JP2001358059A - Method for evaluating exposure apparatus and exposure apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the remaining aberration in a projection optical system and the best focusing position in an exposure apparatus in a short time. SOLUTION: An image of a wedge mark group for measuring the best focusing position and images of box and in-box marks for measuring a coma aberration of the projection optical system are exposed at a plurality of focusing positions Z1 to Z5 at positions near a wafer by a micro-step system, and a resist pattern is formed by the following development. Lengths of the images 72XP1 to 72XP5 of the formed mark group are measured by a laser step alignment sensor, and the best focusing position is obtained based on the measured values. A shifting amount of the mark of the inside and the mark of the outside of the image 73P3 of the box and in-box marks exposed at the nearest position to the best focusing position is measured by an image processing sensor, and the coma aberration in the optical system is obtained from the measured result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating an exposure apparatus used in a lithography process for manufacturing a device such as a semiconductor device, a liquid crystal display device, a plasma display device, or a thin film magnetic head. It is suitable for use when evaluating the imaging characteristics of an exposure apparatus.

[0002]

2. Description of the Related Art In order to cope with an improvement in the degree of integration and fineness of a semiconductor device, a lithography process (typically, a resist coating process, an exposure process, and a resist development process) for manufacturing a semiconductor device is performed. Exposure apparatuses used are required to improve imaging characteristics such as resolution and transfer fidelity. In order to improve such image forming characteristics, the exposure apparatus needs to measure the best focus position, the optimal exposure amount, the residual aberration (mainly coma) of the projection optical system, and the like in advance.

In a conventional exposure apparatus, for example, an image of a predetermined pattern is projected via a projection optical system onto a wafer coated with a photoresist, and the line width of a resist pattern obtained after developing the wafer is scanned. Scanning electron microscope (Scan
The best focus position and the optimal exposure amount have been obtained by measuring with a ning electron microscope (SEM). Then, the residual aberration of the projection optical system is measured by projecting and exposing the image of the pattern for aberration measurement on the wafer at the obtained best focus position and optimum exposure amount, and performing measurement again by the scanning electron microscope. Was.

[0004]

As described above, in the conventional exposure apparatus, an image of a predetermined pattern is projected and exposed on a wafer, and measurement is performed with a scanning electron microscope to obtain a best focus position. By projecting and exposing the image of the pattern for aberration measurement on the wafer at the obtained best focus position and performing measurement again with the scanning electron microscope,
The residual aberration of the projection optical system was measured.

However, in this method, a scanning electron microscope is required separately from the exposure apparatus, so that there is an inconvenience that equipment for performing the evaluation becomes expensive. Also,
Scanning electron microscopy requires a very long time to measure one point, and a few to several tens of hours to measure a number of points required to measure the optimal exposure and best focus position. There was a necessary inconvenience. Furthermore, since it is necessary to repeat the measurement with the scanning electron microscope when measuring the best focus position and when measuring the residual aberration of the projection optical system, the measurement work is complicated and the time required for the measurement is lengthened. was there.

In view of the above, it is a first object of the present invention to enable an exposure apparatus to measure a best focus position and an imaging characteristic in a short time. It is a second object of the present invention to be able to measure the residual aberration of the projection optical system as an imaging characteristic with high accuracy and in a short time.

[0007]

A first method for evaluating an exposure apparatus according to the present invention is a method for evaluating an exposure apparatus (50) for exposing a second object (W) through a first object (R). Then, the exposure apparatus uses a first mark (72X) for measuring the best focus position and a second mark (73) for evaluating a predetermined characteristic of the exposure apparatus to perform evaluation at a plurality of focus positions. W1) exposing a plurality of exposure positions different from each other on the first exposure position;
From the state of the mark image (72XP1 to 72XP5), the substantial best focus position of the exposure device is determined, and from the state of the second mark image (73P1 to 73P5), the exposure at the best focus position or a position in the vicinity thereof. Evaluating the predetermined characteristics of the device.

According to the present invention, for example, in an exposure apparatus having a projection system including a lens and a mirror for projecting an image of a pattern of a first object onto a second object, the projection The image formed by the system is deformed to some extent by residual aberration of the projection system caused by manufacturing errors such as curvature and refractive index of the lens. In addition, it is composed of an ideal lens,
Even in the case of a projection system in which image deformation due to aberration does not substantially occur, if the exposure surface (image surface) of the second object is deviated from the best focus position, the image by the projection system will not appear. When the contrast is lowered (blurred) and a certain degree of collapse remains in the telecentricity on the image plane side of the projection system, the image is displaced. That is, since the state of the image formed by the projection system changes depending on the focus position (the position of the object plane or the image plane in the optical axis direction of the projection system), the first mark for measuring the best focus position and the predetermined characteristic thereof The image of the second mark for evaluation is projected in parallel, the best focus position is obtained using the first mark, and then, at that position or a position in the vicinity thereof, the predetermined characteristic, for example, the connection of the projection system. The evaluation accuracy is improved by evaluating the image characteristics. Further, the best focus position and its predetermined characteristics can be measured (evaluated) in a short time by only one exposure step.

In this case, as an example, the first mark is a plurality of wedge-shaped marks (72X) arranged in the width direction.
The second mark is a box-in-box mark (7
3) In the case where the exposure apparatus has a projection system (PL), an example of the predetermined characteristic is coma as an imaging characteristic of the projection system. In this case, for example, a laser
Using a step alignment type alignment sensor, the length of a plurality of wedge-shaped marks is measured, and the focus position when the length is the longest is obtained, so that the effective best focus position of the exposure apparatus can be determined. It can be obtained easily and with high accuracy. Then, the second exposure performed at the best focus position or a position in the vicinity of the best focus position
The state of the mark image, for example, the amount of displacement between the image of the outer box mark and the image of the inner box mark is measured using, for example, an alignment sensor of an image processing method (FIA method), so that the projection system can be obtained. Can be obtained. As a result, the best focus position of the exposure apparatus and the coma as a predetermined characteristic can be evaluated in a shorter time and at a lower cost than the measurement by the conventional scanning electron microscope.

Next, a second method for evaluating an exposure apparatus according to the present invention is an evaluation method for an exposure apparatus (50) for exposing a second object (W) through a first object (R). A first mark group (82A, 8A) composed of line and space patterns (81A to 81C) respectively by the exposure apparatus.
2B), a first step of exposing a predetermined exposure position on the evaluation substrate through the evaluation apparatus, and the exposure apparatus includes a line-and-space pattern (83A to 83C) for each of the first mark groups. A second step of overlappingly exposing the exposure position on the evaluation substrate via the second mark group (84A, 84B) intersecting at an angle, and a predetermined step in an image of the exposure position on the substrate. A third step of performing exposure for erasing the mark image, and a mark group image (88LA to 88LA) left at the exposure position on the evaluation substrate.
LC, 88RA to 88RC) to evaluate predetermined characteristics of the exposure apparatus.

According to the present invention, by superposing and exposing the images of the first mark group and the second mark group, it is substantially equivalent to exposing a plurality of wedge-shaped images. . At this time, when exposing an image of two intersecting fine line-and-space patterns, a fine pattern with high resolution is compared with directly exposing an image of a fine wedge-shaped mark. Since exposure can be performed, both the best focus position and the imaging characteristics can be evaluated with high accuracy. In an exposure apparatus having a projection system, when images of a plurality of wedge-shaped marks arranged in the width direction are projected on a substrate for evaluation, if coma aberration remains in the projection system, the The lengths of the images of the wedge-shaped marks at both ends of the images of the plurality of wedge-shaped marks formed on the substrate are different from each other. Therefore, by determining the difference in the image lengths of the wedge-shaped marks at both ends, it is possible to measure the coma aberration of the projection system as a predetermined characteristic of the exposure apparatus.

