JP2513282B2 - Alignment device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an alignment apparatus, for example, in an exposure apparatus for manufacturing a semiconductor element, a first object plane such as a mask or reticle (hereinafter referred to as “mask”). When performing relative two-dimensional or three-dimensional positioning (alignment) between the mask and the wafer when exposing and transferring the fine electronic circuit pattern formed on the second object surface such as the wafer The present invention relates to a positioning device suitable for.

(Prior Art) Conventionally, in an exposure apparatus for manufacturing a semiconductor, relative alignment between a mask and a wafer has been an important factor for improving performance. Especially in the alignment of the recent exposure apparatus, in order to achieve high integration of semiconductor elements,
For example, one having a positioning accuracy of submicron or less is required.

In many alignment devices, a so-called alignment pattern for alignment is provided on the mask and wafer surfaces, and the alignment of both is performed using the positional information obtained from them. As the alignment method at this time, for example, the deviation amount of both alignment patterns can be detected by performing image processing, or the alignment can be performed as proposed in U.S. Pat. No. 4037969 or JP-A-56-157033. This is performed by using a zone plate as a pattern, irradiating the zone plate with a light beam, and detecting the position of the light condensing point on a predetermined surface of the light beam emitted from the zone plate at this time.

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

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

In the figure, the parallel light flux emitted from the light source 72 passes through the half mirror 74, is condensed by the condenser lens 76 at the condensing point 78, and is then placed on the mask alignment pattern 68a on the mask 68 surface and the support 62. The wafer alignment pattern 60a on the surface of the formed wafer 60 is irradiated. These alignment patterns 68a, 60a are composed of reflective zone plates,
Condensing points are formed on a plane orthogonal to the optical axis including the converging points 78. At this time, the amount of deviation of the position of the condensing point on the plane is guided by the condensing lens 76 and the lens 80 onto the detection surface 82 to be detected.

Then, based on the output signal from the detector 82, the control circuit 84
In this way, the drive circuit 64 is driven to position the mask 68 and the wafer 60 relative to each other.

The zone plates 68a, 60a on the mask 68 and the wafer 60 differ in the focal length by an amount equal to a predetermined spacing value between the mask 68 and the wafer 60, with the zone plate 60a on the wafer 60 generally having a focal length greater than the focal length. large.

FIG. 12 shows the mask alignment pattern shown in FIG.
FIG. 68 is an explanatory diagram showing an imaging relationship of light fluxes from 68a and the wafer alignment pattern 60a.

In the figure, a part of the light beam diverging from the condensing point 78 is diffracted by the mask alignment pattern 68a, and a condensing point 78a indicating the mask position is formed in the vicinity of the condensing point 78.
The other part of the light flux passes through the mask 68 as zero-order transmitted light and is incident on the wafer alignment pattern 60a on the surface of the wafer 60 without changing the wavefront. At this time, the light beam is diffracted by the wafer alignment pattern 60a, and then again passes through the mask 68 as 0th-order transmitted light and is condensed near the condensing point 78 to form a condensing point 78b representing the wafer position. In the figure, when the light beam diffracted by the wafer 60 forms a converging point, the mask 68 acts as a simple transparent state.

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

In such a method, when the wafer surface is inclined with respect to the reference surface such as the mask surface or the mask holder surface in the semiconductor exposure apparatus, and the ground surface of the exposure apparatus, the center of gravity of the light flux incident on the sensor is measured. Changes and causes an alignment error.

In general, providing an absolute coordinate system on a sensor and setting its reference origin is due to other alignment error factors, such as inclination having a warpage or deflection of a wafer surface, fluctuation of the center of gravity of a light beam due to uneven coating of resist, alignment light source. There is a problem that it is very difficult to set the origin with high accuracy due to fluctuations in the oscillation wavelength, oscillation output, light beam emission angle, fluctuations in sensor characteristics, fluctuations due to repeated alignment head positions, and the like.

(Problems to be Solved by the Invention) The present invention provides a first signal as a means for removing an error factor in detecting a deviation amount when aligning a first object such as a mask and a second object such as a wafer. It is an object of the present invention to provide an alignment device capable of highly accurate alignment by newly forming an alignment light flux as the second signal light with respect to the alignment light flux as the light and utilizing the alignment light flux.

In particular, in the present invention, the action of the center of gravity movement on the sensor with respect to the inclination of the wafer surface of the second signal light is made to be completely equal to the alignment light flux (first signal light flux), and the variation of the position of the alignment head is prevented. Is set so that the second signal light is subjected to the action of movement of the center of gravity, which is exactly the same as the alignment light flux, so that the relative position fluctuations of the second signal light and the alignment light flux on the sensor are theoretically different between the mask and the wafer. It is an object of the present invention to provide a position aligning device capable of performing highly accurate position adjustment by relying only on the position deviation of.

(Means for Solving Problems) A first physical optical element having a function as a physical optical element is formed on a first object surface, and a second physical element having a function as a physical optical element is formed on a second object surface. When an optical element is formed and one of the first or second physical optical element A is composed of a lens element having a single mark shape, and a light beam is incident on the first physical optical element. Incident diffracted light of a predetermined order on the second physical optical element, the light amount centroid of the diffracted light of the predetermined order from the second physical optical element is detected by the first detection means, and the first physical optical element is detected. To the second physical optical element, and diffracted light of an order different from the order generated from the first physical optical element is incident on the second physical optical element, and diffracted light of an order different from the order generated from the second physical optical element. The light amount center of gravity of the Using both the signal of the signal from the second detecting means, said first object and a second
When performing positioning with respect to the object, the barycentric position of the light beam incident on the first detection means and the barycentric position of the light beam incident on the second detection means are relative to each other with respect to the positional deviation between the first object and the second object. That is, each element is set so as to be displaced at a magnification of a different sign.

