DE102020116790B4 - Method of determining misalignment and alignment apparatus for aligning two flat objects relative to each other - Google Patents

Abstract

The invention relates to a method for determining a misalignment of (a) a first flat object (12) having a first marking (16) and (b) a second flat object (14) having a second marking (18). According to the invention it is provided that (c) the first marking (16) has a first extent (D16) and the second marking (18) has a second extent (D18) relative to one another, with the steps: (i) Bringing the first marking (16) and the second marking (18) into a focus (F) of a laser beam (28) of laser light, so that scattered laser light is produced by scattering, (ii) allowing the scattered laser light to interfere with direct laser light that is not present at any of the markings has been scattered so that a measuring laser beam (32) is formed, (iii) moving the first flat object (12) relative to the focus (F) and/or relative to the second flat object (14) and (iv) measuring a first Intensity (11) of a first part of the measuring laser beam (32.1) by means of a first detector (34) and a second intensity (I2) of a second part of the measuring laser beam (32.2) by means of a second detector (34) depending on the position of the flat objects relative to each other so that the marking ments are aligned with one another, (v) the laser light having a lasing wavelength and the extents being smaller than the lasing wavelength.

Description

In the manufacture of semiconductor devices, it is necessary to align two flat objects relative to each other. The first object is a wafer, and the second object is a mask, for example, which must be positioned as precisely as possible relative to the wafer.

It's from the DE 37 19 539 A1 and the U.S. 5,465,148 A known to provide each of the two flat objects with a marking in the form of a grid, by means of which the objects are aligned relative to one another. If the gratings are shifted relative to each other, a different diffraction pattern results than the diffraction pattern that results when the two flat objects are properly aligned.

A disadvantage of this method is the comparatively long measuring time caused by the low sensitivity. In all methods, it is desirable to have the lowest possible measurement uncertainty when determining the orientation of the flat objects relative to one another.

From the U.S. 6,529,625 B2 a method and an apparatus for position detection are known which enable the relative positions of two semiconductor devices spaced apart in the direction of the optical axis of a detection optical system to be detected with high accuracy by an image processing method. In detecting the relative positions of a first object, such as a mask, and a second object, such as a wafer, a third object is provided which is provided with separate reference alignment marks. Optical images of the reference alignment mark on the third object and optical images of the position detection marks on the first and second objects are captured by an image capturing device. As a result, a positional deviation between the first and second objects can be detected.

the DE 19 19 991 A describes a method for the automatic alignment of two objects to be adjusted to one another using a light microscope. Each object has an alignment mark and both alignment marks are imaged by the same optical measurement system. Such a procedure is time consuming.

the U.S. 5,446,542 A describes an apparatus for determining the position of a mark and has a laser light source for projecting a laser beam onto an alignment mark on a substrate to be exposed. The alignment mark has a central face and a pair of side faces. A spatial filter is arranged to block the light reflected from the central planar surface of the alignment mark. The spatial filter has a pair of windows that allow the passage of stray light originating from the side faces of the alignment mark. An image sensor is arranged to receive the scattered light that has passed through the spatial filter, thereby generating an image signal. An image processor receives the image signal and calculates whether light intensity peaks included in the obtained light intensity distribution are substantially symmetrical or not. If this is the case, the desired position has been reached.

The object of the invention is to improve the alignment of two flat objects relative to one another.

The invention solves the problem by a method having the features of claim 1.

It is particularly favorable if the laser light has a laser wavelength and the dimensions are less than three times the laser wavelength, in particular less than the laser wavelength. It is favorable if the laser beam is monochromatic.

According to a second aspect, the invention solves the problem by an alignment device having the features of claim 7.

It is favorable but not necessary if the markings have a cylindrical, hemispherical or spherical shape.

The laser light source is preferably designed to emit a laser beam of laser light with a laser wavelength, the dimensions being smaller than three times the laser wavelength, in particular smaller than the laser wavelength.

