JP2023099104A - Semiconductor device - Google Patents

Abstract

To provide a semiconductor device im which carriers such as holes accumulated near trench bottom portions can be extracted efficiently.SOLUTION: A semiconductor device includes: a plurality of dummy trench portions 30 provided on the top surface of the semiconductor substrate; a mesa portion 71 that is a region of the semiconductor substrate sandwiched by the dummy trench portions, the mesa portion including a first conductivity type emitter region 12 and a second conductivity type base region 14; a dummy mesa portion 72 that is a region of the semiconductor substrate sandwiched by the dummy trench portions, the dummy mesa portion including a second conductivity type first well region that is deeper than a bottom edge of the trench portion: a drift region; a gate electrode provided above the semiconductor substrate; and an emitter electrode provide above the semiconductor substrate. The first well region has a higher doping concentration than the base region, and is provided up to the bottom of the first mesa portion beyond the bottom 35 of the dummy trench portion in the width direction of the dummy trench portion.SELECTED DRAWING: Figure 13

Description

The present invention relates to semiconductor devices.

2. Description of the Related Art Conventionally, power semiconductor devices such as insulated gate bipolar transistors (IGBTs) are known (see Patent Document 1, for example). In a semiconductor element such as an IGBT, the ON voltage can be lowered by accumulating carriers such as holes in the drift region.
Patent Document 1: JP 2015-72950 A

Holes gather at the lower end of the gate trench portion and the lower end of the dummy trench portion. In particular, since the dummy conductive portion has the same potential as that of the emitter electrode, a hole inversion layer is likely to be formed on the side wall of the dummy trench portion.

A first aspect of the present invention provides a semiconductor device comprising a semiconductor substrate. The semiconductor device may include a plurality of trench portions provided on the upper surface of the semiconductor substrate. The semiconductor device may include a first mesa portion including an emitter region of the first conductivity type in a region of the semiconductor substrate sandwiched between the trench portions. The semiconductor device may include a second mesa portion extending to a position deeper than the lower ends of the trench portions in a region of the semiconductor substrate sandwiched between the trench portions and including a first well region of the second conductivity type. A semiconductor device may comprise a gate electrode and an emitter electrode over a semiconductor substrate. The first well region may extend beyond the bottom of the trench to below the first mesa in the width direction of the trench.

The first mesa portion may include a second conductivity type base region. The doping concentration of the first well region may be higher than the doping concentration of the base region.

The trench portion may include a gate trench portion connected to the gate electrode and a dummy trench portion connected to the emitter electrode. The second mesa portion may be a dummy mesa portion sandwiched between two dummy trench portions.

The first mesa portion may be a mesa portion sandwiched between the gate trench portion and the dummy trench portion.

Each of the two dummy trench portions may have an extending portion extending in the first direction when viewed from above. The two extensions may be connected by a tip that is a trench extending in a second direction perpendicular to the first direction.

The dummy mesa may be surrounded by two extensions and a tip.

A difference in depth between the first well region and the dummy trench may be larger than the width of the second mesa in the second direction.

The length from the sidewall of the dummy trench portion on the first mesa portion side to the position of the end of the first well region is the center in the second direction from the sidewall of the dummy trench portion on the first mesa portion side to the bottom portion of the dummy trench portion. It may be shorter than the length up to

The length from the sidewall of the dummy trench portion on the first mesa portion side to the position of the end of the first well region is the center in the second direction from the sidewall of the dummy trench portion on the first mesa portion side to the bottom portion of the dummy trench portion. It may be longer than the length to

The semiconductor device may further comprise a second well region of the second conductivity type covering the bottom of the tip and having a higher doping concentration than the base region. The second well region may be electrically connected to the first well region of the second mesa.

The second well region may have the same doping concentration as the first well region.

The width of the second mesa portion in the second direction may be larger than the width of the first mesa portion in the second direction.

The width of the second mesa portion in the second direction may be 2.0 times or more and 4.0 times or less of the width of the first mesa portion in the second direction.

The above summary of the invention is not an exhaustive list of all features of the present invention. Subcombinations of these features can also be inventive.

1 is a diagram partially showing the top surface of a semiconductor device 100 according to an embodiment of the present invention; FIG. FIG. 2 is a diagram showing an example of a cross section taken along line aa in FIG. 1; FIG. 2 is a diagram showing an example of a cross section taken along line aa in FIG. 1; FIG. 2 is a diagram showing an example of a cross section taken along line aa in FIG. 1; FIG. 2B is an example of a doping concentration distribution diagram taken along the cc section and the dd section of FIG. 2A. FIG. 2B is another example of a doping concentration distribution diagram taken along the cc section and the dd section of FIG. 2A. FIG. 4 is a diagram showing another example of the top surface of the semiconductor device 100; FIG. 4 is a diagram showing an example of a cross section taken along line aa in FIG. 3; FIG. 4 is a diagram showing an example of a cross section taken along line aa in FIG. 3; FIG. 4C is an example of a doping concentration distribution diagram when the cc section and the dd section of FIG. 4B are cut. FIG. 4C is another example of a doping concentration distribution diagram taken along the cc section and the dd section of FIG. 4B. FIG. 4 is a diagram showing an example of a cross section taken along line aa in FIG. 3; FIG. 4 is a diagram showing another example of the top surface of the semiconductor device 100; FIG. 6 is a diagram showing an example of a cross section taken along line aa in FIG. 5; 6 is a diagram showing another example of the aa cross section in FIG. 5. FIG. 6 is a diagram showing another example of the aa cross section in FIG. 5. FIG. FIG. 4 is a diagram showing another example of the aa cross section in FIG. 3; FIG. 4 is a diagram showing another example of the aa cross section in FIG. 3; 3 is an enlarged cross-sectional view of the vicinity of a first well region 13; FIG. 12 is a cross-sectional view showing an example in which the position of the end portion 36 of the first well region 13 covering the bottom portion 35 is changed in the structure shown in FIG. 11; FIG. 12 is a cross-sectional view showing an example in which the position of the end portion 36 of the first well region 13 covering the bottom portion 35 is changed in the structure shown in FIG. 11; FIG. FIG. 4 is a diagram showing another example of the dummy trench portion 30 and the gate trench portion 40; FIG. 4 is a diagram showing another example of the first well region 13; 3 is a diagram showing another example of the aa cross section of the semiconductor device 100; FIG. 4 is a diagram showing an example of a bb cross section shown in FIG. 3; FIG. It is a figure which shows partially the upper surface of the semiconductor device 200 which concerns on other embodiment of this invention. FIG. 19 is a diagram showing an example of the aa cross section in FIG. 18; FIG. 19 is a diagram showing another example of the aa cross section in FIG. 18; FIG. 4 is a diagram showing an arrangement example of emitter regions 12 and contact regions 15 on the upper surfaces of a first mesa portion 71-1 and a second mesa portion 71-2; FIG. 10 is a diagram showing another arrangement example of emitter regions 12 and contact regions 15 on the upper surfaces of the first mesa portion 71-1 and the second mesa portion 71-2; FIG. 10 is a diagram showing another arrangement example of emitter regions 12 and contact regions 15 on the upper surfaces of the first mesa portion 71-1 and the second mesa portion 71-2; 4 is a diagram showing an arrangement example of an accumulation area 16; FIG. 4A to 4C are diagrams illustrating an example of a method for manufacturing the semiconductor device 100; FIG.

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. Also, not all combinations of features described in the embodiments are essential for the solution of the invention.

In this specification, one side in a direction parallel to the depth direction of the semiconductor substrate is called "upper", and the other side is called "lower". One of the two main surfaces of a substrate, layer or other member is called the upper surface and the other surface is called the lower surface. The directions of "up" and "down" are not limited to the direction of gravity or the mounting direction to a substrate or the like when the semiconductor device is mounted. In this specification, technical matters may be described using X-, Y-, and Z-axis orthogonal coordinate axes. Let the depth direction of the semiconductor substrate be the Z-axis. Also, the orthogonal coordinate system is a so-called right-handed system in this example.

