WO2016052700A1 - Bonding layer structure using alloy bonding material, forming method for same, semiconductor device having said bonding layer structure, and method for manufacturing same - Google Patents
Bonding layer structure using alloy bonding material, forming method for same, semiconductor device having said bonding layer structure, and method for manufacturing same Download PDFInfo
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- WO2016052700A1 WO2016052700A1 PCT/JP2015/077938 JP2015077938W WO2016052700A1 WO 2016052700 A1 WO2016052700 A1 WO 2016052700A1 JP 2015077938 W JP2015077938 W JP 2015077938W WO 2016052700 A1 WO2016052700 A1 WO 2016052700A1
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Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K1/00—Soldering, e.g. brazing, or unsoldering
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/24—Selection of soldering or welding materials proper
- B23K35/28—Selection of soldering or welding materials proper with the principal constituent melting at less than 950 degrees C
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C18/00—Alloys based on zinc
- C22C18/04—Alloys based on zinc with aluminium as the next major constituent
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/50—Assembly of semiconductor devices using processes or apparatus not provided for in a single one of the subgroups H01L21/06 - H01L21/326, e.g. sealing of a cap to a base of a container
- H01L21/52—Mounting semiconductor bodies in containers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
- H01L2224/73—Means for bonding being of different types provided for in two or more of groups H01L2224/10, H01L2224/18, H01L2224/26, H01L2224/34, H01L2224/42, H01L2224/50, H01L2224/63, H01L2224/71
- H01L2224/732—Location after the connecting process
- H01L2224/73251—Location after the connecting process on different surfaces
- H01L2224/73265—Layer and wire connectors
Definitions
- the present invention relates to a bonding layer structure using an alloy bonding material that has high bonding strength at high temperatures and can improve connection reliability by a stress relaxation effect, a method for forming the bonding layer structure, and a semiconductor device having the bonding layer structure and a method for manufacturing the semiconductor device.
- a bonding layer structure using an alloy bonding material that has high bonding strength at high temperatures and can improve connection reliability by a stress relaxation effect a method for forming the bonding layer structure, and a semiconductor device having the bonding layer structure and a method for manufacturing the semiconductor device.
- solder bonding is used for die bonding of power semiconductor elements, bonding of semiconductor elements mounted on power modules to mounting boards, and bonding of heat sinks to mounting boards.
- Sn—Pb-based solder containing lead is well known, but in order to cope with recent environmental problems, low-temperature solder such as Sn—Si type solder or Sn—In type solder, Sn—Ag—Cu Medium-temperature lead-free solders such as Sn solder and Sn-Cu solder have been developed and put into practical use.
- lead-free solder material for high temperature solder used at 250 ° C. or higher, and high lead solder is used. This high lead solder contains 85% by mass or more of lead as a constituent component and has a larger environmental load than the Sn—Pb eutectic solder.
- SiC silicon carbide
- GaN Gallium nitride
- C diamond
- Ga 2 O 3 gallium oxide
- SiC or GaN semiconductor elements that have been commercialized are excellent in heat resistance, but when these wide gap semiconductors are bonded to a mounting substrate or the like, heat resistance is required not only for the semiconductor elements but also for the bonding material.
- the above-mentioned high lead solder material has a high melting point, it has a large environmental load and is restricted from being used in the future.
- solder examples include Au-based solders such as Au-Sn, Au-Si, and Ai-Ge, Bi-based solders such as Bi, Bi-Cu, and Bi-Ag, Zn, and Zn-Al-based solder. It has been reported. Among them, Zn, Zn—Al solder has a higher melting point, and therefore has high expectations as a bonding material for power wide gap semiconductor elements such as SiC or GaN.
- Zn—Al based solder for example, in Patent Document 1, Al: 2 to 9% by weight, Ge and / or Mg: 0.05 to 1% by weight, the balance being Zn and inevitable impurities, Zn alloy for high temperature soldering Is disclosed.
- the Zn—Al solder described in Patent Document 1 is Ge and / or Mg, or further Sn and further in order to appropriately lower the melting point of a Zn—Al eutectic alloy having a eutectic temperature of around 380 ° C. / Or In is added.
- Patent Document 2 discloses a sheet-like Pb-free solder produced using a rolling mill with plastic deformation in a Zn-Al solder containing Al in an amount of 1.0 mass% or more and 15.0 mass% or less.
- An alloy is disclosed. Since this sheet-like solder alloy has a high elongation and tensile strength, it is excellent in wettability and reliability, and particularly excellent in workability and stress relaxation properties.
- the present inventors have also noted that a Zn—Al eutectoid alloy bonding material containing 17 to 30% by mass of Al exhibits a superplastic phenomenon in a predetermined temperature range, and by utilizing this superplastic phenomenon, Patent Document 3 proposes a bonding material excellent in workability and stress relaxation properties.
- Patent Document 4 proposes a bonding material using a Zn / Al / Zn clad material.
- This bonding material has a structure in which an Al-based alloy layer is sandwiched between Zn-based alloy layers in order to suppress a decrease in wettability caused by Al oxide forming a film on the surface of the melted part by heating during connection.
- the bonding material described in Patent Document 4 can ensure good wettability with a Zn / Al / Zn clad material, and since the Al-based alloy layer functions as a stress buffer after connection, it has high connection reliability. Obtainable.
- Bonding materials used in power modules and power electronics products must have a high melting point and excellent stress relaxation from the viewpoints of wettability with materials to be bonded, workability during bonding, and connection reliability. .
- the temperature at the time of bonding is preferably relatively low in order to reduce the influence of stress due to the thermal expansion coefficient resulting from a large temperature difference when cooled to room temperature, but even if the bonding temperature becomes high, stress relaxation As long as the bonding material has excellent properties, connection reliability can be sufficiently ensured. Therefore, it is indispensable to form a structure having a stress buffering property in Zn—Al solder having a relatively high bonding temperature as compared with conventional solder materials.
- the Zn—Al solder described in Patent Document 1 has a reducibility that is stronger than that of Zn and easily oxidizes, so that the wettability is lowered. Therefore, the wettability of the alloy is not sufficient within the range of the composition.
- Zn and Al become a soft metal with a certain degree of flexibility by making a eutectic alloy, but because of the high Zn content, improvement in hardness is necessary to have good workability .
- there is a small amount of Al phase functioning as a stress buffer material in the Zn—Al solder after bonding it is insufficient in terms of stress buffer.
- the Zn—Al solder described in Patent Document 2 is formed into a sheet by plastic deformation, but the strength increases as the Al content exceeds 9.0 mass%, but the elongation is low. Tend to be. Further, it cannot be said that the Al phase functioning as a stress buffer material is present in a sufficient ratio, and considering the point that the bonding temperature becomes high, further improvement in stress relaxation properties is required. This is easily inferred from the fact that, in Patent Document 2, “Al content is more preferably 2.0% by mass or more and 9.0% by mass”.
- the Zn—Al eutectoid alloy bonding material described in Patent Document 3 can be bonded at a relatively low temperature using the superplastic phenomenon due to the formation of fine crystal grains, and is excellent in workability and stress relaxation properties. .
- the point of optimizing the structure of the bonding interface layer and the bonding layer has not been sufficiently studied.
- further improvement is required for the stress relaxation required when the bonding temperature is raised.
- the bonding material using the Zn / Al / Zn clad material described in Patent Document 4 is excellent in stress relaxation because an Al-based alloy layer that functions as a stress buffer material is formed after connection.
- the crack is likely to propagate at the interface between the Al-based mixed metal layer and the Zn-Al alloy layer formed by melting, which is desirable in terms of bonding reliability.
- the fact is that the effect of has not been obtained.
- the Zn / Al / Zn clad material has been studied to make the Al layer thinner and to disappear the Al-based mixed metal layer during bonding heating, but the Al alloy composition part tends to remain as a large lump in the bonding layer. It is difficult to obtain a sufficient effect of suppressing crack propagation.
- the present invention has been made in view of the above-described conventional problems, and sufficiently secures wettability as a bonding material, has high bonding strength at high temperatures, and has connection reliability due to a stress relaxation effect.
- the present invention relates to a bonding layer structure using an alloy bonding material that can be improved, a method for forming the bonding layer structure, a semiconductor device having the bonding layer structure, and a method for manufacturing the same.
- the present invention applies a Zn—Al eutectoid alloy having a relatively high Al content as a bonding material, and the stress of Al in the bonding layer of the Zn—Al eutectoid alloy obtained after bonding.
- the present inventors have found that the above problem can be solved by forming a structure in which the density of the crystal structure of Al ( ⁇ phase) contained in the bonding layer is increased so that the buffering function can be sufficiently expressed. It was.
- the configuration of the present invention is as follows.
- the present invention is a structure of a bonding layer formed by bonding materials A and B to be bonded by an alloy bonding material, wherein the alloy bonding material is a Zn—Al eutectoid alloy, and In each of the bonding surfaces of the materials A and B to be bonded and the alloy bonding material, in the bonding surface of the bonding material having the smaller area, or in the bonding surface of the bonding materials having the same area.
- a bonding layer structure made of an alloy bonding material, wherein the Al-rich phase ( ⁇ phase) contained in the existing bonding layer has a dendritic arm spacing (DAS) of more than 0.06 ⁇ m and less than 0.3 ⁇ m. .
- DAS dendritic arm spacing
- the bonding surface of the material to be bonded in each of the bonding surfaces of the materials to be bonded A and B and the alloy bonding material, the bonding surface of the material to be bonded, which has the smaller area, or both have the same area.
- the bonding layer present in the bonding surface of the material to be bonded has a composition comprising an Al-0 to 1.5 mass% Cu-0 to 0.05 mass% Mg—Zn system that exceeds 30 mass% and is 97 mass% or less.
- a bonding layer structure using the alloy bonding material according to the above [1] is provided.
- the present invention is a method for forming the structure of the bonding layer according to the above [1] or [2], and is between 17 mass% and 30 mass between the materials A and B to be bonded.
- a Zn-Al eutectoid alloy bonding material composed of% Al-0 to 1.5 mass% Cu-0 to 0.05 mass% Mg-Zn is interposed, and the bonding material is placed in a semi-melting temperature region while applying pressure.
- a method for forming a bonding layer structure characterized by repeating the operation of holding for a desired time in a heated state once or twice or more and then gradually cooling.
- the present invention is a method for forming the structure of the bonding layer according to [1] or [2], wherein the bonding material between A and B exceeds 30% by mass.
- a Zn-Al eutectoid alloy bonding material composed of Al-0 to 1.5% by mass Cu-0 to 0.05% by mass Mg-Zn based on the mass% or less is interposed, and the pressure is applied or no pressure is applied.
- a method for forming a bonding layer structure characterized in that a bonding material is heated to a semi-melting temperature region, and is gradually cooled after being held for a desired time.
- the operation of holding the bonding material for a desired time in a state heated to a temperature region that develops a superplastic phenomenon is performed before the operation for holding the bonding material in a state heated to a semi-melting temperature region for a desired time.
- the method for forming a bonding layer structure according to the above [3] or [4] is provided.
- the bonding material is heated to a semi-melting temperature region and held for a desired time in a pressurized state.
- the bonding layer structure having a composition composed of ⁇ 0 to 0.05 mass% Mg—Zn is formed, and then cooled in a pressurized state as it is, and an operation of passing through the transformation superplastic point is performed.
- a method for forming a bonding layer structure according to any one of [3] to [5] is provided.
- the present invention includes a semiconductor substrate and a metal substrate bonded to the semiconductor substrate directly or via a ceramic substrate, and the bonding layer has the structure described in [1] or [2].
- a semiconductor device is provided.
- the present invention provides the semiconductor device according to [7], wherein the semiconductor substrate is a wide gap semiconductor.
- the present invention includes a semiconductor substrate, and a metal substrate bonded to the semiconductor substrate directly or via a ceramic substrate with a bonding layer, and the structure of the bonding layer is any one of [3] to [6]
- a method for manufacturing a semiconductor device characterized by being formed by the described forming method.
- the present invention provides the method for manufacturing a semiconductor device according to [9], wherein the semiconductor substrate is a wide gap semiconductor.
- the bonding layer structure of the present invention uses a Zn—Al eutectoid alloy in which the Al crystal structure is uniformly distributed as the bonding material, a bonding layer in which the ⁇ crystal phase of Al is finely distributed after bonding is formed.
- the amount of Al having a stress buffering function increases, the stress relaxation effect is enhanced in the bonding layer, and the bonding reliability can be improved.
- Al is a metal having high thermal conductivity
- the bonding layer structure of the present invention is also excellent in thermal conductivity. The wettability can also be sufficiently ensured by melting of Zn and Zn—Al eutectic in the Zn—Al eutectoid alloy.
- the bonding material made of the Zn—Al eutectoid alloy is held for a desired time in a state where it is heated to a temperature region where a superplastic phenomenon occurs, and then held for a desired time in a state where it is heated to a semi-melting temperature region.
- the wettability of the bonding interface is ensured and the stress relaxation effect is obtained, so the high-temperature bonding strength and bonding reliability are greatly improved, and high-reliability and long-life bonding. Part formation can be realized. Furthermore, by using a superplastic phenomenon obtained by cooling a bonding material made of a Zn-Al eutectoid alloy under pressure from the semi-melting temperature range and passing through the transformation superplasticity point, higher stress relaxation is achieved. A bonding layer structure having a function can be formed.
- the semiconductor device in which wide gap semiconductor elements such as SiC, GaN, C (diamond) and Ga 2 O 3 are mounted by the bonding layer structure of the present invention answers the heat resistance requirement required for power devices or power electronics products. And can withstand long-term use in a high temperature use environment of 200 ° C. or higher, particularly 250 ° C. or higher.
- FIG. 3 is an equilibrium diagram of a Zn—Al eutectoid alloy.
- FIG. 3 is a diagram showing the relationship between the Al content ratio and DAS in a bonding layer made of a Zn—Al eutectoid alloy. It is a figure which shows the structure
- Example 1 It is a figure which shows the result of the heating temperature dependence of the junction shear strength measured in Example 1 of this invention. It is a figure which shows the result of the joining process and joining reliability of the SiC semiconductor device by Example 3 of this invention. It is a figure which shows the schematic diagram of the joining process of the SiC semiconductor device by Example 6 of this invention. It is a figure which shows the external appearance photograph after joining of the SiC semiconductor device by Example 6 of this invention. It is a figure which shows the joining reliability result of the SiC semiconductor device by Example 6 of this invention with a cross-sectional photograph. It is a schematic sectional drawing of the diode which has a junction layer structure of this invention. 1 is a schematic plan view of an IGBT module having a bonding layer structure according to the present invention.
- FIG. 10 is a schematic cross-sectional view taken along line AA in FIG.
- FIG. 10 is a schematic sectional view taken along line BB in FIG. 1 is a schematic plan view of a power MOS transistor having a junction layer structure according to the present invention.
- the bonding layer of the present invention is a bonding layer formed by bonding materials to be bonded A and B with a Zn—Al eutectoid alloy, and has a smaller area of either of the materials to be bonded A or B.
- a structure in which the crystal structure of the Al-rich phase ( ⁇ phase) included in the bonding layer existing in the bonding surface of the material or in the bonding surface of the material to be bonded having the same area is included in a denser state than before. It is characterized by having.
- the Al-rich phase ( ⁇ phase) is clearly distinguished from the Zn-rich phase, it is easy to identify the crystal structure of the Al-rich phase ( ⁇ phase) in the bonding layer. .
- This bonding layer structure means that Al crystals functioning as a stress buffering material are present at a high density inside the bonding layer, and an effect of increasing the stress relaxation property of the bonding layer can be obtained.
- Examples of the combination of the materials to be bonded A and B include a semiconductor element and a metal frame, a semiconductor element and a printed circuit board, a mounting substrate such as a ceramic substrate or a metal substrate, and the mounting substrate and a heat dissipation plate. It is not necessary to specify the bonding materials A and B individually. In the present invention, attention is focused on the bonding surface formed by bonding both of the materials to be bonded A and B through a Zn—Al eutectoid alloy. On the other hand, since only one of the materials to be joined A and B is in contact with the Zn—Al eutectoid alloy joining material, the other joining surface is not constrained, so the generated stress is relatively low. Get smaller.
- the Al-rich material contained in the bonding layer existing in the bonding surface of the bonded material having the smaller area of the bonded materials A and B or in the bonded surface of the bonded material having the same area It is an important factor in the present invention to define the fineness of the crystal structure of the phase ( ⁇ phase).
- the denseness of the crystal structure of the Al-rich phase can be defined by the value of dendrid arm spacing (DAS).
- DAS Dendride Arm Spacing
- the measuring method is to cut out a joining surface formed by joining both of the materials to be joined A and B through a Zn—Al eutectoid alloy in a direction perpendicular to the joining surface, and use the entire joining surface as a resin. After embedding, mirror finishing is performed by emery paper and buffing until it is observable, and after etching, the structure is observed using an optical microscope of about 200 to 400 times.
- DAS secondary dendritic arm spacing
- the bonding layer structure of the present invention requires that the dendritic arm spacing (DAS) is more than 0.06 ⁇ m and less than 0.3 ⁇ m.
- DAS dendritic arm spacing
- the Zn—Al eutectoid alloy bonding material comprising 22 mass% Al-78 mass% Zn system described in Patent Document 3 is applied at a temperature range of 430 to 480 ° C. for 1 to 30 minutes.
- the bonding layer obtained by heating and gradually cooling after a semi-molten state has a measured dendritic arm spacing (DAS) of 0.3 ⁇ m.
- the Zn—Al eutectoid alloy bonding material having this composition has a slightly higher shear strength at 200 ° C.
- DAS dendritic arm spacing
- FIG. 1 is an equilibrium diagram of a Zn—Al eutectoid alloy.
- DAS dendritic arm spacing
- FIG. 2 plots the relationship between the content ratio of Zn—Al and the dendritic arm spacing (DAS) based on the results of FIG.
- dendritic arm spacing shows a smaller value as the Al content ratio increases, and converges to 0.06 ⁇ m as the Al content ratio approaches 100%.
- Al content of 100% that is, pure aluminum
- the melting point is very high at 660 ° C., but a single composition cannot form a solid-liquid phase, and melting by joining heating is very difficult.
- the temperature that can be heated in a short time is less than 600 ° C., preferably 500 ° C. or less.
- a single composition of Al cannot be used as a bonding material. Therefore, the bonding layer structure of the present invention needs to have an Al-rich phase ( ⁇ phase) crystal structure with a dendritic arm spacing (DAS) exceeding 0.06 ⁇ m.
- the Al content is preferably more than 30% by mass and 97% by mass or less.
- the stress buffering function of Al can be sufficiently exhibited.
- the stress buffering function accompanying the increase in the Al content is realized when the Al content is in the range of 22 to 30% by mass, and has a remarkable effect on the bonding reliability when the Al content exceeds 30% by mass. It becomes like this.
- the heating temperature at the time of bonding is more preferably at least less than 600 ° C., and particularly preferably 500 ° C. or less.
- the upper limit of the content ratio of Al contained in the bonding layer made of a Zn—Al eutectoid alloy is preferably 97% by mass or less, more preferably less than 80% by mass, and particularly preferably less than 60% by mass.
- a Zn—Al eutectoid alloy bonding layer having an Al content ratio of more than 30% by mass and 97% by mass or less, more preferably less than 80% by mass, and particularly preferably less than 70% by mass is provided.
- it may be defined by dendritic arm spacing (DAS) estimated from the curve shown in FIG.
- the dendride arm spacing (DAS) should be defined as a bonding layer structure having a range of less than 0.22 ⁇ m and 0.068 ⁇ m, more preferably 0.08 ⁇ m, and particularly preferably more than 0.09 ⁇ m. it can.
- the Zn—Al eutectoid alloy used in the present invention must contain Al and Zn as constituent components, but it can lower the melting point, workability, high temperature strength, fatigue strength (creep resistance) or stress relaxation.
- Cu, Mg, Ge, Sn, In, Ag, Ni, P, or the like may be added as a trace component for the purpose of improving the properties.
- the superplastic phenomenon is utilized, and particularly attention is focused on improving high temperature strength and fatigue strength (creep resistance) as the most effective trace component for those effects. It is preferable to contain at least one element of Cu and Mg.
- the contents of Cu and Mg are preferably in the range of 0 to 1.5 mass% and 0 to 0.05 mass%, respectively, with respect to 100 mass parts of the total weight of the eutectoid alloy.
- the contents of Cu and Mg exceed 1.5% by mass and 0.05% by mass, respectively, the Zn—Al eutectoid alloy becomes brittle, and the stress relaxation effect that is a feature of the present invention is lost.
- the Zn—Al eutectoid alloy is weighed and blended so as to have a predetermined alloy ratio, including the case where at least one element of Cu and Mg is contained as a trace component, and uniformly at a temperature equal to or higher than the melting point. After melting, it is obtained from a mother alloy (ingot) poured into a mold having a desired shape.
- a mother alloy ingot
- As an ingot production method for example, 99.9% by mass or more of Zn and Al, and in some cases, 99.9% by mass or more of Cu and Mg are prepared as trace addition components. What is made fine by cutting and pulverizing so that it can be uniformly mixed is weighed so as to have a predetermined alloy ratio and put into a graphite crucible.
- the mixture of each alloy component contained in the graphite crucible is put into a melting furnace such as a high-frequency melting furnace, heated and melted while flowing an inert gas such as nitrogen or argon to prevent oxidation, and uniformly in a molten state. Mix.
- a melting furnace such as a high-frequency melting furnace
- an inert gas such as nitrogen or argon
- the high frequency power supply is turned off, and the molten metal is taken out of the melting furnace and poured into a mold, whereby a Zn—Al eutectoid alloy ingot can be produced.
- the surface portion of the ingot may be chamfered with a slicer or the like in order to remove surface scratches.
- the Zn—Al eutectoid alloy of the present invention is disclosed in Patent Document 4 because an ingot having a structure in which crystals of each alloy composition are distributed in a nearly uniform state by melting is applied as a bonding material. Unlike the Zn / Al / Zn clad material, it is possible to suppress the formation of a layer or a large lump made of only an Al-based alloy separately from the Zn—Al alloy layer. Accordingly, to solve the technical problem of Zn / Al / Zn clad materials in which cracks are likely to progress due to the existence of a wide range of interfaces formed between an Al-based alloy layer and a Zn—Al alloy layer. Is possible.
- the Al content ratio in the Zn—Al eutectoid alloy increases, but in the present invention, the Al content ratio is 80 mass%. It has been found that a certain degree of effect can be obtained even in the case of exceeding.
- a bonding layer structure having a dendritic arm spacing (DAS) of more than 0.06 ⁇ m and less than 0.3 ⁇ m can be formed by the following two forming methods.
- the first forming method is composed of 17% to 30% by mass Al-0 to 1.5% by mass Cu-0 to 0.05% by mass Mg—Zn between the materials to be joined A and B.
- a method in which a Zn-Al eutectoid alloy bonding material is interposed, and the operation of holding the bonding material in a state of being heated to a semi-melting temperature region while being pressed is held for a desired time and then gradually cooled after being repeated once or twice. is there.
- a second forming method between Al to B to be bonded, Al-0 to 1.5% by mass, Cu-0 to 0.05% by mass, Mg—Zn, exceeding 30% by mass and not more than 97% by mass.
- This is a method in which a Zn—Al eutectoid alloy bonding material composed of a system is interposed, the bonding material is heated to a semi-molten temperature region in a pressurized or non-pressurized state, and is gradually cooled after being held for a desired time.
- the first forming method is to form a bonding layer structure having a dendritic arm spacing (DAS) of more than 0.06 ⁇ m and less than 0.3 ⁇ m.
- DAS dendritic arm spacing
- the Zn—Al eutectoid alloy bonding material composed of Al-0 to 1.5 mass% Cu-0 to 0.05 mass% Mg—Zn
- the Zn—Al It is necessary to pressurize at the same time when performing an operation of holding the deposition alloy joining material for a desired time in a state heated to the semi-melting temperature region.
- the Zn-Al eutectoid alloy bonding material heated to the semi-melting temperature region is deformed, and the lamella structure Zn having a relatively low melting point is melted to the outside from the bonding surface with the bonded material.
- the Al-rich phase ( ⁇ phase) does not dissolve in the semi-melting temperature region and remains inside the joint surface. Since the melting point of Zn-Al eutectic is somewhat low, a part of the Zn-Al eutectic may be pushed out of the joint surface, but there are some that remain inside the joint surface due to the interaction with the Al-rich phase ( ⁇ phase). To do.
- the operation of holding for a desired time in a state heated to the semi-melting temperature region is not limited to once, and may be repeated twice or more as necessary.
- the microstructure of the eutectoid Al—Zn solder during the pressure bonding changes, and the Al-rich phase ( ⁇ phase) dendrite after the semi-melt bonding Shaped crystals (black line portions in FIG. 3) are formed in a denser state.
- a bonding layer structure in which the Al-rich phase ( ⁇ phase) dendritic arm spacing (DAS) exceeds 0.06 ⁇ m and less than 0.3 ⁇ m can be obtained.
- the thickness of the bonding layer after being formed for a certain period of time in the semi-melting temperature range is adjusted according to the Al-rich phase ( ⁇ phase) dendritic arm spacing (DAS).
- the specific thickness of the bonding layer formed after bonding is practically 20 ⁇ m to 200 ⁇ m from the viewpoints of voidless bonding, bonding reliability, and thermal conductivity.
- the thickness of the matching layer after bonding is less than 20 ⁇ m, not only is voidless bonding difficult, but the bonding reliability is significantly reduced.
- the thickness of the bonding layer exceeds 200 ⁇ m, the effect of improving the thermal conductivity cannot be obtained sufficiently.
- the Al-rich phase ( ⁇ phase) dendritic arm spacing (DAS) is small, and the Al content in which the thermal conductivity is superior to Zn in the vertical direction of the bonding surface is large.
- the thickness of the bonding layer that can fully utilize this feature is 200 ⁇ m or less, preferably 150 ⁇ m or less. .
- a Zn-Al eutectoid alloy bonding material composed of 17 mass% to 30 mass% Al-0 to 1.5 mass% Cu-0 to 0.05 mass% Mg-Zn system has a higher Al content than the conventional one.
- FIG. 4 shows a process schematic diagram of the joining method when utilizing the superplastic phenomenon which is manifested by heating in the temperature range of 200 to 275 ° C. as an example of the joining method of the present invention utilizing the superplastic phenomenon.
- the surface of the metallized portion 3 of the semiconductor element 2 (corresponding to the material A to be bonded) and the Cu substrate / Ni / Cu plating are formed in the solid phase Zn—Al eutectoid alloy bonding material 1.
- Superplasticity is achieved by heating at 200 to 275 ° C. while applying pressure from above and below both surfaces of the substrate 4 having a film structure (corresponding to the material B to be bonded) on which the Cu plating film 5 is formed.
- the temperature range showing the semi-molten state is higher than the eutectic temperature of the Zn-Al alloy and exceeds 380 ° C. and less than 600 ° C.
