Semiconductor device
By arranging high-injection and low-injection diode regions in an RC-IGBT, the semiconductor device minimizes hole injection and recovery losses, enhancing thermal management and performance.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- MINEBEA POWER SEMICON DEVICE INC
- Filing Date
- 2025-10-15
- Publication Date
- 2026-07-02
AI Technical Summary
Existing RC-IGBT designs experience increased recovery losses due to the injection of holes into the diode region near the boundary between the IGBT and diode regions, leading to high reverse current and thermal resistance.
The semiconductor device incorporates a high-injection diode region adjacent to the IGBT region and a low-injection diode region spaced apart, with ohmic and Schottky connections, reducing hole injection and optimizing the arrangement to minimize recovery losses.
This configuration effectively suppresses hole injection, reducing recovery losses and thermal resistance while maintaining desired forward voltage and current characteristics.
Smart Images
Figure JP2025036269_02072026_PF_FP_ABST
Abstract
Description
Semiconductor device
[0001] The present invention relates to a semiconductor device.
[0002] An RC-IGBT (RC: Reverse-Conducting, reverse-conducting IGBT) incorporating an IGBT (Insulated Gate Bipolar Transistor) and a diode within the same chip has the advantage of reducing the chip size because it can share the termination regions of the IGBT having a switching function and the diode having a reflux function. Also, since the timings at which the IGBT and the diode operate are different from each other, heat generated due to losses occurring in one of the IGBT region and the diode region is dispersed to the other, and thus the entire chip can dissipate heat, which also has the advantage of reducing the thermal resistance.
[0003] As a technology related to RC-IGBT, for example, there is Patent Document 1.
[0004] In FIGS. 1 to 3 and paragraph 0009 of Patent Document 1, an RC-IGBT having an IGBT region (20) in which an IGBT is formed and a diode region (50) in which a diode is formed on a semiconductor substrate (12) is described as a semiconductor device (10).
[0005] Also, in paragraphs 0017 and 0018 of Patent Document 1, it is described that the anode region (52) of the diode region (50) has an anode contact region (52a) and a low-concentration anode region (52b). And it is described that the p-type impurity concentration of the anode contact region (52a) is higher than the p-type impurity concentration of the low-concentration anode region (52b). Further, it is described that the anode contact region (52a) is ohmically connected to the upper electrode (80).
[0006] Furthermore, paragraph 0028 of Patent Document 1 describes that when a voltage is applied between the upper electrode (80) and the lower electrode (90) such that the upper electrode (80) is at a high potential, the diode in the diode region (50) turns on, and holes flow from the upper electrode (80) to the anode contact region (52a), pass through the low-concentration anode region (52b) and the cathode region (54) and flow to the lower electrode (90). Furthermore, it is described that although the low-concentration anode region (52b) is in contact with the upper electrode (80), the contact resistance between them is high, so the inflow of holes from the upper electrode (80) to the low-concentration anode region (52b) through the interface between the low-concentration anode region (52b) and the upper electrode (80) is suppressed. Furthermore, it is described that when the applied voltage between the upper electrode (80) and the lower electrode (90) switches to a reverse voltage (a voltage at which the lower electrode (90) becomes high potential), the diode performs a reverse recovery operation, and holes present in the cathode region (54) flow to the upper electrode (80) via the anode region (52), causing a reverse current to flow instantaneously through the diode. At this time, in the semiconductor device (10) of Patent Document 1, as described above, the amount of holes flowing into the cathode region (54) when the diode is ON is limited, so the amount of holes flowing from the cathode region (54a) toward the upper electrode (80) during the reverse recovery operation is small, resulting in a smaller reverse current flowing through the diode during the reverse recovery operation, and thus reducing the losses that occur during the reverse recovery operation of the diode.
[0007] Japanese Patent Publication No. 2015-231037
[0008] However, in the arrangement shown in Figures 1 to 3 of Patent Document 1, the interface between the low-concentration anode region (52b) and the upper electrode (80) is located adjacent to the IGBT region (20) near the boundary between the IGBT region (20) and the diode region (50).
