JPH042902A - position detection device - Google Patents

Abstract

PURPOSE:To accurately detect a positional deviation by regulating a light intensity distribution of a passed luminous flux based on a relative distance of incident position of two fluxes incident on a predetermined surface 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, light intensity distribution regulating means 20 and a polarizer 21. Here, the light intensity distribution of an emitted light on the article 1 is arbitrarily controlled in a real time manner by using the means 20 and the polarizer 21. Then, the flux diffracted by the marks 5, 6 is, 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 flux which is dispersed by the mark 3 and converted 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 wafer 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 deviation 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 Japanese Patent No. 157033, a zone plate is used as an alignment mark, a light beam is irradiated onto the zone plate, and the position of a converging point on a predetermined plane of the light beam emitted from the zone plate is detected at this time. Is going.

In general, an alignment method using a zone plate has the advantage of being able to achieve relatively high-grain alignment without being affected by alignment mark defects, compared to a method using an alignment mark (A11).

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 it is attached to an aligner body 115 using a mask jack 1.
16. A helad 114 is arranged in a part of the main body 115J to the alignment member 1. In order 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 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 from the reflective zone plates 1 to 1 to the convergence point Q and forms an image on the detection surface 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, if 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 light intensity (center of gravity) shifts. There is a certain relationship between the displacement amount ΔδW on the detection surface 119 and the position displacement amount ΔσW at this time, and the displacement amount ΔδW on the detection surface 119 at this time
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 alignment 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

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

The present invention prevents the alignment head from changing its position relative to the alignment mark even if the distance between the first and second objects to be aligned varies beyond a preset value. 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 flux to the alignment mark, it is possible to reduce the amount of relative positional deviation between the two objects. Our objective is to provide a position detection device that can detect with high accuracy.

(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 after passing through each alignment mark provided on the first object and the second object via a light intensity distribution adjusting means, and the two light beams on the predetermined surface are When detecting the amount of relative positional deviation between the first object and the second object by detecting the incident position of the light beam with the detection means,
At least one of the two luminous fluxes is on the first object surface."
- and the alignment mark on the second object surface are each subjected to imaging action, and the light intensity distribution adjusting means adjusts the relative distance between the incident positions of the two light beams incident on the predetermined surface -42. It is characterized in that the light intensity distribution of the passing light flux is adjusted based on the following.

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 not aligned and are separated into a first object and a second object. AI and A2 are formed, and alignment marks B1 and B2 for first and second signals having a function as a physical optical element are also formed on the object plane B, and a light beam is made to enter the alignment mark A1. The diffracted light generated at this time is made incident on the alignment mark B1, and the center of gravity of the light beam within the plane of incidence of the diffracted light from the alignment mark B1 is detected by the first detection section as the incident position of the first 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 varies 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 beams according to the magnitude of the relative distance between the incident positions of the two light beams on the predetermined plane.

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 deviation between the object plane A and the object plane B. Alignment mark AI, A2. B1. B2 is set.

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

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 1112 denote first and second detection units for detecting the first and second signal beams, respectively. The optical distance from the second object 2 to the first or second detection unit 11.12 will be described for convenience of explanation. The distance between object 1 and second object 2 is g, and the focal length of alignment marks 5 and 6 is fill+fa, respectively.
2, and the amount of relative positional deviation between the first object 1 and the second object 2 is Δ
σ, then the first degree of the second detection unit 11.
and the amount of displacement of the center of gravity of the second signal beam from the coincident state, S
, , S2. 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, , F, of the alignment marks 5 and 6, and the alignment mark 3.
, 4. A straight line Ll connects the optical axis centers of 4.

It is determined geometrically as the intersection between L2 and the light receiving surfaces of the detection units 11 and 12. Therefore, with respect to the relative positional deviation between the first object 1 and the second object 2, the amount of displacement S, , S
2 to obtain alignment marks 3.4 in opposite directions to each other.
This is achieved by making the signs of the optical imaging magnifications opposite to 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.
The light is incident on the alignment marks 5 and 6 of the first object 1'' through the polarizer 21 and obliquely with respect to the normal to the object surface.

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

The light intensity distribution of the approximately parallel light beam that reached the first surface of the first object is 2
This is a valley-shaped distribution with a minimum at the center of the two alignment mark areas, resulting in an uneven intensity distribution.

