Metal-ceramic composite material

Abstract

The present invention relates to a metal-ceramic composite material comprising: a ceramic substrate comprising a front surface and a back surface and comprising beta-silicon nitride; the metal coating is located on the front face of the ceramic substrate, the metal coating comprises at least one concave part, and the surface of the ceramic substrate is exposed through the concave part.

Description

[0001] The present invention relates to a metal-ceramic composite material which can be used as a ceramic circuit carrier in power electronic devices.

[0002] In power electronic devices, the printed circuit board must be designed for high currents, serve as a carrier for power components such as MOSFETs, and be able to dissipate waste heat quickly.

[0003] Since ceramic materials such as alumina, aluminum nitride, and silicon nitride have a much higher thermal conductivity than the polymers used to produce conventional printed circuit boards, ceramic circuit carriers are often used in power modules.

[0004] Silicon nitride-based ceramic substrates have very high mechanical strength, along with high thermal conductivity, and are therefore very suitable for applications in power electronic devices.

[0005] Silicon nitride can exist in a crystalline structure called the "α-phase" or "β-phase". These two phases differ in their X-ray diffraction patterns. The phase that is stable under normal sintering conditions is the β-phase (also referred to hereinafter as β-silicon nitride). Thus, β-silicon nitride is usually present in silicon nitride-based ceramic substrates.

[0006] β-silicon nitride contains 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 microcrystals in the ceramic body. For example, if most of the acicular microcrystals are oriented such that their longitudinal axes are substantially parallel to the ceramic surface, it may be advantageous for the mechanical strength of the ceramic, while if most of the acicular microcrystals are aligned such that their longitudinal axes are substantially perpendicular to the ceramic surface, it may be more advantageous for the thermal conductivity.

[0007] T. Okuno et al., in "Si substrates with anisotropic thermal conductivity suitable for power module applications (Si 3 N 4 substrates (Si 3 N 4"Substrates with Anisotropic Thermal Conductivity Suitable for Power Module Applications)", PCIM Europe digital days 2021; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, online, 2021, pp. 1-5, which describe ceramic substrates each containing β-silicon nitride, where the substrates differ in the alignment of the elongated β-silicon nitride microcrystals. As the number of microcrystals aligned with their longitudinal axes parallel to the thickness direction of the ceramic substrate (i.e., perpendicular to the front or back) 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:

[0009] N. Chasserio et al., "Ceramic Substrates for High-Temperature Electronic Integration", Journal of Electronic Materials, Vol. 38 (2009), pp. 164-174;

[0010] K. Hirao et al., "High Thermal Conductivity Silicon Nitride Ceramics", Journal of the Korean Ceramic Society, Vol. 49 (2012), pp. 380-384;

[0011] K. Hirao et al., "High Thermal Conductivity

[0012] Silicon Nitride Ceramics)", Journal of the

[0013] Korean Ceramic Society, Volume), Vol. 49 (2012), pp. 380-384;

[0014] Y. Zhou et al., "Development of high-thermal-conductivity silicon nitride ceramics", Journal of Asian Ceramic Societies, 3 (2015), pp. 221-229.

[0015] An overview of methods for producing silicon nitride ceramics with different textures can be found in the following publications, for example:

[0016] X. Zhu and Y. Sakka, "Textured silicon nitride: processing and anisotropic properties", Sci. Technol. Adv. Mater., 9, 2008, 033001.

[0017] Silicon nitride-based ceramic substrates are commercially available, which exhibit a good compromise between high mechanical strength and high thermal conductivity and can be used in electronic components.

[0018] A ceramic circuit carrier contains a ceramic substrate that is provided with metal layers on at least one side, usually on both sides. In the final module, semiconductor components are applied to one of these metal layers, while the metal layer on the opposite side of the ceramic substrate is thermally connected to a heat sink. The ceramic substrate electrically insulates the metal layers from each other.

[0019] It is known to those skilled in the art that a metallized ceramic substrate serving as a ceramic circuit board is produced, for example, by bringing the front and back sides of the ceramic substrate into contact with a metal film (such as a copper film or an aluminum film) and bonding them together. The bonding of the metal foil material is achieved, for example, by eutectic bonding or active metal brazing (AMB). If the metal film is a copper film, eutectic bonding is also referred to as the DCB method or the DBC method (DCB: "direct copper bonding"; DBC: "direct bonded copper"). In the case of an aluminum film, the term "DAB" ("direct aluminum bonding") is also used for eutectic bonding. Metallized ceramic substrates produced using the DCB or AMB process are sometimes also referred to as DCB substrates (alternatively: DBC substrates) or AMB substrates.