[0009] Here, when the diode is ON, the holes injected may flow not only perpendicular to the main surface of the semiconductor substrate when viewed in cross-section, but also obliquely to the main surface of the semiconductor substrate.
[0010] Therefore, in the case of the arrangement described in Figures 1 to 3 of Patent Document 1, near the boundary between the IGBT region (20) and the diode region (50), both holes from the IGBT region (20) and holes from the region overlapping the anode contact region (52a) are injected into the region overlapping the interface between the low-concentration anode region (52b) and the upper electrode (80). This results in a large reverse current (recovery current) flowing during reverse recovery operation (recovery), leading to increased recovery losses.
[0011] The problem that the present invention aims to solve is to provide a semiconductor device that can reduce recovery loss in an RC-IGBT by suppressing the injection of holes into the diode region near the boundary between the IGBT region and the diode region.
[0012] To solve the above-mentioned problems, the present invention provides a semiconductor device comprising an RC-IGBT having an IGBT region and a diode region on the same chip, wherein the IGBT in the IGBT region has a trench, a gate electrode provided inside the trench, an emitter electrode, a drift layer of a first conductivity type, a body layer of a second conductivity type provided between adjacent trenches, an emitter layer of a first conductivity type having a higher impurity concentration than the drift layer, and a contact layer of a second conductivity type having a higher impurity concentration than the body layer, wherein the emitter electrode and the body layer are ohmic connected via the contact layer, and the diode in the diode region is The diode region comprises an anode electrode electrically connected to an emitter electrode, the trench, a cathode of a first conductivity type, and an anode of a second conductivity type provided between adjacent trenches, wherein the diode region comprises a low-injection diode region in which the anode electrode and the anode are Schottky connected, and a high-injection diode region in which the anode electrode and the anode are ohmic connected via the contact layer, the high-injection diode region is arranged adjacent to the IGBT region, and the low-injection diode region is arranged spaced apart from the IGBT region via the high-injection diode region.
[0013] According to the present invention, in an RC-IGBT, it is possible to realize a semiconductor device that can reduce recovery loss by suppressing the injection of holes into the diode region near the boundary between the IGBT region and the diode region.
[0014] A top view showing an example of a semiconductor device of Example 1. A cross-sectional view showing an example of a semiconductor device of Example 1. A cross-sectional view showing an example of a semiconductor device of Example 2. A cross-sectional view showing an example of a semiconductor device of Example 3. A cross-sectional view showing an example of a semiconductor device of Example 4. A top view of a semiconductor device of a comparative example.
[0015] The embodiments of the present invention will be described below with reference to the drawings. In each figure and each embodiment, the same or similar components are denoted by the same reference numerals, and redundant explanations are omitted.
[0016] In this embodiment, an RC-IGBT having an n-type IGBT with a side gate structure will be described as an example. The impurity concentration of the semiconductor layer will increase in the order n- < n < n+, and then in the order p- < p < p+. The concentrations of n+ and p+ will be high enough to enable ohmic connection. Note that the impurity concentration of the semiconductor layer in this embodiment is just an example, and it can be changed as appropriate within a range that allows the intended operation in this embodiment to be achieved.
[0017] Figure 1 is a top view showing an example of a semiconductor device of Example 1.
[0018] The semiconductor device 100 in this embodiment is an RC-IGBT and has an IGBT region 21 and a diode region 22 within the same chip (on the same semiconductor substrate). The IGBT region 21 and the diode region 22 extend in the vertical direction of Figure 1, which is the direction in which a trench (not shown) extends, and are alternately arranged in the left-right direction of Figure 1, which is perpendicular to the direction in which the trench extends.
[0019] Furthermore, the semiconductor device 100 of this embodiment also includes a termination region 23 surrounding the IGBT region 21 and the diode region 22, a gate pad 24 which is an external terminal to which a gate drive signal is input from the outside, and a gate runner 25 which is a routing wire that inputs the gate drive signal input to the gate pad 24 to a gate electrode (not shown) of the IGBT region 21.
