Method for separating a first substrate layer, device for carrying out such separating, and substrate comprising a first substrate layer

Abstract

The invention relates to a method for separating a first substrate layer (1) along at least one separating line, comprising: – providing the first substrate layer (1), and – separating the first substrate layer (1) along the separating line produced by irradiating the first substrate layer (1) by means of laser light (2), characterized in that in order to form the separating line, a power of the laser light (2) is set in such a way that the power of the laser light (2) assumes a value above a critical power value for forming self-focusing of the laser light (2) in the first substrate layer (1).

Description

[0001] Method for separating a first substrate layer, device for carrying out such a separation and substrate with a first substrate layer

[0002] The present invention relates to a method for separating a first substrate layer, a device for carrying out such a separation and a substrate with a first substrate layer.

[0003] There are several prior art processes for specifically separating substrates along a plane. One of the most important and best-known processes is the SmartCut® process. In the SmartCut® process, atoms, particularly hydrogen atoms, are implanted into a substrate. In a first process step, the atoms are ionized and accelerated onto the substrate using an electric field. The kinetic energy of the ions is sufficient to penetrate the substrate. The acceleration voltage allows the penetration depth to be adjusted very precisely. In a second process step, the substrate thus processed is bonded to another substrate. It is also conceivable to form an oxide layer on the substrate before the bonding process. In a third process step, the substrate is heated. As the substrate is heated, the hydrogen atoms recombine to form hydrogen molecules.The hydrogen atoms are not directly incorporated into the crystal lattice of the substrate, so the substrate is merely hydrogenated. The hydrogen molecules, however, form a gas. The phase transition from atomic hydrogen to hydrogen gas causes a volume expansion, which leads to a fracture of the structure along the implantation plane. This process allows very thin layers to be transferred from one substrate to another. Even more importantly, however, it enables the production of a substrate stack with a very thin crystalline layer on its upper surface, beneath which lies an oxide layer. Such substrate stacks are referred to as silicon-on-insulator (SOI).

[0004] Other substrate separation methods include chemical and / or mechanical aids. Some methods use a laser beam to pre-damage a plane in the substrate, but this damage is not sufficient to fracture the substrate along that plane. The substrate must then be etched with chemicals. The chemicals then react with the atoms along the plane in which the pre-damage was applied, etching the substrate along that plane. This process is time-consuming. Mechanical aids such as blades or wires can be used to fracture the substrate along the pre-damaged plane. The use of mechanical release agents speeds up the process but can lead to unintentional fracture of the substrate outside the plane along which fracture should occur.

[0005] US Pat. No. 7,052,978 B2 describes laser-induced damage to a substrate. The laser causes damage within the substrate through various effects. However, laser focusing is not disclosed.

[0006] All prior art processes have the disadvantage that an additional component is required to create the desired separation effect or that controlling the fracture process is either impossible or very difficult. In the SmartCut® process, for example, atoms must be implanted into the substrate. In a chemical etching process, chemicals must be made available. In a mechanical separation process, only mechanical separation agents such as a blade or wire would be required, but experience has shown that these only allow the separation of comparatively thick layers from a substrate. They are not suitable for separating thin layers from the substrate, especially not for separating layers with thicknesses in the micrometer or nanometer range. In addition, controlling the fracture along the desired plane is difficult or even impossible using mechanical separation agents.In processes in which a laser beam is fired into the substrate, optics are used to focus the laser beam.

[0007] Based on this, the present invention seeks to provide a method that simplifies the separation of substrates, in particular by eliminating the described disadvantages, and is particularly suitable for providing the thinnest possible substrate sublayers after separating a substrate layer. The present invention achieves this object with the separation method according to claim 1, with a separation device according to claim 13, and with a substrate according to claim 15. Further preferred embodiments of the invention will become apparent from the following description and from the drawings.

[0008] According to a first aspect of the present invention, a method for separating a first substrate layer along at least one separating line is provided, comprising:

[0009] - Providing the first substrate layer, and

[0010] - separating the first substrate layer along the separating line which is produced by irradiating the first substrate layer with laser light, wherein, to form the separating line, a power of the laser light is adjusted such that the power of the laser light assumes a value above a critical power value for forming self-focusing of the laser light in the first substrate layer.

[0011] In contrast to the prior art, the invention provides that the power of the laser light used is adjusted such that the phenomenon of self-focusing of the laser light occurs in the first substrate layer to be treated, in particular in the first substrate layer to be separated. This phenomenon of self-focusing is based on the Kerr effect and occurs particularly when a spatially profiled intensity profile of the laser light with a sufficiently high intensity amplitude interacts with the material of the first substrate layer. Non-linear effects occur here. In an alternative embodiment, the phenomenon of self-focusing is based on non-linear absorption.Since refractive index properties depend on light intensity, a sufficiently high light intensity can result in a refractive index profile in the material that causes the light to be focused in a plane within the first substrate layer due to the changes in the refractive index profile initiated by the light itself. This defines or determines a sub-area or sub-section of the subsequent dividing line or dividing plane at the focal point or focus established by the self-focusing.

