JPH042903A - Position detector - Google Patents

Abstract

PURPOSE:To accurately detect a positional deviation by regulating a light intensity distribution of passed luminous fluxes in response to the code of an angle formed between the main light rays of two fluxes emitted from two alignment marks by using light intensity distribution regulating means. CONSTITUTION:Alignment luminous flux emitted from a light source 13 such as a semiconductor laser, etc., is incident to alignment marks 5, 6 on the surface of an article 1 through a collimator lens system 14, a beam splitter 15, and light intensity distribution regulating means 20. Here, the light intensity distribution of passed fluxes is regulated in response to the code of an angle formed between optical paths of main light rays of two fluxes to be emitted from the two marks 5, 6 or 3, 4 provided on the surface of one of the articles 1, 2. Then, the fluxes diffracted by the marks 5, 6 are, for example, converged at convex power by the mark 5, dispersed at concave power by the mark 6, and then introduced to alignment marks 3, 4 on the article 2. Thereafter, the fluxes which are dispersed by the mark 3 and converged by the mark 4 becomes first, second signal lights, which are emitted from the article 2, passed through the article 1, and introduced to detecting surfaces 11, 12 to detect positional deviations.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a position detection device, and for example, in an exposure apparatus for manufacturing semiconductor elements, the present invention relates to a position detection device that detects a position on a first object surface such as a mask or a reticle (hereinafter referred to as "mask"). Suitable for determining the amount of relative positional deviation between the mask and wafer and aligning them when exposing and transferring a fine electronic circuit pattern formed on a wafer onto a second object surface such as a wafer. The present invention relates to a position detection device.

(Prior Art) Conventionally, in exposure apparatuses for semiconductor manufacturing, relative alignment between a mask and a sea urchin has been an important element for improving performance. Particularly in alignment in recent exposure apparatuses, alignment accuracy of, for example, submicron or less is required due to the high integration of semiconductor devices.

In many position detection devices, so-called alignment marks for positioning are provided on the mask and the eight faces of the sea urchin, and position information obtained from these marks is used to perform alignment of both. As an alignment method at this time, for example, detecting the amount of misalignment between both alignment marks by performing image processing, or using U.S. Patent No. 4037
No. 969, U.S. Patent No. 4,514,858, and JP-A-56-
As proposed in Publication No. 157033, a zone plate is used as an alignment mark, a light beam is irradiated onto the zone plate 1, and at this time, the position of a converging point on a predetermined plane of the light beam emitted from the zone plate is detected. etc.

In general, alignment methods using zone plates are
Compared to a method using a simple alignment mark, this method has the advantage of being able to achieve relatively high-grain alignment without being affected by defects in flymen 1 marks.

FIG. 11 is a schematic diagram of a conventional position detection device using a zone plate.

In the figure, a mask M is attached to a membrane 117, and is attached to a mask chuck 1 on an aligner body 115.
16. An alignment head 114 is arranged above the main body 115. Mask alignment mark M is used to align the mask M and wafer W.
M and wafer alignment mark WM are printed on mask M and wafer W, respectively.

The light beam emitted from the light source 110 is turned into parallel light by the projection lens system 111, passes through the half mirror 112, and enters the mask alignment mark MM. The mask alignment mark MM is composed of a transmission type zone plate, and the incident light beam is diffracted, and the +1st-order diffracted light is subjected to a convex lens action to converge on a point Q.

Further, the wafer alignment mark WM has the function of a convex mirror (divergent function) that reflects and diffracts the light condensed to the convergence point Q by the reflective zone plate and forms an image on the detection section 119.

At this time, when the signal light flux that has undergone the 11th-order reflection and diffraction action at the wafer alignment mark WM passes through the mask alignment mark MM, it is transmitted as 0-order light without being subjected to lens action, and is condensed onto the detection surface 119. It is something that comes.

In the position detection device shown in the figure, when the wafer W is misaligned by a predetermined amount relative to the mask M, the incident position of the light beam incident on the detection surface 119 (the amount of light (center of gravity) shifts. There is a certain relationship between the amount of deviation ΔδW on the detection surface 119 and the amount of positional deviation ΔσW at this time, and the amount of deviation ΔδW on the detection surface 119 at this time is
By detecting W, the relative positional deviation amount ΔσW between the mask M and the wafer W is detected.

(Problems to be Solved by the Invention) However, in conventional position detection devices, the distance between two objects placed facing each other in order to perform positioning may vary from a preset value. In this case, with this variation, the positional deviation detection magnification, which is the ratio ΔδW/ΔσW of the deviation amount ΔδW of the incident position of the light beam on the detection surface to the positional deviation amount ΔσW, also changes, resulting in a detection error of the positional deviation amount. There was a problem with the

In addition, the position relative to the alignment head or alignment mark that has a built-in light source, a light projecting optical system for guiding the light beam from the light source onto the mask surface, a light receiving system for receiving signal light, etc. When the fluctuation occurs, the incident position of the light beam onto the detection surface of the detection section also changes, resulting in a problem in that a detection error of the positional deviation amount ΔδW occurs.

