Abstract:
A semiconductor device provided with transistors or other semiconductor elements formed on a semiconductor substrate, external connection terminals connecting these elements to an external circuit, and interconnection patterns connecting electrodes of the semiconductor elements to the external connection terminals, wherein the external connection terminals are formed by wires comprised of a conductive material and the parts of the wires bonded to the interconnection patterns are buried in the metal layer forming the interconnection patterns. A method of production of the semiconductor device is also disclosed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a semiconductor device and a method of production of the same, more particularly relates to a semiconductor device produced by forming external connection terminals on an electrode formation surface of a semiconductor wafer and a method of production of the same. 
     2. Description of the Related Art 
     FIGS. 12A to  12 I show a method of production of a semiconductor device formed with metal posts as external connection terminals on an electrode formation surface of a semiconductor wafer. In this method of production, first, an electrode formation surface of a semiconductor wafer  10  from which electrodes  12  are exposed and which is covered by a passivation film  14  (FIG. 12A) is covered with a conductive layer  16  by sputtering (FIG.  12 B). Next, the surface of the conductive layer  16  is covered by a photosensitive resist  18  (FIG.  12 C), then the photosensitive resist  18  is exposed and developed to expose portions for forming interconnection patterns at the surface of the conductive layer  16  (FIG.  12 D). 
     The electrodes  12  are arranged at an extremely high density at for example the periphery of the electrode formation surface of the semiconductor wafer  10 . As shown in FIG. 12E, the interconnection patterns  20  are formed by electroplating the exposed surfaces of the conductive layer  16  by copper. The interconnection patterns  20  are formed led out from the electrodes  12  so as to secure spaces for arrangement of the external connection terminals. 
     Next, the photosensitive resist  18  is removed and the surfaces of the interconnection patterns  20  and conductive layer  16  are covered by a dry film  22  (FIG.  12 F), This dry film  22  is for forming the copper posts  24  forming the external connection terminals (FIG.  12 G). The dry film  22  is exposed and developed to form holes for plating at portions for forming the copper posts  24  on the interconnection patterns  20 . By electroplating these portions by copper, copper is built up in the plating holes and metal posts  24  of heights of about 100 μm are formed. Next, the surfaces of the copper posts  24  are successively plated by nickel, palladium, etc. to form the barrier layers  26 . 
     The dry film  22  is removed, then the portions of the conductive layer  16  exposed at the electrode formation surface are removed by etching (FIG.  12 H). In this way, the electrode formation surface of the semiconductor wafer  10  is formed with copper posts  24  electrically connected with the electrodes  12  through the interconnection patterns  20 . 
     Next, as shown in FIG. 12I, the electrode formation surface of the semiconductor wafer  10  is covered with a resin  28  for sealing. The resin  28  is formed to substantially the same thickness as the copper posts  24 . The end faces of the copper posts  24  are exposed at the surface of the resin  28 . After the resin sealing, solder balls are placed on the surfaces of the barrier layers  26  and the solder made to reflow to form solder bumps (not shown). Finally, the semiconductor wafer  10  can be diced along with the resin  28  to obtain chip-sized semiconductor devices. 
     FIGS. 13A to  13 I show another method for producing a chip-sized semiconductor device. The semiconductor device obtained by this method of production has gold wires bent in L-shapes for use as external connection terminals. The steps shown in FIGS. 13A to  13 E are basically no different from the steps shown in the above FIGS. 12A to  12 E. In this method, however, the interconnection patterns  20  are not sealed by resin. The interconnection patterns  20  are formed by gold plating so as to enable them to be left as they are exposed at the outside surface of the semiconductor device. 
     As shown in FIG. 13F, the photosensitive resist  18  (FIG. 13E) is removed. Next, as shown in FIG. 13G, the electrode formation surface is covered by a resist, then holes  30   a  are formed in the interconnection patterns  20  at portions for later bonding of the gold wires. The electrode formation surface is covered by the resist  30  so as to cover only the outer surfaces of the gold wires with reinforcement plating after bonding the gold wires. As shown in FIG. 13H, the gold wires are bonded to the interconnection patterns  20  in register with the openings  30   a  (FIG.  13 G). Next, the gold wires are bent into L-shapes and the ends thereof are cut off to form the external connection terminals  32 . The outer surfaces of the gold wires are plated to reinforce the wires (the plating material is not shown in the drawing), then the resist  30  is removed and, as shown in FIG. 13I, the exposed portions of the conductive layer  16  are removed by etching. 
