Method and apparatus for bonding substrate

Abstract

To provide a substrate holder, an apparatus, and a method for bonding two substrates together.SOLUTION: A substrate holder (1') for bending a substrate (7) has a fixed plate (3) for mounting the substrate (7) and bending means (6) for bending the fixed plate (3), and the fixed plate (3) is formed such that the bending of the substrate (7) can be adjusted to a target.SELECTED DRAWING: Figure 2b

Description

[Technical field]

[0001] The invention describes a substrate holder, an apparatus and a method for bonding two substrates together according to the respective independent claims.

[0002] The prior art shows many different substrate holders. In particular in fusion bonding, substrate holders are becoming more and more complex and sophisticated in order to keep up with the ever-higher demands of the bonding process. WO 2012083978 describes a substrate holder that can compensate for local and / or global distortions by active control using thermocouples, piezoelectric elements or fluidic elements. The substrate holder of WO 2013023708 shows the possibility of contaminating the rear side of the substrate as little as possible and a method for releasing the substrate by targeted control of the fixing elements. WO 2017162272 shows a substrate holder, which has a number of fixing zones. These fixing zones are in particular distributed symmetrically over the substrate holder and can be switched individually. WO 2018028801 shows a method in which the substrate is fixed not radially symmetrically but uniaxially and also released with the uniaxial curvature. WO2014191033 discloses a substrate holder, the surface of which is curved or can be curved, so that the substrate fixed thereon has a non-uniform curvature before and / or during bonding. WO2014191033, particularly on page 9, mentions that the adjustable curvature is not a uniform curvature, i.e. a non-uniform curvature. With each new generation of substrate holder, better and faster bonding results are obtained. However, the bonding result can still be optimized by further technical improvements. In the meantime, it has been found that the two substrate holders are crucial in a bonding process. The control of the successive bonding waves, especially in a fusion bond, is crucial for a proper bonding result. The control is also influenced by the technique for bending the substrates involved in the bonding process.

[0003] One of the problems in the prior art is that not only the surface on which the substrate is fixed is curved in a well-defined manner, but also other components of the substrate holder are mechanically affected and in particular curved during the bending process. In terms of construction technology, substrate holders in solid constructions, i.e. in constructions consisting of very thick and solid parts with a high bending resistance, are also possible. However, most substrate holders must be constructed small and compact, i.e. relatively delicately, and therefore necessarily have a relatively low bending resistance. This low bending resistance can then lead to a slight undesirable elastic deformation of some parts of the substrate holder that should not be curved. This elastic deformation and curvature reacts against the surface of the clamping plate, the surface on which the substrate is fixed, and thus affects the curvature of the substrate. It should be mentioned here that the resulting elastic deformations naturally only occur in the nanometer or micrometer range, but elastic deformations of this order are already sufficient to negatively react on the clamped substrate and its curvature.

[0004] It is possible to form a curved uniform clamping surface on the substrate holder by milling, grinding, polishing, etching and lapping processes, so that the substrate clamped on this clamping surface also has a uniform curvature. However, this clamping surface is static and the curvature cannot be changed. On the other hand, it is possible to configure a substrate holder that can indeed have a curved clamping surface, as in WO 2014191033. However, with such substrate holders, it has proven extremely difficult to target-adjust, and in particular to keep constant, the curvature of the clamping surface and thus the curvature of the substrate as a function of position. In particular, adjusting the uniform curvature of the substrate is extremely difficult and can never be performed or at least cannot be performed reproducibly.

[0005] The problem to be solved by the present invention is to eliminate the disadvantages of the prior art and, in particular, to provide an improved substrate holder, an improved device and an improved method for bonding.

[0006] This problem is solved by the features of the respective independent claims. Advantageous refinements of the invention are defined in the dependent claims. The scope of the invention also includes all combinations of at least two of the features described in the description, the claims and / or the drawings. In the stated numerical ranges, values ​​lying within the stated limits are to be regarded as disclosed as limits and can be claimed in any combination.

[0007] Of technical importance is in particular the configuration of the substrate holder such that it provides a targetably adjustably, in particular uniformly, curvature of the substrate.

[0008] The present invention relates to a substrate holder for bending a substrate, the substrate holder comprising: - a fixing plate for mounting the circuit board; - bending means for bending the fixing plate; having The fixing plate is related to the substrate holder, which is shaped so that the curvature of the substrate or the fixing plate is adjustable to a desired extent.

[0009] The fixing plate has a front side, on which the substrate is attached, and a rear side opposite to the front side. The fixing plate has a width, a length and a thickness. In another embodiment, the fixing plate is designed radially symmetrically, in which case it is defined via a radius and a thickness. The width and the length extend in the direction of the fixing plate surface at the front side of the fixing plate, on which the substrate is fixed. The thickness extends perpendicular to the fixing plate surface.

[0010] Preferably, the fixation plate has a varying thickness, i.e. the thickness is not equal at each location, and the fixation plate is thicker at at least one location of the fixation plate than another location. Specific configurations / preferred forms are described below.

[0011] Preferably, it is specified that the uniform curvature of the fixed plate or substrate is adjustable.

[0012] Preferably, it is specified that the fixed plate is pivotally supported.

[0013] "Target adjustable" means that the value of the curvature can be determined. "Uniform" means that when the value of the curvature is determined, the curvature is equal or constant within very small tolerances at every location on the fixture plate or substrate.

[0014] Preferably, the rear side of the clamping plate is shaped so that a uniform curvature of the clamping plate occurs or a uniform curvature of the clamping plate or the clamping plate front side and thus the substrate, and thus an equal curvature at every position, is adjustable.

[0015] As a preferred embodiment, and as an independent aspect of the invention, the substrate holder is configured such that reaction forces and / or moments generated upon bending of the fixing plate can be compensated for by at least one compensation means.

[0016] As an independent aspect, the present invention provides a substrate holder for bending a substrate, comprising: - a fixing plate for mounting the circuit board; - bending means for bending the fixing plate; having The present invention relates to a substrate holder, in which reaction forces generated upon bending of the fixing plate can be compensated for by at least one compensation means.

[0017] The invention further relates to an apparatus, in particular a bonding apparatus, comprising at least one substrate holder according to the invention.

