Semiconductor unit for a power converter, semiconductor device, method for manufacturing a semiconductor unit and method for operating a semiconductor unit

Abstract

Semiconductor unit (100) for a power converter, wherein the semiconductor unit (100) comprises a power semiconductor (102) having a III nitride semiconductor layer (110), and a drain contact (104) and a source contact (106), and wherein the power semiconductor (100) in an operating state has a conductive channel (108) of a two-dimensional electron gas in a III nitride semiconductor layer (110) facing away from the contacts (104, 106), and a printed circuit board (112) in which the power semiconductor (102) is embedded, wherein the printed circuit board (112) has a recess (114) leading to the III nitride semiconductor layer (110) for guiding a positively charged liquid coolant (116) for cooling the power semiconductor (100) and for neutralizing opposite the drain contact (104) accumulated negative electron charges (118) on the power semiconductor (102).

Description

The present invention relates to a semiconductor unit for a power converter, to a semiconductor device, to a method for manufacturing a semiconductor unit, to a method for operating a semiconductor unit, to a power converter, an electric axle drive and to a motor vehicle. Power semiconductors typically heat up during operation, which is why cooling is common. Against this background, the present invention provides an improved semiconductor unit for a power converter, an improved semiconductor device, an improved method for manufacturing a semiconductor unit, an improved method for operating a semiconductor unit, an improved power converter, an improved electric axle drive, and an improved motor vehicle according to the main claims. Advantageous embodiments are described in the dependent claims and the following description. A semiconductor unit for a power converter is presented, comprising a power semiconductor with a III nitride semiconductor layer, a drain contact, and a source contact. The III nitride semiconductor layer consists, for example, of an aluminum gallium nitride layer and a gallium nitride layer. In an operating state, the power semiconductor forms a conductive channel from a two-dimensional electron gas within a III nitride semiconductor layer facing away from the contacts. Furthermore, the semiconductor unit includes a printed circuit board (PCB) in which the power semiconductor is embedded. The PCB has a recess leading to the III nitride semiconductor layer for the passage of a positively charged liquid coolant to cool the power semiconductor and to neutralize negative electron charges that accumulate on the power semiconductor opposite the drain contact. The semiconductor unit can be used, for example, in a power converter, which in turn can be used, for example, in vehicles. The power semiconductor can be implemented as a transistor or as part of a transistor, which, in addition to the drain and source contacts, can have a gate contact. The two-dimensional electron gas can also be referred to as 2DEG, for example. Negative electron charges can therefore accumulate on the III nitride semiconductor layer, which can be neutralized by the positively charged liquid coolant, thus advantageously reducing parasitic charges. The liquid coolant can advantageously be implemented with high resistance.The presented approach allows for an improved cooling option for a power converter, where a blocking voltage can be increased by selecting the coolant and creating an advantageous cooling surface to solve the problem of the backside potential, which leads to a high dynamic Ron resistance if ignored. The printed circuit board (PCB) can represent a circuit carrier that may include one or more embedded power semiconductors. A power semiconductor, together with a substrate, can be, for example, a power transistor, such as a GaN-on-Si transistor. For the power converter mentioned as an example, the PCB could contain six or twelve embedded power transistors. The power semiconductor can be a component consisting of a III nitride semiconductor layer, in particular layers of different semiconductor materials with varying band gaps, such as gallium nitride (GaN), aluminum gallium nitride (AlGaN), or aluminum indium nitride (AlInN). Thus, the power semiconductor can be a high-electron mobility transistor (HEMT). The substrate can be silicon.Power semiconductor structures can be grown or deposited on the substrate. The layered structure of power semiconductor and substrate can also be referred to as a bare die, which may be embedded in the printed circuit board (PCB) using a process called embedding. The PCB can, for example, be a printed circuit board (PCB) that serves as a carrier for electronic components. According to one embodiment, the semiconductor unit can have a coolant guide structure formed from a