Method for bonding substrates

Abstract

The invention relates to a method for joining a first substrate (2) to a second substrate (2') at contact surfaces (2o, 2o') of the substrates (2, 2'), comprising the following steps, in particular the following sequence: H1 The first substrate (2) is held on the first sample holder surface (1o) of the first sample holder (1) and a holding force F is applied. H2 The second substrate (2') is held on a second sample holder surface (1o') of a second sample holder (1'), the contact surfaces (2o, 2o') are brought into contact at a bonding initiation location (20) and at least the second sample holder surface (1o, 1o') is heated to a heating temperature T H ,-joining the first substrate (2) and the second substrate (2') along a joining wave extending from the joining initiation site (20) to the side edge (2s, 2s') of the substrate (2, 2'), characterized in that the heating temperature T on the second sample holder surface (1o') is reduced during joining H .

Description

[0001] The present application is a divisional application of an invention patent application with an application date of February 16, 2016, application number 201680003082.2 (international application number PCT / EP2016 / 053270) and an invention name of “Method for bonding substrates”. Technical Field

[0002] The invention relates to a method for bonding a first substrate to a second substrate. Background Art

[0003] In the semiconductor industry, substrates have been aligned and connected to one another for many years. This connection (so-called bonding) is used to create multi-substrate stacks. In such multi-substrate stacks, functional units, in particular memories, microprocessors, MEMs, etc., are connected to one another and thus combined. These combination options offer a wide variety of application possibilities.

[0004] The density of functional units is increasing year by year. Due to ongoing technological development, the size of functional units is being increasingly reduced. Consequently, this increased density results in a greater number of functional units per substrate. This increase in unit count significantly contributes to a reduction in unit costs.

[0005] The disadvantage with regard to increasingly smaller functional units is primarily the increasingly difficult realization of an error-free, in particular but also complete, superposition of all functional units along the joining interface of the two substrates.

[0006] The biggest challenge in current alignment technology is therefore not always simply aligning two substrates, especially two wafers, with one another using alignment marks; rather, it is creating an error-free, especially complete, correlation between points on the first substrate and points on the second substrate, a correlation that thus extends over the entire surface of the substrates. Experience has shown that the structures on the surfaces of the substrates after the bonding process are often not identical. Therefore, a general (especially global) alignment of the two substrates and the subsequent bonding step is not always sufficient to achieve complete and error-free correspondence of the desired points at every point on the substrate surfaces.

[0007] In the prior art, there are two basic problems that hinder the simple overall alignment and subsequent joining steps.

[0008] Firstly, the positions of the structures of the first substrate and / or the second substrate often deviate from the theoretical positions. This deviation may have various causes.

[0009] For example, it is conceivable that the actually produced structure deviates from its ideal position because the production process already has errors or at least tolerances. An example of this could be the repeated application of lithography in a step-and-repeat process, which introduces small but noticeable errors in position with each translational shift of the stamp.

[0010] Another less significant cause may be deformation of the substrate due to mechanical loads, but especially thermal loads. For example, the substrate has a defined temperature at the time of manufacturing these structures. This temperature typically does not remain constant throughout the entire process flow of the substrate, but rather changes. Temperature changes lead to thermal expansion, which in the best case results in a change in diameter, and in the worst case results in complex thermal deformations.

[0011] Furthermore, even two substrates that had this consistency, i.e., an overlap of all structures, shortly before contact and the actual joining process, can lose their error-free, in particular full-surface, consistency during the joining process. Therefore, the joining process itself plays a decisive role in producing an error-free substrate stack with perfect structural consistency.

[0012] Third, the layers and structures applied to the substrate may generate stress in the substrate. These layers may be, for example, insulating layers such as through-silicon-vias (TSVs).

[0013] One of the greatest technical challenges in permanently connecting two substrates is the alignment accuracy of the functional units between the individual substrates. Although these substrates can be aligned very precisely with one another using alignment equipment, distortions of the substrates may occur during the joining process itself. Due to the resulting distortions, the functional units are not necessarily correctly aligned with one another at all locations. Alignment inaccuracies at specific points on the substrate may be the result of distortions, scaling errors, lens errors (magnification errors or reduction errors), etc. In the semiconductor industry, all subject areas that study such problems are grouped under the term "overlay accuracy." A corresponding introduction to this topic can be found, for example, in "Fundamental Principles of Optical Lithography" by Mack, Chris (The Science of Microfabrication, WILEY, 2007, reprinted in 2012).

[0014] Before the actual manufacturing process, each functional unit is designed in a computer. For example, printed circuit boards, microchips, MEMS, or any other structure that can be manufactured using microsystems technology are designed using CAD (computer-aided design) programs. However, during the manufacturing of these functional units, it has been shown that there are always deviations between the ideal functional unit constructed on the computer and the actual functional unit produced in the cleanroom. These differences are primarily due to hardware limitations—engineering issues—but are also often due to physical limitations. Thus, the resolution accuracy of structures produced using photolithography is limited by the aperture size of the photomask and the wavelength of the light used. Mask distortions are directly transferred to the photoresist. The machine's linear motors can only approximate positions that are reproducible within predefined tolerances, and so on. Therefore, it's no surprise that the functional units on the substrate don't exactly match the structures constructed on the computer. Consequently, all substrates exhibit significant deviations from the ideal state even before the bonding process.

[0015] If the position and / or shape of two opposing functional units of the two substrates are now compared, assuming that neither substrate has been distorted by the joining process, it is determined that there is often already an imperfect fit of the functional units, since these deviate from the ideal computer model due to the errors described above. The most common errors are shown in FIG. 8 of the following document: http: / / commons.wikimedia.org / wiki / File:Overlay_ typical_model_terms_DE.svg(May 24, 2013), and Mack, Chris, "Fundamental Principles of Optical Lithography" (The Science of Microfabrication, WILEY, p. 312, 2007, reprinted in 2012). Based on these illustrations, a rough distinction can be made between global and local or symmetrical and asymmetrical overlay accuracy errors. The global overlay accuracy error is uniform and therefore independent of the positioning (Ort). This global overlay accuracy error produces the same deviation between two opposing functional units that is independent of the position. Conventional global overlay accuracy errors are the I error and the II error, which are formed via the translation or rotation of the two substrates relative to each other. The translation or rotation of the two substrates produces a corresponding translation or rotation error for all respectively opposing functional units on the substrate. Local overlay errors are formed in a positioning-related manner, mainly due to elasticity problems and / or plasticity problems and / or due to the initial process (Vorprozesse), which in this case are mainly caused by continuously propagating bonding waves. Among the overlay errors shown, the III error and the IV error are mainly called "run-out" errors. This error is mainly caused by the 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 relative to the functional units of the second substrate. However, the I error and the II error may also be formed due to the bonding process, but the I error and the II error are mostly strongly superimposed on the III error and the IV error, making these errors only difficult to identify or measure. This applies to the latest structural types of bonders (Bonder), especially fusion bonders (Fusionsbonder), which have extremely accurate possibilities for x correction and / or y correction and / or rotation correction.

[0016] Devices are already known in the prior art with which local distortions can be at least partially reduced, in this case by local correction using active control elements (WO 2012 / 083978 A1).

[0017] Initial solutions for correcting "jump" errors exist in the prior art. US20120077329A1 describes a method for achieving the desired alignment accuracy between functional units on two substrates during and after bonding by not securing the lower substrate. This method eliminates boundary conditions and allows for free bonding to the upper substrate during the bonding process. The key feature of this prior art is the flat securing of the substrates, which is typically achieved using vacuum equipment.

[0018] The resulting "runout" error usually increases radially symmetrically around the contact point, thus increasing from the contact point to the periphery. In most cases, this involves a linear increase in the "runout" error. Under certain conditions, the "runout" error may also increase nonlinearly.

[0019] Under particularly optimal conditions, the "jump" error cannot be determined solely by a corresponding measuring device (EP2463892), but can also be described by a mathematical function. Since the "jump" error is a translation and / or rotation and / or scaling between well-defined points, the "jump" error is preferably described by a vector function. Typically, this vector function is the function f:R 2 →R 2 , which is the following mapping rule: This mapping rule maps the two-dimensional definition range of the position coordinates to the two-dimensional value range of the "jump" vector. Although an exact mathematical analysis of the corresponding vector field is not yet possible, assumptions are made about the functional properties. These vector functions are most likely at least C n (n>=1) function, and is therefore continuously differentiable at least once. Since the "jump" error increases from the contact point towards the edge, the divergence of this vector function is likely different from zero. The vector field is therefore very likely to be the source field.

