JP2000097633A - Device for detecting mark location and method for detecting mark location using the device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the effects of intensity irregularity of the noise and illumination of an optical system. SOLUTION: A device for detecting mark locations includes a light source 1 to generate coherent luminous flux, a half mirror 3 to divide the coherent luminous flux into reference luminous flux and luminous flux for measurement and to synchronize the return light of the above-mentioned reference luminous flux and the return light of the above-mentioned luminous flux for measurement, an objective lens 4 to guide the above-mentioned luminous flux for measurement to a mark 6 for location detection formed on a substrate 5, a Z-stage 13 on which the substrate 5 is placed, a Z-state control device 17 connected to the Z-stage 13, a CCD camera 11 to pick up the image of the luminous flux synthesized by the half mirror 3, and a computing means 12 for computing an interference image obtained by the CCD camera 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a mark position detecting device for detecting a position of a position detecting mark formed on an observation object with high accuracy, and a mark position detecting method using the same.

[0002]

2. Description of the Related Art Conventionally, as a method of detecting the position of a position detection mark formed on an observation object, for example, Japanese Patent Laid-Open No.
There is one as disclosed in Japanese Patent Application No. -283580. In this method, first, a microscope image of two measurement marks having different sizes formed by being superimposed on a wafer as an observation object is captured, and then converted into a digital image, and image processing is performed. Then, the position of each edge on the wafer is determined to determine the position of each measurement mark, and the errors are measured by superimposing them.

Further, there is a method as disclosed in Japanese Patent Application Laid-Open No. Hei 9-148663. In this method, a phase difference microscope is used as an optical system for detecting a mark on a substrate, which is an observation object, and signal processing is performed on the obtained intensity image to determine a mark position. Further, Japanese Patent Laid-Open No. 7-2392
As disclosed in Japanese Patent Laid-Open No. 12, there is also a method of using a so-called differential interference microscope for detecting the position of a concave / convex mark.

[0004]

In a method of detecting a mark position based on a normal intensity image (dark field image), image processing is performed on an intensity image showing a gradual change with respect to an actual structural change of an observed object. , The resolution obtained is limited. In addition, there is a problem that the detection sensitivity is reduced when the mark is made of the same material or when the step of the mark is small.

Therefore, in order to ensure high detection sensitivity even for such marks having the same material or a small step, it is conceivable to use a phase contrast microscope or a differential interference microscope. However, when using a phase contrast microscope or differential interference microscope, although the detection sensitivity is improved, the in-plane resolution on the observed object is the same as that using a normal intensity image because the phase information of the detected object is converted into intensity information. Stay on the order. further,
The method using the differential interference microscope has a problem that the detection sensitivity has a direction. Further, in any of the detection methods using the microscope, the intensity information and the phase information cannot be completely separated, and the problem remains that the information is easily affected by the noise of the optical system and the intensity unevenness of the illumination.

In view of the above-mentioned problems of the prior art, the present invention provides a mark position detecting apparatus which is not affected by noise of an optical system or unevenness of illumination intensity, and a detecting method using the same. With the goal. It is still another object of the present invention to provide a position detection device capable of detecting a mark position with high resolution and a detection method using the same.

[0007]

In order to achieve the above object, a mark position detecting apparatus according to the present invention comprises: means for generating a coherent light beam; and dividing the coherent light beam into a reference light beam and a measuring light beam. Beam splitting means, an objective optical system that guides the measurement light beam to a position detection mark formed on the observation object, a light beam synthesis means that synthesizes the measurement light beam and the reference light beam, and the light beam synthesis means. Interference measurement result analysis having an interference measurement device having means for imaging a combined light beam, and means for performing arithmetic processing on the interference measurement result obtained by the interference measurement device to form a phase image of the position detection mark And a phase image calculation device having calculation means for determining the position of the position detection mark from the phase image.

In the detection device according to the present invention, the interference measurement device executes an interference measurement process of performing interference measurement on the position detection mark, and the interference measurement result analysis device obtains the interference measurement process. Performing an interference measurement result analysis step of analyzing the obtained interference measurement result to form a phase image of the position detection mark, and calculating the phase image obtained in the interference measurement result analysis step in the phase image calculation device. The position of the position detection mark on the observation object plane is determined.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a means for generating a coherent light beam, a light beam splitting means for splitting the coherent light beam into a reference light beam and a measurement light beam, and applying the measurement light beam to an observation object. An objective optical system for guiding to the formed position detection mark,
A light beam combining unit that combines the measurement light beam and the reference light beam, an interference measurement device having a unit that captures an image of the light beam combined by the light beam combination unit, and an interference measurement result obtained by the interference measurement device. An interference measurement result analysis device having means for performing arithmetic processing to form a phase image of the position detection mark, and a phase image calculation device having operation means for determining the position of the position detection mark from the phase image It becomes possible by using the detecting device described above.

