Metal-ceramic composite

Abstract

To provide a metallized silicon nitride-containing ceramic substrate whose exposed surface allows formation of a bond of high adhesive strength with a casting compound.SOLUTION: A metal-ceramic composite comprises: a ceramic substrate comprising a front side and a rear side and containing β-silicon nitride; and a metal coating on the front side of the ceramic substrate. The metal coating comprises at least one recess, and a surface of the ceramic substrate is exposed by the recess. At least in the region of the recess, the ceramic substrate satisfies the specific condition: SO-βSN / SB-βSN≥0.8. When the formula is satisfied, the adhesive strength of a casting compound onto the ceramic substrate can be improved.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a metal-ceramic composite that can be used as a ceramic circuit carrier in power electronics.

[0002] In power electronics, printed circuit boards should be designed for high current as carriers for power components such as MOSFETs and should be able to dissipate waste heat quickly.

[0003] Ceramic materials such as aluminum oxide, aluminum nitride, and silicon nitride have much higher thermal conductivities than the polymers used to manufacture conventional printed circuit boards, so ceramic circuit carriers are often used in power modules.

[0004] Silicon nitride-based ceramic substrates have very high mechanical strength and high thermal conductivity at the same time, so they are very suitable for applications in power electronics.

[0005] Silicon nitride can exist in a crystal structure known as the "α-phase" or "β-phase". These two phases have different X-ray diffraction patterns. The phase that is stable under normal sintering conditions is the β-phase (hereinafter also referred to as β-silicon nitride). Therefore, β-silicon nitride usually exists in silicon nitride-based ceramic substrates.

[0006] β-silicon nitride contains acicular crystallites (acicular microcrystals). It is known that the mechanical properties or thermal conductivity of ceramics can be affected by the alignment of these acicular β-silicon nitride crystallites in the ceramic body. For example, when most of the acicular crystallites are oriented with a longitudinal axis substantially parallel to the ceramic surface, it can be advantageous for the mechanical strength of the ceramic, while when most of the acicular crystallites are aligned with a longitudinal axis substantially perpendicular to the ceramic surface, it can be more advantageous for the thermal conductivity.

[0007] "Si 3 N 4 "Substrates with Anisotropic Thermal Conductivity Suitable for Power Module Applications" by T. Okuno et al., PCIM Europe digital days 2021; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, Online, 2021, pp. 1-5 describes ceramic substrates each containing β-silicon nitride, and the substrates have different alignments of elongated β-silicon nitride crystallites. As the number of crystallites aligned along the longitudinal axis parallel to the thickness direction of the ceramic substrate (i.e., perpendicular to the front or back surface) increases, the intensity of the (101) reflection of β-silicon nitride in the X-ray diffraction pattern also increases.

[0008] Silicon nitride-based ceramic substrates are described, for example, in the following publications: N. Chasserio et al., "Ceramic Substrates for High-Temperature Electronic Integration," Journal of Electronic Materials, Volume 38 (2009), pp. 164-174; K. Hirao et al., "High Thermal Conductivity Silicon Nitride Ceramics," Journal of the Korean Ceramic Society, Volume 49 (2012), pp. 380-384; Y. Zhou et al., "Development of high-thermal-conductivity silicon nitride ceramics," Journal of Asian Ceramic Societies, 3 (2015), pp. 221-229.

[0009] An overview of the method for manufacturing silicon nitride ceramics having different textures can be found, for example, in the following publications. "Textured silicon nitride: processing and anisotropic properties" by X. Zhu and Y. Sakka, Sci. Technol. Adv. Mater., 9, 2008, 033001.

[0010] Silicon nitride-based ceramic substrates exhibit a good balance between high mechanical strength and high thermal conductivity, can be used in electronic components, and are commercially available.

[0011] A ceramic circuit carrier has a ceramic substrate, and metal layers are provided on at least one surface thereof, usually on both surfaces. In the final module, semiconductor components are applied to one of these metal layers, and the metal layer on the opposite side of the ceramic substrate is thermally conductively connected to a heat sink. The ceramic substrate electrically insulates the metal layers from each other.

