Semiconductor equipment

Abstract

The present invention provides a semiconductor device that improves the variation in donor concentration of a semiconductor layer formed by hydrogen ion implantation. [Solution] A semiconductor device comprising a semiconductor substrate having an upper surface and a lower surface, wherein the semiconductor substrate has one or more hydrogen peaks 221, which are peaks of hydrogen chemical concentration, in the depth direction, and one or more of the hydrogen peaks include the deepest peak furthest from the lower surface of the semiconductor substrate, and the semiconductor substrate has a lower region 201 from the lower surface to the deepest peak and an upper region 202 located from the deepest peak 221-5 to the upper surface, and the concentration in the lower region is at least twice the concentration in the upper region for at least one of the carbon chemical concentration and the oxygen chemical concentration.

Description

[Technical Field]

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

[0002] Semiconductor devices are known in which hydrogen ions such as protons are implanted into a semiconductor substrate (see, for example, Patent Documents 1 and 2). Patent Document 1: Specification of U.S. Patent Application Publication No. 2016 / 0141399 Patent Document 2: Problems to be solved by the specification of U.S. Patent Application Publication No. 2015 / 0076650

[0003] Hydrogen donors are formed by implanting hydrogen ions, such as protons, into a semiconductor substrate. However, the degree to which hydrogen ions become donors varies depending on the oxygen concentration or carbon concentration in the semiconductor substrate, resulting in fluctuations in the donor concentration. (General Disclosure)

[0004] To solve the above problems, a first embodiment of the present invention provides a semiconductor device comprising a semiconductor substrate having an upper surface and a lower surface. In the above semiconductor device, the semiconductor substrate has one or more hydrogen peaks, which are peaks of hydrogen chemical concentration, in the depth direction, and one or more of the hydrogen peaks may include the deepest peak furthest from the lower surface of the semiconductor substrate. In any of the above semiconductor devices, the semiconductor substrate may have a lower region from the lower surface to the deepest peak and an upper region located from the deepest peak to the upper surface. In any of the above semiconductor devices, the concentration in the lower region may be at least twice the concentration in the upper region for at least one of the carbon chemical concentration and the oxygen chemical concentration.

[0005] In any of the above semiconductor devices, the semiconductor substrate may have a drift region of a first conductivity type. In any of the above semiconductor devices, the semiconductor substrate may have a buffer region of a first conductivity type, disposed between the lower surface and the drift region, and having a higher doping concentration than the drift region. In any of the above semiconductor devices, the deepest peak may be located in the buffer region.

[0006] In any of the above semiconductor devices, the lower region may have a flat area in which at least one of the carbon chemical concentration and the oxygen chemical concentration is uniform.

[0007] In any of the above semiconductor devices, the lower region may have one or more carbon peaks in the depth direction, which are peaks of the carbon chemical concentration.

[0008] In any of the above semiconductor devices, the lower region may have multiple carbon peaks in the depth direction.

[0009] In any of the above semiconductor devices, the lower region may have a plurality of hydrogen peaks in the depth direction. In any of the above semiconductor devices, at least one carbon peak may be located between two hydrogen peaks in the depth direction.

[0010] In any of the above semiconductor devices, the upper region may have one or more carbon peaks.

[0011] In any of the above semiconductor devices, the lower region may have one or more oxygen peaks in the depth direction, which are peaks of the oxygen chemical concentration.

[0012] In any of the above semiconductor devices, the lower region may have multiple oxygen peaks in the depth direction.

[0013] In any of the semiconductor devices described above, the lower region may have a plurality of the hydrogen peaks in the depth direction. In any of the semiconductor devices described above, at least one of the oxygen peaks may be disposed between two of the hydrogen peaks in the depth direction.

[0014] In any of the semiconductor devices described above, the upper region may have one or more of the oxygen peaks.

[0015] In any of the semiconductor devices described above, the lower region may have one or more carbon peaks, which are peaks of the carbon chemical concentration, and one or more oxygen peaks, which are peaks of the oxygen chemical concentration, in the depth direction.

[0016] In any of the semiconductor devices described above, at least one of the carbon peaks and at least one of the oxygen peaks may be disposed at the same depth position.

[0017] In any of the semiconductor devices described above, the lower region may have a plurality of doping concentration peaks in the depth direction. In any of the semiconductor devices described above, the plurality of doping concentration peaks may have a plurality of first doping concentration peaks corresponding to the plurality of hydrogen peaks. In any of the semiconductor devices described above, the plurality of doping concentration peaks may have a second doping concentration peak disposed between two of the hydrogen peaks.

[0018] In any of the semiconductor devices described above, at least one of the carbon peaks may be disposed at a depth position different from any of the oxygen peaks.

[0019] In any of the semiconductor devices described above, the carbon chemical concentration in the lower region may be 1×10 14 atoms / cm 3 or more.

[0020] In any of the semiconductor devices described above, the oxygen chemical concentration in the lower region may be 2×10 17 atoms / cm 3That's all.

[0021] A second aspect of the present invention provides a method for manufacturing a semiconductor device. The semiconductor device comprises a semiconductor substrate having an upper surface and a lower surface, the semiconductor substrate having one or more hydrogen peaks, which are peaks of hydrogen chemical concentration, in the depth direction, one or more of the hydrogen peaks including the deepest peak furthest from the lower surface of the semiconductor substrate, and the semiconductor substrate may have a lower region from the lower surface to the deepest peak and an upper region located from the deepest peak to the upper surface. The manufacturing method may involve implanting at least one of carbon, oxygen, and silicon into the region where the lower region is to be formed. Any of the manufacturing methods may involve annealing the semiconductor substrate at a temperature of 700°C or higher. Any of the manufacturing methods may involve implanting hydrogen ions into the depth positions where one or more of the hydrogen peaks are to be formed.

[0022] The above summary of the invention does not enumerate all the necessary features of the present invention. Furthermore, subcombinations of these features may also constitute an invention. [Brief explanation of the drawing]

[0023] [Figure 1] This is a top view showing an example of a semiconductor device 100 according to one embodiment of the present invention. [Figure 2] This is a magnified view of region D in Figure 1. [Figure 3] Figure 2 shows an example of an ee cross-section. [Figure 4] Figure 3 shows an example of the distribution of doping concentration, hydrogen chemical concentration, oxygen chemical concentration, and carbon chemical concentration along the ff line. [Figure 5] Figure 3 shows other examples of the distributions of doping concentration, hydrogen chemical concentration, oxygen chemical concentration, and carbon chemical concentration along the ff line. [Figure 6] Figure 3 shows other examples of the distributions of doping concentration, hydrogen chemical concentration, oxygen chemical concentration, and carbon chemical concentration along the ff line. [Figure 7]Figure 3 shows other examples of the distributions of doping concentration, hydrogen chemical concentration, oxygen chemical concentration, and carbon chemical concentration along the ff line. [Figure 8] Figure 3 shows other examples of the distributions of doping concentration, hydrogen chemical concentration, oxygen chemical concentration, and carbon chemical concentration along the ff line. [Figure 9] This figure shows an example of the relative positions of oxygen peak 232 and carbon peak 242. [Figure 10] This figure shows another example of the relative positions of oxygen peak 232 and carbon peak 242. [Figure 11] Figure 3 shows other examples of the distributions of doping concentration, hydrogen chemical concentration, oxygen chemical concentration, and carbon chemical concentration along the ff line. [Figure 12] Figure 3 shows other examples of the distributions of oxygen and carbon chemical concentrations along the ff line. [Figure 13] This figure shows some of the steps involved in the manufacturing process of the semiconductor device 100. [Figure 14] This figure shows an overview of the manufacturing method for the semiconductor device 100. [Modes for carrying out the invention]

[0024] The present invention will be described below through embodiments of the invention, but these embodiments are not intended to limit the invention as defined in the claims. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0025] In this specification, one side of a semiconductor substrate parallel to its depth direction is referred to as "top," and the other side as "bottom." Of the two main surfaces of a substrate, layer, or other component, one surface is referred to as the top surface, and the other surface as the bottom surface. The directions of "top" and "bottom" are not limited to the direction of gravity or the direction in which the semiconductor device is mounted.

