JPH021508A - Position detecting device - Google Patents

Abstract

PURPOSE:To exactly detect the misalignment between two objects by forming two alignment marks on two objects and detecting the misalignment between deflection luminous fluxes of an alignment light beam and a reference light beam which have passed through these marks. CONSTITUTION:A first alignment mark 5 is formed on a mask 1, and a second alignment mark 3 is formed on a wafer 2, respectively. In this state, an incident light 6 is made incident on the alignment mark 5, an alignment luminous flux 7 which have been deflected by both the alignment mark 5 and the alignment mark 3 is detected by a first detector 11, and also, a position of a reference light 8 which has been deflected by each alignment mark 5, 3 is detected by a second detector 12. Subsequently, based on both signals which have been obtained by the detectors 11, 12, a misalignment between the mask 1 and the wafer 2 is detected. In such a way, the misalignment can be detected exactly without being influenced by an inclination of the surface of the wafer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a position detection device, and for example, in an exposure device for manufacturing semiconductor elements, a first object such as a mask or a reticle (hereinafter collectively referred to as "mask"), etc. Suitable for relative positioning (alignment) of the mask and wafer in the horizontal and vertical directions when exposing and transferring a fine electronic circuit pattern formed on a surface onto a second object surface such as a wafer. The present invention relates to a position detection device.

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

In many 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 JP-A-56-157033, a zone plate is used as an alignment pattern and a light beam is irradiated onto the zone plate, and at this time, the light beam emitted from the zone plate is focused at a focal point on a predetermined surface. This is done by detecting the position.

In general, alignment methods using zone plates are
Compared to a method using a simple alignment pattern, this method has the advantage of being able to perform alignment with relatively high precision without being affected by defects in the 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 base 62. The wafer alignment pattern 60a on the surface of the wafer 60 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 84 drives the drive circuit 64 to position the mask 68 relative to the wafer 60.

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 as a signal light beam. In addition, the other part of the light flux passes through the mask 68 as zero-order transmitted light and T, and enters the wafer alignment pattern 60a on the surface of the wafer 60 without changing its wavefront. At this time, the light beam is aligned with the wafer alignment pattern 60.
After being diffracted by a, the mask 68 returns as a signal beam.
The light is transmitted as zero-order transmitted light and condensed near the condensing point 78 to form a condensing point 78b that focuses on the wafer position. 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 by the shift of the wafer 60 with respect to the mask 68 along the lower surface perpendicular to the optical axis including the focal point 78 according to the deviation ↑■Δσ. It is formed as a deviation amount Δ0' corresponding to the amount Δ0.

In this method, if the wafer surface is tilted with respect to a reference plane such as a mask surface, a mask holder surface in a semiconductor exposure device, or a ground plane of an exposure device, the center of gravity of the light beam incident on the sensor is changes, resulting in an alignment error.

In general, an absolute coordinate system is provided on the sensor, a reference origin is set, and evaluation is performed based on this because of other alignment error factors, such as tilting of the wafer surface due to warping or deflection, and luminous flux due to uneven resist coating. fluctuations in the center of gravity, oscillation wavelength of the alignment light source, oscillation output, and luminous flux output angle,
There has been a problem in that it is very difficult to set the origin with high precision due to variations in sensor characteristics and variations due to repeated alignment head positions. In order to solve this problem, it was necessary to separately measure the distance between the mask and the wafer, the inclination of the wafer, etc.

Among these, it is particularly important to study the effects caused by local changes in substrate inclination in areas such as alignment marks. This causes errors depending on the position of the mark on the wafer surface. This is because if the evaluation area of a separately provided measurement system is misaligned, changes in shape during that time will cause measurement errors.

FIG. 13 is an explanatory diagram showing a change in the center of gravity of a light beam due to, for example, a local inclination on the wafer surface.

The same figure (A) shows the detection surface 2 when the wafer 26 is tilted by θ.
This figure shows the variation of the center of gravity position of the light beam on the seven surfaces, and FIG. 3B shows a cross-sectional state in which the wafer 26 has a different inclination depending on the location.

Now, assume that the alignment light beam that has passed through the mask is incident on the wafer 26 as shown in FIG. 2A.

At this time, if the surface of the wafer is tilted by an angle θ on average at the location where the alignment mark 26' is located, the center of gravity of the light amount on the detection surface 27 is Pθ, which is the focal point when there is no tilt. P. Therefore, it has moved by Δδθ. Expressing this in the form of Δδθ=bw-Lan2θ Δ, then Δδθ= 18.7X 10+3x 2 X 10-
' = 3.74 μm.

That is, the positional deviation error is 3.74 μm, and it becomes impossible to align the mask and wafer with higher precision.

(Problems to be Solved by the Invention) The present invention is capable of detecting the horizontal or vertical position of a second object such as a wafer with respect to a first object such as a mask without being affected by local substrate effects. In particular, the present invention is characterized by providing a position detection device that enables highly accurate position detection.In particular, the present invention utilizes physical optical elements (such as crating) that utilize the characteristics of light waves as alignment marks provided on a mask or wafer surface. The object of the present invention is to provide a position detection device that enables high-granularity position detection by providing a plurality of overlapping wavefront conversion elements in the same area and utilizing a plurality of light beams emitted from the area.

In addition, in the present invention, one of the plurality of light beams emitted from the alignment mark provided on the mask or wafer is an alignment light beam having a lateral deviation signal between the mask and the wafer, and the other one is used as an alignment light beam having a lateral deviation signal between the mask and the wafer. It is used as a reference light flux that is not affected, and at this time, the reference light flux
The effect of the movement of the center of gravity on the sensor with respect to the inclination of the surface is made to be exactly equal to the alignment light flux (signal light flux), and the reference light flux is made to be exactly the same as the alignment light flux even when the position of the alignment head is changed. This allows the variation in the relative positions of the reference light beam and alignment light beam on the sensor to depend only on the misalignment between the mask and the wafer, allowing for highly accurate positioning. The purpose is to provide a position detection device that allows alignment.

(Means for Solving the Problems) The present invention provides a plurality of marks (for example, a physical optical element or a reflective deflection device that deflects light on two object surfaces for position detection, each having different optical properties). Reflective surfaces, etc.) are formed overlappingly in the same area, and two or more types of position detection signals are obtained from the light flux passing through the mark formed in this one area, and from this, it is possible to detect the direction of lateral displacement of the two objects. It is characterized by performing position detection in the horizontal direction and the vertical direction, which is the interval direction.

Specifically, a first alignment mark is formed on a first object plane, a second alignment mark is formed on a second object plane, and the second alignment mark is deflected by both the first alignment mark and the second alignment mark. The position of one light beam is detected by a first detection means, and the obtained first signal and the light beam position of a second light beam that is different from the first light beam and is deflected by the first alignment mark and the second alignment mark are detected. When detecting the position of the second object with respect to the first object by using both of the second signals detected by the second detection means, the first alignment mark and/or the second alignment mark are optically detected. It is characterized in that at least two marks with different physical properties are formed overlappingly in the same area.

(Example) Figure 1 shows how to align the horizontal direction (X direction or Y direction), which is the lateral shift between the first object and the second object, in the first embodiment of the present invention using a reference beam in addition to the alignment beam. FIG.

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; 5 and 3 are respectively the 1st. These are second alignment marks, and are provided on the first surface of the mask and the second surface of the wafer, respectively. 1st. The second alignment mark 5.3 is configured by forming at least two marks having different optical properties overlappingly in the same area, as will be described later. The mark at this time is made of a grating lens such as a Fresnel zone plate, for example. The first and second alignment marks 5.3 are provided on the scribe line 9.10 on the first surface of the mask and the second surface of the wafer. 6 is an incident light, 7 is an alignment light beam as a signal light, and 8 is a reference light beam. The light beam 6 is emitted from a light source in an alignment head (not shown) and is collimated to a predetermined beam diameter.