[0012] The occurrence of the "self-focusing" phenomenon depends on material and laser properties. Depending on the selected material, different critical powers or pulse energies arise, above which self-focusing occurs. Based on experimental findings and / or simulations, it is possible to define, estimate, or determine a critical power value for the laser type or laser light used on the one hand, and the material used in the first substrate layer on the other. The effect is based on the fact that the refractive index of a material, especially for high intensities, depends linearly on the intensity. If a laser beam with an inhomogeneous, particularly Gaussian, intensity cross-section is fired into a transparent material, then polarization in the part of the laser beam near the center leads to a different phase shift than in surrounding parts.It can be proven mathematically and physically that this circumstance leads to self-focusing of the laser beam, ie photons of the laser beam are focused on a point in a focal plane in the first substrate layer, even if the laser beam was not focused when entering the material.

[0013] In particular, self-focusing establishes or creates a focus or focal point in the area through which the dividing line is to run. In particular, the dividing line is to be understood as a two-dimensional dividing plane. By appropriately moving or shifting the first substrate layer relative to the laser light or the beam path of the laser light, the dividing line, which then forms the dividing plane, is formed over a large area.

[0014] Self-focusing advantageously makes it possible to induce such high intensities within the first substrate layer that these high light intensities in turn lead to physical and / or chemical modification within a plane or within a point in which the self-focusing occurs. This modification in the material properties then leads to the formation of the separating line or plane, for example a predetermined breaking point or even to independent separation along the separating line or plane. Advantageously, the use of extensive etching agents or complex optical systems or the injection of ions into the first substrate layer can be dispensed with or their extent can be significantly reduced. This at least makes it possible to further reduce the effort required for the actual breaking or separation of the first substrate layer, thereby improving the separation of the first substrate layer.

[0015] Another particularly advantageous feature is that only the power of the laser light needs to be adjusted to achieve self-focusing. Even though a large number of parameters must be taken into account to determine the critical power, it is sufficient to increase the power of the laser light in order to initiate self-focusing and, in particular, to determine the position of the self-focusing. This provides a comparatively simple way of determining or influencing the location of the interaction between the material of the first substrate layer and the laser light. In particular, it is possible to react relatively quickly to a change of material, for example if the first substrate layers to be treated are swapped or the position of the dividing line is changed. No extensive adaptation of the system is required to carry out the process.

[0016] In particular, it is provided that the first substrate layer is part of a substrate composite or is to become part of a substrate composite with the first substrate layer and a second substrate layer. For example, the first substrate layer is a wafer or part of a wafer and / or a bonding layer that, for example, connects two other wafer substrate layers to one another. Preferably, the first substrate layer and / or a second substrate layer comprise materials such as silicon or germanium. The first substrate layer preferably has a thickness between 1 nm and 5 mm, preferably between 1 nm and 1 pm, and particularly preferably between 1 nm and 3,000 nm.

[0017] Using a Czochralski process, for example, an ingot can be drawn from a silicon melt. The described process is also suitable for separating sub-layers of substrates from this ingot, so that the separated sub-layer can then form its own substrate. The sub-layers of substrate, which are then further processed as independent substrates, would in this case have thicknesses in the millimeter range. In particular, separation occurs before the first substrate layer is bonded to the second substrate layer.

[0018] Substrate sublayers with thicknesses in the micrometer or nanometer range arise primarily from processes in which layer transfer is to take place. In this case, the first substrate layer to be separated is first bonded to a second substrate layer and only then is the process for separating the first substrate layer used. In particular, separation takes place after the first substrate layer has been bonded to the second substrate layer. The surface of the first substrate layer preferably has a roughness between 0.01 and 300 nm, more preferably between 0.01 and 30 nm, and particularly preferably between 0.01 and 10 nm. The scattering of the laser beam coupled into the first substrate layer is lower, the lower the roughness of the substrate layer surface. Low surface roughnesses on the substrate layer surfaces are therefore preferred.

[0019] In a preferred embodiment of the method, the laser beams have a wavelength between 0.1 pm and 500 pm, preferably between 0.2 pm and 100 pm, particularly preferably between 0.3 pm and 50 pm, particularly preferably between 0.5 pm and 10 pm, or even between 1 pm and 2.5 pm. In this way, the separating layer can be irradiated particularly efficiently and precisely.

