Patent Publication Number: US-2020294962-A1

Title: Method for Producing a Connection Between Component Parts, and Component Made of Component Parts

Description:
This patent application is a national phase filing under section 371 of PCT/EP2019/052781, filed Feb. 5, 2019, which claims the priority of German patent application 102018103431.8, filed Feb. 15, 2018, each of which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     A method for establishing a connection, in particular a mechanical and at the same time electrical connection between two or a plurality of component parts, is specified. Furthermore, a component made of component parts is specified. 
     BACKGROUND 
     In the manufacture of a pixelated LED or an LED radiating in several colors, it is often the case that several functional layers are stacked on top of each other and are individually contacted. Here, the direct bonding process can be used for the mechanical fixing of the component parts and for the contacting of functional layers of the component parts, for example, using metallic contact posts. In a direct bonding process, the surfaces of the component parts should be planarized as best as possible. The metallic posts should be moved back from the planarized surfaces of the component parts in order not to interfere with the direct bonding process. On the other hand, the metallic posts should not be moved back too far, as otherwise the contact between the metallic posts will not close during a subsequent annealing step. Altogether, for a planarization process, there is only a relatively narrow process window. 
     SUMMARY OF THE INVENTION 
     Embodiments provide a simplified and cost-efficient method for producing a mechanical and/or electrical connection between different component parts. Further embodiments provide a compact and mechanically stable component having a stable and reliable electrical connection between the component parts. 
     According to at least one embodiment of the method, an electrical connection is established between a first component part and a second component part. Preferably, the establishment of the electrical connection between the component parts is carried out simultaneously with a mechanical fixing between the component parts or only after the establishment of a mechanical connection between the component parts. 
     A first component part is provided which has a first, in particular exposed insulation layer. A second component part is provided, wherein the second component part has a second, in particular exposed insulation layer. Each of the insulation layers can have at least one opening or a plurality of openings arranged next to each other. In the openings of the first and/or the second insulation layer, connecting stacks may be arranged. The respective connecting stack may have a plurality of layers, in particular electrically conductive layers, arranged one above the other. In particular, the connecting stack is formed from layers which preferably comprise a solder material such as gold or tin. For example, at least 50, 60, 70, 80, 90 or 95 percent by volume and/or weight of the connecting stack is made up of solder materials such as gold and tin. The connecting stack may be free of layers such as copper and/or nickel. 
     According to at least one embodiment of the method, the component parts are joined together such that the opening of the first insulation layer and the opening of the second insulation layer overlap in top view. In at least one or in each of the openings of the first insulation layer and/or the second insulation layer, a connecting stack may be arranged. In particular, the connecting stack comprises a gold layer and a tin layer which are arranged one above the other. It is possible for a barrier layer to be arranged vertically between the gold layer and the tin layer. 
     A vertical direction is understood to mean a direction which is in particular perpendicular to a main extension surface of the first and/or of the second insulation layer. A lateral direction is understood to mean a direction which is in particular parallel to the main extension surface of the first and/or of the second insulation layer. The vertical direction and the lateral direction are in particular orthogonal to each other. 
     According to at least one embodiment of the method, the connecting stack has a protective layer which is arranged on the gold layer or on the tin layer. When the component parts are joined together, the opening of the first insulation layer and the corresponding opening of the second insulation layer can form a closed intermediate space, such as a common closed cavity. In the common cavity, a first connecting stack and a second connecting stack can be arranged opposite each other, wherein the first connecting stack and the second connecting stack are arranged for instance in the opening of the first insulation layer and in the opening of the second insulation layer, respectively. After the component parts have been joined together, the first insulation layer may be directly adjacent to the second insulation layer. However, the first connecting stack can still be spaced apart from the second connecting stack by an intermediate space. 
     According to at least one embodiment of the method, the gold layer and the tin layer are melted to form a gold-tin alloy. After cooling, the gold-tin alloy can form a through-via which connects the first component part with the second component part in an electrically conductive manner. The gold layer and the tin layer can be assigned to the first and/or the second connecting stack. For forming the through-via, both the first connecting stack and the second connecting stack can be melted. 
     In particular prior to the melting, the first connecting stack and the second connecting stack are not in direct physical contact. During melting, the volume of the respective connecting stack, especially the total volume of the gold layer and of the tin layer, increases. In the liquid phase, the connecting stacks expand and come into direct physical contact. After cooling, the molten connecting stacks form a through-via which is formed in one piece and connects the first component part with the second component part in an electrically conductive manner. 
     In at least one embodiment of the method for producing an electrical connection between a first component part and a second component part, the first component part having a first exposed insulation layer and the second component part having a second exposed insulation layer are provided, wherein the insulation layers each have at least one opening. The component parts are joined together such that the opening of the first insulation layer and the opening of the second insulation layer overlap in top view. In at least one of the openings or in each of the openings, a gold layer and a tin layer are arranged one above the other. The gold layer and the tin layer are melted to form a gold-tin alloy, wherein after cooling, the gold-tin alloy forms a through-via which connects the first component part to the second component part in an electrically conductive manner. 
