Substrate for semiconductor device and method for manufacturing same

Abstract

A substrate for a semiconductor device according to the present invention is provided with: a ceramic substrate; and a copper plate bonded to at least one surface of the ceramic substrate, the ceramic substrate having a Cu-present region, the Cu-present region having a Cu-present depth of 11.0-20.0 [mu] m when the cumulative Cu mass concentration is displayed to be 90% from the bonding interface with the copper plate.

Description

Technical Field

[0001] The present invention relates to a substrate for a semiconductor device and a method for manufacturing the same. Background Art

[0002] As a semiconductor device substrate used for a power transistor module or the like, a DBOC substrate (Direct Bonding of Copper Substrate) having a copper plate on the surface of a ceramic substrate is known (for example, Patent Documents 1 to 3).

[0003] Prior art literature Patent Literature Patent Document 1: International Publication No. 2022 / 118802 Summary of the invention Problems to be solved by the invention However, in the above-mentioned semiconductor device substrate, due to the heat generated by the high voltage / high current applied to the semiconductor, the constituent components cause thermal expansion, and the ceramic substrate and the electrode may be peeled off. Therefore, in order to improve the reliability of the device, the bonding interface between the ceramic substrate and the electrode is required to have a high bonding strength.

[0004] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a semiconductor device substrate and a method for manufacturing the same, which can improve the bonding strength between a copper plate and a ceramic substrate.

[0005] Technical solutions to solve problems Technical solution 1. A semiconductor device substrate comprises: a ceramic substrate; and a copper plate bonded to at least one surface of the ceramic substrate. The ceramic substrate has a Cu existing region, and the Cu existing depth of the Cu existing region when the cumulative Cu mass concentration from the bonding interface with the copper plate is 90% is 11.0 to 20.0 μm.

[0006] Technical solution 2. The semiconductor device substrate according to claim 1, wherein the ceramic substrate contains: aluminum oxide; and zirconium oxide or partially stabilized zirconium oxide, In the Cu existing region, the content of the copper in the crystal grains of the zirconium oxide is greater than the content of the copper in the crystal grains of the aluminum oxide.

[0007] Technical solution 3. The semiconductor device substrate according to claim 1 or 2, wherein a load per unit width for peeling the copper plate from the ceramic substrate is 5.5 kg / cm or more.

[0008] Technical solution 4. A method for manufacturing a substrate for a semiconductor device, comprising the steps of oxidizing a copper plate by a wet oxidation method, and bonding at least one surface of a ceramic substrate to the copper plate by a direct bonding method. The oxidized copper plate contains CuO and Cu 2 O before being bonded to the ceramic substrate, and a copper oxide layer rich in CuO is formed on the surface.

[0009] Technical solution 5. The method for manufacturing a semiconductor device substrate according to claim 3 or 4, wherein on each surface of the ceramic substrate, the Cu presence depth when the cumulative Cu mass concentration from the bonding interface with the copper plate is 90% is 11.0 to 20.0 μm.

[0010] Effects of the Invention According to the present invention, the bonding strength between the ceramic substrate and the copper plate can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a cross-sectional view showing one embodiment of a semiconductor device including a semiconductor device substrate according to the present invention.

[0012] Figure 2 These are the XRD measurement results of the surface of the copper plate in Examples of the present invention.

[0013] Figure 3 This is a cross-sectional SEM image of the copper plate of Example 1 according to the present invention.

[0014] Figure 4 This is an EPMA mapping image of Zr and Cu in the cross section of the semiconductor device substrate of Example 1 according to the present invention.

[0015] Figure 5 (a) is a backscattered electron image near the interface between the copper plate and the ceramic substrate. Figure 5 (b) is a schematic diagram describing a subdivision and averaging method used for contouring an EPMA mapping image in a cross section of a semiconductor device substrate according to Example 1 of the present invention.

[0016] Figure 6 This is a diagram showing the dependency of the mass concentration of Cu and Al in the ceramic substrate according to the present invention with respect to the depth in the direction of the ceramic substrate from the bonding interface.

