Method for separating first substrate layer, device for carrying out such separation and substrate having first substrate layer

Abstract

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

Description

Field of the Invention

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

[0002] In the prior art, there are various methods for selectively separating substrates along a plane. One of the most important and best-known methods is the so-called method. In the method, atoms, in particular hydrogen atoms, are implanted into the substrate. In a first method step, the atoms are ionized and accelerated onto the substrate by means of an electric field. The kinetic energy of the ions is sufficient to penetrate into the substrate. The penetration depth can be set very precisely by the acceleration voltage. In a second method step, the thus processed substrate is bonded to another substrate. It is also conceivable 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 into hydrogen molecules. The hydrogen atoms are not directly incorporated into the lattice of the substrate, so the substrate is only hydrogenated. Instead, the hydrogen molecules form a gas. The phase change from atomic hydrogen to hydrogen gas causes a volume expansion, and the volume expansion causes a structural break along the implantation plane. By this method, a very thin layer can be transferred from one substrate to another. However, even more importantly, it is possible to fabricate a substrate stack having a very thin crystal layer on its upper side, with an oxide layer being located below the crystal layer. Such a substrate stack is referred to as silicon-on-insulator (SOI).

[0003] Additional methods for substrate separation include chemical and / or mechanical assistance mechanisms. Some methods perform pre-damage along a plane in the substrate by means of a laser beam, but this is not sufficient to break the substrate along the plane. Subsequently, the substrate must be etched with chemicals. Then, the chemicals react with atoms along the plane where the pre-damage has been performed, and the substrate is etched along the plane. The method is time-consuming. Here, mechanical assistance mechanisms, such as a blade or a wire, can be used to break the substrate along the pre-damaged plane. However, accelerating the process using a mechanical separation mechanism causes an undesired breakage of the substrate out of the plane, and the breakage should only occur along the plane.

[0004] Publication US 7 052 978B2 shows laser-induced damage to a substrate. The laser generates damage in the substrate through different effects. However, the focusing of the laser cannot be known therefrom.

[0005] All methods existing in the prior art have the following disadvantages: additional components are required to produce the desired separation effect, or the control of the breaking process is not feasible or very difficult to achieve. For example, in In the method, atoms must be implanted into the substrate. In the chemical etching process, chemicals must be provided. In the mechanical separation process, although only mechanical separation means such as a blade or a wire are required, empirically, the mechanical separation means only allows the separation of relatively thick layers from the substrate. The mechanical separation means is not suitable for separating thin layers from the substrate, especially not for separating layers with a thickness in the micrometer or nanometer range. In addition, it is very difficult or even infeasible to control the fracture along the desired plane by means of the mechanical separation means. In the method of injecting a laser beam into the substrate, an optical device is used to focus the laser beam. Summary of the Invention

[0006] Based on this, an object of the present invention is to provide a method that simplifies the separation of the substrate, especially by eliminating the described disadvantages, and is especially suitable for providing as thin a substrate sublayer as possible after separating the substrate layer.

[0007] The present invention achieves the above object by means of a separation method according to claim 1, a separation device according to claim 13, and a substrate according to claim 15. Other preferred embodiments of the present invention are derived from the following description and from the accompanying drawings.

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

[0009] - providing a first substrate layer, and

[0010] - separating the first substrate layer along the separation line, the separation line being generated by irradiating the first substrate layer with a laser,

[0011] wherein in order to form the separation line, the power of the laser is set such that the power of the laser has a value higher than the critical power value for forming self-focusing of the laser in the first substrate layer.

[0012] Compared with the prior art, according to the present invention, the power of the laser used is set such that the phenomenon of self-focusing of the laser occurs in the first substrate layer to be processed, especially in the first substrate layer to be separated. The phenomenon of self-focusing is based on the Kerr effect and especially occurs when the intensity distribution of the spatial distribution of the laser with a sufficiently high intensity amplitude interacts with the material of the first substrate layer. Nonlinear effects occur here. In an alternative embodiment, the phenomenon of self-focusing is based on nonlinear absorption. Since the refractive index characteristic is related to the light intensity, in the case of a sufficiently high light intensity, a refractive index distribution will appear in the material, and the refractive index distribution causes the light to be focused in a plane within the first substrate layer due to the change in the refractive index distribution caused by the light itself. Thus, in the focal point or focus determined by self-focusing, a sub-region or sub-segment of the subsequent separation line or separation plane is defined or determined.

