JPH0274806A - Alignment apparatus - Google Patents

Abstract

PURPOSE:To make it possible to perform highly accurate position alignment by forming alignment luminous flux as a first signal light on the surface of a first body, newly forming alignment luminous flux as a second signal light for the first signal light on the surface of a second body, and utilizing the luminous fluxes. CONSTITUTION:A first physical optic element 3 which functions as a convex lens element and a concave lens element at the same time as one element is provided on, e.g. the surface of the body 1 of first and second bodies 1 and 2. The luminous fluxes in the diffraction orders having the different signs from the optical element 3 are used through a second physical optic element 4 which is formed on the surface of the body 2. The patterns of a convex lens element and a concave lens element are formed in the optic element 4. Or the sequential order of the luminous fluxes passing through the first and second physical optic elements 3 and 4 is reversed, and the luminous fluxes are used. The positions of the centers of gravity of the amounts of lights are changed on the surfaces of sensors 38 and 39 at the expanding magnification factors having the different signs with respect to the relative position-deviating amount between the first and second bodies 1 and 2 in two alignment signal luminous fluxes. Such luminous fluxes are formed. The distance between the positions of the centers of gravity of the amounts of the lights is detected. In this way, the position deviation can be accurately detected regardless of the inclination of the surface of a wafer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an alignment device, and for example, in an exposure device for manufacturing semiconductor elements, aligning a mask or a reticle (hereinafter referred to as “mask”) or the like on a first object surface. When performing relative two-dimensional or three-dimensional positioning (alignment) between a mask and a wafer when exposing and transferring a fine electronic circuit pattern formed on a second object surface such as a wafer. The present invention relates to a suitable alignment 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. Especially in alignment in recent exposure equipment, due to the high integration of semiconductors,
For example, there is a demand for alignment accuracy of submicron or less.

In many alignment devices, a so-called alignment pattern for alignment is provided on the mask and wafer surface.
Alignment of both is performed using the position information obtained from them. As an alignment method at this time, for example, the amount of deviation between both alignment patterns may be detected by performing image processing, or U.S. Pat.
As proposed in No. 037969 and Japanese Unexamined Patent Publication No. 56-157033, a zone plate is used as an alignment pattern and a light beam is irradiated onto the zone plate.
This is accomplished by, for example, detecting the position of the focal point.

In general, an alignment method using a zone plate has the advantage of being able to perform alignment with relatively high precision without being affected by defects in the alignment pattern, compared to a method using a simple alignment pattern.

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

In the same figure, a parallel light beam emitted from a light source 72 passes through a half mirror 74 and is condensed at a condensing point 78 by a condensing lens 76, after which it is placed on a mask alignment pattern 68a on the surface of a mask 68 and a support metal 62. The wafer alignment pattern 60a on the surface of the sea urchin 8 60 thus prepared is irradiated. These alignment patterns 68a and 60a are composed of reflective zone plates, and each form a focal point on a plane perpendicular to the optical axis including the focal point 78. At this time, the amount of deviation of the focal point position on the plane is detected by guiding the light onto the detection surface 82 using the condensing lens 76 and the lens 80.

Based on the output signal from the detector 82, the control circuit 8
4 drives the drive circuit 64 to perform relative positioning of the mask 68 and the wafer 60.

a zone plate 68a on the mask 68 and the wafer 60;
60a differs in focal length by an amount equal to the predetermined spacing value between mask 68 and wafer 60, and generally
The upper zone plate 60a has a larger focal length.

FIG. 12 is an explanatory diagram showing the imaging relationship between the light beams from the mask alignment pattern 68a and the wafer alignment pattern 60a shown in FIG. 11.

In the figure, a part of the light beam diverging from the condensing point 78 is diffracted by the mask alignment pattern 68a,
A focal point 78a indicating the mask position is formed near the focal point 78. The other part of the light flux passes through the mask 68 as zero-order transmitted light and enters the wafer alignment pattern 60a on the entire wafer 60 surface without changing the wavefront. At this time, the light beam is diffracted by the wafer alignment pattern 60a, and then passes through the mask 68 again as zero-order transmitted light, and is focused near the converging point 78, which focuses on the wafer position.
form b. In the figure, when the light beam diffracted by the wafer 60 forms a condensing point, the mask 68 simply acts as a transparent state.

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

In this method, if the surface is tilted relative to the mask surface, the reference plane such as the mask holder in the semiconductor exposure equipment, and the ground plane of the exposure equipment, the center of gravity of the light beam incident on the sensor will be The position changes, resulting in an alignment error.

In general, establishing an absolute coordinate system on the sensor and setting its reference origin is difficult to avoid due to other alignment error factors, such as tilting of the wafer surface due to warpage or deflection, fluctuations in the center of gravity of the light beam due to uneven resist coating, and alignment. Fluctuations in the oscillation wavelength of the light source, oscillation output, luminous flux output angle, fluctuations in sensor characteristics,
There is also a problem in that it is very difficult to set the origin with high precision due to fluctuations in the position of the alignment head due to repeated changes.

(Problems to be Solved by the Invention) The present invention provides a means for eliminating error factors in detecting the amount of deviation when aligning a first object such as a mask and a second object such as a wafer. Particularly, the present invention is characterized by providing an alignment device that newly forms an alignment light beam as a second signal light with respect to the alignment light beam as a second signal light, and uses this to perform highly accurate alignment. , the effect of the movement of the center of gravity in the sensor on the tilt of the wafer of the second signal light is the alignment light flux (first
The second signal light is set to be exactly equal to the signal light flux), and the second signal light is set so that it is subjected to the movement of the center of gravity that is exactly equal to the alignment light flux even with changes in the position of the alignment head. The object of the present invention is to provide an alignment device that allows highly accurate alignment by making the variation in the relative position of the alignment light beam on the sensor depend in principle only on the positional deviation between the mask and the wafer.

