Substrate composite, method and device for bonding substrates

Abstract

Method for bonding a first substrate (1) designed as a carrier wafer to a second substrate (7) designed as a product wafer, comprising the following steps, in particular the following sequence: - Contacting a first contact surface (1k) of the first substrate (1) with a second contact surface (18k) of the second substrate (7) aligned parallel to the first contact surface (1k), thereby forming a common contact surface (22), - Formation of a materially bonded connection between the first substrate (1) and the second substrate (7) outside the common contact surface (22), wherein the first substrate (1) has a diameter D2 that is smaller than the diameter D3 of the second substrate (7).

Description

[0001] The present invention relates to a method for bonding a first substrate to a second substrate according to claim 1, as well as a corresponding device according to claim 14 and a substrate composite produced in particular according to the method and / or with the device according to claim 7.

[0002] US 2009 / 0218560A1 discloses the joining of a device wafer to a support wafer only at its outer circumference. JP 2012-79836A discloses that a substrate and a support substrate are laminated, with a connecting section arranged between them. DE 102006000687A1 discloses a combination of a support and a wafer, wherein they are bonded together with an adhesive layer located between them.

[0003] In the semiconductor industry, carrier wafers several hundred micrometers thick are used to fix a product wafer using various processes. A fundamental distinction is made between permanent and temporary bonding methods.

[0004] In permanent bonding, carrier wafers and product wafers are bonded together with the intention of permanently bonding them. Very often, the carrier wafers themselves are product wafers that, at this stage, still possess sufficient thickness to function as carriers, but are functionally classified as product wafers. These permanent bonding processes are diverse, highly varied, and material-specific.

[0005] Furthermore, it is often necessary to temporarily bond the product wafer to a carrier wafer to allow for subsequent processing steps. In this temporarily bonded state, the product wafers are frequently thinned down to thicknesses below 100 µm, typically below 50 µm, and currently around 20 µm, with even lower thicknesses likely in the near future. This temporary bonding must be simple, quick, inexpensive, efficient, reversible, and physically and chemically stable. Most commonly, the carrier wafers are coated with a bonding adhesive and bonded to the product wafer using a bonding process. The resulting temporary bond should withstand high temperatures and forces. Ideally, the bond interface should prevent the penetration of liquids and / or gases into the space between the carrier and product wafers.

[0006] The most common type of temporary bonding uses a material-bonding adhesive layer. This adhesive layer can be applied to the entire surface of the substrate wafer and / or the product wafer. Up to a certain temperature range, this layer has sufficient adhesive properties (a permanent bond) to adequately fix the two substrates. To separate them, the two substrates are heated above this temperature range, causing the adhesive to lose its bonding properties. Applying horizontal and vertical force then separates the two wafers, the substrate wafer and the product wafer.

[0007] The adhesive layer can also be applied only to the edge of the product wafer and / or the support wafer. The inner area does not necessarily contain an adhesive layer. The layer of the inner area can have any desired properties, but is usually introduced as a support material into the spaces between the individual bumps. The separation process is similar to that of a full-surface bond; however, only the edge zones need to be treated physically and / or chemically to cause the temporary bond to lose its adhesion. This results in lower temperatures, shorter processing times, and reduced chemical consumption.

[0008] There are countless other methods to dissolve a temporary bond, for example using special lasers, or carrier wafers with small diameter holes through which a suitable solvent is introduced into the bond over its entire surface.

[0009] The object of the invention is to provide a device and a method for achieving, on the one hand, a high bond strength between the substrates for all necessary process steps, and on the other hand, enabling non-destructive separation of the thin substrate from the substrate composite after processing. In addition, the process steps required for this should be cost-effective and universally applicable to a wide variety of substrates / wafers.

[0010] This problem is solved by the features of claims 1, 7 and 14. Advantageous embodiments of the invention are specified in the dependent claims.

[0011] The invention describes a device and a method by which a carrier wafer can be temporarily and / or permanently bonded to a product wafer. Furthermore, the end product, a carrier wafer-product wafer composite (substrate composite), is described.

