Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/10—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide
  • C04B35/111—Fine ceramics
  • C04B35/117—Composites
  • C04B35/119—Composites with zirconium oxide
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K1/00—Printed circuits
  • H05K1/02—Details
  • H05K1/03—Use of materials for the substrate
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10W—GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
  • H10W70/00—Package substrates; Interposers; Redistribution layers [RDL]
  • H10W70/60—Insulating or insulated package substrates; Interposers; Redistribution layers
  • H10W70/67—Insulating or insulated package substrates; Interposers; Redistribution layers characterised by their insulating layers or insulating parts
  • H10W70/69—Insulating materials thereof
  • H10W70/692—Ceramics or glasses

Definitions

• the present invention relates to a ceramic substrate and a semiconductor device substrate including the same.
• a DBOC substrate Direct Bonding of Copper Substrate
• Patent Documents 1 to 3 a DBOC substrate (Direct Bonding of Copper Substrate), which has a copper plate on the surface of a ceramic substrate.
• a copper plate is bonded to the surface of the ceramic substrate, but the inventor of the present invention has discovered that when the oxygen ion conductivity of the ceramic substrate increases, the ceramic substrate and the copper plate bond when a DC voltage is applied. It has been found that the bonding strength of the copper plate decreases and there is a risk that the copper plate may peel off.
• the present invention has been made to solve the above problems, and provides a ceramic substrate and a semiconductor device substrate that can suppress peeling when a DC voltage is applied when copper plates are bonded.
• the purpose is to
• Item 1 Alumina and Zirconia and Yttria and glassy and Contains The glassy substance is The first component contains Si, an alkali metal, and O as an element, The second component contains at least one element selected from Ca, Sr, and Ba, The content of the zirconia is 5 to 14% by mass, The value obtained by dividing the concentration in terms of oxide of the alkali metal, which is the first component of the glass, by the total distance of the interfaces (grain boundary length) where Al 2 O 3 , ZrO 2 , and SiO 2 are adjacent to each other.
• the concentration of Si, which is the first component of the glass, in terms of oxide is B
• the total mass concentration in terms of oxides of Ca, Sr, and Ba, which are the glassy second components, is C is C
• Item 2. The ceramic substrate according to item 1, wherein a mass ratio of the content of the alkali metal to the content of the glassy second component is 1.0 or less.
• Item 3. The ceramic substrate according to Item 1 or 2, wherein the zirconia content is 11% by mass or more.
• Item 4. The ceramic substrate according to any one of Items 1 to 3, wherein the molar fraction of the yttria to the zirconia is 0.015 to 0.035.
• Item 5 The ceramic substrate according to any one of Items 1 to 4, wherein a mass ratio of the total content of the zirconia and the yttria to the content of the alumina is 0.10 or more.
• Item 6. The ceramic according to any one of Items 1 to 5, wherein the mass ratio of the total content of the silica, the magnesia, and the glassy second component to the content of the alkali metal oxide is 25.0 or more. substrate.
• Item 7 The ceramic substrate according to any one of Items 1 to 6, which has a bending strength of 550 MPa or more.
• Section 8. Item 7. The ceramic substrate according to any one of Items 1 to 6, which has a bending strength of 700 MPa or more.
• Item 9 A semiconductor device substrate for mounting electronic components, The ceramic substrate according to any one of Items 1 to 8, a copper plate bonded to the ceramic substrate; A substrate for semiconductor devices, which is equipped with:
• FIG. 1 is a cross-sectional view showing one embodiment of a semiconductor device having a semiconductor device substrate according to the present invention.
• FIG. 2 is a diagram showing a boundary map and grain boundary length of Al 2 O 3 , ZrO 2 , and SiO 2 in a cross section of a ceramic substrate of Example 1 according to the present invention. It is a cross-sectional SEM image of the ceramic substrate of Example 1 according to the present invention. It is a cross-sectional SEM image of a ceramic substrate of Comparative Example 3 according to the present invention.
• FIG. 3 is a diagram showing the relationship between impedance and frequency in ceramic substrates of Example 1 and Comparative Example 3 according to the present invention.
• FIG. 1 is a cross-sectional view of a semiconductor device having a semiconductor device substrate according to this embodiment.
• the semiconductor device is, for example, a personal computer, a large white goods appliance, a railway, an electric vehicle, a power generation (wind power generation, a solar power generation, a fuel cell, etc.), an air conditioner, an industrial robot, a commercial elevator, a home use It is used as a power module in various electronic devices such as microwave ovens, IH electric rice cookers, and UPS (uninterruptible power supplies).
