Composite substrate

Abstract

Provided is a composite substrate capable of accommodating a conductor pattern having a desired thickness between an inorganic material substrate and a support substrate, and of improving heat dissipation and bonding reliability. A composite substrate according to one embodiment of the present invention comprises an inorganic material substrate, a conductor pattern, a dielectric film, and a support substrate. The inorganic material substrate has a substrate surface. A recess is provided on the substrate surface. The conductor pattern is embedded in the recess. The conductor pattern exposes at least a part of the substrate surface. The dielectric film is provided so as to cover the conductor pattern and the substrate surface exposed from the conductor pattern. The support substrate is positioned on the side opposite to the inorganic material substrate with respect to the dielectric film. The dielectric film and the support substrate are directly bonded to each other.

Description

Composite PCB

[0001] The present invention relates to a composite substrate.

[0002] It is known to bond an inorganic material substrate provided with a conductor pattern to a support substrate to form a composite substrate. In recent years, as the applications of composite substrates have become more diverse, there has been a demand for the conductor pattern to be positioned between the inorganic material substrate and the support substrate. It is also desirable to reduce conductor loss in the conductor pattern by making the thickness of the conductor pattern sufficiently larger than the skin depth. However, in a composite substrate in which a conductor pattern is positioned between the inorganic material substrate and the support substrate, increasing the thickness of the conductor pattern results in insufficient bonding between the inorganic material substrate and the support substrate.

[0003] Japanese Patent Application Laid-Open No. 2023-10103

[0004] Therefore, studies have been conducted to simultaneously increase the thickness of the conductor pattern and improve the bonding reliability of the inorganic material substrate and the support substrate by forming recesses on the surface of the inorganic material substrate (hereinafter referred to as the substrate surface) and embedding the conductor pattern. As a method for bonding such an inorganic material substrate and a support substrate, direct bonding without using an adhesive is expected from the viewpoint of the heat dissipation and / or bonding reliability of the composite substrate. However, when the support substrate is directly bonded to the surface of the inorganic material substrate with the embedded conductor pattern as the bonding surface, the presence of different materials (the conductor pattern and the inorganic material substrate) on the bonding surface makes it difficult to stably directly bond the inorganic material substrate and the support substrate. As a result, there is a problem in that a composite substrate in which a conductor pattern having a desired thickness is located between the inorganic material substrate and the support substrate cannot be imparted with sufficient heat dissipation and bonding reliability. The main object of the present invention is to provide a composite substrate in which a conductor pattern having a desired thickness can be disposed between the inorganic material substrate and the support substrate, and which can achieve improved heat dissipation and bonding reliability.

[0005] [1] A composite substrate according to one embodiment of the present invention includes an inorganic material substrate, a conductor pattern, a dielectric film, and a support substrate. The inorganic material substrate has a substrate surface. A recess is formed on the substrate surface. The conductor pattern is embedded in the recess. The conductor pattern exposes at least a portion of the substrate surface. The dielectric film is provided so as to cover the conductor pattern and the substrate surface exposed from the conductor pattern. The support substrate is located on the opposite side of the inorganic material substrate with respect to the dielectric film. The dielectric film and the support substrate are directly bonded. [2] In the composite substrate described in [1] above, an amorphous layer formed by the direct bonding may be disposed between the dielectric film and the support substrate. [3] In the composite substrate described in [1] or [2] above, the dielectric film and the support substrate may be directly bonded without the use of an adhesive. [4] In the composite substrate described in [2] above, the amorphous layer may contain constituent elements of the dielectric film and constituent elements of the support substrate. [5] In the composite substrate according to any one of [1] to [4] above, the thickness of the conductor pattern may be 1.5 μm or more. [6] In the composite substrate according to any one of [1] to [5] above, the inorganic material substrate may be made of quartz glass. [7] In the composite substrate according to [1] to [6] above, the thickness of the inorganic material substrate may be 100 μm or less. [8] In the composite substrate according to [1] to [7] above, the support substrate may be made of Si, AlN, SiC, LTCC (low temperature co-fired ceramics), diamond, or Si ３ N ４[9] A composite substrate according to another embodiment of the present invention comprises an inorganic material substrate, a conductor pattern, a dielectric film, a support substrate, and a bonding portion. The inorganic material substrate has a substrate surface. A recess is provided on the substrate surface. The conductor pattern is embedded in the recess. The conductor pattern exposes at least a portion of the substrate surface. The dielectric film is provided so as to cover the conductor pattern and the substrate surface exposed from the conductor pattern. The support substrate is located on the opposite side of the inorganic material substrate with respect to the dielectric film. The bonding portion bonds the dielectric film and the support substrate. The bonding portion includes an amorphous layer.

[0006] According to the embodiments of the present invention, a conductor pattern having a desired thickness can be disposed between an inorganic material substrate and a support substrate, and a composite substrate can be realized that can improve heat dissipation and bonding reliability.

[0007] FIG. 1 is a schematic cross-sectional view of a composite substrate according to one embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a conductor pattern provided on the composite substrate of FIG. 1. FIG. 3 is a schematic cross-sectional view of a composite substrate according to another embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of a composite substrate according to yet another embodiment of the present invention. FIG. 5 is a schematic cross-sectional view of a composite substrate according to yet another embodiment of the present invention. FIG. 6 is a schematic explanatory view for describing a method for manufacturing a composite substrate according to another aspect of the present invention, and is a schematic explanatory view for describing a step of preparing an inorganic material substrate. FIG. 7 is a schematic explanatory view for describing a step of forming a conductor film subsequent to FIG. 6. FIG. 8 is a schematic explanatory view for describing a step of polishing the conductor film to form a conductor pattern subsequent to FIG. 7. FIG. 9 is a schematic explanatory view for describing another embodiment of the step of forming a conductor pattern. FIG. 10 is a schematic explanatory view for describing yet another embodiment of the step of forming a conductor pattern. FIG. 11 is a schematic explanatory view for describing a step of forming a dielectric film subsequent to any of FIGS. 8 to 10.

