Semiconductor device

Abstract

To precisely control a range and a donor concentration of a donor region generated by hydrogen bonding with crystal defects.SOLUTION: A semiconductor device comprises: a drift region of a first conductivity type provided on a semiconductor substrate; a buffer region of the first conductivity type provided between a lower surface of the semiconductor substrate and the drift region, having one or more donor concentration peaks with a donor concentration higher than that of the drift region; and a helium chemical concentration peak arranged at the upper surface side of the semiconductor substrate in a depth direction connecting between an upper surface and the lower surface of the semiconductor substrate. The donor concentration of the drift region is higher than a base doping concentration of the semiconductor substrate over the whole drift region in the depth direction.SELECTED DRAWING: Figure 7

Description

[Technical field]

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

[0002] It has been known that when hydrogen is implanted into a semiconductor substrate and diffused, the hydrogen bonds with crystal defects present in the diffusion region to become donors (see, for example, Patent Document 1). Patent Document 1: JP2016-204227A Problem to be Solved

[0003] It is preferable that the range of the donor region generated by the bonding of the crystal defects with hydrogen and the donor concentration can be precisely controlled.

[0004] In order to solve the above problem, one aspect of the present invention provides a semiconductor device including a semiconductor substrate having an upper surface and a lower surface, the semiconductor substrate including a first conductivity type drift region, a first conductivity type buffer region between the lower surface of the semiconductor substrate and the drift region, the first conductivity type buffer region having one or more donor concentration peaks having a higher donor concentration than the drift region, and a helium chemical concentration peak disposed on the upper surface side of the semiconductor substrate in a depth direction connecting the upper surface to the lower surface of the semiconductor substrate, the donor concentration of the drift region being higher than the base doping concentration of the semiconductor substrate throughout the drift region in the depth direction. The drift region may have a flat region, and the flat region may be a region in which a donor concentration is between a maximum value of the donor concentration in the flat region and 50% of the maximum value, the region being continuous in the depth direction. In the depth direction, the thickness of the flat region may be 10% or more of the thickness of the semiconductor substrate. The drift region may have a flat region, and the flat region may be a portion whose length in the depth direction is 10% or more of the thickness in the depth direction of the semiconductor substrate, and the value of the donor concentration distribution in the portion may be within ±50% of the average concentration of the donor concentration distribution. The entire drift region may be the flat region. The semiconductor device may further include a base region of a second conductivity type provided between the upper surface of the semiconductor substrate and the drift region, and an accumulation region provided between the drift region and the base region and having a higher donor concentration than the drift region. The semiconductor device may further include a base region of a second conductivity type provided between the upper surface of the semiconductor substrate and the drift region, and the helium chemical concentration peak may be disposed between the flat region and the base region. The drift region may be disposed between the helium chemical concentration peak and the base region. The donor concentration of the drift region between the helium chemical concentration peak and the base region may be lower than the donor concentration of the drift region between the buffer region and the helium chemical concentration peak. The flat region may include a hydrogen donor, and the length of the flat region in the depth direction may be greater than the length of the buffer region in the depth direction.The semiconductor device may further include an emitter region of a first conductivity type provided in contact with the upper surface of the semiconductor substrate and having a higher donor concentration than the drift region, a base region of a second conductivity type provided between the emitter region and the drift region, a collector region of a second conductivity type provided in contact with the lower surface of the semiconductor substrate, a gate trench portion provided on the upper surface of the semiconductor substrate, and an accumulation region provided between the drift region and the base region and having a higher donor concentration than the drift region, the accumulation region having the donor concentration peak due to a donor other than hydrogen.The semiconductor device may further include an active portion provided in the semiconductor substrate, and an edge termination structure provided surrounding the active portion in a top view of the semiconductor substrate, the semiconductor substrate having a passage region through which helium injected at a position of the helium chemical concentration peak passes, and the passage region provided in the edge termination structure may be at the same depth as the passage region provided in the active portion in the depth direction. A region where the passing region is not formed may be provided in a portion of the edge termination structure that contacts the upper surface of the semiconductor substrate, and a donor concentration in the region where the passing region is not formed may be the same as the base doping concentration. The semiconductor device may further include an active section provided in the semiconductor substrate and an edge termination structure provided surrounding the active section in a top view of the semiconductor substrate, the semiconductor substrate having a passing region through which helium injected at a position of the helium chemical concentration peak has passed, and the passing region provided in the edge termination structure may be shorter than the passing region provided in the active section in the depth direction, or the edge termination structure may not have the passing region. The semiconductor device may further include a transistor section and a diode section provided in the semiconductor substrate, the semiconductor substrate having a passing region through which helium injected at a position of the helium chemical concentration peak has passed, and the passing region may be provided in the diode section and the transistor section in the depth direction.The semiconductor device may further include a transistor portion and a diode portion provided on the semiconductor substrate, the semiconductor substrate having a passage region through which helium injected at a position of the helium chemical concentration peak passes, and the passage region provided in the diode portion may be shorter than the passage region provided in the transistor portion in the depth direction, or the diode portion may not be provided with the passage region.The semiconductor device may further include a transistor portion and a diode portion provided on the semiconductor substrate, the semiconductor substrate having a passage region through which helium injected at a position of the helium chemical concentration peak passes, and the passage region provided in the transistor portion may be shorter than the passage region provided in the diode portion in the depth direction, or the transistor portion may not be provided with the passage region.

[0005] In a second aspect of the present invention, a semiconductor device is provided that includes a semiconductor substrate having an upper surface and a lower surface. In a depth direction connecting the upper surface and the lower surface of the semiconductor substrate, a hydrogen concentration distribution may have a hydrogen concentration peak. A helium concentration distribution may have a helium concentration peak. In a depth direction, a donor concentration distribution may have a first donor concentration peak and a second donor concentration peak. The hydrogen concentration peak and the first donor concentration peak may be disposed at a first depth. The helium concentration peak and the second donor concentration peak may be disposed at a second depth that is deeper than the first depth with respect to the lower surface. Each concentration peak may have an upward slope in which the concentration value increases from the lower surface to the upper surface. A value obtained by normalizing the upward slope of the second donor concentration peak by the upward slope of the helium concentration peak may be smaller than a value obtained by normalizing the upward slope of the first donor concentration peak by the upward slope of the hydrogen concentration peak. Each of the concentration peaks may have a downward slope with decreasing concentration value from the lower surface to the upper surface. The helium concentration peak may have an upward slope with a smaller slope than the downward slope. The second donor concentration peak may have an upward slope with a smaller slope than the downward slope.

[0006] The donor concentration distribution between the first depth and the second depth may have a plateau region where the donor concentration is approximately constant, and the length of the plateau region in the depth direction may be 10% or more of the thickness of the semiconductor substrate in the depth direction.

[0007] The donor concentration distribution between the first depth and the second depth may have a plateau region where the donor concentration is approximately constant. The length of the plateau region in the depth direction may be 10 μm or more.

[0008] The minimum donor concentration of the flat region may be higher than the donor concentration of the semiconductor substrate.

[0009] The minimum value of the donor concentration between the first depth and the second depth may be higher than the donor concentration of the semiconductor substrate.

[0010] The concentration value of the helium concentration peak may be less than the concentration value of the hydrogen concentration peak.

[0011] The semiconductor device may include an N-type drift region provided in a semiconductor substrate. The semiconductor device may include an emitter region provided in contact with an upper surface of the semiconductor substrate and having a higher donor concentration than the drift region. The semiconductor device may include a P-type base region provided between the emitter region and the drift region. The semiconductor device may include a P-type collector region provided in contact with a lower surface of the semiconductor substrate. The semiconductor device may include an N-type buffer region provided between the collector region and the drift region and having one or more donor concentration peaks having a higher donor concentration than the drift region. The first donor concentration peak may be a donor concentration peak of the buffer region.

[0012] The semiconductor device may include an accumulation region between the base region and the drift region, the accumulation region having one or more donor concentration peaks having a higher donor concentration than the drift region, and the second donor concentration peak may be a donor concentration peak of the accumulation region.

[0013] The accumulation region may have a donor concentration peak due to a donor other than hydrogen, in addition to the second donor concentration peak.

[0014] The second donor concentration peak may be located between the buffer region and the reservoir region.

[0015] The semiconductor device may include a gate trench portion disposed on a top surface of a semiconductor substrate, and the second donor concentration peak may be located between a bottom of the gate trench portion and the top surface of the semiconductor substrate.

[0016] The semiconductor device may include an active portion provided in a semiconductor substrate. The semiconductor device may include an edge termination structure provided surrounding the active portion in a top view of the semiconductor substrate. The semiconductor substrate may have a passage region through which helium injected at a position of a helium concentration peak passes. In the depth direction, the passage region provided in the edge termination structure may be shorter than the passage region provided in the active portion, or the edge termination structure may not have a passage region.

[0017] The semiconductor device may include a transistor portion and a diode portion provided on a semiconductor substrate, and a passing region provided in the diode portion may be shorter than a passing region provided in the transistor portion in a depth direction, or the diode portion may not be provided with a passing region.

[0018] In the depth direction, the passing region provided in the transistor portion may be shorter than the passing region provided in the diode portion, or the transistor portion may not be provided with a passing region.

[0019] The first depth may be included in a range of 5 μm or less in a depth direction from the lower surface.

[0020] The donor concentration at the hydrogen concentration peak is 1×10 15 / cm 3 That's it, 1×10 17 / cm 3 It may be the following:

[0021] In a third aspect of the present invention, there is provided a semiconductor device including a semiconductor substrate having an upper surface and a lower surface, wherein a hydrogen concentration distribution in a depth direction connecting the upper surface and the lower surface of the semiconductor substrate may have a hydrogen concentration peak located within a range of 5 μm or less in the depth direction from the lower surface, and a helium concentration peak located on the upper surface side of the hydrogen concentration peak.

[0022] The semiconductor substrate has an impurity concentration peak between the underside and the hydrogen concentration peak, and the impurity may be argon or fluorine.

[0023] A fourth aspect of the present invention provides a method for manufacturing a semiconductor device according to the first aspect. The manufacturing method may include a first implantation step of implanting hydrogen to a first depth from a lower surface of a semiconductor substrate. The manufacturing method may include a second implantation step of implanting helium to a second depth from a lower surface of the semiconductor substrate to form a passage region through which the helium has passed. The manufacturing method may include a diffusion step of heat-treating the semiconductor substrate to diffuse the hydrogen implanted to the first depth into the passage region. A dose of hydrogen in the first implantation step may be determined so that the minimum value of the donor concentration in the passage region in the semiconductor substrate heat-treated in the diffusion step is higher than the donor concentration of the semiconductor substrate before the hydrogen is implanted.

[0024] In the first implantation stage, hydrogen may be implanted at a dose equal to or greater than a minimum dose determined based on the diffusion coefficient of hydrogen in the semiconductor substrate and the second depth.

[0025] The semiconductor substrate is a silicon substrate, and when the second depth from the bottom surface is x (μm), the dose of hydrogen in the first implantation step is Q (ions / cm 2 ) may satisfy the following formula: Q ≥ 1.6 × 10 13 ×e 0.06x

[0026] In the first implantation step, hydrogen may be implanted to a first depth by plasma doping.

[0027] After plasma doping, the bottom surface of the semiconductor substrate may be ground.

[0028] After plasma doping, the bottom surface of the semiconductor substrate may be laser annealed.

[0029] The above summary of the invention does not list all of the necessary features of the present invention. Also, subcombinations of these features may also be inventions. [Brief description of the drawings]

[0030] [Figure 1] 1 is a cross-sectional view showing an example of a semiconductor device 100. FIG. [Diagram 2] 1. The hydrogen concentration distribution, helium concentration distribution, donor concentration distribution and vacancy defect concentration distribution 175 in the depth direction are shown at the position indicated by the line AA in FIG. [Figure 3A] 1 is a diagram illustrating the relationship between a hydrogen concentration peak 131 and a first donor concentration peak 111. FIG. [Figure 3B] 13 is a diagram illustrating the relationship between a helium concentration peak 141 and a second donor concentration peak 121. FIG. [Figure 3C] 13 is a diagram illustrating the inclination of an upward slope 142. FIG. [Figure 4A] FIG. 13 is a diagram for explaining another definition of the standardization of the inclination of the upward slope 112. [Figure 4B] FIG. 13 is a diagram for explaining another definition of the standardization of the inclination of the upward slope 122. [Diagram 5] FIG. 2 is a diagram illustrating a flat region 150. [Figure 6] 1 is a diagram illustrating an example of the structure of a semiconductor device 100. FIG. [Figure 7] 7 is a diagram showing an example of a carrier concentration distribution in the depth direction at the position of the line BB in FIG. 6. [Figure 8] 3 is a diagram showing another example of the structure of the semiconductor device 100. FIG. [Figure 9] 9 is a diagram showing an example of a carrier concentration distribution in the depth direction at the position of line CC in FIG. 8. FIG. [Figure 10]The hydrogen concentration distribution, helium concentration distribution, and carrier concentration distribution in the depth direction are shown at the position indicated by the line AA in FIG. [Figure 11] 2 is a diagram showing an example of the arrangement of elements on an upper surface 21 of a semiconductor substrate 10. FIG. [Figure 12] 12 is a diagram showing an example of a cross section taken along the line cc' in FIG. [Figure 13] 13 is a diagram showing another example of the arrangement of the passage area 106. FIG. [Figure 14] 13 is a diagram showing another example of the arrangement of the passage area 106. FIG. [Figure 15] 13 is a diagram showing another example of the arrangement of the passage area 106. FIG. [Figure 16A] 13 is a diagram showing another example of the arrangement of the passage area 106. FIG. [Figure 16B] 13 is a diagram showing another example of the arrangement of the passage area 106. FIG. [Figure 17A] 13 is a diagram showing another example of the arrangement of the passage area 106. FIG. [Figure 17B] 13 is a diagram showing another example of the arrangement of the passage area 106. FIG. [Figure 17C] 1 is a diagram illustrating a minimum film thickness M of a photoresist film 200 for preventing helium ions from penetrating into a semiconductor substrate 10. FIG. [Figure 18A] 13 is a diagram showing another example of the arrangement of the passage area 106. FIG. [Figure 18B] 13 is a diagram showing another example of the arrangement of the passage area 106. FIG. [Figure 19] 1 is a diagram showing a step of forming a passing region 106 in a manufacturing method of the semiconductor device 100. FIG. [Figure 20] FIG. 19 is a diagram showing an example of a carrier concentration distribution in the semiconductor substrate 10 after the diffusion step S1904. [Figure 21] 1 is a diagram showing the relationship between the diffusion coefficient D of hydrogen and the first dose Q. FIG. [Figure 22] FIG. 1 is a diagram showing the relationship between the diffusion coefficient D and the annealing temperature T. [Figure 23] FIG. 11 is a diagram showing the relationship between the diffusion depth of hydrogen and the first dose amount. [Figure 24]FIG. 1 is a diagram showing the relationship between the diffusion coefficient D and the diffusion depth x. [Diagram 25] FIG. 13 is a diagram showing a straight line defining a minimum dose for each annealing temperature. [Figure 26] FIG. 11 is a diagram showing the relationship between the second dose and the minimum dose of the first dose. [Figure 27] 11 is a diagram illustrating an example of a first depth Z1. FIG. [Figure 28] 13 shows other examples of the donor concentration distribution, the hydrogen chemical concentration distribution, and the helium chemical concentration distribution in the depth direction of the semiconductor substrate 10. [Figure 29] 1 is a diagram showing an example of a hydrogen chemical concentration distribution and an argon chemical concentration distribution in the vicinity of a hydrogen concentration peak 131. FIG. [Diagram 30] 3 is a diagram showing another example of the structure of the semiconductor device 100. FIG. [Diagram 31] 30. An example of the carrier concentration distribution, the hydrogen chemical concentration distribution, and the boron chemical concentration distribution is shown in the DD line of FIG. [Diagram 32] 30. An example of the carrier concentration distribution, the hydrogen chemical concentration distribution, and the phosphorus chemical concentration distribution is shown in the E-E line of FIG. [Diagram 33] 2A to 2C are diagrams illustrating some steps in a manufacturing method of the semiconductor device 100. [Diagram 34] 2A to 2C are diagrams illustrating some steps in a manufacturing method of the semiconductor device 100. [Diagram 35] An example of a process for implanting hydrogen ions to a first depth Z1 and helium ions to a second depth Z2 in the lower surface side structure formation stage is shown. [Diagram 36] Another example of a process for implanting hydrogen ions to a first depth Z1 and helium ions to a second depth Z2 in the lower surface side structure formation stage is shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0032] 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.

