Semiconductor device and method for manufacturing the same

Abstract

To adjust a carrier concentration distribution in an N-type region.SOLUTION: In a semiconductor device, a carrier concentration distribution includes: a first carrier concentration peak; a second carrier concentration peak closest to the first carrier concentration peak, among carrier concentration peaks arranged at an upper surface side from the first carrier concentration peak; a third carrier concentration peak arranged at an upper surface side from the second carrier concentration peak; a first peak-to-peak region arranged between the first carrier concentration peak and the second carrier concentration peak; a second peak-to-peak region arranged between the second carrier concentration peak and the third carrier concentration peak; and a peak-to-peak concentration peak arranged in the second peak-to-peak region and not overlapped with respective hydrogen chemical concentration peaks of the second and third carrier concentration peaks. The minimum value of a carrier concentration in the first peak-to-peak region is smaller than that in the second peak-to-peak region.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] Conventionally, it is known that an N-type region is formed by implanting hydrogen into a semiconductor substrate (see, for example, Patent Document 1). Patent Document 1: U.S. Patent Application Publication No. 2016 / 141399 Problem to be Solved

[0003] It is preferable that the carrier concentration distribution in the N-type region can be appropriately adjusted.

[0004] In order to solve the above problems, In one aspect of the present invention, there is provided a semiconductor device comprising a semiconductor substrate having an upper surface and a lower surface and having a base doping concentration, the semiconductor substrate having a hydrogen-containing region containing hydrogen, the hydrogen-containing region having three or more hydrogen chemical concentration peaks in a depth direction of the semiconductor substrate, the three or more hydrogen chemical concentration peaks being The present invention provides a semiconductor device including a first hydrogen chemical concentration peak, a second hydrogen chemical concentration peak disposed on an upper surface side of the semiconductor substrate relative to the first hydrogen chemical concentration peak and adjacent to the first hydrogen chemical concentration peak, and a third hydrogen chemical concentration peak disposed on an upper surface side of the semiconductor substrate relative to the second hydrogen chemical concentration peak and adjacent to the second hydrogen chemical concentration peak, wherein a carrier concentration distribution between the second hydrogen chemical concentration peak and the third hydrogen chemical concentration peak has a peak-to-peak concentration peak. In another aspect of the present invention, there is provided a semiconductor device including a semiconductor substrate having an upper surface and a lower surface and a base doping concentration, the semiconductor substrate having a hydrogen-containing region containing hydrogen, the hydrogen-containing region having two or more hydrogen chemical concentration peaks in a depth direction of the semiconductor substrate, a carrier concentration distribution between any two adjacent hydrogen chemical concentration peaks in the depth direction of the semiconductor substrate has a valley, and a minimum value of the carrier concentration in the valley of the carrier concentration distribution is smaller than the base doping concentration. In another aspect of the present invention, there is provided a method for manufacturing a semiconductor device including an MCZ semiconductor substrate having a base doping concentration of a first conductivity type, the method comprising the step of forming a buffer region of the first conductivity type having a higher concentration than the base doping concentration in the MCZ semiconductor substrate, wherein in the step of forming the buffer region, a density peak of a lifetime killer is formed in the buffer region, and by forming the density peak, a carrier concentration distribution in the depth direction of the buffer region is changed. The present invention other In one aspect, there is provided a semiconductor device including a semiconductor substrate having an upper surface and a lower surface, the semiconductor substrate having a hydrogen-containing region containing hydrogen, the hydrogen-containing region having one or more hydrogen chemical concentration peaks in a depth direction, a carrier concentration distribution in the depth direction of the hydrogen-containing region including a first carrier concentration peak, a second carrier concentration peak closest to the first carrier concentration peak among the carrier concentration peaks disposed on the upper surface side of the first carrier concentration peak, a third carrier concentration peak disposed on the upper surface side of the second carrier concentration peak, a first inter-peak region disposed between the first carrier concentration peak and the second carrier concentration peak, a second inter-peak region disposed between the second carrier concentration peak and the third carrier concentration peak, and an inter-peak concentration peak disposed in the second inter-peak region so as not to overlap with each of the hydrogen chemical concentration peaks in the second carrier concentration peak and the third carrier concentration peak, and a minimum carrier concentration value of the carrier concentration in the first inter-peak region is smaller than a minimum carrier concentration value of the carrier concentration in the second inter-peak region. The inter-peak concentration peaks may not overlap with any of the hydrogen chemical concentration peaks.

[0005] In a second aspect of the present invention, there is provided a semiconductor device including a semiconductor substrate having an upper surface and a lower surface, the semiconductor substrate having a hydrogen-containing region containing hydrogen, a hydrogen chemical concentration distribution in a depth direction of the hydrogen-containing region having a first hydrogen chemical concentration peak, a second hydrogen chemical concentration peak closest to the first hydrogen chemical concentration peak among the hydrogen chemical concentration peaks located on the upper surface side of the first hydrogen chemical concentration peak, a third hydrogen chemical concentration peak located on the upper surface side of the second hydrogen chemical concentration peak, a first inter-peak region located between the first hydrogen chemical concentration peak and the second hydrogen chemical concentration peak, and a second inter-peak region located between the second hydrogen chemical concentration peak and the third hydrogen chemical concentration peak, a carrier concentration distribution in a depth direction of the hydrogen-containing region having an inter-peak concentration peak located in the second inter-peak region, and a minimum value of the carrier concentration in the first inter-peak region is smaller than the minimum value of the carrier concentration in the second inter-peak region. The third hydrogen chemical concentration peak may be the hydrogen chemical concentration peak that is closest to the second hydrogen chemical concentration peak among the hydrogen chemical concentration peaks located on the upper surface side of the second hydrogen chemical concentration peak.

[0006] The hydrogen-containing region may have a lifetime control region containing an adjustment impurity for adjusting a lifetime of carriers, and the concentration distribution of the adjustment impurity in the depth direction may have an impurity concentration peak located in the first inter-peak region. In the depth direction, a width between two vacancy defect concentration positions that are 10% of a peak concentration of the vacancy defect concentration distribution in the lifetime control region may be smaller than a width of the second inter-peak region.

[0007] In the depth direction, a full width at half maximum of the impurity concentration peak may be greater than a width of the second inter-peak region.

[0008] The minimum value of the carrier concentration in the first inter-peak region may be less than a base doping concentration of the semiconductor substrate.

[0009] The inter-peak concentration peak may be a peak that is gentler than both the second carrier concentration peak and the third carrier concentration peak.

[0010] In the depth direction, a width of the peak-to-peak concentration peak may be greater than a width of the second carrier concentration peak and a width of the third carrier concentration peak.

[0011] The width of the peak-to-peak concentration peak, the width of the second carrier concentration peak, and the width of the third carrier concentration peak may be the full width at half maximum of the respective concentration peaks.

[0012] The width of the inter-peak concentration peak, the width of the second carrier concentration peak, and the width of the third carrier concentration peak may be the width of a portion of each concentration peak having a concentration that is 80% or more of the maximum value.

[0013] The maximum value of the peak-to-peak concentration peak may be smaller than at least one of the maximum value of the second carrier concentration peak and the maximum value of the third carrier concentration peak.

[0014] The maximum value of the peak-to-peak concentration peak may be greater than at least one of the maximum value of the second carrier concentration peak and the maximum value of the third carrier concentration peak.

[0015] In a third aspect of the present invention, there is provided a semiconductor device including a semiconductor substrate. The semiconductor substrate may have a hydrogen-containing region containing hydrogen. The hydrogen-containing region may have a high-concentration region having a carrier concentration higher than a virtual carrier concentration determined by the concentration of contained hydrogen and the activation rate of hydrogen.

[0016] The carrier concentration of the high concentration region may be higher than a base doping concentration of the semiconductor substrate.