[0026] In this specification, technical matters may be described using the Cartesian coordinate axes, the X, Y, and Z axes. The Cartesian coordinate axes merely specify the relative positions of components and do not limit any particular direction. For example, the Z axis does not limit the direction to height relative to the ground. Note that the +Z axis direction and the -Z axis direction are opposite directions. When the sign is not specified and only the Z axis direction is written, it means the direction parallel to the +Z and -Z axes.

[0027] In this specification, the orthogonal axes parallel to the top and bottom surfaces of the semiconductor substrate are defined as the X and Y axes. The axis perpendicular to the top and bottom surfaces of the semiconductor substrate is defined as 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 top and bottom surfaces of the semiconductor substrate, including the X and Y axes, may be referred to as the horizontal direction.

[0028] The region from the center of the semiconductor substrate in the depth direction to the top surface of the semiconductor substrate is sometimes referred to as the top surface. Similarly, the region from the center of the semiconductor substrate in the depth direction to the bottom surface of the semiconductor substrate is sometimes referred to as the bottom surface.

[0029] In this specification, the terms "identical" or "equal" may include cases where there are errors due to manufacturing variations, etc. Such errors are, for example, within 10%.

[0030] In this specification, the conductivity type of a doped region containing impurities is described as either P-type or N-type. In this specification, impurities may specifically refer to either N-type donors or P-type acceptors, and may be referred to as dopants. In this specification, doping means introducing donors or acceptors into a semiconductor substrate to make it a semiconductor exhibiting either an N-type conductivity or a P-type conductivity.

[0031] In this specification, doping concentration means the concentration of the donor or acceptor at thermal equilibrium. In this specification, net doping concentration means the net concentration obtained by adding up the charge polarity, with the donor concentration being the concentration of positive ions and the acceptor concentration being the concentration of negative ions. As an example, the donor concentration is N D , the acceptor concentration is N A Therefore, the net doping concentration at any given position is N D -N A In this specification, net doping concentration may be simply referred to as doping concentration.

[0032] Donors have the function of supplying electrons to a semiconductor. Acceptors have the function of receiving electrons from a semiconductor. Donors and acceptors are not limited to impurities themselves. For example, a VOH defect in a semiconductor, where a vacancy (V), oxygen (O), and hydrogen (H) are bonded, functions as an electron-supplying donor. A hydrogen donor may be a donor in which at least a vacancy (V) and hydrogen (H) are bonded. Alternatively, interstitial Si-H, where interstitial silicon (Si-i) and hydrogen are bonded in a silicon semiconductor, and CiOi-H, where interstitial carbon (Ci) and interstitial oxygen (Oi) and hydrogen are bonded, also function as electron-supplying donors. In this specification, VOH defects, CiOi-H, or interstitial Si-H may be referred to as hydrogen donors.

[0033] In this specification, the semiconductor substrate has N-type bulk donors uniformly distributed throughout. The bulk donors are donors formed by dopants that were contained substantially uniformly in the ingot during the production of the ingot from which the semiconductor substrate is derived. The bulk donors in this example are elements other than hydrogen. The dopants of the bulk donors are, for example, phosphorus, antimony, arsenic, selenium or sulfur, but are not limited thereto. The bulk donor in this example is phosphorus. The bulk donors are also included in P-type regions. The semiconductor substrate may be a wafer cut out from a semiconductor ingot, or may be a chip obtained by singulating the wafer. The semiconductor ingot may be manufactured by any of the Czochralski method (CZ method), the magnetic field applied Czochralski method (MCZ method), or the float zone method (FZ method). The ingot in this example is manufactured by the MCZ method. The oxygen concentration contained in the substrate manufactured by the MCZ method is 1×10 17 ~7×10 17 / cm 3 . The oxygen concentration contained in the substrate manufactured by the FZ method is 1×10 15 ~5×10 16 / cm 3 . A higher oxygen concentration tends to more easily generate hydrogen donors. The bulk donor concentration may be the chemical concentration of the bulk donors distributed throughout the semiconductor substrate, and may be a value between 90% and 100% of the chemical concentration. Also, a non-doped substrate that does not contain dopants such as phosphorus may be used as the semiconductor substrate. In that case, the bulk donor concentration (D0) of the non-doping substrate is, for example, 1×10 10 / cm 3 or more and 5×10 12 / cm 3 or less. The bulk donor concentration (D​​0) of the non-doping substrate is preferably 1×10 11 / cm 3 or more. The bulk donor concentration (D​​0) of the non-doping substrate is preferably 5×10 12 / cm 3 or less. Incidentally, each concentration in the present invention may be a value at room temperature. As an example, the value at room temperature may be the value at 300 K (Kelvin) (about 26.9 °C).

[0034] In this specification, when P+ type or N+ type is mentioned, it means a higher doping concentration than P type or N type, and when P- type or N- type is mentioned, it means a lower doping concentration than P type or N type. Furthermore, when P++ type or N++ type is mentioned in this specification, it means a higher doping concentration than P+ type or N+ type. Unless otherwise specified, the units used in this specification are SI units. Although units of length may be expressed in cm, calculations may be performed after converting to meters (m).

[0035] In this specification, chemical concentration refers to the atomic density of impurities measured independently of the electrical activation state. Chemical concentration can be measured, for example, by secondary ion mass spectrometry (SIMS). The net doping concentration described above can be measured by voltage-capacitance (CV) spectroscopy. Alternatively, the carrier concentration measured by broadened resistance (SR) spectroscopy may be used as the net doping concentration. The carrier concentration measured by CV or SR spectroscopy may be the value at thermal equilibrium. Furthermore, in the N-type region, since the donor concentration is sufficiently larger than the acceptor concentration, the carrier concentration in that region may be used as the donor concentration. Similarly, in the P-type region, the carrier concentration in that region may be used as 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.

[0036] If the concentration distribution of the donor, acceptor, or net doping has a peak, the peak value may be used as the concentration of the donor, acceptor, or net doping in that region. If the concentrations of the donor, acceptor, or net doping are nearly uniform, the average value of the concentrations of the donor, acceptor, or net doping in that region may be used as the concentration of the donor, acceptor, or net doping. In this specification, concentrations per unit volume are expressed as atoms / cm³. 3 , or / cm 3This unit is used for donor or acceptor concentrations in semiconductor substrates, or for chemical concentrations. The atom notation may be omitted.

[0037] The carrier concentration measured by the SR method may be lower than the donor or acceptor concentration. When measuring spreading resistance, the carrier mobility of the semiconductor substrate may be lower than the value for the crystalline state in the range where current flows. The decrease in carrier mobility occurs because carriers are scattered due to disorder in the crystal structure caused by lattice defects, etc.

