Semiconductor Devices

Abstract

The present invention provides a semiconductor device that is provided with: a semiconductor substrate which has an upper surface, a lower surface and a drift region of a first conductivity type; and a buffer region of the first conductivity type, the buffer region being provided between the drift region and the lower surface of the semiconductor substrate, while having a higher doping concentration than the drift region. With respect to this semiconductor device, the buffer region has a first recombination center density peak and a second recombination center density peak which is positioned closer to the upper surface of the semiconductor substrate than the first recombination center density peak; and the integral value of the second recombination center density peak in the depth direction is larger than the integral value of the first recombination center density peak in the depth direction.

Description

[Technical Field]

[0001] The present invention relates to a semiconductor device. [Background technology]

[0002] BACKGROUND ART Conventionally, a technique for forming lattice defects by injecting particles such as helium into a semiconductor device is known (see, for example, Patent Documents 1 and 2). [Prior art document] [Patent documents] [Patent Document 1] WO2019 / 181852 [Patent Document 2] Problems to be solved in WO2017 / 146148

[0003] It is preferable to suppress leakage current caused by generating lattice defects while adjusting carrier lifetime by generating lattice defects.

[0004] To solve the above problems, a first aspect of the present invention provides a semiconductor device. The semiconductor device may include a semiconductor substrate having an upper surface and a lower surface, and a drift region of a first conductivity type. The semiconductor device may include a buffer region of the first conductivity type provided between the drift region and the lower surface of the semiconductor substrate, the buffer region having a doping concentration higher than that of the drift region. In any of the above semiconductor devices, the buffer region may have a first recombination center density peak. In any of the above semiconductor devices, the buffer region may have a second recombination center density peak located closer to the upper surface of the semiconductor substrate than the first recombination center density peak. In any of the above semiconductor devices, an integral value in the depth direction of the second recombination center density peak may be greater than an integral value in the depth direction of the first recombination center density peak.

[0005] In any of the above semiconductor devices, the buffer region may have a third recombination center density peak disposed farther from the lower surface of the semiconductor substrate than the second recombination center density peak. In any of the above semiconductor devices, an integral value of the second recombination center density peak in the depth direction may be greater than an integral value of the third recombination center density peak in the depth direction.

[0006] In any of the above semiconductor devices, the second recombination center density peak may have a peak value greater than both the first recombination center density peak and the third recombination center density peak.

[0007] In any of the above semiconductor devices, the buffer region may have one or more doping concentration peaks in a depth direction of the semiconductor substrate. In any of the above semiconductor devices, the first recombination center density peak may be located between any of the doping concentration peaks and the bottom surface of the semiconductor substrate. In any of the above semiconductor devices, the second recombination center density peak may be located between any of the doping concentration peaks and the top surface of the semiconductor substrate.

[0008] In any of the above semiconductor devices, the one or more doping concentration peaks may include a shallowest doping concentration peak closest to the bottom surface of the semiconductor substrate. In any of the above semiconductor devices, the first recombination center density peak may be located between the shallowest doping concentration peak and the bottom surface of the semiconductor substrate. In any of the above semiconductor devices, the second recombination center density peak may be located between the shallowest doping concentration peak and the top surface of the semiconductor substrate.

[0009] In any of the above semiconductor devices, the buffer region may have three or more doping concentration peaks. In any of the above semiconductor devices, the second recombination center density peak may be located between any two of the doping concentration peaks. In any of the above semiconductor devices, the third recombination center density peak may be located between any two of the doping concentration peaks different from the second recombination center density peak.

[0010] In any of the above semiconductor devices, the three or more doping concentration peaks may include a first top-side doping concentration peak located farthest from the bottom surface of the semiconductor substrate. In any of the above semiconductor devices, the three or more doping concentration peaks may include a second top-side doping concentration peak adjacent to the first top-side doping concentration peak in the depth direction. In any of the above semiconductor devices, the third recombination center density peak may be located closer to the bottom surface of the semiconductor substrate than the second top-side doping concentration peak.

[0011] In any of the above semiconductor devices, a recombination center density peak may not be located between the first top surface side doping concentration peak and the second top surface side doping concentration peak.

[0012] In any of the above semiconductor devices, the doping concentration peak may be a concentration peak of a hydrogen donor.

[0013] In any of the above semiconductor devices, the doping concentration peak closest to the bottom surface may be a phosphorus concentration peak. In any of the above semiconductor devices, the doping concentration peak other than the doping concentration peak closest to the bottom surface may be a hydrogen donor concentration peak.

[0014] In any of the above semiconductor devices, a transistor section and a diode section may be arranged side by side in an arrangement direction on the semiconductor substrate, and the diode section may have the buffer region.

[0015] In any of the semiconductor devices described above, the transistor section may have the buffer region. In any of the semiconductor devices described above, the integrated value of the first recombination center density peak may be the same in the diode section and the transistor section.

[0016] In any of the above semiconductor devices, the first recombination center density peak may be a first helium chemical concentration peak. In any of the above semiconductor devices, the second recombination center density peak may be a second helium chemical concentration peak. In any of the above semiconductor devices, the third recombination center density peak may be a third helium chemical concentration peak.

[0017] In any of the above semiconductor devices, an integral value of the second helium chemical concentration peak in the depth direction is 1×10 11 ( / cm 2 ) or more, 1×10 12 ( / cm 2 ) or less.

[0018] In any of the above semiconductor devices, an integral value of the first helium chemical concentration peak in the depth direction is 1×10 11 ( / cm 2 ) or more, 1×10 12 ( / cm 2 ) or less.

[0019] In any of the above semiconductor devices, an integral value of the third helium chemical concentration peak in the depth direction is 1×10 10 ( / cm 2 ) or more, 1×10 11 ( / cm 2 ) or less.

[0020] A second aspect of the present invention provides a semiconductor device. The semiconductor device may include a semiconductor substrate having an upper surface and a lower surface and a drift region of a first conductivity type. The semiconductor device may include a buffer region of the first conductivity type provided between the drift region and the lower surface of the semiconductor substrate and having a doping concentration higher than that of the drift region. In any of the above semiconductor devices, the buffer region may have two or more doping concentration peaks provided at different positions in the depth direction, including a shallowest doping concentration peak located closest to the lower surface of the semiconductor substrate. In any of the above semiconductor devices, the buffer region may have a plurality of inter-peak regions provided between the lower surface of the semiconductor substrate and the shallowest doping concentration peak, and between two adjacent doping concentration peaks in the depth direction. In any of the above semiconductor devices, the plurality of inter-peak regions may include a first inter-peak region provided with one or more first recombination center density peaks. In any of the above semiconductor devices, the plurality of inter-peak regions may include a second inter-peak region disposed farther from the lower surface of the semiconductor substrate than the first inter-peak region and including one or more second recombination center density peaks. In any of the above semiconductor devices, an integral value of the recombination center density in the depth direction in the second inter-peak region may be greater than an integral value of the recombination center density in the depth direction in the first inter-peak region.

[0021] In any of the above semiconductor devices, the integral value of the second helium chemical concentration peak is 1×10 11 ( / cm 2 ) or more, 1×10 12 ( / cm 2 ) or less.

[0022] In any of the above semiconductor devices, the integral value of the first helium chemical concentration peak is 0.9×10 11 ( / cm 2 ) or more, 0.9 × 10 12 ( / cm 2 ) or less.

[0023] The above summary of the invention does not list all of the necessary features of the present invention, and subcombinations of these features may also constitute inventions. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a top view showing an example of a semiconductor device 100. FIG. [Figure 2] FIG. 2 is an enlarged view of an area D in FIG. [Figure 3] FIG. 3 is a diagram showing an example of an ee cross section in FIG. 2. [Figure 4A] 4 is a diagram showing an example of a doping concentration distribution, a hydrogen chemical concentration distribution, and a helium chemical concentration distribution on the FF line of FIG. 3. [Figure 4B] FIG. 10 is a diagram showing the relationship between the ion implantation depth (Rp) and the acceleration energy required for implantation. [Figure 4C] FIG. 10 is a diagram showing the relationship between the ion implantation depth (Rp) and straggling (ΔRp, standard deviation) in the implantation direction. [Figure 5] FIG. 2 is a diagram showing a first recombination center density peak 220-1 and a second recombination center density peak 220-2. [Figure 6] 10A to 10C are diagrams showing examples of a doping concentration distribution, a hydrogen chemical concentration distribution, a helium chemical concentration distribution, a recombination center density distribution, and an integrated concentration distribution of the doping concentration in the buffer region 20. [Figure 7] FIG. 10 is a diagram showing the relationship between the helium dose and the reverse recovery loss Err at the first recombination center density peak 220-1 and the second recombination center density peak 220-2. [Figure 8] FIG. 10 is a diagram showing the relationship between the helium dose and the leakage current Ices at the first recombination center density peak 220-1 and the second recombination center density peak 220-2. [Figure 9] 1 shows an example of a carrier concentration distribution and a helium chemical concentration distribution in the buffer region 20 of the comparative example. [Figure 10]10A to 10C are diagrams showing other examples of the doping concentration distribution, the hydrogen chemical concentration distribution, the helium chemical concentration distribution, the recombination center density distribution, and the integrated concentration distribution of the doping concentration in the buffer region 20. [Figure 11] FIG. 2 is a diagram illustrating an inter-peak region in the buffer region 20. [Figure 12] 2A to 2C are diagrams illustrating some steps in a manufacturing method of the semiconductor device 100. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention as claimed. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0026] In this specification, one side in a direction parallel to the depth direction of a semiconductor substrate is referred to as "upper" and the other side as "lower." Of the two main surfaces of a substrate, layer, or other member, one surface is referred to as the upper surface and the other surface is referred to as the lower surface. The directions of "upper" and "lower" are not limited to the direction of gravity or the directions when the semiconductor device is mounted.

[0027] In this specification, technical matters may be explained using the Cartesian coordinate axes of the X-axis, Y-axis, and Z-axis. The Cartesian coordinate axes merely identify the relative positions of components and do not limit a specific direction. For example, the Z-axis does not limit the height direction relative to the ground. Note that the +Z-axis direction and the -Z-axis direction are opposite directions. When the Z-axis direction is written without specifying positive or negative, it means the direction parallel to the +Z-axis and -Z-axis.

[0028] In this specification, orthogonal axes parallel to the top and bottom surfaces of the semiconductor substrate are referred to as the X-axis and Y-axis. Furthermore, an axis perpendicular to the top and bottom surfaces of the semiconductor substrate is referred to as the Z-axis. In this specification, the direction of the Z-axis may be referred to as the depth direction. Furthermore, in this specification, the direction parallel to the top and bottom surfaces of the semiconductor substrate, including the X-axis and Y-axis, may be referred to as the horizontal direction.

[0029] The region from the center of the semiconductor substrate in the depth direction to the top surface of the semiconductor substrate may be referred to as the top surface side. Similarly, the region from the center of the semiconductor substrate in the depth direction to the bottom surface of the semiconductor substrate may be referred to as the bottom surface side.

[0030] In this specification, when we say "same" or "equal," it may include cases where there is an error due to manufacturing variations, etc. The error is, for example, within 10%.

[0031] In this specification, the conductivity type of a doped region doped with an impurity is described as P-type or N-type. In this specification, the impurity may particularly mean either an N-type donor or a P-type acceptor, and may be referred to as a dopant. In this specification, doping means introducing a donor or an acceptor into a semiconductor substrate to form a semiconductor exhibiting N-type conductivity or a semiconductor exhibiting P-type conductivity.

[0032] In this specification, the doping concentration refers to the concentration of donors or acceptors in a thermal equilibrium state. In this specification, the net doping concentration refers to the net concentration obtained by adding together the donor concentration as the concentration of positive ions and the acceptor concentration as the concentration of negative ions, taking into account the polarity of the charge. As an example, the donor concentration is N D , acceptor concentration N A Then, the net doping concentration at any point is N D -N A In this specification, the net doping concentration may be simply referred to as the doping concentration.

[0033] Donors have the function of supplying electrons to semiconductors. Acceptors have the function of receiving electrons from semiconductors. Donors and acceptors are not limited to impurities themselves. For example, VOH defects, which are formed by the combination of vacancies (V), oxygen (O), and hydrogen (H) present in semiconductors, function as donors that supply electrons. In addition, Sii-H defects formed by interstitial silicon and hydrogen, and CiOi-H defects formed by interstitial carbon, interstitial oxygen, and hydrogen may also function as donors that supply electrons. In this specification, VOH defects, Sii-H defects, and CiOi-H defects may be referred to as hydrogen donors.

