Method and apparatus for aligning a substrate - Patents.com

Abstract

The present invention relates to a method and apparatus for aligning a substrate.

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for aligning a substrate.

[0002] In the semiconductor industry, alignment equipment (English: aligner) is used to align substrates, in particular wafers, with respect to each other or with respect to other components. The substrates may have any arbitrary shape, preferably circular. The diameter of the substrate is in particular industrially standardized. For wafers, industrially common diameters are 1 inch (2.54 cm), 2 inch (5.08 cm), 3 inch (7.62 cm), 4 inch (10.16 cm), 5 inch (12.7 cm.), 6 inch (15.24 cm), 8 inch (20.32 cm), 12 inch (30.48 cm) and 18 inch (45.72 cm). With special embodiments of the alignment equipment, in particular angular substrates or panels can also be aligned with high precision with respect to each other and bonded.

[0003] In particular, joining of aligned semiconductor substrates is called bonding.

[0004] During so-called bonding, the substrates to be bonded are aligned with one another and are then joined to one another in a subsequent process step, whereby particularly precise alignment of the substrates with respect to one another is required.

[0005] An alignment process in which the alignment markings are located on the surfaces of the substrates to be bonded is called face-to-face alignment.

[0006] In order to be able to detect and / or determine the position and orientation of the alignment markings from the outer substrate surface facing away from the substrate surfaces to be joined, if at least one of the substrates is not transparent to the electromagnetic beam used to measure the substrate, in the prior art the alignment markings are detected between the substrates using image detection means before the substrates are brought close together.

[0007] This has several drawbacks, in particular that the camera can introduce particles onto the substrate surface. Moreover, to place the camera between the two substrates for detection, the substrates must be moved over a large distance, which leads to larger alignment errors due to the more complex alignment and the correspondingly larger movement distances.

[0008] In particular, when bringing the substrates to be joined close together and setting a specific spacing between the bonding surfaces, optimal alignment is important to obtain the best possible bonding results.

[0009] Another problem with the prior art is that ever increasing alignment accuracy requirements can no longer be met by simple means, such as methods for measuring a substrate relative to a reference point and aligning it without seeing it after, for example, approaching for contact.

[0010] For example, the publication US6214692 is based on the comparison of two images of alignment markings and position correction. The orientations of the alignment markings on two substrates placed face-to-face are detected separately using a camera system. From the calculated relative orientations and relative positions of the alignment markings, the positioning tables (substrate holder and stage) are driven and controlled so that erroneous positions are corrected.

[0011] Another publication US 10692747 is based on the comparison of all three images of flat alignment markings and position correction. The orientation of the alignment markings on two substrates placed face-to-face is detected separately using a camera system. A third detection unit detects a third alignment marking, which creates a correlation between the alignment marks of the substrates and the back side of the substrate holder or the back side of the substrate, which allows a more accurate alignment of the two substrates.

[0012] In this respect, visual control during face-to-face alignment of two substrates is either not possible or only possible if at least one of the substrates is at least partially transparent, and therefore precise alignment of the surfaces during face-to-face alignment is cumbersome and only possible to a limited extent.

[0013] A particular disadvantage has been found to be the need for refocusing or refocusing when detecting the alignment markings. Here, refocusing is essentially necessary when performing a readjustment movement of the optical system, in particular for detecting the alignment markings. The readjustment movement is carried out in addition to the necessary movement with superimposed parasitic movements, which cause deviations from the ideal movement of the respective optical system. The focus is therefore displaced during the movement. The focus is displaced, for example, in the optical system or in the plane xy perpendicular to the optical axis of the optical system. The focus displacement reduces the accuracy of the measurement of the alignment markings, which in turn reduces the alignment accuracy.

[0014] It is therefore an object of the present invention to provide a method and an apparatus for aligning a substrate, which at least partially eliminates, in particular completely eliminates, the drawbacks mentioned in the prior art. It is in particular an object of the present invention to provide an improved method and an improved apparatus for aligning a substrate. It is in particular an object of the present invention to provide a method and an apparatus for aligning a substrate, which does not require refocusing of the detection unit during alignment. It is further an object of the present invention to provide a method and an apparatus for aligning a substrate, which can be performed particularly reliably, precisely and without contamination, or which aligns particularly reliably, precisely and without contamination.

[0015] The object of the present invention is achieved by the features of several parallel independent claims. Advantageous developments of the invention are set out in the dependent claims. All combinations of at least two features shown in the description, claims and / or drawings are also included within the scope of the present invention. In the ranges of values ​​given, values ​​lying within the enumerated boundaries are also to be considered as disclosed as boundary values ​​and can be claimed in any combination.

[0016] The present invention therefore relates to a method for aligning a substrate, comprising at least the following steps: i) providing a substrate holder having a substrate holder surface configured to receive a substrate and an alignment marking field disposed at a fixed position relative to the substrate holder; ii) aligning the substrate, The method further comprises aligning a substrate based on alignment marks arranged above and below an alignment marking field.

[0017] Here, the substrate or the substrate stack is aligned on the basis of alignment marks arranged one above the other, which alignment marking fields are arranged on the substrate holder or on the substrate holder surface in a fixed position. Here, in particular, the exact orientation of the alignment marking fields and the respective orientation of the alignment marks in the alignment marking fields relative to the substrate holder are known. Here, the alignment mark or at least two alignment marks of the alignment marking fields are arranged one above the other.

[0018] At least two alignment marks of an alignment marking field are arranged one above the other means that these alignment marks are arranged in different planes, such that the alignment marking field has a certain height (z-direction) relative to the substrate holder surface, such that the at least two alignment marks are arranged in different z-planes relative to each other.

[0019] In this case, preferably, the alignment marks do not hide each other in the z-direction, so that at least two alignment marks of the alignment marking field can be observed unhindered from one observation direction, in other words, the alignment marks of the alignment marking field are preferably arranged above and below each other in mutually parallel planes, displaced from each other, so that any alignment mark in any plane of the alignment marking field can be captured.

[0020] It is further conceivable that at least two alignment marks arranged above and below the alignment marking field are arranged partially or completely overlapping in the z-direction. In other words, at least two alignment marks arranged above and below the alignment marking field may be arranged at least partially aligned with one another in the z-direction. In this case, different z-planes or layers of the alignment marking field are particularly transparent for different wavelengths, so that any other alignment marks in any other plane of the alignment marking field can be detected. In this case, the plane / layer arranged upstream in the observation direction and / or the alignment marks arranged upstream are pierced for observation, so that the alignment marks of the following plane, which are at least partially aligned, can be detected.

[0021] Thus, when detecting the alignment marks and subsequently detecting the alignment marks arranged thereon, the respective known orientations of these alignment marks can be compared. Thus, the spacing between the alignment marks can be detected, since the nature and structure as well as the orientation of the alignment marking fields are preferably known. Based on this spacing, for example, alignment based on the alignment marks arranged above and below can be performed by a relative movement of the substrate holder without the need for refocusing of the detection means. In this way, the substrate can be aligned particularly accurately in at least one direction, since the known spacing between the alignment marks arranged above and below can be detected and thus set.

[0022] Furthermore, due to the precise alignment in at least one direction, the bonding distance (bonding gap) can advantageously be approached very simply and precisely. In this case, the substrate holder can advantageously be aligned by direct visual control, relying on the alignment marking fields. Furthermore, only one detection means is required for alignment, which reduces the susceptibility to malfunctions. Thus, particularly when bonding non-transparent substrates in face-to-face methods, the exact position of the substrate holder and thus of the substrate can advantageously be determined. Thus, by means of the alignment marks arranged above and below and the height information provided thereby, alignment can advantageously be carried out without refocusing the detection means. This allows the substrate to be aligned to be moved particularly precisely and under visual control by a specific distance.

[0023] In one preferred embodiment of the method for aligning a substrate, the alignment of the substrate in step ii) comprises at least the following steps, particularly in the following order: a) detecting, by a detection unit, a first alignment mark in a first plane of an alignment marking field; b) after the detection in step a), fixing a focal position of the detection unit; c) moving the substrate holder perpendicular to a first plane of the alignment marking field; d) detecting, by a detection unit, a second alignment mark in a second plane of the alignment marking field; The first plane and the second plane are arranged parallel to each other, and it is specified that the first plane and the second plane are spaced apart from each other.

[0024] In the alignment marking field, preferably, a number of alignment marks are arranged side by side in the respective plane. This allows for detecting at least one first alignment mark or at least one second alignment mark of the corresponding plane. Furthermore, the alignment marking field is preferably configured between the planes transparently with respect to the detection unit, so that the alignment marks arranged above and below can be detected. It is also conceivable to arrange the alignment marks of the first plane displaced with respect to the alignment marks of the second plane, and also for the alignment marking field to have different steps. In addition to the respective first alignment mark, the detection unit can also detect further alignment marks of the first plane, if these are arranged in the focal region. In this case, the same applies for the second plane. The detection unit is configured in this case to detect a number of alignment marks of the respective plane, in particular alignment marks arranged side by side.

[0025] When detecting the first alignment marks in the first plane of the alignment marking field, the detection unit identifies the respective alignment marks. The detection unit preferably has a focusing means, preferably an objective lens, for focusing or focusing on the first alignment marks during detection. In this case, the detection unit or the objective lens assumes a focus position in which the detection unit can detect a specific focus region. As a result, the alignment marks focused on the focus region of the specific focus position of the detection unit or the objective lens and arranged in the focus region can be detected. During detection, preferably only the alignment marks of the respective planes can be detected or identified, since the focus regions of the detection unit each include exactly one plane. As a result, the distance between the first plane and the second plane is preferably greater than the depth of the focus region.