[0033] In this specification, technical matters may be explained using orthogonal coordinate axes of 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 indicating positive or negative, it means a direction parallel to the +Z-axis and -Z-axis.

[0034] In this specification, when the term "same" or "equal" is used, it may include cases where there is an error due to manufacturing variations, etc. The error is, for example, within 10%.

[0035] In this specification, chemical concentration refers to the concentration of an impurity measured regardless of the activation state. The chemical concentration can be measured, for example, by secondary ion mass spectrometry (SIMS). In this specification, the concentration difference between the donor and the acceptor may be the concentration of the donor or the acceptor that is greater. The concentration difference can be measured by voltage-capacitance measurement (CV method). The carrier concentration measured by spreading resistance measurement (SR) may be the concentration of the donor or the acceptor. In addition, when the concentration distribution of the donor or the acceptor has a peak, the peak value may be the concentration of the donor or the acceptor in the region. In cases where the concentration of the donor or the acceptor in the region where the donor or the acceptor is present is almost uniform, the average value of the donor or the acceptor concentration in the region may be the donor or the acceptor concentration. 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).

[0036] FIG. 1 is a cross-sectional view showing an example of a semiconductor device 100. The semiconductor device 100 includes a semiconductor substrate 10. The semiconductor substrate 10 is a substrate formed of a semiconductor material. As an example, the semiconductor substrate 10 is a silicon substrate. The semiconductor substrate 10 has a donor concentration determined by impurities implanted during manufacture. The conductivity type of the semiconductor substrate 10 in this example is N-type. In this specification, the donor concentration in the semiconductor substrate 10 may be referred to as the substrate concentration.

[0037] The semiconductor substrate 10 has an upper surface 21 and a lower surface 23. The upper surface 21 and the lower surface 23 are the two main surfaces of the semiconductor substrate 10. In this specification, orthogonal axes in a plane parallel to the upper surface 21 and the lower surface 23 are defined as the X-axis and the Y-axis, and an axis perpendicular to the upper surface 21 and the lower surface 23 is defined as the Z-axis. Semiconductor elements such as IGBTs or FWDs are formed on the semiconductor substrate 10, but these element structures are omitted in FIG. 1.

[0038] Hydrogen ions and helium ions are implanted into the semiconductor substrate 10 from the lower surface 23 side. In this example, the hydrogen ions are protons. The hydrogen ions are implanted to a depth Z1 in the depth direction (Z-axis direction) of the semiconductor substrate 10. The helium ions are implanted to a depth Z2. In this example, of the two depths, the one closer to the lower surface 23 is defined as a first depth Z1, and the one deeper than the first depth Z1 as viewed from the lower surface 23 is defined as a second depth Z2. In FIG. 1, the implanted hydrogen and helium are shown diagrammatically by x marks, but hydrogen and helium are also distributed around the implantation positions Z1 and Z2.

[0039] The first depth Z1 may be disposed on the lower surface 23 side in the depth direction of the semiconductor substrate 10. For example, the first depth Z1 may be disposed in a range of half or less of the thickness of the semiconductor substrate 10 based on the lower surface 23, or may be disposed in a range of ¼ or less of the thickness of the semiconductor substrate 10. The second depth Z2 may be disposed on the upper surface 21 side in the depth direction of the semiconductor substrate 10. For example, the second depth Z2 may be disposed in a range of half or less of the thickness of the semiconductor substrate 10 based on the upper surface 21, or may be disposed in a range of ¼ or less of the thickness of the semiconductor substrate 10. However, the first depth Z1 and the second depth Z2 are not limited to these ranges.

[0040] The helium ions implanted to the second depth Z2 pass through a passage region 106 from the lower surface 23 to the second depth Z2. In the passage region 106, vacancy defects such as vacancies (V) and divacancies (VV) are generated due to the passage of the helium ions. In this specification, unless otherwise specified, vacancies include divacancies. The vacancy density in the passage region 106 can be adjusted by the dose of the helium ions implanted to the second depth Z2, etc.

[0041] By subjecting the semiconductor substrate 10 to a heat treatment after implanting hydrogen ions to the first depth Z1, the hydrogen implanted to the first depth Z1 diffuses into the passage region 106. VOH defects are formed by combining vacancies (V) and oxygen (O) present in the passage region 106 with hydrogen (H). The VOH defects function as donors that supply electrons. This allows the donor concentration in the passage region 106 to be higher than the donor concentration Db (or resistivity, base doping concentration) during the manufacture of the semiconductor ingot that is the basis of the semiconductor substrate 10. Therefore, the donor concentration of the semiconductor substrate 10 can be easily adjusted according to the characteristics that the element formed in the semiconductor substrate 10 should have. In this specification, unless otherwise specified, both VOH defects having a distribution similar to the chemical concentration distribution of hydrogen and VOH defects similar to the distribution of vacancy defects in the passage region 106 are referred to as hydrogen donors or hydrogen as a donor.

[0042] The dopant for setting the base doping concentration Db is a dopant added during the manufacture of a semiconductor ingot. For example, if the semiconductor ingot is silicon, phosphorus, antimony, or arsenic may be used for n-type, and boron or aluminum may be used for p-type. In the case of compound semiconductors and oxide semiconductors other than silicon, the respective dopants may be used. The manufacturing method of the semiconductor ingot may be any of the float zone (FZ) method, the Czochralski (CZ) method, and the magnetic field Czochralski (MCZ) method.

[0043] Usually, the semiconductor substrate 10 having the base doping concentration Db must be prepared according to the characteristics of the element to be formed in the semiconductor substrate 10, particularly the rated voltage or withstand voltage. In contrast, according to the semiconductor device 100 shown in FIG. 1, the donor concentration of the semiconductor substrate 10 and the range of the passage region 106 when the semiconductor device 100 is completed can be partially higher than the base doping concentration Db by controlling the dose amount and implantation depth of the hydrogen ions and helium ions. Therefore, even if a semiconductor substrate 10 having a different base doping concentration is used, an element having a predetermined rated voltage or withstand voltage characteristic can be formed. In addition, although the variation in the donor concentration during the manufacture of the semiconductor substrate 10 is relatively large, the dose amount of the hydrogen ions and helium ions can be controlled with relatively high accuracy. Therefore, the concentration of the vacancies (V) generated by implanting the helium ions can also be controlled with high accuracy, and the donor concentration of the passage region 106 can be controlled with high accuracy.

[0044] FIG. 2 shows the hydrogen concentration distribution, helium concentration distribution, donor concentration distribution, and vacancy defect concentration distribution 175 in the depth direction at the position shown by the AA line in FIG. 1. The horizontal axis of FIG. 2 shows the depth position from the lower surface 23, and the vertical axis shows the hydrogen concentration, helium concentration, donor concentration, and vacancy defect concentration per unit volume on a logarithmic axis. The vacancy defect concentration distribution 175 is the distribution immediately after ion implantation of hydrogen ions and helium ions. When the semiconductor device 100 is completed, the vacancies are reduced or disappeared compared to those immediately after the ion implantation, and a concentration distribution different from that of FIG. 2 is shown. The hydrogen concentration and helium concentration in FIG. 2 are chemical concentrations measured by, for example, the SIMS method. The donor concentration in FIG. 2 is an electrically activated doping concentration measured by, for example, the CV method or the SR method. In FIG. 2, the hydrogen concentration distribution, helium concentration distribution, and vacancy defect concentration distribution 175 are shown by dashed lines, and the donor concentration distribution is shown by a solid line.

[0045] The hydrogen concentration distribution has a hydrogen concentration peak 131. The helium concentration distribution has a helium concentration peak 141. The hydrogen concentration peak 131 has a maximum value at a first depth Z1. The helium concentration peak 141 has a maximum value at a second depth Z2.

[0046] The donor concentration distribution has a first donor concentration peak 111 and a second donor concentration peak 121. The first donor concentration peak 111 shows a maximum value at a first depth Z1. The second donor concentration peak 121 shows a maximum value at a second depth Z2. However, the position where the first donor concentration peak 111 shows a maximum value does not have to strictly match the first depth Z1. For example, if the position where the first donor concentration peak 111 shows a maximum value is included within the range of the full width at half maximum of the hydrogen concentration peak 131 based on the first depth Z1, the first donor concentration peak 111 may be substantially located at the first depth Z1. Similarly, if the position at which the second donor concentration peak 121 shows its maximum value is included within the full width at half maximum range of the helium concentration peak 141 based on the second depth Z2, then the second donor concentration peak 121 may be said to be substantially located at the second depth Z2.

[0047] The vacancy defect concentration distribution 175 has a first vacancy concentration peak corresponding to the hydrogen concentration peak 131 and a second vacancy concentration peak (vacancy concentration peak 171) corresponding to the helium concentration peak 141. However, the first vacancy concentration peak is not shown in the figure. The vacancy concentration peak 171 has a maximum value at the second depth Z2.

[0048] Each concentration peak has an upward slope where the concentration value increases and a downward slope where the concentration value decreases from the lower surface 23 to the upper surface 21 of the semiconductor substrate 10. In this example, the hydrogen concentration peak 131 has an upward slope 132 and a downward slope 133. The helium concentration peak 141 has an upward slope 142 and a downward slope 143. The first donor concentration peak 111 has an upward slope 112 and a downward slope 113. The second donor concentration peak 121 has an upward slope 122 and a downward slope 123. The vacancy concentration peak 171 has an upward slope 172 and a downward slope 173.

[0049] The donors of the semiconductor substrate 10 include donors that existed in the semiconductor substrate 10 before the hydrogen ions were implanted, i.e., the base doping concentration (concentration Db), donors activated by the implanted hydrogen, and the above-mentioned VOH defects. The ratio of hydrogen activated as a donor is, for example, about 1%. In a region of the passing region 106 that is somewhat distant from the first depth Z1 and the second depth Z2, the ratio of donors due to VOH defects corresponding to the vacancy defect concentration becomes higher than the ratio of donors due to VOH defects corresponding to the hydrogen chemical concentration, and the donor concentration is determined by the concentration of vacancy defects. The VOH defects corresponding to the hydrogen chemical concentration refer to VOH defects in which the hydrogen chemical concentration is more dominant than the vacancy defect concentration. The VOH defects corresponding to the vacancy defect concentration refer to VOH defects in which the vacancy defect concentration is more dominant than the hydrogen chemical concentration.

[0050] Here, VOH defects with a dominant hydrogen chemical concentration distribution have the following meaning. When vacancies, oxygen, and hydrogen form clusters to form VOH defects, the hydrogen chemical concentration is sufficiently high relative to the vacancy defect concentration, so that the donor concentration distribution due to VOH defects is similar to the hydrogen chemical concentration distribution. As an example, when the hydrogen chemical concentration is higher than the vacancy defect concentration at a certain depth and nearby depths, it can be said that the donor concentration distribution of VOH defects is dominated by the hydrogen chemical concentration distribution.

[0051] On the other hand, a VOH defect dominated by a vacancy defect concentration distribution 175 means that the vacancy defect concentration is sufficiently high relative to the hydrogen chemical concentration, so that the donor concentration distribution due to the VOH defect is similar to the vacancy defect concentration distribution. For example, when the vacancy defect concentration is higher than the hydrogen chemical concentration at a certain depth and its neighboring depths, it can be said that the vacancy defect concentration distribution 175 becomes the donor concentration distribution of the dominant VOH defect.

[0052] In the passage region 106, except for the vicinity of the first depth Z1 and the second depth Z2, vacancies (V, VV, etc.) generated by the passage of hydrogen are considered to be distributed in a substantially uniform concentration in the depth direction as shown in FIG. 2. In addition, oxygen (O) implanted during the manufacture of the semiconductor substrate 10 is also considered to be distributed uniformly in the depth direction. In addition, a sufficient amount of hydrogen is present in the passage region 106 because hydrogen at the hydrogen concentration peak 131 diffuses. These form a flat donor distribution as VOH defects.

[0053] Therefore, in the passing region 106 other than the vicinity of the first depth Z1 and the second depth Z2, there is a flat region 150 in which VOH defects functioning as donors are distributed almost uniformly. The donor concentration distribution in the flat region 150 is almost constant in the depth direction. The donor concentration being almost constant in the depth direction may refer to, for example, a state in which a region in which the difference between the maximum and minimum values ​​of the donor concentration is within 50% of the maximum donor concentration is continuous in the depth direction. The difference may be 30% or less of the maximum donor concentration in the region, or 10% or less.

[0054] Alternatively, the value of the donor concentration distribution may be within ±50%, ±30%, or ±10% of the average concentration of the donor concentration distribution in a predetermined range in the depth direction. The predetermined range in the depth direction may be as follows, for example. That is, the length from the first depth Z1 to the second depth Z2 is Z L From the center Zc between Z1 and Z2, 0.25Z is provided on the first depth Z1 side and the second depth Z2 side. L The distance between two points is 0.5Z LThe length of the predetermined range may be set to 0.75Z according to the length of the flat region 150. L It can also be 0.3Z L It can also be 0.9Z L It is also possible to use the following.

