Method and device for the alignment of a substrate

Abstract

This 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. [Previous Technology]

[0002] In the semiconductor industry, alignment systems are used to align substrates (specifically wafers) to each other or to other components. The substrates can have any shape, but are preferably circular. Specifically, the diameter of the substrate is industry-standard. For wafers, industry standard diameters are 1 inch, 2 inches, 3 inches, 4 inches, 5 inches, 6 inches, 8 inches, 12 inches, and 18 inches. In particular embodiments of alignment systems, square substrates or panels can also be aligned and bonded to each other with extreme accuracy.

[0003] Specifically, the connection between aligned semiconductor substrates is called bonding.

[0004] In the so-called bonding process, the substrates to be bonded are aligned with each other and bonded together in a further process step. Herein, it is necessary for the substrates to be particularly precisely aligned with one of them.

[0005] The alignment process in which the alignment mark is positioned on the surface of the substrate to be joined is called face-to-face alignment.

[0006] If at least one of the substrates is not transparent to electromagnetic radiation used to measure the substrate, in order to detect and / or determine the position and location of the alignment mark from a substrate surface other than the surface of the substrate to be joined, in the prior art, the alignment mark is detected between the substrates by an image detection member before the substrates are brought close to each other.

[0007] This has various drawbacks. Specifically, particles from the camera may be introduced onto the substrate surface. Furthermore, a considerable distance must be traveled between the substrates to position the camera for detection. Consequently, a significant alignment error arises due to the more complex alignment and the corresponding larger travel distance.

[0008] Especially when setting a specific distance between the substrates to be joined and the joint surfaces, an optimal alignment system is essential to obtain the best possible joint result.

[0009] Another problem with the prior art is that the increased alignment accuracy requirements may no longer be achievable by simple means. No new alignment accuracy requirements have been achieved with respect to methods that measure the substrate relative to a reference point and, for example, blindly align the substrate until contact after approaching it.

[0010] For example, US6214692B1 discloses a method based on the comparison and position correction of two images of alignment marks. A camera system individually detects the positions of alignment marks on two substrates arranged face-to-face. From one of the alignment marks, relative positioning and relative position are calculated, and a positioning stage (substrate holder and support) is manipulated to correct mispositioning.

[0011] Further disclosure US10692747B2 is based on the comparison and position correction of a total of three images of planar alignment marks. A camera system individually detects the position of alignment marks on two substrates arranged face-to-face. A third alignment mark is detected from a third detection unit, and using this third alignment mark, a correction is generated relative to the rear side of the substrate holder or the rear side of the substrate to one of the alignment marks on the substrate, thereby achieving more precise alignment of one of the two substrates.

[0012] To this extent, visual control of one of the two substrates being face-to-face aligned is not feasible, or is only feasible if at least one of the substrates is at least partially transparent. Therefore, precise alignment of the surfaces in a face-to-face alignment is only feasible in a complex and limited manner.

[0013] Specifically, it has been demonstrated that the need for refocusing in the detection of one of the alignment marks is disadvantageous. This means that, as a matter of principle, refocusing is necessary using the adjustment movement of the optics used specifically for the detection of the alignment marks. In addition to the necessary movement, the adjustment movement occurs together with parasitic movements superimposed thereon, which cause deviations from the ideal movement of the respective optics. Therefore, a movement results in a displacement of the focal point. The focal point, for example, is displaced in the xy plane normal to or extending from the optical axis of the optics. The displacement of the focal point reduces the accuracy of the measurement of the alignment mark, thus reducing alignment accuracy. [Summary of the Invention]

[0014] Therefore, the problem of the present invention is to provide a method and apparatus for at least partial removal (specifically, complete removal) of the disadvantages listed in the prior art for a basic alignment. Specifically, one problem of the present invention is to provide an improved method and apparatus for aligning a substrate. Specifically, one problem of the present invention is to provide a method and apparatus for aligning a substrate without requiring any refocusing of a detection unit during alignment. Furthermore, one problem of the present invention is to provide a method and apparatus for aligning a substrate that can be carried out particularly reliably, accurately, and without contamination, or that aligns particularly reliably, accurately, and without contamination.

[0015] The present problem is solved by the features of a coordinated technical solution. Further advantageous developments of the invention are given in the accompanying technical solutions. All combinations of at least two features stated in the description, technical solutions, and / or drawings also fall within the scope of the invention. Values ​​within the stated range, values ​​within the stated limitations, should also be considered as limiting values ​​and can be claimed in any combination.

[0016] Therefore, the present invention relates to a method for aligning a substrate, comprising at least the following steps: i) providing a substrate holder having a substrate holder surface designed for mounting the substrate and an alignment mark field fixedly configured relative to the substrate holder; ii) aligning the substrate, characterized in that the substrate is aligned with the aid of alignment marks of the alignment mark fields configured vertically to each other.

[0017] Alignment of substrates or substrate stacks is aided by alignment marks arranged vertically to each other. Alignment mark fields are fixedly disposed relative to substrate holders or substrate holder surfaces. Specifically, the precise positions of the alignment mark fields and the respective positions of the alignment marks within the alignment mark fields relative to the substrate holders are known. Alignment marks or at least two alignment marks within the alignment mark fields are arranged vertically to each other.

[0018] The fact that at least two alignment marks in the alignment mark field are arranged one above the other means that the latter are arranged in different planes. Therefore, the alignment mark field has a specific height (z direction) relative to one of the substrate holder surfaces. Therefore, at least two alignment marks are arranged in different z planes.

[0019] The alignment marks are preferably not obscured from each other in the z-direction, such that viewing of at least two alignment marks in an alignment mark field can occur from an unobstructed viewing direction. In other words, the alignment marks of an alignment mark field are preferably offset relative to each other and arranged vertically above each other in mutually parallel planes, such that any alignment mark in any plane of the alignment mark field can be observed.

[0020] Furthermore, it is conceivable that at least two alignment marks of alignment mark domains arranged vertically to each other in the z-direction are partially or completely overlapping. In other words, at least two alignment marks arranged vertically to each other can be configured to be at least partially aligned with each other in the z-direction. In this case, different z-planes or layers of the alignment mark domains are transparent to different wavelengths, making it possible to detect any further arbitrary alignment domain in any different plane of the alignment mark domain. The upstream plane / layer and / or the upstream alignment mark in the viewing direction are penetrated for viewing, making it possible to detect alignment marks that are at least partially aligned with the next plane.

[0021] By detecting an alignment mark and subsequently detecting another alignment mark positioned above it, the known positions of the alignment marks can be compared. Since the properties, structure, and position of the alignment mark fields are preferably known, the distance between the alignment marks can be detected. Based on this distance, alignment can be performed, for example, by relative movement of a substrate holder with the aid of the vertically positioned alignment marks, without requiring refocusing of the detection component. In this way, a substrate can be aligned particularly precisely in at least one direction because the known distance between the vertically positioned alignment marks can be detected and thus set.

[0022] Furthermore, a joining gap can be advantageously and very easily and precisely approached by means of precise alignment in at least one direction. The substrate holder can be advantageously aligned based on the alignment mark area through direct visual control. Additionally, alignment requires only one detection element, thus reducing sensitivity to errors. Therefore, specifically for joining opaque substrates in a face-to-face manner, the substrate holder and thus the substrate can be advantageously positioned precisely. Alignment can therefore advantageously occur through the alignment marks arranged vertically above and below each other and the height information provided therefrom, without the need for refocusing of the detection element. Thus, the substrate to be aligned can be moved particularly precisely and under visual control within a specific distance.

[0023] In a preferred embodiment of the method for aligning a substrate, the alignment of the substrate includes at least the following steps in step ii), specifically in the following order: a) detecting a first alignment mark in a first plane of an alignment mark field by a detection unit; b) after detection in step a), fixing a focal position of a detection unit; c) moving a substrate holder perpendicular to the first plane of the alignment mark field; d) detecting a second alignment mark in a second plane of an alignment mark field by a detection unit, wherein the first plane and the second plane are arranged parallel to each other and wherein the first plane and the second plane have a distance between them.

[0024] A plurality of alignment marks are preferably arranged close to each other in alignment mark fields within their respective planes. Therefore, at least one first alignment mark or at least one second alignment mark on a corresponding plane is detected. Furthermore, the alignment mark fields are preferably configured to be transparent between the planes of the detection unit, allowing the detection of alignment marks arranged vertically to each other. It is also conceivable that the alignment marks on the first plane are offset relative to the alignment marks on the second plane, and that the alignment mark fields have different gradations. In addition to their respective first alignment marks, the detection unit can also detect further alignment marks on the first plane, provided that these alignment marks are arranged within the focal range. This also applies to the second plane. The detection unit is configured to detect a plurality of alignment marks on each plane, specifically alignment marks arranged close to each other.

[0025] In the detection of one of the first alignment marks on the first plane of the alignment mark domain, the respective alignment mark is identified by a detection unit. The detection unit preferably includes a focusing member, preferably a lens, which clearly focuses the first alignment mark during detection. The detection unit or lens occupies a focal position within a specific focal range in which the detection unit can detect. Therefore, the focal range of a specific focal position of the detection unit or lens is focused, and alignment marks disposed within the focal range can be detected. In a detection, it is preferable to detect or identify only the alignment marks of the respective plane, because in each case, a focal range in the detection unit precisely contains a plane. Therefore, the distance between the first plane and the second plane is preferably greater than the depth of the focal range.