[0020] The metallization of silicon nitride substrates is usually carried out by active metal brazing.

[0021] In addition to the main components (such as Cu, Ag or Au), the active metal solder contains one or more elements that can react with the ceramic to form an adhesion-promoting reaction layer (see, for example, Brevier Technische Keramik, chapter 8.2.4.3 (“Active metal brazing”) in the Ceramic Industry Association, pages 203 - 204, 2003, Fahner Verlag). Reactive elements such as hafnium (Hf), titanium (Ti), zirconium (Zr), niobium (Nb), cerium (Ce), tantalum (Ta) and vanadium (V) are used. When metallizing a silicon nitride substrate by active metal brazing, the reaction layer contains, for example, nitrides, oxynitrides and / or silicides of a reactive element (A. et al., “Active metal brazing of copper with aluminum nitride and silicon nitride ceramics”, Keramische Zeitschrift, 63(5), 2011, 334 - 342).

[0022] The metal layer supporting the semiconductor component is structured (for example by etching). Structuring of the AMB substrate can be carried out, for example, in a two-stage process, in which in the first step, the metal layer is first removed in defined areas (for example, using a first etching solution), and then in the second step, the adhesion-promoting layer produced by the active metal brazing process is removed (for example, using a second etching solution). By removing the metal layer in the defined areas, the ceramic substrate is exposed again in these areas.

[0023] Modules based on ceramic circuit carriers used in power electronics devices can be encapsulated as part of the packaging process, for example by embedding the power module into a casting material.

[0024] For example, embedding into the casting material increases the electrical breakdown strength. In addition, the semiconductor component and the metal conductor tracks are protected from moisture and are mechanically stable.

[0025] In the areas exposed by structuring, the ceramic substrate is in direct contact with the casting material. When operating the power module, significant temperature fluctuations can occur. Since the ceramic material and the casting material usually have significantly different coefficients of thermal expansion, these temperature fluctuations cause mechanical stresses to occur at the interface between the ceramic and the casting material. This can in turn cause the casting material to become at least partially detached from the ceramic substrate and form cavities. Moisture penetrating these cavities can damage the power module. In addition, the electrical breakdown strength may be significantly reduced, at least locally.

[0026] As described above, silicon nitride-based ceramic substrates are used as circuit carriers in power electronic devices due to their very high mechanical strength and high thermal conductivity. To fully utilize their potential as circuit carriers, it is desirable that after being embedded in a casting material, there is a high adhesion strength between the casting material and the silicon nitride surface.

[0027] An object of the present invention is to provide a ceramic substrate containing metallized silicon nitride, the exposed surface of which allows bonding with a casting material to form a high adhesion strength.

[0028] This object is achieved by a metal-ceramic composite material containing:

[0029] - A ceramic substrate, which includes a front side and a back side and contains β-silicon nitride,

[0030] - A metal coating, which is located on the front side of the ceramic substrate,

[0031] wherein the metal coating includes at least one recess, and the surface of the ceramic substrate is exposed through the recess,

[0032] wherein the ceramic substrate satisfies the following condition at least in the region of the recess:

[0033] S O-βSN / S B-βSN ≥0.8

[0034] where

[0035] S O-βSN =I O-βSN (101) / [0.5×(I O-βSN (200)+I O-βSN (120))]

[0036] S B-βSN =I B-βSN (101) / [0.5×(I B-βSN (200)+I B-βSN (120))]

[0037] I O-βSN (101), I O-βSN (200) and I O-βSN (120) are the relative peak heights of the (101) reflection, (200) reflection and (120) reflection of the β-silicon nitride in the X-ray diffraction pattern measured at a grazing incidence of 3°

[0038] where the relative peak height is normalized to the peak height of the (200) reflection.

[0039] I B-βSN(101), I B-βSN (200) and I B-βSN (120) is the relative peak height of the (101) reflection, (200) reflection, and (120) reflection of this β-silicon nitride in the X-ray diffraction pattern measured by Bragg-Brentano geometry and Cu-Kα radiation, where the relative peak height is normalized to the peak height of the (120) reflection.

