Abstract:
A method of manufacturing a semiconductor device includes preparing a semiconductor chip having a main surface, forming a conductive portion made from a material having conductivity and malleability on the main surface, arranging the semiconductor chip within a die after the step of forming the conductive portion, the die having an inner surface facing the main surface with a spacing therebetween, and a protruding portion protruding from the inner surface to press the conductive portion, and forming a sealing resin portion having a surface and an opening by filling the die with a resin and then removing the die, the surface facing the main surface, the opening passing through between the conductive portion and the surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Divisional Application of U.S. patent application Ser. No. 12/266,718, filed Nov. 7, 2008, the entire contents of which are incorporated herein by reference. This application is based upon and claims the benefit of priority from Japanese Patent Application No.  2008 - 180154 , filed Jul. 10, 2008. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a semiconductor device, and in particular, to a semiconductor device having a semiconductor chip and a resin sealing portion. 
         [0004]    2. Description of the Background Art 
         [0005]    As a semiconductor device for use as an inverter, there is a power module having a plurality of semiconductor elements such as IGBTs (Insulated Gate Bipolar Transistors) and free wheel diodes sealed with a mold resin and an insulating sheet. For example, Japanese Patent Laying-Open No. 2006-319084 discloses such a power module. 
         [0006]    As an art for downsizing a semiconductor device sealed with a resin, there is an art disclosed in Japanese Patent Laying-Open No. 2003-007966, for example. According to this art, a semiconductor device includes a radiation substrate, a semiconductor element provided on this radiation substrate, a plurality of main electrode plates having respective one ends electrically connected to a main electrode of the semiconductor element, and a resin package for sealing the radiation substrate, the semiconductor element and the plurality of main electrode plates with a resin. The respective other ends of the plurality of main electrode plates are exposed to the outside on the upper surface side of the resin package. The resin package is integrally formed by a molding method. 
         [0007]    In the art disclosed in foregoing Japanese Patent Laying-Open No. 2003-007966,the electrode on the surface of the semiconductor chip and the main electrode plate are connected by wire bonding. Therefore, a region required for the wire bonding must be ensured and it is difficult to further downsize the semiconductor device. Furthermore, for example, a special die is required to allow the main electrode to project from the surface of the resin package (the upper surface side) directly on the surface of the semiconductor chip, which leads to a rise in manufacturing costs. 
       SUMMARY OF THE INVENTION 
       [0008]    Therefore, an object of the present invention is to provide a semiconductor device that can further be downsized, at a relatively low cost. 
         [0009]    A semiconductor device of the present invention has a semiconductor chip, a conductive portion, a sealing resin portion, and an electrode. The semiconductor chip has a main surface. The conductive portion is provided on the main surface and made from a material having conductivity and malleability. The sealing resin portion has a surface facing the main surface. The electrode is provided on the conductive portion and passes through the sealing resin portion between the conductive portion and the surface. 
         [0010]    A method of manufacturing a semiconductor device of the present invention has the following steps. 
         [0011]    First, a semiconductor chip having a main surface is prepared. A conductive portion made from a material having conductivity and malleability is formed on this main surface. The semiconductor chip having this conductive portion formed is arranged within a die. The die has an inner surface facing the main surface with a spacing therebetween, and a protruding portion protruding from the inner surface to press the conductive portion. A sealing resin portion having a surface facing the main surface and an opening passing through between the conductive portion and the surface is formed by filling the die with a resin and then removing the die. 
         [0012]    According to the semiconductor device of the present invention, the electrode can be provided at a region on the main surface of the semiconductor chip, so that the semiconductor device can be downsized. 
         [0013]    Furthermore, since the conductive portion is provided on the main surface of the semiconductor chip, it is not necessary to ensure a region required to provide the conductive portion in a region other than the region on the semiconductor chip in the two-dimensional layout. Therefore, the semiconductor device can further be downsized. 
         [0014]    The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a cross-sectional view schematically illustrating a configuration of a semiconductor device in a first embodiment of the present invention. 
           [0016]      FIG. 2  is a plan view schematically illustrating the configuration of the semiconductor device in the first embodiment of the present invention. 
           [0017]      FIG. 3  is a diagram corresponding to  FIG. 2  in which a mold resin is not shown. 
           [0018]      FIG. 4  is a diagram schematically illustrating a circuit configuration of the semiconductor device in the first embodiment of the present invention. 
           [0019]      FIG. 5  is a plan view schematically illustrating a first step of a method of manufacturing the semiconductor device in the first embodiment of the present invention. 