[0026] Following the detection of the first alignment mark in the first plane, the focal position of the detection unit is fixed. In particular, a focal region is thereby determined, so that the detection unit can subsequently preferably only detect alignment marks in the determined focal region. The substrates are then moved together and thus aligned on the substrate holder surface of the substrate holder by moving the substrate holder perpendicularly to the first plane of the alignment marking field. The substrate holder is moved at least until the detection unit can detect the second alignment mark in the second plane of the alignment marking field. In this respect, the substrate is advantageously moved by the movement of the substrate holder by a distance required for focusing. For example, in this way, a bonding distance between the substrate and another substrate to be bonded can be set. This advantageously prevents alignment errors due to refocusing of the detection unit.

[0027] In a preferred embodiment of the method for aligning a substrate, in step a) it is provided that an additional alignment mark is detected in the substrate holder or on the substrate by means of at least one additional detection unit.

[0028] In this case, the additional alignment mark or additional alignment markings can advantageously be correlated or spatially associated with the position of the first alignment mark. The additional alignment marks are in particular flat alignment marking fields that do not have alignment marks arranged above and below. In other words, these additional alignment markings are not arranged above and below in multiple planes.

[0029] The additional alignment markings can advantageously also be used to align the substrate holder relative to the alignment marks of the alignment marking field. Furthermore, the detection unit can align the substrate holder or the substrate arranged on the substrate holder relative to the additional alignment markings. The at least one additional detection unit can in particular determine the position of the additional substrate to be bonded to the substrate relative to the alignment marking field. The alignment can be performed even more precisely by the additional alignment marks and the additional detection unit.

[0030] In a preferred embodiment of the method for aligning a substrate, it is determined that while moving the substrate holder in step iv), the detection unit measures the alignment marking fields continuously at the focus position.

[0031] If a further alignment mark is arranged in a further plane between the first and second plane, this further alignment mark can be measured by the detection unit when moving the substrate holder, which allows a particularly accurate and controlled movement of the substrate holder. Furthermore, a plurality of detected alignment marks, the orientation of which in the alignment marking field is known, allows for an even more accurate alignment.

[0032] In a preferred embodiment of the method for aligning a substrate, it is specified that after fixing the focal position in step b), the detection unit is kept in a fixed position.

[0033] In this case, the detection unit is not only fixed at a specific distance relative to the alignment marking field, but also fixed in a horizontal position. As a result, the fixed position relative to the alignment marking field also results in a fixed position relative to the substrate holder and, consequently, the substrate arranged on the substrate holder. In this way, it is advantageously ensured that in addition to fixing the focal position of the detection unit or the objective lens, the position of the detection unit is also determined. In this way, the substrate can be aligned more precisely and alignment errors due to inaccurate movements of the detection unit are avoided.

[0034] In a preferred embodiment of the method for aligning a substrate, it is specified that when detecting the first alignment mark in step a) and / or when detecting the second alignment mark in step d), the detection unit additionally provides information regarding the orientation of the respective alignment mark within the alignment marking field.

[0035] The alignment marks preferably have information about their respective orientation in the alignment marking field. In addition to the orientation along the alignment marking field (xy orientation), the respective heights of the planes or their distance from one another are also known. This allows, when the first alignment mark is detected, advantageously to determine in which plane the alignment mark is located. This allows for easier open-loop or closed-loop control of the alignment, especially when the alignment marking field has more than two planes with different distances from one another, since the respective height information is detected for the alignment marks. For example, during successive detection during movement or during detection of the first alignment mark, it can advantageously be determined which plane or step in the focal region is detected. Furthermore, when a position is detected between two planes or steps, advantageously a plane or step arranged above or below can be approached. Advantageously, the orientation in the xy position can also be detected and controlled.

[0036] The advantages and features described above with respect to the alignment method are also disclosed in relation to the following apparatus:

[0037] The present invention further provides an apparatus for aligning a substrate, comprising at least: A) a substrate holder having a substrate holder surface configured to receive a substrate; B) an alignment marking field with an alignment mark arranged in a fixed position relative to the substrate holder and / or relative to the substrate, wherein the substrate can be aligned based on the alignment marks arranged above and below.

[0038] The alignment marks arranged above and below the alignment marking field have a known mutual distance in the direction of the alignment marking field, and thus advantageously an alignment of the substrate holder or of the substrate arranged on the substrate holder surface can be carried out solely on the basis of the alignment marks and with one detection means, in particular with just one detection means.

[0039] In a preferred embodiment of the apparatus for aligning a substrate, the apparatus further comprises: C) a detection unit for detecting an alignment mark in the alignment marking field; D) a moving device for moving the substrate holder, wherein the alignment marks of the alignment marking field are arranged in a first plane and a second plane, the first plane and the second plane are arranged parallel to each other and have a gap between each other, a first alignment mark of the alignment marks of the first plane is detectable at a focal position of the detection unit, the focal position of the detection unit can be fixed, and at this focal position, a second alignment mark of the alignment marks of the second plane can be detected by the detection unit, and the substrate holder can be moved perpendicular to the first plane by the moving device.

[0040] Here, the device is especially configured in such a way that the focal position of the detection unit can be fixed immediately after detecting the first alignment mark in the first plane of the alignment marking field. Here, the fixed focal position of the detection unit determines the sharply imaged focal region. In this way, the distance of the first plane relative to the second plane can be advantageously approached by the movement device, so that the substrate holder or the substrate can be moved exactly by this distance in one direction based on the alignment marking field. The detection unit is further advantageously held in a fixed position, so that the distance between the planes is approached only by detecting the alignment marks and moving the substrate holder. If an alignment device is used to set the bonding distance between the two substrates to be bonded, the distance between the first and second planes is preferably the desired distance before starting the bonding process. In other words, the bonding distance corresponds to the bonding gap. In this case, the alignment by the device can advantageously be directly controlled by detecting the second alignment mark in the second plane. This allows the correct alignment to be advantageously verified by direct visual control by just one detection unit.

[0041] In one preferred embodiment of the apparatus for aligning a substrate, it is specified that the alignment mark of the first plane and the alignment mark of the second plane are aligned above each other, in particular congruently, in the alignment marking field.

[0042] Between these planes, the alignment marking fields are preferably configured transparently to the detection unit. By arranging the alignment markings in one-on-one alignment, it is advantageously possible to determine whether the movement of the substrate holder by the movement device has been performed exactly perpendicular to the first plane when detecting the second alignment marks. In this case, the detection unit has a focus in which the respective orientation of the second alignment marks corresponds to the first alignment marks in the focus position. It is further conceivable that the alignment marks of the first plane are rotated or mirrored with respect to the correspondingly aligned alignment marks of the second plane. In this case, the alignment marks preferably have a shape or outer contour that is not point-symmetric, so that at least some of these alignment marks can be detected by rotation or mirroring.

[0043] In a preferred embodiment of the apparatus for aligning a substrate, it is specified that the alignment marks of the first plane are arranged displaced in a step relative to the alignment marks of the second plane.

[0044] In this embodiment, the alignment marking field itself can be formed in a stepped shape, with each plane with the alignment marking forming a surface of the alignment marking field. In this case, the detection unit is preferably configured to detect multiple steps of the alignment marking field without relative movement. For example, the focal area of ​​the detection means has a width such that multiple steps are detectable. It is also conceivable that the detection unit has multiple means arranged side by side for detecting the steps. For example, the detection unit can have multiple optics arranged side by side with corresponding objective lenses. In this case, the focal positions of all detection means of the detection unit are fixed after detecting the first alignment mark. In this case, the alignment marking field is preferably formed round, with the transition between the planes being circular. In other words, the plane with the alignment marking is annular and the centrally located plane is round.

[0045] In this way, the detection unit can advantageously detect alignment marks arranged on or in the vicinity of the surface of the alignment marking field, respectively.

[0046] In one preferred embodiment of the apparatus for aligning a substrate, it is specified that the alignment marking fields are arranged on a back surface of the substrate holder, facing away from the substrate holder front surface.

[0047] The alignment marking field can be attached to the back surface or embedded in the substrate holder, for example. The alignment marking field can also be formed by the substrate holder itself. The detection unit can advantageously be arranged on the back surface facing away from the substrate holder surface.

[0048] In one preferred embodiment of the present apparatus for aligning a substrate, it is determined that a centre point of the alignment marking field on the backside of the substrate holder is at least partially aligned with a centre point of the front side of the substrate holder.

[0049] The central positioning of the alignment marking field advantageously allows the substrate holder to be aligned accurately. In this embodiment, it is also advantageously possible to sense the linearity error components or rotation of the substrate holder, and thus of the basic holder surface, relative to the detection unit. In particular, wedge errors relative to the lenses of the optical system can also be detected and removed. The alignment error can be divided into error components. Thus, linearity errors, rotation errors and magnification errors as well as errors of large orders can be characterized.

[0050] In one preferred embodiment of the apparatus for aligning a substrate, it is specified that the alignment marking fields are arranged on the side of the substrate that faces towards the substrate holder surface.