(Embodiment) FIG. 1 (A) is a schematic view of a main portion of a first embodiment of the present invention. In the figure, 1 is a first object, for example, a mask. A second object 2 is a wafer aligned with the mask 1, for example. Reference numerals 3 and 4 denote first and second physical optical elements for alignment, which are provided on the mask 1 surface and the wafer 2 surface, respectively.

In the present embodiment, the light flux emitted from the light source 31 passes through the projection optical system (collimator lens system) 9 and becomes a parallel light flux, which is reflected by the first physical optical element 3 on the first object 1 to the first object plane. The light is obliquely incident at a predetermined angle α with respect to the normal.

The first physical optical element 3 is composed of a lens element such as an amplitude type grating lens having a single mark shape, and a transmitting portion and an opaque portion of the alignment light beam are formed as shown in FIG. The mark shape (mark pattern) of the grating lens 3 is a hologram pattern and a pattern shape formed on the surface of the physical optical element 3 by a predetermined light beam emitted from an object point (light source) and an image point by previously specifying an imaging relationship. Are set to match as will be described later.

The light beam diffracted by a predetermined order in the first physical optical element 3 is subjected to a lens action (convergence or divergence action), and for example, a light beam diffracted in the + 1st order as shown in FIG. It receives a convex lens action (converging action) so that the image point F1 becomes (0,0, z ₁ ). On the other hand, the light flux that has been diffracted in the −1st order is subjected to the concave lens action (divergence action) so that the virtual image point F2 becomes (0,0, −z ₁ ).

The two luminous fluxes generated in this way, namely the convergent luminous flux La
The divergent light beam Lb is further diffracted by the second physical optical element 4 which is separated by a predetermined distance g, and is subjected to a lens action.

The second physical optical element 4 is composed of a lens element having a plurality of mark shapes, and is composed of, for example, two types of grating lenses 4a and 4b having a pattern as shown in FIG. 2 (A).

In this embodiment, the second physical optical element 4 is composed of a mixed amplitude and phase type grating lens element, and the sectional structure is, for example, a concavo-convex pattern, and generally the valleys and the peaks have different amplitude reflectances. The convergent light beam diffracted by the first physical optical element among the light beams diffracted by the second physical optical element 4 in the predetermined order is the grating lens 4a of the second physical optical element 4.
The first luminous flux La generated by the first-order diffraction at
It is used as an alignment signal light beam.

On the other hand, the divergent light beam diffracted by the first physical optical element 3 is reflected by the grating lens 4b of the second physical optical element 4 to be 1
A light beam which is diffracted next time and which is generated by the action of the convex lens is used as the second alignment signal light beam Lb.

The first and second alignment signal light beams diffracted by the second physical optical element 4 are emitted from the second object plane 2, transmitted through the first object 1 in the 0th order, and are set on the predetermined plane. 38,39
Incident on.

Next, the first and second alignment signal light beams La and Lb are
The action of displacement on the sensors 38, 39 corresponding to the displacement of the object will be described with reference to FIG.

FIG. 3 is a schematic view of a main part of a system for expanding the amount of positional deviation by the grating lenses 3 and 4 of the light flux from the projection optical system 9 of the embodiment shown in FIG. In the figure, the first physical optical element 3
The parallel light beam that has entered the
The first-order diffracted light 31 becomes a convergent light beam La so as to converge on the point F1, and the −1st-order diffracted light becomes a divergent light beam Lb having a point F2 as a virtual image point.

In this way, by using diffracted lights of different orders, a single grating lens effectively produces two functions, a convex lens action and a concave lens action.

The convergent light beam La and the divergent light beam Lb are respectively subjected to the -1st-order diffracting action by the grating lenses 4a and 4b of the second physical optical element 4, respectively, and at this time, they are subjected to the concave lens action and the convex lens action, respectively, and the respective image points F1, F2 is imaged on the sensor surfaces 38, 39. Here, the distance between the first and second objects is g, the distance between the second object 4 and the sensor is L, the focal length of the first physical optical element 3 is f ₁ (at convex power), −f ₁ (at concave power). ), The focal length of the grating lens 4a of the second physical optical element 4
f ₂ and the focal length of the grating lens 4 b are f ₃ ,
When the relative displacement amount of the second object is ε, the displacement amounts S1 and S2 with respect to the displacement amount 0 of the light amount centroid position of the sensor surface of the first and second alignment light beams La and Lb are 0, respectively. Becomes

At this time, the position shift amount expansion magnification of the displacement amounts S1 and S2 depends on the focal lengths f ₁ and −f ₁ of the first physical optical element, the distance L from the second object surface to the sensor surface, and the interval g.

In addition, each magnification is the first alignment signal light flux.
La is negative and the second alignment signal light flux Lb has a positive sign.
The positions of the displacement amounts S1 and S2 can be geometrically associated with each other as a position where a straight line connecting the image points F1 and F2 and the optical axis center of the second physical optical element 4 intersects the detection surface.

The sensors 38 and 39 detect the light amount centroid positions S1 and S2 of the first and second alignment signal light beams La and Lb, respectively, and detect the distance ΔS between the points S1 and S2.
= S1−S2, the distance ΔS becomes Becomes

The light beam diffracted by the second physical optical element 4 and emitted from the second object plane 2 under the effect of the lens acts on the normal to the second object plane.
The light is obliquely emitted at a predetermined angle β in the yz plane.

Thus, by setting the physical optical element on the alignment object in the alignment optical system so that the alignment light beam is obliquely incident on the first and second objects and obliquely emitted and received, the projection optical system This makes it easy to arrange and configure the light receiving optical system, the sensor, etc. in a single housing (pickup head).

In this embodiment, the first and second light beams emitted from the second physical optical element 4 are emitted.
Both the alignment signal light beams La and Lb are diffracted in the -1st order,
The pattern shape of the second physical optical element is set, for example, as shown in FIG. 2A so that each of them undergoes a concave lens action and a convex lens action, and then obliquely emits to the same side as the light projecting optical system.