[0012] A metallized ceramic substrate that functions as a ceramic circuit board, known to those skilled in the art, is manufactured, for example, by bringing the front and rear surfaces of the ceramic substrate into contact with a metal film (e.g., a copper or aluminum film) and joining them together. The material joining of the metal foil is achieved, for example, by eutectic bonding or the active metal brazing method (AMB). When the metal film is a copper film, eutectic bonding is also called the DCB method or the DBC method (DCB: "direct copper bonding", DBC: "direct bonding copper"). In the case of an aluminum film, the term "DAB" ("direct aluminum bonding") is also used for eutectic bonding. A metallized ceramic substrate manufactured using the DCB process or the AMB process may also be called a DCB substrate (or a DBC substrate) or an AMB substrate.

[0013] The metallization of a silicon nitride substrate is usually performed by the active metal brazing method.

[0014] The active metal brazing filler metal contains, in addition to a main component such as Cu, Ag, or Au, one or more elements that can react with the ceramic to form an adhesion-promoting reaction layer (see, for example, Chapter 8.2.4.3 (“Active metal brazing”) of Brevier Technische Keramik, Verband der Keramischen Industrie eV, 2003, Fahner Verlag, pages 203-204). Reactive elements such as hafnium (Hf), titanium (Ti), zirconium (Zr), niobium (Nb), cerium (Ce), tantalum (Ta), and vanadium (V) are used. In the metallization of a silicon nitride substrate by the active metal brazing method, the reaction layer contains, for example, nitrides, oxynitrides, and / or silicides of the reactive elements (A. Ponicke et al., “Active metal brazing of copper with aluminum nitride and silicon nitride ceramics”, Keramische Zeitschrift, 63(5), 2011, 334-342).

[0015] The metal layer supporting the semiconductor component is structured (for example, by etching). The structuring of the AMB substrate can be carried out, for example, in a two-step process. In the first step, the metal layer is first removed in defined regions (for example, using a first etching solution), and then, in the second step, the adhesion-promoting layer obtained from the active metal brazing process is removed (for example, using a second etching solution). By removing the metal layer in the defined regions, the ceramic substrate is exposed again in these regions.

[0016] Modules based on ceramic circuit carriers used in power electronics can be encapsulated, as part of the packaging process, for example, by embedding the power module in a casting compound.

[0017] For example, by embedding in a casting compound, the dielectric breakdown strength is increased. Further, the semiconductor components and the metal conductor tracks are protected from moisture and mechanically stabilized.

[0018] In the regions exposed by structuring, the ceramic substrate is in direct contact with the casting compound. When operating the power module, significant temperature fluctuations can occur. Since the ceramic material and the casting compound usually have significantly different coefficients of thermal expansion, these temperature fluctuations cause mechanical stress at the interface between the ceramic and the casting compound. And this can result in the casting compound being at least partially detached from the ceramic substrate, forming voids. Moisture entering these voids can damage the power module. Further, at least locally, the dielectric breakdown strength can be significantly reduced.

[0019] As already described above, silicon nitride-based ceramic substrates are used as circuit carriers in power electronics due to their very high mechanical strength and high thermal conductivity. To maximize their potential as circuit carriers, it is desirable that there is a high adhesive strength between the casting compound and the silicon nitride surface after embedding in the casting compound.

[0020] The object of the present invention is to provide a metallized silicon nitride-containing ceramic substrate, the exposed surface of which enables the formation of a joint with high adhesive strength to a casting compound.

