Liability-enhancing structures for a package

Abstract

Package (100) comprising an electronic chip (102) with a pad (104), wherein the pad (104) comprises copper, wherein the pad (104) is at least partially covered with adhesion-enhancing structures (106) comprising aluminum, thereby increasing the roughness of a surface of the pad (104) compared to a roughness of the surface of the pad (104) without adhesion-enhancing structures (106).

Description

Field of invention The present invention relates to a package and to a method for forming a semiconductor package. Background of the invention Description of the state of the art A package, for example for automotive applications, provides a physical enclosure for one or more electronic chips, which in turn contain one or more integrated circuit elements. Examples of integrated circuit elements in packages include a field-effect transistor, an insulated-gate bipolar transistor (IGBT), a diode, and passive components (such as an inductor, a capacitor, or a resistor). Furthermore, such packages can also be used to create a system-in-a-package. To manufacture a package, at least one electronic chip can be encapsulated by a suitable encapsulating agent or another dielectric structure of the package. US 2010 0 052 137 A1 discloses a method comprising providing a final metallization layer formed over a semiconductor chip substrate, wherein the final metallization layer includes a contact area with an exposed copper-containing surface for receiving a bonding wire; connecting the bonding wire to the exposed copper-containing surface; and encapsulating the exposed copper-containing surface and at least a portion of the bonding wire connected to the exposed copper-containing surface. Improved adhesion is achieved through a specific chemical pairing, as the wire can be soldered more effectively to aluminum by wire bonding than to the copper of the underlying pad. Further packages and procedures are known from US 8 410 586 B2 , US 4 946 518 A , US 2007 0 262 432 A1 and US 7 049 683 B1 . However, there is still potential for improving the reliability of a package, especially with regard to the mechanical integrity of the package. Summary There may be a need for a chip package that is mechanically robust. This need is met by a package having the features of claim 1 or claim 10 and by a method for forming a semiconductor package having the features of claim 12. Advantageous further developments are the subject of the dependent claims. According to an exemplary embodiment, a robust package is provided which includes an electronic chip with a pad, wherein the pad is at least partially covered with adhesion-enhancing structures and wherein the pad and the adhesion-enhancing structures have at least one chemical element in common (preferably, but not necessarily, aluminum). According to a further exemplary embodiment, a package is provided comprising a chip carrier, an electronic chip mounted on the chip carrier and a dielectric structure covering at least part of a surface of at least one of the chip carriers and the electronic chip, wherein at least part of the covered surface comprises hydrothermally formed adhesion-enhancing structures. According to yet another exemplary embodiment, a method for forming a semiconductor package is provided, wherein the method comprises providing an aluminum-based surface and roughening the surface with adhesion-enhancing structures formed by a hydrothermal process. According to one exemplary embodiment, a surface (for example, made of aluminum) can be treated by a hydrothermal process to induce the formation of adhesion-enhancing structures. These structures can improve the adhesion between the treated surface and a dielectric structure formed on it. As a result, a package can be produced that exhibits highly advantageous properties with respect to mechanical integrity and electrical performance. The excellent mechanical integrity results from the significantly suppressed tendency for delamination between the surface and the dielectric structure due to the presence of the hydrothermally generated adhesion-enhancing structures.The advantageous electrical integrity results from ensuring a proper connection between the surface and the dielectric structure, preventing undesirable phenomena such as moisture ingress into small gaps between an improperly connected dielectric structure and electrically conductive surfaces within the package. It is advantageous that the aforementioned (preferably aluminum-containing) adhesion-enhancing structures can be produced hydrothermally on the (preferably aluminum-containing) surface, i.e., by combining an aqueous medium and heat—a simple process without the use of hazardous substances. In particular, it can be advantageous that no chromium is required for such a hydrothermal process. One exemplary embodiment uses adhesion-enhancing structures, grown by thermal hydrolysis on aluminum-based metal surfaces or on copper surfaces covered with Al₂O₃ layers, as adhesion promoters for robust packages. These adhesion-enhancing structures can be easily monitored by optical inspection. The implementation can keep the effort required for the adhesion-promoting process relatively low. The adhesion-enhancing structures can be advantageously used as adhesion promoters between the pad or other surfaces on the one hand and a dielectric structure such as an encapsulator on the other. Furthermore, hydrothermally formed adhesion-enhancing structures can help to reduce or even eliminate harmful and hazardous substances. One exemplary embodiment involves forming a semiconductor package with improved adhesion between an aluminum contact pad and a dielectric structure (such as a mold component) within the semiconductor package. A dendrite structure or other adhesion-enhancing structures can be arranged on the surface of the aluminum contact pad to create a rough surface. Furthermore, these adhesion-enhancing structures can be grown using a hydrothermal process. In particular, the grown adhesion-enhancing structures can enable cost-effective and high-quality adhesion of molding compounds to aluminum pads or other surfaces covered with these structures. According to an exemplary embodiment, a method for forming a semiconductor package is provided that can ensure improved adhesion between an aluminum contact pad and a dielectric structure, such as a component of the semiconductor package. Dendrite structures or other types of adhesion-enhancing structures can be arranged on a surface of the aluminum contact pad to create a roughened surface. Advantageously, the adhesion-enhancing structures can be grown in a hydrothermal process. Description of further exemplary embodiments Further exemplary embodiments of the packages and the method are explained below. Within the scope of this application, the term "package" may in particular refer to at least one partially or fully encapsulated and / or coated electronic chip with at least one direct or indirect external electrical contact. Within the scope of this application, the term "electronic chip" can refer in particular to a chip (especially a semiconductor chip) that performs an electronic function. The electronic chip can be an active electronic component. In one embodiment, the electronic chip is configured as a control chip, processor chip, memory chip, sensor