Semiconductor Devices

Abstract

The range and donor concentration of the donor region that is generated by the bonding of crystal defects with hydrogen are precisely controlled. [Solution] A semiconductor device is provided, comprising: a semiconductor substrate having an upper surface and a lower surface; and an n-type drift region implanted with hydrogen, the drift region being located at a position including the center of the semiconductor substrate in a depth direction connecting the upper surface and the lower surface; wherein in the donor concentration distribution of the semiconductor substrate in the depth direction, the drift region includes a flat region having a length of at least 10 μm or more, and a decrease portion which is located contiguous to the upper surface side of the flat region and in which the donor concentration decreases with increasing distance from the flat region.

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: JP 2016-204227 A Problem to be Solved

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

[0004] In order to solve the above-mentioned problems, one aspect of the present invention provides a semiconductor device comprising: a semiconductor substrate having an upper surface and a lower surface; and an n-type drift region implanted with hydrogen, the n-type drift region being disposed at a position including the center of the semiconductor substrate in a depth direction connecting the upper surface and the lower surface. In the donor concentration distribution of the semiconductor substrate in the depth direction of the semiconductor device, the drift region may include a flat region having a length of at least 10 μm or more. In the donor concentration distribution of the semiconductor substrate in the depth direction of the semiconductor device, the drift region may include a decreasing portion that is disposed contiguous with the flat region on the upper surface side and in which the donor concentration decreases with increasing distance from the flat region.

[0005] In any of the above semiconductor devices, a lifetime control region may be provided on an upper surface side of the center of the semiconductor substrate.

[0006] In any of the above semiconductor devices, helium may be injected into the semiconductor substrate on an upper surface side of the center.

[0007] Any of the above semiconductor devices may include a p-type base region provided between the upper surface and the drift region, and any of the above semiconductor devices may have a helium chemical concentration peak between the base region and the reduced portion in the depth direction.

[0008] In any of the above semiconductor devices, the donor concentration distribution may have a first donor concentration peak at a first depth below the center of the semiconductor substrate, and the flat region may be located closer to the top surface than the first donor concentration peak.

[0009] In any of the above semiconductor devices, the flat region may have a length that is 30% or more of the thickness of the semiconductor substrate in the depth direction.

[0010] In any of the above semiconductor devices, the flat region may be a region in which the donor concentration is between the maximum value of the donor concentration in the flat region and 50% of the maximum value, and the region is continuous in the depth direction.

[0011] In any of the above semiconductor devices, the flat region may be a region in which the donor concentration is between the maximum value of the donor concentration in the flat region and 70% of the maximum value, and the region is continuous in the depth direction.

[0012] In any of the above semiconductor devices, the flat region may be a region in which the donor concentration is between the maximum value of the donor concentration in the flat region and 90% of the maximum value, and the region is continuous in the depth direction.

[0013] In any of the above semiconductor devices, the flat region may have a concentration continuously in the depth direction within ±50% of the average concentration of the flat region.

[0014] In any of the above semiconductor devices, hydrogen donors may be formed throughout the flat region in the depth direction.

[0015] In any of the above semiconductor devices, the donor concentration of the drift region may be higher than the base doping concentration of the semiconductor substrate over the entire flat region in the depth direction.

[0016] In any of the above semiconductor devices, the flat region may be provided at a position that includes the center of the semiconductor substrate in the depth direction.

[0017] In any of the above semiconductor devices, the reduced portion may be provided on an upper surface side of the center of the semiconductor substrate.

[0018] Any of the above semiconductor devices may further include an n-type buffer region provided closer to the lower surface than the drift region and having one or more donor concentration peaks with a higher donor concentration than the drift region.

[0019] A second aspect of the present invention provides 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 has a hydrogen concentration peak.

[0020] The helium concentration distribution may have a helium concentration peak.

[0021] A third aspect of the present invention provides 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 toward the upper surface relative to 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 bottom surface of a semiconductor substrate. The manufacturing method may include a second implantation step of implanting helium to a second depth from the bottom 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. The dose of hydrogen in the first implantation step may be determined so that the minimum 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 implantation.

[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 underside 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, and subcombinations of these features may also constitute inventions. [Brief explanation of the drawings]

[0030] [Figure 1]1 is a cross-sectional view showing an example of a semiconductor device 100. FIG. [Figure 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] 10 is a diagram illustrating the relationship between a helium concentration peak 141 and a second donor concentration peak 121. FIG. [Figure 3C] 10 is a diagram illustrating the inclination of an upward slope 142. FIG. [Figure 4A] FIG. 10 is a diagram illustrating another definition of the normalization of the gradient of the upward slope 112. [Figure 4B] FIG. 10 is a diagram illustrating another definition of the normalization of the gradient of the upward slope 122. [Figure 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] FIG. 7 is a diagram showing an example of a carrier concentration distribution in the depth direction at the position of the BB line in FIG. 6. [Figure 8] 10A and 10B are diagrams illustrating another example of the structure of the semiconductor device 100. [Figure 9] 9 is a diagram showing an example of a carrier concentration distribution in the depth direction at the position of the CC line 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 the upper surface 21 of the semiconductor substrate 10. FIG. [Figure 12] FIG. 12 is a diagram showing an example of a cross section taken along the line cc' in FIG. [Figure 13] 10 is a diagram showing another example of the arrangement of the passing area 106. FIG. [Figure 14] 10 is a diagram showing another example of the arrangement of the passing area 106. FIG. [Figure 15]10 is a diagram showing another example of the arrangement of the passing area 106. FIG. [Figure 16A] 10 is a diagram showing another example of the arrangement of the passing area 106. FIG. [Figure 16B] 10 is a diagram showing another example of the arrangement of the passing area 106. FIG. [Figure 17A] 10 is a diagram showing another example of the arrangement of the passing area 106. FIG. [Figure 17B] 10 is a diagram showing another example of the arrangement of the passing area 106. FIG. [Figure 17C] 1 is a diagram illustrating the minimum film thickness M of the photoresist film 200 required to prevent helium ions from penetrating into the semiconductor substrate 10. FIG. [Figure 18A] 10 is a diagram showing another example of the arrangement of the passing area 106. FIG. [Figure 18B] 10 is a diagram showing another example of the arrangement of the passing area 106. FIG. [Figure 19] 1A and 1B are diagrams showing a step of forming a passage region 106 in the method of manufacturing 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] FIG. 10 is a diagram showing the relationship between the diffusion coefficient D of hydrogen and the first dose Q. [Figure 22] FIG. 1 is a diagram showing the relationship between the diffusion coefficient D and the annealing temperature T. [Figure 23] FIG. 10 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. [Figure 25] FIG. 10 is a diagram showing a straight line defining the minimum dose for each annealing temperature. [Figure 26] FIG. 10 is a diagram showing the relationship between the second dose and the minimum dose of the first dose. [Figure 27] FIG. 10 is a diagram illustrating an example of a first depth Z1. [Figure 28] 10 shows other examples of the donor concentration distribution, hydrogen chemical concentration distribution, and helium chemical concentration distribution in the depth direction of the semiconductor substrate 10. [Figure 29]10 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. [Figure 30] 10A and 10B are diagrams illustrating another example of the structure of the semiconductor device 100. [Figure 31] 30 shows an example of a carrier concentration distribution, a hydrogen chemical concentration distribution, and a boron chemical concentration distribution along the DD line. [Figure 32] 30 shows an example of a carrier concentration distribution, a hydrogen chemical concentration distribution, and a phosphorus chemical concentration distribution along the EE line. [Figure 33] 2A to 2C are diagrams illustrating some steps in a method for manufacturing the semiconductor device 100. [Figure 34] 2A to 2C are diagrams illustrating some steps in a method for manufacturing the semiconductor device 100. [Figure 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. [Figure 36] Another example of the process of implanting hydrogen ions to a first depth Z1 and helium ions to a second depth Z2 in the lower surface side structure formation stage will be described. DETAILED DESCRIPTION OF THE INVENTION

