Semiconductor device

Abstract

The present invention provides a semiconductor device in which a buffer region has a plurality of doping concentration peaks having mutually-different depth positions. The plurality of doping concentration peaks include a first doping concentration peak closest to the upper surface and a second doping concentration peak second closest to the upper surface. At the first doping concentration peak, an activation rate at which impurities function as a donor or an acceptor is lower than the activation rate at the second doping concentration peak.

Description

Semiconductor Devices

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

[0002] In semiconductor devices such as IGBTs, a structure in which a buffer region including one or more doping concentration peaks is provided is known (see, for example, Patent Document 1: International Publication No. 2020 / 100997). Problem to be solved

[0003] In a semiconductor device, it is preferable to be able to control the doping concentration with precision. General disclosure

[0004] To solve the above problems, a first aspect of the present invention provides a semiconductor device provided on a semiconductor substrate having an upper surface and a lower surface. The semiconductor device may include a drift region of a first conductivity type provided in the semiconductor substrate. Any of the semiconductor devices 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 semiconductor devices, the buffer region may have multiple doping concentration peaks at different depth positions. In any of the semiconductor devices, the multiple doping concentration peaks may include a first doping concentration peak closest to the upper surface and a second doping concentration peak second closest to the upper surface. In any of the semiconductor devices, an activation rate at which impurities function as donors or acceptors at the first doping concentration peak may be lower than the activation rate at the second doping concentration peak.

[0005] In any one of the semiconductor devices described above, the plurality of doping concentration peaks may include a third doping concentration peak that is third closest to the top surface, and the activation rate at the second doping concentration peak may be lower than the activation rate at the third doping concentration peak.

[0006] In any one of the semiconductor devices described above, the plurality of doping concentration peaks may include a fourth doping concentration peak that is fourth closest to the top surface, and the activation rate at the third doping concentration peak may be lower than the activation rate at the fourth doping concentration peak.

[0007] In any of the above semiconductor devices, the doping concentration of the first doping concentration peak may be higher than the doping concentration of the second doping concentration peak.

[0008] In any one of the semiconductor devices described above, the doping concentration of the first doping concentration peak may be higher than the doping concentration of the second doping concentration peak. In any one of the semiconductor devices described above, the doping concentration of the second doping concentration peak may be lower than the doping concentration of the third doping concentration peak.

[0009] In any of the above semiconductor devices, the doping concentration of the first doping concentration peak may be lower than the doping concentration of the second doping concentration peak.

[0010] In any one of the semiconductor devices described above, the doping concentration of the first doping concentration peak may be lower than the doping concentration of the second doping concentration peak. In any one of the semiconductor devices described above, the doping concentration of the second doping concentration peak may be higher than the doping concentration of the third doping concentration peak.

[0011] In any of the semiconductor devices described above, the plurality of doping concentration peaks may include a shallowest concentration peak closest to the bottom surface and an adjacent concentration peak disposed adjacent to the shallowest concentration peak in the depth direction, and the activation rate at the shallowest concentration peak may be lower than the activation rate at the adjacent concentration peak.

[0012] In any of the above semiconductor devices, the first doping concentration peak and the second doping concentration peak may contain a hydrogen donor.

[0013] In any of the above semiconductor devices, the buffer region may have a plurality of doping concentration valleys at different depth positions. In any of the above semiconductor devices, the plurality of doping concentration valleys may include a first concentration valley closest to the top surface and a second concentration valley second closest to the top surface. In any of the above semiconductor devices, the activation rate in the first concentration valley may be lower than the activation rate in the second concentration valley.

[0014] In any of the above semiconductor devices, the activation rate at the first doping concentration peak may be smaller than the activation rate at the second doping concentration peak by 0.3% or more.

[0015] In any one of the above semiconductor devices, the oxygen chemical concentration in the semiconductor substrate is 1×10 １７ / cm ３ It may be less than.

[0016] In any of the above semiconductor devices, the activation rate at the first doping concentration peak may be smaller than the activation rate at the second doping concentration peak by 0.4% or more.

[0017] In any one of the above semiconductor devices, the oxygen chemical concentration in the semiconductor substrate is 1×10 １７ / cm ３ It may be more than that.

[0018] In any of the above semiconductor devices, the distance between the first doping concentration peak and the lower surface may be 20 μm or more.

[0019] In any of the above semiconductor devices, at the first doping concentration peak, an integrated concentration of the CiO i-H donors may be higher than an integrated concentration of the Si-H donors.

[0020] The above summary of the invention does not list all of the necessary features of the present invention. In addition, subcombinations of these features may also constitute inventions.

[0021] 1 is a top view showing an example of a semiconductor device 100 according to an embodiment of the present invention. It is an enlarged view of region D in FIG. 1. It is a diagram showing an example of the e-e cross section in FIG. 2. It is a diagram showing an example of the distribution of hydrogen chemical concentration and doping concentration along the ff line in FIG. 3. It is a diagram showing an example of the distribution of hydrogen chemical concentration and doping concentration along the ff line in FIG. 4. It is a diagram showing the relationship between acceleration energy and activation rate when hydrogen is implanted into a semiconductor substrate 10 that is an MCZ substrate. It is a diagram showing the relationship between hydrogen dose and activation rate when hydrogen is implanted into a semiconductor substrate 10 that is an MCZ substrate. It is a diagram showing an example of the relationship between depth position and oxygen chemical concentration in an MCZ substrate and an FZ substrate. It is a diagram showing another example of the distribution of doping concentration along the ff line. It is a diagram showing the activation rate of each doping concentration peak 201 in the example shown in FIG. 9. It is a diagram showing the relationship between acceleration energy and activation rate when hydrogen is implanted into a semiconductor substrate 10 that is an FZ substrate. It is a diagram showing the doping concentration distribution shown in FIG. 4, with the doping concentration of the drift region 18 as the reference value. 12 is a diagram showing an example of calculating the activation rate of each doping concentration peak 201 using the doping concentrations shown in FIG. 12. This diagram shows the doping concentration distribution shown in FIG. 9, with the doping concentration in the drift region 18 set as a reference value. This diagram shows an example of calculating the activation rate of each doping concentration peak 201 using the doping concentrations shown in FIG. 14. This diagram shows the interstitial Si—H donors and CiOi-H donors included in the k-th doping concentration peak 201-k. This diagram shows the interstitial Si—H donors and CiOi-H donors when the range Rk is relatively wide. This diagram shows another example of the doping concentration distribution in the buffer region 20. This diagram shows the activation rate of each doping concentration peak 201 in the example shown in FIG. 18. This diagram shows another example of the doping concentration distribution along the ff line. This diagram shows the activation rate of each doping concentration peak 201 in the example shown in FIG. 20. This diagram shows the doping concentration distribution shown in FIG. 18, with the doping concentration in the drift region 18 set as a reference value. FIG. 23 is a diagram showing an example in which the activation rate of each doping concentration peak 201 is calculated using the doping concentrations shown in FIG. 22.20 with the doping concentration of the drift region 18 as a reference value. FIG. 21 is a diagram showing an example of calculating the activation rate of each doping concentration peak 201 using the doping concentrations shown in FIG.

[0022] 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.

[0023] 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.

[0024] In this specification, technical matters may be explained using orthogonal coordinate axes of the X-axis, Y-axis, and Z-axis. The orthogonal 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 described without specifying positive or negative, it means a direction parallel to the +Z-axis and -Z-axis.

[0025] In this specification, orthogonal axes parallel to the upper and lower surfaces of the semiconductor substrate are referred to as the X-axis and Y-axis. Furthermore, an axis perpendicular to the upper and lower 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 upper and lower surfaces of the semiconductor substrate, including the X-axis and Y-axis, may be referred to as the horizontal direction.

[0026] 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.

