Method and apparatus for influencing bonding waves when bonding

Abstract

The invention relates to a method and a device for influencing a bonding wave (6) when bonding a first substrate (4) to a second substrate (4 '), at least the first substrate (4) is fixed to a first substrate holder (1) having at least one zone (7 ', 7' '), and the at least one zone (7', 7 '') each has at least one separating element (10) at least partially forming a substrate holder surface, and wherein the at least one zone (7 ', 7' ') has at least one separating element (10); the at least one separating element (10) separates the at least one zone (7 ', 7' ') from a further zone (7, 7') of the first substrate holder (1) or the surroundings, and wherein the at least one zone (7 ', 7' ') each has at least one fastening element (12), furthermore the at least one fixing element (12) provides a holding force for fixing the first substrate (4) on the first substrate holder (1).

Description

Technical Field

[0001] The invention relates to a method and a device for influencing a bonding wave when bonding substrates. In addition, the invention relates to a method and a device for bonding using a substrate holder having at least one zone. Such a zone is necessary in some devices and methods for processing a substrate individually, fixing the substrate and bonding the substrate to other substrates or substrate stacks. Background Art

[0002] In the prior art, there are a number of publications describing substrate holders for fixing substrates. Some of these substrate holders are used for the connection process of two substrates, the so-called bonding. In the bonding process, the so-called fusion bonding or direct bonding is particularly important. In fusion bonding, the two substrates are connected to each other only based on their hydrophobic or hydrophilic substrate surface properties. In the first method step, the so-called pre-bonding (English: pre-bonding), the contact of the two substrates occurs at one point, especially the center point. After this contact, the fixation of at least one substrate, especially the upper substrate, is released so that the two substrates are connected to each other along their substrate surfaces facing each other. Here, the connection process is carried out by an advancing bonding wave, which propagates from the contact point toward the periphery of the two substrates. After this connection process, it is still conceivable to separate the two substrates using corresponding methods and devices. This separation is necessary when it is found that the substrates have not been connected to each other in an optimal manner. Very few substrates have untreated substrate surfaces. In most cases, the substrates have been processed and have different structures. For example, switching circuits (integrated circuits), microprocessors, LEDs, MEMS, etc. can be envisioned. These structures should then be aligned with and connected to the structures on the second substrate. It is particularly important here that each individual structure of the first substrate must be correctly aligned and connected to its structure on the opposite second substrate.

[0003] After the pre-bonding is produced, the resulting substrate stack is usually subjected to a heat treatment in order to increase the adhesion strength between the two substrate surfaces. After this heat treatment is completed, it is called fusion bonding or permanent bonding. From this point on, the two substrates can no longer be separated from each other without being destroyed.

[0004] Due to the progression of the bonding wave, individual substrate regions in the vicinity of the bonding wave may be distorted so that the alignment accuracy between structures relative to one another no longer exists. In particular, due to a plurality of such distortions, even global distortions may result which increase towards the periphery, in particular starting from the center. In extreme cases, these distortions may even be anisotropic, i.e. direction-dependent.

[0005] Therefore, industry has developed a variety of substrate holders, the goal of which is to influence the bonding wave. The control or regulation is preferably carried out by means of fixing elements, with the help of which the substrate can be fixed to the substrate holder. For example, the publications WO2017162272A1, WO2018028801A1 or WO2019057286A1 describe ways to influence the bonding wave by means of zones of a zone substrate holder. A zone is understood to be an area with at least one fixing element and possibly a plurality of fixing elements. These zones are usually physically separated from each other, but can also simply be areas in which fixing elements are switched according to a specified plan.

[0006] In particular, the substrate holder can also have only a single zone, in which generally a plurality of fixing elements are present. However, substrate holders having a plurality of zones separated from one another by partition walls are particularly preferred. In the case of a substrate holder having only one zone, the periphery can be regarded as a partition wall in the sense of the invention, which separates the single zone from the surroundings.

[0007] A vacuum substrate holder is a type of substrate holder. The space between the substrate and the substrate holder is evacuated by fixing elements, which are usually only small holes, and the atmospheric pressure presses the substrate and fixes it to the substrate holder. Initially, only individual holes were drilled in the substrate holder, and these holes formed very simple fixing elements. The entire area between the substrate and the substrate holder surface is evacuated. All the fixing elements present are connected to the same vacuum line. Thus, when a vacuum is applied, a fixation of the entire surface of the substrate that cannot be controlled or adjusted locally is formed.

[0008] Due to the development of these substrate holders and the possibility of controlling individual fixing elements, the fixing can be controlled or regulated in a spatially resolved manner.

[0009] A further development of the substrate holder is to combine the fixing elements and the zones with a pin substrate holder (English: pinschuck). A pin substrate holder is a substrate holder that has been milled at multiple, especially symmetrically distributed positions. The milling is not performed over the entire surface, but preferably symmetrically along radial, azimuthal or rectangular lines. As a result, protrusions are left between such lines relative to the back-milled area, which are referred to as pins in the prior art. By placing the substrate on these pins, on the one hand, more or less full-surface support can still be always performed, although the contact area is greatly reduced. In addition, the intermediate spaces of these pins can be evacuated, which will lead to a balance of contact pressure caused by the surrounding atmosphere. In particular, the density of the pins can also vary as a function of position, especially as a function of radius, so as to obtain a more uniform force action on the substrate when multiple fixing elements are used for each zone. By means of the milled pins, a concave structure substantially the same as the zone is produced. Adjacent zones are delimited relative to each other by partition walls. The partition wall is a material without back milling or an intentionally introduced seal, in particular a polymer seal. The partition wall completely surrounds the zone and can at the same time be regarded as a vacuum seal in the case of a vacuum substrate holder.