Specifically, the interference measurement device performs an interference measurement step of performing interference measurement on the position detection mark, and the interference measurement result analysis device performs an interference measurement result obtained in the interference measurement process. To perform a phase measurement result analysis process of forming a phase image of the position detection mark, and calculate the phase image obtained in the phase measurement analysis process in the phase image calculation device, The position of the use mark on the observation object plane can be determined. According to this detection method, in detecting the position of the position detection mark formed on the observation object, phase information obtained by separating the intensity information from the interference image is measured. It is possible to detect a mark position that is not received.

Further, when the mark position is detected by the method of the present invention, it is preferable that the position detection mark formed on the observation object has a shape such that a phase singularity is generated.
When an optical property discontinuity point (a step or a boundary between two different substances, etc.) exists on the surface of the observation object, a phase singularity may be generated in the vicinity of the discontinuity point. For example, C. Bouwhius, et.a
l, "Principles of Optical Disc Systems", Intern, Tren
s inOptics, Acad. Press (1991). The phase singularity is a point where the light intensity becomes zero. At the phase singular point, the value of the phase becomes indefinite, and the value of the phase changes abruptly in the vicinity thereof.

According to the simulation performed by the inventor, the phase singularity may not be generated depending on the structure and the material of the observation object. It did not appear when they met. Hereinafter, a model of the simulation and a result of the simulation will be described.

FIG. 9 shows a model of an observation object used in the simulation. This model has a period of 2 μm, a width of 1.5 μm, and an interval of 0.1 μm on a silicon oxide (SiO ₂ ) substrate 31.
Silicon nitride (Si ₃ N ₄ ) film 32 having a thickness of 5 μm and a thickness of 0.2 μm
Is formed. The refractive index n (SiO ₂ ) of the silicon oxide substrate 31 was 1.5, and the refractive index n (Si ₃ N ₄ ) of the silicon nitride film 32 was 2. Then, a plane wave of polarized light having a parallel electric field (in a direction perpendicular to the paper surface) having a wavelength λ of 0.63 μm and a parallel (perpendicular to the paper) is vertically incident on the observation object along the groove 33 from above. In this state, the observation object has a numerical aperture of 0.
Observation with the objective lens No. 9 reveals that a singular point appears when focusing on a position of about 0.08 μm downward from the upper surface of the silicon oxide substrate 31.

FIG. 10 shows the observed object shown in FIG.
± 0.4μ from the vertical position z ₀ where the phase singularity appears
10 is a graph showing a state of a change in a phase distribution measured by the objective lens when the focal position of an objective lens having a numerical aperture of 0.9 is changed every 0.1 μm within the range of m. In this graph, the vertical axis indicates the phase, and the horizontal axis indicates the horizontal position of the step on the observation object surface. Z ₀₊ indicates a position slightly above the phase singularity, and z ₀₋ indicates a position slightly below the singularity. A point on the horizontal axis corresponding to a portion where the phase value changes substantially vertically in z ₀₊ and z ₀₋ represents the position on the observation object plane where the phase singularity occurs.

As is clear from the graph of FIG. 10, when the focal position of the objective lens moves downward from above through z ₀ , the phase jump at the position z ₀ of the phase singularity increases by +1.
It changes from 80 ° to -180 °. This is because the phase jumps are mathematically equivalent at + 180 ° and −180 °. However, since the origin of the phase axis can be set arbitrarily, here, for convenience of explanation, as shown in FIG.
The point was taken as the root of the phase jump at the phase singularity at z ₀ . FIG. 11 is a partially enlarged view of FIG.

In the graph shown in FIG. 10 or FIG. 11, when the focal point of the objective lens is at z ₀ and its vicinity, a sharp phase change is observed. Theoretically, the size of the phase singularity is infinitesimal. However, even when the focal point of the objective lens slightly deviates from z ₀ , for example, when the focal point deviates from z ₀ by 0.1 μm, the phase value is changed from 150 ° to 3 °.
It shows a steep change in which the width of change to 0 ° is 0.05 μm or less. This is the resolution of the intensity image of the objective lens (0.61
.Lambda. / NA = 0.4 .mu.m). Therefore, if the position detection mark formed on the observation object is shaped to generate a phase singularity, and this phase singularity is observed, high-resolution measurement far exceeding the resolution of a normal optical system can be performed. Will be possible.