[0020] In this embodiment, the diode region 22 has a high-injection diode region 22A and a low-injection diode region 22B. The low-injection diode region 22B is a region where fewer holes are injected than in the high-injection diode region 22A when the diode is conducting. The high-injection diode region 22A is located adjacent to the IGBT region 21, while the low-injection diode region 22B is located spaced apart from the IGBT region 21, with the high-injection diode region 22A in between. The effects of this arrangement will be described later.
[0021] Figure 2 is a cross-sectional view showing an example of a semiconductor device according to Example 1.
[0022] The IGBT in IGBT region 21 has a trench 3, a gate electrode 5 provided inside the trench 3, an emitter electrode 14A, a drift layer 1 of first conductivity type, a body layer 2 of second conductivity type provided between adjacent trenches 3, an emitter layer 7 of first conductivity type with a higher impurity concentration than the drift layer 1, and a contact layer 8 of second conductivity type with a higher impurity concentration than the body layer 2, and the emitter electrode 14A and the body layer 2 are ohmic connected via the contact layer 8.
[0023] Furthermore, the IGBT in this embodiment is a side-gate IGBT, and compared to the general trench-gate IGBT described later, the trench 3 is formed wider, and the gate electrode 5 is composed of a first gate electrode 5A and a second gate electrode 5B. Specifically, the IGBT in this embodiment has a first gate electrode 5A provided on one side wall inside the trench 3, a second gate electrode 5B provided on the other side wall inside the trench 3, and an insulating film (interlayer insulating film 9A inside the trench) provided inside the trench 3 to insulate between the first gate electrode 5A and the second gate electrode 5B. In a side-gate IGBT, the feedback capacitance can be reduced compared to a general trench-gate IGBT, and turn-off losses can be reduced while maintaining the same on-voltage as a general trench-gate IGBT.
[0024] Furthermore, it is desirable that the IGBT in this embodiment has a field plate 16 provided inside the trench 3. The field plate 16 is electrically connected to the emitter electrode 14A and is insulated from the drift layer 1 by an insulating film that is about the same thickness as the gate insulating film 4A. The field plate 16 is also insulated from the first gate electrode 5A and the second gate electrode 5B by an insulating film (interlayer insulating film 9A inside the trench).
[0025] The IGBT in the IGBT region 21 of this embodiment more specifically comprises an n-type drift layer 1, a p-type body layer 2 provided on the surface side of the drift layer 1, an n+-type emitter layer 7 provided on the surface side of the body layer 2, an emitter electrode 14A provided on the surface side and electrically connected to the emitter layer 7, a p+-type contact layer 8 that ohmic connects the emitter electrode 14A and the body layer 2, a trench 3 that penetrates the body layer 2 and reaches the drift layer 1, a gate insulating film 4A provided inside the trench 3, and a trench The structure includes a first gate electrode 5A and a second gate electrode 5B located inside the trench 3, facing the body layer 2, emitter layer 7, and drift layer 1 via a gate insulating film 4A; an interlayer insulating film 9A located inside the trench 3 that insulates the first gate electrode 5A and the second gate electrode 5B; a field plate 16 located inside the trench 3; a p-type collector layer 11 located on the back side of the drift layer 1; and a collector electrode 15A located on the back side and electrically connected to the collector layer 11. Furthermore, it is desirable that the IGBT in the IGBT region 21 has an n-type buffer layer 10 between the drift layer 1 and the collector layer 11, with a higher impurity concentration than the drift layer 1. Although only one second gate electrode 5B is shown in Figure 2, in reality, the second gate electrode 5B and the first gate electrode 5A are arranged alternately on the left side of Figure 2 as well.
[0026] The diode in the diode region 22 has an anode electrode 14B electrically connected to the emitter electrode 14A, a trench 3, a first-conductivity type cathode (drift layer 1, buffer layer 10, cathode contact layer 13), and a second-conductivity type anode (anode layer 12) provided between adjacent trenches 3.