In this embodiment, the types of light sources include semiconductor lasers, H, -Ne lasers, A, lasers, and other light sources that emit coherent light beams, and light sources that emit non-coherent light beams, such as light emitting diodes. 11 and 12 are sensors (light receivers) as the first detection means and the second detection means, respectively.
It is made up of, for example, a one-dimensional CCD, etc., which receives the alignment light beam 7 and the reference light beam 8.

In this embodiment, after the incident light 6 enters the first alignment mark 5 on the mask 1 surface at a predetermined angle, a plurality of deflected light beams, that is, a plurality of diffracted lights are transmitted and diffracted, and among these diffracted lights, Two predetermined diffracted lights (in the figure, only the principal rays are shown, so they overlap) are further deflected by the second alignment mark 3 on the wafer 2 surface, that is, reflected and diffracted, and are reflected and diffracted onto the sensor 11 and 12 surfaces. are incident on each. and sensor 1
The alignment light beam 7 incident on the sensor surface at 1 and 12
and the center of gravity of the reference beam 8, and the sensors 11 and 12
The mass 1 and the wafer 2 are aligned in the scribe lines 9 and 10 direction (x direction) using the output signals from the wafer 2.

Next, the first example in this embodiment. 2nd alignment mark 5
, 3 will be explained.

The alignment mark 3.5 is made up of a plurality of Fresnel zone plates (or grating lenses) having a focal length of a predetermined value superimposed in the same area. The dimensions of each of these marks are 180 μm in the scribe line direction and 50 μm in the scribe line width direction (y direction).
It is μm.

In this embodiment, the incident light 6 is incident on the mask 1 at an incident angle of 17.5° so that the projected component onto the mask 1 surface is orthogonal to the scribe line direction (x direction).

The incident light 6 that has entered the mask 1 at this predetermined angle is subjected to the diffraction and lens effects of the grating lens 5 and becomes a plurality of diffracted convergent (or diverging) lights, whose chief rays are directed from the mask 1 to the normal line of the mask 1. It is ejected at a predetermined angle.

A plurality of diffracted lights transmitted through the first alignment mark 5, for example, an alignment light beam 7 and a reference light beam 8, are focused on points 217 μm and 18.7 mm vertically below the wafer surface 2, respectively. The distance between the mask 1 and the wafer 2 at this time is 30 μm.

Among the plurality of diffracted lights transmitted and diffracted by the alignment mark 5, the alignment light is subjected to a lens action by the second alignment mark 3 on the wafer 2 surface, and is focused on a single point on the sensor 11 surface as the first detection means. . At this time, sensor 11
On the surface, the light beam or the alignment mark 5.3 is misaligned,
In other words, the center of gravity position changes by an amount proportional to the magnification of the shift of the center of the lens.

Here, the center of gravity of the luminous flux is the point within the luminous flux cross section where the integral value becomes 0 vector when the product of the position vector of each point of the cross-sectional circle from that point multiplied by the light intensity of that point is integrated over the entire light receiving surface. It is about.

As another example, the position of the point where the light intensity is at its peak may be detected.

In this embodiment, when the misalignment between the mask 1 and the wafer 2 is O, that is, when the alignment mark 5 on the mask 1 and the alignment mark 3 on the wafer 2 form a coaxial system, the principal ray of the alignment light beam The emission angle from 2 is 13 degrees, and the distance is 18.7 mm from a predetermined position, for example, the 2nd surface of the wafer.
The light is set to be focused on the surface of the sensor 11 located at a height of .

Further, among the plurality of diffracted lights transmitted and diffracted by the alignment mark 5, the reference destination is simply deflected by the second alignment mark 3 on the wafer 2 surface, and is emitted at an exit angle of 7 degrees,
The light is focused on one point on the surface of a sensor 12 serving as a detection means.

At this time, since the reference light beam is not subjected to the lens action by the second alignment mark 3, the center of gravity of the light beam incident on the sensor 12 surface is always constant even if there is a change in positional deviation between the mask 1 and the wafer 2. It has become.

Pattern AI of grating lens 5.3.

In B1, when the mask 1 and the wafer 2 are misaligned, their respective optical axes are relatively misaligned, which is similar to the so-called axis misalignment of a lens. In this case, since the principal ray of the light emitted from the pattern A1 has a different incident position on the pattern Bl before and after the positional shift occurs, the output angle also changes, and therefore the condensing position of the alignment light beam changes. The amount of variation in the focusing position is proportional to the amount of positional shift.

On the other hand, the reference light flux emitted from pattern A2 enters pattern B2 and exits at a predetermined angle.

When the mask and the wafer are misaligned, the incident position of the principal ray of the light emitted from the pattern A2 on the pattern B2 also changes, but the exit angle of the light emitted from the pattern B2 does not change no matter where it is incident. Position of the mask and wafer: In the case of ξ misalignment detection, the mask is generally fixed to the device, so the position of the sensor 12 surface on which the reference beam is focused by pattern A2 of this mask does not change even if misalignment occurs. . From this, it can be seen that the interval between the alignment light beam and the reference light beam is proportional to the amount of positional deviation.

Therefore, in this embodiment, when the position (alignment) deviation between the mask and the wafer is O, the interval between the centroid positions of the alignment light beam and the reference light beam along the position detection direction is determined in advance, and the alignment light beam and the reference light beam are The CPU 11a detects the interval between the center of gravity positions along the position detection direction, and determines the alignment deviation between the mask and the wafer from the amount of variation with respect to the interval when the deviation of the interval is 0.

Next, the principle of the positional deviation amount detection method of the present invention will be explained in more detail using FIGS. 22 to 24.

FIG. 22 is an explanatory diagram showing the optical arrangement of the master, wafer 2, and sensor 1 according to the present invention. This figure shows the optical path of the signal light beam as the first light beam.

Now, the mask 1 and the wafer 2 are shifted by Δσ in the parallel direction, and the distance from the wafer 2 to the convergence point of the signal beam reflected by the grating lens 3 of the wafer 2 is b1 The signal beam that has passed through the pattern A1 of the mask 1 The distance to the focal point of
Then, the deviation amount Δδ of the center of gravity of the condensing point on the detection surface 11 is Δδ=Δσx(-+1) . . .
). In other words, the center of gravity shift amount Δδ is (b / a + 1
) will be magnified twice.

For example, a = 0, 5 mm, b = 50
+nm, the center of gravity shift amount Δδ is expanded by a factor of 101 according to equation (a).

In addition, the center of gravity shift amount Δδ and position shift amount Δσ at this time are (a
) As is clear from the equation, there is a proportional relationship. Assuming that the resolution of the detector 11 is 0.1 μm, the amount of positional deviation Δa is 0.
．． The position resolution is 0.001 μm.

Next, a basic procedure for detecting the amount of positional deviation using the reference light beam as the second light beam according to the present invention will be explained.

In the present invention, as a means for generating a reference light beam, a pattern A2 is set on the first surface of the mask as shown in FIG. Set.

A light beam (
For example, plane waves, spherical waves, etc.) after emitting pattern A2,
The convergent light forms an image (focuses) on a predetermined surface, is reflected by the object-embedded optical element on the wafer 2, and reaches the sensor 12.

By using the incident position (R,) of this light beam on the sensor 12 as a reference point, and measuring the incident position (S,) of the alignment signal light on the sensor 11, the mask 1
, the amount of positional deviation of the wafer 2 is determined.

In the present invention, for example, if the positional deviation detection sensitivity determined by the optical arrangement in FIG. All you have to do is move one of the objects to be aligned.

