Core substrate

Abstract

This ceramic substrate (100) has a first surface (SF1) and a second surface (SF2) opposite the first surface (SF1) in the thickness direction, and includes a through-hole between the first surface (SF1) and the second surface (SF2). A conductor portion (200) passes through the through-hole, and is made of a sintered material containing a sintered metal. A magnetic body portion (300) surrounds the conductor portion (200) in the through-hole, is made of ceramic, and is joined to each of the ceramic substrate (100) and the conductor portion (200) without interposing an organic material therebetween. Between the first surface (SF1) and the second surface (SF2) in at least one cross-sectional view along the thickness direction, the maximum rectangular area included in the conductor part (200) and having a side along the thickness direction has an area ratio of 50-80% with respect to the area of the conductor part (200).

Description

Core Board

[0001] The present invention relates to a core substrate, and more particularly to a core substrate with a built-in inductor for constituting an interposer on which a semiconductor element is mounted.

[0002] According to Japanese Patent Laid-Open Publication No. 2019-179792 (Patent Document 1), in a semiconductor device, an interposer is disposed between a semiconductor element and a motherboard. The semiconductor element and the motherboard are each connected to the interposer using solder balls. The interposer is shown to be a multilayer printed wiring board, which includes a core substrate, three conductor circuit layers stacked on the core substrate so as to face the semiconductor element, and three conductor circuit layers stacked on the core substrate so as to face the motherboard. On the semiconductor element mounting side of the interposer, the wiring dimensions are gradually reduced by passing through the three conductor circuit layers.

[0003] Efficient power management is sometimes required for semiconductor elements such as integrated circuits (ICs). Typically, a voltage regulator controls the supply voltage to each of multiple computing cores in a processor chip (semiconductor element) depending on factors such as the amount of processing power required by the processor. A voltage regulator typically requires a switch, a capacitor, and an inductor. Controlling the supply voltage for each computing core requires a switch, a capacitor, and an inductor for each computing core. In particular, inductors are difficult to incorporate into semiconductor elements, and are typically prepared separately from the semiconductor elements. To ensure sufficient inductance while minimizing the footprint of these inductors, the use of magnetic materials has been proposed.

[0004] U.S. Patent Application Publication No. 2019 / 0279806 (Patent Document 2) discloses a package substrate (here, a type of interposer) disposed between a die (semiconductor element) and a board (motherboard). The package substrate has an inductor built in for the aforementioned purpose. Specifically, the package substrate has a substrate core, a conductive through-hole penetrating the substrate core, and a magnetic coating around the conductive through-hole. The magnetic coating may contain magnetic particles. The substrate core may be any substrate on which a build-up layer (conductor circuit layer) will be formed. An organic material is exemplified as the core substrate.

[0005] In recent years, dies (semiconductor elements) that are to be bonded to interposers have been equipped with multiple processor cores. In particular, high-performance processors for data servers and the like have many processor cores to enhance their processing power, so the number of processor cores per die area is increasing and the die area per processor core is becoming smaller. To address this, there is a demand for high-density inductors that have a larger inductance per unit area of ​​the interposer.

[0006] The above-mentioned U.S. Patent Application Publication No. 2019 / 0279806 exemplifies a method of forming a substrate core primarily made of an organic material with conductive through-holes (conductor portions) and a magnetic coating (magnetic material portion) containing magnetic particles and disposed around the conductor portions. In this case, the magnetic material portion must be formed at a temperature equal to or lower than the heat resistance temperature of the organic material of the substrate core. A typical method for achieving this is to solidify a resin in which magnetic particles are dispersed. However, when the magnetic material portion is formed using magnetic particles dispersed in a resin, it is difficult to ensure high magnetic permeability due to limitations on the magnetic particle filling rate (the proportion of magnetic particles per volume). In response to the above-mentioned increase in interposer density, it is necessary to reduce the size of the inductors built into the interposer. However, because it is difficult to increase the magnetic permeability of the magnetic material portion as described above, it becomes difficult to ensure sufficient inductance when the dimensions of each inductor are reduced due to the increase in density.

[0007] International Publication No. 2022 / 163588 (Patent Document 3) discloses a core substrate with an inductor built in for forming an interposer on which a semiconductor element is mounted. The core substrate includes a ceramic substrate, a conductor portion, and a magnetic material portion. The ceramic substrate has a first surface and a second surface opposite the first surface in the thickness direction, and a through hole between the first surface and the second surface. The conductor portion passes through the through hole. The conductor portion is made of sintered metal. The magnetic material portion surrounds the conductor portion at the through hole. The magnetic material portion is made of ceramics rather than resin with dispersed magnetic particles. By densely sintering the ceramics, the magnetic permeability of the magnetic material portion can be sufficiently increased. Therefore, the core substrate can incorporate an inductor with a large inductance per unit area.

[0008] JP 2019-179792 A U.S. Patent Application Publication No. 2019 / 0279806 WO 2022 / 163588

[0009] The present inventors have discovered a new problem that in the firing process for manufacturing the core substrate disclosed in the above-mentioned International Publication No. 2022 / 163588, the manufacturing yield may decrease due to the conductor portion falling off the core substrate.

[0010] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to provide a core substrate with an inductor built in for forming an interposer on which a semiconductor element is mounted, which has a built-in inductor with a large inductance per unit area of ​​the core substrate, and which has high heat resistance and a high manufacturing yield.

[0011] Aspect 1 is a core substrate with an inductor built in for forming an interposer on which a semiconductor element is mounted. The core substrate includes a ceramic substrate, a conductor portion, and a magnetic material portion. The ceramic substrate has a first surface and a second surface opposite the first surface in the thickness direction, and a through hole between the first surface and the second surface. The conductor portion penetrates the through hole and is made of a sintered material including a sintered metal. The magnetic material portion surrounds the conductor portion in the through hole, is made of ceramic, and is bonded to the ceramic substrate and the conductor portion without an organic material. Between the first surface and the second surface in at least one cross-sectional view along the thickness direction, the area of ​​the largest rectangle included in the conductor portion, having sides along the thickness direction, has an area ratio of 50% to 80% of the area of ​​the conductor portion.

[0012] Aspect 2 is the core substrate according to aspect 1, wherein the core substrate has a laminated structure of three or more layers in the thickness direction.

[0013] Aspect 3 is the core substrate according to aspect 1 or 2, wherein the area ratio is 65% or more.

[0014] A fourth aspect of the present invention is the core substrate according to any one of the first to third aspects, wherein the ceramic substrate is made of a low-temperature co-fired ceramic material or glass alumina.

[0015] Aspect 5 is a core substrate according to any one of aspects 1 to 4, wherein the magnetic material portion has at least one of a protrusion structure toward the ceramic substrate and a step structure facing the ceramic substrate.

[0016] Aspect 6 is a core substrate according to any one of aspects 1 to 5, wherein the conductor portion has at least one of a protrusion structure toward the magnetic material portion and a step structure facing the magnetic material portion.

[0017] Aspect 7 is a core substrate with an inductor built in for forming an interposer on which a semiconductor element is mounted. The core substrate includes a ceramic substrate, a conductor portion, and a magnetic material portion. The ceramic substrate has a first surface and a second surface opposite the first surface in the thickness direction, and a through hole between the first surface and the second surface. The conductor portion penetrates the through hole and is made of a sintered material including a sintered metal. The magnetic material portion surrounds the conductor portion in the through hole, is made of ceramic, and is bonded to the ceramic substrate and the conductor portion without an organic material therebetween. The conductor portion has at least one of a protrusion structure toward the magnetic material portion and a step structure facing the magnetic material portion.

[0018] Aspect 8 is the core substrate according to aspect 7, wherein the magnetic material portion has at least one of a protrusion structure facing the ceramic substrate and a step structure facing the ceramic substrate.

[0019] According to the first aspect, first, the magnetic body portion is made of ceramics, not resin with dispersed magnetic particles. By densely sintering the ceramics, the magnetic permeability of the magnetic body portion can be sufficiently increased. Therefore, the core substrate can incorporate an inductor with a large inductance per unit area. Second, the ceramic substrate and the magnetic body portion are bonded to each other without an organic material. This prevents the core substrate from having a reduced heat resistance due to the use of organic materials. Third, between the first and second surfaces in at least one cross-sectional view along the thickness direction, the area of ​​the largest rectangle encompassed by the conductor portion, having sides along the thickness direction, has an area ratio of 50% to 80% of the area of ​​the conductor portion. Having an area ratio of 80% or less firmly secures the conductor portion to the core substrate. Therefore, during the manufacture of the core substrate, the conductor portion is prevented from falling off the core substrate. As a result, the core substrate can incorporate an inductor with a large inductance per unit area, while also having high heat resistance and a high manufacturing yield.