[0017] Figure 7 This is a graph showing the integral of the Cu mass concentration with respect to the depth in the ceramic substrate direction from the bonding interface in the ceramic substrate according to the present invention. DETAILED DESCRIPTION

[0018] Hereinafter, one embodiment of a ceramic substrate and a semiconductor device substrate using the ceramic substrate according to the present invention will be described with reference to the drawings. Figure 1 It is a cross-sectional view of a semiconductor device including the semiconductor device substrate according to the present embodiment.

[0019] <1. Overview of semiconductor devices> The semiconductor device involved in this embodiment can be used as a power module in various electronic devices such as smartphones, personal computers, large white appliances, railways, electric vehicles, power generation (wind power generation, solar power generation, fuel cells, etc.), air conditioners, industrial robots, business elevators, household microwave ovens, IH rice cookers, UPS (uninterruptible power supply), etc.

[0020] like Figure 1 As shown, the semiconductor device 1 according to the present embodiment includes a semiconductor device substrate 2 , a first bonding material 5 , a second bonding material 5 ′, a semiconductor chip 6 , bonding wires 7 , and a heat sink 8 .

[0021] The semiconductor device substrate 2 is a so-called DBOC substrate (Direct Bonding of Copper Substrate), and includes a plate-shaped ceramic substrate 3 as an insulator, a first copper plate 4 bonded to one surface (upper surface) thereof, and a second copper plate 4' bonded to the other surface (lower surface) thereof. The ceramic substrate 3 will be described in detail later.

[0022] A transmission circuit is formed on the first copper plate 4. On the other hand, the second copper plate 4' is formed in a flat plate shape.

[0023] A semiconductor chip 6 is bonded to the upper surface of the semiconductor device substrate 2, that is, to a part of the upper surface of the first copper plate 4, via a first bonding material 5. The semiconductor chip 6 and the first copper plate 4 are connected to each other by bonding wires 7.

[0024] On the other hand, a heat sink 8 is bonded to the lower surface of the semiconductor device substrate 2, that is, the lower surface of the second copper plate 4', via a second bonding material 5'. The heat sink 8 is a well-known heat sink and can be made of metal such as copper.

[0025] <2. Structure of ceramic substrate> Next, the ceramic substrate 3 is described in detail. The ceramic substrate 3 includes aluminum oxide (Al2O3), zirconium oxide (ZrO2), yttrium oxide (Y2O3), a glass component, and the remainder other than these. The glass component includes silicon dioxide (SiO2). The content of the constituent elements of the ceramic substrate 3 is described below.

[0026] The base component of the ceramic substrate 3 is composed of aluminum oxide. The content of aluminum oxide is, for example, preferably 75 mass % or more and 90 mass % or less, and more preferably 85 mass % or more and 90 mass % or less.

[0027] The content of zirconium oxide is preferably 10% by mass or more and 25% by mass or less, and more preferably 10% by mass or more and 15% by mass or less. When the content of zirconium oxide is 10% by mass or more, the strength of the ceramic substrate 3 can be improved. In addition, it is believed that the linear thermal expansion coefficient of the ceramic substrate 3 can be suppressed from becoming too small, and the difference in linear thermal expansion coefficient between the ceramic substrate 3 and the first copper plate 4 and the second copper plate 4' can be reduced. As a result, it is believed that the thermal stress generated at the bonding interface can be reduced, which helps to suppress the generation of cracks in the ceramic substrate 3 at the bonding interface.

[0028] In addition, as shown in the embodiment described later, Cu diffused from the copper plates 4, 4' joined to the ceramic substrate 3 diffuses into the ceramic substrate 3 via the grains of zirconium oxide preferentially rather than via the grains of aluminum oxide constituting the matrix component to form a Cu existence region. Therefore, when the zirconium oxide content is set as described above, the diffusion of Cu is promoted, and the bonding strength of the copper plates 4, 4' becomes higher as described later, which is preferred.

[0029] On the other hand, it is believed that by setting the content of zirconium oxide to 25% by mass or less, it is possible to suppress excessive reaction at the bonding interface when the copper plates are bonded, and to suppress the generation of voids at the bonding interface. This is because the wettability of aluminum oxide and zirconium oxide to the Cu-O eutectic liquid phase is different when the copper plates are bonded. In addition, by setting the content of zirconium oxide to 25% by mass or less, as described later, the impedance of the ceramic substrate 3 can be increased without increasing the content of silicon dioxide.

