JPH05226222A - Alignment device of aligner - Google Patents

Abstract

PURPOSE:To reduce the loss of the light quantity of a beam of irradiation light for alignment use when the beam of irradiation light for alignment use is made incident via a dichroic mirror. CONSTITUTION:A mark on a reticle R is irradiated with a beam of light from a light source 3 via a polarizing beam splitter 9, a phase compensation plate 11 and a dichroic mirror 2. A beam of reflected light from the mark on the reticle R is returned to the polarizing beam splitter 9 via the dichroic mirror 2 and the phase compensation plate 11. The beam of reflected light at the polarizing beam splitter 9 is guided to photoelectric sensors 13, 14. The phase compensation plate 11 and the dichroic mirror 2 act as a quarter-wave plate as a whole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aligner for an exposure apparatus suitable for application to an alignment apparatus for aligning a reticle and a wafer in a reduction projection type exposure apparatus for manufacturing semiconductor devices, for example.

[0002]

2. Description of the Related Art When manufacturing a semiconductor device or the like, an original image pattern formed on a reticle is sequentially transferred to a predetermined position on a substrate such as a wafer by a step-and-repeat method via a projection optical system having a predetermined reduction magnification. A reduction projection type exposure apparatus (stepper) for exposing is used. When a semiconductor element is manufactured using such an exposure apparatus, a mask work of several times to several tens of times is required because a large number of layers of circuit patterns are formed on the wafer surface. The main work of this mask work is an alignment work for precisely aligning the pattern image of the reticle to be newly superimposed and exposed with the circuit pattern region already formed on the wafer.

Currently, many of the projection exposure apparatuses that have been put into practical use incorporate an automatic alignment apparatus for optically and automatically aligning a reticle and a wafer, which improves the throughput of semiconductor device manufacturing. is doing. By the way, there are various methods for this automatic alignment apparatus, and one of the methods expected to have the highest accuracy among them is called a TTR (through-the-reticle) method. .. The alignment mark around the circuit pattern area of the reticle and the alignment mark formed around each shot area on the wafer are
This is a method in which an alignment optical system arranged above the reticle detects the deviations at the same time by directly detecting the deviations of both marks, and finely moves the reticle or the wafer so that the deviation amount becomes a predetermined amount.

FIG. 6 is a simplified view of a main part of a conventional projection type exposure apparatus incorporating such a TTR type alignment apparatus. In FIG. 6, 1 is a main condenser lens and 2 is a wavelength selectivity. Have dichroic mirror,
R is a reticle, and the dichroic mirror 2 is fixed on the reticle R at an inclination angle of 45 °. Further, an alignment mark RM and a window are formed in the peripheral portion of the pattern area of the reticle R. The exposure light IL supplied from an exposure optical system (not shown) is supplied to the main condenser lens 1
By this, the principal ray is converted into a substantially parallel luminous flux, and the converted exposure light IL is reflected by the dichroic mirror 2 to illuminate the pattern area of the reticle R with uniform illuminance.
The exposure light transmitted through the reticle R is focused on the wafer W via the projection optical system PL which is telecentric on both sides or one side, and the circuit pattern of the reticle R is transferred to a predetermined shot area on the wafer W. The alignment mark WM is also provided near each shot area on the wafer W.
Are formed.

As the exposure light IL, a g-line, an i-line of a mercury lamp, a KrF excimer laser beam, or the like, which is a light in a wavelength band that is sensitive to the resist on the wafer W, is used. The wafer W is used as the illumination light for alignment.
Light having a low photosensitivity to the above resist, which is usually in a longer wavelength band than the exposure light, is used. As the illumination light for alignment, for example, He-Ne laser light having a wavelength of 633 nm or the like is used. And the dichroic mirror 2
It has a reflectance of 90% or more for exposure light and a transmittance of 50% or more for illumination light for alignment.

