JPH06260389A - Alignment device - Google Patents

Abstract

PURPOSE:To simplify the configuration of an alignment optical system and at the same time reduce load of a projection optical system in terms of designing and structure. CONSTITUTION:Wafer illumination light WB1-WB4 from an alignment optical system 1 enter a projection optical system 5 via a dichroic mirror 3, a reticle window 34 etc. of a reticle 4 and wafer illumination light WB1-WB4 enter a wafer mark 37 on a wafer 6 while axial color aberration difference is compensated by axial aberration difference control elements on each aberration control plate 10. Detection light WB1 (+1) and WB2(-1), detection light WB3(+2) and WB4(-2) from the wafer mark 37 return to an alignment optical system 1 via the projection optical system 5 and the reticle window 35 of the reticle 4 without causing color aberration to be compensated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alignment apparatus for a projection exposure apparatus for transferring a pattern formed on a reticle onto a wafer via a projection optical system, and more particularly to transferring a pattern. The present invention relates to an alignment apparatus that performs relative alignment between a reticle and a wafer by using alignment light having a wavelength different from that of the exposure light.

[0002]

2. Description of the Related Art When a semiconductor device, a liquid crystal display device, or the like is manufactured by a lithography process, a pattern of a photomask or reticle (hereinafter referred to as "reticle") is exposed under exposure light through a projection optical system. A projection exposure apparatus is used in which a material is applied and transferred onto a substrate (wafer, glass plate, or the like). Taking manufacturing of a semiconductor device as an example, generally, a semiconductor device is formed by stacking a plurality of layers of circuit patterns on a wafer. Therefore, in order to manufacture a semiconductor device with a high yield, a circuit of a previous layer on the wafer is manufactured. It is necessary to keep the overlay accuracy of the pattern and the pattern of the reticle to be transferred from now on within a predetermined allowable range. Therefore, the projection exposure apparatus is provided with an alignment device for aligning the reticle and the wafer with high accuracy.

Among the conventional alignment apparatuses, the TTR (Through the Reticle) type apparatus for directly aligning the relative position between the reticle and the wafer through the projection optical system can realize the highest accuracy in principle. Is expected as. Further, in the alignment apparatus, it is required to use light having a wavelength different from the wavelength of the exposure light as the alignment light so that the photoresist coated on the wafer is not exposed to light. However, when the wavelength of the alignment light is different from the wavelength of the exposure light, there is a problem that chromatic aberration occurs in the projection optical system with respect to the alignment light, and an alignment apparatus that corrects this chromatic aberration is disclosed in Japanese Patent Laid-Open No. It is proposed in Japanese Patent No. 3224, Japanese Patent Publication No. 1-40490, and the like.

First, in the alignment apparatus disclosed in Japanese Patent Laid-Open No. 3-3224, the wavelength of the exposure light and the alignment are aligned by disposing one correction lens at the center of the optical axis at the position of the entrance pupil of the projection optical system. It corrects chromatic aberration with respect to the wavelength of light. Thereby, the ± 1st-order diffracted light from the alignment mark (wafer mark) on the wafer is detected to perform the alignment.

In the alignment apparatus disclosed in Japanese Patent Publication No. 1-40490, a correction optical system is arranged outside or inside the exposure optical path between the reticle and the projection optical system, and the alignment light is projected onto the projection optical system. To correct chromatic aberration. Then, the image of the reticle mark (alignment mark on the reticle) formed on the wafer and the wafer mark are detected through the projection optical system, and the reticle and the wafer are aligned.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the alignment apparatus disclosed in Japanese Patent No. 3224, the correction lens for correcting chromatic aberration, which is arranged at the center of the entrance pupil of the projection optical system, is small enough not to adversely affect the exposure light. However, in order to improve the alignment accuracy, it is necessary to make the pitch of the diffraction grating forming the wafer mark finer. Therefore,
If the pitch of the diffraction grating that forms the wafer mark is reduced, the distance between the ± first-order diffracted lights as the detection light is increased in the entrance pupil of the projection optical system, and the correction lens must be increased. As a result, the influence of the correction lens on the exposure light cannot be ignored, and there is the inconvenience that it cannot be applied to applications for performing more accurate alignment.

Further, the intensity of the ± 1st-order diffracted light may be significantly weakened depending on the condition of the step of the alignment mark and the duty ratio. In this case, it is effective to use the higher-order diffracted light. However, when high-order diffracted light is used, the diameter of the correction lens becomes large and the influence on the exposure light cannot be ignored. Therefore, in the alignment apparatus disclosed in Japanese Patent Laid-Open No. 3-3224, The higher order diffracted light could not be used.

Further, in the alignment apparatus disclosed in Japanese Patent Publication No. 1-40490 as described above, the correction optical system is arranged outside or inside the exposure light path between the reticle and the projection lens, so that the projection optical system is provided. In principle, it is possible to correct the axial chromatic aberration of the system. However, since the wavelength of the alignment light is longer than the wavelength of the exposure light, seeing the image of the wafer mark through the projection optical system,
Due to the lateral chromatic aberration of the projection optical system, there arises a disadvantage that the wafer mark image is included in the exposure area on the reticle. As a method of avoiding this inconvenience, a parallel plane plate with a variable tilt angle is provided outside the exposure optical path between the reticle and the projection optical system, and lateral chromatic aberration of the projection optical system is corrected to bring the wafer mark image out of the exposure area. The method of shifting to. However, this parallel flat plate blocks a part of the exposure light this time, and this method cannot sufficiently deal with the problem.

However, to realize a projection optical system free of chromatic aberration (axial chromatic aberration and lateral chromatic aberration) with respect to light of two different wavelengths (exposure light and alignment light), both in terms of design and manufacturing. Very difficult. Particularly, in an exposure apparatus that uses an excimer laser light source as a light source for exposure light, since the glass material of the projection optical system is limited to quartz, fluorite, and the like, the chromatic aberration causes the bright line (g line, i line, etc.) of the mercury lamp to occur. Compared to an exposure device that uses exposure light, it reaches several tens of times.

In view of the above point, the present invention simplifies the configuration of the alignment optical system by making it possible to control the axial chromatic aberration and / or the lateral chromatic aberration of the projection optical system with a simple configuration. An object of the present invention is to provide a high-performance alignment device that does not impose a load on the design and manufacturing of the projection optical system. The lateral chromatic aberration referred to in the present invention means the off-axis light having the same wavelength as the exposure light which is imaged on the Gaussian image plane by passing through the projection optical system, and the above-mentioned Gaussian light when passing through the projection optical system. It is defined by the positional deviation between the intersecting positions where the chief rays of both the exposure light that forms an image on the image plane or before and after the exposure light and that has a different wavelength from the exposure light intersect on the Gaussian image plane.

Further, from the crossing position where the chief ray in the off-axis light having the same wavelength as the exposure light imaged on the Gauss image plane by passing through the projection optical system intersects on the Gauss image plane,
The distance to the optical axis position of the projection optical system on the Gaussian image plane is δ ₁ , and by passing through the projection optical system, alignment of a different wavelength from the exposure light imaged on the Gaussian image plane or before and after the Gaussian image plane. When the distance from the crossing position where the chief ray of light crosses the Gaussian image plane to the optical axis position of the projection optical system on the Gaussian image plane is δ ₂ , the lateral chromatic aberration amount ΔT is Defined by ΔT = | δ ₂ −δ ₁ | (1)

[0012]

A first alignment apparatus according to the present invention uses a projection optical system for projecting a pattern formed on a mask (4) under exposure light as shown in FIGS. 1 to 6, for example. It is provided in a projection exposure apparatus that projects and exposes on a substrate (6) on a stage (8, 9) which is two-dimensionally movable via (5), and the mask (4) and the substrate (6) are relative to each other. In an alignment apparatus that detects a large positional deviation with alignment light having a wavelength different from that of the exposure light, the lattice-shaped alignment marks (36) formed on the mask (4) have frequencies Δf ₁ as the alignment light. A first light irradiating means (1) for irradiating two different coherent light fluxes (RB ₁ , RB ₂ ) respectively from different directions,
Two coherent light beams (RB ₃ and RB ₄ ) having different frequencies from each other by Δf ₂ different from each other as Δf ₁ are generated as alignment light for the lattice-shaped alignment mark (36) formed on the mask (4). The second light irradiation means (1) for irradiating from different directions and the lattice-shaped alignment marks (37) formed on the substrate (6) are passed through the mask (4) and the projection optical system (5). , The coherent light whose frequencies are different from each other by Δf ₁ as the alignment light
The mask (4) is applied to the third light irradiation means (1) for irradiating the light fluxes (WB ₁ and WB ₂ ) from different directions and the grid-like alignment marks (37) formed on the substrate (6). ) And the projection optical system (5), as the alignment light, a coherent two light beams (WB ₃ , WB ₄ ) whose frequencies are different from each other by Δf ₂ are irradiated from different directions. 1) and.