- a temperature exceeding 410 ° C. is preferable as a temperature that can be sufficiently maintained.
- the pressure during pressurization is preferably 1 to 50 MPa, more preferably 5 to 30 MPa.
- the pressure is less than 1 MPa, the above-mentioned cleaning and adhesion are hardly improved.
- the pressure exceeds 50 MPa the bonding layer becomes too thin due to pressurization at the semi-melting temperature of the bonding material, and it becomes difficult to improve the bonding reliability.
- the dendritic arm spacing (DAS) of the Al-rich phase ( ⁇ phase) exceeds 0.06 ⁇ m and less than 0.3 ⁇ m. It becomes easy to form a bonding layer structure.
- the first forming method can use a superplastic phenomenon to clean the bonding interface and improve the adhesion, the temperature at which the temperature is raised after heating is maintained at a temperature indicating a semi-molten state. There is no need to raise the temperature to near 600 ° C. Therefore, it is possible to set the temperature indicating the semi-molten state to a relatively low temperature, and it is possible to obtain an effect that the damage to the materials to be joined at the time of joining and the stress generated by the high temperature heating can be reduced.
- the second forming method is a method in which a Zn—Al eutectoid alloy bonding material having a higher Al content than the first forming method is applied as a bonding material.
- a Zn—Al eutectoid alloy bonding material composed of Al-0 to 1.5% by mass Cu-0 to 0.05% by mass Mg—Zn and exceeding 30% by mass and 97% by mass or less is used.
- This Zn—Al eutectoid alloy bonding material has an Al-rich phase ( ⁇ phase) dendrid arm spacing (DAS) of more than 0.06 ⁇ m and less than 0.3 ⁇ m in the ingot state.
- ⁇ phase Al-rich phase
- DAS dendrid arm spacing
- a Zn-Al eutectoid alloy bonding material with a high Al content is characterized in that the thermal conductivity of Al is approximately twice that of Zn and is excellent in thermal conductivity.
- the entire bonding material can be heated to the semi-melting temperature region. Thereby, melting of Zn and Zn—Al eutectic having a relatively low melting point is promoted, and the effect that the wettability of the bonding material can be sufficiently secured is obtained.
- the alloy when an alloy ingot having an Al content close to 30% by mass is used as a bonding material, the alloy is heated to a semi-melting temperature region in order to reduce the dendritic arm spacing (DAS) of the Al-rich phase ( ⁇ phase). You may pressurize when doing.
- DAS dendritic arm spacing
- the second forming method can be bonded with no pressure or low pressure as compared with the first forming method, and thus is a preferable bonding method for simplifying the bonding apparatus.
- the pressure at that time is preferably 30 MPa or less, more preferably 20 MPa or less. If it exceeds 30 MPa, the bonding layer becomes too thin due to pressurization at the semi-melting temperature, and it becomes difficult to improve the bonding reliability.
- the bonding material when an alloy ingot having a composition with an Al content close to 30% by mass is used as the bonding material, the super-expressing characteristic of the Zn—Al eutectoid alloy bonding material used in the present invention is used.
- Plastic phenomena can be used. If the bonding material is held for a certain period of time while being pressurized in a temperature range showing a superplastic phenomenon, the bonding interface can be cleaned and adhesion can be improved.
- the superplastic phenomenon can be sufficiently exhibited at a pressure of 30 MPa or less, the lower limit of the pressure is preferably 0.5 MPa or more.
- the present invention is a joint having a stress relaxation function by utilizing superplastic deformation due to superplastic flow before the step of pressurizing the joining material in a state of being heated to a semi-molten temperature region during joining.
- a layered structure can be formed, other methods for developing superplastic deformation can be used.
- Superplastic deformation is different from fine crystal superplasticity (see Patent Document 3) that appears when crystal grains are made very fine (see Patent Document 3), and is superheated by repeating heating and cooling while passing through the transformation point while applying stress. It is known that it is manifested even when transformation superplasticity for plastic working is used.
- the bonding layer structure having the effect of low stress can obtain the bonding layer structure having the stress relaxation function of the present invention even by utilizing transformation superplasticity.
- this transformation superplasticity there are almost no conventional examples in which a bonding layer having a stress relaxation function is specifically formed, and it is quite effective in forming a bonding layer structure having a high Al content. It was not recognized.
- the bonding layer structure is formed using transformation superplasticity, it can be applied not only to the first forming method but also to the second forming method.
- a method of forming the bonding layer of the present invention using transformation superplasticity will be described with reference to an equilibrium diagram of a Zn—Al eutectoid alloy shown in FIG. In FIG. 1, the effect of transformation superplasticity can be obtained in the same way at any temperature as long as the solid-liquid coexistence region is at a temperature.
- a 450% Zn-22% Al alloy is used. The case of heating to ° C will be described.
- the heating temperature is heated from 450 ° C. to the liquidus temperature as b ⁇ e, and simultaneously pressurizing, whereby Zn is further pushed out of the bonding layer and discharged, and the composition of Al is increased.
- a joining layer of 60% by mass is formed (e ⁇ f in the figure).
- it passes through the transformation superplastic point indicated by c2 and the transformation superplasticity point indicated by d2 (f ⁇ c2 ⁇ d2 in the figure), so that Al is 60% by mass.
- a bonding layer having a higher stress relaxation mechanism can be formed.
- the same effect can be obtained at any temperature as long as it has a solid-liquid coexistence region.
- the content of Al contained in the bonding material can also be arbitrarily selected. For example, even when a bonding material having an Al composition exceeding 30% by mass in advance is used, Zn is extruded from the bonding layer. If the heating temperature to be discharged is selected, a bonding layer having a stress relaxation function can be formed in the same manner by applying pressure at the heating temperature. At this time, the degree of developing the stress relaxation function is determined according to the content of Al contained in the formed bonding layer.
- the method of forming using transformation superplasticity is not limited to the first forming method, and can be applied to the second forming method by applying pressure.
- the method of forming the bonding layer structure of the present invention by utilizing transformation superplasticity is a bonding method in which the low-stress function is further enhanced by combining with the superplasticity phenomenon manifested by heating in the temperature range of 200 to 275 ° C. shown in FIG. A layer can be formed.
- the temperature of the semi-molten / diffusion bonding shown in FIG. 4 may be heated to such a temperature that Zn contained in the bonding material becomes a liquid phase and is discharged to the outside of the bonding layer.
- the bonding layer structure of the present invention includes die bonding of power semiconductor elements, which have strong requirements for heat resistance, connection reliability and thermal conductivity, bonding of semiconductor elements mounted on power modules to mounting boards, and heat sinks to mounting boards. It can be applied as a bonding layer formed in the bonding.
- an SiC semiconductor element having an Al wiring / SiC / metallized structure is formed on a Cu / SiN / Cu structured metal frame with a Zn—Al eutectoid alloy as a bonding material.
- SiC high-temperature power semiconductor having the bonding layer structure of the present invention formed by die bonding by the first or second forming method.
- connection material for die bonding of ordinary semiconductor devices a connection material between metal caps and module substrates of semiconductor devices that require hermetic sealing, or bumps of semiconductor devices that require flip chips. It can also be applied as a connection layer formed at the time.
- a semiconductor element, a frame connecting the semiconductor element, a lead having one end as an external terminal, a wire connecting the electrode of the semiconductor element of the lead, the semiconductor element and the wire A resin for sealing, and the semiconductor element and the frame are formed by bonding with the first or second forming method through a Zn—Al eutectoid alloy bonding material. It constitutes the bonding layer structure of the present invention.
- Example 1 A basic experiment was conducted on the shear strength of the joint obtained by the joint layer structure of the present invention. Using a Zn-Al eutectoid alloy composed of 22 mass% Al-78 mass% Zn obtained by melting and casting as a bonding material, a sample for measuring the joint shear strength was prepared according to the method shown in FIG. In this experiment, instead of using the semiconductor element 2 shown in FIG. 4, two bonded materials 4 made of a Cu substrate / Ni / Cu plating film were used.
- a Zn—Al eutectoid alloy bonding material having a thickness of 60 ⁇ m is interposed between the two materials to be bonded made of the Cu substrate / Ni / Cu plating film in a nitrogen gas atmosphere (in this embodiment, non-oxidizing property).
- the atmosphere may be sufficient, and in addition to nitrogen, a non-oxidizing mixed gas containing argon, helium, or hydrogen can be used.
- the pressure is maintained at 250 ° C. for 10 minutes while being pressurized, and then in that state up to 390 ° C.
- the temperature was raised and held at the same temperature of 390 ° C. for 5 minutes, and then gradually cooled to room temperature.
- the pressurization was performed by changing the conditions under three conditions of 5 MPa, 10 MPa, and 24 MPa.
- the Zn—Al eutectoid alloy bonding material is deformed by being pushed out of the bonding surface by deforming a Zn—Al alloy or the like having a melting point of 400 ° C. or lower by holding at 390 ° C. for 5 minutes while applying pressure.
- the thickness decreased from 60 ⁇ m to 55 ⁇ m, 54 ⁇ m, and 52 ⁇ m, respectively.
- DAS dendritic arm spacing
- a bonding experiment was conducted using a Zn-Al eutectoid alloy composed of 22 mass% Al-78 mass% Zn and under conditions where superplasticity does not occur.
- the Zn—Al eutectoid alloy interposed between the two materials to be joined consisting of the Cu substrate / Ni / Cu plating film is left as it is without passing through the heating step from room temperature to 250 ° C. for 10 minutes.
- the temperature was raised to 0 ° C., held at 390 ° C. for 5 minutes while being pressurized at 24 MPa, and then gradually cooled to room temperature.
- the thickness of the bonding layer after bonding was reduced from 60 ⁇ m to 53 ⁇ m, and the DAS value was 0.21 ⁇ m.
- Comparative Example 1 As Comparative Example 1, a bonding layer was formed according to a conventional bonding method using conventional high-temperature lead solder (Pb—Sn—Ag) instead of the Zn—Al eutectoid alloy bonding material of this example.
- Pb—Sn—Ag high-temperature lead solder
- FIG. 6 shows the results of the heating temperature dependence of the shear strength measured for the joints of Example 1 and Comparative Example 1 obtained in this way.
- the Zn—Al eutectoid alloy bonding material of the present invention can form a bonding layer having a very high bonding strength compared to conventional high-temperature lead solder, and at a high temperature of 250 ° C. or higher. Has a high shear strength and an excellent high-temperature bonding strength.
- the shear strength is slightly improved as compared with the conventional high-temperature lead solder, but the effect is small.
- a Zn—Al eutectoid alloy composed of 17 mass% to 30 mass% Al-0 to 1.5 mass% Cu-0 to 0.05 mass% Mg—Zn is used as the bonding material.
- Example 2 Using the same bonding material (thickness 60 ⁇ m) and the material to be bonded used in Example 1, holding at 250 ° C. for 10 minutes while applying pressure in the range of 10 to 20 MPa, the temperature was increased to 430 to 480 ° C. in that state. Warm, hold at the same temperature of 430-480 ° C. for 5 minutes, and then slowly cool to room temperature.
- the Zn-Al eutectoid alloy bonding material is deformed by preferentially extruding part of the Zn and Zn-Al alloy from the bonding surface by holding for 5 minutes at a temperature of 430 to 480 ° C while applying pressure. Therefore, the thickness can be reduced from the initial 60 ⁇ m to 30 to 25 ⁇ m, which is less than half.
- the DAS value was in the range of 0.14 to 0.12 ⁇ m under pressure conditions of 10 to 20 M. .
- the Al content can be increased to 50% by mass or more.
- the shear strength measured for the joints having the respective joint layer structures obtained in this way is the same as that of Example 1 in which the Zn—Al eutectoid alloy joint was joined using the superplastic phenomenon under the same pressure condition.
- the value was the same as or slightly lower than that of the material.
- the reason for this is that although the bonding layer of this example increases the Al content which has a great effect on the stress relaxation mechanism, the Al-rich phase ( ⁇ phase) dendritic crystals become slightly larger or approach each other. It is conceivable that the fracture is likely to occur at the interface with the Zn—Al alloy layer formed inside.
- Example 3 In this embodiment, the SiC semiconductor element and the Cu / SiN / Cu insulating substrate are bonded via a bonding material (thickness: 60 ⁇ m) of a Zn—Al eutectoid alloy composed of 22 mass% Al—78 mass% Zn.
- the junction microstructure and the junction reliability of the actual semiconductor device obtained in this way were evaluated.
- the actual semiconductor device of this example has the configuration and structure shown in FIG. 5, and the size of the SiC semiconductor element is 4.7 mm ⁇ 4.7 mm.
- the result of the bonding reliability of the SiC semiconductor device according to this example is shown in FIG. 7 together with the bonding process.
- the bonding process is carried out in a nitrogen gas atmosphere while being pressurized at 18 MPa and held at 240 ° C. for about 20 minutes, and then heated to 390 ° C. in the pressurized state. Hold for 20 minutes and then cool slowly.
- the heating at 240 ° C. is a process adopted to promote surface cleaning and adhesion of the joint surface by utilizing the superplastic phenomenon of the Zn—Al eutectoid alloy.
- the bonding layer formed by the bonding process shown in FIG. 7A has a measured Al-rich phase ( ⁇ phase) dendritic arm spacing (DAS) of 0.20 ⁇ m, and was obtained from the curve shown in FIG.
- the Al content is 32% by mass.
- a temperature cycle test is performed using the SiC semiconductor device bonded in this way, and the cross section after the test is cut and polished in the vertical direction at the left end, the center, and the right end.
- the observed cross-sectional photograph is shown in FIG.
- the result of (b) of FIG. 7 is a thing after performing the temperature cycle test of 100 cycles on the conditions of room temperature ⁇ 300 degreeC.
- both the interface with the SiC / solder bonding material and the solder bonding material / Cu interface are photographed at 500 times and 2000 times, respectively. It shows.
- the bonding layer of the present example is a voidless, and the SiC / solder bonding material and the solder bonding material / Cu interface even after a temperature cycle test performed under severe conditions of room temperature to 300 ° C. No cracks were observed at both interfaces, confirming excellent connection reliability. It can also be seen that the wettability of the joint surface is sufficiently secured.
- Example 4 In the joining process shown in Example 3, instead of 390 ° C. set as the half-melting temperature, the junction microstructure and joining reliability of the actual semiconductor device when the temperature was set to 450 ° C. were evaluated by the same method as Example 3.
- the temperature After holding at 240 ° C. for about 20 minutes while applying pressure of 18 MPa in a nitrogen atmosphere, the temperature is raised to 450 ° C. in the pressurized state, and the temperature is maintained at that temperature for 5 to 10 minutes, and then gradually. This is a method of cooling.
- the superplastic phenomenon of the Zn—Al eutectoid alloy was utilized by heating at 240 ° C. as in Example 3.
- the bonding layer formed in this way is a voidless, the measured Al-rich phase ( ⁇ phase) dendritic arm spacing (DAS) is 0.13 ⁇ m, and the Al content obtained from the curve shown in FIG. 50% by mass.
- the temperature cycle test of the actual semiconductor device after bonding is performed under the condition of room temperature to 300 ° C., and the bonding reliability is evaluated by observing the cross section of the bonded portion after each cycle of 100 cycles, 300 cycles and 500 cycles. did. As a result, even after 500 cycles, no cracks were observed in both the SiC / solder bonding material and the solder bonding material / Cu interface, and it was confirmed that the connection reliability was excellent.
- the bonding layer thus formed had a measured Al-rich phase ( ⁇ phase) dendrid arm spacing (DAS) of 0.30 ⁇ m, and the Al content determined from the curve shown in FIG. 2 was 22% by mass. There was no change in composition.
- ⁇ phase Al-rich phase
- DAS dendrid arm spacing
- a temperature cycle test of the actual semiconductor device after bonding was performed under conditions of room temperature and 300 ° C., and the bonding reliability was evaluated by observing a cross section of the bonded portion after the completion of each cycle of 100 cycles, 300 cycles, and 500 cycles. As a result, it was found that after 300 cycles, the presence of minute cracks was observed from both edges at both the SiC / solder joint material and the solder joint material / Cu joint interface, and a large crack was developed at 500 cycles.
- Example 5 an example of a joining structure formed by repeating the operation of holding a desired time in a state in which a joining material of a Zn—Al eutectoid alloy is pressurized and heated to a semi-melting temperature region will be shown. .
- a joining material of a Zn—Al eutectoid alloy is pressurized and heated to a semi-melting temperature region.
- pressurization was performed at 450 ° C. in the semi-melting temperature range according to the same conditions as those shown in Example 4, and then cooled to 400 ° C. in the solid phase temperature range.
- the composition of the joint becomes a Zn—Al eutectoid alloy composed of 50 mass% Al-50 mass% Zn as shown in Example 4. It can be seen from FIG. 1 that the semi-melting temperature region of the bonding material having the above composition changes from 470 ° C. to 500 ° C. or more. Therefore, as the second operation, the temperature was raised to 500 ° C. in the semi-melting temperature range while pressurizing again in a nitrogen gas atmosphere, and kept at that temperature for 20 minutes, and then gradually cooled.
- the bonding layer thus formed is a voidless, the measured Al-rich phase ( ⁇ phase) dendritic arm spacing (DAS) is 0.11 ⁇ m, and the Al content obtained from the curve shown in FIG. 55% by mass.
- a temperature cycle test of the actual semiconductor device after bonding was performed under conditions of room temperature and 300 ° C., and the bonding reliability was evaluated by observing a cross section of the bonded portion after the completion of each cycle of 100 cycles, 300 cycles and 500 cycles. As a result, even after 500 cycles, no cracks were observed at both of the SiC / solder bonding material and the solder bonding material / Cu interface, and it was confirmed that the connection reliability was excellent as in Example 4. .
- the actual semiconductor device having the SiC semiconductor element has the Al-rich phase ( ⁇ phase) dendritic arm spacing (DAS) reduced and the Al content contained in the bonding layer is increased.
- a large stress buffering effect can be obtained by forming the structure.
- SiC Al-rich phase
- DAS dendritic arm spacing
- the SiC semiconductor element and the Cu / SiN / Cu insulating substrate are bonded via a bonding material (thickness 200 ⁇ m) of a Zn—Al eutectoid alloy composed of 22 mass% Al-78 mass% Zn.
- the junction microstructure and the junction reliability of the actual semiconductor device obtained in this way were evaluated.
- the real semiconductor device of the present embodiment has the same configuration and structure as that shown in FIG. In the temperature profile shown in FIG. 7 (a), the junction of the SiC semiconductor device according to the present example is 250 ° C. instead of 240 ° C. in the temperature profile shown in FIG. The same process as shown in FIG. 7 was performed except that 450 ° C.
- FIG. 8 shows a schematic diagram of the bonding process according to this embodiment.
- the bonding layer formed in this example has a measured Al-rich phase ( ⁇ phase) dendrid arm spacing (DAS) of 0.16 ⁇ m, and the Al obtained from the curve shown in FIG. Content is 42 mass% (63 atomic%).
- FIG. 9 shows an appearance photograph after joining. As can be seen from FIG. 9, after bonding, Al—Zn solder is pushed out of the SiC semiconductor element and eluted to the periphery. The eluted Al—Zn solder contained more Zn than the initial Al—Zn bonding material.
- FIG. 10 is a cross-sectional photograph in which a temperature cycle test is performed using the SiC semiconductor device bonded in this manner, and the bonded section after the test is cut and polished in the vertical direction and observed at the substantially central portion. Show.
- the results in FIG. 10 are the results after conducting a temperature cycle test after 500 cycles under the condition of ⁇ 40 to 200 ° C. and additionally 1000 cycles under the condition of 50 to 300 ° C.
- (a) and (b) are cross-sectional photographs showing different magnifications.
- the bonding layer of this example is voidless, and SiC / Al— even after a temperature cycle test conducted under very severe conditions of ⁇ 40 ° C. to 200 ° C. ⁇ 500 cycles + 50 ° C. to 300 ° C. ⁇ 1000 cycles. No cracks are observed at both the Zn solder joint and the Al—Zn solder joint / Cu interface, and it has very excellent connection reliability due to the development of a higher stress relaxation function utilizing transformation superplasticity. confirmed. It can also be seen that the wettability of the joint surface is sufficiently secured.
- FIG. 11 shows a diode using the Zn—Al eutectoid alloy bonding material of the present invention.
- 7 is a cylindrical heat sink made of, for example, copper whose bottom is closed and the top is opened
- 8 is a silicon chip having a diode function
- 9 is a buffer plate made of copper-invar (iron nickel alloy) -copper
- 10 is A buffer electrode 9 is formed on the bottom of the cylindrical heat sink 7 via a Zn-Al eutectoid alloy bonding material 11 on a lead electrode composed of a disk portion 10a and a lead 10b extending vertically from the disk portion.
- the silicon chip 8 is bonded via the Zn—Al based alloy bonding material 12, and the disk portion 4 a of the lead electrode 4 is bonded thereto via the Zn—Al eutectoid alloy bonding material 13.
- a Ni—P plating film is formed on the surfaces of the silicon chip 8, the buffer plate 9, and the disk portion 10 a that are in contact with the Zn—Al eutectoid alloy bonding material.
- the Zn—Al eutectoid alloy bonding materials 11, 12, and 13 an alloy composed of 22 wt% Al—78 wt% Zn is used, and the cylindrical heat sink 1 and the heat sink 1 according to the bonding process shown in Example 4 or 6 are used.
- Reference numeral 14 shown in FIG. 11 denotes silicon rubber filled in the cylindrical heat sink 1.
- the diode having such a configuration is press-fitted into a through hole of a cooling fin having a predetermined number of through holes and used in a rectifier for an automobile. Since this type of rectifier is disposed in an engine room and is used in a severely and thermally severe environment, a bonding material having a high temperature and high mechanical strength is required.
- the bonding layer structure of the Zn—Al eutectoid alloy bonding material of the present invention it is possible to realize a bonded portion that can withstand high temperatures of 250 ° C. or more and has ductility and strength.
- SiC silicon carbide
- 13 and 14 are a plan view and a cross-sectional view of a 300A class IGBT module using the Zn—Al eutectoid alloy bonding material of the present invention.
- FIG. 12 shows an embodiment of the present invention, and shows a plan view of one 300A class module unit.
- 13 is a cross-sectional view taken along line AA in FIG. 12
- FIG. 14 is a cross-sectional view taken along line BB in FIG.
- 101 is a metal substrate that functions as a heat dissipation plate and a support plate
- 102 is a two-layered metal substrate 101
- a Zn-Al eutectoid alloy bonding layer 103 made of 22 mass% Al-78 mass% Zn is formed.
- 104 is a circuit layer made of, for example, Ni / Cu formed on each ceramic substrate 102, and the circuit layer 104 is separated.
- a first part 104a serving as a T-shaped collector common electrode
- a strip-shaped second part 104b serving as an emitter electrode
- a strip-shaped third serving as a gate electrode.
- Part 104c the first part 104a at the center, the second part 104b on one leg side of the first part 104a, and the third part 104c on the other side. It is located.
- an Al layer 105 is formed on the Ni layer.
- the anode side 106 is arranged on the legs of the first portion 104a of the circuit layer 104, and is arranged through the Zn—Al eutectoid alloy bonding layer 107 made of 22 mass% Al-78 mass% Zn series.
- the IGBT chip 108 bonded according to the bonding process shown in Example 4 or 6 is a Zn—Al eutectoid system in which the cathode side is made of 22 mass% Al-78 mass% Zn series on the upper side of the first portion 104a.
- the diode chip 110 which is bonded according to the bonding process shown in Example 4 or 6 through the alloy bonding layer 109, is a metal layer 111 mainly composed of Al formed on the emitter layer of the IGBT chip 106 and the second layer.
- a circuit element in which three parallel-connected IGBT chips 106 and one diode chip 108 are connected in reverse parallel is formed on one ceramic substrate 102, and 2 on one metal substrate 101. Circuit elements are formed.
- two circuit elements on one metal substrate 101 are connected in series, three of them are connected in parallel, and the connection point of each circuit element is used as an AC output terminal. May be used as a DC input terminal.
- the number of parallel connections of the IGBT chip 106 and the diode chip 108 is increased, and when the voltage is increased, the number of serial connections of the IGBT chip 106 and the diode chip 108 may be increased.
- FIG. 15 is a schematic cross-sectional view showing a power MOS transistor having a bonding layer structure formed from the Zn—Al eutectoid alloy bonding material of the present invention.
- 21 is a metal substrate that functions as a heat sink and a support plate
- 22 is the above-described implementation by the Zn—Al eutectoid alloy bonding layer 23 made of 22 mass% Al-78 mass% Zn based on the metal substrate 21.
- the power MOS transistor substrate 26, 27 and 28 bonded and fixed in accordance with the bonding process shown in the fourth or sixth embodiment are anode electrodes made of aluminum provided in the anode region, the cathode region and the gate region of the power MOS transistor substrate. A cathode electrode and a gate electrode. Naturally, the gate electrode 28 is provided on the gate region via the insulating layer 29.
- Reference numerals 30 and 31 denote a Zn-Al eutectoid alloy bonding layers 32 and 33 made of 22 mass% Al-78 mass% Zn based on the cathode electrode 27 and the gate electrode 28, respectively, according to the bonding process shown in Example 4 or 6.
- the cathode external electrode and the gate external electrode are bonded and fixed.
- the cathode external electrode 30 and the gate external electrode 31 may be integrated with, for example, a resin filled therebetween.
- This embodiment is characterized in that the cathode electrode 27 and the gate electrode 28 are directly joined to the cathode external electrode 30 and the gate external electrode 31 without using bonding wires.
- the MOS transistor base 24 in this embodiment can use silicon and silicon carbide.
- silicon carbide can maintain stable characteristics even at 500 ° C., it is possible to realize a high-temperature MOS transistor that can be used up to a temperature close to the temperature at which the bonding material is transformed into a solid-liquid shared state.
- the bonding layer structure formed from the Zn—Al eutectoid alloy bonding material of the present invention can be applied not only to the IGBT module but also to a general power module, a diode module and the like.
- the bonding layer structure of the present invention since the amount of Al having a stress buffering function increases, the stress relaxation effect is enhanced in the bonding layer, the bonding reliability can be improved, and the thermal conductivity can be improved.
- the superplastic phenomenon of the Zn-Al eutectoid alloy used in the present invention the wettability of the bonding interface is ensured and the stress relaxation effect is obtained, so that the high-temperature bonding strength and bonding reliability can be obtained. It is greatly improved and a long-life joint can be formed. Therefore, the semiconductor device in which wide gap semiconductor elements such as SiC, GaN, C (diamond), and Ga 2 O 3 are mounted by the bonding layer structure of the present invention meets the heat resistance requirement required for power devices or power electronics products. It is possible to answer, and it becomes possible to endure long-term use in a high temperature use environment of 200 ° C. or higher, particularly 250 ° C. or higher.
- connection structure of the present invention can be applied to other semiconductor devices such as a general power module and a diode module, and is extremely useful in industry.