The first flat object is preferably a wafer or an exposure mask for exposing the wafer. It is favorable if the second flat object is preferably also a wafer or an exposure mask.

The wafer is preferably a silicon wafer. It is favorable if the distance between the flat objects is at most 1 millimeter, in particular at most 0.5 millimeters.

The detectors are preferably point detectors, ie detectors that have no spatial resolution. However, it is possible for the detectors to be composed of individual sub-detectors as long as the measurement result is determined from individual measured values of the individual partial detectors. For example, the detectors can also be formed by CCD chips or other area detectors, as long as the measurement result is calculated from individual measurement values of the individual pixels.

The advantage of the invention is that mostly comparatively short measurement times can be achieved. So it is likely that a measurement time of less than 10 seconds, in particular less than 5 seconds, can be achieved.

The invention is based on the knowledge that it is not necessary to use periodic structures in order to detect an orientation of the flat objects relative to one another. The scattering behavior of the markings changes depending on the position of the markings within the focus and the markings relative to one another. These changes can be detected and allow conclusions to be drawn about the orientation of the flat objects relative to one another.

The step (ii) of allowing the scattered laser light to interfere with direct laser light that has not been scattered at any of the markings, so that a measurement laser beam is produced, is not absolutely necessary. In accordance with the invention, therefore, in its broadest form, is also a method of determining misalignment of (a) a first flat object having a first marking, and (b) a second flat object having a second marking, (c) the first marking has a first extent and the second mark has a second extent relative to each other, comprising the steps of: (i) bringing the first mark and the second mark into a focus of a laser beam of laser light such that scattering produces scattered laser light, (ii) moving the first flat object relative to the focus and/or relative to the second flat object and (iii) measuring a first intensity of a first portion of the scattered laser light using a first detector and a second intensity of a second portion of the scattered laser light using a second detector depending on the position of the flat objects relative to each other, so the marks line up with each other and become It is advantageous if the laser light has a laser wavelength and the dimensions are less than three times the laser wavelength, in particular less than the laser wavelength. In this case, the scattered laser light forms the measuring laser beam.

The preferred embodiments described below also relate to this and the above-mentioned method.

It is favorable if exactly one first marking and exactly one second marking are brought into focus. A signal that is particularly easy to evaluate is thus obtained.

It is favorable if the detectors are arranged in such a way that the absolute value of the difference in the intensities is minimal when the markings are aligned in a desired position relative to one another. In particular, the markings lie on an optical axis of the laser beam in the target position.

It is favorable if the detectors are arranged in such a way that the difference in intensities is zero when the markings are aligned in the desired position relative to one another.

The feature that the difference in intensities is zero is understood to mean that the difference in intensities disappears in the technical sense. Of course, noise in the measured value is unavoidable, so that the difference in strictly mathematical terms is never zero. That is not what is meant either, what matters is that the difference in intensities is so small that it can be regarded as zero.

Preferably, the flat object is transparent to the laser light. The markings can be transparent or opaque to the laser light. The decisive factor is that the markings scatter the laser light, for example by Rayleigh scattering. In this way, the laser light can pass through the flat objects and the intensities and/or the difference in intensities depend at least predominantly, preferably essentially exclusively, on the position of the markings relative to one another and/or relative to the focus.

The feature that the intensities and/or the difference in intensities depend essentially exclusively on the position of the markings relative to one another and/or relative to the focus means in particular that other effects can have an influence on the intensities, but that these are negligibly small and affect, for example, the difference in intensities by less than 10%.

It is favorable if the laser wavelength is at least 0.9 micrometers, in particular at least 1.4 micrometers. It is favorable if the laser wavelength is shorter than 3 micrometers, in particular shorter than 2 micrometers. In this wavelength range, silicon is largely transparent, so this method can be used to align silicon wafers relative to another flat object.

