External electrode connector

Abstract

An external electrode connector connects together external electrodes. The external electrode comprises a first metal layer, a first buffer layer and a second metal layer. The first buffer layer is formed on the first metal layer and electrically connected to the first metal layer. Conductors and elastic bodies are alternately provided or the conductors are arranged within a principal plane of the elastic body in the first buffer layer. The second metal layer is formed on the first buffer layer and electrically connected to the first buffer layer. The elastic body is lower in Young's modulus than the first metal layer, the conductor, and the second metal layer.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to an external electrode connector to be used for electrically connecting together external electrodes of a substrate, and those of a semiconductor element, or the like.

[0003] 2. Background Art

[0004] A conventional semiconductor device is formed by integrally bonding together a semiconductor element and an anisotropic conductive film. Ends of conduction channels of the film are connected to respective pads formed from external electrodes of the element. Thus, the pads are connected to the outside by way of the film. The anisotropic conductive film has a construction such that a plurality of metal conductors are isolated from each other in a film substrate formed from insulating resin and provided in the form of conduction channels while penetrating through the film substrate in the thicknesswise direction thereof (as described in, e.g., JP-A-2000-286293).

SUMMARY OF THE INVENTION

[0005] In the related-art semiconductor device, electrical connection is established between pads of the semiconductor device and the outside by means of metal conduction channels provided in the thicknesswise direction of the insulating film substrate. Hence, the area of electrical connection between the conduction channels of the anisotropic conductive film and the pads and the area of electrical connection between the conduction channels and the outside are small, thereby presenting a problem of occurrence of conduction failures between the pads of the semiconductor device and the outside. Even when conduction failures do not arise, contact resistance developing between the pads of the semiconductor device and the conduction channels or that developing between the conduction channels and the outside becomes greater, thereby presenting a problem of deterioration of a transmission signal. The contact pressure developing between the pads of the semiconductor device and the conduction channels and that developing between the conduction channels and the outside are increased by posing load between the semiconductor device and the outside, thereby enhancing the conductivity therebetween. In this case, there arises a problem of the load causing a fracture in an interlayer dielectric film serving as a base layer of an external electrode of the semiconductor device.

[0006] The invention has been conceived to solve the problem and is aimed at providing an external electrode connector which exhibits superior conductivity and is less likely to cause a fracture in a base layer of an external electrode, which would otherwise be caused by connection between external electrodes.

[0007] According to one aspect of the present invention, an external electrode connector connects together external electrodes. The external electrode comprises a first metal layer, a first buffer layer and a second metal layer. The first buffer layer is formed on the first metal layer and electrically connected to the first metal layer. Conductors and elastic bodies are alternately provided or the conductors are arranged within a principal plane of the elastic body in the first buffer layer. The second metal layer is formed on the first buffer layer and electrically connected to the first buffer layer. The elastic body is lower in Young's modulus than the first metal layer, the conductor, and the second metal layer.

[0008] Other and further objects, features and advantages of the invention will appear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 shows the external electrode connector according to a first embodiment of the invention.

[0010] FIG. 2 shows the semiconductor element.

[0011] FIG. 3 shows the external electrode connector according to a first embodiment of the invention, connected to one of the pads of the semiconductor element.

[0012] FIG. 4 shows that semiconductor elements are connected together by means of the external electrode connector according to a first embodiment of the invention.

[0013] FIG. 5 shows the formation process of the external electrode connector according to a first embodiment of the invention.

[0014] FIG. 6 shows the formation process of the external electrode connector according to a first embodiment of the invention.

[0015] FIG. 7 shows the other external electrode connector according to a first embodiment of the invention.

[0016] FIG. 8 shows the external electrode connector according to a second embodiment of the invention.

[0017] FIG. 9 shows the other external electrode connector according to a second embodiment of the invention.

[0018] FIG. 10 shows that semiconductor elements are connected together by means of the external electrode connector according to a second embodiment of the invention.

[0019] FIG. 11 shows the external electrode connector according to a second embodiment of the invention, connected to one of the pads of the semiconductor element.