     In this way, the electrode formation surface of the semiconductor wafer  10  is formed with external connection terminals  32  electrically connected with the electrodes  12  through the interconnection patterns  20 . Finally, the semiconductor wafer  10  is diced to obtain semiconductor devices provided with external connection terminals  32  comprised of wires bent into L-shapes. 
     In the examples shown in the above FIGS. 12A to  12 I and FIGS. 13A to  13 I, the conductive layer  16  was formed on the passivation film  14 , but it is also possible to cover the passivation film  14  by a polyimide film and form the conductive layer  16  on the surface of the polyimide film. 
     Steps for producing a semiconductor device using the above copper posts as external connection terminals and steps for producing a semiconductor device using gold wires bent into L-shapes as external connection terminals are shown in FIGS. 14 and 15. The steps produce chip-sized semiconductor devices by processing the semiconductor wafer to form external connection terminals electrically connected to the electrode terminals formed on it, then dicing the semiconductor wafer. In this way, the methods of the prior art utilize complicated steps, so there are the problems that the production efficiency is reduced and the manufacturing costs increased. 
     Further, there have been the following problems when mounting a semiconductor device produced by a method of production of the prior art to a board: When mounting a semiconductor device using copper posts as external connection terminals by solder, the solder does not form meniscuses and the external connection terminals are not reliably bonded with the board. When mounting a semiconductor device provided with external connection terminals formed by bending gold wires in L-shapes, due in part to the fact that the heights of the external connection terminals are about 700 to 800 μm, the semiconductor device and the board are bonded spaced away from each other. 
     SUMMARY OF THE INVENTION 
     The present invention was made to solve the problems in the methods of production of the prior art for producing semiconductor devices by processing a semiconductor wafer. An object of the present invention is to provide a highly reliable semiconductor device able to be produced by a simpler method and thereby able to improve the production efficiency and able to arrange external connection terminals at a higher density and thereby able to handle a greater number of pins and a method of production of the same. 
     To attain the above object, according to a first aspect of the present invention, there is provided a semiconductor device provided with semiconductor elements, such as transistors, formed on a semiconductor substrate, external connection terminals connecting these elements to an external circuit, and interconnection patterns connecting electrodes of the semiconductor elements to the external connection terminals, wherein the external connection terminals are formed by wires comprised of a conductive material and the parts of the wires bonded to the interconnection patterns are buried in the metal layer forming the interconnection patterns. 
     The metal layer forming the interconnection patterns is preferably formed by copper plating, gold plating or the like. 
     As the wires of the conductive material forming the external connection terminals, it is preferable to use gold wires, copper wires, etc. 
     More preferably, the metal layer and the wires are fabricated by the same material. Therefore, preferably the metal layer is formed by gold plating and the wires are comprised of gold or the metal layer is formed by copper plating and the wires are comprised of copper. 
     The external connection terminals can be covered by the material of the metal layer forming the interconnection patterns. 
     The surface of the semiconductor device where the interconnection patterns are formed can be sealed so as to leave exposed the external connection terminals. 
     According to a second aspect of the present invention, there is provided a method of production of a semiconductor device provided with semiconductor elements formed on a semiconductor substrate, external connection terminals connecting the elements to an external circuit, and interconnection patterns connecting electrodes of the semiconductor elements to the external connection terminals, comprising the steps of forming a conductive layer on the entire surface of the semiconductor substrate where the electrodes are formed, forming a resist pattern on the surface of the conductive layer exposing the conductive layer at portions where pads to which the external connection terminals are to be connected and the interconnection patterns are to be formed, bonding wires comprised of a conductive material to the conductive layer at portions where the pads are to be formed to form external connection terminals, forming a metal layer at the exposed portions of the conductive layer, removing the resist, and removing the conductive layer exposed by the removal of the resist to form interconnection patterns. 
