Joint, ceramic circuit board, semiconductor device, and method for manufacturing joint

Abstract

Provided is a ceramic circuit board that is capable of suppressing a decrease in conductivity of a copper plate while maintaining bonding strength. A bonded body according to an embodiment comprises a ceramic substrate, a copper plate, and a bonding layer that bonds the ceramic substrate and the copper plate. The bonding layer contains Ag, Cu, an active metal, and a first element. The first element is one or two selected from Sn and In. As determined by SEM-EDX analysis of an arbitrary cross section, when a point at which a detection amount of Cu is not less than 80 mass% and at which a change in slope in a graph of the detection amount of Cu is the largest is assumed to be a first measurement point, a detection amount of the first element (mass%) / a detection amount of Ag (mass%) at the first measurement point is within the range of 0-0.4. The detection amount of the first element (mass%) / the detection amount of Ag (mass%) at the first measurement point is preferably within the range of 0.05-0.2.

Description

[Technical Field]

[0001] The embodiments described below generally relate to a bonded body, a ceramic circuit board, a semiconductor device, and a method for manufacturing the bonded body. [Background technology]

[0002] A bonded structure of a ceramic substrate and a copper plate is used as a circuit board on which semiconductor elements and the like are mounted. International Publication No. 2017 / 056360 (Patent Document 1) discloses a ceramic-copper circuit board in which a ceramic substrate and a copper plate are bonded. In Patent Document 1, the hardness and size of the protruding portion of the bonding layer are controlled. In addition, International Publication No. 2018 / 199060 (Patent Document 2), the diffusion region of Ag into the copper plate is controlled.

[0003] The ceramic circuit boards described in Patent Documents 1 and 2 have excellent thermal cycling resistance (TCT) characteristics. As semiconductor elements become more powerful, their guaranteed operating temperatures are expected to reach 170°C or higher, and even 200°C or higher. Miniaturization of semiconductor devices incorporating semiconductor elements is also being considered. Power density is used to evaluate the performance of semiconductor devices. Power density can be calculated as follows: "power density = (rated current × rated voltage × number of semiconductor elements mounted in a module) / module volume." For example, power density can be increased by increasing the number of semiconductor elements mounted in a module or by reducing the module volume. To improve these two parameters, it is necessary to mount multiple semiconductor elements on a ceramic metal circuit board. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 056360 [Patent Document 2] International Publication No. 2018 / 199060 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, the electrical conductivity of oxygen-free copper is about 101% IACS. However, there is a local variation in the electrical conductivity of copper plates. The variation in electrical conductivity has a negative effect on electrical resistance and heat dissipation.

[0006] When the cause of this was investigated, it was found to be due to the amount of tin (Sn) or indium (In) diffused into the copper plate. In both Patent Document 1 and Patent Document 2, an active metal joining method is used. In the active metal joining method, an active metal brazing material containing Ag, Cu, and Ti is used. In order to improve the joinability, Sn or In is added to the active metal brazing material. Sn or In has the effect of lowering the melting point of the active metal brazing material, thereby improving the joinability.

[0007] For example, in the active metal bonding method, the copper plates are heated and bonded at high temperatures of around 700 to 950°C. During the heat bonding process, the active metal brazing material components diffuse into the copper plates. The melting point of AgCu alloy is around 780°C, while the melting point of AgSn alloy or AgIn alloy is around 400°C. As Sn or In diffuses into the copper plate, a large amount of AgSn alloy or AgIn alloy with a low melting point is formed.

[0008] The embodiments of the present invention are intended to address these problems and to provide a bonded body in which the generation of AgSn alloys and AgIn alloys is suppressed. [Means for solving the problem]

[0009] A bonded body according to an embodiment includes a ceramic substrate, a copper plate, and a bonding layer bonding the ceramic substrate and the copper plate. The bonding layer contains Ag, Cu, an active metal, and a first element. The first element is one or two elements selected from Sn and In. When an arbitrary cross section is analyzed by SEM-EDX, the detected amount of Cu is 80% by mass or more, and the first measurement point is determined to be the point where the change in slope in the graph of the detected amount of Cu is greatest. At the first measurement point, the ratio of the detected amount of the first element (mass%) to the detected amount of Ag (mass%) is within the range of 0 to 0.4. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a view showing an example of a bonded body according to an embodiment. [Figure 2] FIG. 3 is a diagram showing an example of a first measurement point and a second measurement point of a bonded structure according to the embodiment. [Figure 3] 1A and 1B are diagrams showing an example of a ceramic circuit substrate according to an embodiment. [Figure 4] 1A and 1B are diagrams showing an example of a semiconductor device according to an embodiment; [Figure 5] FIG. 10 is a graph showing an example of the amount of detected Cu. DETAILED DESCRIPTION OF THE INVENTION

[0011] A bonded body according to an embodiment includes a ceramic substrate, a copper plate, and a bonding layer bonding the ceramic substrate and the copper plate. The bonding layer contains Ag, Cu, an active metal, and a first element. The first element is one or two elements selected from Sn and In. When an arbitrary cross section is analyzed by SEM-EDX, the detected amount of Cu is 80% by mass or more, and the first measurement point is determined to be the point where the change in slope in the graph of the detected amount of Cu is greatest. At the first measurement point, the ratio of the detected amount of the first element (mass%) to the detected amount of Ag (mass%) is within the range of 0 to 0.4.

[0012] FIG. 1 shows an example of a bonded body according to an embodiment. In FIG. 1, reference numeral 1 denotes a bonded body, reference numeral 2 denotes a ceramic substrate, reference numeral 3 denotes a bonding layer, reference numeral 4 denotes a copper plate (front copper plate), and reference numeral 5 denotes a copper plate (rear copper plate). FIG. 1 shows an example in which copper plates (copper plate 4, copper plate 5) are bonded to both sides of a ceramic substrate 2. In the bonded body according to an embodiment, a copper plate may be bonded to only one side of the ceramic substrate 2. Furthermore, the number of copper plates bonded to one side may be one or more. The copper plate 4 bonded to the front side may be referred to as the front copper plate. The copper plate 5 bonded to the rear side may be referred to as the rear copper plate.

[0013] In the bonded body 1, a ceramic substrate 2 and a copper plate 4 are bonded via a bonding layer 3. The bonding layer 3 contains Ag, Cu, an active metal, and a first element. The first element is one or two elements selected from Sn and In. The active metal is one or more elements selected from Ti (titanium), Zr (zirconium), and Hf (hafnium). A bonding method using an active metal is called an active metal bonding method. In other words, the bonded body according to the embodiment is a bonded body produced by the active metal bonding method.

[0014] An arbitrary cross section of the bonded body is analyzed by scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX). At this time, the first measurement point is determined to be a point where the detected amount (concentration) of Cu is 80 mass % or more and the change in slope in the graph (profile) of the detected amount of Cu is greatest. In this case, in the bonded body 1 according to the embodiment, the ratio of the detected amount of the first element (mass %) / the detected amount of Ag (mass %) at the first measurement point is in the range of 0.05 to 0.4.