Further, in the present invention, in order to accurately measure the difference between the lengths of the images of the wedge-shaped marks at both ends of the images of the plurality of wedge-shaped marks, a third step of the wedge-shaped mark on the substrate is performed. The images of the other wedge-shaped marks are left so that only the image of the wedge-shaped mark at one end of the one wedge-shaped mark group and the image of the wedge-shaped mark at the other end of the second wedge-shaped mark group remain. Erase by exposure. Thus, the length of the image of the wedge-shaped mark at one end of the first wedge-shaped mark group and the second
And the length of the image of the wedge-shaped mark at the other end of the wedge-shaped mark group can be measured. Therefore, coma aberration of the projection system can be obtained in a shorter time and at lower cost than in a measurement by a conventional scanning electron microscope.

Further, since these measurements can be automatically performed by computer control or the like, the measurement efficiency and the measurement accuracy can be improved. Further, since the pattern formed by two exposures of the first mark group exposure and the second mark group exposure is measured by one measurement,
The measurement results of coma are those obtained by averaging them. Further, since a decrease in measurement accuracy due to a variation in pattern accuracy when forming the first mark group and the second mark group on the evaluation mask is reduced, it is necessary to obtain the imaging characteristics of the projection system with high accuracy. Can be.

Next, a first exposure apparatus according to the present invention is an exposure apparatus (50) for exposing a second object (W) via a first object (R), and holds the first object. A first stage (31), a second stage (39) for holding and moving the second object and adjusting the position of the second object in the focus direction, and a first mark (best mark position measurement) 72X) and an evaluation mask (R1) as the first object on which a predetermined characteristic evaluation second mark (73) of the exposure apparatus is formed, and a plurality of focuses via the evaluation mask. The images (72XP1 to 72XP1) of the first and second marks exposed at a plurality of different exposure positions on the evaluation substrate (W1) as the second object at the positions.
72XP5, 73P1 to 73P5) and first and second mark detection systems (24, 23), respectively.
Based on the detection result by the mark detection system, a substantial best focus position of the exposure device is obtained, and based on the detection result by the second mark detection system, the exposure device at the best focus position or a position near the best focus position is determined. A determination system (27) for evaluating the predetermined characteristic. The first exposure apparatus evaluation method of the present invention can be performed by such an exposure apparatus.

A second exposure apparatus according to the present invention is an exposure apparatus for exposing a second object (W) via a first object (R), and a first stage (31) for holding the first object.
And a second stage (3
9) and a first mark group (82A, 82B) which is exposed at a predetermined exposure position on the evaluation substrate as a second object and is formed of a line and space pattern, respectively.
And a second mark group (84A, 84B) composed of a line-and-space pattern intersecting the first mark group at a predetermined angle, and being exposed at the exposure position on the evaluation substrate. And a pattern group (86A, 86B) for erasing an image of a predetermined mark from among the images at the exposure position on the evaluation substrate, the evaluation mask (R2) as the first object. ), A mark detection system (24) for detecting an image of a mark group left at the exposure position on the evaluation substrate, and a predetermined characteristic of the exposure apparatus based on a detection result by the mark detection system. (27) that evaluates According to such an exposure apparatus, it is possible to carry out the second exposure apparatus evaluation method of the present invention.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In this example, the present invention is applied to a case where the best focus position and the imaging characteristics of the projection optical system are measured by a step-and-repeat projection exposure apparatus. FIG. 1 shows a projection exposure apparatus 5 of the present embodiment.
FIG. 1 is a schematic configuration diagram showing an ArF excimer laser light source (wavelength 193 n) as an exposure light source 1.
m) are used. However, as the exposure light source 1, K
rF excimer laser (wavelength 248 nm), F ₂ laser (wavelength 157 nm), Kr ₂ laser (wavelength 146n
m), a harmonic generator of a YAG laser, a harmonic generator of a semiconductor laser, a mercury lamp, or the like can be used. Exposure light IL (exposure beam) composed of ultraviolet pulse light having a wavelength of 193 nm from the exposure light source 1 passes through a beam matching unit (BMU) 2 and enters a variable dimmer 3 as an optical attenuator. Exposure control unit 21 for controlling the amount of exposure to the photoresist on the wafer
Controls the start and stop of light emission of the exposure light source 1 and the output (oscillation frequency, pulse energy), and adjusts the dimming rate in the variable dimmer 3 stepwise or continuously.

The exposure light IL passing through the variable dimmer 3 passes through a beam shaping system 5 comprising lens systems 4A and 4B, and a first fly-eye lens as a first-stage optical integrator (uniformizer or homogenizer). 6 is incident. The exposure light IL emitted from the first fly-eye lens 6 passes through a first lens system 7A, a mirror 8 for bending the optical path, and a second lens system 7B as a second stage optical integrator. The light enters the eye lens 9.

An aperture stop plate 10 is provided on the exit surface of the second fly-eye lens 9, that is, an optical Fourier transform surface (pupil surface of the illumination system) with respect to the pattern surface (reticle surface) of the reticle R to be exposed. 10e rotatably arranged. The aperture stop plate 10 includes a circular aperture stop 10a for normal illumination, an aperture stop 10b for annular illumination, and an aperture stop (not shown) for deformed illumination comprising a plurality (for example, four) of eccentric small apertures. And a small circular aperture stop (not shown) for a small coherence factor (σ value) are arranged so as to be switchable. The main control system 22, which controls the overall operation of the projection exposure apparatus 50, rotates the aperture stop plate 10 via the drive motor 10e to set illumination conditions.

In FIG. 1, exposure light IL emitted from a second fly-eye lens 9 and having passed through an aperture stop 10a for normal illumination enters a beam splitter 11 having a high transmittance and a low reflectance. The exposure light reflected by the beam splitter 11 is incident on an integrator sensor 20 composed of a photoelectric detector via a condenser lens 19, and a detection signal of the integrator sensor 20 is supplied to an exposure control unit 21. The relationship between the detection signal of the integrator sensor 20 and the illuminance of the exposure light IL on the wafer W as a substrate to be exposed is measured in advance with high accuracy, and the exposure control unit 21
Is stored in the internal memory. Exposure control unit 21
Is configured so that the illuminance (average value) of the exposure light IL on the wafer W and the integrated value thereof can be monitored indirectly from the detection signal of the integrator sensor 20.

Exposure light I transmitted through beam splitter 11
L enters the field stop (reticle blind) 14 via the lens systems 12 and 13 along the optical axis IAX. The exposure light IL that has passed through the field stop 14 passes through a mirror 15 for bending the optical path, a lens system 16 for imaging, a sub-condenser lens system 17, and a main condenser lens system 18, and the pattern surface of a reticle R as a mask. The (lower) illumination area (illumination viewing area) 70 is illuminated. Under the exposure light IL, an image of the circuit pattern in the illumination area of the reticle R is projected through a double-sided telecentric projection optical system PL at a predetermined projection magnification β (β is, for example, ４ ，, ５, etc.). The image is transferred to an exposure area of a photoresist layer on a wafer W as a substrate (substrate to be exposed) arranged on the image plane of the projection optical system PL.
The reticle R and the wafer W can be regarded as a first object and a second object, respectively, and the wafer (wafer) W is a disk-shaped substrate such as a semiconductor (eg, silicon) or an SOI (silicon on insulator). Hereinafter, the optical axis A of the projection optical system PL
The description will be made by taking the Z axis parallel to X, the X axis in a direction perpendicular to the plane of FIG. 1 in a plane perpendicular to the Z axis, and the Y axis in a direction parallel to the plane of FIG.

