Substrate stack, modified layer system, method for processing a substrate stack and apparatus for such a method

Abstract

A substrate stack comprising: - a carrier substrate (1), and - a product substrate (3), wherein between the carrier substrate (1) and the product substrate (3) a modified layer system (2) is constituted for a main function, which layer system comprises a layer system material for implementing the main function, wherein for providing additional functionality arranged in addition to the main function, the layer system (2) is designed such that the absorption behavior of the region between the carrier substrate (1) and the product substrate (3) at least locally differs from the absorption behavior which would occur if the region between the carrier substrate (1) and the product substrate (3) were completely filled with the layer system material.

Description

Technical Field

[0001] The present invention relates to a substrate stack, a modified layer system, a method for processing the substrate stack, and an apparatus for the method. Background Technology

[0002] In the semiconductor industry, numerous methods exist for bonding product substrates to carrier substrates. This bonding is always necessary while the product substrate must be stabilized during at least one process step. Without a corresponding carrier substrate, the product substrate may be vulnerable and could be damaged or completely fractured. After the product substrate has undergone the corresponding processing, it must be completely and non-destructively removed from the carrier substrate. In some methods, the product substrate is bonded to a second carrier substrate with its free surface before removing the first carrier substrate. This can be repeated multiple times until all sides of the product substrate have been correspondingly processed. This method of temporary bonding is called temporary bonding. The separation method is called debonding.

[0003] Temporary bonding can be understood as a connection method in which two substrates are temporarily and firmly connected to each other, allowing one of the two substrates to be processed. However, a characteristic of temporary bonding is that the two substrates can be separated from each other again without damage.

[0004] Over the past few decades, various methods and devices have been developed to produce such temporary bonds. In particular, so-called bonding adhesives, or simply adhesives, are used to establish a connection between two substrates. The adhesive is applied to at least one of the two substrates. These adhesives are mostly polymers. In most cases, carbon-containing, i.e., organic polymers, are involved. These adhesives are characterized by establishing an adhesive bond between the substrates. That is, the substrates do not necessarily have to be flat, but can have raised portions. After the temporary bond is established, pressure and / or heat are applied to the substrates, thereby temporarily connecting them to each other.

[0005] To enable the removal of the carrier substrate after processing the product substrate, different debonding methods are employed. One of these debonding methods is so-called sliding debonding.

[0006] In this method, a stack of substrates is heated to a temperature at which the viscosity of the adhesive decreases to the point that the polymer loses its adhesive properties. After reaching the desired temperature, a shear force is applied along the substrate surface, shearing the two substrates apart. Shearing is performed by the shearing motion of a substrate holder that holds the substrates in place.

[0007] Another method is edge region debonding. In these methods, a special carrier substrate is created that exhibits high adhesion to the adhesive only at its edges. The majority of the carrier substrate surface is covered with an anti-adhesion layer. The adhesive strength at the edges is sufficient to process the product substrate without defects. Debonding is then achieved by breaking the adhesive in the edge regions outside the carrier substrate. Due to the very small thickness of this region, breaking can be performed rapidly. Chemical and / or mechanical means are used to break the adhesive.

[0008] Another method combines an adhesive with a so-called release layer. The release layer is applied to a carrier substrate and / or a product substrate. Preferably, it is applied to the carrier substrate so that the product substrate is not contaminated by the release layer material. The carrier substrate with the release layer is then bonded to the product substrate using an adhesive. After the product substrate has been treated, delamination is induced by a laser that breaks down the release layer, preferably focused on the release layer from the carrier substrate side. The energy input can be focused and metered very precisely so as not to damage the product substrate. Although this method is considered a further development in the prior art due to the significant simplification of the bonding process using a laser, an adhesive is still required. Therefore, temperature stability is still lacking in this method.

[0009] The aforementioned debonding method has the following disadvantages: the maximum permissible temperature for processing the product substrate must be low. If the product substrate must undergo process steps requiring higher temperatures, the adhesive strength may decrease to the point that the product substrate can no longer be fixed to the carrier substrate and may be damaged or completely broken.

[0010] Other temporary bonding and debonding methods based on the use of adhesives exist, which will not be fully listed here.

[0011] A further development of temporary bonding methods lies in using only metal and / or ceramic layers instead of polymer-based adhesives. This allows for significantly increased processing temperatures for the product substrate due to its high temperature stability. Separation layers known and used in the prior art are retained and are also used in these methods for delamination of the product substrate from the carrier substrate. Summary of the Invention

[0012] The object of the present invention is to improve the bonding layers known from the prior art so that the bonding layers allow for additional functionality that is advantageous in one or more process steps when processing substrate stacks.