[0020] The "jump" error is preferably determined with respect to the structure. A "structure" is understood to be any arbitrary element of the first substrate or the second substrate that is associated with a structure on the second substrate or the first substrate. Thus, for example, a structure is:

[0021] ●Alignment mark

[0022] Corners or edges, especially corners and edges of functional units

[0023] Contact pads, especially through-silicon vias (TSVs) or through-polymer vias (TPVs)

[0024] Printed conductors

[0025] A recess, in particular a hole or a depression.

[0026] "Runout" error is generally related to position and, in mathematical terms, is the offset vector between a true point and an ideal point. Because "runout" error is generally related to position, it is ideally described using a vector field. In the following text, unless otherwise mentioned, "runout" error is often viewed only as a point to simplify the description.

[0027] The "jump" error R consists of two subcomponents.

[0028] The first subcomponent R1 describes the intrinsic portion of the "jump" error, that is, the portion attributable to incorrect manufacturing of the structures or distortions of the substrate. Therefore, the intrinsic portion of the "jump" error is contained within the substrate. It should be noted that a substrate can also have intrinsic "jump" errors if, despite correctly manufacturing the structures at a first temperature, it is subjected to a temperature change to a second temperature during the bonding process, resulting in thermal expansion that distorts the entire substrate and, therefore, the structures located thereon. Temperature differences of a few degrees (sometimes even tenths of a degree) are sufficient to produce such distortions.

[0029] The second subcomponent R2 describes the extrinsic portion of the "runout" error, that is, the portion caused by the bonding process. This extrinsic portion of the "runout" error did not exist before the bonding process. This extrinsic portion of the "runout" error primarily includes local and / or global distortions of the first and / or second substrates due to forces acting between the substrates, which can result in deformations in the nanometer range. Summary of the Invention

[0030] The object of the present invention is to provide a method for joining two substrates, with which the joining accuracy is increased at any location on the substrates. Furthermore, the object of the present invention is to specify a method with which the structures of the two substrates can be matched without error (in particular over the entire surface).

[0031] This object is achieved by the following solution. Advantageous improvements of the invention are also described in the present application. A method for joining a first substrate to a second substrate at the contact surface of the substrates according to the invention comprises the following steps, in particular the following process: H1 The first substrate is held on the first sample holder surface of the first sample holder and the holding force F H2 holding the second substrate on a second sample support surface of a second sample support; contacting the contact surfaces at a bonding initiation site and heating at least the second sample support surface to a heating temperature T H Along the bonding wave extending from the bonding initiation site to the side edge of the substrate, the first substrate and the second substrate are bonded, during the bonding, the heating temperature T is reduced at the surface of the second sample holder H Preferably, the heating temperature T is reduced HThe process of the joining wave is carried out according to the change of the joining wave, in particular by switching off the heating part. The change of the joining wave is detected at least in sections by a measuring device. During the joining, at time t1, the holding force F is reduced. H1 , in particular, greatly reducing the holding force F H1 , so that the first substrate is separated from the first sample holder. During the bonding, at time point t2, the holding force F is reduced. H2 , in particular, greatly reducing the holding force F H2 , so that the second substrate on the second sample holder can be deformed along the second sample holder surface. At time t3, the second substrate is ventilated from the second sample holder surface using an overpressure, in particular an overpressure between 10 mbar and 500 mbar, preferably between 10 mbar and 200 mbar. At time t4, in particular after the joining, the holding force F is increased. H2 All combinations of at least two of the features described in this application also fall within the scope of the present invention. In the value ranges described, values ​​within the aforementioned limits are also to be considered disclosed as limit values, and these values ​​are to be claimable in any combination. Insofar as individual method steps or multiple method steps can be implemented on different devices or modules, these method steps are each disclosed separately as independent methods.

[0032] The invention is based on the idea of ​​reducing the heating temperature T H Alternatively, the heating is switched off during joining. Heating temperature T H In particular, it serves to generate a temperature sufficient for bonding at the bonding surfaces of the substrates. An important aspect of another embodiment of the invention is the release of the substrates, in particular during bonding, in order to allow free deformability of the bonded substrate stack. Another important aspect of a third embodiment of the invention is the possibility of ventilating the substrate stack, in particular its interface, or applying pressure to the substrate stack, in particular its interface, during bonding.

[0033] Suitable first and / or second substrates include, in particular, wafers.

[0034] A characteristic process in the present invention for joining (especially permanent joining, preferably fusion joining) is to contact the two substrates as centrally as possible and in a point-like manner. In particular, the contact of the two substrates can also be achieved non-centrally. A joining wave propagating from a non-central contact point will reach different locations on the substrate edge at different times. A complete mathematical and physical description of the joining wave behavior and the resulting "jump" error compensation can be correspondingly complex. In particular, the contact point is positioned not far from the center of the substrate so that any resulting effects are negligible at least at the edge. The distance between the center of the substrate and any non-central contact point 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 at most preferably less than 0.01 mm. In the following description, "contact" should generally refer to centered contact. In a broader sense, "center" is preferably understood to mean the geometric center point of the underlying ideal body, which is compensated for asymmetries as required. In the case of wafers with notches, which are common in the industry, the center is the center point of a circle that encloses an ideal wafer without a notch. In the case of wafers with flat edges (flattened sides), which are common in the industry, the center is the center point of a circle that encloses an ideal wafer without a flat edge. Similar considerations apply to substrates of any shape. However, in certain embodiments, it may be useful to understand "center" as the center of gravity of the substrate. To ensure accurate, centered, point-like contact, the upper receiving device (sample holder), which is equipped with a centered borehole and a pin that can be moved translationally therein, is equipped with a radially symmetrical fixing. It is also conceivable to use a nozzle that uses a fluid (preferably a gas) for pressure application instead of a pin. Furthermore, the use of such an element can even be completely dispensed with if a device is provided which can bring two substrates closer to one another by a translational movement under the further prerequisite that at least one of the two substrates (preferably the upper substrate) has an imposed curvature towards the other substrate due to gravity and thus automatically comes into contact during the aforementioned translational approach at a sufficiently small distance from the respective second substrate.

[0035] The radially symmetrical fixing / holding elements are either arranged vacuum holes, circular vacuum lips, or similar vacuum elements, by means of which the upper substrate can be fixed. The use of an electrostatic holding device is also conceivable. A pin in a centrally bored hole in the upper sample holder is used to controllably flex the fixed upper substrate.

[0036] In another embodiment according to the present invention, the receiving device can be configured such that the first and / or second substrate bends convexly and / or concavely due to the overpressure and / or underpressure generated in the sample holder. To this end, a vacuum rail and / or a cavity through which a fluid can flow or be evacuated is preferably provided in the receiving device. In particular, the use of nozzles for precisely applying pressure can be omitted, which facilitates the overall pressure buildup. According to the present invention, embodiments are conceivable in which the substrates are sealed and / or otherwise secured (particularly at the edges). If, for example, the receiving device is configured to generate an underpressure relative to the external atmosphere, sealing at the edges of the substrates is sufficient. If an overpressure is generated within the receiving device in order to cause the substrates to bend outward (i.e., convexly), the substrates are preferably secured at the edges (particularly mechanically). By applying the underpressure or overpressure to the substrates from below, the curvature of the substrates can be precisely adjusted.

[0037] After the two substrates have been brought into contact at their centers, the fixings of the upper sample holder are released (in particular in a controlled and gradual manner). The upper substrate falls downwards due to gravity on the one hand and due to the bonding forces acting along the bonding wave and between the substrates on the other hand. The upper substrate is connected to the lower substrate radially from the center toward the side edges. This results in the inventive construction of a radially symmetrical bonding wave, which extends in particular from the center to the side edges. During the bonding process, the two substrates squeeze (herdruecken) the gas, in particular air, present between the substrates before the bonding wave, thereby ensuring a bonding interface free of gas inclusions. During the descent, the upper substrate is actually resting on a kind of air cushion.