[0040] 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 microcrystals. As the number of microcrystals aligned with their longitudinal axes 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 and the intensity ratio of the (101) reflection to the (200) reflection and (120) reflection also increase. The peak height (normalized to the height of the base peak) in the X-ray diffraction pattern can be used as a measure of the intensity of the reflection.

[0041] Glancing-incidence X-ray diffraction is used to examine the structure of the region near the surface of the sample, while X-ray diffraction using Bragg-Brentano geometry provides structural information averaged over the entire irradiated volume of the sample.

[0042] Within the scope of the present invention, it has surprisingly been found that if the ratio defined above is satisfied (i.e., S

[0043] / S O-βSN / S B-βSN ≥ 0.8), then the adhesion strength of the casting material to the ceramic substrate can be improved.

[0044] For example:

[0045] S O-βSN / S B-βSN ≥ 0.95

[0046] In one exemplary embodiment, the following relationship is satisfied:

[0047] 2.2 ≥ S O-βSN / S B-βSN ≥ 0.8

[0048] In another exemplary embodiment, the following relationship is satisfied:

[0049] 2.2 ≥ S O-βSN / S B-βSN ≥ 0.95

[0050] In another exemplary embodiment, the following relationship is satisfied:

[0051] 1.75 ≥ S O-βSN / S B-βSN≥0.95

[0052] 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 a ceramic substrate by irradiating with a pulsed laser beam, in particular an ultrashort pulsed laser. This treatment appears to cause a relative increase in elongated β-silicon nitride microcrystals in the region near the surface of the ceramic substrate, and these microcrystals are oriented with their longitudinal axes substantially parallel to the thickness direction of the ceramic substrate (i.e., perpendicular to the front or back surface). This in turn means that the value of S O-βSN (i.e., I O-βSN (101) / [0.5×(I O-βSN (200)+I O-βSN (120))]) shows a stronger increase than the value of S B-βSN (i.e., I B-βSN (101) / [0.5×(I B-βSN (200)+I B-βSN (120))]), and thus the ratio S O-βSN / S B-βSN increases.

[0053] In one exemplary embodiment, the ceramic substrate satisfies the following conditions at least in the region of the recess:

[0054] 0.4≤S O-βSN ≤2.0,

[0055] where S O-βSN has the meaning given above.

[0056] In another exemplary embodiment, the following conditions are satisfied:

[0057] 0.6≤S O-βSN ≤1.3

[0058] The indexing of X-ray diffraction reflections in the X-ray diffraction pattern and diffraction diagram of β-silicon nitride is known to those skilled in the art. For example, 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°.

[0059] Optionally, the ceramic substrate may contain one or more metal oxides. These oxides are added, for example, as sintering aids during the production 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 (e.g., one or more rare earth oxides such as yttrium oxide or erbium oxide); silicon oxide (e.g., SiO 2 ) or silicate.

[0060] The ceramic substrate has, for example, a thickness in the range of 0.1 mm to 1.0 mm.

[0061] A metal coating is present on the front side of the ceramic substrate, the metal coating including at least one recess such that the surface of the ceramic substrate is exposed through the recess. The metal coating is also referred to as a structured metal coating. A semiconductor component may be attached to the structured metal coating.

[0062] Optionally, the metal coating may also be used on the back side of the ceramic substrate. The back side metal coating may also optionally include at least one recess through which the surface of the ceramic substrate is exposed. To achieve the most efficient heat dissipation possible, it may be preferable that the back side metal coating does not include such recesses.

[0063] The metal coating present on the front side and optionally on the back side of the ceramic substrate is, for example, a copper coating or an aluminum coating. The metal coating has, for example, a thickness in the range of 0.05 mm to 1.5 mm, more preferably 0.2 mm to 0.8 mm.

[0064] If the metal coating is a copper coating, it has, for example, a copper content of at least 97 wt%.

[0065] If the metal coating is an aluminum coating, it has, for example, an aluminum content of at least 97 wt%.

[0066] Methods known to those skilled in the art can be used to apply the metal coating to the front side and optionally the back side of the ceramic substrate.

[0067] For example, a metal foil (e.g., a copper foil or an aluminum foil) is bonded to the front side of the ceramic substrate by active metal brazing.

[0068] In active metal brazing, for example, an active metal solder is used to form a connection between the metal foil and the ceramic substrate at a temperature of about 600 °C to 1000 °C. Due to their alloy composition, active metal solders are able to wet non-metallic inorganic materials such as ceramic substrates. In addition to the main components such as copper, silver, and / or gold, active metal solders also contain one or more active metals such as Hf, Ti, Zr, Nb, V, Ta, or Ce, which can react with the bonding partner (e.g., the ceramic substrate).

