JP3221057B2 - Alignment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to alignment of a semiconductor exposure apparatus having a projection lens for transferring a pattern formed on a reticle (mask) onto a wafer.
The present invention relates to an apparatus, and more particularly to an alignment apparatus for performing relative positioning between a reticle and a wafer by using alignment light having a wavelength different from exposure light for transferring a reticle pattern onto a wafer.

[0002]

2. Description of the Related Art Conventionally, an apparatus for aligning a reticle with a wafer by detecting an alignment mark on the wafer through a projection objective lens has been applied on a wafer by alignment light having a wavelength different from exposure light. Care was taken not to expose the resist.

However, since alignment is performed based on alignment light having a wavelength different from that of the exposure light, there is a problem that chromatic aberration is generated by the projection lens. And Japanese Patent Publication No. 1-40490 are proposed. JP
In Japanese Patent Application Laid-Open No. 3-3224, chromatic aberration due to alignment light having a wavelength different from the exposure light is corrected by disposing one correction lens at the center of the optical axis at the entrance pupil position of the projection lens. Thus, the alignment is performed by detecting the ± 1st-order diffracted light from the wafer mark.

In Japanese Patent Publication No. 1-40490, a correction optical system is arranged outside or in an exposure light path between a reticle and a projection lens to correct chromatic aberration caused by alignment light passing through the projection lens. are doing. Then, alignment is performed by detecting a reticle mark image formed on the wafer and the wafer mark via the projection lens.

[0005]

In JP-A-3-3224, a correction lens for correcting chromatic aberration is arranged at the center of the entrance pupil of the projection lens, and this correction lens does not adversely affect the exposure light. It is configured as small as possible. However, in order to improve the alignment accuracy, it is necessary to make the pitch of the wafer mark (diffraction grating) small at the entrance pupil of the projection lens, although it is necessary to make the pitch of the diffraction grating forming the wafer mark finer. The more you do,
Since the interval of ± first-order light as the detection light is widened, there is a defect in principle that the correction lens cannot be reduced in size. As a result, the correction lens becomes so large that it adversely affects the exposure light. Therefore, there is a problem that it cannot cope with higher-precision alignment.

In Japanese Patent Publication No. 1-40490, the longitudinal chromatic aberration of the projection lens is corrected by disposing a correction optical system outside or within the exposure light path between the reticle and the projection lens. Is possible in principle. However, since the alignment light has a longer wavelength than the exposure light, when the image of the wafer mark is viewed through the projection lens, the wafer mark image may enter the exposure area on the reticle due to chromatic aberration of magnification of the projection lens. is there. In this case, the chromatic aberration of magnification of the projection lens can be corrected and the wafer mark image can be shifted to the outside of the exposure area by the parallel flat plate having a variable tilt angle provided outside the exposure optical path between the reticle and the projection lens. It is possible. However, this parallel plane plate shields a part of the exposure, so that this case cannot be dealt with.

A so-called through-the-reticle (TTR) for performing alignment via a reticle and a projection lens.
When a so-called through-the-lens (TTL) method for performing alignment through a projection lens or a so-called through-the-lens (TTL) method is used, light from an alignment mark on a substrate (wafer) is passed through a reflector disposed above or below the reticle. However, if the wafer mark image tends to shift to the inside of the exposure area on the reticle side due to the chromatic aberration of magnification of the projection lens, there is a possibility that the reflector or the like may block a part of the exposure light, The arrangement condition of the alignment optical system becomes severe.

Although the projection lens is sufficiently corrected for chromatic aberration (on-axis chromatic aberration and lateral chromatic aberration) with respect to exposure wavelength light, chromatic aberration (on-axis chromatic aberration and magnification) with respect to alignment light having a wavelength different from that of the exposure light is used. Chromatic aberration)
The design and manufacture of the projection lens becomes more difficult. In particular, in an excimer projection lens that uses an excimer light source as exposure light, it is limited by extremely limited glass materials such as quartz and fluorite.
Moreover, the output of the excimer light source is high, and it is difficult to bond glass materials such as quartz and fluorite due to chromatic aberration, and it is difficult to correct chromatic aberration for alignment light having a wavelength different from that of the exposure light. This made design and manufacturing more difficult.

The present invention has been made in view of the above problems, and has a relatively simple structure.
It is an object of the present invention to provide a high-performance alignment apparatus capable of simplifying the design and manufacture of a projection lens while simplifying the arrangement of an alignment optical system by correcting longitudinal chromatic aberration of a projection lens and controlling lateral chromatic aberration at the same time. .

The chromatic aberration of magnification referred to in the present invention is defined as a lateral direction.
Chromatic aberration, which can pass through the projection lens.
And the same wavelength as the exposure light that forms an image on the Gaussian
By passing off-axis light and passing through the projection lens,
Wavelength different from the exposure light that forms an image at or near the image plane
And the chief rays of both are aligned with the Gaussian image plane
It defines the deviation between the intersection positions
You. The lateral chromatic aberration (lateral chromatic aberration) ΔT is
Image on Gaussian image plane by passing through projection lens
The chief ray of off-axis light of the same wavelength as the exposure light
From the position of intersection at the Gauss image plane
The distance to the optical axis position of the projection objective is δ ₁, Projection len
The Gaussian image plane or
To alignment light of a different wavelength from the exposure light that forms an image before and after
From the intersection of the chief ray at the Gaussian image plane
Up to the optical axis position of the projection objective lens on the Gaussian image plane
Distance δ_TwoΔT = | δ_Two−δ₁Defined by |
It is what is done.

[0011]

In order to achieve the above-mentioned object, the invention according to claim 1 is directed to a method in which a predetermined pattern formed on a reticle is formed on a substrate by exposure light to achieve the above-mentioned object. Provided in an exposure apparatus having a projection lens for transferring, in an alignment apparatus for performing relative positioning between the reticle and the substrate, the alignment light of wavelength light different from the exposure light through the projection lens Light irradiating means for irradiating an alignment mark formed on the substrate, and detecting means for detecting light from the alignment mark via the projection lens, and irradiating light between the reticle and the substrate An irradiation light correcting optical element for generating axial chromatic aberration and lateral chromatic aberration in directions opposite to the axial chromatic aberration and lateral chromatic aberration of the projection lens, and projecting the detection light A detection light correction optical element for generating a magnification chromatic aberration in a direction opposite to the magnification chromatic aberration of the lens, wherein the irradiation light correction optical element is configured to project a virtual image of the alignment mark under the irradiation light by a projection lens. An axial chromatic aberration equivalent to the axial chromatic aberration of the projection lens at the first position projected on the reticle side is generated, and the chromatic aberration of magnification is equal to or greater than the chromatic aberration of magnification of the projection lens at the first position. Generating an amount of light, deflecting an irradiation optical path to a peripheral side of a non-exposure area including a second position where the alignment mark image is projected on the reticle by the projection lens under the exposure light as a boundary, and detecting The light correcting optical element generates a chromatic aberration of magnification equal to or larger than the chromatic aberration of magnification of the projection lens at the first position, and moves toward a peripheral side of a non-exposure area including the second position as a boundary. The Idemitsu path is obtained so as to deflect.

According to another aspect of the present invention, there is provided an exposure apparatus having a projection lens for transferring a predetermined pattern formed on a reticle onto a substrate by exposure light. An alignment apparatus for performing relative positioning between the reticle and the substrate, wherein an alignment light having a wavelength different from the exposure light is applied to an alignment mark formed on the substrate via the projection lens. Irradiating means, and detecting means for detecting light from the alignment mark through the projection lens, between the reticle and the substrate, a direction opposite to the chromatic aberration of magnification of the projection lens with respect to the irradiation light. An irradiation light correction optical element that generates lateral chromatic aberration of magnification, and axial chromatic aberration and magnification of detection light that are opposite to the axial chromatic aberration and lateral chromatic aberration of the projection lens. A detection light correction optical element for generating chromatic aberration, wherein the irradiation light correction optical element is configured to project a virtual image of the alignment mark on the reticle side by a projection lens under the irradiation light. A chromatic aberration of magnification equal to or larger than the chromatic aberration of magnification of the projection lens at the position of, and the second position where the alignment mark image is projected on the reticle by the projection lens under the exposure light is used as a boundary. The detection light correcting optical element deflects the irradiation optical path to the peripheral side of the non-exposure area including the non-exposure area, and generates the same amount of axial chromatic aberration as the amount of axial chromatic aberration of the projection lens at the first position. A chromatic aberration of magnification equal to or greater than the chromatic aberration of magnification of the projection lens at the position of, and deflects the detection optical path to the peripheral side of the non-exposure area including the second position as a boundary. It is.

[0013]

[Operation] An alignment light (laser light) having a wavelength different from the exposure light is irradiated onto an alignment mark (diffraction grating) on a wafer through a projection lens, and the diffraction light from the alignment mark on the wafer is projected onto the projection lens. During detection through the projection lens, axial chromatic aberration and lateral chromatic aberration occur in the projection lens. For this reason, in the present invention, a first optical element that controls lateral chromatic aberration while correcting axial chromatic aberration for one of alignment light for irradiation and alignment light for detection between a reticle and a wafer. And a second optical element for controlling the chromatic aberration of magnification with respect to the other alignment light are provided independently.