[0038] After the bonding is initiated, the first / upper substrate is not subjected to any additional fixation at the bonding initiation site. That is, apart from the fixation at the bonding initiation site, the first / upper substrate is free to move and may also distort. Due to the advancing bonding wave according to the present invention, the stress conditions occurring at the bonding wave front, and the prevailing geometric boundary conditions, each circular arc segment, which is infinitesimal relative to its radial thickness, is subject to distortion. However, since the substrates are rigid bodies, these distortions are summed as a function of the distance from the center. This results in "jump" errors, which are intended to be eliminated by the method and apparatus according to the present invention.

[0039] The present invention therefore also relates to a method and an apparatus for reducing or even completely avoiding "jump" errors between two bonded substrates during bonding (in particular by means of thermodynamic and / or mechanical compensation mechanisms). Furthermore, the present invention relates to a corresponding article that is produced using the apparatus and the method according to the invention.

[0040] The "runout" error is particularly dependent on the position along the substrate surface. This means, in particular, that the "runout" error increases from the center of the substrate toward the periphery. Such radially symmetrical runout occurs primarily in the case of fusion-bonded substrates, which are contacted centrally by a pin and whose bonding wave propagates autonomously (especially radially) after contact.

[0041] The "runout" error is particularly related to the speed of the joining wave. Generally, the higher the joining wave speed, the greater the "runout" error. According to the present invention, the joining wave speed is preferably set to less than 100 mm / s, preferably less than 50 mm / s, even more preferably less than 10 mm / s, most preferably less than 1 mm / s, and most preferably less than 0.1 mm / s. In a particular embodiment according to the present invention, the joining wave speed is detected using a measuring device.

[0042] The "jump" error is particularly related to the spacing (English: gap) between the two substrates immediately before the start of the "pre-" bonding process. As long as the deformation device deforms, in particular the upper first substrate, with a first force F1, the spacing between these substrates is a function of the positioning. In particular, the spacing between the substrates is greatest at the edges. The minimum spacing is located in the area of ​​the convexity maximum of the deformed substrate. Therefore, the shape of the deformed substrate also has an influence on the "jump" error. Immediately before bonding, the spacing between the substrates at the edges (substrate edge spacing D) is set to, in particular, less than 5 mm, preferably less than 2 mm, more preferably less than 1 mm, most preferably less than 0.5 mm, most preferably less than 0.1 mm. Immediately before bonding, the spacing between the substrates below the convexity maximum is set to, in particular, less than 1 mm, preferably less than 100 μm, more preferably less than 10 μm, most preferably less than 1 μm, most preferably less than 100 nm.

[0043] The "jump" error is particularly related to the type and shape of the sample holder and the resulting fixation / holding of the respective substrate. The publication WO 2014 / 191033 A1 discloses a number of preferred embodiments of the sample holder, to which reference is made in this respect. In the disclosed process, separation of the substrate from the sample holder after release of the fixation, in particular vacuum fixation, is of decisive importance. The surface roughness of the sample holder is selected to be as large as possible, and the fluctuations (Welligkeit) of the sample holder are selected to be as small as possible. The large surface roughness ensures the fewest possible contact points between the sample holder surface and the substrate. The separation of the substrate from the sample holder is thus carried out with minimal energy expenditure. The fluctuations are preferably minimal so as not to create new sources of "jump" due to the sample holder surface. It should be pointed out that the statement about fluctuations does not mean that the surface of the sample holder must not also bend as a whole.

[0044] The roughness is specified either as the average roughness, the square roughness or as the mean roughness depth. The measured values ​​for the average roughness, the square roughness and the mean roughness depth are usually different for the same measuring section or measuring surface, but are within the same order of magnitude. Therefore, the following numerical ranges for the roughness should be understood either as values ​​for the average roughness, the square roughness or as values ​​for the mean roughness depth. The roughness is set to be, in particular, greater than 10 nm, preferably greater than 100 nm, even more preferably greater than 1 μm, most preferably greater than 10 μm, and most preferably greater than 100 μm. "Jump" errors are particularly relevant in terms of time. A joining wave that propagates too quickly does not give the materials of the substrates sufficient time to optimally connect to one another shortly after and / or shortly above and / or shortly before the joining wave. Therefore, it may also be decisive to control the joining wave in a time-dependent manner.

[0045] "Jump" errors are particularly relevant during the loading process of the substrate onto the sample holder. During the application and fixation of the substrate, distortions of the substrate may occur. These distortions are maintained by the fixation and are also introduced into the substrate stack during (pre-)bonding. The substrate is thus transferred from the end effector to the sample holder with as little distortion as possible.

[0046] The "jump" error is particularly related to temperature differences and / or temperature fluctuations between the two substrates. These substrates are fed to the joining module, in particular, from different process steps or process modules. Different processes may have been performed at different temperatures in these process modules. Furthermore, the upper and lower sample holders may have different structures, different configurations, and thus different physical, particularly thermal, properties. For example, it is conceivable that the sample holders have different thermal masses and / or thermal conductivities. This could result in different loading temperatures or temperatures at the time of (pre-)joining. The sample holders used for the process according to the present invention are therefore preferably equipped with a heating and / or cooling system to precisely regulate the temperature of at least one (preferably both) substrates. In particular, it is conceivable to adjust the temperatures of the two substrates to different values ​​so that thermal loading of at least one of the two substrates causes thermal distortion of the substrate as a whole. This allows the substrates to be adjusted to a desired initial state, in particular to compensate for the "jump" error component R1.

[0047] The "jump" error is particularly related to the ambient pressure. The influence of ambient pressure has been discussed and disclosed in detail in WO 2014 / 191033 A1. In this respect, reference is made thereto.

[0048] The "jump" error is particularly related to the symmetry of the system, so that preferably as many components as possible (and more preferably at least the majority) are constructed and / or arranged symmetrically. In particular, the thickness of the substrates is different. In addition, different layer sequences of different materials with different mechanical properties can be present and must be taken into account on each substrate. In addition, one of the substrates is preferably deformed, while the other substrate is placed flat on the sample holder. All characteristics, parameters and embodiments that lead to asymmetries have an impact on the "jump" error in particular. Some of these asymmetries cannot be avoided. Thus, the thickness of the substrate, the layers thereon and the functional units are defined by the process and customer specifications. According to the invention, an attempt is made to minimize the "jump" as much as possible, in particular to completely eliminate the "jump", in particular by varying other variable parameters.

[0049] The "jump" error is particularly position-dependent. The aim of the measures according to the invention is in particular to achieve a "jump" error at any position that is less than 10 μm, preferably less than 1 μm, even more preferably less than 100 nm, most preferably less than 10 nm, and most preferably less than 1 nm.

[0050] Sample holder

[0051] The sample holder preferably used in accordance with the embodiment of the present invention has a fixing portion. The fixing portion is used to fix the substrate using a fixing force or using a corresponding fixing pressure. The fixing portion can in particular be the following fixing portion:

[0052] ● Mechanical fixings, especially clamps, or

[0053] ● Vacuum fixing part, especially having:

[0054] Individually controllable vacuum rails, or

[0055] ○ interconnected vacuum rails, or

[0056] Electrical fixings, especially electrostatic fixings, or

[0057] Magnetic fixing part, or

[0058] ● Adhesive fixing part, especially

[0059] ○Gel-Pak fixing part, or

[0060] o A fastening element with an adhesive, in particular manipulable, surface.

[0061] These fixing parts can be controlled electronically in particular. Vacuum fixing parts are the preferred fixing method. The vacuum fixing part preferably comprises a plurality of vacuum tracks, which appear on the surface of the sample holder. The vacuum tracks are preferably individually controllable. In a technically preferred application, several vacuum tracks are combined into vacuum track segments (Vakuumbahnsegment), which are individually controllable, that is, can be emptied or filled individually. Each vacuum segment is preferably independent of the other vacuum segments. This makes it possible to construct individually controllable vacuum segments. These vacuum segments are preferably constructed in an annular shape. This makes it possible to fix and / or separate the substrate and the sample holder in a targeted and radially symmetrical manner (in particular from the inside out), or vice versa.