Although the terms "emitter" and "collector" are used in this specification, semiconductor devices are not limited to IGBTs. "Sources" and "drains" in transistors such as MOSFETs may also be included within the scope of the terms "emitter" and "collector" herein.

In each embodiment, an example in which the first conductivity type is the N type and the second conductivity type is the P type is shown, but the first conductivity type may be the P type and the second conductivity type may be the N type. In this case, the conductivity types of the substrate, layers, regions, etc. in each embodiment have opposite polarities. When comparing doping concentrations between regions herein, the peak concentration in each region may be used.

In the present specification, the term "same" may include the case where there is an error due to manufacturing variations or the like. The error is, for example, within 10%.

FIG. 1 is a diagram partially showing the top surface of a semiconductor device 100 according to an embodiment of the present invention. The semiconductor device 100 of this example is a semiconductor chip including transistors such as IGBTs. FIG. 1 shows the top surface of the chip around the edge of the chip, omitting other regions.

Also, although FIG. 1 shows an active region of a semiconductor substrate in semiconductor device 100, semiconductor device 100 may have edge terminations surrounding the active region. The active region refers to a region through which current flows when the semiconductor device 100 is controlled to be on. The edge termination relieves electric field concentration on the upper surface side of the semiconductor substrate. Edge terminations may include, for example, guard rings, field plates, RESURF, and combinations thereof.

The semiconductor device 100 of this example includes a gate trench portion 40, a dummy trench portion 30, an emitter region 12, a base region 14, a contact region 15, a first well region 13 and a second well region 11 provided inside a semiconductor substrate. Prepare. The semiconductor device 100 of this example also includes an emitter electrode 52 and a gate electrode 46 provided above the upper surface of the semiconductor substrate. Emitter electrode 52 and gate electrode 46 are provided separately from each other.

An interlayer insulating film is provided between the emitter electrode 52 and the gate electrode 46 and the upper surface of the semiconductor substrate, but is omitted in FIG. A contact hole 54, a contact hole 55, and a contact hole 56 are provided through the interlayer insulating film of this example.

Emitter electrode 52 contacts emitter region 12 , contact region 15 , base region 14 and first well region 13 on the upper surface of the semiconductor substrate through contact hole 54 . The contact holes 54 of this example are provided between the respective trench portions. Also, the emitter electrode 52 is connected to the dummy conductive portion in the dummy trench portion 30 through the contact hole 56 . Between the emitter electrode 52 and the dummy conductive portion, a connection portion 57 made of a conductive material such as impurity-doped polysilicon may be provided. The connecting portion 57 is provided on the upper surface of the semiconductor substrate with an insulating film such as a thermal oxide film interposed therebetween. In this example, the contact hole 56 is arranged at the tip of the dummy trench portion 30 in the X-axis direction.

Gate electrode 46 is in contact with gate wiring 45 through contact hole 55 . The gate wiring 45 is formed of impurity-doped polysilicon or the like. An insulating film such as a thermal oxide film is provided between the gate wiring 45 and the semiconductor substrate. The gate wiring 45 is connected to the gate conductive portion in the gate trench portion 40 on the upper surface of the semiconductor substrate. Gate wiring 45 is not connected to the dummy conductive portion in dummy trench portion 30 . The gate wiring 45 of this example is provided from below the contact hole 55 to the tip portion 43 of the gate trench portion 40 . The gate conductive portion is exposed on the upper surface of the semiconductor substrate at the tip portion 43 of the gate trench portion 40 and is in contact with the gate wiring 45 .

Emitter electrode 52 and gate electrode 46 are formed of a material containing metal. For example, at least a partial region of each electrode is made of aluminum or an aluminum-silicon alloy. Each electrode may have a barrier metal made of titanium, a titanium compound, or the like under a region made of aluminum or the like. Further, the contact hole may have a plug formed by embedding tungsten or the like so as to be in contact with the barrier metal and the aluminum or the like.

One or more gate trench portions 40 and one or more dummy trench portions 30 are arranged at predetermined intervals along a predetermined arrangement direction (transverse direction) on the upper surface of the semiconductor substrate. The arrangement direction in FIG. 1 is the Y-axis direction.

The gate trench portion 40 of this example includes two extending portions 41 that extend linearly along the extending direction (longitudinal direction of the trenches, which is the X-axis direction in this example) perpendicular to the arrangement direction, and It may have a tip 43 connecting the two extensions 41 . At least a part of the tip portion 43 is preferably formed in a curved shape on the upper surface of the semiconductor substrate. By connecting the tips of the two extending portions 41 of the gate trench portion 40 with the tip portion 43, electric field concentration at the ends of the extending portions 41 can be alleviated. In this specification, the two extending portions 41 connected by the tip portion 43 may be treated as two gate trench portions 40 .

One or more dummy trench portions 30 are provided between each extension portion 41 of the gate trench portion 40 . Like the gate trench portion 40 , the dummy trench portion 30 may have a tip portion 33 that connects the tips of the two extending portions 31 . In this example, a dummy trench portion 30 having two extension portions 31 and a tip portion 33 is provided between each extension portion 41 of the gate trench portion 40 . Another example of the dummy trench portion 30 may have a linear shape without the tip portion 33 . The dummy trench portion 30 is provided at a position not overlapping the gate wiring 45 . In this specification, the two extending portions 31 connected by the tip portion 33 may be treated as two dummy trench portions 30 .

Emitter electrode 52 is provided above gate trench portion 40 , dummy trench portion 30 , first well region 13 , second well region 11 , emitter region 12 , base region 14 and contact region 15 . The second well region 11 is provided within a predetermined range away from the longitudinal end of the contact hole 54 in the direction toward the gate electrode 46 . The diffusion depth of second well region 11 may be deeper than the depths of gate trench portion 40 and dummy trench portion 30 . A partial region of gate trench portion 40 and dummy trench portion 30 on the gate electrode 46 side is provided in second well region 11 . The ends of the dummy trench portion 30 in the extending direction and the bottom of the tip portion may be covered with the second well region 11 .

In this example, a region of the semiconductor substrate sandwiched between trench portions is called a mesa portion 71 . However, a region of the semiconductor substrate sandwiched between two dummy trench portions 30 (or two extension portions 31) is called a dummy mesa portion 72. As shown in FIG. The mesa portion 71 and the dummy mesa portion 72 are regions on the upper surface side of the deepest bottom of the trench portions in the region of the semiconductor substrate sandwiched between the trench portions.

A base region 14 is provided in the mesa portion 71 . The second well region 11 is of the second conductivity type. The base region 14 is of P− type with a lower doping concentration than the second well region 11, which is of P+ type.

A P + -type contact region 15 having a higher doping concentration than the base region 14 is provided on the upper surface of the base region 14 of the mesa portion 71 . The second well region 11 is provided apart in the direction of the gate electrode 46 from the contact region 15 arranged at the end in the extending direction of the trench portion among the contact regions 15 in the active region. An N + -type emitter region 12 having a doping concentration higher than that of the semiconductor substrate is selectively formed on the upper surface of the base region 14 .

Each of contact region 15 and emitter region 12 is provided from one trench portion to the other adjacent trench portion in the Y-axis direction. The contact regions 15 and the emitter regions 12 are alternately exposed on the upper surface of the semiconductor substrate along the extending direction (X-axis direction) of the trench portion. The contact region 15 and the emitter region 12 may be provided on the upper surface of the mesa portion 71 in a region sandwiched between the base regions 14 exposed at both ends in the X-axis direction.

In another example of the mesa portion 71, the contact regions 15 and the emitter regions 12 may be provided in stripes along the extending direction (X-axis direction). For example, an emitter region 12 is provided in a region adjacent to the trench portion, and a contact region 15 is provided in a region sandwiched between the emitter regions 12 .

The dummy mesa portion 72 is provided with the first well region 13 of the second conductivity type having a higher doping concentration than the base region 14 . The first well region 13 in this example is of P+ type. The doping concentration of the first well region 13 may be the same as or different from the doping concentration of the second well region 11 . The doping concentration of the first well region 13 may be 5 times or more, or 10 times or more, the doping concentration of the base region 14 .

