JPH11297614A - Coma aberration measuring device and projection aligner provided with the device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure an amount of remained coma aberration of a projection optical system accurately by detecting a synthetic space image intensity distribution obtained by synthesizing space image intensity distributions of patterns, based on information on variation of a light amount, and detecting an amount of remained coma aberration of a detected optical system, based on the synthetic space image intensity distribution. SOLUTION: A pattern space image of a measuring mask 9 is formed via a projection optical system 10 on a stage substrate 15, and a light amount distribution corresponding to the pattern space image is obtained in accordance with an output from a light receiving sensor 18. Based on the variation of the light amount distribution, a space image synthetic intensity distribution is detected in a synthetic space image intensity distribution detecting section 43a of a processing system 43. The space image synthetic intensity distribution is formed by synthesizing a periodic space image intensity distributions of a first pattern and a second pattern. Based on the synthetic space image intensity distribution, an amount of remained coma aberration of the projection optical system 10 of a detected optical system is detected by a coma aberration detecting section 43d of the processing system 43.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coma aberration measuring apparatus and a projection exposure apparatus having the apparatus, and more particularly to a projection optical apparatus used in manufacturing a semiconductor element or a liquid crystal display element in a lithography process. The present invention relates to measurement of a residual coma aberration amount of a system.

[0002]

2. Description of the Related Art Conventionally, as a method of measuring the amount of residual coma aberration of a projection optical system in a projection exposure apparatus, a method of measuring five line marks close to a critical resolution line width on a resist (photosensitive member) coated on a wafer has been used. The line width of the resist image remaining after the mask pattern image is projected and exposed and developed is measured by a scanning electron microscope (SEM), and the residual coma aberration amount is determined from the difference between the two line widths at both ends of the five bottom line widths. There is a way to ask. In this method, since the pattern for coma aberration measurement is printed in the same process as the normal printing of the projection exposure apparatus, it is not necessary to provide a special mechanism for measuring coma aberration, and the residual coma aberration amount of the projection optical system can be reduced. Can be measured.

[0003] Further, at the time of manufacturing adjustment of the projection optical system alone, a method of measuring the residual coma aberration amount of the projection optical system by measuring the wavefront aberration of the projection optical system using an interferometer and a mirror, A method of measuring the amount of residual coma aberration of a projection optical system from deterioration of an aerial image by enlarging and projecting a spatial image of a mask pattern formed through a system onto a two-dimensional image sensor through an imaging optical system is used. ing. The use of interferometer and aerial image methods is limited to inspection of the projection optics during the manufacturing and adjustment stages.

In a method using a scanning electron microscope, a method using an interferometer, and a method using an aerial image,
The measurable aberration is not limited to coma, and coma is positioned as one of various measurable aberrations. Further, the projection optical system is provided with an aberration adjusting mechanism so that the residual coma aberration amount measured by these methods can be brought within the standard, and the aberration adjustment of the projection optical system is favorably performed by the operation of the aberration adjusting mechanism. Is made.

[0005]

As described above, in order to measure the amount of residual coma aberration of the projection optical system incorporated in the finally manufactured projection exposure apparatus, a printed resist image is scanned. Observation was made with a scanning electron microscope. Although this method is a very direct method using a resist image, many steps such as printing, development, SEM measurement, and calculation processing are required to judge the quality of the resist image, and the number of processes is extremely large. Time and effort. Also, the measurement of CD (Critical Dimension) bottom line width by SEM is not completely automated, and errors due to the operator may occur.

On the other hand, in the method using an interferometer, the configuration of the wavefront aberration measuring apparatus is large, and if this apparatus is incorporated in a projection exposure apparatus, the original function of the projection exposure apparatus may be impaired. Also, since the optical configuration of the wavefront aberration measurement device is significantly different from the optical configuration of the projection exposure device,
At present, it is difficult to mount a wavefront aberration measuring apparatus on a projection exposure apparatus as a final product. Furthermore, even if the wavefront aberration measuring device is mounted on the projection exposure apparatus, the wavefront aberration measuring device will impose a heavy load on the ultra-high-speed movable wafer stage and main illumination optical system, which are important components of the projection exposure apparatus. Conceivable. Technical development of ultra-high-speed movable wafer stages and main illumination optical systems aiming at higher performance is still ongoing, and it is desirable to avoid the loads described above.

In the method of enlarging and projecting an aerial image of a mask pattern onto a two-dimensional image pickup device via an imaging optical system, an image forming optical system for detecting an aerial image is provided inside a wafer stage in order to detect the aerial image. The system and the two-dimensional image sensor must be mounted. Generally, the internal space of the wafer stage is limited, and the size of the imaging optical system mounted inside the wafer stage is also restricted. Therefore, the imaging optical system needs to be a small optical system. On the other hand, an imaging optical system is an optical system that re-forms an image based on light from a spatial image formed via a projection optical system. Therefore, due to its properties, the imaging optical system allows only a sufficiently small aberration as compared with the projection optical system. as a result,
It is difficult to reduce the size of the imaging optical system sufficiently, and the imaging optical system that cannot be reduced in size is mounted inside the wafer stage, and the amount of coma aberration of the projection optical system is measured by detecting an aerial image. How to do it is not practical.

Further, when the imaging optical system having almost no aberration is mounted inside the wafer stage which repeatedly moves at a high speed as described above, the influence of the generated vibration and heat on the imaging optical system is neglected. Can not. From this viewpoint, it is not practical to mount the imaging optical system inside the wafer stage and measure the amount of coma aberration of the projection optical system by detecting an image of the aerial image.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems. For example, a projection exposure apparatus uses a simple mechanism without actually performing operations such as pattern printing, development, SEM measurement, and calculation processing. An object of the present invention is to provide a coma aberration measuring apparatus capable of accurately measuring a residual coma aberration amount of an optical system, a projection exposure apparatus including the coma aberration measuring apparatus, and a method for manufacturing a semiconductor device using the projection exposure apparatus. Aim.

[0010]

According to a first aspect of the present invention, there is provided a coma aberration measuring apparatus for measuring an amount of residual coma aberration of an optical system to be measured. A measurement member having a knife edge pattern formed having an edge line along a direction intersecting with the measurement direction, the measurement member being positioned on the image formation plane, and a pattern having a plurality of patterns arranged in parallel along the measurement direction The reference member in which the group is formed is set on the object plane of the optical system to be inspected, so that the light from the spatial image of the pattern group formed on the image plane of the optical system to be inspected is transmitted to the knife edge pattern. And a knife-edge pattern for relatively moving the spatial image of the pattern group formed on the imaging surface of the test optical system and the knife-edge pattern. Relative moving means, and the intensity of the spatial image of the pattern group based on light amount change information from the photoelectric detecting means when the spatial image of the pattern group and the knife edge pattern are relatively moved by the relative moving means. An intensity distribution detecting means for detecting a combined spatial image intensity distribution comprising a combination of the intensity distributions of the spatial images of the respective patterns forming the pattern group; and a combined spatial image intensity obtained by the intensity distribution detecting means. And a processing system for detecting a residual coma aberration amount of the optical system to be detected based on a distribution.