[0013] The present invention achieves the stated objective by means of the substrate stack according to claim 1, the modified layer system according to claim 9, the method according to claim 10, and the bonding apparatus according to claim 14. Advantageous improvements of the invention are given in the dependent claims. The scope of the invention also includes all combinations of at least two features given in the specification, claims, and / or drawings. Values ​​within the given numerical ranges should also be considered as limit values ​​and can be claimed in any combination.

[0014] According to a first aspect of the present invention, a substrate stack is provided, comprising:

[0015] - Support substrate, and

[0016] - Product substrate,

[0017] For its primary function, a modified layer system is formed between the carrier substrate and the product substrate. This layer system includes layer system materials designed to fulfill the primary function.

[0018] In order to provide additional functionality in addition to the main function, the modified layer system is designed such that the absorption performance in the region between the carrier substrate and the product substrate is at least locally different from the absorption performance that would occur if the region between the carrier substrate and the product substrate were completely filled with the layer system material.

[0019] Compared to layer systems known in the prior art, the layer system proposed according to the present invention possesses additional functionalities beyond its primary function. The primary function is, for example, establishing a connection between a product substrate and a carrier substrate, particularly bonding, especially preferably temporary bonding between the product substrate and the carrier substrate, or enabling the possibility of simple, particularly laser-executed, debonding, in which the carrier substrate and the product substrate are first connected to each other via the layer system. Through these additional functionalities, for example, it is feasible to prepare or modify the layer system in a way that, for example, assists the alignment process or improves debonding. Thus, the layer system proves advantageous because it provides, for example, other additional functionalities, particularly those unrelated to the layer system material used and its optical absorption performance, which would otherwise have to be achieved costly through other methods. Therefore, the feature of the present invention is particularly preferably a multifunctional layer system.

[0020] In the following sections of this document, the product substrate can also be understood as a plurality of layers produced directly, particularly without bonding, on a layer system of a carrier substrate by various methods, especially at least one epitaxial method. Preferably, the modified layer system and / or the product substrate are part of a plurality of laminations, which are formed, for example, by epitaxial methods to form a substrate stack. For example, the product substrate and the layer system each comprise a plurality of laminations, which are applied to or formed on the carrier substrate.

[0021] Here, it is particularly preferred that the bonding be temporary. The uppermost layer of the layer system, serving as the bonding layer, particularly possesses adhesive properties, which are specifically designed for temporary bonding. Here, it is particularly preferred that the carrier substrate is thicker than the product substrate to ensure corresponding stability. Furthermore, it is preferred that regions with altered absorption performance are particularly completely surrounded by the layer system material, especially in planes extending parallel to the main extension plane, and / or where a reduced amount of layer system material is formed in regions with altered absorption performance. The layer system material is particularly understood as the material used to achieve the primary function, such as the material used for bonding and / or separating the carrier substrate and the product substrate. The layer system can also include other elements, such as other sheets or layers, which are not part of the layer system material but cause additional functionality. The layer system material is determined by the primary function. If the primary function refers to bonding, then the layer system material is considered to be the material responsible for bonding. If the layer system has additional materials, this determines the additional functionality and does not associate it with the layer system material associated with the primary function. This also applies to material sheets added to enhance the primary function.

[0022] In particular, the additional functionality is a functionality related to optical absorption performance, such as utilizing altered optical absorption performance for a specific function. Preferably, the additional functionality utilizes absorption performance or is a result of absorption performance. For example, in a region with altered absorption performance, light is selectively absorbed and / or transmitted in order to utilize this functionality. In summary, it is therefore preferable to relate to additional optical functions.

[0023] Preferably, absorption performance is understood as an absorption spectrum. For example, such an absorption spectrum is characterized by the absorption and / or transmission of light in relation to wavelength. Changes in absorption performance are particularly present when, for example, absorption capacity decreases and / or increases for a particular wavelength. It is currently proposed to use absorption performance, especially the absorption spectrum, as a reference when only layer system material is present in the observed sub-region of the layer system between the product substrate and the carrier substrate. It is advantageously possible to reduce absorption performance by corresponding spatial modulation or reduction of the layer system, thereby reducing the effective optical path length through the layer system material. As an additional functionality, local transparency can be achieved.

[0024] According to a preferred embodiment of the invention, the material distribution of the layer system material within the layer system is at least temporarily spatially modulated. Preferably, the material distribution of the layer system material is designed to be persistent, i.e., persistent at least during the time period during which the bonding exists between the product substrate and the carrier substrate. This can be achieved, for example, by forming transparent regions within the layer system, such as by providing vacant regions and / or by incorporating a material transparent to a specific wavelength into regions of the layer system that are otherwise substantially composed of the layer system material.