[0055] The range in which flat region 150 is provided can be controlled by the position of helium concentration peak 141. Flat region 150 is provided between hydrogen concentration peak 131 and helium concentration peak 141. The donor concentration in flat region 150 can be controlled by the dose of helium ions at helium concentration peak 141. By increasing the dose of helium ions, more vacancies (V) are generated in passage region 106, and the donor concentration increases.

[0056] When implanting helium ions at a position deeper than the hydrogen concentration peak 131, the acceleration energy of the helium ions may be increased to a value at which the helium ions penetrate (penetrate) the semiconductor substrate 10. In other words, the helium concentration peak 141 may not remain in the semiconductor substrate 10. This makes it possible to increase the concentration of vacancy defects. On the other hand, if the acceleration energy is excessively large, the damage received by the substrate during ion implantation may be too strong, and the distribution of vacancy defects in the passage region 106 may not be kept flat. For this reason, the helium concentration peak 141 may be positioned inside the semiconductor substrate 10.

[0057] Since the helium concentration peak 141 is located deeper than the hydrogen concentration peak 131, the broadening of the peak is likely to be greater than that of the hydrogen concentration peak 131. For this reason, the second donor concentration peak 121 is also likely to be greater than that of the first donor concentration peak 111. In other words, the second donor concentration peak 121 is likely to be a gentler peak than the first donor concentration peak 111.

[0058] Furthermore, in this example, the concentration value of the hydrogen concentration peak 131 is greater than the concentration value of the helium concentration peak 141. The concentration value of the hydrogen concentration peak 131 may be 10 times or more, or may be 100 times or more, greater than the concentration value of the helium concentration peak 141. In another example, the concentration value of the hydrogen concentration peak 131 may be equal to or less than the concentration value of the helium concentration peak 141.

[0059] In this example, since the concentration value of the hydrogen concentration peak 131 is high, the amount of hydrogen activated as a donor at the hydrogen concentration peak 131 is also relatively large. In other words, the ratio of donors of VOH defects, which are dominated by the hydrogen chemical concentration distribution, becomes high compared to the vacancy defect concentration distribution 175. In this case, the shape of the first donor concentration peak 111 is similar to the shape of the hydrogen concentration peak 131.

[0060] On the other hand, since the helium concentration peak 141 is far from the hydrogen concentration peak 131, the amount of hydrogen activated as a donor at the helium concentration peak 141 is small. That is, the ratio of donors of VOH defects dominated by vacancy defect concentration distribution 175 is relatively high compared to donors of VOH defects dominated by hydrogen chemical concentration distribution. In this case, the similarity between the shape of the second donor concentration peak 121 and the shape of the helium concentration peak 141 is smaller than the similarity between the shape of the first donor concentration peak 111 and the shape of the hydrogen concentration peak 131. Since the VOH defects are considered to be distributed almost uniformly in most of the passing region 106, the second donor concentration peak 121 has an even more gentle shape. The similarity of the peak shapes may be an index that indicates a smaller value as the difference in the corresponding slope between the hydrogen concentration peak or helium concentration peak and the donor concentration peak increases.

[0061] With such a structure, a flat region 150 can be provided between the first depth Z1 and the second depth Z2. The length of the flat region 150 in the depth direction may be 10% or more, 30% or more, or 50% or more of the thickness of the semiconductor substrate 10 in the depth direction. The length of the flat region 150 in the depth direction may be 10 μm or more, 30 μm or more, 50 μm or more, or 100 μm or more.

[0062] The minimum value of the donor concentration in the flat region 150 may be higher than the base doping concentration Db of the semiconductor substrate 10. In other words, the donor concentration in the flat region 150 may be higher than the base doping concentration Db over the entire flat region 150. The difference between the donor concentration in the flat region 150 and the base doping concentration Db of the semiconductor substrate 10 can be adjusted by, for example, the helium dose at the helium concentration peak 141.

[0063] The minimum value of the donor concentration between the first depth Z1 and the second depth Z2 may be higher than the base doping concentration of the semiconductor substrate 10. An N-type region may be continuously provided between the hydrogen concentration peak 131 and the helium concentration peak 141. In addition, the minimum value of the donor concentration between the second depth Z2 and the lower surface 23 of the semiconductor substrate 10 may be higher than the donor concentration of the semiconductor substrate 10.

[0064] 3A is a diagram illustrating the relationship between a hydrogen concentration peak 131 and a first donor concentration peak 111. In this example, the gradient 114 of the upward slope 112 of the first donor concentration peak 111 is normalized using the gradient 134 of the upward slope 132 of the hydrogen concentration peak 131. As an example of the normalization, the gradient 114 is divided by the gradient 134. Note that in this specification, the gradient may be used to mean the absolute value of the gradient.

[0065] The gradient of the upward slope may be the gradient between the position where the concentration shows a maximum value and the position where the concentration is a predetermined ratio to the maximum value. The predetermined ratio may be 80%, 50%, 10%, 1%, or other ratios. In addition, for the hydrogen concentration peak 131 and the first donor concentration peak 111, the gradient of the concentration distribution between the first depth Z1 and the lower surface 23 of the semiconductor substrate 10 may be used. In the example shown in FIG. 3A, the gradient 134 of the hydrogen concentration peak 131 is given by (H1-aH1) / (Z1-Z3), and the gradient 114 of the first donor concentration peak 111 is given by (D1-aD1) / (Z1-Z4). H1 is the hydrogen concentration at first depth Z1, D1 is the donor concentration at first depth Z1, a is a predetermined ratio, Z3 is the depth at which the hydrogen concentration becomes aH1 on the upward slope 132 of the hydrogen concentration peak 131, and Z4 is the depth at which the donor concentration becomes aD1 on the upward slope 112 of the first donor concentration peak 111. For example, when the slope 114 is normalized by the slope 134, it becomes (D1-aD1)(Z1-Z3) / {(H1-aH1)(Z1-Z4)}. The slope obtained by normalizing the slope 114 by the slope 134 is defined as α.

[0066] 3B is a diagram illustrating the relationship between the helium concentration peak 141 and the second donor concentration peak 121. In this example, the gradient 144 of the upward slope 142 of the helium concentration peak 141 is used to normalize the gradient 124 of the upward slope 122 of the second donor concentration peak 121.

[0067] 3B, the slope 144 of the helium concentration peak 141 is given by (H2-aH2) / (Z2-Z5), and the slope 124 of the second donor concentration peak 121 is given by (D2-aD2) / (Z2-Z6). H2 is the helium concentration at the second depth Z2, D2 is the donor concentration at the second depth Z2, a is a predetermined ratio, Z5 is the depth at which the helium concentration is aH2 on the upward slope 142 of the helium concentration peak 141, and Z6 is the depth at which the donor concentration is aD2 on the upward slope 122 of the second donor concentration peak 121. The ratio a used to normalize the slope of the second donor concentration peak 121 may be the same as or different from the ratio a used to normalize the slope of the first donor concentration peak 111. For example, normalizing the slope 124 by the slope 144 results in (D2-aD2)(Z2-Z5) / {(Z2-Z6)(H2-aH2)}. The slope normalized by the slope 144 is denoted as β.

[0068] The normalized gradient β of the upward slope 122 of the second donor concentration peak 121 is smaller than the normalized gradient α of the upward slope 112 of the first donor concentration peak 111. In other words, the second donor concentration peak 121 is a gentler peak relative to the concentration peak of hydrogen or helium than the first donor concentration peak 111. By implanting hydrogen ions and helium ions so as to form such a second donor concentration peak 121, the flat region 150 can be formed. In addition, by making the second donor concentration peak 121 have a gentle shape, the change in the donor concentration at the tip of the flat region 150 can be made gentle. The normalized gradient β of the upward slope 122 of the second donor concentration peak 121 may be 1 or less, 0.1 or less, or 0.01 or less times the normalized gradient α of the upward slope 112 of the first donor concentration peak 111.

[0069] Furthermore, gradient 144 of upward slope 142 of helium concentration peak 141 may be smaller than gradient 145 of downward slope 143. The concentration distribution of helium ions implanted deep from undersurface 23 may have a gentle tail toward undersurface 23, so by comparing gradient 144 of upward slope 142 with gradient 145 of downward slope 143, it may be possible to determine whether or not the helium of helium concentration peak 141 was implanted from undersurface 23. Gradient 145 is given by (H2-aH2) / (Z7-Z2). Gradient 125 is given by (D2-aD2) / (Z7-Z2). In FIG. 3B, the slope 124 of the upward slope 122 of the second donor concentration peak 121 is greater than the slope 125 of the downward slope 123; however, similar to the helium concentration peak 141, the slope 124 of the upward slope 122 of the second donor concentration peak 121 may be smaller than the slope 125 of the downward slope 123.

[0070] FIG. 3C is a diagram for explaining the gradient of the upward slope 142. The gradient of the upward slope 142 may be considered as follows. As shown in FIG. 3C, the width (10% full width) between two positions Z8 and Z9 at which the helium concentration peak 141 has a concentration of 10% (0.1×H2) of the peak concentration H2 is defined as FW10%M. The two positions Z8 and Z9 are the two positions closest to the peak position Z2 among the points at which the helium concentration is 0.1×H2, sandwiching the peak position Z2. Of the two positions Z8 and Z9, the position on the hydrogen concentration peak side is defined as Z8. The gradient of the donor concentration at position Z8 is almost flat. The gradient of the helium concentration at position Z8 is more than 100 times the gradient of the donor concentration at position Z8. For example, the gradient of the helium concentration at position Z8 may be 100 times or more, or 1000 times or more, the gradient of the donor concentration at position Z8.

[0071] FIG. 4A is a diagram for explaining another definition of the normalization of the gradient of the upward slope 112. In the normalization of the gradient of the upward slope 112, for example, the following index γ is introduced. In the example of FIG. 3A, the position Z3 and the position Z4 are different, but in this example, the position Z3 and the position Z4 are the same position (Z3=Z4). Here, the position Z3 is a predetermined position. The position Z3 may be a position where the hydrogen concentration distribution and the donor concentration distribution are upward slopes 132, 112 on the lower surface side of the position Z1. The hydrogen concentration at the position Z3 is a×H1, and the donor concentration is b×D1. a is the ratio of the hydrogen concentration at the position Z3 to the concentration H1 of the hydrogen concentration peak 131 at the position Z1. b is the ratio of the donor concentration at the position Z3 to the concentration D1 of the first donor concentration peak 111 at the position Z1. Here, we introduce the ratio of the slopes of the hydrogen concentration and the donor concentration in the section Z3 to Z1, and the slope ratio γ obtained by normalizing the slope ratio. The ratio of the slopes of the hydrogen concentration in the section Z3 to Z1 is defined as (H1 / aH1) / (Z1-Z3). Similarly, the ratio of the slopes of the donor concentrations in the section Z3 to Z1 is defined as (D1 / bD1) / (Z1-Z3). Then, the slope ratio γ obtained by normalizing the ratio of the slopes of the donor concentrations by the ratio of the slopes of the hydrogen concentrations in the section Z3 to Z1 is defined as {(D1 / bD1) / (Z1-Z3)} / {(H1 / aH1) / (Z1-Z3)}. The normalized slope ratio γ becomes the simple ratio a / b by calculating the above formula.

[0072] FIG. 4B is a diagram for explaining another definition of the normalization of the gradient of the upward slope 122. In the normalization of the gradient of the upward slope 122, for example, an index ε similar to the index γ is introduced. In the example of FIG. 3B, the position Z5 and the position Z6 are different, but in this example, the position Z5 and the position Z6 are the same position (Z5=Z6). Here, the position Z5 is a predetermined position. The position Z5 may be a position where the helium concentration distribution and the donor concentration distribution are upward slopes 142, 122 on the lower surface side from the position Z2. The helium concentration at the position Z5 is c×H2, and the donor concentration is d×D2. c is the ratio of the helium concentration at the position Z5 to the concentration H2 of the helium concentration peak 141 at the position Z2. d is the ratio of the donor concentration at the position Z5 to the concentration D2 of the second donor concentration peak 121 at the position Z2. Here, we introduce the ratio of the slopes of the helium concentration and the donor concentration in the section Z5 to Z2, and the slope ratio ε obtained by normalizing the slope ratio. The slope ratio of the helium concentration in the section Z5 to Z2 is defined as (H2 / cH2) / (Z2-Z5). Similarly, the slope ratio of the donor concentration in the section Z5 to Z2 is defined as (D2 / dD2) / (Z2-Z5). Then, the slope ratio ε obtained by normalizing the slope ratio of the donor concentration by the slope ratio of the helium concentration in the section Z5 to Z2 is defined as {(D2 / dD2) / (Z2-Z5)} / {(H2 / cH2) / (Z2-Z5)}. The normalized slope ratio ε becomes the simple ratio c / d by calculating the above formula.

[0073] For the hydrogen concentration peak 131 and the first donor concentration peak 111, the hydrogen concentration distribution and the donor concentration distribution often have similar shapes. Here, being similar means that, for example, when the horizontal axis represents depth and the vertical axis represents common logarithm of concentration, the donor concentration distribution reflects the hydrogen concentration distribution. That is, by implanting hydrogen ions in a predetermined section Z3 to Z1 and then performing thermal annealing, the donor concentration distribution reflects the hydrogen concentration distribution. As an example, when H1 of the hydrogen concentration peak 131 is 1×10 17 atoms / cm 3 And the hydrogen concentration aH1 at position Z3 is 2×10 16 atoms / cm 3Then, a is 0.2. On the other hand, D1 of the first donor concentration peak 111 is 1×10 16 atoms / cm 3 And the donor concentration bD1 at position Z3 is 2×10 15 atoms / cm 3 Then, b is 0.2. Therefore, the normalized slope ratio γ is a / b, which is 1. In other words, at the depth position Z1 close to the bottom surface, the slope ratio a of the hydrogen concentration distribution and the slope ratio b of the donor concentration distribution are almost the same value, and can be said to be similar in shape.

[0074] On the other hand, for the helium concentration peak 141 and the second donor concentration peak 121, the helium concentration distribution and the donor concentration distribution do not have to be similar to each other. That is, in the predetermined section Z5 to Z2, the donor concentration distribution does not have to reflect the helium concentration distribution. As an example, if H2 of the helium concentration peak 141 is 1×10 16 atoms / cm 3 And the helium concentration cH2 at position Z5 is 1×10 15 atoms / cm 3 Then, c is 0.1. On the other hand, D2 of the second donor concentration peak 121 is 3×10 14 atoms / cm 3 And the donor concentration dD2 at position Z5 is 1.5×10 14 atoms / cm 3 Then, d is 0.5. Therefore, the normalized slope ratio ε is c / d, which is 0.2. In other words, at position Z2, which is sufficiently deep from the bottom surface, the slope ratio c of the helium concentration distribution is 0.2 times the slope ratio d of the donor concentration distribution, which can be said to be a shape that is far from similar.