In the alignment optical system arranged above the dichroic mirror 2, the illumination light AL for alignment emitted from the light source 3 is converted into a substantially parallel light flux by the second objective lens 4 of the light transmission system and is then beam splitter. It is incident on 5. The illumination light AL reflected by the cemented surface of the beam splitter 5 is focused by the first objective lens 6, transmitted through the dichroic mirror 2, and illuminates the alignment mark RM and the window portion on the reticle R. Light source 3
And the pattern surface of the reticle R are almost conjugate. The illumination light AL reflected from the alignment mark RM passes through the dichroic mirror 2, is converted into a substantially parallel light flux by the first objective lens 6, enters the beam splitter 5, and is transmitted through the joint surface of the beam splitter 5. The illumination light is focused on the light receiving surface of the photoelectric sensor 8 by the second objective lens 7 of the light receiving system, and the image of the alignment mark RM of the reticle R is formed on this light receiving surface. As the photoelectric sensor 8, a two-dimensional charge-coupled image sensor (CC
D) or the like is used.

On the other hand, the illumination light AL transmitted through the window portion of the reticle R is focused on the alignment mark WM on the wafer W via the projection optical system PL. The illumination light AL reflected from the alignment mark WM enters the beam splitter 5 through the projection optical system PL, the window portion of the reticle R, the dichroic mirror 2 and the first objective lens 6, and passes through the joint surface of the beam splitter 5. The illumination light AL is focused on the light receiving surface of the photoelectric sensor 8 by the second objective lens 7 of the light receiving system. An image of the alignment mark WM on the wafer W is formed on the light receiving surface in parallel with the image of the alignment mark RM of the reticle R. The image pickup signal from the photoelectric sensor 8 is processed to obtain a signal corresponding to the positional deviation of the images of both marks, and based on this signal, the reticle stage on which the reticle R is placed or the wafer on which the wafer W is placed. The alignment is automatically performed by slightly moving the stage.

The projection optical system PL has its aberration corrected with respect to the exposure light IL, and there may be chromatic aberration with respect to the illumination light AL of the alignment optical system. In such a case, for example, the photoelectric sensor 8 is used. 2 are provided apart from each other in the optical axis direction, and the alignment mark R is individually set for each photoelectric sensor.
The image of M and the image of the alignment mark WM are detected.

[0009]

However, in the prior art, since the beam splitter is used to separate the light-transmitting system and the light-receiving system of the alignment optical system, the amount of light is half when passing through the beam splitter. Will be lost. In the case shown in this example, 3/4 of the amount of light is lost in the round trip. In this regard, for example, JP-A-63-2293
As disclosed in Japanese Patent Publication No. 05, by using a polarization beam splitter for separating the light transmitting system and the light receiving system,
In principle, it is possible to reduce the amount of light loss.

FIG. 7 shows a simplified alignment optical system using a polarization beam splitter 9 in place of the beam splitter 5 in FIG. 6, and in FIG. 7, the alignment optical system between the polarization beam splitter 9 and the first objective lens 6 is shown. Further, a quarter-wave plate 10 is arranged on. Illumination light linearly polarized in a direction perpendicular to the paper surface of FIG. 7, that is, S-polarization illumination light is emitted from the prism type polarization beam splitter 9, and this S-polarization illumination light is emitted from the light transmitting system. Second
It enters the polarization beam splitter 9 via the objective lens 4. The joint surface of the polarization beam splitter 9 reflects almost all S-polarized light components and almost all the P-polarized light components, and the S-polarized illumination light reflected by the joint surface of the polarization beam splitter 9 is 1/4 wave plate 1
It is incident on 0. Then, the illuminating light converted into circularly polarized light by the ¼ wavelength plate 10 is irradiated onto the reticle R by the first objective lens 6 through a dichroic mirror (not shown), and the illuminating light transmitted through the window of the reticle R is Further, the wafer W is irradiated.

The rotation direction of the circularly polarized light of the reflected light scattered or diffracted by the reticle R or the wafer W is reversed. The circularly polarized reflected light whose rotation direction is reversed enters the quarter wavelength plate 10 again through the first objective lens 6, and the quarter wavelength plate 1
By 0, it is converted into linearly polarized light in a direction parallel to the paper surface of FIG. 7, that is, P-polarized reflected light to the polarization beam splitter 9. The P-polarized reflected light passes through the joint surface of the polarization beam splitter 9 as it is, and is focused on the light receiving surface of the photoelectric sensor 8 by the second objective lens 7 of the light receiving system. In this way, in principle, when the influence of the dichroic mirror is ignored, the loss of the light quantity can be eliminated.