The present invention can be used even if there is a change in the distance between the first object and the second object to be aligned, which deviates from a preset value, or the position of the alignment head changes relative to the alignment mark. However, by appropriately setting each element such as the shape of the alignment mark provided on the first and second object planes and the angle of incidence of the emitted light beam onto the alignment mark, the amount of relative positional deviation between the two objects can be reduced. The purpose of the present invention is to provide a position detection device that can detect the position accurately.

(Means for Solving the Problems) The position detection device of the present invention includes a first object and a second object, each provided with an alignment mark made of at least two physical optical elements, which are placed facing each other, The two light beams are guided onto a predetermined surface through alignment marks provided on the first object and the second object through a light intensity distribution adjusting means, and the two light beams on the predetermined surface are When detecting the relative positional displacement between the first object and the second object by detecting the incident position of the light beam with the detection means, the two objects on each of the first and second object surfaces are detected. The alignment marks have their axes grazing each other, and at least one of the two light beams is subjected to imaging action by the alignment mark on the first object plane and the alignment mark on the second object plane, respectively. , the light intensity distribution adjusting means is configured to adjust the first
The light intensity distribution of the passing light beam is adjusted in accordance with the sign of the angle formed by the optical path of the principal ray of the two light beams emitted from two alignment marks provided on the object surface of one of the object and the second object. It is characterized by

That is, the present invention provides alignment marks for first and second signals that function as physical optical elements on the object plane A when the object plane A and the object plane B are a first object and a second object to be aligned. A1 and A2 are formed with their axes aligned with each other,
Also on the object plane B, there are alignment members 1 to mark B1 for the first and second signals which also function as physical optical elements.
and B2 are formed with their axes shifted from each other, a light beam is made incident on the alignment mark 2A1, and the diffracted light generated at this time is made incident on the alignment mark B1. The center of gravity of the luminous flux is the first
The first detection unit detects the incident position of the signal light beam.

Here, the center of gravity of the light beam is the point in the cross section of the light beam where the integral value becomes 0 vector when the product of the position vector of each point of the cross section circle from that point multiplied by the light intensity of that point is integrated over the entire cross section. However, for convenience, the point where the light intensity is at its peak may be used as the center of gravity of the light flux. Similarly, a light beam is made incident on the alignment mark A2, and the diffracted light generated at this time is made incident on the alignment mark B2, and the center of gravity of the light beam on the incident surface of the diffracted light from the alignment mark B2 is set as the incident position of the second signal light beam and sent to the second detection section. Detect. Then, the object plane A and the object plane B are positioned using the two position information from the first and second detection sections. At this time, a light beam from a light projecting means that emits a light beam having a non-uniform light intensity distribution is made to enter the alignment mark via a light intensity distribution adjusting means. Then, the light intensity distribution adjusting means adjusts the light intensity distribution of the passing light flux according to the sign of the angle formed by the optical path of the principal rays of the two light fluxes from the two alignment marks on the first object or the second object surface. There is.

In this Ikemizu invention, the center of gravity of the light beam incident on the first detection section and the center of gravity of the light flux incident on the second detection section are displaced in opposite directions with respect to the positional misalignment of the object plane A and the object plane B. Alignment 1~Mark AI, A2. Bl and B2 are set.

(Example) Fig. 1 is an explanatory diagram showing the principles and constituent elements of the present invention developed, and Fig. 2 is a perspective view of main parts of the first embodiment of the present invention based on the configuration of Fig. 1. .

In the figure, 1 is the first object corresponding to object plane A, and 2 is object plane B.
The second object corresponds to , and the case where the amount of relative positional deviation between the first object 1 and the second object 2 is detected is shown.

In FIG. 1, two first objects 1 are shown because the light that passes through the first object 1 and is reflected by the second object 2 passes through the first object 1 again. 5 is an alignment mark provided on the first object 1, and 3 is an alignment mark provided on the second object 2, for obtaining the first signal. Similarly, 6 is an alignment mark provided on the first object 1, and 4 is an alignment mark provided on the second object 2, for obtaining the second signal light.

Each alignment mark 3, 4, 5.6 has the function of a physical optical element with or without a one-dimensional or two-dimensional lens effect. 9 is the wafer scribe line,
10 is a mask scribe line. 7 and 8 are the first and second alignments described above. A second signal beam is shown. Reference numerals 11 and 12 indicate first and second detection units for detecting the first and second signal beams, respectively. from the second object 2 to the first
Alternatively, the optical distance to the second detection unit 11.12 will be referred to as L for convenience of explanation. The distance between the first object 1 and the second object 2 is g
, the focal lengths of alignment marks 5 and 6 are respectively fal
+f a2, and the amount of relative positional deviation between the first object 1 and the second object 2 is Δσ, and the first . Second detection unit 11.
The amount of displacement of the 12 first and second signal beam centers from the coincident state is 5182, respectively. Note that the alignment light beam incident on the first object 1 is assumed to be a plane wave for convenience, and the symbols are as shown in the figure.