[0013] Here, the occurrence of the phenomenon of "self-focusing" is related to the material properties and the laser properties. Depending on the material selected, different critical powers or pulse energies occur, at which self-focusing occurs when the critical power or pulse energy is exceeded. Based on experimental knowledge and / or simulations, it is possible to specify, estimate or determine the critical power value of the laser type used or the laser used on one side and the critical power value of the material used in the first substrate layer on the other side. The effect is based on the fact that the refractive index of the material is linearly related to the intensity, especially for high intensities. If a laser beam with an inhomogeneous, especially Gaussian-shaped intensity cross-section is incident on a transparent material, the polarization in the central part of the laser beam causes a different phase shift than in the surrounding parts. Mathematically and physically, it can be shown that this situation causes the self-focusing of the laser beam, i.e., even if the laser beam is not focused when entering the material, the photons of the laser beam are focused at a point in the focal plane in the first substrate layer.

[0014] In particular, by self-focusing, a focus or focal point is determined or realized in the following region through which a separation line should extend. In particular, the separation line is understood as a two-dimensional separation plane. By correspondingly shifting or moving the first substrate layer relative to the laser or the optical path of the laser, a planar configuration of the separation line, which is subsequently configured as a separation plane, is achieved.

[0015] Advantageously, by self-focusing, it is possible to cause a high intensity within the first substrate layer, such that the high light intensity in turn causes physical and / or chemical modification in the following plane or at the following point: in which plane or at which point self-focusing is achieved. The modification of the material properties subsequently causes the formation of a separation line or a separation plane, such as an intended fracture site, or even causes autonomous separation along the separation line or the separation plane. Here, it is possible to advantageously dispense with the use of large amounts of etchant or complex optical systems or the implantation of ions into the first substrate layer or significantly reduce their scale. Thereby, it is at least possible to further reduce the cost when the first substrate layer is actually fractured or separated, whereby the separation of the first substrate layer can be improved.

[0016] It has also proven to be particularly advantageous that only the power of the laser has to be adjusted in order to achieve self-focusing. Even if several parameters have to be taken into account to determine the critical power, increasing the power of the laser is sufficient to cause self-focusing in this way and in particular also to determine the orientation of self-focusing. Thereby, the feasibility of determining or influencing the position of the interaction between the material of the first substrate layer and the laser is given in a relatively simple way and method. In particular, if the first substrate layer to be processed is replaced or the orientation of the separation line is changed, it is possible, for example, to react relatively quickly to the material replacement. No major adjustments to the facility are required to carry out the method.

[0017] In particular, it is proposed that the first substrate layer is part of a substrate composite or should become part of a substrate composite having 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, such as a bonding layer that connects two other wafer-substrate layers to each other. The first substrate layer and / or the second substrate layer preferably comprises a material such as silicon or germanium. Preferably, the first substrate layer has a thickness between 1 nm and 5 mm, preferably between 1 nm and 1 μm, and particularly preferably between 1 nm and 3000 nm.

[0018] By means of the Czochralski method, for example, an ingot can be grown from a silicon melt. Finally, the described method is also suitable for separating a substrate sublayer from the ingot or barren, such that the separated substrate sublayer can then form an independent substrate. The substrate sublayer, which is then further processed as an independent substrate, will in this case have a thickness in the millimeter range. The separation is carried out in particular before bonding the first substrate layer to the second substrate layer.

[0019] Substrate sublayers having a thickness in the micrometer range or nanometer range are mainly obtained in a method in which layer transfer should be carried out. In this case, first the first substrate layer to be separated is bonded to the second substrate layer, and only then is the method for separating the first substrate layer used. The separation is carried out in particular after bonding the first substrate layer to the second substrate layer.

[0020] Preferably, the surface of the first substrate layer has a roughness between 0.01 nm and 300 nm, preferably between 0.01 nm and 30 nm, and particularly preferably between 0.01 nm and 10 nm. The smaller the roughness of the substrate layer surface, the smaller the scattering of the laser beam coupled into the first substrate layer. Therefore, a low surface roughness on the substrate layer surface is preferred.

[0021] In a preferred embodiment of the method, it is proposed that the laser beam has a wavelength between 0.1 μm and 500 μm, preferably between 0.2 μm and 100 μm, particularly preferably between 0.3 μm and 50 μm, particularly preferably between 0.5 μm and 10 μm, or even between 1 μm and 2.5 μm. In this way, the separation layer can be irradiated particularly effectively and specifically.

[0022] In a preferred embodiment of the method, it is proposed that the laser has a power 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, and most preferably between 20 W and 200 W.

[0023] In a preferred embodiment of the method, it is proposed that the laser area is less than 2000 μm 2 , preferably less than 500 μm 2 , preferably less than 80 μm 2 and particularly preferably less than 20 μm 2 or even less than 1 μm 2 . The area of the separation layer or separation line on which the laser beam acts is advantageously small and targeted in order to locally reduce or destroy the adhesion properties of the separation layer.

