JPH11251225A - Image-forming system, aligner comprising the same, method for using the image-forming system, and manufacture of device using the aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging system which is used as an objective optical system for an alignment sensor while its imaging characteristics is adjusted in short time and with high accuracy. SOLUTION: With illuminating light from a light source 21, a wafer mark WMY on a Y-axis on a wafer W is illuminated through a field stop 23, etc., a lighting relay lens 24, a half-prism 25, and a first objective lens 26. A reflected light L1 from the wafer mark WMY is condensed on an imaging surface of an imaging element 28 through the first objective lens 26, the half-prism 25, and a second objective lens 27, with the image of the wafer mark WMY formed on the image-forming surface. The characteristics of wave-front aberration of the first objective lens 26 is measured in advance, and the direction in which the wave-front aberration becomes minimum is set parallel to the measurement direction (the-direction) of the wafer mark WMY.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for manufacturing a semiconductor device such as a semiconductor device, an image pickup device (such as a CCD), a liquid crystal display device, or a thin film magnetic head by using a photolithography technique, and uses a mask pattern. The present invention relates to an objective optical system of an alignment system of an exposure apparatus that exposes a light onto a substrate via a projection optical system, or an imaging system suitable for use in the projection optical system. Further, the present invention relates to an exposure apparatus having the imaging system, a method of using the imaging system, and a method of manufacturing a device using the exposure apparatus.

[0002]

2. Description of the Related Art When manufacturing a semiconductor device or the like, a pattern of a reticle as a mask is transferred to each shot area on a wafer (or a glass plate or the like) coated with a resist through a projection optical system. In a projection exposure apparatus (stepper or the like) to be used, alignment marks (wafers) attached to each shot area are required to perform high-accuracy alignment (alignment) between each shot area on the wafer and a reticle pattern. An alignment sensor for detecting the position of the mark is provided.

In a conventional alignment sensor, as a method capable of detecting a position with high accuracy, a wafer mark is irradiated with illumination light of a relatively wide wavelength range from a halogen lamp or the like, and an obtained image is subjected to image processing. Image processing method to detect the position of the wafer mark, or FIA (Fiel
d Image Alignment) method is known. In addition, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2-227602, a pair of coherent laser beams is irradiated to a diffraction grating wafer mark, and the laser beam is generated in the same direction from the wafer mark. A so-called LIA (Laser Interferometric Alignment) for detecting the position of a wafer mark based on the phase of a beat signal obtained by photoelectrically converting a pair of diffracted lights.
In addition, as disclosed in, for example, Japanese Patent Application Laid-Open No. Sho 60-130742, a dot-row-shaped wafer mark arranged in a direction perpendicular to the measurement direction and a slit-shaped laser beam emitted from a sensor are used. A laser step alignment method (LSA method) for detecting the coordinates of the wafer mark by performing relative scanning in the measurement direction is also known.

In order to improve the measurement accuracy of this type of alignment sensor, it is necessary to reduce various aberrations of an objective optical system that receives a light beam from a wafer mark. Therefore, conventionally, the processing accuracy of each lens constituting the objective optical system has been made higher than the processing accuracy of other lenses constituting the illumination optical system. However, even if the processing accuracy was increased in this way, the objective optical system assembled due to the processing error still had variation in aberration due to the direction around the optical axis. After that, the objective optical system is rotated about the optical axis, and for example, the rotation angle at which the detection error is minimized is experimentally determined.

[0005]

In the prior art as described above, the rotational angle of the objective optical system is experimentally determined after the objective optical system is incorporated in the alignment sensor. This requires a great deal of time, and the manufacturing cost of the exposure apparatus is high.

In recent years, as a projection exposure apparatus, in order to transfer a pattern of a large-area reticle without increasing the size of the projection optical system, a reticle and a wafer are moved synchronously with respect to the projection optical system for exposure. Attention has been focused on a scanning exposure type projection exposure apparatus such as a step-and-scan method for performing the above. In such a scanning exposure type projection exposure apparatus,
Since the exposure area by the projection optical system is a slit-shaped area narrow in the scanning direction, it is desirable that the aberration of the projection optical system be adjusted by a method utilizing the characteristic of the shape of the exposure area.

In view of the foregoing, the present invention can be used as an objective optical system of an alignment sensor or a projection optical system of a scanning exposure type projection exposure apparatus, and can adjust the image forming characteristics in a short time and effectively. A first object is to provide an imaging system that can be performed (with high accuracy). It is a second object of the present invention to provide an exposure apparatus which is provided with such an imaging system and which can perform alignment with high accuracy or can transfer a reticle pattern with high accuracy.