However, when the illumination light for alignment is actually transmitted through the dichroic mirror 2 shown in FIG. 6, the amount of change in phase between P-polarized light and S-polarized light is different, so that the state of circular polarization is not maintained. However, there is a problem that a loss of light quantity occurs in the polarization beam splitter 9 of FIG. As will be described in detail with respect to this, in the TTR type alignment optical system, both the wafer and the reticle are aligned with the projection optical system PL at a position where an alignment mark is placed according to an exposure area of a pattern to be transferred for performing an alignment operation on the exposure apparatus. It must be variable with respect to the center. Therefore, the visual field position of the alignment optical system must be variable.

Furthermore, it is necessary to prevent the optical system that influences the exposure performance from being affected (eg, vignetting). For that purpose, it is necessary to provide the dichroic mirror 2 on the illumination optical system side of the reticle R as shown in FIG. 6 so as to separate the exposure light IL and the alignment light AL. In addition, in order to increase the light quantity of the alignment light by the above means, it is necessary to prevent the circularly polarized light from changing in the circularly polarized light state even after passing through the dichroic mirror 2. However, in order to obtain high resolution, the exposure light is g
Since ultraviolet rays such as X-rays and i-rays are used, there are restrictions on vapor deposition materials and the like. Furthermore, since the amount of light is large in order to shorten the exposure time, if there is absorption or the like, the dichroic mirror 2 will break due to thermal expansion. Therefore, dichroic mirror 2
The absorption in the coating film and the glass substrate in 1 must be suppressed until it becomes almost zero. Therefore, it is difficult to design the coating film, and it is difficult to design the phase difference between the P-polarized light and the S-polarized light for the alignment light AL to be 0 while satisfying the above conditions. It has been difficult to increase the light amount of the alignment light AL by combining and.

In view of the above problems, the present invention performs alignment of an exposure apparatus in which the alignment illumination light is incident through a dichroic mirror and alignment is performed with less loss of the alignment illumination light quantity. The purpose is to provide a device.

[0015]

The alignment device for an exposure apparatus according to the present invention illuminates a first object R with exposure light IL from an exposure light source via a dichroic mirror (2), as shown in FIG. 1, for example. Then, when the pattern of the first object R is exposed on the second object W, the dichroic alignment device of the exposure apparatus performs relative alignment between the first object R and the second object W. A light transmission system (3, 4, 6) for illuminating the alignment marks of the first object R and the second object W through the mirror (2) from a direction different from the exposure light IL, and the dichroic mirror (2). ), Which receives light from the alignment marks of the first object R and the second object W returning via the light receiving system (6, 7,
12, 13, 14), and a polarization beam splitter (9) for separating the alignment light AL directed from the light transmitting system to the dichroic mirror (2) and the alignment light AL directed from the dichroic mirror (2) to the light receiving system. And an optical element (11) arranged in the optical path between the polarization beam splitter (9) and the first object R and acting as a quarter-wave plate together with the dichroic mirror (2). ..

In this case, for example, as shown in FIG. 2, the relative angle between the optical axis of the polarization beam splitter (9) and the optical axis of the dichroic mirror (2) may be set to 45 °.

[0017]

According to the present invention, the quarter wave plate is constituted by the optical element (11) and the dichroic mirror (2) by positively utilizing the phase characteristic of the dichroic mirror (2). It Therefore, when a predetermined linearly polarized light is supplied from the alignment light sending system to the polarization beam splitter (9), the light is emitted from the polarization beam splitter (9) and these optical elements (11) and dichroic mirror (2) are emitted. The polarization state of the alignment light passing through becomes circularly polarized light. Then, the alignment light reflected from the first object R and the second object W is circularly polarized light in the reverse direction, and when this circularly polarized alignment light passes through the dichroic mirror (2) and the optical element (11). It becomes linearly polarized light in a direction almost orthogonal to the time of incidence. Therefore, the polarization beam splitter (2) can efficiently separate the alignment light from the light-transmitting system and the alignment light to the light-receiving system, a signal with a high contrast of the detection signal and a good SN ratio can be obtained, and the position detection accuracy can be improved. improves.