     After forming the interconnection patterns, it is possible to seal the surface of the semiconductor device where the interconnection patterns are formed so as to leave exposed the external connection terminals. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and features of the present invention will become clearer from the following description of the preferred embodiments given with reference to the attached drawings, wherein: 
     FIGS. 1A to  1 I are views for explaining a method of production of a semiconductor device according to a first embodiment of the present invention; 
     FIGS. 2A to  2 H are views for explaining a method of production of a semiconductor device according to a second embodiment of the present invention; 
     FIG. 3 is a flow chart of a method of production of a semiconductor device according to the first embodiment of the present invention; 
     FIG. 4 is a flow chart of a method of production of a semiconductor device according to the second embodiment of the present invention; 
     FIG. 5 is a plan view of the state of etching of a photosensitive resist covering an electrode formation surface of a semiconductor wafer; 
     FIG. 6 is a view of a semiconductor wafer for forming a large number of semiconductor devices before dicing; 
     FIG. 7A is an enlarged sectional view of a portion bonding an external connection terminal with an interconnection pattern in a semiconductor device according to the present invention, while FIG. 7B is an enlarged sectional view of a portion bonding an external connection terminal with an interconnection pattern in a semiconductor device of the prior art; 
     FIG. 8A is an enlarged sectional view of a portion bonding an external connection terminal with an interconnection pattern in another semiconductor device according to the present invention, while FIG. 8B is an enlarged sectional view of a portion bonding an external connection terminal with an interconnection pattern in another semiconductor device of the prior art; 
     FIGS. 9A to  9 C are views for explaining bonding of a copper wire or gold wire with the conductive layer in the present invention; 
     FIG. 10A is a view of a semiconductor device according to the present invention mounted on a board, while FIG. 10B is a view of a semiconductor device of the prior art mounted on a board; 
     FIG. 11A is a view of another semiconductor device according to the present invention mounted on a board, while FIG. 11B is a view of another semiconductor device of the prior art mounted on a board; 
     FIGS. 12A to  12 I are views explaining a method of production of a semiconductor device of the prior art; 
     FIGS. 13A to  13 I are views explaining another method of production of a semiconductor device of the prior art; 
     FIG. 14 is a flow chart of the method of production of a semiconductor device of the prior art shown in FIGS. 12A to  12 I; and 
     FIG. 15 is a flow chart of the method of production of a semiconductor device of the prior art shown in FIGS. 13A to  13 I. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will be described in detail below while referring to the attached figures. 
     FIGS. 1A to  1 I are views for explaining a method of production of a semiconductor device according to a first embodiment of the present invention. 
     As shown in FIG. 1A, the surface of a semiconductor wafer  10  formed with electrodes  12  is covered by passivation film  14  leaving the electrodes  12  exposed. In the method of production of a semiconductor device of this embodiment, a conductive layer  16  is formed on the electrode formation surface of the semiconductor wafer  10  (FIG.  1 B). In the present embodiment, a chromium layer is formed by sputtering, then a copper layer is formed by sputtering to obtain the conductive layer  16 . The surface of the passivation film  14  may be formed with a polyimide or other electrical insulating layer (not shown) as a protective film, then the conductive layer  16  formed. 
     Next, a photosensitive resist  18  is coated on the entire electrode formation surface of the semiconductor wafer  10  to cover the surface of the conductive layer  16  by the photosensitive resist  18  (FIG.  1 C). The photosensitive resist  18  is exposed and developed for patterning to, as shown in FIG. 1D, leave exposed only the portions for forming the interconnection patterns for rewiring on the surface of the conductive layer  16 . 
     FIG. 5 is a plan view of one chip section of the semiconductor wafer in the state with the photosensitive resist  18  exposed and developed. Reference numeral  18  indicates a photosensitive resist covering the electrode formation surface of the semiconductor wafer  10 ,  16   a  portions where the conductive layer  16  is left exposed in accordance with the arrangement of the interconnection patterns,  16   b  portions forming pads formed at the ends of the interconnection patterns, and  16   c  portions of base ends of the interconnection patterns connected to the electrodes  12 . 
     The method of production of a semiconductor device of the present embodiment is characterized by the formation of external connection terminals  50  by the method of bonding copper wires to portions  16   b  forming the pads after patterning the photosensitive resist  18  as shown in FIG.  1 E. At the time of the wire bonding, the tips of the copper wires are melted into ball shapes, the ball-shaped portions are bonded with the portions  16   b  forming the pads, then the wires are pulled up and cut, whereby external connection terminals  50  with projections  50   a  made of the wires projecting up from the ball-shaped portions are formed. In this way, external connection terminals  50  are formed at all of the portions  16   b  forming the pads formed on the electrode formation surface. 