2 (B) to 2 (F) are schematic views of another embodiment showing the arrangement state of the second physical optical element 4 according to the present embodiment. In the figure, 4a is a first alignment mark, and 4b is a second alignment mark, both of which are made up of a grating lens.

It should be noted that FIG. 2D is an example in which the first alignment mark 4a and the second alignment mark 4b are overlapped and arranged in the same region.

Next, an example of a method of manufacturing and setting the first and second physical optical elements 3 and 4 in this example will be described.

First, the mask mark 3 which is the first object is designed so that a parallel light beam having a predetermined beam diameter is incident at a predetermined angle and is condensed at a predetermined position. Generally, the pattern of the grating lens is an interference fringe pattern on the lens surface when coherent light sources are placed at the light source (object point) and the image point, respectively.

Now, as shown in FIG. 1, a coordinate system on the surface of the first object 1 is determined. Here, the origin is at the center of the mark, and the x-axis is in the direction of displacement detection, the y-axis is in the direction orthogonal to the x-axis on the first object plane, and the z-axis is in the direction normal to the first object plane 1. A parallel light beam which is incident at an angle α with respect to the normal to the first object plane 1 and whose projection component is orthogonal to the x-axis direction is transmitted and diffracted through the mark of the first object 1 and then converged (x ₁ , y ₁ , z ₁ ), the equation of the curve group of the grating lens that forms an image at the position of
When the grating has the same power in the directions, the contour position of the grating is represented by x, y, ysin α + P ₁ (x, y) −P ₂ = mλ / 2 (1) Given in. Where λ is the wavelength of the alignment light and m is an integer.

Assuming that the principal ray is incident at an angle α, passes through the origin on the first object plane 1 and reaches the condensing point (x ₁ , y ₁ , z ₁ ), the right side of equation (1) depends on the value of m. m / 2 times the light path length of the wavelength longer than the light (short) indicates that the point on the first object relative to the optical path of the left principal ray (x, y, 0) the street point (x _1, y ₁ , z ₁ ) represents the difference in the length of the optical path of the light beam reaching. First in Figure 1
1 shows a first physical optical element 3 on an object 1.

On the other hand, the grating lens on the second object 2 is designed to focus the spherical wave emitted from a predetermined point light source on a predetermined position (on the sensor surface). The point light sources are the first object 1 and the second
If the gap at the time of exposure of the object 2 is set as g, (x ₁ , y ₁ , z ₁ −
It is represented by g) and is the position of the image forming point by the first physical optical element (y is a variable). It is assumed that the alignment of the first object 1 and the second object 2 is performed in the x-axis direction, and that the alignment light is focused on the position of the point (x ₂ , y ₂ , z ₂ ) on the sensor surface when the alignment is completed. Then, the equation of the curve group of the grating lens on the second object is in the coordinate system defined earlier. Is represented.

In equation (2), the second object plane is at z = -g, the chief ray is the origin on the first object plane and the point (0,0, -g) on the second object plane,
Furthermore, assuming that the ray is a ray passing through a point (x ₂ , y ₂ , z ₂ ) on the sensor surface, the difference in optical path length between the ray passing through the grating (x, y, −g) on the second object plane and the chief ray Is an equation that satisfies the condition that is an integral multiple of a half wavelength.

The pattern of the grating lenses 4a and 4b of the second physical optical element 4 can be designed by using the above equation (2). Of these, the grating lens 4b
Pattern is the position of the object point (light source) and the image point P (0,0, z ₁ +
g), Q (X _2, given by -Y _2, Z _2). At this time, the position P of the object point is the position of the virtual image point of the light flux that has undergone the concave lens action in the first physical optical element 3, and the position Q of the image point is the point (x ₂ , y ₂ , z on the sensor surface. ₂ ) and the XZ plane are symmetrical points.

By thus setting the coordinates of the image point Q and setting the grating lens 4b, the grating lens 4a
In the grating lens 4a, although the same sign as the order in which the alignment signal light beam La is diffracted in the pattern of
While giving the effect of a concave lens to the alignment signal light beam La, the grating lens 4b has a second effect of a convex lens.
It is possible to bring the alignment signal light flux Lb.

Further, a grating lens having a lens action in the misregistration detection direction, but having a function of deflecting the traveling direction of the light flux at a constant angle in the direction orthogonal thereto may be set and used for alignment.

The pattern shown in FIG. 2 (H) has the same lens action in both the x direction and the y direction, and has the action of deflecting the traveling direction of the light beam in the y direction at a constant angle.

The pattern shown in FIG. 2 (G) is the same as the cross section of the Fresnel zone plate having the same focal length in the x direction cross section,
The cross section in the y direction is the same as the cross section of the uniform pitch grating. Generally, the shape of the curve is a parabola or a shape close to a hyperbola. The pattern of FIG. 2 (H) is a so-called off-axis type Fresnel zone plate pattern.

The alignment mark 3 for the first object 1 is designed so that a parallel light beam having a predetermined beam diameter is incident at a predetermined angle and is linearly condensed at a predetermined position.

Generally, the pattern of the grating lens is an interference fringe pattern on the lens surface when coherent light sources are placed at the light source (object point) and the image point, respectively. Now, the coordinate system on the first object plane is determined as shown in FIG. Here, the origin is at the center of the scribe line width, and the x axis is in the scribe line direction, the y axis is in the width direction, and the z axis is in the normal direction of the first object plane. A parallel light beam that is incident at an angle α with respect to the normal line of the first object and has a projection component orthogonal to the x-axis direction is transmitted and diffracted through the alignment mark 3 for the mask, and then converged at the focal point (x ₁ , y, z ₁ The equation of the curve group of the grating lens that linearly forms an image at the position of) is such that when the power of the grating is only in the x direction, the contour position of the grating is x,
Expressed as y, ysinα + P ₁ (x) −P ₂ = mλ / 2 (3) Given in. Where λ is the wavelength of the alignment light and m is an integer.

