JP2569793B2 - Position detecting device and position detecting method using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a position detecting device and a position detecting method using the same, for example, in an exposure apparatus for manufacturing a semiconductor element.
A first mask or reticle (hereinafter, referred to as a “mask”);
A position detecting device suitable for performing relative positioning (alignment) between a mask and a wafer when exposing and transferring a fine electronic circuit pattern formed on an object surface onto a second object surface such as a wafer; The present invention relates to a position detection method using the same.

2. Description of the Related Art Conventionally, in an exposure apparatus for manufacturing a semiconductor, relative positioning between a mask and a wafer has been an important factor for improving performance. In particular, in recent aligners in an exposure apparatus, for high integration of semiconductor elements,
For example, one having a positioning accuracy of sub-micron or less is required.

In many alignment apparatuses, a so-called alignment pattern for alignment is provided on a mask and a wafer surface, and both alignments are performed using positional information obtained from the alignment patterns. As an alignment method at this time, for example, the amount of deviation between the two alignment patterns is detected by performing image processing, or alignment is proposed as proposed in U.S. Pat. No. 4,037,969 or Japanese Patent Application Laid-Open No. 56-157033. This is performed by using a zone plate as a pattern, irradiating the zone plate with a light beam, and detecting the position of a light-converging point on a predetermined surface of the light beam emitted from the zone plate.

Generally, an alignment method using a zone plate has a feature that relatively high-precision alignment can be performed without being affected by a defect in an alignment pattern, as compared with a method using a simple alignment pattern.

FIG. 17 is a schematic view of a conventional positioning device using a zone plate.

In the same figure, a parallel light beam emitted from a light source 72 passes through a half mirror 74 and is condensed at a converging point 78 by a converging lens 76, and is then placed on a mask alignment pattern 68a on a mask 68 and a support 62. The wafer alignment pattern 60a on the surface of the wafer 60 is irradiated. These alignment patterns 68a and 60a are constituted by reflection type zone plates,
Focus points are formed on planes orthogonal to the optical axis each including the focus point 78. At this time, the amount of shift of the condensing point position on the plane is detected by guiding the light onto the detection surface 82 by the condensing lenses 76 and 80.

Then, based on the output signal from the detector 82, the control circuit 84
Drives the drive circuit 64 to position the mask 68 relative to the wafer 60.

FIG. 18 shows the mask alignment pattern shown in FIG.
FIG. 8 is an explanatory diagram showing an image forming relationship of a light beam from 68a and a wafer alignment pattern 60a.

In the figure, a part of the luminous flux diverging from the converging point 78 is diffracted from the mask alignment pattern 68a to form a converging point 78a indicating the mask position near the converging point 78.
Further, some other light beams pass through the mask 68 as zero-order transmission light and enter the wafer alignment pattern 60a on the wafer 60 without changing the wavefront. At this time, after the light beam is diffracted by the wafer alignment pattern 60a, the light beam is transmitted again through the mask 68 as zero-order transmission light, condensed in the vicinity of the converging point 78, and forms a converging point 78b representing the wafer position. In the figure, when the light beam diffracted by the wafer 60 forms a converging point, the mask 68 acts as a simple transparent state.

The position of the focal point 78b by the wafer alignment pattern 60a formed in this way is determined by the amount of the deviation along a plane orthogonal to the optical axis including the focal point 78 according to the deviation Δσ of the wafer 60 with respect to the mask 68. The deviation amount Δ of the amount corresponding to Δσ
σ '.

In the positioning apparatus shown in the figure, when obtaining a relative displacement amount, light from a mask and a zone plate provided on a wafer surface are independently imaged on a predetermined surface to be evaluated, and each is used as a reference. The amount of deviation from the position is determined.

However, in this method, for example, in order to reduce the size of the detector and make it less susceptible to noise, even when it is desired to perform measurement in only one direction, if the mask or wafer moves in a direction perpendicular to this direction, the focal point will be measured. There is a problem that it moves in a direction perpendicular to the direction.

(Problems to be Solved by the Invention) The present invention improves on the above-mentioned drawbacks of the conventional position detecting device, that is, even if the first object and the second object move in the direction perpendicular to the position detection direction, An object of the present invention is to provide a position detecting device having a measurement principle capable of increasing the degree of design freedom of the entire device and performing the position detection of the second object with high accuracy, and a position detecting method using the same.

The present invention further responds greatly to the relative movement of the first object and the second object along the predetermined direction on the surface of the detection means, but hardly reacts or reacts to the relative movement of the first object and the second object along the vertical direction outside the predetermined direction. An object of the present invention is to provide a position detecting device capable of obtaining an optical signal which is not used and performing high-accuracy position detection and a position detecting method using the same.

In addition, the features of the configuration relating to the position detection of the second object with respect to the first object, which is a feature of the present invention, are described in the section of the embodiment.

(Means for Solving the Problem) A position detecting device according to the present invention includes a first object optical element formed on a first object surface, and a second physical object formed on a second object surface opposed to the first object. When forming an optical element, each of the first and second physical optical elements has a condensing or diverging action in at least one direction, and at least one of the first and second physical optical elements The element has a focal length different from the focal length f1 based on light collection or divergence in the one direction in the direction perpendicular to the one direction.
f2 has a condensing or diverging action, and among the luminous flux from the illumination means, the luminous flux condensed or diverged by both the first physical optical element and the second physical optical element is detected by the detecting means, A relative positional relationship between the first object and the second object in a predetermined direction is detected using an output signal from the detecting means.

For example, one of the first and second physical optical elements according to the present invention has a focal length f2 different from the focal length f1 based on light collection or divergence in the one direction in the direction perpendicular to the one direction. The other physical optical element is characterized in that it does not have the light condensing or diverging function in the direction perpendicular to the one direction. Specifically, one of the physical optical elements has a toric lens action, and the toric lens action causes a light flux on a detection surface of the detection means to be relatively displaced in the first direction between the first object and the second object. The deviation amount of the luminous flux on the detection surface with respect to the relative positional deviation of the first object and the second object in the second direction is smaller than the deviation amount of the first object and the second object. First output of the first object and the second object using the output signal related to the quantity
In which the relative positional relationship in the direction is detected.

(Embodiment) Next, a description will be given of an embodiment of the present invention in which a mask is used as a first object and a wafer is used as a second object, and a relative positional deviation is detected along the facing direction and the vertical direction. First, the principle of the displacement detection method is shown in FIG.
This will be described with reference to FIG.

FIGS. 1 (A) and 1 (B) are a side view and a plan view, respectively, as a first explanatory diagram for explaining a position shift detecting method.
In the figure, reference numeral 1 denotes a first object such as a mask fixedly installed in an apparatus (not shown), 2 denotes a second object such as a wafer to be aligned with the first object 1, and 3s and 4s denote the first object 1 and the second object, respectively. First and second physical optical elements (elements for changing the incident wavefront, for example, including a linear pitch grating and a Fresnel zone plate) provided on two surfaces of two objects, and here a grating lens such as a Fresnel zone plate (Hereinafter also referred to as “grating lens”). Reference numeral 5 denotes a light beam which is incident on the first physical optical element 3s of the first object 1 in parallel. Reference numeral 9 denotes a detection surface of the detection means for detecting a component of the incident position of the light beam in the X direction.