[0030] The content of yttrium oxide is preferably set to 0.8 mass % or more and 1.9 mass % or less. It is believed that by setting the content to 0.8 mass % or more, the proportion of the monoclinic phase in the zirconium oxide crystal phase can be suppressed from becoming too large, and on the other hand, the proportion of the tetragonal phase can be increased. As a result, it is believed that the mechanical strength of the ceramic substrate 3 can be improved, which helps to suppress the generation of cracks in the ceramic substrate 3 at the bonding interface.

[0031] The ratio of the yttrium oxide content to the zirconium oxide content is preferably 4.5 mass % or more and 7.9 mass % or less. This is believed to maintain the stability of the tetragonal phase of zirconium oxide at an appropriate level, which helps to suppress the reduction in the mechanical strength of the ceramic substrate 3 .

[0032] On the other hand, it is believed that by setting the content of yttrium oxide to 1.9 mass % or less, the proportion of cubic crystals in the zirconium oxide crystal phase can be suppressed from becoming too large, and the proportion of tetragonal crystals can be increased. As a result, it is believed that the mechanical strength of the ceramic substrate 3 can be improved, which helps to suppress the generation of cracks in the ceramic substrate 3 at the bonding interface.

[0033] Next, the glass component is described. The content of silicon dioxide is preferably 0.1 mass % or more and 2.5 mass % or less. If the content of silicon dioxide is 0.1 mass % or more, as described later, the oxygen ion conductivity of the ceramic substrate 3 is suppressed, and the impedance can be improved. On the other hand, if the content of silicon dioxide becomes high, the strength of the ceramic substrate 3 may be reduced. In order to suppress this situation, the content of silicon dioxide is preferably 2.5 mass % or less.

[0034] In particular, when the content of zirconium oxide is 10% by mass or more and 15% by mass or less, the content of silicon dioxide is preferably 0.7% by mass or more and 1.5% by mass or less. In addition, when the content of zirconium oxide is higher than 15% by mass and is 25% by mass or less, the content of silicon dioxide is preferably 1.5% by mass or more and 2.0% by mass or less. In this way, by changing the content of silicon dioxide according to the content of zirconium oxide, the impedance of the ceramic substrate 3 can be effectively improved.

[0035] The glass component may contain at least one of magnesium oxide (MgO) and calcium oxide (CaO). For example, the content of magnesium oxide is preferably 0.1% by mass or more and 0.8% by mass or less, and more preferably 0.15% by mass or more and 0.3% by mass or less. It is believed that by setting the content of magnesium oxide to 0.1% by mass or more, the ceramic substrate 3 can be sintered even without excessively increasing the firing temperature, and the coarsening of aluminum oxide particles and zirconium oxide particles can be suppressed. As a result, it is believed that the mechanical strength of the ceramic substrate 3 can be improved, which helps to suppress the generation of cracks in the ceramic substrate 3 at the bonding interface. In addition, it is believed that a sufficient amount of MgAl2O4 crystals (hereinafter referred to as "spinel crystals") can be generated in the ceramic substrate 3, which can improve the wettability relative to the Cu-O eutectic liquid phase when the copper plate is bonded. As a result, it is believed that it helps to suppress the generation of voids at the bonding interface.

[0036] On the other hand, by setting the content of magnesium oxide to 0.8 mass % or less, it is considered that excessive formation of spinel crystals having low mechanical strength can be suppressed, and the mechanical strength of the ceramic substrate 3 can be improved. As a result, it is considered that this contributes to suppressing cracks in the ceramic substrate 3 at the bonding interface.

[0037] When calcium oxide is contained in the glass component, the content of calcium oxide is preferably set to 0.03 mass % or more and 0.35 mass % or less. Thus, it is believed that the ceramic substrate 3 can be sintered even without excessively increasing the firing temperature, and the coarsening of the aluminum oxide particles and the zirconium oxide particles can be suppressed. As a result, it is believed that the mechanical strength of the ceramic substrate 3 can be improved, which helps to suppress the generation of cracks in the ceramic substrate 3 at the bonding interface.