However, the optical system and signal processing system are set so that the value of the positional deviation id necessarily converges to 0, and the control does not need to be performed. For example, when the positional deviation id is 0, the positional deviation amount d is set to a predetermined target value ε( It may be possible to converge to a finite value). The above procedure is shown in FIG. This target value may be determined, for example, by evaluating the overlay accuracy after exposure and transfer of the mask pattern.

In this embodiment, one diffracted light of a predetermined order from the first alignment mark 5 enters the second alignment mark 3, and two of the plurality of diffracted lights generated at this time are used as the alignment light 7 and the reference light. 8, and the light may be guided to the sensors 11 and 12, respectively.

FIG. 2 is an explanatory diagram showing the basic principle of the optical system in the first embodiment shown in FIG. 1. In the figure, a first object 1 and a second object 2 whose relative positional deviations are to be evaluated are each connected to a first object such as a zone plate. A second alignment mark 5.3 is provided. A light beam 6 is made incident on the first alignment mark 5, and an emitted light 21 is made incident on the second alignment mark 3. and second alignment mark 3
The emitted light 22 is focused on a detection surface 27 of a detector such as a position sensor.

At this time, a center-of-gravity shift amount Δδ of the amount of light occurs on the detection surface 27 in accordance with the relative positional shift 1Δσ between the first object 1 and the second object 2.

In this embodiment, in the same figure, the center of gravity shift amount Δδ of the light amount on the detection surface 27 due to the light beam 22 shown by the solid line is calculated based on the center of gravity position of the light amount on the detection surface 27 due to the light beam 24 shown by the dotted line, and from this The relative position (l deviation ■Δσ) between the first object 1 and the second object 2 is detected.

FIG. 3 is an explanatory diagram showing the relationship between the relative displacement amount Δσ between the first object 1 and the second object 2 and the gravity center displacement amount Δδ of the light beam on the detection surface 27 at this time.

In this embodiment, the relative positional relationship between the first object 1 and the second object 2 is detected using the basic principle as described above.

Now, using the first alignment mark 5 as a reference, the second
If the alignment mark 3 is deviated by Δσ in the parallel direction to the first alignment mark 5, the deviation Δδ of the center of gravity of the focal point on the detection surface 27 is w. That is, the center of gravity shift amount Δδ is expanded by (-+ 1) times W.

For example, a w = 0.5mm, b w = 50mm
Then, the center of gravity shift amount Δδ is expanded by a factor of 101 from equation (1).

In addition, the center of gravity shift amount Δδ and position shift amount Δσ at this time are (1
) As is clear from the equation, there is a proportional relationship as shown in FIG. 4, for example. Assuming that the resolution of the detector 8 is 0.1 μm, the positional deviation amount Δσ has a positional resolution of 0.001 μm.

If the second object is moved based on the positional deviation ■Δ0 thus obtained, the first object and the second object can be positioned with high precision.

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

The first method is to use a center of gravity shift signal Δδ of the amount of light on the detection surface 27 of the detector with respect to the amount of positional shift Δσ between the two objects.
A curve showing the relationship with S is determined in advance, and the amount of positional deviation Δσ between both objects is determined from the value of the center of gravity deviation signal ΔδS,
The first object or the second object is moved by an amount corresponding to the positional deviation amount Δσ at that time.

The second method is to find a direction that cancels the positional deviation amount Δσ from the gravity center deviation signal ΔδS from the detector, and move the first object or the second object in that direction until the positional deviation amount Δσ falls within the allowable range. Repeat.

Next, the first example in this embodiment. 2nd alignment mark 5
, 3 (grating lens) will be described.

First, the mask mark 5 is designed so that a parallel beam of light having a predetermined beam diameter enters at a predetermined angle and is focused 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, the first
Define the coordinate system on one surface of the mask as shown in the figure. Here, the origin is located at the center of the scribe line width, with the X limb in the scribe line direction, the Y axis in the width direction, and the two axes in the normal direction of the mask surface 1. A parallel beam of light that is incident at an angle α with respect to the normal line of the mask surface 1 and whose projected component is orthogonal to the scribe line direction passes through the mask mark and is diffracted.
The equation of the curve group of a grating lens that forms an image at the position of
λ/2-(1)P+(x,y)=(x-xi)
""(y-3'+)2"Zl"P2 =5
Core 77y completed 7 is given. Here, 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 mask surface 1,
Assuming that the ray reaches the focal point (xl, yI, Zl), the right side of equation (1) indicates that the optical path length is longer (shorter) by m/2 times the wavelength with respect to the principal ray depending on the value of m, and the left side is It represents the difference in the length of the optical path of the ray that passes through the point (x, y, 0) on the mask and reaches the point (XI, yI, Zl) with respect to the optical path of the principal ray.

On the other hand, the grating lens 3 on the wafer 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, let g be the gap between mask 1 and wafer 2 during exposure (X+, y++ z+
g).

(y is a variable) It is assumed that the alignment of the mask 1 and the wafer 2 is performed in the X-axis or y-axis direction, and that the alignment light is focused on the position of the point (x2, y2+22) on the sensor surface when the alignment is completed. For example, the equation of the curve group of the grating lens on the wafer is 10mλ/2 in the coordinate system determined earlier.
2).

Equation (2) indicates that the wafer surface is at z=-g, and the principal ray passes through the origin on the mask surface, a point on the wafer surface (0,0°-g), and a point on the sensor surface (X2 + y2Z2). As a light beam, the grating (x, y, -g) on the wafer surface
This is an equation that satisfies the condition that the difference in optical path length between the ray passing through and the principal ray is an integral multiple of a half wavelength.

One alignment mark is created by overlapping the alignment and reference patterns obtained as described above.

FIGS. 5A and 5B are pattern diagrams of a first alignment mark for a mask and a second alignment mark for a wafer in this embodiment.

In the same figure, (AI) and (81) are alignment patterns for masks and wafers, (A2) and (B2
) is a reference pattern for masks and wafers, (A3) is a pattern obtained by overlapping pattern (AI) and pattern (A2) to form the first alignment mark, and (B3) is a pattern (Ill) and pattern ( A second alignment mark is formed by a pattern in which the openings 2) are overlapped.

- The zone plate (grating lens) for the mask at fJ2 is a 0, 1 amplitude grating 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 (shade part). It is created as an element. Further, a zone plate for a wafer is formed, for example, as a phase grating pattern with a rectangular cross section. (1),
In equation (2), the contour of the grating is defined at a position that is an integer multiple of a half wavelength with respect to the principal ray. This means that the ratio of the line width of the transparent part and the light-shielding part of the grating lens on mask 1 is 1:1. This means that in the grating lens on the wafer 2, the ratio of the lines and spaces of the rectangular grating is 1=1.

The grating lens on the mask 1 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 upper mark on the wafer 1 was formed by forming an exposure pattern of the wafer on a mask and then transferring it by exposure.

Next, a description will be given of the relationship between the signal light, which is alignment light, and the reference light, which are incident on a sensor (for example, a one-dimensional storage type one-dimensional CCD) as a detection means in this embodiment.

In this embodiment, the reference light and the alignment signal light are each emitted at an angle of 7013° with respect to the normal to the wafer surface. The spatial arrangement of the sensors 11 and 12 is set in advance so that the light beam will be incident on the approximately central position of the sensor upon completion of alignment.

The center distance between the sensors 11 and 12 is 1.96501111, and they are set on the same Si substrate with an accuracy of about 0.1 μm. Further, the Si substrates on which the sensors 11 and 12 are arranged are arranged so that their normal lines are substantially parallel to the bisector of the alignment light emission angle and the reference destination emission angle when the positional deviation is O.

The size of the sensors 11 and 12 is that the sensor 11 for signal use has a width of 1+1101 and the length of 601111, and the sensor 12 for reference use 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. In addition, the center of gravity of the sensor is 1N
Although the resolution depends on the power of the alignment light, it was approximately 0.2 μm when measured using a semiconductor laser of 50 mW and a wavelength of 0.83 μm, for example.

