Method and apparatus for bonding substrates

Abstract

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

Description

[Technical Field]

[0001] The present 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 describes many different substrate holders. In particular, in fusion bonding, substrate holders are becoming increasingly complex and sophisticated in order to meet the increasingly high demands of the bonding process. International Publication No. 2012083978 describes a substrate holder capable of compensating for local and / or global distortions through active control using thermocouples, piezoelectric elements, or fluidic elements. The substrate holder of International Publication No. 2013023708 describes the possibility of minimizing contamination of the backside of the substrate and a method for releasing the substrate by targeted control of the clamping elements. International Publication No. 2017162272 describes a substrate holder having multiple clamping zones. These clamping zones are particularly symmetrically distributed across the substrate holder and can be individually switched. International Publication No. 2018028801 describes a method for clamping a substrate uniaxially, rather than radially symmetrically, and also releasing it by bending in that uniaxial direction. WO 2014191033 discloses a substrate holder. The surface of the substrate holder is curved or can be curved, so that a substrate fixed to the surface has a non-uniform curvature before and / or during bonding. WO 2014191033, particularly on page 9, states that the adjustable curvature is not uniform, i.e., non-uniform. With each new generation of substrate holder, better and faster bonding results have been achieved. However, these bonding results can still be optimized through further technical improvements. Meanwhile, it has been found that the two substrate holders are crucial in a single bonding process. Control of the successive bonding waves, especially in a single fusion bonding process, is crucial for proper bonding results. Control is also influenced by the technique for bending the substrates involved in the bonding process.

[0003] One of the problems with 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. While construction technology allows for substrate holders with solid structural forms, i.e., structures consisting of very thick, solid components with high bending resistance, most substrate holders must be small and compact, i.e., relatively delicately constructed, and therefore necessarily have relatively low bending resistance. In this case, this low bending resistance can lead to undesirable slight elastic deformation of some parts of the substrate holder that should not be curved. This elastic deformation and bending react against the surface of the fixing plate, on which the substrate is fixed, and thus affect the bending of the substrate. It should be noted here that the resulting elastic deformation naturally occurs only in the nanometer or micrometer range, but elastic deformations of this order are already sufficient to negatively affect the fixed substrate and its bending.

[0004] By milling, grinding, polishing, etching, and lapping processes, a substrate holder can be formed with a curved, uniform clamping surface, 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, as in WO 2014191033, it is possible to construct a substrate holder that can actually curve the clamping surface. However, with such substrate holders, it has proven extremely difficult to target, 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 a uniform curvature of the substrate is extremely difficult and is never possible, or at least cannot be done reproducibly.

[0005] The problem to be solved by the present invention is to eliminate the drawbacks 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 each independent claim. Advantageous refinements of the invention are set forth in the dependent claims. The scope of the invention also includes all combinations of at least two of the features set forth in the description, claims and / or drawings. In the case of stated numerical ranges, values ​​lying within the stated limits are also to be considered as disclosed limits and can be claimed in any combination.

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

[0008] 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 fixation plate; and The fixing plate is related to the substrate holder, which is configured 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 the front side. The fixing plate has a width, a length, and a thickness. In another embodiment, the fixing plate is designed to be radially symmetrical, in which case it is defined via a radius and a thickness. The width and 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 at 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 fixation plate is pivotally supported.

[0013] "Targetable" 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 surface of the fixing plate is shaped so that a uniform curvature of the fixing plate occurs or a uniform curvature of the fixing plate or the fixing plate front surface and thus the substrate, and thus an equal curvature at every position, can be adjusted.

[0015] In a preferred embodiment, but also 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] In 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 fixation plate; and The present invention relates to a substrate holder, in which the 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: - attaching a first substrate to a first, in particular inventive, substrate holder; - attaching a second substrate to a second, in particular inventive, substrate holder; - aligning the substrates (7) with each other; - bending at least one of the substrates (7); - contacting the substrates together; and 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 level, preferably uniform.

[0019] Preferably, as an independent aspect of the invention, when bending the fixation plate, moments and / or reaction forces generated in the remaining components are compensated for, but preferably are not transmitted to the fixation plate at all or are transmitted only to a small extent to the extent possible from the start.

