Method and device for bonding substrates

Abstract

The invention relates to a method and device for bonding substrates. Fig 1a Nothing to translate

Description

[0001] Description

[0002] Method and device for bonding substrates

[0003] The present invention relates to a method and a device for bonding substrates, in particular wafers. During bonding, substrates are aligned with each other, contacted with each other, and connected to each other. For alignment, the substrates are each held in a substrate holding device, in particular a vacuum substrate holder, and the substrate surfaces to be joined are precisely aligned with each other prior to bonding. The goal is to create a bond that is as full-surface, distortion-free, and strain-free as possible.

[0004] In the prior art, the upper and lower substrates are loaded in the bonding orientation, so that the bonding side of the upper substrate and the bonding side of the lower substrate are already facing each other before bonding. This has the advantage that the bonding devices take up less space, since the upper substrate holder does not need to be rotated, turned, or moved. However, the different adhesive forces acting on the upper and lower substrate holders create different tensions in the respective substrates to be bonded.

[0005] In document US9,613,840B2, the upper and lower substrates are loaded in the bonding orientation. The upper substrate is deformed by means of deformation means, in particular a mechanical pin, wherein the deformation means act, in particular due to their shape, on the side facing away from the bonding side. The central deformation of the upper substrate with the pin influences the start of contacting, while after contacting, the upper substrate is released and bonds automatically to the opposite substrate due to its prestress. In US9,613,840B2, at least one substrate is no longer fixed to the holding device during the bonding process. Furthermore, the upper and lower holding devices are not constructed identically due to their different designs and thus provide different stress patterns due to the loading or fixation in the substrates.

[0006] US8,918,989B2 provides fixing means for at least partially pre-fixing the aligned substrate to the carrier substrate. Both substrates are loaded one on top of the other in the bonding orientation. Spacers are used to maintain a distance between the substrate and carrier substrate during alignment before a force-controlled actuator acting in the center acts on the substrate stack to fix the substrates. In US8,918,989B2, the bonding or pre-bonding process takes place entirely without prior fixation of the upper substrate on an upper holding device.

[0007] In document US6,383,890B2, both substrates are loaded from above. By rotating the pivoting upper support device by 180°, both substrates are positioned parallel to each other in the bonding orientation for bonding. A pin penetrates the upper support device and initiates the bonding process by centrally bending the upper substrate. This releases the upper substrate from the fixture. The symmetrical design of all features, especially the fixing elements of the upper and lower substrate support devices, especially the loading pins of the upper and lower substrate support devices, is not provided. Furthermore, different holding forces or fixing forces are provided.

[0008] In WO2015 / 183197A1, the upper substrate holding device is rotated 180° around its own axis for bonding. The upper substrate holding device is moved between a substrate loading position and a substrate bonding position. The advantage here is easier control of the alignment of the structured substrate on the holding device from the free upper side. The symmetrical design of all features of the upper and lower substrate holding devices is not intended, as these are designed differently due to the construction of the device. Furthermore, different holding forces are provided in different patterns.

[0009] The substrates to be bonded, especially wafers, are often structured and coated with up to several layers of different materials. These pre-process steps generate mechanical stresses that can distort the wafer in its free form. This distortion manifests itself, for example, in the form of warping, bending, distortion, and / or local deformation. As soon as one of the substrates to be bonded is not, or is no longer, fixed to a substrate support device during the bonding process, part of this stress is incorporated into the bonding interface as distortion.

[0010] The crystal structure of the substrate material also determines whether its properties are isotropic or anisotropic, which can influence the bonding process. The mechanical properties of silicon (Si), for example, are anisotropic. Monocrystalline silicon has different elastic moduli (E-modulus) in different directions. This difference in stiffness causes a generated bond wave to propagate at uneven speeds. These differences in stiffness become more pronounced when the substrate, particularly the upper substrate, is released from the substrate holder during bonding. Due to the directionality of the E-modulus, other mechanical properties, particularly strains, are also direction-dependent.

[0011] For several years, the semiconductor industry has been bonding substrates together using so-called bonding processes. Before bonding, these substrates must be aligned as precisely as possible, with deviations in the nanometer range now playing a role. The alignment of the substrates is usually achieved using alignment marks. In addition to the alignment marks, other elements, particularly functional ones, may be located on the substrates, which must also be aligned during the bonding process.

[0012] One of the greatest challenges in bonding lies in the bonding process itself, i.e., from the bond initiation stage until the contact surfaces of the substrates are fully connected. During this time, the alignment of the two substrates relative to each other can change significantly compared to their previous alignment. Once the two substrate surfaces are bonded, separation is theoretically possible, but is associated with high costs and a high risk of errors. Several methods and systems exist in the state of the art that can be used to influence the bonding process.

[0013] During the bonding process, stress patterns can lead to distortions and susceptibility to defects. The substrates to be bonded, especially wafers, are often structured and coated with up to several layers of different materials. These pre-process steps generate mechanical stresses that can distort the wafer in its free form. In addition to mechanical stresses from pre-process steps, further stress patterns can arise during substrate loading. Components of the holding device that can influence the substrate shape and lead to loading stress include, in particular, the loading pins and the fixation and support elements, as well as other surface features of the holding device.

[0014] Part of this stress is then incorporated into the bond interface as distortion during bonding. Stresses can either relax through additional defect formation, cancel each other out, or remain as residual stress in the bonded stack.

[0015] Residual stress has a particularly strong impact on thin substrates or thin substrate stacks. Thinned substrates must be used and maintained in their original, preferably flat, shape. Therefore, the object of the invention is to at least partially eliminate, and in particular completely eliminate, the disadvantages cited in the prior art. In particular, the object of the invention is to provide improved methods and devices for bonding. Furthermore, the object of the invention is to produce a bonded substrate stack with minimal residual stress.

[0016] The present object is achieved by the features of the independent claims. Advantageous developments of the invention are specified in the dependent claims. The scope of the invention also includes all combinations of at least two features specified in the description, the claims, and / or the drawings. For specified value ranges, values ​​within the specified limits are also considered to be disclosed as limit values ​​and can be claimed in any combination.

[0017] Surprisingly, it has been found that the bonding result can be improved if, in addition to the mechanical stresses already generated in the substrate during pre-process steps, new stress patterns are compensated or prevented by design features of the substrate holding device that come into direct contact with the substrate, such as during the substrate loading process on the substrate holding device. In the prior art, the stress patterns are different in the upper and lower substrates due to different effects. For example, different stress patterns are generated in the substrates to be bonded due to the different designs of the upper and lower substrate holding devices, in particular the substrate holder surface, the fixing elements, and the holding forces.

[0018] If a force, particularly gravitational force, acts on substrates resting on loading pins or structures of the holding surface, an asymmetric deformation occurs. This asymmetric deformation is still present during contact between the two substrates and / or during the bonding process and leads to an asymmetric propagation of the bond wavefront, thus causing an undesirable run-out effect.

[0019] Loading the upper and lower substrates in the bond orientation also inevitably leads to different stress patterns, which can also be incorporated into the bond interface as distortion, especially if the different, asymmetric stress patterns cannot later cancel each other out.