[0051] In this embodiment, the substrate holder has a through-opening in the region of the alignment marking field. It is further conceivable that the substrate holder is configured transparently with respect to the detection unit, so that the alignment marking field arranged on the substrate can be detected, in particular from the rear side of the substrate holder. In this way, a visual control can be advantageously performed directly on the substrate to be aligned. In this case, the substrate, and thus the alignment marking field, is held in a fixed position relative to the substrate holder. Alignment errors, for example due to an uneven substrate holder surface, are avoided. Furthermore, the alignment marking field can advantageously be individually adapted to the substrate. The alignment marking field can additionally be formed or imaged by the substrate.

[0052] In one preferred embodiment of the apparatus for aligning a substrate, it is specified that the alignment marking field has at least one other plane having alignment marks, the at least one other plane being arranged parallel to the first plane and the second plane.

[0053] The alignment marking field preferably has at least three planes with alignment marks. The alignment marks are then provided with information on which plane the alignment marks are arranged on. Furthermore, in this way, a number of specific intervals can be approached by the device. The intervals between the planes can be of the same size. However, the planes are preferably arranged with different distances from one another. In this way, a number of intervals can be approached flexibly. This is advantageous, particularly when using the device for bonding substrates, in that different bonding distances can be set or a substrate can be aligned particularly precisely with respect to another substrate.

[0054] In a preferred embodiment of the apparatus for aligning a substrate, it is specified that the apparatus has at least one further alignment marking field and at least one further detection unit for detecting the at least one further alignment marking field, and that the at least one further alignment marking field is arranged in a fixed position on the substrate holder.

[0055] This further alignment marking field allows even more accurate alignment, since detection takes place at multiple points. For example, in this way, displacement and / or rotation errors can be particularly well identified and removed. Here, this alignment marking field and at least one further alignment marking field are preferably arranged displaced along the substrate holder. Particularly preferably, the device has a total of three alignment marking fields and three detection units, which are each arranged uniformly displaced from one another, in particular in the radial direction, and distributed around a center point of the substrate holder surface.

[0056] Preferably, the respective planes of the alignment marking field and the at least one further alignment marking field have the same distance from each other. In this way, alignment is possible particularly accurately, since the distance can be verified at least at two points, preferably at points whose positions are displaced.

[0057] A core aspect of the present invention is to detect at least two alignment marks in at least two different planes or heights of the alignment marking field before aligning the substrate. In this case, the alignment marking field is preferably attached to one of the substrates to be aligned or to the substrate holder. In this case, the alignment marks provide 3D position information for aligning the substrate, respectively. The alignment marking field is preferably not arranged on the contact surface of the substrate. The alignment marking field is preferably arranged on a surface of the substrate or substrate holder facing away from the contact surface or arranged parallel to the contact surface.

[0058] The substrates are indirectly aligned with each other, in particular by means of alignment markings located on the contact surfaces of the substrates. The alignment markings on the opposing surfaces of the opposing substrates are in particular complementary to each other. The alignment markings can be any object that can be aligned with each other, such as, for example, crosses, circles or squares or propeller-shaped formations or grating structures, in particular phase gratings for the spatial frequency domain.

[0059] In one particularly advantageous embodiment of the device, the alignment markings may at least partially comprise QR codes, which in particular represent an absolute, machine-readable position coding (x, y, z position) of the respective alignment mark.

[0060] In another particularly advantageous embodiment, the alignment markings may at least partially comprise alphanumeric symbols, which in particular represent the absolute, machine-readable position coding (x, y, z position) of the respective alignment mark.

[0061] The alignment markings and / or alignment marking fields are preferably detected using electromagnetic beams of a certain wavelength and / or wavelength range. These electromagnetic beams include, for example, infrared beams, visible light or ultraviolet beams. It is also possible to use beams of shorter wavelengths, such as EUV (extreme ultraviolet beams) or X-ray beams.

[0062] One particularly important aspect of the invention is that the alignment and the setting of the bonding spacing are performed exclusively by detection of the alignment marks, which are arranged in particular above and below the alignment marking field. By "detection only" it is meant that the additional alignment markings are not or cannot be detected during alignment. Thus, the alignment marks arranged above and below allow the bonding spacing to be set precisely and under visual control.

[0063] In this case, the alignment marking field preferably contains alignment markings or alignment marks that are uniquely associated and / or can be associated in at least two different planes. In this case, the alignment marking field has a step or an at least partially transparent layer, whereby the alignment marks are arranged one above the other. In addition to the usual xy position, height information is also indirectly provided. In this case, it is also possible to directly provide 3D position information by the alignment marks of the alignment marking. The height information is provided by the arrangement in different planes. In this case, it is sufficient to provide information in which plane the detected alignment mark is arranged in the alignment marking field, since the distance between the planes is known.

[0064] Thereby, the alignment marking field consists of or comprises position-coded and height-coded alignment markings, which provide unique position and height information of the substrate and / or substrate holder for alignment without refocusing the third detection unit. The alignment markings or alignment marks of the alignment marking field should be understood hereinafter as height-coded alignment markings or alignment marks, even without explicit reference to height-coding and / or 3D position information.

[0065] Preferably, the size or dimensioning of the alignment marking fields is adapted to the respective field of view of the optical detection means, so that at least two steps or alignment marking planes, respectively, can be observed.

[0066] In this case, the number of steps and the overall height of the alignment marking field are likewise adjusted to the spacing to be set. For example, if a bonding spacing of 500 micrometers is to be set, then preferably height-coded position information of 550 micrometers is imaged in the alignment marking field, so that this spacing can be approached without refocusing.

[0067] The detection is preferably performed by corresponding imaging optics, whereby the depth of field can be selected such that it is smaller than the step height or layer thickness of the alignment marking field. The depth of field (English: depth of focus, DOF) is the region in the image space of the imaging optics in which a sufficiently sharp image of the focused object, in particular the alignment marking, occurs. Conversely, this means that the image plane (image detection means, sensor) can be displaced in the region of the depth of field without the image of the object being significantly blurred.

[0068] When detection of the alignment marks of the alignment marking field is performed with a small depth of field which is smaller than the step height, preferably smaller than half this step height, particularly preferably smaller than 0.1 x the step height, the position of the alignment marking field can be uniquely identified, in particular in the z direction.

[0069] The depth of field of the detection means is less than 50 micrometers, preferably less than 20 micrometers, particularly preferably less than 10 micrometers, very particularly preferably less than 5 micrometers and in the most optimal case less than 4 micrometers.

[0070] On the other hand, if the depth of field is large and at least two step heights are sharply imaged, the positioning uncertainty of the device increases, since this does not allow a unique mapping of a z-height to one step.

[0071] In a preferred embodiment of the device, the image detection means or the detection means of the detection unit can be reproducibly displaced by 0.2× step height without refocusing on the image side. This can be used to determine which alignment marking of the alignment marking field should be used for positioning when the focal plane on the image side is directly located at two adjacent step heights and the two steps are equally clearly visible. Small displacements of the image detection means allow the determination of the alignment marking to be used (also as a computer-implemented independent method according to the invention).

[0072] When detecting the alignment marking field, only one plane or step, respectively, is sharply imaged due to physical limitations. In this respect, preferably, only one step or step, respectively, is located in the focal area of ​​the detection unit. The alignment markings of the alignment marking field are position-coded and spatially coded, so that position information, particularly of the substrate holder, in the spatial coordinate system can be determined from the sharply detected alignment marks of the plane.

[0073] According to one advantageous embodiment of the invention, the first and second substrates are arranged between the first and second substrate holders with a distance A in the Z direction between the first and second contact surfaces.

[0074] The spacing A is in particular less than 500 micrometers, preferably less than 100 micrometers, particularly preferably less than 50 micrometers and most preferably less than 10 micrometers.

[0075] The method for aligning substrates is suitable for aligning at least two substrates with respect to each other by any electromagnetic beam, in particular by UV light, more preferably by infrared light, most preferably by visible light, whereby the substrate to be aligned or the substrate placed on the substrate holder surface of the substrate holder can also be moved accurately by the spacing between the planes relative to another component and thus aligned.

[0076] The method allows the observation or detection of the first and second alignment markings, supplemented by at least one additional optical path for accurately reproducing the substrate position and the substrate holder position, which additional optical path is not arranged or extends between the substrates during the alignment of the substrates, but can be detected externally, in particular by observation or detection of at least one alignment marking field, wherein the alignment marking field preferably provides height information for setting a desired bonding distance between the first and second planes.

[0077] In a particularly preferred method, the substrates may be non-transparent to the electromagnetic beam used to detect the alignment markings of the first and second substrates, with detection of the alignment markings being performed by a back surface of the substrate that is transparent to the electromagnetic beam used to detect the alignment markings.

[0078] The method for alignment increases the alignment accuracy, in particular by providing separate XYZ position information and / or orientation information, which are detected by separate alignment marking fields and corresponding separate detection units, and used for open-loop and / or closed-loop control of the alignment.

[0079] For this purpose, the device for alignment preferably has a control unit, in particular software supported, by means of which the steps described herein are carried out and the components are open-loop controlled, whereby closed control loops and closed-loop control are to be understood as being included in the control unit.

[0080] By X-direction and Y-direction or X-position and Y-position is understood a direction extending or a position located in an XY coordinate system or in any Z-plane of the XY coordinate system. The Z-direction is located orthogonal to the XY-direction. The X-direction and Y-direction in particular preferably correspond to a lateral direction along the plane of the alignment marking field. The Z-direction is preferably the direction in which the substrate holder is moved when the focal position of the detection unit is fixed in the XY-plane.

[0081] The position features are calculated or detected from position and / or orientation values ​​of the alignment markings of the substrate and of the alignment markings on the substrate holder, in particular by detecting and evaluating alignment marking fields.