[0020] Accordingly, another independent aspect of the present invention is a method for bonding two substrates together, comprising the steps of: - attaching a first substrate to a first, in particular inventive, substrate holder; - attaching a second substrate to 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; and The present invention relates to a method in which moments and / or reaction forces that are generated in the remaining components when bending the fixing plate are compensated for, but are preferably not transmitted at all or only transmitted to a small extent to the fixing plate from the start. Preferably, this is achieved by using supports that transmit as little or as 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 present invention is the ability to impart a curvature to the substrate that can be tailored to a particular purpose. In particular, it is possible to generate a curvature with a constant, i.e., uniform, radius of curvature. Generating a constant curvature is the most preferred approach for forming a bond according to the present invention. In the inventive extension of the embodiment, the reaction forces that always arise according to Newton's third axiom are not absorbed by the substrate holder components connected to the plate that fixes the substrate via a mechanical connection, but by a second plate, the compensating plate. This second plate is located inside the substrate holder and is freely (pivotably) supported together with the first plate. Ideally, this means that no or only very little moment is transmitted.

[0023] "Bow" means a deviation in the shape of an object from its starting unloaded state, particularly 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 reciprocal of the radius of curvature at 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] The term "bow" still exists in the semiconductor industry. It refers to the deviation of the center point of the mid-plane of an unclamped, free 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 precise definition is found in the now-defunct ASTM F534 standard.

[0026] In the following text, bending lines and bending surfaces are used as synonyms, especially since 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 clear to a 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 on the substrate. In this case, the curvature is also called uniform. A constant curvature of the substrate creates a particularly optimal bond between two substrates. Such curvature can be achieved, in particular, when reaction forces and / or moments do not act on the fixing plate via another component. Preferably, this is achieved by using a support that allows no or only very little transmission of reaction forces and / or moments.

[0028] Generally, the curvature may vary across the substrate. However, preferably, the curvature is radially symmetric, i.e., it varies only with radial position, measured from the center of the substrate, and not with angle. Substrates that exhibit anisotropic curvature, i.e., substrates with curvature that generally varies with radial position and angle, have the property of forming a saddle-shaped surface. However, since the rigidity of the fixing plate according to the invention, and in particular the rigidity of the entire substrate holder according to the invention, is sufficiently greater than the rigidity of the substrate, and the substrate is fixed to the fixing plate by the fixing elements, it can be assumed that the substrate contacts the fixing plate at all points. In this case, residual stresses may occur in the substrate due to forcing conditions that do not allow the occurrence of 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 radius of curvature is less than 1 m, 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 present invention and the method according to the present invention calculates the surfaces or bend lines in the cross-sectional shape according to the following mathematical function: Elliptical segments, preferably ○ Yen classification Parabola · Hyperbola Sine, specifically the numeric range [0,Pi] Negative hyperbolic cosine The substrate can 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: Ellipsoidal divisions, 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 resulting 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 the precisely defined and precisely manufactured cavity-side plate surface of the fixing plate. Due to the precisely defined and precisely manufactured cavity-side plate surface of the fixing plate, the final shape of the fixing surface of the fixing plate and thus the substrate is precisely defined. To determine the shape of the cavity-side plate surface of the fixing plate, calculation methods, preferably finite element methods, are used. The shape of the cavity-side plate surface of the fixing plate can be described, in particular, by one of the mathematical functions mentioned above.

[0037] However, the actual shape of the cavity-side plate surface of the fixing plate to be produced depends on many factors, namely: - Bending resistance of the fixing plate - Bending resistance of the entire board holder - the curvature 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, by means of a controllable adjustment means, to adjust any curvature with the cavity-side plate surface relative to the fixing surface of the fixing plate and thus to the substrate, in particular so that the curvature in the substrate is uniform, i.e. equal at all positions.

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

[0040] Preferably, it is specified that the at least one compensation means comprises, in particular, a bendable compensation plate.

[0041] Preferably, the compensation plate is specified to be able to bend 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 fixed plate and the compensation plate.

[0043] Preferably, it is specified that the bending of the fixed plate and the compensation plate can be caused by a fluid that can be forced into the intermediate chamber.