[0015] First, we will explain how to determine the first measurement point. SEM-EDX is used for the measurement. A cross section is used for SEM-EDX analysis. The cross section is a surface obtained by cutting the bonded body 1 along a direction perpendicular to the surface of the ceramic substrate 2. The cross section to be measured is mirror-polished. A JEOL JSM-7200F or a device with equivalent or higher performance is used for SEM-EDX. The measurement conditions are set as follows: acceleration voltage 15 kV, magnification 500x, and count rate 10,000 cps or higher. Correction is applied to the measurement results using the ZAF method. The JSM-7200F is a field emission scanning electron microscope (FE-SEM). Using an FE-SEM can improve measurement accuracy. An FE-SEM is used for the measurement.

[0016] The count rate is the number of X-rays that enter the detector or are counted per second. The unit cps is an abbreviation for counts per second. The ZAF method is a method for correcting characteristic X-ray intensity during quantitative analysis by taking into account three effects: (1) the atomic number (Z) effect, (2) the absorption (A) effect, and (3) the fluorescence excitation (F) effect. If the SEM-EDX instrument has a built-in program for executing the ZAF method, the measurement results can be corrected using that program.

[0017] An example of a method for identifying the first measurement point will be described with reference to the copper plate 4 (front copper plate). By replacing "copper plate 4" in the following description with "copper plate 5," the first measurement point on the copper plate 5 (back copper plate) can also be identified in the same way.

[0018] The dimensions of the SEM-EDX measurement area are set to 280 μm in length and 2.5 μm in thickness, and area analysis is performed on the cross section. Area analysis is performed from the interface between the ceramic substrate 2 and the bonding layer 3 toward the surface of the copper plate 4. The measurement areas (280 μm in length and 2.5 μm in thickness) are set so that they do not overlap with each other. The detected amount of each element is measured for each area analysis. A graph of the detected amount (concentration) of Cu is created based on the detected amount of Cu obtained by area analysis. The point on the graph of the detected amount of Cu where the detected amount is 80 mass% or more and the change in slope is the largest is designated as the "first measurement point." The approximate position of the interface between the ceramic substrate 2 and the bonding layer 3 can be determined based on the difference in contrast in the SEM image.

[0019] The horizontal axis of the Cu graph represents the distance (μm) from the interface between the ceramic substrate 2 and the bonding layer 3. The location where the detected amount of Cu is 0 mass% is taken as the interface between the ceramic substrate 2 and the bonding layer 3. The vertical axis of the Cu graph represents the mass% (wt%) of Cu.

[0020] The Cu graph is created using the following procedure. First, the detected amount for each measurement area obtained by SEM-EDX is plotted to create a scatter diagram. Next, the points plotted on the scatter diagram are connected with smooth lines to create a graph. The functions of the calculation software are used to create the scatter diagram and smooth lines. Microsoft Excel (registered trademark) is used as the calculation software.

[0021] The point where the change in slope is greatest is identified by the second derivative of the Cu graph. That is, first, the region where the detected amount of Cu is 80 mass % or more is identified from the Cu graph. Next, the second derivative of the Cu graph is calculated in the identified region. The minimum value is identified from the value obtained by the second derivative. The point where the minimum value is obtained is the point where the change in slope is greatest, and is the first measurement point.

[0022] At the first measurement point, the mass percentages of components other than Cu are also analyzed. In the bonded body 1 according to the embodiment, the bonding layer 3 contains Ag, Cu, the active metal, and the first element. Therefore, at the first measurement point, analysis is also performed on Ag, the active metal, and the first element in addition to Cu.

[0023] When creating a Cu graph, it is effective to perform a qualitative analysis of the bonding layer 3 in advance. As a result of the qualitative analysis, the mass percentage of Cu is calculated, with the total mass of the metal components being 100 mass%. As an example, qualitative analysis of the bonding layer 3 detects Ag (silver), Cu (copper), Sn (tin), Ti (titanium), Si (silicon), O (oxygen), N (nitrogen), and C (carbon) in the bonding layer 3. In this case, the metal components are Ag, Cu, Sn, and Ti. The Cu concentration is detected with the sum of these elements being 100 mass%. In other words, Si (silicon), O (oxygen), N (nitrogen), and C (carbon) are not counted as metal components. When metal components are detected as alloys or compounds, they are converted into the individual metal elements. In other words, when an AgCu alloy is detected, the AgCu alloy is counted as both the Ag amount and the Cu amount. Analysis using EDX allows the amount of detection converted into the individual metal elements to be measured. Quantitative analysis using EDX tends to produce variations in the measurement results for non-metallic elements. For this reason, it is preferable to count only metallic elements. In other words, a graph of the detected amount (concentration) of Cu is created with the total of the metallic components as 100% by mass.

[0024] FIG. 5 shows an example of a graph of the amount of detected Cu. In the graph shown in FIG. 5, the horizontal axis represents the distance from the interface between the ceramic substrate 2 and the bonding layer 3. The vertical axis represents the amount of detected Cu (mass %). The point where the amount of detected Cu is 0 mass % is taken as the interface between the ceramic substrate 2 and the bonding layer 3. The slope of the graph is calculated by software that performs second-order differentiation. If the SEM-EDX device comes with software, the software is used to perform second-order differentiation.

[0025] In the example shown in FIG. 5, the detected amount of Cu increases from the interface between the ceramic substrate 2 and the bonding layer 3 toward the copper plate 4. At a distance of approximately 19.5 μm, the detected amount of Cu exceeds 80 mass %. Then, at a distance of 20 μm, the rate of increase in the detected amount decreases. In other words, there is a point where the slope changes in the graph. When second-order differentiation is performed, a minimum value is obtained at this point. This point where the slope changes is the first measurement point.

[0026] Here, the region from the interface between the ceramic substrate 2 and the bonding layer 3 to the first measurement point is referred to as the "first region." The region on the opposite side of the first measurement point from the first region is referred to as the "second region." The slope of the detected amount of Cu in the first region is referred to as "slope A." The slope of the detected amount of Cu in the second region is referred to as "slope B." The ratio of slope B to slope A is preferably 0.5 or less.

[0027] In the graph shown in Figure 5, the ratio of the slope B of the detected amount of Cu in the second region to the slope A of the detected amount of Cu in the first region is 0.26. The fact that the slope B / slope A is 0.5 or less indicates the presence of a change point where the amount of Ag diffusion decreases. The change point where the amount of Ag diffusion decreases is thought to be the boundary between the bonding layer 3 and the copper plate 4. The presence of a change point where the slope B / slope A is 0.5 or less indicates that the amount of Ag diffusion into the copper plate 4 is suppressed. The absence of a change point where the slope B / slope A is 0.5 or less indicates that the amount of Ag diffusion into the copper plate is large.