[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 as claimed. 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 the Cartesian coordinate axes of the X-axis, Y-axis, and Z-axis. The Cartesian coordinate axes merely identify the relative positions of components and do not limit a specific direction. For example, the Z-axis does not limit the height direction relative to the ground. Note that the +Z-axis direction and the -Z-axis direction are opposite directions. When the Z-axis direction is written without specifying positive or negative, it means the direction parallel to the +Z-axis and -Z-axis.

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

[0035] As used herein, chemical concentration refers to the concentration of an impurity measured regardless of its activation state. Chemical concentration can be measured, for example, by secondary ion mass spectrometry (SIMS). In this specification, the difference in donor and acceptor concentrations may be referred to as the concentration of the larger donor or acceptor. This concentration difference can be measured by voltage-capacitance (CV) measurement. Alternatively, the carrier concentration measured by spreading resistance (SR) measurement may be used as the donor or acceptor concentration. When the donor or acceptor concentration distribution has a peak, the peak value may be used as the donor or acceptor concentration in that region. In cases where the donor or acceptor concentration in a region where the donor or acceptor is present is approximately uniform, the average donor or acceptor concentration in that region may be used as the donor or acceptor concentration. The units used in this specification are SI units unless otherwise specified. Although the unit of length may be expressed in cm, calculations may be performed after converting it 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 manufacturing. 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 planes 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 from FIG. 1.

[0038] Hydrogen ions and helium ions are implanted into the semiconductor substrate 10 from the bottom 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 bottom surface 23 is referred to as the first depth Z1, and the one deeper than the first depth Z1 as viewed from the bottom surface 23 is referred to as the second depth Z2. In FIG. 1, the implanted hydrogen and helium are schematically indicated by crosses, but the hydrogen and helium are also distributed around the implantation positions Z1 and Z2.

[0039] The first depth Z1 may be located on the lower surface 23 side in the depth direction of the semiconductor substrate 10. For example, the first depth Z1 may be located in a range of less than half the thickness of the semiconductor substrate 10, or may be located in a range of less than ¼ the thickness of the semiconductor substrate 10, based on the lower surface 23. The second depth Z2 may be located on the upper surface 21 side in the depth direction of the semiconductor substrate 10. For example, the second depth Z2 may be located in a range of less than half the thickness of the semiconductor substrate 10, or may be located in a range of less than ¼ the thickness of the semiconductor substrate 10, based on the upper surface 21. 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. When the helium ions pass through the passage region 106, vacancy defects such as vacancies (V) and divacancies (VV) are generated. In this specification, unless otherwise specified, the term "vacancy" includes divacancies. The vacancy density in the passage region 106 can be adjusted by, for example, the dose of helium ions implanted to the second depth Z2.

[0041] By subjecting the semiconductor substrate 10 to 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 when vacancies (V) and oxygen (O) present in the passage region 106 combine 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 manufacturing of the semiconductor ingot that forms the semiconductor substrate 10. Therefore, the donor concentration in the semiconductor substrate 10 can be easily adjusted depending on the characteristics that the element formed in the semiconductor substrate 10 is intended to have. Unless otherwise specified, in this specification, 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 semiconductor ingot production. For example, if the semiconductor ingot is silicon, phosphorus, antimony, or arsenic may be used for n-type, and boron, aluminum, or the like may be used for p-type. For compound semiconductors and oxide semiconductors other than silicon, the respective dopants may also be used. Furthermore, the semiconductor ingot may be produced by any of the float zone (FZ) method, the Czochralski (CZ) method, and the magnetic field-applied Czochralski (MCZ) method.

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

[0044] FIG. 2 shows the depth-wise hydrogen concentration distribution, helium concentration distribution, donor concentration distribution, and vacancy defect concentration distribution 175 at the position indicated by line AA in FIG. 1. The horizontal axis of FIG. 2 indicates the depth from the lower surface 23, and the vertical axis indicates the hydrogen concentration, helium concentration, donor concentration, and vacancy defect concentration per unit volume on a logarithmic scale. Note that 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 have decreased or disappeared compared to immediately after ion implantation, resulting in a concentration distribution different from that shown in FIG. 2. The hydrogen concentration and helium concentration in FIG. 2 are chemical concentrations measured, for example, by SIMS. The donor concentration in FIG. 2 is an electrically activated doping concentration measured, for example, by CV or SR. In FIG. 2, the hydrogen concentration distribution, helium concentration distribution, and vacancy defect concentration distribution 175 are indicated by dashed lines, and the donor concentration distribution is indicated by solid lines.

