Metal-ceramic composite

Abstract

To provide a metalized silicon nitride-containing ceramic substrate having improved moisture protection.SOLUTION: A metal-ceramic composite comprises: a ceramic substrate comprising a front side and a rear side and containing silicon nitride; and a metal coating on the front side of the ceramic substrate, where the metal coating has at least one recess, and a surface of the ceramic substrate is exposed by the recess. The ceramic substrate shows an Si2p signal in the range of 96 to 107 eV in an energy spectrum recorded by X-ray photoelectron spectroscopy at least in the region of the recess. The Si2p signal has the following: one or more peaks that each have a maximum in the range of 98.0 to 100.0 eV; one or more peaks that each have a maximum in the range of 101.0 to 102.2 eV; and one or more peaks that each have a maximum in the range of 102.5 to 104.0 eV.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-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.

[0006] 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.

[0007] A ceramic circuit carrier has a ceramic substrate, and a metal layer is provided on at least one, usually both, of its 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.

[0008] The production of metallized ceramic substrates that function as ceramic circuit boards, which is known to those skilled in the art, is carried out, for example, by bringing the front and back 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 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 process or the AMB process are sometimes called DCB substrates (or DBC substrates) or AMB substrates.

[0009] The metallization of silicon nitride substrates is usually carried out by the active metal brazing method.

[0010] The active metal brazing filler metal contains one or more elements that can react with the ceramic to form an adhesion promoting reaction layer in addition to a main component such as Cu, Ag, or Au (see, for example, Chapter 8.2.4.3 of Brevier Technische Keramik, Verband der Keramischen Industrie eV, 2003, Fahner Verlag, “Active metal brazing,” 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 element (A. Ponicke et al., “Active metal brazing of copper with aluminum nitride and silicon nitride ceramics,” Keramische Zeitschrift, 63(5), 2011, 334-342).

[0011] The metal layer carrying the semiconductor components contains one or more recesses and is thus also referred to as a structured metal coating. By structuring, for example, metal conductor tracks are formed on the ceramic substrate. The adjacent conductor tracks are spatially separated by the recesses and are thus electrically insulated from each other. 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 and optionally the adhesion promoting layer, the ceramic substrate is exposed again in defined regions.

[0012] 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.

[0013] For example, by embedding in a casting compound, the dielectric breakdown strength is increased. Furthermore, the semiconductor components and metal conductor tracks are protected from moisture and mechanically stabilized.

[0014] 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 peeled off from the ceramic substrate, forming voids. Moisture entering these voids can damage the power module. Furthermore, the dielectric breakdown strength can be significantly reduced, at least locally. This is particularly problematic when moisture condenses in one of the recesses in the metal coating separating adjacent conductor tracks or chip carrier regions from each other.

[0015] As already mentioned 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.

[0016] The object of the present invention is to provide a metallized silicon nitride-containing ceramic substrate with improved protection from moisture. In particular, protection from moisture should still be provided even when the casting compound peels off from the ceramic surface in the region of the recesses of the metal coating.

[0017] This object is achieved by a ceramic substrate having a front surface and a rear surface and containing silicon nitride, and a metal coating that is present on the front surface of the ceramic substrate, has at least one recess, and the surface of the ceramic substrate is exposed by the recess, and includes the ceramic substrate exhibits a Si2p signal in the range of 96 to 107 eV in the energy spectrum recorded by X-ray photoelectron spectroscopy (hereinafter also referred to as the XPS spectrum) at least in the region of the recess, the Si2p signal is the following one or more peaks each having a maximum value in the range of 98.0 to 100.0 eV, one or more peaks each having a maximum value in the range of 101.0 to 102.2 eV, one or more peaks each having a maximum value in the range of 102.5 to 104.0 eV, and is achieved by a metal-ceramic composite.

[0018] The signal of an element in the XPS spectrum is affected by its oxidation state and its chemical environment (e.g., its chemical bonding partner). For example, if the Si atoms present in the ceramic substrate have a uniform oxidation state and a consistent chemical environment, a Si2p signal with a relatively narrow half-width should be expected in the XPS spectrum. This applies to conventional silicon nitride-based ceramic substrates. Even after contact with an etching medium, for example, when removing a metal coating on silicon nitride, the XPS spectrum usually shows a Si2p signal with a small half-width.