This makes it possible to control the chromatic aberration of magnification while correcting the axial chromatic aberration of the projection lens with respect to the alignment light, so that the projection lens does not need to correct the chromatic aberration with respect to the alignment light in principle. And the manufacture becomes much easier. Moreover,
Even if chromatic aberration of magnification exists in the projection lens, the alignment optical path can be arbitrarily deflected to the outside of the exposure optical path, so that the arrangement condition of the alignment optical system can be relaxed.

Further, even when the pitch of the diffraction grating of the wafer mark is made fine and high-precision alignment is performed, the ratio of the correction optical element in the exposure optical path can be greatly reduced in principle. Therefore, there is no adverse effect on the exposure light. Therefore, a fine pattern on the reticle can be faithfully transferred onto the wafer.

[0016]

FIG. 1 is a schematic block diagram of a first embodiment of the present invention. The first embodiment of the present invention will be described with reference to FIG. A reticle (mask) 2 on which a predetermined circuit pattern is formed and a wafer (substrate) 4 are arranged conjugate with respect to a projection lens (projection objective lens) 1 under exposure light. , Are held on a two-dimensionally movable stage (not shown). Although not shown, an illumination optical system is provided above the projection lens 1, and from this illumination optical system, as exposure light,
For example, excimer light (λ = 249 nm: KrF or λ = 193 nm: ArF) uniformly illuminates the reticle 2, and the circuit pattern on the reticle 2 is transferred onto the wafer by the projection lens 1.

Here, the projection lens 1 is configured to be telecentric on the reticle side and the wafer side, and chromatic aberration is well corrected for excimer light as exposure light. On the reticle 2 and the wafer 4, the diffraction grating mark RM _X for alignment, WM _X are formed.

The wafer 4 is adsorbed on a stage (not shown) which moves two-dimensionally in a step-and-repeat manner.
When the transfer exposure of the reticle 2 to one shot area on the wafer 4 is completed, stepping is performed to the next shot position. A part of a reticle stage (not shown) includes an X direction, a Y direction, and a rotation (θ) of the reticle 2 in a horizontal plane.
A movable mirror that reflects a laser beam from a laser light wave interferometer (hereinafter referred to as an interferometer) for detecting a position in a direction is fixed. This interferometer has three laser beams for length measurement for independently detecting the positions in the X, Y, and θ directions, but is not shown here for simplicity. The moving stroke of the reticle stage is several millimeters or less, and the detection resolution of the interferometer is set to, for example, about 0.01 μm.

On the other hand, a moving mirror that reflects a laser beam from an interferometer for detecting the position of the wafer 4 in the X and Y directions in the horizontal plane is also fixed to a part of the wafer stage (not shown). . This interferometer also has two laser beams for length measurement for independently detecting the positions in the X and Y directions, but is not shown here for simplicity. The reticle stage is driven in the X, Y, and θ directions by a drive motor (not shown).
The dimensional movement is also performed by a drive motor independent of the drive motor of the reticle stage.

Next, the alignment system of the exposure apparatus shown in FIG. 1 will be described. The irradiation light for alignment is a laser light source 10 emitting light having a wavelength different from the exposure light, for example, 63.
The luminous flux emitted from a He-Ne laser emitting 3 nm light is
Are each divided into a light beam LB ₁ and the light beam LB ₂ by half mirror 11 as an optical path splitting member. The light beam LB ₁ transmitted through the semi-transmissive mirror 11 passes through a first acousto-optical element 13a (hereinafter, referred to as AOM 13a) as a first light modulator, while
The light beam LB ₂ reflected by the semi-transmissive mirror 11 passes through the reflecting mirror 12 and then passes through a second acousto-optical element 13b (hereinafter, referred to as a second optical modulator).
AOM13b. Through).

Here, the AOM 13a is driven by a high frequency signal having a frequency f ₁ , and the AOM 13b is driven by a frequency f ₂ (f
₂ = f ₁ −Δf). The relationship between the drive frequencies f ₁ and f ₂ and the frequency difference Δf is desirably f ₁ >> Δf, f ₂ >> Δf,
The upper limit of Δf is determined by the responsiveness of an alignment photoelectric detector described later.

Now, via AOM13a and AOM13b
Luminous flux LB₁, LB_TwoAre transmitted light by the semi-transmissive mirror 14, respectively.
Each light flux that is divided into reflected light and reflected by this semi-transmissive mirror 14
LB ₁, LB_TwoAre condensed by the condenser lens 15. This
The light-collecting position of
The quasi-diffraction grating 16 is arranged on the
Fluxes LB such that is Δf₁, LB_TwoBy diffraction
On the grating 16, a flowing interference fringe is formed. And diffraction
Diffracted light passing through the grating 16 is photoelectrically detected by the photoelectric detector 17.
You. The detected reference signal (reference signal) is a diffraction grating
Depending on the period of the light-dark change of the flowing interference fringes formed on 16
It becomes a sinusoidal AC signal (optical beat signal).

On the other hand, two light beams L passing through the semi-transmissive mirror 14
B₁, LB_TwoIs the objective lens 18 for alignment and the reflecting mirror
A reticle provided outside the exposure area of the reticle 2 via
Kulmark RM_XFocused on top. At this time, the reticle
Mark RM_XLuminous flux LB on top ₁, LB_TwoAnd frequency difference Δ
An interference fringe flowing due to f is formed. Reticle mark R
M_XIs the exposure area 2a of the reticle 2, as shown in FIG.
Outside, diffraction with pitch in X direction (measurement direction)
It is composed of a lattice. Also, reticle mark RM_XWhen
A transmissive window WI (hereinafter referred to as a reticle window)
You. ) Is formed.

Therefore, the objective lens 18 of the alignment system
Therefore, the irradiation light LB condensed on the reticle₁, LB_TwoIs
Reticle mark RM_XNot only the reticle window WI
Illuminate in two directions with a certain intersection angle to cover
I will tell. Here, first, reticle mark RM_XThe given exchange
Luminous flux LB illuminated at the difference angle₁, LB_TwoReferring to FIG.
I will explain it. Luminous flux LB₁Is the reticle mark RM_XTo
When irradiated obliquely, the light flux LB_TwoDirection to follow the light path of
Light beam LB (specular reflection direction) ₁0th order optical DB_R1(0) is a dotted line
And the luminous flux LB₁Tracing the light path in reverse
Luminous flux LB in the direction₁Primary light DB_R1(+1) as shown by the dotted line
appear.

On the other hand, the luminous flux LB ₂ has the reticle mark RM _X
When the irradiated obliquely, the direction following the optical path of the light beam LB ₁ Conversely (specular direction) to the light beam LB ₂ of the zero-order light LB _R2 (0) is generated as indicated by the dashed line, also the optical path of the light beam LB ₂ a Conversely, a minus first order light beam LB _R2 (−1) of the light beam LB ₂ is generated as shown by a dashed line. Here, the pitch P _R of the reticle mark RM _X is the wavelength of the alignment light and lambda, when the crossing angle 2 [Theta] _R of the irradiation light _{LB 1, LB 2, sin2θ R} =
It is set so as to satisfy the relation of λ / P _R. 1 and 3, the zero-order light DB _R2 (0) and the + 1st-order light DB _R1 (+1) are shown as the detection light DB _R1 , and the zero-order light DB _R1.
R1 (0) and −1st order light DB _R2 (−1) are shown as detection light DB _R2 .

Returning to FIG. 1, the detection light DB _R1 (the first-order light LB _R1 (+1) and the zero-order light L which follow the optical path of the light beam LB _{1 in} the reverse direction
B _R2 (0)) is again a reflecting mirror 19, an objective lens 18, and a semi-transmitting mirror.
After passing through 13, the light reaches the photoelectric detector 20a provided at a position conjugate with the pupil of the objective lens 18. And this photoelectric detector
Position signal from the reticle mark RM _X (optical beat signal) is detected at 20a. At the same time, the detection light DB follows the optical path of the light beam LB ₂ on the opposite _R2 (-1 order light DB _R2 (-1) 0
The secondary light DB _R1 (0)) again passes through the reflecting mirror 19, the objective lens 18, and the semi-transmissive mirror 14, and then reaches the photoelectric detector 20b provided at a position conjugate with the pupil of the objective lens 18. Then, the position signal from the reticle mark RM _X (optical beat signal) is detected by the photoelectric detector 20b. Here, the photoelectric detector 20
a, at 20b, the position signal of the detected reticle 2 is a sinusoidal AC signal corresponding to the period of dark change of the interference fringes flowing formed on the reticle mark RM _X (optical beat signal).

Next, luminous fluxes LB ₁ and LB ₂ for illuminating reticle window WI provided adjacent to reticle mark RM _X in two directions having a predetermined intersection angle will be described. The luminous fluxes LB ₁ and LB ₂ illuminating the reticle window WI in two directions with a predetermined intersection angle θ _R are, as shown in FIG.
It passes through I as it is and enters the projection lens 3 from off-axis.

Here, the projection lens 3 is sufficiently corrected for chromatic aberration with respect to the exposure light, but is not corrected for the alignment light having a wavelength different from that of the exposure light.
For this reason, on the pupil (entrance pupil) plane P of the projection lens 3, as shown in FIG. 4, the pitches are different from each other along the measurement direction (X direction) passing through the center of the optical axis of the projection lens 3. Three diffraction gratings G _{XA1 to} G _XA3 (correction optical elements) are arranged on a transparent circular substrate 1. Diffraction grating G
_XA3 is on the optical axis Ax ₀ of the projection lens 3, a diffraction grating G _XA1
And G _XA2 are respectively provided symmetrically with respect to the diffraction grating G _XA3 (optical axis of the projection lens 3). Then, the diffraction gratings G _XA1 ~G _XA3 is, G _XA2, G _{XA 3,} the pitch of the diffraction grating in the order of G _XA1 are arranged along the measuring direction (X direction) so as to close. The specific configuration and function of the diffraction gratings G _{XA1 to} G _XA3 (correction optical elements) in this embodiment will be described later in detail.

