How to bond a 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 according to claim 1. [Background technology]

[0002] In the semiconductor industry, substrates have been aligned and bonded to one another for many years. Bonding, also known as joining, is used to create multi-layer substrate stacks. In such multi-layer substrate stacks, functional units, such as memories, microprocessors, and MEMS, among others, can be bonded to one another and thus combined with one another. This combinability allows for a wide variety of applications.

[0003] The density of functional units is increasing year by year. With the advancement of technological development, 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 primarily responsible for the reduction of component costs.

[0004] A drawback 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 joining interface of both substrates.

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

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

[0007] For one thing, the positions of the structures on the first and / or second substrates generally deviate from their theoretical positions. There can be several reasons for this deviation.

[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 errors in position.

[0009] Another, not insignificant reason is the deformation of the substrate due to mechanical loads, 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 rather varies. The temperature change causes thermal expansion, which in the most ideal case leads to a change in diameter and in the most unfavorable case to complex thermal deformations.

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

[0011] Third, layers and structures placed on the substrate can create stress 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 significant technical challenges in permanently bonding two substrates is the alignment accuracy of the functional units between the individual substrates. Although the substrates can be aligned very precisely with respect to each other using alignment equipment, distortion of the substrates can occur during the bonding process itself. Due to this distortion, the functional units are not necessarily properly aligned with each other at all positions. Inaccuracies in the alignment of a particular point on the substrate can result in distortions, scaling errors, lens defects (enlargement or reduction errors), etc. In the semiconductor industry, all such topic areas are encompassed by the concept of "overlay." A corresponding overview of this topic can be found, for example, in Mack, Chris, "Fundamental Principles of Optical Lithography - The Science of Microfabrication" (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 structure that can be manufactured using microsystem technology are also designed in a CAD (computer-aided design) program. However, during the manufacturing of the functional unit, deviations are always found between the ideal functional unit constructed in the computer and the actual functional unit manufactured in the clean room. The differences can be primarily due to hardware limitations, i.e., technical engineering issues, but can also often be due to physical limitations. Namely, the resolution accuracy of structures manufactured by photolithography processes is limited by the size of the photomask aperture and the wavelength of the light used. Mask distortions are directly transferred to the photoresist. The machine's linear motors can only reach positions that are reproducible within a specified tolerance. Therefore, it is not surprising that the functional unit on the substrate cannot be exactly equivalent to the structure constructed in the computer. Therefore, all substrates already have negligible deviations from the ideal state before the bonding process. If we compare the position and / or shape of two functional units located opposite each other on two substrates, 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 the two functional units, since they deviate from the ideal computer model due to the errors described above. The most common errors are illustrated in Figure 8 (copied 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," Wiley, p. 312, 2007, reprinted 2012).As shown in the drawings, overlay errors can be roughly divided 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 oppositely positioned functional units, regardless of their location. Typical global overlay errors are errors I and II, which are caused by the relative translation or rotation of the two substrates. The translation or rotation of the two substrates generates corresponding translational or rotational errors on the substrates for all oppositely positioned functional units, respectively. Local overlay errors are location-related and are primarily caused by elastic and / or plastic problems and / or pre-processing, particularly in this case by elastic and / or plastic problems and / or pre-processing caused by the continuously propagating bonding wave. Of the illustrated overlay errors, errors III and IV are referred to as "run-out" errors. These "run-out" errors are caused in particular by distortion of at least one substrate during the bonding process. Due to distortion of at least one substrate, the functional units of the first substrate are also distorted relative to the functional units of the second substrate. However, errors I and II can also be caused by the bonding process, but are often significantly superimposed by errors III and IV, making errors I and II extremely difficult to detect or measure. This applies to modern bonders, particularly fusion bonders, which are capable of very precise correction in the x- and / or y-directions and / or rotational directions.

[0014] In the known prior art, there are already facilities that can at least partially reduce local distortions: 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 "runout" errors. U.S. Patent Application Publication No. 20120077329 (US20120077329A1) describes a method for achieving a desired alignment accuracy between functional units of two substrates during and after bonding by not fixing the lower substrate in position. This allows the lower substrate to be free from boundary conditions and to be freely bonded to the upper substrate during the bonding process. An important feature in the known prior art is, among other things, fixing one substrate in position flat, usually using a vacuum device.

[0016] The generated "runout" error usually increases radially symmetrically around the contact point, and therefore increases from the contact point to the periphery. This usually results in a linearly increasing amplification of the "runout" error. Under special conditions, the "runout" error can also increase nonlinearly.

[0017] Particularly under optimal conditions, the "runout" error can not only be detected by suitable measuring instruments (EP 2463892), but can also be recorded by a mathematical function. Since the "runout" error is a translation and / or rotation and / or scaling between well-defined points, the "runout" error is advantageously described by a vector function. In general, such a vector function is the function f:R 2 →R 2 and is therefore a 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. A vector function can, with great probability, be n It is an n≧1 function and therefore continuously differentiable at least once. The divergence of the vector function is likely to be different from zero, since the "runout" error increases from the contact point towards the edge. Therefore, the vector field is a well-spring field with great probability.

[0018] "Runout" errors are best determined in relation 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 could be, 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 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 a combination of two components.