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 mark 5.6 on the first object plane as a light beam with a single unconstrained light intensity distribution. The light beam diffracted by the alignment marks 5 and 6 on the first object surface 1-42 is subjected to the converging effect of convex power at the alignment mark 5 and the diverging effect of concave power at the alignment mark 6, and then to the second object surface. alignment mark 3.4 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 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. Note that this embodiment shows a case where the amount of positional deviation is detected in the illustrated X direction.

The present invention is based on a simulation based on ray tracing.
The light beams projected onto the alignment marks 5 and 6 are adjusted according to the relative distance # (relative center of gravity distance) of the incident positions in the X direction, which is the position detection direction of the two signal beams incident on the detection unit and the second detection unit. It has been found that by changing the intensity distribution, it is possible to extremely effectively suppress the occurrence of positional deviation amount detection errors caused by variations 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, the detection unit 11. 12
The error in detecting the amount of positional deviation due to fluctuations in the distance between the two alignment signal beam incident positions (equivalently, the light intensity gravity center position) can be suppressed well by employing a light intensity distribution 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. 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 procedure for alignment is as follows:
For example, you can use the following method.

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 the stage is driven 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 turn the edges 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 the light i13 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. 7 is an explanatory diagram of the incident state of the second signal light beam 7.8 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 distributed on one mask surface at a angle of 1 in the yz plane with respect to the normal to the mask surface.
Oblique incidence at an angle of 75°.

Light intensity distribution of alignment light flux on one mask surface (1(x
, y)) takes the coordinate system as shown in the figure as the initial setting value (1a) σX = 680 μm, a, = 120p
m. Furthermore, the amount of positional deviation is detected in the X direction.

The sizes of the two alignment mark areas on the mask and wafer surface are both 90 μm in the X direction and 50 μm in the X direction.
They are placed adjacent to each other as shown in Figure 2.

The alignment mark 5 on the mask 1 surface is a grating lens with convex power that has a light flux convergence effect, the focal length corresponding to the +1st order diffracted light is 214723 μm, and the deflection angle in the yz plane of the principal ray of the +1st order transmitted diffraction light is 17 .56, 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 Oo in the xz plane, and the principal ray direction does not change.

In this example, the light flux incident position α on one mask surface is 10°〈　α　　〈80゜ It is desirable to set it within the range of .

A beam of light that has been diffracted and transmitted in the +1st order by the alignment mark 5 on the first mask surface is incident on the alignment mark 3 on the second surface of the wafer. 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 a concave power, and the focal length is -182,912 μm. After being emitted so that the principal ray direction forms an angle of 13° with respect to the normal to the wafer surface in the xz plane, As shown in FIG. 4, it reaches the detection section 11-F while maintaining the angle.

Similarly, the alignment mark 4 on the wafer 1 is a grating lens (focal length 190.378 μm) with a convex power corresponding to the +1st-order reflected diffraction light, and for the light beam 8 transmitted and diffracted 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, the first one when ejecting from the second side of the wafer. Second signal beam 7
．． The emission angles of 8 in the yz plane are 7° and 13° with respect to the normal to the sea urchin surface, respectively, and the 2
Elements such as the alignment mark shape and the optical system are set so that the light enters two detection units 11 and 12.

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 focal point 01 of the luminous flux reflected by the grating lens 3
Let b be the distance of the light beam passing through the grating lens 5 of the mask 1, and a be the distance to the condensing point F1 of the light beam passing through the grating lens 5 of the mask 1. Then, the amount of gravity shift Δδ of the condensing point on the detection unit 11 is Δδ=ΔσX(-+1 ) ・・・・・・・・・(a
), that is, the center of gravity shift amount Δδ is (b / a +1
) double enlarged Sarel. For example, a = 0, 5 mm
, if b = 50 mm, the center of gravity shift amount Δδ is (a)
It is magnified 101 times according to the formula.

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.

Also, the total diameter of the grating lens 340 on the wafer 2 is 1
The diameter of the crouting lenses 5 and 6 on the mask 1 is 180 μm, and the positional deviation between the mask and the sea urchin (
The center of gravity of the light flux on the detection unit 11.12 is magnified by 100 times (axis deviation), and as a result, the diameter of the light flux on the detection unit 11.12 (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 of 12 is 0.1 μm, the positional deviation amount Δσ has a position 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 + nm), the first. Detection unit 11 for second signal light 7.8
The designed detection sensitivity (i.e., the ratio of the amount of variation in the light beam incident position on the detection surface to the amount of relative positional deviation variation (X direction) between the mask and wafer) on each of the 12 surfaces is +100.
．． -100.

