Abstract:
A semiconductor apparatus according to embodiments of the invention can include a first semiconductor device made of silicon, the first semiconductor devices being arranged collectively, whereby to form a first device group, and a second semiconductor device made of silicon carbide, the second semiconductor devices being arranged collectively, whereby to form a second device group. The apparatus can also include a wiring conductor connecting the first semiconductor device and the second semiconductor device, a cooling fin base comprising a projection formed thereon, whereby to dissipate heat generated from the first and second semiconductor devices, and the projections arranged under the second device group being spaced apart from each other more widely than the projections arranged under the first device group.

Description:
FIELD OF THE INVENTION 
       [0001]    Embodiments of the present invention relate to semiconductor apparatuses mounting an electric circuit such as an inverter circuit thereon and including a Si (“Silicon”) semiconductor device and a SiC (“Silicon Carbide”) semiconductor device. 
       BACKGROUND 
       [0002]      FIG. 10  is a circuit diagram of a three-phase inverter. The three-phase inverter circuit shown in  FIG. 10  includes an upper arm; a lower arm; a U-terminal, a V-terminal, and a W-terminal connected to the respective connection points of the upper and lower arms; a P-terminal connected to the high-potential side of the upper arm; an N-terminal connected to the low-potential side of the lower arm; semiconductor switching devices such as IGBT&#39;s constituting the upper and lower arms; and free-wheeling diodes (hereinafter referred to as “FWD&#39;s”) connected in opposite parallel to the respective IGBT&#39;s. 
         [0003]      FIG. 11(   a ) is the top plan view of a conventional semiconductor apparatus.  FIG. 11(   b ) is the cross sectional view along the single-dotted chain line X-X in  FIG. 11(   a ).  FIG. 11(   c ) is the bottom plan view of the conventional semiconductor apparatus showing the base including fins formed thereon. 
         [0004]    Referring now to these drawings, conventional semiconductor apparatus  600  is a power semiconductor module that constitutes the three-phase inverter circuit shown in  FIG. 10  thereon. 
         [0005]    In the following descriptions, Si-IGBT chip  54  is a silicon insulated-gate bipolar transistor chip and SiC-Di chip  55  is an FWD chip made of a silicon carbide Schottky barrier diode (SBD). 
         [0006]    The three-phase inverter circuit includes the U-phase, V-phase and W-phase. Since the chip arrangements in these phases are the same, the chip arrangement in the U-phase is described exemplary. 
         [0007]    In semiconductor apparatus  600 , electrically conductive film  52   c  of insulated substrate  52  is fixed onto base  51 . Insulated substrate  52  includes electrically conductive patterns  52   a  and  53   a  formed thereon. Base  51  includes fins  51   a  formed thereon. The collector of Si-IGBT chip  54  on the upper arm and the cathode of SiC-Di chip  55  on the upper arm are fixed onto electrically conductive pattern  52   a . The collector of Si-IGBT chip  54  on the lower arm and the cathode of SiC-Di chip  55  on the lower arm are fixed onto electrically conductive pattern  53   a.    
         [0008]    The emitter of Si-IGBT chip  54  on the upper arm and the cathode of SiC-Di chip  55  on the upper arm are connected to each other with wiring bar  56 . The emitter of Si-IGBT chip  54  on the lower arm and the cathode of SiC-Di chip  55  on the lower arm are connected to N-terminal bar  59 . Electrically conductive pattern  52   a  is connected to P-terminal bar  58 . The cathode of SiC-Di chip  55  on the upper arm and electrically conductive pattern  53   a  are connected to each other with wiring bar  57 . Wiring bar  57  is connected to U-terminal bar  57   a.    
         [0009]    Since the chip arrangements in the V- and W-phases are the same with the chip arrangement in the U-phase, the duplicated descriptions on the chip arrangements in the V- and W-phases are omitted for the sake of simplicity. 
         [0010]    U-terminal bar  57   a , V-terminal bar  57   b , and W-terminal bar  57   c  are connected to a not-shown load. P-terminal bar  58  and N-terminal bar  59  are connected to a not-shown power supply. The connection points of these terminals are exposed from a not-shown resin case. 
         [0011]    On each of three insulated substrates  52 , two Si-IGBT chips  54  and two SiC-Di chips  55  constituting the upper and lower arms are mounted and arranged in adjacent to each other. By arranging Si-IGBT chips  54  and SiC-Di chips  55  constituting the upper and lower arms collectively on the same insulated substrate  52 , the heat values generated by operating Si-IGBT chips  54  and SiC-Di chips  55  on insulated substrates  52  are set to be the same. 
         [0012]    Therefore, the generated heat values on insulated substrates  52  are equalized, fins  51   a  constituting base  51  are arranged with an equal spacing. Fin  51   a  is a plate-shaped tooth (rectangular parallelepiped). The spaces between fins  51   a  under insulated substrates  52  are equal. The spaces between fins  51   a  are set to be narrow for dissipating the heat generated by chips  54  and  55  effectively. 
         [0013]      FIG. 12(   a ) is a cross sectional view describing the way of cooling semiconductor apparatus  600 .  FIG. 12(   b ) is a bottom plan view describing the way of cooling semiconductor apparatus  600 . 
