Connection structure, semiconductor device and method for manufacturing connection structure

Abstract

To provide a connection structure body and a semiconductor device that can suppress adjacent connection terminals from short-circuiting.SOLUTION: A semiconductor device 10 has a first connection terminal 30 having a first opposite surface 31, a first roughened copper metal film 40 formed on the first opposite surface 31, a second connection terminal 60 having a second opposite surface 61 opposed to the first opposite surface 31, and a second roughened copper metal film 70 formed on the second opposite surface 61 and joined to the first roughened copper metal film 40. The first roughened copper metal film 40 has a structure having first deposits 41, made of copper, laid one over another in a mixed state on the first opposite surface 31, and the second roughened copper metal film 70 has a structure having second deposits 71, made of copper, laid one over another in a mixed state on the second opposite surface 61. The joint part between the first roughened copper metal film 40 and the second roughened copper metal film 70 has a structure having the first deposits 41 and second deposits 71 laid one over the other, and also has a gap.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a connection structure, a semiconductor device, and a method for manufacturing the connection structure. [Background technology]

[0002] BACKGROUND ART Conventionally, semiconductor devices have been known in which electrode pads of a semiconductor element and connection terminals of a wiring board are joined by a solder layer (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-93547 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, the pitch of connection terminals on wiring boards has been narrowed as semiconductor devices have become more sophisticated. However, as the pitch of connection terminals becomes narrower, adjacent solder layers are more likely to short-circuit after reflow. If adjacent solder layers short-circuit, this can lead to the problem of adjacent connection terminals shorting out. [Means for solving the problem]

[0005] According to one aspect of the present invention, there is provided a semiconductor device comprising: a first connection terminal having a first opposing surface; a first roughened copper metal film formed on the first opposing surface; a second connection terminal having a second opposing surface opposite the first opposing surface; and a second roughened copper metal film formed on the second opposing surface, wherein the first roughened copper metal film has a structure in which first precipitates made of copper intersect and overlap on the first opposing surface; the second roughened copper metal film has a structure in which second precipitates made of copper intersect and overlap on the second opposing surface; and the junction between the first roughened copper metal film and the second roughened copper metal film has a structure in which the first precipitates and the second precipitates overlap, and has a void. [Effects of the Invention]

[0006] According to one aspect of the present invention, it is possible to suppress short circuits between adjacent connection terminals. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view showing a semiconductor device according to a first embodiment. [Figure 2] 1 is a schematic exploded cross-sectional view showing a part of a semiconductor device according to a first embodiment. [Figure 3] 1 is a schematic cross-sectional view showing a part of a semiconductor device according to a first embodiment. [Figure 4] 2A to 2C are schematic cross-sectional views illustrating a method for manufacturing the semiconductor device of the first embodiment. [Figure 5] 2A to 2C are schematic cross-sectional views illustrating a method for manufacturing the semiconductor device of the first embodiment. [Figure 6] 2A to 2C are schematic cross-sectional views illustrating a method for manufacturing the semiconductor device of the first embodiment. [Figure 7] 3 is a scanning electron microscope photograph of the surface of the first roughened copper metal film of the first embodiment, observed from above. [Figure 8] 3 is a scanning ion microscope photograph of the cross-sectional structure of the connection structure of the first embodiment. [Figure 9] FIG. 10 is a schematic exploded cross-sectional view showing a part of a semiconductor device according to a second embodiment. [Figure 10] FIG. 10 is a schematic cross-sectional view showing a part of a semiconductor device according to a second embodiment. [Figure 11] 10 is a scanning electron microscope photograph of the surface of a first roughened copper metal film of a second embodiment, observed from above. [Figure 12] 10 is a scanning ion microscope photograph of a cross-sectional structure of a connection structure according to a second embodiment. [Figure 13] FIG. 10 is a schematic cross-sectional view showing a semiconductor device according to a third embodiment. [Figure 14] FIG. 10 is a schematic exploded cross-sectional view showing a part of a semiconductor device according to a third embodiment. [Figure 15]FIG. 10 is a schematic cross-sectional view showing a part of a semiconductor device according to a third embodiment. [Figure 16] FIG. 10 is a schematic cross-sectional view showing a semiconductor device according to a modified example. [Figure 17] FIG. 10 is a schematic cross-sectional view showing a rough surface structure of a comparative example. [Figure 18] FIG. 10 is a schematic cross-sectional view showing a semiconductor device of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0008] Each embodiment will be described below with reference to the accompanying drawings. For convenience, the accompanying drawings may show characteristic portions enlarged to make the features more clearly visible, and the dimensional proportions of each component may differ between drawings. In cross-sectional views, the hatching of some components is replaced with a matte finish, and the hatching of some components is omitted, to make the cross-sectional structure of each component more clearly visible. In this specification, "plan view" refers to viewing an object from the vertical direction (the up-down direction in the drawing) as in Figure 1, and "planar shape" refers to the shape of an object viewed from the vertical direction as in Figure 1. The terms "up-down direction" and "left-right direction" in this specification refer to directions in which the symbols indicating each component in each drawing can be correctly read, assuming the correct position. In this specification, "parallel," "orthogonal," and "vertical" refer not only to strictly parallel, orthogonal, and vertical, but also to roughly parallel, orthogonal, and vertical within the scope of the effects of this embodiment.

[0009] (First embodiment) The first embodiment will be described below with reference to FIGS. (Overall configuration of semiconductor device 10) As shown in FIG. 1, the semiconductor device 10 includes a wiring substrate 20, one or more (here, one) semiconductor elements 50, and external connection terminals 80.

[0010] (Overall configuration of wiring board 20) The wiring board 20 has, for example, a substrate body 21. A wiring layer 22 and a solder resist layer 23 are laminated in this order on the lower surface of the substrate body 21. A wiring layer 24, an insulating layer 25, a wiring layer 26, and a first roughened copper metal film 40 are laminated in this order on the upper surface of the substrate body 21.

[0011] The substrate body 21 may be, for example, a wiring structure in which insulating resin layers and wiring layers are alternately laminated. The wiring structure may or may not have a core substrate. The insulating resin layer may be, for example, a thermosetting insulating resin. Examples of the thermosetting insulating resin include insulating resins such as epoxy resin, polyimide resin, and cyanate resin. The insulating resin layer may also be, for example, an insulating resin whose main component is a photosensitive resin such as a phenolic resin or polyimide resin. The insulating resin layer may contain a filler such as silica or alumina.

[0012] The wiring layer of the substrate main body 21 and the wiring layers 22 and 24 may be made of, for example, copper (Cu) or a copper alloy. The solder resist layer 23 may be made of, for example, an insulating resin whose main component is a photosensitive resin such as a phenolic resin or a polyimide resin. The solder resist layer 23 may contain a filler such as silica or alumina.

[0013] (Structure of wiring layer 22) The wiring layer 22 is formed on the lower surface of the substrate body 21. The wiring layer 22 is the lowest wiring layer of the wiring substrate 20.

[0014] (Structure of solder resist layer 23) The solder resist layer 23 is laminated on the lower surface of the substrate body 21 so as to cover the wiring layer 22. The solder resist layer 23 is an insulating layer that is the outermost layer of the wiring substrate 20 (here, the bottom layer).

[0015] A plurality of openings 23X are formed in the solder resist layer 23 to expose portions of the lower surface of the wiring layer 22 as external connection pads P1. External connection terminals 80 are connected to the external connection pads P1, which are used when mounting the wiring board 20 on a mounting board such as a motherboard.

[0016] A surface treatment layer is formed, if necessary, on the lower surface of the wiring layer 22 exposed at the bottom of the opening 23X. Examples of the surface treatment layer include a gold (Au) layer, a nickel (Ni) layer / Au layer (a metal layer formed by laminating a Ni layer and an Au layer in this order), and a Ni layer / palladium (Pd) layer / Au layer (a metal layer formed by laminating a Ni layer, a Pd layer, and an Au layer in this order). Other examples of the surface treatment layer include a Ni layer / Pd layer (a metal layer formed by laminating a Ni layer and a Pd layer in this order) and a Pd layer / Au layer (a metal layer formed by laminating a Pd layer and an Au layer in this order). Here, the Au layer is a metal layer made of Au or an Au alloy, the Ni layer is a metal layer made of Ni or an Ni alloy, and the Pd layer is a metal layer made of Pd or a Pd alloy. The Au layer, Ni layer, and Pd layer may be, for example, a metal layer formed by electroless plating (electroless plated layer) or a metal layer formed by electrolytic plating (electroplated layer). The surface treatment layer may be an OSP (organic solderability preservative) film formed by applying an anti-oxidation treatment such as an OSP treatment to the lower surface of the wiring layer 22 exposed in the opening 23X. The OSP film may be an organic coating such as an azole compound or an imidazole compound. When a surface treatment layer is formed on the lower surface of the wiring layer 22, the surface treatment layer functions as the external connection pad P1.

[0017] In this example, an external connection terminal 80 is provided on the underside of the wiring layer 22, but the wiring layer 22 itself exposed in the opening 23X, or if a surface treatment layer is formed on the underside of the wiring layer 22, the surface treatment layer itself may also be used as the external connection terminal.

[0018] (Structure of wiring layer 24) The wiring layer 24 is formed on the upper surface of the substrate body 21. The wiring layer 24 is electrically connected to the wiring layer 22 via, for example, a wiring layer or a through electrode in the substrate body 21.