[0075] Comparing the normalized slope ratios γ and ε, γ is close to 1 when the peak position of the helium concentration distribution is close to the bottom surface, and ε may be a value sufficiently smaller than 1 when the peak position of the helium concentration distribution is sufficiently deep from the bottom surface. That is, the normalized slope ratio ε may be smaller than the normalized slope ratio γ. Furthermore, the slope ratio ε may be 0.9 or less, 0.5 or less, or 0.2 or less. Alternatively, it may be 0.1 or less, or 0.01 or less.

[0076] Furthermore, as another example of the second donor concentration peak 121, due to a decrease in carrier mobility, the donor concentration calculated from the spreading resistance, i.e., the carrier concentration, may be lower at the depth position Z2 than the carrier concentration at the previous and next positions. In such a case, the upward slope 122 is a decreasing slope, so the sign of d is made negative. That is, d is a negative number whose absolute value is 1 or more. As a result, ε is a negative number. That is, the normalized slope ratio ε may be smaller than the normalized slope ratio γ. Furthermore, the slope ratio ε may be 0.9 or less, 0 or less, or -1 or less. Alternatively, it may be -10 or less, or -100 or less.

[0077] Note that the actual position of the helium concentration peak 141 and the actual position of the second donor concentration peak 121 may differ. Also, the position of the hydrogen concentration peak 131 and the position of the first donor concentration peak 111 may not exactly match. In this way, when the position of the hydrogen or helium concentration peak and the position of the donor concentration peak do not match, the concentration at the peak position of the hydrogen or helium concentration may be taken as the peak position for the sake of convenience for the donor concentration. This makes it possible to perform calculations using the above definition.

[0078] An important point in the above explanation is that the helium concentration peak 141 has a maximum value. That is, the distribution of the helium concentration has a maximum value at depth Z2. The fact that the helium concentration peak 141 has a maximum value makes it possible to compare the normalized slope ratios described above.

[0079] FIG. 5 is a diagram illustrating the flat region 150. As described above, the donor concentration distribution in the flat region 150 is almost constant in the depth direction. The flat region 150 is a portion in which a region in which the donor concentration is between a predetermined maximum value max and a predetermined minimum value min is continuous in the depth direction. The maximum value max may be the maximum value of the donor concentration in the region. The minimum value min may be 50%, 70%, or 90% of the maximum value max.

[0080] Alternatively, as described above, the value of the donor concentration distribution may be within ±50%, ±30%, or ±10% of the average concentration of the donor concentration distribution in a predetermined range in the depth direction. The predetermined range in the depth direction may also be the same as described above.

[0081] FIG. 6 is a diagram showing a structural example of a semiconductor device 100. The semiconductor device 100 of this example functions as an IGBT. 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 54. The interlayer insulating film 38 is formed so as to cover at least a part of the upper surface 21 of the semiconductor substrate 10. Through holes such as contact holes are formed in the interlayer insulating film 38. The upper surface 21 of the semiconductor substrate 10 is exposed through the contact holes. The interlayer insulating film 38 may be silicate glass such as PSG or BPSG, or may be an oxide film, a nitride film, or the like.

[0082] The emitter electrode 52 is formed on the upper surfaces of the semiconductor substrate 10 and the interlayer insulating film 38. The emitter electrode 52 is also formed inside the contact hole, and is in contact with the upper surface 21 of the semiconductor substrate 10 exposed by the contact hole.

[0083] The collector electrode 54 is formed on the lower surface 23 of the semiconductor substrate 10. The collector electrode 54 may be in contact with the entire lower surface 23 of the semiconductor substrate 10. The emitter electrode 52 and the collector electrode 54 are formed of a metal material such as aluminum.

[0084] In this example, the semiconductor substrate 10 is provided with an N-type drift region 18, an N+ type emitter region 12, a P- type base region 14, an N+ type accumulation region 16, an N+ type buffer region 20, and a P+ type collector region 22.

[0085] The emitter region 12 is provided in contact with the upper surface 21 of the semiconductor substrate 10, and is a region having a higher donor concentration than the drift region 18. The emitter region 12 contains an N-type impurity such as phosphorus.

[0086] The base region 14 is provided between the emitter region 12 and the drift region 18. The base region 14 contains a P-type impurity such as boron. In the extension direction of the trench portion (the Y-axis direction in FIG. 6), the base region 14 is provided with P-type contact regions (not shown) that are alternately arranged with the emitter regions 12. The contact regions are formed on an upper surface 21 of the base region, and may be formed deeper than the emitter regions 12. The contact regions suppress latch-up of the IGBT when it is turned off.

[0087] The accumulation region 16 is provided between the base region 14 and the drift region 18, and has one or more donor concentration peaks having a higher donor concentration than the drift region 18. The accumulation region 16 may contain N-type impurities such as phosphorus, or may contain hydrogen.

[0088] The collector region 22 is provided in contact with the lower surface 23 of the semiconductor substrate 10. The acceptor concentration of the collector region 22 may be higher than the acceptor concentration of the base region 14. The collector region 22 may contain the same P-type impurity as the base region 14, or may contain a different P-type impurity.

[0089] The buffer region 20 is provided between the collector region 22 and the drift region 18, and has one or more donor concentration peaks having a higher donor concentration than the drift region 18. The buffer region 20 contains N-type impurities such as hydrogen. The buffer region 20 may function as a field stop layer that prevents a depletion layer extending from the lower surface side of the base region 14 from reaching the collector region 22.

[0090] The gate trench portion 40 extends from the upper surface 21 of the semiconductor substrate 10 through the emitter region 12, the base region 14, and the accumulation region 16 to reach the drift region 18. The accumulation region 16 in this example is disposed above the lower end of the gate trench portion 40. The accumulation region 16 may be provided so as to cover the entire lower surface of the base region 14. By providing the accumulation region 16 between the drift region 18 and the base region 14 and having a higher concentration than the drift region 18, the carrier injection enhancement effect (IE effect) can be enhanced, and the on-voltage of the IGBT can be reduced.

[0091] The gate trench portion 40 has a gate trench, a gate insulating film 42, and a gate conductive portion 44 formed on the upper surface side of the semiconductor substrate 10. The gate insulating film 42 is formed 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 formed inside the gate insulating film 42 inside the gate trench. 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.

[0092] The gate conductive portion 44 includes a region facing the base region 14 with the gate insulating film 42 interposed therebetween. The gate trench portion 40 in this cross section is covered with the interlayer insulating film 38 on the upper surface of the semiconductor substrate 10, but the gate conductive portion 44 is connected to the gate electrode in another cross section. 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.

[0093] The first donor concentration peak 111 may be provided in the buffer region 20. The second donor concentration peak 121 may be provided in an N-type region above the buffer region 20. The second donor concentration peak 121 may be provided between the buffer region 20 and the accumulation region 16. The second donor concentration peak 121 in this example is provided in the drift region 18. The second donor concentration peak 121 may be disposed below the lower end of the gate trench portion 40, may be disposed in contact with the lower end of the gate trench portion 40, or may be disposed above the lower end of the gate trench portion 40. In addition, a base doping region 180, which is a region of a base doping concentration Db of the substrate, may be provided between the second donor concentration peak 121 and the accumulation region 16.

[0094] Fig. 7 is a diagram showing an example of a carrier concentration distribution in the depth direction at the position of the line BB in Fig. 6. Fig. 7 also shows a part of the hydrogen concentration distribution and the helium concentration distribution. The vertical axis in Fig. 7 is a logarithmic axis.

[0095] The carrier concentration distribution in the buffer region 20 of this example has a plurality of peaks 24 located at different positions in the depth direction. The peaks 24 are donor concentration peaks. The peaks 24 may contain hydrogen as an impurity. By providing the plurality of peaks 24, it is possible to further suppress the depletion layer from reaching the collector region 22. The first donor concentration peak 111 may function as the peak 24 in the buffer region 20.

[0096] As an example, the first donor concentration peak 111 may function as the peak farthest from the lower surface 23 of the semiconductor substrate 10 among the multiple peaks 24 in the buffer region 20. The flat region 150 is disposed between the first donor concentration peak 111 and the second donor concentration peak 121 included in the buffer region 20.

[0097] The first donor concentration peak 111 may have a higher donor concentration than the peak 24 next farthest from the lower surface 23 after the first donor concentration peak 111, among the multiple peaks 24 in the buffer region 20. By increasing the concentration of the first donor concentration peak 111, it becomes easier to form the flat region 150 even if the first donor concentration peak 111 and the second donor concentration peak 121 are far apart. The hydrogen concentration distribution may have one or more hydrogen concentration peaks 194 between the first depth Z1 and the lower surface 23. The hydrogen concentration peaks 194 may be located in the buffer region 20 described with reference to FIG. 6 and the like. The hydrogen concentration peaks 194 may be located at the same depth position as the peak 24.

[0098] The accumulation region 16 in this example has a plurality of peaks 25. The peaks 25 are donor concentration peaks. The second donor concentration peak 121 is located closer to the lower surface 23 than the accumulation region 16. A region of the base doping concentration Db of the substrate (base doping region 180) may be provided between the second donor concentration peak 121 and the accumulation region 16. In another example, the donor concentration between the second donor concentration peak 121 and the accumulation region 16 may be higher than the base doping concentration Db of the semiconductor substrate.

[0099] Furthermore, the semiconductor device 100 may use, as the semiconductor substrate 10, a non-doped substrate in which a dopant such as phosphorus (P) is not doped into the entire semiconductor ingot during manufacturing. In this case, the base doping concentration Dn of the semiconductor substrate 10 is lower than the base doping concentration Db. In the example of FIG. 7, a region in which the doping concentration is the base doping concentration Dn is defined as a non-doped region 181. The base doping concentration Dn of the non-doped region 181 is, for example, 1×10 10 atoms / cm 3 That's it, 5 x 10 12 atoms / cm 3 The base doping concentration Dn is 1×10 11 atoms / cm 3 The base doping concentration Dn may be 5×10 12 atoms / cm 3The concentrations in this specification may be values ​​at room temperature. As an example of room temperature, values ​​at 300 K (Kelvin) (approximately 26.9° C.) may be used.

[0100] Fig. 8 is a diagram showing another example of the structure of the semiconductor device 100. The semiconductor device 100 of this example differs from the semiconductor device 100 described in Fig. 6 and Fig. 7 in that the second donor concentration peak 121 (and the helium concentration peak 141) is disposed in the accumulation region 16. The other structures may be the same as those of the semiconductor device 100 described in Fig. 6 and Fig. 7.

[0101] Fig. 9 is a diagram showing an example of a carrier concentration distribution in the depth direction at the position of line CC in Fig. 8. Fig. 9 also shows a part of the hydrogen concentration distribution and the helium concentration distribution. The vertical axis in Fig. 9 is a logarithmic axis.

[0102] The carrier concentration distribution in the accumulation region 16 in this example has multiple peaks at different positions in the depth direction. The peaks are donor concentration peaks. The peaks in the accumulation region 16 may have hydrogen or phosphorus as impurities. By providing multiple peaks in the accumulation region 16, it is possible to suppress the displacement current to the gate trench portion in a structure in which the gate trench portion and the dummy trench portion are arranged adjacent to each other (see, for example, WO2018 / 030440). The dummy trench portion has a structure similar to that of the gate trench portion, and is a trench portion to which an emitter potential is applied.

[0103] The second donor concentration peak 121 in this example functions as any of the donor concentration peaks in the accumulation region 16. As an example, the second donor concentration peak 121 may function as the peak that is farthest from the upper surface 21 of the semiconductor substrate 10 among the multiple peaks in the accumulation region 16. The flat region 150 in this example is disposed between the first donor concentration peak 111 included in the buffer region 20 and the second donor concentration peak 121 included in the accumulation region 16.

[0104] The donor concentration of the second donor concentration peak 121 may be lower, the same, or higher than the donor concentrations of other peaks 25 in the accumulation region 16. When the accumulation region 16 has three or more peaks, the donor concentrations of the peaks 25 other than the second donor concentration peak 121 may be the same. The donor concentration of the second donor concentration peak 121 may be determined according to the donor concentration that the flat region 150 should have.

[0105] The carrier concentration of the drift region 18 in this example may be higher than the base doping concentration Db of the substrate over the entire depth direction. With this structure, the entire carrier concentration of the drift region 18 can be adjusted with high precision.

[0106] The peak 25 other than the second donor concentration peak 121 may be a peak due to a donor other than hydrogen. For example, the peak 25 is a peak in which phosphorus functions as a donor. By using phosphorus as a donor, VOH defects are less likely to occur, and the donor concentration of the peak 25 and its vicinity can be easily controlled by the concentration of phosphorus. Furthermore, the width in the depth direction of the second donor concentration peak 121 may be wider than the width in the depth direction of the peak 25. This can further suppress the displacement current to the gate trench portion. In addition, between the second donor concentration peak 121 and the peak 25 of the accumulation region 16, there may be a valley in the donor concentration distribution as shown in FIG. 9. Alternatively, as shown by the dotted line between the two peaks in FIG. 9, the donor concentration distribution of the accumulation region 16 may be a kink rather than a valley.

[0107] Fig. 10 shows the hydrogen concentration distribution, helium concentration distribution and carrier concentration distribution in the depth direction at the position indicated by line AA in Fig. 1. The carrier concentrations were measured by SR method. More defects are likely to occur in the vicinity of the range (Z2) of the helium concentration peak 141 than in the passing region 106. Defects that remain without bonding with hydrogen may cause a valley 151 in the carrier concentration distribution in the vicinity of the second depth Z2.

[0108] When the valley 151 occurs, the gradient of the upward slope 122 of the second donor concentration peak 121 may be calculated to be steep. For this reason, it is preferable to calculate the gradient of the upward slope 122 by excluding the influence of the valley 151. For example, the gradient of the upward slope of each of the second donor concentration peak 121 and the helium concentration peak 141 may be calculated by using each concentration at the second depth Z2 and each concentration at the depth Zc. The depth Zc may be a position on the lower surface 23 side from the valley 151. In this example, the depth Zc is the central depth in the depth direction of the flat region 150. This allows the gradient of the upward slope 122 of the second donor concentration peak 121 to be normalized by excluding the influence of the valley 151. For normalization, the gradient of the concentration difference or the gradient of the concentration ratio may be used as described above.

[0109] 11 is a diagram showing an example of the arrangement of elements on the upper surface 21 of the semiconductor substrate 10. In FIG.

[0110] Semiconductor device 100 includes active portion 120 and edge termination structure 90. Active portion 120 is a region where a main current flows between upper surface 21 and lower surface 23 of semiconductor substrate 10 when semiconductor device 100 is controlled to be in an on-state. In other words, active portion 120 is a region where a current flows in the depth direction inside semiconductor substrate 10 from upper surface 21 to lower surface 23 of semiconductor substrate 10, or from lower surface 23 to upper surface 21.

