Method for separating a support substrate, solvent for such a method, and device for such a method

Abstract

The invention relates to a method for separating a support substrate (1) from a product substrate (4, 4n), involving: - providing the support substrate (1) and the product substrate (4, 4n) in a bonded state, in which the support substrate (1) and the product substrate (4, 4n) are bonded to one another, in particular temporarily, via a layer system between the support substrate (1) and the product substrate (4, 4n), the layer system having a separating layer (2, 2') and a first additional layer (3) which is different from the separating layer (2, 2'), the separating layer (2, 2') and the first additional layer (3) being inorganic, - separating the support substrate (1) and the product substrate (4, 4n) by irradiating the layer system, preferably the separating layer, with laser light (12), and - cleaning the product substrate (4, 4n) and / or the support substrate (1) with a common solvent, by means of which residue is removed from both the separating layer (2, 2') and the first additional layer (3), preferably in a common cleaning step.

Description

[0001] ■□I

[0002] EV Group E. Thallner GmbH MSP Ref: 46721 PT-WO PM / SK

[0003] Method for separating a support substrate, solvent for such a method and apparatus for such a method

[0004] The present invention relates to a method for separating a carrier substrate, a solvent for such a method and an apparatus for such a method.

[0005] In substrate bonding and debonding, two substrates are first joined together so that one of the substrates—which, for example, lacks sufficient internal stability for a subsequent process or treatment due to its thinness or strength—can be processed with the support of the second substrate. The processed substrate is called the product substrate. The supporting substrate is called the carrier substrate.

[0006] In the prior art, polymers are predominantly used to create a so-called temporary bond, i.e., a non-destructively removable bond. For this purpose, at least one polymer is applied to a substrate using a process, in particular a centrifugal coating process. The organic polymer layer serves as the bonding adhesive. The support substrate is predominantly coated with the polymer, and the support substrate is bonded to the product substrate. After bonding the product substrate to the support substrate, the product substrate is further processed so that it can be separated from the support substrate in a subsequent process step. The organic polymer layer used as the bonding layer can also be used as an organic or polymeric separation layer to separate the bonded substrates from each other (debonding). Various methods exist in the prior art for separating the support substrate.

[0007] The debonding of both substrates is achieved, for example, through a shearing process at elevated temperature, as in slide-off debonding. Debonding can also be accomplished through additional mechanical action or chemical treatment of the bonding adhesive. Another possibility is the use of photosensitive release layers. A particularly preferred method for separating substrate stacks is laser debonding. In laser debonding, laser light is coupled into the substrate side, for example, through a substrate that is as transparent as possible, and absorbed in the adjacent release layer on the back side. The laser light is preferably coupled into the substrate through a largely transparent support substrate. The transparency of the support substrate to a specific electromagnetic radiation allows the photons largely unimpeded access to the release layer.

[0008] Laser debonding allows the use of polymers, particularly polyimide-based polymers, as the release layer, since these can be selectively ablated with a UV laser beam source. The separation occurs at a substrate-bonding adhesive interface. The UV laser beam source used for this requires glass substrates that possess the necessary transparency for the specific electromagnetic radiation in the UV range. US 9,827,740 B2, for example, discloses a system consisting of a bonding adhesive and a polyimide release layer applied directly to the glass substrate.

[0009] Since polymer layers are not always suitable as a release layer for laser debonding, especially when silicon substrates are required which have the necessary transparency for the specific electromagnetic radiation in the IR range, a combination of at least two layers consisting of an inorganic separating layer for laser debonding and an organic, polymeric bonding adhesive layer for temporary bonding has been increasingly used in the prior art.

[0010] Another method for separating two substrates involves applying a special release agent in combination with a bonding adhesive to a support substrate, particularly a transparent one. The transparency of the support substrate to a specific electromagnetic radiation allows unimpeded access of photons to the release agent. The photons modify the release agent accordingly, reducing its bond strength to the bonding adhesive. US Patent 10,468,286 B2 describes such a method. Depending on where the bonding adhesive is applied—i.e., directly to the support substrate or after the release agent—it must also be largely transparent to the selected electromagnetic radiation.The devices and methods described in the prior art thus describe a separation process that uses organic layers, in particular polymer layers, as separating layers or combines organic bonding layers with organic or inorganic separating layers. However, the use of polymers as bonding layers and / or separating layers that temporarily connect two substrates has several disadvantages.

[0011] Polymers are long-chain molecules whose main component is usually carbon. Organic materials are often disadvantageous and undesirable in the semiconductor industry because they can contaminate cleanroom environments, especially the equipment used to process the substrates. Furthermore, polymers have the disadvantage of maintaining their adhesive properties only up to relatively low temperatures. While this is advantageous for debonding, it is a disadvantage if the product substrate needs to be processed on the support substrate at high temperatures. In addition to the low temperature resistance of organic layers, organic release agents often need to be applied relatively thickly to provide adequate adhesion.

[0012] The combination of bonding layer and release layer in a substrate stack with a product substrate and a support substrate must, on the one hand, withstand holding forces during processing regardless of the process temperature, and on the other hand, the substrates should be able to be separated from each other after processing with the least possible force. An alternative to organic bonding adhesives is the use of inorganic bonding layers.

[0013] If an inorganic bonding layer, for example a metal layer, is applied to the product substrate and / or the support substrate and used as a bonding layer, further layers are necessary beforehand in the prior art to enable gentle and largely non-destructive laser debonding, since the surface of the coating is destructively removed.

[0014] One problem is that exposure to laser light or laser beams can damage the product substrates, especially expensive functional components. Therefore, in addition to the release layer and the bonding layer, further layers are required, which serve as protective layers. These additional layers protect the product substrate and are, for example, anti-reflective coatings. Usually, these consist of several layers of dissimilar materials. Furthermore, in the prior art, alternating layers of metals or metal salts and dielectrics are used as protective and / or barrier layers. The dielectrics can be oxides such as silicon dioxide.

[0015] If several layers, particularly inorganic ones, are used, differing in material composition, especially the separating layer and the first subsequent layer, complex cleaning of the substrates after debonding is necessary. This is because each individual layer must be cleaned differently, for example, if at least one layer of the multilayer system consists of a metal and at least one layer of a dielectric such as silicon dioxide or amorphous silicon dioxide. If an alternating sequence of layers made of several different inorganic materials is present, the cleaning processes after debonding must also be applied alternately multiple times. The complex cleaning of the product substrates after laser debonding, using different cleaning methods such as wet and dry etching, slows down further processing and / or application of the product substrates.In wet etching, impurities are selectively removed from the product substrate using solvents or etching solutions. The selectivity of the etching solutions can be high. Depending on the material of the individual layers, different etching solutions are used in the prior art. These etching solutions can be single solvents or mixtures of two or more solvents.

[0016] However, progress in the semiconductor industry requires a continuous reduction in costs per component, which can be achieved in particular through cost reduction via productivity optimization in manufacturing.

[0017] It is therefore an object of the present invention to provide a method for separating product substrate and support substrate, with which the support substrate and / or the product substrate can be further processed or used for a subsequent process as quickly as possible after the product substrate and support substrate have been separated from each other. In particular, it is an object of the present invention to make the product substrate and support substrate available for further processing as quickly as possible when using inorganic, especially polymer-free, separating layers, in order to retain the advantages of using inorganic separating layers and to make these separating layers useful in mass production.

[0018] According to a first aspect, a method for separating a carrier substrate from a product substrate is provided, comprising:

[0019] Providing the support substrate and the product substrate in a connected state, in which the support substrate and the product substrate are connected to each other via a layer system between the support substrate and the product substrate, in particular temporarily connected to each other, wherein the layer system has a separating layer and a first further layer different from the separating layer, wherein the separating layer and the first further layer are inorganic,

[0020] Separation of the support substrate and the product substrate by irradiating the layer system, preferably the separation layer, with laser light and

[0021] Cleaning the product substrate and / or support substrate with a common solvent, which removes residues from both the separating layer and the layer, preferably in a single cleaning step.

[0022] This method advantageously allows for the quick and easy cleaning of a product substrate, which has been temporarily bonded to the substrate system for further processing, after detachment, preferably in a single cleaning step or in a single cleaning environment. This eliminates the need for multiple individual cleaning steps that would otherwise be required to remove the individual layers. Furthermore, there is no risk of unintentional reactions between different solvents used for different layers, thus preventing the need for targeted intermediate rinsing. All of this contributes to a reduction and simplification of the separation time between the product substrate and the support substrate, making the use of inorganic separating layers and other layers economically viable in mass production.The product substrate and support substrate can thus be prepared more quickly for further processing, even if an inorganic, and in particular a polymer-free, layer is used as the separating layer and the first subsequent layer. The product substrates are preferably cleaned after laser debonding. If the separating layer and the first subsequent layer consist of different materials, prior art employs various cleaning techniques sequentially to remove the different material residues. The product substrates undergo a series of cleaning steps. The chemical composition of the separating layer and the at least one subsequent layer on the product substrate, as well as their sequence, defines the cleaning process sequence in the prior art. Cleaning is carried out by means of wet chemical etching and / or dry etching. This is advantageously eliminated in the present case, thus simplifying the cleaning process.