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Abstract
Provided are a bonding layer structure using the alloy bonding material, forming method for the same, semiconductor device having said bonding layer structure and method for manufacturing the same, said bonding layer structure being a structure for a bonding layer formed by bonding materials A and B to be bonded using an alloy bonding material, wherein the alloy bonding material is a Zn-Al eutectoid alloy and, at the bonding surface for each of the materials A and B to be bonded and the alloy bonding material, the dendrite arm spacing (DAS) of the Al rich phase (α phase) included in the bonding layer present within the bonding surface for the material to be bonded having the smaller surface area or within the bonding surfaces for the materials to be bonded having the same surface areas is greater than 0.06 µm and less than 0.3 µm. Thus, it is possible to assure sufficient wettability, achieve high temperature bonding strength, and improve connection reliability due to the stress-relaxation effect.
Description
本発明は、高温の接合強度が高く、応力緩和効果によって接続信頼性の向上を図ることができる合金接合材による接合層構造及びその形成方法、並びに該接合層構造を有する半導体装置及びその製造方法に関する。
The present invention relates to a bonding layer structure using an alloy bonding material that has high bonding strength at high temperatures and can improve connection reliability by a stress relaxation effect, a method for forming the bonding layer structure, and a semiconductor device having the bonding layer structure and a method for manufacturing the semiconductor device. About.
パワー半導体素子のダイボンディングやパワーモジュールに搭載される半導体素子の実装基板への接合及び実装基板への放熱板の接合には従来からはんだ接合が使用されている。はんだ材としては、Ｓｎ－Ｐｂ系等の鉛を含むはんだは周知であるが、近年の環境問題への対応からＳｎ－Ｓｉ型はんだやＳｎ－Ｉｎ型はんだ等の低温はんだ、Ｓｎ－Ａｇ－Ｃｕ系はんだやＳｎ－Ｃｕ系はんだ等中温はんだの鉛レスはんだが開発・実用化されている。しかしながら、２５０℃以上で使用する高温はんだについては適当な鉛レスはんだ材がなく、高鉛はんだが使用されている。この高鉛はんだは、構成成分として８５質量％以上の鉛を含有しており、前記Ｓｎ－Ｐｂ共晶はんだに比べて環境への負荷が大きい。
Conventionally, solder bonding is used for die bonding of power semiconductor elements, bonding of semiconductor elements mounted on power modules to mounting boards, and bonding of heat sinks to mounting boards. As a solder material, Sn—Pb-based solder containing lead is well known, but in order to cope with recent environmental problems, low-temperature solder such as Sn—Si type solder or Sn—In type solder, Sn—Ag—Cu Medium-temperature lead-free solders such as Sn solder and Sn-Cu solder have been developed and put into practical use. However, there is no suitable lead-free solder material for high temperature solder used at 250 ° C. or higher, and high lead solder is used. This high lead solder contains 85% by mass or more of lead as a constituent component and has a larger environmental load than the Sn—Pb eutectic solder.
一方、パワーモジュールやパワーエレクトロニクス製品に使用されるパワー半導体素子としては、近年、従来のＳｉに代わり、耐熱性に優れ、１５０～２００℃の高温下で性能を安定して発揮できる炭化珪素（ＳｉＣ）、窒化ガリウム（ＧａＮ）、ダイアモンド（Ｃ）及び酸化ガリウム（Ｇａ２Ｏ３）等のワイドギャップ半導体への適用が検討されている。製品化が先行するＳｉＣ又はＧａＮの半導体素子は耐熱性に優れるが、それらのワイドギャップ半導体を実装基板等に接合した場合に、耐熱性は半導体素子だけでなく接合材料にも要求される。前記の高鉛はんだ材は高融点を有するものの、環境への負荷が大きく今後の使用が制限されるため、鉛レス代替はんだの検討が進められている。
On the other hand, as a power semiconductor element used in power modules and power electronics products, in recent years, silicon carbide (SiC), which has excellent heat resistance and can stably perform at a high temperature of 150 to 200 ° C., has been replaced with conventional Si. ), Gallium nitride (GaN), diamond (C), gallium oxide (Ga 2 O 3 ) and other wide gap semiconductors are being studied. SiC or GaN semiconductor elements that have been commercialized are excellent in heat resistance, but when these wide gap semiconductors are bonded to a mounting substrate or the like, heat resistance is required not only for the semiconductor elements but also for the bonding material. Although the above-mentioned high lead solder material has a high melting point, it has a large environmental load and is restricted from being used in the future.
鉛レスの代替高温はんだとしては、Ａｕ－Ｓｎ、Ａｕ－Ｓｉ、Ａｉ－Ｇｅ等のＡｕ系はんだ、Ｂｉ、Ｂｉ－Ｃｕ、Ｂｉ－Ａｇ等のＢｉ系はんだ、Ｚｎ、Ｚｎ－Ａｌ系はんだ等が報告されている。それらの中で、Ｚｎ、Ｚｎ－Ａｌ系はんだは、より高い融点を有するため、ＳｉＣ又はＧａＮ等のパワー用ワイドギャップ半導体素子の接合材としての期待が大きい。
Examples of lead-free alternative high-temperature solder include Au-based solders such as Au-Sn, Au-Si, and Ai-Ge, Bi-based solders such as Bi, Bi-Cu, and Bi-Ag, Zn, and Zn-Al-based solder. It has been reported. Among them, Zn, Zn—Al solder has a higher melting point, and therefore has high expectations as a bonding material for power wide gap semiconductor elements such as SiC or GaN.
Ｚｎ－Ａｌ系はんだとしては、例えば、特許文献１においてＡｌ：２～９重量％、Ｇｅ及び／又はＭｇ：０．０５～１重量％、残部をＺｎ及び不可避不純物からなる高温はんだ付用Ｚｎ合金が開示されている。前記特許文献１に記載のＺｎ－Ａｌ系はんだは、３８０℃付近の共晶温度を有するＺｎ－Ａｌ系共晶合金の融点を適当にさらに下げるために、Ｇｅ及び／又はＭｇ、又は更にＳｎ及び／又はＩｎが添加されている。
As the Zn—Al based solder, for example, in Patent Document 1, Al: 2 to 9% by weight, Ge and / or Mg: 0.05 to 1% by weight, the balance being Zn and inevitable impurities, Zn alloy for high temperature soldering Is disclosed. The Zn—Al solder described in Patent Document 1 is Ge and / or Mg, or further Sn and further in order to appropriately lower the melting point of a Zn—Al eutectic alloy having a eutectic temperature of around 380 ° C. / Or In is added.
また、特許文献２には、Ａｌを１．０質量％以上及び１５．０質量％以下を含有するＺｎ－Ａｌ系はんだにおいて、塑性変形を伴う圧延機を用いて作製したシート状のＰｂフリーはんだ合金が開示されている。このシート状はんだ合金は、高い伸び率と引張強度を有するため、濡れ性及び信頼性に優れ、特に加工性及び応力緩和性に優れる。本発明者等も、Ａｌを１７～３０質量％含有するＺｎ－Ａｌ共析系合金接合材が所定の温度領域で超塑性現象を発現することに着目し、この超塑性現象を利用することによって加工性や応力緩和性に優れる接合材を特許文献３において提案している。
Patent Document 2 discloses a sheet-like Pb-free solder produced using a rolling mill with plastic deformation in a Zn-Al solder containing Al in an amount of 1.0 mass% or more and 15.0 mass% or less. An alloy is disclosed. Since this sheet-like solder alloy has a high elongation and tensile strength, it is excellent in wettability and reliability, and particularly excellent in workability and stress relaxation properties. The present inventors have also noted that a Zn—Al eutectoid alloy bonding material containing 17 to 30% by mass of Al exhibits a superplastic phenomenon in a predetermined temperature range, and by utilizing this superplastic phenomenon, Patent Document 3 proposes a bonding material excellent in workability and stress relaxation properties.
一方、特許文献４には、Ｚｎ／Ａｌ／Ｚｎクラッド材を用いた接合材料が提案されている。この接合材料は、接続時の加熱によりＡｌ酸化物が溶融部表面に膜を生成することによって起こる濡れ性の低下を抑制するため、Ａｌ系合金層がＺｎ系合金層の間に挟まれた構造を有する。前記特許文献４に記載の接合材料は、Ｚｎ／Ａｌ／Ｚｎクラッド材によって良好な濡れ性を確保することができ、接続後にＡｌ系合金層が応力緩衝材として機能するため、高い接続信頼性を得ることができる。
On the other hand, Patent Document 4 proposes a bonding material using a Zn / Al / Zn clad material. This bonding material has a structure in which an Al-based alloy layer is sandwiched between Zn-based alloy layers in order to suppress a decrease in wettability caused by Al oxide forming a film on the surface of the melted part by heating during connection. Have The bonding material described in Patent Document 4 can ensure good wettability with a Zn / Al / Zn clad material, and since the Al-based alloy layer functions as a stress buffer after connection, it has high connection reliability. Obtainable.
パワーモジュールやパワーエレクトロニクス製品に使用される接合材料は、融点が高く、被接合材との濡れ性、接合時の加工性、及び接続信頼性の観点から応力緩和性に優れることが必要条件である。また、接合時の温度は、室温まで冷却されるときの大きな温度差から生じる熱膨張係数による応力の影響を低減するために比較的低い方が好ましいが、仮に接合温度が高くなっても応力緩和性に優れる接合材料であれば、接続信頼性を十分に確保することができる。したがって、従来のはんだ材料と比べて接合温度が比較的高いＺｎ－Ａｌ系はんだでは、応力緩衝性を有する構造を形成することが不可欠である。
Bonding materials used in power modules and power electronics products must have a high melting point and excellent stress relaxation from the viewpoints of wettability with materials to be bonded, workability during bonding, and connection reliability. . In addition, the temperature at the time of bonding is preferably relatively low in order to reduce the influence of stress due to the thermal expansion coefficient resulting from a large temperature difference when cooled to room temperature, but even if the bonding temperature becomes high, stress relaxation As long as the bonding material has excellent properties, connection reliability can be sufficiently ensured. Therefore, it is indispensable to form a structure having a stress buffering property in Zn—Al solder having a relatively high bonding temperature as compared with conventional solder materials.
しかしながら、前記特許文献１に記載のＺｎ－Ａｌ系はんだは、ＡｌがＺｎよりも還元性が強く酸化されやすく濡れ性を低下させるため、その組成の範囲内では合金の濡れ性が十分でない。この濡れ性の低下という問題に加え、はんだ接合における加工性や応力緩和性の点でも問題がある。ＺｎとＡｌは共晶合金を造ることによってある程度の柔軟性を持った軟らかい金属となるものの、Ｚｎの含有量が多いため、良好な加工性を有するには硬さの点で改良が必要である。また、接合後のＺｎ－Ａｌ系はんだ中に応力緩衝材として機能するＡｌ相の存在量が少ないため、応力緩衝性の点で不十分である。
However, the Zn—Al solder described in Patent Document 1 has a reducibility that is stronger than that of Zn and easily oxidizes, so that the wettability is lowered. Therefore, the wettability of the alloy is not sufficient within the range of the composition. In addition to the problem of reduced wettability, there are also problems in terms of workability and stress relaxation in solder joints. Zn and Al become a soft metal with a certain degree of flexibility by making a eutectic alloy, but because of the high Zn content, improvement in hardness is necessary to have good workability . In addition, since there is a small amount of Al phase functioning as a stress buffer material in the Zn—Al solder after bonding, it is insufficient in terms of stress buffer.
前記特許文献２に記載のＺｎ－Ａｌ系はんだは塑性変形によってシート状のものが作製されるが、Ａｌ含有量が９．０質量％を超えるに伴い、強度は高くなるものの、伸び率が低くなる傾向にある。また、応力緩衝材として機能するＡｌ相が十分な比率で存在するとは言えず、接合温度が高くなる点を考慮すると応力緩和性の一層の向上が求められる。このことは、前記特許文献２において、「Ａｌの含有量は、２．０質量％以上９．０質量％であるとさらに好ましい」と記載されていることからも容易に推察される。
The Zn—Al solder described in Patent Document 2 is formed into a sheet by plastic deformation, but the strength increases as the Al content exceeds 9.0 mass%, but the elongation is low. Tend to be. Further, it cannot be said that the Al phase functioning as a stress buffer material is present in a sufficient ratio, and considering the point that the bonding temperature becomes high, further improvement in stress relaxation properties is required. This is easily inferred from the fact that, in Patent Document 2, “Al content is more preferably 2.0% by mass or more and 9.0% by mass”.
前記特許文献３に記載のＺｎ－Ａｌ共析系合金接合材は、微細結晶粒の形成による超塑性現象を利用して比較的低い温度で接合を行うことができ加工性及び応力緩和性に優れる。しかしながら、被接合材の接合面とＺｎ－Ａｌ共析系合金接合材とを十分に接合させるため、接合界面層及び接合層の構造を最適化する点については十分に検討されておらず、高温の接合強度の向上が必要であるとともに、接合温度を上げた時に必要な応力緩和性についても、前記特許文献２に記載のＺｎ－Ａｌ系はんだと同様に、一層の向上が求められる。
The Zn—Al eutectoid alloy bonding material described in Patent Document 3 can be bonded at a relatively low temperature using the superplastic phenomenon due to the formation of fine crystal grains, and is excellent in workability and stress relaxation properties. . However, in order to sufficiently bond the bonding surface of the material to be bonded and the Zn—Al eutectoid alloy bonding material, the point of optimizing the structure of the bonding interface layer and the bonding layer has not been sufficiently studied. As with the Zn—Al solder described in Patent Document 2, further improvement is required for the stress relaxation required when the bonding temperature is raised.
また、前記特許文献４に記載のＺｎ／Ａｌ／Ｚｎクラッド材を用いた接合材料は、接続後に応力緩衝材として機能するＡｌ系合金層が形成されるため、応力緩和性に優れる。しかしながら、接合層に微小な亀裂が発生した場合には、その亀裂がＡｌ系合金属層と溶融して形成されるＺｎ－Ａｌ合金層との界面で進展しやすく、接合信頼性の点で所望の効果が得られていないのが実情である。前記Ｚｎ／Ａｌ／Ｚｎクラッド材は、Ａｌ層を薄くして接合加熱時にＡｌ系合金属層を消失することも検討されているが、Ａｌ合金組成部分が接合層内で大きな塊として残存しやすく、亀裂進展の抑制効果を十分に得ることが難しい。また、Ｚｎ／Ａｌ／Ｚｎクラッド材の作製工程において、Ｚｎ系合金層とＡｌ合金層との厚さを精度良く加工し、両者の接合面を最適な状態とするための熟練と細かな調整が必要となる。さらに、十分な応力緩和性を得るためには、Ｚｎ系合金層とＡｌ合金層の両者の厚さを、適用するデバイスごとに最適化して変える必要があり、汎用性のある接続材料として前記Ｚｎ／Ａｌ／Ｚｎクラッド材が適当であるとは必ずしも言えなかった。
The bonding material using the Zn / Al / Zn clad material described in Patent Document 4 is excellent in stress relaxation because an Al-based alloy layer that functions as a stress buffer material is formed after connection. However, when a minute crack occurs in the bonding layer, the crack is likely to propagate at the interface between the Al-based mixed metal layer and the Zn-Al alloy layer formed by melting, which is desirable in terms of bonding reliability. The fact is that the effect of has not been obtained. The Zn / Al / Zn clad material has been studied to make the Al layer thinner and to disappear the Al-based mixed metal layer during bonding heating, but the Al alloy composition part tends to remain as a large lump in the bonding layer. It is difficult to obtain a sufficient effect of suppressing crack propagation. In addition, in the manufacturing process of the Zn / Al / Zn clad material, skill and fine adjustment are required to accurately process the thicknesses of the Zn-based alloy layer and the Al alloy layer and to optimize the joint surface between them. Necessary. Furthermore, in order to obtain sufficient stress relaxation properties, it is necessary to optimize and change the thicknesses of both the Zn-based alloy layer and the Al alloy layer for each device to be applied. / Al / Zn clad material was not necessarily suitable.
本発明は、上記した従来の問題点に鑑みてなされたものであって、接合材としての濡れ性を十分に確保しつつ、且つ、高温の接合強度が高く、応力緩和効果によって接続信頼性の向上を図ることができる合金接合材による接合層構造及びその形成方法、並びに該接合層構造を有する半導体装置及びその製造方法に関する。
The present invention has been made in view of the above-described conventional problems, and sufficiently secures wettability as a bonding material, has high bonding strength at high temperatures, and has connection reliability due to a stress relaxation effect. The present invention relates to a bonding layer structure using an alloy bonding material that can be improved, a method for forming the bonding layer structure, a semiconductor device having the bonding layer structure, and a method for manufacturing the same.
本発明は、接合材としてＡｌの含有量が従来よりも比較的多いＺｎ－Ａｌ共析系合金を適用するとともに、接合後に得られるＺｎ－Ａｌ共析系合金の接合層において、Ａｌが有する応力緩衝機能を十分に発現できるように前記接合層に含まれるＡｌ（α相）の結晶組織の緻密度を高くした構造を形成することによって、上記の課題を解決できることを見出して本発明に到った。
The present invention applies a Zn—Al eutectoid alloy having a relatively high Al content as a bonding material, and the stress of Al in the bonding layer of the Zn—Al eutectoid alloy obtained after bonding. The present inventors have found that the above problem can be solved by forming a structure in which the density of the crystal structure of Al (α phase) contained in the bonding layer is increased so that the buffering function can be sufficiently expressed. It was.
本発明の構成は以下の通りである。
［１］本発明は、被接合材ＡとＢとを合金接合材によって接合し形成される接合層の構造であって、前記合金接合材がＺｎ－Ａｌ共析系合金であり、且つ、前記被接合材Ａ及びＢと前記合金接合材とのそれぞれの接合面において、どちらか小さな面積を有する方の被接合材の接合面内、又はどちらとも同じ面積を有する被接合材の接合面内に存在する接合層に含まれるＡｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）が０．０６μｍを超え、０．３μｍ未満であることを特徴とする合金接合材による接合層構造を提供する。
［２］本発明は、前記被接合材Ａ及びＢと前記合金接合材とのそれぞれの接合面において、どちらか小さな面積を有する方の被接合材の接合面内、又はどちらとも同じ面積を有する被接合材の接合面内に存在する接合層が、３０質量％を超え９７質量％以下のＡｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなる組成を有することを特徴とする前記［１］に記載の合金接合材による接合層構造を提供する。
［３］本発明は、前記［１］又は［２］に記載の接合層の構造を形成するための方法であって、前記被接合材ＡとＢとの間に、１７質量％～３０質量％Ａｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合材を介在し、加圧しながら前記接合材を半溶融温度領域に加熱した状態で所望の時間保持する操作を１回又は２回以上繰り返した後に徐冷することを特徴とする接合層構造の形成方法を提供する。
［４］本発明は、前記［１］又は［２］に記載の接合層の構造を形成するための方法であって、前記被接合材ＡとＢとの間に、３０質量％を超え９７質量％以下のＡｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合材を介在し、加圧又は無圧の状態で前記接合材を半溶融温度領域に加熱し、所望の時間保持した後に徐冷することを特徴とする接合層構造の形成方法を提供する。
［５］本発明は、前記接合材を半溶融温度領域に加熱した状態で所望の時間保持する操作の前に、超塑性現象を発現する温度領域に加熱した状態で所望の時間保持する操作を行うことを特徴とする前記［３］又は［４］に記載の接合層構造の形成方法を提供する。
［６］本発明は、前記接合材を半溶融温度領域に加熱し、加圧した状態で所望の時間保持し、３０質量％を超え９７質量％以下のＡｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなる組成を有する接合層構造を形成した後、そのまま加圧した状態で冷却し、変態超塑性点を通過させる操作を行うことを特徴とする前記［３］～［５］の何れかに記載の接合層構造の形成方法を提供する。
［７］本発明は、半導体基体、該半導体基体に直接又はセラミック基板を介して接合層によって接合された金属基板を備え、前記接合層が前記［１］又は［２］に記載の構造を有することを特徴とする半導体装置を提供する。
［８］本発明は、前記半導体基体がワイドギャップ半導体であることを特徴とする前記［７］に記載の半導体装置を提供する。
［９］本発明は、半導体基体、該半導体基体に直接又はセラミック基板を介して接合層によって接合された金属基板を備え、前記接合層の構造が前記［３］～［６］の何れかに記載の形成方法によって形成されることを特徴とする半導体装置の製造方法を提供する。
［１０］本発明は、前記半導体基体がワイドギャップ半導体であることを特徴とする前記［９］に記載の半導体装置の製造方法を提供する。 The configuration of the present invention is as follows.
[1] The present invention is a structure of a bonding layer formed by bonding materials A and B to be bonded by an alloy bonding material, wherein the alloy bonding material is a Zn—Al eutectoid alloy, and In each of the bonding surfaces of the materials A and B to be bonded and the alloy bonding material, in the bonding surface of the bonding material having the smaller area, or in the bonding surface of the bonding materials having the same area. Provided is a bonding layer structure made of an alloy bonding material, wherein the Al-rich phase (α phase) contained in the existing bonding layer has a dendritic arm spacing (DAS) of more than 0.06 μm and less than 0.3 μm. .
[2] In the present invention, in each of the bonding surfaces of the materials to be bonded A and B and the alloy bonding material, the bonding surface of the material to be bonded, which has the smaller area, or both have the same area. The bonding layer present in the bonding surface of the material to be bonded has a composition comprising an Al-0 to 1.5 mass% Cu-0 to 0.05 mass% Mg—Zn system that exceeds 30 mass% and is 97 mass% or less. A bonding layer structure using the alloy bonding material according to the above [1] is provided.
[3] The present invention is a method for forming the structure of the bonding layer according to the above [1] or [2], and is between 17 mass% and 30 mass between the materials A and B to be bonded. A Zn-Al eutectoid alloy bonding material composed of% Al-0 to 1.5 mass% Cu-0 to 0.05 mass% Mg-Zn is interposed, and the bonding material is placed in a semi-melting temperature region while applying pressure. Provided is a method for forming a bonding layer structure, characterized by repeating the operation of holding for a desired time in a heated state once or twice or more and then gradually cooling.
[4] The present invention is a method for forming the structure of the bonding layer according to [1] or [2], wherein the bonding material between A and B exceeds 30% by mass. A Zn-Al eutectoid alloy bonding material composed of Al-0 to 1.5% by mass Cu-0 to 0.05% by mass Mg-Zn based on the mass% or less is interposed, and the pressure is applied or no pressure is applied. There is provided a method for forming a bonding layer structure, characterized in that a bonding material is heated to a semi-melting temperature region, and is gradually cooled after being held for a desired time.
[5] In the present invention, the operation of holding the bonding material for a desired time in a state heated to a temperature region that develops a superplastic phenomenon is performed before the operation for holding the bonding material in a state heated to a semi-melting temperature region for a desired time. The method for forming a bonding layer structure according to the above [3] or [4] is provided.
[6] In the present invention, the bonding material is heated to a semi-melting temperature region and held for a desired time in a pressurized state. The bonding layer structure having a composition composed of −0 to 0.05 mass% Mg—Zn is formed, and then cooled in a pressurized state as it is, and an operation of passing through the transformation superplastic point is performed. A method for forming a bonding layer structure according to any one of [3] to [5] is provided.
[7] The present invention includes a semiconductor substrate and a metal substrate bonded to the semiconductor substrate directly or via a ceramic substrate, and the bonding layer has the structure described in [1] or [2]. A semiconductor device is provided.
[8] The present invention provides the semiconductor device according to [7], wherein the semiconductor substrate is a wide gap semiconductor.
[9] The present invention includes a semiconductor substrate, and a metal substrate bonded to the semiconductor substrate directly or via a ceramic substrate with a bonding layer, and the structure of the bonding layer is any one of [3] to [6] A method for manufacturing a semiconductor device, characterized by being formed by the described forming method.
[10] The present invention provides the method for manufacturing a semiconductor device according to [9], wherein the semiconductor substrate is a wide gap semiconductor.
［１］本発明は、被接合材ＡとＢとを合金接合材によって接合し形成される接合層の構造であって、前記合金接合材がＺｎ－Ａｌ共析系合金であり、且つ、前記被接合材Ａ及びＢと前記合金接合材とのそれぞれの接合面において、どちらか小さな面積を有する方の被接合材の接合面内、又はどちらとも同じ面積を有する被接合材の接合面内に存在する接合層に含まれるＡｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）が０．０６μｍを超え、０．３μｍ未満であることを特徴とする合金接合材による接合層構造を提供する。
［２］本発明は、前記被接合材Ａ及びＢと前記合金接合材とのそれぞれの接合面において、どちらか小さな面積を有する方の被接合材の接合面内、又はどちらとも同じ面積を有する被接合材の接合面内に存在する接合層が、３０質量％を超え９７質量％以下のＡｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなる組成を有することを特徴とする前記［１］に記載の合金接合材による接合層構造を提供する。
［３］本発明は、前記［１］又は［２］に記載の接合層の構造を形成するための方法であって、前記被接合材ＡとＢとの間に、１７質量％～３０質量％Ａｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合材を介在し、加圧しながら前記接合材を半溶融温度領域に加熱した状態で所望の時間保持する操作を１回又は２回以上繰り返した後に徐冷することを特徴とする接合層構造の形成方法を提供する。
［４］本発明は、前記［１］又は［２］に記載の接合層の構造を形成するための方法であって、前記被接合材ＡとＢとの間に、３０質量％を超え９７質量％以下のＡｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合材を介在し、加圧又は無圧の状態で前記接合材を半溶融温度領域に加熱し、所望の時間保持した後に徐冷することを特徴とする接合層構造の形成方法を提供する。
［５］本発明は、前記接合材を半溶融温度領域に加熱した状態で所望の時間保持する操作の前に、超塑性現象を発現する温度領域に加熱した状態で所望の時間保持する操作を行うことを特徴とする前記［３］又は［４］に記載の接合層構造の形成方法を提供する。
［６］本発明は、前記接合材を半溶融温度領域に加熱し、加圧した状態で所望の時間保持し、３０質量％を超え９７質量％以下のＡｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなる組成を有する接合層構造を形成した後、そのまま加圧した状態で冷却し、変態超塑性点を通過させる操作を行うことを特徴とする前記［３］～［５］の何れかに記載の接合層構造の形成方法を提供する。
［７］本発明は、半導体基体、該半導体基体に直接又はセラミック基板を介して接合層によって接合された金属基板を備え、前記接合層が前記［１］又は［２］に記載の構造を有することを特徴とする半導体装置を提供する。
［８］本発明は、前記半導体基体がワイドギャップ半導体であることを特徴とする前記［７］に記載の半導体装置を提供する。
［９］本発明は、半導体基体、該半導体基体に直接又はセラミック基板を介して接合層によって接合された金属基板を備え、前記接合層の構造が前記［３］～［６］の何れかに記載の形成方法によって形成されることを特徴とする半導体装置の製造方法を提供する。
［１０］本発明は、前記半導体基体がワイドギャップ半導体であることを特徴とする前記［９］に記載の半導体装置の製造方法を提供する。 The configuration of the present invention is as follows.