substrate for supporting the power semiconductor, for guiding the liquid coolant along the III nitride semiconductor layer. Advantageously, the substrate and the coolant guide structure can increase the cooling surface area for heat dissipation. This means that more heat can be removed. The coolant guide structure can advantageously form a plurality of cooling channels. Advantageously, the base of the cooling channels can be formed by the III nitride semiconductor layer of the power semiconductor. According to one embodiment, the coolant guide structure can be rib-like, labyrinthine, or pin-like. Advantageously, this allows the flow direction and, for example, the flow rate of the liquid coolant to be controlled. The substrate can be a silicon substrate. Thus, a substrate known in connection with semiconductors can be used. The substrate can have a contact section located adjacent to the coolant guide structure for electrically contacting the power semiconductor. For example, the contact section can be used to contact a gate of the power transistor. Furthermore, the printed circuit board can have vias for electrically connecting the drain and source contacts. This enables electrical connection of the embedded power semiconductor. The semiconductor unit can contain the liquid coolant, which can be arranged in the recess. Advantageously, heat can be easily dissipated by directing the liquid coolant through the recess. The semiconductor unit can have a cooling element mounted on the circuit board with an intermediate wall, wherein the cooling element, together with the recess, can form a first cooling channel and a second cooling channel. For example, at least one sealing element for sealing the cooling channels can be arranged between the cooling element and the circuit board. Advantageously, a breakdown voltage between the drain contact and source contact can be increased, which can lead to easier generation of potential differences between the channels. The cooling element, together with the recess, can, for example, form a cooling channel. The semiconductor unit can include an additional power semiconductor, which may have a III nitride semiconductor layer, as well as an additional drain contact and an additional source contact. In an operating state, the additional power semiconductor can have a conductive channel of a two-dimensional electron gas in a further III nitride semiconductor layer located away from the additional contacts, and the additional power semiconductor can be embedded in the printed circuit board. The printed circuit board can have a further recess leading to the further III nitride semiconductor layer for guiding the positively charged liquid coolant, and the recess and the further recess can be connected to each other by a guide channel in the printed circuit board for guiding the liquid coolant from the power semiconductor to the additional power semiconductor.The additional power semiconductor can advantageously be of the same design as the power semiconductor. Advantageously, a plurality of power semiconductors can be arranged on the circuit board, for example, at regular intervals. Furthermore, a semiconductor device for a power converter is presented, wherein the semiconductor device comprises a first semiconductor unit in a previously mentioned variant and a second semiconductor unit in a previously mentioned variant, wherein the III nitride semiconductor layer of the first semiconductor unit and the III nitride semiconductor layer of the second semiconductor unit are arranged opposite each other to form a common cooling channel. Instead of a power converter, a DC-DC converter or an on-board charger is also conceivable. Advantageously, the semiconductor units can be implemented in a uniform manner. The semiconductor device can advantageously be used for a power converter, such as those used in vehicles. Furthermore, the invention relates to a power converter, in particular an inverter, for a motor vehicle with a semiconductor unit or a semiconductor device in a previously mentioned variant. Furthermore, the invention relates to an electric axle drive for a motor vehicle comprising at least one electric motor, a transmission unit, and an inverter. The electric axle drive is characterized by the fact that the power converter is designed as described. The transmission device may include a gearbox for reducing the speed of the electric machine as well as a differential. Furthermore, the invention relates to a motor vehicle with an electric axle drive and / or a power converter and / or a semiconductor unit. The motor vehicle is characterized in that the electric axle drive and / or the power converter and / or a semiconductor unit is configured as described. Furthermore, a method for fabricating a semiconductor unit is presented, comprising a provisioning step, a removal step, and a at least partial