[0023] The first additional layer can fulfill the function of a bonding layer, an absorption layer (especially a protective layer), an absorption-enhancing layer, a nucleating layer, and / or an overgrowth layer. In particular, the first additional layer fulfills the function of a bonding layer and / or a protective layer. A dielectric can be present on the product substrate as an inorganic bonding layer for connection to the layer system, thus forming the first additional layer.

[0024] In a preferred embodiment of the method, it is provided that the separating layer and the first further layer are removed from the product substrate in a single common cleaning step.

[0025] The laser light is preferably supplied as a laser beam from a laser unit. The laser beams first penetrate the substrate, for example, and are then absorbed by the release layer. An IR laser beam source is preferably used in combination with silicon substrates. The laser unit preferably acts on the release layer in a targeted manner and with precisely calibrated parameters in different, preferably regularly defective, areas. The inorganic release layer, which is preferably opaque to the laser radiation from the laser unit, absorbs the laser radiation, thus locally reducing the adhesive properties and / or the stability of the release layer. In particular, due to the high local energy concentration, lateral cracks form in the release layer, allowing the substrate to be easily separated from the at least one further layer or the product substrate.In a further embodiment of the process, the first additional layer absorbs the laser radiation so strongly that the product substrate is advantageously protected. The inorganic separating layer, which is preferably opaque to the laser radiation, absorbs the laser radiation during laser debonding, so that the adhesive properties and / or the stability of the separating layer are reduced, preferably with gas formation. In particular, lateral cracks form in the separating layer due to the high local energy concentration, which can propagate in different directions. Since the separation of the support substrate and the product substrate at the separating layer during laser debonding is usually not homogeneous or uniform along the layer boundaries, a product substrate surface is conceivable after debonding in which areas of material from the separating layer and areas of material from at least one additional layer are present.Alternatively, the release layer or the material of the release layer may still be largely present on the surface of the first subsequent layer after laser treatment. After IR laser debonding, the release layer, or the remaining release layer still present on the first subsequent layer after laser treatment, as well as the first subsequent layer itself, must be completely removed.

[0026] In a preferred embodiment of the method, the laser beams for laser debonding have a wavelength between 0.1 pm and 500 pm, preferably between 0.2 pm and 100 pm, more preferably between 0.3 pm and 50 pm, most preferably between 0.5 pm and 10 pm, and most preferably between 1 pm and 2.5 pm. This allows the separation layer to be irradiated particularly efficiently and precisely. The substrate is preferably transparent to the laser beams.

[0027] Laser debonding is preferably carried out in the infrared range. The IR laser light is preferably coupled through a largely transparent silicon support substrate. This allows the laser debonding to be advantageously performed from the back of the substrate stack, and the separation layer is reached through the support substrate.

[0028] In a preferred embodiment of the method, the pulse energy of the laser beams is between 0.01 pJ and 128 pJ.

[0029] In a preferred embodiment of the method, the pulse duration of the laser beams is between 10,000 ps and 1 ps, preferably between 1,000 ps and 1 ps, more preferably between 500 ps and 1 ps, most preferably between 100 ps and 1 ps, and most preferably between 50 ps and 1 ps. This pulse duration allows for targeted action for separation.

[0030] In a preferred embodiment, the laser radiation is ultra-short pulsed. According to a preferred embodiment, the separation results from multi-photon excitation caused by the laser radiation, in particular a femtosecond laser or a picosecond laser.

[0031] The laser spot size is the effective cross-sectional area of ​​the laser beam in the separation layer. In a preferred embodiment of the method, the laser spot size is less than 2,000 pm. 2 , preferably smaller than 500 pm 2 , preferably smaller than 80 pm 2 , preferably smaller than 20 pm 2 , preferably smaller than 1 pm 2 The area of ​​the separating layer on which the laser acts is advantageously small and targeted in order to locally reduce or destroy the adhesive properties of the separating layer.

[0032] In a preferred embodiment of the method, the laser beam areas do not overlap. This prevents or reduces condensation or resublimation of sublimated separating layer material. Preferably, the distance between the laser beam areas on the separating layer is at least 0.1 pm, more preferably at least 1 pm, more preferably at least 5 pm, even more preferably at least 10 pm, and most preferably at least 50 pm, so that the laser beam areas do not overlap. This enables a particularly simple and efficient separation process.

[0033] By correctly combining selected physical parameters, especially the substrate material, pulse length, laser wavelength, and laser energy, the behavior of the electromagnetic wave or photons in the substrate can be adjusted so that the laser beam is focused in the interface. High power density makes it possible to heat the material within a very short time to achieve ablation or sublimation. Thus, the short exposure times result in less thermal energy input into the underlying material and therefore minimal damage to the untreated area. Pulse energy, numerical aperture, pulse duration, pulse repetition rate, pulse shape, and beam profile can be adjusted using control and regulation devices.

[0034] The laser beam source used for this purpose in the IR range requires silicon substrates that have the necessary transparency for the specific electromagnetic radiation in the IR range.

[0035] Silicon as a substrate is transparent at wavelengths A > 1300 nm and A > 1900 nm, so lasers in the near-infrared (NIR) and mid-infrared (MIR) ranges are selected. Therefore, silicon is the preferred substrate in this case, and laser debonding is performed in the infrared range.

[0036] The preferred silicon support substrate is opaque below a wavelength of 1.3 pm. Particularly preferred lasers and their wavelengths suitable for irradiation through Si support substrates are, for example:

[0037] • Nd:YAG (1.064 pm; 1.320 pm; 1.444 pm)

[0038] • Ho:YLF (2:05 pm)

[0039] • Ho:YAG (2:09 pm)

[0040] • CrZnSe, Cr:ZnS (MIR)

[0041] In a particularly preferred embodiment, a pulsed solid-state laser, preferably an Nd:YAG laser or a Ho:YAG laser, is used. Pulsed solid-state lasers operating in the infrared range above 1.3 pm are doped with ions of Er³⁺ (1.55 pm), Tm³⁺ (1.9 pm), Ho³⁺ (2.09 pm), or Cr³⁺ (2.4 pm). Other preferred laser wavelengths for use with silicon substrates are, for example, 1940 pm, 1960 pm, or 2030 pm.

[0042] Preferably, the separating layer and the first subsequent layer are selected such that they can be removed with the common solvent. The purely inorganic layer system with a separating layer and the first subsequent layer is selected so that, after targeted IR laser debonding following the finished processing of the product substrate, the product substrate can be cleaned easily and quickly with only one cleaning method in a single cleaning step for the entire layer system. By reducing the product substrate cleaning to only one solvent mixture, the cleaning process is simplified and the throughput is optimized. Since the selection of the solvents, the concentration of the solvents, and the addition of additives such as salts affect the dissolution rate (i.e., the removal rate), the cleaning process is simplified and the throughput is optimized.Since the etch rate can be strongly influenced, the selection of the solvent mixture must be tailored to the chemical composition of the layers of the coating system in order to dissolve the different compounds, materials, or chemical substances equally well, so that only a single solvent mixture is used for product substrate cleaning.

[0043] This allows a substrate stack with at least the carrier substrate, the separating layer and another layer to be advantageously processed by targeted laser treatment in such a way that the product substrate can be easily and with minimal contamination removed from the at least one other layer, and the product substrate can then be easily and largely residue-free cleaned in a single cleaning step.

[0044] When layers are generally mentioned, the layers of the layer system are meant, i.e., the separating layer, the first subsequent layer, a second subsequent layer, and / or a third subsequent layer, as well as further potential layers. Preferably, all layers of the layer system are inorganic but preferably differ from one another, particularly with regard to their material composition.

[0045] The inorganic layers of the layer system preferably comprise at least one material from one of the following material classes:

[0046] - Dielectric, in particular

[0047] - Nitrates, especially

[0048] TiN, TaN, AIN, GaN, InN, SiN, Si3N4, SiCN, SiOCN, SiON, CrN, NiN, WN, W2N, WN2

[0049] - Carbide, especially carbon layers, SiC, SiOC

[0050] - Oxide, especially SiO x , TiO2, ZrO2, AI2O3, indium tin oxide (ITO), indium titanium oxide (ITiO)

[0051] - Electric, preferably

[0052] - Metal, especially

[0053] Cr, Al, Ta, Co, Ni, Mn, Fe, Au, Ga, Sn, Ge, W, Cu, In, Ti, Mo, Ta, Nb, Zr and combinations or alloys thereof.

[0054] The following materials and material classes are preferably used for the separating layer: • Nitrides,

[0055] especially TiN, TaN, AIN, GaN, InN, SiN, Si3N4, SiCN, CrN, NiN, WN, W2N, WN2 • semiconductors,

[0056] especially Ge

[0057] • Metals,

[0058] especially Ti, Al, Cu, W, Ta, Au, Ag, Fe, Ni, Cr, Pt, Sn, In

[0059] In particular, it is provided that the separating layer (2, 2') has or consists of a metal nitride, for example titanium nitride.

[0060] Preferably, the first further layer is provided to have or consist of a metal or a metal oxide.