[0062] Possible sample holders are disclosed in the publications 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.

[0063] Monitoring of the splicing wave

[0064] During at least one (preferably all) of the process steps according to the invention, it is advantageous to detect the progression of the joining wave or at least the state of the joining wave and thus determine it at a specific point in time. For this purpose, a measuring device, in particular a measuring device with a camera, is preferably provided. Monitoring is preferably performed by:

[0065] a camera, in particular a visual camera or an infrared camera, and / or

[0066] ●Conductivity measuring equipment (Leitfaehigkeitsmessgeraeten).

[0067] If the position of the joining wave is determined using a camera, the position of the joining wave, in particular its progression, can be detected at any point in time. The camera is preferably an infrared camera, which digitizes the data and transmits it to a computer. The computer then makes it possible to analyze this digital data, in particular to determine the position of the joining wave, the size of the joined surfaces, or other parameters.

[0068] Another way to monitor the progress of the bonding wave is to measure the surface conductivity, which changes as the bonding wave advances. To do this, the prerequisites for such a measurement must be established. The surface conductivity is measured, in particular, by contacting two electrodes at two opposite locations on the substrate. In a particular embodiment according to the invention, the electrodes contact the edge of the substrate, without hindering bonding at the edge. In a second, less preferred embodiment according to the invention, the electrodes are withdrawn from the surface before the bonding wave reaches the side edge of the substrate.

[0069] A number of steps are described below, wherein these steps are preferably carried out in the described order, in particular as individual steps. Unless otherwise indicated, these steps and the disclosure can be transferred from one embodiment to another (if this is technically feasible for a person skilled in the art).

[0070] Process according to the first embodiment of the present invention

[0071] In a first process step of a first embodiment of the method according to the invention, the positions of the two substrates are determined and the two substrates are fixed on sample holders, one substrate on a first / upper sample holder and the second substrate on a second / lower sample holder. The transport of the substrates can be carried out manually, but is preferably carried out by a robot (i.e. automatically). The upper sample holder preferably has a deformation device for deforming the upper first substrate in a targeted, in particular controllable, manner using a first force F1. The upper sample holder has, in particular, at least one opening through which the deformation device (in particular a pin) can cause a mechanical deformation of the upper first substrate. Such a sample holder is disclosed, for example, in the publication WO 2013 / 023708 A1.

[0072] In a second process step, a deforming device (in particular a pin) contacts the back side of the upper first substrate and produces a slight deformation, in particular a deflection which is referred to as a concave surface from the side of the deforming device (i.e. from the top). The deforming device loads the first substrate with, in particular, a first force F1 which is greater than 1 mN, preferably greater than 10 mN, even more preferably greater than 50 mN, most preferably greater than 100 mN, but in particular less than 5000 mN. This force is too small to then cause the upper first substrate to detach from the sample holder, but is strong enough to produce the deflection according to the invention. The force preferably acts on the substrate as point-like as possible. Since a point-like effect does not actually exist, the force preferably acts on a very small area. This area is in particular less than 1 cm 2 , preferably less than 0.1 cm 2 , still more preferably less than 0.01 cm 2 , most preferably less than 0.001cm 2 . When acting on 0.001cm 2 In the case of an area of ​​?, the effective pressure is in particular greater than 1 MPa, preferably greater than 10 MPa, more preferably still greater than 50 MPa, most preferably greater than 100 MPa, and most preferably greater than 1000 MPa according to the present invention. The disclosed pressure ranges also apply to the other areas disclosed above.

[0073] In the third process step, the two substrates are brought into relative proximity, in particular by bringing the sample holders closer together. Preferably, the lower sample holder is raised so that the lower, second substrate actively approaches the upper, first substrate. However, it is also conceivable for the upper sample holder to actively approach the lower sample holder, or for the two sample holders to approach each other simultaneously. The two substrates are brought closer together, in particular, until a distance of between 1 μm and 2000 μm is reached, preferably between 10 μm and 1000 μm, even more preferably between 20 μm and 500 μm, and most preferably between 40 μm and 200 μm is reached. This distance is defined as the minimum vertical distance between two surface points of the substrates.

[0074] Before bonding or pre-bonding or contacting, the first substrate and / or the second substrate are heated by a heating device and / or cooled by a cooling device, ie, are temperature-controlled.

[0075] In a fourth process step, the upper first substrate is subjected to a further force loading. In the first mode of operation according to the invention, the first substrate is loaded with a second force F2 of the deformation device, which is in particular greater than 100 mN, preferably greater than 500 mN, even more preferably greater than 1500 mN, most preferably greater than 2000 mN, and most preferably greater than 3000 mN. This creates or at least supports a first contact between the upper first substrate and the lower second substrate. The pressure that preferably occurs is again calculated by dividing this force by an assumed minimum value of 0.001 cm 2 area to be carried out.

[0076] In a fifth process step, in particular the heating device is deactivated, in particular the heating of the lower sample holder which is arranged in particular integrally in the lower sample holder is deactivated.

[0077] In the sixth process step, the propagation of the advancing bonding wave is monitored (see also "Monitoring the Bonding Wave" above). Monitoring, in particular, tracks the propagation of the bonding wave and, thus, the progress of the bonding process, during a period of time greater than 1 second, preferably greater than 2 seconds, even more preferably greater than 3 seconds, most preferably greater than 4 seconds, and most preferably greater than 5 seconds. Instead of tracking / controlling the bonding process during time intervals, the tracking of the bonding wave can also be described by the (especially radial) position of the bonding wave. The bonding process is tracked, in particular, until the bonding wave is 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, most preferably at least 0.4 times, and most preferably 0.5 times the diameter of the substrate. If the bonding progress is tracked via a conductivity measurement of the surface, the bonding progress can also be measured as a percentage of the bonded or unbonded surface. The monitoring of the progress of the joining according to the invention is then carried out in particular until more than 1%, preferably more than 4%, even more preferably more than 9%, most preferably more than 16%, most preferably more than 25% of the area has been joined. Alternatively, the monitoring is carried out continuously.

[0078] The control of the process flow is preferably based on predefined / set or settable values ​​from monitoring, which are within the above-mentioned value ranges. This results in a first waiting time for the progression of the joining wave and until the start of the next process step.

[0079] In the seventh process step, the fixing of the upper first sample holder is particularly disconnected. It is also conceivable to release the upper first substrate by targeted release. In particular, in the case of a vacuum fixing comprising a plurality of individually controllable vacuum rails, the targeted release is achieved by continuously releasing the vacuum (in particular from the center to the edge). The seventh process step particularly begins at time t1, at which time one of the parameters of the measuring device reaches a predetermined / set or adjustable value (see in particular the sixth process step).

[0080] More generally or in other words, during engagement, the holding force F is reduced at time t1. H1 , especially greatly reducing the holding force F H1 , so that the first substrate is separated from the first sample holder.

[0081] In an eighth process step, the propagation of the advancing bonding wave is monitored again or further by a measuring device. This monitoring preferably tracks the progress of the bonding wave and thus the progress of the bonding process during a period of time greater than 5 seconds, preferably greater than 10 seconds, more preferably greater than 50 seconds, most preferably greater than 75 seconds, and most preferably greater than 90 seconds. Instead of tracking the bonding process during a time interval, the tracking of the bonding wave can also be measured by the (especially radial) position of the bonding wave. The tracking of the bonding process is carried out in particular until the bonding wave is 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 0.6 times, and most preferably 0.7 times the diameter of the substrate. If tracking the bonding progress is possible via conductivity measurements with respect to the surface, the bonding progress can also be achieved by the percentage ratio of the bonded or unbonded surface. According to the invention, the progress of the joining is monitored until more than 9%, preferably more than 16%, even more preferably more than 25%, most preferably more than 36%, most preferably more than 49% of the area is joined. Alternatively, monitoring is performed continuously.

[0082] The control of the process flow is preferably based on predefined / set or settable values ​​from monitoring, which are within the above-mentioned value ranges. This results in a second waiting time for the progression of the joining wave and until the start of the next process step.