[0019] (Structure of insulating layer 25) The insulating layer 25 is laminated on the upper surface of the substrate main body 21 so as to cover a portion of the wiring layer 24. The insulating layer 25 is an outermost insulating layer provided on the outermost layer (here, the uppermost layer) of the wiring substrate 20. The insulating layer 25 may be, for example, the same insulating resin layer as the insulating resin layer used in the substrate main body 21. Alternatively, for example, a solder resist layer may be used as the insulating layer 25. For example, the same material as that of the solder resist layer 23 may be used as the material of the solder resist layer.

[0020] An opening 25X is formed in the insulating layer 25, penetrating the insulating layer 25 in the thickness direction (vertical direction in the figure) and exposing a portion of the upper surface of the wiring layer 24. The planar shape of the opening 25X can be set to any shape and size. In this example, the planar shape of the opening 25X is formed in a circular shape. In this example, the opening 25X is formed in a tapered shape such that the opening width (opening diameter) decreases from the upper side (the upper surface side of the insulating layer 25) to the lower side (the wiring layer 24 side) in FIG. 1.

[0021] (Structure of wiring layer 26) The wiring layer 26 is formed on the wiring layer 24 exposed from the opening 25X. The wiring layer 26 has, for example, a via wiring 26V formed in the opening 25X and a first connection terminal 30 electrically connected to the wiring layer 24 through the via wiring 26V and formed on the upper surface of the insulating layer 25. The first connection terminal 30 functions as, for example, an electronic component mounting pad for electrically connecting to an electronic component such as a semiconductor element 50.

[0022] The via wiring 26V is formed, for example, so as to fill the opening 25X. The via wiring 26V is formed in the same shape as the opening 25X. The via wiring 26V is formed, for example, in the shape of an inverted truncated cone in which the diameter of the upper surface is larger than the diameter of the lower surface.

[0023] The first connection terminal 30 is formed, for example, in a columnar shape so as to protrude upward from the upper surface of the insulating layer 25. The first connection terminal 30 is, for example, a metal post. In this example, the first connection terminal 30 is formed in a cylindrical shape. The first connection terminal 30 is, for example, formed integrally with the via wiring 26V. The planar shape of the first connection terminal 30 can be set to any shape and size. The planar shape of the first connection terminal 30 can be, for example, a circle with a diameter in the range of 15 μm to 40 μm. The thickness of the first connection terminal 30 can be, for example, in the range of 2 μm to 50 μm.

[0024] The first connection terminal 30 has a first opposing surface 31 (here, the upper surface) that faces the semiconductor element 50. The first opposing surface 31 of the first connection terminal 30 is formed, for example, as a flat surface. The first opposing surface 31 is formed, for example, so as to extend parallel to the upper surface of the substrate body 21. The first opposing surface 31 is, for example, a smooth surface with few irregularities.

[0025] Here, "facing" in this specification refers to surfaces or components facing each other, and includes not only cases where they are completely facing each other, but also cases where they are partially facing each other. Furthermore, "facing" in this specification includes both cases where a component separate from the two components is interposed between the two components, and cases where nothing is interposed between the two components.

[0026] The via wiring 26V and the first connection terminal 30 can be made of, for example, copper or a copper alloy. The first connection terminal 30 in this example is made of copper. The via wiring 26V and the first connection terminal 30 can be made of, for example, an electroless plated layer formed by electroless plating or an electrolytic plated layer formed by electrolytic plating.

[0027] (Structure of the first roughened copper metal film 40) The first roughened copper metal film 40 is formed on the first opposing surface 31 of the first connection terminal 30. The first roughened copper metal film 40 is formed, for example, so as to cover the entire first opposing surface 31. The first roughened copper metal film 40 is formed, for example, so as to expose the side surface of the first connection terminal 30. In other words, the first roughened copper metal film 40 is formed, for example, so as to cover only the first opposing surface 31 of the surface of the first connection terminal 30. The thickness (film thickness) of the first roughened copper metal film 40 can be, for example, in the range of 1 μm to 5 μm.

[0028] As shown in FIG. 2, the first roughened copper metal film 40 is a plating film whose surface (top and side surfaces, or only the top surface) is roughened. The surface of the first roughened copper metal film 40 has a fine uneven structure. The first roughened copper metal film 40 has a structure in which first deposits 41 made of copper intersect and overlap on the first opposing surface 31 of the first connection terminal 30. The first roughened copper metal film 40 has a structure in which plate-shaped first deposits 41 made of copper intersect and overlap on the first opposing surface 31. The first roughened copper metal film 40 is a plating film formed by electrolytic copper plating. The first roughened copper metal film 40 is, for example, a metal film made of a plating film of only copper. Here, the "structure in which first deposits 41 made of copper intersect and overlap" refers to a structure (porous structure) in which a large number of first deposits 41 (electrodeposits) made of copper, which is the plating metal, intersect and overlap in random directions, forming a large number of voids in the metal film (plating film). Note that Fig. 2 shows a cross-sectional structure of a portion of the semiconductor device 10 before the semiconductor element 50 is bonded to the wiring substrate 20.

[0029] The first roughened copper metal film 40 of this embodiment has a structure in which sheet-like (thin plate-like) first precipitates 41 made of copper are folded in various directions, and voids are formed between the sheet-like first precipitates 41. Here, the thickness of the sheet-like first precipitates 41 can be, for example, in the range of 20 nm to 100 nm. The thickness of the sheet-like first precipitates 41 is more preferably, for example, in the range of 20 nm to 50 nm. The first roughened copper metal film 40 has a structure in which the sheet-like first precipitates 41 are stacked in multiple layers. The first roughened copper metal film 40 has a three-dimensional nanostructure in which fine, nano-sized sheet-like first precipitates 41 are folded in multiple layers and intertwined in random directions. The first roughened copper metal film 40 has a structure in which the sheet-like first precipitates 41 are densely folded over the entire thickness of the first roughened copper metal film 40, with numerous voids formed therein. That is, the first roughened copper metal film 40 has a structure in which numerous fine voids are formed therein throughout the entire thickness. In the first roughened copper metal film 40, for example, the density of the first precipitates 41 varies in the thickness direction. In other words, in the first roughened copper metal film 40, for example, the porosity varies in the thickness direction. For example, in the first roughened copper metal film 40, the density of the first precipitates 41 increases toward the first opposing surface 31 in the thickness direction, i.e., the porosity decreases toward the first opposing surface 31. The porosity of the entire first roughened copper metal film 40 can be, for example, in the range of 8% to 20%.

[0030] As described above, the first roughened copper metal film 40 has a structure in which numerous first precipitates 41 intersect and overlap, resulting in an uneven surface and a roughened surface structure with numerous voids in the thickness direction. This roughened surface structure of the first roughened copper metal film 40 differs from roughened surface structures formed by general roughening treatments, such as roughening treatments using chemical solutions or physical processing. Examples of general roughening treatments include blackening, etching, and blasting.

[0031] More specifically, as shown in Fig. 17, the rough surface structure 100 formed by applying a general roughening treatment to the first connection terminal 30 has unevenness formed only on the surface of the first connection terminal 30. The rough surface structure 100 has a high density of copper precipitates inside the rough surface structure 100 throughout the thickness and width directions (i.e., the direction perpendicular to the thickness direction). Such a rough surface structure 100 does not have a structure in which the first precipitates 41 intersect and overlap as shown in Fig. 2, and does not have voids in the thickness direction or inside the metal film. Furthermore, the rough surface structure 100 does not have a structure in which the porosity varies in the thickness direction.

[0032] As shown in FIG. 2 , the first roughened copper metal film 40 is bonded to the first opposing surface 31 of the first connection terminal 30. Here, no intermetallic compound is formed at the interface (bonding interface) between the first connection terminal 30 and the first roughened copper metal film 40. That is, the first connection terminal 30 made of copper and the first roughened copper metal film 40 made of copper are directly bonded to each other without any intervening member made of a material other than copper. The first roughened copper metal film 40 is integrated with the first connection terminal 30. In each drawing, the first connection terminal 30 and the first roughened copper metal film 40 are distinguished by solid lines to make them easier to understand. In reality, the interface between the first connection terminal 30 and the first roughened copper metal film 40 may disappear, and the boundary may not be clear.

[0033] (Configuration of semiconductor element 50) 1, the semiconductor element 50 has a plurality of second connection terminals 60 and a second roughened copper metal film 70 formed on the circuit formation surface (here, the lower surface) of the semiconductor element 50. The semiconductor element 50 is flip-chip mounted on the wiring board 20. Specifically, the second connection terminals 60 of the semiconductor element 50 are electrically connected to the first connection terminals 30 of the wiring board 20. The second connection terminals 60 are electrically connected to the first connection terminals 30 via the second roughened copper metal film 70 and the first roughened copper metal film 40. As a result, the semiconductor element 50 is electrically connected to the first connection terminals 30 via the second connection terminals 60, the second roughened copper metal film 70, and the first roughened copper metal film 40.

[0034] The semiconductor element 50 may be, for example, a logic chip such as a CPU (Central Processing Unit) chip or a GPU (Graphics Processing Unit) chip. The semiconductor element 50 may also be, for example, a memory chip such as a DRAM (Dynamic Random Access Memory) chip, an SRAM (Static Random Access Memory) chip, or a flash memory chip. When multiple semiconductor elements 50 are mounted on the wiring board 20, a logic chip and a memory chip may be combined and mounted on the wiring board 20.

