Solder the conductor to the aluminum layer

Abstract

A device for welding a conductor and an aluminum layer together, comprising a substrate and an aluminum layer disposed on the substrate. The aluminum forms a first bonding metal. An intermetallic compound layer is disposed on the aluminum layer. A solder layer is disposed on the intermetallic compound layer, wherein the solder comprises a low melting point main component. A conductor is disposed on the solder layer, wherein the conductor has a welding surface comprising a second bonding metal. The intermetallic compound comprises aluminum and the second bonding metal and is substantially free of the low melting point main component.

Description

Technical Field

[0001] The present disclosure relates generally to soldering techniques in semiconductor device fabrication, and more particularly to aspects of soldering conductors to aluminum layers. Background Art

[0002] Soldering processes are widely used in semiconductor device manufacturing for a variety of purposes, including die bonding, wire / clip / ribbon bonding, device mounting, etc. A variety of solder materials, fluxes, and soldering techniques are available. Soldering methods and soldering materials can have a significant impact on the cost, yield, performance, and reliability of semiconductor devices.

[0003] While wire bonding on aluminum (Al) has become a widely established process, soldering on aluminum surfaces requires the application of highly reactive chemicals (flux) to remove the highly stable Al on the Al. 2 O 3 This highly reactive chemistry is incompatible with standard semiconductor manufacturing processes. Therefore, welding on Al surfaces is currently limited to applications outside of semiconductor device manufacturing technology.

[0004] DE 10 2017 012 210 A1 relates to soldering conductors to aluminum layers and shows a device comprising a replacement metal layer located above the aluminum metallization and a solder layer to which the conductor is connected. Summary of the invention

[0005] According to one aspect of the present disclosure, a device for welding a conductor and an aluminum layer together is described. The device includes a substrate. The aluminum layer is disposed on the substrate, wherein the aluminum of the aluminum layer forms a first bonding metal. The device also includes an intermetallic compound layer disposed on the aluminum layer and a solder layer disposed on the intermetallic compound layer, wherein the solder of the solder layer includes a low melting point main component. The conductor is disposed on the solder layer. The conductor has a welding surface including a second bonding metal. The intermetallic compound of the intermetallic compound layer includes aluminum and a second bonding metal, and is substantially free of a low melting point main component.

[0006] According to another aspect of the present disclosure, a method for soldering a conductor to an aluminum layer on a substrate is described. At least a portion of an aluminum oxide layer covering the aluminum layer is removed. A protective layer is applied over the aluminum layer to prevent the aluminum oxide layer from regenerating on the aluminum layer. Solder is placed between the protective layer and the conductor, wherein the solder includes a low melting point main component and the conductor has a soldering surface including a second bonding metal. The conductor is soldered to the aluminum layer by heating the device to a soldering temperature to melt the low melting point main component. The protective layer is at least partially dissolved in the molten solder. The second bonding metal is transported from the soldering surface to the aluminum layer. An intermetallic compound layer is formed over the aluminum layer, wherein the intermetallic compound of the intermetallic compound layer includes aluminum as a first bonding metal and a second bonding metal and is substantially free of the low melting point main component. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The elements of the drawings are not necessarily to scale with respect to each other. The same reference numerals refer to corresponding similar parts. Unless the features of the various embodiments shown exclude each other, they may be combined and / or omitted if not described as essential. Embodiments are depicted in the drawings and are exemplarily described in detail in the following description.

[0008] Figure 1 is a cross-sectional view showing one example of a device in which a conductor is welded to an aluminum layer on a substrate.

[0009] Figure 2 is a cross-sectional scanning electron microscope (SEM) image depicting two intermetallic phases of the AlCu intermetallic compound layer formed between the Al layer and the solder layer.

[0010] Figures 3A-3D Without image processing ( Figure 3A ) and after image processing ( Figure 3B-3D ) to show an example device of a zinc-impregnated Al layer soldered with Pb solder.

[0011] Figures 4A-4D Without image processing ( Figure 4A ) and after image processing ( Figures 4B-4D ) to show an example device of a zinc-impregnated Al layer soldered with Sn / Sb solder.

[0012] Figure 5 is a cross-sectional view of an exemplary device showing a conductor and an aluminum layer welded together, wherein the conductor is a chip carrier or clip and the aluminum layer is a chip electrode.

[0013] Figure 6is a flow chart schematically illustrating one exemplary method of soldering a conductor to an aluminum layer on a substrate.