[0026] After the detection of the first alignment mark on the first plane, the focal position of the detection unit is fixed. Specifically, the focal range is thus fixed, allowing the detection unit to subsequently detect only the alignment marks within the fixed focal range. By moving the substrate holder toward one of the first planes of the alignment mark area, the substrates on the substrate holder surface of the substrate holder then move together and are thus aligned. The substrate holder moves at least this far until the detection unit can detect the second alignment mark in the second plane of the alignment mark area. To this extent, by moving the substrate holder, the substrate is advantageously moved the distance required for focusing. For example, a bonding gap can be set between the substrate and another substrate to be bonded. Thus, alignment errors due to refocusing of the detection unit can be advantageously prevented.

[0027] In a preferred embodiment of a method for aligning a substrate, a layout is performed such that in step a), at least one additional detection unit detects the substrate holder or additional alignment marks on the substrate.

[0028] Additional alignment marks or additional alignment markers may be advantageously positioned in relation to or specifically referencing the position of the first alignment mark. Specifically, the additional alignment marks are flat alignment mark areas without alignment marks arranged vertically above each other. In other words, these additional alignment marks are not arranged on a plane above each other.

[0029] Using additional alignment marks, alignment of the substrate holder relative to the alignment marks in the alignment mark area can also advantageously occur. Furthermore, the substrate holder or the substrate disposed on the substrate holder can be aligned relative to the additional alignment marks by a detection unit. Specifically, the position of an additional substrate to be bonded to the substrate relative to the alignment mark area can be determined by at least one additional detection unit. With the additional alignment marks and the additional detection unit, alignment can be performed more precisely.

[0030] In a preferred embodiment of a method for aligning a substrate, the deployment is made such that during the movement of the substrate holder in step iv), the detection unit at the focal position continuously misses the alignment mark field.

[0031] If further alignment marks are arranged in a further plane between the first plane and the second plane, these further alignment marks can be measured by the detection unit during the movement of the substrate holder, so that the movement of the substrate holder can be performed in a particularly precise and controlled manner. In addition, alignment can be performed more precisely by means of a plurality of detected alignment marks, the positions of which are known in the alignment mark field.

[0032] In a preferred embodiment of a method for aligning a substrate, the layout is performed such that the focal position of the detection unit remains fixed after the focal position is fixed in step b).

[0033] The detection unit is not only fixed at a specific distance from one of the alignment mark areas, but also in a horizontal position. Therefore, this immovable fixation relative to the alignment mark areas specifically results in the immovable fixation of the substrate holder and thus the substrate disposed on the substrate holder. In this way, it is advantageously ensured that, in addition to fixing the focal position of the detection unit or lens, the position of the detection unit is also fixed. In this way, the substrate can be aligned more accurately, and alignment errors due to inaccurate movement of one of the detection units are prevented.

[0034] In a preferred embodiment of the method for aligning a substrate, the layout is performed such that in step a) the detection of the first alignment mark by the detection unit and / or in step d) the detection of the second alignment mark by the detection unit, additional information about the position of each alignment mark within the alignment mark domain is provided.

[0035] The alignment marks preferably contain information about their respective positions within the alignment mark domain. In addition to the position along the alignment mark domain (xy position), the respective heights or distances between the planes are also known. If the first alignment mark is thus detected, it can be advantageously determined in which plane it is positioned. Particularly when the alignment mark domain has two or more planes with different distances between them, the detection of information about the respective heights of the alignment marks makes alignment easier to control or adjust. For example, in a continuous detection, it can be advantageously determined which plane or step is detected within the focal range during movement or during the detection of the first alignment mark. If, in addition, a position between two planes or steps is detected, it can be advantageously approached from the plane positioned above or below that position. Furthermore, the position can be advantageously detected and controlled in the xy position.

[0036] The aforementioned advantages and features of the method for alignment are also intended to be disclosed in conjunction with the following apparatus.

[0037] Furthermore, the present invention relates to an apparatus for aligning a substrate, comprising at least: A) a substrate holder having a substrate holder surface designed for mounting the substrate, and B) an alignment mark field having alignment marks fixedly disposed relative to the substrate holder and / or the substrate, characterized in that the substrate can be aligned with the aid of alignment marks disposed vertically above each other.

[0038] The alignment marks of the alignment mark fields arranged vertically to each other have a known distance between them in one direction of the alignment mark fields. In this way, the alignment of the substrate holder or the substrate disposed on the substrate holder by a particularly precise detection member can be advantageously performed with the help of the alignment marks alone.

[0039] In a preferred embodiment of the apparatus for aligning a substrate, the arrangement further includes: C) a detection unit for detecting alignment marks in the alignment mark field, and D) a movable configuration for moving the substrate holder, wherein the alignment marks in the alignment mark field are disposed in a first plane and a second plane, wherein the first plane and the second plane are arranged parallel to each other, wherein the first plane and the second plane are spaced apart from each other, wherein a first alignment mark of the alignment mark on the first plane can be detected at a focal position of the detection unit, wherein the focal position of the detection unit can be fixed, wherein a second alignment mark of the alignment mark on the second plane can be detected by the detection unit at the focal position, and wherein the substrate holder can be moved toward the first plane by the movable configuration.

[0040] The device is specifically designed such that the focus position of the detection unit can be fixed immediately after one of the first alignment marks on the first plane of the alignment mark field is detected. The fixed focus position of the detection unit defines a clearly defined focus range. In this way, the distance from the first plane to the second plane can be advantageously traversed by a movable configuration, allowing the substrate holder or substrate to move precisely in one direction with the aid of the alignment mark field. In addition, the detection unit is also preferably kept fixed, so that the distance between the planes can be traversed solely by the detection of the alignment mark and the movement of one of the substrate holders. When the device for alignment is used to set a bonding gap between two substrates to be bonded, the distance between the first plane and the second plane is preferably the distance required before the start of the bonding process. In other words, the bonding distance corresponds to the bonding gap. The alignment with the device can be advantageously controlled directly by detecting the second alignment mark on the second plane. Therefore, a correct alignment can be advantageously confirmed by direct visual control through precise detection of one of the detection units.

[0041] In a preferred embodiment of the apparatus for aligning a substrate, the alignment marks of the first plane and the alignment marks of the second plane are arranged such that they are aligned vertically with each other in the alignment mark field, specifically, they are matched.

[0042] The alignment mark domain is preferably configured to be transparent to the detection unit between the planes. By aligning the alignment marks vertically to each other, when the second alignment mark is detected, it can be advantageously determined whether the movement of the substrate holder by the moving configuration has been precisely normal to the first plane. The detection unit has a focal point at the focal position, where the respective positions of the second alignment marks correspond to the first alignment mark. Furthermore, it is conceivable that the alignment marks on the first plane are rotated or mirrored relative to the corresponding aligned alignment marks on the second plane. The alignment marks preferably do not have a point of symmetry or outer contour, such that at least a portion of the alignment marks can be detected by rotation or mirroring.

[0043] In a preferred embodiment of the apparatus for aligning a substrate, the alignment marks of the first plane are arranged such that the alignment marks of the first plane are offset relative to the alignment marks of the second plane in a stepped manner.

[0044] In this embodiment, the alignment mark field itself may be configured as a stepped shape, including a plane of the alignment mark forming one surface of the alignment mark field. In this case, the detection unit is preferably configured such that a plurality of steps of the alignment mark field can be detected without relative movement. For example, the focal range of the detection member is so wide that a plurality of steps can be detected. It is also conceivable that the detection unit includes a plurality of members arranged close to each other for the detection of a step in each case. For example, the detection unit may include a plurality of optical devices arranged close to each other with corresponding lenses. In this case, after the detection of the first alignment mark, the focal positions of all detection members of the detection unit are fixed. The alignment mark field is preferably configured as circular and cyclically passed between planes. In other words, the plane including the alignment mark is annular, wherein the plane disposed at a center is circular.

[0045] In this manner, the detection unit can advantageously detect one of the alignment mark fields disposed on or near the surface in various situations.

[0046] In a preferred embodiment of the apparatus for aligning a substrate, the alignment mark fields are arranged such that the substrate holder is disposed on a rear side away from the substrate holder surface.

[0047] The alignment mark area may be applied to the rear side or recessed into the substrate holder, for example. Alternatively, the alignment mark area may also be formed by the substrate holder itself. Advantageously, the detection unit may be disposed on the rear side away from the surface of the substrate holder.

[0048] In a preferred embodiment of the apparatus for aligning a substrate, the arrangement is made such that the center point of one of the alignment mark areas on the rear side of the substrate holder is at least partially aligned with the center point of one of the substrate holder surfaces.

[0049] By centrally aligning the alignment mark areas, precise alignment of the substrate holder can be advantageously achieved. In this embodiment, linear error compensation or rotation of the substrate holder and thus the substrate holder surface relative to a detection unit can also be advantageously observed. Specifically, wedge errors with respect to the lens of the optics can also be detected and removed. Alignment errors can be divided into error components. Therefore, linear, rotational, and magnification errors, as well as errors of larger orders of magnitude, can be characterized.