         [0014]    Referring now to these drawings, cover  60  is set on base  51  including fins formed thereon. Although not illustrated, cover  60  includes an inlet for making coolant  61  flow in and an outlet for making coolant  61  flow out. Coolant  61  made to flow in from the inlet passes through the spaces between fins  51   a  and flows to the outlet. Coolant  61  flows through the close spaces between fins  51   a . For making coolant  61  pass through the spaces between fins  51   a , it is necessary to pressurize coolant  61 . The pressure necessary to make coolant  61  pass through the spaces between fins  51   a  (the different pressure between at the inlet and at the outlet) is referred to as the “pressure loss.” Usually, coolant  61  is circulated by a not-shown pump. 
         [0015]      FIG. 13(   a ) is a cross sectional view describing the thermal interference caused between the chips in semiconductor apparatus  600 .  FIG. 13(   b ) is the cross sectional view along the single-dotted chain line X-X in  FIG. 13(   a ) describing the thermal interference occurred between the chips in semiconductor apparatus  600 .  FIG. 13(   c ) is the cross sectional view along the single-dotted chain line Y-Y in  FIG. 13(   a ) describing the thermal interference occurred between the chips in semiconductor apparatus  600 . 
         [0016]    When the three-phase inverter circuit operates, thermal interference occurs between Si-IGBT chip  54  and SiC-Di chip  55 . 
         [0017]    Now thermal interference  71  will be described below with reference to  FIG. 13(   b ). 
         [0018]    When Si-IGBT chip  54  on the U-phase upper arm is operating but SiC-Di chip  55  on the U-phase lower arm is not, Si-IGBT chip  54  generates heat and the heat generated is transferred from electrically conductive pattern  52   a  to adjacent electrically conductive pattern  53   a  through insulator substrate  52   b . The transferred heat makes the temperature, which is low, of chip  55  fixed to electrically conductive pattern  53   a  rise. When SiC-Di chip  55  on the U-phase lower arm is operating but Si-IGBT chip  54  on the U-phase upper arm is not, the Si-IGBT chip  54  temperature, which is low, is raised. 
         [0019]    Now, thermal interference  72  will be described below with reference to  FIG. 13(   c ). 
         [0020]    Because SiC-Di chip  55  on the U-phase upper arm is not operating, while Si-IGBT chip  54  on the U-phase upper arm is operating, Si-IGBT chip  54  generates heat and the generated heat makes the adjacent SiC-Di chip  55  temperature, which is low, rise via electrically conductive pattern  52   a . When SiC-Di chip  55  on the U-phase upper arm is operating but Si-IGBT chip  54  on the U-phase upper arm is not, the Si-IGBT chip  54  temperature, which is low, is raised. 
         [0021]    Because thermal interference  71  occurs via insulator substrate  52   b  and thermal interference  72  via electrically conductive pattern  52   a , thermal interference  72  is larger than thermal interference  71 . Thermal interference  71   a  caused through base  51  including fins  51   a  formed thereon is small, therefore the heat generated is dissipated almost to coolant  61  via fins  51   a . The distances M 1  and M 2  between chips  54  and  56 , and the distance M 3  between insulated substrates  52  including an electrically conductive pattern formed thereof are several mm. 
         [0022]    Thermal interference  72  between Si-IGBT chip  54  and SiC-Di chip  55  occurs through electrically conductive pattern  52   a  exhibiting a high thermal conductivity and near to the heat sources. Thermal interference  71  between Si-IGBT chip  54  and SiC-Di chip  55  occurs through insulator substrate  52   b  near to the heat sources and far from the coolant. Therefore, thermal interference  72  and thermal interference  71  caused in conventional semiconductor apparatus  600  are large. 
         [0023]      FIG. 14  is a top plan view describing the heat exchanges between the chips via terminal bars in conventional semiconductor apparatus  600 . 
         [0024]    Thermal interference  65  occurs through wiring bar  56  connecting the Si-IGBT chip  54  emitter and the SiC-Di chip  55  anode on the upper arm. Thermal interference  66  occurs through N-terminal bar  59  connecting the Si-IGBT chip  54  emitter and the SiC-Di chip  55  anode on the lower arm. Thermal interference  67  occurs through wiring bar  57  connecting the Si-IGBT chip  54  anode on the upper arm and electrically conductive pattern  53   a  on the lower arm. 
         [0025]    The distance between the connection point of wiring bar  56  and the Si-IGBT chip  54  emitter on the upper arm and the connection point of wiring bar  56  and the SiC-Di chip  55  anode on the upper arm is designated by N 1 . The distance between the connection point of N-terminal bar  59  and the Si-IGBT chip  54  emitter on the lower arm and the connection point of N-terminal bar  59  and the SiC-Di chip  55  anode on the lower arm is designated by N 2 . The distance between the connection point of wiring bar  57  and the Si-IGBT chip  55  anode on the upper arm and the connection point of wiring bar  57  and electrically conductive pattern  53   a  is designated by N 3 . Since the distances N 1 , N 2 , and N 3  are short, from  1  cm to several cm, thermal interference  65 , thermal interference  66 , and thermal interference  67  are large. 
         [0026]    The operable temperature of SiC-Di chip  55  is 250° C. However, the operable temperature of Si-IGBT chip  54  is 175° C. If SiC-Di chip  55  is operated at 250° C., the Si-IGBT chip  54  temperature will exceed 175° C. to the higher side, causing thermal destruction of Si-IGBT chip  54 . 
         [0027]    Because the operable temperature of the semiconductor apparatus is determined by the operable temperature of Si-IGBT chip  54 , it is necessary to restrict the operating temperature of SiC-Di chip  55  to be 175° C. or lower. 