removal step. In the provisioning step, a printed circuit board (PCB) apparatus is provided, which includes a PCB in which a power semiconductor mounted on a substrate is embedded. The power semiconductor has a III nitride semiconductor layer, a drain contact, and a source contact. In an operating state, the power semiconductor also has a conductive channel of a two-dimensional electron gas in a III nitride semiconductor layer facing away from the contacts. In the removal step, a portion of the PCB is removed to at least partially expose a side of the substrate facing away from the power semiconductor.In the step of at least partial removal, the substrate is removed down to a surface of the III nitride semiconductor layer in order to guide a positively charged liquid coolant along the III nitride semiconductor layer to cool the power semiconductor and to neutralize negative electron charges that have accumulated opposite the drain contact on the power semiconductor. The process advantageously enables the fabrication of the semiconductor unit for the power converter, which in turn can advantageously be used in conjunction with vehicles. The printed circuit board assembly can, for example, be designed as a blank that can be processed by the process. The printed circuit board can, for example, be a PCB (printed circuit board) that can serve as a substrate for electronic components. The substrate can advantageously comprise silicon on which the power semiconductor can be arranged. The substrate can advantageously be partially or, alternatively, completely removed down to the power semiconductor.The coolant guide structure can advantageously form a plurality of cooling channels, at least partially, so that heat can be dissipated more effectively through the multitude of contact surfaces of the liquid coolant with the substrate, thus reducing the risk of overheating during operation of the power converter. Furthermore, a method for operating a semiconductor unit in a previously mentioned variant is presented, wherein the method comprises a step of electrically contacting the drain contact and the source contact and a step of guiding the liquid coolant directly along a surface of the III nitride semiconductor layer. The invention is explained in more detail by way of example with reference to the accompanying drawings. These show: Fig. 1 a schematic representation of an embodiment of a semiconductor unit; Fig. 2 a schematic representation of an embodiment of a semiconductor unit; Fig. 3 a schematic representation of an embodiment of a semiconductor unit; Fig. 4 a schematic representation of an embodiment of a semiconductor unit; Fig. 5 a schematic representation of an embodiment of a semiconductor unit; Fig. 6 a schematic representation of an embodiment of a semiconductor device; Fig. 7 a schematic representation of an embodiment of a semiconductor unit; Fig. 8 a schematic representation of an embodiment of a semiconductor unit; Fig. 9 a schematic representation of an embodiment of a semiconductor unit; Fig.Figure 10 shows a flowchart of an embodiment of a method for manufacturing a semiconductor unit; Figure 11 shows a flowchart of an embodiment of a method for operating a semiconductor unit; and Figure 12 shows a schematic representation of an embodiment of a motor vehicle. In the following description of preferred embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, without repeating these elements. Fig. 1 shows a schematic representation of an embodiment of a semiconductor unit 100. The semiconductor unit 100 is used, for example, in power converters, which in turn are used in vehicles. The semiconductor unit 100 comprises a power semiconductor 102, which has a III nitride semiconductor layer 110, consisting, for example, of aluminum gallium nitride and gallium nitride, as well as a drain contact 104 and a source contact 106. In an operating state, the power semiconductor 102 forms a conductive channel 108 from a two-dimensional electron gas (2DEG) in a III nitride semiconductor layer 110 oriented away from the contacts 104 and 106. The semiconductor unit 100 also includes a printed circuit board 112 in which the power semiconductor 102 is embedded.The printed circuit board 112 has a recess 114 leading to the III nitride semiconductor layer 110 for guiding a positively charged, high-resistance liquid coolant 116 to cool the power semiconductor 102 and to neutralize negative electron charges 118 that have accumulated on the power semiconductor 102 opposite the drain contact 104. According to this embodiment, the liquid coolant 116 is arranged in the recess 114. The liquid coolant 116 flows, for example, through the recess 114 and contacts a surface of the III nitride semiconductor layer 110. This reduces parasitic charges, for example. According to this embodiment, the printed circuit board 112 has vias 120 designed to electrically