JP2001272310A - Aberration measuring device and method in projection optical system, and mask and exposure device used for them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aberration measuring device and method, capable of measuring accurately in a simple composition an aberration which occurs on the lens axis of a projection optical system, and to provide an exposing device with finer exposing accuracy. SOLUTION: An internal mark Mip and an external mark Mop, which a translucent part Pt and phase shift parts Ppi and Ppo are arranged via a shading part Ps with the same pitch on a phase shift reticle Rps, are formed so that the external mark Mop interposes the internal mark Mip at certain space. The phase difference at the internal mark Mip is set to π-ϕ (rad) and the phase difference at the external mark Mop is set to π+ϕ (rad). The displacement of the focal point, which remains in the aberration optical system and caused by spherical surface aberrations, is measured by illuminating marks Mip and Mop vertically with normal illumination and by converting the displacement into the displacement of the relative positions of the images of the marks Mip and Mop on the plane, which is perpendicular to the lens axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used in a photolithography process in a process of manufacturing a micro device such as a semiconductor device, a liquid crystal display device, an image pickup device, a thin film magnetic head, and an aberration of a projection optical system thereof. The present invention relates to a measuring device, a mask used for the same, and a method for measuring aberrations of a projection optical system.

[0002]

2. Description of the Related Art As an exposure apparatus of this type, for example, the following configuration is known. That is, a pattern formed on a photomask, a reticle, or the like is illuminated with exposure light having a predetermined wavelength emitted from the illumination optical system. An image of a pattern formed by the illumination is projected and transferred onto a substrate such as a wafer or a glass plate coated with a photoresist having sensitivity to the exposure light via a projection optical system. I have. Such an exposure apparatus is provided with an aberration measuring device for measuring various aberrations remaining in the projection optical system in order to form a pattern image on the mask on the substrate with high accuracy.

Here, among the above-mentioned various aberrations, there are longitudinal aberrations in which the focal position changes in the optical axis direction of the projection optical system.
A spherical aberration having a different focal position depending on a distance between an optical axis and a position where light emitted from the pattern passes through a pupil plane in the projection optical system is included. In the aberration measuring device, the spherical aberration is measured by, for example, the following method. That is, using a mask in which a plurality of patterns having different pitches P are formed, while illuminating each pattern vertically, changing the position in the optical axis direction of the substrate, transferring an image of each pattern onto the substrate, It is measured by a method of finding the focal position for each.
According to this method, the diffraction angle θ of the n-th order diffracted light generated from the diffraction grating pattern is defined by the pattern pitch P and the wavelength λ of the illumination light.

[0004]

(Equation 1) By using the above relationship, the focal position corresponding to the diffraction angle is obtained. Then, the spherical aberration is obtained from the measurement result of the focal position corresponding to the diffraction angle.

[0005]

By the way, in the above-mentioned conventional structure, at least two methods of measuring the focal position are used.
There are two. In the first method, the image of each pattern transferred onto the substrate is developed, and the line width of the image of each pattern after development is measured using a scanning electron microscope. Here, in the image of the exposed pattern, the center of the range between the maximum and minimum allowable line widths is obtained. Then, the position in the optical axis direction of the substrate corresponding to the center of the range is set as the focal position. On the other hand, in the second method, the cross-sectional shape of the image of each pattern similarly developed is observed using a scanning electron microscope, and the direction of the optical axis of the substrate at the time of transfer of the image showing the sharpest rise is obtained. The position is a focal position.

However, a slight shift may occur between the focal positions detected by the above two methods, and the spherical aberration of the projection optical system to be measured depends on which method uses the result of detecting the focal position. The amount may be different. For this reason, the accuracy of correction of the spherical aberration remaining in the projection optical system may be reduced, and the accuracy at the time of transferring a pattern image may be reduced.

In particular, semiconductor elements which project and transfer an image of a pattern on a reticle onto a wafer have become more and more highly integrated in recent years, and their circuit patterns have become very fine. In order to manufacture such a semiconductor device, it is necessary to more accurately form an image of a pattern on a reticle on a substrate, and high-precision measurement of spherical aberration is required. For this reason, there has been a problem that the measurement of the spherical aberration by the conventional configuration may be insufficient.

The present invention has been made by paying attention to such problems existing in the prior art. An object of the present invention is to provide an aberration measurement device and a measurement method capable of accurately measuring an aberration generated in a direction of an optical axis of a projection optical system with a simple configuration. Another object of the present invention is to provide an exposure apparatus in which the aberration generated in the optical axis direction of the projection optical system is accurately corrected, and the exposure accuracy is improved.

[0009]

In order to achieve the above object, the present invention according to the first aspect of the present invention, which relates to an aberration measuring apparatus for a projection optical system, comprises a pattern (Mip) formed on a mask (R, Rps, Rc). , Mop, Mic, Moc) on the image plane, for measuring the aberration of the projection optical system (PL) in the direction of the optical axis (AX) of the projection optical system (PL). The generated aberration is corrected by the pattern (Mip, Mop, Mp) in a direction crossing the optical axis (AX).
A conversion unit (Rps, 61, 62, Rc) for converting the displacement (ΔFh) of the image of Mic, Moc) and the displacement (ΔFh) of the image of the pattern (Mip, Mop, Mic, Moc) are measured. The gist is that measurement means (42, 44, 45) are provided.

For this reason, according to the first aspect of the present invention, the image formation state of an image of a pattern including aberration generated in the optical axis direction of the projection optical system is detected as position information in a direction intersecting the optical axis. Becomes possible. Here, measurement of the position of the image in the direction intersecting with the optical axis can be performed much easier and more accurately than measurement of the position of the image in the direction of the optical axis. Then, as in the above-described conventional configuration, the aberration can be accurately and directly measured without through the detection of the focal position where the detection result may cause a slight shift by the detection method.

Further, according to a second aspect of the present invention, in the first aspect of the present invention, the converting means (Rps) comprises:
A plurality of predetermined patterns (Mi) provided with a phase shift unit (Pp) for changing the phase of the transmitted illumination light (EL)
p, Mop) and a phase shift mask (Rps) of a spatial frequency modulation type, and the phase shift unit (Pp) includes a plurality of phase shift units (Ppi, Ppo) for generating a plurality of phase differences different from each other, The measuring means (42,
44, 45) are the positions (Fhi, Fh) of the images of the predetermined patterns (Mip, Mop) formed on the image plane.
The gist of the invention is to have a position detecting means (42, 44, 45) for detecting o).

Therefore, according to the second aspect of the present invention, in addition to the effect of the first aspect, the use of a phase shift mask causes the image of the pattern to be formed by two-beam interference. . Then, since the phase shift portion of the phase shift mask causes a plurality of different phase differences, the diffraction angles of the two diffracted lights contributing to the image formation are different. Accordingly, the point at which the two diffracted lights intersect again, that is, the focal position, is shifted from the optical axis of the projection optical system. By utilizing the deviation of the focal position from the projection optical system, the deviation of the focal position that changes in the optical axis direction according to the diffraction angle can be easily converted to the positional deviation in the direction intersecting the optical axis. it can.

According to a third aspect of the present invention, in the first aspect of the present invention, the conversion means (61, 62,
Rc) includes a plurality of patterns (Mic, Moc) and an inclined illumination unit (6) that illuminates the mask (Rc) from a direction inclined with respect to the optical axis (AX) of the projection optical system (PL).
, 62), and the oblique illumination means (61, 62).
Is a first illumination stop (61) having an opening (63) at a position decentered from the optical axis (AX) of the illumination optical system (30) for illuminating the mask (Rc), and light from the illumination optical system (30). A second illumination stop (62) having an opening (64) at a position symmetrical to the first illumination stop (61) about an axis (AX); and a part of a plurality of patterns (Mic, Moc). The gist is that the pattern (Mic) is illuminated using a first illumination stop (61) and the other pattern (Moc) is illuminated using a second illumination stop (62). is there.