In the design example of the grating lens for a mask and the grating lens for a wafer according to this embodiment, the positional deviation between the mask and the wafer is magnified by 100 times, and the center of gravity of the signal light beam moves on the sensor surface. Therefore, if there is a misalignment of 0.01 μm between the mask and the wafer, an effective center of gravity shift of 1 μm occurs on the sensor surface, which the sensor system can measure with a resolution of 0.2 μm.

In this example, the sea urchin surface 2 is 1 mra in the xz plane.
If the sensor 11'' is tilted, the center of gravity of the signal light beam shifts by approximately 37.4 μm. On the other hand, since the reference light beam 8 also undergoes the same angular change as the signal light beam 7, the center of gravity shifts on the sensor 12 in the same way as the signal light beam.

As a result, the sensor system performs signal processing so that the difference between the signals of the fluctuation of the effective center of gravity position from each sensor is output as the true value of the amount of positional deviation of the mask and wafer in the X direction.
Even if the wafer is tilted in the xz plane, the output signal from the sensor system does not change.

Also, if the wafer is tilted in the yz plane, the center of gravity of both the signal and reference beams will shift, so the 1 mrad
A slight inclination does not result in an effective alignment error.

Furthermore, if the position of the alignment head containing the alignment light source, light projection lens system, sensor, etc. changes, or the mask-wafer system changes, the position change in the X direction will also occur around the mark area. In principle, alignment errors can be avoided by applying the projected light beam in the same manner as -.

Fluctuations in two directions between the mask surface and the head on the four pillars are equivalent to the fluctuations in the X direction by using a light projecting system that directs parallel light to the mask, and in principle alignment errors are avoided. .

It can also be seen that the change in position in the X-axis direction results in movement of the pair of signal light and reference destination, and does not result in an alignment error.

Next, regarding the influence of the inclination of the mark substrate, in the first embodiment, since the marks for signal use and reference use are set in exactly the same area, the average inclination of each mark substrate is equal.
It is not affected by this.

FIG. 6(A) and FIG. 7(A) respectively show the second embodiment of the present invention. Third
FIG. 2 is a schematic diagram of an example. Second. In the third embodiment, incident light 6 enters the first alignment mark 5 on the first surface of the mask, is diffracted, then enters the second alignment mark 3 on the second surface of the wafer, and is emitted from the second alignment mark 3. The alignment light 7 and the reference light 8 are connected to the sensors 11 and 12, respectively.
The state in which the light is incident on the light source is the same as that in the first embodiment shown in FIG.

The second example 71ζ in FIG. 6(A) is the first example. The line width ratio of the light shielding part and the transmitting part of the grating constituting the second alignment mark 5.3 is set to 1:2, and the transmitting part is widened.

FIG. 6(B) shows the pattern of the first alignment mark for the mask, and FIG. 6(C) shows the pattern of the second alignment mark for the wafer.

The third embodiment shown in FIG. 7(A) is similar to the first embodiment. The ratio of the light-shielding part to the transmitting part of the grating constituting the second alignment mark 5.3 is different. The line width ratio between the light shielding part and the transmitting part of the first alignment mark 5 is 1:1, and the line width ratio between the light shielding part and the transmitting part of the second alignment mark 3 for reference is 1:2.

FIG. 7(B) shows the pattern of the first alignment mark, and FIG. 7(C) shows the pattern of the second alignment mark for the wafer.

In addition, in the present invention, the distance between the first object 1 and the second object 2 and the distance between the first object 1 and the second object 2 and the distance between the first object 1 and the second object 2 are determined. It is preferable to select the refractive power of each mark depending on the size of the aperture of the second alignment mark.

For example, 1st. If the interval is larger than the opening of the second alignment mark, a convex curved type is preferable.

On the other hand, if the distance between the openings and the Y is small, the uneven system shown in FIG. 9 or the uneven system shown in FIG. 8 is preferable.

Furthermore, the 8th. As shown in Fig. 9, if the second alignment mark can have a larger opening than the first alignment mark, the uneven system shown in Fig. 9 is better; conversely, the first alignment mark can make the opening larger than the second alignment mark. If possible, the uneven system shown in FIG. 8 is preferable.

In each of the above embodiments, a transmissive physical optical element is shown, but the object of the present invention can be similarly achieved using a reflective physical optical element.

FIG. 10 is a schematic diagram of a fourth embodiment of the present invention. This embodiment relates to an alignment device for aligning a mask and a wafer in an exposure apparatus for semiconductor manufacturing using a so-called proximity method, and specifically shows only the alignment light.

In FIG. 10, the same elements as those shown in FIG. 1 are given the same reference numerals. In the figure, 1 is a mask, and 2 is a wafer, which respectively correspond to a first object and a second object for relative positioning. Reference numeral 5 denotes a mask alignment pattern on the mask surface, which corresponds to the first physical optical element, and numeral 3 denotes a wafer alignment pattern on the wafer 2 surface, which corresponds to the reflective second physical optical element.

In the figure, a light beam emitted from a light source 91 is converted into a parallel light beam by a projection lens system 92, and is irradiated onto an alignment pattern 5 for a mask via a half mirror 93. The mask alignment pattern 5 consists of a zone plate that focuses the incident light beam at a point Q in front of the wafer. The light beam condensed at the point Q then diverges and enters the alignment pattern 3 for the wafer. The alignment pattern 3 is composed of a reflective zone plate, which reflects the incident light beam, passes through a mask and a half mirror 93, and then focuses the light onto the detection surface 11.

This provides an alignment signal. Note that the reference signal from the reference destination is also obtained in the same manner.

FIG. 14A) is a schematic diagram of a main part of a fifth embodiment of the present invention. Figure 14 (B) shows the first mask on one side of the mask in Figure 14 (A).
A schematic diagram of the alignment mark, Figure 14 (C) is the same figure (
FIG. 3 is a schematic diagram of the second alignment mark on the second surface of the wafer in FIG.

In this embodiment, a second signal light having a sensitivity opposite to that of the signal light (first signal light, alignment light) described above is used instead of the reference target in the first embodiment. Using a so-called two-signal system with opposite directions, the amount of positional deviation between the mask and the wafer is detected from the spot positions of both signal lights on the detection surface.

Next, the principle and structural requirements of the so-called reverse two-signal system used in this embodiment will be explained using FIG. 15.

In the figure, l is the first object, 2 is the second object, 205.20
Reference numeral 3 designates alignment marks for obtaining the first signal light, which are provided on the first object 1 and the second object 2, respectively. Similarly, 206 and 204 are alignment marks for obtaining the second signal light, which are similarly provided on the first object 1 and the second object 2, respectively.

In the figure, the two signal systems are shifted vertically for convenience of explanation, but in reality, the centers of the alignment marks 205° and 206 and the centers of the alignment marks 203° and 204 coincide. Alignment marks 205 and 206 are overlapped to form an alignment mark 205a, and alignment marks 203 and 204 are overlapped to form an alignment mark 203a. The overlaid alignment marks 205a, 203a each have the functions of two alignment marks before being overlaid.

Each alignment mark 203, 204° 205, 206
has the function of a physical optical element with one-dimensional or two-dimensional lens action.

207 and 208 indicate the aforementioned first and second alignment signal beams. Reference numerals 211 and 212 are first and second detection units for detecting the first and second signal light beams, respectively, and the optical distances from the object 2 are assumed to be the same value for convenience of explanation. Furthermore, the distance between object 1 and object 2 is δ, the focal length of alignment marks 205 and 206 is each fal+fa2, and the amount of relative positional deviation between object 1 and object 2 is 6, and the center of gravity of the first and second signal beams at that time is Displacement 1 from the matching state of
are respectively s, , S2. Note that the alignment light flux incident on the object 201 is assumed to be a plane wave for convenience, and the symbols are as shown in the figure.