The displacement amount 81 and S2 of the center of gravity of the signal beam are the focal points F, , F2 of the alignment marks 5 and 6 and the alignment mark 3,
A straight line LIL2 connecting the optical axis centers of 4 and the detection units 11 and 1
It is determined geometrically as the intersection with the light-receiving surface of No. 2. Therefore, in order to obtain the displacement amounts S, , S2 of the center of gravity of each signal beam in opposite directions with respect to the relative positional deviation between the first object 1 and the second object 2, the sign of the optical imaging magnification of the alignment mark 3.4 is adjusted. This is achieved by reversing each other.

Next, the 1st column for alignment shown in FIGS. 1 and 2. Second
The optical path of the chief ray of the signal beams 7 and 8 will be explained.

In the following explanation, the principal ray refers to a ray passing through the axis of the alignment mark when the alignment mark has an imaging effect, and refers to the central ray of the effective beam diameter when the alignment mark does not have an imaging effect.

A light beam emitted from a light source (not shown) that emits a light beam with a non-uniform light intensity distribution is expanded to a predetermined beam diameter through a projection optical system (not shown), and becomes substantially parallel light, which is then transmitted to the light intensity distribution adjusting means 2.
0 to the alignment marks 5 and 6 on the first object 1 obliquely to the normal to the object surface.

At this time, the light intensity distribution adjusting means 20 may be, for example, a half mirror or a liquid crystal member whose transmittance is varied depending on the location. As will be described later, the light intensity distribution of the light flux that has passed through the light intensity distribution adjustment means is the first because the angle formed by the optical path of the principal ray of the light flux from the two alignment marks is positive.
As shown in the figure, there is a non-uniform distribution that becomes minimum near the center of the luminous flux. That is, each type distribution is such that the light intensity is minimum in the boundary area between the two alignment marks 5 and 6.

The alignment mark according to the present invention consists of two regions whose center-to-center distance is a predetermined value other than zero, and is formed on each object surface to be aligned.

As described above, the alignment light beam enters the alignment marks 5 and 6 on the first object plane as a single light beam with a non-uniform light intensity distribution. The light beam diffracted by the alignment marks 5 and 6 on the first object surface is subjected to a converging effect of convex power at the alignment mark 5, a diverging effect of concave power at the alignment mark 6, and then to the alignment mark 3 on the second object surface. .4 is reached.

Further, the light beams which have undergone the diverging effect of concave power at the alignment mark 3 on the second object surface and the convergence effect of the convex power at the alignment mark 4 become first and second signal beams 7 and 8, respectively, and exit the second object surface 2. , after passing through the surface of the first object, enters the detection unit 11.12 located at a predetermined position.

In this embodiment, a case is shown in which the amount of positional deviation is detected in the illustrated X direction. Furthermore, each detection section uses a one-dimensional sensor that measures the light intensity distribution in the X direction.

The present invention is based on a simulation based on ray tracing.
The first . If the angle formed by the optical path of the principal ray of the second signal beam 7.8 is positive (in the direction in which the principal rays diverge from each other), the light intensity distribution adjusting means 2° adjusts the light intensity distribution of the light beam passing through it to the two alignment marks. If the angle is negative (the direction in which the principal rays approach each other), the light intensity distribution of the light flux passing through it is adjusted by the light intensity distribution adjusting means 20. Setting the two alignment marks 5 and 6 to a maximum near the center of the arrangement minimizes the occurrence of positional deviation detection errors caused by fluctuations in the distance between the first object 1 and the second object 2. It has been found that this can be suppressed well.

That is, in this embodiment, even if the amount of relative positional deviation between the first object and the second object remains unchanged, the detection unit 11 that occurs due to a change in the distance between the first object and the second object, which has conventionally been a problem. .12
The error in detecting the amount of positional deviation due to the variation in the distance between the above two alignment signal light beam incident positions (isometrically, the light intensity gravity center position) can be suppressed well by adopting a light intensity adjustment means. That's what I do.

Furthermore, the inventors have found that the occurrence of positional deviation amount detection errors caused by fluctuations in the irradiation center position of the alignment light beam on the first object plane can also be effectively suppressed.

The present invention suppresses the occurrence of the above-mentioned positional deviation amount detection error by controlling the light intensity distribution of the light beam using the light intensity distribution adjusting means, and thereby reduces the relative positional deviation between the first object and the second object. This enables highly accurate detection.

FIG. 3(A) shows a configuration diagram of the peripheral portion of the apparatus when the first embodiment shown in FIG. 2 is applied to a proximity type semiconductor manufacturing apparatus. Elements not shown in FIG. 2 include a light source 13, a collimator lens system (or beam diameter conversion lens) 14, a projection light beam bending mirror 15, a pickup housing (alignment head housing) 16, and a wafer stage 1.
7, a positional deviation signal processing section 18, a wafer stage drive control section 19, etc. E indicates the exposure beam width.

In this embodiment as well, detection of the amount of relative positional deviation between the mask 1 as the first object and the wafer 2 as the second object is performed in the same manner as described in the first embodiment.

In this example, the alignment procedure is as follows:
For example, the following method can be adopted.