[0020] In a preferred embodiment of the method, it is provided that the laser has a power that is between 1 W and 1000 W, preferably between 5 W and 800 W, more preferably between 7 W and 600 W, most preferably between 10 W and 500 W, most preferably between 20 W and 200 W.

[0021] In a preferred embodiment of the method, the laser area is smaller than 2000 pm 2 , preferably less than 500 pm 2 , preferably less than 80 pm 2and especially preferably less than 20 pm 2 , or even less than 1 pm 2 The area of ​​the separating layer or separating line on which the laser beam acts is advantageously small and targeted in order to locally reduce or destroy the adhesive properties of the separating layer.

[0022] In a preferred embodiment of the method, the separation layer is separated by at least 0.1 pm, preferably at least 1 pm, more preferably at least 5 pm, particularly preferably at least 10 pm, or even at least 50 pm, between the areas of action of the laser beams, so that the areas of action of the laser beams do not overlap. This enables particularly simple and efficient separation.

[0023] Preferably, ultrashort laser pulses are used as laser light, preferably ns (nanosecond) pulses, preferably ps (picosecond) pulses, and particularly preferably fs (femtosecond) pulses or even attoseconds (attosecond) pulses. The duration of the light pulses is thus preferably less than 10'. 9 s, preferably less than 10' 11 s, preferably less than 10' 13 s, preferably less than 10' 15 s or even less than 10' 16 see

[0024] With correspondingly short pulse durations, it is advantageously possible to easily generate the laser power or light intensities required for self-focusing. Such pulses generally require the use of special optics, such as refractive, reflective and / or grating-type optical components. It is preferable to avoid the high-intensity laser light passing through material as far as possible. Such propagation through a medium can otherwise lead to modifications in the pulse shape and / or a reduction in intensity. However, it is conceivable to use beam expansion, whereby the overall intensity is initially reduced across the spatial profile of the laser pulse, in order to refocus the laser beam, preferably immediately before it enters the first substrate layer, and to cancel out the expansion. This makes it possible, for example, toModulating or influencing the intensity profile at low intensity in order to achieve the best possible self-focusing in the first substrate layer. In principle, the spatial intensity profile of the laser beam can also be influenced using simple apertures or other optical components. The intensity profile is preferably generated using refraction optics. The use of apertures, field mappers, lens arrays, integrators, beam homogenizers, and / or axicons is also conceivable.

[0025] The laser light is preferably provided with a spatial profile, in particular a Gaussian, a Lorenzian, or a Cauchy-shaped intensity profile. A corresponding intensity profile proves to be particularly advantageous because it is particularly suitable for the refractive index profiling that leads to self-focusing by means of the Kerr effect. It is preferably also conceivable that a corresponding spatial intensity profile is specifically realized using appropriate optical components, for example if the intensity profile provided by a laser source deviates from a preferred intensity profile. Finally, to generate the Kerr effect, it is preferably provided to generate an intensity profile of the laser radiation that is non-homogeneous in cross-section. Preferably, an intensity profile with a Gaussian, Lorentzian, and / or Cauchy-shaped geometry is generated.Preferably, the separating line extends along a plane running essentially parallel to the main extension plane. This advantageously makes it possible to separate the first substrate layer along a plane running essentially parallel to its own main extension plane. Separating along the separating line, which runs essentially parallel to the main extension plane, is particularly advantageous when comparatively thin substrate sublayers are to be produced. In particular, the separation leads to the separation of a primary substrate sublayer and a secondary substrate sublayer, which arise from the first substrate layer as a result of the separation. For example, coatings can be reduced to a desired dimension.

[0026] Alternatively, it is conceivable that the dividing line runs substantially perpendicular to the main extension plane and thus enables separation, i.e. dicing, into individual sections of the first substrate layer, which are arranged adjacent to one another in the main extension plane, in particular before separation.

[0027] Preferably, the first substrate layer is connected to a second substrate layer during irradiation. In particular, the first substrate layer and the second substrate layer are connected to one another in a materially bonded, positively bonded, and / or non-positively bonded manner, and the second substrate layer faces the incident laser light. In other words, the laser light first propagates through the second substrate layer before entering the first substrate layer and creating a dividing line or a partial section of the dividing line there due to the self-focusing that occurs. In particular, the laser light passes through the second substrate layer, and the focus is formed by self-focusing in the first substrate layer after passing through the second substrate layer.When adjusting the laser light power, particular care is taken to ensure that partial focusing preferably already takes place in the second substrate layer and the desired final focusing is realized in the first substrate layer.

[0028] The depth of the focal plane can be adjusted by the laser parameters, particularly the wavelength of the laser used. The closer the focal plane should be to the substrate layer surface, the shorter the wavelength of the laser radiation should be. In the laboratory, neodymium-YAG lasers with a wavelength of 1064 nm have proven effective for near-surface processing. With wavelengths around 1550 nm, depths of several hundred pm can be achieved.

