Method and apparatus for aligning substrates

Abstract

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

Description

Technical Field

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

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

[0003] In particular, the bonding of aligned semiconductor substrates is referred to as bonding.

[0004] During so-called bonding, the substrates to be bonded are aligned with each other and joined to each other in subsequent process steps. In this case, particularly accurate alignment of the substrates with each other is required.

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

[0006] In order to be able to detect and / or identify the position and orientation of the alignment markings from the outer surface of the substrate facing away from the surface of the substrate to be joined, when at least one of the substrates is not transmissive to the electromagnetic beam used for measuring the substrate, in the prior art, before the substrates are brought close to each other, the alignment markings are detected between the substrates using image detection means.

[0007] This had several drawbacks. In particular, the camera could bring particles onto the substrate surface. Furthermore, positioning the camera between two substrates for detection required moving a large distance between them. This resulted in more complicated alignment and correspondingly larger movement distances, leading to greater alignment errors.

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

[0009] Another problem with conventional technology is that the increasingly stringent alignment accuracy requirements can no longer be achieved by simple means. Methods that measure a substrate relative to a reference point and then align it, for example, after bringing it close for contact, without visual inspection, cannot meet these new alignment accuracy requirements.

[0010] For example, U.S. Patent No. 6,214,692 is based on the comparison and positioning correction of two images of alignment markings. The orientation of the alignment markings on two substrates placed face to face is detected individually using a camera system. From the calculated relative orientation and relative position of the alignment markings, a positioning table (substrate holder and stage) is driven and controlled to correct any incorrect positions.

[0011] Another publication, U.S. Patent No. 10692747, is based on the comparison and positioning correction of a total of three images of a flat alignment marking. The orientation of the alignment markings on two substrates positioned face to face is detected individually using a camera system. A third detection unit detects a third alignment marking, which creates a correlation between the substrate alignment marking and the back surface of the substrate holder or the substrate, thereby enabling more accurate alignment of the two substrates.

[0012] In this respect, visual control during face-to-face alignment of two substrates is either impossible or only possible if at least one of the substrates is at least partially transparent. Therefore, precise surface alignment during face-to-face alignment is cumbersome and only possible to a limited extent.

[0013] A particular drawback that has emerged is the need for refocusing or readjustment when detecting alignment markings. Here, refocusing is essentially necessary when readjusting the optical system to detect the alignment marks. The readjustment movement is performed along with parasitic movements superimposed on the necessary movements, but these parasitic movements cause deviations from the ideal movement of each optical system. Therefore, the focal point is displaced during movement. The focal point is displaced, for example, in the xy plane stretched perpendicular to the optical system or the optical axis of the optical system. This displacement of the focal point reduces the accuracy of the alignment marking measurement, and this reduced accuracy, in turn, reduces the alignment accuracy.

[0014] Therefore, an object of the present invention is to provide a method and apparatus for aligning a substrate that at least partially, and especially completely, eliminates the drawbacks of the prior art. An object of the present invention is particularly to provide an improved method and apparatus for aligning a substrate. An object of the present invention is particularly to provide a method and apparatus for aligning a substrate that does not require refocusing of the detection unit during alignment. An object of the present invention is further 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 problems of the present invention are solved by the features of a plurality of parallel independent claims. Advantageous extensions of the present invention are presented in the dependent claims. Within the framework of the present invention are all combinations of at least two features shown in the specification, claims, and / or drawings. Within the range of values ​​presented, values ​​that fall within the enumerated boundaries should also be considered disclosed as boundary values ​​and may 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) A step of preparing a substrate holder having a substrate holder surface configured to accommodate a substrate, and an alignment marking field positioned in a fixed position relative to the substrate holder, ii) A method comprising the step of aligning a substrate, The present invention relates to a method characterized by aligning a substrate based on alignment marks arranged above and below an alignment marking field.

[0017] Here, the substrate or substrate stack is aligned based on alignment marks positioned vertically. This alignment marking field is fixedly positioned on or on the substrate holder surface. In particular, the precise orientation of the alignment marking field and the orientation of each alignment mark in the alignment marking field relative to the substrate holder are known. Here, the alignment marks of the alignment marking field, or at least two alignment marks, are positioned vertically.

[0018] The statement that at least two alignment marks in the alignment marking field are positioned vertically means that these alignment marks are positioned in different planes. This means that the alignment marking field has a specific height (in the z direction) relative to the substrate holder surface. This means that at least two alignment marks are positioned in different z-planes.

[0019] Preferably in this case, the alignment marks do not obscure each other in the z direction, so that at least two alignment marks of the alignment marking field can be observed from one observation direction without obstruction. In other words, the alignment marks of the alignment marking field are preferably positioned vertically and displaced from each other in planes parallel to each other, so that any alignment mark in any plane of the alignment marking field can be captured.

[0020] Furthermore, it is conceivable that at least two alignment marks positioned vertically within the alignment marking field may be positioned to partially or completely overlap in the z-direction. In other words, at least two vertically positioned alignment marks may be positioned to be at least partially aligned with each other in the z-direction. In this case, different z-planes or layers of the alignment marking field are particularly transparent to different wavelengths, thereby enabling the detection of any other alignment mark in any other plane of the alignment marking field. In this case, the plane / layer and / or alignment mark positioned upstream in the observation direction are penetrated for observation, thereby enabling the detection of alignment marks in subsequent planes that are at least partially aligned.

[0021] This allows for the detection of alignment marks, and subsequently the detection of other alignment marks placed on top of them, by comparing the known orientations of each of these alignment marks. Since the properties, structure, and orientation of the alignment marking field are preferably known, the spacing between the alignment marks can be detected. Based on this spacing, alignment based on the vertically positioned alignment marks can be performed, for example, by relative movement of the substrate holder without requiring refocusing of the detection means. In this way, the known spacing between the vertically positioned alignment marks can be detected and, consequently, set, allowing for particularly accurate alignment of the substrate in at least one direction.

[0022] Furthermore, the advantage of precise alignment in at least one direction allows for extremely easy and accurate access to the bonding gap. This is advantageous because the substrate holder can be aligned by direct visual control, relying on the alignment marking field. Moreover, only one detection means is required for alignment, thereby reducing the likelihood of failure. Therefore, particularly when bonding non-transparent substrates in the face-to-face method, the precise positioning of the substrate holder, and consequently the substrate, can be set. This is advantageous because, with the vertically positioned alignment marks and the height information they provide, alignment can be performed without refocusing the detection means. This allows the substrate to be moved with particular precision and under visual control by a specific interval.

[0023] In one preferred embodiment of the present method for aligning a substrate, the substrate alignment in step ii) has at least the following steps, in particular in the following order: a) A step of detecting a first alignment mark on the first plane of the alignment marking field using a detection unit, b) After detection in step a), the step of fixing the focal position of the detection unit, c) A step of moving the substrate holder perpendicular to the first plane of the alignment marking field, d) The detection unit detects a second alignment mark on the second plane of the alignment marking field, The first plane and the second plane are positioned parallel to each other, and it is determined that there is a gap between the first plane and the second plane.

[0024] Preferably, the alignment marking field has multiple alignment marks arranged side by side on each plane. This allows for the detection of at least one first alignment mark, or at least one second alignment mark on the corresponding plane. Furthermore, the alignment marking field is preferably transparent to the detection unit between planes, thereby enabling the detection of alignment marks arranged vertically. It is also conceivable that the alignment marks on the first plane be positioned displaced relative to the alignment marks on the second plane, and that the alignment marking field have different levels. The detection unit can also detect other alignment marks on the first plane if they are located in the focal area, in addition to each first alignment mark. The same applies to the second plane. In this case, the detection unit is configured to detect multiple alignment marks on each plane, particularly alignment marks arranged side by side.