The focus diameter of the focus is at most ten times, preferably at most three times, the laser wavelength. Such a small focus leads to a low measurement uncertainty with regard to the alignment of the markings relative to one another and/or relative to the focus.

Preferably the markers do not form a periodic pattern. In particular, the intensities are not measured in a diffraction pattern. It should be pointed out that diffraction effects can never be completely ruled out, at least theoretically a small proportion of the distribution of the light can always be traced back to diffraction. What is decisive, however, is that the method would also work if no diffraction pattern was produced.

It is particularly favorable if the movement of the first flat object relative to the focus and/or relative to the second flat object oscillates at an oscillation frequency and the first intensity and/or the second intensity is measured using carrier frequency amplification with respect to the oscillation frequency. The carrier frequency amplification is also referred to as the log-in amplification and leads to a particularly low measurement uncertainty.

The method preferably comprises the steps of (a) moving a first object recording, by means of which the first flat object is recorded, and a second object recording, by means of which the second flat object is recorded, relative to one another and/or relative to the focus, (b) detecting a difference between the first intensity and the second intensity and (c) determining a target position of the first object recording and the second object recording relative to one another. This target position preferably corresponds to that position which the two flat objects must have relative to one another in order to be able to optimally carry out a subsequent production step.

The first object recording and the second object recording are preferably positioned according to the target position. Thereafter, the first flat object in the form of a wafer is preferably exposed by means of the second flat object in the form of a mask.

According to a preferred embodiment, the method comprises the steps (i) measuring a third intensity I _{3 of} a first section of the measurement laser beam, in particular by means of a third detector, and a fourth intensity of a second section of the measurement laser beam, in particular by means of a fourth detector, as a function of the position of the flat objects relative to one another, and (ii) determining the target position from the intensities. The detectors are preferably arranged in such a way that a first difference between the first intensity and the second intensity is minimal and a second difference between the third intensity and the fourth intensity is minimal when the markings are in the desired position relative to one another.

It should be pointed out that the detectors can be virtual detectors, which are created by guiding the partial light beams and sections to a detector element in chronological succession and measuring the respective light intensity in chronological succession.

It is favorable if the alignment device according to the invention is designed to carry out a method according to the invention.

• 1a eine schematische Ansicht einer erfindungsgemäßen Ausrichtvorrichtung gemäß einer ersten Ausführungsform,
• 1b eine zweite Ausführungsform einer erfindungsgemäßen Ausrichtvorrichtung,
• 2a eine schematische Ansicht zweier flacher Objekte, deren Markierungen nicht in der Soll-Lage zueinander ausgerichtet sind,
• 2b die zwei flachen Objekte gemäß 2a, wobei die Markierungen in der Soll-Lage zueinander ausgerichtet sind und
• 2c ein Diagramm, in dem die maximal erreichbare Messunsicherheit beim Ausrichten der flachen Objekte relativ zueinander gegen die numerische Apertur, die Wellenlänge und den Abstand der beiden flachen Objekte aufgetragen ist.

The invention is explained in more detail below with reference to the accompanying drawings. while showing

• 1a a schematic view of an alignment device according to the invention according to a first embodiment,
• 1b a second embodiment of an alignment device according to the invention,
• 2a a schematic view of two flat objects whose markings are not aligned with each other in the desired position,
• 2 B the two flat objects according to 2a , where the markings are aligned with each other in the target position and
• 2c a diagram in which the maximum achievable measurement uncertainty when aligning the flat objects relative to each other is plotted against the numerical aperture, the wavelength and the distance between the two flat objects.

1a shows schematically an alignment device 10 for aligning a first flat object 12 relative to a second flat object 14. The first flat object 12 has a first marking 16. The second flat object 14 has a second marking 18.

The first flat object 12 is recorded by a first object holder 20, which is, for example, an x-y table. The second flat object 14 is recorded by a second object recording 22, which can be structurally identical to the first object recording 20, but this is not necessary.