Further, according to the present invention, on the pupil plane in the projection optical system (5) or on a plane in the vicinity thereof, the light from the third light irradiating means is provided.
A projection optical system (5) arranged in a region through which the light flux and the two light fluxes from the fourth light irradiation means pass, and for the light flux from the third light irradiation means and the light flux from the fourth light irradiation means, respectively. Irradiation light control means (G1 _{1A to} G1 _1D ) for controlling the on-axis chromatic aberration to a predetermined value, and the mask (4), respectively.
Two or more sets of light fluxes (RB ₁ (+1), RB) consisting of two light fluxes diffracted in the same direction by the alignment mark (36) above.
Diffract in the same direction by the first detection means (1) for detecting ₂ (-1) and RB ₃ (+2), RB ₄ (-2)) and the alignment mark (37) on the substrate (6). Two or more pairs of light fluxes (WB ₁ (+1), WB ₂ (-1) and WB ₃ (+2), W
B ₄ (-2)) second detecting means (1) and its first
Comparing the phases of the components of the frequency Δf ₁ in the detection signals obtained from the detecting means and the second detecting means.
Of the phase comparison means (53) and the detection signals obtained from the first detection means and the second detection means thereof.
_Second phase comparing means (54) for comparing the phases of the components of f ₂ and the mask (4) and the substrate (6) based on the phase differences respectively obtained by these two phase comparing means.
And a positional deviation detecting means (57) for detecting a relative positional deviation amount with respect to.

In this case, the alignment mark (37) on the substrate (6) is measured by the two light beams (WB ₁ , WB ₂ ) emitted from the third light emitting means, and the alignment mark (37) on the substrate (6). The alignment mark (37) may be orthogonal to the measurement direction of the two light beams (WB ₃ , WB ₄ ) emitted from the fourth light emitting means. Further, the second alignment apparatus of the present invention, as shown in, for example, FIGS. 11 to 14, passes a pattern formed on the mask (4) through the projection optical system (5) under exposure light. It is provided in a projection exposure apparatus that projects and exposes onto a substrate (6) on a stage (8, 9) that is two-dimensionally movable, and exposes the relative displacement between the mask (4) and the substrate (6). In an alignment apparatus that detects alignment light having a wavelength different from that of light, the alignment marks (41) formed on the mask (4) have a coherent frequency difference of Δf ₁ as the alignment light. Luminous flux (RB ₁ ,
The first light irradiating means (1) for irradiating RB ₂ ) from different directions and the lattice-like alignment mark (41) formed on the mask (4) have mutually different frequencies Δf as alignment light. Second light irradiating means (1) for irradiating two coherent light fluxes (RB ₃ , RB ₄ ) different from each other by Δf ₂ different from _1, and a grid-like pattern formed on the substrate (6). Alignment mark (3
For 7), through the mask (4) and the projection optical system (5), two coherent light beams (WB ₁ , WB ₂ ) having different frequencies by Δf ₁ are emitted as alignment light from different directions. Third light irradiation means (1) for
The alignment marks (37) in the form of a grid formed on the substrate (6) have a frequency of Δf as alignment light through the mask (6) and the projection optical system (5).
Only _two different two coherent light beams (WB _3, WB _4), the fourth light irradiating means for irradiating from different directions (1)
Have and.

The present invention further relates to the pupil plane in the projection optical system (5).
Or, on the surface in the vicinity thereof, 2 from the third light irradiation means.
The light flux and the two light fluxes from the fourth light irradiation means pass therethrough.
The third light irradiating means arranged respectively in the areas.
Projection of luminous flux and its luminous flux from the fourth light irradiation means
An illumination for controlling the lateral chromatic aberration of the optical system (5) to a predetermined value.
Emission control means (G3_1A~ G3_1D) And projection optical system (5)
On the substrate (6) on the inner pupil plane or the plane near this plane, respectively.
Diffracted in the same direction from the alignment mark (37) of
Placed in an area where two or more sets of two light fluxes
Alignment marks (3
Generates a certain amount of lateral chromatic aberration for the light flux from 7)
Detection light control means (G3_1E) And a mask
(4) Alignment mark (41) on the same direction
Two or more light fluxes (RB₁(+
1), RB₂(-1) and RB₃(+2), RB_FourThe first to detect (-2))
Detection means (1) and aligning means on the substrate (6) respectively.
Two light beams diffracted in the same direction by the dot mark (37)
2 or more sets of luminous flux (WB₁(+1), WB₂(-1) and WB
₃(+2), WB_FourSecond detecting means (1) for detecting (-2)),
Obtained from the first detection means and the second detection means
Frequency Δf of the detected signal₁ Compare the phases of the components of
First phase comparing means, first detecting means thereof, and the first
Frequency Δf of the detection signals obtained from the second detection means₂ 
Second phase comparing means for comparing the phases of the components of
Based on the phase difference obtained by the two phase comparison means,
Detects the amount of relative displacement between the disk (4) and the substrate (6)
And a position shift detecting means for performing the above.

In this case, the irradiation light control means also sets the axial chromatic aberration of the projection optical system (5) for the light flux from the third light irradiation means and the light flux from the fourth light irradiation means to a predetermined value. It is preferable that the detection light control means controls the axial chromatic aberration of the projection optical system (5) with respect to the light flux from the alignment mark (37) on the substrate (6) to a predetermined value.

Further, the alignment mark (37) on the substrate (6) is measured on the alignment mark (37) on the substrate (6) and the measurement direction by the two light beams emitted from the third light emitting means. 2 emitted from the fourth light emitting means
The measurement direction by the light flux may be orthogonal.

[0018]

In the first alignment apparatus of the present invention, when the two light fluxes as one set of alignment light pass through the pupil plane of the projection optical system (5) or its vicinity, they are spatially separated from each other. Pass through. The interval becomes wider as the angle θ formed by the two light fluxes when the alignment mark (37) of the substrate (6) is irradiated becomes larger. On the other hand, the angle of the diffracted light generated by the lattice-shaped alignment mark (37) is inversely proportional to the lattice pitch P.
The condition of the angle θ ₁ formed by the two light fluxes because the first-order diffracted light is generated in the same direction is as follows, where λ is the wavelength of the alignment light.

[0019] _{sin (θ 1/2) =} λ / P (2) In contrast, ± 2-order diffracted light of the two beams to be irradiated on the alignment mark (37) is formed by those two beams in order to generate the same direction The condition for the angle θ ₂ is as follows. _{sin (θ 2/2) =} 2λ / P (3) i.e., 2 when passing through the vicinity of the pupil plane of the projection optical system (5)
The spacing of the light flux will be doubled. Therefore, if a correction lens is inserted in the pupil plane, the lens diameter needs to be twice as large as when only the ± 1st order diffracted light is detected, and the area ratio becomes four times.

On the other hand, in the present invention, since the chromatic aberration is controlled by the chromatic aberration control means, a set of alignment lights (WB ₁ , WB ₂ and WB) each consisting of two light fluxes is used.
₃ and WB ₄ ), it is only necessary to increase the number of chromatic aberration control means. Therefore, since the areas of the individual chromatic aberration control means may be the same, in the case of two sets of alignment light, the area of the chromatic aberration control means need only be doubled. The position of the mask (4) detected from the two light beams (RB ₁ , RB ₂ ) on the first mask side and the two light beams (WB on the first substrate side (WB
₁ , WB ₂ ) from the position of the substrate (6) detected by the first displacement of the mask (4) and the substrate (6), and the second light flux (RB) on the second mask side (RB). ₃ , RB ₄ ) and the position of the substrate (6) detected from the two light beams (WB ₃ , WB ₄ ) on the second substrate side, the mask (4) is detected. A second misalignment between the substrate and the substrate (6) is obtained. Then, for example, by calculating a weighted average of the plurality of positional deviation amounts by the positional deviation detection means, the ± from the alignment mark (37) of the substrate (6) is determined.
Mask (4) and substrate (6) even when the first-order diffracted light is weak
The positional shift between and is accurately obtained.