         [0028]    Japanese Unexamined Patent Application Publication No. 2009-272482 (also referred to herein as “Patent Document 1”), discloses a semiconductor apparatus that includes a first laminate structure, a second laminate, and a connection section connecting the first and second laminates electrically to each other. The first laminate structure includes a first heatsink, a first isolation layer, a first electrically conductive layer, and a first semiconductor device (silicon IGBT). The second laminate structure includes a second heatsink, a second isolation layer, a second electrically conductive layer, and a second semiconductor device (SiC diode). The semiconductor apparatus separates the first and second laminate structures from each other such that the first and second laminate structures are thermally insulated from each other. 
         [0029]    In the semiconductor apparatus disclosed in the Patent document 1, the Si-IGBT chips constituting an upper arm are aligned to form an upper arm Si-IGBT chip group. The SiC-Di chips constituting the upper arm are aligned to form an upper arm SiC-Di chip group. The Si-IGBT chips constituting a lower arm are aligned to form a lower arm Si-IGBT chip group. The SiC-Di chips constituting the lower arm are aligned to form a lower arm SiC-Di chip group. The upper arm Si-IGBT chip group and the upper arm SiC-Di chip group are arranged alternately. The lower arm Si-IGBT chip group and the lower arm SiC-Di chip group are arranged alternately. The coolant flows through the Si-IGBT chip group and, then, through the SiC-Di chip group. In other words, the semiconductor apparatus disclosed in the Patent Document 1 includes two coolant paths for cooling the chips constituting the upper arm and for cooling the chips constituting the lower arm. The coolant path is long. 
         [0030]    Since the operable temperature of Si-IGBT chip  54  is 175° C. as described above, it is impossible to operate SiC-Di chip  55  at the operable temperature thereof, that is 250° C. Since Si-IGBT chip  54  and SiC-Di chip  55  are arranged in close proximity to each other, the thermal interference between Si-IGBT chip  54  and SiC-Di chip  55  is large. Therefore, for improving the cooling efficiency, it is necessary to set the distance between fins  51   a  to be short (to arrange fins  51   a  more closely). However, the close arrangement of fins  51   a  increases the pressure loss of coolant  61 , further increasing the size of the pump for circulating the coolant. As a result, the manufacturing costs of the entire inverter system soar. 
         [0031]    In the Patent Document 1, the cooling structure in which Si-IGBT chip is positioned, is the same with the cooling structure in which SiC-Di chip is positioned. Moreover, the Si-IGBT chip group and the SiC-Di chip group are arranged in adjacent to each other. Therefore, it is impossible to raise the operating temperature of the SiC-Di chip to the operable temperature thereof. Although a thermal insulation structure is formed between the Si-IGBT chip group and the SiC-Di chip group, thermal interference occurs between the Si-IGBT chip and the SiC-Di chip because of a connecting wire that is not shown. 
         [0032]    Two coolant paths are formed in the cooling structure. Since the coolant paths are complicated and long, the coolant pressure loss is large. Therefore, the pump for circulating the coolant is large inevitably. As a result, the manufacturing costs of the entire inverter system soar. 
         [0033]    In view of the foregoing, it would be desirable to obviate or lessen the problems described above. It would be also desirable to provide a semiconductor apparatus, including a Si semiconductor device, a SiC semiconductor device, and a base including fins formed thereon, that facilitates operating the semiconductor devices at the respective operating temperatures and reducing the pressure loss of the coolant. 
       SUMMARY OF THE INVENTION 
       [0034]    According to embodiments of the invention, there is provided a semiconductor apparatus including; 
         [0035]    a first semiconductor device made of silicon, the first semiconductor devices being arranged collectively for forming a first device group; 
         [0036]    a second semiconductor device made of silicon carbide, the second semiconductor devices being arranged collectively for forming a second device group; 
         [0037]    a wiring conductor connecting the first semiconductor device and the second semiconductor device; 
         [0038]    a cooling fin base including a projection formed thereon for dissipating the heat generated from the first and second semiconductor devices; and 
         [0039]    the projections arranged under the second device group being spaced apart from each other more widely than the projections arranged under the first device group. 
         [0040]    According to embodiments of the invention, the first semiconductor device is a MOS type transistor, and the second semiconductor device is a Schottky barrier diode. 
         [0041]    According to embodiments of the invention, the first semiconductor device and the second semiconductor device constitute an electric circuit. 
         [0042]    According to embodiments of the invention, the projection is nearly a rectangular parallelepiped or a cylindrical column. 
         [0043]    According to embodiments of the invention, the wiring conductor includes a first thermal interference reduction section between the connection points of the wiring conductor and the first and second semiconductor devices. 
         [0044]    According to embodiments of the invention, the first thermal interference reduction section is an opening or a recess. 
         [0045]    According to embodiments of the invention, the wiring conductor is cut into two between the connection points of the wiring conductor and the first and second semiconductor devices. 
         [0046]    According to embodiments of the invention, the cooling fin base includes a second thermal interference reduction section formed therein between the first and second device groups. 
         [0047]    According to embodiments of the invention, the second thermal interference reduction section is a cutout or a thermal insulator stuff inserted into the portion of the cooling fin base between the first and second device groups. 
         [0048]    According to embodiments of the invention, the semiconductor apparatus further includes a cover covering the cooling fin base for making a coolant flow between the inner wall of the cover and the projections and between the projections and for dissipating the heat from the cooling fin base to the coolant; and the cover includes a partition that makes the coolant meander. 