[0038] The donor or acceptor concentrations calculated from carrier concentrations measured by the CV method or SR method may be lower than the chemical concentrations of the elements that act as donors or acceptors. For example, in silicon semiconductors, the donor concentrations of phosphorus or arsenic, or the acceptor concentration of boron, are approximately 99% of their respective chemical concentrations. On the other hand, the donor concentration of hydrogen, which also acts as a donor in silicon semiconductors, is approximately 0.1% to 10% of the hydrogen chemical concentration.

[0039] Figure 1 is a top view showing an example of a semiconductor device 100 according to one embodiment of the present invention. In Figure 1, the positions of each component projected onto the upper surface of the semiconductor substrate 10 are shown. In Figure 1, only some components of the semiconductor device 100 are shown, and some components are omitted.

[0040] The semiconductor device 100 comprises 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 edges 162 when viewed from above. In this specification, when simply referred to as "top view," it means viewing from the top side of the semiconductor substrate 10. In this example, the semiconductor substrate 10 has two pairs of edges 162 that face each other when viewed from above. In Figure 1, the X and Y axes are parallel to either edge 162. The Z axis is perpendicular to the top surface of the semiconductor substrate 10.

[0041] The semiconductor substrate 10 is provided with an active area 160. The active area 160 is a region in which the main current flows in the depth direction between the upper and lower surfaces of the semiconductor substrate 10 when the semiconductor device 100 is operating. An emitter electrode is provided above the active area 160, but it is omitted in Figure 1. The active area 160 may refer to the region that overlaps with the emitter electrode when viewed from above. Also, the region sandwiched between the active areas 160 when viewed from above may be included in the active area 160.

[0042] The active section 160 is provided with at least one of a transistor section 70 including a transistor element such as an IGBT (Insulated Gate Bipolar Transistor), and a diode section 80 including a diode element such as a freewheeling diode (FWD). In the example shown in Figure 1, the transistor section 70 and the diode section 80 are arranged alternately along a predetermined arrangement direction (in this example, the X-axis direction) on the upper surface of the semiconductor substrate 10. The semiconductor device 100 in this example is a reverse-conducting IGBT (RC-IGBT).

[0043] In Figure 1, the region where the transistor section 70 is located is denoted by the symbol "I," and the region where the diode section 80 is located is denoted by the symbol "F." In this specification, the direction perpendicular to the arrangement direction in a top view may be referred to as the extension direction (Y-axis direction in Figure 1). The transistor section 70 and the diode section 80 may each have their longitudinal length in the extension direction. That is, the length of the transistor section 70 in the Y-axis direction is greater than its width in the X-axis direction. Similarly, the length of the diode section 80 in the Y-axis direction is greater than its width in the X-axis direction. The extension direction of the transistor section 70 and the diode section 80 may be the same as the longitudinal direction of each trench section described later.

[0044] The diode section 80 has an N+ type cathode region in the area in contact with the lower surface of the semiconductor substrate 10. In this specification, the region in which the cathode region is provided is referred to as the diode section 80. In other words, the diode section 80 is the region that overlaps with the cathode region when viewed from above. A P+ type collector region may be provided on the lower surface of the semiconductor substrate 10 in areas other than the cathode region. In this specification, an extension region 81, which is an extension of the diode section 80 in the Y-axis direction to the gate wiring described later, may also be included in the diode section 80. A collector region is provided on the lower surface of the extension region 81.

[0045] The transistor section 70 has a P+ type collector region in the area in contact with the lower surface of the semiconductor substrate 10. Furthermore, the transistor section 70 has a gate structure periodically arranged on the upper surface side of the semiconductor substrate 10, which includes an N type emitter region, a P type base region, a gate conductive portion, and a gate insulating film.

[0046] The semiconductor device 100 may have one or more pads on the semiconductor substrate 10. In this example, the semiconductor device 100 has a gate pad 164. The semiconductor device 100 may also have pads such as an anode pad, a cathode pad, and a current sensing pad. Each pad is located near the edge 162. The vicinity of the edge 162 refers to the area between the edge 162 and the emitter electrode in a top view. When the semiconductor device 100 is mounted, each pad may be connected to an external circuit via wiring such as wires.

[0047] A gate potential is applied to the gate pad 164. The gate pad 164 is electrically connected to the conductive portion of the gate trench of the active portion 160. The semiconductor device 100 is provided with gate wiring that connects the gate pad 164 to the gate trench. In Figure 1, the gate wiring is shown with diagonal hatching.

[0048] The gate wiring in this example has an outer gate wiring 130 and an active gate wiring 131. The outer gate wiring 130 is positioned between the active portion 160 and the edge 162 of the semiconductor substrate 10 in a top view. In this example, the outer gate wiring 130 surrounds the active portion 160 in a top view. The area surrounded by the outer gate wiring 130 in a top view may be considered the active portion 160. Furthermore, a well region is formed below the gate wiring. The well region is a P+ type region with a higher concentration than the base region, which will be described later, and is formed from the top surface of the semiconductor substrate 10 to a position deeper than the base region. The area surrounded by the well region in a top view may be considered the active portion 160.

[0049] The outer perimeter gate wiring 130 is connected to the gate pad 164. The outer perimeter gate wiring 130 is located above the semiconductor substrate 10. The outer perimeter gate wiring 130 may be a metal wiring containing aluminum or the like.

[0050] The active gate wiring 131 is provided in the active section 160. By providing the active gate wiring 131 in the active section 160, variations in the wiring length from the gate pad 164 can be reduced for each region of the semiconductor substrate 10.

[0051] The outer periphery gate wiring 130 and the active side gate wiring 131 are connected to the gate trench portion of the active portion 160. The outer periphery gate wiring 130 and the active side gate wiring 131 are positioned above the semiconductor substrate 10. The outer periphery gate wiring 130 and the active side gate wiring 131 may be wirings formed from a semiconductor such as polysilicon doped with impurities.

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

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

[0054] In this example, the semiconductor device 100 includes an edge termination structure 90 between the active portion 160 and the edge 162 when viewed from above. In this example, the edge termination structure 90 is positioned between the outer peripheral gate wiring 130 and the edge 162. The edge termination structure 90 mitigates electric field concentration on the upper surface side of the semiconductor substrate 10. The edge termination structure 90 may include at least one of a guard ring, a field plate, and a resurf, which are provided in an annular shape surrounding the active portion 160.

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

[0056] An interlayer insulating film is provided between the emitter electrode 52 and the active gate wiring 131 and the upper surface of the semiconductor substrate 10, but this is omitted in Figure 2. In this example, contact holes 54 are provided in the interlayer insulating film, penetrating the film. In Figure 2, each contact hole 54 is hatched with diagonal lines.

[0057] The emitter electrode 52 is provided above the gate trench 40, dummy trench 30, well region 11, emitter region 12, base region 14, and contact region 15. The emitter electrode 52 contacts the emitter region 12, contact region 15, and base region 14 on the upper surface of the semiconductor substrate 10 through a contact hole 54. The emitter electrode 52 is also connected to a dummy conductive part in the dummy trench 30 through a contact hole provided in the interlayer insulating film. The emitter electrode 52 may be connected to a dummy conductive part of the dummy trench 30 at its tip in the Y-axis direction. The dummy conductive part of the dummy trench 30 does not need to be connected to the emitter electrode 52 and the gate conductive part, and may be controlled to a potential different from the potential of the emitter electrode 52 and the gate conductive part.

