Method for bonding substrate

Abstract

To provide a method for increasing bonding accuracy at any positions of a substrate.SOLUTION: Provided is a method for reducing the heating temperature of a surface of a second sample holder during bonding of a first substrate (2) to a second substrate (2') at contact surfaces (2o, 2o') of both substrates, the method including the steps of: holding the first substrate on a surface of a first sample holder (1) with a holding force FH1, and holding the second substrate on a surface of a second sample holder (1') with a holding force FH2; bringing both the contact surfaces into contact at a predetermined bonding start point, and heating at least the surface of the second sample holder to a heating temperature TH; and bonding the first substrate to the second substrate along a bonding wave advancing from the bonding start point up to the side edges of both substrates.SELECTED DRAWING: Figure 1d

Description

[Technical field]

[0001] The present invention relates to a method for bonding a first substrate to a second substrate as claimed in claim 1. [Background technology]

[0002] For many years in the semiconductor industry, substrates are aligned with respect to one another and bonded to one another. Bonding, also known as bonding, is used to form multi-layer substrate stacks. In such multi-layer substrate stacks, functional units, especially memories, microprocessors, MEMS, etc., can be bonded to one another and thus combined with one another. This combinability allows a wide variety of applications to be realized.

[0003] The density of functional units is increasing year by year. Due to the development of technology, the size of functional units is becoming smaller and smaller. Therefore, with the increase in density, the number of functional units per board increases. This increase in number is mainly responsible for the decrease in component cost.

[0004] A disadvantage of increasingly smaller functional units is that it becomes increasingly difficult to achieve error-free, and in particular perfect, overlay, in particular of all functional units along the joint interface of both substrates.

[0005] That is to say, the biggest problem in today's alignment technology does not always lie only in aligning two substrates, in particular two wafers, with respect to each other based on alignment marks, but also in forming an error-free, in particular complete, and thus error-free, correlation between each point of the first substrate and each point of the second substrate over the entire surface of the substrate. Experience has shown that the structures on the surfaces of the substrates after the bonding process are generally not congruent with each other. Therefore, a general, in particular global, alignment of the two substrates and a subsequent bonding step are not always sufficient to obtain error-free complete congruence of any point at any point on the substrate surface.

[0006] In the known prior art, there are two fundamental problems which prevent a simple global alignment and subsequent bonding process.

[0007] For one thing, the positions of the structures on the first and / or second substrate generally deviate from their theoretical positions. This deviation can have several reasons.

[0008] For example, the manufacturing process may have errors, or at least tolerances, that cause the actual structures produced to deviate from their ideal positions. An example of this would be the repetitive use of lithography in a step-and-repeat process, where each translation of the stamp introduces small but significant positional errors.

[0009] Yet another, not inconsiderable reason would be the deformation of the substrate due to mechanical and especially thermal loads. The substrate has a certain temperature, for example at the time of manufacturing the structure. This temperature is generally not maintained throughout the entire process flow of the substrate, but changes. With the temperature change comes thermal expansion, which in the most ideal case leads to a change in diameter and in the most unfavourable case leads to complex thermal deformations.

[0010] Secondly, even if two substrates have all structures perfectly congruent, i.e. overlapping, immediately before contacting and immediately before the actual bonding process, this congruence can be lost during the bonding process, so that the bonding process itself has a decisive influence on forming a substrate stack whose structures are perfectly congruent, i.e. error-free.

[0011] Third, layers and structures disposed on the substrate can create stresses in the substrate, the layers can be, for example, insulating layers, and the structures can be, for example, through silicon vias (TSVs).

[0012] One of the most important technical problems when permanently bonding two substrates is the alignment accuracy of the functional units between the individual substrates. The substrates can be very precisely aligned with respect to each other by means of alignment equipment, but during the bonding process itself, distortions of the substrates can occur. Due to the distortions thus created, the functional units are not always properly aligned with respect to each other in all positions. Inaccuracies in the alignment at certain points of the substrates can result in distortions, scaling errors, lens defects (enlargement or reduction errors), etc. In the semiconductor industry, all topic areas related to such problems are subsumed under the concept of "overlay". A corresponding overview on this subject can be found, for example, in Mack, Chris, "Fundamental Principles of Optical Lithography - The Science of Microfabrication" (Publisher WILEY, 2007, reprinted 2012).

[0013] Each functional unit is designed in a computer before the actual manufacturing process. For example, conductor tracks, microchips, MEMS, or any other structures that can be manufactured using microsystem technology are also designed in a CAD (computer aided design) program. However, it turns out that during the manufacturing of the functional units, deviations always exist between the ideal functional unit constructed in the computer and the actual functional unit manufactured in the clean room. The differences can be mainly due to hardware limitations, i.e. technical engineering problems, but often also due to physical limitations. The resolution accuracy of the structures manufactured by the photolithography process is limited by the size of the aperture of the photomask and the wavelength of the light used. Mask distortions are directly transferred to the photoresist. The linear motors of the machine can only reach positions that are reproducible within a defined tolerance. It is therefore not surprising that the functional units of the substrate cannot be exactly equal to the structures constructed in the computer. Therefore, all substrates already have negligible deviations from the ideal state before the bonding process. If we compare the positions and / or shapes of two functional units of two substrates located opposite each other, assuming that neither of the substrates is distorted by the bonding process, we will generally already find that there is a non-perfect alignment of both functional units, because they deviate from the ideal computer model due to the errors explained above. The most frequent errors are illustrated in Figure 8 (taken from http: / / commons.wikimedia.org / wiki / File:Overlaytypical model terms DE.svg. 24.05.2013 and Mack, Chris, Fundamental Principles of Optical Lithography- the Science of Microfabrication. Chichester, Publishers WILEY, p. 312, 2007, reprinted 2012).As shown in the figures, overlay errors can be roughly distinguished into global and local overlay errors or symmetric and asymmetric overlay errors. Global overlay errors are uniform and therefore location independent. Global overlay errors cause the same deviation between two functional units located opposite each other, independent of their location. Typical global overlay errors are errors I. and II. caused by translation or rotation of both substrates relative to each other. The translation or rotation of both substrates respectively causes corresponding translation or rotation errors on the substrates for all functional units located opposite each other. Local overlay errors are location related and are mainly caused by elastic and / or plastic problems and / or pre-processing, in this case in particular by elastic and / or plastic problems and / or pre-processing caused by the continuously propagating bonding wave. Among the illustrated overlay errors, errors III. and IV. in particular are called "run-out" errors. These "run-out" errors are caused in particular by distortion of at least one substrate during the bonding process. Due to the distortion of at least one substrate, the functional units of the first substrate are also distorted with respect to the functional units of the second substrate. However, errors I. and II. can also be caused by the bonding process, but are usually significantly superimposed by errors III. and IV., so that errors I. and II. are very difficult to detect or measure. This applies to modern bonders, in particular fusion bonders, which can perform corrections in the x-direction and / or y-direction and / or rotational direction very precisely.

[0014] In the known prior art there are already provisions which make it possible to at least partially reduce local distortions: this is local distortion correction by using active control elements (WO 2012 / 083978 A1).

[0015] In the known prior art, there is a first solution for correcting the "runout" error. US20120077329A1 describes a method for obtaining a desired alignment accuracy between the functional units of the two substrates during and after bonding by not fixing the lower substrate in position. This allows the lower substrate to be free to bond to the upper substrate during the bonding process without being subjected to boundary conditions. An important feature in the known prior art is, among other things, fixing one substrate flat in position, usually using a vacuum device.

