阅读说明：本技术 用于封装的粘附增强结构 (Adhesion enhancing structure for packaging ) 是由 E·纳佩特施尼格 李伟杰 林慧莉 F·伦纳 M·罗加利 于 2019-07-30 设计创作，主要内容包括：本发明提供了一种用于封装(100)的粘附增强结构,所述封装包括具有焊盘(104)的电子芯片(102),其中,所述焊盘(104)至少部分地被粘附增强结构(106)覆盖,并且其中,所述焊盘(104)和所述粘附增强结构(106)具有至少一种共同的化学元素,特别是铝。(The invention provides an adhesion enhancing structure for a package (100) comprising an electronic chip (102) with pads (104), wherein the pads (104) are at least partially covered by an adhesion enhancing structure (106), and wherein the pads (104) and the adhesion enhancing structure (106) have at least one chemical element in common, in particular aluminum.)

1. A package (100) comprising an electronic chip (102) with a pad (104), wherein the pad (104) is at least partially covered by an adhesion enhancing structure (106), and wherein the pad (104) and the adhesion enhancing structure (106) have at least one chemical element in common, in particular aluminum.

2. The package (100) of claim 1, comprising a dielectric structure (108) at least partially covering the electronic chip (102).

3. The package (100) of claim 2, comprising at least one of the following features:

wherein at least part of the adhesion enhancing structure (106) is directly covered by the dielectric structure (108);

wherein the dielectric structure (108) comprises or consists of an encapsulant, in particular a molding compound, at least partially encapsulating the electronic chip (102).

4. The package (100) of any of claims 1 to 3, wherein the adhesion-enhancing structure (106) comprises at least one of the group consisting of aluminum oxide and aluminum hydroxide.

5. The package (100) of any of claims 1 to 4, wherein the pads (104) comprise or consist of at least one of pure aluminum, aluminum-copper, aluminum-silicon-copper, and copper with an aluminum oxide coating.

6. The package (100) of any of claims 1 to 5, wherein the adhesion-enhancing structure (106) forms a substantially uniform layer.

7. The package (100) according to any of claims 1 to 6, wherein the adhesion enhancing structure (106) has a height (h) in a range between 50nm and 1000nm, in particular in a range between 100nm and 700 nm.

8. The package (100) according to any of claims 1 to 7, wherein the adhesion enhancing structure (106) comprises or consists of adhesion enhancing fibers, in particular at least one of nano-fibers or micro-fibers.

9. A package (100) 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) of at least one of the chip carrier (110) and the electronic chip (102);

wherein at least a portion of the covered surface (112) comprises a hydro-thermally formed adhesion enhancing structure (106).

10. The package (100) of claim 9, wherein at least one of the adhesion-enhancing structure (106) and the surface (112) comprises aluminum.

11. The package (100) according to claim 9 or 10, comprising a connection element (114) electrically coupling the electronic chip (102) with the chip carrier (110) and having a surface (112) at least partially covered by the dielectric structure (108), wherein the covered surface (112) of the connection element (114) comprises a hydrothermally formed adhesion-enhancing structure (106).

12. A method of forming a semiconductor package (100), the method comprising:

providing an aluminum-based surface (112);

the surface (112) is roughened by forming adhesion enhancing structures (106) by means of a hydrothermal process.

13. The method of claim 12, wherein the method comprises forming the adhesion enhancing structure (106) comprising aluminum.

14. The method of claim 12 or 13, wherein the method comprises forming the adhesion enhancing structure (106) on a conductive surface (112).

15. The method according to any of the claims 12 to 14, wherein the method comprises converting the material of the surface (112) into at least part of the adhesion enhancing structure (106).

16. A method according to any of claims 12 to 15, wherein the method comprises providing an electronic chip (102) with pads (104), wherein the pads (104) form at least part of the surface (112).

17. The method of any of claims 12 to 16, wherein the method comprises forming the adhesion enhancing structure (106) by placing the surface (112) in a heated aqueous solution.

18. The method of claim 17, comprising at least one of the following features:

wherein the method comprises heating the aqueous solution to a temperature in the range between 50 ℃ and 90 ℃, in particular in the range between 70 ℃ and 80 ℃;

wherein the method comprises providing at least one of purified water, deionized water or distilled water as the aqueous solution;

wherein the method comprises maintaining the surface (112) in the heated aqueous solution for a time interval of between 1 minute and 10 hours, in particular for a time interval of between 10 minutes and 3 hours.

19. The method according to any one of claims 12 to 18, wherein the method comprises at least partially encapsulating the surface (112) with the adhesion enhancing structure (106) by a dielectric structure (108), in particular by molding.

