JP2833145B2 - Position detection device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a position detecting device, for example, in an exposure apparatus for manufacturing a semiconductor element, on a first object surface such as a mask or a reticle (hereinafter, referred to as a “mask”). When exposing and transferring a fine electronic circuit pattern formed on a second object surface such as a wafer by exposure, a relative positional shift amount between the mask and the wafer is obtained, and it is suitable for performing both positioning (alignment). The present invention relates to a simple position detecting device.

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 position detecting devices, so-called alignment marks for positioning are provided on a mask and a wafer surface, and both alignments are performed using position information obtained from the alignment marks. As the alignment method at this time, for example, the amount of deviation between both alignment marks is detected by performing image processing, or US Pat.
No. 9, US Pat. No. 4,514,858 and Japanese Patent Application Laid-Open No. 56-157030, use a zone plate as an alignment mark, irradiate the zone plate with a light beam, and at this time, a light beam emitted from the zone plate. This is performed by detecting the position of the condensing point on a predetermined surface.

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 of an alignment mark, as compared with a method using a simple alignment mark.

FIG. 11 is a schematic view of a conventional position detecting device using a zone plate.

In the figure, a mask M is attached to a membrane 117, which is supported on an aligner body 115 via a mask chuck 116. An alignment head 114 is arranged above the main body 115. To align the mask M and the wafer W, a mask alignment mark MM and a wafer alignment mark WM are printed on the mask M and the wafer W, respectively.

The light beam emitted from the light source 110 becomes parallel light by the light projecting lens system 111, passes through the half mirror 112, and enters the mask alignment mark MM. Mask alignment mark
The MM is formed 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 function of converging to a point Q.

The wafer alignment mark WM is formed of a reflection type zone plate and reflects and diffracts the light condensed on the point Q, thereby detecting the light on the detection surface.
It has the action of a convex mirror (divergent action) that forms an image on 119.

At this time, the signal light beam subjected to the -1st-order reflection and diffraction action at the wafer alignment mark WM is the mask alignment mark.
When passing through the MM, the light is transmitted as zero-order light without being affected by a lens and is condensed on the detection surface 119.

In the position detecting device shown in FIG. 3, when the wafer W is displaced relative to the mask M by a predetermined amount, the incident position of the light beam incident on the detection surface 119 (the amount of light The position of the center of gravity) shifts. At this time, the shift amount Δδw on the detection surface 119 and the positional shift amount Δσw have a fixed relationship. By detecting the shift amount Δδw on the detection surface 119 at this time, the relative position between the mask M and the wafer W is determined. The position shift amount Δσw is detected.

(Problems to be Solved by the Invention) However, in the conventional position detection device, the distance may deviate from a preset value between two objects arranged opposite to each other in order to perform alignment. in this case,
Along with the fluctuation, the ratio of the positional deviation detection ratio, which is Δδw / Δσw, which is the ratio of the positional deviation amount Δσw to the deviation amount Δδw of the incident position of the light beam on the detection surface, also causes a detection error of the positional deviation amount. There was a point.

Further, an alignment head incorporating a light source, a light projecting optical system for guiding a light beam from the light source onto the mask surface, a light receiving system for receiving signal light, and the like is positioned relatively to the alignment mark. When the variation occurs, the incident position of the light beam on the detection surface of the detection unit also varies, resulting in a problem that a detection error of the positional deviation amount Δδw results.

The present invention relates to a first object and a second object to be aligned.
Even if the distance between the two objects deviates from a preset value and the position of the alignment head relatively changes with respect to the alignment mark, the alignment marks provided on the first object and the second object surface An object of the present invention is to provide a position detecting device capable of accurately detecting a relative displacement amount between two objects by appropriately setting each element such as a shape and an incident angle of a projected light beam on an alignment mark. .

(Means for Solving the Problems) The position detecting device of the present invention arranges a first object and a second object, each provided with an alignment mark composed of at least two physical optical elements, in opposition to each other, After the light flux passes through the alignment marks provided on the first object and the second object via the light intensity distribution adjusting means, the two light fluxes are guided on a predetermined surface, and the two light beams on the predetermined surface are guided. When detecting the relative position shift amount between the first object and the second object by detecting the incident position of the light beam by the detection means,
At least one of the two light beams is subjected to an image forming action by the alignment mark on the first object surface and the alignment mark on the second object surface. The light intensity distribution of the light beam incident on the at least two alignment marks on the first or second object is adjusted based on the relative distance between the incident positions of the two light beams incident on the first and second objects.

That is, according to the present invention, the first and second signal alignment marks having a function as a physical optical element on the object plane A when the object plane A and the object plane B are to be positioned as a first object and a second object. A1 and A2 are formed, and first and second signal alignment marks B1 and B2 having the same function as a physical optical element are also formed on the object plane B, and a light beam is incident on the alignment mark A1. The diffracted light generated at this time is incident on the alignment mark B1, and the first detection unit detects the center of the light flux on the incident surface of the diffracted light from the alignment mark B1 as the incident position of the first signal light flux.