[0024] In a preferred embodiment of the method, it is proposed that there is at least 0.1 μm, preferably at least 1 μm, preferably at least 5 μm, particularly preferably at least 10 μm or even at least 50 μm between the action areas of the laser beam on the separation layer, such that the action areas of the laser beam do not overlap. In this way, a particularly simple and effective separation is feasible.

[0025] Preferably, it is proposed to use ultrashort laser pulses as the laser, preferably ns (nanosecond) pulses, preferably ps (picosecond) pulses, and particularly preferably fs (femtosecond) pulses or even as (attosecond) pulses. Therefore, the duration of the light pulse is preferably less than 10 -9 s, preferably less than 10 -11 s, preferably less than 10 -13 s, most preferably less than 10 -15 s or even less than 10 -16 s.

[0026] With a correspondingly short pulse duration, it is advantageously possible in a simple manner to generate the laser power or light intensity required for self-focusing. Corresponding pulses usually require the use of special optical devices, such as refractive, reflective, and / or grating-like optical elements. Preferably, the passage of a laser with high intensity through the material is avoided as much as possible. Otherwise, such propagation through the medium may cause modification of the pulse shape and / or reduction of the intensity. However, it is conceivable to use beam expansion, whereby the total intensity is first reduced via the spatial distribution of the laser pulse, so that the laser beam is refocused again and the beam expansion is eliminated preferably directly before incidence into the first substrate layer. In this way, for example, it is possible to modulate or influence the laser distribution or intensity distribution in the case of low intensity in order to cause as optimal self-focusing as possible in the first substrate layer. In principle, the spatial intensity distribution of the laser beam can also be influenced by means of a simple baffle or other optical components. Preferably, the intensity distribution is generated by refractive optical devices. It is also conceivable to use apertures, field mappers, lens arrays, integrators, or beam homogenizers and / or cone lenses.

[0027] Preferably, the laser has a spatial distribution, in particular a Gaussian, Lorentzian or Cauchy intensity distribution. The corresponding intensity distribution has proven to be particularly advantageous because it is particularly suitable for a refractive index that causes self-focusing by means of the Kerr effect to have a specific distribution. It is also preferably conceivable that, for example, when the intensity distribution provided by the laser source is different from the preferred intensity distribution, the corresponding spatial intensity distribution is achieved by means of the corresponding optical devices. Finally, in order to generate the Kerr effect, it is preferably proposed to generate an intensity distribution that is inhomogeneous in the cross-section of the laser radiation. Preferably, an intensity distribution having a Gaussian, Lorentzian and / or Cauchy geometry is generated.

[0028] Preferably, it is proposed that the separation line extends along a plane that extends substantially parallel to the main extension plane. In this way, it is advantageously possible for the first substrate layer to be separated along a plane that extends substantially parallel to its own main extension plane. The separation along a separation line that extends substantially parallel to the main extension plane is particularly advantageous when relatively thin substrate sub-layers are to be produced. In particular, the separation causes the separation of a primary substrate sub-layer and a secondary substrate sub-layer, which are produced from the first substrate layer by the separation. For example, the cladding can be reduced to the desired size.

[0029] Alternatively, it is conceivable that the separation line extends substantially perpendicular to the main extension plane so that a division, i.e., a cutting into individual sub-segments of the first substrate layer, can be achieved, which sub-segments are arranged adjacent to one another in the main extension plane, in particular before the cutting.

[0030] Preferably, it is proposed that the first substrate layer is connected to the second substrate layer during irradiation. In particular, it is proposed that the first substrate layer and the second substrate layer are connected to one another in a material-locking, form-fitting and / or force-locking manner, and that the second substrate layer faces the incident laser. In other words: The laser first propagates through the second substrate layer before entering the first substrate layer, and there a separation line or a sub-segment of the separation line is generated due to the incident self-focusing. In particular, it is proposed that the second substrate layer is traversed by the laser, and after passing through the second substrate layer, a focal point is formed by self-focusing in the first substrate layer. Here, particular attention should be paid when setting the laser power, preferably partial focusing already takes place in the second substrate layer and the desired final focusing is achieved in the first substrate layer.

[0031] The depth of the focal plane can be set by the laser parameters, in particular by the wavelength of the laser used. The closer the focal plane should be to the substrate surface, the shorter the wavelength of the laser radiation should be. In the laboratory, a Neodym-YAG laser with a wavelength of 1064 nm has proven suitable for near-surface processing. With a wavelength in the vicinity of 1550 nm, a depth of several hundred μm is obtained.

[0032] It is measured that an energy of approximately 10 μJ per pulse is obtained with a wavelength of 1950 μm, a pulse duration of approximately 5 ps, and a spot diameter of approximately 20 μm - 30 μm. Starting from said energy, silicon damage is approximately caused.