• a semiconductor device 1 As shown in FIG. 1, a 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, a bonding wire 7, and a heat sink 8. There is.
• the semiconductor device substrate 2 is a so-called DBOC substrate (Direct Bonding of Copper Substrate), and includes a plate-shaped ceramic substrate 3 that is an insulator, a first copper plate 4 bonded to one surface (upper surface) of the ceramic substrate 3, and a first copper plate 4 bonded to one surface (upper surface) of the ceramic substrate 3. and a second copper plate 4' joined to the surface (lower surface) of the second copper plate 4'. Details of the ceramic substrate 3 will be described later.
• DBOC substrate Direct Bonding of Copper Substrate
• a transmission circuit is formed on the first copper plate 4.
• the second copper plate 4' is formed into a flat plate shape.
• a semiconductor chip 6 is bonded to the upper surface of this semiconductor device substrate 2, that is, a part of the upper surface of the first copper plate 4 via a first bonding material 5. Further, the semiconductor chip 6 and the first copper plate 4 are connected by a bonding wire 7.
• 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 known one, and can be made of metal such as copper, for example.
• the ceramic substrate 3 contains alumina (Al 2 O 3 ), zirconia (ZrO 2 ), yttria (Y 2 O 3 ), glass, and the remainder other than these. Further, the glassy substance includes a first component and a second component. The first component contains Si, Mg, an alkali metal, and O as elements, and the second component contains at least one element selected from Ca, Sr, and Ba. However, the glassy material may contain components other than these. The contents of the constituent elements of this ceramic substrate 3 will be explained below.
• the content of alumina is, for example, preferably 75% by mass or more and 90% by mass or less, and more preferably 85% by mass or more and 90% by mass or less.
• the content of zirconia is, for example, preferably 5% by mass or more and 14% by mass or less, and more preferably 10% by mass or more and 14% by mass or less.
• the strength of the ceramic substrate 3 can be improved.
• the bending strength of the ceramic substrate 3 can be increased (for example, as shown in Examples 3 and 6 described later, the bending strength is set to 700 MPa or more). be able to.).
• the zirconia content it is thought that by setting the zirconia content to 14% by mass or less, it is possible to suppress excessive reaction at the bonding interface during copper plate bonding, and it is possible to suppress the formation of voids at the bonding interface. This is because alumina and zirconia have different wettability with the Cu--O eutectic liquid phase when bonding copper plates. Further, by setting the zirconia content to 14% by mass or less, the impedance of the ceramic substrate 3 can be improved without increasing the silica content, as described later.
• the content of yttria is preferably 0.3% by mass or more and 2.0% by mass or less, and more preferably 0.5% by mass or more and 1.2% by mass or less. It is considered that by setting the content to 0.3% by mass or more, the proportion of the monoclinic phase in the zirconia crystal phase can be suppressed from becoming excessive, and on the other hand, the proportion of the tetragonal phase can be increased. As a result, the mechanical strength of the ceramic substrate 3 can be improved, which is thought to contribute to suppressing the occurrence of cracks in the ceramic substrate 3 at the bonding interface.
• yttria By setting the mole fraction of yttria to the zirconia content within the range of 0.015 to 0.035, yttria is partially stabilized, exhibiting a behavior of increasing volume due to martensitic transformation at the tips of microcracks.
• oxidized zirconia (YSZ) is formed.
• YSZ oxidized zirconia
• yttria is dissolved in zirconia.
• zirconia and yttria exist as yttria partially stabilized zirconia, but they may exist alone. However, in the present invention, these two aspects will be described as being equivalent. Therefore, even when zirconia and yttria are explained individually, they may exist in the ceramic substrate 3 as yttria partially stabilized zirconia.
• the mass ratio of the total content of zirconia and yttria to the content of alumina is 0.10 or more. This is because when this mass ratio is 0.10 or more, the bending strength can be improved. On the other hand, this mass ratio is preferably 0.30 or less. This is because the thermal conductivity of zirconia is lower than that of alumina, so if this mass ratio exceeds 0.30, there is a possibility that sufficient thermal conductivity cannot be maintained as an insulating heat dissipation circuit board.
• the glassy substance includes a first component containing Si, an alkali metal, and O as elements, and a second component containing at least one element selected from Ca, Sr, and Ba. Contains.
• these elements mainly exist as oxides such as silica (SiO 2 ), alkali metal oxides, calcium oxide (CaO), strontium oxide (SrO), and barium oxide (BaO), they will be explained below.