[0018] The present invention further provides a method for bonding two substrates together, comprising the steps of: - mounting a first substrate on a first, in particular inventive, substrate holder; - mounting a second substrate on a second, in particular inventive, substrate holder; - aligning the substrates (7) with respect to one another; - bending at least one of the substrates (7); - contacting the substrates together; having The present invention relates to a method for adjusting the curvature of at least one of the substrates or the fixing plate to a desired value, preferably uniform.

[0019] Advantageously, as an independent aspect of the invention, when bending the fixed plate, moments and / or reaction forces generated in the remaining components are compensated, but preferably are never or only slightly transmitted to the fixed plate in the first place.

[0020] Accordingly, another independent aspect of the invention is a method for bonding two substrates together, comprising the steps of: - mounting a first substrate on a first, in particular inventive, substrate holder; - mounting a second substrate on a second, in particular inventive, substrate holder; - aligning the substrates with respect to each other; - bending at least one of the substrates; - contacting the substrates together; having The present invention relates to a method in which moments and / or reaction forces generated in the remaining components when bending the fixing plate are compensated, but preferably are not transferred at all or only slightly to the fixing plate from the start. Preferably, this is achieved by the use of supports which transfer as little or only very little reaction forces and / or moments as possible.

[0021] It is preferably specified that the fixing plate is thicker in the center than at the edges, which advantageously allows a particularly uniform curvature of the fixing plate and the substrate to be achieved. It is preferably specified that the fixing plate is formed so as to become thinner towards the edges. It is preferably specified that the fixing plate is formed symmetrically with respect to the center.

[0022] A key feature of the invention is that the substrate can be given a curvature that can be adjusted to a particular target. It is possible to generate a curvature that has a constant, i.e. uniform, radius of curvature in particular. The generation of a constant curvature is the most preferred approach according to the invention for forming a bond. With the inventive extension of the embodiment, the reaction forces that always necessarily occur according to Newton's third axiom are not absorbed by the components of the substrate holder that are connected to the plate that fixes the substrate via a mechanical connection, but by a second plate, which is a compensation plate. This second plate is located inside the substrate holder and is supported freely (pivotally) together with the first plate. This means that ideally no or only very little moments are transmitted.

[0023] "Bend" means a deviation in the shape of an object from its starting unloaded condition, and particularly a deviation characterized by a change in the position of the object's centerline or center plane under load.

[0024] Curvature is most simply described as the inverse of the radius of curvature for a point on a curve. The radius of curvature at a point is the radius of the osculating circle to the curve that passes through this point. The larger the radius of curvature, the less curvature there is.

[0025] In the semiconductor industry, the term "bow" still exists. It means the deviation of the center point of the mid-plane of a free, unclamped substrate, especially a wafer, from the mid-plane of a reference plane. A reference plane is simply a horizontal, flat surface on which the substrate rests. The exact definition is found in the now defunct ASTM F534 standard.

[0026] In the following text, bending lines and bending surfaces are used as synonyms, since in particular the substrate holder according to the invention is preferably shown in cross section in the drawings and therefore only bending lines can be seen instead of bending surfaces. It is self-evident to the person skilled in the art that two-dimensional surfaces of three-dimensional objects generally have bending surfaces and that only bending lines can be seen or drawn in cross sections of such bending surfaces.

[0027] In a particularly preferred embodiment of the substrate holder and method according to the invention, the substrate is bent with a constant curvature, i.e. the curvature is equal at every position of the substrate. In this case, the curvature is also called uniform. A constant curvature of the substrate produces a particularly optimal joint between the two substrates. Such a curvature can be achieved in particular if the reaction forces and / or moments do not act on the fixing plate via another component. Preferably, this is achieved by the use of supports that do not allow any or only very little transmission of reaction forces and / or moments.

[0028] In general, the curvature may vary across the substrate. However, preferably, the curvature is radially symmetric, i.e. it only varies with the radial position, measured from the center of the substrate, and not with the angle. Substrates that form anisotropic curvature, i.e. substrates with a curvature that generally varies with the radial position and with the angle, have the property of forming a saddle-shaped surface. However, it can be assumed that the stiffness of the fixing plate according to the invention, in particular the stiffness of the entire substrate holder according to the invention, is sufficiently greater than the stiffness of the substrate, and that the substrate is fixed to the fixing plate by the fixing elements, so that the substrate contacts the fixing plate at all points. In this case, residual stresses may also occur in the substrate due to the forcing conditions that do not allow the occurrence of a curvature in the form of a saddle-shaped surface.

[0029] The radius of curvature of the plate or substrate is greater than 0.01 m, preferably greater than 0.1 m, more preferably greater than 1 m, most preferably greater than 10 m, and most preferably greater than 100 m.

[0030] If the radius of curvature along the bending line or surface is not constant, the absolute value of the difference between the maximum and minimum radii of curvature is less than lm, preferably less than 0.1 m, even better less than 0.01 m, most preferably less than 0.001 m, and most preferably less than 0.0001 m.

[0031] The bow is less than 1000 μm, preferably less than 500 μm, more preferably less than 100 μm, most preferably less than 10 μm, and most preferably less than 1 μm.

[0032] Preferably, the embodiment according to the invention and the method according to the invention calculates the surfaces or bend lines in the cross-sectional shape according to the following mathematical function: Elliptical segments, preferably ○ Circle category Parabola · Hyperbola Sine, specifically the numeric range [0,Pi] Negative hyperbolic cosine The substrate may be curved such that it can be described by one of the functions:

[0033] In this case, the bending surface is determined in particular by the following function: Ellipsoid division, especially ○ Circular surface division (Kreisschalenabschnitt) Paraboloid · Hyperboloid can be explained by one of the functions:

[0034] Thus, in general, a bend surface is a surface that results from the rotation of a bend line.

[0035] Of all the possible bent line or surface shapes mentioned above, shapes with uniform curvature, ie circular sections or circular curved surface sections, are most preferred.