(Means for solving the problem) A first optical element having a function as a physical optical element on the first object plane
forming a physical optical element, forming a second physical optical element having a function as a physical optical element on a second object plane;
Alternatively, one of the second physical optical elements A is composed of a lens element having a single mark shape, and the first physical optical element
Diffraction light of a predetermined order generated when a light flux is incident on the physical optical element is made to enter the second physical optical element, and the center of gravity of the light amount of the diffracted light of the predetermined order from the second physical optical element is detected by the first detection means. detecting the light flux, and making the light beam incident on the first physical optical element, making the diffracted light of an order different from the order generated from the first physical optical element incident on the second physical optical element z=t'-, A second detection means detects the center of gravity of the light amount of the diffracted light of an order different from the supplementary order generated from the physical optical element, and the first. Second
When positioning the first object and the second object using both signals from the detection means, the center of gravity of the light beam incident on the first detection means and the center of gravity of the light beam incident on the second detection means are determined. Each element is set so that the center of gravity of the light beam is displaced by a magnification of a different sign with respect to the positional deviation between the first object and the second object.

(Embodiment) FIG. 1(A) is a schematic diagram of a main part of a first embodiment of the present invention. In the figure, 1 is a first object, for example a mask. 2 is a second object, for example a wafer to be aligned with the mask 1; 3 and 4 are the first ones for alignment. This is a second physical optical element, and is provided on one surface of the mask and on the second surface of the wafer, respectively.

In this embodiment, the light beam emitted from the light source 31 passes through the projection optical system (collimator lens system) 9, becomes a parallel light beam, and is delivered to the first physical optical element 3 on the first object l on 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 has a transparent part and a non-transparent part for the alignment light beam, as shown in the figure. The mark shape (mark pattern) of this grating lens 3 is a hologram pattern and pattern shape formed by a predetermined light beam emitted from an image point (a light source that focuses on an object by specifying an imaging relationship in advance) and a physical optical element 3 surface. are set to match as described below.

A light beam that has been diffracted at a predetermined order by the first physical optical element 3 is subjected to a lens effect (convergence or divergence). For example, as shown in FIG. 3, a light beam that has been diffracted at a +1st order is A convex lens action (convergence action) is applied so that the image point F1 becomes (0,0°z+). On the other hand, the light beam subjected to diffraction at the -1st order is subjected to a concave lens effect (divergent effect) so that the virtual image point F2 becomes (0, O, Z+).

Two luminous fluxes generated in this way, namely a convergent luminous flux La
The divergent light beam Lb is further diffracted by the second physical optical element 4 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 two types of grating lenses 4a and 4b having a pattern as shown in FIG. 2(A), for example.

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

On the other hand, the diverging light beam that has been diffracted by the first physical optical element 3 is reflected by the grating lens 4b of the second physical optical element 4.
The light beam that is diffracted next time and generated by the convex lens action is used as the second alignment signal light beam Lb.

The 1st and 2nd alignment signal beams subjected to diffraction by the second physical optical element 4 exit the second object plane 2, pass through the first object 1 in the zeroth order, and are set at a predetermined plane north. sensor 38,
39.

Next, the first. Second alignment signal beam La.

Lb is the first. The sensor 38 responds to the positional deviation of the second object.
, 39 will be explained with reference to FIG.

FIG. 3 is a schematic diagram of a main part of a system for enlarging the amount of positional deviation by the grating lens 3.4 of the light beam from the light projecting optical system 9 of the embodiment shown in FIG. In the figure, the first physical optical element 3
The parallel light beam incident on the +
The first-order diffracted light 31 is converted into a convergent light beam La so as to converge on the point F1.
Therefore, the −1st-order diffracted light becomes a divergent light beam Lb with point F2 as the virtual image point.

In this way, by using the diffracted lights of orders with different signs, a single grating lens can effectively produce two functions: a convex lens function and a concave lens function.

The converging light flux La and the diverging light flux Lb are both unified by the grating lenses 4a and 4b of the second physical optical element 4, respectively.
Under the following diffraction effects, at this time, the concave lens effect,
Under the action of a convex lens, respective image points Fl and F2 are imaged onto the sensor surface 38°39. Here is the first one. The distance between the second object 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 r+ (at the time of convex power),
r+ (at the time of concave power), the focal length of the grating lens 4a of the second physical optical element 4 is -f2, the focal length of the grating lens 4b is f3, and the first. If the amount of relative positional deviation of the second object is ε, then the first object. Second alignment light beam La.

The respective displacements 11sI and S2 of the light quantity gravity center position of the sensor surface of Lb when the positional deviation amount is 0 are as follows.

At this time, the displacement is1. The positional deviation magnification magnification in S2 depends on the focal length m fr-fl of the first physical optical element, the distance fiL from the second object plane to the sensor plane, and the interval g.

In addition, each magnification factor is the first alignment signal light flux L
a has a negative sign, and the second alignment signal nine bundles Lb has a positive sign. Note that the position of the displacement ist, S2 can be correlated in terms of geometric optics as a position where a straight line connecting the image points Fl, F2 and the center of the optical axis of the second physical optical element 4 intersects with the detection surface.

Sensor 38.39 and 281. The light intensity gravity center positions Sl and S2 of the second alignment signal beams La and Lb are detected, and the point S1
When calculating the distance Δ5=s1−S2 between the point 82 and the point 82, the distance ΔS becomes r+−g according to the positional deviation amount ε.