Assuming that the chief ray is incident at an angle α, passes through the origin on the first object plane, and reaches the focal point (x ₁ , y, z ₁ ), the right side of equation (3) becomes the chief ray depending on the value of m. On the other hand, it shows that the optical path length is m / 2 times the wavelength, which is long (short), and the left side passes through the point (x, y, 0) on the first object plane with respect to the optical path of the chief ray and passes through the point (x ₁ , y , z ₁ )
Represents the difference in the optical path lengths of the rays reaching the.

In the equation (3), the light passing through the point y on the first object plane is not converted in the y direction at the image forming point.

On the other hand, the grating lens 4 on the second object plane is designed to focus a cylindrical wave emitted from a predetermined linear light source on a predetermined position (on the sensor surface). For each point on the linear light source, if the gap between the first object and the second object during exposure is g (x ₁ , y ₁ ,
z ₁ -g). Assuming that the alignment of the first object and the second object is performed in the x-axis direction, and the alignment light is focused at the position of the point (x ₂ , y, z ₂ ) on the sensor surface 9 when the alignment is completed. , The basic equation of the curve group of the grating lens on the second object is the coordinate system defined earlier. Is represented.

Here, β represents a deflection angle in the y direction (emission angle with respect to the second object plane normal).

In equation (4), the second object plane is at z = -g, the principal ray is the origin on the first object plane and the point (0,0, -g) on the second object plane, and the point on the detection plane ( x ₂ , y, z ₂ )
It is an equation that satisfies the condition that the difference in optical path length between the ray passing through the grating (x, y, −g) on the second object plane and the principal ray is an integral multiple of half wavelength.

Generally, the zone plate (grating lens) for the first object is of an amplitude type of 0, 1 in which two regions, that is, a region through which light rays are transmitted (transparent part) and a region through which light rays are not transmitted (light shielding part) are formed alternately. Created as a grating element. The zone plate for the second object is created as a phase grating pattern having a rectangular cross section, for example. (3),
In the formula (4), defining the contour of the grating at the position of an integral multiple of a half wavelength with respect to the principal ray means that in the grating lens 3 on the first object, the line width ratio of the transparent portion and the light shielding portion is 1: This means that the grating lens 4 on the second object has a line-to-space ratio of 1: 1 in the rectangular lattice.

The grating lens 3 on the first object was formed by transferring the grating lens pattern of the reticle previously formed by EB exposure on the organic thin film made of polyimide.

Further, the mark on the second object was formed by exposing and transferring after forming the exposure pattern of the first object and the second object.

Next, the relationship between the first alignment light and the second alignment light, which are the alignment light incident on the sensor (for example, the one-dimensional storage type one-dimensional CCD or the like) as the detection means in the present embodiment, will be described.

Each 8 first alignment signal light and the second alignment signal light to the normal of the second object plane in this embodiment ^0, 5
^The light is emitted at an angle of ^{0 and at} an angle at which the second object plane projection component is orthogonal to the x-axis direction. The spatial arrangement of the sensors 38, 39 is set in advance so that the light beam is incident on the substantially central position of the sensors when the alignment is completed.

The centers of the sensors 38 and 39 are 2 mm apart, and are set on the same Si substrate with an accuracy of about 0.1 μm. Also, the sensors 38, 39
The normal line of the arranged Si substrate is arranged substantially parallel to the bisector of the first alignment light emission angle and the second alignment signal light emission angle.

The size of the sensors 38 and 39 is the width 1 of the sensor 11 for the first signal light.
mm, length 6 mm, and the sensor 12 for the second signal light has width 1 mm and length
It is 1 mm. The size of each pixel is 25 μm × 500 μm.

Each sensor measures the position of the center of gravity of the incident light beam, and the output of the sensor is signal-processed so as to be normalized by the total amount of light in the light receiving area. Thereby, even if the output of the alignment light source fluctuates to some extent, the measurement value output from the sensor system is set so as to accurately indicate the position of the center of gravity. Although the resolution of the center of gravity of the sensor depends on the power of the alignment light,
It was 0.2 μm as a result of measurement using a semiconductor laser having a wavelength of 50 mW and a wavelength of 0.83 μm.

In the design example of the grating lens for the first object and the grating lens for the second object according to the present embodiment, the first,
The first alignment light is -100 times the position shift of the second object,
The second signal light is magnified 100 times and the signal light flux moves on the sensor surface at the center of gravity. Therefore, 0.01 between the first and second objects
If there is a displacement of .mu.m, the effective center of gravity shifts by -1 .mu.m for the alignment light and 1 .mu.m for the second signal light on the sensor surface, and the sensor system can measure this with a resolution of 0.2 .mu.m.

In the present embodiment, assuming that the second object plane 2 is tilted by 1 mrad in the yz plane, the first signal light flux on the sensor 38 is about 20 μm.
Move the center of gravity. On the other hand, the second signal light also passes through the optical path having the same optical path length and being axially symmetric with respect to the first signal light flux which is the alignment light, so that the center of gravity moves exactly the same as the signal light on the sensor 39. As a result, if the sensor system performs signal processing so as to output the difference between the signals of the effective barycentric positions from the sensors, the output signal from the sensor system does not change even if the second object plane is tilted in the yz plane.

On the other hand, when the second object tilts in the yz plane, both the first signal light flux and the second signal light flux move the center of gravity in the width direction orthogonal to the longitudinal direction of the sensor. Since the direction is orthogonal to the direction in which the center of gravity of the luminous flux moves, the effective alignment error does not occur even without the second signal light.