[0036] This favorable adjustability of the uniform curvature is achieved by a precisely defined and precisely manufactured cavity-side plate surface of the fixing plate. Due to the defined and precisely manufactured manufacturing of the cavity-side plate surface of the fixing plate, the fixing surface of the fixing plate and thus the final shape of the substrate are precisely defined. In particular, calculation methods, preferably finite element methods, are used to determine the shape of the cavity-side plate surface of the fixing plate. The shape of the cavity-side plate surface of the fixing plate can be described in particular by one of the above-mentioned mathematical functions.

[0037] However, the actual shape of the cavity-facing plate surface to be produced depends on many factors, namely: - Bending resistance of the fixing plate - Bending resistance of the entire board holder - the bending means used, in particular - Fluid pressure used when using the fluid - others It depends on.

[0038] The idea according to the invention is in particular to precisely manufacture only one rigid cavity-side plate surface of the fixing plate and then to adjust any curvature relative to the fixing surface of the fixing plate and thus to the substrate by means of a controllable adjustment means with the cavity-side plate surface, in particular so that the curvature in the substrate becomes uniform, i.e. is equal at all positions.

[0039] According to the invention, this method of adjustably bending the substrate to a desired position by providing a precisely manufactured cavity-side plate surface of the fixing plate is further assisted and improved in that at least one compensation means is used to reduce or completely prevent mechanical reactions during bending of the fixing plate.

[0040] It is preferably specified that the at least one compensation means comprises in particular a bendable compensation plate.

[0041] Preferably, it is specified that the compensation plate is capable of bending in a direction opposite to the bending of the fixed plate.

[0042] It is preferably specified that an intermediate chamber, preferably sealed, can be formed between the fixing plate and the compensation plate.

[0043] It is preferably specified that the bending of the fixing plate and the compensation plate can be caused by a fluid which can be forced into the intermediate chamber.

[0044] It is specified that the intermediate chamber can preferably be formed by fluid means, mechanical adjustment means and / or electrostatic forces.

[0045] It is preferably specified that the fixed plate and the compensation plate are connected to one another, preferably via a pivotable support.

[0046] It is preferably specified that the fixing plate and the compensation plate are preferably connected to the remaining components of the substrate holder via pivotable supports.

[0047] It is preferably specified that only a small moment, preferably no moment, can be transmitted via the peripheral edge of the fixing plate and / or the compensation plate. The transmitted moment is less than 1 Nm, preferably less than 10 -3 Nm or less, more preferably 10 -5 Nm, most preferably less than 10 -7 Nm, most preferably 0 Nm.

[0048] It is preferably specified that the compensation plate has in its outer region a closed groove, preferably over its entire circumference, the distance between this groove and the outer periphery of the compensation plate being less than 50 mm, preferably less than 40 mm, more preferably less than 30 mm, most preferably less than 20 mm and most preferably less than 10 mm.

[0049] It is preferably specified that the compensator plate has in its outer region a sealing means, preferably a sealing ring, which is preferably arranged in a particularly circumferential closed seat, which allows the generation of pressures greater than 1 bar, preferably greater than 1.2 bar, more preferably greater than 1.5 bar, most preferably greater than 2 bar, most preferably greater than 2.5 bar.

[0050] It is preferably specified that the at least one compensation means comprises a pivotable support of the fixing plate, i.e. a pivotable support which is not capable of transmitting reaction forces and / or moments from other components of the substrate holder according to the invention to the fixing plate is even considered as a compensation means in the sense of the present disclosure.

[0051] Another preferred embodiment of the invention is based on the idea of ​​constructing a substrate holder with two plates that can be bent in two opposite directions. The bending is then effected by the use of adjustment means (hereinafter also referred to as bending means), in particular a fluid that is forced into an intermediate chamber of both plates. The use of two plates ensures that the reaction forces generated by the deformation of the first plate do not act on the underside of the substrate holder holding the first plate, but on the second plate incorporated according to the invention. This eliminates the harmfully influencing reaction of the reaction forces on the substrate holder and thus the substrate. Instead, the reaction forces are absorbed (compensated) by the second plate that can be freely deformed in the direction of the substrate holder. Furthermore, the invention describes an apparatus, in particular a bonding apparatus, in which a substrate holder according to the invention is used on at least one side of the apparatus.

[0052] Substrate Holder In the following, the substrate holder according to the invention is described in detail. It is particularly important to understand all the design technical means by which an adjustable, in particular uniform, curvature can be generated. Furthermore, design technical means are disclosed by which the forces and moments acting on the upper plate and their avoidance can be understood.

[0053] All substrate holders according to the invention have a fastening surface, which is in particular part of a fastening plate, which has a cavity-side surface located opposite the fastening surface, which is preferably shaped according to a mathematical function. The shape of the cavity-side surface produces a well-defined, in particular uniform, curvature by the use of adjustment elements.

[0054] The normal component of the force acting on a lever generates a moment at the point of application of the lever. In order to simplify the description of the invention, in the following text we always refer only to forces, even though the forces generated also generate moments. The sum of the moments and the sum of the forces must be zero. All results obtained on this basis are hereby considered to be disclosed.

[0055] The substrate holder according to the invention is preferably always designed in such a way that a force causes the upper first plate to bend and the resulting reaction forces are not absorbed via the components supporting or holding the plate, but via compensation components provided specifically for this purpose, in particular the lower second plate. In this case, the lower second plate can be mechanically connected not at all or only very weakly to the remaining components of the substrate holder, since otherwise the lower second plate would also be mechanically connected to the upper first plate from the start and would transmit moments. A characteristic feature is that no moments are transmitted at all, or at least only very little, in particular via the periphery of both plates. This means that the plates and any further mechanical elements required must form as ideal a movable support as possible, in particular a pivot as ideal as possible, at their periphery.

[0056] Therefore, in a particularly preferred embodiment, the substrate holder according to the invention consists of at least two plates which are flexibly, in particular pivotably, supported.

[0057] In a first particular preferred embodiment according to the invention, the plates themselves are the adjustment elements which are placed at an electric potential and generate surface charges, which in turn generate electrostatic forces for bending the plates, thereby generating the bending of the plates. In this case, the plates are electrically insulated from one another. Such insulation may consist in that the surface of the substrate at the periphery consists of or is coated with a dielectric material.