[0025] When detecting the first alignment mark in the first plane of the alignment marking field, the detection unit identifies each alignment mark. The detection unit preferably has focusing means, preferably an objective lens, for focusing or autofocusing on the first alignment mark during detection. At this time, the detection unit or the objective lens takes a focal position where the detection unit can detect a specific focal region. Thereby, the detection unit or the objective lens is focused on the focal region of a specific focal position, and the alignment mark arranged in the focal region can be detected. Preferably during detection, only the alignment marks of each plane are detectable or distinguishable. This is because each focal region in the detection unit contains only one plane. Thereby, the distance between the first plane and the second plane is preferably greater than the depth of the focal region.

[0026] Following the detection of the first alignment mark in the first plane, the focal position of the detection unit is fixed. Thereby, particularly since the focal region is determined, the detection unit can subsequently preferably detect only the alignment marks within the determined focal region. Thereafter, by moving the substrate holder perpendicularly to the first plane of the alignment marking field, the substrate is moved together and thus aligned on the substrate holder surface of the substrate holder. The substrate holder is moved at least until the detection unit can detect the second alignment mark in the second plane of the alignment marking field. In this regard, by moving the substrate holder, the substrate is advantageously moved by only the distance required for focusing. For example, in this way, the bonding distance between the substrate and another substrate to be bonded can be set. Thereby, it is possible to advantageously prevent an alignment error caused by refocusing of the detection unit.

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

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

[0029] Advantageously, the substrate holder can also be aligned relative to the alignment marks of the alignment marking field by means of the additional alignment markings. Furthermore, the detection unit can align the substrate holder or the substrate arranged on the substrate holder relative to the additional alignment markings as well. In particular, at least one additional detection unit can identify the position of an additional substrate to be bonded relative to the alignment marking field. The alignment can be carried out more precisely by means of the additional alignment marks and the additional detection unit.

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

[0031] If another alignment mark is arranged in another plane between the first plane and the second plane, this other alignment mark can be measured by the detection unit when moving the substrate holder, whereby the substrate holder can be moved particularly precisely and in a controlled manner. Furthermore, the alignment can be carried out more precisely by means of a plurality of detected alignment marks, the orientation of which in the alignment marking field is known.

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

[0033] The detection unit is fixed not only at specific intervals relative to the alignment marking field, but also in a horizontal position. This fixes the detection unit's position relative to the substrate holder, and consequently, the substrate placed in the substrate holder, in addition to fixing its position relative to the alignment marking field. This advantageously ensures that, in addition to fixing the focal position of the detection unit or objective lens, the position of the detection unit is also determined. In this way, the substrate can be aligned more accurately, and alignment errors caused by inaccurate movement of the detection unit are avoided.

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

[0035] The alignment marks preferably have information about the orientation of each within the alignment marking field. In this case, in addition to the orientation along the alignment marking field (xy orientation), the height of each plane or the spacing between them is also known. This allows, advantageously, when a first alignment mark is detected, to determine which plane the alignment mark is located on. This makes it easier to control the alignment in open-loop or closed-loop, especially when the alignment marking field has more than two planes with different spacings, because the height information for each alignment mark is detected. For example, advantageously, during continuous detection during movement or when detecting the first alignment mark, it is possible to determine which plane or step in the focal region is detected. Furthermore, if a position is detected between two planes or steps, advantageously, it is possible to approach the plane or step located above or below it. Advantageously, the orientation at the xy position can also be detected and controlled.

[0036] The aforementioned advantages and features of the alignment method are also disclosed in relation to the following apparatus.

[0037] The present invention further provides a device for aligning a substrate, comprising at least the following: A) A substrate holder having a substrate holder surface configured to accommodate a substrate, B) The present invention relates to an apparatus having an alignment marking field with alignment marks, which is fixedly positioned relative to a substrate holder and / or a substrate, wherein the substrate can be aligned based on the alignment marks positioned above and below.

[0038] Alignment marks positioned above and below the alignment marking field have a known relative spacing in the direction of the alignment marking field. This is advantageous because, based solely on the alignment marks, the alignment of the substrate holder or the substrate placed on the surface of the substrate holder can be performed by a single detection means, particularly just one detection means.

[0039] In one preferred embodiment of the apparatus for aligning substrates, the apparatus further includes: C) A detection unit for detecting alignment marks in the alignment marking field, D) The system includes a moving device for moving a substrate holder, wherein the alignment marks of the alignment marking field are located in a first plane and a second plane, the first and second planes are parallel to each other, the first and second planes are spaced apart from each other, the first alignment mark of the alignment marks in the first plane is detectable at the focal position of the detection unit, the focal position of the detection unit is fixed, at this focal position the detection unit can detect the second alignment mark of the alignment marks in the second plane, and the substrate holder is movable perpendicular to the first plane by the moving device.

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

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

[0042] Between these planes, the alignment marking field is preferably configured to be transparent to the detection unit. By arranging the alignment markings vertically, it is advantageous that when detecting the second alignment mark, it is possible to determine whether the movement of the substrate holder by the moving device was performed precisely perpendicular to the first plane. In this case, the detection unit has a focal point at the focal position where the orientation of each second alignment mark corresponds to the first alignment mark. Furthermore, it is conceivable that the alignment marks on the first plane are rotated or mirrored with respect to the correspondingly aligned alignment marks on the second plane. In this case, the alignment marks preferably have a non-point-symmetric shape or outer contour, so that at least a portion of these alignment marks can be detected by rotation or mirroring.

[0043] In one preferred embodiment of the apparatus for aligning a substrate, it is specified that the alignment marks on the first plane are positioned in a stepped manner relative to the alignment marks on the second plane.

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

[0045] In this way, the detection unit can advantageously detect alignment marks located on or near the surface of the alignment marking field.

[0046] In one preferred embodiment of the apparatus for aligning a substrate, the alignment marking field is located on the back surface of the substrate holder, facing away from the surface of the substrate holder.

[0047] The alignment marking field may be mounted, for example, on the back surface or fitted into the substrate holder. The alignment marking field may also be formed by the substrate holder itself. The detection unit can advantageously be positioned on the back surface facing away from the front surface of the substrate holder.

[0048] In one preferred embodiment of the apparatus for aligning a substrate, it is specified that the center point of the alignment marking field on the back surface of the substrate holder is at least partially aligned with the center point on the front surface of the substrate holder.

[0049] By centrally positioning the alignment marking field, the alignment of the substrate holder can be performed with advantage and accuracy. In this embodiment, it is also advantageous that linearity error components or rotation of the substrate holder, and consequently the base holder surface, relative to the detection unit can be sensed. In particular, wedge errors with respect to the lenses of the optical system can also be detected and eliminated. Alignment errors can be divided into error components. Thus, linearity errors, rotational errors, and magnification errors, as well as errors of a higher order, can be characterized.

[0050] In one preferred embodiment of the apparatus for aligning a substrate, the alignment marking field is located on the surface of the substrate, facing the surface of the substrate holder.

[0051] In this embodiment, the substrate holder has a through-opening in the region of the alignment marking field. Furthermore, the substrate holder can be configured to be transparent to the detection unit, thereby allowing the alignment marking field placed on the substrate to be detected, particularly from the back surface of the substrate holder. This thus advantageously enables direct visual control of the substrate being aligned. In this case, the substrate, and consequently the alignment marking field, is held in a fixed position relative to the substrate holder. For example, alignment errors caused by an uneven substrate holder surface are avoided. Furthermore, the alignment marking field can be advantageously adapted to the substrate individually. Additionally, the alignment marking field can be formed or imaged by the substrate.