[0028] The bonded body 1 according to the embodiment is characterized in that the ratio of the detected amount of the first element (mass%) to the detected amount of Ag (mass%) is within the range of 0 to 0.4 at the first measurement point. This indicates that the amount of Sn or In is small relative to the amount of Ag at the first measurement point.

[0029] When Sn or In reacts with Ag, an AgSn alloy or AgIn is formed. The more Sn contained in the AgSn alloy, the lower the melting point. For example, the melting point of an AgSn solid solution is approximately 200°C to 500°C. AgIn alloys have a similar tendency. The melting point of a CuSn alloy is 400°C to 700°C, and the more Sn contained in the alloy, the lower the melting point. CuIn alloys have a similar tendency. On the other hand, the melting point of an AgCu eutectic is approximately 780°C.

[0030] At the first measurement point, the ratio of the detected amount of the first element (mass %) to the detected amount of Ag (mass %) being 0 or more and 0.4 or less indicates that the amount of diffusion of the first element into the copper plate 4 is suppressed. If the ratio of the detected amount of the first element (mass %) to the detected amount of Ag (mass %) is greater than 0.4, an alloy with low conductivity is formed. If an alloy with low conductivity is formed, the conductivity of the copper plate 4 decreases.

[0031] JIS-H-3100 (ISO1337, etc.) stipulates that the conductivity of oxygen-free copper is 98% IACS or higher. In contrast, the conductivity of Sn is approximately 15% IACS, and the conductivity of In is approximately 20% IACS. As the amount of the first element diffused into the copper plate 4 increases, areas with low conductivity are formed within the copper plate 4. When the ratio of the detected amount of the first element (mass%) to the detected amount of Ag (mass%) exceeds 0.4, the amount of the first element diffused into the copper plate 4 is large, and the conductivity of the copper plate 4 decreases by 10% or more.

[0032] A ratio of the detected amount of the first element (mass%) to the detected amount of Ag (mass%) of 0 indicates that the first element is below the detection limit. If the ratio of the detected amount of the first element (mass%) to the detected amount of Ag (mass%) is less than 0.05 (including 0), an alloy with low conductivity is not formed. On the other hand, the components of the bonding layer 3 are not diffused into the copper plate, which may result in insufficient bonding strength.

[0033] By controlling the ratio of the detected amount of the first element (mass%) to the detected amount of Ag (mass%), it is possible to suppress a decrease in the electrical conductivity of the copper plate 4 and improve the bonding strength at the same time. For this reason, the ratio of the detected amount of the first element (mass%) to the detected amount of Ag (mass%) is preferably 0 to 0.4, and more preferably 0.05 to 0.2. When both Sn and In are detected at the first measurement point, the ratio of the total detected amount of Sn and In (mass%) to the detected amount of Ag (mass%) is preferably within the range of 0.05 to 0.4.

[0034] In the bonded body 1 according to the embodiment, at any of the first measurement points, the ratio of the detected amount (mass %) of the first element to the detected amount (mass %) of Ag is within the range of 0 to 0.4. That is, when two or more ranges at different in-plane positions on one cross section are analyzed by SEM-EDX, the ratio of the detected amount (mass %) of the first element to the detected amount (mass %) of Ag is within the range of 0 to 0.4 at the first measurement points in any of the ranges.

[0035] Furthermore, the first measurement point is substantially located at the boundary between the bonding layer 3 and the copper plate 4 (or copper plate 5). The bonding layer 3 contains Cu, Ag, the first element, etc. These components diffuse into the copper plate 4 from the boundary between the bonding layer 3 and the copper plate 4 during the bonding process. The fact that the amount of the first element is reduced at the first measurement point indicates that the amount of the first element diffusing into the copper plate 4 is also suppressed.

[0036] At the first measurement point, the detected amount of Ag is preferably in the range of 3% by mass or more and less than 20% by mass. Diffusion of Ag from the bonding layer 3 to the copper plate 4 is effective in improving bonding strength. On the other hand, excessive diffusion of Ag into the copper plate 4 may cause Ag ion migration. A detected amount of Ag of 3% by mass or more and less than 20% by mass at the first measurement point indicates that excessive diffusion of Ag into the copper plate 4 is suppressed and that the Ag necessary for bonding the bonding layer 3 and the copper plate 4 is present at the boundary between them. For this reason, the detected amount of Ag at the first measurement point is preferably 3% by mass or more and less than 20% by mass.

[0037] At the first measurement point, the ratio of the detected amount of active metal (mass%) to the detected amount of Ag (mass%) is preferably within the range of 0 to 0.1. The active metal can react with the ceramic substrate to improve the bonding strength. For example, when Ti is used as the active metal and a silicon nitride substrate is used as the ceramic substrate, the Ti reacts with the silicon nitride substrate to form a titanium nitride (TiN) layer. If the ratio of the detected amount of active metal (mass%) to the detected amount of Ag (mass%) at the first measurement point exceeds 0.1, this indicates that a large amount of active metal exists that has not reacted with the ceramic substrate 2. If the ratio of the detected amount of active metal (mass%) to the detected amount of Ag (mass%) at the first measurement point is 0.1 or less, the amount of active metal that contributes to the reaction with the ceramic substrate 2 can be increased.

[0038] The "second measurement point" is a point shifted 10 μm from the first measurement point toward the surface of the copper plate 4. In this case, the ratio of the detected amount of Ag (mass %) at the second measurement point to the detected amount of Ag at the first measurement point is preferably within a range of 0.1 to 0.7.

[0039] A conceptual diagram of the first and second measurement points is shown in Figure 2. In Figure 2, reference numeral 3 denotes the bonding layer, reference numeral 4 denotes the copper plate, reference numeral 6 denotes the first measurement point, and reference numeral 7 denotes the second measurement point. The second measurement point is located at a point in the measurement area (length 280 μm × thickness 2.5 μm) shifted 10 μm from the first measurement point toward the surface of the copper plate 4. The second measurement point is set so that the distance from the midpoint in the thickness direction of the measurement area (the first measurement point) to the midpoint in the thickness direction of the measurement area (the second measurement point) is 10 μm.

[0040] The fact that the ratio of the detected amount of Ag (mass %) at the second measurement point to the detected amount of Ag at the first measurement point is in the range of 0.1 to 0.7 indicates that the amount of Ag diffused toward the surface of the copper plate 4 is decreasing. In other words, this indicates that the amount of Ag diffused is decreasing within a short distance of 10 μm.

[0041] At the second measurement point, the ratio of the detected amount of the first element (mass %) to the detected amount of Ag (mass %) is preferably within a range of 0 to 0.1. By reducing the amount of the first element diffused at the second measurement point, the amount of an alloy with low conductivity formed in the copper plate 4 can be reduced.