20. The method according to any one of claims 12 to 19, wherein the hydrothermal process comprises hydrothermally converting the material of the surface (112) into the adhesion enhancing structures (106).

Technical Field

The invention relates to a package and a method.

Background

Packages, such as those used in automotive applications, provide a physical protective shell for one or more electronic chips that include one or more integrated circuit elements. Examples of packaged integrated circuit elements are field effect transistors, Insulated Gate Bipolar Transistors (IGBTs), diodes and passive components (e.g. inductors, capacitors, resistors). Furthermore, such a package may be used to fabricate a system in package.

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

However, there may still be room for improvement in the reliability of the package, particularly in terms of the mechanical integrity of the package.

Disclosure of Invention

A mechanically robust chip package may be required.

According to an exemplary embodiment, a robust package is provided comprising an electronic chip with pads, wherein the pads are at least partially covered by an adhesion enhancing structure, and wherein the pads and the adhesion enhancing structure have at least one chemical element in common (preferably, but not limited to, aluminum).

According to another exemplary embodiment, a package is provided that includes 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 includes a hydro-thermally formed adhesion-enhancing structure.

According to another exemplary embodiment, there is provided a method of forming a semiconductor package, wherein the method includes: providing an aluminium-based surface, and roughening the surface by means of an adhesion-enhancing structure formed by a hydrothermal process.

According to an exemplary embodiment, a surface (e.g., comprising aluminum) may be treated by a hydrothermal process for triggering the formation of adhesion enhancing structures. The adhesion-enhancing structure is capable of enhancing adhesion between the covered surface and a dielectric structure formed thereon. As a result, a package having highly advantageous characteristics in terms of mechanical integrity and electrical performance can be manufactured. Suitable mechanical integrity results from a strong tendency to inhibit delamination between the surface and the dielectric structure due to the provision of a hydrothermally generated adhesion enhancing structure. The advantageous electrical integrity derives from the fact that: a proper connection between the surface and the dielectric structure can be ensured, which prevents undesired phenomena (e.g. moisture) from entering micro-gaps in the encapsulation between the improperly connected dielectric structure and the conductive surface. Advantageously, the mentioned adhesion-promoting structure (preferably comprising aluminum) on the (preferably aluminum-comprising) surface can be produced hydrothermally, i.e. by means of a combination of an aqueous medium and heat, i.e. in a simple manner and without involving harmful substances. Particularly advantageously, such hydrothermal processes may not require chromium.

Thus, exemplary embodiments use on aluminum-based metal regions or on Al ₂O ₃Adhesion enhancing structures grown via temperature hydrolysis on the layer-covered copper areas serve as adhesion promoters for robust packaging. These adhesion enhancing structures can be easily monitored by optical detection. Embodiments can keep the adhesion promotion process reasonably low. The adhesion enhancing structure may be advantageously used as an adhesion promoter between a pad or other surface (on the one hand) and a dielectric structure such as an encapsulant (on the other hand). Furthermore, the hydrothermally formed adhesion enhancing structures may serve to reduce, or even eliminate, unhealthy and hazardous materials.

It is a gist of an exemplary embodiment to form a semiconductor package with improved adhesion between its aluminum contact pads and dielectric structures such as molded parts. At the surface of the aluminum contact pad, a dendrite structure or other kind of adhesion enhancing structure may be arranged to provide a rough surface. Furthermore, the adhesion enhancing structure may be grown by a hydrothermal process. In particular, the grown adhesion enhancing structures may enable low cost and high quality molding compound adhesion on aluminum pads or other surfaces covered with the adhesion enhancing structures.

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

Description of other exemplary embodiments

In the following, further exemplary embodiments of the package and the method will be explained.

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.

In the context of the present application, the term "electronic chip" may particularly denote a chip (more particularly a semiconductor chip) providing an electronic function. The 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 microelectromechanical system (MEMS). In alternative embodiments, 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, for example in 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. Such integrated circuit elements may be fabricated, for example, by silicon technology or based on wide band gap semiconductors such as silicon carbide, gallium nitride or gallium nitride on silicon. The semiconductor power chip may include one or more field effect transistors, diodes, inverter circuits, half bridges, full bridges, drivers, logic circuits, other devices, and the like. The electronic chip may be a bare die or may have been packaged or encapsulated. However, the electronic chip may also be a passive component, such as a capacitor or a resistor.

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 base 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.

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

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

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

In an embodiment, the adhesion enhancing structure comprises or consists of adhesion enhancing fibers, in particular at least one of nanofibers and microfibers. The fibers may represent long strands of material. The adhesion enhancing fibers may have a random orientation and may be interwoven to form a layer having a rough outer surface. The nanofibers may be fibers having a size in the range of nanometers. The microfibers may be fibers having a size in the range of microns.