Further, the polarization beam splitter (9)
When the relative angle between the optical axis of the optical axis and the optical axis of the dichroic mirror (2) is set to 45 °, the polarization direction of the alignment light from the light transmitting system and the polarization direction of the alignment light to the light receiving system are completely set. Since it can be perpendicular to, the loss of the amount of light in the polarization beam splitter (9) can be minimized. Therefore, the loss of alignment light can be minimized as a whole.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the alignment apparatus for an exposure apparatus according to the present invention will be described below with reference to FIGS.
In this example, the present invention is applied to an apparatus in which the beam splitter 5 in the projection exposure apparatus of FIG. 6 is replaced by the polarization beam splitter 9 of FIG. 7, and corresponds to FIGS. 6 and 7 in FIGS. 1 and 2. The same reference numerals are given to the parts, and detailed description thereof will be omitted.

FIG. 1 is a simplified view of the main part of the exposure apparatus of this embodiment. In FIG. 1, the dichroic mirror 2 is fixed above the reticle R at an inclination angle of 45 °, and is arranged on the side surface. The exposure light IL obtained by converting the chief ray into a substantially parallel light flux by the condenser lens 1 is used as a dichroic mirror 2.
Is reflected by the reticle R to illuminate the reticle R with uniform illuminance. The pattern of the reticle R is transferred onto the wafer W by the projection optical system PL. Above the dichroic mirror 2,
The first objective lens 6, the phase compensating plate 11, and the prism type polarization beam splitter 9 are arranged, and the second objective lens 4 and the second objective lens 4 of the light transmitting system are arranged in order in the direction of passing through the joint surface (reflection surface) of the polarization beam splitter 9. Light source 3 for alignment light AL
To place. Further, the second objective lens 7 of the light receiving system is sequentially arranged in the direction reflected by the cemented surface of the polarization beam splitter 9.
The photoelectric sensor 14 for the reticle mark, which is composed of the light beam separating prism 12 and the two-dimensional CCD, is arranged, and the photoelectric sensor 13 for the wafer mark, which is composed of the two-dimensional CCD, is arranged in the direction reflected by the joint surface of the light beam separating prism 12. ..

The phase compensating plate 11 is formed of a crystal plate or the like,
The phase characteristics are determined so that the dichroic mirror 2 and the alignment light AL act as a quarter-wave plate. In this case, the polarization direction of the P-polarized component incident on the dichroic mirror 2 is DY and the polarization direction of the S-polarized component incident on the dichroic mirror 2 is DX, and the directions DX and DY are respectively taken as the X axis and the Y axis. For example, when the alignment light AL reciprocates through the dichroic mirror 2, P
When the phase of the polarization component advances by δ with respect to the S polarization component, the phase of the P polarization component with respect to the phase of the S polarization component ((( It is sufficient to advance by n + 1/2) π−δ) (however, n is an integer).

FIG. 2 is a plan view from the direction of arrow A in FIG. 1. As shown in FIG. 2, in this example, the relative angle between the optical axis of the dichroic mirror 2 and the optical axis of the polarization beam splitter 9 is shown. Set to 45 °. The light source 3 supplies the polarization beam splitter 9 with the alignment light AL which is P-polarized light having a polarization direction of D1, and the direction D1 intersects the Y axis (or the X axis) at 45 °. ..

Returning to FIG. 1, in order to explain the operation of this example, the alignment light AL from the light source 3 is polarized through the second objective lens 4 of the light-sending system to separate the light-sending light and the light-receiving light. It is incident on the beam splitter 9. The polarization direction D1 of the alignment light AL from the light source 3 is the P-polarized direction with respect to the polarization beam splitter 9, and the alignment light AL passes through the joint surface of the polarization beam splitter 9 as it is. The alignment light emitted from the polarization beam splitter 9 passes through the phase compensating plate 11, the first objective lens 6 and the dichroic mirror 2, and illuminates the alignment mark RM and the window portion on the reticle R. The alignment light that has passed through the window of the reticle R illuminates the alignment mark WM on the wafer W by the projection optical system PL. At each alignment mark, light having position information of the reticle and the wafer is generated due to light diffraction and scattering phenomenon. These lights are condensed again by the first objective lens 6 via the dichroic mirror 2.

