Method for separating a first substrate layer, an apparatus for performing such separation, and a substrate having a first substrate layer - Patent Application 20070122997

Abstract

A method for separating a first substrate layer (1) along at least one separation line, comprising the steps of: preparing the first substrate layer (1); and separating the first substrate layer (1) along separation lines generated by irradiating the first substrate layer (1) with laser light (2), wherein, in order to form the separation lines, the power of the laser light (2) is set so that the power of the laser light (2) has a value that exceeds a critical power value for forming self-focusing of the laser light (2) within the first substrate layer (1).

Description

[Technical Field]

[0001] The present invention relates to a method for separating a first substrate layer, an apparatus for performing such separation, and a substrate having a first substrate layer. [Background technology]

[0002] In the prior art, several methods exist for selectively separating substrates along a plane. One of the most important and best-known methods is the so-called SmartCut® method. In the SmartCut® method, atoms, in particular hydrogen atoms, are implanted into a substrate. In a first method step, the atoms are ionized and accelerated toward the substrate using an electric field. The kinetic energy of the ions is sufficient to penetrate the substrate. The penetration depth can be adjusted very precisely by the acceleration voltage. In a second method step, the substrate thus treated is bonded to another substrate. It is also possible to form an oxide layer on the substrate before the bonding process. In a third method step, the substrate is heated. By heating the substrate, the hydrogen atoms recombine to form hydrogen molecules. Since the hydrogen atoms are not directly incorporated into the crystal lattice of the substrate, the substrate is merely hydrogenated. Meanwhile, the hydrogen molecules form a gas. The phase transition from atomic hydrogen to hydrogen gas causes a volume expansion, which leads to the destruction of the microstructure along the implanted plane. This method allows for the transfer of very thin layers from one substrate to another. But more importantly, it allows for the fabrication of substrate stacks with a very thin crystalline layer on top and an oxide layer underneath. Such substrate stacks are called silicon-on-insulator (SOI).

[0003] Other methods of substrate separation include chemical and / or mechanical means. Some methods use a laser beam to create pre-damage along a plane in the substrate, but this is not sufficient to break the substrate along this plane. The substrate then needs to be etched with a chemical. The chemical then reacts with atoms along the plane where the existing damage was created, etching the substrate along that plane. This method is time-consuming. Mechanical tools such as blades or wires can then be used to break the substrate along the previously damaged plane. Using mechanical means of separation can speed up the process, but can also lead to unintended breaking of the substrate outside of the plane where the break should occur.

[0004] Patent Document 1 discloses laser-induced damage to a substrate. The laser generates damage inside the substrate through various effects. However, the document does not disclose laser focusing.

[0005] All methods available in the prior art have the disadvantage that additional components are required to generate the desired separation effect, or that it is impossible or very difficult to control the fracture process. For example, the SmartCut® method requires implanting atoms into the substrate. Chemical etching processes require the preparation of chemicals. Mechanical separation processes can use only mechanical separation means such as blades or wires, but experience has shown that these are only suitable for separating relatively thick layers from the substrate. They are not suitable for separating thin layers from the substrate, especially layers with thicknesses in the micrometer or nanometer range. In addition, it is difficult, if not impossible, to control the fracture along a desired plane using mechanical separation means. In methods that irradiate a substrate with a laser beam, an optical system is used to focus the laser beam. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 7,052,978 Summary of the Invention [Problem to be solved by the invention]

[0007] Based on the above, the present invention relates to providing a method that simplifies the separation of substrates, in particular by eliminating the above-mentioned drawbacks, and in particular a method that is also suitable for providing as thin as possible substrate sublayers after separation of the substrate layers. [Means for solving the problem]

[0008] The present invention solves the problem by a method for separating according to claim 1, a device for separating according to claim 13 and a substrate according to claim 15. Further preferred embodiments of the invention will become apparent from the following description and drawings.

[0009] According to a first aspect of the present invention, there is provided a method of separating a first substrate layer along at least one separation line, the method comprising: providing a first substrate layer; separating the first substrate layer along a separation line generated by irradiating the first substrate layer with laser light; To form the separation line, the power of the laser light is adjusted so that the power of the laser light has a value above a critical power value for forming self-focusing of the laser light in the first substrate layer.