[0020] FIG. 12 shows the other external electrode connector according to a third embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] First Embodiment

[0022] FIG. 1A is a cross-sectional view showing an external electrode connector 1 according to a first embodiment of the invention, and FIG. 1B is a cross-sectional view of the external electrode connector 1 taken along line I-I. As illustrated, each of the external electrode connectors 1 is formed by stacking, in the sequence given, a first metal layer 2a formed from gold or the like; a first buffer layer 5a formed by alternately arranging a conductor member 3a formed from gold or the like and an elastic body 4a formed from polyimide or rubber; and a second metal layer 2b formed from gold or the like. The first metal layer 2a and the conductor 3a remain in a conductive state, and the conductor 3a and the second metal layer 2b also remain in a conductive state. The elastic body 4a is lower in Young's modulus than the first metal layer 2a, the conductor 3a, and the second metal layer 2b.

[0023] FIG. 2A is a plan view of a semiconductor element; FIG. 2B is a cross-sectional view taken along line II-II; and FIG. 2C is an enlarged cross sectional view of a periphery of a pad. Pads 7, each constituting an external electrode of a semiconductor element 6 and being formed from aluminum or the like, are arranged on the principal plane of the semiconductor element 6 in a lattice of uniform squares. The principal plane is covered with a protective surface film 9, except at pad openings 8. As shown in FIG. 2B or 2C, the cross section of the semiconductor element 6 is formed by forming an interlayer dielectric film 11 which is to serve as an external electrode base layer on the semiconductor substrate 10, and forming the pads 7 on the interlayer dielectric film 11. Although not illustrated, the pads 7 are electrically connected to internal metal interconnections formed on or in the interlayer dielectric film 11 as well as to an internal circuit.

[0024] FIG. 3A is a view showing that the external electrode connector 1 is connected to one of the pads of the semiconductor element; FIG. 3B is a view showing that the semiconductor element connected to the external electrode connector 1 is mounted on a mount board 12; and FIG. 3C is an enlarged view showing the periphery of the pads when the semiconductor element is mounted on the mount board. By means of a bonder, the external electrode connector 1 whose connection surface is coated with a conductive adhesive (not shown) is bonded onto barrier metal 13 which is formed from titanium or the like on the surface of each pad 7 and prevents diffusion of metal of the first metal layer 2a of the external electrode connector 1 into aluminum or the like of the pad 7. The semiconductor element 6—on which the external electrode connectors 1 are mounted—and the mount board 12 are connected together, by means of aligning the external electrode connectors 1 whose connection surfaces are coated with the conductive adhesive (not shown) with board electrodes 14, and applying load in the vertical direction of the drawing, wherein the board electrodes 14 are formed on the mount board 12 and serve as external electrodes of the mount board 12.

[0025] FIG. 4A shows that semiconductor elements are connected together by means of the external electrode connector. FIG. 4B is an enlarged view of a periphery of one pad when the semiconductor elements are connected together. Here, the semiconductor elements 6 are connected together by application of load in the vertical direction of the drawing, by means of aligning the external electrode connectors 1 whose connection surfaces are coated with a conductive adhesive (not shown) with the pads 7 of both the semiconductor elements 6. Barrier metal 13 is formed on the surface of each of the pads 7 of the semiconductor elements 6, for the same reason as in the case where the semiconductor element 6 is mounted on the mount board.

[0026] By reference to FIGS. 5A to 6D, a method for manufacturing the external electrode connector 1 will now be described. FIG. 5A is a view of the periphery of a pad before formation of the external electrode connectors 1, showing only the pad 7, the surface protective film 9, and the interlayer dielectric film 11. The barrier metal 13 is formed on the surface of the pad 7 by means of sputtering (FIG. 5B). A metal layer which is to become the first metal layer 2a is formed on the surface of the barrier metal 13 by means of sputtering (FIG. 5C). Next, a polyimide layer which is to serve as the resilient member 4a is formed on the surface of the first metal layer 2a by means of spin coating (FIG. 5D). Opening sections 15 to be used for forming the conductor member 3a in the elastic body 4a are formed by means of photolithography (FIG. 6A). By means of plating, the opening sections 15 are filled with gold, which is to act as the conductor member 3a (FIG. 6B). A gold layer which is to act as the second metal layer 2b is formed by means of sputtering (FIG. 6C). After photolithography, unnecessary portions of the second metal layer 2b, those of the elastic body 4a, those of the first metal layer 2a, and those of the barrier metal 13 are eliminated by means of etching (FIG. 6D). Here, layers formed through the processes shown in FIGS. 5D to 6B constitute the first buffer layer 5a.