[0111] The active section 120 of this example is provided with a transistor section 70 and a diode section 80. The transistor section 70 and the diode section 80 may be arranged side by side in the X-axis direction. In the example of FIG. 11, the transistor sections 70 and the diode sections 80 are arranged alternately in contact with each other in the X-axis direction. In the active section 120, the transistor sections 70 may be provided at both ends in the X-axis direction. The emitter electrode 52 may cover the transistor section 70 and the diode section 80. The active section 120 may refer to the area covered by the emitter electrode 52.

[0112] The transistor section 70 of this example has an IGBT (Insulated Gate Bipolar Transistor) described in FIG. 6 to FIG. 10. The diode section 80 of this example has an FWD (Freewheeling Diode). In each diode section 80, an N+ type cathode region 82 is provided in a region in contact with the lower surface 23 of the semiconductor substrate 10. In FIG. 11, the diode section 80 shown by the solid line is a region in which the cathode region 82 is provided on the lower surface 23 of the semiconductor substrate 10. In the semiconductor device 100 of this example, a collector region 22 is provided in a region in contact with the lower surface 23 of the semiconductor substrate 10 other than the cathode region 82.

[0113] The diode section 80 is a region obtained by projecting the cathode region 82 in the Z-axis direction. The transistor section 70 is a region in which the collector region 22 is provided on the lower surface 23 of the semiconductor substrate 10, and unit structures including the emitter region 12 are periodically provided on the upper surface 21 of the semiconductor substrate 10. The boundary between the diode section 80 and the transistor section 70 in the Y-axis direction is the boundary between the cathode region 82 and the collector region 22. The diode section 80 may also include a portion in which the region in which the cathode region 82 is projected is extended in the Y-axis direction to the end of the active section 120 or the gate runner 48 (the portion indicated by the dashed line in FIG. 11 that is an extension of the diode section 80). The emitter region 12 is not provided in the extended portion.

[0114] The semiconductor device 100 of this example further includes a gate metal layer 50 and a gate runner 48. The semiconductor device 100 may also include pads such as a gate pad 116 and an emitter pad 118. The gate pad 116 is electrically connected to the gate metal layer 50 and the gate runner 48. The emitter pad 118 is electrically connected to the emitter electrode 52.

[0115] The gate metal layer 50 may be provided so as to surround the active portion 120 in a top view. The gate pad 116 and the emitter pad 118 may be disposed within a region surrounded by the gate metal layer 50. The gate metal layer 50 may be formed of a metal material such as aluminum or an aluminum-silicon alloy. The gate metal layer 50 is insulated from the semiconductor substrate 10 by an interlayer insulating film 38. The interlayer insulating film 38 is omitted in FIG. 11. The gate metal layer 50 is provided separately from the emitter electrode 52. The gate metal layer 50 transmits a gate voltage applied to the gate pad 116 to the transistor portion 70. The gate conductive portion 44 of the transistor portion 70 is directly connected to the gate metal layer 50 or indirectly connected via another conductive member.

[0116] The gate runner 48 connects the gate metal layer 50 and the gate conductive portion 44. The gate runner 48 may be formed of a semiconductor material such as polysilicon doped with impurities. A part of the gate runner 48 may be provided above the active portion 120. The gate runner 48 shown in FIG. 11 is provided across the active portion 120 in the X-axis direction. This makes it possible to suppress a drop and delay in the gate voltage even inside the active portion 120 away from the gate metal layer 50. A part of the gate runner 48 may be disposed along the gate metal layer 50, surrounding the active portion 120. The gate runner 48 may be connected to the gate conductive portion 44 at an end of the active portion 120.

[0117] Edge termination structure 90 is provided on top surface 21 of semiconductor substrate 10, between active portion 120 and outer periphery edge 140 of semiconductor substrate 10. In this example, gate metal layer 50 is disposed between edge termination structure 90 and active portion 120. Edge termination structure 90 may be disposed in an annular shape surrounding active portion 120 on top surface 21 of semiconductor substrate 10. Edge termination structure 90 in this example is disposed along outer periphery edge 140 of semiconductor substrate 10. Edge termination structure 90 relieves electric field concentration on top surface 21 side of semiconductor substrate 10. Edge termination structure 90 has, for example, a guard ring, a field plate, a resurf, or a structure combining these.

[0118] Fig. 12 is a diagram showing an example of the c-c' cross section in Fig. 11. Fig. 12 shows an example of the arrangement of the passing region 106 described in Figs. 1 to 10 in the cross section. In Fig. 12, the passing region 106 is hatched with oblique lines. Note that Fig. 12 shows only the passing region 106 in the drift region 18, and omits the passing region 106 in the buffer region 20, the collector region 22, and the cathode region 82.

[0119] The cross section shown in Figure 12 is an XZ plane including edge termination structure 90, transistor portion 70, and diode portion 80. Note that gate metal layer 50 and gate runner 48 are disposed between edge termination structure 90 and transistor portion 70, but are omitted in Figure 12. The structure of transistor portion 70 is similar to that of the IGBT described in Figures 6 to 10.

[0120] The diode section 80 includes a base region 14, a drift region 18, a cathode region 82, and a dummy trench section 30 inside the semiconductor substrate 10. The base region 14 and the drift region 18 are the same as the base region 14 and the drift region 18 in the transistor section 70.

[0121] A base region 14 or a contact region 15 may be provided in a region of the diode section 80 that contacts the upper surface 21 of the semiconductor substrate 10. The contact region 15 is a P+ type region having a higher doping concentration than the base region 14. The diode section 80 of this example is not provided with an emitter region 12. Also, the diode section 80 may or may not have an accumulation region 16.

[0122] The dummy trench portion 30 has the same structure as the gate trench portion 40. However, the dummy trench portion 30 is electrically connected to the emitter electrode 52. The dummy trench portion 30 is provided from the upper surface 21 of the semiconductor substrate 10, penetrating the base region 14, to the drift region 18. The dummy trench portion 30 may also be provided in the transistor portion 70. In the transistor portion 70, the dummy trench portion 30 and the gate trench portion 40 may be arranged at a predetermined period.

[0123] There may be an intermediate boundary region 190 between the transistor section 70 and the diode section 80. The intermediate boundary region 190 is a region where neither the transistor section 70 nor the diode section 80 directly operates. As an example, the region of the intermediate boundary region 190 in contact with the upper surface 21 may have the same structure as the upper surface 21 side of the diode section 80. In addition, the collector region of the transistor section 70 may be extended and provided in the region of the intermediate boundary region 190 in contact with the lower surface 23 in the top view. In FIG. 12, only an example of the range of the intermediate boundary region 190 is indicated by an arrow. In FIG. 12, the range illustrated as the intermediate boundary region 190 also has the same structure as the transistor section 70.

[0124] A lifetime control region 192 may be provided in the drift region 18 of the diode section 80, closer to the top surface 21 than the center in the depth direction. The lifetime control region 192 is a region in which recombination centers of carriers (electrons or holes) are provided at a higher concentration than in the surrounding area. The recombination centers may be vacancy-based defects such as vacancies or divacancies, dislocations, interstitial atoms, transition metals, or the like. The lifetime control region 192 may extend from the diode section 80 to the intermediate boundary region 190.

[0125] Edge termination structure 90 is provided with a plurality of guard rings 92, a plurality of field plates 94, and a channel stopper 174. In edge termination structure 90, a collector region 22 may be provided in a region in contact with bottom surface 23. Each guard ring 92 may be provided to surround active portion 120 on top surface 21. The plurality of guard rings 92 may have the function of spreading a depletion layer generated in active portion 120 to the outside of semiconductor substrate 10. This makes it possible to prevent electric field concentration inside semiconductor substrate 10, and improve the breakdown voltage of semiconductor device 100.

[0126] The guard ring 92 of this example is a P+ type semiconductor region formed by ion implantation near the upper surface 21. The depth of the bottom of the guard ring 92 may be deeper than the depth of the bottom of the gate trench portion 40 and the dummy trench portion 30.

[0127] The upper surface of the guard ring 92 is covered with the interlayer insulating film 38. The field plate 94 is made of a conductive material such as metal or polysilicon. The field plate 94 may be made of the same material as the gate metal layer 50 or the emitter electrode 52. The field plate 94 is provided on the interlayer insulating film 38. The field plate 94 is connected to the guard ring 92 through a through hole provided in the interlayer insulating film 38.

[0128] A protective film 182 is provided on the top surface 21 side of the semiconductor substrate 10. The protective film 182 may cover the edge termination structure 90, the gate metal layer 50, the boundary portion 72, and a part of the active portion that contacts the boundary portion 72. The protective film 182 may be an insulating film or an organic thin film. In this example, the protective film 182 is polyimide. A plating layer 184 may be provided on the entire surface of the exposed portion of the emitter electrode 52 where the protective film 182 is not formed. The surface of the plating layer 184 may be located closer to the top surface 21 than the surface of the protective film 182. The plating layer 184 is connected to an electrode terminal of a power module on which the semiconductor device 100 is mounted.

[0129] The channel stopper 174 is provided so as to be exposed on the upper surface 21 and the side surface at the outer circumferential end 140. The channel stopper 174 is an N-type region having a higher doping concentration than the drift region 18. The channel stopper 174 has a function of terminating the depletion layer generated in the active portion 120 at the outer circumferential end 140 of the semiconductor substrate 10.

[0130] A boundary portion 72 may be provided between the transistor portion 70 and the edge termination structure portion 90. The boundary portion 72 may have a contact region 15, a base region 14, and a dummy trench portion 30 on the upper surface 21 side of the semiconductor substrate 10. The boundary portion 72 may have a P+ type well region 11 having a doping concentration higher than that of the base region 14. The well region 11 is provided in contact with the upper surface 21 of the semiconductor substrate 10. A gate metal layer 50 and a gate runner 48 may be provided above the well region 11. The depth of the bottom of the well region 11 may be the same as the depth of the bottom of the guard ring 92. A part of the trench portion in the boundary portion 72 may be formed in the well region 11. A collector region 22 may be provided in a region of the boundary portion 72 that is in contact with the lower surface 23.

[0131] In this example, the helium concentration peak 141 is located between the bottom of the gate trench portion 40 in the Z-axis direction and the upper surface 21 of the semiconductor substrate 10. In the example of Fig. 12, the helium concentration peak 141 is located at a position deeper than the accumulation region 16, but the helium concentration peak 141 may be located at the same depth as the accumulation region 16, the same depth as the base region 14, or the same depth as the emitter region 12. The accumulation region 16 may also be formed in the diode portion 80, as shown by the dotted line in Fig. 12.

[0132] Passage region 106 is formed in the range from lower surface 23 of semiconductor substrate 10 to helium concentration peak 141. In each drawing, helium concentration peak 141 and passage region 106 do not overlap, but passage region 106 is formed to the depth of helium concentration peak 141.

[0133] Furthermore, in this example, the passing region 106 is provided in each of the transistor portion 70, the diode portion 80, the boundary portion 72, and the edge termination structure portion 90. The depth of the passing region 106 may be the same in each of the transistor portion 70, the diode portion 80, the boundary portion 72, and the edge termination structure portion 90. The passing region 106 may be provided over the entire semiconductor substrate 10 in a top view. According to this example, the donor concentration can be adjusted over almost the entire depth direction of the semiconductor substrate 10. Furthermore, the donor concentration can be adjusted over almost the entire semiconductor substrate 10 in a top view.

[0134] In this example, the region where the passing region 106 is not formed is provided particularly in a portion in contact with the top surface 21 of the edge termination structure 90. The region where the passing region 106 is not formed is a portion where the donor concentration is the same as the base doping concentration Db. The region where the passing region 106 is not formed is located on the top surface 21 side relative to the depth of the helium concentration peak 141. In other words, the region where the passing region 106 is not formed may be a region where the doping concentration is approximately the base doping concentration Db. The region where the doping concentration is the base doping concentration Db is defined as the base doping region 180. In this example, the base doping region 180 is provided in a portion in contact with the top surface 21 and shallower than the well region 11.

[0135] Fig. 13 is a diagram showing another example of the arrangement of the passage area 106. The passage area 106 of this example has a different width in the depth direction from the passage area 106 in Fig. 12. The arrangement in top view is the same as that of the passage area 106 in Fig. 12.

[0136] In this example, the helium concentration peak 141 is located between the bottom of the gate trench portion 40 and the lower surface 23 of the semiconductor substrate 10. The thickness of the semiconductor substrate 10 in the depth direction is defined as T1, and the distance between the helium concentration peak 141 and the lower surface 23 of the semiconductor substrate 10 is defined as T2. The distance T2 corresponds to the thickness of the passing region 106 in the depth direction. The distance T2 may be 40% or more and 60% or less of the thickness T1. In other words, the passing region 106 may be provided from the lower surface 23 of the semiconductor substrate 10 to approximately the center of the semiconductor substrate 10 in the depth direction. However, the distance T2 can be changed as appropriate.

[0137] As described above, the base doped region 180 is provided on the upper surface 21 side of the helium concentration peak 141. The base doped region 180 in this example is a region from the bottom surface of the trench portion to the helium concentration peak 141, and has a depth of approximately T1-T2. When viewed from above, the base doped region 180 in this example is provided on the entire surface of the semiconductor substrate 10.

[0138] Fig. 14 is a diagram showing another example of the arrangement of the passage area 106. The passage area 106 of this example has a different arrangement in a top view from the passage area 106 in Fig. 12. The arrangement in the depth direction may be the same as that of the passage area 106 in Fig. 12.

[0139] In this example, at least a portion of the edge termination structure 90 in the top view does not have the passing region 106 and the helium concentration peak 141. FIG. 14 shows an example in which the entire edge termination structure 90 in the top view does not have the passing region 106 and the helium concentration peak 141. In another example, the passing region 106 and the helium concentration peak 141 may be provided at the end of the edge termination structure 90 closer to the active section 120. That is, the passing region 106 and the helium concentration peak 141 are not provided in the region in contact with the outer peripheral end 140 of the semiconductor substrate 10. In this example, since the helium concentration peak 141 is not provided near the outer peripheral end 140, the formation of defects near the outer peripheral end 140 can be suppressed. Therefore, the increase in leakage at the outer peripheral end 140 can be suppressed.

[0140] That is, the base doped region 180 in this example is provided in a region that contacts the outer peripheral edge 140 of the semiconductor substrate 10. The base doped region 180 in this example is provided in at least a portion of the edge termination structure 90 in a top view. Furthermore, the base doped region 180 may be provided in the entire edge termination structure 90 and in the boundary portion 72 in a top view.

[0141] The arrangement of the pass region 106 in the boundary portion 72 may be the same as that in the edge termination structure portion 90, the same as that in the transistor portion 70, or the same as that in the diode portion 80. Figure 14 shows an example in which the pass region 106 is not provided in the boundary portion 72.