     In this method, since the external connection terminals  50  are formed by wire bonding, the work is extremely efficient. Further, the external connection terminals  50  can be formed using conventional bonding tools. Further, since the tips of the copper wires are shaped into balls and bonded with the conductive layer  16  and then the copper wires are cut while being pulled up to form the external connection terminals  50 , the operation of bending the wires to L-shapes as in the prior art is not required, the dimensions and shapes of the external connection terminals  50  are easily kept uniform, and the work can be performed efficiently. 
     Next, the exposed surfaces of the conductive layer  16  are electroplated with copper to form the interconnection patterns  52  as shown in FIG.  1 F. At this time, as illustrated, the surfaces of the external connection terminals  50  are also covered by copper plating. Next, the surfaces of the external connection terminals and the surfaces of the interconnection patterns  52  are plated to prevent diffusion of the solder at the time of mounting. In the present embodiment, they were successively plated with nickel, palladium, and gold. 
     Next, as shown in FIG. 1G, the photosensitive resist  18  (FIG. 1F) is removed from the electrode formation surface of the semiconductor wafer  10 , then the exposed portions of the conductive layer  16  are etched away (FIG.  1 H). The conductive layer  16 , which has a thickness of the order of 0.5 to 1 micrometer, is formed far thinner than the copper plating forming the interconnection patterns  52 , which has a thickness of the order of 5 to 20 micrometers, so can be easily removed, and the etching for removing the conductive layer  16  does not have, in practice, an effect on the interconnection patterns  52 . The exposed portions of the conductive layer  16  can be removed without covering the interconnection patterns  52  by a resist etc. Due to this, the passivation film  14  is exposed and the interconnection patterns  52  become independent. 
     Next, the electrode formation surface of the semiconductor wafer  10  is sealed by a resin to seal the interconnection patterns  52  and the passivation film  14  by the resin  28  (FIG.  1 I). In the resin sealing step, a transfer mold method using a sealing mold or a potting method is used. Due to the resin sealing step, a semiconductor wafer  10  with external connection terminals  50  projecting from a resin sealed surface is obtained. FIG. 6 shows the thus obtained semiconductor wafer  10 . By dicing this, individual semiconductor devices  54  are obtained. 
     FIGS. 2A to  2 H are views for explaining a method of production of a semiconductor device according to a second embodiment of the present invention. The method of production of this embodiment is basically the same as the method of production of the above embodiment, but in this embodiment, after forming the interconnection patterns for rewiring on the electrode formation surface of the semiconductor wafer, the electrode formation surface is left as it is without sealing by a resin in the final product. 
     As shown in FIG. 2A, the surface of a semiconductor wafer  10  formed with electrodes  12  is covered by a passivation film  14  leaving the electrodes  12  exposed, then, as shown in FIG. 2B, a conductive layer  16  is formed. In the present embodiment, chromium, titanium-tungsten alloy, and gold are deposited in that order on the electrode formation surface by sputtering to form the conductive layer  16 . 
     Next, a photosensitive resist  18  is coated on the surface of the conductive layer  16  (FIG.  2 C), then the photosensitive resist  18  is exposed and developed for patterning (FIG. 2D) so as to expose the portions  16   a  (FIG. 5) later forming the interconnection patterns, portions  16   b  (FIG. 5) forming the pads, and portions  16   c  (FIG. 5) connecting with the electrodes  12  at the surface of the conductive layer  16 . 
     Next, as shown in FIG. 2E, gold wires are bonded to the portions  16   b  forming the pads to form the external connection terminals  60 . Also when forming external connection terminals  60  using gold wires, external connection terminals  60  having projections  60   a  at their tops are formed, in the same way as the above embodiment, by melting the tips of the gold wires into balls, bonding the ball-shaped portions to the portions  16   b  forming the pads, then pulling up and cutting the wires. 
     Using the conductive layer  16  as a plating power feed layer, the exposed surfaces of the conductive layer  16  are electroplated with gold to form the interconnection patterns  62  as shown in FIG.  1 F. In the present embodiment, since the interconnection patterns  62  are left exposed at the outer surface of the semiconductor device in the final product, the interconnection patterns  62  are formed by gold plating. By gold plating, as illustrated, the surfaces of the external connection terminals  60  are covered by gold plating as well. 