• the first component may contain Mg, which exists in the form of an oxide such as magnesia (MgO) in the glassy substance.
• the content of silica is preferably 0.1% by mass or more and 2.5% by mass or less.
• the silica content is 0.1% by mass or more, as will be described later, the oxygen ion conductivity of the ceramic substrate 3 can be suppressed and the impedance can be improved.
• the silica content is preferably 2.5% by mass or less.
• the content of magnesia is preferably 0.05% by mass or more and 0.5% by mass or less, and more preferably 0.10% by mass or more and 0.3% by mass or less. It is believed that by setting the magnesia content to 0.05% by mass or more, the ceramic substrate 3 can be sintered without increasing the firing temperature excessively, and coarsening of alumina particles and zirconia particles can be suppressed. . As a result, the mechanical strength of the ceramic substrate 3 can be improved, which is thought to contribute to suppressing the occurrence of cracks in the ceramic substrate 3 at the bonding interface with the copper plate 4.
• spinel crystals MgAl 2 O 4 crystals
• Alkali metal ions have the function of cutting the Si-O bond of SiO 2 and forming non-bridging oxygen (NBO), and when NBO becomes an ion diffusion site, oxygen ion conductivity is created.
• alkali metals include sodium, potassium, and lithium, and two or more of these may be included. These are present in the ceramic substrate 3 as sodium oxide (Na 2 O), potassium oxide (K 2 O), and lithium oxide (Li 2 O). The present inventor has confirmed that any of these alkali metal oxides will be similarly shown in the Examples described below.
• the second component is a glassy network-modifying oxide, which is incorporated into the framework of the network-forming oxide mainly composed of glassy silica (SiO 2 ), changing the chemical and physical properties of the glass. It shows the function of In particular, when calcium oxide (CaO), strontium oxide (SrO), and barium oxide (BaO) are included in the glass containing the alkali metal oxides mentioned above, ion conduction using NBO as a diffusion site is suppressed. It is known that electrical conductivity decreases when Further, the effect of reducing electrical conductivity increases in the order of CaO ⁇ SrO ⁇ BaO.
• the insulating properties can be further improved by including CaO, SrO, and BaO in the glass containing the alkali metal oxide. Therefore, the problem to be solved by the present invention is that by applying a DC voltage, oxygen ions are conducted inside the ceramic substrate from the negative electrode side to the positive electrode side, reducing the bonding strength between the electrode and the ceramic substrate. It becomes possible to improve.
• the second component of the glass may contain one or more of CaO, SrO, and BaO.
• the mass ratio of the content of the alkali metal oxide to the content of the second component in terms of glassy oxide is preferably 1.0 or less, more preferably 0.5 or less, Particularly preferably 0.1 or less.
• the mass ratio of the total content of silica, magnesia, and vitreous second components to the content of alkali metal oxide is preferably 25.0 or more, and more preferably 30.0 or more.
• oxygen ion conduction can be suppressed more effectively.
• this value is less than 25.0, the smaller the value, the more the bonding strength between the ceramic substrate 3 and the copper plates 4, 4' decreases after applying the DC voltage.
• the upper limit of this value can be, for example, 65.0 or less.
• the content of sodium in terms of oxide in the ceramic substrate 3 is preferably 0% by mass or more than 0% by mass and 0.05% by mass or less. .
• the content in terms of glassy oxide in the ceramic substrate 3 can be, for example, 0.9% by mass to 3% by mass. This is because if it is less than 0.9% by mass, oxygen ion conduction cannot be sufficiently suppressed, while if it exceeds 3% by mass, sufficient bending strength cannot be obtained.
• the content of the remainder is preferably 0.5% by mass or less, more preferably 0.05% by mass or less in terms of oxide. It is thought that this makes it possible to suppress excessive sintering of the ceramic substrate 3 even though the firing temperature is not excessively high, and to reduce the porosity of the ceramic substrate 3. As a result, the mechanical strength of the ceramic substrate 3 can be improved, which is thought to contribute to suppressing the occurrence of cracks in the ceramic substrate 3 at the bonding interface with the copper plate 4.
• the content of the constituent elements of the ceramic substrate 3 is calculated in terms of oxides as described above, but the constituent elements of the ceramic substrate 3 may exist in the form of oxides, It does not have to exist in the form of an oxide.
• the constituent elements of the ceramic substrate 3 may exist in the form of oxides, It does not have to exist in the form of an oxide.
• at least one of Y, Mg, and Ca may not exist in the form of an oxide, but may be dissolved in solid solution in ZrO 2 .
