Device and method for bonding substrate

Abstract

To provide improved device and method for bonding a substrate.SOLUTION: A method for bonding a first substrate (3) and a second substrate (8) at contact surfaces (3k and 8k) of both substrates (3 and 8), includes: a step of mounting the first substrate to a first mounting surface (2o) provided to a first mounting device (1), and mounting the second substrate to a second mounting surface (2o') provided to a second mounting device (4); a step of contacting both contact surfaces at a predetermined bonding start position (20); and a step of bonding the first substrate with the second substrate along a bonding wave that is progressed from the bonding start position (20) up to side edge parts (3s and 8s) of both substrates.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The invention relates to a method for bonding a first substrate to a second substrate according to claim 1 and to a corresponding device according to claim 9.

[0002] The progressive miniaturization of almost all parts of microelectronics and microsystems technology leads to the continuous further development of all technologies, which can be used to increase the density of all kinds of functional units on a substrate, such as, for example, microcontrollers, memory components, MEMS, sensors of all kinds or microfluidic elements.

[0003] In recent years, the technology for increasing the lateral density of such functional units has improved significantly. In some sub-areas of microelectronics or microsystem technology, it has even progressed to the point where a further increase in the lateral density of the functional units is no longer possible. In microchip manufacturing, the maximum achievable resolution limit for substrates to be produced by lithography has already been reached. This means that in just a few more years, due to physical or technological limitations, an increase in the lateral density of the functional units will no longer be possible at all. In order to address this issue, the industry has already been working on the development of 2.5D and 3D technologies for several years. With 2.5D and 3D technologies, it is possible to align identical or even different types of functional units with respect to one another, stack them one on top of the other, permanently bond them to one another and wire them to one another by corresponding conductor tracks.

[0004] One of the key technologies to realize such structures is permanent bonding. By "permanent bonding" we mean all the methods by which substrates can be joined together in such a way that separation of the substrates is only possible with high energy consumption and therefore destruction of the substrates. There are different types of permanent bonding.

[0005] One of the most important permanent bonding methods is fusion bonding (Fusionsbonden), also called "direct bonding" or "molecular bonding". "Fusion bonding" refers to the process of permanent bonding of two substrates through the formation of covalent bonds. Fusion bonding occurs especially on the surfaces of non-metallic, non-organic materials.

[0006] Basically, a distinction should be made between pre-bonding and the actual permanent bond. By "pre-bonding" is meant a bond between the two surfaces which is formed spontaneously when they are brought into contact, the strength of which is lower than that of the permanent bond formed by a subsequent heat treatment. However, the strength of the bond created by pre-bonding is sufficient to transport the two substrates without causing any relative displacement of the two substrates. This means that the bond strength between the two substrates is sufficient to transport the substrate stack without problems, but is low enough that a new separation of the substrates without destruction can be performed using special equipment. This has the following important advantages: after pre-bonding, the structures of the two substrates can be measured and their relative positions, distortions and orientations can be measured. If during the measurement process it is detected that there is a misorientation of the structures and / or a local and / or global distortion or that particles are present at the interface, the substrate stack can be separated again and processed again accordingly. After it has been determined that the pre-bonding has been successful and that there are no particular disadvantages, a permanent bond is formed by a heat treatment process. During the heat treatment process, the supply of thermal energy leads to a chemical and / or physical strengthening of the bond of the surfaces of both substrates. This permanent bond is irreversible in the sense that a destruction-free separation of the two substrates is no longer possible. In the following, a clear distinction is no longer made between pre-bonding and permanent bonding, but is generally referred to only as "bonding".

[0007] The very common fusion bonding is carried out on silicon and silicon oxide substrates. Due to its semiconducting properties, silicon is often used as a base material for producing microelectronic components, such as microchips and memories. "Direct bonding" can also occur between highly polished metal surfaces. The underlying bonding properties are indeed different from those of fusion bonding, but the mechanism by which both surfaces are brought into contact with each other by a traveling bonding wave can be explained by the same physical properties. It is also conceivable to bond two hybrid surfaces by "hybrid bonding". By "hybrid surface" is meant a surface made of two different materials. Of the two materials, the first is usually confined to a small space, whereas the second surrounds the first. For example, a metal contact is surrounded by a dielectric. When a hybrid bond is formed by bonding two hybrid surfaces, the bonding wave is driven by fusion bonding, especially between the dielectric, and the metal contact is automatically matched by the bonding wave. Examples of dielectric and low-k materials are: ● Non-silicone, mainly composed of the following ingredients Polymer Polyimide Aromatic Polymers Parylene PTFR Aromatic carbon ● Silicone made mainly from the following ingredients ○ Silicate mainly composed of the following components TEOS (Tetraethyl orthosilicate) SiOF SiOCH Glass (borosilicate glass, aluminosilicate glass, lead silicate glass, alkali silicate glass, etc.) ○ General S 3 N 4 Silicon Carbide Silicon Carbide 2 SiCN Silsesquioxane HSSQ MSSQ One of the most important technical problems when permanently bonding two substrates is the alignment accuracy of the functional units between the individual substrates. The substrates can be aligned very precisely relative to each other by alignment equipment, but during the bonding process itself, distortions of the substrates can occur. Due to the distortions thus created, the functional units are not always properly aligned relative to each other in all positions. Inaccuracies in the alignment of a particular point of the substrate can result in distortions, scaling errors, lens defects (enlargement or reduction errors), etc. In the semiconductor industry, all topic areas related to such problems are subsumed under the concept of "overlay". A corresponding overview on this subject is given, for example, in "Fundamental Principles of Optical Lithography-The Science of Microfabrication" by Mack, Chris (Publisher WILEY, 2007, reprinted 2012).