[0044] It is preferably specified that the intermediate chamber can 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 compensating plate. The transmitted moment is less than 1 Nm, preferably 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 the entire periphery, the distance between this groove and the outer periphery of the compensation plate being less than 50 mm, preferably less than 40 mm, even 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, and most preferably greater than 2.5 bar.

[0050] Preferably, it is specified that the at least one compensation means comprises a pivotable support of the fixing plate, i.e. a pivotable support which is not able to transmit 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 present invention is based on the idea of ​​constructing a substrate holder with two plates that can bend in two opposite directions. The bending is achieved by the use of an adjustment means (hereinafter also referred to as a bending means), in particular a fluid forced into the intermediate chambers of both plates. The use of two plates ensures that the reaction force generated by the deformation of the first plate does not act on the underside of the substrate holder holding the first plate, but on the second plate incorporated according to the present invention. This eliminates the harmful effects of the reaction force on the substrate holder and thus the substrate. Instead, the reaction force is absorbed (compensated) by the second plate, which is free to deform in the direction of the substrate holder. Furthermore, the present invention describes an apparatus, in particular a bonding apparatus, in which the substrate holder according to the present invention is used on at least one side of the apparatus.

[0052] Substrate Holder In the following, the substrate holder according to the invention will be described in detail. It is particularly important to understand all the design technical measures that allow for the generation of an adjustable, in particular uniform, curvature. Furthermore, the design technical measures that allow for the understanding of the forces and moments acting on the upper plate and their avoidance will be disclosed.

[0053] All substrate holders according to the invention have a clamping surface, which is in particular part of a clamping plate. The clamping plate has a cavity-side surface located on the side opposite the clamping surface. Preferably, this cavity-side surface is shaped according to a mathematical function. The shape of the cavity-side surface can be precisely defined by the use of adjustment elements, resulting in a particularly uniform curvature.

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

[0055] The substrate holder according to the present invention is preferably always configured so that a force bending the upper first plate and the resulting reaction force are absorbed not via the components supporting or holding the plate, but via compensation components specifically provided for this purpose, in particular the lower second plate. In this case, the lower second plate may not be mechanically connected 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 and transmit moments. A distinctive feature is that no moments are transmitted, or at least only very little, via the peripheries of both plates. This means that the plates and any other necessary mechanical elements must form as ideal a movable support, in particular a pivot, as close as possible to the periphery.

[0056] Therefore, in a particularly preferred embodiment, the substrate holder according to the invention consists of at least two plates which are supported so as to be flexible, in particular so as to be pivotable.

[0057] In a first particularly preferred embodiment of the present invention, the plates themselves are the adjusting elements that are placed at an electric potential and generate a surface charge, which generates an electrostatic force to bend the plates, thereby causing the plates to bend. In this case, the plates are electrically insulated from one another. Such insulation can be achieved by the surface of the substrate at its periphery being made of or coated with a dielectric material.

[0058] Other partial regions of the plates, in particular those on 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 relative to earth. It is also possible to place both plates at a negative potential relative to earth. Charges of the same polarity on both plates repel each other. If the plates were not electrically insulated at their peripheries, charges would migrate to the outer surfaces of both plates. There would be no charges on the inner surfaces of both plates facing the cavity, resulting in a field-free cavity.

[0059] Correspondingly, the plates would no longer be able to bend outward in accordance with the present invention. Therefore, the electrical isolation of both plates, which is brought to an electrical potential, is a key inventive aspect of this very particular embodiment. In a particular extension of the inventive embodiment, the electrically isolated regions of both plates may be electrically conductive, and each of these electrically conductive regions may be placed at a suitably defined electrical potential, individually and independently of the other electrical regions. This allows for a locally precise adjustment of the repulsion between the plates. The finer the separation of the electrically conductive regions, the more precise the spatial resolution of the adjustable bending.

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

[0061] In a third specific and particularly preferred embodiment of the invention, the plates are bent 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 bending of both plates.

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

[0063] plate The substrate holder according to the invention comprises at least one plate that is specially shaped, in particular on 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 compensating plates. Fixing plates are plates on which the substrate to be bent is fixed. Compensating plates are plates that take on the inventive effect of absorbing the forces and / or moments of the adjusting means and sufficiently prevent mechanical feedback to other 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 other components to the fixing plate.