[0021] The first component R1 describes the substantial portion of the "runout" error, i.e., the portion resulting from manufacturing errors of the structure or distortion of the substrate. In other words, the first component R1 is inherent in the substrate. In this case, it should be noted that if the structure is properly manufactured at a first temperature, but undergoes a temperature change to a second temperature prior to the bonding process, the substrate may also have substantial "runout" errors, which will cause thermal expansion that will distort the entire substrate and, consequently, the structures present on it. A temperature difference of just a few Kelvins, or even a tenth of a Kelvin, is already sufficient to cause such distortion.

[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. This extrinsic part does not exist before the bonding process. This extrinsic part includes, in particular, local and / or global distortions of the first and / or second substrates 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 that allows for error-free, especially 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, claims and / or drawings are within the scope of the invention. In the ranges of values ​​described, the values ​​within the ranges mentioned are themselves considered to be disclosed as limit values ​​and can be claimed in any combination. If one or more method steps can be performed in several different devices or several 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 of the invention is that the substrates are released from their fixed positions, particularly during bonding, to allow the substrate stack to deform freely during bonding. A further important feature of a third embodiment of the invention is that the substrate stack can be ventilated or pressurized during bonding, particularly at the interfaces of the substrate stack.

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

[0027] A characteristic process of the present invention for bonding, particularly permanent bonding, preferably fusion bonding, is the most concentric point-like contacting of both substrates. In particular, the contacting of both substrates can also be performed non-concentrically. Bonding waves propagating from non-concentric contact points reach different locations on the substrate edges at different times. This complicates a complete mathematical and physical description of the bonding wave characteristics and the resulting compensation for "runout" errors. In particular, the contact points are not located so far from the substrate center that any potential effects arising from this are negligible, at least at the edges. The distance between a possible non-concentric contact point and the substrate center is preferably less than 100 mm, preferably less than 10 mm, more preferably less than 1 mm, most preferably less than 0.1 mm, and most preferably less than 0.01 mm. Hereinafter, "contacting" generally refers to concentric contacting. The term "center" in its broadest sense preferably refers to the geometric center of an ideal, basic object, compensated for asymmetrical features, if necessary. For industrially common wafers with notches, the center is the center of a circle that would enclose an ideal wafer without a notch. For industrially common wafers with flats (flat chamfered surfaces), the center is the center of a circle that would enclose an ideal wafer without a flat. A similar concept applies to arbitrarily shaped substrates. However, in special configurations, it may be useful to refer to the "center" as the center of gravity of the substrate. To ensure accurate, concentric point contact, a radially symmetrical positioning device (substrate holder) is provided with a central hole and a pin that can be translated within the hole. It is also conceivable to use a nozzle that applies pressure to a fluid, preferably a gas, instead of the pin.Furthermore, if a device is provided that can bring the substrates closer to each other by translational movement, under the further prerequisite that at least one of the substrates, preferably the upper one, has a curvature that is imparted to it by gravity in the direction of the other substrate, and therefore automatically contacts the corresponding second substrate at a sufficiently small distance during said translational approach, the use of such elements can be completely eliminated.

[0028] The radially symmetrical fixing / holding means are provided with vacuum holes, circular vacuum lips or comparable vacuum elements that can fix the upper substrate in place. Electrostatic mounting devices are 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 so that the first and / or second substrate is curved concavely and / or convexly by generating 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 through which fluid or air can flow or be evacuated. The use of a nozzle for pinpoint pressure application can be omitted in favor of a globally established pressure. According to the invention, embodiments are conceivable in which the substrate is sealed and / or otherwise fixed, particularly at its edges. For example, if the mounting device is configured to create a negative pressure relative to the external atmosphere, sealing at the substrate edges is sufficient. If an overpressure is generated inside the mounting device to curve the substrate outward, i.e., convexly, the substrate is preferably mechanically fixed, particularly at its edges. By applying a negative or overpressure to the substrate from the backside, the substrate's curvature can be precisely set.

[0030] After the centers of the two substrates are brought into contact, the upper substrate holder is gradually released in a controlled manner. The upper substrate falls downward due to gravity and the bonding force acting between the two substrates along the bonding wave. The upper substrate is bonded to the lower substrate in a radial direction from the center toward the side edges. This results in the formation of a radially symmetrical bonding wave, particularly one extending from the center toward the side edges, according to the present invention. During the bonding process, the two substrates expel gas, particularly air, present between the two substrates from the front of the bonding wave, thereby creating a bonding interface free of gas inclusions. The upper substrate essentially falls on a sort of gas cushion.

[0031] The first / upper substrate is not subject to additional positional fixation after the initiation of bonding at the bond initiation point; that is, 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 geometric 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 as a function of the distance from the center. This leads to a "runout" error that is to be eliminated by the method and apparatus of 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 bonded substrates during bonding, in particular by thermodynamic and / or mechanical compensation mechanisms. Furthermore, the present invention deals with corresponding products manufactured using the apparatus according to the present invention and the method according to the present invention.