[0035] (Structure of second connection terminal 60) The multiple second connection terminals 60 are provided so as to face the multiple first connection terminals 30, respectively. The second connection terminals 60 are formed, for example, in a columnar shape so as to protrude downward from the circuit formation surface of the semiconductor element 50. The second connection terminals 60 are, for example, metal posts. The second connection terminals 60 in this example are formed in a cylindrical shape. The planar shape of the second connection terminals 60 can be set to any shape and size. The planar shape of the second connection terminals 60 can be, for example, a circular shape with a diameter in the range of 15 μm to 40 μm. The thickness of the second connection terminals 60 can be, for example, in the range of 2 μm to 50 μm.

[0036] The second connection terminal 60 may be made of, for example, copper or a copper alloy. The second connection terminal 60 in this example is made of copper. The second connection terminal 60 may be made of an electroless plated layer or an electrolytic plated layer.

[0037] The second connection terminal 60 has a second opposing surface 61 (here, the lower surface) opposing the first opposing surface 31 of the first connection terminal 30. The second opposing surface 61 of the second connection terminal 60 is formed, for example, as a flat surface. The second opposing surface 61 is formed, for example, so as to extend parallel to the circuit formation surface of the semiconductor element 50. The second opposing surface 61 is, for example, a smooth surface with few irregularities.

[0038] (Structure of second roughened copper metal film 70) The second roughened copper metal film 70 is formed on the second opposing surface 61 of the second connection terminal 60. The second roughened copper metal film 70 is formed, for example, so as to cover the entire second opposing surface 61. The second roughened copper metal film 70 is formed, for example, so as to expose the side surface of the second connection terminal 60. In other words, the second roughened copper metal film 70 is formed, for example, so as to cover only the second opposing surface 61 of the surface of the second connection terminal 60. The thickness (film thickness) of the second roughened copper metal film 70 can be, for example, in the range of 1 μm to 5 μm.

[0039] As shown in FIG. 2 , the second roughened copper metal film 70 has a structure similar to that of the first roughened copper metal film 40. The second roughened copper metal film 70 is a plated film whose surface (bottom and side surfaces, or bottom surface only) is roughened. The surface of the second roughened copper metal film 70 has a fine uneven structure. The second roughened copper metal film 70 has a structure in which second deposits 71 made of copper intersect and overlap on the second opposing surface 61 of the second connection terminal 60. The second roughened copper metal film 70 has a structure in which plate-shaped second deposits 71 made of copper intersect and overlap on the second opposing surface 61. The second roughened copper metal film 70 is a plated film formed by electrolytic copper plating. The second roughened copper metal film 70 is, for example, a metal film made of only copper. Here, "a structure in which second deposits 71 made of copper intersect and overlap" refers to a structure in which a large number of second deposits 71 (electrodeposits) made of copper, the plating metal, intersect and overlap in random directions, forming a large number of voids in the plating film.

[0040] The second roughened copper metal film 70 of this embodiment has a structure in which sheet-like (thin plate-like) second precipitates 71 made of copper are folded in various directions, and voids are formed between the sheet-like second precipitates 71. Here, the thickness of the sheet-like second precipitates 71 can be, for example, in the range of 20 nm to 100 nm. The thickness of the sheet-like second precipitates 71 is more preferably, for example, in the range of 20 nm to 50 nm. The second roughened copper metal film 70 has a structure in which the sheet-like second precipitates 71 are stacked in the form of multiple layers. The second roughened copper metal film 70 is formed in a structure in which the sheet-like second precipitates 71 are densely folded over the entire thickness direction of the second roughened copper metal film 70, with multiple voids formed therein. The second roughened copper metal film 70 has a three-dimensional nanostructure formed by nano-sized, sheet-like second precipitates 71 that are randomly oriented and folded into numerous layers. This second roughened copper metal film 70 has a structure in which numerous microscopic voids are provided throughout the entire thickness direction. In the second roughened copper metal film 70, for example, the density of the second precipitates 71 varies in the thickness direction. In other words, the second roughened copper metal film 70 has a porosity that varies in the thickness direction. For example, in the second roughened copper metal film 70, the density of the second precipitates 71 increases toward the second opposing surface 61 in the thickness direction, i.e., the porosity decreases toward the second opposing surface 61. The porosity of the entire second roughened copper metal film 70 can be, for example, in the range of 8% to 20%.

[0041] In this way, the second roughened copper metal film 70 has a structure in which numerous second precipitates 71 intersect and overlap, resulting in a rough surface structure with unevenness on the surface and numerous voids in the thickness direction.

[0042] The second roughened copper metal film 70 is bonded to the second opposing surface 61 of the second connection terminal 60. Here, no intermetallic compound is formed at the interface (bonding interface) between the second connection terminal 60 and the second roughened copper metal film 70. That is, the second connection terminal 60 made of copper and the second roughened copper metal film 70 made of copper are directly bonded to each other without any other member made of a material other than copper. The second roughened copper metal film 70 is integrated with the second connection terminal 60. In each drawing, the second connection terminal 60 and the second roughened copper metal film 70 are distinguished by solid lines to make them easier to understand. In reality, the interface between the second connection terminal 60 and the second roughened copper metal film 70 may disappear, and the boundary may not be clear.

[0043] 3, the second roughened copper metal film 70 is bonded to the first roughened copper metal film 40. The second roughened copper metal film 70 is diffusion bonded to the first roughened copper metal film 40 by, for example, sintering. No intermetallic compound is formed at the interface (bonding interface) between the first roughened copper metal film 40 and the second roughened copper metal film 70. In other words, the first roughened copper metal film 40 made of copper and the second roughened copper metal film 70 made of copper are bonded directly to each other without any other member made of a material other than copper.

[0044] The bonded portion between the first and second roughened copper metal films 40 and 70 has a structure in which the first precipitate 41 and the second precipitate 71 overlap each other. At the bonded portion between the first and second roughened copper metal films 40 and 70, the first precipitate 41 and the second precipitate 71 are diffusion-bonded by, for example, sintering. This integrates the first precipitate 41 and the second precipitate 71, and the first and second roughened copper metal films 40 and 70 are integrated together. The bonded portion between the first and second roughened copper metal films 40 and 70 has a structure in which the first precipitate 41 and the second precipitate 71 are diffusion-bonded together with voids present. The porosity at the bonded portion between the first and second roughened copper metal films 40 and 70 can be, for example, in the range of 5% to 18%. The porosity at the junction between the first and second roughened copper metal films 40 and 70 is higher than the porosity inside the first and second roughened copper metal films 40 and 70. In other words, the porosity is highest at the junction between the first and second roughened copper metal films 40 and 70, and between the first and second roughened copper metal films 40 and 70. In the first roughened copper metal film 40, the porosity decreases in the thickness direction from the junction between the first and second roughened copper metal films 40 and 70 toward the first opposing surface 31. In addition, in the second roughened copper metal film 70, the porosity decreases in the thickness direction from the junction between the first roughened copper metal film 40 and the second roughened copper metal film 70 toward the second opposing surface 61.

[0045] The bonded portion between the first and second roughened copper metal films 40 and 70 does not protrude outward beyond the side surface of the first connection terminal 30, for example. That is, in the bonded portion between the first and second roughened copper metal films 40 and 70, excess bonding metal material (solder, etc.) does not protrude outward beyond the side surface of the first connection terminal 30 in the planar direction (left-right direction in the figure). Here, the planar direction is, for example, a direction perpendicular to the thickness direction of the first and second roughened copper metal films 40 in a cross-sectional view. The bonded portion between the first and second roughened copper metal films 40 and 70 does not protrude outward beyond the side surface of the second connection terminal 60, for example. The first and second roughened copper metal films 40 and 70 vertically bond the first and second connection terminals 30 and 60.

[0046] The first connection terminal 30, the first roughened copper metal film 40, the second connection terminal 60, and the second roughened copper metal film 70 described above constitute a connection structure. (Structure of external connection terminal 80) As shown in FIG. 1 , the external connection terminals 80 are formed on external connection pads P1 of the wiring substrate 20. The external connection terminals 80 are connection terminals that are electrically connected to pads provided on a mounting substrate such as a motherboard (not shown). For example, solder balls or lead pins can be used as the external connection terminals 80. In this embodiment, solder balls are used as the external connection terminals 80.

[0047] (Method of manufacturing the semiconductor device 10) Next, a method for manufacturing the semiconductor device 10 will be described with reference to Figures 4 to 6. Here, a method for manufacturing the connection structure will be described in detail. For ease of explanation, the parts that will ultimately become the components of the semiconductor device 10 will be described using the reference numerals of the final components.

[0048] First, as shown in FIG. 4, a wiring substrate 20 is prepared, in which a wiring layer 22 and a solder resist layer 23 are formed on the lower surface of a substrate main body 21, and a wiring layer 24, an insulating layer 25, and a wiring layer 26 are formed on the upper surface of the substrate main body 21. This wiring substrate 20 can be manufactured by a known manufacturing method, and detailed description thereof will be omitted here. The wiring layer 26 having the via wiring 26V and the first connection terminal 30 can be formed, for example, by a semi-additive method. Specifically, first, a seed layer (not shown) is formed to cover the inner surface of the opening 25X and the upper surface of the wiring layer 24 and the upper surface of the insulating layer 25 exposed at the bottom of the opening 25X. Then, a resist pattern (not shown) having openings corresponding to the shape of the first connection terminal 30 is formed on the seed layer. Then, the via wiring 26V and the first connection terminal 30 are formed by electrolytic copper plating using the resist pattern as a plating mask. In the process shown in FIG. 4, a semiconductor element 50 having a second connection terminal 60 formed on its circuit-forming surface is prepared.

