Patent Publication Number: US-2022238705-A1

Title: Insulated Gate Bipolar Transistor, Power Module, and Living Appliance

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application of International (PCT) Patent Application No. PCT/CN2019/125921, filed on Dec. 17, 2019, which claims the priority of Chinese Patent Application No. 201911013226.4, filed on Oct. 23, 2019, in the title of “INSULATED GATE BIPOLAR TRANSISTOR, POWER MODULE, AND LIVING APPLIANCE”, in China National Intellectual Property Administration, the entire contents of which are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to the field of power electronics, and in particular to an insulated gate bipolar transistor, a power module and an electrical appliance. 
     BACKGROUND 
     An insulated gate bipolar transistor (IGBT) is a power semiconductor device, which consists of a bipolar triode and an insulated gate field effect tube and is a composite all-control device driven by voltages. Since the IGBT has a high input impedance, a low conduction voltage drop, a low driving power and a low voltage drop, the IGBT is widely used in various fields as a new type of power electronic device. 
     The IGBT is a non-ideal element that has a certain conduction resistance. The higher the conduction resistance, the higher the conduction loss is generated while the IGBT is operating. The conduction resistance includes a conduction resistance of a drift region. Therefore, an improved technical solution is needed to reduce the conduction resistance of the drift region. 
     SUMMARY OF THE DISCLOSURE 
     The present disclosure provides an insulated gate bipolar transistor, a power module and an electrical appliance to reduce the conduction resistance of the drift region. 
     In a first aspect, the present disclosure provides an insulated gate bipolar transistor, including a semiconductor substrate. The semiconductor substrate includes: a collector region doped in a first type, wherein the collector region comprises a bump region; a first drift region doped in a second type and a second drift region doped in the second type; wherein the first drift region and the second drift region locate on a side of the collector region having the bump region, a profile contour of the first drift region matches a profile contour of the bump region, such that the second drift region does not contact the bump region, and a doping concentration of the first drift region is greater than a doping concentration of the second drift region; and a first active region and a second active region, formed at two opposite ends of the second drift region. 
     In some embodiments, the first drift area covers the bump region, such that the second drift region does not contact the bump region, and the second drift region contacts other portions of the collector region; or the first drift region comprises regions that cover the bump region and a surface of the collector region disposed on two ends of the bump region, such that the second drift region does not contact the collector region. 
     In some embodiments, each of the first active region and the second active region includes: a first type of well region, formed in the second drift region; and an emission region doped in the second type, formed in the first type of well region. 
     In some embodiments, the first type of well region includes: a lightly doped region in the first type, formed in the second drift region; a region doped in the first type, formed on a side of the lightly doped region in the first type; wherein the emission region is formed in the region doped in the first type, and at least a portion of the region doped in the first type contacts the second drift region. Alternatively, the first type of well region comprises: a lightly doped region in the first type, formed in the second drift region; and a region doped in the first type, formed in the lightly doped region in the first type; wherein the emission region is formed in the region doped in the first type. 
     In some embodiments, the transistor further includes: a collector electrode, disposed on a first surface of the semiconductor substrate and contacting the collector region; and a first emitter electrode and a second emitter electrode, disposed on a second surface of the semiconductor substrate opposite to the first surface and contacting the first active region and the second active region, respectively. 
     In some embodiments, the transistor further includes: a gate insulating layer, disposed on the second surface of the semiconductor substrate and arranged between the first emitter electrode and the second emitter electrode; a gate electrode, disposed on the gate insulating layer, wherein an overlap is present between a projection of the gate electrode in a thickness direction of the semiconductor substrate and a projection of the first type of well region in the thickness direction of the semiconductor substrate. The bump region and the first drift region include portions extending into a gap between the first active region and the second active region. 
     In some embodiments, the semiconductor substrate further includes a recessed portion, and the recessed portion is configured between the first active region and the second active region. The transistor further includes: a gate insulating layer and a gate electrode, wherein the gate insulating layer and the gate electrode are received in the recessed portion, the gate electrode contacts the gate insulating layer but does not directly contact the semiconductor substrate, and an overlap is present between a projection of the gate electrode in a direction parallel to the first surface F and a projection of the first type of well region in the direction parallel to the first surface F. The bump region is arranged at a position of the collector region corresponding to the first active region and at another position of the collector region corresponding to the second active region. 
     In some embodiments, in a direction from the second drift region to the collector region, a cross section of the bump region is V-shaped or U-shaped. 
     In a second aspect, the present disclosure provides a power module, including the insulated gate bipolar transistor according to any one of the above embodiments. 