According to a preferred aspect of the first invention, the pattern group includes a first pattern composed of a line and space pattern having a first pitch P1, and a first pattern which is larger than the first pitch P1 and is larger than the first pitch P1. A second pattern consisting of a line-and-space pattern having a second pitch P2 substantially different from a pitch that is an integral multiple of the pitch P1, and the product of the pitch P1 of the first pattern and the number of lines is It is almost equal to the product of the pitch P2 of the second pattern and the number of lines. Further, the processing system performs signal processing on the combined spatial image intensity distribution obtained by the intensity distribution detecting means, thereby forming at least two patterns forming the pattern group on the image plane. A Fourier coefficient for a predetermined spatial frequency based on the pitch of the pattern image is determined, and a relative position shift on the image plane between the spatial frequency components for the at least two patterns is determined based on the determined Fourier coefficients. It is preferable that the calculated amount of residual coma of the optical system to be detected be detected based on the calculated relative positional deviation.

According to a second aspect of the present invention, there is provided a coma aberration measuring apparatus according to the first aspect, an illumination optical system for illuminating the mask, and a photosensitive pattern for transferring an image of a transfer pattern formed on the mask. A projection optical system for projecting on the substrate,
The coma aberration measuring device measures a residual coma aberration amount of the projection optical system as the test optical system, and provides a projection exposure apparatus. According to a preferred aspect of the second invention, the relative moving means has a substrate stage that holds the photosensitive substrate and is movable with respect to the projection optical system, and the measuring member of the coma aberration measuring device is , On the substrate stage, at a position corresponding to the exposure surface of the photosensitive substrate. It is preferable that a correction system for correcting coma aberration remaining in the projection optical system based on an output from the processing system is further provided.

According to a third aspect of the present invention, in the method for manufacturing a semiconductor device using the projection exposure apparatus according to the second aspect of the present invention, it is preferable that the measurement pattern is formed on an object plane of the projection optical system. A measuring step of setting a reference member and measuring the coma remaining in the projection optical system by the coma aberration measuring device; a correcting step of correcting the coma remaining in the projection optical system; and an object of the projection optical system. An exposure illuminating step of setting a transfer mask having a transfer pattern formed on a surface thereof and illuminating the transfer mask with the illumination optical system, and exposing the pattern of the transfer mask to the light through the projection optical system. An exposing step of exposing a conductive substrate to light.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, for example, a reference member on which a pattern group having a plurality of patterns arranged in parallel along a measurement direction is formed is positioned on an object surface of an optical system to be inspected, and measurement is performed. A measurement member on which a knife edge pattern having an edge line along a direction intersecting with the direction (for example, a direction orthogonal to the direction) is positioned on an imaging surface of the optical system to be measured. Then, while relatively moving the aerial image of the pattern group formed on the image forming surface of the test optical system and the knife edge pattern along a predetermined direction, the pattern pair formed on the image forming surface of the test optical system is Light from the aerial image is photoelectrically detected via the knife edge pattern.

In this manner, the spatial distribution of each pattern forming the pattern group is determined as the intensity distribution of the spatial image of the pattern group based on the light amount change information detected in accordance with the relative scan between the spatial image of the pattern group and the knife edge pattern. A composite spatial image intensity distribution is detected, which is composed of the image intensity distributions.
Then, a residual coma aberration amount of the test optical system is detected based on the detected composite spatial image intensity distribution. More specifically, when a pattern pair composed of two patterns is used as the measurement pattern, the detected combined spatial image intensity distribution is subjected to signal processing, and the respective two patterns forming the pattern pair are formed on the image plane. Fourier coefficients for a predetermined spatial frequency based on the pitch of the formed pattern image are obtained. Next, a relative position shift on the imaging plane between the spatial frequency components of the two patterns is calculated based on the obtained Fourier coefficients, and based on the calculated relative position shift, the remaining optical system remains. The amount of coma is measured.

As described above, according to the present invention, the residual coma aberration amount of the test optical system can be accurately measured by a simple mechanism. In particular, when the coma aberration measuring apparatus of the present invention is mounted on a projection exposure apparatus, pattern printing, development,
By using a simple mechanism without actually performing operations such as SEM measurement and calculation processing, it is possible to accurately measure the amount of residual coma aberration of the projection optical system that is the test optical system. That is, even if the NA of the projection optical system, the NA of the illumination optical system, and the illumination conditions (normal illumination, annular illumination, deformed illumination, and the like) are changed, even if the imaging of the projection optical system is significantly affected, In addition, the residual coma amount of the projection optical system can be easily measured at any time. As a result, the aberration of the projection optical system is adjusted based on the measured residual coma aberration amount, and a good semiconductor device can be manufactured via the projection optical system having a good aberration state.

An embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a view schematically showing a configuration of a projection exposure apparatus provided with a coma aberration measuring apparatus according to an embodiment of the present invention. In FIG. 1, the Z axis is parallel to the optical axis AX of the projection optical system 10, and the X axis is parallel to the paper surface of FIG. 1 in a plane perpendicular to the optical axis AX of the projection optical system 10. In the plane perpendicular to the axis AX, the Y axis is set perpendicular to the plane of FIG.

The projection exposure apparatus shown in FIG.
The light source 1 includes, for example, a mercury lamp. As the exposure light, for example, a bright line such as a g-line or an i-line of a mercury lamp, an excimer laser beam using KrF, ArF or the like as a medium can be used. The light source 1 is positioned at a first focal position of an elliptical reflecting mirror 2 having a reflecting surface formed of a spheroid. Therefore, the illumination light beam emitted from the light source 1 forms a light source image at the second focal position 3 of the elliptical reflecting mirror 2.

A light beam from the light source image formed at the second focal position 3 of the elliptical reflecting mirror 2 is converted into a substantially parallel light beam by the input lens 4 and then transmitted through a band-pass that transmits only a light beam in a desired wavelength range. The light enters a filter (not shown).
Illumination light having an exposure wavelength (for example, an i-line having a wavelength of 365 nm or a g-line having a wavelength of 436 nm) selected by the bandpass filter enters the fly-eye integrator 5. The light beam incident on the fly-eye integrator 5 is divided by a plurality of lens elements constituting the fly-eye integrator 5 to form a secondary light source composed of a plurality of light source images on a focal plane on the exit side of the fly-eye integrator 5.

The luminous flux from the secondary light source is restricted by an aperture stop 6 arranged near a focal plane on the exit side of the fly-eye integrator 5 and then passes through a condenser lens 7 and a bending mirror 8 to a predetermined surface. Is illuminated in a superimposed manner. Mask 9 is X
It is supported on the mask stage 12 in the Y plane. The XY coordinates of the mask stage 12, and thus the mask 9
Are always measured by a mask stage laser interferometer (not shown). The light flux transmitted through the pattern of the mask 9 reaches the wafer 11 as a photosensitive substrate via the projection optical system 10. Thus, on the wafer 11,
A pattern image of the mask 9 is formed.

The wafer 11 is supported on a wafer stage 14 in an XY plane via a wafer holder 13. The wafer stage 14 includes an XY stage for positioning the wafer 11 two-dimensionally in an XY plane, a Z stage for positioning the wafer 11 along the Z direction, and a leveling stage for correcting the tilt angle of the wafer 11. It is configured. The XY stage, the Z stage, and the leveling stage are configured to be driven and controlled by the processing system 43 via the driving system 45. Further, the XY coordinates of the wafer stage 14 and thus the XY coordinates of the wafer 11 are constantly measured by a wafer stage laser interferometer (not shown).

