Copper-ceramic substrate with a sinterable top surface

Abstract

The present invention relates to a copper-ceramic substrate, its use, and a method for producing a bonded connection between a copper-ceramic substrate and an electronic component. The copper-ceramic substrate comprises: a) a ceramic body; and b) a copper layer planarly connected to the ceramic body, the copper layer having a top surface. Before and after sputtering the top surface for 120 seconds, the copper-ceramic substrate has an energy spectrum obtained by X-ray photoelectron spectroscopy during analysis of the top surface of the copper layer, the energy spectrum giving the copper-ceramic substrate particular suitability for being bonded to an electronic component using a sintered material containing silver.

Description

[Technical Field]

[0001] The present invention relates to copper-ceramic substrates, uses of copper-ceramic substrates, and methods for producing bonded connections between copper-ceramic substrates and electronic components.

[0002] Copper-ceramic substrates play an important role in the field of power electronics. They are a key element when constructing electronic assemblies, ensuring the rapid dissipation of large amounts of heat during the operation of the assembly. Copper-ceramic substrates typically consist of a ceramic layer and a copper layer connected to the ceramic layer.

[0003] Several methods for connecting copper layers to ceramic layers are known from the prior art. In the so-called DCB ("direct copper bonding") method, copper is reacted with a reactive gas (usually oxygen) to provide the surface of a copper foil with a copper compound (usually copper oxide) that has a lower melting point than copper. When the copper foil treated in this way is applied to a ceramic body and the composite is heated, the copper compound melts and wets the surface of the ceramic body, creating a stable cohesive bond between the copper foil and the ceramic body. This method is described, for example, in U.S. Pat. No. 3,744,120 (A) or German Patent No. 2,319,854 (C2).

[0004] In an alternative method, copper foil can be bonded to a ceramic body at temperatures of approximately 650 to 1000°C. This involves using an active solder containing a metal (usually silver) with a melting point of at least 700°C and an active metal. The role of the active metal is to react with the ceramic material, thus facilitating bonding of the ceramic material to the remaining solder and forming a reaction layer, while the metal with a melting point of at least 700°C serves to bond the reaction layer to the copper foil. For example, Patent No. 4812985 (B2) proposes bonding copper foil to a ceramic body using a solder containing 50 to 89 weight percent silver, copper, bismuth, and an active metal. This method allows for a strong connection of the copper foil to the ceramic body. Alternatively, a silver-free active solder can be used to connect the copper foil to the ceramic body. These solders are based, for example, on a high-melting-point metal (especially copper), a low-melting-point metal (such as bismuth, indium, or tin), and an active metal (such as titanium). Such a technique is proposed, for example, in DE 102017114893 A1, which essentially results in a new and independent class of compounds, since the basis of the solder used is formed by another metal (copper instead of silver), leading to changes in the material properties and adaptation with regard to other solder constituents and modified joining conditions.

[0005] In the construction of electronic assemblies, electronic components are typically mounted on copper-ceramic substrates. The electronic components must be firmly bonded to the copper-ceramic substrate. Because electronic assemblies are often exposed to high temperatures during operation, electronic components are often connected to the copper-ceramic substrate using a sintering material containing silver. During the sintering process, the silver forms a bond between the electronic components to be connected and the surface of the copper-ceramic substrate. Due to the high melting point of silver, the resulting compound is temperature-stable. To achieve high bond strength, the surfaces of the copper-ceramic substrates to be connected are typically coated with a noble metal, particularly silver or gold, before the sintering process. This facilitates bonding of the sintered materials because the silver contained in the sintering material can easily diffuse into the noble-metal-containing coating of the copper-ceramic substrate. However, coating a copper-ceramic substrate with a noble metal has the disadvantage of being technically complex and requiring additional manufacturing steps. Therefore, it would be desirable to be able to firmly bond electronic components to a copper-ceramic substrate without providing a noble-metal-containing coating on the surface of the copper-ceramic substrate to be connected.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a copper-ceramic substrate that is preferably suitable for bonded connection to electronic components.

[0007] It is a further object of the present invention to provide a copper-ceramic substrate suitable for bond connection to electronic components, preferably without the need for a noble metal-containing coating on the surface of the copper-ceramic substrate to be connected.

[0008] Contributions to achieving these objectives include: A copper-ceramic substrate, a) a ceramic body; b) a copper layer planarly connected to the ceramic body, the copper layer having a top surface; (In the formula, (A) Energy spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy. (i) at least one signal S1 (t=0 sec) including at least one peak P1 (t=0 sec) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1 (t=0 sec) has an area PF1 (t=0 sec), and the areas PF1 (t=0 sec) of all peaks P1 (t=0 sec) of the at least one signal S1 (t=0 sec) result in a total area GF1 (t=0 sec); (ii) at least one signal S2 (t=0 sec) including at least one peak P2 (t=0 sec) having a maximum value in the range of 0 eV to 1400 eV, wherein the at least one peak P2 (t=0 sec) has an area PF2 (t=0 sec), and the areas PF2 (t=0 sec) of all peaks P2 (t=0 sec) of the at least one signal S2 (t=0 sec) result in a total area GF2 (t=0 sec); The ratio GF1(t=0 sec) / GF2(t=0 sec) has a value V(t=0 sec), (B) Energy spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy after sputtering the top surface of the copper layer for 120 seconds (sputtering gas: argon, accelerating voltage: 1 kV). (i) at least one signal S1 (t=120 sec) including at least one peak P1 (t=120 sec) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak has an area PF1 (t=120 sec), and the areas PF1 (t=120 sec) of all peaks P1 (t=120 sec) of the at least one signal S1 (t=120 sec) result in a total area GF1 (t=120 sec); (ii) at least one signal S2 (t=120 s) including at least one peak P2 (t=120 s) having a maximum value in the range of 0 eV to 1400 eV, wherein the at least one peak P2 (t=120 s) has an area PF2 (t=120 s), and the areas PF2 (t=120 s) of all peaks P2 (t=120 s) of the at least one signal S2 (t=120 s) result in a total area GF2 (t=120 s); the ratio GF1(t=120 s) / GF2(t=120 s) has a value V(t=120 s); This is done with a copper-ceramic substrate, where the ratio V(t=120 s) / V(t=0 s) ranges from 0.05 to 0.75.

[0009] The present invention further provides uses of copper-ceramic substrates and methods for producing bonded connections between copper-ceramic substrates and electronic components.

[0010] The copper-ceramic substrate according to the present invention comprises a ceramic body.

[0011] The ceramic body is preferably a body made of ceramic. The body can have any geometric shape, but is preferably designed as a rectangular parallelepiped. The ceramic body has boundary surfaces, and in the case of a rectangular parallelepiped, it has six boundary surfaces. The ceramic body preferably has a primary boundary surface. The primary boundary surface in this specification preferably refers to the boundary surface with the largest surface area that is planarly connected to the copper layer. The primary boundary surface is preferably located in the main extension plane or extends parallel to the main extension plane. Therefore, the main extension plane of the ceramic body is preferably understood to be a plane that extends parallel to or surrounds the primary boundary surface of the ceramic body.

[0012] The ceramic of the ceramic body is preferably an insulating ceramic. According to a preferred embodiment, the ceramic is selected from the group consisting of oxide ceramics, nitride ceramics, and carbide ceramics. According to a further preferred embodiment, the ceramic is selected from the group consisting of metal oxide ceramics, silicon oxide ceramics, metal nitride ceramics, silicon nitride ceramics, boron nitride ceramics, and boron carbide ceramics. According to a particularly preferred embodiment, the ceramic is selected from the group consisting of aluminum nitride ceramics, silicon nitride ceramics, and aluminum oxide ceramics (such as ZTA ("zirconia toughened alumina") ceramics). According to yet another very particularly preferred embodiment, the ceramic body comprises (1) at least one element selected from the group consisting of silicon and aluminum, (2) at least one element selected from the group consisting of oxygen and nitrogen, optionally (3) at least one element selected from the group consisting of (3a) rare earth metals, (3b) metals of Group 2 of the Periodic Table of the Elements, (3c) zirconium, (3d) copper, (3e) molybdenum, and (3f) silicon, and optionally (4) unavoidable impurities. According to yet another very particularly preferred embodiment, the ceramic body is free of bismuth, gallium, and zinc.