In the figure, a first position for which a relative displacement is to be evaluated is described.
The object 1 and the second object 2 are provided with first and second physical optical elements 3s and 4s having the same light condensing action in both the x and y directions. The light beam 5 is made incident on the first physical optical element 3s, and the light 6 emitted therefrom is made incident on the second physical optical element 4s. The emitted light 7 from the second physical optical element 4s is condensed on a detection surface 9 of a detection means such as a CCD line sensor.

At this time, the center of gravity shift Δσ of the light amount occurs on the detection surface 9 in accordance with the relative position shift Δσ between the first object 1 and the second object 2.

Next, a description will be given of the center-of-gravity deviation amount Δσ of the light amount at this time.

When the first object and the second object are displaced from a predetermined position, the optical axes of the grating lenses 3s and 4s are relatively displaced from each other.
In this case, the principal ray of the light emitted from the grating lens 3s is a grating lens before and after the displacement occurs.
Since the incident position on 4s is different, the exit angle also varies, thereby varying the condensing position of the position detecting light beam 7 (alignment light beam) on the light receiving surface 9. The amount of change in the light condensing position is substantially proportional to the displacement.

Here, the center of gravity of the light beam is defined as the value obtained by multiplying the position vector of each point in the light receiving surface from that point by a quantity that can be limited as a function of the light intensity at that point in the light receiving surface over the entire light receiving surface. A point at which the integral value becomes a zero vector.

Now, the second object 2 is shifted from the first object 1 by, for example, Δαx in the x direction, and the second object 2 is shifted from the second physical optical element 4s.
Let a be the distance from the converging point (or the origin of divergence) of the light beam incident on the surface, and let b be the distance from the second physical optical element 4s to the detection surface 9. (Hereinafter, “a” is positive when the focal point (divergence origin) is on the front side of the physical optical element and “b” is positive when it is on the rear side.) At this time, the center of gravity of the focal point on the detection surface 9 in the x direction Deviation Δ
δ _x is Becomes That is, the positional deviation amount Δσ _x is converted into a light flux center-of-gravity deviation amount Δδ _x enlarged by (b / a + 1) times.

Therefore, positional deviation amount .DELTA..delta _x in the x direction of the second object relative to the first object by obtaining the center of gravity shift amount [delta] _x is obtained from the equation (a).

With reference to the positional relationship between the first and second objects 1 and 2 in FIG. 1 (A), the light flux 7 on the detection surface 9 when the second object 2 is displaced in the x direction from this state. Change in the incident position in the x direction, that is, the amount of displacement Δ of the center of gravity of the incident light beam in the x direction
δ _x is obtained, and the deviation Δσ _{x of} the second object in the x direction is detected from the equation (a). The incident position (reference position) of the light beam 7 on the detection surface 9 when the first and second objects are in the reference position relationship is obtained in advance by, for example, trial printing.

By the way, in the case of detecting the displacement only in the x direction by the method shown in FIG. 1, even if the second object is displaced in the y direction with respect to the first object as shown in FIG. And the light beam 7 moves in the y direction at the same magnification. There is a small and simple CCD line sensor as a detector used for detecting light beam movement only in the x direction.

When the CCD line sensor is installed on the detection surface 9 with the element arrangement direction set in the x direction, if the second object moves in the y direction, the light beam 7 moves in a direction perpendicular to the element arrangement direction and deviates from the detection surface 9 and is detected. It becomes impossible state. In order to avoid this, for example, the detection surface may be enlarged in the y direction. However, this method is easily affected by noise.

FIGS. 2A and 2B are a side view and a plan view, respectively, as a second explanatory view of a main part of an optical system in a method of detecting a displacement.

In the figure, the same elements as those shown in FIGS. 1A and 1B are denoted by the same reference numerals.

In the figure, a first physical optical element 3c, a second physical optical element
4c uses a grating lens that has a light condensing function only in one direction of the x direction and that functions as a so-called cylindrical lens that does not condense or diverge the light beam in the y direction.

As such a grating lens, for example, a lens as shown in US Pat. No. 4,131,389 can be used. If the second object is displaced in the x direction with respect to the first object, the light beam 7 is applied to the detection surface 9 according to the same principle as in FIG.
Move up in the x direction. Therefore, similarly to FIGS. 1A and 1B, the position shift of the second object with respect to the first object can be detected by detecting the amount of shift of the incident position of the light beam by the detector 9 such as a CCD line sensor. On the other hand, when the second object moves in the y direction, the grating lenses 3c and 4c have neither the light condensing function nor the diverging function in the y direction as shown in FIG. Even if the lens 4c moves, the light beam does not move in the y direction. Therefore, FIG. 1 (A),
Unlike the case (B), even when the detector 9 has a small light receiving surface in the y direction, the light beam does not move with respect to the light receiving surface due to the movement of the second object in the y direction. However, as shown in FIG. 2 (B), the light flux 7 is not converged at all in the y direction, so that the loss of the received light amount is large. If the size of the detector 9 is increased in the y direction in order to avoid a loss of light amount at this time, the problem of noise occurs as described above.

3A and 3B are schematic diagrams of a first embodiment of the present invention. FIG. 1A is a side view, and FIG. 1B is a plan view. In the present embodiment, a light beam emitted from a light source 10 such as a semiconductor laser is converted into a parallel light beam by a light projecting lens system 11, and the first physical optical element 3a provided on the first object 1 is irradiated.

The first physical optical element 3a is a grating lens having a different light condensing function in the x direction and the y direction, that is, a grating lens having the function of a toric lens, as shown in FIG. 3 (A).
In the plane, the outgoing light is focused from the first physical optical element 3a to the focal length.
The light is focused on the point Q of f _1x . And are made incident on the second physical optic element 4a is provided a light beam diverging from the point Q from the point Q to the second object 2 arranged at a distance a _x. Second
Like the first physical optical element 3a, the physical optical element 4a is a grating lens having the function of a toric lens having different light condensing functions in the x direction and the y direction, and is separated from the second physical optical element 4a in the xz plane. Out of the second object b
The light is condensed on the detection surface 9 of the detector 8 at a distance.

In this embodiment, the first and second physical optical elements 3a and 4a constitute a so-called convex-convex system.

In the figure, a first object 1 and a second object 2 whose relative displacement is to be evaluated are provided with the first and second physical optical elements 3 and 4 having the above-described configuration, respectively. The light beam 5 is made incident on the first physical optical element 3, and the emitted light 6 is made incident on the second physical optical element 4. The emitted light 7 from the second physical optical element 4 is condensed on a detection surface 9 of a detector 8 such as a CCD line sensor or a position sensor in the xz plane.

At this time, on the detection surface 9 according to the relative positional shift amount Δσ _x between the first object 1 and the second object 2, the same as that shown in FIGS. 1 (A) and 2 (A) the center of gravity shift amount Δδ _x quantity of light arises to.

In this embodiment, the center of gravity of the amount of light on the detection surface 9 due to the light beam 7a indicated by the solid line is based on the center of gravity of the amount of light on the detection surface 9 indicated by the dotted line in FIG.
_x is obtained, and the relative positional deviation amount Δσ _x between the first object 1 and the second object 2 is detected from this.

The detection method at this time is the same as that shown in FIGS. 1 (A) and 2 (A).

In the present embodiment, the relative positional relationship between the first object 1 and the second object 2 in the x direction is detected using the above basic principle.