Therefore, in the third aspect of the present invention, in addition to the effect of the first aspect, the use of the oblique illumination means enables the pattern image to be divided into 0-order light and + 1-order light or -1 order light. An image is formed by two-beam interference with the next light. The two luminous fluxes resulting from the combination of the first illumination stop and some of the patterns, and the two luminous fluxes resulting from the combination of the second illumination stop and other patterns are directed in opposite directions. Accordingly, the relative position between the image forming position of the partial pattern and the image forming position of the other pattern in a direction orthogonal to the optical axis changes according to the amount of aberration generated in the optical axis direction of the projection optical system. . Then, the amount of aberration remaining in the projection optical system can be measured by measuring the amount of displacement between the two imaging positions in a direction orthogonal to the optical axis.

The invention according to claim 4 of the present application is the invention according to any one of claims 1 to 3, wherein the plurality of patterns (Mip, Mop, Mic, M
oc) is the first two light beams (BLc1, BLc2, BLe0, BLe) having different diffraction angles (ψ1, ψ2) from each other.
1) and the first two light fluxes (BLc1, BLc2, BLe0, BLe) of the first pattern (Mip, Mic).
1) means a second light beam (BLd2, BLd1, BLf1, BLf0) having a diffraction angle (ψ2, ψ1) symmetric with respect to the optical axis (AX) direction of the projection optical system (PL). The gist is to include a pattern (Mop, Moc).

Therefore, according to the invention of claim 4 of the present application, in addition to the function of the invention of any one of claims 1 to 3, the first two light beams generated from the first pattern and The second two light beams generated from the second pattern are directed in directions opposite to each other. Thereby, according to the amount of aberration generated in the optical axis direction of the projection optical system, the image forming position of the first pattern in the direction orthogonal to the optical axis and the second
The relative position of the pattern to the image forming position changes. And
The amount of aberration remaining in the projection optical system can be measured by measuring the amount of displacement between the two imaging positions in a direction orthogonal to the optical axis.

The invention according to claim 5 relating to a method for measuring aberrations of a projection optical system is characterized in that a pattern (Mip, Mop, Mic, Mo) formed on a mask (R, Rps, Rc) is provided.
c) in the aberration measuring method for measuring the aberration of the projection optical system (PL) that forms the image on the image plane, wherein the aberration generated in the optical axis (AX) direction of the projection optical system (PL) is The pattern (Mip, Mop, Mic, Moc) is converted into an image displacement (ΔFh) in a direction intersecting the optical axis (AX), and the pattern (Mip, Mop, Mop) is converted.
The gist of the present invention is to measure the displacement (ΔFh) of the image of (Mic, Moc).

Therefore, in the invention of claim 5 of the present application, the same action as the invention of claim 1 is exhibited. The invention according to claim 6 of the present invention relates to a pattern (Mi) formed on a mask (R, Rps, Rc).
p, Mop, Mic, Moc) is projected onto a projection optical system (P
L), the projection optical system performs projection transfer onto a substrate (W) via an optical axis (A) of the projection optical system (PL).
X), the aberration generated in the direction (Mip, Mop, Mi) in a direction intersecting the optical axis (AX).
The conversion means (Rps, 61, 62, Rc) for converting the displacement of the image of (c, Moc) into an image (ΔFh) and the displacement (ΔFh) of the image of the pattern (Mip, Mop, Mic, Moc) are measured. Measuring means (42, 44, 45)
And a correcting means (53, 54) for correcting the aberration based on the measurement result of the measuring means (42, 44, 45).

According to the sixth aspect of the present invention, the amount of aberration occurring in the optical axis direction of the projection optical system is measured based on position information in a direction intersecting the optical axis, which enables more accurate position measurement. can do. Then, based on the measurement result, the aberration of the projection optical system is corrected by the correction unit, so that the image of the pattern on the mask can be more accurately formed on the substrate.

The invention according to claim 7 of the present invention relates to a mask (R, Rps) formed on a mask (R, Rps).
In a mask used for measuring aberration of a projection optical system (PL) for forming an image of (ip, Mop) on an image plane, the aberration generated in the direction of the optical axis (AX) of the projection optical system (PL). Is a position shift (ΔF) of the image of the pattern (Mip, Mop) in a direction intersecting the optical axis (AX).
h), the converting means (Rps) includes a plurality of predetermined patterns (Mip, Pp) provided with a phase shift portion (Pp) for changing the phase of the transmitted illumination light (EL). Mop) and a phase shift mask (Rps) of a spatial frequency modulation type having a plurality of phase shift portions (Ppi, Ppo) for generating a plurality of phase differences different from each other. It is assumed that.

Therefore, in the invention of claim 7 of the present application, substantially the same operation as that of the invention of claim 2 is exerted.
In addition, even in the existing exposure apparatus, by using the mask having the configuration according to the present invention, the shift of the focal position that changes in the optical axis direction according to the diffraction angle can be changed in the direction intersecting the optical axis. Can be easily converted to the positional deviation of

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) The present invention will be described below with reference to a step-and-repeat batch exposure apparatus for manufacturing a semiconductor device and an aberration measuring apparatus for a projection optical system in the apparatus. A specific first embodiment will be described with reference to FIGS. This embodiment is applied to a case where spherical aberration is measured as aberration occurring in the optical axis direction of the projection optical system.

First, a schematic configuration of the entire exposure apparatus will be described.
A description will be given based on FIG. Exposure light EL as illumination light emitted from the exposure light source 21 enters the collimator lens 22 and is converted into a substantially parallel light beam having a predetermined diameter. The exposure light EL is, for example, an excimer laser beam such as KrF or ArF, an F2 laser beam, a harmonic such as a metal vapor laser or a YAG laser, or a bright line of an ultra-high pressure mercury lamp such as a g-line, an h-line, or an i-line. .

The exposure light EL that has passed through the collimator lens 22 is
(It may be a rod lens) and is converted into a composite light beam of a large number of light beams, and a number of secondary light sources are formed on the exit side. A turret plate 25 for changing illumination conditions is arranged near the plurality of secondary light sources formed by the fly-eye lens 24. The turret plate 25 is formed with an aperture stop 26 corresponding to normal illumination and various modified illuminations such as annular illumination, small σ illumination, and inclined illumination. The turret plate 25 is connected to the turret plate
The illumination conditions are changed by rotating the aperture stop 5a and setting one of the aperture stops 26 on the exit surface of the secondary light source.

Exposure light EL from each secondary light source image passing through a predetermined aperture stop 26 enters a reticle blind 27, a mirror 28, and a condenser lens 29. The exposure light EL that has passed through the condenser lens 29 is incident on a reticle R as a mask that is held on the reticle stage RST so as to be orthogonal to the optical axis of the exposure light EL during the normal illumination. On the reticle R, a circuit pattern of a semiconductor element or the like is drawn.

As described above, the combining system from the exposure light source 21 to the condenser lens 29 constitutes the illumination optical system 30 for illuminating the circuit pattern and the like formed on the reticle R with the exposure light EL. Also, a number of secondary light source images emitted from the fly-eye lens 24 are superimposed on the reticle R, so that the reticle R is illuminated with uniform illuminance.

The reticle blind 27 is arranged so that its light-shielding surface has a conjugate relationship with the pattern area of the reticle R. The reticle blind 27 is composed of a plurality of movable light shielding units (for example, two L-shaped movable light shielding units) that can be opened and closed by a reticle blind driving unit 27a. By adjusting the size (slit width or the like) of the opening formed by the movable light-shielding portions, the shape of the illumination area that illuminates the reticle R can be changed.

The exposure light EL passing through the reticle R is:
For example, the light enters the projection optical system PL that is telecentric on both sides. The projection optical system PL outputs a projection image obtained by reducing the circuit pattern on the reticle R to, for example, 1/5 or 1/4.
It is formed on a wafer W as a substrate having a surface coated with a photoresist having photosensitivity to the exposure light EL. This wafer W is held on wafer stage WST so as to be substantially orthogonal to the optical axis of projection optical system PL.

The wafer stage WST allows the surface of the wafer W to be tilted in an arbitrary direction with respect to the optimum image forming plane of the projection optical system PL by the wafer stage driving section 33, and the optical axis AX of the projection optical system PL. Fine movement is possible in the direction (Z direction). Further, wafer stage WST is configured to be movable in two directions (X direction and Y direction) orthogonal to optical axis AX in order to make an arbitrary shot area correspond to projection optical system PL. This enables a step-and-repeat operation in which the operation of batch exposure of each shot area on the wafer W and the operation of moving to the next shot area are repeated. In FIG. 1,
The direction perpendicular to the optical axis AX (Z direction) and parallel to the paper
The direction, that is, the direction orthogonal to the optical axis AX and the paper surface is defined as the Y direction.