[0008] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments. In addition, in order to clarify the explanation, the width, thickness, shape, etc. of each part may be shown schematically in the drawings compared to the embodiments, but this is merely an example and does not limit the interpretation of the present invention.

[0009] A. Overview of Composite Substrate FIG. 1 is a schematic cross-sectional view of a composite substrate according to one embodiment of the present invention. As shown in FIG. 1, the composite substrate 100 includes an inorganic material substrate 1, a conductor pattern 2, a dielectric film 3, and a support substrate 6. The support substrate 6 is located on the opposite side of the inorganic material substrate 1 with respect to the dielectric film 3. The inorganic material substrate 1 has a first substrate surface 15 and a second substrate surface 16. The first substrate surface 15 is the surface of the inorganic material substrate 1 facing the support substrate 6 in the thickness direction. The second substrate surface 16 is the surface of the inorganic material substrate 1 opposite the first substrate surface 15 in the thickness direction. A recess 11 is provided on the first substrate surface 15. The first substrate surface 15 includes a first portion 15a located outside the recess 11 and a second portion 15b that is the inner surface of the recess 11. The first portion 15a of the first substrate surface 15 is typically a portion of the first substrate surface 15 other than the recess 11 and extends in a direction perpendicular to the thickness direction of the inorganic material substrate 1. The conductor pattern 2 is embedded in the recess 11. The conductor pattern 2 exposes at least a portion of the first substrate surface 15. The dielectric film 3 is provided so as to cover the conductor pattern 2 and the first substrate surface 15 exposed from the conductor pattern 2. The dielectric film 3 and the support substrate 6 are directly bonded. In this specification, "direct bonding" means that two layers or substrates are bonded without the intermediary of an organic material (typically an organic adhesive). In other words, the dielectric film 3 and the support substrate 6 are typically directly bonded without the intermediary of an adhesive. The form of direct bonding can be appropriately set depending on the configuration of the layers or substrates to be bonded to each other. With this configuration, the conductor pattern 2 is embedded in the recess 11 of the inorganic material substrate 1, so that the thickness of the conductor pattern 2 can be made sufficiently large, thereby reducing conductor loss in the conductor pattern 2. Furthermore, even if such a conductor pattern 2 is located between the inorganic material substrate 1 and the support substrate 6, the dielectric film 3 covers the conductor pattern 2 and the first substrate surface 15 exposed therefrom, so the dielectric film 3 and the support substrate 6 can be stably and directly bonded together. Furthermore, when the dielectric film 3 and the support substrate 6 are directly bonded together, the thermal resistance of the bonding interface between the dielectric film 3 and the support substrate 6 can be dramatically reduced compared to resin bonding. Therefore, the heat dissipation properties of the composite substrate 100 can be sufficiently improved.As a result, even if an external device is connected to the composite substrate 100 and heat generated from the external device is transmitted to the inorganic material substrate 1, the heat can be smoothly dissipated from the inorganic material substrate 1 to the package via the dielectric film 3 and the support substrate 6. As a result, heat can be efficiently dissipated from the inorganic material substrate 1, and deterioration of the characteristics of the external device can be suppressed.

[0010] The bonding strength between the dielectric film 3 and the support substrate 6 is, for example, 0.5 J / m ２ or more, preferably 1.0 J / m ２ On the other hand, the upper limit of the bonding strength between the dielectric film 3 and the support substrate 6 is typically 5.0 J / m ２ The bonding strength is measured by, for example, a crack opening method.

[0011] In the illustrated example, the composite substrate 100 further includes a bonding portion 4 formed by the above-described direct bonding. The bonding portion 4 is located between the dielectric film 3 and the support substrate 6 and bonds them together.

[0012] The bonding portion 4 typically has a structure according to the direct bonding method described below. The bonding portion 4 may have a single layer structure or a laminated structure in which two or more layers are laminated. When the bonding portion 4 has a laminated structure, layers made of different materials or the same material but with different compositions or densities are laminated.

[0013] In one embodiment, the bonding portion 4 includes an amorphous layer 41. In the illustrated example, the bonding portion 4 is made of the amorphous layer 41. In other words, the amorphous layer 41 formed by direct bonding is disposed between the dielectric film 3 and the support substrate 6. When the bonding portion 4 includes the amorphous layer 41, the bonding strength between the dielectric film 3 and the support substrate 6 can be stably adjusted to within the above-described range, and the thermal resistance of the bonding interface between the dielectric film 3 and the support substrate 6 can be further reduced, thereby further improving the heat dissipation properties of the composite substrate 100.

[0014] B. Details of the Composite Substrate Hereinafter, each component of the composite substrate will be described in detail with reference to FIG.

[0015] B-1. Inorganic Material Substrate 1 The inorganic material substrate 1 is made of any suitable inorganic material. Examples of inorganic materials that make up the inorganic material substrate 1 include glass materials such as amorphous quartz (quartz glass); and ceramic materials other than glass materials, such as spinel, AlN, sapphire, SiC, magnesium oxide, and silicon. The inorganic materials may be used alone or in combination. In one embodiment, the inorganic material substrate 1 is made of amorphous quartz (quartz glass). When the inorganic material substrate 1 is made of amorphous quartz, for example, the dielectric loss of an antenna or circuit board can be reduced, and stability against humidity and temperature changes can be improved.

[0016] The inorganic material substrate 1 typically has electrical insulation properties. The resistivity of the inorganic material substrate 1 is, for example, 10 ８ kΩ·cm or more, preferably 10 １０ When the inorganic material substrate 1 has such a resistivity, it is possible to stably prevent the conductive pattern 2 from short-circuiting. From this viewpoint, the higher the resistivity of the inorganic material substrate 1, the more preferable it is. The upper limit of the resistivity of the inorganic material substrate 1 is typically 10 １３ It is kΩ·cm.