[0034] In this specification, the semiconductor substrate has N-type bulk donors distributed throughout. The bulk donors are donors due to dopants that are uniformly contained in the ingot that is the base of the semiconductor substrate when it is manufactured. In this example, the bulk donors are elements other than hydrogen. The dopants of the bulk donors are, for example, phosphorus, antimony, arsenic, selenium, or sulfur, but are not limited to these. In this example, the bulk donor is phosphorus. The bulk donors are also contained in the P-type region. The semiconductor substrate may be a wafer cut from a semiconductor ingot, or may be a chip obtained by dividing the wafer. The semiconductor ingot may be manufactured by any of the Czochralski method (CZ method), the magnetic field-applied Czochralski method (MCZ method), or the float zone method (FZ method). The ingot in this example is manufactured by the MCZ method. The oxygen concentration in the substrate manufactured by the MCZ method is 1×10 17 ~7×10 17 / cm 3 The oxygen concentration in the substrate manufactured by the FZ method is 1×10 15 ~5×10 16 / cm 3 The higher the oxygen concentration, the easier it is to generate hydrogen donors. The bulk donor concentration may be the chemical concentration of bulk donors distributed throughout the semiconductor substrate, and may be between 90% and 100% of that chemical concentration. Alternatively, a non-doped substrate that does not contain dopants such as phosphorus may be used as the semiconductor substrate. In this case, the bulk donor concentration (D0) of the non-doped substrate is, for example, 1×1010 / cm 3 That's it, 5 x 10 12 / cm 3 The bulk donor concentration (D0) of the non-doped substrate is preferably 1×10 11 / cm 3 The bulk donor concentration (D0) of the non-doped substrate is preferably 5×10 12 / cm 3 The concentrations in the present invention may be values ​​at room temperature, for example, values ​​at 300 K (Kelvin) (approximately 26.9° C.).

[0035] In this specification, when P+ type or N+ type is used, it means that the doping concentration is higher than that of P type or N type, and when P- type or N- type is used, it means that the doping concentration is lower than that of P type or N type. Furthermore, when P++ type or N++ type is used in this specification, it means that the doping concentration is higher than that of P+ type or N+ type. The unit system used in this specification is the SI unit system unless otherwise specified. The unit of length may be expressed in cm, but various calculations may be performed after converting to meters (m).

[0036] As used herein, chemical concentration refers to the atomic density of impurities measured regardless of their electrical activation state. Chemical concentration can be measured, for example, by secondary ion mass spectrometry (SIMS). The net doping concentration can be measured by voltage-capacitance (CV) measurement. The carrier concentration measured by spreading resistance (SR) measurement may also be used as the net doping concentration. Carriers refer to charge carriers, such as electrons or holes. The carrier concentration measured by CV or SR may be a value in a thermal equilibrium state. In addition, since the donor concentration in an N-type region is significantly greater than the acceptor concentration, the carrier concentration in that region may also be used as the donor concentration. Similarly, in a P-type region, the carrier concentration in that region may also be used as the acceptor concentration. In this specification, the doping concentration in an N-type region may also be referred to as the donor concentration, and the doping concentration in a P-type region may also be referred to as the acceptor concentration.

[0037] In addition, when the concentration distribution of the donor, acceptor, or net doping has a peak, the peak value may be taken as the concentration of the donor, acceptor, or net doping in that region. In cases where the concentration of the donor, acceptor, or net doping is almost uniform, the average value of the concentration of the donor, acceptor, or net doping in that region may be taken as the concentration of the donor, acceptor, or net doping. In this specification, the concentration per unit volume is expressed in atoms / cm. 3 , or / cm 3 This unit is used for donor or acceptor concentration or chemical concentration in a semiconductor substrate. The atom notation may be omitted.

[0038] The carrier concentration measured by the SR method may be lower than the donor or acceptor concentration. In the range where current flows when measuring spreading resistance, the carrier mobility of the semiconductor substrate may be lower than the value in the crystalline state. A decrease in carrier mobility occurs when carriers are scattered due to disorder in the crystalline structure caused by lattice defects, etc. The reason for the decrease in carrier concentration is as follows: In the SR method, spreading resistance is measured and the carrier concentration is calculated from the measured spreading resistance. The carrier mobility used here is the mobility in the crystalline state. On the other hand, at locations where lattice defects are introduced, the carrier mobility is decreased, but the carrier concentration is calculated using the carrier mobility in the crystalline state. Therefore, the value obtained is lower than the actual carrier concentration, i.e., the donor or acceptor concentration.

[0039] The donor or acceptor concentration calculated from the carrier concentration measured by the CV or SR method may be lower than the chemical concentration of the element that represents the donor or acceptor. As an example, the donor concentration of phosphorus or arsenic, which act as donors in silicon semiconductors, or the acceptor concentration of boron, which acts as an acceptor, is approximately 99% of the chemical concentration. On the other hand, the donor concentration of hydrogen, which acts as a donor in silicon semiconductors, is approximately 0.1% to 10% of the chemical concentration of hydrogen.

[0040] Fig. 1 is a top view showing an example of a semiconductor device 100. Fig. 1 shows the positions of each component projected onto the top surface of a semiconductor substrate 10. Fig. 1 shows only some of the components of the semiconductor device 100, and some components are omitted.

[0041] The semiconductor device 100 includes a semiconductor substrate 10. The semiconductor substrate 10 is a substrate made of a semiconductor material. As an example, the semiconductor substrate 10 is a silicon substrate. The semiconductor substrate 10 has edges 162 in a top view. In this specification, the term "top view" simply refers to a view from the top surface side of the semiconductor substrate 10. The semiconductor substrate 10 of this example has two pairs of edges 162 facing each other in a top view. In FIG. 1, the X-axis and Y-axis are parallel to either edge 162. The Z-axis is perpendicular to the top surface of the semiconductor substrate 10.

[0042] An active portion 160 is provided on the semiconductor substrate 10. The active portion 160 is a region through which a main current flows in the depth direction between the upper and lower surfaces of the semiconductor substrate 10 when the semiconductor device 100 is in operation. An emitter electrode is provided above the active portion 160, but is not shown in FIG.

[0043] The active section 160 is provided with at least one of a transistor section 70 including a transistor element such as an IGBT, and a diode section 80 including a diode element such as a free wheel diode (FWD). In the example of Fig. 1, the transistor sections 70 and the diode sections 80 are alternately arranged along a predetermined arrangement direction (the X-axis direction in this example) on the upper surface of the semiconductor substrate 10. In another example, the active section 160 may be provided with only one of the transistor section 70 and the diode section 80.

[0044] In FIG. 1, the region where the transistor section 70 is arranged is marked with the symbol "I," and the region where the diode section 80 is arranged is marked with the symbol "F." In this specification, the direction perpendicular to the arrangement direction in a top view may be referred to as the extension direction (the Y-axis direction in FIG. 1). The transistor section 70 and the diode section 80 may each have a longitudinal direction in the extension direction. In other words, the length of the transistor section 70 in the Y-axis direction is greater than the width in the X-axis direction. Similarly, the length of the diode section 80 in the Y-axis direction is greater than the width in the X-axis direction. The extension direction of the transistor section 70 and the diode section 80 may be the same as the longitudinal direction of each trench section, which will be described later.

[0045] The diode section 80 has an N+ type cathode region in a region in contact with the lower surface of the semiconductor substrate 10. In this specification, the region in which the cathode region is provided is referred to as the diode section 80. In other words, the diode section 80 is a region that overlaps with the cathode region in a top view. A P+ type collector region may be provided in a region of the lower surface of the semiconductor substrate 10 other than the cathode region. In this specification, an extension region 81 in which the diode section 80 is extended in the Y-axis direction to a gate wiring (described later) may also be included in the diode section 80. A collector region is provided on the lower surface of the extension region 81.

[0046] The transistor section 70 has a P+ type collector region in a region in contact with the lower surface of the semiconductor substrate 10. In addition, the transistor section 70 has a gate structure periodically arranged on the upper surface side of the semiconductor substrate 10, the gate structure having an N type emitter region, a P type base region, a gate conductive portion, and a gate insulating film.

[0047] The semiconductor device 100 may have one or more pads above the semiconductor substrate 10. The semiconductor device 100 of this example has a gate pad 164. The semiconductor device 100 may also have pads such as an anode pad, a cathode pad, and a current detection pad. Each pad is disposed near an edge 162. The vicinity of the edge 162 refers to the region between the edge 162 and the emitter electrode in a top view. When the semiconductor device 100 is mounted, each pad may be connected to an external circuit via wiring such as a wire.

[0048] A gate potential is applied to the gate pad 164. The gate pad 164 is electrically connected to a conductive portion of the gate trench portion of the active portion 160. The semiconductor device 100 includes a gate wiring that connects the gate pad 164 and the gate trench portion. In FIG. 1, the gate wiring is indicated by diagonal hatching.

[0049] The gate wiring in this example has a peripheral gate wiring 130 and an active side gate wiring 131. The peripheral gate wiring 130 is arranged between the active portion 160 and an edge 162 of the semiconductor substrate 10 in a top view. The peripheral gate wiring 130 in this example surrounds the active portion 160 in a top view. The area surrounded by the peripheral gate wiring 130 in a top view may also be the active portion 160. The peripheral gate wiring 130 is connected to a gate pad 164. The peripheral gate wiring 130 is arranged above the semiconductor substrate 10. The peripheral gate wiring 130 may be a metal wiring containing aluminum or the like.

[0050] The active side gate wiring 131 is provided in the active section 160. By providing the active side gate wiring 131 in the active section 160, it is possible to reduce variations in wiring length from the gate pad 164 for each region of the semiconductor substrate 10.

[0051] The active side gate wiring 131 is connected to the gate trench portion of the active section 160. The active side gate wiring 131 is disposed above the semiconductor substrate 10. The active side gate wiring 131 may be a wiring formed of a semiconductor such as polysilicon doped with impurities.

[0052] The active-side gate wiring 131 may be connected to the peripheral gate wiring 130. In this example, the active-side gate wiring 131 extends in the X-axis direction from one peripheral gate wiring 130 to the other peripheral gate wiring 130 that sandwich the active section 160, crossing the active section 160 at approximately the center in the Y-axis direction. When the active section 160 is divided by the active-side gate wiring 131, the transistor sections 70 and the diode sections 80 may be arranged alternately in the X-axis direction in each divided region.

[0053] The semiconductor device 100 may also include a temperature sensing section (not shown) which is a PN junction diode formed of polysilicon or the like, and a current detecting section (not shown) which simulates the operation of a transistor section provided in the active section 160.

[0054] In the present example, semiconductor device 100 includes an edge termination structure 90 between active section 160 and edge 162 when viewed from above. Edge termination structure 90 in the present example is disposed between peripheral gate wiring 130 and edge 162. Edge termination structure 90 alleviates electric field concentration on the top surface side of semiconductor substrate 10. Edge termination structure 90 may include at least one of a guard ring, a field plate, and a resurf, which are arranged in an annular shape surrounding active section 160.

[0055] 2 is an enlarged view of region D in FIG. 1. Region D is a region including a transistor section 70, a diode section 80, and an active-side gate wiring 131. The semiconductor device 100 of this example includes a gate trench section 40, a dummy trench section 30, a well region 11, an emitter region 12, a base region 14, and a contact region 15 provided inside the upper surface side of a semiconductor substrate 10. The gate trench section 40 and the dummy trench section 30 are each an example of a trench section. The semiconductor device 100 of this example also includes an emitter electrode 52 and an active-side gate wiring 131 provided above the upper surface of the semiconductor substrate 10. The emitter electrode 52 and the active-side gate wiring 131 are provided separately from each other.

[0056] An interlayer insulating film is provided between the emitter electrode 52 and the active-side gate wiring 131 and the upper surface of the semiconductor substrate 10, but is not shown in Fig. 2. In this example, contact holes 54 are provided in the interlayer insulating film so as to penetrate the interlayer insulating film. In Fig. 2, each contact hole 54 is hatched with diagonal lines.

[0057] The emitter electrode 52 is provided above the gate trench portion 40, the dummy trench portion 30, the well region 11, the emitter region 12, the base region 14, and the contact region 15. The emitter electrode 52 contacts the emitter region 12, the contact region 15, and the base region 14 on the upper surface of the semiconductor substrate 10 through a contact hole 54. The emitter electrode 52 is also connected to a dummy conductive portion in the dummy trench portion 30 through a contact hole provided in the interlayer insulating film. The emitter electrode 52 may be connected to the dummy conductive portion of the dummy trench portion 30 at the tip of the dummy trench portion 30 in the Y-axis direction.

[0058] The active side gate wiring 131 is connected to the gate trench portion 40 through a contact hole provided in the interlayer insulating film. The active side gate wiring 131 may be connected to the gate conductive portion of the gate trench portion 40 at the tip portion 41 of the gate trench portion 40 in the Y-axis direction. The active side gate wiring 131 is not connected to the dummy conductive portion in the dummy trench portion 30.