[0020] The method and device for bonding, in particular, improve the bonding result through the proposed feature combinations.

[0021] Accordingly, the invention relates to a method for bonding substrates comprising the following steps, in particular the following sequence: i) providing a first substrate on a first substrate holder surface of a first substrate holder and a second substrate on a second substrate holder surface of a second substrate holder, ii) fixing the first substrate to the first substrate holder and the second substrate to the second substrate holder in a loading state, iii) positioning the second substrate holder relative to the first substrate holder in a bonding position such that the first substrate and the second substrate face each other with surfaces to be bonded, iv) bonding the first substrate to the second substrate, wherein in the loading state, the first substrate holder surface and the second substrate holder surface are arranged at the same angle relative to the earth's gravity,and wherein, in the loaded state, the first substrate holder surface and the second substrate holder surface are oriented in the same direction relative to the force of gravity, and wherein, during the fixation of the first substrate and the second substrate, identical holding forces are exerted on the first substrate and the second substrate, respectively. In other words, two substrates are provided under identical gravity conditions on the substrate holders, which are equally oriented relative to the weight force, and identical holding forces are applied to the substrates for fixation. This allows an equal tension to be generated in the substrates, particularly advantageously.This has a beneficial effect on the bonding result. The symmetrical arrangement of the fixing elements on the substrate holders with respect to the bonding interface in the bonding position is particularly preferred. During positioning, the substrates or the substrate holder surfaces are particularly preferably positioned symmetrically to each other and parallel to each other, so that the surfaces to be bonded face each other. Symmetrical positioning or alignment means that the fixing locations, holding forces at the fixing locations, and contact surfaces of the substrate holders are congruent or symmetrical due to the reflection in the plane spanned between the substrates. In other words, all features that influence the stress in the substrates in the loaded state are aligned.

[0022] The first substrate and the second substrate are preferably of the same size. In particular, the substrates have the same weight. The first substrate holder surface is designed symmetrically to the second substrate holder surface, in particular axially symmetrically. The substrate holder surfaces preferably correspond such that, in the loaded state, the support surfaces of the respective substrate holder surfaces are arranged symmetrically to one another, and during bonding, the opposing support surfaces are aligned. The substrate holder surfaces are in particular the surfaces of the substrate holders on which the substrates rest. The substrate holder surfaces comprise, for example, loading pins, elevations, or full-surface surfaces with recesses for fixing agents.

[0023] In the loaded state, the substrate holders or the substrate holder surfaces, and thus the substrates, are arranged equally with respect to the acting weight force. The substrate holder surfaces are oriented in the same direction with respect to the weight force. For example, both substrate holder surfaces are oriented upwards or downwards. In the loaded state, the substrates are not loaded from above and below, but both equally, so that gravity acts in an identical manner at the time of loading and the same stress, in particular the same stress pattern, acts on both substrates even when the identical holding forces are applied.

[0024] The surfaces of the substrates to be bonded do not rest on the substrate holder surface, but rather face away from the substrate holders. The substrate holders are preferably both perpendicular or horizontal to the Earth's gravity. The substrate holders, which are preferably arranged side by side, exhibit the same angle relative to the Earth's gravity when loaded. The slightly different gravity due to the offset arrangement and a slightly different distance from the Earth's center can be neglected.

[0025] When fixing the substrates, equally acting and identical holding forces are applied to the substrates. This advantageously creates a corresponding stress pattern in the substrates, which improves the bonding result. The holding forces are preferably maintained even during transfer to the bonding position.

[0026] The positioning can be done arbitrarily and can include moving both substrate holders in all directions.

[0027] When bonding substrates or substrate stacks, the substrates to be bonded are loaded into appropriate holding devices in a minimally invasive manner, aligned with the Earth's gravity, and held in place by means of identical or symmetrical holding forces acting on both substrates. Different holding forces are typically provided, since the substrates to be bonded must rest on the lower substrate holder after positioning and be held by the upper one. The upper substrate holder typically exerts the greater holding force, as the weight of the fixed upper substrate must also be compensated for.

[0028] Symmetry preferably also applies to all other components of the substrate holder that can influence the tension in the substrates (support surfaces, type of fixing elements, alignment marks, hoses, etc.). An axially symmetrical arrangement of all components is preferred.

[0029] In a preferred embodiment of the bonding method, the first substrate rests on the first substrate holder surface and the second substrate rests on the second substrate holder surface in the loaded state. "Rest" means that the first substrate and the second substrate rest on the identically aligned substrate holder surfaces due to their own weight and theoretically do not need to be fixed. In other words, the surfaces to be bonded are both oriented counter to the force of gravity, while the backs of the substrates rest on the substrate holder surfaces. In this way, a particularly advantageous and stress-free loading process can be carried out.

[0030] In a preferred embodiment of the bonding method, the angle is provided to be a perpendicular angle. In other words, the same angle at which the substrate holder surfaces are aligned relative to the force of gravity is 90°. The substrates and the substrate holder surfaces are preferably flat. The substrates are therefore also aligned virtually parallel to the force of gravity and consequently to the center of the earth. In this way, a particularly good bonding result can be achieved. Furthermore, slipping of the substrates can be prevented. In a preferred embodiment of the bonding method, it is provided that during fixation in the loaded state, the identical holding forces are each provided in a mutually corresponding pattern on the first substrate and the second substrate, so that in the bonding position the pattern of the holding forces is aligned.In other words, in the bonding positions, the opposing substrate surfaces are congruent with respect to the provided fixation pattern. In the bonding position, identical holding forces are thus provided in precisely opposite positions. This ensures that the stresses prevailing in the substrates, due to the fixation at the opposite areas of the substrate surfaces, are of equal magnitude and positioned equally in the bonding position. The stress distribution in the first substrate is thus aligned with the stress distribution in the second substrate in the bonding position. In the loaded state, the holding forces are thus provided, for example, in an axisymmetric arrangement, so that a simple pivoting movement is sufficient for positioning.

[0031] In a preferred embodiment of the bonding method, the first substrate and the second substrate are fixed simultaneously and within the same period of time. In other words, the holding forces are applied within the same time and occur simultaneously. Preferably, the increase in the holding force per unit of time is also identical at the same locations. This allows for an even better bonding result.

[0032] In a preferred embodiment of the bonding method, the positioning comprises pivoting the second substrate holder by 180°. Preferably, pivoting the second substrate holder performs the positioning, so that the first substrate holder does not need to be moved. After positioning or transfer into the bonding position, it may be necessary to bring the substrate holders closer together. Pivoting the second substrate holder by 180° around the axis of symmetry can advantageously result in a particularly simple and error-free transfer into the bonding position. After pivoting, the second substrate holder is preferably aligned exactly perpendicular to the direction in the loading state.

[0033] "Toward each other" means that the substrate holder surfaces are aligned facing each other. An additional movement for initial contacting for bonding then occurs, in particular, only by bringing the first substrate holder surface and the second substrate holder surface, or the first substrate holder and the second substrate holder, closer together. In this case, the identical holding forces are preferably maintained, and the corresponding patterns are merely moved further toward each other. Alignment preferably occurs only by pivoting.