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

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

[0060] The well region 11 is provided overlapping with the active gate wiring 131. The well region 11 also extends to a predetermined width in an area that does not overlap with the active gate wiring 131. In this example, the well region 11 is provided away from the Y-axis end of the contact hole 54 towards the active gate wiring 131. The well region 11 is a second conductivity type region with a higher doping concentration than the base region 14. In this example, the base region 14 is P-type, and the well region 11 is P+-type.

[0061] Each of the transistor section 70 and the diode section 80 has multiple trench sections arranged in the direction of arrangement. In this example, the transistor section 70 has one or more gate trench sections 40 and one or more dummy trench sections 30 alternately provided along the direction of arrangement. In this example, the diode section 80 has multiple dummy trench sections 30 provided along the direction of arrangement. In this example, the diode section 80 does not have gate trench sections 40.

[0062] The gate trench portion 40 in this example may have two linear portions 39 (the trench portion which is linear along the extension direction) that extend along the extension direction perpendicular to the alignment direction, and a tip portion 41 that connects the two linear portions 39. In Figure 2, the extension direction is the Y-axis direction.

[0063] Preferably, at least a portion of the tip portion 41 is provided in a curved shape when viewed from above. By connecting the ends of the two straight portions 39 in the Y-axis direction with the tip portion 41, electric field concentration at the ends of the straight portions 39 can be mitigated.

[0064] In the transistor section 70, the dummy trench section 30 is provided between each of the straight sections 39 of the gate trench section 40. There may be one dummy trench section 30 between each of the straight sections 39, or there may be multiple dummy trench sections 30. The dummy trench section 30 may have a straight shape extending in the extension direction, and like the gate trench section 40, it may have a straight section 29 and a tip section 31. The semiconductor device 100 shown in Figure 2 includes both a dummy trench section 30 with a straight shape without a tip section 31 and a dummy trench section 30 with a tip section 31.

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

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

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

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

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

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

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

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

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

[0074] The cathode region 82 is positioned away from the well region 11 in the Y-axis direction. This ensures a distance between the P+-type region (well region 11), which has a relatively high doping concentration and is formed to a deep position, and the cathode region 82, thereby improving pressure resistance. In this example, the Y-axis end of the cathode region 82 is positioned further from the well region 11 than the Y-axis end of the contact hole 54. In other examples, the Y-axis end of the cathode region 82 may be positioned between the well region 11 and the contact hole 54.

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

[0076] The interlayer insulating film 38 is provided on the upper surface of the semiconductor substrate 10. The interlayer insulating film 38 is a film that includes at least one layer of insulating film such as silicate glass with impurities such as boron or phosphorus added, a thermal oxide film, and other insulating films. The interlayer insulating film 38 is provided with contact holes 54 as described in Figure 2.

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

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

[0079] The mesa portion 60 of the transistor portion 70 is provided with an N+ type emitter region 12 and a P type base region 14, arranged sequentially from the upper surface 21 of the semiconductor substrate 10. A drift region 18 is provided below the base region 14. An N+ type storage region 16 may also be provided in the mesa portion 60. The storage region 16 is located between the base region 14 and the drift region 18.

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

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

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

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

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

[0085] The buffer region 20 may have two or more concentration peaks in the depth direction (Z-axis direction) of the semiconductor substrate 10. The concentration peaks of the buffer region 20 may be located at the same depth as, for example, the chemical concentration peaks of hydrogen (proton) or phosphorus. The buffer region 20 may function as a field stop layer that prevents the depletion layer extending from the lower end of the base region 14 from reaching the P+ type collector region 22 and the N+ type cathode region 82.

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

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

[0088] One or more gate trenches 40 and one or more dummy trenches 30 are provided on the upper surface 21 of the semiconductor substrate 10. Each trench extends from the upper surface 21 of the semiconductor substrate 10, through the base region 14, and down to below the base region 14. In regions where at least one of the emitter region 12, contact region 15, and storage region 16 is provided, each trench also penetrates these doping regions. The statement that a trench penetrates a doping region is not limited to manufacturing in the order of forming the doping region before forming the trench. Manufacturing in which doping regions are formed between the trenches after the trenches have been formed is also included in the statement that a trench penetrates a doping region.

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

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

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

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

[0093] In this example, the gate trench portion 40 and the dummy trench portion 30 are covered by an interlayer insulating film 38 on the upper surface 21 of the semiconductor substrate 10. The bottom portions of the dummy trench portion 30 and the gate trench portion 40 may be curved (curved in cross-section) with a downward convex shape.

[0094] Figure 4 shows an example of the distribution of doping concentration, hydrogen chemical concentration, oxygen chemical concentration, and carbon chemical concentration at the ff line in Figure 3. The doping concentration may be the carrier concentration measured by the SR method or the like. The chemical concentrations of hydrogen, oxygen, and carbon may be measured by the SIMS method or the like. The ff line is a line parallel to the Z axis and passing through a part of the buffer region 20 and the drift region 18. The horizontal axis in Figure 4 shows the depth position (position in the Z axis direction) within the semiconductor substrate 10. In this specification, unless otherwise specified, the bottom surface 23 of the semiconductor substrate 10 is taken as the reference position (0) in the Z axis direction, and the distance from the bottom surface 23 is taken as the position in the Z axis direction.

[0095] A drift region 18 is provided above the buffer region 20. The doping concentration in the drift region 18 may be approximately constant. The doping concentration in the drift region 18 may be the same as the bulk donor concentration BD, or it may be higher than the bulk donor concentration BD. In this example, the doping concentration in the drift region 18 is the same as the bulk donor concentration BD.

[0096] The bulk donor concentration BD may be the minimum chemical concentration of bulk donor in the semiconductor substrate 10, the chemical concentration of bulk donor at the center of the depth direction of the semiconductor substrate 10, or the average value of the chemical concentration of bulk donor in the drift region 18. The bulk donor is a dopant other than oxygen and carbon that is distributed throughout the semiconductor substrate 10. The bulk donor is, for example, phosphorus, but may be arsenic or antimony, and is not limited to these. When both P-type bulk acceptor and N-type bulk donor are distributed throughout the semiconductor substrate 10, the bulk donor concentration BD is the net concentration determined by the difference between the bulk donor concentration and the bulk acceptor concentration. The concentrations of bulk donor and bulk acceptor may be values ​​measured by SIMS or the like.

[0097] Let Zb be the depth position at the boundary between the drift region 18 and the buffer region 20. In this example, depth position Zb is the depth position where the doping concentration first becomes the bulk donor concentration BD in the direction from the buffer region 20 toward the drift region 18.

[0098] A buffer region 20 is provided between the drift region 18 and the lower surface 23. A collector region 22 is provided between the buffer region 20 and the lower surface 23. The boundary position Z0 between the collector region 22 and the buffer region 20 is the position of the PN junction between the collector region 22 and the buffer region 20.

[0099] In this example, buffer region 20 is a region containing hydrogen donors. In this specification, buffer region 20 is defined as an N-type region between drift region 18 and collector region 22 where hydrogen atoms are present (for example, the hydrogen chemical concentration is greater than the detection limit) and the doping concentration is higher than the bulk donor concentration BD.

[0100] The buffer region 20 has one or more doping concentration peaks 211 in the depth direction. In the example in Figure 4, the doping concentration peaks 211-1, 211-2, 211-3, 211-4, and 211-5 are arranged in the buffer region 20 in order from the peak closest to the bottom surface 23 of the semiconductor substrate 10. In this specification, the doping concentration peak 211-1 closest to the bottom surface 23 may be referred to as the shallowest doping concentration peak, and the doping concentration peak 211-5 furthest from the bottom surface 23 may be referred to as the deepest doping concentration peak.