The first method is the detection surface 11a of the detection unit 11.12 for the amount of positional deviation Δσ between the two objects.

12b is obtained, the signal processing unit 18 calculates the positional deviation amount Δσ between both objects from the gravity center deviation signal, and drives the stage by an amount corresponding to the positional deviation amount Δσ at that time. The wafer stage 17 is moved by the control unit 19.

The second method is to use the signal processing unit 18 to determine the direction in which the positional deviation amount Δσ is canceled from the signals from the detection units 11 and 12.
The stage drive control unit 19 moves the wafer stage 1 in that direction.
7 and repeat this process until the positional deviation amount Δσ falls within the allowable range.

Flowcharts of the above alignment procedure are shown in FIGS. 3(B) and 3(C), respectively.

In this embodiment, as can be seen from FIG. 3(A), the light beam from light #13 is directed from the outside of the exposure light beam to the alignment mark 5,
6 and exits from the alignment mark 3.4 to the outside of the exposure light beam, which is received by a detection unit 11.12 provided outside the exposure light beam, thereby detecting the position of the incident light beam.

With such a configuration, it is possible to realize a system in which the pickup housing 16 does not require a retracting operation during exposure.

Next, details of the configuration of each part of the first embodiment will be explained with reference to FIGS. 2, 3(A), and 4.

Figure 4 is 1. FIG. 4 is an explanatory diagram of the incident state of the second signal light beams 7 and 8 to the 1° second detection section 11.12. The alignment light beam emitted from the semiconductor laser (center wavelength 0.785 μm), which is the light source 13 in the pickup housing 16 for alignment, passes through a projection optical system consisting of a collimator lens system 14 and a beam splitter (or half mirror) 15. After becoming a parallel light beam and passing through the light intensity distribution adjusting means 20, it is placed on one mask surface in the yz plane with respect to the normal to the mask surface.
Oblique incidence at an angle of 7.5°.

Light intensity distribution of alignment light flux on one mask surface (1(x
, y)), if the coordinate system is taken as shown in the figure, (1a) σ, = 680 μm, σ, = 120 μm. Furthermore, the amount of positional deviation is detected in the X direction.

The sizes of the two alignment marks on the mask and the eight faces of the sea urchin are both 90 μm in the X direction and 50 μm in the X direction.
m and are arranged adjacent to each other as shown in FIG.

The alignment mark 5 on the first surface of the mask is a grating lens with convex power that has a light flux convergence effect, and the focal length corresponding to the +1st-order diffracted light is 214°723 μm, +1
The deflection angle in the yz plane of the principal ray of the next transmitted diffracted light is 17.5°
The direction of the principal ray exiting one surface of the mask is parallel to the normal line of the mask surface.

In addition, the alignment mark 6 on the first surface of the mask is a grating lens with concave power that has a luminous flux diverging effect, and has a +
The focal length corresponding to the first-order diffracted light is 158.455 μm,
Similar to the alignment mark 5, the deflection angle of the chief ray is 17.5° in the yz plane.

In both alignment marks 5.6, the polarization angle is 0° in the xz plane, and the principal ray direction does not change.

In this example, the angle of oblique incidence α of the light beam on one surface of the mask is 10°〈　α　〈80゜ It is desirable to set it within the range of .

At the alignment mark 3 on the wafer surface 2-7, the light beam that has been diffracted and transmitted in the +1st order by the alignment mark 5 on the mask 1 surface is incident. Here, the first signal light beam 7 that is further diffracted and reflected in the +1st order is subjected to a diverging effect. The alignment mark 3 is a grating lens with concave power, and the focal length is 82.9]2 μm.In the xz plane, the principal ray direction is emitted to the sea urchin at an angle of 13° with respect to the surface normal. After that, as shown in FIG. 4, it reaches above the detection unit 11 while maintaining the angle.

Similarly, the alignment mark 4 on the wafer 1 is a grating lens (focal length 1i1t 190.378 μm) with convex power corresponding to the +1st-order reflected diffraction light, and the alignment mark 4 on the mask 1 corresponds to the light beam 8 transmitted and refracted by the alignment mark 6 on the mask 1. It has an optical effect.

Further, as shown in FIG. 4, the second signal beam 8 emitted from the alignment mark 4 is emitted such that its principal ray direction forms an angle of +3.35° in the xz plane with respect to the normal to the wafer 2 surface. After that, it reaches above the detection unit 12 while maintaining the angle. In this embodiment, it is assumed that the angle formed by the two optical paths is positive for the optical paths as described above.

On the other hand, when ejecting from the second side of the wafer, the first. The exit angles of the second signal beams 7 and 8 in the yz plane are 7 degrees and 130 degrees, respectively, with respect to the normal to the surface of the sea urchin, and the second signal beams 7 and 8 are arranged so as to be incident on two spatially separated detection units 11 and 12. Elements such as alignment mark shape and optical system are set in .