It is favorable if the first object holder 20 has a drive, by means of which the first object holder 20 can be positioned in two spatial directions. These spatial directions are preferred with respect to a coordinate system 24 wise viewed as x and y coordinates. It is favorable if the second object holder 22 is also designed to be positionable in the x and y direction by means of a drive. With this choice of coordinate system 24, a distance d corresponds to the difference in the z coordinates.

The first marker 16 has a first dimension D ₁₆ . The second marker 18 has a second dimension D ₁₈ . The dimensions D ₁₆ and D ₁₈ are the diameters of the respective envelope spheres. An enveloping sphere is that imaginary sphere of minimum diameter that completely contains the corresponding marking.

The alignment device 10 also has a laser light source 26 for emitting a laser beam 28 which has a focus F. After interacting with the markings 16, 18, the laser beam 28 forms a measuring laser beam 32. The measuring laser beam 32 strikes a beam splitter 30, which splits the laser beam into a first part 32.1 and a second part 32.2. The first part 32.1 falls on a first detector 34.1. The second part 32.2 falls on a second detector 34.2. The first detector 34.1 measures a first intensity I ₁ , the second detector 34.2 measures a second intensity I ₂ . The detectors 34.1 and 34.2 are part of the evaluation unit 36, which determines a difference ΔI=I ₁ -I ₂ .

To carry out a method according to the invention, the flat objects 12, 14 are positioned in the focus F in such a way that scattered light 32 is produced by the scattering of the laser beam 28. Depending on the position of the markings 16, 18 relative to one another and relative to the focus F, the intensities I ₁ , 12 change and thus the difference ΔI=(I _{1 -I 2} ).

The laser light of the laser beam 28 has a wavelength λ. The recesses D ₁₆ , D ₁₈ are smaller than 10λ, in particular smaller than 3λ. The object recordings 20, 22 are moved in such a way that the flat objects 12, 14 move relative to one another and/or relative to the focus F. For example, the object recordings 20, 22 are moved in an oscillating manner, for example with different frequencies.

It is possible, but not necessary, for the movement to take place along only one axis, for example the x-axis. This case is described below.

The difference in the intensities ΔI is recorded by the evaluation unit 36 . In addition, the respective coordinates of the flat objects 12, 14 relative to one another and relative to the focus and/or relative to the focus F are recorded by the evaluation unit 36. The evaluation unit 36 determines at which setpoint position Lsetpoint={x ₁₂ , y ₁₂ , x ₁₄ , y ₁₄ } the absolute value of the difference in intensities ΔI becomes minimal. The y-positions are fixed. This position is in 2 B shown. Since the position of the zero point of the coordinate system 24 can be freely selected, the desired position L _{desired is} a position of the two flat objects 12, 14 relative to one another.

In order to determine an optimal target position in both translational degrees of freedom, i.e. here in the x and y directions, the alignment _{device 10 has a third detector 34.3 for measuring a third intensity I 3} and a fourth detector 34.4 for measuring a fourth intensity I ₄ . The detectors 34.i (i=1, 2, 3, 4) are arranged in such a way that both the absolute value of the first difference ΔI ₁ (which is referred to as ΔI ₁ above) from the first intensity I ₁ and the second intensity I ₂ and the magnitude of a second difference ΔI ₂ =|I _{3 -I 4} | from the third intensity I ₃ and the fourth intensity I _{4 is} minimal when the markings 16, 18 are in the desired position L _desired relative to one another.

For example, the 34.i form a detector 34, which has four sub-detectors. Such a detector is in 1a shown in the partial image above. In this case, the first intensity I ₁ and the second intensity I ₁ are calculated from the measurement results of two partial detectors, for which it applies that a movement of the objects 12, 14 in the x-direction relative to one another affects the intensities that this part -Detectors measure, changed relative to each other, but not a movement in the y-direction. The third intensity I ₃ and the fourth intensity I ₄ are calculated from the measurement results of two partial detectors, for which it applies that a movement of the objects 12, 14 in the y-direction relative to one another determines the intensities that these partial detectors measure , changed relative to each other, but not a movement in the x-direction.