[0069] Preferably, a reaction layer produced by active metal brazing is present between the metal coating and the front side of the ceramic substrate. The reaction layer contains, for example, one or more elements E RS , selected from Hf, Ti, Zr, Nb, V, Ta, and Ce, preferably selected from Hf, Ti, Zr, Nb, and Ce, and more preferably selected from Hf, Ti, and Zr. Element E particularly preferred in the reaction layer RS is titanium. For example, element E RS is present in the reaction layer in the form of nitrides, oxynitrides, and / or silicides. For example, the reaction layer contains a total of at least 50% by weight of element E RS . For example, the reaction layer contains a total of at least 70% by weight, more preferably at least 85% by weight, of nitrides, oxynitrides, and silicides of element ESR. In a semiconductor module of a power electronic device, the migration of silver may cause problems. Therefore, it may be preferred that the reaction layer contains silver in a proportion of not more than 5% by weight, more preferably not more than 1% by weight, or even contains no silver.

[0070] The surface of the exposed ceramic substrate is carried out, for example, in multiple steps. First, for example, the metal coating is removed by etching, and the reaction layer formed during active metal brazing is exposed. Then, the exposed reaction layer is removed, for example, by etching or laser ablation. Preferably, an ultrashort pulse laser (e.g., an IR picosecond or femtosecond laser) is used to remove the exposed reaction layer.

[0071] In order to electrically insulate the regions of the metal coating separated from each other by the recesses, it is sufficient to perform material removal only using a pulsed laser beam until the conductive material in the processed region has been completely removed, but structural changes of the β-silicon nitride phase on the surface of the ceramic substrate are avoided.

[0072] However, within the scope of the present invention, the treatment using an ultrashort pulse laser not only exposes the surface of the ceramic substrate but also structurally changes the β-silicon nitride phase on the surface of the ceramic substrate. It has been found that if the pulsed laser beam passes over the surface of the ceramic substrate multiple times, where the laser pulse has a pulse energy of, for example, at least 10 μJ, it is advantageous for setting the peak height ratio according to the present invention.

[0073] Within the scope of the present invention, the surface of the ceramic substrate can also be first exposed by a single-stage or multi-stage etching process, and then the exposed surface of the ceramic substrate is treated with an ultrashort pulse laser (e.g., an IR femtosecond laser or picosecond laser) until the peak height ratio according to the present invention is achieved.

[0074] However, for reasons of process efficiency, it may be preferred to use a pulsed laser beam to perform both the exposure of the surface of the ceramic substrate and the structural change of the β-silicon nitride phase on the surface of the ceramic substrate.

[0075] The region of the ceramic substrate presenting the recesses according to the peak height ratio of the present invention includes, for example, at least 50%, more preferably at least 70% of the surface of the ceramic substrate exposed through the recesses, or may even include substantially the entire surface of the ceramic substrate exposed through the recesses.

[0076] The exposed surface of the ceramic substrate satisfying the peak height ratio according to the present invention results in an improved adhesion strength between the casting material and the ceramic substrate. In addition, the metal-ceramic composite according to the present invention also has high mechanical strength.

[0077] The present invention also relates to a semiconductor module comprising: the above metal-ceramic composite, one or more semiconductor components.

[0078] Preferably, the semiconductor module further comprises a casting material, wherein the casting material contacts the surface of the ceramic substrate of the metal-ceramic composite exposed through the recesses.

[0079] Casting materials for electronic components are known to those skilled in the art. The casting material contains, for example, a polymer (e.g., a thermoplastic polymer or a thermosetting polymer). For example, the casting material contains an optionally cured epoxy resin or silicone resin, polyurethane, or inorganic cement (e.g., phosphate cement).

[0080] Measurement method

[0081] Determination of peak height of diffractive reflection

[0082] X-ray diffraction measurements were carried out in two arrangements to determine the peak heights of the diffraction reflections.

[0083] In the initial measurement, the so-called Bragg-Brentano geometry was used. The peak heights of the reflections (101), (200), and (120) were determined in the diffraction pattern recorded using this geometry. The peak heights were normalized to the peak height of the (120) reflection.