[0049] Next, in the step shown in FIG. 5 , a first roughened copper metal film 40 is formed on the first opposing surface 31 of the first connection terminal 30 of the wiring layer 26. The first roughened copper metal film 40 can be formed by an electrolytic copper plating method. For example, the first roughened copper metal film 40 can be formed by an electrolytic copper plating method using an electrolytic copper plating bath containing a roughening agent (additive) as the plating bath and using the first connection terminal 30 and the like as the plating power supply layer. In the electrolytic copper plating method of this step, for example, the resist pattern (not shown) used in forming the wiring layer 26 can be used as a plating mask. Furthermore, polyacrylic acid can be used as the roughening agent added to the electrolytic copper plating bath. Here, in order to form the first roughened copper metal film 40 into a desired rough surface structure, i.e., a structure in which first deposits 41 (see FIG. 2) made of copper intersect and overlap, it is necessary to appropriately adjust the composition of the plating bath used in the electrolytic copper plating method, the current density, and the amount of current flow. The following describes an example of plating conditions for forming the first roughened copper metal film 40. Specifically, when using an electrolytic copper plating bath containing polyacrylic acid, the plating bath composition and electrodeposition conditions are as follows:

[0050] (First plating condition) [1] Plating bath composition Basic bath: CuSO4·5H2O: 0.85M H2SO4:0.55M Additives: Polyacrylic acid (molecular weight 5000): 3.0 x 10 -4 M [2] Electrodeposition conditions Current mode: Current regulation method Current flow: 4Ccm -2 Current density: 1Adm -2 Temperature: room temperature Agitation: None Anode: Cu plate Cathode: Object to be plated (wiring board or semiconductor element) In this way, by appropriately adjusting the composition of the plating bath used and the electrodeposition conditions, the first roughened copper metal film 40 can be formed to have a desired rough surface structure.

[0051] FIG. 7 is a scanning electron microscope (SEM) photograph of the surface of a first roughened copper metal film 40 formed by electrolytic copper plating using the first plating conditions described above, observed from above. The SEM image in FIG. 7 reveals that the first roughened copper metal film 40 has a roughened surface structure in which numerous sheet-like (thin plate or plate-like) first precipitates 41 randomly intersect and overlap, forming voids within. In other words, the SEM image in FIG. 7 confirms that the first roughened copper metal film 40 can be formed with a desired roughened surface structure by performing electrolytic copper plating using the first plating conditions described above. The thickness of the first precipitates 41 in the SEM image in FIG. 7 is in the range of 20 nm to 100 nm.

[0052] The plating conditions (plating bath composition and electrodeposition conditions) described above are merely examples, and the composition and conditions are not particularly limited as long as they are adjusted to give the first roughened copper metal film 40 a desired roughened surface structure. The shape and density of the first precipitates 41 in the first roughened copper metal film 40 can be controlled by adjusting the polyacrylic acid concentration, current density, amount of current flow, plating bath temperature, and the like in the electrolytic copper plating method.

[0053] 5, a second roughened copper metal film 70 is formed on the second opposing surface 61 of the second connection terminal 60. The second roughened copper metal film 70 can be formed by electrolytic copper plating using an electrolytic copper plating bath containing polyacrylic acid, as in the formation of the first roughened copper metal film 40. The plating conditions in this step can be set to the same conditions as the first plating conditions used to form the first roughened copper metal film 40. The second roughened copper metal film 70 formed by such electrolytic copper plating has a rough surface structure similar to that shown in the SEM image in FIG.

[0054] 6, a semiconductor element 50 having second connection terminals 60 and a second roughened copper metal film 70 is placed above the wiring substrate 20. At this time, the wiring substrate 20 and the semiconductor element 50 are placed so that the first connection terminals 30 and the second connection terminals 60 face each other. Then, the second roughened copper metal film 70 is superimposed on the first roughened copper metal film 40.

[0055] Next, the first and second roughened copper metal films 40 and 70 are bonded together. In this example, the first and second roughened copper metal films 40 and 70 are diffusion bonded by sintering. In this process, the wiring substrate 20 and the semiconductor element 50 are bonded together by heating and pressurizing them with the second roughened copper metal film 70 superimposed on the first and second roughened copper metal films 40. The heating temperature can be, for example, from 180°C to 250°C. The pressure can be, for example, from 8 MPa to 15 MPa. The heating and pressurizing treatment can last for, for example, from 3 minutes to 10 minutes. The heating and pressurizing treatment can be performed, for example, in the atmosphere. The first and second roughened copper metal films 40 and 70 are diffusion bonded together by sintering through this heating and pressurizing treatment. 3, the first precipitate 41 of the first roughened copper metal film 40 and the second precipitate 71 of the second roughened copper metal film 70 are diffusion-bonded by sintering, and the first precipitate 41 and the second precipitate 71 are integrated together. As a result, the first roughened copper metal film 40 and the second roughened copper metal film 70 are bonded and integrated together.

[0056] 8 is a scanning ion microscope (SIM) photograph of the cross-sectional structure of the bonded portion when the first roughened copper metal film 40 and the second roughened copper metal film 70 were bonded by a heating and pressurizing treatment set at a heating temperature of 200°C, a pressure of 10 MPa, and a treatment time of 5 minutes. The SIM image in FIG. 8 reveals that the first precipitate 41 and the second precipitate 71 are bonded together with voids present at the bonded portion between the first roughened copper metal film 40 and the second roughened copper metal film 70. The bonding between the first precipitate 41 and the second precipitate 71 bonds and integrates the first roughened copper metal film 40 and the second roughened copper metal film 70. In other words, the SIM image in FIG. 8 confirms that the first roughened copper metal film 40 and the second roughened copper metal film 70 can be bonded together by a heating and pressurizing treatment set at a heating temperature of 200°C, a pressure of 10 MPa, and a treatment time of 5 minutes. Thus, the heating and pressurizing treatment of this step can bond the first roughened copper metal film 40 and the second roughened copper metal film 70 at a relatively low temperature (approximately 200°C). This is thought to be because the first roughened copper metal film 40 and the second roughened copper metal film 70 are composed of sheet-like first precipitates 41 and second precipitates 71, respectively, several tens of nanometers thick, i.e., nano-sized precipitates. The nano-sized first precipitates 41 and second precipitates 71 have high surface reactivity, allowing diffusion at particle interfaces to proceed and sintering to occur even at temperatures lower than their natural melting points. This is thought to enable the first precipitate 41 and the second precipitate 71 to be sintered at a low temperature.

[0057] In contrast, a roughened surface structure produced by a typical roughening treatment, i.e., the roughened surface structure 100 shown in FIG. 17, only has a structure with unevenness formed on the surface, but does not have a structure in which precipitates intersect and overlap, and does not contain nano-sized metal particles. Therefore, even if two overlapping roughened surface structures 100 are subjected to a heating and pressure treatment under the same conditions as those described above, the two roughened surface structures 100 cannot be bonded to each other. The inventors have experimentally confirmed that when two overlapping roughened surface structures 100 are heated to approximately 250°C and pressurized at a pressure of 15 MPa for 10 minutes, the two roughened surface structures 100 are not bonded to each other.

[0058] 18, smooth surface 111 of connecting terminal 110 made of copper and smooth surface 121 of connecting terminal 120 made of copper can be diffusion bonded to each other by performing a heating and pressure treatment. However, in order to diffusion bond smooth surfaces 111 and 121 to each other, it is necessary to heat overlapping smooth surfaces 111 and 121 to a high temperature of about 500°C to 900°C. Therefore, when diffusion bonding smooth surfaces 111 and 121 to each other during mounting of semiconductor element 50, there is a problem in that semiconductor element 50 is exposed to a high temperature of 500°C or more.

[0059] 6, the process of bonding the first roughened copper metal film 40 and the second roughened copper metal film 70 can be performed at a temperature lower than the heating temperature used to bond the smooth surfaces 111, 121 (see FIG. 18), that is, at a temperature of about 200° C. This allows the temperature during mounting of the semiconductor element 50 to be lower, thereby preventing the semiconductor element 50 from being exposed to high temperatures and reducing thermal stress in the semiconductor element 50.

[0060] Before the step of bonding the first and second roughened copper metal films 40 and 70, plasma treatment may be performed on the surfaces of the first and second roughened copper metal films 40 and 70, as needed. By performing plasma treatment, even if an oxide film is formed on the surfaces of the first and second roughened copper metal films 40 and 70, the oxide film can be removed. This can improve the sinterability of the first and second roughened copper metal films 40 and 70.

[0061] Through the steps described above, the semiconductor element 50 can be mounted on the wiring substrate 20. After that, the external connection terminals 80 shown in Fig. 1 are formed on the external connection pads P1. In this way, the semiconductor device 10 shown in Fig. 1 can be manufactured.