[0142] Figure 15 is a diagram showing another example of the arrangement of the passing region 106. The arrangement of the passing region 106 in this example in the depth direction is the same as that of the passing region 106 shown in Figure 13, and the arrangement in top view is the same as that of the passing region 106 shown in Figure 14. In other words, the edge termination structure 90 is not provided with the passing region 106. Furthermore, the passing region 106 is provided in the transistor section 70 and the diode section 80 from the lower surface 23 of the semiconductor substrate 10 to near the center of the semiconductor substrate 10 in the depth direction.

[0143] In this example, the base doped region 180 is formed in the boundary portion 72 and the edge termination structure portion 90 from the top surface 21 to the buffer region 20. In the active portion, the base doped region 18 is formed in the drift region 18 on the top surface 21 side of the helium concentration peak 141. On the top surface 21 side of the helium concentration peak 141, the base doped region 180 in this example is provided over the entire surface of the semiconductor substrate 10 in a top view.

[0144] Fig. 16A is a diagram showing another example of the arrangement of the passing region 106. This example differs from the examples in Fig. 12 to Fig. 15 in that the passing region 106 and the helium concentration peak 141 are not provided in at least a part of the diode portion 80 in the top view. The other structures are the same as the examples described in Fig. 12 to Fig. 15.

[0145] 16A shows an example in which the passing region 106 and the helium concentration peak 141 are not provided in the entire diode section 80 in the top view. That is, the base doping region 180 is provided in the entire diode section 80 in the top view. The base doping region 180 is also provided in the entire boundary section 72 and the edge termination structure section 90. In another example, the passing region 106 and the helium concentration peak 141 may be provided in the end of the diode section 80 that contacts the transistor section 70. By making the arrangement of the passing region 106 different between the transistor section 70 and the diode section 80, the distribution of the doping concentration of the diode section 80 and the transistor section 70 can be appropriately made different.

[0146] Fig. 16B is a diagram showing another example of the arrangement of the passing region 106. Fig. 16B shows a configuration in which the passing region 106 and the base doping region 180 are formed in the active section in the opposite order to that shown in Fig. 16A. By forming the passing region 106 in the diode section 80, the expansion of the space charge region during reverse recovery is suppressed, and waveform oscillation during reverse recovery is suppressed. On the other hand, by forming the transistor section 70 as the base doping region 180, the expansion of the space charge region is promoted when a short circuit occurs, for example, and hole injection is promoted, thereby suppressing short circuit breakdown.

[0147] 17A is a diagram showing another example of the arrangement of the passing region 106. The passing region 106 of this example is arranged in the depth direction in the same manner as the passing region 106 shown in FIG. 13, and arranged in the top view in the same manner as the passing region 106 shown in FIG. 16A. That is, the passing region 106 is not provided in the diode section 80. The passing region 106 is provided in the transistor section 70 from the lower surface 23 of the semiconductor substrate 10 to near the center in the depth direction of the semiconductor substrate 10. In the example of FIG. 17A, the helium concentration peak 141 is set back from the bottom surface of the trench section toward the lower surface 23, and the base doping region 180 is formed on the entire surface in the top view on the upper surface 21 side of the helium concentration peak 141.

[0148] Fig. 17B is a diagram showing another example of the arrangement of the passing region 106. In the example of Fig. 17B, in the active section, the passing region 106 and the base doping region 180 are formed in the opposite order to that of Fig. 17A. The example of Fig. 17B also provides the same effect as that of Fig. 16B.

[0149] 14 to 17B, in a second implantation step S1902 described below, helium ions are selectively implanted in a top view. For example, the selective helium ion implantation can be performed using the photoresist film 200 shown in FIGS. 14 to 17B.

[0150] In this case, before the second implantation step S1902, a photoresist film 200 of a predetermined thickness is selectively formed on a part of the lower surface 23 of the semiconductor substrate 10. The thickness of the photoresist film 200 is a thickness capable of blocking helium ions.

[0151] After the photoresist film 200 is formed, the second implantation step S1902 is performed. In the region where the photoresist film 200 is formed, helium ions are blocked by the photoresist film 200. Therefore, helium ions do not penetrate into the region of the semiconductor substrate 10 covered with the photoresist film 200. In the region where the photoresist film 200 is not formed, helium ions are implanted at the second depth position Z2 according to the acceleration energy. In each example of FIG. 14, FIG. 15, FIG. 16A, FIG. 16B, FIG. 17A, and FIG. 17B, the photoresist film 200 is formed in contact with the lower surface 23 of the semiconductor substrate 10. In the step of forming the photoresist film 200, the collector electrode 54 is not provided on the lower surface 23.

[0152] Fig. 17C is a diagram for explaining the minimum film thickness M of the photoresist film 200 for preventing helium ions from penetrating into the semiconductor substrate 10. Fig. 17C shows the film thickness M relative to the range Rp of the helium ions.

[0153] The helium ions in this example may be implanted into the semiconductor substrate 10 from an accelerator without passing through any absorber other than the photoresist film 200. The range Rp of the helium ions is uniquely determined by the acceleration energy in the accelerator.

[0154] Furthermore, the minimum film thickness M of the photoresist film 200 that can block helium ions is determined by the acceleration energy of the helium ions. Therefore, the minimum film thickness M of the photoresist film 200 can be expressed by the range Rp of the helium ions. Figure 17C is a diagram in which the relationship between the range Rp of the helium ions and the film thickness M is measured at three points and approximated by a straight line. The relationship between the film thickness M (μm) and the range Rp (μm) can be expressed by the following formula. M=1.76×Rp+12.32 The thickness of the photoresist film 200 is preferably equal to or greater than the minimum film thickness M shown in the above formula.

[0155] As another example, helium ions may be implanted into the semiconductor substrate 10 from an accelerator through an absorber other than the photoresist film 200. The range Rp of the helium ions is determined by the acceleration energy in the accelerator and the thickness of the absorber along the implantation direction of the helium ions.

[0156] 18A is a diagram showing another example of the arrangement of the passing region 106. In this example, the width T5 in the depth direction of the passing region 106 provided in the edge termination structure 90 is shorter than the width T4 in the depth direction of the passing region 106 provided in the active section 120 (the diode section 80 in this example).

[0157] In diode portion 80, helium concentration peak 141 may be located between a bottom of dummy trench portion 30 and top surface 21 of semiconductor substrate 10. In edge termination structure 90, helium concentration peak 141 may be located between guard ring 92 and bottom surface 23 of semiconductor substrate 10. Width T5 of passing region 106 in edge termination structure 90 may be greater than half thickness T1 of semiconductor substrate 10.

[0158] Moreover, the width T3 in the depth direction of the passing region 106 provided in the transistor section 70 may be shorter than the width T4 in the depth direction of the passing region 106 provided in the diode section 80. That is, in the transistor section 70, the base doping region 180 is formed deeper than the trench section depth. That is, the helium concentration peak 141 of the transistor section 70 is located closer to the lower surface 23 than the bottom surface of the trench section. In the transistor section 70, the helium concentration peak 141 may be disposed between the bottom of the gate trench section 40 and the lower surface 23 of the semiconductor substrate 10. The width T3 may be the same as the width T5, may be larger than the width T5, or may be smaller than the width T5. The width T3 of the passing region 106 in the transistor section 70 may be larger than half the thickness T1 of the semiconductor substrate 10. This allows the base region 14 in which the channel is formed in the transistor section 70 to be disposed away from the helium concentration peak 141. This allows the increase in defects in the vicinity of the channel to be suppressed.

[0159] Passage region 106 in boundary portion 72 may have the same structure as pass region 106 in edge termination structure portion 90, may have the same structure as pass region 106 in transistor portion 70, or may have the same structure as pass region 106 in diode portion 80. Also, in the example of FIG. 18A , pass region 106 may not be provided in transistor portion 70. Passage region 106 may not be provided in diode portion 80. Passage region 106 may not be provided in edge termination structure portion 90. Passage region 106 may not be provided in boundary portion 72.

[0160] 18B is a diagram showing another example of the arrangement of the passing region 106. In this example, the width T5 in the depth direction of the passing region 106 provided in the edge termination structure 90 is shorter than the width T3 in the depth direction of the passing region 106 provided in the active section 120 (the transistor section 70 in this example).

[0161] In transistor portion 70, helium concentration peak 141 may be located between the bottom of gate trench portion 40 and upper surface 21 of semiconductor substrate 10. The structure of passing region 106 and helium concentration peak 141 in edge termination structure portion 90 is similar to the example in FIG.

[0162] The width T4 in the depth direction of the passing region 106 provided in the diode section 80 may be shorter than the width T3 in the depth direction of the passing region 106 provided in the transistor section 70. That is, in the diode section 80, the base doping region 180 is formed deeper than the trench section depth. That is, the helium concentration peak 141 in the diode section 80 is located closer to the lower surface 23 than the bottom surface of the trench section. In the diode section 80, the helium concentration peak 141 may be located between the bottom of the dummy trench section 30 and the lower surface 23 of the semiconductor substrate 10. The width T4 may be the same as the width T5, may be larger than the width T5, or may be smaller than the width T5. The width T4 of the passing region 106 in the diode section 80 may be larger than half the thickness T1 of the semiconductor substrate 10.

[0163] The pass region 106 in boundary portion 72 may have the same structure as the pass region 106 in edge termination structure portion 90, may have the same structure as the pass region 106 in transistor portion 70, or may have the same structure as the pass region 106 in diode portion 80. Also, in the example of FIG. 18B , the pass region 106 may not be provided in the transistor portion 70. The pass region 106 may not be provided in the diode portion 80. The pass region 106 may not be provided in the edge termination structure portion 90. The pass region 106 may not be provided in boundary portion 72.

[0164] 12 to 18B, by adjusting the structure of the pass region 106, it is possible to easily adjust the donor concentration distribution in the transistor portion 70, the diode portion 80, and the edge termination structure portion 90. The structure of the pass region 106 is not limited to the examples shown in Figures 12 to 18B.

[0165] 19 is a diagram showing a step of forming the passage region 106 in the manufacturing method of the semiconductor device 100. When forming the passage region 106, in a first implantation step S1900, hydrogen ions are implanted to a first depth Z1 from the lower surface 23 of the semiconductor substrate 10. In addition, in a second implantation step S1902, helium ions are implanted to a second depth Z2 from the lower surface 23 of the semiconductor substrate 10 to form the passage region 106. Either the first implantation step S1900 or the second implantation step S1902 may be performed first.

[0166] In addition, when the first implantation step S1900 is performed first, if a heat treatment is performed between the first implantation step S1900 and the second implantation step S1902, the donor concentration of the passage region 106 may not be increased. In other words, if a heat treatment is performed before the formation of the passage region 106, the hydrogen implanted in the first implantation step S1900 may not be able to bond with the crystal defects of the passage region 106 and may escape to the outside of the semiconductor substrate 10. For this reason, it is preferable not to perform a heat treatment between the first implantation step S1900 and the second implantation step S1902. The heat treatment is a process of heating the semiconductor substrate 10 at, for example, 300° C. or higher.

[0167] After the first implantation step S1900 and the second implantation step S1902, a diffusion step S1904 is performed. In the diffusion step S1904, the semiconductor substrate 10 is heat-treated to diffuse the hydrogen implanted at the first depth Z1 into the passage region 106. In the diffusion step S1904, the semiconductor substrate 10 may be heated to 300° C. or higher. The heating temperature may be 350° C. or higher. In the diffusion step S1904, the semiconductor substrate 10 may be heated for one hour or more, or may be heated for three hours or more.

[0168] By diffusing hydrogen in the diffusion step S1904, crystal defects in the passage region 106 are bonded with hydrogen to become donors. This makes it possible to increase the donor concentration in the passage region 106. In the diffusion step S1904, it is preferable that the minimum value of the donor concentration in the passage region 106 is higher than the donor concentration (base doping concentration) of the semiconductor substrate 10 before the first implantation step S1900 and the second implantation step S1902. In other words, it is preferable that the donor concentration is higher than the base doping concentration in the entire passage region 106.

[0169] In order to increase the donor concentration in the entire passage region 106, it is preferable that the hydrogen implanted at the first depth position Z1 diffuses to the vicinity of the second depth position Z2. In the first implantation step S1900, by adjusting the dose of hydrogen implanted at the first depth position Z1, sufficient hydrogen can be diffused to the vicinity of the second depth position Z2. In the first implantation step S1900, it is preferable to determine the dose of hydrogen so that the minimum value of the donor concentration in the passage region 106 is higher than the base doping concentration.

[0170] In the first implantation step S1900, hydrogen ions may be implanted near the stopping region (range Rp) of the helium ions. The hydrogen ion implantation in the first implantation step may be performed before or after the helium ion implantation in the second implantation step S1902. Ion implantation damage (disorders) is also localized near the stopping region of the helium ions. Many dangling bonds exist in the disorders. By also implanting hydrogen ions near the stopping region of the helium ions in the first implantation step S1900, the dangling bonds of the disorders are terminated by hydrogen, thereby reducing the disorders.

[0171] 9 and other figures, hydrogen ion implantation may be performed multiple times in addition to the hydrogen ion implantation in the first implantation step S1900. The multiple hydrogen ion implantations for forming the peaks 24 may be performed in the first implantation step S1900. In other words, the first implantation step S1900 may be performed multiple times.

[0172] 20 to 26 are diagrams for explaining a method for determining the dose of hydrogen ions to be implanted to the first depth Z1 (referred to as the first dose). In the first implantation step S1900 of this example, hydrogen is implanted at a dose equal to or greater than the minimum dose determined from the diffusion coefficient of hydrogen in the semiconductor substrate 10 and the position of the second depth Z2 (i.e., the distance that hydrogen implanted to the first depth position Z1 should diffuse).

[0173] Fig. 20 is a diagram showing an example of a carrier concentration distribution in the semiconductor substrate 10 after the diffusion step S1904. The carrier concentration distribution in Fig. 20 can be obtained by, for example, spreading resistance profiling. In each of Figs. 20 to 26, the lower surface 23 of the semiconductor substrate 10 is set as the reference position (0 µm) of the depth (µm). The first depth Z1 is 10 µm or less. The first depth Z1 may be treated as 0 µm.

[0174] FIG. 20 shows carrier concentration distributions of five types of semiconductor substrates 10. A first example 161, a second example 162, and a third example 163 are examples in which hydrogen ions are implanted to the first depth Z1 and helium ions are implanted to the second depth Z2. A fourth example 164 and a fifth example 165 are examples in which helium ions are implanted to the second depth Z2 and hydrogen is not implanted to the first depth Z1. In each example, the dose of helium ions to the second depth Z2 (referred to as the second dose) is 1×10 13 / cm 2 The range of the helium ions to the second depth Z2 was set to 100 μm, and the acceleration energy was set to 4.0 Mev. The range of the helium ions may be adjusted by the acceleration energy, or may be adjusted by an aluminum absorber or the like.