As a result of examining the results of the above simulation in more detail, it has been found that the position where the phase singularity occurs on the surface of the observation object does not always coincide with the optical physical discontinuity of the observation object. For this reason, if the mark position is determined based on the occurrence position of the phase singularity, an error is generated, albeit slightly, by the deviation. Therefore, in order to solve such a problem, it is preferable that the observation object including the position detection mark has at least one or more cross sections having a shape symmetrical with respect to a symmetry axis parallel to the optical axis. That is, as shown in FIG. 9, it is preferable that the cross section of the observation object is symmetrical about the symmetry axis B parallel to the optical axis. Because, when the position detection mark thus formed is measured, the obtained phase image is also symmetric. In other words, even if the occurrence position of the phase singularity is very slightly shifted from the optical property discontinuity, it will be symmetrically shifted about the axis of symmetry. Therefore, if the average of the occurrence positions of the phase singularities is regarded as the mark position, the position can be detected with high error-free resolution.

Further, if the phase image calculation device of the apparatus of the present invention is provided with a means for binarizing the phase image, and a step of binarizing the phase image is added to the detection procedure by such a device, it can be performed in a shorter time. The position of the position detection mark on the observation object plane can be obtained. Further, even if a method of taking the differential value of the phase image is adopted instead of performing the binarization of the phase image,
The position of the position detection mark on the observation object plane can be obtained in a short time. Further, if the position detection mark is formed by superimposing a plurality of marks and the respective mark positions are detected, it is possible to detect a shift between the marks. In addition, if the shape of the position detection mark is square, it is easy to detect positional deviation in two orthogonal directions.

In the apparatus of the present invention, when the projection magnification of the position detection mark onto the image pickup means is m, the position detection mark is projected onto the image pickup means at a size of m times. In order to detect the position of the position detection mark with the resolution Δ, it is necessary to image the detected interference fringes at intervals equal to or smaller than m × Δ. Accordingly, the following relationship is established between the arrangement distance d of the image sensor, the projection magnification m of the position detection mark onto the imaging means, and the resolution Δ required for mark position detection: d ≦ m × Δ (1) Must be established. In practice, the required resolution Δ and the arrangement interval d of the image sensor are often determined first, so that in most cases, the projection magnification m is set so as to satisfy m ≧ d / Δ (2) Will be adjusted.

Only when the relational expression (2) is satisfied, it becomes possible to obtain a phase change in a minute area which is about the same as or less than the resolution Δ required in the position detection mark detection method. Therefore, when the relational expression (2) is satisfied, the phase image can be measured with high resolution, and the mark position can be detected with high resolution.

Whether or not a phase singular point appears depends on parameters such as the shape of the position detection mark and the wavelength of illumination light emitted from the light source. Therefore, there may be a situation in which when a position detection mark having a certain shape is illuminated with light of a certain wavelength, a phase singularity is generated and is not generated with light of another wavelength. For this reason, when only the illumination light of a single wavelength is used, the shape of the position detection mark where the phase singularity occurs is limited. Therefore, in the apparatus of the present invention, any one wavelength can be selected from the coherent light beams having a plurality of different wavelengths, thereby enabling position detection of position detection marks having various shapes.

Hereinafter, the present invention will be described in detail with reference to examples.

First Embodiment FIG. 1 is a diagram showing a configuration of a mark position detecting device according to the present embodiment. As shown in FIG. 1, the apparatus of the present embodiment includes a helium-neon laser light source 1, a condensing lens 2, and a light beam from the light source 1 transmitted through the condensing lens 2 as a first light beam and a second light beam. And a half mirror 3 for dividing the light into a half mirror.

An objective lens 4 of infinity design and a Z stage 13 are arranged on the optical path of the first light beam split by the half mirror 3. The objective lens 4 is arranged such that the position where the first light beam is condensed by the condenser lens 2 is on the pupil side surface of the objective lens 4. The substrate 5 on which the position detection marks 6 are formed is placed on the Z stage 13. Z stage 1
3 is connected to a Z stage control device 17. In the drawing, the z direction indicates a direction along the optical axis of the objective lens 4.

On the other hand, an objective lens 7 of infinity design and a reference mirror 8 are arranged on the optical path of the second light beam. The objective lens 7 is arranged such that the position where the second light beam is focused by the condenser lens 2 is on the pupil plane of the objective lens 7. A piezo element 9 for moving the reference mirror 8 in a direction along the optical axis of the objective lens 7 is connected to the back side of the reference mirror 8.
The piezo element 9 is controlled by a piezo element driving device (not shown).

Further, an imaging lens 10 is arranged on an optical path which is traced after the return light from the position detection mark 6 and the return light from the reference mirror 8 are combined by the half mirror 3,
The CCD camera 11 is arranged so that the image receiving surface of the CCD camera 11 is located at the rear focal position of the imaging lens 10. The focal position of the imaging lens 10 on the side of the CCD camera 11 is referred to as a rear focal position. In addition, the CCD camera 11 is connected to a calculating means 12 so that the image picked up by the CCD camera 11 can be calculated.