Now, the mask 1 and the wafer 2 are shifted by Δσ in the direction parallel to the positional shift detection direction (X direction).
The convergence point o1 of the luminous flux reflected by the grating lens 3 of
Let b be the distance between the beams and a be the distance to the focal point F1 of the light beam that has passed through the grating lens 5 of the mask 1, then the shift amount Δδ of the center of gravity of the focal point on the detection unit 11 is Δδ = Δσx (- +1) ・・・・・・・・・(a
), that is, the center of gravity shift amount Δδ is (b / a + 1
) will be magnified twice. For example, a=0.5mm, b=5
If it is set to 0 mm, the center of gravity shift amount Δδ will be expanded by a factor of 101 according to equation (a).

In this embodiment, the concave power and the convex power are determined depending on whether minus order diffracted light or positive order diffracted light is used.

The diameter of the grating lenses 3.4 on the wafer 2 is 180 μm, and the diameter of the grating lenses 5, 6 on the mask 1 is 180 μm.
The diameter of the umbrella is 180 μm, and the positional deviation (axis deviation) between the mask and the sea urchin is magnified by 100 times, causing the center of gravity of the light beam to shift on the detection unit 11.12.
The diameter of the upper luminous flux (Airy disk e-2 diameter) is 200 μm
The arrangement and focal length of each element were determined so that the

In addition, the center of gravity shift amount Δδ and position shift amount Δσ at this time are (a
) As is clear from the equation, there is a proportional relationship. Detection unit 11
．． If the resolution is 12 or 01 μm, the positional deviation amount Δ
σ is a positional resolution of 0.001 μm.

In this example, the focal length of each alignment mark on the mask and wafer is set as described above, the distance between the mask and the sea urchin is 30.0 μm, and the center positions of the detection parts 11 and 12 are set at (0, 0, -4, respectively). ,203,18,204)(0,0
, -2,277,18,543) (unit: mm), the 1st. Detection sensitivity of the second signal beams 7 and 8 on the detection unit 11 and 12 surfaces (i.e., the amount of variation in the light beam incident position on the detection unit surface with respect to the relative positional deviation variation ff1 (X direction) between the mask and the wafer) percentage) is +100. -100
Became.

Next, the pattern shapes of the mask crating lenses 5 and 6 and the wafer crating lenses 3 and 4 in this embodiment will be explained.

First, the mask crating lenses 5 and 6 are set so that a parallel beam of a predetermined beam diameter enters at a predetermined angle and is condensed at a predetermined position.

In general, the pattern of a crating lens is an interference fringe pattern on the lens surface when a coherent light source is placed at each of the light source (object point) and image point.

Here, the origin is located at the center of the scribe line width, with the X axis in the scribe line direction, the Y axis in the width direction, and the Z axis in the normal direction of the mask surface. α in the yz plane with respect to the normal to the mask surface
A parallel light beam whose projected component is incident at an angle of The equation of the group of curves is ysjn a P, (x, y) - P2 = mλ, where x and y are the contour positions of the grating.
/ 2-...(+)P+(X,y)=(x-x+
)2 + (y-y+)2 + z, 2P2
= XI"!l'l"Zl' is given. Here ^
is the center wavelength of the wavelength range in which the alignment light beam is used, and m is an integer.

Assuming that the principal ray is incident at an angle α, passes through the origin on the mask surface, and reaches the focal point (XI, Y+, Z+), the right side of equation (1) is determined by the value of m, which changes the wavelength to the principal ray. m72 times indicates that the optical path length is long (short), and the left side is the optical path of the ray that passes through the point (x, y, 0) on the mask and reaches the point (XI, y+, Z+) with respect to the optical path of the principal ray. Represents the difference in length.

On the other hand, grating lenses 3 and 4 on the wafer are set so as to focus the spherical waves emitted from a predetermined point light source onto a predetermined position (on the detection surface). Let the position of the point light source be g, which is the cap during exposure of the mask and wafer (XI, 'j+,
Zl g). Assuming that the mask and wafer are aligned in the X-axis direction, and that the alignment beam is focused on the point (X2 + y2 + 22) on the detection surface when alignment is completed, the grating lens on the wafer The equation of the curve group is expressed as 10 mλ/2 (2) in the coordinate system determined earlier.

Equation (2) indicates that the sea urchin surface is at z=-g, the principal ray is the origin on the sea urchin surface, the point on the mask surface (0,0°-g), and the point on the detection surface (X2 + y2 '+22), and the grating (x, y
, -g) and the principal ray satisfy the condition that the difference in optical path length is an integral multiple of a half wavelength.

Generally, a zone plate (crating lens) for a mask has two areas formed alternately: an area through which light rays pass (transparent area) and an area through which light rays do not pass (shading area).
1 amplitude type grating element. Further, a zone plate for a wafer is made, for example, as a phase grating pattern with a rectangular cross section. (]), In equation (2), the outline of the grating is defined at a position that is an integer multiple of half a wavelength with respect to the chief ray. Ratio is 1=
1, and the ratio of the lines and spaces of the rectangular grating is 1:1 in the grating lens 3 or 4 on the wafer.
It means that.