[0014] Figures 7A-7D is a schematic cross-sectional view of the various stages of the welding process using an initial zinc immersion treatment of an aluminum oxide layer.

[0015] Figures 8A-8D is a schematic cross-sectional view of the various stages of a welding process using an initial halogenation treatment of the aluminum oxide layer. DETAILED DESCRIPTION

[0016] It should be understood that the features of the various exemplary embodiments and examples described herein may be combined with each other, unless specifically stated otherwise.

[0017] In the detailed description that follows, reference is made to the accompanying drawings that form a part of the specification in which some specific embodiments are illustrated by way of illustration. In this regard, directional terms such as "top," "bottom," "front," "rear," "upper," "lower," etc. are used with reference to the orientation of the figures being described. Because the components of the embodiments can be positioned in a plurality of different orientations, the directional terms are used for illustrative purposes and are not restrictive. It should be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of this specification. Therefore, the detailed description that follows should not be considered restrictive.

[0018] The terms “combined”, “attached”, “connected”, “coupled” and / or “electrically connected / electrically coupled” used in this specification do not mean that the elements or layers must be directly in contact with each other; rather, intervening elements or layers may be provided between the elements being “combined”, “attached”, “connected”, “coupled” and / or “electrically connected / electrically coupled”, respectively. However, according to the present disclosure, the above terms may also optionally have such a specific meaning: that the elements or layers are directly in contact with each other, that is, no intervening elements or layers are provided between the elements being “combined”, “attached”, “connected”, “coupled” and / or “electrically connected / electrically coupled”.

[0019] In addition, the term "on..." used herein in relation to a component, element, or material layer formed, disposed, or positioned "on" a surface may be used to alternatively indicate that the component, element, or material layer is "directly" positioned (e.g., placed, formed, disposed, arranged, deposited, etc.) "on the surface," such as in direct contact with the surface. The term "on..." used herein in relation to a component, element, or material layer formed, disposed, or positioned "on" a surface may also be used to indicate that the component, element, or material layer is "indirectly" positioned (e.g., placed, formed, disposed, arranged, deposited, etc.) on the surface with one or more other components, elements, or layers disposed between the surface and the component, element, or material layer.

[0020] Furthermore, "X alloy" (including further components Y, Z, ...) means that X is the main component of the alloy, i.e. the proportion of X in wt. % (weight percentage) is greater than the proportion in wt. % of Y and the proportion in wt. % of Z, respectively. In particular, this may mean that the proportion of X is at least 50 wt. %. The same applies to solder compositions.

[0021] The symbol XY refers to an X alloy which includes at least Y as an additional component. In particular, it may refer to an X alloy which contains Y as the only residual component (i.e. a closed composition). That is, in the second case, the symbol XY means that the alloy XY has a composition consisting of X (weight percentage of X) and Y (weight percentage of Y), the remainder being only inevitable elements. The symbols XYZ... have a similar meaning, i.e. an "open composition" or "closed composition" with X, Y, Z... forming the only composition of the alloy (except for the inevitable elements). The same applies to solder compositions.

[0022] The embodiments described herein may be used for soldering a semiconductor substrate, such as a semiconductor chip or a semiconductor wafer, having a conductive electrode including an aluminum layer (also referred to as an aluminum metallization layer) to a metal conductor.

[0023] As is known in the art, the aluminum layer is made of highly stable Al 2 O 3 Layer of cloth. 2 O 3 With free formation enthalpy ΔGf 0 = -1582.3 kJ / mol. This highly stable oxide can only be removed by highly reactive chemicals, such as strong and aggressive flux systems. However, due to the presence of HCl and / or HF and / or H 2 SO 4 The flux residues can create a significant corrosion risk due to compounds such as Al2O3, Al2O3, Al2O4, Al2O6 ... 2 O 3 layer.

[0024] In addition, due to the Al 2 O 3 High formation rates on bare aluminum, so bare aluminum surfaces can only be welded for a short time.

[0025] Due to Al 2 O 3High thermodynamic stability, reducing Al 2 O 3 Very low oxygen levels and high temperatures are required, so using specialized welding equipment with hydrogen or formic acid is not an option either.

[0026] Various methods of providing a solderable aluminum layer before or during soldering of a conductor to the aluminum layer are described further below. Figure 1 is a cross-sectional view showing one example of the device 100 in which the conductor 110 and the aluminum layer 140 on the substrate 150 are welded together.