Now, returning to FIG.
Incident off the axis and reaches the pupil (entrance pupil) of the projection lens.
Irradiation light LB₁, LB_TwoIs the diffraction grating G_XA1Passing
And G _XA2(Irradiation light correction optical element)
θ₁, Θ_TwoIs deflected (diffracted) to correct only
Wafer mark WM formed on Eha 4_xThe given
Irradiate in two directions with crossing angles. Then the wafermer
Ku WM_xOn top, flowing interference fringes are formed. here,
Wafer mark WM_xIs a one shot area as shown in FIG.
Area WM_xX direction on outside street line SL
(Differential direction)
You.

Now, as shown in FIG. 6, the irradiation light LB ₁ , L
By B ₂ irradiates the wafer mark WM _x having a predetermined crossing angle, the irradiation light LB ₁ -1 order light DB _W1 (-1)
And the +1 order light DB _W2 (+1) of the irradiation light LB ₂
Normal direction to the surface (direction parallel to the optical axis of the projection lens 6)
Occurs. Here, the pitch P _W of the wafer mark WM _x
Is the irradiation light LB ₁ , L
When the crossing angle 2 [Theta] _W of B _2, is set so as to satisfy a relation of _{sin θ W = λ / P W} . In FIGS. 1 and 6, the −1st order light DB _W1 (−1) and the + 1st order light DB
And _W2 (+1) are indicated as the detection light DB _W.

[0031] Returning to FIG. 1, the detection light DB _W generated in the normal direction of the wafer mark WM _x (-1 order light LBW ₁ (-1) and + 1st-order light LBW ₂ (+1)) is the projection lens 3 _Travels on the optical path of the principal ray of light, and is corrected by a diffraction grating G _XA3 (detection light correction optical element) provided at the center of the pupil P of the projection lens 6.
After being deflected by _three (diffraction), the photoelectric detector again passes through the reticle window WI, the reflecting mirror 19, the objective lens 18, and the semi-transmitting mirror 14.
Reach 21. Incidentally, the photoelectric detector 21 is provided at a pupil conjugate position of the objective lens 18 (or the projection lens 3), similarly to the photoelectric detectors 20a and 20b described above.

As described above, according to the basic configuration of the first embodiment of the present invention, the reference signal obtained by the photoelectric detector 17 and the position information of the reticle 2 obtained by the photoelectric detectors 20a and 20b are included. A reticle position signal and a wafer position signal including the position information of the wafer 4 obtained by the photoelectric detector 21 are respectively detected. Therefore, the relative positioning between the reticle 2 and the wafer 4 will be described. Photoelectric detector 17
Photoelectric signal (sine wave AC signal) from
Reticle mark RM _X obtained by photoelectric detectors 20a and 20b
A phase difference phi _r the photoelectric signal of the diffracted light from (AC sinusoidal wave signal) detected by the phase detection system (not shown). Similarly, to detect a phase difference phi _w of the photoelectric signal and the basic signal of the diffracted light from the wafer mark WM _x obtained by the photoelectric detector 20 by the phase detecting system. Then, if the difference between the phase differences φ _r and φ _w is obtained, the amount of displacement between the reticle 2 and the wafer 4 in the X direction can be determined.
This detection method is called a so-called optical heterodyne method. If the reticle 2 and the wafer 4 are within a position error range within one pitch of the reticle mark and within one-half pitch of the wafer mark, even in a stationary state. Since the positional deviation can be detected with high resolution, it is convenient to apply a closed-loop position servo so that a minute positional deviation does not occur during the exposure of the pattern on the reticle 2 to the resist on the wafer 4. In this detection method, after phi _r -.phi _w is moving the reticle 2 or the wafer 4 to complete the alignment to be zero (or a predetermined value), subsequently the reticle 2 and the wafer 4 at the alignment position relative Servo lock can be applied to prevent movement.

In this embodiment, during the exposure of the step-and-repeat method, the movement of the wafer stage to each shot area on the wafer is performed based on the measured value of the interference system.
Wafer mark W in the irradiation area of _two light beams LB ₁ and LB ₂
When _Mx is positioned with an accuracy of ± 1/2 pitch, the reticle stage or wafer stage can be servo-controlled by a servo system (not shown) based only on information from a phase detection system (not shown). At this time, the reticle stage and the wafer stage are driven by a DC motor, and the phase difference φ _r
An analog voltage corresponding to -.phi _w produced by D / A converter or the like, the analog voltage can be applied directly as a deviation voltage to the servo circuit of the DC motor. This servo is performed until the exposure of the shot area is completed.

In this case, since the servo is not based on the measurement value of the interferometer, it is possible to reduce the minute fluctuation of the stage due to the fluctuation of the air density in the beam path of the interferometer. Therefore, when phase difference information capable of servo control is obtained from a phase detection system (not shown), the measurement value of the interferometer on the wafer stage side is separated from the servo system on the wafer stage side and applied to the motor of the wafer stage. The voltage is reduced to zero, and the above-described analog voltage is applied to the servo system on the reticle stage side.

In this way, during the exposure operation, the minute fluctuation generated particularly on the wafer stage side is suppressed, and it is possible to make a gentle drift-like fine movement. By moving the reticle stage at high speed, the reticle stage can be moved. It is possible to keep the relative displacement with respect to the wafer almost zero. Therefore, there is no increase in the line width of the exposed pattern and no reduction in resolution, and extremely faithful transfer is achieved.

Incidentally, the two AC signals having the frequency of the interference beat signal obtained by the photoelectric detectors 20a and 20b are the same in terms of the nature of the signals. It may be sent to the system. However, the optical information from the reticle in the present embodiment is 0% of the light fluxes LB ₁ and LB _2.
Since it is created by the interference between the first-order diffracted light and the first-order diffracted light, 1
If the light intensity (light amount) of the next-order light and the zero-order light is largely different, an offset may be generated at the time of measuring the phase difference. Therefore, after passing through an analog circuit that calculates the sum (or difference) of the two signals from the photoelectric detectors 20a and 20b,
It is preferable to measure the phase difference φ _r between the reference signal from the reference signal 17 and the reference signal from the reference signal 17. Of course, a switching type may be used so as to use either one of the two signals from the photoelectric detectors 20a and 20b or a signal obtained by combining the two signals.

Next, the specific configuration and functions of the diffraction gratings G _{XA1 to} G _XA3 (correction optical elements) which are the characteristic configurations of the first embodiment of the present invention will be described.

As shown in FIG. 1, at the pupil position of the projection lens 3, diffraction gratings G _{XA1 to} G _XA3 are arranged along the measurement direction (X direction), but now, diffraction gratings G _{XA1 to} G _XA3. Are not arranged. Projection lens 3
Has been corrected for chromatic aberration for the exposure light,
No chromatic aberration correction is performed on the alignment light having a different wavelength from the exposure light from the laser light source 10. Therefore, the image forming relationship of the light beams LB ₁ and LB ₂ irradiating the position A on the wafer mark WM _{x in} two directions with a predetermined intersection angle with respect to the projection lens 8 will be described.

Now, the projection lens 3 under the alignment light
Given a virtual image of the position A of the wafer mark WM _x being backprojected the reticle side, the irradiation light beam LB _1, LB
The light beam traveling in the opposite direction through the optical path ₂ and the irradiation light beam L
Optical path D of detection light (diffraction light) obtained by B ₁ and LB ₂
Rays traveling through B _W, as shown by the dotted line, the projection lens 3
Intersect at a position above B ₁ of the reticle 2 by chromatic aberration due to a virtual image of a position A in the wafer mark WM _x This intersection is formed.

On the other hand, under the exposure light, the projection lens 3
Wafer mark WM projected back to reticle side_xPosition A
Considering the image of the wafer mark WM_xImage is position B
₀Formed. Therefore, the wafer mark W by the exposure light
M_xPosition B of the image₀In the Z direction (projection lens
In the optical axis direction), the axial chromatic aberration of the projection lens 3 (hereinafter, referred to as the chromatic aberration).
It is simply referred to as axial chromatic aberration. ) Occurs by ΔL,
X direction (optical axis Ax of projection lens 3) ₀In the direction perpendicular to
Is the chromatic aberration of magnification of the projection lens 3 (hereinafter simply referred to as chromatic aberration of magnification).
Called. ) Occurs to the exposure region side by ΔT.

However, the chromatic aberration of magnification (lateral chromatic aberration) ΔT
As shown in FIG. 1, the principal ray of the off-axis light having the same wavelength as the exposure light that forms an image on the Gaussian image plane (reticle 2) by passing through the projection lens 3 is reflected on the Gaussian image plane (reticle 2). The distance from the crossing position B ₀ to the optical axis position o of the projection objective lens 3 on the Gaussian image plane (reticle 2) is δ ₁ , and the Gaussian image plane (reticle 2) by passing through the projection lens 3 or the projection objective from intersection B ₁ on the Gaussian image plane (reticle 2) of the principal ray in another wavelength of alignment light and exposure light image before and after this crossing by the Gaussian image plane (reticle 2) When the distance to the optical axis position o of the lens 3 is δ ₂ , Δ
T = | δ ₂ −δ ₁ |.