[0013] The ceramic body preferably has a thickness in the range of 0.05 to 10 mm, more preferably 0.1 to 5 mm, and particularly preferably 0.15 to 3 mm.

[0014] A copper-ceramic substrate according to the present invention comprises a copper layer planarly connected to a ceramic body, the copper layer having an upper surface.

[0015] The copper layer comprises copper. In addition to copper, the copper layer preferably also comprises oxygen, which is present as copper oxide, in particular copper(I) oxide (CuO) and / or copper(II) oxide (CuO). According to a preferred embodiment, the copper layer therefore comprises copper, oxygen, and unavoidable impurities. According to a further preferred embodiment, the copper proportion is at least 90 weight percent, more preferably at least 95 weight percent, even more preferably at least 99 weight percent, and particularly preferably at least 99.9 weight percent, based on the total weight of the copper layer (preferably including any bonding layer that may be present). According to a further highly preferred embodiment, the copper layer consists of copper, oxygen, and unavoidable impurities.

[0016] The copper layer preferably has a thickness in the range of 0.01 to 10 mm, particularly preferably in the range of 0.03 to 5 mm, very particularly preferably in the range of 0.05 to 3 mm.

[0017] The copper layer is preferably bonded and connected to the ceramic body. According to a preferred embodiment, the copper layer is connected to the ceramic body by a method selected from the group consisting of the DCB (Direct Copper Bonding) method and the active soldering method, in particular the AMB (Active Metal Brazing) method.

[0018] When connecting a copper layer to a ceramic body by the DCB method, a copper foil is preferably connected to the ceramic body, and a melt layer containing a compound containing copper and a reactive gas, preferably oxygen, is generated on the surface of the copper foil by heating to a temperature in the range of 1025 to 1083°C, particularly 1071°C. This melt layer forms a eutectic with a melting temperature lower than that of copper, so that a secure connection is formed between the copper foil and the ceramic body by placing the copper foil on the ceramic body and heating it. Such a method is disclosed, for example, in DE 2319854 A1.

[0019] When connecting a copper layer to a ceramic body using the AMB method, it is preferable to use an active solder to connect the copper foil to the ceramic body. For this purpose, the active solder is preferably positioned between the ceramic body and the copper foil and melted (particularly preferably at a temperature in the range of 800 to 1000°C). When the active solder solidifies, a secure connection is formed between the ceramic body and the copper foil. Thus, the copper layer can also be connected to the ceramic body in a planar manner via a connecting layer. The connecting layer can be, for example, an active solder layer or a diffusion layer. Such a method is disclosed, for example, in European Patent Application No. 153618A2.

[0020] The copper layer is connected to the ceramic body in a planar manner. Therefore, the copper layer is preferably connected to the primary boundary surface of the ceramic body in a planar manner. The copper layer is preferably not connected to the entire primary boundary surface of the ceramic body. In particular, the primary boundary surface of the ceramic body can be larger than the surface of the copper layer connected to the ceramic body. In these cases, the primary boundary surface of the ceramic body protrudes. It may further be provided that the copper layer is structured. Structured portions are preferably understood to mean recesses in the copper layer that separate individual portions of the copper layer from one another and thus electrically insulate them from one another. Such structured portions are typically produced by etching techniques.

[0021] The copper layer has a top surface, which is preferably the side of the copper layer facing away from the ceramic body, particularly the primary boundary surface of the ceramic body, and thus is preferably the side of the copper layer provided for bonding connection to an electronic component.

[0022] The top surface of the copper layer is preferably designed to allow for strong bonding to electronic components using a sintered material that includes silver.The top surface of the copper layer is characterized in that (A) an energy spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy (i) has at least one signal S1 (t=0 sec) including at least one peak P1 (t=0 sec) having a maximum in the range of 526 eV to 538 eV, the at least one peak P1 (t=0 sec) having an area PF1 (t=0 sec), and the areas PF1 (t=0 sec) of all peaks P1 (t=0 sec) of the at least one signal S1 (t=0 sec) yield a total area GF1 (t=0 sec), and (ii) has a maximum in the range of 0 eV to 1400 eV. (B) X-ray photoelectron spectra of at least one signal S2 (t=0 s) including at least one peak P2 (t=0 s) with a maximum value, wherein the at least one peak P2 (t=0 s) has an area PF2 (t=0 s), and the areas PF2 (t=0 s) of all peaks P2 (t=0 s) of the at least one signal S2 (t=0 s) result in a total area GF2 (t=0 s), and the ratio GF1 (t=0 s) / GF2 (t=0 s) has a value (t=0 s). (C) X-ray photoelectron spectra of the copper layer after sputtering for 120 seconds (sputtering gas: argon, accelerating voltage: 1 kV). The energy spectrum obtained during the analysis of the top surface of the copper layer by spectroscopy (i) has at least one signal S1 (t=120 s) including at least one peak P1 (t=120 s) having a maximum in the range of 526 eV to 538 eV, the at least one peak P1 having an area PF1 (t=120 s), and the areas PF1 (t=120 s) of all peaks P1 (t=120 s) of the at least one signal S1 (t=120 s) yield a total area GF1 (t=120 s), and (ii) has a few peaks S1 (t=120 s) having a maximum in the range of 0 eV to 1400 eV. There is at least one signal S2 (t=120 s) containing at least one peak P2 (t=120 s), and the at least one peak P2 (t=120 s) has an area PF2 (t=120 s), and the areas PF2 (t=120 s) of all peaks P2 (t=120 s) of the at least one signal S2 (t=120 s) result in a total area GF2 (t=120 s), and the ratio GF1 (t=120 s) / GF2 (t=120 s) has a value V (t=120 s), and the ratio V (t=120 s) / V (t=0 s) takes a value in the range of 0.05 to 0.75.

[0023] The energy spectrum preferably includes the range from 0 eV to 1400 eV.

[0024] An energy spectrum is recorded using X-ray photoelectron spectroscopy before sputtering the top surface of the copper layer, where the signals S1 and S2, peaks P1 and P2, areas PF1 and PF2, and total areas GF1 and GF2, as well as the ratio V, are obtained and are represented by the sum (t = 0 seconds).

[0025] Furthermore, the energy spectrum is also recorded by X-ray photoelectron spectroscopy after sputtering the top surface of the copper layer for 120 seconds (sputtering gas: argon, acceleration voltage: 1 kV), where the signals S1 and S2, peaks P1 and P2, areas PF1 and PF2, and total areas GF1 and GF2, as well as the ratio V, are obtained, which are expressed by summation (t=120 seconds).

[0026] According to a preferred embodiment, an energy spectrum is also recorded by X-ray photoelectron spectroscopy after sputtering the top surface of the copper layer for 240 seconds (sputtering gas: argon, acceleration voltage: 1 kV), where signals S1 and S2, peaks P1 and P2, areas PF1 and PF2, and total areas GF1 and GF2, as well as the ratio V, are obtained and expressed by summation (t=240 seconds).

[0027] The energy spectrum has at least one signal S1, and therefore may have multiple signals S1.

[0028] At least one signal S1 includes at least one peak P1 having a maximum value in the range of 526 eV to 538 eV. Thus, peak P1 is characterized by having a maximum value in the range of 526 eV to 538 eV.