However, in general, this designed detection sensitivity changes with changes in the distance between the mask and the sea urchin, and it is difficult to keep it constant.

In this embodiment, as shown in FIG. 1, a light beam is projected onto two left and right alignment marks placed on the mask and the surface of the sea urchin, respectively, and the optical path of the light beam that finally reaches the light receiving part from the alignment mark is the mask. In a configuration where the alignment mark on the left hand side with respect to the surface normal is emitted diagonally to the left, and the alignment mark on the right hand side emits diagonally to the right, (a) The light intensity distribution of the projected light is an inverse Caussian distribution as shown in Figure 4 (The light intensity is minimum at the center, for example (A
1) Distribution shown by the formula.

(b) The shape of the above distribution is modulated in accordance with the distance between the centers of gravity of the two light beams on the surface of the light receiving section (value measured in the X direction). Specifically, the longer the center of gravity distance mentioned above, the steeper or smaller the distribution (
In other words, the distribution is moderate (however, the minimum point is kept approximately constant).

In particular, (b) is a 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 a polarizer 21 to modulate the light intensity distribution of the projected light.

By configuring as described above, it is possible to suppress to the maximum extent variations in positional deviation detection sensitivity due to variations in the distance between the mask and the sea urchin.

For example, the X-direction distribution shape 1 (x, y) of the light intensity distribution of the light intensity distribution shown by equation (1a) is modulated as follows using the real-time light intensity distribution adjustment means 20.

σX(ρ)=α 1 σ・0(3) Il.

〃, Center of gravity distance between two signal beams ρ0: Distance in the X direction between two signal beams when positional deviation is 0, where α is a value obtained by experiment or simulation, and is the positional deviation detection sensitivity with respect to mask-to-wafer spacing fluctuations. This is the value chosen to minimize the range of variation in .

Next, the pattern shapes of grating lenses 5 and 6 for masks and grating lenses 3 and 4 for wafers in this embodiment will be explained.

First, the grating lenses 5 and 6 for the mask are set so that a parallel light beam having a predetermined beam diameter is emitted from the person at a predetermined angle and is condensed at a predetermined position.

Generally, the pattern of a grating 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. A parallel beam of light that is incident at an angle α to the normal line of the mask surface and whose projected component is orthogonal to the scribe line direction passes through the grating lens 5 or 6 and is diffracted at the focal point (X+, y+, Z+). The equation for the group of curves of a grating lens that forms an image is ysin, where x and y represent the contour position of the grating.
a p+(x,y)-P2 =mλ/2-(1)
P+(x,y)=(X-x+)2"(y-L)2
+z, 2P2 -1 door 2. T+z, given by 2. Here, λ 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 (x+, y+, Z+), the right side of equation (1) has a wavelength relative to the principal ray depending on the value of m. m / 2 times the optical path length or longer (shorter), and the left side is the point of mask-L (X, y, 0
) to reach the point (X+ + y+ + Z+).

On the other hand, grating lenses 3 and 4 on the second 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). The position of the point light source is determined by (X+, y+), where g is the gap between the mask and the wafer during exposure.
, Z+g). Assuming that the alignment between the mask and the sea urchin is performed in the X-axis direction, if the alignment beam is focused at the point (X2 + y2 + 22) on the detection surface when alignment is completed, then the crater on the wafer The equation of the curve group of the lens is 10 mλ/2 in the coordinate system determined earlier.
).

Equation (2) shows that the wafer surface is at z=-g, the chief ray is at the origin on the wafer surface, the point on the mask surface (0,0°g), and the point (X2, '12 .
g) This is an equation that satisfies the condition that the difference in optical path length between the ray passing through and the principal ray is an integral multiple of a half wavelength.

