JP7487471B2 - Metal paste, conductor, and substrate having through-electrode and method for manufacturing same - Google Patents

Description

The present invention relates to a metal paste, a conductor, and a substrate having a through electrode and a method for manufacturing the same.

In recent years, in order to miniaturize, improve functionality, and integrate electronic devices and components, attention has been focused on three-dimensional packaging technology, in which silicon substrates arranged above and below are electrically connected via electrodes called through-silicon vias (TSVs) on the silicon substrate, and semiconductor chips are densely stacked vertically (in the height direction).

As a method for forming a silicon through-hole electrode, for example, Patent Document 1 discloses a method for manufacturing a semiconductor device having a silicon through-hole electrode, which includes a step of electroplating a non-through-hole via formed in a silicon substrate with copper using a specific copper plating solution.

JP 2019-16712 A

However, the method described in Patent Document 1 requires plating to be performed while suppressing the deposition rate of the copper coating, which lengthens the work time and poses a problem in terms of productivity.

On the other hand, substrates with silicon through-hole electrodes are required to not only have sufficient conductivity, but also to have excellent connection reliability, meaning that resistance is unlikely to increase even when subjected to temperature changes.

Therefore, one aspect of the present invention aims to provide a conductor that has sufficient conductivity and is resistant to an increase in resistance even when subjected to temperature changes, a substrate having a through electrode that has sufficient conductivity and excellent connection reliability, a method for manufacturing the same, and a metal paste used to form the through electrode.

As a result of intensive research conducted by the inventors to achieve the above object, they discovered that in a conductor comprising a copper sintered body having a porous structure, by dispersing a specific metal in the copper sintered body and providing a metal body having voids in specific locations, it is possible to form a conductor that is less susceptible to cracking. The inventors then discovered that a substrate having a through electrode in which the through holes are filled with such a conductor exhibits a sufficiently low initial resistance value and is also less susceptible to an increase in resistance value in a temperature cycle connection reliability test, which led to the completion of the present invention.

That is, one aspect of the present disclosure provides the following invention.
[1] A conductor comprising a copper sintered body having a porous structure and solder present interspersedly in the copper sintered body, the conductor comprising a metal body having voids, the metal body including, as the voids, voids present inside the solder and/or voids present between the solder and the copper sintered body.
[2] The conductor according to [1], wherein the solder contains tin or a tin alloy.
[3] The conductor according to [1], wherein the solder is In--Sn, In--Sn--Ag, Sn--Bi, Sn--Bi--Ag, Sn--Ag--Cu, or a Sn--Cu based alloy.
[4] The conductor according to any one of [1] to [3], further comprising a cured resin present in the pores of the metal body.
[5] The conductor according to [4], wherein the porosity of the metal body is 1 to 15 volume % based on the volume of the metal body, and the content of the cured resin in the conductor is 80 volume % or more based on the total volume of the internal spaces of the pores of the metal body.

Further, other aspects of the present disclosure provide the following inventions.
[6] A substrate having a through electrode, comprising: an insulating substrate having a through hole, the through hole communicating with both main surfaces; and a conductor filling the through hole, the conductor being the conductor according to any one of [1] to [5] above.
[7] The substrate having a through electrode according to [6], wherein the substrate has a metal coating provided on at least a wall surface of the through hole.
[8] The substrate having a through electrode according to [6] or [7], wherein the ratio L/D of the length L of the through electrode to the hole diameter D is 10 or more.
[9] A substrate having the through electrode according to any one of [6] to [8], wherein the conductor covers at least a portion of a main surface of the substrate.
[10] The substrate having a through electrode according to any one of [6] to [9], wherein the insulating substrate is a silicon wafer and the through electrode is a silicon through electrode.

Further, other aspects of the present disclosure provide the following inventions.
[11] A method for manufacturing a substrate having a through electrode, comprising: a preparation step of preparing a substrate including an insulating substrate having through holes, the through holes communicating with both main surfaces; and a conductor formation step of forming a conductor in the through hole, the conductor formation step including a metal body formation step of forming a metal body having voids, the metal body containing a copper sintered body having a porous structure and solder so as to fill at least the through hole.
[12] The method according to [11], wherein the conductor forming step further includes a resin impregnation step of impregnating the metal body with a curable resin composition, and a resin curing step of curing the curable resin composition impregnated into the metal body.
[13] A method for manufacturing a substrate having a through electrode, comprising: a preparation step of preparing a substrate including an insulating substrate having non-through holes, the substrate having one main surface on which the non-through holes are opened; a conductor formation step of forming a conductor in the non-through holes; and a grinding step of providing a through electrode by grinding the side of the substrate having the conductor formed thereon opposite to the surface on which the non-through holes are opened, the conductor formation step including a metal body formation step of forming a metal body having voids, the metal body containing a copper sintered body having a porous structure and solder so as to fill at least the non-through holes.
[14] The method according to [13], wherein the conductor forming step further includes a resin impregnation step of impregnating the metal body with a curable resin composition, and a resin curing step of curing the curable resin composition impregnated into the metal body.
[15] The method according to any one of [11] to [14], wherein the solder contains tin or a tin alloy.
[16] The method according to any one of [11] to [14], wherein the solder is In--Sn, In--Sn--Ag, Sn--Bi, Sn--Bi--Ag, Sn--Ag--Cu, or a Sn--Cu based alloy.
[17] The method according to any one of [11] to [16], wherein the porosity of the metal body is 1 to 15 volume % based on the volume of the metal body.
[18] The method according to [12] or [14], wherein the content of the cured resin in the conductor is 80 volume% or more based on the total volume of the internal space of the pores of the metal body.
[19] The method according to any one of [11] to [18], wherein in the metal body forming step, the metal body is formed so as to cover at least a portion of a main surface of the base.
[20] The method according to [19], further comprising a conductor removing step of removing at least a portion of the conductor formed on the main surface of the substrate.
[21] The method according to any one of [11] to [20], wherein the ratio L/D of the length L to the hole diameter D of the through electrode is 10 or more.
[22] The method according to [11] or [12], wherein the metal body forming step includes a paste filling step of filling a through hole of a base with a metal paste containing copper particles and solder particles, and a paste firing step of firing the metal paste to form the metal body.
[23] The method according to [13] or [14], wherein the metal body forming step includes a paste filling step of filling non-through holes in the base with a metal paste containing copper particles and solder particles, and a paste firing step of firing the metal paste to form the metal body.
[24] The method according to [22] or [23], wherein the metal paste contains, as the copper particles, first copper particles having a particle size of 0.8 μm or more and second copper particles having a particle size of 0.5 μm or less.
[25] The method according to [24], wherein the first copper particles are flat.
[26] The method according to any one of [22] to [25], wherein the solder particles contain tin or a tin alloy.
[27] The method according to any one of [22] to [25], wherein the solder particles are In--Sn, In--Sn--Ag, Sn--Bi, Sn--Bi--Ag, Sn--Ag--Cu, or a Sn--Cu based alloy.
[28] The method according to any one of [22] to [27], wherein the metal paste is fired under a pressure of 0.1 MPa or more.
[29] The method according to any one of [22] to [28], wherein the metal paste is fired in an atmosphere containing nitrogen, hydrogen, or formic acid.
[30] The method according to any one of [11] to [29], wherein the insulating substrate is a silicon wafer and the through electrode is a silicon through electrode.

Further, other aspects of the present disclosure provide the following inventions.
[31] A metal paste used for forming a through electrode, the metal paste containing copper particles and solder particles, the copper particles including first copper particles having a particle size of 0.8 μm or more and second copper particles having a particle size of 0.5 μm or less.
[32] The metal paste according to [31], wherein the first copper particles are flat.
[33] The metal paste according to [31] or [32], wherein the solder particles contain tin or a tin alloy.
[34] The metal paste according to [31] or [32], wherein the solder particles are In--Sn, In--Sn--Ag, Sn--Bi, Sn--Bi--Ag, Sn--Ag--Cu, or a Sn--Cu based alloy.

According to one aspect of the present invention, it is possible to provide a conductor that has sufficient conductivity and is resistant to an increase in resistance even when subjected to temperature changes, a substrate having a through electrode that has sufficient conductivity and excellent connection reliability, a method for manufacturing the same, and a metal paste used to form the through electrode.

In addition, when the conductor further comprises a cured resin, the above substrate and method can provide a substrate having a through electrode that is also excellent in airtightness and impermeability (property that prevents liquid from penetrating).

1A to 1C are schematic diagrams illustrating a method for manufacturing a substrate having a through electrode according to a first embodiment. 1A to 1C are schematic diagrams illustrating a method for manufacturing a substrate having a through electrode according to a first embodiment. 1A to 1C are schematic diagrams illustrating a method for manufacturing a substrate having a through electrode according to a first embodiment. 1A to 1C are schematic diagrams illustrating a method for manufacturing a substrate having a through electrode according to a first embodiment. 1A to 1C are schematic diagrams illustrating a method for manufacturing a substrate having a through electrode according to a first embodiment, and a substrate having a through electrode according to the first embodiment. 1 is a schematic diagram showing a semiconductor device according to a first embodiment; 5A to 5C are schematic diagrams illustrating a method for manufacturing a substrate having a through electrode according to a second embodiment. 5A to 5C are schematic diagrams showing a method for manufacturing a substrate having a through electrode according to a second embodiment, and a substrate having a through electrode according to the second embodiment. FIG. 11 is a schematic diagram showing a semiconductor device according to a second embodiment. FIG. 2 is a schematic diagram showing a test piece. 1 is a cross-sectional photograph of a portion in which there is a void inside the solder (SnBi58) in the sample produced in Example 1. 1 is a cross-sectional photograph of a portion of the sample produced in Example 1 in which there is a void on the outer periphery of the solder (SnBi58). 13 is a cross-sectional photograph of a portion in which there is a void inside the solder (Sn96.5Ag3Cu0.5) in the sample produced in Example 46. 1 is a cross-sectional photograph of a portion in which a crack exists inside a copper layer in a sample produced in Comparative Example 1.

Below, the embodiments for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and duplicate explanations will be omitted.

(Method for manufacturing a substrate having a through electrode according to the first embodiment)
1 to 5 are schematic diagrams showing a method for manufacturing a substrate having a through electrode according to the first embodiment.

The method for manufacturing a substrate having a through electrode according to the first embodiment includes a preparation step of preparing a substrate including an insulating substrate having through holes and having through holes on both main surfaces, and a conductor formation step of forming a conductor in the through hole. The conductor formation step includes a metal body formation step of forming a metal body having voids, which contains a copper sintered body and solder having a porous structure so as to fill at least the through hole, a resin impregnation step of impregnating the metal body with a curable resin composition, and a resin curing step of curing the curable resin composition impregnated in the metal body.

The method according to the first embodiment will be described using an example in which a silicon substrate, in which the insulating substrate is a silicon wafer, is prepared as the substrate, and a substrate having a silicon through electrode (hereinafter, sometimes referred to as a silicon through electrode substrate) is manufactured as the substrate having a through electrode, but the following description may be interpreted as replacing the silicon wafer with another insulating substrate. Examples of other insulating substrates include glass substrates, ceramic substrates, printed wiring boards, and semiconductor package substrates.

<Substrate Preparation Step>
1(a), a silicon substrate 40 can be prepared, which has a silicon wafer 1 with a through hole 30 formed therein and a metal coating 2 formed on the wall surface of the through hole and on the surface of the silicon wafer 1. The through hole 30 communicates with both main surfaces of the silicon substrate 40.

The thickness of the silicon wafer 1 may be 100 μm or more, 200 μm or more, or 300 μm or more from the viewpoint of suppressing warping of the substrate after sintering, and may be 800 μm or less, 300 μm or less, 200 μm or less, or 100 μm or less from the viewpoint of reducing the weight and increasing the density of the substrate.

From the viewpoint of increasing the density of the resulting semiconductor device, the upper limit of the diameter of the through holes 30 may be 200 μm or less, 100 μm or less, or 60 μm or less, and the lower limit of the diameter of the through holes 30 is not particularly limited, but may be 20 μm or more, or 50 μm or more.

The number of through holes 30 provided in the silicon substrate 40 may be 100 or more, or 300 or more per 1 cm ² of the main surface of the substrate, from the viewpoint of increasing the density of the resulting semiconductor device.

The metal coating 2 may be provided on both main surfaces of the silicon wafer 1 and on the wall surface of the through hole 30, or on at least one main surface of the silicon wafer 1 and on the wall surface of the through hole 30, or may be provided only on the wall surface of the through hole 30, or may not be provided at all. In the embodiment shown in FIG. 1(a), the silicon substrate 40 has the metal coating 2 on both main surfaces of the silicon wafer 1 and on the wall surface of the through hole 30.

Examples of the metal coating 2 include titanium, nickel, chromium, copper, aluminum, palladium, platinum, and gold. From the viewpoint of adhesion, the metal coating 2 is preferably a coating in which titanium, nickel, and copper are layered in this order. Adhesion is improved by oxidizing the surface of the silicon wafer 1 to silicon oxide and forming a titanium layer on the silicon oxide. Furthermore, by providing a nickel layer on the titanium layer and then a copper layer on top of that, diffusion of copper into the silicon wafer 1 can be suppressed compared to the case where a copper layer is directly provided on the titanium layer. Furthermore, by providing a copper layer on the surface, adhesion between the metal body formed in the metal body forming process described below and the silicon substrate 40 is improved.

<Metal body forming process>
In this process, a metal body containing a copper sintered body and solder having a porous structure and having voids is formed so as to fill at least the through holes. In this embodiment, the metal body may be formed so as to cover at least a part of the main surface of the silicon substrate 40. In this case, a conductor is formed to fill the through holes of the silicon substrate 40, and a conductor can also be provided on the main surface of the silicon substrate 40. The conductor provided on the main surface of the silicon substrate 40 can form wiring and silicon through electrodes.

The metal body forming process may include a metal paste filling process in which a metal paste containing copper particles and solder particles is filled into the through holes of the silicon substrate, and a metal paste firing process in which the metal paste is fired to form the metal body. When the metal body is formed on the main surface of the silicon substrate, a layer of metal paste may be provided on both main surfaces of the silicon substrate during or after the metal paste filling process.

