Adhesion enhancing structure for package

Abstract

The present invention provides an adhesion enhancing structure for a package (100), the package comprising an electronic chip (102) having a pad (104), where the pad (104) is at least partially covered by an adhesion enhancing structure (106), and where the pad (104) and the adhesion enhancing structure (106) have at least one common chemical element, in particular aluminum.

Description

[0001] This application is a divisional application of an application with an application date of July 30, 2019, application number 201910709904.4, and invention name “Adhesion Enhanced Structure for Packaging”. Technical Field

[0002] The present invention relates to packaging and methods. Background Art

[0003] For example, packaging for automotive applications provides a physical protective shell for one or more electronic chips that include one or more integrated circuit components. Examples of packaged integrated circuit components are field effect transistors, insulated gate bipolar transistors (IGBTs), diodes, and passive components (e.g., inductors, capacitors, resistors). In addition, such packaging can be used to make system-level packages.

[0004] To produce the package, at least one electronic chip may be encapsulated by a suitable encapsulant or another dielectric structure of the package.

[0005] However, there may still be room for improvement in package reliability, especially in terms of the mechanical integrity of the package. Summary of the invention

[0006] A mechanically robust chip package may be required.

[0007] According to an exemplary embodiment, a robust package is provided, comprising an electronic chip having a pad, wherein the pad is at least partially covered by an adhesion enhancing structure, and wherein the pad and the adhesion enhancing structure have at least one common chemical element, preferably but not limited to aluminum.

[0008] According to another 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 a portion of a surface of at least one of the chip carrier and the electronic chip, wherein at least a portion of the covered surface comprises a hydrothermally formed adhesion enhancing structure.

[0009] According to another exemplary embodiment, a method of forming a semiconductor package is provided, wherein the method includes providing an aluminum-based surface and roughening the surface with an adhesion enhancement structure formed by a hydrothermal process.

[0010] According to an exemplary embodiment, a surface (e.g., including aluminum) can be treated by a hydrothermal process for triggering the formation of an adhesion enhancement structure. The adhesion enhancement structure can enhance the adhesion between the covered surface and the dielectric structure formed thereon. As a result, a package with highly favorable characteristics in terms of mechanical integrity and electrical performance can be manufactured. The appropriate mechanical integrity is derived from the strong inhibition tendency of peeling between the surface and the dielectric structure, which is attributed to the provision of the hydrothermally generated adhesion enhancement structure. The favorable electrical integrity is derived from the fact that a proper connection between the surface and the dielectric structure can be ensured, which prevents undesirable phenomena (e.g., moisture) from entering the tiny gaps between the improperly connected dielectric structure and the conductive surface in the package. Advantageously, the mentioned adhesion enhancement structure (preferably including aluminum) on the surface (preferably including aluminum) can be manufactured in a hydrothermal manner, that is, manufactured by a combination of an aqueous medium and heat, that is, manufactured in a simple manner and without involving harmful substances. It is particularly advantageous that such a hydrothermal process may not require chromium.

[0011] Thus, exemplary embodiments use adhesion enhancement structures grown via temperature hydrolysis on aluminum-based metal areas or on copper areas covered by Al2O3 layers as adhesion promoters for robust packaging. These adhesion enhancement structures can be easily monitored by optical detection. Implementations can keep the adhesion promotion process to a reasonably small workload. Adhesion enhancement structures can be advantageously used as adhesion promoters between pads or other surfaces (on the one hand) and dielectric structures such as encapsulation (on the other hand). In addition, hydrothermally formed adhesion enhancement structures can play a role in reducing or even eliminating unhealthy and harmful materials.

[0012] The subject of the exemplary embodiment is to form a semiconductor package having improved adhesion between its aluminum contact pad and a dielectric structure such as a molded component. At the surface of the aluminum contact pad, a dendrite structure or other kind of adhesion enhancement structure may be arranged to provide a rough surface. In addition, the adhesion enhancement structure may be grown by a hydrothermal process. Specifically, the grown adhesion enhancement structure may achieve low-cost and high-quality molding compound adhesion on the aluminum pad or other surface covered with the adhesion enhancement structure.

[0013] According to an exemplary embodiment, a method for forming a semiconductor package is provided that can provide improved adhesion between an aluminum contact pad of the semiconductor package and a dielectric structure such as a molded component. At the surface of the aluminum contact pad, a dendrite structure or other type of adhesion enhancing structure can be arranged to provide a rough surface. Advantageously, the adhesion enhancing structure can be grown by a hydrothermal process.

[0014] Description of Other Exemplary Embodiments

[0015] In the following, further exemplary embodiments of packages and methods will be explained.

[0016] In the context of the present application, the term “package” may particularly denote at least one partially or completely encapsulated and / or coated electronic chip having at least one direct or indirect external electrical contact.

[0017] In the context of the present application, the term "electronic chip" may particularly refer to a chip (more particularly, a semiconductor chip) that provides electronic functions. An electronic chip may be an active electronic component. In one embodiment, the electronic chip is configured as a controller chip, a processor chip, a memory chip, a sensor chip, or a micro-electromechanical system (MEMS). In an alternative embodiment, the electronic chip may be configured as a power semiconductor chip. Thus, an electronic chip (e.g., a semiconductor chip) may be used for power applications in, for example, the automotive field, and may, for example, have at least one integrated insulated gate bipolar transistor (IGBT) and / or at least one other type of transistor (e.g., MOSFET, JFET, etc.) and / or at least one integrated diode. For example, such an integrated circuit element may be made by silicon technology or based on a wide bandgap semiconductor (e.g., silicon carbide, gallium nitride, or gallium nitride on silicon). A semiconductor power chip may include one or more field effect transistors, diodes, inverter circuits, half bridges, full bridges, drivers, logic circuits, other devices, etc. An electronic chip may be a bare die, or may be packaged or encapsulated. However, an electronic chip may also be a passive component, such as a capacitor or a resistor.

