JPH06229717A - Position detector - Google Patents

Abstract

PURPOSE:To allow the selective switching of the extending direction of scanning beam by forming a stripe beam spot on an object and shifting the beam spot relatively to a mark put on the object thereby detecting the position of the mark. CONSTITUTION:When a stage 4 is moved in X-direction and a stripe beam spot Spa impinges on an alignment mark AMa, diffracted light is produced from the mark AMa. The diffracted light passes through an objective lens 16a, a beam splitter 15a, and a relay lens 18a to a photoelectric detector 19a where it is subjected to photoelectric conversion. Since the diffracted light from the mark AMa has a maximum intensity when the spot SPa is superposed on the mark AMa, position of the mark AMa can be detected based on a maximum value of photoelectrically converted output from the photoelectric detector 19a. Alternatively, scanning can be carried out with the spot SPa using an oscillatory mirror or the like or the marks AMa, AMb can be imaged using an observation camera 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting apparatus suitable for a projection exposure apparatus used in a lithography process for manufacturing semiconductor integrated circuits and liquid crystal devices.

[0002]

2. Description of the Related Art In recent years, in a lithography process, as a device for transferring a fine pattern onto a photosensitive substrate (semiconductor wafer or glass plate on which a resist layer is formed) with high resolution, a step-and-repeat type projection exposure apparatus ( Hereinafter referred to as a stepper) is often used. When projecting and transferring this fine pattern, the pattern of a mask or reticle (hereinafter, referred to as a mask) and a wafer or plate (hereinafter, referred to as a plate) 1 are aligned with an alignment accuracy suitable for the resolution of the stepper. It is necessary to align with one shot area.

Therefore, in the conventional position detecting device, the mark provided on the plate is measured one dimension at a time and the position of this mark is detected. The conventional position detecting device will be described below with reference to FIG. In FIG. 4A, the light beam from the light source 100 is split into two by the beam splitter 102 via the mirror 101. A shutter 103a and a cylindrical lens 104a having a generatrix in the direction perpendicular to the paper surface are arranged in the transmission direction of the beam splitter 102, and a shutter 103b and a cylindrical lens having a generatrix in the paper direction are arranged in the reflection direction of the beam splitter 102. The lens 104a is arranged.

Now, these shutters 103a and 103b are provided so as to open and close in a staggered manner.
When is open, the light beam from the light source 100 passes through the cylindrical lens 104a and the mirror 105a,
Reach the half mirror 106. Further, when the shutter 103b is open, the light beam from the light source 100 reaches the half mirror 106 via the cylindrical lens 104b and the mirror 105b. Then, the light beam from the cylindrical lens 104a via the objective lens 107 provided on the exit side of the half mirror 106 forms a belt-like beam spot extending in the direction perpendicular to the paper surface on the object plane 108, and the objective lens
The light beam from the cylindrical lens 104b via 107 forms a strip-shaped beam spot extending in the direction of the paper surface on the object plane 10.
Form on 8 Here, a cross-shaped alignment mark AM is provided on the object plane 108, and when detecting the position of this alignment mark AM in the X direction, the shutter 103a is opened and the alignment mark AM is displayed on the object plane. A band-shaped beam spot SPx as shown in 4 (b) is formed. Then, the alignment mark AM and the band-shaped beam spot SPx are relatively moved in the X direction to receive the diffracted light by the light beam generated at the alignment mark, and the X-axis of the alignment mark AM is received.
Detect the direction position.

Further, when detecting the position of the alignment mark AM in the Y direction, the shutter 103b is opened to form a strip beam spot SPy as shown in FIG. 4 (c) on the object plane. Then, the alignment mark AM and the band-shaped beam spot SPy are relatively moved in the Y direction to detect the position of the alignment mark AM in the Y direction.

[0006]

However, in the conventional position detecting device as described above, the optical path of the optical system of the position detecting device is divided to form strip beam spots extending in mutually orthogonal directions. Therefore, there are problems that the optical system becomes complicated and that the light amount is lost due to the optical path division. Also, on the exit side of the cylindrical lens,
It is possible to arrange an image rotating optical member such as an image rotator, but in this way, in order to provide the image rotating optical member, it is necessary to provide a large space in the optical path on the exit side of the cylindrical lens. There is a problem that the optical system of the detection device becomes large.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a position detecting device having a simple structure and capable of selectively switching the extending direction of a scanning beam.