[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 has a maximum value at a first depth Z1. The second donor concentration peak 121 has a maximum value at a second depth Z2. However, the position where the first donor concentration peak 111 has a maximum value does not have to exactly coincide with the first depth Z1. For example, if the position where the first donor concentration peak 111 has 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 considered to be located substantially 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 range of the full width at half maximum of the helium concentration peak 141 based on the second depth Z2, then the second donor concentration peak 121 may be considered 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 shows 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 as the concentration moves 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 in the semiconductor substrate 10 include donors that existed in the semiconductor substrate 10 before the hydrogen ion implantation, i.e., the base doping concentration (concentration Db), donors activated by the implanted hydrogen, and the VOH defects described above. The ratio of hydrogen activated as donors is, for example, approximately 1%. In the 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 is higher than the ratio of donors due to VOH defects corresponding to the hydrogen chemical concentration, and the donor concentration is determined by the vacancy defect concentration. 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 higher than the vacancy defect concentration, so 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 its neighboring 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 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 dominant donor concentration distribution of the VOH defect.

[0052] In the passage region 106, excluding the vicinity of the first depth Z1 and the second depth Z2, vacancies (V, VV, etc.) generated by the passage of hydrogen are thought to be distributed at a substantially uniform concentration in the depth direction as shown in FIG. 2. Also, oxygen (O) implanted during the manufacture of the semiconductor substrate 10 is thought to be distributed uniformly in the depth direction. Furthermore, a sufficient amount of hydrogen exists 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, a flat region 150 exists in the passage region 106 other than the vicinity of the first depth Z1 and the second depth Z2, 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. An almost constant donor concentration in the depth direction may refer to, for example, a state in which a region in which the difference between the maximum and minimum donor concentrations is within 50% of the maximum donor concentration is continuous in the depth direction. The difference may be 30% or less, or may be 10% or less, of the maximum donor concentration in the region.

[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, there are 0.25Z on the first depth Z1 side and the second depth Z2 side. L The distance between two points is 0.5Z L The length of the predetermined range may be set to 0.75Z depending on the length of the flat region 150. L It can also be 0.3Z L It can also be 0.9Z L It may also be possible to use the following.

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

[0056] When implanting helium ions deeper than the hydrogen concentration peak 131, the acceleration energy of the helium ions may be increased to a value that allows the helium ions to penetrate (pierce) the semiconductor substrate 10. In other words, the helium concentration peak 141 may not remain in the semiconductor substrate 10. This may also increase the concentration of vacancy defects. On the other hand, if the acceleration energy is excessive, the substrate may be damaged too much during ion implantation, making it impossible to maintain a flat distribution of vacancy defects in the passage region 106. Therefore, the helium concentration peak 141 may be positioned inside the semiconductor substrate 10.

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

[0058] 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 even 100 times or more, 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, is 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, because helium concentration peak 141 is far from hydrogen concentration peak 131, the amount of hydrogen activated as a donor at helium concentration peak 141 is small. In other words, the proportion of VOH defect donors dominated by vacancy defect concentration distribution 175 is relatively high compared to VOH defect donors dominated by hydrogen chemical concentration distribution. In this case, the similarity between the shape of second donor concentration peak 121 and the shape of helium concentration peak 141 is smaller than the similarity between the shape of first donor concentration peak 111 and the shape of hydrogen concentration peak 131. Because VOH defects are considered to be distributed almost uniformly throughout most of passage region 106, second donor concentration peak 121 has a more gentle shape. The similarity of 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 this 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. Furthermore, 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 throughout 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. Furthermore, 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 134 of the upward slope 132 of the hydrogen concentration peak 131 is used to normalize the gradient 114 of the upward slope 112 of the first donor concentration peak 111. As an example, normalization is a process of dividing the gradient 114 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 reaches a maximum and the position where the concentration reaches a predetermined ratio to the maximum. The predetermined ratio may be 80%, 50%, 10%, 1%, or another ratio. Furthermore, 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). where 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 upslope 132 of hydrogen concentration peak 131, and Z4 is the depth at which the donor concentration becomes aD1 on the upslope 112 of first donor concentration peak 111. For example, normalizing slope 114 by slope 134 gives (D1-aD1)(Z1-Z3) / {(H1-aH1)(Z1-Z4)}. The slope obtained by normalizing slope 114 by 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 , slope 144 of helium concentration peak 141 is given by (H2−aH2) / (Z2−Z5), and slope 124 of second donor concentration peak 121 is given by (D2−aD2) / (Z2−Z6). H2 is the helium concentration at second depth Z2, D2 is the donor concentration at second depth Z2, a is a predetermined ratio, Z5 is the depth at which the helium concentration becomes aH2 on upslope 142 of helium concentration peak 141, and Z6 is the depth at which the donor concentration becomes aD2 on upslope 122 of second donor concentration peak 121. Ratio a used to normalize the slope of second donor concentration peak 121 may be the same as or different from ratio a used to normalize the slope of first donor concentration peak 111. For example, when the slope 124 is normalized by the slope 144, it becomes (D2-aD2)(Z2-Z5) / {(Z2-Z6)(H2-aH2)}. The slope obtained by normalizing the slope 124 by the slope 144 is defined as β.

[0068] The normalized slope β of the upward slope 122 of the second donor concentration peak 121 is smaller than the normalized slope α of the upward slope 112 of the first donor concentration peak 111. In other words, the second donor concentration peak 121 has a gentler slope relative to the concentration peak of hydrogen or helium than the first donor concentration peak 111. By implanting hydrogen ions and helium ions to form such a second donor concentration peak 121, a flat region 150 can be formed. Furthermore, by forming the second donor concentration peak 121 in a gentle shape, the change in donor concentration at the end of the flat region 150 can be made gentle. The normalized slope β of the upward slope 122 of the second donor concentration peak 121 may be 1 time or less, 0.1 times or less, or 0.01 times or less the normalized slope 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 the helium of helium concentration peak 141 was implanted from the undersurface 23 side. Slope 145 is given by (H2 - aH2) / (Z7 - Z2). Slope 125 is given by (D2 - aD2) / (Z7 - Z2). In FIG. 3B, the gradient 124 of the upward slope 122 of the second donor concentration peak 121 is greater than the gradient 125 of the downward slope 123, but similar to the helium concentration peak 141, the gradient 124 of the upward slope 122 of the second donor concentration peak 121 may be smaller than the gradient 125 of the downward slope 123.