[0012] The invention is based on the idea that specially manufactured connecting elements exist at several positions, preferably at least three positions, on the carrier wafer and / or the product wafer, which can be fused and / or separated together by physical and / or chemical processes. In particular, mechanically moving parts for fixation are dispensed with.

[0013] The invention is based on the further idea of ​​improving a generic device and method in such a way that the temporary bonding of two or more substrates is cost-effective (suitable for all process requirements, including high temperatures and vacuum) and allows reuse in subsequent processes without costly cleaning of the carrier wafer. Furthermore, fixatives are provided that enable a suitable bond at high process temperatures and easy debonding.

[0014] The invention is based on the general concept of creating a material-bonded connection outside of an effective or common contact surface between the substrates. This eliminates the need for both mechanically movable fixings and any application of pressure to the contact surface between the substrates themselves, making cleaning the contact surfaces after breaking the connection much simpler and more efficient. The substrates are then available for further processing or reuse more quickly. The effective or common contact surface is the area where – apart from any coatings – there is direct contact between the first and second substrates. According to the invention, it is particularly advantageous if the bond is applied in a point-like manner, which also includes a narrow, circular application.

[0015] In the semiconductor industry, substrates are understood to be product or support substrates used. The support substrate serves to reinforce the functional substrate (product substrate) during the various processing steps, especially during the thinning of the functional substrate. Suitable substrates include wafers, either flat or notched.

[0016] As an independent invention, a substrate composite (or a product substrate-support substrate combination) is provided, which consists of a support substrate and a product substrate that have been aligned, contacted, and pre-fixed and / or bonded together using the device and / or method according to the invention, and are characterized in particular by the fact that the diameter D2 of the first substrate (support substrate) is minimally smaller than the diameter D3 of the second substrate (product substrate). According to the invention, this ensures that the support substrate is not exposed to any contamination, soiling, unwanted treatment, etc., during the processing of the product substrate and can therefore be reused more frequently.

[0017] According to an advantageous embodiment of the invention, the material-bonded connection on the first substrate is formed at least partially, preferably predominantly, on a first fixing surface of the first substrate that is angled relative to the common contact surface, and / or on the second substrate at least partially, preferably predominantly, on a second fixing surface of the second substrate that is angled relative to the common contact surface. This enables optimal, space-saving force transmission for fixing the substrates (product substrate and carrier substrate). "Angled" is understood to mean, in particular, angles between 3 degrees and 90 degrees, preferably between 10 degrees and 90 degrees. In some particularly advantageous embodiments, the first and / or second fixing surface is arranged substantially orthogonally, and in particular exactly orthogonally, to the common contact surface.

[0018] Provided that the first fixing surfaces and / or the second fixing surfaces are arranged rotationally symmetrically to an axis of rotation of the first substrate and / or second substrate, the substrates are fixed to each other with optimal force distribution of the bonding force.

[0019] According to a further advantageous aspect of the present invention, adhesives and / or, in particular, metallic, connecting elements are used to form the material-bonded connection. The material-bonded connection also serves, in particular, to seal the common contact surface from the environment.

[0020] According to a further advantageous embodiment of the invention, a first area ratio between the first fixing surface and the first contact surface is less than 1:5, in particular less than 1:10, and more preferably less than 1:20, and / or a second area ratio between the second fixing surface and the second contact surface is less than 1:5, in particular less than 1:10, and preferably less than 1:20. This minimizes the space required for fixing, leaving more space for the formation of structures on the product wafer.

[0021] Advantageously, the second substrate, particularly before the first and second contact surfaces are made, is provided with an intermediate layer to flatten solder balls placed on one of the top surfaces of the second substrate. This intermediate layer serves to receive the solder balls (bumps) and is preferably non-adherent or only slightly adhering to the first substrate.

[0022] Furthermore, the present invention makes it possible to reuse the carrier substrate multiple times without having to clean it through complex and expensive processes.