[0052] In one preferred embodiment of the apparatus for aligning a substrate, the alignment marking field is characterized to have at least one other plane having alignment marks, wherein this at least one other plane is arranged parallel to the first and second planes.

[0053] The alignment marking field preferably has at least three planes with alignment marks, where the alignment marks are provided with information on which plane they are located on. In this way, the apparatus can access multiple specific intervals. The intervals between these planes may be the same. However, preferably, these planes are spaced differently from each other. This allows for flexible access to multiple intervals. This is particularly advantageous when using the apparatus for bonding substrates, as it allows for setting different bonding intervals or for aligning a substrate particularly accurately to another substrate.

[0054] In one preferred embodiment of the apparatus for aligning a substrate, the apparatus comprises at least one additional alignment marking field and at least one additional detection unit for detecting the at least one additional alignment marking field, wherein the at least one additional alignment marking field is positioned in a fixed position on the substrate holder.

[0055] This additional alignment marking field allows for detection at multiple points, enabling even more precise alignment. For example, in this way, displacement and / or rotational errors can be particularly well identified and eliminated. Here, this alignment marking field and at least one other alignment marking field are preferably displaced and positioned along the substrate holder. Particularly preferably, the device has a total of three alignment marking fields and three detection units, each of which is displaced equally from one another, particularly radially, and distributed around the center point of the substrate holder surface.

[0056] Preferably, the planes of the alignment marking field and at least one other alignment marking field are equally spaced from each other. In this way, alignment can be made particularly accurate because the spacing can be verified at at least two points, preferably points of displacement.

[0057] One core aspect of the present invention is the detection of at least two alignment marks in at least two different planes or heights of the alignment marking field before the substrate is aligned. The alignment marking field is preferably mounted on one of a plurality of substrates to be aligned, or on a substrate holder. The alignment marks provide 3D positional information for the alignment of the substrates. The alignment marking field is preferably not located on the contact surface of the substrate. Preferably, the alignment marking field is located on a surface of the substrate or substrate holder, facing away from the contact surface or parallel to the contact surface.

[0058] The relative alignment of substrates is performed indirectly, particularly using alignment markings located on the contact surfaces of the substrates. The alignment markings on opposing surfaces of opposing substrates are especially complementary to each other. The alignment markings may be any object that can be aligned with each other, such as cross, circle, square, or propeller-shaped formations or grid structures, particularly phase grids in the spatial frequency domain.

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

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

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

[0062] One particularly important aspect of the present invention is that the alignment and bonding interval are set solely by detecting alignment marks positioned above and below the alignment marking field. "Detection only" means that additional alignment markings are not detected or cannot be detected during alignment. Thus, the bonding interval can be set accurately and under visual control by the alignment marks positioned above and below.

[0063] In this case, the alignment marking field preferably includes alignment markings or alignment marks that are uniquely associated and / or can be associated with at least two different planes. In this case, the alignment marking field has steps or at least partially transparent layers, thereby arranging the alignment marks vertically. This indirectly provides height information in addition to the usual x and y positions. In this case, it is also possible to directly provide 3D position information using the alignment marks of the alignment markings. The height information is provided by the arrangement in different planes. Since the spacing between the planes is known, it is sufficient to provide information on which plane the detected alignment marks are located in within the alignment marking field.

[0064] As a result, the alignment marking field consists of or includes position-coded and height-coded alignment markings, which provide unique position and height information of the substrate and / or substrate holder for alignment without refocusing the third detection unit. Alignment markings or alignment marks in the alignment marking field should be understood below as height-coded alignment markings or / or alignment marks, even without explicit reference to height coding and / or 3D position information.

[0065] Preferably, the size or dimensions of the alignment marking field are adapted to the field of view of each optical detection means, thereby allowing observation of at least two steps or alignment marking planes.

[0066] In this process, the number of rows and the overall height of the alignment marking field are similarly adjusted to the interval to be set. For example, if a bonding interval of 500 micrometers is to be set, preferably 550 micrometers of height-coded positional information is imaged in the alignment marking field, thereby allowing the system to approach this interval without refocusing.

[0067] Detection is preferably performed by a corresponding imaging optical system, thereby allowing the depth of field to be selected such that it is smaller than the step height or layer thickness of the alignment marking field. Depth of field (DOF) is the region in the image space of the imaging optical system in which a sufficiently sharp image of the object being focused on, particularly the alignment marking, is produced. Conversely, this means that the image plane (image detection means, sensor) can be displaced in the region of the depth of field without the image of the object becoming significantly blurred.

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

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

[0070] In contrast, when the depth of field is large and at least two step heights are clearly imaged, the positioning uncertainty of this device increases. This is because it becomes impossible to uniquely associate the z height with a single step.

[0071] In one preferred embodiment of the apparatus, the image detection means or detection means of the detection unit can be reproducibly displaced by 0.2 × step height without refocusing on the image side. This can be used to determine which alignment marking of the alignment marking field should be used for positioning when the focal plane on the image side is directly located at two adjacent step heights and both steps appear equally clear. The determination of which alignment marking to use can be made by slight displacement of the image detection means (also as a computer-implemented, independent method according to the present invention).

[0072] When detecting the alignment marking field, it is physically restricted so that only one plane or step is clearly imaged. Preferably, only one step or plane is located in the focal region of the detection unit. Since the alignment markings in the alignment marking field are position-coded and spatial-coded, the positional information of the substrate holder in the spatial coordinate system can be determined from the clearly detected alignment marks on the plane.

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

[0074] The interval A is particularly less than 500 micrometers, preferably less than 100 micrometers, especially preferably less than 50 micrometers, and most preferably less than 10 micrometers.

[0075] This method for aligning substrates is suitable for aligning at least two substrates relative to each other using any electromagnetic beam, particularly UV light, more preferably infrared light, and most preferably visible light. In this process, the substrate to be aligned, or the substrate placed on the surface of the substrate holder of the substrate holder, can also be moved precisely by the distance between the planes relative to another component, and thus aligned.

[0076] This method enables observation or detection of the first and second alignment markings, and supplements them with at least one additional optical path to accurately reproduce the substrate position and the substrate holder position. This additional optical path is not located between the substrates or extends between them during substrate alignment, and is particularly detectable from the outside by observation or detection of at least one alignment marking field. Preferably, the alignment marking field provides height information for setting a desired bonding gap between the first and second planes.

[0077] In 11 particularly preferred methods, the substrate may be opaque to the electromagnetic beam used to detect the alignment markings on the first and second substrates. In this case, the detection of the alignment markings is performed by the back surface of the substrate, which is transparent to the electromagnetic beam used to detect the alignment markings.

[0078] This method for alignment enhances alignment accuracy, particularly through additional XYZ position and / or orientation information, which is detected by a separate alignment marking field and a corresponding separate detection unit, and is used to control the alignment in an open-loop and / or closed-loop manner.

[0079] For this purpose, the alignment apparatus preferably has a software-supported control unit, which is used to perform the steps described herein and to control the components in an open loop. Here, it should be understood that closed control loops and closed-loop control are included in the control unit.