[0027] The substrate 150 may be, for example, a semiconductor substrate 150. The semiconductor substrate 150 may include or consist of a semiconductor material such as Si, SiC, SiGe, GaAs, GaN, AlGaN, InGaAs, InAlAs, etc. For example, the semiconductor substrate 150 may be a wafer or a chip.

[0028] In particular, the semiconductor substrate 150 may include one or more integrated circuits (ICs). The IC may be monolithically implemented in the semiconductor substrate 150. The IC may be a power IC such as a power transistor, a power diode, or a power system on a chip (SoC) such as a power amplifier. Although the disclosure herein is not limited to power applications, power devices based on the principles described herein may be of particular interest because solder bonding provides high electrical and thermal conductivity between components soldered together.

[0029] The substrate 150 is covered by an aluminum layer 140. The aluminum layer 140 does not have to be only aluminum, but can be an aluminum alloy, i.e., it may contain components such as Si and / or Cu and / or Mg and / or SiCu and / or other elements, such as Ti, Zn, etc. For example, the aluminum layer can be an AlCuSi alloy, which contains, for example, 0% by weight ≤ Cu ≤ 5% by weight, 0% by weight ≤ Si ≤ 1% by weight. As an example, the aluminum layer 140 can be a 98.5Al-1.0Si-0.5Cu (i.e., 98.5% by weight of Al, 1.0% by weight of Si, 0.5% by weight of Cu) aluminum alloy. Any such aluminum alloy, in particular a layer of AlCu, AlSiCu, AlTiCu, AlMg, AlSi or AlMgSiZn will also be referred to herein as an "aluminum layer".

[0030] The aluminum layer 140 may be smooth or may be rough.

[0031] The aluminum layer 140 may be a front side metallization or a back side metallization of a semiconductor substrate 150 (eg, a semiconductor chip). For example, the aluminum layer 140 may form a load electrode (eg, a drain or a source) of a semiconductor power chip represented by the substrate 150 .

[0032] As will be described in more detail further below, the aluminum layer 140 is soldered to the conductor 110 via the solder layer 120 and the intermetallic compound layer 130. The (electrical) conductor 110 may be, for example, a clip, a lead frame, or a heat sink. The electrical conductor 110 may be configured to be able to provide high current to the substrate 150 and, for example, to an IC implemented in the substrate 150 via the solder layer 120, the intermetallic compound layer 130, and the aluminum layer 140.

[0033] The conductor 110 has a soldering surface 110A including or made of a second bonding metal. The soldering surface 110A may directly contact the solder layer 120. The soldering surface 110A may be made of the same metal material as the conductor 110 (e.g., may be the exposed surface of the conductor 110), or may be the surface of a specific solder joint layer plated on the conductor 110. In the latter case, the conductor 110 may then be made of a material different from the second bonding metal of the solder joint layer providing the soldering surface 110A.

[0034] In various examples described herein, the second bonding metal is Cu or a Cu-based alloy, and may also form, for example, the bulk material of the conductor 110. However, in other embodiments, the second bonding metal is Ni, Ag, Fe, Au, Pt, Pd, Mn, Zn, Si, Cr, V, Mg, or an alloy based on any of these metals (e.g., AuAg, NiP, MgSiZn), and may or may not form the bulk material of the conductor 110 (which may still be, for example, Cu, Alloy 42 (Fe / Ni), Ni, Ag, Fe, FeC (steel), or even Al). However, the second bonding metal is different from Ag as the main component, which is not applicable to the embodiments described herein.

[0035] The welding surface 110A of the conductor 110 may be smooth or may be rough.

[0036] like Figure 1 As shown, the electrical and mechanical connection between the conductor 110 and the aluminum layer 140 is formed by a system of at least two layers, namely an intermetallic compound (IMC) layer 130 disposed on the aluminum layer 140 and a solder layer 120 on top of the IMC layer 130 .

[0037] The IMC of the IMC layer 130 includes or is formed of aluminum and a second bonding metal. As will be described in further detail below, the second bonding metal is transported to the interface between the solder and the aluminum during the soldering process by the solder of the solder layer 120. At this interface, the aluminum from the aluminum layer 140 (the first bonding metal) and the second bonding metal (from the soldering surface 110A of the conductor 110) undergo a chemical reaction to generate a new compound, namely the IMC.

[0038] In other words, the solder layer 120 has the function of transporting the second bonding metal from the soldering surface 110A of the conductor 110 to the aluminum layer 140 to form an IMC (thereby forming the IMC layer 130). The second bonding metal is transported (or diffused) by the solder layer 120. Figure 1 Indicated by dashed arrow A.