[0101] The buffer region 20 has one or more hydrogen peaks 221 in the depth direction. A hydrogen peak 221 is a peak of hydrogen chemical concentration. In the example in Figure 4, hydrogen peaks 221-1, 221-2, 221-3, 221-4, and 221-5 are arranged in the buffer region 20 in order from the peak closest to the bottom surface 23 of the semiconductor substrate 10. In this specification, the hydrogen peak 221-1 closest to the bottom surface 23 is sometimes referred to as the shallowest peak, and the hydrogen peak 221-5 furthest from the bottom surface 23 is sometimes referred to as the deepest peak. Note that the doping concentration peak 211-1 closest to the bottom surface 23 of the semiconductor substrate 10 may have a phosphorus dopant. In this case, peak 211-1 becomes the phosphorus peak 211-1.

[0102] Let Zm be the depth position of the peak of the hydrogen peak 221-m (where m is an integer greater than or equal to 1). In this specification, the position of the peak peak may be referred to as the peak position. Also, the concentration at the peak peak may be referred to as the peak concentration. The doping concentration peak 211-m may be located at the same depth position Zm as the hydrogen peak 221-m. Two peaks may be considered to be located at the same depth position if the depth position of the peak of one of the two peaks is included within the full width at half maximum in the depth direction of the other peak.

[0103] The semiconductor substrate 10 has a lower region 201 and an upper region 202. The lower region 201 is the region from the bottom surface 23 to the deepest peak (hydrogen peak 221-5 in this example). The depth position of the upper end of the lower region 201 may be the depth position Z5 of the peak of hydrogen peak 221-5, or it may be the depth position (Zb in the example of Figure 4) on the upper surface 21 side of the peak of hydrogen peak 221-5 where the hydrogen chemical concentration is below the detection limit, or it may be the depth position Zb of the boundary between the buffer region 20 and the drift region 18. In this example, the upper end position of the lower region 201 is Zb. In this example, the lower region 201 includes the buffer region 20, but in other examples, the lower region 201 may be a region different from the buffer region 20. In this case as well, the lower region 201 includes one or more hydrogen peaks 221.

[0104] The upper region 202 is the region located from the deepest peak (hydrogen peak 221-5 in this example) to the top surface 21. The upper region 202 is located closer to the top surface 21 than the lower region 201. The depth position of the lower end of the upper region 202 may be the same as or different from the depth position of the upper end of the lower region 201. In this example, the depth position of the lower end of the upper region 202 is Zb, which is the same as the depth position Zb of the upper end of the lower region 201. The upper region 202 may be the entire region from depth position Zb to the top surface 21, or it may be a part of the region. In this example, the upper region 202 is a part of the region from depth position Zb to the top surface 21. The top end position Zu of the upper region 202 may be located in the drift region 18. The length of the upper region 202 in the depth direction (Zu-Zb in this example) may be the same as, smaller than, or larger than the length of the lower region 201 in the depth direction (Zb).

[0105] Let the carbon concentration in the lower region 201 be Ca1 and the oxygen concentration be Ox1. Let the carbon concentration in the upper region 202 be Ca2 and the oxygen concentration be Ox2. The carbon concentration Ca1 and oxygen concentration Ox1 in the lower region 201 may be the average value or the maximum value of the carbon and oxygen concentrations in the lower region 201. The carbon concentration Ca2 and oxygen concentration Ox2 in the upper region 202 may be the average value or the maximum value of the carbon and oxygen concentrations in the upper region 202.

[0106] For at least one of the carbon chemical concentration and the oxygen chemical concentration, the concentration in the lower region 201 is at least twice the concentration in the upper region 202. In the example in Figure 4, the carbon chemical concentration Ca1 in the lower region 201 is at least twice the carbon chemical concentration Ca2 in the upper region 202, and the oxygen chemical concentration OX1 in the lower region 201 is at least twice the oxygen chemical concentration Ox2 in the upper region 202.

[0107] The carbon chemical concentration Ca1 is 1 × 10⁻⁶ 14 atoms / cm 3 The above is acceptable. The carbon chemical concentration Ca1 is 5 × 10 14 atoms / cm 3 The above is sufficient, 1 × 1015 atoms / cm 3 The above is sufficient, 5 × 10 15 atoms / cm 3 The above is sufficient, 1 × 10 16 atoms / cm 3 The above is also acceptable. The oxygen chemical concentration Ox1 is 2 × 10⁻⁶. 17 atoms / cm 3 The above is sufficient. The oxygen chemical concentration Ox1 is 3 × 10⁻⁶. 17 atoms / cm 3 The above is sufficient, 5 × 10 17 atoms / cm 3 That's fine too.

[0108] A semiconductor substrate 10 (semiconductor wafer) cut from a semiconductor ingot has a nearly uniform distribution of carbon and oxygen. However, the carbon and oxygen chemical concentrations vary from substrate to substrate. Hydrogen ions can be implanted into the semiconductor substrate 10 to form hydrogen donors, creating high-concentration regions such as buffer regions 20. The degree to which hydrogen donors are formed in relation to the dose of hydrogen ions varies depending on the carbon and oxygen chemical concentrations of the semiconductor substrate 10. For example, the degree to which VOH defects are formed varies depending on the oxygen chemical concentration, and the degree to which CiOi-H is formed varies depending on the oxygen and carbon chemical concentrations. Therefore, the doping concentration in high-concentration regions such as buffer regions 20 will vary depending on the carbon and oxygen chemical concentrations of the semiconductor substrate 10.

[0109] In the semiconductor device 100 of this example, at least one of carbon and oxygen is selectively injected into the lower region 201 of the semiconductor substrate 10 to adjust at least one of the carbon chemical concentration and oxygen chemical concentration in the lower region 201. This reduces the influence of variations in the carbon chemical concentration and oxygen chemical concentration of the semiconductor substrate 10, and allows for precise control of the doping concentration in the lower region 201 (buffer region 20 in this example).

[0110] For one or both of the carbon and oxygen chemical concentrations, the concentration in the lower region 201 may be 5 times or more, or 10 times or more, than the concentration in the upper region 202. The dose of carbon and oxygen injected into the lower region 201 can be controlled with relatively high precision. Therefore, by injecting a large amount of carbon or oxygen into the lower region 201, the proportion of the variation in carbon and oxygen chemical concentrations in the semiconductor substrate 10 to the total carbon and oxygen chemical concentrations can be reduced. For both carbon and oxygen chemical concentrations, the concentration in the lower region 201 may be 1000 times or less, 100 times or less, or 50 times or less, than the concentration in the upper region 202.

[0111] In this example, the lower region 201 has a flat portion 231. In the flat portion 231, at least one of the carbon chemical concentration and oxygen chemical concentration is uniform, with concentrations at least twice as high as in the upper region 202. In the example of Figure 4, both the carbon chemical concentration and oxygen chemical concentration are uniform in the flat portion 231. In the flat portion 231, for at least one of the carbon chemical concentration and oxygen chemical concentration, the maximum concentration may be 1.1 times or less, 1.07 times or less, or 1.05 times or less than the minimum concentration. The length of the flat portion 231 in the depth direction may be 10% or more of the lower region 201, 30% or more, 50% or more, 70% or more, 90% or more, or 100%. The length of the flat portion 231 in the depth direction may be 5 μm or more, 10 μm or more, or 20 μm or more. By providing the flat portion 231, the hydrogen donor concentration in the lower region 201 can be precisely controlled, thereby enabling precise control of the doping concentration.

