Multilayer system consisting of thin layers for temporary bonding

Abstract

The present invention relates to a method for providing a multilayer system, a multilayer system, and a method for bonding and peeling.

Description

Technical Field

[0001] The present invention relates to a method for providing a multilayer system, a substrate laminate, and a method for bonding and separating using the multilayer system.

[0002] In the prior art, a plurality of methods for dissociating or separating two temporarily bonded substrates are known. The substrates are, in particular, a product substrate and a support substrate, where the support substrate enables the handling, further processing, and transportation of the product substrate. After processing, the support substrate is separated from the product substrate.

[0003] The use of a bonding adhesive is very widespread in order to enable a temporary and relatively easily dissociable bond between two substrates. This temporarily adhered coating is used, in particular, as an intermediate layer within the substrate laminate. The bonding adhesive is often a polymer, in particular a thermoplastic resin. The separation of the two substrates is performed, for example, by a shearing process at high temperature. This separation can also be performed by an additional mechanical action or chemical treatment of the bonding adhesive.

[0004] One of the latest and most important methods for separating a substrate laminate is laser lift-off. In this laser lift-off, laser light is input-coupled through a substrate that is as transmissive as possible on the substrate side and is absorbed by an adjacent coating (release layer) on the back side. The laser light is preferably input-coupled through a sufficiently transmissive support substrate. The transmissibility of the support substrate to a specific electromagnetic beam enables substantially unobstructed access of photons to the release layer.

[0005] A method of separating two substrates from each other consists in inserting and adhering a special release layer in combination with a bonding adhesive, especially on a particularly transparent support substrate. The transparency of the support substrate for a specific electromagnetic beam allows unobstructed access of photons to the release layer. The release layer is correspondingly changed by photons, reducing the adhesive force to the bonding adhesive. US Patent No. 10,468,286 describes this type of method. Depending on the location where the bonding adhesive is applied, i.e., directly on the support substrate or after the release layer, the bonding adhesive must also be sufficiently transparent for the selected electromagnetic beam.

[0006] In laser delamination, polymers, especially polyimide-based polymers, can be used as the release layer. This is because polymers can be selectively removed using a UV laser beam source. This separation occurs at the support substrate-bonding adhesive interface. The UV laser source used for this requires a support substrate made of glass that has the necessary transparency for a specific electromagnetic beam in the UV region. US Patent No. 9,827,740 shows a system consisting of a bonding adhesive and a polyimide release layer directly applied to a support substrate made of glass. In US Patent No. 10,703,945, the bonding adhesive contains a light-absorbing material, whereby only one polymer layer is used for simultaneous bonding and delamination.

[0007] The release layer may especially be a metal layer. For example, in International Publication No. 2011 / 159456, an adhesive layer having a metal layer for laser delamination is used. According to the strong absorption of the laser beam by the metal coating, separation of the product substrate and the support substrate is possible. However, in International Publication No. 2011 / 159456, bonding of the two substrates is impossible without a bonding adhesive. US Patent No. 9,269,561 also shows a release layer consisting of a bonding adhesive and a metal coating between a Si support substrate and a product substrate.

[0008] U.S. Patent No. 10,112,377 discloses various materials consisting of individual layers that can be used for the dissociation layer for laser lift-off. Here too, in addition to the dissociation layer, a bonding adhesive is necessary for the temporary bonding of the substrate.

[0009] The use of polymer bonding adhesives has the drawback that surface cleaning is essential to remove bonding adhesive residues after UV laser lift-off. Furthermore, the requirements of 3D stacked bodies and CMOS-compatible processes lead to the need for high-quality silicon support substrates that are non-transmissive in the UV region. Furthermore, polymer-based bonding adhesives are not heat-resistant in the case of relatively high temperatures.

[0010] When a metal layer is deposited on a product substrate and / or a support substrate and used as a bonding layer, in the prior art, an additional layer is indispensable in advance in order to enable gentle and sufficiently non-destructive laser lift-off. This is because the surface of the coating is removed destructively. This at least one additional layer is used as protection for the product substrate and is in particular an anti-reflection coating (AR coating). The additional protective layer is, for example, a relaxation layer. WO 2015 / 014265 discloses such AR coatings and relaxation layers additionally with respect to the metal layer used as the dissociation layer.

[0011] The problem in the prior art is that the application using a laser beam can cause damage to the substrate, in particular to the expensive functional components of the substrate. This requires an additional layer, in particular a polymer-based adhesive layer, in addition to the dissociation layer. Furthermore, a bonding adhesive curable in the UV region for laser lift-off is not compatible with a support substrate made of silicon. Therefore, additional layers are indispensable in the prior art and are used as an adhesive layer for protecting the substrate and / or for bonding the substrate.

[0012] Many products in the semiconductor industry, for example electronic and optoelectronic components, consist in part of layers of inhomogeneous materials. Many of these multilayer systems are used during the bonding process, but at the same time are necessary for many manufacturing processes where they are bonded and also peeled off. In particular, in laser lift-off, only a laser of a specific wavelength can be operated efficiently.

[0013] Therefore, the object of the present invention is to at least partially eliminate, in particular completely eliminate, the drawbacks described in the prior art. In particular, the object of the present invention is to show an improved method for providing and using a multilayer system for bonding and peeling.

[0014] The object of the present invention is solved by the features of the independent claims in parallel. Advantageous developments of the present invention are described in the dependent claims. All combinations consisting of at least two features described in the description, the claims, and / or the drawings are also included within the scope of the present invention. In the numerical ranges described, values within the above boundaries should also be regarded as a disclosure of the limit values and may be claimable in any combination.

[0015] Accordingly, the present invention relates in particular to a method for providing a multilayer system consisting of at least two layers for temporarily bonding a substrate to a substrate stack, the method comprising the following steps in the following order: i) providing a multilayer system; ii) determining the absorption rate of the multilayer system for a laser beam of a specific wavelength; iii) changing at least one parameter of the multilayer system; iv) determining the absorption rate of the multilayer system for a laser beam of a specific wavelength using at least one parameter changed in step iii); v) repeating steps i) to iv) until the absorption rate is maximized, where in step i), a multilayer system with a greater absorption rate is provided each time; and including.

[0016] The multilayer system consists of at least two layers. These layers preferably have a uniform layer thickness and are arranged flatly one above the other. Here, the layer may be structured and deposited instead of being flat. In this case, the same material exists within the layers of the multilayer system. These layers are so-called thin films, particularly preferably thin films having a layer thickness in the nanometer range. Here, advantageously, known multilayer systems can be used with respect to the layer structure and arrangement.

[0017] The provision in step i) also includes the provision of the material data of the multilayer system, whereby, similarly during the determination, computer-aided calculations or simulations can be performed for each parameter. In other words, the parameters of the multilayer system are determined in various combinations with respect to the absorption rate, and the largest one of each is selected. When repeating, when the multilayer system is changed or adapted again depending on the parameters, technically significant values are selected. Based on this, the wavelength of the laser beam for which each absorption rate or adsorption degree comparison is carried out remains constant.

[0018] The parameters may be, for example, the order or structure of the layers of the multilayer system, as well as the layer thickness. When determining the absorption rate, this can be measured or calculated for each case. Preferably, the simulation of the multilayer system is carried out for each parameter.

[0019] In searching for solutions to the drawbacks described in the prior art, surprisingly, it has been found that in certain parameters, each provided multilayer system, especially in the case of established multilayer systems, can be significantly improved in terms of its absorption characteristics. In this way, the multilayer system or combination of materials can be used in other fields of use. Furthermore, thinner layers can be used for peeling, and the multilayer system can be used for bonding without additional polymer adhesives / adhesive layers and without anti-reflection layers, and at the same time can be used for peeling. Furthermore, due to the higher absorption rate, the introduction of energy, and thus heat, into the substrate arranged behind the multilayer system is minimized. Advantageously, therefore, destruction within the framework of laser peeling can be prevented.

[0020] In a preferred embodiment of the method for providing a multilayer system, it is assumed that at least one parameter of the multilayer system is the layer thickness of the layers of the multilayer system. That is to say, in other words, the layer thickness of a specific layer of the multilayer system is changed, that is, increased or reduced in order to achieve the largest possible absorption rate. Here, surprisingly, it has been found that by changing the layer thickness in a multilayer system consisting of thin layers due to the interference effect, a higher absorption rate can be achieved. Therefore, according to the present method, advantageously, the absorption rate can be significantly increased by changing the layer thickness. Here, due to the systematic change, the influence on the absorption characteristics that are otherwise not noticeable remains undetected. Advantageously, therefore, the present method requires a layer structure that is particularly optimized for interference with respect to the multilayer system. Here, the wavelength of the laser beam at which the absorption rate should be maximized remains the same.