[0042] Therefore, the vibration or inclination of the alignment optical system by axial chromatic aberration becomes large detection error, highly accurate and stable not only can not or to achieve alignment, the reticle which is provided adjacent to the reticle mark RM _X The window WI must be enlarged. Further, since the position B ₁ is shifted to the left (toward the exposure area) from the position B ₀ by ΔT due to the chromatic aberration of magnification, the reticle 2
When viewed from above, the intersection B ₁ represents intrudes into the exposure area of the reticle. As a result, the wafer mark W
Taken out of alignment light from the M _X becomes difficult.

In order to overcome the above-described problems, the present invention first provides a function of simultaneously correcting axial chromatic aberration (ΔL) and chromatic aberration of magnification (ΔT) with respect to irradiation light (LB ₁ , LB ₂ ). The diffraction gratings G _XA1 and G _XA2 (irradiation light correcting optical elements) are provided at positions symmetric with respect to the center of the pupil (entrance pupil) plane of the projection lens. The diffraction gratings G _XA1 and G _XA2 (irradiation light correcting optical elements) are formed to have mutually different pitches. Accordingly, the irradiation light LB ₁ directed to the wafer mark WM _X is deflected by the correction angle θ ₁ by being diffracted by the diffraction grating G _XA1 , and the irradiation light LB ₂ directed to the wafer mark WM _X is also converted to the diffraction grating G _XA2. Are deflected by the correction angle θ ₂ . However, the relationship between the correction angles is θ ₂ <θ ₁ .

As a result, the optical paths of the irradiation light LB ₁ and the irradiation light LB ₂ are corrected, so that the irradiation light LB ₁ and LB ₂ have a predetermined intersection angle not only on the reticle window WI but also on the wafer mark WM _X. Intersect with the state maintained. Therefore, the conjugate relationship between the reticle 2 and the wafer 4 is apparently maintained with respect to the projection lens 3 with respect to the irradiation light (LB ₁ , LB ₂ ) having a different wavelength from the exposure light.

Further, the center position of the pupil plane P of the diffraction grating G _XA3 (detection light correction optical element) is the projection lens 3 so as to correct the lateral chromatic aberration ([Delta] T) with respect to the diffracted detection beam DB _W from the wafer mark WM _X It is provided in. Thereby, the detection light DB _W from the wafer mark WM _X which travels through optical path of the principal ray of the projection lens 3 toward the reticle window WI
Is the correction angle θ by being diffracted by the diffraction grating G _XA3 .
Deflected by _three . As a result, the optical path of the detection light DB _W is corrected, the detection light DB _W is incident to the reticle window WI vertically in a state in which telecentricity is maintained,
The light passes through the intersection of the irradiation lights LB ₁ and LB ₂ at the reticle window WI, travels along the optical axis of the alignment objective lens 19, and finally reaches the photoelectric detector 21. Note that the relationship between the correction angles is θ ₂ <θ ₃ <θ ₁ .

As described above, each alignment light is corrected so that chromatic aberration (axial chromatic aberration and chromatic aberration of magnification) of the projection lens 3 is _{properly corrected by} the diffraction action of the diffraction gratings G _{XA1 to} G _XA3 as correction optical elements. Are deflected by predetermined angles (correction angles) θ ₁ , θ ₂ , and θ _3, respectively. Thereby, the problem of entering the exposure area of the reticle 2 due to the chromatic aberration of magnification of the projection lens 3 and the problem of axial chromatic aberration can be solved. It is possible to realize a high-performance alignment device capable of achieving a remarkable improvement in the degree of freedom.

Here, a diffraction grating G as a correction optical element
_XA1~ G_XA3Pitch of P _XA1, P_XA2, P
_XA3And the wavelength of the alignment light is λ_aAnd when
The following relationship holds between the conformal angle and the pitch of each diffraction grating
You. P_XA1= Mλ_a/ Sin θ₁... (1) P_XA2= Mλ_a/ Sin θ_Two..... (2) P_XA3= Mλ_a/ Sin θ_Three(3) where m is the order (integer) of the diffracted light.

[0048] Thus, the correction angle theta ₁ by the diffraction grating _{G XA1 ~G XA3, θ 2,} θ 3 is, as is clear from FIG. 1, theta ₂
<Θ ₃ <θ ₁ , and the above formula (1)
From the equation (3), the pitch of the diffraction gratings G _{XA1 to} G _XA3 is P
_XA2> and has a relationship of P _XA3> P _XA1. Therefore, in the present embodiment, as shown in FIG. 2, the pitch of the grating is configured to be dense in the order of the diffraction grating G _XA2, diffraction gratings G _XA3, diffraction grating G _XA1.

[0049] Also, a transparent circular substrate 1 is formed.
Grating G as correction optical element _XA1~ G_XA3The stone
Etching the substrate 1 made of a material such as British glass
It is constituted so that it may become a type diffraction grating. At this time, Ara
The diffraction efficiency of m-order diffracted light that deflects the optical path
The step d of the phase type diffraction grating is
Wavelength of λ_aAnd the alignment wavelength of the substrate
Refractive index is n_a, And an integer m, d = (2m + 1) λ_a/ 2 (n_a-1) It is desirable to configure so as to satisfy (4).

In this case, the diffraction grating is also capable of
Diffraction has an adverse effect on the imaging function of the projection lens 3
May be affected. Therefore, on the diffraction grating,
Wavelength classification that reflects light and transmits alignment light
It is more preferable to form a functional thin film by evaporation or the like.
Good. Also, the diffraction efficiency for alignment light is slightly
Although it decreases, the diffraction efficiency for exposure light is reduced to almost zero.
In order to achieve this, the step d of the phase type diffraction grating makes the wavelength of the exposure light λ
_eAnd the refractive index of the substrate with respect to the exposure light is n_eAnd the integer m
Then, d = λm_e/ (N_e-1) It is desirable to configure so as to satisfy (5).

As described above, in the first embodiment of the present invention, the irradiation light LB for irradiating the wafer mark WM _X in two directions is provided.
_1, the diffraction grating for correcting the axial chromatic aberration and lateral chromatic aberration of the projection lens 3 to LB ₂ G _XA1, and G _XA2, to correct the lateral chromatic aberration of the projection lens 3 to detect light DB _W from the wafer mark WM _X Projection objective lens 3 with diffraction grating G _XA3
Pupil position or on the same plane near the pupil position.

Therefore, if the wafer mark WM is temporarily_XPosition of
In the direction (Y direction) perpendicular to the measurement direction (X direction)
Washi mark WM_XArai to break
When the optical system is moved in the Y direction,
By using a reticle with an exposure area size
Reticle mark RM on tickle_XAnd reticle window WI
When the position moves in the measurement direction (X direction),
Irradiation light LB for alignment₁, LB_TwoAnd wafer
WM_XDetection light DB from_WIs the pupil of the projection lens 3
It is the principle that the position passing through the (entrance pupil) position is not changed
It is possible. Therefore, the correction optical element in the present embodiment
Child G_XA1~ G_XA3Is the wafer mark WM _XChange
And reticles of different sizes
It is possible to respond.

Also, a diffraction grating G as a correction optical element
_XA1~ G_XA3Is the irradiation light LB₁, LB _TwoAnd detection light DB_W
Is formed only at the part that passes through the pupil position of the projection lens.
Good. Therefore, the diffraction grating G as a correction optical element_XA1
~ G_XA3Has a negligible effect on the exposure light,
Minimize the proportion of the projection lens in the pupil plane
In principle.

Further, a higher precision alignment is performed.
In order to save the wafer mark WM_X(Diffraction grating) pitch
Finer reticle mark RM_XAnd wafer mark W
M_XLight LB for irradiating light from two directions₁, LB_TwoIntersection of
The angle increases, but in this case,
Irradiation light LB between objective lens 18 and AOM 13a₁Light of
Lens and AOM in path and alignment optics
Illumination light LB between 13b _TwoVariable intersection angle means in the optical path of
The parallel flat plates whose tilt angle is variable
By changing the tilt angle of the face plate, the intersection angle can be made variable
It becomes possible. At this time, the light passes through the pupil plane P of the projection lens 3.
Irradiation light LB₁, LB_TwoIs measured in Fig. 1.
Since it changes in the direction (X direction), an auxiliary
Replaceable with another transparent circular substrate with positive optics
You may.

[0055] In order to simplify the explanation in this embodiment, an example is shown to align the X-direction, was Tonaria' the unexposed regions and the reticle mark RM _X and the reticle window WI are provided Needless to say, if a reticle mark having a pitch in the Y direction and a reticle window adjacent to the reticle window are provided in the non-exposure area and a second alignment optical system is provided above them, alignment in the Y direction can be performed. At this time, the diffraction grating as a correction optical element has Y
A diffraction grating similar to the diffraction gratings G _{XA1 to} G _XA3 may be provided along the direction.