Alternatively, it is possible to divide at least one of the two parts 32.1 and/or 32.2 again and direct it to the detectors 34.3, 34.4 in such a way that the above condition is met.

1a shows the arrangement of the detectors 34.1, 34.2 in a transmission arrangement. 1b shows the arrangement of the detectors 34.1 34.2 in retro-reflection arrangement. It can be seen that the alignment device 10 can have a plurality of mirrors 40.j.

2a 12 shows the scattered light 38 and schematically the intensities 11, 12 in the case in which the objects 12, 14 are not in the desired position relative to one another. In other words, the markings 16, 18 are not arranged on an optical axis A of the laser beam 28.

2 B shows the case that the two markings 16, 18 are both arranged on the optical axis. The intensities I ₁ , I ₂ are equal. This is according to the arrangement 2a not the case. In 2 B the difference ΔI of the intensities is therefore zero. In other words, the two markings 16, 18 are arranged within the focus F of the laser beam 28 in such a way that both markings 16, 18 are irradiated. When one of the marks is passed from the optical axis A in a direction perpendicular to the optical axis A, the scattering in that direction increases.

In 2a is the mark 18 shifted to the right relative to the optical axis, therefore increases the intensity I ₂ , which is also in the direction to the right of the optical axis with respect to the plane of the 2a is measured. The scattering of the laser light is symmetrical only if the markings 16, 18 lie exactly on the optical axis. The situation is in 2 B shown. In this case the difference ΔI is equal to zero.

The highest sensitivity for the detection of a deviation from the desired position is obtained when the two structures 16 are exactly arranged in a focal plane E _F 18th The focal plane is that plane perpendicular to the optical axis in which the focus F occupies the minimum area. Minor variations of the layers of the label 16, 18 of the focal plane E _F sensitivity but affect only slightly. The sensitivity thus depends on a numerical aperture NA. The numerical aperture refers to an optics 42 in the 1a , 1b is drawn in schematically.

2c shows the dependency of the maximum detectable resolution with regard to a deviation q of the position of the markings 16, 18 from the desired position, which is shown in 2 B is shown and the numerical aperture NA, the wavelength λ and / or a distance d between the two objects 12,14 from each other.

the inside 1a The structure shown in a transmission arrangement is particularly favorable if the objects 12, 14 are transparent to the laser light 28. the inside 1b The structure shown in the retro-reflection arrangement is particularly suitable when one of the objects 12, 14 is opaque to the laser beam 28. In both cases the scattered light and the light of the laser beam 28 are superimposed on the detectors 34.1, 34.2. The detectors 34.1, 34.2 are preferably photodiodes.

in 1a In the transmission mode shown, the laser beam 28 passes through the flat objects 12, 14. The laser beam 28 can thus be viewed as a local oscillator for homodyne detection. in 1b In the retro-reflection mode shown, the scattered light interferes with a reference beam generated by the mirrors 40.3., 40.4.

In the 1a , 1b the detection of the target position in the x-direction is shown. For detection in the x and y direction, it is favorable if the alignment device has a third and a fourth detector, which are arranged such that a movement of the flat objects in the y direction leads to a change in an intensity difference ΔI _y .

wobei n der Berechnungsindex des Materials der Markierungen 14, 16 und V₁₆ das Volumen der ersten Markierung 16 ist bzw. V₁₈ das Volumen der zweiten Markierung 18, wobei V = V₁₆ = V₁₈ der Einfachheit gelten solle.The scattering can be viewed as Rayleigh scattering. The parameters of such a scattering process result for a sphere in a vacuum $$a=3V\frac{n^2-1}{n^2+2}$$

where n is the refractive index of the material of markers 14, 16 and V _{16 is} the volume of first marker 16 and V _{18 is} the volume of second marker 18, respectively, where V = V ₁₆ = V ₁₈ for simplicity.