[0010] Now, the problem in the prior art is that during the movement of the bonding wave over the partition walls of the zones, the adjacent zones or separated areas are usually evacuated with different strengths. As a result, a significant pressure gradient acts on the bonding wave during its movement over the partition walls of the two zones. This pressure gradient leads to significant distortions between the substrates.

[0011] In this respect, there is also a problem in the prior art: even in the case of a substrate holder with only one zone, there is a pressure gradient between this single zone and the surroundings. In this case, the partition wall of the substrate holder is at the same time the periphery separating the zone from the surroundings. If a bonding wave propagates to the edge on such a substrate holder, the same problem occurs as when crossing a partition wall separating a plurality of zones from one another, i.e. the substrate region close to the bonding wave may be distorted. Summary of the invention

[0012] The object of the present invention is therefore to at least partially eliminate, in particular completely eliminate, the disadvantages listed in the prior art. In particular, the object of the present invention is to specify an improved method and device for bonding. Furthermore, the object of the present invention is to specify a method and device that can be used to improve the bonding result, in particular to reduce the distortion between two substrates.

[0013] The object is achieved by means of the features of the independent claims. Advantageous expansions of the invention are described in the dependent claims. All combinations of at least two features described in the specification, the claims and / or the drawings also fall within the scope of the invention. For the value ranges described, values ​​within the mentioned limits should also be regarded as disclosed as limit values ​​and can be claimed in any combination.

[0014] The present invention therefore relates to a method for influencing a bonding wave when bonding a first substrate to a second substrate, wherein at least the first substrate is fixed on a first substrate holder having at least one zone, and the at least one zone respectively has at least one separating element which at least partially forms a surface of the substrate holder, and wherein the at least one separating element separates the at least one zone from further zones of the first substrate holder or from the surroundings, and wherein the at least one zone respectively has at least one fixing element, and the at least one fixing element respectively provides a holding force for fixing the first substrate to the first substrate holder, wherein the method comprises at least the following steps: i) initiating a bonding wave by bringing the second substrate into contact with the first substrate; and then ii) adapting the holding force of the at least one fixing element of the at least one zone to the holding force of a fixing element of a further zone which is located immediately upstream of the at least one zone in the propagation direction of the bonding wave or to the ambient pressure of the surroundings.

[0015] In other words, the at least one zone is manipulated by adjusting the holding force of the holding element of the zone substrate holder so that the pressure gradient of the at least one zone in the direction of propagation of the bonding wave, in particular in the region of the partitioning element, is as small as possible. When the holding force of the at least one holding element is adapted to the ambient pressure, in particular to the pressure of the last zone in the direction of propagation, it is ensured that during bonding, at the moment when the bonding wave passes over the partition wall at the edge of the substrate holder, the atmospheric pressure matches the holding force of the zone at the outer edge.

[0016] In this case, the pressure within the at least one zone, in particular the last zone, can be adapted to the ambient pressure. Since the pressure within the zone can be adjusted more quickly and more efficiently than a pressure change in a large chamber or the surroundings, the bonding wave is advantageously influenced. In this case, in particular, the holding force for the lower substrate is reduced or even completely eliminated, so that the lower substrate can extend unhindered at the edge.

[0017] Preferably, the at least one zone has a plurality of controllable fixing elements, wherein the holding force can be varied in a targeted manner. As a result, a holding force gradient can be generated within the zone, so that the advancing bonding wave can be better controlled while still within the at least one zone. Preferably, the bonding wave is initiated by the central contact of the second substrate with the first substrate, so that the propagation of the bonding wave proceeds radially symmetrically.

[0018] Particularly preferred is: a substrate holder having a plurality of zones, namely the at least one zone and at least one further zone. Therefore, in the following part of the text, embodiments of substrate holders having a plurality of zones are generally described, in which there is at least one partition wall separating two zones from each other. For an alternative embodiment of the method with a substrate holder having only one zone, in which the outermost partition wall is at the same time the periphery of the substrate holder and in which there is no second zone, but there is an adjacent surrounding environment for this purpose, the holding force, preferably the holding force of the last zone or the outermost zone, is adjusted so that it can be particularly uniform across the last or outermost partition wall. The partition wall can also be an inserted element, in particular a sealing lip. Therefore, the partition wall does not necessarily have to be produced by the back-milling area of ​​the substrate holder, but can be an attached component. Here, in particular, the pressure in the outermost zone is adapted to the ambient pressure.

[0019] In this case, the zones can be divided into a plurality of segments perpendicular to the propagation direction of the bonding wave. Thus, a plurality of isosceles trapezoidal segments can form a zone, wherein the segments in turn preferably each have at least one fixing element. Thus, regardless of the radial position, the bonding wave can advantageously be adjusted simultaneously at a plurality of positions along the preferably circular substrate holder. In this case, the adjustment is carried out after the initiation of the bonding wave and preferably in each case in the region where the bonding wave is advancing (the first and second substrates are in contact or bonding). In this way, a particularly torsion-free bonding can be achieved.

[0020] In a preferred embodiment of the alignment method, provision is made that during the adaptation in step ii), the ambient pressure is additionally adapted to the holding force of the fixing element of the at least one zone. In this respect, the prevailing atmospheric pressure or the ambient pressure in the bonding chamber is adjusted. In this way, the holding force in the at least one zone can advantageously be adjusted indirectly due to the ambient pressure acting on the first substrate.