[0027] In this specification, when we say "same" or "equal," it may also include cases where there is an error due to manufacturing variations, etc. The error is, for example, within 10%.

[0028] 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 an N-type conductivity or a P-type conductivity.

[0029] In this specification, the doping concentration means the concentration of donors or acceptors in a thermal equilibrium state. In this specification, the net doping concentration means 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 is N Ａ Then, the net doping concentration at any position is N Ｄ -N Ａ In this specification, the net doping concentration may be simply referred to as the doping concentration.

[0030] A donor has the function of supplying electrons to a semiconductor. An acceptor has the function of receiving electrons from a semiconductor. Donors and acceptors are not limited to impurities themselves. For example, interstitial Si—H, in which interstitial silicon (Si-i) and hydrogen are bonded in a silicon semiconductor, and CiOi-H, in which interstitial carbon (Ci), interstitial oxygen (Oi), and hydrogen are bonded, function as donors that supply electrons. In this specification, CiOi-H or interstitial Si—H may be referred to as hydrogen donors.

[0031] In this specification, the semiconductor substrate has N-type bulk donors distributed throughout. The bulk donors are donors due to dopants contained substantially uniformly in the ingot that is the base of the semiconductor substrate when the ingot is manufactured. In this example, the bulk donors are elements other than hydrogen. The dopants of the bulk donors include, but are not limited to, phosphorus, antimony, arsenic, selenium, or sulfur. In this example, the bulk donors are 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), and the float zone method (FZ method). The ingot in this example is manufactured by the MCZ method. The oxygen concentration contained in the substrate manufactured by the MCZ method is 1×10 １７ ~7 x 10 １７ / cm ３ The oxygen concentration in the substrate manufactured by the FZ method is 1×10 １５ ~5 x 10 １６ / cm ３ The higher the oxygen concentration, the more likely it is that hydrogen donors are generated. The bulk donor concentration may be the chemical concentration of bulk donors distributed throughout the semiconductor substrate, or may be a value between 90% and 100% of the 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, 1×10 １０ / 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.).

[0032] In this specification, when P+ type or N+ type is described, it means that the doping concentration is higher than that of P type or N type, and when P- type or N- type is described, it means that the doping concentration is lower than that of P type or N type. Furthermore, when P++ type or N++ type is described in this specification, it means that the doping concentration is higher than that of P+ type or N+ type. The unit system 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).

[0033] In this specification, chemical concentration refers to the atomic density of an impurity measured regardless of its state of electrical activation. Chemical concentration can be measured, for example, by secondary ion mass spectrometry (SIMS). The net doping concentration can be measured by voltage-capacitance measurement (CV). The carrier concentration measured by spreading resistance measurement (SR) may also be used as the net doping concentration. The carrier concentration measured by CV or SR may be used as a value in a thermal equilibrium state. In addition, since the donor concentration in an N-type region is sufficiently 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.

[0034] 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 atoms notation may be omitted.

[0035] The carrier concentration measured by the SR method may be lower than the concentration of donors or acceptors. 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. The reduction in carrier mobility occurs when carriers are scattered due to disorder in the crystal structure caused by lattice defects or the like.

[0036] The donor or acceptor concentration calculated from the carrier concentration measured by the CV method or the SR method may be lower than the chemical concentration of the element representing the donor or acceptor. As an example, the donor concentration of phosphorus or arsenic, which acts as a donor in a silicon semiconductor, or the acceptor concentration of boron, which acts as an acceptor, is about 99% of the chemical concentration. On the other hand, the donor concentration of hydrogen, which acts as a donor in a silicon semiconductor, is about 0.1% to 10% of the chemical concentration of hydrogen.

[0037] Fig. 1 is a top view showing an example of a semiconductor device 100 according to an embodiment of the present invention. The semiconductor device 100 is provided on a semiconductor substrate 10 having an upper surface and a lower surface. Fig. 1 shows the positions of each component as projected onto the upper surface of the semiconductor substrate 10. Fig. 1 shows only some of the components of the semiconductor device 100, and some components are omitted.

[0038] 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 end 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 in this example has two pairs of end edges 162 that face each other in a top view. In FIG. 1 , the X-axis and Y-axis are parallel to either of the end edges 162. The Z-axis is perpendicular to the top surface of the semiconductor substrate 10.

[0039] An active portion 160 is provided in 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 omitted from FIG. 1 . The active portion 160 may refer to a region that overlaps with the emitter electrode in a top view. The active portion 160 may also include a region sandwiched between the active portions 160 in a top view.

[0040] The active section 160 is provided with at least one of a transistor section 70 including a transistor element such as an insulated gate bipolar transistor (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 (in this example, the X-axis direction) on the top surface of the semiconductor substrate 10. The semiconductor device 100 of this example is a reverse conducting IGBT (RC-IGBT).

[0041] 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.

[0042] The diode section 80 has an N+ type cathode region in a region that contacts 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 that extends the diode section 80 in the Y-axis direction to the gate wiring described below may also be included in the diode section 80. A collector region is provided on the lower surface of the extension region 81.

[0043] The transistor section 70 has a P+ type collector region in a region in contact with the lower surface of the semiconductor substrate 10. The transistor section 70 also has a gate structure, which has an N type emitter region, a P type base region, a gate conductive portion, and a gate insulating film, periodically arranged on the upper surface side of the semiconductor substrate 10.

[0044] 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.

[0045] 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 hatched with diagonal lines.

[0046] 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 disposed 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 region surrounded by the peripheral gate wiring 130 in a top view may be the active portion 160. In addition, a well region is formed below the gate wiring. The well region is a P-type region with a higher concentration than a base region, which will be described later, and is formed from the top surface of the semiconductor substrate 10 to a position deeper than the base region. The region surrounded by the well region in a top view may be the active portion 160.

[0047] The peripheral gate wiring 130 is connected to the gate pad 164. The peripheral gate wiring 130 is disposed above the semiconductor substrate 10. The peripheral gate wiring 130 may be a metal wiring containing aluminum or the like.

[0048] 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.

[0049] The peripheral gate wiring 130 and the active side gate wiring 131 are connected to the gate trench portion of the active portion 160. The peripheral gate wiring 130 and the active side gate wiring 131 are disposed above the semiconductor substrate 10. The peripheral gate wiring 130 and the active side gate wiring 131 may be wiring formed of a semiconductor such as polysilicon doped with impurities.

[0050] 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 section 70 and the diode section 80 may be arranged alternately in the X axis direction in each divided region.

[0051] The semiconductor device 100 may 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.

[0052] In the present example, the semiconductor device 100 includes an edge termination structure 90 between the active section 160 and the edge 162 when viewed from above. The edge termination structure 90 in the present example is disposed between the peripheral gate wiring 130 and the edge 162. The edge termination structure 90 relieves electric field concentration on the upper surface side of the semiconductor substrate 10. The 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 the active section 160.

[0053] 2 is an enlarged view of region D in FIG. 1 . Region D includes 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 the 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.

[0054] 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.

[0055] 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. The dummy conductive portion of the dummy trench portion 30 does not need to be connected to the emitter electrode 52 and the gate conductive portion, and may be controlled to a potential different from the potential of the emitter electrode 52 and the potential of the gate conductive portion.

[0056] 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.

[0057] 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 a metal 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.

[0058] 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 higher doping concentration than the base region 14. In this example, the base region 14 is P- type, and the well region 11 is P+ type.

[0059] 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.

[0060] The gate trench portion 40 in this example may have two straight line portions 39 (portions of the trench that are straight 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.

[0061] At least a portion 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.

[0062] 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 a tip section 31, similar to the gate trench section 40. The semiconductor device 100 shown in FIG. 2 includes both linear dummy trench sections 30 without tip sections 31 and dummy trench sections 30 with tip sections 31.