wobei κ der Anteil der gestreuten Photonen ist, No die Gesamtzahl aller einfallenden Photonen. f beschreibt den Impulsübertrag auf das Licht. Für ein kugelförmiges Rayleigh-Partikel in einem fokussierten Gauß-Strahl ergibt sich $$\kappa =\frac{2}{3}{\mathrm{\pi }}^{5}N{A}^2{\left(\frac{d}{\lambda }\right)}^6{\left(\frac{n^2-1}{n^2+2}\right)}^2$$

wobei d der Durchmesser des Partikels ist. NA ist die nummerische Apertur. Der Parameter f kann als $${ƒ}_y=\frac{1}{\sqrt{5}}\sqrt{1-\text{cos}\left(\text{arcsin}NA\right)}$$

approximiert werden, wobei $${ƒ}_x=\frac{{ƒ}_y}{\sqrt{2}}$$

für einen in x-Richtung polarisierten Dipol gilt.The minimum positional difference Δq that can be measured with scattered light is ideally given as $$\delta q_i=\frac{\lambda }{4\pi {ƒ}_i\sqrt{k{N}_0}}$$

where κ is the proportion of scattered photons, No the total number of all incident photons. f describes the momentum transfer to the light. For a spherical Rayleigh particle in a focused Gaussian beam, we have $$k=\frac{2}{3}{\mathrm{\pi }}^{5}N{A}^2{\left(\frac{\mathrm{i.e}}{\lambda }\right)}^6{\left(\frac{n^2-1}{n^2+2}\right)}^2$$

where d is the diameter of the particle. NA is the numerical aperture. The parameter f can be used as $${ƒ}_y=\frac{1}{\sqrt{5}}\sqrt{1-\text{cos}\left(\text{arcsin}NA\right)}$$

be approximated, where $${ƒ}_x=\frac{{ƒ}_y}{\sqrt{2}}$$

for a dipole polarized in the x-direction.

In 2c the minimum detectable position difference q is calculated for the following parameters: NA = 0.5, I = 1550 nanometers, d = 100 nanometers, n = 3.4. A laser power of 100 milliwatts was assumed. An integration time of 1 millisecond results $$\delta q_y\approx 0.2\stackrel{\circ }{\text{A}}$$

Reference List

10

alignment device

12

first flat object

14

second flat object

16

first mark

18

second mark

20

first object recording

22

second object shot

24

coordinate system

26

laser light source

28

laser beam

30

beam splitter

32

measuring laser beam

32.1

part of the laser beam

32.2

part of the laser beam

34

detector

36

evaluation unit

38

scattered light

40

mirror

42

optics

λ

wavelength

A

optical axis

i.e

distance

D16

first expansion

D18

second expansion

EF

focal plane

f

focus

I

intensity

Lset

= {X _12, y _12, x _14, y _14}

N / A

numerical aperture

q

deviation

V

volume

ΔI

difference

Claims (9)