A movable mirror 35 for reflecting the laser beam from the interferometer 34 is fixed to the end of the wafer stage WST. The position of the wafer stage WST in the XY directions is, for example, about 0.01 μm. Is always detected with a resolution of. In the drawing, an interferometer 34 and a movable mirror 35 only in the Y direction are shown. The position information of wafer stage WST is sent to main control system 36 that controls the entire exposure apparatus, and main control system 36 controls wafer stage drive unit 33 based on this position information.

An oblique incidence type wafer position detection system (focus detection system) 39 comprising a pair of irradiation optical system 37 and light receiving optical system 38 is provided so as to sandwich the projection optical system PL. The irradiation optical system 37 supplies an image forming light beam for forming a pinhole or a slit image toward the surface of the wafer W or the like from an oblique direction with respect to the optical axis AX direction. The light receiving optical system 38 receives a light beam reflected by the surface of the wafer W of the image forming light beam through a slit.

The configuration and the like of the focus detection system 39 are disclosed in, for example, JP-A-60-168112, and a detailed description thereof will be omitted. The focus detection system 39 detects a positional deviation in the Z direction of the surface of the wafer W with respect to a preset reference position. The detected position information of the wafer W is sent to the main control system 36. The main control system 36 drives the wafer stage WST in the Z direction based on the position information of the wafer W so that the wafer W and the projection optical system PL maintain a predetermined interval.

On the side of the projection optical system PL, a wafer W
An off-axis type wafer alignment microscope 42 for detecting an alignment mark formed near each shot area is provided. In this case, the distance between the detection center of the wafer alignment microscope 42 and the center of the projection area of the reticle R, that is, the so-called base line amount is obtained in advance. Then, based on the baseline amount and the position information of the alignment mark measured by the wafer alignment microscope 42, the wafer stage driving unit 3
3, the position of the wafer W is adjusted. Thereby, each shot area on the wafer W is arranged at a predetermined position, and the alignment of each shot area is accurately performed.

In the vicinity of the wafer W on the wafer stage WST, a reference mark plate 43 having a reticle alignment reference mark is fixed. The reticle R
A reticle alignment microscope 44 for simultaneously observing the reference mark on the reference mark plate 43 and the measurement mark formed on the reticle R is provided above the reference mark plate 43. Then, based on the relative position of the measurement mark with respect to the reference mark, reticle stage RST
The position of the reticle R above is finely adjusted. Thus, the pattern on the reticle R is arranged at a predetermined position, and the pattern is accurately aligned.

An aerial image detection system 45 is provided near the wafer W and the reference mark plate 43 on the wafer stage WST. This aerial image detection system 45 includes:
The reference surface 46 is set to substantially match the height of the surface of the wafer W.
Is set. At the center of the reference surface 46, a rectangular opening 47 is formed, and wafer stage WST
A light receiving sensor 48 composed of a CCD or the like is provided below the opening 47 in the inside. The light receiving sensor 48 is for measuring the intensity of the exposure light EL passing through the opening 47. A signal relating to the light intensity distribution of the exposure light EL detected by the light receiving sensor 48 is transmitted to the main control system 36.
To be entered.

An example of the detection of the image forming position of the projection optical system PL using the aerial image detection system 45 is as follows. That is, a predetermined pattern,
For example, using a reticle R on which a line-and-space pattern is formed, an image of the pattern is projected near the opening 47 of the reference surface 46 via a projection optical system PL. From this state, the wafer stage WST is driven to relatively move the image and the opening 47, and the light receiving sensor 48 detects the light intensity distribution of the image of the pattern passing through the opening 47. As for the detected signal related to the light intensity distribution, the contrast of the image of the pattern is obtained based on the signal waveform in the main control system 36.

The measurement of the contrast is performed by using the reference surface 4
6 is repeated at a plurality of positions in the optical axis direction of the projection optical system PL, and among those measurement results, a measurement position showing a high contrast is set as an optimum image plane position in the projection optical system PL. is there. Such information on the position of the optimum image forming plane is obtained by, for example, calibrating the reference position of the focus detection system 39 and exposing the exposure light E in the image plane of the projection optical system PL.
It is used for measuring the illuminance distribution of L and the like.

The projection optical system PL is connected to an imaging characteristic adjusting unit 53 for adjusting the interval between a plurality of lens elements 52 held in a lens barrel 51 of the projection optical system PL. Further, a pressure adjusting unit 54 for adjusting the pressure in the lens barrel 51 (the pressure between the lens elements 52) is connected to the projection optical system PL. The main control system 36 includes:
The operation of the imaging characteristic adjustment unit 53 and the pressure adjustment unit 54 is controlled so that various aberrations including spherical aberration measured as described later that remain in the projection optical system PL are corrected. As described above, the imaging characteristic adjustment unit 53 and the pressure adjustment unit 54 constitute a correction unit. The correction corrects the imaging characteristic of the projection optical system PL, and corrects the pattern image on the reticle R. Exposure is ensured.

Next, the projection optical system PL in the present embodiment
A method for measuring the spherical aberration remaining in the image will be described. First, as shown in FIGS. 1 to 3, the reticle stage R
On ST, a spatial frequency modulation type phase shift reticle Rps as a conversion means is mounted on reticle stage RST. Then, the turret plate 25 is rotated, and the phase shift reticle Rps is normally illuminated vertically with the exposure light EL so that the aperture stop 26 for normal illumination corresponds to the optical path of the exposure light EL.

As shown in FIG. 2, the phase shift reticle Rps has an inner mark Mip as a first pattern.
And an outer mark Mop as a second pattern. These marks Mip, Mop are so-called box-in-box marks in which the inner mark Mip is arranged inside the outer mark Mop. The reticle substrate 55 of the phase shift reticle Rps is formed of a material that transmits the exposure light EL, for example, glass, quartz, fluorite, or the like.
The op and the inner mark Mip are formed on one surface side (the lower surface side in the present embodiment) of the reticle R.

The outer marks Mop are arranged so as to be spaced apart from each other by a predetermined distance, and extend in the X direction along a pair of first line and space patterns (first L and L).
/ S pattern) P1 and a pair of second line and space patterns (second L / S pattern) that are arranged at a predetermined distance from each other and extend along the Y direction.
P2.

The inner marks Mip are arranged so as to be separated from each other by a predetermined distance, and extend in the X direction along a pair of third line and space patterns (third L
/ S pattern) A pair of fourth line-and-space patterns (fourth L / S pattern) that are arranged to be spaced apart from P3 by a predetermined distance and extend along the Y direction
P4. The third and fourth L / S patterns P3, P4 are formed so that their extending directions are shorter than the corresponding first and second L / S patterns P1, P2. The inner mark Mip is completely accommodated in the outer mark Mop.

Next, the configuration of each of the L / S patterns P1 to P4 will be described. As shown in FIGS. 2 and 3, each of the L / S patterns P1 to P4 includes a light-transmitting portion Pt (through which the exposure light EL passes) and a phase shift portion Pp.
s (the exposure light EL does not pass through), and are arranged alternately at the same repetition interval. This allows
The images of the L / S patterns P1 to P4 are equally affected by the coma remaining in the projection optical system PL, and the influence of the coma is canceled when measuring the spherical aberration described later.

The light shielding portion Ps is provided on the reticle substrate 55.
And a layer of a material opaque to the exposure light EL, such as chromium or aluminum, formed on the surface of the substrate. The light-transmitting portion Pt is formed with a part of the surface of the reticle substrate 55 in which the opaque material layer is not formed and the transparent material is exposed as it is. In the phase shift portion Pp, a dug having a predetermined depth is formed on the surface of the reticle substrate 55.