[0042] At the second measurement point, the ratio of the detected amount of active metal (mass%) to the detected amount of Ag (mass%) is preferably within a range of 0 to 0.1. By reducing the amount of diffused active metal at the second measurement point, the active metal that contributes to the reaction between ceramic substrate 2 and bonding layer 3 can be increased.

[0043] The Ag diffusion region is preferably present between the ceramic substrate 2 and a point shifted 30 μm from the first measurement point toward the surface of the copper plate 4. In other words, it is preferable that the Ag diffusion region does not exist in an area more than 30 μm away from the first measurement point toward the surface of the copper plate 4. The Ag diffusion region is a collection of measurement areas (length 280 μm × thickness 2.5 μm) where Ag is detected at 0.01 mass% or more. A detected amount of Ag less than 0.01 mass% is below the detection limit (including 0 mass%). By reducing the Ag diffusion region, Ag ion migration can be suppressed.

[0044] When Ag diffuses from the bonding layer 3 to the surface of the copper plate 4, Ag precipitates on the surface of the copper plate 4. Ag ion migration is a phenomenon in which Ag precipitated on the surface of the copper plate 4 ionizes and migrates. The migrated Ag precipitates in another location, which causes poor insulation. Ag ion migration is likely to occur when a voltage is applied to the bonded body in a high-humidity environment. By reducing the Ag diffusion area in the copper plate 4, the diffusion of Ag near the surface of the copper plate 4 can be suppressed. This prevents Ag from being present on the surface of the copper plate 4. As a result, the occurrence of Ag ion migration can be suppressed. Furthermore, by reducing the amount of Sn or In diffusion, the migration of Sn or In can also be suppressed.

[0045] Various materials can be used for the ceramic substrate 2. Examples of ceramic substrates include silicon nitride substrates, aluminum nitride substrates, alumina substrates, zirconia substrates, and alu-zirconia substrates. The alu-zirconia substrate is a sintered ceramic body made of a mixture of alumina and zirconia. The thickness of the ceramic substrate 2 is preferably within a range of 0.2 mm to 3 mm.

[0046] The three-point bending strength of the silicon nitride substrate is preferably 600 MPa or more. The thermal conductivity of the silicon nitride substrate is preferably 80 W / m·K or more. Increasing the strength of the silicon nitride substrate allows the substrate to be made thinner. Therefore, the three-point bending strength of the silicon nitride substrate is preferably 600 MPa or more, and more preferably 700 MPa or more. The thickness of the silicon nitride substrate can be made as thin as 2 mm or less, or even 0.40 mm or less.

[0047] The three-point bending strength of an aluminum nitride substrate is approximately 300 to 450 MPa. On the other hand, the thermal conductivity of an aluminum nitride substrate is 160 W / m·K or more. Because the strength of an aluminum nitride substrate is low, the substrate thickness is preferably 0.60 mm or more. The three-point bending strength of an aluminum oxide substrate is approximately 300 to 450 MPa, but aluminum oxide substrates are inexpensive. The three-point bending strength of an alusil substrate is high, approximately 550 MPa, but the thermal conductivity of an alusil substrate is approximately 30 to 50 W / m·K.

[0048] A silicon nitride substrate is preferable as the ceramic substrate 2. Silicon nitride substrates have high strength and can withstand the thermal contraction of the molding resin. Furthermore, by using a silicon nitride substrate with a thermal conductivity of 80 W / m K or more, heat dissipation can be improved.

[0049] Silicon nitride substrates and aluminum nitride substrates are called nitride ceramic substrates. When nitride ceramics and a copper plate 4 are bonded using an active metal bonding method, the active metal reacts with the nitride ceramic substrate, forming an active metal nitride layer in the bonding layer 3. When Ti is used as the active metal, a titanium nitride (TiN) layer is formed. The formation of this active metal nitride layer can improve the bonding strength.

[0050] Aluminum oxide substrates, zirconium oxide substrates, and aluminium oxide substrates are called oxide-based ceramic substrates. When an oxide-based ceramic substrate and a copper plate 4 are joined using an active metal joining method, the active metal reacts with the oxide-based ceramic substrate to form an active metal oxide layer. When Ti is used as the active metal, a titanium oxide (TiO2) layer is formed. The formation of this active metal oxide layer can improve the joining strength.

[0051] The thickness of the copper plate 4 is preferably 0.3 mm or more. By making the copper plate 4 thicker, the heat dissipation properties can be improved. The current-carrying capacity of the copper plate 4 can be increased. For this reason, the thickness of the copper plate 4 is preferably 0.3 mm or more, and more preferably 0.6 mm or more. There is no particular upper limit to the thickness of the copper plate, but it is preferably 5 mm or less. If it exceeds 5 mm, it may be difficult to form a circuit on the copper plate 4 by etching. Furthermore, it is preferable that the thickness of each of the front copper plate and the back copper plate is 0.3 mm or more.

[0052] A copper alloy plate may be used as the copper plate. The copper plate is preferably an oxygen-free copper plate. As defined in JIS-H-3100, oxygen-free copper has a copper purity of 99.96 wt% or more. JIS-H-3100 corresponds to ISO1337 and other standards.

[0053] The bonded body as described above can be applied to a ceramic circuit board, and the ceramic circuit board can be applied to a semiconductor device on which a semiconductor element is mounted.

[0054] Fig. 3 shows an example of a ceramic circuit substrate according to an embodiment. Fig. 4 shows an example of a semiconductor device according to an embodiment. In Fig. 3 and Fig. 4, reference numeral 4a denotes a copper circuit, reference numeral 8 denotes a semiconductor element, reference numeral 10 denotes a ceramic circuit substrate, and reference numeral 20 denotes a semiconductor device.

[0055] A ceramic circuit board 10 is produced by imparting a circuit shape to the copper plate 4 of the bonded body 1. An etching process or the like is used to impart the circuit shape. FIG. 3 shows an example in which a copper circuit 4a is provided on the front side of the ceramic substrate 2 and a back copper plate 5 is used as a heat sink. For example, one or more copper circuits 4a are formed by imparting a circuit shape to the front copper plate 4 shown in FIG. 1 through an etching process. In the ceramic circuit board 10 according to the embodiment, a circuit shape may be imparted to both the front copper plate 4 and the back copper plate 5. FIG. 3 also shows an example in which two copper circuits 4a are provided. In the ceramic circuit board 10, any number of copper circuits 4a may be provided.

[0056] In the semiconductor device 20, a semiconductor element 8 is mounted on a ceramic circuit substrate 10. FIG. 4 shows an example in which one semiconductor element 8 is mounted. The structure of the semiconductor device 20 according to the embodiment is not limited to the example shown in the figure, and multiple semiconductor elements 8 may be mounted. Multiple semiconductor elements 8 may be mounted on one copper circuit 4a. A lead frame, wire bonding, terminals, etc. (not shown) may be bonded to the copper circuit 4a. Furthermore, a molding resin that covers the semiconductor element 8 may be provided as necessary.