[0021] In a preferred embodiment of the alignment method, provision is made that the adaptation is carried out in step ii) so that the holding force is of equal magnitude immediately before and after at least one partition element, respectively, along the propagation direction of the bonding wave. In other words, by adjusting the holding force in the region of the partition element during the time period over which the bonding wave passes, it is ensured that a less-distorted bond occurs even in the region of the zone transition. Here, the holding force can also be adjusted continuously. It is essential that the differences in the holding forces of these zones, which are large and required for adjusting the bonding wave, are minimal immediately before and after the bonding wave crosses the partition wall. In this way, distortions in the region of the zone transition can advantageously be ensured.

[0022] In a preferred embodiment of the alignment method, provision is made that after the bonding wave is initiated in step i), the position of the bonding wave is continuously determined and the holding force of the at least one zone is adjusted so that when the bonding wave crosses the at least one separating element, the holding force is equally large in front of and behind the at least one separating element. By determining the position of the bonding wave, the adaptation in step ii) can advantageously be carried out precisely during the time period in which the bonding wave moves through the separating element. In this way, the required holding force differences can also be achieved in areas outside the separating elements or between these separating elements for adjusting the bonding wave without distortions being generated in the area of ​​the zone transition.

[0023] In a preferred embodiment of the alignment method, it is provided that at least one fixing element of the at least one zone is respectively designed as a vacuum fixing, and that the at least one separating element separates the at least one zone from the other zone or the surrounding fluid. Particularly preferably, the substrate holder is a vacuum zone substrate holder, which is divided into a plurality of vacuum zones which are adjustable and arranged symmetrically in the radial direction and in the propagation direction. Thus, the substrate arranged on the separating element is sucked and fixed. Here, the holding force of the vacuum fixing is advantageously set individually in each zone (or segment), because these zones are fluid-tight and therefore suitable for vacuum. In this way, the fixing element can advantageously act over the entire area and an adjustment of the bonding wave can be carried out over the entire surface as much as possible. The substrate holder can be flushed in particular with an inert gas, preferably with helium. It is also conceivable that the vacuum line is flushed with an inert gas.

[0024] In a preferred embodiment of the alignment method, provision is made that the adaptation in step ii) is carried out by flooding or evacuating the at least one zone or by flooding or evacuating the surroundings. In this way, the holding force can advantageously be provided simply, quickly and over a large area. In addition, the holding force can be adjusted particularly quickly in the area of ​​the zone transition or in the area of ​​the separation element at the transition and can then advantageously be quickly equalized to the holding force required for adjusting the bonding wave in the area between the separation elements.

[0025] In a preferred embodiment of the alignment method, provision is made for the adaptation in step ii) to include determining a pressure difference between the at least one zone and the further zone or the surroundings, wherein the pressure difference is compensated by the adaptation. In this way, it can be ensured that there is a particularly small pressure gradient in front of and behind the partition element and distortions during bonding are reduced to a minimum. In addition, the area in front of the partition element can also advantageously be flooded instead of being evacuated.

[0026] In a preferred embodiment of the alignment method, provision is made for the pressure of the at least one zone to be equal to the pressure of the further zone. In this way, there is advantageously enough time to precisely determine the position of the bonding wave and then only to adjust the pressure in the zone downstream in the propagation direction.

[0027] In an embodiment of the alignment method, provision is made for the holding forces of the at least one zone and the further zone to be adapted to one another in order to compensate for the pressure gradient. In this case, the further zone also has a corresponding fixing element with a variable holding force. In addition, in the case of adapting the ambient pressure to the last zone in the propagation direction, the holding force of the at least one zone can also be adjusted simultaneously.

[0028] Furthermore, the present invention relates to a device for influencing a bonding wave when bonding a first substrate to a second substrate, the device comprising at least: a first substrate holder having at least one zone for fixing the first substrate, wherein the at least one zone has at least one separating element which at least partially forms a substrate holder surface of the first substrate holder; and at least one fixing element arranged in the at least one zone, the fixing element having a holding force for fixing the first substrate on the first substrate holder; and a control unit for adjusting the holding force of the at least one fixing element of the at least one zone, wherein the control unit is configured to adapt the holding force of the at least one fixing element of the at least one zone to the holding force of a fixing element of another zone located immediately upstream of the at least one zone in the propagation direction of the bonding wave or to the ambient pressure during the advancement of the bonding wave.

[0029] Therefore, the control unit is set up to make the holding force of the at least one fixing element equal to the holding force of the upstream zone. Regarding the alternative scheme in which the holding force is adapted to the ambient pressure, the holding force of the last zone at the periphery of the substrate holder is adjusted in particular according to the ambient pressure. In other words, a zone substrate holder having a plurality of controllable fixing elements is provided, wherein these fixing elements are manipulated so that: during bonding, an optimal holding force is provided in front of and behind the partition wall separating the zones, thereby reducing distortion during the transition. Here, the first substrate is placed on a partition element that at least partially forms the surface of the substrate holder with the side facing away from the second substrate. By controlling the holding force before and after crossing the partition wall, the bonding wave can advance particularly uniformly and undisturbed in the area of ​​the partition wall. Therefore, the undesirable influence of different holding forces in front of and behind the partition wall on the bonding wave, especially propagating from the inside to the outside, is reduced. Here, holding forces that act unequally between these zones can be expected to adjust the bonding wave. If the bonding process does not start from the center, the outer zones with the fixing elements with variable holding forces can also be arranged closer to the center of the substrate holder. It is essential that the holding forces of the subsequent zones can be adjusted in the direction of the expected bonding wave, especially in the region of the separating elements, in order to compensate for the influence of the holding forces acting differently (in front of and behind the separating wall). In this way, advantageously low distortions can be ensured in the region of the separating elements.