[0027] The embodiment shows a method for forming the external electrode connectors 1 integrally on the semiconductor element 6. Alternatively, instead of being formed around respective pads of the semiconductor element 6, the external electrode connectors 1 may be manufactured as individual parts through processes similar to the above-described processes while molds having prismatic recesses therein are used as a base. The individual external electrode connectors 1 may be bonded to the areas on the semiconductor element 6 occupied by the barrier metal 13, through use of a conductive adhesive (not shown). In the embodiment, the barrier metal 13 is formed in order to prevent diffusion of material of the first metal layer 2a into the pads 7. However, when the first metal layer 2a and the pads 7 are formed from the same material or when occurrence of a problem stemming from diffusion of material does not need to be taken into consideration, the barrier metal 13 may be eliminated.

[0028] The effect of the external electrode connectors 1 will now be described by reference to FIGS. 3A to 3C. When the semiconductor element 6 having the external electrode connectors 1 provided thereon is mounted on the mount board 12, heavy load is applied in the vertical direction in FIG. 3C. A portion of the load received by the elastic bodies 4a while the elastic bodies 4a are being deformed in the horizontal direction in FIG. 3C is dispersed in the horizontal direction in FIG. 3C. Therefore, the load exerted on the pads 7 and the interlayer dielectric film 11 is mitigated, thereby rendering the interlayer dielectric film 11 less susceptible to fracture. Further, the entire surface of each of the external electrode connectors 1, the surface being bonded to the corresponding pad 7 and the corresponding board electrode 14, is formed from metal. Therefore, the pads 7 and the board electrodes 14 can be stably and electrically connected together. The same effect can be achieved on the same principle even when the semiconductor elements 6 are connected together as shown in FIGS. 4A and 4B. The embodiment has described the effect of the external electrode connector 1, through use of the pads of the semiconductor element—in which connection sections serving as external electrodes occupy small areas and in which an interlayer dielectric film serving as external electrode base layer is susceptible to fracture—and board electrodes of the mount board. However, the field of application of the external electrode connector 1 of the invention is not limited to this embodiment. The external electrode connector 1 can be used as an electrical connection part for general components having external electrodes, such as liquid-crystal boards and flexible boards.

[0029] In the first buffer layer 5a of the first embodiment, the conductors 3a and the elastic bodies 4a are arranged one after another. However, as shown in FIGS. 7A and 7B, columnar conductors 3a may be arranged in a lattice of uniform squares within the principal plane of the elastic body 4a.

[0030] The first metal layer 2a, the conductor 3a, and the elastic body 4a may each be formed from a single material or a plurality of materials such as an alloy or a mixed body consisting of polyimide and rubber. The first metal layer 2a, the conductor 3a, and the second metal layer 2b may be formed from the same material or different materials.

[0031] Second Embodiment

[0032] FIG. 8A is a cross-sectional view showing an external electrode connector 1 and the periphery of the pad 7 according to a second embodiment of the invention, and FIG. 8B is a cross-sectional view of the external electrode connector 1 when taken along line IV-IV and line V-V. Those elements which are identical with or correspond to those described in connection with the first embodiment shown in FIGS. 1A through 7B are assigned the same reference numerals, and repetition of their explanations is omitted. As illustrated, the external electrode connector 1 comprises a second buffer layer 5b provided on the second metal layer 2b; a third metal layer 2c provided on the second buffer layer 5b; and conductors 3a, 3b, wherein the conductors 3a of the first buffer layer 5a and the conductors 3b of the second buffer layer 5b do not overlap each other with reference to the direction perpendicular to the principal plane of the second buffer layer 5b. When load caused by connection of semiconductor elements or by mounting a semiconductor element on a mount board is exerted on the conductors 3b of the second buffer layer 5b, the load is primarily exerted on areas located directly below the conductors 3b. In the present embodiment, the elastic bodies 4a of the first buffer layer 5a are located at positions immediately below the conductors 3b without fail, and hence the load is more easily dispersed.

[0033] In the first and second buffer layers 5a, 5b of the second embodiment, the conductors 3a, 3b and the elastic bodies 4a, 4b are arranged alternately. However, as shown in FIGS. 9A and 9B, the conductors 3a, 3b may be arranged in a lattice of uniform squares within the respective principal planes of the elastic bodies 4a, 4b. Moreover, the external electrode connectors 1 of the second embodiment can be manufactured by forming the external electrode connectors 1 up to the second metal layers 2b through the same processes as those employed in forming the external electrode connectors 1 of the first embodiment shown in FIGS. 5A to 6D. Subsequently, locations at which the conductors 3b are to be formed are changed to different locations which do not overlap the conductors 3a with reference to the direction perpendicular to the principal plane of the second buffer layer 5b. The external electrode connectors 1 can be manufactured through repetition of processing pertaining to FIGS. 5D to 6D.