[0027] Specifically, the diode in the diode region 22 has an n-type drift layer 1 formed in common with the IGBT region 21, a p-type anode layer 12 provided on the surface side of the drift layer 1, a trench 3 that penetrates the anode layer 12 and reaches the drift layer 1, an in-trench insulating film 4B provided inside the trench 3, an in-trench electrode 6 provided inside the trench 3 that faces the anode layer 12 and the drift layer 1 via the in-trench insulating film 4B, a field plate 16 provided inside the trench 3, an in-trench interlayer insulating film 9A provided inside the trench 3 that insulates the two in-trench electrodes 6 and the field plate 16 from each other, an n+-type cathode contact layer 13 provided on the back side of the drift layer 1, and a cathode electrode 15B provided on the back side that is electrically connected to the collector electrode 15A and the cathode contact layer 13. Furthermore, it is desirable that the diode in the diode region 22 has an n-type buffer layer 10, which is formed in common with the IGBT region 21, between the drift layer 1 and the cathode contact layer 13.
[0028] In the high-injection diode region 22A, the anode electrode 14B and the anode (anode layer 12) are ohmic-connected via the contact layer 8, resulting in a low-resistance connection and a region where a large number of holes are injected when the diode conducts. In contrast, the low-injection diode region 22B does not have a contact layer 8, and the anode electrode 14B and the anode (anode layer 12) are Schottky-connected, resulting in a high-resistance connection and a region where a small number of holes are injected when the diode conducts.
[0029] The semiconductor device 100 also includes an interlayer insulating film 9, a surface electrode 14, and a back surface electrode 15.
[0030] The surface electrode 14 is formed on the surface side of the semiconductor device 100, common to both the IGBT region 21 and the diode region 22. In the IGBT region 21, it functions as the emitter electrode 14A, and in the diode region 22, it functions as the anode electrode 14B. The emitter of the IGBT and the anode of the diode are electrically connected. Therefore, the surface electrode 14 is at both the emitter potential and the anode potential.
[0031] The back electrode 15 is formed on the back side of the semiconductor device 100, common to both the IGBT region 21 and the diode region 22. In the IGBT region 21, it functions as a collector electrode 15A, and in the diode region 22, it functions as a cathode electrode 15B. The collector of the IGBT and the cathode of the diode are electrically connected. Therefore, the back electrode 15 is at both the collector potential and the cathode potential.
[0032] The interlayer insulating film 9 is provided between the various semiconductor layers, the gate electrode 5, the trench electrode 6, and the surface electrode 14. The trench interlayer insulating film 9A is also a part of the interlayer insulating film 9.
[0033] In this embodiment, the structure of the diode region 22 is almost identical to that of the IGBT region 21, except for a few parts. Therefore, the manufacturing process for the IGBT region 21 and the manufacturing process for the diode region 22 can be largely standardized. Note that the structures of the IGBT region 21 and diode region 22 described above are just examples and are not limited thereto.
[0034] Next, the effects of the semiconductor device 100 of this embodiment will be explained in comparison with the comparative example shown in Figure 6.
[0035] Figure 6 is a top view of a comparative example semiconductor device.
[0036] As shown in Figure 6, the semiconductor device 100 of the comparative example has the arrangement of the high-injection diode region 22A and the low-injection diode region 22B reversed compared to Example 1. That is, in the semiconductor device 100 of the comparative example, the low-injection diode region 22B is located between the IGBT region 21 and the high-injection diode region 22A, adjacent to the IGBT region 21 and the high-injection diode region 22A. Therefore, the cross-sectional view of the comparative example has the same structure as that of Figure 2, but with the high-injection diode region 22A and the low-injection diode region 22B swapped. In order to compare the effects of the difference in arrangement, Example 1 and the comparative example are set so that the total area of the high-injection diode region 22A is equal to the total area of the low-injection diode region 22B.