[0008]

In order to achieve the above object, the position detecting device according to the present embodiment has the following configuration. For example, as shown in FIGS. 1 and 2, a strip beam spot (SPa, SPb) is formed on the object (2), and the strip beam spot and the mark (AMa, AMb) provided on the object are relatively moved. Then, the position detecting device for detecting the position of the mark is composed of a light source means (11) for supplying a light beam and a strip beam for converging the light beam from the light source means to form a strip beam spot on the object. Spot forming means (12,13,16a, 1
6b, 17), a first reflecting member (20) rotatably provided in the optical path of the band-shaped beam spot forming means and having a plurality of reflecting surfaces, a position inside the optical path, and a position outside the optical path. And a second reflecting member (21) configured to selectively move between the second reflecting member and the second reflecting member while rotating the first reflecting member when switching the extension direction of the band-shaped beam spot. Configured to move.

[0009]

In the present invention having the above-mentioned structure, the extension direction of the band-shaped beam spot is switched by utilizing the fact that the direction of the image changes depending on the number of reflections in the optical path. Further, in the present invention, since the optical path of the light beam from the light source is not divided, the extension direction of the band-shaped beam spot can be switched without causing a light amount loss.

The present invention has an advantage that it can be arranged in a narrow space as compared with an image rotator or the like which rotates the direction of an image.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. Here, FIG. 1 is a diagram schematically showing an embodiment in which the position detecting device according to the present invention is applied to a projection exposure apparatus for semiconductor manufacturing. In FIG. 1, an illumination optical system (not shown) for illuminating the mask 3 is provided above the mask 3 on which a predetermined circuit pattern is formed, and the circuit pattern illuminated by this illumination optical system is projected by the projection optical system 1. , And is projected and transferred onto the glass substrate (plate) 2 placed on the stage 4. The stage 4 is provided so as to be movable in a two-dimensional direction by a driving unit (not shown).

The laser light source 11 supplies coherent light having a wavelength range different from that of the illumination light from the illumination optical system. As the laser light source 11, for example, a He-Ne laser (633 nm) can be applied. The light beam from the laser light source 11 is converted by the cylindrical lens 12 having a generatrix in a predetermined direction into a light beam having a slit-shaped luminous flux cross section extending in the generatrix direction, and then to the rear focal position Fc of the cylindrical lens 12. Form a focal line extending in a strip shape. Then, the light beam from the cylindrical lens 12 is reflected by the beam splitter 14 via the relay lens 13, and is split into two by the beam splitter 15a. Then, the light beam reflected by the beam splitter 15a is an objective lens.
A strip-shaped converging region (belt beam spot SPa) extending in a predetermined direction is formed on the plate 2 via 16a. Here, since the focal position of the cylindrical lens 12 and the plate 2 are arranged so as to be conjugate with respect to the relay lens 13 and the objective lens 16a, the image of the focal line formed by the cylindrical lens 12 becomes the band-shaped beam spot SPa. .

Here, the wavelength of the light beam is λ, and the objective lens is
When the numerical aperture on the exit side of 16a is NA, the width ω of the strip beam spot SPa can be approximately expressed as ω = 2λ / (π · NA). Meanwhile, beam splitter
The light beam that has passed through 15a is reflected by the beam splitter 15b via the second relay lens 17, and the objective lens 16b
Be led to. Then, by this objective lens 16b, a belt-like beam spot SPb extending in a predetermined direction on the plate 2 is formed.
To form. Since the relay lens 13, the relay lens 17, and the objective lens 16b have a conjugate relationship between the focal point positions of the plate 2 and the cylindrical lens 12, the image of the focal line by the cylindrical lens 12 is a band-shaped beam spot.
SPa.

On the plate 2, L-shaped alignment marks AMa and AMb are provided. The alignment marks AMa and AMb are macroscopically formed in a linear shape or a slit shape, and may be formed of a set of dots or small-angle sides. And this alignment mark
The positions of the alignment marks AMa, AMb can be detected by relatively scanning the AMa, AMb and the strip beam spots SPa, SPb and detecting the diffracted light generated at the alignment marks AMa, AMb.