[0010] In contrast to the prior art, the present invention intends to adjust the power of the laser light used so that a self-focusing phenomenon of the laser light occurs in the first substrate layer to be processed, particularly in the first substrate layer to be separated. The self-focusing phenomenon is based on the Kerr effect, and occurs particularly when the spatially profiled intensity profile of laser light with a sufficiently high intensity amplitude interacts with the material of the first substrate layer. Here, nonlinear effects occur. In an alternative embodiment, the self-focusing phenomenon is based on nonlinear absorption. Since refractive index properties depend on the light intensity, if the light intensity is sufficiently high, a refractive index profile can be formed in the material that focuses the light to a certain plane within the first substrate layer due to a change in the refractive index profile induced by the light itself. As a result, a portion or subsection of the subsequent separation line or separation surface is established or determined at the focal point or focus formed by self-focusing.

[0011] The occurrence of the "self-focusing" phenomenon depends on the material and laser characteristics. Depending on the material selected, different critical powers or pulse energies are set, above which self-focusing occurs. Based on experimental results and / or simulations, it is possible to define, estimate, or determine critical power values ​​for each laser type or laser beam used, on the one hand, and for the material used in the first substrate layer, on the other hand. This effect is based on the fact that the refractive index of a material changes intensity-dependently, particularly linearly, at high intensities. When a laser beam with a non-uniform, particularly Gaussian, intensity cross-section is irradiated onto a transparent material, the polarization of the central portion of the laser beam exhibits a different phase shift than the peripheral portions. It can be mathematically and physically proven that, under these circumstances, self-focusing of the laser beam occurs, i.e., the photons of the laser beam are focused to a single point at the focal plane within the first substrate layer, even if the laser beam was not focused when it entered the material.

[0012] In particular, by self-focusing a focal point or a focal point is established or realized in the area through which the separation line will extend. In particular, the separation line should be understood as a two-dimensional separation surface. The separation surface is formed in a corresponding manner or by two-dimensional formation of the separation line by displacement of the laser light or the first substrate layer relative to the beam path of the laser light.

[0013] Self-focusing advantageously allows for the induction of such high intensities within the first substrate layer, which in turn leads to physical and / or chemical modifications within or at the planes or points where self-focusing occurs. This modification of material properties results in the formation of a separation line or plane, e.g., a predetermined break point, or spontaneous separation along the separation line or plane. Advantageously, the use of expensive etchants or complex optics or the implantation of ions into the first substrate layer can be eliminated or significantly reduced. Thus, at least, the amount of work involved in actually breaking or separating the first substrate layer can be further reduced, improving separation of the first substrate layer.

[0014] The fact that only the power of the laser light needs to be adjusted to achieve self-focusing is also particularly advantageous. Even though determining the critical power requires taking into account numerous parameters, increasing the power of the laser light is sufficient to cause self-focusing, particularly to determine the position of self-focusing. This makes it possible to determine or influence the position of interaction between the material of the first substrate layer and the laser light in a relatively simple manner. In particular, it is possible to respond relatively quickly to changes in material, for example, if the first substrate layer to be processed is replaced or the position of the separation line is changed. No major reconfiguration of the apparatus for carrying out the method is required.

[0015] In particular, the first substrate layer is part of, or is intended to be part of, a substrate composite comprising a 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 for connecting, for example, two other wafer substrate layers. Preferably, the first substrate layer and / or the second substrate layer comprise a material such as silicon or germanium. Preferably, the first substrate layer has a thickness of 1 nm to 5 mm, more preferably 1 nm to 1 μm, and most preferably 1 nm to 3,000 nm.

[0016] The Czochralski method can be used, for example, to extract an ingot from a silicon melt. Finally, the described method is also suitable for separating a substrate sublayer from this ingot, which can then form a free-standing substrate. The substrate sublayer, which is then further processed as a free-standing substrate, in this case has a thickness in the millimeter range. In particular, the separation is performed before joining a first substrate layer with a second substrate layer.

[0017] Substrate sublayers with thicknesses in the micrometer or nanometer range are primarily used in methods in which layer transfer is performed, where a first substrate layer to be separated is first bonded to a second substrate layer, and only then is a method used to separate the first substrate layer, in particular after bonding the first substrate layer to the second substrate layer.

[0018] Preferably, the surface of the first substrate layer has a roughness of 0.01 to 300 nm, more preferably 0.01 to 30 nm, and most preferably 0.01 to 10 nm. The smaller the surface roughness of the substrate layer, the less scattering of the laser beam coupled to the first substrate layer. Therefore, it is more preferable that the surface roughness of the substrate layer is small.

[0019] In a preferred embodiment of the method, the laser beam has a wavelength of 0.1 μm to 500 μm, preferably 0.2 μm to 100 μm, more preferably 0.3 μm to 50 μm, most preferably 0.5 μm to 10 μm, or even 1 μm to 2.5 μm. In this way, the separation layer can be irradiated in a particularly efficient and targeted manner.

