Patent ID: 12261058

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all combinations of features described in the embodiments are essential to the solution of the invention.

In the present specification, one side in a direction parallel to the depth direction of the semiconductor substrate is referred to as “upper”, and the other side is referred to as “lower”. One of two main surfaces of a substrate, a layer, or another member is referred to as an upper surface, and the other surface is referred to as a lower surface. The “upper” and “lower” directions are not limited to the gravity direction or the direction at the time of mounting the semiconductor device.

In the present specification, technical matters may be described using orthogonal coordinate axes of an X axis, a Y axis, and a Z axis. The orthogonal coordinate axes merely identify relative positions of the components, and do not limit a specific direction. For example, the Z axis does not limit the height direction with respect to the ground. The +Z axis direction and the −Z axis direction are opposite to each other. When the positive and negative are not described and described as the Z axis direction, it means a direction parallel to the +Z axis and the −Z axis.

In the present specification, orthogonal axes parallel to the upper surface and the lower surface of the semiconductor substrate are defined as an X axis and a Y axis. An axis perpendicular to the upper surface and the lower surface of the semiconductor substrate is defined as a Z axis. In the present specification, the Z axis direction may be referred to as a depth direction. In addition, in the present specification, a direction parallel to the upper surface and the lower surface of the semiconductor substrate including the X axis and the Y axis may be referred to as a horizontal direction.

In addition, a region from the center of the semiconductor substrate in the depth direction to the upper surface of the semiconductor substrate may be referred to as an upper surface side. Similarly, a region from the center of the semiconductor substrate in the depth direction to the lower surface of the semiconductor substrate may be referred to as a lower surface side.

In the present specification, the term “same” or “equal” may include a case where there is an error due to manufacturing variation or the like. The error is, for example, within 10%.

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

In the present specification, the doping concentration means the concentration of the donor or the concentration of the acceptor in the thermal equilibrium state. In the present specification, the net doping concentration means the net concentration obtained by adding the donor concentration as the concentration of positive ions and the acceptor concentration as the concentration of negative ions including the polarity of charges. As an example, when the donor concentration is NDand the acceptor concentration is NA, the net doping concentration at an arbitrary position is ND−NA. In the present specification, the net doping concentration may be simply referred to as a doping concentration.

The donor has a function of supplying electrons to the semiconductor. The acceptor has a function of receiving electrons from the semiconductor. The donor and acceptor are not limited to the impurities themselves. For example, a VOH defect in which vacancies (V), oxygen (O), and hydrogen (H) are attached in a semiconductor works as a donor for supplying electrons. The VOH defect may be referred to herein as a hydrogen donor.

In the present specification, when described as a P+ type or an N+ type, it means that the doping concentration is higher than that of a P type or an N type, and when described as a P− type or an N− type, it means that the doping concentration is lower than that of the P type or the N type. In addition, in the present specification, the description of the P++ type or the N++ type means that the doping concentration is higher than that of the P+ type or the N+ type. The unit system in this specification is an SI unit system unless otherwise specified. The unit of length may be expressed in cm, but various calculations may be performed after conversion into meters (m).

In the present specification, the chemical concentration refers to the atomic density of impurities measured regardless of the state of electrical activation. The chemical concentration can be measured by, for example, secondary ion mass spectrometry (SIMS). The above-described net doping concentration can be measured by a voltage-capacitance measurement method (CV method). In addition, the carrier concentration measured by a spread resistance measurement method (SR method) may be a net doping concentration. The carrier concentration measured by the CV method or the SR method may be a value in a thermal equilibrium state. In addition, since the donor concentration is sufficiently larger than the acceptor concentration in a region of the N type, the carrier concentration in the region may be used as the donor concentration. Similarly, in a region of the P type, the carrier concentration in the region may be set as the acceptor concentration. In the present specification, the doping concentration of the region of the N type may be referred to as a donor concentration, and the doping concentration of the region of the P type may be referred to as an acceptor concentration.

In addition, when the concentration distribution of the donor, acceptor, or net doping has a peak, the peak value may be the concentration of the donor, acceptor, or net doping in the region. In a case where the concentration of the donor, the acceptor, or the net doping is substantially uniform or the like, an average value of the concentration of the donor, the acceptor, or the net doping in the corresponding region may be used as the concentration of the donor, the acceptor, or the net doping. In the present specification, atoms/cm3or/cm3is used for concentration display per unit volume. This unit is used for the donor or acceptor concentration or the chemical concentration in the semiconductor substrate. The expression of atoms may be omitted.

The carrier concentration measured by the SR method may be lower than the concentration of the donor or the acceptor. In a range where the current flows when measuring a spreading resistance, there is a case where the carrier mobility of the semiconductor substrate is lower than the value of the crystal state. The decrease in carrier mobility occurs by disorder of the crystal structure caused by a lattice defect or the like to make the carrier scatter.

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

FIG.1Ais a cross-sectional view illustrating an example of a semiconductor device100. The semiconductor device100includes a semiconductor substrate10. The semiconductor substrate10is a substrate formed of a semiconductor material. As an example, the semiconductor substrate10is a silicon substrate.

At least one of a transistor device such as an insulated gate bipolar transistor (IGBT) and a diode device such as a freewheeling diode (FWD) is formed on the semiconductor substrate10. InFIG.1A, the respective electrodes of the transistor device and the diode device, and the respective regions provided in the semiconductor substrate10are omitted. Configuration examples of the transistor device and the diode device will be described later.

In the semiconductor substrate10of this example, bulk donors of the N type are distributed throughout. The bulk donor is a dopant donor substantially uniformly contained in an ingot during the production of the ingot from which the semiconductor substrate10is based. The bulk donor of this example is an element other than hydrogen. The dopant of the bulk donor is, for example, phosphorus, antimony, arsenic, selenium, or sulfur, but the invention is not limited to these. The bulk donor of this example is phosphorus. The bulk donor is also contained in the region of the P type. The semiconductor substrate10may be a wafer cut out of a semiconductor ingot, or may be a chip obtained by cutting a wafer into individual pieces. The semiconductor ingot may be manufactured by either a Czochralski method (CZ method), a magnetic field applied Czochralski method (MCZ method), or a float zone method (FZ method). The ingot in this example is manufactured by the MCZ method. The substrate manufactured by the MCZ method has an oxygen concentration of 1×1017to 7×1017/cm3. The oxygen concentration contained in the substrate manufactured by the FZ method is 1×1015to 5×1016/cm3. When the oxygen concentration is high, hydrogen donors tend to be easily generated. As the bulk donor concentration, the chemical concentration of the bulk donor distributed throughout the semiconductor substrate10may be used, or a value between 90% to 100% of the chemical concentration may be used. As the semiconductor substrate10, a non-doped substrate not containing a dopant such as phosphorus may be used. In that case, the bulk donor concentration (D0) of the non-doped substrate is, for example, from 1×1010/cm3to 5×1012/cm3. The bulk donor concentration (D0) of the non-doped substrate is preferably 1×1011/cm3or more. The bulk donor concentration (D0) of the non-doped substrate is preferably 5×1012/cm3or less. Each concentration in the present invention may be a value at room temperature. As the value at room temperature, a value at 300 K (Kelvin) (about 26.9° C.) may be used as an example.

The semiconductor substrate10has an upper surface21and a lower surface23. The upper surface21and the lower surface23are two main surfaces of the semiconductor substrate10. In the present specification, an orthogonal axis in a plane parallel to the upper surface21and the lower surface23is defined as an X axis and a Y axis, and an axis perpendicular to the upper surface21and the lower surface23is defined as a Z axis.

Hydrogen ions (for example, protons) are implanted into the semiconductor substrate10from the lower surface23so as to penetrate the semiconductor substrate10. The average distance (also referred to as a range) over which hydrogen ions pass through the inside of the semiconductor substrate10can be controlled by acceleration energy for accelerating hydrogen ions. In this example, the acceleration energy is set such that the range of hydrogen ions is larger than the thickness of the semiconductor substrate10. Hydrogen ions may be accelerated with acceleration energy that is twice or more the acceleration energy corresponding to the thickness of the semiconductor substrate10.

In the semiconductor substrate10, some hydrogen ions remain in a region through which hydrogen ions have passed. Therefore, by implanting hydrogen ions so as to penetrate the semiconductor substrate10, hydrogen can be distributed over the entire semiconductor substrate10.

In the present specification, a region through which the implanted hydrogen ions have passed may be referred to as a pass-through region. In the example ofFIG.1A, the entire semiconductor substrate10is the pass-through region. In another example, hydrogen ions may penetrate only a partial region of the semiconductor substrate10in the XY plane. As a result, hydrogen ions can be locally implanted.

In the pass-through region through which the hydrogen ions have passed in the semiconductor substrate10, lattice defects mainly including vacancies such as monatomic vacancies (V) and divacancies (VV) are formed by the passage of hydrogen. Atoms adjacent to the vacancies have dangling bonds. The lattice defect also includes inter-lattice atoms, dislocates, or the like, and in a broader way donors and acceptors can also be included. However, in the present specification, the lattice defect mainly composed of vacancies may be called a lattice defect of a vacancy type, a vacancy defect, or simply a lattice defect. In the present specification, the concentration of lattice defects mainly including vacancies may be referred to as a vacancy concentration. In addition, since a large number of lattice defects are formed due to the implantation of hydrogen ions into the semiconductor substrate10, the crystallinity of the semiconductor substrate10may be strongly disturbed. In the present specification, the crystallinity disturbance may be called a disorder.

In addition, oxygen is contained in the entire semiconductor substrate10. The oxygen is introduced intentionally or unintentionally at the time of manufacturing a semiconductor ingot. In the semiconductor substrate10, hydrogen (H), a vacancy (V), and oxygen (O) are attached to form a VOH defect. In addition, the heat treatment of the semiconductor substrate10diffuses hydrogen to promote the formation of VOH defects. The VOH defect works as a donor that supplies electrons. In the present specification, the VOH defect may be simply called as a hydrogen donor.

In the semiconductor substrate10of this example, hydrogen donors are formed in the pass-through region of hydrogen ions. The hydrogen donor in the pass-through region is formed by terminating hydrogen at a dangling bond of a lattice defect of a vacancy type formed in the pass-through region and further bonding to oxygen. Therefore, the doping concentration distribution of the hydrogen donor in the pass-through region may follow a vacancy concentration distribution. The hydrogen chemical concentration in the pass-through region may be 10 times or more, or 100 times or more of the vacancy concentration formed in the pass-through region. The hydrogen in the pass-through region may be hydrogen remaining after the passage of hydrogen ions, or may be hydrogen diffused from a hydrogen supply source described later. The doping concentration of the hydrogen donor is lower than the chemical concentration of hydrogen. When the ratio of the doping concentration of the hydrogen donor to the chemical concentration of hydrogen is defined as an activation rate, the activation rate may be a value of 0.1% to 30%. In this example, the activation rate is 1% to 5%.

By forming a hydrogen donor in the pass-through region of the semiconductor substrate10, the donor concentration in the pass-through region can be made higher than the bulk donor concentration. Usually, it is necessary to prepare the semiconductor substrate10having a predetermined bulk donor concentration in accordance with characteristics of an element to be formed in the semiconductor substrate10, particularly a rated voltage or a withstand voltage. On the other hand, according to the semiconductor device100illustrated inFIG.1A, the donor concentration of the semiconductor substrate10can be adjusted by controlling the dosage of hydrogen ions. Therefore, the semiconductor device100can be manufactured using a semiconductor substrate having a bulk donor concentration that does not correspond to the characteristics and the like of the element. The variation in the bulk donor concentration at the time of manufacturing the semiconductor substrate10is relatively large, but the dosage of hydrogen ions can be controlled with relatively high accuracy. Therefore, the concentration of lattice defects generated by implanting hydrogen ions can also be controlled with high accuracy, and the donor concentration of the pass-through region can be controlled with high accuracy.