[0033] "Runout" errors are particularly related to the position of the substrate along its surface. In particular, it has been found that "runout" errors increase 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 particularly related to the bonding wave speed. Generally, the faster the bonding wave speed, the greater the "runout" error. Therefore, according to the present invention, a bonding wave speed is preferably set that is slower than 100 mm / s, preferably slower than 50 mm / s, even more preferably slower than 10 mm / s, very preferably slower than 1 mm / s, and most preferably slower than 0.1 mm / s. In one particular embodiment according to the present 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 immediately before the start of the (pre)bonding process. The gap between the substrates is a function of position, especially as long as the upper first substrate is deformed by the deformation means with a first force F1. The gap between the substrates is particularly largest at the edges. The smallest gap is located in the region of the maximum convexity of the deformed substrate. Therefore, the shape of the deformed substrate also influences the "runout" error. The gap between the substrates at the edges (substrate edge gap D) is particularly set to be less than 5 mm, preferably less than 2 mm, more preferably less than 1 mm, very preferably less than 0.5 mm, and most preferably less than 0.1 mm immediately before bonding. The gap between the substrates below the maximum convexity is particularly set to be less than 1 mm, preferably less than 100 μm, more preferably less than 10 μm, very preferably less than 1 μm, and most preferably less than 100 nm immediately before bonding. The "runout" error is particularly related to the type of sample holder and the resulting type of fixation / holding of each substrate. International Publication No. WO 2014 / 191033 (WO 2014 / 191033 A1) discloses several embodiments of preferred sample holders, and reference is made to this document in this regard. In the disclosed process, it is crucial to release the substrate from the sample holder after release of fixation, especially after release of 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 minimizes contact points between the sample holder surface and the substrate. Thus, the separation of the substrate from the sample holder is performed with minimal energy cost. Waviness is preferably minimized to prevent the sample holder surface from creating new sources of "runout." In this regard, it should be noted that the description of waviness does not imply that the sample holder surface must not be curved as a whole.

[0036] Roughness can be expressed as either the average roughness, the squared roughness, or the average roughness depth. The calculated average roughness, the squared roughness, and the calculated average roughness depth generally vary for the same measurement path or surface, but are within the same order of magnitude. Therefore, the following numerical ranges for roughness should be understood as either the average roughness, the squared roughness, or the average roughness depth. The roughness is preferably set to be greater than 10 nm, preferably greater than 100 nm, more preferably greater than 1 μm, most preferably greater than 10 μm, and most preferably greater than 100 μm. The "runout" error is particularly related to the time aspect. Because the bonding wave propagates very quickly, there is not enough time for the substrate materials to optimally bond to each other immediately after, during, and / or immediately before the bonding wave. Therefore, controlling the bonding wave in terms of time can also be crucial.

[0037] "Runout" errors are particularly related to the process of loading the substrate onto the specimen holder. During loading and fixation, the substrate may be distorted, which is maintained by the fixation and is incorporated into the substrate stack during (pre-)bonding. The substrate is therefore brought onto the specimen holder by the end effector with as little distortion as possible.

[0038] The "runout" error is particularly related to the temperature difference and / or temperature fluctuation between the two substrates. The substrates are fed to the bonding module from different process steps or process modules, where different processes may have been performed at different temperatures. Furthermore, the upper and lower sample holders may have different structures, configurations, and thus different physical properties, especially thermal properties. For example, the sample holders may have different thermal masses and / or thermal conductivities. This may result in different loading temperatures or different temperatures at the time of (pre)bonding. Therefore, the sample holder for carrying out the process according to the invention is equipped with a heating and / or cooling system to enable the temperature of at least one (preferably both) substrates to be precisely set. It is particularly possible to adapt the temperatures of the two substrates to different values ​​and 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, among other things, for the "runout" error component R1.

[0039] The "runout" error is related, 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] Runout errors are particularly related to the symmetry of the system, and therefore, preferably, as many components as possible (and more preferably, at least the majority) are configured 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 the substrates in different orders, and this should be taken into consideration. Furthermore, one of the substrates is preferably deformed, while the other substrate rests flat on the sample holder. All characteristics, parameters, and embodiments that result in asymmetries have an effect on 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 present invention, it is attempted to significantly minimize, and in particular completely eliminate, runout by, among other things, varying other changeable parameters.

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

[0042] Sample holder A sample holder preferably used for an embodiment according to the invention uses a positioning fixture, which is used to hold a substrate with a positioning force or a corresponding positioning pressure. The positioning fixture may comprise, among other things: Mechanical position fixing parts, especially clamps, or ● Vacuum fixing parts, especially individually controllable vacuum passages, or ○Interconnected vacuum passages or Electrical positioning devices, especially electrostatic positioning 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 clamping device is preferably electronically controllable. A vacuum clamping device is a preferred form of clamping device. The vacuum clamping device preferably comprises 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 into each vacuum channel segment, which is individually controllable, i.e., can be individually evacuated or inflated. 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 a ring shape. This allows the substrate to be clamped and / or released from the sample holder in a targeted manner with radial symmetry, especially 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 regard.

[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 in particular have a camera. The monitoring preferably includes: cameras, in particular visual or infrared cameras, and / or Conductivity measuring equipment This is carried out using

[0046] When the determination of the bonding wave is carried out using a camera, it is possible to detect the position of the bonding wave at any time, and in particular its progress. The camera is preferably an infrared camera that digitizes the data and transmits it to a computer. On this basis, the computer can evaluate the digital data and determine, in particular, 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 provided. The measurement of the surface conductivity is performed, inter alia, by contacting two electrodes with the substrate at two locations facing each other. In one particular embodiment of the invention, the electrodes contact the edge of the substrate without interfering with the bonding of the substrate at the edge. In a second, less preferred embodiment of the invention, the electrodes are retracted from the substrate before the bonding wave reaches the side edge of the substrate.