Therefore, the pattern of the mask 9 is sequentially transferred to each exposure area of the wafer 11 by performing projection exposure while controlling the wafer stage 14 and thus the wafer 11 two-dimensionally via the drive system 45. be able to. In the vicinity of the wafer holder 13 on the wafer stage 14, a stage substrate 15 made of, for example, a light-transmitting glass substrate is provided. The upper surface of the stage substrate 15 is set at almost the same height (almost the same position in the Z direction) as the exposure surface of the wafer 11. A predetermined knife edge pattern is formed on the upper surface of the stage substrate 15, the details of which will be described later.

A focus detection system for detecting the position of the surface of the wafer 11 (ie, the exposure surface) or the position of the surface of the stage substrate 15 (ie, the upper surface) is provided above the wafer stage 14. This focus detection system
An irradiation unit 40 for irradiating the surface of the wafer 11 or the surface of the stage substrate 15 with light obliquely; a focus detection unit 41 for detecting the position of light reflected from the surface of the wafer 11 or the surface of the stage substrate 15; It is composed of The focus detection unit 41 detects the position of the reflected light from the surface of the wafer 11 or the surface of the stage substrate 15 based on the position of the wafer 11.
Or the position of the surface of the stage substrate 12 (height position in the Z direction) is detected. The detection signal from the focus detection unit 41 is supplied to the processing system 43.

FIG. 2 is a diagram schematically showing an aberration measurement pattern formed on a measurement mask used for measuring the amount of residual coma aberration of the projection optical system. As shown in FIG. 2, on the lower surface of the measurement mask, a large number of pattern pairs including a pair of line and space (hereinafter, referred to as “L / S”) patterns are formed. Each pattern pair is configured by arranging two L / S patterns having different pitches in parallel in the pitch direction. In FIG. 2, the black line part is a light transmitting part, and the white part is a light shielding part. The structural features of each pattern pair will be described later with reference to FIG.

The number of pattern pairs is divided into four pattern groups, and each pattern group has M pattern pairs. The pattern groups are arranged so that the pitch direction is oriented at 0, 45, 90, and 135 degrees with respect to the X axis. Therefore, each pattern pair is represented by LS (m,
n) (m = 1 to M, n = 0, 45, 90, 135). That is, the first pattern group whose pitch direction is oriented at 0 degree with respect to the X axis is M pattern pairs LS (1,0), LS (2,0)... LS (M, 0) Having. The second pattern group whose pitch direction is oriented at 45 degrees with respect to the X axis includes M pattern pairs LS (1,45),
LS (2,45)... LS (M, 45). Hereinafter, the same applies to the third pattern group whose pitch direction is oriented at 90 degrees to the X axis and the fourth pattern group whose pitch direction is oriented at 135 degrees to the X axis. These four pattern groups are arranged at N positions on the lower surface of the measurement mask.

FIG. 3 is a diagram for explaining the structural features of each pattern pair. In FIG. 3, a shaded portion is a light-shielding portion 30, and the light-shielding portion 30 is formed of, for example, a deposited film of chrome or the like having a light-shielding property against exposure light. As shown in FIG. 3, each pattern pair includes J1 lines (6 in FIG. 3) of rectangular light transmitting portions (lines) 31 extending in the vertical direction in the figure at a pitch P1 along the horizontal direction in the figure.
1), and J2 (10 in FIG. 3) rectangular light transmitting portions 32 extending in the vertical direction in the figure at a pitch P2 along the horizontal direction in the figure. The second pattern is arranged in parallel so that the pitch directions of the patterns are parallel to each other.

Pitches P1 and P2 of two patterns
Satisfies the conditions of P1> P2 and P1 ≠ kP2 (k is a natural number). Further, “the number of lines × the pitch” of the two patterns is equal, that is, P1 × J1 = P2 ×
The condition of J2 is also satisfied. The positional relationship between the two patterns is measured by coordinates, and the positional deviation between the patterns can be easily known. In this embodiment, in each pattern, the width of each light transmitting portion (line) along the pitch direction is equal to the width of each light shielding portion (space) formed between the two light transmitting portions. . In other words, the pitch of each pattern is twice the width of each light transmitting portion (line), and its duty ratio (line / pitch) is 0.5. However, the duty ratio need not be particularly limited to 0.5.

For signal post-processing, it is preferable that each pattern group includes a pattern pair including a pattern having a pitch equal to the pitch of any one of the pattern pairs. That is, for example, each pattern group (M
= 3), the first pattern pair LS (1, n) has a pitch P1
And P2, as a first example, it is desirable that the second pattern pair LS (2, n) has pitches P1 and P3 and the third pattern pair LS (3, n) has pitches P1 and P4. As a second example, the second pattern pair LS
Preferably, (2, n) has pitches P1 and P3, and third pattern pair LS (3, n) has pitches P3 and P4. Further, as a third example, the second pattern pair LS (2,
n) have pitches P1 and P3, and a third pattern pair L
Preferably, S (3, n) has pitches P2 and P4. The same applies to cases other than M = 3.

FIG. 4 is a diagram showing a knife edge pattern formed on the upper surface of the stage substrate. As shown in FIG. 4, the upper surface of the stage substrate 15 is entirely covered with a light-shielding portion (indicated by oblique lines) 50, and two square light-transmitting portions 51 and 52 are provided at predetermined positions of the light-shielding portion 50. Is formed. The light-shielding portion 50 is formed of, for example, a deposited film of chrome or the like having a light-shielding property with respect to exposure light.

The two opposing sides 51a and 51b of the square light transmitting portion 51 are arranged so as to face 90 degrees with respect to the X axis, and the other two opposing sides 51c and 51d are connected to the X axis. It is arranged so as to face a direction of 0 degree. On the other hand, two opposing sides 52a and 52b of the square light transmitting portion 52 are arranged so as to face a direction of 135 degrees with respect to the X axis, and the other two opposing sides 52c and 52d are positioned with respect to the X axis. Are arranged so as to face 45 degrees. Therefore, the portion of the light blocking portion 50 and the light transmitting portion 51 sandwiching the sides 51a and 51b is a knife edge in which the normal line of the knife edge (edge line) composed of the sides 51a and 51b is oriented at 0 degree with respect to the X axis. A pattern KE (0) is formed.

The portions of the light shielding portion 50 and the light transmitting portion 51 sandwiching the sides 51c and 51d are connected to the sides 51c and 51d.
A knife edge pattern KE (90) in which the normal line of the knife edge made of d is oriented at 90 degrees to the X axis. Further, the light shielding unit 50 sandwiching the sides 52a and 52b
The light transmitting portion 52 forms a knife edge pattern KE (45) in which the normal line of the knife edge composed of the sides 52a and 52b is oriented at 45 degrees to the X axis. The light-shielding portion 50 and the light transmitting portion 52 sandwiching the sides 52c and 52d have a knife edge pattern KE (135) in which the normal line of the knife edge composed of the sides 52c and 52d is oriented at 135 degrees with respect to the X axis. ).