[0033] In one embodiment, the laser beam is normal to the first substrate layer, and the first substrate layer moves actively relative to the entire optical configuration, i.e., the laser beam. For said embodiment, the first substrate layer must be fixed on a substrate holder that can move as fast as possible. However, the substrate holder should have the highest possible resolution of the movement axis in order to be able to precisely position the laser beam.

[0034] In another embodiment, the optical configuration, in particular the laser beam, can move actively relative to the first substrate layer. For this purpose, a laser beam steering device is preferably used.

[0035] In another preferred embodiment, a special optical element, in particular an optical element in the form of a galvanometric scanner, is used as the laser beam steering device in order to scan the laser beam over the first substrate layer so as to form a separatrix layer that is formed in a planar manner and extends along the main extension plane. Preferably, the laser beam steering device includes a telecentric objective, preferably a telecentric objective with a telecentric optical path on both sides. Here, the laser beam is guided by the laser beam steering device through one or more lenses that refract the laser beam such that the laser beam always enters the first substrate layer and / or the second substrate layer normally. The lenses used are generally smaller than the first substrate layer to be scanned. Therefore, the first substrate layer must move relative to the optical configuration in a step-and-repeat process. Then the process is repeated at multiple locations until the entire first substrate layer to be scanned is irradiated.

[0036] It is conceivable to change the laser parameters, in particular the laser power, such that the position of the focal plane can be changed.

[0037] Preferably, it is proposed that the first substrate layer is connected to the third substrate layer, wherein the first substrate layer, the second substrate layer, and the third substrate layer are arranged one above the other along a stacking direction that extends perpendicular to the main extension plane, and the first substrate layer is a bonding layer between the second substrate layer and the third substrate layer. By correspondingly autofocusing into the first substrate layer configured as the bonding layer, it is advantageously possible to separate an existing or fabricated substrate composite. Therefore, it is also possible with the method described herein to perform de-bonding in order to separate specific substrate layers, for example the second substrate layer and the third substrate layer, from each other.

[0038] In order to separate a second substrate layer and a third substrate layer connected to each other via a first substrate layer, or in order to separate the first substrate layer, an additional device, in particular a corresponding substrate holder with a corresponding fixing mechanism, can be used. For example, a first substrate holder and a second substrate holder are provided, the first substrate holder and the second substrate holder being opposite each other, and a first substrate layer to be separated is arranged between the first substrate holder and the second substrate holder. The first device, in particular the first substrate holder, is on the side facing the second substrate layer. The second device, in particular the second substrate holder, is on the side facing the third substrate layer. The devices fix the substrate or substrate layers by means of corresponding fixing mechanisms, in particular by means of a vacuum fixing device and / or a clamping mechanism. By a relative movement of the two devices away from each other, the two substrate layers, namely the second substrate layer and the third substrate layer, can be separated from each other and at the same time fixed to the devices, namely the first substrate layer and the second substrate layer. The same applies to a device fixed directly to the upper side of the first substrate layer to be separated.

[0039] In order to overcome the last remaining attraction between the substrate layers separated by means of the method, a force is applied between 1 N and 100 kN, preferably between 1 N and 10 kN, preferably between 1 N and 1 kN, particularly preferably between 1 N and 100 N or even between 1 N and 10 N.

[0040] The separation plane or separation line has a thickness between 1 nm and 10 μm, preferably between 1 nm and 1 μm, preferably between 1 nm and 100 nm, and particularly preferably between 1 nm and 10 nm. If volume defects, in particular pores, local melting and / or similar defects, occur in the separation plane or separation line, the size of the volume defects is between 1 nm and 10 μm, preferably between 1 nm and 1 μm, preferably between 1 nm and 100 nm, and particularly preferably between 1 nm and 10 nm.

[0041] Preferably, it is proposed to use a lens in order to pre-focus the laser before it enters the first substrate layer. Thereby, the optical power of the laser beam when it enters the first substrate layer can be advantageously set in a controlled manner and, for example, matched to the material properties of the first substrate layer. It is also conceivable to use a concave mirror for focusing, whereby it is advantageously possible not only to focus the laser beam but also to deflect the laser beam, which can advantageously ensure the economy of the structural space of the device. Finally, a straight extension of the laser beam is not required.

[0042] Alternatively, it is conceivable that no lens is arranged between the laser source and the first substrate layer, that is to say the optical path of the laser has no lens and / or concave mirror.

