Method and apparatus for substrate bonding

Abstract

The invention relates to a method and apparatus for substrate bonding.

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for bonding substrates, in particular wafers. During bonding, the substrates are aligned with each other, brought into contact with each other, and connected to each other. For alignment, the substrates are each held in a substrate receiving device, in particular a vacuum substrate holder, and the surfaces of the substrates to be connected are precisely aligned with each other before bonding. This results in a connection that is as distortion-free and expansion-free as possible over the entire surface. Background Art

[0002] In the prior art, the upper substrate and the lower substrate are loaded in a bonding orientation such that the bonding sides of the upper substrate and the lower substrate are already facing each other before bonding. This has the advantage that the bonding apparatus occupies less space because the upper substrate holder does not have to be turned, rotated, or moved, but due to the different adhesion forces acting at the upper substrate holder and the lower substrate holder, different stresses are generated in the respective substrates in the substrates to be bonded.

[0003] In the printed document US9,613,840B2, the upper substrate and the lower substrate are loaded in a bonding orientation. The upper substrate is deformed by a deformation member, in particular a mechanical pin, where the deformation member acts on the side facing away from the bonding side, in particular due to its shape. The start of contact is affected by the central deformation of the upper substrate and the pin, and after contact, the upper substrate is released and automatically bonded due to its prestress with the oppositely placed substrate.

[0004] In US9,613,840B2, at least one substrate is no longer fixed to the receiving device during the bonding process. In addition, the upper receiving device and the lower receiving device are constructed differently due to different embodiments and thus different stress patterns are provided in the substrates due to loading or fixing.

[0005] In US8,918,989B2, fixing members are provided for at least partially pre-fixing the aligned substrates to a carrier substrate. The two substrates are loaded one above the other in a bonding orientation. Spacers are used during alignment to maintain the distance between the substrates and the carrier substrate before a force-adjusted actuator acting at the center acts on the substrate stack to fix the substrates. In US8,918,989B2, the bonding or pre-bonding occurs completely without previously fixing the upper substrate to the upper receiving device.

[0006] In the printed document US6,383,890B2, two substrates are loaded from above. By rotating the upper receiving device mounted in a rotatable manner by 180°, the two substrates are placed opposite each other in parallel to be joined in a joining orientation. A pin penetrates the upper receiving device and starts the joining process by bending through the center of the upper substrate. Here, the upper substrate is released from the fixation. The full features of the upper substrate receiving device and the lower substrate receiving device, in particular the loading pins of the upper substrate receiving device and the lower substrate receiving device, and in particular the symmetric embodiment of the fixing elements are not provided. Additionally, different holding forces or fixing forces are provided.

[0007] In the printed document WO2015 / 183197A1, the upper substrate receiving device rotates by 180° around its own axis for joining. Here, the upper substrate receiving device is moved between a substrate loading position and a substrate joining position. The advantage here is that it is possible to more easily control the alignment of the substrate equipped with structures on the receiving device from the free upper side.

[0008] A symmetric embodiment of all the features of the upper substrate receiving device and the lower substrate receiving device is not provided because the upper substrate receiving device and the lower substrate receiving device are designed differently due to the construction of the device. Additionally, different holding forces are provided in different styles.

[0009] The substrates to be joined (in particular wafers) are usually structured and coated with up to several layers of different materials. This pre-treatment step generates mechanical stresses that can cause the wafer to warp in its free form. This warping occurs, for example, in the form of warping tendency, bending, twisting, and / or local deformation. Once one of the substrates to be joined is not fixed or is no longer fixed to the substrate receiving device during the joining process, a part of this stress is incorporated into the joining interface as a twist.

[0010] The crystal structure of the substrate material also determines whether the properties are isotropic or anisotropic and can thus possibly affect the joining process. The mechanical properties of silicon (Si), for example, are anisotropic. Monocrystalline silicon has different elastic moduli (E-moduli) in different directions. This different rigidity causes the generated joining waves to propagate at non-uniform speeds. When the substrate, in particular the upper substrate, is released from the fixation of the substrate receiving device during joining, the rigidity difference also has a strong influence. Due to the direction dependence of the E-modulus, other mechanical properties, in particular expansion, are also direction-dependent.

[0011] For several years, in the semiconductor industry, substrates have been connected to each other by a so-called joining process. Before the connection, these substrates must be aligned with each other as accurately as possible, where deviations in the nanometer range also play a role. The alignment of the substrates is usually carried out via alignment marks. In addition to the alignment marks, there can still be other, in particular functional elements, on the substrates that must also be aligned with each other during the joining process.

[0012] One of the greatest challenges in bonding lies in the bonding process itself, namely, during the period from the start of bonding until the full contact of the contact surfaces of the substrates. In this case, the alignment of the two substrates relative to each other can still change decisively with respect to the previous alignment. Once the two substrate surfaces are connected to each other, although they can theoretically be separated again, this is associated with high costs and error-proneness. There are various methods and facilities in the prior art with the help of which an attempt can be made to influence the bonding process.

[0013] In the bonding process, stress patterns can lead to distortion and error-proneness. The substrates to be bonded, especially wafers, are usually structured and coated with up to several layers of different materials. These pretreatment steps generate mechanical stresses that can cause the wafers to warp in their free form. In addition to the mechanical stresses from the pretreatment steps, further stress patterns can also be generated during the loading of the substrates. Components of the receiving device that can affect the substrate shape and cause loading stresses especially include loading pins and fixing and supporting elements as well as further surface features of the receiving device.

[0014] Then, a part of this stress is incorporated into the bonding interface as distortion during bonding. The stress can relax due to additional defect formation, cancel each other out, or remain as residual stress in the bonded stack.

[0015] Especially in the case of thin substrates or thin substrate stacks, the residual stress has a strong effect. The back-thinned substrates must return to their original state, preferably a flat shape and be maintained. Summary of the Invention

[0016] Therefore, the task of the present invention is to at least partially eliminate, especially completely eliminate, the disadvantages listed in the prior art. In particular, the task of the present invention is to present an improved method and device for bonding. In addition, the task of the present invention is to produce a bonded substrate stack with minimal residual stress.

[0017] The current problem is solved by using the features of the independent claims in parallel. Advantageous expansion solutions of the present invention are described in the dependent claims. All combinations of at least two technical features described in the description, claims, and / or drawings also fall within the scope of the present invention. In the case of the stated value ranges, the values within the said boundaries should also be regarded as being disclosed as limit values and can be claimed in any combination.

[0018] It has surprisingly been shown that the bonding result can be improved if, in addition to the mechanical stress already generated in the substrate during the pre-treatment step, new stress patterns caused by the construction features of the substrate receiving device in direct contact with the substrate and, for example, caused during the substrate loading procedure onto the substrate receiving device are also compensated for or prevented. 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 different embodiments of the upper substrate receiving device and the lower substrate receiving device - in particular the substrate holder surfaces, the fixing elements and the holding forces.

[0019] If a force, in particular gravity, acts on the substrate located on the loading pins or structures of the holding surface, an asymmetric deformation occurs. This asymmetric deformation remains during the contact between the two substrates and / or during the bonding process and leads to an asymmetric propagation of the bonding wave front and thus to an undesired run-out effect.