[0050] In a preferred embodiment of the apparatus for aligning a substrate, the alignment mark fields are arranged such that the alignment mark fields are disposed on one side of the substrate facing the substrate holder surface.

[0051] In this embodiment, the substrate holder has a through opening in the area of ​​the alignment mark region. Furthermore, it is conceivable that the substrate holder is configured to be transparent to the detection unit, so that the alignment mark region disposed on the substrate can be detected specifically from the rear side of the substrate holder. In this way, visual control can advantageously be performed directly at the substrate to be aligned. The substrate and therefore the alignment mark region remain fixed relative to the substrate holder. For example, this prevents alignment errors due to an uneven substrate holder surface. Furthermore, the alignment mark region can advantageously be individually adjusted for each substrate.

[0052] In addition, the alignment mark field may be formed by the substrate or may be reproducible.

[0053] In a preferred embodiment of the apparatus for aligning a substrate, the alignment mark field is configured such that the alignment mark field includes at least one further plane having alignment marks, wherein the at least one further plane is configured to be parallel to the first plane and the second plane.

[0054] Preferably, the alignment mark field has at least three planes with alignment marks. Information about which plane the alignment mark is positioned on is provided on the alignment mark. Furthermore, the device can thus traverse a plurality of specific distances. The distances between the planes can be equal. However, preferably, the planes are arranged at different distances from each other. In this way, a plurality of distances can be flexibly traversed. Especially when the device is used to join substrates, different joining gaps can be advantageously set, or the substrate can be aligned with another substrate with particular precision.

[0055] In a preferred embodiment of the apparatus for aligning a substrate, the apparatus is configured such that it includes at least one further alignment mark field and at least one further detection unit for detecting the at least one further alignment mark field, wherein the at least one further alignment mark field is fixedly configured relative to the substrate holder.

[0056] Further alignment mark fields allow for more precise alignment because detection is performed at multiple points. For example, displacement and / or rotation errors are particularly well identified and eliminated. The alignment mark fields and at least one alignment mark field are preferably offset along the substrate holder. More preferably, the device includes a total of three alignment mark fields and three detection units, each distributed around a center point on the surface of the substrate holder, specifically configured to be uniformly offset relative to each other in the radial direction.

[0057] Preferably, the respective planes of the alignment mark field and at least one further alignment mark field are at the same distance from each other. In this way, alignment can occur with particular precision because the distance can be confirmed at at least two points (preferably local offset points).

[0058] A core aspect of this invention is that, prior to alignment of one of the substrates, at least two alignment marks are detected on at least two different planes or heights of the alignment mark area. The alignment mark area is preferably attached to one of the substrates to be aligned or to a substrate holder. Each alignment mark provides 3D positional information for substrate alignment. The alignment mark area is preferably not disposed on the contact surface of the substrate. The alignment mark area is preferably disposed on the side of the substrate or substrate holder facing away from the contact surface, or disposed parallel to the contact surface.

[0059] Alignment of the substrates with each other occurs indirectly with the aid of alignment marks positioned on the contact surfaces of the substrates. Alignment marks on opposite sides of the substrates are complementary to each other. Alignment marks can be any objects that can be aligned with each other, such as cross-shaped, circular or square or propeller-shaped formations or grid structures, specifically for phase gratings in the spatial frequency range.

[0060] In a particularly advantageous embodiment of the device, the alignment mark may contain at least a QR code that specifically describes the absolute machine-readable position code (x, y, z position) of one of the respective alignment marks.

[0061] In another particularly advantageous embodiment, the alignment mark may contain at least part of alphanumeric characters that specifically describe the absolute machine-readable position code (x, y, z position) of one of the respective alignment marks.

[0062] The alignment mark and / or alignment mark field is preferably detected by electromagnetic radiation of a specific wavelength and / or wavelength range. Such radiation includes, for example, infrared radiation, visible light or ultraviolet radiation. The use of shorter wavelength radiation (such as EUV (extreme ultraviolet radiation) or X-ray radiation) is also feasible.

[0063] One particularly important aspect of the present invention is that the alignment and setting of the engagement gap are specifically performed by detecting alignment marks of alignment mark fields arranged vertically above each other. Specifically, this means that no additional alignment marks are detected or can be detected during alignment. Therefore, an engagement gap can be precisely and visually controlled by the alignment marks arranged vertically above each other.

[0064] The alignment mark field preferably contains explicitly assigned and / or assignable alignment marks or alignment markers in at least two different planes. The alignment mark field includes a stepped or at least partially transparent layer, such that the alignment marks are arranged vertically relative to each other. Thus, in addition to the usual xy position, height information is also indirectly provided. The alignment marks of the alignment marks also directly provide 3D position information. Height information is provided by the arrangement in the different planes. Since the distance between the planes is known, providing information about which plane the detected alignment marks in the alignment mark field are arranged on is, in particular, sufficient.

[0065] Therefore, the alignment mark field consists of or includes alignment marks with position and height encoding, which deliver specific position and height information for alignment of the substrate and / or substrate holder without refocusing the third detection unit. In the following text, the alignment mark or alignment mark of the alignment mark field should also be understood without explicitly referring to the height encoding and / or 3D position information of the alignment mark or alignment mark as height encoding.

[0066] The size or dimensions of the alignment mark area are preferably adapted to the respective field of view of the optical detection components so that at least two steps or alignment mark planes can be observed in each case.

[0067] The number of steps and the total height of the alignment mark area are also matched with the expected distance. For example, if a joint gap of 500 micrometers is to be set, it is preferable to map 550 micrometers of height-encoded position information in the alignment mark area so that the distance can be traversed without refocusing.

[0068] Detection is preferably performed using a corresponding imaging optical system, allowing for the selection of a depth of focus such that it is less than the step height or layer thickness of the alignment mark domain. Depth of focus (DOF) is the region of image space in an imaging optical system in which a sufficiently clear image of a focused object (specifically, an alignment mark) appears. Conversely, this means that the image plane (image detection component, sensor) can be shifted within the depth of focus without the image object becoming significantly blurred.

[0069] If the detection of one of the alignment marks in the alignment mark field is performed with a small depth of focus less than the step height, preferably less than half of the step height, and especially preferably less than 0.1 of the step height, then the position of the alignment mark field in the z direction can be clearly determined.

[0070] The total depth of focus of the detection element is less than 50 micrometers, preferably less than 20 micrometers, especially preferably less than 10 micrometers, most preferably less than 5 micrometers, and in the best case less than 4 micrometers.

[0071] On the other hand, if the depth of focus is sufficient to form a clear image of at least one of the two step heights, the positioning uncertainty of the device is increased because it is impossible to clearly assign a height z to a step.

[0072] In a preferred embodiment of the apparatus, a detection component of an image detection element or a detection unit can reproduce a displacement of 0.2 steps without requiring image-side refocusing. If the image-side focal plane is directly at the height of two adjacent steps and the two steps appear equally sharp, this can be used to determine which alignment mark in the alignment mark domain will be used for positioning. A decision regarding the alignment mark to be used can be made using a small displacement of the image detection element (also as a separate computer-implemented method according to the invention).

[0073] In the detection of the alignment mark field, due to physical reasons, only one plane or step is clearly imaged. In this respect, it is preferable that only one step or plane is located within the focal range of the detection unit. Since the alignment marks of the alignment mark field are positionally encoded and spatially encoded, the position information of a specific substrate holder in a spatial coordinate system can be determined from the clearly detected alignment mark of a plane.

[0074] According to an advantageous embodiment of the present invention, a first substrate and a second substrate are disposed between a first substrate holder and a second substrate holder, wherein a distance A is provided between the first contact surface and the second contact surface in a Z direction.

[0075] The distance from A is specifically less than 500 micrometers, preferably less than 100 micrometers, particularly preferably less than 50 micrometers, and most preferably less than 10 micrometers.

[0076] A method for aligning a substrate is applicable to aligning at least two substrates with each other using any electromagnetic radiation, specifically UV light, preferably infrared light, and most preferably visible light. The substrate to be aligned or the substrate disposed on the surface of the substrate holder of the substrate holder can also be precisely moved relative to other components to make the distance between the planes, and thus be aligned.

[0077] The method enables the observation or detection of the first and second alignment marks, wherein at least one additional optical path is provided to supplement the method for accurately reproducing the substrate position and the substrate holder position. This additional optical path is not positioned between or extends between the substrates during substrate alignment, but rather enables detection from the outside (specifically, using the observation or detection of at least one alignment mark field). The alignment mark field provides height information for setting a desired engagement gap, preferably between the first and second planes.

[0078] In a particularly preferred method, a substrate may be opaque to electromagnetic radiation used for detecting alignment marks on the first and second substrates. Subsequently, the detection of the alignment marks is performed through the rear side of the substrate, which is transparent to the electromagnetic radiation used for detecting the alignment marks.

[0079] The method for alignment specifically improves alignment accuracy by means of XYZ positioning information and / or position information, which is detected by further alignment mark fields and corresponding further detection units and used for alignment control and / or adjustment.

[0080] For this purpose, the alignment apparatus preferably includes a software-supported control unit, by which the steps and control components described herein are performed. Closed control loops and control are understood to be subordinate to the control unit.