[0019] Within the scope of the present invention, it has been recognized that the treatment of a ceramic substrate by an ultrashort pulse laser can result in a significant increase in the hydrophobicity of the treated silicon nitride surface. Thereby, for example, it becomes clear that the contact angle with water increases significantly compared to an untreated silicon nitride ceramic or a silicon nitride ceramic contacted with an etching medium. Thereby, the protection of the silicon nitride ceramic from moisture is improved.

[0020] Furthermore, within the scope of the present invention, in the Si2p signal of the XPS spectrum of the silicon nitride surface hydrophobized by laser treatment, it has been recognized that additional peaks appear that are not present in the Si2p signal of the untreated silicon nitride ceramic nor in the Si2p signal of the silicon nitride ceramic treated with the etching medium.

[0021] In the XPS spectra of the untreated silicon nitride ceramic and the silicon nitride ceramic contacted with the etching medium, the Si2p signal shows substantially only one peak, and its maximum value is in the range of 101.0 to 102.2 eV. In the XPS spectrum of the silicon nitride ceramic treated with a pulsed laser and showing a significantly high water contact angle as a result of this treatment, additional peaks are observed in the Si2p signal, and its maximum values are in the ranges of 98.0 to 100.0 eV and 102.5 to 104.0 eV.

[0022] For example, in the ranges of 98.0 to 100.0 eV, 101.0 to 102.2 eV, and 102.5 to 104.0 eV, there are at least one peak, but no more than two peaks, having a maximum value within the relevant range.

[0023] In a further exemplary embodiment, in the ranges of 98.0 to 100.0 eV, 101.0 to 102.2 eV, and 102.5 to 104.0 eV, there is only a single peak having a maximum value within the relevant range.

[0024] In an exemplary embodiment, the following applies: I 1 / I ges ≥ 0.02, 2.0 ≤ I 2 / I 1 ≤ 8.0, provided that (I 1 + I 2 ) / I ges ≤ 0.85, (I 1 + I 2 + I 3 ) / I gesis ≧0.95, wherein, I ges is the total intensity of the Si2p signal, I 1 is the total intensity of the peaks each having a maximum value in the range of 98.0 to 100.0 eV, I 2 is the total intensity of the peaks each having a maximum value in the range of 101.0 to 102.2 eV, I 3 is the total intensity of the peaks each having a maximum value in the range of 102.5 to 104.0 eV.

[0025] The total intensity I of the Si2p signal ges is obtained from the sum of the intensities of all the peaks constituting the Si2p signal.

[0026] The intensity of a peak is the area under that peak.

[0027] When there is only one peak having a maximum value in the range of 98.0 to 100.0 eV in the Si2p signal, the total intensity I 1 corresponds to the intensity of this peak. When there are a total of two peaks each having a maximum value in the range of 98.0 to 100.0 eV, the total intensity I 1 corresponds to the sum of the intensities of the two peaks. The total intensities I 2 and I 3 are determined in the same manner in the ranges of 101.0 to 102.2 eV and 102.5 to 104.0 eV.

[0028] For example, the following applies: I 1 / I ges ≧0.05, 2.5≦I 2 / I 1 ≦7.0, provided that (I 1 +I 2 ) / I ges ≦0.80, (I 1 +I 2 +I 3 ) / I ges ≧0.95.

[0029] In a further exemplary embodiment, the following applies: 2.0 ≤ I 2 / I 1 ≤ 8.0 0.40 ≤ (I 1 + I 2 ) / I ges ≤ 0.85, (I 1 + I 2 + I 3 ) / I ges ≥ 0.95.

[0030] For example, the following applies: 2.5 ≤ I 2 / I 1 ≤ 7.0 0.50 ≤ (I 1 + I 2 ) / I ges ≤ 0.80, (I 1 + I 2 + I 3 ) / I ges ≥ 0.95.