[0048] The following describes processes, which preferably proceed in the order described, particularly as separate steps, and unless otherwise stated, the process steps and disclosures can be transferred from one embodiment to another, respectively, if 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 present invention, one of the two substrates is positioned and fixed on a first / upper sample holder, and the second substrate is positioned and fixed on a second / lower sample holder. The substrates may be fed manually, but preferably robotically, i.e., automatically. The upper sample holder preferably uses a deformation means for deforming the upper first substrate in a targeted, particularly controllable manner, by a first force F1. The upper sample holder preferably has at least one opening through which a deformation means, particularly a pin, can mechanically deform the upper first substrate. Such a sample holder is preferably disclosed in WO 2013 / 023708 A1.

[0050] In a second process step, a deformation means, in particular a pin, contacts the rear side of the upper first substrate and produces a slight deformation, in particular a deflection called a concave, from the side of the deformation means (i.e. from above). The deformation means applies a first force F1 to the first substrate, 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. This force is too weak to detach the upper first substrate from the sample holder, but is strong enough to produce a deflection according to the invention. The force preferably acts on the substrate in a point-like manner as much as possible. Since a point-like action does not actually exist, the force preferably acts on a very small area. This area is in particular less than 1 cm. 2 Smaller than 0.1 cm, preferably2 less than 0.01 cm, and preferably less than 0.01 cm 2 less than 0.001 cm, most preferably 2 Smaller than 0.001cm 2 In the case of acting on an area of ​​1000 MPa, the applied force is in accordance with 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 the third process step, the substrates are brought closer together, in particular by bringing the sample holders closer together. Preferably, the lower sample holder is raised, thereby actively bringing the lower, second substrate closer to the upper, first substrate. However, it is also conceivable to actively bring the upper sample holder closer to the lower sample holder, or to simultaneously bring the two sample holders closer to each other. The substrates are brought closer together until they are separated by a distance of, in particular, between 1 μm and 2000 μm, preferably between 10 μm and 1000 μm, more preferably between 20 μm and 500 μm, and most preferably between 40 μm and 200 μm. This distance is defined as the smallest vertical distance between the surface points of the two substrates.

[0052] The first and / or second substrate is heated by a heating means and / or cooled by a cooling means, ie, temperature-regulated, before 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, a second force F2 of the deformation means is applied to the first substrate, in particular greater than 100 mN, preferably greater than 500 mN, more preferably greater than 1500 mN, very preferably greater than 2000 mN, and most preferably greater than 3000 mN. This causes or at least supports a first contact between the upper first substrate and the lower second substrate. The calculation of the pressure that is preferably generated is based on the smallest assumed area of ​​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 the sixth process step, 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, particularly over a period of more than 1 second, preferably more than 2 seconds, 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 predetermined time interval, the tracking of the bonding wave can also be determined in terms of the position of the bonding wave, particularly 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, 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, the progress of the bonding can also be measured 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 based on 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, the clamping mechanism of the upper first sample holder is switched off. It is also conceivable to release the upper first substrate by deliberately releasing the clamping mechanism. In particular, in the case of a vacuum clamping mechanism consisting of several individually controllable vacuum channels, the deliberate release of the clamping mechanism is carried out by progressively releasing the vacuum, particularly from the center toward the edge. The seventh process step is initiated, in particular, at the time t1 when one of the parameters of the measuring means reaches a defined / set or settable value (see in particular the sixth process step).

[0057] Generally speaking, or in other words, at time t1 during bonding, the holding force F H1 is reduced.

[0058] In the eighth process step, the propagation of the ongoing bonding wave is monitored again or continuously by a measuring device. This monitoring tracks the progress of the bonding wave, and thus the progress of the bonding process, particularly over a period of more than 5 seconds, preferably more than 10 seconds, more preferably more than 50 seconds, most preferably more than 75 seconds, and most preferably more than 90 seconds. Instead of tracking the bonding process over a predetermined time interval, it is also possible to measure the position of the bonding wave, particularly its radial position. In this case, the bonding process is tracked, particularly 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, most preferably at least 0.6 times, and most preferably at least 0.7 times the diameter of the substrate. If the bonding progress can be tracked by measuring the surface conductivity, the bonding progress can also be measured by the percentage of the bonded or unbonded surface. In this 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 based on 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 determined.