[0037] When the anode electrode 14B reaches a higher potential than the cathode electrode 15B, the diode turns on and conducts, and holes are injected from the anode to the cathode. At this time, the low-injection diode region 22B has less hole injection than the high-injection diode region 22A.
[0038] However, when the diode is on, the holes injected may flow not only perpendicular to the main surface of the semiconductor substrate when viewed in cross-section, but also obliquely to the main surface of the semiconductor substrate.
[0039] The reason is as follows: The low injection diode region 22B has a higher contact resistance between the anode electrode 14B and the anode layer 12 of the low injection diode region 22B compared to the high injection diode region 22A. Therefore, a larger potential difference is generated between the anode layer 12 and the anode electrode 14B in the low injection diode region 22B compared to the high injection diode region 22A, and the potential on the surface side of the drift layer 1 of the low injection diode region 22B decreases. As a result, an electric field (for example, a lateral electric field generated laterally in Figure 2) is generated from the IGBT region 21 and the high injection diode region 22A, which have relatively high potentials, toward the low injection diode region 22B. Then, due to this lateral electric field, holes injected into the drift layer 1 from the contact layer 8 of the IGBT region 21 and the contact layer 8 of the high injection diode region 22A drift toward the low injection diode region 22B, and holes are injected into the drift layer 1 of the low injection diode region 22B. For these reasons, when the diode is on, some of the holes injected flow obliquely to the main surface of the semiconductor substrate when viewed in cross-section.
[0040] Therefore, in the comparative example configuration, near the boundary between the IGBT region 21 and the diode region 22, both holes from the IGBT region 21 and holes from the high-injection diode region 22A are injected into the low-injection diode region 22B.
[0041] As a result, when excess holes accumulate in the drift layer 1 and the anode electrode 14B becomes lower in potential than the cathode electrode 15B, causing diode recovery, the recovery current that flows during recovery becomes large, leading to increased recovery losses.
[0042] In contrast, in the semiconductor device 100 of this embodiment, as shown in Figures 1 and 2, the high-injection diode region 22A is located adjacent to the IGBT region 21, and the low-injection diode region 22B is located spaced apart from the IGBT region 21, with the high-injection diode region 22A in between.
[0043] Therefore, in the case of the arrangement of this embodiment, when the diode is on, in the vicinity of the boundary between the IGBT region 21 and the diode region 22, although the injection of holes from the high-injection diode region 22A into the low-injection diode region 22B is the same as in the comparative example, since the low-injection diode region 22B is arranged at a distance from the IGBT region 21, the injection of holes from the IGBT region 21 into the low-injection diode region 22B decreases. Furthermore, if the IGBT region 21 and the low-injection diode region 22B are sufficiently separated, the injection of holes from the IGBT region 21 into the low-injection diode region 22B can be eliminated.
[0044] As a result, in this embodiment, compared with the comparative example, the injection of holes into the low-injection diode region 22B when the diode is on can be reduced. Therefore, the holes accumulated in the drift layer 1 of the low-injection diode region 22B can be reduced, the recovery current flowing during the recovery of the diode can be made small, and the recovery loss can be reduced.
[0045] Next, other effects of the semiconductor device 100 of this embodiment will be described.
[0046] In this embodiment, a configuration having a high-injection diode region 22A and a low-injection diode region 22B is adopted. If only the high-injection diode region 22A is provided, although the forward voltage can be lowered, there is a problem that the recovery current increases and the recovery loss increases. On the contrary, if only the low-injection diode region 22B is provided, although the recovery current can be made small and the recovery loss can be made small, there is a problem that the forward voltage becomes high. Therefore, as in this embodiment, by adopting a configuration having a high-injection diode region 22A and a low-injection diode region 22B and adjusting the arrangement and area, the forward voltage and the recovery loss can be adjusted to desired values.
[0047] In addition, since the IGBT has a pnpn parasitic thyristor composed of a p-type collector layer 11, an n-type drift layer 1, a p-type body layer 2, and an n+-type emitter layer 7 inside the element, in order to prevent the latch-up of this parasitic thyristor, the emitter electrode 14A and the body layer 2 are connected with low resistance via a p+-type contact layer 8.