In general, a zone plate (grating lens) for a mask has two regions formed alternately: a region through which light rays pass (transparent section) and a region through which light rays do not pass (light shielding section).
It is manufactured as a single amplitude 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 21, the outline of the grating is defined at a position that is an integer multiple of a half wavelength with respect to the principal ray. This means that in the grating lens 5 or 6 on the mask, the line width ratio of the transparent part and the light-shielding part is is 1:
1, and the ratio of the lines and spaces of the rectangular grid for the crating lens 3 or 4 on the wafer is 1:1.
It means that.

The grating lenses 5 and 6 of the second mask are formed by transferring the grating lens pattern of the reticle, which was previously formed by EB exposure, onto an organic thin film made of polyimide.
Alternatively, a crating lens on a wafer is formed by forming an exposure pattern of the wafer on a mask and then transferring the exposure pattern.

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

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 and 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, using the light intensity distribution adjusting means 20, the above-mentioned (2)
, By irradiating the alignment mark with a light beam having the light intensity distribution shown by equation (3), the gap variation is ±3.0μ.
m, the variation amount of the spot interval is 1.9 μm,
Relative positional deviation detection error between mask and wafer is 0.000
It became 4 μm.

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

On the other hand, with respect to the positional fluctuation of the pickup housing 16 (translation in the xy plane), the positional deviation detection error is 0.003 μm for a fluctuation of ±10 μm (0.019 μm in the conventional optical path system).
), which has been reduced to about one-sixth of the conventional value.

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 autoclave, etc. are used. By adjusting the output of the light intensity distribution, 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. (However, the minimum point of the light intensity distribution is kept approximately constant.) The optical paths of the principal rays of the two signal beams 7 and 8, the arrangement of the alignment marks, and the configuration of other elements are the same as in the first embodiment. At this time, the light intensity distribution of the projected light is modulated 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 surface increases, the separation distance between the two light sources 13-1 and 13-2 also increases. It is set to be long.

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 intensity is minimized near the center of the gap, and increases as the distance from the center increases. The optical path of the two signal beams 7.8 that finally reach the light receiving section 11.12 from the left and right alignment marks 5 and 6 is from the alignment mark 5 on the left hand side to the left hand in the cross section including the positional deviation 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 signal beams 7 and 8 for alignment are arranged at a predetermined distance, for example, 100 μm, on the mask 1 and wafer 2 surfaces.

Here, assuming that the diameter of the projection light beam projected onto the alignment mark 56 on the first surface of the mask is the same as in the first embodiment, the first . The final relative angle of the second signal beam is not the optimum value, and the positional deviation measurement error due to cap fluctuations and fluctuations in the position of the alignment head housing increases.

Therefore, in this embodiment, the adjustment of the light intensity distribution of the projected light beam diameter is the same as in the first embodiment. The final exit angles of the second signal beam in the xz plane are 4.0° and +4.8°, respectively.

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

In this way, 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 values are obtained through a simulation using ray tracing, 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 beam7.
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 the first surface of the mask and alignment marks 1 to 3 and 4 on the second surface of the wafer.

Ite area 70 is shown in Fig. 8 and Fig. 10 (G) and (D).
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 onto reticle alignment marks 3L1 and 3L2 on a reticle 5 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 reduced by the reducing lens system 18 to a point Q which is a distance 11aw and aw' away from the wafer W as the second object.
, Q'.

In the figure, 7 and 8 are alignment marks 3L1 and 3, respectively.
．． The first . caused by L2. 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 a beam of light 7.8 converging on points Q and Q' respectively enters,
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 beam having a light intensity distribution such as a non-uniform Calacian 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, the difference in the distance between the first object and the second object due to the variation in the distance between the first object and the second object, which has been a problem in the prior art, is 2
By employing the above-mentioned light intensity distribution adjustment means and crossed optical paths, it is possible to suppress the positional deviation amount detection error due to variations in the distance between the incident positions of the two alignment signal light beams (equivalently, the light intensity barycenter position). I'm trying to make it possible.

Further, the present inventor has achieved similar spacing fluctuations by appropriately setting the diameter at which the intensity of the alignment light beam on the first object plane decreases to 1/e2 by using a light intensity distribution adjustment means and a crossed optical path. It has been found that the occurrence of errors in detecting the amount of positional deviation caused by the above can also be effectively suppressed.