[0060] In a ninth process step, the deformation means is deactivated. If the deformation means is a pin, the pin is retracted. 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 monitored again or continuously. This monitoring tracks the progress of the bonding wave, and thus the progress of the bonding process, particularly over a period of more than 5 seconds, preferably more than 10 seconds, more preferably more than 50 seconds, most preferably more than 75 seconds, and most preferably more than 90 seconds. Instead of tracking the bonding process over a predetermined time interval, it is also possible to track the bonding wave with respect to its position, particularly its radial position. In this case, the bonding process is tracked, particularly while the bonding wave is present at a radial position corresponding to at least 0.6 times, preferably at least 0.7 times, more preferably at least 0.8 times, and most preferably at least 0.9 times the diameter of the substrate. If the substrate has an edge profile, the bonding process cannot be tracked all the way to the outermost edge, because, due to the edge profile, approximately 3 to 5 mm will not be bonded. If it is desired to monitor the progress of bonding by measuring the surface conductivity, the progress of bonding can also be measured by the percentage of the bonded or unbonded surface. In this case, the monitoring of the progress of bonding according to the present invention is carried out 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 based on 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 determined.

[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) ● Two wafers are brought relatively close to each other (interval 40 to 200 μm) Apply force to the wafer (1500-2800mN force) to initiate the fusion bond between the two substrates. ●Stop the heater Wait until the bonding wave has propagated sufficiently (typically 1-5 seconds) - the first waiting period Switch off (exhaust) the vacuum on the wafer surface (especially both zones simultaneously) Wait for the bonding wave to propagate further (typically 2-15 seconds) - the third waiting period Pull back the pin ●Waiting until the bonding wave has fully propagated (especially 5-90 seconds) - the fourth waiting period.

[0064] The individual method steps can be generalized by 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 lower second specimen holder is reduced or the clamping mechanism is switched off. It is also conceivable to release the lower second substrate by selectively releasing the clamping mechanism. This is achieved, particularly in the case of a vacuum clamping mechanism consisting of several individually controllable vacuum channels, by sequentially releasing the vacuum, particularly from the center toward the edge. The eighth process step according to the invention is an important step for reducing "runout" errors. According to the invention, the lower / second substrate can be adapted to the upper first substrate by reducing the holding force of the lower second specimen holder or by switching off the clamping mechanism. By releasing the clamping mechanism, additional (mathematical and mechanical) boundary conditions that may limit the bonding process are essentially removed.

[0067] Generally speaking, or in other words, at time t2 during bonding, the holding force F 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, the already partially bonded second substrate is re-fixed in the second lower sample holder. This tenth process step according to the invention is also an important step for reducing "runout" errors. By re-fixing, and in particular by switching on the vacuum again, the bonding process is again limited by (mathematical and mechanical) boundary conditions.

[0070] Generally speaking, or in other words, at time t4, 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 of the present invention, the switching off of the fixing member in the eighth process step and the re-switching on of the fixing member in the tenth process step can be repeated several times before the end of the bonding process. In particular, the switching off and re-fixing can even be performed spatially resolved. According to the present invention, this works in particular with the individually controllable vacuum channels or vacuum segments already described in this disclosure. In other words, in the ideal case, the release or fixation of the lower / second substrate is performed spatially and / or temporally resolved.

[0073] An example process sequence for the second embodiment is given below: ●Loading the board Contacting the pin (deformation means) with 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 a distance of 40 to 200 μm) - First distance Press the wafers together (typically 1500-2800 mN) to initiate the fusion bond between the two substrates - the second force of the pins ●Stop the heater Wait until the bonding wave has propagated sufficiently (typically 1-5 seconds) - the first waiting period Switch off (exhaust) the vacuum for the upper wafer (especially both zones simultaneously) Switch off (exhaust) the vacuum for the lower wafer Wait for the bonding wave to propagate further (typically 2-15 seconds) - the third waiting period Switch on the vacuum suction for the bottom wafer - first vacuum Pull back the pin ●Waiting until the bonding wave has fully propagated (especially 5-90 seconds) - the fourth waiting period.

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

[0075] Process according to a 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, each parameter is preferably set to be 10 to 40% smaller than in the second embodiment. This shortens the waiting time until the tenth process step, and 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 placed thereon in a loosely fixed manner, is ventilated at a predetermined pressure. "Pressure" in this context should be understood to mean absolute pressure. An absolute pressure of 1 bar corresponds to atmospheric pressure. That is, to carry out the process according to the invention, the chamber must be evacuated beforehand and then opened to the atmosphere, i.e., vented. This facilitates free substrate mobility, thereby further minimizing distortion of the first substrate. The pressure is preferably 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, and most preferably between 10 mbar and 200 mbar. In yet another embodiment according to the invention, the process according to the invention is carried out under atmospheric pressure up to the tenth process step, after which an overpressure is created in the chamber by 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, most preferably between 1 bar and 1.2 bar.

[0077] In an eleventh process step, the propagation of the ongoing bonding wave is monitored again or continuously by a measuring device. This monitoring tracks the progress of the bonding wave, and thus the progress of the bonding process, particularly over a period of more than 1 second, preferably more than 2 seconds, more preferably more than 5 seconds, most preferably more than 10 seconds, and most preferably more than 15 seconds. Instead of tracking the bonding process over a predetermined time interval, the tracking of the bonding wave can also be determined in terms of the position, particularly the radial position, of the bonding wave. In this case, the tracking of the bonding process is carried out, particularly 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, most preferably at least 0.6 times, and 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, the bonding progress can also be measured in terms of the percentage of the bonded or unbonded surface. In this 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 based on 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, the second substrate, which is in particular already partially bonded, is again fixed in place on the lower second sample holder.