Here, the center of gravity of the luminous flux is a point in the luminous flux cross section at which the integral value becomes a zero vector when the value obtained by multiplying the position vector of each point in the cross section by the light intensity at that point is integrated over the entire cross section. However, for convenience, a point at which the light intensity reaches a peak may be used as the luminous flux center of gravity. 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 alignment mark B2
The second detection unit detects the barycenter of the light beam on the incident surface of the diffracted light from the light source as the incident position of the second signal light beam. And the first
Then, the object plane A and the object plane B are positioned using two pieces of position information from the second detection unit. At this time, a light beam from a light projecting unit that emits a light beam having a non-uniform light intensity distribution is incident on the alignment mark via the light intensity distribution adjusting unit. The light intensity distribution adjusting means adjusts the light intensity distribution of the transmitted light beam according to the value of the relative distance between the incident positions of the two light beams on the predetermined surface.

In addition, in the present invention, the position of the center of gravity of the light beam incident on the first detection unit and the position of the center of gravity of the light beam incident on the second detection unit are displaced in directions opposite to each other with respect to the displacement between the object plane A and the object plane B. Each alignment mark A1, A2, B1, B2 is set.

The exposure apparatus of the present invention uses the position detection device described above,
The first object and the second object are aligned relative to each other, and the pattern on the first object surface is exposed and transferred onto the second object surface.

Further, in the method of manufacturing a semiconductor device according to the present invention, the first object and the second object are relatively aligned with each other by using the above-described position detecting device, and the pattern on the first object surface is shifted on the second object surface. The semiconductor device is manufactured by exposing and transferring to a semiconductor device.

(Embodiment) FIG. 1 is an explanatory diagram showing the principle and configuration requirements of the present invention in an expanded manner, and FIG. 2 is a first embodiment of the present invention based on the configuration of FIG.
It is a principal part perspective view of an Example.

In the drawing, reference numeral 1 denotes a first object corresponding to the object plane A, 2 denotes a second object corresponding to the object plane B, and a first object 1 and a second object 2
5 shows a case where a relative displacement amount with respect to is detected.

In FIG. 1, two first objects 1 are shown because light passing through the first object 1 and reflected by the second object 2 passes through the first object 1 again. Reference numeral 5 denotes an alignment mark provided on the first object 1 and reference numeral 3 denotes an alignment mark provided on the second object 2 for obtaining a first signal. Similarly, reference numeral 6 denotes an alignment mark provided on the first object 1 and reference numeral 4 denotes an alignment mark provided on the second object 2 for obtaining a 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 action. 9 is a wafer scribe line, and 10 is a mask scribe line. Reference numerals 7 and 8 denote the first and second signal beams for the first and second alignments, respectively. 11,1
Reference numeral 2 denotes first and second detectors for detecting the first and second signal light beams, respectively. First or second detector from second object 2
The optical distance to 11 and 12 is L for convenience of explanation. The distance between the object 1 and the second object 2 is g, and the focal lengths of the alignment marks 5 and 6 are f _a1 and f _a2 , respectively.
The relative displacement of the object 2 is represented by Δσ, and the displacements of the first and second detectors 11 and 12 at that time from the coincidence state of the first and second signal light beam centroids are represented by S ₁ and S ₂ , respectively. The alignment light beam incident on the first object 1 is a plane wave on the toilet, and the reference numerals are as shown in the figure.

Displacement S ₁ and S ₂ of the signal light beam centroid to the straight line L1, L2 connecting the center of the optical axis of the focus F _1, F ₂ and the alignment marks 3 and 4 of the alignment marks 5 and 6, the light receiving surface of the detector 11 and 12 Geometrically as the intersection with Therefore, in order to obtain the displacement amounts S ₁ and S ₂ of the center of gravity of each signal light beam in directions opposite to each other with respect to the relative positional deviation between the first object 1 and the second object 2,
This is achieved by reversing the signs of the optical imaging magnifications of 3 and 4.

Next, the first and second alignments shown in FIGS.
The optical paths of the principal rays of the signal light beams 7, 8 will be described.

In the following description, the principal ray refers to a ray passing through the axis when the alignment mark has an image forming action, and refers to a central ray of the effective light beam diameter when there is no image forming action.

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 light projecting optical system (not shown), and becomes substantially parallel light.
The light enters the alignment marks 5 and 6 on the first object 1 obliquely with respect to the normal to the object plane via the polarizer 21 and 20.

The light intensity distribution adjusting means 20 comprises, for example, a liquid crystal cell array sandwiched between patterned electrodes in a two-dimensional matrix, and transmits light by controlling a voltage applied to each liquid crystal cell by using this and a polarizer 21. The distribution of the polarization state of the light is arbitrarily controlled in real time, and furthermore, by using this and the polarizer 21, the light intensity distribution of the projection light on the mask 1 surface is arbitrarily controlled in real time.