[0016] The generated "runout" error usually grows radially symmetrically around the contact point and therefore grows from the contact point towards the periphery. This is usually a linearly growing amplification of the "runout" error. Under special conditions, the "runout" error can also grow nonlinearly.

[0017] Particularly under optimal conditions, the "runout" errors can not only be detected by suitable measuring instruments (EP 2463892), but also recorded by mathematical functions. Since the "runout" errors are translations and / or rotations and / or scalings between well-defined points, the "runout" errors are advantageously described by vector functions. In general, such vector functions are represented by the function f:R 2 →R 2 and thus is the mapping rule that maps the two-dimensional definition range of position coordinates to the two-dimensional value range of the "runout" vector. An exact mathematical analysis of the corresponding vector field has not yet been performed, but conjectures about the functional properties can be made. The vector function can be determined with great probability by at least C n n>1 function and therefore continuously differentiable at least once. The divergence of the vector function is probably different from zero since the "runout" error increases from the contacting point towards the edge. Thus the vector field is a well field with great probability.

[0018] The "runout" error is best determined with respect to a structure, where "structure" is understood to be any arbitrary element of a first or second substrate that is to be correlated with a structure on a second or first substrate. So a structure, for example, ●Alignment marks Corners or edges, especially corners and edges of functional units Contact pads, especially through silicon vias (TSVs) or through polymer vias (TPVs) Conductor path, Recesses, especially holes or depressions It is.

[0019] "Runout" errors are generally position-related and, in the mathematical sense, are displacement vectors between real and ideal points. Because "runout" errors are generally position-related, they are ideally represented by vector fields. In the following description, "runout" errors will be considered simply point-like for ease of explanation, unless otherwise stated.

[0020] The "runout" error R is combined from two components.

[0021] The first component R1 describes the substantial part of the "runout" error, i.e. the part due to the manufacturing error of the structure or the distortion of the substrate. That is, the first component R1 is inherent to the substrate. It should be noted that in this case, if the structure is properly manufactured at a first temperature, but undergoes a temperature change to a second temperature until the bonding process, the substrate may also have a substantial "runout" error, which will cause a thermal expansion that will distort the entire substrate and thus the structures present on it. A temperature difference of only a few Kelvins, or even a tenth of a Kelvin, is already sufficient for such distortion to occur.

[0022] The second component R2 describes the extrinsic part of the "runout" error, i.e. the part that is initially caused by the bonding process, which is not present before the bonding process. This extrinsic part includes in particular local and / or global distortions of the first and / or second substrate due to forces acting between the substrates, which can cause deformations in the nanometer range. Summary of the Invention [Problem to be solved by the invention]

[0023] The object of the present invention is to provide a method for bonding two substrates, which allows for high bonding accuracy even at the very top of the substrates.A further object of the present invention is to provide a method which allows for error-free, in particular perfect congruence, of the structures of the two substrates. [Means for solving the problem]

[0024] This problem is solved by the features of claim 1. Advantageous developments of the invention are described in the dependent claims. All combinations of at least two features described in the description, the claims and / or the drawings also fall within the scope of the invention. In the stated value ranges, the values ​​within the stated ranges are themselves considered as disclosed limits and can preferably be claimed in any combination. If single or multiple method steps can be performed in multiple different devices or multiple different modules, these method steps are each disclosed separately as an independent method.

[0025] The idea underlying the present invention is to H The heating temperature T His used to generate a sufficient temperature for bonding, particularly at the bonding surface of the substrate. An important feature of yet another embodiment according to the invention is that the substrates are released from the fixed position, particularly during bonding, in order to allow the substrate stack to deform freely during bonding. A further important feature of a third embodiment according to the invention is that it is possible to ventilate or pressurize the substrate stack, particularly at the interfaces of the substrate stack, during bonding.

[0026] As first and / or second substrate, inter alia wafers come into consideration.

[0027] A characteristic process according to the invention for bonding, in particular for permanent bonding, preferably for fusion bonding, is the most concentric point-like contacting of the two substrates. In particular, the contacting of the two substrates can also be performed non-concentrically. The bonding waves propagating from the non-concentric contact points reach different points on the substrate edges at different times. This complicates the complete mathematical-physical description of the bonding wave characteristics and the resulting compensation of the "runout" errors. In particular, the contacting points are not located so far away from the substrate center that the effects possibly resulting from this are negligible, at least at the edges. The distance between the possible non-concentric contacting points and the substrate center is preferably less than 100 mm, preferably less than 10 mm, more preferably less than 1 mm, very preferably less than 0.1 mm, most preferably less than 0.01 mm. In the following, "contacting" is generally understood to mean concentric contacting. "Center" in the broad sense preferably means the geometric center of the basic ideal object, compensated for asymmetrical features if necessary. That is, for industrially common wafers with a notch, the center is the center of a circle that surrounds an ideal wafer without a notch. For industrially common wafers with a flat (flat chamfered surface), the center is the center of a circle that surrounds an ideal wafer without a flat. The same idea applies to arbitrarily shaped substrates. However, in special configurations, it may be beneficial for "center" to mean the center of gravity of the substrate. To ensure accurate concentric point contacting, the upper mounting device (substrate holder) is equipped with a radially symmetrical positioning device with a central hole and a pin that is translationally movable in this hole. It is also conceivable to use a nozzle that uses a fluid, preferably a gas, for pressurization instead of the pin.Furthermore, the use of such elements can be completely eliminated if a device is provided that can bring the substrates closer together by translational movement, under the further prerequisite that at least one of the substrates, preferably the upper one, has a curvature applied in the direction of the other substrate due to gravity and therefore, during said translational approach, automatically contacts the corresponding second substrate at a sufficiently small distance.

[0028] Radially symmetrical fixation / holding means are provided vacuum holes, circular vacuum lips or comparable vacuum elements which can fix the upper substrate. The use of electrostatic mounting devices is also conceivable. A pin in a central hole in the upper substrate holder is used for controllable deflection of the fixed upper substrate.

[0029] In yet another embodiment according to the invention, the mounting device can be configured such that the first and / or second substrate is curved concavely and / or convexly by the creation of an overpressure and / or a negative pressure in the sample holder. For this purpose, the mounting device is preferably provided with a vacuum passage and / or a hollow space that can be fluidly or evacuated. The use of a nozzle for pinpoint pressure application can in particular be omitted in favor of an overall pressure build-up. According to the invention, embodiments are conceivable in which the substrate is sealed and / or in other ways fixed, in particular at the edge. If the mounting device is configured, for example, to create a negative pressure with respect to the external atmosphere, sealing at the edge of the substrate is sufficient. If an overpressure is created inside the mounting device in order to bend the substrate outward, i.e. convexly, the substrate is preferably mechanically fixed, in particular at the edge. By applying a negative or overpressure to the substrate from the backside, the curvature of the substrate can be set precisely.

[0030] After the two substrates have been brought into contact with each other at their centers, the upper substrate holder is gradually released from its fixed position in a particularly controlled manner. The upper substrate falls downwards due to gravity on the one hand and the bonding forces acting between the two substrates along the bonding wave on the other hand. The upper substrate is bonded to the lower substrate in a radial direction from the center toward the side edges. This results in the inventive formation of a radially symmetrical bonding wave, which in particular runs from the center toward the side edges. During the bonding process, the two substrates push out any gas, in particular air, present between the two substrates from the front of the bonding wave, thus resulting in a bonding interface free of gas inclusions. When the upper substrate falls, it essentially falls on a sort of gas cushion.