The displacement ffi s + and S2 of the center of gravity of the signal beam are defined by a straight line connecting the focal points F, , F2 of the alignment marks 205 and 206 and the optical axis centers of the alignment marks 203 and 204,
It is determined geometrically as the intersection with the light receiving surfaces of the detection units 211 and 212. Therefore, with respect to the relative positional deviation between object 1 and object 2, the displacement is1. In order to obtain s2 in opposite directions, alignment marks 203 and 204 are used.
This can be achieved by reversing the signs of the optical imaging magnifications. Also, quantitatively, s, = L-f, δ fal-δ 6 s2 = L-f, total δ f. 2-δ 6 , and the deviation magnification is β1=S1/ε.

It can be defined as β2=S2/ε. Therefore, in order to make the deviation magnification have the opposite sign, it is sufficient to satisfy the following. Among these, one of the practically appropriate configuration conditions
One of the conditions is L>lf, 1 f a+/f β2<0 If-+I>δ lf, zl>δ.

That is, the focal path of the alignment marks 205 and 206 @f
The configuration is such that the distance 11iL to the detection unit is made larger than that of a, fa□, the distance δ between the objects 1 and 2 is made small, and one of the alignment marks is a convex lens and the other is a concave lens.

On the upper side of FIG. 15, an alignment mark 205 condenses the incident light flux, and before reaching the convergence point F, the light flux is irradiated onto the alignment mark 203, which is then imaged on the first detection unit 211. alignment mark 203
The focal path 1!1 f b I of is determined to satisfy the lens equation. Similarly, on the lower side of FIG. 15, an alignment mark 206 changes the incident light flux into a light flux that diverges from the point F2 on the incident side, and this is imaged on the second detection unit 212 via the alignment mark 204. The focal path alfbz of the mark 204 is determined so as to satisfy.

Under the above configuration conditions, the imaging magnification for the condensed images of the alignment marks 203 and 205 is clearly positive as shown in the figure, and the movement ε of the object 2 and the detection unit 211
The direction of the light spot displacement amount S is reversed, and the shift magnification β1 defined earlier becomes negative. Similarly, alignment mark 206
The imaging magnification of the alignment mark 204 with respect to the point image (virtual image) is negative, the movement 6 of the object 2 and the direction of the light spot displacement ffi S 2 on the detection unit 212 are in the same direction, and the deviation magnification β
2 is positive.

Therefore, for the relative deviation ε between object 1 and object 2, the system of alignment marks 205 and 203 and the alignment mark 2
The signal beam deviations S, , S, of the 06 and 204 systems are in opposite directions.

In the fifth embodiment shown in FIG. 14(A), the first object and the second object are aligned using the principle of the above-described two-signal system in opposite directions.

Next, the fifth embodiment shown in FIG. 14(A) will be described.

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; Each alignment mark 2 shown in Fig. 15
03.204, 205, and 206 are composed of grating lenses such as one-dimensional or two-dimensional Fresnel zone plates, and alignment marks 2 are placed on the scribe line 10.9 on the mask 1 side and the wafer 2 side, respectively.
05°206 are overlapped and alignment marks 20
As shown in FIG. 5a, alignment marks 203 and 204 are overlapped to form an alignment mark 203a.

Reference numeral 207 denotes a first light beam, and 208 a second light beam. These light beams (signal light beams) 207 and 208 are emitted from a light source in an alignment head (not shown) and are collimated to a predetermined beam diameter.

In this embodiment, the types of light sources include a light source that emits a coherent light beam such as a semiconductor laser (Ha-N) and an Ar laser, and a light source that emits a non-coherent light beam such as a light emitting diode. 211 and 212 are sensors (charge conversion elements) as a first detection section and a second detection section, respectively, and are made of, for example, a one-dimensional CCD or the like, which receive the light beams 207 and 208.

In this embodiment, each of the light beams 207 and 208 enters the alignment mark 205a on the first surface of the mask at a predetermined angle, is transmitted and diffracted, is further reflected and diffracted by the alignment mark 203a on the second surface of the wafer, and is reflected on the sensor 211, 212 surface. It is incident on the top. The sensors 211 and 212 detect the center of gravity of the alignment light flux incident on the sensor surface, and the positional deviation between the mask 1 and the wafer 2 is detected using the output signals from the sensors 211 and 212.

Each alignment mark 203 before being superimposed next.
The pattern shapes of 204, 205, and 206 will be explained.

The alignment marks 203, 204, 205, 206 are each made of Fresnel zone plates (or grating lenses) having different focal lengths.

The alignment mark 205a in FIG. 14(CB) is a mark on a mask made by overlapping the alignment marks 205 and 206, and is the same as the alignment mark 2 in FIG. 14(C).
03a is a mark on the wafer in which alignment marks 203 and 204 are superimposed.

Practically appropriate dimensions of the marks are 50 to 300 .mu.m in the direction of the scribe lines 9 and 10, and 20 to 100 .mu.m in the scribe line width direction (X direction).

In this embodiment, the light beams 207 and 208 are both incident on the mask 1 so as to be orthogonal to the incident angle frame 17.5'' (the projected component onto the mask 1 surface is in the scribe line direction, the X direction). are doing.

The alignment light beams 207 and 208 that are incident on the mask l at these predetermined angles are each passed through the grating lens 205.
The light becomes converging or diverging light under the lens action of a, and is emitted from the mask 1 with its chief ray at a predetermined angle with respect to the normal line of the mask 1.

The light beams 207 and 208 that have been transmitted and diffracted through the alignment mark 205a are directed to the vertically downward direction 184 of the surface 2, respectively.
It has a focal point and a divergence origin at a point 7228 μm and 188.4545 μm vertically upward. The focal lengths of the alignment marks 205a at this time are 214.7228. -158
．． It is 4545 μm. Further, the distance between the mask 1 and the wafer 2 is 30 μm.The first signal light beam is transmitted and diffracted by the mark 205 of the alignment marks 205a before being overlapped, and is reflected by the alignment mark 203 on the wafer 2 surface.
It receives a concave lens effect due to the effect of the mark 203 before being superimposed in a, and the light is focused on one point on the surface of the sensor 211 serving as the first detection section. At this time, the amount of change in the incident position of the light beam onto the surface of the sensor 211 corresponds to the amount of positional deviation in the X direction of the alignment marks 205 and 203, that is, the amount of axial deviation, and the amount is expanded. becomes incident. As a result, the sensor 211 detects a change in the center of gravity position of the incident light beam.

In this embodiment, when the misalignment between the mask 1 and the wafer 2 is 0, that is, when the alignment mark 205 on the mask 1 and the alignment mark 203 on the wafer 2 form a coaxial system, the principal ray of the alignment light beam Output angle from 2 The incident surface projected component is 13 degrees, the xz in-plane projected component is 3 degrees, and the projected component of the emitted light onto the wafer 2 surface at this time is perpendicular to the scribe line width direction (X direction) The light is set to be focused on a predetermined position, for example, on the sensor 211 surface located at a height of 18.65711101 from the wafer 2 surface.

The second signal light beam is transmitted and diffracted by the alignment mark 206 of the alignment mark 205a before superimposition, and is reflected at the imaging point by the action of the alignment mark 204 of the alignment mark 203a on the second surface of the wafer before superimposition. The spot position is moved in a direction different from that of the first signal beam, and the outgoing angle in-plane component is 13 degrees, the xz-plane component is 13 degrees, and the sensor 212 serves as a second detection section.
The light is focused on one point on the surface.