[0021] This object is a metal-ceramic composite, comprising a ceramic substrate having a front surface and a rear surface and containing β-silicon nitride, and a metal coating on the front surface of the ceramic substrate, the metal coating includes at least one recess, and the surface of the ceramic substrate is exposed by the recess, the ceramic substrate satisfies the following conditions at least in the region of the recess: SO-βSN / S B-βSN ≥0.8 wherein S O-βSN =I O-βSN (101) / [0.5 × (I O-βSN (200) + I O-βSN (120))] S B-βSN =I B-βSN (101) / [0.5 × (I B-βSN (200) + I B-βSN (120))] I O-βSN (101), I O-βSN (200) and I O-βSN (120) are the relative peak heights of the (101), (200), and (120) reflections of β-silicon nitride in the X-ray diffraction pattern measured under 3° glancing incidence using Cu-Kα radiation. The relative peak heights are normalized with respect to the peak height of the (200) reflection, I B-βSN (101), I B-βSN (200) and I B-βSN (120) are the relative peak heights of the (101), (200), and (120) reflections of β-silicon nitride in the X-ray diffraction pattern measured with Bragg-Brentano geometry and Cu-Kα radiation. The relative peak heights are normalized with respect to the peak height of the (120) reflection and are achieved by the metal-ceramic composite.

[0022] As described above, the intensity of the (101) reflection of β-silicon nitride in the X-ray diffraction pattern is affected by the alignment of the elongated β-silicon nitride crystallites. As the number of crystallites aligned along the longitudinal axis parallel to the thickness direction of the ceramic substrate (i.e., perpendicular to the front or back surface) increases, the intensity of the (101) reflection of β-silicon nitride in the X-ray diffraction pattern, as well as the intensity ratios of the (101) reflection to the (200) and (120) reflections, also increase. The peak height in the X-ray diffraction pattern normalized with respect to the height of the reference peak can be regarded as a measure of the intensity of the reflection.

[0023] Glancing-incidence X-ray diffraction is used to examine the structure of the region near the surface of the sample, while X-ray diffraction in Bragg-Brentano geometry provides structure information averaged over the entire irradiated volume of the sample.

[0024] Surprisingly, within the scope of the present invention, when the ratio defined above (i.e., S O-βSN / S B-βSN ≧0.8) is satisfied, it has been found that the adhesion strength of the cast compound on the ceramic substrate can be improved.

[0025] For example, in the following cases. S O-βSN / S B-βSN ≧0.95

[0026] In an exemplary embodiment, the following relationship is satisfied. 2.2≧S O-βSN / S B-βSN ≧0.8

[0027] In another exemplary embodiment, the following relationship is satisfied. 2.2≧S O-βSN / S B-βSN ≧0.95

[0028] In another exemplary embodiment, the following relationship is satisfied. 1.75≧S O-βSN / S B-βSN ≧0.95

[0029] As will be described in more detail below, the ratio according to the present invention (i.e., S O-βSN / S B-βSN ≧0.8) can be adjusted in the ceramic substrate by irradiating it with a pulsed laser beam, particularly an ultrashort pulsed laser. This treatment appears to cause a relative increase in the elongated β-silicon nitride crystallites oriented along the longitudinal axis substantially parallel to the thickness direction of the ceramic substrate (i.e., perpendicular to the front or rear surface) in the region near the surface of the ceramic substrate. This is the value of S O-βSN (i.e., I O-βSN(101) / [0.5 x (I O-βSN (200) + I O-βSN (120))]) is greater than S B-βSN 's value, that is, I B-βSN (101) / [0.5 x (I B-βSN (200) + I B-βSN (120))]) and shows an increase, and thus means that the ratio S O-βSN / S B-βSN increases.

[0030] In an exemplary embodiment, the ceramic substrate satisfies the following conditions, at least in the region of the recess. 0.4 ≤ S O-βSN ≤ 2.0 wherein S O-βSN has the above meaning.

[0031] In another exemplary embodiment, the following conditions are satisfied. 0.6 ≤ S O-βSN ≤ 1.3

[0032] Indexing of X-ray diffraction reflections in the X-ray diffraction pattern and diffractogram of β-silicon nitride is known to those skilled in the art. For example, when using Cu-Kα radiation, the (101) reflection appears at a diffraction angle (2θ) of 33.7 ± 1.0°, the (200) reflection appears at a diffraction angle (2θ) of 27.1 ± 1.0°, and the (120) reflection appears at a diffraction angle (2θ) of 36.1 ± 1.0°.