Referring again to FIG. 1, the stage substrate 15
In the lower part of the figure, a condensing optical system 16 for condensing light from the spatial primary image of the measurement pattern formed via the projection optical system 10 to form a spatial secondary image of the measurement pattern Is provided. A light receiving sensor 18 having a light receiving surface positioned on a surface on which a spatial secondary image is formed by the light collecting optical system 16 is provided below the light collecting optical system 16 in the drawing. The output of the light receiving sensor 18 is supplied to the processing system 43. In addition,
The condensing optical system 16 does not need to be an optical system in which the aberration is satisfactorily corrected, and an optical system enough to converge light from the spatial primary image on the light receiving surface of the light receiving sensor 18 is sufficient. Further, it is desirable that the light receiving sensor 18 has a sufficiently large area for the light beam to be received, and has little unevenness in sensitivity of the light receiving surface and sensitivity in the angular direction with respect to the received light. In this embodiment, since the diffusing plate 17 for diffusing the light from the spatial primary image is disposed in the optical path of the condensing optical system 16,
The effect of sensitivity unevenness on the light receiving surface when receiving light with the light receiving sensor 18 can be suppressed.

Next, in this embodiment, the projection optical system 10
, The intensity distribution (intensity-position) of the aerial image of the measurement pattern formed on the imaging plane is detected, and the residual coma aberration of the projection optical system 10 is measured based on the detected aerial image intensity distribution. The operation will be described. First, the measurement mask shown in FIG. 2 is placed on the mask stage 12, and the pattern surface of the measurement mask is projected onto the projection optical system 10 as shown in FIG.
Is set to match the object plane of. Then, when detecting the spatial image intensity distribution of the pattern of the measurement mask, the wafer stage 14 is moved via the drive system 45 so that the stage substrate 15 is located below the projection optical system 10. In this state, a pattern space image of the measurement mask is formed on the stage substrate 15 via the projection optical system 10.

In this state, the wafer stage 14 is moved along a predetermined direction via the drive system 45, so that a predetermined pattern group on the stage substrate 15 with respect to the aerial image of a predetermined pattern group of the measurement patterns. While scanning the knife edge pattern, light from the aerial image via the knife edge pattern is received by the light receiving sensor 18 via the condensing optical system 16 and the diffusion plate 17. Thus, in the processing system 43, a light amount distribution (light amount-time) corresponding to the aerial image is obtained based on the output from the light receiving sensor 18. Processing system 43
Then, the time-dependent intensity distribution (intensity-time) of the aerial image is detected by differentiating the obtained light quantity distribution with time.

Further, the processing system 43 converts the time information into position information based on the time-related intensity distribution of the aerial image and the position information from the laser interferometer for the wafer stage.
The intensity distribution (intensity-position) related to the position of the aerial image, that is, the aerial image intensity distribution is detected. The aerial image intensity distribution thus obtained is in good agreement with the actual intensity distribution of the aerial image formed on the imaging plane via the projection optical system 10. In the present embodiment, after obtaining the light intensity distribution by time division and obtaining the intensity distribution with respect to time, the intensity distribution with respect to the position is detected based on the position information of the interferometer. good. For example, while driving the stage, the position information of the interferometer is continuously captured at very short time intervals,
By simultaneously taking in the signal voltage from the light receiving element when the desired stage position is reached, it is possible to directly obtain the intensity distribution with respect to the position. In this embodiment, since each pattern pair is configured by arranging two L / S patterns having different pitches in parallel in the pitch direction, the aerial image intensity distribution of each pattern pair is the same as that of the first pattern. A composite intensity distribution of the aerial image intensity distribution and the aerial image intensity distribution of the second pattern is obtained.

FIG. 5 is a diagram showing a composite spatial image intensity distribution of the pattern pair shown in FIG. As shown in FIG. 5, the detected combined aerial image intensity distribution is obtained by combining the periodic aerial image intensity distribution of the first pattern with the pitch P1 and the periodic aerial image intensity distribution of the second pattern with the pitch P2. Therefore, it is not entirely periodic. Here, the information of the pattern pairs included in the combined spatial image intensity distribution of FIG. 5 detected by the combined spatial image intensity distribution detection unit 43a of the processing system 43 to be described later and the optimal combination of each pitch of the pattern pairs are shown in FIG. This will be described with reference to FIG.

FIG. 6 is a diagram showing the spatial frequency distribution of the first pattern spatial image and the spatial frequency distribution of the second pattern spatial image of the pattern pair shown in FIG. 3 when the projection optical system has no aberration. In FIG. 6, the vertical axis represents amplitude, and the horizontal axis represents spatial frequency (1 / P3 interval). The inverse Fourier transform of the combined spatial frequency distribution obtained by combining the spatial frequency distribution of the first pattern spatial image shown by the solid line in FIG. 6 and the spatial frequency distribution of the second pattern spatial image shown by the dotted line in FIG. The composite aerial image intensity distribution shown in FIG. In other words, FIG.
By performing a Fourier transform on the composite spatial image intensity distribution of the pattern pair shown in (1), the spatial frequency distribution of the composite spatial image of the pattern pair can be obtained.

Here, the pitch P3 for indicating the spatial frequency shown in FIG. 6 is defined as twice the value of "the number of lines × pitch" of each pattern (31, 32) constituting the pattern pair shown in FIG. Is what is done. Therefore, since the patterns (31, 32) constituting the pattern pair shown in FIG. 3 are selected such that “the number of lines × pitch” is equal to each other as described above, the image of the first pattern 31 is formed. The pitch is p1, and the pitch of the image of the second pattern 32 is p.
2, the number of images of the first pattern 31 is j1, the second
When the number of images of the pattern 32 is j2, 1 / p1 =
12 / P3 (= 2 × j1 / P3) and 1 / p2 = 20
/ P3 (= 2 × j2 / P3) holds. In addition,
Pitch p1 of image of first pattern 31 and first pattern 31
, And between the pitch p2 of the image of the second pattern 32 and the pitch P2 of the second pattern 32,
Assuming that the imaging magnification of the projection optical system 10 is β, p1 = β × P
1 and p2 = β × P2.

The spatial frequency distribution indicated by the solid line in FIG. 6 is the spatial frequency distribution of the first pattern spatial image.
Spatial frequency (1 / p) determined from pattern image pitch p1
1 = 12 / P3) as a primary component, and a spatial frequency (m / p1 = 12 m / P) determined by m times (m is a natural number)
3) has a main maximum or zero point. The spatial frequency distribution indicated by the broken line in FIG. 6 is the spatial frequency distribution of the second pattern spatial image, and the spatial frequency (1 / p2 = 20 / P3) determined from the pitch p2 of the second pattern image is the primary component. , And a main maximum or zero point at a spatial frequency (m / p2 = 20 m / P3) determined by m times (m is a natural number). Therefore, it can be understood from FIG. 6 that the influence of each pattern can be remarkably reduced by configuring each pattern constituting the pattern pair on the measurement mask so that “the number of lines × the pitch” is equal to each other. .

In this embodiment, four pattern groups LS (m, 0) and LS (m, 4) are set at N positions of the measurement mask.
5), LS (m, 90) and LS (m, 135) are arranged respectively. Therefore, at each position, four pattern groups LS (m, 0), LS (m, 45), LS (m, 90) and LS (m, 1
35) and the knife edge patterns KE (0), K
E (45), KE (90) and KE (135) are relatively scanned in the corresponding directions. This relative scanning may be performed by moving the mask stage 12 (ie, moving the aerial image) via a drive system (not shown) in the pitch direction of the L / S pattern on the XY plane, or may be performed on the XY plane. In the above, the wafer stage 14 may be moved via the drive system 45 in the normal direction of the edge line of the knife edge pattern (that is, the knife edge may be moved).