• alkali metals some may not exist in the form of oxides. Even for alkali metals that do not exist in the form of oxides, the content is calculated in terms of oxides.
• the content of the constituent elements of the ceramic substrate 3 in terms of oxides is calculated as follows. First, the constituent elements of the ceramic substrate 3 are qualitatively analyzed using an X-ray fluorescence analyzer (XRF) or an energy dispersive analyzer (EDS) attached to a scanning electron microscope (SEM). Next, each element detected by this qualitative analysis is subjected to quantitative analysis using an ICP emission spectrometer. Next, the content of each element measured by this quantitative analysis is converted into oxides.
• XRF X-ray fluorescence analyzer
• EDS energy dispersive analyzer
• SEM scanning electron microscope
• the elements contained in the remainder may be elements added intentionally or elements mixed unavoidably.
• the elements contained in the remainder are not particularly limited, and examples thereof include Fe (iron), Ti (titanium), Mn (manganese), and the like.
• the glassy substance described above cannot exist within the matrix grains, but rather exists at the grain boundaries, which are regions surrounded by the matrix grains.
• grain boundaries There are three types of grain boundaries, for example, Al 2 O 3 /Al 2 O 3 , Al 2 O 3 /YSZ, and YSZ/YSZ.
• grain boundaries there are two types of grain boundaries: inside the ceramic substrate 3 that is not exposed to the outside (the three types described above), and in the surface layer that is exposed to the outside.
• there is a possibility that a very small amount of glassy components will be dissolved in Al 2 O 3 and YSZ.
• the present inventor obtained the following findings regarding glassy grain boundaries. Specifically, the knowledge regarding glassy grain boundaries was quantified and evaluated as follows. First, the following A to C were defined. A: By calculating the mass concentration ratio (wt%/ ⁇ m) of alkali metal to the total interface distance (grain boundary length) where Al 2 O 3 , ZrO 2 , and SiO 2 are adjacent to each other, the alkali metal concentration at the grain boundary can be calculated. The density was simulated and designated as A. A method for measuring grain boundary length will be described later. B: Mass concentration (weight %) of SiO 2 was defined as B. A/B: By calculating the ratio of B to A, the effect of an alkali metal on the electrical insulation properties of silica to form NBO was simulated.
• C C is the total mass concentration (% by weight) of CaO, SrO, and BaO that suppresses the formation of NBO by alkali metals.
• A/B/C ( A/(B ⁇ C)): The difficulty of NBO generation was simulated by calculating the ratio of C to A/B (1/ ⁇ m ⁇ wt%). Note that A/(B ⁇ C) can also be defined as (SiO 2 mass concentration/total interface distance) ⁇ (alkali metal mass concentration/total mass concentration of Ca, Ba, and Sr).
• the above calculated value (A/(B x C)) varies depending on the blending ratio of the components, raw material powder diameter, firing time/temperature, etc., but the inventor has determined that it is within the range of 7.1 x 10 -4 or less. It has been found that if there is, DC durability is improved and the bonding strength ratio is also excellent. The inventors also found that the lower the calculated value, the higher the bending strength. From the viewpoint of improving transverse strength, it was found that this calculated value is more preferably 2.0 ⁇ 10 ⁇ 4 or less, and particularly preferably 1.5 ⁇ 10 ⁇ 4 or less.
• an organic binder eg, polyvinyl butyral
• a solvent xylene, toluene, etc.
• a plasticizer dioctyl phthalate, etc.
• the slurry material is molded into a desired shape by a desired molding method (e.g., mold press, cold isostatic press, injection molding, doctor blade method, extrusion molding method, etc.) to form a ceramic molded product.
• a desired molding method e.g., mold press, cold isostatic press, injection molding, doctor blade method, extrusion molding method, etc.
• the maximum temperature is preferably 1450 to 1650°C, more preferably 1555 to 1565°C.
• the holding time at the maximum temperature is preferably 0.7 to 1.0 hours, more preferably 0.8 to 0.9 hours.
• the temperature increase rate from 1,000°C to the maximum temperature is preferably 5 to 15°C/min, preferably 8 to 12°C/min, and particularly preferably 9 to 11°C/min. .
• the heating time from start to maximum temperature is preferably 3 to 20 hours, more preferably 5 to 15 hours.
• a method for manufacturing a semiconductor device substrate will be described.