[0029] Thus, an energy spectrum can have, for example, a signal S1 that includes one or more peaks P1. On the other hand, an energy spectrum can also have multiple signals S1, each including one or more peaks P1.

[0030] At least one peak P1 has an area PF1, and the areas PF1 of all peaks P1 of at least one signal S1 result in a total area GF1. For example, if an energy spectrum has multiple signals S1, each of which has multiple peaks P1, the total area GF1 is obtained from the sum of the areas PF1 of all peaks P1.

[0031] Peak P1, which has a maximum in the range of 526 eV to 538 eV, indicates the presence of oxygen species, which may be, for example, a species selected from the group consisting of copper oxides (e.g., copper(I) oxide, copper(II) oxide), copper hydroxide, and organic compounds.

[0032] Therefore, the total area GF1 correlates with the percentage of oxygen species on the top surface of the copper layer of the copper-ceramic substrate.

[0033] The energy spectrum has at least one signal S2, and therefore the energy spectrum may also have multiple signals S2.

[0034] The at least one signal S2 includes at least one peak P2 having a maximum value in the range of 0 eV to 1400 eV. Thus, the peak P2 is characterized by having a maximum value in the range of 0 eV to 1400 eV. The at least one signal S2 may also include, in particular, at least one signal S2 described herein as signal S1 (e.g., a signal including at least one peak having a maximum value in the range of 526 eV to 538 eV). Thus, the signal S2 also includes the signal S1.

[0035] Thus, an energy spectrum can have, for example, a signal S2 that includes one or more peaks P2. On the other hand, an energy spectrum can also have multiple signals S2, each including one or more peaks P2.

[0036] At least one peak P2 has an area PF2, and the areas PF2 of all peaks P2 of at least one signal S2 result in a total area GF2. For example, if an energy spectrum has multiple signals S2, each of which has multiple peaks P2, the total area GF2 is obtained from the sum of the areas PF2 of all peaks P2.

[0037] Typically, the energy spectrum has multiple signals S2.

[0038] The energy spectrum includes a signal S2 (e.g., a signal including at least one peak having a maximum in the range of 526 eV to 538 eV) described herein as signal S1. Thus, signal S2 includes at least one peak P2 having a maximum in the range of 526 eV to 538 eV, which indicates the presence of an oxygen species. The oxygen species may be, for example, a species selected from the group consisting of copper oxide, copper hydroxide, and organic compounds.

[0039] Furthermore, the energy spectrum preferably comprises a further signal S2 comprising at least one further peak P2.

[0040] The further signal S2 may, for example, include at least one peak P2 indicative of the Cu2p region of the energy spectrum and thus indicating the presence of a copper species, which may, for example, be copper(I) oxide, copper(II) oxide, metallic copper, or copper hydroxide.

[0041] The further signal S2 may include, for example, a peak P2 indicating the presence of carbon species, which may be, for example, an adsorbate for copper (e.g., carbon dioxide from ambient air) or a common organic impurity.

[0042] The further signal S2 may, for example, comprise a peak P2 indicating the presence of further species, which may, for example, be nitrogen species that accumulate on the top surface of the copper layer during the production of the copper-ceramic substrate.

[0043] Therefore, the total area GF2 correlates with the proportion of copper species on the top surface of the copper layer of the copper-ceramic substrate.

[0044] According to a preferred embodiment, the ratio V(t=120 seconds) / V(t=0 seconds) has a value in the range of 0.10 to 0.75.

[0045] According to a particularly preferred embodiment, the ratio V(t=120 seconds) / V(t=0 seconds) has a value in the range of 0.25 to 0.75.

[0046] According to a very particularly preferred embodiment, the ratio V(t=120 s) / V(t=0 s) takes a value in the range 0.30 to 0.75.

[0047] According to a further preferred embodiment, the energy spectrum obtained during analysis of the upper surface of the copper layer by X-ray photoelectron spectroscopy after sputtering the upper surface of the copper layer for 240 seconds (sputtering gas: argon, acceleration voltage: 1 kV) is (iii) at least one signal S1 (t=240 s) including at least one peak P1 (t=240 s) having a maximum in the range of 526 eV to 538 eV, wherein the at least one peak P1 (t=240 s) has an area PF1 (t=240 s), and the areas PF1 (t=240 s) of all peaks P1 (t=240 s) of the at least one signal S1 (t=240 s) result in a total area GF1 (t=240 s); (iv) at least one signal S2 (t=240 s) including at least one peak P2 (t=240 s) having a maximum in the range of 0 eV to 1400 eV, wherein the at least one peak P2 (t=240 s) has an area PF2 (t=240 s), and the areas PF2 (t=240 s) of all peaks P2 (t=240 s) of the at least one signal S2 (t=240 s) result in a total area GF2 (t=240 s); The ratio GF1(t=240 s) / GF2(t=240 s) has a value V(t=240 s), The ratio V(t = 240 s) / V(t = 0 s) ranges from 0.04 to 0.40.

[0048] According to a preferred embodiment, the ratio V(t=240 sec) / V(t=0 sec) has a value in the range of 0.05 to 0.35.

[0049] According to a particularly preferred embodiment, the ratio V(t=240 seconds) / V(t=0 seconds) has a value in the range of 0.05 to 0.30.

[0050] According to a very particularly preferred embodiment, the ratio V(t=240 s) / V(t=0 s) takes a value in the range 0.05 to 0.20.

[0051] Surprisingly, the copper-ceramic substrate (A) has an energy spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy, which (i) has at least one signal S1(t=0 s) including at least one peak P1(t=0 s) having a maximum in the range of 526 eV to 538 eV, the at least one peak P1(t=0 s) having an area PF1(t=0 s), and the areas PF1(t=0 s) of all peaks P1(t=0 s) of the at least one signal S1(t=0 s) yield a total area GF1(t=0 s), and (ii) has a maximum in the range of 0 eV to 1400 eV. (B) X-ray photoelectron spectroscopy of the top surface of the copper layer after sputtering for 120 seconds (sputtering gas: argon, accelerating voltage: 1 kV) on the top surface of the copper layer. The energy spectrum obtained during the analysis (i) has at least one signal S1 (t=120 s) including at least one peak P1 (t=120 s) having a maximum in the range of 526 eV to 538 eV, and the at least one peak P1 has an area PF1 (t=120 s), and the areas PF1 (t=120 s) of all peaks P1 (t=120 s) of the at least one signal S1 (t=120 s) result in a total area GF1 (t=0 s), and (ii) has at least one peak P2 (t=120 s) having a maximum in the range of 0 eV to 1400 eV. It has been found that the sintered material containing silver can be firmly bonded to electronic components, wherein the sintered material has at least one signal S2(t=120 s), at least one peak P2(t=120 s) has an area PF2(t=120 s), the areas PF2(t=120 s) of all peaks P2(t=120 s) of the at least one signal S2(t=120 s) result in a total area GF2(t=120 s), the ratio GF1(t=120 s) / GF2(t=120 s) has a value V(t=120 s), and the ratio V(t=120 s) / V(t=0 s) has a value in the range of 0.05 to 0.75.