The case where the position of the alignment mark AMa is detected will be specifically described below as an example. First, it is assumed that a strip-shaped beam spot SPa extending in the Y direction is projected on the plate 2 as shown. Next, stage 4
Is moved in the X direction by a drive unit (not shown) or the like. Here, the band-shaped beam spot SPa is the alignment mark AMa.
When it hits, diffracted light is generated from the alignment mark AMa. The diffracted light is photoelectrically converted by the photoelectric detector 19a via the objective lens 16a, the beam splitter 15a and the relay lens 18a. At this time, the intensity of the diffracted light emitted from the alignment mark AMa reaches its maximum value when the band-shaped beam spot SPa and the alignment mark AMa overlap, so the maximum value of the photoelectric conversion output output from the photoelectric detector 19a can be taken. For example, the position of the alignment mark AMa can be detected. Needless to say, the zonal beam spot SPa may be scanned using a vibrating mirror or the like. Further, in the present embodiment, the observation camera 22 can also detect the images of the alignment marks AMa and AMb, respectively.

Next, when detecting the position of the alignment mark AMa in the Y direction, it is necessary to make the strip-shaped beam spot SPa extend in the X direction. Therefore, in this embodiment, the bending prism 20 and the movable mirror 21 shown in FIGS. 2A and 2B are provided to switch the number of reflections in the optical path between the cylindrical lens 12 and the relay lens 13. ing. Specifically, as shown in FIGS. 2A and 2B, the cylindrical lens 12
A bending prism 20 having three reflecting surfaces and provided rotatably around the optical axis of the cylindrical lens 12 (center of the light beam emitted from the cylindrical lens 12) in the optical path between the relay lens 13 and the relay lens 13. And a movable mirror 21 provided so as to be selectively movable between positions inside and outside the optical path.

Here, when the folding prism 20 and the movable mirror 21 are arranged as shown in FIG. 2A, that is, when the light beam from the cylindrical lens 12 is reflected three times by the folding prism. , The light beam emitted from the cylindrical lens 12 passes through the three reflecting surfaces of the bending prism 20, and
A focal line fl1 (a linearly focused light beam) extending in the Z direction (the device vertical direction) is formed at the rear focal position Fc of the cylindrical lens 12. Then, when the bending prism 20 is rotated 90 ° from the arrangement of FIG. 2 (a) and the movable mirror 21 is inserted on the exit side (in the optical path) of the bending prism 20, the light beam from the cylindrical lens 12 is bent. After passing through the bending prism 20, it is reflected by the movable mirror 21, and the cylindrical lens 12
A focal line fl2 extending in the X direction (the device horizontal direction) is formed at the rear focus position Fc. That is, the cylindrical lens
Depending on whether the number of reflections in the optical path between the relay lens 12 and the relay lens 13 is odd or even, the cylindrical lens 12
The focal line formed by will rotate 90 °.

Then, returning to FIG. 1, the above-mentioned focal lines fl1, fl
2 and the band-shaped beam spot SPa formed on the plate are conjugate, the band-shaped beam spot SPa is rotated when the focal line extension direction is rotated by switching the number of reflections as described above.
The extension direction of a will also rotate 90 °. This allows
The position of the alignment mark AMa in the Y direction can also be detected. The strip beam spot SPb is the bending prism 20.
By the operation of the movable mirror 21 and the movable mirror 21, the extension direction is switched similarly to the strip beam spot SPa. At this time, the extension directions of the strip beam spot SPa and the strip beam spot SPb are the same.

As described above, in this embodiment, the traveling direction of the light beam emitted from the bending prism 20 and the movable mirror 21 does not change before and after the switching of the extension direction of the strip-shaped beam spot, and the optical path Since the lengths are also equal, there are very few restrictions on the arrangement of these reflecting members (bending prism 20, movable mirror 21). And in this embodiment,
Since the reflecting surface is moved integrally by using the bending prism 20, there is an advantage that there is little deterioration in accuracy when switching the extension direction of the band-shaped beam spot.