connect the drain contact 104 and the source contact 106. The described approach enables liquid-on-liquid-on-chip cooling for higher III-N blocking voltages, e.g., GaN blocking voltages, and a low dynamic on-resistance. According to one embodiment, no substrate is arranged on the power semiconductor 102, so only the III nitride semiconductor layer 110 remains unaffected. Because no substrate is arranged on the power semiconductor 102, the semiconductor unit 100, also referred to as a transistor, lacks a bulk connection, and negative electron charges 118 accumulate in surface states under the drain contact 104 during operation, i.e., when current flows through the 2DEG channel 108. These electron charges 118 affect the channel 108 and lead to a higher ron. According to this embodiment, the semiconductor unit 100 is cooled by direct liquid cooling of the III nitride semiconductor layer 110.The 2DEG channel 108, where most of the power losses of the semiconductor unit 100 occur during operation, is cooled very effectively, thus increasing thermal performance. Furthermore, the use of the positively charged liquid coolant 116 neutralizes the negatively charged electrons 118 that accumulate below the drain contact 104, thereby reducing the parasitic capacitance of the semiconductor unit 100. The liquid coolant has a high resistance, for example, to further increase the breakdown voltage of the semiconductor unit 100. To further enhance the thermal capabilities of the liquid cooling on the chip, i.e., on the power semiconductor 102, a silicon substrate can be partially preserved. Structures can be etched into the silicon substrate for this purpose, as described, for example, in at least one of the following figures. Fig. 2 shows a schematic representation of an embodiment of a semiconductor unit 100, which is similar, for example, to the semiconductor unit 100 described in Fig. 1. According to this embodiment, the semiconductor unit 100 has a substrate 200 for supporting the power semiconductor 102, which is formed in a coolant guide structure 202. The coolant guide structure 202 is designed to guide the liquid coolant along the III nitride semiconductor layer 110. Furthermore, according to this embodiment, the coolant guide structure 202 is rib-like and can alternatively be implemented in a labyrinthine or pin-like configuration, as described by way of example in Figs. 4 and 5. The substrate 200 is, for example, implemented as a silicon substrate. Optionally, the substrate 200 also features a contact section 204 arranged adjacent to the coolant guide structure 202 for electrically contacting the power semiconductor 102. The contact section 204 is contacted using at least one of the vias 120. Thus, the power semiconductor 104 can have electrical connections on both sides. For example, the contact section 204 can be used to contact a gate contact of the power semiconductor 102. According to this embodiment, the power semiconductor 102 together with the substrate 200 is aligned longitudinally to a main axis 206 of the semiconductor unit 100 and thus also of the printed circuit board 112. The coolant guide structure 202 is, for example, the result of an etching process. According to one embodiment, the substrate 102 with the power semiconductor 104 is completely enclosed by the printed circuit board 112, except for the recess 114 leading to the coolant guide structure 202. In other words, according to one embodiment, the coolant guide structure 202 has a plurality of fins 208 which increase the cooling surface area between the liquid coolant and the substrate 200 and are oriented transversely to the main axis of extension 206. This, in turn, increases the cooling capacity. Furthermore, the direction of the coolant flow can be controlled by the orientation of the fins 208. According to this embodiment, only a small pressure drop of the liquid coolant occurs. According to one embodiment, additional printed circuit board material adjacent to the recess 114 of the printed circuit board 112 has been removed to form a channel for guiding the liquid coolant along the printed circuit board 112. The liquid coolant used for cooling can be guided through the channel to the coolant guide structure 202 or directly along the surface of the power semiconductor 104, or discharged from the recess 114. Furthermore, the recess 114 can be connected via the channel to at least one optional additional recess 114 for cooling an additional power semiconductor, as shown, for example, in Fig. 9. Fig. 3 shows a schematic representation of an embodiment of a semiconductor unit 100, as described, for example, in Fig. 2. In this embodiment, the semiconductor unit 100 is shown in a sectional view. In this embodiment, the substrate 200 is surrounded on at least two sides by the printed circuit board 112. The substrate 200 also has, in this embodiment, the rib-like