[0017] The carrier concentration distribution in the depth direction of the hydrogen-containing region may have a first peak.

[0018] In a fourth aspect of the present invention, there is provided a method for manufacturing a semiconductor device including a semiconductor substrate. In the manufacturing method, hydrogen may be injected into the semiconductor substrate to form a hydrogen-containing region. In the manufacturing method, a lifetime control region for adjusting a carrier lifetime may be formed in the hydrogen-containing region. In the manufacturing method, a high-concentration region having a carrier concentration higher than a virtual carrier concentration determined from the concentration of the contained impurities and the activation rate of the impurities may be formed in the hydrogen-containing region by heat-treating the semiconductor substrate.

[0019] The above summary of the invention does not list all of the necessary features of the present invention. Also, subcombinations of these features may also be inventions. [Brief description of the drawings]

[0020] [Figure 1] 1 is a cross-sectional view showing an example of a semiconductor device 100. FIG. [Diagram 2] 2 is a diagram showing an example of the distribution of carrier concentration and virtual carrier concentration along line AA in FIG. 1; [Diagram 3] 1A and 1B are diagrams showing a carrier concentration distribution and a virtual carrier concentration distribution. [Figure 4] 11 is a diagram illustrating a second peak 112 in a high-concentration region 106-1. [Diagram 5] FIG. 13 is a diagram illustrating a third peak 113 in the helium concentration distribution. [Figure 6] 11A and 11B are diagrams showing other examples of the carrier concentration distribution and the virtual carrier concentration distribution. [Figure 7] 11A and 11B are diagrams showing other examples of the carrier concentration distribution and the virtual carrier concentration distribution. [Figure 8] 1 is a diagram illustrating an example of the structure of a semiconductor device 100. FIG. [Figure 9] 9 is a diagram showing an example of a carrier concentration distribution in the depth direction at the position of the line BB in FIG. 8. FIG. [Figure 10] 2A to 2C are diagrams illustrating some steps in a manufacturing method of the semiconductor device 100. [Figure 11] 3 is a diagram showing an example of voltage and current waveforms during reverse recovery operation of the semiconductor device 100. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0022] 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.

[0023] In this specification, technical matters may be explained using orthogonal coordinate axes of X-axis, Y-axis, and Z-axis. The orthogonal coordinate axes merely identify the relative positions of components, and do not limit a specific direction. For example, the Z-axis does not limit the height direction relative to the ground. Note that the +Z-axis direction and the -Z-axis direction are opposite directions. When the Z-axis direction is described without indicating positive or negative, it means a direction parallel to the +Z-axis and -Z-axis.

[0024] In this specification, the orthogonal axes parallel to the upper and lower surfaces of the semiconductor substrate are the X-axis and the Y-axis. The axis perpendicular to the upper and lower surfaces of the semiconductor substrate is the Z-axis. In this specification, the direction of the Z-axis may be referred to as the depth direction. In this specification, the direction parallel to the upper and lower surfaces of the semiconductor substrate, including the X-axis and the Y-axis, may be referred to as the horizontal direction.

[0025] In this specification, when the term "same" or "equal" is used, it may include cases where there is an error due to manufacturing variations, etc. The error is, for example, within 10%.

[0026] In this specification, the conductivity type of a doped region doped with impurities is described as P type or N type. In this specification, the impurity may particularly mean either an N type donor or a P type acceptor, and may be described as a dopant. In this specification, doping means introducing a donor or an acceptor into a semiconductor substrate to make it a semiconductor exhibiting an N type conductivity type or a semiconductor exhibiting a P type conductivity type.

[0027] In this specification, the doping concentration means the concentration of donors or acceptors in a thermal equilibrium state. In this specification, the net doping concentration means the net concentration obtained by adding up the donor concentration as the concentration of positive ions and the acceptor concentration as the concentration of negative ions, including the polarity of the charge. As an example, the donor concentration is N D , acceptor concentration N A Then, the net doping concentration at any position is N D -N A In this specification, the net doping concentration may be simply referred to as the doping concentration.

[0028] A donor has the function of supplying electrons to a semiconductor. An acceptor has the function of receiving electrons from a semiconductor. Donors and acceptors are not limited to impurities themselves. For example, a VOH defect, which is a combination of a vacancy (V), oxygen (O), and hydrogen (H) present in a semiconductor, functions as a donor that supplies electrons. In this specification, a VOH defect may be referred to as a hydrogen donor.

[0029] In this specification, when it is described as P+ type or N+ type, it means that the doping concentration is higher than that of P type or N type, and when it is described as P- type or N- type, it means that the doping concentration is lower than that of P type or N type. Also, when it is described as P++ type or N++ type, it means that the doping concentration is higher than that of P+ type or N+ type.

[0030] In this specification, the chemical concentration refers to the concentration of an impurity measured regardless of the state of electrical activation. The chemical concentration can be measured, for example, by secondary ion mass spectrometry (SIMS). The above-mentioned net doping concentration can be measured by voltage-capacitance measurement (CV). The carrier concentration measured by spreading resistance measurement (SR) may be the net doping concentration. The carrier concentration measured by CV or SR may be a value in a thermal equilibrium state. In the N-type region, the donor concentration is sufficiently larger than the acceptor concentration, so the carrier concentration in the region may be the donor concentration. Similarly, in the P-type region, the carrier concentration in the region may be the acceptor concentration. In this specification, the doping concentration in the N-type region may be referred to as the donor concentration, and the doping concentration in the P-type region may be referred to as the acceptor concentration.

[0031] In addition, when the concentration distribution of the donor, acceptor or net doping has a peak, the peak value may be taken as the concentration of the donor, acceptor or net doping in the region. In cases where the concentration of the donor, acceptor or net doping is almost uniform, the average value of the concentration of the donor, acceptor or net doping in the region may be taken as the concentration of the donor, acceptor or net doping.

[0032] The carrier concentration measured by the SR method may be lower than the concentration of the donor or acceptor. In the range where the current flows when measuring the spreading resistance, the carrier mobility of the semiconductor substrate may be lower than the value in the crystalline state. The reduction in carrier mobility occurs when the carriers are scattered due to a disorder in the crystal structure caused by lattice defects, etc.

[0033] The donor or acceptor concentration calculated from the carrier concentration measured by the CV method or the SR method may be lower than the chemical concentration of the element representing the donor or acceptor. As an example, the donor concentration of phosphorus or arsenic, which acts as a donor in a silicon semiconductor, or the acceptor concentration of boron, which acts as an acceptor, is about 99% of the chemical concentration. On the other hand, the donor concentration of hydrogen, which acts as a donor in a silicon semiconductor, is about 0.1% to 10% of the chemical concentration of hydrogen. In this specification, the SI system of units is adopted. In this specification, the unit of distance or length may be expressed in cm (centimeter). In this case, various calculations may be performed in m (meter). As an example, when simply referring to concentration in this specification, it refers to the concentration per unit volume ( / cm 3 For example, the chemical concentration of an impurity is expressed as the number of atoms of that impurity contained per unit volume (atoms / cm 3 ).

[0034] Fig. 1 is a cross-sectional view showing an example of a semiconductor device 100. The semiconductor device 100 is provided with transistor elements such as insulated gate bipolar transistors (IGBTs) and diode elements such as free wheel diodes (FWDs), but the details of the structures of these elements are omitted in Fig. 1.

[0035] 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 includes impurities that are intentionally or unintentionally added during the manufacture of a semiconductor ingot. The semiconductor substrate 10 has a doping concentration that is determined by the impurities injected during the manufacture. The conductivity type of the semiconductor substrate 10 in this example is N-type. In this specification, the doping concentration in the semiconductor substrate 10 may be referred to as a base doping concentration Db.