[0017] The Young's modulus of the inorganic material substrate 1 is, for example, 30 GPa to 500 GPa, and preferably 50 GPa to 400 GPa.

[0018] The thickness of the inorganic material substrate 1 is, for example, 500 μm or less, preferably 200 μm or less, more preferably 100 μm or less, even more preferably 80 μm or less, and particularly preferably 60 μm or less. When the thickness of the inorganic material substrate 1 is below this upper limit, the composite substrate 100 can be made thinner. Furthermore, when such a composite substrate 100 is applied to a waveguide element, the induction of a slab mode can be suppressed and the occurrence of substrate resonance can be suppressed. On the other hand, the thickness of the inorganic material substrate 1 is, for example, 1 μm or more, preferably 2 μm or more, more preferably 10 μm or more, even more preferably 20 μm or more, particularly preferably 30 μm or more, and particularly preferably 40 μm or more.

[0019] As described above, the inorganic material substrate 1 has a first substrate surface 15 and a second substrate surface 16. In the illustrated example, the first substrate surface 15 is the lower surface of the inorganic material substrate 1 and is located within the composite substrate 100. The second substrate surface 16 is the upper surface of the inorganic material substrate 1.

[0020] A recess 11 is provided on the first substrate surface 15. The recess 11 has any appropriate pattern shape corresponding to the conductor pattern 2. The recess 11 has any appropriate shape in a cross section obtained by cutting the inorganic material substrate 1 in the thickness direction. The cross section of the recess 11 is typically approximately U-shaped or V-shaped. In the illustrated example, the cross section of the recess 11 is approximately U-shaped. The inner surface of the recess 11 having the approximately U-shaped cross section (the second portion 15b of the first substrate surface 15) includes a bottom surface, a first side surface, and a second side surface. The bottom surface of the recess 11 is typically substantially parallel to the first portion 15a of the first substrate surface 15. The first side surface and the second side surface are typically spaced apart from each other in a direction perpendicular to the thickness direction of the inorganic material substrate 1. In the illustrated example, the first side surface and the second side surface each extend from the bottom surface of the recess 11 to the first portion 15a of the first substrate surface 15 in the thickness direction of the inorganic material substrate 1.

[0021] The dimension (depth) of the recesses 11 in the thickness direction of the inorganic material substrate 1 is adjusted arbitrarily and appropriately depending on the thickness of the conductive pattern 2. When the thickness of the inorganic material substrate 1 is taken as 100%, the depth of the recesses 11 is, for example, 0.5% to 30%, and preferably 1% to 20%. The depth of the recesses 11 is, for example, 0.5 μm to 5.0 μm, and preferably 1.0 μm to 3.0 μm. When the depth of the recesses 11 is within this range, the thickness of the conductive pattern 2 can be made sufficiently large.

[0022] B-2. Conductive Pattern 2 As described above, the conductive pattern 2 is embedded in the recess 11 and has any appropriate pattern shape. Therefore, the conductive pattern 2 typically exposes the portion of the first substrate surface 15 other than the recess 11 (i.e., the first portion 15a).

[0023] The configuration of the conductor pattern 2 is not particularly limited. The conductor pattern 2 may include, for example, an electrode, a transmission line, an antenna, and a substrate through-electrode (conductive via). As shown in FIG. 2 , in one embodiment, the conductor pattern 2 includes a transmission line 25, a ground electrode 26, and an antenna 27.

[0024] The conductor pattern 2 is made of any suitable conductor material. Examples of conductor materials include metals. Examples of metals include chromium (Cr), nickel (Ni), copper (Cu), gold (Au), silver (Ag), palladium (Pd), titanium (Ti), aluminum (Al), platinum (Pt), molybdenum (Mo), and alloys thereof. In one embodiment, the conductor pattern 2 contains copper and / or gold. When the conductor pattern 2 contains copper and / or gold, excellent electrical conductivity can be imparted to the conductor pattern 2.

[0025] The conductive pattern 2 may have a single-layer structure or a laminated structure in which two or more layers are laminated. When the conductive pattern 2 has a laminated structure, layers made of different materials or the same material but with different compositions or densities are laminated.

[0026] The conductive pattern 2 has electrical conductivity. The resistivity of the conductive pattern 2 is, for example, 20 μΩ·cm or less, and preferably 8.0 μΩ·cm or less. On the other hand, the lower limit of the resistivity of the conductive pattern 2 is typically 1.0 μΩ·cm.

[0027] The linear expansion coefficient of the conductive material constituting the conductive pattern 2 is preferably closer to that of the inorganic material constituting the inorganic material substrate 1. The linear expansion coefficient of the conductive material constituting the conductive pattern 2 is, for example, 10 to 70 times, and preferably 20 to 50 times, the linear expansion coefficient of the inorganic material constituting the inorganic material substrate 1. The linear expansion coefficient of the conductive material is, for example, 4×10 －６ / K~30×10 －６ / K, preferably 10×10 －６ / K~25 x 10 －６ / K. If the linear expansion coefficient of the conductive material constituting the conductive pattern 2 is in this range, peeling of the conductive pattern 2 from the inner surface of the recess 11 can be stably prevented even when the composite substrate 100 is heated.

[0028] The conductive pattern 2 may be harder than the inorganic material substrate 1, softer than the inorganic material substrate 1, or substantially the same hardness as the inorganic material substrate 1. The Young's modulus of the conductive pattern 2 is, for example, 20 GPa to 400 GPa, and preferably 50 GPa to 150 GPa. When the Young's moduli of the inorganic material substrate 1 and the conductive pattern 2 are substantially different, the absolute value of the difference in Young's modulus between the inorganic material substrate 1 and the conductive pattern 2 is, for example, 1 GPa to 300 GPa, and preferably 2 GPa to 100 GPa.