[0021] In laser lift-off, it is restricted to a laser beam of a specific wavelength because this laser beam can be generated efficiently. Thus, rather surprisingly, it has been found that a greater absorption rate for a specific wavelength can be achieved by varying the layer thickness. By systematically varying the layer thickness of the individual layers of the coating in a multilayer system, rather surprisingly, greater absorption can be achieved, whereby the multilayer system can be used not only as a bonding layer but also simultaneously as a dissociation layer in laser lift-off.

[0022] The provision of the multilayer system can advantageously be carried out without replacement or exchange of materials, and thus existing systems (i.e., coatings or multilayer systems known to those skilled in the semiconductor industry) can be used. The existing multilayer system or materials can also be partially modified in the arrangement of the materials. However, in particular, the layer thickness is adapted with respect to the absorption characteristics of the entire multilayer system, in particular the absorptance and reflectance. This is because rather surprisingly, it has been found that the same or a greater absorption rate can be achieved when the total thickness of the multilayer system is the same or less. In this way, the multilayer system with optimized layer thickness can advantageously be used not only for bonding but also for peeling. In so doing, advantageously, the introduction of energy into another material can be slightly maintained. Furthermore, materials can be saved and the thickness of the multilayer system can be reduced. By irradiating with a laser beam of a specific wavelength and reducing the holding force of the multilayer system of the substrate laminate to be peeled as desired, advantageously, the multilayer system can also be used as a peeling layer.

[0023] In a preferred embodiment of the method for providing a multilayer system, it is assumed that at least one parameter of the multilayer system is the layer thickness of a further layer of the multilayer system. Thereby, in addition to the layer thickness of one layer, the layer thickness of a further layer of the multilayer system is also changed simultaneously. Therefore, advantageously, an efficient and rapid provision of a multilayer system having an absorption rate as large as possible is made possible by thickness change with respect to a laser beam and layer structure of a specific wavelength. If the multilayer system has three layers, preferably, one layer thickness is kept constant and simulations or a series of tests for two adjacent layers are required.

[0024] In a preferred embodiment of the method for providing a multilayer system, it is assumed that the wavelengths in steps ii) and iv) of determining are between 1100 nm and 10000 nm, preferably between 1100 nm and 5000 nm, and even more preferably between 1500 nm and 2500 nm. In the research on the multilayer system, furthermore, it has been found that for laser peeling using a multilayer system composed of thin layers, especially polymer-free layers, the absorption characteristics can be affected by parameter changes, particularly in a specific wavelength range. The laser peeling of the multilayer system according to the present invention is preferably performed in the infrared region.

[0025] Furthermore, the present invention relates to a substrate laminate including at least one multilayer system having at least two layers made of various materials provided by the method for providing a multilayer system. This multilayer system is preferably formed here as an intermediate layer to connect two substrates to the substrate laminate. This multilayer system has a layer structure with optimized layer thickness here, where the layer thickness is selected such that the multilayer system has the maximum absorption rate for a specific wavelength, and at the same time, the layer can be kept as thin as possible. That is, this multilayer system is optimally adapted with respect to layer thickness or other parameters for the highest possible absorption of an electromagnetic beam of a specific wavelength. Therefore, the multilayer system can advantageously be used as a bonding layer and a peeling layer in the substrate laminate.

[0026] Therefore, the substrate laminate can be separated non-destructively, efficiently, and easily using a laser beam, or in particular, the product substrate can be dissociated. Since the multilayer system is preferably formed on a substrate and then bonded to a further substrate, the multilayer system can be used as a bonding layer and at the same time as a release layer.

[0027] In a preferred embodiment of the substrate laminate, the multilayer system is assumed to have a total thickness between 1 nm and 10 μm, more preferably between 5 nm and 2 μm, most preferably between 10 nm and 1 μm, and most preferably between 10 nm and 500 nm in every aspect. In this way, the substrate laminate is stable and small. More advantageously, the separation can be carried out simply and efficiently along or in the region of the multilayer system.

[0028] In a preferred embodiment of the substrate laminate, each layer of the multilayer system is assumed to have a layer thickness between 1 nm and 1 μm, preferably between 1 nm and 500 nm, and more preferably between 1 nm and 250 nm. Surprisingly, it has been found that even very thin layers can achieve a high absorption rate by optimizing the layer thickness. Therefore, interference can be generated particularly well in the multilayer system with respect to thin layers having a layer thickness in the sub-wavelength range in relation to the laser beam. In particular, by combining the layer thicknesses, it is possible to advantageously achieve a high level of structural interference of the laser beam in the multilayer system.

[0029] In a preferred embodiment of the substrate laminate, the multilayer system is assumed to comprise at least one layer having a layer thickness between 10 nm and 100 nm, preferably between 20 nm and 100 nm, more preferably between 25 nm and 75 nm, and most preferably between 35 nm and 65 nm. In the development process of a method for providing a multilayer system and a substrate laminate having the multilayer system, it has been found that a particularly high improvement in the absorption rate can be achieved when at least one layer has a corresponding layer thickness.

[0030] In a preferred embodiment of the substrate laminate, at least one layer of the multilayer system is preferably assumed to contain or consist of titanium (Ti), aluminum (Al), aluminum nitride (AlN), tantalum nitride (TaN), germanium (Ge), tin (TiN), or copper (Cu). In this case, the layer thickness is particularly preferably between 25 and 75 nm.

[0031] In a preferred embodiment of the substrate laminate, at least one layer of the multilayer system is assumed to consist of amorphous silicon dioxide (SiO2). The layer thickness of this layer in the multilayer system is preferably greater than that of the other layers. Preferably, the layer thickness is greater than 100 nm, more preferably greater than 200 nm.

[0032] In a preferred embodiment of the substrate laminate, the substrate laminate is assumed to have at least one support substrate and a product substrate, and the support substrate is bonded to the product substrate by a multilayer system. Therefore, the multilayer system is arranged as an intermediate layer and at the same time as a bonding layer between the support substrate and the product substrate. In this way, the substrate laminate can be peeled off particularly quickly and efficiently.

[0033] In a preferred embodiment of the substrate laminate, it is assumed that the multilayer system, preferably the substrate laminate, does not have a polymer-based bonding adhesive. In other words, an additional bonding layer or auxiliary layer can be omitted due to the high absorption rate of the multilayer system. Particularly preferably, since the substrate laminate does not contain a polymer-based material, the substrate laminate can be processed at particularly high temperatures. Furthermore, advantageously, the subsequent and laborious removal of the adhesive layer and thus the residue can be omitted.

[0034] In a preferred embodiment of the substrate laminate, it is assumed that the multilayer system, preferably the substrate laminate, does not have an anti-reflection layer. Usually, the anti-reflection layer arranged during laser peeling on the side of the intermediate layer arranged on the opposite side of the laser beam of the multilayer system or the bonding layer can be omitted based on the high absorption rate of the optimally configured multilayer system. Furthermore, even without an anti-reflection layer, the multilayer system can advantageously prevent destruction.

[0035] In a preferred embodiment of the substrate laminate, at least one substrate arranged in a multilayer system, in particular the support substrate, is assumed to be made of silicon. In this way, the multilayer system can advantageously be irradiated through the substrate using a laser beam having a wavelength of more than 1300 nm. Therefore, laser delamination can advantageously be carried out from the back side of the substrate laminate.

[0036] In a preferred embodiment of the substrate laminate, the absorption rate of the multilayer system with respect to a laser beam of a specific wavelength is assumed to be greater than 0.5, preferably greater than 0.65, more preferably greater than 0.75, even more preferably greater than 0.85, and most preferably greater than 0.9. In this way, it is possible to ensure that the destruction of other substrates arranged behind the multilayer system during delamination of the substrate laminate, in particular the destruction of the product substrate, is prevented.

[0037] In a preferred embodiment of the substrate laminate, the multilayer system is assumed to have exactly three layers, two of the three layers being made of the same material and separated from each other by the remaining one layer. Therefore, the layer of the multilayer system in contact with the substrate includes a smaller layer made of the same material, preferably a metal.

[0038] In a preferred embodiment of the substrate laminate, the substrate laminate is assumed to be peelable by irradiating the multilayer system with a laser beam of a specific wavelength.

[0039] Furthermore, the present invention relates to a method for bonding a substrate to a substrate laminate according to the present invention, the method comprising the following steps: 1) providing a first substrate, in particular a support substrate; 2) bonding a second substrate, in particular a product substrate, to the first substrate. The method includes these steps.

[0040] The substrate provided in step 1) functions in particular as a bonding layer. By using this multilayer system, bonding can be made particularly simple and efficient.