FIG.1Billustrates an example of a distribution of hydrogen chemical concentration Dh, a distribution of donor concentration Dd, and a distribution of concentration Db of a termination dangling bond terminated with hydrogen in the depth direction at a position indicated by line A-A inFIG.1A. InFIG.1B, the horizontal axis represents the depth position from the lower surface23, and the vertical axis represents the concentration per unit volume on a logarithmic axis. The donor concentration inFIG.1Bis measured by, for example, the CV method or the SR method. The hydrogen chemical concentration inFIG.1Bis, for example, a hydrogen concentration measured by the SIMS method. The concentration of termination dangling bonds is the concentration of VOH defects described above and is the concentration of hydrogen donors. The termination dangling bond concentration may be a concentration obtained by subtracting the concentration of donors other than hydrogen from the donor concentration measured by the SR method or the like. The concentration of donors other than hydrogen is, for example, the concentration of impurities of the N type such as phosphorus. As an example, the concentration of donors is a concentration obtained by subtracting a bulk donor concentration D0from the donor concentration measured by the SR method or the like. InFIG.1B, the hydrogen chemical concentration Dh is indicated by a broken line, and the donor concentration Dd and the termination dangling bond Db are indicated by a solid line. InFIG.1B, the bulk donor concentration is D0. Further, the center position of the semiconductor substrate10in the depth direction is defined as Zc. In addition, the hydrogen chemical concentration in the lower surface23of the semiconductor substrate10is denoted by Dh1, the donor concentration is denoted by Dd1, the termination dangling bond concentration is denoted by Db1, the hydrogen chemical concentration in the upper surface21is denoted by Dh2, the donor concentration is denoted by Dd2, and the termination dangling bond concentration is denoted by Db2. The bulk donor concentration is D0for both the lower surface23and the upper surface21.

The distribution of the hydrogen chemical concentration Dh may be flat, monotonically increasing, or monotonically decreasing from the lower surface23to the upper surface21of the semiconductor substrate10, except for a portion where a local hydrogen concentration peak is provided. In this example, the distribution of the hydrogen chemical concentration increases monotonically. A local hydrogen concentration peak210is, for example, a hydrogen concentration peak formed by implanting hydrogen ions in a range smaller than half the thickness of the semiconductor substrate10.

InFIG.1B, as an additional example, a local peak in the hydrogen concentration or the like is indicated by a dashed line. The local hydrogen concentration peak210is, for example, a hydrogen concentration peak210formed by implanting hydrogen ions from the lower surface23of the semiconductor substrate10to a region on the lower surface23side of the semiconductor substrate10. In the hydrogen concentration peak210due to hydrogen ions having a small range, the half-value width of the distribution becomes relatively small. The half-value width of the local peak in each concentration distribution may be 1/10 or less or 1/20 or less of the thickness of the semiconductor substrate10. A plurality of hydrogen concentration peaks210may be present in the semiconductor substrate10. When the hydrogen concentration peak210is in the vicinity of the lower surface23and has a high hydrogen concentration, it may be a hydrogen supply source. If the local hydrogen concentration peak210is present, the donor concentration Dd may also have a local peak211at the same depth position and the termination dangling bond Db may also have a local peak212.

When hydrogen ions are implanted, damage is introduced into a region from the implantation surface of the semiconductor substrate10to a range portion of the hydrogen ions. The damage refers to disturbance of a crystal lattice, and may be in an amorphous state in addition to vacancies and dislocations.FIG.1Billustrates an example of the distribution of the vacancy concentration Dv after hydrogen ions are implanted through the semiconductor substrate10. In the vacancy concentration Dv inFIG.1B, the vacancy concentration peak corresponding to the local hydrogen concentration peak210is omitted. Here, the term “after the implantation of hydrogen ions” means from the implantation of hydrogen ions to before the first heat treatment at a temperature higher than room temperature. In a region deeper than the implantation surface (the lower surface23in this example) of hydrogen ions, the concentration of vacancies may be flat, monotonically increasing, or monotonically decreasing from the lower surface23to the upper surface21of the semiconductor substrate10. In this example, the concentration of vacancies increases monotonically. InFIG.1B, the vacancy concentration in the lower surface23is denoted by Dv1, and the vacancy concentration in the upper surface21is denoted by Dv2.

Hydrogen terminates the dangling bonds in the vacancies by heat treatment after the implantation of hydrogen ions. As a result, donors of VOH defects (termination dangling bonds) are formed. Since the vacancy concentration is often smaller than the hydrogen chemical concentration and the oxygen chemical concentration, the distribution of the termination dangling bond concentration Db is mainly limited by the distribution of the vacancy concentration. As a result, the distribution of the termination dangling bond concentration is flat, monotonically increases, or monotonically decreases from the lower surface23to the upper surface21of the semiconductor substrate10except for a local peak. When a portion of the local hydrogen concentration peak is excluded from the distribution of the hydrogen chemical concentration Dh, the distribution of the hydrogen chemical concentration Dh of the portion may be replaced with a straight line. Similarly, when a local peak portion is removed from each concentration distribution, the concentration distribution of the portion may be replaced with a straight line.

InFIG.1B, the hydrogen chemical concentration in the lower surface23when not affected by the local hydrogen concentration peak210is denoted by Dh1a, and the hydrogen chemical concentration in the lower surface23when affected by the local hydrogen concentration peak210is denoted by Dh1b. Further, inFIG.1B, the donor concentration in the lower surface23when not affected by the local hydrogen concentration peak210is denoted by Dd1a, and the donor concentration in the lower surface23when affected by the local hydrogen concentration peak210is denoted by Dd1b. Further, inFIG.1B, the termination dangling bond concentration in the lower surface23when not affected by the local hydrogen concentration peak210is denoted by Db1a, and the termination dangling bond concentration in the lower surface23when affected by the local hydrogen concentration peak210is denoted by Db1b.

When the variation range of the concentration distribution in a predetermined region is 30% or less of the average value of the concentrations at both ends of the region, the distribution in the region may be flat. The above-described ratio may be 20% or less or 10% or less. The variation range of the concentration distribution is a difference between the maximum value and the minimum value of the concentration in the region.

In this example, the distribution of the hydrogen chemical concentration Dh is flat from the lower surface23to the entire upper surface21except for a local hydrogen concentration peak. That is, the variation range of the hydrogen chemical concentration distribution from the lower surface23to the upper surface21is 30% or less of the average value of the hydrogen chemical concentration Dh1in the lower surface23and the hydrogen chemical concentration Dh2in the upper surface21.

The semiconductor substrate10may be provided with a hydrogen supply source in the vicinity of at least one of the upper surface21and the lower surface23. The hydrogen supply source of this example is an example of the local hydrogen concentration peak210. The hydrogen supply source (local hydrogen concentration peak210) may be provided at a depth within 5 μm from the upper surface21or the lower surface23of the semiconductor substrate10. In order for hydrogen to terminate the dangling bond in the pass-through region of hydrogen ions, it is preferable that sufficient hydrogen exists in the pass-through region. By providing the hydrogen supply source, a large amount of hydrogen is diffused from the hydrogen supply source toward the inside of the semiconductor substrate10. As a result, the dangling bond can be efficiently terminated with hydrogen in the pass-through region.

A distribution obtained by connecting the concentrations at both ends of the predetermined region with a straight line may be a linear approximation distribution. The linear approximation distribution may be a straight line obtained by fitting a concentration in a predetermined region with a linear function. In addition, the linear approximation distribution may be a straight line obtained by fitting a distribution excluding local peaks of each concentration distribution with a linear function. Further, a range of a band shape having a width of 30% of the value of the linear approximation distribution around the linear approximation distribution is referred to as a band-shaped range. The monotonically increasing or decreasing concentration distribution in a predetermined region refers to a state in which the concentration values at both ends of the predetermined region are different and the concentration distribution is included in the band-shaped range described above. The band-shaped range may have a width of 20% or 10% of the value of the linear approximation distribution.

FIG.2Ais a cross-sectional view illustrating an example of semiconductor device100. The semiconductor device100includes a semiconductor substrate10.FIG.2Ais different fromFIG.1Ain that hydrogen ions (for example, protons) are implanted so as to penetrate the semiconductor substrate10from the upper surface21of the semiconductor substrate10. The other configurations may be the same as those inFIG.1A.

FIG.2Billustrates an example of the distribution of the hydrogen chemical concentration Dh, the distribution of the donor concentration Dd, and the distribution of the concentration Db of the termination dangling bond terminated with hydrogen in the depth direction at the position indicated by line A-A inFIG.2A.FIG.2Bis different fromFIG.1Bin that the concentrations of Dh, Dd, Db, and Dv increase from the upper surface21toward the lower surface23. The other configurations may be the same as those inFIG.1B.

The distribution of the hydrogen chemical concentration Dh may be flat, monotonically increasing, or monotonically decreasing from the lower surface23to the upper surface21of the semiconductor substrate10, except for a portion where a local hydrogen concentration peak is provided. In this example, the distribution of the hydrogen chemical concentration monotonously decreases toward the upper surface21. The vacancy concentration distribution Dv2may monotonously decrease from the lower surface23toward the upper surface21that is the implantation surface. Similarly to the vacancy concentration distribution Dv2, the doping concentration Dd2may monotonously decrease from the lower surface23toward the upper surface21.

FIG.2Cillustrates another example of the distribution of the hydrogen chemical concentration Dh, the distribution of the donor concentration Dd, and the distribution of the concentration Db of the termination dangling bond terminated with hydrogen in the depth direction at the position indicated by line A-A inFIG.2A.FIG.2Cis different fromFIG.1Bin that the concentrations of Dh, Dd, Db, and Dv do not substantially increase or decrease from the upper surface21toward the lower surface23, that is, are substantially uniform or flat. The other configurations may be the same as those inFIG.1B. The hydrogen ions may be implanted from the upper surface21or may be implanted from the lower surface23. The range uniquely determined by the acceleration energy of hydrogen ions may be sufficiently larger than the thickness of the semiconductor substrate10. The range uniquely determined by the acceleration energy of hydrogen ions may be 2 times or more, 3 times or more, or 5 times or more of the thickness of the semiconductor substrate10.

FIG.3is a distribution example of the bulk donor concentration D0, the termination dangling bond concentration Db, and the donor concentration Dd. The thickness of the semiconductor substrate10of this example is 120 μm. The vertical axis in this drawing is a linear scale. The depth of 20 μm to 80 μm from the implantation surface of hydrogen ions is defined as a predetermined region. The predetermined region is a region through which hydrogen ions penetrate and in which there is no local peak in the donor concentration Dd. The thickness of the predetermined region in this example is 50% of the thickness of the semiconductor substrate10. The bulk donor concentration D0in this example is 3.1×1013/cm3, corresponding to 150 Ωcm. The sum of the bulk donor concentration D0at each depth and the value of the termination dangling bond Db is the donor concentration Dd.

A linear approximation distribution214of the donor concentration Dd is a distribution in which the concentration increases as the distance from the implantation surface increases. In this example, in a predetermined region through which hydrogen ions penetrate, the donor concentration Dd varies by about ±7% with respect to the linear approximation distribution214. The variation of the donor concentration Dd is defined as a band-shaped range216. That is, the width of the band-shaped range216in this example is ±7% of the value of the linear approximation distribution214. In a predetermined region having a thickness of 30% or more of the thickness of the semiconductor substrate10, when the distribution of the donor concentration Db exists within the band-shaped range216, the distribution of the donor concentration Db may be a flat distribution. That is, the predetermined region may be a termination dangling bond flat region.

FIG.4is another example of the distribution of the bulk donor concentration D0, the termination dangling bond concentration Db, and the donor concentration Dd. In this example, the depth position of the predetermined region, the distribution of the termination dangling bond concentration Db, and the distribution of the donor concentration Dd are different from those inFIG.3. In this example, a region from 10 μm to 70 μm in depth from the implantation surface of hydrogen ions is defined as a predetermined region. Also in this example, the thickness of the predetermined region with respect to the thickness (120 μm) of the semiconductor substrate10is 50%, which is the same as the example ofFIG.3.

The linear approximation distribution214of the donor concentration Dd is a distribution in which the concentration increases as the distance from the implantation surface increases. However, the linear approximation distribution214of this example has a larger slope of increase than the linear approximation distribution214ofFIG.3. In addition, in a predetermined region, the donor concentration Dd varies by about ±17% with respect to the linear approximation distribution214. The variation of the donor concentration Dd is defined as a band-shaped range216. The width of the band-shaped range216is ±17% of the value of the linear approximation distribution214. Therefore, in a predetermined region having a thickness of 30% or more of the thickness of the semiconductor substrate10, when the distribution of the donor concentration Db exists within the band-shaped range216, the distribution of the donor concentration Db may be a flat distribution. That is, this predetermined region may be a termination dangling bond flat region.