Next, as shown in FIG. 1, Xs orthogonal to each other in the horizontal plane
Consider the Y coordinate. Since the optical axis of the alignment optical system is the vertical direction, the polarization direction of the alignment light AL is within the horizontal plane (XY plane). When the alignment light AL passes through the dichroic mirror 2, a phase difference occurs between the polarized light in the X axis direction and the linearly polarized light in the Y axis direction. The phase compensating plate 11 is arranged so that the direction D3 of the optical axis coincides with the X-axis direction, and when the alignment light passes through the phase compensating plate 11 and the dichroic mirror 2, linearly polarized light in the X-axis direction and Y-axis direction. Of the phase compensation plate 11 so that the phase difference of the linearly polarized light of
The amount of compensation is set. Now, the polarization direction is 4 with the X axis
Linearly polarized alignment light AL with a direction of 5 °
When passes through the phase compensation plate 11, the first objective lens 6 and the dichroic mirror 2, the polarization state becomes circularly polarized.

After the circularly polarized alignment light AL is applied to the reticle R and the alignment mark on the wafer W, it is condensed again by the first objective lens 6 through the dichroic mirror 2 due to reflection, diffraction or scattering. Since the alignment light reflected, diffracted, or scattered by the alignment mark is circularly polarized in the reverse direction, the polarization state of the alignment light AL transmitted through the dichroic mirror 2, the first objective lens 6 and the phase compensation plate 11 and returned is It becomes a linearly polarized light in a direction D2 orthogonal to the polarization direction D1 when the light is incident. Since the polarization beam splitter 9 is arranged so as to form an angle of 45 ° with the X axis, the returned alignment light AL is totally reflected by the joint surface of the polarization beam splitter 9 and is horizontally reflected by the first light receiving system. 2 It enters the objective lens 7.

The alignment light AL which has passed through the second objective lens 7 is divided into two by the light beam separation prism 12, and the reflected light from the alignment mark RM of the reticle R is incident on the photoelectric sensor 14 and the alignment mark WM of the wafer W.
The reflected light from is incident on the photoelectric sensor 13. Positioning can be performed by driving a reticle stage or wafer stage (not shown) based on the reticle position shift signal and the wafer position shift signal output from the photoelectric sensor 14 and the photoelectric sensor 13.

In this embodiment, the optical axis of the alignment optical system is shown as one, but a plurality of optical axes may be used for alignment in the X direction and alignment in the Y direction. Even in that case, as long as the dichroic mirror 2 is manufactured uniformly, the phase compensating plate 11 only needs to perform compensation for the dichroic mirror, and thus only one type is required. However, when a total reflection prism, a mirror, or the like is used to bend the alignment optical system, a phase difference occurs between the two orthogonally polarized lights, and therefore it is necessary to consider the effect and compensate. is there.

The phase compensator 11 may be a Babinet-Soleil compensator capable of changing the phase difference. In this case, when the position of the alignment mark is changed within the exposure area, the phase compensation amount is changed so that the amount of light returning to the light receiving system is maximized to compensate for the phase difference fluctuation due to the nonuniformity of the film such as the dichroic mirror 2. You can also do it.

Next, another embodiment of the present invention will be described with reference to FIGS. In this example, a total reflection prism is used instead of the phase compensation plate 11 of FIG. 1. In these FIGS. 3 and 4, parts corresponding to those of FIG. 1 are denoted by the same reference numerals and detailed description thereof is omitted. To do.

FIG. 3 shows a simplified main part of the projection exposure apparatus of this example. In FIG. 3, the reticle R is the same as in FIG.
Is used as the XY plane, and the optical axis of the optical system including the light source 3, the second objective lens 4 of the illumination system, the polarization beam splitter 9, and the first objective lens 6 is made parallel to the X axis in the horizontal plane (XY plane). .. Reference numeral 15 denotes a total reflection prism. The total reflection prism 15 is arranged above the dichroic mirror 2, and the alignment light AL emitted from the first objective lens 6 is totally reflected by the total reflection prism 15 and bent vertically downward.

FIG. 4 is a side view seen from the direction of arrow B in FIG. 3, and as shown in FIG. 4, the optical axis of the polarization beam splitter 9 is the axis (Z axis) perpendicular to the reticle R. The polarization beam splitter 9 is attached so as to be inclined at 45 °. Then, the polarization direction of the alignment light emitted from the light source 3 is changed to P polarization with respect to the polarization beam splitter 9, that is, 45 ° clockwise with respect to the Z axis.
Set in the inclined direction. In this case, the P-polarized alignment light passes through the polarization beam splitter 9 as it is, and enters the total reflection prism 15 via the first objective lens 6.