It is a third object of the present invention to provide an effective method of using such an imaging system and a device manufacturing method capable of manufacturing a highly accurate device using such an exposure apparatus. .

[0009]

A first image forming system according to the present invention is an image forming system (26, 27) for projecting an image of a mark to be inspected (WMY) onto a predetermined image forming surface. At least a part of the image system is constituted by an optical system (26) having known characteristics of aberrations (wavefront aberration, Seidel's five aberrations, etc.), and the direction in which the aberration of the optical system is substantially minimized is measured. This is to match the measurement direction of the mark.

According to the present invention, for example, the wavefront aberration or the like of the optical system (26) facing the test mark in the imaging system is measured in advance, and the aberration is minimized around the optical axis. Find the direction that will be. And the optical system (26)
When is incorporated in the imaging system, the imaging system can be adjusted in a short time and with high accuracy by setting the direction in which the aberration is minimized in parallel with the measurement direction of the test mark. .

In this case, when the test mark is one mark having a plurality of measurement directions or a plurality of marks (WMX, WXY) having different measurement directions, the optical system (26) is moved around the optical axis. Rotating member (2)
9), and it is desirable to rotate the optical system via the rotating member in accordance with the direction to be measured among the plurality of measurement directions. Thus, position detection can be performed with high accuracy in each of the plurality of measurement directions.

A first exposure apparatus according to the present invention comprises a first image forming system (26, 27) according to the present invention and a position detecting system for detecting an image of a test mark via the image forming system. (2
8, 14) and an exposure main unit (6 to 8, PL) for transferring a pattern of a mask (R) onto a substrate (W) on which a positioning mark (WMY) as a target mark is formed.
And a stage system (2, 3) for moving the substrate. Based on the position of the alignment mark on the substrate detected by the imaging system and the detection system, the stage system (2, 3) To align the substrate. Since the position of the alignment mark can be detected with high accuracy by using the imaging system of the present invention, the alignment accuracy or the overlay accuracy is improved.

Next, a second imaging system according to the present invention comprises a substantially rectangular exposure area (15) having a longitudinal direction along a predetermined direction (Y direction) on a substrate (W) or the substrate. The pattern image of the mask is projected in a substantially arc-shaped exposure region (15S) extending along the upper predetermined direction (Y direction) (that is, the predetermined direction is a direction connecting both ends of the arc). In the imaging system (PL), the direction in which the aberration (wavefront aberration, Seidel's five aberration, etc.) of the imaging system is substantially the smallest is adjusted to the predetermined direction.

The second image forming system can be used as a projection optical system of a scanning exposure type projection optical system such as a step-and-scan system. In this case, the scanning is performed in a direction orthogonal to the predetermined direction, and the exposure area is spread in the predetermined direction. Therefore, the aberration (distortion or the like) of the imaging system is minimized in the predetermined direction to transfer the image. The aberration of the image to be obtained is minimized as a whole.

A second exposure apparatus according to the present invention moves the second imaging system (PL) of the present invention, the mask (R) and the substrate (W) in synchronization with the imaging system. And a stage system (6, 7, 2, 3) for performing scanning exposure by moving the mask and the substrate in a direction orthogonal to the predetermined direction. According to this exposure apparatus, the pattern image of the mask can be transferred onto the substrate in a state of small aberration.

Further, a first device manufacturing method according to the present invention is a device manufacturing method using the first exposure apparatus of the present invention, wherein a step of coating a photosensitive material on the substrate (W) is performed. And a mask (R) on which a pattern corresponding to a circuit pattern of a predetermined layer of the device is formed as a mask, and a positioning mark (WMX, WMX, WMX, WM
Y) detecting the position, based on the detection result, aligning the substrate with the mask through the stage system, transferring the pattern of the mask onto the substrate, Developing the photosensitive material on the substrate to form the circuit pattern. According to the present invention, since the position alignment (alignment) between the mask and the substrate can be performed with high accuracy, the overlay accuracy between the layers is improved and the device yield is improved.

Next, a method of using the imaging system according to the present invention is as follows.
An image of a test mark (WMY) having a predetermined measurement direction is formed on a predetermined image plane by the first image forming system of the present invention, and an image of the test mark formed on the image plane is detected. In the method of using the imaging system (26, 27), the imaging system or at least one optical member (2
6) includes a measurement step of measuring residual aberration, and an adjustment step of adjusting the measurement direction to a direction in which the measured residual aberration indicates a desired value. According to the present invention, for example, the direction in which the balance of the residual aberration is the best is matched with the measurement direction, thereby improving the measurement accuracy.