[0031] In a further exemplary embodiment, the following applies: 0.05 ≤ I 1 / I ges ≤ 0.20, 0.20 ≤ I 2 / I ges ≤ 0.70, (I 1 + I 2 + I 3 ) / I ges ≥ 0.95.

[0032] For example, the ceramic substrate contains at least 70% by weight, more preferably at least 80% by weight, of silicon nitride.

[0033] The silicon nitride is present, for example, in the β-phase (β-silicon nitride).

[0034] 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 may contain 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.

[0035] The ceramic substrate has a thickness in the range of, for example, 0.1 mm to 1.0 mm.

[0036] 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.

[0037] 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 for the rear surface metal coating not to include such recesses.

[0038] 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.

[0039] When the metal coating is a copper coating, it has, for example, a copper content of at least 97 wt%, more preferably at least 99 wt%.

[0040] The metal coating, when it is an aluminum coating, has, for example, an aluminum content of at least 97% by weight, more preferably at least 99% by weight.

[0041] The metal coating can be applied to the front surface and optionally the back surface of the ceramic substrate using methods known to those skilled in the art.

[0042] For example, a metal foil (e.g., a copper foil or an aluminum foil) is joined to the front surface of the ceramic substrate by an active metal brazing method.

[0043] In the active metal brazing method, for example, an active metal brazing material is used at a temperature of about 600 - 1,000 °C to establish a connection between the metal foil and the ceramic substrate. Due to their alloy composition, 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 the ceramic substrate to form a reaction layer.

[0044] Preferably, a reaction layer obtained from the active metal brazing method is present between the metal coating and the front surface of the 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 including. Particularly preferred element E 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 element E RSIt contains at least 50% by weight in total. For example, the reaction layer contains nitrides, oxynitrides, and silicides of elemental 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 can cause problems. Therefore, the reaction layer preferably contains silver at a ratio of 5% by weight or less, more preferably 1% by weight or less, or even preferably does not contain silver.

[0045] The exposure of the surface of the ceramic substrate is carried out in several steps, for example. 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 (for example, an IR picosecond or femtosecond laser).

[0046] In order to electrically insulate the regions of the metal coating separated by the recesses, it is sufficient to perform material removal by a pulsed laser only for a time or under such conditions until the conductive material is completely removed in the treated region while avoiding the modification of the silicon nitride on the surface of the ceramic substrate.

[0047] However, within the scope of the present invention, the treatment by a pulsed laser not only exposes the surface of the ceramic substrate but also modifies the silicon nitride on the surface of the ceramic substrate. As a result of this modification, the ceramic substrate exhibits an Si2p signal having additional peaks with maxima in the ranges of 98.0 to 100.0 eV and 102.5 to 104.0 eV in the XPS spectrum, at least in the region of the recesses. For the production of a metal-ceramic substrate having an Si2p signal according to the present invention in the XPS spectrum, the pulses of the laser beam are at least 2 J / cm 2 , for example, 2 J / cm 2 ~7 J / cm 2It has been proven to be advantageous when having an energy density within a certain range. The pulse frequency of the laser beam is, for example, 1000 kHz. The region of the ceramic substrate showing the Si2p signal according to the present invention can, for example, constitute at least 50%, more preferably at least 70% of the surface of the ceramic substrate exposed by the recess, or even can constitute substantially the entire surface of the ceramic substrate exposed by the recess.

[0048] Within the scope of the present invention, it is also possible to first expose the surface of the ceramic substrate by a one-step or multi-step etching process, and then process the exposed surface of the ceramic substrate with a pulsed laser beam until the Si2p signal according to the present invention is realized in the XPS spectrum.

[0049] However, for reasons of method efficiency, it may be preferable to use a pulsed laser both for exposing the surface of the ceramic substrate and for modifying the silicon nitride on the surface of the ceramic substrate.

[0050] The exposed surface of the ceramic substrate having the Si2p signal according to the present invention in the XPS spectrum shows a higher water contact angle. This provides better protection of the metal-ceramic composite from moisture.

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

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

[0053] The casting compound for electronic components is 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 contains optionally cured epoxy resin or silicone resin, polyurethane, or inorganic cement (e.g., phosphate cement).