Returning to FIG. 3, the alignment light and the window of the reticle R are irradiated with the alignment light totally reflected by the total reflection prism 15 via the dichroic mirror 2. The alignment light reflected from the alignment mark of the reticle R and the alignment mark of the wafer W is transmitted through the dichroic mirror 2 and then totally reflected again by the total reflection prism 15 to be returned to the first objective lens 6. In this case, the amount of change in phase between the P-polarized component and the S-polarized component at the time of total reflection by the total reflection prism 15 is different, and this difference in amount of phase change can be adjusted by evaporating a thin film on the total reflection surface. Since the total reflection prism 15 and the dichroic mirror 2 are a quarter wavelength plate for the alignment light, the total reflection prism 15 and
Adjust the amount of phase change at. The alignment light returned to the first objective lens 6 receives the polarization beam splitter 9
On the other hand, since it is S-polarized, it is entirely reflected by the joint surface of the polarization beam splitter 9 and goes to the second objective lens 7 of the light receiving system. The subsequent operation is the same as in the case of FIG.

Reticle R and total reflection prism 15 of this example
The configuration will be described in detail. Figure 5 (a) shows the reticle R
As shown in FIG. 5A, a pair of alignment marks PMY1 and a window WMY1 are formed at one end in the Y direction around the pattern area PA of the reticle R, and a pair of alignment marks is also formed at the other end. PMY2 and window WM
Y2 is formed. A pair of alignment marks PMX1 and a window WMX1 are formed at one end in the X direction around the pattern area PA of the reticle R, and a pair of alignment marks PMX2 and a window WMX2 are also formed at the other end. Similarly, four alignment marks are formed around each shot area of the wafer W.

FIG. 5B is a side view of the total reflection prism 15. As shown in FIG. 5B, the slope of the total reflection prism 15 is made of a dielectric material of a predetermined material and a predetermined thickness. The multilayer film 16 is formed. Thereby, a desired phase difference can be generated between the P-polarized light and the S-polarized light of the alignment light totally reflected by the total reflection prism 15. In this example, the total reflection prism 15 serves as both a mirror for bending the optical path and a phase compensating plate, so that the configuration is simplified.

In the above embodiment, the exposure light is reflected by the dichroic mirror 2 to illuminate the reticle R, and the alignment illumination light is transmitted through the dichroic mirror 2 to illuminate the reticle R. The present invention can also be applied to the case where the light passes through the dichroic mirror to illuminate the reticle R, and the illumination light for alignment is reflected by the dichroic mirror to illuminate the reticle R.

In the above embodiment, the image of the alignment mark RM on the reticle R side and the image of the alignment mark WM on the wafer W side are fetched and the positional deviation between the two is detected by image processing. The present invention can also be applied to a two-beam interference type alignment optical system that irradiates an alignment mark with a laser beam. As described above, the present invention is not limited to the above-described embodiments, and various configurations can be taken without departing from the gist of the present invention.

Next, for reference, the operation of the phase compensating plate 11 of FIG. 1 will be analyzed using mathematical expressions. Here, we will use the Jones Vector to display the state of polarization more accurately. The Jones vector is a vector indicating the direction of polarization in a plane perpendicular to the traveling direction of light. In the example of FIG. 1, that plane coincides with the horizontal plane (XY plane), so that the light is parallel to the X axis. Separately consider the component and the component parallel to the Y-axis. First, since the plane of polarization of the incident light on the polarization beam splitter 9 is inclined by 45 ° with respect to the X axis, both the X axis component and the Y axis component of the incident light have the same value. The X-axis component is shown in the upper stage of the vector and the Y-axis component is shown in the lower stage, and the vector display of the incident light to the polarization beam splitter 9 is expressed as the following (Equation 1).

[Equation 1]

Next, the light is transmitted through the polarization beam splitter 9 for separating the transmitted light and the received light, but the polarization direction of the incident light is P-polarized with respect to the polarization beam splitter 9, and the incident light is transmitted as it is. Since it is only, the state of (Equation 1) is saved. The function of this polarization beam splitter 9 is represented by (Equation 2).

[Equation 2]

Next, in the phase compensating plate 11, since the optical axis is oriented in the X-axis direction, the Y-axis component with respect to the X-axis component is
The phase is delayed by the phase compensation amount φ. The vector display of the alignment light after passing through the phase compensation plate 11 is as shown on the right side of (Equation 3).