A second device manufacturing method according to the present invention is a device manufacturing method using the second exposure apparatus according to the present invention, and has a longitudinal direction along a predetermined direction on the substrate. A substantially rectangular exposure area (15) or an arc-shaped exposure area (15) extending along a predetermined direction thereof.
S) projecting an image of the pattern of the mask onto the substrate, exposing the image of the pattern of the mask onto the substrate by synchronously moving the mask and the substrate with respect to the imaging system; Prior to the exposure step, the imaging system, or a measurement step of measuring the aberration remaining in at least one optical member constituting the imaging system, and simultaneously with the exposure step, or prior to the exposure step, Adjusting the predetermined direction to a direction in which the residual aberration measured by the measuring step shows a desired value. According to the present invention, for example, the transfer fidelity of a pattern image of a mask that is scanned and exposed on the substrate may be improved by, for example, adjusting a direction in which the balance of the residual aberration is the best in the predetermined direction. .

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a projection exposure apparatus used in the present embodiment. In FIG. 1, at the time of exposure, an exposure light source such as a mercury lamp or an excimer laser light source, for uniformizing the illuminance distribution of exposure light from this exposure light source. The exposure light IL is applied to a rectangular illumination area on the reticle R from an optical integrator, a field stop (reticle blind) defining an illumination area, and an illumination optical system 8 including a condenser lens system. Then, under the exposure light IL, the image of the pattern formed on the reticle R is changed to a projection optical system P which is telecentric on both sides.
A projection magnification β (β is ５ ，, ４, etc.) is projected onto a rectangular exposure area 15 on the exposure target shot area on the wafer W via L. A resist is applied to the surface of the wafer W, and a measurement system for indirectly monitoring the exposure amount of the resist is provided in the illumination optical system 8. Based on the measurement result of this measurement system and the control information of the main control system 5 composed of a computer for controlling the operation of the entire apparatus, the exposure control system 11 controls the illuminance of the exposure light and adjusts the exposure to the resist. Become

Hereinafter, the Z axis is taken parallel to the optical axis AX of the projection optical system PL, and the X axis is taken perpendicularly to the plane of FIG. 1 (scanning direction) in a plane perpendicular to the Z axis. The description will be made taking the Y axis in parallel (non-scanning direction). At this time, reticle R
Is held on a reticle stage 7 by suction, and the reticle stage 7 is supported on a reticle base 6 so as to float via an air bearing. The reticle stage 7 is continuously moved in the X direction by a driving mechanism such as a linear motor. direction,
Fine movement in Y direction and rotation direction. The side surface of the reticle stage 7 is processed into a Y-axis mirror surface 7y and an X-axis mirror surface, and these mirror surfaces are irradiated with, for example, a three-axis laser beam from a reticle laser interferometer 9. The X coordinate, the Y coordinate, and the rotation angle are measured, and the measured values are supplied to the reticle stage drive system 10 and the main control system 5. The reticle stage drive system 10 controls the scanning operation and the positioning operation of the reticle stage 7 based on the measured values and the control information from the main control system 5.

On the other hand, the wafer W is held on a wafer holder (not shown) by vacuum suction, and the wafer holder is fixed on a Z tilt stage 3, and the Z tilt stage 3 is placed on the surface plate 1 via an air bearing. It is fixed on an XY stage 2 which is supported so as to float. The Z tilt stage 3 controls the position (focus position) of the wafer W in the Z direction (focus position) and the tilt angle to adjust the surface of the wafer W to the image plane of the projection optical system PL by an autofocus method. The wafer W is continuously moved in the X direction by a driving mechanism such as a linear motor, and
The Z tilt stage 3 (wafer W) is step-moved in the Y direction. The Z tilt stage 3 and the XY stage 2 constitute a wafer stage. The side surface of the Z tilt stage 3 is processed into a mirror surface 3y on the Y axis and a mirror surface on the X axis, and these mirror surfaces are irradiated with, for example, a three-axis laser beam from the laser interferometer 12 on the wafer side. Measures the X coordinate, the Y coordinate, and the rotation angle of the Z tilt stage 3, and supplies the measured values to the wafer stage drive system 13 and the main control system 5. Coordinate system (X, Y) composed of X coordinate and Y coordinate of Z tilt stage 3 (wafer W) measured by laser interferometer 12 on the wafer side
Is called a coordinate system of the wafer stage or a stationary coordinate system.
Wafer stage drive system 13 controls the operation of XY stage 2 based on the measured values and control information from main control system 5.