[0048] First, the latch-up of the parasitic thyristor will be described. When a large current flows through the IGBT, current also flows through the body layer 2 directly below the emitter layer 7. As a result, a voltage drop corresponding to the resistance of the body layer 2 occurs. Thereby, a potential difference between the emitter layer 7 and the body layer 2 is generated, and electrons are injected from the emitter layer 7 into the body layer 2. As a result, the parasitic npn transistor formed by the emitter layer 7, the body layer 2, and the drift layer 1 is turned on. The current of this parasitic npn transistor becomes the base current of the parasitic pnp transistor formed by the body layer 2, the drift layer 1, and the collector layer 11, and the parasitic pnp transistor is turned on. Thereby, the potential difference between the emitter layer 7 and the body layer 2 further increases, resulting in positive feedback. As a result, the latch-up of the pnpn parasitic thyristor occurs.
[0049] Next, the reason why the latch-up of the parasitic thyristor can be prevented by the contact layer 8 will be explained. By connecting the emitter electrode 14A and the body layer 2 with low resistance via a p+-type contact layer 8, for example, in the RBSOA (Reverse Bias Safe Operating Area) where a high voltage is applied, holes generated by dynamic avalanche flow into the contact layer 8 and are discharged to the emitter electrode 14A. Since the contact layer 8 can reduce the contact resistance, it becomes difficult for a potential difference to occur between the emitter layer 7 and the body layer 2, the base current of the parasitic npn transistor is suppressed, and it becomes possible to prevent the on-state of the parasitic npn transistor, the on-state of the parasitic pnp transistor, and the latch-up of the parasitic thyristor.
[0050] On the other hand, the provision of a contact layer 8 in the IGBT makes it easier for holes to be injected from the contact layer 8 into the drift layer 1. Therefore, in this embodiment, in order to reduce or eliminate the injection of holes from the IGBT region 21 into the low injection diode region 22B, the IGBT region 21 and the low injection diode region 22B are separated, as previously explained, thereby solving this problem.
[0051] Furthermore, in this embodiment, a contact layer 8 is also provided in the high-injection diode region 22A. The impurity concentration of the contact layer 8 in the IGBT region 21 and the impurity concentration of the contact layer 8 in the high-injection diode region 22A are substantially the same. This makes it possible to unify the manufacturing process of the contact layer 8 in the IGBT region 21 and the manufacturing process of the contact layer 8 in the diode region 22.
[0052] In this specification, "the impurity concentrations of two semiconductor layers are substantially the same" means that the difference in impurity concentrations between the two layers is within 10%.
[0053] As described above, according to the semiconductor device 100 of this embodiment, in an RC-IGBT, the injection of holes into the diode region 22 near the boundary between the IGBT region 21 and the diode region 22 can be suppressed, thereby reducing recovery loss.
[0054] Example 2 is a modification of Example 1. The differences from Example 1 will be explained below.
[0055] Figure 3 is a cross-sectional view showing an example of the semiconductor device of Example 2.
[0056] The semiconductor device 100 of this embodiment is characterized in that the impurity concentration (p2) of the contact layer 8 in the high injection diode region 22A is lower than the impurity concentration (p1) of the contact layer 8 in the IGBT region 21.
[0057] In Example 1, the impurity concentration of the contact layer 8 in the IGBT region 21 and the impurity concentration of the contact layer 8 in the high-injection diode region 22A are both p1. Therefore, the impurity concentration of the contact layer 8 in the high-injection diode region 22A is lower in Example 2 than in Example 1.
[0058] As a result, in Example 2, the injection of holes from the contact layer 8 in the high-injection diode region 22A is reduced compared to Example 1, and the injection of holes from the high-injection diode region 22A to the low-injection diode region 22B is also reduced compared to Example 1. Therefore, Example 2 can reduce recovery loss compared to Example 1.