[1] The present invention is a structure of a bonding layer formed by bonding materials A and B to be bonded by an alloy bonding material, wherein the alloy bonding material is a Zn—Al eutectoid alloy, and In each of the bonding surfaces of the materials A and B to be bonded and the alloy bonding material, in the bonding surface of the bonding material having the smaller area, or in the bonding surface of the bonding materials having the same area. Provided is a bonding layer structure made of an alloy bonding material, wherein the Al-rich phase (α phase) contained in the existing bonding layer has a dendritic arm spacing (DAS) of more than 0.06 μm and less than 0.3 μm. .
[2] In the present invention, in each of the bonding surfaces of the materials to be bonded A and B and the alloy bonding material, the bonding surface of the material to be bonded, which has the smaller area, or both have the same area. The bonding layer present in the bonding surface of the material to be bonded has a composition comprising an Al-0 to 1.5 mass% Cu-0 to 0.05 mass% Mg—Zn system that exceeds 30 mass% and is 97 mass% or less. A bonding layer structure using the alloy bonding material according to the above [1] is provided.
[3] The present invention is a method for forming the structure of the bonding layer according to the above [1] or [2], and is between 17 mass% and 30 mass between the materials A and B to be bonded. A Zn-Al eutectoid alloy bonding material composed of% Al-0 to 1.5 mass% Cu-0 to 0.05 mass% Mg-Zn is interposed, and the bonding material is placed in a semi-melting temperature region while applying pressure. Provided is a method for forming a bonding layer structure, characterized by repeating the operation of holding for a desired time in a heated state once or twice or more and then gradually cooling.
[4] The present invention is a method for forming the structure of the bonding layer according to [1] or [2], wherein the bonding material between A and B exceeds 30% by mass. A Zn-Al eutectoid alloy bonding material composed of Al-0 to 1.5% by mass Cu-0 to 0.05% by mass Mg-Zn based on the mass% or less is interposed, and the pressure is applied or no pressure is applied. There is provided a method for forming a bonding layer structure, characterized in that a bonding material is heated to a semi-melting temperature region, and is gradually cooled after being held for a desired time.
[5] In the present invention, the operation of holding the bonding material for a desired time in a state heated to a temperature region that develops a superplastic phenomenon is performed before the operation for holding the bonding material in a state heated to a semi-melting temperature region for a desired time. The method for forming a bonding layer structure according to the above [3] or [4] is provided.
[6] In the present invention, the bonding material is heated to a semi-melting temperature region and held for a desired time in a pressurized state. The bonding layer structure having a composition composed of −0 to 0.05 mass% Mg—Zn is formed, and then cooled in a pressurized state as it is, and an operation of passing through the transformation superplastic point is performed. A method for forming a bonding layer structure according to any one of [3] to [5] is provided.
[7] The present invention includes a semiconductor substrate and a metal substrate bonded to the semiconductor substrate directly or via a ceramic substrate, and the bonding layer has the structure described in [1] or [2]. A semiconductor device is provided.
[8] The present invention provides the semiconductor device according to [7], wherein the semiconductor substrate is a wide gap semiconductor.
[9] The present invention includes a semiconductor substrate, and a metal substrate bonded to the semiconductor substrate directly or via a ceramic substrate with a bonding layer, and the structure of the bonding layer is any one of [3] to [6] A method for manufacturing a semiconductor device, characterized by being formed by the described forming method.
[10] The present invention provides the method for manufacturing a semiconductor device according to [9], wherein the semiconductor substrate is a wide gap semiconductor.
本発明の接合層構造は、接合材料としてＡｌの結晶構造が均一に分布したＺｎ－Ａｌ共析系合金を使用するため、接合後にＡｌのα結晶相が微細に分布した接合層が形成されるとともに、応力緩衝機能を有するＡｌの存在量が増えるため、接合層において応力緩和効果が高くなり、接合信頼性の向上を図ることができる。さらに、Ａｌは熱伝導性の高い金属であるため、本発明の接合層構造は熱伝導性にも優れる。濡れ性に関しても、Ｚｎ－Ａｌ共析合金中のＺｎ及びＺｎ－Ａｌ共晶の溶融によって十分に確保することができる。
Since the bonding layer structure of the present invention uses a Zn—Al eutectoid alloy in which the Al crystal structure is uniformly distributed as the bonding material, a bonding layer in which the α crystal phase of Al is finely distributed after bonding is formed. At the same time, since the amount of Al having a stress buffering function increases, the stress relaxation effect is enhanced in the bonding layer, and the bonding reliability can be improved. Furthermore, since Al is a metal having high thermal conductivity, the bonding layer structure of the present invention is also excellent in thermal conductivity. The wettability can also be sufficiently ensured by melting of Zn and Zn—Al eutectic in the Zn—Al eutectoid alloy.
本発明のように、従来よりもＡｌ含有量が比較的多い、Ｚｎ－Ａｌ共析系合金で発現する超塑性現象を利用することによって、被接合材との接合界面の酸化膜層の破壊除去等による清浄化を行うことができ、ボイドの発生が少ない接合界面を形成することができる。したがって、前記Ｚｎ－Ａｌ共析系合金からなる接合材を、超塑性現象が発現する温度領域に加熱した状態で所望の時間保持した後、半溶融温度領域に加熱した状態で所望の時間保持する操作を行う工程を行うことによって、接合界面の濡れ性が確保されるともに応力緩和効果が得られるため、高温の接合強度及び接合信頼性が大幅に向上し、高信頼性で、長寿命の接合部形成を実現できる。さらに、Ｚｎ－Ａｌ共析系合金からなる接合材を半溶融温度領域から加圧した状態で冷却し、変態超塑性点を通過させるによって得られる超塑性現象を利用することによって、より高い応力緩和機能を有する接合層構造を形成することができる。
As in the present invention, by utilizing the superplastic phenomenon that occurs in Zn-Al eutectoid alloy, which has a relatively higher Al content than conventional ones, the oxide film layer at the interface with the material to be bonded is destructively removed. Therefore, it is possible to form a bonding interface with less voids. Therefore, the bonding material made of the Zn—Al eutectoid alloy is held for a desired time in a state where it is heated to a temperature region where a superplastic phenomenon occurs, and then held for a desired time in a state where it is heated to a semi-melting temperature region. By performing the operation step, the wettability of the bonding interface is ensured and the stress relaxation effect is obtained, so the high-temperature bonding strength and bonding reliability are greatly improved, and high-reliability and long-life bonding. Part formation can be realized. Furthermore, by using a superplastic phenomenon obtained by cooling a bonding material made of a Zn-Al eutectoid alloy under pressure from the semi-melting temperature range and passing through the transformation superplasticity point, higher stress relaxation is achieved. A bonding layer structure having a function can be formed.
本発明の接合層構造によってＳｉＣ、ＧａＮ、Ｃ（ダイヤモンド）及びＧａ２Ｏ３等のワイドギャップ半導体素子を実装した半導体装置は、パワーデバイス又はパワーエレクトロニクス製品等で求められる耐熱性の要求に答えることができ、２００℃以上、特に２５０℃以上の高温使用環境において長期間の使用に耐えることが可能になる。
The semiconductor device in which wide gap semiconductor elements such as SiC, GaN, C (diamond) and Ga 2 O 3 are mounted by the bonding layer structure of the present invention answers the heat resistance requirement required for power devices or power electronics products. And can withstand long-term use in a high temperature use environment of 200 ° C. or higher, particularly 250 ° C. or higher.
本発明の接合層は、被接合材ＡとＢとをＺｎ－Ａｌ共析系合金によって接合し形成される接合層において、前記被接合材Ａ及びＢのどちらか小さな面積を有する方の被接合材の接合面内、又はどちらとも同じ面積を有する被接合材の接合面内に存在する接合層に含まれるＡｌリッチ相（α相）の結晶組織が従来よりも緻密な状態で含まれる構造を有することを特徴とする。本発明の接合層においてＡｌリッチ相（α相）はＺｎリッチ相とは明確に区別して観測されるため、Ａｌリッチ相（α相）の結晶組織を接合層内で同定することが容易である。この接合層構造は、応力緩衝材として機能するＡｌ結晶が接合層内部で高密度に存在することを意味し、接合層の応力緩和性を高める効果を得ることができる。
The bonding layer of the present invention is a bonding layer formed by bonding materials to be bonded A and B with a Zn—Al eutectoid alloy, and has a smaller area of either of the materials to be bonded A or B. A structure in which the crystal structure of the Al-rich phase (α phase) included in the bonding layer existing in the bonding surface of the material or in the bonding surface of the material to be bonded having the same area is included in a denser state than before. It is characterized by having. In the bonding layer of the present invention, since the Al-rich phase (α phase) is clearly distinguished from the Zn-rich phase, it is easy to identify the crystal structure of the Al-rich phase (α phase) in the bonding layer. . This bonding layer structure means that Al crystals functioning as a stress buffering material are present at a high density inside the bonding layer, and an effect of increasing the stress relaxation property of the bonding layer can be obtained.
前記被接合材ＡとＢとの組合せは、例えば、半導体素子と金属フレーム、半導体素子とプリント基板、セラミック基板又は金属基板等の実装基板、及び前記実装基板と放熱板等であるが、前記被接合材ＡとＢを個別に特定する必要はない。本発明において接合層構造として着目するのは、前記被接合材Ａ及びＢの両者がＺｎ－Ａｌ共析系合金を介して接合して形成される接合面である。それに対して、前記被接合材Ａ及びＢのどちらか一方だけが前記Ｚｎ－Ａｌ共析系合金接合材と接触する接合面は、他方の接合面が拘束されていないため発生応力が相対的に小さくなる。したがって、前記被接合材Ａ及びＢのどちらか小さな面積を有する方の被接合材の接合面内、又はどちらとも同じ面積を有する被接合材の接合面内に存在する接合層に含まれるＡｌリッチ相（α相）の結晶組織の緻密さを規定することが本発明において重要な因子となる。
Examples of the combination of the materials to be bonded A and B include a semiconductor element and a metal frame, a semiconductor element and a printed circuit board, a mounting substrate such as a ceramic substrate or a metal substrate, and the mounting substrate and a heat dissipation plate. It is not necessary to specify the bonding materials A and B individually. In the present invention, attention is focused on the bonding surface formed by bonding both of the materials to be bonded A and B through a Zn—Al eutectoid alloy. On the other hand, since only one of the materials to be joined A and B is in contact with the Zn—Al eutectoid alloy joining material, the other joining surface is not constrained, so the generated stress is relatively low. Get smaller. Therefore, the Al-rich material contained in the bonding layer existing in the bonding surface of the bonded material having the smaller area of the bonded materials A and B or in the bonded surface of the bonded material having the same area. It is an important factor in the present invention to define the fineness of the crystal structure of the phase (α phase).
本発明において、Ａｌリッチ相（α相）の結晶組織の緻密さはデンドライドアームスペーシング（ＤＡＳ）の値によって規定することができる。デンドライドアームスペーシング（ＤＡＳ）の値は、軽金属協会指定の二次技法により測定した値である。測定方法は、前記被接合材Ａ及びＢの両者がＺｎ－Ａｌ共析系合金を介して接合して形成される接合面を、接合面に対して垂直方向に切り出し、接合面全体を樹脂に埋め込んだ後、観察可能な状態までエメリー紙及びバフ研磨によって鏡面仕上げを行い、エッチングの後、２００～４００倍程度の光学顕微鏡を用いて組織観察を行う。顕微鏡組織観察して、α－Ａｌ晶［Ａｌリッチ相（α相）］の樹枝状晶（デンドライド）の実質的に平行に成長している２次アームの複数本（ｎ本とする、ただしｎは５本以上）を視野に選び、それらのデンドライドアームとほぼ直交するように直線Ｐを引き、ｎ本のデンドライドアームが直線Ｐを横切る距離Ｌｉを、それらのデンドライドアームの本数ｎより１本少ない数、すなわち（ｎ－１）で除し、これをＤＡＳとする。つまり二次デンドライドアームスペーシング（ＤＡＳ）＝Ｌｉ／（ｎ－１）とする。この測定を数視野繰り返した後、平均値をＤＡＳとして求める。
In the present invention, the denseness of the crystal structure of the Al-rich phase (α phase) can be defined by the value of dendrid arm spacing (DAS). The value of Dendride Arm Spacing (DAS) is a value measured by a secondary technique designated by the Light Metal Association. The measuring method is to cut out a joining surface formed by joining both of the materials to be joined A and B through a Zn—Al eutectoid alloy in a direction perpendicular to the joining surface, and use the entire joining surface as a resin. After embedding, mirror finishing is performed by emery paper and buffing until it is observable, and after etching, the structure is observed using an optical microscope of about 200 to 400 times. By microscopic observation, α-Al crystals [Al-rich phase (α-phase)] dendrites (dendrites) of a plurality of secondary arms growing in parallel (n, where n 5 or more) is selected for the field of view, and a straight line P is drawn so as to be substantially orthogonal to the dendritic arms, and the distance Li that the n dendritic arms cross the straight line P is determined from the number n of the dendritic arms. Divide by one less number, ie, (n-1), and let this be DAS. That is, the secondary dendritic arm spacing (DAS) = Li / (n−1). After repeating this measurement for several fields, the average value is determined as DAS.
本発明の接合層構造は、前記デンドライドアームスペーシング（ＤＡＳ）が０．０６μｍを超え、０．３μｍ未満であることが必要である。本発明者等の検討によると、前記特許文献３に記載の２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合材を４３０～４８０℃の温度範囲で１～３０分加熱して半溶融状態の後に徐冷して得られる接合層は、測定したデンドライドアームスペーシング（ＤＡＳ）が０．３μｍである。この組成のＺｎ－Ａｌ共析系合金接合材は、２００℃のせん断強度が高鉛はんだ（Ｐｂ－Ｓｎ－Ａｇ）よりもやや高いものの、十分な強度とは言えず、温度サイクル試験によって評価した接合信頼性も所望の結果を得ることが困難であった。本発明者等はさらに検討を進め、Ｚｎ－Ａｌ共析系合金接合材により形成される接合層のＡｌリッチ相（α相）結晶組織の緻密度を高めれば接合信頼性の一層の向上を図れることが分かった。本発明においては、Ａｌリッチ相（α相）結晶組織の緻密度を把握できる物理量としてデンドライドアームスペーシング（ＤＡＳ）に着目し、このＤＡＳを０．３μｍ未満と規定することによって所望の効果を奏することができる。
The bonding layer structure of the present invention requires that the dendritic arm spacing (DAS) is more than 0.06 μm and less than 0.3 μm. According to the study by the present inventors, the Zn—Al eutectoid alloy bonding material comprising 22 mass% Al-78 mass% Zn system described in Patent Document 3 is applied at a temperature range of 430 to 480 ° C. for 1 to 30 minutes. The bonding layer obtained by heating and gradually cooling after a semi-molten state has a measured dendritic arm spacing (DAS) of 0.3 μm. The Zn—Al eutectoid alloy bonding material having this composition has a slightly higher shear strength at 200 ° C. than high lead solder (Pb—Sn—Ag), but it cannot be said to be sufficient strength, and was evaluated by a temperature cycle test. It has been difficult to obtain a desired result for the bonding reliability. The present inventors have further studied, and if the density of the Al-rich phase (α phase) crystal structure of the bonding layer formed by the Zn—Al eutectoid alloy bonding material is increased, the bonding reliability can be further improved. I understood that. In the present invention, attention is paid to dendritic arm spacing (DAS) as a physical quantity capable of grasping the density of the Al-rich phase (α phase) crystal structure, and a desired effect is obtained by defining this DAS as less than 0.3 μm. be able to.
本発明者等は、次に、本発明の接合層についてＺｎ－Ａｌの含有比率を変えたときのデンドライドアームスペーシング（ＤＡＳ）の変化を測定した。図１はＺｎ－Ａｌ共析系合金の平衡状態図であり、図中には、各Ａｌ含有比率において測定したデンドライドアームスペーシング（ＤＡＳ）の一部を四角で囲んだ枠内に示している。四角で囲んだ枠内のデンドライドアームスペーシング（ＤＡＳ）の値は、点線矢印で示す各Ａｌ含有比率に対応するものである。図１の結果に基づいて、Ｚｎ－Ａｌの含有比率とデンドライドアームスペーシング（ＤＡＳ）の関係をプロットしたのが図２である。
Next, the inventors measured the change in dendritic arm spacing (DAS) when the Zn—Al content ratio of the bonding layer of the present invention was changed. FIG. 1 is an equilibrium diagram of a Zn—Al eutectoid alloy. In the figure, a part of dendritic arm spacing (DAS) measured at each Al content ratio is shown in a frame surrounded by a square. . The value of Dendride Arm Spacing (DAS) in the frame surrounded by a square corresponds to each Al content ratio indicated by a dotted arrow. FIG. 2 plots the relationship between the content ratio of Zn—Al and the dendritic arm spacing (DAS) based on the results of FIG.
図２から、デンドライドアームスペーシング（ＤＡＳ）はＡｌ含有比率が大きくなるほど小さな値を示し、Ａｌ含有率が１００％に近づくにつれて０．０６μｍに収束することが分かる。Ａｌ含有率が１００％、すなわち純アルミの場合は融点が６６０℃と非常に高いだけでなく、単独組成では固液相を形成することができず、接合加熱による溶融が非常に困難である。半導体素子として耐熱性を有するＳｉＣ、ＧａＮ、Ｃ（ダイヤモンド）及びＧａ２Ｏ３等のワイドギャップ半導体を使用したとしても、短時間に加熱できる温度は６００℃未満、好ましくは５００℃以下であるため、Ａｌ単独組成を接合材として使用することはできない。したがって、本発明の接合層構造は、デンドライドアームスペーシング（ＤＡＳ）が０．０６μｍを超えるＡｌリッチ相（α相）結晶構造を有する必要がある。
From FIG. 2, it can be seen that dendritic arm spacing (DAS) shows a smaller value as the Al content ratio increases, and converges to 0.06 μm as the Al content ratio approaches 100%. In the case of Al content of 100%, that is, pure aluminum, not only the melting point is very high at 660 ° C., but a single composition cannot form a solid-liquid phase, and melting by joining heating is very difficult. Even when a wide-gap semiconductor such as SiC, GaN, C (diamond), and Ga 2 O 3 having heat resistance is used as the semiconductor element, the temperature that can be heated in a short time is less than 600 ° C., preferably 500 ° C. or less. A single composition of Al cannot be used as a bonding material. Therefore, the bonding layer structure of the present invention needs to have an Al-rich phase (α phase) crystal structure with a dendritic arm spacing (DAS) exceeding 0.06 μm.
本発明の接合層構造は、少なくともデンドライドアームスペーシング（ＤＡＳ）が０．０６μｍを超え、０．３μｍ未満であることが必要であるが、応力緩和性の効果を十分に得るためには、Ｚｎ－Ａｌ共析系合金からなる接合層においてＡｌの含有比率が３０質量％を超え、９７質量％以下であることが好ましい。Ａｌの含有比率が３０質量％を超え、９７質量％以下であるときに、Ａｌが有する応力緩衝機能を十分に発現することができる。Ａｌの含有率増大に伴う応力緩衝機能は、Ａｌの含有比率が２２～３０質量％の範囲で発現するようになり、３０質量％を超えたときに接合信頼性に対して顕著な効果を示すようになる。また、Ａｌの含有比率が９７質量％を超えると、接合材中のＺｎ含有比率が非常に小さいため、濡れ性の点で接合材としての使用が困難になる。さらに、図１に示すように、Ａｌの含有比率の増大に伴い固液溶融状態を示す温度が高くなるため、半導体素子の耐熱限界温度を超えた加熱温度で接合を行うことが必要になる場合がある。ＳｉＣ、ＧａＮ、Ｃ（ダイヤモンド）又はＧａ２Ｏ３の半導体素子の短時間耐熱温度等を考慮すると、接合時の加熱温度は少なくとも６００℃未満がより好ましく、５００℃以下が特に好ましい。したがって、Ｚｎ－Ａｌ共析系合金からなる接合層に含まれるＡｌの含有比率の上限は９７質量％以下にあることが好ましく、８０質量％未満がより好ましく、さらに６０質量％未満が特に好ましい。
In the bonding layer structure of the present invention, at least the dendritic arm spacing (DAS) needs to be more than 0.06 μm and less than 0.3 μm, but in order to obtain a sufficient stress relaxation effect, Zn In the bonding layer made of an Al eutectoid alloy, the Al content is preferably more than 30% by mass and 97% by mass or less. When the Al content ratio exceeds 30% by mass and is 97% by mass or less, the stress buffering function of Al can be sufficiently exhibited. The stress buffering function accompanying the increase in the Al content is realized when the Al content is in the range of 22 to 30% by mass, and has a remarkable effect on the bonding reliability when the Al content exceeds 30% by mass. It becomes like this. On the other hand, if the Al content exceeds 97% by mass, the Zn content in the bonding material is very small, making it difficult to use as a bonding material in terms of wettability. Furthermore, as shown in FIG. 1, when the Al content ratio increases, the temperature indicating the solid-liquid molten state becomes higher, so that it is necessary to perform bonding at a heating temperature exceeding the heat resistance limit temperature of the semiconductor element. There is. Considering the short-time heat-resistant temperature of the semiconductor element of SiC, GaN, C (diamond) or Ga 2 O 3 , the heating temperature at the time of bonding is more preferably at least less than 600 ° C., and particularly preferably 500 ° C. or less. Therefore, the upper limit of the content ratio of Al contained in the bonding layer made of a Zn—Al eutectoid alloy is preferably 97% by mass or less, more preferably less than 80% by mass, and particularly preferably less than 60% by mass.
本発明のＡｌの含有比率が３０質量％を超え、且つ、９７質量％以下、より好ましくは８０質量％未満、特に好ましくは７０質量％未満の範囲を有するＺｎ－Ａｌ共析系合金接合層は、図２に示す曲線から概算されるデンドライドアームスペーシング（ＤＡＳ）によって規定しても良い。その場合は、デンドライドアームスペーシング（ＤＡＳ）として０．２２μｍ未満で、且つ、０．０６８μｍ、より好ましくは０．０８μｍ、特に好ましくは０．０９μｍを超える範囲を有する接合層構造に規定することができる。
A Zn—Al eutectoid alloy bonding layer having an Al content ratio of more than 30% by mass and 97% by mass or less, more preferably less than 80% by mass, and particularly preferably less than 70% by mass is provided. Alternatively, it may be defined by dendritic arm spacing (DAS) estimated from the curve shown in FIG. In such a case, the dendride arm spacing (DAS) should be defined as a bonding layer structure having a range of less than 0.22 μm and 0.068 μm, more preferably 0.08 μm, and particularly preferably more than 0.09 μm. it can.
本発明で使用するＺｎ－Ａｌ共析系合金は、構成成分としてＡｌ及びＺｎを含むことが必須であるが、融点を下げたり、加工性、高温強度、疲労強度（耐クリープ性）又は応力緩和性を向上させる目的で、それら以外にもＣｕ、Ｍｇ、Ｇｅ、Ｓｎ、Ｉｎ、Ａｇ、Ｎｉ、Ｐ等を微量成分として添加しても良い。本発明においては、後述するように、超塑性現象を利用し、且つ、高温強度や疲労強度（耐クリープ性）を向上させる点を特に着目し、それらの効果に対して最も有効な微量成分としてＣｕ及びＭｇの少なくとも何れかの元素を含有することが好ましい。Ｃｕ及びＭｇの含有量は、共析系合金の全重量１００質量部に対してそれぞれ０～１．５質量％及び０～０．０５質量％の範囲が好ましい。Ｃｕ及びＭｇの含有量がそれぞれ１．５質量％及び０．０５質量％を超えると、Ｚｎ－Ａｌ共析系合金が脆くなり、本発明の特徴である応力緩和効果が失われる。
The Zn—Al eutectoid alloy used in the present invention must contain Al and Zn as constituent components, but it can lower the melting point, workability, high temperature strength, fatigue strength (creep resistance) or stress relaxation. In addition to these, Cu, Mg, Ge, Sn, In, Ag, Ni, P, or the like may be added as a trace component for the purpose of improving the properties. In the present invention, as will be described later, the superplastic phenomenon is utilized, and particularly attention is focused on improving high temperature strength and fatigue strength (creep resistance) as the most effective trace component for those effects. It is preferable to contain at least one element of Cu and Mg. The contents of Cu and Mg are preferably in the range of 0 to 1.5 mass% and 0 to 0.05 mass%, respectively, with respect to 100 mass parts of the total weight of the eutectoid alloy. When the contents of Cu and Mg exceed 1.5% by mass and 0.05% by mass, respectively, the Zn—Al eutectoid alloy becomes brittle, and the stress relaxation effect that is a feature of the present invention is lost.
前記Ｚｎ－Ａｌ共析系合金は、Ｃｕ及びＭｇの少なくとも何れかの元素を、微量成分として含有する場合も含めて、所定の合金比率になるように秤量配合し、融点以上の温度で均一に溶解した後、所望の形状を有する鋳型に流し込んだ母合金（インゴット）から得られる。インゴットの製造方法としては、例えば、９９．９質量％以上のＺｎとＡｌ、場合によっては微量添加成分として９９．９質量％以上のＣｕ、Ｍｇを準備し、それらを組成のバラツキがなく、できるだけ均一に混合できるように切断及び粉砕等により細かにしたものを、所定の合金比率になるように秤量し黒鉛製るつぼに入れる。次いで、黒鉛製るつぼに入った各合金成分の混合物を高周波溶解炉等の溶解炉に入れ、酸化を防止するために窒素、アルゴン等の不活性気体を流しながら加熱溶解させ、溶融状態で均一に混合する。十分に溶解したことを確認した後、高周波電源を切り、溶湯を溶解炉から取り出して鋳型に流しこんで、Ｚｎ－Ａｌ共析系合金のインゴットを製造することができる。必要に応じて、表面傷を除去するために、インゴットの表面部分をスライス盤などで面削しても良い。また、微量添加成分であるＣｕ又はＭｇを高純度のＡｌ及びＺｎと混合させるときに、Ｃｕ又はＭｇの代わりに、Ａｌ－Ｃｕ又はＡｌ－Ｍｇの母合金の形で、所定の合金比率になるように秤量配合してから溶解する方法を使用しても良い。
The Zn—Al eutectoid alloy is weighed and blended so as to have a predetermined alloy ratio, including the case where at least one element of Cu and Mg is contained as a trace component, and uniformly at a temperature equal to or higher than the melting point. After melting, it is obtained from a mother alloy (ingot) poured into a mold having a desired shape. As an ingot production method, for example, 99.9% by mass or more of Zn and Al, and in some cases, 99.9% by mass or more of Cu and Mg are prepared as trace addition components. What is made fine by cutting and pulverizing so that it can be uniformly mixed is weighed so as to have a predetermined alloy ratio and put into a graphite crucible. Next, the mixture of each alloy component contained in the graphite crucible is put into a melting furnace such as a high-frequency melting furnace, heated and melted while flowing an inert gas such as nitrogen or argon to prevent oxidation, and uniformly in a molten state. Mix. After confirming sufficient melting, the high frequency power supply is turned off, and the molten metal is taken out of the melting furnace and poured into a mold, whereby a Zn—Al eutectoid alloy ingot can be produced. If necessary, the surface portion of the ingot may be chamfered with a slicer or the like in order to remove surface scratches. In addition, when Cu or Mg, which is a trace addition component, is mixed with high-purity Al and Zn, a predetermined alloy ratio is obtained in the form of an Al—Cu or Al—Mg master alloy instead of Cu or Mg. Thus, a method of dissolving after weighing and blending may be used.