Incidentally, the light beam diffracted by the second physical optical element 4 and outputted from the second object surface 2 after being subjected to lens action is y relative to the normal to the second object surface.
Oblique surgery is performed at a predetermined angle β in the z-plane.

In this way, the first. By setting the physical optical element on the alignment object in the alignment optical system so as to project the alignment beam at oblique incidence to the second object and receive the alignment beam at an oblique angle, the alignment optical system, the light receiving optical system, and the sensor are set. etc. in one case (
(Pickup head) is easy to place and configure.

In this embodiment, the first optical element emitting light from the second physical optical element 4. Second
The pattern shape of the second physical optical element is such that the nine alignment signal bundles La and Lb are both diffracted by the 11th order, and after receiving concave lens action and convex lens action, they are emitted obliquely to the same side as the projection optical system. are set, for example, as shown in FIG. 2(A).

FIG. 2(B) to FIG. 2(F) are schematic diagrams of another embodiment showing the arrangement state of the second physical optical element 4 according to the present embodiment. In the figure, 4a is the first alignment mark, 4b is the second
Each alignment mark consists of a grating lens.

Note that FIG. 2(D) is an example in which the first alignment mark 4a and the second alignment mark 4b are arranged in the same area so as to be overlapped.

Next, the first example in this embodiment. An example of a method for manufacturing and setting the second physical optical element 3.4 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 enters at a predetermined angle and is condensed at a predetermined position. In general, the pattern of a grating lens is an interference fringe pattern on the lens surface when coherent light sources are placed at the light source (object point) and image point, respectively.

Now, as shown in Figure 1, a coordinate system on the first surface of the first object is determined.

Here, the origin is located at the center of the mark, the X axis is in the positional deviation detection direction, the y axis is in the direction orthogonal to the X axis on the first object surface, and the four axes are in the normal direction of the first object surface 1. A parallel beam of light that is incident at an angle α with respect to the normal to the first object 1 and whose projected component is perpendicular to the X-axis direction passes through the mark of the first object 1 and is diffracted.
The equation for the group of curves of a grating lens that forms an image at positions X+, 'J+, Z+) is, when the grating lens has the same power in the Expressed as ysin a P, (x,y)-P2=mλ/2
- given by (1). Here, λ is the wavelength of the alignment light, and m is an integer.

If the principal ray is incident at an angle α, passes through the origin on the first object plane 1, and reaches the focal point (X+,!+, Z+), then the right side of equation (1) changes the principal ray depending on the value of m. On the other hand, it shows that the optical path length m/2 times the wavelength is long (short), and the left side shows that the optical path of the chief ray passes through the point (x, y, 0) on the first object and reaches the point (xI + 3' r21). It represents the difference in the length of the optical path of the arriving light ray. FIG. 1 shows a first physical optical element 3 on a first object 1. As shown in FIG.

On the other hand, the grating lens on the second object 2 is designed to condense a spherical wave emitted from a predetermined point light source onto a predetermined position (on the sensor surface). For a point light source, if the gap between the first object 1 and the second object 2 during exposure is g, then (X+r'!
+ + Z+ g), which is the position of the imaging point by the first physical optical element (y is a variable). Assuming that the first object 1 and the second object 2 are aligned in the X-axis direction,
When the alignment is completed, the point on the sensor surface (X2 r y2
*22) If the alignment light is focused at the position of
...It is expressed as (2).

Equation (2) shows that the second object plane is at z=-H and the chief ray is at the first
Origin on the object plane and point on the second object plane (0, 0, -g)
, Furthermore, assuming that the ray passes through the point (x2°y2, Z2) on the sensor surface, the crating (x
, y, -g) and the principal ray, which satisfy the condition that the difference in optical path length is an integral multiple of a half wavelength.

Grating lenses 4a and 4b of the second physical optical element 4
The pattern can be designed by using equation (2) of sailing speed. Among these, the pattern of the grating lens 4b is the position of the object point (light 12) and the image point P (0
, 0, z, +g).

Q (X2, Y2, 22) is given.

In this case, the position P of the object point is the position of the virtual image point of the light flux subjected to the concave lens action by the first physical optical element 3, and the position of the image point @
Q is a point (X2, Y2) on the sensor surface.

Z2) and the xZ plane are symmetrical points.

By setting the coordinates of the image point Q and setting the grating lens 4b in this way, the grating lens 4b
In the pattern a, the grating lens 4a has the same sign as the order of diffraction of the alignment signal beam La, but the grating lens 4a has a concave lens effect on the first alignment signal beam La, while the grating lens 4b has the effect of a convex lens on the second alignment signal beam La. It becomes possible to bring it to Lb.

In addition, a grating lens is set that has a lens effect in the positional deviation detection direction, and has a grating lens effect that deflects the traveling direction of the light beam at a certain angle in the direction perpendicular to that direction.
It may also be used for alignment.

Further, the pattern shown in FIG. 2(H) has the same lens effect in both the X direction and the X direction, and also has the effect of deflecting the traveling direction of the light beam at a fixed angle in the X direction.

The pattern shown in Figure 2 (G) has a cross section in the X direction that is the same as the cross section of a Fresnel zone plate with the same focal length, and
The directional cross section is the same as the cross section of equal pitch crating. Generally, the shape of the curve is a parabola or a shape close to a hyperbola. The pattern shown in FIG. 2(H) is that of a so-called off-axis Fresnel zone plate.

The alignment mark 3 for the first object 1 is designed so that a parallel light beam having a predetermined beam diameter enters at a predetermined angle and converges in a line at a predetermined position.