In the mark position detecting device of the present embodiment configured as described above, the light beam emitted from the light source 1 is condensed by the condensing lens 2 and is incident on the half mirror 3.
It is split into a first light beam and a second light beam. The first light beam split by being reflected by the half mirror 3 is condensed on the pupil plane of the objective lens 4 and converted into a parallel light beam by the objective lens 4 to illuminate the position detection mark 6 on the substrate 5. I do. The return light from the position detection mark 6 passes through the objective lens 4 again and enters the half mirror 3. On the other hand, the second light beam split by passing through the half mirror 3 is condensed on the pupil plane of the objective lens 7, converted into a parallel light beam by the objective lens 7, and illuminates the reference mirror 8. The return light from the reference mirror 8 passes through the objective lens 7 again and enters the half mirror 3.

The return light from the position detection mark 6 and the return light from the reference mirror 8 are combined by the half mirror 3, enter the imaging lens 10, and are condensed on the image receiving surface of the CCD camera 11. The interference fringe is imaged by the camera 11. At this time, the reference mirror 8 is moved by a small amount in the direction along the optical axis of the objective lens 7 by the piezo element 9 to change the phase difference between the first light beam and the second light beam to generate a plurality of interference fringes. The position detection mark 6 is obtained by capturing the
Can be measured (phase shift measurement).
A method of calculating a phase image from a measurement result in the phase shift measurement is known, and thus a description thereof will be omitted.

Next, the structure of the position detecting mark 6 is shown in FIG.
A description will be given based on (a) and (b). FIG. 2A is a diagram showing the shape of the substrate 5 on which the position detection marks 6 are formed as viewed from the objective lens 4 shown in FIG. FIG.
2B is a diagram illustrating a cross-sectional shape of the substrate 5 including the position detection marks 6 along the xz direction and the yz direction illustrated in FIG. 1. As shown in FIGS. 2A and 2B, the position detection mark 6 is a square depression formed in the center of the surface of the substrate 5, and the substrate 5 on which the position detection mark 6 is formed is x.
It has a cross-sectional shape that is symmetrical about a symmetry axis B parallel to the optical axis in the −z cross section and the yz cross section. It is preferable that the position detection mark 6 is formed in a shape in which a phase singularity occurs.

Hereinafter, the measurement procedure will be described. When performing the measurement, the wavelength of the light emitted from the light source 1 is determined in advance.
A simulation is performed based on the numerical aperture of the objective lens 4, the complex refractive index of the substrate 5, and the like, and the width and depth at which a phase singular point in the position detection mark 6 occurs are obtained. At this time, the shift amount between the occurrence position of the phase singularity and the upper surface position of the position detection mark 6 in the z direction in FIG. 1 is further obtained, and this is recorded in the Z stage controller 17.

Then, the position detecting mark 6 is illuminated by the light beam from the light source 1. At this time, a cover (not shown) is inserted into the optical path between the half mirror 3 and the reference mirror 8,
The illumination light beam from the light source 1 is prevented from entering the reference mirror 8. In this state, an intensity image of the position detection mark 6 is captured by the CCD camera 11. Next, the CCD camera 11
Is displayed on an image display device (not shown), a signal is sent from the Z stage controller 17 while viewing the image, and the Z stage 13 is moved to focus on the upper surface of the position detection mark 6. Alternatively, focusing on the upper surface of the position detection mark 6 may be performed using an automatic focusing mechanism (not shown). Further, the Z stage 13 is moved by the amount of shift between the position of occurrence of the phase singularity stored in the Z stage controller 17 in the preliminary stage described above and the upper surface of the position detection mark 6. Then, the cover arranged in the optical path between the half mirror 3 and the reference mirror 8 is removed.

After the positioning of the observation object is completed through the above procedure, the phase shift is measured. First, the piezo element 9 is controlled to move the reference mirror 8 in a direction along the optical axis of the objective lens 7. At this time, the reference mirror 8 is moved to five positions at a distance of 1/8 of the wavelength of the light emitted from the light source 1, and the interference image at each position is transferred to the CCD camera 11
To image. The position of the position detection mark 6 is detected by the arithmetic unit 12 based on the five interference images captured here.

Next, a method of determining the position of the position detecting mark 6 from the phase image will be described with reference to FIGS. The solid line in the graph shown in FIG. 3 represents the cross-sectional shape in the x direction of the phase image obtained by the above-described processing. When the binarization is performed on the phase image of FIG. 3 with reference to the threshold φ ₀ , the result shown in FIG. 4 is obtained. In FIG. 4, x _a and x _b indicate the positions of the phase singularities in the x direction of the phase image of FIG. From the positions x _a and x _{b of the} phase singularity, (x _a +
_xb ) / 2 is determined, and this value is determined as the position of the position detection mark 6 in the x direction. Further, the position of the position detection mark 6 in the y direction can be determined by performing the same processing on the cross section of the phase image in the y direction.