coolant guide structure 202, which forms a plurality of small cooling channels by means of the ribs 208. The ribs 208 are arranged transversely to the main axis of extension 206 of the semiconductor unit 100 and thus define a flow direction 300 of the liquid coolant, which is represented symbolically in this embodiment. Thus, the ribs 208 form a plurality of straight cooling channels running parallel to one another. Fig. 4 shows a schematic representation of an embodiment of a semiconductor unit 100, which is similar, for example, to the semiconductor unit described in Fig. 3. Only the coolant guide structure 202 differs from that described in Fig. 3. According to this embodiment, the coolant guide structure 202 is implemented in a labyrinthine manner. More precisely, according to this embodiment, the coolant guide structure 202 has a plurality of longitudinal struts 400, each with a plurality of transverse struts 402 arranged on the longitudinal struts 400. The longitudinal struts 400 are arranged parallel and spaced apart from one another and extend at least approximately over the entire length of the substrate 102. According to this embodiment, the substrate 200 has a coolant inlet 404 for introducing the liquid coolant into the cooling channel formed by the coolant guide structure 202.According to this embodiment, the coolant inlet 404 is arranged in a first corner region 406 of the substrate 202. Furthermore, according to this embodiment, the substrate 202 has a coolant outlet 408 for discharging the liquid coolant from the cooling channel formed by the coolant guide structure 202. According to this embodiment, the coolant outlet 408 is arranged in a second corner region 410 of the substrate 200, which is diagonally opposite the first corner region 406. According to this embodiment, the liquid coolant flows through the substrate 200 in a meandering pattern with respect to the longitudinal struts 400 and additionally in a meandering pattern with respect to the transverse struts 402 until it is discharged via the coolant outlet 408.The multiple meandering flow direction 300 of the liquid coolant through the coolant guide structure 202 slows the flow velocity, resulting in a higher pressure drop according to this embodiment than, for example, in Fig. 3. In this embodiment as well, the coolant guide structure 202 increases the cooling surface area between the liquid coolant and the substrate 200, thus increasing the cooling capacity. Furthermore, the direction of the coolant flow is controlled. Fig. 5 shows a schematic representation of an embodiment of a semiconductor unit 100, which is at least similar to the semiconductor unit described or at least mentioned in Figs. 3 to 4. Only the coolant guide structure 202 differs from that described in Figs. 3 and 4. According to this embodiment, the coolant guide structure 202 is pin-like or implemented as an etched silicon labyrinth structure, which increases the cooling surface area between the liquid and the substrate 200 and thus increases the cooling capacity. The flow direction 300 of the liquid coolant corresponds to the flow direction described in Fig. 3. According to this embodiment, the coolant guide structure 202 causes a mean pressure drop of the liquid coolant. The coolant guide structure 202 was formed, for example, by an etching process.For example, the pin fins increase the cooling surface area between the liquid and the substrate by 200, which increases the cooling performance. Fig. 6 shows a schematic representation of an embodiment of a semiconductor device 600, comprising a first semiconductor unit 100 and a second semiconductor unit 100'. The semiconductor units 100 and 100' are identical and correspond, for example, to the semiconductor unit described or mentioned in at least one of Figs. 1, 2 to 3. The coolant guide structure 202 of the first semiconductor unit 100 and the coolant guide structure 202' of the second semiconductor unit 100' are arranged opposite each other to form a common cooling channel 602. Like the first semiconductor unit 100, the second semiconductor unit 100' comprises a power semiconductor 102', the structure of which corresponds to the power semiconductor 102 described in Fig. 1. In other words, an etched rib structure is shown as a possible cooling channel structure 202 for substrate cooling. Optionally, two identical etched coolant guide structures 202, 202', also referred to as silicon structures, are joined together to create a single coolant flow channel 602. For example, a reduction in the number of channels per design is possible. Fig. 7 shows a schematic representation of an embodiment of a semiconductor unit 100, which is at least similar to the semiconductor unit described or at least mentioned in Figs. 1, 2, 3, 4, 5 to 6. According to this embodiment, the semiconductor unit 100 has no substrate. Instead, the semiconductor unit 100 