By using the lens parameters of the alignment mark described above, the amount of displacement of the centers of gravity of the two signal beams on the detection unit with respect to the relative positional deviation between object 1 and object 2 can be set to be 100 times larger and in opposite directions. That is, the deviation magnification β, = -100, β2 =
It becomes +100. The amount of movement in the X direction of the light beam positions obtained on the sensors 211 and 212 gives the amount of alignment shift.

The distance in the X direction between the two light beam spots 211a and 212a when the misalignment is 0 is determined in advance from a design value or actual firing, and the two spots 211a are set accordingly.

The alignment deviation in the X direction is determined from the deviation of the distance value 212a from D.

This embodiment has the advantage of compensating for errors caused by the inclination of the object 2.3 in principle.

In this embodiment, if the wafer surface 2 is tilted by 1 mrad in the XZ plane of FIG.

On the other hand, the second signal beam 20 also has y
It has a plane of symmetry parallel to the z-plane and passes through an optical path with the same optical path length, so that the center of gravity shifts exactly the same as the signal light 207 on the sensor 212. As a result, if the sensor system performs signal processing to output the difference between the signals of the effective center of gravity position from each sensor, the output signal from the sensor system will not change even if the wafer surface is tilted in the yz plane.

On the other hand, when the wafer is tilted in the yz plane, the center of gravity of both the two signal beams 207 and 208 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 beams due to positional deviation, there will be no effective alignment error even if there are not two light beams.

Furthermore, when the alignment head, which contains the alignment light source, the light projecting lens system, the sensor, etc., changes its position with respect to the master wafer system, the position changes on a one-to-one basis. For example, if the head is moved in the direction of 5 μm with respect to the mask, the signal light will be transmitted 5 μm on the sensor 211.
This causes the effective center of gravity to shift, and in response to this, the
2, the center of gravity shifts by 5 μm in exactly the same way.

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

Furthermore, it can be seen that the variation in position in the z+I'qb direction does not result in an essential alignment error even if there are no two light beams.

In each of the above embodiments, the horizontal positions of the first object and the second object are detected using two light beams, an alignment light beam and a reference light beam.

In addition, the present invention uses two alignment marks provided on the first object and the second object to detect the positions of the first object and the second object in the horizontal direction as well as the positions of the opposing vertical direction. It is also possible to detect the distance between two objects.

For example, the first. The first one provided on the second object plane. An alignment signal for horizontal position detection is obtained from one type of second alignment mark, and a vertical interval signal is obtained from the other type of mark. Position detection can also be performed.

In this case, the reference signal is the first. The position of the second object may be obtained from another mark provided in the second alignment mark, or the position of the second object relative to the first object may be detected without using the reference signal. FIG. 7 is a schematic view of a main part of a sixth embodiment of the present invention, showing a part of the case where the distance between the object and the second object is detected.

This embodiment shows a case where the distance between the first object and the second object is detected using two distance detection marks 4 inn 5 out provided on the surface of the first object.

FIG. 17 is an enlarged schematic diagram of the vicinity of the first object and second object in FIG. 16.

16 and 17, 101 is a luminous flux, for example H,
-N, luminous flux from laser, semiconductor laser, etc., 10
2 is a plate-shaped first object, for example a mask, and 103 is a plate-shaped second object, for example a wafer.

4, n, and 5° are the first angles provided on a portion of the mask 102 surface. These physical optical elements 41 are the second physical optical elements.
．． ．． 5° is made up of, for example, a diffraction grating or a zone plate. 107 is a condensing lens, the focal length of which is f3, and 163 is an optical axis of the condensing lens 107.

Reference numeral 108 denotes a light receiving means, which is arranged at the focal point of the condensing lens 107, and is composed of a line sensor, a PSD, etc., and detects the center of gravity of the incident light beam.

Reference numeral 109 denotes a signal processing circuit, which uses the signal from the light receiving means 108 to determine the center of gravity of the light beam incident on the surface of the light receiving means 108, and calculates the position of the center of gravity of the light beam incident on the surface of the light receiving means 108, and as will be described later,
The distance d. is calculated and found.

Reference numeral 100 denotes an optical probe, which has a condensing lens 107, a light receiving means 108, and, if necessary, a signal processing circuit 109, and is movable relative to the mask 102 and the wafer 103.

In this embodiment, the luminous flux from the semiconductor laser LD is 10
1 (wavelength λ = 830 nm) on the first surface of the mask 102.
Fresnel zone plate (hereinafter abbreviated as FZP) 4□
. The light is incident perpendicularly to point A on the surface. and the first F
Diffracted light of a predetermined order is deflected, ie, diffracted, at an angle θ1 from ZP4+n, and is deflected, ie, reflected, at a point B (C) on the surface of the wafer 103. Of these, reflected light 131 is reflected light when the wafer 103 is located at position P1 with a distance d0 from the mask 102, and reflected light 132 is reflected light when the wafer 103 is displaced from position P1 by a distance JlIIda and is located at position P2. This is the reflected light.

Next, the reflected light from the wafer 103 is made incident on a point D (point E when the wafer 103 is at position P2) on the second FZP 5°1 surface on the first object 102 surface.

Note that the second FZP 5°ut has an optical function of changing the exit angle of the outgoing diffracted light according to the incident position of the incident light beam, like a condensing lens.

Then, diffracted light 161 of a predetermined order (diffracted light 162 when the wafer 103 is at position P2) diffracted at an angle θ2 from the second FZP 5° is guided onto the surface of the light receiving means 108 via the condensing lens 107. ing.

Then, the center of gravity of the incident light beam 161 (diffracted light 162 when the wafer 103 is at position P2) on the surface of the light receiving means 108 at this time is detected, and the mask 102 and the wafer 1 are
03 is calculated and determined.

In this embodiment, the first and second F provided on the surface of the mask 102
ZP4mm no 5out is configured with a known pitch set in advance, and the predetermined order (
For example, the diffraction angle θ1 of diffracted light of ±1st order). θ2 is determined in advance.

FIG. 18 shows the first image on the surface of the mask 102. Second FZP4i
, , 5°, and the relationship between the distance between the mask 102 and the wafer 103.

FIG. 18(A) shows the physical optical element 4. Figure 18 (B) is a top view of the physical optical element 4 inches.

18(C) is an explanatory diagram of the optical path passing through 5 out viewed from direction B, and FIG. 18(C) is an explanatory diagram similarly viewed from direction C.

In this embodiment, the first FZP4. . has the effect of simply bending the incident light, but it may also have a converging or diverging effect.

As shown in (A), (B), and ((:) in the same figure, the second FZP5゜ut has a structure in which the diffraction direction can be changed little by little depending on the location. For example, the point 111 is located between the mask 102 and the wafer 103. As the distance between the mask 102 and the wafer 103 increases, the transmission point of the outgoing light beam moves to the right in FIG. is set so that point 112 is transparent.

Although the FZP pattern does not have convergence or divergence power in the B direction in FIG.

In this embodiment, for the six directions, as shown in FIG. 16, the distance is 1 in the direction of the emission angle of 5°! The second FZP 5° is given convergence power so as to condense the light at a position of if,=1000 μm.

In FIG. 18, if the distance measurement range between the mask 102 and the wafer 103 is, for example, 100 μm to 200 μm, the 1° second FZP4. . ,
It is sufficient to set the size of the area at 5°.

Next, a method for determining the distance between the mask 102 and the wafer 103 will be explained using FIG. 16.

As shown in FIG. 16, if the distance from the intersection F of the diffracted light 161 and the diffracted light 162 to the mask 102 is fM, AD -2 dotan θI AE = 2(d, + da) tan θl.