         [0049]    According to embodiments of the invention, the semiconductor apparatus further includes a cover covering the cooling fin base for making a coolant flow between the inner wall of the cover and the projections and between the projections and for dissipating the heat from the cooling fin base to the coolant; and the projections include a long projection and a short projection, which are extended in parallel to the flow direction of the coolant. 
         [0050]    According to embodiments of the invention, the projections are arranged in a planar triangular pattern. 
         [0051]    According to embodiments of the invention, the fin arrangement under the Si semiconductor devices (chips) and the fin arrangement under the SiC semiconductor devices (chips) are made to differ to make the Si semiconductor devices operate at a temperature of 175° C. or lower and to make the SiC semiconductor devices operate at a higher temperature. As a result, the Si and SiC semiconductor devices are made to improve the performances thereof to the maximums thereof. 
         [0052]    By widening the space between the fins under the SiC semiconductor devices, the pressure loss of the coolant is reduced. 
     
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         [0053]      FIG. 1(   a ) is the top plan view of a semiconductor apparatus according to a first embodiment of the invention. 
           [0054]      FIG. 1(   b ) is the bottom plan view of the semiconductor apparatus according to the first embodiment. 
           [0055]      FIG. 2(   a ) is the cross sectional view along the single-dotted chain line X-X in  FIG. 1(   a ). 
           [0056]      FIG. 2(   b ) is the cross sectional view along the line segment Y 1 -Y 1  in  FIG. 1(   a ). 
           [0057]      FIG. 2(   c ) is the cross sectional view along the line segment Y 2 -Y 2  in  FIG. 1(   a ). 
           [0058]      FIG. 3(   a ) is the top plan view of a U-phase terminal in  FIG. 1(   a ). 
           [0059]      FIG. 3(   b ) is the cross sectional view along the single-dotted chain line X-X in  FIG. 3(   a ). 
           [0060]      FIG. 4(   a ) is the cross sectional view of the semiconductor apparatus according to the first embodiment describing the cooling method thereof. 
           [0061]      FIG. 4(   b ) is the bottom plan view of the semiconductor apparatus according to the first embodiment describing the cooling method thereof. 
           [0062]      FIG. 5(   a ) is the top plan view of the semiconductor apparatus according to the first embodiment describing the heat generated from the chips. 
           [0063]      FIG. 5(   b ) is the cross sectional view along the single-dotted chain line X-X in  FIG. 5(   a ) describing the heat generated from the chips. 
           [0064]      FIG. 6(   a ) is the bottom plan view of a base including fins formed thereon in a semiconductor apparatus according to a second embodiment of the invention. 
           [0065]      FIG. 6(   b ) is the cross sectional view along the single-dotted chain line X-X in  FIG. 6(   a ). 
           [0066]      FIG. 7(   a ) is the top plan view of a semiconductor apparatus according to a third embodiment of the invention. 
           [0067]      FIG. 7(   b ) is the top plan view of a U-terminal bar in the semiconductor apparatus according to the third embodiment. 
           [0068]      FIG. 7(   c ) is the cross sectional view of the U-terminal bar along the single-dotted chain line X-X in  FIG. 7(   b ). 
           [0069]      FIG. 8  is the top plan view of a semiconductor apparatus according to a fourth embodiment of the invention. 
           [0070]      FIG. 9(   a ) is the cross sectional view of a semiconductor apparatus according to a fifth embodiment of the invention. 
           [0071]      FIG. 9(   b ) is the top plan view of a base including fins formed thereon seen in the direction A in  FIG. 9(   a ). 
           [0072]      FIG. 10  is the circuit diagram of a three-phase inverter. 
           [0073]      FIG. 11(   a ) is the top plan view of a conventional semiconductor apparatus. 
           [0074]      FIG. 11(   b ) is the cross sectional view along the single-dotted chain line X-X in  FIG. 11(   a ). 
           [0075]      FIG. 11(   c ) is the bottom plan view of the conventional semiconductor apparatus showing the base including fins formed thereon. 
           [0076]      FIG. 12(   a ) is a cross sectional view describing the way of cooling the conventional semiconductor apparatus. 
           [0077]      FIG. 12(   b ) is a bottom view describing the way of cooling the conventional semiconductor apparatus. 
           [0078]      FIG. 13(   a ) is the top plan view describing the thermal interference occurred between the chips in the conventional semiconductor apparatus. 
           [0079]      FIG. 13(   b ) is the cross sectional view along the single-dotted chain line X-X in  FIG. 13(   a ) describing the thermal interference occurred between the chips in the conventional semiconductor apparatus. 
           [0080]      FIG. 13(   c ) is the cross sectional view along the single-dotted chain line Y-Y in  FIG. 13(   a ) describing the thermal interference occurred between the chips in the conventional semiconductor apparatus. 
           [0081]      FIG. 14  is a top plan view describing the heat exchanges between the chips via terminal bars in the conventional semiconductor apparatus. 
           [0082]      FIG. 15(   a ) is the bottom plan view of a modified base modified from the base described in  FIG. 1(   b ) and including a partition disposed in the coolant path. 
           [0083]      FIG. 15(   b ) is the bottom plan view of a further modified base modified from the base described in  FIG. 15(   a ) and including partitions disposed in the coolant path. 
           [0084]      FIG. 16  is the bottom plan view of a modified base modified from the base described in  FIG. 15(   b ) and including partitions disposed in the coolant path and spaced apart from the respective nearest fins. 
           [0085]      FIG. 17(   a ) is the bottom plan view of a modified base modified from the bases described in  FIGS. 1(   b ) and  4 ( b ). 