[0034] In a further preferred embodiment of the bonding method, the positioning comprises pivoting the first substrate holder and the second substrate holder by 90° towards each other. Both substrate holders are pivoted along the axis of symmetry or through parallel center axes at the respective center point of the substrate holders. In this way, the force of gravity for the first and second substrate is the same even after positioning if the orientation to the earth's gravity was perpendicular in the loaded state. Particularly preferably, in the loaded state, the first substrate holder surface and the second substrate holder surface are aligned exactly perpendicular to the force of gravity. The bonding result can thus be improved by pivoting in both directions.

[0035] In a preferred embodiment of the bonding method, identical holding forces are maintained throughout the bonding process. This ensures that the identical holding forces are maintained not only during fixation and transfer or positioning into the bonding position, but also afterward until the bonding process is complete. This allows the residual stresses due to the loading to equalize, improving the bonding result.

[0036] Furthermore, the invention relates to a device for bonding substrates, at least comprising a first substrate holder with a first substrate holder surface, first fixing means for fixing a first substrate to the first substrate holder surface, a second substrate holder with a second substrate holder surface, second fixing means for fixing a second substrate to the second substrate holder surface, and positioning means for positioning the second substrate holder relative to the first substrate holder, wherein the device can be transferred into a loading state in which the first substrate holder surface and the second substrate holder surface are arranged at the same angle relative to the earth's gravity,wherein in the loading state, the first substrate holder surface and the second substrate holder surface are aligned in a same direction relative to the force of gravity, and wherein the first fixing means and the second fixing means are each configured to provide identical holding forces for fixing in the loading state.

[0037] In other words, the first fixing means and the second fixing means act in an identical manner on a first substrate and a second substrate. The device is configured such that the holding forces provided by the first fixing means and the second fixing means are of equal magnitude. Particularly preferably, the fixing means are configured to provide identical holding forces simultaneously and within the same period of time. The increase in the holding forces per unit time is preferably also identical for the fixing means, or the device is configured so. By loading in the loaded state, an identical stress pattern is generated in the two substrates to be bonded. In this way, the bonding result is unexpectedly improved. The device can have a control unit configured to establish the respective conditions in the loaded state.The further advantages and features of the previously described bonding process should also apply analogously to the device.

[0038] In a preferred embodiment of the device for bonding substrates, the device is configured such that, in the loaded state, the first substrate holder surface and the second substrate holder surface are arranged parallel and offset next to one another. In particular, a center point of the substrate holder surfaces is offset in relation to the direction. Preferably, the first substrate holder surface and the second substrate holder surface are arranged offset next to one another in the loaded state such that they are not aligned, but are spaced apart from one another at the same angle. In this way, a particularly uniform loading can be achieved, thus improving the bonding result.

[0039] In a preferred embodiment of the device for bonding substrates, it is provided that the second substrate holder can be pivoted from the loaded state into a bonding position. The bonding position is characterized in particular in that the substrate holder surfaces face one another and are aligned parallel to one another, so that bonding can occur merely by approaching one another. In other words, in the bonding position, the substrates are already aligned and positioning is complete. Approaching means can be provided for this purpose. By simply pivoting into the bonding position from the loaded state after fixation by the fixing means, the bonding result can advantageously be improved. The design of the device as a flip bonder is preferred. In a preferred embodiment of the device for bonding substrates, it is provided that the positioning means comprise a pivot joint.In this way, the substrate holders can be positioned particularly easily and precisely around the pivot axis, which improves the bonding result.

[0040] In a preferred embodiment of the device for bonding substrates, the second fixing means are arranged axially symmetrically to the first fixing means in the loading state. In other words, after loading, there is a position in which the stress patterns of the substrates are aligned, or the substrate holder surfaces and the fixing elements are aligned, i.e., in the bonding position. In this case, all features and components of the two substrate holders that influence the stress in the substrates are particularly preferably axially symmetrical.

[0041] The axial symmetry is preferably defined by a mirror axis that runs through the pivot joint. In other words, in the loaded state, the first substrate holder surface and the second substrate holder surface, in particular the first and second fixing means, are arranged symmetrically with respect to the pivot axis, so that after pivoting into the bonding position, the arrangement of the fixing elements is aligned with one another. If the first substrate holder and the second substrate holder are arranged offset next to one another at different heights in the loaded state, the mirror axis runs through the plane spanned by the pivot axis and the specific angle of the substrate holder in the loaded state.In any case, the pattern of the fixing elements is designed to correspond to one another, so that after transfer to the bonding state, the opposing substrate holder surfaces have an identical and aligned voltage pattern due to the load. In a preferred embodiment of the device for bonding substrates, the first fixing means and the second fixing means are electrostatic fixing means. The first and second fixing means are particularly preferably embedded in the substrate holder surfaces. In this case, the corresponding recessed grooves are particularly preferably arranged in symmetrical patterns like the first and second fixing means. If the electrostatic fixing means are designed to cover the entire surface, the dimensions and arrangements are also aligned in the bonding position. In another embodiment, the fixing means are vacuum tracks, wherein the arrangement and other design is also congruent orare formed correspondingly in the bond position.

[0042] In a preferred embodiment of the device for bonding substrates, it is provided that in the bonding position, the first substrate holder and the second substrate holder form a fluidically sealed bonding chamber. In this way, a bonding chamber can be formed between the first substrate holder and the second substrate holder by pivoting and, if necessary, approaching each other. The substrates are arranged within the bonding chamber. In this way, bonding can advantageously take place in a protected space, thereby improving the bonding result. Furthermore, in a particularly preferred fluidically sealed bonding chamber, a vacuum can be set in the bonding chamber before bonding, or a fluid can be introduced.

[0043] In a preferred embodiment of the device for aligning substrates, it is provided that the first fixing means and the second fixing means are configured to provide identical holding forces at least until transfer to the bonding position. Particularly preferably, the identical holding forces are provided by the fixing means until immediately after the first substrate has been bonded to the second substrate. In this way, the stress in the pattern in the first and second substrates can advantageously be kept the same, at least that which is provided due to the loading / fixing in the loaded state. In this way, stresses can be compensated and the bonding result can be improved.

[0044] A particularly important aspect of the present invention is that both substrates are held in an identical manner on symmetrically constructed holding devices prior to contacting or bonding, such that the substrates are contacted and bonded with corresponding stress patterns. The loading of the two substrates is carried out in particular with identical gravity, for example both from above. All features of the holding devices which can indirectly influence the substrate shape are carried out symmetrically for the first substrate and for the second substrate, preferably within the same time, particularly preferably simultaneously, such that the first and the second substrate display identical, opposite stress patterns determined by the holding device prior to bonding. At least one of the holding devices is preferably pivotably mounted. For this purpose, the fixing orThe holding force is provided such that, after pivoting, the surfaces to be bonded exhibit the same stress patterns relative to each other. Preferably, both substrates remain fixed to the holding device during bonding. The symmetrical design of the holding devices minimizes the influence of loading stress, thereby minimizing residual stress after bonding. By fixing at least one of the substrates, preferably both substrates, during bonding, further distortions are minimized.