[0038] The content of the remaining part is preferably set to 0.05% by mass or less in terms of oxide. As a result, it is believed that over-sintering of the ceramic substrate 3 can be suppressed even though the firing temperature is not excessively increased, and the porosity of the ceramic substrate 3 can be reduced. As a result, it is believed that the mechanical strength of the ceramic substrate 3 can be improved, which helps to suppress cracks in the ceramic substrate 3 at the bonding interface. It should be noted that the elements contained in the remaining part can be intentionally added elements or inevitably mixed elements. The elements contained in the remaining part are not particularly limited, and examples thereof include Fe (iron), Ti (titanium), Mn (manganese), etc.

[0039] In the present embodiment, the content of the constituent elements of the ceramic substrate 3 is calculated by oxide conversion as described above, but the constituent elements of the ceramic substrate 3 may exist in the form of oxides or not. For example, at least one of Y, Mg and Ca may not exist in the form of oxides but may be dissolved in ZrO2. For example, yttrium oxide may be dissolved in zirconium oxide to form PSZ (partially stabilized zirconium oxide).

[0040] The content of the constituent elements of the ceramic substrate 3 in terms of oxides is calculated as follows. First, a fluorescent X-ray analyzer (XRF) or an energy dispersive analyzer (EDS) attached to a scanning electron microscope (SEM) is used to qualitatively analyze the constituent elements of the ceramic substrate 3. Next, an ICP emission spectrometer is used to quantitatively analyze each element detected by the qualitative analysis. Next, the content of each element measured by the quantitative analysis is converted into oxides.

[0041] Here, XRF is the abbreviation of X-ray Fluorescence Analysis, SEM is the abbreviation of Scanning Electron Microscope, EDS is the abbreviation of Energy Dispersive X-ray Spectrocsopy, and ICP is the abbreviation of Inductively Coupled Plasma.

[0042] <3. Method for manufacturing ceramic substrate> Next, a method for producing a ceramic substrate is described. First, the powder materials of the above-mentioned constituent elements are mixed. Then, the mixed powder materials are pulverized and mixed using, for example, a ball mill.

[0043] Next, an organic binder (such as polyvinyl butyral), a solvent (such as xylene and toluene), and a plasticizer (such as dioctyl phthalate) are added to the pulverized and mixed powder material to form a slurry.

[0044] Next, the slurry is molded into a desired shape by a desired molding method (eg, mold pressing, cold isostatic pressing, injection molding, a doctor blade method, extrusion molding, etc.) to produce a ceramic molded body.

[0045] Then, when the ceramic molded body is fired in an oxygen atmosphere or an air atmosphere (1555° C. to 1565° C., for 0.7 hour to 1.0 hour), the ceramic sintered body 3 is completed.

[0046] <4. Method for manufacturing semiconductor device substrate> First, the copper plates 4 and 4' are wet treated by a wet oxidation method to be oxidized. The wet treatment method is described as follows. First, the oil and organic residues during the copper plate processing are treated by degreasing and cleaning. Next, the copper plates 4 and 4' are subjected to fine concave-convex processing by micro-etching. Next, the copper plates 4 and 4' are immersed in the oxidation treatment solution for a given time. For example, they are immersed in the oxidation treatment solution adjusted to pH = 14 for 5 minutes. As a result, the surface of the copper plates 4 and 4' before being bonded to the ceramic substrate 3 contains Cu2O and CuO and forms a CuO-rich oxide film.

[0047] Next, a laminated body is formed in which the copper plates 4 and 4' whose surfaces are oxidized as described above are arranged on the upper and lower surfaces of the ceramic substrate 3, and is heated for about 10 to 60 minutes under a nitrogen atmosphere at 1065°C to 1083°C. By heating, a Cu-O eutectic liquid phase is generated at the interface between the ceramic substrate 3 and the copper plates 4 and 4'. The thickness of each copper plate 4 and 4' can be set to 0.1 to 2.0 mm, for example.