     Preferably, the component parts are joined together and fixed by a direct bonding process. As a result, a firm mechanical connection between the component parts can be established even before the connecting stack, in particular the gold layer and the tin layer, is melted. In a direct bonding process, planarized surfaces, in particular the surfaces of the insulation layers, are brought into physical contact. The mechanical bond is mainly or exclusively based on hydrogen bonds and/or Van-der-Waals interactions in the immediate vicinity of a common interface between the planarized surfaces. For forming covalent bonds between atoms or molecules on the surfaces standing in physical contact, for example, a thermal treatment is applied subsequently to achieve increased bond strength. In particular, the electrical connection between the component parts only takes place during or after the formation of the through-via. 
     The method described here particularly relates to a direct bonding process, wherein the through-vias are preferably formed from a gold-tin alloy or essentially from a gold-tin alloy. The electrical connection of the functional layers of the component parts is realized in particular by melting the gold and tin layer in a subsequent annealing step. Using this approach, a wider process window can be guaranteed. In comparison with conventional processes, wherein the through-vias are formed from a metal or predominantly formed, i.e., more than 50% by volume and/or weight, from a metal such as nickel or copper, the gold-tin alloy connecting stack can be easily adjusted so that it is retracted very precisely over a predetermined distance from a direct bond interface so that during the annealing step, on the one hand it results in the formation of the through-vias but on the other hand does not result in delamination of the direct bond interface. 
     According to at least one embodiment of the method, the first insulation layer and the second insulation layer each have a planarized exposed surface outside the openings. The planarized exposed surface has a roughness which is in particular 500 nm, 30 nm, 20 nm, 10 nm or 5 nm at most. The first component part and the second component part are preferably mechanically bonded together by a direct bonding process at a common interface between the planarized surfaces of the component parts. In particular, the common interface is free of any joining material, such as solder or adhesion promoter material. The common interface is in particular an overlapping surface between the planarized exposed surfaces of the insulation layers which arises during the joining process. 
     According to at least one embodiment of the method, the component parts are mechanically joined together during the joining process. The step of melting the gold layer and/or the tin layer or the connecting stacks in particular follows the step of mechanically joining the component parts. In other words, the electrical connection is made after the mechanical connection between the component parts has been formed. 
     According to at least one embodiment of the method, the gold layer and the tin layer are integral parts of the connecting stack. The connecting stack has an overall vertical height that is less than a vertical depth of the associated opening in which the connecting stack is located. In addition to the gold layer and/or the tin layer, the connecting stack may have other layers, such as a barrier layer and/or a protective layer. Preferably, the other layers of the layer stack, such as the protective layer and the barrier layer, are formed from an electrically conductive material. 
     If the total vertical height of the connecting stack is less than the vertical depth of the associated opening, the connecting stack is located completely within the opening. In particular, along the vertical direction, the connecting stack does not protrude above the surface of the associated insulation layer. In this sense, the connecting stack is retracted a predetermined distance from the surface of the insulation layer, in particular from the direct bond interface. For example, the predetermined distance is between 1 nm and 1 μm inclusive, preferably between 1 nm and 500 nm, for instance between 1 nm and 100 nm inclusive, or between 1 nm and 50 nm inclusive. The total vertical height of the connecting stack and the total depth of the opening may differ by at least 1 nm and at most by 100 nm, 300 nm or 1 μm. 
     According to at least one embodiment of the method, a first opening of the first insulation layer and a second opening of the second insulation layer form a common closed cavity when the component parts are joined together. In each of the first and second openings, a connecting stack comprising at least a gold layer and a tin layer can be arranged. It is possible for the first insulation layer to have a plurality of first openings and/or for the second insulation layer to have a plurality of second openings. It is also possible that a plurality of sealed cavities are formed when the component parts are joined together, wherein each sealed cavity is formed from a first opening of the first insulation layer and a second opening of the second insulation layer. 
     According to at least one embodiment of the method, prior to the melting, the connecting stacks arranged in the openings are spaced apart from each other by an intermediate space. A vertical spacing between the connecting stacks may be between 10 nm and 2 μm inclusive, for example between 50 nm and 500 nm inclusive, or between 20 nm and 100 nm inclusive. In particular, the connecting stacks are in direct mechanical contact with each other at first only during or after the melting process. 
     During the melting process, the total volume of the gold-tin alloy increases, as a result of which the intermediate space between the stacks is bridged by the material of the connecting stacks. After cooling, a through-via is formed from the connecting stack, as a result of which the through-via mechanically and electrically conductively connects the component parts with each other. It has been found that in a direct bonding process, an increase of the volume of about 4.5% during the conversion of pure tin and gold into an alloy having an eutectic composition is particularly suitable for forming of the through-via or of the plurality of through-vias. An AuSn connecting stack 3 μm in height melted at about 280° C. and, wherein the Au layer and the Sn layer are previously separated by a temporary diffusion barrier, would grow by about 135 nm while retaining its shape. 