has a cooling element 700 arranged on the circuit board 112 with an intermediate wall 702, wherein the cooling element 700, together with the recess 114, forms a first cooling channel 704 and a second cooling channel 706. In particular, at least one sealing element 708, 710 for sealing the cooling channels 704, 706 is arranged between the cooling element 700 and the circuit board 112. This increases, for example, the breakdown voltage between the drain contact 104 and the source contact 106, which simplifies the creation of a potential difference between the channels. Fig. 8 shows a schematic representation of an embodiment of a semiconductor unit 100, which corresponds to a combination of the semiconductor unit described in at least one of Figs. 2 to 3 and the semiconductor unit described in Fig. 7. More precisely, according to this embodiment, the semiconductor unit 100 has both the substrate 200 with the rib-like coolant guide structure 202 and a cooling element 700 with the partition 702 to form two separate cooling channels 704, 706. This, for example, increases thermal performance. Fig. 9 shows a schematic representation of an embodiment of a semiconductor unit 100, which is at least similar to the semiconductor unit described in at least one of Figs. 1, 2, 3, 4 to 5 and / or 7 to 8, but which, in addition to a power semiconductor 102, has a further power semiconductor 900 and a plurality of additional power semiconductors 902. Each of the power semiconductors 102, 900, 902 represents, for example, a power transistor. Thus, the semiconductor unit 100 shown in Fig. 9 can be used, for example, for the power converter shown with reference to Fig. 12. In particular, the semiconductor unit 100 according to this embodiment is similar to the semiconductor unit described in Fig. 5, since the semiconductor unit 100 shown in Fig. 9 has the pin-like structured substrate 200, i.e., the coolant conduction structure described with reference to Fig. 5. According to this embodiment, the semiconductor unit 100 thus additionally comprises at least one further power semiconductor 900, 902, which corresponds to the power semiconductor 102 and therefore has a III nitride semiconductor layer 110 as well as a further drain contact and a further source contact, which are only mentioned here due to the schematic representation. Like the power semiconductor 102, the at least one further power semiconductor 900, 902 also has, in an operating state, a further conductive channel consisting of a two-dimensional electron gas in a further III nitride semiconductor layer 110 arranged facing away from the other contacts. The at least one further power semiconductor 900, 902 is also embedded in the printed circuit board 112.The circuit board 112 has a further recess 904 leading to the further III nitride semiconductor layer 110 of the further power semiconductor 902 for guiding the positively charged liquid coolant, wherein the recess 114 and the further recess 904 are connected to a guide channel 906 and are connected to each other by a section of the guide channel 906 of the circuit board 112 for guiding the liquid coolant from the power semiconductor 102 to the further power semiconductor 900. According to this embodiment, the printed circuit board 112 has a plurality of guide channels 906, 908, which, for example, branch out and / or are arranged parallel to each other and can also converge again. Each of the plurality of guide channels 906, 908, 910 can therefore cool several of the power semiconductors 102, 900, 902. According to one embodiment, each of the power semiconductors 102, 900, 902, together with the respective substrate 200, forms a transistor embedded in the printed circuit board 112. This is referred to in the industry as "embedding". That is, the bare transistor (also called a bare die) consists, in simplified terms, of the layers shown in Fig. 1, for example, AlGaN / GaN for the power semiconductor 102, 900, 902 and silicon for the substrate 200. According to one embodiment, these transistors are manufactured individually and embedded in the printed circuit board 112 during its manufacturing process. This printed circuit board 112, plus several embedded transistors, forms, for example, a converter unit or another circuit. Fig. 9 merely shows an example of a possible representation of the cooling channels, here designated as guide channels 906, 908, 910, in a converter unit. Fig. 10 shows a flowchart of an embodiment of a method 1000 for manufacturing a semiconductor unit, as described or at least mentioned, for example, in at least one of Figs. 1, 2, 3, 4, 5, 6, 7, 8 to 9. The method 1000 comprises a step 1002 of providing a printed circuit board (PCB) device, which has a PCB in which a power semiconductor arranged on a substrate is embedded. The PCB device is, for example, a blank to be processed in the method 1000. The power semiconductor