, °, dM −DE −8E −AD −2d(
ltanθl --------(3)dy -2・fM
' tanθ2 -------- (4
). The interval is d. From d. The amount of movement S of the incident light on the surface of the light receiving means 108 when the height changes is S =
2・fs-tanθ2 --------
(5) According to equations (1), (2), and (3),

The deviation amount ΔS of the incident light beam on the surface of the light receiving means 108 with respect to the unit gap change amount between the mask 102 and the wafer 103, that is, the sensitivity ΔS is as follows.

In this embodiment, by detecting the positional deviation S of the incident light beam on the surface of the light receiving means 108, the distance 51 a a
Find this value d. Wafer 1 with respect to mask 102
The distance between the mask 102 and the wafer 103 is measured by determining the distance deviation amount from the predetermined distance position P1 of 03.

The mask 102 and the wafer 103 are first placed facing each other with a reference distance do therebetween, as shown in FIG. 18, for example. The interval do at this time is, for example, TM-23ON (
(trade name: manufactured by Canon Inc.).

In this embodiment, the first FZP4. . By imparting a deflection effect to bend the incident light, the following effects are obtained.

1st FZP4. . The angle θ1 of the emitted light is a parameter for setting the sensitivity ΔS as shown in equation (7). In a state where the first F Z P 4 in is not present and the transmitted light of the mask is used, this angle θ1 corresponds to the incident angle of the incident light to the mask, that is, the projection direction on the light source side. in this case,
The arrangement of the light projecting means is restricted in consideration of the sensitivity ΔS. First FZP4 with bending deflection action. . By providing a
The output angle of FZP4 + n can be easily adjusted to angle θ1, thereby increasing the degree of freedom on the light projecting means side.

In addition, in this embodiment, by making the size of the light beam incident on the first FZP4in larger than the size of the first FZP4+, , even if the incident light changes somewhat in the direction of the mask surface, the first The state of the luminous flux emitted from the F Z P 4 in is prevented from changing.

Sensitivity ΔS in this example is calculated from equation (7) when the focal length Knt s of the condensing lens 107 is 30 mm.
・ -15 (μm/μm) 1000 +0
0, and the luminous flux on the light receiving means 108 surface is 15% for a change per 1 μm of the distance between the mask 102 and the wafer 103.
It will move by μm. When a PSD with a positional resolution of 0.3 μm is used as the light receiving means 108, in principle, the position resolution is 0.3 μm.
It becomes possible to measure the distance between the mask 102 and the wafer 103 with a resolution of 0.2 μm.

In this embodiment, the diffracted light from the second physical optical element 5°ut for one position on the wafer 103 enters the condenser lens 107 at a specific angle with respect to the optical axis 163, and the light receiving means 108 Since the optical probe 100 is installed at the focal position of the optical axis 107, no matter where the optical probe 100 is installed on the optical axis 163, or even if it is slightly deviated in the direction perpendicular to the optical axis, the position of the incident light on the light receiving means 108 will remain unchanged. remains unchanged. This reduces measurement errors caused by fluctuations in the optical probe.

However, if the positional error of the optical probe 100 is allowed to some extent, or if a positional error occurs but is corrected by another means, the light receiving means 108 needs to be placed strictly at the focal point of the condensing lens 107. There isn't.

Incidentally, even if the embodiment shown in FIG. 16 is configured as shown in FIGS. 19(A) and 19(B) without using the condensing lens 107, the amount of light incident on the light receiving means 108 is higher than in the embodiment shown in FIG. Although the luminous flux becomes somewhat larger, the object of the present invention can be substantially achieved.

FIG. 19(A) is a schematic diagram of an embodiment in which the condenser lens 107 is omitted in the embodiment of FIG. 16.

FIG. 19(B) shows that the physical optical element 5° on the surface of the mask 102 in the embodiment of FIG. 19(A) has an optical function of emitting the incident light flux in a certain direction, and has a condensing function. This example shows an example in which the

Specifically, a physical optical element, a diffraction grating made of parallel, equally spaced linear gratings, etc. are used. In this case as well, the object of the present invention can be substantially achieved as in the embodiment of FIG. 19(A).

In the embodiment shown in FIG. 19(B), the diffraction grating 5° is omitted, and the light beam reflected from the wafer 103 is
02 may be transmitted, and a light receiving means may be arranged at a position to receive this transmitted light. Also, Figure 19 (A)
, (B) diffraction grating 4 on the incident side. . may be omitted, and the configuration may be such that the incident light beam from the light source LD is inclined with respect to the normal line of the mask surface even before it enters the mask 102.

Furthermore, please refer to Figure 19 (A) and (8)! Ha10
A diffraction grating is formed on the diffraction grating 4. . The diffraction light from the diffraction grating may be diffracted by the diffraction grating and guided in the direction of the diffraction grating 5° out.

FIG. 20(A) is a schematic diagram of a main part of a seventh embodiment of the present invention.

In this embodiment, the positions of the first object and the second object are detected in both the horizontal direction (lateral displacement direction) and the vertical direction (interval direction).

The same figure (B) is a schematic diagram showing the arrangement of the first alignment mark 5 on the first surface of the mask in the same figure (A), and the same figure (C) is the same figure (
FIG. 3 is a schematic diagram showing the arrangement of second alignment marks 3 on the second surface of the wafer in FIG.

A mark 5A for detecting a lateral shift signal and a mark 42 for detecting an interval are provided on the surface of the mask shown in FIG. 1B. , 42° are provided overlappingly in the same area to form the first alignment mark 5.

(Here, in indicates the input, and out indicates the output.) Also, only a mark 3A for detecting a lateral shift signal is provided as the second alignment mark 3 on the wafer 2 surface, and a mark 3A for detecting the interval is simply provided. It uses reflected 0th order diffracted light.

The horizontal position detection method is as follows.

The alignment light beam 7 transmits and diffracts the mark 5A on the mask 1 and reflects and diffracts the mark 3A on the wafer 2, so that the alignment light beam 7 is directed to a predetermined surface by an amount corresponding to the amount of misalignment between the mask and the wafer and an enlarged amount. The incident position changes.

That is, the misalignment of the optical axis between the mask and the grating lens on the wafer is magnified and converted by the magnification of the grating lens system as a misalignment of the center of gravity of the incident light beam by n times, and enters the light receiving @11 in the alignment head. and receiver 11
The center of gravity of the light beam is detected by

Now, the mask 1 and the wafer 2 are shifted by Δσ in the parallel direction, and the distance from the wafer 2 to the convergence point of the light beam reflected by the mark 3A on the wafer 2 is b. If the distance to the convergence point (or divergence origin) of the incident light beam is a, then the amount of gravity shift Δδ of the convergence point on the detection surface 11 is b Δδ=Δσx(-+1)・・・(
a). In other words, the center of gravity shift amount Δδ is (b / a +
1) Expanded twice.

For example, a = 0, 5 mm, b = 5011
If it is set to 101, the heavy strain amount Δδ will be expanded by a factor of 101 from equation (a).

In addition, the center of gravity shift amount Δδ and position shift amount Δσ at this time are (a
) As is clear from the equation, there is a proportional relationship. Detector 11
If the luminous flux incident position detection resolution is 0.1 μm, the positional deviation amount Δσ has a position resolution of o,oot μm.

If the second object is moved based on the positional deviation amount Δσ determined in this manner, the first object and the second object can be positioned with high precision.

The reference position on the detection surface 11 (the position of the center of gravity of the light beam when the first and second physical optical elements are in a state where there is no positional deviation) is determined as follows. First, for example, a mask having the first physical optical element 5A is fixed at an appropriate position. Next, for example, a wafer having the second physical optical element 3A is placed at an appropriate position with respect to the mask. At this time, the luminous flux is changed to the first. The light beam is made incident on the second physical optical element to detect the center of gravity position of the light beam on the detection surface 11 in this state. Next, in this state, for example, the pattern on the mask is transferred onto the wafer.