[0063] 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.

[0064] 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.

[0065] 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 located at one end of each mesa portion in the extension direction, a base region 14-e is also located at the other end of each mesa portion. In each mesa portion, at least one of a first-conductivity-type emitter region 12 and a second-conductivity-type contact region 15 may be provided 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.

[0066] 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.

[0067] 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).

[0068] 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 of the trench portion (Y-axis direction). 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.

[0069] The mesa portion 61 of the diode section 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] Fig. 3 is a diagram showing an example of the e-e cross section in Fig. 2. The e-e 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.

[0074] 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 holes 54 described with reference to FIG. 2 .

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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. In this example, the buffer region 20 is provided between the drift region 18 and the lower surface 23 of the semiconductor substrate 10. The doping concentration of the buffer region 20 is higher than the doping concentration 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. Furthermore, 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.

[0083] 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.

[0084] 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.

[0085] 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 the donor concentration 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 donors and acceptors 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 are 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.

[0086] One or more gate trenches 40 and one or more dummy trenches 30 are provided on the upper surface 21 of the semiconductor substrate 10. Each trench extends from the upper surface 21 of the semiconductor substrate 10, penetrating the base region 14, to below the base region 14. 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 penetrates these doped regions. The trenches penetrating the doped regions do not necessarily mean that the trenches are formed in the order of forming the doped regions and then the trenches. The trenches penetrating the doped regions also include trenches formed in the order of forming the trenches and then forming the doped regions.

[0087] 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.

[0088] 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 further inside than 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.

[0089] 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.

[0090] 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.

[0091] The gate trench portion 40 and the dummy trench portion 30 in this example are covered with an interlayer insulating film 38 on the upper surface 21 of the semiconductor substrate 10. The bottoms of the dummy trench portion 30 and the gate trench portion 40 may have a downwardly convex curved shape (a curved shape in cross section).

[0092] Fig. 4 is a diagram showing an example of the distribution of hydrogen chemical concentration and doping concentration along line ff in Fig. 3. In the graphs of concentration distribution in Fig. 4 and the like, the carrier concentration measured by the SR method or the like is taken as the doping concentration. The vertical axis in Fig. 4 is a common logarithm (log) scale for both the hydrogen chemical concentration and the doping concentration. The horizontal axis (depth position) in Fig. 4 is a linear scale. The hydrogen chemical concentration may be a value measured by the SIMS method or the like.

[0093] The line f-f is a line parallel to the Z axis that passes through the buffer region 20. The horizontal axis in Fig. 4 indicates the depth position (position in the Z axis direction) in the semiconductor substrate 10. In the concentration distribution graphs in Fig. 4 and the like, the bottom end position of the buffer region 20 is set as the reference position (0) in the Z axis direction, and the distance from the reference position is set as the position in the Z axis direction. At the bottom end position of the buffer region 20, there is a valley in the doping concentration distribution due to the PN junction between the collector region 22 and the buffer region 20, but this valley is omitted in Fig. 4 and the like.

[0094] The semiconductor substrate 10 of this example is an MCZ substrate manufactured by the MCZ method. As described above, the MCZ substrate contains a relatively high concentration of oxygen. The oxygen chemical concentration in the semiconductor substrate 10 is 1×10 １７ / cm ３ The maximum value of the oxygen chemical concentration in the semiconductor substrate 10 may be set as the value of the oxygen chemical concentration in the semiconductor substrate 10. The oxygen chemical concentration in the semiconductor substrate 10 may be 7×10 １７ / cm ３ The carbon chemical concentration in the semiconductor substrate 10 may also be 1×10 １７ / cm ３The doping concentration of the drift region 18 may be the same as or different from the bulk donor concentration. The doping concentration of the buffer region 20 is higher than that of the drift region 18.

[0095] The depth position of the boundary between the buffer region 20 and the drift region 18 is designated Zb. The drift region 18 may have an approximately constant doping concentration in the depth direction. "Almost constant" may mean that the maximum value is 1.5 times or less, or 1.1 times or less, of the minimum value. The depth position Zb may be a position where the doping concentration is higher than that of the drift region 18 in the direction from the drift region 18 toward the buffer region 20, or a position where the doping concentration is 1.1 times or more, or 1.5 times or more, of the doping concentration of the drift region 18. The depth position Zb may be a position where the hydrogen chemical concentration first becomes 0 (or below the detection limit) in the direction from the buffer region 20 toward the drift region 18.

[0096] A dopant such as hydrogen is implanted into the buffer region 20 at multiple depth positions. Therefore, the chemical concentration distribution of the dopant in the buffer region 20 has peaks at multiple depth positions. In the example of FIG. 4, the dopant is hydrogen, and the hydrogen chemical concentration distribution is shown. In this example, hydrogen ions such as protons are implanted from the lower surface 23 of the semiconductor substrate 10. In another example, the dopant implanted into the buffer region 20 may include a dopant such as phosphorus. A dopant other than hydrogen, such as phosphorus, may be implanted into the buffer region 20 at least at one depth position, and hydrogen may be implanted into at least another depth position.

[0097] The semiconductor substrate 10 has a plurality of hydrogen concentration peaks 211 arranged in a line in the depth direction in the buffer region 20. The hydrogen concentration peaks 211 are mountain-shaped portions where the hydrogen chemical concentration exhibits a maximum value in the depth direction. In this specification, the hydrogen concentration peak 211 having the kth greatest distance from the lower surface 23 is referred to as the kth hydrogen concentration peak 211-k. In the example of FIG. 4 , a first hydrogen concentration peak 211-1, a second hydrogen concentration peak 211-2, a third hydrogen concentration peak 211-3, and a fourth hydrogen concentration peak 211-4 are shown in order of decreasing distance from the lower surface 23. However, the number of hydrogen concentration peaks 211 is not limited to four.

[0098] The buffer region 20 has a plurality of doping concentration peaks 201 at different depth positions. In this example, the plurality of doping concentration peaks 201 are arranged corresponding to the plurality of hydrogen concentration peaks 211. In this specification, the doping concentration peak 201 having the kth largest distance from the lower surface 23 is referred to as the kth doping concentration peak 201-k. In the example of FIG. 4 , the plurality of doping concentration peaks 201 include a first doping concentration peak 201-1 closest to the upper surface 21, a second doping concentration peak 201-2 second closest to the upper surface 21, a third doping concentration peak 201-3 third closest to the upper surface 21, and a fourth doping concentration peak 201-4 fourth closest to the upper surface 21. The distance between the first doping concentration peak 201-1 and the lower surface 23 may be 20 μm or more, 30 μm or more, or 40 μm or more. The distance may be 50 μm or less, 40 μm or less, or 30 μm or more.

[0099] In this specification, the doping concentration at the apex of the kth doping concentration peak 201-k is designated as Pk. In the example of FIG. 4, doping concentrations P1, P2, P3, and P4 of four doping concentration peaks 201 are shown. In this specification, of the multiple doping concentration peaks 201 provided in the buffer region 20, the doping concentration peak 201 closest to the lower surface 23 (the fourth doping concentration peak 201-4 in the example of FIG. 4) may be referred to as the shallowest concentration peak. Furthermore, of the multiple doping concentration peaks 201, the doping concentration peak 201 arranged adjacent to the shallowest concentration peak in the depth direction (the third doping concentration peak 201-3 in the example of FIG. 4) may be referred to as the adjacent concentration peak.