In this embodiment, since the position detection mark 6 is measured at the focal position where the phase singularity occurs, a phase image showing a rapid change corresponding to the structure is obtained.
Therefore, the position of the position detection mark 6 can be measured with high resolution almost without being affected by the setting of the threshold value φ ₀ .

[0035] In the description so far, helium neo
Although the use of a laser was shown,
Light source, such as an argon ion laser
Or a combination of a mercury lamp and a narrow band filter
May be. Also, the position detection mark 6 is formed in a square.
As described above, the shape of the position detection mark 6 is described.
Is not limited to squares, but rectangles and other shapes
Shape. Structure of position detection mark 6
Also explained using an example in which a step is formed on the substrate surface,
The position detection mark 6 has another structure, for example, a different material.
It is like the surface is flat with the boundary line
There may be.

[0036] In the present embodiment, the position detection mark 6
Is assumed to have a shape that generates a phase singularity.
However, the present invention is not limited to this.
The same applies to position detection marks that do not
The same effects can be obtained. In this case, simulation
Phase image in the direction along the optical axis of the objective lens 4
Find a position that changes rapidly, and the position detection mark
Place the formed substrate and measure, follow the procedure described above.
What is necessary is just to carry out the process. However, in this case, the phase singularity
Since no points are generated, the obtained phase image changes slightly
Although it becomes a kana, measure the phase image after separating the intensity image
The illumination intensity.
The advantage is that there is no change.

[0037] In this embodiment, the phase measurement is used as the interference measurement method.
Ft measurement method, but is not limited to this.
Use other methods, such as heterodyne interferometry
Can also. When using heterodyne interferometry,
Of the frequency of the light beam illuminating the color
Make the frequency of the luminous flux different from that of the
The interference signal will be detected. Here, the circumference of both luminous fluxes
Although there are various methods for making the wave number different,
In the device configuration, the reference mirror 8 is moved at a constant speed to the objective lens 7.
Moving in the direction along the optical axis of the
realizable. However, in this case, the imaging means is a CCD camera
Change to a camera with a faster image capture speed instead of 11
There is a need.

[0038] In this embodiment, the position is detected from the phase image.
As a method of determining the position of the use mark 6, the binary
To find the position of the phase singularity and take the average value
Although a method has been shown, other methods can be used. example
For example, at the phase singularity, the phase value changes rapidly,
When the derivative of the image is calculated, it is extremely large
Value is obtained. Therefore, taking the derivative of the phase image
And the phase singularity can be determined by
Determining the position of the position detection mark 6 by taking
Can be.

Second Embodiment FIG. 5 is a diagram showing the configuration of a mark position detecting device according to the second embodiment . As shown in FIG. 5, the apparatus according to the present embodiment includes a multi-wavelength simultaneous oscillation argon ion laser light source 21, a wavelength selection filter 22, a condenser lens 2, and a light beam from the light source 21 transmitted through the condenser lens 2. Is provided with a half mirror 23 for deflecting the light toward the observation object. Several kinds of wavelength selection filters 22 having a property of transmitting only a light flux near a predetermined wavelength with respect to a plurality of wavelengths emitted from the light source 21 are prepared, and one of them is used according to the wavelength used for measurement. I do.

On the optical path of the light beam deflected by the half mirror 23, a Michelson type interference objective lens 24 is arranged. The interference objective lens 24 includes an objective lens 25, a half mirror 26 that divides a light beam from the light source 21 into a first light beam and a second light beam, and a reference mirror 27. The objective lens 25 is arranged such that the light beam condensing position from the light source 21 condensed by the condenser lens 2 is on the pupil plane of the objective lens 25. The Z stage 13 is disposed on the optical path of the first light beam split by the half mirror 26, and the position detection marks 28 and 30 are provided on the Z stage 13.
The substrate 5 on which is formed is placed. The z direction in the drawing indicates a direction along the optical axis of the objective lens 25. on the other hand,
A reference mirror 27 is arranged on the optical path of the second light beam split by the half mirror 26, and the inclination with respect to the optical axis split by the half mirror 26 can be adjusted by a stage mechanism (not shown). The Z stage 13 is connected to a Z stage controller 17.

On the optical path along which the return light from the position detection marks 28 and 30 passes through the half mirror 23,
Imaging lens 10, magnifying lens 29, CCD camera 1
1 is arranged. At this time, the magnifying lens 29 is arranged so that the rear focal position of the imaging lens 10 and the image receiving surface of the CCD camera 11 are conjugate to each other. The imaging lens 10
Is referred to as the rear focal position. An arithmetic unit 12 is connected to the CCD camera 11.