[0080] Generally speaking, or in other words, at time t4, especially 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, 100 mN force on the wafer) - the first force on the pin ● Bring two wafers relatively close to each other (especially a distance of 40 to 200 μm) - First distance Press the wafers together (typically 1500-2800 mN) to initiate the fusion bond between the two substrates - the second force of the pins ●Stop the heater Wait until the bonding wave has propagated sufficiently (typically 1-5 seconds) - the first waiting period Switch off (exhaust) the vacuum for the upper wafer (especially both zones simultaneously) Switch off (exhaust) the vacuum for the lower wafer Wait for the bonding wave to propagate further (typically 1-10 seconds) - the second waiting period Ventilate the space between the lower wafer and the chuck (lower sample holder) at a predetermined pressure (in particular 10-200 mbar) for a predetermined period of time - first pressure Wait for the bonding wave to propagate further (typically 2-15 seconds) - the third waiting period Switch on the vacuum suction for the bottom wafer - first vacuum Pull back the pin ●Waiting until the bonding wave has fully propagated (especially 5-90 seconds) - the fourth waiting period.

[0083] The individual method steps can be generalized by 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 may in particular: Alignment errors, especially Global alignment errors, and / or Runout error and / or Defects, especially Voids, and / or bubbles, and / or ○Cracks, This includes measuring 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 2697823 B1 and WO 2013 / 091714 A1, to which reference is made in this respect. The inspection of the bonded interface is preferably carried out before a subsequent heat treatment.

[0087] In a second possible subsequent step, the formed substrate stack is heat-treated, which in particular strengthens the bonds formed between the substrates of the substrate stack. The heat treatment is carried out in particular at a temperature above 25° C., preferably above 100° C., more preferably above 250° C., very preferably above 500° C., and most preferably above 750° C. This temperature is substantially equal to the heating temperature T H The bond strength formed corresponds to 1.0 J / m 2greater than 1.5 J / m 2 more preferably 2.0 J / m 2 greater than 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, and more preferably less than 10 -3 Less than millibars, very preferably 10 -5 Less than millibars, most preferably 10 -8 It is smaller than a millibar.

[0088] However, it is also conceivable to carry out the heat treatment in a protective gas atmosphere. This is particularly advantageous 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 approximately 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 is.

[0089] Preferably, the substrates have approximately the same 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] 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, variations in the present invention can be realized even more easily.

[0092] The results of the process according to the invention are related to a number of physical parameters that can be directly correlated to the substrate or the surrounding environment. In the following of this 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. A single parameter cannot be correlated to a symmetric side, in particular to a substrate. A paired parameter can have a different value on one symmetric side, in particular a first substrate, than on the opposite symmetric side, in particular a second substrate. There is a first upper symmetric side and a second lower symmetric side. An example of a single parameter is the bonding wave velocity v or the gas (mixture) pressure p. An example of a paired parameter is the substrate thicknesses d1 and d2.

[0093] In the following description, when the influence of pair parameters on bonding results 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 for illustrative purposes. When the influence of thicknesses d1 and d2 of two different substrates on bonding results 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" error by means of a calculated and / or experimentally determined optimal curvature line, particularly 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 position of the substrate, i.e., the substrate surface, as a function of position coordinates, particularly radial coordinates. "Reduced symmetry" means that, based on the radial symmetry of both substrates, it is sufficient to calculate a one-dimensional curvature line to infer a two-dimensional contact between the substrates, such that the "runout" error is minimized or completely eliminated as described above. Simply put, the curvature line of a 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 and d2 of the substrates are linked by their volumes V1 and V2 and densities p1 and p2 to their masses m1 and m2, and thus to their gravitational forces G1 and G2. The gravitational force G1 of the first substrate directly influences the acceleration behavior of the first upper substrate in the direction of the second lower substrate. When the lower fixation is switched off, the gravitational force G2 is a measure of the inertial force of the second lower substrate, and thus of the force with which the second lower substrate tends to move, resist, 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 substrates. They have a decisive influence on the curvature line and therefore together define a function that allows describing how the substrates move towards each other.

[0098] The forces F1 and F2 influence the area where the two substrates are bonded together, especially in the center. Since point contacting only exists in the ideal case, it must always be assumed that the contacting of the two substrates is carried out in the center in an area-like manner. The size of the area is primarily determined 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 determine how strongly the substrates are distorted by thermal expansion relative to a reference temperature. Therefore, precise temperature control of the upper and / or lower substrate is an important feature for as precise and complete compensation of the "runout" as possible. Preferably, the temperatures of the two substrates can be set differently. In particular, the temperatures are set so that the substrates are in a state of expansion in which the structures to be bonded together are congruent with one another, i.e., in which the "runout" error has disappeared (assuming that no additional "runout" errors are created during bonding due to the parameters already mentioned 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 regard, reference is made to WO2014191033A1.

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

[0102] The initial radii of curvature r10 and r20 are the initial radii of the substrate before the process according to the invention is performed. The initial radii of curvature r10 and r20 are functions of position, but in particular are constant with respect to position. In a first special embodiment according to the invention, the initial radius of curvature r10 of the second lower substrate is infinite because the second lower substrate is placed flat at the start of the process according to the invention. In a second special 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 certain 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 International Publication No. WO2014191033A1, to which reference is made in this regard. In particular, the initial radius of curvature r10 of at least the second lower substrate coincides with the surface of the second lower sample holder on which the second substrate rests.