[0030] Here, the dependence can also be determined based on empirical experiments or initial experiments and adjusted accordingly. Here, the control unit is not limited to simple control, but can also adjust the holding force according to other parameters (for example, bonding wave position). Here, the holding force of the fixing element can preferably be set by the control unit. In addition, the substrate holder preferably has a plurality of partition elements, which can be divided into a plurality of segments along the preferably circular substrate holder. These segments distributed in the circumferential direction of the zone are especially aligned along the propagation direction, so that, for example, the trapezoidal segments become larger toward the peripheral direction. On the whole, the device can be advantageously used to minimize stress and distortion, especially stress and distortion in the area of ​​zone transition or from the inner zone to the outer zone. Here, the control unit can also perform adjustment of the corresponding holding force according to other parameters.

[0031] In a preferred embodiment of the device for influencing a bonding wave during bonding, it is provided that the device additionally has a device for adapting the ambient pressure to the holding force of the at least one zone. In this way, the bonding wave can be advantageously indirectly influenced or the holding force can be adjusted due to the ambient pressure acting on the first substrate. If the fixing element is a vacuum fixing element that works with pressure, these pressures can advantageously be equalized so that the bonding wave flows out particularly slowly.

[0032] In a preferred embodiment of the device for influencing a bonding wave during bonding, it is provided that the control unit is set up to adjust the holding force of the at least one fixing element or the ambient pressure after contact when bonding the second substrate to the first substrate. The control unit is therefore designed such that during bonding, the holding force or the ambient pressure is adjusted only after initiation of the bonding wave. In this way, the device or the control unit can perform the adjustment taking into account the position of the bonding wave, in particular based on empirical data in the control unit.

[0033] In a preferred embodiment of the device for influencing a bonding wave during bonding, it is provided that the control unit is set up to determine the holding force of at least one fixing element of the at least one zone by means of a sensor. Preferably, the sensor is arranged in the region of the separating element in at least one outer and / or inner zone, respectively. In addition, a sensor for determining the ambient pressure can preferably be provided. In this way, the control unit can advantageously regulate the adjustment of the holding force based on the actual value, so that distortions can be further reduced.

[0034] In a preferred embodiment of the device for influencing a bonding wave during bonding, it is provided that the control unit is set up to keep the holding force of the at least one fixing element of the at least one zone and the holding force of the at least one further fixing element of the further zone equally strong during the bonding of the first substrate to the second substrate. In this way, the bonding wave can make a particularly smooth and distortion-free transition from the inner zone to the outer zone. In addition, a uniform holding force can be set evenly in a plurality of, in particular consecutive, zones in an efficient manner. As a result, the bonding result is further improved and low distortions are ensured when crossing the partition wall.

[0035] In a preferred embodiment of the device for influencing the bonding wave during bonding, it is provided that the control unit is set up to keep the holding force of the at least one fixing element of the at least one zone as great as the holding force of the at least one fixing element of the other zone directly in the region of the at least one separating element and in the time period during which the bonding wave passes over the at least one separating element. Preferably, the position of the bonding wave is also determined by a measuring device, particularly preferably an optically designed measuring device, and the adjusted time period is adapted in an optimal manner to the position of the bonding wave. In this way, after the separation element is passed, the holding force between the separation elements can advantageously continue to be adjusted quickly for influencing the bonding wave. In addition, in particular in the region of the separation elements, further improved bonding results can be achieved.

[0036] In a preferred embodiment of the device for influencing a bonding wave during bonding, it is provided that at least one fixing element of the further zone and at least one fixing element of the at least one zone are designed as vacuum fixings, and that a separation element fluidically separates the inner zone from the outer zone. Thus, when the substrate is placed on the first substrate holder, the fixing of the substrate to the first substrate holder can advantageously be produced over a large area in the entire zone area by means of a negative pressure (relative to the atmosphere or the surroundings). The holding force can advantageously be varied quickly, precisely and within each zone. In addition, contamination of the first substrate can be kept minimal, since the application of the force does not require contact with the substrate. Therefore, zones that are fluidically separated from one another and controlled by vacuum fixing elements are inherently suitable for use in a device for influencing a bonding wave.

[0037] In a preferred embodiment of the device for influencing a bonding wave during bonding, it is provided that the control unit is set up to keep the pressure difference between the pressure of the further zone and the pressure of the at least one zone as small as possible, preferably the same, during bonding. Preferably, the pressure is regulated by means of a pressure sensor arranged in the respective zone. Thus, when bonding the first substrate to the second substrate, in particular in the region of the separating element, a uniform and distortion-free bond can advantageously be provided.

[0038] In a preferred embodiment of the device for influencing a bonding wave during bonding, it is provided that the control unit is set up such that the means for changing the ambient pressure equalizes the ambient pressure with the pressure of the at least one zone immediately before and after the bonding wave passes over the at least one separating element. The aforementioned effects and advantages of the outer zones apply analogously to the other outer zones. With the aid of a plurality of zones in the direction of the propagation direction of the bonding wave, the bonding can be performed particularly precisely and uniformly and without distortion.

[0039] In the following, the outer zone is understood to be the downstream zone of the at least one zone or the direction of propagation of the bonding wave. If the ambient pressure is adjusted, the inner zone is the further zone or the last zone. The inner zone is the upstream zone in the direction of propagation. Preferably, the holding force of the downstream zone or the at least one zone is adapted to the holding force of the upstream zone.

[0040] A particularly advantageous effect of the device and method for influencing the bonding wave during bonding is that no or only negligible distortions are formed between the two substrates in the vicinity of the partition wall separating the zones from one another. The bonding wave front can thus cross the partition wall seamlessly, smoothly and without distortion. In this case, distortions are reduced, especially in the region of the partition wall, and stresses in the bonded substrate stack are reduced.