In FIG. 3, it is assumed that the first and second physical optical elements 3a and 4a and the detection surface 9 are parallel to each other, and the center of gravity 7c of the amount of light on the detection surface 9 where the light flux 7 is condensed is indicated by a dotted line. And the second physical state is based on the first physical optical element 3a.
Physical optic element 4a is x-direction center of gravity shift amount .DELTA..delta _x of the focal point of on the detection surface 9 and a deviated .DELTA..sigma _x in the x direction as the first physical optic element 3a and the drawing Becomes That is, the displacement amount Δσ _x is Fold it is detected as expanded light beam center of gravity shift amount .DELTA..delta _x to.

As is apparent from the equation (1), it is desirable that b≫a _x is satisfied in order to perform high-accuracy position shift detection. Specifically, b / a _x
It is good to make the value of about 50 to 400.

As shown in FIG. 3B, in the arrangement of the optical system of the present embodiment, the light source and the light receiving surface are not conjugated in the y direction.

As shown in FIG. 3 (B), the grating lenses 3a, 4a
Has the function of converging and emitting the incident light beam even in the yz plane. At this time, the value of the focal length of each grating lens 3a, 4a in the yz plane is a finite value different from the value in the xz plane.

Now, the distance from the second physical optical element to the virtual converging point of the light beam incident on the second physical optical element (the point where the light beam 6 converges when there is no grating lens 4a) is a _y , Assuming that the distance from the optical element to the detection surface 9 is b as described above, when the second object 2 is displaced by Δσ _y in the y direction, the amount of displacement Δδ _y of the center of gravity of the light beam 7 in the y direction on the detection surface 9 is Is represented by

In the present embodiment, | a _y | ≫ | a _x | is set, whereby the magnification of the displacement of the center of gravity of the light beam with respect to the displacement of the second object in the y direction is made smaller than that in the x direction.

Further, as shown in FIG. 3 (B), the light beam 7 is condensed to a certain extent on the detection surface 9 and made incident, thereby reducing the loss of the detected light amount and miniaturizing the detector in the y direction.

As described above, in this embodiment, by using a physical optical element composed of a grating lens having the function of a toric lens for the first object and the second object, the light beam emitted from the physical optical element can be efficiently reflected on the second object plane. Of the light amount, and the position of the center of gravity of the light amount on a predetermined surface can be detected with high accuracy.

In this embodiment, there is no problem if the magnification of Δδ _y with respect to Δσ _y is set such that the detection surface 9 does not deviate in the y direction in consideration of a possible position error in the y direction.

Further, if the light beam diameter in the y direction on the light receiving surface is also made smaller than the original light beam diameter, there is an effect of preventing a light quantity loss.

As a procedure for performing the alignment in the present embodiment, for example, the following method can be adopted.

As a first method, a positional shift amount Δσ _x between two objects
Of the amount of light on the detection surface of the detector 8 with respect to the center of gravity signal Δ
[delta] _x and advance decide the characteristics showing the relationship (e.g., proportional coefficient) in advance, obtains positional deviation amount .DELTA..sigma _x and between both objects from the value of the center of gravity shift signal .DELTA..delta _x, corresponds to the displacement amount .DELTA..sigma _x at that time The first object or the second object is moved by an amount to be performed.

As a second method, the center-of-gravity deviation signal Δδ from the detector 8 is used.
_The direction in which the positional deviation amount Δσ _x is canceled is obtained from _x , and the first object or the second object is moved in that direction, and the positional deviation amount Δ
Repeat until σ _x falls within the allowable range.

In the case where the physical optical element having the above-mentioned operation is constituted by, for example, an amplitude type zone plate, its pattern may be constituted by the following shape.

As shown in FIG. 4 (A), when a parallel light beam is applied to the zone plate 51 having a focal length f _x in the xz plane, the number of zones of the zone plate 51 is mI _x , the wavelength is λ, and the aperture diameter is D. On the x-axis passing through the center of the zone plate, assuming that the converging half angle of the light beam is θ, Becomes Accordingly, the relationship with the zone blade radius D / 2 from the center of the opening of the zone of the ith _x- th surface on the x-axis passing through the center is Becomes

In addition, as shown in FIG. 4B, a zone provided on the second object 2 in FIG. 3 such that a light beam from the line light source 52 is condensed on the light receiving surface 9 in the xz plane by the zone plate 51. In the case of a plate, the distance from the line light source 52 to the zone plate 51 is a, the distance from the zone plate 51 to the light receiving surface 9 is b,
Assuming that the half angle of divergence from the line light source 52 is θa, and the half angle of condensing the light beam on the light receiving surface 9 is θb Becomes Therefore, mII _x on the x-axis passing through the center of the opening
Zone plate radius D / 2 from the center of the opening of the second zone
Relationship with Becomes

Similarly, assuming that the focal length of the zone plate 51 in the yz plane is f _x , each of the zone plates in the y-axis direction mI _y
The relation with the (mII, _y) th zone plate radius can be obtained by replacing f _x and f _{y in the} equations (2) and (2a).

Therefore, the two-dimensional shape of the zone plate has an ellipticity of f _x /
The shape may be an elliptical shape that is f _y .

For example D = 180μm, λ = 0.83μm, f x = 1000μm, f y = 250
If μm, a = 500 μm, b = 50,000 μm, the number of zones of the zone plate 3 a provided on the first object 1 is mI _x = 4.9, mI _y = 9.8,
The number of zones of the zone plate 4a provided on the second object 2 is mII
_x = 10.4, a mII _y = 20.8.

In the present embodiment, the geometric chief ray shift is proportional to the relative position shift for convenience. However, in practice, the center of gravity shift of the light quantity on the detection surface 9 due to the aberration of the Fresnel zone plate is relative. When the displacement becomes extremely large, nonlinearity occurs. For this non-linearity, for example, the non-linear relationship may be stored and corrected at the time of calculation.

In this embodiment, as described above, since the grating lens having a lens function different from the detection direction in the direction orthogonal to the position shift amount detection method is used, the detection surface 9 can be downsized and Noise such as unnecessary scattered light and diffracted light components is unlikely to enter, and the displacement detection accuracy is, for example, 0.00
High-accuracy position deviation detection of about 5 μm becomes possible.

On the other hand, even when the displacement amount is given 20 μm in the y direction (the direction orthogonal to the displacement detection direction), the light flux barycenter position is configured to move only a small barycenter position of, for example, 41 μm on the detection surface 9. It has gained.

In this embodiment, the case where the parallel light beam is vertically incident on the first physical optical element 3a is shown, but a convergent light beam or a divergent light beam may be made incident. In this case, the second physical optical element 4a may be set so that the position of the condensing point of the incident light beam by the first physical optical element 3a has an image-forming relationship with the detection surface 9.

FIG. 5 and FIG. 6 are schematic views of main parts of the second and third embodiments of the present invention, respectively. In the second embodiment shown in FIG. 5, the first physical optical element 3b is a grating lens having a diverging function in the xz plane, and the second physical optical element 4b is a grating lens having a condensing function in the xz plane.

This constitutes a so-called concavo-convex system. The light condensing state in the yz plane is the same as in FIG. 3 (B).

The relationship between the position deviation amount sigma _x relative centroid shift amount .DELTA..delta _x are the same as previously described (1).

In the third embodiment shown in FIG. 6, the first physical optical element 3d is a grating lens having a condensing action in the xz plane, and the second physical optical element 4d is a grating lens having a diverging action in the xz plane.

This constitutes a so-called concavo-convex system in the xz plane. The light condensing state in the yz plane is the same as in FIG. 3 (B).