[0031] The first / upper substrate is not subject to additional positional fixation after the start of bonding at the bond initiation point, i.e. apart from the positional fixation at the bond initiation point it is free to move and even distort. Due to the advancing bonding wave in the present invention, the stress state created at the bonding wave front and the existing geometrical boundary conditions, any circle segment that is infinitesimally small with respect to its radial thickness will be distorted. However, since the substrate is a rigid object, the distortions will sum up as a function of the distance from the center. This leads to a "runout" error that should be eliminated by the method and the device according to the present invention.

[0032] The present invention therefore also relates to a method and an apparatus for reducing or even completely avoiding "runout" errors between the bonded substrates during bonding, in particular by means of thermodynamic and / or mechanical compensation mechanisms. Furthermore, the present invention deals with corresponding products which are manufactured using the apparatus according to the invention and the method according to the invention.

[0033] The "runout" error is particularly related to the position of the substrate along its surface. It has been found that the "runout" error increases from the center of the substrate towards its periphery. Such radially symmetric runout occurs particularly when substrates are fusion bonded, where the substrates are contacted at the center by a pin, and the bonding wave of the substrates propagates autonomously, particularly radially, after contacting.

[0034] The "runout" error is inter alia related to the bonding wave speed. In general, the higher the bonding wave speed, the higher the "runout" error. Therefore, according to the invention, a bonding wave speed is set that is preferably lower than 100 mm / s, preferably lower than 50 mm / s, even more preferably lower than 10 mm / s, very preferably lower than 1 mm / s, most preferably lower than 0.1 mm / s. In a particular embodiment according to the invention, the bonding wave speed is detected by a measuring means.

[0035] The "runout" error is particularly related to the gap between the two substrates just before the start of the (pre)bonding process. 1Insofar as the substrates are deformed at , the spacing between them is a function of position. In particular the spacing between the substrates is greatest at the edges. The smallest spacing is located in the region of the convex maximum of the deformed substrate. The shape of the deformed substrate therefore also has an influence on the "runout" error. The spacing between the substrates at the edges (substrate edge spacing D) is set in particular to less than 5 mm, preferably less than 2 mm, more preferably less than 1 mm, very preferably less than 0.5 mm, most preferably less than 0.1 mm immediately before bonding. The spacing between the substrates below the convex maximum is set in particular to less than 1 mm, preferably less than 100 μm, more preferably less than 10 μm, very preferably less than 1 μm, most preferably less than 100 nm immediately before bonding. The "runout" error is related in particular to the type of sample holder and thus to the type of position fixing / holding of the respective substrates. WO2014 / 191033A1 discloses several embodiments of preferred sample holders, to which reference is made in this respect. In the disclosed process, it is crucial that the substrate is released from the sample holder after the release of the positional fixation, in particular after the release of the vacuum fixation. The surface roughness of the sample holder is selected to be as large as possible so that its waviness is as small as possible. A large surface roughness leads to as few contact points as possible between the sample holder surface and the substrate. Thus, the separation of the substrate from the sample holder is performed with minimal energy costs. The waviness is preferably minimized in order to avoid the formation of new sources for "runout" by the sample holder surface. In this respect, it is mentioned that the statement regarding waviness does not mean that the sample holder surface must not be curved as a whole.

[0036] Roughness is expressed either as average roughness, roughness squared or average roughness depth. The calculated values ​​of average roughness, roughness squared and roughness depth are generally different for the same measurement path or surface, but are within the same order of magnitude. The following numerical ranges for roughness should therefore be understood as either values ​​of average roughness, roughness squared or average roughness depth. Roughness is set in particular to be greater than 10 nm, preferably greater than 100 nm, more preferably greater than 1 μm, very preferably greater than 10 μm and most preferably greater than 100 μm. The "runout" error is especially related to the time aspect. The bonding wave propagates very quickly, so that there is not enough time for the materials of the substrates to bond optimally to each other immediately and / or during and / or immediately before the bonding wave. Therefore, it may also be very important to control the bonding wave in terms of time.

[0037] The "runout" errors are especially related to the process of loading the substrate onto the sample holder. During loading and fixation of the substrate, it can become distorted, which is maintained by the fixation and is carried along in the substrate stack during (pre-)bonding. The substrate is therefore brought onto the sample holder by the end effector with as little distortion as possible.

[0038] The "runout" errors are related, inter alia, to temperature differences and / or temperature fluctuations between the two substrates. The substrates are fed to the bonding module from different process steps or from different process modules, in which different processes may have been carried out at different temperatures. Furthermore, the upper and lower sample holders may have different structures, configurations and thus different physical properties, in particular different thermal properties. For example, the sample holders may have different thermal masses and / or thermal conductivities. This leads to different loading temperatures or different temperatures at the time of (pre-)bonding. The sample holder for carrying out the process according to the invention is therefore equipped with a heating and / or cooling system in order to be able to set the temperature of at least one (preferably both) substrates precisely. It is inter alia conceivable to adapt the temperatures of the two substrates to different values ​​and to apply heat to at least one of the two substrates, thereby thermally distorting the substrate as a whole. In this way, the substrates can be adapted to a desired initial state in order to compensate, inter alia, for the component R1 of the "runout" errors.

[0039] The "runout" error is linked inter alia to ambient pressure, the effect of which is explained and disclosed in detail in WO 2014 / 191033 A1, to which reference is made in this respect.

[0040] The "runout" errors are related, inter alia, to the symmetry of the system, so that preferably as many as possible (and even more preferably at least the majority) of the components are constructed and / or arranged symmetrically. In particular, the thicknesses of the substrates are different. Furthermore, layers of different materials with different mechanical properties can be provided on each substrate in different orders, and this should be taken into account. Furthermore, one of the substrates is preferably deformed, while the other substrate is placed flat on the sample holder. All properties, parameters and embodiments that result in asymmetries have an effect, inter alia, on the "runout" errors. Some of these asymmetries cannot be avoided. For example, the thickness of the substrate, the layers on the substrate and the functional units are determined by the process and customer specifications. According to the invention, it is attempted to significantly minimize, in particular completely eliminate, the "runout" by changing, inter alia, other changeable parameters.

[0041] The "runout" error is especially position related: the aim of the method according to the invention is to maintain a "runout" error, especially at any position, of less than 10 μm, preferably less than 1 μm, more preferably less than 100 nm, very preferably less than 10 nm, most preferably less than 1 nm.

[0042] Sample Holder A sample holder preferably used for an embodiment according to the invention uses a position fixing part, which is used to hold the substrate with a position fixing force or a corresponding position fixing pressure. The position fixing part may be, inter alia: Mechanical position fixing parts, especially clamps or Vacuum fixing parts, especially ○ Individually controllable vacuum passages, or ○Interconnected vacuum passages or Electrical position fixing devices, in particular electrostatic position fixing devices, or ● Magnetic position fixing part, or Adhesive position fixing parts, especially ○ Gel pack position fixing part, or Position fixing part with, inter alia, a controllable adhesive surface It can be said that:

[0043] The positioning device is in particular electronically controllable. A vacuum fixture is a preferred type of positioning device. The vacuum fixture preferably consists of a plurality of vacuum channels, which emerge at the surface of the sample holder. The vacuum channels are preferably individually controllable. In a technically preferred application, several vacuum channels are integrated in each vacuum channel segment, which is individually controllable, i.e. can be individually evacuated or pumped. Each vacuum segment is preferably independent of the other vacuum segments. This provides a means for configuring individually controllable vacuum segments. The vacuum segments are preferably configured in the shape of a ring. This allows the substrate to be targetedly fixed and / or released from the sample holder with radial symmetry, in particular from the inside to the outside, or vice versa.

[0044] Possible sample holders are disclosed in WO 2014 / 191033 A1, WO 2013 / 023708 A1, WO 2012 / 079597 A1 and WO 2012 / 083978 A1, to which reference is made in this respect.