[0025] Preferably, the layer system has at least one transparent region, particularly a free area. Specifically, before bonding the product substrate and the carrier substrate, material in designated areas can be selectively removed or separated to ensure corresponding free areas that allow, especially in the case of a transparent carrier substrate, orientation based on alignment marks on the product substrate. In this case, the transparent region advantageously constitutes a window-like area that allows visual inspection of the product substrate, and particularly the alignment marks on the product substrate, when visual inspection, for example by a camera or the human eye, is directed toward the side of the substrate stack on which the carrier substrate extends. The layer system can also, for example, be provided as a single layer whose primary function is to establish bonding.

[0026] The area resembling a window is preferably square. The size of this area ranges from 50 μm × 50 μm to 500 μm × 500 μm, preferably from 100 μm × 100 μm to 200 μm × 200 μm. Non-square rectangular areas resembling a window, for example, within the range of 40 μm × 200 μm, are also acceptable.

[0027] Preferably, the layer system has alignment marks in and / or on at least one of its layers, especially when the layer system is formed of multiple layers. It is advantageous to thus orient the product substrate, particularly a structured product substrate, specifically relative to the alignment marks in the layer system. Here, the alignment marks are made of a material different from the layer system material, i.e., the material of the layer on which the alignment marks are formed, thereby altering the absorption behavior in the region where the alignment marks are located, relative to the absorption behavior that would occur if the layer system were entirely composed of the layer system material in that region. Thus, the bonding layer acquires additional functionality. Intermediate layers or alignment marks disposed in addition to the layer system material are not part of the layer system material.

[0028] In particular, it is proposed that, in order to selectively influence absorption performance, the layer system comprises a layer system material and intermediate sheets, preferably serving as dielectric layers. Preferably, it is proposed that, in order to selectively influence the absorption performance of the layer system, the layer system is formed of different, especially alternating, layers or monolayer sheets. It is advantageously possible to selectively influence the absorption performance in the bonding layer through targeted layer arrangements, particularly through staggered layer arrangements of different, especially alternating, layer system materials. This has proven particularly advantageous when the absorption capability for a specific, prescribed laser wavelength needs to be specifically enhanced. Thus, for example, it is possible to achieve: the laser is selectively absorbed only in the separation layer and / or bonding layer, so as to trigger the debonding process by the heat input generated locally in this case. Here, the individual sheets or layers of the layer system particularly act together and / or are configured relative to each other so that absorption can be selectively enhanced according to interference effects or superposition. Preferably, some layers of the layer system are relatively thin metallic layers. However, combinations of metallic and non-metallic layers are also contemplated.

[0029] In another preferred embodiment, the layer system is closed along the main extension plane, and preferably, the absorption over the entire region between the carrier substrate and the product substrate is spatially constant. This preferably ensures that the bonding process and subsequent debonding process can effectively act on the entire surface that facilitates bonding between the product substrate and the carrier substrate.

[0030] Preferably, the primary function is the connection, particularly bonding, between the product substrate and the carrier substrate, wherein the layer system preferably includes at least one bonding layer having a bonding layer material. In particular, the layer system has multiple dielectric layers and / or the layer system material includes a polymer.

[0031] Preferably, the light used is a laser. For example, in this case, a pulsed laser can be used, in which particularly high energy input or energy can be generated. The laser should be absorbed by the substrate, which is the substrate through which the laser must penetrate, with the least possible absorption. Preferably, the wavelength of the laser is tuned such that the carrier substrate and / or the product substrate is transparent or at least semi-transparent to the wavelength used. The separation layer within the layer system should absorb the laser to the maximum extent possible in order to induce debonding. Since the substrate is typically much thicker than the layer system, the absorption performance of the substrate through which the laser penetrates is crucial. As an example, silicon, the material used in the semiconductor industry to make most substrates, can be mentioned.

[0032] If the carrier substrate or product substrate is a silicon substrate, then the laser wavelength should be between 1 μm and 10 μm, because silicon has a very high transmittance, i.e., penetrability, of up to 50% in this wavelength range. If other substrates are chosen, then lasers with different wavelengths may need to be selected.

[0033] In particular, it is proposed that a laser, especially a pulsed laser, be used for separation. In a preferred embodiment of the method, the wavelength of the laser beam is proposed to be between 0.1 μm and 500 μm, preferably between 0.2 μm and 100 μm, more preferably between 0.3 μm and 50 μm, most preferably between 0.5 μm and 10 μm, and most preferably between 1 μm and 2.5 μm. In this way, the separation layer can be irradiated particularly effectively and specifically. The carrier substrate is preferably permeable to the laser beam.