[0029] The thickness of the conductor pattern 2 is, for example, 1.0 μm or more, preferably 1.5 μm or more, and more preferably 2.0 μm or more. When the conductor pattern 2 has such a thickness, the thickness of the conductor pattern 2 can be made sufficiently larger than the skin depth, and the conductor loss in the conductor pattern 2 can be stably reduced. On the other hand, the upper limit of the thickness of the conductor pattern 2 can be arbitrarily and appropriately set depending on the application of the composite substrate 100. The upper limit of the thickness of the conductor pattern 2 is, for example, 20 μm or less, or, for example, 10 μm or less, or, for example, 2.0 μm or less.

[0030] The thickness variation of the conductive pattern 2 is, for example, 0.001 μm to 2.0 μm, preferably 0.05 μm to 1.0 μm, and more preferably 0.1 μm to 1.0 μm. The thickness variation of the conductive pattern 2 is measured using, for example, a step gauge, an atomic force microscope, or a scanning electron microscope.

[0031] The conductor pattern 2 typically has a conductor surface 2a. The conductor surface 2a is one surface of the conductor pattern 2 in the thickness direction of the inorganic material substrate 1. In the illustrated example, the conductor surface 2a is the lower surface of the conductor pattern 2 and is located within the composite substrate 100. The conductor surface 2a typically extends in a direction perpendicular to the thickness direction of the inorganic material substrate 1. In one embodiment, the conductor surface 2a is substantially parallel to the first portion 15a of the first substrate surface 15.

[0032] The conductor surface 2 a may form a step 5 together with the first portion 15 a of the first substrate surface 15 , or may be substantially flush with the first portion 15 a of the first substrate surface 15 .

[0033] When the conductor surface 2a and the first substrate surface 15 form a step 5, the conductor surface 2a of the conductor pattern 2 may be located closer to the support substrate 6 than the first portion 15a of the first substrate surface 15 of the inorganic material substrate 1, or may be located on the opposite side of the support substrate 6 from the first portion 15a of the first substrate surface 15 of the inorganic material substrate 1.

[0034] As shown in FIG. 1 , when the conductor surface 2a is located closer to the support substrate 6 than the first portion 15a of the first substrate surface 15, the conductor pattern 2 integrally has an embedded portion 21 and a protruding portion 22 in the thickness direction of the inorganic material substrate 1. The embedded portion 21 is located within the recess 11. The protruding portion 22 protrudes from the first portion 15a of the first substrate surface 15 in the thickness direction of the inorganic material substrate 1. The protruding portion 22 has the above-mentioned conductor surface 2a and conductor side surface 2b. The conductor side surface 2b typically extends in the thickness direction of the inorganic material substrate 1. The end of the conductor side surface 2b opposite the embedded portion 21 is connected to the conductor surface 2a. In the illustrated example, the first portion 15a of the first substrate surface 15, the conductor surface 2a, and the conductor side surface 2b form a step 5.

[0035] 3 , when the conductor surface 2a is located on the opposite side of the first portion 15a of the first substrate surface 15 from the support substrate 6, the entire conductor pattern 2 is located within the recess 11. In this case, the side surface of the recess 11 (i.e., a part of the second portion 15b of the first substrate surface 15) has a contact portion 11a that contacts the conductor pattern 2 and an exposed portion 11b that is exposed from the conductor pattern 2. The exposed portion 11b is located closer to the support substrate 6 than the contact portion 11a in the thickness direction of the inorganic material substrate 1. The exposed portion 11b typically extends in the thickness direction of the inorganic material substrate 1. The end of the exposed portion 11b opposite to the contact portion 11a is connected to the first portion 15a of the first substrate surface 15. In the illustrated example, the first portion 15a of the first substrate surface 15, the conductor surface 2a, and the exposed portion 11b form a step 5.

[0036] 1 and 3, the distance between the first portion 15a of the first substrate surface 15 and the conductor surface 2a in the thickness direction of the inorganic material substrate 1 (i.e., the height of the step 5) is, for example, 0.005 μm to 3.0 μm, and preferably 0.01 μm to 2.0 μm. If the step 5 has such a height, the dielectric film 3 can stably cover the step 5, and therefore the bonding stability between the inorganic material substrate 1 and the support substrate 6 can be sufficiently improved.

[0037] As shown in FIG. 4 , when the conductor surface 2 a is substantially flush with the first portion 15 a of the first substrate surface 15, the distance between the first portion 15 a of the first substrate surface 15 and the conductor surface 2 a in the thickness direction of the inorganic material substrate 1 is less than the lower limit of the height of the step 5 described above, preferably less than 0.005 μm, and more preferably 0 μm.

[0038] An adhesion layer (not shown) may be provided on the conductor surface 2a of the conductor pattern 2. If an adhesion layer is provided on the conductor surface 2a, peeling at the interface between the conductor pattern 2 and the dielectric film 3 can be suppressed. The adhesion layer is made of any appropriate metal. Examples of metals that make up the adhesion layer (hereinafter sometimes referred to as adhesion layer materials) include chromium (Cr), nickel (Ni), palladium (Pd), titanium (Ti), and alloys thereof. When the conductor pattern 2 is made of a metal, the adhesion layer is typically made of a metal different from that of the conductor pattern 2. The thickness of the adhesion layer is, for example, 0.01 μm to 0.3 μm, and preferably 0.02 μm to 0.15 μm.