Further, in this embodiment, the irradiation light LB ₁ , L
Diffraction gratings G _XA1 -G corresponding to B ₂ and detection light DB _W
Are provided _XA3, but each with progressively Umate and with different pitches, the reticle position conjugate with _one individual irradiation light LB, LB ₂ and the detection light DB _W along the pitch direction in each diffraction grating A configuration for condensing light may be adopted. This configuration can be employed in each of the embodiments described below. Next, a second embodiment according to the present invention will be described with reference to FIG. 7 to 10, members having the same functions as in the first embodiment are denoted by the same reference numerals. FIG. 7A shows a state of alignment light passing through the projection lens 3 when the projection lens 3 is viewed from the XZ plane side parallel to the X direction (meridional direction), and FIG. )
Is the direction perpendicular to FIG. 7A, that is, the measurement direction (Y
(Direction or sagittal direction) when the projection lens is viewed from the YZ plane side parallel to the projection lens 3.

[0057] The reticle window WI adjacent to the wafer mark WM _Y and its diffraction grating on the reticle 2 in the second embodiment, as shown in FIG. 8, as compared with those of the first embodiment,
Although provided outside the same exposure area 2a, the arrangement direction (the pitch direction) of the diffraction grating of the wafer mark WM _Y has a Y-direction orthogonal to the first embodiment. That is, this embodiment shows an example in which the Y direction is set as the measurement direction.

Although not shown, above the reticle 2,
Reticle mark RM_YAnd wafer mark WM_YIrradiation
Of the same configuration as in the first embodiment for detecting
G optical system is provided. Also, the pupil of the projection lens (input
Diffraction grating as correction optical element
G _YA1, G_YA2, G_YA3Transparent circular substrate 1 having
The top is provided. And, as an irradiation light correction optical element,
Diffraction grating G_YA1, G_YA2In the measurement direction (Y direction)
Along the pupil center so that they face in opposite directions.
Diffraction grating as a detection light correction optical element
Child G_YA3Has a pitch in the non-measurement direction (X direction)
It is formed at the center of the pupil.

The irradiation on the reticle mark RM _Y and the wafer mark WM _Y and the detection by the diffracted light therefrom are the same as those in the first embodiment, and the description is omitted. Now, in the present invention, as shown in FIG. 7B, two irradiation lights LB ₁ and LB ₂ from the alignment optical system are
When the reticle window WI is irradiated in two directions having a predetermined intersection angle, the correction angles θ ₁ are set in opposite directions by the diffraction effect of the diffraction gratings G _YA1 and G _YA2 formed on the pupil plane P of the projection lens 3. only being deflected, so that the irradiated on the wafer mark WM _Y at two predetermined directions. Here, as shown in FIG. 10, the wafer mark WM _Y is formed on the street line SL outside the one shot area 4a on the wafer, and in the Y direction to measure the position of the wafer 4 in the Y direction. It has a pitch.

The diffracted light DB _W generated in the direction normal to the wafer mark WM _Y is not shown via a diffraction grating G _YA3 provided at the center of the pupil plane P of the projection lens and a reticle window WI. Reaches the detection system of the alignment optical system as shown in FIG. On the other hand, in the direction perpendicular to FIG.
As shown in FIG.
The two irradiation lights LB ₁ and LB ₂ enter the projection lens 3 from off-axis so as to travel on the same optical path, and
To the center of the pupil plane P. In this position, the diffraction grating G
_YA1, G _YA2, since G _YA3 is being arranged along the measuring direction (Y-direction), in the FIG. 7 (a), the looks like these were provided in the same position, the irradiation light LB _1, LB
₂ is deflected by the correction angle θ ₂ by the diffraction gratings G _YA1 and G _YA2 , and irradiates the off-axis wafer mark WM _Y vertically. The diffraction light DB _W for detection generated in the vertical direction from the wafer mark WM _Y is again deflected by the correction angle θ ₂ by the diffraction grating GXA ₃ provided at the center of the pupil plane of the projection lens, and the reticle window WI , Reaches a detection system of an alignment optical system (not shown).

As described above, the diffraction gratings G _YA1 and G _YA2 functioning as irradiation light correcting optical elements are arranged in the measurement direction (Y direction).
When viewed from the YZ plane side parallel to, the irradiation light LB ₁ , L
B ₂ correction angle theta ₁ only to deflect the which A when viewed from the X direction parallel to the XZ plane side at the same time, has a function of deflecting by a correction angle theta _2. In other words, the diffraction gratings G _YA1 and G _YA2 correct the irradiation light LB ₁ and LB ₂ on the Y direction (measurement direction) side so as to correct the axial chromatic aberration ΔL of the projection lens 3. only ₁ is deflected, this and to correct lateral chromatic aberration ΔT of the projection lens 3 at the same time,
In the X direction, the irradiation lights LB ₁ and LB ₂ are deflected by the correction angle θ ₂ .

[0062] The diffraction grating G _YA3 functioning as the detection light correcting optical element, so as to correct the magnification chromatic aberration ΔT of the projection lens 3, and is deflected by a correction angle theta ₂ of the detection light DB _W in the X direction. Next, explaining the arrangement of the diffraction grating _{G YA1, G YA2, G YA} 3 as the correction optical element in the present embodiment. The diffraction grating G _YA1 ,
G _YA2 and G _YA3 are different from the first embodiment in that the arrangement direction is the Y direction, and that the pitches of the diffraction gratings G _YA1 and G _YA2 as the irradiation light correcting optical element are equal. The point is that the arrangement directions of both lattices are inclined in directions opposite to each other. This irradiation light LB _1, LB _2, the correction angle theta ₁ with each other in opposite directions in the Y-direction (measuring direction) side
This is for deflecting only by the correction angle θ ₂ on the X direction side.

[0063] Here, the diffraction grating G _YA1 ~G pitch of _YA3 and P _YA1, P _YA2, P _YA3 respectively, the wavelength of the alignment light lambda _a, the diffraction grating with respect to the Y direction G _YA1 G _YA2
Is the inclination of θ ₄ , the following relationship is established between the correction angle and the pitch of each diffraction grating. tan θ ₄ = sin θ ₂ / sin θ ₁ (6) P _YA1 = P _YA2 = mλ _a cos θ ₄ / sin θ ₁ (7) P _YA3 = mλ _a / sin θ ₂ (8) where m is the diffraction order (integer).

As in the first embodiment, the diffraction gratings G _{YA1 to} G _YA3 of the correction optical element in this embodiment are also different from the projection lens 3.
Are arranged on the pupil (entrance pupil) plane P, the size of the pupil plane P can be made extremely small with respect to the size of the pupil plane P, so that the influence on the exposure light can be ignored. However, it is desirable that the steps of these gratings satisfy the above condition (4) or condition (5).

As described above, in the second embodiment, similarly to the first embodiment, the optical paths of the irradiation light and the detection light are independently controlled so as to correct the chromatic aberration (axial chromatic aberration and chromatic aberration of magnification) of the projection lens 3. Therefore, the same effects as in the first embodiment can be achieved. In order in the second embodiment to simplify the explanation, an example is shown for alignment in the Y direction, the non-exposure Tonaria' the unexposed regions and the reticle mark RM _Y and the reticle window WI are provided X in area
Obviously, if a reticle mark having a pitch in the direction and a reticle window adjacent to the mark are provided, and a second alignment optical system is provided above the reticle mark, alignment in the X direction can be performed. At this time, the diffraction grating as a correction optical element is provided along the X-direction with the diffraction gratings G _{YA1 to} G _{YA1 to
What} is necessary is just to provide the diffraction grating similar to _YA3 .

Next, a third embodiment according to the present invention shows an example in which the correction optical elements of the first embodiment and the second embodiment are combined, and will be described with reference to FIG. As shown in FIG. 11, the reticle 2 has a reticle mark RM _XA for detection in the X direction, a reticle mark RM _YA for detection in the Y direction, and a reticle window WI provided adjacent _thereto outside the exposure region 2a. _It has a first reticle mark group consisting of 1.

On the other hand, this reticle 2 has reticle marks RM _XB , Y for detection in the X direction outside the exposure area 2 a facing this first reticle mark group (RM _XA , RM _YA , WI ₁ ). and a second reticle mark group consisting of the reticle window WI ₂ provided adjacent to the direction of the reticle mark RM _YB for detection and these. Although not shown, two first and second alignment optical systems for irradiating each mark group with alignment light are provided corresponding to each mark group. Here, a first alignment optical system (not shown) will be described based on FIG. 1 of the first embodiment. First, in order to obtain two-dimensional position information in the XY directions with respect to the reticle 2 and the wafer 4, first, Another set of AOMs is arranged in a direction orthogonal to the paper surface of FIG. 1, and is configured to divide a light beam from the laser light source 10 into four and guide each light beam to two sets of AOMs. Then, each of the AOMs has a predetermined crossing angle with respect to the first reticle mark group via the semi-transmissive mirror 14, the objective lens 18, and the reflecting mirror 19, for two sets of irradiation lights having optical frequencies mutually. Irradiated in four directions. On the other hand, the detection system (20a, 20b, 21) shown in FIG. 1 has a configuration as shown in FIG. 12 in this embodiment. The photoelectric detectors 20a and 20b are X
The detection light from the reticle mark RM _XA for direction detection, the photoelectric detector 20c and 20d are configured to detect the detection light from the reticle mark RM _YA for Y-direction detection, respectively. The photoelectric detector 21a detects the detection light from the wafer mark WM _XA for X-direction detection as shown in FIG. 14, and the photoelectric detector 21b detects the detection light from the wafer mark WM _YA for Y-direction detection as shown in FIG. Is configured.