[0041] The layers of the multilayer system may be arranged on the first substrate and / or the second substrate.

[0042] The present invention further relates to a method for separating a substrate laminate, the method comprising the following steps: a) providing a substrate laminate according to at least one of claims 5 to 13; b) irradiating the multilayer system with a laser beam of a specific wavelength through at least one substrate of the substrate laminate, and then c) separating the substrate laminate in the region of the multilayer system. The method includes the steps above.

[0043] Peeling or laser peeling can be carried out particularly simply, reliably and quickly using a substrate laminate having a substrate laminate or a thickness-optimized multilayer system.

[0044] Since the layer arrangement is often set by the process or purpose of use and by each useful substrate, layer thickness optimization is an extremely beneficial effect that is unexpected with respect to the absorption rate. This is because this arrangement provides, among other things, a hitherto unrecognized means for adapting the absorption characteristics of thin layers for laser bonding. The order of materials in the multilayer system is often maintained here due to the purpose.

[0045] In an exemplary embodiment of a method for providing a multilayer system, first, the layer thickness optimization for each individual layer L1 to Ln of a given multilayer system consisting of layers L1 to Ln is preferably carried out using three layers (L1 to L3), particularly preferably two layers (L1, L2), where the absorption of the entire multilayer system is numerically determined and also measured experimentally.

[0046] Here, parameters such as the support substrate (preferably Si), the wavelength (preferably in the IR region suitable for the Si support substrate), and the laser incident angle (e.g., 0° with respect to the surface, i.e., perpendicular in the main beam) are constant. The layer thickness can be changed simultaneously under the same laser wavelength in the simulation. Therefore, in the simulation, the thickness distribution having the maximum absorption rate of the multilayer system is required. In this test, at a predetermined layer thickness, the substrate laminate having the multilayer system is tested with respect to the remaining bonding force, ablation morphology, uniformity, and the stability of manufacturing and processing parameters.

[0047] In a preferred embodiment of the present method, it is further assumed that the material layers of the multilayer system are first identified in the arrangement of the materials, and then optimized such that maximum light absorption is achieved and reflection loss is minimized at that layer thickness. Thereby, the substrate laminate generated by bonding and optimized for laser lift-off can be separated again by laser lift-off in subsequent process steps together with the multilayer system (especially as an intermediate layer).

[0048] The separation of the substrate is here carried out by peeling or delaminating along the interface using laser irradiation. In a preferred embodiment, during peeling, laser irradiation through the support substrate is performed using light of a selected wavelength, intensity, and pulse duration (ΔΤ in the range of μs to fs). In this case, particularly preferably, the pulse is in the picosecond range.

[0049] The dissociation of the product substrate from the support substrate is carried out in a method for peeling the substrate laminate by focusing a laser beam of a specific wavelength through the support substrate onto the multilayer system optimized through interference or thickness. Thereby, at least one layer of the multilayer system is destroyed by melting, evaporation, and / or sublimation using photo- or thermochemical conversion of the light of the multilayer temporary bonding layer, or its adhesion characteristics are significantly reduced.

[0050] An important aspect of a method for providing a multilayer system is to provide a multilayer system having a maximum possible absorption rate preferably with an equal or thinner total thickness. Thus, the absorption rate of a multilayer system having a layer structure with an optimized layer thickness distribution for interference is as large as possible or nearly 1 (100%). By adapting the layer thicknesses of the individual layers in the multilayer system, higher absorption can be achieved, whereby an existing multilayer system can be used as a bonding layer and at the same time as a dissociation layer during laser lift-off.

[0051] The arrangement of the individual layers is often given by the bonding method and by bonded substrate laminates that are common and known to those skilled in the semiconductor industry. Thus, the optimization of the multilayer system is preferably carried out without material exchange, making it possible to use existing systems. The existing materials are optimized with respect to the absorbency and reflectivity of the entire multilayer system in terms of layer thickness. For example, if the optimal layer thickness is exceeded or undershot, the interference changes, and thus the absorption of the multilayer system is reduced. The layer thicknesses of the individual layers are in the nm range, thus enabling a high interaction with electromagnetic waves. Furthermore, a layer structure optimized with respect to interference enables easy laser lift-off. This is because the product substrate does not need to be protected with an additional anti-reflection coating (AR). Since this multilayer system is used for bonding and laser lift-off, preferably no additional bonding adhesive for bonding is required.

[0052] The layer thicknesses of the individual bonding and laser lift-off layers depend in particular on the technique (CVD, PVD, MBE, surface oxidation, etc.). They are in particular between 10 nm and 500 nm, preferably between 20 nm and 100 nm.

[0053] The optimization of the multilayer system is, in particular, a graphic optimization using preferably two parameters to be optimized. Multidimensional (i.e., three or more parameters) optimization is possible, but the preference is somewhat inferior. The layer thickness is determined in the optimization, in particular by simulation. In this test, further criteria for laser lift-off using layer thicknesses selected from the simulation are examined, in particular process efficiency and process stability as well as the remaining bonding force, ablation pattern and uniformity.

[0054] If the layers, substrates, and support substrates are known from a given substrate stack, it is easiest to control and change the layer thickness d of the individual layers of the multilayer system. Therefore, the layer thickness d of the individual layers of the multilayer system is first varied or changed. The laser wavelength and the laser angle (English notation: angle of incidence) remain particularly unchanged. If the multilayer system consists of two layers, both layer thicknesses d1 and d2 may be changed simultaneously. In that case, the multilayer system consists of a plurality of layers L1 to Ln, preferably layers L1 to L3. The selected parameters, in particular, for example, the two layer thicknesses d1 and d2 are changed, and the absorption rate in the lift-off structure is calculated and shown in a graph. The absorption rate in the lift-off structure should be as high as possible. Preferably, up to three layers are used to maximize absorption. In the illustrated graph, the region with high absorption must be large enough so as not to be too sensitive to changes. The layer thicknesses d1 and d2 consisting of the region with high absorption are selected with respect to the thicknesses of layers L1 and L2.

[0055] Here, the method for providing a multilayer system, the multilayer system, and the method for bonding and peeling are particularly advantageous. Because - Laser lift-off becomes possible for a significant number of bonding layers for the first time with an optimized multilayer system, - The combination of a plurality of very thin layers enables high absorption achievable through the interference of the layers of the multilayer system, - By optimizing the individual layer thicknesses of the multilayer system, the layer thickness (in the nm range) is reduced, whereby less material needs to be deposited, - The available pulse energy is orders of magnitude smaller for shorter pulses (in the range of J for high-power lasers compared to the range of μJ for "ultrafast" picosecond and femtosecond lasers), resulting in a reduced total energy incidence on the material to be processed. This leads to a shorter action time and, based on the reduced heat diffusion, a smaller heat damage zone. - The separation efficiency is further enhanced by peeling or delamination along the interface using laser irradiation with ultrashort laser pulses. - No additional layer is required to protect the product substrate (anti-reflection (AR) layer). - This is because no bonding adhesive is needed either.

[0056] Therefore, the manufacture of a substrate laminate using a multilayer system is suitable not only for bonding the substrate laminate but also for laser peeling. In this case, in particular, the existing materials of the multilayer bonding layer (multilayer system) between the support substrate and the product substrate are used. Subsequently, a transmissive support substrate is selected for irradiation on the substrate side using a laser beam. Silicon as a support substrate is transmissive, for example, when the wavelength λ > 1300 nm or λ > 1900 nm. Therefore, in this case, near-infrared (NIR) and mid-infrared (MIR) lasers are selected. Thus, silicon is suitable as a support substrate in the present invention, and laser peeling in the infrared region is possible. Therefore, a support substrate (Si) and a laser source having a laser wavelength (selection at the time of application using the Si support substrate: for example, 1940 μm, 1960 μm, or 2030 μm) are determined.

[0057] Next, the optimal layer thickness of each layer of the multilayer system, which is neither exceeded nor fallen below, is determined. The layer thickness of the material layer is optimized such that maximum light absorption (absorption rate) is achieved and reflection loss is minimized, especially in simulations. A plurality of layer thicknesses, preferably two layer thicknesses, are changed simultaneously here. Next, the substrate laminate having the multilayer system with optimized layer thickness can be laser peeled by laser irradiation having a selected wavelength, intensity, and pulse duration (ΔΤ in the range of μs to ps). Complete dissociation or separation of the product substrate by peeling or delamination along the interface using laser irradiation is performed in the region of the multilayer system.