[0020] Loading the upper and lower substrates in the bonding orientation will necessarily result in different stress patterns, which can also be introduced as a twist into the bonding interface, especially if the different asymmetric stress patterns cannot subsequently cancel each other out.

[0021] The method and device for bonding improve the bonding result, in particular by the proposed combination of features.

[0022] Accordingly, the present invention relates to a method for bonding substrates, the solution having the following steps, in particular having the following process: 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 the loaded 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 the surfaces to be bonded; iv) bonding the first substrate to the second substrate, wherein in the loaded state, the first substrate holder surface and the second substrate holder surface are arranged at the same angle relative to gravity, and wherein in the loaded state, the first substrate holder surface and the second substrate holder surface are aligned in the same direction relative to gravity, and wherein when fixing the first substrate and the second substrate, the same holding force is applied to the first substrate and to the second substrate, respectively.

[0023] In other words, two substrates are provided on substrate holders that are aligned identically with respect to gravity under the same gravity conditions, and the same holding force is provided on the substrates for fixation. Thus, it is possible to particularly advantageously generate the same stress in the substrates, which has a favorable effect on the bonding result. A symmetrical arrangement of the fixing elements on the substrate holder with respect to the bonding interface in the bonding position is particularly advantageous. Particularly advantageously, in this positioning situation, the surfaces of the substrates or the substrate holders are positioned symmetrically and parallel to each other such that the surfaces to be bonded face each other. Symmetrical positioning or alignment means that the fixing positions, the holding forces at the fixing positions, and the support surfaces of the substrate holders are congruent or symmetrical due to the mirror image of the plane spanned between the substrates. In other words, all the characteristics that affect the stress in the substrates in the loaded state are aligned.

[0024] The first substrate and the second substrate are preferably dimensioned identically here. In particular, the substrates have the same weight. The surface of the first substrate holder is configured to be symmetrical to the surface of the second substrate holder, in particular axisymmetric. The surfaces of the substrate holders preferably correspond such that in the loaded state, the support surfaces of the respective substrate holding surfaces are arranged symmetrically to each other and the opposing support surfaces are aligned during bonding. The surface of the substrate holder is here in particular the surface of the substrate holder on which the substrate is located. The surface of the substrate holder includes, for example, loading pins, protrusions, or a full surface having a receiving portion for the fixing member.

[0025] In the loaded state, the substrate holders or the surfaces of the substrate holders and thus the substrates are arranged identically with respect to the acting gravity. Here, the surfaces of the substrate holders are aligned in the same direction with respect to gravity. Here, for example, the surfaces of the two substrate holders are aligned upward or downward. In the loaded state, the substrates are not loaded from above and below, but both are the same, such that gravity acts identically at the loading moment and also the same stress, in particular the same stress pattern, acts on the two substrates when the same holding force is applied.

[0026] Here, the surfaces of the substrates to be bonded are not located on the surfaces of the substrate holders, but point away from the substrate holders. The substrate holders are here preferably both perpendicular or horizontal to gravity. The substrate holders preferably arranged side by side next to each other laterally have the same angle with respect to gravity in the loaded state. Here, the slightly different gravity due to the offset arrangement and the slightly different distances to the center of the earth can be neglected.

[0027] When fixing the substrates, the same acting and the same holding force are provided at the substrates. In this way, a corresponding stress pattern can be advantageously generated in the substrates, which improves the bonding result. The holding force preferably also remains when transferred to the bonding position.

[0028] The positioning can be carried out arbitrarily and can include the movement of the two substrate holders in all directions.

[0029] When joining substrates or a stack of substrates, the substrate to be joined can be loaded in a minimally invasive manner, so to speak, in the same orientation as gravity into a corresponding receiving device and held by a holding force acting equally or symmetrically on both substrates. Here, usually different holding forces are provided, since the substrate to be joined is only placed on the lower substrate holder after positioning and must be held at the upper substrate holder. At the upper substrate holder, a greater holding force usually acts, since the weight of the fixed upper substrate must additionally be compensated for.

[0030] Symmetry preferably also relates to all other components of the substrate holder that can have an influence on the stress in the substrate (support surface, type of fixing element, alignment marks, tubes, etc.). An axially symmetric arrangement of all components is preferred.

[0031] In a preferred embodiment of the method for joining, it is provided that in the loaded state, the first substrate is placed on the surface of the first substrate holder and the second substrate is placed on the surface of the second substrate holder. "Placed on..." means that the first substrate and the second substrate are each placed on the surface of the substrate holder that is additionally identically aligned by their own weight and do not theoretically have to be fixed. In other words, both the surfaces to be joined are aligned against gravity, while the back sides of the substrates are located on the surface of the substrate holder. In this way, a particularly advantageous and stress-free loading can be carried out.

[0032] In a preferred embodiment of the method for joining, it is provided that the angle is a vertical angle. The same angle at which the surface of the substrate holder is aligned relative to gravity is, in other words, 90°. Here, the substrate and the surface of the substrate holder are preferably flat. Thus, the substrate is also quasi-parallel to gravity and thus aligned towards the center of the earth. In this way, particularly good joining results can be achieved. In addition, sliding of the substrate can be prevented.

[0033] In a preferred embodiment of the method for joining, it is provided that in the loaded state during fixing, the same holding force is provided at the first substrate and the second substrate in respective corresponding patterns such that the patterns of the holding forces are aligned in the joining position. In other words, the substrate surfaces facing each other in the joining position are congruent with respect to the provided fixing pattern. Thus, the same holding force is provided at precisely opposite positions in the joining position. It is thus ensured that the stress prevailing in the substrate in the region of the opposing substrate surfaces due to fixing is identically positioned and of equal magnitude in the joining position. Thus, the stress distribution in the first substrate is aligned with the stress distribution in the second substrate in the joining position. Thus, in the loaded state, the holding force is provided, for example, in an axially symmetric arrangement such that a simple swinging is sufficient for positioning.

[0034] In a preferred embodiment of the method for joining, it is provided that the fixation of the first substrate and the second substrate is carried out simultaneously and within the same time period. In other words, the holding force is applied within the same time and simultaneously. Here, at the same point, the increase in the holding force per unit time is preferably also the same. In this way, better joining results can also be achieved.

[0035] In a preferred embodiment of the method for joining, it is provided that the positioning includes a 180° swing of the second substrate holder. The swing of the second substrate holder preferably constitutes the positioning such that the first substrate holder does not have to move. After the positioning or transfer to the joining position, the approach of the substrate holders may be required. By swinging the second substrate holder 180° around the axis of symmetry, a particularly easy and trouble-free transfer to the joining position can be advantageously achieved. After the swing, the second substrate holder is preferably precisely perpendicular to the direction alignment in the loaded state.

[0036] Here, "towards each other" means that the surfaces of the substrate holders are aligned facing each other. Then, in particular, the additional movement for the initial contact for joining is carried out only by the approach of the first substrate holder surface and the second substrate holder surface or the first substrate holder and the second substrate holder. Here, the same holding force preferably remains and the corresponding pattern is only further moved towards each other. The alignment is preferably carried out only by swinging.