Thus, each position L (m, n) on the image plane of the projection optical system 10 (where m = 1 to M, n = 0, 4
5, 90, and 135) (L)
A composite aerial image intensity distribution can be obtained for each of the aerial images of S (m, 0), LS (m, 45), LS (m, 90), and LS (m, 135). Note that the composite aerial image intensity distribution can be measured in all four directions, or in two directions of the sagittal direction and the meridional direction at each position. If the knife edge pattern has a rotation error relative to the pattern group, the mask stage may be slightly rotated to match the knife edge pattern.

In the above description, as shown in FIGS. 2 and 3, each pattern group (LS (m, 0), LS (m, 45), LS (m) on the measurement mask having a plurality of pattern pairs. , 90), L
S (m, 135)), the spatial image of each pattern group obtained through the projection optical system 10 is scanned by the knife edge pattern shown in FIG. The method of photoelectrically detecting the intensity distribution and the optimal training of two patterns forming a pattern pair in each pattern group have been described.

Next, the operation of the processing system 43 based on the output from the light receiving sensor 18 will be described below. The aerial image intensity distribution detector 43a in the processing system 43 includes a light receiving sensor 18 that photoelectrically detects a combined aerial image of each pattern group formed at each position L (m, n) in the image plane of the projection optical system 10. Based on the output (measurement result), the differential and smoothing processing is performed by digital processing to obtain the combined spatial image intensity distribution data from which unnecessary noise components have been removed (see FIG. 5).

Next, the Fourier coefficient deriving unit 43b in the processing system 43 firstly outputs the combined spatial image intensity distribution detecting unit 43a
The center position of each combined aerial image intensity distribution is electrically detected via a wafer interferometer based on data on a number of combined aerial image intensity distributions (see FIG. 5) for each pattern group output from the I do. As an example, the Fourier coefficient deriving unit 43b electrically detects the peak positions A and B at both ends of the combined spatial image intensity distribution of a certain pattern pair shown in FIG. The points are electrically determined, and the center position C of each composite spatial image intensity distribution is determined for each composite spatial image intensity distribution of each pattern pair. Then, these center positions C are used as reference positions of the composite spatial image intensity distribution of each pattern pair.

At the same time, the reference position of each combined spatial image intensity distribution obtained by the Fourier coefficient deriving unit 43b is
Based on the positional information on the two-dimensional coordinate position of the wafer stage 14 detected by the above, the correspondence on the two-dimensional coordinate position of the wafer stage 14 is performed. Here, for easy understanding, the calculation of the Fourier coefficient in the Fourier coefficient deriving unit 43b will be described using the pattern pair (31, 32) shown in FIG. 3 and the composite spatial image intensity distribution shown in FIG. . Now, the first pattern 31 and the second pattern 32 in the pattern pair shown in FIG. 3 each have a periodic pitch (P
1, P2), the information on the combined aerial image intensity distribution shown in FIG. 5 is obtained by moving the wafer stage 14 in the x-direction and receiving the light receiving sensor 18 and the combined aerial image intensity distribution detector 43a. Via the Fourier coefficient deriving unit 4
3b.

The composite spatial image intensity distribution shown in FIG. 5 is defined as i (x) as a function of the position x, and the center position (reference position) C of the composite spatial image intensity distribution at the coordinate position of the wafer stage 14 shown in FIG. And Then, as shown below, in the first pattern 31 shown in FIG. 3, the spatial frequency (1
/ P1) and two Fourier coefficients (a1, a2) that can be expressed by a sine function and a cosine function. Further, as shown below, in the second pattern 32 shown in FIG.
, Two Fourier coefficients (b1, b2) for the spatial frequency (1 / p2) can be obtained.

[0047]

(Equation 1)

Therefore, the Fourier coefficient deriving unit 43b
Calculates four Fourier coefficients for each pattern pair in each pattern group by the above-described Fourier coefficient deriving method. By the way, next, for each pattern pair in each pattern group output from the Fourier coefficient deriving unit 43b, 4
Based on the data on the information of the four Fourier coefficients, the position shift detecting unit 43c multiplies the pitch of the pattern corresponding to the phase shift component from the origin by multiplying the position shift on the image plane of the projection optical system 10. calculate.
In other words, the displacement detection unit 43c calculates the displacement amount using the pitch of each pattern in each pattern pair from the origin position as the center position (reference position) of the combined spatial image intensity distribution of each pattern pair as the basic spatial frequency. Δ1 and Δ2) are calculated, and the relative positional deviation between the basic spatial frequency components with respect to the pitch of each pattern in each pattern pair (projection optical system 1
The relative positional deviation amount Δ between each pair of patterns on the 0 imaging plane is determined.

For example, the above-described four Fourier coefficients (a
1, a2, b1, b2) as an example, a deviation of the position of the spatial frequency (1 / p1) of the image of the first pattern 31 from the origin position as the center position (reference position) of the combined spatial image intensity distribution Amount Δ1 and second pattern 32 from the origin position as the center position (reference position) of the combined spatial image intensity distribution
The shift amount Δ2 of the position of the spatial frequency (1 / p1) of the image of
The unit of the angle is radian as follows. Δ1 = (p1 / 2π) · tan ⁻¹ (b1 / a1) Δ2 = (p2 / π) · tan ⁻¹ (b2 / a2)

The information Δ0 relating to the relative positional relationship between the first pattern 31 and the second pattern 32 in each pattern pair formed on the measurement mask is stored in advance in a storage unit (position shift detection unit) inside the processing system 43. 43c). The reason is that the relative position between the position of the first pattern 31 (the center position of the first pattern) and the position of the second pattern 32 (the center position of the second pattern) is due to factors such as a manufacturing error of the measurement mask. The relationship is likely to be shifted. For this reason, using a pattern position measuring device such as a coordinate measuring device (not shown), a relative positional shift amount of each pair of patterns formed on the measurement mask with respect to the design value of the first pattern 31 and the second pattern 32. Is measured in advance, and the measured value is stored in a storage unit inside the processing system 43.

When the relative displacement between the first pattern 31 and the second pattern 32 in each pattern pair formed on the measurement mask is δ0 and the imaging magnification of the projection optical system 10 is β, The relative shift amount Δ0 between the image of the first pattern 31 and the image of the second pattern 32 formed by the projection optical system 10 can be expressed by the relationship Δ0 = β × δ0.
From the above, finally, the positional shift Δ1 of the aerial image obtained from the spatial frequency component (1 / P1) of one of the first patterns in each pattern pair and the spatial frequency component of the other second pattern The relative positional deviation amount Δ12 from the positional deviation △ 2 of the aerial image obtained from (1 / P2) is, as shown by the following relational expression, between the first pattern 31 in each pattern pair formed on the measurement mask. By offsetting by a relative position error Δ0 with respect to the second pattern 32,
It is detected with high accuracy. Δ12 = Δ1-Δ2-Δ0

By the way, in this embodiment, 2 of each pattern pair is used.
The pitch and the number of lines of one pattern satisfy the above two conditions. In this case, FIG.
As shown by the spatial frequency distribution of 1 / p1
The amplitude (Fourier coefficient) at (= 12 / P3) is substantially only the component caused by the first pattern image, the component caused by the second pattern image is very small, and the spatial frequency is 1 / p2 (= 20). The amplitude (Fourier coefficient) in (/ P3) is substantially only the component resulting from the second pattern image, and the component resulting from the first pattern image is very small. This is the same even when an aberration occurs in the projection optical system.