[0057] A method for manufacturing the bonded body 1 according to the embodiment will be described. The method for manufacturing the bonded body 1 according to the embodiment is not limited as long as it has the above-described configuration. Here, a method for manufacturing the bonded body 1 with a high yield will be described.

[0058] First, prepare a ceramic substrate 2. The ceramic substrate 2 is preferably one selected from a silicon nitride substrate, an aluminum nitride substrate, an alumina substrate, a zirconia substrate, and an aluminium nitride substrate. Also, prepare a copper plate 4.

[0059] Next, an active metal brazing material is prepared. First, powders of the components that make up the active metal brazing material are prepared. The active metal is one or more selected from Ti, Zr, and Hf. As the active metal, one or two selected from the active metal element and the active metal hydride are used. For example, when the active metal is Ti, Ti powder or titanium hydride (TiH2) powder is used. Also, Ag powder, Cu powder, and powder of the first element are prepared.

[0060] The proportion of Ag is preferably in the range of 40% by mass to 95% by mass. The proportion of Cu is preferably in the range of 3% by mass to 50% by mass. The total proportion of active metal and active metal hydride is preferably in the range of 1% by mass to 15% by mass. The total proportion of Sn and In is preferably in the range of 1% by mass to 30% by mass.

[0061] Ag and Cu are elements that are the main components of the bonding layer 3. The active metal or active metal hydride is a component that reacts with the ceramic substrate 2 to obtain a strong bond. Sn or In has the effect of lowering the melting point of the active metal brazing material.

[0062] The active metal brazing material may contain 0.1% by mass or more and 2% by mass or less of carbon (C). The active metal brazing material may contain 0.1% by mass or more and 10% by mass or less of one or more elements selected from tungsten (W), molybdenum (Mo), and rhenium (Re). The fluidity of the active metal brazing material can be controlled by adding carbon, tungsten, molybdenum, or rhenium. The active metal brazing material may contain magnesium (Mg).

[0063] The component ratios of the active metal brazing material described above are the ratios when the total of each metal component is 100% by mass. For example, when titanium nitride powder is used, the mass percentage of titanium nitride is controlled within the above range. The mass of organic substances such as binders is not counted. The brazing material components are mixed, and binders and other additives are added to prepare an active metal brazing material paste.

[0064] Next, a laminate including a ceramic substrate 2, an active metal brazing material paste layer, and a copper plate 4 is prepared. The active metal brazing material paste is applied to the ceramic substrate 2, and the copper plate 4 is placed thereon. The active metal brazing material paste may be applied to both sides of the ceramic substrate 2, and the copper plate 4 may be placed on each side. Alternatively, the active metal brazing material paste may be applied to the copper plate 4, and the ceramic substrate 2 may be placed thereon. If necessary, the number of layers of the ceramic substrate 2 and the copper plate 4 may be increased. For example, the number of layers may be increased to copper plate / active metal brazing material paste layer / ceramic substrate / active metal brazing material paste layer / copper plate / active metal brazing material paste layer / ceramic substrate / active metal brazing material paste layer / copper plate. This process prepares a laminate including the ceramic substrate 2, the active metal brazing material paste layer, and the copper plate 4.

[0065] Next, a heat bonding step is carried out. The bonding temperature is preferably in the range of 700°C to 950°C. The bonding temperature is a temperature at which the components are maintained for a predetermined time or longer. When the active metal brazing material described above is used, the bonding temperature is preferably in the range of 700°C to 950°C. below Therefore, the bonding temperature is within the range of 700°C to 950°C. below If the bonding temperature is lower than 700°C, the bonding strength may be insufficient. If the bonding temperature is higher than 950°C, the amount of Ag, the active metal, or the first element diffusing into the copper plate 4 may increase. For this reason, the bonding temperature is preferably within a range of 700°C or higher and 950°C or lower, and more preferably within a range of 850°C or higher and 920°C or lower.

[0066] Furthermore, the holding time at the bonding temperature is preferably within a range of 3 minutes to 60 minutes. Considering temperature variations within the furnace, the time during which the laminate is held at a temperature range of the bonding temperature ±30°C is counted as the holding time at the bonding temperature. For example, when the bonding temperature is 880°C, the time during which the laminate is held at a temperature range of 880°C ±30°C is the holding time at the bonding temperature.

[0067] If the bonding temperature is maintained for less than 3 minutes, the bonding strength may be insufficient. If the bonding temperature is maintained for more than 60 minutes, the time exposed to high temperatures will be longer. This may increase the amount of Ag, active metal, or first element diffusing into the copper plate 4. For this reason, the bonding temperature is preferably maintained for 3 to 60 minutes, more preferably 5 to 40 minutes.

[0068] It is preferable to use a continuous furnace for the thermal bonding process. By using a continuous furnace, it is possible to bond the laminate in a nitrogen atmosphere. A nitrogen atmosphere is an atmosphere with a nitrogen content of 98 vol% or more and 100 vol% or less. In a continuous furnace, the laminate can be thermally bonded while transporting the article on a belt conveyor or the like. By using a continuous furnace, it is possible to shorten the time required to heat the laminate from room temperature to the bonding temperature and the time required to cool the laminate from the bonding temperature to room temperature. This reduces the time the laminate is exposed to high temperatures more than necessary.

[0069] For example, in conventional active metal bonding methods, laminates are thermally bonded in a vacuum. A batch furnace is used for bonding in a vacuum. In a batch furnace, the laminate is placed in a sealed space and heated. When a batch furnace is used, it takes time for the furnace body (sealed space) itself to heat up and cool down due to its heat capacity. Therefore, the temperature of the furnace body must be adjusted, and the heating and cooling processes take time. The heating and cooling rates of a batch furnace are approximately 1 to 3°C / min. In a batch furnace, it takes a long time to return to room temperature after being held at the bonding temperature. Therefore, the bonded body is exposed to high temperatures for a long time. As a result, the amount of Ag and the first element diffusing into the copper plate 4 increases. On the other hand, in a continuous furnace, the sample passes through the furnace, so the heating time is determined only by the heat capacity of the sample itself. Therefore, the heating and cooling rates can be increased.

[0070] When the thermal bonding process is performed using a continuous furnace, the active metal content of the active metal brazing material is preferably 5% by mass or more. In a continuous furnace, the laminate is bonded in an inert atmosphere. Examples of the inert atmosphere include a nitrogen atmosphere and an argon atmosphere. When cost is a consideration, a nitrogen atmosphere is used. On the other hand, active metals have high reactivity with nitrogen. By setting the active metal content in the active metal brazing material to 5% by mass or more, the proportion of active metal that contributes to bonding without reacting with the nitrogen atmosphere can be increased. This can improve the yield when using a continuous furnace.