The termination dangling bond flat region may be provided in a range of 40% or more, a range of 20% or more, or a range of 10% or more of the thickness of the semiconductor substrate. The termination dangling bond flat region may be provided in a range of 60% or less, a range of 70% or less, a range of 80% or less, or a range of 90% or less of the thickness of the semiconductor substrate. The absolute value of the slope of the linear approximation distribution214in the termination dangling bond flat region may be from 0/(cm3·μm) to 2×1012/(cm3·μm), or may be larger than 0/(cm3·μm) and 1×1012/(cm3·μm) or less with respect to the depth (μm). Furthermore, the absolute value of the slope of the linear approximation distribution214in the termination dangling bond flat region may be from 1×1010/(cm3·μm) to 1×1012/(cm3·μm), and may be from 1×1010/(cm3·μm) 5×1011/(cm3·μm) with respect to the depth (μm). Here, 5×1011/(cm3·μm) is the same slope (equivalent) as 5×1015/cm4.

A semi-logarithmic slope may be used as another index of the slope of the linear approximation distribution214. The position of one end of a predetermined region is defined as x1(cm), and the position of the other end is defined as x2(cm). The concentration at x1is denoted by N1(/cm3), and the concentration at x2is denoted by N2(/cm3). A semi-logarithmic slope η (/cm) in a predetermined region is defined as η=(log10(N2)−log10(N1))/(x2−x1). The absolute value of the semi-logarithmic slope η of the linear approximation distribution214in the termination dangling bond flat region may be from 0/cm to 50/cm, and may be from 0/cm 30/cm. Furthermore, the absolute value of the semi-logarithmic slope η of the linear approximation distribution214in the termination dangling bond flat region may be from 0/cm to 20/cm, and may be from 0/cm 10/cm. In the termination dangling bond flat region, a donor concentration flat region in which the concentration distribution is substantially flat may be provided for the donor concentration. The slope in the donor concentration flat region may be the same as the slope in the termination dangling bond flat region. The semi-logarithmic slope in the donor concentration flat region may be the same as the semi-logarithmic slope in the termination dangling bond flat region.

In the distribution of the hydrogen chemical concentration Dh illustrated inFIG.1B, the difference between the hydrogen chemical concentration Dh1in the lower surface23and the hydrogen chemical concentration Dh2in the upper surface21may be 50% or less, 30% or less, or 10% or less of the average value of Dh1and Dh2. As the difference is smaller, the donor concentration of the semiconductor substrate10can be made uniform. The larger the range of hydrogen ions is, the smaller the difference can be made.

In the pass-through region through which hydrogen ions have passed, it is considered that vacancies (V, VV, etc) generated by passing of hydrogen are distributed at approximately uniform concentration in the depth direction. In addition, oxygen (O) implanted at the time of manufacturing the semiconductor substrate10or the like is also considered to be uniformly distributed in the depth direction. On the other hand, in the process of manufacturing the semiconductor device100, oxygen may diffuse from the upper surface21or the lower surface23of the semiconductor substrate10to the outside of the semiconductor substrate10in the process of performing the high temperature treatment of 1100° C. or higher. As a result, the oxygen concentration may decrease toward the upper surface21or the lower surface23of the semiconductor substrate10.

In this example, hydrogen is approximately uniformly distributed from the lower surface23to the entire upper surface21of the semiconductor substrate10. Therefore, termination dangling bonds (that is, VOH defects) are approximately uniformly distributed over the entire semiconductor substrate10. The semiconductor substrate10may be provided with a termination dangling bond flat region in which the concentration of the termination dangling bonds is flat, monotonically increases, or monotonically decreases. The definition of flat, monotonic increase or monotonic decrease in the termination dangling bond concentration distribution is the same as the example of the hydrogen chemical concentration distribution. In addition, a region where the hydrogen chemical concentration is more than 100 times the bulk donor concentration and both the hydrogen chemical concentration distribution and the donor concentration distribution are flat or monotonically increase or decrease may be used as the termination dangling bond flat region.

In the example ofFIG.1B, the termination dangling bond flat region is provided over the entire semiconductor substrate10in the depth direction, but the termination dangling bond flat region may be provided in a part of the semiconductor substrate10. For example, in a region in which hydrogen ions are locally implanted, such as a buffer region described later, the termination dangling bond concentration also has a local peak. A region other than the region into which hydrogen ions are locally implanted may be a termination dangling bond flat region. In the semiconductor substrate10, the termination dangling bond flat region may be continuously provided over a range from 30% to 80% of the thickness of the semiconductor substrate10in the depth direction. The termination dangling bond flat region may be provided over 50% or more, 60% or more, or 70% or more of the thickness of the semiconductor substrate10.

The concentration of the termination dangling bonds can be controlled with high accuracy by the dosage of hydrogen ions. As a result, the donor concentration can be accurately controlled over the entire semiconductor substrate10. The donor concentration of the semiconductor substrate10is higher than the bulk donor concentration throughout the upper surface21to the lower surface23.

The hydrogen supply source (local hydrogen concentration peak)210illustrated inFIG.1Bhas a hydrogen chemical concentration higher than the hydrogen chemical concentration of the linear approximation distribution214in the termination dangling bond flat region. The maximum value of the hydrogen chemical concentration of the hydrogen supply source may be 10 times or more, or 100 times or more of the hydrogen chemical concentration of the linear approximation distribution214. The hydrogen chemical concentration of the hydrogen supply source may be 1×1016/cm3or more, 1×1017/cm3or more, or 1×1018/cm3or more.

FIG.5is a diagram for explaining a semiconductor device200according to a comparative example. The semiconductor device200implants hydrogen ions from the lower surface23of the semiconductor substrate10into a region on the upper surface21side of the semiconductor substrate10. That is, the range of hydrogen ions is smaller than the thickness of the semiconductor substrate10and larger than half of the thickness. As an example, the range of hydrogen ions is smaller than ¾ of the thickness of the semiconductor substrate10and larger than half of the thickness.

FIG.6illustrates the distribution of the hydrogen chemical concentration Dh, the distribution of the donor concentration Dd, and the distribution of the concentration Db of the termination dangling bond terminated with hydrogen in the depth direction at the position indicated by line B-B inFIG.5. When a range of hydrogen ions is arranged in the semiconductor substrate10, a large amount of hydrogen is implanted in the vicinity of the range. Therefore, the hydrogen chemical concentration distribution has a concentration peak201in the vicinity of the range. Similarly, the termination dangling bond concentration distribution has a concentration peak203and the donor concentration distribution has a concentration peak202.

In this example, hydrogen ions are implanted from the lower surface23to a deep position away from the lower surface23of the semiconductor substrate10. As a result, the donor concentration can be adjusted in a wide range in the depth direction of the semiconductor substrate10. However, in each concentration distribution, a concentration peak having a relatively large half-value width occurs.

As described above, when the range of hydrogen ions is arranged inside the semiconductor substrate10, the hydrogen chemical concentration distribution is not flattened, and an unnecessary peak is generated in the donor concentration. Therefore, the peak may affect the characteristics of the semiconductor device100. On the other hand, according to the example described inFIG.1AtoFIG.2B, since the range of hydrogen ions is arranged outside the semiconductor substrate10, the hydrogen chemical concentration distribution can be flattened. Therefore, generation of an unnecessary peak in the donor concentration can be suppressed.

Even when the range of hydrogen ions is matched with the upper surface21of the semiconductor substrate10, each concentration distribution has a peak at the position of the upper surface21. For this reason, it is difficult to planarize the donor concentration, the hydrogen chemical concentration distribution, and the like up to the upper surface21.

FIG.7is a diagram for explaining the semiconductor device200according to a comparative example. The semiconductor device200implants hydrogen ions from the lower surface23of the semiconductor substrate10to a region on the upper surface21side of the semiconductor substrate10, and also implants hydrogen ions from the upper surface21of the semiconductor substrate10to a region on the lower surface23side of the semiconductor substrate10. As an example, the range of hydrogen ions is smaller than ¾ of the thickness of the semiconductor substrate10and larger than half of the thickness.

FIG.8illustrates the distribution of the hydrogen chemical concentration Dh, the distribution of the donor concentration Dd, and the distribution of the concentration Db of the termination dangling bond terminated with hydrogen in the depth direction at the position indicated by line C-C inFIG.7. InFIG.8, a hydrogen chemical concentration distribution by hydrogen ions implanted onto the lower surface23side is defined as a distribution a, and a hydrogen chemical concentration distribution by hydrogen ions implanted onto the upper surface21side is defined as a distribution b. The distribution a has a concentration peak on the lower surface23side, and the distribution b has a concentration peak on the upper surface21side.

The hydrogen chemical concentration distribution of the semiconductor substrate10is a distribution obtained by synthesizing the distribution a and the distribution b. Thus, the hydrogen chemical concentration distribution has two concentration peaks201. Similarly, the termination dangling bond concentration distribution and the donor concentration distribution each have two concentration peaks (202,203).

By implanting hydrogen ions from different planes, the hydrogen chemical concentration distribution becomes nearly flat, but the concentration peaks201near the respective ranges remain. For this reason, it is difficult to flatten the donor concentration distribution and the like. On the other hand, according to the example described inFIG.1AtoFIG.2B, since the range of hydrogen ions is arranged outside the semiconductor substrate10, the hydrogen chemical concentration distribution can be flattened. Therefore, generation of an unnecessary peak in the donor concentration can be suppressed.

FIG.9is a top view illustrating an example of the semiconductor device100.FIG.9illustrates a position where each member is projected on the upper surface of the semiconductor substrate10. InFIG.9, only some members of the semiconductor device100are illustrated, and some members are omitted.

The semiconductor device100includes the semiconductor substrate10. The semiconductor substrate10may have the hydrogen chemical concentration distribution, the termination dangling bond concentration distribution, and the donor concentration distribution described inFIG.1AtoFIG.8. However, the semiconductor substrate10may further have another concentration peak different from each concentration peak described inFIG.1AtoFIG.8. As in a buffer region20to be described later, hydrogen ions may be implanted to form a region of the N type in the semiconductor substrate10. In this case, the hydrogen chemical concentration distribution may have a local hydrogen concentration peak in addition to the hydrogen chemical concentration distribution described inFIG.1AtoFIG.8. Further, as in the emitter region12to be described later, an impurity of the N type other than hydrogen such as phosphorus may be implanted to form a region of the N type in the semiconductor substrate10. In this case, the donor concentration distribution may have a local donor concentration peak in addition to the donor concentration distribution described inFIG.1AtoFIG.8.

The semiconductor substrate10has an edge162in a top view. In the case of simply mentioning “in a top view” in the present specification, it means viewing from the upper surface side of the semiconductor substrate10. The semiconductor substrate10of this example includes two sets of edges162facing each other in a top view. InFIG.9, the X axis and the Y axis are parallel to any one of the edges162. In addition, the Z axis is perpendicular to the upper surface of the semiconductor substrate10.

The semiconductor substrate10is provided with an active portion160. The active portion160is a region in which a main current flows in the depth direction, between the upper surface and the lower surface of the semiconductor substrate10in a case where the semiconductor device100operates. An emitter electrode is provided above the active portion160, but is omitted inFIG.9.

In the active portion160, there is provided at least one of a transistor portion70which includes a transistor device such as an IGBT, and a diode portion80which includes a diode device such as a freewheeling diode (FWD). In the example ofFIG.9, the transistor portion70and the diode portion80are disposed alternately along a predetermined arrangement direction (the X axis direction in this example) in the upper surface of the semiconductor substrate10. In another example, only one of the transistor portion70and the diode portion80may be provided in the active portion160.