[0080] The X-direction and Y-direction, or X-position and Y-position, are understood to be directions or positions that extend or are positioned on the XY coordinate system, or on any Z-plane of the XY coordinate system. The Z-direction is positioned orthogonal to the XY direction. The X-direction and Y-direction preferably correspond to the lateral directions along the plane of the alignment marking field. The Z-direction preferably is the direction in which the substrate holder moves when the focal position of the detection unit is fixed on the XY plane.

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

[0082] The alignment marking field is preferably located in a local vicinity of the alignment marking on the substrate. Particularly preferably, at least one alignment marking on the substrate and the alignment marking field are located on opposite sides of the substrate. Alternatively, the alignment marking field may be located on the back surface of the substrate holder and opposite any additional alignment markings. When the additional alignment marks and alignment marks of the alignment marking field are located on opposite sides of the substrate holder surface, orientation correlation can be performed particularly easily.

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

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

[0085] In one particularly highly preferred embodiment of the apparatus, the two alignment marking fields are preferably aligned in the z-direction to additional alignment markings on the substrate, and are located particularly on the back surface of the substrate holder.

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

[0087] In one further embodiment of the apparatus, at least two alignment marking fields are included near the substrate edge on the substrate side of the substrate holder to optically detect an accessible position. This advantageously allows the substrate holder to be positioned horizontally.

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

[0089] By correlating at least one of the additional alignment markings measured on the first and / or second substrates, particularly on the contact surfaces, with at least one alignment mark on an alignment marking field that is freely accessible and visible during substrate alignment, the alignment marks can be directly observed, thereby enabling real-time measurement and closed-loop control during alignment. This improves the alignment accuracy of the substrates.

[0090] Another advantage of the alignment marking field is that it detects additional height information, which allows for more accurate positioning of the lower substrate holder with respect to the upper substrate in the upper substrate holder. This eliminates, in particular, the resulting positional inaccuracies due to the focusing movement of the detection unit.

[0091] By improving the accuracy of the height positioning of the gap between the upper substrate and the lower substrate during bonding, the preload of at least one of the multiple substrates can be set to a small tolerance. This preload reduces substrate distortion during bonding, thereby reducing, and preferably eliminating, substrate pop-out after bonding. In this regard, the present method and apparatus for alignment are used for alignment during the bonding process.

[0092] In a further embodiment of the apparatus, at least one additional alignment marking field is positioned on the substrate side of the substrate holder, near the periphery of the substrate, in a location that is continuously accessible to another detection unit. Particularly preferably, the surface of the alignment marking field is in the same plane as the surface of the substrate to be bonded, which is fixed to the substrate holder.

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

[0094] By adding 3D positional features to the substrate holder that can be uniquely correlated with the positional features on the substrate, direct observation of alignment markings on the substrate can be replaced by direct observation of alignment markings on the substrate holder. This has the advantage that an observable portion of the substrate holder can be positioned substantially always within the field of view or detection area of ​​the detection unit. 3D positional information enables more accurate alignment of substrates.

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

[0096] By actively feeding back data for positioning and position correction, accuracy is improved compared to open-loop controlled positioning in conventional techniques. This is because a closed control loop offers the possibility of controlling the actual state of the position.

[0097] One aspect of this method and apparatus for alignment is to improve the accuracy of the alignment of two substrates. This method for alignment allows for real-time observation of alignment or movement, particularly from outside the bonding interface. The 3D position information, incorporating the provided height information, enables alignment with significantly greater accuracy than previously known methods. Here, the substrates are positioned with minimal spacing from each other, and preferably, no apparatus objects, particularly detection units, are located between the substrates.

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

[0099] The ability to directly detect or observe at least one alignment mark in the alignment marking field enables real-time measurement of the 3D position of the substrate holder. In this process, the detection of the first and second alignment marks, and the height information provided thereby, eliminates positioning uncertainty, thereby increasing alignment accuracy and reducing error propagation. This means that the number of required feed movements is reduced, and alignment accuracy is improved by closed-loop control and height adjustment during bonding.

[0100] A first embodiment of the apparatus for alignment is used in a bonding apparatus and includes an upper substrate holder. An upper substrate can be fixed to the upper substrate holder. The upper substrate holder is formed to be sufficiently transparent, at least locally, so that alignment markings on the upper substrate on the contact surface of the upper substrate, which is the surface facing away from the mounting surface of the upper substrate, can be detected with sufficient resolution, contrast, and intensity.

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

[0102] A sufficiently transparent substrate is understood to be one whose transmittance to an electromagnetic beam used to detect additional alignment markings is sufficient to detect the additional alignment markings with sufficient resolution, contrast, and intensity.

[0103] A substrate holder that is locally sufficiently transparent is understood to be one in which the transmittance of the substrate holder to the electromagnetic beam used to detect the alignment markings is sufficiently high. Alternatively, the substrate holder may be fitted with a viewing window and / or through-hole for observing the substrate and / or the substrate pair.

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

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

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

[0107] A detection unit for detecting an alignment marking field is, in particular, part of an optical system for detecting an alignment marking field, and according to one advantageous embodiment, includes a beamforming element and / or deflection element, e.g., a mirror, lens, prism, a beam source in particular for Kohler illumination, an image detection means, e.g., a camera (CMOS sensor or CCD, or surface detection means, row detection means, or point detection means, e.g., a phototransistor), a moving means for focusing, and an evaluation means for closed-loop control of the optical system.

[0108] In another embodiment of this apparatus, the optical system can be used in combination with a rotation system for substrate positioning according to a turnover adjustment method (see Friedrich Hansen, Justierung, VEB Verlag Technik, 1964, Section 6.2.4, Umschlagmethode). According to this, during turnover adjustment, at least one measurement is taken at a predetermined position on each substrate, and at least one measurement is taken at the position after it has been rotated 180 degrees, oriented in the opposite direction, and turned over. The measurement results obtained in this way are particularly free from eccentricity errors.

[0109] One development of the apparatus for alignment includes, in particular, two optical systems of the same structure, each equipped with additional detection units that are aligned with each other and can be fixed relative to each other for detecting additional alignment marks.

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

[0111] In another embodiment of the apparatus, at least one substrate holder having an opening and / or a through-hole and / or viewing window is used at a location specifically designated for observing two substrate surfaces simultaneously.

[0112] The apparatus may further include a system for fabricating prebonding. For this purpose, pressure pins and / or configurable nozzles may be used to initiate fusion bonding for joining the substrates. In particular, the configurable nozzles may be height-adjustable, thereby changing their relative position to the back surface of the substrate, and the nozzle volume flow rate may be modifiable under closed-loop control. These nozzles can be advantageously aligned based on alignment markings positioned above and below.

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

[0114] These moving devices can form any movement as a result of individual movements, and thus these moving devices may preferably include a high-speed coarse positioning device that does not meet precision requirements and a fine positioning device that operates precisely.

[0115] A positioning device is understood to be a coarse positioning device if, with respect to the overall travel path or rotation range where one rotation in a rotatable rotary drive unit is 360 degrees, the approach accuracy and / or repeatability deviate from the target value by more than 0.1%, preferably more than 0.05%, and particularly preferably more than 0.01%.

[0116] Therefore, for example, in a coarse positioning device with a travel distance exceeding 600 mm (twice the substrate diameter), an approach accuracy of 600 mm × 0.01%, i.e., an approach accuracy exceeding 60 micrometers, is consequently obtained as residual uncertainty.

[0117] In another embodiment of coarse positioning, the residual uncertainty of approach accuracy or repeatability is less than 100 micrometers, preferably less than 50 micrometers, and particularly preferably less than 10 micrometers. Thermal disturbances should also be taken into consideration.