[0018] In the context of the present application, the term "chip carrier" may particularly denote an at least partially electrically conductive structure which simultaneously serves as a mounting substrate for one or more electronic chips and also facilitates the electrical connection of the electronic chips to the electronic environment of the package. In other words, the chip carrier may fulfill both a mechanical support function and an electrical connection function. A preferred embodiment of the carrier is a lead frame.

[0019] In the context of the present application, the term "adhesion enhancing structure" or adhesion promoting structure may particularly refer to a physical body extending from a surface (e.g., a pad), preferably in a manner having a random orientation and / or in an intermingling manner, thereby increasing the roughness compared to the roughness of the surface without the adhesion enhancing structure. The adhesion enhancing structure may be an adhesion enhancing fiber, which may have a random orientation and may form a fiber network. In particular, the adhesion enhancing structure may share at least one material (preferably aluminum) with the surface, wherein the adhesion enhancing structure extends from the surface or is formed integrally with the surface. For example, the adhesion enhancing structure may be a fiber, a filament, a hair, or a strand. Descriptively speaking, the adhesion enhancing structure may be embodied as or may be represented as a dendrite.

[0020] In the context of the present application, the term "hydrothermal process" may particularly denote a process that combines the presence of water (particularly only water or substantially only water) and thermal energy (particularly thermal energy provided by heating water to a temperature above room temperature but below the evaporation temperature) for treating the material of a surface (particularly an aluminum surface, such as an aluminum pad). Preferably, the hydrothermal process may cause the formation of an adhesion enhancing structure based on the material of the underlying surface.

[0021] In the context of the present application, the term "dielectric structure" may particularly denote an electrically insulating material covering the surface and in contact (preferably in direct contact) with at least part of the adhesion enhancing structure. For example, such a dielectric structure may be an encapsulant, such as a molding compound.

[0022] In an embodiment, the adhesion enhancement structure comprises or consists of adhesion enhancement fibers, in particular at least one of nanofibers and microfibers. The fibers may represent long strands of material. The adhesion enhancement fibers may have a random orientation and may be interwoven to form a layer with a rough outer surface. Nanofibers may be fibers with a size in the nanometer range. Microfibers may be fibers with a size in the micrometer range.

[0023] In an embodiment, the package comprises a dielectric structure at least partially directly covering the electronic chip. More specifically, the dielectric structure may at least partially directly cover one or more pads of the electronic chip. Preferably, the dielectric structure may at least partially directly cover the adhesion enhancement structure on the pads. Alternatively or in addition, such a dielectric structure may also cover at least a portion of a chip carrier on which at least one electronic chip may be mounted, and / or such a dielectric structure may cover at least a portion of a connecting element connecting the electronic chip to the chip carrier.

[0024] In an embodiment, the dielectric structure comprises an encapsulant that at least partially encapsulates at least the electronic chip, or is composed of the encapsulant. In the context of the present application, the term "encapsulant" can particularly refer to a substantially electrically insulating and preferably thermally conductive material that surrounds a portion of the electronic chip and / or a chip carrier and / or a portion of a connecting element to provide mechanical protection and electrical insulation, and optionally contributes to heat dissipation during operation. For example, such an encapsulant can be a molding compound. For example, filler particles (e.g., SiO2, Al2O3, Si3N4, BN, AlN, diamond, etc.) for improving thermal conductivity can be embedded in a plastic-based (e.g., epoxy-based) matrix of the encapsulant.

[0025] Forming the dielectric structure may include at least one of the group consisting of molding (particularly injection molding), coating and casting. Molding may be referred to as a manufacturing process in which a liquid or plastic raw material is shaped using a rigid frame that may be referred to as a mold. The mold may be a hollowed-out block or tool set having an internal hollow volume filled with a liquid or plastic material. The liquid hardens within the mold, thereby taking the shape of the mold.

[0026] In an embodiment, the adhesion enhancing structure comprises aluminum oxide and / or aluminum hydroxide. Aluminum oxide may be represented as a chemical compound of aluminum and oxygen (particularly having the chemical formula Al2O3). Aluminum hydroxide may be formed in the presence of aluminum and water (and may particularly have the chemical formula Al(OH)3). Aluminum oxide and / or aluminum hydroxide may be formed when a surface of an aluminum material in contact with hot water is hydrothermally treated.

[0027] In an embodiment, the pad comprises or consists of aluminum. Specifically, the pad may comprise at least one of pure aluminum, aluminum-copper, aluminum-silicon-copper, and copper with an aluminum oxide coating. When the bulk material or substrate material of the pad comprises aluminum (and optionally one or more other materials such as copper, silicon, etc.), treatment of the pad material with hot water in a hydrothermal process may cause the formation of an adhesion enhancement structure. However, it has been demonstrated that it is possible to hydrothermally treat a pad comprising, for example, copper as a bulk or substrate material and covered with a thin surface layer of aluminum oxide (e.g., having a thickness in the range between 1 nm and 20 nm, e.g., having a thickness of 6 nm) to thereby produce an adhesion enhancement structure. In the latter embodiment, the aluminum material of the surface layer may be converted into and / or may react to form adhesion enhancement fibers. In the study, it was demonstrated that it is possible to successfully grow dendrites on aluminum-based pads and copper pads with an Al2O3 layer of atomic layer deposition (ALD, atomic layer deposition) on top.