[0061] The following materials and material classes are preferred for the first subsequent layer:

[0062] • Metals,

[0063] especially Ti, Al, Cu, W, Ta, Au, Ag, Fe, Ni, Cr, Pt, Sn, In

[0064] • Semiconductors,

[0065] especially Ge

[0066] • Nitrides,

[0067] especially TiN, TaN, AIN, GaN, InN, SiN, Si3N4, SiCN, CrN, NiN, WN, W2N, WN2• oxides

[0068] especially aluminum oxide (Al2O3), titanium oxide (TiO2), zirconium oxide (ZrO2)

[0069] • Ceramic material,

[0070] in particular silicon carbide (SiC), silicon carbonitride (SiCN), aluminum oxide (Al2O3) and / or

[0071] • Alloys,

[0072] In a preferred embodiment of the method, the separating layer is made of a metal or a nitride, preferably titanium nitride (TiN). An inorganic separating layer made of metal or nitride is particularly suitable because it can also enable stable bonding.

[0073] The high adhesive properties of the inorganic separating layer enable a thin separating layer and thus an overall thinner layer structure in the substrate system being processed. In a preferred embodiment of the process, the first additional layer consists of a metal.

[0074] In a further embodiment of the method, the first additional layer is a titanium layer that serves simultaneously as a bonding layer and / or a protective layer. In this embodiment, at least one additional layer is arranged between the titanium nitride separating layer and the product substrate, the first of which is a titanium layer. For fusion bonding, an additional dielectric layer may be necessary, so that at least two additional layers are arranged between the titanium nitride separating layer and the product substrate, the first of which is a titanium layer and the second of which is a dielectric layer or a layer made of a dielectric material.This method advantageously allows a substrate system comprising at least the support substrate, the TiN release layer on the support substrate, and a titanium layer to be treated by targeted IR laser irradiation in such a way that the support substrate can be easily detached from the at least one further titanium layer. The thickness of the titanium layer is adjusted to optimize its function as a protective layer and / or reflector layer, as well as its function as an interface with titanium nitride for laser debonding. Potential diffusion of titanium into titanium nitride must also be considered, and the thickness of the titanium layer is selected accordingly.

[0075] In particular, it is provided that the separating layer and the first subsequent layer contain at least one common chemical element. Specifically, it is provided that the material of the separating layer and the material of the first subsequent layer have at least one common element or chemical compound. If the separating layer and the first subsequent layer have the same element in different forms and / or bonds and / or in different compounds, simplified, uniform, and faster cleaning in just one step for the at least two layers with a single cleaning agent is possible. Preferably, the common element or compound is a major component of the separating layer or the first subsequent layer. A proportion of more than 50% by weight, more preferably more than 60% by weight, and particularly preferably more than 75% by weight is assumed to be the major component.Preferably, the at least one common chemical element in different forms and / or bonds and / or compounds is a major component of the material for the separating layer and for the first further layer. Preferably, the separating layer comprises titanium nitride and the first further layer comprises titanium. In one embodiment, the layer system arranged between the support substrate and the product substrate consists of a separating layer made of titanium nitride and exactly one further inorganic protective layer made of titanium. A separating layer made of TiN and a first further layer made of Ti can, for example, be advantageously removed from the product substrate in a single wet-chemical cleaning step after the separation process, since titanium (Ti) and the titanium-containing titanium nitride (TiN) can be dissolved with the same chemicals.

[0076] In particular, no dielectrics or alternating layers with dielectrics requiring selective etching with hydrogen fluoride (HF) or buffered oxide etching (BOE, a mixture of hydrogen fluoride and ammonium fluoride) are used as a further layer, i.e., as a first further layer, second further layer, or third further layer, thus eliminating the need for a second, different cleaning technique. These are dielectrics such as silicon dioxide or silicon carbon nitride, for which a second cleaning with wet or dry etching would be necessary, as they are removed with hydrogen fluoride or reactive ion etching, which uses etching gases containing fluorine compounds such as CF4 and SF6 for the removal of silicon-containing layers. Preferably, the layer system with a separating layer and a first further layer is free of silicon dioxide and silicon carbon nitride.

[0077] In a further embodiment of the process, the first additional layer is an aluminum layer and / or an aluminum oxide layer. Titanium and titanium nitride are used in the semiconductor industry as diffusion barriers in aluminum and copper metallization. The thickness of an additional aluminum layer can therefore be thinner than the thickness of a first additional titanium layer. The solubility of aluminum increases at a pH value below 6 or above 8, and aluminum is removed in the same wet-chemical cleaning step as the separating layer. In one embodiment, the layer system arranged between the support substrate and the product substrate consists of a separating layer of titanium nitride and exactly one additional inorganic layer of aluminum and / or aluminum oxide.

[0078] If higher process temperatures, especially above 400 °C, are necessary during the processing of the product substrate bonded to the carrier substrate with the layer system, aluminum oxide may form at the interface between the TiN layer and the aluminum layer, as oxygen atoms may be present as impurities in the titanium nitride layer. Aluminum oxide is soluble in strong acids and is removed along with the separating layer in the same wet-chemical cleaning step.

[0079] In a further embodiment of the method, the first additional layer is an aluminum and / or aluminum oxide layer. In one embodiment, the layer system arranged between the support substrate and the product substrate consists of a separating layer of titanium nitride and exactly one further inorganic layer of aluminum oxide.

[0080] Preferably, the layer system comprises an additional second and / or third layer. It is particularly advantageous that the common solvent also removes the second and / or third layer, especially during the common cleaning step. The specifications, properties, and advantages described for the first layer apply analogously to the second and third layers, and vice versa. In a further embodiment of the process, at least two additional layers, i.e., the first layer and at least the second and / or third layer, are used, wherein the at least two additional layers are inorganic. In a preferred embodiment of the process, the at least two additional layers consist of at least one aluminum oxide layer and one titanium layer.The second and / or third additional layer are preferably inorganic and differ from the separating layer and the first additional layer. The stacking order of the separating layer, first additional layer, second additional layer, and / or third additional layer can be arbitrary.

[0081] In one embodiment, the layer system arranged between the support substrate and the product substrate comprises a separating layer made of titanium nitride and two further inorganic layers made of aluminum oxide and aluminum.

[0082] In a preferred embodiment, the layer system arranged between the support substrate and the product substrate consists of a separating layer made of titanium nitride and two further inorganic layers made of aluminum oxide and titanium.

[0083] The method advantageously allows a substrate system comprising at least the support substrate, the TiN separating layer on the support substrate, an aluminum oxide layer and a titanium layer to be processed by targeted IR laser treatment in such a way that the support substrate can be easily detached from the at least two further layers.

[0084] The preferred sequence is: substrate - TiN - Al₂O₃ - Ti. Depending on its thickness, the titanium layer is used as either an absorber or a reflector layer to protect the product substrate. This layer system can be advantageously removed from the product substrate in a single wet-chemical cleaning step after separation, since titanium (Ti), aluminum oxide (Al₂O₃), and titanium nitride (TiN) can be dissolved with the same chemicals.

[0085] In a preferred embodiment of the substrate stack, at least one layer of the substrate system comprises, preferably consists of, titanium (Ti), aluminum (Al), aluminum oxide (Al₂O₃), aluminum nitride (Al₂O₃), tantalum (Ta), tantalum nitride (TaN), titanium nitride (TiN), or copper (Cu). The layer thickness is particularly preferably between 10 and 200 nm.

[0086] In one embodiment of the method, the separating layer is arranged directly on the support substrate. In another embodiment of the method, further layers, preferably a first further layer, a second further layer, and / or a third further layer, can be present between the separating layer and the support substrate. These further layers must be largely transparent to the laser beams of the laser unit.

[0087] In one embodiment, the silicon substrate is coated with a dielectric thin layer. This layer serves as a light-focusing layer and amplifies the IR laser radiation used for debonding, which is directed or focused onto the separation layer and penetrates from the back of the substrate. This dielectric coating consists in particular of silicon dioxide (SiCh) and / or silicon carbonitride (SiCN) and / or silicon carbide (SiC) and / or aluminum oxide (Al₂O₃) and / or aluminum nitride (Al₃).

[0088] Preferably, the solvent for cleaning the product substrate after laser debonding across the separation layer comprises hydrochloric acid (HCl), sulfuric acid (H₂SO₄), nitric acid (HNO₃), phosphoric acid (H₃PO₄), ammonia (NH₃), hydrogen peroxide (H₂O₂), or hydrofluoric acid (HF), preferably diluted with water or deionized water, and preferably buffered with a salt. The terms solvent, solvent mixture, etching solution, and cleaning agent are used synonymously and refer to the same thing here, namely the agent used for chemical cleaning of the support substrate or the product substrate. The etching solutions can be single solvents or mixtures of two or more solvents. The solvent mixture comprises or consists of at least two or more solvents and / or chemicals.Sulfuric acid, nitric acid and hydrogen peroxide, as well as combinations thereof, are also used as oxidizing agents.

[0089] The acid solutions can be buffered with salts, for example, with ammonium salts such as ammonium fluoride (NH₄F) or ammonium hydrogen difluoride (NH₄HF₂). The solvent mixture is selected according to the material of the multiple layers of the coating system. Mixtures of hydrochloric acid and hydrogen peroxide are used, for example, to remove metals. Oxide layers are removed with hydrofluoric acid. Silicon nitride, for example, is etched with phosphoric acid. Crystalline and polycrystalline silicon are first oxidized with nitric acid (HNO₃), and then the resulting silicon dioxide is etched with hydrofluoric acid. Aluminum can be etched at approximately 60 °C with a mixture of nitric and phosphoric acid.