[0034] In a preferred embodiment of the method, the pulse energy of the laser beam is between 0.01 μJ and 128 μJ, preferably between 0.125 μJ and 64 μJ, more preferably between 0.25 μJ and 32 μJ, most preferably between 0.5 μJ and 16 μJ, and most preferably between 1 μJ and 8 μJ. It has been found that these pulse energies can prevent damage to the product substrate. In a preferred embodiment of the method, the pulse duration of the laser beam 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.

[0035] Another subject of the invention is a modified layer system for a substrate stack according to the invention, wherein at least one layer comprises, preferably, a ceramic material. All the advantages and properties described for the substrate stack similarly apply to this layer system. In particular, the layer system is understood as a system in which the individual layers are combined such that they satisfy a specific optical purpose. Here, it is conceivable that the layer system material itself is provided and only needs to be disposed between the product substrate and the carrier substrate. For example, in the provided layer system, such as in the bonding layer of a monolayer sheet, a void for forming a transparent region is already provided, either a component from another material can fill the void, and / or the void has been used, and / or the void remains permanently vacant.

[0036] The layer system preferably comprises at least one layer. Preferably, all layers of the layer system are rigid material layers, particularly metal and / or ceramic layers. However, the use of at least one polymer layer, particularly an adhesive, is also contemplated. The layers used to constitute the layer system are preferably layers from one of the following material categories:

[0037] • Dielectrics, especially

[0038] ○ Nitrogen compounds, especially

[0039] ▪ TiN, CrN, TaN, AlN, NiN, Si3N4

[0040] ○ Carbides, especially carbon layers

[0041] ○ Oxides

[0042] ○ Less preferred polymers

[0043] • Conductor, preferably

[0044] ○ Metals, especially

[0045] ▪ Cr, Al, Ta, Co, Ni, Mn, Fe, Au, Ga, Sn, Ge, W, Cu, In.

[0046] The layer system is modified, for example, in at least one of the following ways.

[0047] In a first embodiment, the layer system has transparent regions to allow for back-side alignment of the product substrate. The transparent regions allow the surface of the product substrate, which is connected to the carrier substrate via the layer system, to be seen through the carrier substrate. This enables alignment of the product substrate, fixed to the carrier substrate, with another product substrate. This requires the carrier substrate to be transparent to the wavelength used. Here, the carrier substrate may not have absorbent layers or regions.

[0048] The transparent region can be understood as a sub-segment within a layered system through which measurements can be performed. Therefore, the transparent region can be constructed of a material transparent to electromagnetic radiation. However, it is also possible to consider the transparent region as a volumetric element without solids within the layered system, i.e., a region devoid of material. Transparency then relates to a vacuum or the contained gas or gas mixture, particularly the atmosphere.

[0049] In a second embodiment, the layer system has alignment marks that can be used to position the substrate and / or at least one die and / or chip. For example, it is also conceivable that, in a multilayer layer system, the alignment marks are disposed between two layers or layers of the layer system. The die is either produced directly in the product substrate or cast into a chip in a casting. The casting then forms the product substrate together with the cast chip. The die and / or chip have alignment marks. By using an optical system, it is possible to simultaneously observe the alignment marks on the die and / or chip and the alignment marks on the layer system. In this case, at least one layer of the layer system serves as an alignment mark layer.

[0050] Another aspect of the invention is a method for processing a substrate stack according to the invention, the substrate stack having a carrier substrate, a product substrate, and a layer system, wherein the layer system is disposed between the carrier substrate and the product substrate. All the advantages and characteristics described for the substrate stack can be similarly applied to the method, and vice versa. By forming corresponding layer systems in the substrate stack, it is advantageously feasible to ensure additional functionality and permissibility during further manufacturing and / or processing of the substrate stack, which simplifies further processes. For example, it is conceivable to simplify the alignment of the product substrate relative to another product substrate, or to simplify the debonding process, or to facilitate the bonding process with another product stack.

[0051] Preferably, the light is directed towards the substrate stack. This is particularly suitable, for example, when photographing or detecting alignment marks using corresponding optical devices, such as a corresponding camera system. For this purpose, the corresponding alignment marks need to be illuminated by a corresponding light source. Preferably, for targeted absorption by the layer system, the light, especially laser light, is directed towards the layer system, and particularly preferably focused onto the bonding layer.