[0082] The alignment marking field is preferably located locally in the vicinity of the alignment marking of the substrate. Particularly preferably, at least one alignment marking of the substrate and the alignment marking field are arranged on opposite sides of the substrate. The alignment marking field may also be arranged on the rear side of the substrate holder and opposite the additional alignment marking. If the additional alignment mark and the alignment mark of the alignment marking field are arranged on opposite sides of the substrate holder surface, the pose correlation can be particularly easily performed.

[0083] In one particularly preferred embodiment, the at least one alignment marking field is preferably aligned in the z-direction with the additional alignment markings of the substrate, preferably located on the backside of the substrate holder.

[0084] In another preferred embodiment of the apparatus, at least one alignment marking field is preferably located on the backside of the substrate holder, preferably aligned in the z-direction with the centre of the substrate or with the centre point of the substrate holder surface.

[0085] In one particularly highly preferred embodiment of the device, two alignment marking fields are preferably aligned in the z-direction respectively with additional alignment markings of the substrate, in particular on the rear surface of the substrate holder.

[0086] In another preferred embodiment of the apparatus, at least one alignment marking field is located near the substrate on the substrate side of the substrate holder or on the substrate holder surface side for optically detecting an accessible position.

[0087] A further embodiment of the device comprises at least two alignment marking fields on the substrate side of the substrate holder near the substrate edge for optically detecting the accessible positions, which advantageously allows the substrate holder to be leveled.

[0088] Thereby, the method for alignment and the device for alignment in particular have at least one additional detection unit with a corresponding measuring system and / or closed-loop control system and at least one additional alignment marking field, whereby by correlation of the additional measurement values ​​with at least one of the measurement values ​​of the additional detection unit the alignment accuracy is further increased, in particular without refocusing, preferably without refocusing on the image side.

[0089] By correlating at least one of the measured additional alignment markings of the first and / or second substrate, in particular on the contact surface, with at least one alignment mark of the alignment marking field, which is also freely accessible and visible when aligning the substrates, the alignment mark can be directly observed and thus allows real-time measurements and closed-loop control during alignment, which increases the alignment accuracy of the substrates.

[0090] Another advantage of the alignment marking fields is that they detect additional height information, which allows a more accurate positioning of the lower substrate holder with the lower substrate relative to the upper substrate on the upper substrate holder, in particular by eliminating the resulting position inaccuracies of the focusing movement of the detection unit.

[0091] By increasing the accuracy of the height positioning of the gap between the upper substrate and the lower substrate during bonding, a preload of at least one of the substrates is set with a small tolerance, which reduces distortion of the substrate during bonding, thereby at least reducing and preferably eliminating the protrusion of the substrate after bonding. In this respect, the present method for alignment and the present apparatus for alignment are used for alignment during the bonding process.

[0092] In a further embodiment of the device, at least one further alignment marking field is positioned on the substrate side of the substrate holder near the periphery of the substrate in a position that is permanently accessible to the further detection unit, particularly preferably with a surface of the alignment marking field lying in the same plane as the surface to be bonded of the substrate fixed to the substrate holder.

[0093] Additionally, a unique correlation is formed between the 3D positional features on the substrate holder and the positional features on the substrates, which is preferably not altered during alignment and is maintained until the substrates are bonded together.

[0094] Due to additionally added 3D position features on the substrate holder, which can be uniquely correlated with position features on the substrate, the direct observation of the alignment markings on the substrate can be replaced by the direct observation of the alignment markings on the substrate holder. This has the advantage that the observable part of the substrate holder can be located substantially always in the field of view or detection area of ​​the detection unit. The 3D position information allows the substrates to be aligned with each other with higher accuracy.

[0095] Preferably, the detection area of ​​the detection unit has an area of ​​less than 3 mm×3 mm, preferably less than 2 mm×2 mm, particularly preferably less than 1 mm×1 mm.

[0096] The active feedback of data for positioning and position correction increases accuracy compared to the open-loop controlled positioning of the prior art, since in a closed control loop it is possible to control the actual state of the position.

[0097] One aspect of the method and the device for alignment is to increase the accuracy of the alignment of two substrates. The method for alignment allows the alignment or movement to be observed in real time, in particular from outside the bonding interface. The 3D position information provided, incorporating height information, allows for a much more accurate alignment than previously known methods. Here, the substrates are in particular arranged with a minimum distance from each other, and preferably no device objects, in particular no detection units, are located between the substrates.

[0098] A correlation is formed between the additional alignment markings of the first substrate and / or the second substrate on the respective contact surfaces of the substrates and at least one alignment mark of the alignment marking field, the alignment mark of the alignment marking field being in particular directly detectable by the detection unit during alignment.

[0099] Direct detection or observation of at least one alignment mark of the alignment marking field allows real-time measurement of the 3D position of the substrate holder, where detection of the first and second alignment marks and the height information it provides increases alignment accuracy by eliminating positioning uncertainties, thereby reducing error propagation. By such measures, the number of required feed movements is reduced and alignment accuracy is improved by closed-loop controlled height adjustment during bonding.

[0100] A first embodiment of the device for alignment is used in a bonding apparatus and comprises an upper substrate holder, on which an upper substrate can be fixed, which is at least locally made sufficiently transparent so that alignment markings of the upper substrate on the contact side of the upper substrate, which faces away from the mounting side of the upper substrate, can be detected with sufficient resolution, contrast and intensity.

[0101] For this purpose, the upper substrate is sufficiently transparent to the beam used to detect the first additional alignment marking of the upper substrate.

[0102] A sufficiently transparent substrate is understood to be one in which the transmissivity of the substrate to the electromagnetic beam for detecting the additional alignment markings is sufficient to detect the additional alignment markings with sufficient resolution and contrast and intensity.

[0103] A locally sufficiently transparent substrate holder is understood to mean that the substrate holder has a sufficiently high transmittance for the electromagnetic beam for detecting the alignment markings. Alternatively, viewing windows and / or through-openings for observing the substrates and / or substrate pairs may be attached to the substrate holder.

[0104] During detection of the additional alignment markings on the substrate, in particular the upper substrate and the upper substrate holder are moved out of the focus of this additional detection unit.

[0105] In this case, the upper substrate holder and, through the upper substrate, additional alignment markings, in particular on the lower substrate or on the lower substrate holder, can be detected.

[0106] During detection of the additional alignment markings, at least one alignment mark of the alignment marking field is correlated, in particular at the back side of the substrate holder, to determine 3D position information of the substrate holder, in particular the lower substrate holder.

[0107] The detection unit for detecting the alignment marking fields is in particular part of an optical system for detecting the alignment marking fields and, according to one advantageous embodiment, comprises beam shaping and / or deflection elements, e.g. mirrors, lenses, prisms, a beam source, in particular for Köhler illumination, image detection means, e.g. a camera or the like (CMOS sensor or CCD, or surface detection means or line detection means or point detection means, e.g. a phototransistor, etc.), movement means for focusing and evaluation means for closed-loop control of the optical system.

[0108] In another embodiment of the device, the optical system can be used in combination with a rotation system for substrate positioning according to the turnover adjustment method (see Friedrich Hansen, Justierung, VEB Verlag Technik, 1964, section 6.2.4, Umschlagmethod). During the turnover adjustment, at least one measurement is carried out of the respective substrate in a given position and at least one measurement is carried out in a position rotated by 180 degrees, oriented in the opposite direction and turned over. The measurement results obtained in this way are in particular free of eccentricity errors.

[0109] One development of the device for alignment includes two optical systems, in particular of identical construction, with additional detection units that are aligned with one another and can be fixed relative to one another for detecting additional alignment marks.

[0110] In another embodiment of the apparatus for alignment, at least one substrate holder is used which is at least partially, preferably more than 95%, transparent at a defined location, in particular for simultaneous observation of two substrate surfaces.

[0111] In another embodiment of the device, at least one substrate holder is used which has openings and / or penetrations and / or viewing windows at designated locations for observing two substrate surfaces in particular simultaneously.

[0112] The device may further comprise a system for producing a pre-bond. For this purpose, the joining of the substrates can use pressure pins and / or configurable nozzles to initiate the fusion bonding. In particular, the configurable nozzles can be height-configurable, so that their relative position with respect to the rear surface of the substrate can be changed, and the volumetric flow rate of the nozzles can be changed under closed-loop control. The alignment of these nozzles can advantageously be performed on the basis of alignment markings arranged above and below.

[0113] Furthermore, the apparatus preferably includes a movement device with a drive system, a guide system, a holding part and a measurement system for moving, positioning and accurately aligning at least the detection unit and the substrate holder and thus the substrate to be aligned.

[0114] These movement devices can form any movement as a result of individual movements, so that these movement devices can preferably include high speed coarse positioning devices that do not meet the accuracy requirements, and fine positioning devices that operate accurately.

[0115] A positioning device is understood to be a coarse positioning device if, for the entire travel path or rotation range, which is 360 degrees in one revolution of the rotatable rotary drive, the approach accuracy and / or repeatability deviation from the target value is greater than 0.1%, preferably greater than 0.05%, particularly preferably greater than 0.01%.

[0116] Thus, for example, a coarse positioner with a travel distance of more than 600mm (twice the substrate diameter) would result in a residual uncertainty of 600mm x 0.01% approach accuracy, i.e. better than 60 micrometers.

[0117] In another embodiment of the coarse positioning, the residual uncertainty of the approach or repeatability is less than 100 micrometers, preferably less than 50 micrometers, particularly preferably less than 10 micrometers, whereby thermal disturbances should likewise be taken into account.