In the apparatus of the present embodiment, all the lenses used in each optical system are capable of favorably correcting aberrations in a range of a plurality of wavelengths emitted from the light source 21.

In the mark position detecting device of the present embodiment configured as described above, only the wavelength used for measurement is selected and transmitted by the wavelength selection filter 22 for the light beam emitted from the light source 21, And is incident on the half mirror 23. This light beam is reflected and deflected by the half mirror 23, condensed on the pupil plane of the objective lens 25, converted into a parallel light beam by the objective lens 25, and enters the half mirror 26. The light beam incident on the half mirror 26 is split into a first light beam and a second light beam. The first light flux transmitted through the half mirror 26 illuminates the position detection marks 28 and 30 on the substrate 5. On the other hand, the second light flux reflected by the half mirror 26 illuminates the reference mirror 27. The return light from the position detection marks 28 and 30 and the return light from the reference mirror 27 are combined by the half mirror 26, and sequentially pass through the lens 25, the half mirror 23, the imaging lens 10, the magnifying lens 29, and the CCD camera 11. And an interference image is captured.

Here, assuming that the resolution required for the mark position detecting device is Δ, the distance between the arrangement distance d of each image sensor and the total magnification m of the optical system is m ≧ d / Δ (2) As described above, it is preferable that the relational expression (3) is satisfied. Therefore, in the apparatus according to the present embodiment, the CCD camera 11 in which the arrangement intervals of the mounted image pickup devices are 11 μm is used, and when the resolution required for the mark position detection device is 0.05 μm, the objective lens 24 is used. If the magnification of the imaging lens 10 is 100 times and the magnification of the magnifying lens 29 is 5 times, the above-mentioned relational expression (2) can be satisfied.

Next, the structure of the position detecting marks 28 and 30 will be described with reference to FIGS. 6 (a) and 6 (b). FIG. 6A is a diagram showing the shape of the substrate 5 on which the position detecting marks 28 and 30 are formed as viewed from the interference objective lens 24 shown in FIG. FIG. 6B shows the xz direction and the y-direction shown in FIG.
Substrate 5 including position detecting marks 28 and 30 along the z direction
It is a figure which shows the cross-sectional shape of. In this embodiment, the layer 14 is formed on the substrate 5, and the position detection mark 28 formed of a square depression is formed by pattern exposure and etching. Further, a layer 1 is provided inside the position detecting mark 28.
5 is formed, and a position detecting mark 30 having a square convex shape is formed by pattern exposure and etching. At this time, the heights of the upper surfaces of the position detection marks 28 and 30 match. Further, the xz plane of the position detection mark 28, y
The cross-sectional shape on the −z plane is bilaterally symmetric, and the same applies to the position detection mark 30. In the ideal case, the symmetry axes of the position detection marks 28 and 30 coincide with the symmetry axis B in FIG. 6, but may actually differ from the symmetry axis B.

In this embodiment, the position detecting marks 28, 3
The shape of 0 is determined based on the result of the simulation. First, a simulation is performed on light of a wavelength having a large output, for example, light of 488 nm, out of a plurality of wavelengths of light emitted from the light source 21 to determine a width and a depth at which a phase singularity occurs. Then, from this result, the width at which the phase singularity occurs,
The depth position detection marks 28 and 30 are formed. At this time, the shift amount between the position where the phase singularity occurs and the upper surface of the position detection mark 28 in the z direction shown in FIG.

By the way, the position detecting marks 28 and 30 that can be formed can be formed due to restrictions on the processing of the layers 14 and 15.
In some cases, the phase singularity does not occur in the shape of. In this case, while changing the light emitted from the light source 21 to another wavelength, a simulation is performed with the shape of the position detection marks 28 and 30 that can be formed, and the wavelength at which a phase singularity occurs and the position detection marks 28 and 30 Find the shape. Then, the shift amount between the position where the phase singularity occurs and the upper surface of the position detecting mark 28 in the z direction shown in FIG. 5 is recorded in the Z stage controller 17.

Hereinafter, the measurement procedure will be described. First,
The position detection marks 28 and 30 are illuminated by the light beam transmitted through the wavelength selection filter 22, and the position detection marks 28 and 30 are illuminated.
After focusing on the upper surface of the Z stage 13, the Z stage 13 is moved by the amount of shift between the position of occurrence of the phase singularity stored in the Z stage controller 17 in the preliminary stage and the upper surface of the position detection mark 28. To end the positioning of the observation object.
After the positioning, the interference measurement is performed. As a method of the interference measurement and a method of obtaining a phase image from the interference measurement result, for example, a Fourier transform method can be used, and details thereof are described in “Optics, Vol. 13, No. 1, page 59-60. Therefore, the description here is omitted.