[0048] Next, the Cu-O eutectic liquid phase is solidified by cooling the laminate, and the copper plates 4, 4' are bonded to the ceramic substrate 3. In this way, the semiconductor device substrate 2 is completed. It should be noted that the transmission circuit formed on the copper plate 4 on the surface bonded to the semiconductor chip 6 can be formed by, for example, a subtractive method or an additive method.

[0049] <5. Copper Existence Area in Ceramic Substrate> As described above, in the interior of the ceramic substrate 3 bonded with the copper plates 4 and 4', a Cu existing region is formed due to the copper diffused from the copper plates 4 and 4'. This point is described in detail in the embodiment described later. The Cu existing region existing along the internal direction of the ceramic substrate 3 from the interface between the copper plates 4 and 4' and the ceramic substrate 3 is studied. As a result, the inventors found that: in the Cu existing region, if the Cu existing depth from the interface with the ceramic substrate 3 is a given depth, the bonding strength of the copper plates 4 and 4' becomes higher. In particular, it is found that: if the Cu existing depth at which the cumulative Cu mass concentration in the Cu existing region shows 90% is 11.0 to 20.0 μm, more preferably 13.0 to 18.0 μm, and further preferably 13.0 to 16.0 μm, the bonding strength of the copper plates 4 and 4' becomes higher.

[0050] That is, it was found that if the Cu presence depth at which the cumulative Cu mass concentration is 90% is less than 11.0 μm, the copper presence region is narrow, so the bonding strength becomes weak. On the other hand, it was also found that if the Cu presence depth at which the cumulative Cu mass concentration is 90% exceeds 20.0 μm, the bonding strength decreases.

[0051] In the examples described below, the load per unit width for peeling the copper plates 4 and 4' from the ceramic substrate 3 is measured and is preferably 5.5 kg / cm or more, more preferably 6.0 kg / cm or more, and particularly preferably 8.0 kg / cm or more.

[0052] In addition, it is known that if the copper plate is oxidized by the wet oxidation method as described above and Cu2O and CuO are contained on the surface of the copper plate 4, 4' and a CuO-rich oxide film is formed, then the diffusion region of Cu becomes wider as described above compared with the copper plate oxidized by the dry oxidation method. It should be noted that even if a method is used in which a copper plate oxidized by a method other than the wet oxidation method is used, as long as the semiconductor device substrate can achieve the above-mentioned Cu presence depth, the bonding strength between the copper plate 4, 4' and the ceramic substrate 3 can be improved as described above. That is, the above-mentioned Cu presence region can also be formed by a method other than the method of diffusing copper from the copper plate 4, 4' into the ceramic substrate 3.

[0053] In the above embodiment, copper plates 4 and 4' are bonded to both surfaces of the ceramic substrate 3, but it is also possible to bond a copper plate to only one surface and use it as a semiconductor device substrate. In the case where copper plates 4 and 4' are bonded to both surfaces of the ceramic substrate 3, the Cu presence depth at which the cumulative Cu mass concentration in the Cu presence region is 90% may be different on each surface of the ceramic substrate 3, as long as it is within the range of 11.0 to 20.0 μm as described above.

[0054] Example Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples.

[0055] <1. Production of ceramic substrate> The ceramic substrates involved in Examples 1, 2 and Comparative Examples 1, 2, which are composed of the following materials, are prepared as the main component. That is, the ceramic substrates involved in Examples 1, 2 and Comparative Examples 1, 2 are the same. Specifically, first, a powder material prepared by mixing the composition shown in Table 1 in a given ratio is pulverized and mixed using a ball mill. In Table 1, mass % is expressed as wt%. It should be noted that the numerical values ​​shown in Table 1 are values ​​converted to oxides of each element.

[0056] [Table 1] Next, polyvinyl butyral as an organic binder, xylene as a solvent, and dioctyl phthalate as a plasticizer were added to the pulverized and mixed powder material to form a slurry.

[0057] Next, the slurry-like substance is formed into a sheet-like shape by a doctor blade method to produce a ceramic molded body.

[0058] Next, the ceramic molded body was fired in air at 1565° C. for 0.8 hours to obtain ceramic substrates according to Examples 1 and 2 and Comparative Examples 1 and 2. The dimensions of the ceramic substrates were 0.32 mm thick, 39 mm long, and 45 mm wide.