At the time of exposure of the wafer W, the XY stage 2 is step-moved after the exposure of one shot area on the wafer W is completed.
The next shot area on wafer W is moved to a position short of exposure area 15 by projection optical system PL. Thereafter, the reticle stage 7 and the XY stage 2 are driven to move the reticle R and the wafer W to each other using the projection optical system P with a projection magnification β as a speed ratio.
The operation of synchronously scanning L and irradiating exposure light IL is repeated in a step-and-scan manner, and scanning exposure is performed on each shot area on the wafer W.

Next, the image forming characteristics of the projection optical system PL of this embodiment will be described. The projection optical system PL of this example is divided into a front group 16 and a rear group 17 across an optical Fourier transform plane with respect to the pattern surface of the reticle R.
Numerals 7 are each held in a lens barrel (not shown) that can be rotated around the optical axis AX. The rotation angles of the front group 16 and the rear group 17 are adjusted as follows.

FIG. 2 shows an exposure area 15 by the projection optical system PL of FIG. 1. In FIG. 2, the exposure area 15 is a rectangle which is narrow in the scanning direction (X direction) and wide in the non-scanning direction (Y direction). is there. Further, the exposure area 15 is substantially the projection optical system P
L inscribes the contour of the effective field of view. In the present example, as an example, when the projection optical system PL is incorporated in the projection exposure apparatus of the present example, the rotation angles of the front group 16 and the rear group 17 are set so that the distortion in the exposure area 15 is minimized. I do. For this purpose, a test reticle on which an evaluation pattern is formed is mounted as the reticle R in FIG. 1, and for example, while changing the rotation angles of the front group 16 and the rear group 17 by a predetermined amount, the evaluation pattern is changed. Is exposed on an unexposed wafer for evaluation, and the distortion of the projected image obtained after development may be measured. Alternatively, a spatial image measurement system having a slit or the like may be provided on the wafer stage side, and the measurement pattern may be used to actually measure the projection position of the evaluation pattern. As a result, after the scanning exposure, the distortion is minimized on the entire surface of the shot area, and high overlay accuracy is obtained.

In addition to minimizing the distortion in the exposure region 15, other Seidel aberrations such as spherical aberration, astigmatism, coma aberration, or field curvature, higher order aberrations, or wavefront aberrations Group 16, so that
Alternatively, the rotation angle of the rear group 17 may be adjusted. In addition, when assembling the projection optical system PL in advance, the direction in which the predetermined aberration is minimized is measured, and when the projection optical system PL is incorporated in the projection exposure apparatus of this example, the direction in which the aberration is minimized is determined. It may be aligned with the longitudinal direction of the region 15, that is, the non-scanning direction (Y direction). Further, the rotation angles of the front group 16 and the rear group 17 may be adjusted at the time of maintenance after the exposure is continuously performed. Further, the rotation angle may be adjusted for each unit finer than the front group 16 and the rear group 17, or only the rotation angle of the entire projection optical system PL may be adjusted.

Further, in practice, it may not always be necessary to adjust the predetermined aberration in the longitudinal direction of the exposure area 15 so as to minimize the predetermined aberration. That is, since the imaging characteristics of the projection optical system PL are determined by the balance of various aberrations, for example, a direction in which a plurality of aberrations decrease on average may be set as the longitudinal direction of the exposure region 15. Further, the projection optical system PL of this example is a refraction system. However, when the exposure light becomes shorter in wavelength such as recent ArF (wavelength 193 nm) excimer laser light, there is not much glass material having good transmittance. It is considered that the projection optical system PL is constituted by a catadioptric system (catadioptric system). In such a case, the exposure area on the wafer W may be an arc-shaped exposure area 15S that spreads in the non-scanning direction (Y direction), as indicated by a two-dot chain line in FIG. Also at this time, by adjusting the predetermined aberration of the projection optical system in the direction (spreading direction) of the exposure area 15S, for example, to minimize the aberration, the characteristics of the projected image after the scanning exposure can be improved.

Next, when overlay exposure is performed by the projection exposure apparatus shown in FIG. 1, it is necessary to align the reticle R and the wafer W before exposure. Therefore, a reticle alignment microscope (not shown) is disposed above the reticle R, and the reticle R is moved relative to the stage coordinate system (stationary coordinate system) (X, Y) based on the measurement result of the reticle alignment microscope. Aligned.

As shown in FIG. 4, an X-axis wafer mark WMX for alignment and a Y-axis wafer mark WMY are attached to each shot area SA on the wafer W, respectively. In order to detect the position, an alignment sensor 4 of an off-axis type image processing system is arranged on the side surface of the projection optical system PL of FIG. In FIG. 4, an X-axis wafer mark WMX
Is a mark in which, for example, a line and space pattern of irregularities is formed at a predetermined pitch in the X direction as a measurement direction, and the wafer mark WMY of the Y axis is a line of irregularities at a predetermined pitch in the Y direction as a measurement direction. ·and·
This is a mark that forms a space pattern.