     The connecting stacks are therefore preferably slightly retracted from the direct bond interface before melting, as a result of which the risk of delamination of the direct bond interface is minimized. Gold and tin can be used to precisely and reliably adjust an optimum distance of the connecting stack from the planarized surface of the insulation layer or from the direct bond interface. In addition, the thermal treatment for melting the gold and tin layer can be carried out very reliably, since the melting temperature of the AuSn alloy is precisely defined and can be kept constant over all component parts. This is not the case in a direct bond interconnection (DBI) using metal posts made of copper or nickel, since compared to the material in which the metal posts are embedded, effect of higher thermal expansion of the metal posts is used. Variations in the distances of the metal posts to the bonding surface result in different temperatures which are necessary to bring the metal posts into contact and to form the electrical contact. In total, compared to Cu and/or Ni contact posts, a larger process window can be achieved when using AuSn posts. 
     According to at least one embodiment of the method, a barrier layer is arranged in the vertical direction at least in places between the gold layer and the tin layer. The barrier layer is preferably made of a material whose melting temperature is higher than that of gold and/or tin. The barrier layer thus forms a temporary diffusion barrier between the gold layer and the tin layer. Using the barrier layer, an undesired early intermetallic reaction can be avoided, since the increase in volume should preferably start only after the adjusted bonding of the component parts. In particular, the increase in volume should occur only after the adjusted bonding and the subsequent heating and melting of the Au/Sn layer. 
     For example, the gold layer is separated from the tin layer only by the barrier layer. It is possible that the barrier layer is formed such that it completely encloses the gold layer and/or the tin layer at least in lateral directions. It is also conceivable that the barrier layer is arranged along the vertical direction between the protective layer and the gold layer and/or the tin layer. An early reaction, especially an early intermetallic reaction between the protective layer and the gold layer and/or the tin layer can thus be avoided. The barrier layer preferably comprises titanium or platinum or consists of titanium and/or platinum. 
     According to at least one embodiment of the method, before joining together the component parts, the gold layer and the tin layer are covered by a particularly exposed protective layer. The protective layer is preferably formed from a material whose mechanical hardness is greater than that of tin or of gold and tin. The protective layer may be made of a metal, for example of gold, copper, nickel, titanium or aluminum. It is also possible that the protective layer is a combination of different metals, for example a combination of gold, copper, nickel, titanium and/or aluminum. 
     According to at least one embodiment of the method, the first component part or the second component part is a wafer carrier, a semiconductor wafer, a carrier, an electronic or an optoelectronic component part such as a semiconductor chip, a control element or a component part having at least one carrier, a main body and a contact structure. The through-via represents in particular an electrical connection between the contact structures of the component parts. The contact structure of the respective component part can have a plurality of contact layers, for example at least two contact layers, which are assigned to different electrical polarities of the component part. In particular, the through-via connects a contact layer or a contacting structure of a first component part with a contact layer or a contacting structure of a second component part. The main body of the respective component part can be a semiconductor body or a control structure having transistors. The main body may comprise a light-emitting or a light-detecting semiconductor body and/or electrical circuit elements. 
     According to at least one embodiment of a component, it comprises a first component part having a first insulation layer and a second component part having a second insulation layer. The first component part is preferably electrically conductively connected to the second component part via a through-via, wherein the through-via extends throughout the first insulation layer and the second insulation layer. 
     In particular, the first insulation layer directly adjoins the second insulation layer. Preferably, the first component part is mechanically connected to each other at a common interface between the insulation layers. An electrical connection between the component parts is established via the through-via which extends throughout the common interface between the insulation layers. In particular, the through-via also forms a mechanical connection between the component parts. The common interface between the insulation layers is in particular free of a connecting material, for example free of a solder material or free of an adhesion promoter material. The first insulation layer is mechanically connected to the second insulation layer, in particular by using a direct bonding process. The through-via is made in particular in one piece. 
     In at least one embodiment of the component, it has a first component part, a second component part and a through-via. The through-via is in particular a gold-tin alloy which connects the first component part with the second component part in an electrically conductive manner. The first component part has a first insulation layer and the second component part has a second insulation layer, wherein the through-via is arranged in a first opening of the first insulation layer and in a second opening of the second insulation layer. The through-via can thus be located partly within the first opening and partly within the second opening. In the lateral directions, the through-vias can be completely enclosed by both the first insulation layer and the second insulation layer. 
     According to at least one embodiment of the method or of the component, the first component part or the second component part is a radiation-inactive carrier wafer. In particular, the first component part or the second component part is not configured for generating electromagnetic radiation or for detecting electromagnetic radiation. Alternatively, the first component part or the second component part may be a semiconductor wafer comprising, for example, a semiconductor body having a radiation-active layer. The radiation-active layer is configured in particular to generate or detect electromagnetic radiation. For example, the radiation-active layer is configured to generate electromagnetic radiation in the UV-IR—or in the visible spectral range, for example in the blue, yellow or yellow spectral range. 
     It is possible that the first component part is a radiation-inactive carrier wafer and the second component part is a semiconductor wafer having a radiation-active layer. It is possible that the first component part is a radiation-inactive carrier wafer which is in particular a carrier body, and the second component part is a semiconductor chip. The component may have a plurality of second component parts which are arranged on the first component part and are mechanically and electrically connected to it. The second component parts may be semiconductor chips which are configured for generating and/or detecting electromagnetic radiation. The plurality of second component parts may be semiconductor chips fixed side by side on the first component part. For example, the second component parts may be fixed on the first component part and electrically contacted therewith either simultaneously or consecutively. 