[0081] The X and Y directions or X and Y positions are understood to mean directions or positions extending in or within an XY coordinate system or any Z plane of the XY coordinate system. The Z direction is configured to be orthogonal to the XY direction. The X and Y directions specifically correspond to a lateral direction, preferably along the plane of the alignment mark domain. The Z direction is preferably the direction along which the substrate holder moves when the focal position of the detection unit is fixed in the XY plane.

[0082] The positional characteristics are calculated / detected from the position and / or positioning value of the alignment marks on the substrate and the alignment marks on the substrate holder, specifically by detecting and evaluating the alignment mark domain.

[0083] The alignment mark field is preferably located in local proximity to the alignment mark of the substrate. More preferably, at least one alignment mark and the alignment mark field of the substrate are disposed on opposite sides of the substrate. The alignment mark field may also be disposed on the rear side of the substrate holder and opposite to the additional alignment mark. If the alignment mark of the additional alignment mark and the alignment mark field are disposed on opposite sides of the substrate holder surface, a correlation of position can be particularly easy to occur.

[0084] In a particularly preferred embodiment, at least one alignment mark field is preferably positioned to align with additional alignment marks of the substrate in the z-direction, preferably on the rear side of one of the substrate holders.

[0085] In another preferred embodiment of the device, at least one alignment mark field is preferably positioned in the z-direction aligned with the center of the substrate or the center point of the substrate holder surface, specifically on one rear side of the substrate holder.

[0086] In one of the preferred embodiments of the device, two alignment mark fields are preferably positioned to align with additional alignment marks on the substrate in the z-direction, specifically on the rear side of one of the substrate holders.

[0087] In another preferred embodiment of the device, at least one alignment mark field is located on the substrate side of the substrate holder or on the side near the substrate of the substrate holder surface, in an optically detectable position.

[0088] Another embodiment of the device includes at least two alignment mark areas on the substrate side of the substrate holder near the edge of the substrate, in an optically detectable access position. Therefore, leveling of the substrate holder can be advantageously performed.

[0089] Therefore, the method and apparatus for alignment specifically include at least one additional detection unit having a corresponding measurement and / or control system and at least one additional alignment mark field, wherein, specifically, in the absence of refocusing, preferably in the absence of image-side refocusing, the alignment accuracy can be further increased by the correlation between the additional measurement value and at least one of the measured values ​​of the additional detection unit.

[0090] By correlating at least one of the measured additional alignment marks on the contact surfaces of a first substrate and / or a second substrate with at least one alignment mark in an alignment mark field that is freely accessible and visible during substrate alignment, direct observability of an alignment mark and thus real-time measurement and control during alignment are achieved. This increases the alignment accuracy of the substrate.

[0091] Another advantage of the alignment mark field is the detection of additional height information, which allows the lower substrate holder with the lower substrate to be accurately positioned relative to the upper substrate on an upper substrate holder. Specifically, there is no longer any positional inaccuracy resulting from the focusing movement of the detection unit.

[0092] Due to the increased accuracy of height positioning of the distance from the upper substrate to the lower substrate during bonding, the pre-tension of at least one of the substrates is set to have a small tolerance, which reduces deformation of the substrates during bonding, thereby at least reducing, and preferably eliminating, deflection of the substrates after bonding. To this extent, the method and apparatus for alignment are destined for one alignment in a bonding process.

[0093] In another embodiment of the device, at least one further alignment mark region is located on the substrate side of a substrate holder near the peripheral edge of the substrate in a position where a further detection unit can permanently access it. More preferably, one surface of the alignment mark region is located in the same plane as the surface of the substrate fastened to the substrate holder and to be joined.

[0094] A specific correlation is generated between the additional 3D positional features added on the substrate holder and the positional features on the substrate, which preferably remains unchanged during alignment and is maintained until the substrates are bonded together.

[0095] By using additional 3D positional features on the substrate holder (which can be clearly correlated with positional features on the substrate), direct observation of one of the alignment marks on the substrate can be replaced by direct observation of one of the alignment marks on the substrate holder. The advantage of this is that the observable portion of the substrate holder can be almost always positioned within the field of view or within the detection area of ​​one of the detection units. With 3D positional information, the accuracy of substrate alignment can be increased.

[0096] The detection area of ​​a detection unit is preferably less than 3 mm x 3 mm, preferably less than 2 mm x 2 mm, and especially preferably less than 1 mm x 1 mm.

[0097] Compared with the controlled positioning in the prior art, the active feedback of positioning and position correction data increases accuracy due to the possibility of providing control over the actual state of the position in a closed control loop.

[0098] One aspect of the alignment method and apparatus is to increase the accuracy of alignment between two substrates. Using the alignment method, specifically, alignment or movement can be observed in real time from outside the bonding interface. By integrating 3D position information and providing height information, alignment can be performed more accurately than with previously known methods. Specifically, the substrates are arranged with a minimum distance between them, and preferably there are no device objects, specifically no detection unit positioned between the substrates.

[0099] A correlation is generated between additional alignment marks on the respective contact surfaces of a first substrate and / or a second substrate and at least one alignment mark in the alignment mark field. Specifically, the alignment mark in the alignment mark field can be directly detected by a detection unit during alignment.

[0100] The direct detectability or observability of at least one alignment mark in the additional alignment mark field enables real-time measurement of one of the 3D positions of the substrate holder. Because the first and second alignment marks and the height information they provide eliminate positioning uncertainty, error propagation is reduced, thus increasing alignment accuracy. Due to this measure, alignment accuracy is improved by reducing the number of necessary feed movements and controlled height displacement during engagement.

[0101] A first embodiment of an alignment device is used in a bonding device and is included in an upper substrate holder. An upper substrate can be fastened to the upper substrate holder. The upper substrate holder is configured to be at least partially transparent enough to allow detection of alignment marks on a contact surface of the upper substrate with sufficient resolution, contrast and intensity, the contact surface being the surface opposite to the mounting surface of the upper substrate.

[0102] For this purpose, the upper substrate is sufficiently transparent to the radiation used for the detection of one of the first additional alignment marks on the upper substrate.

[0103] A sufficiently transparent substrate is understood to mean that the transmittance of the substrate to the electromagnetic radiation used to detect the additional alignment mark is sufficient to detect the additional alignment mark with sufficient resolution, contrast and intensity.

[0104] A substrate holder that is partially transparent is understood to mean that the substrate holder has sufficiently high transmittance to the electromagnetic radiation of the detection alignment mark. Alternatively, a viewing window and / or through opening may be provided for observation of the substrate and / or substrate pair within the substrate holder.

[0105] During the detection of additional alignment marks on the substrate, specifically the upper substrate and the upper substrate holder are removed from the focus of the additional detection unit.

[0106] Additional alignment marks on the lower substrate or the lower substrate holder can be detected through the upper substrate holder and the upper substrate.

[0107] During the detection of additional alignment marks, specifically, at least one alignment mark of the alignment mark field on the rear side of the substrate holder is correlated to determine the 3D position information of the substrate holder (specifically, the substrate holder below).

[0108] The detection unit for detecting the alignment mark area is specifically part of an optical system for detecting the alignment mark area, and according to an advantageous embodiment, includes beam shaping and / or deflection elements, such as mirrors, lenses, prisms, specifically radiation sources for Köhler illumination, and image detection components, such as cameras (CMOS sensors, or CCDs, or area, line, or point detection components, such as a photoelectric crystal), and a focusing movement component, as well as an evaluation component for controlling the optical system.

[0109] In another embodiment of the device, the optical system may be used in combination with a rotational system for positioning the substrate according to the principle of rotational adjustment (see, in this regard, Hansen, Friedrich: Justierung, VEB Verlag Technik, 1964, paragraph 6.2.4, Umschlagmethode). Thus, in rotational adjustment, at least one measurement is performed at one defined position of the respective substrate, and at least one measurement is performed at a rotational position of 180 degrees in the opposite orientation. The resulting measurement results are, in particular, free of eccentricity error.

[0110] One of the devices for alignment is developed to contain two specific optical systems that are identical in structure, the optical systems having additional detection units that can be aligned with each other and fixed relative to each other for the detection of additional alignment marks.

[0111] In a further embodiment of the device for alignment, at least one substrate holder is used, which is at least partially transparent, preferably more than 95%, when viewed simultaneously from both substrate sides at a defined point.

[0112] In another embodiment of the device, at least one substrate holder is used, which includes an opening and / or aperture and / or viewing window at a defining point for simultaneous observation, specifically, of both substrate sides.

[0113] Furthermore, an apparatus may include a system for generating a pre-bonding. For the connection of substrates, pins and / or adjustable nozzles may be used to initiate fusion bonding. Specifically, the adjustable nozzle may be height-adjustable, allowing for changes in its relative position to the rear side of the substrate, and adjustable adjustment of the nozzle's volumetric flow rate. Alignment of the rear side of the substrate can be advantageously achieved with the aid of alignment marks arranged vertically above and below each other.

[0114] In addition, an apparatus preferably includes a movable configuration having a drive system, a guidance system, a constraint and a measurement system to at least move, position and accurately align the detection unit and the substrate holder and thus the substrate to be aligned.

[0115] The movable configuration can be moved by any individual movement, so that the movable configuration can preferably contain a fast coarse positioning device that does not meet the accuracy requirements and a fine positioning device for precise operation.