[0029] Measurements have shown that with a wavelength of 1950 pm, a pulse duration of approximately 5 ps, and a spot diameter of approximately 20-30 pm, an energy of approximately 10 pJ per pulse is achieved. This energy is roughly the starting point for damage to silicon.

[0030] In one embodiment, the laser beam is positioned perpendicular to the first substrate layer, and the first substrate layer actively moves relative to the entire optical structure, i.e., the laser beam. For this embodiment, the first substrate layer must be fixed to a substrate holder that can move as quickly as possible. The substrate holder should nevertheless have the highest possible resolution of the process axes to enable precise positioning of the laser beam.

[0031] In another embodiment, the optical structure, in particular the laser beam, can actively move relative to the first substrate layer. A laser light alignment device is preferably used for this purpose.

[0032] In a further preferred embodiment, special optical elements, in particular in the form of a galvanometric scanner, are used as laser light alignment devices in order to scan the laser beam over the first substrate layer and thus form a flat separating layer running along a main extension plane. The laser light alignment device preferably comprises a telecentric lens, preferably a telecentric lens with a telecentric beam path on both sides. The laser beam is guided by the laser light alignment device through one or more lenses, which refract the laser beam in such a way that the laser beam always strikes the first substrate layer and / or the second substrate layer normally. The lens used is usually smaller than the first substrate layer to be scanned. The first substrate layer must therefore be scanned in a step-by-step process.The laser beam can be moved relative to the optical setup (step-and-repeat). The process is then repeated at several points until the entire first substrate layer to be scanned has been irradiated. It is conceivable to change the laser parameters, particularly the laser power, so that the position of the focal plane can be changed.

[0033] Preferably, the first substrate layer is connected to a third substrate layer, the first substrate layer, the second substrate layer, and the third substrate layer being arranged one above the other in a stacking direction running perpendicular to the main extension plane, and the first substrate layer being the bonding layer between the second substrate layer and the third substrate layer. The corresponding self-focusing into the first substrate layer formed as a bonding layer advantageously makes it possible to separate an existing or manufactured substrate composite. Thus, the method described here also makes it possible to debond in order to separate certain substrate layers, for example the second substrate layer and the third substrate layer, from one another.

[0034] To separate the second substrate layer from the third substrate layer, which are connected to one another via the first substrate layer, or to separate the first substrate layer, additional devices, in particular corresponding substrate holders with corresponding fixing means, can be used. For example, a first substrate holder and a second substrate holder are provided, which lie opposite one another, while the first substrate layer to be separated is arranged between the first substrate holder and the second substrate holder. A first device, in particular the first substrate holder, is located on a side facing the second substrate layer. A second device, in particular a second substrate holder, is located on a side facing the third substrate layer. The devices fix the substrates or the substrate layers with corresponding fixing means, in particular with a vacuum fixation and / or a clamping means.By moving the two devices away from each other relative to each other, the two substrate layers, i.e., the second and third substrate layers, can be separated from each other and simultaneously fixed to the devices, i.e., the first and second substrate holders. The same applies to a device that is fixed directly to the upper side of the first substrate layer to be separated.

[0035] To overcome the last remaining attraction between the substrate layers separated by means of the method, forces of between 1 N and 100 kN, preferably between 1 N and 10 kN, more preferably between 1 N and 1 kN, particularly preferably between 1 N and 100 N or even between 1 N and 10 N are applied. The parting plane or parting line has a thickness of between 1 nm and 10 pm, preferably between 1 nm and 1 pm, preferably between 1 nm and 100 nm and particularly preferably between 1 nm and 10 nm. If volume defects are created in the parting plane or parting line, in particular holes, local melting and / or similar, then the size of these volume defects is between 1 nm and 10 pm, preferably between 1 nm and 1 pm, preferably between 1 nm and 100 nm and particularly preferably between 1 nm and 10 nm.

[0036] It is preferably provided that a lens is used to pre-focus the laser light before it enters the first substrate layer. This advantageously allows the light output of the laser beam to be controlled upon entering the first substrate layer and, for example, adapted to the material properties of the first substrate layer. The use of a concave mirror for focusing is also conceivable; this advantageously enables both focusing and deflection of the laser beam, which can advantageously ensure space-saving installation of the device. Finally, a straight path for the laser beam is not required.

[0037] Alternatively, it is conceivable that no lens is arranged between the laser source and the first substrate layer, i.e. a beam path of the laser light is free of lenses and / or concave mirrors.