           [0086]      FIG. 17(   b ) is the cross sectional view along the single-dotted chain line X-X in  FIG. 17(   a ). 
           [0087]      FIG. 17(   c ) is the cross sectional view along the single-dotted chain line Y 1 -Y 1  in  FIG. 17(   a ). 
           [0088]      FIG. 17(   d ) is the cross sectional view along the single-dotted chain line Y 2 -Y 2  in  FIG. 17(   a ). 
           [0089]      FIG. 18(   a ) is the bottom plan view of the base describing a modified arrangement of the fins described in  FIG. 6(   a ). 
           [0090]      FIG. 18(   b ) is the bottom plan view of the base describing another modified arrangement of the fins described in  FIG. 6(   a ). 
       
    
    
     DETAILED DESCRIPTION 
       [0091]    Now the invention will be described in detail hereinafter with reference to the accompanied drawings which illustrate the preferred embodiments of the invention. 
       First Embodiment 
       [0092]      FIG. 1(   a ) is the top plan view of a semiconductor apparatus according to a first embodiment of the invention.  FIG. 1(   b ) is the bottom plan view of the semiconductor apparatus according to the first embodiment.  FIG. 2(   a ) is the cross sectional view along the single-dotted chain line X-X in  FIG. 1(   a ).  FIG. 2(   b ) is the cross sectional view along the line segment Y 1 -Y 1  in  FIG. 1(   a ).  FIG. 2(   c ) is the cross sectional view along the line segment Y 2 -Y 2  in  FIG. 1(   a ).  FIG. 3(   a ) is the top plan view of a U-phase terminal in  FIG. 1(   a ).  FIG. 3(   b ) is the cross sectional view along the single-dotted chain line X-X in  FIG. 3(   a ). 
         [0093]    In  FIG. 1(   a ), cover  12  is taken off. Semiconductor apparatus  100  in  FIG. 1(   a ) is a power semiconductor module constituting a three-phase inverter circuit thereon. 
         [0094]    Semiconductor apparatus  100  includes base  1  including fins  1   a  formed thereon. According to the first embodiment, fin  1   a  is a plate-shaped tooth (rectangular parallelepiped). Base  1  includes first section  31 , in which the space between fins  1   a  is narrow (fins  1   a  are arranged densely), and second section  32 , in which the space between fins  1   a  is wide (fins  1   a  are arranged not so densely). First insulated substrate  2  is fixed to first section  31  with a solder. Second insulated substrate  3  is fixed to second section  32  with a solder. 
         [0095]    First insulated substrate  2  is a direct-copper-bonding substrate (hereinafter referred to a “DCB substrate”) including first insulator substrate  2   b  made of a ceramics and such a stuff exhibiting a high thermal conductivity and a high electrical insulation, first electrically conductive film  2   c  formed on the back surface of first insulator substrate  2   b , and first electrically conductive pattern  2   a  formed on the front surface of first insulator substrate  2   b . Second insulated substrate  3  is a DCB substrate including second insulator substrate  3   b  made of a ceramics and such a stuff exhibiting a high thermal conductivity and a high electrical insulation, second electrically conductive film  3   c  formed on the back surface of second insulator substrate  3   b , and second electrically conductive pattern  3   a  formed on the front surface of second insulator substrate  3   b.    
         [0096]    Three first electrically conductive patterns  2   a  are aligned on an upper line for constituting an upper arm and remaining three first electrically conductive patterns  2   a  are aligned on a lower line for constituting a lower arm. The collector of Si-IGBT chip  4  is fixed to each first electrically conductive pattern  2   a  with a solder. Three second electrically conductive patterns  3   a  are aligned on an upper line for constituting the upper arm and remaining three second electrically conductive patterns  3   a  are aligned on a lower line for constituting the lower arm. The cathode of SiC-Di chip  5  is fixed to each second electrically conductive pattern  3   a  with a solder. 
         [0097]    Three first electrically conductive patterns  2   a  on the upper line and three second electrically conductive patterns  3   a  on the upper line are connected to P-terminal bar  8  with wires  34  (by ultrasonic bonding). The emitters of three Si-IGBT chips  4  on the lower line and the anodes of three SiC-Di chips  5  on the lower line are connected to N-terminal bar  9  with wires  35  (by ultrasonic bonding). 
         [0098]    The emitter of Si-IGBT chips  4  for the U-phase (V-phase or W-phase) on the upper line and first electrically conductive pattern  2   a  for the U-phase (V-phase or W-phase) on the lower line are fixed with a solder to projections  6   a  and  6   b , respectively, formed on the under surface of first (second or third) connection bar  6  from the left-hand side. The anode of SiC-Di chips  5  for the U-phase (V-phase or W-phase) on the upper line and second electrically conductive pattern  3   a  for the U-phase (V-phase or W-phase) on the lower line are fixed with a solder to projections  6   a  and  6   b , respectively, formed on the under surface of fourth (fifth or sixth) connection bar  6  from the left-hand side. The solder is a high temperature solder, the melting point thereof is 300° C. or higher. 
         [0099]    Among six connection bars  6 , first and fourth connection bars  6  from the left-hand side are fixed to U-terminal bar  7   a  via projections  6   c  formed on first and fourth connection bars  6  by laser welding. Second and fifth connection bars  6  from the left-hand side are fixed to V-terminal bar  7   b  via projections  6   c  formed on second and fifth connection bars  6  by laser welding. Third and sixth connection bars  6  from the left-hand side are fixed to W-terminal bar  7   c  via projections  6   c  formed on third and sixth connection bars  6  by laser welding. 