[0008] Each functional unit is designed in a computer before the actual manufacturing process. For example, conductor tracks, microchips, MEMS, or any other structures that can be manufactured using microsystem technology are also designed in a CAD (computer aided design) program. However, it is found that during the manufacturing of the functional units, deviations always exist between the ideal functional unit constructed in the computer and the actual functional unit manufactured in the clean room. The differences can be mainly attributed to hardware limitations, i.e. technical engineering problems, but often also to physical limitations. The resolution accuracy of structures manufactured by photolithography processes is limited by the size of the aperture of the photomask and the wavelength of the light used. Mask distortions are directly transferred to the photoresist. The linear motors of the machine can only reach positions that are reproducible within a defined tolerance. It is therefore not surprising that the functional units of the substrate cannot be exactly equal to the structures constructed in the computer. Therefore, all substrates already have negligible deviations from the ideal state before the bonding process. If we compare the positions and / or shapes of two functional units of two substrates, located opposite each other, assuming that neither of the substrates is distorted by the bonding process, we will generally already find that there is a non-perfect alignment of both functional units, because they deviate from the ideal computer model due to the errors explained above. The most frequent errors are illustrated in Figure 8 (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, Reprint 2012).As shown in the figures, overlay errors can be roughly distinguished into global and local or symmetric and asymmetric overlay errors. Global overlay errors are uniform and therefore location independent. Global overlay errors cause the same deviation between two functional units located opposite each other, independent of their location. Classical global overlay errors are errors I. and II. caused by a translation or rotation of both substrates relative to each other. The translation or rotation of both substrates respectively causes corresponding translational or rotational errors on the substrates for all functional units located opposite each other. Local overlay errors are location related and are mainly caused by elastic and / or plastic problems, in this case in particular by elastic and / or plastic problems caused by the continuously propagating bonding wave. Among the illustrated overlay errors, errors III and IV are called "run-out" errors. These run-out errors are caused in particular by distortion of at least one substrate during the bonding process. Due to the distortion of at least one substrate, the functional units of the first substrate are also distorted with respect to the functional units of the second substrate. However, errors I and II can also be caused by the bonding process, but are usually significantly superimposed by errors III and IV, so that errors I and II are very difficult to detect or measure.

[0009] In the known prior art there are already provisions which make it possible to at least partially reduce local distortions: this is local distortion correction by using active control elements (WO 2012 / 083978).

[0010] In the known prior art, there is a first solution for correcting runout errors. US Patent Application Publication No. 20120077329 describes a method for obtaining a desired alignment accuracy between the 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 to bond to the upper substrate during the bonding process without being subjected to boundary conditions. An important feature in the known prior art is, among other things, the flat fixing of one substrate, usually by using a vacuum device.

[0011] The generated runout error generally grows radially symmetrically around the contact point and therefore grows from the contact point towards the periphery. This generally results in a linearly growing amplification of the runout error. Under special conditions, the runout error can also grow nonlinearly.

[0012] Particularly under optimal conditions, the runout error can not only be detected by suitable measuring instruments (EP 2463892), but also recorded by a mathematical function. Since the runout error is a translation and / or rotation and / or scaling between clearly 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 thus is the mapping rule that maps the two-dimensional definition range of position coordinates to the two-dimensional value range of the "runout" vector. An exact mathematical analysis of the corresponding vector field has not yet been performed, but conjectures about the functional properties can be made. The vector function can be determined with great probability by at least C n n>1 function and therefore continuously differentiable at least once. The divergence of the vector function is probably different from zero since the "runout" error increases from the contacting point towards the edge. Thus the vector field is a well field with great probability.

[0013] SUMMARY OF THE DISCLOSURE It is an object of the present invention to provide an apparatus and method for bonding two substrates, which provides increased bonding accuracy, particularly at the edges of the substrates.

[0014] This problem is solved by the features recited in the characterizing part of claim 1 and by the features recited in the characterizing part of claim 9. Advantageous refinements of the invention are recited in the dependent claims. All combinations of at least two features recited in the description, claims and / or drawings also fall within the scope of the invention. In the stated value ranges, the values ​​lying within the stated ranges are themselves to be considered as disclosed as limit values ​​and can preferably be claimed in any combination.

[0015] The idea underlying the invention is to deform at least one of the two substrates, preferably the second substrate and / or the first substrate, outside the bonding initiation point, in particular only outside the bonding initiation point, before and / or during bonding, in particular during the progression (propagation) of the bonding wave, preferably during fusion bonding, for the purpose of aligning the contact surfaces. "Deformation" means in particular a state different from the initial state of the substrate, in particular an initial geometry. According to the invention, bonding is initiated after contacting of the contact surfaces, in particular by dropping (releasing) the first / upper substrate. Corresponding bonding means are specially defined depending on the configuration of the device.

[0016] In the initial state, the substrate is usually formed more or less flat, especially at the contact surface, apart from any structures (microchips, functional components) that may protrude beyond the contact surface and substrate errors, such as bowing and / or thickness variations. In the initial state, however, the substrate usually has a curvature different from zero. For a 300 mm wafer, curvatures of less than 50 μm are common. Mathematically, the curvature can be considered as a measure of the local deviation of a curve from its flat state. In the concrete case, a substrate is considered that has a small thickness compared to its diameter. It can therefore be called, with a good approximation, the curvature of a flat surface. In the case of a flat surface, the first-mentioned flat state is the tangential plane of the curve at the point at which the curvature is considered. In general, objects, and in the special case substrates, do not have a uniform curvature, so that the curvature is an explicit function of the position. That is to say, for example, it is conceivable that a non-flat substrate has a concave curvature in the center, but a convex curvature in other places. In the following, in the simplest cases, curvature is always described only as "concave" or "convex", without going into mathematical details known to mathematicians, physicists and engineers.

[0017] The particularly unique central idea for most embodiments of the invention is that the radii of curvature of two substrates to be bonded together are equal or at least only slightly different from each other, at least in the contacting area of ​​the substrates, i.e. at the bonding front or bonding line of the bonding wave, with the difference between the two radii of curvature at the bonding front or bonding line of the substrates being less than 10 m, preferably less than 1 m, more preferably less than 1 cm, very preferably less than 1 mm, most preferably less than 0.01 mm and most preferably less than 1 μm. In general, all embodiments of the invention which minimize the radius of curvature R1 are advantageous. In other words, the invention relates to a method and an installation which allow two substrates to be bonded together such that their local alignment errors, called "runout" errors, are minimized. Furthermore, the idea underlying the invention is that the two substrates to be bonded together are controlled, in particular by means of geometrical, thermodynamic and / or mechanical compensation mechanisms, so that influencing factors for the formed bonding wave are selected in such a way that the two substrates are not locally misaligned relative to one another during bonding, i.e. are correctly aligned. Furthermore, the invention describes a product consisting of two substrates bonded together, with a reduced "runout" error according to the invention.