The first well region 13 is exposed on the top surface of the dummy mesa portion 72 . The first well region 13 of this example is provided in a range facing the emitter region 12 and the contact region 15 in the mesa portion 71 adjacent in the Y-axis direction. The first well region 13 is continuously provided in the Y-axis direction on the upper surface of the dummy mesa portion 72 from a position in contact with one dummy trench portion 30 to a position in contact with the other dummy trench portion 30 . The first well region 13 may be provided continuously on the upper surface of the dummy mesa portion 72 in a region sandwiched between the exposed base regions 14 at both ends in the X-axis direction.

Contact hole 54 provided in mesa portion 71 is provided above contact region 15 and emitter region 12 . The contact hole 54 provided in the dummy mesa portion 72 is provided above the first well region 13 . Contact hole 54 is not provided in a region corresponding to base region 14 and second well region 11 . An emitter region may not be provided on the upper surface of the dummy mesa portion 72 . A contact region 15 may be provided on the upper surface of the dummy mesa portion 72 at least in a region where the contact hole 54 is formed.

FIG. 2A is a diagram showing an example of the aa cross section in FIG. The aa section of this example is the YZ plane passing through the emitter region 12 . The semiconductor device 100 of this example has a semiconductor substrate 10, an interlayer insulating film 26, an emitter electrode 52 and a collector electrode 58 in the cross section. The interlayer insulating film 26 is, for example, silicate glass doped with impurities such as boron and phosphorus. The interlayer insulating film 26 is selectively formed on the upper surface 21 of the semiconductor substrate 10 . Emitter electrode 52 is provided on top surface 21 of semiconductor substrate 10 and interlayer insulating film 26 . A collector electrode 58 is provided on the lower surface 23 of the semiconductor substrate 10 . The collector electrode 58 may be provided over the entire bottom surface 23 of the semiconductor substrate 10 .

The semiconductor substrate 10 may be a silicon substrate, a silicon carbide substrate, a nitride semiconductor substrate such as gallium nitride, or the like. The semiconductor substrate 10 of this example is a silicon substrate.

An N− type drift region 18 is provided inside the semiconductor substrate 10 . The drift region 18 in the cross section is a region of the semiconductor substrate 10 where the emitter region 12, the base region 14, the first well region 13, the buffer region 20 and the collector region 22 are not formed.

A P− type base region is provided between the upper surface 21 of the semiconductor substrate 10 and the drift region 18 in the region of the semiconductor substrate 10 adjacent to any gate trench portion 40 . In this example, each mesa portion 71 is provided with a P− type base region. The base region 14 may be formed by implanting a P-type impurity such as boron from the upper surface of the semiconductor substrate 10 .

In the mesa portion 71 , an N + -type emitter region 12 is provided on the upper surface of the base region 14 . The emitter region 12 may be formed by implanting an N-type impurity such as phosphorus or arsenic from the upper surface of the semiconductor substrate 10 .

A first well region 13 is provided between the upper surface 21 of the semiconductor substrate 10 and the drift region 18 in a region of the semiconductor substrate 10 adjacent to any dummy trench portion 30 . The first well region 13 is provided from the upper surface 21 of the semiconductor substrate 10 to a position deeper than the lower ends of the dummy trench portions 30 . In the cross section shown in FIG. 2A, the first well region 13 is provided in the entire dummy mesa portion 72 and the region below the dummy mesa portion 72 .

The lower end of the first well region 13 may be determined based on the doping concentration distribution in the depth direction (Z-axis direction) of the first well region 13 and drift region 18 . As used herein, the doping concentration refers to the concentration of impurities (dopants) that have become donors or acceptors. The depth position at which the concentration difference (net doping concentration) distribution between donors and acceptors measured by the spreading resistance (SR) method or the like has a minimum value may be the lower end of the first well region 13 .

Gate trench portion 40 is formed from upper surface 21 of semiconductor substrate 10 to the inside of semiconductor substrate 10 and is in contact with emitter region 12 and base region 14 at sidewalls. The gate trench portion 40 of this example is not in contact with the first well region 13 . The gate trench portion 40 of this example is provided from the upper surface 21 of the semiconductor substrate 10 so as to penetrate through the emitter region 12 and the base region 14 .

The dummy trench portion 30 is formed from the upper surface 21 of the semiconductor substrate 10 to the inside of the semiconductor substrate 10 and is in contact with the first well region 13 at the sidewall. Of the sidewalls of dummy trench portion 30 , those sidewalls facing gate trench portion 40 may be in contact with emitter region 12 and base region 14 . The gate trench portion 40 and the dummy trench portion 30 may be provided up to the same depth position Z1 in the Z-axis direction.

The bottom of the gate trench portion 40 in this example is located within the drift region 18 . A bottom portion of the dummy trench portion 30 may be arranged in the drift region 18 and may be covered with the first well region 13 . It should be noted that the fact that the trench penetrates through each doping region is not limited to the order in which the doping region is formed and then the trench is formed. A structure in which a doping region is formed between the trench portions after the trench portions are formed is also included in the structure in which the trench portion penetrates the doping regions.

Buffer region 20 is formed on the lower surface side of drift region 18 . The doping concentration of buffer region 20 is higher than the doping concentration of drift region 18 . The buffer region 20 may function as a field stop layer that prevents the depletion layer spreading from the lower surface side of the base region 14 from reaching the P + -type collector region 22 . A P+ type collector region 22 is formed on the lower surface side of the buffer region 20 .

The gate trench portion 40 has a gate insulating film 42 and a gate conductive portion 44 . A gate insulating film 42 is formed to cover the inner wall of the gate trench. The gate insulating film 42 may be formed by oxidizing or nitriding the semiconductor on the inner wall of the gate trench. The gate conductive portion 44 is covered with the gate insulating film 42 inside the gate trench. That is, the gate insulating film 42 insulates the gate conductive portion 44 and the semiconductor substrate 10 from each other. The gate conductive portion 44 is formed of a conductive material such as polysilicon.

The gate conductive portion 44 includes a region facing at least the adjacent base region 14 with the gate insulating film 42 interposed therebetween in the depth direction. The gate trench portion 40 in the cross section is covered with the interlayer insulating film 26 on the upper surface of the semiconductor substrate 10 . When a predetermined voltage is applied to the gate conductive portion 44 , a channel is formed by an electron inversion layer in the surface layer of the interface of the base region 14 in contact with the gate trench portion 40 .

The dummy trench portion 30 of this example has a dummy insulating film 32 and a dummy conductive portion 34 . The dummy insulating film 32 is formed covering the inner wall of the dummy trench. The dummy conductive portion 34 is formed inside the dummy trench portion 30 and covered with the dummy insulating film 32 . The dummy insulating film 32 insulates the dummy conductive portion 34 from the semiconductor substrate 10 . The dummy conductive portion 34 may be made of the same material as the gate conductive portion 44 . For example, the dummy conductive portion 34 is made of a conductive material such as polysilicon. The dummy conductive portion 34 may have the same length as the gate conductive portion 44 in the depth direction. The dummy trench portion 30 in the cross section is covered with the interlayer insulating film 26 on the upper surface of the semiconductor substrate 10 . The bottoms of the dummy trench portion 30 and the gate trench portion 40 may be curved (curved in cross section) convex downward.

The width of the mesa portion 71 and the width of the dummy mesa portion 72 may be equal. The width of the mesa portion 71 is typically 1.0 μm, and may be 0.1 μm or more and 3.0 μm or less. The width _WGT of the gate trench portion and the width _WDT of the dummy trench portion 30 may be equal or different. In this example, they are equal. Also, the width C of the mesa portion 71 may be equal to the width D of the dummy mesa portion 72 .

The width of the contact hole 54 in the Y-axis direction may be the same between the mesa portion 71 and the dummy mesa portion 72 . The width of the contact hole 54 is typically 0.6 μm, and may be 0.05 μm or more and 2.0 μm or less within a range not exceeding the mesa width or the dummy mesa width.