In an embodiment, the package includes 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 enhancing structure on the pad. Alternatively or in addition, such a dielectric structure may also cover at least part of a chip carrier on which at least one electronic chip may be mounted, and/or such a dielectric structure may cover at least part of a connection element connecting the electronic chip with the chip carrier.

In an embodiment, the dielectric structure comprises or consists of an encapsulant at least partially encapsulating at least the electronic chip. In the context of the present application, the term "encapsulant" may particularly denote a substantially electrically insulating and preferably thermally conductive material that surrounds the electronic chip and/or parts of the chip carrier and/or parts of the connection elements to provide mechanical protection and electrical insulation, and optionally contributes to heat dissipation during operation. Such an encapsulant may be, for example, a molding compound. Such as filler particles (e.g., SiO) for improved thermal conductivity ₂、Al ₂O ₃、Si ₃N ₄BN, AlN, diamond, etc.) may be embedded in a plastic-based (e.g., epoxy-based) matrix of the encapsulant.

Forming the dielectric structure may comprise at least one of the group consisting of molding (in particular injection molding), coating and casting. Molding may be represented as a manufacturing process that shapes a liquid or plastic raw material by using a rigid frame, which may be referred to as a mold. The mold may be a hollowed-out block or set of tools having an internal hollow volume filled with a liquid or a moldable material. The liquid hardens within the mold, taking the shape of the mold.

In an embodiment, the adhesion enhancing structure comprises aluminum oxide and/or aluminum hydroxide. Alumina can be expressed as a chemical compound of aluminum and oxygen (particularly, having the chemical formula Al) ₂O ₃). The aluminum hydroxide may be formed in the presence of aluminum and water (and may in particular have the chemical formula Al (OH)) ₃). Oxygen gasThe aluminum oxide and/or hydroxide may be formed when the aluminum material of the surface in contact with the hot water is hydrothermally treated.

In an embodiment, the pad comprises or consists of aluminum. Specifically, the pad may include at least one of pure aluminum, aluminum-copper, aluminum-silicon-copper, and copper with an aluminum oxide coating. When the bulk or base material of the bond pad comprises aluminum (and optionally one or more other materials such as copper, silicon, etc.), treatment of the bond pad material with hot water in a hydrothermal process may result in the formation of an adhesion enhancing structure. However, it has proved possible to hydrothermally treat pads comprising, for example, copper as bulk or base material and covered with a thin surface layer of aluminum oxide (for example, having a thickness in the range between 1nm and 20nm, for example, having a thickness of 6 nm) to thereby produce an adhesion-enhancing structure. In the latter embodiment, the aluminum material of the surface layer may be converted and/or may react to form adhesion enhancing fibers. In the studies, it turned out to be possible to successfully have atomic layer deposited (ALD, atomic layer deposition) Al on the Al-based pads and on top ₂O ₃Dendrites are grown on the copper pads of the layer.

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 with a substantially constant strength over a large area. It is thus possible to prevent weak points with respect to adhesion between the dielectric material and the surface.

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

In an embodiment, the package includes a chip carrier on which the electronic chip is mounted. For example, such a chip carrier may comprise a lead frame and/or a ceramic wafer (in particular a Direct Aluminum Bonding (DAB) substrate and/or a Direct Copper Bonding (DCB) substrate) covered on two opposite main surfaces with respective metal layers.

In an embodiment, the carrier is a leadframe. Such a leadframe may be a thin sheet-like metal structure that may 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 an electronic environment when the electronic chips are mounted onto the leadframe. In an embodiment, the lead frame may be a metal plate (in particular made of copper), which may be patterned by, for example, stamping or etching. Forming the chip carrier as a lead frame is a cost-efficient and mechanically and electrically very advantageous configuration, wherein a low ohmic connection of the at least one electronic chip can be combined with a robust support capability of the lead frame. Furthermore, due to the high thermal conductivity of the metal material of the lead frame (in particular copper), the lead frame may contribute to the thermal conductivity of the package and may remove heat generated during operation of the electronic chip. The lead frame may comprise, for example, aluminum and/or copper.

In an embodiment, the method includes forming an adhesion-enhancing structure on a conductive surface. In particular, the surface (preferably comprising aluminum) on which the adhesion enhancing structure can be hydrothermally grown can be a metal surface (e.g., comprising a metallic aluminum material). However, it is also possible to create an adhesion promoting effect by hydrothermally growing adhesion promoting fibers on a dielectric or electrically insulating surface (e.g., comprising a dielectric alumina material). As a result, it is also possible to improve adhesion at the surface of the dielectric (preferably comprising aluminum) in the package that is to be encapsulated by the molding compound.