[0103] The substrate curvature radii r1 and r2 of both substrates along the bonding wave are the result of solving equations based on elasticity theory, taking into account the above parameters. The substrate curvature radii r1 and 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 explanation 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. 10 is a schematic cross-sectional view, not to scale, of a second process step. [Figure 1c] FIG. 10 is a schematic cross-sectional view, not to scale, of a third process step. [Figure 1d] FIG. 10 is a schematic cross-sectional, not-to-scale, view of a fourth process step. [Figure 1e] FIG. 10 is a schematic cross-sectional view, not to scale, of a fifth process step. [Figure 1f] FIG. 10 is a schematic cross-sectional, not-to-scale, view of a sixth process step. [Figure 1g] FIG. 10 is a schematic cross-sectional view, not to scale, of a seventh process step. [Figure 1h] FIG. 10 is a schematic cross-sectional view, not to scale, of an eighth process step. [Figure 1i] FIG. 10 is a schematic cross-sectional view, not to scale, of a ninth process step. [Figure 1j] FIG. 13 is a schematic cross-sectional, not-to-scale, view of the tenth process step. [Figure 2] 5A-5C are schematic cross-sectional views, not to scale, of additional process steps of a third embodiment of the method according to the invention. [Figure 3] 10A-10C are schematic cross-sectional views, not to scale, of optional additional process steps. [Figure 4] 1 is a schematic cross-sectional view, not to scale, of two substrates. DETAILED DESCRIPTION OF THE INVENTION

[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 which a first, in particular upper, substrate 2 is fixed in position on a sample holder surface 1o of a first, in particular upper sample holder 1. Fixation is achieved via a fixing means 3 with a holding force F H1 It is carried out by

[0109] The first sample holder 1 has a central through-opening, in particular a hole 4, which 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 sample 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 notches.

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

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

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

[0114] All of the parameters or forces listed 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′. Since the temperatures T1 or T2 may generally be related to position, 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. In the drawings, these two gravitational forces G1 and G2 represent the total gravitational force acting on the substrates 2, 2′. However, it will be obvious to those skilled in the art that both substrates 2, 2′ can be decomposed into infinitesimal (mass) portions dm and that the effect of gravity can be applied to each of these mass portions dm. Therefore, gravity should generally be expressed as a function of position and / or time.

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

[0116] 1b shows a second process step according to the invention, in which the deformation means 6, in particular the pins, apply pressure to the back 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 performed by a first force F1.

[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 predetermined distance is achieved, which can be carried out during or before the second process step.

[0118] 1d, bonding, particularly pre-bonding, is initiated by a second force F2, which causes a further, particularly infinitesimally small, deflection, bringing the substrates 2, 2′ closer together and ultimately contacting them at the contact point 7.

[0119] The bonding wave, more particularly the bonding wave front 8, starts to propagate radially symmetrically, preferably concentrically, from the contact point 7 with a bonding wave speed v. The bonding wave speed v can be varied during the course of further process steps, and thus 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, thereby interrupting further heating of the first and / or second substrate 2, 2′. In a further process step of FIG. 1f, the bonding wavefront 8 is monitored by a measurement means 9, in particular by an optical system, preferably an infrared optical system. Through at least one hole 5 (preferably a number corresponding to the number of optical systems), the measurement means 9 detects the backside 2i of the first substrate 2, and more preferably the bonding interface between the two substrates 2, 2′, and thus the bonding wavefront 8. The detection of the bonding interface is performed by the measurement means 9, which is particularly sensitive to electromagnetic radiation, which can penetrate the two 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 substrates 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 unbonded areas. The transition area between the two areas is the bonding wave. Such a measurement makes it possible, inter alia, to determine the position of the bonding wave front 8 and thus the bonding wave velocity v, especially in the case of multiple such positions.

[0121] Figure 1g shows a further seventh process step, in which the holding force F H1 The position fixing 3 of the first sample holder 1 is released by at least reducing the holding force F. If the position fixing part 3 is a vacuum fixing part, it preferably has a plurality of separately controllable vacuum segments (a plurality of holding forces F H1 In the case of vacuum fastenings (with a holding force F), it is particularly important to switch off multiple vacuum segments in a targeted manner from the inside to the outside (or to switch off one or more holding forces F H1 Dissociation is achieved by targeted reduction of

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

[0123] 1i shows a further process step, in which the action of 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 carried out by pulling it back. If a nozzle is used, the interruption is carried out by interrupting the flow of fluid. In the case of an electric and / or magnetic field, the interruption is carried out 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, inter alia, the bonding wavefront 8 (which is no longer shown in the figure at this stage of the process, since bonding has already been completed) 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 particularly located after the process step of FIG. 1g, in which the holding force F of the second lower positioning part 3′ of the second lower sample holder 1′ is increased. H2 In particular, the holding force F H2 is reduced to 0, i.e. the positional fixation is released, which in particular allows the second substrate 2′ to move unhindered, in particular laterally along the lower sample holder surface 1o′.