The grating lens 5.6 on the mask is formed, for example, by transferring the grating lens pattern of the reticle previously formed by EB exposure onto an organic thin film made of polyimide, or the grating lens on the wafer is formed by transferring the exposure pattern of the wafer onto the mask. After forming, it is formed by exposure transfer.

FIG. 1.theta.('A) shows the pattern of the grating lenses 5, 6 on the mask surface, and FIG. 1(B) shows the pattern of one embodiment of the grating lenses 3, 4 on the surface of the mask.

With the configuration explained above, the gap between the mask and the wafer (
1. due to the change in distance (interval) and the change in position (parallel movement) of the pickup housing 16. The magnitude of the variation in the interval between the light quantity gravity center positions (hereinafter referred to as spot interval) measured along the X direction of the second signal light beam was measured. As a result, by using the light intensity distribution adjusting means 20 to irradiate the alignment mark with a light beam having a light intensity distribution expressed by the above-mentioned equation (1a), the variation amount of the spot interval is 1.9 for a gap variation of ±30 μm.
μm, and the relative positional deviation detection error between the mask and the wafer was 0.0095 μm.

On the other hand, in a conventional position detection device that irradiates the alignment mark with a light beam whose light intensity distribution has a Calacian distribution, although the positional deviation detection sensitivity is the same, the variation in the spot interval is 12.56 μm, resulting in a positional deviation detection error. is 0.063
It was μm. That is, by using the light intensity distribution adjusting means according to the present invention, the detection error is reduced to about 1/60th.

On the other hand, with respect to positional fluctuations of the pickup housing 16 (translation in parallel to the
μm), which is about half that of the conventional one.

FIG. 5 is a perspective view of essential parts of a second embodiment of the present invention.

In this embodiment, two light sources 13-1.13-2 made of semiconductor lasers, superluminescent diodes, etc. are used. By adjusting the output, it functions as a light intensity distribution adjusting means. The light intensity distribution on the alignment mark surface at this time is, for example, the first
It is similar to that shown in FIG. Optical path of the principal rays of the two signal beams 7 and 8 (arrangement of alignment marks),
The configuration of other elements is the same as in the first embodiment. however,
The alignment mark is placed a predetermined distance ahead as shown in the figure.

In this embodiment, there are two light sources 13-1 and 13-2.
are separated by a predetermined distance, and the two alignment marks 5,
Adjust the light intensity distribution on the 6th plane using the left and right alignment marks 5 and 6.
The structure is such that the intensity is minimum near the center of the gap, and increases as the distance from the center increases. Then, the optical paths of the two signal beams 7 and 8 that finally arrive at the light receiving section 11.12 from the left and right alignment marks 5 and 6 are aligned, and from the alignment mark 5 on the left hand side to the left hand in the cross section including the misalignment detection direction, The alignment mark 6 on the right hand side is configured to emit light obliquely to the right hand object surface normal. As a result, the amount of errors in detecting the amount of positional deviation due to variations in the distance between the mask 1 and the wafer 2, variations in the position between the alignment head housing and the mask, etc. can be suppressed in a good manner as in the first embodiment.

FIG. 6 is a perspective view of essential parts of a third embodiment of the present invention.

In this embodiment, alignment mark areas for the first and second (g-minute beams 7 and 8) are arranged at predetermined distances, for example, 100 μm, on the mask 1 and wafer 2 surfaces.

Here, assuming that the diameter of the projected light beam projected onto the alignment mark 5°6 on the mask 1 surface is the same as in the first embodiment, the first . The final relative angle of the second signal light beam is not the optimum value, and the positional deviation measurement error due to gap fluctuations and fluctuations in the position of the alignment head housing increases.

Therefore, in this embodiment, the diameter of the projected light beam is the same as that of the first embodiment, and the diameter of the projected light beam is the same as that of the first embodiment. The final emission angles of the second signal beam in the xz plane are −4 and +4.8 degrees, respectively.

FIGS. 10A and 10B show examples of patterns of alignment marks on the mask and the eight faces of the sea urchin, respectively, in this embodiment.

As described above, the optimum conditions for setting the optical path and the light intensity distribution of the projected light are determined by various factors such as the diameter of the projected beam, the size and arrangement of the alignment mark, and the focal length. In this embodiment, the optimum value is obtained through simulation using a large number of ray tracings, and each element is configured based on this.

FIG. 7 is a perspective view of essential parts of a fourth embodiment of the present invention.

In this embodiment, the first . second signal beam 7,
As shown in the figure, the alignment mark areas for No. 8 are arranged adjacently so that some of them overlap.

FIGS. 10C and 10D show an embodiment showing patterns of alignment marks 5 and 6 on one surface of the mask and alignment marks 3 and 4 on one surface of the wafer.

In FIG. 8 and FIG. 10 (C) and (D), the area 70
1° 702 is an area where alignment marks overlap with each other.

In this embodiment, the diameter of the projected light beam of the luminous flux is the same as that of the first embodiment, and the diameter of the projected light beam is the same as that of the first embodiment. The final exit angles of the second signal beam in the xz plane were set to -2 and +2.8 degrees, respectively. Also, the distance between the centers of the alignment marks on each surface is 60 μm, and the area where the alignment marks overlap in the X direction (701, 702)
is 30 μm.