In the present embodiment, the positional deviation amount Δ of the second object from the reference position
The shift amount Δδc of the center of gravity of the light amount on the detection surface 9 with respect to σc is Becomes

In the present embodiment, the distinction between the concave lens and the convex lens of the physical optical element is determined by using the positive order diffracted light or the negative order diffracted light.

Also in the second and third embodiments, alignment marks having different focal lengths are used in directions orthogonal to the misalignment amount detection direction, similarly to the first embodiment, whereby scattering on the detection surface is performed as in the first embodiment. High-accuracy position shift detection without light or unnecessary diffracted light can be performed.

Further, the magnification sensitivity to the displacement can be set to be small, for example, about twice in a direction orthogonal to the displacement detection direction, that is, in a direction perpendicular to the paper surface.

In the present invention, it is preferable to select the optical system in each of the above-described embodiments according to the distance between the first object 1 and the second object 2 and the size of the openings of the first and second physical optical elements.

For example, when the interval is larger than the openings of the first and second physical optical elements, the convex-convex system shown in FIG. 3 is preferable. Conversely, when the interval is smaller than the opening, the concavo-convex system shown in FIG.
Alternatively, an uneven system shown in FIG. 6 is preferable.

Further, when the second physical optical element can have a larger aperture than the first physical optical element as shown in FIGS. 5 and 6, the concavo-convex system shown in FIG. 5 is better. In the case where the aperture can be made larger than that of the two physical optical elements, an uneven system shown in FIG. 6 is preferable.

In each of the above embodiments, the transmission type physical optical element has been described. However, the object of the present invention can be similarly achieved by using a reflection type physical optical element.

FIG. 7 is a schematic diagram of a fourth embodiment of the present invention. The present embodiment relates to a positioning apparatus for aligning a mask M and a wafer W in an exposure apparatus for manufacturing a semiconductor by a so-called proximity method.

7, the same elements as those shown in FIG. 3 are denoted by the same reference numerals. In the figure, M is a mask, and W is a wafer, which respectively correspond to a first object and a second object for performing relative positioning. 3M is a mask alignment pattern on the mask M surface, corresponding to the first object optical element, and 4W is a wafer 4
The wafer alignment pattern on the surface corresponds to a reflective second physical optical element.

In FIG. 1, a light beam emitted from a light source 10 is converted into a parallel light beam by a light projecting lens system 11 and is irradiated with a mask alignment pattern 3M via a half mirror 12. The mask alignment pattern 3M includes a zone plate that focuses the incident light beam at a point Q in front of the wafer W.

Incidentally, 10 denotes a semiconductor laser, H _e -N _e laser, coherent light beam at a light source A _R laser or the like, or generates incoherent light beam from the light emitting diode or the like.

The light beam condensed at the point Q then diverges and enters the wafer alignment pattern 4W. The wafer alignment pattern 4W is composed of a reflection type zone plate, reflects an incident light beam, passes through the mask M and the half-Muller 12, and then condenses it on the detection surface 9.

The fourth embodiment of FIG. 7 is based on the principle shown in FIG.
In the configuration shown in (B), the same configuration as that in which the grating lens 4a is a reflection type and the light beam 7 and the detector 8 on the right side of the drawing from the grating lens 4a are folded back on the left side of the drawing. Accordingly, the displacement of the center of gravity of the light beam in the x direction when the wafer W is displaced in the x direction, the method of detecting the displacement based on the displacement, and the state of the displacement of the light beam in the y direction when the wafer W moves in the y direction are the third. This is the same as the first embodiment shown in FIG.

In the present embodiment, after detecting the displacement in the x direction, the wafer W is moved in the x direction by a wafer driving mechanism (not shown) so as to correct the displacement, thereby aligning the position of the mask M with the position of the wafer W.

FIG. 8 is a schematic view of a main part of a fifth embodiment of the present invention. 7, the same elements as those shown in FIG. 7 are denoted by the same reference numerals.

In this embodiment, the alignment marks 4W and 3M on the surface of the wafer W and the mask M are arranged on the scribe lines 101 on the surface of the wafer W and the mask M, respectively. 102 is a semiconductor laser, incoherent light beam from H _e -N _e laser, coherent light beam from a light source of A _r laser, or a light emitting diode or the like in the head for alignment not shown.

In the figure, a light beam 102 is incident on a surface of a mask M at a predetermined angle, and is diffracted by alignment marks 3M and 4W on the surface of the mask M and the wafer W, and then on a detection surface 9 composed of a one-dimensional CCD or the like as signal light. Shows the optical path of the principal ray incident on.

In this embodiment, the alignment is set in the longitudinal direction (x direction) of the scribe line 101.

Next, the alignment marks 3M and 4W in the present embodiment will be described.

The alignment marks 3M and 4W are so-called Fresnel zone plates (or grating lenses) having a predetermined focal length. Among them, the alignment marks 3M receive alignment light projected obliquely at a predetermined incident angle by the action of the grating lens. Is converged (or diverged), and the principal ray of the light emitted from the mask M is set to form a predetermined angle with respect to the normal to the mask surface.

However, in the present embodiment, the longitudinal direction of the scribe line (x direction) and the direction perpendicular to it (y direction) have different lens functions as in the fourth embodiment.

In the present embodiment, for example, the incident angle of the alignment light is 10 ° in the yz plane with respect to the normal to the mask surface M, and the projected component of the incident light on the mask surface M is orthogonal to the scribe line direction. (I.e., coincides with the y direction).

When it is assumed that there is no wafer, the light beam transmitted and diffracted through the alignment pattern 3M is, for example, vertically below the wafer W surface.
Light is condensed linearly at 238.0 μm in the xz plane and at 20.107 mm in the yz plane. At this time, the focal length in the xz plane is 268μ
m.

However, at this time, the distance between the mask M and the wafer W is 30 μm.
m, dimensions of alignment marks 3M and 4W are 280 μm each in scribe line direction and 7 each in scribe line width direction.
It is 0 μm.

The alignment mark 4W is a grating lens for signal light on the wafer surface W. The convergent (or divergent) light transmitted and diffracted through the mask surface M in the xz plane is further concave (convex) by the alignment mark 4W on the wafer surface W. (Good) It is set so as to converge on a predetermined position on the sensor 9 under the action of a lens. For example, in the present embodiment, the grating pattern of the alignment pattern 4W is the mask M
When the misalignment between the wafer and the wafer W is 0, and thus the alignment marks 3M and 4W form a coaxial system, the emission angle of the alignment light from the alignment mark 4W on the wafer surface W is relative to the normal to the wafer surface W. 5 ° and orthogonal to the scribe line direction, and the position deviation detection direction (x direction) on the sensor 9
It is set so that a spot spread in a band shape in the direction orthogonal to the light beam enters near the center of the sensor.

As described above, the mask M and the alignment marks 3M and 4W on the wafer W have a lens function in the displacement detection direction of the light flux center-of-gravity position detection sensor, that is, the scribe line direction. As in the example, it is constituted by a grating element having a lens action having a different focal length.

Here, as for the focal length in the displacement detection direction (that is, the longitudinal direction of the scribe line), the grating lens for the mask generates a convex power of 268 μm, and the grating lens for the wafer generates a concave power of 279 μm. On the other hand, the grating lens for the mask generates a convex power of 2 mm and the grating lens for the wafer generates a concave power of -2.2 mm in the direction y perpendicular to the direction of detecting the displacement.

FIG. 9 shows a typical pattern example of such a grating lens.