[0028] In an embodiment, the adhesion enhancing structure forms a substantially uniform layer. Such a substantially uniform layer may have a substantially constant thickness over the entire surface covered by the adhesion enhancing structure and / or may have a substantially uniform density. This ensures that the promoted adhesion effect acts over a large area with a substantially constant intensity. Thus, weak points regarding adhesion between the dielectric material and the surface may be prevented.

[0029] In an embodiment, the adhesion enhancing structure has a height in the range between 50 nm and 1000 nm, in particular between 100 nm and 300 nm.The main design parameter for adjusting the thickness is the treatment time of the hydrothermal treatment of the surface, in particular immersion in hot water.

[0030] In an embodiment, the package includes a chip carrier on which the electronic chip is mounted. For example, such a chip carrier may include a lead frame and / or a ceramic sheet (particularly a direct aluminum bonding (DAB) substrate and / or a direct copper bonding (DCB) substrate) covered with corresponding metal layers on two opposing main surfaces.

[0031] In an embodiment, the carrier is a lead frame. Such a lead frame can be a thin plate-like metal structure, which can be patterned to form one or more mounting sections for mounting one or more electronic chips of the package and one or more lead sections for electrically connecting the package to the electronic environment when the electronic chip is mounted on the lead frame. In an embodiment, the lead frame can be a metal plate (particularly made of copper), which can be patterned by, for example, stamping or etching. It is cost-effective to form the chip carrier as a lead frame, and it is a very advantageous configuration mechanically and electrically, wherein, the low-ohmic connection of at least one electronic chip can be combined with the robust support capacity of the lead frame. In addition, due to the high thermal conductivity of the metal material (particularly copper) of the lead frame, the lead frame can contribute to the thermal conductivity of the package, and can remove the heat generated during the operation of the electronic chip. The lead frame can include, for example, aluminum and / or copper.

[0032] In an embodiment, the method comprises forming an adhesion enhancing structure on a conductive surface. In particular, the surface (preferably comprising aluminum) on which the adhesion enhancing structure may be hydrothermally grown may be a metallic surface (e.g. comprising a metallic aluminum material). However, it is also possible to form an adhesion promoting effect by hydrothermally growing adhesion promoting fibers on a dielectric or electrically insulating surface (e.g. comprising a dielectric aluminum oxide material). As a result, it is also possible to improve adhesion at a dielectric (preferably comprising aluminum) surface in a package to be encapsulated by a molding compound.

[0033] In a preferred embodiment, the method includes converting the material of the surface into at least part of the adhesion enhancement structure. For example, the adhesion enhancement structure can therefore be formed integrally with the surface of their growth and extension. In other words, the hydrothermal process can include the process of converting or modifying the material of the surface into the adhesion enhancement structure in a hydrothermal manner. Therefore, the adhesion enhancement structure (particularly the adhesion enhancement fiber) can be created by the surface material (particularly by the pad material, the chip carrier material and / or the connecting element material). Specifically, by hydrothermal treatment of the surface, the material of the surface itself can be chemically modified to form the adhesion enhancement structure. As a result, the appropriate integrity between the remaining material of the surface (on the one hand) and the adhesion enhancement structure (on the other hand) formed as a whole can be obtained. As a result of this material conversion, the material of the surface (on the one hand) and the material of the adhesion enhancement structure (on the other hand) can share at least one chemical element, or can even be chemically equivalent.

[0034] In an embodiment, the method includes providing a pad for an electronic chip, the pad providing a surface (particularly a conductive surface). Such a pad can provide electrical contact between a semiconductor die (on the one hand) and a conductive connection element (e.g., a bonding wire, a bonding tape or a clamp) encapsulated in a package (on the other hand). The clamp can be a three-dimensional curved plate-type connection element having two planar sections that will be connected to the upper main surface of the corresponding electronic chip and the upper main surface of the chip carrier, wherein the two mentioned planar sections are interconnected by an inclined connection section. As an alternative to such a clamp, it is possible to use a bonding wire or a bonding tape as a flexible conductive wire or a strip-shaped body, having an end portion connected to the upper main surface of the corresponding chip and another opposite end portion electrically connected to the chip carrier. In the encapsulation, a conductive connection can be formed by a connecting element between a chip pad at the upper main surface of the chip mounted on the mounting section of the carrier (on the one hand) and a lead section of the carrier (on the other hand).

[0035] In an embodiment, the package includes a connection element that electrically couples the electronic chip to the chip carrier and has a surface that is at least partially covered by a dielectric structure. The covered surface of the connection element may include an adhesion enhancement structure formed in a hydrothermal manner. Thus, adhesion promotion may also be provided on a connection element such as a bonding wire, a bonding tape or a clamp, which may also be encapsulated by an encapsulant such as a molding compound. This further improves the mechanical integrity of the package.