As the metal body forming process, for example, as shown in FIG. 1(b), a metal paste 3 containing copper particles and solder particles is applied to a silicon substrate 40, the metal paste 3 is filled into the through-holes 30, and layers of the metal paste 3 are also formed on both main surfaces of the silicon substrate 40. Details of the metal paste 3 will be described later.

Methods for applying the metal paste 3 to the silicon substrate 40 include, for example, screen printing, transfer printing, offset printing, jet printing, a dispenser, a jet dispenser, a needle dispenser, a comma coater, a slit coater, a die coater, a gravure coater, a slit coat, letterpress printing, intaglio printing, gravure printing, stencil printing, soft lithography, a bar coat, an applicator, a particle deposition method, a spray coater, a spin coater, a dip coater, etc.

When the metal paste is also applied onto the main surface of the silicon substrate, the thickness of the metal paste layer may be 1 μm or more, 2 μm or more, 3 μm or more, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more, and may be 300 μm or less, 250 μm or less, 200 μm or less, 150 μm or less, 120 μm or less, 100 μm or less, 80 μm or less, or 50 μm or less.

The metal paste 3 may be dried as appropriate from the viewpoint of preventing the copper particles and solder particles from flowing when the metal paste 3 is sintered, and preventing the occurrence of voids in the copper sintered body contained in the metal body. When the metal paste 3 is dried, the atmosphere during drying may be an oxygen-free atmosphere such as nitrogen and a rare gas, or a reducing atmosphere such as hydrogen and formic acid.

The drying method may be drying at room temperature, drying by heating, or drying under reduced pressure. For example, a hot plate, a hot air dryer, a hot air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far-infrared heating furnace, a microwave heating device, a laser heating device, an electromagnetic heating device, a heater heating device, a steam heating furnace, a hot plate press device, etc. may be used for drying by heating or drying under reduced pressure. The drying temperature and time may be appropriately adjusted according to the type and amount of the dispersion medium used. The drying temperature may be, for example, 50°C or higher and 180°C or lower. The drying time may be, for example, 1 minute or more and 120 minutes or less.

After the metal paste filling step, the metal paste 3 is fired to sinter the copper particles contained in the metal paste 3. In this way, as shown in FIG. 2(c1), a metal body-filled silicon substrate 50 is obtained, which includes a copper sintered body having a porous structure and solder, and in which a metal body 5 having voids (pores) 4 fills the through-holes 30. In this embodiment, a metal body-filled silicon substrate 50 is obtained in which the metal body 5 is also provided on both main surfaces of the silicon substrate 40. FIG. 2(c2) is a schematic diagram showing the configuration of the metal body. The metal body includes a copper sintered body 12 having a porous structure, solder 14 scattered in the copper sintered body 12, and voids 4. The metal body can include, as voids 4, the pores of the copper sintered body 12, voids present inside the solder 14, and voids present between the copper sintered body 12 and the solder 14.

The firing can be carried out by a heat treatment. For the heat treatment, a heating means such as a hot plate, a hot air dryer, a hot air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far-infrared heating furnace, a microwave heating device, a laser heating device, an electromagnetic heating device, a heater heating device, or a steam heating furnace can be used.

The atmosphere during firing may be an oxygen-free atmosphere from the viewpoint of suppressing oxidation of the copper sintered body, or a reducing atmosphere from the viewpoint of removing the surface oxide of the copper particles in the metal paste 3. Examples of the oxygen-free atmosphere include the introduction of an oxygen-free gas such as nitrogen or a rare gas, or under a vacuum. Examples of the reducing atmosphere include pure hydrogen gas, a mixed gas of hydrogen and nitrogen represented by forming gas, nitrogen containing formic acid gas, a mixed gas of hydrogen and a rare gas, and a rare gas containing formic acid gas. When the metal paste 3 is sintered by heating without pressurization, it is preferably in pure hydrogen gas or a mixed gas of hydrogen and nitrogen represented by forming gas, and preferably in pure hydrogen gas. By heating in pure hydrogen gas, it is possible to lower the sintering temperature of the copper particles. When pure hydrogen gas is used, even if the thickness of the substrate is as thick as 600 μm and the diameter of the through hole 30 is as small as 10 μm, the gas reaches the center of the through hole 30, making it easy to obtain the metal body 5 containing the copper sintered body.

The maximum temperature reached during the heat treatment may be 150°C or higher, and may be 350°C or lower, 300°C or lower, or 260°C or lower, from the viewpoint of reducing thermal damage to each component and improving yield. If the maximum temperature reached is 150°C or higher, sintering tends to proceed sufficiently when the maximum temperature is held for 60 minutes or less. From the viewpoint of volatilizing all the dispersion medium and improving yield, the maximum temperature held for may be 1 minute or more, and may be 60 minutes or less, 40 minutes or less, or 30 minutes or less.

The metal paste may be fired under pressure. In this case, in an atmosphere containing pure hydrogen gas, the pressure may be 0.05 MPa or more, 0.1 MPa or more, or 0.3 MPa or more, and 20 MPa or less, 15 MPa or less, or 10 MPa or less. In an atmosphere containing nitrogen gas, the pressure may be 1 MPa or more, or 3 MPa or more, and 20 MPa or less, 15 MPa or less, or 10 MPa or less.

When pure hydrogen gas is used, the pressure is set to 0.05 MPa or more, and when nitrogen gas is used, the pressure is set to 1 MPa or more, which makes it easier to suppress the generation of voids in the metal body 5 formed in the center of the through hole 30, and makes it easier to obtain a metal body with good conductivity. In addition, when the silicon substrate 40 has a metal coating 2, the pressure is set to the above-mentioned lower limit value or more, and when pressure is applied to the silicon substrate 40 having a metal paste layer by sandwiching it from above and below with the pressure jig A, as shown in FIG. 1 (b), the pressure applied to the pressure jig A is set to the above-mentioned lower limit value or more, which makes it easier to smooth the surface of the metal body formed on the main surface of the silicon substrate 40. If the surface of the metal body is smooth, there is an advantage that fine wiring is easily formed when wiring is formed by etching or the like in a later process. The pressure jig A is not particularly limited, but may be a commercially available one, and may also be produced using a metal member having a flat portion. For example, a pressure jig having two or more of the above-mentioned metal members can pressurize a silicon substrate by sandwiching the silicon substrate between the metal members arranged so that the flat portions face each other. Pressure jig A may have a mechanism for adjusting the pressure applied to the silicon substrate. A spring or the like can be used as the pressure adjustment means.

If the pressure is 20 MPa or less, warping of the silicon substrate 40 is easily suppressed. The inventors speculate that the reason for this effect is as follows. First, when the pressure is increased, the sintered density of the copper particles contained in the metal paste (particularly the density of the side in contact with the pressure jig A) increases, and the thermal expansion coefficient of the formed copper sintered body approaches the thermal expansion coefficient of 16.5 μm/(m·K) of general copper at 25°C. On the other hand, the thermal expansion coefficient of silicon at 25°C is 2.6 μm/(m·K). Therefore, as the density of the copper sintered body increases, the difference in the thermal expansion coefficient between the copper sintered body and silicon increases, and warping is likely to occur. In this embodiment, by setting the pressure to 20 MPa or less, the increase in the density of the copper sintered body is appropriately suppressed, and as a result, the difference in the thermal expansion coefficient between the copper sintered body and silicon becomes smaller, and warping is suppressed.

In addition, if the pressure applied during firing is within the above range, no special pressure device is required, and the yield is not compromised, and voids can be reduced and the bonding strength and connection reliability can be further improved. Methods for applying pressure to a silicon substrate coated with a metal paste include, for example, placing a weight on the substrate, applying pressure using a pressure device, and applying pressure using a fixed jig for applying pressure.

From the viewpoint of reducing the volume resistivity of the metal body, the porosity (proportion of voids contained in the metal body) of the metal body formed on the main surface of the silicon substrate may be 15 volume % or less, 14 volume % or less, 12 volume % or less, or 9 volume % or less based on the total volume (including voids) of the metal body. In addition, from the viewpoint of suppressing cracking and warping of the silicon substrate 40, the porosity of the metal body 5 may be 1 volume % or more, 3 volume % or more, or 5 volume % or more.

By having the metal body formed on the main surface of the silicon substrate have the above-mentioned porous structure, it is possible to lower the thermal expansion coefficient, reduce the difference in thermal expansion coefficient with the silicon wafer, and suppress cracking and warping of the silicon substrate.

From the viewpoint of reducing the volume resistivity of the metal body, the porosity of the metal body filled in the through holes (the proportion of voids contained in the metal body) may be 15 vol.% or less, 14 vol.% or less, 12 vol.% or less, or 9 vol.% or less based on the total volume (including voids) of the metal body. In addition, from the viewpoint of alleviating the stress applied to the copper sintered body and suppressing cracking and warping of the silicon substrate, the porosity of the metal body 5 may be 1 vol.% or more, 3 vol.% or more, or 5 vol.% or more.

By having the metal body filled in the through holes have the above-mentioned porous structure, the stress applied to the metal body can be alleviated, suppressing cracking and warping of the silicon substrate.

The porosity of the metal body is calculated by the following procedure.
(i) A cross section of a metal body of a metal body-filled silicon substrate (a cut surface in the thickness direction of the substrate) is exposed by a focused ion beam.
(ii) A cross-sectional image of the exposed cross section (within a range of 10 μm in the thickness direction of the substrate and a range of 10 μm in the direction perpendicular to the thickness direction of the substrate) is photographed using a scanning electron microscope.
(iii) The cross-sectional image obtained is binarized so that the metal portion and the porous portion are separated.
(iv) From the binarized cross-sectional image, the ratio of the area of the porous portion to the total area of the cross-section of the metal body is determined as the porosity of the metal body.
When calculating the porosity of the metal body filled in the through hole, in the above (i), a cross section of the central part of the metal body filled in the through hole is exposed. When calculating the porosity of the central part of the metal body filled in the through hole, a range of ±5 μm in the thickness direction of the substrate and ±5 μm in the direction perpendicular to the thickness direction of the substrate is observed from the central part of the metal body filled in the through hole. When calculating the porosity of the metal body formed on the main surface of the metal body-filled silicon substrate, in the above (i), a cross section of the metal body on the main surface is exposed. When calculating the porosity of the metal body formed on the main surface of the metal body-filled silicon substrate, a region up to 5 μm from the surface of the metal body formed on the main surface is observed.
When calculating the porosity of the metal body used to calculate the filling rate of the cured resin in the conductor described below, the observation points of the metal body can be appropriately set to be the same as the observation points of the conductor.

In addition, if the pressure applied during firing is within the above range, no special pressure device is required, and the yield is not compromised, and voids can be reduced and the bonding strength and connection reliability can be further improved. Methods for applying pressure to a silicon substrate coated with a metal paste include, for example, placing a weight on the substrate, applying pressure using a pressure device, and applying pressure using a fixture for applying pressure.

The copper sintered body contained in the metal body may have a copper element ratio of 95% by mass or more, 97% by mass or more, 98% by mass or more, or 100% by mass, among the constituent elements excluding light elements. If the copper element ratio in the copper sintered body is within the above range, the formation of intermetallic compounds or the precipitation of different elements at the metallic copper crystal boundaries can be suppressed, the properties of the metallic copper constituting the copper sintered body are likely to be strengthened, and even better connection reliability is likely to be obtained.

The amount of solder contained in the metal body may be 3 parts by mass or more, 10 parts by mass or more, or 10 parts by mass or more, relative to 100 parts by mass of the copper sintered body contained in the metal body, from the viewpoint of suppressing cracks in the metal body, and may be 20 parts by mass or less, 15 parts by mass or less, or 10 parts by mass or less, from the viewpoint of reducing the volume resistivity of the metal body.

In the metal body forming process, the metal paste may be heated and fired without being pressurized. In this case, the porosity of the metal body formed on the main surface of the silicon substrate tends to increase, and by lowering the thermal expansion coefficient of the metal body, cracks and warping of the silicon substrate become less likely to occur.

<Resin impregnation process>
In this step, for example, the metal body 5 can be impregnated with the curable resin composition by applying the curable resin composition to the metal body-filled silicon substrate 50 obtained through the metal body formation step. In this embodiment, the metal body 5 filling the through hole 30 and the metal body 5 formed on both main surfaces of the silicon substrate 40 are impregnated with the curable resin composition. It is preferable that the voids 4 of the metal body 5 are sufficiently filled with the impregnated curable resin composition.

(Curable resin composition)
The components constituting the curable resin composition include a thermosetting compound. Examples of the thermosetting compound include an oxetane compound, an epoxy compound, an episulfide compound, a (meth)acrylic compound, a phenol compound, an amino compound, an unsaturated polyester compound, a polyurethane compound, a silicone compound, and a polyimide compound. Among them, an epoxy compound may be used in order to further improve the curability and viscosity of the curable resin composition and improve the characteristics and insulation reliability when left at high temperatures.

The curable resin composition may further include a heat curing agent. Examples of heat curing agents include imidazole curing agents, amine curing agents, phenol curing agents, polythiol curing agents, acid anhydrides, thermal cationic initiators, and thermal radical generators. These may be used alone or in combination of two or more. Among these, imidazole curing agents, polythiol curing agents, and amine curing agents are preferred because they can be cured quickly at low temperatures. In addition, latent curing agents are preferred because they have high storage stability when mixed with a thermosetting compound and a heat curing agent. The latent curing agent is preferably a latent imidazole curing agent, a latent polythiol curing agent, or a latent amine curing agent. The heat curing agent may be coated with a polymeric substance such as a polyurethane resin or a polyester resin.

The imidazole curing agent is not particularly limited, and examples thereof include 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, and 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct.