[0033] Optionally, the ceramic substrate may contain one or more metal oxides. These are added, for example, as sintering aids during the manufacture of the ceramic substrate. For example, the ceramic substrate contains one or more of the following oxides: one or more alkaline earth metal oxides such as magnesium oxide, one or more transition metal oxides (for example, one or more rare earth oxides such as yttrium oxide or erbium oxide), silicon oxide (for example, SiO 2 ), or one or more of silicates.

[0034] The ceramic substrate has a thickness in the range of, for example, 0.1 mm to 1.0 mm.

[0035] On the front surface of the ceramic substrate, there is a metal coating including at least one recess such that the surface of the ceramic substrate is exposed by the recess. This metal coating is also called a structured metal coating. The semiconductor component can be attached to the structured metal coating.

[0036] Optionally, the metal coating can also be used on the rear surface of the ceramic substrate. This rear surface metal coating can also optionally include at least one recess through which the surface of the ceramic substrate is exposed. In order to achieve the most efficient heat dissipation possible, it may be preferable that the rear surface metal coating does not include such recesses.

[0037] The metal coatings present on the front surface and optionally the rear surface of the ceramic substrate are, for example, copper coatings or aluminum coatings. The metal coating has a thickness in the range of, for example, 0.05 mm to 1.5 mm, more preferably 0.2 mm to 0.8 mm.

[0038] When the metal coating is a copper coating, it has, for example, a copper content of at least 97% by weight.

[0039] When the metal coating is an aluminum coating, it has, for example, an aluminum content of at least 97% by weight.

[0040] The metal coating can be applied to the front surface and optionally the rear surface of the ceramic substrate using methods known to those skilled in the art.

[0041] For example, a metal foil (e.g., copper foil or aluminum foil) is joined to the front surface of the ceramic substrate by an active metal brazing method.

[0042] In the active metal brazing method, for example, an active metal brazing material is used at a temperature of about 600 to 1,000 °C to connect between a metal foil and a ceramic substrate. Due to their alloy compositions, the active metal brazing materials can wet non-metallic inorganic materials such as ceramic substrates. In addition to main components such as copper, silver, and / or gold, the active metal brazing materials also contain one or more active metals such as Hf, Ti, Zr, Nb, V, Ta, or Ce that can react with a bonding partner (e.g., a ceramic substrate).

[0043] Preferably, a reaction layer obtained from the active metal brazing method exists between a metal coating and the front surface of a ceramic substrate. The reaction layer contains, for example, one or more elements E selected from Hf, Ti, Zr, Nb, V, Ta, and Ce, preferably selected from Hf, Ti, Zr, Nb, and Ce, more preferably selected from Hf, Ti, and Zr RS and is included. A particularly preferred element E in the reaction layer RS is titanium. For example, the element E RS exists in the reaction layer in the form of nitrides, oxynitrides, and / or silicides. For example, the reaction layer contains the element E RS in a total amount of at least 50% by weight. For example, the reaction layer contains nitrides, oxynitrides, and silicides of the element ESR in a total amount of at least 70% by weight, more preferably at least 85% by weight. In a power electronics semiconductor module, the movement of silver may cause problems. Therefore, in some cases, it is preferable that the reaction layer contains silver at a ratio of 5% by weight or less, more preferably 1% by weight or less, or even does not contain silver at all.

[0044] The exposure of the surface of the ceramic substrate is performed, for example, in several steps. First, the metal coating is removed, for example, by etching, and the reaction layer formed during the active metal brazing method is exposed. Next, the exposed reaction layer is removed, for example, by etching or laser ablation. Preferably, the exposed reaction layer is removed using an ultrashort pulse laser (e.g., an IR picosecond or femtosecond laser).

[0045] In order to electrically insulate regions of the metal coating separated from each other by the recesses, it is sufficient to perform material removal by a pulsed laser beam only up to a state where the conductive material has been completely removed in the treated regions, while avoiding structural modification of the β-silicon nitride phase on the surface of the ceramic substrate.