[0036] In an embodiment, the method comprises providing an aluminum-based surface (particularly a conductive surface). By means of a hydrothermal process, such an aluminum material can then be used to form an adhesion enhancing structure. As a result, the adhesion enhancing structure then also comprises or consists of an aluminum material.

[0037] In the following, some specific embodiments related to the hydrothermal process will be described:

[0038] In an embodiment, the method comprises forming the adhesion enhancing structure by placing the conductive surface in a hot (ie heated to above ambient temperature) aqueous solution. Such an aqueous solution may comprise or consist of water.

[0039] In an embodiment, the method comprises heating the aqueous solution to a temperature in the range between 50°C and 90°C, in particular in the range between 70°C and 80°C. The temperature of the hot or heated water should be high enough to ensure effective generation of an adhesion enhancement structure based on the material of the underlying surface, in particular the underlying pad. On the other hand, the temperature of the aqueous solution should be low enough to prevent evaporation of the aqueous solution. Good results can be achieved in the entire temperature range from 50°C to 90°C. Excellent results can be obtained in the temperature range between 70°C and 80°C.

[0040] In an embodiment, the method includes providing distilled water or purified water as the aqueous solution. Distilled water can refer to water that is boiled into steam and condensed into a liquid in a separate container. Impurities in the original water that do not boil below or at the boiling point of the water are retained in the original container. Thus, distilled water is a type of purified water that can be advantageously used in exemplary embodiments, wherein other types of purified water can also be used for aqueous solutions. Thus, pure water can serve as a highly biocompatible and highly effective medium for triggering the hydrothermal formation of adhesion-enhancing structures, particularly adhesion-enhancing fibers or dendrites.

[0041] In an embodiment, the method comprises maintaining the conductive surface (particularly the entire electronic chip) in the heated aqueous solution for a time interval between 1 minute and 10 hours, particularly for a time interval between 10 minutes and 3 hours. The duration can be used as a design parameter for defining the thickness of the layer of the adhesion enhancement structure. For example, maintaining an aluminum pad in hot water at 75° C. for 10 minutes can result in the formation of an adhesion enhancement structure with a thickness of approximately 500 nm.

[0042] In an embodiment, the method comprises at least partially encapsulating (particularly by molding) a surface having an adhesion enhancement structure thereon. After roughening the surface (particularly the pad) by forming the adhesion enhancement structure, the adhesion enhancement structure is directly covered with an encapsulant. Thus, the encapsulant is properly attached to the adhesion enhancement structure, thereby ensuring high mechanical integrity of the entire formed package.

[0043] In an embodiment, at least one electronic chip comprises a semiconductor chip, in particular a power semiconductor chip. Specifically, when at least one electronic chip is a power semiconductor chip, a large amount of heat generated during operation of the package may cause thermal loads acting on the electrical and mechanical interfaces of the package. However, due to the adhesion enhancement structure disclosed herein, damage to the package can be prevented even under such harsh conditions.

[0044] In an embodiment, the electronic chip comprises at least one, in particular at least three or at least eight transistors (eg field effect transistors, in particular metal oxide semiconductor field effect transistors). Typically, an electronic chip may comprise many transistors.

[0045] As a substrate or wafer forming the basis of the electronic chip, a semiconductor substrate may be used, preferably a silicon substrate. Alternatively, a silicon oxide or another insulator substrate may be provided. It is also possible to implement a germanium substrate or a III-V semiconductor material. For example, exemplary embodiments may be implemented using GaN or SiC technology.

[0046] In addition, exemplary embodiments can utilize standard semiconductor processing techniques, such as appropriate etching techniques (including isotropic and anisotropic etching techniques, in particular plasma etching, dry etching, wet etching), patterning techniques (which may involve photolithography masks), deposition techniques (such as chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), sputtering, etc.).

[0047] The above and other objects, features and advantages of the present invention will become apparent from the following description and appended claims taken in conjunction with the accompanying drawings in which like parts or elements are designated by like reference numerals. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The accompanying drawings are included to provide a further understanding of exemplary embodiments and constitute a part of the specification, and illustrate exemplary embodiments.

[0049] In the figure:

[0050] Figure 1 Surface morphology of an aluminum-based pad is shown before performing a hydrothermal process according to an exemplary embodiment.

[0051] Figure 2 shows a hydrothermal process according to an exemplary embodiment. Figure 1 Surface morphology of an aluminum-based pad.

[0052] Figure 3 A side view of an adhesion enhancement structure on an aluminum pad fabricated in accordance with an exemplary embodiment after a hydrothermal process is shown.

[0053] Figure 4 A top view of an adhesion enhancement structure on an aluminum pad fabricated in accordance with an exemplary embodiment after a hydrothermal process is shown.

[0054] Figure 5 An aluminum-based surface with an adhesion enhancing structure according to an exemplary embodiment before attaching an adhesive tape is shown in an adhesion test.

[0055] Figure 6 Adhesion tests showed that the attached tape Figure 5 Aluminum-based surfaces with adhesion-enhancing structures.

[0056] Figure 7 The adhesion test showed that after removing the tape Figure 6 Aluminum-based surfaces with adhesion-enhancing structures.

[0057] Figure 8 A cross-sectional view of a package according to an exemplary embodiment is shown.

[0058] Figures 9 to 13 The results are shown in Figure 2. Fig. 9 )、20 minutes( Fig.10 )、30 minutes( Fig.11 )、60 minutes( Fig.12 ) and 180 minutes ( Fig.13 ) top view of the aluminum pad surface after exposure time.