[0020] In a more preferred embodiment of the method, the laser is intended to have a power output of 1W to 1000W, preferably 5W to 800W, even more preferably 7W to 600W, most preferably 10W to 500W, and even most preferably 20W to 200W.

[0021] In a preferred embodiment of the method, the laser irradiation area is 2000 μm 2 Less than 500 μm, preferably 2 less than 80 μm, more preferably 2 less than, most preferably 20 μm 2 Less than, or even 1 μm 2 It is intended that the area of ​​the separation layer or separation line that is affected by the laser beam is advantageously small and targeted in order to locally reduce or destroy the adhesive properties of the separation layer.

[0022] In a preferred embodiment of the method, it is intended that there is a distance of at least 0.1 μm, preferably at least 1 μm, more preferably at least 5 μm, most preferably at least 10 μm, or even at least 50 μm between the areas of action of the laser beam in the separating layer so that the areas of action of the laser beam do not overlap, thus enabling a particularly simple and efficient cutting.

[0023] More preferably, ultrashort laser pulses, preferably ns (nanosecond) pulses, more preferably ps (picosecond) pulses, most preferably fs (femtosecond) pulses, or even as (attosecond) pulses are intended to be used as laser light. Thus, the duration of the light pulses is preferably 10 -9 Less than 10 seconds, preferably -11Less than 10 seconds, preferably -13 Less than 10 seconds, most preferably -15 Less than a second, even 10 -16 Less than a second.

[0024] The corresponding short pulse duration advantageously allows for easy generation of the laser power or light intensity required for self-focusing. Corresponding pulses are typically associated with the use of specialized optical components, such as refractive, reflective, and / or diffractive optical devices. Preferably, propagation of high-intensity laser light through the material is avoided as much as possible. Otherwise, such propagation through the medium can result in a change in pulse shape and / or intensity reduction. However, the use of beam expansion is also contemplated, whereby the total intensity is first reduced across the spatial profile of the laser pulse, preferably immediately before entering the first substrate layer, to refocus the laser beam and cancel the expansion. This makes it possible, for example, to modulate or adjust the laser profile or intensity profile at low intensities to generate the best possible self-focusing in the first substrate layer. In principle, simple apertures or other optical components can also be used to adjust the spatial intensity profile of the laser beam. The intensity profile is preferably generated by refractive optics. The use of apertures, field mappers, lens arrays, integrators or beam homogenizers, and / or axicons is also contemplated.

[0025] Preferably, the laser light has a spatial profile, in particular an intensity profile with a Gaussian, Lorenz or Cauchy shape. Corresponding intensity profiles prove to be particularly advantageous, as they are particularly suitable for refractive index profiling, which generates self-focusing due to the Kerr effect. More preferably, it is also envisaged that a corresponding spatial intensity profile is specifically realized by corresponding optical components, for example, when the intensity profile provided by the laser light source deviates from a preferred intensity profile. Finally, in order to generate the Kerr effect, it is more preferable to generate an intensity profile of the laser beam that is non-uniform in cross section. Preferably, an intensity profile with a Gaussian, Lorenz and / or Cauchy geometric shape is generated.

[0026] Preferably, the separation line is intended to extend along a plane substantially parallel to the main extension plane. This advantageously allows the first substrate layer to be separated along a plane substantially parallel to its own main extension plane. Separation along a separation line substantially parallel to the main extension plane is particularly advantageous when relatively thin substrate sublayers need to be produced. In particular, the separation results in the separation of a primary substrate sublayer and a secondary substrate sublayer obtained from the first substrate layer as a result of the separation. For example, a coating can be thinned to a desired dimension.

[0027] Alternatively, the separation line is envisaged to extend substantially perpendicular to the main extension plane, which in particular allows separation, i.e. dicing, into individual portions of the first substrate layer arranged adjacent to one another in the main extension plane before separation.

[0028] Preferably, the first substrate layer is intended to be connected to the second substrate layer during irradiation. In particular, the first substrate layer and the second substrate layer are bonded to each other by physical adhesion, form-fitting, and / or pressure-fitting, and the second substrate layer is intended to face the incident laser light. In other words, the laser light first propagates through the second substrate layer before impinging on the first substrate layer, and a separation line or a portion of a separation line is generated in the first substrate layer by incident self-focusing. In particular, the laser light is intended to pass through the second substrate layer and then, after passing through the second substrate layer, to form a focus by self-focusing in the first substrate layer. In particular, when setting the power of the laser light, it is adjusted to ensure that partial focusing preferably already occurs in the second substrate layer and that the desired final focusing is achieved in the first substrate layer.

