Abstract:
A ground working tool comprising a tubular base body with an inner receiving space for receiving a cylindrical core of solid ground material, connector mechanism for connecting the tubular base body with a rotary drive and locking mechanism for locking the core in the receiving space of the tubular base body. The locking mechanism involves at least one locking unit having a guide rail being disposed at an inner side of the tubular base body and arranged with a deviation angle relative to a tangential direction of the tubular base body and the locking unit further comprises at least one locking element, which is moveably mounted on the guide rail between a radially outer releasing position and a radially inner locking position, in which the core is clamped within the receiving space by means of the at least one locking element.

Description:
TECHNICAL FIELD 
     The present invention relates to a semiconductor device in which a switching element and a temperature sensing diode that measures the operation temperature of the switching element are located on a chip. 
     BACKGROUND ART 
     Power modules including power chips (semiconductor devices) mounted thereon, such as insulated gate bipolar transistors (IGBTs) and metal oxide semiconductor field effect transistors (MOSFETs), are used as switching devices that perform the switching operation of energizing and interrupting a current speedily. 
     The continuous switching operation causes the power loss being the integral of the product of the current flowing through the switching device and the voltage applied to the switching device, resulting in the heat generation in the power chip. If the temperature of the power chip exceeds the guaranteed range of operation, the power chip would malfunction. 
     To prevent the temperature of the power chip from exceeding the guaranteed range of operation, the power chip including a temperature sensing diode that monitors the surface temperature of the power chip has been used (see, for example, Patent Documents 1 to 3). 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     
         
         Patent Document 1: Japanese Patent Application Laid-Open No. 2007-287919 
         Patent Document 2: Japanese Patent Application Laid-Open No. 08-213441 (1996) 
         Patent Document 3: Japanese Patent Application Laid-Open No. 10-116987 (1998) 
       
    
     SUMMARY OF INVENTION 
     Problem to be Solved by the Invention 
     The forward voltage VF of the diode decreases with increasing temperature. Therefore, the temperature of the power chip can be detected by converting the value of the forward voltage VF of the temperature sensing diode into a temperature. 
     The processing of converting the forward voltage VF of the temperature sensing diode into a temperature has been performed by the control circuit provided in the power module separately from the power chip and connected to the power chip. To establish a connection between the power chip and the control circuit, the cathode electrode (terminal) of the temperature sensing diode in the power chip and the main electrode of the switching element (such as, the emitter electrode in a case where the switching element is the IGBT) in the power chip have been connected to each other within the control circuit or through the relay terminals. That is, the cathode electrode pad for the temperature sensing diode and the main electrode pad for the switching element have been separately provided in the power chip. Each of these electrode pads needs to be wired to the relay terminal located outside the power chip such that these electrode pads are short-circuited. This has deteriorated the assembly performance. 
     The present invention has been made to solve the problem described above and has an object to provide a semiconductor device capable of achieving improved assembly performance and downsizing. 
     Means to Solve the Problem 
     To solve the above-mentioned problem, the semiconductor device according to the present invention includes: a switching element formed in a semiconductor substrate; a temperature sensing diode formed in the semiconductor substrate; a main current electrode pad for the switching element, the main current electrode pad being provided on the semiconductor substrate; and a conductive film that is provided above the semiconductor substrate and electrically connects one electrode of the temperature sensing diode and a main current electrode. 
     Effects of the Invention 
     According to the present invention, the semiconductor device includes: the switching element formed in the semiconductor substrate; the temperature sensing diode formed in the semiconductor substrate; the main current electrode pad for the switching element, the main current electrode pad being provided on the semiconductor substrate; and the conductive film that is provided above the semiconductor substrate and electrically connects the one electrode of the temperature sensing diode and the main current electrode pad. Thus, the present invention can achieve improved assembly performance and downsizing. 
     These 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 DRAWINGS 
         FIG. 1  is a plan view illustrating a configuration example of a semiconductor device according to a first embodiment of the present invention. 
         FIG. 2  is a cross-sectional view illustrating the configuration example of the semiconductor device according to the first embodiment of the present invention. 
         FIG. 3  is a cross-sectional view illustrating the configuration example of the semiconductor device according to the first embodiment of the present invention. 
         FIG. 4  is a cross-sectional view illustrating a configuration example of a semiconductor device according to a second embodiment of the present invention. 
         FIG. 5  is a plan view illustrating another configuration example of the semiconductor device according to the second embodiment of the present invention. 
         FIG. 6  is a plan view illustrating still another configuration example of the semiconductor device according to the second embodiment of the present invention. 
         FIG. 7  is a plan view illustrating a configuration example of a semiconductor device according to an underlying technique. 
         FIG. 8  is a cross-sectional view illustrating the configuration example of the semiconductor device according to the underlying technique. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The following describes embodiments of the present invention with reference to the drawings. 