[0045] Bonding Wave Monitoring During at least one, preferably all, process steps according to the invention, it is advantageous to detect the progress of the bonding wave or at least one state of the bonding wave, thereby determining the progress of the bonding wave or at least one state of the bonding wave at a given time. For this purpose, it is preferable to provide measuring means which, inter alia, have a camera. The monitoring is preferably carried out by: ● cameras, in particular visual or infrared cameras, and / or Conductivity measuring equipment This is carried out using

[0046] If the determination of the bonding wave is carried out by means of a camera, it is possible to detect the position of the bonding wave at any one time, and in particular its progress. The camera is preferably an infrared camera which digitizes the data and transmits it to a computer. On this basis, the computer allows the evaluation of the digital data, in particular the determination of the position of the bonding wave, the size of the bonded surface, or further parameters.

[0047] Yet another means of monitoring the progress of the bonding wave is to measure the surface conductivity, which changes as the bonding wave progresses. For this, the prerequisites for such a measurement must be given. The measurement of the surface conductivity is carried out in particular by contacting the substrate with two electrodes at two locations opposite each other. In a particular embodiment according to the invention, the electrodes contact the edge of the substrate, but do not prevent the bonding of the substrate at the edge. In a second, less preferred embodiment according to the invention, the electrodes are pulled back from the substrate before the bonding wave reaches the side edge of the substrate.

[0048] In the following, processes are described, which preferably proceed in the order described, particularly as separate steps. Unless otherwise stated, the process steps and disclosures can be transferred from one embodiment to another, respectively, if it is technically feasible for those skilled in the art.

[0049] Process according to the first embodiment of the invention In a first process step of the first embodiment of the method according to the invention, one of the two substrates is positioned and fixed on the first / upper sample holder and the second substrate on the second / lower sample holder. In this case, the feeding of the substrates may be performed manually, but preferably by a robot, i.e. automatically. The upper sample holder preferably presses the upper first substrate with a first force F 1 The upper sample holder is preferably provided with a deformation means for deforming the upper first substrate in a targeted and, in particular, controllable manner. The upper sample holder has, in particular, at least one opening through which the deformation means, in particular a pin, can mechanically deform the upper first substrate. Such a sample holder is preferably disclosed in WO2013 / 023708A1.

[0050] In a second process step, the deformation means, in particular the pin, contacts the rear side of the upper first substrate and produces a slight deformation, in particular a deflection called concavity from the side of the deformation means (i.e. from above). The deformation means applies a first force F, in particular greater than 1 mN, preferably greater than 10 mN, more preferably greater than 50 mN, very preferably greater than 100 mN, in particular greater than 5000 mN. 1 is applied to the first substrate. This force is too weak to detach the upper first substrate from the sample holder, but strong enough to produce a deflection according to the invention. The force acts on the substrate preferably as point-like as possible. Since point-like action does not exist in practice, the force acts preferably over a very small area. This area may in particular be less than 1 cm2 Smaller than 0.1 cm, preferably 0.1 cm 2 less than 0.01 cm 2 Less than 0.001 cm, most preferably 2 Less than 0.001cm 2 In the case of acting on an area of ​​0.1 mm or more, the applied force is according to the invention in particular greater than 1 MPa, preferably greater than 10 MPa, more preferably greater than 50 MPa, very preferably greater than 100 MPa, and most preferably greater than 1000 MPa. These disclosed pressure ranges also apply to the further aspects disclosed above.

[0051] In a third process step, the relative approach of the two substrates is carried out, in particular by bringing the sample holders closer together. Preferably, the lower sample holder is raised, whereby the lower second substrate is actively brought closer towards the upper first substrate. However, it is also conceivable to actively bring the upper sample holder closer towards the lower sample holder or to bring the two sample holders closer towards each other simultaneously. The approach of the two substrates is carried out in particular until a separation between 1 μm and 2000 μm, preferably between 10 μm and 1000 μm, further preferably between 20 μm and 500 μm, very preferably between 40 μm and 200 μm, is reached. This separation is defined as the smallest vertical distance between the respective surface points of the two substrates.

[0052] The first and / or second substrate are heated by a heating means and / or cooled by a cooling means, ie temperature regulated, prior to bonding or pre-bonding or contacting.

[0053] In a fourth process step, a further force is applied to the upper first substrate. In a first embodiment according to the invention, the second force F of the deformation means is in particular greater than 100 mN, preferably greater than 500 mN, more preferably greater than 1500 mN, very preferably greater than 2000 mN, most preferably greater than 3000 mN. 2is applied to the first substrate, which causes or at least assists in the first contacting of the upper first substrate with the lower second substrate. The calculation of the pressure that is preferably generated is based on the smallest area assumed, 0.001 cm. 2 In a fifth process step, the heating means, in particular the heater of the lower sample holder, which is integrated and arranged in the lower sample holder, is switched off.

[0054] In a sixth process step, in particular the propagation of the ongoing bonding wave is monitored (see also "Monitoring the bonding wave" above). This monitoring tracks the progress of the bonding wave and thus the progress of the bonding process, in particular over a period of more than 1 second, preferably more than 2 seconds, even more preferably more than 3 seconds, very preferably more than 4 seconds, and most preferably more than 5 seconds. Instead of tracking / controlling the bonding process over a predefined time interval, it is also possible to define the tracking of the bonding wave in terms of the position of the bonding wave, in particular the radial position. The tracking of the bonding process is carried out in particular while the bonding wave is present at a radial position corresponding to at least 0.1 times, preferably at least 0.2 times, even more preferably at least 0.3 times, very preferably at least 0.4 times, and most preferably 0.5 times the diameter of the substrate. If it is desired to track the progress of the bonding by measuring the surface conductivity, it is also possible to carry out the bonding progress by the percentage of the bonded or unbonded surface. In that case, monitoring of the bonding progress according to the invention is carried out in particular until more than 1%, preferably more than 4%, more preferably more than 9%, very preferably more than 16% and most preferably more than 25% of the area has been bonded. Alternatively, monitoring is carried out continuously.

[0055] The control of the process sequence is preferably carried out on the basis of a defined / set or settable value from monitoring within the above-mentioned value range, from which a first waiting time for the advancement of the bonding wave before the start of the next process step is known.

[0056] In the seventh process step, in particular the clamping of the upper first sample holder is switched off. It is also conceivable to release the upper first substrate by releasing the clamping in a targeted manner. In particular in the case of a vacuum clamping consisting of several individually controllable vacuum channels, the clamping is released in a targeted manner by releasing the vacuum successively from the center towards the edge. The seventh process step is in particular the clamping at a time t 1 (see especially process step 6).

[0057] Generally speaking or in other words, at time t during bonding 1 In particular, a holding force F is applied until the first substrate is released from the first sample holder. H1 is reduced.

[0058] In an eighth process step, the propagation of the bonding wave, in particular during the bonding process, is once again or subsequently monitored by the measuring means. This monitoring tracks the progress of the bonding wave and thus the progress of the bonding process, in particular over a period of more than 5 seconds, preferably more than 10 seconds, more preferably more than 50 seconds, very preferably more than 75 seconds, and most preferably more than 90 seconds. Instead of tracking the bonding process over a predefined time interval, it is also possible to measure the position of the bonding wave, in particular the radial position. In this case, the bonding process is tracked in particular while the bonding wave is at a radial position that corresponds to at least 0.3 times, preferably at least 0.4 times, more preferably at least 0.5 times, very preferably at least 0.6 times, and most preferably 0.7 times the diameter of the substrate. If the bonding progress can be tracked by measuring the surface conductivity, it is also possible to measure the bonding progress by the percentage of the bonded or unbonded surface. In that case, monitoring of the bonding progress according to the invention is carried out in particular until more than 9%, preferably more than 16%, more preferably more than 25%, very preferably more than 36% and most preferably more than 49% of the area has been bonded. Alternatively, monitoring is carried out continuously.