[0045] The bonding process leads to a reduction of stress patterns that are incorporated into the bond interface as distortion during bonding. The relaxation of corresponding stress patterns leads to minimized residual stress, even after the substrate stack has been detached. The basic idea is that both substrates are mounted identically on symmetrically constructed fixtures before contacting or bonding, so that the stress on the substrate caused by the mounting and loading on the fixture is minimized, and the substrates are contacted and bonded with corresponding stress patterns. In the following, the terms stress, strain, and tension are used synonymously.Another important aspect is that the substrates remain fixed to the holding devices after contacting during bonding, so that distortions are minimized by corresponding stress patterns canceling each other out as much as possible, thereby achieving a reduction in residual stress.

[0046] It is proposed to carry out a method and a device for bonding a first substrate to a second substrate with contact surfaces of the substrates facing each other, with the following steps, in particular the following sequence:

[0047] -receiving the first substrate on a first receiving surface of a first receiving device, wherein the loading takes place from above,

[0048] -Receiving the second substrate on a second receiving surface of a second receiving device, wherein the loading takes place from above, -Securing the substrates to the receiving surfaces by means of fixing elements, -Rotating the pivotally mounted first and / or second receiving device so that both substrate surfaces to be bonded are aligned with each other and symmetrically,

[0049] -Alignment of the substrates,

[0050] -Approaching the two substrates and bonding them by contacting, wherein the first and second support devices have a symmetrical design of all components, and wherein, after contacting, the substrates remain fixed to the first and / or second support device during bonding. The two support devices or substrate holders can be rotated around any axis and then brought into an adjusted, symmetrical position by X / Y rotation.

[0051] The key is to load both substrates in a symmetrical orientation with identical gravity on the first and second fixtures. For bonding, it is preferable to either rotate one fixture with the substrate upside down by 180°, or rotate both fixtures with the substrate 90° relative to each other so that they also meet symmetrically.

[0052] The components of the first and second receiving device, which are constructed symmetrically with respect to the tilt axis and / or the mirror axis between the first and second receiving device, include in particular the loading pins and the fixing and supporting elements as well as other possible characteristic surface features of the receiving device.

[0053] The loading pins, preferably three loading pins, are arranged symmetrically in a circle on both holding devices at the same radius. If the substrates are loaded onto the loading pins on the first and second holding devices from above, the substrates bend, for example, due to the effect of gravity. After the substrates have been picked up onto the holding surface of the holding devices, the loading stress or the stress patterns remain on the fixed substrate. Due to the symmetry of the components of the holding devices, the stress patterns on the first and second substrates are also symmetrical. The effect of gravity on the loading stress of the substrates is thus minimized or preferably eliminated because the effects on both substrates can cancel each other out after contact due to the symmetry.

[0054] The stress patterns of both substrates are thus symmetrical along the bonding interface. After the bonded substrate stack is released, both substrates can reduce the remaining residual stress equally by relaxing the stress, thus minimizing any remaining stresses.

[0055] The first and / or second substrate is preferably radially symmetrical. Although the substrate can have any desired diameter, the substrate diameter is in particular 1 inch, 2 inches, 3 inches, 4 inches, 5 inches, 6 inches, 8 inches, 12 inches, 18 inches or greater than 18 inches. The thickness of the first and / or second substrate is between 1 μm and 2000 μm, preferably between 10 μm and 1500 μm, more preferably between 100 μm and 1000 μm. In particular embodiments, a substrate can also have a rectangular shape or at least a shape deviating from a circular shape. Wafers are preferably used as substrates, particularly preferably circular wafers.

[0056] Reception facility

[0057] The mounting devices enable reliable and even support and fixation of the substrates. Fixation is achieved, for example, by applying a vacuum between the substrate and the mounting device, by mechanical clamping, by electrostatic charging, or by other controllable chemical-physical adhesion properties.

[0058] Electrostatic pick-up devices are preferably used to pick up and hold a substrate. The embodiments of the bonding device or bonding apparatus can handle any substrate, regardless of its diameter.

[0059] Electrodes are particularly preferably used in electrostatic holding devices to generate an electrostatic holding force for fixing the substrate. The substrate is fixed to a holding surface or substrate holder surface. The holding surface is a surface of a holding device designed for substrate fastening, preferably a flat one, which is integrated as a component in the substrate holder. In the further course of action, flatness is used as a measure of the perfection of a flat surface (mathematically ideal plane). Flatness describes the structure of a surface that is located between two ideal planar surfaces. The distance between the two planar surfaces defines the tolerance. Deviations from a flat surface arise from macroscopic and / or microscopic surface defects. These defects can also be defined as waviness and roughness.The waviness of a surface can be described as a periodic elevation and depression of the surface, especially in the millimeter and micrometer range. Roughness, on the other hand, is a more aperiodic phenomenon in the micrometer and / or nanometer range.

[0060] To address the various deviations from the ideal surface, the term "roughness" will be used synonymously throughout this description to describe the superposition of all such effects. Roughness is expressed either as mean roughness, root mean square roughness, or averaged roughness depth.

[0061] The determined values ​​for mean roughness, root mean square roughness, and average roughness depth generally differ for the same measurement section or surface, but are within the same order of magnitude. Therefore, the following numerical ranges for roughness should be understood as values ​​for either mean roughness, root mean square roughness, or average roughness depth.

[0062] In a preferred embodiment, the electrostatic holding devices or substrate holders with electrostatic fixing means have a particularly flat holding surface to electrostatically press the substrate and ensure highly stable holding. The electrostatic attraction ensures an even distribution of the holding forces across the entire surface. The flatness of the holding device is better or more precise than the thickness variation and nanotopography of the substrates. The substrates may already exhibit mechanical stresses due to pre-process steps, which could cause deformation in the unfixed state. Substrates with wedge defects are not a problem for holding devices in the prior art. Wedge defects can be compensated.

[0063] Higher-order thickness variations (e.g., center vs. edge, four quadrants, etc.) are more problematic. Substrates with high flatness and curvature requirements, such as reflection masks, require support surfaces with high flatness; otherwise, defects such as image placement errors and overlay errors (distortions) arise. Therefore, a means for wedge error compensation in conjunction with the bonding device is preferred.

[0064] The flatness of the holding surfaces of the electrostatic fixing means is less than 1000 nm, preferably less than 200 nm, more preferably less than 50 nm, most preferably less than 1 nm (difference between the highest point and the lowest point of the surface or the holding surface).

[0065] Nanotopography, in particular, is a key parameter for surface quality. Local (erratic) irregularities must be avoided. The roughness is less than 100 nm, preferably less than 10 nm, more preferably less than 1 nm, and most preferably less than 1 Å. The roughness is also particularly less than 1 nm / pm flatness change, and even more preferably less than 1 Å / pm flatness change.

[0066] For structures in the nm range and precise overlays, reproducible flatness of the substrates to be bonded is very important. The holding force of the ultra-flat electrostatic fixatives with a particularly flat holding surface enables conformal planarization of the substrates.

[0067] Both substrates are preferably loaded from above, i.e., perpendicular to gravity. The back of the substrates is brought onto the holding surface using charging pins and held in place by electrostatic forces. The substrates are held in place with high positioning accuracy and high holding force. The electrodes are preferably recessed or embedded relative to the substrate holder surface and can be unipolar or bipolar. The electrodes are designed symmetrically with respect to the axes of the two substrates or the bonding interface.