The alignment sensor 4 shown in FIG. 1 includes an illumination system that illuminates a test mark with substantially white (broadband) illumination light, an enlarged image forming system that forms an enlarged image of the test mark,
And a CCD type two-dimensional image sensor for capturing the image. From the imaging signal from the alignment sensor 4,
The alignment signal processing system 14 determines the amount of positional deviation of the mark to be detected from a predetermined detection center and supplies it to the main control system 5. The main control system 5 adds the positional deviation amount to the X coordinate and Y coordinate of the Z tilt stage 3 (wafer W) detected via the laser interferometer 12 on the wafer side,
The array coordinates of the mark to be detected in the stage coordinate system (X, Y) can be obtained.

When aligning reticle R, Z
By detecting the position of a predetermined reference mark on the tilt stage 3 via the alignment sensor 4, a baseline amount BL, which is the distance between the center of the pattern image of the reticle R and the detection center of the alignment sensor 4, is obtained. ,
It is stored in the storage unit of the main control system 5. Thereafter, the array coordinates of each shot area on the wafer W obtained from the detection result of the alignment sensor 4 are shifted by the amount of the base line BL, so that the circuit pattern already formed in each shot area and the reticle Exposure can be performed by superposing the pattern image of R with high accuracy.

FIG. 3 shows the configuration of the alignment sensor 4 of this embodiment. In FIG. 3, the illumination light having a relatively low sensitivity to a resist emitted from a light source 21 such as a halogen lamp and having a relatively wide band is transmitted by a condenser lens 22. The light is collected and uniformly illuminates the field stop 23. For example, in FIG.
Assuming that the axis wafer mark WMY is a detection target, the wafer mark WMY moves into the field of view 18Y set by the field stop 23 based on a rough positional relationship obtained in advance by, for example, search alignment.
On the other hand, when the X-axis wafer mark WMX is a detection target, the wafer mark WMX moves into the field of view 18X set by the field stop 23.

In FIG. 3, the illumination light passing through the field stop 23 is collimated by an illumination relay lens 24 and branched downward by a half prism 25. The branched illumination light is condensed by the first objective lens 26 and illuminates a test mark on the wafer W (here, a Y-axis wafer mark WMY). Field stop 23 and wafer W
Has a conjugate positional relationship with the surface (wafer surface), and a field similar to the opening in the field stop 23 is illuminated with a uniform illuminance distribution. The first objective lens 26 has this optical axis A
A rotation drive unit 29 such as a motor for rotating around X1
The main control system 5 shown in FIG. 1 rotates the first objective lens 26 via the rotation driving unit 29 in accordance with the measurement direction of the wafer mark to be detected, so that the first The direction in which the wavefront aberration of the objective lens 26 is minimized is set parallel to the measurement direction (X direction or Y direction).

Further, assuming that the reflected light from the illuminated wafer mark WMY on the wafer W is a light beam L1, the light beam L1 is collimated by the first objective lens 26 and passes through the half prism 25. The light beam L1 transmitted through the half prism 25 is condensed by the second objective lens 27,
An enlarged image of the wafer mark WMY is formed on an imaging surface of a two-dimensional imaging device 28 such as a CCD type. The image pickup signal from the image pickup device 28 is supplied to the alignment signal processing system 14, and the alignment signal processing system 14 processes the image pickup signal, for example, the center (detection center) of a predetermined pixel in the image pickup device 28.
Is used as a reference to determine the amount of misalignment of the image of the alignment mark WMY in the measurement direction (here, the Y direction). Further, the alignment signal processing system 14 supplies the positional shift amount obtained by multiplying the positional shift amount by the projection magnification from the imaging surface of the image sensor 28 to the wafer surface to the main control system 5 in FIG.

Next, a description will be given of the first objective lens 26 which has the greatest effect on the imaging characteristics of the wafer mark in the alignment sensor 4 of FIG. First objective lens 26
The state of the aberration is measured in advance before mounting on the projection exposure apparatus of this example. In general optical lenses, various aberrations remain, albeit minute, due to variations in processing conditions during manufacturing. Further, when an optical lens is manufactured by the current production technology, a component of the remaining wavefront aberration that is asymmetric with respect to the optical axis usually has directionality about the optical axis. Therefore, the first objective lens 26 still has a small amount of wavefront aberration having directivity about the optical axis AX1 although it is small as a whole.