• a laminate is formed in which copper plates 4 and 4' whose surfaces are oxidized are arranged on the upper and lower surfaces of the ceramic substrate 3, and the laminate is placed under nitrogen atmosphere conditions at 1065°C to 1083°C for about 5 to 20 minutes (for example, 10 minutes). Heat for about a minute).
• the thickness of each copper plate 4, 4' can be, for example, 0.1 to 2.0 mm.
• the Cu--O eutectic liquid phase is solidified by cooling this laminate, and the copper plates 4 and 4' are bonded to the ceramic substrate 3. In this way, the semiconductor device substrate 2 is completed.
• the transmission circuit formed on the copper plate 4 on the surface to which the semiconductor chip 6 is bonded can be formed by, for example, a subtractive method or an additive method.
• 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-like substance.
• the slurry-like material was formed into a sheet shape using a doctor blade method to produce a ceramic molded body.
• the ceramic molded bodies were fired in the air at a maximum temperature of 1565° C. for 0.8 hours to obtain ceramic substrates according to Examples 1 to 6 and Comparative Examples 1 to 3.
• the heating rate from 1000°C to the maximum temperature was 85°C/min, and the heating time from the rise to the maximum temperature was 70 minutes.
• the size of this ceramic substrate was 0.32 mm thick, 39 mm long, and 45 mm wide.
• Example 1 After capturing the crystal grain orientation distribution of Al 2 O 3 , ZrO 2 , and SiO 2 using the EBSD (Electron BackScatter Diffraction) method, the interfaces where Al 2 O 3 , ZrO 2 , and SiO 2 are adjacent to each other are determined. The total distance (grain boundary length) was calculated. A grain boundary was defined as a case where the orientation difference between crystal grains was 5° or more.
• the measurement site was the center of the cross section of the ceramic substrate sandwiched between the copper plates, and within the area observed at a magnification of 3,000 times, a range of 30 x 30 ⁇ m (900 ⁇ m 2 ) was set as the EBSD observation area. The measurement results of Example 1 are shown in FIG.
• Example 1 and Comparative Example 3 although the contents of zirconia and yttria were the same, there was a significant difference in bonding strength before and after DC application. Therefore, SEM images of the cross section of the ceramic substrate were obtained and shown in FIGS. 3 and 4, respectively. Comparing Figures 3 and 4, YSZ (white parts indicated by B2 and C2 in the figure) exhibits scattered behavior, and no mechanism of communication at grain boundaries was confirmed. It can be said that the effect is not due to differences in distribution. Therefore, despite the same amount of YSZ added, there was a significant difference in the degree of deterioration of the bonding strength before and after DC application due to the mass ratio of the alkali metal oxide to the oxide equivalent mass of the glassy second component. considered to be a thing. That is, in Example 1, it can be said that the bonding strength is maintained when this value is 1.0 or less. On the other hand, in Comparative Example 3, since this value was higher than 1.0, it can be said that the bonding strength decreased.
• Example 1 has a higher calcia content than Comparative Example 3.
• Comparative Example 3 the results of impedance measurements for Example 1 and Comparative Example 3 are shown in FIG. In FIG. 5, for example, 1.0E+03 means 1 times 10 to the third power.
• the measurement method is an AC impedance measurement method. After applying a DC voltage of 98.4 V to the semiconductor device substrate, an AC voltage of 1 Vrms was further applied to measure the impedance. As a result, it was confirmed that the impedance in the low frequency range from 1.0E-03 to 1.0E+01 (HZ) was larger in Example 1 than in Comparative Example 3, and the insulation was improved. This is considered to be because Example 1 has a higher calcia content than Comparative Example 3.
• the bending strengths all showed values of 550 MPa or more.
• the bending strength is 550 MPa or more, it can be used as a DBOC substrate that can be applied to various uses.
• Examples 3 and 4 have higher zirconia content and lower silica content than Examples 1, 2, 5, and 6, and therefore have higher transverse strength.
• Table 3 shows the results.
• the above-mentioned A, B, C, A/B, and A/(B ⁇ C) were calculated. As shown in Examples 1 to 6, it was found that when it was in the range of 7.1 ⁇ 10 -4 or less, DC durability was improved and the bonding strength ratio was also excellent. It was also found that the lower the calculated value, the higher the bending strength. Particularly, as shown in Examples 3 and 6, it was found that the bending strength becomes higher when it is smaller than 1.5 ⁇ 10 ⁇ 4 . On the other hand, in Comparative Examples 1 to 3, the above calculated values (A/(B x C)) are all larger than 7.1 x 10 -4 , and the bending strength and bonding strength ratio are higher than those of Examples 1 to 6. It was low.

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