[0036] For example, when the semiconductor ingot is silicon, the N-type impurities (dopants) for setting the base doping concentration Db are phosphorus, antimony, arsenic, etc., and the P-type impurities (dopants) are boron, aluminum, etc. The base doping concentration Db may be lower than the chemical concentration of the dopant in the semiconductor ingot. For example, when the dopant is phosphorus or boron, the base doping concentration Db may be 50% or more or 90% or more of the chemical concentration of the dopant. For another example, when the dopant is antimony, the base doping concentration Db may be 5% or more, 10% or more, or 50% or more of the chemical concentration of the dopant. The semiconductor substrate 10 may also contain carbon and oxygen. The carbon and oxygen may be distributed throughout the semiconductor substrate 10. For example, the manufacturing method of the semiconductor ingot is the magnetic field applied Czochralski (MCZ) method, but other methods may also be used. Other methods may include the Czochralski (CZ) method and the float zone (FZ) method.

[0037] The semiconductor substrate 10 has an upper surface 21 and a lower surface 23. The upper surface 21 and the lower surface 23 are the two main surfaces of the semiconductor substrate 10. In this specification, orthogonal axes in a plane parallel to the upper surface 21 and the lower surface 23 are defined as the X-axis and the Y-axis, and an axis perpendicular to the upper surface 21 and the lower surface 23 is defined as the Z-axis.

[0038] The semiconductor substrate 10 has a hydrogen-containing region 102 containing hydrogen. In this example, hydrogen ions are implanted into the hydrogen-containing region 102 from the lower surface 23 side of the semiconductor substrate 10. In this example, the hydrogen ions are protons. The hydrogen ions may be deuthrone or triton. The hydrogen-containing region 102 is a region in which the chemical concentration of hydrogen is higher than the chemical concentrations of any of other N-type impurities and P-type impurities. In the hydrogen-containing region 102, the chemical concentration of hydrogen may be 100 times or more higher than the chemical concentration of the impurity with the highest chemical concentration among the other N-type impurities and P-type impurities. The hydrogen-containing region 102 may be a region in which the chemical concentration of hydrogen is 10 times or more higher than the base doping concentration Db. The hydrogen-containing region 102 may be a region in which the chemical concentration of hydrogen is higher than the base doping concentration Db. The hydrogen-containing region 102 may contain impurities such as helium that do not function as N-type impurities or P-type impurities. The chemical concentration of the impurity, such as helium, in the hydrogen-containing region 102 may be higher than the chemical concentration of hydrogen. The impurity, such as helium, may function as an adjusting impurity that adjusts the lifetime of carriers in the semiconductor substrate 10.

[0039] Hydrogen ions implanted from the lower surface 23 of the semiconductor substrate 10 pass through the interior of the semiconductor substrate 10 to a depth corresponding to the acceleration energy. In the region through which the hydrogen ions have passed, vacancy defects such as vacancies (V) and divacancies (VV) are generated. In this specification, unless otherwise specified, vacancies include divacancies. The vacancy defects may include dangling bonds present in the vacancies or divacancies, and may also include unpaired electrons of the dangling bonds. Hydrogen is diffused by heat-treating the semiconductor substrate 10 after the hydrogen ions are implanted. The diffused hydrogen combines with the vacancies (V) and oxygen (O) to form VOH defects. The VOH defects function as donors that supply electrons. In addition, the diffused hydrogen itself is activated and functions as a hydrogen donor. As a result, the hydrogen-containing region 102 becomes an N+ type region with a higher concentration than the base doping concentration Db.

[0040] In this specification, the ratio of the concentration of the dopant (donor or acceptor) caused by the impurity to the chemical concentration of the impurity is called the activation rate of the impurity. In the case of hydrogen, the dopant caused by the impurity is a VOH defect and a hydrogen donor. In the case of other P-type impurities and N-type impurities, the impurity itself is an activated dopant. In general, the doping concentration in the semiconductor substrate 10 is a concentration obtained by multiplying the concentration of the contained impurity by the activation rate of the impurity. For example, when the impurity contained in the hydrogen-containing region 102 is substantially only hydrogen, it is assumed that the doping concentration in the hydrogen-containing region 102 is a value obtained by multiplying the chemical concentration of hydrogen by the activation rate of hydrogen. The activation rate of hydrogen may be about 0.1% to 80%, for example, about 1%. In this specification, the concentration obtained by multiplying the chemical concentration of the impurity by the activation rate of the impurity is called the virtual carrier concentration (or virtual doping concentration). The virtual carrier concentration is determined for each position on the semiconductor substrate 10 from the chemical concentration and activation rate of the impurity.

[0041] The hydrogen-containing region 102 has a high-concentration region 106. The high-concentration region 106 is a region in which the carrier concentration is higher than the virtual carrier concentration described above. Alternatively, the high-concentration region 106 is a region in which the doping concentration is higher than the virtual doping concentration described above. In this specification, the carrier concentration and the virtual carrier concentration are used for the explanation, but the carrier concentration and the virtual carrier concentration can be appropriately interpreted as the doping concentration and the virtual doping concentration. As an example, the high-concentration region 106 can be formed by adjusting the distribution of vacancy defects in the hydrogen-containing region 102. When the semiconductor substrate 10 is manufactured, it is considered that the vacancy defects are uniformly distributed over the entire substrate. By injecting hydrogen into the hydrogen-containing region 102, the vacancy defects are distributed according to the distribution of the injected hydrogen. By performing heat treatment after injecting hydrogen, hydrogen donors or VOH defects are generated, resulting in a carrier concentration distribution according to the hydrogen distribution. Then, when new vacancy defects are generated in the hydrogen-containing region 102 in addition to the vacancy defects generated by the hydrogen injection and heat treatment is performed, the hydrogen in the hydrogen-containing region 102 and the new vacancy defects combine to form new hydrogen donors or VOH defects. The new VOH defects form high-concentration regions 106. The new vacancy defects can be formed by injecting an adjustment impurity, such as helium, that does not function as a dopant into the hydrogen-containing region 102. In this specification, unless otherwise specified, the term "VOH defects" is used to include hydrogen donors or donors newly formed by hydrogen ion injection.

[0042] The hydrogen-containing region 102 in this example has a lifetime control region 104. The lifetime control region 104 is a region in which the lifetime of the carriers is reduced by the formation of a lifetime killer that adjusts the lifetime of the carriers. The lifetime killer is a carrier recombination center, and may be a crystal defect, a vacancy defect such as a vacancy or a divacancy, a complex defect of these with an element constituting the semiconductor substrate 10 or an impurity other than the element, a dislocation, a rare gas element such as helium, neon, or argon, or a metal element such as platinum. In this example, a vacancy defect or the like generated by injecting an adjustment impurity such as helium into the semiconductor substrate 10 functions as a lifetime killer.

[0043] As described above, the vacancy defects can combine with hydrogen by heat treatment to become VOH defects. However, if many vacancy defects are formed, the amount of hydrogen is insufficient, and the proportion of vacancy defects that do not combine with hydrogen and remain as vacancy defects increases. In the region where many vacancy defects exist, the carrier lifetime decreases, and it becomes a lifetime control region 104. On the other hand, vacancy defects formed by irradiation of the adjustment impurity such as helium are formed in large numbers near the range of the adjustment impurity, and decrease as they move away from the range of the adjustment impurity. Therefore, in the region away from the range of the adjustment impurity, there is sufficient hydrogen for the vacancy defects, and the proportion of vacancy defects that combine with hydrogen to become VOH defects increases. The region where many VOH defects are formed functions as a high concentration region 106.

[0044] In this example, the lifetime control region 104 is formed by injecting an adjustment impurity from the lower surface 23 side of the semiconductor substrate 10. The high concentration region 106 may be provided at a position away from the lifetime control region 104 in the depth direction (Z-axis direction). The high concentration region 106 in this example is provided at a position deeper than the lifetime control region 104 with the lower surface 23 as the reference.