The polythiol curing agent is not particularly limited, and examples thereof include trimethylolpropane tris-3-mercaptopropionate, pentaerythritol tetrakis-3-mercaptopropionate, and dipentaerythritol hexa-3-mercaptopropionate. The solubility parameter of the polythiol curing agent is preferably 9.5 or more, and preferably 12 or less. The solubility parameter is calculated by the Fedors method. For example, the solubility parameter of trimethylolpropane tris-3-mercaptopropionate is 9.6, and the solubility parameter of dipentaerythritol hexa-3-mercaptopropionate is 11.4.

The above amine curing agent is not particularly limited, and examples thereof include hexamethylenediamine, octamethylenediamine, decamethylenediamine, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraspiro[5.5]undecane, bis(4-aminocyclohexyl)methane, metaphenylenediamine, and diaminodiphenylsulfone.

The above-mentioned thermal cationic curing agents include iodonium cationic curing agents, oxonium cationic curing agents, and sulfonium cationic curing agents. The above-mentioned iodonium cationic curing agents include bis(4-tert-butylphenyl)iodonium hexafluorophosphate. The above-mentioned oxonium cationic curing agents include trimethyloxonium tetrafluoroborate. The above-mentioned sulfonium cationic curing agents include tri-p-tolylsulfonium hexafluorophosphate.

The thermal radical generator is not particularly limited, and examples thereof include azo compounds and organic peroxides. Examples of the azo compounds include azobisisobutyronitrile (AIBN). Examples of the organic peroxides include di-tert-butyl peroxide and methyl ethyl ketone peroxide.

Methods for applying the curable resin composition include screen printing, transfer printing, offset printing, jet printing, dispenser, jet dispenser, needle dispenser, comma coater, slit coater, die coater, gravure coater, slit coat, letterpress printing, intaglio printing, gravure printing, stencil printing, soft lithography, bar coat, applicator, particle deposition method, spray coater, spin coater, dip coater, etc.

The curable resin composition may be applied to one of the main surfaces of the metal body-filled silicon substrate 50, or may be applied to a portion of the main surface. When applying the resin composition to both sides of the metal body-filled silicon substrate 50, the resin composition may be applied to one of the main surfaces of the metal body-filled silicon substrate 50, the resin composition may be allowed to penetrate to the main surface side of the metal body-filled silicon substrate 50 to which the resin composition has not been applied, and then the resin composition may be applied to the main surface to which the resin composition has not been applied. This allows the resin composition to permeate the voids 4.

The metal body-filled silicon substrate 50 coated with the curable resin composition can be left in a reduced pressure environment to improve the impregnation of the curable resin composition into the pores 4 of the metal body 5.

In the resin impregnation step, it is preferable to impregnate the metal body with the cured resin composition so that the filling rate of the cured resin in the conductor formed through the resin curing step falls within the preferred range described below.

<Resin curing process>
In this step, as shown in FIG. 3(d1), the curable resin composition impregnated into the metal body 5 (the curable resin composition filled in the pores 4) is cured to form a conductor 35 including the metal body 5 in which the pores 4 are filled with the resin cured material 6, and a substrate 51 having a silicon through-hole electrode in which a silicon through-hole 30 is provided can be obtained. In the case of this embodiment, a conductor 35 including a metal body 5 in which the pores 4 are filled with the resin cured material 6 is also provided on both main surfaces of the silicon substrate 40. FIG. 3(d2) is a schematic diagram showing the configuration of the conductor. The conductor includes a copper sintered body 12, a solder 14, and a resin cured material 6 filled in the pores. The solder 14 may be scattered in the conductor 35. The resin cured material 6 may be present in the pores of the copper sintered body 12, the voids present inside the solder 14, and the voids present between the copper sintered body 12 and the solder 14.

The curable resin composition can be cured by a heat treatment. For the heat treatment, a heating means such as a hot plate, a hot air dryer, a hot air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far-infrared heating furnace, a microwave heating device, a laser heating device, an electromagnetic heating device, a heater heating device, or a steam heating furnace can be used.

The atmosphere in the resin curing step may be an oxygen-free atmosphere from the viewpoint of suppressing oxidation of the metal body 5 (particularly the copper sintered body), or may be a reducing atmosphere from the viewpoint of removing surface oxides of the metal body 5 (particularly the copper sintered body). Examples of the oxygen-free atmosphere include the introduction of an oxygen-free gas such as nitrogen or a rare gas, or a vacuum. Examples of the reducing atmosphere include a pure hydrogen gas, a mixed gas of hydrogen and nitrogen such as forming gas, nitrogen containing formic acid gas, a mixed gas of hydrogen and a rare gas, and a rare gas containing formic acid gas.

The maximum temperature reached during the heat treatment in the resin curing process may be 150°C or higher, and may be 350°C or lower, 300°C or lower, or 260°C or lower, from the viewpoint of reducing thermal damage to each component and improving yield. If the maximum temperature reached is 150°C or higher, the curing of the resin composition tends to proceed sufficiently when the maximum temperature is held for 60 minutes or less.

The conductor 35 formed in the resin curing process (the conductor before the conductor removal process) may have a content (filling rate) of the cured resin 6 that satisfies the following conditions:

(Through-hole conductor)
(a) In a region (see (d1) in FIG. 3 ) that passes through central portion C of through hole 30 (the center of the hole length and the center of the hole diameter there) and extends from point S1, where line L1 extending in the thickness direction of the substrate intersects with the surface of conductor 35, to a depth of 10 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the internal space of the pores (voids) of the metal body.
(b) In the region 10 to 20 μm deep from point S1, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(c) In the region from point S1 to a depth of 20 to 30 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(d) Within a range of ±5 μm from the center C of the through hole 30 in the thickness direction of the substrate and in a direction perpendicular to the thickness direction of the substrate, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.

(Conductors on the main surface of the substrate)
(e) In the region from the surface S2 of the conductor 35 formed on the main surface of the substrate to a depth of 5 μm (see (d1) in FIG. 3), the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(f) In the region from the surface S2 of the conductor 35 formed on the main surface of the substrate to a depth of 10 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(g) In a region 10 to 20 μm deep from the surface S2, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(h) In the region 20 to 30 μm deep from the surface S2, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.

The filling rate of the cured resin 6 in the conductor 35 is calculated by the following procedure.
(i) A cross section of the conductor of a conductor-filled silicon substrate (a cut surface in the thickness direction of the substrate) is exposed by a focused ion beam.
(ii) A cross-sectional image of the exposed cross section (within a range of 10 μm in the thickness direction of the substrate and a range of 10 μm in the direction perpendicular to the thickness direction of the substrate) is photographed using a scanning electron microscope.
(iii) The cross-sectional image obtained is binarized so that the metal and cured resin portions are separated from the porous portions not filled with the cured resin.
(iv) From the binarized cross-sectional image, the ratio of the area of the porous portion not filled with the cured resin to the total area of the cross-section of the conductor is calculated, and this is regarded as the porosity of the conductor.
(v) The filling rate of the cured resin in the conductor is calculated by substituting the porosity of the metal body before impregnation with the curable resin composition and the porosity of the conductor into the following formula (1).
Filling rate (%) of cured resin in conductor=[(B−A)/B]×100 Equation (1)
[In formula (1), A represents the porosity (%) of the conductor, and B represents the porosity (%) of the metal body.]
In the case where the porosity of the conductor filled in the through-hole is calculated, a cross section of the central part of the conductor in the through-hole is exposed in the above (i).In the case where the porosity of the conductor formed on the main surface of the conductor-filled silicon substrate is calculated, a cross section of the conductor on the main surface is exposed in the above (i).

<Conductor Removal Process>
In this step, it is possible to remove at least a part of the conductor 35 formed on the main surface of the silicon substrate 40. Means for removing the conductor include chemical polishing, mechanical polishing, chemical mechanical polishing, fly-cut processing, plasma processing, etc. Fly-cut processing refers to cutting and flattening with a surface planer.

In this embodiment, from the viewpoint of being easily applicable using a general method, it is preferable that the removal means is one or more selected from the group consisting of etching, mechanical polishing, and chemical mechanical polishing.

The manufacturing method of the silicon substrate having the silicon through electrode of this embodiment includes a conductor removal process, which, for example, makes the surface of the conductor 35 formed on the main surface of the silicon substrate 40 flat, making it easier to form wiring.

In this embodiment, the filling rate of the resin cured material 6 in the conductor 35 after the conductor removal process may satisfy the following condition. The filling rate can be calculated in the same manner as above.

(Through-hole conductor)
(a) In a region extending from a point S3 at a depth of 10 μm from the central portion C of the through hole 30 (the center of the hole length and the center of the hole diameter D there) where a line L1 extending in the thickness direction of the substrate intersects with the surface of the conductor 35 (see (e) of FIG. 4), the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the internal space of the pores (voids) of the metal body.
(b) In the region 10 to 20 μm deep from point S3, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(c) In the region from point S3 to a depth of 20 to 30 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(d) Within a range of ±5 μm from the center C of the through hole 30 in the thickness direction of the substrate and in a direction perpendicular to the thickness direction of the substrate, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.

(Conductors on the main surface of the substrate)
(e) In a region from the surface S4 of the conductor 35 formed on the main surface of the substrate to a depth of 5 μm (see (e) of FIG. 4), the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the internal space of the porous (void) parts of the metal body.
(f) In the region from the surface S4 of the conductor 35 formed on the main surface of the substrate to a depth of 10 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(g) In the region 10 to 20 μm deep from the surface S4, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(h) In the region 20 to 30 μm deep from the surface S4, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.

From the viewpoint of increasing the density of the resulting semiconductor device, the ratio L/D of the length L of the silicon through-hole electrode to the hole diameter D may be 1 or more, 5 or more, or 10 or more, and may be 15 or less, 10 or less, or 5 or less. The length L of the silicon through-hole electrode may be the thickness of the substrate having the silicon through-hole electrode. In this case, the ratio T/D of the thickness T of the substrate having the silicon through-hole electrode to the hole diameter D of the silicon through-hole electrode may be in the above range.

In the manufacturing method of the substrate having a through electrode of this embodiment, the conductor is filled with a resin cured material, but the resin impregnation process and the resin curing process described above may be omitted and the through electrode may be formed from a metal body.

The method for manufacturing a substrate having a through electrode of this embodiment may further include a wiring formation process. The wiring formation process may include a resist formation process, an etching process, and a resist removal process, which are described below.

<Resist Forming Process>
In the resist formation step, as shown in FIG. 4( f ), an etching resist 8 is formed on the conductor 35 formed on the main surface of the silicon substrate 40 .

Methods for forming the etching resist 8 include, for example, silk screen printing resist ink, or laminating a negative photosensitive dry film for etching resist onto copper foil, placing a light-transmitting photomask on top of it in the shape of the wiring, exposing it to ultraviolet light, and removing the unexposed areas with a developer.

<Etching process>
5(g), the conductor 35 in the portion not covered with the etching resist 8 is removed by etching. In this embodiment, a part of the metal coating 2 provided on each of the main surfaces of the silicon wafer 1 is removed by etching.

Examples of etching methods include those using chemical etching solutions typically used for wiring boards, such as a solution of cupric chloride and hydrochloric acid, a solution of ferric chloride, a solution of sulfuric acid and hydrogen peroxide, or an ammonium persulfate solution.

<Resist Removal Process>
In the resist removal step, the etching resist 8 formed on the conductor 35 is removed.

The method for manufacturing a substrate having a through electrode according to this embodiment further includes a wiring formation process having the above steps, thereby forming wiring 9 including a conductor 35 on the main surface of the silicon substrate 40.

(Base having through electrodes according to the first embodiment)
5(h) is a cross-sectional view showing one embodiment of a substrate having a silicon through-hole that can be manufactured by the method according to the first embodiment described above. The substrate 52 having a silicon through-hole shown in FIG. 5(h) includes a silicon wafer 1 having a through-hole 30, and includes a silicon substrate having the through-hole 30 on both main surfaces, and a conductor filling the through-hole 30. The conductor 35 includes a copper sintered body having a porous structure and solder scattered in the copper sintered body, and includes a metal body 5 having voids 4, and the metal body 5 includes, as the voids 4, voids present inside the solder and/or voids present between the solder and the copper sintered body. The conductor 35 further includes a resin cured material 6 filled in the voids 4.

The substrate 52 having a silicon through-hole electrode shown in FIG. 5(h) has a metal coating 2 on both main surfaces of the silicon wafer 1 and on the wall surface of the through-hole, but the metal coating 2 does not have to be provided on the main surfaces, it may be provided only on one main surface, or it may not be provided on the wall surface of the through-hole. Also, the substrate 52 having a silicon through-hole electrode has wiring 9 including the metal coating 2 and the conductor 35 provided on both main surfaces of the silicon substrate 40, but the wiring 9 may be provided on one main surface of the silicon substrate 40.

The substrate 52 having a silicon through electrode may have a filling rate of the cured resin 6 in the conductor that satisfies the following conditions. The filling rate can be calculated in the same manner as above.

(Through-hole conductor)
(a) In a region extending from a point S5 passing through a central portion C of the through hole 30 (the center of the hole length and the center of the hole diameter there) where a line L1 extending in the thickness direction of the substrate intersects with the surface of the conductor to a depth of 10 μm (see FIG. 5(h)), the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the internal space of the pores (voids) of the metal body.
(b) In the region from point S5 to a depth of 10 to 20 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(c) In the region from point S5 to a depth of 20 to 30 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(d) Within a range of ±5 μm from the center C of the through hole 30 in the thickness direction of the substrate and in a direction perpendicular to the thickness direction of the substrate, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.

(Conductors on the main surface of the substrate)
(e) In a region from the surface S6 of the conductor formed on the main surface of the substrate to a depth of 5 μm (see FIG. 5(h)), the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(f) In the region from the surface S6 of the conductor 35 formed on the main surface of the substrate to a depth of 10 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(g) In the region 10 to 20 μm deep from the surface S6, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(h) In the region 20 to 30 μm deep from the surface S6, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.