Here, the outer phase shift portion Ppo of the outer mark Mop and the inner phase shift portion Ppi of the inner mark Mip have different digging depths. The digging depth of the inner phase shift portion Ppi is such that the phase of the exposure light EL passing through the inner phase shift portion Ppi is π−φ (rad) compared to the phase of the exposure light EL passing through the light transmitting portion Pt. ). On the other hand, the depth of the digging of the outer phase shift portion Ppo is such that the phase of the exposure light EL passing through the outer phase shift portion Ppo is equal to the exposure light EL passing through the light transmitting portion Pt.
Is set so as to be shifted by π + φ (rad) as compared with the phase of Here, the depth of the digging is smaller in the outer phase shift portion Ppo than in the inner phase shift portion Ppi.

Here, the diffraction phenomenon of the exposure light EL passing through the inner mark Mip and the outer mark Mop will be described. Here, in order to facilitate understanding, the value of φ is set to π / 2 (rad), that is, 90 °, the phase shift generated in the inner phase shift unit Ppi is set to 90 °, and the outer phase shift unit is set to 90 °. The phase shift caused by Ppo is 270 °.

FIG. 5A shows a normal line-and-space pattern (a pattern which does not have a phase shift portion Pp and is composed of only a light transmitting portion Pt and a light shielding portion Ps). FIG. 6 shows a state of interference of light beams passing through adjacent light transmitting portions Pt when illuminated with the exposure light EL through the aperture stop 26. Here, in the drawing, the solid line indicates the wavefront of the peak in the exposure light EL, and the broken line indicates the wavefront of the valley.

Here, the wavefront of the mountain portion referred to here is a surface formed by connecting points where the field vectors have the same phase at the same time. On the other hand, the wavefront of the valley portion has a field vector of π (rad), that is, 180
° It is a surface that connects points having different phases. Also,
The exposure light EL is converted from a plane wave to a curved wave when passing through the L / S pattern.

In this combination of the normal L / S pattern and the normal illumination, the phase of the light beam passing through the adjacent light transmitting portions Pt does not shift. For this reason, the diffracted light generated by the peaks of the light fluxes strengthening each other and the valleys weakening each other as shown by the arrows in the figure,
The three light beams are the zero-order light BLa0 and the ± first-order lights BLa + 1 and BLa-1. This zero-order light BLa0 is generated in the extension direction of the optical axis AX0 before the exposure light EL is incident on the reticle R, and the ± first-order lights BLa + 1 and BLa-1 are the zero-order light BLa.
It occurs in an angle direction symmetrical with respect to a0.

FIG. 5B shows that the value of φ is set to 0,
The phase shift reticle Rps set so that the phase of the exposure light EL passing through the phase shift portion Pp is shifted by πrad, that is, 180 °, with respect to the phase of the exposure light EL passing through the light transmitting portion Pt, is illuminated with normal illumination. In this case, the state of interference of light beams passing through the adjacent light transmitting portion Pt and phase shift portion Pp is shown.

In this case, the light beam passing through the phase shift portion Pp is delayed by a half wavelength from the light beam passing through the light transmitting portion Pt. The position where the peaks and valleys of both light beams overlap with each other is different from the case of FIG. 5A, in which the zero-order light disappears. Then, as indicated by the arrow in the figure, the diffracted light BLb
The two light beams 1 and BLb2 are generated with an intermediate diffraction angle ± 0 between the zero-order light BLa0 and the ± first-order lights BLa + 1 and BLa-1. At this time, since the value of φ is set to 0, the two diffracted lights BLb1 and BLb2
In this case, the symmetry of the exposure light EL incident on the phase shift reticle Rps with respect to the optical axis AX0 is maintained.

On the other hand, FIG. 5C shows the diffraction phenomenon of the exposure light EL passing through the adjacent translucent portion Pt and the inner phase shift portion Ppi when the inner mark Mip is illuminated by normal illumination. It is shown. Here, the inner phase shift portion Ppi has a phase of the exposure light EL passing therethrough compared to the phase of the exposure light EL passing through the light transmitting portion Pt by π−π / 2 = π / 2 (rad), that is, 90. It is set to be shifted by °.

In this case, the light beam passing through the inner phase shift portion Ppi is added to the light beam passing through the light transmitting portion Pt by one.
A delay of ４ wavelength occurs, and the zero-order light disappears as in the case of FIG. 5B. On the other hand, the mountains of both luminous fluxes,
5 (a) and FIG.
This is different from any of the cases (b). Then, as indicated by the arrow in the figure, the diffracted light B constituting the first two light fluxes
Lc1 and BLc2 are generated with diffraction angles ψ1 and ψ2 that are asymmetric with respect to the optical axis AX0 of the exposure light EL incident on the reticle R. At this time, the diffraction angle ψ1 of the diffracted light BLc1 generated on the inner phase shift portion Ppi side is:
It becomes larger than the diffraction angle ψ0. On the other hand, the diffraction angle ψ2 of the diffracted light BLc2 generated on the light transmitting portion Pt side is equal to the diffraction angle ψ
It becomes smaller than 0.

Therefore, the image of the inner mark Mip is
As shown by the solid line in FIG.
An image is formed by two-beam interference of Lc1 and BLc2. When spherical aberration remains in the projection optical system PL, the image of the inner mark Mip is displayed on the reticle R
Does not form an image on the optical axis AX0 of the exposure light EL incident on the diffracted light beam BL, but has a smaller diffraction angle than the optical axis AX0.
An image is formed at the position Fhi on the c2 side.

FIG. 5D shows the outer mark Mo.
Exposure light EL that passes through the adjacent translucent portion Pt and outer phase shift portion Ppo when p is illuminated with normal illumination
FIG. Here, the outer phase shift portion Ppo has a phase of the exposure light EL passing therethrough compared to the phase of the exposure light EL passing through the light transmitting portion Pt by π + π /.
2 = 3π / 2 (rad), that is, set so as to be shifted by 270 °.

In this case, the light beam passing through the outer phase shift portion Ppo is added to the light beam passing through the light transmitting portion Pt by three times.
A delay of ／ wavelength, in other words, an advance of １ ／ wavelength occurs, and the zero-order light disappears as in the case of FIG. 5B. On the other hand, the positions where the peaks and valleys of the two light beams overlap each other are different from those shown in FIGS. 5A and 5B. Also, the overlapping position is different from that in the case of FIG.

The outer marks Mop are formed at the same pitch as the inner marks Mip.
As shown by the arrows in the figure, the diffracted lights BLd1 and BLd2 constituting the second two light fluxes have diffraction angles ψ1, 非 対 称 that are asymmetric with respect to the optical axis AX0 of the exposure light EL incident on the reticle R.
2 will occur. That is, each diffracted light B
Ld1 and BLd2 are generated so as to be symmetrical with respect to the optical axis AX0 and each of the diffracted lights BLc1 and BLc2 generated in the inner mark Mip. Then, the diffraction angle ψ1 of the diffracted light BLd1 generated on the light transmitting portion Pt side is:
It becomes larger than the diffraction angle ψ0. On the other hand, the diffraction angle ψ2 of the diffracted light BLd2 generated on the outer phase shift portion Ppo side is:
It becomes smaller than the diffraction angle ψ0.

For this reason, the image of the outer mark Mop is
As shown by the broken line in FIG.
An image is formed by two-beam interference of Ld1 and BLd2. When spherical aberration remains in the projection optical system PL, the image of the outer mark Mop is displayed on the reticle R
No image is formed on the optical axis AX0 of the exposure light EL incident on the diffracted light BL, and the diffraction light BL having a smaller diffraction angle than the optical axis AX0.
An image is formed at the position Fho on the d2 side.

By the way, as shown in FIG. 4, when illuminated with normal illumination, the diffracted light BLc1,
It is assumed that there is a normal reticle R having an L / S pattern with a pitch that generates BLd1. In this case, the L
The image of the / S pattern is the diffracted light BLc1, BLd1
And an optical axis AX0 incident on the reticle R (in this case,
An image is formed by three-beam interference with zero-order light generated along the optical axis AX of the projection optical system PL). Here, if spherical aberration remains in the projection optical system PL, the positions of incidence of the diffracted lights BLc1 and BLd1 on the projection optical system PL are relatively far from the optical axis AX, so that the L / S The image forming position of the pattern image is the focal position F on the side of the projection optical system PL.
v1.