chip, or microelectromechanical system (MEMS). In an alternative embodiment, the electronic chip is also configured as a power semiconductor chip. Thus, the electronic chip (e.g., a semiconductor chip) can be used for power applications, for example, in the automotive sector, and can, for instance, include at least one integrated insulated-gate bipolar transistor (IGBT) and / or at least one transistor of another type (e.g., MOSFET, JFET, etc.) and / or at least one integrated diode.Such integrated circuit elements can be manufactured, for example, using silicon technology or based on broadband semiconductors (such as silicon carbide, gallium nitride, or gallium nitride on silicon). A semiconductor power chip can include one or more field-effect transistors, diodes, inverter circuits, half-bridges, full-bridges, drivers, logic circuits, and other devices. The electronic chip can be a bare die or already packaged or encapsulated. The electronic chip can also be a passive component such as a capacitor or a resistor. In the context of this application, the term "chip carrier" can, in particular, refer to a structure that is at least partially electrically conductive and simultaneously serves as a mounting surface for one or more electronic chips and also contributes to the electrical connection of the electronic chip(s) to an electronic environment within the package. In other words, the chip carrier can fulfill both a mechanical support function and an electrical connection function. A preferred embodiment of a carrier is a leadframe. In the context of this application, the term "adhesion-enhancing structures" or "adhesion-promoting structures" can refer in particular to physical bodies extending from a surface (e.g., a pad), preferably randomly oriented and / or mixed, to increase the surface roughness compared to the roughness of the surface without adhesion-enhancing structures. The adhesion-enhancing structures can be adhesion-enhancing fibers, which may be randomly oriented and form a fiber network. In particular, the adhesion-enhancing structures can share at least one material (preferably aluminum) with the surface from which they extend and / or with which they are integrally formed. For example, fibers, filaments, hairs, or strands can improve adhesion. Descriptively, the adhesion-enhancing structures can be designed or described as dendrites. In the context of this application, the term "hydrothermal process" can, in particular, refer to a process that combines the presence of water (especially only or substantially only water) and thermal energy (especially thermal energy provided by heating the water to a temperature above room temperature and below its evaporation temperature) for treating the material of a surface (especially an aluminum surface, such as an aluminum pad). Preferably, the hydrothermal process can lead to the formation of adhesion-enhancing structures based on the material of the underlying surface. In the context of this application, the term "dielectric structure" can refer, in particular, to an electrically insulating material that covers the surface and is in (preferably direct) contact with at least part of the adhesion-enhancing structures. For example, such a dielectric structure could be an encapsulating agent such as a molding compound. In one embodiment, the adhesion-enhancing structures comprise or consist of adhesion-enhancing fibers, in particular at least either nano- or microfibers. Fibers can denote long strands of material. The adhesion-enhancing fibers can be randomly oriented and mixed to form a layer with a rough outer surface. Nanofibers can be fibers having dimensions in the nanometer range. Microfibers can be fibers having dimensions in the micrometer range. In one embodiment, the package comprises a dielectric structure that directly covers at least part of the electronic chip. In particular, the dielectric structure can directly cover at least part of one or more pads of the electronic chip. Preferably, the dielectric structure can directly cover at least part of the adhesion-enhancing structures on the pad. Additionally or alternatively, such a dielectric structure can also cover at least part of a chip carrier on which the at least one electronic chip can be mounted, and / or at least part of a connecting element that connects the electronic chip to the chip carrier. In one embodiment, the dielectric structure comprises or consists of an encapsulating agent that at least partially encapsulates the electronic chip. In the context of this application, the term "encapsulation" can, in particular, refer to a substantially electrically insulating and preferably thermally conductive material that surrounds an electronic chip and / or part of a chip carrier and / or part of a connecting element to provide mechanical protection, electrical insulation, and optionally contribute to heat dissipation during operation. Such an encapsulating agent can, for example, be a molding compound. Filler particles (e.g., SiO2, Al2O3, Si3N4, BN, AlN, diamond, etc.), for example, to improve thermal conductivity, can be embedded in a polymer-based (e.g., epoxy-based) matrix of the encapsulating agent. The formation of the dielectric structure can include at least one process from a group consisting of casting (especially injection molding), coating, and potting. Casting can be defined as a manufacturing process in which liquid or malleable raw material is shaped using a rigid frame, which can be called a mold. A mold can be a hollowed-out block or tool set with an internal cavity filled with a liquid or malleable material. The liquid solidifies inside the mold and takes its shape. In one embodiment, the adhesion-enhancing structures comprise aluminum oxide and / or aluminum hydroxide. Aluminum oxide can be described as a chemical compound of aluminum and oxygen (in particular with the chemical formula Al₂O₃). Aluminum hydroxide can be formed in the presence of aluminum and water (and can in particular have the chemical formula Al(OH)₃). Aluminum oxide and / or aluminum hydroxide can be formed during a hydrothermal treatment of an aluminum surface in contact with hot water. In one embodiment, the pad comprises or consists of aluminum. In particular, the pad can comprise at least one of pure aluminum, aluminum-copper, aluminum-silicon-copper, and copper with an aluminum oxide coating. If the bulk or base material of the pad comprises aluminum (and optionally one or more other materials such as copper, silicon, etc.), treatment of this pad with hot water in a hydrothermal process can lead to the formation of adhesion-enhancing structures. However, it has also been shown that it is possible to hydrothermally treat a pad comprising, for example, copper as bulk material or base material and covered with a thin surface layer of aluminum oxide (e.g., with a thickness in the range of 1 nm to 20 nm, e.g., 6 nm) to create adhesion-enhancing structures.In the latter embodiment, the aluminum material of the surface layer can be converted into adhesion-enhancing fibers and / or react with them. The investigations revealed that dendrites could successfully grow on both aluminum-based pads and copper pads with an atomically layered (ALD, or Al₂O₃) Al₂O₃ layer. In one embodiment, the adhesion-enhancing structures form a substantially homogeneous layer. Such a substantially