Joined body and method for manufacturing joined body

Abstract

To appropriately join members to each other and to suppress reduction in joining strength between the members.SOLUTION: The joined body 100 includes a first member 20, a second member 30, and a joining layer 10A made of copper located between the first member 20 and the second member 30, and the joining layer 10A has a density of 50% or more and 99% or less.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a bonded body and a method for manufacturing the bonded body. [Background technology]

[0002] In order to bond two or more components, a copper paste containing copper particles may be used as a bonding material. Patent Document 1 describes that a first member and a second member are bonded by sintering a copper paste applied between the first member and the second member. There is also known a technique for directly bonding members by diffusion bonding without using a bonding material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-45514 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when directly joining components together, there are cases where the joining surfaces of the components have different heights and therefore the joining cannot be performed properly. Furthermore, depending on the joining method, there is a risk that the joining strength may be reduced.

[0005] Therefore, it is required to appropriately join the members and to prevent a decrease in the joining strength between the members.

[0006] The present invention has been made in consideration of the above, and aims to provide a joined body that can appropriately join members together and suppress a decrease in the joining strength between the members, and a method for manufacturing the joined body. [Means for solving the problem]

[0007] The bonded body of the present disclosure has a first member, a second member, and a copper bonding layer located between the first member and the second member, and the bonding layer has a density of 50% or more and 99% or less.

[0008] The first member and the second member have bonding surfaces that come into contact with the bonding layer and are made of copper.

[0009] The bonded body has a shear strength of more than 5 MPa.

[0010] The method for manufacturing a bonded body of the present disclosure includes the steps of placing a solid bonding layer made of copper having an average porosity of 5% or more and 80% or less on the surface of at least one of a first member and a second member, overlapping the first member and the second member with the bonding layer interposed therebetween, and heating the overlapping first member and the second member with the bonding layer interposed therebetween to form a bonded body.

[0011] In the step of forming the bonded body, the first member and the second member that are stacked with the bonding layer interposed therebetween are heated at a heating temperature of 100° C. or higher and 350° C. or lower.

[0012] In the step of forming the bonded body, the first member and the second member that are stacked with the bonding layer interposed therebetween are pressed together at a pressure of 1 MPa or more and 30 MPa or less.

[0013] In the manufacturing method, the first member and the second member are superposed on each other in a state where a sintering aid is provided on the surface of the bonding layer. [Effects of the Invention]

[0014] According to the present invention, it is possible to appropriately join members together and to suppress a decrease in the joining strength between the members. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram of a bonding layer according to this embodiment. [Figure 2]FIG. 2 is a schematic diagram illustrating a bonding method for a bonded body according to this embodiment. [Figure 3] FIG. 3 is a schematic diagram illustrating a bonding method for a bonded body according to this embodiment. [Figure 4] FIG. 4 is a schematic diagram illustrating a bonding method for a bonded body according to this embodiment. [Figure 5] FIG. 5 is a diagram showing an example of a binarized image of a junction. [Figure 6] FIG. 6 is a table showing the conjugates for each example. [Figure 7] FIG. 7 shows images of the cross sections of the bonded bodies of the examples. [Figure 8] FIG. 8 shows images of the cross sections of the bonded bodies of the examples. [Figure 9] FIG. 9 shows images of the cross sections of the bonded bodies of the examples. [Figure 10] FIG. 10 shows images of the cross sections of the bonded bodies of the examples. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described in detail below with reference to the drawings. The present invention is not limited to the following modes for carrying out the invention (hereinafter referred to as "embodiments"). The components in the following embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiments can be combined as appropriate. Numerical values ​​include the range of rounding.

[0017] (Joining layer) FIG. 1 is a schematic diagram of a bonding layer according to this embodiment. The bonding layer 10 according to this embodiment is a member that bonds a first member 20 and a second member 30, which will be described later. The bonding layer 10 is a porous copper member, and is solid, rather than a liquid phase such as paste or ink. The bonding layer 10 may have any shape, but in this embodiment it is plate-shaped. Note that the bonding layer 10 is not limited to having only copper, and may also contain materials other than copper. When a liquid-phase material such as paste or ink is used as the bonding layer, the bonded components may become misaligned, which may reduce the alignment accuracy between the components. In contrast, by using a solid bonding layer 10, it is possible to prevent the components from becoming misaligned and reduce the alignment accuracy between the components.

[0018] As shown in FIG. 1 , the bonding layer 10 according to this embodiment includes a plurality of copper particles 12. The copper particles 12 are particles made of copper. The bonding layer 10 may be a layer having only a plurality of copper particles 12, or may include other components. For example, the bonding layer 10 may have a copper sheet layer that is a copper sheet, and a porous layer containing a plurality of copper particles 12 may be formed on one or both sides (preferably both sides) of the copper sheet layer.