[0071] When a continuous furnace is used, the temperature rise rate of the laminate and the temperature fall rate of the bonded body can be 15°C / min or more. By increasing the temperature rise rate and the temperature fall rate, the time that the laminate or the bonded body is exposed to high temperatures can be shortened. The upper limit of the temperature rise rate and the temperature fall rate is not particularly limited, but is preferably 100°C / min or less. If the temperature rise rate exceeds 100°C / min, the temperature change will be too large, which may cause distortion of the bonded body.

[0072] The difference between the heating rate and the temperature decrease rate is preferably 20°C / min or less. The difference between the heating rate and the temperature decrease rate is expressed as |heating rate - temperature decrease rate|. In other words, it is preferable that |heating rate - temperature decrease rate|≦20°C / min. By reducing the difference between the heating rate and the temperature decrease rate, the amount of diffusion of the active metal brazing material components can be made uniform. As a result, regardless of which first measurement point on the bonded body 1 is measured, the ratio of the detected amount of the first element (mass %) to the detected amount of Ag (mass %) can be kept within the range of 0 to 0.4.

[0073] The temperature profile of the thermal bonding process uses the temperature of the laminate. An effective method for measuring the temperature of the laminate is to attach a thermocouple to the laminate and pass it through a continuous furnace. The temperature profile of the laminate is measured after the heating process, heating bonding process, and cooling process. From the temperature profile, the heating rate, the holding time at the bonding temperature, and the temperature decreasing rate are calculated. Here, the heating rate is the average rate of heating from 200°C to the bonding temperature. The temperature decreasing rate is the average rate of cooling from the bonding temperature to 200°C.

[0074] The space in which the temperature-raising step is carried out may be divided into multiple zones. For example, the multiple zones include a room temperature zone, a room temperature to 200°C zone, a 200°C to 400°C zone, a 400°C to 600°C zone, a 600°C to bonding temperature zone, and a zone for holding the laminate at the bonding temperature. The temperature of the laminate is sequentially raised in each zone. The temperature-raising step is carried out by the laminate passing through the multiple zones.

[0075] In the heating step, the temperature of the laminate in the first treatment zone where the laminate is heated is preferably in the range of 150°C to 400°C. The first treatment zone is the zone where the laminate is first heated in the continuous furnace. In the manufacturing method of the bonded body according to the embodiment, the heating rate from 200°C to the bonding temperature is controlled in the heating step. By keeping the temperature of the laminate in the first treatment zone in the range of 150°C to 400°C, the heating rate from 200°C can be easily controlled. Therefore, in the first treatment zone, the temperature of the laminate is preferably in the range of 150°C to 400°C, and more preferably in the range of 180°C to 370°C. In addition, this temperature range also has the effect of degreasing the binder in the brazing filler paste. Removing the binder is effective in suppressing the diffusion of the active metal brazing filler components into the copper plate 4.

[0076] The average conveying speed of the laminate is preferably 1 cm / min or more. The average conveying speed is the average value of the moving speed of the laminate when conveying through the temperature increasing process, the heat bonding process, and the temperature decreasing process. If the average conveying speed is less than 1 cm / min, the conveying speed is slow, which may reduce mass productivity. If a process includes a step of stopping conveying, the conveying speed in that process is counted as 0 cm / min. For example, if 30 minutes of conveying is performed at a conveying speed of 5 cm / min and 10 minutes of conveying is performed at a conveying speed of 10 cm / min, the average conveying speed is 6.3 cm / min. If 60 minutes of conveying is performed at a conveying speed of 5 cm / min and then a 30-minute conveying stop is performed, the average conveying speed is 3.3 cm / min.

[0077] The upper limit of the average conveying speed is not particularly limited, but is preferably 30 cm / min or less. If the average conveying speed is too fast, the conveying distance required for heating, thermal bonding, and cooling becomes long, which may lead to an increase in the size of the manufacturing equipment. Furthermore, if the average conveying speed is too fast, there is a possibility that heat will be transferred unevenly to the laminate. For this reason, the average conveying speed is preferably in the range of 1 cm / min to 30 cm / min, and more preferably in the range of 8 cm / min to 20 cm / min. Within this range, mass productivity can be improved while ensuring uniform heat transfer to the laminate.

[0078] The bonded body 1 can be manufactured through the above steps. Next, a step of imparting a circuit shape to the copper plate 4 is performed. An effective method for imparting the circuit shape is to perform an etching step on the copper plate 4. Through the etching step, the copper plate 4 is processed into a copper circuit 4a. By imparting a circuit shape to the copper plate 4 of the bonded body 1, a ceramic circuit substrate 10 is obtained. Alternatively, the copper circuit 4a may be produced by previously processing the copper plate 4 into a circuit shape. The ceramic circuit substrate 10 is obtained by bonding the copper circuit 4a to the ceramic substrate 2. A large bonded body may be produced and multiple pieces may be obtained. In other words, one bonded body may be divided into multiple bonded bodies 1. Furthermore, a semiconductor device 20 can be manufactured by mounting a semiconductor element 8 or the like on the obtained ceramic circuit substrate 10.

[0079] (Example) (Examples 1 to 8, Comparative Examples 1 and 2) Silicon nitride substrates, aluminum nitride substrates, and aluminum oxide substrates were prepared as ceramic substrates. The thermal conductivity of the silicon nitride substrate is 90 W / m K and the three-point bending strength is 650 MPa. The thermal conductivity of the aluminum nitride substrate is 170 W / m K and the three-point bending strength is 400 MPa. The thermal conductivity of the aluminum oxide substrate is 20 W / m K and the three-point bending strength is 430 MPa. The length, width, and thickness of each substrate are as shown in Table 1.

[0080] [Table 1]

[0081] Next, the active metal brazing filler metals shown in Table 2 were prepared. In Table 2, the compositions of the active metal brazing filler metals are shown with the total of the brazing filler metal components being 100 mass %.

[0082] [Table 2]

[0083] Next, a copper plate was prepared. Oxygen-free copper was used for the copper plate. The thickness of the copper plate is shown in Table 3.

[0084] [Table 3]

[0085] An active metal braze paste was prepared by adding a binder to the active metal braze. The active metal braze paste was applied to a ceramic substrate. A copper plate was placed on the ceramic substrate to create a laminate. In the laminate, a copper plate was placed on each side of the ceramic substrate via the active metal braze paste. The combination of ceramic substrate, active metal braze, and copper plate in each laminate is shown in Table 4.

[0086] [Table 4]

[0087] Next, the laminate was subjected to a heat bonding step to manufacture a bonded body. In Examples 1 to 8 and Comparative Example 1, the heat bonding step was performed using a continuous furnace. In Comparative Example 2, the heat bonding step was performed using a vacuum batch furnace. The bonding conditions are as shown in Table 5.