homogeneous layer can have a substantially constant thickness and / or a substantially homogeneous density over the entire surface covered by the adhesion-enhancing structures. This ensures that the enhanced adhesion effect is effective over a large area with substantially constant intensity. Weaknesses regarding the adhesion between the dielectric material and the surface can thus be avoided. In one embodiment, the adhesion-enhancing structures have a height in a range between 50 nm and 1000 nm, particularly between 100 nm and 300 nm. The main design parameter for adjusting the thickness is the treatment time during which the surface is hydrothermally treated, in particular immersed in hot water. In one embodiment, the package comprises a chip carrier on which the electronic chip is mounted. For example, such a chip carrier can comprise a leadframe and / or a ceramic plate covered on both opposing main surfaces with a corresponding metal layer (in particular a direct aluminum bonding (DAB) substrate and / or a direct copper bonding (DCB) substrate). In one embodiment, the carrier is a leadframe. Such a leadframe can be a sheet-like metallic structure that can be structured to form one or more mounting sections for attaching the one or more electronic chips of the package and one or more lead sections for electrically connecting the package to an electronic environment when the electronic chip(s) are mounted on the leadframe. In one embodiment, the leadframe can be a metal plate (particularly made of copper) that can be structured, for example, by stamping or etching. Forming the chip carrier as a leadframe is a cost-effective and mechanically and electrically very advantageous configuration that combines a low-resistance connection of the at least one electronic chip with robust support from the leadframe.Furthermore, a leadframe can contribute to the thermal conductivity of the package and dissipate the heat generated during the operation of the electronic chip(s) due to the high thermal conductivity of the metallic (especially copper) material of the leadframe. A leadframe can, for example, comprise aluminum and / or copper. In one embodiment, the method comprises forming the adhesion-enhancing structures on an electrically conductive surface. In particular, the (preferably aluminum-containing) surface on which adhesion-enhancing fibers can be hydrothermally grown can be a metallic surface (e.g., comprising metallic aluminum material). However, it is also possible for the adhesion-promoting effect to be generated by hydrothermally growing adhesion-promoting fibers on a dielectric or electrically insulating surface (e.g., made of dielectric aluminum oxide material). This also makes it possible to improve adhesion to a dielectric (preferably aluminum-containing) surface that is to be encapsulated by a molding compound in the package. In a preferred embodiment, the method comprises converting surface material into at least a portion of the adhesion-enhancing structures. For example, the adhesion-enhancing structures can be formed integrally with the surface from which they grow and expand. In other words, the hydrothermal process can include the method of hydrothermally converting or modifying surface material into the adhesion-enhancing structures. Thus, the adhesion-enhancing structures (in particular, adhesion-enhancing fibers) can be produced from surface material (especially pad material, chip carrier material, and / or fastener material). In particular, the surface material itself can be modified by hydrothermal processing of the surface. In one embodiment, the method comprises providing an electronic chip with a pad that provides the (in particular, electrically conductive) surface. Such a pad can establish an electrical contact between a semiconductor on the one hand and an electrically conductive connecting element (such as a bond wire, bond tape, or clamp) on the other, which is encapsulated in the package. A clip can be a three-dimensionally curved, plate-like connecting element having two planar sections that are to be connected to a top main surface of the respective electronic chip and a top main surface of the chip carrier, the two said planar sections being connected to each other by an inclined connecting section.As an alternative to such a clip, a bond wire or bond tape can be used. This is a flexible, electrically conductive wire or tape body, one end of which is connected to the upper main surface of the chip, and the opposite end of which is electrically connected to the chip carrier. Within the encapsulation, an electrically conductive connection can be formed by the bonding element between a chip pad on an upper main surface of the chip, mounted on a mounting section of the carrier, and a conductor section of the carrier. In one embodiment, the package comprises the connecting element that electrically couples the electronic chip to the chip carrier and has a surface that is at least partially covered by the dielectric structure. The covered surface of the connecting element can include hydrothermally formed adhesion-enhancing structures. Thus, adhesion can also be mediated by a connecting element such as a bonding wire, a bonding tape, or a clamp, which can also be encapsulated by an encapsulating agent such as a molding compound. This further improves the mechanical integrity of the package. In one embodiment, the method comprises providing the (particularly electrically conductive) aluminum-based surface. This aluminum material can then be used for the formation of adhesion-enhancing structures via a hydrothermal process. Consequently, the adhesion-enhancing structures also comprise or consist of aluminum material. The following describes some specific embodiments of the hydrothermal process: In one embodiment, the process involves forming the adhesion-enhancing structures by placing the electrically conductive surface in a hot (i.e., heated above ambient temperature) aqueous solution. Such an aqueous solution may contain water or consist of water. In one embodiment, the method comprises heating the aqueous solution to a temperature in the range of 50°C to 90°C, particularly in the range of 70°C to 80°C. The temperature of the hot or heated water should be high enough to ensure the efficient formation of adhesion-enhancing structures based on the material of the underlying surface (especially an underlying pad). On the other hand, the temperature of the aqueous solution should be sufficiently low to prevent evaporation. Good results can be achieved across the entire temperature range of 50°C to 90°C. Exceptional results can be achieved in the temperature range between 70°C and 80°C. In one embodiment, the method comprises providing distilled or purified water as an aqueous solution. Distilled water can refer to water that has been boiled to steam and then condensed back into liquid in a separate container. Impurities in the original water that do not boil below or at the boiling point of water remain in the original container. Thus, distilled water is a type of purified water that can be advantageously used in exemplary embodiments, in which other types of purified water can also be used for the aqueous solution. Purified water can therefore serve as a highly biocompatible and highly efficient medium for triggering the hydrothermal formation of adhesion-enhancing