[0020] According to the second aspect, the ceramic substrate, the conductor portion, and the magnetic portion each have a laminated structure of three or more layers. This allows the conductor portion to have more undulations due to the laminated structure. This allows the conductor portion to be more firmly fixed to the core substrate.

[0021] According to the above-mentioned aspect 3, the area ratio is 65% or more, which makes it possible to sufficiently suppress the deterioration of the electrical characteristics of the conductor portion caused by an excessively small area ratio.

[0022] According to the fourth aspect, the ceramic substrate is made of a low-temperature co-fired ceramic material or glass alumina, which makes it easier to form the ceramic substrate and the conductor portion by co-firing.

[0023] According to the fifth aspect, the magnetic body has at least one of a protrusion structure facing the ceramic substrate and a step structure facing the ceramic substrate. This strengthens the mechanical bond between the magnetic body and the ceramic substrate. This prevents the conductor from falling off the ceramic substrate together with the magnetic body.

[0024] According to the sixth aspect, the conductor portion has at least one of a protrusion structure toward the magnetic material portion and a step structure facing the magnetic material portion, thereby strengthening the mechanical bond between the conductor portion and the magnetic material portion and preventing the conductor portion from falling off the magnetic material portion.

[0025] According to the seventh aspect, first, the magnetic body is made of ceramics, not resin with dispersed magnetic particles. By densely sintering the ceramics, the magnetic permeability of the magnetic body can be sufficiently increased. Therefore, the core substrate can incorporate an inductor with a large inductance per unit area. Second, the ceramic substrate and the magnetic body are bonded to each other without an organic material. This prevents the core substrate from having a reduced heat resistance due to the use of organic materials. Third, the conductor has at least one of a protrusion structure toward the magnetic body and a step structure facing the magnetic body. This strengthens the mechanical bond between the conductor and the magnetic body. This prevents the conductor from falling off the magnetic body. As a result, the core substrate can incorporate an inductor with a large inductance per unit area, while also having high heat resistance and a high manufacturing yield.

[0026] According to the eighth aspect, the magnetic body has at least one of a protrusion structure facing the ceramic substrate and a step structure facing the ceramic substrate. This strengthens the mechanical bond between the magnetic body and the ceramic substrate. This prevents the conductor from falling off the ceramic substrate together with the magnetic body.

[0027] The objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

[0028] FIG. 1 is a cross-sectional view schematically showing the configuration of an electronic device. FIG. 2 is a cross-sectional view showing an electronic device that is a modified example of FIG. 1. FIG. 3 is a schematic view showing the configuration of an inductor built into a core substrate. FIG. 4 is a circuit diagram showing an example of electrical connection of the first inductor and the second inductor shown in FIG. 3. FIG. 5 is a view schematically showing an example of a core substrate, and is a partial cross-sectional view taken along line V-V in FIG. 6. FIG. 6 is a partial cross-sectional view taken along line VI-VI in FIG. 5. FIG. 7 is a partial cross-sectional view schematically showing the configuration of a core substrate of a first comparative example. FIG. 8 is a partial cross-sectional view schematically showing the configuration of another example of a core substrate. FIG. 9 is a partial cross-sectional view schematically showing one step of a method for manufacturing the core substrate of FIG. 8. FIG. 10 is a partial cross-sectional view schematically showing one step of a method for manufacturing the core substrate of FIG. 8. FIG. 11 is a partial cross-sectional view schematically showing one step of a method for manufacturing the core substrate of FIG. 8. FIG. 12 is a partial cross-sectional view schematically showing one step of a method for manufacturing the core substrate of FIG. 8. FIG. 13 is a partial cross-sectional view schematically showing one step of a method for manufacturing the core substrate of FIG. 8. FIG. 14 is a partial cross-sectional view schematically showing a step of a method for manufacturing the core substrate of FIG. 8 . FIG. 15 is a partial cross-sectional view schematically showing a step of a method for manufacturing the core substrate of FIG. 8 . FIG. 16 is a partial cross-sectional view schematically showing a modified example of the step of FIG. 13 . FIG. 17 is a partial cross-sectional view schematically showing a modified example of the step of FIG. 15 . FIG. 18 is a micrograph showing a cross-section of a core substrate having a defect caused by a magnetic material portion falling off together with a conductor portion. FIG. 19 is a micrograph showing a cross-section of a core substrate having a defect caused by a conductor portion falling off from a magnetic material portion. FIG. 20 is a partial cross-sectional view schematically showing the configuration of a core substrate of a second comparative example. FIG. 21 is a partial cross-sectional view showing the phenomenon in which a conductor portion falls off from a magnetic material portion in the core substrate of FIG. 20 . FIG. 22 is a partial cross-sectional view schematically showing the configuration of a core substrate in embodiment 1. FIG. 23 is a micrograph showing a cross-section of one sample of the core substrate. FIG. 24 is a diagram for explaining calculation of the area of ​​the conductor portion in the cross-section of FIG. 23 . Fig. 25 is a diagram for explaining calculation of the area of ​​the largest rectangle included in the conductor portion in the cross section of Fig. 23. Fig. 26 is a micrograph showing the cross section of another core substrate sample. Fig. 27 is a diagram for explaining calculation of the area of ​​the conductor portion in the cross section of Fig. 26.FIG. 28 is a diagram for explaining the calculation of the area of ​​the largest rectangle included in the conductor portion in the cross section of FIG. 26 . FIG. 29 is a micrograph showing the cross section of another sample of the core substrate. FIG. 30 is a diagram for explaining the calculation of the area of ​​the conductor portion in the cross section of FIG. 29 . FIG. 31 is a diagram for explaining the calculation of the area of ​​the largest rectangle included in the conductor portion in the cross section of FIG. 29 . FIG. 32 is a graph showing the frequency characteristics of inductance for the samples shown in FIGS. 26 to 28 (solid lines) and the samples shown in FIGS. 29 to 31 (dashed lines), together with calculated values ​​at a design frequency of 100 MHz. FIG. 33 is a partial cross-sectional view schematically showing the configuration of a conductor portion of a core substrate in accordance with the second embodiment. FIG. 34 is a diagram showing a modified example of FIG. 33 . FIG. 35 is a partial cross-sectional view schematically showing the configuration of a conductor portion and a magnetic material portion of a core substrate in accordance with the third embodiment. FIG. 36 is a diagram showing a modified example of FIG. 35 .

[0029] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, and a preliminary description will be given. In the drawings, the same or corresponding elements are designated by the same reference numerals, and the description thereof may be omitted in the specification.

[0030] In the specification, the term "green" refers to the state before firing. Thus, a component marked with the term "green" is a component that will be fired but has not yet been fired.

[0031] <Preliminary Explanation> First, a preliminary explanation will be given below before describing the embodiment. In the description of the embodiment to be described later, differences from this preliminary explanation will be mainly described.

[0032] 1 is a cross-sectional view schematically showing the configuration of an electronic device 901. The electronic device 901 has an interposer 700, a semiconductor element 811 (die), a motherboard 812, and a package substrate 813. The interposer 700 has a core substrate 601, a wiring layer 791, and a wiring layer 792.

[0033] The wiring layer 791 and the wiring layer 792 are respectively stacked on one surface and the other surface of the core substrate 601 (specifically, directly or indirectly on a first surface SF1 and a second surface SF2 described later). The wiring layer 791 and the wiring layer 792 may each be stacked on the core substrate 601 by a build-up method or a sputtering method, or may be joined as a separate wiring board.

[0034] The wiring layer 791 is preferably a multi-layer wiring layer configured so that the wiring dimensions (e.g., line and space (L / S) dimensions) are reduced from the side facing the core substrate 601 to the side facing the semiconductor element 811. This makes it possible to configure the interposer 700 on which the semiconductor element 811 having a small terminal pitch can be mounted, even if the wiring dimensions (L / S) of the core substrate 601 are not particularly fine. Specifically, the wiring layer 791 may be a laminate of a normal wiring layer facing the core substrate 601 and a fine wiring layer facing the semiconductor element 811.