Since there is no light quantity loss when switching the extension direction of the band-shaped beam spot, it is not necessary to increase the output of the laser light source. Therefore, the size of the laser light source itself can be reduced. Further, in this embodiment, there is an advantage that the reflecting member (the bending prism 20 and the movable mirror 21) for rotating the extending direction of the band-shaped beam spot can be arranged in an extremely narrow space.

The bending prism 20 and the movable mirror 21 are
If it is placed on the exit side of the cylindrical lens 12,
The object of the present invention can be achieved. Then, in the present embodiment, the light emitted from the cylindrical lens 12 is reflected by the first reflecting member (the bending prism 20) and the second reflecting member (the movable mirror 21).
The cylindrical lens 12
It is also possible to have a configuration in which the light from is guided in the order of the second reflecting member and the first reflecting member. Further, instead of the cylindrical lens 12, a lens having a toric surface may be applied.

Further, as a configuration for switching the extension direction of the band-shaped beam spot, for example, the configuration shown in FIG. 3 can be considered. In FIG. 3, the laser light source 31 supplies linearly polarized laser light, and λ / 2 provided on the emission side thereof.
The plate 32 is configured to be selectively movable between a position inside the optical path on the exit side and a position outside the optical path. And
For example, consider the case where the laser light source 31 supplies P-polarized light.
At this time, if the λ / 2 plate 32 is located in the optical path, λ / 2
The laser light passing through the plate 32 becomes S-polarized light and reaches the polarization beam splitter 33 (hereinafter referred to as PBS 33). The S-polarized laser light is reflected by the PBS 33 and goes to the cylindrical lens 34a arranged in the reflection direction of the PBS 33. The cylindrical lens 34a has a generatrix in the direction perpendicular to the paper surface, and forms a focal line extending in the direction perpendicular to the paper surface at the focal position thereof. Then, the laser light from the cylindrical lens 34 passes through the reflection surface 35a and the polarization beam splitter 36.
It is reflected by (hereinafter referred to as PBS36), and a band-shaped beam spot is formed on the substrate by an objective lens (not shown).

When switching the extension direction of the belt-like beam spot, the λ / 2 plate 32 may be moved to a position outside the optical path indicated by the broken line in the figure. At this time, the P-polarized light from the laser light source 31 passes through the PBS 33 and forms a focal line extending in the in-plane direction through the cylindrical lens 34b having a generatrix in the in-plane direction. And the cylindrical lens
The laser beam from 34b passes through the PBS 36 via the reflecting surface 35b and goes to an objective lens (not shown). in this way,
The extension direction of the band-shaped beam spot can also be switched by switching the polarization direction of the laser light emitted from the laser light source 31.

Needless to say, the position detecting apparatus according to the present invention can be applied not only to the projection exposure apparatus but also to the proximity type exposure apparatus.

[0025]

As described above, according to the present invention, it is possible to provide a position detecting device capable of selectively switching the extension direction of the belt-like beam spot without loss of light quantity with a simple structure.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an embodiment according to the present invention.

FIG. 2 is a schematic diagram specifically showing a configuration of an optical path selecting unit according to the present invention.

FIG. 3 is a schematic diagram partially showing a modified example of the embodiment.

FIG. 4 is a diagram showing a conventional position detection device.

[Explanation of symbols]

 11 ・ ・ ・ Light source, 12 ・ ・ ・ Cylindrical lens, 13 ‥‥ Relay lens, 16a, 16b ・ ・ ・ Objective lens, SPa, SPb ・ ・ ・ Band-shaped beam spot, AMa, AMb ‥‥ Alignment mark,

Claims (1)

[Claims] 1. A position detecting device for forming a band-shaped beam spot on an object, and moving the band-shaped beam spot and a mark provided on the object relative to each other to detect the position of the mark. Light source means for supplying a beam, band-shaped beam spot forming means for condensing the light beam from the light source means to form a band-shaped beam spot on the object, and a beam-shaped beam spot forming means for circulating the light beam in the optical path of the band-shaped beam spot forming means. A first reflecting member that is movably provided and has a plurality of reflecting surfaces; and a second reflecting member that is configured to selectively move between a position inside the optical path and a position outside the optical path. A position detecting device, characterized in that, when switching the extension direction of the band-shaped beam spot, the second reflecting member is moved while rotating the first reflecting member.