Furthermore, when the alignment head including the alignment light source, the projection lens system, the sensor, and the like causes a position shift with respect to the first object-second object system, for example, the head is moved relative to the first object. It is assumed that it has moved in the y direction by 5 μm. At this time, the first signal light causes an effective center-of-gravity shift of 5 μm on the sensor 38, while the second signal light also causes a uniform center-of-gravity shift of 5 μm on the sensor 39.

Similarly, when a variation of 10 μm occurs in the z direction between the first object surface and the head, both the first signal light sensor 38 and the second signal light sensor 39 move the center of gravity of the 10 μm light flux.

Therefore, the final output from the sensor system, that is, the difference signal between the barycentric position output of the first signal light and the barycentric position output of the second signal light does not fluctuate at all.

Further, it can be seen that the fluctuation of the position in the x-axis direction does not become an essential alignment error even without the second signal light beam.

In this embodiment, the positional displacement amount x between the first and second objects is
First signal light and second light as alignment light on the sensor
The barycentric position of the signal light is set to w ₁ and w ₂ , respectively, the inclination angle of the second object plane with respect to the first object plane at that time is Δθ, and the variation amount of the alignment head position is set to Δ1r = (Δx, Δy, Δz). And w ₁ = m · x + c ₁ (Δθ, Δ1r) w ₂ = n · x + c ₂ (Δθ, Δ1r) where m and n are magnifications of the positional deviation amounts of the first alignment system and the second alignment system, respectively. c _i (Δθ, Δ1r) is
If the first alignment signal light and the second signal light are axially symmetric with respect to the sensor surface normal and the optical path lengths are equal due to the shift of the center of gravity of the light beam on the sensor caused by Δθ and Δ1r, c ₁ (Δθ, Δ1r) = It becomes c ₂ (Δθ, Δ1r), and after all, the amount of displacement can be obtained from the relative center of gravity of the two lights on the sensor as follows.

x = (w ₁ −w ₂ ) / (m−n) Thus, the error factors at the time of measuring the barycentric position of the alignment light flux such as the inclination of the second object surface and the position variation of the alignment head are removed, and The amount of displacement can be detected.

In addition, in this embodiment, the focal length f ₁ of the first physical optical element is
217 μm, the distance g is 30 μm, and the distance L from the second physical optical element to the sensor is 18.7 μm. As a result, the positional deviation amount expansion magnifications m ₁ and m ₂ of the first and second alignment signal light beams are respectively m ₁ = −99.0, m ₂ = 73.7085, and by obtaining the position detection direction distance ΔS of both light fluxes on the sensor surface, obtain the magnification sensitivity of | m ₁ | + | m ₂ | times the displacement amount, that is, 175.70885 times. You can The focal length of the second physical optical elements 4a, 4b is such that the diameter of the alignment light beam on the sensor surface is about 200 μm.
It was set as follows.

The basic algorithm for positioning (lateral deviation detection, control) of the first object and the second object according to the present embodiment is as follows.

(A) First, after measuring the light amount distribution of the first positional deviation signal light beam on the sensor 38, the light amount centroid position X _S defined previously is obtained.

(B) At this time, the light amount barycentric position X _R of the light beam is obtained from the light amount distribution of the second positional deviation signal light beam on the sensor 39.

(C) The difference Δδ _S between X _S and X _R is obtained, and the relative positional deviation amount Δσ ₁ between the first object and the second object is obtained from the magnification shown in equation (C).

(D) Relative displacement amount Δσ of the first object or the second object
Move only ₁ by the drive stage to correct the positional deviation.

(E) The operations of steps (a) to (c) are performed to determine whether the relative positional deviation amount Δσ ₂ between the first object and the second object is within the allowable value range.

(F) Step (a) until Δσ ₂ is within the allowable value range
Repeat (e).

An outline of the above procedure is shown as a flowchart in FIG.

Incidentally, FIGS. 1 (B) to (D) are the same as those shown in FIG. 1 (A).
It is a principal part schematic diagram when an Example is applied to the exposure apparatus for semiconductor manufacture. When viewed from the side, FIG. 6B shows the alignment pickup device section extracted and FIG. 6D is a schematic view of the stage section and the stage controller section.

In this embodiment, the dual power grating lens method is used as the lateral deviation detection system, and the mask lens A ² F method is used as the interval measurement system. A brief description of these methods is as follows.

It is a type of alignment method that uses a grating lens element such as a dual power grating method or a Fresnel zone plate, and passes a light beam between the grating lens on the mask and the grating on the wafer.
At this time, the mask lens and the grating lens system on the wafer enlarge the displacement amount by a predetermined magnification to deflect the light beam, and detect the displacement amount from the barycentric position of the light beam on the sensor.

Here, as the center of gravity of the luminous flux,
When the position vector of each point in the cross section is multiplied by the amount of light at that point, the integrated value becomes 0 when integrated over the entire cross section.
The point that becomes a vector may be taken, or the position of the point where the light intensity peaks may be taken as the representative point.

As the light source H _e -N _e laser, a semiconductor laser (LD)
A light source having a high coherency such as, for example, may be used, or a light source having a low coherency such as a light emitting diode (LED), an X _e -lamp, or a mercury lamp may be used.

In this method, since the amount of positional deviation is detected by magnifying it with the magnification of the grating lens system, it is possible to detect the positional deviation with higher accuracy and higher resolution.

FIG. 1 (F) shows a schematic view of the arrangement of a system for magnifying and detecting the positional deviation amount in the grating lens system. In the figure, for convenience, a case where a light beam is vertically incident on the first object is shown.

The first object 1 is attached to the membrane 97, and is supported by the aligner body 95 via the chuck 96. Alignment head 94 for the first and second objects on top of main body 95
Is arranged. In order to align the first object 1 and the second object 2, alignment marks 3 and 4 are printed on the first object 2 and the second object 2, respectively.