           [0020]      FIGS. 6-9  are cross-sectional views schematically and sequentially illustrating the first to fourth steps of the method of manufacturing the semiconductor device in the first embodiment of the present invention. 
           [0021]      FIG. 10  is a cross-sectional view schematically illustrating a configuration of a semiconductor device in a comparative example. 
           [0022]      FIG. 11  is a plan view schematically illustrating a configuration of a semiconductor device in a second embodiment of the present invention. 
           [0023]      FIG. 12  is a cross-sectional view taken along line XII-XII in  FIG. 11 . 
           [0024]      FIG. 13  is a cross-sectional view schematically illustrating a configuration of a semiconductor device in a third embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    The embodiments of the present invention will be described hereinafter based on the drawings. 
       FIRST EMBODIMENT 
       [0026]    First, a configuration of a semiconductor device of the present embodiment will be described with reference to  FIGS. 1-4 . It should be noted that a line I-I in each of  FIGS. 2 and 3  indicates a position where a cross section in  FIG. 1  is taken. 
         [0027]    Referring to  FIGS. 1-3 , the semiconductor device of the present embodiment is a transfer-mold type power module having a plurality of power devices mounted thereon (embedded therein). This semiconductor device has a plurality of free wheel diodes  13   f  (semiconductor chips), a plurality of IGBTs  13   i,  a plurality of electrode joint solder portions  11   f  (conductive portions), an electrode joint solder portion  11   h,  a mold resin portion  15  (a sealing resin portion), main electrode pins  12   fu  and  12   fn  (electrodes), a main electrode pin  12   hp , a plurality of wires  14 , a plurality of external electrode leads  16 , a plurality of heat spreaders  17 , a high thermal conductivity insulating sheet  40 , a plurality of die bonding solder portions  20   f,  and a plurality of die bonding solder portions  20   i.    
         [0028]    Free wheel diode  13   f  and IGBT  13   i  are power devices and have main surfaces MS (surfaces shown in  FIG. 3 ), respectively. An anode pad of free wheel diode  13   f  as well as an emitter pad and a control pad of IGBT  13   i  that will be described hereinafter are formed on these main surfaces MS. 
         [0029]    Electrode joint solder portion  11   f  is provided on main surface MS of free wheel diode  13   f.  Electrode joint solder portion  11   h  is provided on heat spreader  17 . These electrode joint solder portions  11   f  and  11   h  are made from solder, that is, a material having conductivity and malleability (plasticity under pressure). 
         [0030]    Mold resin portion  15  covers respective main surfaces MS of free wheel diode  13   f  and IGBT  13   i.  Thus, mold resin portion  15  has a surface SF facing main surfaces MS. Mold resin portion  15  is a member containing a resin material. Mold resin portion  15  may further contain a filling material made from an inorganic material. Mold resin portion  15  is preferably made from a material suitable for the transfer molding method. In other words, mold resin portion  15  is preferably made from a material having sufficient fluidity at the time of resin molding. 
         [0031]    Main electrode pins  12   fu  and  12   fn  are electrodes corresponding to free wheel diode  13   f  portion, and main electrode pin  12   hp  is an electrode corresponding to heat spreader  17  portion. Main electrode pins  12   fu  and  12   fn  are provided on electrode joint solder portion  11   f  and pass through mold resin portion  15  between electrode joint solder portion  11   f  and surface SF of mold resin portion  15 . Main electrode pin  12   hp  is provided on electrode joint solder portion  11   h  and passes through mold resin portion  15  between electrode joint solder portion  11   h  and surface SF of mold resin portion  15 . 
         [0032]    High thermal conductivity insulating sheet  40  has an insulator portion  18  and copper foil  19 . Insulator portion  18  and copper foil  19  are stacked and integrally formed. Insulator portion  18  is made from an insulator having higher thermal conductivity than that of the material of mold resin portion  15 . This insulator is, for example, an epoxy resin containing a high thermal conductivity filler. Copper foil  19  has the function of protecting insulator portion  18  as a base material of high thermal conductivity insulating sheet  40 . It should be noted that foil made from metal other than copper such as aluminum can also be used instead of copper foil  19 . 
         [0033]    A wire  14  is a thin metallic wire and made from, for example, aluminum. 
         [0034]    Die bonding solder portions  20   f  and  20   i  are provided under free wheel diode  13   f  and IGBT  13   i,  respectively. 