First, reticle R is mounted on reticle stage 3
The reticle stage 31 is adsorbed and held on the reticle base 1 and is mounted on a reticle base 32 so as to be finely movable in the X direction, the Y direction, and the rotation direction. The two-dimensional position and rotation angle of the reticle stage 31 (reticle R) are measured in real time by a laser interferometer in the drive control unit 34. The drive motor (such as a linear motor or a voice coil motor) in the drive control unit 34 controls the position of the reticle stage 31 based on the measurement result and the control information from the main control system 22.

The wafer W is held by suction on a wafer stage 39 via a wafer holder 38. The wafer stage 39 is two-dimensionally arranged on a wafer base 40 along an XY plane parallel to the image plane of the projection optical system PL. Move. That is, the wafer stage 39 moves stepwise in the X direction and the Y direction. Further, the wafer W
Also, a Z leveling mechanism for controlling the position in the optical axis AX direction (the Z direction in this example), that is, the focus position, and the tilt angles around the X axis and the Y axis is incorporated. Further, a projection optical system 25A that projects a slit image obliquely onto a plurality of measurement points on the surface (test surface) of the wafer W on the side surface of the projection optical system PL.
And multi-point auto-focus sensors 25A and 25B which receive light reflected from the surface to be detected and generate a focus signal corresponding to the focus positions of the plurality of measurement points. The focus signals are supplied to a focus control unit in the main control system 22.

At the time of exposure, the focus control section in the main control system 22 continuously drives the Z leveling mechanism in the wafer stage 39 by an autofocus method based on the information of the focus signal (focus position). . Thereby, the surface of wafer W is focused on the image plane of projection optical system PL. Further, at the time of evaluating the characteristics, the focus position of the wafer W can be controlled by an arbitrary amount by driving the Z leveling mechanism.

The positions of the wafer stage 39 in the X and Y directions and the rotation angles around the X, Y and Z axes are measured in real time by a laser interferometer in the drive control unit 41. The drive motor (such as a linear motor) in the drive control unit 41 controls the moving speed and the position of the wafer stage 39 based on the measurement result and the control information from the main control system 22.

When performing exposure, it is necessary to previously align the reticle R with the wafer W. Therefore, the reticle R is placed on the reticle stage 31.
A reticle alignment microscope (not shown) for measuring the position of the alignment mark (reticle mark) is provided. Further, in order to measure the position of an alignment mark (wafer mark) on the wafer W, a first alignment sensor of an image processing method (FIA method: Field Image Alignment method) is provided on the side surface of the projection optical system PL by an off-axis method. 23 are installed. Alignment sensor 2
3 irradiates the test mark with illumination light of a relatively wide wavelength range from, for example, a halogen lamp, captures an image of the test mark together with the index mark, processes the obtained image signal, The amount of displacement of the test mark with respect to the index mark in the X and Y directions is obtained, the line width of each mark constituting the test mark is obtained, and the obtained measurement value is supplied to the main control system 22. .

Further, a second alignment sensor 24 of an off-axis system is provided on the side surface of the projection optical system PL so that the position of the wafer mark can be measured by another system. The alignment sensor 24 irradiates the diffraction grating-shaped test mark with two light beams (or in some cases, one light beam) having slightly different frequencies, and generates an interference composed of a plurality of diffracted lights generated from the test mark. LIA (Laser Interferometric Alignment) type sensor 24a that detects light (hereinafter, referred to as “LIA sensor 24a”)
And a laser step alignment type sensor 24b (hereinafter, referred to as "the laser beam") which relatively scans a dot-shaped test mark and a laser beam irradiated in a slit shape to detect diffracted light generated from the test mark. LSA sensor 24b "
Say ). LIA sensor 24a
A more detailed configuration is disclosed in, for example, JP-A-2-227602 (Japanese Patent No. 2814520), and the LSA sensor 24b is described in, for example, JP-A-6-227602.
A more detailed configuration is disclosed in Japanese Patent Publication No. 0-130742 (Japanese Patent Publication No. 6-16478).

The photoelectric conversion signal (detection signal) of the interference light of the LIA sensor 24a and the photoelectric conversion signal (detection signal) of the diffracted light of the LSA sensor 24b are supplied to the main control system 22 via the alignment signal processing unit 26, respectively. ing. At the time of alignment, the alignment signal processing unit 26
The coordinates of the test mark are detected using the detection signal of the IA sensor 24a or the LSA sensor 24b and the measured value of the coordinates of the wafer stage 39. Further, when evaluating the characteristics of the exposure apparatus, the alignment signal processing unit 26
The length of the test mark in the measurement direction is calculated using the detection signal of the sensor 24b and the coordinates of the wafer stage 39.

When the image of the pattern on the reticle R is actually transferred onto the wafer W, the reticle R is aligned using a reticle alignment microscope (not shown), and then, as an example, the wafer stage 39 is driven. In this way, the positions of the wafer marks in a plurality of predetermined shot areas of the wafer W are sequentially detected by the alignment sensor 23 (or the alignment sensor 24 can be used), thereby enhancing the enhanced global alignment (EG).
A) The wafer W is aligned by the method A). Thereafter, the reticle R is illuminated with the exposure light IL, and a reduced image of the pattern of the reticle R is exposed to one shot area on the wafer W via the projection optical system PL. The operation of moving to the exposure field of the projection optical system PL is repeated in a step-and-repeat manner, so that reduced images of the pattern of the reticle R are transferred to all the shot areas on the wafer W.

In order to transfer the image of the pattern of the reticle R to the photoresist layer in each shot area on the wafer W at a high resolution during the exposure, the best focus of the projection optical system PL must be set in advance. Find the position,
It is necessary to match the surface of the shot area of the wafer W during exposure to the best focus position within the width of the depth of focus (allowable range). Further, the projection magnification and various aberrations (distortion, spherical aberration, coma, astigmatism, etc.) as the imaging characteristics of the projection optical system PL need to be kept within an allowable range with respect to the target value. For this reason, in the projection optical system PL of the projection exposure apparatus of FIG. 1, the position in the optical axis direction of a predetermined lens (a concave mirror or the like) among a plurality of optical members constituting the projection optical system PL, and the optical axis An imaging characteristic control system (not shown) for controlling a predetermined imaging characteristic by controlling an inclination angle with respect to a plane perpendicular to the plane is provided. As the imaging characteristic control system, a mechanism for controlling the pressure of gas between predetermined lenses in the projection optical system PL, a mechanism for controlling the position of the reticle R in the optical axis direction, and a tilt angle, or the like is also used. be able to. First, the main focus system 22 drives the imaging characteristic control system such that the best focus position and the imaging characteristic thereof are measured, and the error of the measured value of the imaging characteristic from the target value is offset. , The imaging characteristics are corrected.