[0062] Next, the effects of this embodiment will be described. (1) A first roughened copper metal film 40 is formed on the first opposing surface 31 of the first connection terminal 30, and a second roughened copper metal film 70 is formed on the second opposing surface 61 of the second connection terminal 60. The first roughened copper metal film 40 and the second roughened copper metal film 70 are then bonded together. With this configuration, the first roughened copper metal film 40 and the second roughened copper metal film 70 are bonded together, thereby bonding the first connection terminal 30 and the second connection terminal 60 via the first roughened copper metal film 40 and the second roughened copper metal film 70. That is, the first connection terminal 30 and the second connection terminal 60 can be bonded together via the first roughened copper metal film 40 and the second roughened copper metal film 70. The first roughened copper metal film 40 and the second roughened copper metal film 70 are less likely to spread in the planar direction than a solder layer. Therefore, compared to when the first connection terminals 30 and the second connection terminals 60 are joined by a solder layer, it is possible to prevent the joint portion from spreading in the planar direction. As a result, even when the pitch of the first connection terminals 30 becomes narrower, it is possible to preferably prevent short circuits between adjacent first connection terminals 30. In other words, it is possible to design the adjacent first connection terminals 30 to have a narrow pitch.

[0063] (2) Both the first roughened copper metal film 40 and the second roughened copper metal film 70 are made of copper. Therefore, the joint portion joining the first connection terminal 30 and the second connection terminal 60 can be made of copper. This makes it possible to reduce the electrical resistance at the joint portion between the first connection terminal 30 and the second connection terminal 60 compared to when the first connection terminal 30 and the second connection terminal 60 are joined by a solder layer.

[0064] (3) The bonded portion between the first and second roughened copper metal films 40 and 70 has a structure in which the first precipitate 41 and the second precipitate 71 overlap each other. The bonded portion between the first and second roughened copper metal films 40 and 70 has a structure in which the first precipitate 41 and the second precipitate 71 are bonded together with voids present. This configuration facilitates deformation of the first precipitate 41 and the second precipitate 71 at the bonded portion by providing voids at the bonded portion between the first and second roughened copper metal films 40 and 70. This facilitates relaxation of stress applied to the bonded portion between the first and second roughened copper metal films 40 and 70. This effectively prevents cracks and other problems from occurring at the bonded portion between the first and second roughened copper metal films 40 and 70 due to stress. As a result, the connection reliability between the first roughened copper metal film 40 and the second roughened copper metal film 70 can be improved.

[0065] (4) The first roughened copper metal film 40 has a structure in which sheet-like first precipitates 41, each several tens of nanometers thick, are intertwined and overlapped on the first opposing surface 31, with voids formed between the sheet-like first precipitates 41. The second roughened copper metal film 70 has a structure in which sheet-like second precipitates 71, each several tens of nanometers thick, are intertwined and overlapped on the second opposing surface 61, with voids formed between the sheet-like second precipitates 71. As such, both the first roughened copper metal film 40 and the second roughened copper metal film 70 are composed of numerous nano-sized metal particles. This increases the reactivity of the surfaces of the first precipitates 41 and the second precipitates 71, and improves the sinterability of the first precipitates 41 and the second precipitates 71. This allows the first precipitates 41 and the second precipitates 71 to be sintered at a low temperature. As a result, it is possible to reduce the temperature when bonding the first roughened copper metal film 40 and the second roughened copper metal film 70, i.e., when mounting the semiconductor element 50. This prevents the semiconductor element 50 from being exposed to high temperatures, and reduces thermal stress in the semiconductor element 50.

[0066] (5) The first connection terminal 30 is made of copper, and the second connection terminal 60 is made of copper. According to this configuration, the first connection terminal 30, the first roughened copper metal film 40, the second connection terminal 60, and the second roughened copper metal film 70 are all made of copper. Therefore, the first connection terminal 30, the first roughened copper metal film 40, the second connection terminal 60, and the second roughened copper metal film 70 are connected by a single metal, that is, copper. Therefore, no intermetallic compounds are formed at the interfaces between the first connection terminal 30, the first roughened copper metal film 40, the second connection terminal 60, and the second roughened copper metal film 70. This effectively prevents Kirkendall voids from forming due to the formation of intermetallic compounds. Furthermore, it effectively prevents problems such as breakage caused by Kirkendall voids. In other words, the reliability of the connection between the first connection terminal 30 and the second connection terminal 60 can be improved. This ultimately improves the mounting reliability of the semiconductor element 50.

[0067] (Second embodiment) The second embodiment will be described below with reference to Figures 9 to 12. The semiconductor device of this embodiment differs from the first embodiment in the roughened surface structures of the first and second roughened copper metal films. The following description will focus on the differences from the first embodiment. The same components as those shown in Figures 1 to 8 above are designated by the same reference numerals, and detailed description of each element will be omitted. Note that Figure 9 shows the cross-sectional structure of the connection structure before a semiconductor element 50 is mounted on a wiring board 20.

[0068] 9 and 10 , a semiconductor device 10 includes a wiring board 20 having a first connection terminal 30 and a first roughened copper metal film 45 formed on a first opposing surface 31 of the first connection terminal 30. That is, in the wiring board 20 of this embodiment, the first roughened copper metal film 45 is formed on the first opposing surface 31 instead of the first roughened copper metal film 40 shown in FIG. 1 . The semiconductor device 10 includes a semiconductor element 50 having a second connection terminal 60 and a second roughened copper metal film 75 formed on a second opposing surface 61 of the second connection terminal 60. That is, in the semiconductor element 50 of this embodiment, the second roughened copper metal film 75 is formed on the second opposing surface 61 instead of the second roughened copper metal film 70 shown in FIG. 1 .

[0069] (Structure of the first roughened copper metal film 45) As shown in FIG. 9 , the first roughened copper metal film 45 is formed to cover the entire surface of the first opposing surface 31. The first roughened copper metal film 45 is directly bonded to the first opposing surface 31. The first roughened copper metal film 45 is integrated with the first connection terminal 30. In each drawing, the first connection terminal 30 and the first roughened copper metal film 45 are distinguished from each other by solid lines to make them easier to understand. In reality, the interface between the first connection terminal 30 and the first roughened copper metal film 45 may disappear, and the boundary may not be clear. The thickness (film thickness) of the first roughened copper metal film 45 may be, for example, in the range of 0.5 μm to 2 μm.

[0070] The surface (top and side surfaces, or only the top surface) of the first roughened copper metal film 45 has a finely uneven structure. The first roughened copper metal film 45 has a structure in which granular first deposits 46 made of copper, which is the plating metal, intersect and overlap on the first opposing surface 31 of the first connection terminal 30. The first roughened copper metal film 45 has a structure in which voids are formed between the granular first deposits 46. The first roughened copper metal film 45 is a plating film formed by an electrolytic copper plating method. The first roughened copper metal film 45 is, for example, a metal film made of a plating film of only copper.

[0071] The granular first precipitates 46 are formed, for example, in a spherical shape. Here, the particle size of the granular first precipitates 46 can be, for example, in the range of 20 nm to 100 nm. More preferably, the particle size of the granular first precipitates 46 is, for example, in the range of 20 nm to 50 nm. The first roughened copper metal film 45 has a structure in which the granular first precipitates 46 are stacked in multiple layers. The first roughened copper metal film 45 has a three-dimensional nanostructure in which the nano-sized fine granular first precipitates 46 are randomly oriented and folded into multiple layers. Such a first roughened copper metal film 45 is formed in a structure in which the granular first precipitates 46 are densely folded over the entire thickness of the first roughened copper metal film 45, with multiple voids provided therein. That is, the first roughened copper metal film 45 has a structure in which multiple fine voids are provided therein throughout the entire thickness. In the first roughened copper metal film 45, for example, the density of the first precipitates 46 varies in the thickness direction. For example, in the first roughened copper metal film 45, the density of the first precipitates 46 increases in the thickness direction toward the first opposing surface 31. The porosity of the entire first roughened copper metal film 45 can be set to, for example, in the range of 10% to 25%.

[0072] In this way, the first roughened copper metal film 45 has a structure in which numerous granular first precipitates 46 intersect and overlap, resulting in a rough surface structure with unevenness on the surface and numerous voids in the thickness direction.

[0073] (Structure of second roughened copper metal film 75) The second roughened copper metal film 75 is formed, for example, so as to cover the entire second opposing surface 61. The second roughened copper metal film 75 is directly bonded to the second opposing surface 61. The second roughened copper metal film 75 is integrated with the second connection terminal 60. In each drawing, the second connection terminal 60 and the second roughened copper metal film 75 are distinguished from each other by solid lines to make them easier to understand. In reality, the interface between the second connection terminal 60 and the second roughened copper metal film 75 may disappear, and the boundary may not be clear. The thickness (film thickness) of the second roughened copper metal film 75 may be, for example, in the range of 0.5 μm to 2 μm.

[0074] The surface (bottom and side surfaces, or bottom surface only) of the second roughened copper metal film 75 has a finely uneven structure. The second roughened copper metal film 75 has a structure in which granular second deposits 76 made of copper, which is the plating metal, intersect and overlap on the second opposing surface 61 of the second connection terminal 60. The second roughened copper metal film 75 has a structure in which voids are formed between the granular second deposits 76. The second roughened copper metal film 75 is a plating film formed by copper electroplating. The second roughened copper metal film 75 is, for example, a metal film made of a plating film of only copper.