         [0100]    The constituent elements described above are surrounded by resin case  10 . Gel  11  is poured into resin case  10 . Resin case  10  filled with gel  11  poured therein is covered with cover  12 . 
         [0101]    Si-IGBT chips  4  arranged in first section  31 , in which fins  1   a  are arranged densely (the space between fins  1   a  is narrow), are made to operate at the operable temperature thereof, that is 175° C. SiC-Di chips  5  arranged in second section  32 , in which fins  1   a  are arranged not so densely (the space between fins  1   a  is wide), are made to operate at the operable temperature thereof, that is 250° C. 
         [0102]    By disposing first section  31 , in which fins  1   a  are arranged densely (the space between fins  1   a  is narrow), and second section  32 , in which fins  1   a  are arranged not so densely (the space between fins  1   a  is wide), chips  4  and  5  are made to operate at the respective operable temperatures. 
         [0103]      FIG. 4(   a ) is the cross sectional view of semiconductor apparatus  100  according to the first embodiment describing the way of cooling semiconductor apparatus  100 .  FIG. 4(   b ) is the bottom plan view describing the way of cooling semiconductor apparatus  100 . 
         [0104]    Cover  13 , which is a water jacket, is set on base  1  including fins formed thereon. Cover  13  includes inlet  13   a  and outlet  13   b  for coolant  14  (e.g. water). Coolant  14  enters cover  13  from inlet  13   a  and passes through the spaces between fins  1   a  toward outlet  13   b . The disposition of section  32 , in which the space between fins  1   a  is wide, facilitates reducing the pressure loss of coolant  14 . By reducing the pressure loss, the size of the not shown pump for circulating coolant  14  is reduced and the manufacturing costs of the entire inverter system are reduced. Cover  13  may be fixed to base  1  and formed into a unit with base  1  in advance in the stage of fixing first insulated substrate  2  onto base  1 . 
         [0105]      FIG. 5(   a ) is the top plan view of semiconductor apparatus  100  according to the first embodiment describing the heat generated from the chips.  FIG. 5(   b ) is the cross sectional view along the single-dotted chain line X-X in  FIG. 5(   a ) describing the heat generated from the chips. 
         [0106]    By arranging first insulated substrate  2  and second insulated substrate  3  with the spacing L 1  left therebetween, thermal interference  15  between Si-IGBT chip  4  and SiC-Di chip  5  is reduced. The spacing L 1  around several mm is effective. Thermal interference  15  includes thermal interference  15   a  occurred via base  1 , and thermal interference  15   b  occurred via U-terminal bar  7   a , V-terminal bar  7   b , and W-terminal bar  7   c . Thermal interference  15   b  is larger than thermal interference  15   a . If the spacing L 1  is several mm, the heat, which reaches base  1 , will be dissipated almost to coolant  14  via fins  1   a.    
         [0107]    Thermal interference  15   b  is larger than thermal interference  15   a . However, if the distance L 2  between the connection point of Si-IGBT chip  4  and a terminal bar and the connection point of SiC-Di chip  5  and the terminal bar is set to be several cm, thermal interference  15   b  will be reduced more greatly than by the conventional structure, in which the corresponding distance is several mm. In other words, Si-IGBT chips  4  and SiC-Di chips  5  are arranged collectively to form the respective groups and the IGBT group center and the FWD group center are spaced apart from each other for several cm. Therefore, the thermal interference via the terminal bars is reduced by the structure according to the first embodiment more effectively than by the conventional structure. As a result, the operating temperature of Si-IGBT chips  4  will be suppressed to be 175° C. or lower, even if SiC-Di chips  5  are operated at 250° C. Therefore, Si-IGBT chips  4  are operated safely. 
         [0108]    Since thermal interference  15  (interference  15   b  mainly) is reduced, it is possible to widen the space between fins  1   a  under SiC-Di chips  5  more widely than that in the conventional structure. Therefore, the pressure loss of coolant  14  is reduced. 
         [0109]    The inverter circuit may be configured using Si-MOSFET&#39;s instead of Si-IGBT chips  4 . Although the semiconductor apparatus according to the first embodiment is described in connection with a three-phase inverter circuit, the semiconductor apparatus according to the first embodiment may constitute an electric circuit such as a single-phase inverter circuit and a chopper circuit. 
         [0110]    The semiconductor apparatus according to the first embodiment arranges Si-IGBT chips  4  collectively and SiC-Di chips collectively, changes the spacing between fins  1   a  under Si-IGBT chips  4  and the spacing between fins  1   a  under SiC-Di chips  5  from each other, and makes Si-IGBT chips  4  operate at 175° C. or lower and SiC-Di chips  5  at 250° C. or lower. Therefore, Si-IGBT chip  4  and SiC-Di chip  5  improve the performances thereof to the respective maximums. 
         [0111]    By widening the space between fins  1   a  under SiC-Di chips  5 , the pressure loss of coolant  14  is reduced. As a result, the cooling pump (or the cooling fan) is simplified and the manufacturing costs of the entire inverter system are reduced. 
         [0112]      FIG. 15(   a ) is the bottom plan view of modified base  1  modified from bases  1  described in  FIGS. 1(   b ) and  4 ( b ) and including a partition disposed in the coolant path.  FIG. 15(   b ) is the bottom plan view of further modified base  1  modified from base  1  described in  FIG. 15(   a ) and including partitions disposed in the coolant path. 