[0052] Preferably, it is proposed that light be transmitted through an empty area in the layer system in order to align structural elements or another product substrate. It is advantageously feasible to use layer system materials that, in other cases, would impede light transmission through the layer system due to their typical absorption properties. It is also feasible to identify alignment marks on the product substrate from the side where the carrier substrate is located through a corresponding transparent area, similar to a window. In other words, the alignment marks can also be identified through the corresponding transparent area when viewing the product substrate from the direction of the carrier substrate or when visual inspection of it in the corresponding direction is desired, for example, by optical devices, especially a camera system.

[0053] If infrared light is used for observation through silicon, then choosing infrared light with a wavelength of about 1 μm may be advantageous in order to improve the contrast between silicon and non-silicon areas.

[0054] Preferably, the light used to debond the carrier substrate and the product substrate is absorbed. This advantageously allows for the triggering of the debonding process between the product substrate and the carrier substrate, particularly when further bonding between the product substrate and the carrier substrate is no longer desired. This can be induced by irradiation with light of a corresponding wavelength, and especially with an intensity above a threshold intensity.

[0055] Another aspect of the invention is an apparatus for performing the method according to the invention, wherein the apparatus includes a light source and / or a camera. By correspondingly using a light source and / or a camera, it is particularly possible to utilize altered absorption performance in order to achieve or utilize corresponding additional functionality. All the advantages and characteristics described for the substrate stack and the method can be similarly applied to the apparatus.

[0056] Particularly preferably, the light source is adapted to the layer system. In particular, it is proposed that, for example, the wavelength of the laser is coordinated with the absorption or absorption behavior of the bonding layers and / or separating layers of the layer system. Attached Figure Description

[0057] Other advantages, features, and details of the invention are given below in the description of preferred embodiments and with reference to the accompanying drawings. The drawings show:

[0058] Figure 1 A side view of a substrate stack having a first bonding layer according to the invention is shown.

[0059] Figure 2 A side view showing one method step of the face-to-face method is provided.

[0060] Figure 3 A side view showing one method step of the face-to-face method is provided.

[0061] Figure 4 This shows a side view of one method step of the face-to-back method.

[0062] Figure 5 This shows a side view of one method step of the face-to-back method.

[0063] Figure 6 A side view showing one step of the back-to-back method.

[0064] Figure 7 A side view showing one method step of the back-to-face method is provided.

[0065] Figure 8 A side view of the bonded substrate stack is shown.

[0066] Figure 9 A side view showing the debonding process, and

[0067] Figure 10 A side view of a substrate stack having a second bonding layer according to the invention is shown.

[0068] Figure 11 This illustrates a specific embodiment of the layer system, and

[0069] Figure 12 This demonstrates another possibility for using layer system 2.

[0070] In the accompanying drawings, the same components or components with the same function are indicated by the same reference numerals. Detailed Implementation

[0071] The following figure shows a simplified side view of one step of the alignment process. For clarity, the location of alignment marks using optical sub-devices is only visually shown on the right side (see figure). Figures 2 to 7 Typically, a corresponding optical sub-device is also present to the left of the corresponding orientation device. Possible orientation devices are described in detail in US 6,214,692 B1, US 10,692,747 B2, US 9,851,645 B2, US 9,418,882 B2, and US 9,576,825 B2. The optical sub-device is simplified as an upper optics and a lower optics mechanically coupled to each other. Each of these two optics is oriented relative to each other with multiple (ideally six) degrees of freedom. The optics are considered to be calibrated to each other. The corresponding calibration methods are known, for example, from US 9,418,882 B2 and US 9,464,884 B2. Ideally, the optical axes of the two optics are collinear. However, since collinearity is difficult to achieve, the optics are preferably oriented such that their optical axes intersect in the focal region, especially the focal point. Typically, the depths of field of the two optics also intersect in this focal region. The image recorded by each optic is schematically shown within a circle on the left side of each optic. In the following sections of this document, such recorded images will be referred to simply as images.

[0072] A face-to-face alignment process is understood as a method in which the alignment mark 5 is located at the bonding interface. A face-to-back or back-to-face alignment process is understood as a method in which the alignment mark 5 of the first product substrate is located at its bonding interface, while the alignment mark of the second product substrate is located on the surface of the product substrate opposite to the bonding interface. A back-to-back alignment process is understood as a method in which the alignment mark is located only on the surface of the product substrate opposite to the bonding interface, i.e., on the outside.

[0073] Furthermore, the second product substrate 3' is always shown to be thick enough that it does not need to be stabilized by the second carrier substrate 1. However, it is also possible to stabilize the product substrate 1' by another carrier substrate 1.