The measurement direction on the substrate (6) by the _first two light fluxes (WB ₁ , WB ₂ ) and the second two light fluxes (WB
_When the measurement directions on the substrate (6) by ( ₃ , WB ₄ ) are orthogonal to each other, one alignment device can simultaneously detect the positional deviation amounts in the X direction and the Y direction, for example. In this case, since the axial chromatic aberration of the projection optical system (5) with respect to the alignment light with which the alignment mark on the substrate (6) side is irradiated can be controlled, the alignment light on the mask (4) side is irradiated with the alignment light. The light irradiating means and the light irradiating means for irradiating the alignment mark on the substrate (6) side with the alignment light can be shared in a considerable part.

Further, according to the second alignment apparatus of the present invention, the projection optical system (5) is laterally moved with respect to both the illumination light with respect to the alignment mark of the substrate (6) and the detection light from this alignment mark. Means are provided for controlling directional chromatic aberration. Therefore, it is possible to set the point where the alignment light passes through the mask (4) outside the exposure area and set the alignment mark on the substrate (6) side within the exposure area. This makes it possible to provide a light-shielding band on the mask (4) side so that exposure light does not strike the alignment marks on the substrate (6) side, and the alignment mark replacement count for each layer on the substrate (6) can be changed. It can be reduced. In addition, since the lateral chromatic aberration control amount can be freely adjusted, the burden of designing the projection optical system can be reduced.

In this case, the optical system for the alignment light for the mask (4) and the optical system for the alignment light for the substrate (6) are shared in a considerable part by providing a function of controlling the chromatic aberration in the axial direction. Can be converted. Also in this case, the measurement direction on the substrate (6) by the _first two light fluxes (WB ₁ , WB ₂ ) and the second two light fluxes (WB ₃ , WB 2).
_When the measurement direction on the substrate (6) by ₄ ) is orthogonal, a single alignment device can be used, for example, in the X direction and the Y direction.
It is possible to detect the positional deviation amount in the same direction at the same time.

[0024]

EXAMPLE A first example of an alignment apparatus according to the present invention will be described below.
An example will be described with reference to FIGS. In this embodiment, a TTR (through / through) provided in a projection exposure apparatus that exposes a reticle pattern onto a wafer via a projection optical system.
The present invention is applied to an alignment device of the reticle type. Further, the present embodiment is an example in which only the axial chromatic aberration of the projection optical system with respect to the alignment light with which the alignment mark (wafer mark) on the wafer is irradiated is controlled.

FIG. 1A shows the main part of the projection exposure apparatus of this embodiment, and FIG. 1B shows the state of FIG. 1A viewed from the right side, showing the optical axis of the projection optical system 5. In a plane perpendicular to
The Y axis is taken parallel to the paper surface of (a), and the X axis is taken parallel to the paper surface of FIG. In FIG. 1A, a dichroic mirror 3 is obliquely installed on a reticle 4 at an inclination angle of 45 °, and exposure light of a wavelength λ ₁ from an illumination optical system (not shown) is reflected by the dichroic mirror 3 to form a reticle. 4. Illuminate the circuit pattern drawn on 4 with uniform illuminance. Under the exposure light of the wavelength λ ₁ , the image of the circuit pattern on the reticle 4 is reduced to ⅕ by the projection optical system 5 and transferred onto the wafer 6 coated with the photoresist. The wafer 6 is placed on a Z stage 7 that can move up and down in the Z direction parallel to the optical axis AX of the projection optical system 5, and the Z stage 7 is placed on an X stage 8 that can move in the X direction perpendicular to the optical axis AX. The X stage 8 is placed and is placed on a Y stage 9 which is movable in the Y direction which is perpendicular to the optical axis AX and perpendicular to the X direction.

In FIGS. 1A and 1B, the alignment apparatus of this embodiment comprises an alignment optical system 1, an objective lens 2 and a chromatic aberration control plate 10 arranged on the pupil plane of the projection optical system 5. ing. The detailed configuration of the alignment optical system 1 is shown in FIG. In addition, in fact,
Although an alignment optical system for four axes is arranged above the dichroic mirror 3, the alignment optical system 1 for a certain one axis will be described below.

From the alignment optical system 1, reticle alignment illumination lights RB ₁ and RB ₂ (shown by broken lines in FIG. 1 (a)) each consisting of two light beams having a frequency difference Δf ₁ (= 50 kHz). And wafer alignment illumination light WB ₁ and WB _2, and frequency difference Δf ₂ (= 75 kHz)
z) reticle alignment illumination light RB consisting of two light fluxes
₃ , RB ₄ (indicated by a broken line in FIG. 1A) and wafer alignment illumination light WB ₃ , WB ₄ are emitted. Also, the average wavelengths of the four sets of illumination light are λ respectively.
₂ and the wavelength λ ₂ is different from the wavelength λ _{1 of the} exposure light. The reticle alignment illumination light (reticle illumination light) RB ₁ and RB ₂ among them is focused on the reticle 4 via the objective lens 2 and the dichroic mirror 3.

FIG. 4 shows the vicinity of the circuit pattern area on the reticle 4, and as shown in FIG. 4, the vicinity of the circuit pattern area on the reticle 4 is composed of a diffraction grating having a grating pitch P _{R in} the X direction. A reticle mark 36 is formed, and a reticle window 35 made of a light transmitting portion is formed near the reticle mark 36. Returning to FIG. 1B, the reticle illumination lights RB ₁ and RB ₂ are irradiated onto the reticle mark 36 (in front of the reticle window 35) at incident angles −θ _R and θ _R , respectively. At this time, since the grating pitch P _R of the reticle mark 36 satisfies the following equation, the + _1st- order diffracted light RB ₁ (+1) of the illumination light RB 1 and the −1st-order diffracted light RB ₂ (-1) of the illumination light RB ₂ are obtained.
Are generated directly above in the measurement direction (X direction) and return to the alignment optical system 1.

Sin (θ _R ) = λ ₂ / P _R (3) Similarly, reticle alignment illumination lights RB ₃ and RB ₄
Also through the objective lens 2 and the dichroic mirror 3,
The incident angle on the reticle mark 36 on the reticle 4 is −
Irradiation is performed at 2θ _R and 2θ _R. At this time, the illumination light RB ₃
The + 2nd-order diffracted light RB ₃ (+2) and the −2nd-order diffracted light RB ₄ (-2) of the illumination light RB ₄ are generated right above the reticle mark 36 and return to the alignment optical system 1.

On the other hand, the wafer alignment illumination lights (wafer illumination lights) WB ₁ and WB ₂ are, as shown in FIG.
After passing through the reticle window 35 on the reticle 4 via the objective lens 2 and the dichroic mirror 3, the projection optical system 5
The chromatic aberration control plate 10 is reached. FIG. 6 shows the chromatic aberration control plate 1.
0, as shown in FIG. 4, on the chromatic aberration control plate 10 made of a transparent substrate, it is axially symmetric with respect to the straight line Y1 passing through the optical axis AX and parallel to the Y axis, and passing through the optical axis AX and parallel to the X axis. A pair of on-axis chromatic aberration control elements G1 _1A and G1 _1B are formed at positions separated from the straight line X1 by a predetermined distance. In the present embodiment, the on-axis chromatic aberration control elements G1 _1A and G1 _1B correct the on-axis chromatic aberration of the _two wafer illumination lights WB ₁ and WB ₂ irradiated on one wafer mark on the wafer 6. Outside the axial chromatic aberration control elements G1 _1A and G1 _1B, a pair of diffraction grating-shaped axial chromatic aberration control elements G1 _1C and G1 _1D are formed axially symmetrical with respect to the straight line Y1, and these axial chromatic aberration control elements G1 _1C are formed. , G1 _1D corrects the axial chromatic aberration of the remaining two wafer illumination lights WB ₃ and WB ₄ irradiated on one wafer mark on the wafer 6.

Further, in this embodiment, a total of 16 on the chromatic aberration control plate 10 so that the positions of four different wafer marks in the exposure field of the projection optical system 5 can be detected.
(= 4 × 4) on-axis chromatic aberration control elements are provided. That is, with respect to the optical axis AX, the axial chromatic aberration control element G1 _1A
~ Axial chromatic aberration control element G1 _{3A at} a position point-symmetrical with G1 _1D
˜G1 _3D are provided, and the axial chromatic aberration control elements G1 _{2A to} G are located at positions where the above eight axial chromatic aberration control elements are rotated by 90 °.
1 _2D and G1 _{4A to} G1 _4D are provided. That is, a pair of on-axis chromatic aberration control elements G1 _3B and G1 _3A in the form of a diffraction grating are formed at positions with different distances from the optical axis AX, and two pairs of on-axis chromatic aberration control elements G1 _2A are symmetrical about the straight line X1. G1
_2B and G1 _4B and G1 _4A are formed. These axial chromatic aberration control elements (G1 _1A, etc.) are composed of a phase grating having an uneven pattern.