InFIG.9, Symbol “I” is attached to the region where the transistor portion70is disposed, and Symbol “F” is attached to the region where the diode portion80is disposed. In the present specification, a direction perpendicular to the arrangement direction in a top view may be referred to as an extending direction (the Y axis direction inFIG.9). Each of the transistor portion70and the diode portion80may have a longitudinal length in the extending direction. In other words, the length of the transistor portion70in the Y axis direction is larger than the width in the X axis direction. Similarly, the length of the diode portion80in the Y axis direction may be larger than the width in the X axis direction. The extending direction of the transistor portion70and the diode portion80and the longitudinal direction of each trench portion described later may be the same.

The diode portion80includes a cathode region of the N+ type in a region in contact with the lower surface of the semiconductor substrate10. In the present specification, the region where the cathode region is provided is referred to as the diode portion80. In other words, the diode portion80is a region overlapping with the cathode region in a top view. In the lower surface of the semiconductor substrate10, a collector region of the P+ type may be provided in the region other than the cathode region. In the present specification, an extension region81extending from the diode portion80to a gate runner to be described later in the Y axis direction may also be included in the diode portion80. In the lower surface of the extension region81, a collector region is provided.

The transistor portion70includes a collector region of the P+ type in a region in contact with the lower surface of the semiconductor substrate10. In addition, in the transistor portion70, there is periodically disposed a gate structure, which includes an emitter region of the N type, a base region of the P type, a gate conductive portion, and a gate insulating film, on the upper surface side on the semiconductor substrate10.

The semiconductor device100may include one or more pads on the upper side of the semiconductor substrate10. The semiconductor device100of this example includes a gate pad164. The semiconductor device100may include pads such as an anode pad, a cathode pad, and a current detection pad. Each pad is disposed in the vicinity of the edge162. The vicinity of the edge162indicates a region between the edge162and the emitter electrode in a top view. When mounting the semiconductor device100, each pad may be connected to an external circuit via a wiring such as a wire.

A gate potential is applied to the gate pad164. The gate pad164is electrically connected to the conductive portion of a gate trench portion of the active portion160. The semiconductor device100includes a gate runner that connects the gate pad164and the gate trench portion. InFIG.9, the gate runner is hatched with inclined lines.

The gate runner of this example includes an outer circumferential gate runner130and an active-side gate runner131. The outer circumferential gate runner130is disposed between the active portion160and the edge162of the semiconductor substrate10in a top view. The outer circumferential gate runner130of this example surrounds the active portion160in a top view. The region surrounding the outer circumferential gate runner130in a top view may be called the active portion160. In addition, the outer circumferential gate runner130is connected to the gate pad164. The outer circumferential gate runner130is disposed on the upper side of the semiconductor substrate10. The outer circumferential gate runner130may be a metal wiring containing aluminum or the like.

The active-side gate runner131is provided in the active portion160. With the provision of the active-side gate runner131in the active portion160, it is possible to reduce a variation in wiring length from the gate pad164in each region of the semiconductor substrate10.

The active-side gate runner131is connected to the gate trench portion of the active portion160. The active-side gate runner131is disposed on the upper side of the semiconductor substrate10. The active-side gate runner131may be a wiring formed of a semiconductor such as polysilicon doped with an impurity.

The active-side gate runner131may be connected to the outer circumferential gate runner130. The active-side gate runner131of this example is provided to extend in the X axis direction from one outer circumferential gate runner130in almost the center of the Y axis direction up to the other outer circumferential gate runner130so as to traverse the active portion160. In a case where the active portion160is divided by the active-side gate runner131, the transistor portion70and the diode portion80may be alternately disposed in the X axis direction in each divided region.

In addition, the semiconductor device100may be provided with a temperature sense portion (not illustrated) which is a PN junction diode formed of polysilicon or the like, and a current detection portion (not illustrated) which simulates the operation of the transistor portion provided in the active portion160.

The semiconductor device100of this example includes an edge termination structure portion90between the active portion160and the edge162in a top view. The edge termination structure portion90of this example is disposed between the outer circumferential gate runner130and the edge162. The edge termination structure portion90reduces an electric field strength on the upper surface side of the semiconductor substrate10. The edge termination structure portion90may be provided with at least one of a guard ring, a field plate, and a RESURF provided annularly around the active portion160.

FIG.10is an enlarged view of a region D inFIG.9. The region D is a region where the transistor portion70, the diode portion80, and the active-side gate runner131are included. The semiconductor device100of this example is provided with a gate trench portion40, a dummy trench portion30, a well region11, an emitter region12, a base region14, and a contact region15, which are provided in the inside on the upper surface side of the semiconductor substrate10. The gate trench portion40and the dummy trench portion30each are an example of the trench portion. In addition, the semiconductor device100of this example is provided with an emitter electrode52and the active-side gate runner131which are provided on the upper side of the upper surface of the semiconductor substrate10. The emitter electrode52and the active-side gate runner131are provided to be separated from each other.

An interlayer dielectric film is provided between the upper surface of the semiconductor substrate10and the emitter electrode52and the active-side gate runner131, but is omitted inFIG.10. In the interlayer dielectric film of this example, a contact hole54is provided to pass through the interlayer dielectric film. InFIG.10, each contact hole54is hatched with oblique lines.

The emitter electrode52is provided on the upper side of the gate trench portion40, the dummy trench portion30, the well region11, the emitter region12, the base region14, and the contact region15. The emitter electrode52is in contact with the emitter region12, the contact region15, and the base region14in the upper surface of the semiconductor substrate10through the contact hole54. In addition, the emitter electrode52is connected to a dummy conductive portion in the dummy trench portion30through the contact hole provided in the interlayer dielectric film. The emitter electrode52may be connected to the dummy conductive portion of the dummy trench portion30at the edge of the dummy trench portion30in the Y axis direction.

The active-side gate runner131is connected to the gate trench portion40through the contact hole provided in the interlayer dielectric film. The active-side gate runner131may be connected to a gate conductive portion of the gate trench portion40in an edge portion41of the gate trench portion40in the Y axis direction. The active-side gate runner131is not connected to the dummy conductive portion in the dummy trench portion30.

The emitter electrode52is formed of a material containing metal.FIG.10illustrates a range in which the emitter electrode52is provided. For example, at least a partial region of the emitter electrode52is formed of aluminum or an aluminum-silicon alloy, for example, a metal alloy such as AlSi or AlSiCu. The emitter electrode52may have a barrier metal formed of titan or a titan compound in the lower layer of the region formed of aluminum or the like. Further, in the contact hole, a plug formed with tungsten buried therein may be included to be in contact with the barrier metal, aluminum, or the like.

The well region11is provided to be overlapped with the active-side gate runner131. The well region11is provided to extend with a predetermined width even in a range where the active-side gate runner131is not overlapped. The well region11of this example is provided to be separated from the end of the contact hole54in the Y axis direction toward the active-side gate runner131. The well region11is a region of a second conductivity type in which its doping concentration is higher than that of the base region14. The base region14in this example is a P− type, and the well region11is a P+ type.

Each of the transistor portion70and the diode portion80includes a plurality of trench portions disposed in the arrangement direction. In the transistor portion70of this example, one or more gate trench portions40and one or more dummy trench portions30are alternately provided along the arrangement direction. In the diode portion80of this example, the plurality of dummy trench portions30are provided along the arrangement direction. In the diode portion80of this example, the gate trench portion40is not provided.

The gate trench portion40of this example may include two linear portions39(trench portions that are linear along the extending direction) extending along the extending direction perpendicular to the arrangement direction, and the edge portion41for connecting the two linear portions39. The extending direction inFIG.10is the Y axis direction.

At least a part of the edge portion41is desirably provided in a curved shape in a top view. The ends of two linear portions39in the Y axis direction are connected to the edge portion41, so that the electric field strength in the end portion of the linear portion39can be reduced.

In the transistor portion70, the dummy trench portion30is provided between the linear portions39of the gate trench portion40. Between the linear portions39, one dummy trench portion30may be provided, or a plurality of dummy trench portions30may be provided. The dummy trench portion30may be in a linear shape extending in the extending direction, or may include a linear portion29and an edge portion31similarly to the gate trench portion40. The semiconductor device100illustrated inFIG.10includes both the linear dummy trench portion30having no edge portion31, and the dummy trench portion30having the end portion31.

A diffusion depth of the well region11may be deeper than the depths of the gate trench portion40and the dummy trench portion30. The end portions of the gate trench portion40and the dummy trench portion30in the Y axis direction are provided in the well region11in a top view. In other words, the bottom of each trench portion in the depth direction is covered with the well region11at the end portion of each trench portion in the Y axis direction. With this configuration, the electric field strength in the bottom of each trench portion can be reduced.

A mesa portion is provided between the trench portions in the arrangement direction. The mesa portion indicates a region sandwiched between the trench portions in the semiconductor substrate10. As an example, the upper end of the mesa portion is the upper surface of the semiconductor substrate10. The depth position of the lower end of the mesa portion is the same as the depth position of the lower end of the trench portion. The mesa portion of this example is provided to extend in the extending direction (Y axis direction) along the trench in the upper surface of the semiconductor substrate10. In this example, a mesa portion60is provided in the transistor portion70, and a mesa portion61is provided in the diode portion80. In the case of simply mentioning “mesa portion” in the present specification, the portion indicates each of the mesa portion60and the mesa portion61.

Each mesa portion is provided with the base region14. In the base region14exposed to the upper surface of the semiconductor substrate10in the mesa portion, a region disposed nearest to the active-side gate runner131is referred to as a base region14-e. InFIG.10, the base region14-edisposed in one end portion in the extending direction of each mesa portion is illustrated. However, the base region14-eis disposed even the other end portion of each mesa portion. In each mesa portion, at least one of the emitter region12of a first conductivity type and the contact region15of the second conductivity type may be provided in the region sandwiched between the base regions14-ein a top view. The emitter region12of this example is an N+ type, and the contact region15is a P+ type. The emitter region12and the contact region15may be provided between the base region14and the upper surface of the semiconductor substrate10in the depth direction.

The mesa portion60of the transistor portion70includes the emitter region12exposed to the upper surface of the semiconductor substrate10. The emitter region12is provided in contact with the gate trench portion40. The mesa portion60in contact with the gate trench portion40may be provided with the contact region15exposed to the upper surface of the semiconductor substrate10.

Each of the contact region15and the emitter region12in the mesa portion60is provided from one trench portion in the X axis direction to the other trench portion. As an example, the contact region15and the emitter region12of the mesa portion60are alternately disposed along the extending direction (Y axis direction) of the trench portion.

In another example, the contact region15and the emitter region12of the mesa portion60may be provided in a stripe shape along the extending direction (Y axis direction) of the trench portion. For example, the emitter region12is provided in a region in contact with the trench portion, and the contact region15is provided in a region sandwiched between the emitter regions12.

The emitter region12is not provided in the mesa portion61of the diode portion80. The base region14and the contact region15may be provided on the upper surface of the mesa portion61. The contact region15may be provided in contact with each of the base regions14-ein a region sandwiched between the base regions14-eon the upper surface of the mesa portion61. The base region14may be provided in a region sandwiched between the contact regions15on the upper surface of the mesa portion61. The base region14may be disposed in the entire region sandwiched between the contact regions15.

The contact hole54is provided above each mesa portion. The contact hole54is disposed in a region sandwiched between the base regions14-e. The contact hole54of this example is provided above each region of the contact region15, the base region14, and the emitter region12. The contact hole54is not provided in a region corresponding to the base region14-eand the well region11. The contact hole54may be disposed at the center in the arrangement direction (X axis direction) of the mesa portion60.

In the diode portion80, a cathode region82of the N+ type is provided in a region adjacent to the lower surface of the semiconductor substrate10. On the lower surface of the semiconductor substrate10, a collector region22of the P+ type may be provided in a region where the cathode region82is not provided. The cathode region82and the collector region22are provided between the lower surface23of the semiconductor substrate10and the buffer region20. InFIG.10, the boundary between the cathode region82and the collector region22is indicated by a dotted line.

The cathode region82is disposed away from the well region11in the Y axis direction. As a result, a distance between the region (well region11) of the P type having a relatively high doping concentration and formed up to a deep position and the cathode region82is secured, and the withstand voltage can be improved. The end of the cathode region82of this example in the Y axis direction is disposed away from the well region11than the end of the contact hole54in the Y axis direction. In another example, the end of the cathode region82in the Y axis direction may be disposed between the well region11and the contact hole54.