By providing the dummy trench portion 30, the effect of accumulating carriers can be enhanced, the conductivity modulation can be promoted, and the ON voltage can be lowered. Further, by adjusting the ratio of the dummy trench portion 30 to the gate trench portion 40, the switching speed of the semiconductor device 100 can be adjusted.

When the semiconductor device 100 is turned off, carriers accumulated near the bottom of the trench in the drift region 18 are extracted to the emitter electrode 52 through the region of the second conductivity type. If the withdrawal speed of carriers at the time of turn-off is slower than the concentration of accumulated carriers, the withstand capability of the semiconductor device 100 is lowered. The carrier extraction speed refers to the amount of carriers such as holes that are extracted per unit time from the drift region 18 to the emitter electrode 52 or the like when the semiconductor device 100 is turned off.

In the semiconductor device 100, by providing the first well region 13 formed deeper than the dummy trench portion 30, carriers such as holes accumulated in the vicinity of the trench bottom portion can be efficiently extracted. Therefore, it is possible to easily achieve both reduction of the ON voltage of the semiconductor device 100 and maintenance of the withstand voltage of the semiconductor device 100 .

FIG. 2B is a diagram showing an example of the aa cross section in FIG. In the semiconductor device 100 of this example, the contact width of the contact for connecting with the semiconductor substrate 10 is different from that in FIG. 2A. In this example, the contact width B of the contact formed on the first well region 13 is different from the contact width A of the contact formed on the emitter region 12 . The contact width B in this example may be larger or smaller than the contact width A. The contact width B is larger than the contact width A in this example. That is, by making the contact width B between the dummy trench portions 30 larger than the contact width A between the dummy trench portion 30 and the gate trench portion 40, the turn-off resistance of the semiconductor device 100 can be improved.

A ratio (A/B) between the contact width A and the contact width B may be 0.2 or more and 2.0 or less. When the contact width B is larger than the contact width A, the ratio (A/B) is 0.2 or more and less than 1.0, and may be 0.4 or more and 0.7 or less. On the other hand, when the contact width B is smaller than the contact width A, the ratio (A/B) is greater than 1.0 and 2.0 or less, and may be 1.3 or more and 1.7 or less.

FIG. 2C is a diagram showing an example of the aa cross section in FIG. The semiconductor device 100 of this example differs from the case of FIG. 2A in that the width of the dummy mesa portion 72 in the Y-axis direction is different from the width of the mesa portion 71 in the Y-axis direction. In this example, the width D of the dummy mesa portion 72 is different from the width C of the mesa portion 71 between the dummy trench portion 30 and the gate trench portion 40 . The width D of the dummy mesa portion 72 in this example may be larger than the width C of the mesa portion 71 . By making the width D of the dummy mesa portion 72 larger than the width C of the other mesa portions 71, the turn-off resistance of the semiconductor device 100 can be improved.

A ratio (D/C) between the width C of the mesa portion 71 and the width D of the dummy mesa portion 72 may be greater than 0.2 and less than or equal to 5.0. When the width D of the dummy mesa portion 72 is smaller than the width C of the mesa portion 71, the ratio (D/C) is 0.2 or more and less than 1.0, and may be 0.4 or more and 0.7 or less. On the other hand, when the width D of the dummy mesa portion 72 is greater than the width C of the mesa portion 71, the ratio (D/C) is greater than 1.0 and less than or equal to 5.0, and moreover, more than or equal to 2.0 and less than or equal to 4.0. good.

FIG. 2D is an example of a distribution map of doping concentration when the cc section and the dd section of FIG. 2A are cut. In the cc cross section, the emitter region 12, the base region 14, and the drift region 18 are arranged in this order from the upper surface side of the semiconductor substrate 10. As shown in FIG. In the dd cross section, the doping concentration distribution of the first well region 13 may have a Gaussian distribution from the top surface of the semiconductor substrate 10 . A Gaussian distribution is a profile when a dopant introduced into the upper surface of the semiconductor substrate 10 is diffused by thermal diffusion.

The depth from the upper surface of the pn junction between the base region 14 and the drift region 18, that is, the depth of the base region 14 is deeper than the lower end position Z1 of the trench portion. On the other hand, the depth of the pn junction between the first well region 13 and the drift region 18, that is, the depth of the first well region 13 may be deeper than the lower end position Z1 of the trench portion. The depth of the base region 14 is typically 3.0 μm, and may be between 0.5 μm and 5.0 μm. The depth of the first well region 13 is typically 7.0 μm, and may be 2.0 μm or more and 10 μm or less.

FIG. 2E is another example of a doping concentration distribution diagram taken along the cc section and the dd section of FIG. 2A. The doping concentration distribution along the cc section in this example is the same as the doping concentration distribution along the cc section in FIG. 2D. In this example, the doping concentration distribution in the dd cross section is different from that in FIG. 2D. The first well region 13 of this example has four peaks of first well region 13-1 to first well region 13-4. For example, in the dd cross section, the doping concentration distribution of the first well region 13 has a concentration peak at a position deeper than the base region 14 in the first step of lowering the contact resistance, the second step of the doping concentration distribution which is almost the same as that of the base region 14, and the base region 14. It consists of a third stage provided and a fourth stage provided with a concentration peak at a deeper position than the third stage.

The number and depth of peak positions of the first well region 13 are not limited to this example. The fourth stage of the first well region 13 is in contact with the drift region 18 and has a pn junction. The local minimum concentration in the valley between each concentration peak may be higher than the doping concentration of the drift region 18 . The third and fourth peak concentrations of the first well region 13 in FIG. 2E may be higher than the peak concentration of the base region 14 and may be lower than that of the base region 14 .

Also, the third stage peak position may be deeper than the position of the pn junction between the base region 14 and the drift region 18 . Also, the peak position of the fourth stage may be shallower than the lower end position Z1 of the trench portion.

FIG. 3 is a diagram showing another example of the top surface of the semiconductor device 100. As shown in FIG. The semiconductor device 100 of this example further includes an accumulation region 16 in addition to the configuration of the semiconductor device 100 described with reference to FIGS. 1 and 2A. The accumulation region 16 is a region of first conductivity type that is more heavily doped than the drift region 18 . The accumulation region 16 in this example is of the N+ type.

The accumulation region 16 is not exposed on the top surface of the semiconductor substrate 10 . Accumulation region 16 may be formed between drift region 18 and base region 14 . In FIG. 3, the region where the accumulation region 16 is provided in the XY plane parallel to the upper surface 21 of the semiconductor substrate 10 is indicated by broken lines. In this example, a plurality of accumulation regions 16 separated from each other are provided within the plane.

An accumulation region 16 is provided in at least a partial region of the mesa portion 71 sandwiched between two trench portions, at least one of which is the gate trench portion 40 . The accumulation region 16 in this example is provided below at least the emitter region 12 . The accumulation region 16 may also be provided below the contact region 15 . The accumulation region 16 of this example is provided over the entire mesa portion 71 in the width direction (Y-axis direction). The accumulation region 16 may not be provided below the base region 14 exposed on the upper surface of the mesa portion 71 . On the other hand, the dummy mesa portion 72 is not provided with the accumulation region 16 having a higher doping concentration than the base region 14 .

FIG. 4A is a diagram showing an example of the aa cross section in FIG. The aa section of this example is the YZ plane passing through the emitter region 12 . The semiconductor device 100 of this example further includes an accumulation region 16 in addition to the configuration of the semiconductor device 100 shown in FIG. 2A. The accumulation region 16 is provided between the base region 14 and the drift region 18 in each mesa portion 71 . The accumulation region 16 of this example is provided in each mesa portion 71 from a region adjacent to one trench portion to a region adjacent to the other trench portion.

The accumulation region 16 is an N+ type region with a higher doping concentration than the drift region 18 . For example, the accumulation region 16 may be a region between the drift region 18 and the base region 14 that has a doping concentration ten times or more higher than the average doping concentration of the drift region 18 . The doping concentration of accumulation region 16 may be 50 times or more, and may be 100 times or more, that of drift region 18 . The accumulation region 16 may be formed by implanting N-type impurities such as phosphorus or protons from the top surface 21 of the semiconductor substrate 10 .