In a preferred embodiment, the method comprises converting the material of the surface into at least part of an adhesion enhancing structure. For example, the adhesion enhancing structures may thus be integrally formed with their grown and extended surfaces. In other words, the hydrothermal process may include a process of hydrothermally converting or modifying the material of the surface into an adhesion enhancing structure. Thus, the adhesion-promoting structure (in particular the adhesion-promoting fibers) can be created from a surface material (in particular from a pad material, a chip carrier material and/or a connecting element material). In particular, by subjecting the surface to a hydrothermal treatment, the material of the surface itself may be chemically modified to form an adhesion enhancing structure. As a result, a suitable integrity between the remaining material of the surface (on the one hand) and the integrally formed adhesion enhancing structure (on the other hand) may be obtained. As a result of this material transformation, the material of the surface (on the one hand) and the material of the adhesion-promoting structure (on the other hand) may share at least one chemical element, or may even be chemically equivalent.

In an embodiment, the method comprises providing the electronic chip with a pad, which provides a surface (in particular a conductive surface). Such pads may provide electrical contact between the semiconductor die (on the one hand) and electrically conductive connection elements (e.g., bond wires, bond ribbons, or clips) encapsulated in the package (on the other hand). The clip may be a three-dimensional bent plate type connection element having two planar sections to be connected to the upper main surface of the respective electronic chip and the upper main surface of the chip carrier, wherein the two mentioned planar sections are interconnected by an oblique connection section. As an alternative to such a clamp, it is possible to use a bonding wire or a bonding strip as a flexible conductive wire or strip-like body having one end portion connected to the upper main surface of the respective chip and the other opposite end portion electrically connected to the chip carrier. Within the encapsulation, an electrically conductive connection can be formed by connection elements between the chip pads (on the one hand) at the upper main surface of the chip mounted on the mounting section of the carrier and the lead sections (on the other hand) of the carrier.

In an embodiment, the package comprises a connection element electrically coupling the electronic chip with the chip carrier and having a surface at least partly covered by the dielectric structure. The covered surface of the connecting element may include a hydrothermally formed adhesion enhancing structure. Thus, adhesion promotion may also be provided on connecting elements such as bond wires, bond tapes or clips, which may also be encapsulated by an encapsulant such as a molding compound. This further improves the mechanical integrity of the package.

In an embodiment, the method comprises providing an aluminium-based surface (in particular an electrically conductive surface). Such aluminum materials may then be used to form adhesion enhancing structures by hydrothermal processes. As a result, the adhesion-promoting structure then also comprises or consists of an aluminum material.

In the following, some specific examples will be described in relation to a hydrothermal process:

in an embodiment, the method includes forming the adhesion enhancing structure by placing the conductive surface in an aqueous solution that is hot (i.e., heated above ambient temperature). Such an aqueous solution may comprise or consist of water.

In an embodiment, the method comprises heating the aqueous solution to a temperature in the range between 50 ℃ and 90 ℃, in particular in the range between 70 ℃ and 80 ℃. The temperature of the hot water or heated water should be high enough to ensure efficient generation of the adhesion enhancing structure based on the material of the underlying surface (particularly 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 over the entire temperature range from 50 ℃ to 90 ℃. Excellent results can be obtained in a temperature range between 70 ℃ and 80 ℃.

In an embodiment, the method comprises providing distilled or purified water as the aqueous solution. Distilled water may mean water that is boiled to steam and condensed to liquid in a separate container. Impurities in the original water that do not boil below or at the boiling point of the water remain in the original container. Thus, distilled water is one type of purified water that may be advantageously used in exemplary embodiments, wherein other types of purified water may also be used for the aqueous solution. Thus, pure water may serve as a highly biocompatible and highly effective medium for triggering hydrothermal formation of adhesion enhancing structures (particularly adhesion enhancing fibers or dendrites).

In an embodiment, the method comprises maintaining the conductive surface (in particular the whole electronic chip) in the heated aqueous solution for a time interval of between 1 minute and 10 hours, in particular for a time interval of between 10 minutes and 3 hours. The duration may be used as a design parameter for defining the thickness of the layer of the adhesion enhancing structure. For example, holding an aluminum pad in hot water at 75 ℃ for 10 minutes may result in the formation of an adhesion enhancing structure of approximately 500nm thickness.

In an embodiment, the method comprises at least partially encapsulating (in particular by molding) the surface having the adhesion-promoting structure thereon. After roughening the surface, in particular the pads, by forming the adhesion enhancing structure, the adhesion enhancing structure is directly covered with an encapsulant. Thus, the encapsulant is suitably attached to the adhesion enhancing structure, thereby ensuring high mechanical integrity of the overall formed package.