[0034] Third Embodiment

[0035] FIG. 10A is a cross-sectional view showing the periphery of a pad of a semiconductor element according to a third embodiment of the invention; FIG. 10B is an enlarged view of the pad; and FIG. 10C is a cross-sectional view of a buffer layer taken along line VIII-VIII. Those elements which are identical with or correspond to those described in connection with the first embodiment shown in FIGS. 1A to 7B are assigned the same reference numerals, and repetition of their explanations is omitted. External electrode connectors of the third embodiment constitute pads 107. Specifically, the first metal layer 2a is connected to the barrier metal 13 formed from titanium or the like so as to extend over the interlayer dielectric film 11, which serves as an external electrode substrate of the semiconductor element 6, and over an internal metal interconnection 16 formed from aluminum or the like. The surface of the second metal layer 2b acts as the pad surface 17.

[0036] FIG. 11A is a view showing that a semiconductor element having the pads 107 of the third embodiment is mounted on a mount board, and FIG. 11B is a view showing that the semiconductor elements are connected together. As shown in FIG. 11A, in the semiconductor element 6 having the pad 107, a solder 18 whose connection surfaces are coated with a conductive adhesive (not shown) is sandwiched between the pad 107 and the board electrode 14. Load is applied to the semiconductor element 6 and the mount board 12 in the vertical direction in the drawing, whereby the semiconductor element 6 is mounted on the mount board 12. As shown in FIG. 11B, the pads 107 of the semiconductor elements 6 are bonded together by means of applying load to the semiconductor elements 6 in the vertical direction in the drawing while the solder 18 whose connection surfaces are coated with a conductive adhesive (not shown) is sandwiched between the pads 107.

[0037] The pads 107 of the semiconductor 6 according to the third embodiment are formed while including the elastic bodies 4a. As a result of deformation of the elastic bodies 4a, the load stemming from interconnection of the pads 107 of the semiconductor elements 6 and the load exerted on the pads 107 when the semiconductor element 6 is mounted on the mount board 12 are dispersed in the direction parallel to the pad surfaces 17. Accordingly, the damage inflicted on the interlayer dielectric film 11 can be mitigated. Further, the damage inflicted on the interlayer dielectric film 11 is also caused as a result of a probe needle (not shown) used in a wafer test coming into contact with the pad surfaces 17. The pads 107 of the semiconductor element 6 of the third embodiment structurally disperse load, and, therefore, the damage inflicted on the interlayer dielectric film 11 can also be mitigated. In addition, metal is used for both surfaces of each pad 107 of the third embodiment, with which the solder 18 and the probe needle are brought into contact. For this reason, stable conduction can be established between the internal metal interconnection 16 and the solder 18 and between the internal metal interconnection 16 and the probe needle. The pads can be manufactured through use of an existing facility for manufacturing a semiconductor device and through the same processes as those employed for manufacturing the external electrode connectors shown in FIGS. 5A to 6D.

[0038] In the semiconductor element 6 of the third embodiment, the barrier metal 13 is formed between the internal metal interconnection 16 and the first metal layer 2a. When the internal metal interconnection 16 and the first metal layer 2a are formed from the same material or when diffusion of material between the internal metal interconnection 16 and the first metal layer 2a does not pose any problem, the barrier metal 13 may be obviated. In contrast, when diffusion of material between the conductor 3a and the first metal layer 2a poses problems, forming the barrier metal 13 between the first metal layer 2a and the first buffer layer 5a is preferable, in view of preventing diffusion of the material. When diffusion of material between the conductors 3a and the second metal layer 2b poses problems, forming the barrier metal 13 between the first buffer layer 5a and the second metal layer 2b is preferable, in view of preventing diffusion of the material.

[0039] In the semiconductor element 6 of the third embodiment, the internal metal interconnection 16 is formed in the interlayer dielectric film 11. The pads 107 are constructed such that each pad is located over both the interlayer dielectric film 11 and the internal metal interconnection 16. However, when the internal metal interconnection 16 is formed on the interlayer dielectric film 11 in such a manner as shown in FIG. 12, the pads 107 are formed on the interlayer dielectric film 11, and the interlayer metal interconnection 16 is connected to a side surface of the first metal layer 2a.