[0054] Measurement method Measurement of XPS spectrum The recording and evaluation of the XPS energy spectrum were performed as follows.

[0055] In the preparation for the measurement using X-ray photoelectron spectroscopy, the ceramic sample was exposed Si 3 N 4The sample pieces were cut with a side length of 2(±0.1) cm × 2(±0.1) cm so that a ceramic region could be obtained. Dust was removed from the sample pieces by blowing nitrogen gas onto them. The sample pieces were adhered to a sample holder using non-conductive adhesive tape. X-ray photoelectron spectra were recorded with a PHI 5800 ESCA manufactured by Physical Electronics using a Mg anode (monochromatic Kα = 1.253 keV) as the radiation source. First, an overview spectrum (range 0 - 1400 eV) of the sample pieces was recorded. Conclusions were drawn about the elements present on the inspected upper surface of the sample pieces from the overview spectrum. Next, detailed spectra of the sample pieces were recorded in the energy range where signals could be identified in the overview spectrum. To record the detailed spectra, an X-ray beam (diameter 200 μm, 50 W at 15 kV, measurement time: 25 - 40 minutes (e.g., 30 minutes), integration time of 20 ms per measurement point) was used, the peak-to-noise setting was enabled, and a neutralizer (a combination of Ar+ and e- with low kinetic energy) was used. The spectra were evaluated using the analysis software CasaXPS (version 5 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. The Shirley function was used for background correction. Peaks were generated from the obtained signals using the analysis software. The number of peaks was adjusted based on a fitting model from the literature (XPS-NIST10 database), and the peaks were assigned to elements or compounds. Using the analysis software, the peak areas of the generated peaks were calculated taking into account the relative sensitivity coefficients.

[0056] Composition of the adhesion promoting layer The composition of the adhesion promoting layer was determined by energy-dispersive X-ray spectroscopy (EDX) combined with scanning electron microscopy (SEM-EDX).

[0057] 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, version 2.8, for example, Thermo Scientific Inc) are used. In the case of the scanning electron microscope, 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 are 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).

[0058] The composition of the adhesion promoting layer can be determined both qualitatively (detection of specific elements and phases, e.g., metal nitride phases present in the adhesion promoting layer) and quantitatively by SEM-EDX. For example, the measurement is performed at least at 10 points on the adhesion promoting layer.

Example

[0059] Five individual silicon nitride substrates (S1, S2, S3, S4, and S5) were separated from a silicon nitride starting substrate having a predetermined breaking point for separation. The ceramic substrates S1 - S5 had matching dimensions (174 mm × 139 mm × 0.32 mm).

[0060] The ceramic substrate S1 was used in Comparative Example 1 (VB1), the ceramic substrate S2 was used in Example 1 (EB1) according to the present invention, the ceramic substrate S3 was used in Example 2 (EB2) according to the present invention, and the ceramic substrate S4 was used in Comparative Example VB2.

[0061] For each of the individual silicon nitride substrates S1 to S4, the Si2p signal in the XPS spectrum was measured in the region of the front surface that was exposed again after metallization. The XPS-Si2p signal was also measured in the corresponding region on the ceramic surface of substrate S5.

[0062] In each of these substrates S1 to S5, the Si2p signal in the XPS spectrum showed only one peak. The maximum values of these peaks were substantially the same and were 101.8 + / - 0.1 eV.

[0063] The silicon nitride substrates were metallized by the same active metal brazing process under the conditions described below.

[0064] On one surface of the ceramic substrate, an active metal brazing paste was applied by screen printing to an area of 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%, dimensions of 170 mm × 132 mm × 0.3 mm, was placed on the pre-dried paste. Next, the obtained arrangement was turned over, 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 by the active metal brazing method, an adhesion promoting reaction layer exists between the metal coating and the ceramic substrate. The reaction layer contains titanium (for example, in the form of a nitride).

[0065] Each of the three metal-ceramic composites was subjected to a first structuring process using an etching solution containing CuCl 2 . The metal coating of the etched area on the front surface of the ceramic substrate was removed. However, the reaction layer obtained from the active metal brazing process was not removed by the CuCl 2 -containing etching solution.