[0038] Preferably, the separation is assisted by the application of mechanical force, further laser light irradiation, the introduction of ions, atoms and / or molecules, a chemical effect and / or the introduction of heat. In other words: the creation of the separation line is not entirely sufficient to cause the separation of the first substrate layer; rather, a type of predetermined breaking plane or line is created as the separation line, which is ultimately broken by the addition of a further influence, such as the application of force, further light exposure and / or chemical exposure, in order to cause separation within the first substrate layer. For example, it is conceivable that corresponding suction devices adhere to the top and / or bottom of the first substrate layer and that corresponding tensile and / or shear forces cause a mechanical effect on the first substrate layer.If a force is necessary for separation, the force is less than 1000 N, preferably less than 500 N, more preferably less than 100 N, most preferably less than 10 N, most preferably less than 1 N.

[0039] In an exemplary embodiment, the laser beam is directed at at least one point of a focal plane to melt the material through a high energy density or even directly sublimate it. If the material is melted, a separation process, such as additional mechanical action, should preferably be carried out while the material is still in the molten state. Finally, the melting range is comparatively small due to the highly focused introduction of energy by the laser beam, and the heat stored in the melt is very quickly released back into the environment via the substrate, so very rapid cooling can be expected, especially before the actual separation process.

[0040] The structure of the solidified melt areas could still exhibit a lower fracture strength than the original structure and thus serve as a predetermined breaking point. If the material is sublimated, it can only rarely resublimate to such an extent that a new bond is created between the substrate halves of the first substrate layer that are to be separated. Although the material will still be in the boundary region, it is technically considered to have been removed.

[0041] In another exemplary embodiment, the high intensity of the laser beam creates a chemical reaction in material within the focal plane, which subsequently leads to fracture.

[0042] It is preferably provided that, in particular in a preparatory process step, ions are introduced into the first substrate layer, in particular into the region of the later parting line, in particular by accelerating them and shooting them into the first substrate layer. The focal plane is then created in the regions with ions by self-focusing. For example, the known SmartCut® process could be expanded such that the entire substrate stack no longer needs to be heated, but that the effect of self-focusing allows the heat to be introduced by the laser in such a targeted manner that the hydrogen atoms recombine to form hydrogen molecules along the focal plane and thus lead to the fracture of the structure according to the SmartCut® process. It is preferably provided that ions are admitted in an implementation plane.The distance between the implementation plane and the focal plane is less than 1 mm, preferably less than 100 pm, more preferably less than 1 pm, particularly preferably less than 100 nm, or even less than 10 nm. Furthermore, it is conceivable that the first substrate layer is connected to the implementation plane via at least one coating with a second substrate layer before the first substrate layer is separated by supplying heat in the region of the implementation plane by means of self-focusing. Processing with the self-focusing light creates a physical or chemical effect that leads to a recombination of the atoms or molecules implanted in the implantation plane. In particular, when implanted hydrogen ions are used, the hydrogen atoms recombine to form hydrogen molecules. The hydrogen molecules have a higher molar volume.The resulting hydrogen gas expands and causes damage along the implantation plane. By connecting the second substrate layer via the at least one coating, it is advantageously possible to provide an overall substrate with the second substrate layer, which is provided with a comparatively thin substrate sublayer that remains after separation and is bonded to the second substrate layer via the coating. This allows, for example, the formation of a silicon-on-insulator (SOI) substrate.

[0043] It is also conceivable that other atoms are present in the structure which, upon thermal stress, recombine to form their corresponding molecular gases, producing an effect similar to the SmartCut® process. It would also be conceivable for halides, particularly fluorine, chlorine, bromine, or iodine, to be ionized and injected into the substrate. It would also be conceivable to use nitrogen or oxygen atoms which recombine to form their corresponding molecular gases. The invention extends the SmartCut® process in such a way that the entire substrate stack is no longer subjected to thermal treatment, which can have a gentle effect on existing functional units, particularly microchips, memory chips, MEMS, LEDs, etc. Preferably, the introduction of ions, atoms, and / or molecules takes place before the dividing line forms, resulting in self-focusing.

[0044] In another exemplary embodiment, atoms and / or molecules with a high absorption for the laser radiation used are implanted into the substrate and / or layer to be destroyed. As a result, the photons of the laser radiation are preferentially absorbed by the implanted atoms and / or molecules, resulting in very strong thermal movement and thus damage to the surrounding structure.

[0045] Preferably, the method is used to produce a substrate layer composite, for example comprising a first substrate layer and a second substrate layer, wherein, after separation, a first thickness of the first substrate layer is less than a second thickness of the second substrate layer. The first thickness and second thickness are measured along a stacking direction running perpendicular to the main extension plane. This advantageously makes it possible to reduce coatings of substrate layers to a desired, in particular comparatively small, layer thickness. This makes it possible, for example, to realize layer thicknesses whose value is less than 1000 nm, preferably less than 500 nm, particularly preferably less than 100 nm.