[0088] [Table 5]

[0089] In Table 5, the temperature rise rate is the average rate at which the temperature is raised from 200° C. to the bonding temperature. The temperature drop rate is the average rate at which the temperature is lowered from the bonding temperature to 200° C. A bonded body was produced by this process.

[0090] Next, the diffusion state of the active metal brazing material components into the copper plate of each of the joined bodies according to the example and comparative example was examined. The diffusion state was measured using an arbitrary cross section of the joined body. Each cross section was mirror-finished to prepare a measurement sample.

[0091] A graph of the detected amount of Cu was created using SEM-EDX. A JSM-7200F was used as the SEM-EDX. The measurement area was set to 280 μm in length and 2.5 μm in thickness. Other measurement methods were as described above. The first measurement point, second measurement point, and Ag diffusion region were determined from the Cu graph. The first measurement point was identified by the minimum value in the second-order derivative of the graph, where the detected amount (concentration) of Cu was 80 mass% or more. The results are shown in Table 6.

[0092] [Table 6]

[0093] As can be seen from Table 6, for the bonded bodies according to the examples, the ratio of the detected amount of the first element (mass%) to the detected amount of Ag (mass%) at the first measurement point was within the range of 0 to 0.4. The ratio of the detected amount of Ag (mass%) at the second measurement point to the detected amount of Ag (mass%) at the first measurement point was within the range of 0.1 to 0.7. The Ag diffusion regions were all 30 μm or less. The distance from the first measurement point to the second measurement point was 10 μm. It can be seen that the amount of diffusion of elements such as Ag and Sn was reduced over a short distance of 10 μm. Furthermore, in the graph of Cu for the bonded bodies according to the examples, the slope of the detected amount of Cu in the second region / the slope of the detected amount of Cu in the first region was both 0.5 or less.

[0094] In contrast, in Comparative Example 1, although a continuous furnace was used, the heating and cooling rates were slow. This is thought to have resulted in a large amount of heat being applied to the laminate, increasing the amount of diffusion of Ag, Sn, and other elements. In Comparative Example 2, a vacuum batch furnace was used. Compared to a continuous furnace, a batch furnace imposes a larger heat load on the laminate, resulting in an increased amount of diffusion of Ag and Sn. Furthermore, in the graph of Cu for the bonded body according to the comparative example, the slope of the detected amount of Cu in the second region / the slope of the detected amount of Cu in the first region both exceeded 0.5.

[0095] Furthermore, in Examples 1 and 3 to 9, in which the Ti content in the active metal braze alloy was 5 mass% or more, the yield was good. In contrast, in Example 2, the Ti content in the active metal braze alloy was as low as 2 mass%, so the yield was slightly reduced.

[0096] Next, each of the bonded bodies according to the examples and comparative examples was subjected to etching to prepare ceramic circuit substrates. The ceramic circuit substrates were subjected to tests for the bonding strength of the copper circuit, the conductivity of the copper circuit, and Ag migration.

[0097] The bonding strength of the copper circuit was measured using a peel test. The measurement conditions for the peel test were as follows: First, a portion of the bonded copper circuit was peeled off, and a 10 mm section of the peeled copper circuit was bent at a right angle to the ceramic substrate to create a clamp part. Using a test stand, the clamp part was pulled against the ceramic substrate at a constant speed (50.0 mm / min). During the pull, the average value of the memory on the force gauge (spring scale) was read.

[0098] The following equation 1 shows the relationship between peel strength δf (kgf / cm), the joining width W (mm) of the copper circuit being pulled, and the measured value P (kgf). The peel strength δf in equation 1 is converted to peel strength F (N / m) in SI units using equation 2. The average value read from the force gauge was converted to peel strength using equation 2 below. δf=(10 / W)×P (1) F=δf×9.8×10 2 ···(2)

[0099] The conductivity of the copper circuit was measured by resistance value using a tester. When the resistance value of the oxygen-free copper plate before bonding was taken as 100, ceramic circuit boards in which the resistance value of the copper circuit was 90 or more were evaluated as "maintained," and ceramic circuit boards in which the resistance value of the copper circuit was less than 90 were evaluated as "decreased." In each example and comparative example, the resistance value was measured at 10 points on the ceramic substrate, and if even one point was less than 90, it was evaluated as "decreased."

[0100] To evaluate Ag migration properties, a voltage was applied to the ceramic circuit board at high temperature and high humidity, and the occurrence rate of Ag migration marks was measured. An electrochemical migration evaluation system manufactured by Espec Corporation was used as the measuring device. An AC voltage of 2000 V (peak voltage 2820 V) was applied to the ceramic circuit board continuously for 30 hours in an environment of 85°C temperature and 85% humidity. The surface of the ceramic circuit board was then inspected for the presence of Ag migration marks. One hundred ceramic circuit boards from each example and comparative example were evaluated. Ceramic circuit boards with 0 to 5 ceramic circuit boards containing one or more Ag migration marks were evaluated as "good." Ceramic circuit boards with 6 or more ceramic circuit boards containing one or more Ag migration marks were evaluated as "poor." The results are shown in Table 7.

[0101] [Table 7]

[0102] As can be seen from Table 7, the TCT characteristics and Ag migration characteristics were improved in the Examples compared to the Comparative Examples. Furthermore, Sn migration was also suppressed in the Examples. Although the bonding strength was comparable between the Examples and the Comparative Examples, the improved TCT characteristics and Ag migration characteristics improved the performance of the ceramic circuit substrate. Furthermore, the ceramic circuit substrate according to the Examples was able to suppress a decrease in the conductivity of the copper plate.