[0059] The emitter electrode 52 is made of a material containing metal. FIG. 2 shows the area where the emitter electrode 52 is provided. For example, at least a portion of the emitter electrode 52 is made of aluminum or an aluminum-silicon alloy, such as AlSi or AlSiCu. The emitter electrode 52 may have a barrier metal made of titanium, a titanium compound, or the like below the region made of aluminum or the like. Furthermore, the contact hole may have a plug formed by embedding tungsten or the like so as to contact the barrier metal and aluminum or the like.

[0060] The well region 11 is provided so as to overlap with the active-side gate wiring 131. The well region 11 is also provided so as to extend by a predetermined width into an area where it does not overlap with the active-side gate wiring 131. In this example, the well region 11 is provided away from the end of the contact hole 54 in the Y-axis direction toward the active-side gate wiring 131. The well region 11 is a region of a second conductivity type having a doping concentration higher than that of the base region 14. In this example, the base region 14 is P- type, and the well region 11 is P+ type.

[0061] Each of the transistor section 70 and the diode section 80 has a plurality of trench sections arranged in the arrangement direction. In the transistor section 70 of this example, one or more gate trench sections 40 and one or more dummy trench sections 30 are alternately provided along the arrangement direction. In the diode section 80 of this example, a plurality of dummy trench sections 30 are provided along the arrangement direction. In the diode section 80 of this example, no gate trench section 40 is provided.

[0062] The gate trench portion 40 in this example may have two straight line portions 39 (parts of the trench that are linear along the extension direction) that extend along an extension direction perpendicular to the arrangement direction, and a tip portion 41 that connects the two straight line portions 39. The extension direction in FIG. 2 is the Y-axis direction.

[0063] At least a part of the tip portion 41 is preferably curved in a top view. By connecting the ends of the two straight portions 39 in the Y-axis direction with each other by the tip portion 41, electric field concentration at the ends of the straight portions 39 can be alleviated.

[0064] In the transistor section 70, the dummy trench section 30 is provided between each of the linear portions 39 of the gate trench section 40. One or more dummy trench sections 30 may be provided between each of the linear portions 39. The dummy trench section 30 may have a linear shape extending in the extension direction, and may have a linear section 29 and an end portion 31, similar to the gate trench section 40. The semiconductor device 100 shown in FIG. 2 includes both linear dummy trench sections 30 without end portions 31 and dummy trench sections 30 with end portions 31.

[0065] The diffusion depth of the well region 11 may be deeper than the depths of the gate trench portion 40 and the dummy trench portion 30. The ends of the gate trench portion 40 and the dummy trench portion 30 in the Y-axis direction are provided in the well region 11 when viewed from above. In other words, at the ends of each trench portion in the Y-axis direction, the bottom of each trench portion in the depth direction is covered by the well region 11. This makes it possible to alleviate electric field concentration at the bottom of each trench portion.

[0066] A mesa portion is provided between each trench portion in the arrangement direction. The mesa portion refers to a region inside the semiconductor substrate 10 that is sandwiched between the trench portions. As an example, the upper end of the mesa portion is the upper surface of the semiconductor substrate 10. The depth position of the lower end of the mesa portion is the same as the depth position of the lower end of the trench portion. In this example, the mesa portion is provided on the upper surface of the semiconductor substrate 10, extending in the extension direction (Y-axis direction) along the trench. In this example, the transistor portion 70 is provided with a mesa portion 60, and the diode portion 80 is provided with a mesa portion 61. In this specification, the mesa portion simply referred to as a mesa portion refers to both the mesa portion 60 and the mesa portion 61.

[0067] A base region 14 is provided in each mesa portion. Of the base regions 14 exposed on the upper surface of the semiconductor substrate 10 in the mesa portion, the region closest to the active-side gate wiring 131 is referred to as the base region 14-e. While FIG. 2 shows the base region 14-e at one end of each mesa portion in the extension direction, a base region 14-e is also provided at the other end of each mesa portion. Each mesa portion may be provided with at least one of a first-conductivity-type emitter region 12 and a second-conductivity-type contact region 15 in a region sandwiched between the base regions 14-e in a top view. In this example, the emitter region 12 is N+ type, and the contact region 15 is P+ type. The emitter region 12 and the contact region 15 may be provided between the base region 14 and the upper surface of the semiconductor substrate 10 in the depth direction.

[0068] The mesa portion 60 of the transistor portion 70 has an emitter region 12 exposed on the upper surface of the semiconductor substrate 10. The emitter region 12 is provided in contact with the gate trench portion 40. The mesa portion 60 in contact with the gate trench portion 40 may be provided with a contact region 15 exposed on the upper surface of the semiconductor substrate 10.

[0069] The contact regions 15 and the emitter regions 12 in the mesa portion 60 are each provided from one trench portion to the other trench portion in the X-axis direction. As an example, the contact regions 15 and the emitter regions 12 in the mesa portion 60 are alternately arranged along the extension direction of the trench portions (the Y-axis direction).

[0070] In another example, the contact region 15 and the emitter region 12 of the mesa portion 60 may be provided in a stripe shape along the extension direction (Y-axis direction) of the trench portion. For example, the emitter region 12 is provided in a region in contact with the trench portion, and the contact region 15 is provided in a region sandwiched between the emitter regions 12.

[0071] The mesa portion 61 of the diode portion 80 does not have an emitter region 12. A base region 14 and a contact region 15 may be provided on the upper surface of the mesa portion 61. In the region sandwiched between the base regions 14-e on the upper surface of the mesa portion 61, a contact region 15 may be provided in contact with each of the base regions 14-e. In the region sandwiched between the contact regions 15 on the upper surface of the mesa portion 61, a base region 14 may be provided. The base region 14 may be disposed in the entire region sandwiched between the contact regions 15.

[0072] A contact hole 54 is provided above each mesa portion. The contact hole 54 is arranged in a region sandwiched between the base regions 14-e. In this example, the contact holes 54 are provided above the contact region 15, the base region 14, and the emitter region 12. The contact holes 54 are not provided in regions corresponding to the base region 14-e and the well region 11. The contact hole 54 may be arranged in the center of the arrangement direction (X-axis direction) of the mesa portions 60.

[0073] In the diode section 80, an N+ type cathode region 82 is provided in a region adjacent to the lower surface of the semiconductor substrate 10. A P+ type collector region 22 may be provided in a region of the lower surface of the semiconductor substrate 10 where the cathode region 82 is not provided. The cathode region 82 and the collector region 22 are provided between the lower surface 23 of the semiconductor substrate 10 and the buffer region 20. In FIG. 2, the boundary between the cathode region 82 and the collector region 22 is indicated by a dotted line.

[0074] The cathode region 82 is disposed away from the well region 11 in the Y-axis direction. This ensures a distance between the cathode region 82 and a P-type region (well region 11) that has a relatively high doping concentration and is formed deep, thereby improving the breakdown voltage. In this example, the end of the cathode region 82 in the Y-axis direction is disposed farther from the well region 11 than the end of the contact hole 54 in the Y-axis direction. In another example, the end of the cathode region 82 in the Y-axis direction may be disposed between the well region 11 and the contact hole 54.

[0075] Fig. 3 is a diagram showing an example of an ee cross section in Fig. 2. The ee cross section is an XZ plane passing through the emitter region 12 and the cathode region 82. In this cross section, the semiconductor device 100 of this example has a semiconductor substrate 10, an interlayer insulating film 38, an emitter electrode 52, and a collector electrode 24.

[0076] The interlayer insulating film 38 is provided on the upper surface of the semiconductor substrate 10. The interlayer insulating film 38 is a film including at least one layer of an insulating film such as silicate glass doped with impurities such as boron or phosphorus, a thermal oxide film, and other insulating films. The interlayer insulating film 38 is provided with the contact hole 54 described with reference to FIG. 2.

[0077] The emitter electrode 52 is provided above the interlayer insulating film 38. The emitter electrode 52 passes through a contact hole 54 in the interlayer insulating film 38 and contacts the upper surface 21 of the semiconductor substrate 10. The collector electrode 24 is provided on the lower surface 23 of the semiconductor substrate 10. The emitter electrode 52 and the collector electrode 24 are made of a metal material such as aluminum. In this specification, the direction connecting the emitter electrode 52 and the collector electrode 24 (the Z-axis direction) is referred to as the depth direction.

[0078] The semiconductor substrate 10 has an N-type or N-type drift region 18. The drift region 18 is provided in each of the transistor section 70 and the diode section 80.

[0079] In the mesa portion 60 of the transistor section 70, an N+ type emitter region 12 and a P- type base region 14 are provided in this order from the upper surface 21 side of the semiconductor substrate 10. A drift region 18 is provided below the base region 14. An N+ type accumulation region 16 may be provided in the mesa portion 60. The accumulation region 16 is disposed between the base region 14 and the drift region 18.

[0080] The emitter region 12 is exposed on the upper surface 21 of the semiconductor substrate 10 and is provided in contact with the gate trench portion 40. The emitter region 12 may be in contact with the trench portions on both sides of the mesa portion 60. The emitter region 12 has a higher doping concentration than the drift region 18.

[0081] The base region 14 is provided below the emitter region 12. In this example, the base region 14 is provided in contact with the emitter region 12. The base region 14 may be in contact with the trench portions on both sides of the mesa portion 60.

[0082] The accumulation region 16 is provided below the base region 14. The accumulation region 16 is an N+ type region with a higher doping concentration than the drift region 18. That is, the accumulation region 16 has a higher donor concentration than the drift region 18. By providing the high-concentration accumulation region 16 between the drift region 18 and the base region 14, the carrier injection enhancement effect (IE effect) can be enhanced and the on-voltage can be reduced. The accumulation region 16 may be provided so as to cover the entire lower surface of the base region 14 in each mesa portion 60.

[0083] A P-type base region 14 is provided in the mesa portion 61 of the diode section 80 in contact with the upper surface 21 of the semiconductor substrate 10. A drift region 18 is provided below the base region 14. An accumulation region 16 may be provided below the base region 14 in the mesa portion 61.

[0084] In each of the transistor section 70 and the diode section 80, an N+ type buffer region 20 may be provided below the drift region 18. The doping concentration of the buffer region 20 is higher than that of the drift region 18. The buffer region 20 may have a concentration peak with a higher doping concentration than the drift region 18. The doping concentration of the concentration peak refers to the doping concentration at the apex of the concentration peak. The doping concentration of the drift region 18 may be the average value of the doping concentration in a region where the doping concentration distribution is approximately flat.

[0085] The buffer region 20 may have two or more concentration peaks in the depth direction (Z-axis direction) of the semiconductor substrate 10. The concentration peak of the buffer region 20 may be located at the same depth as the chemical concentration peak of hydrogen (protons) or phosphorus, for example. The buffer region 20 may function as a field stop layer that prevents the depletion layer extending from the lower end of the base region 14 from reaching the P+ type collector region 22 and the N+ type cathode region 82. In this specification, the depth position of the upper end of the buffer region 20 is referred to as Zf. The depth position Zf may be a position where the doping concentration is higher than the doping concentration of the drift region 18.

[0086] In the transistor section 70, a P+ type collector region 22 is provided below the buffer region 20. The acceptor concentration of the collector region 22 is higher than the acceptor concentration of the base region 14. The collector region 22 may contain the same acceptor as the base region 14, or may contain a different acceptor. The acceptor of the collector region 22 is, for example, boron.

[0087] In the diode section 80, an N+ type cathode region 82 is provided below the buffer region 20. The donor concentration of the cathode region 82 is higher than that of the drift region 18. The donor of the cathode region 82 is, for example, hydrogen or phosphorus. Note that the elements that serve as the donor and acceptor in each region are not limited to the above-mentioned examples. The collector region 22 and the cathode region 82 are exposed on the lower surface 23 of the semiconductor substrate 10 and connected to the collector electrode 24. The collector electrode 24 may be in contact with the entire lower surface 23 of the semiconductor substrate 10. The emitter electrode 52 and the collector electrode 24 are formed of a metal material such as aluminum.

[0088] One or more gate trenches 40 and one or more dummy trenches 30 are provided on the top surface 21 of the semiconductor substrate 10. Each trench extends from the top surface 21 of the semiconductor substrate 10 through the base region 14 to reach the drift region 18. In regions where at least one of the emitter region 12, the contact region 15, and the accumulation region 16 is provided, each trench also extends through these doped regions to reach the drift region 18. The trenches extending through the doped regions do not necessarily mean that the trenches are formed after the doped regions are formed. The trenches also include those in which the doped regions are formed between the trenches after the trenches are formed.

[0089] As described above, the transistor section 70 is provided with the gate trench section 40 and the dummy trench section 30. The diode section 80 is provided with the dummy trench section 30, but is not provided with the gate trench section 40. In this example, the boundary between the diode section 80 and the transistor section 70 in the X-axis direction is the boundary between the cathode region 82 and the collector region 22.