(Semiconductor Device According to the First Embodiment)
A semiconductor device manufactured using a base body (substrate having a silicon through electrode) having a through electrode according to the first embodiment will be specifically described with reference to FIG. 6. FIG. 6 is a schematic cross-sectional view showing one embodiment of the semiconductor device of the present invention. In the semiconductor device 100 shown in FIG. 6(a), the wiring 27 on the interposer substrate 25 is directly connected to the conductor 35 of the substrate 52 having a silicon through electrode, so that the interposer substrate 25 and the substrate 52 having a silicon through electrode are flip-chip connected. The gap between the interposer substrate 25 and the substrate 52 having a silicon through electrode is filled with a cured product 20 of the adhesive without any gaps, and is sealed. On the main surface of the substrate 52 having a silicon through electrode on the opposite side to the interposer substrate 25, the substrates 52 having a silicon through electrode are repeatedly stacked. The substrates 52 having a silicon through electrode are connected to each other by the conductor 35. The gap between the substrates 52 having a silicon through electrode is filled with a cured product 20 of the adhesive without any gaps, and is sealed.

The semiconductor device 100 may be obtained, for example, by the following method. That is, substrates 52 having silicon through-hole electrodes are laminated via an adhesive to obtain a laminate. The adhesive may be cured during lamination. The obtained laminate and the interposer substrate 25 are electrically connected by pressure bonding, forming a connection body in which the laminate and the interposer substrate 25 are electrically connected. A dicing tape is attached to the surface of the formed connection body opposite to the surface on which the interposer substrate 25 is provided, and dicing is performed along the dicing lines to obtain the semiconductor device 100.

In the semiconductor device 200 shown in FIG. 6(b), the wiring 27 on the interposer substrate 25 and the conductor 35 of the substrate 52 having the silicon through electrode are connected via the fine bumps 15, so that the interposer substrate 25 and the substrate 52 having the silicon through electrode are flip-chip connected. The gap between the interposer substrate 25 and the substrate 52 having the silicon through electrode is filled with the cured adhesive 20 without any gaps, and is sealed. On the main surface of the substrate 52 having the silicon through electrode on the side opposite to the interposer substrate 25, the substrates 52 having the silicon through electrode are repeatedly stacked via the fine bumps 15. The gap between the substrates 52 having the silicon through electrode is filled with the cured adhesive 20 without any gaps, and is sealed.

The semiconductor device 200 may be obtained, for example, by the following method. That is, a substrate 52 having a silicon through electrode with fine bumps 15 provided on one main surface is laminated via an adhesive to obtain a laminate. The adhesive may be cured during lamination. The obtained laminate and the interposer substrate 25 are electrically connected by pressure bonding, forming a connection body in which the laminate and the interposer substrate 25 are electrically connected. A dicing tape is attached to the surface of the formed connection body opposite to the surface on which the interposer substrate 25 is provided, and dicing is performed along the dicing lines to obtain the semiconductor device 200.

(Method of Manufacturing a Substrate Having Through Electrodes According to the Second Embodiment)
7 and 8 are schematic diagrams showing a method for manufacturing a substrate having a silicon through electrode, as a method for manufacturing a base body having a through electrode according to the second embodiment.

The method for manufacturing a substrate having a through electrode according to the second embodiment includes a preparation step of preparing a substrate having an insulating substrate with non-through holes and one of the main surfaces on which the non-through holes are opened, a conductor formation step of forming a conductor in the non-through hole, and a grinding step of providing a through electrode by grinding the surface opposite to the surface on which the non-through hole of the substrate on which the conductor is formed is opened. The conductor formation step includes a metal body formation step of forming a metal body having voids, which contains a copper sintered body and solder having a porous structure so as to fill at least the non-through holes, a resin impregnation step of impregnating the metal body with a curable resin composition, and a resin curing step of curing the curable resin composition impregnated in the metal body.

As with the method according to the first embodiment, the method according to the second embodiment will be described using an example in which a silicon substrate, whose insulating substrate is a silicon wafer, is prepared as the substrate, and a substrate having a silicon through-hole electrode is manufactured as the substrate having the through-hole electrode, but the following description can be interpreted with the silicon wafer as another insulating substrate.

<Substrate Preparation Step>
7(a), a silicon substrate 41 can be prepared, which has a silicon wafer 1 with non-through holes 31 formed therein, and a metal coating 2 formed on the wall and bottom surfaces of the non-through holes 31 and on the surface of the silicon wafer 1. The non-through holes 31 open on one main surface of the silicon wafer 1.

The thickness of the silicon wafer 1 may be 20 μm or more, 30 μm or more, or 50 μm or more, and may be 500 μm or less, 400 μm or less, or 300 μm or less, from the viewpoint of suppressing warping of the substrate after sintering.

From the viewpoint of increasing the density of the resulting semiconductor device, the upper limit of the diameter of the non-through holes 31 may be 200 μm or less, 100 μm or less, or 60 μm or less, and the lower limit of the diameter of the non-through holes 31 is not particularly limited, but may be 10 μm or more, or 30 μm or more.

The length (depth) of the non-through hole 31 can be set appropriately according to the length of the silicon through electrode to be formed.

The metal coating 2 may be provided on the surface of the silicon wafer 1 where the non-through holes 31 are open and on the wall and bottom surfaces of the non-through holes 31, or may or may not be provided on the wall and bottom surfaces of the non-through holes 31. In the embodiment shown in FIG. 7(a), the silicon substrate 41 is provided with the metal coating 2 on the surface of the silicon wafer 1 where the non-through holes 31 are open and on the wall and bottom surfaces of the non-through holes 31.

The metal coating 2 can be made of the same material as in the first embodiment.

<Metal body forming process>
In this step, a metal body having voids is formed, containing a copper sintered body having a porous structure and solder, so as to fill at least the non-through holes. In this embodiment, the metal body may be formed so as to cover at least a part of the surface of the silicon substrate 41 where the non-through holes 31 are open. In this case, a conductor is formed to fill the non-through holes 31 of the silicon substrate 41, and a conductor can also be provided on the surface of the silicon substrate 41 where the non-through holes 31 are open.

The metal body forming process may include a metal paste filling process in which a metal paste containing copper particles and solder particles is filled into the non-through holes of the silicon substrate, and a metal paste firing process in which the metal paste is fired to form the metal body. When the metal body is formed on the surface of the silicon substrate where the non-through holes are open, a layer of metal paste can also be provided on the surface of the silicon substrate where the non-through holes are open during or after the metal paste filling process.

As the metal body forming process, for example, as shown in FIG. 7(b), a metal paste 3 containing copper particles and solder particles is applied to a silicon substrate 41, and the metal paste 3 is filled into the non-through holes 31, and a layer of the metal paste 3 can also be provided on the surface of the silicon substrate 41 where the non-through holes 31 are open. Details of the metal paste 3 will be described later.

The method for applying the metal paste 3 to the silicon substrate 41 can be the same as that in the first embodiment.

When the metal paste is also applied to the surface of the silicon substrate 41 where the non-through holes 31 are open, the thickness of the metal paste layer may be 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less from the viewpoint of suppressing warping of the silicon substrate 41 and reducing the burden in the conductor removal process described below.

The metal paste 3 may be dried appropriately in the same manner as in the first embodiment. When drying the metal paste 3, the atmosphere, drying method, and drying temperature during drying may be the same as in the first embodiment.

After the metal paste filling step, the metal paste 3 is fired to sinter the copper particles contained in the metal paste 3. In this way, as shown in FIG. 8(c), a metal body-filled silicon substrate 60 is obtained in which the non-through holes 31 are filled with metal bodies 5 including pores 4, i.e., having a porous structure. In this embodiment, a metal body-filled silicon substrate 60 is obtained in which the metal bodies 5 are provided even on the surface of the silicon substrate 41 where the non-through holes 31 are open.

The firing conditions may be the same as in the first embodiment.

The porosity of the metal body formed on the surface of the silicon substrate where the non-through holes are open may be the same as the porosity of the metal body formed on the main surface of the silicon substrate in the first embodiment. The porosity of the metal body can be calculated using the same procedure as in the first embodiment.

The porosity of the metal body filled in the non-through holes may be similar to the porosity of the metal body filled in the through holes in the first embodiment.

The proportion of copper elements in the constituent elements, excluding light elements, of the copper sintered body contained in the metal body may be the same as in the first embodiment. The content of solder contained in the metal body may also be the same as in the first embodiment.

<Resin impregnation process>
In this step, for example, the metal body 5 can be impregnated with the curable resin composition by applying the curable resin composition to the metal body-filled silicon substrate 60 obtained through the metal body formation step. In this embodiment, the metal body 5 filling the non-through holes 31 and the metal body 5 formed on the surface of the silicon substrate 41 where the non-through holes are open are impregnated with the curable resin composition. It is preferable that the voids 4 of the metal body 5 are sufficiently filled with the impregnated curable resin composition.

The curable resin composition may be the same as that in the first embodiment. The method of applying the curable resin composition may be the same as that in the first embodiment. The filling rate of the curable resin composition in the holes 4 of the metal body 5 may be appropriately changed according to the filling rate of the resin cured material 6 of the conductor 35 after the resin curing process.

<Resin curing process>
In this step, the curable resin composition impregnated into the metal body 5 (the curable resin composition filled in the holes 4) is cured to form a conductor 35 including the metal body 5 with the holes 4 filled with the cured resin 6. In the case of this embodiment, the conductor 35 including the metal body 5 with the holes 4 filled with the cured resin 6 is also provided on the surface of the silicon substrate 41 where the non-through holes are open.

The curing conditions for the resin composition in the resin curing process may be the same as those in the first embodiment.

The conductor formed in the resin curing process (the conductor before the conductor removal process and the grinding process) may have a filling rate of the cured resin adjusted so that the filling rate of the cured resin in the silicon through electrode to be formed satisfies the conditions described below. For example, the conductor may have a filling rate of the cured resin that satisfies the following conditions:

(Blind Hole Conductor)
(a) In a region up to a depth of 10 μm from the point where a line passing through the center of a non-through hole (the center of the hole length and the center of the hole diameter there) and extending in the thickness direction of the substrate intersects with the surface of the conductor, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(b) In a region 10 to 20 μm deep from the point where a line passing through the center of the non-through hole and extending in the thickness direction of the substrate intersects with the surface of the conductor, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the internal space of the pores (voids) of the metal body.
(c) In a region 20 to 30 μm deep from the point where a line passing through the center of the non-through hole and extending in the thickness direction of the substrate intersects with the surface of the conductor, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.

(Conductors on the main surface of the substrate)
(e) In a region from the surface of the conductor formed on the main surface of the substrate to a depth of 5 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(f) In a region from the surface of the conductor formed on the main surface of the substrate to a depth of 10 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(g) In a region 10 to 20 μm deep from the surface of the conductor formed on the main surface of the substrate, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(h) In a region 20 to 30 μm deep from the surface of the conductor formed on the main surface of the substrate, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.

The filling rate of the cured resin 6 in the conductor is calculated in the same manner as described in the manufacturing method of the substrate having the silicon through electrode according to the first embodiment.

<Conductor Removal Process>
The method for manufacturing a substrate having a silicon through electrode according to the present embodiment may further include a conductor removing step after the resin curing step. In this step, at least a part of the conductor 35 formed on one main surface of the silicon substrate 41 can be removed. The means for removing the conductor may be the same as that in the first embodiment.

<Grinding process>
In this step, as shown in Fig. 8(d), the side of the silicon substrate on which the conductor 35 is formed opposite to the side on which the non-through hole 31 is open is ground to obtain a substrate 61 having a silicon through electrode provided with a silicon electrode. That is, in this step, the conductor 35 is exposed by grinding also on the side on which the non-through hole 31 is open in the silicon substrate, thereby forming a silicon through electrode. In Fig. 8(d), the conductor 35 formed on the side on which the non-through hole 31 is open in the silicon substrate is removed by the conductor removal step.

Grinding methods include, for example, mechanical polishing and chemical-mechanical polishing.

In this embodiment, the filling rate of the resin cured material 6 in the conductor 35 after the grinding process may satisfy the following condition. The filling rate can be calculated in the same manner as above.

(a) In a region (see (d) of FIG. 8 ) from a point S21 at which a line L2 passing through a central portion E of the silicon through electrode (the center of the length L and the center of the hole diameter D there) and extending in the thickness direction of the substrate intersects with the surface of the conductor 35 to a depth of 10 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the internal space of the pores (vacant holes) of the metal body.
(b) In the region 10 to 20 μm deep from point S21, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(c) In the region from point S21 to a depth of 20 to 30 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(d) Within a range of ±5 μm from the center E of the silicon through electrode in the thickness direction of the substrate and ±5 μm in a direction perpendicular to the thickness direction of the substrate, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.

The ratio L/D of the length L of the silicon through-hole electrode to the hole diameter D may be the same as in the first embodiment.

In the manufacturing method of the substrate having a through electrode of this embodiment, the conductor is filled with a resin cured material, but the resin impregnation process and the resin curing process described above may be omitted and the through electrode may be formed from a metal body.

The method for manufacturing a substrate having a through electrode according to the second embodiment can further include a wiring formation step similar to the method according to the first embodiment described above.

(Substrate having through electrodes according to the second embodiment)
8(d) is a cross-sectional view showing one embodiment of a substrate having a silicon through-hole that can be manufactured by the method according to the second embodiment described above. The substrate 61 having a silicon through-hole shown in FIG. 8(d) includes a silicon wafer 1 having through-holes, a silicon substrate having through-holes on both main surfaces, and a conductor 35 filling the through-holes. The conductor 35 includes a copper sintered body having a porous structure and solder scattered in the copper sintered body, and includes a metal body 5 having voids 4, and the metal body 5 includes, as the voids 4, voids present inside the solder and/or voids present between the solder and the copper sintered body. The conductor 35 further includes a resin cured material 6 filled in the voids 4.

The substrate 61 having a silicon through electrode shown in FIG. 8(d) does not have a conductor 35 formed on either main surface, but a conductor 35 may be formed on one main surface. The substrate 61 having a silicon through electrode shown in FIG. 8(d) has a metal coating 2 provided on the wall surface of the through hole, but the metal coating 2 does not have to be provided on the wall surface of the through hole.

The filling rate of the cured resin 6 in the conductor 35 contained in the substrate 61 having a silicon through electrode may be the same as the filling rate of the cured resin 6 in the conductor 35 after the grinding process.