structures (in particular, adhesion-enhancing fibers or dendrites). In one embodiment, the method comprises holding the electrically conductive surface (in particular, an entire electronic chip) in the heated aqueous solution for a period of time between 1 minute and 10 hours, particularly between 10 minutes and 3 hours. The duration can be used as a design parameter to define the thickness of the layer of adhesion-enhancing structures. For example, holding the aluminum pads in 75°C hot water for 10 minutes can lead to the formation of adhesion-enhancing structures with a thickness of approximately 500 nm. In one embodiment, the method comprises at least partially encapsulating the surface with the adhesion-enhancing structures, particularly by casting. After roughening the surface (especially the pad) by forming the adhesion-enhancing structures, these can be directly covered with the encapsulating material. The encapsulating material thus adheres perfectly to the adhesion-enhancing structures and ensures high mechanical strength of the entire encapsulated package. In one embodiment, the at least one electronic chip comprises a semiconductor chip, in particular a power semiconductor chip. Especially when the at least one electronic chip is a power semiconductor chip, a significant amount of heat generated during the operation of the package can lead to thermal stress on the electrical and mechanical interfaces of the package. However, due to the adhesion-enhancing structures disclosed herein, damage to the package can be prevented even under these harsh conditions. In one embodiment, the electronic chip contains at least one, in particular at least three or at least eight transistors (such as field-effect transistors, in particular metal-oxide-semiconductor field-effect transistors). Typically, the electronic chip can consist of many transistors. A semiconductor substrate, preferably a silicon substrate, can be used as the substrate or wafer that forms the basis of the electronic chip(s). Alternatively, a silicon oxide or another insulating substrate can be used. It is also possible to implement a germanium substrate or a III-V semiconductor material. For example, exemplary embodiments can be realized using GaN or SiC technology. Furthermore, exemplary embodiments can utilize standard semiconductor processing technologies such as suitable etching technologies (including isotropic and anisotropic etching technologies, in particular plasma etching, dry etching, wet etching), structuring technologies (which may include lithographic masks), deposition technologies (such as chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), sputtering, etc.). The aforementioned and other objects, features and advantages of the present invention will become apparent from the following description and the attached claims, which are to be considered in conjunction with the attached drawings, in which similar parts or elements are identified by the same reference numerals. Brief description of the drawings The accompanying drawings, which provide a further understanding of exemplary embodiments and are part of the specification, illustrate exemplary embodiments. In the drawings: Fig. 1 shows a surface morphology of an aluminum-based pad before a hydrothermal process is carried out according to an exemplary embodiment. Fig. 2 shows a surface morphology of the aluminum-based pad of Fig. 1 after the hydrothermal process has been carried out according to an exemplary embodiment. Fig. 3 shows a side view of adhesion-enhancing structures on an aluminum pad produced according to an exemplary embodiment via a hydrothermal process. Fig. 4 shows a top view of adhesion-enhancing structures on an aluminum pad produced according to an exemplary embodiment via a hydrothermal process. Fig. 5 shows an aluminum-based surface with adhesion-enhancing structures according to an exemplary embodiment before a tape is applied for an adhesion test.Figure 6 shows the aluminum-based surface with adhesion-enhancing structures from Figure 5 with adhesive tape applied, for the adhesion test. Figure 7 shows the aluminum-based surface with adhesion-enhancing structures from Figure 6 after the tape has been removed, for the adhesion test. Figure 8 shows a cross-sectional view of a package according to an exemplary embodiment. Figures 9, 10, 11, 12 to 13 show top views of an aluminum pad surface after an exposure time of 10 (Figure 9), 20 (Figure 10), 30 (Figure 11), 60 (Figure 12), and 180 minutes (Figure 13), respectively. Figs. 14, 15, 16, 17 to 18 show side views of the pad surface of Figs. 9, 10, 11, 12 to 13 after exposure times of 10 (Fig. 14), 20 (Fig. 15), 30 (Fig. 16), 60 (Fig. 17) and 180 (Fig. 18) minutes, respectively. Fig. 19 shows a top view and Fig.Figure 20 shows a side view of a pad surface after 20 minutes of exposure of a copper pad covered with an Al₂O₃ layer using an ALD (Atomic Layer Deposition) process. Figure 21 shows a top view and Figure 22 shows a side view of Al-OH dendrites on copper pads covered with an Al₂O₃ layer formed by ALD after 10 minutes of spraying with 70°C hot deionized water. Figure 23 illustrates a cross-sectional view of a package according to an exemplary embodiment. Figure 24 illustrates a cross-sectional view of a package according to another exemplary embodiment. Figure 25 is a flowchart illustrating a method for forming a semiconductor package according to an exemplary embodiment. Detailed description of exemplary embodiments The representation in the drawing is schematic. Before further exemplary embodiments are described in more detail, some basic considerations of the present invention, on the basis of which exemplary embodiments were developed, are summarized. According to an exemplary embodiment, adhesion-enhancing structures (in particular aluminum oxide dendrites) can grow on a (particularly aluminum-containing) surface such as a pad to enable good adhesion of the molding compound to this surface. High reliability is essential in semiconductor packaging. One of the main challenges is the adhesion of the molding compound within the package, particularly the adhesion between metal pad areas and the compound. At this interface, it is advantageous to design the surface to be as rough as possible, thereby creating an interdiffusion zone between the molding compound resin and the surface. According to an exemplary embodiment, a reliable protection against unwanted package delamination can be achieved through a very simple process using basic chemistry. It has been shown that good homogeneity in the growth of adhesion-enhancing structures can ensure good adhesion without quality issues. In addition to its ease of processing, this exemplary embodiment also offers advantages in terms of occupational safety and health concerns due to the use of safe and non-toxic components. The simple process and associated tooling enable cost-effective manufacturing using inexpensive materials and simple tools, requiring minimal space. One exemplary embodiment produces aluminum hydroxide adhesion-enhancing structures (in particular, adhesion-enhancing fibers) that grow in a hydrothermal process, offering low cost and a healthy solution. The results have shown very good conformity and reproducibility of dendrite growth. Experiments were conducted on samples with both aluminum-based pads and