The pattern shown in FIG. 9 has a lens function with a predetermined focal length in the x direction, has a different focal length in the y direction from the x direction, and shifts the principal ray of the light beam at a fixed angle according to the diffraction order. Has the effect of deflecting.

In this pattern, the distribution of the pitch of the grating in an arbitrary xz section corresponds to the distribution of the pitch of the Fresnel zone plate having the same in-plane focal length as in the present embodiment, and the lens of the present embodiment in the yz section. , And corresponds to the pitch distribution of the off-axis Fresnel zone plate that forms an image at a predetermined position in the same manner as the focal length in the y direction.

Next, an embodiment of a method of manufacturing the alignment marks 3M and 4W (grating lens) in this embodiment will be described.

First, the mask alignment mark 3M is designed such that a parallel light beam having a predetermined beam diameter enters at a predetermined angle and is condensed linearly at a predetermined position. Generally, the pattern of the grating lens is an interference fringe pattern on the lens surface when coherent light sources are placed at the light source (object point) and the image point, respectively. Now, a coordinate system on the mask M plane is determined as shown in FIG. Here, the origin is at the center of the scribe line width, and the x axis is taken in the scribe line direction, the y axis is taken in the width direction, and the z axis is taken in the normal direction of the mask M surface. A parallel light beam whose projection component is orthogonal to the scribe line direction (x direction) at an angle of α in the yz plane with respect to the normal line of the mask plane M is incident on an arbitrary point (x, y, 0) on the mask. Shall be.

Here, it is assumed that the alignment mark 3M on the mask has a focal length z ₁ in the xz plane and a focal length z ₂ (z ₁ ≠ z ₂ ) in the yz plane. After the incident parallel beam is transmitted diffracted alignment mark 3M, in the xz plane _{(x 1, yA, z 1} ) position of (x _1, z ₁ is a constant) is condensed with, whereas in the yz plane (xA, y ₂ , z ₂ ) (y ₂ , z ₂
Is a constant), the design equation of the curve group of the grating lens pattern (x, y) that condenses light is expressed by equation (4).

(Z ₁ ≠ 0, z ₂ ≠ 0) where λ is the wavelength and n is the total number of zones, m is 1 to 2n
Take an integer value up to.

Assuming that the principal ray is incident at an angle α, passes through the origin on the mask surface M, and reaches the focal point (x ₁ , y ₁ , z ₁ ) (4)
The left side of the equation is a point (x, y,
0) represents the difference from the optical path length of the light beam that reaches the point (x ₁ , yA, z ₁ ). Equation (4) eventually shows that the difference in the optical path length is m / 2 of the wavelength.
It shows that it becomes double.

On the other hand, the grating lens 4W on the wafer W is designed such that the incident light has a wavefront having different powers (divergence and convergence angles) in the x direction and the y direction, and similarly to the grating lens on the mask M, the x direction and the y direction. Are grating lenses having different focal lengths.

A light beam of a wavefront having a different light condensing position (or a divergence origin position) in the xz plane and the yz plane is incident on the on-wafer grating lens 4W, and condensed differently in the xz plane and the yz plane of the lens (or The following is a case in which light is condensed in the X and Y directions on each plane of z = z ₃ and z = z ₄ after the effect of divergence is applied.

A linear light source (x ₁ , z ₁ is a constant) parallel to the y direction where the incident light beam is located at (x ₁ , yA, z ₁ ), and a linear light source parallel to the x direction located at (xA, y ₂ , z ₁ ) a linear light source (x _2, z ₂ are constants) incident on the wavefront grating lens 4W as a virtual light source and, in the xz plane (x _3, yB, z _3), in yZ plane ( If design is performed so that light is condensed at each position of xB, y ₄ , z ₄ ), it is expressed as equation (5) of the grating lens curve group.

It is.

In general, a mask zone plate (grating lens) is formed with two regions, a region through which a light beam is transmitted (a transparent portion) and a region through which a light beam is not transmitted (a light shielding portion), alternately.
It is created as a 0, 1 amplitude type grating element. The zone plate for the wafer is created, for example, as a phase grating pattern having a rectangular cross section. (4), (5)
The fact that the contour of the grating is defined at a position that is an integral multiple of a half wavelength with respect to the principal ray in the formula means that the ratio of the line width of the transparent part to the light shielding part in the grating lens 3M on the mask M
1: 1, grating lens 4W on wafer W
Means that the ratio of lines to spaces in the rectangular grid is 1: 1.

FIG. 9 shows a grating lens pattern designed in this way.

The grating lens 3M on the mask M was formed by transferring a grating lens pattern of a reticle previously formed by EB exposure onto an organic thin film made of polyimide.

The marks on the wafer were formed by forming an exposure pattern of the wafer on a mask and exposing and transferring the pattern. Incidentally, the forming method is not particularly limited to this.

In the present embodiment, when the lens power is increased in the direction of the scribe line, the number of gratings can be increased, so that the light collection efficiency of the grating lens is good, and the lens power is provided in the width direction of the scribe line to be used for position shift detection. Can be improved as compared with.

In addition, the magnification is reduced to 5 times in the direction orthogonal to the direction of detecting the displacement amount, and the use of an alignment mark having a relatively long focal length reduces scattering and unnecessary diffraction components on the sensor. Even if there is a displacement of about 20 μm in the orthogonal direction, it is set so as not to protrude from the sensor.

Also, when the diameter of the alignment light beam on the sensor is evaluated as 1 / e ^{2 of the} peak level, a maximum of 40
It is suppressed to 0 μm. As a result, the amount of light per unit area on the sensor increases, and the S / N of the sensor signal improves,
The displacement detection accuracy can be improved in a direction orthogonal to the displacement detection direction as compared with the case where there is no lens action.

In the present invention, the alignment marks are arranged such that the displacement amount is determined to be 0 when the alignment marks on the wafer are located immediately below the alignment marks on the mask. The alignment of the alignment marks on the mask and the alignment marks on the wafer may be shifted in a direction perpendicular to the detection direction. For example, when detecting the amount of misalignment between the mask and the wafer in the scribe line direction (x direction) on the mask as in the fourth embodiment of FIG. 7, the short direction of the alignment mark on the wafer is set in the y direction. Shift to Here, the scribe line direction is the x direction. By providing the position of the alignment mark on the wafer in this manner, the incident angle of the light beam incident on the mask surface from the alignment head can be reduced, and the interval between the gratings can be reduced by the wavelength (λ) of the alignment light.
= 0.83 μm) or more, which facilitates the production of alignment marks.

FIG. 10 is a schematic view of a sixth embodiment of the present invention. FIGS. 3A and 3B are schematic views seen through cross sections orthogonal to the y and x directions, respectively. In the figure, the combination of the grating lens powers in the direction orthogonal to the displacement detection direction is different from the displacement detection direction.

That is, in the present embodiment, the first physical optical element functions as a convex lens having a focal length of a _x + g in the displacement detection direction (x direction), and in the direction (y direction) orthogonal to the displacement detection direction.
There is a concave lens action having a focal length of-(a _y -g).
The second physical optic element to the displacement detection direction - (1 / a <sub>x)
+ (1 / b x) =</sub> - (1 / f x) concave action of focal length -f _x satisfying, in the y direction _{(1 / a y) + (} 1 / b y) = (1 / f y) Has a function of a convex lens having a focal length f _y that satisfies the following condition.