[0083] In a ninth process step, application of the deformation device is discontinued. If the deformation device is a pin, the pin is withdrawn. If the deformation device is one or more nozzles, the fluid flow is interrupted. If the deformation device is an electric field and / or a magnetic field, the electric field and / or the magnetic field are disconnected. The ninth process step is initiated, in particular, at a point in time when one of the parameters of the measuring device reaches a predetermined / set or adjustable value (see, in particular, the eighth process step).

[0084] In the tenth process step, the propagation of the advancing joining wave is again or further monitored. This monitoring preferably tracks the progress of the joining wave and thus the progress of the joining process during a period of time greater than 5 seconds, preferably greater than 10 seconds, more preferably greater than 50 seconds, most preferably greater than 75 seconds, and most preferably greater than 90 seconds. Instead of tracking the joining process during a time interval, the tracking of the joining wave can also be described by the (especially radial) position of the joining wave. The tracking of the joining process is carried out until the joining wave is 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 0.9 times the diameter of the substrate. As long as the substrate has an edge profile, it is impossible to track the joining process to the outermost edge because, due to the edge profile, approximately 3-5 mm is not joined. If tracking the progress of the joining is possible via conductivity measurements on the surface, then the joining progress can also be achieved by the percentage ratio of the joined or unjoined surface. According to the invention, the progress of the joining is monitored until more than 36%, preferably more than 49%, more preferably more than 64%, most preferably more than 81%, and most preferably more than 100% of the area is joined. Alternatively, monitoring can be performed continuously.

[0085] The control of the process flow is preferably based on predetermined / set or settable values ​​from monitoring, which are within the above-mentioned value ranges. This results in a third waiting time for the progression of the joining wave and until the start of the next process step.

[0086] An example of the process flow of the first embodiment is repeated below:

[0087] - Loading substrate

[0088] - Bring the pins into contact with the wafer (force on the wafer is 100 mN) without initiating bonding

[0089] - The two wafers are relatively close to each other (40-200μm spacing)

[0090] - Force loading of the wafer in order to initiate fusion bonding between the two substrates (force 1500-2800 mN)

[0091] - Deactivate the heating unit

[0092] - Wait until the splice wave has propagated far enough (typically 1-5 seconds) - Waiting time 1

[0093] - (especially two areas simultaneously) disconnect (deplete) the top wafer to maintain vacuum (Top WaferHaltevakuum).

[0094] - Wait until the splice wave has propagated further (typically 2-15 seconds) - Waiting time 3

[0095] - Withdraw the pin

[0096] - Wait until the splicing wave has fully propagated (especially 5-90 s) - Waiting time 4.

[0097] The individual method steps can be summarized via the general technical teachings described above.

[0098] Process according to the second embodiment of the present invention

[0099] From the first to the seventh process step and including the seventh process step, the process according to the second embodiment corresponds to the first embodiment.

[0100] In the eighth process step, the holding force is reduced or the fixing of the lower second sample holder is disconnected. It is also conceivable that the lower second substrate is detached by the targeted release of the fixing. In particular, in the case of a vacuum fixing comprising a plurality of individually controllable vacuum rails, the fixing is preferably released in a targeted manner by continuously releasing the vacuum (in particular from the center to the edge). The eighth process step according to the invention is an important process for reducing "jump" errors. By reducing the holding force or disconnecting the fixing of the lower second sample holder, according to the invention, the lower / second substrate can be adapted to the upper first substrate. By abolishing the fixing, additional (mathematical-mechanical) boundary conditions that would limit the joining process are seemingly eliminated.

[0101] More generally or in other words, during engagement, the holding force F is reduced at time t2. H2 , especially greatly reducing the holding force F H2 , so that the second substrate can be deformed on the second sample holder.

[0102] The ninth process step corresponds to the eighth process step of the first embodiment.

[0103] In the tenth process step according to the present invention, the second substrate, which has already been partially bonded, is fixed again to the lower second sample holder. This tenth process step according to the present invention is also an important step for reducing "jump" errors. Due to the re-fixing, in particular the re-activation of the holding vacuum, the continued development of the bond is again subject to (mathematical mechanical) boundary conditions.

[0104] More generally or in other words, at time t4 (particularly after engagement), the holding force F is increased. H2 .

[0105] 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.

[0106] In a very specific embodiment according to the invention, disconnection of the fixing according to process step 8 and reconnection of the fixing according to process step 10 can be repeated several times before the joining process is completed. In particular, it is even possible to perform disconnection and reconnection in a positionally resolved manner. According to the invention, this is primarily accomplished using the individually controllable vacuum rails or vacuum sections already mentioned in this disclosure. In the optimal case, this results in a positionally resolved and / or time-resolved release or fixation of the lower / second substrate.

[0107] An example of the process flow of the second embodiment will be repeated below:

[0108] - Loading substrate

[0109] - The pin (deformation means) is brought into contact with the wafer (particularly with a force of 100 mN on the wafer) without initiating bonding - pin force 1

[0110] - The two wafers are relatively close to each other (especially with a spacing of 40-200 μm) - spacing 1

[0111] - Pressing onto the wafer in order to initiate a fusion bond between the two substrates (especially with a force of 1500-2800 mN) - Pin force 2

[0112] - Deactivate the heating unit

[0113] - Wait until the splice wave has propagated far enough (typically 1-5 seconds) - Waiting time 1

[0114] - breaking (exhausting) the holding vacuum of the upper wafer (especially in both areas simultaneously)

[0115] - disconnect (exhaust) the holding vacuum of the lower wafer,

[0116] - Wait until the splice wave has propagated further (typically 2-15 seconds) - Waiting time 3

[0117] - Turn on the hold vacuum for the lower wafer - Vacuum 1

[0118] - Withdraw the pin

[0119] - Wait until the splicing wave has fully propagated (especially 5-90 s) - Waiting time 4.

[0120] The individual method steps can be summarized by the general technical teachings described above.

[0121] Process according to the third embodiment of the present invention

[0122] From the first process step up to and including the ninth process step, the process according to the third embodiment corresponds to the second embodiment. In the ninth process step, the parameters are preferably set 10% to 40% lower than in the second embodiment. This reduces the waiting time up to the tenth process step, wherein in the third embodiment, an additional waiting time is introduced or the second waiting time is divided into parts.

[0123] In the tenth process step according to the present invention, the space between the lower second sample holder and the lower / second substrate, which is not actually fixedly placed thereon, is ventilated according to a defined pressure. "Pressure" in this context is to be understood as absolute pressure. An absolute pressure of 1 bar corresponds to atmospheric pressure. To carry out the process according to the present invention, the chamber must therefore be evacuated beforehand and then opened to the atmosphere, i.e., ventilated. This facilitates the free mobility of the substrate, further minimizing distortion relative to the first substrate. The pressure is particularly between 1 mbar and 1000 mbar, preferably between 2.5 mbar and 800 mbar, even more preferably between 5 mbar and 600 mbar, most preferably between 7.5 mbar and 400 mbar, and most preferably between 10 mbar and 200 mbar. In another embodiment according to the present invention, it is conceivable that the embodiment according to the present invention is carried out at atmospheric pressure until the tenth process step, and then an overpressure is generated in the chamber by a compressor. The pressure in this case is in particular between 1 bar and 3 bar, preferably between 1 bar and 2.5 bar, even more preferably between 1 bar and 2 bar, most preferably between 1 bar and 1.5 bar, most most preferably between 1 bar and 1.2 bar.

[0124] In an eleventh process step, the propagation of the advancing bonding wave is monitored again or further by a measuring device. This monitoring tracks the progress of the bonding wave and thus the progress of the bonding process during a period of time that is greater than 1 second, preferably greater than 2 seconds, more preferably greater than 5 seconds, most preferably greater than 10 seconds, and most preferably greater than 15 seconds. Instead of tracking the bonding process during time intervals, the tracking of the bonding wave can also be described by its (especially radial) position. The bonding process is tracked until 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, most preferably 0.6 times, and most preferably 0.7 times the diameter of the substrate. If the tracking of the bonding progress is measurable via conductivity measurements on the surface, the bonding progress can also be carried out as a percentage of the bonded or unbonded surface. The monitoring of the progress of the joining according to the invention is carried out until more than 9%, preferably more than 16%, even more preferably more than 25%, most preferably more than 36%, most preferably more than 49% of the area has been joined. Alternatively, the monitoring is carried out continuously.