[0023] Furthermore, it is possible to install / integrate the device according to the invention into a bonder.

[0024] To the extent that device features are disclosed here and / or in the subsequent figure description, these shall also be deemed disclosed as process features, and vice versa. The same applies to the substrate composite.

[0025] Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. These show: Fig. 1a, Fig. 1b and Fig. 1c: each a schematic top view of a first substrate with different outer contours before an adaptation according to the invention of a diameter D1 of the first substrate, Fig. 2a a schematic cross-sectional view of the substrate according to Fig. 1a, Fig. 2b a schematic cross-sectional view of the substrate after an adjustment (reduction) of the diameter D1 , Fig. 3a a schematic cross-sectional view of the first substrate before contact with a second substrate with connecting elements according to the invention in a first embodiment, Fig. 3b a schematic cross-sectional view of a substrate composite produced according to the invention Fig. 3a, Fig. 4a a schematic cross-sectional view of the first substrate before contact with the second substrate with connecting elements according to the invention in a second embodiment, Fig. 4b a schematic cross-sectional view of a substrate composite produced according to the invention Fig. 4a, Fig. 5a a schematic cross-sectional view of the first substrate before contact with the second substrate with connecting elements according to the invention in a third embodiment, Fig. 5b a schematic cross-sectional view of a substrate composite produced according to the invention Fig. 5a, Fig. 6a a schematic cross-sectional view of the first substrate before contact with the second substrate with connecting elements according to the invention in a fourth embodiment, Fig. 6b a schematic cross-sectional view of a substrate composite produced according to the invention Fig. 6a, Fig. 6c a schematic top view according to section line AA from Fig. 6g, Fig. 7a a schematic cross-sectional view of the first substrate before contact with a second substrate with connecting elements according to the invention in a fifth embodiment, Fig. 7b a schematic cross-sectional view of a substrate composite produced according to the invention Fig. 7a, Fig. 8a a schematic cross-sectional view of the first substrate before contact with the second substrate with connecting elements according to the invention in a sixth embodiment, Fig. 8b a schematic cross-sectional view of a substrate composite produced according to the invention Fig. 8a, Fig. 8c a schematic top view according to section line BB from Fig. 8g, Fig. 9a a schematic cross-sectional view of a substrate surface according to the invention with a milled recess surrounding the substrate, Fig. 9b a schematic cross-sectional view of a substrate surface according to the invention with a milled recess surrounding the substrate in which a metal was deposited, Fig. 9c a schematic cross-sectional view of a surface of a substrate according to the invention on which a metal has been deposited, Fig. 10a a schematic cross-sectional view of a device according to the invention for local soldering and desoldering Fig. 10b a schematic cross-sectional view of a device according to the invention for the local application of a material

[0026] In the figures, advantages and features of the invention are identified by reference numerals according to embodiments of the invention, wherein components or features with the same or equivalent function are identified by identical reference numerals.

[0027] For the generic process, a support wafer made of any material, but preferably silicon, is used as the first substrate 1. A second substrate 7 (here: product wafer) to be contacted with the first substrate 1 and the support wafer preferably consist of the same material. Due to identical or at least similar materials, the mechanical and thermal parameters of the product and support wafers are the same or at least similar.

[0028] The second substrate 7 has 70 solder balls 15 (bumps) on its upper surface, which serve for the electrical connection of chips. For leveling and pressure equalization, an intermediate layer 18 is arranged on the upper surface 70 as part of the second substrate 7, where contact with the first substrate 1 takes place. Thus, the first substrate 1 has a first contact surface 1k and the second substrate 7 has a second contact surface 18k. If no solder balls 15 are provided, the second substrate 7 can be contacted directly with the first substrate 1 without the intermediate layer 18, in which case the upper surface 70 becomes the first contact surface.