     In the embodiments, the description is given assuming that the switching element formed on the substrate (semiconductor substrate) of the semiconductor device is an IGBT. 
     Underlying Technique 
     Firstly, the following describes the technique (underlying technique) underlying the present invention. 
       FIG. 7  is a plan view illustrating a configuration example of a semiconductor device  1  (a power chip) according to the underlying technique. 
     In the semiconductor device  1 , an emitter electrode pad  6  (a main current electrode pad) and a gate electrode pad  7  are provided on a substrate and trenches  8  are provided in the substrate, whereby an IGBT (a switching element) is formed. In the semiconductor device  1 , a temperature sensing diode  2  is formed above the substrate. 
     A cathode electrode  2   a  of the temperature sensing diode  2  is connected with a cathode electrode pad  3  via a cathode trace  4   a . An anode electrode  2   b  of the temperature sensing diode  2  is connected with an anode electrode pad  5  via an anode trace  4   b.    
     The cathode electrode pad  3 , the anode electrode pad  5 , and the gate electrode pad  7  are each connected to relay terminals  9   a  via relay terminal connection traces  10 . The relay terminal  9   a  is one of the constituent components of a terminal portion  9  provided in the power module including the semiconductor device  1  and the control circuit (not shown). The relay terminal connection traces  10  may be, for example, aluminum wires or may be wires made of another metal. 
     Although not shown in the drawings, traces drawn from the control circuit are also connected with the relay terminals  9   a  as needed. 
       FIG. 8  is a cross-sectional view illustrating an example of the cross section taken along line A-A in  FIG. 7 . For easy understanding of the description,  FIG. 8  illustrates, in a simplified manner, only the main constituent components necessary for the description. 
     The cathode electrode pad  3  and the emitter electrode pad  6  are formed above an Si substrate  13  (a semiconductor substrate) with an insulating film  14  located therebetween. The Si substrate  13  consists of an N −  layer  11  and a P layer  12 . 
     The trenches  8  for forming the gate electrodes of the individual cells of the IGBT are formed in the Si substrate  13  below the emitter electrode pad  6 . The pitch between the individual trenches  8  in  FIG. 7  does not correspond with the pitch between the individual trenches  8  in  FIG. 8 . 
     Doped polysilicon  15  and a gate metal trace  16  are formed as a lamination, which is disposed separately between the cathode electrode pad  3  and the emitter electrode pad  6 . The doped polysilicon  15  and the gate metal trace  16  are consist of a gate trace portion  17 . The gate trace portion  17  is connected with the gate electrode pad  7 . 
     A protective film  18  is formed so as to cover the insulating film  14 , the gate metal trace  16 , a part of the cathode electrode pad  3 , and a part of the emitter electrode pad  6 . 
     Although not shown in the cross-sectional view in  FIG. 8 , the temperature sensing diode  2  is also formed above the Si substrate  13 . 
     In the semiconductor device  1  according to the underlying technique, the cathode electrode pad  3  and the emitter electrode pad  6  are insulated from each other (are not in electrical connection) as mentioned above. However, the cathode electrode pad  3  and the emitter electrode pad  6  are short-circuited for use in some cases. In these cases, the cathode electrode pad  3  and the emitter electrode pad  6  need to be short-circuited in the following manner. The relay terminal connection traces  10  are drawn from the cathode electrode pad  3  and the emitter electrode pad  6 , and then, the relay terminal connection traces  10  drawn from the individual electrode pads are connected to each other in the relay terminals  9   a . This has deteriorated the assembly performance of the semiconductor device  1 . 
     The present invention therefore has been made to solve the problem mentioned above and will be described below in detail. 
     First Embodiment 
       FIG. 1  is a plan view illustrating a configuration example of the semiconductor device  1  according to a first embodiment of the present invention.  FIG. 2  is a cross-sectional view illustrating an example of the cross section taken along line A-A in  FIG. 1 . 
     As illustrated in  FIG. 2 , the semiconductor device  1  according to the first embodiment features a cathode-emitter connection trace  19  (a conductive film) that has electrical conductively and electrically connects the cathode electrode pad  3  and the emitter electrode pad  6 . The configuration except for the above is similar to that of the semiconductor device  1  according to the underlying technique illustrated in  FIG. 7  and a description thereof is omitted. 
     The cathode-emitter connection trace  19  is provided so as to cover the protective film  18  such that the cathode electrode pad  3  and the emitter electrode pad  6  are connected (short-circuited). Thus, the cathode-emitter connection trace  19  is provided above the Si substrate  13  and establishes an electrical connection between the cathode electrode pad  3  (one electrode pad) connected with the cathode electrode  2   a  (one electrode) of the temperature sensing diode  2  and the emitter electrode pad  6  (the main current electrode pad). 
     The cathode-emitter connection trace  19  may be made of, for example, an aluminum film or may be made of another conductive metal film. 