[0018] A characteristic process according to the invention for bonding, in particular for permanent bonding, preferably for fusion bonding, is the most possible concentric point-like contacting of the two substrates. In general, the contacting of the two substrates can also be performed non-concentrically. The bonding waves propagating from the non-concentric contact points reach different points on the substrate edges at different times. This complicates the complete mathematical and physical description of the bonding wave characteristics and the resulting compensation of the "runout" errors. However, in general, the contacting points are not located so far away from the substrate center that the effects possibly resulting from this are negligible, at least at the edges. The distance between the possible non-concentric contacting points and the substrate center is less than 100 mm, preferably less than 10 mm, more preferably less than 1 mm, very preferably less than 0.1 mm, most preferably less than 0.01 mm. In the following, "contacting" is generally taken to mean concentric contacting. "Center" in the broad sense preferably means the geometric center of the basic ideal object, compensated for asymmetrical features if necessary. That is, for industrially common wafers with a notch, the center is the center of a circle that surrounds an ideal wafer without a notch. For industrially common wafers with a flat (flat chamfered surface), the center is the center of a circle that surrounds an ideal wafer without a flat. A similar idea applies to arbitrarily shaped substrates. However, in special configurations, it may be beneficial for "center" to mean the center of gravity of the substrate. To ensure accurate concentric point contacting, the upper mounting device (substrate holder) is equipped with a radially symmetrical positioning device with a central hole and a pin that is translationally movable in this hole. It is also conceivable to use a nozzle that uses a fluid, preferably a gas, for pressurization instead of the pin.Furthermore, the use of such elements can be completely eliminated if a device is provided that can bring the substrates closer together by translational movement, under the further prerequisite that at least one of the substrates, preferably the upper one, has a curvature applied in the direction of the other substrate due to gravity and therefore automatically contacts the corresponding second substrate at a sufficiently small distance during said translational approach.

[0019] The radially symmetrical fixation can be a provided vacuum hole, a circular vacuum lip or a comparable vacuum element that can fix the upper wafer. The use of electrostatic mounting devices is also conceivable. A pin in a central hole in the upper substrate holder is used for the controllable bending of the fixed upper substrate.

[0020] After the two substrates have been contacted at their centers, the upper substrate holder is released from its fixed position. The upper substrate falls downwards due to gravity on the one hand and the bonding forces acting between the two substrates along the bonding wave on the other hand. The upper substrate is bonded to the lower substrate in a radial direction from the center towards the side edges. This results in the inventive formation of a radially symmetrical bonding wave, which in particular runs from the center towards the side edges. During the bonding process, the two substrates push out any gas, in particular air, present between the two substrates from the front of the bonding wave, thus resulting in a bonding interface free of gas inclusions. When the upper substrate falls, it essentially falls on a sort of gas cushion.

[0021] The first / upper substrate is not subject to additional positional fixation after the start of bonding at the bond initiation point, i.e. apart from the positional fixation at the bond initiation point it is free to move and even distort. Due to the advancing bonding wave in the present invention, the stress state created at the bonding wave front and the existing geometrical boundary conditions, any circle segment that is infinitesimally small with respect to its radial thickness will be distorted. However, since the substrate is a rigid object, the distortions will sum up as a function of the distance from the center. This leads to a "runout" error that should be eliminated by the method and the device according to the present invention.

[0022] The present invention therefore also relates to a method and an apparatus for reducing or even completely avoiding "runout" errors between two bonded substrates during bonding, in particular by means of thermodynamic and / or mechanical compensation mechanisms. Furthermore, the present invention deals with corresponding products manufactured using the apparatus according to the invention and the method according to the invention.

[0023] In a first embodiment of the invention, the first, in particular the lower, mounting device is ground convexly or concavely and / or polished and / or lapped at its mounting surface for mounting the first substrate, preferably the first mounting device is ground convexly so that the substrate fixed in position on the first mounting device is curved in the direction of the contact point or bonding initiation.

[0024] The radius of curvature of the first and / or second mounting surface is in particular configured to be greater than 0.01 m, preferably greater than 0.1 m, more preferably greater than 1 m, even more preferably greater than 10 m, most preferably greater than 100 m, most advantageously greater than 1000 m. In a particular embodiment, the radius of curvature of the first / lower mounting device is the same as the radius of curvature of the second / upper substrate formed by the second / upper mounting device by the actuation means, in particular the pins, in particular at least within the same power of 10. This results in a geometrically symmetric initial position for bonding.

[0025] Advantageously, the first / lower mounting surface is ground in such a way that physical asymmetries are compensated for by a gravitational field acting perpendicular to the mounting surface, causing the bonding wavefront to always move in the same horizontal plane.

[0026] The first and / or second substrate is preferably formed with radial symmetry. The substrate can have any diameter, but the wafer diameter is particularly formed to be 1 inch, 2 inches, 3 inches, 4 inches, 5 inches, 6 inches, 8 inches, 12 inches, 18 inches or larger than 18 inches. The thickness of the first and / or second substrate is 1 μm to 2000 μm, preferably 10 μm to 1500 μm, more preferably 100 μm to 1000 μm.

[0027] In particular embodiments, the substrate may have a shape which is different from a rectangular or at least circular shape.In the following, "substrate" means in particular a wafer.

[0028] In a second embodiment of the lower / first mounting device, the radius of curvature of the lower / first mounting surface is adjustable. In a particularly simple embodiment, the lower mounting device has a mounting plate that is made thick enough to prevent it from being deformed by unintended external influences, but thin enough to be brought into a convex or concave shape by the intended forces acting from below. In particular, this mounting plate has a thickness of 10- 7 Nm 2 greater than 10- 3 Nm 2 greater than 1 Nm 2 More preferably still, 10 3 Nm 2 greater than 10, most preferably 7 Nm 2 In one embodiment of the invention, the lower / first mounting device, in particular the part located on the inside, consists of a pneumatically and / or hydraulically and / or piezoelectrically expandable and / or contractible, preferably high-strength elastic diaphragm, in which the pneumatic and / or hydraulic and / or piezoelectric elements are preferably equally distributed and individually controllable.