[0052] Without wishing to be bound by any theory, this may be due to the presence of oxygen species at a certain concentration in the upper surface region of the copper layer. Conventional copper-ceramic substrates are easily passivated on the surface by contact with an oxygen-containing atmosphere. The presence of this surface passivation layer appears to be sufficient for the formation of a sintered bond between the copper layer of the copper-ceramic substrate and the electronic component.The copper-ceramic substrate according to the present invention is characterized in that (A) the energy spectrum obtained during analysis of the upper surface of the copper layer by X-ray photoelectron spectroscopy (XPS) has at least one signal S1 (t=0 s) including at least one peak P1 (t=0 s) having a maximum in the range of 526 eV to 538 eV, the at least one peak P1 (t=0 s) having an area PF1 (t=0 s), and the areas PF1 (t=0 s) of all peaks P1 (t=0 s) of the at least one signal S1 (t=0 s) result in a total area GF1 (t=0 s), and (ii) the energy spectrum obtained during analysis of the upper surface of the copper layer by X-ray photoelectron spectroscopy (XPS) has at least one signal S1 (t=0 s) including at least one peak P1 (t=0 s) having a maximum in the range of 526 eV to 538 eV. 0 eV), and the at least one peak P2(t=0 s) has an area PF2(t=0 s), and the areas PF2(t=0 s) of all peaks P2(t=0 s) of the at least one signal S2(t=0 s) result in a total area GF2(t=0 s), and the ratio GF1(t=0 s) / GF2(t=0 s) has a value (t=0 s); (B) after sputtering the top surface of the copper layer for 120 seconds (sputtering gas: argon, acceleration voltage: 1 kV), The energy spectrum obtained during the analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy (i) has at least one signal S1 (t=120 s) including at least one peak P1 (t=120 s) having a maximum in the range of 526 eV to 538 eV, the at least one peak P1 having an area PF1 (t=120 s), and the areas PF1 (t=120 s) of all peaks P1 (t=120 s) of the at least one signal S1 (t=120 s) yield a total area GF1 (t=120 s), and (ii) has a maximum in the range of 0 eV to 1400 eV. The at least one signal S2 (t = 120 s) includes at least one peak P2 (t = 120 s), the at least one peak P2 (t = 120 s) has an area PF2 (t = 120 s), the areas PF2 (t = 120 s) of all peaks P2 (t = 120 s) of the at least one signal S2 (t = 120 s) result in a total area GF2 (t = 120 s), the ratio GF1 (t = 120 s) / GF2 (t = 120 s) has a value V(t = 120 s), and the ratio V(t = 120 s) / V(t = 0 s) takes a value in the range of 0.05 to 0.75.

[0053] A copper-ceramic substrate comprising a copper layer having such an energy spectrum at its upper surface contains a predetermined proportion of oxygen species. The oxygen species are present not only immediately above the upper surface of the copper layer, but also in a deeper region at the upper surface. The specified proportion of oxygen species present in the deeper region at the upper surface of the copper layer, quite surprisingly, appears to promote the formation of a sintered bond between the copper layer of the copper-ceramic substrate and the electronic component, in contrast to a smaller proportion of oxygen species, or a proportion of oxygen species present directly at the upper surface of the copper layer, as in the case of an upper surface of a copper layer of a copper-ceramic substrate that has been conventionally passivated or thermally passivated in a manner customary in the art.

[0054] According to a further preferred embodiment, the energy spectrum obtained during the analysis of the upper surface of the copper layer by X-ray photoelectron spectroscopy has at least one signal S2 comprising at least one peak P2a having a maximum in the range of 933.2 eV to 934.0 eV.

[0055] The signal S2, which includes the peak P2a with a maximum in the range of 933.2 eV to 934.0 eV, indicates the presence of copper(II) oxide (CuO) on the top surface of the copper layer.

[0056] According to a preferred embodiment, the upper surface of the copper layer is designed so that the energy spectrum obtained during analysis of the upper surface of the copper layer by X-ray photoelectron spectroscopy has at least one signal S2 including at least one peak P2b having a maximum in the range of 932.2 eV to 932.8 eV, wherein peak P2a occupies area F2a and peak P2b occupies area F2b, and the ratio of area F2a to area F2b is at least 0.4.

[0057] The signal S2 including at least one peak P2b having a maximum value in the range of 932.2 eV to 932.8 eV indicates the presence of copper(I) oxide (CuO) and / or metallic copper (Cu(0)) on the upper surface of the copper layer. Therefore, the signal S2 may also have multiple peaks P2b, for example, a peak P2b indicating the presence of copper(I) oxide (CuO) and a peak P2b indicating the presence of metallic copper (Cu(0)). The area F2b preferably includes the area of ​​all peaks P2b having a maximum value in the range of 932.2 eV to 932.8 eV. Therefore, the area F2b is preferably the sum of the areas of all peaks P2b having a maximum value in the range of 932.2 eV to 932.8 eV.

[0058] Thus, the area F2a of peak P2a correlates with the proportion of copper(II) oxide (CuO) on the top surface of the copper layer. In contrast, the area F2b of at least one peak P2b correlates with the proportion of copper(I) oxide (CuO) and / or metallic copper (Cu(0)) on the top surface of the copper layer.

[0059] According to a preferred embodiment, the ratio of the area F2a to the area F2b is at least 0.5, particularly preferably at least 5.0, very particularly preferably at least 8.0.

[0060] According to a further preferred embodiment, the ratio of the area F2a to the area F2b is 1000 or less, more preferably 500 or less, particularly preferably 100 or less, very particularly preferably 50 or less, in particular 30 or less.

[0061] According to a preferred embodiment, the ratio of the area F2a to the area F2b is in the range 0.4-1000, more preferably in the range 0.5-500, particularly preferably in the range 5.0-100 and very particularly preferably in the range 8.0-30.

[0062] Surprisingly, it has been found that copper-ceramic substrates designed such that the energy spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy has a signal comprising at least one peak P2a having a maximum in the range of 933.2 eV to 934.0 eV can be firmly bonded to electronic components using a sintering material comprising silver.

[0063] Without wishing to be bound by any theory, this may be due to the presence of copper(II) oxide (CuO) on the upper surface of the copper layer. Prior art copper-ceramic substrates are easily passivated by contact with oxygen-containing atmospheres. It has been found that copper(I) oxide (CuO) primarily forms on the upper surface of the copper layer. The presence of copper(I) oxide (CuO) does not appear to contribute to the formation of a sintered bond between the copper layer of the copper-ceramic substrate and the electronic component. According to a preferred embodiment, the copper-ceramic substrate is one in which the energy spectrum obtained during analysis of the upper surface of the copper layer by X-ray photoelectron spectroscopy has at least one signal, including at least one peak P2a having a maximum in the range of 933.2 eV to 934.0 eV. This peak P2a indicates the presence of copper(II) oxide (CuO). In contrast to copper(I) oxide (CuO), copper(II) oxide (CuO) surprisingly appears to promote the formation of a sintered bond between the copper layer of the copper-ceramic substrate and the electronic component.

[0064] Furthermore, it has surprisingly been found that if the upper surface of the copper layer is designed so that the energy spectrum obtained during analysis of the upper surface of the copper layer by X-ray photoelectron spectroscopy has at least one signal including at least one peak P2b having a maximum in the range of 932.2 eV to 932.8 eV, wherein peak P2a occupies area F2a and peak P2b occupies area F2b, and the ratio of area F2a to area F2b is at least 0.4, then the sintered material can be used to achieve a particularly strong bonded connection to an electronic component of a copper-ceramic substrate.

[0065] Without wishing to be bound by any theory, this may be due to the fact that in this case, the ratio of copper(II) oxide (CuO) to copper(I) oxide (CuO) and metallic copper (Cu(0)) increases at the top surface of the copper layer. Peak P2a, which has a maximum between 933.2 and 934.0 eV, indicates the presence of copper(II) oxide (CuO), and at least one peak P2b, which has a maximum between 932.2 and 932.8 eV, indicates the presence of copper(I) oxide (CuO) and metallic copper (Cu(0)). The presence of copper(II) oxide (CuO) has a beneficial effect on the formation of a bonded connection between the top surface of the copper-ceramic substrate and an electronic component using the sintered material, and this effect appears to be greater the higher the ratio of copper(II) oxide (CuO) to copper(I) oxide (CuO) and metallic copper (Cu(0)) on the top surface of the copper layer. Particularly high bond strengths are ultimately achieved if a certain ratio of copper(II) oxide (CuO) to copper(I) oxide (CuO) and metallic copper (Cu(0)) is not exceeded, so that the ratio of area F2a to area F2b is in the range of 0.4 to 1000.