The light beam emitted from the light source 31 becomes parallel light by the light projecting lens 32, passes through the beam splitter 92, and is incident on the alignment mark 3. The alignment mark 3 is a transmissive zone plate and has the function of a convex lens that focuses light on the point Q. The wafer alignment mark 4 is a reflection type zone plate and has a function of a convex mirror for forming an image of the light focused on the point Q on the detection surface 90 of the sensor 38.

Under such an arrangement, when the second object laterally deviates from the first object by Δδw, the positional deviation Δδ of the light amount center of gravity on the detection surface 90 is expressed as follows.

That is, The position shift amount is increased.

For example, if the mark 3−Q interval aw = 0.5 mm and the mark 4−detection surface interval bw = 50 mm, it becomes 99 times. At this time, Δσ has a proportional relationship with Δσ as is clear from the equation, and if the sensor resolution is 0.1 μm, the detected positional deviation amount Δσ has a positional resolution of 0.001 μm. If the object 2 is moved based on the positional deviation amount Δσ obtained in this way, the positions of the object 1 and the object 2 can be accurately aligned.

FIG. 1D is a detailed view of the stage unit and the stage controller unit. Alignment pickup head 24
Has a flat surface 10 on the super flat surface 10 on the support pair 26 having a super flat surface 10 at a constant pressure.
It is attached to a clamper portion 27 for pressing against and is placed on the upper part of the alignment device main body via a super flat base 23. The clamper portion 27 is connected to the movement support portion 28 on the two-dimensional movement stage 21 via a parallel leaf spring 30. The stage 21 includes a base portion 21B and an x-direction slide portion 2
1X, y-direction slide portion 21Y, slide portion 21X provided on the guide portion 21G for guiding the x, y bidirectional slide, the base portion 21B,
Drive sources 21MX and 21 that drive 21Y in the x and y directions, respectively
Composed of MY. The operation of the driving sources MX and MY is controlled by the controller 22 so that the head 24 is moved in each direction and positioned at a predetermined position. The amount of movement of each stage is precisely measured by the laser length measuring devices 29X and 29Y, and this data is input to the controller 22. Based on this data, the controller 22 detects the current position of the head 24, and the position is set to a predetermined position. The position of the head 24 is precisely controlled by sending a command signal to the drive sources MX and MY. After the detection position is moved, the lateral deviation and the interval detection are executed as described above, and based on the detection result, the wafer stage 25 is moved in the lateral deviation and the interval error correction direction to complete the alignment and the interval control, and then the head 24 is masked. , Return to the original position so as not to disturb the wafer exposure. The alignment pickup head 24 incorporates a lateral deviation detection system, a gap detection system, and a light projection system.
The light beam emitted from the light source 31, specifically, the semiconductor laser, is projected onto the evaluation mark 20 via the collimator lens 32, the projection lens 33, and the projection mirror 34. The light beam emitted from the mark is guided to the detection system by the detection lens 36, is split by the half mirror 37, enters the light receiving element 38 for lateral deviation detection, and becomes respective signals. It should be noted that the light projecting / receiving window 35 of the alignment pickup head 24 is provided with a filter through which light from the light source for exposure does not pass.

In the present embodiment, the projection light 47 is designed to be parallel on the evaluation marks are projected simultaneously as lateral shift detecting mark 41M and mark interval measurement 42 _in the projection area 43. For this reason, the light-projection means for lateral deviation detection and interval measurement is composed of one system.

FIG. 4 is a schematic view of the essential portions of the second embodiment of the present invention. The alignment marks 4a, 4b on the second object are formed by the pattern shown in FIG. 2 (B). Similar to the first embodiment, the alignment marks 4a and 4b show that the -1st order diffracted light has a concave lens action and a convex lens action with respect to the first and second signal light beams, respectively.

In the present embodiment, the power of the grating lens that is the first physical optical element 3 is not the cylindrical laser,
The first physical optical element is one that has a lens action (convergence of light flux, divergence action) in the same direction, that is, in the xy plane, or a toric type lens element having different lens powers in the X direction and the Y direction. The second physical optical element is suitable for the mark arrangement as shown in FIG. 2 (B).

FIG. 5 is a schematic view of the essential portions of a third embodiment of the present invention. First
The first and second physical optical elements are all off-axis type one-dimensional grating lens (Fresnel lens) elements.
The first and second objects similar to those in the first and second embodiments are provided with a single projecting device, a light receiving optical system, a sensor, a light source, etc. by obliquely projecting light at a predetermined angle and obliquely emitting and receiving light. An alignment pickup head is housed in the housing.

Positioning and position shift detection are performed in the Y-axis direction in FIG. The first physical optical element 3 is composed of a single-pattern grating lens as shown in FIG.
The physical optical element 4 is composed of two types of grating lens patterns 4a and 4b, and has a pattern as shown in FIG. 2 (C).

The sectional views of the optical paths of the first and second alignment signal light beams in the YZ plane are set in the same manner as in the first and second embodiments. However, this figure corresponds to a sectional view of the optical path when the relative positional deviation amount is zero.

Also, as in the first and second embodiments, the second physical optical element 4a is the first
The first-order diffracted light is designed so that a concave lens effect is exerted on the light flux of convex power diffracted by the physical optical element 3, and the second physical optical element 4b is applied to the light flux of concave power diffracted by the first physical optical element 3. The −1st order diffracted light is set so as to undergo a convex lens action.

FIG. 6 is a schematic view of the essential portions of the fourth embodiment of the present invention. In the figure, the second physical optical element 4 on the second object 2 is the first
In the embodiment, the -1st-order diffracted light is a pattern in which a pattern set to exhibit a concave lens action and a pattern set to exhibit a convex lens action are overlapped with each other, and a pattern as shown in FIG. have.