[0029] The substrates 1, 7 can either be perfectly radially symmetrical or possess a "notch" 2, a "flat" 3 or any other deviation from radial symmetry ( Fig. 1), but otherwise also be radially symmetrical. The substrates 1, 7 are in particular shape-congruent, preferably substantially radially symmetrical (apart from the aforementioned features). In other words, or more generally, the substrates 1, 7 have corresponding outer contours 1a, 7a.

[0030] For the bonding process according to the invention, the carrier wafer (first substrate 1) is prepared, in particular by grinding and / or etching processes, with a diameter D1, in particular a commercially available diameter ( Fig. 2a) on a diameter D2 ( Fig. 2b) processed, which is smaller than the diameter D3 of the product wafer 7.

[0031] Ideally, at the transition from the outer contour 1a to the first contact surface 1k, an angular edge is created (with a significantly smaller radius of curvature compared to the opposite edge or before the reduction in diameter, in particular in a ratio of less than 1:5), so that a lower section of the first substrate 1 has a cylindrical outer contour (apart from any features according to Fig. 1b and Fig. 1c).

[0032] A key, and in particular independent, aspect of the invention relates to a metal alloy that, on the one hand, creates a bond and, optionally, seals the common contact surface between the support wafer and the product wafer. This can be achieved by several embodiments of the invention as described below.

[0033] In a first embodiment ( Fig. 3) A circumferential section, particularly rotationally symmetrical, is metallized on the outer contour 1a of the first substrate 1. Preferably, this is a metallization 11 that covers the entire circumference of the outer contour 1a of the first substrate 1'. This preferably creates a complete seal that is also gas- and / or liquid-tight. In a special embodiment, metallizations 11 can also be applied only at certain points around the circumference of the support wafer 11. This does not create a gas- and / or liquid-tight seal. However, the resulting seal can be strong enough to temporarily and / or permanently bond the two wafers together. The metallization 11 is fixed to the first substrate at a first fixing surface 1f.

[0034] Preferably, the second substrate 7 is also provided with a metallization 11', namely on the top surface 70 (or on the side of the intermediate layer 18 facing the first substrate 1) in a ring section 7r which lies outside a common contact surface 22 which is formed between the first and second contact surfaces 1k, 18k upon contacting.

[0035] The metallizations 11 of the first substrate 1 and the metallizations 11' of the second substrate 7 can consist of different metals. Preferably, metals whose alloys form a eutectic are used. Furthermore, at least one of the two metallizations should preferably consist of a metal with the lowest possible melting point. The melting point should be less than 500°C, preferably less than 400°C, more preferably less than 300°C, most preferably less than 200°C, and most preferably less than 100°C. Furthermore, the two metallizations 11 and 11' can consist of the same metal. This metal should preferably have the lowest possible melting point. Since, due to the geometry of the embodiment, pressurization of the metallizing areas 11 and 11' is not possible or only possible to a very limited extent, the metallization 11'' is produced primarily by thermal stress.Therefore, in general, it is preferably a welding or soldering process.

[0036] In Fig. Figure 3b shows the molten and re-solidified metallization 11", which is composed of the two metallizations 11, 11' (if present) and has a different shape due to flow during melting. The metallization 11'' creates a metallurgical bond between the first substrate 1 and the second substrate 7, as well as the intermediate layer 18 belonging to the second substrate 7.

[0037] The material-bonded connection to the first substrate 1 exists at the outer contour 1a on a fixing surface 1f', which is angled approximately orthogonally to the common contact surface 22. Thus, the material-bonded connection is located outside the common contact surface 22. Preferably, the fixing surface 1f' extends only over a portion of the outer contour 1a.

[0038] The metallurgical bond to the second substrate 7 is provided on one side at the ring section 7r and on the other side at a second fixing surface 18f, which is formed by a free space 30 in the intermediate layer 18, created in particular by the metallization 11'. The metallization 11' can be produced in a very simple manner, especially by lithographic processes. The second fixing surface 18f consists of a circumferential wall that delimits the free space 30. The ring section 7r delimits the free space 30 towards the second substrate 7 and thus forms part of the second fixing surface.