[0070] FIG. 3C is a diagram illustrating 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 the helium concentration peak 141 where the concentration is 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 where the helium concentration is 0.1 × H2 on either side of the peak position Z2. Of the two positions Z8 and Z9, the position closest to the hydrogen concentration peak 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 illustrating another definition of the normalization of the gradient of the upward slope 112. For example, the following index γ is introduced when normalizing the gradient of the upward slope 112. In the example of FIG. 3A, positions Z3 and Z4 are different, but in this example, positions Z3 and Z4 are the same (Z3 = Z4). Position Z3 is a predetermined position. Position Z3 may be any position where the hydrogen concentration distribution and donor concentration distribution form upward slopes 132, 112 on the lower surface side of position Z1. The hydrogen concentration at position Z3 is defined as a × H1, and the donor concentration is defined as b × D1. a is the ratio of the hydrogen concentration at position Z3 to the concentration H1 of the hydrogen concentration peak 131 at position Z1. b is the ratio of the donor concentration at position Z3 to the concentration D1 of the first donor concentration peak 111 at 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, which is the normalized ratio of these slopes. 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, which is the normalized 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 is simply the ratio a / b, calculated using the above formula.

[0072] FIG. 4B is a diagram illustrating another definition of the normalization of the gradient of the upward slope 122. For example, an index ε similar to the index γ is introduced to normalize the gradient of the upward slope 122. In the example of FIG. 3B, positions Z5 and Z6 are different, but in this example, positions Z5 and Z6 are the same (Z5 = Z6). Position Z5 is a predetermined position. Position Z5 may be any position where the helium concentration distribution and donor concentration distribution form upward slopes 142, 122 on the lower surface side of position Z2. The helium concentration at position Z5 is defined as c×H2, and the donor concentration is defined as d×D2. c is the ratio of the helium concentration at position Z5 to the concentration H2 of the helium concentration peak 141 at position Z2. d is the ratio of the donor concentration at position Z5 to the concentration D2 of the second donor concentration peak 121 at 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, which is the normalized ratio of these slopes. The ratio of the slopes of the helium concentrations in the section Z5 to Z2 is defined as (H2 / cH2) / (Z2-Z5). Similarly, the ratio of the slopes of the donor concentrations in the section Z5 to Z2 is defined as (D2 / dD2) / (Z2-Z5). Then, the slope ratio ε, which is the normalized ratio of the slopes of the donor concentrations by the ratio of the slopes of the helium concentrations 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, "similar shapes" means that, for example, when the horizontal axis represents depth and the vertical axis represents the 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 The hydrogen concentration aH1 at position Z3 is 2×10 16 atoms / cm 3On the other hand, D1 of the first donor concentration peak 111 is 1×10 16 atoms / cm 3 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 in shape. 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 at the helium concentration peak 141 is 1×10 16 atoms / cm 3 The helium concentration cH2 at position Z5 is 1×10 15 atoms / cm 3 On the other hand, D2 of the second donor concentration peak 121 is 3×10 14 atoms / cm 3 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 approaches 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] As another example of the second donor concentration peak 121, the donor concentration calculated from the spreading resistance, i.e., the carrier concentration, may be lower at depth position Z2 than at positions before and after due to a decrease in carrier mobility. In such a case, the upward slope 122 is a decreasing slope, so d has a negative sign. That is, d is a negative number with an absolute value of 1 or greater. As a result, ε becomes 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, or -10 or less, or -100 or less.

[0077] Note that the actual position of the helium concentration peak 141 may differ from the actual position of the second donor concentration peak 121. Furthermore, the position of the hydrogen concentration peak 131 may not exactly match the position of the first donor concentration peak 111. In this case, when the position of the hydrogen or helium concentration peak does not match the position of the donor concentration peak, the concentration at the peak position of the hydrogen or helium concentration may be conveniently taken as the peak position for the donor concentration. This allows calculations based on the above definition.

[0078] The important point in the above explanation is that helium concentration peak 141 has a maximum value. That is, the helium concentration distribution has a maximum value at depth Z2. The fact that 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 approximately constant in the depth direction. The flat region 150 is a region in which the donor concentration is between a predetermined maximum value max and a predetermined minimum value min, and the region 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 an example of the structure 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 to cover at least a portion 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 has 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. P-type contact regions (not shown) are provided in the direction in which the trench portion extends (the Y-axis direction in FIG. 6) and are arranged alternately with the emitter regions 12. The contact regions are formed on the 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 turned off.

[0087] The accumulation region 16 is disposed between the base region 14 and the drift region 18 and has one or more donor concentration peaks with 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 with 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, passing through the emitter region 12, the base region 14, and the accumulation region 16, and reaching the drift region 18. In this example, the accumulation region 16 is located 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, which has a higher concentration than the drift region 18, between the drift region 18 and the base region 14, 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 formed on the upper surface side of the semiconductor substrate 10, a gate insulating film 42, and a gate conductive portion 44. 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 trench, more inward than the gate insulating film 42. In other words, the gate insulating film 42 insulates the gate conductive portion 44 from the semiconductor substrate 10. The gate conductive portion 44 is formed of a conductive material such as polysilicon.

[0092] The gate conductive portion 44 includes a region facing the base region 14 with the gate insulating film 42 sandwiched 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 other cross sections. 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. In this example, the second donor concentration peak 121 is provided in the drift region 18. The second donor concentration peak 121 may be located below the lower end of the gate trench portion 40, may be located in contact with the lower end of the gate trench portion 40, or may be located 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 the carrier concentration distribution in the depth direction at the position of line BB in Fig. 6. Fig. 7 also shows a portion 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 multiple 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 multiple peaks 24, it is possible to further prevent 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 that is 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 as the peaks 24.