[0116] A coarse positioning device is understood to mean a positioning device in the case of a complete 360-degree rotational drive, when the approximation or repeatability accuracy deviates from the set point value by more than 0.1%, preferably more than 0.05%, and especially more preferably more than 0.01% relative to the total travel path or rotation range.

[0117] For example, as a residual uncertainty, a coarse positioning device with a travel path of more than 600 mm (twice the diameter of the substrate) thus results in an accuracy of 600 mm ⁎ 0.01% (i.e., more than 60 micrometers).

[0118] In another embodiment of coarse positioning, the residual uncertainty in approximation or repeatability accuracy is less than 100 micrometers, preferably less than 50 micrometers, and particularly preferably less than 10 micrometers. Thermal disturbance variables should also be considered.

[0119] A coarse positioning device performs a positioning task with sufficient accuracy only if the deviation in the traversal range of an assigned fine positioning device is between the actual current position reached and the set point value of that position.

[0120] An alternative coarse positioning device performs a positioning task with sufficient accuracy only if the deviation in half of the traversal range assigned to a fine positioning device is between the actual current position reached and the set point value of that position.

[0121] If the residual uncertainty of the approximation and / or repeatability accuracy is no more than 500 ppb, preferably less than 100 ppb, and more preferably 1 ppb of a setpoint value relative to the entire travel path or rotation range, then a positioning device is understood to mean a fine positioning device.

[0122] A fine positioning device will preferably compensate for an absolute positioning error of less than 5 micrometers, preferably less than 1 micrometer.

[0123] Alignment of the substrates with each other can occur in all six degrees of freedom of movement: three translations in the coordinate directions x, y, and z, and three rotations about the coordinate directions. Movement can be performed in any direction and orientation. Specifically, the alignment of the substrates includes a passive and an active wedge error compensation, preferably according to the disclosure in disclosure EP2612109B1.

[0124] Robots used for substrate handling are classified as mobile configurations. Constraints may be structurally or functionally integrated into the mobile configuration.

[0125] Furthermore, the device for aligning the detection unit preferably includes a control system and / or an evaluation system, specifically a computer, to perform the described steps, specifically to execute the movement sequence to perform correction, analyze and store the operating status of the device.

[0126] The method is preferably formulated as a formula and configured in a machine-readable form. The formula is a set of optimized values ​​for parameters that are functionally or procedurally related. The use of the formula allows for ensuring the reproducibility of the operation.

[0127] Furthermore, according to an advantageous embodiment, the alignment device includes a supply system and auxiliary and / or replenishment systems (compressed air, vacuum, electrical energy, liquids such as hydraulic fluid, coolant, heating medium, components and / or devices for temperature stabilization, electromagnetic shielding).

[0128] In addition, the device for alignment may include a frame, cladding, active or passive subsystem for suppressing, attenuating or absorbing vibrations.

[0129] Furthermore, one of the alignment devices preferably includes at least one measurement system, which preferably has measurement units for each movement axis, specifically configured as a path measurement system and / or an angle measurement system. The measurement system preferably includes at least one detection unit or an additional detection unit.

[0130] Tactile (i.e., touch) or non-tactile measurement methods may be used. The measurement standard (unit of measurement) may be presented as a physical object, specifically as a scale, or implicitly presented in the measurement method, such as the wavelength of the radiation used.

[0131] To achieve alignment accuracy, at least one of the following measurement systems may be selected and used. The measurement system implements the measurement method. ▪ Inductive method and / or ▪ Capacitive method and / or ▪ Resistive method and / or ▪ Comparison method, specifically optical image recognition method, detection of position markers and / or QR codes, and / or ▪ Incremental or absolute method (specifically using a glass standard as a scale, or an interferometer, specifically a laser interferometer, or using a magnetic standard), and / or ▪ Time-of-flight measurement (Doppler method, time-of-flight method) or other time detection method, and / or ▪ Triangulation method, specifically laser triangulation ▪ Autofocus method, and / or ▪ Intensity measurement method, such as specifically using a fiber optic rangefinder.

[0132] Furthermore, one particularly preferred embodiment of the alignment apparatus includes at least one measurement system that detects the XYZ positioning and / or alignment position and / or angular position of at least one of the substrates and / or one of the substrate holders relative to a defined reference (specifically, relative to a frame). The measurement system includes at least one detection unit.

[0133] Using a measurement system or a detection unit of a measurement system, the 3D position of the substrate or preferably the substrate holder is determined without refocusing, so that height information can be determined from the measurement of flat position data. In addition, at least one alignment mark area consisting of steps and / or layers is detected using clear position marks.

[0134] A frame can be understood as a component made specifically of natural hard stone or mineral casting or ductile iron or hydraulically bound concrete, specifically designed to dampen and / or isolate vibration and / or absorb vibration.

[0135] One of the reversed concepts can also be advantageously implemented by attaching the detection unit to the substrate holder and attaching the alignment mark field to, for example, a frame. In this case, the detection unit moves together with the substrate holder, and the alignment mark field is fixed to the frame.

[0136] To enable detection, evaluation, and control to be performed at any point in time (specifically, permanently), according to an advantageous embodiment, alignment marks of alignment mark fields are distributed on an area of ​​their respective planes that is larger than the field of view of an image detection system of a detection unit, specifically, to continuously supply measurement values ​​to a control unit (and / or adjustment unit). However, the alignment marks of the alignment mark fields are configured at various positions within the field of view of an image detection system, so that height information can be detected from the alignment mark fields and / or extended plane position information. In other words, by the configuration of the alignment marks of the alignment mark fields, the spatial position of the substrate holder can be detected, and the correct engagement gap can be set at each lateral position of the substrate holder. Since the position of the substrate holder, specifically, exists as 3D position information, more precise spatial alignment relative to one of the substrates fastened above each other can be achieved.

[0137] In one advantageous embodiment of the alignment apparatus, additional alignment marks are specifically uniformly distributed on the contact surface of a substrate up to an edge region (edge ​​exclusion region) of the substrate. Therefore, in other words, an alignment can be performed using the additional alignment marks of the substrate, which are positioned such that they are less than 3 mm apart, preferably less than 2 mm, and particularly preferably less than 500 micrometers apart. The increased local alignment accuracy can be achieved, specifically, by the correlation between the additional alignment marks of the substrate and a spatially defined alignment mark region of a substrate holder.

[0138] For an XYZ positioning determination, at least one three-beam interferometer, specifically a monolithic reflector, with a corresponding configuration for detecting and / or determining the XYZ positioning of the substrate holder, can also be used in the alignment apparatus. In another potentially advantageous embodiment of the apparatus, a prism-type monolithic reflector having a plurality of specific three-beam interferometers can be used for measurement. Therefore, error propagation can be eliminated by averaging, difference formation, and measurement series formation, and alignment accuracy can be further increased. In other words, the control system for the trajectory of movement can be used with sufficiently fast position measurement, thereby further reducing the position error of the substrate holder.

[0139] Specifically, a substrate holder for an alignment device formed from a single block preferably includes at least two of the following functions: ▪ Securement of the substrate using vacuum (vacuum track, port) and / or electrostatic components; ▪ Shape compensation for substrate deformation by mechanical and / or hydraulic and / or piezoelectric and / or thermoelectric and / or electrothermal actuation elements; ▪ Position and / or positioning determination (measuring standards, reflective surfaces and / or prisms, specifically reflectors for interferometric measurements, registration marks and / or registration mark fields, measuring standards for planar composition of a plane, volume standards, specifically steps, layer systems with known layer heights having alignment marks distributed in the plane); ▪ Movement (guide track).

[0140] The motion configuration not used for fine adjustment is specifically configured as a robot system, preferably having an incremental linear encoder. The accuracy of such motion configuration used for assisting motion is decoupled from the accuracy of the alignment of the substrate stack, so that assisting motion is performed with a low repeatability accuracy of less than 1 mm, preferably less than 500 micrometers, and particularly preferably less than 150 micrometers.

[0141] Specifically, this refers to the control and / or adjustment of the movement configuration of a device for (lateral) alignment (fine adjustment) based on detected XYZ positioning and / or alignment position. Additionally, the additional alignment marks on the substrate are related to alignment marks in the alignment mark field uniquely assigned to it in the field of view behind the substrate holder. Height information is calculated from the alignment marks in the alignment mark field. This provides an XYZ positioning that can be continuously observed, specifically, during the feed movement for alignment and during the setting of the gap for engagement, and specifically, can be used in real-time for error correction of the feed movement.

[0142] The accuracy of the moving configuration used for alignment is less than 500 nm, preferably less than 100 nm, especially more preferably less than 50 nm, most preferably less than 10 nm, more preferably less than 5 nm, and most preferably less than 1 nm.

[0143] In one particularly preferred embodiment of the device, the total error of the alignment accuracy of the device is less than 20% of the maximum allowable alignment error, preferably less than 10%, and most preferably less than 1%.

[0144] In other words, if the total allowable alignment error of the substrate is, for example, 10 nm, then the total positioning error is at most 20% of that value, that is, 2 nm.

[0145] An exemplary joining method for implementing the alignment method. A first embodiment specifically includes the following steps performed sequentially and / or simultaneously, specifically in the following sequence:

[0146] First procedure step: The upper substrate is mounted on the upper substrate holder with a mounting surface, wherein at least one first additional alignment mark is present on the opposite side (so-called contact side) of the upper substrate.