[0046] However, within the scope of the present invention, treatment with an ultrashort pulsed laser not only exposes the surface of the ceramic substrate but also structurally modifies the β-silicon nitride phase on the surface of the ceramic substrate. For example, it has been found that it is advantageous for setting the peak height ratio according to the present invention when a pulsed laser beam having a pulse energy of at least 10 μJ passes over the surface of the ceramic substrate several times.

[0047] Within the scope of the present invention, it is also possible to first expose the surface of the ceramic substrate by a single-step or multi-step etching process and then treat the exposed surface of the ceramic substrate with an ultrashort pulsed laser (for example, an IR femtosecond or picosecond laser) until the peak height ratio according to the present invention is achieved.

[0048] However, for reasons of process efficiency, it may be preferable to use a pulsed laser beam for both exposing the surface of the ceramic substrate and structurally modifying the β-silicon nitride phase on the surface of the ceramic substrate.

[0049] The region of the recesses in the ceramic substrate exhibiting the peak height ratio according to the present invention includes, for example, at least 50%, more preferably at least 70% of the surface of the ceramic substrate exposed by the recesses, or can even include substantially the entire surface of the ceramic substrate exposed by the recesses.

[0050] The exposed surface of the ceramic substrate satisfying the peak height ratio according to the present invention results in improved adhesion strength of the casting compound to the ceramic substrate. Furthermore, the metal-ceramic composite according to the present invention also has high mechanical strength.

[0051] The present invention relates to a semiconductor module comprising: the above-described metal-ceramic composite; and one or more semiconductor components.

[0052] Preferably, the semiconductor module also includes a casting compound that contacts the surface of the ceramic substrate of the metal-ceramic composite exposed by the recess.

[0053] Casting compounds for electronic components are known to those skilled in the art. The casting compound contains, for example, a polymer (e.g., a thermoplastic polymer or a thermosetting polymer). For example, the casting compound optionally contains a cured epoxy resin or silicone resin, polyurethane, or an inorganic cement (e.g., a phosphate cement).

[0054] Measurement method Determination of peak height of diffraction reflection To determine the peak height of diffraction reflection, X-ray diffraction measurements were performed in two configurations.

[0055] In the first measurement, the so-called Bragg-Brentano geometry was used. The peak heights of the reflections (101), (200), and (120) were determined in the diffractogram recorded with this geometry. The peak heights were normalized with respect to the peak height of the (120) reflection.

[0056] Further measurements were performed under grazing incidence (3°). The peak heights of the reflections (101), (200), and (120) were also determined in the diffractogram measured under grazing incidence. The peak heights were normalized with respect to the peak height of the (200) reflection.

[0057] Diffractometer: Stoe & Cie GmbH, two-circuit X-ray powder diffractometer, type Stadi P Focusing: Using a secondary monochromator and a scintillation counter, Bragg-Brentano geometry or grazing incidence angle (3°) X-ray tube: Copper anode Wavelength: 1.54060 Å Cu-Kα Operating voltage: 40 kV Operating current: 30 mA Measurement range: 2θ: 5° - 100° in 0.02° steps, omega: 2.5° - 50° in 0.01 steps GI measurement range: 2θ: 5° - 100° in 0.03° steps, omega: 3° Time / step: 10 seconds

[0058] Adjust the diffractometer and calibrate it using the NIST standard Si(640d). Samples for XRD measurement were cut out in the form of 20×20×0.23 mm platelet in the area of the exposed ceramic substrate.

[0059] Composition of the adhesion promoting layer The composition of the adhesion promoting layer is determined by energy dispersive X-ray spectroscopy (EDX) combined with scanning electron microscopy (SEM-EDX).