[0084] Further measurements were carried out at a grazing incidence angle of 3°. The peak heights of the reflections (101), (200), and (120) were also determined in the diffraction pattern measured at the grazing incidence. The peak heights were normalized to the peak height of the (200) reflection.

[0085] Diffractometer: Stoe & Cie GmbH, 2-circuit X-ray powder diffractometer, type Stadi P

[0086] Focusing: Bragg-Brentano geometry or grazing incidence angle of 3°, with a secondary monochromator and a scintillation counter

[0087] X-ray tube: copper anode

[0088] Wavelength: Cu-Kα

[0089] Operating voltage: 40 kV

[0090] Operating current: 30 mA

[0091] Measurement range: 2θ: 5° - 100°, step size 0.02°; ω: 2.5° - 50°, step size 0.01°

[0092] GI measurement range: 2θ: 5° - 100°, step size 0.03°; ω: 3°

[0093] Time / step: 10 s

[0094] The diffractometer was adjusted and calibrated using the NIST standard Si(640d). Samples for XRD measurement were cut out in the form of 20 mm × 20 mm × 0.23 mm thin slices in the area of the exposed ceramic substrate.

[0095] Composition of adhesion promoting layer

[0096] The composition of the adhesion-promoting layer was determined by combining energy-dispersive X-ray spectroscopy (EDX) with scanning electron microscopy (SEM-EDX).

[0097] In SEM-EDX, a focused primary electron beam is rastered (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 microscopic image of the sample surface displayed in grayscale. In addition, 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 examination, for example, a scanning electron microscope (JSM-6060 SEM, JEOL Ltd) with a silicon drift EDX detector (NORAN, Thermo Scientific Inc) and analysis software (Pathfinder Mountaineer EDS System, version 2.8, for example, Thermo Scientific Inc) was used. For scanning electron microscopy, the following settings were used: magnification: 1000 times, acceleration voltage = 15 kV, working distance = 10 mm, spot size (50 - 60) (set to achieve 25% + / - 5% of the dwell time of the EDX detector). The following settings of the EDX detector were used to detect the EDX spectrum: real time = 30 s, rate = automatic, low energy cut-off = 100 keV, high energy cut-off = automatic (per SEM acceleration voltage).

[0098] With SEM-EDX, the composition of the adhesion-promoting layer can be determined both qualitatively (detecting certain elements and phases, such as the metal nitride phase present in the adhesion-promoting layer) and quantitatively. For example, the measurement is carried out at at least 10 points on the adhesion-promoting layer. Example

[0099] Five silicon nitride ceramic substrates from the same product batch were used for the example. The silicon nitride is present substantially in the β-phase. The ratio S O-βSN / S B-βSN was determined for each of these substrates. The starting substrates had substantially the same S O-βSN / S B-βSN ratio value.

[0100] The S O-βSN / S B-βSN of the starting substrates: 0.63 + / - 0.02

[0101] Four of the five silicon nitride substrates were metallized by the same active metal brazing process under the following conditions.

[0102] On one of the sides of the ceramic substrate, an active metal brazing paste was applied by screen printing over an area measured at 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 carrier. The thickness of the pre-dried paste was 25 μm + / - 5 μm. Subsequently, a copper film made of oxygen-free high-conductivity copper with a purity of 99.99% and dimensions of 170 mm × 132 mm × 0.3 mm was placed on the pre-dried paste. Then the resulting arrangement was flipped, the paste was similarly applied to the opposite side of the ceramic substrate by screen printing, pre-dried and assembled using the copper film to obtain a sandwich arrangement. The sandwich arrangement was weighted with a 1 kg weight, fired at a maximum temperature of 910 °C for 20 minutes and then cooled to room temperature to obtain an unstructured metal-ceramic composite. Due to the production by active metal brazing, an adhesion-promoting reaction layer exists between the metal coating and the ceramic substrate. It contains titanium (e.g., in the form of a nitride).

[0103] 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 side of the ceramic substrate was substantially completely removed. However, the reaction layer produced by the active metal brazing process was not removed by the etching solution containing CuCl 2 .

[0104] In Comparative Example VB1, an etchant containing ammonium fluoride, fluoboric acid, and hydrogen peroxide was used to remove the exposed reaction layer.

[0105] In Examples EB1 to EB3 according to the present invention, the exposed reaction layer was removed by laser treatment with 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 the pulsed laser beam along the designated scan line. In Examples EB2 and EB3, the scan line was scanned twice with the laser beam, where a higher pulse energy was used in EB3 than in EB2.