[0029] In yet another embodiment of the invention, the lower / first mounting arrangement is configured in such a way that the lower / first substrate is intentionally deformed by the heating and / or cooling means, still before contacting, in particular compressed or stretched laterally, and only by the amount required to compensate as well as possible, ideally completely, for the "runout" errors that occur during subsequent contacting. In this embodiment, no particular importance needs to be attached to the thermal expansion coefficients of the lower / first substrate or of the lower / first mounting arrangement, since the lower / first substrate is fixed in position only after a corresponding deformation.

[0030] In yet another particular embodiment of the invention, the contacting of the lower / first substrate is carried out before the heating and / or cooling process. Due to the fixing in position before the heating and / or cooling process, the lower / first substrate follows the thermal expansion of the lower / first mounting device, so that the thermal expansion coefficient of the lower / first mounting device can be used to define the (thermal) expansion of the substrate. Particularly preferably, the thermal expansion coefficients of the lower / first substrate and the lower / first mounting device are equal, so that no or at least only low thermal stresses occur in the lower / first substrate during the heating and / or cooling process. It is also conceivable according to the invention that the thermal expansion coefficients are different from one another. In this case, the lower / first substrate follows the thermal expansion of the lower / first mounting device on average.

[0031] In this case, the temperature difference to be adjusted between the first and second mounting devices is less than 20° C., preferably less than 10° C., more preferably less than 5° C., very preferably less than 2° C., and most preferably less than 1° C. Each mounting device is heated as uniformly as possible according to the invention. In particular, a temperature field is provided in which the temperature difference at any two points is smaller than 5° C., preferably smaller than 3° C., more preferably smaller than 1° C., very preferably smaller than 0.1° C., and most preferably smaller than 0.05° C.

[0032] In yet another embodiment of the invention, the first mounting device is configured such that it can be intentionally deformed, in particular compressed and / or stretched, at the mounting surface by mechanical actuation means. The first substrate, which is fixed in position on the surface of the first mounting device, is deformed together with the deformation of the mounting device due to its small thickness in relation to the mounting device. The deformation of the mounting device is carried out by means of a number of pneumatic and / or hydraulic and / or piezoelectric actuators, which are preferably rotationally symmetrically distributed and arranged around the substrate mounting part. For a completely symmetrical purely radial distortion, at least three actuators are required, which are arranged at an angular interval of 120° with respect to each other. Preferably more than 5 actuators are used, more preferably more than 10 actuators, even more preferably more than 20 actuators, very preferably more than 30 actuators, most preferably more than 50 actuators.

[0033] In a further embodiment of the invention, the contact surfaces of both substrates are bonded to one another in a vertical orientation. This particular embodiment has the task, inter alia, of reducing, preferably at least symmetrically arranging and particularly preferably completely preventing and / or compensating for deformations of the wafers due to gravity. Preferably, in the vertical position, both substrates are bent, particularly simultaneously and symmetrically to the bonding start point, by an actuating means, in particular by a pin, towards the bonding start point, so that the convex surface at the bonding start point can be contacted. The bonding process, particularly automatic, with a bonding wave is initiated by removing at least one of the substrates from the mounting surface.

[0034] The embodiments of the present invention are preferably operated in a defined, especially controllable, atmosphere, especially at atmospheric pressure.

[0035] All of the above-mentioned embodiments of the invention can be carried out in a particular variant in low vacuum, more preferably in high vacuum, even more preferably in ultra-high vacuum, in particular at pressures below 100 mbar, preferably below 10 -1 Pressures below millibars, preferably below 10 -3 Pressures below 10 millibars, more preferably below 10 -5 Pressures below millibars, most preferably below 10 -8 It is carried out at pressures below millibar.

[0036] In a further embodiment of the invention, at least one influencing factor for the propagation of the bonding wave, in particular the propagation speed and / or at least one influencing factor for the orientation of the contact surface is controlled. The bonding wave is controlled in particular with respect to its speed. The speed is controlled in particular indirectly via the composition and / or density and / or temperature of the gas in the atmosphere in which bonding takes place. The method according to the invention should preferably be carried out in a low-pressure atmosphere, preferably in a vacuum, but it may be advantageous to carry out the bonding process in another atmosphere, in particular in an area of ​​normal pressure. Due to the point-like contact, during bonding according to the invention, the bonding wave always proceeds radially symmetrically from the center towards the side edge and in the process displaces an annular gas cushion in front of the bonding wave itself. Along the bonding line (bonding front), in particular the approximately annular bonding line of the bonding wave, such a high bonding force is generated that no inclusions of gas bubbles can occur at all. The upper / second substrate therefore rests on a kind of gas cushion during the bonding process.

[0037] The inventive selection of gas / gas mixture and the definition of the properties of the gas cushion set how quickly and how strongly the second substrate can drop and / or stretch. Furthermore, the speed of the bonding wave can also be controlled via the properties of the gas.

[0038] According to a further, particularly independent, feature of the invention, the composition of the gas mixture is selected. Preferably, a gas is used which has as light a species of atoms and / or molecules as possible at a given temperature, with a correspondingly small inertia. The molar mass of at least one of the gas components is therefore less than 1000 g / mol, preferably less than 100 g / mol, more preferably less than 10 g / mol, very preferably less than 1 g / mol. Furthermore, preferably, the density of the gas mixture used is adjusted, in particular to be as small as possible, and / or the temperature is adjusted, in particular to be as high as required. The gas density according to the invention is less than 10 kg / m 3 less than 1 kg / m 3 less than 0.1 kg / m 3 less than 0.01 kg / m 3 The temperature of the gas is adjusted according to the invention to be higher than 0° C., preferably higher than 100° C., more preferably higher than 200° C., very preferably higher than 300° C., and most preferably higher than 400° C. According to the invention, the above-mentioned parameters are selected in such a way that the selected gas mixture or individual components of the gas mixture do not condense. This avoids liquid inclusions at the surface of the substrate during the bonding process.