[0147] Second procedure step: The lower substrate to be aligned is mounted on a mounting surface on the lower substrate holder, wherein at least one second additional alignment mark is present on the opposite side (so-called contact side) of the lower substrate.

[0148] Third procedure step: An additional detection unit detects at least a first additional alignment mark and (as the case may be) a further additional alignment mark on the upper substrate through the upper substrate.

[0149] Fourth procedure step: Store the focal position of one of the lenses of the additional detection unit and fix the lens.

[0150] Fifth procedure step: With the assistance of the upper substrate holder, the upper substrate is moved upward in the direction of the additional detection unit, away from the focal plane. The total traverse path is preferably less than 500 micrometers.

[0151] Sixth procedure step: With the assistance of the lower substrate holder, the lower substrate is specifically moved upward to the fixed focal position of the additional detection unit. Specifically, wedge error compensation can also occur simultaneously.

[0152] In order to detect the second additional alignment mark on the lower substrate, the lower substrate is moved in the Z direction with the help of the lower substrate holder until the contact side of the lower substrate is focused.

[0153] Seventh procedure step: A second additional detection unit locates and detects a second additional alignment mark on the lower substrate.

[0154] Alternatively, the lower substrate holder is focused by z-movement to displace the lower substrate in the XY plane or rotate it about the Z-axis, such that the sought second additional alignment mark is positioned within the focal range of the first additional detection unit and detected by the first additional detection unit. Preferably, the lower substrate is further aligned such that the sought alignment mark or multiple sought alignment marks are specifically concentrically arranged relative to the optical axis of the fixed lens of the device.

[0155] In an advantageous embodiment, the alignment mark being sought can be detected in the vicinity of the optical axis of the respective lens of the detection unit within a radius of less than 3 mm, preferably less than 2 mm, particularly preferably less than 1 mm, extremely preferably less than 500 micrometers, and more preferably less than 250 micrometers.

[0156] Eighth procedure step: A measurement system (specifically, a measurement microscope with a lens) having at least one detection unit for detecting an alignment mark in an alignment mark field is preferably used to detect a first alignment mark on a first plane and thus an XYZ positioning and / or alignment position of the lower substrate holder from the rear side of the substrate holder. The lower substrate holder remains fixed, and the position or multiple positions of additional alignment marks on the lower substrate are related to the detected position. To detect the position of the lower substrate holder, an alignment mark field fixed relative to the substrate holder is used.

[0157] A step of the alignment mark domain is detected with better focus, which is close to the free surface of the alignment mark domain and the alignment mark can be observed throughout the entire depth of the alignment mark domain.

[0158] In this focusing position, the focal position of the detection unit (specifically the lens) is fixed for the detection of the marking area. Furthermore, the detection unit remains partially fixed or immovable.

[0159] Ninth procedure step: When measuring the alignment marks of the steps on different planes in the alignment mark area, the lower substrate is moved downward by a defined distance using the lower substrate holder. This total distance is less than 500 micrometers. The distance by which the lower substrate is lowered is the so-called bonding gap, that is, the correct distance at which a bonding can be performed, especially a fusion bonding and / or hybrid bonding with as little deformation as possible.

[0160] In one of the exemplary methods, particularly in a preferred embodiment, the lower substrate and the lower substrate holder are lowered together to the extent that an alignment mark of the nearest step on the other plane is focused within the alignment mark area. In this way, blind or controlled movement of one of the substrate holders used for alignment is avoided.

[0161] The movement of the substrate holder is detected by a detection unit at least in an initial position and a target position, thereby observing the alignment mark field in different steps. At least one alignment mark on a first plane is detected in the initial position, and at least one alignment mark on a second plane of the alignment mark field is detected in the target position.

[0162] Tenth (optional) procedure step: The position of the substrate holder is corrected at least in the lateral plane by means of the measured position error. The substrate holder is moved such that at least one corresponding second alignment mark on the second plane is focused or located within the focal range of the detection unit. In this way, it can be ensured by visual control that the distance (i.e., the engagement gap) between the first plane and the second plane is set sufficiently accurately.

[0163] Therefore, the refocusing of the detection unit can be eliminated, and alignment errors are prevented. Height information is provided by the alignment mark field, allowing visual control to approach the desired engagement gap related to the procedure without blind movement. The focusing and / or refocusing of the detection unit is no longer required, thus eliminating errors in focusing movement.

[0164] Eleventh procedure step: With the help of the upper substrate holder, lower the upper substrate back to the focal position of the additional detection unit or its lens.

[0165] Twelfth procedure step: With the help of the relevant XYZ positioning of the lower substrate holder, the upper substrate is aligned with the lower substrate, and the upper substrate moves and / or rotates around the Z axis in the XY plane.

[0166] In this processing step, the first additional alignment mark is aligned relative to the second additional alignment mark. The actual position of the lower substrate on the lower substrate holder is known because the relative position of the alignment mark of the lower substrate to the alignment mark field has been measured, so that the alignment mark of the upper substrate can be aligned relative to the known hidden position of the second alignment mark of the lower substrate.

[0167] Thirteenth procedure step: Raise the lower substrate to set the correct bonding gap, thereby allowing for observation and correction of divergence movement with the help of the alignment mark area.

[0168] Fourteenth procedure step: Contact the contact surfaces of the upper and lower substrates to join the substrates together.

[0169] In the alignment of substrates, if the alignment error exceeds a fixed limit value, the relative positions of the substrates on each other can be corrected.

[0170] The alignment error of the displacement correction is less than 500 micrometers, preferably less than 100 micrometers, especially more preferably less than 100 nanometers, very preferably less than 10 nanometers, more preferably less than 5 nanometers, and most preferably less than 1 nanometer.

[0171] The alignment error using rotation correction is less than 50 microradians, preferably less than 10 microradians, especially more preferably less than 5 microradians, very preferably less than 1 microradian, more preferably less than 0.1 microradian, and most preferably less than 0.05 microradians.

[0172] In another embodiment of the method for alignment, acceleration can be achieved by parallelizing the processing steps, specifically the loading of the second substrate that has been performed during a pattern detection step on the first substrate.

[0173] In this disclosure, the terms coincidence or uniformity or parallelism or normality are used as a measure of tolerance, such that the tolerance applies to length or angular dimensions that are not tolerated according to ISO 2768, unless the tolerance is explicitly stated.

[0174] Further advantages, features, and details of the present invention will become apparent from the following description of preferred embodiments and with the aid of the drawings. These drawings illustrate:

Implementation Method

[0176] Figure 1 shows a functional representation (not to scale) of one of the main components of an embodiment of an alignment system 1. The alignment system 1 can align substrates (not shown in Figure 1) with each other and at least partially and / or temporarily bond the substrates together (so-called pre-bonding). The terms device and system are equivalent and synonymous.

[0177] The alignment system 1 includes a first substrate holder 9, on which a first substrate can be mounted and fixed to the surface of the substrate holder. In addition, the alignment system 1 includes a second substrate holder 11, on which a second substrate can be mounted and fixed.

[0178] The first (specifically) substrate holder 9 to be joined is disposed on a first moving configuration 10 for holding and implementing the feed movement and adjustment movement (alignment) of the first substrate holder 9. The second (specifically) substrate holder 11 is disposed on a second moving configuration 12 for holding and implementing the feed movement and adjustment movement (alignment) of the second substrate holder 11. Moving configurations 10 and 12 are specifically fixed to a common solid worktable or frame 8 to reduce / minimize vibration of all functional components. The frame may specifically contain active vibration damping.

[0179] In order to observe (detect) additional alignment marks on the substrate, one of the optical systems 2 of the alignment system 1 contains at least one additional detection unit 3, specifically an image detection component, for detecting additional alignment marks.

[0180] The optical system 2 can be focused on a focal plane or focal point located between the first substrate and the second substrate, preferably between the substrate holder 9 and the substrate holder 11, and these holders are configured for alignment. Specifically, movement of the optical system 2 in the X, Y, and Z directions is achieved by a positioning device 4 for positioning the optical system 2. The positioning device 4 can specifically be fixed to a solid worktable or frame.

[0181] At least one additional (specifically optical) measurement system 5, having at least one detection unit 6 for detecting an alignment mark field 14, is used to increase alignment accuracy by detecting alignment marks on different planes of the alignment mark field 14. Movement of one of the additional measurement systems is performed using a positioning device 7.

[0182] If an optical measurement system 5 is involved, the positioning device 7 can perform focusing on one of the alignment marks of the first plane 18 of the alignment mark field 14 by moving the detection unit 6 in the Z direction. Positioning in the XY direction is also conceivable, wherein, specifically during alignment, fixation preferably occurs on the worktable / frame.

[0183] In the illustrated embodiment of the alignment system 1, the measurement system 5 or the detection unit 6 can detect, with particularly high accuracy, the XY positioning and / or position (also the rotational position) and / or height position of the substrate holder 9.

[0184] To initiate a fusion bond, at least the upper substrate may be pre-tensioned using a substrate pre-tensioning device 13. Pre-tensioning may be performed by mechanical pre-tensioning having a pre-tensioning element (a so-called bonding pin). In another embodiment of the substrate pre-tensioning device, the substrate pre-tensioning may be performed using a fluid, specifically a gas from a nozzle, specifically a moving nozzle.