[0041] Another aspect is that the pressure in these zones is continuously controlled or adjusted before and / or during and / or shortly after the bonding wave front crosses the partition wall. Preferably, the pressure in the zone behind the bonding wave or the zone where the bonding wave is located is continuously changed so that the pressure is adapted to the pressure in the zone to which the bonding wave is moving.

[0042] One aspect of the device and the method is to influence the bonding wave with respect to its advancing behavior by controlling or regulating the holding force of a zone along the propagation direction of the initiated bonding wave. In this case, the speed or acceleration of the bonding wave is set in a targeted manner by controlling / regulating at least one fixing element in the zone, in particular by adjusting the pressure state over time. In this case, in particular, the advancing bonding wave is enabled to cross the partition walls of the zone without distortion, continuously and smoothly.

[0043] In the method below, idealized processes are assumed and described in order to present an exemplary method for bonding. In particular, it is assumed that the bonding wave propagates radially symmetrically, i.e. as circularly as possible, from the contact point to the periphery. This approach facilitates the description of the method, since it is generally always possible to refer to a bonding wave that needs to be adjusted. In general, an asymmetric propagation of a bonding wave is also conceivable. However, all methods, devices and approaches mentioned here are taken into account with respect to the following aspect: the bonding wave can generally propagate in an anisotropic manner, and therefore it is necessary to consider the adjustment of the zone in front of and / or behind the bonding wave portion, i.e., the adjustment of the zone is usually adapted to the individual bonding wave portions that are to cross the partition wall at a specific position.

[0044] In the following part of the text, reference is made to regulation. Regulation refers to a method in which a measurement signal is obtained for a first physical value and a second physical value is set depending on the desired result. For example, it is conceivable that the position of the bonding wave is measured (first physical value) and then the pressure in the zone in front of the bonding wave and / or the pressure in the zone behind the bonding wave (second physical measurement value) is set so that the desired result (minimal distortion of one or more substrates on the partition wall) is achieved.

[0045] In contrast, control is understood as merely specifying a physical value without a corresponding measurement signal. In this way, based on the determined empirical data, it is known when a physical value needs to be set in order to achieve a result. For example, it may be known how a bonding wave behaves under the same initial and boundary conditions, for always the same type of substrate. In this case, starting from the point in time of contact, it is possible to control the pressure in the individual zones as a function of time, without having to measure the advancing bonding wave.

[0046] The method and the device are described with reference to a vacuum substrate holder. This means that the holder is a vacuum holder, in particular a simple hole drilled into the surface of the substrate holder, which can be evacuated or flooded. It is also conceivable to use other fixing elements such as electrostatic fixings, magnetic fixings, etc. These fixing elements are then also divided into zones and are suitable for adjusting the corresponding holding forces. Even in this case, the fixing elements or the holding forces of these fixing elements can be changed / adjusted. Therefore, the term fixing element should be interpreted generally and does not only, but preferably, relate to vacuum holders.

[0047] In a first method step of an exemplary method for influencing a bonding wave during bonding, a lower substrate is loaded onto a lower substrate holder and an upper substrate is loaded onto an upper substrate holder. Preferably, the two substrates are fixed using fixing elements provided for this purpose.

[0048] In a second method step of the exemplary method for influencing a bonding wave during bonding, the two substrates are aligned with each other. Preferably, the alignment is performed using an alignment system provided for this purpose. The alignment between the two substrates is preferably performed based on alignment marks located on the substrates. Alignment methods and alignment devices are not discussed in more detail.

[0049] In a third method step of the exemplary method for influencing a bonding wave during bonding, the two substrates are brought close to one another. Here, the distance between the two substrate surfaces to be connected to one another is less than 10 mm, preferably less than 5 mm, even more preferably less than 1 mm, most preferably less than 0.1 mm, and most preferably less than 0.01 mm.

[0050] It is also conceivable that the third method step is carried out first and only then the second method step.

[0051] In a fourth method step of the exemplary method for influencing a bonding wave during bonding, at least one of the two substrates is deformed so that the deformed substrate comes into contact with the second substrate. Preferably, this contact is made as point-shaped as possible. Preferably, this contact is also made as centrally as possible. The contact point is the starting point of the bonding wave that subsequently advances.

[0052] In a fifth method step of the exemplary method for influencing a bonding wave during bonding, the fixtures are switched or adjusted so that at least one substrate can be deformed so that a bonding wave starts to propagate. Preferably, the bonding wave is initiated at the respective center of the substrate and propagates radially symmetrically. With the advancing bonding wave, other fixtures are switched or adjusted so that the bonding wave continuously moves further toward the periphery.

[0053] The sixth method step of the exemplary method for influencing the bonding wave during bonding is generally performed multiple times and each time the bonding wave portion moves toward the dividing wall between the zones. In this case, the pressure is adjusted in at least one zone, especially in the zone in front of and / or behind the bonding wave portion. Therefore, the bonding wave portion is the region in which the upper and lower substrates are connected and propagates in an especially radially symmetrical manner. The adjustment is performed so that the bonding wave portion produces minimal distortion, in particular even no distortion, between the substrate regions located near the dividing wall. To this end, it is necessary to continuously adjust the pressure in the zone in front of the bonding wave portion and / or the pressure in the zone behind the bonding wave portion so that the bonding wave portion is not subjected to a pressure gradient, or is subjected to only a very small pressure gradient.