[0039] In a second embodiment, analogous to the first embodiment apart from subsequent descriptions, according to Fig. 3a / 3b designed embodiment ( Fig. 4) A material 19 is used to seal the two substrates 1, 7 along the outer contour 1a (over the entire circumference). This protects the common contact surface 22 from dirt / contamination. The material 19 can be any type of adhesive or metal. The metallizations 11, in particular together with any adhesive properties of the material 19, ensure sufficient bond strength between the substrates 1, 7. According to the invention, however, the metallizations 11, 11' can also be omitted.

[0040] In a third embodiment ( Fig. 5) The two substrates 1, 7 are bonded together by a material overlay 28 produced in a single process step. The material overlay 28 covers at least predominantly, preferably almost completely, a ring section 29 that projects beyond the first substrate 1 from the second substrate 7. The material overlay 28 is applied laterally to the first substrate (1') and over the second substrate 7, and after curing, the first substrate 1 is fixed to the second substrate 7 by the material overlay 28. This fixing method is also preferably radially symmetrical. Preferably, the material overlay 28 is applied only laterally to the support wafer 1' and only to the edge surface of the product wafer 7. A light covering of a top surface 10' of the first substrate 1 would also be conceivable.The material coating 28 is applied by means of an application device, in particular comprising a mask which allows access of the material to be applied only at the desired location. Vertical immersion of the two substrates 1, 7 into a melt and rotation of both substrates 1, 7 in the melt would also be conceivable. This immersion method, relating to the ring section 29, allows the wetting of the outer ring section 29 to be protected. In a particular embodiment, the material coating 28 is a metallization; however, adhesives or ceramic materials would also be conceivable according to the invention.

[0041] In a fourth embodiment ( Fig. 6) Holes 6, in particular those passing through the first substrate 1'', are drilled and / or etched into the first substrate 1''. Preferably, the holes 6 are provided with metallizations 11''' on their inner circumference 6i to enable a point-like, metallurgical bond. Structures 16 are located on the product wafer 7. Preferably, the structures 16 are bumps. Depending on the shape of the holes 6, the metallizations 11''', and the size of the structures 16, it is possible to enable self-adjustment at these points during melting as the solder melts and the resulting surface tensions occur. With this type of fixation, the substrates 1'', 7 are primarily joined directly to each other at a few points by material penetration into the holes 6. Fig. 6c refers to the hardened metallized compounds 11 IV for fixings, in particular between the metallizations 11IV Additional sealing elements 21 are arranged, which serve to completely seal the common contact surface 22 of the two substrates 1'', 7. The sealing elements 21 can advantageously be linearly applied strips, preferably in the form of metallizations, which also weld together during a thermal treatment. The welding is carried out in particular by thermocompression bonding and / or eutectic bonding.

[0042] In a fifth embodiment ( Fig. 7) Cavities 10 of arbitrary shape are introduced into the first substrate 1''' on the contact side encompassing the first contact area 1k. Preferably, the cavities 10 are metallized 11, particularly at specific points. V The cavities 10 are distinguished from the holes 6 in Fig. 6. This is characterized by the fact that they do not completely penetrate the support wafer 1''', but can instead extend radially symmetrically as a closed ring around the entire wafer. According to the invention, the cavities 10 could be produced by etching or milling. In particular, crystallographic etching of support wafers of a certain crystallographic orientation can produce cavities 10 very efficiently. The radial symmetry of the cavities 10 creates a very efficient seal of the interface between the two wafers.

[0043] Together with the metallization 11' (as Fig. 4a) the metallization 11 V melted and metallized 11 VI hardened. The latter in turn ensures the material-bonded connection between substrates 1 and 7.

[0044] In a sixth embodiment ( Fig. 8) Small depressions of any shape (especially radially symmetrical milling or drilling) are made at the edge of the first substrate 1 V introduced. The connection between the first substrate 1 V and the second substrate 7 is joined using appropriate bonding agents, in particular adhesives or metallizations.