[0065] The space between the 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, which can be 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 that fastens the substrate has a well-defined shape that positively influences the bending characteristics of the plate and thus the bending characteristics of the substrate.

[0067] If a distinction is required between the cavity-side plate surface of the fixing plate and the cavity-side plate surface of the compensating plate, they are referred to accordingly as the cavity-side fixing plate surface and the cavity-side compensating plate surface. The cavity-side plate surface may be shaped in any way, but is preferably described according to the functions already used to describe the bending lines or bending surfaces. Therefore, all functions disclosed for the bending lines and / or bending surfaces are also considered to be disclosed for the description of the cavity-side plate surface.

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

[0069] The surface of the fixing plate has fixing means for fixing the substrate. The fixing means may in particular be 1. Mechanical fastening means, especially Clamp 2. Vacuum fixing means, especially 2.1. 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 fastening devices and / or 7. Fixing means with an adhesive, particularly controllable, surface is.

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

[0071] A vacuum clamping means is a preferred type of clamping means. The vacuum clamping means preferably consists of several vacuum channels that extend onto the surface of the substrate holder. These vacuum channels are preferably individually controllable. In technically feasible applications, several vacuum channels are grouped together to form vacuum zones that are individually controllable and can therefore be evacuated or flooded. However, each vacuum zone is independent of the other vacuum zones. This allows for the construction of individually controllable vacuum zones. The vacuum zones are preferably configured in an annular shape. This allows for targeted, radially symmetric clamping and / or release of the substrate from the substrate holder, particularly from the inside out.

[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 very particularly preferred embodiment of the invention, so-called pins (in English: pins) are located on the surface of the clamping plate. WO 2015113641 describes such a configuration. These pins allow the substrate to contact the clamping surface primarily only at the pins, rather than resting on the entire surface. This, on the one hand, reduces contamination, and, on the other hand, allows a vacuum to be created along the entire clamping surface of the clamping plate in the intermediate spaces between the pins. In particular, the pins are grouped into the aforementioned vacuum zones. This embodiment is also disclosed in detail in WO 2017162272. In particular, the grouping of pins with vacuum ducts distributed on the clamping plate, which in particular form individually controllable vacuum zones, is hereby explicitly disclosed and represents 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 according to WO2017162272, which can in particular be evacuated or flooded through at least one vacuum hole each, 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 only a small number of vacuum holes are located in the surface of the fixing plate, in particular centrally.

[0075] In embodiments of the present invention in which the substrates are clamped by vacuum clamping, a vacuum is generated between the substrate and the clamping plate surface, preferably via a plurality of vacuum holes. These vacuum holes are drilled along a circle whose center is the center of the clamping plate. This allows for precise positioning of one of the pins in the center of the clamping plate when using a multi-pin substrate holder. This has a clear positive effect on the bonding result. A precise description and illustration are provided in the description and drawings of the drawings. Therefore, it is a further feature of the present invention to disclose a multi-pin substrate holder having one of the pins directly below the point where both substrates first come into contact with each other. This pin below the contact point of both substrates mechanically stabilizes the substrates at this point. Since this is the point from which the bonding wave begins to advance, the alignment of this pin with the contact point along a line normal to the clamping plate surface is important for a stable initiation of the bonding wave. The effect of the pin directly below the contact point is to clarify that the pin is below the contact point and prevents the substrate from being pushed through at this point, thus creating a stable mechanical starting situation.

[0076] The second plate is a compensating plate. This plate preferably has a circumferentially closed groove in its outer region. This groove ensures that the bending of the lower plate does not continue completely to its edge, but mainly to this groove. In other words, the groove prevents bending before it reaches the periphery. This further reduces small counter-forces that may still occur on the substrate holder. If the support of the compensating plate at the periphery is so good that no moment is transmitted, the corresponding groove can be omitted. Nevertheless, such a groove configuration is always advantageous. The compensating plate preferably also supports a sealing means, in particular a sealing ring. The sealing means is preferably located in a small, circumferentially closed seat.