The light intensity distribution of the substantially parallel light beam that has reached the surface of the first object 1 is a valley-type distribution that is minimum at the center of the two alignment mark regions, and is an uneven intensity distribution.

The alignment mark according to the present invention is composed of two regions in which the center-to-center distance has a predetermined value other than zero, and is formed on each object plane on which positioning is performed. As described above, the alignment light beam enters the alignment marks 5 and 6 on the first object plane as a single light beam having a non-uniform light intensity distribution.
The light beams diffracted by the alignment marks 5 and 6 on the first object 1 surface are subjected to, for example, a convex power convergence action at the alignment mark 5 and a concave power divergence action at the alignment mark 6, and then to the alignment mark on the second object face. Reach 3,4.

Further, the luminous fluxes subjected to the diverging function of the concave power at the alignment mark 3 on the second object surface and the convergence of the convex power at the alignment mark 4 become the first and second signal lights 7, 8 respectively, and are emitted from the second object 2 surface. Then, after passing through the surface of the first object 1, the light enters the detection units 11 and 12 at predetermined positions. In the present embodiment, a case is described in which the amount of positional deviation is detected in the illustrated x direction.

According to the present invention, alignment is performed according to the relative distance (relative center-of-gravity distance) between the incident positions in the x direction, which is the position detection direction of the two signal light beams incident on the first detection unit and the second detection unit, by simulation based on ray tracing. Changing the light intensity distribution of the light beam projected onto the marks 5 and 6 extremely effectively suppresses the occurrence of misregistration amount detection errors caused by fluctuations in the distance between the first object 1 and the second object 2. I found that I can do it.

That is, in the present embodiment, even if the relative displacement between the first object and the second object is unchanged, the detection unit 11, which has been a problem in the past due to the change in the distance between the first object and the second object, By using the light intensity distribution adjusting means, it is possible to effectively suppress a positional deviation amount detection error due to a change in the distance between the incident positions (equivalently, the light intensity center of gravity) of the two signal light beams for alignment on FIG. I can do it.

Furthermore, the present inventor has found that the occurrence of a positional deviation amount detection error caused by a change in the irradiation center position of the alignment light beam on the first object plane can be similarly suppressed.

The present invention controls the light intensity distribution of the light beam using the light intensity distribution adjusting means as described above, thereby suppressing the occurrence of the above-described position shift amount detection error and suppressing the relative position shift amount between the first object and the second object. High-precision detection is possible.

FIG. 3 (A) shows a configuration diagram of a peripheral portion of the first embodiment of FIG. 2 when the first embodiment 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, a wafer stage 17, and a position shift signal processing. And a wafer stage drive control unit 19 and the like. E indicates the exposure light beam width.

Also in the present embodiment, the mask 1 as the first object and the second
The relative displacement of the wafer 2 as an object is detected in the same manner as described in the first embodiment.

In this embodiment, as a procedure for performing the alignment, for example, the following method can be adopted.

As a first method, a signal of the amount of displacement of the center of gravity of light flux Δδ on the detection surfaces 11a and 12b of the detection units 11 and 12 with respect to the amount of displacement of two objects Δσ is obtained. The amount of positional deviation Δσ between the objects is determined, and the stage drive control unit 19 moves the wafer stage 17 by an amount corresponding to the amount of positional deviation Δσ at that time.

As a second method, a direction in which the positional deviation Δσ is canceled out from the signals from the detection units 11 and 12 is obtained by the signal processing unit 18, and the wafer stage 17 is moved by the stage drive control unit 19 in that direction to obtain the positional deviation amount Δσ. Repeat until love is within the acceptable range.

FIGS. 3 (B) and 3 (C) show flowcharts of the above alignment procedure, respectively.

In this embodiment, as can be seen from FIG. 3A, the light beam from the light source 13 is aligned with the alignment marks 5 and 6 from the outside of the exposure light beam.
Into the detectors 11 and 1 provided outside the exposure light beam.
The light is received at 2 and the position of the incident light beam is detected.

With such a configuration, the pickup housing 16 can also realize a system that does not require a retreat operation during exposure.

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

FIG. 4 shows the first and second detectors 11 and 12 of the first and second signal light beams 7 and 8.
FIG. 4 is an explanatory view of a state of incidence on the substrate. An alignment light beam emitted from a semiconductor laser (center wavelength 0.785 μm), which is a light source 13 in an alignment pickup housing 16, passes through a light projecting optical system including a collimator lens system 14 and a beam splitter (or half mirror) 15. After passing through the light intensity distribution adjusting means 20 as a parallel light beam, it is obliquely incident on the mask 1 surface at an angle of 17.5 ° in the yz plane with respect to the mask surface normal.

The light intensity distribution (I
(X, y)) is a coordinate system as shown in the figure. σ _x = 680 μm and σ _y = 120 μm. The detection of the displacement is performed in the x direction.

The size of the regions of the two alignment marks on the mask and the wafer surface are both 90 μm in the x direction and 50 μm in the y direction, and are arranged adjacent to each other as shown in FIG.