[0118] The coarse positioning device performs its positioning role with sufficient accuracy only when there is a deviation in the range of motion of the corresponding fine positioning device between the actual position reached and the target value of that position.

[0119] A selective coarse positioning device performs its positioning role with sufficient accuracy only when there is a deviation of half the range of motion of the corresponding fine positioning device between the actual position reached and the target value of that position.

[0120] A positioning device is understood to be a fine positioning device if the residual uncertainty of the approach accuracy and / or repeatability with respect to the overall travel or rotation range does not exceed 500 ppb, preferably 100 ppb, and more preferably 1 ppb from the target value.

[0121] Preferably, a precision positioning device can compensate for an absolute positioning error of less than 5 micrometers, preferably less than 1 micrometer.

[0122] The alignment of the substrates can be performed in all six degrees of freedom of movement, namely by three translational movements along the coordinate directions x, y, and z, and three rotations around the coordinate directions. Here, movement can be performed in any direction and orientation. The alignment of the substrates preferably includes passive or active wedge error compensation, as disclosed in publication European Patent No. 2612109.

[0123] A robot for handling circuit boards is included in the mobile device. The holding unit may be incorporated into the mobile device as a component or functionally integrated.

[0124] Furthermore, the alignment apparatus preferably includes a closed-loop control system and / or evaluation system, in particular a computer, to perform the steps described, especially the movement flow, to make corrections, and to analyze and store the operating state of the apparatus.

[0125] The procedure is preferably prepared as a recipe and executed in a machine-readable format. A recipe is a set of optimal values ​​for functionally or process-technically relevant parameters. By utilizing a recipe, the reproducibility of the manufacturing flow can be ensured.

[0126] Apparatus for alignment according to an advantageous embodiment further includes a power supply system and auxiliary and / or supplementary systems (compressed air, vacuum, electrical energy, fluids such as hydraulic pressure, refrigerants, heat transfer media, means and / or devices for temperature stabilization, electromagnetic shielding).

[0127] The alignment device may further include a frame, an exterior, and active or passive subsystems for suppressing, damping, or eliminating vibrations.

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

[0129] Both tactile and non-tactile measurement methods can be used. Measurement standards and units may exist as physical or material objects, particularly as scales, or they may be implicitly present in the measurement method, such as the wavelength of the beam used.

[0130] To achieve alignment accuracy, at least one of the following measurement systems can be selected and used. The measurement system performs the measurement procedure. In particular, • Induction methods, and / or • Capacity method, and / or • Resistive method and / or • Comparison methods, particularly optical image recognition methods, detection of location marks and / or QR codes, and / or • Incremental or absolute methods (especially by glass standards as scales, or by interferometers, especially laser interferometers, and by magnetic standards), and / or • Propagation time measurement (Doppler method, time-of-flight method) or other time detection method, and / or Triangulation methods, especially laser triangulation, • Autofocus system, and / or For example, intensity measurement methods such as optical fiber distance meters can be used.

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

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

[0133] The frame can be understood as a part composed of natural hard stone or mineral casting or spheroidal graphite casting or hydraulic concrete, which are formed in a vibration-damping and / or vibration-isolating manner and / or vibration-eliminating manner.

[0134] The idea can be similarly reversed by attaching the detection unit to the substrate holder and the alignment marking field to, for example, the frame. In this case, the detection unit moves with the substrate holder, and the alignment marking field is fixed to the frame.

[0135] To enable detection, evaluation, and open-loop control at any given time, particularly continuously, the alignment marks of the alignment marking field are distributed, according to one advantageous embodiment, to an area larger than the field of view of the image detection system of the detection unit, thereby supplying measurements to the open-loop control unit (and / or closed-loop control unit) in particular continuously. However, here, for each position in the field of view of the image detection system, the alignment marks of the alignment marking field are designed so that height information can be detected from the alignment marking field and / or from the same height position information extended. In other words, at each lateral position of the substrate holder, the arrangement of the alignment markings of the alignment marking field allows for the detection of the spatial position of the substrate holder and the setting of the correct bonding interval. In particular, since the position of the substrate holder is 3D position information, more accurate spatial alignment of the substrates fixed thereon can be performed.

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

[0137] For XYZ positioning, the alignment apparatus may also utilize at least one three-beam interferometer, correspondingly equipped with a reflector, particularly integrated, for determining the XYZ position and / or orientation of the substrate holder. Another possible advantageous embodiment of the apparatus may be measured by an integrated reflector of a prism, particularly equipped with multiple three-beam interferometers. Thus, error propagation can be eliminated by averaging, difference formation, and measurement sequence formation, further improving alignment accuracy. In other words, with sufficiently fast position measurement, a closed-loop control system can be used for the movement trajectory, thereby further reducing positional errors of the substrate holder.

[0138] The substrate holder of this alignment device, in particular, which is formed from a single block, preferably has the following functions, namely, • Fixing of the substrate by vacuum (vacuum track, connection part) and / or by electrostatic means, • Shape compensation for substrate deformation using mechanical and / or hydraulic and / or piezoelectric and / or pyroelectric and / or electrothermal operating elements, • Positioning and / or orientation determination (measurement standards, reflective surfaces and / or prisms, especially reflectors for interferometry, registration marks and / or registration mark fields, measurement standards for planarly formed planes, volumetric standards, especially steps, layer systems of known layer heights with registration markings divided into planes), It has at least two of the following: movement (guide track).

[0139] Movement devices not used for fine adjustment are preferably configured as robotic systems equipped with incremental displacement sensors. The precision of these movers for auxiliary movement is decoupled from the precision for positioning the substrate stack, so that this auxiliary movement is performed with a low repeatability of less than 1 mm, preferably less than 500 micrometers, and particularly preferably less than 150 micrometers.

[0140] Open-loop and / or closed-loop control of the alignment device's moving mechanism for (lateral) alignment (fine-tuning) is performed based on the detected XYZ position and / or alignment orientation. For this purpose, additional alignment markings on the substrate are correlated with alignment marks on the alignment marking field, which are uniquely associated with them in the field of view on the back surface of the substrate holder. Height information is calculated from the alignment markings on the alignment marking field. This provides the XYZ position, which can be continuously observed, especially during alignment feed movements and when setting the spacing for bonding, and can be used in real time, particularly for correcting feed movement errors.

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

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

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

[0144] A first embodiment of an exemplary bonding method for performing the present method for alignment includes the following steps, in particular sequentially and / or concurrently, in the following order:

[0145] Step 1: Load the upper substrate into the upper substrate holder using the mounting surface. Here, at least one first additional alignment marking is provided on the opposite side, the so-called contact surface of the upper substrate.

[0146] Step 2: Using the mounting surface, load the substrate to be aligned on the lower substrate holder. Here, at least one second additional alignment marking is provided on the opposite side, the so-called contact surface of the lower substrate.

[0147] Step 3: An additional detection unit detects at least the first additional alignment marking and, if necessary, another additional alignment marking on the upper substrate, by penetrating the upper substrate.

[0148] Step 4: Store the focal position of the objective lens of the additional detection unit and fix the objective lens in place.

[0149] Step 5: Using the upper substrate holder, the upper substrate is moved in the direction of the additional detection unit, particularly upward from the focal plane. The distance of movement is preferably less than 500 micrometers.

[0150] Step 6: Using the lower substrate holder, move the lower substrate, particularly upward, to the fixed focal position of the additional detection unit. Wedge error compensation can also be performed simultaneously.

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

[0152] Step 7: A second additional detection unit searches for and detects a second additional alignment marking on the lower substrate.