In order to measure the best focus position and the imaging characteristics, a test reticle having a predetermined focus position measurement mark and an evaluation mark formed as described below is used in this embodiment. Here, as an example,
Assume that coma aberration and astigmatism are measured as the imaging characteristics of the projection optical system PL. FIG. 2A shows the best focus position of the projection optical system PL of this example and the projection optical system P.
FIG. 2A shows a test reticle R1 used for measuring coma aberration and astigmatism of L. In FIG. 2A, a set of marks including a plurality of marks is provided at the center of a pattern region 71 of the test reticle R1. A group 74A is formed.
Also, at positions near the four vertices of the pattern area 71,
The same mark group 74B to 74B as the mark group 74A, respectively.
E is formed. In this case, the central mark group 74A
When the optical axis AX of FIG.
4A and its surrounding four mark groups 74B to 74E are arranged so as to fit within the object-side field of view (illumination area) of the projection optical system PL, whereby the central portion of the exposure area of the projection optical system PL is arranged. And at each of the five measurement points at the four corners, the best focus position, coma aberration and astigmatism can be measured.

FIG. 2B is an enlarged view of the center mark group 74A of FIG. 2A. In FIG. 2B, the mark group 74A has a diamond shape elongated in the X direction, that is, X. A plurality of wedge-shaped marks having wedge-shaped ends at Y direction
X-axis wedge-shaped marks 7 arranged at a predetermined pitch in the direction
2X, a Y-axis wedge-shaped mark group 72Y in which a plurality of wedge-shaped marks each having a wedge-shaped end at each end are arranged at a predetermined pitch in the X-direction, and a small square frame-shaped mark 7
This is a two-dimensional mark obtained by combining a box-in-box mark 73 composed of 3A and a large square frame-like mark 73B arranged so as to surround it. here,
The wedge-shaped mark groups 72X and 72Y are used for measuring the best focus position of the projection exposure apparatus 50 and the astigmatism of the projection optical system PL. The length of the group 72Y in the Y direction is designed to be equal. That is, the wedge-shaped mark group 72
X and 72Y also serve as the first mark for measuring the best focus position of the present invention and the second mark for evaluating a predetermined characteristic.

The field of view (illumination area) of the projection optical system PL
In each of the two sets of wedge-shaped marks 72X, 72
The arrangement direction (or width direction) of Y is not limited to the X direction and the Y direction, and the arrangement direction may be the sagittal direction (S direction) and the meridional direction (M direction). Alternatively, within the illumination area, the X direction, the Y direction and S
At positions where the directions do not coincide with the M direction, in addition to the two sets of wedge-shaped marks 72X and 72Y arranged in the X and Y directions, two sets of wedge-shaped marks arranged in the S and M directions May be added.

Also, box-in-box mark 7
Numeral 3 is used to measure the coma aberration of the projection optical system PL. The two marks 73A and 73B constituting the box-in-box mark 73 are designed so that the centers of the two marks 73A and 73B are at the same position. ing. That is, the box-in-box mark 73 corresponds to the second mark for the predetermined characteristic evaluation of the present invention. The wedge-shaped mark group 72
X and 72Y are light-shielding marks, and the box-in-box mark 73 is a transmission mark in the light-shielding film.

Here, a method of measuring the best focus position using the X-axis wedge-shaped mark group 72X will be described with reference to FIG. First, as shown in FIG. 3A, the image 72XP of the group of wedge-shaped marks 72X formed on the wafer W via the projection optical system PL of FIG. 1 has the best focus position when the exposure is performed. As it deviates from the position, it becomes shorter in the measurement direction (X direction) as indicated by an image A indicated by a dotted line. The symbol 72XP in FIG. 3A also indicates a convex or concave resist pattern obtained by developing the photoresist on the wafer after exposing the image of the wedge-shaped mark group 72X.

In this embodiment, the image of the wedge-shaped mark group 72X is exposed at different positions on the wafer at a plurality of focus positions, and the resist pattern 72XP formed by developing the photoresist on the wafer in the X direction. Length LS
Measure X. To perform this measurement, the LSA sensor 24b of FIG. 1 can be used. That is, as shown in FIG. 3A, a laser beam 90X extending in a slit shape in the Y direction is irradiated onto the wafer from the LSA sensor 24b, and the resist pattern 72XP and the laser beam 90X are relatively scanned in the X direction. The length LSX of the resist pattern 72XP can be obtained by obtaining the range of the X coordinate of the wafer stage 39 where the level of the detection signal of the diffracted light generated from the resist pattern 72XP is equal to or more than a predetermined value. Then, as shown in FIG. 3B, in a curve 75 obtained by interpolating each measurement data 75D of the length LSX of a plurality of resist patterns exposed at a plurality of different focus positions, the length of the resist pattern LSX
The best focus position BFX can be obtained by obtaining the focus position Z when the maximum is obtained.

The best focus position BFX is X
This is the X-axis best focus position determined by the wedge-shaped mark group 72X on the axis, and similarly, the wedge-shaped mark group 7 on the Y-axis.
By using 2Y, the best focus position on the Y axis can be obtained. Then, the difference between these two best focus positions becomes astigmatism. Note that the X-axis wedge-shaped mark group 72X actually generates diffracted light that spreads in the Y direction, and the Y-axis wedge-shaped mark group 72Y generates diffracted light that spreads in the X direction.
The best focus position by the wedge-shaped mark group 72Y is the best focus position by the diffracted light spreading in the X direction.

Further, when exposing the wedge-shaped mark groups 72X and 72Y on the wafer at a plurality of focus positions, the box-in-box mark 73 is exposed at the same time.
Coma at the best focus position or at a position near the best focus position can be evaluated. That is, the box-in-box mark 7 shown in FIG.
By exposing the image 3 and developing the photoresist, a resist pattern 73P having a concave mark portion is formed as shown in FIG. 3C. At this time, the projection optical system P
If coma remains in L, the resist pattern 73
The center of the pattern 73AP inside the P is ΔΔ in the X and Y directions with respect to the center of the outside pattern 73BP, respectively.
Shift by CX and ΔCY. Therefore, the shift amounts ΔCX and ΔCY at the position closest to the best focus position
Thus, the coma in the X direction and the Y direction can be obtained. The shift amounts ΔCX and ΔCY correspond to F
It can be measured using the IA type alignment sensor 23.

Next, the best focus position and the procedure for measuring the coma and astigmatism of the projection optical system PL in this embodiment will be described with reference to FIGS. First, a positive photoresist is applied to the unexposed wafer W1 in FIG. 4A using a resist coater (not shown) under the control of the host computer 27 in FIG.
Is loaded on the wafer stage 39 (wafer holder 38) of the projection exposure apparatus 50, and is placed on the reticle stage 31 as shown in FIG.
The test reticle R1 is loaded.

Then, the images of the five mark groups 74A to 74E in the pattern area 71 of the test reticle R1 are exposed on the first shot area 76A of the wafer W1 in FIG. 4A via the projection optical system PL. I do. As a result, FIG.
As shown in (1), the images of the mark groups 74A to 74E are exposed in the measurement area QA at the center of the shot area 76A and the measurement areas QB to QE at the four corners, respectively.