[0040] As in the case of the external electrode connector 1 described in connection with the second embodiment shown in FIGS. 8A to 9B, the second buffer layer 5b is formed on the second metal layer 2b; the third metal layer 2c is formed on the second buffer layer 5b; and the conductors 3a, 3b are arranged such that the conductors 3a of the first buffer layer 5a do not overlap the conductors 3b of the second buffer layer 5b in the direction perpendicular to the principal plane of the second buffer layer 5b. By means of such a construction, the damage—which would be inflicted on the interlayer dielectric film 11 when the semiconductor element is mounted on the mount board—is mitigated to a much greater extent. In each of the pads 107 of the third embodiment, the conductors 3a and the elastic bodies 4a are arranged alternately. As in the case of the external electrode connector 1 described in connection with the first embodiment shown in FIGS. 7A and 7B, the columnar conductors 3a may be arranged in a lattice of uniform squares within the principal plane of the elastic body 4a. Further, the first metal layer 2a, the conductors 3a, and the elastic bodies 4a may each be formed from single material or a plurality of materials, such as an alloy or a mixed member consisting of polyimide and rubber. The first metal layer 2a, the conductors 3a, and the second metal layer 2b may be formed from a single material or from different materials. In the embodiment, the external electrode connector is applied to the pads of the semiconductor element, wherein connection sections occupy small areas and in which an interlayer dielectric film 11 serving as an external electrode base layer is susceptible to fracture. The external electrode connector may be applied to board electrodes of amount board or pads of a liquid-crystal substrate.

[0041] The features and advantages of the present invention may be summarized as follows.

[0042] As described above, the external electrode connector of the invention comprises a first metal layer; a first buffer layer in which conductors and elastic bodies are alternately provided or in which conductors are arranged within a principal plane of an elastic body; and a second metal layer. The elastic body is lower in Young's modulus than the first metal layer, the conductors, and the second metal layer. Therefore, a base layer of the external electrode is less susceptible to fractures which would be caused when external electrodes are connected together. Further, stable conduction can be established between external electrodes.

[0043] Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may by practiced otherwise than as specifically described.

[0044] The entire disclosure of a Japanese Patent Application No. 2002-347708, filed on Nov. 29, 2002 including specification, claims, drawings and summary, on which the Convention priority of the present application is based, are incorporated herein by reference in its entirety.

Claims

1. An external electrode connector for connecting together external electrodes, comprising: a first metal layer; a first buffer layer which is formed on the first metal layer and electrically connected to the first metal layer and in which conductors and elastic bodies are alternately provided or in which the conductors are arranged within a principal plane of the elastic body; and a second metal layer which is formed on the first buffer layer and electrically connected to the first buffer layer, wherein the elastic body is lower in Young's modulus than the first metal layer, the conductor, and the second metal layer.

2. The external electrode connector according to claim 1, further comprising: a second buffer layer which is formed on the second metal layer and electrically connected to the second metal layer and in which conductors and elastic bodies are alternately provided or in which the conductors are arranged within a principal plane of the elastic body; and a third metal layer which is formed on the second buffer layer and electrically connected to the second buffer layer, wherein the conductors of the first buffer layer and the conductors of the second buffer layer are arranged at positions such that the conductors of the first buffer layer do not overlap the conductors of the second buffer layer with reference to the direction perpendicular to the principal plane of the second buffer layer.

3. The external electrode connector according to claim 1, wherein the external electrodes correspond to an internal metal interconnection of a semiconductor element; the internal metal interconnection and the first metal layer are connected together; and the surface of the second metal layer constitutes a pad surface.

4. The external electrode connector according to claim 2, wherein the external electrodes correspond to an internal metal interconnection of a semiconductor element; the internal metal interconnection and the first metal layer are connected together; and the surface of the second metal layer constitutes a pad surface.

5. The external electrode connector according to claim 3, wherein barrier metal is provided between the internal metal interconnection and the first metal layer, between the first metal layer and the first buffer layer, or between the first buffer layer and the second metal layer.

6. The external electrode connector according to claim 4, wherein barrier metal is provided between the internal metal interconnection and the first metal layer, between the first metal layer and the first buffer layer, or between the first buffer layer and the second metal layer.