[0043] Preferably, it is proposed that the separation is assisted by mechanical force action, another laser incidence, introduction of ions, atoms and / or molecules, chemical action and / or introduction of heat. In other words: creating a separation line is not yet sufficient to cause the separation of the first substrate layer, but rather creates a desired fracture plane or desired fracture line as the separation line, which finally fractures in the case of adding other influences, such as force action, another light action and / or chemical action, in order to cause separation within the first substrate layer. For example, it can be envisaged here that a corresponding suction device adheres to the upper side and / or lower side of the first substrate layer and causes mechanical action on the first substrate layer by means of corresponding tensile force and / or shear force. If a force action 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 10 N, and most preferably less than 1 N.

[0044] In an exemplary embodiment, the laser beam is directed to at least one point of the focal plane in order to melt or even directly sublime the material by means of a high energy density. If the material melts, the separation process, for example an additional mechanical action, should preferably also be carried out in the molten state. Finally, by introducing energy very focally by means of the laser beam, the molten region is relatively small and the heat stored in the melt is very quickly discharged again via the substrate into the environment, such that a very rapid cooling is expected especially before the separation process to be actually carried out.

[0045] The microstructure of the solidified molten region can still have a fracture strength smaller than the original microstructure and thus serve as a desired fracture site. If the material sublimes, the material can in the rarest cases sublime again, such that re-bonding occurs between the substrate halves to be cut of the first substrate layer. Although the material is still in the critical region, it is considered to have been removed in the technical sense.

[0046] In another exemplary embodiment, the high intensity of the laser beam produces a chemical reaction in the material within the focal plane, which chemical reaction causes a fracture in a further process.

[0047] Preferably, it is proposed that, especially in the preparatory method step, ions are introduced into the first substrate layer, especially into the region of the subsequent separation line, in particular in such a way that the ions are accelerated and implanted into the first substrate layer. Subsequently, a focal plane is generated by self-focusing in the region with ions. For example, the known method can be extended such that it is no longer necessary to heat the entire substrate stack, but rather the heat caused by the laser is introduced in a targeted manner by means of the self-focusing effect, such that hydrogen atoms recombine into hydrogen molecules along the focal plane, thereby causing a fracture of the microstructure according to the method.

[0048] It is preferably proposed here to embed ions in the implantation plane. Here, the distance between the implantation plane and the focal plane is less than 1 mm, preferably less than 100 μm, preferably less than 1 μm, particularly preferably less than 100 nm, or even less than 10 nm. It is also conceivable that, before separating the first substrate layer, the first substrate layer having the implantation plane is connected to the second substrate layer via at least one cladding layer in such a way that heat is transported in the region of the implantation plane by means of autofocusing. Physical or chemical effects are achieved by processing with light by means of autofocusing, which effects cause the recombination of the atoms or molecules implanted in the implantation plane. In particular, in the case of the use of implanted hydrogen ions, hydrogen atoms recombine into hydrogen molecules. Hydrogen molecules have a relatively high molar volume. The hydrogen gas thus generated expands and causes damage along the implantation plane. By being connected to the second substrate layer via at least one cladding layer, it is advantageously possible to provide the entire substrate having the second substrate layer, the second substrate layer being provided with a relatively thin substrate sublayer which is retained after separation and joined to the second substrate layer via the cladding layer. Thereby, for example, a silicon-on-Insulator (SOI) substrate can be formed.

[0049] It is also conceivable that there are other atoms in the tissue structure which recombine into their corresponding molecular gases during the heat load and cause an effect similar to the method. It is also conceivable to ionize halides, in particular fluorine, chlorine, bromine or iodine and inject them into the substrate. It is also conceivable to use nitrogen atoms or oxygen atoms which recombine into their corresponding molecular gases. By the present invention, the method is extended such that the entire substrate stack is no longer subjected to heat treatment, which can gently affect the already existing functional units, in particular microchips, memory chips, MEMS, LEDs, etc. Preferably, the penetration of the ions, atoms and / or molecules takes place in time before the formation of the separation line in order to form autofocusing.

[0050] In another exemplary embodiment, atoms and / or molecules are implanted into the substrate to be destroyed and / or the layer to be destroyed with a high absorption for the laser radiation used. Thereby, the photons of the laser radiation are preferably absorbed by the implanted atoms and / or molecules, which causes very strong thermal motion and thus causes damage to the surrounding tissue structure.

[0051] Preferably, it is proposed that the method is used to manufacture a substrate layer composite including, for example, 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. Here, the first thickness and the second thickness are measured along a stacking direction extending perpendicular to the main extension plane. Advantageously, it is thus possible to reduce the cladding of the substrate layer to a desired, particularly relatively small layer thickness. This allows, for example, achieving a layer thickness with a value less than 1000 nm, preferably less than 500 nm, and particularly preferably less than 100 nm.