[0059] Next, prepare the copper plates involved in Examples 1 and 2 and Comparative Examples 1 and 2, and perform oxidation treatment on the surface. Examples 1 and 2 are oxidized by the above-mentioned wet oxidation method, and Comparative Examples 1 and 2 are oxidized by the dry oxidation method. In the dry oxidation method, the copper plates involved in Comparative Examples 1 and 2 are heated in a heat treatment furnace heated to 300°C for 5 minutes to form an oxide film of Cu2O. The thickness of the copper plates is about 0.3 mm. Next, the copper plates involved in the examples and comparative examples with oxidized surfaces are arranged on the upper and lower surfaces of the ceramic substrate, and heated under a nitrogen atmosphere at 1065°C for the time shown in the following Table 2. In this way, the substrates for semiconductor devices involved in Examples 1 and 2 and Comparative Examples 1 and 2 are obtained.

[0060] [Table 2] <2. Evaluation> <2-1. State of the copper plate surface> Before bonding to the ceramic substrate, the surfaces of the copper plates by wet oxidation (Examples 1 and 2) and the copper plates by dry oxidation (Comparative Examples 1 and 2) were measured by XRD (X-ray Diffraction). The measurement was performed using SmartLab (Rigaku Co., Ltd.) at a rated voltage of 45 kV and a rated current of 200 mA. The results are shown in Figure 2 .like Figure 2 As shown, the surface of the copper plate treated by the wet oxidation method shows a peak of CuO, so it can be known that a copper oxide layer rich in CuO is formed on the surface. On the other hand, the surface of the copper plate treated by the dry oxidation method shows a peak of Cu2O, so it can be known that a copper oxide layer rich in Cu2O is formed on the surface.

[0061] <2-2. Quantitative analysis of elements (point analysis method)> In Example 1, a field emission electron probe microanalyzer was used to quantitatively analyze the O, Al, Cu, Y, and Zr elements contained in the ZrO2 particles (point 1) and the Al2O3 matrix (point 2) at a depth of 1.5 μm from the bonding interface in the direction of the ceramic substrate. Figure 3 The results of the point analysis method are shown in Table 3.

[0062] [Table 3] From the results in Table 3, it can be seen that the Cu mass concentration in the ZrO2 particle (point 1) is 2.7 times higher than that in the Al2O3 matrix (point 2), and the Cu diffusion path is preferentially diffused in the ZrO2 particle and through the ZrO2 particle. In this way, it can be seen that a Cu existence area is formed.

[0063] <2-3. Quantitative analysis of elements (surface analysis method)> In Example 1, Zr and Cu were analyzed using an electric field emission electron probe microanalyzer (EPMA) for the region including the Cu electrode, the bonding interface, and the ceramic substrate. Figure 4 shown.

[0064] The distribution positions of Zr and Cu are roughly the same. In addition, it is confirmed that the concentration of Cu decreases as it moves from the bonding interface to the inside of the ceramic substrate. The above-mentioned diffusion behavior of Cu (Table 3 and Figure 4 ) is not limited to Example 1, and the same properties are also confirmed in Example 2.

[0065] <2-4. Analysis of Cu and Al Contents> In order to confirm the distribution of each element in detail, the following analysis was performed. A cross-section sample obtained by cutting a semiconductor device substrate and further polishing the cut surface was used for this analysis. The cross section was analyzed using a scanning electron microscope (SEM) and a field emission electron probe microanalyzer. Figure 5 (a) is a backscattered electron image near the bonding interface between the copper plate and the ceramic substrate. The image area of ​​the backscattered electron image is 25μm in width and 100μm in depth. The area is divided into 256×1024 small areas. Then, the concentration of the element in each small area is calculated. On this basis, Figure 5 As shown in (b), the concentration (mass %) of the element is averaged in 256 small areas in the horizontal direction (X direction) (this is called the average element concentration in the X direction). The element concentration distribution is measured by an electric field emission electron probe microanalyzer (EPMA). As the EPMA, a field emission electron probe microanalyzer FE-EPMA, JXA-8530F, JEOL is used.