copper pads with an Al₂O₃ layer produced by ALD. The dendrites grew by placing bare or mounted chips on the leadframe in, for example, 75°C hot water for an appropriate time. Exemplary embodiments enable the production of robust packages with no or extremely low delamination tendency. At the same time, exemplary embodiments can be advantageously implemented without adding further materials to the system, thus avoiding complicated and hazardous processes. In general, a manufacturing process for forming a semiconductor package 100 according to an exemplary embodiment, which also relates to Fig. 5 described in more detail below, can be as follows: First, an electronic chip 102 can be provided with one or more contact pads 104 comprising aluminum and having an exposed electrically conductive surface 112. For example, a corresponding contact pad 104 can be made of pure aluminum, aluminum-copper, or aluminum-silicon-copper. It is also possible for a corresponding contact pad 104 to consist of a copper base with a thin aluminum oxide layer. Aluminum oxide is electrically insulating, so the surface 112, on which adhesion-enhancing structures 106 subsequently grow, can also be electrically insulating and not electrically conductive. The process can then involve roughening a surface 112 of one or more contact surfaces 104 using a hydrothermal process. During this hydrothermal process, adhesion-enhancing structures 106 (in particular, adhesion-enhancing fibers or dendritic structures, which can have dimensions on the order of nanometers to micrometers) can grow on the pad 104 and on the pad 104's base material. In other words, the pad 104 itself can be the source of the material forming the adhesion-enhancing structures 106, which are integral to the pad 104. Therefore, the hydrothermal process hydrothermally transforms the surface 112 material into the adhesion-enhancing structures 106, allowing them to grow intrinsically rather than being deposited.Consequently, the adhesion-enhancing structures 106, formed based on the pad 104 (comprising aluminum), can also comprise aluminum. Thus, both the adhesion-enhancing structures 106 and the pad 104 can comprise aluminum, i.e., share at least one chemical element (in particular Al). Therefore, the adhesion-enhancing structures 106 can be formed by modifying or converting material from the surface 112 of the respective pad 104 into the adhesion-enhancing structures 106. With regard to the aforementioned hydrothermal process for forming the adhesion-enhancing structures 106, the electronic chip 102, with one or more pads 104 having the electrically conductive surface 112, can be immersed in a hot aqueous solution, in particular in heated water. Preferably, the aqueous solution can be heated to a temperature preferably between 70°C and 80°C, e.g., to 75°C. This temperature selection can ensure efficient formation of the adhesion-enhancing fibers. Deionized or distilled water can be used as the aqueous solution. The electronic chip 102, with the at least one pad 104 having the electrically conductive surface 112, can be kept immersed in the heated aqueous solution for a selectable period of time, for example, from 10 minutes to 3 hours.The duration for which the electronic chip 102 remains immersed in the purified water determines the thickness of the layer of adhesion-enhancing structures 106, which are integrally formed on the surface 112 of the respective pad 104. After the formation of the adhesion-enhancing structures 112, the surface 112 exhibits an increased roughness, which improves the adhesion properties of a molding compound or other encapsulating agent subsequently formed. The process thus includes the subsequent encapsulation of the electronic chip 102 with the one or more pads 104, the surface 112 of which is covered with adhesion-enhancing structures 106, by an encapsulating agent as a dielectric structure 108, such as a molding compound, by carrying out a molding process. Fig. 1 shows the surface morphology of an aluminum-based pad 104 before an exposed surface 112 of the pad 104 is subjected to a hydrothermal process according to an exemplary embodiment. Fig. 2 shows the surface morphology of the aluminum-based pad 104 from Fig. 1 after the hydrothermal process, according to an exemplary embodiment, has formed adhesion-enhancing structures 106 on the surface 112, i.e., after the adhesion-enhancing structures 106 have been formed in the form of nanofibers. Thus, Fig. 1 and Fig. 2 illustrate the surface morphology of an aluminum-based pad 104 before (Fig. 1) and after (Fig. 2) the hydrothermal process described above. Fig. 1 and Fig. 2 show scanning electron microscope (SEM) images. As can be seen from Fig. 2, after the described treatment a homogeneous covering of the surface 112 by the adhesion-enhancing structures 106 was found. According to the exemplary embodiment of the method to which Figures 1 and 2 refer, a Teflon (polytetrafluoroethylene) beaker was soaked with deionized water (DI water) for 30 minutes. The beaker was then filled with 80 ml of deionized water at room temperature. The beaker and water were heated to 75°C on a hot plate, and a sample, on which adhesion-enhancing structures were to form, was immersed in the water. After a suitable exposure time, the beaker was removed from the hot plate to cool to room temperature. The sample was then removed from the beaker. Fig. 3 shows a side view of adhesion-enhancing structures 106 on an aluminum pad 104, which was produced according to an exemplary embodiment via a hydrothermal process. Fig. 4 shows a top view of the adhesion-enhancing structures 106 on the aluminum pad 104, which was produced according to this exemplary embodiment via the hydrothermal process. Thus, Figs. 3 and 4 show the adhesion-enhancing structures 106 in experimentally acquired images (SEM, TEM, transmission electron microscope). Analyses using SEM, TEM, and EDX (energy-dispersive X-ray spectroscopy) show that the adhesion-enhancing structures 106 grow very homogeneously, for example, with a thickness of approximately 200 nm. As can be seen particularly in Fig. 3, the adhesion-enhancing structures 106 form an essentially homogeneous layer. Experimentally, it can also be observed that the interface between the pad 104 and the adhesion-enhancing structures 106 is very smooth, without any signs of inhomogeneous corrosion. It can also be experimentally confirmed that the composition is homogeneous and that the adhesion-enhancing structures 106 are aluminum (hydro)oxides. Figures 5, 6 to 7 show results of an adhesion test of an aluminium-based surface 112 with adhesion-enhancing structures 106 according to an exemplary embodiment. Fig. 5 shows the aluminium-based surface 112 with adhesion-enhancing structures 106 according to an exemplary embodiment, before a band is applied for adhesion testing. Fig. 6 shows the aluminum-based surface 112 with the adhesion-enhancing structures 106 from Fig. 5, with the tape 170 applied to a section 172 only for the purpose of the adhesion test. Another section 174 was not covered by the tape 170. Fig. 7 shows the aluminium-based surface 112 with the adhesion-enhancing structures 106 from Fig. 6 after removal of the tape 170 for the adhesion test, i.e., after removal of the tape 170 from section 172. As can be seen from Fig. 7, adhesive residues 176 are visible, indicating