[0175] In the first example 161, the second example 162, and the third example 163, the acceleration energy of the hydrogen ions to the first depth Z1 was set to 400 keV. In the first example 161, the first dose was set to 1×10 15 / cm 2In the second example 162, the first dose was set to 3×10 14 / cm 2 In the third example 163, the first dose was set to 1×10 14 / cm 2 It was decided.

[0176] After the hydrogen ions were implanted, the semiconductor substrate 10 of each example was annealed in the same annealing furnace at 370° C. for 5 hours. However, the fifth example 165 was not annealed. FIG. 20 shows the carrier concentration distribution after annealing. Before annealing in each example, crystal defects are formed in the passage region 106 (the range from the lower surface 23 of the semiconductor substrate 10 to the second depth position Z2). As a result, the carrier concentration in the passage region 106 decreases.

[0177] After annealing, hydrogen bonds with crystal defects to become donors, and the carrier concentration increases. However, in the fourth example 164, hydrogen is not implanted into the first depth Z1, so the carrier concentration hardly increases. As shown in the first example 161, the second example 162, and the third example 163, the carrier concentration in the passing region 106 increases as the first dose increases. Also, as the first dose increases, the region in which the donor concentration is higher than the base doping concentration spreads from the first depth Z1 to a region farther away. In other words, as the first dose increases, hydrogen diffusion from the first depth Z1 reaches a farther region.

[0178] The first dose is Q, the diffusion depth of hydrogen from the first depth Z is x (x1, x2, x3) (cm), and the diffusion coefficient of hydrogen is D (cm 2 / s, the diffusion time is t, and the base doping concentration of the semiconductor substrate 10 is C0 (atoms / cm 3 ), then the relationship between these is expressed by the following equation (1). Equation (1) is a value calculated from the solution of the diffusion equation. When the diffusion equation is solved under the boundary condition that the total amount of hydrogen is constant, the solution is a Gaussian distribution. In the solution of the Gaussian distribution obtained, x when the concentration C(x, t) is equal to the base doping concentration C0 is Equation (1).

number

[0179] From formula (1), the diffusion coefficient D of hydrogen in the first example 161, the second example 162, and the third example 163 can be numerically calculated. The diffusion depth x in each example may be determined from the profile shape in FIG. 20. For example, the diffusion depth x may be the distance from the first depth position Z1 to the first inflection point of the valley of the carrier concentration. Alternatively, the diffusion depth x may be the distance from the first depth position Z1 to the position where the carrier concentration first falls below the base doping concentration.

[0180] The crystal defects formed when helium ions are implanted to the second depth Z2 include various defects such as point defects and dislocations. In particular, among point defects, vacancy-based defects such as vacancies and multivacancies are formed. In this case, the concentration of crystal defects has a peak at a position slightly closer to the ion implantation surface (the lower surface 23 of the semiconductor substrate 10) than the second depth Z2.

[0181] FIG. 21 is a diagram showing the relationship between the diffusion coefficient D of hydrogen and the first dose Q. In FIG. 21, the first example 161, the second example 162, and the third example 163 shown in FIG. 20 are plotted. When the first dose Q increases, the diffusion coefficient D increases. Hydrogen implanted at the first depth Z1 diffuses toward the second depth Z2 while terminating the dangling bonds in the passage region 106. When the first dose Q increases, the ratio of hydrogen diffusing in the region where the dangling bonds are terminated increases, so it is considered that hydrogen is more likely to diffuse. Note that the value of the diffusion coefficient D varies depending on the experimental conditions, etc. An error of at least ±50% is acceptable for the diffusion coefficient D shown in FIG. 21. An error of ±100% is also acceptable.

[0182] 22 is a graph showing the relationship between the diffusion coefficient D and the annealing temperature T. FIG. 22 is an Arrhenius plot of the diffusion coefficients described in FIG. 20 and FIG. 21 obtained for a plurality of annealing temperatures T. In this example, the first dose is Q=1×10 15 / cm 2 It was decided.

[0183] The diffusion coefficient D is D=D0exp(-Ea / k B T), where D0 is a constant, Ea is the activation energy, and k B is the Boltzmann constant. From the graph in Figure 22, D0 = 0.19095 (cm 2 / s), and Ea=1.204 (eV). From this, the diffusion coefficient of hydrogen in the semiconductor substrate 10 can be calculated.

[0184] Fig. 23 is a diagram showing the relationship between the diffusion depth of hydrogen and the first dose amount, in which the first example 161, the second example 162, and the third example 163 shown in Fig. 20 are plotted with black circles.

[0185] As shown in FIG. 23, by connecting the plots with a straight line, the first dose for each diffusion depth x can be determined. That is, the straight line indicates the minimum first dose for each diffusion depth x. In the first implantation step S1900, by setting a first dose larger than the straight line, the overall donor concentration in the passing region 106 can be made larger than the base doping concentration. As an example, the first dose Q (ions / cm 2 ) may satisfy the following formula when the second depth Z2 is the diffusion depth x (μm). Q ≥ 1.6491 × 10 13 ×e 0.061619x

[0186] As described above, the peak of the crystal defect concentration when helium ions are implanted to the second depth Z2 is located at a position slightly shallower than the second depth Z2. The horizontal axis of Fig. 23 corresponds to the peak position of the crystal defect concentration. Therefore, when forming a passage region 106 having a length X0 corresponding to the horizontal axis of Fig. 23, helium ions are implanted to the second depth Z2 with a range Rp of the following formula, taking into account straggling ΔRp in ion implantation. Rp ≧ X0 + ΔRp By setting the concentration peak position of crystal defects (the position of length X0 from the lower surface 23) at a position closer to the upper surface 21 than the bottom of the trench portion provided in the upper surface 21 of the semiconductor substrate 10, a passing region 106 can be formed over almost the entire depth direction of the semiconductor substrate 10.

[0187] The minimum dose may be calculated based on the following formula (2) obtained by modifying formula (1).

number

[0188] Fig. 24 is a diagram showing the relationship between the diffusion coefficient D and the diffusion depth x. In Fig. 24, a first example 161, a second example 162, and a third example 163 in Fig. 20 are plotted. As shown in Fig. 24, as the diffusion depth x increases, the diffusion coefficient D also increases.

[0189] When the diffusion depth x increases, the distance from the first depth Z1 to the concentration peak of the crystal defects increases. Therefore, the ratio of the area with relatively few crystal defects increases in the passage region 106. Since the diffusion coefficient increases when the number of crystal defects is small, the average diffusion coefficient of the passage region 106 also increases when the diffusion depth x increases.

[0190] In addition, in FIG. 20 to FIG. 24, the second dose is set to 1×10 13 / cm 2 However, even if the second dose is changed, the minimum dose of the first dose can be determined in a similar manner. The donor concentration in the passage region 106 may be adjusted by adjusting the second dose. The concentration of crystal defects formed in the passage region 106 can be adjusted by adjusting the second dose. Although the annealing temperature is set to 370° C., the minimum dose can be determined from formula (2) even if the annealing temperature is changed.

[0191] 25 is a diagram showing a straight line that defines the minimum dose for each annealing temperature. In this example, the diffusion coefficient D is constant regardless of the diffusion depth. In the first implantation step S1900, hydrogen ions are implanted to a first depth Z1 with a dose that is larger than the minimum dose shown by the straight line in FIG.

[0192] 26 is a diagram showing the relationship between the second dose and the minimum dose of the first dose. In this example, the relationship is shown for each diffusion depth x. In the first implantation step S1900, hydrogen ions are implanted to the first depth Z1 with a dose larger than the minimum dose shown by the straight line in FIG.

[0193] Fig. 27 is a diagram for explaining an example of the first depth Z1. Fig. 27 shows the donor concentration distribution, hydrogen chemical concentration distribution, and helium chemical concentration distribution in the depth direction of the semiconductor substrate 10. The hydrogen chemical concentration distribution and the helium chemical concentration distribution are shown only in the vicinity of the peak. Fig. 27 omits the distribution in the vicinity of the upper surface 21 of the semiconductor substrate 10 (a region 100 µm or more away from the lower surface 23). The carrier concentration distribution in the N-type region of the semiconductor substrate 10 may be used as the donor concentration distribution.

[0194] In this example, the first depth Z1 of the hydrogen concentration peak 131 is included in a range of 5 μm or less in the depth direction from the lower surface 23 of the semiconductor substrate 10. In the semiconductor device 100, the configuration other than the first depth Z1 is the same as any of the embodiments described with reference to Figures 1 to 26. The donor concentration distribution of the semiconductor device 100 of this example is similar to the example of Figure 10.

[0195] By disposing the first depth Z1 in the vicinity of the lower surface 23, the distance between the first depth Z1 and the second depth Z2 can be increased. Therefore, the donor concentration can be adjusted with high precision over a wider range of the semiconductor substrate 10. The first depth Z1 may be within a range of 4 μm or 3 μm from the lower surface 23.

[0196] In order to diffuse hydrogen over a wider range, it is preferable to implant hydrogen at a higher dose to the first depth Z1. In this example, the dose of hydrogen implanted to the first depth Z1 is 1×10 15 atoms / cm 2 It may be greater than or equal to 1 x 10 16 atoms / cm 2 It may be greater than or equal to 1 x 10 17 atoms / cm 2 It may be greater than or equal to 1 x 10 18 atoms / cm 2 At the first depth Z1, a first donor concentration peak 111 due to hydrogen donors may be formed. The donor concentration of the first donor concentration peak 111 may be 1×10 15 / cm 3 It may be greater than or equal to 1 x 10 16 / cm 3 The donor concentration of the first donor concentration peak 111 may be 1×10 17 / cm 3 It may be the following:

[0197] The injection of hydrogen to the first depth Z1 may be performed by plasma doping. In the plasma doping, a gas for plasma excitation and a raw material gas containing hydrogen are supplied into a container that contains the semiconductor substrate 10. The excitation gas may contain an inert element such as argon. The raw material gas may be phosphine (PH3) or the like. By generating plasma using these gases in the container and exposing the lower surface 23 of the semiconductor substrate 10 to the plasma, high concentration hydrogen can be easily injected into a shallow position as viewed from the lower surface 23. In addition, by using plasma doping to inject hydrogen into a shallow position near the lower surface 23, the occurrence of crystal defects in the semiconductor substrate 10 can be suppressed. In addition, since there are few crystal defects, the annealing temperature can be lowered, and the throughput in the manufacture of the semiconductor device 100 can be improved. However, the method of injecting hydrogen to the first depth Z1 is not limited to plasma doping.

[0198] Helium may be injected into the second depth Z2 of the helium concentration peak 141 by a method other than plasma doping. Helium ions may be accelerated by an electric field or the like to inject helium into the second depth Z2. The second depth position Z2 may be 80 μm or more away from the lower surface 23 in the depth direction. The second depth position Z2 may be 90 μm or more away from the lower surface 23, or may be 100 μm or more away. The distance in the depth direction between the first depth position and the second depth position may be 50% or more, 65% or more, or 80% or more of the thickness of the semiconductor substrate 10 in the depth direction.

[0199] 28 shows another example of the donor concentration distribution, hydrogen chemical concentration distribution, and helium chemical concentration distribution in the depth direction of the semiconductor substrate 10. The hydrogen chemical concentration distribution and the helium chemical concentration distribution are shown only in the vicinity of the peak. The first depth Z1 in this example is the same as the example in FIG. 27. The second depth Z2 may be located on the upper surface 21 side of the semiconductor substrate 10. The upper surface 21 side refers to the region from the center in the depth direction of the semiconductor substrate 10 to the upper surface 21.

[0200] 27 and 28, the hydrogen chemical concentration distribution may have one or more hydrogen concentration peaks 194 between the first depth Z1 and the second depth Z2. The hydrogen concentration peaks 194 may be located in the buffer region 20 described in FIG. 6 and the like. The hydrogen concentration peaks 131 may be located in the buffer region 20, or may be located between the buffer region 20 and the lower surface 23.

[0201] 29 is a diagram showing an example of a hydrogen chemical concentration distribution and an argon chemical concentration distribution in the vicinity of a hydrogen concentration peak 131. In this example, the hydrogen concentration peak 131 is a peak corresponding to hydrogen injected by plasma doping, and the hydrogen concentration peak 194 is a peak corresponding to hydrogen injected by a method other than plasma doping.

[0202] When hydrogen is injected into the first depth position Z1 by plasma doping, impurities other than hydrogen may be injected near the first depth position Z1. For example, when argon gas is used for plasma excitation, argon may be injected near the first depth position Z1. In FIG. 29, an argon concentration peak 196 is shown at the depth position Z0.

[0203] The depth position Z0 may be located between the lower surface 23 and the first depth position Z1. Since argon is a heavier element than hydrogen, the argon concentration peak 196 is likely to be formed at a position shallower than the hydrogen concentration peak 131.

[0204] In this example, there is no peak of the argon chemical concentration between the first depth position Z1 and the second depth position Z2. The hydrogen concentration peak 194 between the first depth position Z1 and the second depth position Z2 is formed by a method other than plasma doping, so argon is not implanted near the hydrogen concentration peak 194. The argon chemical concentration between the first depth position Z1 and the second depth position Z2 is smaller than the argon concentration peak 196. The maximum value of the argon chemical concentration between the first depth position Z1 and the second depth position Z2 may be equal to or smaller than the minimum value of the argon chemical concentration between the lower surface 23 and the first depth position Z1.

[0205] Depending on the composition of the gas used for the plasma doping, other impurities may be implanted into the semiconductor substrate 10 instead of argon. When PH3 gas is used for the plasma doping, a phosphorus concentration peak may be provided between the lower surface 23 and the first depth position Z1. When BF3 gas is used for the plasma doping, a fluorine concentration peak may be provided between the lower surface 23 and the first depth position Z1, or a boron concentration peak may be provided. The concentration value of the concentration peak of argon, phosphorus, fluorine, or boron may be smaller than the concentration value of the hydrogen concentration peak 131. The concentration value of the concentration peak of argon, phosphorus, fluorine, or boron may be half or less of the concentration value of the hydrogen concentration peak 131, or may be 1 / 10 or less.

[0206] Fig. 30 is a diagram showing another structural example of the semiconductor device 100. The semiconductor device 100 of this example includes a transistor section 70 and a diode section 80, similar to the example shown in Fig. 11. The structure of the transistor section 70 is the same as the example shown in Fig. 6. The transistor section 70 and the diode section 80 are provided adjacent to each other in the X-axis direction.

[0207] The diode section 80 of this example differs from the transistor section 70 in that it has a dummy trench section 30 instead of the gate trench section 40, has a cathode region 82 instead of the collector region 22, and does not have the emitter region 12. The other structures are similar to those of the transistor section 70.