Returning to FIG. 1B, the illumination lights WB ₁ and WB ₂
Respectively enter the axial chromatic aberration control elements G1 _1B and G1 _1A on the chromatic aberration control plate 10, and the optical paths respectively form the angles −θ _G1 and
Can be bent by θ _G1 . Then, the illumination light WB ₁ , WB ₂
Are irradiated onto the wafer mark 37 on the wafer 6 at incident angles of −θ _W and θ _W , respectively. FIG. 5 shows a wafer mark 37 on the wafer 6. As shown in FIG. 5, the wafer mark 37 has a diffraction grating shape having a grating pitch P _{W in} the X direction which is the measurement direction. The lattice pitch P of the wafer mark 37
_{Since W} satisfies the following equation, as shown in FIG.
Illumination light WB ₁ + _{1st order} diffracted light WB ₁ (+1) and illumination light WB ₂
The −1st-order diffracted light WB ₂ (−1) is generated directly above in the measurement direction (X direction) and becomes alignment detection light.

Sin (θ _W ) = λ ₂ / P _W (4) Similarly, the wafer illumination lights WB ₃ and WB ₄ respectively enter the axial chromatic aberration control elements G1 _1C and G1 _1D on the chromatic aberration control plate 10, The optical paths are bent by angles −θ _G1 and θ _G1 respectively. Then, the wafer illumination lights WB ₃ and WB ₄ are applied to the wafer mark 37 at incident angles of −2θ _W and 2θ _W , respectively. Then, the + 2nd order diffracted light WB ₃ (+2) of the illumination light WB ₃
And the −2nd-order diffracted light WB ₄ (−2) of the illumination light WB ₄ are generated directly above the wafer mark 37 and serve as alignment detection light.

Further, the illumination light W for the wafer mark 36
As shown in FIG. 1A, B _{1 to} WB ₄ have an angle θ _{m with} respect to the normal line of the wafer 6 in the Y direction which is the non-measurement direction.
Therefore, the positions where the above two sets of alignment detection lights pass through the chromatic aberration control plate 10 are different from the positions where they are passed at the time of incidence, and the axial chromatic aberration control element G1 is incident.
It does not pass through _1A , G1 _1B , G1 _1C and G1 _1D . After that, each alignment detection light returns to the alignment optical system 1 again through the reticle window 35 on the reticle 4.

Next, the alignment optical system 1 in FIG. 1 will be described in detail with reference to FIG. 2A is a view of the alignment optical system 1 viewed from the same direction as FIG. 1A,
2B is a view of the alignment optical system 1 viewed from the same direction as FIG. 1B, and FIG. 2C is a bottom view of FIG. 2B. In FIG. 2, a laser beam emitted from a laser light source 11a is split into two light beams by a beam splitter prism 12a, one light beam enters an acousto-optic modulator (hereinafter referred to as "AOM") 14a, and the other light beam. Is reflected by the reflection prism 13a and enters the AOM 15a.

AOMs 14a and 15a are respectively frequency
F₁ And F₂ Driven by the frequency F ₁ And F₂ Frequency
Difference Δf₁ Is 50 kHz. AOM 14a and 15a
Of the laser beams of each order diffracted by
Only the + 1st order diffracted light is generated by the slits 16a and 17b.
Is selected and this is the alignment illumination light B₁ And B ₂ 
become. At this time, it is incident on the AOMs 14a and 15a.
The frequency of the laser beam is f₀ If so, the alignment light
Meiko B₁ And B₂ The frequencies of AOM14 and
Driving frequency F of 15₁ And F₂ Higher frequency f₁ Over
And f₂ Becomes That is, the following relational expression holds.

F ₁ = f ₀ + F ₁ (5) f ₂ = f ₀ + F ₂ (6) Of these illumination lights, the illumination light B ₁ is synthesized through the parallel plate glass 18 a for adjusting the optical path and the reflection prism 20 a. The illumination light B ₂ on the other side is incident on the prism 21a, and then is incident on the synthetic prism 21a via the parallel plate glass 19a for adjusting the optical path. Two illumination lights (heterodyne beams) B emitted from the combining prism 21a and having frequencies different from each other by Δf _1
1 and B ₂ travel toward the combining prism 23 via the reflecting prism 22.

Further, the laser light source 11a to the synthetic prism 2
A second heterodyne beam generation system including a laser light source 11b to a combining prism 21b is provided in symmetry with the first heterodyne beam generation system including 1a. In this second heterodyne beam generation system, the laser beam emitted from the laser light source 11b is split into two light beams by the beam splitter prism 12b, one light beam incident on the AOM 14b having the drive frequency F ₃ , and the other light beam. The light is reflected by the reflection prism 13b and enters the AOM 15b having the driving frequency F ₄ . The frequency difference Δf ₂ between the frequencies F ₃ and F ₄ is 75 kHz. AOM 14b and 15b
Among the laser beams of the respective orders diffracted by, only the + 1st order diffracted lights are selected by the slits 16b and 17b, respectively, and become the alignment illumination lights B ₃ and B ₄ whose frequencies are different from each other by Δf ₂ . These illumination lights B
₃ and B ₄ head toward the combining prism 23 almost in parallel via the combining prism 21b.

Then, the optical path is almost flat by the combining prism 23.
Illumination light B set in the row₁ ~ B_Four By the lens 24
Field slit 25 at a conjugate position with the reticle and wafer
Focused on top. After the field slit 24, the entrance surface is
A plane parallel plate 2 with a thin film deposited to be a mirror
6 are arranged. And the opening of the field slit 25
Light B emitted from the section₁ ~ B_Four Is a plane-parallel plate 26
By reticle illumination light RB₁ ~ RB_Four (Fig. 2 (a)
(Indicated by a broken line in the figure) and wafer illumination light WB₁ ~ WB _Four And to minutes
To be split. Illumination light RB₁ ~ RB_Four And illumination light WB₁ ~ W
B_Four Passes through the lens 28 and the beam splitter 29.
And is emitted from the alignment optical system 1.

The alignment detection light composed of the alignment light returned from the reticle mark 36 and the alignment light returned from the wafer mark 37 of FIG. 1 is, as shown in FIG. 2B, a beam splitter 29 of the alignment optical system 1. Incident on. The alignment detection light reflected by the beam splitter 29 is incident on the detection light separation prism 31 at a position conjugate with the reticle and the wafer by the lens 30, and in the detection light separation prism 31, the reticle detection light from the reticle mark and the wafer mark. From the wafer detection light. In this case, as shown in FIG. 2C, since the reticle detection light shown by the broken line and the wafer detection light shown by the solid line are incident on different areas on the detection light separation prism 31, the reflection surface of the detection light separation prism 31. By using a part of the as a transparent part, it is possible to completely separate the both.

Then, ± 1 next time as reticle detection light
Origami RB₁(+1), RB₂(-1) and ± 2nd order diffracted light RB₃(+2),
RB_Four(-2) is after passing through the detection light separation prism 31,
The reticle signal is photoelectrically converted by the photoelectric detection element 32.
SR is output. On the other hand, ± 1st order as wafer detection light
Diffracted light WB₁(+1), WB₂(-1) and ± 2nd order diffracted light WB₃(+
2), WB_Four(-2) is reflected by the detection light separation prism 31.
After passing through the lens 33,
Each is photoelectrically converted and a wafer signal SW is output. Obey
The reticle signal SR is the ± first-order diffracted light RB.₁(+1), RB
₂Frequency Δf due to (-1)₁ Beat signal and ± 2nd order diffraction
Optical RB₃(+2), RB_FourFrequency Δf due to (-2) ₂ Beat of
Signal is a mixed signal, and similarly, the wafer signal SW
Is the ± first-order diffracted light WB₁(+1), WB₂Frequency Δ due to (-1)
f₁ Beat signal and ± 2nd order diffracted light WB₃(+2), WB_Four(-
2) Frequency Δf₂ Signal mixed with the beat signal of
No.

FIG. 3 shows an example of the signal processing system of this example.
3, the reticle signal SR is filtered by a low-pass filter.
Circuit (LPF) 51 and high-pass filter circuit (HP
F) Supply to 52. In this example, the frequency Δf₁ And frequency
Δf₂ Since the intermediate frequency between and is 60 kHz,
Of the pass filter circuit 51 and the high pass filter circuit 52
The cutoff frequencies are set to 60 kHz respectively. This
As a result, the frequency extracted by the low-pass filter circuit 51
Δf₁ Reticle signal S_R(± 1) of the phase difference detector 53
It is supplied to one of the input parts and extracted by the high-pass filter circuit 52.
Output frequency Δf ₂ Reticle signal S_R(± 2) is the phase difference
It is supplied to one input unit of the detection unit 54.