[0125] The control of the process flow is preferably based on predefined / set or settable values ​​from monitoring, which are within the above-mentioned value ranges. This results in a first waiting time for the progression of the joining wave and until the start of the next process step.

[0126] In a twelfth process step according to the invention, the second substrate, which has in particular already been partially bonded, is again fixed to the lower second sample holder.

[0127] More generally or in other words, at time t4 (particularly after engagement), the holding force F is increased. H2 .

[0128] The thirteenth process step corresponds to the ninth process step of the first embodiment, and the fourteenth process step corresponds to the tenth process step of the first embodiment.

[0129] An example of the process flow of the third embodiment will be repeated below:

[0130] - Loading substrate

[0131] - The pin is brought into contact with the wafer (specifically, the force applied to the wafer is 100 mN), without initiating bonding - Pin Force 1

[0132] - The two wafers are relatively close to each other (especially with a spacing of 40-200 μm) - spacing 1

[0133] - Pressing onto the wafer in order to initiate a fusion bond between the two substrates (especially with a force of 1500-2800 mN) - Pin force 2

[0134] - Deactivate the heating unit

[0135] - Wait until the splice wave has propagated far enough (typically 1-5 seconds) - Waiting time 1

[0136] - breaking (exhausting) the holding vacuum of the upper wafer (especially in both areas simultaneously)

[0137] - Disconnect (exhaust) the holding vacuum on the lower wafer

[0138] - Wait until the splice wave has propagated further (typically 1-10 seconds) - Waiting time 2

[0139] Ventilate the volume between the lower wafer and the chuck (lower sample holder) at a defined pressure (especially 10-200 mbar) - pressure 1 for a defined period of time

[0140] - Wait until the splice wave has propagated further (typically 2-15 seconds) - Waiting time 3

[0141] - Turn on the hold vacuum for the lower wafer - Vacuum 1

[0142] - Withdraw the pin

[0143] - Wait until the splicing wave has fully propagated (especially 5-90 s) - Waiting time 4.

[0144] The individual method steps can be summarized by the general technical teachings described above.

[0145] Post-Processing

[0146] The described process can in particular be continued in further process modules.

[0147] In a first conceivable further development, the produced substrate stack is inspected (in particular in a metrology module). The inspection primarily involves measuring the bonding interface to determine:

[0148] ●Alignment errors, especially

[0149] ○ Overall alignment errors, and / or

[0150] ○ Runout error, and / or

[0151] ● Defects, especially

[0152] ○ Porosity, and / or

[0153] ○ bubbles, and / or

[0154] ○Cracks.

[0155] If the inspection of the substrate stack reveals intolerable errors, the stack is preferably separated again. Separation is preferably performed using the following procedures and equipment: these are disclosed in publications EP 2697823 B1 and WO 2013 / 091714 A1. Reference is hereby made to these publications. Inspection of the bonding interface is particularly performed before further heat treatment.

[0156] In a second conceivable further development, the resulting substrate stack is heat treated. This heat treatment leads in particular to a strengthening of the resulting bonds between the individual substrates of the substrate stack. This heat treatment is carried out in particular at a temperature of more than 25° C., preferably more than 100° C., even more preferably more than 250° C., most preferably more than 500° C., and most preferably more than 750° C. This temperature corresponds substantially to the heating temperature T H The resulting bond strength is in particular greater than 1.0 J / m 2 , preferably greater than 1.5 J / m 2 , still more preferably greater than 2.0 J / m 2 , most preferably 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 mbar, most preferably less than 10 -5 mbar, most preferably less than 10 -8 mbar.

[0157] 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 greater than 0 W / (m*K), preferably greater than 0.01 W / (m*K), even more preferably greater than 0.1 W / (m*K), and most preferably greater than 1 W / (m*K). The thermal conductivity of helium is, for example, approximately between 0.15 W / (m*K) and 0.16 W / (m*K). The protective gas is in particular:

[0158] Inert gases, especially helium, neon, argon, krypton and / or xenon

[0159] Molecular gases, especially carbon dioxide and / or nitrogen

[0160] ●Any combination of the gases mentioned above.

[0161] Preferably, the substrates have approximately identical diameters D1 , D2 , which in particular deviate from one another by less than 5 mm, preferably by less than 3 mm, even more preferably by less than 1 mm.

[0162] According to a further, in particular independent, aspect of the invention, the deformation is effected by a mechanical actuation device and / or by temperature control of the first receiving device and / or the second receiving device.

[0163] By fixing the first substrate and / or the second substrate to the first receiving surface and / or the second receiving surface only in the region of the side walls, the deformation according to the invention can be achieved more easily.

[0164] The results of the process according to the invention depend on a number of physical parameters that can be directly assigned to the substrate or the environment. The most important parameters and their influence on the "jump" error are described in the further course of this disclosure. These parameters are roughly divided into single parameters and paired parameters. Single parameters may not be assigned to a symmetry side, in particular not to a substrate. Paired parameters may have different values ​​on one symmetry side, in particular the first substrate, than on the respectively opposite symmetry side, in particular the second substrate. There is an upper first symmetry side and a lower second symmetry side. Examples of single parameters are the bonding wave velocity v or the gas (mixture) pressure p. Examples of paired parameters are the substrate thicknesses d1 and d2.

[0165] If the effects of paired parameters on the bonding result are described further in the following, it is assumed, unless otherwise stated, that all other values ​​of each paired parameter are preferably equal. The following example should be mentioned as an example. If the effects of two different substrate thicknesses d1 and d2 on the bonding result are described, it is assumed that the two E moduli E1 and E2 of the two substrates are equal.

[0166] The aim is to minimize or completely eliminate the "jump" error by means of an optimal, calculated and / or empirically determined (especially time-dependent) bending line. A "bend line" is to be understood here as a diagram of a reduced symmetry of a one-dimensional function, which maps the surface position of the substrate (i.e. the substrate surface) as a function of positioning coordinates, especially radial coordinates. Reduced symmetry means that, based on the symmetry of the radial symmetry of the two substrates, the calculation of a one-dimensional bending line is sufficient to obtain an inference about the two-dimensional contact of the substrates with each other: this two-dimensional contact produces the aforementioned minimal or completely eliminated "jump" error. In simple terms, the bending line of the substrate can be described as the substrate surface, especially towards the bonding interface. Preferably, the description of the bending line of the first substrate applies analogously to the second substrate.

[0167] According to the invention, the bending line (ie, the substrate surface) is significantly influenced, in particular, by one or more of the following parameters.

[0168] The substrate thicknesses d1 and d2 are linked to the masses m1 and m2 of the two substrates, and thus to their respective weights G1 and G2, via the volumes V1 and V2 and densities ρ1 and ρ2. The weight G1 of the first substrate has a direct influence on the acceleration of the upper first substrate toward the lower second substrate. When the lower mounting is switched off, the weight G2 is a measure of the inertial force of the lower second substrate and, therefore, the effort to move the lower second substrate toward the upper first substrate along the bonding wave or to maintain it against or in contact with it.

[0169] The E-modules E1, E2 are a measure of the stiffness of the substrates. These E-modules contribute decisively to the bending line and thus together define a function with which it is possible to describe how the substrates move toward one another.

[0170] Forces F1 and F2 act on the surface of the two substrates, particularly the central surface, that are connected to each other. Since point contact only occurs ideally, it must always be assumed that the two substrates are in contact centrally on the surface. The size of the surface is decisively determined by forces F1 and F2. The size of the contact surface is crucial for the boundary conditions.

[0171] The temperatures T1 and T2 of the two substrates can influence the overall thermal expansion state of the substrates. According to the present invention, it is therefore possible to determine how severely the substrates as a whole are distorted by thermal expansion relative to a reference temperature. Correct temperature control of the upper and / or lower substrate is therefore crucial for achieving the most accurate and complete possible "jump" compensation. The temperatures of the two substrates can preferably be set differently. These temperatures are particularly set so that the substrates are in an expanded state in which the structures to be joined are identical, i.e., "jump" errors are eliminated (assuming that no additional "jump" errors are incorporated during joining due to the parameters already mentioned above). The temperatures required for this purpose can be determined using measuring devices and / or empirically.