Thus, despite the simultaneous measurement of two pattern images to obtain a composite spatial image intensity distribution, the positional deviation of the spatial frequency 1 / P1 component is the same as the spatial frequency 1 / p1 component of the first pattern image. Misalignment, air frequency 1 / P2
The component displacement is the spatial frequency 1 / p2 of the second pattern image.
This results in misalignment of components. Thus, since they are not influenced by each other, the spatial frequency 1 / p1 of the first pattern image
A relative position shift (hereinafter, referred to as a “position shift between pitches”) on the imaging plane between the component and the spatial frequency 1 / p2 component of the second pattern image can be detected with high accuracy. Also,
In the present embodiment, since two pattern pairs are measured simultaneously, it is possible to eliminate the deterioration of measurement accuracy due to the influence of fluctuation of the interferometer when measured independently.

Next, the coma aberration detector 4 in the processing system 43
In 3d, the relative positional deviation between the two pitches of each pattern pair obtained by the relative positional deviation detecting unit 43c can be integrated to determine the relative positional deviation relationship between a large number of pitches. As in the present embodiment, by configuring each pattern group to include a pattern having a pitch equal to the pitch of any one of the pattern pairs, as shown in FIG. This is convenient because a relative displacement relationship between the pitches can be obtained. Here, the relative positional deviation relationship will be described. For example, 3
In a pattern group including M pattern pairs (M = 3),
The first pattern pair LS (1, n) has pitches P1 and P2
When the second pattern pair LS (2, n) has the pitches P1 and P3 and the third pattern pair LS (3, n) has the pitches P1 and P4, as described above, Each relative shift amount Δ (for example, Δ12, Δ1
3, Δ14) can be obtained.

Here, for example, the pitch p of the pattern image when a pattern having a pitch P1 that forms a part of the first to third pattern pairs is formed on the image plane of the projection optical system 10.
1 is 0.8 μm, the pattern image pitch p2 is 1.2 μm when a pattern having a pitch P2 forming a part of the first pattern pair is formed on the imaging surface of the projection optical system 10, and the second When a pattern having a pitch P3 forming a part of the pattern pair is formed on the imaging surface of the projection optical system 10, the pitch p3 of the pattern image is set to 2 μm, and the pitch P4 forming a part of the third pattern pair is set to The pitch p4 of the pattern image when the held pattern is formed on the image plane of the projection optical system 10.
Is set to 3 μm. Then, the horizontal axis is the pitch, the vertical axis is the relative displacement amount, and the reference pitch of the graph is, for example, p
1 is taken, and the relative displacement is set to zero. Thereafter, if the relative displacement amount for each pitch is determined based on the pitch p1, a relative displacement relationship for a plurality of pitches can be obtained as shown in FIG. 7B.

It should be noted that the combination of pitches of each pattern pair changes, the second pattern pair LS (2, n) has pitches P1 and P3, and the third pattern pair LS (3, n) has pitches P3 and P4. Or the second pattern pair L
Even when S (2, n) has pitches P1 and P3 and third pattern pair LS (3, n) has pitches P2 and P4, the above configuration may be satisfied. FIG. 7A shows an example in which the relative positional deviation relationship between more pitches is obtained by the above method and displayed in a graph.
Shows an example in which coma remains. In FIG. 7A, the measurement points are connected by a smooth line to represent the overall tendency. Here, the absolute position of the vertical axis shown in FIG. 7A is not important, and the measured minimum pitch value is set to zero. Therefore, the coma aberration detector 43
d is based on positional deviation information for each pattern pair in each pattern group from the relative positional deviation detecting unit 43c, as shown in FIG.
The relationship shown in FIG.

Next, the coma aberration detecting section 43 d
From the relationship shown in (a), the average value and the variance of the relative positional deviation amount in each pitch component are obtained based on the value of the minimum pitch (here, zero) of the minimum positional deviation relationship, and the minimum pitch is calculated from the average value. The sign when subtracting the value of (here, zero) is obtained. At this time, the obtained variance value and sign have a correlation between the magnitude of the coma aberration generated on the image plane through the projection optical system 10 and the sign thereof. Therefore, the coma aberration detecting unit 43d calculates the residual coma aberration amount of the projection optical system 10 from the obtained dispersion value and sign using a predetermined appropriate function (such as a linear function). Thus, each position L on the image plane of the projection optical system 10 is
(M, n) (m = 1 to M, n = 0, 45, 90, 13
By repeating the measurement on the image of the pattern pair formed in 5), the amount of residual coma aberration of the projection optical system 10 can be measured. It is desirable that the minimum pitch is closer to the minimum pitch that can be resolved by the projection optical system.

In the above description, the processing system 43 measures the amount of one coma aberration remaining in the projection optical system 10 by using the four pattern groups shown in FIG. In the mask for use, N groups of the four patterns shown in FIG. 2 are formed at different positions. Therefore, the processing system 43 uses the four pattern groups formed at different positions on the measurement mask, respectively.
Performs the above-described processing N times and detects N coma aberration amounts.

In general, for example, the state of coma of a test optical system such as a projection optical system is determined by the amount of lateral aberration generated when a light beam emitted from one point on the object plane reaches the image plane. A low-order component having a distribution that increases in proportion to the square of the numerical aperture (NA) (an aberration shape similar to the coma aberration defined by Seidel's five aberrations and also referred to as a third-order coma aberration), It is divided into a higher-order component that is added to the lower-order component and causes undulation in the lateral aberration distribution. The low-order component and the high-order component slightly remain in the design values, but the amounts of the components are often corrected to be small enough.

On the other hand, during the production and actual use of the projection optical system as the test optical system, it is generally considered that there are the following factors that cause aberration. The low-order coma is a component generated by a lens curvature radius error, a lens interval error, a lens (or lens group) eccentricity error, and a refractive index error at the time of manufacturing a lens. This is a component that occurs when a minute change such as a change in the refractive index occurs. On the other hand, high-order coma aberration is a component other than a radius of curvature error such as unevenness of a lens surface or a component caused by a non-uniform distribution error of a refractive index in a lens during manufacturing.
At the time of actual use, it is said to be a component generated due to unevenness in temperature distribution in the lens. The error component at the time of manufacture is static and does not fluctuate after manufacture, but the error component at the time of actual use is dynamic and can be a factor of performance fluctuation. However, coma aberration variation is generally small as a dynamic variation factor, and magnification variation is often overwhelmingly a problem.

The coma aberration measurement according to the present embodiment is for obtaining a measured value (dispersion value and sign) having a correlation with the coma aberration, and the measured value and the change of the low-order coma aberration have a very good correlation. In particular, the correlation can be satisfactorily approximated by a linear function in a very small generation region. However, this correlation has the property that it changes depending on the illumination conditions (illumination NA and modified illumination) of the illumination system.

When only a low-order coma aberration component is generated in the projection optical system 10 as the test optical system,
The correlation itself changes due to a change in lighting conditions,
If the low-order coma aberration component can be corrected to approximately 0 by the aberration adjusting mechanism or the like of the projection optical system 10, the coma aberration itself becomes approximately 0, so that the dispersion value becomes approximately 0 regardless of a difference in illumination conditions. In other words, if the coma aberration of the projection optical system 10 can be adjusted to approximately 0 under a certain illumination condition, the coma aberration of the projection optical system 10 can also be approximately 0 under other illumination conditions. That is, it is considered that the constant term of the correlation is 0 irrespective of the difference in the illumination condition, and only the primary coefficient (slope) is different. In addition, such a low-order coma aberration adjustment mechanism can be easily realized by adjusting the intervals of optical components constituting the projection optical system 10, adjusting the eccentricity / tilt, partially changing the pressure inside the lens, and the like.