[0035] Typically, the wiring layer may be formed by providing a wiring structure on a plate-shaped organic material (e.g., an epoxy-based member) or inorganic material (e.g., a low temperature co-fired ceramics (LTCC) material or non-magnetic ferrite). To form the wiring structure on this organic material, for example, Cu plating is used. To form the wiring structure on an inorganic material, when the inorganic material is formed by a firing process, the wiring structure is simultaneously formed by firing Ag (silver), AgPd (silver palladium), or Cu (copper).

[0036] From the viewpoint of ease of forming fine wiring, the fine wiring layer is preferably formed by providing a wiring structure on a plate-shaped organic material (e.g., an epoxy-based or polyimide-based member). To form the wiring structure on this organic material, for example, Cu plating is used.

[0037] The semiconductor element 811 is mounted on the wiring layer 791 of the interposer 700. The semiconductor element 811 is connected to the wiring layer 791 of the interposer 700 by, for example, solder balls 821. The semiconductor element 811 may be an IC (Integrated Circuit) chip. In particular, when the IC chip is a processor chip having multiple processing cores, the voltage regulator described above can be configured using an inductor, which will be described later.

[0038] The interposer 700 is mounted on the package substrate 813 by bonding the wiring layer 792 to the package substrate 813. This bonding is performed, for example, by solder balls 823. The package substrate 813 is mounted on the motherboard 812, and this bonding is performed, for example, by using solder balls 822.

[0039] According to the above, the element side (the side facing the semiconductor element 811) of the interposer 700 is configured by the wiring layer 791, and the substrate side (the side facing the package substrate 813 and the motherboard 812) of the interposer 700 is configured by the wiring layer 792. A plurality of terminals (not shown) are provided on each of the element side and the substrate side of the interposer 700. The terminal pitch on the element side may be smaller than the terminal pitch on the substrate side, in which case the interposer 700 has a function of converting the terminal pitch. As a modification, depending on the application of the interposer, one or both of the wiring layer 791 and the wiring layer 792 may be omitted.

[0040] 2 is a cross-sectional view showing an electronic device 902, which is a modified example of the electronic device 901 (FIG. 1). In the electronic device 902, the interposer 700 is bonded to the motherboard 812 without the package substrate 813 (FIG. 1), and this bonding is performed by, for example, solder balls 822.

[0041] 3 is a schematic diagram showing the configuration of the inductors built into the core substrate 601. The core substrate 601 has multiple inductors L1 and L2 built into it, and may also have further inductors L3 to L6 built into it, with any number of inductors. Note that, while the configuration of inductors L1 and L2 will be described in detail below, inductors L3 to L6 may also have a similar configuration.

[0042] 4 is a circuit diagram showing an example of the electrical connection of inductor L1 and inductor L2 shown in FIG. 3. The series connection of inductor L1 and inductor L2 forms an inductor having a combined inductance greater than the inductance of each of the inductors, and both ends of the inductor are disposed on the second surface SF2 that faces the semiconductor element 811 (FIG. 1). This allows an inductor having a sufficiently large inductance to be easily connected to the semiconductor element 811. Note that the electrical connections between the multiple inductors built into the core substrate are not limited to those shown in FIG. 4 and may be designed appropriately depending on the application of the core substrate. This may form a series structure of any number of inductors, a parallel structure of any number of inductors, or a combination thereof.

[0043] FIG. 5 is a diagram schematically illustrating the configuration of the core substrate 601, and is a partial cross-sectional view taken along line V-V in FIG. 6 . FIG. 6 is a partial cross-sectional view taken along line VI-VI in FIG. 5 . As described above, the core substrate 601 is used to form the interposer 700 and incorporates the inductors L1 and L2. The core substrate 601 includes a ceramic substrate 100, a first conductor portion 201, a second conductor portion 202, a first magnetic material portion 301, a second magnetic material portion 302, an interconnection portion 450 (terminal), an electrode portion 401 (terminal), and an electrode portion 402 (terminal). The first conductor portion 201 and the second conductor portion 202 are also collectively referred to as the conductor portion 200. The first magnetic material portion 301 and the second magnetic material portion 302 are also collectively referred to as the magnetic material portion 300.

[0044] The ceramic substrate 100 has a first surface SF1 and a second surface SF2 opposite the first surface SF1 in the thickness direction. The ceramic substrate 100 is a substrate made of a ceramic sintered body. The ceramic sintered body may contain substantially no organic components but may contain glass components. In other words, the ceramic substrate 100 may be made of glass ceramics. The ceramic substrate 100 is preferably made of an LTCC material. LTCC materials are ceramics that can be sintered at approximately 900°C or less, which is well below the melting points of Ag, AgPd, or Cu. This allows for the simultaneous sintering of embedded conductors with low electrical resistance, primarily composed of Ag, AgPd, or Cu. The ceramic substrate 100 has a first through-hole HL1 and a second through-hole HL2 between the first surface SF1 and the second surface SF2. Note that, hereinafter, the through-holes HL1 and HL2 may be collectively referred to as the through-holes HL. Ceramic substrate 100 preferably has a thermal expansion coefficient of 4 ppm / ° C. or more and 16 ppm / ° C. or less. Ceramic substrate 100 preferably has a relative dielectric constant of 8 or less and a dielectric loss tangent of 0.01 or less at 1 GHz.

[0045] The first conductor portion 201 and the second conductor portion 202 pass through the first through hole HL1 and the second through hole HL2, respectively. These conductor portions 200 may be substantially solid. Specifically, the conductor portion 200 does not need to have a hollow portion connecting the first surface SF1 and the second surface SF2. Furthermore, these conductor portions 200 are made of a sintered material containing a sintered metal. The sintered metal may be made of at least one of Ag, AgPd, and Cu, for example. The sintered material of the conductor portion 200 may contain a ceramic material that has lower conductivity than the sintered metal, as long as its function as electrical wiring is maintained. The ratio of the ceramic material to the sintered metal is preferably 5% by volume or more and 30% by volume or less. By including the ceramic material in the material of the conductor portion 200, the bond between the conductor portion 200 and the magnetic body portion 300 can be strengthened. The particle size of the ceramic material is preferably 0.5 μm or more and 10 μm or less. The ceramic material is, for example, alumina, zirconia, magnesium oxide or titanium oxide.

[0046] The first magnetic material portion 301 surrounds the first conductor portion 201 at the first through hole HL1. The second magnetic material portion 302 surrounds the second conductor portion 202 at the second through hole HL2. The first magnetic material portion 301 and the second magnetic material portion 302 may be in direct contact with the first conductor portion 201 and the second conductor portion 202, respectively. Each of these magnetic material portions 300 may have a circular inner edge and a circular outer edge in a cross-sectional view perpendicular to the thickness direction ( FIG. 6 ). Note that these inner and outer edges may have other shapes instead of circles, such as ovals or polygons such as rectangles. Corners of the polygonal shape may be chamfered. Similarly, in a cross-sectional view, the first through hole HL1, the second through hole HL2, and each conductor portion 200 may also have other shapes instead of circles as shown in FIG. 6 .

[0047] The magnetic body portion 300 is made of ceramics (sintered ceramic) and does not contain organic components. To reduce the volume of the inductor, the magnetic material constituting the magnetic body portion 300 preferably has high magnetic permeability, and the magnetic body portion 300 preferably has a density of 70% or more. To reduce the electrical loss of the inductor, the magnetic material constituting the magnetic body portion 300 is preferably a soft magnetic material with low magnetic loss at high frequencies, for example, a soft magnetic material with a magnetic loss tangent of 0.1 or less at a frequency of 100 MHz. To reduce magnetic loss at high frequencies, the magnetic material constituting the magnetic body portion 300 preferably has a high volume electrical resistivity, specifically, is preferably an electrical insulator. The magnetic body 300 is preferably made of a ferrite-based material, and the crystal structure of the material is preferably a spinel structure from the viewpoint of ease of manufacturing, for example, Ni-Zn ferrite or Ni-Zn-Cu ferrite, and from the viewpoint of high magnetic permeability, it is preferably a hexagonal structure with c-axis orientation along the thickness direction (vertical direction in Figure 5).