[0046] Preferably, the first substrate layer comprises a ceramic material, a polymer material, silicon, and / or germanium. Depending on the materials selected for the first substrate layer, the second substrate layer, and / or the third substrate layer, the laser light power is adjusted accordingly to achieve the desired self-focusing effect.

[0047] It is preferably provided that during irradiation the first substrate layer is moved along a direction predetermined by a planned course of the separating line within the first substrate layer. In other words: While the laser beam is stationary and in particular is not offset or shifted by pivoting mirrors, a movement takes place to create the separating line by moving the first substrate layer relative to the laser source and in particular relative to the stationary laser beam. This advantageously ensures that the laser light strikes every point as perpendicularly as possible in order to prevent the separating line from becoming uneven due to changing alignment. Furthermore, it is advantageously possible to prevent laser light from being reflected to the side by the irradiated substrate.Instead, with appropriate constancy regarding the surface orientation of the first substrate layer, the reflected light can be limited to a defined spatial volume. Preferably, the separation is brought about solely by irradiation with laser light. In other words: in a particularly preferred embodiment, the breaking is already initiated by self-focusing. This provides a particularly simple method to carry out, since no further additional work steps are required to cause breaking. In an exemplary embodiment, the laser beam is directed at at least one point of a focal plane in order to create a direct break in the chemical bond there. In particular, covalent bonds in a ceramic or polymer material can be directly broken.The energy density of the self-focused laser beam is so high that the electrons that create the covalent bond are removed from the molecular orbital.

[0048] A further subject matter of the present invention is a device for carrying out the method according to the invention, using a laser source suitable for providing laser light outputs that achieve self-focusing in a first substrate layer. All of the advantages and features described for the method can be analogously transferred to the device. In particular, it proves advantageous to use an ultrashort pulse laser source, since the desired intensities can be achieved comparatively easily with the laser pulses provided here. Furthermore, it is conceivable for the source to provide a control device for adjusting the laser power, whereby the laser power can advantageously be set to the desired level in order to initiate self-focusing in specific areas in a controlled manner.

[0049] Preferably, the device comprises a holding element that is movable, in particular in a plane running parallel to the main extension plane of the first substrate layer. This advantageously enables a relative movement of the first substrate layer or the substrate layer composite to occur while the laser beam remains stationary. A further subject matter of the present invention is a substrate comprising at least one first substrate layer, produced using a method according to the invention. All features and properties of the method can be analogously transferred to the device. Further advantages, features, and details of the invention will become apparent from the following description of preferred exemplary embodiments and from the drawings.

[0050] They show in:

[0051] Fig. 1 is a schematic representation of a method according to a first preferred embodiment of the present invention,

[0052] Fig. 2 is a schematic representation of a method according to a second preferred embodiment of the present invention,

[0053] Fig. 3 is a schematic representation of a method according to a third preferred embodiment of the present invention,

[0054] Fig. 4a is a schematic representation of a first method step of a method according to a fourth preferred embodiment of the present invention,

[0055] Fig. 4b is a schematic representation of a second method step of a method according to the fourth preferred embodiment of the present invention,

[0056] Fig. 4c is a schematic representation of a third method step of a method according to the fourth preferred embodiment of the present invention,

[0057] Fig. 4d is a schematic representation of a fourth method step of a method according to the fourth preferred embodiment of the present invention and

[0058] Fig. 4e is a schematic representation of a fifth method step of a method according to the fourth preferred embodiment of the present invention. In the figures, identical components or components with the same function are identified by the same reference numerals. The figures are not to scale. To increase clarity, a laser beam 2 provided for the method is shown wider. In particular, the laser beam 2 is symbolically drawn as a beam, although high-energy laser light pulses are preferably generated and directed onto a first substrate layer 2 and / or a second substrate layer 4. Self-focusing 2k of the laser beam 2 is represented in simplified form by a convergent beam bundle whose tip ends in a focal plane 3.Preferably, however, a large number of ultrashort laser pulses are directed along the path indicated as laser beam 2 onto the first substrate layer 1 and / or the second substrate layer 4, resulting in self-focusing 2k due to nonlinear effects in the materials of the first substrate layer 1 and / or the second substrate layer 4. Of particular importance is the high intensity at the focal point or focus 2f, which is created in particular by the self-focusing 2k.

[0059] Figure 1 shows a first embodiment of the present invention. The laser beam 2 is directed onto a focal plane 3 of a first substrate layer 1. By knowing the material properties of the substrate 1 in conjunction with the properties of the laser beam 2 used, the focal plane 3 can be determined and fixed. A Kerr effect is preferably utilized to generate a chemical and / or physical (consequential) effect, particularly in the focal plane 3 or its immediate vicinity, which subsequently leads to the possibility of separating a primary substrate sublayer 1o from a second substrate sublayer 1u.