good adhesion. The described adhesion test with adhesive tape 170 shows that the adhesion-enhancing structures 106 increase the adhesion, while the adhesion-enhancing structures 106 are not easily destroyed, see Fig. 5, Fig. 6 to Fig. 7. Fig. 8 illustrates a cross-sectional view of a package 100 configured as an encapsulated electronic chip 102 on a chip carrier 110 according to an exemplary embodiment. The electronic chip 102 can have one or more pads 104. More precisely, Fig. 8 illustrates a cross-sectional view of the package 100, which is implemented as a transistor outline (TO) package according to an exemplary embodiment. The package 100 is mounted on a mounting base 118, which here is implemented as a printed circuit board (PCB). The mounting base 118 includes an electrical contact 134, which is formed as a coating in a through-hole of the mounting base 118. When the package 100 is mounted on the mounting base 118, the electronic chip 102 of the electronic component 100 is electrically connected to the electrical contact 134 via the electrically conductive chip carrier 110, here implemented as a leadframe, of the package 100. The electronic chip 102 (here implemented as a power semiconductor chip) is glued or soldered (e.g., by electrically conductive adhesive, solder paste, solder wire, or diffusion soldering) to the chip carrier 110 (see reference numeral 136). An encapsulating agent (here implemented as a molding compound) forms a dielectric structure 108 and encapsulates part of the leadframe chip carrier 110 and the electronic chip 102. As can be seen in Fig. 8, the pad 104 on an upper main surface of the electronic chip 102 is electrically coupled to the partially encapsulated leadframe chip carrier 110 via a fully encapsulated connecting element 114. During operation of the power package 100, the power semiconductor chip, in the form of the electronic chip 102, generates heat. To ensure the electrical insulation of the electronic chip 102 and to dissipate heat from the interior of the electronic chip 102 to the environment, an electrically insulating and thermally conductive interface structure 152 is provided. This interface structure covers an exposed surface section of the leadframe chip carrier 110 and a connected surface section of the dielectric encapsulation structure 108 at the base of the package 100. The thermally conductive properties of the interface structure 152 facilitate heat dissipation from the electronic chip 102, through the electrically conductive leadframe chip carrier 110, and to a heat sink 116.The heat dissipation body 116, which can be made of a highly thermally conductive material such as copper or aluminum, has a base body 154 that is directly connected to the interface structure 152, and it has a plurality of cooling fins 156 that extend from the base body 154 and parallel to each other to dissipate the heat to the environment. Typically, a package 100 of the type shown in Fig. 8 can suffer from delamination between the mold material of the dielectric structure 108 on the one hand and the material of the various components (in particular, pad 104, chip carrier 110, connecting element 114) of the package 100 on the other, which is encapsulated in and directly in contact with the dielectric structure 108. It is highly advantageous that the package 100 reliably prevents any tendency toward delamination or poor adhesion within the dielectric structure 108 by providing hydrothermally formed adhesion-enhancing structures 106 at an interface between the dielectric structure 108 on the one hand and one or more of the aforementioned components on the other. This is described in more detail below: First, with reference to detail 180, Fig. 8 shows that the dielectric structure 108 covers an electrically conductive surface 112 of the pad 104 of the electronic chip 102.To improve the roughness and thus the adhesion properties, the electrically conductive surface 112 is provided with adhesion-enhancing structures 106, which are formed as mixed nanofibers. For example, the pad 104 can be made of aluminum, and the adhesion-enhancing structures 106 can also comprise aluminum, for example, aluminum oxide or aluminum hydroxide as a result of a hydrothermal manufacturing process, as described above. Consequently, the dielectric structure 108 directly covers exposed sections of the adhesion-enhancing structures 106 on the pad 104 and therefore adheres properly to the pad 104 via these structures. The adhesion-enhancing structures 106 can have a height, h, of, for example, 500 nm. Referring to further detail 182, the package 100 also includes hydrothermally formed adhesion-enhancing structures 106, which comprise aluminum at an interface between the leadframe chip carrier 110 and the dielectric structure 108. To form the adhesion-enhancing structures 106 on the chip carrier 110 in the manner described above, it is advantageous for the chip carrier 110 to be made of aluminum or at least to have aluminum material on the surface 112 on which the adhesion-enhancing structures 106 grow hydrothermally. The material on the surface of the chip carrier 110 can then be modified or transformed into the adhesion-enhancing structures 106 during the hydrothermal process. A further detail 184 in Fig. 8 shows the (e.g., clip or bond wire) connecting element 114, which electrically connects the chip carrier 110 to the pad 104 of the electronic chip 102. As shown, the package 100 includes further hydrothermally formed adhesion-enhancing structures 106, which comprise aluminum at an interface between the connecting element 114 and the dielectric structure 108. In order to form the adhesion-enhancing structures 106 on the connecting element 114 in the manner described above, it is advantageous for the connecting element 114 to be made of aluminum or at least to have aluminum material on the surface 112 on which the adhesion-enhancing structures 106 grow hydrothermally. The material on the surface of the connecting element 114 can then be modified or transformed into the adhesion-enhancing structures 106 during the hydrothermal process.The connecting element 114, which electrically couples the electronic chip 102 to the chip carrier 110, also has a surface 112 which is covered by the dielectric structure 108 and is provided with hydrothermally formed adhesion-enhancing structures 106. With these embodiments, it is possible to form adhesion-enhancing structures 106 on a pad surface for Al-based pads 104 and for Cu pads covered with ALD 104. The homogeneous dendrite layer results in a homogeneous optical appearance, which allows for visual control of process efficiency. Figures 9, 10, 11, 12 to 13 show top views of the aluminum pad surface after exposure times of 10, 20, 30, 60, and 180 minutes, respectively. In other words, Figures 9, 10, 11, 12 to 13 show the surface morphology of aluminum-based pads 104 after different exposure times. Figures 14, 15, 16, 17 to 18 show side views of this pad surface after exposure times of 10, 20, 30, 60, and 180 minutes. The side views show the Al-OH dendrites or adhesion-enhancing structures 106 on aluminum-based pads 104 after different durations (images for 10-60 min of the broken wafer with SEM, image for 180 min with TEM). Fig. 19 shows a top view and Fig. 20 shows a side view of the surface after 20 minutes of exposure of a copper pad 104 