[0045] Because the diameter D2 of the first substrate is smaller than the diameter D3 of the second substrate 7, the carrier wafer (first substrate 1) is protected by the ring section 29 during subsequent processes, especially sputtering and plasma processes. This eliminates the need for complex and costly cleaning of the first substrate, particularly due to metallic contamination. The first substrate can therefore be reused immediately for other / further steps.

[0046] Advantageously, a non-adhesive or only slightly adhesive removable sealing layer and / or release layer is applied to the entire surface of the first substrate 1 that comes into contact with the product wafer 7. The first substrate 1', 1'', 1''', 1 equipped with this sealing layer IV , 1 V With the exception of the area of ​​the solder or glue points, it has no adhesive, fixed contact with the second substrate 7.

[0047] According to this new method, in which the product wafer 7 is fixed to the carrier wafer 1' only at precisely defined points and this fixation is then separated again after completion of the processes, any material that ensures a suitable fixation for the process(es) can be used. Chemical or biological materials can also be used instead of metallic solder; these materials may lose their fixing properties completely or partially through the introduction of other materials or energy.

[0048] The type of solder depends on the temperatures and requirements of the subsequent processes and is defined on a process-specific basis. Since solders have a defined melting point depending on their composition, a wide range of temperature adjustments is possible. The melting point is higher than the maximum expected temperature input from the manufacturing processes.

[0049] However, solder metals that are also used for creating bumps on the product wafer can be used as well. Since heat is only applied to the points intended for fixing during desoldering, the bumps on the product wafer are not melted.

[0050] It is also possible to apply any other material that enables wafer fixation instead of metallization 11. This material can have an adhesive and / or sealing effect. The material can be applied radially symmetrically using an apparatus known in the semiconductor industry.

[0051] In all embodiments, the temperature required to melt the bonding material for bonding and / or debonding can be introduced in any conceivable way. In particular, it would be possible to introduce the heat across the entire surface, preferably by contacting the support wafer and / or the product wafer with a heating plate. In a special and preferred embodiment, the heat is introduced by a heating element 32 only at those positions where the corresponding metallizations or fixations are located. This localized heating has the decisive advantage that the entire wafer is not subjected to thermal stress, and thus any structures already present on the product wafer are not subjected to thermal stress, or at least only to a very minimal degree.

[0052] In the apparatus used for bonding, heat is applied to the points containing these cavities 10 after contacting in order to melt the solder metal so that soldering occurs at these points. Debonding is carried out in the same way, by heating and then mechanically separating the wafers by introducing movement using the actuating units of a device according to the invention.

[0053] Should one of the metallizations 11, 11', 11'' need to be remelted, heat of fusion is preferably introduced only in the immediate vicinity of the metallizations 11, 11', 11''.

[0054] Fig. Figures 9a-9c show three possible embodiments for introducing heat of fusion locally via the surface 10 of the first substrate 1, independently of any of the embodiments shown. The introduction can therefore be applied to any of the embodiments mentioned and is hereby disclosed as an independent invention.

[0055] In a first embodiment, a very narrow heating element 32 is preferably used, which contacts the top surface 10 of the first substrate 1. Preferably, the heating element 32 is surrounded by two cooling elements 33, which reduce the heat dissipation across the entire first substrate 1. Even more preferably, a recess 31 is located opposite (or on the side of the first substrate 1, 1' facing away from) the area of ​​application of the metallizations 11, 11', 11'' in the first substrate 1, into which a heating element 32, in this case a heating element 32 with a wedge-shaped contour, can be inserted to optimize heat transfer to the metallization 1.

[0056] In a further embodiment, a metallization 34 is deposited in the recess 31 for heating, particularly in conjunction with the heating element 32. A high current is passed through the metallization 34, which generates Joule heating, which in turn heats the surrounding area of ​​the metallization and thus, according to the invention, leads to the melting of the metallization 34 in the surrounding area (function of the heating element 32).

[0057] In a further embodiment, a metallization 34', in particular in conjunction with the heating element 32, is deposited flush with the top surface 10 of the first substrate 1, 1', i.e. without a depression in the first substrate 1, 1'.