The wafer signal SW has a low-pass filter circuit (LP) having a cutoff frequency of 60 kHz.
F) 55 and a high pass filter circuit (HPF) 56. Then, the wafer signal S _W (± 1) of the frequency Δf ₁ extracted by the low-pass filter circuit 55 is supplied to the phase difference detection unit 5
3 to the other input portion of the high-pass filter circuit 56.
In supplies the extracted frequency Delta] f ₂ of the wafer signal S _W a (± 2) to the other input of the phase difference detecting unit 54. The phase difference detected by each of the phase difference detectors 53 and 54 is supplied to the calculator 57. The calculation unit 57 calculates the reticle mark 36 (reticle 4) of FIG. 1 based on the two phase differences.
Then, the positional deviation amount between the wafer mark 37 and the wafer mark 37 (wafer 6) is obtained.

7 and 8 show the reticle signal and wafer signal obtained in the signal processing system of FIG. The reticle signal S _R (± 1) and the wafer signal _SW (±) shown in FIG.
1) means ± first-order diffracted light RB having a frequency difference Δf _1
1 (+1), RB ₂ (-1) and ± 1st-order diffracted light W with frequency difference Δf ₂
It is a sine wave generated by the interference of B ₁ (+1) and WB ₂ (-1). By detecting the phase difference Δφ ₁ between these two signals, the relative positional deviation Δx ₁ between the reticle 4 and the wafer 6 can be detected from the following equation.

Δx ₁ = Pw · Δφ ₁ / 4π (7) Similarly, the reticle signal S _R (± 2) and the wafer signal _SW (± 2) shown in FIG. ₂ ± 2nd order diffracted light RB ₃ (+2), RB ₄ (-2) and frequency difference Δf ₂
Is a sine wave generated by the interference of the ± 2nd-order diffracted lights WB ₃ (+2) and WB ₄ (-2). Therefore, by detecting the phase difference Δφ ₂ between these two signals, the reticle 4 can be calculated from the following equation.
The relative positional deviation Δx ₂ between the wafer 6 and the wafer 6 can be detected.

Δx₂ = Pw / Δφ₂ / 4π (8) Positional deviation obtained by equation (7) and equation (8) respectively Δ
x₁ And △ x₂ There are various ways to use
To be As an example, for example, the wafer signal S_W(± 1) belief
Signal level and wafer signal S_WLarge and small with (± 2) signal level
It is possible to use the one with higher signal level, depending on
It As another method, a typical sample wafer is prepared in advance.
Using the wafer signal S_W(± 1) average amplitude level A1
And wafer signal S_WCalculate the average amplitude level A2 of (± 2)
The wafer signal S for the actual wafer 6_W(± 1)
Deviation σ1 from the average amplitude level A1 of
Eha signal S_WAverage amplitude level A2 of the signal level of (± 2)
And the deviation σ2 from. And the function of the deviation σ1
Position deviation Δx using a function of₁ And △ x ₂ of
Take a weighted average and use this average for reticle 4 and wafer
It is conceivable that the relative displacement with respect to 6 is set. Well
Wafer signal S_W(± 1) and wafer signal S_WWith (± 2)
Only the signal that is closer to the corresponding average amplitude level
You may stay.

By the way, in the above embodiment, made different and a beat frequency Delta] f ₂ by the beat frequency Delta] f ₁ and ± 2-order diffracted light by ± 1-order diffracted light, is divided by the Fourier series method at the stage of signal processing. In this Fourier series method, a bandpass filter that allows a signal having a frequency of ΔF _{1 and} a signal of a frequency of Δf ₂ to pass from a detection signal in which a component of frequency Δf _{1 and} a component of frequency Δf ₂ are mixed. (Or a low-pass filter or the like) is used to separate the interference light signal of the ± first-order diffracted light and the interference light signal of the ± second-order diffracted light. Other than that, the laser light source 11
Dispose shutters at the exit ends of a and 11b,
By alternately turning on and off these shutters,
The beat frequency Δf ₁ component and the beat frequency Δf ₂ component may be detected in a time division manner. In this case, it is clear that the frequency Δf ₁ and the frequency Δf ₂ may be the same in principle. In this case, the light emission of the laser light source itself may be turned on / off by using a semiconductor laser element as the laser light sources 11a and 11b instead of turning on / off the shutter. In addition, AOM14
You may turn on / off a, 14b, 15a, 15b.

Next, a second embodiment of the present invention will be described with reference to FIGS. 9 and 10. The second embodiment not only corrects the axial chromatic aberration and the lateral chromatic aberration of the projection optical system 5 with respect to the alignment light with which the wafer mark is irradiated, but also the axial chromatic aberration and the lateral direction with respect to the alignment light returned from the wafer mark. This is an example in which the chromatic aberration of is also corrected.
9, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 9A shows an X-ray projection exposure apparatus of this embodiment.
9B is a right side view of FIG. 9A. In the present embodiment, the chromatic aberration control plate 38 is arranged on the pupil plane of the projection optical system 5, but the arrangement and role of the chromatic aberration control element on this chromatic aberration control plate 38 are different from those of the chromatic aberration control plate 10 of the first embodiment. Is different. FIG. 10 shows the arrangement and shape of chromatic aberration control elements on the chromatic aberration control plate 38 of the second embodiment. On the chromatic aberration control plate 38 made of this transparent substrate, a straight line Y1 passing through the optical axis AX and parallel to the Y axis is shown. A pair of on-axis and lateral chromatic aberration control elements G2 _1A and G2 _1B are formed in axial symmetry with respect to, and also on the outside thereof, a pair of on-axis and lateral directions of a diffraction grating are axially symmetric with respect to the straight line Y1. Chromatic aberration control elements G2 _1C and G2 _1D are formed. In this embodiment, these axial and lateral chromatic aberration control elements G2 _{1A to} G 2
The 2 _1D controls the axial chromatic aberration and the lateral chromatic aberration of the four light beams with which one wafer mark on the wafer 6 is irradiated.

Further, with respect to a straight line X1 which passes through the optical axis AX and is parallel to the X direction, diffraction is performed at a position symmetrical to the midpoint of the chromatic aberration control elements G2 _{1A to} G2 _1D , that is, on the straight line Y1 and at a predetermined pitch in the direction of the straight line Y1. A lattice-shaped lateral chromatic aberration control element G2 _1E is formed. The lateral chromatic aberration control element _G21E corrects lateral chromatic aberration with respect to the alignment detection light from the wafer mark 37. Also in this embodiment, a total of 20 (= 5 × 4) chromatic aberration control elements are provided on the chromatic aberration control plate 38 so that the positions of four different wafer marks in the exposure field of the projection optical system 5 can be detected. Is provided. That is, the chromatic aberration control elements G2 _{1A to} G2 _1E are respectively rotated by 90 °, 180 ° and 270 ° about the optical axis AX, and the chromatic aberration control elements G2 _{2A to} G2 ₁
2 _2E , chromatic aberration control elements G2 _{3A to} G2 _3E, and chromatic aberration control elements G2 _{4A to} G2 _4E are provided.

Returning to FIGS. 9A and 9B, the wafer alignment illumination lights WB _{1 to} WB ₄ applied to the wafer mark 37 on the wafer 6 in this embodiment pass through the reticle window 34 on the reticle 4. It is incident on the projection optical system 5. Then, the illumination lights WB _{1 to} WB ₄ are transferred to the wafer in a state where not only the axial chromatic aberration but also the lateral chromatic aberration is controlled by the axial and lateral chromatic aberration control elements G2 _{1A to} G2 _1D on the chromatic aberration control plate 38. The wafer mark 37 on 6 is irradiated. At this time, as shown in FIG. 9A, the positions of the illumination lights WB _{1 to} WB ₄ irradiated on the wafer mark 37 are Δβ as compared with those in the first embodiment, the optical axis of the projection optical system 5. It is approaching the AX direction, that is, the meridional direction.

From the wafer mark 37, the wafer detection lights WB ₁ (+1), WB ₂ (-1) and the wafer detection lights WB ₃ (+2), WB ₄ (-2) are obtained as in the first embodiment. ) Occurs. When the wafer detection light reaches the chromatic aberration control plate 32 again, the lateral chromatic aberration of each of the wafer detection lights is controlled by the lateral chromatic aberration control element _G21E . As a result, each wafer detection light returns to the alignment optical system 1 through the reticle window 35 that has passed at the time of incidence. The other structure and operation are the same as those in the first embodiment, and the description thereof will be omitted.