         [0035]    Referring to  FIG. 4 , each of a pair of IGBTs  13   i  has an emitter terminal and a collector terminal as main terminals that are terminals for input/output of main current. IGBT  13   i  is a semiconductor switching element that switches a current path between the emitter terminal and the collector terminal. The switching is performed in accordance with a control signal applied to a gate G. 
         [0036]    The emitter of one IGBT  13   i  and the collector of the other IGBT  13   i  are connected to each other, and this connecting portion corresponds to an output terminal U of the semiconductor device. Furthermore, the collector terminal of one IGBT  13   i  and the emitter terminal of the other IGBT  13   i  correspond to input terminals P and N of the semiconductor device, respectively. In addition, free wheel diode  13   f  is connected in anti-parallel to each IGBT  13   i.  With this configuration, an output in accordance with the control signal can be obtained from output terminal U by applying a control signal to each gate G with a direct current high voltage being applied across input terminals P and N such that a potential of input terminal P becomes higher than that of input terminal N. 
         [0037]    Referring to  FIGS. 1-4 , each IGBT  13   i  has the control pad (not shown) corresponding to gate G. This control pad is connected to external electrode lead  16  by wire  14 . Each IGBT  13   i  also has the emitter pad (not shown) for connection of wire  14 . Furthermore, a collector (a rear electrode) of each IGBT  13   i  is connected to heat spreader  17  by die bonding solder portion  20   i.    
         [0038]    Each free wheel diode  13   f  has the anode pad (not shown) on one side (a side shown in  FIG. 3 ). This anode pad is connected to IGBT  13   i  by wire  14 . Electrode joint solder portion  11   f  is arranged on the anode pad. The other side (a side opposite to the side shown in  FIG. 3 ) of each free wheel diode  13   f  serves as a cathode and is connected to heat spreader  17  by die bonding solder portion  20   f.    
         [0039]    Referring to  FIGS. 1-3 , main electrode pins  12   hp ,  12   fu  and  12   fn  protrude from the inside of mold resin portion  15  through surface SF to the outside of mold resin portion  15 . Furthermore, main electrode pins  12   fu  and  12   fn  are electrically connected to electrode joint solder portion  11   f  inside mold resin portion  15 . Main electrode pin  12   hp  is electrically connected to electrode joint solder portion  11   h  inside mold resin portion  15 . 
         [0040]    Heat spreader  17  is provided on a surface opposite to respective main surfaces MS of free wheel diode  13   f  and IGBT  13   i.  Heat spreader  17  is a member made from a material having high conductivity and thermal conductivity, and is, for example, a plate-like member made from copper (Cu) (having a thickness of, for example, 3 mm). Heat spreader  17  has the function as a part of a wiring path and the function of promoting heat radiation by dissipation of heat generated from free wheel diode  13   f  and IGBT  13   i.    
         [0041]    Next, a method of manufacturing the semiconductor device of the present embodiment will be described. 
         [0042]    Referring mainly to  FIGS. 5 and 6 , a structure that will be sealed with the resin is formed. Specifically, free wheel diode  13   f  and IGBT  13   i  are first joined to heat spreader  17  with die bonding solder portion  20   f  and die bonding solder portion  20   i  interposed therebetween, respectively. A lead frame  21  having external electrode lead  16  is arranged to surround heat spreader  17 . In order to form a circuit shown in  FIG. 4 , wire bonding by wires  14  is performed among free wheel diode  13   f,  IGBT  13   i,  external electrode lead  16 , and heat spreader  17 . Then, high thermal conductivity insulating sheet  40  is placed on the underside of heat spreader  17 . Furthermore, electrode joint solder portion  11   f  and electrode joint solder portion  11   h  are formed on main surface MS of free wheel diode  13   f  and main surface MS of heat spreader  17 , respectively. 
         [0043]    Referring to  FIG. 7 , a lower die  23  and an upper die  24  for the transfer molding method are prepared. Upper die  24  has a plurality of through holes located at positions corresponding to electrode joint solder portions  11   f  and  11   h  and leading to an inner surface IS of a cavity, as well as pressing pins  22  inserted into these plurality of through holes, respectively. The depth of insertion of pressing pin  22  into the through hole can be controlled by a well-known actuator (not shown). With this configuration, upper die  24  is configured to allow pressing pin  22  to protrude from inner surface IS. 