The alignment mark 5 on the surface of the mask 1 is a grating lens of convex power having a light beam converging function, and +1
The focal length corresponding to the second order diffracted light is 214.723 μm, the deflection angle of the principal ray of the + 1st order transmitted diffracted light in the yz plane is 17.5 °, and the mask 1
The direction of the principal ray exiting the surface is parallel to the normal to the mask surface.

The alignment mark 6 on the mask 1 is a concave power grating lens having a luminous flux diverging effect.
The focal length corresponding to the + 1st-order diffracted light is −158.455 μm, and the deflection angle of the principal ray in the yz plane is the same as the alignment mark 5.
17.5 ゜. Both the alignment marks 5 and 6 have a deflection angle of 0 ° in the xz plane and the principal ray direction does not change.

 In the present embodiment, it is desirable that the oblique incidence angle α of the light beam on one surface of the mask is set in the range of 10 ° <α <80 °.

On the alignment mark 3 on the surface of the wafer 2, a light beam diffracted and transmitted in +1 order at the alignment mark 5 on the surface of the mask 1 is incident. Here, the first signal light flux 7 that is further diffracted and reflected in the +1 order receives a diverging effect. The alignment mark 3 is a grating lens having a concave power, has a focal length of -182.912 μm, and emits a principal ray at an angle of -3 ° with respect to a normal to the wafer surface in the xz plane. As shown in FIG. 4, the light reaches the detection unit 11 while maintaining the angle.

Similarly, the alignment mark 4 on the wafer 1 is a grating lens (focal length 190.378 μm) having a convex power corresponding to the + 1st-order reflected and diffracted light, and optically reflects the light beam 8 transmitted and diffracted by the alignment mark 6 on the mask 1. Has a positive effect.

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

On the other hand, the emission angles of the first and second signal light beams 7, 8 in the yz plane when emitted from the wafer 2 surface are respectively 7 ° and 13 ° with respect to the normal to the wafer surface, and are spatially separated and arranged. Each element such as an alignment mark shape and an optical system is set so as to be incident on the two detection units 11 and 12 thus obtained.

Now, the mask 1 and the wafer 2 are displaced by Δσ in a direction parallel to the misalignment detection direction (x direction), and the condensing point o1 of the light beam reflected from the wafer 2 by the grating lens 3 of the wafer 2
The distance from the detector to the focusing point F1 of the light beam passing through the grating lens 5 of the mask 1 is denoted by b.
The difference Δδ of the center of gravity of the focal point on That is, the center-of-gravity shift amount Δδ is enlarged by (b / a + 1) times. For example, if a = 0.5 mm and b = 50 mm, the center-of-gravity shift amount Δδ is expanded 101 times from the equation (a).

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

The total diameter of the grating lenses 3 and 4 on the wafer 2 is 1
The total diameter of the grating lenses 5 and 6 on the mask 1 is 180 μm, and the position shift (axis shift) between the mask and the wafer is enlarged by 100 times to cause the center of gravity of the light beam to move on the detection units 11 and 12. As a result, the arrangement and the focal length of each element were determined so that the diameter of the light beam (the diameter of the Airy disk e- ² ) on the detection units 11 and 12 was about 200 μm.

Note that, at this time, the center-of-gravity shift amount Δδ and the positional shift amount Δσ have a proportional relationship, as is clear from the equation (a). Detection unit
Assuming that the resolution of 11, 12 is 0.1 μm, the displacement Δσ
Has a position resolution of 0.001 μm.

In this embodiment, the focal length of each alignment mark on the mask and the wafer is set as described above, the distance between the mask and the wafer is 30.0 μm, and the center positions of the detection units 11 and 12 are (0.0, −4.203, 18.204), respectively. By setting (0.0, -2.277, 18.543) (unit: mm), the detection unit 1 for the first and second signal lights 7, 8 can be used.
The detection sensitivity in design on the 1,12 surfaces (that is, the ratio of the variation of the incident position of the light beam on the detection unit surface to the variation of the relative displacement between the mask and the wafer (x direction)) is +100 and −, respectively.
Can be 100.

However, in general, the detection sensitivity in the design changes according to the fluctuation of the distance between the mask and the wafer, and it is difficult to keep the detection sensitivity constant.

In this embodiment, as shown in FIG. 1, a light beam is projected onto two left and right alignment marks respectively arranged on a mask and a wafer surface. In a configuration in which light is emitted obliquely to the left from the alignment mark on the left hand side and obliquely to the right from the alignment mark on the right hand side to the line, (a) the light intensity distribution of the projected light is inverse Gaussian distribution (center Where the light intensity is at a minimum, for example (A
1) distribution).

(B) The shape of the distribution is modulated in accordance with the distance between the centers of gravity of the two light beams on the light receiving unit surface (the value measured in the x direction). Specifically, the steepness of the distribution becomes smaller (that is, the distribution becomes gentler (however, the minimum point is kept substantially constant) as the distance of the center of gravity becomes longer.