FIG. 8 is a schematic view of a main part of a fifth embodiment showing a position detection part in which the present invention is applied to a reduction projection exposure apparatus.

In the figure, a light beam emitted from a light source 13 is converted into parallel light by a projection lens system 14 and is irradiated to reticle alignment marks 3L1 and 3L2 on a reticle L surface as a first object via a light intensity distribution adjusting means 20. At this time, the reticle alignment marks 3L1 and 3L2 direct the passing light to point Q, respectively. .

It constitutes a transmission type physical optical element having a lens function to focus light on Qo'. And point Q. .

The light flux from Qo' is focused by a reduction lens system 18 on points Q and Q' that are separated by a distance of 1 [faw, aw' from the wafer W as the second object.

In the figure, 7.8 is the alignment mark 3'L1,
The first . caused by 3L2. 807 indicates a second signal beam;
, 808 are respective chief rays.

Wafer alignment marks 4wl, 4w are on the wafer W.
2 is provided, and this wafer alignment mark 4
wl and 4w2 constitute reflective physical optical elements, and when light beams 7 and 8 converge on points Q and Q', respectively, enter,
The light flux is reflected and passed through the half mirror 19 to the detection unit 1.
It has the function of a convex mirror that forms an image on one surface.

The 1st. As for the second signal beam, only principal rays 807 and 808 are representatively shown in FIG.

FIGS. 9(A) and 9(B) are a perspective view of a main part and a schematic diagram of an optical path of a sixth embodiment of the present invention.

In this embodiment, the first. Second signal beam 7
, 8, after emitting the second object surface 2, the second object surface (
The alignment marks and the incident angle of the projected light flux are configured so that the projection trajectories on the first object plane (or the first object plane) always intersect. Hereinafter, such an optical path configuration will be referred to as a "crossing optical path."

Further, the angle formed by the optical paths of the two signal beams 7 and 8 is defined as negative in the case of the figure.

As a result of a simulation study, the inventors of the present invention found that by employing the above-mentioned light intensity distribution adjustment means and crossed optical paths, the above-mentioned alignment mark system can be achieved with an alignment light flux having a light intensity distribution such as a non-uniform Gaussian distribution. It has been found that in the case of irradiation, it is possible to extremely effectively suppress the occurrence of positional deviation amount detection errors caused by fluctuations in the distance between the first object 1 and the second object 2.

That is, in this embodiment, even if the amount of relative positional deviation between the first object and the second object remains unchanged, there is a problem on the detection unit 11. 2
To satisfactorily suppress a positional deviation amount detection error due to a change in the distance between the incident positions of two alignment signal light beams (isometrically, light intensity barycenter positions) by employing the above-mentioned light intensity distribution adjustment means and crossed optical paths. We are making it possible to do so.

Furthermore, by using the light intensity distribution adjusting means and the crossed optical paths, the inventors have also found that the occurrence of positional deviation amount detection errors caused by fluctuations in the irradiation center position of the alignment light beam on the first object plane can be suppressed in a similar manner. I discovered that it can be done.

The present invention suppresses the occurrence of the above-mentioned positional deviation amount detection error by setting each element so that such crossed optical paths are formed, and increases the accuracy of the relative positional deviation amount between the first object and the second object. This enables accurate detection.

Next, the first alignment plate shown in FIG. 9(A). The optical path of the principal ray of the second signal beam 7.8 will be explained.

A light beam emitted from a light source (not shown) that emits a light beam with a non-uniform light intensity distribution is expanded to a predetermined beam diameter through a projection optical system (not shown), becomes a substantially parallel beam, and is converted into a parallel beam through a light intensity distribution adjusting means. The light is incident on the alignment marks 5 and 6 on the object 1 obliquely with respect to the normal to the object surface. The light intensity distribution of the substantially parallel light beam reaching the surface of the first object 1 is a non-uniform Calacian distribution.

The alignment mark according to the present invention consists of two regions in which the center-to-center distance is a predetermined value other than zero, and is formed on each object surface to be aligned. As described above, the alignment light beam enters the alignment marks 5 and 6 on the first object plane as a single Gaussian beam. The light beam diffracted by the alignment marks 5 and 6 on the surface of the first object 1 receives, for example, a converging effect of convex power at the alignment mark 5 and a diverging effect of concave power at the alignment mark 6, and then
The alignment mark 3°4 on the second object plane is reached.

Further, the light beams which are subjected to the diverging effect of the concave power at the alignment mark 3 on the second object surface and the convergence effect of the convex power at the alignment mark 4 become 1° and second signal beams 7 and 8, respectively, and exit the second object surface 2. After passing through the surface of the first object, the light enters a detection unit 11.12 located at a predetermined position.