     According to at least one embodiment of the method or of the component, the first insulation layer is formed from silicon oxide, in particular from silicon dioxide. The second insulation layer may be formed from silicon oxide, in particular from silicon dioxide. The first insulation layer and/or the second insulation layer can be formed from silicon dioxide or consist of silicon dioxide. Insulation layers made of silicon oxide are particularly suitable for the direct bonding process. In addition, silicon oxide insulation layers can withstand high temperatures, such as temperatures around 280° C. or higher, at which the gold layer and tin layer are fused to form a gold-tin alloy layer. 
     According to at least one embodiment of the method or of the component, an opening of the first insulation layer and an opening of the second insulation layer form a common closed cavity. The cavity may, at least in places, have a greater lateral extent than the through-via. In this case, the through-via fills the cavity only partially. There may be intermediate spaces in the lateral directions between the through-via and the inner walls of the cavity. The intermediate spaces can be filled with a gaseous medium such as air. These spaces can be filled with a gaseous medium, such as air, to provide space for excess solder material, which in this case may be the gold-tin alloy, so that no force is exerted on the direct bond interface during the formation of the through-via which could lead to delamination of the insulation layers. 
     Alternatively, it is possible that the amount of solder material is selected such that the resulting through-via completely fills the common closed cavity. In this case, the through-via can be immediately adjacent to the first insulation layer and/or to the second insulation layer. In lateral directions, the through-via can be completely surrounded by the first insulation layer and by the second insulation layer, wherein the insulation layers directly adjoin the through-via and can completely cover lateral surfaces of the contact. 
     According to at least one embodiment of the method or of the component, the through-via is formed in one piece. In particular, the through-via is a gold-tin eutectic. However, the through-via may show traces of materials of the barrier layer and/or of the protective layer. For example, the gold-tin eutectic shows traces of copper, nickel, titanium and/or aluminum. The through-via is preferably formed mainly from a gold-tin alloy, wherein the gold-tin alloy content may be at least 50, 60, 70, 80, 90 or at least 95% by weight or volume. It is possible that the through-via is free of metals such as copper and/or nickel or that the through-via has a copper and/or nickel content of at most 30, 20, 10, 5 or at most 3% by weight or volume. 
     The method described here is particularly suitable for the production of a component made of component parts described here. The features described in connection with the method can therefore also be used for the component, and vice versa. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other preferred embodiments and further developments of the component and of the method will become apparent in the exemplary embodiments explained: 
         FIGS. 1A, 1B, 1C, 1D, 1E, 1F and 1G  show an embodiment of a method for forming a mechanical and electrical connection between the component parts in schematic sectional views; 
         FIGS. 2A and 2B  show schematic illustrations of some method steps of a further exemplary embodiment of a method for establishing a mechanical and electrical connection between the component parts; 
         FIGS. 3A, 3B and 3C  show schematic illustrations of some further method steps of a further exemplary embodiment of a method for producing a component or an assembly of component parts; 
         FIGS. 4A, 4B, 4C, 4D, 4E, 4F, 4G, 4H and 4I  show schematic illustrations of some method steps of a further exemplary embodiment of a method for establishing a mechanical and electrical connection between the component parts; and 
         FIGS. 5A, 5B, 6A and 6B  show schematic illustrations of some further method steps of a further exemplary embodiment of a method for producing an assembly or a component made of a plurality of component parts. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     Identical, equivalent or equivalently acting elements are indicated with the same reference numerals in the figures. The figures are schematic illustrations and thus not necessarily true to scale. Comparatively small elements and particularly layer thicknesses can rather be illustrated exaggeratedly large for the purpose of better clarification. 
       FIG. 1A  schematically shows a first component part  1  and a second component part  2  in sectional view. The component part  1  or  2  has a carrier  1 T or  2 T. The component part  1  or  2  has a first insulation layer  1 I or a second insulation layer  2 I, wherein the insulation layer  1 I or  2 I is located on the carrier  1 T or  2 T. The component part  1  or  2  may have a main body  1 H or  2 H, wherein the main body  1 H or  2 H is disposed in the vertical direction between the carrier  1 T or  2 T and the insulation layer  1 I or  2 I. 
     The second component part  2  may be a semiconductor wafer. In particular, the component part  2  can have a carrier  2 T, for example made of sapphire, on which the main body  2 H, which is in particular a semiconductor body, is arranged. The main body  2 H can be applied to the carrier  2 T by an epitaxial process, wherein the carrier  2 T is in particular a growth substrate. The main body  2 H may have a semiconductor body which is based, for example, on a III-V or on a II-VI compound semiconductor material. In particular, the main body  2 H has a radiation-active layer  23  which is configured to generate or detect electromagnetic radiation during operation of the component part  2  ( FIG. 1F ). The radioactive layer  23  can be a p-n-junction. The main body  2 H may have further semiconductor layers which are for example intrinsic, p-doped or n-doped. In particular, the radiation-active layer  23  of the main body  2 H is arranged in the vertical direction between a first semiconductor layer and a second semiconductor layer, wherein the first semiconductor layer is arranged on the n-side and the second semiconductor layer is arranged on the p-side, or vice versa. In particular, the main body  2 H forms a diode structure comprising the semiconductor layers and the radiation-active layer  23 . The second component part  2  can be an LED. 