[0037] In a further preferred embodiment of the method for joining, it is provided that the positioning includes a 90° swing of the first substrate holder and the second substrate holder towards each other. Here, the two substrate holders swing along the axis of symmetry or through the parallel center point axes in the corresponding center points of the substrate holders. In this way, if in the loaded state, the alignment is perpendicular to gravity, then the gravity of the first and second substrates is also the same after the positioning. Particularly preferably, in the loaded state, the first substrate holder surface and the second substrate holder surface are precisely perpendicular to gravity. Therefore, the joining result can be improved in the case of bilateral swinging.

[0038] In a preferred embodiment of the method for joining, it is provided that the same holding force is maintained during the joining. In this way, not only the same holding force remains during the fixation and during the transfer or positioning to the joining position, but also the same holding force is maintained thereafter until after the joining is completed. In this way, the residual stress generated due to loading can be compensated and the joining result can be improved.

[0039] Furthermore, the present invention relates to an apparatus for substrate bonding, which apparatus at least comprises: a first substrate holder having a first substrate holder surface; a first fixing member for fixing a first substrate to the first substrate holder surface; a second substrate holder having a second substrate holder surface; a second fixing member for fixing a second substrate to the second substrate holder surface; and a positioning member for positioning the second substrate holder relative to the first substrate holder, wherein the apparatus is transferable to a loading state in which the first substrate holder surface and the second substrate holder surface are arranged at the same angle relative to gravity, wherein in the loading state, the first substrate holder surface and the second substrate holder surface are aligned in the same direction relative to gravity and wherein the first fixing member and the second fixing member are configured to each provide the same holding force for fixing in the loading state.

[0040] In other words, the first fixing member and the second fixing member act on the first substrate and the second substrate in the same manner. The apparatus is configured such that the holding forces provided by the first fixing member and the second fixing member are of the same magnitude. The fixing members are particularly preferably configured to provide the same holding force simultaneously and within the same time period. Herein, the increase in the holding force per unit of time is preferably also the same in the case of the fixing members or the apparatus is constructed therefor. Due to the loading in the loading state, the same stress pattern is generated in the two substrates to be bonded. In this way, the bonding result is unexpectedly improved. The apparatus may comprise a control unit which is configured to establish the corresponding conditions in the loading state. The further advantages and features of the aforementioned method for bonding should similarly apply to the apparatus.

[0041] In a preferred embodiment of the apparatus for substrate bonding, it is provided that the apparatus is configured to arrange the first substrate holder surface and the second substrate holder surface parallel to each other and offset side by side in the loading state. Herein, in particular, the center points of the substrate holder surfaces are offset relative to the direction. Preferably, in the loading state, the first substrate holder surface and the second substrate holder surface are arranged offset side by side such that they are not aligned but have a distance from each other relative to the same angle. In this way, particularly uniform loading can be carried out and thus the bonding result can be improved.

[0042] In a preferred embodiment of the apparatus for substrate bonding, it is provided that the second substrate holder is swingable from the loading state into a bonding position. The bonding position is particularly characterized in that the substrate holder surfaces face each other and are aligned parallel to each other such that bonding can be carried out only by approaching. In other words, the substrates are aligned and positioned in the bonding position. An approaching member may be provided therefor. By simply swinging from the loading state into the bonding position after being fixed by the fixing members, the bonding result can be advantageously improved. An embodiment of the apparatus as a flip bonder is preferred.

[0043] In a preferred embodiment of the device for substrate bonding, it is provided that the positioning member includes a swing hinge. In this way, the substrate holder can be positioned particularly simply and precisely about the swing hinge, thereby improving the bonding result.

[0044] In a preferred embodiment of the device for substrate bonding, it is provided that in the loaded state, the second fixing member is arranged axially symmetrically with respect to the first fixing member. In other words, after loading, there is a position in which the stress pattern of the substrate is aligned or the surface of the substrate holder and the fixing elements are aligned, i.e., in the bonding position. Here, it is highly preferred that all the features and components of the two substrate holders that affect the stress in the substrate are axially symmetric.

[0045] The axial symmetry is preferably defined by a mirror axis extending through the swing hinge. 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 members, are arranged axially symmetrically with respect to the swing axis, such that the arrangement of the fixing elements is aligned with each other after swinging into the bonding position. If in the loaded state the first substrate holder and the second substrate holder are arranged offset side by side at different heights, the mirror axis extends through the plane spanned by the swing axis and a specific angle of the substrate holders in the loaded state. In any case, the patterns of the fixing elements are implemented corresponding to each other such that after transfer to the bonding state, the opposing substrate holder surfaces have the same and aligned stress patterns due to loading.

[0046] In a preferred embodiment of the device for substrate bonding, it is provided that the first fixing member and the second fixing member are electrostatic fixing members. Particularly preferably, the first and second fixing members engage into the substrate holder surface. Here, the corresponding engaging grooves are also particularly preferably arranged in a symmetric pattern, like the first and second fixing members. In the case of the full-surface configuration of the electrostatic fixing member, the dimensions and the arrangement are also aligned in the bonding position. In another embodiment, the fixing member is a vacuum track, where the arrangement and other configurations are also configured to be congruent or corresponding in the bonding position.

[0047] In a preferred embodiment of the device for substrate bonding, it is provided that in the bonding position, the first substrate holder and the second substrate holder form a liquid-tight bonding chamber. In this way, the bonding chamber can be formed between the first substrate holder and the second substrate holder by swinging and, if necessary, approaching. The substrate is arranged in the bonding chamber here. In this way, the bonding can advantageously be carried out in a protected space, thus improving the bonding result. Additionally, in the case of a particularly preferred liquid-tight bonding chamber, a vacuum can be adjusted or a liquid can be introduced before bonding in the bonding chamber.

[0048] In a preferred embodiment of the apparatus for substrate alignment, it is provided that the first fixing member and the second fixing member are configured to provide the same holding force at least before being transferred to the bonding position. Particularly preferably, the same holding force is provided by the fixing members until after the first substrate is bonded to the second substrate. In this way, the stress in the pattern can advantageously remain the same in the first substrate and in the second substrate, at least due to the stress provided in the loaded state by loading / fixing. In this way, the stress can be compensated and the bonding result can be improved.

[0049] A particularly important aspect of the present invention is that the two substrates are accommodated in the same way on a symmetrically configured accommodating device before contact or bonding, such that the substrates contact and bond with corresponding stress patterns. In particular, the loading of the two substrates is carried out under the same influence of gravity, for example, both are loaded from above. All features of the accommodating device that can indirectly affect the substrate shape are implemented symmetrically for the first substrate and for the second substrate, preferably at the same time, particularly preferably simultaneously, such that the first and second substrates exhibit the same stress patterns facing each other caused by the accommodating device before bonding. Here, at least one of the accommodating devices is preferably mounted in a swingable manner. For this purpose, a fixing or holding force is provided such that the surfaces to be bonded have the same stress pattern with respect to each other after swinging. The two substrates are preferably held fixed on the accommodating device during bonding. The influence of the loading stress is minimized by the symmetric implementation of the accommodating device, such that the residual stress is minimized after bonding. Further distortion is minimized by fixing at least one of the substrates, preferably both substrates, during bonding.