[0058] In particular, an exemplary method for providing a multilayer system for temporarily bonding a substrate is - a first layer made of a first material having a first layer thickness, - a second layer made of a second material having a second layer thickness, and wherein the method comprises at least the following steps in at least the following order: a) determining the absorption rate of the multilayer system for a specific laser beam for various different first layer thicknesses, where the second layer thickness is constant; b) selecting the first layer thickness so as to maximize the absorption rate of the multilayer system; c) determining the absorption rate of the multilayer system for a laser beam of a specific wavelength for various different second layer thicknesses, where the first layer thickness is the first layer thickness selected in step b) and is constant; d) selecting the second layer thickness so as to maximize the absorption rate of the multilayer system; e) providing a multilayer system having the first layer thickness according to step b) and the second layer thickness according to step d). including.

[0059] In that regard, this exemplary method explains how to determine the respective optimal layer thicknesses to achieve the highest possible absorption rate of the multilayer system. Here, surprisingly, it has been found that the thin layers of the multilayer system have a high absorption straight line despite the small layer thickness. This is because this layer thickness is optimally arranged or configured for laser delamination. Here, in particular, the occurrence of interference in the multilayer system in the case of thin layers having a specific layer thickness distribution is related to a higher absorption rate. For example, if the optimal layer thickness is exceeded or fallen below, the interference changes and the absorption of the multilayer system is reduced. The layer thickness of the individual layers is in the nm range, thus enabling a high interaction with electromagnetic waves. Furthermore, the layer structure optimized through interference enables easy laser delamination. This is because the product substrate does not need to be protected using an anti-reflection coating (AR). Since this multilayer system is used for bonding and laser delamination, preferably, no additional bonding adhesive for bonding is required.

[0060] In this case, the (temporary) bonding layer consists of a multilayer system. This multilayer system is used as a connection layer and at the same time as a dissociation layer during laser delamination. Preferably, the temporary bonding layer is a plurality of layers used for the bonding and delamination methods. The materials of the multilayer system here are known to those skilled in the art. The temporary bonding layer consists of a plurality of layers, and their layer thicknesses are optimized such that the multilayer system is associated with the maximum absorption of the laser beam. The layer structure optimized through interference enables easier and improved laser delamination, in which case additional layers such as an anti-reflection (AR) protection layer and / or a relaxation layer and / or a bonding adhesive for protecting or bonding the substrate become unnecessary. The individual layers can be used, for example, as a selective absorber layer or as a phase shifter.

[0061] In this case, the product substrate is separated from the support substrate during laser delamination via an optimized multilayer system, where damage to the product substrate and / or the support substrate is sufficiently minimized or removed as much as possible. This prerequisite is, in particular, the strong absorption of the laser light by the multilayer system optimized via interference. The heat conduction during removal can be minimized or sufficiently ignored by using ultrashort laser pulses. The distribution of the absorbed laser energy is determined by the absorption in the multilayer material system, which is triggered by linear and non-linear processes during the irradiation of the material system with ultrashort laser pulses, preferably laser pulses in the ps range. Based on the high photon density that can be generated when using very short pulses, rapid removal of the material occurs, so that no or only very little heat is introduced into the remaining adjacent substrate.

[0062] Separation by delamination or detachment along the interface using laser irradiation requires maximum beam absorption of the dissociation layer consisting of a multilayer system by linear and / or non-linear processes. This delamination is mainly carried out thermally, in particular by gas generation, but also partially chemically. The intermediate layer is often an absorption layer that receives the energy of the laser beam. The auxiliary layer reacts / interacts with the absorption layer.

[0063] The transparency of the support substrate to a specific electromagnetic beam enables substantially unobstructed access of photons to the multilayer system. The support material is, for example, silicon (Si), glass, sapphire, and silicon carbide. The use of a support substrate made of glass enables the use of a UV laser, but has several drawbacks such as poor thermal conductivity and incompatibility with certain semiconductor processes and semiconductor processing equipment. Therefore, a support substrate made of silicon (Si) is preferred. Since the Si substrate is non-transparent to the UV spectrum, lasers in the infrared (IR) region, preferably the mid-infrared (MIR) and near-infrared (NIR) regions, are used. This is because a support wafer made of silicon is transparent to selected wavelengths in the mid-infrared and near-infrared. Lasers with high efficiency and high economy could only be used at specific wavelengths until now. Moreover, based on other material properties, the accessible wavelength range is significantly limited. Therefore, the laser source and the laser wavelength are fixed.

[0064] An exemplary method for temporarily bonding a product substrate to a support substrate made of silicon (Si) comprises at least the following steps: - manufacturing a multilayer system as a bonding layer and a dissociation layer for temporarily bonding the support substrate and / or the product substrate; - bonding the product substrate to the support substrate; and includes.

[0065] In this case, a bonding adhesive for temporary bonding is not required. This connection is formed, in particular, using a direct bonding method or further known bonding techniques such as metal diffusion bonding or anodic bonding.

[0066] Furthermore, a substrate laminate can be manufactured, in particular using this method, and has a product substrate and a support substrate, where the product substrate and the support substrate are bonded by a multilayer system as a temporary bonding layer and can be easily separated by laser lift-off using laser irradiation of the multilayer system.

[0067] This substrate laminate preferably has the following components: - A product substrate, - A multilayer system optimized through interference and having a layer structure for temporary bonding and laser lift-off in the IR region, - A support wafer made of silicon, which is transparent to selected wavelengths in the mid-infrared and near-infrared, are included.

[0068] In a preferred embodiment, the layers of the multilayer system are manufactured in their entirety. In a less preferred embodiment, at least one of the plurality of layers is structured and deposited.

[0069] An exemplary method for laser lift-off of a product substrate from a support substrate made of silicon, where the product substrate and the support substrate are bonded via a multilayer system, forming a substrate stack, includes in particular at least the following steps: - Accommodating and fixing the substrate stack on a substrate holder, - Focusing a peel beam, in particular a laser beam from a laser source, through the support substrate onto the multilayer system optimized through interference, thereby melting, evaporating, and / or sublimating the multilayer temporary bonding layer, - Dissociating the product substrate from the support substrate, are included.

[0070] Here, an anti-reflection layer as a protective layer on the product substrate is not necessary. Through the intended energy input and energy conversion in the multilayer system of the bonding layer, the thermal load and / or photothermal load on the substrate, in particular the functional components of the substrate, is minimized.

[0071] Furthermore, an exemplary method for manufacturing and processing a substrate stack includes the following steps: - Providing a support substrate, in particular a silicon support wafer, that is sufficiently transparent to light of a predetermined wavelength, - Manufacturing a multilayer system optimized as a bonding layer and a dissociation layer for temporarily bonding the support substrate and / or the product substrate, - A step of bonding the product substrate to the support substrate; - A step of processing the product substrate; - Focusing a peeling beam, particularly a laser beam from a laser source, through the support substrate via interference onto an optimized multilayer system, thereby dissociating the product substrate from the support substrate by melting, evaporating, and / or sublimating the multilayer temporary bonding layer; may include.

[0072] According to a preferred embodiment, the laser source is a pulse-controlled laser source, particularly an ultrashort pulse laser source.

[0073] In accordance with a further preferred embodiment, the ultrashort pulse laser source is a femtosecond laser source.

[0074] In a further preferred embodiment, the system additionally comprises a scanner for pulse laser beam scanning.

[0075] Depending on the action of the laser beam during absorption by the multilayer system, the multilayer system is separated from the substrate by delamination / lift-off and / or ablation. Preferably, the peeling is performed along the interface between the support substrate and the multilayer system (delamination).

[0076] In a more preferred embodiment, the dissociation means is a substrate holder, on which the product substrate and the support substrate are respectively fixed or can be fixed. This separation is performed, for example, by a parallel shift between the substrate and the support substrate or by lifting the substrate or the support substrate. Both are known to those skilled in the art and a detailed description is omitted. For this separation, it is also possible to use additional mechanical, physical, and / or chemical auxiliary means.

[0077] The laser acts on the multilayer system and reduces the adhesion strength between the Si support substrate and the multilayer system. This adhesion strength is reduced by more than 50%, preferably 75%, and even more preferably 90%.

[0078] Substrate and support substrate The substrate and the support substrate can each have an arbitrary shape, but are preferably circular. The diameter of this substrate is particularly industrially standardized. Industrially common diameters for wafers are 1 inch, 2 inches, 3 inches, 4 inches, 5 inches, 6 inches, 8 inches, 12 inches, and 18 inches. Since the support substrate is adapted in size and shape to the size and shape of the product substrate, the operating techniques used are as easy as possible. Here, for example, fixing, processing, and detaching a non-circular substrate such as a panel are also conceivable.