     The component part  2  may have a contact structure  2 K ( FIG. 1F ) which is arranged in the vertical direction in particular between the main body  2 H and the insulation layer  2 I. The contact structure  2 K is configured in particular for electrically contacting the main body  2 H. 
     The first component part  1  can be formed analogously to the second component part  2 . It is also possible that the first component part  1  is formed as a radiation-inactive wafer carrier. The main body  1 H can be free of a radiation-active layer. The main body  1 H can be formed as an etch stop layer and/or as a starting layer for electroplating further layers on the main body  1 H. The carrier  1 T can be a Si wafer. The first component part  1  can have a contact structure  1 K ( FIG. 1F ) which is arranged in the vertical direction between the first insulation layer  1 I and the first main body  1 H. The first contact structure  1 K and the second contact structure  2 K are not shown in  FIG. 1A , but may be formed similar to the exemplary embodiments shown in  FIGS. 1F, 4A and 4C . 
     According to  FIG. 1B , a mask M is formed on the insulation layer  1 I or  2 I. The mask M can be formed from a resist layer, in particular from a photo-structurable resist layer. The mask M has at least one opening MC or a plurality of openings MC. In the opening MC or in the openings MC, a surface  1 IF or  2 IF of the first insulation layer  1 I or of the second insulation layer  2 I is exposed in places. 
     According to  FIG. 1C , the openings  1 IC and  2 IC of the first or of the second insulation layer  1 I or  2 I are formed in the areas of the openings MC of the mask M, for example, by applying an etching process. In the openings  1 IC or  2 IC of the insulation layer  1 I or  2 I, the contact layers of the contact structure  1 K or  2 K can be freely accessible in places. At an interface between the mask M and the insulation layer  1 I or  2 I, the openings  1 IC or  2 IC can have a larger cross-section than the associated opening MC of the mask M. Along a lateral direction, the mask M may protrude beyond an inner wall of the opening  1 IC or  2 IC in places and thus partially cover the opening  1 IC or  2 IC in top view. 
     As shown in  FIG. 1D , a connecting stack S is applied onto the component part  1  or  2  in layers and in particular in a flat manner over a large area. The connecting stack S may have a first layer S 1 , a second layer S 2  and a layer S 3  between the first and second layers. The first layer S 1  is in particular a gold layer. The second layer S 2  is in particular a tin layer. It is possible that the first layer S 1  is a tin layer and that the second layer S 2  is a gold layer. The third layer S 3  is in particular a barrier layer S 3  which is formed from titanium or platinum, for example. 
     The connecting stack S is located within the opening  1 IC or  2 IC of the first or second insulation layer  1 I or  2 I. In lateral directions, the connecting stack S is in particular completely surrounded by the first insulation layer  1 I or by the second insulation layer  2 I. As shown in  FIG. 1D , there is a lateral intermediate space, in particular between the connecting stack S and the insulation layer  1 I or  2 I. This intermediate space can completely surround the connecting stack S in lateral directions. The intermediate space is formed for instance in that area of the opening  1 IC or  2 IC which is covered by the mask M in top view. The intermediate space can be formed since at a common interface between the mask M and the insulation layer  1 I or  2 I, the opening  1 IC or  2 IC has a larger lateral cross-section than the opening MC of the mask M. When the connecting stack S is applied, the intermediate space is not covered by the layers S 1  to S 3  so that the intermediate space is not filled by material of the connecting stack S. 
     As shown in  FIG. 1E , outside the openings  1 IC or  2 IC, the mask M and the layers S 1  to S 3  are removed. A planarization process, especially a chemical-mechanical planarization process (CMP), is suitable for this purpose. The surface  1 IF and/or  2 IF of the first and/or second insulation layer is/are planarized by this process. In particular, the planarized surface  1 IF or  2 IF outside the openings  1 IC or  2 IC has a maximum roughness that is less than 100 nm, 50 nm, 30 nm, 20 nm or less than 10 nm. 
     Subsequent to the planarization process, the insulation layer  1 I or  2 I has a vertical layer thickness T. The vertical layer thickness T corresponds for instance to the total depth T of the opening or of the openings  1 IC and/or  2 IC. The connecting stack S is located completely within the corresponding opening  1 IC or  2 IC. In particular, the connecting stack S has an overall height H which is preferably smaller than the overall depth T of the opening or openings  1 IC or  2 IC. In particular, the total height H and the total depth T differ by at least 2 nm, 5 nm or 10 nm and at most 30 nm, 50 nm, 100 nm or 1 μm. As shown in  FIG. 1E , the connecting stack H is thus slightly retracted from the planarized surface  1 IF or  2 IF. 
     As shown in  FIG. 1F , the component parts  1  and  2  are joined together. In particular, the component parts  1  and  2  are mechanically joined at the common interface G 12  of the first insulation layer  1 I and of the second insulation layer  2 I using a direct bonding process at normal room temperatures. The first component part  1  can be a radiation-inactive carrier wafer. The second component part  2  can be a radiation-active semiconductor wafer. The component part  2  has a main body  2 H which in particular comprises a radiation-active layer  23 . The first component part  1  can be free of such a radiation-active layer. 