The transferred pattern is observed using another microscope, etc., and the amount and direction of the shift is measured. The obtained deviation amount and direction become the deviation Δσ of the second physical optical element in equation (a). Therefore (a
) Since it is possible to determine how much the center of gravity position of the luminous flux detected before was shifted from the reference position, that is, Δδ, the reference position is calculated backward from this Δδ and the detected center of gravity position.

The vertical direction detection (interval detection) method is as shown in Fig. 6.
This is similar to the example. Note that 39.40 is a sensor for detecting an interval.

FIG. 21(A) is a schematic diagram of a main part of an eighth embodiment of the present invention.

In this embodiment, the positions of the 'fJ1 object and the second object are detected in both the horizontal direction (lateral displacement direction) and the vertical direction (interval direction).

The same figure (B) is a schematic diagram showing the arrangement of the first alignment mark 5 on the first surface of the mask in the same figure (A), and the same figure (C) is the same figure (
FIG. 3 is a schematic diagram showing the arrangement of second alignment marks 3 on the second surface of the wafer in FIG.

In this example, a mask (first object) and a wafer (second object)
Each element is set so that when the position of the light receiving means 11゜12.39.40 changes, the two light beams incident on the surface of the light receiving means move in opposite directions, and the interval between the two light beams moving in opposite directions is This corresponds to the relative positional relationship between the two positions, so this is detected to perform highly accurate position detection. For this reason, in the figure, marks having respective functions are provided on the mask and the wafer, respectively.

On the surface of the mask shown in FIG. 1B, there is a mark 5A for detecting a lateral shift signal and a mark 42 for detecting an interval, which have sensitivities in opposite directions. r, IA, 42. , I.B.

42out IA and 42out IB are provided overlappingly in the same area to form the first alignment mark 5. (Here, in indicates the input, and out indicates the output.) Also, only a mark 3A for detecting a lateral shift signal is provided as the second alignment mark 3 on the wafer 2 surface, and a mark 3A for detecting the interval is simply provided. It uses reflected 0th order diffracted light.

The horizontal position detection method is the same as in the first embodiment shown in FIG. 1, and the vertical direction detection (interval detection) method is the same as in the sixth embodiment shown in FIG.

(Effects of the Invention) According to the present invention, the first object and the first object on the second object plane. By forming the second alignment mark by overlappingly forming a plurality of marks each having different optical properties in the same area as described above, it is possible to obtain a plurality of position detection signals from the same area. Thus, it is possible to achieve a position detection device that enables highly accurate position detection that is not affected by local warping or the like.

In addition, according to the above-mentioned embodiment, the first lens having the above-mentioned optical properties. A second alignment mark is provided on the first and second object planes, and the luminous flux passing through each mark is used to
When aligning the mask as an object and the wafer as a second object, the following effects can be obtained.

(b) Even if the center of gravity of the alignment light changes due to an inclination of the surface, uneven coating of the resist, or local inclination such as warpage during the exposure process, the reference signal light and alignment signal light will not match. By detecting the relative center of gravity position of the sea urchin, it is possible to accurately detect the positional deviation without being affected by the inclination of the surface of the sea urchin.

(0) Even if the position of the center of gravity of the alignment signal light on the sensor changes because the position of the alignment head changes relative to the mask, the relative center of gravity position of the reference signal light and alignment signal light cannot be detected. By doing so, it is possible to accurately detect the positional deviation between the mask and the wafer without being affected by the positional deviation of the alignment head.

(8) Furthermore, even if the gap between the mask and the wafer changes and the center of gravity position in the alignment detection direction on the signal light alignment sensor changes, the relative center of gravity position between the reference signal light and the alignment signal light is detected. This makes it possible to accurately detect positional deviations without being affected by gap fluctuations.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical system according to a first embodiment of the present invention, and FIGS. 2 and 3 are explanatory diagrams showing the principle of the optical operation in FIG. 1, respectively.
FIG. 4 is an explanatory diagram showing the relationship between the amount of positional deviation and the amount of center of gravity deviation in the present invention, FIG. 5 (8) and (B) are explanatory diagrams of the first alignment mark and the second alignment mark according to the present invention, 6th. FIG. 7 shows the second embodiment of the present invention. Schematic diagram of the optical system of the third embodiment, 8th. 9 is an explanatory diagram showing a modification of a portion of FIG. 1, FIG. 10 is a schematic diagram of a fourth embodiment when the present invention is applied to a semiconductor exposure apparatus using the proximity method, and FIG. 12th. FIG. 13 is an explanatory diagram of a positioning device using a conventional zone plate, FIG. 14 is a schematic diagram of a main part of a fifth embodiment of the present invention, and FIG. 15 is a position of the fifth embodiment of FIG. 14. 16 is an explanatory diagram showing the detection principle; FIG. 16 is a schematic diagram of the main part of the sixth practical example Mi showing how interval detection is performed in the present invention; and FIG. 17. 18th. FIG. 19 is an explanatory diagram of a part of FIG. 16, and FIGS. 20 and 21 are respectively 7. A schematic view of the main parts of the eighth embodiment, and FIGS. 22 to 24 are explanatory diagrams of the principle of the positional deviation detection method of the present invention. In the figure, 1,102 is the first object (mask), 2°103 is the second object (wafer), and s and 3 are the first objects, respectively. 2nd alignment mark, 7 is alignment light, 8 is reference light, 9,1
o is the scribe line, 11 is the first detection system (sensor),
12 is a second detection system (sensor). Diagram

Claims (7)

[Claims] (1) A first alignment mark is formed on a first object plane, a second alignment mark is formed on a second object plane, and the first alignment mark is deflected by both the first alignment mark and the second alignment mark. The position of the light beam is detected by a first detection means, and the obtained first signal and the light beam position of the second light beam, which is different from the first light beam and is deflected by the first alignment mark and the second alignment mark, are detected by a second detection means. When detecting the position of the second object with respect to the first object using both signals detected by the detection means and the second signal obtained, the first alignment mark and/or the second alignment mark are optically A position detection device comprising at least two marks with different properties overlappingly formed in the same area. (2) The two marks provided on the first alignment mark and/or the second alignment mark are both physical optical elements, and the first luminous flux and/or the second luminous flux are transmitted at least once by the physical optical element. 2. The position detecting device according to claim 1, wherein the position detecting device is subjected to a diffraction effect. (3) Using the first signal and the second signal, the position of the second object in the horizontal direction with respect to the first object placed facing each other was detected and/or the position detected in the vertical direction where both objects were placed facing each other. The position detection device according to claim 1, characterized in that: (4) A position detection object that is placed opposite to a predetermined object to perform position detection, and the position detection object has an optical beam for position detection in one area on its surface. 1. A position detection object characterized in that at least two types of marks having different optical properties that are subjected to an optical action are formed overlappingly. (5) forming a first alignment mark having a function as a physical optical element on a first object plane; forming a second alignment mark having a function as a physical optical element on a second object plane; The diffracted light generated when the light flux is incident on the alignment mark is made incident on the second alignment mark, the position of the light flux of the diffracted light from the second alignment mark is detected by the first detection means, and the obtained first signal and ,
A second detection means detects a beam position of a diffracted light different from the diffracted light among a plurality of diffracted lights generated from the first alignment mark or the second alignment mark, and a second signal obtained from the second detection means. A position detection device characterized in that the first object and the second object are positioned by using both signals as a reference signal. (6) The position according to claim 5, wherein the pattern of the first alignment mark or the second alignment mark is formed by overlapping a plurality of physical optical element patterns that generate light beams with different emission angles. Detection device. (7) The position detection device according to claim 5, wherein the diffracted light detected by the second detection means is a light beam that is not subjected to a lens action by the first or second alignment mark.