Next, the wafer W1 is step-moved in the Y direction by a very small distance substantially equal to the width of the image of the mark group 74A projected on the wafer W1 in the Y direction, and the projection optical system PL
Is moved to the shot area 76B slightly shifted in the Y direction from the first shot area 76A on the wafer W. That is, the two shot areas 76A and 76B largely overlap. In this case, in the present example, the Z-leveling mechanism of the wafer stage 39 in FIG. 1 is driven by using the auto focus sensors 25A and 25B to move the focus position of the wafer W1 by a predetermined amount, and then the five mark groups 74A The images of .about.74E are exposed on a shot area 76B on the wafer W1. After that, the mark group 74A again
In the state where the wafer W1 is step-moved in the Y direction by a minute distance substantially equal to the width of the image in the Y direction to move the exposure area over the shot area 76C, and the focus position of the wafer W1 is moved by a predetermined amount, The images of the mark groups 74A to 74E are exposed on the shot area 76C. Hereinafter, a mark for measuring the best focus position and a mark for evaluating the characteristic at a plurality of different focus positions on the plurality of exposure positions on the wafer W1 by the micro-step exposure method in which the fine movement and the exposure of the wafer W1 are repeated as described above. An image of the mark is projected.

After a predetermined number of times (in this example, five times) of micro-step exposure, the photoresist on the wafer W1 is developed, and the developed wafer W1 is again placed on the wafer stage 39 of the projection exposure apparatus 50. To load. At this time, in the measurement area QA at the center of the shot area 76A on the wafer W1 in FIG.
The image of A is formed as uneven resist patterns 74A1 to 74A5. The evaluation mark groups 7 are also provided in the measurement areas QB to QE at the four corners of the shot area 76A.
The resist patterns 74B1 to 4E have uneven images.
74B5, 74C1 to 74C5, 74D1 to 74D5
74E1 to 74E5. The five measurement areas QA to QE correspond to five measurement points in the exposure area of the projection optical system PL in FIG.

FIG. 5 shows the measurement area QA at the center of FIG.
FIG. 5 is an enlarged view of FIG.
Resist patterns 74A1-74 exposed at 1-Z5
A5 is a resist pattern 72XP1 to 72XP5 as an image of the wedge-shaped mark group 72X and a resist pattern 72Y as an image of the wedge-shaped mark group 72Y in FIG.
P1-72YP5 and resist patterns 73P1-73P as images of box-in-box mark 73
5. Since the projection optical system PL performs reverse projection, each mark in FIG. 2B and each resist pattern in FIG. 5 are inverted.

The main control system 22 shown in FIG. 1 uses the LSA sensor 24b in the alignment sensor 24 to transmit a detection signal corresponding to, for example, diffracted light from the resist pattern 72XP5 in the measurement area QA in FIG. 39
Is taken in in correspondence with the X coordinate of. The LSA sensor 24b emits a slit-like laser beam 90X extending in the Y direction as shown in FIG. 5, and the main control system 22 drives the wafer stage 39 in the X direction to
The relative scanning between 2XP5 and the laser beam 90X is performed. At this time, as described with reference to FIG. 3, by detecting the diffracted light from the resist pattern 72XP5,
The length LSX of the resist pattern 72XP5 in the X direction is measured. Similarly, the main control system 22 controls all other X
The length LSX in the X direction of the axial resist patterns 72XP1 to 72XP4 is obtained, and the measured value is used as the host computer 27.
To supply. As shown in FIG. 3B, the host computer 27 approximates the measurement data of the length LSX with, for example, a quadratic function of the focus position Z, and focus position Z when the value of the quadratic function becomes maximum. Is obtained as the best focus position BFX by the X-axis mark.

Next, as shown in FIG. 5, a slit-shaped laser beam 90Y extending in the X direction is irradiated near the Y-axis resist pattern 72YP5 from the LSA sensor 24b in FIG. In this state, the wafer stage 39 is driven in the Y direction, the resist pattern 72YP5 and the laser beam 90Y are relatively scanned to detect the diffracted light, and the length L of the resist pattern 722P5 in the Y direction is detected.
SY is measured. Similarly, the main control system 22 controls all other Y-axis resist patterns 72YP1 to 72YP4.
Is obtained, and the measured value is supplied to the host computer 27. The host computer 27 obtains the best focus position BFY based on the X-axis mark by approximating the length LSY by, for example, a quadratic function of the focus position Z. Further, the host computer 27
The average value (BFX + BFX) / 2 of the two best focus positions BFX and BFX is stored as the best focus position BFA at the measurement point QA, and the difference (BFX−BFX) between the two best focus positions remains in the measurement area QA. Stored as astigmatism. Here, it is assumed that the focus position Z3 is the best focus position BFA from FIG.

Subsequently, the main control system 22 sets the best focus position B in the resist patterns 72XP1 to 72XP5.
Resist pattern 72 exposed at the position closest to FA
The shift amounts of the two box marks of the resist pattern 73P3 as the image of the box-in-box mark 73 in XP3 in the X and Y directions are measured using the FIA type alignment sensor 23. In the example of FIG.
Only the shift amount ΔCX in the X direction is measured, and the shift amount in the Y direction is almost zero. The value obtained by multiplying the shift amount ΔCX by a predetermined coefficient is the coma aberration in the measurement area QA. When the best focus position BFA is, for example, an intermediate position between the focus positions Z2 and Z3 in FIG. 5, the weighted average value of the shift amount of the resist pattern 73P2 and the shift amount of the resist pattern 73P3 is used. The coma at the best focus position BFA may be calculated.

As a result, the best focus position at the center of the exposure area of the projection optical system PL, and the coma and astigmatism are obtained. Similarly, the resist pattern 7 formed in the measurement areas QB to QE at the four corners in FIG.
By measuring 4B1 to 74B5,..., 74E1 to 74E5, the best focus position, coma, and astigmatism at the four corners of the exposure area of the projection optical system PL are obtained.

Then, the host computer 27 supplies the best focus positions in the five measurement areas and the measured values of coma and astigmatism to the main control system 22 in FIG. In response, if the coma aberration and the astigmatism remain first, the main control system 22 transmits the coma aberration and the astigmatism of the projection optical system PL via the above-described imaging characteristic control system (not shown). At least one of the aberrations is corrected. Further, the main control system 22
Determines the image plane of the projection optical system PL approximately from the five best focus positions, and controls the surface of the wafer W so that the surface of the wafer W matches the image plane by the autofocus method and the autoleveling method during exposure. You. In this state, a normal device pattern exposure process is performed.

As described above, according to this embodiment, the best focus position (image plane) of the projection optical system PL, coma aberration and non- Astigmatism can be obtained in a short time. In the case of performing exposure by the micro-step method, in each of the measurement areas QA to QE in FIG. 4A, a plurality of positions where exposure is performed by changing the focus position are close to each other by, for example, about several tens μm. Can be set to position. Therefore, the thickness of the photoresist and the state of development in each of the measurement areas QA to QE can be considered to be substantially the same, so that the exposure of the projection optical system PL is performed in a state where there is almost no influence of the unevenness of the coating and development of the photoresist. There is an advantage that the best focus position and the aberration of the projection optical system PL can be measured with high accuracy at a plurality of measurement points in the area.

Further, a best focus position is detected at each measurement point in the exposure area, and a box-in-box formed at the best focus position or a position closest thereto is detected.
Since the coma aberration and the like are obtained by detecting the image of the box mark, for example, even if the telecentricity of the projection optical system PL is not good, it is possible to improve the measurement accuracy of the optical characteristics at each measurement point. It has become.

Further, the measurement can be performed using the LSA sensor 24b for wafer alignment and the FIA type alignment sensor 23 of the projection exposure apparatus 50 without providing a scanning electron microscope separately from the exposure apparatus. There is an advantage that the cost required for evaluating the device can be reduced. Furthermore, since these measurements can be automatically advanced by computer control or the like, there is an advantage that the evaluation accuracy is improved.