[0050] The method for bonding results in a reduction of the stress pattern that is incorporated as distortion into the bonding interface during bonding. Even after the release of the substrate stack, the relaxation of the corresponding stress pattern also results in minimized residual stress.

[0051] The idea is based on the fact that the two substrates are accommodated in the same way on a symmetrically configured accommodating device before contact or bonding, such that the stress at the substrates caused by accommodation and loading onto the accommodating device is minimized and the substrates contact and bond with corresponding stress patterns. Hereinafter, the terms stress, loading, and pressing are used synonymously. Another important aspect is that the substrates are held fixed during bonding after contacting the accommodating device, such that the distortion is minimized by mutually eliminating the corresponding stress patterns as much as possible and thus reducing the residual stress.

[0052] A method and an apparatus for bonding a first substrate to a second substrate are proposed, wherein the contact surfaces of the substrates face each other, having the following steps, in particular the following process:

[0053] - Accommodating the first substrate at a first accommodating surface of a first accommodating device, wherein the loading is carried out from above,

[0054] - Place the second substrate at the second receiving surface of the second receiving device, where the loading is performed from above.

[0055] - Fasten the substrate to the mounting surface by fixing elements.

[0056] - Rotate the first and / or second receiving devices that can swing-mounted so that the surfaces of the two substrates to be joined are aligned with each other symmetrically.

[0057] - Align the substrates.

[0058] - The two substrates approach and are joined by contact.

[0059] Wherein the first and second receiving devices have a symmetric implementation of all components and wherein after contact, the substrates remain fixed to the first and / or second receiving devices during joining.

[0060] The two receiving devices or substrate holders can be rotated about any axis and then brought into an adjusted symmetric position by X / Y rotation.

[0061] It is decisive that the two substrates are loaded in a symmetric orientation under the condition that gravity has the same effect on the first and second receiving devices. For joining, now preferably one receiving device swings 180° upside down with the substrate, or the two receiving devices rotate 90° relative to each other with the substrate, so that they also meet symmetrically.

[0062] The components of the first and second receiving devices constructed symmetrically with respect to the tilt axis and / or mirror axis between the first and second receiving devices include in particular loading pins and fixing and supporting elements as well as other possible characteristic surface features of the receiving devices.

[0063] The loading pins, preferably three loading pins, are symmetrically arranged in a circular manner on the same radius on the two receiving devices. If the substrates are each loaded onto the loading pins from above on the first and second receiving devices, the substrates bend, for example, according to the effect of gravity. After the substrates are placed at the receiving surfaces of the receiving devices, the loading stress or stress pattern remains at the fixed substrates. Due to the symmetry of the components of the receiving devices, the stress patterns at the first and second substrates are also symmetric. Therefore, the effect of gravity on the loading stress of the substrates is minimized or preferably eliminated, because the effect on the two substrates after contact can be eliminated by symmetry.

[0064] Therefore, the stress patterns of the two substrates are symmetric along the joining interface. After releasing the joined substrate stack, the two substrates can reduce the residual stress still present due to relaxation in the same way, so that the remaining stress is minimized.

[0065] Substrate

[0066] The first and / or second substrate is preferably radially symmetric. Although the substrate can have any arbitrary 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 a particular embodiment, the substrate can also have a rectangular shape, or at least a shape different from the circular shape. Preferably a wafer, particularly preferably a circular wafer, is used as the substrate.

[0067] Receiving device

[0068] The receiving device enables reliable and flat support and fixation of the substrate. Fixation is effected, for example, by applying a vacuum between the substrate and the receiving device, by mechanical clamping, by electrostatic charge, or by other controllable chemo-physical adhesion properties.

[0069] Here, an electrostatic receiving device is preferably used for receiving and holding the substrate. Embodiments of the device for bonding or the bonding device can handle any substrate, regardless of its diameter.

[0070] Here, electrodes for generating an electrostatic holding force for fixing the substrate are particularly preferably engaged in the electrostatic receiving device. Here, the substrate is fixed to the holding surface or the surface of the substrate holder. The holding surface is a preferably flat surface of the receiving device that is configured for substrate fixation and is installed as a component in the substrate holder. In the following, flatness is used as a measure of the perfection of a flat surface (mathematically ideal plane).

[0071] Flatness represents the structure of the surface between two ideally flat surfaces. The spacing between the two flat surfaces defines the tolerance. Deviations from the flat surface occur due to macroscopic and / or microscopic surface defects. These defects can also be defined as waviness and roughness. The waviness of the surface can be described as the periodic rise and fall of the surface, particularly in the millimeter and micrometer ranges. And roughness is more of an aperiodic phenomenon in the micrometer and / or nanometer ranges.

[0072] In order to address the different deviations from the ideal surface, in the following of the description, the term roughness is used synonymously for the superposition of all such effects. Roughness is given as average roughness, root mean square roughness or average roughness depth.

[0073] For the same measurement section or measurement area, the determined values of average roughness, root mean square roughness and average roughness depth generally differ, but are in the same order of magnitude range. Therefore, the following numerical ranges for roughness should be understood as values for average roughness, root mean square roughness or average roughness depth.

[0074] In a preferred embodiment, it is provided that a capacitive receiving device or a substrate holder having an electrostatic fixing member has a holding surface which is implemented to be particularly flat in order to electrostatically press the substrate and ensure highly stable holding. The electrostatic attraction results in a uniform distribution of the holding force over the entire surface. The flatness of the receiving device is better or more precise than the thickness variation and the nano-topography of the substrate. Here, due to the pre-treatment step, the substrate already has mechanical stresses which may cause distortion in the non-fixed state.

[0075] A substrate having a wedge error is not a problem for the receiving devices in the prior art. The wedge error can be compensated. Higher-order thickness variations are more problematic (e.g., center-to-edge, four quadrants, etc.). Substrates having high flatness and curvature requirements (such as reflective masks) require a holding surface with a high degree of flatness because otherwise errors such as image alignment errors and superposition errors (distortion) occur. To this extent, components for wedge error compensation are preferred in combination with the equipment for bonding.

[0076] The flatness of the holding surface of the electrostatic fixing member is less than 1000 nm, preferably less than 200 nm, more preferably less than 50 nm, and most preferably less than 1 nm (the difference between the highest and the lowest points of the surface or the holding surface).

[0077] In particular, the nano-topography is a fundamental parameter of the surface quality. Local (jumping) unevenness should be particularly avoided. The roughness is here less than 100 nm, preferably less than 10 nm, more preferably less than 1 nm, and most preferably less than The roughness is in particular also less than a flatness variation of 1 nm / μm, and more preferably less than the flatness variation of.

[0078] For structures in the nm range and precise superposition, the reproducibility of the flatness of the substrates to be bonded is very important. The holding force of a super-flat electrostatic fixing member having a holding surface implemented to be particularly flat enables conformal flattening of the substrate.

[0079] Two substrates are preferably loaded from above, i.e., perpendicular to gravity. The back side of the substrate is brought onto the holding surface by means of loading pins and fixed by electrostatic force. Here, the substrate is fixed with high positioning accuracy and with a high holding force. The electrodes are particularly preferably meshed or embedded relative to the substrate holder surface and can be implemented as monopolar or bipolar. The implementation of the electrodes is symmetric with respect to the axes of the two substrates or the bonding interface.