[0029] The depth of the focal plane can be set by the laser parameters, particularly the wavelength of the laser used. The closer the focal plane is to the substrate layer surface, the shorter the wavelength of the laser beam. In the laboratory, a neodymium-YAG laser with a wavelength of 1064 nm has proven effective for near-surface processing. At wavelengths of around 1550 nm, depths of several hundred microns can be achieved.

[0030] Measurements show that with a wavelength of 1950 μm, a pulse duration of about 5 ps, and a spot size diameter of about 20-30 μm, a power output of about 10 μJ per pulse can be achieved, the power at which silicon begins to be damaged.

[0031] In one embodiment, the laser beam is directed perpendicular to the first substrate layer, and the first substrate layer is actively moved relative to the entire optical assembly, i.e., the laser beam. In this embodiment, the first substrate layer must be fixed to a substrate holder that moves as fast as possible. Nevertheless, the substrate holder must have the highest possible resolution in the process axis so that the laser beam can be accurately positioned.

[0032] In another embodiment, the optical assembly, in particular the laser beam, can be actively moved relative to the first substrate layer, for which a laser beam alignment device is preferably used.

[0033] In a further preferred embodiment, the laser beam alignment device uses special optical elements, particularly in the form of a galvanometer scanner, to scan the laser beam over the first substrate layer to form a two-dimensional separation layer extending along the main extension plane. Preferably, the laser beam alignment device includes a telecentric lens, more preferably a telecentric lens with a bilaterally telecentric beam path. In this case, the laser beam alignment device guides the laser beam through one or more lenses that refract the laser beam so that it is always perpendicular to the first and / or second substrate layer. The lenses used are typically smaller than the first substrate layer to be scanned. Therefore, the first substrate layer must be moved in a step-and-repeat manner relative to the optical assembly. This process is then repeated multiple times until the entire first substrate layer to be scanned is illuminated.

[0034] It is believed that by changing the laser parameters, particularly the laser power, it is possible to change the position of the focal plane. Preferably, the first substrate layer is also connected to a third substrate layer, the first, second, and third substrate layers being arranged one above the other along a stacking direction extending perpendicular to the main extension plane, and the first substrate layer being intended to be a bonding layer between the second and third substrate layers. Due to the corresponding self-focusing of the first substrate layer formed as a bonding layer, it is advantageously possible to enable separation of an existing or fabricated substrate composite. Therefore, the method described herein also allows for debonding in order to separate specific substrate layers, for example, the second and third substrate layers, from each other.

[0035] To separate a second substrate layer from a third substrate layer connected to each other via a first substrate layer, or to separate the first substrate layer, additional devices, particularly corresponding substrate holders with corresponding fixing means, can be used. For example, the first and second substrate holders are intended to be positioned opposite each other, while the first substrate layer to be disconnected is positioned between the first and second substrate holders. The first device, particularly the first substrate holder, is positioned on the side facing the second substrate layer. The second device, particularly the second substrate holder, is positioned on the side facing the third substrate layer. These devices fix the substrates or substrate layers by corresponding fixing means, particularly vacuum suction and / or clamping means. By moving the two devices away from each other, the two substrate layers, i.e., the second and third substrate layers, can be separated from each other while simultaneously remaining fixed to the devices, i.e., the first and second substrate holders. The same principle applies to devices fixed directly on top of the first substrate layer to be separated.

[0036] To overcome any last remaining attractive forces between the substrate layers separated by this method, a force of 1N to 100kN, preferably 1N to 10kN, more preferably 1N to 1kN, and most preferably 1N to 100N, or even 1N to 10N is applied.

[0037] The separation surface or separation line has a thickness of 1 nm to 10 μm, preferably 1 nm to 1 μm, more preferably 1 nm to 100 nm, and most preferably 1 nm to 10 nm. When volume defects, particularly holes, local melting, etc., occur on the separation surface or separation line, the size of these volume defects is 1 nm to 10 μm, preferably 1 nm to 1 μm, more preferably 1 nm to 100 nm, and most preferably 1 nm to 10 nm.

[0038] Preferably, a lens is used to pre-focus the laser light before it strikes the first substrate layer. This allows the optical power of the laser beam to be adjusted in a controlled manner when it strikes the first substrate layer, for example, to match the material properties of the first substrate layer. It is also conceivable to use a concave mirror for focusing, which advantageously allows both focusing and redirecting the laser beam, thereby ensuring an advantageous reduction in the installation space of the device. In other words, a straight path for the laser beam is no longer required.