[0039] For gas mixtures whose thermodynamic properties are plotted in a multi-component phase diagram, a similar concept applies: changing the composition and / or pressure and / or temperature of the gas mixture will affect the kinetic properties of the first substrate and / or the second substrate, thereby also reducing the "runout" error.

[0040] Particularly preferably, all the variable parameters are set in such a way that the bonding wave propagates at the most optimal speed possible with respect to the existing initial and boundary conditions. Particularly in the existing atmosphere, in particular at normal pressure, a bonding wave speed as slow as possible is advantageous. The bonding wave speed in this case is lower than 200 cm / s, preferably lower than 100 cm / s, more preferably lower than 50 cm / s, very preferably lower than 10 cm / s, most preferably lower than 1 cm / s. In particular, the bonding wave speed is higher than 0.1 cm / s. In particular, the bonding wave speed is constant along the bonding front. In a vacuum atmosphere, the bonding wave speed is automatically higher, because the substrates to be bonded along the bonding line do not have to overcome the resistance of the gas.

[0041] In yet another, particularly independent, embodiment of the invention, a stiffening plate is fitted between the mounting surface and the upper / second substrate in the upper / second mounting device. The stiffening plate is bonded, particularly temporarily, to the substrate and changes the properties of the upper / second substrate during bonding. The connection between the stiffening plate and the upper / second substrate is effected by structural-technical fastening at the stiffening plate. Such fastening is preferably a vacuum fastening. Electrostatic fastening, ultrathin mechanical fastening with clamping around the substrate at the edges, adhesive fastening by means of a highly polished stiffening plate surface are also conceivable.

[0042] In yet another, particularly independent, embodiment of the invention, the "runout" errors are accommodated by a very small distance between the two substrates before contacting and / or outside the bonding initiation point, in particular less than 100 μm, preferably less than 50 μm, more preferably less than 20 μm, and most preferably less than 10 μm.

[0043] According to the invention, it is particularly advantageous if the radii of curvature of both substrates, in particular at the bonding front, differ from one another by less than 5% and are preferably equal to one another.

[0044] In another special refinement of all embodiments of the invention, the lower / first mounting device and / or the upper / second mounting device have actuation means, in particular a central hole and a pin, which can be used to produce a convex curvature of the respective substrate in the direction of the bonding start point.

[0045] The control of the steps and / or movements and / or sequences described above, in particular the control of the pins for bending the substrates, the mutual approach of the substrates, the temperature control, the pressure control and the gas composition control, is preferably performed via a central control unit, in particular a computer with control software.

[0046] The mounting and fixing of the substrate in the mounting device can be carried out in any conceivable manner and by any known technique. In particular vacuum sample holders, electrostatic sample holders and sample holders with mechanical clamps are conceivable according to the invention. In order to allow the substrate sufficient flexibility and freedom of expansion and contraction within the fixing, it is preferred that the substrate is fixed only along the outermost circle segment as far as possible in the region of the side edges.

[0047] A further, particularly independent, embodiment of the invention is to perform the contacting as automatically as possible in a coordinated manner and simultaneously, in that at least one of the two substrates is loaded before the contacting with a preload, which in particular extends concentrically radially outwards with respect to the center M of the contact surface of the substrate, and then only influences the start of the contacting, and after the contacting of a certain section, in particular the center M of the substrate, the substrate is released and automatically bonded to the other substrate in a controlled manner based on the preload. The preload is achieved by deforming the first substrate by means of a deformation means, which in this case acts on the side opposite to the bonding side, in particular based on its shape, and the deformation can be controlled accordingly by the use of different, in particular interchangeable, deformation means. The control can also be performed by the pressure or the force with which the deformation means acts on the substrate. In this case, it is advantageous to reduce the effective mounting surface of the mounting device with the semiconductor substrate, so that the semiconductor substrate is only partially supported by the mounting device. A smaller contact surface thus results in a reduced adhesion between the wafer and the specimen holder or mounting device. According to the invention, since the fixing is applied in particular only in the peripheral region of the semiconductor substrate (first substrate), an effective fixing is provided and at the same time an effective mounting surface as small as possible between the mounting contour of the mounting device and the semiconductor substrate is provided. At the same time, therefore, a gentle and reliable detachment of the semiconductor substrate is also possible, since the detachment forces required for the detachment of the wafer are generated as small as possible. The detachment is particularly controllable, in particular by a reduction in the underpressure at the mounting surface. "Controllable" means that after the contact of the first and second wafer, the first wafer still remains fixed in the specimen holder, and only by a deliberate (controlled) reduction in the underpressure at the mounting surface does the detachment of the substrate (wafer) from the specimen holder (mounting device) take place, in particular from the inside to the outside. The above-described embodiment of the invention in particular enables the detachment to be carried out with extremely small forces.

[0048] The substrates (wafers) are aligned relative to one another prior to the bonding process, so that overlap of corresponding structures on the substrate surfaces is guaranteed (precise alignment, in particular with an accuracy of less than 2 μm, preferably less than 250 nm, more preferably less than 150 nm, most preferably less than 100 nm). In the bonding method according to the invention, the wafers are not placed flat on top of one another, but are first brought into contact with one another at the center M, one of the two wafers being pressed lightly against the second wafer or correspondingly deformed in the direction of the opposite wafer. After the deformed and bent wafer (in the direction of the facing wafer) is released, the progression of the bonding wave results in a continuous and uniform welding along the bonding front with minimal forces and thus with minimal distortions, mainly in the horizontal direction, in particular at least almost completely automatic.

[0049] A further, particularly independent, aspect of the invention is the control of the deformation of the first and / or second substrate in relation to defined influence factors on the progression of the bonding wave, such as, inter alia, the ambient pressure of the atmosphere surrounding the substrates, the type of gas / gas mixture present in the atmosphere, the temperature, the distance between the substrates outside the bonding initiation point, the bonding strength of the substrates, any pre-treatment steps present, the nature of the surface, the surface roughness, the material at the surface as well as the wafer thickness / bending stiffness.