[0080] Crucially, the two substrates are loaded in a symmetric orientation or direction such that gravity has the same effect on the substrate holder surfaces for the first and second symmetries. For bonding, the receiving device can now either be swung 180° upside down with respect to the substrate and precisely positioned above the lower receiving device if necessary, or the two receiving devices are rotated 90° towards each other with respect to the substrate such that they also meet symmetrically.

[0081] The assembly of the first and second receiving devices, which is constructed symmetrically with respect to the tilt axis and / or mirror axis between the first and second receiving devices, includes in particular loading pins, fixing and supporting elements, and other surface features of the receiving devices.

[0082] If the receiving device or the substrate holder includes loading pins, there must be holes in the substrate holder surface. The holes into which the loading pins move or the loading pins themselves are preferably equipped with seals. Here, 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 the same and symmetrically implemented on the two receiving devices. After one receiving device is rotated (180°) or two receiving devices are rotated (90°), the symmetric features are opposed to each other. Depending on whether one or two receiving devices are tilted or rotated, the receiving devices are configured to be axisymmetric and / or mirror symmetric. If the device for bonding or the bonding device includes, for example, recesses for measuring components, the recesses are also preferably the same and symmetrically implemented on the two receiving devices.

[0083] Other features such as patterns, structures, or structurings on the holding surfaces are also particularly preferably implemented to be the same and symmetric on the two receiving devices.

[0084] The surface for fixing can also be equipped with patterns, grooves, bumps, pins, or any other topography or surface structuring. The grooves can be shaped, for example, linearly, circularly, or arbitrarily. Any combination is also possible, such as grooves and bumps. The selected topography can further reduce the contact surface in order to obtain the smallest possible contact surface.

[0085] In a preferred embodiment, it is provided that the ultra-flat electrostatic substrate holder includes symmetrically implemented grooves that extend above the substrate edge in order to prevent the air cushion and "swimming" of the wafer after loading (before fixing). The grooves are dimensioned and distributed such that the escape of ambient gas is achieved. The grooves are, for example, micro-grooves.

[0086] In a preferred embodiment, it is provided that the capacitive receiving device includes symmetrically implemented bumps in order to reduce the risk of contamination on the back side of the substrate. Then, the substrate holder surface can be at least partially formed by the surface of the bumps.

[0087] Electrostatic attraction not only causes a uniform distribution of the holding force over the entire surface, but also enables good heat exchange and reduced wear. Therefore, electrostatic fixing elements or fixing members are preferred. Here, materials with minimal thermal expansion are preferably selected for the receiving device (thermal invariance).

[0088] In addition to material selection, surface smoothing is also achieved by machine processing so as to minimize the coefficient of friction between the holding surface and the substrate.

[0089] Not only are the external features of the first and second receiving devices symmetric with respect to the tilt axis and / or mirror axis between the first and second receiving devices and identically configured. The first and second receiving devices are also identical overall (almost), such that both preferably have the same thickness and are composed of the same components and materials. The first and second composites (each consisting of a substrate and a receiving device or a substrate holder) particularly preferably have the same mechanical stiffness.

[0090] The thickness of the receiving device is selected such that the total stiffness of the receiving device together with the substrate is not dominated by the anisotropic Young's modulus (E-modulus) of the substrate.

[0091] Preferably, ultra-flat capacitive receiving devices can be used in vacuum, high vacuum, and / or ultra-high vacuum facilities. Capacitive receiving devices can also be used in ambient pressure situations in a gas atmosphere (especially an inert gas atmosphere).

[0092] In a preferred embodiment, it is provided that the substrate and / or the receiving device can be moved in at least three degrees of freedom, preferably 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 achieves improved mobility of the substrate and / or the receiving device.

[0093] In the loading position, the Z direction or the Z axis extends perpendicular to the surface normal of the holding surface of the receiving device. The X and Y directions or the X and Y axes are perpendicular to each other and parallel to or extend in the holding surface of the receiving device.

[0094] Rotation about the X axis is denoted by r, rotation about the Y axis is denoted by q, and rotation about the Z axis is denoted by j.

[0095] In another preferred embodiment, it is provided that the positioning, fixing, and moving system for at least one degree of freedom is constructed with a rough drive and a fine drive. The fine drive advantageously enables precise adjustment of the movement.

[0096] In another preferred embodiment, it is provided that the receiving device comprises a central control unit and / or regulating unit for controlling and / or regulating movement and / or processes, in particular the fixing of the substrate in the loading state and the position of the receiving device. Here, the receiving device or the substrate holder preferably comprises at least one sensor for measuring influencing factors, in particular at least one distance and / or position sensor. The sensors are also symmetrically positioned and identically constructed.

[0097] Bonding device

[0098] For bonding, a bonding member for bonding and / or pre-bonding and / or temporarily bonding is provided. The terms bonding, pre-bonding and temporarily bonding are used synonymously.

[0099] All embodiments of the device for bonding can be operated in a low vacuum, more preferably in a high vacuum, still more preferably in an ultra-high vacuum, in particular at pressures less than 100 mbar, preferably less than 0.1 mbar, more preferably less than 0.001 mbar, still more preferably less than 10e-5 mbar, most preferably less than 10e-8 mbar.

[0100] Loading two substrates in a symmetric orientation is decisive for the device for bonding in the case where gravity has the same influence on the first and second receiving devices or substrate holders. The two substrates to be bonded are preferably loaded from above. Here, in particular, at least one of the receiving devices is mounted in a swinging manner. For bonding, in particular, the receiving device swings 180° upside down with the substrate, or the two receiving devices rotate 90° towards each other with the substrate, so that they also meet symmetrically. If the receiving device swings 180° upside down with the substrate, a rotational movement or a combination of rotational-translational movements can be envisaged. The receiving device can rotate about any axis. Thus, the 180° rotation of the receiving device with the substrate can be carried out about the mirror axis in the X-Y plane of the receiving device or as a rotational movement via the two swinging banks.

[0101] The device enables high-precision adjustment of the fixed substrate for precise alignment. The receiving device is configured for approaching and contacting the substrate.

[0102] Bonding process or bonding

[0103] The substrates are aligned with each other before the bonding procedure. Alignment is preferably carried out by an alignment facility and with the aid of alignment marks. After the two substrates are aligned with each other, in particular, contact is made.

[0104] The step of bringing into contact the aligned contact surfaces of two substrates facing each other is particularly crucial in the bonding of two substrates, since an increasingly precise adjustment accuracy or an offset of less than 50 μm, in particular less than 1 μm, preferably less than 250 nm, more preferably less than 150 nm, and most preferably less than 50 nm is required. Many influencing factors must be taken into account in these alignment accuracies.

[0105] Errors can occur during the contact and placement of the substrates, where the errors accumulate and thus a reproducible adjustment accuracy cannot be maintained. This can lead to a large number of defective products.

[0106] In a first preferred embodiment, after the contact, the two substrates are each held fixed at a first and a second receiving device or substrate holder during the bonding.