[0112] Figure 5 shows other examples of the distributions of doping concentration, hydrogen chemistry concentration, oxygen chemistry concentration, and carbon chemistry concentration along the ff line in Figure 3. In this example, the distribution of carbon chemistry concentration differs from that in Figure 4. The other distributions are similar to those in Figure 4.

[0113] In this example, the carbon concentration in the lower region 201 is less than twice the carbon concentration in the upper region 202. The carbon concentration in the lower region 201 may be 1.5 times or less the carbon concentration in the upper region 202, or it may be the same as the carbon concentration in the upper region 202. In this example, oxygen is injected locally into the lower region 201, but carbon is not injected locally. By increasing the oxygen chemical concentration in the lower region 201, variations in doping concentration due to variations in oxygen chemical concentration can be suppressed.

[0114] Figure 6 shows other examples of the distributions of doping concentration, hydrogen chemical concentration, oxygen chemical concentration, and carbon chemical concentration along the ff line in Figure 3. In this example, the distribution of oxygen chemical concentration differs from that in Figure 4. The other distributions are similar to those in Figure 4.

[0115] In this example, the oxygen concentration in the lower region 201 is less than twice the oxygen concentration in the upper region 202. The oxygen concentration in the lower region 201 may be 1.5 times or less the oxygen concentration in the upper region 202, or it may be the same as the oxygen concentration in the upper region 202. In this example, carbon is locally injected into the lower region 201, but oxygen is not locally injected. By increasing the carbon chemical concentration in the lower region 201, variations in doping concentration due to variations in carbon chemical concentration can be suppressed.

[0116] Figure 7 shows other examples of the distributions of doping concentration, hydrogen concentration, oxygen concentration, and carbon concentration along the ff line in Figure 3. In this example, the distribution of at least one of the oxygen concentration and carbon concentration differs from that of any of the examples in Figures 4 to 6. The other distributions are the same as those of any of the examples in Figures 4 to 6. In Figure 7, both the oxygen concentration and carbon concentration differ from those of any of the examples in Figures 4 to 6, but one of the oxygen concentration and carbon concentration may be the same as those of any of the examples in Figures 4 to 6.

[0117] In this example, the lower region 201 has one or more carbon peaks 242, which are peaks of carbon chemical concentration, in the depth direction. In the example of Figure 7, there is one carbon peak 242. The apex position of the carbon peak 242 may be located near the center in the depth direction of the lower region 201. Near the center may refer to the central region when the lower region 201 is divided into three equal parts in the depth direction. The full width at half maximum in the depth direction of the carbon peak 242 may be 50% or more, 70% or more, 90% or more, or 100% or more of the depth direction length Zb of the lower region 201.

[0118] The carbon concentration at depth Zb may be greater than the carbon concentration Ca2 in the upper region 202. The carbon concentration at depth Z0 may be greater than the carbon concentration Ca2 in the upper region 202. The carbon concentration at the peak position Zm of each hydrogen peak 221-m may be greater than the carbon concentration Ca2 in the upper region 202, and may be 1.5 times or more, 2 times or more, 5 times or more, or 10 times or more. The carbon concentration Ca1 of carbon peak 242 is 2 times or more than the carbon concentration Ca2 in the upper region 202. The carbon concentration Ca1 of carbon peak 242 may be 5 times or more, or 10 times or more, the carbon concentration Ca2 in the upper region 202.

[0119] By accelerating carbon ions with a relatively high acceleration energy and adjusting the carbon ion range by placing an absorber on the carbon ion implantation surface, it is possible to create a carbon peak 242 with a relatively large full width at half maximum, as shown in Figure 7. This example also suppresses variations in doping concentration due to variations in carbon chemical concentration.

[0120] In this example, the lower region 201 has one or more oxygen peaks 232, which are peaks of oxygen chemical concentration, in the depth direction. In the example of Figure 7, there is one oxygen peak 232. The apex position of the oxygen peak 232 may be located near the center in the depth direction of the lower region 201. The full width at half maximum in the depth direction of the oxygen peak 232 may be 50% or more, 70% or more, 90% or more, or 100% or more of the depth direction length Zb of the lower region 201.

[0121] The oxygen chemical concentration at depth Zb may be greater than the oxygen chemical concentration Ox2 in the upper region 202. The oxygen chemical concentration at depth Z0 may be greater than the oxygen chemical concentration Ox2 in the upper region 202. The oxygen chemical concentration at the peak position Zm of each hydrogen peak 221-m may be greater than the oxygen chemical concentration Ox2 in the upper region 202, and may be 1.5 times or more, 2 times or more, 5 times or more, or 10 times or more. The oxygen chemical concentration Ox1 of oxygen peak 232 is 2 times or more than the oxygen chemical concentration Ox2 in the upper region 202. The oxygen chemical concentration Ox1 of oxygen peak 232 may be 5 times or more, or 10 times or more, the oxygen chemical concentration Ox2 in the upper region 202. This example also demonstrates how variations in doping concentration due to variations in oxygen chemical concentration can be suppressed.

[0122] Figure 8 shows other examples of the distributions of doping concentration, hydrogen concentration, oxygen concentration, and carbon concentration along the ff line in Figure 3. In this example, the distribution of at least one of the oxygen concentration and carbon concentration differs from that of any of the examples in Figures 4 to 7. The other distributions are the same as those of any of the examples in Figures 4 to 7. In Figure 8, both the oxygen concentration and carbon concentration differ from those of any of the examples in Figures 4 to 7, but one of the oxygen concentration and carbon concentration may be the same as those of any of the examples in Figures 4 to 7.

[0123] In this example, the lower region 201 has multiple carbon peaks 242 in the depth direction. In this example, at least one carbon peak 242 is located between two hydrogen peaks 221 in the depth direction. A carbon peak 242 can be considered to be located between the vertices of two hydrogen peaks 221 if its vertex is located in the central region when the region between the vertices of the two hydrogen peaks 221 is divided into three equal parts in the depth direction. In other examples, a carbon peak 242 can be considered to be located between the vertices of two hydrogen peaks 221 if its vertex is located between the vertices of two hydrogen peaks 221 and its vertex is not located within the full width at half maximum of the two hydrogen peaks 221.

[0124] All carbon peaks 242 may be located between two hydrogen peaks 221 in the depth direction. Carbon peak 242-m may be located between hydrogen peak 221-m and hydrogen peak 221-(m+1). In the depth direction, the number of carbon peaks 242 may be less than the number of hydrogen peaks 221.

[0125] By positioning the carbon peak 242 between the two hydrogen peaks 221, the implantation depths for carbon ions and hydrogen ions can be made different. This helps to prevent the density of lattice defects formed by ion implantation from becoming excessively high locally.

[0126] In this example, the lower region 201 has multiple oxygen peaks 232 in the depth direction. In this example, at least one oxygen peak 232 is located between two hydrogen peaks 221 in the depth direction. Oxygen peak 232 can be considered to be located between the vertices of two hydrogen peaks 221 if its vertex is located in the central region when the region between the vertices of two hydrogen peaks 221 is divided into three equal parts in the depth direction. In other examples, oxygen peak 232 can be considered to be located between the vertices of two hydrogen peaks 221 if its vertex is located between the vertices of two hydrogen peaks 221 and its vertex is not located within the full width at half maximum of the two hydrogen peaks 221.