At this time, the interval is smaller than the opening, and the opening diameter can be increased in the scribe line direction like the mark on the scramble line on the mask and wafer in the semiconductor exposure apparatus, and the opening diameter is increased in the orthogonal direction. If the power cannot be obtained, concave power (first physical optical element) and convex power (second physical optical element) in the scribe line direction, and convex power (first physical optical element) in the width direction of the scribe line.
It is appropriate to use a combination of a physical optical element and a physical optical element that is a combination of a lens function of concave power (second physical optical element).

Therefore, it is possible to select a combination of the concave power and the convex power in each direction depending on whether the displacement is detected in the scribe line direction or the displacement in the scribe line width direction.

In FIG. 10, both the first physical optical element and the second physical optical element are shown as transmissive physical optical elements, but when used in a semiconductor exposure apparatus, the second physical optical element (physical optical element on the wafer) is reflected. It consists of a physical optical element of the type. For example, the size of the alignment mark in the scribe line direction is 250 μm, and the size in the scribe line width direction is 60 μm.
m, in a proximity exposure apparatus in which the gap between the mask and the wafer is 30 μm, the lens element on the mask has a concave power of -268 in the scribe line direction.
μm, lens element on wafer has convex power and focal length is 27
Designed to be 9 μm, and the lens on the mask has a convex power of 3.0 mm in the scribe line width direction and a focal length of 3.0 mm.
The lens element on the wafer is set to have a concave power and a focal length of -3.2 mm.

The seventh embodiment shown in FIG. 11 uses a so-called convex-concave convex lens and a mark corresponding to a convex mirror type. The mask M is attached to a membrane 17 and is supported on the aligner body 15 via a mask chuck 16. A mask-wafer alignment head 14 is arranged above the main body 15. In order to align the mask M and the wafer W, a mask alignment pattern 3M and a wafer alignment pattern 4W are printed on the mask M and the wafer W, respectively.

The light beam emitted from the light source 10 becomes parallel light by the light projecting lens system 11, passes through the half mirror 12, and enters the mask alignment pattern 3M. The alignment pattern 3M is a transmissive zone plate and has a convex lens function of converging light to a point Q in the xz plane. The wafer alignment pattern 4W is a reflection type zone plate,
It has the function of a convex mirror that forms an image on the detection surface 9 in the plane.

Under such an arrangement, if the wafer W is displaced by Δσw in the x direction with respect to the mask M, the center of gravity Δσw of the amount of light on the detection surface 9 becomes Becomes The inside of the yz plane is the same as in the fourth embodiment of FIG.

FIGS. 12A and 12B are schematic views for explaining an eighth embodiment of the present invention. Fig. 12 (A) is a side view, Fig. 12 (B)
Is a plan view.

In this embodiment, the grating lens 103M on the first object 1 acts as a convex lens having a focal length f _1x (> 0) for condensing and emitting the incident light beam 5 in the xz plane.
In the yz plane, the focal length f _1y for diverging and emitting the light beam 5
Acts as a concave lens (<0). Also, the grating lens 104W on the second object 2 sets the light flux 6 diverging from the divergence origin at different distances in the xz plane and the yz plane as the outgoing light flux 7, and on the detection surface 9 in any plane. It functions as a toric lens in which the focal length in each plane is set so that light is condensed. The gap between the first and second objects at this time is g, and the distance from the grating lens 104W to the detection surface 9 is b.

In the present embodiment, the light beam is condensed most on both the xz plane and the yz plane on the detection surface 9 by the grating lens 104W to form a spot, thereby improving the light receiving efficiency of the signal light.

Here, in the xz plane, the grating lens 104W is used to detect the relative displacement between the first object 1 and the second object 2 with high sensitivity.
Is an enlargement system in which the imaging magnification of the condensing portion Q on the detection surface 9 is increased. That is, a b»a _x.

In this embodiment as well, the expression (1) is satisfied as described above.

Therefore, if the value in the parentheses on the right side of the equation (1) is, for example, 100, the relative displacement Δσ between the first object 1 and the second object 2 in the x direction.
_{Even if x} is 0.01 μm, it can be detected as a 1 μm spot change on the detection surface 9. Thus, the second in the x direction
The displacement of the object is detected with high accuracy. The detection method at this time is the same as described above.

On the other hand, in the yz cross section orthogonal to this, similarly, assuming that a spot change in the y direction on the detection surface 9 in the y direction is Δδ _y and a change amount of the second object 2 in the y direction is Δσ _y , as described above. Become, FIG when the value of a _y the same as the example b in the state shown in Δδ _y = 2Δσ _y, and the displacement of the second object 2 is temporarily
Even if it is 10 μm, the displacement on the detection surface 9 can be suppressed to 20 μm.

In this way, in this embodiment, the light beam 7 is hardly detached from the detection surface 9.

Here, if a _y = ∞ (that is, the first physical optical element has no power in the yz plane) in the equation (6), Δδ _{y is obtained} from the equation (6).
= .DELTA..delta _y against .DELTA..sigma _y next sigma _y is configured smaller than in the previous case can be achieved.

This means that the grating lens of the first object 1 is yz
This figure shows a case where a so-called cylindrical lens having no power in the plane is operated. In this case, the ninth embodiment will be described.
An example is shown in FIGS. 13 (A) and (B). FIGS. 3A and 3B are a side view and a plan view, respectively. In the figure, 113M and 114W are grating lenses having the same function as the grating lenses 103M and 104W in FIG. 12 in the xz plane, respectively. However, grating lens 113M
Has neither a light condensing effect nor a diverging effect in the yz plane as described above.

The grating lens 114W emits the incident light beam 6 without being converged or diverged in the yz plane as a light beam 7 condensed on the detection surface. In this case, not only the spot variation .DELTA..delta _y shift amount .DELTA..sigma _y As explained earlier, therefore the spot of the light beam 7 on the detection surface 9 even if the second object 2 is moved in the y direction is hardly displaced in the y-direction.

Therefore, in this embodiment, it is not necessary to consider that the light beam 7 is shifted from the detection surface 9 in the y direction. Also, since the light beam 7 is condensed on the detection surface 9 in both the xz and yz surfaces, the light beam 7 has a feature that the light receiving efficiency is good.

Here, the pattern of the grating lens 113M is given as follows, with the center point on the grating lens 113M as the origin. First, the pattern of the grating lens 113M is as follows: Ysin θ ₁ + P ₁ (x) −P ₂ = mλ / 2 P ₁ (x) = ｛(x−x ₁ ) ² + z ₁ ² ｝ ^1/2 P ₂ = ｛x ₁ ² + z _{It is} given by ₁ ² ｝ ^1/2 . Here, λ is the wavelength of the light beam, m is an arbitrary integer, and P ₂ is xz of the grating lens 113M from the origin.
It means the distance to the converging point in the plane, and the coordinates of this converging point are represented by (x ₁ , yA, z ₁ ). g is a gap between the first and second objects, and θ ₁ is an incident angle of the light beam 5.

Next, the pattern of the grating lens 114W will be described. Similarly, the center of the lens 114W is set as the origin.

Position of each point of the linear light source for generating a cylindrical wave is represented the gap of the mask M and the wafer W putting a _{g (x 1, yA, z} 1 -g) and (x _1, z ₁ is a constant). The focus position of the light beam emitted from the grating lens on the wafer is shifted in the x direction (x ₃ , yB,
z ₃ ) and (xB, y ₄ , z ₄ ) in the y direction. Here, xB and yB pass through the position (x, y, −g) on the grating on the wafer,
For example, it indicates the position where the light beams diffracted in the first order reach the z = z ₃ and z = z ₄ planes, respectively. The design equation at this time is (7)
It is shown in the formula.