According to the second embodiment, the wafer mark 3
Since the chromatic aberration of the alignment light radiated to 7 and the chromatic aberration of the alignment light from the wafer mark 37 are controlled, when viewed from the alignment optical system 1, the reticle mark 36 and the wafer mark 37 are conjugated under the alignment light. Therefore, the configuration of the alignment optical system 1 is simplified. In addition, the wafer illumination light and the wafer detection light are transmitted to the reticle 4.
Since the position passing above can be arranged outside the exposure area, the area of the wafer mark area occupying the exposure area on the wafer 6 can be reduced. Further, the position of the reticle window 35 formed on the reticle 4 can be set at a convenient position, and the position of the wafer mark 37 can also be set at a desired position such as a position where the exposure light is less irradiated. Furthermore,
The reticle window 35 can be made smaller.

Next, FIG. 11 to FIG. 11 according to the third embodiment of the present invention.
This will be described with reference to FIG. The third embodiment has the axial chromatic aberration control function removed from the chromatic aberration control element of the second embodiment. 11, parts corresponding to those in FIG. 9 are designated by the same reference numerals, and detailed description thereof will be omitted.
In FIG. 2, parts corresponding to those in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 11A is a view of the projection exposure apparatus of this embodiment seen from the X direction, and FIG. 11B is a right side view of FIG. 11A. In this embodiment, the chromatic aberration control plate 39 is arranged on the pupil plane of the projection optical system 5, but the role of the chromatic aberration control element on this chromatic aberration control plate 39 is different from that of the chromatic aberration control plate 38 of the second embodiment. There is. FIG. 14 shows the arrangement and shape of chromatic aberration control elements on the chromatic aberration control plate 39 of the third embodiment. On the chromatic aberration control plate 39 made of this transparent substrate, a straight line Y1 passing through the optical axis AX and parallel to the Y axis is shown. A pair of diffraction grating-shaped lateral chromatic aberration control elements G3 _1A , which are axially symmetrical with respect to
G3 _1B is formed, and a pair of diffraction grating-shaped lateral chromatic aberration control elements G3 _1C and G3 _1D are also formed on the outside thereof.
In the present embodiment, these lateral chromatic aberration control elements G3 _{1A to} G3 ₁
3 _1D controls the lateral chromatic aberration of the four light beams with which one wafer mark on the wafer 6 is irradiated.

A straight line passing through the optical axis AX and parallel to the X direction
Chromatic aberration control element G3 with respect to X1_1A~ G3_1DPaired with the midpoint
At a nominal position, a diffraction pattern with a predetermined pitch in the direction of the straight line Y1
Child-shaped lateral chromatic aberration control element G3_1EAre formed.
This lateral chromatic aberration control element G3_1EBy the wafer mark
Correction of chromatic aberration for alignment detection light from 37
Done. Also in this embodiment, the exposure field of the projection optical system 5
Can detect the position of 4 different wafer marks
Thus, a total of 20 (= 5 ×
4) There are provided chromatic aberration control elements. That is, color collection
Difference control element G3 _1A~ G3_1E90 about the optical axis AX
Colors at positions rotated by °, 180 ° and 270 ° respectively
Aberration control element G3_2A~ G3_2E, Chromatic aberration control element G3_3A~
G3_3EAnd chromatic aberration control element G3_4A~ G3_4EIs provided
There is.

Returning to FIGS. 11A and 11B, the wafer illumination lights WB _{1 to} WB ₄ applied to the wafer mark 37 on the wafer 6 in this embodiment are reticle windows 40 on the reticle 4.
And then enters the projection optical system 5. And the illumination light WB ₁
.About.WB ₄ is irradiated onto the wafer mark 37 on the wafer 6 in a state where only the lateral chromatic aberration is controlled by the lateral chromatic aberration control elements G3 _{1A to} G3 _1D on the chromatic aberration control plate 39.

From the wafer mark 37, the wafer detection lights WB ₁ (+1), WB ₂ (-1) and the wafer detection lights WB ₃ (+2), WB ₄ (-2) are obtained as in the second embodiment. ) Occurs. When these wafer detection lights reach the chromatic aberration control plate 39 again, the lateral chromatic aberration of each of the wafer detection lights is controlled by the lateral chromatic aberration control element _G31E . As a result, each wafer detection light returns to the alignment optical system 1 through the reticle window 40 that has passed when it was incident. The other structure and operation are the same as those in the first embodiment, and the description thereof will be omitted.

At this time, in this embodiment, since the axial chromatic aberration correction is not performed, the wafer illumination lights WB _{1 to} WB ₄ for illuminating the wafer mark 37 as shown in FIG. 11B.
Are configured so that they are condensed above the reticle 4 by the axial chromatic aberration ΔL. FIG. 12 shows the configuration of the alignment optical system 1 according to the third embodiment, which is shown in FIGS.
As shown in FIGS. 12A to 12C corresponding to
Reticle illumination lights RB _{1 to} R separated by the plane-parallel plate 26
An optical path difference generating element 27 is provided on the optical path of B ₄ . Other configurations are the same as those in FIGS. By the optical path difference generating element 27, in FIGS. 11A and 11B, the reticle illumination lights RB _{1 to} RB ₄ and the wafer illumination light WB _{1 are used.}
~ The crossing position with WB ₄ is different. Other,
By changing the polarization states of both illumination lights, the lens 28 of FIG.
It is also conceivable to use a double focus lens.

FIG. 13 shows a reticle mark 41 and a reticle window 40 on the reticle 4 of this example. In this example, since the axial chromatic aberration of the wafer illumination lights WB _{1 to} WB ₄ is not corrected, it is necessary to widen the reticle window 40 by that amount, as shown in FIG. According to the third embodiment, since the lateral chromatic aberration of the alignment light irradiated on the wafer mark 37 and the lateral chromatic aberration of the alignment light from the wafer mark 37 are controlled, the reticle 4
The position of the reticle window 40 formed on the substrate can be set to a convenient position, and the position of the wafer mark 37 can also be set to a desired position such as a position where the exposure light irradiation is small.
Further, since the axial chromatic aberration of the projection optical system 5 with respect to the wafer illumination light is not corrected, only the lateral chromatic aberration is controlled.
When the on-axis chromatic aberration between the exposure light and the alignment light is not large (for example, when the i-line of a mercury lamp is used as the exposure light and the Ne-Ne laser beam is used as the alignment light), the grating of the chromatic aberration control element is used. The pattern can be formed only in two directions orthogonal to each other, and the chromatic aberration control plate 39 can be easily manufactured.

In the second and third embodiments, the lateral chromatic aberration is controlled in the radial direction with respect to the optical axis AX of the projection optical system 5 as shown in FIG. 9A, for example. That is, it is going in the meridional direction. However, the lateral chromatic aberration can be controlled not only in the meridional direction but also in any direction.

Next, a fourth embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. In this embodiment, unlike the above-mentioned three embodiments, one alignment optical system detects not only the positional deviation between the reticle 4 and the wafer 6 in the X direction but also the positional deviation in the Y direction. . Therefore, the wafer illumination lights WB _{1 to} WB ₄ and the reticle illumination light R for performing the alignment in the X direction as shown in FIG.
In addition to B ₁ ~RB _4, the wafer illumination light WB ₅ ~WB ₈ and the reticle illumination light RB ₅ ~RB ₈ (not shown) for performing alignment in Y direction is, the objective lens corresponding to the objective lens 2 of FIG. 9 Is ejected from. Wafer illumination lights WB _{5 to} WB ₈ (not shown) for performing the alignment in the Y direction
And reticle illumination light RB ₅ ~RB ₈ is irradiated to the wafer mark and the reticle mark respectively in a plane perpendicular to the plane of FIG. 9 (b).

FIG. 15 shows the arrangement and shape of the chromatic aberration control elements on the chromatic aberration control plate 42 arranged on the pupil plane of the projection optical system in the fourth embodiment. In FIG. 15, wafer illumination for the X direction is shown. Chromatic aberration control elements G4 _{1A to} G4 for correcting axial and lateral chromatic aberrations of the lights WB _{1 to} WB _4.
1D and a chromatic aberration control element G4 _1E for correcting lateral chromatic aberration of the detection light from the wafer mark by the wafer illumination light are provided. These chromatic aberration control elements G
The shapes and arrangements of 4 _{1A to} G4 _1E are the same as those of the axial and lateral chromatic aberration control elements G2 _{1A to} G2 _1D and the lateral chromatic aberration control element G2 _1E shown in FIG. 10 of the second embodiment.