[0090] Mixtures of hydrochloric acid and hydrogen peroxide or of nitric acid and phosphoric acid are used, for example, to remove metallic impurities. Oxide layers, especially silicon dioxide, are removed with hydrofluoric acid. Silicon nitride is etched with phosphoric acid. Different solvents are used when silicon dioxide, nitride layers, and metal layers alternate. After each wet-chemical cleaning step, the surface is rinsed with ultrapure water. The etching, and thus the cleaning process, is stopped by dilution with water.

[0091] Combinations known in the semiconductor industry and to experts for cleaning agents for silicon substrates, including oxide surfaces, include:

[0092] • H2SO4 and H2O2 diluted with DL water (also known as "Piranha")

[0093] • NH4OH and H2O2 diluted with DL water (“SC-1” or RCA-1)

[0094] • HCl and H2O2 diluted with dl water (“SC-2” or RCA-2)

[0095] For SC-1 and SC-2, see Kern W., Puotinen D. (1970) “Cleaning solutions based on hydrogen peroxide for use in silicon semiconductor technology”, RCA Review 31(2), 187-206. These three mixtures, the Piranha solution, SC-1, and SC-2, are used sequentially in the semiconductor industry as standard pre-cleaning solutions, often with an RF rinsing step in between. Using many different solvents or solvent mixtures with the highest possible selectivity is complex.

[0096] Titanium can be etched with a mixture of hydrofluoric acid and hydrogen peroxide or with a mixture of dilute hydrofluoric acid and nitric acid. In general, titanium can be etched with various acids. The same applies to other metals, as well as to nitrides and other materials, chemicals, or compositions suitable for the layers of the coating system.

[0097] If the separating layer and the first subsequent layer consist of the same element in different forms and / or in different compounds, a simplified, uniform, and faster cleaning process in just one step for the at least two layers using a single cleaning agent is even easier. In an embodiment with a separating layer made of titanium nitride and at least one further layer made of titanium, for example, titanium and the titanium-containing titanium nitride can be advantageously removed from the product substrate in a single wet-chemical cleaning step after the separation process, since they can be dissolved with the same chemicals.

[0098] The selection of chemicals, particularly the solvent concentration, is further optimized for dissolving an additional layer. A layer system consisting of titanium nitride, aluminum oxide, and titanium can be advantageously removed from the product substrate in a single wet-chemical cleaning step after separation, since titanium nitride, titanium, and aluminum oxide can be dissolved with the same chemicals. The optimization of the solvent and salt proportions depends on the dissolution rates of the layer materials and the layer thicknesses, enabling cleaning within timeframes practical for the semiconductor industry.

[0099] The chemicals or solvent mixture used, unlike the usual state of the art in the semiconductor industry, are not tailored to a specific layer and do not possess high selectivity towards the individual layers of the layer system according to the invention. Preferably, hydrofluoric acid, which is difficult or problematic to handle, is avoided. Combinations with hydrofluoric acid known in the prior art are also avoided to simplify cleaning.

[0100] It is most preferably provided that the solvent mixture according to the invention is a solution of hydrogen peroxide, ammonia and water, with a ratio H2O2: NH4OH: H2O (Dl-water) between 1:1:5 and 1:1:20 vol%.

[0101] The proposed coordinated material composition of the release layer and the first subsequent layer enables rapid and effective cleaning of the product substrate after IR laser bonding in a single cleaning step using a single cleaning method. Preferably, wet chemical cleaning is performed, with the solvent mixture selected to dissolve all layers of the coating system. Therefore, a change of solvent or solvent mixture is not necessary.

[0102] To use a single solvent mixture as an etching solution for different materials or chemical compositions of the at least two layers of the coating system, the selectivity of the solution for selected materials of the coating system can be modified if necessary, for example, by controlling the etch rate through the composition of the solvent mixture and the concentration of the acids. Using a solvent mixture, the etch rate or etching speed for a first material can be reduced, while the etch rate or etching speed for a second material can be increased. This allows the at least two layers of a first and a second material to be removed with the same etching solution and at a controlled, largely uniform etch rate. The etching speed of the solvent mixture for the individual materials (i.e.,The chemical elements or compounds) of the layers can be set within any tolerance range.

[0103] In another embodiment, the selectivity or etch rate of the solvent mixture as the etching solution can differ for the at least two layers, i.e., the separating layer and the first subsequent layer, of a layer system. Preferably, however, the etch rate should be relatively similar for better control of the cleaning process. Furthermore, the etch rate of the chemicals can be controlled by the temperature.

[0104] A single etching solution consisting of a solvent mixture allows for the targeted and time-saving removal of the pre-selected material of the release layer and the material of the first subsequent layer, particularly in the form of a protective layer, in a single process step. These etching solutions can consist of single solvents or mixtures of two or more solvents. Examples of solvents used include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, ammonia, hydrogen peroxide, and hydrofluoric acid, as well as mixtures thereof. The solvents are diluted with dilute water as needed. The acid solutions can be buffered with salts, such as ammonium salts like ammonium fluoride (NH₄F) or ammonium hydrogen difluoride (NH₄HF₂).

[0105] In general, wet chemical etching is suitable for removing entire layers from a product substrate. Wet etching can be performed as immersion etching or spray etching. In immersion etching, several substrates are processed simultaneously in a tank containing an etching solution. While immersion etching allows for a high throughput of substrates, the homogeneity of the layer removal is lower. During immersion etching, the etching process on the substrates is stopped by rinsing them in several immersion tanks.

[0106] In the preferred spray etching process, each substrate is processed individually. Product substrates are fixed to a substrate holding device, rotated, and cleaned with the addition of fresh etching solution via one or more nozzles. If necessary, the processed side of the product substrates can be provided with a transfer carrier substrate prior to laser debonding for simplified handling. In particular, a dicing tape can be applied to the product substrate. Dicing tapes include, for example, adhesive films, thermal films, or UV films. The product substrate is fixed with a film frame. This allows even very thin product substrates to be handled after re-thinning. Preferably, the compatibility of the film and frame materials with the cleaning methods or cleaning chemicals is checked on a case-by-case basis, and the appropriately suitable materials are selected.Following IR laser debonding, a single-wafer cleaning process on a saw frame is possible. Existing wet-chemical cleaning equipment for wafer handling can be advantageously used, thus simplifying and flexibly adapting the post-treatment process. Alternatively, instead of a saw frame, a substrate holder with a receiving surface and fixation for the product substrate separated from the carrier substrate, known to those skilled in the art, can be used.

[0107] The simplified cleaning process also makes it possible to effectively group different modules, for example for bonding, processing, debonding and cleaning, into a module group and to optimize machine utilization and throughput with single-wafer cleaning.

[0108] In an alternative, less preferred embodiment, dry etching cleaning processes are used to clean the product substrates after laser debonding. These dry etching processes enable reproducible, homogeneous etching of most layers used in semiconductor manufacturing. In addition to anisotropic etch profiles, isotropic profiles can also be achieved. Dry etching involves sequential, single-substrate cleaning. Unlike wet chemical etching, dry etching uses gases, which are usually dissociated in gas discharges (plasmas) to generate neutral particles and ions that perform surface reactions, catalyze them, or remove the material purely physically. In some cases, ion beams are also used.The choice of etching gases, pressure range, and electrode configuration leads to a wide variety of etching processes; the etching attack can be physical, chemical, or a combination of both. Examples of chemical-physical etching processes include reactive ion etching (RIE) and reactive ion beam etching (RIBE).

[0109] In another embodiment, ammonium salts can also be added.

[0110] Preferably, the separating layer and / or first further layer, the second further layer and / or the third further layer has a layer thickness between 1 nm and 200 nm, preferably between 10 and 100 nm, and particularly preferably between 25 and 85 nm. In a preferred embodiment of the substrate system, the separating layer has a thickness between 0.1 nm and 100 nm, preferably between 0.1 nm and 25 nm.

[0111] In a preferred embodiment of the substrate system, the first further layer is provided to have a layer thickness between 1 nm and 200 nm, preferably between 1 nm and 100 nm.

[0112] In a further embodiment of the substrate system, it is provided that the first further layer has a layer thickness between 1 nm and 1000 nm, preferably between 100 nm and 500 nm.

[0113] In a further embodiment of the substrate system, it is provided that in the case of a layer system with a first further layer and a second further layer, the first further layer has a layer thickness between 1 nm and 200 nm, preferably between 1 nm and 100 nm, and the second further layer has a thickness between 1 nm and 200 nm, preferably between 1 nm and 100 nm, wherein the separating layer and the at least two further layers can be removed after debonding with one and the same cleaning agent.

[0114] The thicknesses of the separating layer and the at least one further layer are particularly dependent on the method (CVD, PVD, MBE, surface oxidation, etc.). These thicknesses are particularly between 1 nm and 500 nm, preferably between 1 nm and 100 nm. In a further embodiment of the substrate system, the separating layer and the first further layer consist of a compound or material that share at least one common chemical element.

[0115] If an additional bonding layer is required on the product substrate, dielectrics such as silicon dioxide (SiO₂), silicon carbonitride (SiCN), silicon carbide (SiC), silicon carbide (SiCO₃), indium tin oxide, aluminum oxide (Al₂O₃), aluminum nitride (Al₃), and / or indium titanium oxide are used as bonding layer materials. This bonding surface can fuse with the outermost layer of the coating system via heat treatment, for example, in fusion bonding, thus connecting the product substrate and the support substrate. If this layer is required for further processing of the product substrate after separation from the support substrate via the separation layer, then this layer, which is located directly on the product substrate, is not removed during cleaning. This layer is considered part of the product substrate and is not part of the coating system.