Generally, the grating lens pattern is a light source (object point)
This is the interference fringe pattern on the lens surface when a coherent light source is placed at the image point. Now, the coordinate system on the first object plane is determined as shown in FIG. 2(H). Here, the origin is located at the center of the scribe line width, and the y axis is in the scribe line direction, the y axis is in the width direction, and the two axes are in the normal direction of the first object. A parallel beam of light that is incident at an angle α to the normal to the first object and whose projected component is orthogonal to the
The equation of the group of curves of a grating lens that forms a linear image at the position Z+) is that when the power of the grating is only in the
Expressed as ysin a P, (x)-P2
= m λ/2 − (3) P , (x) = (
x−x, )” + z, 2p2 = moon; 1777 where λ is the wavelength of the alignment light and m is an integer.

The chief ray is incident at an angle α, passes through the origin on the first object plane,
If the ray reaches the focal point (x+, y, Z+), then (
3) The eighth side of the equation is the wavelength m for the principal ray depending on the value of m.
/2 times indicates that the optical path is long (short), and the left side of the optical path of the principal ray passes through the point (x, y, 0) on the first object plane and reaches the point (x+, y).

zl) represents the difference in the length of the optical path of the light rays reaching the point zl).

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

On the other hand, the grating lens 4 on the second object plane is designed to condense the cylindrical wave emitted from a predetermined line light source onto a predetermined position (on the sensor surface). Assuming that each point on the line light source is the gap g at the time of exposure between the first object and the second object, (x+,
y, Z+g). Assuming that the alignment of the first object and the second object is performed in the X-axis direction, and that the alignment light is focused at the position of the point (X2, y, Z2) on the sensor surface 9L when the alignment is completed, The basic equation of the group of curves of the grating lens on the object is expressed in the previously defined coordinate system as
It is expressed as (4).

Here, β indicates the deflection angle in the y direction (the exit angle with respect to the normal to the second object surface).

Equation (4) shows that the second object is at z=-H and the chief ray is at the first
The origin on the object plane and the point on the second object plane (0°0, -g),
Furthermore, a point (X2, y) on the detection surface.

This 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 a half wavelength, assuming that the ray passes through Z2). .

In general, the zone plate (grating lens) for the first object has an amplitude of 0 and 1 in which two areas are alternately formed: a region through which light rays pass (transparent part) and a region through which light rays do not pass (shading part). It is made as a type grating element. In addition, zone plays 1 to 1 for the second object are created as (7 phase, child patterns) with a rectangular cross section, for example. (3
), In equation (4), the outline of the crating is defined at a position that is an integral multiple of the wavelength t with respect to the chief ray.
The grating lens 3 on the first object has a line width ratio of 1:l between the transparent part and the light shielding part, and the grating lens 4 on the second object has a line-to-space ratio of 1=1. It means that.

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

Further, the marks on the second object were formed by forming exposure patterns on the first object and the second object and then performing exposure transfer.

Next, a description will be given of the relationship between the first alignment light and the second alignment light, which are alignment lights that are incident on a sensor (for example, a one-dimensional accumulation-type one-dimensional COD) as a detection means in this embodiment.

In this embodiment, the second alignment signal light and the first alignment signal light are Bo, respectively, with respect to the normal to the second object.
The second object plane projection component is emitted at an angle of 5o, and at an angle perpendicular to the X-axis direction. The spatial arrangement of the sensors 38 and 39 is set in advance so that the light beam will be incident on the substantially central position of the sensor when alignment is completed.

The center distance between the sensors 38 and 39 is 2 mm, which is approximately 0.1
They are set on the same Si substrate with μm precision. or,
The Si substrate on which the sensors 38 and 39 are arranged is arranged so that its normal line is 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 same as that of the sensor 11 for the first signal.
The width is 1mm, the length is 6n+m, and the sensor 1 is used for the second signal.
2 has a width of 1 mm and a length of 1 mm. Further, the size of each pixel is 25 μm x 500 μm.

Each sensor measures the position of the center of gravity of the incident light flux, and signal processing is performed so that the output of the sensor is normalized by the total amount of light in the light receiving area. As a result, even if the output of the alignment light source varies somewhat, the measurement value output from the sensor system is set to accurately indicate the position of the center of gravity. Note that the resolution of the center of gravity position of the sensor depends on the power of the alignment light, but for example,
As a result of measurement using a semiconductor laser of 0 mW and wavelength of 0.83 μm, it was 0.2 μm.

In the design example of the grating lens for the first object and the grating lens for the second object according to this embodiment, the first.
The positional deviation of the second object is magnified by 1100 times with the first alignment light and 100 times with the second signal light, and the signal light flux moves the center of gravity on the sensor surface. Therefore, the first. Assuming that there is a positional deviation of 0.01 μmQ) between the second objects, the alignment light is 1 μm on the sensor surface, and the second signal light is 1 μm.
An effective center of gravity shift of m occurs, and the sensor system converts this to 0.
It can be measured with a resolution of 2 μm.

In this embodiment, the second object plane 2 is 1 mr in the yz plane.
If the sensor 380 is tilted, the center of gravity of the first signal beam shifts by about 20 μm in the sensor 380. On the other hand, since the second signal light is also axially symmetrical with the first signal light beam, which is the alignment light, and passes through an optical path having the same optical path length, on the sensor 39, the center of gravity shifts exactly the same as that of the signal light. As a result, if the sensor system performs signal processing to output the difference between the signals of the effective center of gravity positions from each sensor, the output signal from the sensor system will not change even if the second object plane is tilted in the yz plane.

On the other hand, when the second object is tilted in the xz plane, the center of gravity of both the first signal beam and the second signal beam shifts in the width direction perpendicular to the longitudinal direction of the sensor, but this is detected on the sensor.
Since the direction is perpendicular to the direction of the movement of the center of gravity of the light beam due to positional deviation, there will be no effective alignment error even if there is no second signal light.