本発明のＺｎ－Ａｌ共析系合金は、溶解によって各合金組成の結晶が均一に近い状態で分布した組織を有するインゴットを接合材として適用しているため、前記特許文献４に開示されているＺｎ／Ａｌ／Ｚｎクラッド材とは異なり、Ａｌ系合金だけからなる層又は大きな塊がＺｎ－Ａｌ合金層と分離して形成されることを抑制することができる。したがって、Ａｌ系合金層とＺｎ－Ａｌ合金層との間で形成される広範囲な界面の存在によって亀裂（クラック）が進展しやすくなるというＺｎ／Ａｌ／Ｚｎクラッド材が有する技術課題を解決することが可能になる。均一溶解によってクラック進展を抑制するという効果は、Ｚｎ－Ａｌ共析系合金に含まれるＡｌの含有比率が高くなるにつれて徐々に小さくなる傾向にあるが、本発明においてＡｌの含有比率が８０質量％を超える場合であっても、ある程度の効果が得られることが分かった。
The Zn—Al eutectoid alloy of the present invention is disclosed in Patent Document 4 because an ingot having a structure in which crystals of each alloy composition are distributed in a nearly uniform state by melting is applied as a bonding material. Unlike the Zn / Al / Zn clad material, it is possible to suppress the formation of a layer or a large lump made of only an Al-based alloy separately from the Zn—Al alloy layer. Accordingly, to solve the technical problem of Zn / Al / Zn clad materials in which cracks are likely to progress due to the existence of a wide range of interfaces formed between an Al-based alloy layer and a Zn—Al alloy layer. Is possible. The effect of suppressing crack growth by uniform dissolution tends to gradually decrease as the Al content ratio in the Zn—Al eutectoid alloy increases, but in the present invention, the Al content ratio is 80 mass%. It has been found that a certain degree of effect can be obtained even in the case of exceeding.
本発明においては、デンドライドアームスペーシング（ＤＡＳ）が０．０６μｍを超え、０．３μｍ未満である接合層構造を、次の２つの形成方法によって形成することができる。第１の形成方法は、前記被接合材ＡとＢとの間に、１７質量％～３０質量％Ａｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合材を介在し、加圧しながら前記接合材を半溶融温度領域に加熱した状態で所望の時間保持する操作を１回又は２回以上繰り返した後に徐冷する方法である。第２の形成方法は、前記被接合材ＡとＢとの間に、３０質量％を超え９７質量％以下のＡｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合材を介在し、加圧又は無圧の状態で前記接合材を半溶融温度領域に加熱し、所望の時間保持した後に徐冷する方法である。
In the present invention, a bonding layer structure having a dendritic arm spacing (DAS) of more than 0.06 μm and less than 0.3 μm can be formed by the following two forming methods. The first forming method is composed of 17% to 30% by mass Al-0 to 1.5% by mass Cu-0 to 0.05% by mass Mg—Zn between the materials to be joined A and B. A method in which a Zn-Al eutectoid alloy bonding material is interposed, and the operation of holding the bonding material in a state of being heated to a semi-melting temperature region while being pressed is held for a desired time and then gradually cooled after being repeated once or twice. is there. In a second forming method, between Al to B to be bonded, Al-0 to 1.5% by mass, Cu-0 to 0.05% by mass, Mg—Zn, exceeding 30% by mass and not more than 97% by mass. This is a method in which a Zn—Al eutectoid alloy bonding material composed of a system is interposed, the bonding material is heated to a semi-molten temperature region in a pressurized or non-pressurized state, and is gradually cooled after being held for a desired time.
まず、第１の形成方法について説明する。第１の形成方法は、デンドライドアームスペーシング（ＤＡＳ）が０．０６μｍを超え、０．３μｍ未満である接合層構造を形成するために、前記特許文献３に記載の１７質量％～３０質量％Ａｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合材を用いて、被接合材間に介在させた前記Ｚｎ－Ａｌ共析系合金接合材を半溶融温度領域に加熱した状態で所望の時間保持する操作を行うときに、同時に加圧を行う必要がある。接合材を加圧することによって半溶融温度領域に加熱したＺｎ－Ａｌ共析系合金接合材が変形し、比較的融点の低いラメラ構造のＺｎが溶解しながら被接合材との接合面から外部へ押し出され、他方、Ａｌリッチ相（α相）はその半溶融温度領域では溶解しないで前記接合面の内側に留まる。Ｚｎ－Ａｌ共晶は融点がやや低いため、一部が前記接合面の外部へ押し出される場合もあるが、Ａｌリッチ相（α相）との相互作用により前記接合面の内部に留まるものも存在する。ここで、半溶融温度領域に加熱した状態で所望の時間保持する操作は１回だけに限定されず、必要に応じて２回以上繰り返しても良い。
First, the first forming method will be described. The first forming method is to form a bonding layer structure having a dendritic arm spacing (DAS) of more than 0.06 μm and less than 0.3 μm. Using the Zn—Al eutectoid alloy bonding material composed of Al-0 to 1.5 mass% Cu-0 to 0.05 mass% Mg—Zn, the Zn—Al It is necessary to pressurize at the same time when performing an operation of holding the deposition alloy joining material for a desired time in a state heated to the semi-melting temperature region. By pressurizing the bonding material, the Zn-Al eutectoid alloy bonding material heated to the semi-melting temperature region is deformed, and the lamella structure Zn having a relatively low melting point is melted to the outside from the bonding surface with the bonded material. On the other hand, the Al-rich phase (α phase) does not dissolve in the semi-melting temperature region and remains inside the joint surface. Since the melting point of Zn-Al eutectic is somewhat low, a part of the Zn-Al eutectic may be pushed out of the joint surface, but there are some that remain inside the joint surface due to the interaction with the Al-rich phase (α phase). To do. Here, the operation of holding for a desired time in a state heated to the semi-melting temperature region is not limited to once, and may be repeated twice or more as necessary.
このようにして、図３の模式図に示すように、共析Ａｌ－Ｚｎはんだの加圧接合時における微細構造の組織図が変化し、半溶融接合後においてＡｌリッチ相（α相）の樹枝状晶（図３の黒線部分）がより緻密な状態で形成される。それにより、Ａｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）が０．０６μｍを超え、０．３μｍ未満となる接合層構造を得ることができる。半溶融温度領域で一定時間保持して形成された後の接合層の厚さは、Ａｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）に応じて調整を行うが、最初の接合材の厚さに対して４／５～２／５の範囲に加圧変形させることが実用的である。接合後に形成される接合層の具体的な厚さは、ボイドレス接合、接合信頼性及び熱伝導性の観点から２０μｍ～２００μｍが実用的である。接合後の整合層の厚さが２０μm未満ではボイドレス接合が困難であるだけでなく、接合信頼性の低下が顕著になる。また、接合層の厚さが２００μｍを超えると、熱伝導性を向上させるという効果が十分に得られない。本発明の接合層構造は、Ａｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）が小さく、接合面の垂直方向において熱伝導性がＺｎより優れるＡｌの含有量が多くなっているため、従来技術のＺｎ－Ａｌ共析系合金と比べて高い熱伝導性を有するという特徴を有するものであるが、この特徴を十分に活かせる接合層の厚さは２００μｍ以下、好ましくは１５０μｍ以下である。
In this way, as shown in the schematic diagram of FIG. 3, the microstructure of the eutectoid Al—Zn solder during the pressure bonding changes, and the Al-rich phase (α phase) dendrite after the semi-melt bonding Shaped crystals (black line portions in FIG. 3) are formed in a denser state. As a result, a bonding layer structure in which the Al-rich phase (α phase) dendritic arm spacing (DAS) exceeds 0.06 μm and less than 0.3 μm can be obtained. The thickness of the bonding layer after being formed for a certain period of time in the semi-melting temperature range is adjusted according to the Al-rich phase (α phase) dendritic arm spacing (DAS). It is practical to apply pressure deformation in the range of 4/5 to 2/5 with respect to the thickness. The specific thickness of the bonding layer formed after bonding is practically 20 μm to 200 μm from the viewpoints of voidless bonding, bonding reliability, and thermal conductivity. When the thickness of the matching layer after bonding is less than 20 μm, not only is voidless bonding difficult, but the bonding reliability is significantly reduced. On the other hand, if the thickness of the bonding layer exceeds 200 μm, the effect of improving the thermal conductivity cannot be obtained sufficiently. In the bonding layer structure of the present invention, the Al-rich phase (α phase) dendritic arm spacing (DAS) is small, and the Al content in which the thermal conductivity is superior to Zn in the vertical direction of the bonding surface is large. Although it has a feature that it has high thermal conductivity as compared with the prior art Zn-Al eutectoid alloy, the thickness of the bonding layer that can fully utilize this feature is 200 μm or less, preferably 150 μm or less. .
前記第１の形成方法においては、接合時に接合材を半溶融温度領域に加熱した状態で加圧する工程の前に、被接合材との接合界面の酸化膜層の破壊除去等による清浄化を行い、ボイドの発生が少ない接合界面を形成するため、超塑性流動を利用する工程を採用することができる。１７質量％～３０質量％Ａｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合材は、Ａｌの含有量が従来よりも比較的多く、２８０～４１０℃（α’領域）又は２００～２７５℃（α＋β領域）の温度領域で１～３０分加熱し接合材に、微細結晶粒の形成による超塑性現象を発現させることによって優れた加工性を有することが知られている（前記特許文献３を参照）。しかしながら、この超塑性現象が接合界面の清浄化及び高密着化によるボイドレス接合に対して効果があることは従来の接合技術においてほとんど認識されておらず、本発明において前記第１の形成方法を採用する上で鍵となる技術である。
In the first forming method, before the step of pressurizing the bonding material in a state of being heated to a semi-melting temperature region during bonding, cleaning is performed by destructive removal of the oxide film layer at the bonding interface with the material to be bonded. In order to form a bonded interface with less voids, a process utilizing superplastic flow can be employed. A Zn-Al eutectoid alloy bonding material composed of 17 mass% to 30 mass% Al-0 to 1.5 mass% Cu-0 to 0.05 mass% Mg-Zn system has a higher Al content than the conventional one. By relatively heating at a temperature range of 280 to 410 ° C. (α ′ region) or 200 to 275 ° C. (α + β region) for 1 to 30 minutes to cause the superplastic phenomenon due to the formation of fine crystal grains in the bonding material It is known to have excellent processability (see Patent Document 3). However, it is hardly recognized in the conventional joining technique that this superplastic phenomenon has an effect on the voidless joining by the cleaning and high adhesion of the joining interface, and the first forming method is adopted in the present invention. It is a key technology for doing this.
図４に、超塑性現象を利用した本発明の接合方法の一例として、２００～２７５℃の温度領域の加熱で発現する超塑性現象を利用したときの接合法の工程模式図を示す。図４に示すように、固相状態のＺｎ－Ａｌ共析系合金接合材１を半導体素子２（被接合材Ａに相当するもの）のメタライズした部分３の面とＣｕ基板／Ｎｉ／Ｃｕめっき膜の構成を有する基板４（被接合材Ｂに相当するもの）のＣｕめっき膜５が形成された面との間に介し、上下両面から加圧しながら２００～２７５℃で加熱することによって超塑性現象が発現し、前記接合材の変形が容易となる。接合材１は非接合材の接合面に強く押し付けられスクラブされる状態が発生するため、被接合材との接合界面に存在する酸化膜層の破壊除去等による清浄化を行うことができる。加えて、超塑性現象による加工性の付与により、固相状態のＺｎ－Ａｌ共析系合金接合材は被加工材によって押しつけられるため、清浄面同士の密着性が十分に向上し、ボイドの発生が少ない接合界面を形成することができる。引き続き加圧を保持しながら、半溶融状態を示す温度域まで温度を上げて加熱した状態で所定の時間保持することによって、接合材の半溶融だけでなく、被接合材と接合材の間で相互拡散が促進される。Ｚｎ－Ａｌ共析系合金接合材は、被接合材との相互拡散の促進が通常３５０℃付近の温度から起こるため、前記の半溶融状態を示す温度域では相互拡散層６の形成によって強固な接合界面を形成することができる。本発明において半溶融状態を示す温度域、すなわち半溶融温度域としてはＺｎ－Ａｌ合金の共晶温度より高い３８０℃を超え、６００℃未満の範囲で接合工程が行われるが、半溶融状態を十分に維持できる温度として４１０℃を超える温度が好ましい。
FIG. 4 shows a process schematic diagram of the joining method when utilizing the superplastic phenomenon which is manifested by heating in the temperature range of 200 to 275 ° C. as an example of the joining method of the present invention utilizing the superplastic phenomenon. As shown in FIG. 4, the surface of the metallized portion 3 of the semiconductor element 2 (corresponding to the material A to be bonded) and the Cu substrate / Ni / Cu plating are formed in the solid phase Zn—Al eutectoid alloy bonding material 1. Superplasticity is achieved by heating at 200 to 275 ° C. while applying pressure from above and below both surfaces of the substrate 4 having a film structure (corresponding to the material B to be bonded) on which the Cu plating film 5 is formed. A phenomenon appears and the bonding material is easily deformed. Since the bonding material 1 is strongly pressed against the bonding surface of the non-bonding material and is scrubbed, cleaning can be performed by removing the oxide film layer present at the bonding interface with the bonded material. In addition, due to the workability imparted by the superplastic phenomenon, the solid-state Zn-Al eutectoid alloy joint material is pressed by the work material, so the adhesion between clean surfaces is sufficiently improved and voids are generated. It is possible to form a bonding interface with less. While maintaining the pressurization, raising the temperature to the temperature range showing the semi-molten state and holding it for a predetermined time in the heated state, not only the semi-melting of the joining material, but also between the joined material and the joining material Mutual diffusion is promoted. In the Zn—Al eutectoid alloy bonding material, the promotion of mutual diffusion with the material to be bonded usually starts from a temperature around 350 ° C., and therefore, the Zn—Al eutectoid alloy bonding material is strong due to the formation of the mutual diffusion layer 6 in the temperature range showing the semi-molten state. A bonding interface can be formed. In the present invention, the temperature range showing the semi-molten state, that is, the semi-melt temperature range is higher than the eutectic temperature of the Zn-Al alloy and exceeds 380 ° C. and less than 600 ° C. A temperature exceeding 410 ° C. is preferable as a temperature that can be sufficiently maintained.
前記第１の形成方法において、加圧するときの圧力は１～５０ＭＰａが好ましく、５～３０Ｍｐａがより好ましい。圧力が１ＭＰａ未満では前記の清浄化及び密着性の向上がほとんど得られない。また、圧力が５０ＭＰａを超えると、接合材の半溶融温度における加圧によって接合層が薄くなりすぎるため、接合信頼性の向上を図ることが困難になる。加圧するときの圧力を１～５０ＭＰａ、より好ましくは５～３０ＭＰａに設定することによって、Ａｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）が０．０６μｍを超え、０．３μｍ未満となる接合層構造を形成することが容易になる。
In the first forming method, the pressure during pressurization is preferably 1 to 50 MPa, more preferably 5 to 30 MPa. When the pressure is less than 1 MPa, the above-mentioned cleaning and adhesion are hardly improved. On the other hand, when the pressure exceeds 50 MPa, the bonding layer becomes too thin due to pressurization at the semi-melting temperature of the bonding material, and it becomes difficult to improve the bonding reliability. By setting the pressure during pressurization to 1 to 50 MPa, more preferably 5 to 30 MPa, the dendritic arm spacing (DAS) of the Al-rich phase (α phase) exceeds 0.06 μm and less than 0.3 μm. It becomes easy to form a bonding layer structure.
前記第１の形成方法は超塑性現象を利用して接合界面の清浄化と密着性向上を図ることができるため、加熱しながら昇温した後に保持するときの温度を、半溶融状態を示す温度域の６００℃近くの高温にまで上げる必要がなくなる。したがって、半溶融状態を示す温度を比較的低温に設定することが可能となり、接合時の被接合材へのダメージ及び高温加熱によって発生する応力を低減できるという効果が得られる。
Since the first forming method can use a superplastic phenomenon to clean the bonding interface and improve the adhesion, the temperature at which the temperature is raised after heating is maintained at a temperature indicating a semi-molten state. There is no need to raise the temperature to near 600 ° C. Therefore, it is possible to set the temperature indicating the semi-molten state to a relatively low temperature, and it is possible to obtain an effect that the damage to the materials to be joined at the time of joining and the stress generated by the high temperature heating can be reduced.
次に、第２の形成方法について説明する。第２の形成方法は、前記第１の形成方法と比べて、Ａｌ含有量が多いＺｎ－Ａｌ共析系合金接合材を接合材として適用する方法である。具体的には、３０質量％を超え９７質量％以下のＡｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合材を使用する。このＺｎ－Ａｌ共析系合金接合材は、インゴットの状態でＡｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）が０．０６μｍを超え、０．３μｍ未満であるため、被接合材の間に介在させて半溶融温度領域に加熱するときに、必ずしも加圧する必要は無く、無圧の状態で所望の時間保持した後に徐冷しても本発明の接合層構造を得ることができる。Ａｌ含有量の多いＺｎ－Ａｌ共析系合金接合材は、Ａｌの熱伝導性がＺｎに比べて約２倍あり、熱伝導性に優れるという特徴を有するため、無圧に近い状態でも短時間で接合材全体を半溶融温度領域に加熱することができる。それによって、相対的に融点が低いＺｎ及びＺｎ－Ａｌ共晶の溶融が促進され、接合材の濡れ性を十分に確保できるという効果が得られる。
Next, the second forming method will be described. The second forming method is a method in which a Zn—Al eutectoid alloy bonding material having a higher Al content than the first forming method is applied as a bonding material. Specifically, a Zn—Al eutectoid alloy bonding material composed of Al-0 to 1.5% by mass Cu-0 to 0.05% by mass Mg—Zn and exceeding 30% by mass and 97% by mass or less is used. To do. This Zn—Al eutectoid alloy bonding material has an Al-rich phase (α phase) dendrid arm spacing (DAS) of more than 0.06 μm and less than 0.3 μm in the ingot state. When heating to the semi-melting temperature region by interposing them, it is not always necessary to pressurize, and the bonding layer structure of the present invention can be obtained even if it is gradually cooled after being kept for a desired time without pressure. A Zn-Al eutectoid alloy bonding material with a high Al content is characterized in that the thermal conductivity of Al is approximately twice that of Zn and is excellent in thermal conductivity. Thus, the entire bonding material can be heated to the semi-melting temperature region. Thereby, melting of Zn and Zn—Al eutectic having a relatively low melting point is promoted, and the effect that the wettability of the bonding material can be sufficiently secured is obtained.
一方、Ａｌ含有量が３０質量％に近い組成の合金インゴットを接合材として適用する場合は、Ａｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）を小さくするため、半溶融温度領域に加熱するときに加圧しても良い。
On the other hand, when an alloy ingot having an Al content close to 30% by mass is used as a bonding material, the alloy is heated to a semi-melting temperature region in order to reduce the dendritic arm spacing (DAS) of the Al-rich phase (α phase). You may pressurize when doing.
このように、第２の形成方法は、前記第１の形成方法と比べて無圧又は低圧で接合を行うことができるため、接合装置の簡略化を図る上で好適な接合方法である。前記第２の方法において、加圧を行う場合、そのときの圧力は３０ＭＰａ以下が好ましく、２０Ｍｐａ以下がより好ましい。３０ＭＰａを超えると、半溶融温度における加圧によって接合層が薄くなりすぎるため、接合信頼性の向上を図ることが困難になる。
As described above, the second forming method can be bonded with no pressure or low pressure as compared with the first forming method, and thus is a preferable bonding method for simplifying the bonding apparatus. In the second method, when pressure is applied, the pressure at that time is preferably 30 MPa or less, more preferably 20 MPa or less. If it exceeds 30 MPa, the bonding layer becomes too thin due to pressurization at the semi-melting temperature, and it becomes difficult to improve the bonding reliability.
なお、前記第２の形成方法において、Ａｌ含有量が３０質量％に近い組成の合金インゴットを接合材として適用する場合は、本発明で使用するＺｎ－Ａｌ共析系合金接合材で発現する超塑性現象を利用することができる。接合材を,超塑性現象を示す温度域で加圧しながら一定時間保持すれば、接合界面の清浄化と密着性の向上を図ることができる。超塑性現象は３０ＭＰａ以下の圧力で十分に発現させることができるが、圧力の下限値としては０．５ＭＰａ以上であることが好ましい。圧力が０．５ＭＰａ未満であると、超塑性現象を利用しても接合界面の清浄化及び接合材の変形が十分でなく、Ａｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）が０．０６μｍを超え、０．３μｍ未満となる接合層構造を形成することが困難になるためである。
In the second forming method, when an alloy ingot having a composition with an Al content close to 30% by mass is used as the bonding material, the super-expressing characteristic of the Zn—Al eutectoid alloy bonding material used in the present invention is used. Plastic phenomena can be used. If the bonding material is held for a certain period of time while being pressurized in a temperature range showing a superplastic phenomenon, the bonding interface can be cleaned and adhesion can be improved. Although the superplastic phenomenon can be sufficiently exhibited at a pressure of 30 MPa or less, the lower limit of the pressure is preferably 0.5 MPa or more. When the pressure is less than 0.5 MPa, even when the superplastic phenomenon is used, the bonding interface is not sufficiently cleaned and the bonding material is not deformed, and the Al-rich phase (α phase) dendritic arm spacing (DAS) is 0. This is because it becomes difficult to form a bonding layer structure exceeding 0.06 μm and less than 0.3 μm.
本発明は、上記で説明したように、接合時に接合材を半溶融温度領域に加熱した状態で加圧する工程の前に、超塑性流動による超塑性変形を利用することによって応力緩和機能を有する接合層構造を形成できるが、それ以外にも、超塑性変形を発現する別の方法を利用することができる。超塑性変形は、結晶粒を非常に微細化すると現れる微細結晶粒超塑性（前記特許文献３を参照）とは異なり、応力を加えながら、変態点を通過するような加熱冷却を繰り返すことによって超塑性加工を行う変態超塑性を利用しても発現することが知られている。そこで、本発明者等が詳細に検討した結果、低応力の効果を有する接合層構造は、変態超塑性を利用することでも本発明の応力緩和機能を有する接合層構造が得られることが分かった。この変態超塑性を利用することによって具体的に応力緩和機能を有する接合層を形成した従来例はほとんど見当たらず、Ａｌの含有量の多い接合層構造の形成において特に有効な方法であることは全く認識されていなかった。本発明において変態超塑性を利用して接合層構造を形成する場合、前記第１の形成方法だけでなく、前記第２の形成方法においても適用することが可能である。
As described above, the present invention is a joint having a stress relaxation function by utilizing superplastic deformation due to superplastic flow before the step of pressurizing the joining material in a state of being heated to a semi-molten temperature region during joining. Although a layered structure can be formed, other methods for developing superplastic deformation can be used. Superplastic deformation is different from fine crystal superplasticity (see Patent Document 3) that appears when crystal grains are made very fine (see Patent Document 3), and is superheated by repeating heating and cooling while passing through the transformation point while applying stress. It is known that it is manifested even when transformation superplasticity for plastic working is used. Therefore, as a result of detailed studies by the present inventors, it was found that the bonding layer structure having the effect of low stress can obtain the bonding layer structure having the stress relaxation function of the present invention even by utilizing transformation superplasticity. . By utilizing this transformation superplasticity, there are almost no conventional examples in which a bonding layer having a stress relaxation function is specifically formed, and it is quite effective in forming a bonding layer structure having a high Al content. It was not recognized. In the present invention, when the bonding layer structure is formed using transformation superplasticity, it can be applied not only to the first forming method but also to the second forming method.
本発明の接合層を、変態超塑性を利用して形成する方法を図１に示すＺｎ－Ａｌ共析系合金の平衡状態図を用いて説明する。図１において、固液共存領域を温度であればいずれの温度でも変態超塑性の効果は同じように得られるが、例として、前記第１の方法に従って、Ｚｎ－２２％Ａｌ合金を用いて４５０℃に加熱した場合を説明する。
A method of forming the bonding layer of the present invention using transformation superplasticity will be described with reference to an equilibrium diagram of a Zn—Al eutectoid alloy shown in FIG. In FIG. 1, the effect of transformation superplasticity can be obtained in the same way at any temperature as long as the solid-liquid coexistence region is at a temperature. As an example, according to the first method, a 450% Zn-22% Al alloy is used. The case of heating to ° C will be described.
図１において、加熱温度を４５０℃とした場合、この温度においてはＡｌは固相であるがＺｎは液相であるため、加圧により、液相Ｚｎは接合部の外部へ押し出され、その結果、Ａｌの組成は固相線の２２質量％から増加し、３０質量％をやや超える。図１においてはａ→ｂに相当する。このまま冷却することによって、Ａｌの組成が３０質量％を超える接合層は、図１においてｃ１で示す変態超塑性点を通過する（図においてｂ→ｃ１）。さらに、冷却が進むと、図１においてｄ１で示す別の変態超塑性点を通過する（図においてｃ１→ｄ１）。このように、変態超塑性点で加熱冷却が繰り返されるため、応力緩和機能を有する接合層が形成される。
In FIG. 1, when the heating temperature is 450 ° C., at this temperature, Al is a solid phase, but Zn is a liquid phase, so that the liquid phase Zn is pushed out of the joint by pressurization, and as a result The composition of Al increases from 22% by mass of the solidus and slightly exceeds 30% by mass. In FIG. 1, this corresponds to a → b. By cooling as it is, the bonding layer whose Al composition exceeds 30% by mass passes through the transformation superplastic point indicated by c1 in FIG. 1 (b → c1 in the figure). When the cooling further proceeds, it passes through another transformation superplastic point indicated by d1 in FIG. 1 (c1 → d1 in the figure). Thus, since heating and cooling are repeated at the transformation superplastic point, a bonding layer having a stress relaxation function is formed.