Here, the definitions of λ and m are the same as in the previous equation.

(Z ₃ ≠ 0, Z ₄ ≠ 0) Here, in this embodiment, since z ₃ = Z ₄ , yB = y ₃ , xB = x ₃ Therefore, the equation (7) becomes as follows.

This expression represents the pattern of the grating lens 114W in the present embodiment.

FIG. 14 is a schematic view of a main part of the FIG. 10 embodiment of the present invention.
1A and 1B are a side view and a front view, respectively.

In the present embodiment, -a _y = b
Then, the right side becomes 0, and Δδ _y becomes 0 for an arbitrary Δσ _y . That is, even if the second object moves in the y direction, the detection surface 9
The upper spot does not move at all regardless of the focal length of the grating lens 124W in the yz plane.

FIG. 14 specifically shows the state at this time. The (condensing) action of the grating lenses 123M and 124W in the xz plane is the same as that of the grating lenses 103M and 104W in FIG. The grating lens 124W has no power in the yz plane. That is, it has a cylindrical lens action.
The grating lens 123M functions as a convex lens where f _y = g + b, where f _y is the focal length in the yz plane. In this state, even if the second object moves in the y direction as described above, the spot on the detection surface does not shift in the y direction. Also, since the light is focused most on the detection surface, the light receiving efficiency is good
This is the same as the ninth embodiment in FIG. In the present embodiment, the grating lens 124W may have a power to condense light to some extent on the detection surface.

Next, the pattern of the grating lens 123M of the present embodiment will be described.

With the center of the grating lens 123M as the origin, a parallel light beam whose projected component coincides with the y direction at an angle of α in the yz plane with respect to the normal line of the first object plane M is an arbitrary point on the first object ( x, y, 0) and the alignment mark 123
M is a focal length in the xz plane z _1, within the yz plane focal length _{z 2 (z 1 ≠ z 2} )
Shall be provided. After transmitting diffracting the incident parallel light beam alignment marks 123M, in the xz plane _{(x 1, yA, z 1} ) position of (x _1, z ₁ is a constant) is condensed with, whereas in the yz plane (xA, y ₂ , z
The design equation of the curve group of the grating lens pattern (x, y) that condenses light at the position ₂ ) (x ₂ and z ₂ are constants) is as follows.

(Z ₁ ≠ 0, z ₂ ≠ 0) Here, λ is a wavelength, and the total number of orbicular zones is n, and m takes an integer value from 1 to 2n.

On the other hand, the grating fens 124W is set as follows. Assuming that the set distance between the first object 1 and the second object 2 is g, the origin is the center of the lens 124W, the object point with respect to the grating lens 124W is (x ₁ , yA, z ₁ -g). ^{_{-x 2) 2 + z 2 2}} } 1/2 - {(x-x 1) 2 + (z 1 -g) 2} 1/2 + ysinθ 2 = (x 2 2 + z 1 2) 1/2 - (x ₁ ² + z ₁ ² ) ^1/2 + mλ / 2. Here, the photodetector 8 when the displacement is 0
The coordinates of the upper image point are (x ₂ , yA, z ₂ ).

The light beam incident on the grating lens 124W has already been condensed in the yz plane by the grating lens 123M, and as a result, the outgoing light beam 7 is condensed at (x ₂ , y ₂ , z ₂ ).

Further, theta ₂ shows the principal ray exit angle in the yz plane from the lens 124W.

FIG. 15 is a schematic view of a main part of an eleventh embodiment of the present invention. In the case where a light beam from a light source having astigmatism such as a semiconductor laser is used in the position detecting device as in the present embodiment, the light beam 5 incident on the grating lens 133M has different converging and diverging states in the xz plane and the yz plane. ing. That is, the object distances S _x and S _y of the respective surfaces with respect to the first physical optical element have different values.

In this embodiment, the grating lenses 133M and 134W
Are adjusted in the xz plane and the yz plane to form a converging point on the detection surface 9 in both cross sections. By providing the grating lens with the function of the toric lens in this way, even in the case of a light beam from a light source having astigmatism, the present embodiment can be applied to highly accurate position detection.

In the above embodiment, the apparatus for detecting the displacement of the first object (mask) and the second object (wafer) along the direction perpendicular to the facing direction has been described. However, the distance between the first object and the second object is described. The present invention can also be applied to a device for measuring the temperature.

FIG. 16 is a schematic view of a main part of a twelfth embodiment of the present invention in this case. 1A is a side view, and FIG. 1B is a plan view.

In the figure, reference numeral 102 denotes a light beam from a light source (not shown), for example, a semiconductor laser LD.
It may be in place of the H _e -N _e laser or the like. M is a first object such as a mask, and W is a second object such as a wafer.

104 and 105 are first and second parts respectively provided on a part of the mask M surface.
These physical optical elements 104 and 105 are, for example, a diffraction grating and a zone plate. Reference numeral 108 denotes a light receiving means, which is composed of a line sensor, a PSD, or the like, and detects the position of the center of gravity of the incident light beam. Reference numeral 109 denotes a signal processing circuit, which calculates a center of gravity of a light beam incident on the surface of the light receiving means 108 using a signal from the light receiving means 108, and calculates and calculates an interval d _O between the mask M and the wafer 3W as described later. I have.

In this embodiment, the light beam 101 from the semiconductor laser LD is used.
(For example, wavelength λ = 830 nm) is perpendicularly incident on a point on a first Fresnel zone plate (hereinafter abbreviated as FZP) 104 surface on the mask M surface. Then, a predetermined order diffracted light diffracted at an angle θ1 from the first FZP 104 is converted to a point B on the wafer W surface.
The light is reflected at (C). Among the reflected light 131 reflected light when the wafer W is positioned at the position P1 of distance d _O between the mask M, the reflected light 132 is displaced from the wafer W is position P1 by a distance d _G, to the position P2 It is reflected light at a certain time.

Next, the reflected light from the wafer W is transmitted to the second object
D on the FZP105 surface (E when the wafer is at position P2)
Is incident.

Note that the second FZP 5 has an optical function of changing the exit angle of the output diffracted light according to the incident position of the incident light beam, like a condenser lens. The focal length in the xz plane of FZP5 at this time is f _MX.

The diffracted light 16 of a predetermined order diffracted from the second FZP 105
1 (162 when the wafer is at position P2)
The light is guided on the surface of the light receiving means 108 through the. Then, using the position of the center of gravity of the incident light beam 161 (162 when the wafer is at the position P2) on the light receiving means 108 surface at this time, the mask M
The distance between the wafer and the wafer W is calculated.

Here, in the present embodiment, the first FZP 104 simply functions to bend the incident light, but may have a convergence or divergence function.

Next, a calculation method according to the present embodiment will be described. FZ
Assuming that the distance from the focus position of P105 to the light receiving means is a, the image point position 209 via the light receiving lens 204 is b, and the distance from the point b to the sensor is C, the spot position S on the sensor surface is expressed by the following equation. Is required. That is Becomes

In the above equation, θ ₁ , a, b, c, and f _MX can be obtained in advance. Therefore, if the amount of movement S of the light beam is obtained by the light receiving means, d _G is obtained from this equation, and thereby, the mask M and the wafer W are obtained.
Are detected. At this time a, c, increase the value of S with respect to the value of d _G by a large value of theta, it can be detected by converting the light beam moving amount of an enlarged microscopic gap variation.