[0039] B-3. ​​Dielectric film 3 The dielectric film 3 is disposed between the inorganic material substrate 1 and the support substrate 6. As described above, the dielectric film 3 covers the conductor pattern 2 and the first substrate surface 15 exposed from the conductor pattern 2. In the illustrated example, the dielectric film 3 is in contact with the first substrate surface 15 of the inorganic material substrate 1 and the conductor surface 2a of the conductor pattern 2. Furthermore, as shown in FIG. 1 , when a step 5 is formed between the first substrate surface 15 of the inorganic material substrate 1 and the conductor surface 2a of the conductor pattern 2, the dielectric film 3 also covers the step 5.

[0040] The dielectric film 3 is made of any suitable dielectric material, such as amorphous silicon or SiO. ２ , Ta ２ O ５ , Al ２ O ３ , TiO ２ , Nb ２ O ５ , Y ２ O ３ , AlN, ZrO ２ The dielectric materials may be used alone or in combination. Among these dielectric materials, amorphous silicon is preferred. When the dielectric film 3 is made of amorphous silicon, the bonding stability between the dielectric film 3 and the support substrate 6 can be further improved.

[0041] The dielectric film 3 has electrical insulating properties. The resistivity of the dielectric film 3 is, for example, 10 kΩ·cm or more, and preferably 10 １０ When the dielectric film 3 has such a resistivity, it is possible to stably prevent the conductor pattern 2 from short-circuiting. From this viewpoint, the higher the resistivity of the dielectric film 3, the more preferable it is. The upper limit of the resistivity of the dielectric film 3 is typically 10 １５ It is kΩ·cm.

[0042] The linear expansion coefficient of the dielectric material constituting the dielectric film 3 is preferably closer to those of the materials constituting the inorganic material substrate 1 and the support substrate 6. The linear expansion coefficient of the dielectric material constituting the dielectric film 3 is, for example, 0.5 to 20 times, and preferably 1.0 to 10 times, the linear expansion coefficient of the inorganic material constituting the inorganic material substrate 1. The linear expansion coefficient of the dielectric material constituting the dielectric film 3 is, for example, 0.01 to 10 times, and preferably 0.02 to 5 times, the linear expansion coefficient of the inorganic material constituting the support substrate 6. The linear expansion coefficient of the dielectric material is, for example, 0.1×10 －６ / K~20×10 －６ / K, preferably 0.3×10 －６ / K~10 x 10 －６ When the linear expansion coefficient of the dielectric material constituting the dielectric film 3 is within this range, peeling of the dielectric film 3 from the inorganic material substrate 1 and / or the support substrate 6 can be stably suppressed.

[0043] The thermal conductivity of the dielectric film 3 is, for example, 0.5 W / Km or more, preferably 1.0 W / Km or more. On the other hand, the upper limit of the thermal conductivity of the dielectric film 3 is typically 50 W / Km.

[0044] The thickness of the dielectric film 3 is, for example, 0.05 μm to 3.0 μm, and preferably 0.1 μm to 2.0 μm.

[0045] B-4. Support Substrate 6 The support substrate 6 can impart excellent mechanical strength to the composite substrate 100. This allows the inorganic material substrate 1 to be thinned as described above. The support substrate 6 is located on the opposite side of the dielectric film 3 from the inorganic material substrate 1. In one embodiment, the support substrate 6 is bonded to the dielectric film 3 via a bonding portion 4. As a result, the support substrate 6 supports the inorganic material substrate 1 via the dielectric film 3 and the bonding portion 4.

[0046] The support substrate 6 is made of any appropriate inorganic material. The inorganic material that makes up the support substrate 6 may be the same as that of the inorganic material substrate 1, or may be different from that of the inorganic material substrate 1. Examples of the inorganic material that makes up the support substrate 6 (hereinafter, sometimes referred to as the support substrate material) include silicon (Si), aluminum nitride (AlN), silicon carbide (SiC), silicon nitride (Si ３ N ４ ), diamond, indium phosphide (InP), glass, sialon (Si ３ N ４ -Al ２ O ３ ), mullite (3Al ２ O ３ 2SiO ２ , 2Al ２ O ３ 3SiO ２ ), magnesium oxide (MgO), aluminum oxide (Al ２ O ３ ), spinel (MgAl ２ O ４ ), sapphire, quartz, crystal, gallium nitride (GaN), gallium oxide (Ga ２ O ３ ), LTCC (low temperature co-fired ceramics). The inorganic materials may be used alone or in combination. In one embodiment, the support substrate 6 is made of Si, AlN, SiC, LTCC, diamond, or Si. ３ N ４ When the support substrate 6 is made of such an inorganic material, the heat dissipation, mechanical strength, thermal stability, and the like of the composite substrate 100 can be improved.

[0047] The thermal conductivity of the support substrate material is, for example, 100 W / Km or more, preferably 150 W / Km or more, and more preferably 200 W / Km or more. When the support substrate material has such a thermal conductivity, the support substrate 6 can function sufficiently as a heat sink.

[0048] The linear expansion coefficient of the support substrate material is, for example, 0.1×10 －６ / K~20×10 －６ / K, preferably 0.3×10 －６ / K~10 x 10 －６ / K.

[0049] The thickness of the support substrate 6 is, for example, 150 μm to 1100 μm, and preferably 250 μm to 600 μm.

[0050] B-5. Bonding portion 4 As described above, the bonding portion 4 is located between the dielectric film 3 and the support substrate 6. The bonding portion 4 is typically made of an inorganic material. Examples of the inorganic material (hereinafter sometimes referred to as the bonding portion material) that makes up the bonding portion 4 include the above-mentioned supporting substrate material, the above-mentioned dielectric material, and the above-mentioned adhesion layer material. The bonding portion materials may be used alone or in combination.