[0079] The support substrate mainly preferably consists entirely of one or more of the following materials: glass, minerals (especially sapphire), semiconductor materials (especially silicon), polymers, composite materials (SiC). In many cases, a support substrate made of glass is preferred during laser peeling. This is because here, preferably, in order to prevent heating as much as possible, an electromagnetic beam in the UV-VIS wavelength region can preferably be used in combination with a UV-VIS transmissive bonding adhesive.

[0080] When a support substrate made of silicon is preferred, an electromagnetic beam in the infrared (IR) wavelength region, especially near-infrared and mid-infrared, is required depending on the transmissibility of the Si support substrate.

[0081] In a particularly preferred embodiment, the support substrate is made of silicon. The Si support substrate is compatible with the CMOS process or the front-end process.

[0082] The transmissibility of the support substrate to the electromagnetic beam is explained by the transmittance indicating the ratio of the transmitted beam to the incident beam. However, since the transmittance depends on the thickness of the transmitted body, it is shown in units of 1 cm of length.

[0083] The support substrate has a transmittance of more than 60%, preferably more than 70%, more preferably more than 80%, most preferably more than 90%, and most preferably more than 95% in all aspects, with respect to a selected thickness of 1 cm and for each selected wavelength. Particularly preferably, the transmittance is associated with the wavelength of the peeling laser beam.

[0084] The thermal conductivity of the support substrate is preferably in the range of 0.1 W / (m*K) to 5000 W / (m*K), more preferably in the range of 0.5 W / (m*K) to 2500 W / (m*K), and even more preferably in the range of 1 W / (m*K) to 1000 W / (m*K).

[0085] The thickness of the support substrate can be changed depending on the requirements for diameter and structural stability.

[0086] Laser beam The laser beam is selected in particular to penetrate the substrate and reach the interface to be separated, where it is strongly absorbed by the multilayer coating.

[0087] Here, the laser energy is supplied in the form of very short light pulses. In a preferred embodiment, this is an ultrashort pulse laser beam.

[0088] According to a preferred embodiment, the separation results from multiphoton excitation induced by a laser beam, particularly a femtosecond laser or a picosecond laser.

[0089] The laser beam with picosecond (ps) pulses has been shown as an optimal parameter combination for the treatment of silicon in the case of thin metal layers.

[0090] The separation of the multilayer coating from the substrate is carried out by irradiating the support substrate side with light strongly absorbed by the multilayer coating, particularly a laser beam, at or near the interface between the materials to be separated.

[0091] A suitable silicon support substrate is non-transmissive at wavelengths less than 1.3 μm. Particularly suitable lasers and their wavelengths that are suitable for irradiation through the Si support substrate are as follows: - Nd:YAG (1.064 μm; 1.320 μm; 1.444 μm) - Ho:YLF (2.05 μm) - Ho:YAG (2.09 μm) - Cr:ZnSe, Cr:ZnS (MIR) That is.

[0092] In a particularly preferred embodiment, a pulsed solid-state laser, preferably a Nd:YAG laser or a Ho:YAG laser, is used. Pulsed solid-state lasers operating in the infrared region above 1.3 μm are doped with ions consisting of Er3+ (1.55 μm), Tm3+ (1.9 μm), Ho3+ (2.09 μm), or Cr3+ (2.4 μm).

[0093] Even more suitable laser wavelengths when applied together with the Si support substrate are, for example, 1940 μm, 1960 μm, or 2030 μm.

[0094] The optical output that can provide a laser beam and continuously output to the substrate, especially the output of the laser measured as the beam output, is at least 2 W.

[0095] The preferred wavelength range of the laser is between greater than 1100 nm and 10000 nm, preferably between greater than 1100 nm and 5000 nm, and even more preferably between 1500 nm and 2500 nm.

[0096] Here, a laser beam having at least two wavelengths can also be used. Then, layer thickness optimization is performed for the multilayer system with respect to the two wavelengths.

[0097] The total energy of the laser beam per substrate is set especially between 1 mJ and 500 kJ, preferably between 100 mJ and 200 kJ, and particularly preferably between 500 mJ and 100 kJ.

[0098] The laser beam can be operated in continuous mode or preferably in pulse mode. The pulse frequency is set especially between 0.1 Hz and 300 MHz, preferably between 100 Hz and 500 kHz, particularly preferably between 1 kHz and 400 kHz, and most preferably between 1 kHz and 100 kHz.

[0099] The energy incident on the substrate laminate for each pulse irradiation is set especially between 0.1 nJ and 1 J, preferably between 1 nJ and 900 μJ, particularly preferably between 1 nJ and 10 μJ.

[0100] The beam spot size is especially between 1 μm2 and 10 mm2, preferably between 5 μm2 and 1 mm2, particularly preferably between 400 μm2 and 1502 μm2 (measured at 1 / e2 of the irradiation intensity distribution of the laser spot on the substrate).

[0101] The local interval (pitch) of the laser pulses on the substrate is especially between 0.1 μm and 1000 μm, preferably between 1 μm and 500 μm, particularly preferably between 10 μm and 200 μm, and most preferably between 20 and 100 μm.

[0102] The number of pulses per substrate laminate depends on the required total energy and is especially between 10 million pulses and 10 billion pulses, preferably between 10 million pulses and 1 billion pulses, particularly preferably between 20 million pulses and 100 million pulses.

[0103] The total energy of the laser beam per substrate is set especially between 1 mJ and 500 kJ, preferably between 100 mJ and 200 kJ, particularly preferably between 500 mJ and 100 kJ.

[0104] These pulses have a length in the range of microseconds to femtoseconds (μs - fs), preferably in the range of nanoseconds to femtoseconds (ns - fs), especially 100 ns to 100 fs, and preferably 10 ps to 1 ps.

[0105] By using short pulses, very high output peaks can be achieved without increasing the average laser output. Under various different pulse durations, the pulse energy available with shorter pulses is orders of magnitude less (within the J range of high-power lasers as compared to μJ of "ultrafast" picosecond and femtosecond lasers), so the total energy input to the material to be processed is reduced, which generally leads to a smaller heat damage zone based on the shorter action time and thus less heat diffusion.

[0106] Due to the high output density, the material can be heated so that its removal or sublimation is achieved in the shortest time. Thus, the short action time leads to less heat energy introduction to the underlying material, which results in minimal damage to the unprocessed area.

[0107] When the pulse duration is less than a few picoseconds, for most materials, it starts with direct ablation by the laser beam, whereas when the pulse duration is relatively long, additional effects caused by the interaction of the laser, laser-excited plasma and the material in various aggregation states promote thermally induced removal.

[0108] In the case of high beam intensity, plasma illumination during material ablation by the laser beam is used. After the use of plasma illumination, avalanche ionization and thermal ionization occur in such a range that material damage is no longer limited to the laser focus. It is known from the prior art that the energy threshold for forming the illuminated plasma decreases significantly with the shortening of the pulse duration.

[0109] Overall, ultrashort pulses in the ps range are preferred because linear and non-linear absorption occur in the multilayer system. 10 12 From a laser intensity of 10 W / cm2, the interaction between photons and atoms occurs not only by one-photon absorption but also by multi-photon absorption. Thus, depending on the intensity quantity, a linear or non-linear process may be the main proportion of absorption. Achieved with ultrashort pulses 10 12~10 14 At intensities between

[0110] Pulses having a high intensity and a pulse duration of less than 100 ps can generate plasma illumination. This plasma illumination advantageously leads to a significantly enhanced local absorption in the multilayer system due to the interaction of free electrons, ions, and the remaining electromagnetic field.

[0111] Preferably, the pulse energy and / or the pulse duration and / or the length of the pulse train are temporally modulated by a control unit of the laser beam source that generates the pulsed laser beam, where this modulation is preferably driven and controlled via an external signal generator. Preferably, the energy input-coupled into the process zone by the laser beam is temporally modulated by modulation of the pulse duration of the laser pulse, where the pulse duration is preferably modulated between 0.1 ps and 20 ps.

[0112] As a synonym for the irradiation surface, the spot size or the laser spot size is known to those skilled in the art.

[0113] The shape of the irradiation surface is in particular circular, and in other preferred embodiments it is elliptical or rectangular.

[0114] In laser lift-off, the laser light is input-coupled on the substrate side through a substrate that is as transmissive as possible, and absorbed by the adjacent dissociation layer on the back side. The laser light is preferably input-coupled through a sufficiently transmissive support substrate made of silicon. An Si support substrate having a normal thickness between 725 and 775 μm becomes increasingly transmissive for wavelengths starting from 1100 nm. Here, ultrashort pulses in the ps range are used, so that wavelengths above 1300 nm are preferred due to the absorption by the non-linear interaction of silicon in the range below 1300 nm, and wavelengths above 1900 nm are even more preferred. Shorter pulse durations require higher wavelengths due to the sufficient transmissibility of the Si support substrate.