[0153] Alternatively, the lower substrate holder's z-movement displaces the focused lower substrate in the XY plane or rotates it around the Z axis, thereby positioning the searched second additional alignment marking within the focal region of the first additional detection unit for detection by this unit. Preferably, the lower substrate is further aligned, thereby positioning the searched alignment marking particularly at the center with respect to the optical axis of the fixed objective lens of the device.

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

[0155] Step 8: A measuring system (particularly a measuring microscope with an objective lens) having at least one detection unit for detecting the alignment marks on the alignment marking field is used to detect the first alignment marks on the first plane, and by extension, the XYZ position and / or alignment orientation of the lower substrate holder, preferably on the back surface of the substrate holder. In this process, the lower substrate holder is fixed, and the position of additional alignment markings on the lower substrate is correlated with the detected position. An alignment marking field fixed in place on the substrate holder is used to detect the position of the lower substrate holder.

[0156] Preferably, the camera is focused on and detected at a step in the alignment marking field. This step is located near the exposed surface of the alignment marking field, and the alignment marking is observable throughout the entire depth of the alignment marking field.

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

[0158] Step 9: Using the lower substrate holder, measure the alignment marks on different planes in the alignment marking field and move the lower substrate downward by a predetermined distance. The distance is preferably less than 500 micrometers. The distance the lower substrate is lowered is the so-called bonding gap, i.e., the correct spacing to allow bonding, particularly fusion bonding and / or hybrid bonding, to be performed with as little distortion as possible.

[0159] In one particularly preferred embodiment of the exemplary method, for this purpose, the lower substrate with the lower substrate holder is lowered downward in the alignment marking field at a distance that is focused on the alignment mark of the next step on another plane. In this way, movement of the substrate holder for alignment, which is either invisible or open-loop controlled, is avoided.

[0160] In this process, the detection unit detects the movement of the lower substrate holder at least at the initial position and the target position by observing the alignment marking field at different stages. At the initial position, at least one alignment mark on the first plane is detected, and at the target position, at least one alignment mark on the second plane of the alignment marking field is detected.

[0161] (Optional) Step 10: Using the measured position error, correct the position of the lower substrate holder in at least the lateral plane. In this process, move the substrate holder so that it is focused on at least one corresponding second alignment mark on the second plane, or so that it is located in the focal area of ​​the detection unit. In this way, visual control can ensure that the distance between the first and second planes (i.e., the bonding gap) is set sufficiently accurately.

[0162] This eliminates the need to refocus the detection unit and avoids alignment errors. The alignment marking field provides height information, allowing the method to approach the desired bonding interval without visual movement, through visual control. In this case, focusing and / or refocusing of the detection unit is omitted, thus eliminating focusing movement errors.

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

[0164] Step 12: Using the correlated XYZ positions of the lower substrate holder, the upper substrate is aligned with the lower substrate, while preferably moving the upper substrate in the XY plane and / or rotating it around the Z axis.

[0165] In this step, the first additional alignment marking is aligned with the second additional alignment marking. Since the position of the alignment marking on the lower substrate is measured and correlated with the alignment marking field, the actual position of the lower substrate in the lower substrate holder is known, which allows the alignment marking on the upper substrate to be aligned with the known and covered position of the second alignment marking on the lower substrate.

[0166] Step 13: Lift the lower substrate to set the correct bonding interval. At this time, the alignment marking field can be used to observe and correct any deviations in movement.

[0167] Step 14: Bring the contact surfaces of the upper and lower substrates into contact and bond these substrates together.

[0168] When aligning circuit boards, if the alignment error exceeds a determined boundary value, correction can be performed on the relative position of the circuit boards.

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

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

[0171] In another embodiment of this method for alignment, speed is achieved by parallelizing the steps, particularly by loading the second substrate while the pattern recognition step on the first substrate is still in progress.

[0172] In this disclosure, the concepts of axis coincidence, congruence, parallelism, or normality are used as concepts of toleranced quantities, and thereby, in particular, unless tolerances are expressly indicated, tolerances correspond to non-tolerant length dimensions or angular dimensions in accordance with ISO 2768.

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

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

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

[0176] Figure 1 shows a schematic, non-scale functional diagram of the main components of one embodiment of alignment equipment 1. Alignment equipment 1 can align substrates not shown in Figure 1 with each other and at least partially and / or temporarily bond them to each other (so-called pre-bonding). The terms apparatus and equipment are used interchangeably and with the same meaning.

[0177] The alignment equipment 1 includes a first substrate holder 9 on which a first substrate can be loaded and fixed onto the substrate holder surface. The alignment equipment 1 further includes a second substrate holder 11 on which a second substrate can be loaded and fixed.

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

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

[0180] The optical system 2 can focus on a focal plane or focal position located between the first substrate and the second substrate, preferably between the substrate holder 9 and the substrate holder 11, when the focal plane or focal position is positioned for alignment. Movement of the optical system 2, particularly in the X, Y, and Z directions, is performed using a positioning device 4 for positioning the optical system 2. The positioning device 4 can be fixed to a robust table or frame.

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

[0182] If the additional measurement system is an optical measurement system 5, the positioning device 7 can focus on the alignment marks on the first plane 18 of the alignment marking field 14 by moving the detection unit 6 in the Z direction. Positioning in the XY direction can be considered similarly, and fixing in particular during alignment is preferably done on a table / frame.

[0183] In the illustrated embodiment of the alignment equipment 1, the measurement system 5 or detection unit 6 detects the XY position and / or orientation (especially rotational orientation) and / or height position of the lower substrate holder 9 with particularly high accuracy.

[0184] To initiate fusion bonding, the upper substrate can be preloaded by at least the substrate preloading device 13. Preloading can be done by mechanical preloading with preloading elements, so-called bonding pins. In another embodiment of the substrate preloading device, the substrate preloading can be done by fluid, in particular by gas from a nozzle, especially from a movable nozzle.

[0185] In a preferred embodiment of the apparatus, although not shown, the following exemplary steps can be performed. The first substrate / underlying substrate is fixed to the first fixed surface of the first substrate holder 9, particularly the substrate holder surface. For fixing, mechanical clamps and / or electrostatic clamps are used, as well as vacuum fixing, which is formed due to the pressure difference between the ambient environment of standard atmosphere and the negative pressure in the first substrate holder 9. This fixing is performed in particular to prevent the first substrate from moving inaccurately or undesirably relative to the first substrate holder 9 throughout the process. In particular, if the first substrate holder 9 and the first substrate each have corresponding coefficients of thermal expansion, preferably linearly corresponding coefficients of thermal expansion, thermal expansion can be prevented or reduced, and the difference in the coefficients of thermal expansion and / or the linearly corresponding coefficients of thermal expansion is preferably less than 5%, more preferably less than 3%, and particularly preferably less than 1%.

[0186] This equipment is preferably operated in a temperature-stabilized ambient environment, particularly in a cleanroom, where the temperature fluctuation during the alignment cycle is less than 0.5 Kelvin, preferably less than 0.1 Kelvin, particularly preferably less than 0.05 Kelvin, and most preferably less than 0.01 Kelvin.

[0187] The fixed first substrate and the first substrate holder 9 can be understood as a quasi-monolithic body for moving the first substrate, and they do not allow relative movement to each other.

[0188] This substrate fixing can be done by shape coupling and / or preferably by force coupling. The quasi-monolithic coupling reduces, preferably by at least an order of magnitude, and particularly preferably eliminates, any influences that could cause displacement and / or torsion and / or deformation between the substrate holder and the substrate.