Further, the wafer illumination light WB _{5 to} W for the Y direction is used.
As for B ₈ , the direction of the amount of beam position shift on the wafer (the amount corresponding to Δβ in FIG. 9A) coincides with the Y direction, which is the measurement direction, so it is necessary to control the axial chromatic aberration. The direction of the control element and the lattice direction of the control element necessary for controlling the lateral chromatic aberration coincide with each other. Therefore, the control of the chromatic aberration of the wafer illumination light WB _{5 to} WB ₈ for the Y direction is
Illumination light chromatic aberration control elements G4 _{2A to} G4 arranged on a straight line Y1 passing through the optical axis AX on the chromatic aberration control plate 42 and parallel to the Y direction and formed at a predetermined pitch in the direction of the straight line Y1.
It is done by 4 _2D . Further, the wafer illumination light WB _{5 to} W
Control of the chromatic aberration of the detection light generated from the wafer mark by B ₈ can be used also by the chromatic aberration control element G4 _1E for the X direction.

Further, in this embodiment, two alignment optical systems for detecting positional deviations in the X and Y directions can be arranged. Therefore, on the chromatic aberration control plate 42 of FIG. 15, the chromatic aberration control elements G4 _{1A to} G4 _1E and the illumination light chromatic aberration control elements G4 _{2A to} G4 _2D are rotated by 90 °, respectively, and the chromatic aberration control elements G4 _{3A to} G4 _3E , respectively. And illumination light chromatic aberration control elements G4 _{4A to} G4 _4D . Therefore, a total of 18 chromatic aberration control elements are provided on the chromatic aberration control plate 42.

[0066] Figure 16 shows a reticle mark 44 and the reticle window 43 on the reticle of the present embodiment, as shown in FIG. 16, the reticle mark 44 pitch P _R is the grating and the Y-pitch P _R in the X direction It is formed by a two-dimensional lattice which is overlapped with the lattice. Then, on the reticle mark 44,
The reticle illumination lights RB _{1 to} RB ₄ for the X direction and the reticle illumination lights RB _{5 to} RB ₈ for the Y direction are irradiated, and the reticle window 43 is irradiated with the wafer illumination lights WB _{1 to} WB ₄ for the X direction and for the Y direction. Wafer illuminating lights WB _{5 to} WB ₈ are passing.
FIG. 17 shows a wafer mark 45 on the wafer of this example,
As shown in this FIG. 17, the wafer mark 45 is formed in a two-dimensional grid of repeating the grating pitch P _W in a grid and the Y-pitch P _W in the X direction. Then, the wafer mark 45 is irradiated with wafer illumination lights WB _{1 to} WB ₄ for the X direction and wafer illumination lights WB _{5 to} WB ₈ for the Y direction.

In the light receiving system of the alignment optical system of this example, it is necessary to discriminate the wafer detection light and the reticle detection light for the X direction from the wafer detection light and the reticle detection light for the Y direction, respectively. In this case, for example, the wafer detection light for the X direction and the wafer detection light for the Y direction overlap on the wafer and on the pupil plane of the projection optical system, and therefore cannot be separated by an element such as a slit. As a method of separating, for example, a method of making the polarization directions of the illumination light for the X direction and the illumination light for the Y direction different can be considered.

However, in this embodiment, the frequency difference of the alignment illumination light for the X direction is set to Δf ₁ and Δf _2, and the frequency difference of the alignment illumination light for the Y direction is set to Δf ₃ and Δf ₄ different from them. To do. Then, the detection light of four beat frequencies is received by one photoelectric detection element, and the output signal from this photoelectric conversion element is supplied to the high pass filter circuit, the low pass filter circuit, and the two band pass filter circuits. Two independent wafer signals can be obtained. The same applies to the reticle signal.

As described above, according to this embodiment, one objective lens (lens corresponding to the objective lens 2 in FIG. 9B)
Can detect alignment in two directions. Therefore, if only the two-dimensional positional shift amount between the reticle 4 and the wafer 6 (the positional shift amount in the X direction and the Y direction and the shift amount of the rotation angle) is detected, the apparatus can be constructed with only two objective lenses. Not only does this hold, but by using four objective lenses, it is also possible to detect magnification errors between the reticle 4 and the chips on the wafer 6, and the alignment accuracy can be further improved.

Note that, for example, in the embodiment of FIG. 9, the wafer mark 37 is formed by a two-dimensional lattice, and the wafer illumination lights WB ₃ and WB ₄ of FIG. 9B are applied in the Y direction, that is, the paper surface of FIG. 9B. By irradiating the wafer mark 37 in a plane perpendicular to the plane, it is possible to detect the positional deviation between the reticle 4 and the wafer 6 in the Y direction. Further, in common with each of the above-described embodiments, as a method of extracting a signal of each frequency from a signal in which signals of a plurality of frequencies are mixed, the original signal is equal to or more than twice the highest frequency of the plurality of frequencies. It is also possible to use a method in which digital sampling is performed at the frequency of and the data is temporarily stored in the memory. From the signal thus stored in the memory, only the signal of a specific frequency can be taken out by the arithmetic processing by the Fourier series method. In this case, each signal can be completely separated and extracted by setting the ratio of each beat frequency (for example, Δf ₁ , Δf ₂ ) to a simple integer ratio and selecting the sampling time as a common multiple of the period of each signal.

In the above embodiment, the average wavelengths of the wafer illumination lights WB ₁ and WB ₂ and the wafer illumination lights WB ₃ and WB ₄ are set equal to each other in FIG. 1, for example.
Wafer illumination light WB ₁ , WB ₂ average wavelength and wafer illumination light W
The average wavelengths of B ₃ and WB ₄ may be different. When the average wavelength is changed in this way, the wafer illumination lights WB ₁ , W
Detection light from wafer mark by B ₂ and wafer illumination light W
The detection light from the wafer mark by B ₃ and WB ₄ may be separated by wavelength discrimination, for example.

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0073]

According to the first alignment apparatus of the present invention, the irradiation light control means controls only the axial chromatic aberration of the projection optical system with respect to the alignment light irradiated on the alignment mark on the substrate. Even if the lattice pitch of the alignment mark becomes fine, it can be dealt with by changing the position of the irradiation light control element without changing the area. Therefore, the burden on the design and manufacturing of the projection optical system can be reduced, and a high-performance alignment apparatus can be realized. Also, the frequency Δf ₁ component and the frequency Δf
_{Since the second} component is obtained, accurate alignment can be performed even when the surface state of the substrate is changed by the process and the component of the frequency Δf ₁ is reduced.

Further, the alignment mark on the substrate is measured by the two light beams emitted from the third light irradiation unit, and the alignment mark on the substrate is measured by the two light beams emitted from the fourth light irradiation unit. When the directions are orthogonal to each other, the two-dimensional positional deviation between the mask and the substrate can be detected by one alignment device. Further, according to the second alignment apparatus of the present invention, the axial chromatic aberration of the projection optical system with respect to the alignment light is not corrected and only the lateral chromatic aberration is controlled, so that the position where the alignment light passes on the mask is controlled. Can be placed outside the exposure area,
The area of the alignment mark region with respect to the exposure region can be reduced on the substrate. And this alignment device
For example, when it is applied when the axial chromatic aberration between the exposure light and the alignment light is not large, the configuration of the irradiation light control means and the detection light control means is simple, and the manufacture of the alignment apparatus is easy.

The component of frequency Δf ₁ and frequency Δf ₂
Therefore, even if the surface state of the substrate is changed by the process and the component of the frequency Δf ₁ becomes small, the alignment can be accurately performed. Furthermore, since the irradiation light control means and the detection light control means are independent of each other, it is possible to separately control the chromatic aberration amount of the alignment light irradiated on the alignment mark and the chromatic aberration amount of the detection light from the alignment mark. Is. For example, by making the positions of the illumination light passing through the mask and the detection light different and spatially separating the regular reflection light and the detection light of the illumination light by the mask, it is possible to prevent both lights from mixing. .

At this time, if the axial chromatic aberration of the projection optical system is also controlled, the configuration of the alignment optical system is simplified. Then, the measurement direction by the two light beams emitted from the third light irradiation unit onto the alignment mark on the substrate and the measurement direction by the two light beams emitted from the fourth light irradiation unit onto the alignment mark on the substrate are When they are orthogonal to each other, it is possible to detect a two-dimensional displacement between the mask and the substrate with one alignment device.