     In a third aspect, the present disclosure provides an electrical appliance including the power module according to any one of the above embodiments. 
     According to the present disclosure, the insulated gate bipolar transistor has a collector region that is doped in a first type. The collector region includes a bump region. The insulated gate bipolar transistor has a drift region that is doped in a second type. The drift region locates on a side of the collector region and includes a first drift region and a second drift region. The first drift region has a higher doping concentration, directly contacts the bump region, and has a profile matching the bump region, such that the second drift region that has a lower doping concentration does not contact the bump region. While the IGBT is conducted, channels in a first active region and a second active region are unblocked. Due to presence of the bumped region, an effective thickness of the drift region is reduced, and electrons (or holes) from the first active region and the second active region and the holes (or electrons) from the collector region may flow through a shorter conduction path, accelerating electron-hole complex, reducing the conduction loss in the drift region, thus reducing an overall conduction loss of the IGBT. Further, since the first active region and the second active region are formed at two ends of the second drift region that has the lower doping concentration, a voltage withstand range of the IGBT is larger and a voltage withstand capability is better. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, drawings used in the description of the embodiments will be briefly described in the following. Apparently, the drawings in the following description are only some of the embodiments of the present disclosure, and other drawings can be obtained by an ordinary skilled person in the art based on these drawings without any creative work. 
         FIG. 1  is a structural schematic view of an IGBT according to some embodiments of the present disclosure. 
         FIG. 2  is a structural schematic view of an IGBT according to other embodiments of the present disclosure. 
         FIG. 3  is a structural schematic view of an IGBT according to other embodiments of the present disclosure. 
         FIG. 4  is a structural schematic view of an IGBT according to other embodiments of the present disclosure. 
         FIG. 5  is a structural schematic view of an IGBT according to other embodiments of the present disclosure. 
         FIG. 6  is a structural schematic view of a power module according to some embodiments of the present disclosure. 
         FIG. 7  is a structural schematic view of an electrical appliance according to some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Technical solutions in the embodiments of the present disclosure will be clearly and completely described by referring to the accompanying drawings in the embodiments of the present disclosure. Apparently, the embodiments described are only a part of, but not all of, the embodiments of the present disclosure. All other embodiments that are obtained by an ordinary skilled person in the art based on the embodiments of the present disclosure without making creative work shall fall within the scope of the present disclosure. 
     As shown in  FIG. 1 ,  FIG. 1  is a structural schematic view of an IGBT according to some embodiments of the present disclosure. The IGBT includes a semiconductor substrate  10 , which may be made of silicon, silicon carbide, germanium, silicon germanium crystals, gallium nitride, gallium arsenide, and so on. The IGBT may be cube-shaped and the like. The semiconductor substrate  10  includes a collector region  100  that is doped in a first type, a first drift region  102  that is doped in a second type, a second drift region  104  that is doped in a second type, a first active region  106 , and a second active region  108 . In the present embodiments, the first type is a P type, and the second type is an N type. Of course, in other embodiments, the first type may be the N type, and the second type may be the P type. In an actual IGBT preparation process, an ion injection process can be performed to dope a corresponding type of substance in each region and to control a corresponding doping concentration. For example, the doping substance corresponding to the P type may contain boron, and the doping substance corresponding to the N type may contain arsenic or phosphorus. 
     As shown in  FIG. 1 , the collector region  100  includes a bump region  1000 . The first drift region  102  and the second drift region  104  locate on a side of the collector region  100  that has the bump region  1000 . The first drift area  102  has a profile contour that matches a profile contour of the bump region  1000 , such that the second drift region  104  does not contact the bump region  1000 . The doping concentration of the first drift region  102  is greater than the doping concentration of the second drift region  104 . For example, the doping concentration of the first drift region  102  is one or two orders higher than the doping concentration of the second drift region  104 . The first active region  106  and the second active region  108  are formed at two opposite ends of the second drift region  104 . While the IGBT is being conductive, inner channels in the first active region  106  and the second active region  108  are unblocked. Due to the presence of the bump region  1000 , an effective thickness of the drift region is reduced, and electrons (or holes) from the first active region  106  and the second active region  108  and the holes (or electrons) from the collector region  100  may flow through a shorter conduction path, which accelerates electron-hole complex, and reduces a conduction loss of the drift region, such that an overall conduction loss of the IGBT is reduced. Since the first active region  106  and the second active region  108  are formed at the two ends of the second drift region  104  that has the lower doping concentration, a voltage withstand range of the IGBT is larger, and a voltage withstand capability is better. 