[0058] Further partial regions of the plates, in particular those at the surfaces of the plates facing each other, are electrically conductive, i.e. electrically conducting. In particular the entire plate is electrically conducting except for its insulating edge region. Both plates may be placed at a particularly positive potential with respect to earth. It is also possible to place both plates at a negative potential with respect to earth. Due to the same polarity of charge on both plates, they repel each other. If the plates were not electrically insulated at their periphery, charges would be transferred to the outer surfaces of both plates. There would be no charge on the inner surfaces of both plates facing the cavity, which would result in a field-free cavity.

[0059] Correspondingly, the plates will not be able to bend outwards according to the invention. The electrical insulation of both plates, which is brought to an electric potential, is therefore a key inventive aspect of this very particular embodiment. In a particular extension of the inventive embodiment, the mutually electrically insulated regions of both plates may be electrically conductive, and each of these electrically conductive regions may be placed individually and independently of the other electrical regions at a suitably defined electric potential. This allows the repulsion of the plates to be locally and precisely adjusted. The finer the division of the electrically conductive regions, the more precise the spatial resolution of the adjustable curvature.

[0060] In a second particularly preferred embodiment according to the invention, both plates are curved by a mechanical adjustment element located between the plates. This mechanical adjustment element may be electrically and / or pneumatically and / or hydraulically actuated. Particularly preferably, a piezoelectric stack is used as the adjustment means. In particular, the use of several such mechanical adjustment elements, in particular in symmetrical positions, between the plates is also possible. In this case, preferably again, each of the adjustment means may be adjusted independently of all the other adjustment means.

[0061] In a third particular and particularly preferred embodiment according to the invention, the plates are curved by a fluid introduced, in particular pumped, into the intermediate chamber. This fluid is a liquid, a liquid mixture, a gas or a gas mixture. Most preferably, the fluid is air. This results in a particularly symmetrical curvature of both plates.

[0062] The inventive idea behind the particular inventive embodiment is, in particular, that the lower plate can be freely extended and that no forces and / or moments are transmitted to the remaining components of the substrate holder, which in turn causes the substrate holder to be deformed, and in particular that the curvature of the first plate, the fixing plate, and thus of the substrate fixed thereto, should not be altered by mechanically reacting moments or mechanically reacting forces.

[0063] plate The substrate holder according to the invention comprises at least one plate which is specially shaped, in particular at the rear side.In a particular embodiment according to the invention, the substrate holder comprises two plates.

[0064] There are two basic types of plates: fixing plates and compensation plates. Fixing plates are plates on which the substrate to be curved is fixed. Compensation plates are plates which take on the inventive effect of absorbing the forces and / or moments of the adjustment means and thus prevent sufficient mechanical feedback to further components of the substrate holder. In particular the support of the plate also plays an important role in preventing the transmission of forces and / or moments from further components to the fixing plate.

[0065] The space between both plates is called the cavity. Every plate has a cavity-facing plate surface and a second plate surface located opposite the cavity-facing plate surface and which is used in different ways depending on the function of the plate.

[0066] The cavity-side plate surface is always the surface facing the cavity between the two plates. In a particularly preferred embodiment of the invention, the cavity-side plate surface is specially shaped. In particular, the cavity-side plate surface of the plate for fastening the substrate has a well-defined shape that positively influences the bending properties of the plate and thus of the substrate.

[0067] If a distinction must be made between the cavity-side plate surface of the fixing plate and the cavity-side plate surface of the compensating plate, these are correspondingly called the cavity-side fixing plate surface and the cavity-side compensating plate surface. The cavity-side plate surface can be shaped in any way, but is preferably described according to the functions already used in describing the bending lines or bending surfaces. All functions disclosed for the bending lines and / or bending surfaces are therefore considered to be disclosed for the description of the cavity-side plate surface.

[0068] The plate surface that fixes the substrate is called the fixed plate surface, and therefore can only be present on the fixed plate at any one time.

[0069] The surface of the fixing plate has fixing means for fixing the substrate. The fixing means are in particular 1. Mechanical fastening means, especially 1.1. Clamp 2. Vacuum fastening means, especially 2.1. Has individually controllable vacuum paths 2.2. Having interconnected vacuum paths 3. Electrical fastening means, especially 3.1. Electrostatic fastening means 4. Magnetic fastening means 5. Adhesive fastening means, especially 6. Gel-Pak fasteners and / or 7. Fixing means with an adhesive, particularly controllable, surface It is.

[0070] The fixing means can in particular be pneumatically and / or hydraulically and / or electronically controllable.

[0071] Vacuum fastening means are a preferred type of fastening means. They preferably consist of a number of vacuum channels which enter the surface of the substrate holder. These vacuum channels are preferably individually controllable. In technically more feasible applications, several vacuum channels are joined together to form vacuum zones which are individually controllable and can therefore be evacuated or flooded. However, each vacuum zone is independent of the other vacuum zones. This allows the construction of individually controllable vacuum zones. The vacuum zones are preferably configured in an annular manner. This allows targeted, radially symmetric fastening and / or release of the substrate from the substrate holder, in particular from the inside to the outside.

[0072] In a further refinement, the annularly divided vacuum zones are further divided along the annular circumference, whereby each vacuum zone is divided into a plurality of vacuum zones along the annular circumference, such an embodiment being disclosed in detail in WO2017162272.

[0073] In a quite particularly preferred embodiment according to the invention, so-called pins (in English: pins) are located on the clamping plate surface. Such a construction is described in WO 2015113641. With these pins, the substrate is not placed over its entire surface, but contacts the clamping surface mostly only with the pins. This, on the one hand, reduces contamination, and, on the other hand, makes it possible to create a vacuum along the entire clamping surface of the clamping plate in the intermediate spaces between the pins. In particular, the pins are grouped into all the mentioned vacuum zones. This embodiment is likewise disclosed in detail in WO 2017162272. In particular, the grouping of pins with vacuum conductors distributed on the clamping plate and forming, in particular, individually controllable vacuum zones is hereby explicitly disclosed and constitutes an important improvement of the substrate holder according to the invention in relation to the original inventive idea.

[0074] Although the above-mentioned use of vacuum zones as described in WO2017162272, which in particular can be evacuated or flooded through at least one vacuum hole in each case, is regarded as an advantageous and important special extension of the idea according to the invention, in the following text the substrate holder according to the invention will be described with a fixing method in which an extremely small number of vacuum holes are located in the fixing plate surface, in particular centrally.