In particular, (b) shows the light intensity distribution adjusting means 20 (liquid crystal cell array in this embodiment) in real time based on the output signal from the light receiving section.
And the polarizer 21 to modulate the light intensity distribution of the projection light.

With the above-described configuration, it is possible to suppress the fluctuation of the positional deviation detection sensitivity due to the fluctuation of the interval between the mask and the wafer to the maximum.

For example, the x-direction distribution shape I (x, y) of the light beam having the light intensity distribution represented by the expression (1a) is modulated as follows using the light intensity distribution adjusting means 20 in real time.

l; the distance between the center of gravity of the two signal light beams l ₀ ; the distance in the x direction between the two signal light beams when there is no displacement, where α is a numerical value obtained by an experiment or simulation, and the displacement is detected with respect to the variation in the space between the mask and the wafer. This is a value selected so that the fluctuation range of sensitivity is minimized.

Next, the pattern shapes of the grating lenses 5 and 6 for the mask and the grating lenses 3 and 4 for the wafer in the present embodiment will be described.

First, the grating lenses 5 and 6 for the mask are set so that a parallel light beam having a predetermined beam diameter enters at a predetermined angle and is condensed at a predetermined position. Generally, the pattern of the grating lens is a light source (object point) and an image point, and an interference fringe pattern on the lens surface when a coherent light source is placed at each.

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 direction normal to the mask surface. The incident light is incident at an angle of α with respect to the normal to the mask surface, and the projected light component of the parallel light beam orthogonal to the scribe line direction is transmitted and diffracted through the grating lens 5 or 6, and then the light is condensed (x ₁ , y ₁ , z ₁ ) The equation of the group of curves of the grating lens that forms an image at the position of is represented by y sin α + P ₁ (x, y) −P ₂ = mλ / 2 (1) where the contour position of the grating lens is represented by x and y. Given by Here, λ is the center wavelength of the used wavelength range of the alignment light beam, and m is an integer.

The chief ray is incident at an angle α, passes through the origin on the mask surface,
Assuming that the light reaches the focal point (x ₁ , y ₁ , z ₁ ), the right side of equation (1) indicates that the optical path length is longer (shorter) by m / 2 times the wavelength than the principal ray depending on the value of m. , the left side with respect to the optical path of the principal ray, represent the difference in length of the optical path of the light rays reaching the point on the mask (x, y, 0) the street point _{(x 1, y 1, z} 1).

On the other hand, the grating lenses 3 and 4 on the wafer are set so as to converge a spherical wave emitted from a predetermined point light source to a predetermined position (on a detection surface). The position of the point light source is represented by (x ₁ , y ₁ , z ₁ -g), where g is the gap between the mask and the wafer during exposure. If it is assumed that the alignment between the mask and the wafer is performed in the x-axis direction, and the alignment light beam is focused on the point (x ₂ , y ₂ , z ₂ ) on the detection surface when the alignment is completed, The equations of the curve group of the grating lens are in the coordinate system defined above. It is expressed as

In equation (2), the wafer surface is at z = -g, and the principal ray is located on the wafer surface at the origin and a point (0,0, -g) on the mask surface, and further, a point (x ₂ , y ₂ ) on the detection surface. , z ₂ ), it is an equation satisfying the condition that the difference in the optical path length between the principal ray and the ray passing through the grating (x, y, −g) on the mask surface is an integral multiple of half a wavelength.

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 formed, for example, as a phase grating pattern having a rectangular cross section. In the expressions (1) and (2), 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, which means that the grating lens 5 or 6 on the mask has a line width between the transparent portion and the light shielding portion. The ratio is 1:
It means that the ratio of the line to the space of the rectangular grating is 1: 1 in the grating lens 3 or 4 on the wafer.

The grating lenses 5 and 6 on the mask are formed by transferring the grating lens pattern of a reticle previously formed by EB exposure on an organic thin film made of polyimide, for example, or the grating lens on the wafer forms the exposure pattern of the wafer on the mask After that, it is formed by exposure transfer.

FIG. 10 (A) shows the grating lens 5 on the mask surface.
6, (B) shows grating lenses 3 and 4 on the wafer surface.
1 shows a pattern of one embodiment.

With the configuration described above, the distance (spot) between the center of gravity of the light amount measured along the x direction of the first and second signal light beams due to the change in the gap (interval) between the mask and the wafer and the change in the position (parallel movement) of the pickup housing 16. (Hereinafter referred to as an interval) was measured.

As a result, using the light intensity distribution adjusting means 20, the above (2),
By irradiating the alignment mark with the light flux having the light intensity distribution shown by the equation (3), the gap variation is ± 3.0 μm, the variation of the spot interval is 1.9 μm, and the relative positional deviation detection error between the mask and the wafer is 0.0004. μm.

On the other hand, in the conventional system in which the light intensity distribution is irradiated with a light beam having a Gaussian distribution (same displacement detection sensitivity), the variation amount of the spot interval is 12.56 μm, and the displacement detection error is
0.063 μm. That is, if the light intensity distribution adjusting means according to the present invention is used, the detection error is reduced to about 1/130.