[0066] According to a preferred embodiment, the copper-ceramic substrate comprises a further (second) copper layer planarly connected to the ceramic body. The further copper layer is preferably planarly connected to the ceramic boundary surface opposite the primary boundary surface (preferably extending parallel to the primary boundary surface). The further (second) copper layer may be of the same nature as the (first) copper layer, or its properties may differ from those of the (first) copper layer. For the properties of the further (second) copper layer, reference is made to the above explanation.

[0067] The method for producing the copper-ceramic substrate according to the present invention is not further limited.

[0068] Preferably, the method for producing a copper-ceramic substrate according to the present invention comprises: a) providing a copper-ceramic substrate, the copper-ceramic substrate comprising: (i) a ceramic body; (ii) a copper layer planarly connected to the ceramic body, the copper layer having a top surface; (b) treating the top surface of the copper layer of the copper-ceramic substrate, thereby (A) Energy spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy. (i) at least one signal S1 (t=0 sec) including at least one peak P1 (t=0 sec) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1 (t=0 sec) has an area PF1 (t=0 sec), and the areas PF1 (t=0 sec) of all peaks P1 (t=0 sec) of the at least one signal S1 (t=0 sec) result in a total area GF1 (t=0 sec); (ii) at least one signal S2(t=0 sec) including at least one peak P2(t=0 sec) having a maximum value in the range of 0 eV to 1400 eV, wherein the at least one peak P2(t=0 sec) has an area PF2(t=0 sec), and the areas PF2(t=0 sec) of all peaks P2(t=0 sec) of the at least one signal S2(t=0 sec) result in a total area GF2(t=0 sec); The ratio GF1(t=0 sec) / GF2(t=0 sec) has the value V(t=0 sec), (B) Energy spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy after sputtering the top surface of the copper layer for 120 seconds (sputtering gas: argon, accelerating voltage: 1 kV). (i) at least one signal S1 (t=120 s) including at least one peak P1 (t=120 s) having a maximum in the range of 526 eV to 538 eV, wherein the at least one peak has an area PF1 (t=120 s), and the areas PF1 (t=120 s) of all peaks P1 (t=120 s) of the at least one signal S1 (t=120 s) result in a total area GF1 (t=120 s); (ii) at least one signal S2(t=120 s) including at least one peak P2(t=120 s) having a maximum in the range of 0 eV to 1400 eV, wherein the at least one peak P2(t=120 s) has an area PF2(t=120 s), and the areas PF2(t=120 s) of all peaks P2(t=120 s) of the at least one signal S2(t=120 s) result in a total area GF2(t=120 s); The ratio GF1(t=120 s) / GF2(t=120 s) has a value V(t=120 s), The ratio V(t=120 seconds) / V(t=0 seconds) has a value in the range of 0.05 to 0.75.

[0069] A method of producing a copper-ceramic substrate according to the present invention preferably comprises providing a copper-ceramic substrate comprising: (i) a ceramic body; and (ii) a copper layer planarly connected to the ceramic body, the copper layer having an upper surface.

[0070] The copper-ceramic substrate may be a standard copper-ceramic substrate. Therefore, the copper-ceramic substrate preferably includes a ceramic body and a copper layer planarly connected to the ceramic body, the copper layer having an upper surface. The characteristics of the copper-ceramic substrate and its components can be found in the information above.However, the upper surface of the copper layer preferably has: (A) an energy spectrum obtained during analysis of the upper surface of the copper layer by X-ray photoelectron spectroscopy having (i) at least one signal S1(t=0 s) including at least one peak P1(t=0 s) having a maximum in the range of 526 eV to 538 eV, the at least one peak P1(t=0 s) having an area PF1(t=0 s), the areas PF1(t=0 s) of all peaks P1(t=0 s) of the at least one signal S1(t=0 s) resulting in a total area GF1(t=0 s); and (ii) a maximum in the range of 0 eV to 1 (B) After sputtering the top surface of the copper layer for 120 seconds (sputtering gas: argon, accelerating voltage: 1 kV) for 120 seconds. The energy spectrum obtained during the analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy (i) has at least one signal S1 (t=120 s) including at least one peak P1 (t=120 s) having a maximum in the range of 526 eV to 538 eV, the at least one peak P1 having an area PF1 (t=120 s), and the areas PF1 (t=120 s) of all peaks P1 (t=120 s) of the at least one signal S1 (t=120 s) result in a total area GF1 (t=120 s), and (ii) has a maximum in the range of 0 eV to 1400 eV. The at least one signal S2 (t = 120 s) includes at least one peak P2 (t = 120 s), the at least one peak P2 (t = 120 s) has an area PF2 (t = 120 s), the areas PF2 (t = 120 s) of all peaks P2 (t = 120 s) of the at least one signal S2 (t = 120 s) result in a total area GF2 (t = 120 s), the ratio GF1 (t = 120 s) / GF2 (t = 120 s) has a value V(t = 120 s), and the ratio V(t = 120 s) / V(t = 0 s) takes a value in the range of 0.05 to 0.75.

[0071] The method of producing a copper-ceramic substrate according to the present invention preferably includes cleaning the top surface of the copper layer of the copper-ceramic substrate.

[0072] Cleaning is accomplished, for example, by exposing the top surface of the copper layer of the copper-ceramic substrate to a reducing organic compound, which can be, for example, formic acid.

[0073] The method for producing a copper-ceramic substrate according to the present invention preferably comprises treating the upper surface of the copper-ceramic substrate, whereby (A) an energy spectrum obtained during analysis of the upper surface of the copper layer by X-ray photoelectron spectroscopy has (i) at least one signal S1(t=0 sec) including at least one peak P1(t=0 sec) having a maximum in the range of 526 eV to 538 eV, the at least one peak P1(t=0 sec) having an area PF1(t=0 sec), and the area PF of all peaks P1(t=0 sec) of the at least one signal S1(t=0 sec) is 1 (t=0 s) results in a total area GF1 (t=0 s), (ii) at least one signal S2 (t=0 s) including at least one peak P2 (t=0 s) having a maximum in the range of 0 eV to 1400 eV, and the at least one peak P2 (t=0 s) has an area PF2 (t=0 s), and the areas PF2 (t=0 s) of all peaks P2 (t=0 s) of the at least one signal S2 (t=0 s) result in a total area GF2 (t=0 s), and the ratio GF1 (t=0 s) / GF2 (t=0 s) has a value (t=0 s), and (B) the top surface of the copper layer is sputtered for 120 seconds. After sputtering (sputtering gas: argon, acceleration voltage: 1 kV), the energy spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy (i) has at least one signal S1 (t=120 s) including at least one peak P1 (t=120 s) having a maximum in the range of 526 eV to 538 eV, and the at least one peak P1 has an area PF1 (t=120 s), and the areas PF1 (t=120 s) of all peaks P1 (t=120 s) of the at least one signal S1 (t=120 s) result in a total area GF1 (t=120 s), and (ii) There is at least one signal S2 (t = 120 s) including at least one peak P2 (t = 120 s) having a maximum value in the range of 0 eV to 1400 eV, and the at least one peak P2 (t = 120 s) has an area PF2 (t = 120 s), and the areas PF2 (t = 120 s) of all peaks P2 (t = 120 s) of the at least one signal S2 (t = 120 s) result in a total area GF2 (t = 120 s), and the ratio GF1 (t = 120 s) / GF2 (t = 120 s) has a value V (t = 120 s), and the ratio V (t = 120 s) / V (t = 0 s) is between 0.05 and 0.The value ranges from 75.