[0059] The control of the process sequence is preferably carried out on the basis of a defined / set or settable value from monitoring within the above-mentioned value range, from which a second waiting time for the advancement of the bonding wave before the start of the next process step is known.

[0060] In a ninth process step, the deformation means is deactivated. If the deformation means is a pin, the pin is pulled back. If the deformation means is one or more nozzles, the flow of fluid is interrupted. If the deformation means is an electric and / or magnetic field, the electric and / or magnetic field is switched off. The ninth process step is initiated, inter alia, when one of the parameters of the measuring means reaches a defined / set or settable value (see inter alia the eighth process step).

[0061] In a tenth process step, the propagation of the ongoing bonding wave is once again or continuously monitored. This monitoring tracks the progress of the bonding wave and thus the progress of the bonding process, in particular over a period of more than 5 seconds, preferably more than 10 seconds, more preferably more than 50 seconds, very preferably more than 75 seconds, most preferably more than 90 seconds. Instead of tracking the bonding process over a predefined time interval, it is also possible to determine the tracking of the bonding wave with respect to the position, in particular the radial position, of the bonding wave. In this case, the tracking of the bonding process is carried out in particular while the bonding wave is present at a radial position that corresponds to at least 0.6 times, preferably at least 0.7 times, more preferably at least 0.8 times, very preferably at least 0.9 times the diameter of the substrate. In case the substrate has an edge profile, the bonding process cannot be tracked up to the outermost edge, because due to the edge profile, about 3 to 5 mm are not bonded. If it is desired that the bonding progress can be followed by measuring the surface conductivity, it is also possible to carry out the bonding progress by percentage of the bonded or unbonded surface. In that case, the bonding progress monitoring according to the invention is carried out in particular until more than 36%, preferably more than 49%, more preferably more than 64%, very preferably more than 81% and most preferably 100% (or more) of the area is bonded. Alternatively, the monitoring is carried out continuously.

[0062] The control of the process sequence is preferably carried out on the basis of a defined / set or settable value from monitoring within the above-mentioned value range, from which a third waiting time for the advancement of the bonding wave before the start of the next process step is known.

[0063] An example process sequence for the first embodiment is given below: ● Loading the board ● Contact the pin to the wafer without initiating bonding (100mN force on the wafer) ● Place two wafers relatively close to each other (spacing 40~200μm) Apply force to the wafer (1500-2800mN force) to initiate the fusion bond between both substrates. ● Stop the heater Wait until the bonding wave has propagated sufficiently (typically 1-5 seconds) - the first wait period Switch off (pump) the vacuum on the wafer surface (especially both zones at the same time) Wait for the bonding wave to propagate further (typically 2-15 seconds) - the third wait period Pull back the pin ●Waiting until the bonding wave has fully propagated (especially 5 to 90 seconds) - the fourth waiting period.

[0064] The individual method steps can be generalized according to the general technical teachings above.

[0065] Process according to a second embodiment of the invention The process according to the second embodiment corresponds to the first to seventh process steps of the first embodiment.

[0066] In the eighth process step, the holding force of the second lower specimen holder is reduced or the clamping means is switched off. It is also conceivable to release the second lower substrate by releasing the clamping means in a targeted manner. In particular in the case of a vacuum clamping means consisting of several individually controllable vacuum channels, the clamping means is released in a targeted manner by successively releasing the vacuum from the center towards the edge. The eighth process step according to the invention is an important step for reducing the "run-out" errors. According to the invention, by reducing the holding force of the second lower specimen holder or by switching off the clamping means, it is possible to adapt the lower / second substrate to the upper first substrate. By releasing the clamping means, as it were, additional (mathematical and mechanical) boundary conditions that may limit the bonding process are removed.

[0067] Generally speaking or in other words, at time t during bonding 2 In particular, a holding force F is applied until the second substrate on the second sample holder becomes deformable. H2 is reduced.

[0068] The ninth process step corresponds to the eighth process step of the first embodiment.

[0069] In the tenth process step according to the invention, in particular the already partially bonded second substrate is again clamped in the lower second specimen holder. The tenth process step according to the invention is also an important step for reducing the "run-out" errors. By clamping again, in particular by switching on the vacuum suction again, the bonding progress is again limited by (mathematical and mechanical) boundary conditions.

[0070] Generally speaking or in other words, at time t 4 Especially after bonding, the retention force F H2 is increased.

[0071] The eleventh process step corresponds to the ninth process step according to the first embodiment, and the twelfth process step corresponds to the tenth process step according to the first embodiment.

[0072] In a very particular embodiment according to the invention, the switching off of the fixing part in the eighth process step and the re-switching on of the fixing part in the tenth process step can be repeated several times before the end of the bonding process. In particular, it is even possible to perform the switching off and re-fixing in a spatially resolved manner. According to the invention, this works in particular with the individually controllable vacuum passages or vacuum segments already described in the present disclosure. That is to say, in the ideal case, the release or fixing of the lower / second substrate is performed in a spatially and / or time-resolved manner.

[0073] An example process sequence for the second embodiment is given below: ● Loading the board Contacting the pin (deformation means) to the wafer without initiating bonding (specifically a force of 100 mN on the wafer) - the first force of the pin ● Bring two wafers relatively close to each other (especially 40-200μm apart) - First separation Press the wafer together (typically with a force of 1500-2800 mN) to initiate the fusion bond between both substrates - the second force of the pin ● Stop the heater Wait until the bonding wave has propagated sufficiently (typically 1 to 5 seconds) - the first waiting period Switch off (pump) the vacuum for the upper wafer (especially both zones at the same time) Switch off (exhaust) the vacuum for the lower wafer Wait for the bonding wave to propagate further (typically 2-15 seconds) - the third wait period Switch on the vacuum suction for the lower wafer – first vacuum Pull back the pin ●Waiting until the bonding wave has fully propagated (especially 5 to 90 seconds) - the fourth waiting period.

[0074] The individual method steps can be generalized according to the general technical teachings above.

[0075] Process according to the third embodiment of the invention The process according to the third embodiment corresponds to the first to ninth process steps of the second embodiment. In the ninth process step, the parameters are preferably set to be 10-40% smaller than in the second embodiment. This shortens the waiting time until the tenth process step, whereas in the third embodiment, an additional waiting time is introduced or the second waiting time is divided.

[0076] In a tenth process step according to the invention, the space between the lower second sample holder and the lower / second substrate, which is actually placed thereon in a loose manner, is ventilated at a predefined pressure. "Pressure" in this case should be understood as absolute pressure. An absolute pressure of 1 bar corresponds to atmospheric pressure. That is to say, in order to carry out the process according to the invention, the chamber must be previously evacuated and then opened to the atmosphere, i.e. ventilated. This allows to promote free mobility of the substrate, which further minimizes distortions of the first substrate. The pressure is in particular between 1 mbar and 1000 mbar, preferably between 2.5 mbar and 800 mbar, more preferably between 5 mbar and 600 mbar, very preferably between 7.5 mbar and 400 mbar, most preferably between 10 mbar and 200 mbar. In a further embodiment according to the invention, it is conceivable to carry out the embodiment according to the invention up to the tenth process step under atmospheric pressure, after which an overpressure is created in the chamber by means of a compressor. In this case the pressure is in particular between 1 bar and 3 bar, preferably between 1 bar and 2.5 bar, more preferably between 1 bar and 2 bar, very preferably between 1 bar and 1.5 bar and most preferably between 1 bar and 1.2 bar.