     In an implementation, as shown in  FIG. 1 , in a direction from the second drift region  104  to the collector region  100 , a cross section of the bump region  1000  is V-shaped. A cross section of a portion of the first drift region  102  that covers the bump region  1000  is V-shaped. A tip and sides of the V-shaped cross section may be curved to some extent. In this way, the portion of the first drift region  102  that covers the bump region  1000  is closer to the channels of the first active region  106  and the second active region  108 , thereby reducing the effective thickness of the drift region and shortening the conduction path. 
     In other embodiments, as shown in  FIG. 2 ,  FIG. 2  is a structural schematic view of an IGBT according to other embodiments of the present disclosure. In a direction from the second drift region  104   a  to the collector region  100   a , the cross section of the bump region  1000   a  is U-shaped, and the cross section of the portion of the first drift region  102   a  that covers the bump region  1000   a  is U-shaped. Such the configuration can also achieve the above technical effect. 
     In another implementation, as shown in  FIG. 1 , the first drift region  102  covers the bump region  1000 , such that the second drift region  104  does not contact the bump region  1000 , and the second drift region  104  contacts other parts of the collector region  100 . In this way, a production cost of the IGBT may be low. Further, since the second drift region  104  has a partial region that contacts the collector region  100 , carriers in the second drift region  104  may be composited off quickly while the IGBT is being disconnected, improving a disconnection efficiency of the IGBT. 
     In other embodiments, as shown in  FIG. 3 ,  FIG. 3  is a structural schematic view of an IGBT according to other embodiments of the present disclosure. In the present embodiments, the first drift region  102   b  covers surfaces of the bump region  1000   b  and the collector regions  100   b  located on two sides of the bump region  1000   b , such that the second drift region  102   b  does not contact the collector region  100   b . The IGBT in such the configuration has characteristics of a field cutoff type of IGBT, i.e., in the above configuration, the first drift region  102   b , which has the high doping concentration and locates between the collector region  100   b  locating on the two sides of the bump region  1000   b  and the second drift region  104   b  with the low doping concentration, enables the electric field to attenuate rapidly. In this way, the electric field may be cut off in the first drift region  102   b , and a depletion zone may be prevented from extending to the collector region  100   b  and leading to penetration. Further, the thickness of the IGBT may be reduced significantly, and the smaller thickness may indicate that the conduction voltage drop and the conduction loss are smaller. 
     In other embodiments, as shown in  FIG. 1 , each of the first active region  106  and the second active region  108  mentioned in the above includes: a first type of well region  1060 , formed in the second drift region  104 ; and an emission region  1062  that is doped in the second type and is formed in the first type of well region  1060 . The first active region  106  and second active region  108  as mentioned in the above have simple structures and may be achieved by performing an easy process. 
     In an application scenario, as shown in  FIG. 1 , the first type of well region  1060  includes: a lightly doped region  10600  in the first type, formed in the second drift region  104 ; a doped region  10602  in the first type, formed on a side of the lightly doped region  10600  in the first type. The emission region  1062  is formed in doped region  10602  in the first type, and at least a portion of the doped region  10602  in the first type contacts the second drift region  104 . In the present embodiments, the doping concentration of the doped region  10602  in the first type may be one or two orders of magnitude higher than the doping concentration of the lightly doped region  10600  in the first type. The doping concentration as mentioned in the above may be achieved performing an easy process. When the lightly doped region  10600  in the first type as mentioned in the above contacts the second drift region  104  that is lightly doped in the second type, a wide depletion zone may be formed between the two regions, such that the IGBT may not be easily broken through, i.e., a plurality of PN junctions are arranged in series, ensuring that the IGBT has the high voltage withstand capability. 
     In another application scenario, as shown in  FIG. 4 ,  FIG. 4  is a structural schematic view of an IGBT according to other embodiments of the present disclosure. The first type of well region  1060   c  may have other structures. For example, the first type of well region  1060   c  includes: a lightly doped region  10600   c  in the first type, formed in the second drift region  104   c ; a region  10602   c  doped in the first type, formed in the lightly doped region  10600   c  in the first type, i.e., a side of the region  10602   c  doped in the first type facing the second drift region  104   c  is entirely covered by the lightly doped region  10600   c  in the first type. The emission region  1062   c  is formed in the region  10602   c  doped in the first type. In the present embodiments, the doping concentration of the region  10602   c  doped in the first type may be one or two orders of magnitude higher than that of the lightly doped region  10600   c  in the first type, and the doping concentrations may be achieved by performing an easy process. When the lightly doped region  10600   c  in the first type as mentioned in the above contacts the second drift region  104   c  that is lightly doped in the second type, a wide depletion zone can be formed there between, such that the IGBT may not be easily broken through, i.e., a plurality of PN junctions are arranged in series, ensuring that the IGBT has the high voltage withstand capability. 