[0115] In the interaction between a laser beam and a material, optical and physical processes play a role. These are, for example, the numerical aperture (NA) of the lens when focusing the laser beam onto the material and the energy of the laser beam or the laser output density.

[0116] The following parameters: - Pulse energy, - Numerical aperture NA, - Pulse duration, - Pulse sequence frequency, - Laser wavelength, - Beam profile, - Pulse shape, are associated with various interactions between the ultrashort pulse laser and the material.

[0117] Here, the following criteria are evaluated according to the parameter settings for the multilayer system: - Ablation area per shot, - Peeling area or delamination area per shot, - Pulse energy with respect to the ablation threshold per shot, - Pulse energy with respect to the delamination threshold per shot, are evaluated.

[0118] For example, the following parameters of the multilayer system: - Thickness of individual layers using simulation and in tests, - Arrangement / order of individual layers if necessary, - Material of additional layers if further layers are required, can be identified.

[0119] Here, the multilayer system is known to those skilled in the art, and thus, no material optimization is performed. The materials of the multilayer system are coatings known to those skilled in the art, and these coatings are used during bonding and are optimized for the highest possible absorption of the laser beam at their layer thicknesses related to interference. In many cases, laser peeling is made possible by the choice of layer thickness.

[0120] Multilayer System and Multilayer Design Optimization The consideration underlying the present patent invention is to provide an optimized multilayer structure via interference for bonding and laser delamination of substrates.

[0121] During beam absorption, many factors play a role. The interaction is here influenced by both the properties of the laser light and the properties of the material. In the case of laser light, the wavelength, polarization, angle of incidence, as well as the spatial and temporal properties of the beam are most important, while in the case of the material, especially the chemical composition and microscopic or macroscopic properties have an impact.

[0122] In the case of various coatings, in the prior art, the effects of scattering, reflection, and absorption are used empirically. Optimization of individual parameters is also common, but the adaptation of the layer thickness for optimally enhancing absorption here minimizes losses due to reflection or transmission, and comparing the pulse duration with the layer thickness has not been known in the prior art until now. Here, factors such as, for example, the laser wavelength, angle of incidence, and layer material are kept constant.

[0123] In multilayer design optimization, existing materials and coatings known to those skilled in the semiconductor industry are used, which are optimized, especially in terms of their layer thickness, to achieve maximum absorption via the interference of electromagnetic beams in the multilayer system.

[0124] Since the layer thickness is in the sub-wavelength range, the multilayer system has a wave impedance different from that of the materials individually used for the individual layers with respect to the incident wave. Thereby, the absorption of the multilayer system is significantly improved.

[0125] When an electromagnetic beam can be absorbed within a material, the strength of absorption is described by material parameters, and the absorption rate usually depends on multiple parameters (such as temperature, wavelength, etc.). Absorption or the absorption rate is shown between 0 and 1. From the beam incident on the surface of the body, usually, part is reflected, part passes through the body, and the rest is absorbed. The absorbed energy increases the internal energy of the body. The absorption rate (also known as the absorption coefficient or spectral absorption coefficient SAK) indicates what portion of the incident beam is absorbed. This can take a value between 0 and 1. The absorption rate can depend on the incident direction and frequency of the incident beam.

[0126] If the absorption for various wavelengths and various layer thicknesses of the layers selected from the multilayer system is shown in a graph, the display of various absorption regions is possible. Generally, this absorption is mainly an interaction including the loss of the electromagnetic field in the material, which can be described (usually) via the electric susceptibility and thus the complex refractive index n + iκ. For example, it is even possible to display non-linearity such as that which plays a role in the folding of short pulses when the response to the rise of the electric field increases proportionally to a higher potential. Further, the simulation is used to show that due to the change in the thin layer thickness in the nm range, the improvement of the absorption of the entire multilayer system can be achieved by the occurrence of multiple interferences at the interfaces between the individual layers of the multilayer system.

[0127] Preferably, the laser wavelength is constant, and two parameters, in particular the layer thicknesses d1 and d2 of two layers from the multilayer system, are changed simultaneously, and the absorption is calculated. By optimizing the layer thicknesses in the multilayer system, higher absorption and reduction of losses due to scattering or reflection, and thus higher laser ablation efficiency, can be achieved. The scattering or diffraction effect can also be utilized to change the propagation direction of the light and thereby extend the interaction duration. The scattering or diffraction effect can also be utilized to protect the next layer below it or the product substrate below it.

[0128] The layer thicknesses of the individual layers L1 to Ln of the multilayer system, preferably consisting of L1 to L3, are optimized, where the absorption of the entire multilayer system is numerically determined and also experimentally measured. The individual influences of these layers are examined and optimized with respect to the efficiency and stability of the effect.

[0129] The separation of the multilayer system from the substrate is carried out by irradiation from the substrate side using light, in particular a laser beam, which is strongly absorbed at or near the interface between the materials to be separated of the multilayer coating. In adjacent layers, the following exemplary effects are utilized: structural interference, scattering, diffraction, and phase shift.

[0130] The layers of the multilayer system can be deposited by chemical or physical vapor deposition, sputtering, evaporation, epitaxy and / or spin coating, as well as by combinations thereof or other suitable techniques.

[0131] Due to the enhanced and optimized local absorption of the coating, advantageously, an antireflective coating (English notation: antireflective layer, AR) for significantly reducing Fresnel reflection is not required.

[0132] Advantageously, an additional bonding layer, in particular a bonding adhesive, is also not required. This is because a multilayer system, especially one containing a photothermal and multilayer conversion layer that is metallic or contains metal, is also a bonding layer at the same time. An additional sacrificial layer is also not required.

[0133] The energy absorbed in this case induces the decomposition of the multilayer coating, in which case separation is caused at the interface between the substrate and the coating. The decomposition mechanism can be, for example, sublimation or a chemical reaction. This decomposition can be initiated thermally or photochemically here. The separation is assisted especially when gaseous products are formed during decomposition.

[0134] Preferably, at least one layer of the multilayer system is the following compound or element: - Metals, such as Ti, Au, Ag, Cu, Fe, Ni, Al, Cr, Pt, Sn, - Alloys, - Semiconductors (e.g., Ge), - Compounds, particularly nitride compounds, particularly TiN, TaN, AlN, GaN, InN, SiN, Si3N4, - Compounds, particularly oxide compounds, particularly SiO2, TiO2, - Compounds, particularly dielectrics - Ceramic materials, particularly silicon carbide (SiC) and aluminum oxide (Al2O3), - Highly absorbent non-metals, particularly polymers having nanoparticles (polymers having Al or C particles), consisting of any one or a combination thereof.

[0135] Here, each layer of the multilayer system can consist of a material or a combination of materials from one of the main groups 3 (boron group), 4 (carbon group), and 5 (nitrogen group) of the periodic table.

[0136] In a somewhat preferred embodiment, the material is deposited as a 2D structure, such as a graph or a 3D structure, on the individual layers of the multilayer system rather than over the entire surface.

[0137] The multilayer system is deposited on a product substrate and / or a support substrate as a series of layers of various compounds or elements. Here, n coatings may be formed as the multilayer system (L1 to Ln). Preferably, up to three layers are used for the multilayer system (L1 to L3).

[0138] In a further embodiment, at least one compound or one element is deposited alternately a plurality of times.

[0139] Individual layers can be used, for example, as a selective absorber layer or as a phase shifter. Examples of absorbers are metals such as aluminum (Al) or gold (Au). Silicon dioxide (SiO2) can be used, for example, as an auxiliary layer and / or a phase shifter for positioning the maximum magnetic field of the wavelength inside the selective absorber. The layer thickness here is less than the nm range. Thicker (metal) coatings can be used as mirrors if necessary.

[0140] Preferably, additional layers such as a sacrificial layer and / or an antireflection layer and / or a relaxation layer and / or a bonding adhesive are not required and are omitted.

[0141] The individual layers of the multilayer coating have a thickness between 1 nm and 10 μm, preferably between 1 nm and 1 μm, and even more preferably between 5 nm and 500 nm. With a very thin layer sequence, a high interaction with the electromagnetic beam is possible. This high interaction with very thin layers is used to facilitate laser ablation. By optimizing the individual layer thicknesses of the multilayer system, the layer thickness (nm range) is reduced, which advantageously requires depositing less material.

[0142] Metals are strong absorbers and can already block the laser beam from a layer thickness of less than 100 nm. In contrast, organic absorbers often require a layer thickness of more than 3 μm to absorb 67% of the incident light.