FIG.11is a diagram illustrating an example of an e-e cross section inFIG.10. The e-e cross section is an XZ plane passing through the emitter region12and the cathode region82. The semiconductor device100of this example includes the semiconductor substrate10, an interlayer dielectric film38, the emitter electrode52, and a collector electrode24in the cross section.

The interlayer dielectric film38is provided on the upper surface of the semiconductor substrate10. The interlayer dielectric film38is a film including at least one of a dielectric film such as silicate glass to which an impurity such as boron or phosphorus is added, a thermal oxide film, and other dielectric films. The interlayer dielectric film38is provided with the contact hole54described inFIG.10.

The emitter electrode52is provided above the interlayer dielectric film38. The emitter electrode52is in contact with the upper surface21of the semiconductor substrate10through the contact hole54of the interlayer dielectric film38. The collector electrode24is provided on the lower surface23of the semiconductor substrate10. The emitter electrode52and the collector electrode24are made of a metal material such as aluminum. In the present specification, the direction (Z axis direction) connecting the emitter electrode52and the collector electrode24is referred to as a depth direction.

The semiconductor substrate10has a drift region18of the N type or the N− type. The drift region18is provided in each of the transistor portion70and the diode portion80.

In the mesa portion60of the transistor portion70, an emitter region12of the N+ type and a base region14of the P− type are provided in order from the upper surface21side of the semiconductor substrate10. The drift region18is provided below the base region14. The mesa portion60may be provided with an accumulation region16of the N+ type. The accumulation region16is disposed between the base region14and the drift region18.

The emitter region12is exposed to the upper surface21of the semiconductor substrate10and is provided in contact with the gate trench portion40. The emitter region12may be in contact with the trench portions on both sides of the mesa portion60. The emitter region12has a higher doping concentration than the drift region18.

The base region14is provided below the emitter region12. The base region14of this example is provided in contact with the emitter region12. The base region14may be in contact with the trench portions on both sides of the mesa portion60.

The accumulation region16is provided below the base region14. The accumulation region16is an region of the N+ type having a higher doping concentration than the drift region18. That is, the accumulation region16has a higher donor concentration than the drift region18. By providing the high-concentration accumulation region16between the drift region18and the base region14, the carrier injection enhancement effect (IE effect) can be increased, and the ON voltage can be reduced. The accumulation region16may be provided so as to cover the entire lower surface of the base region14in each mesa portion60.

The mesa portion61of the diode portion80is provided with a base region14of the P− type in contact with the upper surface21of the semiconductor substrate10. The drift region18is provided below the base region14. In the mesa portion61, the accumulation region16may be provided below the base region14.

In each of the transistor portion70and the diode portion80, a buffer region20of the N+ type may be provided under the drift region18. The doping concentration of the buffer region20is higher than the doping concentration of the drift region18. The buffer region20has a concentration peak25having a higher doping concentration than the drift region18. The doping concentration of the concentration peak25refers to the doping concentration at the maximum of the concentration peak25. As the doping concentration of the drift region18, an average value of the doping concentration in a region where the doping concentration distribution is approximately flat may be used.

The buffer region20of this example has three or more concentration peaks25in the depth direction (Z axis direction) of the semiconductor substrate10. The concentration peak25of the buffer region20may be provided at the same depth position as the concentration peak of hydrogen (proton) or phosphorus, for example. The buffer region20may work as a field stop layer that prevents a depletion layer extending from the lower end of the base region14from reaching the collector region22of the P+ type and the cathode region82of the N+ type. In the present specification, the depth position of the upper end of the buffer region20is defined as Zf. The depth position Zf may be a position where the doping concentration is higher than the doping concentration of the drift region18.

In the transistor portion70, the collector region22of the P+ type is provided below the buffer region20. The acceptor concentration of the collector region22is higher than the acceptor concentration of the base region14. The collector region22may include the same acceptor as the base region14, and may include a different acceptor. The acceptor of the collector region22is, for example, boron.

In the diode portion80, the cathode region82of the N+ type is provided below the buffer region20. The donor concentration of the cathode region82is higher than the donor concentration of the drift region18. The donor of the cathode region82is, for example, hydrogen or phosphorus. Elements to be donors and acceptors in each region are not limited to the examples described above. The collector region22and the cathode region82are exposed to the lower surface23of the semiconductor substrate10and are connected to the collector electrode24. The collector electrode24may be in contact with the entire lower surface23of the semiconductor substrate10. The emitter electrode52and the collector electrode24are formed of a metal material such as aluminum.

One or more gate trench portions40and one or more dummy trench portions30are provided on the upper surface21side of the semiconductor substrate10. Each trench portion penetrates the base region14from the upper surface21of the semiconductor substrate10to reach the drift region18. In the region where at least any one of the emitter region12, the contact region15, and the accumulation region16is provided, each trench portion also penetrates these doping regions and reaches the drift region18. The trench portion penetrating the doping region is not limited to those manufactured in the order of forming the doping region and then forming the trench portion. A case where a doping region is formed between the trench portions after the trench portion is formed is also included in a case where the trench portion penetrates the doping region.

As described above, the transistor portion70is provided with the gate trench portion40and the dummy trench portion30. The diode portion80is provided with the dummy trench portion30and is not provided with the gate trench portion40. In this example, the boundary between the diode portion80and the transistor portion70in the X axis direction is the boundary between the cathode region82and the collector region22.

The gate trench portion40includes a gate trench provided on the upper surface21of the semiconductor substrate10, a gate insulating film42, and a gate conductive portion44. The gate insulating film42is provided to cover the inner wall of the gate trench. The gate insulating film42may be formed by oxidizing or nitriding the semiconductor of the inner wall of the gate trench. The gate conductive portion44is provided inside the gate insulating film42in the gate trench. That is, the gate insulating film42insulates the gate conductive portion44from the semiconductor substrate10. The gate conductive portion44is formed of a conductive material such as polysilicon.

The gate conductive portion44may be provided longer than the base region14in the depth direction. The gate trench portion40in the cross section is covered with the interlayer dielectric film38in the upper surface21of the semiconductor substrate10. The gate conductive portion44is electrically connected to the gate runner. When a predetermined gate voltage is applied to the gate conductive portion44, a channel by an inversion layer of electrons is formed in a surface layer of the boundary in contact with the gate trench portion40in the base region14.

The dummy trench portion30may have the same structure as the gate trench portion40in the cross section. The dummy trench portion30includes a dummy trench provided in the upper surface21of the semiconductor substrate10, a dummy insulating film32, and a dummy conductive portion34. The dummy conductive portion34is electrically connected to the emitter electrode52. The dummy insulating film32is provided to cover the inner wall of the dummy trench. The dummy conductive portion34is provided in the dummy trench and is provided inside the dummy insulating film32. The dummy insulating film32insulates the dummy conductive portion34from the semiconductor substrate10. The dummy conductive portion34may be formed of the same material as the gate conductive portion44. For example, the dummy conductive portion34is formed of a conductive material such as polysilicon. The dummy conductive portion34may have the same length as the gate conductive portion44in the depth direction.

The gate trench portion40and the dummy trench portion30of this example are covered with the interlayer dielectric film38in the upper surface21of the semiconductor substrate10. Note that the bottoms of the dummy trench portion30and the gate trench portion40may have a curved surface shape protruding downward (a curved shape in a cross section). In the present specification, the depth position of the lower end of the gate trench portion40is defined as Zt.

The drift region18may have the same donor concentration as the donor concentration described inFIG.1AtoFIG.8. That is, the drift region18has a donor concentration determined mainly by the bulk donor concentration and the hydrogen donor (VOH defect) concentration. A dopant is locally implanted in a region other than the drift region18. Therefore, the doping concentration in the region other than the drift region18is different from the donor concentration described inFIG.1AtoFIG.8.

FIG.12Ais a diagram illustrating an example of the doping concentration distribution, the hydrogen chemical concentration distribution, and the termination dangling bond concentration distribution taken along line F-F inFIG.11. The doping concentration distribution may have a shape in which a local concentration peak in each region is superimposed on the donor concentration distribution illustrated inFIG.1AtoFIG.8.

In the entire semiconductor substrate10, bulk donors such as phosphorus and VOH defects (also referred to as hydrogen donor or termination dangling bond) due to hydrogen ion implantation penetrating the semiconductor substrate10are approximately evenly distributed. The emitter region12contains a dopant of the N type such as phosphorus. The base region14contains a dopant of the P type such as boron. The accumulation region16includes a dopant of the N type such as phosphorus or hydrogen.

The buffer region20of this example has a plurality of concentration peaks25-1,25-2,25-3, and25-4in the doping concentration distribution. Each concentration peak25may be formed by locally implanting hydrogen ions. In other examples, each concentration peak25may be formed by implanting a dopant of the N type such as phosphorus. The collector region22contains a dopant of the P type such as boron. The cathode region82illustrated inFIG.11contains a dopant of the N type such as phosphorus.

The drift region18in this example is a region in which a dopant other than hydrogen and the bulk donor is not intentionally implanted. The drift region18may be a region from the upper end of the buffer region20to the lower end of the accumulation region16(or the lower end Zt of the trench portion). Hydrogen may be locally implanted into the drift region18. InFIG.12A, an example of each distribution when hydrogen is locally implanted into the drift region18is indicated by a broken line.

The hydrogen chemical concentration distribution in this example has a plurality of local hydrogen concentration peaks103in the buffer region20. The half-value width of the hydrogen concentration peak103is 1/10 or less of the thickness of the semiconductor substrate10in the depth direction. The hydrogen chemical concentration distribution is flat or monotonically increases or decreases except in the region where the local hydrogen concentration peak103is provided. In the region102from the upper end Zf of the buffer region20to the upper surface21of the semiconductor substrate10, the hydrogen chemical concentration distribution is flat or monotonically increases or decreases.

In this example, the hydrogen chemical concentration in the drift region18monotonously decreases toward the upper surface21. When the buffer region20is close to the lower surface23and the hydrogen in the buffer region diffuses toward the upper surface21, the hydrogen chemical concentration monotonously decreases toward the upper surface21as in this example. The hydrogen chemical concentration in the upper surface21may be the minimum hydrogen chemical concentration in the semiconductor substrate10.

In order to have a donor concentration higher than the bulk donor concentration D0throughout the drift region18, a sufficiently high concentration of hydrogen atoms may be present throughout the semiconductor substrate10. Specifically, the hydrogen chemical concentration in the upper surface21may be higher than the bulk donor concentration D0, may be higher than the minimum peak donor concentration of the donor concentration peak of the buffer region20, and may be higher than the maximum peak donor concentration of the donor concentration peak of the buffer region20. Further, the hydrogen chemical concentration in the upper surface21may be 1×1014/cm3or more, 1×1015/cm3or more, or 1×1016/cm3or more.

In addition, the hydrogen chemical concentration between the base region14or the accumulation region16and the upper surface21may be higher than the bulk donor concentration D0, may be higher than the minimum peak donor concentration of the donor concentration peak of the buffer region20, and may be higher than the maximum peak donor concentration of the donor concentration peak of the buffer region20. Further, the hydrogen chemical concentration between the base region14or the accumulation region16and the upper surface21may be 1×1014/cm3or more, 1×1015/cm3or more, or 1×1016/cm3or more. As described above, the dangling bond of the region through which the hydrogen ions have passed can be terminated with a sufficient amount of hydrogen. In this example, the hydrogen concentration peak103closest to the lower surface23may be a hydrogen supply source (local hydrogen concentration peak210inFIG.1B).

In another example, hydrogen may be locally implanted into the accumulation region16. In this case, in the region102from the upper end Zf of the buffer region20to the upper surface21of the semiconductor substrate10, the hydrogen chemical concentration distribution is flat or monotonically increases or decreases except for the accumulation region16.

The termination dangling bond concentration distribution has a termination dangling bond flat region104and a local concentration peak105. The concentration peak105is disposed at the same depth position as the local hydrogen concentration peak103in the hydrogen chemical concentration distribution.

The termination dangling bond flat region104in this example includes a center position Zc in the depth direction of the semiconductor substrate10. At least a part of the drift region18may be the termination dangling bond flat region104. The entire drift region18in this example is the termination dangling bond flat region104. The termination dangling bond flat region104may be provided from the upper end Zf of the buffer region20to the upper surface21of the semiconductor substrate10.