[0059] Figures 14 to 18 The results are shown in Figure 2. Fig.14 )、20 minutes( Fig.15 )、30 minutes( Fig.16 )、60 minutes( Fig.17 ) and after an exposure time of 180 minutes (18) Figures 9 to 13 Side view of the pad surface.

[0060] Fig.19 and Fig. 20 A top view and a side view of the pad surface of a copper pad covered with an Al2O3 layer using an ALD (atomic layer deposition) deposition process after 20 minutes of exposure are shown, respectively.

[0061] Fig.21 and Fig. 22 Shown are top and bottom views, respectively, of Al-OH dendrites on a copper pad covered with an Al2O3 layer formed by ALD after spraying with hot deionized water at 70°C for 10 minutes.

[0062] Fig.23A cross-sectional view of a package according to an exemplary embodiment is shown.

[0063] Fig.24 A cross-sectional view of a package according to another exemplary embodiment is shown.

[0064] Fig.25 is a flowchart illustrating a method of forming a semiconductor package according to an exemplary embodiment. DETAILED DESCRIPTION

[0065] The illustrations in the drawings are schematic only.

[0066] Before describing other exemplary embodiments in more detail, some basic considerations of the invention upon which the exemplary embodiments were developed will be summarized.

[0067] According to an exemplary embodiment, adhesion enhancing structures, in particular aluminum oxide dendrites, may be grown on a surface, such as a solder pad, in particular comprising aluminum, to achieve good molding compound adhesion on this surface.

[0068] In the case of semiconductor packaging, high reliability is required. One of the main issues is the adhesion of the mold compound in the package, especially the adhesion between the metal pad area and the mold compound. At this interface, it is advantageous to make the surface as rough as possible to achieve (in terms of description) an interdiffusion zone between the mold compound resin and the surface.

[0069] According to exemplary embodiments, reliable protection against undesirable peeling of the package can be achieved by a very simple process with simple chemical properties. It has been shown that appropriate uniformity of the growth of the adhesion enhancing structure can make appropriate adhesion possible without having to face quality problems. In addition to simple processing, the process according to exemplary embodiments also has advantages in terms of job safety and health restrictions due to its healthy and harmless composition. Simple processes and corresponding simple tools allow manufacturing to be completed with low workload due to cheap materials and simple tools with a small footprint.

[0070] The exemplary embodiment manufactures aluminum hydroxide adhesion enhancing structures (particularly adhesion enhancing fibers) grown by a hydrothermal process, thereby providing a low burden and healthy solution. The results show that the dendrite growth has very good consistency and reproducibility. Samples with aluminum-based pads and copper pads covered with an ALD-made Al2O3 layer have been studied in the experiments. Dendrites are grown by placing the bare chip or the assembled chip on the lead frame in hot water, for example at 75°C for a suitable time.

[0071] The exemplary embodiments allow for the manufacture of robust packages with zero or very low delamination tendency. At the same time, the exemplary embodiments can advantageously be performed without adding other materials to the system and avoiding complex and hazardous processes.

[0072] More generally, and with reference also to the more detailed description below Figure 5 , a manufacturing process of forming the semiconductor package 100 according to an exemplary embodiment may be described as follows.

[0073] First, one or more contact pads 104 may be provided for the electronic chip 102, the contact pads 104 comprising aluminum and having an exposed conductive surface 112. For example, the respective contact pads 104 may be made of pure aluminum, aluminum-copper, or aluminum-silicon-copper. The respective contact pads 104 may also be made of a copper substrate with a thin aluminum oxide coating. Aluminum oxide is electrically insulating so that the surface 112 on which the adhesion enhancement structure 106 will be grown later may also be electrically insulating rather than conductive.

[0074] Thereafter, the method may include roughening the surface 112 of one or more contact pads 104 using a hydrothermal process. With respect to the hydrothermal process, it is possible to grow an adhesion enhancement structure 106 (particularly an adhesion enhancement fiber or dendrite structure that may have a size in the order of nanometers to micrometers) on and based on the material of the pad 104. In other words, the pad 104 itself may be a source of material for forming an adhesion enhancement structure 106 integral with the pad 104. Thus, the hydrothermal process hydrothermally converts the material of the surface 112 into the adhesion enhancement structure 106, so as to thereby inherently grow rather than deposit the adhesion enhancement structure 106. As a result, the adhesion enhancement structure 106 formed based on the pad 104 (including aluminum) may also include aluminum. Thus, the adhesion enhancement structure 106 and the pad 104 may both include aluminum, i.e., may have at least one common chemical element (particularly Al). Thus, the adhesion enhancement structure 106 may be formed by modifying or converting the material of the surface 112 of the corresponding pad 104 into the adhesion enhancement structure 106.

[0075] As for the hydrothermal process mentioned for forming the adhesion enhancement structure 106, the electronic chip 102 having one or more pads 104 (having a conductive surface 112) can be placed in a hot aqueous solution, more specifically, can be immersed in hot water. Preferably, the aqueous solution can be heated to a temperature preferably between 70°C and 80°C, for example, heated to 75°C. This temperature selection can ensure the effective formation of adhesion enhancement fibers. Deionized water or distilled water can be used as the aqueous solution. The electronic chip 102 having at least one pad 104 with a conductive surface 112 can be kept immersed in the heated aqueous solution for a selected time interval (for example, between 10 minutes and 3 hours). The duration of the electronic chip 102 remaining immersed in pure water determines the thickness of the layer of the adhesion enhancement structure 106 formed integrally on the surface 112 of the corresponding pad 104. After forming the adhesion enhancement structure 106, the surface 112 has an increased roughness, which improves the adhesion properties of the molding compound or another encapsulation formed next.