[0185] Using an embodiment of the apparatus (not shown but preferred), the following procedural steps, as listed by example, can be performed:

[0186] The first / lower substrate is fastened to a first fixing surface (specifically, the substrate holder surface) of the first substrate holder 9. As a fastening method, mechanical and / or electrostatic clamping or pressing pressure is used, which is generated by a pressure difference between the environment at normal atmospheric pressure and the negative pressure on the first substrate holder 9, also known as vacuum fastening. The fastening occurs in such a way that the first substrate does not experience inaccurate or unintended movement relative to the first substrate holder 9 throughout the entire process. If the first substrate holder 9 and the first substrate each have a corresponding, preferably linearly corresponding, coefficient of thermal expansion, thermal expansion can be specifically prevented or reduced, wherein the difference in the coefficient of thermal expansion and / or the linear progression of the coefficient of thermal expansion is preferably less than 5%, preferably less than 3%, and particularly preferably less than 1%.

[0187] The system preferably operates in a temperature-stable environment, specifically in a clean room, wherein during an alignment cycle, a total temperature fluctuation is less than 0.5 Kelvin, preferably less than 0.1 Kelvin, particularly more preferably less than 0.05 Kelvin, and most preferably less than 0.01 Kelvin.

[0188] The fixed first substrate and the first substrate holder 9 can be understood as quasi-units for performing the movement of the first substrate, and they are not allowed to move relative to each other.

[0189] The substrate fastening can be performed in a form-fit manner and / or preferably in a friction-locking manner. As a result of the quasi-monolithic connection, the effects of displacement and / or rotation and / or deformation between the substrate holder and the substrate can be reduced at least, preferably at least by an order of magnitude, and especially preferably eliminated.

[0190] By using shape fit or friction locking, the substrate can be connected to the substrate holder, which in particular can suppress differences in thermal expansion. In addition, the substrate holder can be used to reduce, eliminate and / or correct independent deformation of the substrate.

[0191] In one embodiment, the lower substrate holder 9 and the upper substrate holder 11 may include additional passive and / or active deformable elements and / or intermediate plates to minimize the mechanical and / or thermal properties of the substrates in order to reduce residual alignment errors after connection.

[0192] During the detection of a first additional alignment mark, the first substrate holder 9 may be positioned in one of the optical paths of the additional detection unit 3. The first additional alignment mark may be disposed on the contact surface of the first substrate to be bonded in the field of view, specifically in the optical path, preferably in the optical axis of the additional detection unit 3. The additional detection unit 3 generates, specifically, a digital image and measures the digital image. The first alignment mark of a substrate may also be composed of a plurality of combined alignment marks.

[0193] A measured value is generated / calculated from the image of the alignment mark, the measured value being specifically a characteristic XY positioning and / or alignment position (specifically in a rotational direction about a Z direction), i.e., the alignment state of a first substrate.

[0194] The lower substrate holder 9 and / or the first substrate includes alignment marks in the alignment mark field 14. With the help of these alignment marks, specifically from another direction, preferably in the Z direction which is completely opposite to the first detection, the XYZ positioning and / or alignment position and spatial alignment state of the substrate holder 9 and / or the first substrate are detected.

[0195] Preferably, the relative movement of the first detection unit 3 relative to one of the third detection units 6 can be measured. More preferably, from the detection of the first additional alignment mark and the alignment mark field 14 to the contact between the first and second substrates, no relative movement between the first additional detection unit 3 and the detection unit 6 is performed.

[0196] The detection unit 6, used for the detection of the alignment mark field 14 of the additional measurement system 5, delivers a measured value of one of the spatial XYZ positioning and / or position of the first / lower substrate holder 9 from the measurement of alignment marks on different planes of the alignment mark field 14.

[0197] The measured values ​​(XY positioning and / or alignment position of the first substrate and XYZ positioning and / or alignment position of the first substrate holder 9 or the first substrate 16) are correlated with each other, so that the XYZ positioning of the substrate holder 9 can be reproduced. The substrate fastened to the substrate holder 9 can be moved in a controlled manner for the alignment and setting of the joint gap, without the additional alignment marks of the substrate being directly observable.

[0198] By assigning the positions of the substrates to the spatial positions and / or positioning of the substrate holder 9, alignment can be performed during alignment and / or contact without directly observing the XY positioning and / or alignment positions of the respective substrates. Furthermore, the distance between the substrates can be set in a defined manner and / or minimized during alignment. This distance preferably corresponds to the distance between the substrates during the detection of the first and second additional alignment marks. In other embodiments, a preferred distance for bonding can be set.

[0199] In other words, a clear optical path can be provided between the substrate holder 9 and the additional measurement system 5, using which the alignment of the substrate can be operated or manipulated in a control circuit. Therefore, the XYZ positioning and / or alignment position of the first substrate holder 9 and the first substrate thus fixed on the first substrate holder 9 can be accurately determined and reproducibly restored, thereby increasing the accuracy of bonding (specifically, fusion bonding).

[0200] Specifically, the restoration and correct setting of the XYZ positioning and / or alignment position of the substrate holder 9 and the substrate individually connected thereto relative to another substrate and / or substrate holder is an important aspect of the alignment device.

[0201] Specifically, achieving a repeatability accuracy (measured as a relative alignment error between two substrates) of positioning less than 500 nm, preferably less than 100 nm, particularly preferably less than 30 nm, extremely preferably less than 10 nm, more preferably less than 5 nm, and most preferably less than 1 nm is also known as reverse play. Reverse play can also be the repeated approach to a given position with the aid of moving configurations 10, 12 and / or 4, 7. Reverse play is caused by the movement of the moving configurations, and only the detected positional change makes the measured value exist as a relative alignment error.

[0202] To further increase alignment accuracy, the first additional detection unit 3 is preferably operated in time synchronization with the second additional detection unit 5. Specifically, the time difference between the detection of the measured value is less than 3 seconds, preferably less than 1 second, particularly preferably less than 500 milliseconds, extremely preferably less than 100 milliseconds, in the best case less than 10 milliseconds, and most preferably less than 1 millisecond, ideally simultaneously. This is particularly advantageous because it eliminates the effects of interference such as mechanical vibration. Mechanical vibration propagates in materials, especially as structure-borne noise at speeds of several thousand m / s. If a control and detection component operates faster than the propagation speed of the structure-borne noise, an interference is reduced or eliminated.

[0203] If a disturbance changes the position of the first substrate on the first substrate holder 9, such that the first additional detection unit 3 has recorded a measurement value, and the measurement system 5 with the detection unit 6 for detecting the alignment mark field 14 has not yet picked up a measurement value, the disturbance can cause a shared reduction in alignment accuracy. This is because a rapid mechanical position change on the order of nanometers or micrometers can occur during the time between the recording of the measurement value by the additional detection unit 3 and the detection unit 6. If the measurement value recording occurs with a time delay (on the order of seconds or minutes), further interference effects such as thermally induced shape changes or length changes can also reduce alignment accuracy.

[0204] If the first additional detection unit 3 and the detection unit 6 used to detect the alignment mark field 14 are synchronized with each other (in particular, by simultaneously triggering the detection and camera system detection time and / or equalizing the same integration time), some interference effects can be reduced, and in the best case eliminated, because the detection should occur at a time when the interference effect has the least impact on the detection accuracy.

[0205] In a preferred embodiment of the method and apparatus for alignment, detection is performed in a manner synchronized with known, specifically periodic, interference effects, specifically at the peak of vibration. In this regard, vibration sensors (accelerometers, interferometers, vibrosensors) are preferably pre-mounted at points on the apparatus related to alignment accuracy. Interference effects are picked up by these vibration sensors and, through calculation, specifically by a computer unit, taken into account or corrected to eliminate them. In another embodiment, vibration sensors may be fixedly mounted at characteristic points of the system.

[0206] Specifically, the setpoint value, once determined / fixed, is used for substrate alignment. The setpoint value specifically includes image data of alignment marks in the alignment mark field 14 of the first substrate holder 9, and / or determined XYZ positioning and / or alignment position data and / or control parameters of the moving configuration 10 of the first substrate holder 9, such as path curves for optimal proximity spatial position and / or, specifically, machine-readable values ​​for the driver.

[0207] By means of the first moving configuration 10, the first substrate holder 9 moves and is positioned and adjusted in a manner that minimizes, ideally eliminates or reaches a stopping criterion, the alignment error calculated from the setting value of the detection unit and the current position and / or positioning of the substrate holder. This movement of the lower substrate holder also includes a gap for the correct setting of the bonding (specifically, fusion bonding). In other words, the lower substrate holder 9 traverses to a known measured XYZ alignment position in a controlled and adjusted manner, and moves specifically in the Z direction in an adjusted manner.

[0208] In a further embodiment, residual errors that may not have been eliminated in the positioning of the upper and / or lower substrates are also taken into consideration as correction values ​​for the positioning of the other (lower or upper) substrate.

[0209] Figure 2a shows an alignment mark field 14' in a diagrammatic, greatly enlarged plan view, in which alignment mark 15 or alignment marker 15 is selected by example.