[0068] The key is to load both substrates in a symmetrical orientation and direction, with identical gravity on the first and second, symmetrically designed, substrate holder surfaces. For bonding, either one fixture with the substrate can be rotated upside down by 180° and positioned directly above the lower fixture if necessary, or both fixtures with the substrate can be rotated 90° relative to each other so that they also meet symmetrically.

[0069] The components of the first and second receiving device, which are constructed symmetrically with respect to the tilt axis and / or the mirror axis between the first and second receiving device, include in particular the loading pins and the fixing and supporting elements as well as other surface features of the receiving device.

[0070] If the mounting device or substrate holder has loading pins, holes will necessarily be present in the substrate holder surface. The holes through which the loading pins move, or the loading pins themselves, are preferably provided with a seal. The position of the loading pins, the openings of the loading pins, the diameter of the openings of the loading pins, and the seals are designed identically and symmetrically on both mounting devices.

[0071] Symmetrical features are positioned opposite one another after rotation of one (by 180°) or both (by 90°) mounting devices. The mounting devices are designed to be axially symmetrical and / or mirror-symmetrical, depending on whether one or both mounting devices are tilted or rotated. If the bonding device or bonding fixture has recesses, for example, for measuring instruments, these are preferably also designed identically and symmetrically on both mounting devices. Other features such as patterns, structures, or structuring on the holding surface are also particularly preferably designed identically and symmetrically on both mounting devices.

[0072] The surfaces where the fixation takes place can also be provided with a pattern, a groove, studs, pins, or any other desired topography or surface structure. The grooves can be linear, circular, or any shape. Any combination is also possible, for example, grooves and studs. The selected topography can further reduce the contact area to achieve the smallest possible absorption surface.

[0073] In a preferred embodiment, the ultra-flat electrostatic substrate holders have symmetrically designed grooves extending beyond the substrate edge to prevent an air cushion and "floating" of the wafer after loading (before fixation). The grooves are dimensioned and distributed to allow the ambient gases to escape. The grooves are, for example, microgrooves.

[0074] In a further embodiment, the electrostatic pickup device comprises symmetrically designed nubs to reduce the risk of contamination of the substrate's backside. The substrate holder surface can then be formed at least partially by the surfaces of the nubs.

[0075] Electrostatic attraction not only ensures an even distribution of holding forces across the entire surface, but also ensures good heat exchange and reduced abrasion. Therefore, electrostatic fixation elements or fixation media are preferred. Materials with minimal thermal expansion (thermal invariance) are preferably selected for the holding device.

[0076] In addition to the material selection, surfaces are also smoothed through machining to minimize the friction coefficient between the holding surface and the substrate. Not only are the external features of the first and second holding devices symmetrical and identical with respect to the tilt axis and / or the mirror axis between the first and second holding devices, but the first and second holding devices are also (almost) identical overall, so that both preferably have the same thickness and are constructed from the same components and materials. Particularly preferably, a first and second composite, each consisting of substrate and holding device or substrate holder, have identical mechanical rigidity.

[0077] The thickness of the support device is selected so that the overall stiffness of the support device including the substrate is not dominated by the anisotropic Young's modulus (Young's modulus) of the substrate.

[0078] The preferred ultra-flat electrostatic pickup devices can be used in vacuum, high-vacuum, and / or ultra-high-vacuum systems. The electrostatic pickup devices can also be used at ambient pressure in a gas atmosphere, particularly an inert gas atmosphere.

[0079] In a preferred embodiment, the substrate and / or the receiving device are movable in at least three degrees of freedom, preferably in at least four degrees of freedom, more preferably in at least five degrees of freedom, and most preferably in all six degrees of freedom. This enables improved mobility of the substrate and / or the receiving device.

[0080] In the loading position, the Z direction, or Z axis, runs perpendicular to the holding surface of the holding device as a surface normal. The X and Y directions, or X and Y axes, run perpendicular to each other and parallel to or within the holding surface of the holding device.

[0081] A rotation about the X-axis is designated r, a rotation about the Y-axis is designated q, and a rotation about the Z-axis is designated j. In another preferred embodiment, the positioning, fixing, and movement system is designed with a coarse drive and a fine drive for at least one degree of freedom. This advantageously enables precise adjustment of the movements.

[0082] In another preferred embodiment, the receiving devices have a central control unit and / or regulating unit for controlling and / or regulating movements and / or processes, in particular the fixation of the substrates and the position of the receiving devices in the loaded state. The receiving devices or substrate holders preferably have at least one sensor for measuring influencing factors, in particular at least one distance and / or position sensor. The sensors are also positioned symmetrically and have an identical design.

[0083] Bonding device

[0084] Bonding agents are intended for bonding and / or prebonding and / or temporary bonding. The terms bonding, prebonding, and temporary bonding are used synonymously.

[0085] All embodiments of the bonding device can be operated in low vacuum, more preferably in high vacuum, even more preferably in ultra-high vacuum, in particular at a pressure of less than 100 mbar, preferably less than 0.1 mbar, more preferably less than 0.001 mbar, even more preferably less than 10e-5 mbar, most preferably less than 10e-8 mbar.

[0086] Crucial for the bonding device is the loading of both substrates in a symmetrical orientation with identical gravitational influence on the first and second holding devices or substrate holders. Both substrates to be bonded are preferably loaded from above. In this case, at least one of the holding devices is particularly preferably pivotally mounted. For bonding, in particular, either one holding device with the substrate is pivoted upside down by 180°, or both holding devices with the substrate are rotated 90° to each other so that they also meet symmetrically. If one holding device with the substrate is pivoted upside down by 180°, a rotational movement or a combination of rotational-translatory movement is conceivable. The holding devices can be rotated about any axis.The rotation of the recording device with substrate by 180° can thus take place around a mirror axis in the XY plane of the recording device or as a rotational movement via a swivel joint.

[0087] The device enables highly precise adjustment of the fixed substrates for exact alignment. The holding devices are designed for approaching and contacting the substrates.

[0088] Bonding processes or bonding

[0089] The substrates are aligned to each other before the bonding process. Alignment is preferably performed using alignment systems and alignment marks. After the two substrates are aligned to each other, contacting takes place.

[0090] Particularly critical when bonding two substrates is the step of contacting the aligned contact surfaces of the two opposing substrates, because the requirement is moving towards ever more precise alignment accuracy or offset of less than 50 pm, in particular less than 1 pm, preferably less than 250 nm, even more preferably less than 150 nm, most preferably less than 50 nm. Many influencing factors must be taken into account for such alignment accuracies.

[0091] Errors can occur during contacting and depositing the substrates. These errors accumulate, making it impossible to maintain reproducible alignment accuracy. This can lead to significant rejects. In a first preferred embodiment, after contacting, both substrates remain fixed to the first and second receiving devices or the substrate holder during bonding.