[0090] The gate trench portion 40 has a gate trench provided on the upper surface 21 of the semiconductor substrate 10, a gate insulating film 42, and a gate conductive portion 44. The gate insulating film 42 is provided to cover the inner wall of the gate trench. The gate insulating film 42 may be formed by oxidizing or nitriding the semiconductor on the inner wall of the gate trench. The gate conductive portion 44 is provided inside the gate trench and on the inner side of the gate insulating film 42. In other words, the gate insulating film 42 insulates the gate conductive portion 44 from the semiconductor substrate 10. The gate conductive portion 44 is formed of a conductive material such as polysilicon.

[0091] The gate conductive portion 44 may be provided to be longer in the depth direction than the base region 14. The gate trench portion 40 in this cross section is covered with an interlayer insulating film 38 on the upper surface 21 of the semiconductor substrate 10. The gate conductive portion 44 is electrically connected to the gate wiring. When a predetermined gate voltage is applied to the gate conductive portion 44, a channel is formed by an electron inversion layer in the surface layer of the interface of the base region 14 that contacts the gate trench portion 40.

[0092] The dummy trench portion 30 may have the same structure as the gate trench portion 40 in the cross section. The dummy trench portion 30 includes a dummy trench, a dummy insulating film 32, and a dummy conductive portion 34 provided on the upper surface 21 of the semiconductor substrate 10. The dummy conductive portion 34 is electrically connected to the emitter electrode 52. The dummy insulating film 32 covers the inner wall of the dummy trench. The dummy conductive portion 34 is provided inside the dummy trench and is provided further inward than the dummy insulating film 32. The dummy insulating film 32 insulates the dummy conductive portion 34 from the semiconductor substrate 10. The dummy conductive portion 34 may be formed of the same material as the gate conductive portion 44. For example, the dummy conductive portion 34 is formed of a conductive material such as polysilicon. The dummy conductive portion 34 may have the same length in the depth direction as the gate conductive portion 44.

[0093] In this example, the gate trench 40 and the dummy trench 30 are covered with an interlayer insulating film 38 on the upper surface 21 of the semiconductor substrate 10. The bottoms of the dummy trench 30 and the gate trench 40 may have a downwardly convex curved shape (a curved shape in cross section). In this specification, the depth position of the lower end of the gate trench 40 is defined as Zt.

[0094] An upper surface-side lifetime killer may be provided on the upper surface 21 side of the semiconductor substrate 10. The upper surface-side lifetime killer is a recombination center such as a lattice defect formed locally in the depth direction. In this example, the recombination center density peak 210 in the recombination center density distribution in the depth direction is the upper surface-side lifetime killer. In each figure, the peak position of the lifetime killer density distribution in the depth direction is schematically indicated by a cross. In this specification, the peak position will be described as the position of the lifetime killer. The crosses are arranged discretely in the X-axis direction, but unless otherwise specified, the lifetime killers are arranged uniformly in the X-axis direction.

[0095] The recombination center density peak 210 can be formed by injecting particles such as helium from the upper surface 21 of the semiconductor substrate 10 to a predetermined depth. A concentration peak of particles such as helium may be located at the same depth as the recombination center density peak 210. The recombination center density peak 210 may be located below each trench portion. Furthermore, the recombination center density peak 210 is preferably located at a position that does not overlap with the gate trench portion 40 in a top view. This allows the recombination center density peak 210 to be formed by injecting particles such as helium without damaging the gate insulating film 42. In this example, the recombination center density peak 210 is located throughout the diode portion 80 in a top view. While the recombination center density peak 210 in FIG. 3 is not located in the transistor portion 70, in other examples, the recombination center density peak 210 may be located in a partial region of the transistor portion 70.

[0096] A bottom-side lifetime killer is provided on the bottom surface 23 side of the semiconductor substrate 10. The bottom-side lifetime killer may be formed by injecting particles such as helium from the bottom surface 23 side of the semiconductor substrate 10. In this example, a recombination center density peak 220 is the bottom-side lifetime killer. A plurality of recombination center density peaks 220 may be arranged at different positions in the depth direction. In the example of FIG. 3, a first recombination center density peak 220-1 and a second recombination center density peak 220-2 are arranged at different depth positions. However, the recombination center density peaks 220 may be arranged at three or more depth positions. A helium chemical concentration peak may be arranged at the same depth position as each of the recombination center density peaks 220.

[0097] Two or more recombination center density peaks 220 may be provided in the buffer region 20. This makes it easier to control the distribution of lifetime killers in the buffer region 20. Therefore, the carrier lifetime can be controlled with high precision.

[0098] The recombination center density peak 220 may be provided over the entire diode section 80 in a top view. The recombination center density peak 220 may be provided over the entire transistor section 70 in a top view. The recombination center density peak 220 may be provided over the entire active section 160 in a top view, or may be provided over the entire semiconductor substrate 10 in a top view. The first recombination center density peak 220-1 and the second recombination center density peak 220-2 may be provided in the same range in a top view.

[0099] Fig. 4A is a diagram showing an example of the doping concentration distribution, hydrogen chemical concentration distribution, helium chemical concentration distribution, and recombination center density distribution along the FF line in Fig. 3. In Fig. 4A, the central position in the depth direction of the semiconductor substrate 10 is designated Zc. That is, the region on the upper surface 21 side of the semiconductor substrate 10 is the region between the upper surface 21 and the central position Zc, and the region on the lower surface 23 side is the region between the lower surface 23 and the central position Zc.

[0100] The emitter region 12 includes an N-type dopant such as phosphorus. The base region 14 includes a P-type dopant such as boron. The accumulation region 16 includes an N-type dopant such as phosphorus or hydrogen. The doping concentration distribution may have concentration peaks in the emitter region 12, the base region 14, and the accumulation region 16, respectively.

[0101] The drift region 18 is a region in which the doping concentration is approximately flat. The doping concentration Dd of the drift region 18 may be the same as the bulk donor concentration of the semiconductor substrate 10, or may be higher than the bulk donor concentration.

[0102] In this example, the buffer region 20 has multiple doping concentration peaks 25-1, 25-2, 25-3, and 25-4 in its doping concentration distribution. Each doping concentration peak 25 may be a hydrogen donor peak formed by locally implanting hydrogen ions. Alternatively, each doping concentration peak 25 may be formed by implanting an N-type dopant such as phosphorus. Alternatively, the N-type dopant of doping concentration peak 25-1 closest to the lower surface 23 may be phosphorus, and the N-type dopant of doping concentration peaks 25-1, 25-2, and 25-3 other than doping concentration peak 25-1 may be hydrogen. In other words, doping concentration peak 25-1 may be a phosphorus concentration peak, and the doping concentration peaks 25 other than doping concentration peak 25-1 may be hydrogen donor concentration peaks. In this case, the hydrogen chemical concentration peak 103-1 at the depth position of doping concentration peak 25-1 may be absent. The collector region 22 includes a P-type dopant such as boron. The cathode region 82 shown in FIG. 3 includes an N-type dopant such as phosphorus. In the buffer region 20, the doping concentration minus the doping concentration Dd of the drift region 18 may be used as the hydrogen donor concentration.

[0103] The hydrogen chemical concentration distribution in this example has multiple localized hydrogen chemical concentration peaks 103 in the buffer region 20. By implanting hydrogen ions into the buffer region 20, hydrogen donors are formed, consisting of hydrogen, lattice defects, and the like, which function as donors. In this example, the hydrogen chemical concentration peaks 103 are located at the same depth as the doping concentration peak 25. Having two peaks at the same depth means that the apex of one peak is located within the full width at half maximum of the other peak. If the concentration of the hydrogen chemical concentration peak 103 is not sufficiently high, a clear doping concentration peak 25 may not be observed at the same depth as the hydrogen chemical concentration peak 103. In this example, the hydrogen chemical concentration drops sharply immediately after entering the drift region 18 from the buffer region 20. Therefore, almost no hydrogen donors are formed in the drift region 18. Alternatively, hydrogen may diffuse deep into the drift region 18 to form hydrogen donors. In this case, the doping concentration in the drift region 18 is higher than the bulk donor concentration.

[0104] Buffer region 20 has two or more helium chemical concentration peaks 221 disposed at different positions in the depth direction of semiconductor substrate 10. In this example, a first helium chemical concentration peak 221-1 and a second helium chemical concentration peak 221-2 are provided in buffer region 20. Second helium chemical concentration peak 221-2 is disposed farther from lower surface 23 than first helium chemical concentration peak 221-1.

[0105] As described above, recombination center density peaks 220 are formed near each helium chemical concentration peak 221. That is, a first helium chemical concentration peak 221-1 and a second helium chemical concentration peak 221-2 are present at positions overlapping with a first recombination center density peak 220-1 and a second recombination center density peak 220-2. "Peaks overlap" may refer to the apex of one peak being located within the full width at half maximum of the other peak.

[0106] In this example, a first recombination center density peak 220-1 and a second recombination center density peak 220-2 are located in the buffer region 20. The second recombination center density peak 220-2 is located farther from the lower surface 23 (i.e., closer to the upper surface 21) than the first recombination center density peak 220-1. The recombination center density peak 220 may be a recombination center that promotes carrier recombination. The recombination center may be a lattice defect. The lattice defect may be primarily a vacancy, such as a monovacancy (V) or a divacancy (VV), or may be a dislocation, an interstitial atom, or a transition metal. For example, an atom adjacent to a vacancy has a dangling bond. In a broad sense, lattice defects may also include donors and acceptors. However, in this specification, vacancy-based lattice defects may be referred to as vacancy-type lattice defects, vacancy-type defects, or simply lattice defects. In this specification, lattice defects, which are recombination centers that contribute to carrier recombination, may be simply referred to as recombination centers or lifetime killers. The lifetime killers may be formed by implanting helium ions into the semiconductor substrate 10. Since the lifetime killers formed by implanting helium may be terminated by hydrogen present in the buffer region 20, the depth position of the lifetime killer density peak may not coincide with the depth position of the helium chemical concentration peak 221.

[0107] By injecting helium into two or more depth positions in the buffer region 20, it becomes easier to control the density distribution of the recombination center density peak 220 in the buffer region 20. 3 He or 4 He may be injected. 3 He is a helium isotope containing two protons and one neutron. 4 He is a helium isotope containing two protons and two neutrons.

[0108] 3 He or 4By implanting He without passing through a buffer material (such as aluminum) at the lowest acceleration energy that uniquely determines the implantation depth, the half-width of the helium chemical concentration peak in the depth direction can be reduced.

[0109] FIG. 4B is a diagram showing the relationship between the ion implantation depth (Rp) and the acceleration energy required for implantation. In this example, helium ions are implanted directly into the silicon semiconductor substrate 10 without going through a buffer material. The horizontal axis in FIG. 4B is the range Rp (μm), and the vertical axis is the acceleration energy E (eV) required for implantation. In FIG. 4B, 3 The example of He is shown by the solid line, 4 The example of He is shown by the dashed line.

[0110] log 10 (Rp) to x, log 10 Let (E) be y. 3 For He, the relationship between the range Rp and the acceleration energy E can be given by equation (1). y=4.52505E-03x 6 - 4.71471E-02x 5 + 1.67185E-01x 4 - 1.72038E-01x 3 - 2.92723E-01x 2 + 1.39782E+00x + 5.33858E+00...Formula (1) In addition, EA is 10 -A and E+A is 10 A is.

[0111] Let E be the acceleration energy calculated by substituting the actual range Rp' during manufacturing of the semiconductor device 100 into equation (1). If the actual acceleration energy E' during manufacturing is within ±20% of the acceleration energy E calculated from equation (1), 3 It can be considered that He is being used.

[0112] 4 For He, the relationship between the range Rp and the acceleration energy E can be given by equation (2). y=2.90157E-03x 6 - 3.66593E-02x 5 + 1.59363E-01x 4 - 2.31938E-01x 3 -2.00999E-01x 2 + 1.45891E+00x + 5.27160E+00...Formula (2) If the actual acceleration energy E' at the time of manufacture is within ±20% of the acceleration energy E calculated from equation (2) using the actual range Rp', 4 It can be considered that He is being used.

[0113] As shown in FIG. 4B, the range Rp is set to a boundary value of 8 μm to 10 μm, and when the range Rp is equal to or greater than the boundary value, 4 The acceleration energy of He is 3 The acceleration energy is about 10% higher than that of He. When the range Rp is below the boundary value, 3 He The acceleration energy of 4 This is about 10% higher than the acceleration energy of He. It is presumed that the balance between the electronic stopping power and the nuclear stopping power changes depending on the number of neutrons in the isotope. For example, when the range Rp is 10 μm or less, 4 He can be used. This allows helium ions to be implanted with an acceleration energy that is approximately 10% smaller. When the range Rp is greater than 10 μm, 3 He may be used.

[0114] FIG. 4C is a diagram showing the relationship between the ion implantation depth (Rp) and straggling in the implantation direction (ΔRp, standard deviation). In this example, the implantation direction is the depth direction of the semiconductor substrate 10. In this example, helium ions are also implanted directly into the silicon semiconductor substrate 10 without going through a buffer material. The horizontal axis in FIG. 4C is the range Rp (μm), and the vertical axis is the straggling ΔRp (μm). In FIG. 4C, 3 The example of He is shown by the solid line, 4 The example of He is shown by the dashed line.