(Semiconductor Device According to Second Embodiment)
A semiconductor device manufactured using a base body having a through electrode (substrate having a silicon through electrode) according to the second embodiment will be specifically described with reference to Fig. 9. Fig. 9 is a schematic cross-sectional view showing one embodiment of a semiconductor device of the present invention. In the semiconductor device 300 shown in Fig. 9, substrates 61 having silicon through electrodes are repeatedly stacked. The substrates 61 having silicon through electrodes are electrically connected to each other.

The semiconductor device 300 may have a filling rate of the cured resin 6 in the conductor 35 that satisfies the following condition. The filling rate can be calculated in the same manner as above.

(Conductor of Through-Silicon Electrode)
(a) In a region (see FIG. 9 ) extending from a point S22 at which a line L2 passing through a central portion E of the silicon through electrode (the center of the length L and the center of the hole diameter D there) and extending in the thickness direction of the substrate intersects with the surface of the conductor 35 to a depth of 10 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the internal space of the pores (vacant holes) of the metal body.
(b) In the region 10 to 20 μm deep from point S22, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(c) In the region from point S22 to a depth of 20 to 30 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.
(d) Within a range of ±5 μm from the center E of the silicon through electrode in the thickness direction of the substrate and within a range of ±5 μm in the direction perpendicular to the thickness direction of the substrate, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the metal body.

(Metal Paste)
A metal paste containing copper particles and solder particles, which is used in the method for manufacturing a base body having a through electrode according to the first and second embodiments, will be described.

The metal paste may contain, as copper particles, first copper particles having a particle size (maximum diameter) of 0.8 μm or more.

The particle size (maximum diameter) of the first copper particles may be 1.2 μm or more. The particle size (maximum diameter) of the first copper particles may be 10 μm or less, or 8.0 μm or less.

The average particle size (average maximum diameter) of the first copper particles contained in the metal paste may be 0.8 μm or more or 1.2 μm or more, and may be 10 μm or less or 8 μm or less, from the viewpoint of improving the sintering density in the through holes and suppressing the generation of voids in the through holes.

The particle size (maximum diameter) and average particle size (average maximum diameter) of the first copper particles can be determined, for example, from an SEM image of the particles. An example of a method for calculating the particle size (maximum diameter) of the first copper particles from an SEM image is shown below. A powder of the first copper particles is placed on a carbon tape for SEM with a spatula to prepare a sample for SEM. This sample for SEM is observed at 5000 times magnification with an SEM device. A rectangle circumscribing the first copper particle in the SEM image is drawn using image processing software, and the long side of the rectangle is taken as the particle size (maximum diameter) of the particle. This measurement is performed on 50 or more first copper particles using multiple SEM images, and the average particle size (average maximum diameter) is calculated.

The shape of the first copper particles may be, for example, spherical, clumpy, needle-like, flat (flake-like), approximately spherical, etc. The first copper particles may be an agglomerate of copper particles having these shapes.

The first copper particles are preferably flat (flake-shaped). In this case, the first copper particles are oriented approximately parallel to the application surface of the metal paste, which suppresses volumetric shrinkage when the copper particles in the metal paste are sintered, making it easier to suppress voids from occurring in the through holes. In addition, suppressing volumetric shrinkage when the copper particles in the metal paste are sintered can suppress cracks in the metal body formed on at least one of the main surfaces of the base (e.g., a silicon substrate).

The aspect ratio of the first copper particles may be 4 or more, or may be 6 or more. If the aspect ratio is within the above range, the first copper particles in the metal paste are more likely to be oriented parallel to the surface of the metal paste, and the volume shrinkage when the copper particles in the metal paste are sintered can be suppressed. This makes it possible to further suppress breakage of the wiring due to thermal stress when wiring is formed from a conductor provided on the main surface of a substrate (e.g., a silicon substrate). In addition, the adhesion between the metal body and the metal coating formed on the substrate (e.g., a silicon substrate) can be improved. The aspect ratio (major axis/thickness) of the copper particles in the metal paste can be determined, for example, by observing an SEM image of the particles and measuring the major axis and thickness.

The metal paste preferably contains first copper particles having a particle size (maximum diameter) of 0.8 μm or more and 10 μm or less and an aspect ratio of 4 or more. By containing such first copper particles in the metal paste, the volumetric shrinkage when the copper particles in the metal paste are sintered can be sufficiently reduced, and it becomes easy to form a metal body having a porous structure and a sufficiently formed conductive network in the through hole or non-through hole. As a result, it is possible to suppress the generation of voids in the through hole or non-through hole, and it is possible to form a metal body on the main surface of the base body (e.g., a silicon substrate) that is less likely to crack, and when wiring is formed from a conductor containing this metal body, it is possible to further suppress breakage of the wiring due to thermal stress.

The metal paste may contain copper particles having a particle size (maximum diameter) of 0.8 μm or more and 10 μm or less and an aspect ratio of less than 2, but the content of the copper particles having a particle size (maximum diameter) of 0.8 μm or more and 10 μm or less and an aspect ratio of less than 2 is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, per 100 parts by mass of the first copper particles having a particle size (maximum diameter) of 0.8 μm or more and 10 μm or less and an aspect ratio of 4 or more. By limiting the content of the copper particles having a particle size (maximum diameter) of 0.8 μm or more and 10 μm or less and an aspect ratio of less than 2, it is possible to form a metal body having a porous structure but a sufficiently formed conductive network in the through hole or non-through hole while suppressing the generation of voids in the through hole by the first copper particles in the metal paste. Furthermore, on the main surface of the base (e.g., a silicon substrate), the first copper particles tend to be oriented approximately parallel to the surface to which the metal paste is applied, and volumetric shrinkage is more effectively suppressed, forming a metal body that is less susceptible to cracking. When wiring is formed from a conductor that includes this metal body, breakage of the wiring due to thermal stress can be further suppressed.

In order to make such effects more easily obtainable, the content of the copper particles having a particle size (maximum diameter) of 0.8 μm or more and 10 μm or less and an aspect ratio of less than 2 may be 20 parts by mass or less, 10 parts by mass or less, or even 0 parts by mass, per 100 parts by mass of the first copper particles having a particle size (maximum diameter) of 0.8 μm or more and 10 μm or less and an aspect ratio of 4 or more.

The content of the first copper particles in the metal paste may be 15% by mass or more, 20% by mass or more, or 50% by mass or more, and may be 85% by mass or less, 70% by mass or less, or 50% by mass or less, based on the total mass of the metal particles contained in the metal paste. If the content of the first copper particles is within the above range, the above-mentioned effect is more easily obtained.

The first copper particles may be treated with a surface treatment agent from the viewpoint of dispersion stability and oxidation resistance. The surface treatment agent may be one that is removed during wiring formation (when the copper particles are sintered). Examples of such surface treatment agents include aliphatic carboxylic acids such as palmitic acid, stearic acid, arachidic acid, and oleic acid; aromatic carboxylic acids such as terephthalic acid, pyromellitic acid, and o-phenoxybenzoic acid; aliphatic alcohols such as cetyl alcohol, stearyl alcohol, isobornylcyclohexanol, and tetraethylene glycol; aromatic alcohols such as p-phenylphenol; alkylamines such as octylamine, dodecylamine, and stearylamine; aliphatic nitriles such as stearonitrile and decanenitrile; silane coupling agents such as alkylalkoxysilanes; and polymer treatment agents such as polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, and silicone oligomers. The surface treatment agents may be used alone or in combination of two or more.

The amount of the surface treatment agent may be an amount equal to or greater than one molecular layer on the particle surface. The amount of such a surface treatment agent varies depending on the specific surface area of the first copper particles, the molecular weight of the surface treatment agent, and the minimum coverage area of the surface treatment agent. The amount of the surface treatment agent is usually 0.001% by mass or more.

The amount of the surface treatment agent can be calculated from the number of molecular layers (n) attached to the surface of the first copper particle, the specific surface area (A _p ) (unit: m ² /g) of the first copper particle, the molecular weight (M _s ) (unit: g/mol) of the surface treatment agent, the minimum coverage area (S _S ) (unit: m ² /piece) of the surface treatment agent, and the Avogadro's number (N _A ) (6.02 × 10 ²³ pieces). Specifically, the amount of the surface treatment agent is calculated according to the formula: amount of surface treatment agent (mass%) = {(n·A _p ·M _s ) / (S _S ·N _A + n·A _p ·M _s )} × 100%.

The specific surface area of the first copper particles can be calculated by measuring the dried copper particles by the BET specific surface area measurement method. The minimum coverage area of the surface treatment agent is 2.05×10 ⁻¹⁹ m ² /1 molecule when the surface treatment agent is a linear saturated fatty acid. In the case of other surface treatment agents, the surface treatment agent can be measured, for example, by calculation from a molecular model or by the method described in "Chemistry and Education" (Katsuhiro Ueda, Sumio Inafuku, Iwao Mori, 40 (2), 1992, pp. 114-117). An example of a method for quantifying the surface treatment agent is shown below. The surface treatment agent can be identified by a thermal desorption gas/gas chromatograph mass spectrometer of the dried powder obtained by removing the dispersion medium from the metal paste, and the carbon number and molecular weight of the surface treatment agent can be determined. The carbon content of the surface treatment agent can be analyzed by carbon content analysis. Examples of carbon content analysis methods include high-frequency induction heating furnace combustion/infrared absorption method. The amount of the surface treatment agent can be calculated from the carbon number, molecular weight and carbon content of the identified surface treatment agent according to the above formula.

Commercially available first copper particles can be used. Examples of commercially available first copper particles include MA-C025 (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size 4.1 μm), 3L3 (manufactured by Fukuda Metal Foil & Powder Co., Ltd., average particle size 7.3 μm), 1110F (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size 5.8 μm), and 2L3 (manufactured by Fukuda Metal Foil & Powder Co., Ltd., average particle size 9 μm).

When manufacturing the metal paste, copper particles can be used that contain first copper particles having a particle size (maximum diameter) of 0.8 μm or more and 10 μm or less and an aspect ratio of 4 or more, and the content of copper particles having a particle size (maximum diameter) of 0.8 μm or more and 10 μm or less and an aspect ratio of less than 2 is 50 parts by mass or less, preferably 30 parts by mass or less, per 100 parts by mass of the first copper particles having a particle size (maximum diameter) of 0.8 μm or more and 10 μm or less and an aspect ratio of 4 or more. A commercially available product made of such copper particles can be selected and used.

The ratio (maximum diameter) of the pore size of the through hole to the particle size (maximum diameter) of the first copper particle (pore size (μm)/particle size (μm)) may be 4 or more, 8 or more, or 10 or more, and may be 150 or less, 100 or less, or 50 or less, from the viewpoint of suppressing volumetric shrinkage and forming a metal body that is less susceptible to cracking. For non-through holes, the ratio (maximum diameter) of the pore size of the non-through hole to the particle size (maximum diameter) of the first copper particle (pore size (μm)/particle size (μm)) can be set so that the ratio (maximum diameter) of the pore size of the silicon through electrode to be formed to the particle size (maximum diameter) of the first copper particle (pore size (μm)/particle size (μm) is within the above range.

In one embodiment, the metal paste may include the first copper particles described above and second copper particles having a particle size (maximum diameter) of 0.5 μm or less. In this case, when the copper particles are sintered, the second copper particles are present between the first copper particles, which tends to improve the conductivity of the resulting wiring. That is, it is preferable to use the first copper particles and the second copper particles in combination. When preparing a metal paste containing only the second copper particles as copper particles, the volume shrinkage and sintering shrinkage associated with drying of the dispersion medium are large, so that when the copper particles are sintered, the sintered body is easily peeled off from the metal coating provided on the insulating base (e.g., silicon wafer), making it difficult to obtain sufficient airtightness and connection reliability. However, by using the first copper particles and the second copper particles in combination, the volume shrinkage when the metal paste is sintered is suppressed, and the adhesion between the metal body formed in the through hole and the metal coating formed on the wall surface of the through hole or non-through hole can be improved. This makes it less likely that the copper sintered body in the through hole will break due to thermal stress, further improving airtightness and connection reliability against thermal stress.

The second copper particles can act as copper particles that suitably bond the first copper particles together. In addition, the second copper particles have better sinterability than the first copper particles and can have the function of promoting the sintering of the copper particles. For example, compared to the case where the first copper particles are used alone as the copper particles, it is possible to sinter the copper particles at a lower temperature. In addition, when preparing a metal paste containing only the second copper particles as the copper particles, the volume shrinkage and sintering shrinkage caused by drying of the dispersion medium are large, so that the metal body formed inside the through hole or non-through hole is likely to shrink in volume, thereby causing voids inside the through hole or non-through hole. In particular, by using the flat first copper particles and the second copper particles in combination, the flat first copper particles act as copper particles that are suitably bonded by the second copper particles, and it becomes easy to form a metal body having voids (porous structure) while suppressing the generation of voids inside the through hole.

The average particle size (average maximum diameter) of the second copper particles contained in the metal paste may be 0.01 μm or more, 0.03 μm or more, 0.05 μm or more, or 0.08 μm or more, and may be 0.5 μm or less, 0.4 μm or less, 0.3 μm or less, or 0.2 μm or less.

If the average particle size (average maximum diameter) of the second copper particles is 0.01 μm or more, it is easy to obtain effects such as reducing the synthesis cost of the second copper particles, good dispersibility, and reducing the amount of surface treatment agent used. If the average particle size (average maximum diameter) of the second copper particles is 0.5 μm or less, it is easy to obtain the effect of excellent sintering properties of the second copper particles. From the viewpoint of further achieving the above effects, the average particle size (average maximum diameter) of the second copper particles may be 0.05 μm or more, 0.1 μm or more, or 0.2 μm or more, and may be 0.5 μm or less, 0.4 μm or less, or 0.3 μm or less.