On the other hand, when illuminated by ordinary illumination, the ordinary reticle R having an L / S pattern of another pitch that generates the diffracted lights BLc2 and BLd2 as ± first-order lights.
Suppose there was. In this case, the image of the L / S pattern includes the diffracted lights BLc2 and BLd2 and the reticle R
An image is formed by three-beam interference with the zero-order light generated along the optical axis AX0 incident on the optical axis AX0.

Here, if spherical aberration remains in the projection optical system PL, the incident positions of the diffracted lights BLc2 and BLd2 on the projection optical system PL are relatively close to the optical axis AX. The image forming position of the image of the L / S pattern is the focal position Fv2 on the side separated from the projection optical system PL. That is, the spherical aberration of the projection optical system PL corresponds to the difference ΔFv between the focal positions Fv1 and Fv2.

On the other hand, the diffracted lights BLc1, BLc2, BLd1, and BLd2 are simultaneously generated by illuminating with normal illumination using the phase shift reticle Rps having the inner mark Mip and the outer mark Mop. be able to. In addition, when spherical aberration remains in the projection optical system PL, the spherical aberration is caused by the position of the inner mark Mip and the position of the outer mark Mop in a plane orthogonal to the optical axis AX of the projection optical system PL. It is represented in a state converted into a positional deviation ΔFh from the position Fho.

The position F of the image of these marks Mip, Mop
The misregistration ΔFh between hi and Fho is measured by, for example, the following method. First, both marks Mip, Mop are illuminated with normal illumination, and the images of both marks Mip, Mop are transferred onto wafer W and developed. The images of the developed marks Mip and Mop are set in the observation field of the wafer alignment microscope 42. Then, the difference between the center position of the inner mark Mip and the center position of the outer mark Mop is measured by the wafer alignment microscope 42. Thus, the wafer alignment microscope 42
It constitutes measuring means and position detecting means.

Next, as described above, the phase difference is (π-φ)
A phenomenon in which the diffraction angles 型 1 and ψ2 of the generated diffracted lights BLc1 and BLc2 are caused to be asymmetry by illuminating the spatial frequency modulation type phase shift reticle Rps as (rad) with normal illumination will be described.

In this case, the light transmitting portions Pt adjacent at the pitch P
The light path length L differs between the transmitted light beam passing through the phase shift unit Pp and the phase shifted light beam passing through the phase shift unit Pp. The difference between the optical path lengths L is as follows, assuming that the wavelength of the incident exposure light EL is λ.
It is obtained by the following equation (2).

[0066]

(Equation 2) If this is replaced with the case where oblique illumination for illuminating the pattern on the reticle R in an oblique direction is considered, the exposure light EL is inclined and illuminated by the incident angle θ0 obtained by the following equation (3). Is equivalent.

[0067]

(Equation 3) Further, the diffraction angle ψ0 of the diffracted lights BLb1 and BLb2 from the phase shift pattern having the pitch P and the phase difference of π (rad) is obtained by the following equation (4).

[0068]

(Equation 4) Accordingly, the diffraction angles パ タ ー ン 1 and ψ2 of the diffracted lights BLc1 and BLc2 when the phase shift pattern having the phase difference of (π−φ) (rad) is illuminated by the normal illumination are expressed by the following equations (5) and (5). 6) It is obtained by the equation.

[0069]

(Equation 5)

[0070]

(Equation 6) Thus, the phase shift reticle Rp having the phase shift pattern such that the phase difference is (π−φ) (rad)
By using s, the diffraction angles ψ1 and ψ2 of the diffracted lights BLc1 and BLc2 can have asymmetry.

Then, the difference ΔFv between the focal position Fv1 and the focal position Fv2 due to the spherical aberration is obtained by the following (7)
According to the equation, both marks Mip, M obtained as described above are obtained.
It can be obtained based on the position shift ΔFh between the positions Fhi and Fho of the op image.

[0072]

(Equation 7) Incidentally, the phase shift amount in the inner mark Mip is 9
0 °, the phase shift amount at the outer mark Mop is 270
When the phase shift reticle Rps formed so that the pitch P corresponds to 0.20 μm of the normal reticle and the exposure light EL is illuminated with KrF excimer laser light (λ = 248 nm) by normal illumination, spherical aberration is obtained. The difference ΔFv between the focal position Fv1 and the focal position Fv2 is obtained as follows.

In this case, the sine sin θ0 of the incident angle θ0 of the exposure light EL is 0.1 when considered in place of the oblique illumination.
6, and the sine sinψ0 of the diffraction angle ψ0 of the diffracted lights BLb1 and BLb2 from the phase shift pattern having a phase difference of 180 ° is 0.31. Thereby, the sine sin of the diffraction angle {1} is obtained from both the marks Mip and Mop.
1, diffracted lights BLc1 and BLd1 are generated in the direction of 0.47. The sine sin 正弦 2 of the diffraction angle ψ2 is −0.1
5, diffracted lights BLc2 and BLd2 are generated.

Thus, each of the diffracted lights BLc1, BLd1
The tangent of the incident angle (equivalent to the diffraction angle ψ1) to the wafer W is 0.53, and the tangent of the incident angle (equivalent to the diffraction angle ψ2) of each of the diffracted lights BLc2 and BLd2 to the wafer W is −0.16.
Is required respectively. Therefore, the difference ΔFv between the focal position Fv1 and the focal position Fv2 due to the spherical aberration in this case.
Can be obtained by the following equation (8).

[0075]

(Equation 8) According to the first embodiment configured as described above, the following effects can be obtained.

(A) In the exposure apparatus, the projection optical system P
The spherical aberration occurring in the direction of the optical axis AX of L is converted into the inner mark Mip and the outer mark M in the direction orthogonal to the optical axis AX.
The image data is converted into a positional deviation ΔFh of the image from the image op and recorded as a latent image on the wafer W. Then, both developed marks Mi
The displacement ΔFh of the images of p and Mop is measured by the wafer alignment microscope 42.

For this reason, in a state where the spherical aberration remains in the projection optical system PL, the image formation state of the pattern image on the reticle R is changed to X which is orthogonal to the optical axis AX of the projection optical system PL.
This can be detected as position information in the Y plane. Here, the measurement of the position of the image in the XY plane can be performed much more easily and accurately using, for example, the wafer alignment microscope 42 as compared with the measurement of the position of the image in the optical axis direction of the projection optical system PL. it can. Therefore, the spherical aberration of the projection optical system, without a slight shift in the detection result by the detection method as in the conventional configuration,
It can be measured accurately and directly.

(B) In the above exposure apparatus, when measuring spherical aberration, a spatial frequency modulation type having a pair of inner marks Mip and outer marks Mop having a phase shift portion Pp for changing the phase of the transmitted exposure light EL. Is used. The inner phase shift portion Ppi of the inner mark Mip and the outer phase shift portion Ppo of the outer mark Mop are formed so as to cause different phase differences. Then, the images of the marks Mip and Mop formed on the image plane of the projection optical system PL are transferred onto a wafer W arranged on the image plane.

As described above, by using the phase shift reticle Rps, the images of the marks Mip and Mop are formed by two-beam interference. And both marks Mi
Different phase differences are caused by the phase shift portions Ppi and Ppo of p and Mop. For this reason, the diffraction angles 回 折 of the diffracted lights BLc1 and BLd2 generated from the marks Mip and Mop on one side of the optical axis AX of the projection optical system PL.
1 and 異 な っ 2 are different. In addition, both marks Mi
The diffraction angles ψ2 and ψ1 of the diffracted lights BLc2 and BLd1 generated on the other side of the optical axis AX from p and Mop are different. Accordingly, 2 for each mark Mip, Mop
Diffracted light BLc1, diffracted light BLc2, diffracted light BLd2
And the diffracted light BLd1 again intersect, that is, the positions Fhi and Fho at which images are formed are different positions deviated from the optical axis AX.

Therefore, by utilizing the deviation of the positions Fhi and Fho from the optical axis AX, the focal positions Fv1 and Fv1, which change in the optical axis direction (Z direction) according to the diffraction angles ψ1 and ψ2.
The shift ΔFv of Fv2 can be easily converted to a position shift ΔFh in the XY plane.