[0045] When the adjustment impurity is injected from the lower surface 23 side at a range near the lifetime control region 104, a relatively large number of vacancy defects and the like are formed in the region through which the adjustment impurity has passed, but a relatively small number of vacancy defects and the like are formed in the region deeper than the range. Therefore, in the region deeper than the range, the rate at which the formed vacancy defects become VOH defects increases, and the high concentration region 106 is more likely to be formed. However, the relationship between the lifetime control region 104 and the high concentration region 106 is not limited to this. The high concentration region 106 may be formed at a position shallower than the lifetime control region 104.

[0046] Moreover, the high concentration region 106 can be formed without providing the lifetime control region 104. For example, by implanting a relatively low concentration of adjusting impurities near the high concentration region 106, it is possible to form vacancy defects that are not as numerous as the hydrogen present in the region. This increases the proportion of vacancy defects that become VOH defects, and the high concentration region 106 can be formed without reducing the lifetime. In this case, the high concentration region 106 can be provided at any position without being limited by the position of the lifetime control region 104.

[0047] It has been confirmed by experiments that the difference between the carrier concentration and the virtual carrier concentration in the high-concentration region 106 increases as the chemical concentration of carbon in the high-concentration region 106 increases. 13 / cm 3 The chemical concentration of carbon in the high concentration region 106 is preferably 1×10 14 / cm 3 It may be greater than or equal to 1 x 10 15 / cm 3 The chemical concentration of carbon in the high concentration region 106 may be 1×10 16 / cm 3 may be less than or equal to 5 x 10 15 / cm 3 may be less than or equal to 1 x 10 15 / cm 3 The entire semiconductor substrate 10 may have the above-mentioned carbon concentration.

[0048] In addition, the higher the oxygen concentration, the more likely the VOH defects are to be formed. The chemical concentration of oxygen in the high concentration region 106 is 1×10 17 / cm 3 The chemical concentration of oxygen in the high concentration region 106 may be 5×10 17 / cm 3 It may be greater than or equal to 1 x 10 18 / cm 3 The chemical concentration of oxygen in the high concentration region 106 may be 1×10 19 / cm 3may be less than or equal to 5 x 10 18 / cm 3 may be less than or equal to 1 x 10 18 / cm 3 The entire semiconductor substrate 10 may have the oxygen concentration described above.

[0049] The above-mentioned carbon concentration and oxygen concentration can be easily achieved by using the MCZ method to manufacture the semiconductor substrate 10. However, the semiconductor substrate 10 is not limited to an MCZ substrate manufactured using the MCZ method.

[0050] The semiconductor substrate 10 may be provided with a drift region 18. The drift region 18 is an N-type region having a lower doping concentration than the hydrogen-containing region 102. The doping concentration of the drift region 18 may be the same as the base doping concentration Db. The drift region 18 may include a region having a doping concentration higher than the base doping concentration Db. The doping concentration distribution of the drift region 18 may be approximately uniform or flat in a predetermined depth range L0. As an example, being uniform or flat means a distribution in which the change in doping concentration in a predetermined depth range L0 shows a range of values ​​from 80% to 120% of the base doping concentration Db. The specified depth range L0 may be a length within 10% of the thickness W0 of the semiconductor substrate 10 (i.e., L0≦0.1W0), a length within 30% (i.e., L0≦0.3W0), a length within 50% (i.e., L0≦0.5W0), or a length within 70% (i.e., L0≦0.7W0).

[0051] FIG. 2 is a diagram showing an example of the distribution of carrier concentration and virtual carrier concentration along the AA line in FIG. 1. The AA line includes the entire hydrogen-containing region 102 in the depth direction and a part of the drift region 18. FIG. 2 shows the hydrogen chemical concentration distribution and the helium concentration distribution along the AA line. Helium is an example of an adjustment impurity for forming a lifetime killer. The vertical axis of FIG. 2 is a logarithmic axis showing each concentration, and the horizontal axis is a linear axis showing the depth position from the lower surface 23. Note that the concentration distribution in each drawing shows the distribution when the semiconductor device 100 is completed (i.e., after heat treatment). The hydrogen chemical concentration and the helium concentration in FIG. 2 are chemical concentrations measured by, for example, the SIMS method. The carrier concentration in FIG. 2 is measured by, for example, the SR method.

[0052] In this example, the carrier concentration distribution has a first peak 111, the helium concentration distribution has a third peak 113, the virtual carrier concentration distribution has a fourth peak 114, and the hydrogen chemical concentration distribution has a fifth peak 115. Each concentration distribution may have multiple peaks. The multiple first peaks 111 are referred to as first peaks 111-1, 111-2, 111-3, and 111-4 in order from the one closest to the lower surface 23 of the semiconductor substrate 10. The multiple third peaks 113 are referred to as third peaks 113-1, 113-2, 113-3, and 113-4 in order from the one closest to the lower surface 23 of the semiconductor substrate 10. The multiple fourth peaks 114 are referred to as fourth peaks 114-1, 114-2, 114-3, and 114-4 in order from the one closest to the lower surface 23 of the semiconductor substrate 10. The fifth peaks 115 are designated as fifth peaks 115-1, 115-2, 115-3, and 115-4 in order from the one closest to the lower surface 23 of the semiconductor substrate 10. The depth positions at which the fifth peaks 115 in the hydrogen chemical concentration distribution show maximum values ​​are designated as PH1, PH2, PH3, and PH4 in order from the one closest to the lower surface 23. The depth position at which the third peak 113 in the helium concentration distribution shows maximum value is designated as PHe. The depth position at which the second peak 112 in the carrier concentration distribution in the high concentration region 106-1 shows maximum value is designated as P2.

[0053] 2, the position where each first peak 111 in the carrier concentration distribution shows a maximum value is the same as the position where each fifth peak 115 in the hydrogen chemical concentration distribution shows a maximum value, but these positions do not have to be exactly the same. For example, if the position where the first peak 111 shows a maximum value is included within the full width at half maximum range of the fifth peak 115, the first peak 111 and the fifth peak 115 may be located at substantially the same position.

[0054] The hydrogen-containing region 102 contains hydrogen. In this example, the hydrogen-containing region 102 does not substantially contain N-type impurities and P-type impurities other than hydrogen. For example, the hydrogen chemical concentration in the hydrogen-containing region 102 is 100 times or more the chemical concentration of the N-type impurities and the P-type impurities. In the example of FIG. 2, the hydrogen-containing region 102 is a region in which the hydrogen chemical concentration is 10 times or more the base doping concentration Db. The fifth peak 115 of the hydrogen chemical concentration distribution is located near the range position at the time of implantation of the hydrogen ions. When the hydrogen-containing region 102 has a plurality of fifth peaks 115, the hydrogen ions may be implanted into the hydrogen-containing region 102 a plurality of times with the range changed. The change in the range may be a change in the acceleration energy of the hydrogen ions at the time of ion implantation.

[0055] The virtual carrier concentration distribution is a distribution obtained by multiplying the hydrogen chemical concentration distribution by an activation rate smaller than 1. That is, the virtual carrier concentration distribution is a distribution having the same shape as the hydrogen chemical concentration distribution, but with a smaller concentration value. The activation rate may be a predetermined value, or may be determined based on the hydrogen chemical concentration distribution and the carrier concentration distribution. For example, the peak value of the fifth peak 115-1, which is the furthest from the third peak 113 of the helium concentration distribution, among the multiple fifth peaks 115 of the hydrogen chemical concentration distribution, is set to D5-1, and the peak value of the first peak 111-1, which is located at the same depth position as the fifth peak 115-1, among the multiple first peaks 111 of the carrier concentration distribution, is set to D1-1. The ratio D1-1 / D5-1 of the peak value D1-1 of the first peak 111-1 to the peak value D5-1 of the fifth peak 115-1 may be used as the activation rate.