[0100] The region between the kth doping concentration peak 201-k and the (k+1)th doping concentration peak 201-(k+1) is referred to as the kth doping concentration valley 203-k. The buffer region 20 of this example has multiple doping concentration valleys 203, each at a different depth. The doping concentration valleys 203 include a portion where the doping concentration exhibits a minimum value. In the example of FIG. 4 , the multiple doping concentration valleys 203 include a first doping concentration valley 203-1 closest to the upper surface 21, a second doping concentration valley 203-2 second closest to the upper surface 21, and a third doping concentration valley 203-3 third closest to the upper surface 21. The first doping concentration valley 203-1, second doping concentration valley 203-2, and third doping concentration valley 203-3 are shown in descending order of distance from the lower surface 23. The doping concentration of the doping concentration valley 203 is also higher than the doping concentration of the drift region 18 .

[0101] The doping concentration peaks 201 are mountain-shaped portions where the doping concentration exhibits a maximum value in the depth direction. The number of doping concentration peaks 201 may be two or more, three or more, four or more, or five or more. In regions where the hydrogen chemical concentration is high, many hydrogen donors are formed, and therefore, doping concentration peaks 201 are formed corresponding to the hydrogen concentration peaks 211. A doping concentration peak 201 may be provided for at least one hydrogen concentration peak 211. In this example, a doping concentration peak 201 is provided for each of the hydrogen concentration peaks 211.

[0102] The correspondence between the hydrogen concentration peak 211 and the doping concentration peak 201 may mean that the apex of one concentration peak is located within the full width at half maximum of the other concentration peak. When the hydrogen concentration peak 211 and the doping concentration peak 201 correspond to each other, the distance between the apexes of the two concentration peaks may be 2 μm or less, 1 μm or less, or 0.5 μm or less.

[0103] The depth position of the kth doping concentration peak 201-k is designated Z1k. In this specification, the depth position of a concentration peak refers to the position of the apex of the concentration peak. In the example of FIG. 4, depth positions Z11, Z12, Z13, and Z14 of four doping concentration peaks 201 are shown. The kth hydrogen concentration peak 211-k may be located at depth position Z1k or may be located at a slightly shifted position. The depth position of the kth doping concentration valley 203-k is designated Z3k. In this specification, the depth position of a concentration valley refers to the position where the concentration shows a minimum value. In the doping concentration valley 203, if the region where the doping concentration shows a minimum value shows a flat region that is continuous in the depth direction, the depth position of the doping concentration valley 203 is designated as the center position of the flat region in the depth direction.

[0104] By implanting hydrogen ions into the semiconductor substrate 10, hydrogen donors are formed near the implantation position of the hydrogen ions and in the region through which the hydrogen ions have passed. In the example of FIG. 4 , hydrogen ions are implanted from the bottom surface 23 to depth positions Z1, Z2, Z3, and Z4. High concentrations of hydrogen donors are formed near depth positions Z1 to Z4, and hydrogen donors are also formed in the region through which the hydrogen ions have passed from the bottom surface 23 to depth position Z1. This forms multiple doping concentration peaks 201 and one or more doping concentration valleys 203. The hydrogen ions may be implanted from the top surface 21 of the semiconductor substrate 10.

[0105] In the examples shown in the figures herein, all doping concentration peaks 201 contain hydrogen donors. The doping concentration peak 201 containing hydrogen donors may mean that 50% or more of the donors are hydrogen donors. For example, if the donors contained in the doping concentration peak 201 are hydrogen donors and bulk donors, the doping concentration peak 201 may be said to contain hydrogen donors when the hydrogen donor concentration is equal to or greater than the bulk donor concentration. In other examples, the doping concentration peak 201 containing hydrogen donors may mean that the hydrogen donor concentration is equal to or greater than twice, five times, or ten times the bulk donor concentration.

[0106] Some doping concentration peaks 201 may contain hydrogen donors, and some doping concentration peaks 201 may not contain hydrogen donors. At least first doping concentration peak 201-1 and second doping concentration peak 201-2 may contain hydrogen donors, and other doping concentration peaks 201 may or may not contain hydrogen donors. The shallowest concentration peak may contain phosphorus donors at more than 50% of the donors.

[0107] In this specification, the rate at which an impurity functions as a donor or an acceptor is referred to as the activation rate. The activation rate is determined by the concentration ( / cm ３ ) to the chemical concentration of the corresponding impurity ( / cm ３ The activation rate can be calculated by dividing the donor or acceptor concentration ( / cm) over a given depth range.３ ) ( / cm ２ ) to the corresponding impurity chemical concentration ( / cm) over the depth range. ３ ) ( / cm ２ ) may be calculated by dividing by

[0108] In this specification, the activation rate of the k-th doping concentration peak 201-k is defined as A / B, which is the value A obtained by integrating the doping concentration in the depth direction in a depth range Rk including the k-th doping concentration peak 201-k, divided by the value B obtained by integrating the hydrogen chemical concentration in the depth direction. The boundary positions of adjacent ranges Rk (i.e., the upper and lower end positions of each range Rk) are the depth positions of the doping concentration valley 203. However, the upper end position of range R1 is depth position Zb. Furthermore, the lower end position of the range Rk closest to the lower surface 23 (R4 in the example of FIG. 4) is depth position Z0. The range Rk may also be defined as the full width at half maximum range of the k-th doping concentration peak 201-k (i.e., the range in which the doping concentration is 0.5×Pk or greater).

[0109] FIG. 5 is a diagram showing the activation rates of each doping concentration peak 201 in the example shown in FIG. 4. The vertical axis in FIG. 5 represents the activation rate (%), and the horizontal axis represents the doping concentration peak 201. When comparing the activation rates at two positions in this specification, the activation rates of the same impurity (in this example, an impurity that serves as a donor) at the two positions are compared. The impurity may be the impurity with the highest concentration other than oxygen and carbon at the position. In this example, the activation rates of each doping concentration peak 201 are compared. For example, each doping concentration peak contains a hydrogen donor, and the activation rate of each doping concentration peak 201 indicates the proportion of hydrogen that functions as a hydrogen donor.

[0110] In this example, the activation rate at the first doping concentration peak 201-1 is lower than the activation rate at the second doping concentration peak 201-2. By lowering the activation rate, even if variations occur in the hydrogen chemical concentration corresponding to the first doping concentration peak 201-1, fluctuations in the doping concentration at the first doping concentration peak 201-1 can be suppressed. This improves the controllability of the doping concentration at the first doping concentration peak 201-1. When the transistor section 70 is turned off, the depletion layer in the buffer region 20 first reaches the first doping concentration peak 201-1, which is farthest from the bottom surface 23. Therefore, large variations in the doping concentration at the first doping concentration peak 201-1 are likely to affect the characteristics of the semiconductor device 100. In this example, by reducing the activation rate of the first doping concentration peak 201-1, the variation in the doping concentration of the first doping concentration peak 201-1 can be reduced, and the variation in the characteristics of the semiconductor device 100 can be suppressed.

[0111] The activation rate of the first doping concentration peak 201-1 may be 0.1% or more less, 0.2% or more less, 0.3% or more less, or 0.4% or more less than the activation rate of the second doping concentration peak 201-2. The activation rate of the first doping concentration peak 201-1 may be 95% or less, 90% or less, or 85% or less of the activation rate of the second doping concentration peak 201-2. The activation rate of the first doping concentration peak 201-1 may be greater than 2.5% and less than 3%. The activation rate of the second doping concentration peak 201-2 may be greater than 3% and less than 3.5%.

[0112] The activation rate at the second doping concentration peak 201-2 may be lower than the activation rate at the third doping concentration peak 201-3. By lowering the activation rate at the doping concentration peak 201 at a deeper position, it is possible to suppress variations in the doping concentration at the doping concentration peak 201 at a deeper position. This makes it possible to suppress variations in the characteristics of the semiconductor device 100.