[0052] Preferably, it is proposed that the first substrate layer includes a ceramic material, a polymer material, silicon, and / or germanium. Corresponding to the selected materials of the first substrate layer, the second substrate layer, and / or the third substrate layer, the laser power is correspondingly adjusted to cause the desired effect of self-focusing.

[0053] Preferably, it is proposed that during irradiation, the first substrate layer moves in a direction preset along a planned extension within the first substrate layer through the separation line. In other words: during the period when the laser beam is fixed in position and particularly not deflected or shifted by a pivotable mirror, the movement is carried out to generate the separation line in such a way that the first substrate layer moves relative to the laser source and particularly relative to the laser beam fixed in position. Thereby, it can be advantageously ensured that the laser hits each part as vertically as possible to avoid the separation line becoming uneven due to the changed orientation. In addition, it is advantageously possible to prevent the laser from being laterally reflected by the irradiated substrate. Instead, with the surface orientation of the first substrate layer being correspondingly constant, the retroreflected light can be restricted to a specified spatial volume.

[0054] Preferably, it is proposed that the separation is achieved only by irradiation with a laser. In other words: in a particularly preferred embodiment, fracture has been caused by self-focusing. Thereby, a method that can be particularly simply implemented is provided because no other additional working steps are required to cause fracture. In an exemplary embodiment, the laser beam is directed to at least one point in the focal plane to generate a direct fracture of the chemical bond there. In particular, the covalent bonds in ceramic or polymer materials can be directly fractured. The energy density of the self-focusing laser beam is large enough here so that the electrons forming the covalent bond are removed from the molecular orbit.

[0055] Another subject matter of the present invention is a device for performing the method according to the present invention, the device having a laser source adapted to provide a power of the laser for achieving self-focusing in a first substrate layer. All the advantages and features described for the method can be similarly transferred to the device. In particular, it has proven advantageous to use an ultrashort pulse laser source because the desired intensity can be achieved relatively simply with the laser pulses provided hereby. Furthermore, it is conceivable that the source provides control means for setting the laser power, whereby the laser power can advantageously be set to a desired magnitude in order to controllably cause self-focusing in a specific region.

[0056] Preferably, it is proposed that the device includes a holding element which is movable, in particular movable in a plane extending parallel to the main extension plane of the first substrate layer. Thereby, it is advantageously possible to perform a relative movement of the first substrate layer or the substrate composite while the laser beam remains fixed in position. Another subject matter of the present invention is a substrate comprising at least one first substrate layer manufactured by means of the method according to the present invention. All the features and characteristics of the method can be similarly transferred to the device. Description of the Drawings

[0057] Other advantages, features and details of the present invention result from the following description of preferred embodiments and from the drawings.

[0058] Shown in the drawings are:

[0059] Figure 1 A schematic diagram showing a method according to a first preferred embodiment of the present invention,

[0060] Figure 2 A schematic diagram showing a method according to a second preferred embodiment of the present invention,

[0061] Figure 3 A schematic diagram showing a method according to a third preferred embodiment of the present invention,

[0062] Figure 4a A schematic diagram showing a first method step of a method according to a fourth preferred embodiment of the present invention,

[0063] Figure 4b A schematic diagram showing a second method step of a method according to a fourth preferred embodiment of the present invention,

[0064] Figure 4c A schematic diagram showing a third method step of a method according to a fourth preferred embodiment of the present invention,

[0065] Figure 4d A schematic diagram showing a fourth method step of a method according to a fourth preferred embodiment of the present invention, and

[0066] Figure 4e Schematic view showing a fifth method step of a method according to a fourth preferred embodiment of the present invention. Detailed implementation

[0067] In the drawings, identical components or components with the same function are denoted by the same reference numerals. The drawings are not to scale. For better overview, in particular, the laser beam 2 provided for the method is shown wider. In particular, the laser beam 2 is symbolically drawn as a beam, although preferably high-energy laser pulses are generated and directed onto the first substrate layer 2 and / or the second substrate layer 4. The self-focusing 2k of the laser beam 2 is simplifiedly shown by a converging beam bunching, the tip of which terminates in the focal plane 3. However, preferably, a large number of ultrashort laser pulses are directed along the path drawn as the laser beam 2 onto the first substrate layer 1 and / or the second substrate layer 4, and self-focusing 2k is caused by non-linear effects in the material of the first substrate layer 1 and / or the second substrate layer 4. Of particular importance is the high intensity in the focal point or focus 2f, which is in particular generated by self-focusing 2k.