[0019] (Average porosity) The average porosity of the bonding layer 10 is preferably 5% or more and 80% or less, more preferably 20% or more and 75% or less, and even more preferably 30% or more and 70% or less. When the lower limit of the average porosity is within this range, it is possible to suppress a decrease in the bonding strength when the first member 20 and the second member 30 are bonded. Furthermore, when the upper limit of the average porosity is within this range, appropriate deformation occurs during bonding, appropriate absorption of variations in height between the first member 20 and the second member 30, and appropriate bonding of the first member 20 and the second member 30 is possible. The average porosity of the bonding layer 10 can be calculated by image analysis of a cross section of the bonding layer 10 using a scanning electron microscope. Specifically, the average porosity is defined as the arithmetic mean of the porosity P (%) calculated by the following formula (1). Specifically, the measurement is performed by taking images three times in different fields of view, and the average value of the calculated porosities is defined as the average porosity.

[0020] P(%) = (S2 / S1) × 100 (1)

[0021] In equation (1), P is the porosity of the bonding layer 10, S1 is the total area of ​​the bonding layer 10 in the cross-sectional image of the bonding layer 10, and S2 is the area of ​​the pore portion in the bonding layer 10 in the cross-sectional image of the bonding layer 10.

[0022] When the bonding layer 10 includes a layer (e.g., a copper sheet layer) other than the porous layer containing a plurality of copper particles 12, the average porosity of the porous layer is taken as the average porosity of the bonding layer 10. In this case, the average porosity can be calculated by image analysis of a cross section of the porous layer using a scanning electron microscope.

[0023] (Thickness) The thickness of the bonding layer 10 is preferably 0.5 μm to 20 μm, more preferably 2 μm to 18 μm, and even more preferably 5 μm to 16 μm. When the thickness is in this range, the first member 20 and the second member 30 can be bonded appropriately.

[0024] The thickness of the bonding layer 10 can be measured as follows: After the bonding layer 10 is completely encapsulated with epoxy resin, it is cut perpendicular to the in-plane direction of the bonding layer 10, and the cut surface is polished with an argon ion beam. The polished surface is then observed with a scanning electron microscope, and the thickness of the bonding sheet is measured at 100 or more random locations. The average value is taken as the thickness of the bonding layer 10.

[0025] (Method of manufacturing the bonding layer) The bonding layer 10 may be manufactured by any method. For example, the bonding layer 10 may be manufactured by electroplating. In this case, for example, a porous layer can be formed on the surface of the copper sheet layer by immersing the copper sheet layer in an acidic electrolytic copper plating solution. Specifically, the copper sheet layer is immersed in an acidic electrolytic copper plating solution, and a copper material made of electrolytic copper or oxygen-free copper is placed in a position facing the surface of the copper sheet layer. Then, the copper sheet layer is connected to the negative electrode as a cathode, and the copper material is connected to the positive electrode as a soluble anode. A voltage is applied between the copper sheet layer and the copper material, and a porous layer is formed on the surface of the copper sheet layer as a copper plating film, thereby manufacturing the bonding layer 10. The copper foil constituting the copper sheet layer can be pure copper or a copper alloy. For example, oxygen-free copper, tough pitch copper, or phosphorus-deoxidized copper can be used. The copper foil can be a rolled copper foil obtained by rolling such a copper material, or an electrolytic copper foil produced by electrolytic copper plating. Here, a copper material is used as the soluble anode, but an insoluble anode such as Pt / Ti can also be used instead of the copper material.

[0026] The acidic copper electroplating solution is a liquid containing a soluble copper salt, an azole compound having two to three nitrogen atoms in a five-membered ring as a copper ion electrodeposition inhibitor, an acid, and water. If necessary, a brightener, a surfactant, an antioxidant, etc. may also be added. Specific examples of soluble copper salts include copper sulfate, copper oxide, copper carbonate, copper alkanesulfonates such as copper methanesulfonate and copper propanoate, copper alkanolsulfonates such as copper isethionate and copper propanolsulfonate, and copper organic acids such as copper acetate, copper citrate, and copper tartrate. These can be used alone or in combination of two or more. The acid may be an organic acid or an inorganic acid. Examples of such acids include sulfuric acid; alkanesulfonic acids such as methanesulfonic acid and propanesulfonic acid; alkanolsulfonic acids such as isethionic acid and propanolsulfonic acid; and organic acids such as citric acid, tartaric acid, and formic acid. These may be used alone or in combination of two or more. Examples of water include pure water such as ion-exchanged water and distilled water. Examples of the azole compound include imidazole, 2-aminoimidazole, pyrazole, 3-aminoimidazole, 1,2,3-triazole, 1,2,4-triazole, 3-amino-1,2,4-triazole, 3,5-diamino-1,2,4-triazole, and 3-amino-5-methylthio-1H-1,2,4-triazole.