[0050] If the bonding initiation point is arranged in the center of the contact surface of the substrate, a uniform, in particular concentric, progression (propagation) of the bonding wave can be achieved.

[0051] It is particularly advantageous if the deformation of the first and / or second substrate takes place laterally and / or convexly and / or concavely, more preferably mirror-symmetrically, in other words the deformation takes place according to the invention in particular by stretching or compressing or bending the first and / or second substrate.

[0052] Preferably, the substrates have approximately identical diameters D1, D2, which differ from one another in particular by less than 5 mm, preferably by less than 3 mm, more preferably by less than 1 mm.

[0053] In yet another, particularly independent, configuration of the invention, said deformation is effected by mechanical actuation means and / or temperature control of the first and / or second mounting device.

[0054] Variations in the present invention can be realized even more easily if the first substrate and / or the second substrate are positioned and fixed to the first mounting surface and / or the second mounting surface only in the area of ​​the side walls.

[0055] The disclosed features relating to the apparatus also apply to the features relating to the method and vice versa.

[0056] Further advantages, features and details of the invention will become apparent from the following detailed description of the embodiments with reference to the drawings. [Brief description of the drawings]

[0057] [Figure 1] 1 is a schematic cross-sectional view of a first embodiment of a device according to the invention; [Diagram 2] FIG. 2 is a schematic cross-sectional view of a second embodiment of the device according to the invention. [Diagram 3] FIG. 4 is a schematic cross-sectional view of a third embodiment of the device according to the invention. [Figure 4] FIG. 11 is a schematic cross-sectional view of a fourth embodiment of the device according to the invention. [Diagram 5] FIG. 11 is a schematic cross-sectional view of a fifth embodiment of the device according to the invention. [Figure 6] 2A-2C are schematic diagrams showing the method steps of bonding according to the present invention; [Figure 7a] FIG. 2 is a schematic diagram showing a bonded substrate pair having an alignment error dx in the range of the substrate side edges. [Figure 7b] FIG. 2 is an enlarged view of two substrates in the range of a bonding wave according to the present invention. [Figure 7c] A close-up of two substrates with no alignment / runout errors. [Figure 7d] FIG. 1 shows a close-up of two substrates with alignment / runout errors. [Figure 8] FIG. 2 is a schematic diagram symbolically illustrating possible overlay or "runout" errors.

[0058] In the drawings, identical components and components having identical functions are designated by the same reference numerals.

[0059] In FIG. 1, the lower first mounting device 1 is shown as a substrate sample holder. The lower first mounting device 1 consists of a base body 9 and a mounting body 2. The mounting body 2 has a first mounting surface 2o arranged upwardly in the direction of the oppositely located second mounting device 4. In the illustrated example, the first mounting surface 2o is curved convexly. The mounting body 2 is designed as a module that can be exchanged and is separable from the base body 9. The base body 9 is thus used as an adapter between the mounting body 2 and a lower mounting unit of a bonder (not shown). This makes it possible according to the invention to carry out a rapid exchange between different modular mounting bodies 2 with different radii of curvature R, if necessary.

[0060] Fixing means 6 in the form of a vacuum path are arranged on the mounting body 2. By means of this fixing means 6 the lower first substrate 3 can be fixed in position on the mounting surface 2o.

[0061] Since the radius of curvature R is preferably so large according to the invention that it is practically not perceptible to the naked eye (it is shown greatly exaggerated in the drawings), it is conceivable according to the invention to configure the first mounting device without fastening means 6 and to simply place the first substrate on the mounting surface 2o. Attachment by electrostatic, electrical or magnetic fastening means is also conceivable according to the invention.

[0062] The second mounting device 4, formed as a substrate sample holder, comprises a base body 2' with a second mounting surface 2o', which is equidistantly positionable, in particular in a concentric section, with respect to a corresponding concentric section of the first mounting surface 2o.

[0063] The base 2' has an opening 5 in the form of a hole and fastening means 6' similar to the fastening means of the first mounting device 1.

[0064] The fixing means 6' is used to fix the upper second substrate 8 in position on the side opposite the contact surface 8k.

[0065] Actuating means in the form of pins 7 are used to deform (in this case deflect) the second substrate 8 and thus in particular to bring the second substrate 8 in a point-like manner closer to the curved first substrate 3, in particular to the area of ​​maximum curvature.

[0066] In a particular configuration of the invention, it is conceivable to form the mounting body 2 as an extensible, pneumatically and / or hydraulically expandable and contractible component, in particular a cushion, in particular made of a heat-resistant and / or corrosion-resistant material.

[0067] FIG. 2 shows a second embodiment with a mounting body 2″, in which a first mounting surface 2o can be deformed in a controlled manner by means of an actuating element 10 configured as a tension and / or pressure rod. The mounting body 2″ has a fixed section 16, which is preferably concentric and extends over the entire circumference, and a deformation section 17, which includes the first mounting surface 2o. The deformation section 17 has at least approximately a constant thickness over the entire circumference and thus an approximately constant bending stiffness. The actuating element 10 is arranged on the actuating side of the deformation section 17, facing away from the first mounting surface 2o, and is preferably fixed in position. By means of the actuating element 10, the deformation section 17 can be deformed in the micrometer range and can be bent in particular in the form of a concave or convex surface. The actuating element 10 in this case moves by more than 0.01 μm, preferably by more than + / - 1 μm, more preferably by more than + / - 10 μm, very preferably by more than + / - 100 μm, most preferably by more than + / - 1 mm and most advantageously by more than + / - 10 mm. In other respects, the embodiment shown in FIG. 2 corresponds to the embodiment shown in FIG.

[0068] FIG. 3 shows a third embodiment of a first mounting device 1 with a mounting body 2'''. The mounting body 2''' has a first mounting surface 2o for mounting a first substrate 3. Furthermore, in this embodiment, the first mounting device 1 has temperature control means 11 for controlling the temperature (heating and / or cooling) of the mounting body 2''' at least in the area of ​​the first mounting surface 2o, preferably in the area of ​​the entire mounting body 2'''.

[0069] In the first method, the first substrate 3 is fixed in place on the heated mounting body 2''' only after the expansion and contraction caused by the temperature difference has been achieved, whereby the first substrate 3 expands and contracts according to its own thermal expansion coefficient.