     Next, as shown in FIG. 2G, the photosensitive resist  18  (FIG. 2F) is removed from the electrode formation surface of the semiconductor wafer  10 , then the exposed portions of the conductive layer  16  are etched away (FIG.  2 H). Due to this, the passivation film  14  is exposed and the interconnection patterns become independent. 
     The semiconductor device is obtained by dicing the semiconductor wafer into individual chips. In the case of the present embodiment as well, after making the interconnection patterns  62  independent (after step explained at FIG.  2 H), it is possible to cover the electrode formation surface of the semiconductor wafer  10  by a resin (not shown) so as to leave exposed the tips of the external connection terminals. 
     FIG. 3 is a flow chart of the method of production of a semiconductor device according to the first embodiment of the present invention, while FIG. 4 is a flow chart of the method of production according to the second embodiment. 
     Comparing the method of the present invention shown in FIGS. 3 and 4 and the methods of production of a semiconductor device of the related art shown in FIGS. 14 and 15, in the case of the method of the prior art for producing a semiconductor device by forming copper posts as the external connection terminals (FIG.  14 ), the operation of laminating a dry film for forming the copper posts  24  or building up copper posts  24  by copper plating was necessary. As opposed to this, according to the method of the present invention, since the external connection terminals are formed by wire bonding using copper wires or gold wires, the production process can be simplified and external connection terminals can be formed easily. 
     In the case of the method of the prior art for producing a semiconductor device by forming external connection terminals by bending wires in an L-shape (FIG.  15 ), a step of bending the wires into the L-shape is required. Further, the operations of coating a resist for giving a reinforcing plating to the external connection terminals and exposing and developing the resist are necessary. As opposed to this, according to the method of the present invention, it is possible to form external connection terminals by the simple wire bonding step. Further, the external connection terminals are given reinforcing plating by the copper plating for forming the interconnection patterns without requiring coating, exposure, and development of a resist. 
     The semiconductor device produced by the method of the present invention has the configurations differing from the configurations of the semiconductor devices of the prior art in the bonding portions between the external connection terminals and the interconnection patterns, so exhibits different actions and effects from the semiconductor devices of the prior art. FIGS. 7A and 7B and FIGS. 8A and 8B are enlarged sectional views of bonding portions of external connection terminals and interconnection patterns of semiconductor devices obtained by the method of production of a semiconductor device according to the present invention and methods of production of a semiconductor device of the prior art. FIGS. 7A and 7B show examples of semiconductor devices sealing the electrode formation surfaces with a resin after formation of the interconnection patterns, while FIGS. 8A and 8B show examples of semiconductor devices with interconnection patterns exposed. 
     As shown in FIG.  7 A and FIG. 8A, in the case of the method of production of a semiconductor device according to the present invention, after forming the conductive layer  16 , copper wires or gold wires are bonded directly to the conductive layer  16  to form external connection terminals  50  and  60 , then interconnection patterns  52  and  62  are formed by copper plating or gold plating. As opposed to this, in the methods of the related art, as shown in FIGS. 7B and 8B, after the interconnection patterns  20  are formed, copper posts  24  or external connection terminals  32  made of gold wires are formed as external connection terminals on the surface of the interconnection patterns  20 . 
     In this way, in the case of the present invention, the external connection terminals  50  and  60  are bonded to the conductive layer  16  and the base sides (bonding parts) of the external connection terminals  50  and  60  are buried in the copper plating layer or gold plating layer forming the interconnection patterns  52  and  62 . Therefore, in the case of the semiconductor device according to the present invention, compared with that of the prior art, the height of the external connection terminals can be lowered by at least the amount of thickness of the interconnection patterns  52  and  62 . Due to this, the method of production of a semiconductor device according to the present invention is effective in forming the semiconductor device thin and compact. Further, as clear from a comparison of FIG.  8 A and FIG. 8B, in the case of the present invention, the overall height of the external connection terminals  60  becomes low. Due to this as well, according to the invention, the semiconductor device can be produced compactly as a whole. 
     Further, when using the method of production of a semiconductor device according to the present invention, since the copper wires or gold wires are directly bonded to the conductive layer  16  to form the external connection terminals  50  and  60 , there is the advantage that the external connection terminals can be formed while being stably supported. 