In this way, by setting and arranging marks having different effects on the alignment light flux, that is, a concave lens action mark and a convex lens action mark in the same area on the alignment object, a positional deviation detection error due to a local inclination of the alignment object surface Can be resolved. Further, similarly to the first and second embodiments, it is possible to generate two alignment signal light fluxes having different magnifications of the positional deviations with respect to the positional deviations. It is possible to detect the amount of displacement with high gain and high resolution with respect to the displacement.

Further, it is possible to eliminate the error in the same manner even with respect to the average inclination of the alignment object.

 FIG. 7 is a schematic view of the essential portions of the fifth embodiment of the present invention.

In this embodiment, after the alignment light beam emitted from the light source 31 is passed through the light projecting optical system to the reflection-type second physical optical element 4 on the second object, at a predetermined angle with respect to the normal to the second object plane. It is irradiated diagonally. At this time, the alignment light beam simply passes through the first object and is not diffracted.

The second physical optical element 4 is an amplitude / phase mixed type grating lens element having the same pattern shape as the first physical optical element of the first embodiment. The light beam incident on the second physical optical element 4 is diffracted there by the + nth order and the −mth order to become a convex power beam and a concave power beam, respectively. In this embodiment, two light beams diffracted in the + 1st order and the -1st order are used as the first and second alignment signal light beams.

These two light fluxes are further diffracted by the first physical optical elements 3a and 3b on one object in a predetermined order, and after being subjected to a lens action, they are incident on the sensors 38 and 39, and the light amount centroid position is detected.

In this embodiment, the convex power light beam generated by the second physical optical element is diffracted by the first physical optical element 3a in the -1st order and is subjected to the concave lens action, and the concave power light beam generated by the second physical optical element is the first The physical optical element 3b is set to diffract in the -1st order and receive a convex lens action.

The entrance and exit angles of the alignment light flux with respect to the aligned object are set in the same manner as in the first embodiment.

FIG. 8 (A) is a schematic view of the essential portions of the sixth embodiment of the present invention.

In the present embodiment, the second physical optical element has two types of asymmetric grating lens patterns 4 as shown in FIG.
It is composed of a and 4b. Similar to the first embodiment, each pattern functions so that the -1st-order reflected diffracted light receives the concave lens action and the convex lens action.

The first physical optical element 3 is a single pattern grating lens element as shown in FIG. 8 (A) as in the first embodiment, and is emitted from the light source to be collimated by the light projecting optical system 9. After being obliquely incident on the normal to the first object plane, the + 1st order diffracted light is emitted so as to be condensed at a point (0,0, −z ₁ ), and −1
The second-order diffracted light becomes a divergent wave that emerges from the point (0,0, z ₁ ) and emerges from the first physical optical element 3.

The optics of the second physical optical elements 4a and 4b exist in the xY coordinate system at positions (δ ₁ , 0), (δ ₂ , 0), and (δ ₁ <0, δ ₂ <g) parallel to the Z axis. To do.

FIG. 8B is a power layout diagram of a main part of the grating lens system of the sixth example of FIG. The parallel light flux incident on the first physical optical element 3 is diffracted and the + _{1st order} diffracted light becomes a convex power (convergent) light flux so as to converge to the point F ₁ , and the −1st order diffracted light sets the point F ₂ as a virtual image point. It is divergent light, that is, a concave power luminous flux.

The convex power light flux and the concave power light flux are respectively subjected to the -1st-order diffracting action by the second physical optical elements 4a and 4b, and the light amount is applied to the respective image points F ₁ and F ₂ or the points S ₁ and S ₂ on the sensor surface. An image is formed as the position of the center of gravity. The positions of the points S ₁ and S ₂ may be geometrically associated as positions where the straight lines connecting the image points F ₁ and F ₂ and the optical axis centers O ₁ and O ₂ of the second physical optical element intersect the detection surface. it can.

In the present embodiment, the optical axis center of the concave lens element 4a of the second physical optical element 4 and the optical axis center of the convex lens element 4b are respectively centered on the optical axis center position of the first physical optical element 3 in the x-axis direction. δ ₁ , δ ₂ (δ ₁ <0, δ ₂ <0) are shifted.

By doing so, when the amount of misalignment is 0, the distances in the misalignment detection direction of the light amount centroid positions of the respective alignment signal light beams do not become 0 but become a predetermined value, and it is easy to separate the two alignment signal light beams. Becomes

FIG. 9 (A) is a schematic view of the essential portions of a seventh embodiment of the present invention.

In this embodiment, the second physical optical element uses axially symmetric grating lenses 4a and 4b having a pattern as shown in FIG.

The optical axis centers of the grating lenses 4a and 4b are respectively in the + and-directions from the center position of the second physical optical element 4 in the longitudinal direction of the mark area, as shown in FIG. In this embodiment, it is set so as to be at the position of the four division points.

FIG. 9B is a power arrangement diagram of the position shift amount expansion detection system by the grating lens of this embodiment. When the positional deviation amount between the optical axis center of the concave lens element 4a of the second physical optical element 4 and the optical axis center of the convex lens element 4b is 0, the optical axis center position of the first physical optical element 3 is used as a reference in the x-axis direction. δ
₁ , δ ₂ (δ ₁ <0, δ ₂ <0).

Thus, even when the amount of displacement is 0, the displacement signal light beam is twisted along the optical path outside the plane of incidence on the first object,
Not only is it possible to avoid crosstalk between unnecessary diffracted light (Fraunhofer diffracted light of the first and second physical optical elements) and the alignment signal, etc. that occur in the plane of incidence, but also to project light in the alignment optical system, Even if a change occurs between the positions of the light receiving optical system and the sensor and the positions of the first and second object systems, the positional deviation amount detection error can be eliminated.