[0189] The substrate and substrate holder can be joined by shape coupling or force coupling, particularly in a way that suppresses differences in thermal expansion. Furthermore, the substrate holder can reduce, eliminate, and / or correct the deformation of the substrate itself.

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

[0191] The first substrate holder 9 may be positioned in the optical path of the additional detection unit 3 during detection of the first additional alignment marking. The first additional alignment marking may be positioned in the field of view, particularly in the optical path, preferably on the optical axis of the additional detection unit 3, on the contact surface of the first substrate to be bonded. The additional detection unit 3 forms a measured image, particularly digital. The first alignment marking on the substrate may consist of a combination of multiple alignment markings. From the image of the alignment markings, measurements are generated / calculated that characterize the alignment state, particularly the XY position and / or alignment orientation (particularly in the rotational direction around the Z direction) of the first substrate.

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

[0193] Preferably, the relative movement of the first detection unit 3 with respect to the third detection unit 6 can be measured. Even more preferably, no relative movement occurs between the first additional detection unit 3 and the detection unit 6 from the detection of the first additional alignment marking and the alignment mark of the alignment marking field 14 until contact between the first substrate and the second substrate.

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

[0195] The measured values ​​(XY position and / or alignment orientation of the first substrate, and the XYZ position and / or alignment orientation of the first substrate holder 9 or the first substrate 16) are correlated with each other, thereby allowing the XYZ position of the substrate holder 9 to be reproducibly restored. This allows the substrate fixed to the substrate holder 9 to be moved in a closed-loop control for alignment and setting the bonding interval, without directly observing additional alignment markings on the substrate.

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

[0197] In other words, an unobstructed optical path is obtained between the substrate holder 9 and the additional measurement system 5, and this optical path allows for or enables substrate alignment in a closed control loop. This makes it possible to accurately identify and reproducibly restore the XYZ position and / or alignment orientation of the first substrate holder 9, and consequently the XYZ position and / or alignment orientation of the first substrate fixed to the first substrate holder 9, thereby improving the accuracy of bonding, especially fusion bonding.

[0198] In particular, the restoration and correct setting of the XYZ position and / or alignment orientation of the substrate holder 9, and especially the substrate integrally bonded thereto, relative to another substrate and / or substrate holder, is one important aspect of this apparatus for alignment.

[0199] In particular, a positioning repeatability accuracy of less than 500 nm, preferably less than 100 nm, especially preferably less than 30 nm, especially very preferably less than 10 nm, even more preferably less than 5 nm, and most preferably less than 1 nm, also known as packlash (measured as the relative alignment error between two substrates), is achieved. This packlash may also be a repeatable approach to a predetermined position using the moving device 10, moving device 12 and / or positioning device 4, positioning device 7. This packlash arises as a result of the movement of the moving device, but only the detection point changes, and thus the measured quantity exists as a relative alignment error.

[0200] To further improve alignment accuracy, it is preferable to operate the first additional detection unit 3 and the second additional detection unit 5 in a time-synchronized manner, particularly with a time difference in the detection of the measured value of less than 3 seconds, preferably less than 1 second, especially preferably less than 500 milliseconds, especially very preferably less than 100 milliseconds, even more preferably less than 10 milliseconds, and most preferably less than 1 millisecond, ideally operating them simultaneously. This is particularly advantageous because it can eliminate the effects of disruptive influences, such as mechanical vibrations. Mechanical vibrations propagate in materials, in particular, as solid-borne sound at several thousand m / s. If the closed-loop control and detection means operate faster than the propagation speed of solid-borne sound, the disruption is reduced or eliminated.

[0201] If a fault alters the orientation of the first substrate in the first substrate holder 9, and a measurement has already been recorded by the first additional detection unit 3, but the measurement has not yet been recorded by the measurement system 5, which includes a detection unit 6 for detecting the alignment marking field 14, this fault may result in a decrease in alignment accuracy. This is because, in the time between the measurement recording by the additional detection unit 3 and the measurement recording by the detection unit 6, rapid mechanical positional changes on the order of nanometers or micrometers, particularly due to vibration, may occur. If the measurement recording is performed with a time delay (on the order of seconds or minutes), other faulty effects, such as shape or length changes due to temperature, may similarly reduce alignment accuracy.

[0202] If the first additional detection unit 3 and the detection unit 6 are synchronized with each other to detect the alignment marking field 14 (particularly by simultaneous triggering of detection, equalization of detection time, and / or the same integration time for the camera system), some disruptive effects can be reduced, and in the best case, eliminated. This is because detection should be performed at the point in time when disruptive effects have the least possible impact on detection accuracy.

[0203] In preferred embodiments of the present method and apparatus for alignment, disruptive effects are detected synchronously, particularly at the peaks of vibrations, especially when periodic disruptive effects are known. Advantageously for this purpose, vibration sensors (accelerometers, interferometers, vibrometers) can be pre-installed in the alignment apparatus at locations relevant to accuracy. These disruptive effects are recorded by these vibration sensors and, for elimination, are considered or removed computationally, particularly by a calculation unit. In another embodiment, vibration sensors can be fixedly integrated at characteristic locations of the equipment.

[0204] In particular, determined target values ​​are used to align the substrate. These target values ​​include, in particular, image data of the alignment marks of the alignment marking field 14 of the first substrate holder 9, and / or determined XYZ position data and / or alignment orientation data for the moving device 10 of the first substrate holder 9, and / or closed-loop control parameters, such as trajectories for optimal approach to the spatial position and / or machine-readable values, especially for the drive unit.

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

[0206] In another embodiment, any residual error that could not be eliminated when positioning the upper and / or lower substrate can, similarly, be considered as a correction value for positioning another (lower or upper) substrate.

[0207] Figure 2a shows an alignment marking field 14' in a greatly enlarged schematic plan view with an exemplary selected alignment mark 15 or alignment marking 15.

[0208] Each alignment mark 15 symbolically and schematically represents an absolute unique coding of the position and orientation of each individual alignment mark or alignment marking 15. Each alignment mark 15 or alignment marking 15 may be located on a different plane of the alignment marking field 14'. Since the properties of the alignment marking field 14' (the xyz position of each alignment marking 15) are known priori, it is sufficient to detect the absolute position of a substrate holder (not shown) by detecting the absolutely coded alignment marks 15 or alignment marking 15.

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

[0210] An advantage is that when aligning a substrate holder that includes an alignment marking field or is positioned at a fixed position relative to an alignment marking field, multiple alignment marks on different planes can be considered. In particular, multiple steps and / or layers 16, 16' of the alignment marking field can be located in the field of view or focal area of ​​the detection unit 6 simultaneously or preferably sequentially, and thus can be detected. Knowing the step height or the spacing between planes allows the step height or the spacing between planes to be used for alignment or for setting a desired spacing between substrates.

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

[0212] It is advantageous if the alignment marks 15, 15' in the alignment marking fields 14, 14', 14'', 14''' provide the spatial position and / or orientation of the substrate holder 9, or of the substrate placed in the substrate holder. It is further advantageous if each alignment mark 15, 15' has detectable orientation information that provides its respective orientation within the alignment marking fields 14, 14', 14'', 14'''. In particular, the orientations of the alignment marks 15, 15' detected relative to the alignment mark 15 in the alignment marking field are also known. Preferably, not only are the orientations of the alignment marks 15, 15' detected relative to the alignment marks 15, 15' in the same plane known, but the orientations of the alignment marks 15, 15' in each plane detected relative to a different plane of the alignment marking field are also known. This respective orientation information is made possible, for example, by different angles and different shapes of the alignment markings 15, 15', and is schematically shown as an example.