By providing the accumulation region 16, the concentration of carriers accumulated below the accumulation region 16 can be further increased. Therefore, the ON voltage of the semiconductor device 100 can be reduced. Further, by providing the first well region 13, carriers accumulated in the accumulation region 16 can be efficiently extracted. Therefore, even if the accumulation region 16 is provided, the tolerance of the semiconductor device 100 can be maintained.

FIG. 4B is a diagram showing an example of the aa cross section in FIG. The semiconductor device 100 of this example differs from the case of FIG. 4A in that the dummy mesa portion 72 has the accumulation region 16 . The accumulation region 16 of this example includes an accumulation region 16-1 formed in the mesa portion 71 and an accumulation region 16-2 formed in the dummy mesa portion 72. FIG. Storage region 16-1 and storage region 16-2 may be formed simultaneously in the same process. Also, accumulation region 16-1 and accumulation region 16-2 may be formed with different dopant concentrations by different processes.

The accumulation region 16 - 2 is formed sandwiched between the dummy trench portions 30 in the dummy mesa portion 72 . That is, the upper and lower ends of the accumulation region 16-2 are provided in contact with the first well region 13. As shown in FIG. The accumulation region 16-2 is a region of the first conductivity type with a higher doping concentration than the drift region 18. FIG. In the semiconductor device 100 of the present example, by providing the accumulation region 16-2 in the dummy mesa portion 72, extraction of carriers via the P-type inversion layer at the bottom of the dummy trench portion 30 is suppressed during turn-on, thereby reducing turn-on loss. can.

FIG. 4C is an example of a doping concentration distribution diagram when the cc section and the dd section of FIG. 4B are cut. In the cc cross section, the emitter region 12, the base region 14, and the drift region 18 are arranged in this order from the upper surface side of the semiconductor substrate 10. As shown in FIG. In the dd cross section, the doping concentration distribution of the first well region 13 may have a Gaussian distribution from the top surface of the semiconductor substrate 10 . A Gaussian distribution is a profile when a dopant introduced into the upper surface of the semiconductor substrate 10 is diffused by thermal diffusion.

The depth from the upper surface of the semiconductor substrate 10 to the peak position of the doping concentration of the accumulation region 16 may be deeper than the depth from the peak position to the lower end position Z1 of the trench portion. The peak position of the accumulation region 16 is typically 4.0 μm, and may be 1.0 μm or more and 6.0 μm or less.

FIG. 4D is another example of a doping concentration distribution diagram taken along the cc section and the dd section of FIG. 4B. The doping concentration distribution in the dd section is different from that in FIG. 2D. The first well region 13 of this example has three peaks of first well regions 13-1 to 13-3. For example, in the dd cross section, the doping concentration distribution is as follows: the first stage of the first well region 13 that lowers the contact resistance; It consists of the third stage of the first well region 13 having a concentration peak at a position deeper than the accumulation region 16-2. The third stage peak concentration of the first well region 13 in FIG. 4D may be higher than the peak concentration of the accumulation region 16-2 or lower than the accumulation region 16-2. In this example, the third stage peak concentration of the first well region 13 is higher than the peak concentration of the accumulation region 16-2.

FIG. 4E is a diagram showing an example of the aa cross section in FIG. The semiconductor device 100 of this example differs from the case of FIG. 4A in that the film thickness d1 of the dummy insulating film 32 and the film thickness d2 of the gate insulating film 42 are different. The film thickness d1 of the dummy insulating film 32 in this example is thicker than the film thickness d2 of the gate insulating film 42 . This suppresses extraction of carriers via the P-type inversion layer at the bottom of the dummy trench portion 30 during turn-on, thereby reducing turn-on loss. The film thickness d2 is typically 0.1 μm, and may be 0.05 μm or more and 0.3 μm or less. The film thickness d1 is typically 0.2 μm, and may be 0.1 μm or more and 1.0 μm or less within a range thicker than the film thickness d2. This suppresses extraction of carriers via the P-type inversion layer at the bottom of the dummy trench portion 30 during turn-on, thereby reducing turn-on loss.

In this example, the dummy trench portion 30 and the gate trench portion 40 have the same width in the Y-axis direction, and the film thickness d1 of the dummy insulating film 32 is increased. 44 in the Y-axis direction. By making the width of the dummy trench portion 30 in the Y-axis direction larger than the width of the gate trench portion 40 in the Y-axis direction, the film thickness d1 of the dummy insulating film 32 is made larger than the film thickness d2 of the gate insulating film 42. You may

FIG. 5 is a diagram showing another example of the top surface of the semiconductor device 100. FIG. The semiconductor device 100 of this example differs in arrangement of the accumulation region 16 from the configuration of the semiconductor device 100 shown in FIGS. 3 and 4A. Other configurations are the same as those of the semiconductor device 100 shown in FIGS. 3 and 4A.

The accumulation region 16 of this example is not provided in a region adjacent to at least one trench portion in at least a portion of the mesa portion 71 . In the example of FIG. 5, the accumulation region 16 is in contact with the gate trench portion 40 and not in contact with the dummy trench portion 30 at each mesa portion 71 . Also, the accumulation region 16 is not provided in the dummy mesa portion 72 .

FIG. 6 is a diagram showing an example of the aa cross section in FIG. The aa section of this example is the YZ plane passing through the emitter region 12 . The semiconductor device 100 of this example differs in arrangement of the accumulation region 16 from the configuration of the semiconductor device 100 shown in FIG. 4A. Other configurations are the same as those of the semiconductor device 100 shown in FIG. 4A.

The accumulation region 16 of this example is provided in a region adjacent to the gate trench portion 40 inside the semiconductor substrate 10 . The accumulation region 16 may be provided in contact with the base region 14 or may be provided apart from the base region 14 . However, the accumulation region 16 is preferably provided inside the mesa portion 71 (that is, the region from the upper surface 21 of the semiconductor substrate 10 to the lower end of the trench portion).

In each mesa portion 71 , the N-type doping concentration of the region 17 adjacent to the dummy trench portion 30 inside the semiconductor substrate 10 and at the same depth as the accumulation region 16 is lower than that of the accumulation region 16 . Region 17 in this example has the same doping concentration as drift region 18 . The accumulation region 16 may be provided in a region that is less than or equal to half the width of the mesa portion 71 in the Y-axis direction, or may be provided in a region that is more than or equal to half the width.

With such a structure, carriers can be accumulated in the vicinity of the lower end of the gate trench portion 40, and carriers such as holes can be extracted also from the mesa portion 71 at the time of turn-off. For example, carriers that have passed near the dummy trench portion 30 are extracted to the emitter electrode 52 through the base region 14 and the contact region 15 .

FIG. 7 is a diagram showing another example of the aa cross section in FIG. The semiconductor device 100 of this example differs from the configuration of the semiconductor device 100 shown in FIG. 6 in the arrangement of the accumulation regions 16 in the Z-axis direction. Other configurations are the same as those of the semiconductor device 100 shown in FIG.

The accumulation region 16 in this example is arranged apart from the base region 14 . A drift region 18 may be provided between the accumulation region 16 and the base region 14 . Note that the accumulation region 16 is in contact with the gate trench portion 40 and is not in contact with the dummy trench portion 30 . A partial region of the accumulation region 16 may be provided below the lower end of the gate trench portion 40 .

The bottom portion of the gate trench portion 40 of this example has a curved shape that protrudes downward. The accumulation region 16 may cover part of the curved surface at the bottom of the gate trench portion 40 . With such a structure as well, carriers can be accumulated in the vicinity of the lower end of the gate trench portion 40, and carriers such as holes can be extracted also from the mesa portion 71 at the time of turn-off.

FIG. 8 is a diagram showing another example of the aa cross section in FIG. The semiconductor device 100 of this example differs from the configuration of the semiconductor device 100 shown in FIG. 6 in the arrangement of the accumulation regions 16 . Other configurations are the same as those of the semiconductor device 100 shown in FIG.