On the other hand, with respect to the position fluctuation of the pickup housing 16 (parallel movement to the xy plane), the position deviation detection error is 0.003 μm (0.019 μm in the conventional optical path system) with respect to the fluctuation of ± 10 μm, which is about 6 minutes compared to the conventional. Reduced to one.

 FIG. 5 is a perspective view of a main part of a second embodiment of the present invention.

In the present embodiment, two light sources 13-1 and 13-2 composed of a semiconductor laser or a super luminescent diode or the like are used, and these two light sources 13-1 and 13-2 are juxtaposed and separated by a predetermined distance. The function as the light intensity distribution adjusting means is exhibited by adjusting the output. The light intensity distribution on the alignment mark surface at this time is the same as that shown in, for example, FIG. 1 or FIG. (However, the minimum point of the light intensity distribution is kept substantially constant.) The optical paths of the principal rays of the two signal light beams 7 and 8, the arrangement of the alignment marks, and the configuration of other elements are the same as those in the first embodiment. At this time, the modulation of the light intensity distribution of the projection light is performed in the same manner as in the first embodiment, and as the distance between the centers of gravity of the two light beams on the detection unit surface increases, the separation distance between the two light sources 13-1 and 13-2 also increases. It is set to be longer.

In this embodiment, the two light sources 13-1 and 13-2 are separated from each other by a predetermined distance in this manner, and the light intensity distribution on the two alignment marks 5 and 6 is set near the center between the left and right alignment marks 5 and 6. The strength is minimized, and increases as the distance from the center increases. Finally, two signal light beams reaching the light receiving units 11 and 12 from the left and right alignment marks 5 and 6, respectively.
In the section including the misalignment detection direction, the optical paths 7 and 8 are configured to be emitted to the left from the alignment mark 5 on the left hand side and obliquely to the normal to the object plane of the right hand from the alignment mark 6 on the right hand side. ing. As a result, as in the first embodiment, the amount of occurrence of a detection error of the amount of displacement due to a change in the distance between the mask 1 and the wafer 2 or a change in the position between the alignment head housing and the mask is suppressed as well as in the first embodiment.

 FIG. 6 is a perspective view of a main part of a third embodiment of the present invention.

In this embodiment, the alignment mark areas for the first and second signal light beams 7 and 8 for alignment are arranged on the surface of the mask 1 and the wafer 2 so as to be separated from each other by a predetermined distance, for example, 100 μ.

Here, assuming that the diameters of the projection light beams projected onto the alignment marks 5 and 6 on the surface of the mask 1 are the same as those in the first embodiment, the final relative angles of the first and second signal light beams in the optical path configuration are the optimum values. However, the gap measurement error due to the gap variation and the variation in the position of the alignment head housing increases. Therefore, in the present embodiment, the adjustment of the light intensity distribution of the projection light beam diameter is the same as in the first embodiment, and the adjustment of the first and second signal light beams is performed.
The final exit angles in the xz plane are -4.0 ° and + 4.8 °, respectively.

FIGS. 10A and 10B show examples of patterns of a mask and an alignment mark on a wafer surface in this embodiment, respectively.

As described above, the optimum conditions of the setting of the optical path and the light intensity distribution of the projection light are determined by the factors such as the diameter of the projection beam, the size, the arrangement, and the focal length of the alignment mark. In this embodiment, an optimum value is obtained by simulation based on ray tracing, and each element is configured based on the optimum value.

 FIG. 7 is a perspective view of a main part of a fourth embodiment of the present invention.

In this embodiment, the first and second signal beams 7, 8 for alignment are used.
Part of the alignment mark area for
They are arranged adjacently so as to overlap.

FIGS. 10C and 10D show an embodiment showing patterns of alignment marks 5 and 6 on the mask 1 surface and alignment marks 3 and 4 on the wafer 2 surface. 8 and 10 (C),
In (D), areas 701 and 702 are areas where the alignment marks overlap each other.

In this embodiment, the projected light beam diameter of the light beam is the same as that of the first embodiment, and the final emission angles of the first and second signal light beams in the xz plane are -2.5 ° and + 2.8 °, respectively. 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 detecting portion in which the present invention is applied to a reduced projection exposure apparatus.

In the same figure, the light beam emitted from the light source 13 is
A reticle alignment mark on a reticle L surface as a first object through a light intensity distribution adjusting means 20 as parallel light at 14
Irradiates 3L1 and 3L2. At this time, the reticle alignment marks 3L1 and 3L2 constitute a transmissive physical optical element having a lens function of condensing the passing light to points Q ₀ and Q ₀ ′, respectively. Then, the light beams from the points Q ₀ and Q ₀ ′ are
As a result, the light is condensed on points Q and Q ′ separated from the wafer W as the second object by distances aw and aw ′.