covered with an Al₂O₃ layer using an ALD deposition method. The top and side views of the Al-OH dendrites on protected copper pads 104 after 20 minutes are shown (taken by TEM). Both pads 104 show dendrite growth in the top view, while the thickness varies with the exposure time, with the copper pad 104 being thinner, as it is covered by the ALD-formed Al₂O₃ layer. While the aluminum-based pad 104 exhibits dendrites approximately 600 nm thick, the latter resulted in a 50 nm thick layer of adhesion-promoting structures 106. In all cases, the dendrite growth is very homogeneous. The interface between the pad metal and the dendrites is very smooth, without any signs of inhomogeneous corrosion and with good composition. Based on these analytical findings, it is possible to use Al-HO dendrites grown by temperature hydrolysis as adhesion promoters for robust packages. The analyses and evaluations have shown that homogeneous dendrites can grow on both aluminum-based metal surfaces and copper surfaces covered with ALD-Al₂O₃ layers. With regard to this growth process, it is also possible to perform hydrolysis at the leadframe (or more generally, at the chip carrier 110) level. The copper areas of a package 100 can be covered with an ALD-Al2O3 layer, which can be applied to the individual package components (e.g., copper pad 104, copper leadframe, or other chip carriers 110), or after a wire bonding process, e.g., to the finished package 100. Fig. 21 shows a top view of Al-OH dendrites on copper pads 104 covered with ALD-Al₂O₃ layers after being sprayed with 70°C hot deionized water for 10 minutes. Fig. 22 shows a corresponding side view. Figs. 21 and 22 show the result of an investigation in which a wafer with a copper pad 104 protected by an ALD-Al₂O₃ layer was exposed to moisture at high temperatures on a wet-chemical etching tool. It shows that thick dendrites grow from a 6 nm thin layer. Fig. 23 illustrates a cross-sectional view of a Package 100 according to an exemplary embodiment. The package 100 of Fig. 23 comprises an electronic chip 102 with pads 104 covered with adhesion-enhancing structures 106. The pads 104 and the adhesion-enhancing structures 106 share a common chemical element, for example, aluminum. Fig. 24 illustrates a cross-sectional view of a Package 100 according to another exemplary embodiment. The package 100 of Fig. 24 comprises a chip carrier 110, an electronic chip 102 mounted on the chip carrier 110, and a dielectric structure 108 covering a surface 112 of the chip carrier 110 and the electronic chip 102. The covered surface 112 includes hydrothermally formed adhesion-enhancing structures 106. Fig. 25 is a flowchart 190 that illustrates a method for forming a semiconductor package 100 according to an exemplary embodiment. The process includes providing an aluminium-based surface 112 (see Block 192) and roughening the surface 112 by forming adhesion-enhancing structures 106 by a hydrothermal process (see Block 194). In one embodiment, a package 100 has an electronic chip 102 with a pad 104, wherein the pad 104 is at least partially covered with adhesion-enhancing structures 106 and wherein the pad 104 and the adhesion-enhancing structures 106 have at least one chemical element, in particular aluminum, in common. In one embodiment, the package 100 has a dielectric structure 108 that at least partially covers the electronic chip 102. In one embodiment, the package 100 has at least one of the following features: wherein at least a part of the adhesion-enhancing structures 106 is directly covered by the dielectric structure 108; wherein the dielectric structure 108 comprises or consists of an encapsulating means, in particular a molding compound, which at least partially encapsulates the electronic chip 102. In one embodiment, the adhesion-enhancing structures 106 comprise at least one from a group consisting of aluminium oxide and aluminium hydroxide. In one embodiment, the pad 104 comprises or consists of at least either pure aluminum, aluminum-copper, aluminum-silicon-copper or copper with an aluminum oxide coating. In one embodiment, the adhesion-enhancing structures 106 form a substantially homogeneous layer. In one embodiment, the adhesion-enhancing structures 106 have a height h in a range between 50 nm and 1000 nm, in particular in a range between 100 nm and 700 nm. In one embodiment, the adhesion-enhancing structures 106 have or consist of adhesion-enhancing fibers, in particular at least either nano- or microfibers. In one embodiment, a package 100 is provided, comprising a chip carrier 110; an electronic chip 102 mounted on the chip carrier 110; a dielectric structure 108 covering at least a portion of a surface 112, either of the chip carrier 110 or the electronic chip 102; wherein at least a portion of the covered surface 112 has hydrothermally formed adhesion-enhancing structures 106. In one embodiment, at least either the adhesion-enhancing structures 106 or the surface 112 comprise aluminium. In one embodiment, the package 100 has a connecting element 114 that electrically couples the electronic chip 102 to the chip carrier 110 and has a surface 112 that is at least partially covered by the dielectric structure 108, wherein the covered surface 112 of the connecting element 114 has hydrothermally formed adhesion-enhancing structures 106. In one embodiment, a method for forming a semiconductor package 100 is provided, wherein the method comprises: providing an aluminum-based surface 112; roughening the surface 112 by forming adhesion-enhancing structures 106 by a hydrothermal process. In one embodiment, the method involves the formation of adhesion-enhancing structures 106, which are made of aluminum. In one embodiment, the method involves forming the adhesion-enhancing structures 106 on an electrically conductive surface 112. In one embodiment, the method involves converting material of the surface 112 into at least a part of the adhesion-enhancing structures 106. In one embodiment, the method includes providing an electronic chip 102 with a pad 104, wherein the pad 104 forms at least a part of the surface 112. In one embodiment, the method involves forming the adhesion-enhancing structures 106 by placing the surface 112 in a heated aqueous solution. In one embodiment, the method comprises at least one of the following: wherein the method comprises heating the aqueous solution to a temperature in a range between 50°C and 90°C, in particular in a range between 70°C and 80°C; wherein the method comprises providing at least purified water, deionized water or distilled water as the aqueous solution; wherein the method comprises holding the surface 112 in the heated aqueous solution for a period of time between 1 minute and 10 hours, in particular for a period of time between 10 minutes and 3 hours. In one embodiment, the method involves at least partial encapsulation of the surface 112 with the adhesion-enhancing structures 106 by a dielectric structure 108, in particular by casting. In one embodiment, the hydrothermal process involves a hydrothermal conversion of material from the surface 112 into the adhesion-enhancing structures 106. It should be noted that the term "comprehensive" does not exclude other elements or features, and that "a" or "an" does not exclude a multitude. Elements described in connection with different embodiments can also be combined.