A method of determining misalignment of (a) a first flat object (12) having a first marking (16) and (b) a second flat object (14) having a second marking (18), (c) wherein the first marker (16) has a first dimension (D ₁₆ ) and the second marker (18) has a second dimension (D ₁₈ ) relative to each other, comprising the steps of: (i) bringing the first marker (16) and the second Marking (18) into a focus (F) of a laser beam (28) of laser light, so that scattered laser light is produced by scattering, (ii) allowing the scattered laser light to interfere with direct laser light that was not scattered at any of the markings, so that a measuring laser beam (32) arises, (iii) moving the first flat object (12) relative to the focus (F) and/or relative to the second flat object (14) and (iv) measuring a first intensity (11) of a first Part of the measuring laser beam (32.1) by means of a first detector (34.1) and a second Intens ity (I ₂ ) of a second part of the measuring laser beam (32.2) by means of a second detector (34.2) depending on the position of the flat objects relative to one another, so that the markings are aligned with one another, (v) the laser light having a laser wavelength has and the extensions are smaller than the laser wavelength. procedure after claim 1 , characterized in that (a) exactly one first marking (16) and exactly one second marking (18) are brought into focus (F) and/or (b) the detectors (34.1, 34.2) are arranged in such a way that they measure a minimum absolute value difference (ΔI) between the first intensity (I ₁ ) and the second intensity (12) when the markings are aligned in a desired position relative to one another. A method according to any one of the preceding claims, characterized in that (a) the flat object is transparent to the laser light and/or (b) the laser wavelength is at least 0.9 microns. Method according to one of the preceding claims, characterized in that a focus diameter of the focus (F) is at most ten times, in particular at most three times, the laser wavelength. Method according to one of the preceding claims, characterized in that (a) moving the first flat object (12) relative to the focus (F) and/or relative to the second flat object (14) involves oscillating with an oscilla is tion frequency, (b) the first intensity (I ₁ ) and / or the second intensity (I ₂ ) is measured by means of carrier frequency amplification (lock-in amplification) with respect to the oscillation frequency. Method according to one of the preceding claims, characterized by the steps: (a) moving the first object recording (20) and the second object recording (22) relative to one another and/or relative to the focus (F), (b) detecting a difference (ΔI) from the first intensity (11) of a first part of the measuring laser beam (32.1) and the second intensity (I ₂ ) of a second part of the measuring laser beam (32.2) and (c) determining a target position of the first object recording (20) and the second object recording (22) relative to each other. Alignment device (10) for aligning - a first flat object (12) having a first marking (16) relative to a second flat object (14) having a second marking (18), - the first marking (16 ) has a first dimension (D ₁₆ ) and the second marking (18) has a second dimension (D ₁₈ ), with (a) a laser light source (26) for emitting a laser beam (28) having a focus (F) and a laser wavelength, (b) a first object holder (20) for recording the first object, a second object holder (22) for recording the second object, (c) a movement device for moving the first flat object (12) relative to the focus ( F) and/or relative to the second flat object (14), (d) a first detector (34.1) for measuring a first intensity (I ₁ ) of light and (e) a second detector (34.2) for measuring a second intensity ( I ₂ ) of light, characterized in that (f) the laser beam (28) has a focus (F) has, the focus diameter of which is at most ten times the laser wavelength, (g) the object holders (20, 22) are arranged for recording the respective object, so that the markings (16, 18) are in the focus (F), (h) the object holders (20, 22), the movement device and the detectors (34.1, 34.2) (34) are arranged in relation to one another in such a way that a measuring laser beam (32) emanating from the focus (F) - with a first part on the first detector ( 34.1) so that the first detector (34.1) _{measures the first intensity (I 1} ) of scattered light, which is caused by the scattering of the laser light at the markings, and - hits the second detector (34.2) with a second part, so that the second detector (34.2) measures the second intensity (12). Alignment device (10) after claim 7 , characterized by an evaluation unit (36), which is designed to automatically carry out a method with the steps: (i) controlling the first object recording (20) and the second object recording (22) so that they are in focus (F) and relatively to each other and / or move relative to the focus (F), (ii) detecting (ΔI) the first intensity (I ₁ ) and the second intensity (12) and (iii) determining a target position of the first object recording (20) and the second object recording (22) relative to each other. Alignment device (10) according to one of Claims 7 or 8th , characterized in that (a) the laser light source (26) has a laser and a focusing device, in particular a lens, (b) a laser wavelength of the laser light source (26) between 0.9 µm and 2 µm and (c) the Focusing device has a numerical aperture (NA) of at least 0.2, in particular at least 0.3.

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