[0075] The granular second precipitates 76 are formed, for example, in a spherical shape. Here, the particle size of the granular second precipitates 76 can be, for example, in the range of 20 nm to 100 nm. More preferably, the particle size of the granular second precipitates 76 is, for example, in the range of 20 nm to 50 nm. The second roughened copper metal film 75 has a structure in which the granular second precipitates 76 are stacked in multiple layers. The second roughened copper metal film 75 has a three-dimensional nanostructure in which the nano-sized fine granular second precipitates 76 are randomly oriented and folded into multiple layers. Such a second roughened copper metal film 75 is formed in a structure in which the granular second precipitates 76 are densely folded over the entire thickness of the second roughened copper metal film 75, with multiple voids provided therein. That is, the second roughened copper metal film 75 has a structure in which multiple fine voids are provided therein throughout the entire thickness. In the second roughened copper metal film 75, for example, the density of the second precipitates 76 varies in the thickness direction. For example, in the second roughened copper metal film 75, the density of the second precipitates 76 increases in the thickness direction toward the second opposing surface 61. The porosity of the entire second roughened copper metal film 75 can be set to, for example, in the range of 10% to 25%.

[0076] In this way, the second roughened copper metal film 75 has a structure in which numerous granular second precipitates 76 intersect and overlap, resulting in a rough surface structure with unevenness on the surface and numerous voids in the thickness direction.

[0077] 10, the second roughened copper metal film 75 is bonded to the first roughened copper metal film 45. The second roughened copper metal film 75 is diffusion bonded to the first roughened copper metal film 45 by, for example, sintering. No intermetallic compound is formed at the interface (bonding interface) between the first roughened copper metal film 45 and the second roughened copper metal film 75. In other words, the first roughened copper metal film 45 made of copper and the second roughened copper metal film 75 made of copper are bonded directly to each other without any other member made of a material other than copper.

[0078] The bonded portion between the first and second roughened copper metal films 45 and 75 has a structure in which the first precipitate 46 and the second precipitate 76 overlap each other. At the bonded portion between the first and second roughened copper metal films 45 and 75, the first precipitate 46 and the second precipitate 76 are diffusion-bonded by, for example, sintering. This integrates the first precipitate 46 and the second precipitate 76, and the first and second roughened copper metal films 45 and 75 are integrated. The bonded portion between the first and second roughened copper metal films 45 and 75 has a structure in which the first precipitate 46 and the second precipitate 76 are diffusion-bonded together with voids present. The porosity at the bonded portion between the first and second roughened copper metal films 45 and 75 can be, for example, in the range of 7% to 20%. The porosity at the junction between the first and second roughened copper metal films 45 and 75 is higher than the porosity inside the first and second roughened copper metal films 45 and 75. In other words, the porosity is highest at the junction between the first and second roughened copper metal films 45 and 75, and between the first and second roughened copper metal films 45 and 75. In the first roughened copper metal film 45, the porosity decreases in the thickness direction from the junction between the first and second roughened copper metal films 45 and 75 toward the first opposing surface 31. In addition, in the second roughened copper metal film 75, the porosity decreases in the thickness direction from the junction between the first roughened copper metal film 45 and the second roughened copper metal film 75 toward the second opposing surface 61.

[0079] The joint portion between the first roughened copper metal film 45 and the second roughened copper metal film 75 does not protrude outward beyond the side surfaces of the first connection terminal 30 and the second connection terminal 60, for example. That is, at the joint portion between the first roughened copper metal film 45 and the second roughened copper metal film 75, excess material of the joining metal member (solder, etc.) does not protrude outward beyond the side surfaces of the first connection terminal 30 and the second connection terminal 60 in the planar direction. The first connection terminal 30 and the second connection terminal 60 are joined vertically by the first roughened copper metal film 45 and the second roughened copper metal film 75.

[0080] The connection structure of this embodiment is composed of the first connection terminal 30, the first roughened copper metal film 45, the second connection terminal 60, and the second roughened copper metal film 75 described above. (Method of manufacturing the semiconductor device 10) Next, a method for manufacturing the semiconductor device 10 will be described. The manufacturing method of this embodiment differs from the manufacturing method of the first embodiment only in the step shown in Fig. 5. Therefore, in the following description, the steps for forming the first roughened copper metal film 45 and the second roughened copper metal film 75 will be described in detail.

[0081] As shown in FIG. 9 , the first roughened copper metal film 45 is formed on the first opposing surface 31 of the first connection terminal 30. The first roughened copper metal film 45 can be formed by an electrolytic copper plating method using an electrolytic copper plating bath containing polyacrylic acid as the plating bath and utilizing the first connection terminal 30 and the like as a plating power supply layer, similar to the first embodiment. However, the composition of the plating bath and the electrodeposition conditions used in the electrolytic copper plating method differ from those of the first embodiment. An example of plating conditions for forming the first roughened copper metal film 45 will be described below. Specifically, the composition of the plating bath and the electrodeposition conditions when using an electrolytic copper plating bath containing polyacrylic acid are as follows:

[0082] (Second plating conditions) [1] Plating bath composition Basic bath: CuSO4·5H2O: 0.85M H2SO4:0.55M Additives: Polyacrylic acid (molecular weight 5000): 5.0 x 10 -4 M [2] Electrodeposition conditions Current mode: Current regulation method Current flow amount: 2Ccm -2 Current density: 1Adm -2 Temperature: room temperature Agitation: None Anode: Cu plate Cathode: Object to be plated (wiring board or semiconductor element) In this way, by appropriately adjusting the composition of the plating bath used and the electrodeposition conditions, the first roughened copper metal film 45 can be formed to have a desired rough surface structure.

[0083] FIG. 11 is a scanning electron microscope photograph of the surface of first roughened copper metal film 45 formed by electrolytic copper plating using the second plating conditions described above, observed from above. The SEM image in FIG. 11 reveals that first roughened copper metal film 45 has a roughened surface structure in which numerous granular first precipitates 46 randomly intersect and overlap, forming voids within. In other words, the SEM image in FIG. 11 confirms that performing electrolytic copper plating using the second plating conditions described above allows first roughened copper metal film 45 to be formed with the desired roughened surface structure. The particle size of first precipitates 46 in the SEM image in FIG. 11 is in the range of 20 nm to 100 nm.

[0084] The plating bath composition and electrodeposition conditions described above are merely examples, and there are no particular limitations on the composition and conditions as long as they are adjusted to give first roughened copper metal film 45 a desired roughened surface structure. The shape and density of first deposits 46 in first roughened copper metal film 45 can be controlled by adjusting the polyacrylic acid concentration, current density, amount of current flow, plating bath temperature, and the like in the electrolytic copper plating method.

[0085] 9, a second roughened copper metal film 75 is formed on the second opposing surface 61 of the second connection terminal 60. Similar to the formation of the first roughened copper metal film 45, the second roughened copper metal film 75 can be formed by an electrolytic copper plating method using an electrolytic copper plating bath containing polyacrylic acid as the plating bath. The plating conditions in this step can be set to the same conditions as the second plating conditions used to form the first roughened copper metal film 45. The second roughened copper metal film 75 formed by such an electrolytic copper plating method has a rough surface structure similar to that shown in the SEM image in FIG.

[0086] Next, as shown in FIG. 10 , the first roughened copper metal film 45 and the second roughened copper metal film 75 are bonded together. In this example, the first roughened copper metal film 45 and the second roughened copper metal film 75 are diffusion bonded together by sintering. In this process, the wiring substrate 20 and the semiconductor element 50 are bonded together by heating and pressurizing them with the second roughened copper metal film 75 superimposed on the first roughened copper metal film 45. The heating temperature can be, for example, from 180°C to 250°C. The pressure can be, for example, from 8 MPa to 15 MPa. The heating and pressurizing treatment can last for, for example, from 3 minutes to 10 minutes. The heating and pressurizing treatment can be performed, for example, in the atmosphere. The first roughened copper metal film 45 and the second roughened copper metal film 75 are diffusion bonded together by sintering through this heating and pressurizing treatment. Specifically, the first precipitates 46 of the first roughened copper metal film 45 and the second precipitates 76 of the second roughened copper metal film 75 are diffusion bonded by sintering, and the first precipitates 46 and the second precipitates 76 are integrated together. As a result, the first roughened copper metal film 45 and the second roughened copper metal film 75 are bonded and integrated together.

[0087] 12 is a scanning ion microscope photograph of the cross-sectional structure of the bonded portion when the first roughened copper metal film 45 and the second roughened copper metal film 75 were bonded by a heating and pressurizing treatment set at a heating temperature of 200°C, a pressure of 10 MPa, and a treatment time of 5 minutes. The SIM image in FIG. 12 reveals that the first precipitate 46 and the second precipitate 76 are bonded together with voids present in the bonded portion between the first roughened copper metal film 45 and the second roughened copper metal film 75. The bonding between the first precipitate 46 and the second precipitate 76 bonds and integrates the first roughened copper metal film 45 and the second roughened copper metal film 75. 12, it was confirmed that the first roughened copper metal film 45 and the second roughened copper metal film 75 can be bonded together by a heating and pressurizing treatment set at a heating temperature of 200°C, a pressure of 10 MPa, and a treatment time of 5 minutes. Thus, in this embodiment, as in the first embodiment, the first roughened copper metal film 45 and the second roughened copper metal film 75 can be bonded together at a relatively low temperature (about 200°C).