[0027] As described above, bonding layer 10 is a layer containing a plurality of copper particles 12, but is not limited to a layer containing a plurality of copper particles 12, as long as it is a porous copper layer. For example, bonding layer 10 may be a layer formed by roughening a copper plate-shaped member by etching or the like. Furthermore, bonding layer 10 may be a sintered body in which a plurality of copper particles 12 are sintered.

[0028] (Method of manufacturing a bonded body) 2 to 4 are schematic diagrams illustrating a bonding method for a bonded body according to this embodiment. In this embodiment, a bonded body 100 is manufactured by bonding a first member 20 and a second member 30 with a bonding layer 10. The first member 20 and the second member 30 may be any member, but in this embodiment, they are preferably semiconductor elements. Examples of semiconductor elements include an IGBT (Insulated Gate Bipolar Transistor), a diode, a Schottky barrier diode, a MOS-FET (Metal Oxide Semiconductor Field Effect Transistor), a thyristor, logic, a sensor, an analog integrated circuit, an LED (Light Emitting Diode), a semiconductor laser, and an oscillator.

[0029] In this embodiment, the first member 20 and the second member 30 are provided with protruding electrodes (bumps) connected to the semiconductor elements. Specifically, as shown in FIG. 2 , the first member 20 has an element layer 22, which is a layer of a semiconductor element, and protruding electrodes 24 provided on the surface of the element layer 22 and electrically connected to the element layer 22. Similarly, as shown in FIG. 3 , the second member 30 has an element layer 32, which is a layer of a semiconductor element, and protruding electrodes 34 provided on the surface of the element layer 32 and electrically connected to the element layer 32. In this embodiment, a bonding layer 10 is disposed between the protruding electrodes 24 of the first member 20 and the protruding electrodes 34 of the second member 30, and the bonding layer 10 is pressurized and sintered to bond the protruding electrodes 24 of the first member 20 and the protruding electrodes 34 of the second member 30 to form a bonded body 100.

[0030] The protruding electrodes 24, 34 are conductive members, and in this embodiment, it is preferable that at least the surface is made of copper. For example, the protruding electrodes 24, 34 may have a base material and a copper layer (copper plated layer) formed on the surface of the base material, or the entire electrode may be a copper layer. It is preferable that the copper layer of the protruding electrodes 24, 34 is not a sintered copper body; in other words, it is preferable that it does not have voids inside. The diameter D (see FIG. 3) of the protruding electrodes 24, 34 is preferably 5 μm or more and 100 μm or less, more preferably 10 μm or more and 50 μm or less, and even more preferably 10 μm or more and 20 μm or less. The bonding layer 10 in this embodiment can appropriately bond protruding electrodes of such sizes to each other. The diameter D refers to the diameter of the surfaces 24 a, 34 a at the tips of the protruding electrodes 24, 34. If the surfaces 24 a, 34 a are not circular, the diameter D may be the diameter of the surfaces 24 a, 34 a converted into a circle. In other words, the diameter D may be the diameter of a circle having the same area as the surfaces 24 a, 34 a. The number of protruding electrodes 24, 34 may be any number.

[0031] The method for producing the bonded body of this embodiment will be specifically described below.

[0032] (Placement step) 2, in this bonding method, a disposing step is performed in which a bonding layer 10 is disposed on at least one of the surface 24a (bonding surface) of the protruding electrode 24 of the first member 20 and the surface 34a (bonding surface) of the protruding electrode 34 of the second member 30. In the example of FIG. 2, the bonding layer 10 is disposed on the surface 24a of the protruding electrode 24 of the first member 20, but this is not limiting, and the bonding layer 10 may be disposed on the surface 34a of the protruding electrode 34 of the second member 30, or on both of them.

[0033] (Overlay step) 3, a lamination step is performed in which the first member 20 and the second member 30 are laminated together with the bonding layer 10 interposed therebetween. In this step, the surfaces 24a of the protruding electrodes 24 of the first member 20 and the surfaces 34a of the protruding electrodes 34 of the second member 30 are laminated together with the bonding layer 10 interposed therebetween. That is, in this step, the surface 24a of the first member 20 and one surface of the bonding layer 10 come into contact with each other, and the surface 34a of the second member 30 and the other surface of the bonding layer 10 come into contact with each other.