On the other hand, when the high-order coma aberration component remains in the projection optical system 10, even if the dispersion value is adjusted so as to be substantially zero under a certain illumination condition, the above-mentioned dispersion value may be obtained under another illumination condition. The variance does not become zero. This means that when the high-order coma aberration component remains, the constant term of the correlation is not 0 and changes depending on the illumination condition. If the constant term of the correlation can be obtained for each illumination condition, the obtained constant term can be an index of the remaining higher-order coma aberration amount. For example, if the primary coefficient is obtained in advance for each lighting condition to be used, the constant term can be calculated by measuring the variance and the sign for each lighting condition. As a method of obtaining the first-order coefficient, a method of obtaining it by an optical simulation when only low-order coma is generated may be used, or the low-order coma may be surely changed by a certain amount by the low-order coma adjustment mechanism. May be measured by measuring the variation in the variance value to obtain a first order coefficient. In the present embodiment, the higher-order coma is detected by the coma aberration detector 43d.

In this embodiment, the coma aberration detecting section 43d
As a method of adjusting when high-order coma is detected by the method described above, a method of changing the interval between a plurality of optical components in the projection optical system 10 and correction polishing of at least one lens surface or a flat plate of the projection optical system 10 are performed. A method can be considered. Also,
Even when the NA of the test optical system such as the projection optical system 10 is changed, a change in the correlation is observed similarly to the change in the illumination condition, but it can be handled in the same manner as the change in the illumination condition.

In the above description, the variance from the average value and the sign between the minimum pitch and the average value are used as the measurement values correlated with the coma aberration, but other methods may be used. For example, the coefficients may be used by performing linear approximation or polynomial approximation on the relative positional relationship with respect to each pitch shown in FIG. For example, when the least-squares straight-line approximation is performed, the inclination and the sign have a correlation with the amount and the sign of the coma aberration, and the amount of the coma aberration can be measured. Further, as a simpler method, it is also possible to use the positional deviation amount obtained for one pattern pair instead of the variance value. However, in this case, it is necessary to set an effective pattern pair having a sufficient resolution with respect to a change in coma aberration.

Now, the coma aberration detector 43 in the processing system 43
When the result obtained by d is not good, that is, when the coma aberration on the imaging surface of the projection optical system 10 is deteriorated, the correction amount calculation unit 43e provided in the processing system 43
Based on the result obtained by the coma aberration detection unit 43d,
In order to correct coma aberration of the projection optical system 10, optical elements (L ₁ , L
₂ ) Calculate the correction amount. Then, the correction amount calculating section 4
3e, based on the calculated result, moves the optical elements (L ₁ , L ₂ ) in the projection optical system 10 in the optical axis direction of the projection optical system 10 via the drive system 46, or moves the optical elements (L ₁ , L
₂₎ or is moved in the optical axis perpendicular to the plane of the projection optical system 10, and or move to tilt the optical element (L _1, L ₂₎ with respect to the optical axis of the projection optical system 10, The coma of the projection optical system 10 is corrected.

As described above, when the step of correcting the coma aberration characteristic (or the image forming characteristic) on the image forming surface of the projection optical system 10 is completed, the process proceeds to the exposure step (photolithography step). First, in the exposure step, the measurement mask set on the object plane of the projection optical system 10 is replaced with an actual exposure mask 9, and the exposure mask 9 is connected via the mask stage 12 to the object plane of the projection optical system 10. Set to.
Then, when the wafer 11 serving as a photosensitive substrate is set on the image forming plane of the projection optical system 10 via the wafer stage 14, the exposure mask 9 is illuminated by the illumination optical system (1 to 8). Then, the pattern of the exposure mask 9 is transferred (exposed) onto the wafer 11 via the projection optical system 10.

The wafer 11 that has undergone the above-described exposure step (photolithography step) is subjected to an etching step of removing portions other than the developed resist after a development step, and to removing unnecessary resist after the etching step. Through a step of removing the resist. Then, the steps of exposure, etching, and resist removal are repeated to complete the wafer process. After that, when the wafer process is completed, in the actual assembling process, dicing is performed to cut and divide the wafer into chips for each baked circuit, bonding for providing wiring and the like to each chip, and package for packaging each chip Finally, a semiconductor device such as an LSI is manufactured through the respective steps such as ringing.

In the above description, an example in which a semiconductor device such as an LSI is manufactured by a photolithography process in a wafer process using an exposure apparatus has been described.
Semiconductor devices such as thin-film magnetic heads and imaging devices (CCD, etc.) can also be manufactured. As described above, in this embodiment, since the coma aberration measuring apparatus is mounted on the projection exposure apparatus, the pattern exposure, development, SEM measurement, calculation processing, etc. are performed by a simple mechanism without actually performing operations. It is possible to accurately measure the residual coma aberration amount of the projection optical system serving as the inspection optical system. That is, the NA of the projection optical system
Also, even if the NA of the illumination optical system and the illumination conditions (normal illumination, annular illumination, deformed illumination, etc.) are changed and the imaging of the projection optical system is significantly affected, the remaining frames of the projection optical system The amount of aberration can be easily measured at any time. As a result, the aberration of the projection optical system is adjusted based on the measured residual coma aberration amount, and a good semiconductor device can be manufactured via the projection optical system having a good aberration state.

In the above-described embodiment, the present invention is applied to a coma aberration measuring device of a type in which the light receiving sensor 18 is built in the wafer stage 14 and receives light inside the wafer stage 14. The present invention can also be applied to a coma aberration measuring device of a type that receives light outside the wafer stage 14 using the same. FIG. 8 is a diagram schematically showing a configuration of a projection exposure apparatus provided with a first type of coma aberration measuring device that receives light outside the wafer stage. In the modification of FIG. 8, light from the aerial image formed on the imaging surface of the projection optical system 10 enters the light-collecting optical system 81 via the knife edge pattern of the stage substrate 15. The light having passed through the condensing optical system 81 is reflected by a mirror 82 and then enters an incident end of a light guide 83 such as an optical fiber. The light that has propagated inside the light guide 83 is guided to the emission end thereof, and reaches a light receiving sensor 84 arranged close to the emission end. The output of the light receiving sensor 84 is supplied to a processing system 43 (not shown). In this way, also in the first type of coma aberration measuring device, the residual coma aberration amount of the projection optical system 10 is measured as in the above-described embodiment.

FIG. 9 is a diagram schematically showing a configuration of a projection exposure apparatus provided with a second type of coma aberration measuring device for receiving light outside the wafer stage. In the modification of FIG. 9, light from the aerial image formed on the image plane of the projection optical system 10 is incident on the condensing optical system 91 via the knife edge pattern of the stage substrate 15. The light passing through the condensing optical system 91 and the diffusion plate 92 disposed therein enters the incident end of a light guide 93 such as an optical fiber. The light emitted from the light emitting end of the light guide 93 is guided to the outside of the wafer stage 14 through, for example, one lens 94 of a relay optical system including a pair of lenses and an opening formed in the wafer stage 14.