[0088] According to the present embodiment described above, it is possible to achieve the same effects as the first embodiment. (Third embodiment) The third embodiment will be described below with reference to Figures 13 to 15. The semiconductor device of this embodiment differs from the first and second embodiments in the configuration of the connection structure. The following description will focus on the differences from the first embodiment. The same components as those shown in Figures 1 to 12 above are designated by the same reference numerals, and detailed description of each element will be omitted. Note that Figure 14 shows the cross-sectional structure of the connection structure in a state before a semiconductor element 50 is mounted on a wiring board 20.

[0089] 13 , the wiring board 20 of this embodiment has a first roughened copper metal film 40 formed on a substrate body 21. The semiconductor element 50 of this embodiment has a second roughened copper metal film 70 formed on the circuit formation surface (here, the lower surface) of the semiconductor element 50. The second roughened copper metal film 70 is bonded to the first roughened copper metal film 40. In the semiconductor device 10 of this embodiment, the second roughened copper metal film 70 is bonded to the first roughened copper metal film 40, thereby mounting the semiconductor element 50 on the wiring board 20. In other words, in the semiconductor device 10 of this embodiment, the first roughened copper metal film 40 functions as a first connection terminal connected to the semiconductor element 50, and the second roughened copper metal film 70 functions as a second connection terminal connected to the wiring board 20. That is, in the semiconductor device 10 of this embodiment, the first connection terminal is entirely made of the first roughened copper metal film 40, and the second connection terminal is entirely made of the second roughened copper metal film .

[0090] (Structure of the first roughened copper metal film 40) The first roughened copper metal film 40 is formed on the upper surface of the substrate body 21. In the wiring board 20 of this embodiment, a plurality of first roughened copper metal films 40 are formed on the upper surface of the substrate body 21. Each first roughened copper metal film 40 is provided on a portion of the upper surface of the substrate body 21. The first roughened copper metal film 40 is electrically connected to the wiring layer 22, for example, via a wiring layer or a through electrode within the substrate body 21. The thickness (film thickness) of the first roughened copper metal film 40 can be, for example, in the range of 1 μm to 20 μm.

[0091] As shown in FIG. 14 , the first roughened copper metal film 40 is a plating film whose surface (top and side surfaces, or only the top surface) is roughened. The surface of the first roughened copper metal film 40 has a fine uneven structure. The first roughened copper metal film 40 has a structure in which sheet-like first deposits 41 made of copper, which is the plating metal, intersect and overlap on the top surface of the substrate body 21. The first roughened copper metal film 40 has a structure in which voids are formed between the sheet-like first deposits 41. The first roughened copper metal film 40 is a plating film formed by copper electroplating. The first roughened copper metal film 40 is, for example, a metal film made of a plating film of only copper.

[0092] The first roughened copper metal film 40 is formed, for example, on a seed layer (not shown) formed on the upper surface of the substrate body 21. The first roughened copper metal film 40 is, for example, integrated with the seed layer. The seed layer may be made of, for example, copper or a copper alloy.

[0093] (Structure of second roughened copper metal film 70) 13, the second roughened copper metal film 70 is formed on the circuit formation surface of the semiconductor element 50. In this embodiment, a plurality of second roughened copper metal films 70 are formed on the circuit formation surface of the semiconductor element 50. Each second roughened copper metal film 70 is provided partially on a part of the circuit formation surface of the semiconductor element 50. The thickness (film thickness) of each second roughened copper metal film 70 can be, for example, in the range of 1 μm to 20 μm.

[0094] As shown in Fig. 14, the surface (bottom and side surfaces, or bottom surface only) of the second roughened copper metal film 70 has a finely textured structure. The second roughened copper metal film 70 has a structure in which sheet-like second deposits 71 made of copper, which is the plating metal, intersect and overlap on the circuit-forming surface. The second roughened copper metal film 70 has a structure in which voids are formed between the sheet-like second deposits 71. The second roughened copper metal film 70 is a plating film formed by copper electroplating. The second roughened copper metal film 70 is, for example, a metal film made of a plating film of only copper.

[0095] The second roughened copper metal film 70 is formed, for example, on a seed layer (not shown) formed on the circuit formation surface of the semiconductor element 50. The second roughened copper metal film 70 is, for example, integrated with the seed layer. The seed layer may be made of, for example, copper or a copper alloy.

[0096] 15, the second roughened copper metal film 70 is bonded to the first roughened copper metal film 40. The second roughened copper metal film 70 is diffusion bonded to the first roughened copper metal film 40 by, for example, sintering. No intermetallic compound is formed at the interface (bonding interface) between the first roughened copper metal film 40 and the second roughened copper metal film 70. In other words, the first roughened copper metal film 40 made of copper and the second roughened copper metal film 70 made of copper are bonded directly to each other without any other member made of a material other than copper.

[0097] The bonded portion between the first and second roughened copper metal films 40 and 70 has a structure in which the first precipitate 41 and the second precipitate 71 overlap each other. At the bonded portion between the first and second roughened copper metal films 40 and 70, the first precipitate 41 and the second precipitate 71 are diffusion-bonded by, for example, sintering. This integrates the first precipitate 41 and the second precipitate 71, and the first and second roughened copper metal films 40 and 70 are integrated together. The bonded portion between the first and second roughened copper metal films 40 and 70 has a structure in which the first precipitate 41 and the second precipitate 71 are diffusion-bonded together with voids present. The porosity at the bonded portion between the first and second roughened copper metal films 40 and 70 can be, for example, in the range of 5% to 18%. The porosity at the junction between the first and second roughened copper metal films 40 and 70 is higher than the porosity inside the first and second roughened copper metal films 40 and 70. In other words, the porosity is highest at the junction between the first and second roughened copper metal films 40 and 70, and between the first and second roughened copper metal films 40 and 70. In the first roughened copper metal film 40, the porosity decreases in the thickness direction from the junction between the first and second roughened copper metal films 40 and 70 toward the first opposing surface 31. In addition, in the second roughened copper metal film 70, the porosity decreases in the thickness direction from the junction between the first roughened copper metal film 40 and the second roughened copper metal film 70 toward the second opposing surface 61.

[0098] The connection structure of this embodiment is composed of the first roughened copper metal film 40 and the second roughened copper metal film 70 described above. (Method of manufacturing the semiconductor device 10) Next, a description will be given of a method for manufacturing the semiconductor device 10. Here, the steps of forming the first roughened copper metal film 40 and the second roughened copper metal film 70 will be described in detail.

[0099] As shown in FIG. 14 , the first roughened copper metal film 40 is formed on the upper surface of the substrate body 21. More specifically, a seed layer (not shown) is first formed to cover the upper surface of the substrate body 21. The seed layer can be formed by, for example, electroless copper plating or sputtering. A resist pattern (not shown) having openings corresponding to the shape of the first roughened copper metal film 40 is then formed on the seed layer. Next, the first roughened copper metal film 40 is formed in the openings of the resist pattern by electrolytic copper plating, which uses the resist pattern as a plating mask and the seed layer as a plating power supply layer. The plating conditions for the electrolytic copper plating in this step can be set to the same conditions as the first plating conditions in the first embodiment.

[0100] The second roughened copper metal film 70 is formed on the circuit formation surface of the semiconductor element 50. More specifically, a seed layer (not shown) is first formed to cover the circuit formation surface. The seed layer can be formed by, for example, electroless copper plating or sputtering. A resist pattern (not shown) having openings corresponding to the shape of the second roughened copper metal film 70 is then formed on the seed layer. Next, the second roughened copper metal film 70 is formed in the openings of the resist pattern by electrolytic copper plating, using the resist pattern as a plating mask and the seed layer as a plating power supply layer. The plating conditions for the electrolytic copper plating in this step can be set to the same conditions as the first plating conditions in the first embodiment.

[0101] Next, as shown in FIG. 15 , the first roughened copper metal film 40 and the second roughened copper metal film 70 are bonded together. In this process, the wiring substrate 20 and the semiconductor element 50 are bonded together by heating and pressurizing them with the second roughened copper metal film 70 superimposed on the first roughened copper metal film 40. The heating temperature can be, for example, in the range of 180°C to 250°C. The pressure can be, for example, in the range of 8 MPa to 15 MPa. The heating and pressurizing treatment can be performed for, for example, in the range of 3 minutes to 10 minutes. The heating and pressurizing treatment can be performed, for example, in the atmosphere. By such heating and pressurizing treatment, the first roughened copper metal film 40 and the second roughened copper metal film 70 can be diffusion-bonded by sintering.

[0102] According to the present embodiment described above, it is possible to achieve the same effects as the first embodiment. (Other embodiments) The above-described embodiments can be modified as follows: The above-described embodiments and the following modifications can be combined with each other within the scope of technical compatibility.

[0103] In the first and second embodiments, the first roughened copper metal films 40, 45 are formed to cover only the first opposing surface 31 of the surface of the first connection terminal 30, but the present invention is not limited to this.

[0104] 16, for example, a first roughened copper metal film 40 may be formed so as to cover the side surface and first opposing surface 31 of the first connection terminal 30. Similarly, a first roughened copper metal film 45 (see FIG. 9) may be formed so as to cover the side surface and first opposing surface 31 of the first connection terminal 30.