[0060] Figure 2 shows a second exemplary embodiment of the present invention. In addition to the first substrate layer 1, a substrate composite comprises at least one second substrate layer 4. It would also be conceivable to use a plurality of second substrate layers 4, which are in particular stacked, wherein the stack of a plurality of second substrate layers 4 is connected to the first substrate layer 1. The non-linear optical effects which lead to self-focusing of the laser beam 2 already begin in the at least one second substrate layer 4. In the present case, the focal plane 3 lies in the first substrate layer 1. If the focal plane 3 were to lie in the second substrate layer 4, an exemplary embodiment according to Figure 1 would be present. When using a plurality of layers 4, the focal plane 3 can also lie within one of the plurality of second substrate layers and does not have to end in the substrate 1.It is therefore preferably provided to use at least one second substrate layer 4 and thus at least one further material in order to start the self-focusing of the laser beam 2 before the first substrate layer 1 and / or before the second substrate layer 4, which is actually to be separated.

[0061] Figure 3 shows a third embodiment of the present invention. In this embodiment, the self-focusing of the laser beam 2 is utilized to place the focal plane 3 in a first substrate layer 1 serving as a bonding layer, the purpose of which is to bond the second substrate layer 4 and the third substrate layer 5 together. Thus, the invention can also be used, in particular, for debonding two substrate layers of a substrate composite.

[0062] Figure 4a shows a first step of a method in which a preferably ionized atom or molecule beam 6 is fired into a first substrate layer 1. Preferably, ionized hydrogen atoms are fired into the substrate layer 1. The kinetic energy of the atoms or molecules in the atom or molecule beam 6 can be used to determine an average penetration depth of the atoms or molecules in the first substrate layer 1. An implantation plane 8 is the plane in which the atoms or molecules accumulate on average.

[0063] Figure 4b shows a second method step of a method in which a coating 7 is applied to the substrate surface, via which the atoms or molecules of the atomic or molecular beam 6 have been introduced. The coating 7 is in particular a thermal, preferably a native, oxide. The thickness of the coating 7 can be reduced by grinding back, thinning back, and / or etching back. This method step is not shown additionally. After the application of the coating 7, it is optionally possible to produce a hybrid bond surface. For this purpose, holes are created in the coating 7 through several method steps (not shown or described), which preferably even extend into the substrate layer 1. The holes are then filled with an electrical medium, preferably copper, through a coating process. The excess copper is then ground back down to the coating 7.The metal in the holes subsequently serves as an electrical contact. This process creates a hybrid surface consisting of electrically conductive copper contacts surrounded by the dielectric material of coating 7. Such hybrid surfaces are familiar to those skilled in the art. To ensure clarity in the drawing, a precise depiction of such hybrid surfaces has been omitted.

[0064] Figure 4c shows a third method step of a method in which the first substrate layer 1 is bonded via the coating 7 to a second, likewise coated, particularly preferably identically coated, substrate layer 4, for example without an implementation layer 8. The bond is preferably a fusion or direct bond. If the substrate layer 1 and the substrate layer 4 both have a hybrid bond surface, the contacts of both hybrid bond surfaces are aligned as precisely as possible with each other in this method step. Before the bonding takes place, functional units such as microchips, MEMS, LEDs, memory modules, etc. already exist in the substrate layer 4, which are thus electrically connected to the first substrate layer 1 via the contacts of the hybrid bond surface (not shown).

[0065] Figure 4d shows a fourth method step of the method, in which the separation method according to a further exemplary embodiment is applied. The focal plane 3 of the laser beam 2 approximately coincides with the implantation plane 8. An average difference between the focal plane 3 and the implantation plane 8 is less than 1 mm, preferably less than 100 pm, more preferably less than 1 pm, particularly preferably less than 100 nm, or even less than 10 nm. Due to the effect of the self-focusing of the laser beam 2 in the focal plane 3, and thus in the implantation plane 8, a very high temperature is generated along the implantation plane 8, which results in a physical and / or chemical effect on the implanted atoms or molecules. The physical or chemical effect is preferably a recombination of the atoms or molecules implanted in the implantation plane 8.Particularly when implanted hydrogen ions are used, the hydrogen atoms recombine to form hydrogen molecules. The hydrogen molecules have a higher molar volume. The resulting hydrogen gas expands and causes damage along the implantation plane 8. This effect is known from the SmartCut™ process and is now improved by the separation with the self-focusing laser light in such a way that the entire substrate stack does not have to be heat-treated in a furnace, but rather the heat treatment is carried out very precisely, locally along the implantation plane 8. The method according to the invention thus significantly expands the SmartCut™ process known from the prior art.Any other type of atom or molecule which, when exposed to the laser beam 2 according to the invention, results in a physical and / or chemical effect which causes damage along the implantation plane 8 can also be used.