[0107] If the two substrates are held fixed to the respective receiving devices during the bonding, the thickness variation (TTV, total thickness variation in English) and the stress pattern of the substrates have little influence on the bonding result. Here, a parallel, spontaneous (1:1) connection of the two substrates fixed to the receiving devices is achieved, where no deformation of the substrates occurs at the front of the bonding. The bonding is preferably carried out in a high vacuum or in an ultra-high vacuum.

[0108] The bonding process consists in particular of force and / or temperature effects. The bonding force is in particular greater than 0.01 kN, preferably greater than 0.1 kN, more preferably greater than 1 kN, most preferably greater than 10 kN, and most most preferably greater than 100 kN. The corresponding pressure range results from the standardization of the bonding force on the surface of the substrate.

[0109] 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, and most most preferably at room temperature.

[0110] In a second embodiment, after the contact, in particular the second upper substrate is held fixed at the receiving device during the bonding. If the second upper substrate is held fixed at the receiving device during the bonding, due to the higher stiffness of the fixed substrate, the upper substrate undergoes less deformation at the front of the bonding.

[0111] In a third embodiment, after the contact, the first and / or the second substrate is in particular held fixed at the receiving device during the bonding. The distortion is minimized by fixing at least one of the substrates during the bonding. Description of the Drawings

[0112] Further advantages, features and details of the present invention result from the following description of the preferred embodiments and from the figures. The figures are schematically shown in the following figures:

[0113] Figure 1a Cross-sectional view of the first embodiment of the bonding apparatus

[0114] Figure 1b According to Figure 1a Top view of the first substrate holder and the second substrate holder of the first embodiment of the apparatus

[0115] Figure 2a Top view of the first and second substrate holders of the first embodiment of the apparatus having the first rotation axis A-A

[0116] Figure 2b Top view of the first and second substrate holders of the first embodiment of the apparatus having the second rotation axis B-B

[0117] Figure 3a Cross-sectional view of the first embodiment of the apparatus having a hinge with a mechanically implemented axis of symmetry, where the loading pins of the first and second receiving means are in the loaded state

[0118] Figure 3b Cross-sectional view of the first embodiment of the apparatus having a hinge with a mechanically implemented axis of symmetry after loading the first and second substrates onto the loading pins

[0119] Figure 3c Cross-sectional view of the first embodiment of the apparatus having a hinge with a mechanically implemented axis of symmetry after receiving the first and second substrates on the first and second substrate holders

[0120] Figure 4 Cross-sectional view of the apparatus in the loaded state and the bonding position before bonding the first and second substrates

[0121] Figure 5a Cross-sectional view of the apparatus in the first method step of an exemplary method for bonding

[0122] Figure 5b Cross-sectional view of the apparatus in the second method step

[0123] Figure 5c Cross-sectional view of the apparatus in the third method step

[0124] Figure 5d Cross-sectional view of the apparatus in the fourth method step

[0125] Figure 5e Cross-sectional view of the apparatus in the fifth method step

[0126] Figure 5f Cross-sectional view of the apparatus in the sixth method step

[0127] Figure 6a Cross-sectional view of the third embodiment of the device in the first method step

[0128] Figure 6b Cross-sectional view of the third embodiment of the device in the second method step

[0129] Figure 6c Cross-sectional view of the third embodiment of the device in the third method step

[0130] Figure 7a Cross-sectional view of the fourth embodiment of the device in the first method step

[0131] Figure 7b Cross-sectional view of the fourth embodiment of the device in the second method step

[0132] Figure 7c Cross-sectional view of the fourth embodiment of the device in the third method step

[0133] Figure 8a Cross-sectional view of the fifth embodiment of the device in the first method step

[0134] Figure 8b Cross-sectional view of the fifth embodiment of the device in the second method step

[0135] In the figures, identical components or components with the same function are denoted by the same reference numerals. Detailed description of the preferred embodiments

[0136] Figure 1a Schematic non-to-scale view showing a cross-section of the 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. The two substrates 3, 4 are loaded in the same way from above. The construction features of the receiving devices 1, 2, such as the substrate fixing elements 5, the openings 6 for the loading pins and other surface features 7 of the receiving devices, are implemented symmetrically such that after rotation of the second receiving device, the first receiving device 1 and the second receiving device 2 are opposite each other and mirror-symmetrical.

[0137] The fixing elements 5 serve to fix the substrates 3, 4 at the receiving devices 1, 2. In a particularly preferred embodiment, the substrates 3, 4 are electrostatically fixed.

[0138] Figure 1b Shows a top view of the first and second receiving devices 1, 2 of the first embodiment of the device according to Figure 1a of the device.

[0139] Two substrates 3, 4 are loaded from above in the same way. All features 5, 6, 7 of the receiving devices 1, 2 that have a direct or indirect influence on the substrate shape are implemented symmetrically for the first substrate 3 and for the second substrate 4, such that the first and second substrates 3, 4 exhibit the same stress pattern caused by the receiving devices before bonding. These features particularly include the substrate fixing elements 5, the openings 6 for the loading pins, and other surface features 7 of the receiving devices, such as openings for measuring devices, sensors, or circuitry.

[0140] It is decisive for the device to load the two substrates 3, 4 in a symmetric orientation in a situation where gravity has the same influence on the first receiving device 1 and on the second receiving device 2. The two substrates 3, 4 are loaded from above into their respective receiving devices (loading position, loading state).

[0141] Here, at least one of the receiving devices 1, 2 is mounted in a swingable manner such that after the loading of the substrates 3, 4, the surfaces of the substrates to be bonded are brought into the bonding position relative to each other.

[0142] Figure 2a A top view of the first and second receiving devices 1, 2 of a first embodiment of the device with a first swing axis A - A is shown. In the first embodiment according to Figure 2a , the second receiving device 2 moves relative to the first receiving device 1 by a rotational movement via a swing hinge (10, not shown) having the swing axis A - A.

[0143] The loading pins and their openings 6 in the holding surfaces of the receiving devices 1, 2 are symmetrically arranged on the same radius on the two receiving devices 1, 2.

[0144] Figure 2b A top view of the first and second receiving devices 1, 2 of a second embodiment of the device with a second rotation axis B - B is shown.

[0145] For bonding, the receiving devices now swing 180° (axis A - A or B - B) upside - down with the substrates, or the two receiving devices rotate 90° towards each other with the substrates, such that they also meet symmetrically. If the receiving devices swing 180° upside - down with the substrates, a rotational movement or a combination of rotational - translational movements can be envisaged. The receiving devices 1, 2 can rotate about any axis. Thus, the 180° rotation of the receiving devices with the substrates can occur about a mirror axis in the X - Y plane of the receiving devices or as a rotational movement via a swing hinge.

[0146] Figures 3a to 3c A cross - sectional view of a first embodiment of a device with a hinge 10 having a mechanical implementation of a symmetry axis or swing axis A - A is shown. First, two chamber sections 12, 13 as shown in Figures 3a to 3c are opened. In the according toFigure 3a In the first process step, the loading pins 8 of the first and second receiving devices 1, 2 are positioned in the loading positions. In accordance with Figure 3b In the second process step, the first substrate 3 and the second substrate 4 are loaded onto the loading pins 8 of the receiving devices 1, 2. Under the influence of the same gravity, the loading of the two substrates 3, 4 is carried out, i.e., the two substrates 3, 4 are loaded from above. The back sides of the substrates 3, 4 are brought to the holding surfaces of the receiving devices 1, 2 by means of the loading pins 8 and fixed by electrostatic force. Here, the substrates 3, 4 are fixed with high positioning accuracy and high holding force. Electrodes are preferably embedded in the receiving devices 1, 2 and can be implemented as monopolar or bipolar. The implementation of the electrodes is axisymmetric with respect to the two substrates 3, 4.