[0113] The activation rate of second doping concentration peak 201-2 may be 0.1% or more less, 0.2% or more less, or 0.3% or more less than the activation rate of third doping concentration peak 201-3. The activation rate of second doping concentration peak 201-2 may be 95% or less, 90% or less, or 85% or less of the activation rate of third doping concentration peak 201-3. The activation rate of third doping concentration peak 201-3 may be greater than 3% and less than 4%. The activation rate of third doping concentration peak 201-3 may be greater than 3.25% and less than 3.75%.

[0114] The activation rate at the shallowest concentration peak (the fourth doping concentration peak 201-4 in this example) may be lower than the activation rate at the adjacent concentration peak (the third doping concentration peak 201-3 in this example). The activation rate at the shallowest concentration peak may be the smallest among the activation rates of the respective doping concentration peaks 201. The activation rate at the shallowest concentration peak may be less than 2%, less than 1.5%, or less than 1%. The activation rate at the shallowest concentration peak may be greater than 0% or greater than 0.5%.

[0115] Although not shown in Figure 5, in the example of Figure 4, the activation rate in the first doping concentration valley 203-1 is lower than the activation rate in the second doping concentration valley 203-2. The activation rate in the first doping concentration valley 203-1 may be 0.1% or more lower, 0.2% or more lower, or 0.3% or more lower than the activation rate in the second doping concentration valley 203-2. The activation rate in the first doping concentration valley 203-1 may be 95% or less of the activation rate in the second doping concentration valley 203-2, 90% or less, or 85% or less. The activation rate in the second doping concentration valley 203-2 may be lower than the activation rate in the third doping concentration valley 203-3.

[0116] 6 is a diagram showing the relationship between acceleration energy and activation rate when hydrogen is implanted into a semiconductor substrate 10, which is an MCZ substrate. The greater the acceleration energy, the deeper the hydrogen is implanted into the semiconductor substrate 10. The horizontal axis of FIG. 6 represents acceleration energy (eV) or depth position (μm) in the semiconductor substrate 10. The hydrogen implantation position can be adjusted by placing an absorber on the lower surface 23 of the semiconductor substrate 10, for example.

[0117] 6, hydrogen ions are implanted into the semiconductor substrate 10 at the same depth positions (Z1 to Z4) and dose amounts as in the example shown in FIG. 4. In FIG. 6, the activation rate at each depth position is calculated by dividing the doping concentration at that depth position by the hydrogen chemical concentration. In addition, the distribution of the calculated activation rates within the buffer region 20 is approximated by a straight line 221. The straight line 221 can be calculated by, for example, the least squares method. As shown by the straight line 221, the hydrogen activation rate tends to decrease as the acceleration energy increases. The slope of the straight line 221 is approximately −4×10 －４ (% / μm).

[0118] FIG. 7 is a diagram showing the relationship between the hydrogen dose and the activation rate when hydrogen is implanted into a semiconductor substrate 10, which is an MCZ substrate. FIG. 7 shows the activation rate when the hydrogen dose is changed for the same depth position. As shown in FIG. 7, increasing the hydrogen dose increases the activation rate until a certain dose is reached. On the other hand, once the dose exceeds a certain dose, increasing the hydrogen dose decreases the activation rate. For example, since the formation of C1Oi-H donors is rate-determined by the amount of carbon or oxygen present in the substrate, increasing the hydrogen dose too much decreases the hydrogen activation rate.

[0119] FIG. 8 shows an example of the relationship between depth and oxygen chemical concentration in an MCZ substrate and an FZ substrate. The distribution of oxygen chemical concentration in the semiconductor substrate 10 can be a variety of distributions. For example, near the upper surface 21 of the semiconductor substrate 10, oxygen may be released outside the substrate during the manufacturing process of the semiconductor substrate 10 or the semiconductor device 100. Therefore, near the upper surface 21 of the semiconductor substrate 10, the oxygen chemical concentration may decrease toward the upper surface 21 as shown in FIG. 8. A similar oxygen chemical concentration distribution may also be obtained near the lower surface 23. On the other hand, after the process of releasing oxygen outside the substrate, the lower surface 23 side of the semiconductor substrate 10 may be ground. In this case, the oxygen may decrease more gradually toward the lower surface 23 of the semiconductor substrate 10 than toward the upper surface 21, or the oxygen concentration may be approximately constant toward the lower surface 23.

[0120] Therefore, by adjusting the depth position of the doping concentration peak 201 and the dose of hydrogen ions according to the oxygen concentration distribution, carbon concentration distribution, and the like of the semiconductor substrate 10, it is possible to achieve the distribution of activation rates shown in FIG. 5 or FIG. 6 . For example, by positioning the first doping concentration peak 201-1 at a deeper position, the activation rate of the first doping concentration peak 201-1 can be reduced. However, if the first doping concentration peak 201-1 is positioned too deep, the depth direction length of the buffer region 20 becomes too long. The distance between the depth position Z11 of the first doping concentration peak 201-1 and the depth position Z12 of the second doping concentration peak 201-2 may be 15 μm or less, or may be 10 μm or less. The distance between the depth positions Z11 and Z12 may be 5 μm or more. The distance between two adjacent doping concentration peaks 201 may all be 15 μm or less, or may be 10 μm or less.

[0121] The activation rate at each doping concentration peak may be adjusted by adjusting at least one of the oxygen concentration distribution and the carbon concentration distribution in the semiconductor substrate 10. The higher the oxygen concentration and the carbon concentration, the higher the hydrogen activation rate tends to be. In the manufacturing process of the semiconductor device 100, a step of introducing at least one of oxygen and carbon into the semiconductor substrate 10 may be provided before implanting hydrogen ions. The activation rate can also be adjusted by adjusting the acceleration energy when implanting hydrogen ions at each depth position. Even if the acceleration energy is increased, hydrogen ions can be implanted at the same depth position by using an absorber.

[0122] The doping concentration P1 of the first doping concentration peak 201-1 may be higher than the doping concentration P2 of the second doping concentration peak 201-2. In this case, too, the activation rate of the first doping concentration peak 201-1 can be made lower than the activation rate of the second doping concentration peak 201-2 by adjusting the depth positions Z11 and Z12, the oxygen concentration, the carbon concentration, and the like. The doping concentration P1 may be 1.1 times or more, 1.5 times or more, or even 2 times or more the doping concentration P2. In another example, the doping concentration P1 may be the same as or lower than the doping concentration P2.

[0123] The doping concentration P1 of the first doping concentration peak 201-1 may be higher than the doping concentration P2 of the second doping concentration peak 201-2, and the doping concentration P2 of the second doping concentration peak 201-2 may be lower than the doping concentration P3 of the third doping concentration peak 201-3. In this case, too, the activation rates of the third doping concentration peak 201-3, the second doping concentration peak 201-2, and the first doping concentration peak 201-1 may decrease with increasing distance from the lower surface 23. The respective activation rates can be adjusted by adjusting the depth positions Z11, Z12, and Z13, the oxygen concentration, the carbon concentration, and the like. In another example, the doping concentration P3 may be equal to or higher than the doping concentration P2, and the doping concentration P2 may be equal to or higher than the doping concentration P1. In this case, too, the activation rates of the respective doping concentration peaks 201 may decrease with increasing distance from the lower surface 23.

[0124] 9 is a diagram showing another example of the distribution of doping concentration along the ff line. The semiconductor substrate 10 in this example is an FZ substrate manufactured by the FZ method. The FZ substrate has a relatively low oxygen chemical concentration. When the oxygen chemical concentration in the semiconductor substrate 10 is 1×10 １７ / cm ３ The oxygen chemical concentration in the semiconductor substrate 10 may be less than 1×10 １５ / cm ３ That's it, 1 x 10 １６ / cm ３ The hydrogen chemical concentration distribution is omitted because it is the same as the example in FIG. 4. This example also has the same doping concentration peaks 201 as the example in FIG. 4. In the example in FIG. 9, the activation rate of each doping concentration peak 201 can be calculated in the same way as in the example in FIG. 4.