The second copper particles may contain 20% by mass or more of copper particles having a particle size (maximum diameter) of 0.01 μm or more and 0.5 μm or less. From the viewpoint of the sinterability of the metal paste, the second copper particles may contain 30% by mass or more, 50% by mass or more, or 85% by mass or less of copper particles having a particle size (maximum diameter) of 0.01 μm or more and 0.5 μm or less. When the content ratio of copper particles having a particle size (maximum diameter) of 0.01 μm or more and 0.5 μm or less in the second copper particles is 20% by mass or more, the dispersibility of the copper particles is further improved, and the increase in viscosity and the decrease in paste concentration can be further suppressed.

The content of the second copper particles in the metal paste may be 20% by mass or more, 30% by mass or more, 35% by mass or more, or 40% by mass or more, and 85% by mass or less, 80% by mass or less, or 75% by mass or less, based on the total mass of the metal particles contained in the metal paste. If the content of the second copper particles is within the above range, it is easy to form a metal body that has excellent adhesion to the metal coating provided on the base (e.g., silicon substrate) while suppressing the generation of voids in the through holes or non-through holes, and a copper sintered body that is less likely to crack on the main surface of the base (e.g., silicon substrate) can be formed, and when wiring is formed from a conductor containing this copper sintered body, breakage of the wiring due to thermal stress can be further suppressed.

The content of the second copper particles in the metal paste may be 20% by mass or more and 85% by mass or less, based on the sum of the mass of the first copper particles and the mass of the second copper particles. If the content of the second copper particles is 20% by mass or more, the spaces between the first copper particles can be sufficiently filled, a metal body that is less likely to crack can be formed, and wiring formed from a conductor containing this metal body is less likely to break due to thermal stress. If the content of the second copper particles is 85% by mass or less, volumetric shrinkage when the copper particles are sintered can be sufficiently suppressed, so that voids can be suppressed from occurring in the through holes or non-through holes, and a metal body that is less likely to crack can be formed, and wiring formed from a conductor containing this metal body is less likely to break due to thermal stress.

In order to make the above-mentioned effect more easily obtainable, the content of the second copper particles may be 30% by mass or more, 35% by mass or more, or 40% by mass or more, and may be 85% by mass or less, or 80% by mass or less, based on the sum of the mass of the first copper particles and the mass of the second copper particles.

The shape of the second copper particles may be, for example, spherical, clumpy, needle-like, flat (flake-like), approximately spherical, etc. The second copper particles may be an aggregate of copper particles having these shapes. From the viewpoint of dispersibility and packing ability, the shape of the second copper particles may be spherical, approximately spherical, or flat (flake-like), and from the viewpoint of combustibility and mixability with the first copper particles, etc., the shape of the second copper particles may be spherical or approximately spherical.

The aspect ratio of the second copper particles may be 5 or less, or may be 3 or less, from the viewpoints of dispersibility, packing ability, and mixability with the first copper particles.

The second copper particles may be treated with a specific surface treatment agent. Examples of specific surface treatment agents include organic acids having 8 to 16 carbon atoms. Examples of organic acids having 8 to 16 carbon atoms include caprylic acid, methylheptanoic acid, ethylhexanoic acid, propylpentanoic acid, pelargonic acid, methyloctanoic acid, ethylheptanoic acid, propylhexanoic acid, capric acid, methylnonanoic acid, ethyloctanoic acid, propylheptanoic acid, butylhexanoic acid, undecanoic acid, methyldecanoic acid, ethylnonanoic acid, propyloctanoic acid, butylheptanoic acid, lauric acid, methylundecanoic acid, ethyldecanoic acid, propylnonanoic acid, butyloctanoic acid, Saturated fatty acids such as pentylheptanoic acid, tridecanoic acid, methyldodecanoic acid, ethylundecanoic acid, propyldecanoic acid, butylnonanoic acid, pentyloctanoic acid, myristic acid, methyltridecanoic acid, ethyldodecanoic acid, propylundecanoic acid, butyldecanoic acid, pentylnonanoic acid, hexyloctanoic acid, pentadecanoic acid, methyltetradecanoic acid, ethyltridecanoic acid, propyldodecanoic acid, butylundecanoic acid, pentyldecanoic acid, hexylnonanoic acid, palmitic acid, methylpentadecanoic acid, ethyltetradecanoic acid, propyltridecanoic acid, butyldodecanoic acid, pentylundecanoic acid, hexyldecanoic acid, heptylnonanoic acid, methylcyclohexanecarboxylic acid, ethylcyclohexanecarboxylic acid, propylcyclohexanecarboxylic acid, butylcyclohexanecarboxylic acid, pentylcyclohexanecarboxylic acid, hexylcyclohexanecarboxylic acid, heptylcyclohexanecarboxylic acid, octylcyclohexanecarboxylic acid, and nonylcyclohexanecarboxylic acid; octene Examples of the organic acid include unsaturated fatty acids such as benzoic acid, nonenoic acid, methylnonenoic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, myristoleic acid, pentadecenoic acid, hexadecenoic acid, palmitoleic acid, and sabienoic acid; and aromatic carboxylic acids such as terephthalic acid, pyromellitic acid, o-phenoxybenzoic acid, methylbenzoic acid, ethylbenzoic acid, propylbenzoic acid, butylbenzoic acid, pentylbenzoic acid, hexylbenzoic acid, heptylbenzoic acid, octylbenzoic acid, and nonylbenzoic acid. The organic acid may be used alone or in combination of two or more. By combining such an organic acid with the second copper particles, it is possible to achieve both the dispersibility of the second copper particles and the detachment of the organic acid during sintering.

The amount of the surface treatment agent may be an amount that adheres to the surface of the second copper particles in a monolayer to trilayer form. The amount of the surface treatment agent may be 0.07% by mass or more, 0.10% by mass or more, or 0.2% by mass or more, and may be 2.1% by mass or less, 1.6% by mass or less, or 1.1% by mass or less. The amount of the surface treatment agent of the second copper particles can be calculated by the method described above for the first copper particles. The same applies to the specific surface area, the molecular weight of the surface treatment agent, and the minimum coverage area of the surface treatment agent.

The second copper particles can be synthetic or commercially available.

The sum of the content of the first copper particles and the content of the second copper particles in the metal paste may be 70% by mass or more, 80% by mass or more, 90% by mass or more, or 93% by mass or more based on the total mass of the metal particles contained in the metal paste. If the sum of the content of the first copper particles and the content of the second copper particles is within the above range, it is easy to suppress the generation of voids in the through holes or non-through holes. From the viewpoint of making such an effect even easier to obtain, the sum of the content of the first copper particles and the content of the second copper particles may be 80% by mass or more, 90% by mass or more, or 95% by mass or more based on the total mass of the metal particles.

The solder particles may contain tin or a tin alloy, such as In-Sn, In-Sn-Ag, Sn-Bi, Sn-Bi-Ag, Sn-Ag-Cu, or Sn-Cu alloys, including the following examples:
In-Sn (In 52% by mass, Bi 48% by mass, melting point: 118°C)
In-Sn-Ag (In 20 mass%, Sn 77.2 mass%, Ag 2.8 mass%, melting point: 175°C)
・ Sn-Bi (Sn 43% by mass, Bi 57% by mass, melting point: 138°C)
Sn-Bi-Ag (Sn 42% by mass, Bi 57% by mass, Ag 1% by mass, melting point: 139°C)
・Sn-Ag-Cu (Sn 96.5% by mass, Ag 3% by mass, Cu 0.5% by mass, melting point: 217°C)
・ Sn-Cu (Sn 99.3 mass%, Cu 0.7 mass%, melting point: 227 ° C.)

The metal paste may contain solder particles having a particle size (maximum diameter) of 1.0 μm or more.

The particle size (maximum diameter) of the solder particles may be 2 μm or more, 15 μm or less, or 8.0 μm or less.

The average particle size (average maximum diameter) of the solder particles contained in the metal paste may be 1.0 μm or more, 2.0 μm or more, 15 μm or less, or 8 μm or less, from the viewpoint of suppressing the volumetric shrinkage caused by sintering in the through holes and suppressing the generation of voids in the through holes. By using solder particles with such a particle size, the volumetric shrinkage when the copper particles in the metal paste are sintered can be sufficiently reduced, and it becomes easy to form a metal body having a porous structure and a sufficiently formed conductive network in the through holes or non-through holes. As a result, it is possible to suppress the generation of voids in the through holes or non-through holes, and it is possible to form a metal body that is less likely to crack on the main surface of the base (e.g., a silicon substrate), and when wiring is formed from a conductor containing this metal body, it is possible to further suppress breakage of the wiring due to thermal stress.

It is preferable that the particle size of the solder particles is uniform. In this case, the solder particles are easily dispersed inside the metal body, and voids are generated inside the scattered solder or on the outer periphery of the solder (between the solder and the copper sintered body), which suppresses the generation of continuous voids and cracks longer than 5 μm, and suppresses breaks inside the vias and breaks in the wiring formed on the main surface of the base (e.g., silicon substrate).

The particle size (maximum diameter) and average particle size (average maximum diameter) of solder particles can be calculated from SEM images, for example, by the following procedure. A powder of solder particles is placed on carbon tape for SEM with a spatula to prepare an SEM sample. This SEM sample is observed at 5000x magnification with an SEM device. A rectangle circumscribing the solder particle in the SEM image is drawn using image processing software, and the long side of the rectangle is taken as the particle size (maximum diameter) of that particle. This measurement is performed on 50 or more solder particles using multiple SEM images, and the average particle size (average maximum diameter) is calculated.

The shape of the solder particles may be, for example, spherical, clumpy, needle-like, flat (flake-like), approximately spherical, etc. The solder particles may also be an agglomerate of solder particles having these shapes.

The solder particles are preferably spherical. In this case, the solder particles are uniformly dispersed inside the metal body, and voids are generated inside the uniformly dispersed solder or on the periphery of the solder (between the solder and the copper sintered body), which suppresses volumetric shrinkage when the copper particles in the metal paste are sintered, making it easier to suppress breaks in the through holes. In addition, suppressing volumetric shrinkage when the copper particles in the metal paste are sintered can suppress cracks in the metal body formed on at least one of the main surfaces of the base (e.g., a silicon substrate).

The content of the solder particles in the metal paste may be 1 part by mass or more, 2 parts by mass or more, or 3 parts by mass or more, and 25 parts by mass or less, 20 parts by mass or less, or 15 parts by mass or less, per 100 parts by mass of the copper particles contained in the metal paste. If the content of the solder particles is within the above range, the above-mentioned effect is more easily obtained. That is, it is easy to form a metal body in which a conductive network is sufficiently formed while having a porous structure, in a through hole or a non-through hole, while suppressing the generation of voids in the through hole. In addition, when the metal paste contains the above-mentioned first copper particles, the first copper particles are likely to be oriented approximately parallel to the coating surface of the metal paste on the main surface of the base (e.g., a silicon substrate), and volume shrinkage is more effectively suppressed to form a metal body that is less likely to crack, and when wiring is formed from a conductor containing this metal body, breakage due to thermal stress of the wiring can be further suppressed. If the content of the solder particles is 1 part by mass or more per 100 parts by mass of the copper particles, it becomes easier to suppress the generation of voids inside the metal body, and it becomes easier to prevent, for example, the generation of cracks longer than 5 μm and the occurrence of breaks inside the via. On the other hand, if the content of the solder particles is 25 parts by mass or less per 100 parts by mass of the copper particles, the resistivity of the wiring is less likely to increase.

The total content of the copper particles (preferably the content of the first copper particles and the content of the second copper particles) and the content of the solder particles in the metal paste may be 90% by mass or more based on the total mass of the metal particles contained in the metal paste. In this case, it is easier to suppress the occurrence of voids in the through holes or non-through holes. From the viewpoint of making such an effect even easier to obtain, the total content of the copper particles (preferably the content of the first copper particles and the content of the second copper particles) and the content of the solder particles may be 95% by mass or more, or may be 100% by mass, based on the total mass of the metal particles.

The metal paste may further contain other metal particles other than copper particles and solder particles. Examples of other metal particles include nickel, silver, gold, palladium, platinum, and the like. The average particle size (maximum diameter) of the other metal particles may be 0.01 μm or more or 0.05 μm or more, and may be 5 μm or less, 3.0 μm or less, or 2.0 μm or less. When other metal particles are contained, the content thereof may be less than 20 mass% and may be 10 mass% or less based on the total mass of the metal particles contained in the metal paste from the viewpoint of obtaining sufficient bonding properties. Other metal particles may not be contained. The shape of the other metal particles is not particularly limited.

The metal paste may contain a dispersion medium. The dispersion medium is not particularly limited and may be, for example, a volatile one. Examples of volatile dispersion media include monohydric and polyhydric alcohols such as pentanol, hexanol, heptanol, octanol, decanol, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, α-terpineol, and isobornylcyclohexanol (MTPH); ethylene glycol butyl ether, ethylene glycol phenyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, diethylene glycol isobutyl ether, diethylene glycol hexyl ether, triethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol butyl ether, diethylene glycol isopropyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl ether, propylene glycol propyl ether, and dipropylene glycol. Examples of the esters include methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, dipropylene glycol dimethyl ether, tripropylene glycol methyl ether, and tripropylene glycol dimethyl ether; esters such as ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, dipropylene glycol methyl ether acetate (DPMA), ethyl lactate, butyl lactate, γ-butyrolactone, and propylene carbonate; acid amides such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide; aliphatic hydrocarbons such as cyclohexane, octane, nonane, decane, and undecane; aromatic hydrocarbons such as benzene, toluene, and xylene; mercaptans having an alkyl group having 1 to 18 carbon atoms; and mercaptans having a cycloalkyl group having 5 to 7 carbon atoms. Examples of mercaptans having an alkyl group with 1 to 18 carbon atoms include ethyl mercaptan, n-propyl mercaptan, i-propyl mercaptan, n-butyl mercaptan, i-butyl mercaptan, t-butyl mercaptan, pentyl mercaptan, hexyl mercaptan, and dodecyl mercaptan. Examples of mercaptans having a cycloalkyl group with 5 to 7 carbon atoms include cyclopentyl mercaptan, cyclohexyl mercaptan, and cycloheptyl mercaptan.