[0054] In an embodiment of the device for influencing the bonding wave during bonding, the substrate holder has a plurality of fixing elements. These fixing elements can be manipulated individually. Preferably, these fixing elements are vacuum fixings. With the help of vacuum fixings, the contact pressure of the surrounding environment on the substrate can be very simply and very accurately controlled. These fixing elements are part of the zone. Generally speaking, the zone may have a plurality of fixing elements so that a more delicate control of the bonding wave can be achieved within the zone. In particular, in the case of vacuum zones, a plurality of fixing elements are used to enable faster evacuation of the zone. Then, through a plurality of fixing elements within the zone, a gas with a larger volume flow can be discharged, and thereby a faster adjustment can be performed. It is also theoretically conceivable that the fixings within the zone suck out the gas at different speeds. In this case, a pressure gradient can be generated within the zone. However, it is better and more convenient to change the pressure within the zone uniformly and isotropically. Therefore, the pressure within the zone is preferably only a function of time, and a plurality of fixing elements are preferably switched in the same manner so that the pressure within the zone is uniformly and isotropically adjusted.

[0055] The device for bonding comprises at least one zone substrate holder, preferably at least one measuring device and at least one control unit. In the case of regulation, the measuring device undertakes the measurement of physical parameters, such as the positioning of the bonding wave or at least one bonding wave part. The measuring device transmits these data to the control unit. The control unit evaluates the measurement and determines the required physical parameters for controlling and / or regulating the fixing elements based on the results.

[0056] The measuring device is preferably an optical system for determining the position of the bonding wave. However, sensors are also conceivable which determine the position of the bonding wave electromagnetically. For example, proximity sensors are conceivable.

[0057] Of particular interest is also the radius of curvature of the substrate at a certain point of the bonding wave. In this respect, the control of the fixing elements can also be carried out as a function of the radius of curvature of the substrate in the region of the bonding wave.

[0058] The control unit is a microchip, a computer, software or a combination thereof. In most cases, it is software in a computer. The measurement signals enter the computer via a peripheral device and are evaluated by the software. The software then adjusts the fixing elements in the substrate holder via the peripheral device. It is also conceivable to use PID controllers in which the regulation is already electronically programmed. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In the drawings, the same components or components with the same function are indicated by the same reference numerals. For the purpose of illustration, all the sketches may be drawn enlarged, so these drawings do not necessarily have the scale of the actual embodiment.

[0060] Further advantages, features and details of the invention emerge from the following description of preferred exemplary embodiments and from the accompanying drawings. These drawings schematically show:

[0061] Figure 1 A top view showing an embodiment of a substrate holder of an apparatus for influencing a bonding wave during bonding;

[0062] Figure 2a shows a first state of a sixth method step of an exemplary method according to the invention for influencing a bonding wave during bonding;

[0063] Figure 2b shows a second state of a sixth method step of the exemplary method according to the invention for influencing a bonding wave during bonding;

[0064] Figure 2c shows a third state of a sixth method step of the exemplary method according to the invention for influencing a bonding wave during bonding;

[0065] Figure 2d The fourth state of the sixth method step of the exemplary method according to the present invention for influencing a bonding wave during bonding is shown.

[0066] In the drawings, the same components or components having the same functions are denoted by the same reference numerals. DETAILED DESCRIPTION

[0067] Figure 1The fixing surface of an embodiment of a substrate holder 1 of a device for bonding is shown. The base body 2 can be mounted on the device by means of a fixing 3. The substrate holder 1 has a plurality of zones 7, 7', 7". which are delimited in particular in radial and azimuthal directions. In this example, the zones 7, 7', 7" are delimited by partition walls 10. When the base body 2 is milled, the partition walls 10 are simply retained, like the bosses 9. Here, the substrate holder 1 may also be designed so that the partition walls 10 are polymer seals or metal seals. In this figure, a radially symmetrical central zone 7 can be seen. In addition, along the first circle and the second circle, sixteen zones 7', 7" are respectively arranged radially around the central zone 7.

[0068] The zones 7, 7', 7" are therefore in particular concave, preferably milled, depressions 11, in some places of which the studs 9 are located. The pin surface of the stud 9 in particular coincides with the web surface of the partition wall 10. The zones 7, 7', 7" are in particular implemented as vacuum zones. These depressions 11 can be evacuated via the fixing device 12, in particular individually and independently of one another via the separation of the partition wall 10. In this simple case, the fixing element 12 is simply a hole through which the space between the studs 9 and thereby the zones 7, 7', 7" can be evacuated or flooded. If the zones 7, 7', 7" are also used for deformation, a fluid can also flow in via the fixing device 12, which fluid causes a deformation, in particular a local deformation, of the fixed substrate.

[0069] Preferably, a deformation element 5 is located in the center of the substrate holder 1, which can deform the fixed substrate, especially in the center. The boss 9 is used in particular to reduce the contact area of ​​the fixed substrate 4, preferably in order to avoid contamination. A plurality of sensors 8, in particular pressure sensors, can be located in the zones 7, 7', 7" of the substrate holder 1.

[0070] Also visible in this figure is a region Q, the cross-section of which will be shown in the other figures.

[0071] It is also clear to the skilled person that pressure can be defined as force per unit area. Since a method for influencing a bonding wave based on a vacuum substrate sample holder is described, and the zone is evacuated to generate a force on the substrate, it is advantageous to mention pressure. Next, physical considerations regarding forces and their effects must be performed according to the level of knowledge.

[0072] Figure 2a The first state of the sixth method step of the method for influencing a bonding wave during bonding is shown. The region Q through the two zones 7', 7" and their partition wall 10 is shown (see Figure 1) in cross section. The lower substrate 4 is placed on the boss 9 and the partition wall 10, and the upper substrate 4' is bonded to the lower substrate 4 exactly in this part of the two zones 7', 7". The propagating bonding wave 6 can be seen. The bonding wave 6 is presented only as a point in the cross section. In the top view, the bonding wave 6 is a completely closed curve, in particular and preferably a circle. Since the advancement of the bonding wave 6 is to be controlled or regulated, the two zones 7', 7" usually have different pressures. In the figure, by way of example, the pressure p1 in the zone 7' is selected to be lower so that the substrate region 13 of the lower substrate 4 can be fixed more firmly and better near the bonding wave 6, so that the substrate region 13' can connect the upper substrate 4' to the lower substrate as distortion-free as possible. The zone 7" has a higher pressure p2, in particular close to the ambient pressure, so that the substrate regions 13, 13' that are still far away from the bonding wave 6 can also be adjusted.