         [0044]    Lower die  23  and upper die  24  are heated. Lead frame  21  is sandwiched between lower die  23  and upper die  24  such that inner surface IS of upper die  24  faces main surface MS of free wheel diode  13   f  with a spacing therebetween. The plurality of pressing pins  22  protruding from inner surface IS of upper die  24  are pressed against electrode joint solder portion  11   f  and electrode joint solder portion  11   h,  respectively, as shown by arrows in  FIG. 7 . The pressure of this pressing is controlled by the foregoing actuator. 
         [0045]    Referring to  FIG. 8 , since electrode joint solder portion  11   f  and electrode joint solder portion  11   h  have malleability, recesses corresponding to the shape of the tips of pressing pins  22  are formed in electrode joint solder portion  11   f  and electrode joint solder portion  11   h,  respectively, as a result of pressing by pressing pins  22 . 
         [0046]    Powder or a tablet mainly composed of an epoxy resin and a filler is melted by heating and pressurization to form a molten material  15   m  having low viscosity. The cavity is filled with this molten material  15   m,  which is cured subsequently. Lower die  23  and upper die  24  having pressing pins  22  are removed. 
         [0047]    Referring mainly to  FIG. 9 , mold resin portion  15  having surface SF as well as openings OPf and OPh is formed. 
         [0048]    After mold resin portion  15  is formed in such a manner, main electrode pin  12   hp  as well as main electrode pins  12   fu  and  12   fn  ( 12   fn  is not shown in  FIG. 9 ) are inserted into opening OPh and openings OPf, respectively, as shown by solid arrows in  FIG. 9 . As a result, main electrode pins  12   fu  and  12   fn  ( 12   fn  is not shown in  FIG. 9 ) as well as main electrode pin  12   hp  are arranged in the recesses in electrode joint solder portions  11   f  and the recess in electrode joint solder portion  11   h,  respectively. Next, main electrode pins  12   fu  and  12   fn  ( 12   fn  is not shown in  FIG. 9 ) as well as main electrode pin  12   hp  are joined to electrode joint solder portions  11   f  and electrode joint solder portion  11   h,  respectively. As the joining method, any of a method by heating, a method by using ultrasonic waves and a pressure bonding method can be used, for example. 
         [0049]    Lead frame  21  other than a portion that will form external electrode leads  16  is removed by cutting. Then, external electrode leads  16  are bent toward surface SF side as shown by a dashed arrow in  FIG. 9 . 
         [0050]    The semiconductor device of the present embodiment is obtained with the above-described method. 
         [0051]    Referring to  FIG. 10 , in a comparative example, a semiconductor device has an external main electrode lead  46   fu  instead of main electrode pin  12   fu . External main electrode lead  46   fu  projects to the outside of mold resin portion  15  from the side located adjacent to surface SF, not from surface SF of mold resin portion  15 . As a result of this projection, the semiconductor device in the comparative example has a larger width dimension (a dimension in a lateral direction in  FIG. 10 ) by a dimension dW than that of the semiconductor device of the present embodiment. 
         [0052]    According to the present embodiment, as shown in  FIG. 1 , main electrode pin  12   fu  can be provided at a region on main surface MS of free wheel diode  13   f,  so that the semiconductor device can be downsized. 
         [0053]    Furthermore, since electrode joint solder portion  11   f  is provided on main surface MS of free wheel diode  13   f,  it is not necessary to ensure a region required to provide electrode joint solder portion  11   f  in a region other than the region on free wheel diode  13   f  in the two-dimensional layout. Therefore, the semiconductor device can further be downsized. 
         [0054]    In addition, electrode joint solder portion  11   f  has malleability. Therefore, as shown in  FIG. 8 , when pressing pin  22  is pressed against electrode joint solder portion  11   f , electrode joint solder portion  11   f  is deformed as a result of this pressing and destruction of free wheel diode  13   f  due to force from pressing pin  22  can be prevented. It should be noted that a conductive resin other than solder, for example, can be used as a material having sufficient malleability and conductivity. 
         [0055]    As shown in  FIG. 9 , main electrode pin  12   fu  is arranged in the recess of electrode joint solder portion  11   f  and then joined to electrode joint solder portion  11   f . As a result, more reliable joint can be achieved. 
         [0056]    Furthermore, as shown in  FIG. 1 , main electrode pin  12   fu  is connected to free wheel diode  13   f  without wire  14 , so that the number of required wires  14  can be reduced. 
         [0057]    Although main electrode pins  12   fu  and  12   fn  are provided on main surface MS of free wheel diode  13   f  in the present embodiment, the present invention is not limited thereto. The main electrode pins may be provided on, for example, main surface MS of IGBT  13   i.    