[0048] The manufacturing method of the core substrate 601 includes a firing process. In this firing process, the conductor portion 200 (first conductor portion 201 and second conductor portion 202) and the magnetic body portion 300 (first magnetic body portion 301 and second magnetic body portion 302) are fired simultaneously with the ceramic substrate 100. Therefore, the inorganic material constituting the conductor portion 200 and the inorganic material constituting the magnetic body portion 300 are bonded to each other without an organic material. In other words, the conductor portion 200 and the magnetic body portion 300 are bonded to each other without an organic material. In other words, the conductor portion 200 and the magnetic body portion 300 are inorganically bonded to each other. Specifically, the conductor portion 200 and the magnetic body portion 300 are sintered to each other. Similarly, the inorganic material constituting the magnetic body portion 300 and the inorganic material constituting the ceramic substrate 100 are bonded to each other without an organic material. In other words, the magnetic body portion 300 and the ceramic substrate 100 are bonded to each other without an organic material. In other words, the magnetic body part 300 and the ceramic substrate 100 are inorganically bonded to each other. Specifically, the magnetic body part 300 and the ceramic substrate 100 are sintered to each other.

[0049] The interconnection portion 450 electrically connects one end of the first conductor portion 201 and one end of the second conductor portion 202 to each other on the first surface SF1 of the ceramic substrate 100. On the second surface SF2 of the ceramic substrate 100, the electrode portion 401 is connected to the other end of the first conductor portion 201, and the electrode portion 402 is connected to the other end of the second conductor portion 202. The electrode portion 401 and the electrode portion 402 are separated from each other. Thus, one end of the first conductor portion 201 and one end of the second conductor portion 202 are electrically connected to each other, and the other end of the first conductor portion 201 and the other end of the second conductor portion 202 are electrically isolated from each other. This forms the circuit shown in FIG. 4 .

[0050] The electrode portion 401 faces each of the first conductor portion 201 and the first magnetic material portion 301 in the thickness direction (vertical direction in FIG. 5 ). The electrode portion 402 faces each of the second conductor portion 202 and the second magnetic material portion 302 in the thickness direction (vertical direction in FIG. 5 ). The interconnection portion 450 faces each of the first conductor portion 201, the second conductor portion 202, the first magnetic material portion 301, and the second magnetic material portion 302 in the thickness direction (vertical direction in FIG. 5 ).

[0051] At least one of the electrode portion 401, the electrode portion 402, and the interconnection portion 450 (preferably each of them) is preferably a terminal made of a sintered material containing a sintered metal. The sintered material may contain a small amount of glass in addition to the sintered metal. The sintered metal may be primarily composed of Ag, AgPd, or Cu, for example. The electrode portion 401 is preferably inorganically bonded to the first conductor portion 201 and the first magnetic material portion 301. The electrode portion 402 is preferably inorganically bonded to the second conductor portion 202 and the second magnetic material portion 302. The interconnection portion 450 is preferably inorganically bonded to the first conductor portion 201, the second conductor portion 202, and the second magnetic material portion 302.

[0052] A design example of the core substrate 601 (FIGS. 5 and 6) is described below. The ceramic substrate 100 has a square shape with sides of 50 mm in the in-plane direction and a thickness dimension of 550 μm. Multiple through holes (such as the first through hole HL1 and the second through hole HL2) are arranged at a pitch of 450 μm. The ceramic substrate 100 is formed, for example, from an LTCC material primarily composed of Ba-Si-Al-O elements or glass alumina. Each of the magnetic material portions 300 (FIG. 6) has an outer diameter of 350 μm and an inner diameter of 100 μm. Each of the conductor portions 200 has an outer diameter of 100 μm. The conductor portions 200 are formed by sintering Ag or AgPd powder. The magnetic material portions 300 are made of a sintered ferrite body, and their relative permeability is estimated to be 16. In this case, the inductance of one inductor (eg, inductor L1) is estimated by the inventors to be about 2 nH at 140 MHz.

[0053] FIG. 7 is a partial cross-sectional view showing the configuration of a core substrate 690 of a comparative example. In the core substrate 690, a first through hole HL1 and a second through hole are formed in a resin substrate 190 made of glass epoxy resin. A first magnetic material portion 391 and a first conductor portion 291 are formed in this order on the side wall of the first through hole HL1. The first conductor portion 291 has a hollow structure filled with a resin material 281. Specifically, the first conductor portion 291 has a hollow connecting the first surface SF1 and the second surface SF2. Similarly, a second magnetic material portion 392 and a second conductor portion 292 are formed in this order on the side wall of the second through hole HL2. The second conductor portion 292 has a hollow structure filled with a resin material 282. Specifically, the second conductor portion 292 has a hollow connecting the first surface SF1 and the second surface SF2. The first conductor portion 291 and the second conductor portion 292 are also collectively referred to as conductor portion 290 .

[0054] As described above, the first magnetic material portion 391 and the second magnetic material portion 392 (collectively referred to as the magnetic material portion 390) are formed within the resin substrate 190. Therefore, the process of forming the magnetic material portion 390 must be performed at a temperature below the heat resistance temperature of the resin substrate 190. Due to this constraint, the magnetic material portion 390 is not made of a sintered ceramic body but of a resin in which magnetic particles are dispersed. In this case, the gaps between the magnetic particles in the magnetic material portion 390 are filled with resin, and it is generally difficult to increase this filling rate to 70% or more. As a result, it is difficult to increase the relative permeability of the first magnetic material portion 391 and the second magnetic material portion 392 compared to the first magnetic material portion 301 and the second magnetic material portion 302 ( FIG. 5 ), and the relative permeability is, for example, approximately 6.

[0055] A design example of the core substrate 690 is described below. The resin substrate 190 has a square shape with sides of 50 mm in the in-plane direction and a thickness of 1000 μm. Multiple through holes (such as the first through hole HL1 and the second through hole HL2) are arranged at a pitch of 500 μm. Each of the magnetic material portions 390 has an outer diameter of 400 μm and an inner diameter of 200 μm. Each of the conductor portions 200 has an outer diameter of 200 μm. The conductor portions 200 are formed by Cu plating. The magnetic material portions 390 are made of resin with dispersed magnetic particles, and their relative permeability is estimated to be 6. In this case, the inductance of one inductor (e.g., inductor L1) is estimated by the inventors to be approximately 1 nH at 140 MHz. This value is half of the estimated value of approximately 2 nH in the present embodiment.

[0056] Unlike the core substrate 690 (FIG. 7), the magnetic body portion 300 (FIG. 5) in the core substrate 601 (FIG. 5) is made of a sintered ceramic body, rather than a resin with dispersed magnetic particles as in the magnetic body portion 390 (FIG. 7). By densely sintering the ceramic, the magnetic permeability of the magnetic body portion 300 can be sufficiently increased. Therefore, the core substrate 601 can incorporate an inductor with a large inductance per unit area. Furthermore, the ceramic substrate 100 and the magnetic body portion 300 are bonded to each other without an organic material. This eliminates the need for resin to bond the ceramic substrate 100 and the magnetic body portion 300 to each other. This avoids the reduction in heat resistance of the core substrate 601 due to the use of resin. As described above, the core substrate 601 can incorporate an inductor with a large inductance per unit area and have high heat resistance.

[0057] The conductor portion 200 is made of a sintered material including a sintered metal. This makes it possible to reduce variations in the electrical properties, particularly the conductivity, of the conductor portion 200 compared to when the conductor portion 200 is made of a plating film. This makes it possible to stabilize the electrical properties of the core substrate.

[0058] The conductor part 200 and the magnetic part 300 are joined to each other without an organic material therebetween, which allows the heat resistance of the core substrate 601 to be improved compared to when the conductor part 200 and the magnetic part 300 are joined to each other via an organic material.

[0059] Ceramic substrate 100 ( FIG. 5 ) has higher rigidity than resin substrate 190 ( FIG. 7 ). As a result, ceramic substrate 100 is less likely to warp even after other components are added to ceramic substrate 100. This makes it possible to obtain core substrate 601 with less warping. Suppressing warping improves, first, the yield of forming wiring layer 791 and wiring layer 792 ( FIG. 1 ), particularly the yield of wiring layer 791 with a high density of wiring structure. Second, the yield of mounting semiconductor elements 811 ( FIG. 1 ) improves.

[0060] The conductor portion 200 may be substantially solid, which can reduce the electrical resistance of the conductor portion 200.

[0061] The magnetic material part 300 may have a circular inner edge and a circular outer edge in a cross section perpendicular to the thickness direction ( FIG. 6 ). In this case, the magnetic material part 300 can be disposed isotropically with respect to the conductor part 200 in the cross section.