[0147] The receiving devices or substrate holders 1, 2 are positioned and loaded such that the two substrates 3, 4 are received in the same way on the symmetrically configured receiving devices 1, 2 before contact or before bonding, such that the substrates come into contact and bond with the respectively corresponding regions in a stress pattern 9. For example, due to the contact with the loading pins 8 and due to the deformation of the wafer between the loading pins 8 under the influence of gravity, regions with a stress pattern 9 are generated.

[0148] In accordance with Figure 3c In the third process step, the first substrate 3 and the second substrate 4 are received in the receiving device and fixed with a fixing member 5.

[0149] If the substrates 3, 4 are only placed on the loading pins 8 as shown in Figure 4 , then gravity causes a change with respect to the flat surface, where in an open swing device, the corresponding regions of the first and second substrates with a stress pattern due to the loading of the substrates on symmetrically implemented loading pins are highlighted. This change in the contact region 9 is symmetric for the two substrates 3, 4 in the bonding device 11, such that at the time of bonding or after bonding, the corresponding stress patterns are located in the regions 9' placed one above the other. Thus, the same stress patterns exist symmetrically around the bonding interface in the substrate stack.

[0150] Here, at least one of the receiving devices 1, 2 is mounted in a swingable manner. The possibility of moving the second chamber section 13 relative to the first chamber section 12 lies in implementing a rotational movement between the chamber sections 12, 13 via a swing hinge 10 in accordance with Figure 5b .

[0151] Figures 5a to 5f The process steps of a first embodiment of a device and a method for bonding 11, preferably permanently bonding, in particular fusion bonding, of a first substrate 3 to a second substrate 4 are shown, including:

[0152] a) A bonding chamber 11, which consists of a first chamber section 12 and a second chamber section 13,

[0153] b) Receiving devices 1, 2 for receiving and fixing substrates 3, 4, wherein the receiving devices 1, 2 are configured for approaching and contacting the substrates.

[0154] First, two chamber sections 12, 13 as shown in Figure 5a are opened and the substrates 3, 4 are electrostatically fixed. Here, electrodes for generating an electrostatic holding force for fixing the substrates are inserted into the electrostatic receiving device.

[0155] The ultra-flat electrostatic receiving devices 1, 2 have a holding surface implemented to be particularly flat in order to electrostatically press the substrates 3, 4 and ensure a highly stable hold. The electrostatic attraction causes the holding force to be evenly distributed over the entire surface. The flatness of the receiving devices 1, 2 is better than the thickness variation and nano-topography of the substrates 3, 4. Here, due to the pretreatment step, the substrates 3, 4 may already have mechanical stress, which may cause distortion in the non-fixed state.

[0156] After loading and fixing the substrates 3, 4, the closing of the bonding chamber 11 according to the Figure 5b embodiment is carried out by the swinging of the second chamber section 13 around the swinging hinge 10. For this purpose, a motor drive (not shown) may be provided. After the second chamber section 13 has swung, according to Figure 5c , the peripheral wall 12u of the first chamber section 12 lies on the peripheral wall 13u of the second chamber section 13. Sealing is carried out via an annular seal 14 on the upper side of the peripheral wall 12u of the first chamber section 12.

[0157] The bonding device 11 can advantageously be operated in a vacuum or also under ambient pressure with an inert gas. The substrates 3, 4 are first adjusted with high precision for precise alignment and are kept separated during the evacuation process according to Figure 5c . Alignment is preferably carried out by an alignment facility and with the aid of alignment marks. Adjustment and approaching are known to a person skilled in the art and are not described in further detail.

[0158] Contact is carried out especially after the alignment of the two substrates. In the next process step according to Figure 5d , the second upper substrate 4 with the receiving device 2 for bonding within the bonding chamber 11 is moved translationally onto the first lower substrate 3 with the moving device 15 and the distance-changing member 16. The approaching and adjustment are carried out in a controlled manner.

[0159] 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 design of the device.

[0160] In accordance with Figures 5a to 5fIn the bonding scheme, substrates 3 and 4 are laid flat on top of each other. For structures in the nm range with precise superposition, the reproducibility of the flatness of the substrates 3 and 4 to be bonded is very important. The holding force of the ultra-flat capacitive holding devices 1 and 2 with a holding surface implemented as particularly flat enables conformal planarization of the substrates 3 and 4.

[0161] In a first preferred embodiment, after contact, the two substrates 3 and 4 are each held fixed at the first and second holding devices 1 and 2 during bonding. If the two substrates 3 and 4 are held fixed at their respective holding devices 1 and 2 during bonding, the thickness change (TTV, total thickness variation in English) and stress pattern of the substrates 3 and 4 have little influence on the bonding result. Here, a parallel and spontaneous (1:1) connection of the two substrates 3 and 4 fixed to the holding device is achieved, where no deformation of the substrates 3 and 4 occurs at the front of the bonding.

[0162] In a second preferred embodiment, after contact, the second upper substrate 4 is held fixed to the holding device 2, especially during bonding. If the second upper substrate 4 is held fixed to the holding device 2 during bonding, a smaller deformation of the upper substrate 2 occurs at the front of the bonding due to the higher stiffness of the fixed substrate 2.

[0163] The idea is based on the fact that the two substrates 3 and 4 are identically accommodated on symmetrically configured holding devices 1 and 2 before contact or bonding, such that the stress at the substrates caused by accommodation and loading onto the holding devices 1 and 2 is minimized and the substrates 3 and 4 are contacted and bonded in respectively corresponding stress patterns. Since the substrates 3 and 4 are fixed to the symmetrically configured ultra-flat capacitive holding devices 1 and 2 during bonding, the distortion in the bonding interface is additionally minimized.

[0164] In an embodiment, the holding devices 1 and 2 are configured such that the substrates 3 and 4 can be heat-treated, especially in segments, by heating elements.

[0165] Pressure application causes the substrate surface to approach the boundary layer along the contact surface.

[0166] If required, the substrates can be pretreated before bonding, especially before alignment. Examples of pretreatment are plasma treatment or amorphization of at least one of the two substrate surfaces. The bonding chamber and the processing chamber for amorphization or plasma treatment can be part of a (vacuum-pumped) cluster facility.

[0167] Figure 5e Shows a completed bonding process. The substrates 3 and 4 are in contact over the entire surface and the bonding process is completed. After disconnecting the upper fixation, the second upper holding device 2 is moved upwards translationally inside the bonding chamber 11, where the moving device 15 and the distance-changing member 16 return to according toFigure 5c In the position. The substrate stack 17 remains on the first lower receiving device 1.

[0168] As Figure 5f shown, the device 11 for engagement is opened again by a rotational movement between the chamber sections 12, 13 via the swing hinge 10 of the second chamber section 13, and the substrate stack 17 can be removed after releasing the fixation of the first lower receiving device. Releasing the engagement stack 17 from the substrate holder enables the substrate stress to be reduced in the same way. This relaxation process results in minimized residual stress.