[0074] Figure 1 A simplified side view of the substrate stack is shown, including a carrier substrate 1 together with a bonding layer 2 and a product substrate 3. The carrier substrate 1 is typically thicker than the product substrate 1 to be stabilized. The product substrate 3 is connected to the carrier substrate 1 via a layer system 2. In this case, the layer system 2 has multiple transparent regions 4.

[0075] The following figures describe the orientation of the two product substrates 3, 3' relative to each other. Here, the alignment mark of each product substrate can be located on the surface of the product substrate that forms the bonding interface (face-to-face alignment) or on the surface of the product substrate opposite to the bonding interface (back-to-back alignment). Correspondingly, there are four possible orientations of the product substrates 3, 3' relative to each other: face-to-face, face-to-back, back-to-back, and back-to-face. Since the layer system 2 exists on the first product substrate 3, the first orientation relates to the first product substrate 3, and the second orientation relates to the second product substrate 3'.

[0076] Figure 2 A simplified right-hand view shows a method step in the face-to-face alignment process between a first product substrate 3 and a second product substrate 3' fixed on a carrier substrate 1. Both product substrates 3 and 3', as well as the carrier substrate 1, are transparent within the wavelength range used by the optics 6. The upper optics 6 measures the alignment mark 5 of the upper product substrate 3'. The alignment mark 5 is shown in gray in image 7 because photons reaching the upper optics 6 must pass through the carrier substrate 3', thus attenuating the intensity, i.e., the number of photons. In the prior art, measuring the alignment mark 5 of the lower product substrate 3 is not feasible because the layer system 2 is typically opaque to the wavelength used. However, it is preferable to have a transparent region 4 in the layer system 2 that allows the alignment mark 5 of the first product substrate 3 to be directly visible. Here, image 7 of the lower optics 6 also shows the attenuated alignment mark 5 because photons must pass through the carrier substrate 1, the transparent region 4, and the product substrate 3. Ideally, at least some portions of the boundary of the transparent region 4 are identifiable in image 7. The transparent region 4 can be a material transparent to the electromagnetic radiation used. However, a simpler and preferred approach is to completely discard the deposited material, leaving the transparent area 4 without any material.

[0077] Figure 3A simplified right-hand view shows a method step of a face-to-face alignment process between a first product substrate 3 and a second product substrate 3' fixed on a carrier substrate 1. The second product substrate 3' and the carrier substrate 1 are transparent, while the first product substrate 3 is opaque. Although the alignment mark 5 at the second product substrate 3' cannot be directly observed from the lower optics 6, the transparent region 4 of the layer system 2 is visible. The transparent region 4 is identifiable in the image 7 of the lower optics 6. That is, if the orientation relationship between the alignment mark 5 of the first product substrate 3 and the transparent region 4 is known, then the transparent region 4 itself can be used as an alignment mark. This orientation relationship is easily measured by measuring the first product substrate 3 solely through the two optics 6 before the actual alignment process of the two product substrates 3, 3'. Here, the upper optics 6 focuses on the alignment mark 5 of the product substrate 3, while the lower optics 6 simultaneously focuses on the transparent region 4 of the layer system 2. The two images 7 thus generated allow for the measurement of the orientation relationship.

[0078] Figure 4 A simplified right-hand view shows a method step of a face-to-back alignment process between a first product substrate 3 and a second product substrate 3' fixed on a carrier substrate 1. The upper substrate 6 allows direct measurement of the alignment mark 5 on the second product substrate 3'. Correspondingly, the alignment mark 5 is clearly visible in the image 7 of the upper optics 6. The first product substrate 3 is similar to... Figure 2 The lower product substrate 3 is measured. Alignment marks 5 and transparent areas 4 of the first product substrate 3 can be identified again, the alignment marks being visible to the lower optical device 6 through the transparent areas 4 of the layer system 2.

[0079] Figure 5 A simplified right-side view shows a method step of a face-to-back alignment process between a first product substrate 3 and a second product substrate 3' fixed on a carrier substrate 1, but in which the first product substrate 3 is opaque. That is, this embodiment is... Figure 3 and Figure 4 The combination that constitutes the composition.

[0080] Figure 6 A simplified right-side view shows a method step of a back-to-back alignment process between a first product substrate 3 and a second product substrate 3' fixed on a carrier substrate 1, wherein alignment marks 5 of the first product substrate 3 and the second product substrate 3' are located on the product substrate surfaces opposite to the bonding interface. In this embodiment, the transparency of the transparent region 4 is also utilized so that the alignment marks 5 of the first product substrate 3 can be observed.