[0077] In an eleventh process step, the propagation of the bonding wave, in particular during the bonding process, is once again or continuously monitored by the measuring means. This monitoring tracks the progress of the bonding wave and thus the progress of the bonding process, in particular over a period of more than 1 second, preferably more than 2 seconds, more preferably more than 5 seconds, very preferably more than 10 seconds, most preferably more than 15 seconds. Instead of tracking the bonding process over a predefined time interval, it is also possible to determine the tracking of the bonding wave with respect to the position of the bonding wave, in particular the radial position. In this case, the tracking of the bonding process is carried out in particular while the bonding wave is present at a radial position corresponding to at least 0.3 times, preferably at least 0.4 times, more preferably at least 0.5 times, very preferably at least 0.6 times, most preferably 0.7 times the diameter of the substrate. If the tracking of the bonding progress is desirably measurable by measuring the surface conductivity, it is also possible to carry out the bonding progress by the percentage of the bonded or unbonded surface. In that case, monitoring of the bonding progress according to the invention is carried out in particular until more than 9%, preferably more than 16%, more preferably more than 25%, very preferably more than 36% and most preferably more than 49% of the area has been bonded. Alternatively, monitoring is carried out continuously.

[0078] The control of the process sequence is preferably carried out on the basis of a defined / set or settable value from monitoring within the above-mentioned value range, from which a first waiting time for the advancement of the bonding wave before the start of the next process step is known.

[0079] In a twelfth process step according to the invention, in particular the second substrate, which has already been partially bonded, is again fixed in place on the lower second sample holder.

[0080] Generally speaking or in other words, at time t 4Especially after bonding, the retention force F H2 is increased.

[0081] The thirteenth process step corresponds to the ninth process step according to the first embodiment, and the fourteenth process step corresponds to the tenth process step according to the first embodiment.

[0082] An example process sequence for the third embodiment is given below: ● Loading the board Contact the pin to the wafer without initiating bonding (specifically 100mN force on the wafer) - the first force on the pin ● Bring two wafers relatively close to each other (especially 40-200μm apart) - First separation Press the wafer together (typically with a force of 1500-2800 mN) to initiate the fusion bond between both substrates - the second force of the pin ● Stop the heater Wait until the bonding wave has propagated sufficiently (typically 1 to 5 seconds) - the first waiting period Switch off (pump) the vacuum for the upper wafer (especially both zones at the same time) Switch off (exhaust) the vacuum for the lower wafer Wait for the bonding wave to propagate further (typically 1-10 seconds) - the second wait time Ventilate the space between the lower wafer and the chuck (lower sample holder) at a predetermined pressure (in particular 10 to 200 mbar) for a predetermined period of time - the first pressure Wait for the bonding wave to propagate further (typically 2-15 seconds) - the third wait period Switch on the vacuum suction for the lower wafer – first vacuum Pull back the pin ●Waiting until the bonding wave has fully propagated (especially 5 to 90 seconds) - the fourth waiting period.

[0083] The individual method steps can be generalized according to the general technical teachings above.

[0084] Post-processing The described process can be continued, inter alia, in further process modules.

[0085] In a first possible subsequent step, the formed substrate stack is inspected, inter alia, in a metrology module. This inspection can in particular include: Alignment errors, especially Global alignment errors, and / or Runout errors and / or Defects, especially Voids, and / or ○ Bubbles, and / or ○ Cracks, This includes measurement of the bond interface to confirm the bond.

[0086] If the inspection of the substrate stack has unacceptable errors, the substrate stack is preferably separated again, preferably by the methods and devices disclosed in EP 2 697 823 B1 and WO 2013 / 091714 A1, to which reference is made in this respect. Inspection of the bond interface is carried out, in particular, before a subsequent heat treatment.

[0087] In a second possible subsequent step, the formed substrate stack is heat-treated. The heat treatment in particular strengthens the bonds formed between the substrates of the substrate stack. The heat treatment is carried out in particular at a temperature higher than 25° C., preferably higher than 100° C., more preferably higher than 250° C., very preferably higher than 500° C. and most preferably higher than 750° C. This temperature is substantially equal to the heating temperature T H The bond strength achieved is notably 1.0 J / m 2greater than 1.5 J / m 2 More preferably, 2.0 J / m 2 more preferably 2.5 J / m 2 The heat treatment is preferably carried out under vacuum. The vacuum pressure is in particular less than 1 bar, preferably less than 800 mbar, more preferably less than 10 -3 Less than millibars, very preferably 10 -5 Less than millibars, most preferably 10 -8 Smaller than a millibar.

[0088] However, it is also conceivable to carry out the heat treatment in a protective gas atmosphere. This is advantageous, in particular if the protective gas used facilitates heat transfer. The thermal conductivity of the protective gas is in particular higher than 0 W / (m·K), preferably higher than 0.01 W / (m·K), more preferably higher than 0.1 W / (m·K) and very preferably higher than 1 W / (m·K). The thermal conductivity of helium is, for example, between about 0.15 W / (m·K) and 0.16 W / (m·K). The protective gas may in particular be: Noble gases, especially helium, neon, argon, krypton, and / or xenon Molecular gases, especially carbon dioxide and / or nitrogen Any combination of the above gases It is.

[0089] Preferably, the substrates have approximately identical diameters D1, D2, which differ from each other in particular by less than 5 mm, preferably by less than 3 mm, and more preferably by less than 1 mm.

[0090] In yet another, particularly independent, configuration of the invention, the deformation is effected by mechanical actuation means and / or temperature control of the first and / or second mounting device.

[0091] Variations in the invention can be realized even more easily if the first and / or second substrate is / are / are fixed in position on the first mounting surface and / or the second mounting surface only in the area of ​​the side walls.

[0092] The results of the process according to the invention are related to a number of physical parameters that can be directly associated with the substrate or the surrounding environment. In the following of the present disclosure, some of the most important parameters and their influence on the "runout" error are described. A rough distinction is made between single and paired parameters. Single parameters cannot be associated with a symmetric side, especially with a substrate. Paired parameters can have a different value on one symmetric side, especially with a first substrate, than on the oppositely located symmetric side, especially with a second substrate. There is a first upper symmetric side and a second lower symmetric side. Examples of single parameters are the bonding wave velocity v or the gas (mixture) pressure p. Examples of paired parameters are the thicknesses d1 and d2 of the substrates.

[0093] In the following description, when the influence of pair parameters on the bonding result is described, it is assumed that all other values ​​of each pair parameter are preferably the same, unless otherwise stated. The following example is given by way of illustration. When the influence of thicknesses d1 and d2 of two different substrates on the bonding result is described, it is assumed that the elastic moduli E1 and E2 of both substrates are the same.

[0094] The goal is to minimize or completely eliminate the "runout" errors by means of a calculated and / or experimentally determined optimal curvature line, in particular with respect to time. A "curvature line" in this case is understood to be a less symmetrical representation of a one-dimensional function that maps the surface positions of the substrates, i.e. the substrate surfaces, as a function of position coordinates, in particular the radial coordinates. "Less symmetrical" means that it is sufficient to calculate a one-dimensional curvature line in order to infer a two-dimensional contact between the substrates in a recursive manner, based on the radial symmetry of both substrates, such that the "runout" errors are minimized or completely eliminated as described above. In simple terms, the curvature line of the substrate can be described in particular as the substrate surface facing the bonding interface. Preferably, the description of the curvature line for the first substrate also applies to the second substrate.