[0075] In an embodiment according to the invention where the substrate is fixed by vacuum fixing means, a vacuum is generated between the substrate and the fixing plate surface, preferably via a number of vacuum holes. These vacuum holes are drilled along a circle whose center point is the center of the fixing plate. This allows the use of a substrate holder with multiple pins (English: pins chuck) to position one of the pins exactly in the center of the fixing plate. This has a clear positive effect on the bonding result. A precise description and illustration is given in the description and drawings of the drawings. It is therefore a further feature according to the invention to disclose a substrate holder with multiple pins, which has one of the pins directly below the position where both substrates first come into contact with each other. Such a pin below the contact point of both substrates mechanically stabilizes the substrate at this point. Since it is from this point that the bonding wave starts to advance, the coincidence of such a pin with the contact point along a line normal to the fixing plate surface is important for a stable start of the bonding wave. The effect of the pin directly below the contact point is to specify that it prevents the substrate from being pushed through at this point below the contact point, thus creating a stable mechanical starting condition.

[0076] The second plate is a compensation plate. This compensation plate preferably has a circumferential closed groove in the outer area. This groove serves to ensure that the curvature of the lower plate does not continue completely to its edge, but mainly to this groove. That is to say, the groove stops the curvature before it reaches the edge. This further reduces and further reduces small reactions that may still occur on the substrate holder. If the support of the compensation plate at the edge is so good that no moment is transferred, the corresponding groove may be omitted. Nevertheless, such an arrangement of the groove is always advantageous in nature. The compensation plate preferably also supports a sealing means, in particular a sealing ring. The sealing means is preferably located in a small circumferential closed seat.

[0077] equipment All substrate holders according to the invention may be used in an installation according to the invention for fixing the lower substrate and / or the upper substrate. Particularly preferably, the substrate holder according to the invention is used in a bonding installation for fixing the lower substrate and the upper substrate. This results in a particularly improved and optimized control of the bonding, in particular the fusion bonding. The use of the substrate holder according to the invention as the upper substrate holder replaces the bending pin (English: pin) that has long been used in particular in the semiconductor industry, which causes a central bending of the substrate.

[0078] A preferred embodiment of the installation according to the invention consists in using a substrate holder according to the invention for clamping an upper substrate and a substrate holder according to the invention for clamping a lower substrate.

[0079] A specific inventive arrangement consists of an inventive substrate holder under the invention and any other substrate holder other than the inventive substrate holder, where the upper substrate holder preferably has a bending means known in the prior art, in particular a bending pin or a nozzle through which a fluid flows, which causes the upper substrate to bend accordingly.

[0080] In a special extension of the installation according to the invention, an alignment device (English: aligner) is also located at the jointer.

[0081] If the substrate is transparent to electromagnetic radiation of a certain frequency, then preferably an observation device is present in order to analyze the course of the bonding wave, which not only makes it possible to observe the bonding process, to influence it and in case of an emergency to interrupt it, but also to analyze the properties of the bonding wave as a function of different parameters, which serves to further improve the substrate holder according to the invention.

[0082] In a particular expansion of the installation according to the invention, the following modules are provided: Purification module Grinding module Etching modules, especially ○ Due to chemical etching ○ Due to physical etching Plasma Module Coating module may be connected in particular vacuum-tightly to the installation according to the invention.

[0083] Such modules are preferably part of a so-called cluster installation, in which there are vacuum-tight gates between the modules. Preferably, gate valves are also located between some of the aforementioned modules. The modules may be arranged in any way with respect to one another. There is preferably a central module inside which is located a robot that can transfer the substrates between the individual modules. Such a centrally designed cluster is called a radial cluster. It is also possible for the modules to be arranged in series.

[0084] method The method according to the invention comprises in particular the following steps, which do not necessarily have to be performed in the order presented:

[0085] A first inventive process step involves the loading and fixing of a first substrate onto a first substrate holder, which is preferably a substrate holder according to the invention.

[0086] A second inventive process step involves the loading and fixing of a second substrate onto a first substrate holder, which is preferably a substrate holder according to the invention.

[0087] In a third process step according to the invention, both substrates are aligned with each other. This alignment is preferably performed based on alignment marks located on the substrate surface of the substrate. Corresponding alignment installations, which may also be part of the installation according to the invention, in particular the bonding chamber, are disclosed in US 6214692, WO 2015082020, WO 2014202106 and WO 2018041326.

[0088] In a fourth process step according to the invention, the substrates are roughly brought into close proximity with each other.

[0089] In a fifth process step according to the invention, a targeted and particularly uniform adjustment of the inventive curvature of at least one of the two substrates by the substrate holder according to the invention is performed. It is also possible to bend both substrates, in particular to bend both substrates by the substrate holder according to the invention. In this case, a particularly uniform curvature is possible due to the specially shaped rear side of the fixing plate. During the targeted and adjustable curvature, contact of the two substrates and thus the generation of a bonding wave occurs at some point.

[0090] For completeness, it is further noted that: if one of the two substrate holders is not the substrate holder according to the invention, this may have a conventional deformation element known in the prior art for deforming the substrate. In this case, the substrate holder which is not the substrate holder according to the invention naturally has all the negative consequences that are excluded from the inventive idea hereof. However, it is also possible to use a conventional substrate holder according to the prior art on the other side, since only one single substrate holder according to the invention is already sufficient to produce a good joint. In this case, the deformation element is preferably a simple bending pin, which should not be confused with the significantly smaller pin of a pin substrate holder (English: pins chuck).

[0091] In a sixth process step according to the invention, a targeted, in particular controlled, continuous release of the substrate from the substrate holder takes place. In this case, it is particularly advantageous if at least the upper substrate holder is not only a substrate holder according to the invention, but also the clamping means can be locally targeted and controlled at its clamping surface. This is possible in particular if the clamping means are grouped into several zones, in particular vacuum zones, as disclosed in detail in WO2017162272.

[0092] A key inventive aspect of the inventive method is therefore the targeted and adjustably bending of the substrate by the inventive substrate holder, which is only possible due to the lack of mechanical feedback to the substrate in combination with a targeted and controllable release of the substrate from its fixed surface during the advancement of the bonding wave.