また、図１においてｂ→ｅのように加熱温度を４５０℃から液相線の温度まで加熱し、同時に加圧することにより、さらにＺｎが接合層の外部に押し出されて排出され、Ａｌの組成が６０質量％である接合層が形成される（図においてｅ→ｆ）。その後、加圧した状態で冷却すれば、前記と同様に、ｃ２で示す変態超塑性点及びｄ２で示す変態超塑性点を通過するため（図においてｆ→ｃ２→ｄ２）、Ａｌが６０質量％の接合層、すなわち、より高い応力緩和機構を有する接合部を形成することができる。
Further, in FIG. 1, the heating temperature is heated from 450 ° C. to the liquidus temperature as b → e, and simultaneously pressurizing, whereby Zn is further pushed out of the bonding layer and discharged, and the composition of Al is increased. A joining layer of 60% by mass is formed (e → f in the figure). Thereafter, when cooled in a pressurized state, similarly to the above, it passes through the transformation superplastic point indicated by c2 and the transformation superplasticity point indicated by d2 (f → c2 → d2 in the figure), so that Al is 60% by mass. In other words, a bonding layer having a higher stress relaxation mechanism can be formed.
図１から分かるように、固液共存領域を有する温度範囲であれば、いずれの温度でも同じ効果が得られる。また、接合材に含まれるＡｌの含有量も任意に選択することができ、例えば、接合材としてあらかじめＡｌの組成が３０質量％を超えるものを使用しても、Ｚｎが接合層から押し出されて排出される加熱温度を選べば、その加熱温度で加圧することによって、同じように応力緩和機能を有する接合層を形成することができる。このとき、応力緩和機能を発現する程度は、形成された接合層に含まれるＡｌの含有量に応じて決まる。このように、変態超塑性を利用して形成する方法は、前記第１の形成方法に限定されず、前記第２の形成方法にも加圧することによって適用できる。
As can be seen from FIG. 1, the same effect can be obtained at any temperature as long as it has a solid-liquid coexistence region. Further, the content of Al contained in the bonding material can also be arbitrarily selected. For example, even when a bonding material having an Al composition exceeding 30% by mass in advance is used, Zn is extruded from the bonding layer. If the heating temperature to be discharged is selected, a bonding layer having a stress relaxation function can be formed in the same manner by applying pressure at the heating temperature. At this time, the degree of developing the stress relaxation function is determined according to the content of Al contained in the formed bonding layer. Thus, the method of forming using transformation superplasticity is not limited to the first forming method, and can be applied to the second forming method by applying pressure.
本発明の接合層構造を変態超塑性の利用によって形成する方法は、図４に示す２００～２７５℃の温度領域の加熱で発現する超塑性現象と組み合わせることによって、低応力機能を一層高めた接合層を形成することができる。その場合は、図４に示す半溶融・拡散接合の温度として、接合材に含まれるＺｎが液相となり接合層の外部へ排出されるような温度に加熱すればよい。
The method of forming the bonding layer structure of the present invention by utilizing transformation superplasticity is a bonding method in which the low-stress function is further enhanced by combining with the superplasticity phenomenon manifested by heating in the temperature range of 200 to 275 ° C. shown in FIG. A layer can be formed. In that case, the temperature of the semi-molten / diffusion bonding shown in FIG. 4 may be heated to such a temperature that Zn contained in the bonding material becomes a liquid phase and is discharged to the outside of the bonding layer.
本発明の接合層構造は、耐熱性、接続信頼性及び熱伝導性の要求が強いパワー半導体素子のダイボンディングやパワーモジュールに搭載される半導体素子の実装基板への接合及び実装基板への放熱板の接合において形成される接合層として適用することができる。例えば、図５に示すように、Ｃｕ／ＳｉＮ／Ｃｕ構造の金属フレーム上に、接合材としてＺｎ－Ａｌ共析系合金を介して、Ａｌ配線／ＳｉＣ／メタライズの構造を有するＳｉＣ半導体素子を上記の第１又は第２の形成方法によってダイボンディングして形成される本発明の接合層構造を有するＳｉＣ高温パワー半導体等が挙げられる。
The bonding layer structure of the present invention includes die bonding of power semiconductor elements, which have strong requirements for heat resistance, connection reliability and thermal conductivity, bonding of semiconductor elements mounted on power modules to mounting boards, and heat sinks to mounting boards. It can be applied as a bonding layer formed in the bonding. For example, as shown in FIG. 5, an SiC semiconductor element having an Al wiring / SiC / metallized structure is formed on a Cu / SiN / Cu structured metal frame with a Zn—Al eutectoid alloy as a bonding material. SiC high-temperature power semiconductor having the bonding layer structure of the present invention formed by die bonding by the first or second forming method.
それら以外にも、通常の半導体装置のダイボンディング用の接続材料、気密封止を必要とする半導体装置の金属キャップとモジュール基板との接続材料、又はフリップチップを必要とする半導体装置のバンプとして適用したときに形成される接続層としても適用が可能である。例えば、通常の半導体装置としては、半導体素子と該半導体素子を接続するフレームと、一端が外部端子となるリードと、該リードの半導体素子の電極とを接続するワイヤと、前記半導体素子及び前記ワイヤを樹脂封止する封止用レジンとを有し、前記半導体素子と前記フレームがＺｎ－Ａｌ共析系合金接合材を介して上記の第１又は第２の形成方法によって接合して形成される本発明の接合層構造を構成するものである。
Other than these, it is used as a connection material for die bonding of ordinary semiconductor devices, a connection material between metal caps and module substrates of semiconductor devices that require hermetic sealing, or bumps of semiconductor devices that require flip chips. It can also be applied as a connection layer formed at the time. For example, as a normal semiconductor device, a semiconductor element, a frame connecting the semiconductor element, a lead having one end as an external terminal, a wire connecting the electrode of the semiconductor element of the lead, the semiconductor element and the wire A resin for sealing, and the semiconductor element and the frame are formed by bonding with the first or second forming method through a Zn—Al eutectoid alloy bonding material. It constitutes the bonding layer structure of the present invention.
以下において、本発明に基づく実施例を具体的に説明するが、本発明はこれらの実施例によって何ら限定されるものではない。ここでは、本発明の接合層構造を有するパワーデバイスとして、ＳｉＣ高温パワー半導体を搭載した金属フレーム、ダイオード、ＩＧＢＴモジュール及び電力用ＭＯＳトランジスタの例を説明する。
Hereinafter, examples based on the present invention will be described in detail, but the present invention is not limited to these examples. Here, examples of a metal frame, a diode, an IGBT module, and a power MOS transistor on which a SiC high-temperature power semiconductor is mounted will be described as power devices having the junction layer structure of the present invention.
＜実施例１＞
本発明の接合層構造によって得られる接合部のせん断強度について基礎的な実験を行った。接合材として溶解鋳造して得られた２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金を用い、図４に示す方法に従って接合部せん断強度測定用の試料を作製した。この実験では、図４に示す半導体素子２を使用する代わりにＣｕ基板／Ｎｉ／Ｃｕめっき膜からなる被接合材４を２枚使用した。厚さ６０μｍのＺｎ－Ａｌ共析系合金接合材を前記Ｃｕ基板／Ｎｉ／Ｃｕめっき膜からなる２枚の被接合材の間に介して、窒素ガス雰囲気中（本実施例においては非酸化性雰囲気であれば良く、窒素の他にも、アルゴン、ヘリウムあるいは水素を含む非酸化性混合ガスを使用することができる。）で加圧しながら２５０℃１０分間保持した後、その状態で３９０℃まで昇温し、同じ３９０℃の温度で５分間保持してから室温まで徐冷した。加圧は、５ＭＰａ、１０ＭＰａ及び２４ＭＰａの３条件でそれぞれ条件を変えて行った。 <Example 1>
A basic experiment was conducted on the shear strength of the joint obtained by the joint layer structure of the present invention. Using a Zn-Al eutectoid alloy composed of 22 mass% Al-78 mass% Zn obtained by melting and casting as a bonding material, a sample for measuring the joint shear strength was prepared according to the method shown in FIG. In this experiment, instead of using the semiconductor element 2 shown in FIG. 4, two bondedmaterials 4 made of a Cu substrate / Ni / Cu plating film were used. A Zn—Al eutectoid alloy bonding material having a thickness of 60 μm is interposed between the two materials to be bonded made of the Cu substrate / Ni / Cu plating film in a nitrogen gas atmosphere (in this embodiment, non-oxidizing property). The atmosphere may be sufficient, and in addition to nitrogen, a non-oxidizing mixed gas containing argon, helium, or hydrogen can be used.) The pressure is maintained at 250 ° C. for 10 minutes while being pressurized, and then in that state up to 390 ° C. The temperature was raised and held at the same temperature of 390 ° C. for 5 minutes, and then gradually cooled to room temperature. The pressurization was performed by changing the conditions under three conditions of 5 MPa, 10 MPa, and 24 MPa.
本発明の接合層構造によって得られる接合部のせん断強度について基礎的な実験を行った。接合材として溶解鋳造して得られた２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金を用い、図４に示す方法に従って接合部せん断強度測定用の試料を作製した。この実験では、図４に示す半導体素子２を使用する代わりにＣｕ基板／Ｎｉ／Ｃｕめっき膜からなる被接合材４を２枚使用した。厚さ６０μｍのＺｎ－Ａｌ共析系合金接合材を前記Ｃｕ基板／Ｎｉ／Ｃｕめっき膜からなる２枚の被接合材の間に介して、窒素ガス雰囲気中（本実施例においては非酸化性雰囲気であれば良く、窒素の他にも、アルゴン、ヘリウムあるいは水素を含む非酸化性混合ガスを使用することができる。）で加圧しながら２５０℃１０分間保持した後、その状態で３９０℃まで昇温し、同じ３９０℃の温度で５分間保持してから室温まで徐冷した。加圧は、５ＭＰａ、１０ＭＰａ及び２４ＭＰａの３条件でそれぞれ条件を変えて行った。 <Example 1>
A basic experiment was conducted on the shear strength of the joint obtained by the joint layer structure of the present invention. Using a Zn-Al eutectoid alloy composed of 22 mass% Al-78 mass% Zn obtained by melting and casting as a bonding material, a sample for measuring the joint shear strength was prepared according to the method shown in FIG. In this experiment, instead of using the semiconductor element 2 shown in FIG. 4, two bonded
Ｚｎ－Ａｌ共析系合金接合材は、加圧しながら３９０℃で５分間保持することによって４００℃以下の融点を有するＺｎ－Ａｌ合金等が接合面から押し出されて変形し、加圧条件５ＭＰａ、１０ＭＰａ及び２４ＭＰａにおいて厚さが６０μｍから、それぞれ５５μｍ、５４μｍ及び５２μｍと薄くなった。接合後の接合層についてＡｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）を測定した結果、加圧条件５ＭＰａ、１０ＭＰａ及び２４ＭＰａにおいて、ＤＡＳの値はそれぞれ０．２２μｍ、０．２１μｍ及び０．２０μｍであった。これらＤＡＳの値から図２に示す曲線を用いて接合層に含まれるＡｌ含有量を求めると、Ａｌ含有量は３０～３４質量％となる。
The Zn—Al eutectoid alloy bonding material is deformed by being pushed out of the bonding surface by deforming a Zn—Al alloy or the like having a melting point of 400 ° C. or lower by holding at 390 ° C. for 5 minutes while applying pressure. At 10 MPa and 24 MPa, the thickness decreased from 60 μm to 55 μm, 54 μm, and 52 μm, respectively. As a result of measuring the dendritic arm spacing (DAS) of the Al-rich phase (α phase) for the bonded layer after bonding, the DAS values were 0.22 μm, 0.21 μm, and 0 under pressure conditions of 5 MPa, 10 MPa, and 24 MPa, respectively. 20 μm. When the Al content contained in the bonding layer is determined from these DAS values using the curve shown in FIG. 2, the Al content is 30 to 34% by mass.
本実施例においては、２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金を用いて、超塑性現象が起きない条件でも接合実験を行った。すなわち、前記Ｃｕ基板／Ｎｉ／Ｃｕめっき膜からなる２枚の被接合材の間に介した前記Ｚｎ－Ａｌ共析系合金を、室温から２５０℃１０分間の加熱工程を経由しないで、そのまま３９０℃まで昇温し、２４ＭＰａで加圧しながら３９０℃の温度で５分間保持した後、室温まで徐冷した。接合後の接合層の厚さは６０μから５３μｍに薄くなり、ＤＡＳの値は０．２１μｍであった。
In this example, a bonding experiment was conducted using a Zn-Al eutectoid alloy composed of 22 mass% Al-78 mass% Zn and under conditions where superplasticity does not occur. In other words, the Zn—Al eutectoid alloy interposed between the two materials to be joined consisting of the Cu substrate / Ni / Cu plating film is left as it is without passing through the heating step from room temperature to 250 ° C. for 10 minutes. The temperature was raised to 0 ° C., held at 390 ° C. for 5 minutes while being pressurized at 24 MPa, and then gradually cooled to room temperature. The thickness of the bonding layer after bonding was reduced from 60 μm to 53 μm, and the DAS value was 0.21 μm.
＜比較例１＞
比較例１として、本実施例のＺｎ－Ａｌ共析系合金接合材の代わりに、従来の高温鉛はんだ（Ｐｂ－Ｓｎ－Ａｇ）を用いて従来の接合方法にしたがって接合層を形成した。 <Comparative Example 1>
As Comparative Example 1, a bonding layer was formed according to a conventional bonding method using conventional high-temperature lead solder (Pb—Sn—Ag) instead of the Zn—Al eutectoid alloy bonding material of this example.
比較例１として、本実施例のＺｎ－Ａｌ共析系合金接合材の代わりに、従来の高温鉛はんだ（Ｐｂ－Ｓｎ－Ａｇ）を用いて従来の接合方法にしたがって接合層を形成した。 <Comparative Example 1>
As Comparative Example 1, a bonding layer was formed according to a conventional bonding method using conventional high-temperature lead solder (Pb—Sn—Ag) instead of the Zn—Al eutectoid alloy bonding material of this example.
このようにして得られた実施例１及び比較例１の接合部について測定したせん断強度の加熱温度依存性の結果を図６に示す。図中のせん断強度は、測定個数ｎ＝４としたときの平均値である。図６に示すように、本発明のＺｎ－Ａｌ共析系合金接合材は、従来の高温鉛はんだと比べて接合強度が非常に高い接合層を形成することができ、２５０℃以上の高温においても大きなせん断強度を有し、優れた高温接合強度を有することが分かった。一方、本発明のＺｎ－Ａｌ共析系合金接合材による接合層であっても超塑性現象を利用しない場合は、せん断強度が従来の高温鉛はんだと比べてやや向上するものの、その効果は小さい。このように、接合材として１７質量％～３０質量％Ａｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなるＺｎ－Ａｌ共析系合金を接合材として使用する場合は、接合面の表面洗浄化及び密着化の効果を得るために、超塑性現象を利用することが好ましい。
FIG. 6 shows the results of the heating temperature dependence of the shear strength measured for the joints of Example 1 and Comparative Example 1 obtained in this way. The shear strength in the figure is an average value when the number of measurement n = 4. As shown in FIG. 6, the Zn—Al eutectoid alloy bonding material of the present invention can form a bonding layer having a very high bonding strength compared to conventional high-temperature lead solder, and at a high temperature of 250 ° C. or higher. Has a high shear strength and an excellent high-temperature bonding strength. On the other hand, when the superplastic phenomenon is not used even in the bonding layer made of the Zn—Al eutectoid alloy bonding material of the present invention, the shear strength is slightly improved as compared with the conventional high-temperature lead solder, but the effect is small. . As described above, a Zn—Al eutectoid alloy composed of 17 mass% to 30 mass% Al-0 to 1.5 mass% Cu-0 to 0.05 mass% Mg—Zn is used as the bonding material. In this case, it is preferable to use a superplastic phenomenon in order to obtain the effect of surface cleaning and adhesion of the joint surface.
なお、本実施例において、加圧条件を５ＭＰａ、１０ＭＰａ及び２４ＭＰａと変えても接合層厚さ及びＤＡＳの変化が小さかった理由は、半溶融温度が３９０℃とやや低く、半溶融状態を維持するために十分な温度ではなかったためと考えられる。そこで、半溶融状態になる温度を３９０℃から４３０～４８０℃まで高めたときの接合層構造及びせん断強度を測定した。
In this example, even when the pressure condition was changed to 5 MPa, 10 MPa, and 24 MPa, the change in the bonding layer thickness and DAS was small because the semi-melting temperature was slightly low at 390 ° C. and the semi-molten state was maintained. This is probably because the temperature was not sufficient. Accordingly, the bonding layer structure and shear strength were measured when the temperature at which the semi-molten state was reached was increased from 390 ° C. to 430 to 480 ° C.
＜実施例２＞
実施例１で使用したものと同じ接合材（厚さ６０μｍ）及び被接合材を用いて、１０～２０ＭＰａの範囲で加圧しながら２５０℃１０分間保持した後、その状態で４３０～４８０℃まで昇温し、同じ４３０～４８０℃の温度で５分間保持してから室温まで徐冷した。 <Example 2>
Using the same bonding material (thickness 60 μm) and the material to be bonded used in Example 1, holding at 250 ° C. for 10 minutes while applying pressure in the range of 10 to 20 MPa, the temperature was increased to 430 to 480 ° C. in that state. Warm, hold at the same temperature of 430-480 ° C. for 5 minutes, and then slowly cool to room temperature.
実施例１で使用したものと同じ接合材（厚さ６０μｍ）及び被接合材を用いて、１０～２０ＭＰａの範囲で加圧しながら２５０℃１０分間保持した後、その状態で４３０～４８０℃まで昇温し、同じ４３０～４８０℃の温度で５分間保持してから室温まで徐冷した。 <Example 2>
Using the same bonding material (
接合後のＺｎ－Ａｌ共析系合金接合材は、加圧しながら４３０～４８０℃の温度で５分間保持することによってＺｎ及びＺｎ－Ａｌ合金の一部が優先的に接合面から押し出されて変形するため、厚さを初期の６０μｍから３０～２５μと半分以下に薄くすることができた。接合後の接合層についてＡｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）を測定した結果、加圧条件１０～２０Ｍにおいて、ＤＡＳの値は０．１４～０．１２μｍの範囲であった。図２に示す曲線から分かるように、Ａｌ含有量は５０質量％以上にまで高めることができる。
After bonding, the Zn-Al eutectoid alloy bonding material is deformed by preferentially extruding part of the Zn and Zn-Al alloy from the bonding surface by holding for 5 minutes at a temperature of 430 to 480 ° C while applying pressure. Therefore, the thickness can be reduced from the initial 60 μm to 30 to 25 μm, which is less than half. As a result of measuring the dendritic arm spacing (DAS) of the Al-rich phase (α phase) for the bonded layer after bonding, the DAS value was in the range of 0.14 to 0.12 μm under pressure conditions of 10 to 20 M. . As can be seen from the curve shown in FIG. 2, the Al content can be increased to 50% by mass or more.
このようにして得られた各接合層構造を有する接合部について測定したせん断強度は、実施例１において同じ加圧条件で超塑性現象を利用して接合を行ったＺｎ－Ａｌ共析系合金接合材と比べて同じか、又はやや低い値を示した。この理由として、本実施例の接合層は応力緩和機構に大きな効果を有するＡｌ含有量が増えるものの、Ａｌリッチ相（α相）の樹枝状結晶がやや大きくなったり、互いに接近するため、接合層内に形成されるＺｎ－Ａｌ合金層との界面で破断が起きやすくなることが考えられる。
The shear strength measured for the joints having the respective joint layer structures obtained in this way is the same as that of Example 1 in which the Zn—Al eutectoid alloy joint was joined using the superplastic phenomenon under the same pressure condition. The value was the same as or slightly lower than that of the material. The reason for this is that although the bonding layer of this example increases the Al content which has a great effect on the stress relaxation mechanism, the Al-rich phase (α phase) dendritic crystals become slightly larger or approach each other. It is conceivable that the fracture is likely to occur at the interface with the Zn—Al alloy layer formed inside.
＜実施例３＞
本実施例において、ＳｉＣ半導体素子とＣｕ／ＳｉＮ／Ｃｕ絶縁基板とを、２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金の接合材（厚さ６０μｍ）を介して接合して得られる実半導体装置の接合部微細構造及び接合信頼性を評価した。本実施例の実半導体装置は図５に示す構成と構造を有し、ＳｉＣ半導体素子のサイズは４．７ｍｍ×４．７ｍｍである。本実施例によるＳｉＣ半導体装置の接合信頼性の結果を、接合プロセスと合わせて図７に示す。 <Example 3>
In this embodiment, the SiC semiconductor element and the Cu / SiN / Cu insulating substrate are bonded via a bonding material (thickness: 60 μm) of a Zn—Al eutectoid alloy composed of 22 mass% Al—78 mass% Zn. The junction microstructure and the junction reliability of the actual semiconductor device obtained in this way were evaluated. The actual semiconductor device of this example has the configuration and structure shown in FIG. 5, and the size of the SiC semiconductor element is 4.7 mm × 4.7 mm. The result of the bonding reliability of the SiC semiconductor device according to this example is shown in FIG. 7 together with the bonding process.
本実施例において、ＳｉＣ半導体素子とＣｕ／ＳｉＮ／Ｃｕ絶縁基板とを、２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金の接合材（厚さ６０μｍ）を介して接合して得られる実半導体装置の接合部微細構造及び接合信頼性を評価した。本実施例の実半導体装置は図５に示す構成と構造を有し、ＳｉＣ半導体素子のサイズは４．７ｍｍ×４．７ｍｍである。本実施例によるＳｉＣ半導体装置の接合信頼性の結果を、接合プロセスと合わせて図７に示す。 <Example 3>
In this embodiment, the SiC semiconductor element and the Cu / SiN / Cu insulating substrate are bonded via a bonding material (thickness: 60 μm) of a Zn—Al eutectoid alloy composed of 22 mass% Al—78 mass% Zn. The junction microstructure and the junction reliability of the actual semiconductor device obtained in this way were evaluated. The actual semiconductor device of this example has the configuration and structure shown in FIG. 5, and the size of the SiC semiconductor element is 4.7 mm × 4.7 mm. The result of the bonding reliability of the SiC semiconductor device according to this example is shown in FIG. 7 together with the bonding process.
図７の（ａ）に示すように、接合プロセスは、窒素ガス雰囲気中、１８ＭＰａで加圧しながら２４０℃約２０分間保持した後、加圧した状態で３９０℃まで昇温し、その温度で約２０分間保持してから徐冷を行う。２４０℃の加熱は、Ｚｎ－Ａｌ共析系合金の超塑性現象を利用することによって接合面の表面清浄化および密着化を促進させるために採用したプロセスである。図７の（ａ）に示す接合プロセスによって形成された接合層は、測定したＡｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）が０．２０μｍであり、図２に示す曲線から求めたＡｌ含有量は３２質量％である。
As shown in FIG. 7 (a), the bonding process is carried out in a nitrogen gas atmosphere while being pressurized at 18 MPa and held at 240 ° C. for about 20 minutes, and then heated to 390 ° C. in the pressurized state. Hold for 20 minutes and then cool slowly. The heating at 240 ° C. is a process adopted to promote surface cleaning and adhesion of the joint surface by utilizing the superplastic phenomenon of the Zn—Al eutectoid alloy. The bonding layer formed by the bonding process shown in FIG. 7A has a measured Al-rich phase (α phase) dendritic arm spacing (DAS) of 0.20 μm, and was obtained from the curve shown in FIG. The Al content is 32% by mass.
このようにして接合が行われたＳｉＣ半導体装置を用いて温度サイクル試験を行い、試験後の接合部を垂直方向に切断し研磨した後の断面を左端部、中央部及び右端部の３箇所で観察した断面写真を図７の（ｂ）に示す。図７の（ｂ）の結果は、室温⇔３００℃の条件で１００サイクルの温度サイクル試験を行った後のものである。図７の（ｂ）には、断面の他にも、ＳｉＣ／はんだ接合材との界面、及びはんだ接合材／Ｃｕ界面の両者について、それぞれ５００倍及び２０００倍に拡大して撮影した写真を合わせて示している。
A temperature cycle test is performed using the SiC semiconductor device bonded in this way, and the cross section after the test is cut and polished in the vertical direction at the left end, the center, and the right end. The observed cross-sectional photograph is shown in FIG. The result of (b) of FIG. 7 is a thing after performing the temperature cycle test of 100 cycles on the conditions of room temperature ⇔300 degreeC. In FIG. 7 (b), in addition to the cross section, both the interface with the SiC / solder bonding material and the solder bonding material / Cu interface are photographed at 500 times and 2000 times, respectively. It shows.
図７の（ｂ）に示すように、本実施例の接合層はボイドレスであり、室温⇔３００℃の厳しい条件で行った温度サイクル試験後でもＳｉＣ／はんだ接合材及びはんだ接合材／Ｃｕ界面の両界面には亀裂が観測されず、優れた接続信頼性を有することが確認された。また、接合面の濡れ性についても十分に確保されていることが分かる。
As shown in FIG. 7B, the bonding layer of the present example is a voidless, and the SiC / solder bonding material and the solder bonding material / Cu interface even after a temperature cycle test performed under severe conditions of room temperature to 300 ° C. No cracks were observed at both interfaces, confirming excellent connection reliability. It can also be seen that the wettability of the joint surface is sufficiently secured.
＜実施例４＞
実施例３に示す接合プロセスにおいて、半溶融温度として設定した３９０℃に代え、４５０℃にしたときの実半導体装置の接合部微細構造と接合信頼性を実施例３と同じ方法で評価した。本実施例の接合プロセスは、窒素雰囲気中で１８ＭＰａに加圧しながら２４０℃約２０分間保持した後、加圧した状態で４５０℃まで昇温し、その温度で５～１０分間保持してから徐冷を行う方法である。本実施例では、接合面の表面清浄化及び密着化を促進させるため、実施例３と同様に２４０℃の加熱によってＺｎ－Ａｌ共析系合金の超塑性現象を利用した。 <Example 4>
In the joining process shown in Example 3, instead of 390 ° C. set as the half-melting temperature, the junction microstructure and joining reliability of the actual semiconductor device when the temperature was set to 450 ° C. were evaluated by the same method as Example 3. In the joining process of this example, after holding at 240 ° C. for about 20 minutes while applying pressure of 18 MPa in a nitrogen atmosphere, the temperature is raised to 450 ° C. in the pressurized state, and the temperature is maintained at that temperature for 5 to 10 minutes, and then gradually. This is a method of cooling. In this example, in order to promote surface cleaning and adhesion of the joint surface, the superplastic phenomenon of the Zn—Al eutectoid alloy was utilized by heating at 240 ° C. as in Example 3.