[0039] The solder of the solder layer 120 can be based on Pb, Sn, Bi, Ga or In, for example. This means that the low melting point main component of the solder can be Pb, Sn, Bi, Ga or In, respectively. It should be noted that all these metals do not participate in the formation of the IMC at the interface between the aluminum layer 140 and the solder layer 120. Therefore, the IMC of the IMC layer 130 is essentially (or except for a small residual portion of, for example, less than 5% by weight, 1% by weight, 0.5% by weight or 0.1% by weight) or completely free of the low melting point main component of the solder of the solder layer 120. Solders based on Zn (as main component) are not suitable because intermetallic phases are formed between Al and Zn.

[0040] Therefore, by using a suitable combination of the first bonding metal material and the solder, an IMC layer 130 can be obtained, which is not only substantially (or, for example, even completely) free of the low-melting point main component of the solder, but also (optionally) substantially (or, for example, even completely) free of any low-melting point component of the solder. As an example, if a PbSnAg solder is used, the IMC of the IMC layer 130 does not contain Pb, Sn and Ag, that is, it is completely or substantially (or at least except for a small residual portion of, for example, less than 5% by weight, 1% by weight, 0.5% by weight or 0.1% by weight) free of any low-melting point metal component of the solder (for example, it may be free of all components of the solder). Similarly, when a SnSb solder (for example, 85Sn-15Sb, i.e., 85% by weight of Sn, 15% by weight of Sb) is used, the IMC of the IMC layer 130 is completely or substantially (for example, within the above-mentioned exceptional residual limit) free of Sn and Sb. Furthermore, when a solder including or consisting of SnSbAg is used, the IMC of the IMC layer 130 is completely or substantially (eg, within the above-mentioned exceptional residual limits) free of Sn, Sb, and Ag.

[0041] The following is a list of suitable solder alloys for the present disclosure:

[0042] Pb-based solder with one or more components of metals from the group consisting of Sn, In, Bi, Ga, Sb, Cd, Ag, Au, Pt, such as PbSn, PbSnAg, PbSnIn, PbSnBi, PbSnInBi, PbSnInAg, PbIn, PbInAg, PbInSb, PbSb or PbBi.

[0043] Bi-based solder with one or more components of metals from the group consisting of Sn, In, Sb, Cd, Ag, Au, Pt, Pd, such as BiSn, BiSb or BiIn.

[0044] Sn-based solder with one or more components of metals from the group consisting of In, Bi, Ga, Sb, Cd, Ag, Au, Pt, Pd, such as SnAg (3-10 wt%), SnAu, SnIn, SnInAg, SnSb, SnSbAg or SnAu.

[0045] In based solders, such as InCd.

[0046] The initial solder material used (i.e., the solder material before the solder joint is established) may not contain the second bonding metal, which means that all the second bonding metal provided for the IMC of the IMC layer 130 may come from the soldering surface 110A of the conductor 110. In other embodiments, the initial solder may contain a certain portion of the second bonding metal. However, in this case, the amount of the second bonding metal (e.g., Cu) in the solder layer 120 is insufficient to form the IMC of the IMC layer 130. That is, the transport process of the second bonding metal through the solder layer 120 is necessary to establish the IMC layer 130.

[0047] In such Figure 1 In the illustrated device 100, even though the initial solder material does not include any second bonding metal, remnants of the second bonding metal may be found in the solder layer 120 due to the transport process through the layer (see arrow A).

[0048] The solder layer 120 may have a thickness D1 in the range of 2 μm to 100 μm. Since the boundary between the IMC layer 130 and the solder layer 120 may be non-uniform (as will be further described below), the thickness D1 should be understood as an average thickness of the solder layer 120 .

[0049] The solder layer 120 may be a soft solder layer. In this case, the thickness D1 of the solder layer 120 may be, for example, in the range between 50 μm and 100 μm, and / or specifically equal to or greater than or less than 60 μm, 70 μm, 80 μm or 90 μm.

[0050] In other embodiments, the solder layer 120 may be a diffusion solder layer. In this case, the thickness D1 of the solder layer 120 may be, for example, in a range between 2 μm and 7 μm, and / or in particular equal to or greater than or less than 3 μm, 4 μm, 5 μm, or 6 μm. The diffusion solder layer 120 is characterized in that all solder of the diffusion solder layer 120 has been chemically reacted to form an intermetallic phase. As an example, if the solder of the diffusion solder layer 120 is based on Sn, one or more intermetallic phases of Sn and a second bonding metal are included in the solder of the solder layer 120 or form the solder of the solder layer 120. For example, if the second bonding metal is Cu, the solder of the solder layer 120 may be formed of 6Cu-5Sn and / or 3Cu-1Sn.