[0074] The treatment of the upper surface of the copper layer of the copper-ceramic substrate is not further limited, and preferably includes plasma treatment of the upper surface of the copper layer or deposition of copper oxide on the upper surface of the copper layer.

[0075] According to a preferred embodiment, the treatment of the top surface of the copper layer of the copper-ceramic substrate comprises a plasma treatment.

[0076] Plasma is understood to mean a partially ionized gas, particularly preferably containing highly excited particles and radicals. The plasma can preferably cause oxidation on the upper surface of the copper layer of the copper-ceramic substrate. Copper(II) oxide is preferably formed in this process.

[0077] According to a particularly preferred embodiment, the plasma treatment is carried out using oxygen plasma, which can be generated by methods conventional in the art. For example, an AP-600 plasma system (Nordson-March) can be used for this purpose.

[0078] The plasma treatment is preferably carried out at a high frequency power in the range of 200 to 1000 W, particularly preferably at a high frequency power in the range of 500 to 700 W, for example, at 600 W.

[0079] The plasma treatment is preferably carried out at a frequency in the range of 10 to 15 MHz, particularly preferably at a frequency in the range of 13 to 14 MHz, for example at a frequency of 13.56 MHz.

[0080] According to a preferred embodiment, the plasma treatment is carried out at a base pressure in the range of 0.1 to 0.5 mbar, particularly preferably at a base pressure in the range of 0.2 to 0.4 mbar.

[0081] According to a preferred embodiment, the plasma treatment is carried out at a process pressure in the range of 0.5 to 1.5 mbar, particularly preferably at a process pressure in the range of 0.7 to 1.0 mbar.

[0082] According to a preferred embodiment, the oxygen gas flow after base pressure is reached is in the range of 50 to 150 standard cubic centimeters per minute, for example 100 to 150 standard cubic centimeters per minute.

[0083] The plasma treatment is preferably carried out for a period in the range of 100 to 1000 seconds, particularly preferably for a period in the range of 150 to 900 seconds.

[0084] According to a further preferred embodiment, the treatment of the upper surface of the copper layer of the copper-ceramic substrate comprises the deposition of copper oxide on the upper surface of the copper layer. The copper oxide may preferably be copper(II) oxide. Preferably, the copper oxide is deposited on the upper surface of the copper layer of the copper-ceramic substrate by a method conventional in the art, such as sputtering.

[0085] The copper-ceramic substrate according to the present invention is preferably used for bonding connections to electronic components.

[0086] Electronic components are preferably understood to mean electronic or electrical components. The electronic components are preferably selected from the group consisting of semiconductor components. The semiconductor components are preferably selected from the group consisting of transistors, diodes and integrated circuits.

[0087] According to a further preferred embodiment, the electronic component comprises a metal coating. The metal coating can be used to facilitate easier bonding of the electronic component to the copper-ceramic substrate via the sintered material. The metal coating may preferably comprise different layers. The metal coating of the electronic component preferably comprises a noble metal. The noble metal may be part of an alloy containing the noble metal. The noble metal preferably comprises at least one element selected from the group consisting of gold, silver, and palladium. According to a preferred embodiment, the metal coating of the electronic component comprises silver or an alloy containing at least one element selected from the group consisting of nickel, palladium, and gold.

[0088] According to a preferred embodiment, the copper-ceramic substrate is also suitable for bonding connections to electronic components, and therefore the top surface of the copper-ceramic substrate is preferably not in contact with further parts, particularly preferably connection layers, which form bonding connections to electronic components.

[0089] The present invention provides a method for producing a bonded connection between a copper-ceramic substrate and an electronic component, comprising: a) A copper-ceramic substrate is provided, the copper-ceramic substrate comprising: (a) a ceramic body; and (b) a copper layer planarly connected to the ceramic body, the copper layer having an upper surface; and (A) an energy spectrum obtained during analysis of the upper surface of the copper layer by X-ray photoelectron spectroscopy has: (i) at least one signal S1(t=0 sec) including at least one peak P1(t=0 sec) having a maximum value in the range of 526 eV to 538 eV, the at least one peak P1(t=0 sec) having an area PF1(t=0 sec), and all of the at least one signal S1(t=0 sec) (ii) at least one signal S2 (t=0 sec) including at least one peak P1 (t=0 sec) having a maximum value in the range of 0 eV to 1400 eV, wherein at least one peak P2 (t=0 sec) has an area PF2 (t=0 sec), and the areas PF2 (t=0 sec) of all peaks P2 (t=0 sec) of at least one signal S2 (t=0 sec) result in a total area GF2 (t=0 sec), and the ratio GF1 (t=0 sec) / GF2 (t=0 sec) has a value (t=0 sec). (B) After sputtering the top surface of the copper layer for 120 seconds (sputtering gas: argon, acceleration voltage: 1 kV), the energy spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy (i) has at least one signal S1 (t=120 seconds) including at least one peak P1 (t=120 seconds) having a maximum in the range of 526 eV to 538 eV, and the at least one peak P1 has an area PF2 (t=120 seconds), and the total area PF1 (t=120 seconds) of all peaks P1 (t=120 seconds) of the at least one signal S1 (t=120 seconds) is (ii) at least one signal S2(t=120 s) including at least one peak P2(t=120 s) having a maximum in the range of 0 eV to 1400 eV, wherein the at least one peak P2(t=120 s) has an area PF2(t=120 s), and the areas PF2(t=120 s) of all peaks P2(t=120 s) of the at least one signal S2(t=120 s) yield a total area GF2(t=120 s), and the ratio GF1(t=120 s) / GF2(t=120 s) has a value V(t=120 s);The ratio V(t=120 s) / V(t=0 s) ranges from 0.05 to 0.75. b) an electronic component is provided; c) a sintered material comprising silver is provided; d) the electronic component, the copper-ceramic substrate, and the sintering material are positioned to form an arrangement in which the electronic component contacts the top surface of the copper layer of the copper-ceramic substrate through the sintering material; and e) The arrangement is subjected to a process to form a sintered bond between the electronic component and the copper-ceramic substrate.

[0090] In this method, a copper-ceramic substrate is provided.

[0091] The copper-ceramic substrate is a copper-ceramic substrate as described herein.

[0092] Therefore, the copper-ceramic substrate a) a ceramic body; b) a copper layer planarly connected to the ceramic body, the copper layer having a top surface; (A) Energy spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy. (i) at least one signal S1 (t=0 sec) including at least one peak P1 (t=0 sec) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1 (t=0 sec) has an area PF1 (t=0 sec), and the areas PF1 (t=0 sec) of all peaks P1 (t=0 sec) of the at least one signal S1 (t=0 sec) result in a total area GF1 (t=0 sec); (ii) at least one signal S2(t=0 sec) including at least one peak P2(t=0 sec) having a maximum value in the range of 0 eV to 1400 eV, wherein the at least one peak P2(t=0 sec) has an area PF2(t=0 sec), and the areas PF2(t=0 sec) of all peaks P2(t=0 sec) of the at least one signal S2(t=0 sec) result in a total area GF2(t=0 sec); The ratio GF1(t=0 sec) / GF2(t=0 sec) has the value V(t=0 sec), (B) Energy spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy after sputtering the top surface of the copper layer for 120 seconds (sputtering gas: argon, accelerating voltage: 1 kV). (i) at least one signal S1 (t=120 s) including at least one peak P1 (t=120 s) having a maximum in the range of 526 eV to 538 eV, wherein the at least one peak has an area PF1 (t=120 s), and the areas PF1 (t=120 s) of all peaks P1 (t=120 s) of the at least one signal S1 (t=120 s) result in a total area GF1 (t=120 s); (ii) at least one signal S2(t=120 s) including at least one peak P2(t=120 s) having a maximum in the range of 0 eV to 1400 eV, wherein the at least one peak P2(t=120 s) has an area PF2(t=120 s), and the areas PF2(t=120 s) of all peaks P2(t=120 s) of the at least one signal S2(t=120 s) result in a total area GF2(t=120 s); The ratio GF1(t=120 s) / GF2(t=120 s) has a value V(t=120 s), The ratio V(t = 120 s) / V(t = 0 s) ranges from 0.05 to 0.75.