[0051] In the illustrated example, the joint 4 includes an amorphous layer 41. The amorphous layer 41 is made of the amorphous part of the above-described joint material. The amorphous layer 41 includes the above-described dielectric material (constituent elements of the dielectric film 3) and / or the above-described support substrate material (constituent elements of the support substrate 6). In one embodiment, the amorphous layer 41 includes the dielectric material (constituent elements of the dielectric film 3) and the above-described support substrate material (constituent elements of the support substrate 6). When the amorphous layer 41 is made of an amorphous material that is a mixture of the dielectric material and the support substrate material, the thermal resistance of the joint interface between the dielectric film 3 and the support substrate 6 can be further reduced, and the joint strength between the dielectric film 3 and the support substrate 6 can be improved.

[0052] The thickness of the joint 4 is, for example, 0.001 μm to 10 μm, and preferably 0.01 μm to 3 μm.

[0053] B-6. First Vias 8a In one embodiment, the composite substrate 100 further includes first vias 8a. The first vias 8a are typically electrically connected to the second conductor pattern 7 described below. The number and arrangement of the first vias 8a are designed arbitrarily and appropriately depending on the application of the composite substrate 100. The first vias 8a are made of any appropriate conductor material. Examples of conductor materials include the same conductor material as that of the conductor pattern 2, and preferably metal.

[0054] The first via 8a is provided in a via hole 12 formed in the inorganic material substrate 1. That is, the inorganic material substrate 1 has a via hole 12 corresponding to the first via 8a. The via hole 12 typically penetrates the inorganic material substrate 1 in the thickness direction. The first via 8a has any appropriate shape. Examples of the shape of the first via 8a include a columnar shape that penetrates the inorganic material substrate 1 in the thickness direction, and a film shape formed on the entire inner surface of the via hole 12. Alternatively, the inside of the conductive film formed on the entire inner surface of the via hole 12 may be further filled with a conductive material to form the columnar first via 8a.

[0055] In the illustrated example, the first via 8a has a columnar shape extending in the thickness direction of the inorganic material substrate 1. The first via 8a has a first end located on the first substrate surface 15 side of the inorganic material substrate 1 and a second end located on the second substrate surface 16 side of the inorganic material substrate 1. The first end of the first via 8a may be flush with the first portion 15a of the first substrate surface 15, may protrude from the first portion 15a of the first substrate surface 15, or may be located on the opposite side of the first portion 15a of the first substrate surface 15 from the support substrate 6. In the illustrated example, the first end of the first via 8a protrudes from the first portion 15a of the first substrate surface 15 to form a step 5. The second end of the first via 8a may be flush with the second substrate surface 16, may protrude from the second substrate surface 16, or may be located on the support substrate 6 side of the second substrate surface 16. In the illustrated example, the second end of the first via 8a is flush with the second substrate surface 16.

[0056] 5, in one embodiment, the composite substrate 100 further includes a second conductor pattern 7. Note that, hereinafter, the conductor pattern 2 located between the inorganic material substrate 1 and the support substrate 6 may be referred to as the first conductor pattern 2.

[0057] The second conductor pattern 7 is located on the opposite side of the inorganic material substrate 1 from the first conductor pattern 2. The second conductor pattern 7 is typically provided on the second substrate surface 16 of the inorganic material substrate 1. In the illustrated example, the second conductor pattern 7 is electrically connected to the first via 8a. The second conductor pattern 7 will be described in the same manner as the first conductor pattern 2, except for its location in the composite substrate 100. Therefore, a detailed description of the second conductor pattern 7 will be omitted.

[0058] B-8. Third Conductive Pattern 9 and Second Via 8b Furthermore, the composite substrate 100 may further include a third conductive pattern 9 and a second via 8b.

[0059] The third conductor pattern 9 is located on the opposite side of the support substrate 6 to the first conductor pattern 2. The third conductor pattern 9 is typically provided on the surface of the support substrate 6 opposite to the first conductor pattern 2. The third conductor pattern 9 will be described in the same manner as the first conductor pattern 2, except for its location in the composite substrate 100. Therefore, a detailed description of the third conductor pattern 9 will be omitted.

[0060] In one embodiment, the second vias 8b typically electrically connect the first conductor pattern 2, the second conductor pattern 7, and the third conductor pattern 9. The number and arrangement of the second vias 8b are arbitrarily and appropriately designed depending on the application of the composite substrate 100.

[0061] The second via 8b is made of any suitable conductive material, such as the same conductive material as that of the conductive pattern 2, preferably metal.

[0062] The second via 8b is provided in a second via hole 13 formed in the composite substrate 100. That is, the composite substrate 100 has a second via hole 13 corresponding to the second via 8b. In the illustrated example, the second via hole 13 penetrates the second conductor pattern 7, the inorganic material substrate 1, the first conductor pattern 2, the dielectric film 3, the bonding portion 4, the support substrate 6, and the third conductor pattern 9 all at once.

[0063] The second via 8b has any appropriate shape. Examples of the shape of the second via 8b include a columnar shape that penetrates the composite substrate 100 in the thickness direction, and a film shape that is formed on the entire inner surface of the second via hole 13. Alternatively, the inside of the conductive film that is formed on the entire inner surface of the second via hole 13 may be further filled with a conductive material to form the columnar second via 8b. In the illustrated example, the second via 8b is a conductive film that is formed on the entire inner surface of the second via hole 13.

[0064] B-9. Cavity 10 The composite substrate 100 may further include a cavity 10. The cavity 10 is located on the opposite side of the inorganic material substrate 1 with respect to the conductor pattern 2. In the illustrated example, the cavity 10 is located on the opposite side of the dielectric film 3 with respect to the first conductor pattern 2. The support substrate 6 may have a recess corresponding to the cavity 10.

[0065] 6 to 11 , a method for manufacturing a composite substrate according to another aspect of the present invention will be described. In one embodiment, the method for manufacturing a composite substrate includes the steps of preparing an inorganic material substrate 1 having a recess 11, forming a conductor pattern 2, forming a dielectric film 3, and bonding the dielectric film 3 to a support substrate 6.