[0092] If both substrates remain fixed to the respective fixture during bonding, thickness variation (TTV) and stress patterns of the substrates have little influence on the bonding result. A parallel, spontaneous (1:1) bond between the two substrates fixed to the fixture is achieved, with no deformation of the substrates at the bond front. Bonding preferably takes place in a high or ultra-high vacuum.

[0093] The bonding process consists, in particular, of a force and / or temperature effect. The bonding force is, in particular, greater than 0.01 kN, preferably greater than 0.1 kN, even more preferably greater than 1 kN, most preferably greater than 10 kN, and most preferably greater than 100 kN. The corresponding pressure ranges are determined by normalizing the bonding force to the surface area of ​​the substrates.

[0094] The bonding temperature is in particular less than 200°C, preferably less than 150°C, more preferably less than 100°C, most preferably less than 50°C, most preferably at room temperature.

[0095] In a second embodiment, after contacting, the second, upper substrate in particular remains fixed to the receiving device during bonding. If the second, upper substrate remains fixed to the receiving device during bonding, less deformation of the upper substrate occurs at the bond front due to the higher rigidity of the fixed substrate.

[0096] In a third embodiment, after contacting, the first and / or second substrate, in particular, remains fixed to the receiving device during bonding. By fixing at least one of the substrates during bonding, distortions are minimized. Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. These schematically show:

[0097] Figure 1a is a cross-sectional view of a first embodiment of the bonding device,

[0098] Figure 1 b is a plan view of the first substrate holder and the second substrate holder of a first embodiment of the device according to Figure 1 a,

[0099] Figure 2a is a plan view of the first and second substrate holders of a first embodiment of the device with a first rotation axis AA,

[0100] Figure 2b shows the first and second substrate holders of a first embodiment of the device with a second rotation axis BB,

[0101] Figure 3a is a cross-sectional view of a first embodiment of the device with a mechanically executed hinge in the axis of symmetry, with loading pins of the first and second receiving device in the loading state,

[0102] Figure 3b is a cross-sectional view of a first embodiment of the device with a mechanically executed hinge in the axis of symmetry after loading the first and second substrates onto the loading pins,

[0103] Figure 3c is a cross-sectional view of a first embodiment of the device with a mechanically executed hinge in the axis of symmetry after receiving the first and second substrates on the first and second substrate holders,

[0104] Figure 4 is a cross-sectional view of a device in the loading state and in the bonding position before bonding the first and second substrates, Figure 5a is a cross-sectional view of the device in a first

[0105] Process step of an exemplary bonding process,

[0106] Figure 5b is a cross-sectional view of the device in a second process step,

[0107] Figure 5c is a cross-sectional view of the device in a third process step,

[0108] Figure 5d is a cross-sectional view of the device in a fourth process step,

[0109] Figure 5e is a cross-sectional view of the device in a fifth process step,

[0110] Figure 5f is a cross-sectional view of the device in a sixth process step,

[0111] Figure 6a is a cross-sectional view of a third embodiment of the device in a first method step,

[0112] Figure 6b is a cross-sectional view of a third embodiment of the device in a second method step,

[0113] Figure 6c is a cross-sectional view of a third embodiment of the device in a third method step,

[0114] Figure 7a is a cross-sectional view of a fourth embodiment of the device in a first method step,

[0115] Figure 7b is a cross-sectional view of a fourth embodiment of the device in a second method step,

[0116] Figure 7c is a cross-sectional view of a fourth embodiment of the device in a third method step,

[0117] Figure 8a is a cross-sectional view of a fifth embodiment of the device in a first method step,

[0118] Figure 8b shows a cross-sectional view of a fifth embodiment of the device in a second method step. In the figures, identical components or components with the same function are identified by the same reference numerals.

[0119] Figure 1a shows a schematic, not to scale, cross-sectional view of a first embodiment of the first and second receiving devices 1, 2, wherein the movement of the second receiving device 2 is shown in a simplified manner. Both substrates 3, 4 are loaded from above in an identical manner. The design features of the receiving devices 1, 2, such as substrate fixing elements 5, openings for loading pins 6, and other surface features of the receiving devices 7, are symmetrical, so that after rotation of the second receiving device, the first receiving device 1 and the second receiving device 2 are opposite one another and mirror-symmetrical.

[0120] The fixing elements 5 serve to fix the substrates 3, 4 to the receiving device 1, 2. In a particularly preferred embodiment, the substrates 3, 4 are fixed electrostatically.

[0121] Figure 1 b shows a plan view of the first and second receiving device 1, 2 of a first embodiment of a device according to Figure 1 a.

[0122] Both substrates 3, 4 are loaded from above in an identical manner. All features 5, 6, 7 of the holding devices 1, 2 that can directly or indirectly influence the substrate shape are designed symmetrically for the first substrate 3 and the second substrate 4, so that the first and second substrates 3, 4 exhibit identical stress patterns determined by the holding device prior to bonding. These features include, in particular, substrate fixation elements 5, openings for loading pins 6, and other surface features of the holding devices 7, such as openings for measuring devices, sensors, or lines.

[0123] Crucial for the device is the loading of both substrates 3, 4 in symmetrical orientation with identical gravity influence on the first receiving device 1 and on the second receiving device 2. Both substrates 3, 4 are loaded from above on the respective receiving device (loading position, loading state).

[0124] At least one of the receiving devices 1, 2 is pivotally mounted so that after loading the substrates 3, 4, the substrate surfaces to be bonded are brought opposite each other in a bonding position.

[0125] Figure 2a shows a plan view of the first and second receiving devices 1, 2 of a first embodiment of a device with a first pivot axis AA. In this first embodiment according to Figure 2a, a second receiving device 2 is moved relative to a first receiving device 1 by a rotational movement via a pivot joint (10, not shown) with the pivot axis AA.

[0126] Loading pins and their openings 6 in the holding surfaces of the receiving devices 1, 2 are arranged symmetrically on the same radius on both receiving devices 1, 2.

[0127] Figure 2b shows a plan view of the first and second receiving device 1, 2 of a second embodiment of a device with a second axis of rotation BB.

[0128] For bonding, either one holding device with the substrate is pivoted upside down by 180° (axis AA or BB), or both holding devices with the substrate are rotated 90° relative to each other so that they meet symmetrically. If one holding device with the substrate is pivoted upside down by 180°, a rotational movement or a combination of rotational-translational movement is conceivable. The holding devices 1, 2 can be rotated about any axis. The rotation of the holding device with the substrate by 180° can thus take place about a mirror axis in the XY plane of the holding device or as a rotational movement via a pivot joint. Figures 3a to 3c show a cross-sectional view of a first embodiment of the device with a mechanically implemented hinge 10 in the axis of symmetry or in the pivot axis AA. Initially, the two chamber sections 12, 13 are open, as shown in Figures 3a to 3c.In a first process step according to Figure 3a, the loading pins 8 of the first and second holding devices 1, 2 are in the loading position. In a second process step according to Figure 3b, the first substrate 3 and the second substrate 4 are loaded onto the loading pins 8 of the holding devices 1, 2. The loading of the two substrates 3, 4 is carried out with identical gravity influence, i.e., both from above. The back of the substrates 3, 4 is brought onto the holding surface of the holding device 1, 2 using loading pins 8 and is held in place by electrostatic forces. The substrates 3, 4 are held in place with high positioning accuracy and with high holding force. The electrodes are preferably embedded in the holding device 1, 2 and can be unipolar or bipolar. The electrodes are designed symmetrically with respect to the axes of the two substrates 3, 4.