[0126] In yet another advantageous embodiment, the second substrate 2' is raised from the second lower sample holder 1' until it lifts off, in particular locally, this being caused in particular by the application of 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 therefore 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, among other things, to control the advancement of the bonding wavefront 8. A detailed description of the influencing means is disclosed in WO 2014 / 191033 A1, to which reference is made in this respect. The ventilation is carried out by means of a gas or gas mixture. In particular, the ventilation is carried out by opening a valve to the ambient atmosphere, whereby the chamber is ventilated with the ambient gas (mixture). Instead of ventilating to the ambient atmosphere, it is also conceivable to overpressure the chamber with a gas or 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 F1,F2 force F H1 ,F H2 holding power v Bonding wave speed T H heating temperature T1, T2 substrate temperature E1,E2 Elastic modulus of the substrate d1,d2: substrate thickness V1, V2 Volume of the board m1,m2 Mass of the board p1, p2 substrate density G1, G2 Gravity of the board r1, r2 Radius of curvature of the substrate r10,r20 Initial curvature radius of the substrate D Board edge spacing

Claims

1. A device for bonding a first substrate (2) and a second substrate (2'), said device comprising a sample holder (1, 1') and a measuring means (9), the sample holder (1, 1') is configured to bend the first substrate (2), the second substrate (2') or a combination thereof convexly or concavely by applying an overpressure or a negative pressure in the sample holder (1, 1'); the measuring means (9) being configured to detect the bonding wave and enable control of the bonding wave; device.

2. The measuring means (9) is further configured to detect the back side of the first substrate (2). The device of claim 1 .

3. The measuring means (9) is further configured to measure the bonding wave. The device of claim 1 .

4. The device comprises: a first sample holder (1) configured to hold said first substrate (2) with a first holding force F H1 ; a second sample holder (1′) configured to hold said second substrate (2′) with a second holding force F H2 ; Furthermore, At least one of the first retention force F H1 and the second retention force F H2 is reduced to 0 to control the bonding wave. The device of claim 1 .

5. The measuring means (9) is further configured to detect at least one of a state of the bonding wave and a progression of the bonding wave. The device of claim 1 .

6. The measuring means (9) is further configured to detect at least one of the position of the bonding wave and the size of the bonding area. The device of claim 1 .

7. The measuring means (9) comprises at least one of an optical system and a camera. The device of claim 1 .

8. The measuring means (9) comprises a conductivity measuring means, The device of claim 1 .

9. The sample holder (1, 1') is further configured to provide first and second holding forces F H1 and F H2 to secure the first and second substrates (2, 2') to the first and second sample holders (1, 1'), respectively; the sample holders (1, 1') are further configured to reduce the first and second holding forces F H1 and F H2 to control the release of the first and second substrates (2, 2') from the first and second sample holders (1, 1'), respectively; The device of claim 4.

10. The sample holder (1, 1') comprises first and second vacuums applied from the first and second sample holders (1, 1'), respectively; the first and second vacuums are configured to provide first and second holding forces F H1 and F H2 to secure the first and second substrates (2, 2') to the first and second sample holders (1, 1'), respectively; the first and second vacuums are further configured to reduce the first and second holding forces F H1 and F H2 to control the release of the first and second substrates (2, 2′) from the first and second sample holders (1, 1′), respectively; 10. The device of claim 9.

11. The method of claim 10, wherein the bonding wave is detected for a period of time greater than 1 second. The device of claim 1 .

12. The measuring means (9) is further configured to detect the bonding wave via a radial position of the bonding wave corresponding to at least 0.1 times the diameter of each of the first and second substrates (2, 2'). The device of claim 1 .

13. The measuring means (9) is further configured to detect the bonding wave via a percentage amount of the bonded surfaces of the first and second substrates (2, 2') relative to the unbonded surfaces of the first and second substrates (2, 2'). The device of claim 1 .

14. The bonding wave is controlled taking into account a defined set of values ​​obtained by the measuring means (9). The device of claim 1 .

15. The bonding wave is controlled by selectively releasing the fixing means by successively releasing the vacuum. The device of claim 1 .

16. A method for bonding a first substrate (2) and a second substrate (2'), said method comprising: bending the first substrate (2), the second substrate (2') or a combination thereof into a convex or concave shape by applying an overpressure or a negative pressure; detecting a bonding wave between the first substrate (2) and the second substrate (2') during contact between the first substrate (2) and the second substrate (2'); controlling the detected bonding wave; A method comprising:

17. The step of detecting the bonding wave further comprises the step of detecting a backside of the first substrate.

17. The method of claim 16.

18. The method further comprising holding the first and second substrates (2, 2′) by a sample holder (1, 1′); The sample holder (1, 1') comprises a first sample holder (1) and a second sample holder (1'), the first sample holder (1) holds the first substrate (2) with a first holding force F H1 ; the second sample holder (1′) holds the second substrate (2′) with a second holding force F H2 ; At least one of the first retention force F H1 and the second retention force F H2 is reduced to 0 to control the bonding wave.

17. The method of claim 16.

19. The step of detecting the bonding wave further includes the step of detecting at least one of a state of the bonding wave and a progression of the bonding wave.

17. The method of claim 16.

20. The step of detecting the bonding wave further includes the step of detecting at least one of a position of the bonding wave and a size of the bonding area.

17. The method of claim 16.

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