[0116] The layer system is particularly suitable for the temporary bonding of a support substrate and a product substrate. The layer system comprises a separating layer and a first further layer distinct from the separating layer, wherein the separating layer and the first further layer are inorganic. The layer system is particularly suitable for product substrates without surface structuring and / or for product substrates with embedded structuring and a largely flat surface. Preferably, the bonding surfaces are planar, i.e., flat.

[0117] Preferably, the product substrate and / or the support substrate are cleaned after separation at a temperature between 10°C and 150°C, preferably between 20°C and 85°C, with the temperature preferably being regulated or controlled. The temperature of the solvent mixture used for cleaning the product substrate is measured, set, and controlled or regulated by means of control means and temperature sensors.

[0118] Furthermore, it has proven advantageous to clean the product substrate and / or the support substrate for a period of between 10 seconds and 20 minutes, preferably between 10 seconds and 10 minutes, and even more preferably between 1 minute and 5 minutes. It has been shown that sufficient cleaning can be achieved in such a short time to ensure the continued use of the product substrate and / or the support substrate. The cleaning process can be terminated by diluting the solvent, for example, by adding water, particularly deionized water. This also allows the product substrate and the support substrate to be rinsed simultaneously.

[0119] The following is an example of a procedure:

[0120] In a first process step, a separating layer is applied to a support substrate. At least one further layer is applied to the separating layer. If several layers are applied, the last, uppermost layer of the layer stack serves in particular as a bonding layer and / or as a protective layer for contacting and bonding to the product substrate. In a second process step, a product substrate is bonded to the last (outermost) layer of the layer system of the support substrate.

[0121] In a third process step, another, unbonded product substrate surface is processed. For example, a thinning to less than 100 pm, preferably less than 50 pm, even more preferably less than 25 pm, most preferably less than 10 pm, and most preferably less than 5 pm, can be carried out. Further process steps, particularly at high temperatures, can be performed on or at the thinned product substrate.

[0122] In a fourth process step, the product substrate with its processed product substrate surface is bonded to another substrate, in particular a second support substrate or a transfer substrate.

[0123] In a fifth process step, the separation layer through the first support substrate is bombarded with a laser beam and the first support substrate is removed or detached.

[0124] In a sixth process step, the now clear surface of the product substrate is cleaned in a single step using a single cleaning method, preferably wet chemical cleaning. A solvent mixture optimized for the layer system with the separating layer and the first subsequent layer is used for the simultaneous removal of materials from the multiple layers on the product substrate without changing the solvent.

[0125] In a seventh process step, the free surface of the product substrate is rinsed with DL water and dried in a heating module for transfer, intermediate storage or further processing.

[0126] In a further embodiment, preferably intended for product substrates with surface structuring or surface structures, the inorganic layer system can be combined with an additional structural protective layer. This structural protective layer serves to protect the structures on the surface of the product substrate. For this purpose, these structures are covered to more than 50%, preferably more than 80%, and particularly preferably more than 90%, or even completely covered. The protective layer can be made of an organic or an inorganic material and can be removed from the product substrate surface and the surface structures by cleaning. The protective layer is preferably located directly on the product substrate surface and has a thickness that is equal to or greater than the highest structure on the product substrate surface, so that the structures are completely covered and thus protected.This protective layer consists, for example, of a polymer and / or a non-metallic inorganic or hybrid polymer material. Depending on the type of structure or structuring, the protective layer has a thickness of, for example, between 0 and 50 pm, preferably between 0 and 25 pm. Alternatively, the thickness of the protective layer is, for example, between 1 and 25 pm. The thickness of the protective layer is less than 10 pm, preferably less than 5 pm, and even more preferably less than 1 pm. The structures can be, for example, functional units (dies and / or chips and / or chiplets). The largely planar structural protective layer simultaneously serves as a bonding layer between the product substrate and the support substrate with the inorganic layer system.

[0127] The first or second additional layer, and especially the last additional layer of the layer system, can fulfill the function of an absorption-enhancing layer, particularly a protective layer for the additional surface structure protection layer. This combination enables temporary bonding and debonding across the layer system, with laser debonding occurring from the back of the substrate. Simultaneously, optimized protection of surface structures on the product substrate is ensured during processing of the back of the product substrate. Preferably, in this embodiment, very high temperatures are not required for processing the product substrate. For example, the process temperature is less than 600°C, preferably less than 450°C.

[0128] Preferably, after debonding the product substrate and support substrate via the release layer, the surface of the product substrate is cleaned in a single step, preferably using a single cleaning method, particularly preferably a wet chemical cleaning method. A solvent mixture optimized for the layer system and the additional surface structure protection layer is used for the simultaneous removal of all materials from the multiple layers on the product substrate, including the surface structure protection layer, without changing the solvent. If the surface structure protection layer consists of a polymer or hybrid polymer material that is more readily soluble compared to the layers of the layer system, this layer can be selectively treated with a solvent or solvent mixture, for example from the periphery, in an alternative cleaning method and thus removed from the accessible side.The action of the solvent or solvent mixture can be accelerated by means of ultrasound. Alternatively, at least one solvent jet can be directed laterally onto the surface structure protective layer. The substrate and the nozzles can be rotated relative to each other. The necessary cleaning devices are known to those skilled in the art and are not described in detail here. Dissolving the surface structure protective layer results in the simultaneous removal of the other layers located on the surface structure protective layer, in particular the inorganic layer system.

[0129] Another object of the present invention is a substrate stack for a method according to the invention, comprising

[0130] - a carrier substrate,

[0131] - a product substrate and

[0132] - a layer system comprising a separating layer and a first further layer, wherein the layer system is designed such that the separating layer and the first further layer can be removed with a common cleaning agent. All properties and advantages described for the process also apply to the substrate stack and vice versa. In particular, this relates to a substrate system, especially for the production of semiconductor components, at least comprising,

[0133] a) a carrier substrate

[0134] b) an inorganic separating layer arranged on the support substrate

[0135] c) at least one further layer arranged on the separating layer and d) a product substrate arranged on the at least one further layer, wherein the carrier substrate is formed by irradiating the separating layer with a

[0136] The laser unit is separable from the product substrate, wherein the separating layer and the first subsequent layer are inorganic layers, and wherein the materials of the separating layer and the at least one subsequent layer can be removed with the same cleaning agent / solvent for quick and easy cleaning of the product substrate. Thus, a simple setup is possible, making temporary bonding, IR laser bonding, and cleaning efficient and system-optimized. The resulting substrate stack is preferably exclusively inorganic. Due to the inorganic structure, the substrate stack, especially the product substrate, can be processed at comparatively high temperatures. Another advantage is the relatively high adhesive strength that prevails between the two substrates or the inorganic layers. Therefore, the inorganic separating layers and, if applicable, inorganic bonding layers can be made thinner.The inorganic material of the release layer can thus be advantageously tailored to the different parameters of the laser unit. This allows the laser unit to target the release layer effectively, without affecting other layers and / or the substrate, or only affecting them minimally.

[0137] In a preferred embodiment of the method, when the substrate stack is irradiated, the laser beams emitted by the laser unit first penetrate the substrate and then strike the separating layer. In other words, the laser beams first pass through the substrate and are subsequently absorbed by the separating layer. The substrate is thus at least partially transparent to the laser radiation. The laser unit can therefore be advantageously arranged on the back side of the substrate, and separation can be carried out flexibly from the back side without placing special demands on the product substrate. In this context, it should be noted that any additional layer also absorbs the laser radiation sufficiently to advantageously protect the product substrate.

[0138] A further object of the present invention is a solvent for a process according to the invention, wherein the solvent is designed for removing the separating layer and the first further layer. All properties and advantages described for the process apply analogously to the solvent and vice versa.

[0139] Another object is an apparatus for carrying out the process according to the invention, in particular using a module for cleaning the product substrate and / or the support substrate, especially a wet-chemical substrate cleaning with the solvent mixture, wherein the chemical composition of the individual layers of the layer system with a separating layer and a first further layer, which remain or partially remain on the product substrate after IR laser debonding, is selected such that they are removed with the same solvent mixture. All advantages and properties described for the process can be transferred analogously to the apparatus and vice versa. The simplified cleaning process also makes it possible to effectively combine modules for bonding, debonding, and cleaning into a single module group and to optimize machine utilization and throughput with single-wafer cleaning.

[0140] In particular, the device is provided for separating a substrate stack according to the invention and has, for example, at least the following:

[0141] a) a provisioning unit for providing the substrate stack,

[0142] b) a laser unit for irradiating a separating layer arranged in the substrate stack, wherein the first further layer is arranged on the side of the separating layer facing away from the support substrate,

[0143] wherein the support substrate can be separated from at least one further layer by irradiation of the separating layer, wherein the separating layer and the first further layer are inorganic, wherein the separating layer and the first further layer can be dissolved from the product substrate with the same solvent or solvent mixture for cleaning the surface of the product substrate.

[0144] In particular, the device comprises means for separating a carrier substrate from a product substrate according to invention disclosure WO 2023 / 179868A1, to which explicit reference is made here with regard to this means for separation.