There is a case where the dangling bonds are locally formed by locally implanting helium or the like into the drift region18, and a lifetime control region for controlling the lifetime of the carrier is formed. In this case, a portion of the drift region18other than the region into which particles such as helium are locally implanted may be the termination dangling bond flat region104.

In a region where a dopant other than hydrogen is locally implanted, such as the emitter region12, the base region14, the accumulation region16, and the collector region22, the dangling bonds are formed by implantation of the dopant. In addition, since there is almost no hydrogen in the region, the dangling bond may remain without being terminated with hydrogen. InFIG.12A, a distribution example of the unterminated dangling bond not terminated with hydrogen is indicated by a chain line.

As in this example, whether hydrogen implanted from the lower surface23passes through the semiconductor substrate10by passing through the upper surface21may be determined based on whether the following two characteristics are provided. Characteristic (A): The hydrogen chemical concentration monotonically decreases from a peak closest to the upper surface21among the concentration peaks of the hydrogen chemical concentration to the upper surface21. Characteristic (B): At least the doping concentration of the entire drift region18is higher than the bulk donor concentration D0. In other words, there is no position where the donor concentration substantially matches between the bulk donor concentration and the doping concentration over the entire semiconductor substrate10. When the semiconductor device has both the characteristic (A) and the characteristic (B), it can be regarded that hydrogen implanted from the lower surface23passes through the upper surface21to pass through the semiconductor substrate10.

FIG.12Bis a diagram illustrating another example of the doping concentration distribution, the hydrogen chemical concentration distribution, and the termination dangling bond concentration distribution taken along line F-F inFIG.11. This example is an example in which the doping concentration and the termination dangling bond concentration in the drift region18monotonously increase from the lower surface23toward the upper surface21. Other concentration distributions may be similar to the example ofFIG.12A.

The hydrogen chemical concentration in the drift region18in this example may monotonically decrease toward the upper surface21. When the buffer region20is close to the lower surface23and the hydrogen in the buffer region diffuses towards the upper surface21, the hydrogen chemical concentration monotonically decreases towards the upper surface21. The hydrogen chemical concentration in the upper surface21may be the minimum hydrogen chemical concentration in the semiconductor substrate10.

The slope of the increase or decrease in the concentration in each distribution may be similar to the slope of the linear approximation distribution214described above. The doping concentration of the drift region18at the boundary between the drift region18and the accumulation region16may be smaller than the maximum doping concentration of the buffer region20, and may be smaller than the smallest peak concentration among the peak concentrations of the buffer region20.

One or more doping concentration peaks may be provided or two or more doping concentration peaks may be provided inside the drift region18. In the example ofFIG.12B, an example in which one peak is provided inside the drift region18is indicated by a broken line. In this example, whether hydrogen ions have passed from the upper surface21toward the lower surface23can be determined in the same manner as inFIG.12A.

FIG.12Cis a diagram illustrating another example of the doping concentration distribution, the hydrogen chemical concentration distribution, and the termination dangling bond concentration distribution taken along line F-F inFIG.11. This example is an example in which the doping concentration and the termination dangling bond concentration in the drift region18monotonously decrease from the lower surface23toward the upper surface21. Other concentration distributions may be similar to the example ofFIG.12A.

The hydrogen chemical concentration in the drift region18in this example may monotonically decrease toward the upper surface21. When the buffer region20is close to the lower surface23and the hydrogen in the buffer region diffuses towards the upper surface21, the hydrogen chemical concentration monotonically decreases towards the upper surface21. The hydrogen chemical concentration in the upper surface21may be the minimum hydrogen chemical concentration in the semiconductor substrate10.

The slope of the increase or decrease in the concentration in each distribution may be similar to the slope of the linear approximation distribution214described above. The doping concentration of the drift region18at the boundary between the drift region18and the accumulation region16may be smaller than the maximum doping concentration of the buffer region20, and may be smaller than the smallest peak concentration among the peak concentrations of the buffer region20.

One or more doping concentration peaks may be provided or two or more doping concentration peaks may be provided inside the drift region18. In the example ofFIG.12C, an example in which one peak is provided inside the drift region18is indicated by a broken line. In this example, whether hydrogen ions have passed from the upper surface21toward the lower surface23can be determined in the same manner as inFIG.12A.

FIG.12Dis a diagram illustrating another example of the doping concentration distribution, the hydrogen chemical concentration distribution, and the termination dangling bond concentration distribution taken along line F-F inFIG.11. This example is different from the example ofFIG.12Bin that hydrogen ions implanted from the lower surface23do not pass through the semiconductor substrate10and stop from the accumulation region16to the upper surface21side. Other structures may be similar to the example ofFIG.12B. In this example, hydrogen ions stop at the depth of the base region14.

The hydrogen chemical concentration in this example may decrease toward the upper surface21in the drift region18. Further, the hydrogen chemical concentration increases again towards the hydrogen ion stopping region (present in the base region14in this example). In addition, the hydrogen chemical concentration may decrease toward the upper surface21on the upper surface21side from the hydrogen ion stopping region. The hydrogen chemical concentration may have a peak in the base region14. The concentration distribution of the termination dangling bond may have a peak at substantially the same depth position as the peak of the hydrogen chemical concentration on the upper surface21side from the accumulation region16.

The hydrogen chemical concentration may have a monotonically decreasing section in which the concentration monotonically decreases toward the upper surface21between the peak closest to the upper surface21of the semiconductor substrate10and the end of the base region14on the lower surface23side. The hydrogen chemical concentration may have an increasing section in which the concentration increases from the end of the base region14on the lower surface23side to the upper surface21of the semiconductor substrate10toward the upper surface21.

In the example ofFIG.12D, whether hydrogen implanted from the lower surface23is stopped between the accumulation region16or the base region14and the upper surface21may be determined based on whether the following two characteristics are provided. Characteristic (A′): The hydrogen chemical concentration monotonously decreases between a peak closest to the upper surface21among the concentration peaks of the hydrogen chemical concentration and the accumulation region16or the base region14, and the hydrogen chemical concentration has a peak between the accumulation region16or the base region14and the upper surface21. Note that a space between the accumulation region16and the upper surface21includes the accumulation region16. In addition, a space between the base region14and the upper surface21includes the base region14. Characteristic (B): At least the doping concentration of the entire drift region18is higher than the bulk donor concentration D0. In other words, there is no position where the donor concentration substantially matches between the bulk donor concentration and the doping concentration over the entire semiconductor substrate10. When the semiconductor device has both of the above characteristics (A′) and (B), it can be regarded that hydrogen implanted from the lower surface23is stopped between the accumulation region16and the upper surface21.

FIG.12Eis a diagram illustrating another example of the doping concentration distribution, the hydrogen chemical concentration distribution, and the termination dangling bond concentration distribution taken along line F-F inFIG.11. This example is different from the example ofFIG.12Cin that hydrogen ions implanted from the upper surface21do not pass through the semiconductor substrate and stop inside the buffer region20. In this example, hydrogen ions implanted from the upper surface21are stopped at the depth of the concentration peak25-1. InFIG.12E, the chemical concentration distribution of hydrogen implanted from the upper surface21is indicated by a chain line.

The hydrogen chemical concentration in this example has substantially no difference or a sufficiently small difference from the distribution inFIG.12C. That is, the concentration of hydrogen ions implanted so as to stop inside the buffer region20from the upper surface21may be equal to or sufficiently smaller than the hydrogen chemical concentration implanted into the buffer region20from the lower surface23. As an example, the peak concentration of hydrogen implanted from the upper surface21is about the same as the peak of low concentration (in this example, the concentration peaks25-3and25-4) in the buffer region20. As a result, at the positions of the high concentration peaks (25-1and25-2in this example) in the buffer region20, the concentration increase can be made 10% or less with respect to the hydrogen chemical concentration and the doping concentration of the buffer region20. The low concentration peak refers to N/2 or less peaks counted from the lower concentration peak among the N concentration peaks25. The high concentration peak refers to N/2 or less peaks counted from the highest concentration among the plurality of concentration peaks25. In this example, whether hydrogen ions have passed from the upper surface21toward the lower surface23can be determined in the same manner as inFIG.12A.

FIG.13AtoFIG.21are diagram for explaining an example of a method for determining the bulk donor concentration and a preferred range for the donor concentration. In this example, the bulk donor concentration and the donor concentration in the region are set such that the final donor concentration in the hydrogen concentration flat region or the termination dangling bond flat region104becomes a relatively stable concentration even when the bulk donor concentration varies. The hydrogen concentration flat region is a region where the hydrogen chemical concentration distribution of the semiconductor substrate in the depth direction is flat, monotonically increases, or monotonically decreases.

In this example, the specification value of the bulk donor concentration is set to NB0, and the actual bulk donor concentration is set to NBre. The specification value of the bulk donor concentration is a specification value defined by a manufacturer of semiconductor wafers. When the specification value has a width, a median value of the specification value may be used. The bulk donor concentration is given by N=1/qμρ with respect to a specific resistance p determined by the concentration of the bulk donor such as phosphorus. q is an elementary electric charge, and μ is electron mobility in the semiconductor substrate10.

The concentration of hydrogen donors (VOH defects) is NH. The variation in a hydrogen donor concentration NHis negligibly small compared to the variation in the bulk donor concentration. In this example, the variation in the hydrogen donor concentration NHis set to 0.

The target value of the final donor concentration is defined as NF0. The final donor concentration actually obtained is defined as NFre. The concentrations described above are all concentrations (/cm3) per unit volume.

The target value NF0of the final donor concentration is obtained by adding the hydrogen donor concentration NHto the specification value NB0of the bulk donor concentration, and thus is given by the following Expression.
NF0=NH+NB0Expression (1)

On the other hand, the actual donor concentration NFreis obtained by adding the hydrogen donor concentration NHto the actual bulk donor concentration NBre, and thus is given by the following Expression.

NF⁢r⁢e=NH+NB⁢r⁢eExpression⁢⁢(2)

The parameter β is defined by the following Expression.
β=NBre/NB0Expression (3)
The parameter β is a ratio between the actual bulk donor concentration NBreand the specification value NB0, and the bulk donor concentration NBredeviates from the specification value NB0as the parameter is far from 1.

The parameter γ is defined by the following Expression.
γ=NFre/NF0Expression (4)
The parameter γ is a ratio between the actual donor concentration NFreand the target value NF0, and the actual donor concentration NFredeviates from the target value NF0as the parameter is far from 1. That is, when γ is sufficiently close to 1, even when the actual bulk donor concentration NBredeviates by 6 times from the specification value NB0, the actual donor concentration NFresubstantially matches the target value NF0almost independently of β. Since the parameter γ is a ratio of the actual donor concentration NFreto the target value NF0of the donor concentration, satisfying 0<γ.

The variation in the withstand voltage of the semiconductor device100is affected by the parameter γ which is the variation in the actual donor concentration NFre. Here, the specific resistance variation of a silicon wafer manufactured by the FZ method in which the variation in the bulk donor concentration is relatively small is generally as follows.Neutron-irradiated FZ wafer . . . ±8% (ratio 0.92 to 1.08)Gas-doped FZ wafer . . . ±12% (ratio 0.88 to 1.12)

The magnitude of the variation in the specific resistance depends on the magnitude of the variation in the donor concentration NFre. Therefore, when γ is from 0.85 1.15, the variation in the final donor concentration NFreis substantially the same as the bulk donor concentration of the silicon wafer of the FZ method described above. In the present specification, the allowable value of γ is from 0.85 to 1.15. When the parameter γ falls within the range, it may be determined that the donor concentration NFreis not affected by the parameter β.

The actual donor concentration NFreis affected by the variation (β) in the actual bulk donor concentration NBre. On the other hand, the variation in the hydrogen donor concentration NHcan be regarded as almost 0 as compared with the variation in the bulk donor concentration NBre. Therefore, by reducing the specification value NB0of the bulk donor concentration with respect to the target value NF0of the donor concentration, it is possible to reduce the ratio of components that vary in the donor concentration NFre. Next, it is examined how much the specification value NB0of the bulk donor concentration is made smaller than the target value NF0of the final donor concentration so that the actual donor concentration NFrecan be made sufficiently close to the target value NF0regardless of the parameter β. That is, the specification value NB0of the bulk donor concentration capable of setting the parameter γ to the above-described range from 0.85 to 1.15, preferably a value sufficiently close to 1, is examined.