Next, the reference mirror 27 is tilted by a small angle θ in a direction perpendicular to the optical axis divided by the half mirror 26 by a stage mechanism (not shown), so that the first light flux and the second light flux are interposed. An interference fringe is generated in which the interference fringe due to the inclination of the wavefront and the phase change due to the position detection mark 28 are superimposed. The interference fringes are imaged by the CCD camera 11. Thereafter, a phase image is obtained by performing signal processing as described on pages 59 to 60 of “Optics, Vol. 13, No. 1,” on one interference image picked up by the CCD camera 11. be able to.

Further, the position detection mark 2 is obtained from the phase image.
7 and 8 are used to determine the positions of 8, 30.
Will be described. The solid line in the graph shown in FIG.
Represents a cross section in the x direction of the phase image obtained by the above. Ma
In addition, a threshold φ for the phase image shown in FIG.₁Based on
When binarization is performed, a result as shown in FIG. 8 is obtained. phase
Singular point position x_c, X_fTo x_g= (X_c+ X_f) / 2
Of the position detection mark 28 in the x direction.
Determine the position. Or coordinate x_d, X_eTo x _h=
(X_d+ X_e) / 2 is calculated and this is used as the position detection marker.
It may be determined as the position of the mark 30 in the x direction. Position detection
Regarding the positions of the arks 28 and 30 in the y direction, the phase image y
By performing the same processing for the cross section in the direction
be able to. Also, (x_g-X_h) To calculate
The process for forming the position detection mark 28 and the position detection
The amount of misalignment with the formation process of the workpiece 30
Can be.

In this embodiment, since the Fourier transform method is employed as the phase measuring method, the positions of the position detecting marks 28 and 30 can be detected from one interference image, and the measuring time can be reduced. . In addition, since means for selecting illumination light having a wavelength to be used for measurement from a plurality of wavelengths is provided, phase singularities can be observed for a wide range of shapes of the position detection marks 28 and 30, and measurement with high resolution is possible. Become. further,
Since the interference objective lens 24 is used, a portion split into the first light beam and the second light beam is shortened, and a device resistant to vibration can be realized. Further, since the magnification of the optical system is set so as to satisfy the relationship of m ≧ d / Δ, measurement with higher resolution is possible.

In the present embodiment, a method of exchanging the wavelength selection filter according to the light of the wavelength to be used has been described, using an argon ion laser of multi-wavelength simultaneous oscillation as the light source 21, but other methods, for example, a frequency variable semiconductor A method using a laser or a method of preparing a plurality of lasers having different wavelengths and selecting a laser having a desired wavelength from among them may be employed.

In this embodiment, an example is shown in which the position where the phase singularity occurs in the phase image is known. However, even in the case where the position where the phase singularity occurs is unknown, the apparatus of this embodiment can be used. It is possible to respond. In this case, after focusing on the upper surfaces of the position detection marks 28 and 30, the Z stage 13 is gradually moved in the z direction in the vicinity thereof to obtain phase images at each position, and the phase images are obtained. The measurement may be performed at the position in the z direction at which the steepest phase change appears.

Further, in this embodiment, the case where the light beam illuminating the position detecting marks 28 and 30 is a parallel light is described, but the present invention is not limited to this, and may be, for example, a condensed light. In this case, the condenser lens 2 may be replaced with a lens having a different focal length or removed from the optical path according to the convergence angle of the illumination light.

As described above, the present invention has the following features (1) to (11) in addition to the features described in the claims.

(1) The mark position detecting method according to claim 2, wherein position detection is performed on a position detecting mark formed in a shape where a phase singularity occurs.

(2) The phase image calculation device obtains an average of positions on the observation object plane of phase singularities in a cross section of the observation object including the position detection mark, which are symmetric with respect to a symmetry axis parallel to the optical axis. 2. The mark position detecting device according to claim 1, further comprising means.

(3) Measurement is performed on a cross section of an observation object including a position detection mark having a shape where a phase singularity is generated, which is symmetrical with respect to an arbitrary symmetry axis parallel to the optical axis. A mark position detecting method using the mark position detecting device according to the above (2).

(4) The mark position detecting device according to claim 1, wherein the phase image calculating device includes means for performing a binarization process of the phase image.

(5) The interference measurement device performs an interference measurement process of performing interference measurement on the position detection mark, and the interference measurement result analysis device analyzes the interference measurement result obtained in the interference measurement process. Performing an interference measurement result analysis step of forming a phase image of the position detection mark, and performing a binarization of the phase image obtained in the interference measurement result analysis step in the phase image calculation device. The mark position detection method using the mark position detection device according to (4), wherein the position of the mark on the observation object plane is determined.

(6) The mark position detecting device according to claim 1, wherein the phase image calculating device includes means for calculating a differential value of the phase image.