[0125] Fig. 10 is a diagram showing the activation rates of the respective doping concentration peaks 201 in the example shown in Fig. 9. In this example, too, the activation rates of the respective doping concentration peaks 201 showed the same tendency as in the example of Fig. 5.

[0126] When the semiconductor substrate 10 is an FZ substrate, the activation rate of the first doping concentration peak 201-1 may be 0.05% or more smaller, 0.1% or more smaller, 0.2% or more smaller, or 0.3% or more smaller than the activation rate of the second doping concentration peak 201-2. The activation rate of the first doping concentration peak 201-1 may be 95% or less, 90% or less, or 85% or less of the activation rate of the second doping concentration peak 201-2. The activation rate of the first doping concentration peak 201-1 may be greater than 1.8% and less than 2.2%. The activation rate of the second doping concentration peak 201-2 may be greater than 2% and less than 2.4%.

[0127] When the semiconductor substrate 10 is an FZ substrate, the activation rate at the second doping concentration peak 201-2 may be 0.05% or more smaller, 0.1% or more smaller, or 0.2% or more smaller than the activation rate at the third doping concentration peak 201-3. The activation rate at the second doping concentration peak 201-2 may be 95% or less, 90% or less, or 85% or less of the activation rate at the third doping concentration peak 201-3. The activation rate at the third doping concentration peak 201-3 may be greater than 2.3% and less than 2.8%. The activation rate at the shallowest concentration peak may be less than 2%, less than 1.5%, or less than 1%. The activation rate at the shallowest concentration peak may be greater than 0% or greater than 0.4%.

[0128] 11 is a diagram showing the relationship between acceleration energy and activation rate when hydrogen is implanted into a semiconductor substrate 10, which is an FZ substrate. In FIG. 11, the distribution of activation rate in the buffer region 20 is approximated by a straight line 222. The method of calculating the activation rate and the straight line 222 is the same as in the example of FIG. 6. In this example, too, the larger the acceleration energy, the smaller the activation rate of hydrogen tends to be. The slope of the straight line 222 is approximately −1.5×10 －４ (% / μm).

[0129] The absolute value of the slope of the straight line 222 in the FZ substrate is smaller than the absolute value of the slope of the straight line 221 in the MCZ substrate. This is thought to be because, as will be described later, in the MCZ substrate, the proportion of CiOi-H donors in all hydrogen donors increases as the depth position increases. The deeper the hydrogen ion implantation depth from the lower surface 23, the more likely it is that the hydrogen ion dose will be reduced. This is more pronounced as the amount of generated CiOi-H donors increases. In this case, the doping concentration approaches the generation concentration of CiOi-H donors. The generation concentration of CiOi-H donors is approximately 5×10 １３ / cm ３ From 3 x 10 １４ / cm. Therefore, the proportion of the CiOi-H donors in the total hydrogen donors is relatively high. The absolute value of the slope of the line obtained by approximating the distribution of the activation rate in the buffer region 20 in the range of depth positions Z0 to Zb by the least squares method is 2×10 －４ (% / μm) or more. This makes it possible to make the activation rate at the first doping concentration peak 201-1 relatively small, thereby suppressing variations in the doping concentration at the first doping concentration peak 201-1. The absolute value of the slope of the line is 1×10 －３ (% / μm) or less. If the absolute value of the slope of the line is too large, it becomes difficult to maintain the doping concentration of the first doping concentration peak 201-1. The absolute value of the slope of the line may be 2.5×10 －４ (% / μm) or more, and －４ (% / μm) or more.

[0130] The absolute value of the gradient obtained by dividing the difference between the activation rate at the first doping concentration peak 201-1 and the activation rate at the second doping concentration peak 201-2 by the distance between the depth positions Z11 and Z12 is 2×10 －４ (% / μm) or more. The absolute value of the gradient may be 2.5×10 －４ (% / μm) or more, and －４ (% / μm) or more.

[0131] Fig. 12 is a diagram showing the doping concentration distribution shown in Fig. 4, with the doping concentration of the drift region 18 as a reference value. In other words, Fig. 12 shows a distribution obtained by subtracting the doping concentration of the drift region 18 from the doping concentration at each depth position in the doping concentration distribution shown in Fig. 4. The bulk donor concentration may be used instead of the doping concentration of the drift region 18.

[0132] 13 is a diagram showing an example in which the activation rate of each doping concentration peak 201 is calculated using the doping concentrations shown in FIG. 12. That is, the activation rate in this example is calculated by dividing the integral value of the doping concentration shown in FIG. 12 by the integral value of the hydrogen chemical concentration in each range Rk (see FIG. 4). As in this example, each activation rate may be calculated excluding the doping concentration in the drift region 18.

[0133] 14 is a diagram showing the doping concentration distribution shown in FIG. 9, with the doping concentration of the drift region 18 as a reference value. The method of calculating the distribution shown in FIG. 14 is the same as the example in FIG.

[0134] Fig. 15 is a diagram showing an example in which the activation rate of each doping concentration peak 201 is calculated using the doping concentrations shown in Fig. 14. The calculation method of the activation rate shown in Fig. 15 is the same as the example in Fig. 13.

[0135] 16 shows the interstitial Si—H donors and the CiOi—H donors contained in the kth doping concentration peak 201-k. Each doping concentration peak 201 contains hydrogen donors. The hydrogen donors include the interstitial Si—H donors and the CiOi—H donors.

[0136] The CiOi-H donor contains carbon and oxygen. The concentration of CiOi-H donor ( / cm ３ ) depends more on the carbon and oxygen chemical concentrations than on the hydrogen chemical concentration. ３ ) may be approximately constant depending on the carbon and oxygen chemical concentrations. Therefore, as the range Rk becomes wider, the integral value of the CiOi-H donors in the depth direction becomes larger.

[0137] On the other hand, the concentration of interstitial Si—H donors is relatively little affected by the carbon chemical concentration and oxygen chemical concentration of the semiconductor substrate 10. The concentration distribution of interstitial Si—H donors has a shape similar or analogous to the hydrogen chemical concentration distribution. The integral value of the concentration of interstitial Si—H donors in the depth direction does not depend on the size of the range Rk, but depends on the integral value of the hydrogen chemical concentration in the depth direction.

[0138] 17 shows interstitial Si—H donors and CiOi—H donors when the range Rk is relatively wide. The hydrogen ion dose in this example is the same as in the example in FIG. 16. However, in this example, hydrogen is distributed widely in the depth direction, and the range Rk is wide. For example, even when hydrogen ions are implanted with the same dose, the hydrogen may be distributed over a wider area as the acceleration energy increases, and the range Rk may become wider. In this example, as the range Rk becomes wider, the integrated value of CiOi—H donors increases.

[0139] In the range R1 corresponding to the first doping concentration peak 201-1, the integrated concentration of the CiOi-H donors may be higher than the integrated concentration of the interstitial Si-H donors. By increasing the ratio of the integrated concentration of the CiOi-H donors, the activation rate in the range R1 can be reduced. The amount of the CiOi-H donors generated depends on the concentrations of carbon and oxygen in the substrate and is generated at a constant concentration from the lower surface 23 to the upper surface 21. On the other hand, the amount of the interstitial Si-H donors generated depends on the amount of hydrogen present. If the amount of the CiOi-H donors generated is large, the amount of hydrogen consumed on the lower surface 23 side is relatively large, and the amount of hydrogen diffusing to the upper surface 21 side is reduced. Therefore, the amount of hydrogen contributing to the generation of the interstitial Si-H donors at the peak on the upper surface 21 side is reduced, and the amount of the interstitial Si-H donors generated is also reduced. In this way, the concentration of the SiOi-H donors becomes relatively higher than that of the interstitial Si-H donors, and the activation rate of the interstitial Si-H donors in the activation rate of the hydrogen donors becomes smaller, which makes the activation rate of the implanted hydrogen ions appear smaller.