has a III nitride semiconductor layer 110 as well as a drain contact and a source contact. In an operating state, the power semiconductor also has a conductive channel of a two-dimensional electron gas in a III nitride semiconductor layer 110 arranged facing away from the contacts.Furthermore, the method 1000 comprises a step 1004 of removing a part of the printed circuit board in order to at least partially expose a side of the substrate facing away from the power semiconductor, and a step 1006 of at least partially removing the substrate up to a surface of the III nitride semiconductor layer 110 in order to be able to guide a positively charged liquid coolant along the III nitride semiconductor layer 110 for cooling the power semiconductor and for neutralizing negative electron charges that have accumulated on the power semiconductor opposite the drain contact. Fig. 11 shows a flowchart of an embodiment of a method 1100 for operating a semiconductor unit, as described or at least mentioned, for example, in at least one of Figs. 1, 2, 3, 4, 5, 6, 7, 8 to 9. The method 1100 comprises a step 1102 of electrically contacting the drain contact and the source contact and a step 1104 of guiding the liquid coolant directly along a surface of the III nitride semiconductor layer 110. Fig. 12 shows a schematic representation of an embodiment of a motor vehicle 1200. The motor vehicle 1200 is also referred to as a vehicle and has an electric axle drive 1202, which in turn comprises at least one electric machine 1204, a transmission unit 1206, and a power converter 1208. The electric machine 1204 is also referred to as a drive unit or an electric motor and is coupled, for example, to the transmission unit 1206. The motor vehicle 1200 further comprises a power supply unit 1210, which is referred to, for example, as a battery. According to this embodiment, the power converter 1208 is connected between the power supply unit 1210 and the electric machine 1204.The power converter 1108 has a plurality of switches 1212, for example six in number, which are implemented as part of a semiconductor unit 100 or a semiconductor device 600, as described and / or mentioned, for example, in at least one of the Figs. 1, 2, 3, 4, 5, 6, 7, 8 to 9. Reference sign 100 Semiconductor unit 102 Power semiconductor 104 Drain contact 106 Source contact 108 Channel 110 III nitride semiconductor layer 112 Printed circuit board 114 Recess 116 Liquid coolant 118 Electron charge 120 Vias 200 Substrate 202 Coolant guide structure 204 Contact section 206 Main extension axis 300 Flow direction 400 Longitudinal struts 402 Transverse struts 404 Coolant inlet 406 First corner area 408 Coolant outlet 410 Second corner area 600 Semiconductor device 602 Cooling channel 700 Cooling element 702 Partition 704 First cooling channel 706 Second cooling channel 708 Sealing element 710 Sealing element 900 Additional power semiconductor 902 Additional power semiconductors 904 Additional recess 906 Guide channel 908 Additional guide channel 910 Additional Guide channel 1000 Method for manufacturing a semiconductor unit 1002 Step of provisioning 1004 Step of removal 1006 Step of at least partial removal 1100 Method for operating a semiconductor unit 1102 Step ofelectrical contacting 1104 step of conducting 1200 motor vehicle 1202 electric axle drive 1204 electric machine 1206 transmission device 1208 power converter 1210 power supply device 1212 multiple switches

Claims

Semiconductor unit (100) for a power converter (1208), wherein the semiconductor unit (100) has the following features: a power semiconductor (102) comprising a III nitride semiconductor layer (110) and a drain contact (104) and a source contact (106), wherein the power semiconductor (100) in an operating state forms a conductive channel (108) from a two-dimensional electron gas in a III nitride semiconductor layer (110) arranged facing away from the contacts (104, 106); and a printed circuit board (112) in which the power semiconductor (102) is embedded, wherein the printed circuit board (112) has a recess (114) leading to the III nitride semiconductor layer (110) for guiding a positively charged liquid coolant (116) for cooling the power semiconductor (100) and for neutralizing negative electron charges (118) accumulated on the power semiconductor (102) opposite the drain contact (104). Semiconductor unit (100) according to claim 1, comprising a coolant guide structure (202) formed from a substrate (200) for supporting the power semiconductor (102) for guiding the liquid coolant (116) along the III nitride semiconductor layer (110). Semiconductor unit (100) according to claim 2, wherein the cooling medium guide structure (202) is rib-like, labyrinth-like or pin-like. Semiconductor unit (100) according to one of claims 2 to 3, wherein the substrate (200) is designed as a silicon substrate. Semiconductor unit (100) according