(7) The interference measurement device performs an interference measurement process of performing interference measurement on the position detection mark, and the interference measurement result analysis device analyzes the interference measurement result obtained in the interference measurement process. Performing an interference measurement result analysis step of forming a phase image of the position detection mark, and taking the differential value of the phase image obtained in the interference measurement result analysis step in the phase image calculation device to obtain the position detection mark. A mark position detecting method using the mark position detecting device according to (6), wherein the position on the observation object plane is determined.

(8) When the image pickup means has a plurality of image pickup elements, the arrangement interval of each image pickup element is d, the resolution required for the mark position detecting device is Δ, and the total magnification of each optical system is m. 2. The mark position detecting device according to claim 1, wherein the following relational expression is satisfied. m ≧ d / Δ

(9) The interference measuring means includes means for generating a plurality of coherent light beams having different wavelengths, and means for transmitting any one wavelength from the plurality of coherent light beams having different wavelengths. The mark position detecting device according to claim 1, wherein

(10) The mark position detecting method according to claim 2, wherein position detection is performed on a position detecting mark formed by superposing a plurality of marks.

(11) The mark position detecting method according to claim 2, wherein position detection is performed on a position detecting mark composed of two squares having different sizes.

[0067]

As described above, according to the present invention, in order to obtain the phase image of the position detection mark, the intensity information can be completely separated from the interference image, and the noise of the optical system and the intensity unevenness of the illumination can be obtained. The position of the position detection mark which is not affected by the above can be detected. Further, since a position detection mark having a shape in which a phase singularity occurs is used for measurement, a sharp phase change appears in the phase image, and the position of the position detection mark can be detected with high resolution.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a mark position detection device according to a first embodiment.

2A is a diagram showing a shape of a substrate 5 on which a position detection mark 6 is formed as viewed from the objective lens 4 shown in FIG. (B) shows the xz direction and y-direction shown in FIG.
FIG. 3 is a diagram showing a cross-sectional shape of a substrate 5 including a position detection mark 6 along the z direction.

FIG. 3 is a graph for explaining a method for detecting the position of a position detection mark 6 from a phase image in the first embodiment.

FIG. 4 is a graph for explaining a method for detecting the position of a position detection mark 6 from a phase image in the first embodiment.

FIG. 5 is a diagram illustrating a configuration of a mark position detection device according to a second embodiment.

6A is a view showing the shape of a substrate 5 on which position detection marks 28 and 30 are formed as viewed from the interference objective lens 24 shown in FIG. (B) is xz shown in FIG.
Detection marks 28, 3 along the direction and the yz direction
FIG. 4 is a view showing a cross-sectional shape of the substrate 5 including 0.

FIG. 7 is a graph for explaining a method of detecting the position of the position detection mark 6 from the phase image in the second embodiment.

FIG. 8 is a graph for explaining a method of detecting the position of the position detection mark 6 from the phase image in the second embodiment.

FIG. 9 is a diagram showing a structure of a model of an observation object.

FIG. 10 is a graph showing a change in a phase distribution appearing when the model of the observation object shown in FIG. 9 is measured.

11 is a partially enlarged view of the graph shown in FIG.

[Explanation of symbols]

 1, 21 light source 2 condenser lens 3, 23, 26 half mirror 4, 7, 25 objective lens 5 substrate 6, 28, 30 position detection mark 8, 27 reference mirror 9 piezo element 10 imaging lens 11 CCD camera 12 arithmetic Means 13 Z stage 14, 15 Layer 17 Z stage control means 22 Wavelength selection filter 24 Interference objective lens 29 Magnifying lens 31 Silicon oxide substrate 32 Silicon nitride substrate

Claims (2)

[Claims] 1. A means for generating a coherent light beam, a light beam splitting means for splitting the coherent light beam into a reference light beam and a measurement light beam, and a device for detecting the position of the measurement light beam formed on an observation object An interference optical system comprising: an objective optical system for guiding to a mark; a light beam combining means for combining the measuring light beam and the reference light beam; and a means for imaging the light beam combined by the light beam combining means; An interference measurement result analysis device having means for calculating the interference measurement result obtained by the apparatus to form a phase image of the position detection mark; and an operation means for determining the position of the position detection mark from the phase image And a phase image calculation device having the same. 2. An interference measurement process for performing interference measurement on the position detection mark in the interference measurement device, and analyzing the interference measurement result obtained in the interference measurement process in the interference measurement result analysis device. Performing an interference measurement result analysis step of forming a phase image of the position detection mark, and calculating the phase image obtained in the interference measurement result analysis step in the phase image calculation device to observe the position detection mark. 2. A mark position detecting method using the mark position detecting device according to claim 1, wherein the position on the object plane is determined.