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

In an embodiment, the electronic chip comprises at least one, in particular at least three or at least eight transistors (e.g. field effect transistors, in particular metal oxide semiconductor field effect transistors). Typically, an electronic chip may include many transistors.

As a substrate or wafer forming the basis of an electronic chip, a semiconductor substrate, preferably a silicon substrate, may be used. 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, the exemplary embodiments may be implemented using GaN or SiC technology.

Furthermore, exemplary embodiments may 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 photolithographic masks), deposition techniques (e.g., Chemical Vapor Deposition (CVD), Plasma Enhanced Chemical Vapor Deposition (PECVD), Atomic Layer Deposition (ALD), sputtering, etc.).

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

Drawings

The accompanying drawings are included to provide a further understanding of the exemplary embodiments and are incorporated in and constitute a part of this specification.

In the figure:

fig. 1 illustrates the surface topography of an aluminum-based pad prior to performing a hydrothermal process according to an example embodiment.

Fig. 2 illustrates a surface topography of the aluminum-based pad of fig. 1 after performing a hydrothermal process according to an example embodiment.

Fig. 3 shows a side view of an adhesion-enhancing structure on an aluminum pad fabricated according to an example embodiment after a hydrothermal process.

Fig. 4 shows a top view of an adhesion-enhancing structure on an aluminum pad fabricated according to an example embodiment after a hydrothermal process.

Fig. 5 shows an aluminum-based surface with adhesion enhancing structures according to an exemplary embodiment prior to attachment of a tape in terms of adhesion testing.

Fig. 6 shows the aluminum-based surface of fig. 5 with the adhesion enhancing structure with the tape attached in terms of adhesion testing.

Fig. 7 shows the aluminum-based surface of fig. 6 with adhesion enhancing structures after removal of the tape in terms of an adhesion test.

Fig. 8 shows a cross-sectional view of a package according to an example embodiment.

Fig. 9-13 show top views of the aluminum pad surface after exposure times of 10 minutes (fig. 9), 20 minutes (fig. 10), 30 minutes (fig. 11), 60 minutes (fig. 12), and 180 minutes (fig. 13), respectively.

Fig. 14-18 show side views of the pad surfaces of fig. 9-13 after exposure times of 10 minutes (fig. 14), 20 minutes (fig. 15), 30 minutes (fig. 16), 60 minutes (fig. 17), and 180 minutes (18), respectively.

FIGS. 19 and 20 respectively show Al using an ALD (atomic layer deposition) deposition process ₂O ₃Top and side views of the pad surface after 20 minutes exposure of the layer covered copper pad.

FIGS. 21 and 22 show the Al capping by ALD after 10 minutes of spraying with hot deionized water at 70 deg.C, respectively ₂O ₃Top and bottom views of Al-O-H dendrites on copper pads of a layer.

Fig. 23 shows a cross-sectional view of a package according to an example embodiment.

Fig. 24 shows a cross-sectional view of a package according to another exemplary embodiment.

Fig. 25 is a flowchart illustrating a method of forming a semiconductor package according to an example embodiment.

Detailed Description

The illustration in the drawings is schematically only.

Before describing other exemplary embodiments in more detail, some basic considerations of the invention on which the exemplary embodiments are developed will be summarized.

According to an exemplary embodiment, an adhesion enhancing structure (particularly an aluminum oxide dendrite) may be grown on a surface (particularly comprising aluminum), such as a pad, to achieve good mold compound adhesion on the surface.

In the case of semiconductor packages, high reliability is required. One of the main problems is mold compound adhesion in the package, especially 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 the descriptive sense) an interdiffusion zone between the molding compound resin and the surface.

According to an exemplary embodiment, reliable protection against undesired peeling of the package can be achieved by a very simple process with simple chemical properties. It has been demonstrated that a suitable uniformity of growth of the adhesion enhancing structure may enable a suitable adhesion without having to face quality issues. In addition to simple disposal, the process according to exemplary embodiments may also have advantages in terms of operational safety and health restrictions due to its healthy and harmless components. Due to the cheap materials and simple tools with small footprint, the simple process and the corresponding simple tools allow to complete the manufacturing with low effort.

Exemplary embodiments fabricate aluminum hydroxide adhesion enhancing structures (particularly adhesion enhancing fibers) grown by hydrothermal processes, providing a low-burden and healthy solution. The results show that the dendrite growth has very good consistency and reproducibility. Having an aluminum-based pad and covering with ALD-fabricated Al has been studied in experiments ₂O ₃Sample of copper pads of the layer. The dendrites are grown by placing the bare chip or assembled chip on a lead frame into hot water, for example, at 75 c for an appropriate time.