[0039] Alternatively, it is envisaged that no lens is arranged between the laser light source and the first substrate layer, ie there is no lens and / or concave mirror in the beam path of the laser light. More preferably, the separation is assisted by the application of mechanical force, additional laser light irradiation, the introduction of ions, atoms, and / or molecules, chemical influences, and / or heat. In other words, the creation of a separation line is not yet completely sufficient to cause separation of the first substrate layer; rather, a certain predetermined fracture surface or fracture line is created as the separation line, which is eventually broken by the addition of additional influences, such as the application of force, additional light irradiation, and / or chemical influences, to cause separation within the first substrate layer. For example, in this case, it is assumed that corresponding adsorption devices are attached to the upper and / or lower sides of the first substrate layer, and corresponding tensile and / or shear forces produce mechanical effects on the first substrate layer. If a force is required for separation, the force is less than 1000 N, preferably less than 500 N, more preferably less than 100 N, most preferably less than 1 N.

[0040] In an exemplary embodiment, the laser beam is irradiated at least one point in the focal plane with a high energy density to melt or even directly sublimate the material. If the material is melted, the separation process, e.g., additional mechanical influence, should preferably be carried out while the material is still in a molten state. After all, the melted area is relatively small due to the highly focused power input by the laser beam, and the heat accumulated in the melt is diffused very quickly to the surroundings through the substrate, so it can be expected to cool very quickly, even before the actual separation process is carried out.

[0041] Nevertheless, the microstructure of the solidified molten region may have a lower fracture strength than the original microstructure and thus function as a predetermined fracture point. In the rare case that material has sublimated, it may re-sublime, creating a new bond between the substrate halves of the first substrate layer being separated. In this case, the material is still in the interface region, but is technically considered to have been removed.

[0042] In another exemplary embodiment, a high intensity laser beam causes a chemical reaction in the material in the focal plane, which further causes destruction. More preferably, in particular in the preparation method step, ions are introduced into the first substrate layer, particularly in the region of the separation line to be subsequently generated, in particular by accelerating and bombarding the ions into the first substrate layer. A focal plane is then generated in the region with the ions by self-focusing. For example, extending the known SmartCut® method, it is no longer necessary to heat the entire substrate stack, but rather heat is introduced by a laser in a targeted manner due to the self-focusing effect, and hydrogen atoms recombine along the focal plane to form hydrogen molecules, which causes the destruction of the microstructure in a manner similar to the SmartCut® method.

[0043] More preferably, the ions are intended to be embedded in the mounting surface. The distance between the mounting surface and the focal plane is less than 1 mm, preferably less than 100 μm, more preferably less than 1 μm, and most preferably less than 100 nm, or even less than 10 nm. It is further envisioned that separation of the first substrate layer is achieved by supplying heat to a region of the mounting surface through self-focusing, with the first substrate layer connected to the mounting surface via at least one coating with the second substrate layer. Treatment with self-focusing light produces physical or chemical effects, resulting in recombination of implanted atoms or molecules at the implanted surface. In particular, when implanted hydrogen ions are used, recombination of hydrogen atoms into hydrogen molecules occurs. Hydrogen molecules have a higher molar volume. The resulting hydrogen gas expands and causes damage along the implanted surface. By bonding to the second substrate layer via at least one coating, it is advantageous to provide an entire substrate with the second substrate layer comprising a relatively 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.

[0044] It is also envisaged that other atoms are present in the microstructure, which recombine in the course of thermal stress to form the corresponding molecular gas, resulting in an effect similar to that of the SmartCut® method. It is also envisaged to ionize halides, in particular fluorine, chlorine, bromine or iodine, and implant them into the substrate. It is also envisaged to use nitrogen or oxygen atoms, which recombine to form the corresponding molecular gas. The present invention extends the SmartCut® method so that the entire substrate stack is no longer subjected to a thermal treatment, thereby reducing the impact on existing functional units, in particular microchips, memory chips, MEMS, LEDs, etc. More preferably, the introduction of ions, atoms and / or molecules is carried out before the formation of the separation line by self-focusing.

[0045] In another exemplary embodiment, atoms and / or molecules that are highly absorbing for the laser beam used are implanted into the substrate and / or layer to be destroyed, so that the photons of the laser beam are preferably absorbed by the implanted atoms and / or molecules, which then cause very strong thermal agitation that damages the surrounding structures.

[0046] Preferably, the method is intended to be used to produce a substrate layer composite, for example, comprising a first substrate layer and a second substrate layer, where, after separation, the first thickness of the first substrate layer is smaller than the second thickness of the second substrate layer. In this case, the first and second thicknesses are measured along a stacking direction extending perpendicular to the main extension plane. This advantageously allows the coating of the substrate layer to be reduced to a desired, particularly relatively thin, layer thickness. This makes it possible to achieve layer thicknesses of, for example, less than 1000 nm, more preferably less than 500 nm, and most preferably less than 100 nm.