Furthermore, an alignment head containing a light source for alignment, a lens system for projecting light, a sensor, etc. is connected to the first object.
When a positional change occurs with respect to the second object system, for example, suppose that the head is moved 57 x m in the y direction with respect to the first object. At this time, the first signal light causes an effective center of gravity movement of 5 μm on the sensor 38, whereas the second signal light also causes an effective center of gravity movement of 5 μm on the sensor 39.

Similarly, when a variation of 10 μm occurs in the Z direction between the first object plane and the head, the center of gravity of both the first signal light sensor 38 and the second signal light sensor 39 shifts by 10 μm.

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

Furthermore, it can be seen that the variation in position in the X-axis direction does not result in an essential alignment error even without the second signal beam.

In this example, the first. Positional deviation between the second object ff1X
are the centroid positions of the first signal light and the second signal light as alignment lights on the sensor as Wl and w2, respectively, and the inclination angle of the second object surface with respect to the first object surface at that time is Δθ
, the amount of variation in the position of the alignment head is expressed as Δ1r=(ΔX
, Δy, ΔZ), then Wl = m + x + c + (Δθ, Δ1r) w2
=n −x+c2(Δθ, Δlr)where, m
, n are the enlargement magnifications of the amount of positional deviation between the first alignment system and the second alignment system, c, and (Δθ, Δlr) are Δθ
, Δ1r, if the first alignment signal light and the second signal light are axially symmetrical with respect to the normal to the sensor surface and have equal optical path lengths, then cl(Δ1r)
θ, Δ1 r) = C2 (Δθ, Δlr), and the amount of positional deviation is finally determined from the relative center of gravity of the two lights on the sensor as follows.

x = (w, -W2) / (m n) In this way, error factors when measuring the center of gravity position of the alignment light beam, such as the inclination of the second object plane and the positional fluctuation of the alignment head, are removed, and the positional deviation can be accurately determined. amount can be detected.

Furthermore, in this example, the focal length M fr of the first physical optical element
is 217 μm, the distance g is 304 m, and the distance from the second physical optical element to the sensor is f! As a result of setting IiL to 18.7 μm, the first. The positional deviation magnification magnification m, , m2 of the second alignment signal beam is m, = -99,0, m, respectively.
2 = 76.7085, and by finding the distance ΔS in the position detection direction of both light beams on the sensor surface, the amount of positional deviation is 1ml l + 1m2 1 times, that is, 175.708
A 5x magnification sensitivity can be obtained.

The focal length of the second physical optical elements 4a and 4b was set to be approximately 200 μm or less, which is the diameter of the alignment light beam on the sensor surface.

The basic algorithm for positioning (lateral shift detection and control) between the first object and the second object according to this embodiment is as follows.

(a) First, after measuring the light intensity distribution of the first positional deviation signal beam on the sensor 38, the previously defined light intensity gravity center position x8 is determined.

(b) At this time, the light intensity gravity center position XR of the second positional deviation signal light beam on the sensor 39 is determined from the light intensity distribution of the second positional deviation signal light beam.

(C) The difference Δδ5 between xS and xR is determined, and the relative positional deviation amount Δσ1 between the first object and the second object is determined from the magnification shown in equation (C).

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

(e) Perform steps (a) to (c) to determine whether the relative positional deviation amount Δσ2 between the first object and the second object is within the tolerance range.

Step (a) until Δσ2 is within the tolerance range
Repeat ~(ne).

An outline of the above procedure is shown as a flowchart in FIG. 1(E).

Incidentally, FIGS. 1(B) to 1(D) are schematic diagrams of main parts when the first embodiment shown in FIG. 1(A) is applied to an exposure apparatus for semiconductor manufacturing. The same figure (B) is when viewed from the side, the same figure (C)
(D) is a schematic diagram of the stage section and the stage controller section.

In this embodiment, a dual power grating lens method is used as a lateral shift detection system, and a mask lens A2F method is used as an interval measurement system. A brief description of these methods is as follows.

Dual power grating method is a type of alignment method that uses a grating lens system such as a Fresnel zone plate, in which a light beam is passed between the mask-L grating lens and the Uni-hat grating lens, and at that time the mask and wafer are In this method, the second grating lens system magnifies the amount of positional deviation by a predetermined magnification, deflects the light beam, and detects the amount of positional deviation from the center of gravity of the light beam on the sensor.

Here, the center of gravity of the luminous flux is the light flux within the cross-section of the luminous flux, and when the product of the position vector from that point in the cross section multiplied by the light intensity at that point is integrated over the entire cross-section, the integral value becomes 0 vector. It is also possible to take a point where the light intensity is at its peak as a representative point.

In addition, as a light source, H8-Ne laser, semiconductor laser (
A light source with high coherency such as a LD) may be used, or a light source with low coherency such as a light emitting diode (LED), an xa-lamp, or a mercury lamp may be used.

In this method, the amount of positional deviation is detected by magnifying it by the magnification of the grating lens system, so positional deviation detection can be performed with higher precision and resolution.

FIG. 1(F) shows a schematic diagram of the arrangement of a system that magnifies and detects the amount of positional deviation using a grating lens system. In the figure, for convenience, the case where the light beam is perpendicularly incident on the first object is shown.

The first object 1 is attached to a membrane 97 and supported by the aligner body 95 via a chuck 96. A first and second object alignment head 94 is disposed above the main body 95. In order to align the first object 1 and the second object 2, alignment marks 3 and 4 are printed on the first object 1 and the second object 2, respectively.

The light beam emitted from the light source 31 is turned into parallel light by the projection lens 32, passes through the beam splitter 92, and enters the alignment mark 3. The alignment mark 3 is a transmissive zone plate that functions as a convex lens to focus light onto a point Q. The wafer alignment mark 4 is a reflective zone plate that directs the light focused on the point Q to the detection surface 9 of the sensor 38.
It has the effect of a convex mirror that forms an image onto 0.