In this embodiment, a positive photoresist is used as the photoresist applied to the wafer W1, but a negative photoresist may be used. next,
A second embodiment of the present invention will be described with reference to FIGS. In this example, the present invention is applied to the case where the coma of the projection optical system PL of the projection exposure apparatus 50 of FIG. 1 is measured. In this example, for the sake of simplicity, the following description will be made assuming that the best focus position has been determined in advance.

FIG. 6A shows a test reticle R2 used for measuring the coma aberration of the projection optical system PL of this embodiment.
In FIG. 6A, a first mark area 80A is formed at the center of the pattern area 77 of the test reticle R2 with a light-shielding film as a background, and the four corners of the pattern area 71 are the same as the mark area 80A. Mark areas 80B to 80E having a size are formed.

FIG. 6B is an enlarged view of the central mark area 80A of FIG. 6A.
The mark area 80A is a first area for forming a wedge-shaped mark in the Y direction.
Mark group 78A, second mark group 78 for wedge-shaped mark formation
B and a third mark group 79 for erasing a predetermined mark. The first mark group 78A is composed of two left mark groups 82A and right mark groups 82B separated in the X direction. The mark groups 82A and 82B each have three openings inclined at a predetermined angle with respect to the Y axis. It is composed of three line-and-space patterns 81A to 81C in which patterns (line patterns) are arranged at a predetermined pitch in the X direction.

The second mark group 78B also includes two left mark groups 84A and right mark groups 84B separated in the X direction, and the mark groups 84A and 84B are respectively line-and-and-line of the first mark group 78A. Space pattern 81
It is composed of three line and space patterns 83A to 83C inclined at a predetermined angle to the opposite side to A to 81C. Further, the third mark group 79 includes a left mark group 86A including three rectangular opening patterns 85A to 85C, and three rectangular opening patterns 87A to 87, respectively.
A right mark group 86B made of C is arranged in the X direction. When the opening patterns 85A to 85C move in parallel in the Y direction and overlap the left and right mark groups 82A and 84A of the first and second mark groups 78A and 78B, the line and space patterns 81A to 81C and 83A to 83C. 83
C is designed to be able to cover line patterns other than the line pattern at the right end of C. On the other hand, when the opening patterns 87A to 87C move in parallel in the Y direction and overlap with the right mark groups 82B and 84B of the first and second mark groups 78A and 78B, the line and space patterns 81A to 81C, The size is designed to cover line patterns other than the line pattern at the left end of each of 83A to 83C.

When measuring the coma aberration of the projection optical system PL of FIG. 1, first, under the control of the host computer 27, a positive type positive resist is applied to an unexposed wafer using a resist coater (not shown). After applying the photoresist, the wafer is loaded on the wafer stage 39 (wafer holder 38) of the projection exposure apparatus 50, and the test reticle R2 of FIG.

Next, the images of the mark groups in the five mark areas 80A to 80E in the pattern area 77 of the test reticle R2 are exposed on the wafer via the projection optical system PL (inverted projection). Then, the wafer is step-moved in the Y direction by a minute distance substantially equal to the width in the Y direction of the image of the first mark group 78A in the mark area 80A projected on the wafer, and the image of the first mark group 78A is formed. Second mark group 78B
And superimpose the images.

As described above, the image of the first mark group 78A and the image of the second mark group 78B, that is, the images of the first set of line and space patterns 81A to 81C crossing each other,
And the second set of line and space patterns 83A
By superposing and exposing the images of ~ 83C, FIG.
As shown in (a), the measurement area QA on the wafer has 3
The images 88A to 88C of the three right wedge-shaped mark groups and the images 89A to 89C of the three left wedge-shaped mark groups are projected. The images 88A to 88C of the right wedge-shaped mark group are typically represented by an image 88 in FIG.
Assuming that 9A to 89C are representatively represented by an image 89, the image 89 is the same as the image 88 as shown in FIG.

In this case, if coma aberration remains in the projection optical system PL, a repetitive pattern such as a line-and-space pattern is deformed asymmetrically at both ends, so that it is shown in FIG. 6C. To form an image 88 (or 89) of a group of wedge-shaped marks projected on the wafer as described above.
The images 88L, 88C, 88R of the wedge-shaped marks are deformed like the images 88LA, 88RA indicated by the dotted lines, and the leftmost image 8
The length LSL of 8LA and the length LSR of the right end image 88RA are different from each other.

Such a difference between the lengths LSR and LSL is caused by an abnormal line width of the line and space pattern due to the coma aberration of the projection optical system PL. The coma aberration is 3 at the best focus position.
The value of the ratio of the difference between the line widths of the images at both ends of the line and space pattern and the sum of the line widths of the images at both ends, that is, in this example, the images of the three wedge-shaped marks And the sum of the lengths of the images at both ends (LSR-LSL) and the length of the images at both ends (L
SR + LSL).

Coma = (LSR-LSL) / (LSR
+ LSL) Therefore, if the focus position at the time of performing exposure is shifted from the best focus position, the amount of deformation of the wedge-shaped mark changes, so that when measuring the coma aberration of the projection optical system PL, It is necessary to find the focus position. For this purpose, the focus position when the sum of the image lengths at both ends of the image of the wedge-shaped mark (LSR + LSL) in FIG. Also, by using the wedge-shaped mark, the change in the width of the image of the line and space pattern is changed by the length L
Since it is expanded by the change of SR and LSL, the detection sensitivity of coma aberration is improved, and the measurement accuracy is also improved.

Next, in this example, the wafer is step-moved in the Y direction by a minute distance substantially equal to the width in the Y direction of the images of the first and second mark groups 78A and 78B, and is shown in FIG. Images 88A to 88 of wedge-shaped marks in measurement area QA on wafer
C, 89A to 89C, the images of the opening patterns 85A to 87C of the third mark group 79 in FIG.

At this time, as shown in FIG. 7B, in the measurement area QA on the wafer, the image 88 of the right wedge-shaped mark group
Opening pattern images 85AP-85CP are exposed so as to erase the wedge-shaped mark images other than the left-end images 88LA-88LC of each of A-88C, and the right end of each of left-hand wedge-shaped mark group images 89A-89C. Images 88RA-88
The images 87AP to 87CP of the opening pattern are exposed so as to erase the images of the wedge-shaped marks other than RC. This allows
A measurement area QA on the wafer has an image 88A of a wedge-shaped mark group.
88LA of the wedge-shaped mark at the left end of each of 88C
88LC and wedge-shaped mark images 88RA to 88RC at the right end of the wedge-shaped mark group images 89A to 89C remain.

After the exposure, the photoresist on the wafer is developed, and the developed wafer is again
Is loaded on the wafer stage 39. As a result, FIG.
As shown in (c), the measurement area QA on the wafer has 3
The three wedge-shaped mark images 88LA to 88LC and the three wedge-shaped mark images 88RA to 88RC are formed by a concavo-convex resist pattern (also 88LA to 88LC, 88RA to 88RC).
).

The main control system 22 shown in FIG. 1 uses the LSA sensor 24b to move the resist patterns 88RA to 88RC on the left side of the measurement area QA and the slit-shaped laser beam 90Y extending in the X direction in the Y direction. Scan,
The length LSR of the resist patterns 88RA to 88RC is measured and supplied to the host computer 27. The main control system 22 moves the laser beam 90Y to the position B in the same manner, and moves the resist patterns 88LA to 8LA in the right region.
8LC and the laser beam 90Y are relatively scanned in the Y direction, and the length LSL of the resist patterns 88LA to 88LC is determined.
Is measured and supplied to the host computer 27. These lengths LSR and LSL are respectively equal to the length of the right end image 88RA and the left end image 88LA of the three wedge-shaped mark images 88 (89) in FIG. 6C. Then, the host computer 27 calculates the coma aberration of the projection optical system PL using the lengths LSR and LSL as described above.