[0058] The three methods presented can also be used to apply heat for soldering (creating the connection).

[0059] In the Fig. 10a, Fig.Figure 10b shows a device according to the invention, which consists of at least one lower sample holder 35 and one upper sample holder 36. The upper sample holder 36 is designed such that a heating element 32 according to the invention can reach the edge of the substrates 1, 7 and provides the heat for the soldering and / or desoldering process according to the invention. Relative movement between the upper and lower sample holders 35, 36 is preferably possible in all three spatial directions. Preferably, the two sample holders 35, 36 can be rotated relative to each other about a rotational axis R. Even more preferably, relative movement of the heating element 32 according to the invention between the two sample holders 35, 36 in all three spatial directions is also possible.The sample holders 35, 36 are also referred to as contacting means for contacting the first contact surface 1k of the first substrate 1 with the second contact surface 18k of the second substrate 7 which is aligned parallel to the first contact surface 1k.

[0060] Sample holders 35 and 36 are preferably vacuum sample holders. However, they can also be electrostatic or other sample holders that can fix the two wafers according to the invention.

[0061] In a further embodiment of the device, a dispensing unit 37 is used instead of a corresponding heating element 32. The dispensing unit can be used for lateral metallization, for depositing adhesives, for applying sealing chemicals, or for applying any desired material. Due to the possible relative displacements and / or rotations of the sample holders 35, 36 relative to each other and / or the relative movement of the dispensing unit 37 relative to the sample holders 35, 36, a purely annular application or a full-surface application of any desired material is possible according to the invention. For example, before a bonding or soldering process, a 500 µm to 2000 µm wide circular layer is applied to the outermost edge of the functional wafer 1 or the carrier wafer 7 in order to create a seal in the edge region, particularly for subsequent chemical processes.When using suitable flatness layers, the application of an additional sealing layer in the edge area can be omitted. The backfilled flatness layer 18 between the bumps of the functional wafer must be removed in a cleaning step. Since, unlike other processes with adhesive layers, this support layer has no or only minimal adhesive properties, cleaning is simpler and more cost-effective than with adhesive processes. Reference symbol list 1, 1', 1'', 1''', 1 IV , 1 V First substrate (carrier substrate) 1a First outer contour 1f First fixing surface 1k First contact area 10 Top 2 Notch 3 Flat 6 holes 6i inner circumference 7 Second substrate (product substrate) 7a Second outer contour 7r Ring section 70 Top 10 cavities 11, 11', 11'' Metallizations 18 Intermediate shift 18f Second fixing surface 18k Second contact surface 20 depressions 21 sealing elements 22 Common contact area 28 Material Overlay 29 Ring section 30 free space 31 In-depth study 32 Heating element 33 cooling elements 34, 34' Metal deposition 35 Lower sample holder 36 Upper sample holder 37 Dispensing unit D1, D2, D3, D4 diameter R axis of rotation

Claims

[1] Method for bonding a first substrate (1) designed as a carrier wafer to a second substrate (7) designed as a product wafer, comprising the following steps, in particular the following sequence: - Contacting a first contact surface (1k) of the first substrate (1) with a second contact surface (18k) of the second substrate (7) aligned parallel to the first contact surface (1k), thereby forming a common contact surface (22), - Formation of a materially bonded connection between the first substrate (1) and the second substrate (7) outside the common contact surface (22), wherein the first substrate (1) has a diameter D2 that is smaller than the diameter D3 of the second substrate (7). [2] Method according to claim 1, in which the material-bonded connection, in particular applied at specific points, preferably only at some points on the circumference of the carrier wafer, is formed at least partially, preferably predominantly, on a first fixing surface (1f) of the first substrate (1) angled relative to the common contact surface (22) and / or on the second substrate (7) at least partially, preferably predominantly, on a second fixing surface (18f) of the second substrate (7) angled relative to the common contact surface (22). [3] Method according to claim 2, wherein the first fixing surfaces (1f) and / or the second fixing surfaces (18f) are arranged rotationally symmetric to an axis of rotation of the first substrate (1) or second substrate (7). [4] Method according to at least one of the preceding claims, wherein adhesives (19) and / or, in particular metallic, connecting elements (11) are used to form the material-jointed connection. [5] Method according to at least one of claims 2 to 4, wherein a first area ratio between the first fixing surface (1f) and the first contact surface (1k) is less than 1:5, in particular less than 1:10, preferably less than 1:20, and / or a second area ratio between the second fixing surface (18f) and the second contact surface (18k) is less than 1:5, in particular less than 1:10, preferably less than 1:

20. [6] Method according to at least one of the preceding claims, wherein the second substrate (7), in particular before contacting the first and second contact surfaces (1k, 18k), is provided with an intermediate layer (18) for leveling solder balls (15) provided on a top surface (7o) of the second substrate (7). [7] Substrate composite consisting of a first substrate (1) designed as a support wafer and a second substrate (7) designed as a product wafer, wherein a first contact surface (1k) of the first substrate (1) forms a common contact surface (22) with a second contact surface (18k) of the second substrate (7) aligned parallel to the first contact surface (1k), wherein outside the common contact surface (22) there is a material bond between the first substrate (1) and the second substrate (7), wherein the first substrate (1) has a diameter D2 which is smaller than the diameter D3 of the second substrate (7). [8] Substrate composite according to claim 7, in which the material-bonding connection, in particular pointwise, preferably only applied pointwise at some points on the circumference of the carrier wafer, is formed at least partially, preferably predominantly, on a first fixing surface (1f) of the first substrate (1) angled relative to the common contact surface and / or on the second substrate (7) at least partially, preferably predominantly, on a second fixing surface (18f) of the second substrate (7) angled relative to the common contact surface. [9] Substrate composite according to claim 8, wherein the first fixing surfaces (1f) and / or the second fixing surfaces (18f) are arranged rotationally symmetric to an axis of rotation of the first substrate (1) or second substrate (7). [10] Substrate composite according to at least one of claims 7 to 9, wherein the material-bonded connection comprises adhesives and / or, in particular, metallic, connecting elements (11). [11] Substrate composite according to at least one of claims 8 to 10, wherein a first area ratio between the first fixing surface (1f) and the first contact surface (1k) is less than 1:5, in particular less than 1:10, preferably less than 1:20, and / or a second area ratio between the second fixing surface (18f) and the second contact surface (18k) is less than 1:5, in particular less than 1:10, preferably less than 1:

20. [12] Substrate composite according to at least one of claims 7 to 11, wherein the second substrate (7) has an intermediate layer (18) for leveling solder balls (15) provided on a top surface (70) of the second substrate (7). [13] Substrate composite according to at least one of claims 7 to 12, wherein a second outer contour (7a) of the second substrate (7) overhangs a first outer contour (1a) of the first substrate (1) upon contact, in particular equidistantly. [14] Device for bonding a first substrate (1) designed as a carrier wafer to a second substrate (7) designed as a product wafer having the following features: - Contacting means for contacting a first contact surface (1k) of the first substrate (1) with a second contact surface (18k) of the second substrate (7) aligned parallel to the first contact surface (1k), thereby forming a common contact surface (22), - Bonding agents for producing a materially bonded connection between the first substrate (1) and the second substrate (7) outside the common contact area (22), wherein the first substrate (1) has a diameter D2 that is smaller than the diameter D3 of the second substrate (7). - a sample holder (36) for holding the first substrate (1), wherein the sample holder (36) is designed such that a heating element (32) can reach the edge of the substrates (1,7) and provide heat for a soldering process and / or desoldering process. [15] Device according to claim 14, comprising application means for applying adhesive and / or, in particular metallic, connecting elements (11) to form the, in particular pointwise, preferably only pointwise applied at some points on the circumference of the carrier wafer, materially bonded connection.

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