[0047] Preferably, the first substrate layer is intended to comprise a ceramic material, a polymer material, silicon and / or germanium. Depending on the selected materials of the first, second and / or third substrate layers, the power of the laser light can be adjusted to adjust the desired effect of self-focusing.

[0048] Preferably, during irradiation, the first substrate layer is intended to be moved along a direction determined by the intended path of the separation line within the first substrate layer. In other words, the laser beam is stationary and is not offset or displaced, particularly by a rotatable mirror, but the movement for generating the separation line is performed by moving the first substrate layer relative to the laser source, particularly relative to the stationary laser beam. This advantageously ensures that the laser light is incident as perpendicularly as possible at each position, avoiding uneven separation lines due to alignment changes. Furthermore, it is advantageously possible to prevent the laser light from being reflected laterally from the irradiated substrate. Instead, appropriate invariance with respect to the surface orientation of the first substrate layer can ensure that the back-reflected light is limited to a fixed spatial region.

[0049] Preferably, the separation is intended to be carried out solely by irradiation with laser light. In other words, in the most preferred embodiment, unraveling is induced by self-focusing. This provides a particularly easy method to implement, since no additional steps are required to cause the breakage. In an exemplary embodiment, the laser beam is irradiated to at least one point in the focal plane, causing direct breakage of chemical bonds at that point. In particular, covalent bonds in ceramic or polymer materials can be directly broken. The energy density of the self-focused laser beam is so high that the electrons that create the covalent bonds are pulled away from the molecular orbitals.

[0050] A further subject of the present invention is an apparatus for carrying out the method according to the present invention using a laser light source suitable for providing a laser light output that achieves self-focusing in the first substrate layer. All advantages and explanations explained with respect to the method are equally applicable to the apparatus. In particular, the use of an ultrashort pulse laser source proves advantageous, since the laser pulses provided herein allow the desired intensity to be achieved relatively easily. Furthermore, it is envisaged that the light source comprises a control device for adjusting the laser output, whereby the laser output can be advantageously adjusted to a desired magnitude in order to cause self-focusing in a specific area in a controlled manner.

[0051] Preferably, the device is provided with a fixing element that is movable, in particular in a plane parallel to the main extension plane of the first substrate layer. This advantageously allows a relative movement of the first substrate layer or of the substrate layer complex while the laser beam remains stationary. A further subject of the invention is a substrate comprising at least one first substrate layer, manufactured by the method according to the invention. All the features and characteristics of the method are equally applicable to the device.

[0052] Further advantages, features and details of the present invention will become apparent from the following description of preferred embodiments and the drawings. [Brief explanation of the drawings]

[0053] [Figure 1] 1 is a schematic diagram of a method according to a first preferred embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram of a method according to a second preferred embodiment of the present invention. [Figure 3] FIG. 2 is a schematic diagram of a method according to a third preferred embodiment of the present invention. [Figure 4a] FIG. 4 is a schematic diagram of a first method step of a method according to a fourth preferred embodiment of the present invention. [Figure 4b] FIG. 4 is a schematic diagram of a second method step of a method according to a fourth preferred embodiment of the present invention. [Figure 4c] FIG. 4 is a schematic diagram of a third method step of a method according to a fourth preferred embodiment of the present invention. [Figure 4d] FIG. 4 is a schematic diagram of a fourth method step of a method according to a fourth preferred embodiment of the present invention. [Figure 4e] FIG. 4 is a schematic diagram of a fifth method step of the method according to the fourth preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0054] In the drawings, identical components or components with the same function are designated by the same reference numerals. The figures are not to scale. For clarity, the laser beam 2, which is specifically intended for the present method, is shown wider. In particular, the laser beam 2 is depicted symbolically as a beam, but more preferably, high-energy laser light pulses are generated and directed toward the first substrate layer 2 and / or the second substrate layer 4. Self-focusing 2k of the laser beam 2 is shown in a simplified manner by a converging beam terminating at the focal plane 3. However, more preferably, multiple ultrashort laser pulses are directed along the path depicted as the 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 material 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 particularly caused by self-focusing 2k.

[0055] 1 shows a first embodiment of the present invention. A laser beam 2 is directed at a focal plane 3 of a first substrate layer 1. By acquiring knowledge of the material properties of the substrate 1 together with the characteristics of the laser beam 2 used, the focal plane 3 can be determined and fixed. More preferably, the Kerr effect is used to generate a chemical and / or physical (resulting) effect, particularly at or near the focal plane 3, which allows for the separation of the primary substrate sublayer 1o from the secondary substrate sublayer 1u in a subsequent process.