[0062] The magnetic material part 300 may have a density of 70% or more. In this case, the magnetic permeability of the magnetic material part 300 can be easily increased sufficiently.

[0063] Ceramic substrate 100 may have a thermal expansion coefficient of 4 ppm / °C or more and 16 ppm / °C or less. In this case, the thermal expansion coefficient of ceramic substrate 100 can be set between the thermal expansion coefficient of semiconductor element 811 ( FIG. 1 ) to be mounted on interposer 700 including core substrate 601 and the thermal expansion coefficient of a typical motherboard 812 ( FIG. 1 ) on which interposer 700 is to be mounted. This makes it possible to suppress warping due to thermal expansion and contraction in electronic device 901 ( FIG. 1 ) or electronic device 902 ( FIG. 2 ).

[0064] The core substrate 601 may have an inductor L1 formed by the first conductor portion 201 and the first magnetic material portion 301, and an inductor L2 formed by the second conductor portion 202 and the second magnetic material portion 302. This allows multiple inductors to be built into the core substrate 601.

[0065] The interconnector 450 electrically connects one end (the lower end in FIG. 5 ) of the first conductor portion 201 to one end (the lower end in FIG. 5 ) of the second conductor portion 202 on the first surface SF1 of the ceramic substrate 100. This allows the inductor L1 formed by the first conductor portion 201 and the first magnetic material portion 301 to be electrically connected to the inductor L2 formed by the second conductor portion 202 and the second magnetic material portion 302.

[0066] 5, when the other end (top end in the figure) of the first conductor portion 201 and the other end (top end in the figure) of the second conductor portion 202 are electrically isolated from each other, an inductor L1 formed by the first conductor portion 201 and the first magnetic material portion 301 and an inductor L2 formed by the second conductor portion 202 and the second magnetic material portion 302 are connected in series rather than in parallel, thereby increasing the combined inductance.

[0067] FIG. 8 is a partial cross-sectional view schematically illustrating the configuration of core substrate 602. Core substrate 602 differs from core substrate 601 ( FIG. 6 ) in that it does not have interconnection portions 450 ( FIG. 5 ). Furthermore, core substrate 602 does not have electrode portions 401 and 402 ( FIG. 5 ). After manufacturing core substrate 602 ( FIG. 8 ), core substrate 601 may be manufactured by additionally forming interconnection portions 450, electrode portions 401, and electrode portions 402 ( FIG. 5 ) as needed. In other words, core substrate 601 may be obtained by firing to form core substrate 602, followed by firing to form interconnection portions 450, electrode portions 401, and electrode portions 402 ( FIG. 5 ). However, the method for manufacturing core substrate 601 is not limited to sequential firing as described above, and may also employ simultaneous firing.

[0068] 9 to 15 are partial cross-sectional views that schematically show steps in the method of manufacturing the core substrate 602 (FIG. 8).

[0069] A green sheet G100 (FIG. 9) is prepared, which will become ceramic substrate 100 (FIG. 5) after firing. The thickness of green sheet G100 is, for example, 0.1 mm or less. Through holes HL1 and HL2 (FIG. 10) are formed in green sheet G100 by, for example, punching. The planar shape of each of through holes HL1 and HL2 is, for example, a circular shape with a diameter of about 0.4 mm.

[0070] Each of the through holes HL1 and HL2 is filled with a magnetic paste portion T300 (FIG. 11) that will become the magnetic portion 300 (FIG. 5) after firing. This filling is performed by printing the magnetic paste, for example.

[0071] Through holes HH1 and HH2 (FIG. 12) are formed in the magnetic paste portion T300 in through hole HL1 and the magnetic paste portion T300 in through hole HL2, respectively, by, for example, laser processing. The planar shape of each of the through holes HH1 and HH2 is, for example, a circular shape with a diameter of about 0.1 mm.

[0072] Each of the through holes HH1 and HH2 is filled with a conductive paste portion T200 (FIG. 13) that will become the conductor portion 200 upon firing, thereby obtaining the green layer LG1 (FIG. 13). This filling is performed, for example, by printing the conductive paste. The conductive paste contains, for example, Ag powder, AgPd powder, or Cu powder, and an organic binder.

[0073] Each of the green layers LG2 to LG6 (FIG. 14) is formed by a method similar to that described above. The green layers LG1 to LG6 are stacked in the thickness direction to form the laminate GP. This stacking may involve heating and pressure, for example, heating at 100°C and pressure at 4 MPa. The number of layers stacked in the laminate GP is two or more, preferably three or more, and in the illustrated example, six layers.

[0074] The core substrate 602 (FIG. 15) is formed by firing the laminate GP. In other words, the core substrate 602 is manufactured using multilayer ceramic technology. Firing is performed, for example, at 900°C for two hours. Firing transforms each of the green layers LG1 to LG6 (FIG. 14) into sintered layers LF1 to LF6. Therefore, in the illustrated example, the laminate GP has a six-layer laminate structure. Note that the interface between adjacent pairs of sintered layers LF1 to LF6 becomes difficult to distinguish as sintering between the layers progresses, but those skilled in the art can often distinguish it from a microscopic photograph.

[0075] When manufacturing core substrate 601 (FIG. 5) from core substrate 602 (FIG. 15), electrode paste portions (not shown) are formed, which will become electrode portions 401 and 402 and interconnection portion 450 when fired. This formation is performed, for example, by printing an electrode paste. The electrode paste contains, for example, Ag powder, an organic binder, and a small amount of glass. These electrode paste portions are then fired. For example, firing is performed at 850° C. for 10 minutes. This results in core substrate 601 (FIG. 5).

[0076] FIG. 16 is a partial cross-sectional view schematically illustrating a modified example of the process shown in FIG. 13 . In this modified example, the conductive paste portion T200 is not only filled into each of the through holes HH1 and HH2, but is also applied to the periphery of the through holes HH1 and HH2 on one main surface (the upper surface in FIG. 16 ) of the green sheet G100. In the resulting green layer LGp, unlike the green layer LG1 ( FIG. 13 ), the conductive paste portion T200 has an eave structure PR. The amount of conductive paste applied to the periphery of the through holes HH1 and HH2 can be easily adjusted by adjusting the size of the printing pattern, etc. In this modified example, each of the green layers LG2 to LG6 ( FIG. 14 ) is also replaced with a material similar to the green layer LGp. These sheets are used to form a laminate similar to the laminate GP ( FIG. 14 ). By firing this laminate, a core substrate 603 ( FIG. 17 ) is obtained.

[0077] In the core substrate 603, in a cross-sectional view including the thickness direction (vertical direction in FIG. 17 ), the conductor portion 200 has an eave structure PR extending in an in-plane direction perpendicular to the thickness direction, toward the magnetic material portion 300. Note that in FIG. 17 , the eave structures PR are shown as small rectangles in schematic form, but in reality, they often become thinner as they extend in the in-plane direction. In this case, the maximum thickness dimension of each eave structure PR is regarded as the thickness dimension described below. In each of the sintered layers LF1 to LF6, the proportion of the eave structures PR in the thickness direction is, for example, 5% to 30%.

[0078] The width dimension WQ and thickness dimension of the eave structure PR are larger than the particle diameter of the sintered metal that forms the magnetic material portion 300. When the particle diameter is 0.1 μm or more and 3 μm or less, the width dimension WQ is preferably 10 μm or more and 100 μm or less. The thickness dimension is preferably 5 μm or more and 30 μm or less. By ensuring that these dimensions are not too small, it is easy to obtain a sufficient anchor effect by the eave structure PR between the conductor portion 200 and the magnetic material portion 300. Furthermore, by ensuring that these dimensions are not too large, it is easy to avoid the occurrence of cracks in the magnetic material portion 300 due to thermal stress concentration near the eave structure PR.

[0079] <Defects Caused by Falling-Off of Some Elements from Core Substrate> Fig. 18 is a micrograph showing the cross section of a core substrate having a defect caused by the magnetic material portion falling off together with the conductor portion. Specifically, in the right side of the bottom layer in the figure, the magnetic material portion has fallen off together with the conductor portion from the core substrate. This phenomenon is more likely to occur when the firing shrinkage of the magnetic material portion is greater than that of the ceramic substrate during the firing process.