[0118] The coarse positioning device performs its positioning function with sufficient accuracy only if there is a deviation in the movement range of the corresponding fine positioning device between the actual position actually reached and the target value of this position.

[0119] The alternative coarse positioning device performs its positioning function with sufficient accuracy only if there is a deviation between the actual position actually reached and the target value of this position of half the movement range of the corresponding fine positioning device.

[0120] A positioning device is understood to be a fine positioning device when, for the entire movement or rotation range, the residual uncertainty in approach accuracy and / or repeatability is less than 500 ppb from the target value, preferably less than 100 ppb, and more preferably not more than 1 ppb.

[0121] Advantageously, the fine positioning device is capable of compensating for absolute positioning errors of less than 5 micrometers, preferably less than 1 micrometer.

[0122] The substrates can be aligned with respect to one another in all six degrees of freedom of movement, i.e. three translational movements in the coordinate directions x, y and z and three rotations around the coordinate directions. Movements can be made in any direction and orientation. The alignment of the substrates includes in particular a passive or active wedge error compensation, preferably as described in the disclosure of the publication EP 2 612 109 B1.

[0123] A robot for handling the substrate is included in the transfer device. The holder may be structurally or functionally integrated in the transfer device.

[0124] Furthermore, the device for alignment preferably comprises a closed-loop control system and / or an evaluation system, in particular a calculator, for carrying out the described steps, in particular the movement flows, for making corrections and for analysing and storing the operating conditions of the device.

[0125] The procedures are preferably written as recipes and implemented in a machine-readable form. A recipe is a collection of optimal values ​​of functionally or process-technologically relevant parameters. By using recipes, the reproducibility of the manufacturing flow can be guaranteed.

[0126] The alignment device according to the preferred embodiments further includes a power supply system and auxiliary and / or supplementary systems (compressed air, vacuum, electrical energy, fluids such as hydraulic pressure, coolants, heat transfer media, means and / or devices for temperature stabilization, electromagnetic shielding).

[0127] The apparatus for alignment may further include a frame, housing, active or passive subsystems for suppressing, damping or eliminating vibrations.

[0128] The alignment device further preferably comprises at least one measuring system with a measuring unit for each axis of movement, which measuring system can in particular be implemented as a displacement measuring system and / or an angle measuring system, the measuring system preferably comprising at least one detection unit or additional detection units.

[0129] Tactile or probe-based measurement methods can be used, as well as non-tactile measurement methods. The measurement standard, the measurement unit, can be present in a physical, material object, in particular a scale, or can be implicit in the measurement method, such as the wavelength of the beam used.

[0130] To achieve the alignment accuracy, at least one of the following measurement systems can be selected and used: Guidance system, and / or Volumetric method, and / or Resistance method and / or Comparison methods, in particular optical image identification methods, detection of position marks and / or QR codes, and / or Incremental or absolute (especially with glass standards as scales or with interferometers, especially laser interferometers, and also with magnetic standards), and / or Time of flight measurements (Doppler, time of flight) or other time detection methods, and / or -Triangulation methods, especially laser triangulation, Autofocus methods, and / or For example, a strength measurement method such as an optical fiber distance meter can be used.

[0131] A particularly preferred embodiment of the apparatus for alignment further comprises at least one measuring system for detecting the XYZ position and / or the alignment orientation and / or the angular position of at least one of the substrate and / or the substrate holder relative to a defined reference, in particular a frame, The measuring system comprises at least one detection unit.

[0132] Here, the 3D position of the substrate or preferably of the substrate holder is determined without refocusing by the measurement system or by a detection unit of the measurement system, so that for the same height position information height information can be determined from the measurement. For this purpose, at least one alignment marking field consisting of steps and / or layers with unique position markings is detected.

[0133] A frame can in particular be understood as a part made of natural hard stone or mineral casting or spheroidal graphite casting or hydraulic concrete, which is formed in particular in a vibration-damping and / or vibration-proof and / or vibration-eliminating manner.

[0134] The idea can likewise be advantageously reversed by mounting the detection unit on the substrate holder and the alignment marking field on, for example, a frame, in which case the detection unit is moved together with the substrate holder and the alignment marking field is fixed to the frame.

[0135] In order to be able to perform detection, evaluation and open-loop control at any time, in particular continuously, the alignment marks of the alignment marking field are distributed in accordance with an advantageous embodiment over a respective planar area larger than the field of view of the image detection system of the detection unit, so that the open-loop control unit (and / or the closed-loop control unit) is supplied with particularly continuous measured values. Here, however, for each position in the field of view of the image detection system, the alignment marks of the alignment marking field are designed in such a way that height information can be determined from the alignment marking field and / or from the extended same height position information. In other words, at each lateral position of the substrate holder, the spatial position of the substrate holder can be determined and the correct bonding distance can be set by the arrangement of the alignment markings of the alignment marking field. In particular, the position of the substrate holder is 3D position information, so that a more precise spatial alignment of the substrates fixed thereon with respect to one another can be performed.

[0136] In an advantageous embodiment of the device for alignment, the additional alignment markings on the contact surface of the substrate are particularly evenly distributed, except for the edge zone (edge ​​exclusion zone) of the substrate. In other words, this allows for the use of additional alignment markings of the substrate, which are positioned at intervals of less than 3 mm, preferably less than 2 mm, particularly preferably less than 500 micrometers, for alignment purposes. This allows for a particularly high local alignment accuracy to be achieved by correlating the additional alignment markings of the substrate with the spatially defined alignment marking fields of the substrate holder.

[0137] For the XYZ position determination, the device for alignment can further use at least one three-beam interferometer with a corresponding, in particular integrally configured, reflector for determining the XYZ position and / or orientation of the substrate holder. Another possible advantageous embodiment of the device can be measured by an integral reflector of a prism with a plurality of, in particular three-beam interferometers. In this way, by averaging, difference formation and measurement sequence formation, the propagation of errors can be eliminated and the alignment accuracy can be further increased. In other words, a sufficiently fast position measurement allows the use of a closed-loop control system for the trajectory of the movement, which can further reduce the position error of the substrate holder.

[0138] The device for alignment, in particular the substrate holder formed from a monolithic block, preferably has the following functions: Fixation of the substrate by vacuum (vacuum tracks, connections) and / or by electrostatic means; shape compensation of deformations of the substrate by means of mechanical and / or hydraulic and / or piezoelectric and / or pyroelectric and / or electrothermal actuating elements; Positioning and / or orientation determination (measuring references, reflecting surfaces and / or prisms, in particular reflectors for interferometry, registration marks and / or registration mark fields, measuring references for surface-shaped planes, volumetric references, in particular steps, layer systems of known layer height with alignment markings divided into planes), · Having at least two of the following: a moving (guide track) and

[0139] In particular, the displacement devices not used for the fine adjustment are preferably configured as robot systems with incremental displacement sensors, and the precision of these displacement devices for the auxiliary movements is decoupled from the precision for the alignment of the substrate stack, so that the auxiliary movements are performed with a low repeatability precision of less than 1 mm, preferably less than 500 micrometers, particularly preferably less than 150 micrometers.

[0140] The open-loop and / or closed-loop control of the movement device of the device for alignment for (lateral) alignment (fine-tuning) is based in particular on the detected XYZ position and / or alignment attitude. For this purpose, the additional alignment markings of the substrate are correlated with the alignment marks of the alignment marking field, which are uniquely associated therewith in the field of view at the rear side of the substrate holder. Height information is calculated from the alignment markings of the alignment marking field. This results in an XYZ position, which can be continuously observed in particular during the feed movement for alignment and during the setting of the gap for bonding and can be used in real time, in particular for error correction of the feed movement.

[0141] The accuracy of the displacement device for the alignment is less than 500 nm, preferably less than 100 nm, particularly preferably less than 50 nm, very particularly preferably less than 10 nm, more preferably less than 5 nm and most preferably less than 1 nm.

[0142] In particularly preferred embodiments of the device, the error in the alignment accuracy of the device is less than 20%, preferably less than 10%, most preferably less than 1% of the maximum allowable alignment error.

[0143] In other words, if the tolerable alignment error of the substrate is, for example, 10 nm, the positioning error is a maximum of 20% of the value, ie 2 nm.

[0144] A first embodiment of an exemplary bonding method implementing the present method for alignment includes the following, particularly sequentially and / or simultaneously performed steps, particularly in the following order:

[0145] 1st step: An upper substrate is loaded onto an upper substrate holder by means of a mounting surface, where the opposite surface, the so-called contact surface of the upper substrate, is provided with at least one first additional alignment marking.

[0146] Second step: The substrate to be aligned underneath is loaded onto the lower substrate holder by means of the mounting surface, where the opposite surface, the so-called contact surface of the lower substrate, is provided with at least one second additional alignment marking.

[0147] Third step: detecting at least the first additional alignment marking and, if necessary, further additional alignment markings of the upper substrate through the upper substrate by means of an additional detection unit.

[0148] Fourth step: The focal position of the objective lens of the additional detection unit is memorized and the objective lens is fixed.

[0149] Fifth step: Using the upper substrate holder, move the upper substrate away from the focal plane in the direction of the additional detection unit, in particular upwards, the movement distance being preferably less than 500 micrometers.

[0150] Sixth step: Using the lower substrate holder, the lower substrate is moved, in particular upwards, to a fixed focal position of the additional detection unit. In particular, at the same time, a wedge error compensation can be performed as well.