Claims

Package (100) comprising an electronic chip (102) with a pad (104), wherein the pad (104) comprises copper, wherein the pad (104) is at least partially covered with adhesion-enhancing structures (106) comprising aluminum, thereby increasing the roughness of a surface of the pad (104) compared to a roughness of the surface of the pad (104) without adhesion-enhancing structures (106). Package (100) according to claim 1, comprising a dielectric structure (108) that at least partially covers the electronic chip (102). Package (100) according to claim 2, comprising at least one of the following features: - wherein at least a part of the adhesion-enhancing structures (106) is directly covered by the dielectric structure (108); - wherein the dielectric structure (108) comprises or consists of an encapsulating means, in particular a molding compound, which at least partially encapsulates the electronic chip (102). Package (100) according to any one of claims 1 to 3, wherein the adhesion-enhancing structures (106) comprise at least one from the group consisting of aluminium oxide and aluminium hydroxide. Package (100) according to any one of claims 1 to 4, wherein the pad (104) comprises or consists of at least either aluminium copper, aluminium silicon copper or copper with an aluminium oxide coating, or wherein the copper of the pad (104) forms a copper base. Package (100) according to any one of claims 1 to 5, wherein the adhesion-enhancing structures (106) form a substantially homogeneous layer. Package (100) according to any one of claims 1 to 6, wherein the adhesion-enhancing structures (106) have a height (h) in a range between 50 nm and 1000 nm, in particular in a range between 100 nm and 700 nm. Package (100) according to any one of claims 1 to 7, wherein the adhesion-enhancing structures (106) comprise or consist of adhesion-enhancing fibers, in particular at least either nano- or microfibers. Package (100) according to any one of claims 1 to 8, wherein the aluminium oxide coating and the adhesion-enhancing structures (106) are electrically insulating and not electrically conductive. Package (100) comprising: - a chip carrier (110), in particular a leadframe, wherein the chip carrier (110) comprises copper; - an electronic chip (102) mounted on the chip carrier (110); - a dielectric structure (108) covering at least a part of a surface (112) of the chip carrier (110); - wherein at least a part of the covered surface (112) has hydrothermally formed adhesion-enhancing structures (106) of aluminum oxide or aluminum hydroxide on the copper, thereby increasing the roughness of the covered surface (112) compared to the roughness of the covered surface (112) without adhesion-enhancing (106) structures. Package (100) according to claim 10, comprising a connecting element (114) which electrically couples the electronic chip (102) to the chip carrier (110) and has a surface (112) which is at least partially covered by the dielectric structure (108), wherein the covered surface (112) of the connecting element (114) comprises the hydrothermally formed adhesion-enhancing structures (106). Method for forming a semiconductor package (100), the method comprising: - providing an electronic chip (102) with a pad (104), wherein the pad (104) comprises copper; - performing atomic layer deposition (ALD) to deposit an Al2O3 layer on the copper of the pad (104), forming at least part of an aluminum-based surface (112); - roughening the aluminum-based surface (112) by forming adhesion-enhancing structures (106) by a hydrothermal process, thereby increasing the roughness of the surface (112) compared to the roughness of the surface (112) without adhesion-enhancing structures (106). Method according to claim 12, wherein the Al2O3 layer has a thickness in the range between 1 nm and 20 nm. Method according to claim 12 or 13, wherein the adhesion-enhancing structures (106) comprise aluminium, in particular wherein the adhesion-enhancing structures (106) comprise at least one from a group consisting of aluminium oxide and aluminium hydroxide. Method according to any one of claims 12 to 14, wherein the Al2O3 layer and the adhesion-enhancing structures (106) are electrically insulating and not electrically conductive. Method according to any one of claims 12 to 15, wherein the method comprises converting at least a part of the aluminum-based surface material (112) into at least a part of the adhesion-enhancing structures (106). Method according to any one of claims 12 to 16, wherein the method comprises forming the adhesion-enhancing structures (106) by placing the aluminium-based surface (112) in a heated aqueous solution. The method according to claim 17, wherein the method comprises at least one of the following: - wherein the method comprises heating the aqueous solution to a temperature in a range between 50°C and 90°C, in particular in a range between 70°C and 80°C; - wherein the method comprises providing at least purified water, deionized water or distilled water as the aqueous solution; - wherein the method comprises holding the surface (112) in the heated aqueous solution for a period of time between 1 minute and 10 hours, in particular for a period of time between 10 minutes and 3 hours. Method according to any one of claims 12 to 18, wherein the method comprises at least partial encapsulation of the aluminium-based surface (112) with the adhesion-enhancing structures (106) by a dielectric structure (108), in particular by casting. Method according to any one of claims 12 to 19, wherein the hydrothermal process comprises a hydrothermal conversion of aluminum-based surface material (112) into the adhesion-enhancing structures (106).

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