[0213] Preferably, in order to accurately set the desired spacing or bonding interval between substrates, the optical system of the detection unit 6 for detecting the alignment marking fields 14, 14', 14'', 14''' may have a smaller depth of field or a smaller depth of the focal region (particularly in the Z direction) than half the spacing between the corresponding planes.

[0214] Figure 3 shows one possible embodiment of the alignment marking field 14'', in which individual exemplary alignment marks 15' are supplemented with machine-readable codes. In this case, the individual alignment marks 15 may be located on different planes (steps and / or layers), and information on which plane each is located on may be included in the code. Furthermore, unique information on the position and orientation of each alignment mark 15' may be included in the code.

[0215] Figure 4 shows a cross-sectional view of one embodiment of the alignment marking field 14''''. The alignment marks 15' of the alignment marking field 14'''' are arranged in three different planes 18, 18', 18'' and are detectable by the detection unit 6. Here, the detection unit 6 can detect only the alignment marks 15' within the focal region 19.

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

[0217] The combination of intervals 17, 17', 17'' can also be approached by moving the fixed-position substrate holder 9 multiple times relative to the alignment marking field 14''''. For example, the interval 17'' can be set first, and then the substrate holder can be moved again in the same direction to approach the interval 17'. For example, the substrate holder can also be moved by twice the interval 17''. For this purpose, alignment is performed in two steps, and the detection unit is set accordingly between these steps, because the focal position of the detection unit 6, and thus the focal area 19, is matched. [Explanation of Symbols]

[0218] 1. Alignment device, alignment equipment 2 Optical system 3. Additional detection units 4 Positioning device 5. Additional measurement systems 6. Detection Unit (Alignment Marking Field) 7. Positioning device for additional measurement systems 8 frames 9. PCB holder, first PCB holder (to be aligned) 10 Moving device for the substrate holder to be aligned, first moving device 11. Second / upper substrate holder 12 Second moving device 13. Substrate deformation device 14,14',14'',14''' Alignment marking field 15,15' Alignment marks, alignment markings 16,16' Alignment marking field layer of alignment markings 17,17', 17'' spacing 18,18',18'' plane of alignment marking field 19 Focal area of ​​the detection unit at the focal position 20 Surface of the substrate holder of the substrate holder (to be aligned)

Claims

1. A method for aligning a substrate, wherein the method comprises at least the following steps, namely, i) A step of preparing a substrate holder (9) having a substrate holder surface (20) configured to accommodate the substrate, and alignment marking fields (14, 14', 14'', 14'''') positioned in a fixed position relative to the substrate holder (9), ii) A method comprising the step of aligning the substrate, Based on the alignment marks (15, 15') positioned above and below the alignment marking fields (14, 14', 14'', 14'''), the substrate is aligned. The alignment of the substrate in step ii) is performed in the following order, namely, the next step, a) A step of detecting the first alignment marks (15, 15') on the first plane (18, 18', 18'') of the alignment marking field (14, 14', 14'', 14''') using a detection unit (6), b) After the detection in step a), the step of fixing the focal position of the detection unit (6), c) The step of moving the substrate holder (9) perpendicular to the first plane (18, 18', 18'') of the alignment marking field (14, 14', 14'', 14''''), d) The detection unit (6) detects a second alignment mark on the second plane (18, 18', 18'') of the alignment marking field (14, 14', 14'', 14''''), and the detection unit (6) has the following steps: A method characterized in that 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 spaced apart from each other (17, 17', 17'').

2. The method according to claim 1, wherein in step a), an additional alignment mark is detected in the substrate holder (9) or on the substrate by at least one additional detection unit (3).

3. The method according to claim 1 or 2, wherein during the movement of the substrate holder (9) in step iv), the detection unit (6) continuously measures the alignment marking field (14, 14', 14'', 14'''') at the focal position.

4. The method according to any one of claims 1 to 3, wherein after fixing the focal position in step b), the detection unit (6) is held in the fixed position.

5. The method according to any one of claims 1 to 4, wherein, when detecting the first alignment mark (15, 15') in step a), and / or when detecting the second alignment mark (15, 15') in step d), the detection unit (6) additionally provides information regarding the orientation of each alignment mark (15, 15') in the alignment marking field (14, 14', 14'', 14'''').

6. A device for aligning a substrate, the device comprising at least, A) A substrate holder (9) having a substrate holder surface (20) configured to accommodate the substrate, B) An apparatus having an alignment marking field (14, 14', 14'', 14'''') with alignment marks (15, 15') positioned in a fixed position relative to the substrate holder (9) and / or the substrate, The substrate can be aligned based on the alignment marks (15, 15') positioned above and below it. The aforementioned device further, C) A detection unit (6) for detecting the alignment marks (15, 15') of the alignment marking field (14, 14', 14'', 14'''), D) A moving device (10) for moving the substrate holder (9), - The alignment marks (15, 15') of the alignment marking field (14, 14', 14'', 14''') are arranged on a first plane (18, 18', 18'') and a second plane (18, 18', 18''), the first plane (18, 18', 18'') and the second plane (18, 18', 18'') are arranged parallel to each other, and the first plane (18, 18', 18'') and the second plane (18, 18', 18'') have a gap (17, 17', 17'') between them. - The first alignment marks (15, 15') of the alignment marks (15, 15') on the first plane (18, 18', 18'') are detectable at the focal position of the detection unit (6), and the focal position of the detection unit (6) is fixed. - At the focal point, the detection unit (6) can detect the second alignment mark (15, 15') of the alignment mark (15, 15') on the second plane (18, 18', 18''), The apparatus is characterized in that the substrate holder (9) is movable perpendicular to the first plane (18, 18', 18'') by the moving device (10).

7. The apparatus according to claim 6, wherein the alignment marks (15, 15') on the first plane (18, 18', 18'') and the alignment marks (15, 15') on the second plane (18, 18', 18'') are vertically aligned and, in particular, congruently arranged in the alignment marking field (14, 14', 14'', 14'''').

8. The apparatus according to claim 6, wherein the alignment marks (15, 15') on the first plane (18, 18', 18'') and the alignment marks (15, 15') on the second plane (18, 18', 18'') are arranged in a stepped manner.

9. The apparatus according to any one of claims 6 to 8, wherein the alignment marking fields (14, 14', 14'', 14''') are arranged on the back surface of the substrate holder (9) facing away from the substrate holder surface (20).

10. The apparatus according to claim 9, wherein the center points of the alignment marking fields (14, 14', 14'', 14''') are at least partially aligned with the center points of the substrate holder surface (20) on the back surface of the substrate holder (9).

11. The apparatus according to any one of claims 6 to 10, wherein the alignment marking fields (14, 14', 14'', 14''') are arranged on the surface of the substrate facing the substrate holder surface (20).

12. The apparatus according to any one of claims 6 to 11, wherein the alignment marking field (14, 14', 14'', 14''') has at least one other surface (18, 18', 18'') having the alignment marks (15, 15'), and the at least one other surface (18, 18', 18'') is arranged at least parallel to the first plane (18, 18', 18'').

13. The apparatus according to any one of claims 6 to 12, comprising at least one additional alignment marking field (14, 14', 14'', 14''') and at least one additional detection unit (6) for detecting the at least one additional alignment marking field (14, 14', 14'', 14'''), wherein the at least one additional alignment marking field (14, 14', 14'', 14''') is fixedly positioned on the substrate holder (9).

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