[0081] Figure 7This is a simplified right-side view illustrating a method step in the back-to-back alignment process between a first product substrate 3 and a second product substrate 3' fixed on a carrier substrate 1, wherein the alignment mark 5 of the first product substrate 3 is located on the surface of the product substrate facing away from the bonding interface. The alignment mark 5 of the second product substrate 3' faces the bonding interface. In this embodiment, the transparency of the transparent region 4 is also utilized to allow observation of the alignment marks.

[0082] Figure 8 A simplified side view of two product substrates 3, 3' bonded to each other is shown. The lower product substrate 3 remains attached to the carrier substrate 1 via the layer system 2. However, the product substrate stack thus formed by the bonding between the two product substrates 3, 3' is much more stable, and the carrier substrate 1 can be removed if necessary. Alternatively, product substrate 3' can be reprocessed, and multiple additional product substrates 3'', 3''' (not shown) can be bonded to the system. Correspondingly, a multi-product substrate stack is thus formed.

[0083] Figure 9 A simplified side view of the debonding process is shown. The debonding process is carried out by means of a laser 8. Here, the carrier substrate 1 must be transparent to the laser radiation used by the laser 8. On the other hand, the layer system 2 must have the highest possible absorption for photons from the laser 8 in order to achieve debonding, i.e., debonding. The layer system 2 consists of at least a separation layer, which is subjected to corresponding ablation by the laser 8. If the separation layer is the only layer in the layer system 2, then it is also the bonding layer. However, it is also possible for the layer system 2 to consist of multiple layers. For example, it is possible to apply a separation layer on the carrier substrate 1 and deposit an oxide layer on the separation layer. In this case, the layer system 2 consists of a separation layer and an oxide layer. The oxide layer is used as the bonding layer, while the separation layer is only used for the debonding process.

[0084] Alternatively, the illustrated method steps can be performed using two product substrates 3, each of which is bonded to its own carrier substrate 1. In this case, the layer system 2 according to the invention is present at both carrier substrates 1 and can be advantageously used at both carrier substrates 1.

[0085] Figure 10A simplified side view of a carrier substrate 1 is shown, on which a second embodiment of the layer system 2 is fabricated. In this case, the layer system 2 has alignment marks 5. Furthermore, a product substrate 3 is shown, having multiple structures, particularly functional units, and most preferably a chip 9, which also has corresponding alignment marks 5'. The first product substrate 3 must be transparent to the optics 6 so that the alignment marks 5 of the layer system 2 and the alignment marks 5' of the chip 9 in the product substrate 3 can be detected simultaneously. It is conceivable that the chip 9 is fabricated directly in the product substrate 3. Thus, the product substrate 3 is, for example, silicon, and infrared light is used for observation and measurement. It is also conceivable that the product substrate 3 is a casting material used to inject the chip 9. In this case, a casting material that is correspondingly transparent to the electromagnetic radiation used must be used. Image 7 of the optics 6 shows that the alignment marks 5' are not located on the horizontally shown line. It is conceivable that the two alignment marks 5, 5' must be located on this line. Correspondingly, the lower carrier substrate and / or the upper product substrate 3 can be moved accordingly. Those skilled in the art will understand that, in this particular case, the goal is to optimally orient all chips 9 relative to the bonding layer 2, which requires observing multiple locations.

[0086] exist Figure 11 The diagram illustrates a specific embodiment of layer system 2, which is conceivable for constituting a substrate stack according to an exemplary embodiment of the present invention. Although Figures 1 to 10 The embodiments primarily focus on optically detecting alignment marks through transparent regions in layer system 2, or optically detecting alignment marks within layer system 2. However, layer system 2 is defined by its layer orientation, giving it specific transmission and absorption capabilities. To this end, layer system 2 is proposed to have alternating layers that influence the transmission and absorption performance of electromagnetic radiation. Preferably, this involves multiple layers 10. Advantageously, by corresponding spacing, i.e., by preferably equidistantly arranging the layers 10, it is possible to selectively influence absorption performance at a frequency. This, in turn, is advantageously possible to enhance absorption for specific wavelengths compared to other wavelengths. This allows for targeted optimization of absorption for wavelengths, for example, when the carrier substrate is transparent to said wavelength. Through the enhanced absorption in layer system 2, it is thus possible to remove the bonding function, i.e., the primary function, based on energy input, thereby allowing the corresponding debonding process. Therefore, by targeting enhanced absorption for specific wavelengths, it is advantageous to reduce the corresponding energy consumption for debonding, especially because the energy transport acting on the bonding layers can be optimized and designed more efficiently. Alternatively or supplementarily, it is conceivable to add materials to the layer system material such that the absorption performance of the material for a specific wavelength is improved.