[0080] 19 is a micrograph showing the cross section of a core substrate having a defect caused by the conductor portion falling off from the magnetic material portion. Specifically, in the figure, the conductor portion has fallen off from the magnetic material portion on both the right and left sides of the bottom layer. This phenomenon is more likely to occur when the conductor portion shrinks more than the magnetic material portion during the firing process.

[0081] 20 is a partial cross-sectional view schematically illustrating the configuration of a core substrate 602Z of a second comparative example. A rectangle AR has sides along the thickness direction (vertical direction in the figure) between the first surface SF1 and the second surface SF2, and is the largest rectangle encompassed by the conductor portion 200. In the core substrate 602Z, the area of ​​the rectangle AR accounts for nearly 100% of the area of ​​the conductor portion 200. With such a high area ratio, the conductor portion 200 is likely to fall off the magnetic material portion 300, as indicated by the arrow in FIG. 21 .

[0082] The above-mentioned dropouts can be suppressed to some extent by optimizing the packing density of the green sheet G100, magnetic paste portion T300, and conductor paste portion T200 (see FIG. 14), which will be fired to form the ceramic substrate 100, magnetic portion 300, and conductor portion 200 (see FIG. 15), respectively. For example, the packing density of the green sheet G100 and magnetic paste portion T300 is set to 55%, and the packing density of the conductor paste portion T200 is set to 35%. However, according to the inventors' investigations, it was difficult to sufficiently suppress the above-mentioned dropouts by optimizing the packing density alone. Therefore, after extensive investigations, the inventors have arrived at the embodiment described below.

[0083] 22 is a partial cross-sectional view schematically showing the configuration of a core substrate 611 according to embodiment 1. Like the core substrate 602 (FIG. 8) described in the preliminary explanation above, the core substrate 611 has the following features.

[0084] The core substrate 611 is a core substrate with a built-in inductor for constituting the interposer 700 on which the semiconductor element 811 is mounted. The core substrate 611 includes a ceramic substrate 100, a conductor portion 200, and a magnetic material portion 300. The ceramic substrate 100 has a first surface SF1 and a second surface SF2 opposite the first surface SF1 in the thickness direction. The ceramic substrate 100 has a through-hole HL between the first surface SF1 and the second surface SF2. The conductor portion 200 penetrates the through-hole HL and is made of a sintered material including a sintered metal. The magnetic material portion 300 surrounds the conductor portion 200 at the through-hole HL. The conductor portion 200 is made of ceramic and is bonded to the ceramic substrate 100 and the conductor portion 200 without an organic material therebetween. As described in the preliminary explanation above, ceramic substrate 100 may be made of an LTCC material containing Ba-Si-Al-O elements as a main component or glass alumina. Other features of core substrate 611 other than those described below are substantially the same as those of core substrate 602 ( FIG. 8 ) in the preliminary explanation above, and therefore detailed description thereof will not be repeated. Furthermore, modifications similar to those made to core substrate 602 ( FIG. 5 ) or core substrate 603 ( FIG. 17 ) may also be applied to core substrate 611.

[0085] In the core substrate 611, between the first surface SF1 and the second surface SF2 in at least one cross-sectional view along the thickness direction ( FIG. 22 ), the area of ​​the largest rectangle AR that has sides along the thickness direction (the vertical direction in the drawing) and is included in the conductor portion 200 has an area ratio of 50% to 80% of the area of ​​the conductor portion 200. This area ratio may be 65% or more.

[0086] The cross-sectional view may be observed by polishing the core substrate 611 so that the cross-sectional view is exposed. When determining the position of the cross-sectional view, first, the normal direction of the cross-sectional view is determined. Then, polishing is performed so that the area of ​​the conductor portion 200 in the cross-sectional view is approximately maximized. In other words, after the normal direction of the cross-sectional view is determined, the position of the cross-sectional view is determined so that the area of ​​the conductor portion 200 is approximately maximized. Note that, if high-precision fluoroscopic inspection is available, it can be used to obtain the cross-sectional view without polishing. For at least one normal direction, the area ratio is set to be within the aforementioned preferred numerical range. Note that for all normal directions, the area ratio may be set to be within the aforementioned preferred numerical range.

[0087] The core substrate 611 has a laminated structure in the thickness direction. The laminated structure has two or more layers, preferably three or more layers. In the illustrated example, it has six layers, sintered layers LF1 to LF6. This laminated structure is obtained by using a manufacturing method that includes a green sheet lamination process (see FIG. 14), similar to the manufacturing method for the core substrate 602. The above-mentioned area ratio can be easily reduced by sufficiently causing misalignment when laminating the six green layers that will become the sintered layers LF1 to LF6 during the manufacturing of the core substrate 611. Conversely, the above-mentioned area ratio increases as the misalignment is suppressed. The eaves structure PR (FIG. 17) also reduces the area ratio, but by using the misalignment in combination, it becomes easier to sufficiently reduce the area ratio.

[0088] In each of the sintered layers LF1 to LF6, the shape of the conductor portion 200 may be approximately cylindrical. In each of the sintered layers LF1 to LF6, the shape formed by one set of the conductor portion 200 and the magnetic material portion 300 may be approximately cylindrical.

[0089] According to the first embodiment, first, the magnetic body portion 300 is made of ceramics, not resin with dispersed magnetic particles. By densely sintering the ceramics, the magnetic permeability of the magnetic body portion 300 can be sufficiently increased. Therefore, the core substrate 611 can incorporate an inductor with a large inductance per unit area. Second, the ceramic substrate 100 and the magnetic body portion 300 are bonded to each other without an organic material. This prevents the core substrate 611 from having a reduced heat resistance due to the use of an organic material. Third, between the first surface SF1 and the second surface SF2 in at least one cross-sectional view along the thickness direction, the area of ​​the largest rectangle that has sides along the thickness direction and is included in the conductor portion 200 has an area ratio of 50% to 80% of the area of ​​the conductor portion 200. The area ratio of 80% or less provides a sufficient anchor effect to the conductor portion 200 in the core substrate 611. This firmly fixes the conductor portion 200 to the core substrate 611. This prevents the conductor portion 200 from falling off from the core substrate 611 during the manufacture of the core substrate 611. As described above, the core substrate 611 can incorporate an inductor having a large inductance per unit area, and can also have high heat resistance and a high manufacturing yield.

[0090] The core substrate 611 preferably has a laminated structure of three or more layers. Specifically, the ceramic substrate 100, the conductor portion 200, and the magnetic material portion 300 each preferably have a laminated structure of three or more layers. This allows the conductor portion 200 to have more undulations by utilizing the laminated structure. Therefore, the conductor portion 200 can be more firmly fixed to the core substrate 611.

[0091] If the above-mentioned area ratio is too small, the electrical characteristics of the electrical path connecting the first surface SF1 and the second surface SF2 of the conductor portion 200 are likely to deteriorate. Specifically, the resistance of the electrical path is likely to increase excessively, and in some cases, a break may occur along the electrical path. The increase in resistance is particularly likely to occur in the high-frequency range where the influence of the skin effect is significant. Since the core substrate is typically used in the high-frequency range of approximately 50 MHz or more and 100 MHz or less, it is significantly affected by the skin effect. An area ratio of 50% or more can prevent significant deterioration of the electrical characteristics, and in particular, an area ratio of 65% or more can largely prevent such deterioration.

[0092] The ceramic substrate 100 may be made of an LTCC material or glass alumina, which makes it easier to form the ceramic substrate 100 and the conductor portion 200 by co-firing.

[0093] Fig. 23 is a micrograph showing the cross section of one sample of the core substrate. Fig. 24 is a diagram for explaining the calculation of the area of ​​the conductor portion in the cross section of Fig. 23. Fig. 25 is a diagram for explaining the calculation of the area of ​​the largest rectangle included in the conductor portion in the cross section of Fig. 23. As a result of the calculation, the area ratio of the conductor portion on the left side was 62%, and the area ratio of the conductor portion on the right side was 76%.

[0094] Fig. 26 is a micrograph showing the cross section of another sample of core substrate. Fig. 27 is a diagram for explaining the calculation of the area of ​​the conductor portion in the cross section of Fig. 26. Fig. 28 is a diagram for explaining the calculation of the area of ​​the largest rectangle included in the conductor portion in the cross section of Fig. 26. As a result of the calculation, the area ratio of the conductor portion on the left side was 73%, and the area ratio of the conductor portion on the right side was 69%.