     The cathode electrode pad  3  and the emitter electrode pad  6  are at the same potential because the cathode-emitter connection trace  19  is provided. Thus, as illustrated in  FIG. 1 , the relay terminal connection traces  10  that connect the cathode electrode pad  3  and the relay terminals  9   a  can be eliminated. 
       FIG. 3  is a cross-sectional view illustrating an example of the cross section taken along line B-B in  FIG. 1 . 
     As illustrated in  FIG. 3 , the gate electrode pad  7  is directly connected with the gate metal trace  16 . 
     The trenches  8  are filled with the doped polysilicon  15 . The doped polysilicon  15  is connected with the gate metal trace  16  (and thus, the trench gate is formed). 
     Thus, in the first embodiment, the cathode electrode pad  3  and the emitter electrode pad  6  can be short-circuited within the semiconductor device  1 . The relay terminal connection traces  10  that connect the cathode electrode pad  3  and the relay terminals  9   a  are accordingly eliminated, thereby achieving the improved assembly performance and the downsizing of the semiconductor device  1 . 
     In a case where the both surfaces of the Si substrate  13  are ready for soldering (soldering can be performed onto the front surface and the back surface of the Si substrate  13 ) and a metal film (a front metal (FM)) capable of being soldered is formed on the emitter electrode pad  6 , the metal film may be formed as the cathode-emitter connection trace  19 . Thus, the metal film (FM) and the cathode-emitter connection trace  19  are formed at the same time (in the same process). This allows for the formation of the cathode-emitter connection trace  19  with no additional process. 
     Second Embodiment 
       FIG. 4  is a cross-sectional view illustrating a configuration example of the semiconductor device  1  according to a second embodiment of the present invention.  FIG. 4  illustrates an example of the cross section taken along line A-A in  FIG. 1 . 
     As illustrated in  FIG. 4 , the semiconductor device  1  according to the second embodiment features the cathode electrode pad  3  and the emitter electrode pad  6  formed to be connected to each other in the same layer and the gate metal trace  16  (a control electrode trace) are divided in the gate trace portion  17  in which the cathode electrode pad  3  and the emitter electrode pad  6  cross the gate trace portion  17 . Thus, the doped polysilicon  15  is formed in a continuous manner in the portion in which the gate metal trace  16  is divided. In this configuration, the conductive film and the gate metal trace  16  can be formed in the same process. The conductive film electrically connects the cathode electrode pad  3  and the emitter electrode pad  6 . The configuration except for the above is similar to that of the first embodiment (see  FIGS. 1 to 3 ), and a description thereof is omitted. 
     Thus, in the second embodiment, the effects of the first embodiment are produced, and furthermore, the conductive film that electrically connects the cathode electrode pad  3  and the emitter electrode pad  6  is formed in the same process, whereby the cathode electrode pad  3  and the emitter electrode pad  6  can be short-circuited with no additional manufacturing process. 
     With reference to  FIG. 5 , a cathode-emitter connecting portion  20  having the configuration illustrated in  FIG. 4  may be provided, so that the cathode trace  4   a  is directly connected with the cathode electrode pad  3  and the emitter electrode pad  6 . Thus, the conductive film that electrically connects the cathode electrode pad  3  and the emitter electrode pad  6  electrically connects the cathode electrode  2   a  of the temperature sensing diode  2  and the emitter electrode pad  6  not via the cathode electrode pad  3  for the temperature sensing diode  2  illustrated in  FIG. 1 . The cathode-emitter connecting portion  20  refers to the portion in which the cathode trace  4   a  and the emitter electrode pad  6  are connected. This configuration can eliminate the cathode electrode pad  3 , thus increasing the effective area in the semiconductor device  1 . 
     The configuration in  FIG. 5  provided as described below can produce the effects similar to the above. As illustrated in  FIG. 6 , the anode electrode pad  5  (the other electrode pad) for the temperature sensing diode  2  is provided above the peripheral portion of the semiconductor substrate and the temperature sensing diode  2  is formed above the central part of the semiconductor substrate. Optionally, the position of the anode electrode pad  5  may be changed. This increases the degree of design flexibility. 
     In the present invention, each embodiment can be appropriately varied or omitted within the scope of the invention. 
     While the invention has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous modifications and variations can be devised without departing from the scope of the invention. 
     EXPLANATION OF REFERENCE 
       1  semiconductor device,  2  temperature sensing diode,  2   a  cathode electrode,  2   b  anode electrode,  3  cathode electrode pad,  4   a  cathode trace,  4   b  anode trace,  5  anode electrode pad,  6  emitter electrode pad,  7  gate electrode pad,  8  trench,  9  terminal portion,  9   a  relay terminal,  10  relay terminal connection trace,  11  N −  layer,  12  P layer,  13  Si substrate,  14  insulating film,  15  doped polysilicon,  16  gate metal trace,  17  gate trace portion,  18  protective film,  19  cathode-emitter connection trace,  20  cathode-emitter connecting portion.