The content of the dispersion medium may be 3 parts by mass or more, 5 parts by mass or more, 20 parts by mass or less, or 12 parts by mass or less, assuming that the total mass of the metal particles contained in the metal paste is 100 parts by mass. If the content of the dispersion medium is within these ranges, the viscosity of the metal paste can be adjusted to a more appropriate value, making it easier to prevent voids from occurring in the through holes.

If necessary, the metal paste may contain appropriate additives such as wetting improvers, such as nonionic surfactants and fluorosurfactants; antifoaming agents, such as silicone oil; and ion trapping agents, such as inorganic ion exchangers.

The above-mentioned metal paste can be prepared by mixing copper particles, solder particles, and optional components (additives, other metal particles, etc.) in a dispersion medium. After mixing the components, a stirring process may be performed. The maximum diameter of the dispersion may be adjusted by a classification operation.

When the metal paste contains the above-mentioned first copper particles and second particles, the second copper particles, the surface treatment agent, and the dispersion medium may be mixed in advance, and a dispersion treatment may be performed to prepare a dispersion of the second copper particles, and the first copper particles, solder particles, and other metal particles and optional additives may be further mixed to prepare the dispersion. By using such a procedure, the dispersibility of the second copper particles is improved, improving the mixability with the first copper particles, and the performance of the metal paste is further improved. The dispersion of the second copper particles may be subjected to a classification operation to remove aggregates.

The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

(Synthesis of second copper particles)
[Synthesis of copper nonanoate]
150 mL of 1-propanol (Kanto Chemical Co., Ltd., special grade) was added to 91.5 g (0.94 mol) of copper hydroxide (Kanto Chemical Co., Ltd., special grade) and stirred, and 370.9 g (2.34 mol) of nonanoic acid (Kanto Chemical Co., Ltd., 90% or more) was added to the mixture. The resulting mixture was heated and stirred at 90°C for 30 minutes in a separable flask. The resulting solution was filtered while still heated to remove undissolved matter. It was then allowed to cool, and the resulting copper nonanoate was suction filtered and washed with hexane until the washing liquid became transparent. The resulting powder was dried in an explosion-proof oven at 50°C for 3 hours to obtain copper nonanoate (II). The yield was 340 g (yield 96% by mass).

[Synthesis of second copper particles]
15.01 g (0.040 mol) of copper (II) nonanoate obtained above and 7.21 g (0.040 mol) of copper (II) acetate anhydride (Kanto Chemical Co., Ltd., special grade) were placed in a separable flask, 22 mL of 1-propanol and 32.1 g (0.32 mol) of hexylamine (Tokyo Chemical Industry Co., Ltd., purity 99%) were added, and the mixture was heated and stirred at 80 ° C. in an oil bath to dissolve. The mixture was transferred to an ice bath and cooled to an internal temperature of 5 ° C., and then 7.72 mL (0.16 mol) of hydrazine monohydrate (Kanto Chemical Co., Ltd., special grade) was stirred in the ice bath. The molar ratio of copper:hexylamine was 1:4. The mixture was then heated and stirred at 90 ° C. in an oil bath. At that time, a reduction reaction accompanied by foaming proceeded, and the reaction was completed within 30 minutes. The inner wall of the separable flask exhibited a copper luster, and the solution turned dark red. Centrifugation was carried out at 9000 rpm (revolutions per minute) for 1 minute to obtain a solid matter. The process of washing the solid matter with 15 mL of hexane was repeated three times to remove acid residues, and a powder of copper particles having a copper luster (second copper particles) was obtained.

The copper particles synthesized above were observed with a transmission electron microscope (manufactured by JEOL Ltd., product name: JEM-2100F). The average major axis length of 200 randomly selected copper particles was 104 nm. The shape of the second particles was spherical.

(Preparation of Metal Paste)
<Examples 1 to 55>
The raw materials shown below were mixed in the ratios shown in Tables 1 to 6 to prepare metal pastes.

[First copper particles]
Flat 1.4 μm: 1100YP (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size 1.4 μm (D50), product name)

[Second copper particles]
Spherical 100 nm: Copper particles synthesized above

[Solder particles]
SnBi58: SnBi58 solder STC-3 (manufactured by Mitsui Mining & Smelting Co., Ltd., product name, average particle size 4.1 μm (D50), spherical)
SnAgCu: Sn96.5Ag3Cu0.5 solder STC-3 (manufactured by Mitsui Mining & Smelting Co., Ltd., product name, average particle size 4.1 μm (D50), spherical)

[others]
Diethylene glycol: Fujifilm Wako Pure Chemical Industries, Ltd.

<Comparative Example 1>
A metal paste was prepared by mixing 70 parts by mass of 1100YP (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size 1.4 μm (D50), trade name) as the first copper particles, 30 parts by mass of the copper particles synthesized above as the second copper particles, 5 parts by mass of diethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 5 parts by mass of a resin component. As the resin component, a mixture of an acrylic resin as an organic binder and a mixture of carbitol and terpineol as organic solvents (the mass ratio of carbitol and terpineol in the mixture is carbitol:terpineol = 1:1) in a mass ratio of 1:2 was used.

(Silicon substrate preparation process)
<Examples 1 to 55 and Comparative Example 1>
A silicon substrate was prepared with a through hole, and a titanium layer, a nickel layer, and a copper layer formed in this order on both main surfaces and the wall surface of the through hole. The silicon substrate had a diameter of 6 inches and a thickness of 500 μm. The diameters of the through holes in the silicon substrate are shown in Tables 1 to 6. The titanium layer, nickel layer, and copper layer were formed in this order by sputtering.

(Metal body forming process)
<Examples 1 to 40, 46 to 55>
The prepared metal paste was applied to both main surfaces of the silicon substrate with a metal spatula, and the through holes were filled with the metal paste. After application, the metal paste was dried in the air at 90° C. for 10 minutes. After drying, a metal paste layer having a thickness of 30 μm was formed on the silicon substrate.

The silicon substrate with the metal paste layer formed was placed in a tube furnace (manufactured by AVC Corporation), and argon gas was flowed at 1 L/min to replace the air in the tube furnace with argon gas. The metal paste was then sintered by a sintering process under conditions of heating for 10 minutes and 250°C for 60 minutes while flowing hydrogen gas at 300 mL/min. The argon gas was then changed to 0.3 L/min, the substrate was cooled, and the substrate was taken out into air at 50°C or less to obtain a silicon substrate filled with metal bodies. The thickness of the metal bodies formed on both main surfaces of the sintered silicon substrate was 25 μm.

<Examples 41 to 45>
A metal body-filled silicon substrate was obtained in the same manner as in Example 1, except that the silicon substrate was pressed by the following pressing method. The thickness of the metal body formed on both main surfaces of the sintered silicon substrate was 30 μm.
[Pressure Method]
The silicon substrate on which the metal paste layer was formed was pressed from both sides using a pressing tool. The pressure applied to the silicon substrate was set to the pressures shown in Tables 1 to 6. The pressing tool was equipped with a flat aluminum plate and a spring, and the pressure during pressing could be adjusted. The silicon substrate pressed by the pressing tool was placed in a tube furnace (manufactured by AVC Corporation), and argon gas was flowed at 1 L/min to replace the air in the tube furnace with argon gas.

<Examples 26 to 30, 51 to 55>
A metal body-filled silicon substrate was obtained in the same manner as in Example 1, except that the temperature rise time was 10 minutes and the sintering treatment was performed for 60 minutes at 225° C. The thickness of the metal body formed on both main surfaces of the sintered silicon substrate was 30 μm.

<Comparative Example 1>
A metal body-filled silicon substrate was obtained in the same manner as in Example 1, except that the temperature rise time was 10 minutes and the sintering treatment was performed for 60 minutes at 300° C. The thickness of the metal body formed on both main surfaces of the sintered silicon substrate was 30 μm.

(Measurement of porosity of metal body)
<Examples 1 to 73 and Comparative Example 1>
Using a focused ion beam processing observation device (manufactured by Hitachi High-Technologies Corporation, product name: MI4050), the cross section of the center of the through hole of the silicon substrate and the cross section of the metal body provided on the main surface of the silicon substrate were exposed by a focused ion beam, and the cross sections were observed. When observing the cross section of the center of the through hole, a range of ±5 μm in the thickness direction of the silicon substrate and ±5 μm in the direction perpendicular to the thickness direction of the silicon substrate from the center of the metal body filled in the through hole was observed. When observing the cross section of the metal body provided on the main surface of the silicon substrate, a range of 10 μm in the thickness direction of the silicon substrate and 10 μm in the direction perpendicular to the thickness direction of the silicon substrate was observed in a region up to 5 μm from the surface of the metal body formed on the main surface of the silicon substrate.
For the observation, a scanning electron microscope (Hitachi High-Technologies Corporation, product name: S-3700N) was used at a magnification of 10,000 times, and a cross-sectional image (approximately 10 μm square) of the metal body was taken. Five observation points were made. The obtained cross-sectional image was binarized using image analysis software (Adobe Photoshop (registered trademark) Elements) so that the metal part and the porous part were separated. For each of the five observation points, the ratio of the area of the porous part to the total area of the cross section of the metal body was taken as the porosity. The average value of the porosity of the five observation points was taken as the porosity of the metal body. The results are shown in Tables 1 to 6.

(Resin impregnation process)
<Examples 1 to 55>
The curable resin composition shown below was applied to one side of the metal body-filled silicon substrate by a roll coater. Next, the metal body-filled silicon substrate was placed in a container, and the container was suctioned so that the gauge pressure was 100 KPa to create a vacuum state. The metal body-filled silicon substrate was held in a vacuum state for 10 minutes, and then the metal body-filled silicon substrate was removed from the container. It was confirmed that the metal body in the through hole was impregnated with the curable resin composition, and the curable resin composition reached the opposite side of the metal body in the through hole to the side to which the curable resin composition was applied. The curable resin composition remaining on the application surface of the curable resin composition of the metal body-filled silicon substrate was removed with a rubber spatula. Next, the curable resin composition was applied to the opposite side to the side to which the curable resin composition was applied by a roll coater, and the curable resin composition remaining on the surface of the metal body-filled silicon substrate was removed as much as possible with a rubber spatula.

[Curable resin composition]
YDF-170 (trade name of bisphenol F type epoxy resin, manufactured by Tohto Kasei Co., Ltd., epoxy equivalent = 170): 95 parts by mass 2PZ-CN (trade name of imidazole compound, manufactured by Shikoku Kasei Co., Ltd.): 5 parts by mass

<Comparative Example 1>
No resin impregnation step was performed.

(Resin curing process)
<Examples 1 to 55>
The silicon substrate with the metal body impregnated with the curable resin composition was held in a nitrogen atmosphere at 180° C. for 1 hour to obtain a silicon substrate having a silicon through electrode.

<Comparative Example 1>
No resin curing step was performed.

(Conductor Removal Process)
<Examples 1 to 55 and Comparative Example 1>
Both sides of the substrate having the silicon through-hole electrode were mechanically polished until the thickness of the metal body on both sides of the substrate having the silicon through-hole electrode reached 20 μm. A ceramic jig (manufactured by Kemet Japan Co., Ltd.) was used as the sample stage to which the substrate having the silicon through-hole electrode was attached, and Alcowax (manufactured by Nikka Seiko Co., Ltd.) was used as the material for attaching the substrate having the silicon through-hole electrode to the sample stage. In addition, DP-Suspension P-3 μm, 1 μm, and 1/4 μm (manufactured by Struers) were used in this order as the abrasive.

[Filling rate of cured resin in conductor]
<Examples 1 to 55 and Comparative Example 1>
A substrate having a silicon through-hole electrode that had been mechanically polished was cut in the thickness direction, and the cross section of the center of the through-hole of the silicon substrate and the cross section of the conductor provided on the main surface of the silicon substrate were exposed by a focused ion beam, and these cross sections were observed. When observing the cross section of the center of the through-hole of the silicon substrate, a range of ±5 μm from the center of the through-hole in the thickness direction of the silicon substrate and ±5 μm in the direction perpendicular to the thickness direction of the silicon substrate was observed. When observing the cross section of the conductor provided on the main surface of the silicon substrate, a range of 10 μm in the thickness direction of the silicon substrate and 10 μm in the direction perpendicular to the thickness direction of the silicon substrate was observed in a region from the surface of the conductor provided on the main surface of the silicon substrate to 5 μm. A focused ion beam processing observation device (manufactured by Hitachi High-Technologies Corporation, product name: MI4050) was used. For the observation, a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, product name: S-3700N) was used at a magnification of 10,000 times, and a cross-sectional image of the conductor (about 10 μm square) was taken. Five observation points were observed. The obtained cross-sectional image was binarized using image analysis software (Adobe Photoshop (registered trademark) Elements) so that the metal part and the cured resin part were separated from the space in the porous part that was not filled with the cured resin. For each of the five observation points, the ratio of the area of the space in the porous part that was not filled with the cured resin to the total area of the cross section of the conductor was obtained, and this was taken as the porosity. The average value of the porosity of the five observation points was taken as the porosity of the conductor. The porosity of the metal body and the porosity of the conductor were substituted into the following formula (1) to calculate the filling rate of the cured resin in the conductor.
Filling rate (%) of cured resin in conductor=[(B−A)/B]×100 Equation (1)
[In formula (1), A represents the porosity (%) of the conductor, and B represents the porosity (%) of the copper sintered body.]

(Wiring formation process (resist formation, etching, and resist removal))
<Examples 1 to 55 and Comparative Example 1>
A dry film for ultraviolet-curable etching resist H-W425 (trade name, manufactured by Hitachi Chemical Co., Ltd.) was pressure-bonded by a laminator to the surfaces of the metal bodies on both sides of the substrate having a silicon through electrode that had been subjected to mechanical polishing treatment. A photomask was then aligned to expose a wiring pattern, and wiring was formed through resist development, etching of the copper sintered body, and removal of the resist, to obtain a substrate having a silicon through electrode (test piece 55) as shown in FIG. 10. In the obtained substrate having a silicon through electrode (test piece 55), the conductors filled in the through holes are electrically connected by the conductors (wiring) provided on the substrate surface.