Exemplary embodiments allow for the manufacture of robust packages with zero or very low tendency to peel. At the same time, the exemplary embodiments may advantageously be performed without adding other materials to the system and avoiding complex detrimental processes.

More generally, and with further reference to fig. 5, which is described in greater detail below, a fabrication process for forming the semiconductor package 100 according to an example embodiment may be as follows.

First, the electronic chip 102 may be provided with one or more contact pads 104, 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. It is also possible that the respective contact pad 104 consists of a copper substrate with a thin aluminum oxide coating. The aluminum oxide is electrically insulating so that the surface 112 on which the adhesion enhancing structure 106 will later be grown may also be electrically insulating rather than electrically conductive.

Thereafter, the method may include roughening the surface 112 of the one or more contact pads 104 using a hydrothermal process. With this hydrothermal process, it is possible to grow adhesion enhancing structures 106 (particularly adhesion enhancing fibers or dendritic structures that may have dimensions on the order of nanometers to micrometers) on the pads 104 and based on the material of the pads 104. In other words, the pad 104 itself may be the source of material forming the adhesion enhancing structure 106 as a whole with the pad 104. Thus, the hydrothermal process hydrothermally converts the material of the surface 112 into the adhesion enhancing structures 106 to thereby inherently grow, rather than deposit, the adhesion enhancing structures 106. As a result, the adhesion enhancing structure 106 formed based on the pad 104 (including aluminum) may also include aluminum. Thus, both the adhesion enhancing structure 106 and the pad 104 may comprise aluminum, i.e., may have at least one chemical element in common (particularly Al). Thus, the adhesion enhancing structures 106 may be formed by modifying or converting the material of the surface 112 of the respective pad 104 into the adhesion enhancing structures 106.

With reference to the hydrothermal process for forming the adhesion enhancing structure 106, the electronic chip 102 having the one or more pads 104 (having the conductive surface 112) may be placed in a hot aqueous solution, and more particularly, may be submerged in hot water. Preferably, the aqueous solution may be heated to a temperature preferably between 70 ℃ and 80 ℃, for example to 75 ℃. This temperature selection may ensure efficient formation of the adhesion enhancing fibers. Deionized or distilled water may be used as the aqueous solution. The electronic chip 102 having at least one pad 104 with a conductive surface 112 may be kept submerged in the heated aqueous solution for a selected time interval (e.g., between 10 minutes and 3 hours). The duration that the electronic chip 102 remains submerged in the purified water determines the thickness of the layer of the integrally formed adhesion enhancing structures 106 on the surface 112 of the respective pads 104. After forming the adhesion enhancing structure 106, the surface 112 has an increased roughness, which improves the adhesion properties of the molding compound or another encapsulant that is subsequently formed.

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

Fig. 1 illustrates the surface topography of an aluminum-based pad 104 prior to subjecting an exposed surface 112 of the pad 104 to a hydrothermal process in accordance with an exemplary embodiment. Fig. 2 shows the surface topography of the aluminum-based pad 104 of fig. 1 after the adhesion enhancing structures 106 have been formed on the surface 112, i.e., after the adhesion enhancing structures 106 in the form of nanofibers have been formed, according to an exemplary embodiment. Thus, fig. 1 and 2 show the surface topography of the aluminum-based pad 104 before (fig. 1) and after (fig. 2) the above-described hydrothermal process. Fig. 1 and 2 show Scanning Electron Microscope (SEM) images.

As can be seen from fig. 2, a uniform coverage of the surface 112 by the adhesion enhancing structure 106 has been found after the described treatment.

According to an exemplary embodiment of the method according to fig. 1 and 2, a teflon (polytetrafluoroethylene) beaker was overflowed with deionized water (DI water) for 30 minutes. Thereafter, the beaker was filled with 80m of deionized water at room temperature. A beaker containing water was heated to 75 ℃ on a baking pan and the sample to form the adhesion enhancing structure was immersed in water. After the appropriate exposure time, the beaker was removed from the bakeware and allowed to cool to room temperature. The sample was removed from the beaker.

Fig. 3 shows a side view of adhesion-enhancing structure 106 on aluminum pad 104 fabricated according to an example embodiment after a hydrothermal process. Fig. 4 shows a top view of adhesion-enhancing structures 106 on aluminum pads 104 fabricated according to this exemplary embodiment after a hydrothermal process. Thus, fig. 3 and 4 show the adhesion enhancing structure 106 on experimentally acquired images (SEM, TEM, transmission electron microscope).