[0076] Thus, the method comprises next encapsulating the electronic chip 102 having one or more pads 104 having a surface 112 covered by the adhesion enhancing structure 106 by an encapsulant (eg a molding compound) as a dielectric structure 108 by performing a molding process.

[0077] Figure 1 The surface topography of the aluminum-based pad 104 is shown before subjecting the exposed surface 112 of the pad 104 to a hydrothermal process according to an exemplary embodiment. Figure 2 FIG. 1 shows an example of a hydrothermal process according to an exemplary embodiment after the adhesion enhancing structure 106 has been formed on the surface 112, ie, after the adhesion enhancing structure 106 in the form of nanofibers has been formed. Figure 1 The surface morphology of the aluminum-based pad 104. Thus, Figure 1 and Figure 2 It is shown that before the above hydrothermal process ( Figure 1 ) and after ( Figure 2 )'s surface morphology of the aluminum-based pad 104. Figure 1 and Figure 2 Scanning electron microscope (SEM) images are shown.

[0078] from Figure 2 As can be seen, uniform coverage of the surface 112 with the adhesion enhancing structure 106 has been found after the described treatment.

[0079] according to Figure 1 and Figure 2An exemplary embodiment of the method involved, a Teflon (polytetrafluoroethylene) beaker is overflowed with deionized water (DI water) for 30 minutes. Thereafter, the beaker is filled with 80 ml of DI water at room temperature. The beaker containing the water is heated to 75° C. on a hotplate, and the sample to be formed into an adhesion enhancement structure is immersed in the water. After the appropriate exposure time, the beaker is removed from the hotplate and allowed to cool to room temperature. The sample is removed from the beaker.

[0080] Figure 3 A side view of an adhesion enhancement structure 106 on an aluminum pad 104 fabricated in accordance with an exemplary embodiment after a hydrothermal process is shown. Figure 4 FIG. 1 shows a top view of the adhesion enhancement structure 106 on the aluminum pad 104 fabricated according to this exemplary embodiment after a hydrothermal process. Figure 3 and Figure 4 The adhesion enhancing structure 106 is shown on images acquired experimentally (SEM, TEM, transmission electron microscopy).

[0081] Analysis via SEM, TEM and EDX (Energy Dispersive X-ray Spectrometry) indicates that the adhesion enhancing structure 106 grows very uniformly, for example, with a thickness of about 200 nm. Figure 3 It can be seen in particular that the adhesion enhancement structure 106 forms a substantially uniform layer. It can also be seen from the experiments that the interface between the pad 104 and the adhesion enhancement structure 106 is very smooth with no signs of uneven corrosion. It can also be confirmed from the experiments that the composition is also uniform and that the adhesion enhancement structure 106 is aluminum (hydr)oxide.

[0082] Figures 5 to 7 Results of adhesion testing of an aluminum-based surface 112 having an adhesion enhancement structure 106 according to an exemplary embodiment are shown.

[0083] Figure 5 An aluminum-based surface 112 with an adhesion enhancing structure 106 according to an exemplary embodiment is shown in an adhesion test before the tape is attached.

[0084] Figure 6 The adhesion test showed that the adhesive tape 170 was attached only in the portion 172. Figure 5 The aluminum-based surface 112 having the adhesion enhancement structure 106 . Another portion 174 is not covered by the tape 170 .

[0085] Figure 7 The adhesion test shows that after removing the adhesive tape 170, that is, after removing the adhesive tape 170 from the portion 172, Figure 6 The aluminum-based surface 112 having the adhesion enhancement structure 106 is provided. Figure 7As can be seen, glue residue 176 is visible, indicating proper adhesion properties.

[0086] The adhesion test using adhesive tape 170 described above shows that the adhesion enhancing structure 106 enhances adhesion and the adhesion enhancing structure 106 is not easily broken, see Figures 5 to 7 .

[0087] Figure 8 1 shows a cross-sectional view of a package 100 configured to encapsulate an electronic chip 102 on a chip carrier 110 according to an exemplary embodiment. The electronic chip 102 may have one or more pads 104. More specifically, Figure 8 A cross-sectional view of a package 100 embodied as a transistor outline (TO) package according to an exemplary embodiment is shown. The package 100 is mounted on a mounting substrate 118, which is here embodied as a printed circuit board (PCB).

[0088] The mounting substrate 118 includes electrical contacts 134 embodied as platings in through-holes of the mounting substrate 118. When the package 100 is mounted on the mounting substrate 118, the electronic chip 102 of the electronic component 100 is electrically connected to the electrical contacts 134 via the conductive chip carrier 110 of the package 100 (here embodied as a lead frame).

[0089] The electronic chip 102 (embodied here as a power semiconductor chip) is mounted on a chip carrier 110 (see reference numeral 136) in an adhesive or soldering manner (e.g., by means of a conductive adhesive, solder paste, solder wires, or diffusion soldering). The encapsulant (embodied here as a molding compound) forms a dielectric structure 108 and encapsulates a portion of the lead frame type chip carrier 110 and the electronic chip 102. Figure 8 It can be seen that the pads 104 on the upper main surface of the electronic chip 102 are electrically coupled to the partially encapsulated leadframe-type chip carrier 110 via fully encapsulated clip-type or bond-wire-type connecting elements 114 .