[0066] In Comparative Example VB1, the exposed reaction layer was removed using an etching solution containing ammonium fluoride, fluoroboric acid, and hydrogen peroxide.

[0067] In Examples EB1 and EB2 according to the present invention and Comparative Example VB2, the exposed reaction layer was removed by treatment with an ultrashort pulse laser. The laser pulses in Examples EB1 and EB2 according to the present invention had energy densities of 2 J / cm 2 and 4 J / cm 2 , while in Comparative Example VB2, pulses having an energy density of 9 J / cm 2 were used. The pulse frequency was 1000 kHz for each.

[0068] XPS spectra were recorded on the exposed ceramic surfaces of Examples EB1 to EB2 according to the present invention and Comparative Examples VB1 and VB2, and the contact angles with water were determined.

[0069] The contact angle was determined using an OCA 15EC contact angle measuring device manufactured by Dataphysics. Three test liquids were used for the determination: distilled water, CH 2 I 2 (diiodomethane), and C 2 H 4 (OH) 2 anhydrous ethylene glycol. For each liquid, at least 20 drops were used to measure the contact angle in sequence, and then the average value was confirmed.

[0070] The XPS spectra were evaluated with respect to the Si2p signal.

[0071] Summarize the results in Table 1 below.

[0072]

Table 1

[0073] By the treatment with the pulsed laser, the silicon nitride substrates in Examples EB1 and EB2 according to the present invention are modified in their structures and thus show significantly different Si2p signals as compared with the starting substrates and the substrates exposed by etching.

[0074] The silicon nitride substrate of Comparative Example VB2 also shows a changed Si2p signal in the XPS spectrum by the treatment with the pulsed laser as compared with the original substrate. However, since this Si2p signal does not have a peak having a maximum value in the range of 98.0 to 100.0 eV, it is not according to the present invention.

[0075] The silicon nitride surface having the Si2p signal according to the present invention shows a significantly higher water contact angle as compared with the silicon nitride surface of the comparative example. This provides better protection from moisture for the silicon nitride ceramic.

Claims

1. a ceramic substrate comprising silicon nitride, the ceramic substrate having a front surface and a rear surface; on the front surface of the ceramic substrate; a metal coating having at least one recess, a surface of the ceramic substrate being exposed by the recess; the ceramic substrate exhibits, at least in the region of the recess, a Si2p signal in the range of 96 to 107 eV in an energy spectrum recorded by X-ray photoelectron spectroscopy; The Si2p signal is as follows: one or more peaks each having a maximum in the range of 98.0 to 100.0 eV; one or more peaks each having a maximum in the range of 101.0 to 102.2 eV; and one or more peaks each having a maximum in the range of 102.5 to 104.0 eV.

2. The following relationships are satisfied: I １ / I ｇｅｓ ≧0.02、 2.0≦I ２ / I １ ≦8.0, where (I １ +I ２ ) / I ｇｅｓ ≦0.85, (I １ +I ２ +I ３ ) / I ｇｅｓ ≧0.95, During the ceremony, I ｇｅｓ is the total intensity of the Si2p signal, I １ is the total intensity of the peaks each having a maximum value in the range of 98.0 to 100.0 eV, I ２ is the total intensity of the peaks each having a maximum value in the range of 101.0 to 102.2 eV, I ３ 2. The metal-ceramic composite of claim 1, wherein m is the total intensity of said peaks, each of which has a maximum in the range of 102.5 to 104.0 eV.

3. 3. The metal-ceramic composite according to claim 1, wherein there are two or less peaks having maxima within the relevant ranges in the ranges of 98.0 to 100.0 eV, 101.0 to 102.2 eV, and 102.5 to 104.0 eV.

4. The metal-ceramic composite according to any one of claims 1 to 3, wherein said ceramic substrate contains said silicon nitride in a proportion of at least 70% by weight.

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

6. 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 5, comprising:

7. A metal-ceramic composite according to any one of claims 1 to 6, one or more semiconductor components; 23. A semiconductor module comprising:

8. 8. The semiconductor module of claim 7, 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