[0068] Figure 1 Shows a first embodiment of the present invention. The laser beam 2 is directed onto the focal plane 3 of the first substrate layer 1. By knowing the material properties of the substrate 1 in combination with the properties of the laser beam 2 used, the focal plane 3 can be determined and specified. Preferably, the Kerr effect is used to generate chemical and / or physical (subsequent) effects especially in the environment in or near the focal plane 3, which effects cause the separation feasibility of the primary substrate sublayer 1o and the second substrate sublayer 1u in a further process.

[0069] Figure 2 Shows a second embodiment of the present invention. The substrate composite includes at least one second substrate layer 4 in addition to the first substrate layer 1. It is also conceivable to use a plurality of second substrate layers 4, which are in particular stacked, and the stack of the plurality of second substrate layers 4 is joined to the first substrate layer 1. The non-linear optical effect causing the self-focusing of the laser beam 2 has already started in at least one second substrate layer 4. In the present case, the focal plane 3 is in the first substrate layer 1. If the focal plane 3 is in the second substrate layer 4, there will be an embodiment according to Figure 1 . When using a plurality of layers 4, the focal plane 3 can also be within one of the plurality of second substrate layers and does not have to terminate in the substrate 1. Therefore, it is preferably proposed to use at least one second substrate layer 4 and thus at least one additional material in order to start the self-focusing of the laser beam 2 already before the first substrate layer 1 to be actually separated and / or before the second substrate layer 4.

[0070] Figure 3Shows a third embodiment of the present invention. In this embodiment, the self-focusing of the laser beam 2 is utilized so that the focal plane 3 is placed in the first substrate layer 1 used as the bonding layer, and the task of the first substrate layer is to connect the second substrate layer 4 and the third substrate layer 5 to each other. Thus, the present invention can also be used in particular for debonding two substrate layers of a substrate composite.

[0071] Figure 4a Shows a first method step of the method, in which an atom beam or molecule beam 6, which is preferably ionized, is injected into the first substrate layer 1. Ionized hydrogen atoms are preferably implanted into the substrate layer 1. The average penetration depth of the atoms or molecules in the first substrate layer 1 can be determined by the kinetic energy of the atoms or molecules in the atom beam or molecule beam 6. The implantation plane 8 is the plane in which the atoms or molecules are concentrated in a statistically averaged sense.

[0072] Figure 4b Shows a second method step of the method, in which a coating 7 is applied to the substrate surface, and the atoms or molecules of the atom beam or molecule beam 6 are introduced via the coating. The coating 7 is in particular a thermal, preferably natural oxide. The thickness of the coating 7 can be reduced by backgrinding, thinning back, and / or etching back. This method step is not additionally shown. Optionally feasible after applying the coating 7 is to manufacture a hybrid bonding surface. For this purpose, holes are produced in the coating 7 by means of a plurality of method steps (not shown or described), and the holes preferably even extend into the substrate layer 1. Subsequently, the holes are filled with a conductive material, preferably copper, by means of a coating process. Subsequently, the excess copper is backgrinded until the coating 7. Subsequently, the metal in the holes serves as an electrical contact. Thus, a hybrid surface composed of conductive copper contact parts surrounded by the dielectric material of the coating 7 is produced by this process. Such a hybrid surface is known to those skilled in the art. To ensure the overview of the drawings, the precise illustration of such a hybrid surface is omitted.

[0073] Figure 4c Shows a third method step of the method, in which the first substrate layer 1 is bonded to the second substrate layer 4, which is also coated, particularly preferably the same coating, for example without an implantation plane 8. The bonding is preferably a fusion bonding or a direct bonding. If both the substrate layer 1 and the substrate layer 4 have hybrid bonding surfaces, then before the bonding, the contact of the two hybrid bonding surfaces is oriented as precisely as possible relative to each other in this method step. If functional units such as microchips, MEMS, LEDs, memory modules, etc. are already present in the substrate layer 4, then the functional units are electrically connected to the first substrate layer 1 via the contact parts of the hybrid bonding surface (not shown).

[0074] Figure 4dIllustrates the fourth method step of the method, where the method is applied to separation according to another exemplary embodiment. The focal plane 3 of the laser beam 2 substantially coincides with the implantation plane 8. Here, the average difference between the focal plane 3 and the implantation plane 8 is less than 1 mm, preferably less than 100 μm, preferably less than 1 μm, particularly preferably less than 100 nm, or even less than 10 nm. Due to the self-focusing effect 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, and the very high temperature causes physical and / or chemical effects in the implanted atoms or molecules. Preferably, the physical or chemical effect is the recombination of the atoms or molecules implanted into the implantation plane 8. Especially when using implanted hydrogen ions, hydrogen atoms recombine into hydrogen molecules. Hydrogen molecules have a higher molar volume. The hydrogen gas generated in this way expands and causes damage along the implantation plane 8. The effect is known from the SmartCut TM method, and the separation by means of a self-focusing laser is now improved so that it is not necessary to perform heat treatment on the entire substrate stack in a furnace, but rather to perform heat treatment very precisely and locally along the implantation plane 8. Thereby, the method according to the invention makes a decisive extension to the SmartCut TM method known from the prior art. Any other atomic type or molecular type that causes physical and / or chemical effects that cause damage along the implantation plane 8 in the action of the laser beam 2 according to the invention can also be used.