[0129] The support devices or substrate holders 1, 2 are positioned and loaded in such a way that both substrates 3, 4 are held identically on symmetrically constructed support devices 1, 2 before contacting or bonding, so that the substrates are contacted and bonded with corresponding zones with stress patterns 9. The areas with stress patterns 9 are created, for example, by the contacts with loading pins 8 and by the deformation of the wafers between the loading pins 8 due to gravity.

[0130] In a third process step according to Figure 3c, the first substrate 3 and the second substrate 4 are picked up on the receiving devices and fixed with fixing means 5. If the substrate 3, 4 rests only on the loading pins 8 as shown in Figure 4, then gravity causes a change compared to a flat surface, whereby the corresponding regions of the first and second substrate are highlighted with stress patterns due to the loading of the substrates on the symmetrically designed loading pins in the open pivoting device. This change in the contact regions 9 is symmetrical for both substrates 3, 4 in the bonding device 11, so that during bonding or after bonding, corresponding stress patterns are located in superimposed regions 9'. Identical stress patterns are therefore present symmetrically around the bonding interface in the substrate stack.

[0131] At least one of the receiving devices 1, 2 is pivotally mounted. One possibility for moving the second chamber section 13 relative to the first chamber section 12 is to perform a rotational movement between the chamber sections 12, 13 via a pivot joint 10 as shown in Figure 5b.

[0132] Figures 5a to 5f show the process steps in a first embodiment of the device and the method for bonding 11, preferably permanent bonding, in particular fusion bonding, a first substrate 3 to a second substrate 4, comprising: a) a bonding chamber 11 consisting of a first chamber section 12 and a second chamber section 13, b) receiving devices 1, 2 for receiving and fixing the substrates 3, 4, wherein the receiving devices 1, 2 are designed to approach and contact the substrates.

[0133] First, the two chamber sections 12, 13 are opened, as shown in Fig. 5a, and the substrates 3, 4 are electrostatically fixed. Electrodes are inserted into electrostatic holding devices to generate an electrostatic holding force for fixing the substrate. The ultra-flat electrostatic holding devices 1, 2 have a particularly flat holding surface to electrostatically press the substrate 3, 4 and ensure highly stable holding. The electrostatic attraction ensures an even distribution of the holding forces over the entire surface. The flatness of the holding device 1, 2 is superior to the thickness variation and nanotopography of the substrates 3, 4. The substrates 3, 4 may already exhibit mechanical stresses due to pre-process steps, which could cause deformation in the unfixed state.

[0134] After loading and fixing the substrates 3, 4, the bonding chamber 11 is closed according to the embodiment of Figure 5b by pivoting the second chamber section 13 about the pivot joint 10. For this purpose, a motor drive (not shown) can be provided.

[0135] After pivoting the second chamber section 13, as shown in Figure 5c, the peripheral wall 12u of the first chamber section 12 rests on the peripheral wall 13u of the second chamber section 13. Sealing is achieved via the annular seal 14 on the upper side of the peripheral wall 12u of the first chamber section 12.

[0136] The bonding device 11 can advantageously be operated in a vacuum or at ambient pressure under an inert gas. The substrates 3, 4 are first adjusted with high precision for exact alignment and are kept separated during an evacuation process as shown in Figure 5c. Preferably, the alignment is performed using alignment systems and alignment marks. The adjustment and approximation are known to those skilled in the art and will not be described in detail.

[0137] After the two substrates have been aligned, contacting takes place. In the next process step according to Figure 5d, the second, upper substrate 4 with the receiving device 2 for bonding is moved translationally within the bonding chamber 11 onto the first, lower substrate 3 using a movement device 15 and distance-changing means 16. Approach and adjustment are carried out in a controlled manner. In order to be able to precisely control the movement of the second, upper substrate 4, at least one measuring device for measuring the position of the second, upper substrate 4 is preferred in the device design.

[0138] In the bonding process shown in Figures 5a to 5f, the substrates 3, 4 are placed flat on top of one another. For structures in the nm range and precise overlays, reproducibility of the flatness of the substrates 3, 4 to be bonded is very important. The holding force of the ultra-flat electrostatic holding devices 1, 2 with a particularly flat holding surface enables conformal planarization of the substrates 3, 4.

[0139] In a first preferred embodiment, after contacting, both substrates 3, 4 remain fixed to the first and second receiving devices 1, 2 during bonding. If both substrates 3, 4 remain fixed to the respective receiving devices 1, 2 during bonding, thickness variations (TTV, total thickness variation) and stress patterns of the substrates 3, 4 have little influence on the bonding result. This results in a parallel, spontaneous (1:1) connection of the two substrates 3, 4 fixed to the receiving device, with no deformation of the substrates 3, 4 occurring at the bond front.

[0140] In a second, less preferred embodiment, after contacting, the second, upper substrate 4 remains fixed to the receiving device 2 during bonding. If the second, upper substrate 4 remains fixed to the receiving device 2 during bonding, less deformation of the upper substrate 2 occurs at the bond front due to the higher rigidity of the fixed substrate 2.

[0141] The idea is that both substrates 3, 4 are picked up in an identical manner on symmetrically constructed receiving devices 1, 2 before contacting or bonding, so that the stress on the substrate caused by the picking up and loading on the receiving device 1, 2 is minimized and the substrates 3, 4 are contacted and bonded with corresponding stress patterns.

[0142] By fixing the substrates 3, 4 during bonding on the symmetrically constructed, ultra-planar electrostatic recording devices 1, 2, distortions in the bonding interface are further minimized.

[0143] In one embodiment, the receiving devices 1, 2 are designed such that the substrate 3, 4 can be tempered, in particular in sections, by heating means.

[0144] The compressive stress leads to an approach of the substrate surfaces at the boundary layer along the contact area.

[0145] The substrates can be pretreated if necessary before bonding, especially before alignment. Examples of pretreatment include plasma treatment or amorphization of at least one of the two substrate surfaces. The bonding chamber and the process chamber for amorphization or plasma treatment can be part of an (evacuated) cluster system.

[0146] Figure 5e shows a completed bonding process. The substrates 3, 4 are fully contacted, and the bonding process is complete. After the upper fixation is switched off, the second, upper holding device 2 is moved upwards within the bonding chamber 11 using a movement device 15 and distance-changing means 16 to return to the position shown in Figure 5c. The substrate stack 17 remains on the first, lower holding device 1.

[0147] As shown in Figure 5f, the bonding device 11 is reopened by a rotational movement between the chamber sections 12, 13 via a pivot joint 10 of the second chamber section 13, and the substrate stack 17 can be removed after the fixation of the first, lower receiving device is released. Releasing the bonded stack 17 from the substrate holders allows the substrates to reduce stress in the same way. This relaxation process leads to minimized residual stress.