[0172] The gas (mixed) pressure p influences the atmospheric resistance to the substrates moving toward each other. The gas (mixed) pressure can directly influence the bonding wave velocity v. In this regard, reference is made to publication WO2014191033A1.

[0173] Before the actual joining process, the holding force F H1 、F H2 Mainly used to fix the substrate. Holding force F H1is the boundary condition for process steps 1 to 6 (including process step 6), but loses its influence on the boundary condition for determining the bending line after the fixing part is turned off. H2 Only the time point for the active lower fixation is included as a boundary condition. For the elasticity-theoretic calculation, therefore, new boundary conditions must be formulated accordingly, starting at process step 7 at the latest.

[0174] Initial curvature radius r 10 、r 20 are the initial radii of the substrate before the process according to the invention. These initial radii of curvature are a function of the positioning, but are in particular constant with respect to the positioning. In a first embodiment of the invention, the initial radius of curvature of the lower second substrate is r 10 Infinite, because the lower second substrate is lying flat at the beginning of the process according to the invention. In another special second embodiment of the invention, the initial curvature radius r of the lower second substrate is 10 is a finite, positive or negative constant corresponding to a constant convex or concave curvature. In this case, the lower second substrate is present at the beginning of the process according to the invention in a convexly or concavely curved shape. Such a sample holder is described in the publication WO2014191033A1, to which reference is made in this respect. In particular, at least the initial radius of curvature r10 of the lower second substrate corresponds to the sample holder curvature radius of the surface of the lower second sample holder on which the second substrate is placed.

[0175] The substrate curvature radii r1, r2 of the two substrates along the joining wave are the result of solving the elasticity theory equations taking into account the parameters mentioned above. These substrate curvature radii are, in particular, a function of position and time.

[0176] The coalescence wave velocity is a result of the parameters already mentioned above. BRIEF DESCRIPTION OF THE DRAWINGS

[0177] Further advantages, features and details of the invention are apparent from the following description of preferred exemplary embodiments and from the accompanying drawings. In these drawings:

[0178] Figure 1a A schematic, not true to scale, cross-sectional illustration shows a first process step of a first embodiment of the method according to the invention,

[0179] Figure 1b A schematic, not to scale, cross-sectional illustration of a second process step is shown,

[0180] Figure 1c A schematic, not to scale, cross-sectional illustration of a third process step is shown,

[0181] Figure 1d A schematic, not to scale, cross-sectional illustration showing a fourth process step,

[0182] Figure 1e A schematic, not to scale, cross-sectional illustration of a fifth process step is shown,

[0183] Figure 1f A schematic, not to scale, cross-sectional illustration of a sixth process step is shown,

[0184] Figure 1g A schematic, not to scale, cross-sectional illustration of a seventh process step is shown,

[0185] Figure 1h A schematic, not to scale, cross-sectional illustration of an eighth process step is shown,

[0186] Figure 1i A schematic, not to scale, cross-sectional illustration of a ninth process step is shown,

[0187] Figure 1j A schematic, not to scale, cross-sectional illustration of the tenth process step is shown,

[0188] Figure 2 A schematic, not to scale, cross-sectional illustration showing an additional process step of a third embodiment of the method according to the invention,

[0189] Figure 3 Schematic, not-to-scale, cross-sectional illustrations showing optional additional process steps, and

[0190] Figure 4 A schematic, not true to scale, cross-sectional illustration of two substrates is shown.

[0191] In the figures, identical components and components having the same function are denoted by the same reference numerals. DETAILED DESCRIPTION

[0192] Figure 1a A first process step is shown in which a first, in particular upper, substrate 2 is already fixed on the sample holder surface 1o of a first, in particular upper, sample holder 1. This fixing is achieved by means of a fixing device 3 with a holding force F H1 conduct.

[0193] The first sample holder 1 has an especially central through-opening, especially a bore 4 , which is used to pass a deformation device 4 for deforming the first substrate 2 .

[0194] In the advantageous embodiment shown here, the first sample holder 1 has holes 5, through which the progress of the joining can be monitored by a measuring device. The holes 5 are preferably longitudinal milled grooves.

[0195] The second substrate 2' is loaded and fixed on the second, in particular lower, sample holder 1'. This fixing is achieved by the fixing device 3' using the holding force F H2 conduct.

[0196] The fixing means 3 , 3 ′ is preferably a vacuum fixing.

[0197] The sample holders 1 , 1 ′ in particular have a heating portion 11 (heating device). In these figures, for the sake of clarity, the heating portion 11 is schematically shown only in the lower second sample holder 1 ′.

[0198] All of the aforementioned parameters or forces that describe or influence the properties of the substrate 2 , 2 ′ are generally functions of position and / or time.

[0199] The temperatures T1 and T2 of the two substrates 2, 2' are referred to as examples of parameters. Typically, the temperature T1 or T2 can be position-dependent, so that a temperature gradient exists. In this case, it is meaningful to describe these temperatures as explicit functions of position and / or time.

[0200] The two gravitational forces G1 and G2 are referred to as force examples. In these figures, these gravitational forces represent the total gravitational forces acting on the substrates 2 and 2 ′. However, it is readily apparent to a person skilled in the art that the two substrates 2 and 2 ′ can be broken down into infinitesimal parts (mass-produced components) dm, and that the influence of the gravitational force can be associated with each of these mass-produced components dm. Therefore, the gravitational force can generally be expressed as a function of position and / or time.

[0201] Similar concepts apply to all other parameters and / or forces.

[0202] Figure 1b A second process step according to the invention is shown, in which deformation means 4, in particular pins, apply pressure to the back side 2i of the first substrate 2 in order to cause a deformation of the first substrate 2. The first substrate 2 is deformed here using a first force F1.

[0203] In accordance with Figure 1c In the second process step, the two sample holders 1 , 1 ′ and thus the two substrates 2 , 2 ′ are brought closer to one another up to a defined distance. The approaching can also take place during or before the second process step.

[0204] In accordance with Figure 1d In the process step, bonding, in particular pre-bonding, is initiated with a second force F2 . The second force F2 ensures further, in particular infinitesimal deflection and brings the two substrates 2 , 2 ′ closer together and finally into contact at the contact point 7 .

[0205] The joining wave (more precisely, the joining wave front 8) propagates at a joining wave velocity v, in particular radially symmetrically, preferably centrally, starting from the contact point 7. During the course of further process steps, the joining wave velocity v can be varied so that it can be defined as a function of position (or time). The joining wave velocity v can be influenced by various measures.

[0206] In accordance with Figure 1e In a further process step, the heating 11 of the first sample holder 1 and / or the second sample holder 1 ′ is switched off, thereby interrupting further heating of the first substrate 2 and / or the second substrate 2 ′. Figure 1f In a further process step, the bonding wavefront 8 is monitored by means of a measuring device 9, in particular at least one optical system, preferably an infrared optical system. Through (at least one (the number preferably corresponds to the number of optical systems)) holes 5, the measuring device 9 can detect the substrate back side 2i of the first substrate 2, more preferably the bonding interface between the two substrates 2, 2', and thus the bonding wavefront 8. The detection of the bonding interface is carried out in particular in the measuring device 9, which is sensitive to electromagnetic radiation that can penetrate the two substrates 2, 2' without significant weakening. Preferably, a light source 12 is positioned above and / or below and / or within the sample holder 1', the electromagnetic radiation of which illuminates and / or transilluminates the substrates 2, 2' and / or the sample holder 1' and can be detected by the measuring device 9. The image captured in this way is preferably a black and white image. The brightness difference allows the bonded area to be clearly identified from the unbonded area. The transition area between the two areas is the bonding wave. By means of such a measurement, it is possible in particular to determine the position of the joining wave front 8 and, thereby, in particular for a plurality of such positions, also the joining wave velocity v.

[0207] Figure 1g A further seventh process step is shown, wherein the holding force F is reduced by at least H1 , the fixing portion 3 of the first sample holder 1 is detached. If the fixing portion 3 is a vacuum fixing portion, it is more preferred to have multiple independently controllable vacuum sections (with multiple holding forces F H1 ) of the vacuum fixing portion, by selectively disconnecting the vacuum section (or reducing one / more holding forces F H1 ), especially separation from the inside out.