[0151] To detect a second additional alignment marking on the lower substrate, the lower substrate is moved in the Z direction using the lower substrate holder until the contact surface of the lower substrate is in focus.

[0152] Seventh step: Searching for and detecting a second additional alignment marking on the lower substrate with a second additional detection unit.

[0153] Alternatively, the z-movement of the lower substrate holder displaces the focused lower substrate in the XY plane or rotates it around the Z axis, so that the located second additional alignment marking is positioned in the focal region of the first additional detection unit and detected by said detection unit. Preferably, the lower substrate is further aligned, so that the located alignment marking is located, in particular centrally, with respect to the optical axis of the fixed objective lens of the apparatus.

[0154] In one advantageous embodiment, the located alignment markings are detectable within a radius of less than 3 millimeters, preferably less than 2 millimeters, particularly preferably less than 1 millimeter, very particularly preferably less than 500 micrometers, and even more preferably less than 250 micrometers around the optical axis of the respective objective lens of the detection unit.

[0155] Eighth step: by means of a measuring system (in particular a measuring microscope with an objective lens) with at least one detection unit for detecting the alignment marks of the alignment marking field, the XYZ position and / or alignment orientation of the first alignment mark in the first plane and thus of the lower substrate holder, preferably of the rear surface of the substrate holder, is determined, the lower substrate holder being fixed and the position of the additional alignment marking of the lower substrate being correlated to the detected position. To determine the position of the lower substrate holder, an alignment marking field is used which is arranged in a fixed position on the substrate holder.

[0156] Preferably, the detection is focused on a step in the alignment marking field, the step being located adjacent an exposed surface of the alignment marking field such that the alignment markings are observable throughout the entire depth of the alignment marking field.

[0157] In this focusing position, the focal position of the detection unit (in particular of the objective lens) is fixed in order to detect the alignment marking field, the detection unit furthermore in particular being fixed in position or held in a fixed position.

[0158] 9th step: Using the lower substrate holder, move the lower substrate downwards by a defined distance, measuring the alignment marks of the different planar steps in the alignment marking field. The distance is preferably less than 500 micrometers. The distance by which the lower substrate is lowered is the so-called bonding gap, i.e. the correct distance to allow bonding, especially fusion bonding and / or hybrid bonding, to be performed as distortion-free as possible.

[0159] In one particularly preferred embodiment of the exemplary method, for this purpose, the lower substrate with the lower substrate holder is lowered downwards in the alignment marking field at a distance focused on the alignment mark of the next stage in another plane, in this way, blind or open-loop controlled movements of the substrate holder for alignment are avoided.

[0160] At this time, the detection unit detects movement of the lower substrate holder at least at the initial position and the target position by observing the alignment marking fields at different stages, where at the initial position, the detection unit detects at least one alignment mark in a first plane and at the target position, the detection unit detects at least one alignment mark in a second plane of the alignment marking fields.

[0161] (Optional) tenth step: Using the measured position error, correct the position of the lower substrate holder at least in the lateral plane by moving the substrate holder so that the at least one corresponding second alignment mark in the second plane is focused on or is located in the focal area of ​​the detection unit. In this way, the visual control can ensure that the spacing (i.e. the bonding gap) between the first and second planes is set sufficiently accurately.

[0162] This allows refocusing of the detection unit to be omitted and alignment errors to be avoided. The alignment marking fields provide height information that allows the visual control to approach the desired bonding spacing associated with the method without blind movements, whereby focusing and / or refocusing of the detection unit is omitted and thus eliminating focusing movement errors.

[0163] 11th step: Using the upper substrate holder, the upper substrate is lowered again to the focal position of the additional detection unit or its objective lens.

[0164] Twelfth step: Using the correlated XYZ position of the lower substrate holder, align the upper substrate with respect to the lower substrate, preferably by translating the upper substrate in the XY plane and / or rotating it about the Z axis.

[0165] In this step, the first additional alignment marking is aligned with respect to the second additional alignment marking. Because the position of the alignment marking of the lower substrate correlated with the alignment marking field has been measured, the actual position of the lower substrate on the lower substrate holder is known, allowing the alignment marking of the upper substrate to be aligned with the known, covered position of the second alignment marking of the lower substrate.

[0166] 13th step: Lift the bottom substrate for setting the correct bonding spacing, using the alignment marking fields any deviating movement can be observed and corrected.

[0167] Fourteenth step: The contact surfaces of the upper and lower substrates are brought into contact and the substrates are bonded together.

[0168] When the substrates are aligned with respect to one another, if the alignment error exceeds a determined boundary value, a correction can be made in the relative position of the substrates to one another.

[0169] The alignment errors to which the correction is applied are for displacements of less than 500 micrometers, preferably less than 100 micrometers, particularly preferably less than 100 nanometers, very particularly preferably less than 10 nanometers, even more preferably less than 5 nanometers and most preferably less than 1 nanometer.

[0170] The alignment error to which the correction for twist is applied is less than 50 microradians, preferably less than 10 microradians, particularly preferably less than 5 microradians, very particularly preferably less than 1 microradian, even more preferably less than 0.1 microradians and most preferably less than 0.05 microradians.

[0171] In another embodiment of the method for alignment, speed is achieved by parallelizing the steps, in particular by loading the second substrate already during the pattern recognition step on the first substrate.

[0172] The concepts of coincident axes or congruence or parallelism or normality are used in this disclosure as concepts of quantities with tolerances, whereby the tolerances correspond to non-tolerance linear or angular dimensions according to ISO 2768, unless a tolerance is expressly stated.

[0173] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. [Brief description of the drawings]

[0174] [Figure 1] 1 is a schematic cross-sectional view of one embodiment of an apparatus according to the present invention; [Figure 2a] 1 is a schematic plan view of an exemplary alignment marking field having alignment marks; FIG. [Figure 2b] 1 is a schematic cross-sectional view of one embodiment of an alignment marking field. [Diagram 3] FIG. 2 is a schematic plan view of one embodiment of an alignment marking field having alignment marks; [Figure 4] 1 is a schematic cross-sectional view of one embodiment of an alignment marking field having a detection unit;

[0175] In the drawings, advantages and features of the present invention are given reference numerals that respectively identify them according to the embodiments of the present invention, and components or features having the same function or effect are given the same reference numerals.

[0176] In Fig. 1 a schematic and not to scale functional diagram of the main components of one embodiment of an alignment facility 1 is depicted. The alignment facility 1 is capable of aligning substrates, which are not depicted in Fig. 1, with one another and at least partially and / or temporarily bonding them to one another (so-called pre-bonding). The terms apparatus and facility are used equivalently and interchangeably.

[0177] The alignment facility 1 includes a first substrate holder 9 onto which a first substrate can be loaded and secured. The alignment facility 1 further includes a second substrate holder 11 onto which a second substrate can be loaded and secured.

[0178] In particular the lower first substrate holder 9 to be aligned is arranged on a first moving device 10 for holding the first substrate holder 9 and for carrying out a supply movement and an adjustment movement (alignment). In particular the upper second substrate holder 11 is arranged on a second moving device 12 for holding the second substrate holder 11 and for carrying out a supply movement and an adjustment movement (alignment). The moving devices 10, 12 are fixed in particular to a common robust table or frame 8 in order to reduce / minimize vibrations of all functional components. The frame may in particular include active vibration damping.

[0179] In order to observe (detect) the additional alignment markings on the substrate, the optical system 2 of the alignment facility 1 comprises at least one additional detection unit 3, in particular an image detection means, for detecting the additional alignment markings.

[0180] The optical system 2 can be focused on a focal plane or focal position, which, when arranged for alignment, is arranged between the first and second substrate, preferably between the substrate holder 9 and the substrate holder 11. The movement of the optical system 2, in particular in the X-, Y- and Z-directions, is performed by means of a positioning device 4 for positioning the optical system 2. The positioning device 4 can in particular be fixed to a robust table or frame.

[0181] At least one additional, in particular optical, measuring system 5 with at least a detection unit 6 for detecting the alignment marking field 14 is used to increase the alignment accuracy by detecting alignment marks in different planes of the alignment marking field 14. The movement of the additional measuring system is performed by a positioning device 7.

[0182] If the additional measuring system is an optical measuring system 5, the positioning device 7 can focus the detection unit 6 in the Z direction on the alignment marks in the first plane 18 of the alignment marking field 14. Positioning in the XY direction is likewise conceivable, with in particular fixation during alignment, preferably on a table / frame.

[0183] In the illustrated embodiment of the alignment apparatus 1, the measuring system 5 or detection unit 6 detects in particular the XY position and / or orientation (in particular also the rotational orientation) and / or height position of the lower substrate holder 9 with particularly high precision.

[0184] A preload can be applied to at least the upper substrate by the substrate preload device 13 in order to initiate fusion bonding. The preload can be achieved by mechanical preloading with preload elements, so-called bonding pins. In another embodiment of the substrate preload device, the substrate is preloaded by a fluid, in particular a gas from a nozzle, in particular a movable nozzle.

[0185] An embodiment of the device, not shown but preferably, allows the following steps, shown by way of example only: The first substrate / lower substrate is fixed to a first fixing surface, in particular the substrate holder surface, of the first substrate holder 9. In particular mechanical and / or electrostatic clamping, a pressing force formed due to the pressure difference between the ambient environment of normal atmosphere and the negative pressure in the first substrate holder 9, also called vacuum fixing, is used as fixing. This fixing is performed in particular in such a way that the first substrate is prevented from moving incorrectly or undesirably relative to the first substrate holder 9 during the entire process. In particular, if the first substrate holder 9 and the first substrate each have corresponding thermal expansion coefficients, which preferably run in a linearly corresponding manner, the thermal expansion can be prevented or reduced, the difference in the thermal expansion coefficients and / or the linear course of the thermal expansion coefficients being preferably less than 5%, preferably less than 3%, particularly preferably less than 1%.