The present invention suppresses the occurrence of the above-mentioned positional deviation amount detection error by setting each element to form such crossed optical paths, thereby increasing 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 beams 7 and 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 light beam for alignment is a single Gaussian beam that is applied to the alignment mark 5.6 on the first object plane.
incident on . First object 1 Alignment mark 5 on blood,
The light beam diffracted by 6 is subjected to a converging effect of convex power at alignment mark 5 and a diverging effect of concave power at alignment mark 6, for example, and then reaches alignment mark 3.4 on second object surface 7.

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 2nd signal beams 7.8, 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.

In this embodiment, the method of modulating the light intensity distribution of the projected light is the centroid distance #! between the two signal beams on the detection surface. It may be determined as follows according to the following equation.

′J20 +σxo (+i)σX(Jl
)=α Sentence here ℃. is the X between the two signal beams when the positional deviation is 0
The distance in the direction, α′, is a numerical value obtained by experiment or simulation, and is selected so that the range of variation in positional deviation detection sensitivity is minimized with respect to variations in the distance between the mask and the wafer, and it depends on the statement. may change. That is, α′−α′(
fl) may be used.

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 adjusted by using the light intensity distribution adjusting means to adjust the light intensity distribution of the light beams emitted from the two alignment marks. When the two light fluxes emitted from the two alignment marks are guided to the light receiving section, the distribution is non-uniform based on the relative distance on the - predetermined plane of (c) the + side with respect to the positional deviation detection direction. The light beam that reaches the light receiving part from the alignment mark on one side 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 one side is emitted diagonally to the side with respect to the normal line of the alignment mark surface. In an optical path configuration in which the two signal beams are emitted, if the relative distance between the incident positions of the two signal beams on a predetermined plane is longer than a preset value, the position will shift near the center of the entire area where the marks are aligned to the two alignment members 1. Based on equations (3) and (4), the light intensity distribution is such that the light intensity in the direction of quantity detection is minimum, and the light intensity increases with a predetermined slope as the distance from the point of minimum light intensity in the direction of positional deviation detection is and irradiates the alignment mark.

(d) With respect to the positional deviation detection direction, as in (c), the radiation is emitted obliquely to one side from the alignment mark on the + side with respect to the normal to the alignment mark surface, and from the alignment mark on the − side, the radiation is emitted from the alignment mark surface. When the relative distance between the incident positions of the two signal beams on the predetermined plane is shorter than a preset value in an optical path configuration in which the light beams are 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 reaches a maximum near the center of the entire area in the positional deviation detection direction, and the light intensity decreases at a predetermined gradient as it moves away from the maximum point in the positional deviation detection direction. ) irradiates the alignment mark based on the formula.

It is characterized by adopting the above configuration.

(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 information on the incident position of the second signal light beam on a predetermined surface, a 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 adjusting based on the relative distance of the incident positions of the two light beams incident on a given surface, it is extremely resistant to the effects of changes in the distance between the two objects being aligned and positional changes of the light beam projected from the light source. It is possible to achieve a position detection device capable of detecting the amount of positional deviation with high precision.

[Brief explanation of the drawing]

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. 3(B) and 3(C) are flowcharts of the measurement control of FIG. 3(A), and FIG. 4 is a flowchart of the measurement control of FIG. 3(A). 2 is an explanatory diagram of a cross-sectional view of the optical path of the first embodiment,
5 to 8 are perspective views of main parts of second to fifth embodiments of the present invention, respectively, and FIGS. 9(A) and (B) are perspective views of main parts and optical paths of a sixth embodiment of the present invention. Cross-sectional explanatory diagram, Fig. 10 (A) to (D)
is an explanatory diagram of the arrangement of alignment marks according to the present invention, the first
FIG. 1 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 master 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.

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 arranged 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, at least one of the two light beams is aligned at the alignment mark on the first object surface and the alignment mark on the second object surface, respectively. The light intensity distribution adjusting means adjusts the light intensity distribution of the passing light beam based on the relative distance between the incident positions of the two light beams incident on the predetermined surface. position detection device. (2) When the relative distance between the incident positions of the two light beams incident on the predetermined surface is longer than a preset distance, the light intensity distribution adjusting means adjusts the light intensity distribution of the passing light beam to the center of the arrangement of the two alignment marks. 2. The position detecting device according to claim 1, wherein the position detecting device is adjusted so that it becomes a minimum near the center of the arrangement of the two alignment marks, and when the distance is short, it becomes a maximum near the center of the arrangement of the two alignment marks.