[0066] As shown in FIG. 6 , in the preparation process of the inorganic material substrate 1 having the recess 11, first, an etching mask (not shown) having a predetermined pattern is formed on the first substrate surface 15 of the inorganic material substrate 1 having a substantially flat plate shape. The etching mask exposes portions of the inorganic material substrate 1 corresponding to the recess 11 and covers other portions. The etching mask also exposes portions corresponding to the first via holes 12 as needed. Thereafter, the inorganic material substrate 1 is etched through the etching mask by any appropriate etching method. Examples of the etching method include reactive ion etching (RIE). As a result, the recess 11 having the pattern is formed in the inorganic material substrate 1, and the via holes 12 are formed as needed.

[0067] Next, in the step of forming the conductor pattern 2, the conductor pattern 2 is formed so as to be embedded in the recess 11. In the step of forming the conductor pattern 2, in addition to the conductor pattern 2, first vias 8a are formed as necessary.

[0068] In one embodiment, as shown in FIG. 7 , the etching mask is removed, and the conductive material is deposited on the entire first substrate surface 15 (first portion 15 a and second portion 15 b (inner surface of recess 11)) by any appropriate deposition method. This forms a conductive film 20. When the inorganic material substrate 1 has a first via hole 12, a first via 8 a may be formed inside the first via hole 12 at the same time as forming the conductive film 20. Examples of deposition methods include electrolytic plating and electroless plating, and preferably electrolytic plating.

[0069] Next, the conductor film 20 is polished from the side opposite to the inorganic material substrate 1 by any appropriate polishing method. Examples of the polishing method include grinding (with a grinder), lapping, and chemical mechanical polishing (CMP polishing). The polishing methods may be performed alone or in combination of two or more.

[0070] Polishing is carried out until the first portion 15a of the first substrate surface 15 of the inorganic material substrate 1 is exposed. As a result, the portion of the conductor film 20 embedded in the recess 11 becomes the conductor pattern 2. At this time, the conductor pattern 2 and the first substrate surface 15 exposed from the conductor pattern 2 may be polished together.

[0071] As shown in FIG. 8 , if the conductive material constituting the conductive pattern 2 is sufficiently harder than the inorganic material constituting the inorganic material substrate 1, the inorganic material substrate 1 is more easily polished than the conductive pattern 2. Therefore, the conductor surface 2 a of the conductor pattern 2 is located on the opposite side of the second substrate surface 16 with respect to the first portion 15 a of the first substrate surface 15. This results in the formation of a step 5. Furthermore, as shown in FIG. 9 , if the conductive material constituting the conductor pattern 2 is sufficiently softer than the inorganic material constituting the inorganic material substrate 1, the conductor pattern 2 is more easily polished than the inorganic material substrate 1. In this case, the conductor surface 2 a of the conductor pattern 2 is located closer to the second substrate surface 16 with respect to the first portion 15 a of the first substrate surface 15. This results in the formation of a step 5. The shape of the step 5 can be changed not only by the difference in hardness between the conductor pattern 2 and the inorganic material substrate 1 but also by the chemical reactivity during CMP. Furthermore, as shown in Figure 10, when the hardness of the conductive material constituting the conductive pattern 2 and the inorganic material constituting the inorganic material substrate 1 are substantially the same, the first portion 15a of the first substrate surface 15 and the conductive surface 2a of the conductive pattern 2 are substantially flush with each other.

[0072] The process for forming such a conductor pattern 2 is not limited to the above-described method. For example, a film of a conductor material may be formed through an etching mask by the above-described film formation method without removing the etching mask. This results in the formation of a conductor pattern 2 embedded in the recesses 11. In this case, after removing the etching mask, the conductor pattern 2 and the first substrate surface 15 exposed by the conductor pattern 2 are polished by the above-described polishing method.

[0073] 11 , in the step of forming the dielectric film 3, the dielectric film 3 is provided on the first substrate surface 15 so as to cover the conductor pattern 2. In one embodiment, the above-mentioned dielectric material is formed into a film so as to cover the first substrate surface 15 of the inorganic material substrate 1, the steps 5, and the conductor surface 2 a of the conductor pattern 2. In this way, the dielectric film 3 is formed.

[0074] Any appropriate film formation method can be used, such as sputtering, chemical vapor deposition (CVD), evaporation, a sol-gel method, and aerosol deposition (AD method), with sputtering being preferred.

[0075] Next, as shown in FIG. 1, in the step of bonding the dielectric film 3 to the support substrate 6, the support substrate 6 is directly bonded to the dielectric film 3 on the side opposite to the inorganic material substrate 1 by any appropriate method.