[0034] (sintering aid) In this embodiment, the first member 20 and the second member 30 are overlapped with each other in a state in which a sintering aid is provided on the surface of the bonding layer 10. That is, the first member 20 and the second member 30 are overlapped with the bonding layer 10 having the sintering aid provided on its surface interposed therebetween. The sintering aid is a film that suppresses the formation of an oxide film (copper oxide film) on the surface of the bonding layer 10 (the surface of the copper particles 12 in this example).

[0035] In this embodiment, a sintering aid that reduces the oxide film (copper oxide) is applied to the surface of the bonding layer 10 (in this example, the surface of the copper particles 12). The timing for applying the sintering aid to the bonding layer 10 may be arbitrary, and may be before the disposing step, after the disposing step and before the overlapping step, or after the overlapping step and before the heating step described below. As such a sintering aid, any reducing agent capable of reducing the oxide film (copper oxide) may be used. For example, the sintering aid may be one or more of alcohols such as methanol and 2-propanol, carboxylic acids such as formic acid, citric acid, and acrylic acid, carboxylic acid salts such as ammonium acetate, copper acetate, and copper formate, silane coupling agents such as octyltrichlorosilane, azoles such as imidazole, triazole, and pyrrole, and thiols such as heptanethiol, dodecanethiol, octadecanethiol, and methylthiadiazolethiol. It is more preferable to use formic acid, triazole, octyltrichlorosilane, or dodecanethiol as the sintering aid.

[0036] In this way, by applying a reducing sintering aid to the surface of the bonding layer 10, the sintering aid can reduce the oxide film during bonding, which prevents the oxide film from hindering sintering of copper in the bonding layer 10 and allows the first member 20 and the second member 30 to be properly bonded. Note that it is preferable that the sintering aid is removed by heating during bonding and does not remain in the bonded body 100.

[0037] However, the sintering aid is not limited to those mentioned above. For example, after the surface of the bonding layer 10 is reduced to remove the oxide film (copper oxide), the surface of the bonding layer 10 (the surface of the copper particles 12 in this example) may be coated in advance with a sintering aid that suppresses oxidation. In other words, in this case, the arranging step and the superposing step are performed using the bonding layer 10 coated with the sintering aid. An organic protective film, which is a film of an organic substance, can be used as the sintering aid that coats the bonding layer 10 (copper particles 12). As the organic protective film, a film derived from citric acid can be used.

[0038] In this way, by coating the surface of the bonding layer 10 in advance with a sintering aid that suppresses oxidation, it is possible to suppress the surface of the bonding layer 10 from oxidizing and forming an oxide film, thereby enabling appropriate bonding of the first member 20 and the second member 30. Note that it is preferable that this sintering aid is removed by heating during bonding and does not remain in the bonded body 100.

[0039] It should be noted that it is not essential to place a sintering aid on the surface of the bonding layer 10 as described above.

[0040] (heating step) 4, a heating step is performed in which the first member 20 and the second member 30, which are stacked with the bonding layer 10 interposed therebetween, are heated to form the bonded body 100. In the heating step, the first member 20 and the second member 30, which are stacked with the coating layer interposed therebetween, are heated at a predetermined temperature for a predetermined time. By performing the heating step, the copper (copper particles 12 in this example) in the bonding layer 10 is sintered to form the bonding layer 10A, and the bonded body 100 is produced in which the protruding electrodes 24 of the first member 20 and the protruding electrodes 34 of the second member 30 are bonded by the bonding layer 10A.

[0041] In the heating step, the first member 20 and the second member 30, which are stacked with the bonding layer 10 interposed therebetween, are preferably heated in a non-reducing atmosphere. The non-reducing atmosphere here refers to a state filled with a non-reducing gas, and can also be referred to as an inert gas atmosphere filled with an inert gas. Examples of non-reducing gases include nitrogen and rare gases such as argon. For example, in this embodiment, the heating step may be performed in a nitrogen atmosphere with an oxygen concentration of 1000 ppm. Performing the heating step in a non-reducing atmosphere eliminates the need for a reducing gas, making the heating step easier to perform.

[0042] In the heating step, it is preferable to heat the first member 20 and the second member 30, which are stacked with the bonding layer 10 interposed therebetween, while applying a predetermined pressure to at least one of them. The predetermined pressure here is preferably 1 MPa to 30 MPa, more preferably 5 MPa to 25 MPa, and even more preferably 10 MPa to 20 MPa. By applying a pressure within this range, the bonding layer 10 is appropriately deformed, and variations in height between the first member 20 and the second member 30 are appropriately absorbed, allowing for appropriate bonding. The pressure here is applied in a direction that presses the first member 20 and the second member 30 against each other relative to each other via the coating layer. The application of the predetermined pressure here is not limited to being performed during heating, but may be performed before heating.