[0098] In this example, the accumulation region 16 has multiple 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 the entire semiconductor ingot is not doped with a dopant such as phosphorus (P) 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, the region in which the doping concentration is the base doping concentration Dn is defined as the 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 or more. 12 atoms / cm 3The concentrations in this specification may be values ​​at room temperature, which may be, for example, 300 K (Kelvin) (approximately 26.9° C.).

[0100] 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 with reference to FIGS. 6 and 7 in that the second donor concentration peak 121 (and the helium concentration peak 141) is located in the accumulation region 16. Other structures may be the same as those of the semiconductor device 100 described with reference to FIGS. 6 and 7.

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

[0102] In this example, the carrier concentration distribution in the accumulation region 16 has multiple peaks located at different positions in the depth direction. These peaks are donor concentration peaks. The peaks in the accumulation region 16 may contain hydrogen or phosphorus as impurities. By providing multiple peaks in the accumulation region 16, it is possible to suppress 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 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 as, or higher than the donor concentrations of the 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] In this example, the carrier concentration of the drift region 18 may be higher than the base doping concentration Db of the substrate throughout the entire depth direction. With this structure, the entire carrier concentration of the drift region 18 can be adjusted with high precision.

[0106] The peaks 25 other than the second donor concentration peak 121 may be peaks due to donors other than hydrogen. For example, peak 25 is a peak where phosphorus functions as a donor. Using phosphorus as a donor reduces the occurrence of VOH defects, making it easier to control the donor concentration at and around peak 25 by the phosphorus concentration. Furthermore, the depth width of second donor concentration peak 121 may be wider than the depth width of peak 25. This further suppresses the displacement current to the gate trench portion. Furthermore, a valley in the donor concentration distribution may exist between the second donor concentration peak 121 and peak 25 in the accumulation region 16, as shown in FIG. 9 . Alternatively, the donor concentration distribution in the accumulation region 16 may have a kink rather than a valley, as indicated by the dotted line between the two peaks in FIG. 9 .

[0107] 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. More defects are likely to occur near the range (Z2) of the helium concentration peak 141 than in the transit region 106. Defects that remain unbonded with hydrogen may cause a valley 151 in the carrier concentration distribution near the second depth Z2.

[0108] When a valley 151 is present, the gradient of the upward slope 122 of the second donor concentration peak 121 may appear steep in calculation. For this reason, it is preferable to calculate the gradient of the upward slope 122 while 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 using the respective concentrations at the second depth Z2 and the respective concentrations at the depth Zc. The depth Zc may be located closer to the lower surface 23 than 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 while excluding the influence of the valley 151. As described above, the normalization may be performed using the gradient of the concentration difference or the gradient of the concentration ratio.

[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 an active portion 120 and an edge termination structure 90. Active portion 120 is a region through which a main current flows between upper surface 21 and lower surface 23 of semiconductor substrate 10 when semiconductor device 100 is controlled to an on state. In other words, active portion 120 is a region through which a current flows in the depth direction within 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 and 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 region covered by the emitter electrode 52.

[0112] The transistor section 70 of this example has an IGBT (insulated gate bipolar transistor) described with reference to FIGS. 6 to 10. The diode section 80 of this example has an FWD (free wheel diode). Each diode section 80 has an N+ type cathode region 82 in a region that contacts the lower surface 23 of the semiconductor substrate 10. In FIG. 11, the diode section 80 indicated 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 that contacts 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 projected region of the cathode region 82 extends 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 , which is an extension of the diode section 80). No emitter region 12 is provided in this 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 to surround the active portion 120 in a top view. The gate pad 116 and the emitter pad 118 may be disposed within the 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 also 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 portion 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 gate voltage even inside the active portion 120 away from the gate metal layer 50. A portion of the gate runner 48 may be arranged 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 region 120 and outer peripheral edge 140 of semiconductor substrate 10. In this example, gate metal layer 50 is disposed between edge termination structure 90 and active region 120. Edge termination structure 90 may be disposed in an annular shape on top surface 21 of semiconductor substrate 10 to surround active region 120. In this example, edge termination structure 90 is disposed along outer peripheral edge 140 of semiconductor substrate 10. Edge termination structure 90 reduces electric field concentration on top surface 21 of semiconductor substrate 10. Edge termination structure 90 has, for example, a guard ring, a field plate, a resurf structure, or a combination thereof.

[0118] Figure 12 is a diagram showing an example of the c-c' cross section in Figure 11. Figure 12 shows an example of the arrangement of the passing regions 106 described in Figures 1 to 10 in that cross section. In Figure 12, the passing regions 106 are hatched with diagonal lines. Note that Figure 12 shows only the passing regions 106 in the drift region 18, and omits the passing regions 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 that includes 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 from 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 the 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 that has a higher doping concentration than the base region 14. The diode section 80 of this example does not include an emitter region 12. The diode section 80 may or may not include 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 portions 30 and the gate trench portions 40 may be arranged at a predetermined interval.

[0123] An intermediate boundary region 190 may be present between the transistor section 70 and the diode section 80. The intermediate boundary region 190 is a region in which 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. Furthermore, in a top view, the collector region of the transistor section 70 may be extended into the region of the intermediate boundary region 190 in contact with the lower surface 23. 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 multiple guard rings 92, multiple field plates 94, and channel stoppers 174. In edge termination structure 90, collector region 22 may be provided in a region that contacts bottom surface 23. Each guard ring 92 may be provided on top surface 21 to surround active portion 120. Multiple guard rings 92 may have the function of spreading a depletion layer generated in active portion 120 outward from semiconductor substrate 10. This prevents electric field concentration within semiconductor substrate 10, improving the breakdown voltage of semiconductor device 100.

[0126] The guard ring 92 in 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 portion 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 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 top surface 21 and the side surfaces at the outer circumferential edge 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 the function of terminating the depletion layer generated in the active portion 120 at the outer circumferential edge 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 include 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 include 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 portion of the trench portion in the boundary portion 72 may be formed within the well region 11. A collector region 22 may be provided in the 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 base region 14, or the emitter region 12. The accumulation region 16 may also be formed in the diode portion 80, as indicated by the dotted line in FIG. 12.