[0210] Individual alignment marks 15 symbolically and graphically represent an absolute and definitive code for the position and location of each individual alignment mark or alignment marker 15. Individual alignment marks 15 or alignment markers 15 may exist in different planes of the alignment mark field 14'. Since the properties of the alignment mark field 14' (the XYZ positions of each alignment mark 15) are known a priori, it is sufficient to detect an absolutely coded alignment mark 15 or alignment marker 15 for the absolute position detection of the substrate holder (not shown).

[0211] FIG2b shows one of the different exemplary marker layers 16, 16' having an alignment marker field 14'' in a schematic cross-section.

[0212] Advantageously, for the alignment of a substrate holder containing alignment mark fields or fixedly configured relative to alignment mark fields, multiple alignment marks on different planes are considered. Specifically, multiple steps and / or layers 16, 16' of the alignment mark fields can be located within the field of view or focal range of the detection unit 6 and thus be detected simultaneously or preferably continuously therein. By means of the known step height or the known distance between the planes, the latter can be used for the alignment or setting of the desired gap between the substrates.

[0213] The total distance between the planes is between 1 micrometer and 300 micrometers, preferably between 5 micrometers and 200 micrometers, more preferably between 10 micrometers and 100 micrometers, in the best case between 25 micrometers and 75 micrometers, and in the ideal case between 48 micrometers and 52 micrometers. In special cases, the total distance between the planes reaches 50.00 micrometers.

[0214] It is advantageous if the alignment marks 15, 15' of an alignment field 14, 14', 14'', 14''' provide the spatial position and / or positioning of the substrate holder 9 or the substrate disposed on the substrate holder. Furthermore, it is advantageous if each alignment mark 15, 15' contains detectable position information that provides its respective position within the alignment mark fields 14, 14', 14'', 14'''. Specifically, the position of each detected alignment mark 15, 15' relative to the alignment mark 15 of the alignment mark field is therefore also known. Not only is the position of the detected alignment marks 15, 15' relative to the alignment marks 15, 15' of the same plane preferably known, but the position of each plane of the detected alignment marks 15, 15' relative to other planes of the alignment mark field is also known. This respective position information is implemented, for example, by different angles and shapes of the alignment marks 15, 15', and is illustrated by example.

[0215] In order to accurately set the desired gap or joint gap between the substrates, the optical system of the detection unit 6 used for aligning the detection of the marking fields 14, 14', 14'', 14''' should preferably have a focal depth or a focal range depth (specifically in the Z direction) that is less than half the distance between the corresponding planes.

[0216] Figure 3 illustrates one possible embodiment of an alignment mark field 14'', wherein individual exemplary alignment marks 15' are supplemented by a machine-readable code. Each alignment mark 15' may be configured on different planes (steps and / or layers), and the code may contain information about which plane is of interest in each case. Furthermore, an explicit indication of the position and orientation of each alignment mark 15' may be included in the code.

[0217] In Figure 4, a cross-sectional view shows one embodiment of an alignment mark field 14''''. The alignment marks 15' of the alignment mark field 14'''' are arranged in three different planes 18, 18', 18'' and can be detected by the detection unit 6. The detection unit 6 can detect only the alignment marks 15' within the focal range 19.

[0218] A first plane 18 has a known distance 17'' relative to a second plane 18'. The second plane 18' also has a known distance 17' relative to a third plane 18''. In addition, the distance 17 between the first plane 18 and the third plane 18'' is known. In the illustrated embodiment, the distances 17'' and 17' have different sizes, such that when the alignment mark field 14'''' is used for the alignment of a substrate, all three distances 17, 17', and 17'' can be traversed or set.

[0219] The combination of distances 17, 17', 17'' can also be traversed by multiple movements of the substrate holder (9) fixed relative to the alignment mark area 14''''. For example, a distance of 17'' can be set first, and then the distance 17' can be traversed in the same direction. For example, the substrate holder can also be moved up to twice the distance of 17''. For this purpose, alignment is performed in two steps and detection units are correspondingly set between the steps, because the focal position of one of the detection units 3 and thus the focal range 19 are adjusted. [Simplified Explanation of the Diagram]

[0175] FIG1 is a cross-sectional view of one embodiment of a device according to the present invention; FIG2a is a plan view of an exemplary alignment mark field having alignment marks; FIG2b is a cross-sectional view of one embodiment of an alignment mark field; FIG3 is a plan view of one embodiment of an alignment mark field having alignment marks; FIG4 is a cross-sectional view of one embodiment of an alignment mark field having a detection unit. In the figures, the advantages and features of the present invention are indicated by respective identifying element symbols according to embodiments of the present invention, wherein components or features having the same function or effect are indicated by the same element symbols.

Claims

1. A method for aligning a substrate, comprising at least the following steps: i) providing a substrate holder (9) having a substrate holder surface (20) designed for mounting the substrate, and an alignment mark field (14, 14', 14'', 14''') fixedly configured relative to the substrate holder (9); ii) aligning the substrate, characterized in that the substrate is aligned with the aid of alignment marks (15, 15') of the alignment mark field (14, 14', 14'', 14''') configured vertically above each other.

2. The method of claim 1, wherein the alignment of the substrate in step ii) comprises the following steps, specifically in the following sequence: a) a detection unit (6) detects a first alignment mark (15, 15') on a first plane (18, 18', 18'') of the alignment mark fields (14, 14', 14'', 14'''); b) after the detection in step a), fixes the focal position of the detection unit (6); c) moves the substrate holder (9) normally to the first plane (18, 18', 18'') of the alignment mark fields (14, 14', 14'', 14'''); d) a second alignment mark on a second plane (18, 18', 18'') of the second plane (18, 18', 18'') of the alignment mark fields (14, 14', 14'', 14''''); 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'') are separated by a distance (17, 17', 17'').

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

4. The method of any one of claims 1 to 3, wherein during the movement of the substrate holder (9) in step iv), the detection unit (6) at the focal position continuously misses the alignment mark fields (14, 14', 14'', 14''').

5. The method of any of the requests 1 to 3, wherein after the fixing at the focal position in step b), the detection unit (6) remains fixed.

6. The method of any one of claims 1 to 3, wherein during the detection period of the first alignment mark (15, 15') by a detection unit (6) in step a) and / or during the detection period of the second alignment mark (15, 15') by a detection unit (6) in step d), additional information is provided regarding the position of each alignment mark (15, 15') within the alignment mark field (14, 14', 14'', 14''').

7. An apparatus for aligning a substrate, comprising at least: A) a substrate holder (9) having a substrate holder surface (20) designed for mounting the substrate, and B) an alignment mark field (14, 14', 14'', 14''') having alignment marks (15, 15') fixedly configured relative to the substrate holder (9) and / or the substrate, characterized in that the substrate can be aligned with the help of the alignment marks (15, 15') arranged vertically above each other.

8. The apparatus of claim 7, further comprising: C) A detection unit (6) for detecting the alignment marks (15, 15') of the alignment mark fields (14, 14', 14'', 14'''), and D) a moving configuration (10) for moving the substrate holder (9), wherein the alignment marks (15, 15') of the alignment mark fields (14, 14', 14'', 14''') are disposed in a first plane (18, 18', 18'') and a second plane (18, 18', 18''), wherein the first plane (18, 18', 18'') and the second plane (18, 18', 18'') are arranged parallel to each other, and wherein the first plane (18, 18', 18'') and the second plane (18, 18', 18'') are at a distance from each other. 17, 17', 17''), and one of the alignment marks (15, 15') of the first plane (18, 18', 18'') can be detected at a focal position of the detection unit (6), and the focal position of the detection unit (6) can be fixed, and one of the alignment marks (15, 15') of the second plane (18, 18', 18'') can be detected by the detection unit (6) at the focal position, and the substrate holder (9) can be moved normally to the first plane (18, 18', 18'') by the moving configuration (10).

9. The apparatus of 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 configured to be vertically aligned with each other in the alignment mark fields (14, 14', 14'', 14'''), specifically, to be in accord.

10. The apparatus of claim 7 or 8, wherein the alignment marks (15, 15') of the first plane (18, 18', 18'') are configured to be offset in a stepped manner relative to the alignment marks (15, 15') of the second plane (18, 18', 18'').

11. The apparatus of claim 7 or 8, wherein the alignment mark fields (14, 14', 14'', 14''') are disposed on one of the rear sides of the substrate holder (9) opposite to the substrate holder surface (20).

12. The apparatus of claim 11, wherein the center point of one of the alignment mark fields (14, 14', 14'', 14''') on the rear side of the substrate holder (9) is at least partially aligned with the center point of one of the surfaces (20) of the substrate holder.

13. The apparatus of claim 7 or 8, wherein the alignment mark fields (14, 14', 14'', 14''') are disposed on one side of the substrate facing the substrate holder surface (20).

14. The apparatus of claim 7 or 8, wherein the alignment mark field (14, 14', 14'', 14''') includes at least one further plane (18, 18', 18'') having the alignment marks (15, 15'), wherein the at least one further plane (18, 18', 18'') is configured to be at least parallel to the first plane (18, 18', 18'').

15. The apparatus of claim 7 or 8, wherein the apparatus includes at least one further alignment mark field (14, 14', 14'', 14''') and at least one further detection unit (6) for detecting the at least one further alignment mark field (14, 14', 14'', 14'''), wherein the at least one further alignment mark field (14, 14', 14'', 14''') is fixedly configured relative to the substrate holder (9).

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