[0043] Furthermore, the heating temperature in the heating step is preferably 100° C. or higher and 350° C. or lower, more preferably 150° C. or higher and 320° C. or lower, and even more preferably 200° C. or higher and 300° C. By setting the heating temperature in such a relatively low range, the bonding layer 10 can be properly sintered, and the first member 20 and the second member 30 can be properly bonded together.

[0044] Furthermore, the predetermined time, which is the heating time in the heating step, is preferably 1 minute to 10 minutes, more preferably 1 minute to 5 minutes, and even more preferably 1 minute to 3 minutes. By setting the heating time within this range, the bonding layer 10 can be appropriately sintered.

[0045] As described above, in this embodiment, the bonded body 100 is manufactured by bonding the protruding electrodes 24 and 34 with the bonding layer 10. However, the present invention is not limited to this. For example, the first member 20 and the second member 30 do not have to have protruding electrodes, and the first member 20 and the second member 30 may be bonded to each other at any positions with the bonding layer 10. In addition, in the example of FIG. 4, the bonded body 100 has two members, the first member 20 and the second member 30 (here, semiconductor elements), but the number of members bonded to the bonding layer 10 in one bonded body 100 is not limited to two and may be three or more.

[0046] (zygote) Next, a description will be given of the bonded body 100. In this embodiment, the bonded body 100 is manufactured by the method described above, but the method is not limited thereto and may be manufactured by any method.

[0047] The bonded body 100 is a member having a first member 20, a second member 30, and a bonding layer 10A located between the first member 20 and the second member 30. That is, the bonded body 100 is a member in which the first member 20 and the second member 30 are bonded together by the bonding layer 10A. In this embodiment, the bonded body 100 has the bonding layer 10A located between the protruding electrode 24 (surface 24a) of the first member 20 and the protruding electrode 34 (surface 34a) of the second member 30.

[0048] The shear strength of the bonded body 100 is preferably higher than 5 MPa, more preferably 10 MPa to 100 MPa, and even more preferably 15 MPa to 100 MPa. When the shear strength is within this range, the bond strength between the first member 20 and the second member 30 can be maintained appropriately. The shear strength can be measured by a method conforming to JIS Z 3198-7 (Lead-Free Solder Test Methods - Part 7: Shear Test Method for Solder Joints of Chip Components). Specifically, a load is applied to the first member 20 or the second member 30 using a tool of a bond tester (Nordson DAGE, SERIES 4000), and the load (maximum shear load) when the first member 20 or the second member 30 peels off from the bonding layer 10A is measured. The tool movement speed is 50 μm / sec, and the gap between the tip of the tool and the first member 20 or the second member 30 is 50 μm. The shear strength (unit: MPa) is calculated by converting the obtained maximum shear load into Newtons and dividing it by the area of ​​the bonding layer 10A.

[0049] (Joining layer) The bonding layer 10A is a porous copper member. The bonding layer 10A is not limited to having only copper, and may contain materials other than copper. In this embodiment, the bonding layer 10A is the member obtained after the bonding layer 10 is heated in the heating step described above. That is, the bonding layer 10A is a sintered body made of copper in which the copper particles 12 of the bonding layer 10 are sintered. When the bonding layer 10 includes a copper sheet layer, the bonding layer 10A is configured such that a layer of a sintered body of copper particles 12 is provided on the surface of the copper sheet layer.

[0050] (density of bonding layer) The density of the bonding layer 10A is 50% or more and 99% or less, preferably 60% or more and 99% or less, and more preferably 70% or more and 99% or less. By setting the lower limit of the density of the bonding layer 10A within this range, it is possible to prevent a decrease in the bonding strength between the first member 20 and the second member 30 due to too many voids in the bonding layer 10A. By setting the upper limit of the density of the bonding layer 10A within this range, the bonding layer is prevented from becoming difficult to deform during bonding (i.e., a bonding layer with a high density that is difficult to deform is not used), and height variations between the first member 20 and the second member 30 are appropriately absorbed, allowing the members to be appropriately bonded to each other. For example, height variations here may refer to the difference between the total height of the protruding electrodes 24, 34 on the left side and the total height of the protruding electrodes 24, 34 on the right side in FIG. 3 . If the total heights of the left and right protruding electrodes differ, a gap may be formed between the protruding electrodes with the shorter total length, potentially preventing the members from being appropriately bonded to each other. In contrast, by deforming the bonding layer during bonding, the difference in total height can be absorbed and the formation of a gap can be suppressed.