[0186] The equipment is preferably operated in a temperature stabilized ambient environment, in particular a clean room, in which the temperature fluctuations during the alignment cycle are less than 0.5 Kelvin, preferably less than 0.1 Kelvin, particularly preferably less than 0.05 Kelvin, most preferably less than 0.01 Kelvin.

[0187] The fixed first substrate and the first substrate holder 9 can be understood as a quasi-monolithic body for the movement of the first substrate, which does not allow a relative movement with respect to each other.

[0188] The substrate fixing can be effected by positive and / or preferably by force coupling. The quasi-monolithic bonding ensures that influences which can cause displacements and / or twists and / or deformations between the substrate holder and the substrate are at least reduced, preferably reduced by at least an order of magnitude, and particularly preferably eliminated.

[0189] The substrate and the substrate holder can be joined by a form or force connection, in particular in such a way that differential thermal expansion is suppressed, and furthermore the substrate holder can reduce, eliminate and / or compensate for deformations of the substrate itself.

[0190] In one embodiment, both the lower substrate holder 9 and the upper substrate holder 11 may include additional passively and / or actively actuated deformation elements and / or intermediate plates, which minimize the mechanical and / or thermal properties of the substrates in order to reduce residual alignment errors after bonding.

[0191] The first substrate holder 9 may be located in the optical path of the additional detection unit 3 during the detection of the first additional alignment marking. The first additional alignment marking may be arranged in the field of view, in particular in the optical path, preferably in the optical axis of the additional detection unit 3, at the contact surface of the bonding object of the first substrate. By means of the additional detection unit 3, an image to be measured, in particular digital, is formed. The first alignment marking of the substrate may consist of a plurality of alignment markings combined together. From the image of the alignment markings, in particular measured values ​​are generated / calculated which characterize the XY position and / or the alignment attitude (in particular in the rotational direction around the Z direction) of the first substrate, i.e. the alignment state.

[0192] The lower substrate holder 9 and / or the first substrate have alignment marks in the alignment marking field 14, based on which the XYZ position and / or alignment attitude, in particular the spatial alignment state of the substrate holder 9 and / or the first substrate, is detected in particular from another direction, preferably from a direction exactly opposite to the initial detection in the Z direction.

[0193] Preferably, a relative movement of the first detection unit 3 with respect to the third detection unit 6 is measurable. Even more preferably, no relative movement takes place between the first additional detection unit 3 and the detection unit 6 from the detection of the first additional alignment marking and the alignment mark in the alignment marking field 14 until the contact of the first and second substrates.

[0194] A detection unit 6 for detecting the alignment marking field 14 of the additional measuring system 5 provides measured values ​​of the spatial XYZ position and / or orientation of the first substrate holder 9 / lower substrate holder 9 from measurements of the alignment marks in different planes of the alignment marking field 14.

[0195] The measurements (XY position and / or alignment orientation of the first substrate and XYZ position and / or alignment orientation of the first substrate holder 9 or first substrate 16) are correlated with each other so that the XYZ position of the substrate holder 9 can be reproducibly restored. This allows a closed-loop controlled movement of the substrate fixed in the substrate holder 9 for alignment and for setting the bonding spacing without directly observing additional alignment markings on the substrate.

[0196] By correlating the positions of the substrates with the spatial position and / or orientation of the substrate holder 9, alignment can be realized without directly observing the XY position and / or alignment orientation of the respective substrate during alignment and / or contact. Furthermore, the spacing between the substrates can be set and / or minimized in a defined manner during alignment. This spacing can preferably already correspond to the spacing of the substrates during detection of the first and second additional alignment markings. In another embodiment, a preferred spacing for bonding can be set.

[0197] In other words, in particular, an unobstructed optical path is obtained between the substrate holder 9 and the additional measuring system 5, by means of which the alignment of the substrate can be or is performed in a closed control loop, so that the XYZ position and / or alignment orientation of the first substrate holder 9 and thus of the first substrate fixed to the first substrate holder 9 can be accurately determined and reproducibly restored, which again increases the precision during bonding, in particular fusion bonding.

[0198] Restoring and correcting the XYZ position and / or alignment attitude, in particular of the substrate holder 9 and in particular of a substrate integrally bonded thereto, relative to another substrate and / or substrate holder, is an important aspect of the present apparatus for alignment.

[0199] In particular, a positioning repeatability of less than 500 nm, preferably less than 100 nm, particularly preferably less than 30 nm, particularly very preferably less than 10 nm, even more preferably less than 5 nm, most preferably less than 1 nm, also known as backlash (measured as the relative alignment error between the two substrates), is achieved. This backlash may be a repeated approach to a given position with the movement device 10, the movement device 12 and / or the positioning device 4, the positioning device 7. This backlash results from the movement of the movement device, but only the detection point changes, so that the measurement quantity is present as a relative alignment error.

[0200] In order to further improve the alignment accuracy, it is preferable to operate the first additional detection unit 3 and the second additional detection unit 5 in a time-synchronous manner, in particular simultaneously, with a time difference between the detection of the measured values ​​of less than 3 seconds, preferably less than 1 second, particularly preferably less than 500 milliseconds, particularly preferably less than 100 milliseconds, even more preferably less than 10 milliseconds, most preferably less than 1 millisecond. This is particularly advantageous, since the action of disturbing influences, such as mechanical vibrations, can be eliminated. Mechanical vibrations propagate in materials, inter alia, with structure-borne sound at several thousand m / s. If the closed-loop control and detection means operate faster than the propagation speed of the structure-borne sound, disturbances are reduced or eliminated.

[0201] If a disturbance causes a change in the orientation of the first substrate on the first substrate holder 9, such that a measured value has already been recorded by the first additional detection unit 3 and a measured value has not yet been recorded by the measuring system 5 with the detection unit 6 for detecting the alignment marking field 14, this disturbance can result in a decrease in the alignment accuracy, since fast mechanical position changes of the order of nanometers or micrometers, in particular due to vibrations, can occur in the time between the measured value recording of the additional detection unit 3 and the measured value recording of the detection unit 6. If the measured value recording takes place with a time delay (of the order of seconds or minutes), other disturbing effects, such as shape or length changes due to temperature, can also decrease the alignment accuracy.

[0202] If the first additional detection unit 3 and the detection unit 6 are synchronized with each other to detect the alignment marking field 14 (in particular by simultaneous triggering of the detection and equalization of the detection times and / or the same integration time for the camera system), some disturbing influences can be reduced and in the optimal case eliminated, since the detection should be performed at a time when disturbing influences have the least possible effect on the detection accuracy.

[0203] In a preferred embodiment of the method and the device for alignment, the detection of disturbing influences, especially periodic disturbing influences, is performed synchronously, especially at the peaks of vibration. For this purpose, vibration sensors (accelerometers, interferometers, vibrometers) can be advantageously pre-mounted on the device for alignment at points relevant for accuracy. These disturbing influences are recorded by these vibration sensors and are taken into account or removed by calculation, especially by a calculation unit, for removal. In another embodiment, vibration sensors can be fixedly integrated at characteristic points of the installation.

[0204] To align the substrate, in particular determined / determined target values ​​are used, which in particular comprise image data of the alignment marks of the alignment marking field 14 of the first substrate holder 9 and / or determined XYZ position data and / or alignment attitude data for the movement device 10 of the first substrate holder 9 and / or closed-loop control parameters, e.g. trajectories for optimally approaching a spatial position and / or machine-readable values, in particular for the drives.

[0205] The first substrate holder 9 is moved in a closed-loop controlled manner by the first movement device 10 in a closed-loop controlled manner in positioning and in particular in a closed-loop controlled manner in orientation until the alignment error calculated from the target value of the detection unit and the actual position and / or orientation of the substrate holder is minimized and, in the ideal case, eliminated or an interruption decision is reached. This movement of the lower substrate holder likewise includes intervals that are precisely set for bonding, in particular for fusion bonding. In other words, the lower substrate holder 9 is moved in a controlled and closed-loop controlled manner to a known and measured XYZ alignment position and is moved in a closed-loop controlled manner, in particular in the Z direction.

[0206] In another embodiment, residual errors that could not be eliminated when positioning the upper and / or lower substrate can again be taken into account as correction values ​​for the positioning of another (lower or upper) substrate.

[0207] FIG. 2 a shows an alignment marking field 14 ′ in a greatly enlarged schematic plan view with an exemplary selection of alignment marks 15 or alignment markings 15 .

[0208] The individual alignment marks 15 symbolically and generally represent an absolutely unique coding of the position and orientation of each individual alignment mark or alignment marking 15. The individual alignment marks 15 or alignment markings 15 may be provided in different planes of the alignment marking field 14'. Since the nature of the alignment marking field 14' (xyz position of each alignment marking 15) is known a priori, it is sufficient to detect the absolutely coded alignment marks 15 or alignment markings 15 for the absolute position detection of the substrate holder, not shown.

[0209] FIG. 2b shows a schematic cross-sectional view of an alignment marking field 14'' with exemplary marked different layers 16, 16' of the alignment marking field 14''.