[0090] During operation of the power package 100, a power semiconductor chip in the form of an electronic chip 102 generates heat. In order to ensure electrical insulation of the electronic chip 102 and to remove heat from inside the electronic chip 102 towards the environment, an electrically insulating and thermally conductive interface structure 152 is provided, which covers exposed surface portions of the leadframe-type chip carrier 110 and connected surface portions of the encapsulant-type dielectric structure 108 at the bottom of the package 100. The thermally conductive properties of the interface structure 152 facilitate the removal of heat from the electronic chip 102 via the electrically conductive leadframe-type chip carrier 110 through the interface structure 152 and towards the heat dissipation body 116. The heat dissipation body 116, which may be made of a highly thermally conductive material such as copper or aluminum, has a base 154 directly connected to the interface structure 152 and has a plurality of cooling fins 156 extending parallel to each other from the base 154 in order to remove heat towards the environment.

[0091] As a rule of thumb, Figure 8 A package 100 of the type shown in the drawings may suffer from delamination between the molding material of the dielectric structure 108 on the one hand and the material of the various components of the package 100 (particularly the pads 104, the chip carrier 110, the connecting elements 114) enclosed within the dielectric structure 108 and in direct contact with the dielectric structure 108 on the other hand. Highly advantageously, the package 100 reliably prevents any delamination or poor adhesion tendency within the dielectric structure 108 by providing a hydrothermally formed adhesion enhancement structure 106 at the interface between the dielectric structure 108 on the one hand and one or more of the mentioned constituent parts on the other hand. This will be described in more detail below.

[0092] First refer to detail 180, Figure 8 1 shows that a dielectric structure 108 covers a conductive surface 112 of a pad 104 of an electronic chip 102. In order to improve the roughness and thus the adhesion properties, a conductive surface 112 having an adhesion enhancing structure 106 is provided, wherein the adhesion enhancing structure 106 is configured as interwoven nanofibers. For example, the pad 104 can be made of aluminum, and the adhesion enhancing structure 106 can also include aluminum, for example, can include aluminum oxide or aluminum hydroxide as a result of a hydrothermal manufacturing process, as described above. As a result, the dielectric structure 108 directly covers the exposed portion of the adhesion enhancing structure 106 on the pad 104 and is therefore properly attached to the pad 104 via the adhesion enhancing structure 106 of the pad 104. The adhesion enhancing structure 106 can have a height h of, for example, 500 nm.

[0093] Referring now to another detail 182, the package 100 further includes a hydrothermally formed adhesion enhancement structure 106 including aluminum at the interface between the leadframe type chip carrier 110 and the dielectric structure 108. In order to form the adhesion enhancement structure 106 on the chip carrier 110 in a corresponding manner as described above, it is advantageous that the chip carrier 110 is made of aluminum or has aluminum material at least on the surface 112 on which the adhesion enhancement structure 106 will be hydrothermally grown. Thereafter, during the hydrothermal process, the material on the surface of the chip carrier 110 is modified or converted into the adhesion enhancement structure 106 thereon.

[0094] Figure 8 A further detail 184 in Figure 1 shows that a connection element 114 (e.g., a clamp-type or bonding wire-type) electrically connects the chip carrier 110 to the pad 104 of the electronic chip 102. As shown, the package 100 also includes a hydrothermally formed adhesion enhancement structure 106, which includes aluminum at the interface between the connection element 114 and the dielectric structure 108. In order to form the adhesion enhancement structure 106 on the connection element 114 in a corresponding manner as described above, it is advantageous that the connection element 114 is made of aluminum or has aluminum material at least on the surface 112 (on which the adhesion enhancement structure 106 is to be grown hydrothermally). Thereafter, during the hydrothermal process, the material on the surface of the connection element 114 is modified or converted into the adhesion enhancement structure 106. Thus, the connection element 114, which electrically couples the electronic chip 102 to the chip carrier 110, also has a surface 112 covered by the dielectric structure 108 and provided with the hydrothermally formed adhesion enhancement structure 106.

[0095] For example, it is possible to form adhesion enhancement structures 106 on pad areas for Al-based pads 104 as well as for Cu pads 104 covered with ALD. A uniform dendrite layer produces a uniform optical appearance, enabling visual inspection of process efficiency.

[0096] Figures 9 to 13 The top view of the aluminum pad surface after exposure time of 10 minutes, 20 minutes, 30 minutes, 60 minutes and 180 minutes is shown respectively. Figures 9 to 13 The surface morphology of the aluminum-based pad 104 after different durations is shown. Figures 14 to 18 The side view of the pad surface after exposure time of 10 minutes, 20 minutes, 30 minutes, 60 minutes and 180 minutes is shown respectively. In the side view, Al-OH dendrites or adhesion enhancement structures 106 on the aluminum-based pad 104 are shown after different durations (10-60 minutes images taken from a broken wafer using SEM or 180 minutes images taken using TEM).

[0097] Fig.19 and Fig. 20 A top view and a side view of the surface after 20 minutes of exposure time of a copper pad 104 covered with an Al2O3 layer using an ALD deposition process are shown, respectively. A top view and a side view (acquired by TEM) of Al-OH dendrites on the protected copper pad 104 after 20 minutes are shown.