[0208] Figure 1hA further process step is shown, in which the joining wave front 8 is monitored by a measuring device 9 after separation from the first substrate holder 1 .

[0209] Figure 1i A further process step is shown, 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 achieved by withdrawing it. In the case of a nozzle, the interruption is achieved by interrupting the fluid flow. In the case of an electric and / or magnetic field, the interruption is achieved by switching off the field.

[0210] Figure 1j A further process step is shown, after which the two substrates 2, 2' are completely joined together. In particular, in this process step, the joining wavefront 8 (not shown again, since the joining is already complete at this process stage) is further monitored by means of a measuring device 9 until the joining is completed, at which point the substrate stack 10 formed by the first substrate 2 and the second substrate 2' is completed.

[0211] Figure 2 Optional process steps are shown, wherein, in particular, Figure 1g After the process steps, reduce the holding force F of the lower second fixing part 3 'and the lower second sample holder 1 ' H2 In particular, the holding force F H2 is reduced to 0, ie the fixing is deactivated. This results in, in particular, an unhindered movement of the second substrate 2 ′, in particular in a lateral direction along the lower sample holder surface 1 o ′.

[0212] In another advantageous embodiment, the second substrate 2 ′ is lifted along the bonding wave front 8 to such an extent that the second substrate 2 ′ is lifted, in particular partially, from the lower second sample holder 2 ′. This is achieved in particular by applying pressure to the second substrate 2 ′ from the second sample holder 1 ′.

[0213] The gravity G2 opposes the lifting of the second substrate 2 ′ during the entire bonding process and thus also influences the contact and thus the “jump” of the two substrates 2 , 2 ′.

[0214] Figure 3An optional process step according to the invention is shown, in which the chamber in which the process according to the invention is carried out is ventilated before the fully bonded substrate stack 10 is produced. This ventilation is used in particular to control the advancing bonding wave front 8. A precise description of the possibilities for influencing is disclosed in the publication WO 2014 / 191033 A1, to which reference is made in this respect. The ventilation is carried out with a gas or a gas mixture. In particular, the ventilation is carried out by opening a valve to the surrounding atmosphere so that the chamber is ventilated with the surrounding gas (mixture). It is also conceivable that the chamber is overpressured with a gas or a gas mixture instead of being ventilated to the surrounding atmosphere.

[0215] Figure 4 A schematic, not true to scale, illustration of two substrates 2, 2' is shown, which are defined by a number of parameters. The substrate surfaces 2o, 2o' correspond to the bending lines of the upper first substrate 2 and the lower second substrate 2' at a defined point in time. These are decisively defined by the parameters mentioned above. Their shape changes as a function of time during the bonding process according to the present invention.

[0216] Reference Signs List

[0217] 1.1' sample holder

[0218] 1o, 1o' Sample holder surface

[0219] 2.2' substrate

[0220] 2o, 2o' substrate surface

[0221] 2i Substrate backside

[0222] 3.3' Fixed part

[0223] 4. Drilling

[0224] 5 holes

[0225] 6 Deformation device

[0226] 7 Touchpoints

[0227] 8 Bonding Wavefront

[0228] 9 Measuring device

[0229] 10 Substrate stack

[0230] 11 Heating unit

[0231] 12 Light Source

[0232] F1, F2 force

[0233] F H1 、FH2 Retention

[0234] v Coupling wave velocity

[0235] T H Heating temperature

[0236] T1, T2 substrate temperature

[0237] E1, E2 substrate E modulus

[0238] d1, d2 substrate thickness

[0239] V1, V2 substrate volume

[0240] m1, m2 substrate quality

[0241] ρ1, ρ2 substrate density

[0242] G1, G2 substrate gravity

[0243] r1, r2 substrate curvature radius

[0244] r10, r20 initial substrate curvature radius

[0245] D Substrate edge distance

Claims

1. An apparatus for bonding a first substrate to a second substrate, comprising: A first sample holder configured to utilize a first holding force (F H1 ) to hold the first substrate, the first holding force (F H1 ) by applying a plurality of individually controllable first vacuum tracks of the first sample holder, so that the first substrate and the first sample holder can be fixed or separated in a targeted manner from the inside out, or the first substrate and the first sample holder can be fixed or separated in a targeted manner from the outside in; A second sample holder configured to utilize a second holding force (F H2 ) to hold the second substrate, the second holding force (F H2 ) applied by a plurality of individually controllable second vacuum rails of the second sample holder, so that the second substrate and the second sample holder can be fixed or separated from each other in a targeted manner from the inside outward, or the second substrate and the second sample holder can be fixed or separated from each other in a targeted manner from the outside inward, wherein the first and second sample holders are configured to be relatively close to each other to achieve relative proximity of the first and second substrates; as well as A measuring device, the measuring device being configured to: detecting, during contact between the first substrate and the second substrate, a percentage of surfaces of the first substrate and the second substrate that are bonded relative to surfaces of the first substrate and the second substrate that are not bonded; as well as The progression of the bonding wave between the first substrate and the second substrate is monitored via the detected percentage number, so that the bonding wave can be controlled by a targeted release of the fixing device by continuously releasing the vacuum.

2. The apparatus according to claim 1, wherein the first holding force (F H1 ) and the second holding force (F H2 ) is reduced to 0 to control the joining wave.

3. The device according to claim 2, wherein The first sample holder secures the first substrate to the first sample holder by applying a vacuum from the first sample holder, and the second sample holder secures the second substrate to the second sample holder by applying a vacuum from the second sample holder, wherein the vacuum applied from the first sample holder imposes the first holding force (F H1 ), and the vacuum applied from the second sample holder imposes the second holding force (F H2 ) to fix the first substrate and the second substrate to the first sample holder and the second sample holder, respectively, and wherein the vacuum is reduced to reduce the first holding force (F H1 ) and the second holding force (F H2 ), and controlling the disconnection of the first substrate and the second substrate from the first sample holder and the second sample holder, respectively.

4. The device according to claim 1, wherein The measuring device is further configured to detect a state of the engagement wave.

5. The apparatus according to claim 1, wherein The measuring arrangement comprises a conductivity measuring device configured to detect the percentage amount and to monitor the advancement.

6. The apparatus according to claim 1, wherein The measuring device further includes at least one of an optical system and a camera configured to detect at least one of a position of the bonding wave and a size of the bonded surfaces between the first substrate and the second substrate to monitor the progress of the bonding wave.

7. The apparatus according to claim 6, wherein The progression of the engagement wave is monitored over a period greater than 1 second.

8. The apparatus according to claim 6, wherein The advancement of the bonding wave is monitored via a radial position of the bonding wave, which corresponds to at least 0.1 times the respective diameter of the first and second substrates.

9. The apparatus according to claim 1, wherein The joining wave is controlled taking into account a defined set of values ​​obtained by the measuring means.

10. The apparatus according to claim 1, wherein The measuring device is further configured to monitor the advancement until the percentage amount is greater than 1%.

11. The apparatus according to claim 1, wherein The measuring device is further configured to monitor the advancement until the percentage amount is greater than 4%.

12. The apparatus according to claim 1, wherein The measuring device is further configured to monitor the advancement until the percentage amount is greater than 9%.

13. The apparatus according to claim 1, wherein The measuring device is further configured to monitor the advancement until the percentage amount is greater than 16%.

14. The apparatus according to claim 1, wherein The measuring device is further configured to monitor the advancement until the percentage amount is greater than 25%.

15. A method for bonding a first substrate to a second substrate by means of an apparatus according to any one of claims 1 to 14, comprising: initiating contact between the first substrate and the second substrate; detecting a percentage of the bonded surfaces of the first and second substrates that have been in contact relative to the unbonded surfaces of the first and second substrates that have been in contact; monitoring the progression of the bonding wave between the contacted first and second substrates via the detected percentage number, so that the bonding wave can be controlled by selectively releasing the fixture by continuously releasing the vacuum; and The first vacuum and the second vacuum included in the first sample holder and the second sample holder, respectively, are reduced to reduce the holding of the contacted first and second substrates by the first sample holder and the second sample holder, respectively, and to control the bonding wave between the contacted first and second substrates.

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