(C) In the exposure apparatus, diffracted lights BLc1 and BLc2 having different diffraction angles ψ1 and ψ2 are generated from the inner mark Mip of the phase shift reticle Rps. At the same time, in-phase shift reticle Rps
From the outer mark Mop of each of the diffracted lights BLc1, B
Diffracted light beams BLd2 and BLd1 that are symmetric with respect to Lc2 and the optical axis AX of the projection optical system PL are generated.

Therefore, the diffracted lights BLc1 and BLc2 generated from the inner mark Mip and the diffracted lights BLd1 and BLd2 generated from the outer mark Mop are directed in directions opposite to each other. Here, according to the spherical aberration of the projection optical system PL, the inner mark Mip in the XY plane is
Is changed from the position Fhi of the outer mark Mop to the position Fho of the outer mark Mop. Therefore, the spherical aberration remaining in the projection optical system PL is determined by the displacement ΔFh between the two positions Fhi and Fho.
By measuring, it is possible to measure accurately and easily.

(D) In the exposure apparatus, both marks Mi
The spherical aberration remaining in the projection optical system PL measured based on the positional deviation ΔFh of p and Mop is changed to the imaging characteristic adjustment unit 53.
The pressure is corrected by the pressure adjusting unit 54.

Therefore, the spherical aberration remaining in the projection optical system PL can be measured more accurately, and the spherical aberration can be corrected based on the measurement result.
The imaging characteristic of L can be adjusted more accurately. Therefore, at the time of actual exposure in which the image of the pattern on the reticle R is transferred onto the wafer W, the image of the pattern can be more accurately formed on the wafer W, and the exposure accuracy can be improved. .

(E) In the exposure apparatus, the diffracted lights BLc1, BLc2 and BLd2, Bd2 symmetric with respect to the optical axis AX of the projection optical system PL are placed on the phase shift reticle Rps.
The inner mark Mip and the outer mark Mop that respectively generate Ld1 are different from the inner mark Mip.
Are arranged so as to be sandwiched at predetermined intervals.

Therefore, when the spherical aberration remains in the projection optical system PL, the images of the marks Mip and Mop move in the opposite directions in the image plane of the projection optical system PL. Here, since the outer mark Mop is disposed so as to sandwich the inner mark Mip, the position Fh of the marks Mip, Mop is measured by measuring the relative positions of the marks Mip, Mop.
The deviation ΔFh between i and Fho can be measured with higher accuracy. Therefore, the effect described in (c) can be exhibited with a simple configuration and efficiently.

(Second Embodiment) Next, a second embodiment of the present invention will be described focusing on parts different from the first embodiment.

In the second embodiment, as shown in FIG. 6, the outer mark Mop of the phase shift reticle Rps
Is different from the first embodiment. That is, the outer phase shift portion Ppo of the outer mark Mop is formed to have the same digging depth as the inner phase shift portion Ppi of the inner mark Mip. Further, a shallow dig is also formed in the outer translucent portion Pto of the outer mark Mop. The difference between the depth of the digging between the outer phase shift portion Ppo and the outer light transmitting portion Pto is determined by the phase of the exposure light EL passing through the outer phase shifting portion Ppo and the exposure light passing through the outer light transmitting portion Pto. Π compared to the phase of light EL
It is set so that a shift of + φ (rad) occurs.

Therefore, according to the second embodiment, the same effect as that of the first embodiment can be obtained. (Third Embodiment) Next, a third embodiment of the present invention will be described focusing on parts different from the above embodiments.

In the third embodiment, FIGS.
As shown in FIG. 0, when measuring the spherical aberration remaining in the projection optical system PL, a normal reticle Rc including only the light transmitting portion Pt and the light shielding portion Ps is used, and the normal reticle Rc is moved in a predetermined direction. This embodiment is different from the above embodiments in that the illumination is performed by inclined illumination from above.

That is, as shown in FIG. 8A, FIG. 8B and FIG. 9, the inner mark Mic and the outer mark Moc are independently formed on the normal reticle Rc. In both marks Mic and Moc, the light-transmitting portions Pt and the light-shielding portions Ps are alternately arranged at the same pitch. In the normal reticle Rc, when measuring the spherical aberration remaining in the projection optical system PL, the exposure using the inner mark Mic and the exposure using the outer mark Moc are performed in an overlapping manner.

Then, the marks Mic and Moc are stored such that the image of the inner mark Mic is accommodated inside the image of the outer mark Moc in a state where the overlay exposure has been performed, and constitutes a box-in-box mark. Is formed.
Further, when performing the overlay exposure, a light-shielding portion is provided outside the inner mark Mic and inside the outer mark Moc so as not to affect the latent image of the inner mark Mic or the outer mark Moc transferred earlier. Psi and Pso are formed.

Further, as shown in FIG.
An inner mark aperture stop 61 as a first illumination stop and an outer mark aperture stop 62 as a second illumination stop are formed on the inner turret plate 25 (see FIG. 1). The inner mark aperture stop 61 is provided on the turret plate 25.
Is rotated so as to correspond to the exit surface of the fly-eye lens 24 (see FIG. 1) in the illumination optical system 30. At this time, a small opening 63 as an opening formed on the inner mark aperture stop 61 is formed by the illumination optical system 30.
Are arranged at positions eccentric from the optical axis AX.

The outer mark aperture stop 62 is also
By rotating the turret plate 25, the turret plate 25 is adapted to correspond to the output surface. At this time, a small opening 64 as an opening formed on the outer mark aperture stop 62 is located at a position where the small opening 63 of the inner mark aperture stop 61 is arranged around the optical axis AX of the illumination optical system 30. It is arranged in a symmetrical position with.

Then, the exposure light EL is applied to these small apertures 6.
3 and 64, the normal reticle R
Each mark Mic, Moc on c is illuminated by the exposure light EL at a predetermined incident angle from oblique directions opposite to each other.

Next, an example of a method of measuring spherical aberration in the third embodiment will be described. First, the position of the reticle stage RST (see FIG. 1) is adjusted using the reticle alignment microscope 44 so that the inner mark Mic on the normal reticle Rc is arranged at a predetermined position. Next, the turret plate driving unit 25a rotates the turret plate 25 to dispose the inner mark aperture stop 61 in the optical path of the exposure light EL, and the exposure light EL obliquely enters the inner mark Mic on the inner mark Mic. Illuminate so as to be θ0.

Based on this illumination, as shown in FIG. 10, through the inner mark Mic, the zero-order light BLe0 and the first-order light BLe0 corresponding to the diffracted light BLc1 and the diffracted light BLc2 in the first embodiment, respectively. On the other hand, BLe1 enters the projection optical system PL. The zero-order light BLe0 and one of the primary lights BLe1 constitute a first two light fluxes. This allows the first optical system PL to be placed on the image plane of the projection optical system PL.
As in the case of the inner mark Mip of the embodiment, the image of the inner mark Mic is formed by two-beam interference. The other primary light generated from the inner mark Mic exits outside the opening of the projection optical system PL and does not contribute to image formation. Then, the image of the inner mark Mic is recorded on the wafer W.

Next, the reticle alignment microscope 44
Reticle stage RST such that outer mark Moc on normal reticle Rc is arranged at a predetermined position.
Adjust the position (see FIG. 1). Then, the turret plate 25 is rotated by the turret plate driving unit 25a,
An aperture stop 62 for the outer mark is arranged in the optical path of the exposure light EL, and the outer mark Moc is moved by the exposure light EL.
Illumination is performed from an oblique direction opposite to that of the inner mark Mic so as to have an incident angle θ0.

Based on this illumination, as shown in FIG. 10, the 0th order light BLf0 and the 1st order light BLf0 corresponding to the diffracted light BLd1 and the diffracted light BLd2 in the first embodiment, respectively, via the outer mark Moc. On the other hand, BLf1 enters the projection optical system PL. The zero-order light BLf0 and one of the primary lights BLf1 constitute a second two-beam. This allows the first optical system PL to be placed on the image plane of the projection optical system PL.
As in the case of the outer mark Mop of the embodiment, the image of the outer mark Moc is formed by two-beam interference. Note that the other primary light generated from the outer mark Moc exits outside the opening of the projection optical system PL and does not contribute to image formation. Then, the image of the outer mark Moc is superimposed and recorded on the wafer W on which the image of the inner mark Mic is recorded. Thus, the conversion means is constituted by the two aperture stops 61 and 62 and the normal reticle Rc.