[0051] The IMC layer 130 may have a thickness D2 ranging from 2 μm to 10 μm. Since the boundaries between the IMC layer 130 and both the aluminum layer 140 and the solder layer 120 may be non-uniform (as will be further described below), the thickness D2 should be understood as the average thickness of the IMC layer 130 .

[0052] The IMC may include one or two or more different intermetallic phases of aluminum and a second bonding metal. Figure 2 is a cross-sectional scanning electron microscope (SEM) image depicting two intermetallic phases of an IMC layer 130, such as AlCu, formed between an aluminum layer 140 and a solder layer 120. Here, the IMC layer 130 includes a first intermetallic phase layer 130_1 and a second intermetallic phase layer 130_2.

[0053] The first intermetallic phase forming the first intermetallic phase layer 130_1 is an aluminum-rich phase, and the second intermetallic phase forming the second intermetallic phase layer 130_2 is a dilute aluminum phase. The aluminum-rich first intermetallic phase layer 130_1 may be directly located on the aluminum layer 140, and the dilute aluminum second intermetallic phase layer 130_2 may be adjacent to the solder layer 120. Aluminum-rich may mean that aluminum may form the main component in the aluminum-rich first intermetallic phase layer 130_1. Dilute aluminum means that the aluminum content in the second intermetallic phase is less than the aluminum content in the first aluminum-rich intermetallic phase. The dilute aluminum second intermetallic phase layer 130_2 may be a second bonding metal-rich layer, i.e., the second bonding metal may form the main component in the dilute aluminum second intermetallic phase layer 130_2.

[0054] For example, the first intermetallic phase layer 130_1 may include or consist of 2Al1Cu, and / or the second intermetallic phase layer 130_2 may include or consist of 4Al9Cu.

[0055] Figure 2It is also shown that the thickness D2 of the intermetallic compound layer 130 can be equal to or greater than the thickness D3 of the aluminum layer 140. For example, the thickness D3 can range from, for example, 1 μm to 5 μm, while D2 can be within the above range and / or can be equal to or greater than or less than 3 μm, 5 μm, 7 μm or 9 μm.

[0056] Figure 2 Also shown are possible residues 120_1 , 120_2 of Cu (or more generally, the second bonding metal) remaining in the solder layer 120 during the solidification process.

[0057] Figure 3A is a cross-sectional SEM image showing the solder layer 120 formed on the intermetallic compound layer 130, the aluminum layer 140 and the substrate 150. In order to better distinguish these layers, Figure 3A The image processing is represented in Figures 3B to 3D More specifically, Figure 3B Shown separately Figure 3A Aluminum layer 140, Figure 3C Shown separately Figure 3A The intermetallic compound layer 130, and Figure 3D Shown separately Figure 3A The solder layer 120. Figure 3B and Figure 3C It is obvious from the comparison that the intermetallic compound layer 130 may be thicker than the aluminum layer 140. The interface between the IMC layer 130 and the solder layer 120 may be undulating or uneven, rather than flat. Figure 3C are visible in the and are marked by different shading styles and dividers. In addition, Figure 3D As shown, the solder of the solder layer 120 may have a somewhat non-uniform structure, ie, may include a distributed component of the second bonding metal (eg, Cu).

[0058] Figure 4A SEM images and Figure 2 The SEM images are the same. Figures 4B to 4D Respectively with Figures 3B to 3D The same way, that is, through Figure 4A That is, Figure 4B Only the aluminum layer 140 is shown, Figure 4C Only the IMC layer 130 (also including the IMC phase layers 130_1 and 130_2) is shown. Figure 4D Only the solder layer 120 (including the second bonding metal residues 120_1 , 120_2 ) of the device is shown.

[0059] exist Figures 3A to 3DIn 4A to 4D, the aluminum layer 140 has a thickness D3 of, for example, 3.2 μm. The initial aluminum oxide layer is removed by zinc immersion treatment of the aluminum oxide layer prior to welding. This process will be described in more detail further below. Figures 3A to 3D , a 20-second zinc dip treatment was applied before welding, and Figures 4A to 4D In the case of a 5 second zinc immersion treatment, Figures 3A to 3D In the case of Pb solder (more specifically PbSnAg), Figures 4A to 4D This is obtained by using Sn / Sb solder (more specifically SnSbAg solder).