[0060] In SEM-EDX, a focused primary electron beam is induced (scanned) point by point on the sample surface. Scattered electrons are detected using a detector, and the number of electrons per pixel results in a grayscale microscopic image of the sample surface. Furthermore, the primary electron beam excites the sample to emit characteristic X-ray radiation, and the elements in the sample and their weight ratios can be determined by analyzing the energy spectrum using an EDX detector. For the inspection, for example, a scanning electron microscope (JSM-6060 SEM, JEOL Ltd) equipped with a silicon drift EDX detector (NORAN, Thermo Scientific Inc) and analysis software (Pathfinder Mountaineer EDS System, for example version 2.8, Thermo Scientific Inc) are used. In the case of scanning electron microscopy, the following settings are used: magnification: 1000 times, acceleration voltage = 15 kV, working distance = 10 mm, spot size (50 - 60) (set to reach 25% + / - 5% of the dead time of the EDX detector). The following settings of the EDX detector were used to detect the EDX spectrum: live time = 30 seconds, speed = automatic, low energy cut-off = 100 keV, high energy cut-off = automatic (following the SEM acceleration voltage).

[0061] The composition of the adhesion promoting layer can be determined both qualitatively (detection of specific elements and phases, for example, metal nitride phases present in the adhesion promoting layer) and quantitatively by SEM-EDX. For example, the measurement is performed at at least 10 points on the adhesion promoting layer.

Example

[0062] Five silicon nitride ceramic substrates from the same product batch were used in the example. The silicon nitride is present substantially in the β phase. S O-βSN / S B-βSN The ratio was determined for each of these substrates. The starting substrates had substantially the same value for the S O-βSN / S B-βSN ratio.

[0063] The S of the starting substrateO-βSN / S B-βSN : 0.63 + / - 0.02

[0064] Four out of five silicon nitride substrates were metallized by the same active metal brazing process under the conditions described below.

[0065] An active metal brazing paste was applied to one surface of the ceramic substrate by screen printing over an area measuring 168 mm × 130 mm and pre-dried at 125 °C for 15 minutes. The active metal brazing paste consisted of 67 wt% copper powder, 19.8 wt% tin powder, 3.7 wt% titanium hydride, and 9.5 wt% organic vehicle. The thickness of the paste after pre-drying was 25 + / - 5 μm. Subsequently, an oxygen-free highly conductive copper film made of copper with a purity of 99.99% and dimensions of 170 mm × 132 mm × 0.3 mm was placed on the pre-dried paste. Next, the resulting arrangement was turned over, and the paste was similarly applied to the opposite side of the ceramic substrate by screen printing, pre-dried, and the copper film was attached to obtain a sandwich arrangement. The sandwich arrangement was loaded with a 1 kg weight and fired at a maximum temperature of 910 °C for 20 minutes and then cooled to room temperature to obtain an unstructured metal-ceramic composite. By manufacturing using the active metal brazing method, an adhesion promoting reaction layer exists between the metal coating and the ceramic substrate. This contains titanium (for example, in the form of a nitride).

[0066] Each of the four metal-ceramic composites was subjected to a first structuring process using an etching solution containing CuCl 2 . The metal coating in the etched area on the front surface of the ceramic substrate was removed substantially completely. However, the reaction layer obtained from the active metal brazing process was not removed by the CuCl 2 -containing etching solution.

[0067] In Comparative Example VB1, the exposed reaction layer was removed using an etching solution containing ammonium fluoride, fluoroboric acid, and hydrogen peroxide.

[0068] In Examples EB1 to EB3 according to the present invention, the exposed reaction layer was removed by laser treatment using a pulsed laser beam from an IR picosecond laser. The energy of the laser pulse was at least 12.5 μJ. In Example EB1, the exposed reaction layer was scanned only once with a pulsed laser beam along a specific scan line. In Examples EB2 and EB3, the scan line was scanned twice with a laser beam, and a higher pulse energy than EB2 was used in EB3.

[0069] For the exposed ceramic surfaces of Examples EB1 to EB3 and Comparative Example VB1 according to the present invention, S O-βSN 、S B-βSN and the ratio S O-βSN / S B-βSN were measured. Subsequently, a casting compound was applied to each of the exposed ceramic surfaces, and the adhesive strength was determined.

[0070] A casting compound was also applied to the unmetallized silicon nitride starting substrate, and the adhesive strength was determined (Comparative Example VB0).