[0056] FIG. 2 illustrates a second embodiment of the present invention. In addition to the first substrate layer 1, the substrate composite includes at least one second substrate layer 4. It is also conceivable to use multiple stacked second substrate layers 4, with the stack of multiple second substrate layers 4 connected to the first substrate layer 1. The nonlinear optical effect causing self-focusing of the laser beam 2 is initiated already within the at least one second substrate layer 4. In this case, the focal plane 3 is located within the first substrate layer 1. The focal plane 3 located within the second substrate layer 4 is an example of an embodiment according to FIG. 1. If multiple layers 4 are used, the focal plane 3 can also be located within one of the multiple second substrate layers and does not necessarily have to terminate within the substrate 1. Therefore, it is more preferable to use at least one second substrate layer 4, and thus at least one additional material, to initiate self-focusing of the laser beam 2 before the first substrate layer 1 and / or before the second substrate layer 4 that is actually to be separated.

[0057] 3 shows a third embodiment of the present invention. In this example embodiment, the self-focusing of a laser beam 2 is used to position the focal plane 3 within a first substrate layer 1, which acts as a bonding layer, and whose role is to bond a second substrate layer 4 and a third substrate layer 5 together. In this way, the present invention can also be used to delaminate two substrate layers, particularly of a substrate composite.

[0058] 4a shows a first method step of the method in which a preferably ionized atomic or molecular beam 6 is irradiated onto a first substrate layer 1. Preferably, ionized hydrogen atoms are implanted into the substrate layer 1. The kinetic energy of the atoms or molecules in the atomic or molecular beam 6 can be used to determine the average penetration depth of the atoms or molecules in the first substrate layer 1. The implantation plane 8 is the plane in which the atoms or molecules accumulate on statistical average.

[0059] FIG. 4b shows a second method step in the method, in which a coating 7 is applied to the substrate surface to which atoms or molecules of the atomic or molecular beam 6 have been introduced. The coating 7 is in particular a thermal oxide, preferably a native oxide. The thickness of the coating 7 can be reduced by back-grinding, back-thinning, and / or back-etching. This method step is not additionally shown. After the application of the coating 7, it is optionally possible to form a hybrid bonding surface. For this purpose, holes are created in the coating 7 by several method steps (not shown or described), which preferably also extend into the substrate layer 1. The holes are then filled with an electrical medium, preferably copper, by a coating process. This is followed by grinding away excess copper down to the coating 7. The metal in the holes then serves as an electrical contact. This process thus forms a hybrid surface with a conductive copper contact surrounded by the dielectric material of the coating 7. Such hybrid surfaces are known to those skilled in the art. For clarity of the drawings, a precise depiction of such a hybrid surface has been omitted.

[0060] 4c shows a third method step of the method in which the first substrate layer 1 is bonded to the second substrate layer 4 via a coating 7, the second substrate layer 4 being similarly coated, more preferably coated in the same way, and e.g., not having a mounting surface 8. More preferably, the bonding is a fusion bond or a direct bond. If the substrate layers 1 and 4 both have hybrid bonding surfaces, the contacts of both hybrid bonding surfaces are aligned as precisely as possible with respect to one another in this method step before bonding takes place. If functional units such as microchips, MEMS, LEDs, memory chips, etc. are already present in the substrate layer 4, these functional units are electrically conductively connected to the first substrate layer 1 via contacts (not shown) of the hybrid bonding surfaces.

[0061] FIG. 4d shows a fourth method step of a method according to a further exemplary embodiment, in which a separation method is used. The focal plane 3 of the laser beam 2 approximately coincides with the implanted surface 8. Therefore, the average difference between the focal plane 3 and the implanted surface 8 is less than 1 mm, preferably less than 100 μm, more preferably less than 1 μm, and most preferably less than 100 nm, or even less than 10 nm. The self-focusing effect of the laser beam 2 at the focal plane 3, and thus at the implanted surface 8, generates very high temperatures along the implanted surface 8, resulting in physical and / or chemical effects on the implanted atoms or molecules. Preferably, the physical and / or chemical effect is a recombination of the implanted atoms or molecules at the implanted surface 8. In particular, if implanted hydrogen ions are used, recombination of hydrogen atoms into hydrogen molecules occurs. Hydrogen molecules have a higher molar volume. The resulting hydrogen gas expands and causes damage along the implanted surface 8. This effect is improved by the separation using a self-focused laser beam, known as the SmartCut® method, in which the entire substrate stack does not have to be heat-treated in a furnace, but in which the heat treatment is carried out very precisely locally along the implanted surface 8. The method according to the invention therefore crucially extends the SmartCut® method known from the prior art. It is also possible to use any other kind of atoms or molecules which, when irradiated by the laser beam 2 according to the invention, produce physical and / or chemical effects that cause damage along the implanted surface 8.