The light guided to the outside of the wafer stage 14 reaches the light receiving sensor 96 via one lens 95 of the relay optical system. Here, the exit end of the light guide 93 and the light receiving surface of the light receiving sensor 96 are connected to a relay optical system (94,
95). Light receiving sensor 96
Is output from the processing system 4 of the coma aberration measuring device (not shown).
3. Thus, in the second type of coma aberration measuring apparatus, similarly to the above-described embodiment, the projection optical system 10
Is measured.

In the projection exposure apparatus having the second type of coma aberration measuring device, a unit including a lens 95 and a light receiving sensor 96 disposed outside the wafer stage 14 and a unit disposed inside the wafer stage 14 are provided. The unit including the condenser lens 91, the light guide 93, and the lens 94 is mechanically separated from each other, and is optically connected only when measuring coma aberration. Therefore, in the second type, unlike the first type, the ride guide does not exert a load on the wafer stage, and
In addition, the use of the light guide has an advantage that the degree of freedom of light transmission is high.

In the above-described embodiments and modifications, the coma aberration measuring apparatus of the present invention is mounted on the projection exposure apparatus. However, the coma aberration measuring apparatus for measuring the residual coma aberration amount of another general optical system to be inspected is used. The present invention can also be applied to an aberration measurement device.
Further, in the above-described embodiment, a pattern pair including two patterns is used as the measurement pattern. However, a pattern group including three or more patterns arranged in parallel may be used. Furthermore, in the above embodiment, the knife edge pattern having the edge line along the direction orthogonal to the measurement direction is used, but the knife edge having the edge line along the direction intersecting at a substantial angle with the measurement direction. Patterns can also be used.

[0075]

As described above, according to the coma aberration measuring apparatus of the present invention, the amount of residual coma aberration of the test optical system can be accurately measured by a simple mechanism. In particular, when the coma aberration measuring apparatus of the present invention is mounted on a projection exposure apparatus, the residual coma aberration amount of the projection optical system can be accurately measured without actually performing operations such as pattern printing, development, SEM measurement, and calculation processing. can do. That is, even if the NA of the projection optical system, the NA of the illumination optical system, and the illumination conditions (normal illumination, annular illumination, deformed illumination, and the like) are changed, even if the imaging of the projection optical system is significantly affected, In addition, the residual coma amount of the projection optical system can be easily measured at any time. As a result, the aberration of the projection optical system is adjusted based on the measured residual coma aberration amount, and a good semiconductor device can be manufactured via the projection optical system having a good aberration state.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a configuration of a projection exposure apparatus including a coma aberration measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram schematically illustrating an aberration measurement pattern formed on a measurement mask used for measuring a residual coma aberration amount of a projection optical system.

FIG. 3 is a diagram for explaining the structural features of each pattern pair.

FIG. 4 is a view showing a knife edge pattern formed on an upper surface of the stage substrate of FIG. 1;

FIG. 5 is a diagram showing a composite aerial image intensity distribution of the pattern pair shown in FIG. 3;

6 is a diagram showing a spatial frequency distribution of a first pattern spatial image and a spatial frequency distribution of a second pattern spatial image of the pattern pair shown in FIG. 3 when the projection optical system has no aberration.

FIG. 7 is a diagram illustrating a relationship between positional shifts with respect to each pitch of a pattern space image.

FIG. 8 is a diagram schematically showing a configuration of a projection exposure apparatus provided with a first type of coma aberration measuring device that receives light outside a wafer stage.

FIG. 9 is a diagram schematically showing a configuration of a projection exposure apparatus provided with a second type of coma aberration measuring device that receives light outside a wafer stage.

[Explanation of symbols]

 Reference Signs List 1 light source 2 elliptical reflecting mirror 3 second focal point position 4 input lens 5 fly-eye integrator 6 aperture stop 7 condenser lens 8 bending mirror 9 mask 10 projection optical system 11 wafer 12 mask stage 13 wafer holder 14 wafer stage 15 stage substrate 16 focusing optics System 17 Diffusion plate 18 Light receiving sensor 40 Irradiation unit 41 Focus detection unit 43 Processing system 45, 46 Drive system

Claims (7)

[Claims] 1. A coma aberration measuring device for measuring an amount of residual coma aberration of an optical system to be inspected, wherein an edge line positioned on an image forming plane of the optical system to be inspected and extending along a direction intersecting a measurement direction is defined. A measurement member on which a knife edge pattern is formed and a reference member on which a pattern group having a plurality of patterns arranged in parallel along the measurement direction are set on the object surface of the optical system to be measured. A photoelectric detection unit for detecting light from the spatial image of the pattern group formed on the imaging surface of the optical system to be detected through the knife edge pattern; Relative moving means for relatively moving the spatial image of the pattern group formed on the surface and the knife edge pattern along the measurement direction; and the space of the pattern group by the relative moving means. And the knife edge pattern, the intensity distribution of the spatial image of each pattern forming the pattern group as an intensity distribution of the spatial image of the pattern group based on the light amount change information from the photoelectric detection means when the pattern is relatively moved. An intensity distribution detecting means for detecting a combined spatial image intensity distribution composed of distributions, and a residual coma aberration amount of the test optical system is detected based on the combined spatial image intensity distribution obtained by the intensity distribution detecting means. A coma aberration measuring device, comprising: 2. The pattern group includes a first pattern including a line-and-space pattern having a first pitch P1, and a pitch larger than the first pitch P1 and an integral multiple of the first pitch P1. Has a second pattern consisting of a line-and-space pattern having a substantially different second pitch P2, and the product of the pitch P1 of the first pattern and the number of lines is
2. The coma aberration measuring apparatus according to claim 1, wherein a product of the pitch P2 of the second pattern and the number of lines is substantially equal. 3. The processing system performs signal processing on the combined aerial image intensity distribution obtained by the intensity distribution detecting means, so that each of at least two patterns forming the pattern group is applied to the image plane. Fourier coefficients with respect to a predetermined spatial frequency based on the pitch of the pattern image to be formed are respectively obtained, and a relative position on the image plane between the spatial frequency components for the at least two patterns based on the obtained Fourier coefficients. The coma aberration measuring apparatus according to claim 1, wherein a position shift is calculated, and a residual coma aberration amount of the test optical system is detected based on the calculated relative position shift. 4. A coma aberration measuring apparatus according to claim 1, an illumination optical system for illuminating a mask, and a photosensitive substrate for transferring an image of a transfer pattern formed on the mask. A projection optical system for projecting the projection optical system onto the projection optical system, wherein the coma aberration measuring device measures a residual coma aberration amount of the projection optical system as the test optical system. 5. The relative movement means includes a substrate stage which holds the photosensitive substrate and is movable with respect to the projection optical system, wherein the measuring member of the coma aberration measuring device is provided on the substrate stage. The projection exposure apparatus according to claim 4, wherein the projection exposure apparatus is provided at a position corresponding to an exposure surface of the photosensitive substrate. 6. The projection system according to claim 4, further comprising a correction system for correcting coma aberration remaining in the projection optical system based on an output from the processing system. Exposure equipment. 7. A method for manufacturing a semiconductor device using the projection exposure apparatus according to claim 4, wherein the reference having the measurement pattern formed on an object surface of the projection optical system. Setting a member, measuring the coma remaining in the projection optical system by the coma aberration measuring device, correcting the coma remaining in the projection optical system, and the object plane of the projection optical system An exposure illumination step of illuminating the transfer mask with the illumination optical system, and setting the pattern of the transfer mask to the photosensitive mask through the projection optical system. An exposing step of exposing a substrate to light.