[0127] All oxygen peaks 232 may be located between two hydrogen peaks 221 in the depth direction. Oxygen peak 232-m may be located between hydrogen peak 221-m and hydrogen peak 221-(m+1). In the depth direction, the number of oxygen peaks 232 may be less than the number of hydrogen peaks 221.

[0128] By positioning the oxygen peak 232 between the two hydrogen peaks 221, the depth at which oxygen ions are implanted and the depth at which hydrogen ions are implanted can be made different. This helps to prevent the density of lattice defects formed by ion implantation from becoming excessively high locally.

[0129] Figure 9 shows an example of the relative positions of oxygen peak 232 and carbon peak 242. In this example, the lower region 201 has one or more carbon peaks 242 and one or more oxygen peaks 232 in the depth direction. Also, at least one carbon peak 242 and at least one oxygen peak 232 are located at the same depth. In the example of Figure 9, an example is shown where oxygen peak 232-2 and carbon peak 242-2 are located at the same depth, but other oxygen peaks 232-m and carbon peaks 242-m may also be located at the same depth. In this example, the peak of carbon peak 242-2 is located within the full width at half maximum (FWHM) of oxygen peak 232-2. In other examples, the peak of oxygen peak 232-2 may be located within the full width at half maximum (FWHM) of carbon peak 242-2.

[0130] When oxygen peak 232 and carbon peak 242 are located at the same depth, both the oxygen and carbon chemical concentrations in the vicinity of that location increase. As a result, the concentration of hydrogen donors such as CiOi-H in the vicinity of that location stabilizes, suppressing variations in doping concentrations.

[0131] Near the peaks of oxygen peak 232-2 and carbon peak 242-2, hydrogen donors such as CiOi-H are more likely to form. Therefore, a second doping concentration peak 213 may be formed at a depth position relative to the peaks of oxygen peak 232-2 and carbon peak 242-2. As shown in Figure 9, when oxygen peak 232-2 and carbon peak 242-2 are located between two hydrogen peaks 221-2 and hydrogen peak 221-3, a second doping concentration peak 213 may be located between two doping concentration peaks 211-2 and doping concentration peak 211-3. In this example, doping concentration peak 211 is an example of a first doping concentration peak.

[0132] Let D3 be the doping concentration at the second doping concentration peak 213. Let D12 be the doping concentration at doping concentration peak 211-2, which is adjacent to the second doping concentration peak 213 in the depth direction, and let D13 be the doping concentration at doping concentration peak 211-3. Doping concentration D3 may be less than or equal to both doping concentrations D12 and D13. Doping concentration D3 may be 50% or less, or 30% or less, of either doping concentrations D12 or D13. Doping concentration D3 may be 1% or more, or 10% or more, of either doping concentrations D12 or D13. According to this example, the doping concentration distribution between doping concentration peaks 211 can be flattened.

[0133] Figure 10 shows another example of the relative positions of oxygen peak 232 and carbon peak 242. In this example, the lower region 201 has one or more carbon peaks 242 and one or more oxygen peaks 232 in the depth direction. At least one carbon peak 242 is located at a different depth from any of the oxygen peaks 232. Also, at least one oxygen peak 232 is located at a different depth from any of the carbon peaks 242. In the example of Figure 10, oxygen peak 232-2 and carbon peak 242-2 are not located at the same depth, but other oxygen peaks 232-m and carbon peaks 242-m do not have to be located at the same depth. In other examples, in combinations of oxygen peaks 232-m and carbon peaks 242-m, some oxygen peaks 232-m and carbon peaks 242-m may be located at the same depth, while other oxygen peaks 232-m and carbon peaks 242-m do not have to be located at the same depth.

[0134] In this example, the peak of carbon peak 242-2 is located outside the full width at half maximum (FWHM) range of oxygen peak 232-2. Conversely, the peak of oxygen peak 232-2 is located outside the full width at half maximum range of carbon peak 242-2. This example demonstrates that it is possible to suppress the localized excessive density of lattice defects formed by oxygen ion implantation and carbon ion implantation.

[0135] Figure 11 shows other examples of the doping concentration, hydrogen chemical concentration, oxygen chemical concentration, and carbon chemical concentration distributions along the ff line in Figure 3. In this example, the upper region 202 has at least one of one or more carbon peaks 242 and one or more oxygen peaks 232. The upper region 202 shown in Figure 11 has one carbon peak 242-5 and one oxygen peak 232-5.

[0136] The carbon peak 242-4 and the oxygen peak 232-5 are located on the upper surface 21 side of the hydrogen peak 221-5. The carbon peak 242-5 may be located near the carbon peak 242-4. The carbon peak 242-5 may be positioned such that the minimum carbon chemical concentration Ca3 between the carbon peaks 242-4 and 242-5 is greater than the carbon chemical concentration Ca2 in the upper region 202. The carbon chemical concentration Ca3 may be more than twice the carbon chemical concentration Ca2. According to this example, the carbon chemical concentration can be increased even near the depth position Zb. Therefore, the doping concentration in the buffer region 20 near the depth position Zb can be stabilized.

[0137] Oxygen peak 232-5 may be positioned near oxygen peak 232-4. Oxygen peak 232-5 may be positioned such that the minimum oxygen chemical concentration Ox3 between oxygen peak 232-4 and oxygen peak 232-5 is greater than the oxygen chemical concentration Ox2 in the upper region 202. The oxygen chemical concentration Ox3 may be more than twice the oxygen chemical concentration Ox2. According to this example, the oxygen chemical concentration can be increased even near the depth position Zb. Therefore, the doping concentration in the buffer region 20 near the depth position Zb can be stabilized.

[0138] The doping concentration distribution in this example has multiple second doping concentration peaks 213. One second doping concentration peak 213 is positioned between each of two hydrogen peaks 221. The carbon peaks 242-4 and oxygen peaks 232-5 may be positioned at the same depth. In this case, the second doping concentration peaks 213-5 may be positioned on the upper surface 21 side of the doping concentration peaks 211-5. This makes it possible to slow down fluctuations in the doping concentration near the depth position Zb. Therefore, when the semiconductor device 100 is turned off, etc., oscillations in the emitter-collector voltage can be suppressed when the space charge region (depletion layer) extending from the boundary between the drift region 18 and the base region 14 reaches the vicinity of the depth position Zb.

[0139] Figure 12 shows another example of the distribution of oxygen and carbon chemical concentrations along the ff line in Figure 3. In this example, the lower region 201 has more peaks than the hydrogen peak 221 in at least one of the oxygen and carbon chemical concentrations. The lower region 201 shown in Figure 12 has more peaks than the hydrogen peak 221 in both the oxygen and carbon chemical concentrations. By gradually changing the acceleration energy of the ions implanted in the semiconductor substrate 10, multiple concentration peaks can be formed. According to this example, at least one of the oxygen and carbon chemical concentrations in the lower region 201 can be flattened. By increasing the density of peaks in the depth direction, a flat portion 231 as shown in Figure 4 can be formed.

[0140] Figure 13 shows a part of the manufacturing process for the semiconductor device 100. Figure 13 shows a concentration adjustment step S1200 in which at least one of carbon, oxygen, and silicon is implanted into the lower region 201 and annealed. The concentration adjustment step S1200 is included in the manufacturing process of the semiconductor device 100. The concentration adjustment step S1200 is performed before the step of implanting hydrogen ions into the lower region 201.