[Equation 3]

Further, since the dichroic mirror 2 is attached obliquely to the Y-axis direction, polarized light in the X-axis direction becomes S-polarized light and polarized light in the Y-axis direction becomes P-polarized light. Therefore, by passing through the dichroic mirror 2,
The phase of the Y-axis component lags behind that of the X-axis component by ψ. The vector display of the alignment light after passing through the dichroic mirror 2 is the right side of (Equation 4).

[Equation 4]

Now, if φ is selected so that φ + ψ = π / 2, (Equation 4) can be transformed into (Equation 5).

[Equation 5]

That is, since the phase of the Y-axis component is delayed by π / 2 with respect to the X-axis component, time advances so that the polarization plane rotates counterclockwise. This state is circularly polarized light. Further, the alignment light is irradiated onto the alignment mark to generate reflected light, diffracted light, scattered light, or the like. Since the alignment light is incident almost vertically, the reflected light or the like is isotropically generated in the X-axis direction and the Y-axis direction. Due to the reflection, the polarization plane becomes as shown in (Equation 6).

[Equation 6]

Next, since the reflected light passes through the dichroic mirror 2 and the phase compensating plate 11, its vector display is as in the last equation of (Equation 7).

[Equation 7]

From (Equation 7), it can be seen that the phase of the Y-axis component of the alignment light returned from the alignment mark to the light receiving system is deviated from the X-axis component by π. this is,
With respect to the incident light from the light source 3 to the polarization beam splitter 9, the alignment light returned from the phase compensation plate 11 to the polarization beam splitter 9 has a polarization plane orthogonal to each other. The return light, whose polarization plane is orthogonal to the incident light, is incident on the polarization beam splitter 9 as S-polarized light and is thus reflected and guided to the light receiving system. As a result, the light is efficiently guided to the photoelectric sensor, so that the signal for alignment can be obtained with a higher SN ratio.

[0045]

According to the present invention, since the optical element and the dichroic mirror act as a quarter-wave plate for the alignment light, there is an advantage that the loss of the alignment light in the polarization beam splitter can be reduced. Also,
When the relative angle between the optical axis of the polarization beam splitter and the optical axis of the dichroic mirror is set to 45 °,
The loss of alignment light in the polarization beam splitter can be minimized.

[Brief description of drawings]

FIG. 1 is a perspective view showing a simplified main part of a projection exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view in the direction of arrow A in FIG.

FIG. 3 is a perspective view showing a simplified main part of a projection exposure apparatus according to another embodiment of the present invention.

FIG. 4 is a side view in the direction of arrow B in FIG.

5A is a plan view showing the pattern configuration of the reticle R of FIG. 3, and FIG. 5B is a side view showing the configuration of the total reflection prism 15 of FIG.

FIG. 6 is a configuration diagram showing a simplified essential part of a conventional projection exposure apparatus.

FIG. 7 is a configuration diagram showing an example of an optical system in which a polarization beam splitter and a quarter-wave plate are combined.

[Explanation of symbols]

 W Wafer PL Projection lens R Reticle 1 Main condenser lens 2 Dichroic mirror 3 Light source 4 Second objective lens of light transmitting system 6 First objective lens of alignment optical system 7 Second objective lens of light receiving system 9 Polarization beam splitter 11 Phase compensation plate 12 Separation prism 13 and 14 Photoelectric sensor 15 Total reflection prism

Claims (2)

[Claims] 1. When exposing a first object with exposure light from an exposure light source through a dichroic mirror and exposing a pattern of the first object onto a second object, the first object and the second object are exposed.
In a positioning device of an exposure device that performs relative positioning with respect to an object, a light transmitting system that illuminates each alignment mark of the first object and the second object through the dichroic mirror from a direction different from the exposure light. And the first coming back through the dichroic mirror
A light receiving system that receives light from each alignment mark of the object and the second object, a polarization beam splitter that separates the alignment light traveling from the light transmitting system to the dichroic mirror and the alignment light traveling from the dichroic mirror to the light receiving system. And an optical element that is arranged between the polarization beam splitter and the optical path between the first object and the dichroic mirror to act as a quarter-wave plate. 2. The relative angle between the optical axis of the polarization beam splitter and the optical axis of the dichroic mirror is 45.
The alignment apparatus for an exposure apparatus according to claim 1, wherein the alignment apparatus is set at °.