projection optical system, and the illumination aperture variable means being provided. A light-receiving system for detecting the position of the image formed through the projection optical system, and measuring the amount of image shift to be formed in accordance with a change in the illumination aperture changing means; 2. The projection exposure apparatus according to claim 1, wherein a wavefront aberration amount of the projection optical system is calculated from the image shift amount information. 3. Illuminating the illumination light incident on the projection optical system in a state where the illumination light has a larger spread than a pupil of the projection optical system;
A light-receiving aperture detecting means for detecting a position of the image formed through the projection optical system, the light-receiving aperture varying means capable of passing a sufficiently small area in the opening of the projection optical system; 2. The projection exposure apparatus according to claim 1, wherein an image shift amount to be formed is measured according to the change, and a wavefront aberration amount of the projection optical system is calculated from the image shift amount information of the plurality of light receiving apertures. 4. A pattern arranged on an image plane of the projection optical system for observing the image shift amount, wherein the pattern of the projection optical system is located on a wafer stage of the projection lens in the vicinity of an image position of the projection optical system. 3. The method according to claim 2, wherein a measurement pattern sufficiently larger than the resolution limit pattern is arranged.
Or the projection exposure apparatus according to 3. 5. The projection exposure apparatus according to claim 2, wherein the illumination system has a dedicated illumination system for measuring aberration. 6. The projection exposure apparatus according to claim 5, wherein the illumination system is configured as a TTR alignment scope. 7. The illumination system according to claim 5, wherein the illumination system illuminates the measurement pattern from a wafer stage side.
The projection exposure apparatus according to claim 1. 8. The light receiving system is configured in common with a TTR alignment scope.
The projection exposure apparatus according to any one of the above. 9. A reference mark is provided at a position on a reticle corresponding to the measurement pattern when the image shift amount is measured,
The projection exposure apparatus according to claim 1, wherein an image shift amount is measured from a relative distance between the reference mark and the measurement pattern. 10. The projection exposure apparatus according to claim 9, wherein said reference mark is constituted by a single edge pattern. 11. The projection exposure apparatus according to claim 9, wherein a position of a reference mark on the reticle is detected in the light receiving system without passing through the projection optical system. 12. An image formation method using the entire aperture of the projection optical system, measuring the position of the image of the measurement pattern as a reference position, and forming a light beam having passed through a sufficiently small area in the aperture of the projection optical system. 9. The projection exposure apparatus according to claim 1, wherein an amount of image shift caused by an image is measured based on the reference position, and a wavefront aberration amount of the projection optical system is calculated. 13. The method according to claim 1, wherein the size of the aperture by the illumination aperture varying means or the light receiving aperture varying means has a diameter which is optically about 1/10 of the diameter of the pupil of the projection optical system. The projection exposure apparatus according to claim 1. 14. A projection exposure apparatus for projecting and exposing a circuit pattern on a reticle or a photomask onto a substrate via a projection optical system.
When the pattern of the projection optical system is arranged, a mechanism for photoelectrically detecting the position of the image of the first pattern via the projection optical system is superimposed on the second pattern arranged on the wafer stage, and Means for forming a partial area in the opening and changing the position of the partial area, wherein an image shift amount of the first pattern with respect to the second pattern caused by imaging of a light beam passing through the partial area Is measured with respect to a plurality of positions in the opening, and a wavefront aberration of the projection optical system is calculated. 15. The projection exposure apparatus according to claim 14, wherein the mechanism for performing photoelectric detection is mounted on a wafer stage. 16. The projection exposure apparatus according to claim 14, wherein a ratio of a pitch between the first pattern and the second pattern is equal to a magnification of the projection optical system. 17. An illumination system for allowing illumination light to enter the projection optical system, the illumination system having an illumination aperture variable hand throw that allows a sufficiently small area in an opening of the projection optical system to pass therethrough. A light-receiving system that detects the position of the image formed through the projection optical system and that passes through the projection optical system; 17. The projection exposure apparatus according to claim 14, wherein the wavefront aberration amount of the projection optical system is calculated from the image shift amount information. 18. A measurement pattern arranged on the reticle surface for observing the image shift amount is a measurement pattern sufficiently larger than a pattern corresponding to a resolution limit of the projection optical system. 18. The projection exposure apparatus according to item 17. 19. The projection exposure apparatus according to claim 17, wherein the illumination system has a dedicated illumination system for measuring aberration. 20. The projection exposure apparatus according to claim 17, wherein the illumination system is shared with an illumination system for projection exposure. 21. The size of an opening in the pupil of the projection optical system formed by the illumination aperture varying means has a diameter about 1/10 of the diameter of the pupil of the projection optical system. The projection exposure apparatus according to any one of claims 14 to 20, 22. The method according to claim 1, wherein a ray aberration of the projection optical system is obtained from the measured image shift amount, and a wavefront aberration amount is calculated from the ray aberration amount. Projection exposure equipment. 23. A projection exposure apparatus for projecting and exposing a circuit pattern on a reticle or a photomask illuminated by an illumination optical system onto a substrate via a projection optical system, wherein a wavefront of the projection optical system is provided in the illumination optical system. A projection exposure apparatus comprising an illumination aperture variable unit for measuring aberration. 24. A projection exposure apparatus for projecting and exposing a circuit pattern on a reticle or a photomask onto a substrate via a projection optical system, wherein the projection optical system has a pupil conjugate position outside the projection optical system for measuring a wavefront aberration. A projection exposure apparatus having a variable aperture. 25. A method for measuring a wavefront aberration of a projection optical system of a projection exposure apparatus for projecting and exposing a circuit pattern on a reticle or a photomask onto a substrate via a projection optical system, the method comprising: A partial area is set in the aperture of the projection optical system from the pupil conjugate position of the projection optical meter, and an image shift amount caused by imaging of a light beam passing through the partial area is measured for a plurality of positions in the aperture, A wavefront aberration measuring method, comprising calculating a wavefront aberration of the projection optical system.