[0115] The straggling ΔRp may be calculated assuming that the helium concentration distribution is a Gaussian distribution. For example, the straggling ΔRp may be the distance (distribution width) between two points where the concentration is 0.60653 times the concentration peak value, or the distance between two points where the concentration is 0.6 times the concentration peak value. If the minimum value or the like between adjacent concentration peaks is greater than 0.6 times the concentration peak value, the distance between the inflection points of the minimum value or the like in the concentration distribution may be used as the straggling ΔRp.

[0116] log 10 (Rp) to x, log 10 Let (ΔRp) be y. 3 For He, the relationship between the range Rp and the straggling ΔRp can be given by equation (3). y=5.00395E-04x 6 + 9.91651E-03x 5 - 9.76015E-02x 4 + 2.12587E-01x 3 + 1.30994E-01x 2 + 2.25458E-01x - 8.59463E-01...Formula (3)

[0117] The straggling calculated by substituting the actual range Rp' during manufacturing of the semiconductor device 100 into equation (3) is defined as ΔRp. If the actual straggling ΔRp' during manufacturing is within ±20% of the straggling ΔRp calculated from equation (3), 3 It can be considered that He is used. The actual straggling ΔRp′ preferably does not include the amount of helium diffusion due to thermal annealing. The actual straggling ΔRp′ may be the value measured after helium injection and before thermal annealing, or may be the value measured after thermal annealing minus the amount of helium diffusion.

[0118] 4 For He, the relationship between the range Rp and the straggling ΔRp can be given by equation (4). y=3.10234E-03x 6 - 9.20762E-03x 5-6.13612E-02x 4 +2.34304E-01x 3 + 3.88591E-02x 2 + 2.22955E-01x - 8.01967E-01 ··· Formula (4) If the actual straggling ΔRp' at the time of manufacture is within ±20% of the straggling ΔRp calculated from equation (4) using the actual range Rp', 4 It can be considered that He is used. It is preferable that the actual straggling ΔRp′ does not include the amount of helium diffused by thermal annealing.

[0119] As shown in FIG. 4C, the range Rp is set to a boundary value of 10 to 20 μm, and when the range Rp is equal to or less than the boundary value, 3 He straggling ΔRp is 4 It is about 10% smaller than the straggling ΔRp of He. When the range Rp is greater than the boundary value, 3 He and 4 The straggling ΔRp is almost the same for He and He. This is presumably due to the change in the balance between the electronic stopping power and the nuclear stopping power depending on the number of neutrons in the isotope.

[0120] As an example, if the range Rp is 20 μm or less, 3 He may be used. This allows for a straggling ΔRp that is about 10% smaller. Alternatively, if a difference of about 10% in the straggling ΔRp has a sufficiently small effect on the helium chemical concentration distribution or electrical characteristics, then even if the range Rp is 20 μm or less, 3 He and 4 In this case, the helium atoms implanted into the semiconductor substrate 10 are 3 He is fine, 4 He is also fine.

[0121] As an example 4When He is implanted, the full width at half maximum of the helium chemical concentration peak 221 is 1 μm or less. The full width at half maximum of the helium chemical concentration peak 221 may be 0.5 μm or less. By arranging multiple helium chemical concentration peaks 221 with small full width at half maximum in the buffer region 20, the shape of the distribution of the recombination center density peak 220 can be easily controlled. In addition, it is possible to prevent hydrogen donors formed by implanting helium from being distributed over a wide range. This makes it possible to prevent the doping concentration distribution in the buffer region 20 from fluctuating over a wide range.

[0122] Furthermore, by providing a plurality of helium chemical concentration peaks 221, it is possible to maintain a high total concentration of the recombination center density peak 220. This makes it possible to shorten the carrier lifetime and suppress the tail current when the semiconductor device 100 is turned off, for example.

[0123] In addition, 3 When the acceleration energy E of He is approximately 20 MeV or more (the range Rp is 270 μm or more), the straggling ΔRp becomes 10 μm or more. 4 When the acceleration energy E of He is approximately 21 MeV or more (range Rp is 250 μm or more), the straggling ΔRp becomes 10 μm or more. In this case, the full width at half maximum of the helium chemical concentration peak 221 cannot be made sufficiently small compared to the width in the depth direction of the buffer region 20. As a result, hydrogen donors are formed over a wide range in the buffer region 20, causing fluctuations in the doping concentration distribution. This can cause localized concentration of an electric field in the buffer region 20 during a short circuit, reducing the short circuit current withstand capability. In response to this, by reducing the full width at half maximum of the helium chemical concentration peak 221, it becomes easier to maintain the short circuit current withstand capability. Therefore, 3 He and 4 When any of He is implanted, the acceleration energy E may be 20 MeV or less, or may be 10 MeV or less. Alternatively, the acceleration energy E of at least one or two or more helium chemical concentration peaks 221 among the multiple helium chemical concentration peaks 221 may be 10 MeV or less, or may be 5 MeV or less.

[0124] FIG. 5 is a diagram showing a first recombination center density peak 220-1 and a second recombination center density peak 220-2. The peak value of the first recombination center density peak 220-1 is denoted by Pk1, and the peak value of the second recombination center density peak 220-2 is denoted by Pk2. The integral value of the first recombination center density peak 220-1 in the depth direction is denoted by S1, and the integral value of the second recombination center density peak 220-2 in the depth direction is denoted by S2. The integral value S1 may be a value obtained by integrating a range (hatched range in FIG. 5) in the first recombination center density peak 220-1 where the recombination center density is equal to or greater than α×Pk1. The coefficient α is a real number greater than 0 and less than 1. For example, when α=0.5, the integral value S1 is a value obtained by integrating the first recombination center density peak 220-1 within the range of the full width at half maximum. Similarly, the integral value S2 may be a value obtained by integrating the range where the recombination center density is equal to or greater than α×Pk2 at the second recombination center density peak 220-2. The coefficient α may be the same for each recombination center density peak 220. The coefficient α may be 0.5, 0.1, 0.01, or another value. The distribution of the recombination center density may be calculated from the distribution of the carrier lifetime or may be measured by other methods. The distribution of the recombination center density may be, for example, the vacancy concentration measured by positron annihilation spectroscopy. Alternatively, the atomic density of helium atoms measured by SIMS may be used as the recombination center density.

[0125] In this example, the integral value S2 of the second recombination center density peak 220-2 is larger than the integral value S1 of the first recombination center density peak 220-1. Each integral value can be adjusted by the dose of a charged particle beam such as helium implanted at each depth position. By increasing the integral value S2, the reverse recovery loss Err can be significantly reduced. The integral value S2 may be two or more times, five or more times, or ten or more times the integral value S1.

[0126] In this example, the peak value Pk2 of the second recombination center density peak 220-2 may be greater than the peak value Pk1 of the first recombination center density peak 220-1. At least one of the conditions of integral value S2 > integral value S1 and peak value Pk2 > peak value Pk1 may be satisfied, or both may be satisfied. The peak value Pk2 may be two or more times, five or more times, or ten or more times the peak value Pk1.

[0127] The peak value of the first helium chemical concentration peak 221-1 may be smaller than, equal to, or larger than the peak value of the second helium chemical concentration peak 221-2. Recombination centers formed by helium irradiation may be terminated by hydrogen and become hydrogen donors. Therefore, even if the peak value of the first helium chemical concentration peak 221-1 is equal to or larger than the peak value of the second helium chemical concentration peak 221-2, the integral value S2 may be greater than the integral value S1, or the peak value Pk2 may be greater than the peak value Pk1, depending on the difference in hydrogen concentration at each position.

[0128] 6 is a diagram showing an example of the doping concentration distribution, hydrogen chemical concentration distribution, helium chemical concentration distribution, recombination center density distribution, and integrated concentration distribution of the doping concentration in the buffer region 20. Each concentration distribution may be the same as the concentration distribution described in FIG. 4A. The integrated concentration distribution in this example is the integral value ( / cm 2 ) distribution. When the P-type layer is formed so as to include the lower end of the trench portion, the lower end position Zt may be the position of the PN junction between the P-type layer and the drift region 18 located on the lower surface 23 side of the semiconductor substrate 10. That is, the integrated concentration distribution in this example is the integral value ( / cm 2 ) can be considered as the distribution.

[0129] The doping concentration distribution in this example has one or more doping concentration peaks 25-1, 25-2, 25-3, and 25-4, in order from the lower surface 23 side of the semiconductor substrate 10. Doping concentration peak 25-1 is an example of the shallowest doping concentration peak closest to the lower surface 23 among the doping concentration peaks 25 in the buffer region 20. Doping concentration peak 25-4 is an example of the deepest doping concentration peak located farthest from the lower surface 23. The depth positions of the respective doping concentration peaks 25 are designated Zd1, Zd2, Zd3, and Zd4, in order from the lower surface 23 side. Each depth position Zd indicates the distance from the lower surface 23. Note that any of the doping concentration peaks 25 does not need to be a distinct peak. For example, an inflection point (kink) in the slope of the doping concentration distribution may be defined as the doping concentration peak 25. Doping concentration peak 25-1 may be the doping concentration peak 25 with the largest concentration value. Doping concentration peak 25-2 may be the doping concentration peak 25 with the second highest concentration value. Doping concentration peak 25-3 may be the doping concentration peak 25 with the lowest concentration value. Doping concentration peak 25-4 may be the doping concentration peak 25 with a higher concentration than doping concentration peak 25-3.

[0130] The hydrogen chemical concentration distribution in this example has hydrogen chemical concentration peaks 103-1, 103-2, 103-3, and 103-4, in order from the bottom surface 23 side of the semiconductor substrate 10. The depth positions of the respective hydrogen chemical concentration peaks 103 are designated Zh1, Zh2, Zh3, and Zh4, in order from the bottom surface 23 side. Each depth position Zh indicates the distance from the bottom surface 23. Depth position Zdk may be the same position as depth position Zhk, where k is an integer from 1 to 4. Hydrogen chemical concentration peak 103-1 may be the hydrogen chemical concentration peak 103 with the highest concentration value. Hydrogen chemical concentration peak 103-2 may be the hydrogen chemical concentration peak 103 with the second highest concentration value. Hydrogen chemical concentration peak 103-3 may be the hydrogen chemical concentration peak 103 with the lowest concentration value. Hydrogen chemical concentration peak 103-4 may be a hydrogen chemical concentration peak 103 with a higher concentration than hydrogen chemical concentration peak 103-3.

[0131] The helium chemical concentration distribution in this example has, in order from the lower surface 23 side of the semiconductor substrate 10, a first helium chemical concentration peak 221-1 and a second helium chemical concentration peak 221-2. The recombination center density distribution in this example has, in order from the lower surface 23 side of the semiconductor substrate 10, a first recombination center density peak 220-1 and a second recombination center density peak 220-2. The depth positions of the respective helium chemical concentration peaks 221 are designated Zk1 and Zk2 in order from the lower surface 23 side. The depth positions of the respective recombination center density peaks 220 may also be designated Zk1 and Zk2 in order from the lower surface 23 side. Each depth position Zk indicates the distance from the lower surface 23.

[0132] The first recombination center density peak 220-1 is located between one of the doping concentration peaks 25 and the lower surface 23 of the semiconductor substrate 10, and the second recombination center density peak 220-2 is located between the doping concentration peak 25 and the upper surface 21. In this example, the first recombination center density peak 220-1 is located closer to the lower surface 23 than the doping concentration peak 25-1, and the second recombination center density peak 220-2 is located closer to the upper surface 21 than the doping concentration peak 25-1. In a more specific example, the second recombination center density peak 220-2 is located between the doping concentration peak 25-1 and the doping concentration peak 25-2. In another example, the second recombination center density peak 220-2 may be located between the doping concentration peak 25-2 and the doping concentration peak 25-3, or may be located between the doping concentration peak 25-3 and the doping concentration peak 25-4. That is, only one doping concentration peak 25 may be disposed between the first recombination center density peak 220-1 and the second recombination center density peak 220-2, or multiple doping concentration peaks 25 may be disposed. As will be described later, by disposing the first recombination center density peak 220-1 closer to the lower surface 23 than the doping concentration peak 25-1, it is possible to suppress the leakage current and the reverse recovery loss. Furthermore, by disposing the second recombination center density peak 220-2 closer to the upper surface 21 than the doping concentration peak 25-1, it is possible to significantly reduce the reverse recovery loss.

[0133] When the carrier concentration distribution measured by the SR method is taken as the doping concentration distribution, the doping concentration distribution may have a valley 35 at the same depth as any of the helium chemical concentration peaks 221. The valley 35 is a region where the doping concentration exhibits a minimum value. In this example, the recombination center density peak 220 is located at the same depth as the helium chemical concentration peak 221, so the carrier mobility at that position decreases. This reduces the carrier concentration as described above. In the following drawings showing the doping concentration distribution, the valley 35 is omitted at the same depth as the helium chemical concentration peak 221, but the valley 35 may be located there.