     As shown in  FIG. 1F , the openings  1 IC and  2 IC form a common, in particular closed cavity  12 K when the component parts  1  and  2  are joined together. The connecting stack S of the first component part  1  and of the connecting stack S of the second component part  2  are arranged in the common cavity  2 K. Since the connecting stacks S are each retracted from the planarized surface  1 IF or  2 IF, there is an intermediate area  12 Z or space  12 Z in the vertical direction between the connecting stacks S. Due to the presence of the intermediate space  12 Z, no electrical connection between component parts  1  and  2  is established, in particular even after the mechanical fixing of the component parts  1  and  2 . 
     The contact formation, i.e., the formation of the through-via  12 , is achieved in particular by melting the connecting stacks S, especially by melting the solder materials gold and tin. Here, the shape of the respective connecting stack S can change from a cylindrical shape to a drop shape, wherein the height of the respective connecting stack S can exceed the common interface G 12 , as a result of which a through-via  12  is formed between the first component part  1  and the second component part  2 . The through-via  12  thus establishes an electrical connection between the first component part  1  and the second component part  2 . 
     Depending on the filling quantity and the geometries of the openings  1 IC and  2 IC, the through-via  12  can have a positive or a negative curvature. Excess solder material can be accommodated in the lateral intermediate space between the through-via  12  and the inner walls of the common cavity  12 K. The intermediate space can be formed, inter alia, by removing the material of the insulation layer/s  1 I and/or  2 I. Thus, no force can be exerted on the planar bond connection, in particular on the direct bond connection, during the formation of the through-via  12  which could lead to a detachment of the insulation layers  1 I and  2 I. 
       FIG. 1G  schematically shows an assembly  10  made of component parts  1  and  2  or a component  10  or  10 B made of component parts  1  and  2 . The through-via  12  electrically connecting the component parts  1  and  2  is formed in particular by melting the connecting stack S or the connecting stacks S. As shown in  FIG. 1G , even after the formation of the through-via  12 , there is still an intermediate space in the lateral direction between the through-via  12  and the insulation layers  1 I and  2 I. In particular, the through-via  12  is a one-piece construction. In particular, the through-via  12  is formed from a gold-tin eutectic. The gold-tin eutectic may contain traces of materials of the barrier layer S 3  or of a protective layer. In particular, the through-via  12  may contain traces of other metals such as copper, nickel, titanium or aluminum. 
     The exemplary embodiment of an assembly  10  or of a component  10  made of the component parts  1  and  2  shown in  FIG. 2A  is essentially the same as the exemplary embodiment of an assembly  10  or a component  10  or  10 B shown in  FIG. 1G . In contrast,  FIG. 2A  shows a plurality of through-vias  12 , wherein each of the through-via  12  is formed in a common cavity  12 K. In the lateral directions, the through-vias  12  are spatially separated from each other. The through-vias  12  are completely enclosed in lateral directions by the first insulation layer  1 I and/or by the second insulation layer  2 I. 
     As shown in  FIG. 2A , the through-via  12  only partially fills its associated cavity  12 K. In particular, there are intermediate spaces between the through-via  12  and the inner walls of the cavity  12 K. The intermediate spaces can be filled with a gaseous medium such as air. The through-via  12  can have a drop shape in places. The through-via  12  has side surfaces that can have a positive curvature some areas and/or a negative curvature in other areas. The through-via  12  can have the shape of a hyperboloid. In sectional view, the through-via  12  can be cylindrical in shape comprising side surfaces having either positive or negative curvature. The through-vias  12  can be assigned to the same electrical polarity of the component  10  or  10 B or different electrical polarities of the component  10  or  10 B. 
     As shown in  FIGS. 1G and 2A , the common interface G 12  between the insulation layers  1 I and  2 I is particularly planar. The common interface G 12  has openings  12 K, especially in the areas of the common cavities. The common interface surface  12  is formed in particular by the overlapping areas of the surfaces  1 IF and  2 IF of the insulation layers  1 I and  2 I. 
     The exemplary embodiment of an assembly  10  or a component  10  shown in  FIG. 2B  essentially corresponds to the exemplary embodiment of an assembly  10  or a component  10  made of component parts  1  and  2  shown in  FIG. 2A . As indicated in  FIG. 2B , the assembly  10  can be separated from component parts  1  and  2  into a plurality of smaller components  10 B. For example, the assembly  10  is separated into a plurality of individual components  10 B at the separation lines TB. The individual component  10 B is thus a subset of the assembly  10 . The individual component  10 B can have a single carrier from the first component part  1  and a single main body, particularly a radiation-active main body, from the component part  2 . The carrier is electrically conductively connected to the main body of the individual component  10 B via the through-via  12 . 
     The exemplary embodiment shown in  FIG. 3A  for a method of establishing a connection between the component parts  1  and  2  essentially corresponds to the exemplary embodiments shown in  FIGS. 1F, 1G and 2A . In contrast, the second component part  2  in  FIG. 3A  is formed as a single component part, for instance as a semiconductor chip  2 C. In particular, the semiconductor chip  2 C has a main body  2 H having a radiation-active layer  23 . The first component part  1  is formed in particular as a carrier for the semiconductor chip  2 C or for a plurality of semiconductor chips  2 C. The semiconductor chips  2 C can be applied onto the component part  1  either simultaneously or successively, wherein the mechanical and electrical connection between the component part  1  and the component part  2 , which in this case is formed as a semiconductor chip  2 C, can be carried out analogously to the exemplary embodiments shown in  FIGS. 1F and 1G . This is illustrated, for example, in  FIGS. 3B and 3C . 