[0070] In the second method, the first substrate 3 is fixed in position on the mounting body 2''' before being subjected to a thermal load by the temperature control means 11. A change in the temperature control means 11 causes the mounting body 2''' and thus the first mounting surface 2o to expand, in particular laterally, together with the first substrate 3 fixed in position on this first mounting surface 2o. Preferably, the mounting body 2''' has approximately the same thermal expansion coefficient as the first substrate 3. In other respects, the third embodiment corresponds to the first and second embodiments described above.

[0071] Figure 4 shows the mount body 2 IV 1. A fourth embodiment is shown having a base body 9' with a receiving section 18 for receiving a mounting body 2. Furthermore, the base body 9' has a shoulder section 19, which is formed in particular annularly and which is adjacent to the receiving section 18. This shoulder section 19 is connected to the mounting body 2. IV The actuating elements 12 are in particular a number of tension and / or pressure elements 12 that are arranged in a manner such that the mounting body 2 is laterally deformed. IV The actuating elements 12 are arranged on the side peripheral surface of the mount body 2. IV is used to deform the mounting body 2 laterally, in particular by mechanical stretching and / or compression, preferably within the micrometer range. IV is in this case expanded / compressed by more than 0.01 μm, preferably more than + / - 1 μm, more preferably more than + / - 10 μm, very preferably more than + / - 100 μm, most preferably more than + / - 1 mm, most preferably more than + / - 10 mm. The actuating element 12 can be formed as a purely mechanical and / or pneumatic and / or hydraulic and / or piezoelectric component.

[0072] In other respects, the fourth embodiment corresponds to the first, second and third embodiments described above. What is particularly important in the fourth embodiment is the substrate 1 and the mount body 2. IVThe adhesive portion between the substrate 1 and the mounting body 2 is formed very large, and the substrate 1 is fixed to the mounting body 2 by the operating element 12. IV During the stretching or compression of the film, it is likewise stretched or compressed accordingly.

[0073] A fifth embodiment is shown in Fig. 5. In the fifth embodiment, the first mounting device 1 and the second mounting device 4 are oriented vertically. The first mounting device 1 includes a base 9'' and a mounting body 2 fixed in position by the base 9''. V Mount body 2 V In this embodiment, the semiconductor device has a first mounting surface 2 o that is disposed vertically, and a first substrate 3 is fixed in position to this first mounting surface 2 o via a fixing means 6 .

[0074] The second mounting device 4 is a mounting body 2 IV The mounting body 2 has a base body 9''' arranged to face each other and to receive and fix the mounting body 2 in position. IV is used for mounting and fixing the second substrate 8 on the vertically arranged mounting surface 2o'. For deforming the second substrate 8, an opening 5 similar to the opening 5 shown in FIG. 1 is provided, which opening 5 is provided with an actuating means in the form of a pin 7. The pin 7 is designed to deform the second substrate 8 through the opening 5, in this case the pin 7 deforms the side of the second substrate 8 opposite the contact surface 8k. The pin 7 defines a bonding start point 20 when the two substrates 3, 8 are contacted by deformation of the second substrate 8.

[0075] Apart from the openings 5 ​​and the pins 7, the first mounting device 1 and the second mounting device 4 are formed symmetrically in the fifth embodiment shown in FIG. 5. The first mounting device 1 preferably also has corresponding openings and corresponding pins, which allows a symmetrical deformation of both substrates 3, 8. By simultaneously releasing both fastening means 6, 6' after contacting the deformed substrates 3, 8, in particular at the centrally arranged bonding initiation points 20 of both substrates 3, 8, both substrates 3, 8 behave identically, so that no alignment errors occur during the advance of the bonding wave, also due to the absence of any influence of gravity on the deformation of the contact surfaces 3k, 8k in the direction of approaching each other. This is especially true when the overwhelming number of influencing factors in the present invention for the bonding wave or alignment errors, in particular the thickness or bending stiffness of the substrates, is the same. The bending stiffness is the resistance of an object to a bending that is forcibly applied to it. The higher the bending stiffness, the higher the bending moment must be generated in order to obtain the same curvature.

[0076] Bending stiffness is a purely material and geometry dependent quantity that is independent of bending moment (assuming that bending moment does not change the moment of inertia or moment of area with cross-sectional changes). The cross-section of the central part of the wafer is, to a very good approximation, a rectangular cross-section with thickness t3 and wafer diameter D. Bending stiffness is the product of the elastic modulus and the moment of area for a uniform cross-section. The moment of area of ​​a rectangular cross-section about an axis perpendicular to the thickness is directly proportional to the cube of the thickness. That is, the thickness affects the moment of inertia and therefore the moment of area. Bending moment is caused by the action of gravity along the substrate. That is, if the bending moment and therefore gravity are constant, a substrate with a large thickness will bend less than a substrate with a small thickness due to its large moment of area.

[0077] The bonding process is illustrated diagrammatically in Figure 6, where the radius of curvature R of the first mounting device 1 is greatly exaggerated for the sake of clarity of the drawing, which according to the invention amounts to several meters for a substrate 3,8 with a diameter in the range 1" to 18" and a thickness in the range 1µm to 2.000µm.

[0078] Bonding begins after contacting the substrate 3,8 with the contact surfaces 3k,8k in the region of a bonding initiation point 20 located in the center of the substrate 3,8 and after de-fixing (detaching) the second substrate 8 from the second mounting device 4. A bonding wave with a bonding front 13 runs concentrically from the bonding initiation point 20 to the side edges 8s,3s of the substrate 3,8.

[0079] In the process, the bonding wave displaces a gas 15 (or a gas mixture 15) indicated by an arrow between the two contact surfaces 3k, 8k.

[0080] According to the invention, the first substrate 3 is deformed by the mounting device 1 in such a way that alignment errors of corresponding structures 14 on both substrates 3, 8 are minimized.

[0081] The second substrate 8 deforms during the bonding wave propagation (after bonding initiation and release from the mounting device 4) based on the acting forces: gas pressure, gas density, bonding wave velocity, gravity, and the natural frequency (spring characteristics) of the second substrate 8.