[0059] Furthermore, the width w shown in Figure 3, which is the dimension perpendicular to the direction in which the trench 3 of the high injection diode region 22A extends when viewed from above, is preferably greater than or equal to the thickness t, which is the thickness of the semiconductor layer on which the high injection diode region 22A is formed when viewed in cross-section.
[0060] In this embodiment, the impurity concentration (p1) of the contact layer 8 in the IGBT region 21 is higher than the impurity concentration (p2) of the contact layer 8 in the high-injection diode region 22A. Therefore, the injection of holes from the contact layer 8 in the IGBT region 21 is greater than the injection of holes from the contact layer 8 in the high-injection diode region 22A. Thus, it is desirable to reduce the injection of holes from the IGBT region 21 to the low-injection diode region 22B by increasing the width w.
[0061] Since the oblique movement of a hole is at an angle of approximately 45 degrees, if the width w is made at least greater than the thickness of the cathode (the total thickness from the drift layer 1 to the cathode contact layer 13), the injection of holes from the IGBT region 21 to the low injection diode region 22B can be eliminated. For greater certainty, it is desirable that the width w is greater than or equal to the thickness t.
[0062] According to this embodiment, the injection of holes into the diode region 22 near the boundary between the IGBT region 21 and the diode region 22 can be suppressed more effectively than in Embodiment 1, thereby reducing recovery losses.
[0063] Example 3 is a modification of Example 1. The differences from Example 1 will be explained below.
[0064] Figure 4 is a cross-sectional view showing an example of a semiconductor device according to Example 3.
[0065] In Example 1, the cathode contact layer 13 is formed in common in both the high-injection diode region 22A and the low-injection diode region 22B. Therefore, in Example 1, the impurity concentration of the portion of the cathode that contacts the cathode electrode 15B in the high-injection diode region 22A (cathode contact layer 13) and the impurity concentration of the portion of the cathode that contacts the cathode electrode 15B in the low-injection diode region 22B (cathode contact layer 13) are substantially the same.
[0066] In contrast, the semiconductor device 100 of Example 3, as shown in Figure 4, has a p-type block layer 17 instead of a cathode contact layer 13 in the low-injection diode region 22B. As a result, in the semiconductor device 100 of this example, the high-injection diode region 22A has an ohmic connection between the cathode electrode 15B and the cathode (the cathode contact layer 13, which is the portion of the cathode that contacts the cathode electrode 15B), and the low-injection diode region 22B has a second-conductivity block layer 17 between the cathode electrode 15B and the cathode (the drift layer 1 and the buffer layer 10). The block layer 17 can be formed simultaneously with the collector layer 11 without increasing the manufacturing process.
[0067] In this embodiment, the low-injection diode region 22B has a pnp transistor structure, so vertical current does not flow, and hole accumulation can be suppressed, thereby reducing recovery loss. However, there is a diagonal current flowing from the anode layer 12 of the low-injection diode region 22B through the drift layer 1 and buffer layer 10 to the cathode contact layer 13 of the high-injection diode region 22A. In this embodiment, recovery loss can be reduced compared to Embodiment 1. On the other hand, the forward voltage becomes higher, but the forward current can be adjusted by adjusting the area of the high-injection diode region 22A and the low-injection diode region 22B.
[0068] Example 4 is a modification of Example 1. In this example, a general trench gate structure n-type IGBT is used as the IGBT in the RC-IGBT. The differences from Example 1 will be explained.
[0069] Figure 5 is a cross-sectional view showing an example of a semiconductor device according to Example 4.
[0070] In this embodiment, the IGBT region 21 is different from that of Embodiment 1 in that the trench 3 is not as wide, and there is only one gate electrode 5 inside the trench 3. Also, the field plate 16 and the interlayer insulating film 9A inside the trench are not formed. Furthermore, in Embodiment 1, the emitter electrode 14A and the body layer 2 were connected ohmically via the contact layer 8 using contact holes, but in Embodiment 4, the connection is made without using contact holes.
[0071] The diode region 22 in this embodiment has also been modified in the same way as the IGBT region 21.