Note that the second alignment optical system is also a first alignment optical system.
The configuration is the same as that of the alignment optical system.
In Ax₁Is the optical axis of the first alignment optical system,
Ax _TwoIndicates the optical axis of the second alignment optical system, respectively.
are doing. Now, the irradiation light from the first alignment optical system
LB_XA1, LB_XA2Is the reticle mark RM_XAAgainst
Cover the first reticle mark group so as to have a predetermined intersection angle.
Irradiated in a bar, also the first alignment optics
Light LB from the system_YA1, LB_YA2Is the reticle mark
RM_YAThe first reticle has a predetermined intersection angle with respect to
Is applied so as to cover the mark group. At this time,
Light LB_XA1, LB_XA2Plane and irradiation light LB_YA1,
LB_YA2Are perpendicular to each other.

Then, the diffracted light from each reticle mark RM _XA following the reverse optical path of each irradiation light LB _XA1 and LB _XA2 , and the diffraction from each reticle mark RM _YA following the reverse optical path of each irradiation light LB _YA1 and LB _YA2. As shown in FIG. 12, light is incident on a pupil (entrance pupil) of an objective lens in an unillustrated alignment optical system.
Photoelectric detectors (20a, 20b, 20c, 20
By detecting at d), two-dimensional position information of the reticle 2 in the X and Y directions can be obtained.

On the other hand, irradiation from the second alignment optical system
Light LB_XB1, LB_XB2Is the reticle mark RM_XBAgainst
The second reticle mark group so as to have a predetermined intersection angle
Irradiated to cover, also the second alignment light
Irradiation light LB from academic system_YB1, LB_YB2Is a reticle mer
KRM_YBThe first retic so that it has a predetermined intersection angle
Irradiation is performed so as to cover the mark group. At this time,
Irradiation light LB_XB1, LB _XB2Plane and irradiation light L
B_YB1, LB_YB2Are perpendicular to each other.
And each irradiation light LB_XB1, LB_XB2Follow the back light path of each
Reticle mark RM_XBLight and each irradiation light LB
_YB1, LB_YB2Reticle mark RM following the back light path of_YB
As shown in FIG. 12, the diffracted light from
At the position conjugate with the pupil of the objective lens in the
Of the reticle 2 with the photoelectric detectors (20a, 20b, 20c, 20d)
Two-dimensional position information in the XY directions is detected.

Now, the reticle window WI₁Irradiation light passing through
LB_XA1, LB_XA2And irradiation light LB _YA1, LB_YA2Is
The light reaches the pupil plane P of the projection lens (not shown). At the same time,
Reticle window WI_TwoLight LB that has passed through_XB1, LB_XB2
And irradiation light LB_YB1, LB_{YB Two}Also not shown projection lens
To the pupil plane P. FIG. 13 shows the pupil plane P of the projection lens.
As shown in FIG.
So that the diffraction grating as the optical element is symmetric with respect to the pupil center
Are formed in parallel along the X and Y directions.

Then, the diffraction grating G_XA1, G_XA2Is the first
As in the embodiment, the axial chromatic aberration and the lateral chromatic aberration of the projection lens are reduced.
Irradiation from the first alignment optical system so as to correct
Light LB_XA1, LB_XA2And deflect each,
Diffraction grating G_XB1, G_XB2In the same manner as in the first embodiment,
To correct the axial chromatic aberration and the lateral chromatic aberration of the lens.
Light LB from the alignment optical system_XB1, LB_XB2
Are respectively deflected. Also, the diffraction grating G_YA1, G_YA2
Represents the axial chromatic aberration and magnification of the projection lens as in the second embodiment.
The first alignment optical system is used to correct chromatic aberration.
Irradiation light LB _YA1, LB_YA2When each is deflected
In both cases, diffraction grating G_YB1, G_YB2Is also the same as in the second embodiment.
To correct axial chromatic aberration and chromatic aberration of magnification of the projection lens
The irradiation light LB from the second alignment optical system_YB1,
LB_YB2Have the function of deflecting the respective light.

Here, irradiation light (LB _XA1 , LB) for detecting the X direction from the first and second alignment optical systems is used.
_XA2 , _LBXB1 , _LBXB2 ), the relationship between each diffraction grating having a deflection function and the pitch is as follows: the pitch of the diffraction grating G _XA1 is GP _XA1, and the pitch of the diffraction grating G _XA2 is G.
P _XA2, pitch GP _XBl diffraction grating G _XBl, when the the GP _XB2 pitch of the diffraction grating G _{XB 2,} becomes as follows.

GP _XA1 (= GP _XB1 ) <GP _XA2 (= GP _XB2 ) (9) Irradiation light for detecting the Y direction from the first and second alignment optical systems ( LB _YA1 , LB _YA2 , L
The pitch directions of the diffraction gratings having a deflecting function with respect to B _YB1 and LB _YB2 ) are inclined in directions opposite to each other with respect to the pupil center of the projection lens.

Accordingly, by arranging the diffraction grating as the irradiation light correcting optical element as shown in FIG. 13, the optical path of the irradiation light from each alignment optical system is corrected, and each wafer mark formed on the wafer is adjusted to a predetermined position. Irradiation is performed in two directions. That is, as shown in FIG. 13, the irradiation lights LB _XA1 and LB _XA2 from the first alignment optical system irradiate the wafer mark WM _XA in two directions, and the irradiation lights LB _YA1 and LB from the first alignment optical system. _YA2 irradiates wafer mark WM _YA in two predetermined directions. As a result, of the diffracted light from each of the wafer marks WM _XA and WM _YA , the diffracted light for detection goes to the center of the pupil of the projection lens.

On the other hand, the illumination from the second alignment optical system
Light LB_XB1, LB_XB2Is the wafer mark WM_XBIrradiate
And the irradiation light LB from the second alignment optical system_YB1,
LB _YB2Is the wafer mark WM_YBIrradiates in two predetermined directions
I do. Thereby, each wafer mark WM_XA, WM_YAOr
Among these diffracted lights, the diffracted light for detection is the pupil center of the projection lens
Head to.

At the center of the pupil of the projection lens, as shown in FIG. 13, a diffraction grating G ₃ as a detection light correcting optical element having a pitch in the X direction is provided.
_3, so as to correct the chromatic aberration of magnification of the projection lens, the wafer mark WM _XA, and the diffracted light for detecting from the WM _YA, wafer marks WM _XA, and the diffracted light for detecting among the diffracted light from WM _YA Is deflected and guided to each alignment optical system. Accordingly, as shown in FIG. 12, these detection lights are two-dimensionally moved in the XY directions of the wafer mark by photoelectric detectors (21a, 21b) provided at the pupil conjugate of the objective lens of each alignment optical system (not shown). Location information is detected.

As described above, in the third embodiment, similarly to the first and second embodiments, the optical paths of the irradiation light and the detection light are corrected so as to correct the chromatic aberration (axial chromatic aberration and chromatic aberration of magnification) of the projection lens 3. Because it can be controlled independently, the first and second
The same effect as that of the embodiment can be achieved. Note that, also in the present embodiment, each diffraction grating (G _XA1 , G _XA2 , G _XB1 , G _XB2 ) as the correction optical element is set to _satisfy the above-mentioned step condition (4).
Alternatively, it is desirable to satisfy the condition (5).

Next, a fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, the position of the diffraction grating G _XA3 is placed in the diffraction grating G _XA1, G _XA2 and detecting light correcting optical element of the irradiation light correcting optical element is the same as the first embodiment, the pitch of the diffraction grating It is configured smaller than that of the first embodiment, thereby deflecting the irradiation light path and the detection light path further out of the exposure area.

Here, B in FIG.₁Is Arai
Wafer mark WM under _XPosition A above is projected
The position where the image is virtually formed by the lens 3 (the axial chromatic aberration and
A state in which chromatic aberration of magnification occurs), B₀Is under the exposure light
Wafer mark WM_XThe upper position A is connected by the projection lens 3.
Image position (state in which chromatic aberration does not occur), B_TwoIs
While correcting the axial chromatic aberration of the projection lens 3, the magnification
When the chromatic aberration is excessively corrected, the wafer mark WM is_X
The upper position A is a position where an image is formed by the projection lens 3.
You.

In the first to third embodiments described above,
Diffraction grating G _XA3 of the diffraction grating G _{XA 1,} G _XA2 and detecting light correcting optical element of the irradiation light correcting optical element is both have to deflect the irradiation light and the detection light so as to correct the chromatic aberration of magnification,
In the fourth embodiment, the diffraction gratings G _XA1 and G _XA2 of the irradiation light correction optical element and the diffraction grating G of the detection light correction optical element
_XA3 emits light LB ₁ , LB so as to generate a magnification chromatic aberration amount ΔT ′ equal to or larger than the magnification chromatic aberration amount ΔT of the projection lens 3.
₂ that deflects the detection light beam DB _W. That is, the diffraction gratings G _XA1 and G _XA2 of the irradiation light correction optical element generate an axial chromatic aberration amount equivalent to the axial chromatic aberration amount ΔL of the projection lens 3 (correct the axial chromatic aberration of the projection lens 3), and
Magnification chromatic aberration ΔT equal to or larger than magnification chromatic aberration ΔT of projection lens 3
In order to generate T ′ (excessively correcting the chromatic aberration of magnification of the projection lens 3), the irradiation lights LB ₁ and LB ₂ are respectively corrected to the positions B ₂ outside the exposure area on the reticle at the correction angles θ ₁ ′ and θ. It is deflected by ₂ '. Also, the diffraction grating G _XA3 of the detection light correction optical element reticle-detects the detection light DB _W so as to generate a magnification chromatic aberration amount ΔT ′ equal to or larger than the magnification chromatic aberration amount of the projection lens (excessively correcting the magnification chromatic aberration of the projection lens). The correction angle θ to the position B ₂ outside the exposure area above
₃ 'has only deflected.