実施例３に示す接合プロセスにおいて、半溶融温度として設定した３９０℃に代え、４５０℃にしたときの実半導体装置の接合部微細構造と接合信頼性を実施例３と同じ方法で評価した。本実施例の接合プロセスは、窒素雰囲気中で１８ＭＰａに加圧しながら２４０℃約２０分間保持した後、加圧した状態で４５０℃まで昇温し、その温度で５～１０分間保持してから徐冷を行う方法である。本実施例では、接合面の表面清浄化及び密着化を促進させるため、実施例３と同様に２４０℃の加熱によってＺｎ－Ａｌ共析系合金の超塑性現象を利用した。 <Example 4>
In the joining process shown in Example 3, instead of 390 ° C. set as the half-melting temperature, the junction microstructure and joining reliability of the actual semiconductor device when the temperature was set to 450 ° C. were evaluated by the same method as Example 3. In the joining process of this example, after holding at 240 ° C. for about 20 minutes while applying pressure of 18 MPa in a nitrogen atmosphere, the temperature is raised to 450 ° C. in the pressurized state, and the temperature is maintained at that temperature for 5 to 10 minutes, and then gradually. This is a method of cooling. In this example, in order to promote surface cleaning and adhesion of the joint surface, the superplastic phenomenon of the Zn—Al eutectoid alloy was utilized by heating at 240 ° C. as in Example 3.
このようにして形成された接合層はボイドレスであり、測定したＡｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）が０．１３μｍであり、図２に示す曲線から求めたＡｌ含有量は５０質量％である。また、接合後の実半導体装置の温度サイ.クル試験を室温⇔３００℃の条件で行い、１００サイクル、３００サイクル及び５００サイクルの各サイクル終了後の接合部について断面観察して接合信頼性を評価した。その結果、５００サイクル後でも、ＳｉＣ／はんだ接合材及びはんだ接合材／Ｃｕ界面の両界面には亀裂が観測されず、優れた接続信頼性を有することが確認された。
The bonding layer formed in this way is a voidless, the measured Al-rich phase (α phase) dendritic arm spacing (DAS) is 0.13 μm, and the Al content obtained from the curve shown in FIG. 50% by mass. In addition, the temperature cycle test of the actual semiconductor device after bonding is performed under the condition of room temperature to 300 ° C., and the bonding reliability is evaluated by observing the cross section of the bonded portion after each cycle of 100 cycles, 300 cycles and 500 cycles. did. As a result, even after 500 cycles, no cracks were observed in both the SiC / solder bonding material and the solder bonding material / Cu interface, and it was confirmed that the connection reliability was excellent.
一方、実施例３で形成した接合部においても、室温⇔３００℃の条件でサイクル数を３００及び５００と増やして温度サイクル試験を行った結果、３００サイクル後ではＳｉＣ／はんだ接合材及びはんだ接合材／Ｃｕ界面の両界面には亀裂が観測されなかったものの、５００サイクル後においてＳｉＣ／はんだ接合材の接合界面に両端縁から進展した微小な亀裂の存在が観測された。
On the other hand, also in the joint formed in Example 3, as a result of performing a temperature cycle test by increasing the number of cycles to 300 and 500 under the condition of room temperature to 300 ° C., after 300 cycles, the SiC / solder joint material and the solder joint material Although no cracks were observed at both interfaces of the / Cu interface, the presence of minute cracks that progressed from both edges at the SiC / solder joint interface was observed after 500 cycles.
＜比較例２＞
実施例３に示す接合プロセスにおいて、半溶融状態を示す３９０℃の加熱温度に代えて、半溶融状態を示さない温度である３００℃を採用して接合したときの実半導体装置の接合部微細構造と接合信頼性を、実施例３と同じ接合材（厚さ６０μｍ）を用いて、同じ方法で評価した。本比較例の接合プロセスは、窒素雰囲気中、１８ＭＰａで加圧しながら２４０℃約２０分間保持した後、加圧した状態で３００℃まで昇温し、その温度で約２０分間保持してから徐冷を行う方法である。この接合プロセスでは、３００℃の再加熱時に接合層の変形はほとんど見られず、接合材の厚さも初期の６０μｍとほとんど同じであった。 <Comparative example 2>
In the bonding process shown in the third embodiment, instead of the heating temperature of 390 ° C. indicating the semi-molten state, the bonding microstructure of the actual semiconductor device when bonding is performed using a temperature of 300 ° C. that does not indicate the semi-molten state. The bonding reliability was evaluated by the same method using the same bonding material (thickness 60 μm) as in Example 3. The bonding process of this comparative example was held at 240 ° C. for about 20 minutes while being pressurized at 18 MPa in a nitrogen atmosphere, then heated to 300 ° C. in the pressurized state, held at that temperature for about 20 minutes, and then gradually cooled. It is a method to do. In this joining process, deformation of the joining layer was hardly observed during reheating at 300 ° C., and the thickness of the joining material was almost the same as the initial 60 μm.
実施例３に示す接合プロセスにおいて、半溶融状態を示す３９０℃の加熱温度に代えて、半溶融状態を示さない温度である３００℃を採用して接合したときの実半導体装置の接合部微細構造と接合信頼性を、実施例３と同じ接合材（厚さ６０μｍ）を用いて、同じ方法で評価した。本比較例の接合プロセスは、窒素雰囲気中、１８ＭＰａで加圧しながら２４０℃約２０分間保持した後、加圧した状態で３００℃まで昇温し、その温度で約２０分間保持してから徐冷を行う方法である。この接合プロセスでは、３００℃の再加熱時に接合層の変形はほとんど見られず、接合材の厚さも初期の６０μｍとほとんど同じであった。 <Comparative example 2>
In the bonding process shown in the third embodiment, instead of the heating temperature of 390 ° C. indicating the semi-molten state, the bonding microstructure of the actual semiconductor device when bonding is performed using a temperature of 300 ° C. that does not indicate the semi-molten state. The bonding reliability was evaluated by the same method using the same bonding material (
このようにして形成された接合層は、測定したＡｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）が０．３０μｍであり、図２に示す曲線から求めたＡｌ含有量は２２質量％と組成の変化はなかった。また、接合後の実半導体装置の温度サイクル試験を室温⇔３００℃の条件で行い、１００サイクル、３００サイクル及び５００サイクルの各サイクル終了後の接合部について断面観察して接合信頼性を評価した。その結果、３００サイクル後で、すでにＳｉＣ／はんだ接合材及びはんだ接合材／Ｃｕの両接合界面に両端縁から微小な亀裂の存在が観測され、５００サイクルでは大きな亀裂に進展することが分かった。
The bonding layer thus formed had a measured Al-rich phase (α phase) dendrid arm spacing (DAS) of 0.30 μm, and the Al content determined from the curve shown in FIG. 2 was 22% by mass. There was no change in composition. In addition, a temperature cycle test of the actual semiconductor device after bonding was performed under conditions of room temperature and 300 ° C., and the bonding reliability was evaluated by observing a cross section of the bonded portion after the completion of each cycle of 100 cycles, 300 cycles, and 500 cycles. As a result, it was found that after 300 cycles, the presence of minute cracks was observed from both edges at both the SiC / solder joint material and the solder joint material / Cu joint interface, and a large crack was developed at 500 cycles.
＜実施例５＞
本実施例において、Ｚｎ－Ａｌ共析系合金の接合材を加圧しながら半溶融温度領域に加熱した状態で所望の時間保持する操作を２回以上繰り返すことによって形成される接合構造の例を示す。
実施例３の温度サイクル評価試験において使用したものと同じＳｉＣ半導体素子とＣｕ／ＳｉＮ／Ｃｕ絶縁基板を用い、接合材として、２２質量％Ａｌ－７８質量％Ｚｎ系を用いて、まず１回目の操作として、実施例４で示すものと同じ条件に従って半溶融温度域の４５０℃で加圧後、固相温度域の４００℃まで冷却した。本操作で接合部の組成は実施例４で示したように５０質量％Ａｌ－５０質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金になる。前記組成の接合材は半溶融温度域が４７０℃から５００℃以上に変わることが図１から分かる。そこで２回目の操作として再度窒素ガス雰囲気中、加圧しながら、半溶融温度域の５００℃まで昇温し、その温度で２０分間保持した後、徐冷した。 <Example 5>
In this embodiment, an example of a joining structure formed by repeating the operation of holding a desired time in a state in which a joining material of a Zn—Al eutectoid alloy is pressurized and heated to a semi-melting temperature region will be shown. .
Using the same SiC semiconductor element and Cu / SiN / Cu insulating substrate as those used in the temperature cycle evaluation test of Example 3, and using 22 mass% Al-78 mass% Zn system as a bonding material, first, As an operation, pressurization was performed at 450 ° C. in the semi-melting temperature range according to the same conditions as those shown in Example 4, and then cooled to 400 ° C. in the solid phase temperature range. With this operation, the composition of the joint becomes a Zn—Al eutectoid alloy composed of 50 mass% Al-50 mass% Zn as shown in Example 4. It can be seen from FIG. 1 that the semi-melting temperature region of the bonding material having the above composition changes from 470 ° C. to 500 ° C. or more. Therefore, as the second operation, the temperature was raised to 500 ° C. in the semi-melting temperature range while pressurizing again in a nitrogen gas atmosphere, and kept at that temperature for 20 minutes, and then gradually cooled.
本実施例において、Ｚｎ－Ａｌ共析系合金の接合材を加圧しながら半溶融温度領域に加熱した状態で所望の時間保持する操作を２回以上繰り返すことによって形成される接合構造の例を示す。
実施例３の温度サイクル評価試験において使用したものと同じＳｉＣ半導体素子とＣｕ／ＳｉＮ／Ｃｕ絶縁基板を用い、接合材として、２２質量％Ａｌ－７８質量％Ｚｎ系を用いて、まず１回目の操作として、実施例４で示すものと同じ条件に従って半溶融温度域の４５０℃で加圧後、固相温度域の４００℃まで冷却した。本操作で接合部の組成は実施例４で示したように５０質量％Ａｌ－５０質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金になる。前記組成の接合材は半溶融温度域が４７０℃から５００℃以上に変わることが図１から分かる。そこで２回目の操作として再度窒素ガス雰囲気中、加圧しながら、半溶融温度域の５００℃まで昇温し、その温度で２０分間保持した後、徐冷した。 <Example 5>
In this embodiment, an example of a joining structure formed by repeating the operation of holding a desired time in a state in which a joining material of a Zn—Al eutectoid alloy is pressurized and heated to a semi-melting temperature region will be shown. .
Using the same SiC semiconductor element and Cu / SiN / Cu insulating substrate as those used in the temperature cycle evaluation test of Example 3, and using 22 mass% Al-78 mass% Zn system as a bonding material, first, As an operation, pressurization was performed at 450 ° C. in the semi-melting temperature range according to the same conditions as those shown in Example 4, and then cooled to 400 ° C. in the solid phase temperature range. With this operation, the composition of the joint becomes a Zn—Al eutectoid alloy composed of 50 mass% Al-50 mass% Zn as shown in Example 4. It can be seen from FIG. 1 that the semi-melting temperature region of the bonding material having the above composition changes from 470 ° C. to 500 ° C. or more. Therefore, as the second operation, the temperature was raised to 500 ° C. in the semi-melting temperature range while pressurizing again in a nitrogen gas atmosphere, and kept at that temperature for 20 minutes, and then gradually cooled.
このようにして形成された接合層はボイドレスであり、測定したＡｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）が０．１１μｍであり、図２に示す曲線から求めたＡｌ含有量は５５質量％である。接合後の実半導体装置の温度サイクル試験を室温⇔３００℃の条件で行い、１００サイクル、３００サイクル及び５００サイクルの各サイクル終了後の接合部について断面観察して接合信頼性を評価した。その結果、５００サイクル後でも、ＳｉＣ／はんだ接合材及びはんだ接合材／Ｃｕ界面の両界面には亀裂が観測されず、実施例４と同じように優れた接続信頼性を有することが確認された。
The bonding layer thus formed is a voidless, the measured Al-rich phase (α phase) dendritic arm spacing (DAS) is 0.11 μm, and the Al content obtained from the curve shown in FIG. 55% by mass. A temperature cycle test of the actual semiconductor device after bonding was performed under conditions of room temperature and 300 ° C., and the bonding reliability was evaluated by observing a cross section of the bonded portion after the completion of each cycle of 100 cycles, 300 cycles and 500 cycles. As a result, even after 500 cycles, no cracks were observed at both of the SiC / solder bonding material and the solder bonding material / Cu interface, and it was confirmed that the connection reliability was excellent as in Example 4. .
以上のように、ＳｉＣ半導体素子を有する実半導体装置は、Ａｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）を小さくし、接合層に含まれるＡｌ含有量を多くした本発明の接合層構造を形成することによって、大きな応力緩衝効果を得ることができる。上記の実施例では半導体素子としてＳｉＣを使用した例を示したが、ＧａＮ、Ｃ（ダイヤモンド）及びＧａ２Ｏ３の何れかによる実半導体装置においても上記実施例と同じ効果を得ることができる。
As described above, the actual semiconductor device having the SiC semiconductor element has the Al-rich phase (α phase) dendritic arm spacing (DAS) reduced and the Al content contained in the bonding layer is increased. A large stress buffering effect can be obtained by forming the structure. In the above embodiment, an example in which SiC is used as a semiconductor element has been shown. However, the same effect as in the above embodiment can be obtained in an actual semiconductor device using any one of GaN, C (diamond), and Ga 2 O 3 .
＜実施例６＞
本実施例において、ＳｉＣ半導体素子とＣｕ／ＳｉＮ／Ｃｕ絶縁基板とを、２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金の接合材（厚さ２００μｍ）を介して接合して得られる実半導体装置の接合部微細構造及び接合信頼性を評価した。本実施例の実半導体装置は、実施例４と同じように、図５に示すものと同じ構成と構造を有する。本実施例によるＳｉＣ半導体装置の接合は、実施例４と同じように、図７の（ａ）に示す温度プロファイルにおいて、超塑性時の温度として２４０℃に代えて２５０℃を、拡散接合時の半溶融状態となる温度として３９０℃に代えて４５０℃を採用する以外は、図７に示すものと同じプロセスで行った。４５０℃で接合後、図１に示すｇの点から冷却を行い、ｃ３（約３５０℃）及びｄ３（２７７℃）の各変態超塑性点を通過させることによって、本実施例による接合層構造を得た。図８に本実施例による接合プロセスの模式図を示す。 <Example 6>
In this embodiment, the SiC semiconductor element and the Cu / SiN / Cu insulating substrate are bonded via a bonding material (thickness 200 μm) of a Zn—Al eutectoid alloy composed of 22 mass% Al-78 mass% Zn. The junction microstructure and the junction reliability of the actual semiconductor device obtained in this way were evaluated. The real semiconductor device of the present embodiment has the same configuration and structure as that shown in FIG. In the temperature profile shown in FIG. 7 (a), the junction of the SiC semiconductor device according to the present example is 250 ° C. instead of 240 ° C. in the temperature profile shown in FIG. The same process as shown in FIG. 7 was performed except that 450 ° C. was adopted instead of 390 ° C. as the temperature at which the semi-molten state was achieved. After bonding at 450 ° C., cooling is performed from the point g shown in FIG. 1, and each of the transformation superplastic points of c3 (about 350 ° C.) and d3 (277 ° C.) is passed through to thereby form the bonding layer structure according to this example. Obtained. FIG. 8 shows a schematic diagram of the bonding process according to this embodiment.
本実施例において、ＳｉＣ半導体素子とＣｕ／ＳｉＮ／Ｃｕ絶縁基板とを、２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金の接合材（厚さ２００μｍ）を介して接合して得られる実半導体装置の接合部微細構造及び接合信頼性を評価した。本実施例の実半導体装置は、実施例４と同じように、図５に示すものと同じ構成と構造を有する。本実施例によるＳｉＣ半導体装置の接合は、実施例４と同じように、図７の（ａ）に示す温度プロファイルにおいて、超塑性時の温度として２４０℃に代えて２５０℃を、拡散接合時の半溶融状態となる温度として３９０℃に代えて４５０℃を採用する以外は、図７に示すものと同じプロセスで行った。４５０℃で接合後、図１に示すｇの点から冷却を行い、ｃ３（約３５０℃）及びｄ３（２７７℃）の各変態超塑性点を通過させることによって、本実施例による接合層構造を得た。図８に本実施例による接合プロセスの模式図を示す。 <Example 6>
In this embodiment, the SiC semiconductor element and the Cu / SiN / Cu insulating substrate are bonded via a bonding material (
図８に示すように、本実施例で形成した接合層は、測定したＡｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）が０．１６μｍであり、図２に示す曲線から求めたＡｌ含有量は４２質量％（６３原子％）である。図９に接合後の外観写真を示す。図９から分かるように、接合後はＡｌ－ＺｎハンダがＳｉＣ半導体素子から押し出されて、周辺に溶出していることが分かる。溶出したＡｌ－ＺｎハンダのＺｎ含有量は、初期のＡｌ－Ｚｎ接合材よりも多く含まれていた。
As shown in FIG. 8, the bonding layer formed in this example has a measured Al-rich phase (α phase) dendrid arm spacing (DAS) of 0.16 μm, and the Al obtained from the curve shown in FIG. Content is 42 mass% (63 atomic%). FIG. 9 shows an appearance photograph after joining. As can be seen from FIG. 9, after bonding, Al—Zn solder is pushed out of the SiC semiconductor element and eluted to the periphery. The eluted Al—Zn solder contained more Zn than the initial Al—Zn bonding material.
このようにして接合が行われたＳｉＣ半導体デバイスを用いて温度サイクル試験を行い、試験後の接合部を垂直方向に切断し研磨した後の断面をほぼ中央部で観察した断面写真を図１０に示す。図１０の結果は、－４０⇔２００℃の条件で５００サイクルの後、さらに５０⇔３００℃の条件で１０００サイクルを追加して温度サイクル試験を行った後のものである。図１０において、（ａ）及び（ｂ）は、それぞれ拡大率を変えて示した断面写真である。
FIG. 10 is a cross-sectional photograph in which a temperature cycle test is performed using the SiC semiconductor device bonded in this manner, and the bonded section after the test is cut and polished in the vertical direction and observed at the substantially central portion. Show. The results in FIG. 10 are the results after conducting a temperature cycle test after 500 cycles under the condition of −40 to 200 ° C. and additionally 1000 cycles under the condition of 50 to 300 ° C. In FIG. 10, (a) and (b) are cross-sectional photographs showing different magnifications.
図１０に示すように、本実施例の接合層はボイドレスであり、－４０⇔２００℃×５００サイクル＋５０⇔３００℃×１０００サイクルの非常に厳しい条件で行った温度サイクル試験後でもＳｉＣ／Ａｌ－Ｚｎハンダ接合材及びＡｌ－Ｚｎハンダ接合材／Ｃｕ界面の両界面には亀裂が観測されず、変態超塑性を利用したより高い応力緩和機能の発現によって非常に優れた接続信頼性を有することが確認された。また、接合面の濡れ性についても十分に確保されていることが分かる。
As shown in FIG. 10, the bonding layer of this example is voidless, and SiC / Al— even after a temperature cycle test conducted under very severe conditions of −40 ° C. to 200 ° C. × 500 cycles + 50 ° C. to 300 ° C. × 1000 cycles. No cracks are observed at both the Zn solder joint and the Al—Zn solder joint / Cu interface, and it has very excellent connection reliability due to the development of a higher stress relaxation function utilizing transformation superplasticity. confirmed. It can also be seen that the wettability of the joint surface is sufficiently secured.
＜実施例７＞
図１１は本発明のＺｎ－Ａｌ共析系合金接合材を使用したダイオードを示す。図において、７は底部が閉鎖され上端が開放された例えば銅製の円筒状ヒートシンク、８はダイオード機能を備えたシリコンチップ、９は銅－インバー（鉄ニッケル合金）－銅からなる緩衝板、１０は円板部１０ａと円板部から垂直に伸びるリード１０ｂとからなるリード電極で、円筒状ヒートシンク７の底部上にＺｎ－Ａｌ共析系合金接合材１１を介して緩衝板９が、その上にＺｎ－Ａｌ系合金接合材１２を介してシリコンチップ８が、その上にＺｎ－Ａｌ共析系合金接合材１３を介してリード電極４の円板部４ａが、それぞれ接合されている。シリコンチップ８、緩衝板９及び円板部１０ａのＺｎ－Ａｌ共析系合金接合材と接する面にはＮｉ－Ｐめっき膜を形成している。Ｚｎ－Ａｌ共析系合金接合材１１、１２，１３としては、２２質量％Ａｌ－７８質量％Ｚｎ系からなる合金を用い、前記実施例４又は６に示す接合プロセスに従って、円筒状ヒートシンク１と、緩衝板９と、シリコンチップ８と、リード電極１０の円板部１０ａとの接合を行う。また、図１１に示す１４は円筒状ヒートシンク１内に充填したシリコンゴムである。かかる構成のダイオードは所定数の貫通孔を有する冷却フィンの貫通孔に圧入されて自動車用整流装置に使用される。この種整流装置はエンジンルームに配置され、熱的及び機械的に過酷な環境で使用されることから、高温でかつ機械的強度の高い接合材が要求されている。本発明のＺｎ－Ａｌ共析系合金接合材による接合層構造を有することにより、２５０℃以上の高温に耐え、延性と強度を有する接合部を実現できる。この実施例ではシリコンチップを使用した場合を説明したが、シリコンチップの代わりに炭化珪素（ＳｉＣ）チップを使用することが出来る。炭化珪素チップは５００℃でも安定した特性を保持できることから、接合材が固液共有状態に相変態する温度近くまで使用可能な高温ダイオードを実現できる。 <Example 7>
FIG. 11 shows a diode using the Zn—Al eutectoid alloy bonding material of the present invention. In the figure, 7 is a cylindrical heat sink made of, for example, copper whose bottom is closed and the top is opened, 8 is a silicon chip having a diode function, 9 is a buffer plate made of copper-invar (iron nickel alloy) -copper, 10 is Abuffer electrode 9 is formed on the bottom of the cylindrical heat sink 7 via a Zn-Al eutectoid alloy bonding material 11 on a lead electrode composed of a disk portion 10a and a lead 10b extending vertically from the disk portion. The silicon chip 8 is bonded via the Zn—Al based alloy bonding material 12, and the disk portion 4 a of the lead electrode 4 is bonded thereto via the Zn—Al eutectoid alloy bonding material 13. A Ni—P plating film is formed on the surfaces of the silicon chip 8, the buffer plate 9, and the disk portion 10 a that are in contact with the Zn—Al eutectoid alloy bonding material. As the Zn—Al eutectoid alloy bonding materials 11, 12, and 13, an alloy composed of 22 wt% Al—78 wt% Zn is used, and the cylindrical heat sink 1 and the heat sink 1 according to the bonding process shown in Example 4 or 6 are used. The buffer plate 9, the silicon chip 8, and the disk portion 10a of the lead electrode 10 are joined. Reference numeral 14 shown in FIG. 11 denotes silicon rubber filled in the cylindrical heat sink 1. The diode having such a configuration is press-fitted into a through hole of a cooling fin having a predetermined number of through holes and used in a rectifier for an automobile. Since this type of rectifier is disposed in an engine room and is used in a severely and thermally severe environment, a bonding material having a high temperature and high mechanical strength is required. By having the bonding layer structure of the Zn—Al eutectoid alloy bonding material of the present invention, it is possible to realize a bonded portion that can withstand high temperatures of 250 ° C. or more and has ductility and strength. In this embodiment, the case where the silicon chip is used has been described, but a silicon carbide (SiC) chip can be used instead of the silicon chip. Since the silicon carbide chip can maintain stable characteristics even at 500 ° C., a high-temperature diode that can be used up to a temperature close to the temperature at which the bonding material is transformed into a solid-liquid shared state can be realized.
図１１は本発明のＺｎ－Ａｌ共析系合金接合材を使用したダイオードを示す。図において、７は底部が閉鎖され上端が開放された例えば銅製の円筒状ヒートシンク、８はダイオード機能を備えたシリコンチップ、９は銅－インバー（鉄ニッケル合金）－銅からなる緩衝板、１０は円板部１０ａと円板部から垂直に伸びるリード１０ｂとからなるリード電極で、円筒状ヒートシンク７の底部上にＺｎ－Ａｌ共析系合金接合材１１を介して緩衝板９が、その上にＺｎ－Ａｌ系合金接合材１２を介してシリコンチップ８が、その上にＺｎ－Ａｌ共析系合金接合材１３を介してリード電極４の円板部４ａが、それぞれ接合されている。シリコンチップ８、緩衝板９及び円板部１０ａのＺｎ－Ａｌ共析系合金接合材と接する面にはＮｉ－Ｐめっき膜を形成している。Ｚｎ－Ａｌ共析系合金接合材１１、１２，１３としては、２２質量％Ａｌ－７８質量％Ｚｎ系からなる合金を用い、前記実施例４又は６に示す接合プロセスに従って、円筒状ヒートシンク１と、緩衝板９と、シリコンチップ８と、リード電極１０の円板部１０ａとの接合を行う。また、図１１に示す１４は円筒状ヒートシンク１内に充填したシリコンゴムである。かかる構成のダイオードは所定数の貫通孔を有する冷却フィンの貫通孔に圧入されて自動車用整流装置に使用される。この種整流装置はエンジンルームに配置され、熱的及び機械的に過酷な環境で使用されることから、高温でかつ機械的強度の高い接合材が要求されている。本発明のＺｎ－Ａｌ共析系合金接合材による接合層構造を有することにより、２５０℃以上の高温に耐え、延性と強度を有する接合部を実現できる。この実施例ではシリコンチップを使用した場合を説明したが、シリコンチップの代わりに炭化珪素（ＳｉＣ）チップを使用することが出来る。炭化珪素チップは５００℃でも安定した特性を保持できることから、接合材が固液共有状態に相変態する温度近くまで使用可能な高温ダイオードを実現できる。 <Example 7>
FIG. 11 shows a diode using the Zn—Al eutectoid alloy bonding material of the present invention. In the figure, 7 is a cylindrical heat sink made of, for example, copper whose bottom is closed and the top is opened, 8 is a silicon chip having a diode function, 9 is a buffer plate made of copper-invar (iron nickel alloy) -copper, 10 is A
＜実施例８＞
図１２、図１３及び図１４は本発明Ｚｎ－Ａｌ共析系合金接合材を用いた３００Ａ級ＩＧＢＴモジュールの平面図及び断面図を示したものである。
図１２は本発明の一実施例であり、１個の３００Ａ級モジュール単位の平面図を示したものである。また、図１３は図１２のＡ－Ａに沿う断面図、図１４は図１２のＢ－Ｂ線に沿う断面図である。図において、１０１は放熱板及び支持板として機能する金属基板、１０２は金属基板１０１上に２枚並べて、２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合層１０３を介して、前記実施例４又は６に示す接合プロセスに従って接合固着された例えばＡｌＮからなるセラミックス基板、１０４は各セラミックス基板１０２上に形成した例えばＮｉ／Ｃｕからなる回路層で、回路層１０４は分離された異なる形状を有する３個の部分、即ち、Ｔ字型のコレクタ共通電極となる第１の部分１０４ａ、エミッタ電極となる片状の第２の部分１０４ｂ、ゲート電極となる片状の第３の部分１０４ｃからなり、第１の部分１０４ａが中央部に、第１の部分１０４ａの脚部一側に第２の部分１０４ｂが、他方側に第３の部分１０４ｃが配置されている。第２の部分１０４ｂ及び第３の部分１０４ｃはＮｉ層上にＡｌ層１０５が形成されている。１０６はそのアノード側が回路層１０４の第１の部分１０４ａの脚部上に３個並べて、２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合層１０７を介して、前記実施例４又は６に示す接合プロセスに従って接合されたＩＧＢＴチップ、１０８はそのカソード側が第１の部分１０４ａの上辺部上に、２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合層１０９を介して、前記実施例４又は６に示す接合プロセスに従って接合されたダイオードチップ、１１０はＩＧＢＴチップ１０６のエミッタ層上に形成したＡｌを主成分とする金属層１１１と第２の部分１０４ｂ上のＡｌ層１０５とを超音波ボンディングによって接続した直径５００μｍＡｌ－０．１～１質量％Ｘ（Ｃｕ、Ｆｅ、Ｍｎ、Ｍｇ、Ｃｏ、Ｌｉ、Ｐｄ、Ａｇ、Ｈｆから選ばれた少なくとも一種類の金属）ボンディングワイヤ、１１２はＩＧＢＴチップ１０５のゲート層上に形成したＡｌを主成分とする金属層１１３と第３の部分１０４ｃ上のＡｌ層１０５とを超音波ボンディングによって接続した直径５００μｍＡｌ－０．１～１質量％Ｘ（同上）ボンディングワイヤ、１１４はダイオードチップ１０８のアノード層上に形成したＡｌを主成分とする金属層１１５と第２の部分１０４ｂ上のＡｌ層１０５とを超音波ボンディングによって接続したＡｌ－０．１～１質量％Ｘ（同上）ボンディングワイヤである。これによって、１枚のセラミックス基板１０２上に３個の並列接続されたＩＧＢＴチップ１０６と１個のダイオードチップ１０８とが逆並列接続された回路要素が形成され、１枚の金属基板１０１上に２個の回路要素が形成される。インバータを構成する場合には、１枚の金属基板１０１上の２個の回路要素を直列接続し、これを３個並列接続して、各回路要素の接続点を交流出力端子に、並列接続点を直流入力端子にすればよい。電流容量を増やすときはＩＧＢＴチップ１０６及びダイオードチップ１０８の並列接続数を増やし、高電圧化するときはＩＧＢＴチップ１０６及びダイオードチップ１０８の直列接続数を増やせばよい。 <Example 8>
12, 13 and 14 are a plan view and a cross-sectional view of a 300A class IGBT module using the Zn—Al eutectoid alloy bonding material of the present invention.