The semiconductor device 100 of this example has a first accumulation region 16-1 and a second accumulation region 16-2 in each mesa portion 71. FIG. The first accumulation area 16-1 is identical to the accumulation area 16 shown in FIG. 6, and the second accumulation area 16-2 is identical to the accumulation area 16 shown in FIG.

The first accumulation region 16-1 and the second accumulation region 16-2 may have the same doping concentration or different doping concentrations. When viewed in the Z-axis direction, at least a portion of the first accumulation region 16-1 and at least a portion of the second accumulation region 16-2 overlap each other.

The first accumulation area 16-1 and the second accumulation area 16-2 may be provided apart in the Z-axis direction. In this case, a drift region 18 may be provided between the first accumulation region 16-1 and the second accumulation region 16-2. The first accumulation region 16-1 and the second accumulation region 16-2 may be provided continuously in the Z-axis direction. In this case, the doping concentration distribution in the depth direction of the first accumulation region 16-1 and the second accumulation region 16-2 is It may have a peak within the region. The doping concentration between the peaks is greater than the doping concentration of drift region 18 .

With such a structure as well, carriers can be accumulated in the vicinity of the lower end of the gate trench portion 40, and carriers such as holes can be extracted also from the mesa portion 71 at the time of turn-off.

FIG. 9 is a diagram showing another example of the aa cross section in FIG. The semiconductor device 100 of this example differs in arrangement of the accumulation region 16 from the configuration of the semiconductor device 100 shown in FIG. 4A. Other configurations are the same as those of the semiconductor device 100 shown in FIG. 4A.

The semiconductor device 100 of this example has a first accumulation region 16-1 and a second accumulation region 16-2 in each mesa portion 71. FIG. The first storage area 16-1 is identical to the storage area 16 shown in FIG. 4A. The second accumulation region 16-2 is provided inside the mesa portion 71 below the first accumulation region 16-1. The second accumulation region 16-2 may have the same doping concentration as the first accumulation region 16-1, or may have a different doping concentration. The semiconductor device 100 may include an accumulation region 16 provided in three or more stages in the depth direction inside the mesa portion 71 .

Like the first accumulation region 16-1, the second accumulation region 16-2 is provided in the Y-axis direction from a region in contact with one trench to a region in contact with the other trench. The first accumulation region 16-1 and the second accumulation region 16-2 may be provided separately in the Z-axis direction, or may be provided continuously. Such a structure can further enhance the carrier accumulation effect.

By providing the accumulation region 16 in multiple stages in the depth direction, the electron current passing through the channel formed in the vicinity of the interface between the base region 14 and the gate trench portion 40 at the time of turn-on is transferred to the Y axis of the mesa portion 71. It becomes easier to flow near the center in the direction.

At the beginning of turn-on, the main current is electron current, not hole current. The initial stage is a period from just before the gate voltage Vge reaches the threshold voltage to before entering the mirror period in which Vge is almost constant at the value of the threshold voltage. As Vge approaches the threshold voltage, the channel begins to open and electrons begin to be injected into the drift region 18 .

Electrons traveling downward from the channel may once flow in the arrangement direction (the Y-axis direction or the direction from the vicinity of the gate trench portion 40 toward the center of the mesa portion 71) in the first accumulation region 16-1. If the second accumulation region 16-2 is not provided, an electron accumulation layer is already formed in the vicinity of the gate trench portion 40 in the drift region 18 below the first accumulation region 16-1. Therefore, it has a lower impedance than the drift region 18 (the threshold voltage at which an accumulation layer of electrons in the N-type region forms is much lower than the threshold voltage of the inversion layer in the P-type region). Therefore, the electron current mainly flows in the vicinity of the gate trench portion 40 .

When the electrons reach the backside collector region 22 , hole injection begins from collector region 22 to buffer region 20 and drift region 18 . As a result, holes are accumulated in the vicinity of the lower end of the trench portion. As an example, holes exist on the order of 1.0×10 ¹⁶ [cm ⁻³ ] from the vicinity of the lower end of the gate trench portion 40 to the side portion of the dummy trench portion 30 below the first accumulation region 16 . .

Holes gather at the lower end of the gate trench portion 40 and the lower end of the dummy trench portion 30 . In particular, since the dummy conductive portion 34 has the same potential as the emitter electrode 52 , a hole inversion layer is likely to be formed on the side wall of the dummy trench portion 30 . Holes injected from the collector region 22 collect in the vicinity of this hole inversion layer. Holes are continuously distributed from the dummy trench portion 30 to the lower end of the gate trench portion 40 . Due to this hole distribution, a large displacement current may flow near the lower end of the gate trench portion 40 at turn-on.

The semiconductor device 100 of this example further includes a second accumulation region 16-2. In this case, the impedance for the electron current is higher in the first accumulation region 16 than in the path flowing from the vicinity of the center of the first accumulation region 16-1 back to the vicinity of the gate trench portion 40 to the second accumulation region 16-2. The path that flows directly from -1 to the second storage region 16-2 is lower.

Holes tend to be accumulated in the high-hole-concentration region adjacent to the gate trench portion 40 below each accumulation region. Further, the electron current flows in the vicinity of the center of the mesa portion 71 instead of in the vicinity of the gate trench portion 40, thereby promoting the accumulation of holes in the high hole concentration region. Therefore, it is promoted that the electron current flows in the vicinity of the center of the mesa portion 71 .

By providing the accumulation regions 16 in multiple stages in the depth direction, it becomes easier for the electron current to travel downward in the vicinity of the center of the mesa portion 71 . When the electron current flows near the center of the mesa portion 71 , the hole distribution near the bottom of the mesa portion 71 is divided by the electron current near the center of the mesa portion 71 . Therefore, holes on the dummy trench portion 30 side of the electron current path do not flow to the gate trench portion 40 side. The division of the hole distribution at the central portion of the mesa portion 71 suppresses accumulation of holes at the lower end of the gate trench portion 40 . Therefore, the displacement current can be reduced. Since the displacement current can be reduced, the charging of the gate conductive portion 44 is also reduced, and the momentary increase in the gate electrode Vge is suppressed. As a result, the voltage reduction rate (dV/dt) of the collector-emitter voltage can also be suppressed.

FIG. 10 is a diagram showing another example of the aa cross section in FIG. The semiconductor device 100 of this example differs in the shape of the first well region 13 from the semiconductor device 100 of any one of the modes described with reference to FIGS. Other configurations are the same as any of the semiconductor devices 100 described with reference to FIGS. FIG. 10 shows an example in which the shape of the first well region 13 is changed in the semiconductor device 100 shown in FIG.

The first well region 13 of this example has a recessed portion 73 with a minimal width in the Y-axis direction on the YZ plane. Also, the first well region 13 may have a plurality of depressions 73 at different positions in the Z-axis direction. At least one recessed portion 73 may be provided below the lower end of the dummy trench portion 30 . The first well region 13 has doping concentration peaks above and below the recess 73 .

The first well region 13 of this example can be formed by implanting P-type impurities a plurality of times with different implantation depths. By changing the impurity implantation depth, the first well region 13 can be formed to a deeper position. That is, the first well region 13 having a relatively small width in the Y-axis direction and a large depth in the Z-axis direction can be easily formed. By forming the first well region 13 deep, carriers such as holes can be easily extracted.

As an example, the first well region 13 may be formed 20% or more, or 50% or more, deeper than the dummy trench portion 30 . Also, the difference in depth between the first well region 13 and the dummy trench portion 30 may be larger than the width of the dummy mesa portion 72 in the Y-axis direction. The first well region 13 may be formed deeper than the second well region 11 .

FIG. 11 is an enlarged sectional view of the vicinity of the first well region 13. As shown in FIG. The dummy trench portion 30 of this example has a first dummy sidewall 38, a second dummy sidewall 37 and a bottom portion 35 on the YZ plane. The first dummy sidewall 38 contacts the first well region 13 . The second dummy sidewall 37 is a sidewall opposite to the first dummy sidewall 38 in the YZ plane.