As shown in each of the above embodiments, according to the present invention, the light intensity distribution in the positional deviation detection direction of the light beam irradiated onto the object surface is arranged with two axes shifted from each other using the light intensity distribution adjusting means.
The distribution is non-uniform depending on the sign of the angle formed by the optical path of the principal ray of the two luminous fluxes emitted from the two alignment marks, and when the two luminous fluxes emitted from the two alignment marks are guided to the light receiving section, ( b) The light beam that reaches the light receiving part from the alignment mark on the + side with respect to the misalignment detection direction is emitted obliquely to the + side with respect to the normal line of the alignment mark surface, and similarly, the light beam that reaches the light receiving section from the alignment mark on the + side with respect to the misalignment detection direction is emitted obliquely to the + side with respect to the normal line of the alignment mark surface. In an optical path configuration in which light is emitted obliquely to one side with respect to the normal to the surface, 2
When the angle formed by the optical path of the two signal beams is positive, the light intensity in the positional deviation detection direction becomes minimum near the center of the entire area including the two alignment marks, and from the point where the light intensity becomes minimum in the position deviation detection direction The alignment mark is irradiated with a light intensity distribution in which the light intensity increases at a predetermined gradient as the distance from the alignment mark increases.

(b) With respect to the misalignment detection direction, as in (a), the + side alignment mark emits light diagonally to one side with respect to the normal line of the alignment mark surface, and the side alignment mark emits light on the alignment mark surface. When the angle formed by the optical path of the two signal beams is negative in an optical path configuration in which the optical path is emitted obliquely to the + side with respect to the normal line, the optical path is positioned near the center of the entire area including the two alignment marks in the misalignment detection direction. The alignment mark is irradiated with a light intensity distribution in which the light intensity reaches a maximum and decreases at a predetermined gradient as it moves away from the maximum point in the positional deviation detection direction.

It is characterized by adopting the configuration described above.

(Effects of the Invention) According to the present invention, the first . Two different wavefront conversion elements (physical optical elements) each having an imaging action (optical action) are formed on the second object plane as an alignment mark, and the imaging action of the alignment mark is applied sequentially (for example, 1st degree second object or 2nd degree first object plane). When detecting the amount of positional deviation based on the incident position information of the second signal light beam on a predetermined surface, the light intensity distribution of the light beam irradiated onto the alignment mark surface is emitted from the two alignment marks using a light intensity distribution adjusting means, By making adjustments according to the sign of the angle formed by the principal rays of the two light beams that enter the light receiving section, the system is highly insensitive to changes in the distance between the two objects being aligned and to changes in the position of the light beam projected from the light source. Therefore, it is possible to achieve a position detection device that can detect the amount of positional deviation with high precision.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the principle and structural requirements of the present invention, FIG. 2 is a perspective view of the main part of the first embodiment of the present invention based on the configuration of FIG. 1, and FIG. A schematic diagram of the main parts of the first embodiment applied to a proximity type semiconductor manufacturing apparatus, FIG. 3(B) and '(C) are flowcharts of the measurement control of FIG. FIG. 2 is a cross-sectional diagram of the optical path of the first embodiment, FIGS. 5 to 8 are perspective views of essential parts of the second to fifth embodiments of the present invention, and FIGS. A perspective view of a main part and an explanatory diagram of an optical path cross section of the sixth embodiment of the invention, ~Figure 10 (A) ~ (
D) is an explanatory diagram of the arrangement of alignment marks according to the present invention,
FIG. 11 is a schematic diagram of the main parts of a conventional position detection device. In the figure, 1 is the first object (mask), 2 is the second object (wafer), 3, 4, and 5.6 are alignment marks, and 7.8
are the first. 2nd signal beam, 9 wafer scribe line, 10 mask scribe line, 11.12 detection unit, 13 light source, 14 collimator lens system, 15 half mirror, 116 alignment head housing, 18 signal processing 19 is a wafer stage drive control section. Patent applicant: Canon Co., Ltd. Hazu (B) (C)

Claims (2)

[Claims] (1) A first object and a second object, each provided with an alignment mark made of at least two physical optical elements, are placed facing each other, and the light beam from the light projecting means is directed to the first object through the light intensity distribution adjusting means. The two light beams are guided onto a predetermined surface through respective alignment marks provided on the first and second objects, and the incident positions of the two light beams on the predetermined surface are detected by the detection means. When detecting the amount of relative positional deviation between one object and a second object, the axes of the two alignment marks on the first and second object surfaces are shifted from each other, and the two light beams are At least one of the light beams is subjected to imaging action by the alignment mark on the first object surface and the alignment mark on the second object surface, and the light intensity distribution adjusting means is configured to The light intensity distribution of the passing light beam is adjusted in accordance with the sign of the angle formed by the optical path of the principal ray of the two light beams emitted from the two alignment marks provided on the surface of one of the two objects. position detection device. (2) The light intensity distribution adjusting means adjusts the light intensity distribution of the passing light beams to two alignments if the angle formed by the optical paths of the principal rays of the two light beams emitted from the two alignment marks on the one object surface is positive. 2. The position detection device according to claim 1, wherein the position detection device is adjusted so that the minimum value occurs near the center of the arrangement of the marks, and the maximum value occurs near the center of the arrangement of the two alignment marks if the angle formed is negative.