[0077] equipment All substrate holders according to the invention may be used to fasten the lower and / or upper substrate in the system according to the invention. Particularly preferably, the substrate holder according to the invention is used to fasten the lower and upper substrate in a bonding system. This allows for particularly improved and optimized control of bonding, especially fusion bonding. The use of a substrate holder according to the invention as the upper substrate holder replaces the bending pins (English: pin) that have long been used, especially in the semiconductor industry, to cause 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 the upper substrate and a substrate holder according to the invention for clamping the lower substrate.

[0079] A specific installation according to the invention comprises a substrate holder according to the invention provided below and any other substrate holder other than the substrate holder according to the invention, where the upper substrate holder preferably has a bending means known in the prior art, in particular a bending pin, or a nozzle from which a fluid flows that 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 splicer.

[0081] If the substrate is transparent to electromagnetic radiation of a certain frequency, an observation device is preferably present to analyze the course of the bonding wave, which not only makes it possible to observe the bonding process, influence it, and interrupt it in an emergency, but also to analyze the characteristics 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 to the installation according to the invention in a particularly vacuum-tight manner.

[0083] Such modules are preferably part of a so-called cluster installation, in which vacuum-tight gates are present between the modules. Preferably, gate valves are also located between some of the aforementioned modules. The modules may be arranged in any order relative to one another. Preferably, there is a central module inside which is located a robot that can transfer 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 process step according to the invention involves loading and fixing a first substrate onto a first substrate holder, which is preferably a substrate holder according to the invention.

[0086] A second process step according to the invention involves loading and fixing 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 respect to one another, preferably on the basis of alignment marks located on the substrate surfaces of the substrates. Corresponding alignment installations, which may also be part of the installation according to the invention, in particular the bonding chamber, are disclosed in US Pat. No. 6,214,692, WO 2015082020, WO 2014202106 and WO 2018041326.

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

[0089] In a fifth process step according to the invention, the substrate holder according to the invention adjusts at least one of the two substrates to a targeted, particularly uniform, inventive curvature. It is also possible to bend both substrates, particularly both substrates, using 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, adjustable curvature, the two substrates come into contact at some point, and thus a bond wave is generated.

[0090] For completeness' sake, it should be further noted that if one of the two substrate holders is not the substrate holder according to the invention, it may have a conventional deformation element known in the prior art for deforming the substrate. In this case, the other substrate holder will of course have all the negative consequences that are excluded from the inventive idea herein. However, since a single substrate holder according to the invention is already sufficient to form a good bond, it is also possible to use a conventional substrate holder according to the prior art on the other side. In this case, the deformation element is preferably a simple bending pin. This 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 if 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 WO 2017162272.

[0092] A key inventive aspect of the inventive method is therefore the targeted and adjustable 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 the targeted and controllable release of the substrate from its fixing surface during the advance of the bonding wave.

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

[0094] [Figure 1a] FIG. 1 illustrates an initial state of a substrate holder in the prior art. [Figure 1b] FIG. 1 shows the final state of the substrate holder in the prior art. [Figure 2a] FIG. 1 shows the initial state of the substrate holder according to the invention without a compensation plate. [Figure 2b] FIG. 1 shows the final state of the substrate holder according to the invention without the compensation plate. [Figure 3a] 1 shows an initial state of an expanded substrate holder according to the invention with a compensation plate. [Figure 3b] 1 shows the final state of the expanded substrate holder according to the invention with compensation plate. [Figure 4] 1 shows a first inventive embodiment of a substrate holder according to the invention with a compensation plate; FIG. [Figure 5] FIG. 2 shows a second inventive embodiment of a substrate holder according to the invention with a compensation plate. [Figure 6a] 10A and 10B show a side view and a plan view 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. 10 is a side view of a third preferred embodiment of a substrate holder with a 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, along with the corresponding drawings showing two states of the substrate holder in the prior art, are kept as schematic as possible to explain the basic concepts, and are intended to be as simple as possible explanations and principle diagrams, and do not claim to be complete.