[0145] Furthermore, the invention relates to a device for wet-chemical cleaning of a product substrate, at least comprising:

[0146] a) a provisioning unit for providing the substrate,

[0147] b) at least one application device, in particular at least one spray unit, for applying a fluid for cleaning the substrate surface,

[0148] c) a rotating device for rotating the substrate around an axis of rotation,

[0149] characterized in that a solvent mixture is used for the simultaneous removal of several layers on the substrate surface.

[0150] The fluid for chemically cleaning the substrate surface can be a gas and / or a liquid. In a further, less preferred embodiment, the fluid can also be a supercritical fluid. In particular, it is provided that a metering device is used to control the solvent supply. This advantageously allows the solvent supply, especially its dosage and / or concentration, to be precisely controlled depending on the chemical composition of the separating layer and the first subsequent layer. After removing the separating layer and the first subsequent layer from the product substrate surface using a solvent mixture, the product substrate surface is preferably cleaned with distilled water to remove solvents and, if necessary, dried using a drying device.

[0151] The system features, in particular, a modular group with a shared workspace that can be sealed off from the ambient atmosphere if required. The independent modules, specifically the alignment and bonding module, processing module, debonding module, and cleaning module, can be arranged in a cluster or star configuration around a central module containing a motion system, such as a robotic system. The robotic system transports the substrates between the modules of the modular group. This process is controlled by the control unit. Individual modules of the modular group can be connected to the workspace in a sealed manner.

[0152] Preferably, the module group includes at least one module for IR laser debonding of substrate stacks. Even more preferably, the module group includes at least two modules, one for IR laser debonding of substrate stacks and one for cleaning the substrates. A module for cleaning the product substrates after debonding is preferably a module for wet-chemical cleaning of individual substrates.

[0153] In a further embodiment, the module group is provided to contain at least three modules, including at least one module for IR laser debonding of substrate stacks, one module for cleaning the substrates, and one module for further processing.

[0154] Other independent modules of the module group could be, for example, a loading module, a plasma chamber, an oven, a metrology module, a CMP module and / or a bonding chamber.

[0155] The substrates and / or substrate stacks are processed in the module group according to a predefined sequence of process steps. An inorganic coating system for temporary bonding and infrared (IR) laser debonding simplifies and accelerates the cleaning process. This system allows for the simple and rapid cleaning of a product substrate after debonding using only one cleaning method in a single cleaning step for the entire coating system within a module group. The simplified cleaning process also makes it possible to effectively integrate modules for bonding and / or processing, debonding, and cleaning into a single module group and to optimize machine utilization and throughput with single-wafer cleaning.

[0156] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings.

[0157] They show in:

[0158] Figure 1a: a cross-sectional view of a substrate with a separating layer,

[0159] Figure 1b: a cross-sectional view of a substrate in a first embodiment with a separating layer and a further layer,

[0160] Figure 1c: a cross-sectional view of a temporarily bonded substrate stack in a first embodiment consisting of a support substrate, a separating layer, a further layer and product substrate,

[0161] Figure 2a: a cross-sectional view of a substrate in a second embodiment with a separating layer and two further layers,

[0162] Figure 2b: a cross-sectional view of a process step in which a product substrate is aligned relative to the carrier substrate,

[0163] Figure 2c: a cross-sectional view of a temporarily bonded substrate stack in a second embodiment consisting of a support substrate, a separating layer, two further layers and a product substrate,

[0164] Figure 3a: a first procedural step of an exemplary procedure,

[0165] Figure 3b: a second process step of an exemplary process, Figure 3c: a third process step of an exemplary process,

[0166] Figure 3d: a fourth process step of an exemplary process,

[0167] Figure 3e: a fifth procedural step of an exemplary procedure,

[0168] Figure 3f: a sixth procedural step of an exemplary procedure,

[0169] Figure 3g: a side view of the product substrate after the sixth process step of an exemplary process,

[0170] Figure 4a: a schematic representation of a first embodiment of a module group connected to a workspace,

[0171] Figure 4b: a schematic representation of a second embodiment of a module group connected to a workspace,

[0172] Figure 4c: a schematic representation of a third embodiment of a module group connected to a workspace.

[0173] In the figures, identical components or components with the same function are marked with the same reference symbols. For clarity, proportions may be inaccurately represented.

[0174] Figure 1a shows a cross-sectional view of a support substrate 1 on which a separating layer 2 has been applied. The separating layer 2 is inorganic. The separating layer 2 is preferably deposited directly onto the support substrate 1 using a method known from the prior art. Alternatively, a dielectric bonding layer can be located on the surface of the support substrate to improve the deposition and / or adhesion of the separating layer 2. According to Figure 1b, at least one first additional layer 3 is deposited onto the separating layer 2. Deposition methods for applying a layer include, for example, chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition. Alternatively, a first additional layer can be grown, for example, by epitaxial growth.A support substrate 1, on which a separating layer 2 and the first further layer 3 are located according to Figure 1b, is aligned and bonded to form a product substrate 4. The product substrate 4 is bonded to layer 3 via a product substrate surface suitable for bonding. For example, the product substrate has an inorganic, dielectric bonding layer (not shown) on its surface. Figure 1c shows a substrate stack 5 after a temporary bonding process. The term substrate stack 5 preferably refers to the support substrate 1 and the product substrate 4 when they are connected to each other in the bonded state via a layer system, in particular temporarily. The layer system comprises at least the separating layer 2 and the first further layer 3. The product substrate 4 is mechanically stabilized by the support substrate 1 during further processing.After processing, the product substrate 4 can be separated from the carrier substrate, to which it was temporarily connected via the layer system, using laser light, for example an IR laser, via the separating layer 2.

[0175] When substrates are generally referred to, the properties and / or specifications apply specifically to either the product substrate 4 or the support substrate 1. The diameter of the substrates is standardized by industry. The substrates, i.e., the product substrate 4 and / or the support substrate 1, can have any shape, but are preferably circular. For wafers, the industry-standard diameters are 1 inch, 2 inches, 3 inches, 4 inches, 5 inches, 6 inches, 8 inches, 12 inches, and 18 inches. If one of the substrates must be irradiated by an electromagnetic wave, the substrate must exhibit a correspondingly high level of transparency for the relevant electromagnetic wavelength.

[0176] Preferably, the support substrate 1 is an inorganic substrate, for example made of silicon, glass, sapphire, or silicon carbide. Silicon support substrates are particularly preferred because they are transparent to selected wavelengths in the mid- and near-infrared range, which are used for the subsequent IR laser debonding.

[0177] Figure 2a shows a cross-sectional view of a first process step of an exemplary first process, in which a carrier substrate 1 is provided with at least one separating layer 2 and a first layer 3a and a second layer 3b. Figure 2b shows a side view of a second process step, in which a product substrate 4' with functional units 6 is aligned relative to the carrier substrate 1. The alignment is achieved using alignment markers (not shown) and alignment devices (not shown) that are, for example, integrated into a module for the temporary bonding of substrates. According to Figure 2c, the carrier substrate 1 and the product substrate 4' are temporarily bonded in a third process step. The product substrate 4' is contacted and bonded to layer 3b via a product substrate surface 4o suitable for bonding.The product substrate surface 4o suitable for bonding can also be a layer, in particular a bonding layer suitable for bonding (not shown).

[0178] Figure 3a shows a cross-sectional view of a substrate stack 5 comprising a support substrate 1, a separating layer 2, a first further layer 3, and product substrate 4. After alignment, the support substrate 1 and product substrate 4 are temporarily bonded to a layer system formed between the support substrate 1 and the product substrate, comprising a separating layer and at least the first further layer according to the embodiments shown in Figures 1c or 2c.

[0179] In a preferred embodiment of the method, the support substrate 1 is made of silicon.

[0180] In a preferred embodiment of the method, the separating layer 2 is made of a metal or a nitride, preferably titanium nitride (TiN).

[0181] In one embodiment, the layer system arranged between the support substrate and the product substrate consists of a separating layer 2 made of titanium nitride and exactly one first layer 3, which is designed as an inorganic protective layer 3 made of metal.

[0182] In one embodiment, the layer system arranged between the support substrate 1 and the product substrate 4 has a separating layer 2 made of titanium nitride and exactly one inorganic first layer made of titanium, which serves as a protective layer and preferably consists essentially exclusively of titanium.

[0183] In a further embodiment of the method, the separating layer 2 is made of a metal or a nitride, preferably titanium nitride (TiN), and the at least first further layer 3 is an aluminum oxide layer.

[0184] In a further embodiment of the method, it is provided that a second further layer 3a and a third further layer 3b are used after the separating layer 2, as shown in Figure 2c, wherein the second further layer 3a and the third further layer 3b are preferably inorganic.

[0185] In a further embodiment of the method, the separating layer 2 is made of a metal or a nitride, preferably titanium nitride (TiN), and the second layer 3a is an aluminum oxide layer 3a and / or the third layer is a titanium layer 3b. The order of the second and third layers 3a and 3b can also be reversed.

[0186] In one embodiment, the layer system arranged between the support substrate 1 and the product substrate 4, 4' comprises a separating layer 2 made of titanium nitride, a second layer 3a made of aluminum oxide, and a third further layer made of titanium. Where layers are generally referred to, the corresponding properties apply specifically to the separating layer, the first further layer, the second further layer, and the third further layer, each and / or selectively.