[0062] FIG. 4e shows the fifth method step of the method, in which the primary substrate sublayer 1o (see FIG. 4d) is removed from the first substrate layer 1. Only the secondary substrate sublayer 1u remains as a very thin layer on the coating 7, specifically the oxide layer. If the material of the secondary substrate sublayer 1u is silicon, the substrate thus obtained is called a silicon-on-insulator (SOI) substrate. If the coating 7 was a hybrid interface, copper contacts are preferably exposed on the top surface here. If functional units such as microchips, MEMS, LEDs, or memory devices are also fabricated in the secondary substrate sublayer 1u, they are automatically connected to the functional units of the substrate layer 4 (not shown).

[0063] In an alternative embodiment, the described method is carried out without coating 7, and the first substrate layer 1 is directly bonded to the second substrate layer 4. This method is also a direct bond. The aim of this method is the direct bonding of two materials, for example two different semiconductor materials.

[0064] For all embodiments described herein, it is possible to determine the focal plane 3 by having knowledge of the material properties of the first substrate layer 1 in combination with the properties of the laser used. More preferably, the Kerr effect is used to generate chemical and / or physical effects, particularly at or near the focal plane 3, which allow for the separation of the primary substrate sublayer 1o from the secondary substrate sublayer 1u in subsequent processing. [Explanation of symbols]

[0065] 1...First substrate layer 1o...Primary foundation sublayer 1u...Secondary board sublayer 2...Laser beam / laser light 2k…Self-focusing effect 2f…Focus point 3…focal plane 4...Second substrate layer 5...Third board layer 6...Atomic or molecular beam 7...Coating 8…Injection Surface

Claims

1. A method for separating a first substrate layer (1) along at least one separation line, comprising: providing the first substrate layer (1); separating the first substrate layer (1) along the separation lines generated by irradiating the first substrate layer (1) with laser light (2), a power of the laser beam (2) being set to have a value above a critical power value for forming self-focusing of the laser beam (2) within the first substrate layer (1) to generate the separation line.

2. 2. The method according to claim 1, wherein ultrashort laser pulses (preferably ns pulses, more preferably ps pulses, most preferably fs pulses, or even as pulses) are used as the laser light (2).

3. 3. The method according to claim 1 or 2, wherein a laser beam (2) having a spatial profile, in particular a Gaussian, Lorentzian and / or Cauchy-shaped profile, is used.

4. 4. The method according to claim 1, wherein the separation line extends along a plane substantially parallel to the main extension plane.

5. 5. The method according to claim 1, wherein the first substrate layer (1) is connected to a second substrate layer (4) during irradiation, and the second substrate layer (4) is preferably passed through by the laser light (2) after passing through the second substrate layer (4) and before being incident on the first substrate layer (1).

6. 6. The method according to claim 5, wherein the first substrate layer (1) is bonded to a third substrate layer, the first substrate layer (1), the second substrate layer (4), and the third substrate layer (5) being arranged one above the other along a stacking direction perpendicular to a main extension plane, and the first substrate layer (1) being a bonding layer between the second substrate layer (4) and the third substrate layer (5).

7. 7. The method according to claim 1, wherein a lens and / or a concave mirror is used for pre-focusing.

8. 8. The method according to claim 1, wherein the separation is assisted by the application of mechanical forces, additional laser light irradiation, the introduction of ions, atoms and / or molecules, chemical influences and / or the introduction of heat.

9. 9. The method according to any one of claims 1 to 8, wherein the method is used to manufacture a substrate layer composite comprising at least the first substrate layer (1) and a second substrate layer (4), and wherein after separation the first thickness (D1) of the first substrate layer (1) is smaller than the second thickness (D2) of the second substrate layer (4).

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

11. 11. A method according to any one of the preceding claims, wherein the first substrate layer (1) is moved during irradiation along a direction predetermined by the path of the separation line.

12. 12. Method according to any one of the preceding claims, wherein the separation is carried out solely by irradiation with laser light (2).

13. 13. Apparatus for carrying out the method of any one of claims 1 to 12, comprising a laser light source adapted to provide a laser light output that causes self-focusing at the first substrate layer.

14. 14. The device according to claim 13, wherein the device comprises a fixing element that is movable in a plane that is in particular parallel to a main plane of extension.

15. 13. A substrate comprising at least one primary substrate sublayer (1o) manufactured by the method of any one of claims 1 to 12, wherein said primary substrate sublayer (1o) is obtained by separating said first substrate layer (1).

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