[0140] 16 and 17, a method for calculating the activation rate of the kth doping concentration 201-k will be described. First, the upper limit position ZH and the lower limit position ZL of the range Rk corresponding to the kth doping concentration 201-k are extracted. As explained in FIG. 4, the upper limit position ZH is the depth position Z3(k-1) or Zb of the doping concentration valley 203-(k-1). The lower limit position ZL is the depth position Z3k or Z0 of the doping concentration valley 203-k.

[0141] Next, in the depth range from the lower limit position ZL to the upper limit position ZH, an integral value Ak obtained by integrating the doping concentration and an integral value Bk obtained by integrating the hydrogen chemical concentration (see, for example, FIG. 4) are calculated. Then, the integral value Ak is divided by the integral value Bk to calculate the activation rate in the range Rk.

[0142] FIG. 18 is a diagram showing another example of the doping concentration distribution in the buffer region 20. The semiconductor substrate 10 in this example is an MCZ substrate. The buffer region 20 in this example differs from the example in FIG. 4 in that it has five doping concentration peaks 201-1 to 201-5 at five depth positions Z11 to Z15. The other structures are similar to the example described in relation to FIG. 4. Although the distribution of hydrogen chemical concentration is omitted in FIG. 18, the buffer region 20 in this example has five hydrogen concentration peaks 211 corresponding to the five doping concentration peaks 201-1 to 201-5.

[0143] In this example, the doping concentration distribution from the second doping concentration peak 201-2 to the fifth doping concentration peak 201-5 is similar to the doping concentration distribution from the first doping concentration peak 201-1 to the fourth doping concentration peak 201-4 in Fig. 4. In other words, this example may be obtained by adding the first doping concentration peak 201-1, which is located closest to the top surface 21, to the doping concentration distribution shown in Fig. 4. In this example, the doping concentration peaks 201 located closest to the top surface 21 are also referred to as the first doping concentration peak 201-1, the second doping concentration peak 201-2, ..., the fifth doping concentration peak 201-5, in order.

[0144] In this example, the doping concentration P1 of the first doping concentration peak 201-1 is lower than the doping concentration P2 of the second doping concentration peak 201-2. The doping concentration P1 may be 0.9 times or less, or even 0.7 times or less, of the doping concentration P2. In another example, the doping concentration P1 may be equal to or greater than the doping concentration P2.

[0145] The doping concentration P2 of the second doping concentration peak 201-2 may be higher than the doping concentration P3 of the third doping concentration peak 201-3. The doping concentration P3 of the third doping concentration peak 201-3 may be lower than the doping concentration P4 of the fourth doping concentration peak 201-4. The doping concentration P4 of the fourth doping concentration peak 201-4 may be lower than the doping concentration P5 of the fifth doping concentration peak 201-5.

[0146] In this example, the distance between two adjacent doping concentration peaks 201 in the depth direction may be 15 μm or less, or may be 10 μm or less. The distance may be 5 μm or more. However, the distance between the first doping concentration peak 201-1 and the second doping concentration peak 201-2 may be greater than any of the distances between the other doping concentration peaks 201.

[0147] Fig. 19 is a diagram showing the activation rates of the respective doping concentration peaks 201 in the example shown in Fig. 18. In this example, too, the activation rate at the first doping concentration peak 201-1 is lower than the activation rate at the second doping concentration peak 201-2.

[0148] The activation rate of the first doping concentration peak 201-1 may be 0.1% or more less, 0.2% or more less, or 0.3% or more less than the activation rate of the second doping concentration peak 201-2. The activation rate of the first doping concentration peak 201-1 may be 95% or less, 90% or less, or 85% or less of the activation rate of the second doping concentration peak 201-2. The activation rate of the first doping concentration peak 201-1 may be greater than 2.7% and less than 3.3%. The activation rate of the second doping concentration peak 201-2 may be greater than 3% and less than 3.5%.

[0149] The activation rate at the second doping concentration peak 201-2 may be lower than the activation rate at the third doping concentration peak 201-3. The activation rate at the second doping concentration peak 201-2 may be 0.01% or more lower, 0.05% or more lower, or 0.1% or more lower than the activation rate at the third doping concentration peak 201-3. The activation rate at the second doping concentration peak 201-1 may be 99% or less, 97% or less, or 95% or less of the activation rate at the third doping concentration peak 201-2. The activation rate at the third doping concentration peak 201-3 may be greater than 3% and less than 3.5%.

[0150] The activation rate at the third doping concentration peak 201-3 may be lower than the activation rate at the fourth doping concentration peak 201-4. The activation rate at the third doping concentration peak 201-3 may be 0.3% or more lower, 0.5% or more lower, or 0.7% or more lower than the activation rate at the fourth doping concentration peak 201-4. The activation rate at the third doping concentration peak 201-3 may be 95% or less of the activation rate at the fourth doping concentration peak 201-4, 90% or less, or 85% or less. The activation rate at the fourth doping concentration peak 201-4 may be greater than 3.5% and less than 4%.

[0151] The activation rate at the shallowest concentration peak (in this example, the fifth doping concentration peak 201-5) may be lower than the activation rate at the adjacent concentration peak (in this example, the fourth doping concentration peak 201-4). The activation rate at the shallowest concentration peak may be similar to the example of FIG.

[0152] 20 is a diagram showing another example of the distribution of doping concentration along the ff line. The semiconductor substrate 10 in this example is an FZ substrate manufactured by the FZ method. This example also has a doping concentration peak 201 similar to the example in FIG. 18.

[0153] 21 is a diagram showing the activation rates of the doping concentration peaks 201 in the example shown in FIG. 20. In this example, the activation rates of the doping concentration peaks 201 also showed a similar trend to the example shown in FIG. 19. However, in this example, the difference between the activation rate of the first doping concentration peak 201-1 and the activation rate of the second doping concentration peak 201-2 was relatively large. Since the first doping concentration peak 201-1 in this example is located at a relatively large distance from the lower surface 23, it is possible that the activation rate was reduced due to a significant decrease in oxygen concentration, as in the example shown in FIG. 8.

[0154] In this example, the activation rate of the first doping concentration peak 201-1 may be 0.2% or more less, 0.3% or more less, or 0.4% or more less than the activation rate of the second doping concentration peak 201-2. The activation rate of the first doping concentration peak 201-1 may be 95% or less, 90% or less, or 85% or less of the activation rate of the second doping concentration peak 201-2. The activation rate of the first doping concentration peak 201-1 may be greater than 1.6% and less than 2.2%. The activation rate of the second doping concentration peak 201-2 may be greater than 2% and less than 2.6%.

[0155] The activation rate of the second doping concentration peak 201-2 may be at least 0.05%, at least 0.1%, or at least 0.2% less than the activation rate of the third doping concentration peak 201-3. The activation rate of the second doping concentration peak 201-2 may be at most 99%, at most 97%, or at most 95% of the activation rate of the third doping concentration peak 201-3. The activation rate of the third doping concentration peak 201-3 may be greater than 2.2% and less than 2.8%.

[0156] The activation rate at third doping concentration peak 201-3 may be at least 0.05%, at least 0.1%, or at least 0.2% less than the activation rate at fourth doping concentration peak 201-4. The activation rate at third doping concentration peak 201-3 may be no more than 99%, no more than 97%, or no more than 95% of the activation rate at fourth doping concentration peak 201-4. The activation rate at fourth doping concentration peak 201-4 may be greater than 2.3% and less than 2.9%.