[0082] In the illustrated embodiment, which corresponds in particular to the first two embodiments shown in Fig. 1 and Fig. 2, the deformation is performed by bending both substrates 3, 8. In this case, the radius of curvature R of the upper substrate 8 corresponds in particular to the radius of curvature R1 of the lower substrate 3 at any point in time at the bonding front 13. If one of the two mounting surfaces 2o, 2o' is flat and thus the radius of the corresponding substrate 3 or substrate 8 supported on this flat mounting surface 2o or 2o' is also infinite, then the radius of the correspondingly oppositely located substrate 8 or substrate 3 is also adjusted accordingly, in the extreme case to infinity. Thus, the compensation according to the invention of the "runout" error by bringing two substrates 3, 8 with infinite radii of curvature close together, i.e. two substrates 3, 8 with contact surfaces 3k, 8k that are parallel to each other, is also disclosed. This special case according to the invention is particularly suitable in a vacuum enclosure for bonding the two substrates 3, 8 to each other. This is because it is not necessary to bond the two substrates 3, 8 to one another by a bonding wave propagating from the bonding center and displacing a gas volume forward from the bonding interface. The difference between the radii of curvature R1, R is in accordance with the invention in particular made smaller than 100 m, preferably smaller than 10 m, more preferably smaller than 1 m, very preferably smaller than 1 cm, particularly preferably smaller than 1 mm.

[0083] In this case, the invention contemplates controlling the environment and the bonding speed by the choice of gas 15 or gas mixture 15 and the setting of pressure and / or temperature.

[0084] As shown in enlarged form in Figures 7a to 7d, the possible alignment error dx shown in Figures 7a and 7d is, according to the invention, at least to a large extent eliminated by deforming both substrates 3, 8 as shown in Figures 7b and 7c.

[0085] The previously described method steps, in particular the movements and parameters, are controlled in particular by a software-assisted control device (not shown). [Explanation of symbols]

[0086] 1 First mounting device 2,2´,2´´,2´´´,2 IV ,2 V ,2 V1 Mount body 2o 1st mounting surface 2o´ Second mounting surface 3 First Board 3k first contact surface 3s side edge 4 Second Mounting Device 5 aperture 6,6´ Fixing means 7-pin 8 Second Board 8k second contact surface 8s side edge 9,9´,9´´,9´´´ Base 10. Actuating Elements 11 Temperature control means 12 Actuating elements 13 Bonding Front 14,14´ structure 15 Gases / Gas Mixtures 16 Fixed category 17 Deformation Classification 18 Housing Category 19 Shoulder Division 20 Bonding start point dx Alignment error d1,d2 diameter R,R1 radius of curvature

Claims

1. A method for bonding a first substrate (3) to a second substrate (8) at contact surfaces (3k, 8k) of both substrates (3, 8), comprising the following steps, in particular the following sequence: Mounting a first substrate (3) on a first mounting surface (2o) provided on a first mounting device (1) and mounting a second substrate (8) on a second mounting surface (2o') provided on a second mounting device (4); contacting both contact surfaces (3k, 8k) at a predetermined bonding initiation point (20); bonding the first substrate (3) to the second substrate (8) along a bonding wave that proceeds from the bonding initiation point (20) to the side edges (3s, 8s) of both substrates (3, 8); In a method having the following structure:

1. A method for bonding substrates, characterized in that the first substrate (3) and / or the second substrate (8) are deformed before and / or during bonding outside the bonding initiation point (20) for alignment of the contact surfaces (3k, 8k).

2. 2. The method according to claim 1, wherein the deformation of the first substrate (3) and / or the second substrate (8) is performed in conjunction with defined influencing factors that influence the progression of the bonding wave.

3. 3. The method according to claim 1, wherein the bonding initiation point (20) is arranged in the center of the contact surface (3k, 8k).

4. 4. The method according to claim 1, wherein the deformation of the first substrate (3) and / or the second substrate (8) is carried out laterally and / or concavely or convexly.

5. 5. The method according to claim 1, wherein the deformation is performed by stretching or compressing or bending the first substrate (3) and / or the second substrate (8).

6. 6. The method according to claim 1, wherein the diameters (d1, d2) of the two substrates (3, 8) differ from one another by less than 5 mm, in particular by less than 3 mm, preferably by less than 1 mm.

7. 7. The method according to claim 1, wherein the deformation is performed by mechanical actuation means and / or by temperature control of the first mounting device (1) and / or the second mounting device (4).

8. 8. The method according to claim 1, further comprising the step of fixing the first substrate (3) and / or the second substrate (8) on the first mounting surface (2o) and / or the second mounting surface (2o') only in the region of the side edges (3s, 8s).

9. 1. An apparatus for bonding a first substrate (3) to a second substrate (8) at contact surfaces (3k, 8k) of both substrates (3, 8), comprising: A first mounting device (1) for mounting a first substrate (3) on a first mounting surface (2o), and a second mounting device (4) for mounting a second substrate (8) on a second mounting surface (2o'); a contact means for contacting both of the contact surfaces (3k, 8k) at a predetermined bonding start point (20); An apparatus for bonding a substrate, comprising:

1. An apparatus for bonding substrates, comprising a deformation means for deforming the first substrate (3) and / or the second substrate (8) outside the bonding start point (20) before and / or during bonding in order to align the contact surfaces (3k, 8k).

10. 10. Apparatus according to claim 9, characterized in that the deformation means comprises the first mounting device (1) which is deformable laterally and / or convexly or concavely, in particular at the first mounting surface (2o).

11. 10. Apparatus according to claim 9, characterized in that the deformation means comprises the second mounting device (4) which is deformable laterally and / or convexly or concavely, in particular at the second mounting surface (2o').

12. 12. The device according to claim 9, wherein the deformation means comprises mechanical actuation means and / or temperature control means for controlling the temperature of the first mounting device (1) and / or the second mounting device (4).

13. 13. The device according to claim 9, further comprising fixing means arranged for fixing the first substrate (3) and / or the second substrate (8) on the first mounting surface (2o) and / or the second mounting surface (2o') only in the area of ​​the side edges (3s, 8s).

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