[0056] In this example, the third peak 113 of the helium concentration distribution is located between the depth positions PH2 and PH3 at which the two fifth peaks 115 (in this example, the fifth peaks 115-2 and 115-3) of the hydrogen chemical concentration distribution have maximum values. Similarly, the third peak 113 is located between the two first peaks 111 (in this example, the first peaks 111-2 and 111-3) of the carrier concentration distribution in the depth direction. For example, the depth position PHe at which the third peak 113 has a maximum value is not included in the range of the full width at half maximum (FWHM) of any of the fifth peaks 115. Similarly, the point at which the third peak 113 has a maximum value is not included in the range of the full width at half maximum of any of the first peaks 111. By making the position of the third peak 113 of the helium concentration distribution different from the fifth peak 115, it is possible to leave the vacancy defects formed by helium irradiation without bonding with hydrogen, thereby reducing the carrier lifetime. This makes it easy to form lifetime control region 104. When helium is injected from the lower surface 23 side, the inclination of the slope on the lower surface 23 side of third peak 113 of the helium concentration distribution tends to be smaller than the inclination of the slope on the opposite side to lower surface 23.

[0057] The carrier concentration distribution has a higher concentration value in the high concentration region 106 than the virtual carrier concentration distribution. The carrier concentration in the high concentration region 106 is higher than the base doping concentration Db of the semiconductor substrate 10. The high concentration region 106 may be disposed between first peaks 111 of the carrier concentration distribution. In this example, the high concentration region 106-1 is provided between the deepest first peak 111-4 and the second deepest first peak 111-3 of the first peaks 111 of the carrier concentration distribution.

[0058] In this example, the carrier concentration distribution of the high concentration region 106-1 has a second peak 112. A depth position P2 of the second peak 112 of the high concentration region 106-1 is located between a depth position PH4 of the first peak 111-4 and a depth position PH3 of the first peak 111-3.

[0059] Further, a high concentration region 106-2 is provided between the first peak 111-4 and the drift region 18. The high concentration regions 106-1 and 106-2 may be provided continuously including the first peak 111-4. In each of the high concentration regions 106, the maximum value of the carrier concentration may be 1.1 times or more, 1.5 times or more, or 2 times or more of the virtual carrier concentration at the corresponding depth position.

[0060] Each high concentration region 106 may contain an adjustment impurity such as helium. The concentration of the adjustment impurity contained in the high concentration region 106 may be higher than the base doping concentration Db. The high concentration region 106 may be provided at a position deeper than the third peak 113 of the helium concentration distribution with respect to the lower surface 23. In the high concentration region 106, vacancy defects and the like are generated due to helium injection. The concentration distribution of the vacancy defects will be described separately in FIG. 5. The vacancy defects are combined with hydrogen and oxygen by heat treatment to become defects containing VOH. Since the defects containing VOH function as donors, the carrier concentration of the high concentration region 106 is higher than the virtual carrier concentration. With this configuration, a carrier concentration distribution different from the virtual carrier concentration distribution can be obtained. On the other hand, since many vacancy defects are formed in the vicinity of the third peak 113 of the helium concentration distribution, the proportion of vacancy defects remaining is high, and the carrier concentration is lower than the virtual carrier concentration. This allows the lifetime control region 104 to be formed. According to this example, the high concentration region 106 can be formed in the same process as the lifetime control region 104 .

[0061] In addition, in the high concentration region 106-2, the slope 117 of the carrier concentration distribution changes more gently than the slope 118 of the virtual carrier concentration. That is, the slope 117 of the carrier concentration distribution extends to a deeper position than the slope 118 of the virtual carrier concentration. This allows the voltage and current waveforms during switching to be gentler when the semiconductor device 100 is used as a switching element such as a transistor. The slope 118 may decrease in gradient as the distance from the lower surface 23 increases. That is, the slope 118 may have a downwardly convex shape. The slope 117 may increase in gradient as the distance from the lower surface 23 increases. That is, the slope 117 may have an upwardly convex shape.

[0062] The carrier concentration in the hydrogen-containing region 102 may be higher than the base doping concentration Db of the semiconductor substrate 10. However, the carrier concentration in the lifetime control region 104 may be lower than the base doping concentration Db. The carrier concentration distribution may have a valley 116 in the lifetime control region 104. When the regions between the fifth peaks 115 of the hydrogen chemical concentration distribution are defined as inter-peak regions, the valley 116 may be disposed in the inter-peak region on the lower surface 23 side of the inter-peak region in which the high concentration region 106-1 is disposed. The valley 116 in this example is disposed in the inter-peak region adjacent to the inter-peak region in which the high concentration region 106-1 is disposed, sandwiching the fifth peak 115-3 therebetween. The valley 116 may be disposed in the same inter-peak region as the third peak 113 of the helium concentration distribution.

[0063] Fig. 3 is a diagram showing a carrier concentration distribution and a virtual carrier concentration distribution. The carrier concentration distribution and the virtual carrier concentration distribution in Fig. 3 are the same as those in the example in Fig. 2. In this example, the maximum value of each first peak 111 in the carrier concentration distribution is D1, and the maximum value of each fourth peak 114 in the virtual carrier concentration distribution is D4. The maximum value of the carrier concentration distribution in the high concentration region 106-1 is D2.

[0064] The maximum value D1 of any one of the first peaks 111 in the carrier concentration distribution may be equal to or less than the virtual carrier concentration at the depth position. For example, the maximum value D1 of at least one of the two first peaks 111-2, 111-3 arranged on either side of the lifetime control region 104 or the valley 116 is smaller than the maximum value D4 of the corresponding fourth peaks 114-2, 114-3. In the vicinity of the lifetime control region 104, many vacancy defects remain without becoming VOH defects, so the carrier concentration is likely to decrease.

[0065] FIG. 4 is a diagram for explaining the second peak 112 of the high-concentration region 106-1. The carrier concentration distribution in FIG. 4 is the same as that in the example of FIG. 2. The second peak 112 is a gentler peak than either of the two first peaks 111-3 and 111-4 that sandwich the second peak 112 in the depth direction. The width W2 of the second peak 112 in the depth direction is larger than either of the widths W1-3 and W1-4 of the first peaks 111-3 and 111-4 in the depth direction. The full width at half maximum of each peak may be used as the width of each peak. If the full width at half maximum of each peak cannot be measured, the width of each peak may be specified using a standard other than the half maximum. For example, the width of each peak may be the width of a region having a concentration of 80% or more (0.8×D) relative to the maximum value D of each peak.

[0066] The width W2 of the second peak 112 may be larger than the width W1 of any of the first peaks 111 in the hydrogen containing region 102. According to this example, the carrier concentration distribution in the region of the hydrogen containing region 102 that is close to the drift region 18 can be made uniform.

[0067] FIG. 5 is a diagram for explaining the third peak 113 in the helium concentration distribution. FIG. 5 also illustrates the vacancy defect concentration distribution. The vacancy defect concentration distribution is a distribution of the concentration of vacancy defects generated by ion implantation of an adjustment impurity such as helium ions. The vacancy defect concentration distribution has a peak 119. The carrier concentration distribution and the helium concentration distribution in FIG. 5 are the same as those in the example of FIG. 2. In this example, the width of the third peak 113 in the depth direction is Wk. The width Wk may be the full width at half maximum of the third peak 113. In addition, the width of the inter-peak region between each first peak 111 in the carrier concentration distribution is L. In the example of FIG. 5, the width of the inter-peak region between the first peaks 111-1 and 111-2 is L12, the width of the inter-peak region between the first peaks 111-2 and 111-3 is L23, and the width of the inter-peak region between the first peaks 111-3 and 111-4 is L34.