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

[0133] Furthermore, in this example, the passing region 106 is provided in each of the transistor section 70, the diode section 80, the boundary section 72, and the edge termination structure section 90. The depth of the passing region 106 may be the same in each of the transistor section 70, the diode section 80, the boundary section 72, and the edge termination structure section 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, a 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. This 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 closer to the top surface 21 than 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 referred to 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 differs in 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 passage 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 passage 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 doping region 180 is provided closer to the upper surface 21 than the helium concentration peak 141. The base doping 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 doping region 180 in this example is provided over 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, the passing region 106 and the helium concentration peak 141 are not provided in at least a portion of the edge termination structure 90 when viewed from above. FIG. 14 shows an example in which the passing region 106 and the helium concentration peak 141 are not provided throughout the entire edge termination structure 90 when viewed from above. In another example, the passing region 106 and the helium concentration peak 141 may be provided in the end of the edge termination structure 90 that is closer to the active section 120. That is, the passing region 106 and the helium concentration peak 141 are not provided in the region that contacts the outer circumferential edge 140 of the semiconductor substrate 10. In this example, because the helium concentration peak 141 is not provided near the outer circumferential edge 140, the formation of defects near the outer circumferential edge 140 can be suppressed. This suppresses an increase in leakage at the outer circumferential edge 140.

[0140] That is, the base doping region 180 in this example is provided in a region that contacts the outer peripheral edge 140 of the semiconductor substrate 10. The base doping 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 doping 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 passing region 106 in the boundary portion 72 may be the same as that in the edge termination structure portion 90, the transistor portion 70, or the diode portion 80. Figure 14 shows an example in which the passing region 106 is not provided in the boundary portion 72.

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

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

[0144] 16A is a diagram showing another example of the arrangement of the passing region 106. This example differs from the examples shown in FIGS. 12 to 15 in that the passing region 106 and the helium concentration peak 141 are not provided in at least a part of the diode section 80 when viewed from above. The other structures are the same as those shown in FIGS. 12 to 15.

[0145] 16A shows an example in which the pass 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 pass 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 differentiating the arrangement of the pass region 106 between the transistor section 70 and the diode section 80, the doping concentration distributions of the diode section 80 and the transistor section 70 can be made to differ as appropriate.

[0146] FIG. 16B is a diagram showing another example of the arrangement of the passing region 106. In FIG. 16B, the passing region 106 and the base doping region 180 in the active section are formed in the reverse order to those in FIG. 16A. Forming the passing region 106 in the diode section 80 suppresses the expansion of the space charge region during reverse recovery, thereby suppressing waveform oscillation during reverse recovery. On the other hand, using the base doping region 180 in the transistor section 70 promotes the expansion of the space charge region and promotes hole injection when a short circuit occurs, for example, thereby suppressing short-circuit breakdown.

[0147] 17A is a diagram showing another example of the arrangement of the passing region 106. The arrangement of the passing region 106 in the depth direction of this example is the same as that of the passing region 106 shown in FIG. 13, and the arrangement in top view is the same as that of the passing region 106 shown in FIG. 16A. In other words, 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 upper surface 21 side of the helium concentration peak 141 over the entire surface in top view.

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

[0149] 14 to 17B, helium ions are selectively implanted in a top view in a second implantation step S1902, which will be described later. 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 having 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 that can block helium ions.

[0151] After the photoresist film 200 is formed, a second implantation step S1902 is performed. Helium ions are blocked by the photoresist film 200 in the region where the photoresist film 200 is formed. 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 a second depth position Z2 depending on the acceleration energy. In each of the examples shown in FIGS. 14, 15, 16A, 16B, 17A, and 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 illustrating the minimum film thickness M of the photoresist film 200 to prevent helium ions from penetrating into the semiconductor substrate 10. Fig. 17C shows the film thickness M relative to the range Rp of helium ions.

[0153] The helium ions in this example may be implanted into the semiconductor substrate 10 from the 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 shows the relationship between the range Rp of the helium ions and the film thickness M, 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 given by 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 (in this example, the diode section 80).

[0157] In diode region 80, helium concentration peak 141 may be located between the bottom of dummy trench region 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] Furthermore, 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 in 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 located 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, or may be greater than or smaller than the width T5. The width T3 of the passing region 106 in the transistor section 70 may be greater than half the thickness T1 of the semiconductor substrate 10. This allows the base region 14, where the channel is formed, in the transistor section 70 to be spaced apart from the helium concentration peak 141. This prevents defects from increasing near the channel.

[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 (in this example, the transistor section 70).

[0161] In transistor portion 70, helium concentration peak 141 may be located between the bottom of gate trench portion 40 and top 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. 18A.

[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 equal to the width T5, or may be greater 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 greater than half the thickness T1 of the semiconductor substrate 10.

[0163] 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. 18B , 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.

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

[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, the passage region 106 is formed by implanting helium ions to a second depth Z2 from the lower surface 23 of the semiconductor substrate 10. 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 in the passage region 106 may not be increased. In other words, if a heat treatment is performed before the passage region 106 is formed, the hydrogen implanted in the first implantation step S1900 may not be able to bond with the crystal defects in 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 to, 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 to 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 longer, or may be heated for three hours or longer.

[0168] By diffusing hydrogen in the diffusion step S1904, crystal defects in the passage region 106 are bonded with hydrogen to form donors. This increases 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 throughout the entire passage region 106.

[0169] To increase the donor concentration throughout the entire transit region 106, it is preferable that the hydrogen implanted at the first depth Z1 diffuses to the vicinity of the second depth Z2. In the first implantation step S1900, adjusting the dose of hydrogen implanted at the first depth Z1 allows sufficient hydrogen to diffuse to the vicinity of the second depth Z2. In the first implantation step S1900, it is preferable to determine the dose of hydrogen so that the minimum donor concentration in the transit 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 (disorder) is also localized near the stopping region of the helium ions. The disorder has many dangling bonds. By also implanting hydrogen ions near the stopping region of the helium ions in the first implantation step S1900, the dangling bonds of the disorder are terminated by hydrogen, thereby reducing the disorder.