FIG. 12 shows an embodiment of the present invention, and shows a plan view of one 300A class module unit. 13 is a cross-sectional view taken along line AA in FIG. 12, and FIG. 14 is a cross-sectional view taken along line BB in FIG. In the figure, 101 is a metal substrate that functions as a heat dissipation plate and a support plate, 102 is a two-layeredmetal substrate 101, and a Zn-Al eutectoid alloy bonding layer 103 made of 22 mass% Al-78 mass% Zn is formed. Thus, a ceramic substrate made of, for example, AlN bonded and fixed in accordance with the bonding process shown in Example 4 or 6, 104 is a circuit layer made of, for example, Ni / Cu formed on each ceramic substrate 102, and the circuit layer 104 is separated. 3 parts having different shapes, that is, a first part 104a serving as a T-shaped collector common electrode, a strip-shaped second part 104b serving as an emitter electrode, and a strip-shaped third serving as a gate electrode. Part 104c, the first part 104a at the center, the second part 104b on one leg side of the first part 104a, and the third part 104c on the other side. It is located. In the second portion 104b and the third portion 104c, an Al layer 105 is formed on the Ni layer. The anode side 106 is arranged on the legs of the first portion 104a of the circuit layer 104, and is arranged through the Zn—Al eutectoid alloy bonding layer 107 made of 22 mass% Al-78 mass% Zn series. The IGBT chip 108 bonded according to the bonding process shown in Example 4 or 6 is a Zn—Al eutectoid system in which the cathode side is made of 22 mass% Al-78 mass% Zn series on the upper side of the first portion 104a. The diode chip 110, which is bonded according to the bonding process shown in Example 4 or 6 through the alloy bonding layer 109, is a metal layer 111 mainly composed of Al formed on the emitter layer of the IGBT chip 106 and the second layer. 500 μm diameter Al—0.1-1% by mass X (Cu, Fe, Mn, Mg, Co, i, Pd, Ag, Hf, at least one kind of metal) bonding wire, 112 is a metal layer 113 mainly composed of Al formed on the gate layer of the IGBT chip 105 and Al on the third portion 104c. A bonding wire 114 having a diameter of 500 μm Al-0.1 to 1% by mass X (same as above) connected to the layer 105 by ultrasonic bonding, 114 is a metal layer 115 mainly composed of Al formed on the anode layer of the diode chip 108 and a first layer. This is an Al-0.1-1 mass% X (same as above) bonding wire in which the Al layer 105 on the second portion 104b is connected by ultrasonic bonding. As a result, a circuit element in which three parallel-connected IGBT chips 106 and one diode chip 108 are connected in reverse parallel is formed on one ceramic substrate 102, and 2 on one metal substrate 101. Circuit elements are formed. When configuring an inverter, two circuit elements on one metal substrate 101 are connected in series, three of them are connected in parallel, and the connection point of each circuit element is used as an AC output terminal. May be used as a DC input terminal. When the current capacity is increased, the number of parallel connections of the IGBT chip 106 and the diode chip 108 is increased, and when the voltage is increased, the number of serial connections of the IGBT chip 106 and the diode chip 108 may be increased.
図１２、図１３及び図１４は本発明Ｚｎ－Ａｌ共析系合金接合材を用いた３００Ａ級ＩＧＢＴモジュールの平面図及び断面図を示したものである。
図１２は本発明の一実施例であり、１個の３００Ａ級モジュール単位の平面図を示したものである。また、図１３は図１２のＡ－Ａに沿う断面図、図１４は図１２のＢ－Ｂ線に沿う断面図である。図において、１０１は放熱板及び支持板として機能する金属基板、１０２は金属基板１０１上に２枚並べて、２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合層１０３を介して、前記実施例４又は６に示す接合プロセスに従って接合固着された例えばＡｌＮからなるセラミックス基板、１０４は各セラミックス基板１０２上に形成した例えばＮｉ／Ｃｕからなる回路層で、回路層１０４は分離された異なる形状を有する３個の部分、即ち、Ｔ字型のコレクタ共通電極となる第１の部分１０４ａ、エミッタ電極となる片状の第２の部分１０４ｂ、ゲート電極となる片状の第３の部分１０４ｃからなり、第１の部分１０４ａが中央部に、第１の部分１０４ａの脚部一側に第２の部分１０４ｂが、他方側に第３の部分１０４ｃが配置されている。第２の部分１０４ｂ及び第３の部分１０４ｃはＮｉ層上にＡｌ層１０５が形成されている。１０６はそのアノード側が回路層１０４の第１の部分１０４ａの脚部上に３個並べて、２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合層１０７を介して、前記実施例４又は６に示す接合プロセスに従って接合されたＩＧＢＴチップ、１０８はそのカソード側が第１の部分１０４ａの上辺部上に、２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合層１０９を介して、前記実施例４又は６に示す接合プロセスに従って接合されたダイオードチップ、１１０はＩＧＢＴチップ１０６のエミッタ層上に形成したＡｌを主成分とする金属層１１１と第２の部分１０４ｂ上のＡｌ層１０５とを超音波ボンディングによって接続した直径５００μｍＡｌ－０．１～１質量％Ｘ（Ｃｕ、Ｆｅ、Ｍｎ、Ｍｇ、Ｃｏ、Ｌｉ、Ｐｄ、Ａｇ、Ｈｆから選ばれた少なくとも一種類の金属）ボンディングワイヤ、１１２はＩＧＢＴチップ１０５のゲート層上に形成したＡｌを主成分とする金属層１１３と第３の部分１０４ｃ上のＡｌ層１０５とを超音波ボンディングによって接続した直径５００μｍＡｌ－０．１～１質量％Ｘ（同上）ボンディングワイヤ、１１４はダイオードチップ１０８のアノード層上に形成したＡｌを主成分とする金属層１１５と第２の部分１０４ｂ上のＡｌ層１０５とを超音波ボンディングによって接続したＡｌ－０．１～１質量％Ｘ（同上）ボンディングワイヤである。これによって、１枚のセラミックス基板１０２上に３個の並列接続されたＩＧＢＴチップ１０６と１個のダイオードチップ１０８とが逆並列接続された回路要素が形成され、１枚の金属基板１０１上に２個の回路要素が形成される。インバータを構成する場合には、１枚の金属基板１０１上の２個の回路要素を直列接続し、これを３個並列接続して、各回路要素の接続点を交流出力端子に、並列接続点を直流入力端子にすればよい。電流容量を増やすときはＩＧＢＴチップ１０６及びダイオードチップ１０８の並列接続数を増やし、高電圧化するときはＩＧＢＴチップ１０６及びダイオードチップ１０８の直列接続数を増やせばよい。 <Example 8>
12, 13 and 14 are a plan view and a cross-sectional view of a 300A class IGBT module using the Zn—Al eutectoid alloy bonding material of the present invention.
FIG. 12 shows an embodiment of the present invention, and shows a plan view of one 300A class module unit. 13 is a cross-sectional view taken along line AA in FIG. 12, and FIG. 14 is a cross-sectional view taken along line BB in FIG. In the figure, 101 is a metal substrate that functions as a heat dissipation plate and a support plate, 102 is a two-layered
＜実施例９＞
図１５は本発明のＺｎ－Ａｌ共析系合金接合材から形成される接合層構造を有する電力用ＭＯＳトランジスタを示す概略断面図である。図において、２１は放熱板及び支持板として機能する金属基板、２２は金属基板２１上に、２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合層２３により、前記実施例４に示す接合プロセスに従って接合固着された例えばＡｌＮからなるセラミックス基板、２４はセラミックス基板２２上に、２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合層２５により、前記実施例４又は６に示す接合プロセスに従って接合固着された電力用ＭＯＳトランジスタ基体、２６、２７及び２８は電力用ＭＯＳトランジスタ基体のアノード領域、カソード領域及びゲート領域に設けられたアルミニウムからなるアノード電極、カソード電極及びゲート電極である。ゲート電極２８は当然のことながら絶縁層２９を介してゲート領域上に設けられている。３０及び３１はカソード電極２７及びゲート電極２８に、２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合層３２及び３３により、前記実施例４又は６に示す接合プロセスに従って接合固着されたカソード外部電極及びゲート外部電極である。これらカソード外部電極３０及びゲート外部電極３１は間に、例えば樹脂を充填して一体構造にしてもよい。この実施例の特徴は、カソード電極２７及びゲート電極２８とカソード外部電極３０及びゲート外部電極３１をボンディングワイヤを使用せずに直接接合している点にある。この実施例におけるＭＯＳトランジスタ基体２４はシリコン及び炭化珪素を使用することが出来る。炭化珪素基体を使用する場合には炭化珪素が５００℃でも安定した特性を保持できることから、接合材が固液共有状態に相変態する温度近くまで使用可能な高温ＭＯＳトランジスタを実現できる。 <Example 9>
FIG. 15 is a schematic cross-sectional view showing a power MOS transistor having a bonding layer structure formed from the Zn—Al eutectoid alloy bonding material of the present invention. In the figure, 21 is a metal substrate that functions as a heat sink and a support plate, and 22 is the above-described implementation by the Zn—Al eutectoidalloy bonding layer 23 made of 22 mass% Al-78 mass% Zn based on the metal substrate 21. A ceramic substrate made of AlN, for example, bonded and fixed in accordance with the bonding process shown in Example 4, is provided on the ceramic substrate 22 by a Zn-Al eutectoid alloy bonding layer 25 made of 22% by mass Al-78% by mass Zn. The power MOS transistor substrate 26, 27 and 28 bonded and fixed in accordance with the bonding process shown in the fourth or sixth embodiment are anode electrodes made of aluminum provided in the anode region, the cathode region and the gate region of the power MOS transistor substrate. A cathode electrode and a gate electrode. Naturally, the gate electrode 28 is provided on the gate region via the insulating layer 29. Reference numerals 30 and 31 denote a Zn-Al eutectoid alloy bonding layers 32 and 33 made of 22 mass% Al-78 mass% Zn based on the cathode electrode 27 and the gate electrode 28, respectively, according to the bonding process shown in Example 4 or 6. The cathode external electrode and the gate external electrode are bonded and fixed. The cathode external electrode 30 and the gate external electrode 31 may be integrated with, for example, a resin filled therebetween. This embodiment is characterized in that the cathode electrode 27 and the gate electrode 28 are directly joined to the cathode external electrode 30 and the gate external electrode 31 without using bonding wires. The MOS transistor base 24 in this embodiment can use silicon and silicon carbide. In the case of using a silicon carbide substrate, since silicon carbide can maintain stable characteristics even at 500 ° C., it is possible to realize a high-temperature MOS transistor that can be used up to a temperature close to the temperature at which the bonding material is transformed into a solid-liquid shared state.
図１５は本発明のＺｎ－Ａｌ共析系合金接合材から形成される接合層構造を有する電力用ＭＯＳトランジスタを示す概略断面図である。図において、２１は放熱板及び支持板として機能する金属基板、２２は金属基板２１上に、２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合層２３により、前記実施例４に示す接合プロセスに従って接合固着された例えばＡｌＮからなるセラミックス基板、２４はセラミックス基板２２上に、２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合層２５により、前記実施例４又は６に示す接合プロセスに従って接合固着された電力用ＭＯＳトランジスタ基体、２６、２７及び２８は電力用ＭＯＳトランジスタ基体のアノード領域、カソード領域及びゲート領域に設けられたアルミニウムからなるアノード電極、カソード電極及びゲート電極である。ゲート電極２８は当然のことながら絶縁層２９を介してゲート領域上に設けられている。３０及び３１はカソード電極２７及びゲート電極２８に、２２質量％Ａｌ－７８質量％Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合層３２及び３３により、前記実施例４又は６に示す接合プロセスに従って接合固着されたカソード外部電極及びゲート外部電極である。これらカソード外部電極３０及びゲート外部電極３１は間に、例えば樹脂を充填して一体構造にしてもよい。この実施例の特徴は、カソード電極２７及びゲート電極２８とカソード外部電極３０及びゲート外部電極３１をボンディングワイヤを使用せずに直接接合している点にある。この実施例におけるＭＯＳトランジスタ基体２４はシリコン及び炭化珪素を使用することが出来る。炭化珪素基体を使用する場合には炭化珪素が５００℃でも安定した特性を保持できることから、接合材が固液共有状態に相変態する温度近くまで使用可能な高温ＭＯＳトランジスタを実現できる。 <Example 9>
FIG. 15 is a schematic cross-sectional view showing a power MOS transistor having a bonding layer structure formed from the Zn—Al eutectoid alloy bonding material of the present invention. In the figure, 21 is a metal substrate that functions as a heat sink and a support plate, and 22 is the above-described implementation by the Zn—Al eutectoid
本発明のＺｎ－Ａｌ共析系合金接合材から形成される接合層構造はＩＧＢＴモジュールに限らず一般のパワーモジュール、ダイオードモジュールなどにも適用することができる。
The bonding layer structure formed from the Zn—Al eutectoid alloy bonding material of the present invention can be applied not only to the IGBT module but also to a general power module, a diode module and the like.
本発明の接合層構造は応力緩衝機能を有するＡｌの存在量が増えるため、接合層において応力緩和の効果が高くなり、接合信頼性の向上を図ることができ、熱伝導性も向上できる。本発明で使用するＺｎ－Ａｌ共析系合金が有する超塑性現象を利用することによって、接合界面の濡れ性が確保されるとともに応力緩和効果が得られるため、高温の接合強度及び接合信頼性が大幅に向上し、長寿命の接合部形成を実現できる。 したがって、本発明の接合層構造によってＳｉＣ又はＧａＮ、Ｃ（ダイヤモンド）及びＧａ２Ｏ３等のワイドギャップ半導体素子を実装した半導体装置は、パワーデバイス又はパワーエレクトロニクス製品等で求められる耐熱性の要求に答えることができ、２００℃以上、特に２５０℃以上の高温使用環境において長期間の使用に耐えることが可能になる。
In the bonding layer structure of the present invention, since the amount of Al having a stress buffering function increases, the stress relaxation effect is enhanced in the bonding layer, the bonding reliability can be improved, and the thermal conductivity can be improved. By utilizing the superplastic phenomenon of the Zn-Al eutectoid alloy used in the present invention, the wettability of the bonding interface is ensured and the stress relaxation effect is obtained, so that the high-temperature bonding strength and bonding reliability can be obtained. It is greatly improved and a long-life joint can be formed. Therefore, the semiconductor device in which wide gap semiconductor elements such as SiC, GaN, C (diamond), and Ga 2 O 3 are mounted by the bonding layer structure of the present invention meets the heat resistance requirement required for power devices or power electronics products. It is possible to answer, and it becomes possible to endure long-term use in a high temperature use environment of 200 ° C. or higher, particularly 250 ° C. or higher.
本発明の接続構造は、一般のパワーモジュール、ダイオードモジュールなどの他の半導体装置にも適用することができ、産業上の有用性は極めて高い。
The connection structure of the present invention can be applied to other semiconductor devices such as a general power module and a diode module, and is extremely useful in industry.
１ Ｚｎ－Ａｌ共析系合金接合材
２ 半導体素子
３ メタライズ部分
４ Ｃｕ基板
５ Ｃｕめっき膜
６ 相互拡散層
７ 円筒状ヒートシンク
８ シリコンチップ
９ 緩衝板
１０ リード電極
１１ Ｚｎ－Ａｌ共析系合金接合材
１２ Ｚｎ－Ａｌ共析系合金接合材
１３ Ｚｎ－Ａｌ共析系合金接合材
１４ シリコーンゴム DESCRIPTION OF SYMBOLS 1 Zn-Al eutectoid alloy bonding material 2Semiconductor element 3 Metallized part 4 Cu substrate 5 Cu plating film 6 Interdiffusion layer 7 Cylindrical heat sink 8 Silicon chip 9 Buffer plate 10 Lead electrode 11 Zn-Al eutectoid alloy bonding material 12 Zn-Al eutectoid alloy bonding material 13 Zn-Al eutectoid alloy bonding material 14 Silicone rubber
２ 半導体素子
３ メタライズ部分
４ Ｃｕ基板
５ Ｃｕめっき膜
６ 相互拡散層
７ 円筒状ヒートシンク
８ シリコンチップ
９ 緩衝板
１０ リード電極
１１ Ｚｎ－Ａｌ共析系合金接合材
１２ Ｚｎ－Ａｌ共析系合金接合材
１３ Ｚｎ－Ａｌ共析系合金接合材
１４ シリコーンゴム DESCRIPTION OF SYMBOLS 1 Zn-Al eutectoid alloy bonding material 2
Claims (10)
- 被接合材ＡとＢとを合金接合材によって接合し形成される接合層の構造であって、
前記合金接合材がＺｎ－Ａｌ共析系合金であり、且つ
前記被接合材Ａ及びＢと前記合金接合材とのそれぞれの接合面において、どちらか小さな面積を有する方の被接合材の接合面内、又はどちらとも同じ面積を有する被接合材の接合面内に存在する接合層に含まれるＡｌリッチ相（α相）のデンドライドアームスペーシング（ＤＡＳ）が０．０６μｍを超え、０．３μｍ未満であることを特徴とする合金接合材による接合層構造。 It is a structure of a joining layer formed by joining the materials to be joined A and B with an alloy joining material,
The alloy bonding material is a Zn—Al eutectoid alloy, and the bonding surface of the bonding material having the smaller area of the bonding surfaces of the bonding materials A and B and the alloy bonding material. Density arm spacing (DAS) of Al-rich phase (α phase) included in the bonding layer existing in the bonding surface of the materials to be bonded having the same area inside or both exceeds 0.06 μm and is less than 0.3 μm A bonding layer structure made of an alloy bonding material. - 前記被接合材Ａ及びＢと前記合金接合材とのそれぞれの接合面において、どちらか小さな面積を有する方の被接合材の接合面内、又はどちらとも同じ面積を有する被接合材の接合面内に存在する接合層は、３０質量％を超え９７質量％以下のＡｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなる組成を有することを特徴とする請求項１に記載の合金接合材による接合層構造。 In each of the bonding surfaces of the materials A and B to be bonded and the alloy bonding material, the bonding surface of the bonding material having the smaller area, or the bonding surface of the bonding materials having the same area. The bonding layer present in the present invention has a composition comprising an Al-0 to 1.5 mass% Cu-0 to 0.05 mass% Mg—Zn system that exceeds 30 mass% and is 97 mass% or less. Item 2. A bonding layer structure using the alloy bonding material according to Item 1.
- 請求項１又は２に記載の接合層の構造を形成するための方法であって、
前記被接合材ＡとＢとの間に、１７質量％～３０質量％Ａｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合材を介在し、加圧しながら前記接合材を半溶融温度領域に加熱した状態で所望の時間保持する操作を１回又は２回以上繰り返した後に徐冷することを特徴とする接合層構造の形成方法。 A method for forming a structure of a bonding layer according to claim 1 or 2,
A Zn—Al eutectoid alloy composed of 17 mass% to 30 mass% Al-0 to 1.5 mass% Cu-0 to 0.05 mass% Mg—Zn based on the materials A and B to be joined. A bonding layer structure characterized by interposing a bonding material and gradually cooling after repeating the operation of holding the bonding material for a desired time in a state where the bonding material is heated to a semi-molten temperature region while being pressed. Forming method. - 請求項１又は２に記載の接合層の構造を形成するための方法であって、
前記被接合材ＡとＢとの間に、３０質量％を超え９７質量％以下のＡｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなるＺｎ－Ａｌ共析系合金接合材を介在し、加圧又は無圧の状態で前記接合材を半溶融温度領域に加熱し、所望の時間保持した後に徐冷することを特徴とする接合層構造の形成方法。 A method for forming a structure of a bonding layer according to claim 1 or 2,
Between the materials A and B to be bonded, a Zn—Al copolymer composed of an Al-0 to 1.5 mass% Cu-0 to 0.05 mass% Mg—Zn system that exceeds 30 mass% and is 97 mass% or less. A method for forming a bonding layer structure, comprising: depositing an alloy-based alloy bonding material, heating the bonding material to a semi-melting temperature region in a pressurized or non-pressurized state, maintaining the desired time, and then gradually cooling. - 前記接合材を半溶融温度領域に加熱した状態で所望の時間保持する操作の前に、超塑性現象を発現する温度領域に加熱した状態で所望の時間保持する操作を行うことを特徴とする請求項３又は４に記載の接合層構造の形成方法。 The operation of holding the bonding material for a desired time in a state heated to a temperature region in which a superplastic phenomenon occurs is performed before the operation for holding the bonding material in a state heated to a semi-melting temperature region for a desired time. Item 5. A method for forming a bonding layer structure according to Item 3 or 4.
- 前記接合材を半溶融温度領域に加熱し、加圧した状態で所望の時間保持し、３０質量％を超え９７質量％以下のＡｌ－０～１．５質量％Ｃｕ－０～０．０５質量％Ｍｇ－Ｚｎ系からなる組成を有する接合層構造を形成した後、そのまま加圧した状態で冷却し、変態超塑性点を通過させる操作を行うことを特徴とする請求項３～５の何れかに記載の接合層構造の形成方法。 The bonding material is heated to a semi-melting temperature region and held in a pressurized state for a desired time, and is more than 30 mass% and 97 mass% or less Al-0 to 1.5 mass% Cu-0 to 0.05 mass. 6. The method according to claim 3, wherein after forming a bonding layer structure having a composition composed of% Mg—Zn, it is cooled in a pressurized state and passed through a transformation superplastic point. A method for forming a bonding layer structure according to claim 1.
- 半導体基体、該半導体基体に直接又はセラミック基板を介して接合層によって接合された金属基板を備え、前記接合層が請求項１又は２に記載の構造を有することを特徴とする半導体装置。 A semiconductor device comprising: a semiconductor substrate; and a metal substrate bonded to the semiconductor substrate directly or via a ceramic substrate, the bonding layer having the structure according to claim 1.
- 前記半導体基体がワイドギャップ半導体であることを特徴とする請求項７に記載の半導体装置。 The semiconductor device according to claim 7, wherein the semiconductor substrate is a wide gap semiconductor.
- 半導体基体、該半導体基体に直接又はセラミック基板を介して接合層によって接合された金属基板を備え、前記接合層の構造が請求項３～６の何れかに記載の形成方法によって形成されることを特徴とする半導体装置の製造方法。 A semiconductor substrate, and a metal substrate bonded to the semiconductor substrate directly or via a ceramic substrate by a bonding layer, wherein the structure of the bonding layer is formed by the forming method according to any one of claims 3 to 6. A method of manufacturing a semiconductor device.
- 前記半導体基体がワイドギャップ半導体であることを特徴とする請求項９に記載の半導体装置の製造方法。 10. The method of manufacturing a semiconductor device according to claim 9, wherein the semiconductor substrate is a wide gap semiconductor.
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| JPS5495957A (en) * | 1978-01-13 | 1979-07-28 | Masanobu Nakamura | Method of bonding metallic materials |
| JPH03285763A (en) * | 1990-03-30 | 1991-12-16 | Showa Alum Corp | Production of laminate plate of iron and aluminum |
| JP2009113050A (en) * | 2007-11-02 | 2009-05-28 | Ibaraki Univ | Zn-al eutectoid-base alloy joining material, method for manufacturing zn-al eutectoid-base alloy joining material, joining method using zn-al eutectpoid-base alloy joining material, and semiconductor device using zn-al eutectpoid-base alloy joining material |
| US20090250442A1 (en) * | 2007-12-03 | 2009-10-08 | Eerc Foundation | Joining of difficult-to-weld materials |
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| JP5738523B2 (en) * | 2009-09-09 | 2015-06-24 | 株式会社日立製作所 | Connection material, connection method, and manufacturing method of semiconductor device |
| JP2014147966A (en) * | 2013-02-04 | 2014-08-21 | Hitachi Ltd | Joining material, joining method, joining structure, and semiconductor device |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5495957A (en) * | 1978-01-13 | 1979-07-28 | Masanobu Nakamura | Method of bonding metallic materials |
| JPH03285763A (en) * | 1990-03-30 | 1991-12-16 | Showa Alum Corp | Production of laminate plate of iron and aluminum |
| JP2009113050A (en) * | 2007-11-02 | 2009-05-28 | Ibaraki Univ | Zn-al eutectoid-base alloy joining material, method for manufacturing zn-al eutectoid-base alloy joining material, joining method using zn-al eutectpoid-base alloy joining material, and semiconductor device using zn-al eutectpoid-base alloy joining material |
| US20090250442A1 (en) * | 2007-12-03 | 2009-10-08 | Eerc Foundation | Joining of difficult-to-weld materials |
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