[0076] In one embodiment, the direct bonding can be achieved by the following procedure: First, if necessary, the bonding material is deposited on the surface of the dielectric film 3 and / or the support substrate 6 by the deposition method described above (preferably sputtering). Then, in a high vacuum chamber (for example, 1×10 －６The neutralization beam is irradiated onto the bonding surfaces of the components (layers or substrates) to be bonded at a pressure of about 100 Pa. The bonding surfaces are pre-planarized by polishing, if necessary. Examples of polishing methods include chemical mechanical polishing (CMP). The arithmetic mean roughness Ra of the bonding surfaces planarized by polishing is, for example, 0.0001 μm to 0.005 μm, and preferably 0.0005 μm to 0.001 μm. In one embodiment, when surface activation is performed using the neutralization beam, an inert gas is introduced into the chamber, and a high voltage is applied from a DC power supply to an electrode disposed in the chamber. With this configuration, an electric field generated between the electrode (positive electrode) and the chamber (negative electrode) causes electrons to move, generating a beam of atoms and ions from the inert gas. Of the beams reaching the grid, the ion beam is neutralized by the grid, and a beam of neutral atoms is emitted from the fast atom beam source. The atomic species constituting the beam are preferably inert gas elements (e.g., argon (Ar) or nitrogen (N)). The voltage during activation by beam irradiation is, for example, 0.5 kV to 2.0 kV, and the current is, for example, 50 mA to 200 mA. The irradiation time of the neutralization beam is, for example, 10 seconds to 300 seconds, preferably 30 seconds to 120 seconds. This activates each bonding surface, more specifically, the beam-irradiated surface. Next, the activated bonding surfaces are brought into contact with each other in a vacuum atmosphere at room temperature (23°C). The load during this contact can be, for example, 100 N to 20,000 N. This forms a bonding portion 4 including an amorphous layer 41, bonding the dielectric film 3 and the support substrate 6 via the bonding portion 4. Integrating the inorganic material substrate 1 and the support substrate 6 by direct bonding in this manner without using a resin can improve heat resistance and chemical resistance in subsequent manufacturing processes, thereby increasing the flexibility of the processing process for the composite substrate 100. Furthermore, the thermal expansion coefficient and water absorption coefficient of the bonding portion 4 can be reduced compared to when the bonding portion 4 contains an organic material. As a result, the connection reliability between the inorganic material substrate 1 and the support substrate 6 can be improved, and the reliability of the composite substrate 100 exposed to the external environment can be improved. In this manner, a laminate having a structure of the inorganic material substrate 1 / the conductor pattern 2 / the dielectric film 3 / the joint portion 4 / the support substrate 6 can be obtained.The direct bonding method is not limited to this, and other methods such as surface activation using FAB (Fast Atom Beam) or an ion gun, atomic diffusion, and plasma bonding can also be applied. The laminate is heat-treated as needed. This can improve the bonding strength between the inorganic material substrate 1 and the support substrate 6. The heating temperature is, for example, 60°C to 140°C, and preferably 80°C to 120°C. The heating time is, for example, 10 minutes to 5 hours, and preferably 30 minutes to 3 hours.

[0077] Alternatively, other bonding methods may be used as the direct bonding method. For example, a method using a high vacuum chamber (for example, 1×10 －６ The components (layers or substrates) to be bonded are introduced into a vacuum chamber (approximately 100 Pa), and a fast atomic beam using an inert gas such as Ar as the atomic species is irradiated onto the bonding surface of one of the components (layers or substrates), the first component. The material of the first component then adheres from the bonding surface to the bonding surface of the other component, the second component, as a sputtered layer. The deposited sputtered layer is made of atoms constituting the first component and may be a material containing atoms contained in the inert gas or the equipment or tool used. In this case, the sputtered layer may be an amorphous layer. A bonding layer made of the material of the first component is thus formed on the bonding surface of the second component. Next, the beam-irradiated surface of the first component is brought into contact with the surface of the bonding layer formed on the second component in a vacuum atmosphere at room temperature (23°C) and pressure is applied. This also allows the first component and the second component to be bonded via the bonding portion. After bonding, amorphous layers of the first component and the second component may be formed between the first component and the bonding layer and / or between the second component and the bonding layer, respectively. By employing this bonding method, the thickness of the bonded portion 4 can be reduced and the bonding strength can be improved, thereby improving the heat dissipation and reliability of the composite substrate 100 as a device.

[0078] In this manner, the composite substrate 100 is manufactured. Thereafter, as shown in Fig. 5, the second conductor pattern 7 and / or the third conductor pattern 9 may be formed by any appropriate method, as needed. Furthermore, the second via hole 13 and the second via 8b may also be formed by any appropriate method.

[0079] The composite substrate according to the embodiment of the present invention can be used in various industrial products, and can be particularly suitably used as a multilayer substrate having electronic circuits.

[0080] REFERENCE SIGNS LIST 1 inorganic material substrate 1a first substrate surface 11 recess 2 conductor pattern 2a conductor surface 3 dielectric film 4 bonding portion 41 amorphous layer 6 supporting substrate 100 composite substrate

Claims

1. A composite substrate comprising: an inorganic material substrate having a substrate surface with a recess formed therein; a conductor pattern embedded in the recess so as to expose at least a portion of the substrate surface; a dielectric film provided so as to cover the conductor pattern and the substrate surface exposed by the conductor pattern; and a support substrate located on the opposite side of the inorganic material substrate with respect to the dielectric film, wherein the dielectric film and the support substrate are directly bonded.

2. The composite substrate according to claim 1, wherein an amorphous layer formed by the direct bonding is disposed between the dielectric film and the support substrate.

3. The composite substrate according to claim 1, wherein the dielectric film and the support substrate are directly bonded together without the use of an adhesive.

4. The composite substrate according to claim 2, wherein the amorphous layer contains constituent elements of the dielectric film and constituent elements of the support substrate.

5. A composite substrate according to any one of claims 1 to 4, wherein the thickness of the conductor pattern is 1.5 μm or more.

6. The composite substrate according to any one of claims 1 to 4, wherein the inorganic material substrate is made of quartz glass.

7. A composite substrate according to any one of claims 1 to 4, wherein the inorganic material substrate has a thickness of 100 µm or less.

8. The support substrate is made of Si, AlN, SiC, low-temperature co-fired ceramics, diamond or Si ３ N ４ 5. The composite substrate according to claim 1, wherein the composite substrate comprises:

9. A composite substrate comprising: an inorganic material substrate having a substrate surface with a recess provided therein; a conductor pattern embedded in the recess so as to expose at least a portion of the substrate surface; a dielectric film provided so as to cover the conductor pattern and the substrate surface exposed from the conductor pattern; a support substrate located on the opposite side of the inorganic material substrate with respect to the dielectric film; and a bonding portion bonding the dielectric film to the support substrate, the bonding portion including an amorphous layer.

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