[0093] In the method, an electronic component is provided.

[0094] For the characteristics of the electronic components, reference can be made to the information above.

[0095] In the method, a sintered material comprising silver is provided.

[0096] The silver-containing sintering material is preferably selected from the group consisting of a sintering paste, a sintering film, and a sintering preform.

[0097] The sintered material preferably comprises silver.

[0098] According to a preferred embodiment, the sintering material comprises a sintering paste. The sintering paste is preferably a sintering paste conventional in the art. Preferably, the sintering paste comprises silver and an organic compound. The silver in the sintering paste may preferably be present as silver particles. The silver particles may have any shape, and thus may be present, for example, as spherical silver particles, silver flakes, or irregularly shaped silver particles. The organic compound is preferably selected from the group consisting of dispersants, binders, fatty acids, and mixtures thereof. The dispersant may be selected from dispersants conventional in the art. An exemplary dispersant is terpineol. The binder may be selected from polymers conventional in the art. Examples include cellulose derivatives, such as methyl cellulose, ethyl cellulose, ethyl methyl cellulose, carboxy cellulose, and hydroxypropyl cellulose. The fatty acid may be selected from fatty acids conventional in the art. The fatty acids are preferably selected from the group consisting of caprylic acid (octanoic acid), capric acid (decanoic acid), lauric acid (dodecanoic acid), myristic acid (tetradecanoic acid), palmitic acid (hexadecanoic acid), margaric acid (heptadecanoic acid), stearic acid (octadecanoic acid), arachidic acid (eicosanoic acid), behenic acid (docosanoic acid) and lignoceric acid (tetracosanoic acid).

[0099] According to a further preferred embodiment, the sintered material comprises a sintered film. Preferably, the sintered film is a sintered film as is conventional in the art, for example as disclosed in EP 3154729 A1. Thus, the sintered film may comprise, for example, a sintering paste comprising metal particles (particularly silver particles) and a binder that is pre-dried on a carrier substrate. The sintered film may have a thickness in the range of 5 to 300 μm.

[0100] According to a further preferred embodiment, the sintered material comprises a sintered preform. Preferably, the sintered preform is a conventional sintered preform, such as those disclosed in European Patent Application No. 2428293A2.

[0101] According to a preferred embodiment, in this regard, the sintering material is applied to the upper surface of the copper layer of the copper-ceramic substrate. The sintering material can be applied to the upper surface of the copper layer of the copper-ceramic substrate using methods conventional in the art. Preferably, in the case of a sintering paste, the sintering material is applied by spraying, dispensing, spraying, brushing, dabbing, dipping, or printing, particularly screen printing or stencil printing, or in the case of a sintering film or sintering preform, by simply placing it on the sintering material. The electronic component can then be positioned with its upper surface to be connected on the sintering material to form an arrangement in which the electronic component contacts the upper surface of the copper layer of the copper-ceramic substrate via the sintering material.

[0102] According to an alternative preferred embodiment, the sintering material is applied to the upper surface of the electronic component to be connected. The sintering material can be applied to the upper surface of the electronic component to be connected using a method conventional in the art. Preferably, in the case of a sintering paste, the sintering material is applied by jetting, dispensing, spraying, brushing, dabbing, dipping, or printing, particularly screen printing or stencil printing, or in the case of a sintering film or sintering preform, by simply placing it on the sintering material. The copper-ceramic substrate can then be positioned with the upper surface of its copper layer on the sintering material to form an arrangement in which the electronic component contacts the upper surface of the copper layer of the copper-ceramic substrate via the sintering material.

[0103] In the method, the arrangement is subjected to a process that forms a sintered bond between the electronic component and the copper-ceramic substrate.

[0104] According to a preferred embodiment, the treatment is carried out by applying temperature and / or pressure.

[0105] When temperature is applied, the arrangement is preferably exposed to a temperature in the range of 150 to 350°C, more preferably a temperature in the range of 180 to 280°C, and particularly preferably a temperature in the range of 200 to 250°C.

[0106] When pressure is applied, the arrangement is preferably subjected to a pressure in the range from above 0 to 300 bar, particularly preferably in the range from 0.1 to 30 bar, very particularly preferably in the range from 0.2 to 10 bar.

[0107] The method forms a sintered bond and therefore a bonded connection between the electronic component and the copper-ceramic substrate. DETAILED DESCRIPTION OF THE INVENTION

[0108] The analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy, the recording of the energy spectrum and the evaluation of the energy spectrum are preferably carried out according to the following method.

[0109] In preparation for measurements using X-ray photoelectron spectroscopy, the copper-ceramic substrate was cut into sample pieces with an edge length of 0.9 (+ / - 0.1) cm x 1.4 (+ / - 0.1) cm using a side cutter. The edges on the trimmed edges were removed using a scalpel to ensure a straight support surface. Dust was removed from the sample pieces by blowing them with nitrogen gas. The sample pieces were attached to a sample holder using non-conductive adhesive tape.

[0110] X-ray photoelectron spectra were recorded on a PHI VersaProbe4 (Physical Electronics) using a monochromated Mg anode (Kα = 1.487 keV) as the source. First, an overview spectrum (range 0-1400 eV) of the sample piece was recorded. From the overview spectrum, conclusions were drawn about the elements present on the inspected top surface of the sample piece. Then, a detailed spectrum of the sample piece was recorded in the energy range where signals could be identified in the overview spectrum. To record the detailed spectrum, an X-ray beam (200 μm diameter, 50 W at 15 kV, measurement time: 25-40 min (e.g., 30 min), 20 ms integration time per measurement point) was used, with the peak-to-noise setting enabled, and a neutralizer (a combination of Ar+ and e- with low kinetic energy) was used.

[0111] After recording all detailed spectra, sputtering was performed at the same location. Sputtering was performed using argon as the sputtering gas at an acceleration voltage of 1 kV for a sputtering time of 2 × 120 s (sputtering gas: argon, acceleration voltage: 1 kV, sputtering area: 4 mm). 2 ), 4mm above the copper foil on the copper-ceramic substrate 2 The sputtering was performed by spraying Ar+ ions onto a sample piece (e.g., 2 mm x 2 mm). After each sputtering step, an X-ray photoelectron spectrum was recorded. Thus, three measurements were performed on each sample piece.

[0112] The spectra were evaluated using the analytical software CasaXPS (version 2.3.224PR1.0; Casa Software Ltd.). The C C / C H component of the C 1s signal (ubiquitously present) was normalized to 284.8 eV, and the binding energies of the detailed spectra were shifted accordingly. A Shirley function was used for background correction. Peaks were generated from the resulting signals using the analytical software. The number of peaks was adjusted based on a literature-based fitted model (XPS-NIST database), and the peaks were assigned to elements or compounds. The analytical software was used to calculate the peak areas of the generated peaks, taking into account the relative sensitivity factors. [Example]

[0113] The invention is explained in more detail below using exemplary embodiments, which should not be understood as limiting.

[0114] Example 1: In this example, a copper-ceramic substrate with dimensions 27 x 38 mm was used, in which a ceramic body made of silicon nitride ceramic was connected on both sides to a copper layer with a thickness of 0.3 mm using the AMB (active metal brazing) method (Condura®, prime AMB, top surface uncoated, Heraeus).