[0095] The curved line, i.e. the substrate surface, is according to the invention primarily influenced by one or more of the following parameters, among others:

[0096] The thicknesses d1, d2 of the substrates are linked by the volumes V1, V2 and densities p1, p2 to the masses m1, m2 of the two substrates and thus to the gravitational forces G1, G2. The gravitational force G1 of the first substrate has a direct effect on the acceleration behavior of the first upper substrate in the direction of the second lower substrate. When the lower positioning fixture is switched off, the gravitational force G2 is a measure for the inertial force of the second lower substrate and thus for the force with which the second lower substrate tends to move, stand or remain along the bonding wave in the opposite direction to the first upper substrate.

[0097] The elastic moduli E1 and E2 are measures for the stiffness of the substrate. They have a decisive influence on the line of curvature and therefore together define a function that allows to describe how the substrates move towards each other.

[0098] The forces F1 and F2 influence the area where the two substrates are joined together, especially in the center. Since point-like contacting only exists in the ideal case, it must always be assumed that the contacting of the two substrates is performed in the center in an area-like manner. The size of the area is set primarily by the forces F1 and F2. The size of the contact area is decisive for the boundary conditions.

[0099] The temperatures T1, T2 of the two substrates can influence the overall thermal expansion state of the substrates. This allows, according to the invention, to set how strongly the substrates are distorted by thermal expansion relative to a reference temperature. Accurate temperature control of the upper and / or lower substrate is therefore an important feature for as precise and complete compensation of the "runout" as possible. The temperatures of the two substrates can preferably be set differently. In particular, the temperatures are set so that the substrates are in an expansion state in which the structures to be bonded to each other are congruent with each other, i.e. in which the "runout" errors have disappeared (assuming that no additional "runout" errors are built up during bonding by the parameters already listed above). The temperatures required for this can be determined by measurement means and / or by experiment.

[0100] The gas (mixture) pressure p influences the resistance that the atmosphere offers to the substrates moving towards each other. The gas (mixture) pressure can have a direct effect on the bonding wave velocity v. In this respect, reference is made to WO2014191033A1.

[0101] Holding force F H1 ,F H2 is used especially to fix the substrate in place prior to the actual bonding process. H1 is a boundary condition for the first to sixth process steps, but after the position fixing part is switched off, the influence of the boundary condition determining the curvature line is lost. H2are only used as boundary conditions as long as the lower position fixation is active. Therefore, in order to calculate based on the theory of elasticity, new boundary conditions must be created accordingly, at the latest from the seventh process step.

[0102] The initial radii of curvature r10, r20 are the initial radii of the substrate before carrying out the process according to the invention. The initial radii of curvature r10, r20 are functions of the position, but in particular are constant with respect to the position. In a first special embodiment according to the invention, the initial radius of curvature r10 of the second lower substrate is infinite, since the second lower substrate is lying flat at the start of the process according to the invention. In yet another special second embodiment according to the invention, the initial radius of curvature r10 of the second lower substrate is a finite positive or negative constant corresponding to a constant convex or concave curvature. In this case, the second lower substrate is present in a convex or concave curved shape at the start of the process according to the invention. Such a sample holder is described in WO2014 / 191033 A1, to which reference is made in this respect. In particular, at least the initial radius of curvature r10 of the second lower substrate coincides with a surface of the second lower sample holder on which the second substrate rests.

[0103] The substrate curvature radii r1, r2 of both substrates along the bonding wave are the result of solving an equation based on elasticity theory taking into account the above parameters. The substrate curvature radii r1, r2 are functions of position and time, among others.

[0104] The bonding wave speed is a result of the above parameters.

[0105] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments, taken in conjunction with the drawings. [Brief description of the drawings]

[0106] [Figure 1a]1 is a schematic, not-to-scale, cross-sectional view of a first process step of a first embodiment of a method according to the invention; FIG. [Figure 1b] FIG. 2 is a schematic, not-to-scale, cross-sectional view of a second process step. [Figure 1c] FIG. 2 is a schematic cross-sectional, not to scale, view of a third process step; [Figure 1d] FIG. 11 is a schematic, not-to-scale, cross-sectional view of a fourth process step. [Figure 1e] FIG. 11 is a schematic cross-sectional, not to scale, view of a fifth process step. [Figure 1f] FIG. 11 is a schematic cross-sectional, not to scale, view of a sixth process step. [Figure 1g] FIG. 13 is a schematic cross-sectional, not to scale, view of a seventh process step. [Figure 1h] FIG. 13 is a schematic cross-sectional, not to scale, view of an eighth process step. [Figure 1i] FIG. 13 is a schematic cross-sectional, not to scale, view of a ninth process step. [Figure 1j] FIG. 15 is a schematic cross-sectional, not to scale, view of a tenth process step. [Diagram 2] 5A-5C are schematic, not-to-scale, cross-sectional views of additional process steps of a third embodiment of the method according to the invention; [Diagram 3] 11A-11C are schematic cross-sectional, not-to-scale, views of optional additional process steps. [Figure 4] FIG. 2 is a schematic cross-sectional view, not to scale, of two substrates. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0107] In the drawings, identical components and components having identical functions are designated by the same reference numerals.

[0108] 1a shows a first process step. In the first process step, a first, in particular upper, substrate 2 is fixed on a sample holder surface 1o of a first, in particular upper sample holder 1. The fixing is effected by a fixing means 3 with a holding force F H1 This is carried out by.

[0109] The first sample holder 1 has a particularly central through-opening, in particular a hole 4. The through-opening is used for the through-insertion of a deformation means 6 (FIG. 1b) for deforming the first substrate 2.

[0110] In an advantageous embodiment not shown here, the first specimen holder 1 has a number of holes 5 through which the bonding progress can be observed by means of measuring means. The holes 5 are preferably elongated cutouts.

[0111] On the second, in particular the lower, sample holder 1', a second substrate 2' is loaded and fixed in position. The fixing is performed by a fixing means 3' with a holding force F H2 This is carried out by.

[0112] The position fixing means 3, 3' are preferably vacuum fixations.

[0113] The sample holders 1, 1' comprise, inter alia, a heater 11 (heating means), which for clarity in the drawings is only diagrammatically shown on the second, lower sample holder 1'.

[0114] All the parameters or forces mentioned above that describe the properties of or affect the substrates 2,2' are generally functions of position and / or time. Examples of parameters include the temperatures T1 and T2 of both substrates 2,2'. The temperatures T1 or T2 may generally be related to the position, so that a temperature gradient exists. In this case, it is advantageous to express the temperature as an explicit function of position and / or time. Examples of forces include the two gravitational forces G1 and G2. These two gravitational forces G1 and G2 represent the total gravitational force acting on the substrates 2,2' in the drawings. However, it is obvious to those skilled in the art that both substrates 2,2' can be decomposed into infinitesimal (mass) parts dm and that the effect of gravity can be applied to each of these mass parts dm. Gravity should therefore generally be expressed as a function of position and / or time.

[0115] Similar considerations apply with respect to all other parameters and / or forces.

[0116] 1b shows a second process step according to the invention. In the second process step, the deformation means 6, in particular the pins, apply pressure to the rear side 2i of the first substrate 2, causing a deformation of the first substrate 2. In this case, the deformation of the first substrate 2 is caused by a first force F 1 This is carried out by.

[0117] In the process step of Fig. 1c, the two sample holders 1, 1' and thus the two substrates 2, 2' are brought closer together until a predefined distance is obtained. This can be carried out either during the second process step or before the second process step.

[0118] In the process step of FIG. 1d, a second force F 2 The bonding, especially the pre-bonding, is initiated by the second force F 2 brings about a further, in particular an infinitesimally small, deflection, bringing the two substrates 2, 2' even closer together, and finally contacting each other at the contact point 7.