[0097] FIG. 1a shows a schematic diagram of a substrate holder 1 according to the prior art in an initial state. 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 its periphery, 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 coupled to the rest of the substrate holder 1. What is important is the presence of the surface described as the 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 is located a substrate clamping means 4 which can clamp a substrate 7 to the plate 3. How this substrate clamping means 4 is controlled is not important for an understanding of the prior art device and will not be described in detail here.

[0099] 1b shows a schematic diagram of the final state of the substrate holder 1 according to the prior art. In this particular case, the substrate holder 1 is curved convexly when viewed from the outside because an overpressure forms in the cavity 5. This overpressure is generated by the flow of a gas or gas mixture having an overpressure relative to the surrounding atmosphere into the cavity 5 via an adjustment means 6, in this 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 therefore merely an example.

[0100] This situation presents several fundamental problems. 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. Non-uniform curvature is difficult to see in drawings. 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] Thus, 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 configured to be pivotable, so in the prior art the support 2 usually transmits moments.

[0102] A further problem is that any adjusting 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 that bends the substrate holder 1 in another direction, is normalized and occurs on the surface. This undesired bending of the substrate holder 1 reacts in particular on the plate support 2, thereby affecting the bending properties of the clamping plate 3 as well as the bending of the substrate 7 fixed to the clamping plate 3.

[0103] This relates to the aforementioned 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 final state is reached in terms of control technology, absolutely undesirable reaction forces can be detected across the substrate holder 1, since measurements have shown that this leads to a deterioration in the intended joining result. 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, either an opening through which the gas or gas mixture flows, or 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 that can bend the fixing plate 3. In these cases, the corresponding cavity 5 does not have to be present. Basic physical laws dictate that mechanical feedback to the substrate holder is always desired.

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

[0106] The inventive idea is again illustrated by an arrangement that uses a fluid to generate an overpressure in the cavity 5 that causes the clamping plate 3, to which the substrate 7 is fixed, to bend. It is emphasized again that the inventive idea is not bound to the use of a fluid and / or the cavity 5. Equally well, the inventive embodiment may be realized by mechanical, pneumatic, electrical or piezoelectric adjusting means 6, as will be further illustrated and described in specific embodiments below.

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

[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 greater bending resistance, the substrate holder 1' must nevertheless be easily bent when using the adjusting 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 that would be transmitted to the fixing plate 3 if the support 2' were not present.

[0109] The special support 2' allows a well-defined, particularly uniform curvature to be generated in the fixing surface 3f and thus in the substrate 7, since possible reaction forces and / or moments are not transmitted at all or only to a lesser extent to the fixing plate 7. The support 2' additionally assists in the formation of a uniform curvature in components already formed in 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 particularly important: the use of a fluid exerting a uniform and isotropic pressure on the cavity-side plate surface 3h 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 easy to calculate the appropriate shape of the cavity-side plate surface 3f by means of numerical simulation, in particular the finite element method, in order to obtain a desired, particularly uniform, curvature at the fixing surface 3f and thus at the fixed substrate 7. This specific shape of the cavity-side plate surface 3f further improves the formation of a uniform curvature of the fixing plate surface 3f and thus at the substrate 7.

[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 generated 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 designed to be relatively thin and has very little 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 of 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 compensating plate 3', which are supported relative to one another via a plate support 2'. Both plates 3, 3' are configured and / or supported so that they can be bent.

[0114] For completeness' sake, the plate 3 does not necessarily have to be an independent component in theory, but could also be part of the substrate holder 1'. All that matters is the presence of one fixing plate surface 3f. However, this can lead to edge conditions that make it nearly impossible to achieve a constant curvature of the fixing plate surface 3f. Therefore, the most preferred embodiment of the invention 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 following description of the drawings, we will explain each embodiment according to the invention with the preferred technical solutions for the construction of the two plates. In particular, the substrate clamping means 4 is located on the clamping plate 3, and by means of this substrate clamping means 4, the substrate 7 can be fixed to the clamping plate 3. How the substrate clamping means 4 is controlled is not important for understanding the device and will not be explained in detail here. The following drawings show how the substrate clamping means 4 formed as a vacuum clamping means is controlled.