         [0113]    Base  1  shown in  FIG. 15(   a ) is different from bases  1  shown in  FIGS. 1(   b ) and  4 ( b ) in that cover  13  in  FIG. 15(   a ) includes partition  40  extended from the inner wall thereof on the inlet  13   a  side and contacting with the most downstream side one of fins  1   a  arranged densely. Partition  40  changes the flow direction of coolant  14  which has flowed in from inlet  13   a . Since coolant  14  flows uniformly through fins  1   a  disposed densely and meanders in cover  13 , the cooling efficiency is improved preferably as compared with the structure shown in  FIG. 4(   b ) which includes no partition. 
         [0114]    In  FIG. 15(   b ), partitions  40  are extended from the parallel inner walls of cover  13  alternately such that some partitions  40  are in contact with some fins  1   a  disposed densely and other partitions  40  are in contact with fins  1   a , the space therebetween is wide. Since coolant  14  changes the flow direction thereof frequently, the cooling efficiency under Si-IGTB chips  4  is improved. Two partitions  40  in contact fins  1   a  disposed densely and two partitions  40  in contact with fins  1   a , the space therebetween is wide, are shown in  FIG. 15(   b ). Since an even number of partitions  40  is formed in  FIG. 15(   b ), inlet  13   a  and outlet  13   b  are formed on the diagonal line of cover  13 . When an odd number of partitions  40  is formed, inlet  13   a  and outlet  13   b  may be formed in close proximity to one of the cover  13  sides. 
         [0115]      FIG. 16  is the bottom plan view of modified base  1  modified from base  1  described in  FIG. 15(   b ) and including partitions disposed in the coolant path and spaced apart from the respective nearest fins. 
         [0116]    In  FIG. 16 , partition  40  is not in contact with any fin  1   a . Since many partitions  40  are formed in  FIG. 15(   b ), the pressure loss of coolant  14  is large. For reducing the pressure loss of coolant  14 , space  41  is formed between partition  40  and fin  1   a  and coolant  14  is made to flow also through space  41 . Space  41  may be adjusted appropriately. Space  41  between partition  40  and fin  1   a  disposed densely and space  41  between partition  40  and fin  1   a  disposed not so densely may be made to differ from each other so that the pressure loss of coolant  14  and the flow rate of coolant  14  between fins  1   a  may be adjusted simultaneously. 
         [0117]      FIG. 17(   a ) is the bottom plan view of modified base  1  modified from bases  1  described in  FIGS. 1(   b ) and  4 ( b ).  FIG. 17(   b ) is the cross sectional view along the single-dotted chain line X-X in  FIG. 17(   a ).  FIG. 17(   c ) is the cross sectional view along the single-dotted chain line Y 1 -Y 1  in  FIG. 17(   a ).  FIG. 17(   d ) is the cross sectional view along the single-dotted chain line Y 2 -Y 2  in  FIG. 17(   a ). 
         [0118]    In  FIG. 17(   a ), fins  1   a , the lengths thereof are different from each other are arranged in the flow direction of coolant  14 . In section  31 , in which the fins should be arranged densely, long fin  1   a  and short fin  1   a  are extended alternately in the flow direction of coolant  14 . In section  32 , in which the fins should be arranged no so densely, only long fins  1   a  are extended in the flow direction of coolant  14 . 
       Second Embodiment 
       [0119]      FIG. 6(   a ) is the bottom plan view of base  21  including fins  21   a  formed thereon in semiconductor apparatus  200  according to a second embodiment of the invention.  FIG. 6(   b ) is the cross sectional view along the single-dotted chain line X-X in  FIG. 6(   a ). 
         [0120]    Fin  21   a  according to the second embodiment is different from fin  1   a  according to the first embodiment in that fin  21   a  is shaped with a cylindrical column. By disposing fins  21   a  densely in section  31  and not so densely in section  32 , the effects the same with the effects which the semiconductor apparatus according to the first embodiment exhibits are obtained. 
         [0121]    The shape of fin  21   a  is not always limited to a rectangular parallelepiped nor to a cylindrical column. Fin  21   a  may be nearly a rectangular parallelepiped, the side wall of which is uneven, or nearly a cylindrical column such as a hexagonal column with no problem. Further, fins  21   a  may be a triangular column or a quadratic column with no problem. 
         [0122]      FIG. 18(   a ) is the bottom plan view of base  21  describing a modified arrangement of fins  21   a .  FIG. 18(   b ) is the bottom plan view of base  21  describing another modified arrangement of fins  21   a.    
         [0123]    In  FIG. 18(   a ), fins  21   a  disposed not so densely are arranged in a planar triangular pattern. In  FIG. 18(   b ), all fins  21   a  dispose densely and not so densely are arranged in the respective planar triangular patterns. 
         [0124]    In  FIGS. 18(   a ) and  18 ( b ), inlet  13   a  and outlet  13   b  are positioned at the respective parallel side centers of cover  13 . By arranging fins  21   a  in a triangular pattern, coolant  14  is made to meander and the cooling efficiency thereof is improved. In the triangular arrangement, the lines connecting the centers of adjacent fins  21  form a triangle. The triangular arrangement is referred to also as the “hexagonal arrangement”. 
       Third Embodiment 
       [0125]      FIG. 7(   a ) is the top plan view of semiconductor apparatus  300  according to a third embodiment of the invention.  FIG. 7(   b ) is the top plan view of U-terminal bar  7   a  (V-terminal bar  7   b  or W-terminal bar  7   c ) in semiconductor apparatus  300  shown in  FIG. 7(   a ).  FIG. 7(   c ) is the cross sectional view of U-terminal bar  7   a  (V-terminal bar  7   b  or W-terminal bar  7   c ) along the single-dotted chain line X-X in  FIG. 7(   b ). 