FIG. 6 shows an example of asymmetrical wavefront aberration remaining in the first objective lens 26. A plurality of curves in FIG. 6A show the pupil plane of the first objective lens 26 (optically with respect to the object plane). ., And the signs of 0, ± 1, ± 2,... Attached to those curves are 2π
(Rad) or the phase in wavelength units. The orthogonal coordinate system (η, ζ) in FIG. 6A is a coordinate system for measuring the wavefront aberration, and the curve in FIG.
6A shows an equiphase wavefront along the η axis, and the curve in FIG. 6C shows an equalphase wavefront along the ζ axis in FIG. 6A.

FIG. 6A shows that the magnitude of the wavefront aberration generated by the first objective lens 26 depends on the direction around the optical axis. In the characteristic of FIG.
The wavefront aberration is smallest in the direction along the axis. Therefore, for example, a mark or the like is provided on the side surface of the lens barrel of the first objective lens 26 in a direction in which the wavefront aberration is minimized, and
The first objective lens 26 is connected to the alignment sensor 4 shown in FIG.
, The direction in which the wavefront aberration is minimized is set parallel to the measurement direction of the test mark. As shown in FIG. 3, when measuring the position of the wafer mark WMY on the Y axis, as shown in FIG. 6C, the direction along the ζ axis at which the wavefront aberration is minimized in the first objective lens 26 is The rotation angle of the first objective lens 26 is controlled via the rotation drive unit 29 in FIG. 3 so as to be in the Y direction.

Next, when detecting the position of the wafer mark WMX on the X axis in FIG.
The direction along the ζ axis where the wavefront aberration is minimized in the objective lens 26 is set parallel to the X direction. by this,
Y-axis wafer mark WMY and X-axis wafer mark W
The position of MX can be detected with high accuracy with the smallest wavefront aberration. The mark to be measured may be not only a wafer mark but also, for example, a registration mark for measuring an overlay error between two adjacent layers on the wafer. Then, depending on the configuration of the stage, instead of rotating the first objective lens 26, the test mark side may be rotated via the stage.
The optical system that measures the wavefront aberration in advance measures the state of the wavefront aberration not only for the first objective lens 26 but also for the second objective lens 27, and measures the wavefront aberration in the measurement direction. The smallest direction may be parallel. In addition, the wavefront aberration as an integral part of the imaging system including the first objective lens 26 and the second objective lens 27 may be measured in advance.

Next, referring to FIG.
An example of a method for measuring the wavefront aberration will be described. First, in FIG. 5, the optical axis A is set on the object side of the first objective lens 26.
A spherical mirror 36 having a spherical reflecting surface centered on the object point 35 on X1 is arranged, and an interference system unit U _IF
And the spherical mirror 36 via the holding member 37, the optical axis AX
It is supported so that it can move two-dimensionally in a plane perpendicular to 1. Further, a coherent and parallel laser beam LB from the laser light source 30 is condensed by the condensing lens 31 to form an optical axis A.
Irradiate the half mirror 32 along an axis parallel to X1.
The laser beam LBD transmitted through the half mirror 32 is converged at one point 34 and then diverges toward the first objective lens 26. The point 34 is the object point 35 of the first objective lens 26.
Are located on the image plane conjugate with the object plane where
The laser beam LBD supplied to the objective lens 26 is condensed on the object plane including the object point 35, is reflected by the spherical mirror 36, passes through the first objective lens 26 again, and enters the half mirror 32.

On the other hand, the laser beam LBR reflected by the half mirror 32 is once condensed, then reflected by the reference mirror 33 having a reflection surface centered on the condensing point, and returned to the half mirror 32 again. The laser beams LBD and LBR returned to the half mirror 32 are
2 and is directed to the condenser lens 38, and the condenser lens 3
8, the laser beams LBD and L synthesized into a parallel beam
The interference light composed of BR enters the photoelectric detector 39, and a detection signal of the photoelectric detector 39 is supplied to a signal processing system (not shown).

The interference system unit U _IF comprises a laser light source 30, a condenser lens 31, a half mirror 32, a reference mirror 33, a condenser lens 38, and a photoelectric detector 39. In this case, since the detection signal of the photoelectric detector 39 changes in phase according to the phase change of the laser beam LBD due to the wavefront aberration of the first objective lens 26, the spherical surface and the interference unit U _IF are interposed via the holding member 37. The mirror 36 is integrally moved two-dimensionally to move the measurement point 34 to the first objective lens 26.
In the object plane (in the field of view). Then, the wavefront aberration of the first objective lens 26 can be measured by measuring the phase distribution of the detection signal at each object point in the field of view of the first objective lens 26, respectively.