[0134] The depletion layer edge position Ze is the position where the integral concentration obtained by integrating the net doping concentration of the drift region 18 and the buffer region 20 from the upper end of the drift region 18 toward the lower surface 23 of the semiconductor substrate 10 reaches the critical integral concentration n c The depletion layer edge position Ze is sometimes referred to as the critical concentration depth position Ze. In this specification, when a forward bias is applied between the collector electrode 24 and the emitter electrode 52 and avalanche breakdown occurs, and the area from the upper end of the drift region 18 to a specific position in the buffer region 20 is depleted, the value obtained by integrating the net doping concentration from the upper end of the drift region 18 to that specific position is referred to as the critical integral concentration. In other words, the depletion layer edge position Ze is the position closest to the lower surface 23 that the depletion layer reaches when avalanche breakdown occurs, as the depletion layer spreads from the lower end of the base region 14 toward the lower surface 23 of the semiconductor substrate 10. The critical integral concentration n c depends on the constituent atoms of the semiconductor substrate 10. When the semiconductor substrate 10 is made of silicon, the critical integral concentration n c is approximately 1.2 x 10 12 / cm 2 The depletion layer edge position Ze may be the position closest to the bottom surface 23 that the depletion layer reaches when the rated voltage of the semiconductor device 100 is applied between the collector electrode 24 and the emitter electrode 52. By locating the depletion layer edge position Ze in the buffer region 20, the depletion layer can be prevented from reaching the collector region 22 or the cathode region 82.

[0135] 3, the upper end of the drift region 18 is the boundary position between the drift region 18 and the accumulation region 16. If it is difficult to determine the boundary position between the drift region 18 and the accumulation region 16, the lower end position Zt of the trench portion may be taken as the lower end of the drift region 18. Furthermore, if the drift region 18 and the base region 14 are in contact with each other, the position of the PN junction at the boundary between the drift region 18 and the base region 14 is the upper end of the drift region 18.

[0136] The depletion layer edge position Ze may be located between the first recombination center density peak 220-1 and the second recombination center density peak 220-2. The depletion layer edge position Ze may be located between the doping concentration peak 25-1 and the doping concentration peak 25-2. The integral value of the recombination center density on the upper surface 21 side of the critical concentration depth position Ze may be greater than, equal to, or smaller than the integral value of the recombination center density on the lower surface 23 side of the critical concentration depth position Ze. In this example, the integral value of the recombination center density on the upper surface 21 side of the critical concentration depth position Ze is greater than the integral value of the recombination center density on the lower surface 23 side of the critical concentration depth position Ze. The integral value of the helium chemical concentration on the upper surface 21 side of the critical concentration depth position Ze may be greater than, equal to, or smaller than the integral value of the helium chemical concentration on the lower surface 23 side of the critical concentration depth position Ze. In this example, the integral value of the helium chemical concentration on the upper surface 21 side of the critical concentration depth position Ze is greater than the integral value of the helium chemical concentration on the lower surface 23 side of the critical concentration depth position Ze.

[0137] 7 is a graph showing the relationship between the helium dose at the first recombination center density peak 220-1 and the second recombination center density peak 220-2 and the reverse recovery loss Err. The arrangement of the first recombination center density peak 220-1 and the second recombination center density peak 220-2 is the same as the example shown in FIG. 4A.

[0138] Increasing the helium dose increases the integral value S and peak value Pk of each recombination center density peak 220. The reverse recovery loss Err indicates the loss during reverse recovery of the diode section 80. In Fig. 7, circles indicate the results of changing the helium dose of the first recombination center density peak 220-1 while maintaining the helium dose of the second recombination center density peak 220-2, and crosses indicate the results of changing the helium dose of the second recombination center density peak 220-2 while maintaining the helium dose of the first recombination center density peak 220-1.

[0139] Increasing the helium dose at any of the recombination center density peaks 220 increases the recombination center density. This shortens the carrier lifetime during reverse recovery in the diode section 80, reducing reverse recovery loss. In particular, since recombination centers are formed in the buffer region 20, the tail current during reverse recovery in the diode section 80 can be reduced, or the duration during which the tail current flows can be shortened. This reduces reverse recovery loss. As shown in FIG. 7 , increasing the helium dose for the second recombination center density peak 220-2 rather than the first recombination center density peak 220-1 can significantly reduce reverse recovery loss. This is presumably because, during the duration during which the tail current flows in the diode section 80 during reverse recovery, more carriers remain on the upper surface 21 side than the doping concentration peak 25-1. Therefore, increasing the integral value of the second recombination center density peak 220-2 efficiently reduces the tail current and shortens the duration during which the tail current flows. Therefore, by making the integral value S2 or peak value Pk2 of the second recombination center density peak 220-2 larger than the integral value S1 or peak value Pk1 of the first recombination center density peak 220-1, the reverse recovery loss can be significantly reduced.

[0140] 8 is a graph showing the relationship between the helium dose at the first recombination center density peak 220-1 and the second recombination center density peak 220-2 and the leakage current Ices. The arrangement of the first recombination center density peak 220-1 and the second recombination center density peak 220-2 is the same as in the example shown in FIG. 4A. The measurement conditions for the circle and cross plots in FIG. 8 are the same as in the example in FIG. 7.

[0141] The leakage current Ices is also referred to as the collector-emitter cutoff current. The leakage current Ices is the leakage current between the collector and the emitter when a predetermined voltage is applied between the collector and the emitter with the gate and the emitter short-circuited (i.e., the transistor section 70 is in an off state). When recombination centers are formed in the semiconductor substrate 10, the leakage current may increase via the recombination centers.

[0142] As shown in Figure 8, increasing the helium dose at the second recombination center density peak 220-2 tends to increase the leakage current Ices. On the other hand, increasing the helium dose at the first recombination center density peak 220-1 hardly increases the leakage current Ices. Therefore, by providing the first recombination center density peak 220-1, it is possible to reduce the reverse recovery loss Err while suppressing an increase in the leakage current Ices. As described above, by appropriately adjusting the ratio between the integral values ​​of the first recombination center density peak 220-1 and the second recombination center density peak 220-2, it is possible to significantly reduce the reverse recovery loss while suppressing an increase in the leakage current Ices.

[0143] On the other hand, the buffer region 20 may be provided in both the diode section 80 and the transistor section 70. The integral value S1 of the first recombination center density peak 220-1 may be the same in the diode section 80 and the transistor section 70. The buffer region 20 may have the same structure in the diode section 80 and the transistor section 70. In this case, if the integral value S1 or the peak value Pk1 of the first recombination center density peak 220-1 is made too large, carrier injection from the collector region 22 of the transistor section 70 is hindered, the carrier injection enhancement effect (IE effect) is reduced, and the on-voltage of the transistor section 70 increases. In contrast, by making the integral value S1 or the peak value Pk1 of the first recombination center density peak 220-1 smaller than the integral value S2 or the peak value Pk2 of the second recombination center density peak 220-2, the characteristics of the diode section 80 can be improved while suppressing an increase in the on-voltage of the transistor section 70.

[0144] 9 shows an example of the carrier concentration distribution and helium chemical concentration distribution in the buffer region 20 of the comparative example. 3 There is only one peak of the helium chemical concentration formed by implanting He. In addition, in Figure 9, the carrier concentration distribution without helium implantation is shown by a solid line, and the carrier concentration distribution with helium implantation is shown by a dashed line. The carrier concentration distribution without helium implantation is similar to the doping concentration distribution in Figure 6 etc.

[0145] In this example, a single helium chemical concentration peak is provided in the buffer region 20. This makes it difficult to control the lifetime killer distribution. Furthermore, if the half-width of the helium chemical concentration peak is large, hydrogen donors formed by recombination centers and hydrogen are distributed over a wide area, resulting in a wider fluctuation in the carrier concentration distribution than in the case where helium is not implanted. In particular, if the helium distribution extends to the upper end of the buffer region 20, a convex portion appears in the carrier concentration distribution, which may cause the characteristics of the semiconductor device 100 to deviate from the design values, such as a decrease in avalanche resistance. In contrast, in the examples of FIGS. 1 to 8, multiple helium chemical concentration peaks are provided in the buffer region 20, allowing for precise adjustment of the lifetime killer distribution. Furthermore, by narrowing the half-width of the helium chemical concentration peak, fluctuations in the carrier concentration distribution over a wide area can be suppressed.

[0146] 10 is a diagram showing another example of the doping concentration distribution, the hydrogen chemical concentration distribution, the helium chemical concentration distribution, the recombination center density distribution, and the integral concentration distribution of the doping concentration in the buffer region 20. The buffer region 20 of this example has a third helium chemical concentration peak 221-3 and a third recombination center 1 to 9 in that it further includes a third helium chemical concentration peak 221-3 and a third recombination center The density peak 220-3 is located at the depth position Zk3. center The peak value of the density peak 220-3 is designated as Pk3.

[0147] The third recombination center density peak 220-3 is located farther from the lower surface 23 of the semiconductor substrate 10 than the second recombination center density peak 220-2. An integral value S2 of the second recombination center density peak 220-2 in the depth direction is greater than an integral value S3 of the third recombination center density peak 220-3 in the depth direction. As in the example described with reference to FIG. 5 , the integral value S3 is a value obtained by integrating a range in the third recombination center density peak 220-3 where the recombination center density is equal to or greater than α×Pk3. The coefficient α may be the same as that of the other recombination center density peaks 220.

[0148] The further the recombination center density peak 220 is located from the lower surface 23, the greater the reduction in reverse recovery loss Err when the integral value S is increased. Therefore, providing the third recombination center density peak 220-3 can further reduce the reverse recovery loss Err. On the other hand, if the integral value S of the recombination center density peak 220 located farther from the lower surface 23 is increased too much, the formation of hydrogen donors may be promoted, resulting in a convex portion in the carrier density distribution near the upper end of the buffer region 20, as described with reference to FIG. 9 . By making the integral value S3 of the third recombination center density peak 220-3 smaller than the integral value S2 of the second recombination center density peak 220-2, the reverse recovery loss Err can be efficiently reduced while suppressing the occurrence of a convex portion in the carrier density distribution. The integral value S2 may be at least two times, at least five times, or at least ten times the integral value S3.

[0149] The peak value Pk2 of the second recombination center density peak 220-2 may be greater than the peak value Pk3 of the third recombination center density peak 220-3. At least one of the conditions of integral value S2 > integral value S3 and peak value Pk2 > peak value Pk3 may be satisfied, or both may be satisfied. The peak value Pk2 may be two or more times, five or more times, or ten or more times the peak value Pk3.

[0150] Peak value Pk of the second recombination center density peak 220-2 2may be greater than both the peak value Pk1 of the first recombination center density peak 220-1 and the peak value Pk3 of the third recombination center density peak 220-3. The integral value S2 of the second recombination center density peak 220-2 may be greater than both the integral value S1 of the first recombination center density peak 220-1 and the integral value S3 of the third recombination center density peak 220-3.

[0151] The integral value S1 of the first recombination center density peak 220-1 and the integral value S3 of the third recombination center density peak 220-3 may be larger or may be the same. The peak value Pk1 of the first recombination center density peak 220-1 and the peak value Pk3 of the third recombination center density peak 220-3 may be larger or may be the same.

[0152] The buffer region 20 of this example has three or more doping concentration peaks 25. The second recombination center density peak 220-2 may be located between any two doping concentration peaks. In the example of FIG. 10, the second recombination center density peak 220-2 is located between the doping concentration peak 25-1 and the doping concentration peak 25-2. The third recombination center density peak 220-3 may be located between any two doping concentration peaks 25 other than the second recombination center density peak 220-2. In the example of FIG. 10, the third recombination center density peak 220-3 is located between the doping concentration peak 25-2 and the doping concentration peak 25-3. In other words, only one doping concentration peak 25 may be located between the second recombination center density peak 220-2 and the third recombination center density peak 220-3. In another example, a plurality of doping concentration peaks 25 may be arranged between the second recombination center density peak 220-2 and the third recombination center density peak 220-3.

[0153] In this example, doping concentration peak 25-4 located farthest from bottom surface 23 of semiconductor substrate 10 is defined as the first top-side doping concentration peak, and doping concentration peak 25-3 adjacent to doping concentration peak 25-4 in the depth direction is defined as the second top-side doping concentration peak. In other words, doping concentration peak 25-4 and doping concentration peak 25-3 are the two doping concentration peaks located closest to top surface 21 in buffer region 20.