[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 illustrating 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 based on the diffusion coefficient of hydrogen in the semiconductor substrate 10 and the position of the second depth Z2 (i.e., the distance over which hydrogen implanted at 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, for example, by spread 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 the 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 a first depth Z1 and helium ions are implanted to a second depth Z2. A fourth example 164 and a fifth example 165 are examples in which helium ions are implanted to a 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 by using 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 implanting the hydrogen ions, 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 were 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 decreased.

[0177] After annealing, hydrogen bonds with crystal defects and becomes donors, increasing the carrier concentration. 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 transit region 106 increases as the first dose increases. Furthermore, as the first dose increases, the region where the donor concentration is higher than the base doping concentration expands 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) matches the base doping concentration C0 is Equation (1).

number

[0179] From equation (1), the hydrogen diffusion coefficient D can be numerically calculated in the first example 161, the second example 162, and the third example 163. 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. Among point defects, vacancy-based defects such as vacancies and divacancies are particularly formed. In this case, the concentration of crystal defects has a peak at a position slightly closer to the ion-implanted surface (the lower surface 23 of the semiconductor substrate 10) than the second depth Z2.

[0181] FIG. 21 shows the relationship between the diffusion coefficient D of hydrogen and the first dose Q. FIG. 21 plots the first example 161, the second example 162, and the third example 163 shown in FIG. 20. As 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 dangling bonds in the passage region 106. As the first dose Q increases, the proportion of hydrogen diffusing through the region where dangling bonds are terminated increases, which is thought to facilitate hydrogen diffusion. 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] FIG. 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 FIGS. 20 and 21 obtained for a plurality of annealing temperatures T. In this example, the first dose is set to 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), 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 the first dose larger than the straight line, the overall donor concentration in the transit 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 Figure 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 Figure 23, helium ions are implanted to the second depth Z2 at a range Rp calculated by the following equation, taking into account straggling ΔRp during ion implantation. Rp≧X0+ΔRp By setting the concentration peak position of crystal defects (position at 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), which is a modification of formula (1).

number

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

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

[0190] 20 to 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. Furthermore, although the annealing temperature was set to 370°C, the minimum dose can be determined from equation (2) even if the annealing temperature is changed.

[0191] 25 is a diagram showing a line defining 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 at a dose greater than the minimum dose indicated by the line in FIG. 25.

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

[0193] FIG. 27 is a diagram illustrating 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 helium chemical concentration distribution are shown only in the vicinity of their peaks. FIG. 27 omits the distributions 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 FIGS. 1 to 26. The donor concentration distribution of the semiconductor device 100 of this example is similar to the example of FIG. 10.

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

[0196] In order to diffuse hydrogen over a wider range, it is preferable to increase the dose of hydrogen implanted 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 May be greater than or equal to 1 x 10 16 atoms / cm 2 May be greater than or equal to 1 x 10 17 atoms / cm 2 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 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 or more. 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 plasma doping, a gas for plasma excitation and a source gas containing hydrogen are supplied into a container containing the semiconductor substrate 10. The excitation gas may contain an inert element such as argon. The source 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 concentrations of hydrogen can be easily injected into a shallow position as viewed from the lower surface 23. Furthermore, 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. Furthermore, since there are fewer crystal defects, the annealing temperature can be lowered, thereby improving the throughput in the manufacture of the semiconductor device 100. However, the method of injecting hydrogen to the first depth Z1 is not limited to plasma doping.

[0198] Helium may be implanted to 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 implant helium to the second depth Z2. The second depth Z2 may be 80 μm or more away from the lower surface 23 in the depth direction. The second depth 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 and the second depth 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 helium chemical concentration distribution are shown only in the vicinity of their peaks. The first depth Z1 in this example is the same as in the example of 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 of the semiconductor substrate 10 in the depth direction 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 with reference to 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 the hydrogen chemical concentration distribution and the argon chemical concentration distribution in the vicinity of hydrogen concentration peak 131. In this example, hydrogen concentration peak 131 is a peak corresponding to hydrogen implanted by plasma doping, and hydrogen concentration peak 194 is a peak corresponding to hydrogen implanted by a method other than plasma doping.

[0202] When hydrogen is implanted at the first depth Z1 by plasma doping, impurities other than hydrogen may be implanted near the first depth Z1. For example, when argon gas is used for plasma excitation, argon may be implanted near the first depth Z1. In FIG. 29, an argon concentration peak 196 is shown at the depth 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 shallower position than the hydrogen concentration peak 131.

[0204] In this example, there is no argon chemical concentration peak between the first depth position Z1 and the second depth position Z2. Because 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, 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 plasma doping, other impurities may be implanted into the semiconductor substrate 10 instead of argon. When PH3 gas is used for plasma doping, a phosphorus concentration peak may be formed between the lower surface 23 and the first depth position Z1. When BF3 gas is used for plasma doping, a fluorine concentration peak or a boron concentration peak may be formed between the lower surface 23 and the first depth position Z1. The concentration value of the argon, phosphorus, fluorine, or boron concentration peak may be smaller than the concentration value of the hydrogen concentration peak 131. The concentration value of the argon, phosphorus, fluorine, or boron concentration peak may be half or less, or even one-tenth or less, of the concentration value of the hydrogen concentration peak 131.

[0206] 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, 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, while 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, some of the gate trench portions 40 in the transistor portion 70 may be replaced with dummy trench portions 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 N-type impurities such as phosphorus. A buffer region 20 may be provided between the cathode region 82 and the drift region 18.

[0210] In addition, 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. The concentration distributions 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 part of the buffer region 20 in the transistor section 70. In this example, the collector region 22 is formed by implanting boron. The boron in the collector region 22 in this example is implanted in a separate process from the hydrogen of the hydrogen concentration peak 131. At least a portion of the boron in the collector region 22 may be implanted in the plasma doping used to implant the hydrogen of the hydrogen concentration peak 131.

[0213] In the example shown in FIG. 7 and other figures, the hydrogen concentration peak 131 was 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. Because the doping concentrations of the cathode region 82 and the collector region 22 are very high, providing the hydrogen concentration peak 131 in the cathode region 82 and the collector region 22 can suppress fluctuations in the shape of the carrier concentration distribution even when a high concentration of hydrogen donors is generated by the hydrogen concentration peak 131. This makes it easier to suppress any effects 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] Furthermore, 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. 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, hydrogen chemical concentration distribution, and phosphorus chemical concentration distribution along the E-E line of FIG. 30. The E-E 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 separate process 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 used to implant 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] Furthermore, 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. 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.