         [0058]    Furthermore, although one main electrode pin is used for one semiconductor chip (at one point), a plurality of main electrode pins may be used in accordance with an amount of current flowing through a main electrode, and the main electrode pin may have a plate-like shape instead of a rod-like shape. 
         [0059]    In addition, instead of the configuration where main electrode pins  12   fu ,  12   fn  and  12   hp  are provided in the semiconductor device, a configuration where electrodes to be inserted into openings OPf and OPh (in  FIG. 9 ), respectively, are provided on the external circuit side connected to this semiconductor device can also be used. 
       SECOND EMBODIMENT 
       [0060]    Referring mainly to  FIGS. 11 and 12 , a semiconductor device of the present embodiment has main electrode portions  42   fu ,  42   fn  and  42   hp  instead of main electrode pins  12   fu ,  12   fn  and  12   hp  in the first embodiment, respectively. Each of main electrode portions  42   fu  and  42   fn  has a pin portion  28   f  and a rotation suppressing portion  26   f.  Main electrode portion  42   hp  has a pin portion  28   h  and a rotation suppressing portion  26   h.  Rotation suppressing portions  26   f  and  26   h  have screw holes  27   f  and  27   h,  respectively. Screw holes  27   f  and  27   h  are arranged to be exposed at surface SF. 
         [0061]    Each of rotation suppressing portions  26   f  and  26   h  has a nut-like shape. As a result, each of rotation suppressing portions  26   f  and  26   h  has a corner portion CR protruding in a direction (in an in-plane direction in  FIG. 11 ) transverse to a direction in which screw holes  27   f  and  27   h  extend in mold resin portion  15  (in a vertical direction in  FIG. 12 ). Each of rotation suppressing portions  26   f  and  26   h  preferably has a plurality of corner portions CR. For example, each of rotation suppressing portions  26   f  and  26   h  is configured to have a hexagonal shape as shown in  FIG. 11 , and has six corner portions CR. 
         [0062]    It should be noted that the configuration is otherwise almost the same as that of the above-described first embodiment. Therefore, the same or corresponding elements are represented by the same reference characters, and the description thereof will not be repeated. A manufacturing method is also almost the same except that pressing pins  22  (upper die  24 ) in the first embodiment need to be shaped in conformity with main electrode portions  42   fu ,  42   fn  and  42   hp  in the present embodiment. According to the present embodiment, connection between the semiconductor device and a circuit to be connected to the semiconductor device can be achieved by tightening screws in respective screw holes  27   f  and  27   h  of rotation suppressing portions  26   f  and  26   h.    
         [0063]    Preferably, each of rotation suppressing portions  26   f  and  26   h  has the plurality of corner portions CR. As a result, unnecessary rotation of rotation suppressing portions  26   f  and  26   h  at the time of tightening the screws can be suppressed. In addition, damage to the mold resin due to concentration of force at the time of tightening the screws is also avoided. 
       THIRD EMBODIMENT 
       [0064]    Referring to  FIG. 13 , a semiconductor device of the present embodiment has a resin portion  33  fixed to mold resin portion  15 , around each of screw holes  27   f  and  27   h  exposed at surface SF. Resin portion  33  can be formed by applying and then curing a liquid resin. Instead of the application of the liquid resin, resin portion  33  can also be formed, for example, by bonding a lid (stopper) having through holes corresponding to screw holes  27   f  and  27   h.    
         [0065]    It should be noted that the configuration is otherwise almost the same as that of the above-described second embodiment. Therefore, the same or corresponding elements are represented by the same reference characters, and the description thereof will not be repeated. 
         [0066]    According to the present embodiment, more sufficient creepage distance between main electrode portions  42   fu  and  42   fn  adjoining each other or between main electrode portions  42   fu  and  42   hp  adjoining each other can be ensured by resin portion  33 . It should be noted that the creepage distance refers to the shortest distance between two conductive portions along the surface of an insulator. 
         [0067]    Furthermore, rotation suppressing portions  26   f  and  26   h  can be fixed by resin portion  33 . 
         [0068]    Although the configuration where the electrode is provided on free wheel diode  13   f  with electrode joint solder portion  11   f  interposed therebetween is used in the above-described first to third embodiments, the present invention is not limited thereto. For example, a configuration where the electrode is provided on IGBT  13   i  with the electrode joint solder portion interposed therebetween can also be used. 
         [0069]    Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being interpreted by the terms of the appended claims.