     FIGS. 9A to  9 C show external connection terminals  60  formed by bonding gold wires to portions  16   b  of the conductive layer  16  forming pads and exposed at openings of a patterned resist  18 . FIG. 9A shows the case where the opening of the resist  18  defining the portion  16   b  forming the pad is formed larger than the bonding part of the gold wire. In this case, the gold wire is merely bonded to the portion  16   b  at its bottom. FIG. 9B shows the case where the opening is formed somewhat smaller than the case of FIG.  9 A. The gold wire is bonded to the portion  16   b  at its bottom. Part of the sides of the bonding part of the gold wire is in contact with the sides of the photosensitive resist  18 . FIG. 9C shows the case where the opening is of a size approximately the same as the bonding part of the gold wire. The bottom of the gold wire is bonded to the portion  16   b  forming the pad. The sides of the bonding part of the gold wire are in overall contact with the sides of the photosensitive resist  18 . 
     In this way, according to the method of forming external connection terminals by bonding gold wires or copper wires directly to the conductive layer  16 , since the gold wires or copper wires are bonded to the conductive layer  16  and the bonding parts of the gold wires or copper wires are supported by the photosensitive resist  18 , slanting of the external connection terminals  50  and  60  is prevented and the gold wires or copper wires can be reliably bonded to the conductive layer  16 . Further, by bonding the external connection terminals  50  and  60  to the conductive layer  16 , then covering the conductive layer  16  by copper plating or gold plating and simultaneously supporting the base parts (bonded parts) of the external connection terminals  50  and  60  by burying them in the interconnection patterns  52  and  62  by copper plating or gold plating, the external connection terminals  50  and  60  are further reliably supported. 
     FIGS. 10A and 10B and FIGS. 11A and 11B show comparisons of semiconductor devices of the present invention mounted on boards as opposed to semiconductor devices of the prior art mounted on boards. FIGS. 10A and 10B show a comparison of a semiconductor device according to the present invention (FIG. 10A) and a semiconductor device of the prior art using copper posts as external connection terminals (FIG.  10 B). As shown in FIG. 10B, when mounting a semiconductor device formed with copper posts  24  onto a board  40  by solder  42 , only the barrier layers  26  formed at the end faces of the copper posts  24  are exposed at the surface of the resin  28  with its poor solder wettability. Therefore, the solder  42  sometimes does not form a meniscus suitable for bonding with the copper posts. As opposed to this, when mounting the semiconductor device according to the present invention, as shown in FIG. 10A, due to the projections  50   a  projecting from the external connection terminals  50 , the solder  42  forms a sufficient meniscus and therefore the device is reliably mounted to the board. 
     FIGS. 11A and 11B show a comparison of a semiconductor device of the present invention with interconnection patterns exposed (FIG. 11A) and a semiconductor device of the prior art (FIG.  11 B). As shown in FIG. 11B, when mounting a semiconductor device of the prior art provided with external connection terminals  32  formed by bending gold wires into L-shapes onto a board  40 , the tips of the external connection terminals  32  are brought into abutment with the board  40  for bonding and therefore the semiconductor device and the board  40  are spaced away from each other. As opposed to this, when mounting the semiconductor device according to the present invention on a board  40 , as shown in FIG. 11A, solder  42  is deposited in a meniscus on projections  60   a  of the external connection terminals  60  and therefore the semiconductor device and board  40  are reliably bonded and, also, the distance between the semiconductor device and board  40  can be shortened. 
     In this way, the semiconductor device according to the present invention can be reliably mounted to a board so as to guarantee a high reliability such as a good electrical connection with the board. 
     According to the semiconductor device and method of production of the same of the present invention, as explained above, it is possible to easily form external connection terminals by bonding wires and thereby possible to simplify the steps for producing a semiconductor device. Further, according to the present invention, it is possible to improve the production efficiency of a semiconductor device and reduce the manufacturing costs of the semiconductor device. The present invention enables external connection terminals to be arranged at a high density and enables larger number of pins to be handled. Further, it is possible to provide a highly reliable semiconductor device where the external connection terminals are reliably bonded with the board. 
     While the invention has been described with reference to specific embodiments chosen for purpose of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention. 
     The present disclosure relates to subject matter contained in Japanese Patent Application No. 2001-157451, filed on May 25, 2001, the disclosure of which is expressly incorporated herein by reference in its entirety.