[0169] Here, at least one of the receiving devices 1, 2 is mounted in a swingable manner. The receiving devices 1, 2 can rotate about any axis here. Thus, rotating one of the receiving devices by 180° with respect to the substrate can be carried out not only as a rotational movement via the Figures 5a to 5e swing hinge according to, but also as a rotation about the mirror axis in the X-Y plane of the receiving devices 1, 2.

[0170] A further possibility is that after the rotation, the chamber sections can be moved translationally towards or away from each other's other chamber sections. For example, movement by means of a lifting cylinder can be envisaged. In addition, side guides can also be provided additionally. A combined rotational-translational movement via, for example, a four-bar kinematic system can also be envisaged.

[0171] In a further embodiment according to Figures 6a to 6c , the two receiving devices 1, 2 are positioned one above the other such that Figure 6a two substrates 3, 4 are loaded in a situation where gravity has the same effect on the first and second receiving devices 1, 2. After the substrates 3, 4 are fixed, the second upper receiving device 2 with the fixed substrate 4 rotates 180° upside down about its own rotation axis B-B according to Figure 6b . After the rotation, the two receiving devices 1, 2 face each other mirror-symmetrically, such that all features of the receiving devices 1, 2, such as the fixing elements 5, the openings 6 for the loading pins, and other surface features 7, are positioned symmetrically.

[0172] In a further embodiment according to Figures 7a to 7c , the two receiving devices 1, 2 are positioned side by side such that also in this embodiment, Figure 7a two substrates 3, 4 are loaded in a situation where gravity has the same effect on the first and second receiving devices 1, 2. A combination of rotational-translational movements is carried out here such that the first and second receiving devices 1, 2 meet symmetrically.

[0173] The two receiving devices 1, 2 can rotate about any axis and are then brought into an adjusted symmetric position by X / Y / Z translation (and rotation).

[0174] In a preferred embodiment, it is provided that the substrate and / or the receiving devices 1, 2 can be moved with at least three degrees of freedom, preferably with at least four degrees of freedom, more preferably with at least five degrees of freedom, and optimally with all six degrees of freedom. This achieves an improved mobility of the substrate and / or the receiving devices.

[0175] In accordance with Figure 8a and Figure 8b In a further embodiment, the two receiving devices 1, 2 are positioned side by side with respect to one another such that also in this embodiment, in accordance with Figure 8a two substrates 3, 4 are loaded in a situation where gravity has the same effect on the first and second receiving devices 1, 2. For the engagement, the two receiving devices 1, 2 are rotated 90° towards one another with respect to the substrates such that they also meet symmetrically in accordance with Figure 8b The second receiving device 2 is rotated 90° via the axis of rotation B-B, and the first receiving device 1 is rotated 90° via the axis of rotation B'-B'. After the adjustment and the approach, the substrates 3, 4 are engaged over their entire surface in this vertical plane.

[0176] List of reference signs

[0177] 1 First receiving device, first substrate holder

[0178] 2 Second receiving device, second substrate holder

[0179] 3 First substrate

[0180] 4 Second substrate

[0181] 5 Fixing element, first fixing member, second fixing member, fixing member

[0182] 6 Opening for the loading pin

[0183] 7 Other features of the receiving device

[0184] 8 Loading pin

[0185] 9, 9' Areas where stress patterns occur during substrate loading

[0186] 10 Swing hinge, swing axis

[0187] 11 Device for engagement, engagement device

[0188] 12 First chamber section

[0189] 13 Second chamber section

[0190] 12u, 13u Peripheral wall

[0191] 14 Annular seal

[0192] 15 Mobile device (drive member)

[0193] 16 Distance changing member, proximity member

[0194] 17 Substrate stack

[0195] Axis of rotation A-A

[0196] Axes of rotation B-B, B’-B’

Claims

1. A method for bonding substrates, the method having the following steps, in particular having the following process: i) providing a first substrate (3) on a first substrate holder surface of a first substrate holder (1) and providing a second substrate (4) on a second substrate holder surface of a second substrate holder (2), ii) in a loaded state, fixing the first substrate (3) to the first substrate holder (1) and fixing the second substrate (4) to the second substrate holder (2), iii) positioning the second substrate holder (2) relative to the first substrate holder (1) 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 loaded state, the first substrate holder surface and the second substrate holder surface are arranged at the same angle relative to gravity, and wherein in the loaded state, the first substrate holder surface and the second substrate holder surface are aligned in the same direction relative to gravity, and wherein when the first substrate (3) and the second substrate (4) are fixed, the same holding force is applied to the first substrate (3) and to the second substrate (4) respectively.

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

3. The method according to at least one of the preceding claims, wherein the angle is a vertical angle.

4. The method according to at least one of the preceding claims, wherein when fixed in the loaded state, the same holding force is provided at the first substrate (3) and the second substrate (4) in respective corresponding patterns such that the patterns of the holding forces are aligned in the bonding position.

5. The method according to at least one of the preceding claims, wherein the fixing of the first substrate (3) and the second substrate (4) is carried out simultaneously and within the same time period.

6. The method according to at least one of the preceding claims, wherein the positioning includes a 180° swing of the second substrate holder (2).

7. The method according to at least one of claims 1 to 5 of the preceding claims, wherein the positioning includes a respective 90° swing of the first substrate holder (1) and the second substrate holder (2) towards each other.

8. The method according to at least one of the preceding claims, wherein the same holding force is maintained during bonding.

9. An apparatus (11) for bonding substrates (3, 4), the apparatus at least comprising: a) a first substrate holder (1) having a first substrate holder surface, a1) a first fixing member (5) for fixing the first substrate (3) to the first substrate holder surface, b) a second substrate holder (2) having a second substrate holder surface, b1) a second fixing member (5) for fixing the second substrate (4) to the second substrate holder surface, c) a positioning member (10, 15, 16) for positioning the second substrate holder (2) relative to the first substrate holder (1), wherein the device (11) is transferable into a loading state, in which the first substrate holder surface and the second substrate holder surface are arranged at the same angle with respect to gravity, and wherein in the loading state, the first substrate holder surface and the second substrate holder surface are aligned in the same direction with respect to gravity, and wherein the first fixing member (5) and the second fixing member (5) are configured to each provide the same holding force for fixing in the loading state.

10. The 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 parallel to each other and offset side by side.

11. The device (11) according to at least one of the preceding claims, wherein the second substrate holder is pivotable from the loading state into an engagement position.

12. The device (11) according to at least one of the preceding claims, wherein the positioning member includes a pivot hinge (10).

13. The device (11) according to at least one of the preceding claims, wherein the first fixing member (5) and the second fixing member (5) are electrostatic fixing members (5).

14. The device (11) according to at least one of the preceding claims, wherein in the engagement position, the first substrate holder (1) and the second substrate holder (2) form an engagement chamber, preferably a liquid-tight engagement chamber.

15. The device (11) according to at least one of the preceding claims, wherein the first fixing member (5) and the second fixing member (5) are configured to provide the same holding force at least before being transferred into the engagement position.

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