     In another implementation, as shown in  FIG. 1 , the IGBT provided in the present disclosure further includes: a collector electrode  101 , disposed on a first surface A of the semiconductor substrate  10  and contacting the collector region  100 ; a first emitter electrode  103  and a second emitter electrode  105 , disposed on a second surface B of the semiconductor substrate  10  opposite to the first surface A. The first emitter electrode  103  and the second emitter electrode  105  contact the first active region  106  and the second active region  108 , respectively. The above-mentioned collector electrode  101 , the first emitter electrode  103  and the second emitter electrode  105  may be metal. The above-mentioned collector electrode  101 , the first emitter electrode  103  and the second emitter electrode  105  may be arranged in a relatively simple manner and may be achieved by performing an easy process. 
     Further, as shown in  FIG. 1 , the IGBT provided in the present disclosure further includes: a gate insulating layer  107 , which may be made of silicon dioxide and the like, disposed on the second surface B of the semiconductor substrate  10 , and arranged between the first emitter electrode  103  and the second emitter electrode  105 ; a gate electrode  109 , disposed on the gate insulating layer  107 . There is an overlap between a projection of the gate electrode  109  along a thickness direction of the semiconductor substrate  10  and a projection of the first type of well region  1060  along the thickness direction of the semiconductor substrate  10 . The IGBT in the above is a planar gate, which has a lower saturation current and a better short-circuit capability. 
     In this case, the bump region  1000  of the collector region  100  and the first drift region  102  may include a portion extending into a gap between the first active area  106  and the second active area  108 , such that the first drift region  102  is as close as possible to the channels of the first active area  106  and the second active area  108 . In this way, the electrons (or holes) from the emission region  1062  and the holes (or electrons) from the collector region  100  may flow through a shorter conduction path, accelerating the electron-hole complex, reducing the conduction loss in the drift region, and thus reducing the overall conduction loss of the IGBT. 
     In other embodiments, as shown in  FIG. 5 ,  FIG. 5  is a structural schematic view of an IGBT according to other embodiments of the present disclosure. The semiconductor substrate  10   d  further includes a recessed portion (not shown). The recessed portion is disposed between the first active region  106   d  and the second active region  108   d . The IGBT further includes: a gate insulating layer  107   d  and a gate electrode  109   d . The gate insulating layer  107   d  and the gate electrode  109   d  are received in the recessed portion. The gate electrode  109   d  contacts the gate insulating layer  107   d  instead of directly contacting the semiconductor substrate  10   d . There is an overlap between a projection of the gate electrode  109   d  in a direction parallel to the first surface F and a projection of the first type of well region  1060   d  in a direction parallel to the first surface F. The IGBT having the above structure may be gate-typed, which reduces or even eliminates a JFET (junction field effect tube) region resistance, such that the entire IGBT has a lower conduction resistance. Further, a feature size of the IGBT in the gate type may be made small to improve a power density of the IGBT. 
     In this situation, the collector region  100   d  may be arranged with two bump regions  1000   d . One of the two bump regions  1000   d  is arranged at a position corresponding to the first active region  106   d , and the other of the two bump regions  1000   d  is arranged at a position corresponding to the second active region  108   d . In this way, the first drift region  102   d  covering the bump region  1000   d  may be disposed as close as possible to the channels of the first active region  106   d  and the second active region  108   d , such that the electrons (or holes) from the emission region  1062   d  and the holes (or electrons) from the collector region  100   d  may flow through a shorter conduction path, accelerating the electron-hole complex, reducing the conduction loss in the drift region, and thus reducing the overall conduction loss of the IGBT. 
     As shown in  FIG. 6 ,  FIG. 6  is a structural schematic view of a power module according to some embodiments of the present disclosure. The power module  20  includes the IGBT  200  in any of the above embodiments, and the specific structure of the IGBT will not be repeated here. The number of IGBTs  200  in the power module may be more than one, such as 4, 6, and so on, which will not be limited by the present disclosure. 
     As shown in  FIG. 7 ,  FIG. 7  is a structural schematic view of an electrical appliance according to some embodiments of the present disclosure. The electrical appliance  30  may be a washing machine (as shown in  FIG. 7 ), an air conditioner, and the like. A control circuit of the electrical appliance  30  may be provided with the above power module (not shown). 
     The above is only an implementation of the present disclosure, but does not limit the scope of the present disclosure. Any equivalent structure or equivalent process transformation made based on the specification and the accompanying drawings of the present disclosure, applied directly or indirectly in other related technical fields, shall be included in the scope of the present disclosure.