[0060] Typically, soldering as described herein may be performed on an aluminum layer 140 , which may, for example, comprise an electrode of a wafer or chip forming the substrate 150 . Figure 5 An exemplary device 500 of a semiconductor chip 550 (representing the substrate 150) is shown. In this example, the aluminum layer 140 can be formed by a first electrode 540_1 at the top surface of the semiconductor chip 550 and / or can be formed by a second electrode 540_2 at the bottom surface of the semiconductor chip 550, or both. One of the electrodes 540_1, 540_2 - in the exemplary device 500, the first electrode 540_1 - can be soldered to the conductor 110, in Figure 5 In the illustrated device 500, the conductor 110 is represented by a clip 510_1. Alternatively or in combination, the second electrode 540_2 can be soldered to the conductor 110, which in the device 500 is represented by a lead frame 510_2. In addition, other types of conductors 110 can be soldered to the electrodes 540_1 and / or 540_2 of the semiconductor chip 550, such as heat sinks, ribbons, etc.

[0061] The semiconductor chip 550 may be, for example, a power chip such as a power transistor. The first and / or second electrodes 540_1, 540_2 may be load electrodes, for example a drain and / or source of the semiconductor chip 550. The first and second electrodes 540_1, 540_2 may be subsequently or simultaneously soldered to the conductor 110, for example to the clip 510_1 and the lead frame 510_2.

[0062] refer to Figure 6 Flow chart of , at S1, the aluminum oxide layer covering the aluminum layer is at least partially removed.

[0063] At S2, a protective layer is applied over the aluminum layer to prevent the aluminum oxide layer from regenerating on the aluminum layer. As will be described in more detail below, S1 and S2 can be performed by zincating the aluminum oxide layer or by halogenating the aluminum oxide layer or by a combined zincating and halogenating treatment of the aluminum oxide layer.

[0064] At S3 , solder is placed on the protective layer, for example, so as to be located between the protective layer and the conductor, wherein the solder includes a low melting point main component and the conductor has a soldering surface including the second bonding metal.

[0065] At S4, a soldering process is performed. The conductor is soldered to the aluminum layer by heating the device to a soldering temperature to melt the low melting point main component of the solder and at least partially dissolving the protective layer in the molten solder. The second bonding metal is transported from the soldering surface of the conductor to the aluminum layer, thereby forming an IMC layer on the aluminum layer. The IMC of the intermetallic compound includes or consists of aluminum as the first bonding metal and the second bonding metal, and is (substantially or completely) free of the low melting point main component of the solder.

[0066] As mentioned before, the IMC of the IMC layer may even be (substantially or completely) free of any low melting point components of the solder.

[0067] refer to Figures 7A to 7D , illustrating the various stages of a welding process using an initial zinc immersion treatment of an aluminum oxide layer. Fig. 7A An aluminum layer 140 is shown covered by a thin aluminum oxide layer 745 .

[0068] Then, a thin Zn layer 750 is deposited on the aluminum oxide layer 745. In the process of replacement with the aluminum oxide layer 745, the aluminum oxide layer is then replaced by the Zn layer 750 and the ZnO layer 755. The replacement of the aluminum oxide layer 745 is determined by the formation enthalpy of ZnO ΔGf 0 =-320.5 kJ / mol Compared to aluminum oxide (Al 2 O 3 )'s formation enthalpy ΔGf 0 =-1582.3 kJ / mol. This is related to copper oxides (such as CuO, Cu 2 O) formation enthalpy, the formation enthalpy of copper oxide (such as CuO, Cu2O) is ΔGf 0 <=-147.9 kJ / mol.

[0069] The ZnO layer 755 and the Zn layer 750 form a protective layer on the aluminum layer 140 , which protects the aluminum layer 140 from oxidation, that is, prevents the aluminum oxide layer from regenerating on the aluminum layer 140 .

[0070] like Figure 7C As shown, solder 720 is then deposited on the protective layer, or more specifically, on the ZnO layer 755. The solder 720 can be activated with a standard flux, i.e., a flux used to activate copper during reflow soldering, so that the aluminum layer 140 can be wetted by the molten solder 720', see Fig.7DDuring heating of the solder 720 to the soldering temperature, the solder 720 (or at least the low melting point main component of the solder 720 ) melts, and the protective layers 750 , 755 are at least partially dissolved in the molten solder 720 ′.