[0143] The thickness of the multilayer system is preferably between 1 nm and 10 μm, even more preferably between 5 nm and 1 μm, and most preferably between 10 nm and 1 μm.

[0144] Laser ablation optimization process for a substrate laminate having a multilayer system and a silicon support substrate The optimization process for separation by ablation or delamination along the interface using laser irradiation includes, for example, the following steps: - Step of selecting a laser; Silicon as a support substrate is mainly transparent at wavelengths λ > 1300 nm or λ > 1900 nm, and thus, here, near-infrared (NIR) and mid-infrared (MIR) lasers that exhibit low linear and non-linear absorption in the Si support substrate are selected. - Step of using an existing material in a multilayer bonding layer between the Si support substrate and the product substrate; This multilayer system enables the optimization of the absorption required for laser lift-off, which is controlled via interference. The individual layers of the multilayer system can be used, for example depending on the layer thickness, as selective absorber layers or as phase shifters or mirrors, and thus the absorption in the multilayer system as a whole can be maximized. Examples of absorbers are metals such as aluminum (Al) or gold (Au). Silicon dioxide (SiO2) and aluminum nitride (AlN) can be used, for example, as phase shift layer to position the maximum magnetic field of the wavelength inside the selective absorber. The layer thickness here is in the range below nm. Thicker coatings can be used as mirrors if necessary. The metal layer can be used, for example depending on the layer thickness, as a mirror layer (layer thickness > 100 nm) or as a selective absorber layer (layer thickness < 10 μm). - Step of optimizing the laser throughput and laser quality; In a preferred embodiment, this is an ultrashort pulsed laser beam. The laser source and laser wavelength are fixed parameters. Here, for example, the following laser parameters: pulse duration, pulse sequence frequency, energy, shape of the irradiated surface per pulse, multi-spot laser are optimized. - Step of optimizing the material layer; The material layer is optimized such that maximum light absorption is achieved via interference at its layer thickness and reflection losses are minimized. The increase in absorption due to the optimization of the layer thickness is spatially localized and amplified inside the multilayer system. Deviations above or below the optimal layer thickness of the individual layers of the multilayer system can lead to a significant reduction in absorption.

[0145] The optimization of the layer thickness is carried out, in particular, by simulation and / or laser lift-off tests on a substrate laminate having a layer thickness selected from the simulation. In this test, the bonding force remaining during laser lift-off, the ablation morphology, and the uniformity are examined. The manufactured system is also examined for the stability of the manufacturing and processing parameters.

[0146] Further advantages, features, and details of the present invention can be obtained based on the following description of the preferred embodiments and the drawings.

Brief Description of the Drawings

[0147]

Fig. 1a

Fig. 1b

Fig. 1c

Fig. 2

Fig. 3a

Fig. 3b

[0148] In the figure, the same reference numerals are given to the same components or components having the same function.

[0149] According to FIG. 1a, three layers L1(5), L2(6), and L3(7) are exemplarily fully deposited on the product substrate 2 and / or the support substrate 3. The structure 8 is present in and / or on the product substrate 2. Here, the layer thicknesses d1, d2, and d3 of the respective coatings L1(5), L2(6), and L3(7) are optimized. Thus, the multilayer system 4 consists of a plurality of layers 5, 6, 7, and these layers are selected such that the multilayer system 4 is associated with maximum absorption of the laser beam during the laser lift-off process. The layer structure 4 optimized via interference enables easier and improved laser lift-off, in which case additional layers such as, for example, an anti-reflection coating and / or a relaxation layer and / or a bonding adhesive for protecting the substrate or for bonding the substrate are not required.

[0150] The individual layers 5, 6, 7 of the multilayer system 4 have a thickness between 1 nm and 1 μm, preferably between 1 nm and 500 nm, and even more preferably between 1 nm and 250 nm. The very thin layer sequence enables a high interaction with the electromagnetic wave of the laser irradiation.

[0151] The thickness of the multilayer system 4 is preferably between 1 nm and 10 μm, even more preferably between 5 nm and 2 μm, most preferably between 10 nm and 1 μm, and most preferably between 10 nm and 500 nm in all aspects.

[0152] After coating the product substrate 2 and / or the support substrate 3 with the multilayer system 4, the product substrate 2 is joined to the support substrate 3 by alignment, contact, and bonding in a (temporary) bonding method according to FIG. 1a. This (temporary) bonding technique is known to those skilled in the art.

[0153] Figures 1a and 1b show three coatings L1 - L3 (5, 5’, 6, 6’, 7, 7’), but any other number n of coatings may be formed. Figure 1c shows one embodiment of a multilayer system having, for example, two coatings 5’’, 6’’. Here, the layer thickness of each individual layer L1 - Ln of the multilayer system consisting of layers L1 - Ln is optimized, where the absorption of the entire multilayer system is measured. Preferably, for example, first two layer thicknesses d1 and d2 are simultaneously changed under the same wavelength in the simulation, and the resulting absorption is determined according to Figure 3b. The layer thicknesses d1max and d2max of the coatings 5’’, 6’’ associated with the maximum, efficient, and stable absorption are selected. Further variable laser parameters are optimized, in particular, by analysis during laser delamination of the substrate laminate in the test.

[0154] Figure 1b shows a further embodiment of a substrate laminate 1’ consisting of a support substrate 3’, a multilayer system 4’ having three layers L1 - L3 (5’, 6’, 7’), and a product substrate 2’ having a structure.

[0155] Figure 1c shows another embodiment of a substrate laminate 1’’ consisting of a support substrate 3’’, a multilayer system 4’’’ having two layers L1 (5’’) and L2 (6’’), and a product substrate 2’’.

[0156] In the following paragraphs, based on the multilayer systems of Figures 1a - 1c, a plurality of non - limiting examples of multilayer systems (for example, L1 - L2 - L3 or L1 - L2) are shown. Multilayer systems known to those skilled in the art and also used in particular for CMOS - compatibility processes or front - end - compatibility processes in the semiconductor industry are, for example, the following: SiO2 - metal - SiO2 (L1 - L2 - L3), SiO2 - metal1 (L1 - L2), metal1 (layer thickness d1) - oxide compound or nitride compound (for example, SiO2) - metal1 (layer thickness d2) (L1 - L2 - L3), SiO2 - nitride compound - SiO2 (L1 - L2 - L3), Nitride compound - SiO2 (L1 - L2), Oxide compound or nitride compound (e.g., SiO2) - Metal1 - Metal2 (L1 - L2 - L3), Metal1 - Metal2 - Metal3 (L1 - L2 - L3), Metal1 - Metal2 (L1 - L2), Metal1 - Metal2 - Metal1 (L1 - L2 - L3), consisting of.

[0157] In particular, the following table:

Table 1

[0158] The TEOS layer is a layer made of amorphous silicon dioxide (SiO2) and is preferably polished densely by chemical - mechanical polishing (CMP).

[0159] The 300 - mm silicon support substrate has a thickness of 725 μm in an alternative embodiment.

[0160] After layer L2, a bonded product substrate follows (also a substrate made of silicon). During lift - off, the laser first penetrates the 775 - μm silicon support substrate and then penetrates layers L1 and L2.

[0161] The laser wavelength is determined by the choice of the support substrate and is not changed. The laser angle of incidence is also maintained constant.

[0162] For the multilayer system, the following further specific examples: SiN - SiO2 (L1 - L2), TEOS (50 - 250 nm) - TiN (20 - 100 nm) - TEOS (50 - 400 nm) (L1 - L2 - L3), TiN (50 nm) - TEOS (400 nm) (L1 - L2), SiO2 (thermal, 50 - 100 nm) - TiN (50 nm) - TEOS (400 nm) (L1 - L2 - L3), is mentioned.

[0163] Preferably, at least one layer of the multilayer system is one of the following compounds or elements: - Metals, such as Ti, Au, Ag, Cu, Fe, Ni, Al, Cr, Pt, Sn, - Alloys, - Semiconductors (e.g., Ge), - Compounds, especially nitride compounds, especially TiN, TaN, AlN, GaN, InN, SiN, Si3N4, - Compounds, especially oxide compounds, especially SiO2, TiO2, - Ceramic materials, especially silicon carbide (SiC) and aluminum oxide (Al2O3), - Highly absorbent non - metals, especially polymers with nanoparticles (e.g., polymers with Al or C particles), consisting of individuals or combinations thereof.

[0164] Individual layers of the multilayer system can be used, for example, as selective absorber layers, auxiliary layers, and / or phase shifter layers, or as mirror layers, depending on, for example, layer thickness and material, and thus absorption in the multilayer system as a whole can be maximized. Metal layers can be used, for example, as mirror layers (layer thickness > 100 nm) or as selective absorber layers (layer thickness < 10 μm) depending on the layer thickness. Silicon dioxide (SiO2) and aluminum nitride (AlN) can be used, for example, as phase shifter layers.