(Initial resistance value)
<Examples 1 to 55 and Comparative Example 1>
The interconnection resistance value was measured as the initial resistance value of the substrate (test piece 55) having the silicon through-hole electrode. When the through-hole diameter of the silicon substrate was 20 μm, the resistance value of 20 through-holes interconnected was measured; when the through-hole diameter of the silicon substrate was 30 μm, the resistance value of 30 through-holes interconnected was measured; when the through-hole diameter of the silicon substrate was 50 μm, the resistance value of 30 through-holes interconnected was measured; when the through-hole diameter of the silicon substrate was 100 μm, the resistance value of 100 through-holes interconnected was measured; and when the through-hole diameter of the silicon substrate was 200 μm, the resistance value of 200 through-holes interconnected was measured. The measured interconnection resistance value was evaluated according to the following criteria. Evaluations of B or higher were judged to be good. The results are shown in Tables 1 to 6.
A: Resistance value is less than 10 mΩ B: Resistance value is 10 mΩ or more but less than 30 mΩ C: Resistance value is 30 mΩ or more but less than 100 mΩ D: Resistance value is 100 mΩ or more but less than 500 mΩ E: Resistance value is 500 mΩ or more

(Temperature cycle connectivity test)
<Examples 1 to 55 and Comparative Example 1>
A substrate (test piece 55) having a silicon through electrode was set in a temperature cycle tester (TSA-72SE-W, manufactured by Espec Corporation), and a temperature cycle connection reliability test was carried out under the following conditions: low temperature side: -40 ° C., 15 minutes, room temperature: 2 minutes, high temperature side: 125 ° C., 15 minutes, defrost cycle: automatic, number of cycles: 50, 100, 300, 500 cycles. When the through hole diameter of the silicon substrate was 20 μm, the resistance value of 20 through holes connected together was measured; when the through hole diameter of the silicon substrate was 30 μm, the resistance value of 30 through holes connected together was measured; when the through hole diameter of the silicon substrate was 50 μm, the resistance value of 30 through holes connected together was measured; when the through hole diameter of the silicon substrate was 100 μm, the resistance value of 100 through holes connected together was measured; and when the through hole diameter of the silicon substrate was 200 μm, the resistance value of 200 through holes connected together was measured. The measured connection resistance was evaluated according to the following criteria. A rating of B or higher after 500 temperature cycle tests was judged to be good. The results are shown in Tables 1 to 6.
A: The rate of resistance change is less than 1% of the initial resistance value. B: The rate of resistance change is 1% or more and less than 3% of the initial resistance value. C: The rate of resistance change is 3% or more and less than 5% of the initial resistance value. D: The rate of resistance change is 5% or more and less than 10% of the initial resistance value. E: The rate of resistance change is 10% or more and less than 20% of the initial resistance value. F: The rate of resistance change is 20% or more of the initial resistance value.

(Cracks in the board)
<Examples 1 to 55 and Comparative Example 1>
The substrate (test piece 55) having the silicon through electrode was visually inspected to confirm the presence or absence of cracks in the silicon substrate. The absence of cracks was evaluated as ◯, and the presence of even partial cracks was evaluated as ×. The results are shown in Tables 1 to 6.

(airtightness)
<Examples 1 to 55 and Comparative Example 1>
The airtightness of the substrate (test piece 55) having a silicon through electrode was evaluated. The evaluation was performed using a helium leak detector (UL200 manufactured by LEYBOLD). Specifically, the substrate having the silicon through electrode was set on a jig, and evacuation was performed until the inlet pressure of the measuring device reached 5 Pa. When the inlet pressure reached 5 Pa, He pressure (0.1 MPa) was applied for 30 seconds, and the amount of leakage was measured and evaluated according to the following criteria. The results are shown in Tables 1 to 6.
A: Leakage amount is less than 1x10 ^-11 Pa.m ³ /sec B: Leakage amount is 1x10 ^-11 or more and less than 1x10 ^-10 Pa.m ³ /sec C: Leakage amount is 1x10 ^-10 or more and less than 1x10 ^-9 Pa.m ³ /sec D: Leakage amount is 1x10 ^-9 or more and less than 1x10 ^-8 Pa.m ³ /sec E: Leakage amount is 1x10 ^-8 or more and less than 1x10 ^-6 Pa.m ³ /sec F: Leakage amount is 1x10 ^-6 Pa.m ³ /sec or more.

(Wiring adhesion - pull strength)
<Examples 1 to 55 and Comparative Example 1>
A stud pin with a tip area of 1 ^mm2 was soldered vertically to a substrate having a silicon through electrode obtained in the same manner except that a wiring pattern of 2 mm x 2 mm was formed in the wiring formation process, and used as a test specimen. The test specimen was fixed, the stud pin was gripped by the chuck of a tensile tester, and pulled vertically upward at an ascending speed of 50 mm/min, and the fracture load when the metal body on the main surface of the silicon substrate peeled off from the silicon substrate was measured. Then, the adhesion strength was calculated using the following formula from the measured fracture load and the fracture area of the metal body. The measured value was the average of 10 points and was evaluated according to the following criteria. The results are shown in Tables 1 to 6.

Adhesion strength (MPa) = breaking load (kgf) / breaking area (mm2) × 9.8 (N / kgf).
A: Adhesion strength (MPa) is 50 MPa or more B: Adhesion strength (MPa) is 40 MPa or more and less than 50 MPa C: Adhesion strength (MPa) is 30 MPa or more and less than 40 MPa D: Adhesion strength (MPa) is 20 MPa or more and less than 30 MPa E: Adhesion strength (MPa) is 5 MPa or more and less than 20 MPa F: Adhesion strength (MPa) is less than 5 MPa

(Wiring formability - presence or absence of cracks -)
<Examples 1 to 55 and Comparative Example 1>
A substrate having a silicon through electrode obtained in the same manner except that five wiring patterns of 2 mm x 2 mm were formed in the wiring formation process was inspected with an optical microscope to check for the presence or absence of cracks (length 0.5 mm or more) in the wiring patterns. The magnification was 500 times, and the evaluation was based on the following criteria. The results are shown in Tables 1 to 6.
A: No cracks B: 1 or more but less than 2 cracks C: 2 or more but less than 5 cracks D: 5 or more but less than 10 cracks E: 10 or more but less than 20 cracks F: 20 or more cracks

(Volume Resistivity)
<Examples 1 to 55 and Comparative Example 1>
The volume resistivity of the conductor formed on the silicon substrate was measured. The volume resistivity was calculated from the sheet resistance measured with a four-point needle sheet resistance meter (manufactured by Mitsubishi Analytec Co., Ltd., product name: Loresta GP) and the film thickness obtained with a non-contact surface/layer cross-sectional shape measurement system (VertScan, Ryoka Systems Co., Ltd.). The results are shown in Tables 1 to 6.

(Observation results of gaps around solder joints)
11 and 12 show cross-sectional images (approximately 20 μm square) of the metal body of the metal body-filled silicon substrate produced in Example 1, taken using a digital microscope (Keyence Corporation, product name: VHX-6000). As shown in FIGS. 11 and 12, the metal body includes a copper sintered body, solder (SiBi58), and voids, and the voids exist in the copper sintered body, inside the solder, and on the outer periphery of the solder (between the solder and the copper sintered body). The voids 4a shown in FIG. 11 exist inside the solder 14a, and the voids 4b shown in FIG. 12 exist on the outer periphery of the solder 14b.

Figure 13 shows a cross-sectional image (approximately 10 μm × 19 μm square) of the metal body of the metal body-filled silicon substrate produced in Example 46, taken using a digital microscope (Keyence Corporation, product name: VHX-6000). The void 4c shown in Figure 13 exists inside the solder 14c.

<Comparative Example 1>
Fig. 14 shows a cross-sectional image (approximately 10 μm × 12 μm square) of the metal body taken with a digital microscope (Keyence Corporation, product name: VHX-6000) for the metal body-filled silicon substrate produced in Comparative Example 1. As shown in Fig. 14, a crack 18 was observed inside the copper sintered body 12d constituting the metal body.

In the metal-filled silicon substrate produced in the examples, it is believed that the occurrence of the above-mentioned cracks is suppressed by the presence of solder dots derived from the solder particles.

1...silicon wafer, 2...metal coating, 3...metal paste, 4...hole (porous, void), 5...metal body, 6...resin hardened product, 8...etching resist, 9...wiring, 12...copper sintered body, 14...solder, 15...fine bump, 20...hardened adhesive, 25...interposer substrate, 27...wiring, 30...through hole, 31...non-through hole, 35...conductor, 40, 41...silicon substrate, 50, 60...silicon substrate filled with metal body, 51, 52, 61...substrate with silicon through electrode, 55...test piece, 100, 200, 300...semiconductor device, A...pressure jig

Claims (30)

The present invention provides a metal body having pores, the metal body including a copper sintered body having a porous structure and solder interspersed in the copper sintered body,
A conductor in which the metal body includes, as the pores, voids present inside the solder and/or voids present between the solder and the copper sintered body. The conductor of claim 1, wherein the solder contains tin or a tin alloy. The conductor according to claim 1, wherein the solder is In-Sn, In-Sn-Ag, Sn-Bi, Sn-Bi-Ag, Sn-Ag-Cu, or a Sn-Cu alloy. The conductor according to any one of claims 1 to 3, further comprising a cured resin present in the pores of the metal body. The porosity of the metal body is 1 to 15 volume % based on the volume of the metal body,
The conductor according to claim 4 , wherein the content of the cured resin in the conductor is 80% by volume or more based on the total volume of the internal spaces of the pores of the metal body. The present invention comprises a base including an insulating base having a through hole, the through hole communicating with both main surfaces of the base, and a conductor filling the through hole,
A substrate having a through electrode, wherein the conductor is the conductor according to any one of claims 1 to 5. The substrate having the through-hole electrode according to claim 6, wherein the substrate has a metal coating provided on at least the wall surface of the through-hole. A substrate having a through electrode according to claim 6 or 7, in which the ratio L/D of the length L of the through electrode to the hole diameter D is 10 or more. A substrate having a through electrode according to any one of claims 6 to 8, in which the conductor covers at least a portion of the main surface of the substrate. A substrate having a through electrode according to any one of claims 6 to 9, wherein the insulating substrate is a silicon wafer and the through electrode is a silicon through electrode. The method includes a preparation step of preparing an insulating substrate having through holes, the through holes communicating with both main surfaces, and a conductor formation step of forming a conductor in the through holes,
The conductor forming step includes:
The method includes a metal body forming step of forming a metal body having pores, the metal body including a copper sintered body having a porous structure and solder interspersedly present in the copper sintered body so as to fill at least the through holes ,
The metal body includes, as the pores, voids present inside the solder and/or voids present between the solder and the copper sintered body.
A method for manufacturing a substrate having a through electrode. The conductor forming step includes:
a resin impregnation step of impregnating the metal body with a curable resin composition;
a resin curing step of curing the curable resin composition impregnated in the metal body;
The method of claim 11 further comprising: The method includes a preparation step of preparing a substrate including an insulating substrate having non-through holes formed therein, the substrate having one main surface on which the non-through holes are opened, a conductor formation step of forming a conductor in the non-through holes, and a grinding step of providing a through electrode by grinding a surface of the substrate on which the conductor is formed opposite to the surface on which the non-through holes are opened,
The conductor forming step includes:
The method includes a metal body forming step of forming a metal body having pores, the metal body including a copper sintered body having a porous structure and solder interspersedly present in the copper sintered body so as to fill at least the non-through holes ,
The metal body includes, as the pores, voids present inside the solder and/or voids present between the solder and the copper sintered body.
A method for manufacturing a substrate having a through electrode. The conductor forming step includes:
a resin impregnation step of impregnating the metal body with a curable resin composition;
a resin curing step of curing the curable resin composition impregnated in the metal body;
The method of claim 13 further comprising: The method according to any one of claims 11 to 14, wherein the solder contains tin or a tin alloy. The method according to any one of claims 11 to 14, wherein the solder is an In-Sn, In-Sn-Ag, Sn-Bi, Sn-Bi-Ag, Sn-Ag-Cu, or Sn-Cu based alloy. The method according to any one of claims 11 to 16, wherein the porosity of the metal body is 1 to 15 volume % based on the volume of the metal body. The method according to claim 12 or 14, wherein the content of the cured resin in the conductor is 80 volume % or more based on the total volume of the internal space of the pores in the metal body. The method according to any one of claims 11 to 18, wherein in the metal body forming step, the metal body is formed so as to cover at least a portion of the main surface of the substrate. The method according to claim 19, further comprising a conductor removal step of removing at least a portion of the conductor formed on the main surface of the substrate. The method according to any one of claims 11 to 20, wherein the ratio L/D of the length L to the hole diameter D of the through electrode is 10 or more. The metal body forming step includes:
a paste filling step of filling the through holes of the base with a metal paste containing copper particles and solder particles;
a paste firing step of firing the metal paste to form the metal body;
13. The method of claim 11 or 12, comprising: The metal body forming step includes:
a paste filling step of filling the non-through holes of the base with a metal paste containing copper particles and solder particles;
a paste firing step of firing the metal paste to form the metal body;
15. The method of claim 13 or 14, comprising: The method according to claim 22 or 23, wherein the metal paste contains, as the copper particles, first copper particles having a particle size of 0.8 μm or more and second copper particles having a particle size of 0.5 μm or less. The method of claim 24, wherein the first copper particles are flat. The method of any one of claims 22 to 25, wherein the solder particles include tin or a tin alloy. The method according to any one of claims 22 to 25, wherein the solder particles are In-Sn, In-Sn-Ag, Sn-Bi, Sn-Bi-Ag, Sn-Ag-Cu, or a Sn-Cu based alloy. The method according to any one of claims 22 to 27, wherein the metal paste is fired under a pressure of 0.1 MPa or more. The method according to any one of claims 22 to 28, wherein the metal paste is fired in an atmosphere containing nitrogen, hydrogen or formic acid. The method according to any one of claims 11 to 29, wherein the insulating substrate is a silicon wafer and the through-electrode is a silicon through-electrode.

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