However, the wavefront aberration of the first objective lens 26 is measured at a plurality of measurement points 34 at a plurality of positions in the field of view of the objective lens 26.
Is desirably obtained by positioning the measurement point 34 at the object point (center of the visual field) on the axis of the objective lens, and only the measured wavefront aberration may be used as the wavefront aberration of the first objective lens 26. . In the above embodiment, the wavefront aberration of the first objective lens 26 is measured in advance, but in addition to the above, Seidel's five aberrations including spherical aberration, coma, astigmatism, field curvature, and distortion Alternatively, higher-order aberrations or chromatic aberrations may be measured, and the direction in which any of these aberrations is minimized may be matched to the measurement direction of the test mark. Also, the direction in which a certain aberration is minimized may not necessarily be adjusted to the measurement direction, but, for example, the direction in which a predetermined plurality of aberrations are minimized as an average may be adjusted to the measurement direction.

In the above embodiment, the imaging system of the present invention is applied to the objective optical system of an image processing type alignment sensor. However, the present invention is applied to an alignment system such as an LIA system or an LSA system. It can also be applied to the objective optical system of the sensor. Also in this case, for example, the direction in which the aberration of at least a part of the objective optical system has the smallest aberration may be adjusted to the measurement direction.

Next, an example of a method for manufacturing a semiconductor device using the projection exposure apparatus of FIG. 1 will be described. FIG.
The main part of an example of a method for manufacturing the device is shown. First, in FIG. 1, each shot area on the wafer W to be exposed includes
A plurality of circuit patterns are formed by the processes up to that point, and alignment wafer marks WMX, WMY are formed.
Is also attached. Then, in step 101,
For example, a metal film is deposited on one lot of wafers including the wafer W, and a resist is applied thereon.

Thereafter, in step 102, wafers of one lot including the wafer W are sequentially loaded on the Z tilt stage 3 of the projection exposure apparatus of FIG. At this time, the reticle R on which the original pattern for a new layer is formed is mounted on the reticle stage 7, and it is assumed that the alignment of the reticle R with respect to the stage coordinate system (X, Y) has been completed. I do. When performing exposure on the wafer W, for example, the position of a search alignment mark (not shown) on the wafer W is detected through the alignment sensor of FIG. X coordinate, Y of wafer marks WMX, WMY of a predetermined number of shot areas selected from on wafer W
Detect coordinates. At this time, the X-axis wafer mark WM
Depending on which mark of the X or Y axis wafer mark WMY is to be detected,
The direction in which the spherical aberration of the objective lens 26 is the smallest is set parallel to the measurement direction. Then, array coordinates of all shot areas on the wafer W are obtained from the detection result by, for example, the enhanced global alignment method (EGA method).

Next, in step 103, the pattern image of the reticle R is scanned and exposed on each shot area on the wafer W while aligning the reticle R with each shot area on the wafer W based on the array coordinates. . Then, in step 104, the resist on the exposed lot of wafers including the wafer W is developed, and etching is performed using the remaining resist pattern as a mask to form a predetermined wiring pattern. In the next step 105, after stripping the resist for the wafer of the lot, a circuit pattern is formed on a further upper layer as necessary.

In the actual assembling process, the wafer of one lot after the completion of the wafer process is cut into chips by cutting the wafer for each printed circuit, and bonding is performed for wiring each chip. A semiconductor device such as an LSI is finally manufactured through a process and a packaging process of packaging each chip.

In the above, an example in which a semiconductor device is manufactured by a photolithography step in a wafer process using a projection exposure apparatus has been described.
Etc.), devices such as a liquid crystal display element or a thin film magnetic head can also be manufactured. It should be noted that the present invention is not limited to the above-described embodiment, and can take various configurations without departing from the spirit of the present invention.

[0048]

According to the first imaging system of the present invention, the direction in which the known aberration of the predetermined optical system is reduced only needs to be adjusted to the measurement direction, so that the aberration of the imaging system is adjusted. Can be performed in a short time and effectively (with high accuracy).
Further, the first imaging system is suitable as an objective optical system of an alignment sensor of a projection exposure apparatus.

Next, according to the second imaging system of the present invention, only the direction in which the aberration of the imaging system is small is adjusted in the non-scanning direction (longitudinal direction) of the exposure area. Can be adjusted in a short time and effectively. Further, the second imaging system is suitable as a projection optical system of a scanning exposure type projection exposure apparatus. Next, the first or second embodiment of the present invention
According to the exposure apparatus described above, the alignment of the substrates or the scanning exposure can be performed with high accuracy.