[0119] The bonding wave, more particularly the bonding wave front 8, starts to propagate, in particular radially symmetrically, preferably concentrically, from the contact point 7 with a bonding wave speed v. The bonding wave speed v can be changed in the course of the further process steps, and thus this bonding wave speed v can be defined as a function of position (or time). The bonding wave speed v can be influenced by various means.

[0120] In a further process step of FIG. 1e, the heater 11 of the first and / or second sample holder 1, 1' is switched off, whereby further heating of the first and / or second substrate 2, 2' is interrupted. In a further process step of FIG. 1f, the bonding wavefront 8 is monitored by a measuring means 9, in particular by means of an optical system, preferably an infrared optical system. The measuring means 9 detects through a hole 5 (at least one, preferably a number corresponding to the number of optical systems) the substrate backside 2i of the first substrate 2 and further preferably the bonding interface between both substrates 2, 2' and thus the bonding wavefront 8. The detection of the bonding interface is carried out in a measuring means 9 which is in particular sensitive to electromagnetic radiation, which can penetrate both substrates 2, 2' without being significantly attenuated. A light source 12 is preferably arranged above and / or below and / or inside the sample holder 1'. The electromagnetic radiation of the light source 12 illuminates and / or penetrates the sample holder 1' and / or the substrate 2, 2' and can be detected by the measuring means 9. The image thus captured is preferably a black and white image. Due to the difference in brightness it is possible to unambiguously distinguish between bonded and non-bonded areas. The transition area between the two areas is the bonding wave. By such a measurement it is possible, inter alia, to determine the position of the bonding wave front 8 and thus also the bonding wave velocity v, especially in the case of multiple such positions.

[0121] Fig. 1g shows a further seventh process step. In the seventh process step, the holding force F H1 The position fixation 3 of the first sample holder 1 is released by at least reducing the holding force F. If the position fixation 3 is a vacuum fixation, it further preferably has a plurality of separately controllable vacuum segments (a plurality of holding forces F H1 In the case of vacuum fastenings, in particular from the inside to the outside, several vacuum segments can be switched off in a targeted manner (or one or more holding forces F H1 The dissociation is achieved by selectively reducing the

[0122] 1h shows a further process step, in which the bonding wavefront 8 after detachment from the first substrate holder 1 is monitored by measurement means 9.

[0123] Fig. 1i shows a further process step, in which the action exerted by the deformation means 6 on the first substrate 2 is interrupted. If the deformation means 6 is a mechanical deformation means, in particular a pin, the interruption is performed by pulling it back. If a nozzle is used, the interruption is performed by interrupting the flow of fluid. In the case of an electric and / or magnetic field, the interruption is performed by switching off the electric and / or magnetic field.

[0124] 1j shows a further process step, after which the two substrates 2, 2' are completely bonded to one another, in which, among other things, the bonding wave front 8 (not shown anymore since bonding has already been completed in this process state) is continuously monitored by the measuring means 9 until bonding is completed, at which point the substrate stack 10 formed from the first and second substrates 2, 2' is complete.

[0125] 2 shows an optional process step, which is in particular located after the process step of FIG. 1g, in which the holding force F of the second lower stationary part 3′ of the second lower sample holder 1′ is increased. H2 In particular, the retention force F H2 is reduced to 0, i.e. the positional fixation is released, which in particular allows the second substrate 2' to be moved unhindered, in particular laterally along the lower sample holder surface 1o'.

[0126] In yet another advantageous embodiment, the second substrate 2' is lifted up from the second lower sample holder 1' until it in particular locally lifts off, this is in particular caused by applying pressure from the second sample holder 1' to the second substrate 2'.

[0127] Gravity G2 opposes the lifting of the second substrate 2' throughout the bonding process and thus affects the contacting of both substrates 2, 2' and thus also the "run-out".

[0128] 3 shows an optional process step according to the invention, in which the chamber in which the process according to the invention is carried out is ventilated before the completely bonded substrate stack 10 is formed. This ventilation is used, inter alia, to control the advancement of the bonding wave front 8. A detailed description of the influencing means is disclosed in WO2014 / 191033A1, to which reference is made in this respect. The ventilation is carried out by means of a gas or a gas mixture. In particular, the ventilation is carried out by opening a valve to the ambient atmosphere, whereby the chamber is ventilated by the ambient gas (mixture). Instead of ventilating to the ambient atmosphere, it is also conceivable to overpressure the chamber by means of a gas or a gas mixture.

[0129] 4 is a schematic, not to scale, cross-sectional view of two substrates 2, 2', which are defined by a number of parameters. The substrate surfaces 2o, 2o' correspond to the curvature lines of the first, upper substrate 2 or the second, lower substrate 2' at a given time. The substrate surfaces 2o, 2o' are primarily defined by the above parameters. The shape of the substrate surfaces 2o, 2o' changes as a function of time during the bonding process according to the invention. [Explanation of symbols]

[0130] 1,1' Sample holder 1o,1o' Sample holder surface 2,2' Board 2o,2o' Substrate surface 2i Back side of the board 3,3' position fixed part 4 Hole 5 Hole 6. Transformation Methods 7 Contact Points 8 Bonding Wave Front 9 Measurement means 10 Board Stack 11 Heater 12 light source F 1 ,F 2 force F H1 ,F H2 holding power v Bonding wave speed T H heating temperature T1, T2 Board temperature E1, E2 Elastic modulus of substrate d1,d2 Thickness of the board V1, V2 Board volume m1,m2 Mass of the board p1,p2 Substrate density G1, G2 Gravity of the board r1, r2 Radius of curvature of the board r10,r20 Initial radius of curvature of the substrate D Board edge spacing

Claims

1. A method for bonding a first substrate (2) to a second substrate (2') at the contact surfaces (2o, 2o') of both substrates (2, 2'), comprising the following steps, in particular the following sequence: ・Holding force F Ｈ１ The first substrate (2) is held on the first sample holder surface (1o) of the first sample holder (1) by a holding force F Ｈ２ - holding said second substrate (2') on a second sample holder surface (1o') of a second sample holder (1') by Both of the contact surfaces (2o, 2o') are contacted at a predetermined bonding initiation point (20) and at least the second sample holder surface (1o, 1o') is heated to a heating temperature T Ｈ and - bonding the first substrate (2) to the second substrate (2') along a bonding wave that proceeds from the bonding initiation point (20) to the side edges (2s, 2s') of both substrates (2, 2'); In a method having the following structure: The heating temperature T of the second sample holder surface (1o′) Ｈ during said bonding. A method comprising:

2. Depending on the progress of the bonding wave, the heating temperature T Ｈ Reduce The method of claim 1.

3. Detecting the progress of the bonding wave at least for each portion by a measuring means.

3. The method according to claim 1 or 2.

4. At a time t during the bonding １ , in particular until the first substrate (2) is detached from the first sample holder (1), the holding force F Ｈ１ Reduce 4. The method according to any one of claims 1 to 3.

5. At a time t during the bonding ２ , in particular until the second substrate (2') on the second sample holder (1') is deformable along the second sample holder surface (2o'). Ｈ２ Reduce 5. The method according to any one of claims 1 to 4.

6. Time t ３ ventilating the second substrate (2') from the second sample holder surface (1o') with an overpressure, in particular between 10 mbar and 500 mbar, preferably between 10 mbar and 200 mbar; 6. The method according to any one of claims 1 to 5.

7. Time t ４ In particular, after the bonding, the retention force F Ｈ２ Increase the 7. The method according to any one of claims 1 to 6.

Images