[0187] In a preferred embodiment of the substrate stack, at least one layer 2, 3, 3a, 3b of the substrate system comprises, preferably consists of, titanium (Ti), aluminum (Al), aluminum oxide (Al₂O₃), aluminum nitride (Al₂O₃), tantalum (Ta), tantalum nitride (TaN), titanium nitride (TiN), or copper (Cu). The layer thickness is particularly preferably between 10 nm and 200 nm.

[0188] In a preferred embodiment of the substrate stack, the separating layer 2 and the at least one further layer 3 of the substrate system preferably comprise titanium (Ti), aluminum (Al), aluminum oxide (Al2O3), aluminum nitride (AlN), tantalum (Ta), tantalum nitride (TaN), titanium nitride (TiN) or copper (Cu).

[0189] In a preferred embodiment of the substrate system, the separating layer has a thickness between 0.1 nm and 100 nm, preferably between 0.1 nm and 25 nm. In a preferred embodiment of the substrate system, the first further layer has a thickness between 1 nm and 200 nm, preferably between 1 nm and 100 nm.

[0190] In a further embodiment of the substrate system, it is provided that the first further layer has a layer thickness between 1 nm and 1000 nm, preferably between 100 nm and 500 nm.

[0191] Figure 3b shows a cross-sectional view of a second process step of an exemplary process. The product substrate 4 is thinned by chemical-mechanical polishing (CMP) with a CMP pad 7 (the scale in Figure 3b is not proportional for clarity). After thinning, the processed product substrate 4n is mechanically stabilized by the carrier substrate 1, the separating layer 2, and at least one further layer 3. Thinning is often desirable to minimize the thickness of the final product.

[0192] As shown in Figure 3c, in a third process step, the processed and preferably re-thinned product substrate 4n is aligned and bonded to a transfer substrate 8 via the processed second product substrate surface. Preferably, the transfer substrate 8 is a film 10 stretched onto a frame 9. In another embodiment, the transfer substrate 8 can be a different substrate, in particular another carrier substrate 1 or another product substrate 4. The transfer substrate 8 is selected such that the product substrate 4, 4', 4n is mechanically stabilized during IR laser bonding to remove the carrier substrate 1 as shown in Figure 3d and during the subsequent cleaning process to remove the remaining layers 2, 2', 3, 3a, 3b as shown in Figure 3f.

[0193] Figure 3d shows a cross-sectional view of a fourth process step of an exemplary process. A laser 11 is used to focus a laser beam 12 onto the separating layer 2. In a preferred embodiment, the laser beams 12 first pass through the support substrate 1 and are subsequently absorbed by the separating layer 2. A support substrate 1 made of silicon is preferably used to provide sufficient transparency for the infrared radiation of an IR laser 11. The laser unit preferably acts selectively and with tailored parameters on the separating layer 2 in different, preferably regularly defective, areas. By using a laser 11 with appropriate laser parameters, in particular a very short pulse duration in the picosecond range, the separating layer 2 is dissolved and / or the adhesion to the support substrate 1 is reduced at least to such an extent that the support substrate 1 can be removed.In particular, due to the high local energy concentration, lateral cracks form in the separation layer 2, so that the support substrate 1 can easily be separated from the product substrate 4.

[0194] After removal of the carrier substrate 1, in one embodiment the product substrate 4n according to Figure 3e remains fixed to the transfer substrate 8 for simplified handling. Preferably, the transfer substrate 8 is a film 10 stretched over a frame 9.

[0195] The inorganic separating layer 2, which is preferably opaque to laser radiation, absorbs the laser radiation, thus reducing the adhesive properties and / or the stability of the separating layer 2, preferably with gas formation. In particular, lateral cracks form in the separating layer 2 due to the high local energy concentration, which can propagate in different directions. After IR laser debonding, the separating layer 2, or the remaining separating layer 2' still present on layer 3 after laser treatment, as well as the first further layer 3, must preferably be removed without residue. Figure 3e shows a top view of a section of the surface on the product substrate 4, 4n after separation from the support substrate 1. If the separation during laser debonding is not homogeneous, orIf the separation occurs uniformly along the layer boundaries, a surface like the exemplary top view in Figure 3e is conceivable, where areas 2' consist of material from the separating layer 2 and areas consist of material from the further layer 3. In an alternative embodiment, the separation could occur more uniformly along a layer boundary, so that layer 3 is largely covered with material from the separating layer 2.

[0196] In an alternative embodiment with more than one further layer 3, it is conceivable that at least one of the further layers 3, in particular layer 3b, which borders the product substrate 4n, remains on the product substrate 4n and is not removed. In particular, the remaining layer can be a bonding surface for further processes. Preferably, this layer comprises silicon dioxide (Si₂O₂) and / or silicon carbonitride (SiCN) and / or silicon nitride (Si₃N₄) and / or aluminum nitride (Al₂O₃), and / or aluminum oxide (Al₂O₃) and / or silicon carbide (SiCO) and / or silicon carbide (SiC), generally a ceramic bonding layer. If an additional bonding layer on the product substrate is necessary, dielectrics such as silicon dioxide (SiCh), silicon carbonitride (SiCN), indium tin oxide, or indium titanium oxide are used, for example, as the material of the bonding layer.If this layer is required for further processing of the product substrate after separation from the support substrate, then this layer, which is located directly on the product substrate, is not necessarily removed during cleaning. This layer can also be considered part of the product substrate and, in this case, is not part of the layer system.

[0197] Following IR laser debonding, a single-wafer cleaning process on frames or saw frames 9 is possible, as shown in Figures 3e to 3g. The existing wet-chemical cleaning devices for wafer handling can be advantageously used, thus simplifying and flexibly designing the post-treatment process. In an alternative embodiment, instead of a saw frame 9, a substrate holder with a receiving surface and fixation for the product substrate 4, 4', 4n separated from the carrier substrate 1, which is also known to those skilled in the art, can be used. The choice depends, among other things, on the resistance to the chemicals used in the cleaning process.

[0198] Figure 3f shows a cross-sectional view of a fifth process step of an exemplary process. The optimized material composition of the separating layer 2, 2' and the first layer 3 enables rapid and effective cleaning of the product substrate 4n after IR laser bonding in a single cleaning step using a single cleaning method. Preferably, wet chemical cleaning is performed according to Figure 3f, wherein the solvent, in particular solvent mixture, is selected such that all layers of the layer system can be dissolved simultaneously, or at least the first further layer 3 and the separating layer. Wet etching can be carried out as spray etching according to Figure 3f or alternatively as immersion etching.

[0199] By coordinating the solvent selection and the choice of materials for the separation layer 2, 2' on the one hand, and the first further layer 3, the second further layer 3a, and / or the third, 3b of the layer system on the other, which is used for temporary bonding and IR laser debonding of the product substrate to the support substrate, a simple, fast, non-selective, and therefore cost- and time-efficient cleaning of the product substrate is possible. The chemicals or solvent mixture used, unlike the usual state of the art in the semiconductor industry, is not tailored to a specific layer and does not possess high selectivity towards the individual layers of the preferred layer system. Therefore, no solvent change is necessary.

[0200] In particular, if after laser debonding the product substrate surface has areas with different materials as shown in the exemplary top view from Figure 3e, where areas 2' are made of material from the separating layer 2 and areas are made of material from the first layer 3, a solvent is suitable for fast and effective cleaning of the product substrate 4 which can remove different materials of the separating layer 2 and the first layer equally and simultaneously.

[0201] In order to use a single solvent mixture as an etching solution for different materials or chemical compositions of the at least two layers (i.e., separating layer and first further layer) of the layer system after debonding, the selectivity of the solution for selected materials of the layer system can be changed, for example by controlling the etch rate through the composition of a solvent mixture.

[0202] The etching solutions can be single solvents or mixtures of two or more solvents. The solvent mixture consists of at least two or more solvents and / or chemicals.

[0203] One or more of the following chemicals are typically chosen as solvents: hydrochloric acid (HCl), sulfuric acid (H₂SO₄), nitric acid (HNO₃), phosphoric acid (H₃PO₄), ammonia (NH₃), hydrogen peroxide (H₂O₂), hydrofluoric acid (HF). The solvents are diluted with dilute water as needed.

[0204] Sulfuric acid, nitric acid and / or hydrogen peroxide, as well as combinations thereof, are also used, in particular, as oxidizing agents.

[0205] If the separating layer and the first subsequent layer consist of the same element in different forms and / or in different compounds, a simplified, uniform, and faster cleaning process in just one step for at least the two layers using a single cleaning agent is even easier. In one embodiment with a separating layer made of titanium nitride and at least one first layer made of titanium, for example, titanium and the titanium-containing titanium nitride can be advantageously removed from the product substrate in a single wet-chemical cleaning step after the separation process, since they can be dissolved with the same chemicals. Preferably, the solvent mixture for removing the titanium nitride and titanium layers is a solution of hydrogen peroxide, ammonia, and dilute water, with an H₂O₂:NH₄OH:H₂O ratio between 1:1:5 and 1:1:20 vol%. In another embodiment, salts can be added.The acid solutions can be buffered with salts, for example with ammonium salts such as ammonium fluoride (NH4F) and / or ammonium hydrogen difluoride (NH4HF2).