[0165] The absorption layer is often the middle layer in a three - layer system. In a two - layer system, the absorption layer is often the first layer. The absorption layer receives the energy of the laser beam.

[0166] In one example, the absorption layer consists of SiN and the auxiliary layer consists of SiO2. Due to the interaction between the SiN and SiO2 layers, NOx gas is generated, which leads to layer splitting and thus peeling.

[0167] In a preferred embodiment, the layer thickness of the absorption layer is 10 nm to 200 nm, and the thickness of the auxiliary layer is 1 to 1000 nm.

[0168] Figure 2 shows a cross-sectional view of the product substrate - support substrate - laminate 1 during laser lift-off by irradiating the multilayer system 4 with the laser beam 11. A suitable light source is, for example, a light source that emits ultrashort light pulses having a duration of 10 ps to 50 ps and a repetition frequency of 1000 Hz.

[0169] The ultrashort pulse laser beam 11 is focused on the process zone 12 via the optical system 9. Here, relative movement between the substrate laminate 1 and the laser beam 11 is carried out using substrate laminate positioning and / or beam positioning (not shown). Further optical elements include, for example, beam shaping elements, scanners, modulators, etc., and are known to those skilled in the art.

[0170] The relevant wavelength range for Si as the support substrate is between 1940 nm and 2140 nm. This is because Si has a very strong non-linearity and non-linear absorption / refraction extends beyond 1700 nm, which leads to self-focusing. The energy density and power density required for ablation are also important here. For other support materials (e.g., sapphire), the wavelength and laser selection often differ.

[0171] Figure 3a describes the flow of a method for optimizing an exemplary multilayer system 4 consisting of three layers L1, L2, and L3 (5, 6, 7) according to Figure 1a to be used for the temporary bonding and laser lift-off of the product substrate 2 and the support substrate 3. The product substrates 2, 2', 2'' may be considered to have no topographical shaped portions either because the structural portion 8 is absent or because the structural portion 8 is directly manufactured within the product substrates 2, 2', 2''. Alternatively, the structural portion may be, for example, a chip or a structured coating and can form a topographical shaped portion.

[0172] According to FIG. 3a, in order to determine the maximum absorption of the multilayer system at different wavelengths, the thickness d1 of the first layer L1 is changed between 0 and 100 nm. Region 1 in FIG. 3a shows the maximum absorption. The region where the numbers in FIG. 3a are increasing indicates that the absorption of the multilayer system is decreasing. Here, the thicknesses d2 and d3 of the other two layers L2 and L3 are kept constant. The individual thicknesses of the layers affect the interference pattern and thus the absorption rate of the multilayer system. By determining the optimal layer thicknesses d1, d2, and d3, the maximum absorption of the multilayer system for easy and improved laser lift-off is obtained. The depiction according to FIG. 3a is shown using simulations and determined using a series of measurements. Here, the optimization or replacement of the materials of the individual layers is omitted, and in the existing multilayer system, by optimizing the layer thickness, easy laser lift-off by maximum absorption is achieved. The absorption can be increased from <10% to >90%.

[0173] First, the absorption rate is calculated using a known solution algorithm that uses a linear estimation based on the Fresnel equation of the multilayer system based on the layer thickness and the (linear but complex-valued) refractive index. Furthermore, the non-linear characteristics can be used in more complex simulations that also take into account the magnetic field strength distribution.

[0174] In an alternative embodiment with respect to FIG. 3a, for example, according to FIG. 3b, for a system consisting of two layers L1 and L2 at a selected laser wavelength, the absorption can be shown to depend on the two layer thicknesses d1 and d2. If the layers, substrates, and support substrates are known from a given substrate stack, the layer thickness d of the individual layers of the multilayer system can be most easily controlled and changed. Thus, the layer thickness d of the individual layers of the multilayer system is first optimized. The laser wavelength and the angle of incidence remain particularly invariant. When the multilayer system consists of two layers, according to FIG. 3b both layer thicknesses d1 and d2 can be changed simultaneously. The selected parameters, in particular, for example, the two layer thicknesses d1 and d2 are changed and the absorption rate in the delamination structure is calculated. The absorption rate in the delamination structure must be as high as possible. Preferably, up to three layers are used to maximize absorption. Similar to FIG. 3a, region 1 in FIG. 3b shows the maximum absorption. The regions where the numbers are increasing indicate that the absorption of the multilayer system is decreasing. Region 1 with greater absorption in the illustrated graph must be large enough so as not to be overly sensitive to changes.

Explanation of Signs

[0175] 1 Substrate stack 2 Product wafer 3 Support wafer 4 Multilayer system 5 Layer L1 6 Layer L2 7 Layer L3 8 Structure 9 Optical system 10 Optical element 11 Laser beam 12 Process zone

Claims

1. In particular, a method for providing a multilayer system (4) consisting of at least two layers (5, 6, 7) for temporarily bonding a substrate to a substrate stack (1), the method comprising the following sequence: i) providing a multilayer system (4); ii) determining the absorption rate of the multilayer system (4) with respect to a laser beam (11) of a specific wavelength; iii) changing at least one parameter of the multilayer system (4); iv) using at least one parameter changed in step iii) to determine the absorption rate of the multilayer system (4) with respect to the laser beam (11) of the specific wavelength; v) repeating steps i) to iv) until the absorption rate reaches a maximum, where in step i), a multilayer system (4) having a greater absorption rate is provided respectively; A method comprising the above.

2. The method according to claim 1, wherein the at least one parameter of the multilayer system (4) is the layer thickness of the layers (5, 6, 7) of the multilayer system (4).

3. The method according to claim 2, wherein the at least one parameter of the multilayer system (4) is additionally the layer thickness of further layers (5, 6, 7) of the multilayer system (4).

4. The method according to any one of claims 1 to 3, wherein the wavelength in steps ii) and iv) of determining is between 1100 nm and 10000 nm, preferably between 1100 nm and 5000 nm, and even more preferably between 1500 nm and 2500 nm.

5. A substrate stack (1) comprising at least one multilayer system (4) having at least two layers (5, 6, 7) made of different materials provided according to at least one of claims 1 to 4.

6. The multilayer system (4) has a total thickness between 1 nm and 10 μm, more preferably between 5 nm and 2 μm, most preferably between 10 nm and 1 μm, and most preferably between 10 nm and 500 nm in all aspects, of the substrate laminate (1) according to claim 5.

7. Each layer (5, 6, 7) of the multilayer system (4) has a layer thickness between 1 nm and 1 μm, preferably between 1 nm and 500 nm, and more preferably between 1 nm and 250 nm, of the substrate laminate (1) according to claim 5 or 6.

8. The multilayer system (4) comprises at least one layer (5, 6, 7) having a layer thickness between 25 nm and 75 nm, of the substrate laminate (1) according to any one of claims 5 to 7.

9. The at least one layer (5, 6, 7) of the multilayer system (4) contains titanium (Ti), aluminum (Al), aluminum nitride (AlN), tantalum nitride (TaN), germanium (Ge), tin (TiN), or copper (Cu), and is preferably composed of them, of the substrate laminate (1) according to any one of claims 5 to 8.

10. At least one layer (5, 6, 7) of the multilayer system (4) consists of amorphous silicon dioxide (SiO₂), of the substrate laminate (1) according to any one of claims 5 to 9.

11. The substrate laminate (1) has at least one support substrate (3) and a product substrate (2), and the support substrate (3) is bonded to the product substrate (2) by the multilayer system (4), of the substrate laminate (1) according to any one of claims 5 to 10.

12. The multilayer system (4), preferably the substrate laminate (1), does not have a polymer-based bonding adhesive, of the substrate laminate (1) according to any one of claims 5 to 11.

13. The multilayer system (4), preferably the substrate laminate (1), does not have an antireflection layer, of the substrate laminate (1) according to any one of claims 5 to 12.

14. A method for joining a substrate to the substrate laminate (1) according to any one of claims 5 to 13, comprising: 1) providing a first substrate, in particular a support substrate (3); 2) joining a second substrate, in particular a product substrate (2), to the first substrate.

15. A method for peeling a substrate laminate (1), the method comprising the following steps: a) providing a substrate laminate (1) according to any one of claims 5 to 13; b) irradiating a laser beam (11) of a specific wavelength through at least one substrate of the substrate laminate (1) onto a multilayer system (4), and then c) separating the substrate laminate (1) in the region of the multilayer system (4). ​

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