[0210] It is advantageous to take into account multiple alignment marks in different planes when aligning a substrate holder which includes an alignment marking field or is arranged in a fixed position relative to the alignment marking field, in which case in particular multiple steps and / or layers 16, 16' of the alignment marking field can be located simultaneously or preferably sequentially in the field of view or focal area of ​​the detection unit 6 and thus detected. Due to the step height or the spacing between the planes being known, the step height or the spacing between the planes can be used for alignment or for setting a desired spacing between the substrates.

[0211] The spacing between the planes is between 1 micrometer and 300 micrometers, preferably between 5 micrometers and 200 micrometers, particularly preferably between 10 micrometers and 100 micrometers, in the most optimal case between 25 micrometers and 75 micrometers, and in the ideal case between 48 micrometers and 52 micrometers. In a special case, the spacing between the planes is 50.00 micrometers.

[0212] It is advantageous if the alignment marks 15, 15' of the alignment marking fields 14, 14', 14'', 14''' provide the spatial position and / or orientation of the substrate holder 9 or of the substrate arranged thereon. It is further advantageous if the respective alignment marks 15, 15' have detectable orientation information which provides the respective orientation in the alignment marking fields 14, 14', 14'', 14'''. In particular this results in the orientation of the respective detected alignment marks 15, 15' relative to the alignment marks 15 of the alignment marking field being known as well. Advantageously, not only is the orientation of the detected alignment marks 15, 15' relative to the same plane of the alignment marking field known, but also the orientation of the respective plane of the detected alignment marks 15, 15' relative to the other planes of the alignment marking field. This respective orientation information is possible, for example, by different angles and different shapes of the alignment markings 15, 15', which are exemplarily shown diagrammatically.

[0213] In order to accurately set the desired spacing or bonding spacing between the substrates, the optical system of the detection unit 6 for detecting the alignment marking fields 14, 14', 14'', 14''' preferably has a depth of field or a smaller depth of the focal area (especially in the Z direction) than half the spacing between the corresponding planes.

[0214] FIG. 3 shows one possible embodiment of the alignment marking field 14″, where each exemplary alignment mark 15′ is supplemented with a machine-readable code. In this case, the individual alignment marks 15 may be arranged in different planes (stages and / or layers), and information about which plane each of them is in may be included in the code. Furthermore, unique information about the position and orientation of each alignment mark 15′ may be included in the code.

[0215] One embodiment of the alignment marking field 14'''' is shown in cross-section in Fig. 4. The alignment marks 15' of the alignment marking field 14'''' are arranged in three different planes 18, 18', 18'' and are detectable by the detection unit 6. Here, only the alignment marks 15' in the focal region 19 can be detected by the detection unit 6.

[0216] The first plane 18 has a known spacing 17'' with respect to the second plane 18'. The second plane 18' has a similarly known spacing 17' with respect to the third plane 18''. Furthermore, the spacing 17 between the first plane 18 and the third plane 18'' is known. The spacings 17'' and 17' are of different sizes in the illustrated embodiment, such that all three spacings 17, 17', 17'', respectively, can be approached or set when using the alignment marking field 14'''' to align a substrate.

[0217] The combination of the spacings 17, 17', 17'' can also be approached by moving the substrate holder 9 in a fixed position with respect to the alignment marking field 14'''' several times. For example, the spacing 17'' can first be set and then the spacing 17' can be approached further in the same direction. For example, the substrate holder can also be moved by twice the spacing 17''. For this, the alignment is performed in two steps and the detection unit is correspondingly set between these steps, since the focal position and thus the focal area 19 of the detection unit 6 are adapted. [Explanation of symbols]

[0218] 1. Alignment equipment, alignment facilities 2 Optical system 3 Additional detection units 4 Positioning device 5 Additional Measurement Systems 6 Detection Unit (Alignment Marking Field) 7 Positioning device for additional measuring systems 8 Frames 9 Substrate holder, first substrate holder (to be aligned) 10: A moving device for a substrate holder to be aligned, a first moving device 11 Second / Upper Board Holder 12 Second moving device 13. Substrate transformation device 14,14',14'',14'''' Alignment marking field 15,15' Alignment mark, alignment marking 16,16' Alignment marking layer of the alignment marking field 17,17', 17'' spacing 18,18',18'' Alignment marking field plane 19 Focal area of ​​the detection unit at the focal position 20 Substrate holder surface of the substrate holder (to be aligned)

Claims

1. A method for aligning a substrate, said method comprising at least the following steps: i) providing a substrate holder (9) having a substrate holder surface (20) configured to receive said substrate and alignment marking fields (14, 14', 14'', 14''') arranged in a fixed position relative to said substrate holder (9); ii) aligning the substrate, aligning the substrate based on alignment marks (15, 15') arranged above and below the alignment marking fields (14, 14', 14'', 14''').

2. Said alignment of said substrate in step ii) comprises the following steps, in particular in the following order: a) detecting a first alignment mark (15, 15') in a first plane (18, 18', 18'') of said alignment marking field (14, 14', 14'', 14''') by a detection unit (6); b) after said detection in step a), fixing the focal position of said detection unit (6); c) moving the substrate holder (9) perpendicular to the first plane (18, 18', 18'') of the alignment marking field (14, 14', 14'', 14'''); d) detecting, by said detection unit (6), a second alignment mark in a second plane (18, 18', 18'') of said alignment marking field (14, 14', 14'', 14'''), 2. The method of claim 1, wherein the first plane (18, 18', 18'') and the second plane (18, 18', 18'') are arranged parallel to each other, and the first plane (18, 18', 18'') and the second plane (18, 18', 18'') have a distance (17, 17', 17'') from each other.

3. 3. The method according to claim 2, wherein in step a) additional alignment marks are detected in the substrate holder (9) or on the substrate by means of at least one additional detection unit (3).

4. 4. The method according to claim 1, further comprising measuring the alignment marking fields (14, 14', 14'', 14''') successively at the focus position by the detection unit (6) during the movement of the substrate holder (9) in step iv).

5. 5. The method according to claim 1, further comprising holding the detection unit (6) in a fixed position after the fixation of the focal position in step b).

6. 6. The method according to claim 1, wherein during the detection of the first alignment mark (15, 15') in step a) and / or during the detection of the second alignment mark (15, 15') in step d), the detection unit (6) additionally provides information regarding the orientation of the respective alignment mark (15, 15') in the alignment marking field (14, 14', 14'', 14''').

7. An apparatus for aligning a substrate, the apparatus comprising at least A) a substrate holder (9) having a substrate holder surface (20) configured to receive the substrate; B) an alignment marking field (14, 14', 14'', 14'') with alignment marks (15, 15') arranged in a fixed position relative to the substrate holder (9) and / or relative to the substrate, An apparatus, characterized in that the substrate can be aligned based on alignment marks (15, 15') arranged above and below.

8. moreover, C) a detection unit (9) for detecting the alignment marks (15, 15') of the alignment marking fields (14, 14', 14'', 14'''); D) a moving device (10) for moving the substrate holder (9), the alignment marks (15, 15') of the alignment marking field (14, 14', 14'', 14''') are arranged in a first plane (18, 18', 18'') and in a second plane (18, 18', 18''), the first plane (18, 18', 18'') and the second plane (18, 18', 18'') being arranged parallel to one another, and the first plane (18, 18', 18'') and the second plane (18, 18', 18'') have a distance (17, 17', 17'') from one another, a first alignment mark (15, 15') of the alignment marks (15, 15') of the first plane (18, 18', 18'') is detectable at a focal position of the detection unit (6), the focal position of the detection unit (6) being fixable, in said focal position, a second alignment mark (15, 15') of said alignment mark (15, 15') of said second plane (18, 18', 18'') is detectable by said detection unit (6), 8. Apparatus according to claim 7, wherein the substrate holder (9) is movable perpendicularly to the first plane (15, 15') by the movement device (10).

9. 9. The apparatus according to claim 7 or 8, wherein the alignment marks (15, 15') of the first plane (18, 18', 18'') and the alignment marks (15, 15') of the second plane (18, 18', 18'') are arranged in one-to-one alignment, in particular congruent, in the alignment marking field (14, 14', 14'', 14''').

10. 10. The device according to claim 7, wherein the alignment marks (15, 15') of the first plane (18, 18', 18'') and the alignment marks (15, 15') of the second plane (18, 18', 18'') are arranged displaced in a step-like manner.

11. 11. The apparatus according to claim 7, wherein the alignment marking fields (14, 14', 14'', 14''') are arranged on a back surface of the substrate holder (9) facing away from the substrate holder front surface (20).

12. The apparatus of claim 11, wherein a center point of the alignment marking field (14, 14', 14'', 14''') is at least partially aligned with a center point of the substrate holder surface (20) on the back surface of the substrate holder (9).

13. The apparatus according to any one of claims 7 to 12, wherein the alignment marking fields (14, 14', 14'', 14''') are arranged on a side of the substrate facing towards the substrate holder surface (20).

14. 14. The apparatus according to claim 7, wherein the alignment marking field (14, 14', 14'', 14''') has at least one further plane (18, 18', 18'') with the alignment marks (15, 15'), the at least one further plane (18, 18', 18'') being arranged at least parallel to the first plane (18, 18', 18'').

15. 15. The apparatus according to claim 7, further comprising at least one further alignment marking field (14, 14', 14'', 14''') and at least one further detection unit (6) for detecting the at least one further alignment marking field (14, 14', 14'', 14'''), the at least one further alignment marking field (14, 14', 14'', 14''') being arranged in a fixed position on the substrate holder (9).

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