FIG. 10 is a schematic view of the essential portions of an eighth embodiment of the present invention. This embodiment is a mask (or reticle) of a semiconductor exposure manufacturing apparatus.
It is applied to the alignment between the wafer and the wafer. In the figure, the light beam emitted from the alignment pickup head 24 is irradiated onto the mark 20 on the mask 1 and the wafer 2, and the reflected or diffracted light is emitted to the alignment pickup head 24 again. The alignment pickup head 24 is attached to the stage 21 as shown in FIGS. 1 (C) and (D), and is configured to be freely two-dimensionally movable according to the alignment area, and is controlled by the stage controller 22. It At this time, the stage 21 is guided by the super flat base plate 23, and is designed so that pitching and yawing do not occur. The stage control unit 22 drives the stage 21 at the start of alignment and interval control to move the head 24 to a position for illuminating and detecting the mask and wafer evaluation mark 20 stored in advance.

The application of the present invention is not limited to the alignment mechanism of a semiconductor manufacturing apparatus, and for example, hologram exposure,
When aligning hologram elements during playback, aligning multicolor printing machines, bonding semiconductor chips, aligning processes in printed circuit boards and circuit inspection equipment, and other adjustments of optical components and optical measurement systems. It is widely applicable to positioning and spacing measurement.

(Effect of the invention) As described above, according to the present invention,
A first physical optical element as an alignment mark having a single pattern that simultaneously functions as a convex lens element and a concave lens element with one element on one object surface on the second object surface is provided. Of light beams of different diffraction orders having different signs of through the second physical optical element on which the pattern for the convex lens element and the pattern for the concave lens element are formed on the other object plane, or the light flux passing through the first and second physical optical elements By reversing the order of, the two alignment signal light fluxes in which the light amount barycenter position is displaced on the sensor surface at the enlargement magnification with a different sign with respect to the relative positional displacement amount between the first object and the second object are used. By generating the light amount and detecting the distance between the positions of the centers of gravity, (a) the wafer surface of the alignment object, which is an anti-slope surface, is tilted, or the resist coating unevenness occurs, or during the exposure process. Even if the position of the center of gravity of the alignment light changes due to a local tilt of the warp or the like, the relative position of the center of gravity of the two alignment signal lights is detected, so that the position of the wafer is accurately shifted regardless of the tilt of the wafer surface. Can be detected.

(B) Since the position of the alignment head changes relative to the mask, even if the position of the center of gravity of the alignment signal light on the sensor changes, the relative position of the center of gravity of the two alignment signal lights is detected. , It is not affected by misalignment of the alignment head.

(C) 2 with the same alignment mark but different magnification code
It is possible to construct a system of lines and earn a total magnification, and it is possible to obtain an alignment signal with about twice the sensitivity as compared with the case of each line alone.

(D) The alignment light beam can be obliquely projected onto the alignment object, and the alignment light beam can be obliquely emitted from the alignment object to receive the alignment light beam. The system, the sensor, and the like can be housed in one housing to make the position shift detection system compact. Further, in the semiconductor exposure process, it is not necessary to evacuate the positional deviation detection system from the exposure area after the alignment is completed, and it is possible to improve the throughput of the exposure process and prevent vibrations and the like due to the evacuation.

(E) Since one of the alignment marks has a single pattern, the mark structure is simple and easy to form.

It is possible to achieve a positioning device having such features.

[Brief description of drawings]

FIG. 1 (A) is a schematic view of a main part of a first embodiment of the present invention.
1 (B), (C) and (D) are schematic views of a main part when a first embodiment of the present invention is applied to an exposure apparatus for semiconductor manufacturing.
FIG. 1E is a flow chart diagram relating to the alignment according to the present invention, FIG. 1F is a schematic diagram for detecting a positional deviation amount in the alignment device according to the present invention, and FIG. 2A.
(H) is an explanatory view of an embodiment of the physical optical element according to the present invention, FIG. 3 is a schematic view of an optical path of a part of FIG. 1, FIG.
5, 6, 7, 7, 8 (A), 9 (A),
FIG. 10 is a schematic view of the essential parts of the second to eighth embodiments of the present invention, and FIGS. 8 (B) and 9 (B) are the first and second embodiments of the sixth and seventh embodiments.
11 and 12 are schematic layout diagrams of a conventional alignment device. In the figure, 1 is a first object, 2 is a second object, 3 is a first physical optical element, 4 is a second physical optical element, 4a and 4b are first and second alignment marks, 9 is a projection lens, 31 Is a light source, and 38 and 39 are sensors.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-1-233305 (JP, A) JP-A-1-285804 (JP, A) JP-A-1-209305 (JP, A) JP-A-1- 209304 (JP, A) JP-A-1-207605 (JP, A) JP-A 64-106427 (JP, A) JP-A 64-63802 (JP, A) JP-A 64-55824 (JP, A) JP-A-64-55823 (JP, A) JP-A-63-247602 (JP, A) JP-B-54603 (JP, B2)

Claims (2)

(57) [Claims] 1. When a first object and a second object are opposed to each other for relative positioning, first and second physical optical elements are formed on the first object surface and the second object surface, respectively. Then, the diffracted light generated when light is incident on the first physical optical element is incident on the second physical optical element, and the light beam position of the diffraction pattern generated on the predetermined surface by the second physical optical element is detected. When the relative positioning of the first object and the second object is performed, one of the first and second physical optical elements A has a single mark shape Two diffracted lights of different orders, which are composed of a lens element and are generated from the physical optical element A, are displaced on a predetermined surface by magnifications having mutually different signs with respect to the relative positional deviation amount of the first object and the second object. Positioning device characterized by being configured to 2. The other physical optical element B of the first or second physical optical element is composed of a lens element having a plurality of mark shapes, and the physical optical element B diffracts an incident light beam in a predetermined order. The two physical optical elements A,
B comprises two detection systems, a concave-convex detection system having a concave lens action and a convex lens action, and a convex-concave detection system having a convex lens action and a concave lens action, respectively, and diffracted light generated by the two detection systems is detected by a detection means. The alignment apparatus according to claim 1, wherein the first object and the second object are positioned by using an output signal from the detection means.