Thus, the coma aberration at the center of the exposure area of the projection optical system PL can be obtained. Similarly, the mark areas 80 at the four corners of the pattern area 77 in FIG.
The line and space pattern group and the opening pattern group formed on B to 80E are superposed and exposed, and the length of the resist pattern obtained after development is measured to measure the four corners of the exposed area. Coma aberration in each of the regions can be determined.

As described above, according to the present embodiment, images 88A to 88C and 89A to 89C of a wedge-shaped mark group formed by exposing two sets of line and space pattern images.
The length LSL of the image 88LA-88LC of the left wedge-shaped mark and the length LSR of the image 88RA-88RC of the right wedge-shaped mark can be measured with high accuracy using the LSA sensor 24b. In addition, the coma aberration of the projection optical system PL can be measured in a short time and at low cost.

The measurement result of the coma aberration of the projection optical system PL is obtained by comparing the portion formed by the first mark group 78A with the second mark group.
The portion formed by the mark group 78B is averaged. Therefore, the first test reticle R2
In addition, since a decrease in the measurement accuracy of coma due to a variation in pattern accuracy when forming the second mark groups 78A and 78B is suppressed, the coma of the projection optical system PL can be obtained with high accuracy.

In the above embodiment, the imaging characteristics (coma aberration and astigmatism) of the projection optical system PL are evaluated as the characteristics of the projection exposure apparatus. The present invention is also applicable when evaluating magnification error, distortion, spherical aberration, wavefront aberration, and the like. FIG. 8 shows a main part of a measurement system disclosed in, for example, US Pat. No. 5,978,085 for measuring the wavefront aberration of the projection optical system PL. In FIG. A test reticle R3 is arranged on the object plane side so as to sandwich the projection optical system PL, and an unexposed wafer W2 coated with a photoresist is arranged on the image plane side.
The other device configuration is the same as that of FIG.

The pattern surface (lower surface) of the test reticle R3 of this embodiment is perpendicular to two directions (X and Y directions).
A plurality of first patterns 93 are formed at a predetermined pitch. In FIG. 8, three first patterns 93 are arranged in one row for easy understanding.
More numbers are arranged as shown in FIG.
Further, an aperture plate 92 is arranged at a predetermined interval from the pattern surface so as to cover the plurality of first patterns 93 of the test reticle R3, and the aperture plate 92 has a plurality of positions at positions directly below each of the first patterns 93. An opening 92a having a predetermined diameter is formed. Further, test reticle R
A plurality of condenser lenses 91 are provided on the upper surface of 3 corresponding to each of the first patterns 93. In addition, a pair of second patterns 94A and 94B (reference marks) are formed on the pattern surface of the test reticle R3 so as to face outside the area covered by the aperture plate 92. In this case, the second patterns 94A and 94B are large frame-shaped patterns, and the first pattern 93 is a small frame-shaped pattern that fits within the second patterns 94A and 94B.

FIG. 9A shows the test reticle R3 shown in FIG.
In FIG. 9A, the positional relationship between the second patterns 94A and 94B and the first pattern 93 (see FIG. 8) on the bottom surface of each condenser lens 91 is determined with high precision in advance. It is measured and stored in a storage device of a main control system (not shown). When the wavefront aberration is evaluated by the measurement system in FIG. 8, first, the plurality of first patterns 93 are simultaneously illuminated with the exposure light IL via the condenser lens 91, and the openings 92 a of the plurality of first patterns 93 and the projection optical system are projected. The image via the system PL is projected onto the wafer W2. At this time, if the projection optical system PL has a wavefront aberration, the position of the projected image of the first pattern 93 is shifted as shown by the dotted optical paths ILC and ILD. In order to detect this shift amount, after exposing the image of the first pattern 93, the second pattern 94A of the test reticle R3 is moved on the optical axis AX, and an illumination area is set in an area surrounding the second pattern 94A. I do. Then, the wafer stage (not shown) is step-moved in the X direction and the Y direction, and the second pattern 94A is irradiated with the exposure light IL so that each first pattern 94A is exposed.
The image of the second pattern 94A is superposed and exposed so as to surround the designed position of the image of the pattern 93.

FIG. 9B shows the state of the wafer W2
FIG. 9 is an enlarged view showing a part of the image exposed above, and FIG.
In (b), a plurality of first patterns 93 are interposed between images 94P of the second patterns 94A continuously exposed in a grid pattern.
Image 93P is exposed. Then, using the resist pattern obtained by developing the wafer W2, the amount of displacement of the image 93P of each first pattern in the X direction and the Y direction with respect to the image 94P of the second pattern is measured. The wavefront aberration of the system PL can be measured (evaluated).

In the above embodiment, a laser step alignment (LSA) type alignment sensor is used to measure the length of a wedge-shaped mark group. For example, an image processing type alignment sensor is used. In the case where the measurement accuracy is improved, the length may be measured using an image processing type alignment sensor. In the above embodiment, the projection optical system PL
Although the wedge-shaped mark group is used to detect the best focus position at each measurement point within the visual field (illumination area), the best focus position may be detected using other marks.

Since the length of the wedge-shaped mark varies depending on the focus position, as in the first embodiment, the coma aberration measurement of this example is placed at a plurality of different positions on the wafer at a plurality of focus positions. By forming the wedge-shaped mark, the best focus position and the coma of the projection optical system can be measured simultaneously. Note that the number of times of performing the micro-step exposure and the number of wedge-shaped marks constituting the wedge-shaped mark group are not limited to the above-described embodiments, and the type of photoresist to be used and the required measurement accuracy are not limited. It is desirable to determine the value appropriately according to the conditions.

In the above embodiment, the exposure apparatus is a step-and-repeat system (batch exposure system).
However, the present invention can also be used to evaluate the best focus position and the imaging characteristics of a projection exposure apparatus of a scanning exposure method such as a step-and-scan method. Further, the exposure light (exposure beam) is not limited to the above-mentioned ultraviolet light, and may be, for example, EU in a soft X-ray region (wavelength 5 to 50 nm) generated from a laser plasma light source or a SOR (Synchrotron Orbital Radiation) ring.
V light may be used. In the EUV exposure apparatus, the illumination optical system and the projection optical system each include only a plurality of reflection optical elements.

Then, semiconductor devices can be manufactured from the wafer W shown in FIG. The semiconductor device has a step of designing the function and performance of the device, a step of manufacturing a reticle based on this step, a step of manufacturing a wafer from a silicon material, and a step of forming a reticle pattern on the wafer by the projection exposure apparatus of the above-described embodiment. , A device assembling step (including a dicing step, a bonding step, and a package step), an inspection step, and the like.

The application of the exposure apparatus is not limited to the production of semiconductor elements. For example, a liquid crystal display element formed on a square glass plate, a lithography system for a display apparatus such as a plasma display, or the like. The present invention can be widely applied to a lithography system for manufacturing various devices such as an imaging device (such as a CCD), a micromachine, and a thin-film magnetic head. Further, the present invention can be applied to a case where a mask (a photomask, a reticle, or the like) on which a mask pattern of various devices is formed by using a photolithography process.