[0051] The density of the bonding layer 10A refers to the proportion of copper in the bonding layer 10A. The density of the bonding layer 10A can be calculated by image analysis of a cross section of the bonding layer 10A using a scanning electron microscope. Specifically, the density D (%) calculated by the following formula (2) is defined as the density of the bonding layer 10A.

[0052] D(%) = (T2 / T1) × 100 (2)

[0053] In formula (2), T1 is the total area of ​​the bonding layer 10A in the cross-sectional image of the bonding layer 10A, and T2 is the area of ​​the portion of the bonding layer 10A other than the pores (ie, the copper portion) in the cross-sectional image of the bonding layer 10A.

[0054] FIG. 5 is a diagram showing an example of a binarized image of the bonded structure. As shown in FIG. 5, the density of the bonding layer 10A may be calculated by image analysis of a cross section of the bonded structure 100 using a scanning electron microscope. In this case, the image of the cross section of the bonded structure 100 is binarized using a predetermined brightness value to create a binarized image. In the binarized image, regions 14A with brightness equal to or lower than the predetermined brightness value correspond to voids, and regions 12A with brightness higher than the predetermined brightness value correspond to portions other than voids. Here, the predetermined brightness value is 140 when the brightness value is expressed as 0 to 255.

[0055] Then, from the obtained binarized image, a line L0a indicating the interface between the bonding layer 10A and the second member 30 and a line L0b indicating the interface between the bonding layer 10A and the first member 20 are set. Here, in the binarized image, the direction along the interface between the bonding layer 10A and the first member 20 (second member 30) (in-plane direction) is defined as the Y direction, one direction of the X directions which are the stacking directions (thickness direction) of the bonding layer 10A and the first member 20 (second member 30) is defined as the X1 direction, and the other direction of the X directions is defined as the X2 direction. In this case, the line L0a is a line connecting the points on the periphery of each selected region 14A closest to the X1 direction among the regions 14A having a predetermined area or more at each position in the Y direction. Furthermore, line L0b is a line that selects, at each position in the Y direction, the regions 14A that are located furthest in the X2 direction from among the regions 14A that have an area equal to or greater than a predetermined area, and connects the points on the periphery of each selected region 14A that are furthest in the X2 direction. Note that the predetermined area here may be set arbitrarily, and may be, for example, the area of ​​a circle with a diameter of 0.1 μm. In the binarized image, the line obtained by shifting line L0a in the X2 direction by 5% of the total length of the binarized image in the Y direction is defined as line La. In addition, in the binarized image, the line obtained by shifting line L0b in the X1 direction by 5% of the total length of the binarized image in the Y direction is defined as line Lb.

[0056] In this case, the area surrounded by lines La and Lb (the area between lines La and Lb) in the binarized image is defined as the total area of ​​the bonding layer 10A (T1 in formula (2)). Also, the total area of ​​the area 12A within the area surrounded by lines La and Lb is defined as the portion of the bonding layer 10A other than the voids (T2 in formula (2)). This allows the density of the bonding layer 10A to be calculated from the cross section of the bonded body 100.

[0057] 5, the bonding layer 10A is formed over the entire area in the Y direction, and therefore the interface of the bonding layer 10A in the Y direction is not defined. However, when the bonding layer 10A is not formed over the entire area in the Y direction in the cross-sectional image, it is preferable to also define the interface of the bonding layer 10A in the Y direction. In this case, at each position in the X direction, among the regions 14A having an area equal to or larger than a predetermined area, the region 14A located furthest to one side in the Y direction (e.g., the right side in FIG. 5) is selected, and a line connecting points on the periphery of each selected region 14A on one side in the Y direction is set as line M0a. Furthermore, among the regions 14A having an area equal to or larger than a predetermined area, among each position in the X direction, the region 14A located furthest to the other side in the Y direction (e.g., the left side in FIG. 5) is selected, and a line connecting points on the periphery of each selected region 14A on the other side in the Y direction is set as line M0b. The predetermined area here may be set arbitrarily, and may be, for example, the area of ​​a circle with a diameter of 0.1 μm. In the binarized image, the line M0a is shifted in the other direction in the Y direction by 5% of the total length of the binarized image in the Y direction to obtain a line Ma. In addition, in the binarized image, the line M0b is shifted in the one direction in the Y direction by 5% of the total length of the binarized image in the Y direction to obtain a line Mb. In this case, the area surrounded by lines La, Lb, Ma, and Mb in the binarized image (the entire area of ​​the bonding layer 10A) is defined as the total area of ​​the bonding layer 10A (T1 in formula (2)), and the sum of the areas of the regions 12A within the area surrounded by lines La, Lb, Ma, and Mb (the entire area of ​​the bonding layer 10A) is defined as the portion of the bonding layer 10A other than the voids (T2 in formula (2)). This allows the density of the bonding layer 10A to be calculated from the cross section of the bonded body 100.