[0093] Further advantages, features and details of the invention are apparent from the following description of preferred embodiments and from the drawings. [Brief description of the drawings]

[0094] [Figure 1a] FIG. 1 illustrates an initial state of a substrate holder in the prior art. [Figure 1b] FIG. 2 shows the final state of the substrate holder in the prior art. [Figure 2a] FIG. 2 shows the initial state of the substrate holder according to the invention without a compensation plate. [Figure 2b] FIG. 2 shows the final state of the substrate holder according to the invention without the compensation plate. [Figure 3a] FIG. 2 shows an initial state of an extended substrate holder according to the invention with a compensation plate. [Figure 3b] FIG. 2 shows the final state of the extended substrate holder according to the invention with compensation plate. [Figure 4] FIG. 1 shows a first inventive embodiment of a substrate holder according to the invention with a compensation plate. [Diagram 5] FIG. 2 shows a second inventive embodiment of a substrate holder according to the invention with a compensation plate. [Figure 6a] 13A and 13B show side and top views of a third preferred embodiment of a substrate holder with a compensation plate according to the present invention in an initial state. [Figure 6b] FIG. 13 is a side view of a third preferred embodiment of a substrate holder with compensation plate according to the present invention in a final state.

[0095] In the drawings, identical components or components having the same functions are given the same reference numerals.

[0096] The following two drawings, and the corresponding drawings showing two states of the substrate holder in the prior art, are kept as schematic as possible to explain the basic concept. They are as simple as possible explanations and principle diagrams, and do not claim to be complete.

[0097] In Fig. 1a, a schematic diagram of an initial state of a substrate holder 1 according to the prior art is shown. The fixing plate surface 3f of this substrate holder 1 can be curved. The substrate holder 1 has a fixing plate 3. This fixing plate 3 can be supported, in particular at the periphery, in particular via a plate support 2. In the illustrated case, the plate support 2 is in particular a fixed support. This fixed support is also not particularly designed to be pivotable. Of course, it is also possible for the fixing plate 3 to be directly mechanically connected to the remainder of the substrate holder 1. What is important is the presence of a surface described as a fixing plate surface 3f that can be curved. The fixing plate 3 is therefore configured and / or supported in such a way that it can be curved.

[0098] In particular, on the plate 3 there are positioned substrate fastening means 4 which are able to fasten a substrate 7 to the plate 3. How this substrate fastening means 4 is controlled is not important for an understanding of the prior art device and will not be described in detail here.

[0099] In Fig. 1b, a schematic diagram of the final state of the substrate holder 1 according to the prior art is shown. In this particular case, the substrate holder 1 is curved convexly as seen from the outside, because an overpressure is formed in the cavity 5. This overpressure is generated by the inflow of a gas or gas mixture having an overpressure relative to the surrounding atmosphere into the cavity 5 via an adjustment means 6, in the particular case an opening, a valve or a nozzle. Alternatively, the adjustment means 6 can be a mechanical adjustment means. In the illustrated configuration, the use of an overpressure is thus merely described by way of example.

[0100] In this situation, several fundamental problems arise. The first problem is that the curvature of the fixing plate surface 3f and thus of the substrate 7 is generally non-uniform, i.e. the curvature varies depending on the position. This is generally an undesirable situation. A non-uniform curvature is only difficult to perceive in a drawing. This problem is particularly related to the fact that the support 2 is configured as a fixed support, i.e. the number of degrees of freedom is too low or even zero.

[0101] A further problem in the prior art is that the support 2 is usually designed to transmit reaction forces and / or moments to the fixed plate 3. In particular, the support 2 in the prior art is not made pivotable, so in the prior art the support 2 usually transmits moments.

[0102] A further problem is that any adjustment element 6 involved in the deformation of the clamping plate 3 always generates a reaction force. Expressed generally physically, according to Newton's third axiom, a reaction force, i.e. a corresponding counter pressure, which bends the substrate holder 1 in another direction, occurs in a normalized manner on the surface. This undesired bending of the substrate holder 1 reacts in particular on the plate support 2, thereby affecting both the bending properties of the clamping plate 3 and also the bending of the substrate 7 fixed to the clamping plate 3.

[0103] This relates to the above-mentioned problem that in the prior art the plate support 2 is designed in such a way that it transmits reaction forces and / or moments. Even when the end state is reached in terms of control technology, absolutely undesirable reactions can be detected across the substrate holder 1, since measurements have shown that this leads to a deterioration of the joining result to be achieved. It should be explicitly stated and emphasized that the described mechanical feedback influence is of course independent of the type of adjustment means 6, in the illustrated exemplary case, of the openings through which the gas or gas mixture flows, or of the presence of a cavity 5.

[0104] The adjustment means 6 can equally well be a mechanical adjustment means, a pin, a piezo stack, a bellows or any other adjustment means which can bend the fixing plate 3. In these cases, the corresponding cavity 5 does not have to be present. Basic physical laws dictate that a mechanical feedback to the substrate holder is always desired.

[0105] The following drawing descriptions or figures showing two respective states of two substrate holders 1', 1'' according to the invention are kept as schematic as possible in order to explain the basic concepts. They are as simple as possible explanations and principle drawings and do not claim to be complete. Therefore, embodiments according to the invention are explained in detail in the further figures.

[0106] The idea according to the invention is again illustrated by a device using a fluid to generate an overpressure in the cavity 5 which causes a bending of the fixing plate 3 to which the substrate 7 is fixed. It is emphasized again that the idea according to the invention is not bound to the use of a fluid and / or to the cavity 5. Equally well, the embodiment according to the invention may be realised by mechanical, pneumatic, electrical or piezoelectric adjustment means 6, as will be further illustrated and described later in specific embodiments.