[0105] In the first and second embodiments, the second roughened copper metal films 70, 75 are formed to cover only the second opposing surfaces 61 of the surfaces of the second connection terminals 60, but the present invention is not limited to this.

[0106] 16, for example, a second roughened copper metal film 70 may be formed so as to cover the side surface and second opposing surface 61 of the second connection terminal 60. Similarly, a second roughened copper metal film 75 (see FIG. 9) may be formed so as to cover the side surface and second opposing surface 61 of the second connection terminal 60.

[0107] In the first and second embodiments, the first roughened copper metal film 40, 45 is directly bonded to the first opposing surface 31 of the first connection terminal 30, but this is not limiting. For example, a surface treatment layer may be formed to cover the first opposing surface 31 of the first connection terminal 30, and the first roughened copper metal film 40, 45 may be formed on the surface treatment layer. Note that the surface treatment layer may be, for example, a metal layer such as an Au layer, a Ni layer / Au layer, or a Ni layer / Pd layer / Au layer.

[0108] In the first and second embodiments, the second roughened copper metal film 70, 75 is directly bonded to the second opposing surface 61 of the second connection terminal 60, but this is not limiting. For example, a surface treatment layer may be formed to cover the second opposing surface 61 of the second connection terminal 60, and the second roughened copper metal film 70, 75 may be formed on the surface treatment layer. Note that the surface treatment layer may be, for example, a metal layer such as an Au layer, a Ni layer / Au layer, or a Ni layer / Pd layer / Au layer.

[0109] In the first and second embodiments, the first roughened copper metal films 40, 45 are formed on the first connection terminals 30 of the wiring layer 26. However, this is not limiting. For example, the entire wiring layer 26 may be formed of the first roughened copper metal films 40, 45. That is, the via wiring 26V and the first connection terminals 30 may be formed of the first roughened copper metal films 40, 45. In this case, the first roughened copper metal films 40, 45 are formed on the upper surface of the wiring layer 24 exposed from the opening 25X. That is, in this case, the first roughened copper metal films 40, 45 are formed on the upper surface of the wiring layer 24 exposed from the opening 25X in a structure in which first deposits 41, 46 made of copper, which is the plating metal, intersect and overlap with each other on the upper surface of the wiring layer 24 exposed from the opening 25X.

[0110] In the first and third embodiments, the first and second roughened copper metal films 40 and 70 are formed to have the same rough surface structure, but this is not limiting. That is, in the first and third embodiments, the first and second roughened copper metal films 40 and 70 are both formed by electrolytic copper plating using the first plating conditions, but this is not limiting. For example, the first and second roughened copper metal films 40 and 70 may be formed to have different rough surface structures. For example, the first roughened copper metal film 40 may be formed by electrolytic copper plating using the first plating conditions, and the second roughened copper metal film 70 may be formed by electrolytic copper plating using the second plating conditions.

[0111] In the second embodiment, the first roughened copper metal film 45 and the second roughened copper metal film 75 are formed to have the same rough surface structure, but this is not limiting. That is, in the second embodiment, the first roughened copper metal film 45 and the second roughened copper metal film 75 are both formed by electrolytic copper plating using the second plating conditions, but this is not limiting. For example, the first roughened copper metal film 45 and the second roughened copper metal film 75 may be formed to have different rough surface structures. For example, the first roughened copper metal film 45 may be formed by electrolytic copper plating using the second plating conditions, and the second roughened copper metal film 75 may be formed by electrolytic copper plating using the first plating conditions.

[0112] The first roughened copper metal film 40 in the third embodiment may be changed to a first roughened copper metal film 45 . The second roughened copper metal film 70 in the third embodiment may be changed to a second roughened copper metal film 75 .

[0113] The structure of the wiring board 20 in each of the above embodiments can be modified as appropriate. For example, as long as the wiring board 20 has the first roughened copper metal films 40, 45, the other structures are not particularly limited.

[0114] The structure of the semiconductor element 50 in each of the above embodiments can be modified as appropriate. For example, as long as the semiconductor element 50 has a structure including the second roughened copper metal films 70 and 75, the other structures are not particularly limited.

[0115] The first connection terminal 30 in the first and second embodiments is not limited to a metal post. The second connection terminal 60 in the first and second embodiments is not limited to a metal post.

[0116] The first connection terminal 30 in the first and second embodiments may be made of a metal material other than copper. The second connection terminal 60 in the first and second embodiments may be made of a metal material other than copper.

[0117] The external connection terminals 80 in the semiconductor device 10 of each of the above embodiments may be omitted. [Explanation of symbols]

[0118] 10 Semiconductor devices 20 Wiring board 26 wiring layer 30 First connection terminal 31 First opposing surface 40,45 First roughened copper metal film 41,46 1st precipitate 50 Semiconductor elements 60 Second connection terminal 61 Second opposing surface 70,75 Second roughened copper metal film 71,76 2nd precipitate

Claims

1. a first connection terminal having a first opposing surface; a first roughened copper metal film formed on the first opposing surface; a second connection terminal having a second opposing surface opposing the first opposing surface; a second roughened copper metal film formed on the second opposing surface, the first roughened copper metal film has a structure in which first deposits made of copper intersect and overlap on the first opposing surface, the second roughened copper metal film has a structure in which second deposits made of copper intersect and overlap on the second opposing surface, A connection structure in which the joint portion between the first roughened copper metal film and the second roughened copper metal film has a structure in which the first precipitate and the second precipitate overlap each other, and has voids.

2. the first roughened copper metal film has a structure in which the sheet-like first precipitates are intertwined and overlapped on the first opposing surface, and has a structure in which voids are formed between the sheet-like first precipitates; The connection structure described in claim 1, wherein the second roughened copper metal film has a structure in which the sheet-shaped second precipitates are intertwined and overlapped on the second opposing surface, and voids are formed between the sheet-shaped second precipitates.

3. the first roughened copper metal film has a structure in which the granular first precipitates are intertwined and overlapped on the first opposing surface, and has a structure in which voids are formed between the granular first precipitates; The connection structure described in claim 1, wherein the second roughened copper metal film has a structure in which the granular second precipitates intersect and overlap on the second opposing surface, and voids are formed between the granular second precipitates.

4. the first roughened copper metal film is formed such that the density of the first precipitates increases toward the first opposing surface in a thickness direction of the first roughened copper metal film, A connection structure described in any one of claims 1 to 3, wherein the second roughened copper metal film is formed so that the density of the second precipitates increases in the thickness direction of the second roughened copper metal film as it approaches the second opposing surface.

5. 5. A connection structure according to claim 1, wherein the porosity at the joint between the first roughened copper metal film and the second roughened copper metal film is higher than the porosity inside the first roughened copper metal film and higher than the porosity inside the second roughened copper metal film.

6. the first connection terminal is made of copper, The connection structure according to claim 1 , wherein the second connection terminal is made of copper.

7. A first roughened copper metal film functioning as a first connection terminal; a second roughened copper metal film joined to the first roughened copper metal film and functioning as a second connection terminal; the first roughened copper metal film has a structure in which first deposits made of copper intersect and overlap one another; the second roughened copper metal film has a structure in which second deposits made of copper intersect and overlap one another, A connection structure in which the joint portion between the first roughened copper metal film and the second roughened copper metal film has a structure in which the first precipitate and the second precipitate overlap each other, and has voids.

8. A wiring board; a semiconductor element mounted on the wiring board, The wiring board is a first connection terminal having a first opposing surface that faces the semiconductor element; a first roughened copper metal film formed on the first opposing surface, The semiconductor element is a second connection terminal having a second opposing surface opposing the first opposing surface; a second roughened copper metal film formed on the second opposing surface, the first roughened copper metal film has a structure in which first deposits made of copper intersect and overlap on the first opposing surface, the second roughened copper metal film has a structure in which second deposits made of copper intersect and overlap on the second opposing surface, The semiconductor device has a structure in which the first precipitate and the second precipitate overlap each other at a junction between the first and second roughened copper metal films, and has a void therein.

9. A wiring substrate having a first roughened copper metal film functioning as a first connection terminal; a semiconductor element mounted on the wiring substrate, the semiconductor element having a second roughened copper metal film bonded to the first roughened copper metal film and functioning as a second connection terminal; the first roughened copper metal film has a structure in which first deposits made of copper intersect and overlap one another; the second roughened copper metal film has a structure in which second deposits made of copper intersect and overlap one another, The semiconductor device has a structure in which the first precipitate and the second precipitate overlap each other at a junction between the first and second roughened copper metal films, and has a void therein.

10. forming a first connection terminal having a first opposing surface; forming a first roughened copper metal film having a structure in which first deposits made of copper intersect and overlap on the first opposing surface by an electrolytic copper plating method; forming a second connection terminal having a second opposing surface; forming a second roughened copper metal film having a structure in which second deposits made of copper intersect and overlap on the second opposing surface by an electrolytic copper plating method; and applying heat and pressure to the first and second roughened copper metal films in a state where the first and second roughened copper metal films are superimposed on each other, thereby bonding the first and second roughened copper metal films together, the first roughened copper metal film and the second roughened copper metal film are formed by an electrolytic copper plating method using an electrolytic copper plating bath containing polyacrylic acid as a plating bath; A method for manufacturing a connection structure in which the first precipitate and the second precipitate are diffusion-bonded while having voids at the joint between the first roughened copper metal film and the second roughened copper metal film.

Images