[0154] The third recombination center density peak 220-3 may be located closer to the lower surface 23 of the semiconductor substrate 10 than the second upper surface side doping concentration peak (doping concentration peak 25-3). The recombination center density peak 220 does not have to be located between the first upper surface side doping concentration peak (doping concentration peak 25-4) and the second upper surface side doping concentration peak (doping concentration peak 25-3). With this configuration, it is possible to suppress the occurrence of a convex portion (see FIG. 9) in the carrier concentration distribution near the upper end of the buffer region 20.

[0155] The helium chemical concentration peak 221 may be considered as the recombination center density peak 220. The helium chemical concentration in the buffer region 20 may be treated as the recombination center density in the buffer region 20. In each example herein, the integral value S1 of the first helium chemical concentration peak 221-1 is 1×10 11 ( / cm 2 ) or more, 1×10 12 ( / cm 2 In each example herein, the integral S2 of the second helium chemical concentration peak 221-2 may be 1×10 11 ( / cm 2 ) or more, 1×10 12 ( / cm 2 In each example herein, the third helium chemical concentration may be less than or equal to 1000 ppm. peak The integral value S3 of 221-3 is 1×10 10 ( / cm 2 ) or more, 1×10 11 ( / cm 2) or less. Even if the ranges of integrals of the respective peaks are the same or overlap, the integrals of the respective peaks may be different. Within the range of integrals of the respective peaks, the integral S2 of the second helium chemical concentration peak 221-2 may be greater than the integral S1 of the first helium chemical concentration peak 221-1. Within the range of integrals of the respective peaks, the integral S2 of the second helium chemical concentration peak 221-2 may be greater than the integral S1 of the third helium chemical concentration peak 221-3. 3 Bigger is better.

[0156] The dose of helium ions for the first helium chemical concentration peak 221-1 is 1×10 11 ions / cm 2 That's it, 1 x 10 12 ions / cm 2 The second helium chemical concentration may be: peak The dose of helium ions for 221-2 is 1×10 11 ions / cm 2 That's it, 1 x 10 12 ions / cm 2 It may be the following: Third helium chemical concentration peak 221-3 The dose of helium ions for 10 ions / cm 2 That's it, 1 x 10 11 ions / cm 2 The buffer region 20 may further include a fourth helium chemical concentration peak closer to the upper surface 21 than the third helium chemical concentration peak 221-3. The integral of the fourth helium chemical concentration peak is smaller than the integral of the third helium chemical concentration peak 221-3. The dose of helium ions for the fourth helium chemical concentration peak may be 0.5×10 10 ions / cm 2 That's it, 5 x 10 10 ions / cm 2 It may be the following:

[0157] In each example herein, the peak value Pk1 of the first helium chemical concentration peak 221-1 is 1×10 15 ( / cm 3) or more, 1×10 17 ( / cm 3 In each example herein, the peak value Pk2 of the second helium chemical concentration peak 221-2 may be 1×10 15 ( / cm 3 ) or more, 1×10 17 ( / cm 3 In each example herein, the peak value Pk3 of the third helium chemical concentration peak 221-3 may be 1×10 14 ( / cm 3 ) or more, 1×10 16 ( / cm 3 ) or less. The full width at half maximum of second helium chemical concentration peak 221-2 may be greater than the full width at half maximum of first helium chemical concentration peak 221-1. In this case, even if the integral value S2 of second helium chemical concentration peak 221-2 is greater than the integral value S1 of first helium chemical concentration peak 221-1, the peak value Pk2 of second helium chemical concentration peak 221-2 may be smaller than the peak value Pk1 of first helium chemical concentration peak 221-1.

[0158] 11 is a diagram illustrating inter-peak regions in the buffer region 20. The doping concentration distribution, hydrogen chemical concentration distribution, helium chemical concentration distribution, recombination center density distribution, and integrated concentration distribution of the doping concentration in the buffer region 20 may be the same as or different from the examples in FIGS. 1 to 10. In this example, the region (R1) between the lower surface 23 of the semiconductor substrate 10 and the doping concentration peak 25-1, the regions (R2 to R4) between two adjacent doping concentration peaks 25 in the depth direction, and the region (R5) between the doping concentration peak 25-4 and the drift region 18 are referred to as inter-peak regions.

[0159] The buffer region 20 of this example has a first inter-peak region R1 in which one or more first recombination center density peaks 220-1 are provided, and a second inter-peak region R2 in which one or more second recombination center density peaks 220-2 are provided. The second inter-peak region R2 is disposed farther from the lower surface 23 of the semiconductor substrate 10 than the first inter-peak region R1. The second inter-peak region R2 may be disposed adjacent to the first inter-peak region R1.

[0160] The integral value S2' of the recombination center density in the depth direction in the second inter-peak region R2 is greater than the integral value S1' of the recombination center density in the depth direction in the first inter-peak region R1. When a single recombination center density peak 220 is located in each inter-peak region as in the example shown in FIG. 4A etc., the integral value in each inter-peak region is the integral value of the recombination center density peak 220.

[0161] As shown in Fig. 11, multiple recombination center density peaks 220 may be provided in any inter-peak region. In the example of Fig. 11, two second recombination center density peaks 220-2 are provided in the second inter-peak region R2. In this case, the integral value S2' in the second inter-peak region R2 is the sum of the integral values ​​S2 of the two second recombination center density peaks 220-2. The relationship between the integral value S2' and the integral value S1' may be the same as the relationship between the integral value S2 and the integral value S1 described with reference to Figs. 1 to 10.

[0162] The integral values ​​S2 of the respective second recombination center density peaks 220-2 may be different from each other or may be the same. The integral value S2 of one second recombination center density peak 220-2 may be smaller than, the same as, or larger than the integral value S1 of one first recombination center density peak 220-1. The integral value S2 of one second recombination center density peak 220-2 may be smaller than, the same as, or larger than the integral value S3 of one third recombination center density peak 220-3.

[0163] The buffer region 20 of this example may have a third inter-peak region R3 in which one or more third recombination center density peaks 220-3 are provided. The third inter-peak region R3 is disposed farther from the lower surface 23 of the semiconductor substrate 10 than the second inter-peak region R2. The third inter-peak region R3 may be disposed adjacent to the second inter-peak region R2.

[0164] The integral S2' of the recombination center density in the depth direction in the second inter-peak region R2 is greater than the integral S3' of the recombination center density in the depth direction in the third inter-peak region R3. The relationship between the integral S2' and the integral S3' may be the same as the relationship between the integral S2 and the integral S3 described with reference to Figures 1 to 10. The relationship between the integral S1' and the integral S3' may be the same as the relationship between the integral S1 and the integral S3 described with reference to Figures 1 to 10.

[0165] 1 to 10, this configuration can reduce the reverse recovery loss Err while suppressing an increase in the leakage current Ices. The number of second recombination center density peaks 220-2 in the second inter-peak region R2 may be greater than the number of first recombination center density peaks 220-1 in the first inter-peak region R1. The number of second recombination center density peaks 220-2 in the second inter-peak region R2 may be greater than the number of third recombination center density peaks 220-3 in the third inter-peak region R3.

[0166] The positions of the first inter-peak region R1, the second inter-peak region R2, and the third inter-peak region R3, in which the first recombination center density peak 220-1, the second recombination center density peak 220-2, and the third recombination center density peak 220-3 are provided, are the same as those in any of the embodiments described with reference to Fig. 1 to Fig. 10. In the example of Fig. 11, the first inter-peak region R1, the second inter-peak region R2, and the third inter-peak region R3 are arranged adjacent to each other, but they may also be arranged apart.

[0167] 12 is a diagram showing some steps in the manufacturing method of semiconductor device 100. In this example, in upper surface side structure formation step S1200, a structure on the upper surface 21 side of semiconductor substrate 10 is formed. The structure on the upper surface 21 side may include at least one of each doped region on the upper surface 21 side of semiconductor substrate 10, such as emitter region 12, base region 14, and accumulation region 16. The structure on the upper surface 21 side may include each trench portion. The structure on the upper surface 21 side may include a structure above the upper surface 21 of semiconductor substrate 10, such as emitter electrode 52. The structure on the upper surface 21 side may include an edge termination structure portion 90.

[0168] Next, in substrate grinding step S1202, the lower surface 23 of the semiconductor substrate 10 is ground to thin the semiconductor substrate 10. In S1202, the semiconductor substrate 10 may be thinned to a thickness according to the breakdown voltage that the semiconductor device 100 should have.

[0169] Next, in bottom surface region formation step S1204, a bottom surface doped region is formed in the semiconductor substrate 10. The bottom surface doped region is a doped region that contacts an electrode formed on the bottom surface 23, such as the collector electrode 24, which will be formed in a later step. The bottom surface doped region may include at least one of the cathode region 82 and the collector region 22.

[0170] Next, in a first ion implantation step S1206, ions for forming the buffer region 20 are implanted into the semiconductor substrate 10. In S1206, ions may be implanted from the lower surface 23 of the semiconductor substrate 10 into the region where the buffer region 20 is to be formed. In S1206, hydrogen ions (e.g., protons) or donor ions such as phosphorus ions may be implanted.

[0171] Next, in a first annealing step S1208, the semiconductor substrate 10 is thermally annealed. In S1208, the semiconductor substrate 10 may be placed in an electric furnace to anneal the entire semiconductor substrate 10 (or wafer). The annealing temperature in S1208 may be 320°C or higher and 420°C or lower. In S1208, annealing may be performed in an atmosphere containing hydrogen and nitrogen.

[0172] Next, in a second ion implantation step S1210, ions for forming the recombination center density peak 220 are implanted into the semiconductor substrate 10. In S1210, ions may be implanted from the lower surface 23 of the semiconductor substrate 10. In S1210, hydrogen ions such as protons or helium ions may be implanted. In this example, helium ions are implanted.

[0173] In S1210, the recombination center density peak 220 described with reference to FIGS. 4A to 11 is formed. By sequentially changing the acceleration energy of helium ions or the like, the recombination center density peak 220 can be formed at a plurality of positions in the depth direction. In S1210, helium ions or the like may be implanted at the plurality of positions in the depth direction in order from the position closest to the lower surface 23, or may be implanted at the position farthest from the lower surface 23. In this example, helium ions are implanted in order from the position farthest from the lower surface 23. Furthermore, in S1210, ions may be implanted at the recombination center density peak 220 in order from the recombination center density peak 220 with the largest dose, or may be implanted at the recombination center density peak 220 with the smallest dose.

[0174] Next, in a second annealing step S1212, the semiconductor substrate 10 is thermally annealed. In S1212, the semiconductor substrate 10 may be placed in an electric furnace to anneal the entire semiconductor substrate 10 (or wafer). The annealing temperature in S1212 may be lower than the annealing temperature in S1208. The annealing temperature in S1212 may be 300°C or higher and 400°C or lower. In S1212, annealing may be performed in a nitrogen atmosphere or an atmosphere containing hydrogen and nitrogen.

[0175] S1212 may be performed each time helium ions or the like are implanted at one depth position in S1210, or may be performed each time helium ions or the like are implanted at multiple depth positions. A set of steps S1210 and S1212 may be repeated multiple times (S1213).

[0176] Next, in lower surface electrode formation step S1214, an electrode is formed in contact with the lower surface 23. In S1214, a collector electrode 24 may be formed. Through these steps, the semiconductor device 100 can be formed.

[0177] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0178] It should be noted that the order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before," "prior to," etc., and that the processes can be performed in any order unless the output of a previous process is used in a subsequent process. Even if the operational flow in the claims, specifications, and drawings is described using "first," "next," etc. for convenience, this does not mean that the processes must be performed in this order. [Explanation of symbols]

[0179] 10 semiconductor substrate, 11 well region, 12 emitter region, 14 base region, 15 contact region, 16 accumulation region, 18 drift region, 20 buffer region, 21 upper surface, 22 collector region, 23 lower surface, 24 collector electrode, 25 doping concentration peak, 29 straight line portion, 30 dummy trench portion, 31 tip portion, 32 dummy insulating film, 34 dummy conductive portion, 35 valley portion, 38 interlayer insulating film, 39 straight line portion, 40 gate trench portion, 41 tip portion, 42 ··Gate insulating film, 44··Gate conductive portion, 52··Emitter electrode, 54··Contact hole, 60, 61··Mesa portion, 70··Transistor portion, 80··Diode portion, 81···Extension region, 82···Cathode region, 90··Edge termination structure portion, 100··Semiconductor device, 103···Hydrogen chemical concentration peak, 130···Periphery gate wiring, 131···Active side gate wiring, 160···Active portion, 162···Edge, 164···Gate pad, 210···Recombination center density peak, 220···Recombination center density peak, 221···Helium chemical concentration peak

Claims

1. A semiconductor substrate having an upper surface and a lower surface and a drift region of a first conductivity type; a buffer region of a first conductivity type provided between the drift region and the lower surface of the semiconductor substrate, the buffer region having a doping concentration higher than that of the drift region; Equipped with The buffer area is a first recombination center density peak; a second recombination center density peak disposed closer to the upper surface of the semiconductor substrate than the first recombination center density peak; a third recombination center density peak disposed farther from the lower surface of the semiconductor substrate than the second recombination center density peak; and a semiconductor device in which an integral value of the second recombination center density peak in the depth direction is greater than an integral value of the first recombination center density peak in the depth direction and an integral value of the third recombination center density peak in the depth direction;

2. A semiconductor substrate having an upper surface and a lower surface and a drift region of a first conductivity type; a buffer region of a first conductivity type provided between the drift region and the lower surface of the semiconductor substrate, the buffer region having a doping concentration higher than that of the drift region; Equipped with The buffer area is a first recombination center density peak; a second recombination center density peak disposed closer to the upper surface of the semiconductor substrate than the first recombination center density peak; and an integral value of the second recombination center density peak in the depth direction is greater than an integral value of the first recombination center density peak in the depth direction, The peak value of the second recombination center density peak is greater than the peak value of the first recombination center density peak. Semiconductor device.