[0107] FIG. 2a shows a schematic diagram of an initial state of a substrate holder 1' according to the invention, which can produce at least a uniform curvature. As a starting point, the substrate holder 1' has such a high bending resistance that the illustrated configuration does not yet produce any mechanical feedback problems, which are eliminated or reduced as will be explained in more detail in the following figures. This increase in bending resistance can be achieved very simply, for example, by making some components of the substrate holder 1', in particular the entire substrate holder 1', thicker. What is important is the support 2', which is made in such a way that no or only very little reaction forces and / or moments are transmitted to the fixing plate 3. In particular, the shape of the cavity-side plate surface 3h is selected in such a way that a well-defined, in particular uniform curvature is generated by the subsequent curvature of the fixing plate 3.

[0108] 2b shows a schematic diagram of the final state of the substrate holder 1' according to the invention, which allows at least a uniform curvature to occur. Even if the substrate holder 1' according to the invention has a higher bending resistance, the substrate holder 1' must nevertheless be easily curved when using the adjustment element 6, even if only to a small extent. However, this curvature is relatively small due to the relatively large bending resistance. Nevertheless, forces and / or moments occur which would be transferred to the fixing plate 3 without the support 2'.

[0109] By means of the special support 2', a well-defined and particularly uniform curvature can be produced in the fixing surface 3f and thus in the substrate 7, since possible reaction forces and / or moments are not transferred at all or are transferred to a lesser extent to the fixing plate 7. The support 2' additionally assists in the formation of a uniform curvature for components already formed in a solid structural form. In the special case, to adjust the curvature, adjustment means 6 are used which are openings, nozzles or valves through which a fluid, in particular a gas mixture, preferably air, is forced.

[0110] The use of a fluid makes the embodiment according to the invention with a specially shaped cavity-side plate surface 3h of particular importance: the use of a fluid exerts a uniform and isotropic pressure on the cavity-side plate surface 3h, which allows a force distribution to be assumed along the cavity-side plate surface 3h, in which the force is always normal to the cavity-side plate surface 3h.

[0111] This assumption makes it particularly simple to calculate a suitable shape of the cavity-side plate surface 3f by means of a numerical simulation, in particular the finite element method, in order to obtain a desired, in particular uniform, curvature at the fixing surface 3f and thus at the fixed substrate 7. By means of such a specific shape of the cavity-side plate surface 3f, the construction of a uniform curvature of the fixing plate surface 3f and thus of the substrate 7 is improved even further.

[0112] 3a shows a schematic diagram of an initial state of a further improved substrate holder 1" according to the invention, which allows at least a uniform curvature to be produced and further minimizes the detrimental effects of mechanical feedback on the plate holder 2'. Such an improvement according to the invention is particularly advantageous when the substrate holder 1" is of a relatively thin design and has a very low bending resistance.

[0113] In this case, mechanical reactions are no longer negligible and should be at least reduced, preferably completely eliminated, by the improved embodiment according to the invention. The advantages of the specially shaped cavity-side plate surface 3h are no longer explained in the illustrated configuration. The substrate holder 1'' has a fixing plate 3 and a compensation plate 3', which are supported relative to one another via a plate support 2'. Both plates 3, 3' are constructed and / or supported in such a way that they can be curved.

[0114] For the sake of completeness, the plate 3 does not necessarily have to be an individual component in theory, but may be part of the substrate holder 1'. All that matters is the presence of one fixing plate surface 3f. However, this may lead to edge conditions that make it almost impossible to produce a constant curvature of the fixing plate surface 3f. The most preferred embodiment according to the invention therefore specifies that the fixing plate 3 forms an independent component. The advantage of the invention therefore lies in the use of a compensation plate 3' in particular.

[0115] Therefore, in the description of the following figures, an embodiment according to the invention will be described with the respective preferred configuration technical solutions of the two plates. In particular, the substrate fastening means 4 is located on the fastening plate 3, by means of which the substrate 7 can be fastened to the fastening plate 3. How the substrate fastening means 4 is controlled is not important for the understanding of the device and will not be described in detail here. In the following figures, it is shown how the substrate fastening means 4 formed as a vacuum fastening means is controlled.

[0116] In Fig. 3b a schematic diagram of the final state of a further improved substrate holder 1'' according to the invention is shown. By means of the adjusting means 6, in the particular case shown an opening, a valve or a nozzle, a fluid is forced into the cavity 5, which causes a bending of both plates 3, 3'. In contrast to the prior art shown in Fig. 1a, no bending of the fixing means 2 or of other parts of the substrate holder 1' takes place and thus no additional moment acts via the fixing means 2 on the fixing plate 3 and on the substrate 7 fixed to this fixing plate 3. The bending of the fixing plate 3 is therefore only effected by the effect of the adjusting means 6.

[0117] The compensation plate 3' can therefore be considered as a kind of "sacrificial plate". Its only role is to prevent or at least minimize the action of forces on the remaining components of the substrate holder 1'. In the specific case, the plates 3, 3' must be sealed, especially at their periphery. The illustration of the individual parts, especially the sealing parts, is omitted in this principle drawing for reasons of clarity. However, sealing is dealt with in more detail in the subsequent figures of the most preferred embodiment.

[0118] In the following figures, different embodiments according to the invention are individually treated in more detail and are shown.

[0119] 4 shows a first preferred embodiment according to the invention, in which both plates 3, 3' are placed at potentials having the same sign, in particular the same numerical value. In order to prevent both plates 3, 3' from forming a self-closed conductive body, the plates 3, 3' must be electrically insulated from each other at their contact points by an electrical insulator 14. Otherwise, according to the laws of physics, all charges on the cavity-side plate surfaces 3h, 3h' forming the cavity 5 would migrate outwards.

[0120] A self-closed body would form a Faraday cage and would only allow the accumulation of charge on the outer surface. The electrical insulator 14 ensures that the two plates 3, 3' do not form, electrostatically speaking, a self-closed conductive body, but rather a conductive body in each case. This allows the generation of charge on the substrate surfaces forming the cavity 5. Correspondingly, the charges located on the cavity-side plate surfaces 3h, 3h' or both plates 3, 3' themselves together with the necessary current circuit 15 form the adjustment means 6'.

[0121] In FIG. 5 a second preferred embodiment according to the invention is shown, in which the adjustment means 6'' is located between both plates 3, 3'. The adjustment means 6'' can be, for example, a mechanical adjustment element that can be controlled electrically and / or pneumatically and / or hydraulically. It is also possible to use an electrically controllable piezo stack. The adjustment means 6'' can also be two very powerful electromagnets, which are electrically controlled to generate two magnetic fields that repel each other so that both plates 3, 3' are moved away from each other. Also possible is an embodiment in which the two plates are placed at the same potential and repel each other due to their electrostatic charge.