[Brief description of drawings]

FIG. 1 (a) shows a first alignment apparatus according to the present invention.
A schematic configuration diagram showing a projection exposure apparatus to which an embodiment is applied,
FIG. 1B is a right side view of FIG.

2A is a configuration diagram showing the alignment optical system 1 in FIG. 1, FIG. 2B is a right side view of FIG. 2A, and FIG.
It is a bottom view of (b).

FIG. 3 is a block diagram showing an example of a signal processing system of the alignment apparatus of FIG.

FIG. 4 is an enlarged plan view showing a reticle mark and a reticle window on the reticle of the first embodiment.

FIG. 5 is an enlarged plan view showing a wafer mark on the wafer of the first embodiment.

FIG. 6 is a plan view showing the arrangement and shape of chromatic aberration control elements of the chromatic aberration control plate 10 of the first example.

FIG. 7 is a waveform diagram showing some reticle signals and some wafer signals obtained in the first embodiment.

FIG. 8 is a waveform diagram showing the remaining reticle signal and the remaining wafer signal obtained in the first embodiment.

9A is a schematic configuration diagram showing a projection exposure apparatus to which a second embodiment of the present invention is applied, and FIG. 9B is a right side view of FIG. 9A.

FIG. 10 is a plan view showing the arrangement and shape of chromatic aberration control elements of the chromatic aberration control plate 38 of the second example.

11A is a schematic configuration diagram showing a projection exposure apparatus to which a third embodiment of the present invention is applied, and FIG. 11B is a right side view of FIG. 11A.

12A is a configuration diagram showing the alignment optical system 1 in FIG. 11, FIG. 12B is a right side view of FIG. 12A, and FIG.
FIG. 12 is a bottom view of FIG.

FIG. 13 is an enlarged plan view showing a reticle mark and a reticle window on the reticle of the third embodiment.

FIG. 14 is a plan view showing the arrangement and shape of chromatic aberration control elements of the chromatic aberration control plate 39 of the third example.

FIG. 15 is a plan view showing the arrangement and shape of chromatic aberration control elements of the chromatic aberration control plate used in the alignment apparatus according to the fourth embodiment of the present invention.

FIG. 16 is an enlarged plan view showing a reticle mark and a reticle window on the reticle of the fourth embodiment.

FIG. 17 is an enlarged plan view showing a wafer mark on the wafer of the fourth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Alignment optical system 2 Objective lens 3 Dichroic mirror 4 Reticle 5 Projection optical system 6 Wafers 10, 38, 39, 42 Chromatic aberration control plate 11a, 11b Laser light source 12a, 12b Beam splitter prism 14a, 14b, 15a, 15b Acousto-optic modulator (AOM) 16a, 16b, 17a, 17b Slit 25 Field slit 26 Parallel plane plate 29 Beam splitter 31 Detection light separation prism 35, 40, 43 Reticle window (transmission window for wafer illumination light) 36, 41, 44 Reticle mark 37 , 45 wafer marks RB ₁ ~RB ₄ reticle alignment illumination light WB ₁ ~WB ₄ wafer alignment illumination light _{G1 1A ~G1 1D, G2 1A ~G2} 1E aberration control element _{G3 1A ~G3 1E, G4 1A ~G4} 1E aberration control element

Claims (5)

[Claims] 1. A projection exposure apparatus which projects and exposes a pattern formed on a mask onto a substrate on a stage that is two-dimensionally movable under exposure light via a projection optical system, In an alignment apparatus that detects a relative displacement between a mask and the substrate with alignment light having a wavelength different from that of the exposure light, a grid-shaped alignment mark formed on the mask has a mutual frequency of the alignment light. Is Δf
_{The first} light irradiating means for irradiating two coherent light fluxes different from each other from different directions and the lattice-shaped alignment mark formed on the mask have a frequency Δf as the alignment light.
_Second masking means for irradiating two coherent light fluxes different from each other by Δf ₂ different from ₁ , respectively from different directions, and the mask and the projection optical system with respect to the lattice-like alignment marks formed on the substrate. A third coherent light flux having a frequency different from each other by Δf ₁ as the alignment light is emitted from different directions via
The light irradiating means and the grid-like alignment mark formed on the substrate, through the mask and the projection optical system, two coherent light beams having different frequencies as the alignment light by Δf ₂ , Fourth irradiation from different directions
On the pupil plane in the projection optical system or on a surface in the vicinity of the pupil plane in the area where the two light beams from the third light irradiation unit and the two light beams from the fourth light irradiation unit pass. Irradiation light control means arranged to control the axial chromatic aberration of the projection optical system with respect to the light flux from the third light irradiation means and the light flux from the fourth light irradiation means to a predetermined value, respectively. First detection means for detecting two or more sets of light beams consisting of two light beams diffracted in the same direction by the alignment mark above, and two sets of two light beams diffracted in the same direction by the alignment mark on the substrate, respectively. First phase comparison for comparing the phases of the components of frequency Δf ₁ in the detection signals obtained from the first detection means and the second detection means with the second detection means for detecting the above luminous flux Means and Respectively obtained by said first detection means and the second and the second phase comparing means for comparing the phase of the component between the frequency Delta] f ₂ of the detection signal obtained from the detection means, the two phase comparing means An alignment apparatus comprising: a positional deviation detection unit that detects a relative positional deviation amount between the mask and the substrate based on the phase difference. 2. The alignment mark on the substrate is irradiated with the two light beams emitted from the third light irradiation unit, and the alignment mark on the substrate is illuminated with the fourth light irradiation unit. The alignment apparatus according to claim 1, wherein the measurement directions of the two light fluxes are orthogonal to each other. 3. A projection exposure apparatus which projects and exposes a pattern formed on a mask onto a substrate on a stage that is two-dimensionally movable under exposure light via a projection optical system, In an alignment apparatus that detects a relative displacement between a mask and the substrate with alignment light having a wavelength different from that of the exposure light, a grid-shaped alignment mark formed on the mask has a mutual frequency of the alignment light. Is Δf
_{The first} light irradiating means for irradiating two coherent light fluxes different from each other from different directions and the lattice-shaped alignment mark formed on the mask have a frequency Δf as the alignment light.
_Second masking means for irradiating two coherent light fluxes different from each other by Δf ₂ different from ₁ , respectively from different directions, and the mask and the projection optical system with respect to the lattice-like alignment marks formed on the substrate. A third coherent light flux having a frequency different from each other by Δf ₁ as the alignment light is emitted from different directions via
The light irradiating means and the grid-like alignment mark formed on the substrate, through the mask and the projection optical system, two coherent light beams having different frequencies as the alignment light by Δf ₂ , Fourth irradiation from different directions
On the pupil plane in the projection optical system or on a surface in the vicinity of the pupil plane in the area where the two light beams from the third light irradiation unit and the two light beams from the fourth light irradiation unit pass. Irradiation light control means arranged to control the lateral chromatic aberration of the projection optical system with respect to the light flux from the third light irradiation means and the light flux from the fourth light irradiation means to a predetermined value, respectively. It is arranged on a pupil plane in the optical system or on a surface in the vicinity thereof in a region through which two or more sets of light fluxes of two light fluxes diffracted in the same direction from the alignment mark on the substrate pass, respectively, on the substrate. Detection light control means for generating a predetermined amount of lateral chromatic aberration with respect to the light beam from the alignment mark, and two or more sets of light beams each consisting of two light beams diffracted in the same direction by the alignment mark on the mask. First detecting means for detecting; second detecting means for detecting two or more sets of light fluxes each of which is diffracted in the same direction by the alignment mark on the substrate; A first phase comparing means for comparing the phases of components of the frequency Δf ₁ in the detection signal obtained from the second detecting means; and a detection signal obtained from the first detecting means and the second detecting means. Second phase comparison means for comparing the phases of the components of the frequency Δf ₂ within, and the relative positional deviation amount between the mask and the substrate is detected based on the phase difference obtained by the two phase comparison means. An alignment apparatus comprising: 4. The irradiation light control means controls the axial chromatic aberration of the projection optical system with respect to the light flux from the third light irradiation means and the light flux from the fourth light irradiation means to a predetermined value. 4. The alignment apparatus according to claim 3, wherein the detection light control means controls the axial chromatic aberration of the projection optical system with respect to the light flux from the alignment mark on the substrate to a predetermined value. 5. The alignment mark on the substrate is irradiated with the two light fluxes measured by the third light irradiation unit, and the alignment mark on the substrate is irradiated with the fourth light irradiation unit. The alignment apparatus according to claim 3 or 4, wherein the measurement directions of the two light fluxes are orthogonal to each other.