[0095] Fig. 29 is a micrograph showing the cross section of another sample of core substrate. Fig. 30 is a diagram for explaining the calculation of the area of ​​the conductor portion in the cross section of Fig. 29. Fig. 31 is a diagram for explaining the calculation of the area of ​​the largest rectangle included in the conductor portion in the cross section of Fig. 29. As a result of the calculation, the area ratio of the conductor portion on the left side was 50%, and the area ratio of the conductor portion on the right side was 42%.

[0096] FIG. 32 is a graph showing the inductance-frequency characteristics of the samples shown in FIGS. 26 to 28 (solid lines) and the samples shown in FIGS. 29 to 31 (dashed lines), along with calculated values ​​at 100 MHz for the design. Specifically, the solid line shows the inductance of a series connection between an inductor with an area percentage of 73% and an inductor with an area percentage of 69%, while the dashed line shows the inductance of a series connection between an inductor with an area percentage of 50% and an inductor with an area percentage of 42%. The "calculated value" in the figure is the calculated value for a conductor having a simple cylindrical shape. These results indicate that reducing the area percentage to approximately 69% has little adverse effect on electrical characteristics. Furthermore, according to the inventors' estimates, as mentioned above, an area percentage of 65% or more can largely prevent degradation of electrical characteristics, while an area percentage of 50% or more can prevent significant degradation of electrical characteristics.

[0097] <Embodiment 2> In the above-mentioned embodiment 1, the conductor portion 200 of the core substrate is mainly described from the perspective of area ratio in a cross-sectional view, but in this embodiment 2 and embodiment 3 described below, it is described from another perspective, specifically, from the perspective of shape in a cross-sectional view.

[0098] FIG. 33 is a partial cross-sectional view schematically illustrating the configuration of the conductor portion 200 of the core substrate 621 according to the second embodiment. The cross-sectional position in FIG. 33 may be determined as described above in connection with FIG. 22 . The core substrate 621 has a laminated structure of three or more layers in the thickness direction (vertical direction in the figure). This laminated structure includes a layer LC1, a layer LC2, and a layer LPa therebetween. The layer LPa is in contact with each of the layers LC1 and LC2. In other words, the layers LC1, LPa, and LC2 are stacked directly on top of each other in the thickness direction. The layers LC1, LPa, and LC2 correspond to layers stacked when the core substrate 621 is manufactured using multilayer ceramic technology. In the core substrate 621, the conductor portion 200 has a protrusion structure PCa toward the magnetic material portion 300, which will be mainly described below.

[0099] The conductor portion 200 is contained within a range BCa in the in-plane direction (direction perpendicular to the thickness direction) in layers LC1 and LC2, but protrudes beyond the range BCa in layer LPa. The portion of the conductor portion 200 protruding beyond the range BCa corresponds to the protrusion structure PCa. Note that in the example shown in FIG. 33 , the arrangement of the conductor portion 200 in the in-plane direction is the same in each of layers LC1 and LC2, but these arrangements may be the same or different as long as they are contained within the range BCa. The range BCa is the smallest range in which the conductor portion 200 can be contained in both layers LC1 and LC2.

[0100] The protrusion structure PCa has a thickness dimension TPa and a width dimension WPa (dimension in a direction perpendicular to the thickness direction). The thickness dimension TPa corresponds to the thickness dimension of the layer LPa and is, for example, 50 μm or more and 200 μm or less. As shown in FIG. 33 , the protrusion structure PCa may have an approximately rectangular shape in cross-section, in which case the width dimension WPa and the thickness dimension TPa correspond to the dimensions of the sides of the rectangle. When the protrusion structure PCa is formed using multilayer ceramic technology as described above, a rectangular protrusion structure PCa can be easily formed. In this case, the protrusion structure PCa has a pair of faces FW that are approximately parallel to the in-plane direction and an end face FT that is approximately parallel to the thickness direction. However, the shape of the protrusion structure PCa is not limited to a rectangular shape and may be other shapes. In this case, the width of the rectangular shape that is encompassed by the shape and has the thickness dimension TPa may be considered the width dimension WPa. The width dimension WPa is preferably 10 μm or more and 100 μm or less. When the width WPa is 10 μm or more, the anchoring effect of the protrusion structure PCa can be sufficiently obtained. When the width WPa is 100 μm or less, it is easy to avoid the occurrence of cracks in the magnetic body 300 due to the concentration of thermal stress near the protrusion structure PCa.

[0101] A depressed structure CCa may be provided on the layer LPa on the opposite side of the protrusion structure PCa (the left side in FIG. 33 ). The portion of the conductor 200 that is depressed into the range BCa corresponds to the depressed structure CCa. The width of the depressed structure CCa is also defined in the same way as the width WPa of the protrusion structure PCa, and is preferably 10 μm or more and 100 μm or less.

[0102] Note that, other than the above, the configuration of core substrate 621 is substantially the same as that of core substrate 602 ( FIG. 8 ) in the preliminary explanation above, and therefore detailed description thereof will not be repeated. In addition, modifications similar to those made to core substrate 602 to core substrate 601 ( FIG. 5 ) or core substrate 603 ( FIG. 17 ) may also be applied to core substrate 611.

[0103] According to the second embodiment, the conductor part 200 has a protrusion structure PCa facing the magnetic material part 300. This strengthens the mechanical bond between the conductor part 200 and the magnetic material part 300. This prevents the conductor part 200 from falling off the magnetic material part 300. The protrusion structure PCa may be applied to the core substrate of the first embodiment or its modified example.

[0104] 34 is a diagram showing a core substrate 622 which is a modification of the core substrate 621 (FIG. 33). The conductor portion 200 has a step structure PCb facing the magnetic material portion 300.

[0105] The core substrate 622 includes a layer LC and a layer LPb that are stacked directly on top of each other in the thickness direction (the vertical direction in the drawing). The layers LC and LPb correspond to layers that are stacked when the core substrate 622 is manufactured using multilayer ceramic technology.

[0106] The conductor portion 200 ( FIG. 34 ) is contained within a range BCb in the in-plane direction (direction perpendicular to the thickness direction) in the layer LC, and extends beyond the range BCb in the layer LPb. The portion of the conductor portion 200 extending beyond the range BCb corresponds to the step structure PCb.

[0107] The step structure PCb has a thickness dimension TPb and a width dimension WPb (a dimension perpendicular to the thickness direction). The thickness dimension TPb corresponds to the thickness dimension of the layer LPb and is, for example, 50 μm or more and 200 μm or less. As shown in FIG. 34 , the step structure PCb may have an approximately rectangular shape in cross section, in which case the width dimension WPb and the thickness dimension TPb correspond to the dimensions of the sides of the rectangle. When the step structure PCb is formed using multilayer ceramic technology as described above, a rectangular step structure PCb can be easily formed. In this case, the step structure PCb has a face FW that is approximately parallel to the in-plane direction and an end face FT that is approximately parallel to the thickness direction. However, the shape of the step structure PCb is not limited to a rectangular shape and may be other shapes. In this case, the width of the rectangular shape that is included in the shape and has the thickness dimension TPb may be considered to be the width dimension WPb. The width dimension WPb is preferably 10 μm or more and 100 μm or less. When the width WPb is 10 μm or more, the anchor effect of the step structure PCb can be sufficiently obtained. When the width WPb is 100 μm or less, it is easy to avoid the occurrence of cracks in the magnetic material part 300 due to the concentration of thermal stress near the step structure PCb.

[0108] According to this embodiment, the conductor part 200 has a step structure PCb facing the magnetic material part 300. This strengthens the mechanical bond between the conductor part 200 and the magnetic material part 300. Therefore, the conductor part 200 is prevented from falling off from the magnetic material part 300.

[0109] The layers LC1 and LPa in the second embodiment (FIG. 33) can be regarded as the layers LC and LPb in this modification, respectively, and therefore the core substrate 621 having the protrusion structure PCa also has a step structure. Compared to the step structure PCb that does not have a protrusion structure, the protrusion structure PCa can strengthen the mechanical bond between the conductor portion 200 and the magnetic material portion 300.