[0141] The concentration adjustment step S1200 includes an ion implantation step S1201 and an annealing step S1202. In the ion implantation step S1201, at least one of carbon, oxygen, and silicon is implanted into the region where the lower region 201 is to be formed. In the examples in Figures 1 to 12, at least one of carbon and oxygen was implanted into the lower region 201, but the concentration of hydrogen donors formed in the lower region 201 can also be adjusted by implanting silicon into the lower region 201. In the ion implantation step S1201, at least one of the carbon concentration and oxygen concentration in the semiconductor substrate 10 may be measured, and the dose amount of at least one of carbon and oxygen may be adjusted based on the measurement results. In the ion implantation step S1201, the dose amount of at least one of carbon and oxygen may be adjusted based on the difference between at least one of the carbon concentration and oxygen concentration in the semiconductor substrate 10 and a preset reference value.

[0142] In annealing step S1202, the semiconductor substrate 10 is annealed by furnace annealing or the like. The annealing temperature in annealing step S1202 is 700°C or higher. The annealing temperature in annealing step S1202 may be 750°C or higher, or 800°C or higher. By annealing at a relatively high temperature, the carbon and other materials injected into the lower region 201 can be diffused, and the distribution of carbon and other materials in the lower region 201 can be made uniform. After annealing step S1202, hydrogen ions are injected into the lower region 201 to form a buffer region 20. Since the concentration of carbon and other materials in the lower region 201 is adjusted, the doping concentration in the lower region 201 can be controlled with high precision.

[0143] Figure 14 is a diagram showing an overview of the manufacturing method for the semiconductor device 100. The manufacturing method for the semiconductor device 100 may include steps other than those shown in Figure 14, and may not include some of the steps shown in Figure 14.

[0144] In this example, the manufacturing method forms the structure on the upper surface 21 of the semiconductor substrate 10 in the upper surface structure formation step S1302. The structure on the upper surface 21 is, for example, the structure above the center in the depth direction of the semiconductor substrate 10. The structure on the upper surface 21 includes at least a portion of the emitter region 12, base region 14, trench portion, insulating film, gate wiring, gate pad 164, and emitter electrode 52.

[0145] Next, in the protective film formation step S1304, a protective film is formed that covers at least a portion of the emitter electrode 52, gate pad 164, and gate wiring. The protective film is, for example, a polyimide film. The protective film may cover the areas of the emitter electrode 52, gate pad 164, and gate wiring that are not connected to wires or lead frames.

[0146] Next, in the substrate thinning step S1306, the lower surface of the semiconductor substrate 10 is ground to thin the semiconductor substrate 10. In the substrate thinning step S1306, the semiconductor substrate 10 may be thinned according to the breakdown voltage that the semiconductor device 100 should have. In the substrate thinning step S1306, the semiconductor substrate 10 may be ground by the CMP method or the like.

[0147] Next, in the bottom surface etching step S1308, the bottom surface of the semiconductor substrate 10 is etched. This removes the area that was damaged in the substrate thinning step S1306.

[0148] Next, in the bottom surface ion implantation step S1310, dopant ions are implanted into the bottom surface 23 of the semiconductor substrate 10. In the bottom surface ion implantation step S1310, dopant ions are implanted into the regions where the collector region 22 and the cathode region 82 are to be formed. Next, in the annealing step S1312, the collector region 22 and the cathode region 82 are laser annealed to activate the dopants.

[0149] Next, in the hydrogen ion implantation step S1314, hydrogen ions are implanted from the lower surface 23 into the region where the buffer region 20 is to be formed. In the hydrogen ion implantation step S1314, hydrogen ions are implanted at depth positions where one or more hydrogen peaks 221 are to be formed.

[0150] Before the hydrogen ion implantation step S1314, a resist may be formed on the bottom surface 23. This resist may be used to adjust the range of hydrogen ions. Next, in the resist removal step S1316, the resist on the bottom surface 23 is removed. Next, in the annealing step S1318, the semiconductor substrate 10 is annealed by furnace annealing or the like. This forms hydrogen donors and creates a buffer region 20. The annealing temperature in the annealing step S1318 is 400°C or less. The annealing temperature in the annealing step S1318 may be 390°C or less, or 380°C or less. Next, in the bottom electrode formation step S1320, a collector electrode 24 is formed. The collector electrode 24 may be formed by sputtering or the like.

[0151] As shown in Figure 14, the concentration adjustment step S1200 is performed at some point before the hydrogen ion implantation step S1314. By performing the relatively high-temperature annealing step S1202 before the hydrogen ion implantation step S1314, the loss of hydrogen donors due to high-temperature annealing can be suppressed.

[0152] The concentration adjustment step S1200 may be performed before the upper surface structure formation step S1302, before the protective film formation step S1304, or before the substrate thinning step S1306. If the concentration adjustment step S1200 is performed before the substrate thinning step S1306, carbon, oxygen, and silicon ions may be implanted from the upper surface 21 of the semiconductor substrate 10. If the concentration adjustment step S1200 is performed after the substrate thinning step S1306, carbon, oxygen, and silicon ions may be implanted from the lower surface 23 of the semiconductor substrate 10.

[0153] The concentration adjustment step S1200 may be performed before the bottom etching step S1308, before the bottom ion implantation step S1310, or before the annealing step S1312. The steps after the concentration adjustment step S1200 are performed at 400°C or below. The steps after the concentration adjustment step S1200 are performed at 390°C or below, or at 380°C or below.

[0154] 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 or improvements can be made to the above embodiments. It will be clear from the claims that such modified or improved forms may also be included in the technical scope of the present invention.

[0155] It should be noted that the execution order of operations, procedures, steps, and stages in the apparatus, systems, programs, and methods shown in the claims, specifications, and drawings is not explicitly stated as "before," "prior to," etc., and that these can be implemented in any order unless the output of a previous process is used in a later process. Even if the operation flow in the claims, specifications, and drawings is described using phrases such as "first," "next," etc. for convenience, it does not mean that it is essential to perform the operations in that order. [Explanation of Symbols]

[0156] 10...Semiconductor substrate, 11...Well region, 12...Emitter region, 14...Base region, 15...Contact region, 16...Storage region, 18...Drift region, 20...Buffer region, 21...Top surface, 22...Collector region, 23...Bottom surface, 24...Collector electrode, 29...Straight section, 30...Dummy trench section, 31...Tip section, 32...Dummy insulating film, 34...Dummy conductive section, 38...Interlayer insulating film, 39...Straight section, 40...Gate trench section, 41...Tip section, 42...Gate insulating film, 44...Gate conductive section, 52...Emitter Electrode, 54...Contact hole, 60, 61...Mesa region, 70...Transistor region, 80...Diode region, 81...Extended region, 82...Cathode region, 90...Edge termination structure, 100...Semiconductor device, 130...Outer periphery gate wiring, 131...Active side gate wiring, 160...Active region, 162...Edge, 164...Gate pad, 201...Lower region, 202...Upper region, 211...Doping concentration peak, 213...Second doping concentration peak, 221...Hydrogen peak, 231...Flat region, 232...Oxygen peak, 242...Carbon peak

Claims

[Claim 1] A semiconductor device comprising a semiconductor substrate having an upper surface and a lower surface, The semiconductor substrate has one or more hydrogen peaks, which are peaks of hydrogen chemical concentration, in the depth direction, and one or more of the hydrogen peaks include the deepest peak furthest from the bottom surface of the semiconductor substrate. The semiconductor substrate has a lower region from the bottom surface to the deepest peak and an upper region located from the deepest peak to the top surface. The concentration in the lower region is at least twice the concentration in the upper region for at least one of the carbon chemical concentration and the oxygen chemical concentration. Semiconductor equipment.

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