Incidentally, the mask M and the wafer W are initially opposed to each other with a reference interval d _O as shown in FIG. At this time, the value of d _O can be measured using an apparatus such as TM-230N (trade name, manufactured by Canon Inc.).

Above but is described to seek gap value d _G by the light beam deviation signal in the xz plane, the focal length of the xz plane as a characteristic of the physical optic element 105 at this time plane perpendicular thereto, i.e. the exit side of the yz plane The following effects can be obtained by setting the focal length f _My different from f _MX . That is, the light receiving means 1 is provided via the light receiving lens 204.
By setting the focal length so that light is condensed at a position conjugate with 08, light can be converged on the light receiving means 108 in a direction orthogonal to the light beam deviation direction, and the effective photosensitive portion size of the light receiving means 108 can be reduced, and Since the noise level of the target is lowered and the probability of entering optically unnecessary light (stray light) is reduced, the S / N ratio can be improved.

The interval detection if there is no FZP104 if brought into incident to tilt theta ₁ to advance the mask surface a light beam is incident from the light source LD to the mask M is possible. Instead of reflecting the light beam on the wafer, a diffraction grating may be provided on the wafer W, and the light beam may be diffracted by the diffraction grating and incident on the FZP 105.

(Effect of the Invention) As described above, according to the present invention, the first object and the second object have a lens function in the direction of detecting the positional deviation, and a lens function having a different focal length in the direction orthogonal to the direction. By providing the provided grating lens element as an alignment mark for detecting a positional deviation, for example, when there is a positional deviation component in a direction orthogonal to the direction of detecting the positional deviation, the alignment light beam deviates from the sensor and the positional deviation cannot be detected. In addition, unnecessary diffracted light and scattered light components other than the alignment signal light are reduced, and as a result, a position detection device and a position detection method using the same that achieve high-accuracy alignment are achieved. be able to.

[Brief description of the drawings]

FIG. 1 and FIG. 2 are explanatory diagrams of the principle of the relative displacement detection method according to the present invention, and FIG. 3 is a perspective view showing the third, fifth, sixth, seventh, eighth, tenth, eleventh,
12, 13, 14, 15, and 16 are schematic diagrams of the main parts of the first to twelfth embodiments of the position detecting device of the present invention in order, FIG. 4 is an explanatory view of the zone plate of FIG. 3, FIG. 9 is an explanatory view of the zone plate of FIG. 8, and FIGS. 17 and 18 are schematic views of a conventional position detecting device. In the figure, 1 is a first object, 2 is a second object, 3S and 3a are first physical optical elements, 4s and 4a are second physical optical elements, 5 is an incident light beam,
8 is a detection means, 9 is a detection surface, 10 is a light source, 11 is a light projection lens, 12 is a half mirror, 51 is a zone plate, 52 is a line light source, M is a mask, W is a wafer, 101 is a scribe line, 3M, 4W is an alignment mark, 15 is an aligner main body, 16 is a mask chuck, 17 is a membrane, and 14 is a mask-wafer alignment head.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tetsushi Nose 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Ryo Kuroda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Shigeyuki Suda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-60-194523 (JP, A) JP-A-57-157033 (JP) , A) US Patent 4037969 (US, A)

Claims (4)

(57) [Claims] A first physical optical element formed on a first object surface; and a second physical optical element formed on a second object surface opposed to the first object. Each of the physical optical elements has a condensing or diverging action in a first direction, and at least one of the first and second physical optical elements has a focal length f1 in the first direction. The first
Has a focal length f2 different from the focal length f1 in a second direction perpendicular to the direction of the first physical optical element and the second physical A light beam which has been acted on by both of the physical optical elements and has become a condensed light beam in the first and second directions is received by the detecting means, and the toric lens effect is based on the first and second objects. The amount of displacement of the light beam on the detection surface of the detection means with respect to the relative displacement in the first direction is determined on the detection surface relative to the relative displacement of the first object and the second object in the second direction. The deviation amount of the luminous flux is smaller than that of the first light beam on the detection surface of the detection means.
A relative position relationship between the first object and the second object in the first direction is detected by using an output signal relating to a shift of a light beam in the direction. 2. When forming a first physical optical element on a first object surface, and forming a second physical optical element on a second object surface disposed opposite to the first object, the first and second physical optical elements are formed. Each of the physical optical elements has a condensing or diverging action in a first direction, and at least one of the first and second physical optical elements has a focal length f1 in the first direction. The first
Has a focal length f2 different from the focal length f1 in a second direction perpendicular to the direction of the first physical optical element and the second physical A light beam which has been acted on by both of the physical optical elements and has become a condensed light beam in the first and second directions is received by the detecting means, and the toric lens effect is based on the first and second objects. The amount of displacement of the light beam on the detection surface of the detection means with respect to the relative displacement in the first direction is determined on the detection surface relative to the relative displacement of the first object and the second object in the second direction. The other physical optical element has a cylindrical lens function that does not converge and diverge in the second direction, and the physical optical element on the detection surface of the detection means Regarding the displacement of the light beam in the first direction Position detecting apparatus characterized by using the output signal so as to detect the first direction relative positional relationship between the first and second objects. 3. When forming a first physical optical element on a first object surface and forming a second physical optical element on a second object surface arranged opposite to the first object, the first and second physical optical elements are formed. Each of the physical optical elements has a condensing or diverging action in a first direction, and at least one of the first and second physical optical elements has a focal length f1 in the first direction. The first
Has a focal length f2 different from the focal length f1 in a second direction perpendicular to the direction of the toric lens, wherein the toric lens behavior is a function of the first object and the second object. Based on the amount of displacement of the light beam on the detection surface of the detection means with respect to the relative displacement in the first direction, the first
The amount of displacement of the light beam on the detection with respect to the relative positional displacement of the object and the second object in the second direction is smaller, and the light beam from the illumination means is incident on the first physical optical element. Then, by making the light incident on the second physical optical element, a light beam that has become a condensed light beam in the first and second directions is received by a detection unit, and the first light beam on the detection surface of the detection unit is received by the detection unit. A position detecting method, wherein a relative positional relationship between the first object and the second object in the first direction is detected using an output signal relating to a direction shift. 4. When forming a first physical optical element on a first object surface, and forming a second physical optical element on a second object surface disposed opposite to the first object, the first and second physical optical elements are formed. Each of the physical optical elements has a condensing or diverging action in a first direction, and at least one of the first and second physical optical elements has a focal length f1 in the first direction. The first
Has a focal length f2 different from the focal length f1 in a second direction perpendicular to the direction of the toric lens, wherein the toric lens behavior is a function of the first object and the second object. Based on the amount of displacement of the light beam on the detection surface of the detection means with respect to the relative displacement in the first direction, the first
The amount of displacement of the light flux on the detection surface with respect to the relative displacement of the object and the second object in the second direction is smaller, and the other physical optical element is in the second direction. The first physical optical element has a cylindrical lens function that does not converge and diverge. The first physical optical element is irradiated with a light beam from an illuminating unit, and then is incident on the second physical optical element. A light beam that has become a condensed light beam is received by a detecting means, and the first object and the second object are separated from each other by using an output signal related to a shift in the first direction on a detecting surface of the detecting means. A position detecting method, wherein a relative positional relationship in one direction is detected.