Analysis via SEM, TEM, and EDX (energy dispersive X-ray spectrometry) indicates that the adhesion enhancing structure 106 is grown very uniformly, e.g., with a thickness of about 200 nm. As can be seen in particular in fig. 3, the adhesion enhancing structure 106 forms a substantially uniform layer. It can also be seen from experiments that the interface between the pad 104 and the adhesion enhancing structure 106 is very smooth without signs of uneven corrosion. It can also be confirmed from experiments: the composition is also uniform and the adhesion enhancing structure 106 is aluminum (hydr) oxide.

Fig. 5-7 illustrate results of adhesion testing of the aluminum-based surface 112 with the adhesion-enhancing structures 106, according to example embodiments.

Fig. 5 shows an aluminum-based surface 112 with an adhesion enhancing structure 106 according to an exemplary embodiment prior to attachment of a tape in terms of an adhesion test.

Fig. 6 shows the aluminum-based surface 112 of fig. 5 with the adhesion enhancing structures 106 with the tape 170 attached only in the portion 172 in terms of adhesion testing. The other portion 174 is not covered by the tape 170.

Fig. 7 shows the aluminum-based surface 112 of fig. 6 with the adhesion enhancing structures 106 in terms of an adhesion test after removal of the tape 170, i.e., after removal of the tape 170 from the portion 172. As can be seen in fig. 7, glue residue 176 is visible, indicating proper adhesion properties.

The described adhesion tests with the adhesive tape 170 show that the adhesion enhancement structure 106 enhances adhesion while the adhesion enhancement structure 106 is not easily broken, see fig. 5-7.

Fig. 8 shows a cross-sectional view of a package 100 formulated to encapsulate an electronic chip 102 on a chip carrier 110, according to an example embodiment. The electronic chip 102 may have one or more pads 104. More specifically, fig. 8 illustrates a cross-sectional view of a package 100 embodied as a Transistor Outline (TO) package, according TO an example embodiment. The package 100 is mounted on a mounting substrate 118, where the mounting substrate 118 is embodied as a Printed Circuit Board (PCB).

The mounting substrate 118 includes electrical contacts 134 embodied as plated layers 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 electrically conductive chip-carrier 110 (here embodied as a lead frame) of the package 100.

The electronic chip 102, here embodied as a power semiconductor chip, is mounted on the chip carrier 110 (see reference numeral 136) in an adhesive or soldering manner (e.g., by a conductive adhesive, solder paste, solder wire, or diffusion soldering). An encapsulant, here embodied as a mold compound, forms dielectric structure 108 and encapsulates portions of leadframe-type chip carrier 110 and electronic chip 102. As can be seen in fig. 8, the pads 104 on the upper major 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 connection elements 114.

During operation of the power package 100, a power semiconductor chip in the form of an electronic chip 102 generates heat. To ensure electrical insulation of the electronic chip 102 and removal of heat from the interior of the electronic chip 102 towards the environment, an electrically insulating and thermally conductive interface structure 152 is provided that covers the exposed surface portions of the leadframe-type chip carrier 110 and the 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 through the interface structure 152 and toward the heat dissipation body 116 via the electrically conductive lead frame type chip carrier 110. The heat dissipating 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 to remove heat toward the environment.

Conventionally, a package 100 of the type shown in fig. 8 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 (in particular the pads 104, the chip carrier 110, the connection elements 114) encapsulated within the dielectric structure 108 and in direct contact with the dielectric structure 108 (on the other hand). It is highly advantageous that the package 100 reliably prevents any peeling or poor adhesion tendency within the dielectric structure 108 by providing a hydrothermally formed adhesion-enhancing 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. As will be described in more detail below.

Referring first to detail 180, it is shown in fig. 8 that the dielectric structure 108 covers the conductive surface 112 of the pad 104 of the electronic chip 102. To improve the roughness and thus the adhesion properties, a conductive surface 112 with adhesion enhancing structures 106 is provided, the adhesion enhancing structures 106 being configured as interwoven nanofibers. For example, the pad 104 may be made of aluminum and the adhesion enhancing structure 106 may also include aluminum, e.g., may 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 thus is suitably attached to the pad 104 via the adhesion enhancing structure 106 of the pad 104. The adhesion enhancing structure 106 may have a height h of, for example, 500 nm.