- Under such an arrangement, when the second object lateralizes by ΔδW with respect to the first object, the light ff1ff on the detection surface 9o
The positional deviation Δδ of the i-center is expressed as follows.

Ru.

For example, mark 3-Q interval aw = 0.5 mm, mark 4-
If the detection surface interval bw is 50 mm, it will be 99 times larger. still,
At this time, Δδ is proportional to Δσ, as is clear from the equation, and if the resolution of the sensor is 0.1 μm, the detected positional deviation amount Δσ has a position resolution of 0.001 μm. By moving the object 2 based on the positional deviation amount Δσ determined in this manner, the positions of the objects 1 and 2 can be achieved with good accuracy.

FIG. 1(D) is a detailed IiF diagram of the stage section and stage controller section. The alignment pickup head 24 is mounted on a support 261. with a super-flat surface 10. A clamper part 27 for pressing the super flat surface 10 of
The super flat base 23 is mounted on the upper part of the alignment device main body. The clamper portion 27 is connected to a movable support portion 28 on the two-dimensional movable stage 21 via a V-row leaf spring 30. stage 21
are provided on the base part 21B, the y-direction sliding part 21X, the y-direction sliding part 21Y, the kite part 21G that kites slides in both x and y directions, and the heath part 21B, and drives the sliding parts 21X and 21Y in the X direction and the X direction, respectively. It consists of drive sources 21MX and 21MY. The operations of the drive sources MX and MY are controlled by the controller 22 to move the head 24 in each direction and position it at a predetermined position.

The amount of movement of each stage is measured using a laser length measuring device 29X.
29Y, this data is input to the controller 22, which detects the current position of the head 24 and sends a command signal to the drive sources MX and MY to bring it to a predetermined position. , the position of the head 24 is precisely controlled. After moving the detection position, 11t ``Execute lateral displacement and spacing detection as described above, and based on the detection results, move the wafer stage 25 in the lateral displacement and spacing error correction direction to complete alignment and spacing control. The head 24 returns to its original position so as not to interfere with mask and wafer exposure.The alignment pickup head 24 incorporates a lateral shift detection system, an interval detection system, and a light projection system. The emitted light beam passes through a collimator lens 32 and a projection lens 33.
and is projected onto the evaluation mark 20 via the projection mirror 34. The light beam emitted from the mark is guided to a detection system by a detection lens 36, split by a half mirror 37, and enters a light receiving element 38 for lateral displacement detection, where it becomes respective signals. In addition, alignment pickup head 2
The light emitting and light receiving windows 35 of No. 4 are filtered with f=t' to prevent light from the exposure light source from passing therethrough.

In this embodiment, the projection light 47 is designed to be parallel to the evaluation mark 1-, and the projection light 47 is parallel to the horizontal deviation detection mark 41M of the projection area 43 and the distance measurement mark 42. . The images are projected at the same time. For this reason, the light projecting means for detecting lateral skidding and measuring the distance are configured in one system.

FIG. 4 is a schematic diagram of main parts of a second embodiment of the present invention. Second
The alignment marks 4a and 4b of object 7 are shown in Figure 2 (B).
It consists of the pattern shown in

Here, the alignment marks 4a and 4b are respectively aligned with the first . The −1st-order diffracted light exhibits a concave lens action and a convex lens action with respect to the second signal light beam.

In this practical hh example, the power of the grating lens, which is the first physical optical element 3, is not cylindrical, but isodirectional, that is, it has a lens action (convergence and divergence action of light flux) in the isodirection in xY blood, or A toric type lens element or the like having different lens powers in the direction and Y direction is used for the first physical optical element, and a second physical optical element is used for the second physical optical element.
It is suitable for configuring the mark arrangement as shown in FIG. 3(B).

FIG. 5 is a schematic diagram of the main parts of a third embodiment of the 7i'es of the present invention. 1st. The second physical optical elements are all off-axis one-dimensional grating lens (Fresnel lens) elements, and the first... The first example is similar to the second example. By projecting obliquely incident light onto a second object at a predetermined angle and receiving obliquely emitted light, an alignment pickup head is constructed in which the light emitting, light receiving optical system, sensor, light source, etc. are housed in one housing. ing.

Positioning and positional deviation detection are performed in the Y-axis direction in FIG. Further, the first physical optical element 3 consists of a single pattern grating lens as shown in FIG. 5, and the second physical optical element f4 consists of two types of grating lens patterns 4a and 4b, as shown in FIG. 2(C). It has a pattern as shown in .

1st. The optical path sectional view in the YZ plane of the second alignment signal beam is the first one. The settings are the same as in the second embodiment. However, this figure corresponds to a cross-sectional view of the optical path when the relative positional deviation (j) is 0.

Also, 1st. Similar to the second practical example, the second physical optical element 4a is designed so that the first-order diffracted light is subjected to a concave lens effect on the light beam of convex power diffracted by the first physical optical element 3, and the second physical optical element 4b is It is set so that the first-order diffracted light is subjected to a convex lens effect on the light flux of concave power diffracted by the first physical optical element 3.

FIG. 6 is a schematic diagram of main parts of a fourth embodiment of the present invention. In the figure, the second physical optical element 4 of the second object 2F superimposes the pattern set to show 11st-order diffracted light or a concave lens action in the first embodiment and the pattern set to show a convex lens action. The pattern is as shown in Figure 2 (
It has a pattern as shown in D).