[0075] Figure 4e Illustrates the fifth method step of the method, where the primary substrate sublayer 1o is removed from the first substrate layer 1 (see Figure 4d ). Only the secondary substrate sublayer 1u remains as a very thin layer on the cladding layer 7, especially an oxide layer. If the material of the secondary substrate sublayer 1u is silicon, the substrate thus produced is called a silicon-on-insulator substrate (English: silicon-on-Insulator, SOI). If the cladding layer 7 is a hybrid bonding surface, the copper contact is now preferably exposed upward. If functional units such as microchips, MEMS, LEDs, memory modules, etc. are also produced in the secondary substrate sublayer 1u now, the functional units are automatically connected to the functional units of the substrate layer 4 (not shown).

[0076] In an alternative embodiment, the described method is performed without the cladding layer 7, but the first substrate layer 1 is directly bonded to the second substrate layer 4. The method also relates to direct bonding. The purpose of the method is to directly connect two materials, for example, two different semiconductor materials.

[0077] Applicable to all embodiments described herein, the focal plane 3 can be determined by knowing the material properties of the first substrate layer 1 in combination with the properties of the laser used. Here, the Kerr effect is preferably used to generate chemical and / or physical effects especially in the environment in or near the focal plane 3, and these effects cause the separation feasibility of the primary substrate sublayer 1o and the secondary substrate sublayer 1u in a further process.

[0078] List of Reference Numerals

[0079] 1 First substrate layer

[0080] 1o Primary substrate sublayer

[0081] 1u Secondary substrate sublayer

[0082] 2 Laser beam / Laser

[0083] 2k Self-focusing effect

[0084] 2f Focus

[0085] 3 Focal plane

[0086] 4 Second substrate layer

[0087] 5 Third substrate layer

[0088] 6 Atomic beam or molecular beam

[0089] 7 Cladding

[0090] 8 Implantation plane

Claims

1. A method for separating a first substrate layer (1) along at least one separation line, the method comprising: - providing the first substrate layer (1), and - separating the first substrate layer (1) along the separation line, the separation line being generated by irradiating the first substrate layer (1) with a laser (2), characterized in that, in order to form the separation line, the power of the laser (2) is set such that the power of the laser (2) has a value higher than the critical power value for forming self-focusing of the laser (2) in the first substrate layer (1).

2. The method according to claim 1, wherein an ultrashort laser pulse, preferably an ns pulse, preferably a ps pulse, and particularly an fs pulse or even an as pulse is used as the laser (2).

3. The method according to any one of the above claims, wherein a laser (2) having a spatial distribution, in particular a Gaussian-shaped, Lorentz-shaped, and / or Cauchy-shaped distribution is used.

4. The method according to any one of the above claims, wherein the separation line extends along a plane extending substantially parallel to the main extension plane.

5. The method according to any one of the above claims, wherein the first substrate layer (1) is connected to a second substrate layer (4) during the irradiation, and preferably the second substrate layer (4) is traversed by the laser (2) before the laser (2) enters the first substrate layer (1) after passing through the second substrate layer (4).

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

7. The method according to any one of the above claims, wherein a lens and / or a concave mirror is used for pre-focusing.

8. The method according to any one of the above claims, wherein the separation is assisted by mechanical force action, another laser incidence, introduction of ions, atoms, and / or molecules, chemical action, and / or introduction of heat.

9. The method according to any one of the above claims, wherein the method is used for manufacturing a substrate layer composite comprising at least the first substrate layer (1) and the second substrate layer (4), wherein after the 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. The method according to any one of the above claims, wherein the first substrate layer (1) comprises a ceramic material, a polymer material, silicon, and / or germanium.

11. The method according to any one of the above claims, wherein the first substrate layer (1) moves in a direction preset along the extension of the separation line during the irradiation.

12. The method according to any one of the above claims, wherein the separation is caused only by irradiation with the laser (2).

13. An apparatus for performing the method according to any one of the preceding claims, the apparatus having a laser source adapted to provide the power of the laser, the power of the laser causing self-focusing in a first substrate layer (1).

14. The apparatus according to any one of the preceding claims, wherein the apparatus includes a holding element that is movable, in particular movable in a plane parallel to the main extension plane.

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

Images