[0206] The selection of chemicals, particularly the solvent concentration, is further optimized for dissolving an additional layer. A layer system comprising titanium nitride, aluminum oxide, and titanium can also be advantageously removed from the product substrate in a single wet-chemical cleaning step after separation, since titanium nitride, titanium, and aluminum oxide can be dissolved with the same chemicals. The optimization of the solvent and salt proportions depends on the dissolution rates of the layer materials and the layer thicknesses, ensuring that cleaning occurs within timeframes practical for the semiconductor industry. Preferably, the solvent mixture for removing titanium nitride, titanium, and aluminum oxide layers is a solution of hydrogen peroxide, ammonia, and dilute water, with an H₂O₂:NH₄OH:H₂O ratio between 1:1:5 and 1:1:20 vol%.In another embodiment, the acid solutions can be buffered with salts, for example with ammonium salts such as ammonium fluoride (NH4F). Other salts include, for example, ammonium hydrogen difluoride (NH4HF2).

[0207] In spray etching, each product substrate 4n is processed individually. Product substrates 4n are fixed to a substrate holding device, rotated, and cleaned with the addition of fresh etching solution using one or more nozzles 13. The at least one nozzle 13 can be set at any angle to the substrate surface. The height of the nozzles and the radial position between the substrate edge and the substrate center can be adjusted as needed. Control can be achieved, in particular, by continuously adjustable settings. In one embodiment, between 1 and 10 nozzles are used, preferably between 1 and 6 nozzles, and even more preferably between 1 and 4 nozzles. The product substrate cleaning is carried out at a temperature between 10 and 150°C, preferably between 20 and 85°C. In a preferred embodiment, the solvents or solvent mixture are heated.They are heated before and / or while exiting the spray device, such as a nozzle. Temperature sensors enable the measurement, control, and / or regulation of the temperature.

[0208] In a further embodiment, preferably intended for product substrates with surface structuring or surface structures, such as functional units, the inorganic layer system can be combined with an additional structural protective layer. Such a structural protective layer is provided to protect structures on the surface of the product substrate and covers them completely, or at least to more than 50%, preferably more than 80%. A solvent mixture optimized for the layer system and the additional surface structure protective layer is preferably used for the simultaneous removal of all materials from the multiple layers on the product substrate, including the surface structure protective layer, without changing the solvent.

[0209] If the surface structure protective layer consists of a material that is more easily soluble than the layers of the coating system, such as a polymer or hybrid polymer, an alternative cleaning method can be used to selectively treat this layer with a solvent or solvent mixture, for example, from the periphery, and thus dissolve it from the accessible side. Dissolving the surface structure protective layer simultaneously removes the other layers located on top of it, particularly the inorganic coating system.

[0210] The substrate receiving device may also contain heating medium and / or coolant to regulate the substrate temperature. Temperature sensors enable the measurement and control of the temperature.

[0211] Wet chemical cleaning is preferably carried out for a time between 10 s and 20 min, more preferably between 10 s and 10 min, and even more preferably between 1 min and 5 min. At least one additional nozzle can be used to rinse the product substrate surface with distilled or demineralized water to stop the reaction of the etching solution or solvent mixture with the product substrate surface and to rinse. Rinsing can preferably be carried out at temperatures between room temperature and 85°C.

[0212] The cleaning modules contain basins and outlets for collecting the chemicals. Cleaning modules are familiar to professionals and will not be described in detail here. The cleaning modules can also be used for ultrasonic cleaning.

[0213] After the simplified cleaning, which is carried out in the cleaning module of the process plant, the product substrate 4n can be further processed in the same plant or in another plant, for example after a heating-out step, without further loss of time, as shown in Figure 3g.

[0214] Figures 4a to 4c show several independent modules 19 of a module group 15, 15', 15", which are connected to an evacuable workspace 17, which is separated and defined from the modules, and in particular sealed.

[0215] The workspace 17 can be set to a cleanroom atmosphere or evacuated to a high vacuum, in particular controlled by a software-based control unit. Within the module group 15, 15', 15" a transfer robot 16 transports the substrates between a loading module 18 and the individual modules 19 of the module group. "Substrate" includes substrate, substrate stack, wafer, product substrate, or support substrate. Several, in particular two, transfer robots can also be present in the workspace (not shown). The process is controlled by the control unit. The modules 19 from the module group 15 according to Figure 4a are, in particular, a laser debonding module and a cleaning module. The modules 19 from the module group 15', 15" according to Figures 4b and / or 4c are, for example, a bonding module, modules for further processing of the product substrates, a laser debonding module, a cleaning module, and / or an oven and / or a CMP module.In another embodiment, multiple modules are present. For example, in one embodiment, in addition to a CMP module and a laser debonding module, two cleaning modules and two ovens can be present in a module group.

[0216] Reference symbol:@

[0217] I Carrier substrate

[0218] 2, 2' Separation layer

[0219] 3, 3a, 3b Further layer

[0220] 4.4' product substrate

[0221] 40 Product substrate surface

[0222] 4n Product substrate after processing 5, 5' Substrate stack

[0223] 6 Functional Unit

[0224] 7 CMP pad (chemical-mechanical polishing) 8 Transfer carrier substrate

[0225] 9 frames

[0226] 10 slides

[0227] II Laser

[0228] 12 Laser beam

[0229] 13 Rinsing / Spraying device

[0230] 14 cleaning / collection basins with substrate holders 15,15',15" module group

[0231] 16 transfer robots

[0232] 17 Workroom

[0233] 18 Lock or storage container (e.g. FOUP) 19 Module

Claims

Claims 1. Method for separating a support substrate (1) from a product substrate (4, 4n), comprising: Providing the support substrate (1) and the product substrate (4, 4n) in a connected state in which the support substrate (1) and the product substrate (4, 4n) are connected to each other via a layer system between the support substrate (1) and the product substrate (4, 4n), in particular temporarily connected to each other, wherein the layer system comprises a separating layer (2, 2') and a first further layer (3) distinct from the separating layer (2, 2'), wherein the separating layer (2, 2') and the first further layer (3) are inorganic, Separation of the support substrate (1) and the product substrate (4, 4n) by irradiating the layer system, preferably the separation layer (2, 2'), with laser light (12) and Cleaning the product substrate (4, 4n) and / or support substrate (1) with a common solvent, with which residues are removed from both the separating layer (2, 2') and the first further layer (3), preferably in a common cleaning step.

2. Method according to claim 1, wherein the separating layer (2, 2') and the first further layer (3) are selected such that they can be removed with the common solvent.

3. Method according to any of the preceding claims, wherein the separating layer (2, 2') comprises or consists of a metal, a semiconductor, a nitride, and / or a metal nitride, for example titanium nitride.

4. Method according to one of the preceding claims, wherein the first further layer (3) comprises or consists of a metal, in particular titanium, a nitride, a semiconductor, a ceramic, an alloy and / or a metal oxide, in particular aluminium oxide. - 42 / 45 -@ 5. Method according to claims 3 and 4, wherein the separating layer (2, 2') and the first further layer (3) contain at least one common chemical element or a common chemical compound.

6. Method according to one of the preceding claims, wherein the separating layer (2, 2') comprises titanium nitride and the first further layer (3) comprises titanium.

7. Method according to one of the preceding claims, wherein the layer system additionally comprises a second further layer (3a) and / or a third further layer (3b).

8. A method according to any of the preceding claims, wherein the solvent comprises hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), phosphoric acid (H3PO4), ammonia (NH3), hydrogen peroxide (H2O2) and / or hydrofluoric acid (HF), preferably diluted with deionized water, wherein the solvent is preferably buffered with a salt.

9. A method according to any of the preceding claims, wherein the solvent comprises hydrogen peroxide and ammonia, preferably diluted with deionized water, wherein the solvent preferably comprises equal parts hydrogen peroxide and ammonia, in particular in the ratio H2O2:NH4OH:H2O between 1:1:5 and 1:1:20 vol%.

10. Method according to one of the preceding claims, wherein the separating layer (2, 2'), the first further layer (3), the second further layer (3a) and / or the third further layer (3c) has a layer thickness that assumes a value between 1 nm and 200 nm, preferably between 10 and 100 nm and particularly preferably between 25 and 85.

11. Method according to one of the preceding claims, wherein the product substrate (4, 4') and / or the support substrate (1) are cleaned at a temperature between 10 and 150°C, preferably between 20 and 85°C, wherein the temperature is preferably regulated or controlled.

12. Method according to any one of the preceding claims, wherein the product substrate (4, 4n) and / or the carrier substrate (1) is incubated for a period of time between 10 s and 20 min, - 43 / 45 -@ preferably cleaned between 10 s and 10 min and even more preferably between 1 min and 5 min.

13. Substrate stack for a method according to one of the preceding claims, comprising - a carrier substrate (1), - a product substrate (4, 4n) and - a layer system comprising a separating layer (2, 2') and a first further layer (3), wherein the layer system is designed such that the separating layer (2, 2') and the first further layer (3) can be removed with a common cleaning agent.

14. Solvent for a method according to one of the preceding claims, wherein the solvent is designed for removing the separating layer (2, 2') and the first further layer (3).

15. Device for carrying out a method according to one of claims 1 to 13, in particular using a module (19) for cleaning the product substrate (4, 4n) and / or the carrier substrate (1). - 44 / 45 -

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