[0068] The width Wk of the third peak 113 in this example is larger than the width L of any inter-peak region. The range of the width Wk of the third peak 113 may include a plurality of first peaks 111. In the example of FIG. 5, the range of the width Wk includes the first peaks 111-2 and 111-3. The width Wk may be 5 μm or more, or may be 10 μm or more. The width Wk may be smaller than the width in the depth direction of the hydrogen-containing region 102. By increasing the width Wk of the third peak 113, helium can be distributed even in a position away from the peak position PHe of the third peak 113. Therefore, VOH defects can be generated in a position away from the peak position PHe, and the high concentration region 106 can be formed. In addition, it becomes easier to form the high concentration region 106 in the vicinity of the drift region 18, and the carrier concentration distribution in the vicinity of the drift region 18 can be gradually changed.

[0069] The peak 119 of the vacancy defect concentration distribution may be located near the third peak 113 of the helium concentration distribution. In this example, the peak position PV of the peak 119 and the peak position PHe of the third peak 113 coincide with each other. The peak position PV of the peak 119 and the peak position PHe of the third peak 113 do not have to coincide with each other. The vacancy defect concentration distribution may be distributed so as to include the position PHe of the third peak 113 of the helium concentration distribution. The peak 119 of the vacancy defect concentration distribution is distributed narrower than the distribution width of the third peak 113 of the helium concentration distribution. The position PV of the peak 119 may be located between two hydrogen concentration peak positions adjacent to each other in the depth direction with the position PHe in between. The peak 119 of the vacancy defect concentration distribution in this example is distributed between the first carrier concentration peak 111-2 and the first carrier concentration peak 111-3. The width Wv between two concentration positions that are 10% of the peak concentration of the vacancy defect concentration distribution may be shorter than the width L23. Vacancy defects are formed inside the semiconductor substrate 10 by ion implantation of the adjustment impurity. Hydrogen present around the vacancy defects terminates the dangling bonds of the vacancy defects. Therefore, the concentration of the formed vacancy defects decreases. In the first peak 111-2 and the first peak 111-3 where the hydrogen chemical concentration is high, the hydrogen chemical concentration is high, so that the vacancy defect concentration is particularly decreased. As a result, the vacancy defect concentration is distributed only between the first peak 111-2 and the first peak 111-3. That is, the recombination center caused by the vacancy defects is locally distributed between the two carrier concentration peaks, so that the depth and width of the recombination center can be controlled with high precision. The gradient of the concentration slope on both sides of the peak position PV of the vacancy defect concentration distribution may be larger than the gradient of the concentration slope on both sides of the peak position PHe of the helium concentration distribution.

[0070] FIG. 6 is a diagram showing another example of the carrier concentration distribution and the virtual carrier concentration distribution. In the carrier concentration distribution described in FIG. 2 to FIG. 5, the maximum value D2 of the second peak 112 is smaller than both of the maximum values ​​D1-3 and D1-4 of the two first peaks 111-3 and 111-4 that sandwich the second peak 112. In contrast, the maximum value D2 of the second peak 112 may be larger than at least one of the maximum values ​​D1-3 and D1-4. In this example, the maximum value D2 of the second peak 112 is larger than both of the maximum values ​​D1-3 and D1-4. With this configuration, the carrier concentration distribution in the vicinity of the drift region 18 can be made more gentle.

[0071] The carrier concentration distribution shown in FIG. 6 has a minimum value (valley) between the first peak 111-3 and the second peak 112, and has a minimum value (valley) between the second peak 112 and the first peak 111-4. Another example of the carrier concentration distribution may not have a minimum value (valley) at least one of between the first peak 111-3 and the second peak 112 and between the second peak 112 and the first peak 111-4. The carrier concentration distribution may have a single peak between the depth positions PH3 and PH4. That is, the carrier concentration distribution between the depth positions PH3 and PH4 may not have a minimum value (valley).

[0072] 7 is a diagram showing another example of the carrier concentration distribution and the virtual carrier concentration distribution. In this example, the width W2 of the second peak 112 is larger than in the examples shown in FIGS. 1 to 6. For example, the second peak 112 with a larger width W2 can be formed by adjusting the oxygen concentration of the semiconductor substrate 10. The oxygen concentration of the semiconductor substrate 10 in this example is 1×10 17 / cm 3 It can be 5 x 10 or more. 17 / cm 3 It may be greater than or equal to 1 x 10 18 / cm 3 or more. Alternatively, 1×10 18 / cm 3 The other configurations may be similar to those of the examples of Figures 1 to 6. The semiconductor substrate 10 may be a substrate manufactured by the MCZ method.

[0073] In this example, helium is also implanted at the depth position PHe. This allows the high concentration region 106 to be formed. The dose of helium is 5×10 10 / cm 2 It may be greater than or equal to 1 x 10 11 / cm 2 It may be greater than or equal to 1 x 10 12 / cm 2 In order to distribute helium evenly over a wide area, the range may be changed and helium may be injected at multiple depths. In this case, the total dose of helium may be 5×10 10 / cm 2 It may be greater than or equal to 1 x 10 11 / cm 2 It may be greater than or equal to 1 x 10 12 / cm 2 Alternatively, the acceleration energy of the helium ions may be increased to increase the full width at half maximum of the helium ions.

[0074] In this example, the full width at half maximum W2 of the second peak 112 may be greater than half the fifth peak interval W5 between the deepest fifth peak 115-4 and the next deepest fifth peak 115-3 among the fifth peaks 115 of the hydrogen chemical concentration distribution. In this example, the dose for the deepest fifth peak 115-4 is 1×10 12 / cm 2 It can be 7 x 10 or more. 12 / cm 2 It may be greater than or equal to 1 x 10 13 / cm 2 By increasing the dose of the fifth peak 115-4, the amount of hydrogen that terminates the vacancy defects can be secured, which makes it easier to form the second peak 112 with a large width W2.

[0075] When observing the carrier concentration from the apex of the second peak 112 toward the drift region 18, the depth position where the carrier concentration first becomes half (D2 / 2) of the apex concentration D2 is defined as Zb. The distance in the depth direction from the apex of the second peak 112 to the depth position Zb may be half the full width at half maximum W2. In other words, the full width at half maximum W2 may be twice the distance. In this case, the full width at half maximum W2 can be specified even if the carrier concentration does not become equal to or less than D2 / 2 on the lower surface 23 side of the apex of the second peak 112.

[0076] By increasing the width W2, the carrier concentration distribution in the hydrogen-containing region 102 can be made high and flat. For example, when the hydrogen-containing region 102 is used as a buffer region described later, the voltage waveform during the reverse recovery operation of the semiconductor device 100 can be made gentle, resulting in soft recovery. In addition, the electric field strength on the lower surface 23 side can be alleviated, improving the avalanche resistance on the lower surface 23 side. The full width at half maximum W2 of the second peak 112 may be equal to or greater than the fifth peak interval W5.

[0077] The apexes of the fifth peak 115-4 and the fifth peak 115-3 may be located in the depth range of the full width at half maximum W2 of the second peak 112. This allows the second peak 112 to be more gentle. In this case, the carrier concentration distribution may have the fourth peak 114 or a kink at the depth positions PH3 and PH4, respectively. A kink refers to a point where the slope of the distribution waveform (i.e., the differential value) changes discontinuously. The full width at half maximum W2 of the second peak 112 may be 5 μm or more, 10 μm or more, or 15 μm or more.