Hereinafter, similarly to the first embodiment, the positional deviation ΔFh between the inner mark Mic and the outer mark Moc is measured, and the difference between the focal position Fv1 and the focal position Fv2 due to spherical aberration is determined based on the deviation ΔFh. ΔFv can be obtained.

Therefore, according to the third embodiment, the following effects are obtained in addition to the effects substantially the same as (a) and (c) to (d) in the first embodiment. Obtainable.

(F) In the exposure apparatus, when measuring spherical aberration, a normal reticle Rc having an inner mark Mic and an outer mark Moc, and an inner mark for obliquely illuminating the normal reticle Rc from an oblique direction. And aperture stops 61 and 62 for outer marks. The small aperture 63 of the inner mark aperture stop 61 and the small aperture 64 of the outer mark aperture stop 62 are located at positions eccentric from the optical axis AX of the illumination optical system 30 and mutually centered on the optical axis AX. It is open at a symmetrical position. Then, the inner mark Mic is illuminated using the inner mark aperture stop 61, and the outer mark Moc is illuminated using the outer mark aperture stop 62.

As described above, by using the oblique illumination, the images of both marks Mic and Moc can be converted into the zero-order lights BLe0 and BLf.
An image is formed by two-beam interference between 0 and one of the primary lights BLe1 and BLf1. Then, two luminous fluxes of the zero-order light BLe0 and the primary light BLe1 generated from the combination of the inner mark aperture stop 61 and the inner mark Mic, and the zero-order light generated from the combination of the outer mark aperture stop 62 and the outer mark Moc. The two luminous fluxes of BLf0 and the primary light BLf1 are directed in directions opposite to each other. This allows
The two marks Mi in an XY plane orthogonal to the optical axis AX according to the amount of spherical aberration remaining in the projection optical system PL.
The shift ΔFh between the positions Fhi and Fho of the images c and Moc changes.

Therefore, the spherical aberration remaining in the projection optical system PL is changed to the positions Fhi, Fc of the images of the marks Mic and Moc.
It can be accurately and easily measured as the deviation ΔFh of Fho.

(Modification) The embodiment of the present invention may be modified as follows. In the first and second embodiments, the inner mark Mip
And phase difference π ± φ (rad) in outer mark Mop
Is set such that φ = π / 2 (rad), but the value of φ may be arbitrarily set in the range of 0 <φ <π (rad).

Here, in particular, when measuring the spherical aberration of the projection optical system PL using the two marks Mip and Mop formed of a fine L / S pattern, or when the numerical aperture (N.
A. For example, when measuring the spherical aberration of the projection optical system PL having a small size, the relatively large diffracted lights BLc1 and BLd1 having the diffraction angles ψ1 generated from the marks Mip and Mop are outside the numerical aperture of the projection optical system PL. There is a risk of coming out. In such a case, by reducing the value of φ, the diffracted lights BLc1 and BLd1 can be surely kept within the range of the numerical aperture of the projection optical system PL,
The effect is obtained that accurate measurement of spherical aberration can be ensured.

In the first and second embodiments, the phase difference at the inner mark Mip is set to π−φ (rad), and the phase difference at the outer mark Mop is set to π + φ (rad). On the other hand, the phase difference at the inner mark Mip may be set to π + φ (rad), and the phase difference at the outer mark Mop may be set to π−φ (rad).

In the first and second embodiments, the phase difference π ± between the inner mark Mip and the outer mark Mop
φ (rad) was set. On the other hand, the phase difference at the inner mark Mip is π-φ1 (rad),
The phase difference at the outer mark Mop is π + φ2 (rad)
Alternatively, the phase difference at the inner mark Mip may be set to π + φ1 (rad), and the phase difference at the outer mark Mop may be set to π−φ2 (rad). Here, the values of φ1 and φ2 are φ1 ≠ φ2, and 0 ≦ φ1 <π and 0 ≦ φ2 <π.

In the first and second embodiments, the inner mark Mip and the outer mark Mop are formed in a box-in-box mark shape on the phase shift reticle Rps, and both marks Mip and Mop are formed. Were simultaneously exposed. On the other hand, similarly to the third embodiment, the inner mark Mip and the outer mark Mop are independently formed on the phase shift reticle Rps, respectively.
The two marks Mip and Mop may be sequentially overlapped and exposed.

In the third embodiment, the inner mark M
After the exposure of ic, the outer mark Moc was superposed and exposed. On the other hand, the outer mark Mo
After the exposure of c, the inner mark Mic may be overlapped and exposed.

In the first and second embodiments, the position Fhi of the inner mark Mip and the position F of the outer mark Mop
The misregistration ΔFh from ho was measured after being transferred onto the wafer W and developed. On the other hand, the displacement ΔFh
By using the aerial image detection system 45, the two marks Mip,
The light intensity distribution of the Mop image may be detected and measured from the signal waveform of the light intensity distribution.

In the above embodiments, the inner mark Mi
The positional deviation ΔFh between the position Fhi of p and Mic and the position Fho of the outer marks Mop and Moc was measured after being transferred onto the wafer W and developed. On the other hand, the positional deviation ΔFh may be measured on the wafer W in a state of a latent image.

In the above embodiments, the inner mark Mi
The positional deviation ΔFh between the position Fhi of p and Mic and the position Fho of the outer marks Mop and Moc was measured using the wafer alignment microscope 42, but may be measured using the reticle alignment microscope 44.

As the exposure light EL, in addition to those described in each of the above embodiments, for example, a single-wavelength laser in the infrared or visible range oscillated from a DFB semiconductor laser or a fiber laser may be used, for example, erbium (or Amplify with both erbium and yttrium doped fiber amplifiers. Then, a harmonic converted to ultraviolet light using a nonlinear optical crystal may be used. Specifically, the oscillation wavelength of the single-wavelength laser is set to, for example, 1.
When the wavelength is in the range of 51 to 1.59, the generated wavelength is 189 to
An 8th harmonic within a range of 199 nm or a 10th harmonic having a generation wavelength within a range of 151 to 159 nm is output.

In each of the above embodiments, the present invention is embodied in a batch exposure type exposure apparatus for manufacturing a semiconductor device. However, the present invention relates to a step-and-scan type scanning exposure type exposure apparatus, Manufacture of exposure devices for manufacturing liquid crystal display elements, which project and transfer circuit patterns on photomasks onto glass plates, as well as exposure devices for manufacturing microdevices such as imaging devices and thin-film magnetic heads, as well as reticles and photomasks. And the like.

Further, as the projection optical system PL, not only a reduction system but also an equal magnification system or an enlargement system may be used, and not only a refraction system but also a catadioptric system may be used. .

With these arrangements, substantially the same effects as those of the above embodiments can be obtained. The phase shift reticle Rps of the first and second embodiments and each of the modifications may be applied when measuring the spherical aberration remaining in the projection optical system PL in an existing exposure apparatus. Further, the normal reticle Rc of the third embodiment
May be applied to the existing exposure apparatus when measuring the spherical aberration remaining in the projection optical system PL. By doing so, the spherical aberration remaining in the projection optical system PL can be more accurately and easily measured in the existing exposure apparatus.

Incidentally, the exposure apparatus of each of the above embodiments is
For example, it can be manufactured as follows. That is, the projection optical system PL in which the plurality of lens elements 52 and the like have optical members incorporated in the lens barrel 51, and the plurality of lenses 22 and 2
At least a part of an illumination optical system 30 including optical members such as mirrors 4 and 29 and mirrors 23 and 28 is fixed to a mount supported by a plurality of vibration isolation pads. Then, the illumination optical system 30 and the projection optical system PL are each optically adjusted, and wiring and piping are connected to a reticle stage RST and a wafer stage WST including a large number of mechanical components. Further, a control system centering on the main control system 36 is connected to perform overall adjustment such as electric adjustment and operation confirmation. It is desirable that the manufacture of the exposure apparatus be performed in a clean room in which the temperature, cleanliness, and the like are controlled.