A parameter ε′ is defined by the following Expression.
ε′=NB0/NF0

Expression (5) is obtained by modifying the above Expression.
NB0=ε′×NF0Expression (5)

Note that ε′ is a ratio of the specification value NB0of the bulk donor concentration to the target value NF0of the donor concentration, satisfying 0<ε′. In addition, since NB0is smaller than NF0, satisfying ε′<1. That is, 0<ε′<1.

In addition, it is assumed that the hydrogen donor concentration NHand the specification value NB0of the bulk donor concentration satisfy a relationship of NH>NB0. In the case of NH<NB0, the influence of the specification value NB0of the bulk donor concentration on the final donor concentration NFrebecomes large, the case of NH>NB0will be considered.

Note that the parameter ε′ is a parameter that means to set the specification value NB0of the bulk donor concentration by ε′ relative to the target value NF0of the donor concentration.

It is examined whether γ approaches sufficiently 1 regardless of β when ε′ is set to a value smaller than 1 within a range not to be 0.

The parameter ε is defined by the following Expression.
ε=1/ε′  Expression (6)

The following Expression is obtained from Expression (5) and Expression (6).
NB0=NF0/ε  Expression (7)

The following Expression is obtained by substituting Expression (7) into Expression (1).

NF⁢0=NH+NF⁢0/ɛ,i.e.,NH=(1-1/ɛ)⁢NF⁢0Expression⁢⁢(8)

The following Expression is obtained by substituting Expression (8) and Expression (3) into Expression (2).
NFre=(1−I/ε)NF0+βNB0Expression (9)

The following Expression is obtained by substituting Expression (7) into Expression (9).

NF⁢r⁢e=(1-1/ɛ)⁢NF⁢0+(β/ɛ)⁢NF⁢0=(1-1/ɛ+β/ɛ)⁢NF⁢0Expression⁢⁢(10)

The following Expression is obtained by substituting Expression (10) into Expression (4).

γ=1-1/ɛ+β/ɛ=1+(β-1)/ɛExpression⁢⁢(11)

The following Expression is obtained from Expression (6) and Expression (11).
γ=1+ε′(β−1)  Expression (12)

FIG.13Ais a graph illustrating a relationship between ε′ and γ expressed by Expression (12) for each β. As described above, γ represents the ratio of the actual donor concentration NFreto the target value NF0, and β represents the ratio of the actual bulk donor concentration NBreto the specification value NB0. An allowable value of γ ranges from 0.85 to 1.15.

For example, the specification value NB0of the bulk donor concentration is 0.5 times or less of the target value NF0of the donor concentration, that is, ε′ is 0.5 or less. In this case, for example, even when β is 1.3, γ is 1.15 or less and falls within the allowable range. That is, even when the actual bulk donor concentration NBreis 30% higher than the specification value NB0, the actual donor concentration NFreis 1.15 times or less of the target value NF0. In addition, even when β is 0.7, if ε′ is 0.5 or less, γ is within an allowable range. As ε′ approaches 0, γ converges to 1. For example, in the case of β=2, if ε′ is approximately 0.2 or less, γ is within an allowable range.

In order to make γ within the above-mentioned allowable range, for example, the following ranges A to D are conceivable as preferable ranges of ε′.

(Range A)

ε′ is 0.5 or less. In a case where ε′ is 0.5, when β is within a range of 0.7 to 1.3, γ is within an allowable range (for example, 0.85≤γ≤1.15.{j}. Other examples are similar) For example, when the specification value NB0of the bulk donor concentration is 1×1014/cm3and ε′ is 0.001, the target value NF0of the donor concentration is 1×1011/cm3, corresponding to about 46000 Ωcm.

(Range B)

ε′ is 0.333 or less. In a case where ε′ is 0.333, if β is within a range of 0.5 to 1.5, γ is within an allowable range. β may be 1.4 or less. For example, when the specification value NB0of the bulk donor concentration is 1×1014/cm3and ε′ is 0.01, the target value NF0of the donor concentration is 1×1012/cm3, corresponding to about 4600 Ωcm.

(Range C)

ε′ is 0.25 or less. In a case where ε′ is 0.25, if β is within a range of approximately 0.3 to 1.6, γ is within an allowable range. β may be 0.4 or more. For example, when the specification value NB0of the bulk donor concentration is 1×1014/cm3and ε′ is 0.03, the target value NF0of the donor concentration is 3×1012/cm3, corresponding to about 1500 Ωcm.

(Range D)

ε′ is 0.2 or less. In a case where ε′ is 0.2, if β is within a range of approximately 0.1 to 1.8, γ is within an allowable range. β may be 0.2 or more. For example, when the specification value NB0of the bulk donor concentration is 1×1014/cm3and ε′ is 0.1, the target value NF0of the donor concentration is 1×1013/cm3, corresponding to about 460 Ωcm.

Note that, since the less variation in specific resistance is suitable for practical use, ε′ is preferably 0.1 or less, and more preferably 0.02 or less. In this case, for example, the following Ranges E to H are conceivable.

(Range E)

ε′ is 0.1 or less. In a case where ε′ is 0.1, if β is within a range of about 0.05 (not illustrated) to 3.0, γ is within a sufficiently allowable range. That is, when β is 3.0 or less, if γ is 1.15 or less and β is 0.05 or more, γ is 0.85 or more. β may be 0.1 or more. β may be 2.5 or less. For example, when the specification value NB0of the bulk donor concentration is 1×1014/cm3and ε′ is 0.1, the target value NF0of the donor concentration is 1×1013/cm3, corresponding to about 460 Ωcm.

(Range F)

ε′ is 0.05 or less. In a case where ε′ is 0.05, if β is within a range of about 0.01 (not illustrated) to 5.0, γ is within a sufficiently allowable range. β may be 0.1 or more. β may be 4 or less. For example, when the specification value NB0of the bulk donor concentration is 1×1014/cm3and ε′ is 0.05, the target value NF0of the donor concentration is 5×1012/cm3, corresponding to about 920 Ωcm.

(Range G)

ε′ is 0.03 or less. In a case where ε′ is 0.03, if β is within a range from about 0.1 to 6.0, γ is within a sufficiently allowable range. In the range G, ε′ may be 0.02 or less. In a case where ε′ is 0.02, if β is within a range of about 0.01 (not illustrated) to 10.0, γ is within a sufficiently allowable range. For example, when the specification value NB0of the bulk donor concentration is 1×1014/cm3and ε′ is 0.02, the target value NF0of the donor concentration is 2×1012/cm3, corresponding to about 2300 Ωcm.

(Range H)

ε′ is 0.01 or less. In a case where ε′ is 0.01, if β is within a range of about 0.01 (not illustrated) to 20.0 (not illustrated), γ is within a sufficiently allowable range.6may be 0.1 or more. β may be 10.0 or less. In the range H, ε′ may have a width of 0.01±0.002 (20%). For example, when the specification value NB0of the bulk donor concentration is 1×1014/cm3and ε′ is 0.01, the target value NF0of the donor concentration is 1×1012/cm3, corresponding to about 4600 Ωcm.

In each of the above ranges, the lower limit of ε′ may be “a value greater than 0”. This is because γ converges to 1 when ε′ approaches 0. The lower limit of ε′ may be any of the following ranges I, J, K, and L. Other ranges may be used as the lower limit of ε′. InFIG.13, each range is indicated by an arrow.

(Range I)

ε′ is 0.001 or more. For example, when the specification value NB0of the bulk donor concentration is 1×1014/cm3and ε′ is 0.001, the target value NF0of the donor concentration is 1×1011/cm3, corresponding to about 46000 Ωcm.

(Range J)

ε′ is 0.01 or more. For example, when the specification value NB0of the bulk donor concentration is 1×1014/cm3and ε′ is 0.01, the target value NF0of the donor concentration is 1×1012/cm3, corresponding to about 4600 Ωcm.

(Range K)

ε′ is 0.03 or more. For example, when the specification value NB0of the bulk donor concentration is 1×1014/cm3and ε′ is 0.03, the target value NF0of the donor concentration is 3×1012/cm3, corresponding to about 1500 Ωcm.

(Range L)

ε′ is 0.05 or more. For example, when the specification value NB0of the bulk donor concentration is 1×1014/cm3and ε′ is 0.05, the target value NF0of the donor concentration is 5×1012/cm3, corresponding to about 920 Ωcm.

As described above, the actual donor concentration NFrecorresponds to the donor concentration in the drift region18. The withstand voltage of the semiconductor device100is determined by the donor concentration of the drift region18. Therefore, a preferable range of the donor concentration NFreof the drift region18is determined by the rated voltage of the semiconductor device100. Depending on the donor concentration NFre, the range of the bulk donor concentration NBrethat can stabilize the donor concentration NFreis determined.

FIG.13Bis a diagram for explaining an example of a preferable range of the parameter β. As described above, the parameter β is the ratio of the actual bulk donor concentration NBreto the specification value NB0. As described inFIG.13A, the deviation ratio γ of the actual donor concentration NFreto the target value NF0of the final donor concentration is set to be within the predetermined allowable range γ0. In the example ofFIG.13A, the allowable range γ0is ±0.15 (that is, from −15% to 15%). The upper limit value and the lower limit value of the deviation ratio γ are 1.15 and 0.85, respectively.

By setting the ratio β of an error of the actual value NBreto the specification value NB0of the bulk donor concentration to a predetermined allowable range, the deviation ratio γ can be suppressed within the allowable range γ0with respect to a relatively wide range ε′. In order to set the allowable range of the parameter β, Expression (12) is deformed using the deviation ratios γ and ε′ to be Expression (13A).
β=(γ0−1)/ε′+1  Expression (13A)

That is, the range of β is expressed by the following Expression.
−γ0/ε′+1≤β≤γ0/ε′+1

In this example, since γ0is ±15%, the following Expression is obtained in each of the upper limit value 1.15 and the lower limit value 0.85 of γ.

β=0.15/ɛ′+1⁢(γ0+=1.15)Expression⁢⁢(13⁢C)β=-0.15/ɛ′+1⁢(γ0-=0.85)Expression⁢⁢(13⁢D)

From Expressions (13C) and (13D), the range β that should be taken with respect to ε′ is the range indicated by hatching inFIG.13B. InFIG.13B, a curve301corresponds to Expression (13C), and a curve302corresponds to Expression (13D). That is, the allowable range of 6 is a range of Expression (13C) or less (that is, the curve301or less) and a range of Expression (13D) or more (that is, the curve302or more) in a case where ε′ is 1 or less. InFIG.13B, the range in which ε′ is less than 0.001 and the range in which 6 is greater than 20 are omitted, but even in these ranges, the region between the curve301and the curve302is the allowable range of 6. The allowable range of γ0may be ±10%, ±7%, ±5%, or ±3%. On the other hand, when the variation in the withstand voltage of the semiconductor device100is more allowable, the allowable range of γ0may be ±30% or ±20%.

From the manufactured semiconductor device100, the actual bulk donor concentration NBreand the actual donor concentration NFrecan be measured. As the bulk donor concentration NBre, a concentration of donor species (for example, phosphorus) distributed over the entire semiconductor substrate10at the central position of the semiconductor substrate10in the depth direction may be used. As the donor concentration NFre, a donor concentration at the central position of the semiconductor substrate10in the depth direction may be used.

In the semiconductor device100, it may be assumed that β=1 (that is, the difference between the specification value NB0of the bulk donor concentration and the actual bulk donor concentration NBreis 0), and NBre=NB0. Assuming that γ=1 (that is, the difference between the target value NF0of the donor concentration and the actual donor concentration NFreis 0), NF0=NFremay be set. As a result, ε′ can be calculated from Expression (5) using NBreand NFre. When ε′=NBre/NBreis 0.5 or less, it may be determined that the influence of the variation in the bulk donor concentration can be sufficiently reduced to reduce the variation in the donor concentration NFre. ε′=NBre/NFremay be any of the ranges indicated in Range A to Range L.