[0098] Both pads 104 show dendritic growth in top view, while the thickness varies with exposure time, and the copper pad 104 covered with the ALD-formed Al2O3 layer is thinner. While the aluminum-based pad 104 has dendrites that are approximately 600nm thick, the latter case produces a 50nm thick layer of adhesion promoting structure 106. In all cases, the dendritic growth is very uniform. The interface between the pad metal and the dendrite is very smooth without any signs of uneven erosion, and the composition is also the same.

[0099] Based on these analytical conclusions, it is possible to implement Al-HO dendrites grown via temperature hydrolysis as adhesion promoters for robust packaging. Analysis and evaluation have demonstrated that it is also possible to grow uniform dendrites on aluminum-based metal areas, as well as on copper areas covered by ALD Al2O3 layers.

[0100] Given this growth process, it is also possible to perform hydrolysis at the level of the leadframe (or more generally the chip carrier 110). The copper areas of the package 100 may be covered by an ALD Al2O3 layer, which may be deposited on individual package components (e.g., copper pads 104, copper leadframes or other chip carriers 110) or on the finished package 100, for example, after a wire bonding process.

[0101] Fig.21 A top view of Al-OH dendrites on a copper pad 104 covered with an ALD Al2O3 layer after spraying with hot deionized water at 70°C for 10 minutes is shown. Fig. 22 A corresponding side view is shown. Fig.21 and Fig. 22 The results of a study are shown, where a wafer with a copper pad 104 protected by an ALD type Al2O3 layer was exposed to moisture at high temperature on a wet chemical etching tool. It shows that thick dendrites grow from a thin layer of 6 nm.

[0102] Fig.23 A cross-sectional view of a package 100 is shown according to an exemplary embodiment.

[0103] Fig.23The package 100 includes an electronic chip 102 having a solder pad 104 covered by an adhesion enhancement structure 106. The solder pad 104 and the adhesion enhancement structure 106 have a common chemical element, such as aluminum.

[0104] Fig.24 A cross-sectional view of a package 100 according to another exemplary embodiment is shown.

[0105] Fig.24 The package 100 includes 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 an adhesion enhancement structure 106 formed hydrothermally.

[0106] Fig.25 1 is a flow chart 190 illustrating a method of forming a semiconductor package 100 according to an exemplary embodiment.

[0107] The method includes providing an aluminum-based surface 112 (see block 192 ), and roughening the surface 112 by forming an adhesion enhancing structure 106 via a hydrothermal process (see block 194 ).

[0108] It should be noted that the term "comprising" does not exclude other elements or features, and the term "a" does not exclude the plural. It is also possible to combine elements described in connection with different embodiments. It should also be noted that the reference numerals should not be understood as limiting the scope of the claims. In addition, the scope of the present application is not intended to be limited to the specific embodiments of the processes, machines, manufactures, compositions of matter, means, methods and steps described in the specification. Accordingly, the appended claims are intended to include such processes, machines, manufactures, compositions of matter, means, methods and steps within their scope.

Claims

1. A package comprising an electronic chip having a pad, wherein: The pad comprises copper and is at least partially covered by an adhesion enhancement structure comprising aluminum. 2 . The package of claim 1 , comprising a dielectric structure at least partially covering the electronic chip.

3. The package according to claim 2, comprising at least one of the following features: in, At least a portion of the adhesion enhancing structure is directly covered by the dielectric structure; Therein, the dielectric structure comprises a molding compound at least partially encapsulating the electronic chip.

4. The package according to any one of claims 1 to 3, wherein: The adhesion enhancing structure includes at least one of the group consisting of aluminum oxide and aluminum hydroxide.

5. The package according to any one of claims 1 to 3, wherein: The adhesion enhancing structure forms a substantially uniform layer.

6. The package according to any one of claims 1 to 3, wherein: The adhesion enhancing structure has a height (h) in the range between 50 nm and 1000 nm.

7. The package according to any one of claims 1 to 3, wherein: The adhesion enhancing structure comprises adhesion enhancing fibers or consists of the adhesion enhancing fibers.

8. A package comprising: A chip carrier comprising copper; an electronic chip mounted on the chip carrier and having a pad, the pad comprising copper; a molding compound covering at least a portion of a surface of at least one of the chip carrier and the electronic chip; and The adhesion enhancing structure on the pad includes at least one of aluminum oxide and aluminum hydroxide.

9. The package of claim 8, comprising a connecting element electrically coupling the electronic chip to the chip carrier and having a surface at least partially covered by the dielectric structure, wherein The covered surface of the connection element includes a hydrothermally formed adhesion enhancing structure.

10. A method for manufacturing a semiconductor package, the method comprising: providing an electronic chip including a copper pad; providing an aluminum-based metal structure formed on a copper pad covered with an aluminum oxide layer; as well as The surface of the aluminum-based metal structure is roughened by a hydrothermal process.

11. The method according to claim 10, wherein: The method includes forming the aluminum-based metal structure by placing the electronic chip in a heated aqueous solution.

12. The method according to claim 11, comprising at least one of the following features: in, The method comprises heating the aqueous solution to a temperature in the range between 50°C and 90°C; Wherein, the method comprises providing at least one of purified water, deionized water or distilled water as the aqueous solution; The method comprises maintaining the electronic chip in the heated aqueous solution for a time interval between 1 minute and 10 hours.

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