The first well region 13 of this example covers at least part of the bottom 35 of the dummy trench portion 30 . The bottom portion 35 of this example has a curved surface shape protruding downward from the lower ends of the first dummy side wall 38 and the second dummy side wall 37 . The lower end position Z2 of the first well region 13 is arranged below the lower end position Z1 of the dummy trench portion 30 .

Of the side walls of the dummy trench portion 30 , a region having the same inclination as that of the portion in contact with the base region 14 may be used as the second dummy side wall 37 . The first dummy sidewall 38 is a sidewall opposite to the second dummy sidewall 37 and has the same depth range as the second dummy sidewall 37 . The bottom portion 35 may refer to a region having a smaller inclination with respect to the upper surface 21 of the semiconductor substrate 10 than the first dummy sidewalls 38 and the second dummy sidewalls 37 . By covering at least a portion of the bottom portion 35 of the dummy trench portion 30 with the first well region 13, the carrier extraction speed can be further improved.

The first well region 13 covers at least part of the region between the center Y1 in the width direction (Y-axis direction) and the first dummy sidewall 38 in the bottom portion 35 of the dummy trench portion 30 . That is, the position Y2 of the Y-axis direction end portion 36 of the first well region 13 covering the bottom portion 35 is located between the center position Y1 of the bottom portion 35 and the first dummy side wall 38 . With such a structure, the carrier withdrawal speed can be further improved.

FIG. 12 is a cross-sectional view showing an example in which the position of the end portion 36 of the first well region 13 covering the bottom portion 35 is changed in the structure shown in FIG. The first well region 13 of this example covers the bottom portion 35 from the center Y1 of the bottom portion 35 to the second dummy side wall 37 side. That is, the position Y2 of the end portion 36 of the first well region 13 is arranged between the central position Y1 of the bottom portion 35 and the second dummy sidewall 37 . With such a structure, the carrier withdrawal speed can be further improved.

FIG. 13 is a cross-sectional view showing an example in which the position of the end portion 36 of the first well region 13 covering the bottom portion 35 is changed in the structure shown in FIG. The first well region 13 in this example covers the entire bottom portion 35 . In other words, the position Y2 of the end portion 36 of the first well region 13 is located closer to the center of the mesa portion 71 than the second dummy side wall 37 is. In this case, the first well region 13 extends below the mesa portion 71 . With such a structure, the carrier withdrawal speed can be further improved.

In the trench portion in contact with the mesa portion 71, the length from the trench portion side wall on the mesa portion 71 side to Y2 may be shorter or longer than the length from the trench portion side wall to Y1. In this example, in the trench portion in contact with the mesa portion 71, the length from the trench portion side wall on the side of the mesa portion 71 to Y2 is shorter than the length from the trench portion side wall to Y1.

14A and 14B are diagrams showing other examples of the dummy trench portion 30 and the gate trench portion 40. FIG. The dummy trench portion 30 of this example is formed deeper than the gate trench portion 40 when viewed from the upper surface 21 of the semiconductor substrate 10 . That is, the lower end position Z3 of the dummy trench portion 30 is arranged below the lower end position Z1 of the gate trench portion 40 . When viewed from the upper surface 21 of the semiconductor substrate 10, the dummy trench portion 30 may be formed 10% or more deeper than the gate trench portion 40, or may be formed 20% or more. With such a structure, the carrier withdrawal speed can be further improved.

FIG. 15 is a diagram showing another example of the first well region 13. As shown in FIG. In the semiconductor device 100 of this example, three or more dummy trench portions 30 are continuously arranged in the Y-axis direction. Three or more dummy trench portions 30 may be sandwiched between the gate trench portions 40 in the Y-axis direction. In this example, the first well regions 13 provided in two or more dummy mesa portions 72 are connected to each other.

In this example, among the plurality of continuously arranged dummy trench portions 30 , the entire bottom portion of the dummy trench portions 30 other than the dummy trench portions 30 arranged at both ends in the Y-axis direction is covered with the first well region 13 . can be broken The relationship between the dummy trench portions 30 arranged at both ends in the Y-axis direction and the first well regions 13 is the same as in any of the modes described with reference to FIGS. 1 to 14 . With such a structure, the carrier withdrawal speed can be further improved.

FIG. 16 is a diagram showing another example of the aa cross section of the semiconductor device 100. As shown in FIG. The semiconductor device 100 of this example differs from the semiconductor device 100 described with reference to FIGS. Other configurations are the same as those of the semiconductor device 100 of any aspect described in FIGS.

The lower surface side region 28 is provided at the same depth position as the collector region 22 in at least a partial region below the dummy mesa portion 72 . The lower surface side region 28 is an N-type region. Bottom side region 28 may be more heavily doped than drift region 18 . Bottom side region 28 may have a higher doping concentration than buffer region 20 .

The lower surface side region 28 may have the same width as the dummy mesa portion 72 in the Y-axis direction. The lower surface side region 28 may have a smaller width or a larger width than the dummy mesa portion 72 in the Y-axis direction. The lower surface side region 28 may also be formed below the dummy trench portion 30 and may also be formed in a partial region below the mesa portion 71 .

By providing the lower surface side region 28, accumulation of carriers of the second conductivity type below the dummy mesa portion 72 can be suppressed. The carrier concentration below the dummy mesa portion 72 has little effect on the ON voltage of the semiconductor device 100 . Therefore, it is possible to facilitate extraction of carriers at the time of turn-off or the like while reducing the on-voltage.

FIG. 17 is a diagram showing an example of the bb section shown in FIG. However, the structure shown in FIG. 17 can also be applied to the semiconductor device 100 shown in addition to FIG. The bb cross section is the XZ plane passing through the contact hole 54 in the dummy mesa portion 72 .

In the semiconductor device 100 of this example, the collector regions 22 and the lower surface side regions 28 are alternately arranged along the longitudinal direction of the dummy trench portion 30 below the dummy mesa portion 72 . With such a structure, the area ratio of the collector region 22 and the lower surface side region 28 can be easily adjusted. The width of one collector region 22 and the width of one lower surface side region 28 in the X-axis direction may be the same. In the X-axis direction, the width of one collector region 22 may be larger than the width of one lower surface side region 28 , and the width of one lower surface side region 28 may be larger than the width of one collector region 22 .

Further, the range in which the collector region 22 is provided in the X-axis direction may at least partially overlap the range in which the emitter region 12 is provided in the X-axis direction. The range in which the collector region 22 is provided in the X-axis direction may match the range in which the emitter region 12 is provided in the X-axis direction. The range in which the collector region 22 is provided in the X-axis direction may be included in the range in which the emitter region 12 is provided in the X-axis direction. may be included in the range provided.

The length _Lp in the X-axis direction of the collector region 22 sandwiched between the two bottom-side regions 28 in the X-axis direction may be longer or shorter than the length _Ln of the bottom-side regions 28 . In this example they are equal. The length _Lp of the collector region 22 in the X-axis direction is typically 10 μm, and may be 5 μm or more and 15 μm or less. The length _Ln of the lower surface side region 28 is typically 5 μm, and may be 5 μm or more and 15 μm or less.

FIG. 18 is a diagram partially showing the top surface of a semiconductor device 200 according to another embodiment of the present invention. Semiconductor device 200 differs from semiconductor device 100 described with reference to FIGS. Other configurations may be the same as any of the semiconductor devices 100 described with reference to FIGS.

In this example, the extended portion 41 of the gate trench portion 40 has a long side and a short side on the upper surface of the semiconductor substrate 10 . In the example of FIG. 18, the extended portion 41 has a long side in the X-axis direction and a short side in the Y-axis direction.

The gate trench portion 40 has first gate sidewalls 74 along the longitudinal direction and second gate sidewalls 75 opposite to the first gate sidewalls 74 . The first gate sidewall 74 and the second gate sidewall 75 are arranged inside the semiconductor substrate 10 so as to face each other.

In this example, of the mesa portion 71, the mesa portion 71 adjacent to the first gate sidewall 74 is designated as a first mesa portion 71-1, and the mesa portion 71 adjacent to the second gate sidewall 75 is designated as a second mesa portion 71-2. and That is, one mesa portion 71 arranged with the gate trench portion 40 interposed therebetween is referred to as a first mesa portion 71-1, and the other mesa portion 71 is referred to as a second mesa portion 71-2.