[0078] FIG. 8 is a diagram showing a structural example of a semiconductor device 100. The semiconductor device 100 of this example functions as an insulated gate bipolar transistor (IGBT). The semiconductor device 100 of this example has a semiconductor substrate 10, an interlayer insulating film 38, an emitter electrode 52, and a collector electrode 54. The interlayer insulating film 38 is formed so as to cover at least a part of the upper surface 21 of the semiconductor substrate 10. Through holes such as contact holes are formed in the interlayer insulating film 38. The upper surface 21 of the semiconductor substrate 10 is exposed through the contact holes. The interlayer insulating film 38 may be silicate glass such as PSG or BPSG, or may be an oxide film, a nitride film, or the like.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] The emitter region 12 is provided in contact with the upper surface 21 of the semiconductor substrate 10, and is a region having a higher donor concentration than the drift region 18. The emitter region 12 contains an N-type impurity such as phosphorus.

[0083] 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.

[0084] The accumulation region 16 is provided between the base region 14 and the drift region 18, and has one or more donor concentration peaks having a higher donor concentration than the drift region 18. The accumulation region 16 may contain N-type impurities such as phosphorus, or may contain hydrogen.

[0085] 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.

[0086] The buffer region 20 is provided between the collector region 22 and the drift region 18, and has one or more donor concentration peaks having a higher donor concentration than the drift region 18. The buffer region 20 contains N-type impurities such as hydrogen. The buffer region 20 may function as a field stop layer that prevents a depletion layer extending from the lower surface side of the base region 14 from reaching the collector region 22.

[0087] The hydrogen-containing region 102 described in Figures 1 to 7 is included in the buffer region 20. In this example, the hydrogen-containing region 102 functions as the entire buffer region 20. The buffer region 20 in this example has the high concentration region 106 described in Figures 1 to 7. The buffer region 20 may further have the lifetime control region 104 described in Figures 1 to 7.

[0088] By providing the high concentration region 106 in the buffer region 20, the carrier concentration distribution in the buffer region 20 can be made gentle in the vicinity of the drift region 18. This allows the voltage and current waveforms to change gently when the semiconductor device 100 is switched. In addition, since the donor concentration in the vicinity of the drift region 18 can be increased, the spread of the depletion layer from the lower surface side of the base region 14 can be further suppressed.

[0089] The gate trench portion 40 extends from the upper surface 21 of the semiconductor substrate 10 through the emitter region 12, the base region 14, and the accumulation region 16 to reach the drift region 18. The accumulation region 16 in this example is disposed above the lower end of the gate trench portion 40. The accumulation region 16 may be provided so as to cover the entire lower surface of the base region 14. By providing the accumulation region 16 between the drift region 18 and the base region 14 and having a higher concentration than the drift region 18, the carrier injection enhancement effect (IE effect) can be enhanced, and the on-voltage of the IGBT can be reduced.

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

[0091] The gate conductive portion 44 includes a region facing the base region 14 with the gate insulating film 42 interposed therebetween. The gate trench portion 40 in this cross section is covered with the interlayer insulating film 38 on the upper surface of the semiconductor substrate 10, but the gate conductive portion 44 is connected to the gate electrode in another cross section. When a predetermined gate voltage is applied to the gate conductive portion 44, a channel is formed by an electron inversion layer in the surface layer of the interface of the base region 14 that contacts the gate trench portion 40.

[0092] Fig. 9 is a diagram showing an example of a carrier concentration distribution in the depth direction at the position of line BB in Fig. 8. The vertical axis of Fig. 9 is a logarithmic axis showing the carrier concentration, and the horizontal axis is a linear axis showing the distance from the lower surface 23.

[0093] The carrier concentration distribution in the buffer region 20 of this example has a plurality of first peaks 111 provided at different positions in the depth direction. The buffer region 20 has a high concentration region 106 between the first peaks 111. The buffer region 20 may have the high concentration region 106 between the drift region 18 and the first peak 111 that is closest to the drift region 18 among the plurality of first peaks 111. Providing the high concentration region 106 makes it easier to suppress the spread of the depletion layer from the upper surface 21 side.

[0094] Although the accumulation region 16 in this example has multiple peaks 25, the accumulation region 16 may have a single peak 25. The peak 25 is a peak of donor concentration. The peak 25 may be formed by implanting hydrogen. In this case, the high concentration region 106 may be provided in the accumulation region 16. The lifetime control region 104 may be provided below the accumulation region 16, and the high concentration region 106 may be provided inside the accumulation region 16. The high concentration region 106 may function as the peak 25 in the accumulation region 16. The high concentration region 106 may also be formed throughout the entire depth direction of the accumulation region 16.

[0095] Fig. 10 is a diagram showing some steps in the manufacturing method of the semiconductor device 100. Fig. 10 shows a step of forming a high concentration region 106. Before and after the step shown in Fig. 10, the respective structures shown in Fig. 8 are formed.

[0096] In S902, hydrogen ions are implanted from the lower surface 23 side of the semiconductor substrate 10. In S902, hydrogen ions may be implanted multiple times by changing the range. Next, in S904, the semiconductor substrate 10 is annealed. This generates hydrogen donors and VOH defects to form hydrogen-containing regions 102.

[0097] Next, in S906, an adjustment impurity such as helium is injected into the hydrogen-containing region 102. In S906, as described with reference to FIG. 5 and the like, it is preferable to inject helium so that the width Wk of the third peak 113 of the helium concentration distribution is wider than the interval between the fifth peaks 115 of the hydrogen chemical concentration distribution. In S906, the third peak 113 having a large width Wk may be formed by injecting helium multiple times with different ranges. The helium concentration distribution may have multiple third peaks 113. The range of helium ions in a silicon substrate is about 10 μm at an acceleration energy of 2.5 MeV.

[0098] In the embodiment shown in FIG. 7, when the width W2 of the second peak 112 is to be increased by one implantation of helium ions, the acceleration energy may be further increased. In this case, since the range of the helium ions becomes deeper than a predetermined position, an absorber such as aluminum having a predetermined thickness is inserted between the accelerator of the helium ions and the semiconductor substrate. The second peak 112 of the helium ions may be adjusted to a predetermined depth from the implantation surface of the semiconductor substrate by absorbing the energy of the helium ions with this absorber. As an example, the acceleration energy of the helium ions is 24 MeV, and the full width at half maximum is about 12 μm.

[0099] Next, in S908, the semiconductor substrate 10 is annealed. The annealing conditions in S908 may be the same as or different from the annealing conditions in S904. By heat-treating the semiconductor substrate 10 in S908, a high concentration region 106 is formed in the hydrogen-containing region 102.

[0100] In S902 and S906, the concentration of hydrogen or helium to be implanted may be adjusted according to the carbon concentration contained in the semiconductor substrate 10. For example, the higher the carbon concentration contained in the semiconductor substrate 10, the lower the concentration of hydrogen or helium to be implanted. This makes it possible to form a high concentration region 106 with a constant concentration, regardless of the carbon concentration contained in the semiconductor substrate 10.

[0101] Fig. 11 is a diagram showing an example of voltage and current waveforms during reverse recovery operation of the semiconductor device 100. Fig. 11 shows waveforms of the semiconductor device 100 according to the embodiment of Fig. 8 and waveforms of a semiconductor device according to a comparative example. The semiconductor device according to the comparative example differs from the semiconductor device 100 in that it does not have the high concentration region 106. The other structure is similar to that of the semiconductor device 100.

[0102] As shown in FIG. 11, in the comparative example, the di / dt of the current waveform becomes large just before the reverse recovery current disappears. This causes a relatively large surge in the voltage waveform. In contrast, according to the embodiment, the carrier concentration distribution in the buffer region 20 is gentle, so the current waveform can be gentle until the end of the reverse recovery operation. This makes it possible to suppress surges in the voltage waveform.

[0103] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is clear to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included in the technical scope of the present invention.