[0082] Thus, it is possible to provide the more exposed areas outside the reticle mark RM _X and the reticle WI, reflecting mirror 18 for deflecting the alignment light path can mitigate the arrangement conditions for not shielding the exposed area . Further, this embodiment has the following advantages. The through-the-reticle (TTR) system, provided with a reticle mark RM _X on the reticle very close to the circuit pattern area, provided the wafer mark WM _X on the wafer in the shot area (for example, street line within ST),
A die-by-die (D / D) alignment method in which the alignment position and the exposure position are matched can be easily realized.
In this case, when the alignment mark WM _X on the wafer, although the resist of the photosensitive does not occur at the time of exposure, exposure light through the reticle window for taking out the alignment light from the wafer mark WM _X is the mark on the wafer May be exposed. As a result, when passed through a process after the development, the wafer mark WM _X is destroy anything, the next exposure step, it may not be able to use the mark.

[0083] In contrast, in the fourth embodiment, by providing the more exposed areas outside the reticle window WI becomes theoretically possible, it is the protection of the wafer mark WM _X. The fourth
In the embodiment, since the correction optical element is provided on the pupil plane of the projection lens, it is needless to say that the same effects as those of the first to third embodiments can be achieved. Further, also in this embodiment, each diffraction grating (G _XA1 , G
_XA2, G _XA3) preferably satisfies the conditions of the step of the condition (4) or the condition (5).

Next, a fifth embodiment of the present invention will be described with reference to FIG. A light beam from a laser light source 30 that emits light having a wavelength different from the exposure light is reflected by a reflecting mirror 31, an objective lens 32,
The light is obliquely incident on the reticle 2 via the reflecting mirror 33. On reticle, as shown in FIG. 17, the reticle window WI, diffraction grating G _R of the transmission type provided adjacent are provided therewith. Also, between the reticle 2 and the projection lens 3,
As shown in FIG. 18A, a circular transmission-type substrate 1a on which a diffraction grating G _{XA11 of} an irradiation light correction optical element is formed is arranged. As shown in (b), the diffraction grating G of the detection light correcting optical element
A circular transmission type substrate 1b formed along the X direction is arranged so that _XA12 and G _XA13 are symmetrical with respect to the center of the pupil.

Now, the light beam LB from the laser light source 30 is
Through a reticle window WI on the reticle, by the diffraction grating G _XA11 of the irradiation light correcting optical element, so as to generate a magnification chromatic aberration amount [Delta] T 'above lateral chromatic aberration of the projection lens, it is deflected by a correction angle theta _11. Then, through the pupil center of the projection lens 3 and illuminates the wafer mark WM _X formed on the wafer 4 vertically. The ± first-order diffracted lights DB (+1) and DB (−1) generated from the wafer mark reach the pupil plane P of the projection lens 3 respectively. Then, the diffraction gratings G _XA12 and G _XA13 of the detection light correction optical element _generate the axial chromatic aberration ΔL and the lateral chromatic aberration ΔT equivalent to the axial chromatic aberration ΔL and the lateral chromatic aberration ΔT of the projection lens 3 ( The + 1st-order diffracted light DB (+1) and the -1st-order diffracted light DB (−) correct the axial chromatic aberration and the lateral chromatic aberration of the projection lens 3).
1) are deflected by correction angles θ ₁₂ and θ ₁₃ , respectively. After that, the + 1st-order diffracted light DB (+1) and the -1st-order diffracted light DB (-1)
The irradiated onto the diffraction grating G _R of the transmission type formed on the reticle 2 in the predetermined two directions, it is diffracted by the diffraction grating G _R. Then, + 1 by irradiation of order diffracted light DB and (+1) -1-order diffracted light DB (-1), the reflector while diffracted light each other interfere with each other occurring in the normal direction of the diffraction grating G _R
33, photoelectrically detected by a photodetector 34 via an objective lens 32.

Here, the position of the wafer 4 is detected by scanning a wafer stage on which the wafer 4 (not shown) is mounted, so that the photodetector 34 can obtain an intensity signal corresponding to the position of the wafer 4. The positioning of the wafer is achieved by detecting the intensity signal. As described above, in the present embodiment, the amount of chromatic aberration of magnification generated by the diffraction grating G _XA11 of the irradiation light correction optical element and the diffraction gratings G _XA12 and G _{XA13 of the} detection light correction optical element is made different. Light and detection light can be easily separated.

In this embodiment, as in the first to fourth embodiments, diffraction gratings G _{XA11 to} G _{XA11 to} G _{XA11 to} G _XA as correction optical elements are used.
_XA13 since the irradiation light LB _1, LB ₂ and the detection light DB _W may be formed only in a portion that passes through the diffraction grating G _XA11 ~G _XA13 as correcting optical element can hardly ignore the influence on the exposure light In principle, it becomes possible in principle to make the ratio of the projection lens occupying the pupil plane extremely small. Further, it is more preferable that the diffraction gratings G _{XA11 to} G _{XA13 satisfy} the condition (4) or the condition (5) of the step.

In the first to fourth embodiments, the target mark is irradiated with diffracted light beams having different optical frequencies in two directions, and the beat interference light diffracted from the mark is photoelectrically detected. The so-called heterodyne alignment method for performing alignment is adopted. However, as shown in the fifth embodiment, light is irradiated to a test mark to cause interference between two diffracted lights diffracted from the mark. It is needless to say that the present invention is also effective when a so-called homodyne alignment method in which alignment is performed by photoelectrically detecting the light intensity corresponding to the position of the wafer is adopted. In addition, the laser light source of the fifth embodiment is replaced with, for example, a Zeeman laser that supplies light beams having slightly different optical frequency differences in directions orthogonal to each other, and a heterodyne type alignment for photoelectrically detecting beat interference light is performed. Is also good.

Further, in the first to fourth embodiments, the irradiation light correction optical element and the detection light correction optical element are provided separately between the reticle and the wafer, and the irradiation light correction optical element It works independently, but 2
Beat interference light following the irradiation optical path is irradiated in the direction reversed (irradiation light LB ₁ of the zero-order light and the irradiation light LB ₂ of -2 order light or the irradiation light LB ₂ 0 order light and the irradiation light LB ₂ +2 If the next light is photoelectrically detected, the detection light correction optical element can be omitted.

In the first to fifth embodiments, TT
Although the alignment of the R type is performed, the present invention is not limited to this. For example, the reticle 2 and the projection lens 3
Needless to say, a TTR type alignment for aligning the wafer mark via the projection lens 3 can be performed by arranging a reflecting mirror between the mirror and the reflecting mirror and arranging an alignment optical system in the reflecting direction of the reflecting mirror.

In the first to fifth embodiments of the present embodiment, a diffraction grating is provided as a correction optical element for controlling an alignment optical path between an irradiation optical path and a detection optical path. An upper minute prism may be provided. At this time, in order to reduce the influence of the prism on the exposure light, a thin film having a wavelength separation function of reflecting the exposure light and transmitting the alignment light is deposited on the prism surface on the side where the exposure light is illuminated. Is desirable.

Further, a configuration may be adopted in which a correction optical element functions as a Fresnel zone plate. For example, correction optical elements G _{XA11 to} G _XA13 as shown in FIGS.
May be configured as concentric Fresnel zone plates centered on R as shown in FIGS. 19 and 20, respectively. Here, each correction optical element G _XA shown in FIGS.
_{11 to} G _XA13 have a lens function because they are configured so that their pitches become denser as they move away from the center R in the radial direction. Thereby, the spread of the beam at the reticle window can be suppressed. In this case, it is preferable that the Fresnel zone plate satisfies the condition (4) or the condition (5) described above.

The correction optical elements G _{XA11 to} G _XA13 shown in FIGS. 19 and 20 may be combined as shown in FIG. Next, a sixth embodiment according to the present invention will be described with reference to FIGS.

[0094] This embodiment is different from the alignment by laser interference of the first to fifth embodiment described above shows an example of applying an image alignment system for detecting an image of the wafer mark WM _x. This embodiment is different from the first embodiment shown in FIG. 1 described above in that an illumination optical system (40 to 45) is provided in the reflection direction of the semi-transmissive mirror 14, and The point is that an image detecting optical system (46, 47) is provided.

As shown in FIG. 21, for example, visible light emitted from the light source 30 is converted into light in a predetermined wavelength range by passing through a σ stop 41 and a filter 42, and then the lens 43 and the field stop 4 are turned on.
4, lens 34, semi-transmissive mirror 14, objective lens 18, reflecting mirror 19,
Through the reticle window WI, and the projection lens 3 to uniformly illuminate the wafer mark WM _x on the wafer 4. Then, reflected light from the wafer mark WM _x is the projection lens 3, the reticle window WI, reflecting mirror 19, the objective lens 18, half mirror 14, an image detector such as a CCD or pickup tube through the imaging lens 46 47
Imaged on top.