In this way, by setting and arranging marks that have different effects on the alignment light beam, that is, a concave lens effect mark and a convex lens effect mark, in the same area of the alignment object,
It is possible to eliminate misalignment detection errors caused by local inclinations of the alignment object surface. Furthermore, the first. Similar to the second example 7ih, the positional deviation magnification Δ has a different sign for the positional deviation.
It is possible to generate two alignment signal beams with a certain ratio, and by detecting the center of light intensity and position on a sensor, it is possible to detect positional deviations with high gain and high resolution.
Detection becomes possible.

Furthermore, it is possible to similarly eliminate errors regarding the average inclination of the alignment object.

FIG. 7 is a schematic diagram of main parts of a fifth embodiment of the present invention.

In this practical hh example, after the alignment light beam emitted from the light source 31 hits the non-conforming second physical optical element 4 on the second object and passes through the projection optical system, is irradiated diagonally. At this time, the alignment light beam simply passes through the first object and is not subjected to any diffraction effect.

The second physical optical element f4 is an amplitude-phase mixing type grating lens element having a pattern shape similar to that of the first physical optical element of the first example/i8. The light flux incident on the second physical optical element 4 is diffracted therein by the +0th order and the mth order, thereby becoming a convex power light flux and a concave power light flux, respectively. In this example, two light beams diffracted in +1st order and -1st order are used as 1st and 2nd beams. It is used as a second alignment signal beam.

These two light beams are transmitted to the first physical optical element 3a of the first object,
3b, the light is further diffracted by a predetermined order and subjected to a lens action, and then enters the sensors 38 and 39, where the light @ center of gravity position is detected.

In the Kinohei example, the convex power light flux generated by the second physical optical element is diffracted at the 11th order by the first physical optical element 3a and receives a concave lens action, and the concave power light flux generated by the second physical optical element is diffracted by the first physical optical element 3a. It is set so that it is diffracted in the -1st order by the physical optical element 3b and subjected to a convex lens action.

The angle at which the alignment light beam emerges from the object to be aligned is set in the same manner as in the first embodiment.

FIG. 8(A) is a schematic diagram of a main part of a sixth embodiment of the present invention.

In this embodiment, the second physical optical element has two types of asymmetric grating lens patterns 4a as shown in FIG. 2(E).
, 4b. As in the first embodiment, each pattern functions to receive the first-order reflected diffraction light, concave lens action, and convex lens action.

Also, the first physical optical element 3 is shown in FIG. 8 (
It is a single pattern grating lens element as shown in A), which emits light from a light source and becomes a parallel light by f-9, and after obliquely entering the normal to the first object, +1
The first-order diffracted light is emitted so as to be condensed at the point (00, -z,), and the -1st-order diffracted light is a diverging wave that is emitted from the point (0,0, Z+) and passes through the first physical optical element 3. Emits light.

The optical axes of the second physical optical elements 4a and 4b are (δ, 0) and (δ2 + 0), respectively, in the xY coordinate system.

It exists at the position (δ, <0.δ2×O) parallel to the Z axis.

FIG. 8(B) is a power distribution diagram of the main parts of the grete lens system of the sixth embodiment shown in FIG. 8(A). The parallel light beam incident on the first physical optical element 3 undergoes a diffraction effect, and the +1st-order diffracted light becomes a convex power (convergent) light flux so as to converge on point F1, and the -1st-order diffracted light becomes diverging light with point F2 as the virtual image point. , month 1
It is a concave power beam.

The convex power beam and the concave power beam are subjected to the 11th-order diffraction effect by the second physical optical elements 4a and 4b, respectively, and the light beams reach the respective image points F, F2 or points S, S2 of the sensor 4-. 1i is imaged as the center of gravity position.

The positions of the points S, , S2 are between the image points F, , F2 and the optical axis center 0.0 of the second physical optical element. ．． 02 can be correlated geometrically as the position where the straight line connecting each point intersects with the detection surface.

In this example, the optical axis center of the concave lens element f-4a of the second physical optical element 4 and the optical axis center of the convex lens element 4b are set with the optical axis center position of the first physical optical element 3 as the center. ,
δ0. δ2 (δ1 × 0. δ2 <0)
It has been shifted.

By doing this, when the positional deviation amount is 0, the distance in the positional deviation detection direction of the light intensity gravity center position of each alignment signal beam does not become 0, but becomes a predetermined value, and the separation between the two alignment signal beams becomes It becomes easier.

FIG. 9CA) is a schematic diagram of the main parts of a seventh embodiment of the present invention.

In this embodiment, the second physical optical element is an axially symmetrical grating lens 4a, 4b having a pattern as shown in FIG. 2(F).
is used.

The optical axis centers of grating lenses 4a and 4b are shown in Figure 2 (
+ respectively from the center position in the longitudinal direction of the mark area of the second physical optical element 4 as shown in F).

It's in one direction. In this embodiment, the positions are set to be at the four-division points.

FIG. 9(B) is a power arrangement diagram of the positional shift-sensitive magnification detection system using the grating lens of this embodiment. When 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 displaced from each other in the X-axis direction with respect to the optical axis center position of the first physical optical element 3 as a reference, δ3. It is shifted by δ2 (δ1>0.δ2×0).

In this way, even when the amount of positional deviation is 0, by twisting the optical path of the positional deviation signal light beam out of the plane of incidence on the first object, unnecessary diffracted light (first and second physical optical elements) generated within the plane of incidence can be avoided. This not only makes it possible to avoid crosstalk between the Fraunhofer diffracted light (of Fraunhofer diffracted light) and the alignment signal light, but also allows the position of the light emitting, light receiving optical system, and sensor in the alignment optical system and the position of the first . Even if a change occurs between the position of the second object system and the second object system, the positional deviation amount detection error can be eliminated.