Further, according to the first or second device manufacturing method of the present invention, devices can be manufactured with a high yield, respectively. Further, according to the first method of using the image forming system of the present invention, the state of aberration of the image forming system can always be maintained in a substantially optimum state.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a projection exposure apparatus used in an example of an embodiment of the present invention.

FIG. 2 is a plan view showing a shape of an exposure area by a projection optical system PL of FIG.

FIG. 3 is a configuration diagram showing an alignment sensor 4 of FIG. 1;

FIG. 4 is a plan view showing a wafer mark attached to each shot area on the wafer W in FIG. 1;

FIG. 5 is a configuration diagram showing an example of a measurement optical system for measuring wavefront aberration.

6 is a diagram illustrating an example of a wavefront aberration of the first objective lens 26 in FIG.

FIG. 7 is a flowchart showing a main part of a process when manufacturing a predetermined device using the projection exposure apparatus according to the embodiment.

[Explanation of symbols]

 2 XY stage 3 Z tilt stage 4 Off-axis type alignment sensor 5 Main control system 7 Reticle stage 15, 15S Exposure area R Reticle PL Projection optical system W Wafer WMY, WMX Wafer mark 21 Light source 22 Condenser lens 24 Lighting relay lens 26 First objective lens 27 Second objective lens 28 Image sensor

Claims (8)

[Claims] 1. An image forming system for projecting an image of a test mark on a predetermined image forming plane, wherein at least a part of the image forming system is constituted by an optical system having a known aberration characteristic. An imaging system in which the direction in which the aberration of the above is substantially minimized is matched with the measurement direction of the test mark. 2. The imaging system according to claim 1, wherein the test mark is one mark having a plurality of measurement directions or a plurality of marks having different measurement directions from each other. An imaging system, comprising: a rotating member that rotates around the optical member; and rotating the optical system via the rotating member in accordance with a direction to be measured among the plurality of measurement directions. 3. An image forming system according to claim 1, wherein: a position detecting system for detecting an image of the test mark via the image forming system; and a position of a mask pattern as the test mark. An exposure main body portion that transfers onto the substrate on which the alignment mark is formed, and a stage system that moves the substrate, comprising: an imaging system and a position detection mark that is detected by a position detection system. An exposure apparatus, wherein the position of the substrate is adjusted via the stage system based on the position. 4. A pattern of a mask on a substantially rectangular exposure area having a longitudinal direction along a predetermined direction on a substrate or a substantially arc-shaped exposure area extending along a predetermined direction on the substrate. An imaging system for projecting an image, wherein a direction in which the aberration is substantially smallest in the imaging system is adjusted to the predetermined direction. 5. An imaging system according to claim 4, further comprising: a stage system for moving the mask and the substrate in synchronization with the imaging system, wherein the mask and the substrate are moved in the predetermined direction. An exposure apparatus that performs scanning exposure by moving in an orthogonal direction. 6. A method for manufacturing a device using the exposure apparatus according to claim 3, wherein a step of applying a photosensitive material on the substrate, and wherein the mask corresponds to a circuit pattern of a predetermined layer of the device. Using a mask on which a pattern to be formed is formed, the position of the alignment mark on the substrate is detected by the imaging system and the position detection system, and based on the detection result, the substrate and the substrate are connected via the stage system. A step of performing alignment with a mask; a step of transferring the pattern of the mask onto the substrate; and a step of forming the circuit pattern by developing the photosensitive material on the substrate. Manufacturing method of the device. 7. An image of a test mark having a predetermined measurement direction is formed on a predetermined image forming surface by the image forming system according to claim 1, and the image of the test mark formed on the image forming surface is formed. A method of using an imaging system for detecting an image, wherein a measurement step of measuring aberration remaining in the imaging system or at least one optical member constituting the imaging system; An adjustment step of adjusting the measurement direction to a direction indicating a value. 8. A method for manufacturing a device using the exposure apparatus according to claim 5, wherein a substantially rectangular exposure region having a longitudinal direction along the predetermined direction on the substrate, or a device in the predetermined direction. An image of the pattern of the mask is exposed to an arc-shaped exposure region extending along the mask, and the image of the pattern of the mask is formed on the substrate by moving the mask and the substrate in synchronization with the imaging system. An exposing step of exposing; prior to the exposing step, a measuring step of measuring an aberration remaining in the image forming system or at least one optical member constituting the image forming system; simultaneously with the exposing step, or An adjusting step of, prior to the exposing step, adjusting the predetermined direction to a direction in which the residual aberration measured in the measuring step shows a desired value.