[0071] Figures 8A to 8D Various stages of a welding process using an initial halogenation treatment of the aluminum oxide layer 745 to provide a protective layer to prevent the aluminum layer 140 from reoxidizing are shown. More specifically, the replacement of the aluminum oxide layer 745 can include applying a halide to the aluminum oxide layer 745 via, for example, a plasma process. Halogenating the aluminum oxide layer 745 produces a halogenated aluminum oxide layer 850, see Figure 8B The halogenated aluminum oxide layer 850 forms a protective layer on the aluminum layer 140 to prevent the aluminum oxide layer from regenerating on the aluminum layer 140 .

[0072] Then, if Figure 8C As shown, solder 720 is deposited on halogenated aluminum oxide layer 850, and heat is applied to reflow solder 720. Again, the solder can be activated with a standard flux for activating copper oxide during solder reflow, thereby enabling wetting of aluminum layer 140 by molten solder 720′, as shown in FIG. Fig.8D During heating of the solder 720 to the soldering temperature, the solder 720 (or at least the low melting point main component of the solder 720 ) melts, and the protective layer (eg, the halogenated aluminum oxide layer 850 ) at least partially dissolves in the molten solder 720 ′.

[0073] As an example, halogenating the aluminum oxide layer 850 may include fluorinating the aluminum oxide layer 850 , which results in the formation of aluminum fluoride or aluminum hydrofluoride as the halogenated oxide layer 850 .

[0074] Summarize Figures 7A to 7D and the processes shown in 8A to 8D, the protective layer covering the aluminum surface that is at least partially free of an aluminum oxide layer may include or consist of zinc plating (e.g., Zn / ZnO) and / or aluminum fluoride and / or aluminum hydrofluoride, which can be activated with conventional flux and dissolved in the molten solder during solder reflow.

[0075] The following examples are related to other aspects of the present disclosure:

[0076] Example 1 is a device in which a conductor is welded together with an aluminum layer, the device comprising: a substrate; an aluminum layer disposed on the substrate; aluminum of the aluminum layer forming a first bonding metal; an intermetallic compound layer disposed on the aluminum layer; a solder layer disposed on the intermetallic compound layer, the solder of the solder layer comprising a low-melting-point main component; and a conductor disposed on the solder layer, the conductor having a welding surface comprising a second bonding metal; wherein the intermetallic compound of the intermetallic compound layer comprises aluminum and the second bonding metal and is substantially free of the low-melting-point main component.

[0077] In Example 2, the subject matter of Example 1 may optionally include: wherein the low melting point main component is Pb, Sn, Bi, Ga, or In.

[0078] In Example 3, the subject matter of Example 1 or 2 can optionally include: wherein the second bonding metal is Cu, Ni, Ag, Fe, Au, Pt, Pd, Mn, Zn, Si, Cr, V, Mg, NiP, or AuAg.

[0079] In Example 4, the subject matter of any of the preceding embodiments can optionally include: wherein the intermetallic compound is substantially free of any low melting point components of the solder.

[0080] In embodiment 5, the subject matter of any of the foregoing examples may optionally include: wherein the intermetallic compound includes at least two different intermetallic phases of aluminum and a second bonding metal, wherein the first intermetallic phase is an aluminum-rich phase and the second intermetallic phase is an aluminum-diluted phase.

[0081] In Example 6, the subject matter of any of the preceding examples can optionally include: wherein a thickness of the intermetallic compound layer is equal to or greater than a thickness of the aluminum layer.

[0082] In Example 7, the subject matter of any of the preceding examples can optionally include: wherein the solder layer is a soft solder layer.

[0083] In Example 8, the subject matter of Examples 1 to 6 can optionally include wherein the solder layer is a diffusion solder layer.

[0084] In Example 9, the subject matter of Example 8 can optionally include wherein the diffusion solder includes one or more intermetallic phases of Sn and a second bonding metal.

[0085] In Example 10, the subject matter of any of the preceding examples can optionally include wherein the solder includes PbSnAg, SnPb, SnSbAg, PbIn, or SnAgCu.

[0086] In Example 11, the subject matter of any of the preceding examples can optionally include: wherein the substrate is a wafer or a chip.

[0087] In Example 12, the subject matter of Example 11 can optionally include: wherein the aluminum layer forms at least one electrode of the wafer or chip.

[0088] In Example 13, the subject matter of any of the preceding examples can optionally include wherein the conductor is a clip, a lead frame, or a heat sink.