[0208] The dummy trench portion 30 may have the same structure as the gate trench portion 40. The dummy trench portion 30 has a dummy insulating film 32 and a dummy conductive portion 34. The dummy insulating film 32 and the dummy conductive portion 34 may have the same structure and material as the gate insulating film 42 and the gate conductive portion 44. However, the gate conductive portion 44 is electrically connected to the gate electrode, whereas the dummy conductive portion 34 is electrically connected to the emitter electrode 52. The dummy trench portion 30 may also be provided in the transistor portion 70. That is, a part of the gate trench portion 40 in the transistor portion 70 may be replaced with the dummy trench portion 30.

[0209] The cathode region 82, like the collector region 22, is exposed at the lower surface 23 of the semiconductor substrate 10. The cathode region 82 is connected to the collector electrode 54 at the lower surface 23. The cathode region 82 is an N+ type region doped with an N-type impurity such as phosphorus. A buffer region 20 may be provided between the cathode region 82 and the drift region 18.

[0210] In the diode section 80, the base region 14 may be exposed on the upper surface 21. The base region 14 of the diode section 80 is electrically connected to the emitter electrode 52. With this configuration, the diode section 80 functions as a diode.

[0211] In this example, hydrogen is implanted at a first depth position Z1 and helium is implanted at a second depth position Z2 in the diode section 80. A passing region similar to that in the transistor section 70 is also formed in the diode section 80. Each concentration distribution in the transistor section 70 may be the same as any of the embodiments described with reference to FIGS. 1 to 29. The hydrogen chemical concentration distribution in the depth direction of the diode section 80 may be the same as the hydrogen chemical concentration distribution in the depth direction of the transistor section 70. The helium chemical concentration distribution in the depth direction of the diode section 80 may be the same as the helium chemical concentration distribution in the depth direction of the transistor section 70.

[0212] 31 shows an example of the carrier concentration distribution, hydrogen chemical concentration distribution, and boron chemical concentration distribution in the DD line of FIG. 30. The DD line passes through the collector region 22 and a part of the buffer region 20 in the transistor section 70. The collector region 22 in this example is formed by implanting boron. The boron in the collector region 22 in this example is implanted in a process separate from the hydrogen of the hydrogen concentration peak 131. At least a part of the boron in the collector region 22 may be implanted in the plasma doping for implanting the hydrogen of the hydrogen concentration peak 131.

[0213] 7 and other examples, the hydrogen concentration peak 131 is located in the buffer region 20. In this example, the hydrogen concentration peak 131 is located in the cathode region 82 and the collector region 22. Since the doping concentrations of the cathode region 82 and the collector region 22 are very high, by providing the hydrogen concentration peak 131 in the cathode region 82 and the collector region 22, it is possible to suppress fluctuations in the shape of the carrier concentration distribution even if a high concentration of hydrogen donors is generated by the hydrogen concentration peak 131. This makes it easier to suppress the influence on the characteristics of the semiconductor device 100.

[0214] The concentration of the hydrogen concentration peak 131 is set so that the hydrogen donor concentration is sufficiently smaller than the carrier concentration at the first depth position Z1. The hydrogen activation rate is about 1%. At the first depth position Z1, 1% of the hydrogen chemical concentration may be smaller than the boron chemical concentration.

[0215] Also, the peak position of the carrier concentration distribution in the collector region 22 is located closer to the boron chemical concentration peak than the hydrogen concentration peak 131. In the example of FIG. 31, the boron chemical concentration peak is located at the lower surface 23. The peak position of the carrier concentration distribution in the collector region 22 may be the same as the peak position of the boron chemical concentration. The hydrogen concentration peak 131 may be located between the peak of the carrier concentration distribution in the collector region 22 and the buffer region 20. In this example, the peak position of the carrier concentration distribution in the collector region 22 coincides with the lower surface 23. Note that in the buffer region 20, the depth position of the hydrogen concentration peak 194 may coincide with the depth position of the carrier concentration distribution peak 24.

[0216] 32 shows an example of the carrier concentration distribution, the hydrogen chemical concentration distribution, and the phosphorus chemical concentration distribution in the EE line of FIG. 30. The EE line passes through the cathode region 82 and a part of the buffer region 20 in the diode section 80. The cathode region 82 in this example is formed by implanting phosphorus. The phosphorus in the cathode region 82 is implanted in a process separate from the hydrogen of the hydrogen concentration peak 131. At least a part of the phosphorus in the cathode region 82 may be implanted in the plasma doping for implanting the hydrogen of the hydrogen concentration peak 131.

[0217] In this example, the hydrogen concentration peak 131 is located in the cathode region 82 and the collector region 22. The concentration of the hydrogen concentration peak 131 is set so that the hydrogen donor concentration is sufficiently smaller than the carrier concentration at the first depth Z1. The hydrogen activation rate is about 1%. At the first depth Z1, 1% of the hydrogen chemical concentration may be smaller than the phosphorus chemical concentration.

[0218] In addition, the peak position of the carrier concentration distribution in the cathode region 82 is located closer to the phosphorus chemical concentration peak than the hydrogen concentration peak 131. In the example of FIG. 32, the phosphorus chemical concentration peak is located on the lower surface 23. The peak position of the carrier concentration distribution in the cathode region 82 may be the same as the peak position of the phosphorus chemical concentration. The hydrogen concentration peak 131 may be located between the peak of the carrier concentration distribution in the cathode region 82 and the buffer region 20. In this example, the peak position of the carrier concentration distribution in the cathode region 82 coincides with the lower surface 23. In the buffer region 20, the depth position of the hydrogen concentration peak 194 may coincide with the depth position of the carrier concentration distribution peak 24.

[0219] Fig. 33 is a diagram showing some steps of a manufacturing method of the semiconductor device 100. Prior to the steps shown in Fig. 33, structures on the upper surface 21 side, such as each trench portion, the emitter region 12, the base region 14, and the accumulation region 16, may be formed.

[0220] In this example, in an implantation step S3300, helium ions are implanted to a second depth Z2 from the lower surface 23 of the semiconductor substrate 10. The implantation step S3300 may be identical to the second implantation step S1902 in the example of FIG.

[0221] Also, in implantation step S3302, hydrogen ions are implanted to a first depth Z1 from the underside 23 of the semiconductor substrate 10. In implantation step S3302, the hydrogen ions are implanted by plasma doping. The dose of hydrogen in implantation step S3302 may be the same as the dose of hydrogen in the first implantation step S1900 in the example of FIG. 19. Either implantation step S3300 or implantation step S3302 may be performed first.

[0222] After the implantation step S3300 and the implantation step S3302, a diffusion step S3304 is performed. The diffusion step S3304 is similar to the diffusion step S1904 in the example of Fig. 19. By diffusing hydrogen in the diffusion step S3304, crystal defects in the passage region 106 are bonded with hydrogen to become donors. This makes it possible to increase the donor concentration in the passage region 106.

[0223] After the diffusion step S3304, a grinding step S3306 is performed. In the grinding step S3306, the lower surface 23 side of the semiconductor substrate 10 is ground by chemical mechanical polishing (CMP) or the like. In the grinding step S3306, a range shallower than the first depth Z1 may be ground, or a range deeper than the first depth Z1 may be ground. This makes it possible to grind the region where hydrogen is distributed at a high concentration, thereby reducing the amount of hydrogen in the vicinity of the lower surface 23.

[0224] After the grinding step S3306, in a bottom surface side structure formation step S3308, a structure on the bottom surface 23 side, such as the collector region 22, the cathode region 82, and the buffer region 20, is formed. In the bottom surface side structure formation step S3308, after dopants are implanted into the cathode region 82 and the buffer region 20, the vicinity of the bottom surface 23 may be laser annealed. This allows the vicinity of the bottom surface 23 of the semiconductor substrate 10 to be locally heat-treated at a high temperature. Also, after the laser annealing, a dopant such as hydrogen may be implanted into the buffer region 20. After dopants are implanted into the buffer region 20, the entire semiconductor substrate 10 may be heat-treated in an annealing furnace.

[0225] Fig. 34 is a diagram showing some steps of a manufacturing method of the semiconductor device 100. The manufacturing method of this example differs in that a laser annealing step S3307 is provided instead of the grinding step S3306 of Fig. 33. The other steps are the same as those of the example of Fig. 33.

[0226] In the laser annealing step S3307, the lower surface 23 of the semiconductor substrate 10 is laser annealed. In the laser annealing step S3307, a laser may be irradiated near the first depth Z1. This allows at least a part of the hydrogen in the vicinity of the first depth Z1 to be released to the outside of the semiconductor substrate 10. This allows the hydrogen chemical concentration in the vicinity of the first depth Z1 to be reduced. In the laser annealing step S3307, a laser may be irradiated so that the hydrogen concentration peak 131 remains, or a laser may be irradiated so that the hydrogen concentration peak 131 does not remain. Even if a laser is irradiated, heavy elements such as argon tend to remain in the semiconductor substrate 10 compared to hydrogen. Therefore, even if the laser annealing step S3307 is performed, the semiconductor substrate 10 may have a concentration peak of impurities such as argon shown in FIG. 29.

[0227] Also, in the laser annealing step S3307, the transistor portion 70 may be irradiated with a laser, but the diode portion 80 may not be irradiated with a laser. Even if a high concentration of hydrogen donors remains on the lower surface 23 of the diode portion 80, the effect on the characteristics is relatively small. In this case, the hydrogen chemical concentration at the first depth Z1 of the diode portion 80 is higher than the hydrogen chemical concentration at the first depth Z1 of the transistor portion 70.

[0228] In the examples shown in Figures 19, 33, and 34, the implantation of hydrogen ions to the first depth Z1, the implantation of helium ions to the second depth Z2, and the heat treatment may be performed before forming the bottom-side structure, after forming the bottom-side structure, or while forming the bottom-side structure.

[0229] 35 shows an example of a process for implanting hydrogen ions to a first depth Z1 and helium ions to a second depth Z2 in a bottom surface side structure formation stage. In this example, the implantation of hydrogen ions to the first depth Z1, the implantation of helium ions to the second depth Z2, and the heat treatment are performed in a buffer region formation stage S3504 for forming the buffer region 20.

[0230] The lower surface side structure forming step may be performed after the upper surface side structure forming step S3500 of the trench portion or the like. The lower surface side structure forming step includes a collector region forming step S3502 and a buffer region forming step S3504. In FIG. 35, other steps of the lower surface side structure forming step are omitted. In this example, in the buffer region forming step S3504, hydrogen ions are implanted to a first depth Z1 and helium ions are implanted to a second depth Z2. In S3504, after the hydrogen ions are implanted, the semiconductor substrate 10 is heat-treated to diffuse the hydrogen ions and helium ions. After the lower surface side structure forming step, a collector electrode forming step S3506 may be performed.

[0231] 36 shows another example of a process for implanting hydrogen ions to a first depth Z1 and helium ions to a second depth Z2 in the bottom side structure formation stage. In this example, the implantation of hydrogen ions to the first depth Z1 and the heat treatment are performed in the cathode region formation stage S3503. The implantation of helium ions to the second depth Z2 and the heat treatment are performed in the buffer region formation stage S3504.

[0232] The lower surface side structure forming step may be performed after the upper surface side structure forming step S3500 of the trench portion, etc. The lower surface side structure forming step in this example includes a cathode region forming step S3503 and a buffer region forming step S3504. In FIG. 36, the other steps of the lower surface side structure forming step are omitted.

[0233] The semiconductor device 100 of this example may include a transistor portion 70 and a diode portion 80. In this case, after forming a cathode region 82 on the entire lower surface 23, a P-type collector region 22 may be formed in a part of the cathode region 82 by selectively implanting a P-type dopant. In the cathode region formation step S3503, a source gas such as PH3 containing an N-type dopant such as phosphorus may be used. In the cathode region formation step S3503, hydrogen ions are implanted into the entire lower surface 23 to a first depth Z1.

[0234] Alternatively, after selectively forming collector region 22 on lower surface 23, N-type dopants and hydrogen ions may be implanted into the entire lower surface 23 to form cathode region 82. In this case, a high concentration of P-type dopant may be implanted in advance into collector region 22 so that the conductivity type is not inverted to N-type. By such a process, first depth Z1 is located in collector region 22 and cathode region 82.

[0235] When the semiconductor device 100 does not include the transistor portion 70 but includes the diode portion 80, the step of forming the collector region 22 can be omitted. Moreover, the hydrogen implantation to the second depth Z2 may be performed in the step of forming the buffer region 20. After the bottom surface side structure formation step, a collector electrode formation step S3506 may be performed.

[0236] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is clear 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 in the technical scope of the present invention.

[0237] 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 indicated as "before," "prior to," etc., and may be realized in any order unless the output of a previous process is used in a later process. Even if the operational flow in the claims, specifications, and drawings is explained using "first," "next," etc. for convenience, it does not mean that it is essential to perform the process in this order. [Explanation of symbols]

[0238] 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, 25 peak, 30 dummy trench portion, 32 dummy insulating film, 34 dummy conductive portion, 38 interlayer insulating film, 40 gate trench portion, 42 gate insulating film , 44 ··· gate conductive portion, 48 ··· gate runner, 50 ··· gate metal layer, 52 ··· emitter electrode, 54 ··· collector electrode, 70 ··· transistor portion, 72 ··· boundary portion, 80 ··· diode portion, 82 ··· cathode region, 90 ··· edge termination structure portion, 92 ··· guard ring, 94 ··· field plate, 100 ··· semiconductor device, 106 ··· pass region, 111 ··· first donor concentration peak, 112, 122, 132, 142, 172···upward slope, 113, 123, 133, 143, 173···downward slope, 114, 124, 125, 134, 144, 145··inclination, 116··gate pad, 118··emitter pad, 120··active area, 121···second donor concentration peak, 131···hydrogen concentration peak, 140··periphery, 141···helium concentration peak, 150··plateau, 151··valley, 161···first example, 162···second example , 163···Third example, 164···Fourth example, 165···Fifth example, 171···Vacancy concentration peak, 174···Channel stopper, 175···Vacancy defect concentration distribution, 180···Base doping region, 181···Non-doped region, 182···Protective film, 184···Plating layer, 190···Intermediate boundary region, 192···Lifetime control region, 194···Hydrogen concentration peak, 196···Argon concentration peak, 200··Photoresist film

Claims

[Claim 1] A semiconductor device comprising a semiconductor substrate having an upper surface and a lower surface, a drift region of a first conductivity type provided in the semiconductor substrate; a buffer region of a first conductivity type provided between the lower surface of the semiconductor substrate and the drift region, the buffer region having one or more donor concentration peaks having a donor concentration higher than that of the drift region; a helium chemical concentration peak located on the upper surface side of the semiconductor substrate in a depth direction connecting the upper surface and the lower surface of the semiconductor substrate; Equipped with Throughout the drift region in the depth direction, the donor concentration of the drift region is higher than the base doping concentration of the semiconductor substrate. Semiconductor device.

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