FIG. 10 is a schematic diagram of the main part of the eighth embodiment of the present invention, and this embodiment is a mask (or reticle) of a semiconductor exposure manufacturing apparatus.
This is suitable for positioning the wafer and the wafer. In the figure, the light beam emitted from the alignment pickup head 24 is directed toward the mark 20 on the mask l and the wafer 2.
The light that is irradiated upward and is reflected or diffracted is emitted to the alignment pickup head 24 again. The alignment pickup head 24 is shown in FIG. 1 (C:), (
As shown in D), it is attached to the stage 21 and is configured to be able to freely move two-dimensionally according to the alignment area, and is controlled by the stage control section 22. At this time, the stage 21 is kited with a super flat base plate 23 and is designed to prevent pitching and yawing. The stage control section 22 drives the stage 21 at the start of alignment and interval control to move the head 24 to a pre-stored position for illuminating and detecting evaluation marks 20 on masks and wafers.

Note that the application of the present invention is not limited to the alignment mechanism of semiconductor manufacturing equipment, but is also applicable to, for example, hologram exposure, alignment during hologram element setting during reproduction,
It can be widely applied to alignment of multi-color printing machines, bonding process of semiconductor chips, alignment process of printed circuit board and circuit inspection equipment, and alignment and spacing measurement during adjustment of optical components and optical measurement systems. .

(Effects of the Invention) As described above, according to the present invention, the first .
711. One element on one object plane on the second object plane functions simultaneously as a convex lens element and a concave lens element. -,
- the first alignment mark having a pattern of
A physical optical element is provided, and the light beams of diffraction orders with different signs from the first physical optical element are passed through a second buried optical element in which a pattern for a convex lens element and a pattern for a concave lens element are formed on the other object plane. , or the first. By reversing the order of the light beams passing through the second physical optical element, the first
Generates two alignment signal beams whose centers of gravity are displaced on the sensor surface at magnifications with different signs relative to the amount of relative positional deviation between the object and the second object, and detects the distance between the light intensity and center of gravity. (a) The position of the center of gravity of the alignment light may be affected by tilting of the alignment object, which is a reflective surface, or by local inclinations such as uneven resist coating or warping that occurs during the exposure process. By detecting the relative center of gravity position of the two alignment signal lights even if the alignment signal light fluctuates, it is possible to accurately detect a positional shift without being influenced by the inclination of the sea urchin convex surface.

(b) Even if the position of the center of gravity of the sensor L of the alignment signal light changes due to a change in the position of the alignment head relative to the mask, the relative f■ center of gravity position of the two alignment signal lights is detected. Therefore, it is not affected by the positional deviation of the alignment head.

(c) Two identical alignment marks with different magnification signs
By configuring a system of systems, it is possible to increase the overall magnification, and it is possible to obtain an alignment signal with approximately twice the sensitivity compared to the case of each system alone.

(d) The alignment light beam can be projected obliquely to the alignment object, and the alignment light beam can be obliquely emitted from the alignment object and received. By housing the system, sensor, etc. in one housing, the positional deviation detection system can be made compact. Furthermore, in the semiconductor exposure process, there is no need to retreat the positional deviation detection system from the exposure area after alignment is completed, making it possible to improve the throughput of the exposure process and prevent vibrations and the like caused by the retreat.

(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 an alignment device having the following features.

[Brief explanation of the drawing]

? ! Figure 1 (A) is a schematic diagram of the main parts of the first embodiment of the present invention, and Figures 1 (H), (C), and (D) are diagrams showing the application of the first embodiment of the present invention to an exposure apparatus for semiconductor manufacturing. FIG. 1(E) is a flowchart regarding positioning according to the present invention, and FIG. 1(F) is a schematic diagram of detecting the amount of positional deviation in the positioning apparatus according to the present invention. , FIGS. 2(A) to 2(H) are explanatory diagrams of one embodiment of the physical optical element according to the present invention, FIG. 3 is a schematic diagram of a part of the optical path of FIG. 1, FIGS. Figures 6, 7, and 8 (A). 9(A) and 10 are schematic diagrams of main parts of the second to eighth embodiments of the present invention, and FIG. 8(B) and FIG. 9(B) are schematic diagrams of the sixth embodiment of the present invention.
The first example of the seventh embodiment. Main part power distribution diagram of the second physical optical element, 11th. FIG. 12 is a schematic diagram 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, and 4a. 4b is the first. A second alignment mark, 9 a projection lens, 31 a light source, and 38.39 a sensor.

Claims (2)

[Claims] (1) When relative positioning is performed by facing a first object and a second object, forming first and second physical optical elements on the first object surface and the second object surface, respectively; Diffraction light generated when light is incident on the first physical optical element is made to enter the second physical optical element, and a detection means detects a light beam position of a diffraction pattern generated on a predetermined surface by the second physical optical element. By doing so, when performing relative positioning between the first object and the second object, one physical optical element A of the first or second physical optical element is replaced with a lens element having a single mark shape. and so that the two diffracted lights of different orders generated from the physical optical element A are displaced by magnifications with different signs relative to the relative positional deviation amount of the first object and the second object on the predetermined plane. A positioning device characterized in that it is configured as follows. (2) The other physical optical element B of the first or second physical optical element is configured from a lens element having a plurality of mark shapes, and the physical optical element B diffracts the incident light beam at a predetermined order. The two physical optical elements A and B constitute two detection systems: a concave-convex detection system having a concave lens action and a convex lens action, and a concave-convex detection system having a convex lens action and a concave lens action, respectively, and the diffracted light generated by the two detection systems 2. The positioning apparatus according to claim 1, wherein the first object and the second object are positioned by a detecting means, and an output signal from the detecting means is used to determine the position of the first object and the second object.