[0089] Example 14 is a method for welding a conductor to an aluminum layer on a substrate, the method comprising: at least partially removing an aluminum oxide layer covering the aluminum layer; applying a protective layer over the aluminum layer to prevent the aluminum oxide layer from regenerating on the aluminum layer; placing a solder between the protective layer and the conductor, wherein the solder includes a low melting point main component and the conductor has a welding surface including a second bonding metal; and welding the conductor to the aluminum layer by heating the device to a welding temperature to melt the low melting point main component so as to at least partially dissolve the protective layer in the molten solder and transport the second bonding metal from the welding surface to the aluminum layer and form an intermetallic compound layer over the aluminum layer, wherein the intermetallic compound of the intermetallic compound layer includes aluminum as a first bonding metal and a second bonding metal and is substantially free of the low melting point main component.

[0090] In Example 15, the subject matter of Example 14 can optionally include wherein removing the aluminum oxide layer and applying the protective layer comprises a zinc immersion treatment of the aluminum oxide layer.

[0091] In Example 16, the subject matter of Example 14 or 15 can optionally include wherein removing the aluminum oxide layer and applying the protective layer includes halogenating the aluminum oxide layer.

[0092] In Example 17, the subject matter of any one of Examples 14 to 16 can optionally include wherein the intermetallic compound is substantially free of any low melting point component of the solder.

[0093] In Example 18, the subject matter of any of Examples 14 to 17 can optionally include: wherein forming the intermetallic compound includes forming at least two different intermetallic phases of aluminum and a second bonding metal, wherein the first intermetallic phase is an aluminum-rich phase and the second intermetallic phase is an aluminum-diluted phase.

[0094] In Example 19, the subject matter of any one of Examples 14 to 18 can optionally include: wherein the welding is performed as a soft soldering process.

[0095] In Example 20, the subject matter of any one of Examples 14 to 18 can optionally include wherein the welding is performed as a diffusion welding process.

[0096] Although specific embodiments have been shown and described herein, it will be appreciated by those of ordinary skill in the art that various alternative and / or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the invention. This application is intended to cover any modifications or variations of the specific embodiments discussed herein. Therefore, it is intended that the present invention be limited only by the claims and their equivalents.

Claims

1. A device for welding a conductor (110) and an aluminum layer (140) together, the device comprising: A substrate (150); An aluminum layer (140) disposed on the substrate (150), wherein the aluminum of the aluminum layer (140) forms a first bonding metal; an intermetallic compound layer (130) disposed on the aluminum layer (140); a solder layer (120) disposed on the intermetallic compound layer (130) and directly contacting the intermetallic compound layer (130), the solder of the solder layer including a low melting point main component; and a conductor (110) disposed on the solder layer, the conductor (110) having a soldering surface (120) including a second bonding metal; in The intermetallic compound of the intermetallic compound layer (130) includes aluminum and a second bonding metal and is substantially free of the low melting point main component, wherein the intermetallic compound includes at least two different intermetallic phases of aluminum and the second bonding metal, wherein a layer (130_1) of a first intermetallic phase directly located on the aluminum layer (140) is an aluminum-rich phase, and a layer (130_2) of a second intermetallic phase adjacent to the solder layer (120) is an aluminum-diluted phase.

2. The device according to claim 1, wherein: The low melting point main component is Pb, Sn, Bi, Ga or In.

3. The device according to claim 1 or 2, wherein: The second bonding metal is Cu, Ni, Ag, Fe, Au, Pt, Pd, Mn, Zn, Si, Cr, V, Mg, NiP or AuAg.

4. The device according to claim 1 or 2, wherein: The intermetallic compound is substantially free of any low melting point components of the solder.

5. The device according to claim 1 or 2, wherein: The thickness of the intermetallic compound layer (130) is equal to or greater than the thickness of the aluminum layer (140).

6. The device according to claim 1 or 2, wherein: The solder layer (120) is a soft solder layer.

7. The device according to claim 1 or 2, wherein: The solder layer (120) is a diffusion solder layer.

8. The device according to claim 7, wherein: The diffusion solder includes one or more intermetallic phases of Sn and a second bonding metal.

9. The device according to any one of claims 1, 2 and 8, wherein: The solder includes PbSnAg, SnPb, SnSbAg, PbIn or SnAgCu.

10. The device according to any one of claims 1, 2 and 8, wherein: The substrate (150) is a wafer or a chip.

11. The device according to claim 10, wherein: The aluminum layer (140) forms at least one electrode of the wafer or the chip.

12. The device according to any one of claims 1, 2, 8 and 11, wherein: The conductor (110) is a clip, a lead frame or a heat sink.

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