to one of claims 2 to 4, wherein the substrate (200) has a contact section (204) arranged adjacent to the coolant guide structure (202) for electrically contacting the power semiconductor (102). Semiconductor unit (100) according to one of the preceding claims, wherein the printed circuit board (112) has vias (120) for electrically contacting the drain contact (104) and the source contact (106). Semiconductor unit (100) according to one of the preceding claims, with the liquid coolant (116) arranged in the recess (114). Semiconductor unit (100) according to one of the preceding claims, with a cooling element (700) arranged on the circuit board (112) with an intermediate wall (702), wherein the cooling element (700) together with the recess (114) forms a first cooling channel (704) and a second cooling channel (706), wherein at least one sealing element (708, 710) for sealing the cooling channels (704, 706) is arranged between the cooling element (700) and the circuit board (112). Semiconductor unit (100) according to one of the preceding claims, comprising a further power semiconductor (900) comprising a III nitride semiconductor layer (110), and comprising a further drain contact and a further source contact, and wherein the further power semiconductor (900) in an operating state comprises a further conductive channel of a two-dimensional electron gas in a further III nitride semiconductor layer (110) arranged facing away from the further contacts, wherein the further power semiconductor (900) is embedded in the printed circuit board (112), wherein the printed circuit board (112) has a further recess (904) leading to the further III nitride semiconductor layer (110) for guiding the positively charged liquid coolant,wherein the recess (114) and the further recess (904) are connected to each other by a guide channel (906) of the printed circuit board (112) for guiding the liquid coolant (116) from the power semiconductor (102) to the further power semiconductor (900). Semiconductor device (600) for a power converter (1208), wherein the semiconductor device (600) has the following features: a first semiconductor unit (100) according to any one of claims 1 to 9; and a second semiconductor unit (100') according to any one of claims 1 to 9, wherein the III nitride semiconductor layer (110) of the first semiconductor unit (100) and the III nitride semiconductor layer (110) of the second semiconductor unit (100') are arranged opposite each other to form a common cooling channel (602). Power converter (1208), in particular inverter, with a semiconductor unit (100) according to one of claims 1 to 9 or a semiconductor device (600) according to claim 10. Electric axle drive (1202) for an at least partially electrified motor vehicle (1200) with at least one electric machine (1204), a transmission device (1206) and a power converter (1208), characterized in that the power converter (1208) is designed according to claim 11. Motor vehicle (1200), in particular at least partially electrified vehicle, comprising an electric axle drive (1202) according to claim 12 and / or a power converter (1208) according to claim 11 and / or a semiconductor unit (100) according to any one of claims 1 to 9 or a semiconductor device (600) according to claim 10. Method (1000) for manufacturing a semiconductor unit (100), wherein the method (1000) comprises the following steps: providing (1002) a printed circuit board apparatus comprising a printed circuit board (112) in which a power semiconductor (102) arranged on a substrate (200) is embedded, wherein the power semiconductor (102) comprises III nitride semiconductor layers (110) and has a drain contact (104) and a source contact (106), and wherein the power semiconductor (102) in an operating state has a conductive channel (108) of a two-dimensional electron gas in a III nitride semiconductor layer (110) arranged facing away from the contacts (104, 106); removing (1004) a portion of the printed circuit board (112) to at least partially expose a side of the substrate (200) facing away from the power semiconductor (102);and at least partial removal (1006) of the substrate (200) up to a surface of the III nitride semiconductor layer (110) in order to allow a positively charged liquid coolant (116) to cool the power semiconductor (102) and to neutralize negative electron charges (118) accumulated opposite the drain contact (104) on the power semiconductor (102) along the III nitride semiconductor layer (110). Method (1100) for operating a semiconductor unit (100) according to any one of claims 1 to 9, wherein the method (1100) comprises the following steps: Electrically contacting (1102) the drain contact (104) and the source contact (106); and guiding (1104) the liquid coolant (116) directly along a surface of the III nitride semiconductor layer (110).

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