In addition, if the target value NF0of the donor concentration and the specification value NB0of the bulk donor concentration can be discriminated from the production conditions and the like, the parameters6and γ can be calculated from Expressions (3) and (4). As a result, a more accurate parameter ε′ can be calculated.

The hydrogen donor concentration NHis represented by the following Expression by the Expressions (1) to (3).
NH=(1−ε′)NF0

That is, by setting ε′ sufficiently smaller than 1 (for example, 0.1 or less), the hydrogen donor concentration NHbecomes approximately the same value as the target value NF0of the donor concentration. Therefore, the dosage of hydrogen or the like may be set such that the hydrogen donor concentration NHbecomes approximately the same value as the target value NF0of the donor concentration. Similarly, the hydrogen donor concentration NHis expressed by the following Expression with respect to the specification value NB0of the bulk donor concentration.
NH=(1/ε′−1)NB0

FIG.14is a diagram illustrating an example of a preferred range for the bulk donor concentration NBre. In this example, the donor concentration NFre(/cm3) at the center Zc of the semiconductor substrate10in the depth direction is from (9.20245×1015)/x to (9.20245×1016)/x. Here, x is the rated voltage (V). The donor concentration NFre(/cm3) is determined with reference to the doping concentration of the drift region in the general semiconductor substrate formed by the FZ method, but may be determined with reference to the doping concentration of the drift region of the semiconductor substrate formed by the MCZ method. InFIG.14, an upper limit111and a lower limit112of the preferable range of the donor concentration NFre(/cm3) are indicated by broken lines.

InFIG.14, the upper limit113and the lower limit114of the preferable range of the bulk donor concentration NBrein the case of the above-described Range A and Range I (ε′ is from 0.001 to 0.5) are indicated by solid lines. The upper limit113of the bulk donor concentration NBreis a value obtained by multiplying the upper limit111of the donor concentration NFre(/cm3) by the upper limit value (0.5) of ε′. The lower limit114of the bulk donor concentration NBreis a value obtained by multiplying the lower limit112of the donor concentration NFre(/cm3) by the lower limit value (0.001) of ε′. The upper limit113and lower limit114of the bulk donor concentration NBreare as follows. The unit of the upper limit113and the lower limit114in each example is (/cm3). As described above, x is the rated voltage (V).Lower limit114: (9.20245×1012)/xUpper limit113: (4.60123×1016)/x

FIG.15is a diagram illustrating an example of a preferred range for the bulk donor concentration NBrewhen ε′ is in Range B and Range J (from 0.01 to 0.333). The upper limit111and the lower limit112of the donor concentration NFre(/cm3) are the same as those in the example ofFIG.14. The upper limit113of the bulk donor concentration NBreis a value obtained by multiplying the upper limit111of the donor concentration NFre(/cm3) by the upper limit value (0.333) of ε′. The lower limit114of the bulk donor concentration NBreis a value obtained by multiplying the lower limit112of the donor concentration NFre(/cm3) by the lower limit value (0.01) of ε′. The upper limit113and lower limit114of the bulk donor concentration NBreare as follows.Lower limit114: (9.20245×1013)/xUpper limit113: (3.06442×1016)/x

FIG.16is a diagram illustrating an example of a preferred range for the bulk donor concentration NBrewhen ε′ is in Range C and Range K (from 0.03 to 0.25). The upper limit111and the lower limit112of the donor concentration NFre(/cm3) are the same as those in the example ofFIG.14. The upper limit113of the bulk donor concentration NBreis a value obtained by multiplying the upper limit111of the donor concentration NFre(/cm3) by the upper limit value (0.25) of ε′. The lower limit114of the bulk donor concentration NBreis a value obtained by multiplying the lower limit112of the donor concentration NFre(/cm3) by the lower limit value (0.03) of ε′. The upper limit113and lower limit114of the bulk donor concentration NBreare as follows.Lower limit114: (2.76074×1014)/xUpper limit113: (2.30061×1016)/x

FIG.17is a diagram illustrating an example of a preferred range for the bulk donor concentration NBrewhen ε′ is in Range D (0.2 or less). The lower limit of ε′ in this example is 0.1 or more. The upper limit111and the lower limit112of the donor concentration NFre(/cm3) are the same as those in the example ofFIG.14. The upper limit113of the bulk donor concentration NBreis a value obtained by multiplying the upper limit111of the donor concentration NFre(/cm3) by the upper limit value (0.2) of ε′. The lower limit114of the bulk donor concentration NBreis a value obtained by multiplying the lower limit112of the donor concentration NFre(/cm3) by the lower limit value (0.1) of ε′. The upper limit113and lower limit114of the bulk donor concentration NBreare as follows.Lower limit114: (9.20245×1014)/xUpper limit113: (1.84049×1016)/x

FIG.18is a diagram illustrating an example of a preferred range for the bulk donor concentration NBrewhen ε′ is in Range E and Range I (from 0.001 to 0.1). The upper limit111and the lower limit112of the donor concentration NFre(/cm3) are the same as those in the example ofFIG.14. The upper limit113of the bulk donor concentration NBreis a value obtained by multiplying the upper limit111of the donor concentration NFre(/cm3) by the upper limit value (0.1) of ε′. The lower limit114of the bulk donor concentration NBreis a value obtained by multiplying the lower limit112of the donor concentration NFre(/cm3) by the lower limit value (0.001) of ε′. The upper limit113and lower limit114of the bulk donor concentration NBreare as follows.Lower limit114: (9.20245×1012)/xUpper limit113: (9.20245×1015)/x

FIG.19is a diagram illustrating an example of a preferred range for the bulk donor concentration NBrewhen ε′ is in Range F (0.05 or less). The lower limit of ε′ is 0.002 or more. The upper limit111and the lower limit112of the donor concentration NFre(/cm3) are the same as those in the example ofFIG.14. The upper limit113of the bulk donor concentration NBreis a value obtained by multiplying the upper limit111of the donor concentration NFre(/cm3) by the upper limit value (0.05) of ε′. The lower limit114of the bulk donor concentration NBreis a value obtained by multiplying the lower limit112of the donor concentration NFre(/cm3) by the lower limit value (0.002) of ε′. The upper limit113and lower limit114of the bulk donor concentration NBreare as follows.Lower limit114: (1.84049×1013)/xUpper limit113: (4.60123×1015)/x

FIG.20is a diagram illustrating an example of a preferred range for the bulk donor concentration NBrewhen ε′ is in Range G (0.03 or less). The lower limit of ε′ is 0.005 or more. The upper limit111and the lower limit112of the donor concentration NFre(/cm3) are the same as those in the example ofFIG.14. The upper limit113of the bulk donor concentration NBreis a value obtained by multiplying the upper limit111of the donor concentration NFre(/cm3) by the upper limit value (0.02) of ε′. The lower limit114of the bulk donor concentration NBreis a value obtained by multiplying the lower limit112of the donor concentration NFre(/cm3) by the lower limit value (0.005) of ε′. The upper limit113and lower limit114of the bulk donor concentration NBreare as follows.Lower limit114: (4.60123×1013)/xUpper limit113: (1.84049×1015)/x

FIG.21is a diagram illustrating an example of a preferred range for the bulk donor concentration NBrewhen ε′ is in Range H (0.01 or less). The lower limit of ε′ is 0.005 or more. The upper limit111and the lower limit112of the donor concentration NFre(/cm3) are the same as those in the example ofFIG.14. The upper limit113of the bulk donor concentration NBreis a value obtained by multiplying the upper limit111of the donor concentration NFre(/cm3) by the upper limit value (0.01) of ε′. The lower limit114of the bulk donor concentration NBreis a value obtained by multiplying the lower limit112of the donor concentration NFre(/cm3) by the lower limit value (0.005) of ε′. The upper limit113and lower limit114of the bulk donor concentration NBreare as follows.Lower limit114: (9.20245×1013)/xUpper limit113: (9.20245×1014)/x

The upper limit113and the lower limit114in each range may have a width of ±20%.

As illustrated inFIG.14toFIG.21, when the bulk donor concentration NBreis set to a concentration between the upper limit113and the lower limit114in each example, γ indicating the variation in the final donor concentration NFrecan be suppressed within an allowable range. The curve of the lower limit114may be smaller than the intrinsic carrier concentration. Here, the intrinsic carrier concentration is 1.45×1010/cm3at room temperature (for example, 300 K). When the value of the curve of the lower limit114is smaller than the intrinsic carrier concentration, the lower limit114may be replaced with the intrinsic carrier concentration.

FIG.22is a diagram illustrating an example of a manufacturing method of the semiconductor device100. The manufacturing method of this example includes a hydrogen irradiation stage S1600, a heat treatment stage S1602, a lower surface grinding stage S1604, and an element forming stage S1606.

In the hydrogen irradiation stage S1600, the upper surface or the lower surface of the semiconductor substrate is irradiated with hydrogen ions so as to penetrate the semiconductor substrate in the depth direction. The semiconductor substrate may be a semiconductor wafer or a chip divided from the wafer. In S1600, the semiconductor substrate is irradiated with hydrogen ions with acceleration energy that is twice or more the acceleration energy corresponding to the thickness of the semiconductor substrate. This makes it easy to flatten the hydrogen chemical concentration distribution in the semiconductor substrate. The acceleration energy of hydrogen ions may be three times or more, or four times or more of the acceleration energy corresponding to the thickness of the semiconductor substrate.

Next, the semiconductor substrate is subjected to heat treatment in the heat treatment stage S1602. In Stage S1602, the entire semiconductor substrate may be heat-treated by an annealing furnace. As a result, formation of VOH defects is promoted, and the distribution described inFIG.1Band the like is easily obtained. The heat treatment temperature in Stage S1602may be from 350° C. to 380° C.

Next, in the lower surface grinding stage S1604, the upper surface or the lower surface of the semiconductor substrate is ground to adjust the thickness of the semiconductor substrate. In S1604, it is preferable to grind the surface implanted with hydrogen ions. As a result, it is possible to grind a region which is greatly damaged by the implantation of hydrogen ions. Next, in the element forming stage S1606, each component described inFIG.9toFIG.11is formed. Thus, the semiconductor device100can be manufactured.

In another example, the hydrogen irradiation stage S1600and the heat treatment stage S1602may be performed after the lower surface grinding stage S1604. In addition, the hydrogen irradiation stage S1600may be performed before the undersurface grinding stage S1604, and the heat treatment stage S1602may be performed after the lower surface grinding stage S1604.

Although the present invention has been described using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is apparent to those skilled in the art that various modifications or improvements can be made to the above embodiments. It is apparent from the description of the claims that modes to which such changes or improvements are added can also be included in the technical scope of the present invention.

It should be noted that the order of execution of each processing such as operations, procedures, steps, and stages in the devices, systems, programs, and methods illustrated in the claims, the specification, and the drawings can be realized in any order unless “before”, “prior to”, or the like is specifically stated, and unless the output of the previous processing is used in the later processing. Even if the operation flow in the claims, the specification, and the drawings is described using “First”, “Next”, and the like for convenience, it does not mean that it is essential to perform in this order.

EXPLANATION OF REFERENCES

10: semiconductor substrate;11: well region;12: emitter region;14: base region;15: contact region;16: accumulation region;18: drift region;20: buffer region;21: upper surface22: collector region;23: lower surface;24: collector electrode;25: concentration peak;29: linear portion;30: dummy trench portion31: edge portion;32: dummy insulating film;34: dummy conductive portion;38: interlayer dielectric film;39: linear portion;40: gate trench portion;41: edge portion;42: gate insulating film;44: gate conductive portion;52: emitter electrode;54: contact hole;60,61: mesa portion;70: transistor portion;80: diode portion;81: extension region;82: cathode region;90: edge termination structure portion;100: semiconductor device;102: region;103: concentration peak;104: termination dangling bond flat region;105: concentration peak;111: upper limit;112: lower limit;113: upper limit;114: lower limit;130: outer circumferential gate runner;131: active-side gate runner;160: active portion;162: edge;164: gate pad;200: semiconductor device;201,202,203: concentration peak210: hydrogen concentration peak;211,212: local peak;214: linear approximation distribution;216: band-shaped range;301,302: curve