In the figure, reference numerals 7 and 8 denote first and second signal beams generated by the alignment marks 3L1 and 3L2, respectively, and reference numerals 807 and 808 denote respective principal rays.

Wafer alignment marks 4w1, 4w2 are provided on the wafer w, and the wafer alignment marks 4w1, 4w
2 constitutes a reflection type physical optical element, and when light fluxes 7 and 8 condensed at points Q and Q ′ respectively enter, the light fluxes are reflected and are reflected on the detection unit 11 surface via a half mirror 19. It has the function of a convex mirror for imaging.

The first and second signal light beams generated by the action of the alignment marks 4w1 and 4w2 on the wafer surface are principal rays 80 in FIG.
Only 7,808 is shown as a representative.

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

In this embodiment, the first and second signal light beams 7,
Reference numeral 8 denotes a second object surface (or a first object surface) of each optical path in a process after emitting the second object 2 surface and reaching the detection units 11 and 12.
The alignment mark, the incident angle of the projected light beam, and the like are configured such that the projected trajectories on the object plane) always cross. Such an optical path configuration is hereinafter referred to as a “crossed optical path”.

The angle formed by the optical paths of the two signal light beams 7, 8 is defined as negative in the case of FIG.

The present inventor has previously conducted simulations,
By employing the above-described light intensity distribution adjusting means and the cross optical path, the first object 1 and the second object can be used when the alignment mark system is irradiated with an alignment light beam having a light intensity distribution such as a non-uniform Gaussian distribution. It has been found that the occurrence of a positional deviation amount detection error caused by a change in the interval between the two can be suppressed extremely well.

That is, in this embodiment, even if the relative displacement between the first object and the second object does not change, the detection unit 11 or 12 due to the change in the distance between the first object and the second object, which has conventionally been a problem, The error in detecting the displacement due to the variation in the distance between the incident positions of the two signal light beams for alignment (equivalently, the position of the center of gravity of the light intensity) is favorably suppressed by employing the above-described light intensity distribution adjusting means and the cross optical path. Have to be able to.

Further, the present inventor uses the light intensity distribution adjusting means and the crossed optical paths to appropriately set the diameter at which the intensity of the alignment light beam on the first object surface decreases to 1 / e ² , thereby setting the same interval. It has also been found that the occurrence of the displacement error detection error caused by the fluctuation can be similarly favorably suppressed.

According to the present invention, by setting each element so that such a crossed optical path is formed, the occurrence of the above-described positional deviation amount detection error is suppressed, and the relative positional deviation amount between the first object and the second object is highly accurate. Detection is possible.

Next, the optical paths of the principal rays of the first and second signal light beams 7, 8 for alignment shown in FIG. 9A will be described.

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 light projecting optical system (not shown), becomes substantially parallel light, and passes through a light intensity distribution adjusting unit. The light enters the alignment marks 5 and 6 on one object 1 at an angle to the normal to the object plane. The light intensity distribution of the substantially parallel light beam that has reached the first object 1 surface is a non-uniform Gaussian distribution.

The alignment mark according to the present invention is composed of two regions in which the center-to-center distance has a predetermined value other than zero, and is formed on each object plane on which positioning is performed. The light beam for alignment enters the alignment marks 5 and 6 on the first object plane as a single Gaussian beam as described above. The light beams diffracted by the alignment marks 5 and 6 on the first object 1 surface are subjected to, for example, a convergence function of the convex power at the alignment mark 5 and a divergence function of the concave power at the alignment mark 6, and then the second light.
The alignment marks 3 and 4 on the object plane are reached.

Further, the luminous fluxes subjected to the divergence of concave power at the alignment mark 3 on the second object surface and the convergence of convex power at the alignment mark 4 become first and second signal lights 7 and 8, respectively.
After emitting the object 2 surface and transmitting through the first object 1 surface, the light enters the detection units 11 and 12 at predetermined positions.

In this embodiment, the manner of modulating the light intensity distribution of the projection light may be determined by the following equation in accordance with the center of gravity distance 1 between two signal light beams on the detection unit surface.

Here, l ₀ is x between the two signal light beams when the displacement is 0.
The distance in the direction, α ′, is a value obtained by experiments or simulations and is a value selected so that the fluctuation width of the positional deviation detection sensitivity with respect to the fluctuation of the distance between the mask and the wafer is minimized. May be. That is, α '= α'
(1) may be used.

As described in each of the above embodiments, according to the present invention, two light beams emitted from two alignment marks by using the light intensity distribution adjusting means to output the light intensity distribution in the direction of detecting the amount of displacement of the light beam irradiated on the object surface. When the two light fluxes emitted from the two alignment marks are guided to the light receiving portions, respectively, the distribution is uneven based on the relative distance on the predetermined surface of (c). Light rays reaching the light receiving portion from the alignment mark are emitted obliquely to the + side with respect to the normal to the alignment mark surface, and similarly, from the-side alignment mark, are obliquely directed to the-side with respect to the normal to the alignment mark surface. In an optical path configuration that emits light, 2
When the relative distance between the incident positions of the two signal light beams on the predetermined surface is longer than a preset value, the light intensity in the position shift amount detection direction becomes minimal near the center of the entire area where the two alignment marks are aligned, and The alignment mark is irradiated with a light intensity distribution such that the light intensity increases at a predetermined gradient as the position moves away from the point where the intensity becomes minimum in the direction of detecting the displacement based on the equations (3) and (4).