     According to  FIG. 3C , the assembly  10  or the component  10  has a common component part  1  and a plurality of second component parts  2 . The second component parts  2 , which are in particular semiconductor chips  2 C, are mechanically contacted side by side on the common component part  1  and electrically connected to it. Each of the component parts  2  can have a second insulation layer  2 I. The mechanical connection between the first component part  1  and the second component parts  2  can be established either successively or simultaneously. Via through-vias  12 , the electrical connections between the first component part  1  and the second component parts  2  can also be established simultaneously or consecutively. As shown in  FIG. 3C , the second component part  2 , in particular the semiconductor chips  2 C, are arranged side by side on the first component part  1 . In particular, the second component parts  2  can be individually electrically contacted via the through-vias  12  and can thus be individually controlled. 
     In  FIGS. 4A to 4I , further method steps for providing a first component part  1  and/or a second component part  2  are shown schematically in sectional views. 
     The exemplary embodiment shown in  FIG. 4A  essentially corresponds to the exemplary embodiment shown in  FIG. 1A , but initially without the insulation layer  1 I or  2 I. In contrast,  FIG. 4A  shows the contact structure  1 K or  2 K in more detail. The contact structure  1 K or  2 K can have contact layers  41  and  42 . The contact layers  41  and  42  are especially configured for electrically contacting the main body  1 H or  2 H. The contact structure  1 K or  2 K can have a separating layer  40  which electrically isolates the contact layer  41  from the other contact layer  42 . 
     The first component part  1  can have a silicon carrier  1 T. The second component part  2  can have a carrier  2 T, which is a growth substrate, on which the main body  2 H, which is in particular a semiconductor body and/or has an LED structure, can be grown epitaxially. For example, the growth substrate is a sapphire substrate. The semiconductor body can be based on gallium nitride. In particular, the semiconductor body has a radiation-active layer, wherein the contact layers  41  and  42  are configured for electrically contacting the semiconductor body. 
     According to  FIG. 4B , a first layer S 1  of the connecting stack S is formed. The first layer S 1  can be a gold layer or a tin layer. The first layer S 1  can first be applied onto the  1 K or  2 K contact structure in a widespread and flat manner and then structured such that the first layer S 1  only remains in the areas of the contact layers  41  and  42 . Alternatively, it is possible to apply the first layer S 1  in a structured manner onto the contact layers  41  and  42 . 
     According to  FIG. 4C , the insulation layer  1 I or  2 I is applied onto the first layer S 1  and/or onto the contact structure  1 K or  2 K. The insulation layer  1 I or  2 I has a surface  1 IF or  2 IF facing away from the main body  1 H or  2 H, which has vertical elevations, especially in the areas of the first layer S 1 , especially in the form of steps. In top view, the insulation layer  1 I or  2 I covers the first layer S 1  and/or the contact layers  41  and  42  in particular completely. 
     According to  FIG. 4D , a plurality of openings  1 IC or  2 IC are formed in the insulation layer  1 I or  2 I by means of a mask M which is formed in particular from a photo-structurable resist layer. In the openings  1 IC and  2 IC, the first layer S 1  is exposed in places. Before the openings  1 IC and  2 IC are formed, the insulation layer  1 I or  2 I can be planarized, for example, using a chemical-mechanical planarization process. The insulation layer  1 I or  2 I is preferably formed from silicon oxide, especially from silicon dioxide. 
     According to  FIG. 4E , a barrier layer S 3  is formed at least in the areas of the openings  1 IC and/or  2 IC. The barrier layer S 3  can cover, in particular completely cover a bottom surface and inner walls of the openings  1 IC or  2 IC. The bottom surface of the opening or openings  1 IC and  2 IC is formed in particular by a surface of the first layer S 1 . The barrier layer S 3  may be directly adjacent to the first layer S 1 . The barrier layer S 3  may be formed of titanium or platinum. For example, the barrier layer S 3  has a vertical layer thickness between 1 nm and 30 nm inclusive, for instance between 1 nm and 20 nm, preferably between 1 nm and 10 nm. 
     According to  FIG. 4F , a second layer S 2  of the connecting stack S is formed. In particular, the second layer S 2  is applied by a sputtering process onto the insulation layer  1 I or  2 I and onto the barrier layer S 3 . For example, a layer thickness of the second layer S 2  is chosen such that the second layer S 2  only partially fills the openings  1 IC or  2 IC of the insulation layer  1 I or  2 I. The second layer S 2  is preferably formed of tin or gold. At least in the areas of the openings  1 IC and  2 IC of the insulation layer  1 I or  2 I, the barrier layer S 3  is located in the vertical direction between the first layer S 1  and the second layer S 2 . 
     According to  FIG. 4G , outside the openings of the insulation layer  1 I or  2 I, the second layer S 2  is removed. 