[0157] The activation rate at the shallowest concentration peak may be less than 1.5%, less than 1%, or less than 0.7%. The activation rate at the shallowest concentration peak may be greater than 0%, or greater than 0.3%.

[0158] Fig. 22 is a diagram showing the doping concentration distribution shown in Fig. 18, with the doping concentration in drift region 18 as a reference value. In other words, Fig. 22 shows a distribution obtained by subtracting the doping concentration in drift region 18 from the doping concentration at each depth position in the doping concentration distribution shown in Fig. 18.

[0159] Fig. 23 is a diagram showing an example in which the activation ratio of each doping concentration peak 201 is calculated using the doping concentrations shown in Fig. 22. That is, the activation ratio in this example is calculated by dividing the integral value of the doping concentration shown in Fig. 22 by the integral value of the hydrogen chemical concentration in each range Rk (see Fig. 4).

[0160] The activation rate at the first doping concentration peak 201-1 may be 0.3% or more smaller, 0.4% or more smaller, or 0.5% or more smaller than the activation rate at the second doping concentration peak 201-2. The activation rate at the first doping concentration peak 201-1 may be 90% or less, 85% or less, or 80% or less of the activation rate at the second doping concentration peak 201-2.

[0161] The activation rate at the second doping concentration peak 201-2 may be 0.05% or more smaller, 0.1% or more smaller, or 0.15% or more smaller than the activation rate at the third doping concentration peak 201-3. The activation rate at the second doping concentration peak 201-2 may be 99% or less, 95% or less, or 90% or less of the activation rate at the third doping concentration peak 201-3.

[0162] The activation rate at the third doping concentration peak 201-3 may be 0.3% or more smaller, 0.4% or more smaller, or 0.5% or more smaller than the activation rate at the fourth doping concentration peak 201-4. The activation rate at the third doping concentration peak 201-3 may be 90% or less, 85% or less, or 80% or less of the activation rate at the fourth doping concentration peak 201-4.

[0163] Fig. 24 is a diagram showing the doping concentration distribution shown in Fig. 20 with the doping concentration in drift region 18 as a reference value. In other words, Fig. 24 shows a distribution obtained by subtracting the doping concentration in drift region 18 from the doping concentration at each depth position in the doping concentration distribution shown in Fig. 20.

[0164] Fig. 25 is a diagram showing an example in which the activation ratio of each doping concentration peak 201 is calculated using the doping concentrations shown in Fig. 24. That is, the activation ratio in this example is calculated by dividing the integral value of the doping concentration shown in Fig. 24 by the integral value of the hydrogen chemical concentration in each range Rk (see Fig. 4).

[0165] The activation rate at the first doping concentration peak 201-1 may be 0.3% or more smaller, 0.4% or more smaller, or 0.5% or more smaller than the activation rate at the second doping concentration peak 201-2. The activation rate at the first doping concentration peak 201-1 may be 90% or less, 85% or less, or 80% or less of the activation rate at the second doping concentration peak 201-2.

[0166] The activation rate at the second doping concentration peak 201-2 may be 0.05% or more smaller, 0.1% or more smaller, or 0.15% or more smaller than the activation rate at the third doping concentration peak 201-3. The activation rate at the second doping concentration peak 201-2 may be 99% or less, 95% or less, or 90% or less of the activation rate at the third doping concentration peak 201-3.

[0167] The activation rate at the third doping concentration peak 201-3 may be 0.3% or more smaller, 0.4% or more smaller, or 0.5% or more smaller than the activation rate at the fourth doping concentration peak 201-4. The activation rate at the third doping concentration peak 201-3 may be 90% or less, 85% or less, or 80% or less of the activation rate at the fourth doping concentration peak 201-4.

[0168] 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.

[0169] 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.

[0170] 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, 29...Straight portion, 30...Dummy trench portion, 31...Tip portion, 32...Dummy insulating film, 34...Dummy conductive portion, 38...Interlayer insulating film, 39...Straight portion, 40...Gate trench portion, 41...Tip portion, 42...Gate insulating film, 4 4...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, 130...Peripheral gate wiring, 131...Active side gate wiring, 160...Active portion, 162...Edge, 164...Gate pad, 201...Doping concentration peak, 203...Doping concentration valley, 211...Hydrogen concentration peak, 221...Straight line, 222...Straight line

Claims

1. A semiconductor device provided on a semiconductor substrate having an upper surface and a lower surface, comprising: a drift region of a first conductivity type provided on the semiconductor substrate; and 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, wherein the buffer region has a plurality of doping concentration peaks at different depth positions, the plurality of doping concentration peaks including a first doping concentration peak closest to the upper surface and a second doping concentration peak second closest to the upper surface, and wherein an activation rate at which impurities function as donors or acceptors at the first doping concentration peak is lower than the activation rate at the second doping concentration peak.

2. The semiconductor device according to claim 1, wherein the plurality of doping concentration peaks include a third doping concentration peak that is third closest to the top surface, and the activation rate at the second doping concentration peak is lower than the activation rate at the third doping concentration peak.

3. The semiconductor device according to claim 2, wherein the plurality of doping concentration peaks include a fourth doping concentration peak that is fourth closest to the top surface, and the activation rate at the third doping concentration peak is lower than the activation rate at the fourth doping concentration peak.

4. The semiconductor device according to any one of claims 1 to 3, wherein the doping concentration of the first doping concentration peak is higher than the doping concentration of the second doping concentration peak.

5. A semiconductor device according to claim 2 or 3, wherein the doping concentration of the first doping concentration peak is higher than the doping concentration of the second doping concentration peak, and the doping concentration of the second doping concentration peak is lower than the doping concentration of the third doping concentration peak.

6. The semiconductor device according to any one of claims 1 to 3, wherein the doping concentration of the first doping concentration peak is lower than the doping concentration of the second doping concentration peak.

7. A semiconductor device according to claim 2 or 3, wherein the doping concentration of the first doping concentration peak is lower than the doping concentration of the second doping concentration peak, and the doping concentration of the second doping concentration peak is higher than the doping concentration of the third doping concentration peak.

8. A semiconductor device according to any one of claims 1 to 3, wherein the plurality of doping concentration peaks include a shallowest concentration peak closest to the underside and an adjacent concentration peak arranged adjacent to the shallowest concentration peak in the depth direction, and the activation rate at the shallowest concentration peak is lower than the activation rate of the adjacent concentration peak.

9. The semiconductor device according to any one of claims 1 to 3, wherein the first doping concentration peak and the second doping concentration peak contain hydrogen donors.

10. A semiconductor device as described in any one of claims 1 to 3, wherein the buffer region has a plurality of doping concentration valleys each at a different depth position, the plurality of doping concentration valleys including a first concentration valley closest to the top surface and a second concentration valley second closest to the top surface, and the activation rate in the first concentration valley is lower than the activation rate in the second concentration valley.

11. The semiconductor device according to any one of claims 1 to 3, wherein the activation rate at the first doping concentration peak is smaller than the activation rate at the second doping concentration peak by 0.3% or more.

12. The oxygen chemical concentration in the semiconductor substrate is 1×10 １７ / cm ３ The semiconductor device according to claim 11, wherein the thickness is less than 1 / 2 mm.

13. The semiconductor device according to any one of claims 1 to 3, wherein the activation rate at the first doping concentration peak is smaller than the activation rate at the second doping concentration peak by 0.4% or more.

14. The oxygen chemical concentration in the semiconductor substrate is 1×10 １７ / cm ３ The semiconductor device according to claim 13 .

15. The semiconductor device according to any one of claims 1 to 3, wherein the distance between the first doping concentration peak and the lower surface is 20 µm or more.

16. The semiconductor device according to any one of claims 1 to 3, wherein at the first doping concentration peak, the integrated concentration of the C1Oi-H donors is higher than the integrated concentration of the Si-H donors.

Images