(D) As in (c), the alignment mark on the positive side is emitted obliquely to the negative side with respect to the normal of the alignment mark surface, and the alignment mark on the negative side is emitted from the negative side. When the relative distance between the incident positions of the two signal light beams on the predetermined surface is shorter than a predetermined value in an optical path configuration in which the light is emitted obliquely to the + side with respect to the normal line, the two alignment marks are aligned. The light intensity distribution is such that the light intensity becomes maximum near the center of the entire area in the direction of detecting the amount of displacement, and decreases as the distance from the maximum point in the direction of detecting the position deviation decreases with a predetermined gradient (5), (6). Irradiation is performed on the alignment mark based on the expression.

 It is characterized by adopting the above configuration.

(Effects of the Invention) According to the present invention, two different wavefront conversion elements (physical optical elements) each having an imaging action (optical action) are formed as alignment marks on the first and second object planes for alignment. On a predetermined surface of two first and second signal light beams which are sequentially subjected to the image forming action of the alignment mark on each object surface (for example, in the order of the first and second objects or the second and first object surfaces). When the positional deviation amount is detected based on the incident position information at the time, the light intensity distribution of the light beam irradiated on the alignment mark surface is emitted from the two alignment marks by using the light intensity distribution adjusting means, and the two light beams incident on the predetermined surface are emitted. By performing adjustment based on the relative distance of the incident position of the light beam, alignment is performed 2
Thus, it is possible to achieve a position detection device capable of detecting a position shift amount with high accuracy, which is very unlikely to be affected by a distance variation between two objects or a position variation of a projection light beam from a light source.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing the principle and configuration requirements of the present invention, FIG. 2 is a perspective view of a main part of a first embodiment of the present invention based on the configuration of FIG. 1, and FIG. 3 (B) and 3 (C) are flow charts of the measurement control in FIG. 3 (A), and FIG. 4 is a flow chart of the measurement control in FIG. 3 (A). FIG. 2 is an explanatory view of an optical path cross section of the first embodiment of FIG.
FIGS. 5 to 8 are perspective views of main parts of the second to fifth embodiments of the present invention, and FIGS. 9A and 9B are perspective views of main parts and an optical path of the sixth embodiment of the present invention. 10 (A) to 10 (D) are explanatory views of the arrangement of an alignment mark according to the present invention, and FIG. 11 is a schematic view of a main part of a conventional position detecting device. In the figure, 1 is a first object (mask), 2 is a second object (wafer), 3, 4, 5, and 6 are alignment marks, and 7, 8 are each a mark.
1, a second signal light beam, 9 is a wafer scribe line, 10 is a mask scribe line, 11 and 12 are detectors, 13 is a light source, 14
Denotes a collimator lens system, 15 denotes a half mirror, 16 denotes an alignment head housing, 18 denotes a signal processing unit, and 19 denotes a wafer stage drive control unit.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01B 11/00-11/30 H01L 21/30 311

Claims (4)

(57) [Claims] A first object provided with an alignment mark comprising at least two physical optical elements and a second object provided opposite to each other, and a light beam from the light projecting means is transmitted to the second object via a light intensity distribution adjusting means; By guiding the two light beams to a predetermined surface after passing through the respective alignment marks provided on the first object and the second object, and detecting the incident positions of the two light beams on the predetermined surface by a detecting unit, When detecting the relative displacement between the first object and the second object, at least one of the two light beams is an alignment mark on the first object surface and an alignment mark on the second object surface. Respectively, and the light intensity distribution adjusting means is configured to control the at least two light beams on the first or second object based on a relative distance between incident positions of the two light beams incident on the predetermined surface. Alignment mark Position detecting device, characterized in that to adjust the light intensity distribution of the incident light beam. 2. The light intensity distribution adjusting means according to claim 1, wherein the light intensity distribution of the passing light beam is 2 when the relative distance between the incident positions of the two light beams incident on the predetermined surface is longer than a predetermined distance.
Minimum near the center of the alignment of the two alignment marks,
2. The position detecting device according to claim 1, wherein when the distance is short, the position is adjusted so as to be maximum near the center of the arrangement of the two alignment marks. 3. A relative position between a first object and a second object is adjusted by using the position detecting device according to claim 1, and a pattern on the first object surface is exposed on a second object surface. An exposure apparatus that performs transfer. 4. A relative position between a first object and a second object is adjusted by using the position detecting device according to claim 1, and a pattern on the first object surface is exposed on a second object surface. A method for manufacturing a semiconductor device, wherein a semiconductor device is manufactured by transferring.