[0071] The adhesive strength was determined as follows. To determine the adhesiveness of the casting compound (silicone), two plates (plate size: 20 × 20 × 0.32 mm) were cut out from each of the exposed areas of the corresponding ceramic substrate. Then, two plates taken from the same ceramic substrate were joined using Sylgard 527 silicone to form a test piece. Since the overlap of both plates was 1 cm, the adhesive surface was always 2 cm 2 . The silicone was cured at 125 °C in air for 2 hours. Each test piece was compressed with a load of 50 g to produce a uniformly thin silicone layer.

[0072] The test pieces thus produced were tested for shear strength (testing machine: model zwicki500, ZwickRoell GmbH&Co.KG). In each case, the maximum shear force was determined.

[0073] The results are summarized in Table 1 below.

[0074]

Table 1

[0075] The treatment of the silicon nitride surface using a pulsed laser caused a structural modification of the β-silicon nitride phase on the surface of the ceramic substrate, as evidenced by the change in the intensity ratio of the (101) reflection to the (200) and (120) reflections.

[0076] This treatment appears to cause a relative increase in the elongated β-silicon nitride crystallites oriented along the longitudinal axis substantially parallel to the thickness direction of the ceramic substrate (i.e., perpendicular to the front or rear surface) in the region near the surface of the ceramic substrate. This is such that the value of S O-βSN shows a greater increase than the value of S B-βSN , and thus, it means that the ratio of S O-βSN / S B-βSN increases.

[0077] The silicon nitride ceramic satisfying the conditions according to the present invention, i.e., S O-βSN / S B-βSN ≧0.8 shows significantly good adhesion strength to the applied casting compound.

Claims

1. 1. A metal-ceramic composite comprising: a ceramic substrate having a front surface and a rear surface and including β-silicon nitride; a metal coating on the front side of the ceramic substrate; the metal coating includes at least one recess, a surface of the ceramic substrate being exposed by the recess; The ceramic substrate satisfies the following conditions at least in the region of the recess: S Ｏ－βＳＮ / S Ｂ－βＳＮ ≧0.8 During the ceremony, S Ｏ－βＳＮ =I Ｏ－βＳＮ (101) / [0.5x(I Ｏ－βＳＮ (200)+I Ｏ－βＳＮ (120))] S Ｂ－βＳＮ =I Ｂ－βＳＮ (101) / [0.5x(I Ｂ－βＳＮ (200)+I Ｂ－βＳＮ (120))] I Ｏ－βＳＮ (101), I Ｏ－βＳＮ (200) and I Ｏ－βＳＮ (120) is the relative peak heights of the (101), (200) and (120) reflections of said β-silicon nitride in an X-ray diffraction pattern measured under grazing incidence of 3° using Cu-Kα radiation, the relative peak heights being normalized to the peak height of the (200) reflection; I Ｂ－βＳＮ (101), I Ｂ－βＳＮ (200) and I Ｂ－βＳＮ (120) is the relative peak heights of the (101), (200) and (120) reflections of said β-silicon nitride in an X-ray diffraction pattern measured in Bragg-Brentano geometry and Cu-Kα radiation, the relative peak heights being normalized to the peak height of the (120) reflection.

2. 2.2≧S Ｏ－βＳＮ / S Ｂ－βＳＮ ≧0.

8.

3. The following conditions are met: 0.4≦S Ｏ－βＳＮ ≦2.0 In the formula, S Ｏ－βＳＮ The metal-ceramic composite according to claim 1 or 2, wherein has the meaning given in claim 1.

4. The metal-ceramic composite according to any one of claims 1 to 3, wherein said metallic coating is a copper or aluminum coating.

5. A reaction layer is present between the ceramic substrate and the metal coating, the reaction layer containing one or more elements E selected from Ti, Hf, Zr, Nb, V, Ta, and Ce. ＲＳ The metal-ceramic composite according to any one of claims 1 to 4, comprising:

6. A semiconductor module, comprising: The metal-ceramic composite according to any one of claims 1 to 5, and one or more semiconductor components.

7. 7. The semiconductor module of claim 6, further comprising a casting compound, said casting compound contacting a surface of said ceramic substrate of said metal-ceramic composite exposed by said recess.

Images