[0106] The S of the exposed ceramic surfaces of Examples EB1 to EB3 according to the present invention and Comparative Example VB1 was measured O-βSN S B-βSN and the ratio S O-βSN / S B-βSN . Subsequently, a casting material was applied to each of the exposed ceramic surfaces, and the adhesion strength was measured.

[0107] The casting material was also applied to the unmetallized silicon nitride starting substrate, and the adhesion strength was measured (Comparative Example VB0).

[0108] The adhesion strength was measured as follows:

[0109] To determine the adhesion of the casting material (silicone), two plates (plate size: 20 mm × 20 mm × 0.32 mm) were cut out from each of the exposed areas of the corresponding ceramic substrate. Then, the two plates obtained from the same ceramic substrate were bonded with Sylgard 527 silicone to form a specimen. The overlap of the two plates was 1 cm, such that the adhesive surface was always 2 cm 2 . The silicone was cured in air at 125 °C for 2 hours. Each specimen was compressed with a weight of 50 g to produce a uniform thin silicone layer.

[0110] The shear strength of the specimens thus produced was tested (testing machine: model zwicki500, ZwickRoell GmbH&Co.KG). The maximum shear force was measured in each case.

[0111] The results are summarized in Table 1 below.

[0112] Table 1: S of silicon nitride ceramics O-βSN , S B-βSN and ratio S O-βSN / S B-βSN and between the silicon nitride surface and the mold material Adhesion strength

[0113] Examples <![CDATA[S B-βSN > <![CDATA[S O-βSN > <![CDATA[S O-βSN / S B-βSN > Maximum adhesion strength [N] VB0 0.59 0.37 0.63 2.9 VB1 0.51 0.36 0.71 2.8 IE1 0.61 0.52 0.85 5.4 IE2 0.65 0.70 1.08 15.1 IE3 0.73 0.91 1.25 19.1

[0114] Treating the surface of silicon nitride with pulsed laser causes a structural change 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) reflection and the (120) reflection.

[0115] This treatment seems to cause a relative increase in the elongated β-silicon nitride microcrystals in the region near the surface of the ceramic substrate, and these microcrystals are oriented with their longitudinal axes substantially parallel to the thickness direction of the ceramic substrate (i.e., perpendicular to the front or back surface). This in turn means that the value of S O-βSN shows a greater increase than the value of S B-βSN , and thus the ratio S O-βSN / S B-βSN increases.

[0116] Silicon nitride ceramics that meet the conditions according to the present invention (i.e., S O-βSN / S B-βSN ≥0.8) show significantly better adhesion strength to the applied casting material.

Claims

1. A metal-ceramic composite material, comprising: - a ceramic substrate comprising a front side and a back side and containing β-silicon nitride, a metal coating, the metal coating being located on the front side of the ceramic substrate, wherein the metal coating comprises at least one recess and the surface of the ceramic substrate is exposed through 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 in 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) is the (101) reflection of the β-silicon nitride in the X-ray diffraction pattern measured with Cu-Kα radiation at 3° grazing incidence, The relative peak heights of the (200) reflection and the (120) reflection, wherein the relative peak heights are 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 height of the (101) reflection, the (200) reflection and the (120) reflection of the β-silicon nitride in the X-ray diffraction pattern measured using Bragg-Brentano geometry and Cu-Kα radiation, wherein the relative peak heights are normalized to the peak height of the (120) reflection.

2. The metal-ceramic composite material according to claim 1, wherein: 2.2≥S O-βSN / S B-βSN ≥0.8。 3. The metal-ceramic composite material according to claim 1 or claim 2, wherein the following conditions are met: 0.4≤S O-βSN ≤2.0， Where S O-βSN has the meaning given in claim 1.

4. The metal-ceramic composite material according to any one of the preceding claims, wherein the metal coating is a copper or aluminum coating.

5. The metal-ceramic composite material according to any one of the preceding claims, wherein there is a reaction layer between the ceramic substrate and the metal coating, wherein the reaction layer contains one or more elements selected from Ti, Hf, Zr, Nb, V, Ta and Ce. RS .

6. A semiconductor module, comprising: The metal-ceramic composite material according to any one of claims 1 to 5, One or more semiconductor components. 7 . The semiconductor module according to claim 6 , further comprising a mold material, wherein the mold material contacts the surface of the ceramic substrate of the metal-ceramic composite material exposed through the recess.