Here, the pupil position of the projection lens 3 of this embodiment
P has a diffraction grating G as shown in FIG._XA1, G_XA2, G
_XA3Are arranged, and the alignment light is
Of axial and lateral chromatic aberration of the projection lens
Corrected. Specifically, the optical axis Ax of the projection lens 3₀To
The first diffraction provided at the eccentric position (off-axis position)
Grid G_XA1, G_XA2Is the axial chromatic aberration amount Δ of the projection lens 3.
L, and corrects the amount of axial chromatic aberration equivalent to L.
To correct the lateral chromatic aberration ΔT of
_xReflected light LB from₁, LB_TwoTo θ ₁,
θ_TwoIs only deflected. Also, the optical axis A of the projection lens 3
x₀The eccentric position (position on the shaft)
2 diffraction grating G_XA3Is the chromatic aberration of magnification ΔT of the projection lens 3
To correct the wafer mark WM_xVertically from
Forward reflected light LB_ThreeTo θ_ThreeIs only deflected.

[0097] Therefore, the correction position B ₀ (a position where the image of the wafer mark WM _x under exposure light is back projected by the projection lens 3) is corrected by the diffraction grating G _XA1, G _XA2, G _XA3 since the image of the wafer mark WM _x are formed, highly accurate alignment can be achieved by the image detector 47. Here, the image alignment system according to the present embodiment will be briefly described with reference to FIG.

[0098] As shown in FIG. 22 (a), is in the reticle window WI of the reticle 2 and an image of the wafer mark WM _x is formed, this time, as shown in FIG. 22 in the image detector 47 (b) A signal is obtained. Therefore, the amount of deviation Δ between the center c of the reticle window W and the center e of the image of the wafer mark WM _x formed in the reticle window WI corresponds to the deviation between the reticle 2 and the wafer 4.

Accordingly, the alignment is achieved by moving the wafer stage (not shown) holding the wafer 2 so that the deviation amount Δ becomes zero. As mentioned above, it is possible to correct the position of the image of the wafer mark WM _x by the diffraction grating _{G XA1, G XA2, G XA3} , high precision image alignment by the image detector 47 can be achieved.

The image alignment according to the present embodiment is as follows.
As shown in FIG. 15, a magnification chromatic aberration amount ΔT ′ equal to or larger than the magnification chromatic aberration amount ΔT of the projection lens 3 is generated, and the wafer mark WM _x
Diffraction more functions to deflect the exposure area outside the reflected light LB ₁ ~LB ₃ from the grating G _XA1, G _XA2, it is needless to say that can be adapted to the case which gave a G _XA3.

[0101]

As described above, according to the present invention, the chromatic aberration of magnification can be controlled while correcting the axial chromatic aberration of the projection lens, despite having a relatively simple structure. And a high-performance alignment apparatus that can easily design and manufacture the projection lens while simplifying the process.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment according to the present invention.

FIG. 2 is a plan view showing a state of the reticle of the first embodiment according to the present invention.

FIG. 3 is a diagram showing a state in which diffracted light is generated when light is applied to the reticle mark of the first embodiment according to the present invention.

FIG. 4 is a plan view showing a state of a diffraction grating formed on a pupil plane of the projection lens of the first embodiment according to the present invention.

FIG. 5 is a diagram showing how diffracted light is generated when light is irradiated on a wafer mark according to the first embodiment of the present invention.

FIG. 6 is a plan view showing a shot area on a wafer exposed by the reticle of the first embodiment according to the present invention.

FIG. 7 is a schematic configuration diagram of a second embodiment according to the present invention.

FIG. 8 is a plan view showing a reticle according to a second embodiment of the present invention.

FIG. 9 is a plan view showing a state of a diffraction grating formed on a pupil plane of a projection lens according to a second embodiment of the present invention.

FIG. 10 is a plan view showing a shot area on a wafer exposed by a reticle according to a second embodiment of the present invention.

FIG. 11 is a perspective view showing a part of an alignment system according to a third embodiment of the present invention.

FIG. 12 is a plan view illustrating a state of a detector according to a third embodiment of the present invention.

FIG. 13 is a plan view showing a state of a diffraction grating formed on a pupil plane of a projection lens according to a third embodiment of the present invention.

FIG. 14 is a plan view showing a shot area on a wafer exposed by a reticle according to a third embodiment of the present invention.

FIG. 15 is a schematic configuration diagram of a fourth embodiment according to the present invention.

FIG. 16 is a schematic configuration diagram of a fifth embodiment according to the present invention.

FIG. 17 is a plan view showing a reticle according to a fifth embodiment of the present invention.

FIG. 18 is a plan view showing a state of a diffraction grating provided between a reticle and a wafer in a fifth embodiment according to the present invention.

FIG. 19 is a plan view showing a configuration in which the correction optical element shown in FIG. 4 is a Fresnel zone plate.

FIG. 20 is a plan view showing a configuration in which the correction optical element shown in FIG. 9 is a Fresnel zone plate.

FIG. 21 is a schematic configuration diagram of a sixth embodiment according to the present invention.

FIG. 22 is a view for explaining image alignment of a sixth embodiment according to the present embodiment.

[Description of Signs of Main Parts]

1, 1a, 1b ··· transparent substrate, 2 ··· reticle, 3 ··· projection lens, 10, 30 ··· laser light source, 11, 14 ··· semi-transmissive mirror, 13
a, 13b ··· Optical modulator (AOM ₁ , AOM ₂ ), 15 ··· Condenser lens, 16 ··· Reference diffraction grating, 18 ··· Objective lens, 12, 19,
31,33 ・ ・ ・ ・ Reflector, 17,20a, 20b, 20c, 20d, 21,21a, 21b, 34
····· Photoelectric detector, 2a ··· Exposure area, 4a ··· Shot area, WI, WI ₁ , WI ₂ ··· Reticle window, RM _XA , RM
_YA , RM _XB , RM _YB ... Reticle mark, WM _XA , WM
_YA , WM _XB , WM _YB ... ・ Wafer mark, G _XA1 , G _XA2 , G
_{YA1, G YA2, G XB1,} G XB2, G YB1, G YB2, G XA11, G XA12 ··
_{..Irradiation} light correction optical elements, G _XA3 , G ₃ , G _YA13 .... Detection light correction optical elements, LB ₁ , LB ₂ , LB _XA1 , LB _XA2 , LB _YA1 , L
B _YA2 , LB _XB1 , LB _XB2 , LB _YB1 , LB _YB2 ...
DB _R , DB _W ··· Detection light

Claims (3)

(57) [Claims] 1. An alignment apparatus provided in an exposure apparatus having a projection lens for transferring a predetermined pattern formed on a reticle onto a substrate by exposure light, and performing relative positioning between the reticle and the substrate. A light irradiating unit that irradiates an alignment light having a wavelength different from the exposure light to an alignment mark formed on the substrate via the projection lens, and emits light from the alignment mark through the projection lens Irradiating light for generating axial chromatic aberration and chromatic aberration of magnification between the reticle and the substrate in directions opposite to the axial chromatic aberration and the chromatic aberration of magnification of the projection lens with respect to the illuminating light. A correction optical element, and a detection light correction optical element for generating a chromatic aberration of magnification in a direction opposite to a chromatic aberration of magnification of the projection lens with respect to the detection light; The positive optical element has an on-axis equivalent to an on-axis chromatic aberration of the projection lens at a first position where a virtual image of the alignment mark is projected on the reticle side by the projection lens under the irradiation light. A chromatic aberration amount is generated, and a chromatic aberration of magnification greater than or equal to a chromatic aberration of magnification of the projection lens at the first position is generated, and the alignment mark image is projected on the reticle by the projection lens under the exposure light. The irradiation light path is deflected to the peripheral side of the non-exposure area including the second position as a boundary, and the detection light correction optical element adjusts the chromatic aberration of magnification equal to or more than the chromatic aberration of magnification of the projection lens at the first position. Raise
An alignment apparatus, wherein a detection optical path is deflected to a peripheral side of a non-exposure area including the second position as a boundary. 2. An alignment apparatus provided in an exposure apparatus having a projection lens for transferring a predetermined pattern formed on a reticle onto a substrate by exposure light, and performing relative positioning between the reticle and the substrate. A light irradiating unit that irradiates an alignment light having a wavelength different from the exposure light to an alignment mark formed on the substrate via the projection lens, and emits light from the alignment mark through the projection lens Detecting means for detecting, between the reticle and the substrate, an irradiation light correction optical element for generating irradiation chromatic aberration of magnification in a direction opposite to the magnification chromatic aberration of the projection lens, and detection light A detection light correction optical element for generating axial chromatic aberration and lateral chromatic aberration in directions opposite to the axial chromatic aberration and lateral chromatic aberration of the projection lens; The positive optical element has a chromatic aberration of magnification equal to or greater than a chromatic aberration of magnification of the projection lens at a first position where a virtual image of the alignment mark is projected by the projection lens toward the reticle under the irradiation light. Generating an alignment mark image under the exposure light, deflecting an irradiation light path to a peripheral side of a non-exposure area including a second position where the alignment mark image is projected on the reticle by a projection lens as a boundary, and correcting the detection light. The optical element generates an amount of axial chromatic aberration equivalent to the amount of axial chromatic aberration of the projection lens at the first position, and reduces the amount of chromatic aberration of magnification equal to or greater than the amount of chromatic aberration of magnification of the projection lens at the first position. An alignment apparatus, wherein the detection light path is generated to deflect a detection optical path to a peripheral side of a non-exposure area including the second position as a boundary. 3. The projection light correcting optical element and the detection light correcting optical element are disposed in a pupil plane of the projection lens or in a plane near the pupil plane. 3. The alignment apparatus according to 2.