         [0126]    U-terminal bar  7   a  (V-terminal bar  7   b  or W-terminal bar  7   c ) according to the third embodiment is different from U-terminal bar  7   a  (V-terminal bar  7   b  or W-terminal bar  7   c ) according to the first embodiment in that U-terminal bar  7   a  (V-terminal bar  7   b  or W-terminal bar  7   c ) according to the third embodiment includes opening  23  formed therein. In the portion of U-terminal bar  7   a  (V-terminal bar  7   b  or W-terminal bar  7   c ), in which opening  23  is formed, the thermal resistance is high enough to reduce the thermal interference between Si-IGBT chip  4  and SiC-Di chip  5 . By reducing the thermal interference, it is possible to widen the space between fins  1   a  and to reduce the pressure loss. 
         [0127]    Alternatively, recess  24 , not bored through U-terminal bar  7   a  (V-terminal bar  7   b  or W-terminal bar  7   c ), may be formed instead of opening  23  as shown by the broken lines in  FIG. 7(   c ). Recess  24  is effective to reduce the wiring inductance, which is made to be high by opening  23 . Opening  23  and recess  24  work as a section for reducing thermal interference (hereinafter referred to as a “thermal interference reduction section”). 
         [0128]    By forming a thermal interference reduction section in U-terminal bar  7   a  (V-terminal bar  7   b  or W-terminal bar  7   c ) and base  1  which connect Si-IGBT chip  4  (Si semiconductor device) and SiC-Di chip  5  (SiC semiconductor device) to each other, thermal interference  15  between the Si semiconductor device and the SiC semiconductor device is made to be small. As a result, it is possible to further widen the spaces between all the fins  1   a  and to further reduce the pressure loss of coolant  14 . 
       Fourth Embodiment 
       [0129]      FIG. 8  is the top plan view of a semiconductor apparatus according to a fourth embodiment of the invention. 
         [0130]    Semiconductor apparatus  400  according to the fourth embodiment is different from semiconductor apparatus  100  according to the first embodiment in that U-terminal bars  7   a  (V-terminal bars  7   b  or W-terminal bars  7   c ) are led out to the Si-IGBT chip  4  side and the SiC-Di chip  5  side respectively such that U-terminal bars  7   a  (V-terminal bars  7   b  or W-terminal bars  7   c ) are not connected to each other. By separating U-terminal bar  7   a  on the Si-IGBT chip  4  side (V-terminal bar  7   b  on the Si-IGBT chip  4  side or W-terminal bar  7   c  on the Si-IGBT chip  4  side) and U-terminal bar  7   a  on the SiC-Di chip  5  side (V-terminal bar  7   b  on the SiC-Di chip  5  side or W-terminal bar  7   c  on the SiC-Di chip  5  side) from each other, thermal interference  15  occurred via the terminal bar between Si-IGBT chip  4  and SiC-Di chip  5  is interrupted. By virtue of the interruption of thermal interference  15 , the space between fins  1   a  is widened and the pressure loss of coolant  14  is reduced. 
         [0131]    U-terminal bars  7   a  on both sides, V-terminal bars  7   b  on both sides, and W-terminal bars  7   c  on both sides are connected to each other by the respective external wirings not shown but arranged outside semiconductor apparatus  400 . 
       Fifth Embodiment 
       [0132]      FIG. 9(   a ) is the cross sectional view of semiconductor apparatus  500  according to a fifth embodiment of the invention.  FIG. 9(   b ) is the top plan view of a base including fins formed thereon seen in the direction A in  FIG. 9(   a ). 
         [0133]    Semiconductor apparatus  500  according to the fifth embodiment is different from semiconductor apparatus  100  shown in  FIG. 1(   b ) in that cutout  25  is formed in the portion of base  1 , through which thermal interference  15   a  occurs, to reduce thermal interference  15   a . Instead of forming cutout  25 , base  1  is divided into two in the portion thereof, in which thermal interference  15   a  occurs, and a thermal insulator stuff is inserted between divided bases  1  (that is between sections  31  and  32 , shown e.g. in  FIGS. 5(   a ) and  5 ( b )). It is preferable for the thermal insulator stuff to be resistive against a temperature of 300° C. or higher and to be in excellent contact with copper or aluminum, of which base  1  is made. 
         [0134]    By combining the structures according to the first through fifth embodiments appropriately, semiconductor apparatuses, which facilitate suppressing the thermal interference and reducing the pressure loss of coolant, are obtained. 
         [0135]    Examples of specific embodiments are illustrated in the accompanying drawings. While the invention is described in conjunction with these specific embodiments, it will be understood that it is not intended to limit the invention to the described embodiments. On the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. In the above description, specific details are set forth in order to provide a thorough understanding of embodiments of the invention. Embodiments of the invention may be practiced without some or all of these specific details. Further, portions of different embodiments can be combined, as would be understood by one of skill in the art. 
         [0136]    This application is based on, and claims priority to, Japanese Patent Application No. 2010-165759, filed on Jul. 23, 2010, and Japanese Patent Application No. 2011-053332, filed on Mar. 10, 2011. The disclosures of the priority applications, in their entirety, including the drawings, claims, and the specifications thereof, are incorporated herein by reference.