[0122] In Fig. 6a, a third preferred embodiment according to the invention is shown in a side view, a detailed view and a plan view in the starting state, which is the embodiment according to the invention shown in Fig. 3a and 3b in greater detail. This arrangement comprises (i) a specially made support 2' which can transmit as little or only slightly the reaction forces and / or moments as possible and (ii) a compensation plate 3'.

[0123] The importance of this embodiment lies in the fact that in order to bend both plates 3, 3' a fluid is used with an isotropic, i.e. uniform force acting on both plates 3, 3', in particular on the fixed plate 3, based on a static pressure. All the features described in figure 6a may also be used in the substrate holders previously dealt with in particular in figures 3 and 4. However, due to the importance of this embodiment all the features are detailed in this figure.

[0124] Preferably, the peripheral portion of the fixed plate surface 3f of the fixed plate 3 is supported or contacted via the plate support projection 2'v, and the plate surface 3h of the fixed plate 3 is supported or contacted via a seal member 12, which preferably rests on the lower compensation plate 3', in particular on the plate support base 2'p. The seal member 12 seals the peripheral portions of the plates 3, 3' from each other, while nevertheless allowing bending of both plates 3, 3'.

[0125] It should be mentioned once again that the curvature is extremely slight, i.e. the radius of curvature is very large. Any point on the surface of one of the two plates 3, 3' is offset in the z-direction by only a few nanometers, a few micrometers, or in the rarest cases, a few millimeters. Such a slight curvature also makes it possible to keep such an elaborate arrangement mechanically stable. In particular, this allows the plate support protrusions 2'v to be formed very precisely.

[0126] The substrate 7 is fixed by the substrate fastening means 4. In the particular case, the drawing shows that a part of the substrate fastening means 4 penetrates the cavity 5. This part is in particular made extendable. It can be, for example, a hose, a feed tube or any other conduit capable of evacuating the area between the substrate 7 and the fastening plate 3. In particular, there are a number of outlet openings of the substrate fastening means 3. These are in particular arranged symmetrically around a centre. This makes it possible that a pin 11 can be present in the centre of the fastening plate 3, which has a positive effect on the joining properties.

[0127] In Fig. 6b a third preferred embodiment according to the invention is shown in a side view in the final state. An adjustment means 6, in this particular case an off-centre opening, valve or nozzle, pumps the fluid into the cavity 5. The fixed substrate 3 is curved according to the invention. The curvature of the compensation plate 3' preferably takes place all the way around to a groove 13 machined in the compensation plate 3'.

[0128] This ensures that the curvature is concentrated in the central part of the compensating plate 3' and that less moments and / or forces act mechanically on the plate support 2' (see the enlarged view in FIG. 6a), which in this case consists in particular of the plate support projection 2'v, the sealing element 12 and the plate support base 2'p. By this further design improvement according to the invention, mechanical feedback to the fixed plate 3 is prevented completely or is minimized to a negligible extent. [Explanation of symbols]

[0129] 1,1',1'',1''' PCB holder 2,2' Plate support 2'v Plate support protrusion 2'p Plate support base 3 Fixing plate 3' Compensation plate 3f Fixing plate surface 3h,3h' Hollow chamber side plate surface 4 Board fixing means 5 Hollow chamber / intermediate chamber 6,6',6'' Adjustment means / curving means 7 Substrate 11 Multiple pins 12 Seal members, especially seal rings 13 Groove 14 Electrical insulators 15 Current circuit

Claims

1. A substrate holder (1', 1'', 1''', 1'''') for bending a substrate (7), - a fixing plate (3) for mounting said substrate (7); bending means (6, 6', 6'') for bending said fixing plate (3); having A substrate holder (1', 1'', 1''', 1''''), characterized in that the fixing plate (3) is formed in such a way that the curvature of the substrate (7) is target-adjustable.

2. The substrate holder (1', 1'', 1''', 1'''') of claim 1 , wherein the thickness of the fixing plate (3) varies.

3. The substrate holder (1', 1'', 1''', 1'''') according to at least one of the preceding claims, wherein the fixing plate (3) is supported so as to be pivotable.

4. The substrate holder (1', 1'', 1''', 1'''') according to at least one of the preceding claims, wherein the uniform curvature of the substrate (7) is adjustable.

5. The substrate holder (1', 1'', 1''', 1'''') according to at least one of claims 1 to 4, wherein the rear side of the fixing plate (3) is shaped in such a way that a uniform curvature of the fixing plate (3) occurs.

6. The substrate holder (1', 1'', 1''', 1'''') according to at least one of claims 1 to 5, wherein reaction forces generated when bending the fixing plate (3) can be compensated by at least one compensation means (3'), in particular a bendable compensation plate (3').

7. The substrate holder (1', 1'', 1''', 1'''') according to at least one of the preceding claims, wherein the fixing plate (3) is thicker in the centre than at the edges.

8. The substrate holder (1', 1'', 1''', 1'''') according to at least one of the preceding claims, wherein the fixing plate (3) is tapered towards its edges.

9. The substrate holder (1', 1'', 1''', 1'''') according to at least one of the preceding claims, wherein the fixing plate (3) is formed symmetrically with respect to a centre.

10. An apparatus, in particular a bonding apparatus, comprising at least one substrate holder (1', 1'', 1''', 1'''') according to at least one of the claims 1 to 9.

11. A method for bonding two substrates (7) together, comprising the steps of: - mounting a first substrate on a first substrate holder (1', 1'', 1''', 1''''), in particular according to any one of claims 1 to 9; - mounting a second substrate on a second substrate holder (1', 1'', 1''', 1''''), in particular according to any one of claims 1 to 9; - aligning said substrates (7) with respect to one another; - bending at least one of said substrates (7); - bringing said substrates (7) into contact with each other; having A method, characterized in that the curvature of at least one of said substrates (7) is tailored.

12. 12. The method according to claim 11, further comprising uniformly adjusting the curvature of at least one of the substrates (7).

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