3. A semiconductor substrate having an upper surface and a lower surface and a drift region of a first conductivity type; a buffer region of a first conductivity type provided between the drift region and the lower surface of the semiconductor substrate and having a doping concentration higher than that of the drift region; a base region of a second conductivity type provided between the drift region and the upper surface of the semiconductor substrate; Equipped with The buffer area is a first recombination center density peak; a second recombination center density peak disposed closer to the upper surface of the semiconductor substrate than the first recombination center density peak; and an integral value of the second recombination center density peak in the depth direction is greater than an integral value of the first recombination center density peak in the depth direction, When an avalanche breakdown occurs, a depletion layer edge position, which is the lowest position reached by a depletion layer spreading from the lower end of the base region toward the lower surface of the semiconductor substrate, is located between the first recombination center density peak and the second recombination center density peak. Semiconductor device.

4. The peak value of the second recombination center density peak is greater than both the peak value of the first recombination center density peak and the peak value of the third recombination center density peak. The semiconductor device according to claim 1 .

5. the buffer region has one or more doping concentration peaks in a depth direction of the semiconductor substrate; the first recombination center density peak is located between any of the doping concentration peaks and the lower surface of the semiconductor substrate; the second recombination center density peak is located between any one of the doping concentration peaks and the top surface of the semiconductor substrate. The semiconductor device according to claim 1 .

6. the one or more doping concentration peaks include a shallowest doping concentration peak closest to the bottom surface of the semiconductor substrate; the first recombination center density peak is located between the shallowest doping concentration peak and the lower surface of the semiconductor substrate; The second recombination center density peak is located between the shallowest doping concentration peak and the top surface of the semiconductor substrate. The semiconductor device according to claim 5 .

7. the buffer region has three or more doping concentration peaks; the second recombination center density peak is located between any two of the doping concentration peaks, The third recombination center density peak is disposed between any two of the doping concentration peaks different from the second recombination center density peak. The semiconductor device according to claim 6.

8. The three or more doping concentration peaks are a first top-side doping concentration peak located furthest from the bottom surface of the semiconductor substrate; a second upper surface side doping concentration peak adjacent to the first upper surface side doping concentration peak in a depth direction; Including, The third recombination center density peak is located closer to the lower surface of the semiconductor substrate than the second upper surface doping concentration peak. The semiconductor device according to claim 7 .

9. No recombination center density peak is located between the first upper surface side doping concentration peak and the second upper surface side doping concentration peak. The semiconductor device according to claim 8 .

10. The doping concentration peak is a concentration peak of a hydrogen donor. The semiconductor device according to claim 5 .

11. the doping concentration peak closest to the lower surface is a phosphorus concentration peak; The doping concentration peaks other than the doping concentration peak closest to the lower surface are concentration peaks of hydrogen donors. The semiconductor device according to claim 5 .

12. a transistor portion and a diode portion are arranged side by side in an arrangement direction on the semiconductor substrate, The diode portion has the buffer region. The semiconductor device according to claim 1 .

13. the transistor portion has the buffer region, The integral value of the first recombination center density peak is the same in the diode section and the transistor section. The semiconductor device according to claim 12.

14. the first recombination center density peak is a first helium chemical concentration peak; the second recombination center density peak is a second helium chemical concentration peak; The third recombination center density peak is a third helium chemical concentration peak. The semiconductor device according to claim 1 or 4 to 9.

15. The integral value of the second helium chemical concentration peak in the depth direction is 1×10 １１ ( / cm ２ ) or more, 1 x 10 １２ ( / cm ２ ) or less The semiconductor device according to claim 14.

16. The integral value of the first helium chemical concentration peak in the depth direction is 1×10 １１ ( / cm ２ ) or more, 1 x 10 １２ ( / cm ２ ) or less The semiconductor device according to claim 15.

17. The integral value of the third helium chemical concentration peak in the depth direction is 1×10 １０ ( / cm ２ ) or more, 1 x 10 １１ ( / cm ２ ) or less The semiconductor device according to claim 16.

18. The integral value of the second recombination center density peak in the depth direction is at least twice the integral value of the first recombination center density peak in the depth direction. The semiconductor device according to claim 1 .

19. The peak value of the second helium chemical concentration peak is greater than the peak value of the first helium chemical concentration peak. The semiconductor device according to claim 14.

20. A semiconductor substrate having an upper surface and a lower surface, the semiconductor substrate having a drift region of a first conductivity type; a buffer region of a first conductivity type provided between the drift region and the lower surface of the semiconductor substrate, the buffer region having a doping concentration higher than that of the drift region; Equipped with The buffer area is two or more doping concentration peaks provided at different positions in a depth direction, including a shallowest doping concentration peak located closest to the lower surface of the semiconductor substrate; a plurality of inter-peak regions provided between the lower surface of the semiconductor substrate and the shallowest doping concentration peak and between two adjacent doping concentration peaks in a depth direction; and The plurality of inter-peak regions are a first inter-peak region provided with one or more first recombination center density peaks; a second inter-peak region disposed farther from the lower surface of the semiconductor substrate than the first inter-peak region and including one or more second recombination center density peaks; Including, an integral value of the recombination center density in the depth direction in the second inter-peak region is greater than an integral value of the recombination center density in the depth direction in the first inter-peak region; Any of the inter-peak regions has a plurality of recombination center density peaks. Semiconductor device.

21. A semiconductor substrate having an upper surface and a lower surface, the semiconductor substrate having a drift region of a first conductivity type; a buffer region of a first conductivity type provided between the drift region and the lower surface of the semiconductor substrate, the buffer region having a doping concentration higher than that of the drift region; Equipped with The buffer area is two or more doping concentration peaks provided at different positions in a depth direction, including a shallowest doping concentration peak located closest to the lower surface of the semiconductor substrate; a plurality of inter-peak regions provided between the lower surface of the semiconductor substrate and the shallowest doping concentration peak and between two adjacent doping concentration peaks in a depth direction; and The plurality of inter-peak regions are a first inter-peak region provided with one or more first recombination center density peaks; a second inter-peak region disposed farther from the lower surface of the semiconductor substrate than the first inter-peak region and including one or more second recombination center density peaks; a third inter-peak region disposed farther from the lower surface of the semiconductor substrate than the second inter-peak region and including one or more third recombination center density peaks; Including, The semiconductor device, wherein the integral value of the recombination center density in the depth direction in the second inter-peak region is greater than the integral value of the recombination center density in the depth direction in the first inter-peak region.

22. A semiconductor substrate having an upper surface and a lower surface, the semiconductor substrate having a drift region of a first conductivity type; a buffer region of a first conductivity type provided between the drift region and the lower surface of the semiconductor substrate, the buffer region having a doping concentration higher than that of the drift region; Equipped with The buffer area is two or more doping concentration peaks provided at different positions in a depth direction, including a shallowest doping concentration peak located closest to the lower surface of the semiconductor substrate; a plurality of inter-peak regions provided between the lower surface of the semiconductor substrate and the shallowest doping concentration peak and between two adjacent doping concentration peaks in a depth direction; and The plurality of inter-peak regions are a first inter-peak region in which a first recombination center density peak is provided; a second inter-peak region disposed farther from the lower surface of the semiconductor substrate than the first inter-peak region and including a second recombination center density peak; Including, an integral value of the recombination center density in the depth direction in the second inter-peak region is greater than an integral value of the recombination center density in the depth direction in the first inter-peak region; The peak value of the second recombination center density peak is greater than the peak value of the first recombination center density peak. Semiconductor device.

23. the first recombination center density peak is a first helium chemical concentration peak; the second recombination center density peak is a second helium chemical concentration peak; The integral value of the second helium chemical concentration peak in the depth direction is greater than the integral value of the first helium chemical concentration peak in the depth direction.

23. The semiconductor device according to claim 22.

24. the integral of the second helium chemical concentration peak is 1×10 １１ ( / cm ２ ) or more, 1 x 10 １２ ( / cm ２ ) or less 24. The semiconductor device according to claim 23.

25. The integral of the first helium chemical concentration peak is 0.9×10 １１ ( / cm ２ ) or more, 0.9 x 10 １２ ( / cm ２ ) or less 25. The semiconductor device according to claim 23 or 24.

26. The integral value of the recombination center density in the depth direction in the second inter-peak region is at least twice the integral value of the recombination center density in the depth direction in the first inter-peak region.

23. The semiconductor device according to claim 20.

27. A semiconductor substrate having an upper surface and a lower surface, the semiconductor substrate having a drift region of a first conductivity type; a buffer region of a first conductivity type provided between the drift region and the lower surface of the semiconductor substrate, the buffer region having a doping concentration higher than that of the drift region; Equipped with The buffer area is a first recombination center density peak; a second recombination center density peak disposed closer to the upper surface of the semiconductor substrate than the first recombination center density peak; and an integral value of the second recombination center density peak in the depth direction is greater than an integral value of the first recombination center density peak in the depth direction, a depth position at which an integrated concentration obtained by integrating net doping concentrations of the drift region and the buffer region from an upper end of the upper surface side of the drift region toward the lower surface side reaches a critical integrated concentration is located between the first recombination center density peak and the second recombination center density peak; Semiconductor device.

28. The critical integral concentration is 1.2×10 12 / cm 2 .

28. The semiconductor device according to claim 27.

29. A semiconductor substrate having an upper surface and a lower surface, the semiconductor substrate having a drift region of a first conductivity type; a buffer region of a first conductivity type provided between the drift region and the lower surface of the semiconductor substrate, the buffer region having a doping concentration higher than that of the drift region; Equipped with The buffer area is two or more doping concentration peaks provided at different positions in a depth direction, including a shallowest doping concentration peak located closest to the lower surface of the semiconductor substrate; a plurality of inter-peak regions provided between the lower surface of the semiconductor substrate and the shallowest doping concentration peak and between two adjacent doping concentration peaks in a depth direction; and The plurality of inter-peak regions are a first inter-peak region provided with one or more first recombination center density peaks; a second inter-peak region disposed farther from the lower surface of the semiconductor substrate than the first inter-peak region and including one or more second recombination center density peaks; Including, an integral value of the recombination center density in the depth direction in the second inter-peak region is greater than an integral value of the recombination center density in the depth direction in the first inter-peak region; a depth position at which an integrated concentration obtained by integrating net doping concentrations of the drift region and the buffer region from an upper end of the upper surface side of the drift region toward the lower surface side reaches a critical integrated concentration is located between the first recombination center density peak and the second recombination center density peak; Semiconductor device.

30. The critical integral concentration is 1.2×10 12 / cm 2 .

30. The semiconductor device according to claim 29.

31. A semiconductor substrate having an upper surface and a lower surface, the semiconductor substrate having a drift region of a first conductivity type; a buffer region of a first conductivity type provided between the drift region and the lower surface of the semiconductor substrate, the buffer region having a doping concentration higher than that of the drift region; Equipped with The buffer area is a first recombination center density peak; a second recombination center density peak disposed closer to the upper surface of the semiconductor substrate than the first recombination center density peak; a third recombination center density peak disposed closer to the upper surface of the semiconductor substrate than the second recombination center density peak; three or more doping concentration peaks; and the second recombination center density peak is located between any two of the three or more doping concentration peaks; The third recombination center density peak is disposed between any two doping concentration peaks different from the second recombination center density peak among the three or more doping concentration peaks. Semiconductor device.

32. Only one doping concentration peak is disposed between the second recombination center density peak and the third recombination center density peak.

32. The semiconductor device according to claim 31.

33. The first recombination center density peak is located on the lower surface side of the doping concentration peak closest to the lower surface.

32. The semiconductor device according to claim 31.

34. The semiconductor device according to claim 34, further comprising a base region of a second conductivity type provided between the drift region and the upper surface of the semiconductor substrate.

34. The semiconductor device according to any one of claims 27 to 33.

35. The integral value of the second recombination center density peak in the depth direction is greater than the integral value of the first recombination center density peak in the depth direction.

34. The semiconductor device according to any one of claims 31 to 33.

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