[0104] It should be noted that the order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically indicated as "before," "prior to," etc., and may be realized in any order unless the output of a previous process is used in a later process. Even if the operational flow in the claims, specifications, and drawings is explained using "first," "next," etc. for convenience, it does not mean that it is essential to perform the process in this order. [Explanation of symbols]

[0105] DESCRIPTION OF SYMBOLS 10 semiconductor substrate, 12 emitter region, 14 base region, 16 accumulation region, 18 drift region, 20 buffer region, 21 upper surface, 22 collector region, 23 lower surface, 25 peak, 38 interlayer insulating film, 40 gate trench portion, 42 gate insulating film, 44 gate conductive portion, 52 emitter electrode , 54...collector electrode, 100...semiconductor device, 102...hydrogen-containing region, 104...lifetime control region, 106...high-concentration region, 111...first peak, 112...second peak, 113...third peak, 114...fourth peak, 115...fifth peak, 116...valley, 117...slope, 118...slope, 119...peak

Claims

1. 1. A semiconductor device comprising a semiconductor substrate having an upper surface and a lower surface and having a base doping concentration, the semiconductor substrate has a hydrogen-containing region that contains hydrogen; the hydrogen-containing region has three or more hydrogen chemical concentration peaks in a depth direction of the semiconductor substrate; The three or more hydrogen chemical concentration peaks are a first hydrogen chemical concentration peak; and a second hydrogen chemical concentration peak disposed on an upper surface side of the semiconductor substrate relative to the first hydrogen chemical concentration peak and adjacent to the first hydrogen chemical concentration peak; a third hydrogen chemical concentration peak disposed on an upper surface side of the semiconductor substrate relative to the second hydrogen chemical concentration peak and adjacent to the second hydrogen chemical concentration peak; Including, a carrier concentration distribution between the second hydrogen chemical concentration peak and the third hydrogen chemical concentration peak having a peak-to-peak concentration peak; Semiconductor device.

2. The semiconductor substrate is An adjustment impurity for adjusting the carrier lifetime; a drift region of a first conductivity type disposed on an upper surface side of the semiconductor substrate relative to the hydrogen-containing region; having The concentration of the adjusting impurity is higher than the concentration of the adjusting impurity in the drift region throughout the entire region between the second hydrogen chemical concentration peak and the third hydrogen chemical concentration peak. The semiconductor device according to claim 1 .

3. The concentration of the adjusting impurity at the second hydrogen chemical concentration peak is higher than the concentration of the adjusting impurity at the third hydrogen chemical concentration peak. The semiconductor device according to claim 2 .

4. A concentration peak of the adjusting impurity is provided between the first hydrogen chemical concentration peak and the second hydrogen chemical concentration peak.

4. The semiconductor device according to claim 2.

5. The full width at half maximum of the concentration peak of the adjusting impurity is greater than the distance between the first hydrogen chemical concentration peak and the second hydrogen chemical concentration peak in the depth direction. The semiconductor device according to claim 4.

6. a carrier concentration distribution in a depth direction of the hydrogen-containing region has a plurality of carrier concentration peaks; The width of the concentration peak of the adjusting impurity is greater than the width of any of the carrier concentration peaks.

6. The semiconductor device according to claim 4.

7. The width of the inter-peak concentration peak in the depth direction is greater than the width of any of the first hydrogen chemical concentration peak, the second hydrogen chemical concentration peak, and the third hydrogen chemical concentration peak in the depth direction. The semiconductor device according to claim 1 .

8. the full width at half maximum of the inter-peak concentration peak is greater than half the depthwise spacing of the second hydrogen chemical concentration peak and the third hydrogen chemical concentration peak; The semiconductor device according to claim 1 .

9. The second hydrogen chemical concentration peak and the third hydrogen chemical concentration peak are included in the full width at half maximum range of the peak-to-peak concentration peak. The semiconductor device according to claim 1 .

10. 1. A semiconductor device comprising a semiconductor substrate having an upper surface and a lower surface and having a base doping concentration, the semiconductor substrate has a hydrogen-containing region that contains hydrogen; the hydrogen-containing region has two or more hydrogen chemical concentration peaks in a depth direction of the semiconductor substrate; a carrier concentration distribution between any two of the hydrogen chemical concentration peaks adjacent to each other in the depth direction of the semiconductor substrate has a valley; The minimum value of the carrier concentration in the valley of the carrier concentration distribution is smaller than the base doping concentration. Semiconductor device.

11. The semiconductor substrate contains an adjustment impurity for adjusting a carrier lifetime, The concentration peak of the adjusting impurity is disposed between the two hydrogen chemical concentration peaks. The semiconductor device according to claim 10.

12. The full width at half maximum of the concentration peak of the adjusting impurity is greater than the distance between the two hydrogen chemical concentration peaks in the depth direction. The semiconductor device according to claim 11.

13. a carrier concentration distribution in a depth direction of the hydrogen-containing region has a plurality of carrier concentration peaks; The width of the concentration peak of the adjusting impurity is greater than the width of any of the carrier concentration peaks. The semiconductor device according to claim 11 or 12.

14. the semiconductor substrate has a drift region of a first conductivity type disposed on an upper surface side of the semiconductor substrate relative to the hydrogen containing region, Throughout the region between the two hydrogen chemical concentration peaks, the hydrogen chemical concentration is higher than the hydrogen chemical concentration in the drift region. The semiconductor device according to claim 10 .

15. 1. A method for manufacturing a semiconductor device comprising: forming a buffer region of a first conductivity type in the MCZ semiconductor substrate, the buffer region having a doping concentration higher than the base doping concentration; In the step of forming the buffer region, a density peak of a lifetime killer is formed in the buffer region, and by forming the density peak, a carrier concentration distribution in a depth direction of the buffer region is changed; In the step of forming the buffer region, hydrogen ions are implanted into three or more depth positions of the MCZ semiconductor substrate to form the buffer region having three or more hydrogen chemical concentration peaks in a depth direction; The three or more hydrogen chemical concentration peaks are a first hydrogen chemical concentration peak; and A second hydrogen chemical concentration peak is disposed on the upper surface side of the MCZ semiconductor substrate relative to the first hydrogen chemical concentration peak and adjacent to the first hydrogen chemical concentration peak; a third hydrogen chemical concentration peak disposed on the upper surface side of the MCZ semiconductor substrate relative to the second hydrogen chemical concentration peak and adjacent to the second hydrogen chemical concentration peak; Including, In the step of forming the buffer region, an adjustment impurity for adjusting a carrier lifetime is implanted between the first hydrogen chemical concentration peak and the second hydrogen chemical concentration peak, and annealed to form the density peak of the lifetime killer, and a concentration peak of a carrier concentration is formed between the second hydrogen chemical concentration peak and the third hydrogen chemical concentration peak. A method for manufacturing a semiconductor device.

16. A method for manufacturing a semiconductor device comprising: a MCZ semiconductor substrate having a base doping concentration of a first conductivity type, the method comprising: forming a buffer region of a first conductivity type in the MCZ semiconductor substrate, the buffer region having a doping concentration higher than the base doping concentration; In the step of forming the buffer region, a density peak of a lifetime killer is formed in the buffer region, and by forming the density peak, a carrier concentration distribution in a depth direction of the buffer region is changed; In the step of forming the buffer region, hydrogen ions are implanted into two or more depth positions of the MCZ semiconductor substrate to form the buffer region having two or more hydrogen chemical concentration peaks in a depth direction; In the step of forming the buffer region, an adjustment impurity for adjusting a carrier lifetime is implanted between any two of the hydrogen chemical concentration peaks adjacent to each other in the depth direction of the MCZ semiconductor substrate, and annealed to form the density peak of the lifetime killer, and a valley portion having a carrier concentration smaller than the base doping concentration is formed between the two hydrogen chemical concentration peaks. A method for manufacturing a semiconductor device.

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