The semiconductor element (device) has a step of designing the function and performance of the device, a step of manufacturing a reticle R based on the design step, a step of manufacturing a wafer W from a silicon material, and the steps of the above embodiments. A step of transferring a pattern on the reticle R to the wafer W by an exposure apparatus (including a photolithography step and an etching step), a doping step, a wiring step,
It is manufactured through a device assembly step (including a dicing step, a bonding step, and a package step), an inspection step, and the like.

Next, other technical ideas that can be understood from the above embodiments and modified examples will be described below together with their effects. (1) On the phase shift mask (Rps), the first pattern (Mip) and the second pattern (Mop)
And each pattern (Mip, Mop) is projected onto the projection optical system (P
L) on the image plane of the second pattern (M).
The aberration measuring apparatus according to claim 4, wherein the first pattern (Mip) is disposed so as to sandwich the first pattern (Mip) at a predetermined interval.

Therefore, according to the invention of (1), the effect of the invention of claim 4 can be exhibited with a simple configuration.

[0122]

As described above in detail, according to the first and fifth aspects of the present invention, it is possible to accurately and directly measure the aberration that occurs in the optical axis direction of the projection optical system.

According to the invention of claim 2 of the present application, in addition to the effect of the invention of claim 1, information relating to aberration occurring in the optical axis direction of the projection optical system is stored in the position in the direction intersecting the optical axis. It can be easily converted to information.

According to the third aspect of the present invention, in addition to the effect of the first aspect, the aberration occurring in the direction of the optical axis of the projection optical system can be corrected by the two patterns in the direction orthogonal to the optical axis. It is possible to accurately and easily measure the amount of displacement of the imaging position.

According to the invention of claim 4 of the present application, in addition to the effects of the invention of any one of claims 1 to 3, the aberration generated in the optical axis direction of the projection optical system is reduced by the light. It is possible to accurately and easily measure the amount of displacement between the imaging positions of the two patterns in the direction perpendicular to the axis.

Further, according to the invention of claim 6, it is possible to form a pattern image on the mask more accurately on the substrate, and it is possible to improve the exposure accuracy. According to the seventh aspect of the present invention, in addition to the effects of the second aspect of the invention, the light of the projection optical system can be also used in the existing exposure apparatus by using the mask having the structure of the seventh aspect of the present invention. Aberrations occurring in the axial direction can be measured more accurately and directly.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an exposure apparatus equipped with an aberration measurement device of the present invention.

FIG. 2 is a plan view showing an inner mark and an outer mark of the phase shift reticle of the first embodiment.

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is an explanatory diagram relating to measurement of spherical aberration in the first and second embodiments.

FIG. 5 is an explanatory diagram relating to a diffraction phenomenon in the phase shift reticle of FIG. 2;

FIG. 6 is a partial cross-sectional view illustrating a phase shift reticle according to a second embodiment.

FIG. 7 is a front view showing a turret plate according to a third embodiment.

FIGS. 8A and 8B are plan views of the normal reticle according to the third embodiment, wherein FIG. 8A shows an inner mark and FIG.

FIG. 9 is a sectional view taken along line 9-9 of FIG. 8;

FIG. 10 is an explanatory diagram relating to measurement of spherical aberration according to the third embodiment.

[Explanation of symbols]

Reference numeral 30: illumination optical system; 42, wafer alignment microscope as measuring means and position detecting means; 44, reticle alignment microscope as measuring means and position detecting means;
5 ... aerial image detection system as measurement means and position detection means,
Reference numeral 53 denotes an image forming characteristic adjustment unit that constitutes a correction unit; 54, a pressure adjustment unit that constitutes a correction unit; 61, an inner aperture stop as a first illumination stop; 62, an outer aperture stop as a second illumination stop; 64: small aperture as an aperture; AX: optical axis of the projection optical system; BLc1, BLc2: diffracted light from the inner mark constituting the first two light beams; BLd1, BLd2: outer mark constituting the second two light beams Diffracted light from BLe
0: 0 from an inner mark constituting one of the first two light beams
Next light, BLe1... One of the primary lights from the inner mark constituting the other of the first two light beams, BLf0... 0th-order light from the outer mark constituting one of the second two light beams, BLf1.
, One of the primary lights from the outer mark constituting the other of the two light beams, EL: exposure light as illumination light, Fhi: position of the image of the inner mark as the position of the image of the pattern, Fho: position of the image of the pattern The position of the image of the outer mark as
p, Mic: inside mark constituting the first pattern, Mo
p, Mop: outer marks constituting the second pattern, PL
... Projection optical system, Pp ... Phase shift unit, Ppi ... Inner phase shift unit forming a part of a plurality of phase shift units, Ppo
... Outer phase shifter constituting a part of a plurality of phase shifters, R ... Reticle as a mask, Rc ... Normal reticle constituting a part of a mask and a converter, Rps ... Phase shift constituting a mask and a converter Reticle, W: wafer as substrate, ΔFh: positional deviation, ψ1, ψ2: diffraction angle.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/30 525W

Claims (7)

[Claims] An aberration measuring apparatus for measuring an aberration of a projection optical system that forms an image of a pattern formed on a mask on an image plane, wherein the aberration generated in an optical axis direction of the projection optical system is measured. An aberration measurement apparatus comprising: a conversion unit configured to convert the position of the image of the pattern in a direction intersecting with the optical axis; and a measurement unit configured to measure the position deviation of the image of the pattern. 2. The conversion means includes a spatial frequency modulation type phase shift mask having a plurality of predetermined patterns provided with a phase shift section for changing a phase of transmitted illumination light, and the phase shift sections are mutually separated. 2. The method according to claim 1, further comprising a plurality of phase shift units for generating a plurality of different phase differences, wherein the measuring unit includes a position detecting unit that detects a position of an image of each of the predetermined patterns formed on the image plane. An aberration measuring device as described in the above. 3. The converting means includes: a plurality of patterns; and a tilt illuminating means for illuminating the mask from a direction tilted with respect to an optical axis of the projection optical system, wherein the tilt illuminating means illuminates the mask. A first illumination stop having an opening at a position decentered from the optical axis of the illumination optical system, and a second illumination stop having an opening at a position symmetrical to the first illumination stop with respect to the optical axis of the illumination optical system. The aberration measurement apparatus according to claim 1, wherein a part of the plurality of patterns is illuminated using a first illumination stop, and the other pattern is illuminated using a second illumination stop. . 4. The plurality of patterns are a first pattern that emits first two light beams having different diffraction angles from each other, and the first two light beams are symmetric with respect to an optical axis direction of the projection optical system. The aberration measurement apparatus according to any one of claims 1 to 3, further comprising a second pattern that emits a second two light beams having a diffraction angle. 5. An aberration measuring method for measuring an aberration of a projection optical system that forms an image of a pattern formed on a mask on an image plane, wherein the aberration generated in an optical axis direction of the projection optical system is determined. An aberration measuring method for converting the image of the pattern in a direction intersecting with the optical axis into a positional deviation and measuring the positional deviation of the image of the pattern. 6. An image of a pattern formed on a mask,
An exposure apparatus configured to project and transfer onto a substrate via a projection optical system, wherein the aberration generated in an optical axis direction of the projection optical system is converted into a positional shift of an image of the pattern in a direction intersecting the optical axis. An exposure apparatus comprising: a conversion unit; a measurement unit configured to measure a displacement of an image of the pattern; and a correction unit configured to correct the aberration based on a measurement result of the measurement unit. 7. A mask used for measuring aberration of a projection optical system that forms an image of a pattern formed on the mask on an image plane, wherein the aberration generated in an optical axis direction of the projection optical system is measured. A conversion unit configured to convert the position of the image of the pattern in a direction intersecting with the optical axis, the conversion unit including a plurality of predetermined patterns provided with a phase shift unit that changes a phase of transmitted illumination light; A mask including a spatial frequency modulation type phase shift mask, wherein the phase shift unit has a plurality of phase shift units that cause a plurality of mutually different phase differences.