[0066] Figure 6 So Figure 5 A curve graph with the Y direction, i.e. the depth direction of the ceramic substrate, as the vertical axis is plotted with the average element concentration in each X direction at each depth as the vertical axis. It should be noted that the horizontal axis of the curve graph takes the bonding interface between the copper plate and the ceramic substrate as the origin. The bonding interface is synonymous with the point where the Al concentration rises from 0wt%. However, when plotting the mass concentration of Cu, when a 10μm interval is randomly taken at a depth in the direction of the ceramic substrate from the bonding interface, when the condition of the slope of the Cu plotting is ≤0.10, the Cu mass concentration after the starting point of the interval is defined as 0wt%. According to Figure 6 As a result, the diffusion distance of Cu tends to be longer when the copper plate is oxidized by wet treatment or when the bonding time of the electrodes is long.

[0067] <2-5. Relationship between Cu diffusion depth and bonding strength in semiconductor device substrate> The bonding strength between the copper plate and the ceramic substrate is measured as follows. First, the bonded rectangular copper plate is peeled off from the end along the long side direction by a given length and bent in a 90° direction. Next, the bent end of the copper plate is clamped with a clamp and pulled in a vertical direction. The maximum value at this time is defined as the measured strength. That is, the bonding strength (kg / cm) = maximum value of the pulling load (kg) / length of the short side of the rectangle (cm). The results are shown in Table 4.

[0068] Will Figure 6 The value curve obtained by integrating the Cu concentration in the Y-axis direction is shown in FIG. Figure 7At this time, the Cu diffusion depth at which the cumulative Cu mass concentration in the Cu diffusion region reached 90% was determined. The above-mentioned bonding strength and Cu diffusion depth are shown in Table 4.

[0069] [Table 4] Comparing Example 1 with Example 2, as the bonding time becomes longer, the Cu diffusion area tends to increase in the Y direction, while the bonding strength tends to decrease. Comparing Example 1 with Comparative Example 1, it is confirmed that although the bonding time is the same, the Cu diffusion area of ​​Comparative Example 1 is narrower and the bonding strength is lower. It can be seen that the melting point of the copper oxide layer decreases, and the Cu diffusion is promoted, resulting in a higher bonding strength. However, there is no proportional relationship between the Cu diffusion area in the Y direction and the bonding strength. When the Cu diffusion area becomes above a certain level, the bonding strength begins to decrease.

[0070] Therefore, it is understood that Examples 1 and 2, in which the Cu diffusion depth when the cumulative Cu mass concentration from the bonding interface is 90% is 11.0 to 20.0 μm, exhibit higher bonding strength than Comparative Examples 1 and 2.

[0071] Explanation of symbols 2: Substrates for semiconductor devices 3: Ceramic substrate 4, 4': Copper plate.

Claims

1. A semiconductor device substrate, comprising: Ceramic substrates; and a copper plate bonded to at least one surface of the ceramic substrate, The ceramic substrate has a Cu existing region, and the Cu existing depth of the Cu existing region when the cumulative Cu mass concentration from the bonding interface with the copper plate is 90% is 11.0 to 20.0 μm.

2. The semiconductor device substrate according to claim 1, wherein The ceramic substrate contains: aluminum oxide; and zirconium oxide or partially stabilized zirconium oxide. In the Cu existing region, the content of the copper in the crystal grains of the zirconium oxide is greater than the content of the copper in the crystal grains of the aluminum oxide.

3. The semiconductor device substrate according to claim 1 or 2, wherein: The load per unit width for peeling the copper plate from the ceramic substrate is 5.5 kg / cm or more.

4. A method for manufacturing a substrate for a semiconductor device, comprising the steps of oxidizing a copper plate by a wet oxidation method, and bonding at least one surface of a ceramic substrate to the copper plate by a direct bonding method, The oxidized copper plate contains CuO and Cu 2 O before being bonded to the ceramic substrate, and a copper oxide layer rich in CuO is formed on the surface.

5. The method for manufacturing a semiconductor device substrate according to claim 3 or 4, wherein: On each surface of the ceramic substrate, the Cu presence depth when the cumulative Cu mass concentration from the bonding interface with the copper plate was 90% was 11.0 to 20.0 μm.

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