[0110] Third Embodiment FIG. 35 is a partial cross-sectional view schematically illustrating the configuration of the conductor portion 200 and magnetic material portion 300 of a core substrate 631 according to a third embodiment. The cross-sectional position in FIG. 35 may be determined as described above with reference to FIG. 22 . The core substrate 631 has a laminated structure of three or more layers in the thickness direction (vertical direction in the figure). This laminated structure includes a layer LC1, a layer LC2, and a layer LPa therebetween. The layer LPa is in contact with each of the layers LC1 and LC2. In other words, the layers LC1, LPa, and LC2 are stacked directly on top of each other in the thickness direction. The layers LC1, LPa, and LC2 correspond to layers stacked when the core substrate 631 is manufactured using multilayer ceramic technology. In the core substrate 631, the magnetic material portion 300 has a protrusion structure PMa extending toward the ceramic substrate 100, which will be primarily described below.

[0111] The magnetic material part 300 ( FIG. 35 ) is contained within a range BMa in the in-plane direction (direction perpendicular to the thickness direction) in the layers LC1 and LC2, and protrudes beyond the range BMa in the layer LPa. The portion of the magnetic material part 300 protruding beyond the range BMa corresponds to the protruding structure PMa. Note that in the example shown in FIG. 35 , the arrangement of the magnetic material part 300 in the in-plane direction is the same in each of the layers LC1 and LC2, but these arrangements may be the same or different as long as they are contained within the range BMa. The smallest range in which the magnetic material part 300 can be contained in both the layers LC1 and LC2 is the range BMa.

[0112] The protrusion structure PMa has a thickness dimension TPa and a width dimension WPa (dimension in a direction perpendicular to the thickness direction). The thickness dimension TPa corresponds to the thickness dimension of the layer LPa and is, for example, 50 μm or more and 200 μm or less. As shown in FIG. 35 , the protrusion structure PMa may have an approximately rectangular shape in cross-section, in which case the width dimension WPa and the thickness dimension TPa correspond to the dimensions of the sides of the rectangle. When the protrusion structure PMa is formed using multilayer ceramic technology as described above, a rectangular protrusion structure PMa can be easily formed. In this case, the protrusion structure PMa has a pair of faces FW that are approximately parallel to the in-plane direction and an end face FT that is approximately parallel to the thickness direction. However, the shape of the protrusion structure PMa is not limited to a rectangular shape and may be other shapes. In this case, the width of the rectangular shape that is encompassed by the shape and has the thickness dimension TPa may be considered the width dimension WPa. The width dimension WPa is preferably 10 μm or more and 100 μm or less. When the width WPa is 10 μm or more, the anchoring effect of the protrusion structures PMa can be sufficiently obtained. When the width WPa is 100 μm or less, it is easy to avoid the occurrence of cracks in the ceramic substrate 100 due to the concentration of thermal stress near the protrusion structures PMa.

[0113] A depressed structure CMa may be provided on the layer LPa on the opposite side (left side in FIG. 35 ) of the protruding structure PMa. The portion of the magnetic body 300 that is depressed into the range BMa corresponds to the depressed structure CMa. The width of the depressed structure CMa is also defined in the same way as the width WPa of the protruding structure PMa, and is preferably 10 μm or more and 100 μm or less.

[0114] Note that the configuration of core substrate 631 other than that described above is the same as that of core substrate 611 (Figure 22: embodiment 1), its modified example, core substrate 621 (Figure 33: embodiment 2), and its modified example (core substrate 622 (Figure 34)), and therefore detailed description thereof will not be repeated.

[0115] According to the third embodiment, the magnetic body part 300 has a protruding structure that projects toward the ceramic substrate 100. This strengthens the mechanical bond between the magnetic body part 300 and the ceramic substrate 100. This prevents the conductor part 200 from falling off from the ceramic substrate 100 together with the magnetic body part 300.

[0116] 36 is a diagram showing a core substrate 632 which is a modification of the core substrate 631 (FIG. 35). The magnetic body 300 has a step structure PMb facing the ceramic substrate 100.

[0117] The core substrate 632 includes a layer LC and a layer LPb that are stacked directly on top of each other in the thickness direction (the vertical direction in the drawing). The layers LC and LPb may correspond to layers that are stacked when the core substrate 632 is manufactured using multilayer ceramic technology.

[0118] The magnetic material part 300 (FIG. 36) is contained within the range BMb in the in-plane direction (the direction perpendicular to the thickness direction) in the layer LC, and extends beyond the range BMb in the layer LPb. The part of the magnetic material part 300 extending beyond the range BMb corresponds to the step structure PMb.

[0119] The step structure PMb has a thickness dimension TPb and a width dimension WPb (a dimension perpendicular to the thickness direction). The thickness dimension TPb corresponds to the thickness dimension of the layer LPb and is, for example, 50 μm or more and 200 μm or less. As shown in FIG. 36 , the step structure PMb may have an approximately rectangular shape in cross-section, in which case the width dimension WPb and the thickness dimension TPb correspond to the dimensions of the sides of the rectangle. When the step structure PMb is formed using multilayer ceramic technology as described above, a rectangular step structure PMb can be easily formed. In this case, the step structure PMb has a surface FW that is approximately parallel to the in-plane direction and an end surface FT that is approximately parallel to the thickness direction. However, the shape of the step structure PMb is not limited to a rectangular shape and may be other shapes. In this case, the width of the rectangular shape that is included in the shape and has the thickness dimension TPb may be considered to be the width dimension WPb. The width dimension WPb is preferably 10 μm or more and 100 μm or less. When the width WPb is 10 μm or more, the anchor effect of the step structure PMb can be sufficiently obtained. When the width WPb is 100 μm or less, it is easy to avoid the occurrence of cracks in the ceramic substrate 100 due to the concentration of thermal stress near the step structure PMb.

[0120] According to this modification, the magnetic body part 300 has a step structure facing the ceramic substrate 100. This strengthens the mechanical bond between the magnetic body part 300 and the ceramic substrate 100. This prevents the conductor part 200 from falling off from the ceramic substrate 100 together with the magnetic body part 300.

[0121] The layers LC1 and LPa in the third embodiment (FIG. 35) can be regarded as the layers LC and LPb in this modification, respectively, and therefore the core substrate 631 having the protrusion structure PMa also has a step structure. Compared to the step structure PMb that does not have a protrusion structure, the protrusion structure PMa can strengthen the mechanical bond between the magnetic body 300 and the ceramic substrate 100.

[0122] 100: Ceramic substrate 200: Conductor portion 300: Magnetic portion 601 to 603, 611, 621, 631, 632: Core substrate HL: Through hole PCa: Projection structure PCb: Step structure PMa: Projection structure PMb: Step structure SF1: First surface SF2: Second surface

Claims

1. A core substrate with a built-in inductor for forming an interposer on which a semiconductor element is mounted, comprising: a ceramic substrate having a first surface and a second surface opposite the first surface in the thickness direction, and having a through hole between the first surface and the second surface; a conductor portion that passes through the through hole and is made of a sintered material including a sintered metal; and a magnetic portion that surrounds the conductor portion in the through hole and is made of ceramics and is bonded to the ceramic substrate and the conductor portion without an organic material therebetween, wherein the area of the largest rectangle that has sides along the thickness direction and is included in the conductor portion between the first surface and the second surface in at least one cross-sectional view along the thickness direction has an area ratio of 50% to 80% of the area of the conductor portion.

2. The core substrate according to claim 1, wherein the core substrate has a laminated structure of three or more layers in the thickness direction.

3. The core substrate according to claim 1 or 2, wherein the area ratio is 65% or more.

4. The core substrate according to claim 1 or 2, wherein the ceramic substrate is made of a low-temperature co-fired ceramic material or glass alumina.

5. The core substrate according to claim 1 or 2, wherein the magnetic material portion has at least one of a protrusion structure facing the ceramic substrate and a step structure facing the ceramic substrate.

6. A core substrate according to claim 1 or 2, wherein the conductor portion has at least one of a protrusion structure facing the magnetic material portion and a step structure facing the magnetic material portion.

7. A core substrate with a built-in inductor for forming an interposer on which a semiconductor element is mounted, comprising: a ceramic substrate having a first surface and a second surface opposite to the first surface in the thickness direction, and having a through hole between the first surface and the second surface; a conductor portion passing through the through hole and made of a sintered material including a sintered metal; and a magnetic portion surrounding the conductor portion in the through hole, made of ceramics, and bonded to both the ceramic substrate and the conductor portion without an organic material therebetween, wherein the conductor portion has at least one of a protrusion structure toward the magnetic portion and a step structure facing the magnetic portion.

8. The core substrate according to claim 7, wherein the magnetic material portion has at least one of a protrusion structure facing the ceramic substrate and a step structure facing the ceramic substrate.

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