[0073] The lower part of the drawing shows a pressure diagram. The abscissa shows the position in arbitrary units, preferably in millimeters, the ordinate the pressure value. Three pressures are shown. On the one hand, the external environment pressure p0. In this case, the external environment pressure is approximately 1 bar.

[0074] It is also conceivable that the substrate holder 1 is located in a chamber with an increased external pressure. The ambient pressure would then be an overpressure relative to the atmosphere.

[0075] It is also conceivable that the substrate holder 1 is located in a chamber with reduced external pressure. The ambient pressure would then be negative relative to the atmosphere. This embodiment is relevant in particular when the substrates must be bonded in an environment with a lower pressure, for example in order to avoid or reduce contamination.

[0076] In the following part of the text it is assumed that the apparatus is open to the atmosphere and that the ambient pressure p0 is approximately 1 bar atmospheric pressure.

[0077] In general, the ambient pressure p0 may be between 2 bar and 0.1 bar, preferably between 1.5 bar and 0.5 bar, still more preferably between 1.25 bar and 0.75 bar, most preferably between 1.10 bar and 0.90 bar, and most preferably exactly 1.0 bar.

[0078] The pressure in the zone 7' is denoted by p1. Accordingly, this pressure is low, since the zone 7' is evacuated very strongly. The pressure in the zone 7" is denoted by p2. This pressure is higher than the pressure p1, since the zone 7" is evacuated less strongly.

[0079] In general, the pressures p1, p2 are always below the ambient pressure p0. In very special embodiments, it is conceivable that at least one of these pressures is above the ambient pressure p0. In this case, the substrate region 13 of the substrate 4 below the zone with a pressure above the ambient pressure p0 would be elevated.

[0080] The bonding wave 6 is still far enough away from the zone 7", so that the pressure difference between the pressure p1 in the zone 7' and the pressure p2 in the zone 7" still does not lead to undesirable distortions between the two substrate regions 13, 13'. However, in this method step, it is already detected, preferably using an optical system, that the bonding wave 6 is moving towards the partition wall 10 and that a significant change in pressure will therefore soon occur, thereby strongly influencing the bonding wave 6 and thereby causing bonding behavior between these substrate regions 13, 13'.

[0081] Of course, the values ​​of the pressures p1, p2 are generally process-dependent and must be determined experimentally and / or by simulation.

[0082] Figure 2b The second state of the sixth method step of the method for influencing a bonding wave is shown, in which the bonding wave 6 has advanced further. In order to ensure that the substrate region 13 of the underlying substrate 4 experiences as gentle a pressure effect as possible when the bonding wave 6 crosses the partition wall 10, the pressure p1 in the zone 7' and the pressure p2 in the zone 7" have now been made equal.

[0083] Of course, according to Figure 2a The first state to Figure 2b The transition to the second state takes place continuously, ie the pressures p1 , p2 are adjusted continuously during the continuous advancement of the bonding wave 6. The goal is to ensure that the substrate regions 13, 13' are bonded to one another without errors or with only minimal errors.

[0084] Of course, the new values ​​of the pressures p1, p2 are generally process-dependent and must be determined experimentally and / or by simulation.

[0085] Figure 2c The third state of the sixth method step of the method for influencing a bonding wave is shown, wherein the bonding wave 6 is located on the partition wall 10. In the prior art, pressures of different strengths would act on the substrate region 13 from the zone 7' and the zone 7", which would lead to a defective bonding between the substrate regions 13 and 13'. By adjusting the holding force or by adjusting the pressures p1, p2 in the zones 7', 7", an optimal bonding process between the substrate regions 13, 13' can be achieved.

[0086] Of course, the values ​​of the pressures p1, p2 are again generally process-dependent and must be determined by experiment and / or simulation. The pressures p1, p2 therefore do not necessarily have to be identical as exemplarily shown in the illustration, but rather these pressures must be set such that the two substrate regions 13, 13' are bonded to one another as optimally as possible. Optimally bonded means that any structures on the substrate surface in the substrate regions 13, 13' are bonded to one another in correct alignment.

[0087] Figure 2d The fourth state of the sixth method step of the method is shown, in which the bonding wave 6 has moved over the partition wall 10. The substrate regions 13, 13' are now located in the new zone 7". In this illustration, the pressure p2 in the zone 7" could exemplarily have been set again to a very low value in order to fix the underlying substrate 4 while the bonding wave 6 advances towards the end of the zone 7". The new values ​​of the pressures p1, p2 generally depend on the process again and must be determined experimentally and / or by simulation.

[0088] exist Figure 2a to Figure 2d The method shown in provides that the fixing element 12 is switched when the bonding wave 6 crosses the dividing wall 10 of the two zones 7', 7", so that the bonding between the substrate regions 13, 13' and thereby generally between the substrates 4, 4' is carried out in an optimal manner, i.e., the deviations between the structures on the substrates 4, 4' relative to each other are minimized. In the special case of the vacuum substrate sample holder 1, this means that the pressure in the zones 7', 7" is adjusted so that when the bonding wave 6 crosses the dividing wall 10, the substrate regions 13, 13' experience a pressure transition that is as continuous and smooth as possible, i.e., the pressures p1, p2 are as equal as possible or deviate only slightly from each other.