[0148] At least one of the support devices 1, 2 is pivotally mounted. The support devices 1, 2 can be rotated about any axis. The rotation of one of the support devices with substrate by 180° can thus take place not only as a rotational movement via a pivot joint according to Figures 5a to 5c, but also as a rotation about a mirror axis in the XY plane of the support device 1, 2.

[0149] Another possibility is to move one chamber section translationally toward or away from the other chamber section after rotation. For example, this movement could be achieved using a lifting cylinder. Additional lateral guides could also be provided. A combined rotational-translational movement, for example, using a four-bar linkage, is also conceivable.

[0150] In a further embodiment according to Figures 6a to 6c, both receiving devices 1, 2 are located one above the other, so that both substrates 3, 4 are loaded with identical gravity on the first and on the second receiving device 1, 2 according to Figure 6a. After the substrates 3, 4 have been fixed, the second, upper receiving device 2 with the fixed substrate 4 is rotated upside down by 180° about its own axis of rotation BB according to Figure 6b. After the rotation, both receiving devices 1, 2 are mirror-symmetrical to one another, so that all features of the receiving devices 1, 2, such as the fixing elements 5, the openings for loading pins 6, and other surface features 7, are positioned symmetrically.

[0151] In a further embodiment according to Figures 7a to 7c, both holding devices 1, 2 are located next to one another, so that in this embodiment too, both substrates 3, 4 are loaded onto the first and second holding devices 1, 2 with identical gravitational influences, as shown in Figure 7a. A combination of rotational-translational movement is performed so that the first and second holding devices 1, 2 meet symmetrically. The two holding devices 1, 2 can be rotated about any axis and then brought into a precisely aligned, symmetrical position by X / Y / Z translation (and rotation).

[0152] In a preferred embodiment, the substrate and / or the receiving device 1, 2 is movable in at least three degrees of freedom, preferably in at least four degrees of freedom, more preferably in at least five degrees of freedom, and most preferably in all six degrees of freedom. This enables improved mobility of the substrate and / or the receiving device.

[0153] 8a and 8b, both holding devices 1, 2 are located next to one another so that in this embodiment too, both substrates 3, 4 are loaded on the first and second holding devices 1, 2 with identical gravity influences as shown in Figure 8a. For bonding, both holding devices 1, 2 with substrate are rotated 90° to one another so that they also meet symmetrically as shown in Figure 8b. The rotary movement of the second holding device 2 by 90° takes place via the rotation axis BB and the rotary movement of the first holding device 1 by 90° takes place via the rotation axis B '-B ' . After adjustment and approach, the substrates 3, 4 are bonded over their entire surface in the vertical plane.

[0154] List of reference symbols

[0155] 1 First receiving device, first substrate holder

[0156] 2 Second holding device, second substrate holder

[0157] 3 First substrate

[0158] 4 Second substrate

[0159] 5 Fixing element, first fixing means, second fixing means, fixing means

[0160] 6 Opening for charging pin

[0161] 7 Further feature of the reception facility

[0162] 8 Charging pin

[0163] 9, 9' Areas with the development of stress patterns in the

[0164] Substrate loading

[0165] 10 Swivel joint, swivel axis

[0166] 11 Bonding device, bonding device

[0167] 12 First Chamber Section

[0168] 13 Second Chamber Section

[0169] 12u, 13u perimeter wall

[0170] 14 Ring seal

[0171] 15 Movement device (drive means)

[0172] 16 Distance changing devices, proximity devices

[0173] 17 substrate stacks

[0174] AA rotation axis

[0175] BB, B'-B' axis of rotation

Claims

P a t e n t a n s p r ü c h e 1. A method for bonding substrates comprising the following steps, in particular the following sequence: i) providing a first substrate (3) on a first substrate holder surface of a first substrate holder (1) and a second substrate (4) on a second substrate holder surface of a second substrate holder (2), ii) fixing the first substrate (3) to the first substrate holder (1) and the second substrate (4) to the second substrate holder (2) in a loading state, iii) positioning the second substrate holder (2) relative to the first (1) substrate holder in a bonding position such that the first substrate (3) and the second substrate (4) face each other with surfaces to be bonded, iv) bonding the first substrate (3) to the second substrate (4), wherein in the loading state, the first substrate holder surface and the second substrate holder surface are arranged at the same angle relative to the earth's gravity,and wherein in the loading state, the first substrate holder surface and the second substrate holder surface are aligned in a same direction relative to the force of gravity, and wherein identical holding forces are exerted on the first substrate (3) and on the second substrate (4) when fixing the first substrate (3) and the second substrate (4).

2. The method according to claim 1, wherein in the loading state the first substrate (3) rests on the first substrate holder surface and the second substrate (4) rests on the second substrate holder surface.

3. Method according to at least one of the preceding claims, wherein the angle is a perpendicular angle.

4. Method according to at least one of the preceding claims, wherein during the fixing in the loading state, the identical holding forces are each provided in a mutually corresponding pattern on the first substrate (3) and the second substrate (4), so that in the bonding position the pattern of the holding forces is aligned.

5. Method according to at least one of the preceding claims, wherein the fixing of the first substrate (3) and the second substrate (4) takes place simultaneously and within the same period of time.

6. Method according to at least one of the preceding claims, wherein the positioning comprises pivoting the second substrate holder (2) by 180°.

7. Method according to at least one of the preceding claims 1 to 5, wherein the positioning comprises pivoting the first substrate holder (1) and the second substrate holder (2) by 90° towards each other.

8. Method according to at least one of the preceding claims, wherein the identical holding forces are maintained while the ground.

9. Device for bonding (11) substrates (3, 4), at least comprising: a) a first substrate holder (1) with a first substrate holder surface, a1) first fixing means (5) for fixing a first substrate (3) to the first substrate holder surface, b) a second substrate holder (2) with a second substrate holder surface, b1) second fixing means (5) for fixing a second substrate (4) to the second substrate holder surface, c) positioning means (10, 15, 16) for positioning the second substrate holder (2) relative to the first substrate holder (1), wherein the device (11) can be transferred into a loading state in which the first substrate holder surface and the second Substrate holder surface are arranged at the same angle relative to the earth's gravity, and wherein in the loading state the first substrate holder surface and the second substrate holder surface are aligned in a same direction relative to the earth's gravity and wherein the first fixing means (5) and the second fixing means (5) are each configured to provide identical holding forces for fixing in the loading state.

10. Device (11) according to claim 9, wherein the device (11) is configured such that in the loading state the first substrate holder surface and the second substrate holder surface are arranged offset parallel to one another.

11. Device (11) according to at least one of the preceding claims, wherein the second substrate holder is pivotable from the loading state into a bonding position.

12. Device (11) according to at least one of the preceding claims, wherein the positioning means comprise a pivot joint (10).

13. Device (11) according to at least one of the preceding claims, wherein the first fixing means (5) and the second fixing means (5) are electrostatic fixing means (5).

14. Device (11) according to at least one of the preceding claims, wherein in the bonding position the first substrate holder (1) and the second substrate holder (2) form a bonding chamber, preferably a fluidically tight bonding chamber.

15. Device (11) according to at least one of the preceding claims, wherein the first fixing means (5) and the second fixing means (5) are designed to provide the identical holding forces at least until transfer into the bonding position.

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