[0115] The copper-ceramic substrate was first cleaned by first exposing it to a vacuum in the chamber of a soldering machine (PINK Vadu 200), then to formic acid at atmospheric pressure of 500 mbar and a temperature of 180° C., and then to nitrogen.

[0116] The copper-ceramic substrate was then subjected to plasma treatment with oxygen plasma. For this purpose, the copper-ceramic substrate was placed in the center of the upper sample carrier of a plasma system (AP-600 (Nordson-March)). The plasma treatment was carried out at a power of 600 W, a frequency of 13.56 Hz, a base pressure of 0.3 mbar, and a process pressure of 0.9 mbar for a process time of 90 seconds. After the plasma treatment, the copper-ceramic substrate was removed from the plasma system.

[0117] The top surface of the copper layer of the copper-ceramic substrate was analyzed by X-ray photoelectron spectroscopy according to the method described above, and the results are shown in Table 1.

[0118] The copper-ceramic substrate was then fitted with a silicon chip. For this purpose, the copper-ceramic substrate was printed with sintering paste (ASP338-28, Heraeus) using a 150 μm thick printing stencil and squeegee. The sintering paste was pre-dried in a convection oven at 140 °C for 20 minutes in a nitrogen atmosphere with a residual oxygen content of 50 ppm and then cooled. A silicon chip measuring 4 × 4 mm (thickness = 250 μm) with bottom metallization (100 nm aluminum, 50 nm titanium, 100 nm nickel, and finally 700 nm silver) was positioned on the pre-dried sintering paste. Sintering was carried out in a PINK sintering press (Pink, Wertheim) in a nitrogen atmosphere at a pressure of 20 MPa and a temperature of 250 °C for 3 minutes.

[0119] Example 2: Example 2 was carried out in the same manner as Example 1, except that the plasma treatment was carried out for 180 seconds instead of 90 seconds.

[0120] Example 3: Example 3 was carried out in the same manner as Example 1, except that the plasma treatment was carried out for 300 seconds instead of 90 seconds.

[0121] Example 4: Example 4 was carried out in the same manner as Example 1, except that the plasma treatment was carried out for 420 seconds instead of 90 seconds.

[0122] Example 5: Example 5 was carried out in the same manner as Example 1, except that the plasma treatment was carried out for 600 seconds instead of 90 seconds.

[0123] Comparative Example 1: Comparative Example 1 was carried out in the same manner as Example 1, but unlike Example 1, cleaning with formic acid and plasma treatment were omitted.

[0124] Comparative Example 2: Comparative Example 1 was carried out in the same manner as Example 1, but unlike Example 1, the plasma treatment was omitted.

[0125] Comparative Example 3: Comparative Example 1 was carried out in the same manner as Example 1, but unlike Example 1, the plasma treatment was carried out for 900 seconds instead of 90 seconds.

[0126] evaluation: The components obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were examined for the mechanical bond strength of the silicon chip on the copper-ceramic substrate. For this purpose, a shear test was carried out using a bond testing machine Nordson Dage 4000Plus (Nordson, USA). For this purpose, the component was first clamped in a fixture. For the test, a 6 mm wide steel shear chisel was used, which applied increasing forces to the component until the silicon chip separated from the copper-ceramic substrate. The force at which the silicon chip separated was referred to as the shear strength and was measured in Nmm. 2 The bond strength was evaluated in units of 16. The average value of the shear strength was calculated. The results are shown in Table 1.

[0127] [Table 1]

[0128] The results show that the copper-ceramic substrates of Examples 1-5 according to the present invention are clearly superior to the copper-ceramic substrates of Comparative Examples 1-3 in terms of their suitability for forming strong bonded connections to electronic components.

Claims

1. A copper-ceramic substrate, a) a ceramic body; b) a copper layer planarly connected to the ceramic body, the copper layer having an upper surface; (A) an energy spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy; (i) at least one signal S1(t=0 sec) including at least one peak P1(t=0 sec) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1(t=0 sec) has an area PF1(t=0 sec), and the areas PF1(t=0 sec) of all peaks P1(t=0 sec) of the at least one signal S1(t=0 sec) result in a total area GF1(t=0 sec); (ii) at least one signal S2(t=0 sec) including at least one peak P2(t=0 sec) having a maximum value in the range of 0 eV to 1400 eV, wherein the at least one peak P2(t=0 sec) has an area PF2(t=0 sec), and the areas PF2(t=0 sec) of all peaks P2(t=0 sec) of the at least one signal S2(t=0 sec) result in a total area GF2(t=0 sec); the ratio GF1(t=0 s) / GF2(t=0 s) has the value V(t=0 s), (B) after sputtering the top surface of the copper layer for 120 seconds (sputtering gas: argon, acceleration voltage: 1 kV), the energy spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy is (i) at least one signal S1(t=120 sec) including at least one peak P1(t=120 sec) having a maximum in the range of 526 eV to 538 eV, said at least one peak having an area PF1(t=120 sec), and the areas PF1(t=120 sec) of all peaks P1(t=120 sec) of said at least one signal S1(t=120 sec) giving a total area GF1(t=120 sec); (ii) at least one signal S2(t=120 sec) including at least one peak P2(t=120 sec) having a maximum in the range of 0 eV to 1400 eV, said at least one peak P2(t=120 sec) having an area PF2(t=120 sec), and the areas PF2(t=120 sec) of all peaks P2(t=120 sec) of said at least one signal S2(t=120 sec) giving a total area GF2(t=120 sec); the ratio GF1(t=120 s) / GF2(t=120 s) has a value V(t=120 s), The ratio V(t=120 seconds) / V(t=0 seconds) is in the range of 0.05 to 0.75; A copper-ceramic substrate comprising:

2. (C) after sputtering the upper surface of the copper layer for 240 seconds (sputtering gas: argon, acceleration voltage: 1 kV), the energy spectrum obtained during analysis of the upper surface of the copper layer by X-ray photoelectron spectroscopy is (iii) at least one signal S1(t=240 sec) including at least one peak P1(t=240 sec) having a maximum in the range of 526 eV to 538 eV, wherein the at least one peak P1(t=240 sec) has an area PF1(t=240 sec), and the areas PF1(t=240 sec) of all peaks P1(t=240 sec) of the at least one signal S1(t=240 sec) give a total area GF1(t=240 sec); (iv) at least one signal S2(t=240 sec) including at least one peak P2(t=240 sec) having a maximum in the range of 0 eV to 1400 eV, said at least one peak P2(t=240 sec) having an area PF2(t=240 sec), and the areas PF2(t=240 sec) of all peaks P2(t=240 sec) of said at least one signal S2(t=240 sec) giving a total area GF2(t=240 sec); the ratio GF1(t=240 s) / GF2(t=240 s) has a value V(t=240 s), The ratio V(t=240 seconds) / V(t=0 seconds) is in the range of 0.04 to 0.40; The copper-ceramic substrate according to claim 1, characterized in that

3. 3. The copper-ceramic substrate according to claim 1, wherein the ceramic of the ceramic body is selected from the group consisting of aluminum nitride ceramic, silicon nitride ceramic, and aluminum oxide ceramic.

4. Use of a copper-ceramic substrate according to any one of claims 1 to 3 for bonding connections to electronic components.

5. 1. A method for producing a bonded connection between a copper-ceramic substrate and an electronic component, comprising: a) a copper-ceramic substrate according to claim 1 is provided; b) an electronic component is provided; c) a sintered material comprising silver is provided; d) the electronic component, the copper-ceramic substrate, and the sintered material are positioned to form an arrangement in which the electronic component contacts the top surface of the copper layer of the copper-ceramic substrate through the sintered material; and e) subjecting said arrangement to a treatment to form a sintered bond between said electronic component and said copper-ceramic substrate.

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