[0089] Reference numerals list

[0090] 1 Substrate holder

[0091] 2 Matrix

[0092] 3 Fixing parts

[0093] 4.4' substrate

[0094] 5 Deformation elements

[0095] 6 Bonding Wave

[0096] 7, 7', 7" Zone, Inner Zone, Outer Zone, Additional Zone

[0097] 8 Sensors

[0098] 9 Boss

[0099] 10. Partition elements, partition walls

[0100] 11 Depression

[0101] 12 Fixing elements

[0102] 13, 13' substrate area

[0103] Q Cross-sectional area

[0104] p0 atmospheric pressure

[0105] p1, p2: Pressure in the upstream zone / inner zone, pressure in the downstream zone / outer zone

Claims

1. A method for influencing a bonding wave (6) when bonding a first substrate (4) to a second substrate (4'), -in, At least the first substrate (4) is fixed on a first substrate holder (1) having at least one zone (7', 7"), and the at least one zone (7', 7") each has at least one separating element (10) which at least partially forms the surface of the substrate holder, and wherein the at least one separating element (10) separates the at least one zone (7', 7") from further zones (7, 7') of the first substrate holder (1) or from the surroundings, and - wherein the at least one zone (7', 7") has at least one fixing element (12) and the at least one fixing element (12) provides a fixing force for fixing the first substrate (4) on the first substrate holder (1), The method is characterized in that the method comprises at least the following steps: i) initiating a bonding wave (6) by bringing the second substrate (4') into contact with the first substrate (4); and then ii) adapting the holding force of the at least one fixing element (12) of the at least one zone (7', 7") a) the holding force of a fixing element of a further zone (7, 7') which is located immediately upstream of the at least one zone in the direction of propagation of the bonding wave (6), or b) The ambient pressure of the surrounding environment.

2. The method according to at least one of the preceding claims, wherein: During the adaptation in step ii), the ambient pressure is additionally adapted to the holding force of the fixing element (10) of the at least one zone (7") .

3. The method according to claim 1, wherein: In step ii), the adaptation is carried out in such a way that the holding force is of equal magnitude in the direction of propagation of the bonding wave (6) immediately before and after the at least one separating element (10).

4. The method according to at least one of the preceding claims, wherein: After the bonding wave (6) is initiated in step i), the position of the bonding wave (6) is continuously determined, and the holding force of the at least one zone (7', 7") is adjusted so that when the bonding wave (6) crosses the at least one partition element (10), the holding force is the same in front of and behind the at least one partition element (10).

5. The method according to at least one of the preceding claims, wherein: The at least one fixing element (12) of the at least one zone (7', 7") is respectively designed as a vacuum fixing, and the at least one separating element (10) separates the at least one zone (7', 7") from the further zone (7, 7') or the surrounding fluid.

6. The method according to at least one of the preceding claims, wherein: Said adaptation in step ii) is performed by flooding or evacuating said at least one zone (7', 7") or said surroundings.

7. The method according to at least one of the preceding claims, wherein: The adaptation in step ii) comprises determining a pressure difference between the at least one zone (7', 7") and the further zone (7, 7') or the surroundings, wherein the pressure difference is compensated by the adaptation.

8. The method according to at least one of the preceding claims, wherein: The pressure (p2) of the at least one zone (7") is made equal to the pressure (p1) of the further zone (7').

9. A device for influencing a bonding wave (6) when bonding a first substrate (4) to a second substrate (4'), the device comprising at least: - a first substrate holder (1) having at least one zone (7', 7") for holding said first substrate (4), wherein: The at least one zone (7) has at least one separating element (10) which at least partially forms a substrate holder surface of the first substrate holder (1); and at least one fixing element (12) arranged in the at least one zone (7), the fixing element having a holding force for fixing the first substrate (4) on the first substrate holder (1); - a control unit for adjusting the holding force of the at least one fixing element (12) of the at least one zone (7), It is characterized in that The control unit is configured to adapt the holding force of the at least one fixing element (12) of the at least one zone (7', 7") during the advancement of the bonding wave. a) the holding force of a fixing element (12) of a further zone (7, 7') located immediately upstream of the at least one zone in the direction of propagation of the bonding wave (6), or b) Environmental pressure.

10. The device according to claim 1, further comprising means for adapting the ambient pressure to the holding force of the at least one zone (7', 7").

11. The device according to at least one of the preceding claims, wherein The control unit is configured to maintain the holding force of at least one fixing element (12) of at least one zone (7', 7") at the same level as the holding force of at least one further fixing element (12) of a further zone during bonding of the first substrate (4) to the second substrate (4').

12. The device according to at least one of the preceding claims, wherein: The control unit is configured to maintain the holding force of the at least one fixing element (12) of the at least one zone (7', 7") at the same level as the holding force of the at least one fixing element (12) of the other zone (7, 7') directly in the region of the at least one separating element (10) and during the time period during which the bonding wave (6) passes over the at least one separating element (10).

13. The device according to at least one of the preceding claims, wherein: The at least one fixing element (12) of the further zone (7, 7') and the at least one fixing element (12) of the at least one zone (7', 7") are designed as vacuum fixings, and the separation element (10) fluidically separates the inner zone (7') and the outer zone (7") from each other.

14. The device according to at least one of the preceding claims, wherein The control unit is designed to keep the pressure difference between the pressure (p1) of the further zone (7, 7') and the pressure (p2) of the at least one zone (7', 7") as small as possible, preferably the same, during the bonding.

15. The device according to at least one of the preceding claims, wherein The control unit is configured such that the means for adjusting the ambient pressure equalizes the ambient pressure with the pressure (p2) of the at least one zone (7") immediately before and after the bonding wave (6) passes over the at least one separation element (10).

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