[0058] In addition, in the binarized image, the entire area of ​​the bonding layer 10A (the area surrounded by lines La, Lb, Ma, and Mb) is divided equally into three parts in the X direction. The area closest to the X1 direction among the three divided areas is designated as the first area, the area closest to the X2 direction is designated as the second area, and the area between the first and second areas is designated as the third area. In this case, the density of the bonding layer 10A in the first and second areas is preferably higher than the density of the bonding layer 10A in the third area. This increases the density of the bonding layer 10A in the first and second areas near the interface, thereby more appropriately bonding the first member 20 and the second member 30. The density of the bonding layer 10A in each area can be calculated by replacing the entire area of ​​the bonding layer 10A with each area in Equation (2).

[0059] (effect) As described above, the bonded body 100 according to the present disclosure includes a first member 20, a second member 30, and a copper bonding layer 10A located between the first member 20 and the second member 30, and the density of the bonding layer 10A is 50% or more and 99% or less. According to the present disclosure, when the lower limit of the density of the bonding layer 10A is within this range, a decrease in bonding strength can be suppressed, and when the upper limit of the density of the bonding layer 10A is within this range, variations in height between the first member 20 and the second member 30 can be appropriately absorbed, and the members can be appropriately bonded to each other.

[0060] The bonding surfaces of the first member 20 and the second member 30 that come into contact with the bonding layer 10A are preferably made of copper. The bonding layer 10A can appropriately bond such copper members together.

[0061] The bonded body 100 preferably has a shear strength of more than 5 MPa. When the shear strength is in this range, a decrease in the bonding strength can be suppressed.

[0062] A manufacturing method of a bonded body 100 according to the present disclosure includes the steps of: disposing a solid copper bonding layer 10 having an average porosity of 5% to 80% on at least one surface of a first member 20 and a second member 30 (disposing step); overlapping the first member 20 and the second member 30 with the bonding layer 10 interposed therebetween (overlapping step); and heating the overlapped first member 20 and second member 30 with the bonding layer 10 interposed therebetween to form a bonded body 100 (heating step). According to the present disclosure, bonding using the solid bonding layer 10 can prevent a decrease in alignment accuracy between the members. Furthermore, using a bonding layer 10 with the above average porosity allows the members to be properly bonded together, preventing a decrease in the bonding strength between the members.

[0063] In the step of forming the bonded body 100, the first member 20 and the second member 30, which are stacked with the bonding layer 10 interposed therebetween, are preferably heated at a heating temperature of 100° C. or higher and 350° C. or lower. This allows the bonding layer 10 to be properly sintered, the members to be properly bonded together, and a decrease in the bonding strength between the members to be suppressed.

[0064] In the step of forming the bonded body 100, the first member 20 and the second member 30, which are stacked with the bonding layer 10 interposed therebetween, are preferably pressed together at a pressure of 1 MPa or more and 30 MPa or less. The bonding layer 10 is appropriately deformed to appropriately absorb variations in height between the first member 20 and the second member 30, thereby appropriately bonding the members together.

[0065] In the manufacturing method of the bonded body 100 of the present disclosure, it is preferable to overlap the first member 20 and the second member 30 with a sintering aid provided on the surface of the bonding layer 10. According to the present disclosure, the formation of an oxide film on the surface of the bonding layer 10 can be suppressed, and the bonding layer 10 can be appropriately sintered.

[0066] (Example) Next, examples will be described. Figure 6 is a table showing the bonded bodies of each example. Figures 7 to 10 are images of the cross sections of the bonded bodies of each example.

[0067] Example 1 In Example 1, a bump pattern with a diameter of 75 μm was formed using photoresist on two Si wafers with seed layers formed thereon, followed by hydrophilization treatment and acid cleaning treatment using 10% diluted sulfuric acid. Then, copper pillars with a thickness of 5 μm were formed on the bumps using a copper sulfate-based plating solution. This resulted in the production of a first member and a second member. The copper sheet layer was plated using an acidic copper electroplating solution containing an azole-based additive, forming a copper porous layer with a thickness of about 5 μm on the copper sheet layer to obtain bonding layer A. The average porosity of bonding layer A was 70%. Then, formic acid was applied to the surface of the obtained bonding layer A as a sintering aid, and the first and second members were stacked together with the bonding layer A interposed therebetween. A pressure of 20 MPa was applied while heating at 300°C for 1 minute to obtain a bonded body.