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

Yet another detail 184 in fig. 8 shows (e.g., clip-type or bond wire type) connection elements 114 electrically connecting chip-carrier 110 with pads 104 of electronic chip 102. As shown, the package 100 also includes a hydrothermally formed adhesion-enhancing structure 106 comprising aluminum at the interface between the connection element 114 and the dielectric structure 108. In order to form the adhesion-promoting structures 106 on the connecting elements 114 in a corresponding manner as described above, it is advantageous if the connecting elements 114 are made of aluminum or have an aluminum material at least on the surface 112 on which the adhesion-promoting structures 106 are to be grown hydrothermally. Thereafter, the material on the surface of the connection element 114 is modified or converted into the adhesion enhancing structure 106 during the hydrothermal process. Thus, the connection elements 114 electrically coupling the electronic chip 102 with the chip carrier 110 also have a surface 112 which is covered by the dielectric structure 108 and which is provided with the hydrothermally formed adhesion-enhancing structures 106.

With embodiments, it is possible to form adhesion enhancing structures 106 on the pad areas for the Al based pads 104 and for the Cu pads 104 covered with ALD. The uniform dendritic layer produces a uniform optical appearance, thereby enabling visual inspection of process efficiency.

Fig. 9-13 show top views of the aluminum pad surface after exposure times of 10 minutes, 20 minutes, 30 minutes, 60 minutes, and 180 minutes, respectively. In other words, fig. 9-13 illustrate the surface topography of the aluminum-based pad 104 after different durations. Fig. 14-18 show side views of the pad surface after exposure times of 10 minutes, 20 minutes, 30 minutes, 60 minutes, and 180 minutes, respectively. In the side view, the Al-O-H dendrites or adhesion enhancing structures 106 on the aluminum based pad 104 are shown after different durations (10-60 minute images taken with SEM from a broken wafer or 180 minute images taken with TEM).

FIGS. 19 and 20 respectively show Al capping using an ALD deposition process ₂O ₃Top and side views of the surface after a 20 minute exposure time of the copper pad 104 of the layer. Top and side views (taken by TEM) of the Al-O-H dendrites on the protected copper pad 104 are shown after 20 minutes.

Both pads 104 exhibit dendritic growth in top view, with thickness varying with exposure time, and are capped with ALD-formed Al ₂O ₃The thickness of the copper pad 104 of the layer is thin. Although the aluminum-based pad 104 has dendrites approximately 600nm thick, the latter case produces a 50nm thick layer of adhesion-promoting structures 106. In all cases, the dendrite growth is very uniform. The interface between the pad metal and the dendrite is very smooth without any signs of uneven corrosion, and so is the composition.

Based on these analytical conclusions, it is possible to implement Al-H-O dendrites grown via temperature hydrolysis as adhesion promoters for robust packaging. Analysis and evaluation have demonstrated that it is also possible to grow homogeneous dendrites on aluminum-based metal regions, like Al by ALD ₂O ₃The same on the copper areas covered by the layer.

In view of this growth process, it is also possible to be on the level of the lead frame (or more generally of the chip carrier 110)Hydrolysis is carried out. The copper regions of the package 100 may be ALD Al ₂O ₃Layer capping, ALD Al ₂O ₃The layers may be deposited on individual package components (e.g., copper pads 104, copper leadframes, or other chip carriers 110) or on, for example, the completed package 100 after a wire bonding process.

FIG. 21 shows ALD Al capped after 10 minutes of spraying with hot deionized water at 70 deg.C ₂O ₃A top view of the Al-O-H dendrites on the copper pads 104 of the layer. Fig. 22 shows a corresponding side view. FIGS. 21 and 22 show the results of the study with Al subjected to ALD type ₂O ₃The wafer of layer protected copper pads 104 is exposed to moisture at high temperature on a wet chemical etch tool. It shows that thick dendrites grow from a thin layer of 6 nm.

Fig. 23 shows a cross-sectional view of a package 100 according to an example embodiment.

The package 100 of fig. 23 includes an electronic chip 102 having pads 104 covered by an adhesion-enhancing structure 106. The bond pad 104 and the adhesion enhancing structure 106 have a common chemical element, such as aluminum.

Fig. 24 shows a cross-sectional view of a package 100 according to another exemplary embodiment.

Package 100 of fig. 24 includes a chip carrier 110, an electronic chip 102 mounted on chip carrier 110, and a dielectric structure 108 covering chip carrier 110 and a surface 112 of electronic chip 102. The coated surface 112 includes a hydrothermally formed adhesion enhancing structure 106.

Fig. 25 is a flowchart 190 illustrating a method of forming the semiconductor package 100 according to an example embodiment.

The method comprises the following steps: providing an aluminum-based surface 112 (see block 192), and roughening the surface 112 by forming the adhesion-enhancing structure 106 by a hydrothermal process (see block 194).

It should be noted that the term "comprising" does not exclude other elements or features, and the terms "a" and "an" do not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that the reference signs shall not be construed as limiting the scope of the claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.