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

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

[0221] Furthermore, 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 hydrogen dose in implantation step S3302 may be the same as the hydrogen dose 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 the hydrogen to form donors. This increases 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 allows the region where hydrogen is distributed at a high concentration to be ground, thereby reducing the amount of hydrogen near the lower surface 23.

[0224] After grinding step S3306, in bottom-side structure formation step S3308, structures on the bottom surface 23 side, such as collector region 22, cathode region 82, and buffer region 20, are formed. In bottom-side structure formation step S3308, dopants may be implanted into cathode region 82 and buffer region 20, and then the vicinity of the bottom surface 23 may be laser annealed. This allows the vicinity of the bottom surface 23 of semiconductor substrate 10 to be locally heat-treated at a high temperature. Furthermore, after laser annealing, dopants such as hydrogen may be implanted into buffer region 20. After dopants are implanted into 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 for semiconductor device 100. The manufacturing method of this example differs in that it includes a laser annealing step S3307 instead of grinding step S3306 of Fig. 33. The other steps are the same as those in 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 portion of the hydrogen near the first depth Z1 to be released to the outside of the semiconductor substrate 10. This reduces the hydrogen chemical concentration near the first depth Z1. In the laser annealing step S3307, the laser may be irradiated so that the hydrogen concentration peak 131 remains, or the laser may be irradiated so that the hydrogen concentration peak 131 does not remain. Note that even after laser irradiation, heavier elements such as argon are more likely to remain in the semiconductor substrate 10 than hydrogen. Therefore, even after the laser annealing step S3307, the semiconductor substrate 10 may still have the concentration peaks of impurities such as argon shown in FIG. 29.

[0227] Furthermore, 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 in the diode portion 80 is higher than the hydrogen chemical concentration at the first depth Z1 in 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 the bottom-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 the buffer region formation stage S3504 for forming the buffer region 20.

[0230] The bottom-side structure forming step may be performed after the top-side structure forming step S3500, which includes trench portions and the like. The bottom-side structure forming step includes a collector region forming step S3502 and a buffer region forming step S3504. Figure 35 omits other steps in the bottom-side structure forming step. 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 bottom-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 step. In this example, the implantation of hydrogen ions to the first depth Z1 and the heat treatment are performed in the cathode region formation step S3503. The implantation of helium ions to the second depth Z2 and the heat treatment are performed in the buffer region formation step S3504.

[0232] The lower surface side structure forming step may be performed after the upper surface side structure forming step S3500, which forms trenches and the like. In this example, the lower surface side structure forming step includes a cathode region forming step S3503 and a buffer region forming step S3504. In Figure 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 over the entire lower surface 23, a P-type collector region 22 may be formed in a portion 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 over the entire lower surface 23 to a first depth Z1.

[0234] Alternatively, after selectively forming collector region 22 on lower surface 23, cathode region 82 may be formed by implanting N-type dopants and hydrogen ions into the entire lower surface 23. In this case, a high concentration of P-type dopants may be implanted into collector region 22 in advance to prevent the conductivity type from being inverted to N-type. By such a process, first depth Z1 is located in collector region 22 and cathode region 82.

[0235] If 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. Furthermore, 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, the collector electrode formation step S3506 may be performed.

[0236] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[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 stated as "before," "prior to," etc., and that the processes can be performed in any order unless the output of a previous process is used in a subsequent process. Even if the operational flow in the claims, specifications, and drawings is described using "first," "next," etc. for convenience, this does not mean that the processes must be performed in this order. [Explanation of symbols]

[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···passing region, 111···first donor concentration peak, 112, 122, 132, 142, 172···Upslope, 113, 123, 133, 143, 173···Downslope, 114, 124, 125, 134, 144, 145···Slope, 116···Gate pad, 118···Emitter pad, 120···Active region, 121···Second donor concentration peak, 131···Hydrogen concentration peak, 140···Outer periphery, 141···Helium concentration peak, 150···Plate region, 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

1. A semiconductor substrate having an upper surface and a lower surface, The upper electrode in contact with the upper surface, The lower electrode in contact with the lower surface, Equipped with, The aforementioned semiconductor substrate is n-type drift layer, A buffer region is provided between the drift layer and the lower surface and has a first donor concentration peak containing hydrogen, The first donor concentration peak has a downward slope on the upper side of the peak, The drift layer has a high-concentration portion in the donor concentration distribution that is higher than the base doping concentration of the semiconductor substrate, extending from the region on the upper surface side of the center in the depth direction of the semiconductor substrate to the upper surface side end of the downward slope. Semiconductor equipment.

2. The drift layer has, in the donor concentration distribution, a base doping region which is the region of the base doping concentration, in a region on the upper surface side rather than the center in the depth direction of the semiconductor substrate. The aforementioned high-concentration region is continuous with the base doping region. The semiconductor device according to claim 1.

3. The high-concentration portion is continuous to the interface on the upper surface side of the drift layer. The semiconductor device according to claim 1.

4. A peak of void defects is formed on the upper surface side of the interface. The semiconductor device according to claim 3.

5. The high-concentration portion includes a flat region having a length of at least 10 μm. The semiconductor device according to any one of claims 1 to 3.

6. The minimum value of the donor concentration in the flat region is 50% or more of the maximum value of the donor concentration in the flat region. The semiconductor device according to claim 5.

7. The flat region is The donor concentration is between the maximum value and the minimum value, and the donor concentration is continuous in the depth direction of the semiconductor substrate. The semiconductor device according to claim 6.

8. The high-concentration portion has the peak of the donor concentration distribution The semiconductor device according to claim 1.

9. The peak of the donor concentration distribution has a second upward slope on the lower side of the peak, The peak of the donor concentration distribution has a second downward slope on the upper surface side of the peak. The incline of the second upward slope is greater than the incline of the second downward slope. The semiconductor device according to claim 8.

10. The high-concentration portion contains hydrogen The semiconductor device according to claim 1.

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