[0072] Note that the structure shown in Figure 5 is merely an example, and other IGBT structures may be used.
[0073] In this embodiment as well, the same effects as in Embodiment 1 can be obtained, except for the effects specific to the side gate structure.
[0074] Although embodiments of the present invention have been described above, the present invention is not limited to the configurations described in the embodiments, and various modifications are possible within the scope of the technical idea of the present invention. Furthermore, some or all of the configurations described in each embodiment may be combined and applied.
[0075] 1: Drift layer, 2: Body layer, 3: Trench, 4A: Gate insulating film, 4B: In-trench insulating film, 5: Gate electrode, 5A: First gate electrode, 5B: Second gate electrode, 6: In-trench electrode, 7: Emitter layer, 8: Contact layer, 9: Interlayer insulating film, 9A: In-trench interlayer insulating film, 10: Buffer layer, 11: Collector layer, 12: Anode layer, 13: Cathode contact layer, 14: Surface electrode, 14A: Emitter electrode, 14B: Anode electrode, 15: Backside electrode, 15A: Collector electrode, 15B: Cathode electrode, 16: Field plate, 17: Block layer, 21: IGBT region, 22: Diode region, 22A: High injection diode region, 22B: Low injection diode region, 23: Termination region, 24: Gate pad, 25: Gate runner, 100: Semiconductor device
Claims
1. A semiconductor device comprising an RC-IGBT having an IGBT region and a diode region on the same chip, wherein the IGBT in the IGBT region has a trench, a gate electrode provided inside the trench, an emitter electrode, a drift layer of a first conductivity type, a body layer of a second conductivity type provided between adjacent trenches, an emitter layer of a first conductivity type having a higher impurity concentration than the drift layer, and a contact layer of a second conductivity type having a higher impurity concentration than the body layer, and the emitter electrode and the body layer are ohmic connected via the contact layer, the diode in the diode region has an anode electrode electrically connected to the emitter electrode, the trench, a cathode of a first conductivity type, and an anode of a second conductivity type provided between adjacent trenches, the diode region has a low-injection diode region in which the anode electrode and the anode are Schottky connected, and a high-injection diode region in which the anode electrode and the anode are ohmic connected via the contact layer. The semiconductor device is characterized in that the high-injection diode region is arranged adjacent to the IGBT region, and the low-injection diode region is arranged between the IGBT region and the high-injection diode region, spaced apart from the IGBT region.
2. The semiconductor device according to claim 1, characterized in that the impurity concentration of the contact layer in the IGBT region and the impurity concentration of the contact layer in the high-injection diode region are substantially the same.
3. The semiconductor device according to claim 1, characterized in that the impurity concentration of the contact layer in the high injection diode region is lower than the impurity concentration of the contact layer in the IGBT region.
4. The semiconductor device according to claim 3, characterized in that the dimension of the high injection diode region in the direction perpendicular to the direction in which the trench extends when viewed from above is greater than or equal to the thickness of the semiconductor layer in which the high injection diode region is formed when viewed in cross-section.
5. The semiconductor device according to claim 1, wherein the IGBT in the IGBT region has a collector electrode and a second-conductivity type collector layer, and the diode in the diode region has a cathode electrode electrically connected to the collector electrode.
6. The semiconductor device according to claim 5, characterized in that the impurity concentration of the portion of the cathode in contact with the cathode electrode in the high injection diode region is substantially the same as the impurity concentration of the portion of the cathode in contact with the cathode electrode in the low injection diode region.
7. The semiconductor device according to claim 5, wherein the high injection diode region is ohmic connected to the cathode electrode and the cathode, and the low injection diode region has a block layer of a second conductivity type between the cathode electrode and the cathode.
8. The semiconductor device according to claim 1, wherein the IGBT in the IGBT region has a first gate electrode provided on one side wall inside the trench, a second gate electrode provided on the other side wall inside the trench, and an insulating film provided inside the trench to insulate between the first gate electrode and the second gate electrode.