The present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted without departing from the gist of the present invention.

[0078]

According to the first method of evaluating an exposure apparatus according to the present invention, the best focus position and the imaging characteristics (such as coma) of the projection system as predetermined characteristics of the exposure apparatus are measured in a short time. can do. Next, according to the second method for evaluating an exposure apparatus according to the present invention, for example, an alignment sensor of a laser step alignment method can be used for mark measurement, which is shorter than measurement by a conventional scanning electron microscope. Coma aberration of the projection system can be obtained in a short time and at low cost. Further, since these measurements can be automatically advanced by computer control or the like, measurement efficiency and measurement accuracy can be improved.

The measurement result of the coma aberration is obtained by averaging the measurement of the first mark group and the measurement of the second mark group, and furthermore, the first mark group and the second mark group are added to the evaluation mask. Since the decrease in the measurement accuracy of the coma aberration due to the variation in the pattern accuracy at the time of formation is reduced, the coma aberration of the projection system can be obtained with high accuracy. Further, according to the first or second exposure apparatus of the present invention, the evaluation method of the first or second exposure apparatus of the present invention can be implemented, respectively.

[Brief description of the drawings]

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

2A is a plan view showing a test reticle R1 for evaluation, and FIG. 2B is a mark group 74 for evaluation in FIG. 2A.
It is an enlarged plan view which shows A.

3A is a diagram illustrating a state of deformation of an image of a wedge-shaped mark group due to a shift of a focus position, FIG. 3B is a diagram illustrating an example of a relationship between the length of a wedge-shaped mark and a focus position,
(C) is a box-in-beam due to the coma of the projection optical system.
It is a figure which shows the mode of deformation | transformation of the image of a box mark.

FIG. 4A is a plan view showing a wafer W1 for evaluation of a projection optical system according to the first embodiment, and FIG. 4B is an enlarged plan view showing a resist pattern group formed on the wafer; .

FIG. 5 is an enlarged plan view showing a resist pattern group formed in a measurement area QA of FIG. 4B.

FIG. 6A shows a test reticle R2 for evaluating a projection exposure apparatus used in a second embodiment of the present invention.
6B is an enlarged plan view showing the mark groups 78A, 78B, 79 in the center mark area 80A in FIG. 6A, and FIG. 6C is a plan view showing a wedge-shaped mark group due to coma aberration of the projection optical system. FIG. 9 is a diagram illustrating a state of image deformation.

FIG. 7 is a diagram showing a process of forming an image of a group of wedge-shaped marks for measuring coma aberration of a projection optical system on a wafer using the test reticle of FIG. 6;

FIG. 8 is a diagram illustrating a main part of a measurement system when measuring a wavefront aberration of a projection optical system in an example of an embodiment of the present invention.

9A is a plan view showing the test reticle of FIG. 8, and FIG. 9B is an enlarged view showing a part of a pattern formed on a wafer by the measurement system of FIG.

[Explanation of symbols]

PL: projection optical system, R: reticle, R1, R2: test reticle, W, W1: wafer, 1: exposure light source, 22: main control system, 27: host computer, 31: reticle stage, 38: wafer holder, 39 ... Wafer stage,
50: Projection exposure apparatus, 71, 77: Pattern area, 72
X, 72Y: wedge-shaped mark group, 73: box-in-box mark, 74A to 74E: mark group, 78A: first mark group, 78B: second mark group, 79: third mark group, 80A to 80E: Mark area, 81A to 81C, 8
3A to 83C: Line and space pattern, 8
5A to 85C, 87A to 87C ... opening pattern

Claims (8)

[Claims] 1. An evaluation method for an exposure apparatus for exposing a second object through a first object, comprising: a first mark for measuring a best focus position by the exposure apparatus; and a predetermined characteristic for evaluating a predetermined characteristic of the exposure apparatus. Second
Exposing a plurality of exposure positions different from each other on the evaluation substrate at a plurality of focus positions via the mark, and substantially exposing the exposure apparatus from the state of the image of the first mark at the plurality of exposure positions. A method of evaluating an exposure apparatus, comprising: obtaining a focus position; and evaluating the predetermined characteristic of the exposure apparatus at or near the best focus position based on an image state of the second mark. 2. The method according to claim 1, wherein the first mark is a plurality of wedge-shaped marks arranged in a width direction, and the second mark is a box-in-mark.
2. The method according to claim 1, wherein the exposure apparatus includes a projection system, and the predetermined characteristic is coma aberration of the projection system. 3. The evaluation apparatus according to claim 1, wherein the first mark is a plurality of wedge-shaped marks arranged in a width direction, and the first mark also serves as the second mark. Method. 4. The apparatus according to claim 1, wherein the exposure apparatus includes a projection system.
And the second mark is arranged at a plurality of positions within the field of view of the projection system, and when exposing the evaluation substrate at a plurality of focus positions via the first and second marks and the projection system, 4. The method according to claim 1, wherein the evaluation substrate is gradually moved at intervals smaller than the width of the field of view of the projection system. 5. An evaluation method for an exposure apparatus for exposing a second object through a first object, the evaluation apparatus comprising: a substrate for evaluation through a first mark group including a line and space pattern by the exposure apparatus; A first step of exposing an upper predetermined exposure position, and the evaluation apparatus through a second mark group formed of a line-and-space pattern by the exposure apparatus and intersecting the first mark group at a predetermined angle. A second step of overlapping and exposing the exposure positions on the substrate, and a third step of performing exposure for erasing an image of a predetermined mark from among the images of the exposure positions on the evaluation substrate, Evaluating a predetermined characteristic of the exposure apparatus from a state of an image of the mark group left at the exposure position on the evaluation substrate. 6. An exposure for leaving a mark group at one end of an image in which the first mark group and the second mark group are superimposed, and an exposure for leaving a mark group at the other end in the third step. 6. The method according to claim 5, wherein in the fourth step, the length of the mark group at the one end and the length of the other mark group are measured. 7. An exposure apparatus for exposing a second object through a first object, comprising: a first stage for holding the first object; a first stage for holding and moving the second object;
A second stage for adjusting the position of the object in the focus direction; and a first stage for best focus position measurement and a second mark for evaluating a predetermined characteristic of the exposure apparatus, for evaluation as the first object. A mask and an image of the first and second marks respectively exposed at a plurality of different exposure positions on the evaluation substrate as the second object at a plurality of focus positions via the evaluation mask. A first and second mark detection system to be detected, and a substantial best focus position of the exposure apparatus are obtained based on a detection result by the first mark detection system, and based on a detection result by the second mark detection system. A determination system for evaluating the predetermined characteristic of the exposure apparatus at or near the best focus position. 8. An exposure apparatus for exposing a second object through a first object, comprising: a first stage for holding the first object; a second stage for holding and moving the second object; A first mark group consisting of a line and space pattern, which is exposed at a predetermined exposure position on the evaluation substrate as the second object, and a line intersecting the first mark group at a predetermined angle. A second mark group, which is composed of an AND space pattern and is exposed in an overlapping manner on the exposure position on the evaluation substrate, and an image of a predetermined mark in the image of the exposure position on the evaluation substrate. A mask for evaluation as the first object on which a pattern group for erasing is formed, a mark detection system for detecting an image of a mark group left at the exposure position on the evaluation substrate, Detection by mark detection system Based on the result, the exposure apparatus characterized by having a determining system for evaluating a predetermined characteristic of the exposure apparatus.