[0116] FIG. 3b shows a schematic diagram of a further improved substrate holder 1" according to the invention in its final state. By means of an adjusting means 6, in the specific case shown, an opening, valve or nozzle, a fluid is forced into the cavity 5, which causes both plates 3, 3' to bend. In contrast to the prior art shown in FIG. 1a, no bending of the fixing means 2 or other parts of the substrate holder 1' occurs, 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 therefore occurs solely by the effect of the adjusting means 6.

[0117] The compensating 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 individual parts, especially sealing parts, has been omitted from this principle drawing for reasons of clarity. However, sealing will be dealt with in more detail in subsequent drawings of the most preferred embodiment.

[0118] In the following figures, different embodiments of the invention are individually addressed and shown in more detail.

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

[0120] A self-enclosed body would form a Faraday cage, allowing charge accumulation only on the outer surface. The electrical insulator 14 ensures that both plates 3, 3' electrostatically form a single conductive body, rather than a self-enclosed conductive body. This allows charge generation on the substrate surfaces forming the cavity 5. Accordingly, 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 adjusting means 6'.

[0121] FIG. 5 shows a second preferred embodiment according to the invention, in which an 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 that are electrically controlled to generate two magnetic fields that repel each other so that both plates 3, 3' are moved away from each other. An embodiment is also possible in which the two plates are at the same potential and are repelled by their electrostatic charges.

[0122] Figure 6a shows a third preferred embodiment of the invention in a side view, a detailed view and a plan view in the starting state. This embodiment of the invention is the embodiment shown in Figures 3a and 3b in greater detail. This configuration comprises (i) a specially made support 2' which transmits as little or as little reaction forces and / or moments as possible, and (ii) a compensating plate 3'.

[0123] The importance of this embodiment lies in the fact that 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 static pressure, in order to bend both plates 3, 3'. 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 will be detailed in this figure.

[0124] Preferably, the peripheral edge of the fixed plate surface 3f of the fixed plate 3 is supported or contacted via the plate support protrusion 2'v, and the plate surface 3h of the fixed plate 3 is supported or contacted via a seal member 12. This seal member 12 is preferably mounted on the lower compensating plate 3', in particular on the plate support base 2'p. The seal member 12 seals the peripheral edges of the plates 3, 3' from each other, while still allowing both plates 3, 3' to bend.

[0125] It should be mentioned 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 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 a delicate arrangement mechanically stable. In particular, this allows the plate support protrusions 2'v to be formed with great precision.

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

[0127] 6b shows a third preferred embodiment of the invention in a side view in its final state. An adjustment means 6, in this particular case an off-center 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 extends to a groove 13 machined in the compensation plate 3' over the entire periphery.

[0128] This concentrates the bending in the central part of the compensating plate 3', ensuring that even smaller moments and / or forces act mechanically on the plate support 2' (see enlarged view in Figure 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. This further design improvement according to the invention prevents mechanical feedback to the fixed plate 3 entirely or minimizes it to a negligible level. [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' Cavity chamber side plate surface 4 Board fixing means 5 Hollow chamber / intermediate chamber 6,6',6'' Adjustment means / curving means 7. Circuit Board 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); and 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) can be adjusted to a desired extent.

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

3. 3. The substrate holder (1', 1'', 1''', 1'''') according to at least one of claims 1 to 2, wherein the fixing plate (3) is pivotally supported.

4. The substrate holder (1', 1'', 1''', 1'''') according to at least one of claims 1 to 3, 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 to produce a uniform curvature of the fixing plate (3).

6. 6. The substrate holder (1', 1'', 1''', 1'''') according to at least one of claims 1 to 5, wherein the reaction forces generated when the fixing plate (3) is bent 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 claims 1 to 6, wherein the fixing plate (3) is thicker in the center 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 configured to be tapered towards its edges.

9. The substrate holder (1', 1'', 1''', 1'''') according to at least one of claims 1 to 8, wherein the fixing plate (3) is formed symmetrically about its center.

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 a substrate holder according to any one of claims 1 to 9; - aligning said substrates (7) with each other; - bending at least one of said substrates (7); - bringing said substrates (7) into contact with each other; and A method characterized in that the curvature of at least one of said substrates (7) is adjusted to a target.

12. 12. The method according to claim 11, wherein the curvature of at least one of the substrates (7) is adjusted uniformly.

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