     After partially removing the second layer S 2 , a further barrier layer S 3  is applied onto the insulation layer  1 I or  2 I and the second layer S 2  as shown in  FIG. 4H . In a subsequent method step, a protective layer S 4  is applied, in particular in a widespread and flat manner, onto the further barrier layer S 3  or onto the insulation layer  1 I or  2 I. The protective layer S 4  can be formed from nickel, copper, aluminum or from a material whose hardness is in particular higher than that of the material of the first layer S 1  and/or of the second layer S 2 . In particular, the protective layer S 4  may be made of gold. 
     According to  FIG. 4I , the insulation layer  1 I or  2 I is planarized. During this process the protective layer S 4  is partially removed. In particular outside the openings  1 IC and  2 IC, the protective layer S 4  is completely removed, thus exposing the insulation layer  1 I or  2 I. Prior to the planarization process, the protective layer S 4  completely fills the opening or the openings  1 IC or  2 IC. After the planarization process, the openings  1 IC or  2 IC are only partially filled by the protective layer S 4 . In other words, the protective layer S 4  is slightly retracted from the surface  1 IF,  2 IF in the areas of the openings of the insulation layer  1 I or  2 I. For example, the protective layer S 4  is retracted from the surface  1 IF,  2 IF by a distance between 1 nm and 1 μm inclusive, preferably between 1 nm and 500 nm, for instance between 1 nm and 100 nm inclusive or between 10 nm and 50 nm inclusive. 
     For the direct bonding process and for the formation of the through-via  12 , it is crucial that a predetermined distance from the protective layer  4  to the particularly planarized surface  1 IF or  2 IF is maintained. If the distance is too small or if the protective layer S 4 , i.e., the connecting stack S, protrudes beyond the surface  1 IF or  2 IF, direct bonding cannot be reliably carried out. The direct bond connection can also be damaged due to its increase in volume when the connecting stack S is heated. If the distance between the protective layer S 4  and the surface  1 IF or  2 IF is too large, there is a risk that the through-via  12  will not be formed continuously. In general, it is preferable that the distance between the protective layer S 4  and the surface  1 IF or  2 IF be maintained at for instance 30 nm±10 nm. The challenge is, among other things, to achieve this distance reliably and reproducibly for all connecting stacks S of the first component part  1  and/or the second component part  2 , if possible. 
     It has been found that such an exact distance can be set very accurately in a planarization process having protective layer  4 . On the other hand, gold and tin are much softer than a material of the protective layer S 4 , e.g., of nickel, and are therefore not particularly suitable for forming the top layer of the connecting stack S. 
     As shown in  FIG. 4I , the second layer S 2  in the corresponding opening of the insulation layer  1 I or  2 I is completely enclosed by the barrier layer S 3 . The barrier layer S 3  is located in particular in the vertical direction between the first layer S 1  and the second layer S 2 . In places, the barrier layer S 3  is located in the vertical direction between the second layer S 2  and the protective layer S 4 . The barrier layer S 3  can thus prevent an early reaction, such as an intermetallic diffusion, between the layers S 1  and S 2  and/or between the layers S 2  and the protective layer S 4 . 
     The exemplary embodiment shown in  FIG. 5A  essentially corresponds to the exemplary embodiment shown in  FIG. 1F , wherein the first component part  1  and the second component part  2  are joined together to produce an assembly  10  or a component  10  or  10 B. In particular, a mechanical connection between the component parts  1  and  2  is achieved by a direct bonding process. The openings  1 IC and  2 IC of the insulation layers  1 I and  2 I can form a common, in particular sealed cavity  12 K. Even after the mechanical connection between the component parts  1  and  2  has been established, there may still be an intermediate space  12 Z between the connecting stacks S in the common cavity  12 K. 
     After the mechanical fixation of the component parts  1  and  2 , an annealing step can be carried out, wherein the connecting stacks S are melted to form the through-via  12  or the plurality of through-vias  12 . The exemplary embodiment shown in  FIG. 5B  is essentially the same as the exemplary embodiment shown in  FIG. 1G . In particular, the through-via  12  is gold-tin eutectic formed in one piece. The gold-tin eutectic may contain traces of materials of the barrier layer S 3  and/or of the protective layer S 4 . In contrast to the exemplary embodiment shown in  FIG. 1G , the through-via  12  can completely fill the common cavity  12 K as shown in  FIG. 5B . 
     The exemplary embodiments shown in  FIGS. 6A and 6B  essentially correspond to the exemplary embodiments shown in  FIGS. 5A and 5B  for establishing a mechanical and electrical connection between the component parts  1  and  2 . In contrast,  FIG. 6A  shows that the first insulation layer  1 I and the second insulation layer  2 I can have steps  3  or jumps  3  at the common interface G 12 , especially in the areas of the common cavities  12 K. Such steps  3  or jumps  3  can be regarded as characteristic features of a so-called hybrid direct bonding process. Such steps  3  or jumps  3  at the common interface G 12  can also be seen in particular on the side faces of the through-via  12  or on the side faces of the through-vias  12 , as shown for example in  FIG. 6B . 
     The invention is not restricted to the exemplary embodiments by the description of the invention made with reference to exemplary embodiments. The invention rather comprises any novel feature and any combination of features, including in particular any combination of features in the claims, even if this feature or this combination is not itself explicitly indicated in the claims or exemplary embodiments.