[0066] Figure 4e shows a fifth process step of a process in which the primary substrate sublayer 1o (see Figure 4d) has been removed from the first substrate layer 1. Only the secondary substrate sublayer 1u remains as a very thin layer on a coating 7, in particular an oxide layer. If the material of the secondary substrate sublayer 1u is silicon, the resulting substrate is called a silicon-on-insulator (SOI) substrate. If the coating 7 was a hybrid bond surface, the copper contacts are now preferably exposed at the top. If functional units such as microchips, MEMS, LEDs, memory modules, etc. are now also produced in the secondary substrate sublayer 1u, these are automatically connected to the functional units of substrate layer 4 (not shown).

[0067] In an alternative embodiment, the described method is performed without a coating 7, but rather the first substrate layer 1 is bonded directly to the second substrate layer 4. This method is also a direct bond. The goal of this method is the direct connection of two materials, for example, two different semiconductor materials.

[0068] For all embodiments described here, the focal plane 3 can be determined by knowing the material properties of the first substrate layer 1 in conjunction with the properties of the laser used. The Kerr effect is preferably used to generate a chemical and / or physical effect, particularly in the focal plane 3 or its immediate vicinity, which subsequently leads to the possibility of separating the primary substrate sublayer 1o from the secondary substrate sublayer 1u.

[0069] List of reference symbols

[0070] 1 first substrate layer

[0071] 1o primary substrate layer

[0072] 1 u secondary substrate layer 2 laser beam / laser light

[0073] 2k self-focusing effect

[0074] 2f focal point

[0075] 3 Focal plane 4 Second substrate layer

[0076] 5 third substrate layer

[0077] 6 Atomic or molecular beam

[0078] 7 Coating

[0079] 8 implantation level

Claims

Claims Method for separating a first substrate layer (1) along at least one separating line, comprising: - providing the first substrate layer (1), and - separating the first substrate layer (1) along the separating line, which is generated by irradiating the first substrate layer (1) with laser light (2), characterized in that, to form the separating line, a power of the laser light (2) is adjusted such that the power of the laser light (2) assumes a value above a critical power value for forming self-focusing of the laser light (2) in the first substrate layer (1). Method according to claim 1, wherein ultrashort laser pulses are used as laser light (2), preferably ns pulses, preferably ps pulses and particularly fs pulses or even as pulses. Method according to one of the preceding claims, wherein laser light (2) with a spatial profile, in particular Gaussian, Lorenz-shaped and / or Cauchy-shaped profile, is used.Method according to one of the preceding claims, wherein the dividing line extends along a plane running substantially parallel to the main extension plane. Method according to one of the preceding claims, wherein the first substrate layer (1) is connected to a second substrate layer (4) during irradiation, wherein the second substrate layer (4) is preferably passed through by the laser light (2) before the laser light (2) enters the first substrate layer (1) after passing through the second substrate layer (4). Method according to claim 5, wherein the first substrate layer (1) is connected to a third substrate layer, wherein the first substrate layer (1), the second substrate layer (4) and the third substrate layer (5) are connected along a plane running perpendicular to the main extension plane. extending stacking direction are arranged one above the other and the first substrate layer (1) is the bonding layer between the second substrate layer (4) and third substrate layer (5).

7. Method according to one of the preceding claims, wherein a lens and / or a concave mirror is used for prefocusing.

8. Method according to one of the preceding claims, wherein the separation is assisted by a mechanical force, a further laser light irradiation, an introduction of ions, atoms and / or molecules, a chemical action and / or an introduction of heat.

9. Method according to one of the preceding claims, wherein the method is used for producing a substrate layer composite which comprises at least the first substrate layer (1) and the second substrate layer (4), wherein after separation a first thickness (D1) of the first substrate layer (1) is smaller than a second thickness (D2) of the second substrate layer (4).

10. Method according to one of the preceding claims, wherein the first substrate layer (1) comprises a ceramic material, a polymeric material, silicon and / or germanium.

11. Method according to one of the preceding claims, wherein the first substrate layer (1) is moved during irradiation along a direction predetermined by a course of the separating line.

12. Method according to one of the preceding claims, wherein the separation is effected solely by irradiation by means of laser light (2).

13. Device for carrying out the method according to one of the preceding claims, with a laser source which is suitable for providing laser light powers which cause self-focusing in a first substrate layer (1).

14. Device according to one of the preceding claims, wherein the device comprises a holding element which is movable, in particular in a plane parallel to the main extension plane. Substrate comprising at least one primary substrate sublayer (1o) produced by a method according to one of claims 1 to 12, wherein the primary substrate sublayer (1o) results from the separation of the first substrate layer (1).

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