[0103] (Configuration 1) a ceramic substrate; Copper plate and a bonding layer that bonds the ceramic substrate and the copper plate, the bonding layer contains Ag, Cu, an active metal, and a first element; the first element is one or two selected from Sn and In, A joined body in which, when an arbitrary cross section is analyzed by SEM-EDX, the detected amount of Cu is 80 mass % or more, and the ratio of the detected amount of the first element (mass %) / the detected amount of Ag (mass %) at the first measurement point is within the range of 0 to 0.4, where the first measurement point is the point where the change in slope of the graph of the detected amount of Cu is the largest. (Configuration 2) 2. The bonded body according to claim 1, wherein at the first measurement point, the ratio of the detected amount (mass %) of the first element to the detected amount (mass %) of Ag is in the range of 0.05 to 0.2. (Configuration 3) The bonded body according to configuration 1 or 2, wherein a region from the interface between the ceramic substrate and the bonding layer to the first measurement point is defined as a first region, and a region on the opposite side of the first measurement point from the first region is defined as a second region, and in the graph, a ratio of a slope of the detected amount of Cu in the second region to a slope of the detected amount of Cu in the first region is 0.5 or less. (Configuration 4) 4. The bonded body according to any one of Configurations 1 to 3, wherein the amount of Ag detected at the first measurement point is within the range of 3% by mass or more and less than 20% by mass. (Configuration 5) 5. The joined body according to any one of Configurations 1 to 4, wherein the ratio of the detected amount of active metal (mass %) / detected amount of Ag (mass %) at the first measurement point is within the range of 0 or more and 0.1 or less. (Configuration 6) When a point shifted 10 μm from the first measurement point toward the surface of the copper plate is set as a second measurement point, 6. The bonded body according to any one of configurations 1 to 5, wherein the ratio of the amount of Ag detected (mass %) at the second measurement point to the amount of Ag detected at the first measurement point is within the range of 0.1 to 0.7. (Configuration 7) 7. The bonded body according to claim 6, wherein at the second measurement point, the ratio of the detected amount (mass %) of the first element to the detected amount (mass %) of Ag is within a range of 0 to 0.1. (Configuration 8) 7. The joined body according to claim 6, wherein at the second measurement point, the ratio of the detected amount of active metal (% by mass) to the detected amount of Ag (% by mass) is within the range of 0 to 0.1. (Configuration 9) 9. The bonded body according to any one of Configurations 1 to 8, wherein an Ag-diffused region is present between the ceramic substrate and a point shifted 30 μm from the first measurement point toward the surface of the copper plate. (Configuration 10) The bonded body according to any one of Configurations 1 to 9, wherein the copper plate has a thickness of 0.3 mm or more. (Configuration 11) The bonded body according to any one of Configurations 1 to 10, wherein the ceramic substrate is a silicon nitride substrate. (Configuration 12) 12. A ceramic circuit board, in which a circuit pattern is imparted to the copper plate of the bonded body according to any one of Configurations 1 to 11. (Configuration 13) A ceramic circuit substrate according to aspect 12; a semiconductor element mounted on the copper plate to which the circuit pattern is imparted; A semiconductor device comprising: (Configuration 14) A method for producing a bonded body according to any one of Configurations 1 to 11, comprising: preparing a laminate including the ceramic substrate, an active metal brazing material having an active metal content of 5% by mass or more and 15% by mass or less, and the copper plate; a step of thermally bonding the ceramic substrate and the copper plate using a continuous furnace; A method for manufacturing a bonded body, comprising:

[0104] Although several embodiments of the present invention have been described above, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, the above-described embodiments can be implemented in combination with each other. [Explanation of symbols]

[0105] 1...Zygote 2...Ceramic substrate 3...Joining layer 4...Copper plate (front copper plate) 4a…Copper circuit 5...Copper plate (back copper plate) 6…1st measurement point 7…Second measurement point 8...Semiconductor element 10...Ceramic circuit board 20...Semiconductor device

Claims

1. a ceramic substrate; Copper plate and A bonded body comprising a bonding layer that bonds the ceramic substrate and the copper plate, the bonding layer contains Ag, Cu, an active metal, and a first element; The bonding layer contains 40% by mass or more of Ag, the first element is one or two selected from Sn and In, When an area of ​​280 μm in length and 2.5 μm in thickness is analyzed by SEM-EDX from the interface between the ceramic substrate and the bonding layer toward the copper plate surface on a cut surface obtained by cutting the bonded body along a direction perpendicular to the surface of the ceramic substrate, the detected amount of Cu is 80 mass% or more, and when the point where the change in slope in a graph of the detected amount of Cu is the largest is taken as a first measurement point, the detected amount of the first element (mass%) / detected amount of Ag (mass%) at the first measurement point is in the range of 0 to 0.4, and the detected amount of Ag is in the range of 3 mass% to less than 20 mass%.

2. 2. The joined body according to claim 1, wherein at the first measurement point, the ratio of the detected amount (mass %) of the first element to the detected amount (mass %) of Ag is in the range of 0.05 to 0.

2.

3. 3. The bonded body according to claim 1, wherein when a region from the interface between the ceramic substrate and the bonding layer to the first measurement point is defined as a first region, and a region on the opposite side of the first measurement point from the first region is defined as a second region, in the graph, a ratio of a slope of the detected amount of Cu in the second region to a slope of the detected amount of Cu in the first region is 0.5 or less.

4. 3. The joined body according to claim 1, wherein the ratio of the detected amount of active metal (mass %) to the detected amount of Ag (mass %) at the first measurement point is within a range of 0 to 0.

1.

5. When a point shifted 10 μm from the first measurement point toward the surface of the copper plate is set as a second measurement point, 3. The joined body according to claim 1, wherein a ratio of the amount (mass %) of Ag detected at the second measurement point to the amount of Ag detected at the first measurement point is within a range of 0.1 to 0.

7.

6. 6. The joined body according to claim 5, wherein at the second measurement point, the ratio of the detected amount (mass %) of the first element to the detected amount (mass %) of Ag is within a range of 0 to 0.

1.

7. 6. The joined body according to claim 5, wherein the ratio of the detected amount (mass %) of active metal to the detected amount (mass %) of Ag at the second measurement point is within a range of 0 to 0.

1.

8. 3. The joined body according to claim 1, wherein an Ag-diffused region exists between the ceramic substrate and a point shifted 30 μm from the first measurement point toward the surface of the copper plate.

9. 3. The joined body according to claim 1, wherein the copper plate has a thickness of 0.3 mm or more.

10. 3. The bonded body according to claim 1, wherein the ceramic substrate is a silicon nitride substrate.

11. A ceramic circuit board in which a circuit pattern is imparted to the copper plate of the bonded body according to claim 1.

12. The ceramic circuit substrate according to claim 11; a semiconductor element mounted on the copper plate to which the circuit pattern is imparted; A semiconductor device comprising:

13. The thickness of the copper plate is 0.3 mm or more, 6. The bonded body according to claim 5, wherein the ceramic substrate is a silicon nitride substrate.

14. The thickness of the copper plate is 0.3 mm or more, 7. The bonded body according to claim 6, wherein the ceramic substrate is a silicon nitride substrate.

15. 6. The joined body according to claim 5, wherein an Ag-diffused region exists between the ceramic substrate and a point shifted 30 μm from the first measurement point toward the surface of the copper plate.

16. 7. The joined body according to claim 6, wherein an Ag diffusion region exists between the ceramic substrate and a point shifted 30 μm from the first measurement point toward the surface of the copper plate.

17. A ceramic circuit board in which a circuit pattern is imparted to the copper plate of the bonded body according to claim 13.

18. A ceramic circuit board in which a circuit pattern is imparted to the copper plate of the bonded body according to claim 14.

19. A ceramic circuit board in which a circuit pattern is imparted to the copper plate of the bonded body according to claim 15.

20. A method for producing the bonded body according to claim 1, preparing a laminate including the ceramic substrate, an active metal brazing material having an active metal content of 5% by mass or more and 15% by mass or less, and the copper plate; a step of thermally bonding the ceramic substrate and the copper plate using a continuous furnace; A method for manufacturing a bonded body, comprising:

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