[0068] The cross section of the obtained bonded body was imaged with a scanning electron microscope using the method described in the above embodiment, and the density of the bonding layer A after bonding was calculated. The shear strength of the obtained bonded body was also measured using the method described in the above embodiment. The measurement results are shown in FIG. 6. FIG. 7 is a scanning electron microscope image of the cross section of the bonded body of Example 1.

[0069] Example 2 In Example 2, a bonded body B was obtained in the same manner as in Example 1 except for the average porosity of the bonding layer B, and the density and shear strength of the bonding layer B after bonding were measured. The average porosity of the bonding layer B in Example 2 was 60%. Fig. 8 is a scanning electron microscope image of a cross section of the bonded body in Example 2.

[0070] Example 3 In Example 3, a bonded structure was obtained using the same method as in Example 1 except for the bonding pressure for bonding layer A, and the density and shear strength of bonding layer A after bonding were measured. The bonding pressure for bonding layer A in Example 3 was 10 MPa. Figure 9 is a scanning electron microscope image of a cross section of the bonded structure of Example 3.

[0071] (Comparative Example 1) In Comparative Example 1, a bonded body was obtained in the same manner as in Example 1 except that the bonding pressure was 5 MPa, and the density and shear strength of the bonding layer A after bonding were measured. Fig. 10 is a scanning electron microscope image of the cross section of the bonded body of Comparative Example 1.

[0072] (Comparative Example 2) In Comparative Example 2, a bonded structure was obtained in the same manner as in Example 1, except that a copper-plated film was formed between the first and second members. That is, in Comparative Example 2, the bonding layer was a copper-plated film between the first and second members. The bonding layer in Comparative Example 2 had no pores and had an average porosity of 0%. Note that, since bonding was not possible in Comparative Example 2, the density of the bonding layer in FIG. 6 was set to the value before bonding (100%). Furthermore, since bonding was not possible, shear strength was not measured.

[0073] (evaluation) The bonded bodies of each example were evaluated for bondability and bond strength. With regard to bondability, if the first and second members were bonded, it was evaluated as pass (◯), and if they were not bonded, it was evaluated as fail (×). With regard to bond strength, if the shear strength of the bonded body was higher than 5 MPa, it was evaluated as pass (◯), and if it was 5 MPa or less, it was evaluated as fail (×).

[0074] As shown in Figure 6, in Examples 1-3, where the density of the bonding layer is 50% or more and 99% or less, both the bondability and the bonding strength evaluations passed, indicating that the members can be properly bonded and the decrease in the bonding strength between the members can be suppressed. On the other hand, in Comparative Example 1, where the density of the bonding layer is less than 50%, the decrease in the bonding strength cannot be suppressed. Also, in Comparative Example 2, where the density of the bonding layer is 100%, the members cannot be properly bonded.

[0075] Although the embodiments of the present invention have been described above, the embodiments are not limited to the contents of these embodiments. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the scope of what is called equivalents. Furthermore, the above-described components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-described embodiments. [Explanation of symbols]

[0076] 10, 10A bonding layer 12 Copper particles 20 First member 30 Second member 100 zygote

Claims

1. A first member; A second member; a copper bonding layer located between the first member and the second member; and The bonding layer has a density of 50% or more and 99% or less. zygote.

2. The first member and the second member have bonding surfaces that are in contact with the bonding layer and are made of copper. The bonded body according to claim 1 .

3. Shear strength is higher than 5 MPa, The bonded body according to claim 1 or 2.

4. disposing a solid copper bonding layer having an average porosity of 5% or more and 80% or less on a surface of at least one of the first member and the second member; overlapping the first member and the second member with the bonding layer interposed therebetween; and heating the first member and the second member superposed with the bonding layer interposed therebetween to form a bonded body. A method for manufacturing a bonded body.

5. In the step of forming the bonded body, the first member and the second member stacked with the bonding layer interposed therebetween are heated at a heating temperature of 100° C. or higher and 350° C. or lower. The method for producing the bonded body according to claim 4 .

6. In the step of forming the bonded body, the first member and the second member that are stacked with the bonding layer interposed therebetween are pressed together at a pressure of 1 MPa or more and 30 MPa or less. The method for producing the bonded body according to claim 4 or 5.

7. The first member and the second member are superimposed on each other in a state where a sintering aid is provided on the surface of the bonding layer. The method for producing the bonded body according to claim 4 or 5.

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