[0087] Figure 12This illustrates another possibility for using layer system 2. Layer system 2 is deposited on carrier substrate 1. In the current case, layer system 2 consists of a separation layer 11 and a seed layer 12. For example, it is also contemplated that layer system 2 may be additionally provided with a layer according to... Figure 11 Layers 10 and 10' are used to achieve the corresponding transmission or absorption effects. However, for simplicity, only the separation layer 11 is shown. The seed layer 12 serves as the starting point for producing the epitaxial layer 13. Typically, the fabrication of this epitaxial layer 13 is complex and must be achieved through multiple process steps, especially by producing multiple other layers. A very common method is to produce the epitaxial layer 13 by overgrowth. For clarity, the precise layer structure is omitted. Only the epitaxial layer 13 on the layer system 2, especially on the seed layer 12, is shown. Functional units can now be produced in this particularly thin epitaxial layer 13. By laser scanning the separation layer 11, the seed layer 12, together with the epitaxial layer 13, can be separated from the carrier substrate 11. Typically, the epitaxial layer 13 has previously been surface-bonded to another substrate (not shown). However, it is also conceivable to remove the epitaxial layer 13 directly from the carrier substrate 1 and, in particular, fix it to a thin film carrier. Figure 12 It is shown that the layer system 2 according to the invention does not necessarily have to be associated with a bonding process. The resulting epitaxial layer can then also be considered as a product substrate for the purposes of this invention.

[0088] List of reference numerals

[0089] 1. Support substrate

[0090] 2-layer system

[0091] 3' Product Substrate

[0092] 4 Transparent areas

[0093] 5 Alignment Marks

[0094] 6. Optical devices

[0095] 7 Images

[0096] 8 Lasers

[0097] 9 chips

[0098] 10 floors

[0099] 11 Separation Layer

[0100] 12 seed crystal layers

[0101] 13 Epitaxial Layer

Claims

1. A substrate stack, comprising: - Support substrate (1), and - Product substrate (3). For its primary function, a modified layer system (2) is formed between the carrier substrate (1) and the product substrate (3), the layer system comprising layer system materials for achieving the primary function. In order to provide additional functionality in addition to the main functions, the layer system (2) is designed such that the absorption performance in the region between the carrier substrate (1) and the product substrate (3) is at least partially different from the absorption performance that occurs when the region between the carrier substrate (1) and the product substrate (3) is completely filled with the layer system material.

2. The substrate stack according to claim 1, wherein the material distribution of the layer system material in the layer system (2) is at least temporarily spatially modulated, preferably along the main extension plane and / or along a direction perpendicular to the main extension plane.

3. The substrate stack according to any one of the preceding claims, wherein the layer system (2) has at least one transparent region (4), particularly an empty region.

4. The substrate stack according to any one of the preceding claims, wherein the layer system (2) has alignment marks (5).

5. The substrate stack according to any one of the preceding claims, wherein, in order to selectively influence the absorption performance, the layer system (2) comprises a layer system material and an intermediate layer sheet (12), preferably as a dielectric layer.

6. The substrate stack according to claim 5, wherein the layer system (2) is closed along the main extension plane, and preferably, the absorption performance is spatially constant over the entire region between the carrier substrate (1) and the product substrate (3).

7. The substrate stack according to any one of the preceding claims, wherein the primary function is the connection, particularly bonding, between the product substrate (3) and the carrier substrate (1), wherein the layer system (2) preferably includes at least one bonding layer having a bonding layer material.

8. The substrate stack according to any one of the preceding claims, wherein the layer system (2) has a plurality of dielectric layers, and / or the layer system material comprises a polymer.

9. A modified layer system (2) for substrate stacking according to any one of the preceding claims, wherein the layer system material for bonding layer (2) preferably comprises a ceramic material.

10. A method for processing temporary bonding of a substrate stack having a carrier substrate (1), a product substrate (3) and a bonding layer (2) according to any one of the preceding claims, wherein the bonding layer (2) is disposed between the carrier substrate (1) and the product substrate (3).

11. The method of claim 10, wherein the light is directed toward the substrate stack.

12. The method according to claim 10 or 11, wherein the light is transmitted through an empty region (4) in the bonding layer (2) in order to align the structural element (5, 5') or another product substrate.

13. The method according to any one of claims 10 to 12, wherein light is absorbed in order to debond the carrier substrate and the product substrate.

14. The method according to any one of claims 10 to 13, wherein bubbles (13) are generated in the region of the bonding layer, the bubbles preferably causing at least local deformation of the product substrate (3).

15. An apparatus for performing the method according to any one of claims 10 to 14, wherein the apparatus has a light source and / or a camera.

Images