The emitter regions 12 and the contact regions 15 are alternately exposed along the X-axis direction on the upper surfaces of the first mesa portion 71-1 and the second mesa portion 71-2. In the semiconductor device 100 of this example, at least a partial region of at least one emitter region 12 in the first mesa portion 71-1 is arranged at a position facing the contact region 15 in the second mesa portion 71-2. there is That is, at least part of the range in the X-axis direction in which at least one emitter region 12 is provided in the first mesa portion 71-1 is the same as the range in the X-axis direction in which the contact region 15 is provided in the second mesa portion 71-2. overlapping.

In the example of FIG. 18, all the emitter regions 12 in the first mesa portion 71-1 are arranged at positions facing any one of the contact regions 15 in the second mesa portion 71-2. The width in the X-axis direction of the emitter region 12 in the first mesa portion 71-1 may be the same as the width in the X-axis direction of the contact region 15 in the second mesa portion 71-2.

At least a partial region of at least one contact region 15 in the first mesa portion 71-1 is arranged at a position facing the emitter region 12 in the second mesa portion 71-2. That is, at least part of the range in the X-axis direction in which at least one contact region 15 is provided in the first mesa portion 71-1 is the same as the range in the X-axis direction in which the emitter region 12 is provided in the second mesa portion 71-2. overlapping.

In the example of FIG. 18, the entirety of each contact region 15 in the first mesa portion 71-1 is arranged at a position facing any one of the emitter regions 12 in the second mesa portion 71-2. The width in the X-axis direction of the contact region 15 in the first mesa portion 71-1 may be the same as the width in the X-axis direction of the emitter region 12 in the second mesa portion 71-2. However, of the contact regions 15 in the first mesa portion 71-1, the contact regions 15 provided at both ends in the X-axis direction face both the emitter region 12 and the contact regions 15 of the second mesa portion 71-2. are placed. That is, in both the first mesa portion 71-1 and the second mesa portion 71-2, the contact regions 15 are arranged adjacent to the base regions 14 provided at both ends in the X-axis direction. As a result, the carriers below the base regions 14 provided at both ends in the X-axis direction can be efficiently pulled out. The width in the X-axis direction of the contact region 15 in the first mesa portion 71-1 may be the same as the sum of the widths in the X-axis direction of the emitter region 12 and the contact region 15 in the second mesa portion 71-2.

By displacing the emitter region 12 and the contact region 15 in the X-axis direction in the two mesa portions 71 adjacent to each other with the gate trench portion 40 interposed therebetween, the contact regions 15 contributing to extraction of holes are arranged in a dispersed manner. can do. For this reason, holes can be extracted evenly in the XY plane, and the withstand voltage when the semiconductor device 100 is turned off can be improved.

In addition, in the semiconductor device 200 of this example, the contact region 15 is exposed on the upper surface of the dummy mesa portion 72 . A base region 14 may be formed below the contact region 15 . Further, in the semiconductor device 200 of this example, the accumulation region 16 is formed in the mesa portion 71 and the dummy mesa portion 72 .

Further, in the first mesa portion 71-1 and the second mesa portion 71-2, a region in which the emitter region 12 or the contact region 15 is formed has a region extending in the lateral direction (Y-axis direction) of the gate trench portion 40. No trench is formed. That is, in the region where the emitter regions 12 and the contact regions 15 are regularly arranged, the gate trench portion 40 does not have branches or branches extending inside the mesa portion 71 . Moreover, the dummy trench part 30 is not provided in the said area|region, either. With such a structure, carriers such as holes can be effectively extracted through the dispersed contact regions 15 without being obstructed by the trench portion.

FIG. 19 is a diagram showing an example of the aa cross section in FIG. The aa section of this example is the YZ plane passing through the contact region 15 of the first mesa portion 71-1 and the emitter region 12 of the second mesa portion 71-2.

As described above, the contact region 15 of the first mesa portion 71-1 and the contact region 15 of the second mesa portion 71-2 are arranged to be shifted in the X-axis direction. Therefore, in the cross section shown in FIG. 19, the contact region 15 is provided in the first mesa portion 71-1, and the emitter region 12 is provided in the second mesa portion 71-2. With such an arrangement, the holes can be extracted evenly.

In the dummy mesa portion 72 of this example, the contact region 15 , the base region 14 and the accumulation region 16 are provided in order from the upper surface 21 side of the semiconductor substrate 10 . In another example, the dummy mesa portion 72 may not be provided with the accumulation region 16 . Further, like the semiconductor device 100 shown in FIGS. 1 and 2A, the storage region 16 may not be provided in the mesa portion 71 either.

FIG. 20 is a diagram showing another example of the aa cross section in FIG. In the semiconductor device 200 of this example, the structure of the dummy mesa portion 72 is the same as that of the semiconductor device 100 described with reference to FIGS. That is, the semiconductor device 200 of this example has the first well region 13 in the dummy mesa portion 72 . Such a structure allows the carrier to be pulled out more easily. Also, the structure of the accumulation region 16 in the semiconductor device 200 may be the same as that of the accumulation region 16 in the semiconductor device 100 . Moreover, the semiconductor device 200 may include the lower surface side region 28 shown in FIGS. 16 and 17 .

FIG. 21 is a diagram showing an arrangement example of the emitter regions 12 and the contact regions 15 on the upper surfaces of the first mesa portion 71-1 and the second mesa portion 71-2. In this example, the emitter region 12 and the contact region 15 in each mesa portion 71 have the same length in the X-axis direction. The contact region 15 in the first mesa portion 71-1 is arranged at a position facing the emitter region 12 in the second mesa portion 71-2, and the emitter region 12 in the first mesa portion 71-1 is located in the second mesa portion. It is arranged at a position facing the contact region 15 of the portion 71-2.

FIG. 22 is a diagram showing another arrangement example of the emitter regions 12 and the contact regions 15 on the upper surfaces of the first mesa portion 71-1 and the second mesa portion 71-2. In this example, the contact region 15 is formed longer than the emitter region 12 in the X-axis direction in the first mesa portion 71-1 and the second mesa portion 71-2. The length of contact region 15 may be more than double the length of emitter region 12 .

The range in the X-axis direction in which the emitter region 12 of the first mesa portion 71-1 is provided is included in the range in the X-axis direction in which the contact region 15 of the second mesa portion 71-2 is provided. The range in the X-axis direction in which the emitter region 12 of the second mesa portion 71-2 is provided is included in the range in the X-axis direction in which the contact region 15 of the first mesa portion 71-1 is provided. With such a structure, it is possible to improve the drawing speed of the carrier.

FIG. 23 is a diagram showing another arrangement example of the emitter regions 12 and the contact regions 15 on the upper surfaces of the first mesa portion 71-1 and the second mesa portion 71-2. In this example, in the first mesa portion 71-1 and the second mesa portion 71-2, the emitter region 12 is formed longer than the contact region 15 in the X-axis direction. The length of emitter region 12 may be more than double the length of contact region 15 .

The range in the X-axis direction in which the contact region 15 of the first mesa portion 71-1 is provided is included in the range in the X-axis direction in which the emitter region 12 of the second mesa portion 71-2 is provided. The range in the X-axis direction in which the contact region 15 of the second mesa portion 71-2 is provided is included in the range in the X-axis direction in which the emitter region 12 of the first mesa portion 71-1 is provided. Such a structure can improve the channel density.

FIG. 24 is a diagram showing an arrangement example of the accumulation area 16. As shown in FIG. The accumulation region 16 of this example has an opening 92 in the XY plane. A drift region 18 may be provided inside the opening 92 . The opening 92 may be arranged so as to overlap the contact region 15 in the first mesa portion 71-1 and the second mesa portion 71-2. With such a structure, the carrier can be pulled out at the first mesa portion 71-1 and the second mesa portion 71-2. The area of the opening 92 on the XY plane may be the same as the area of the contact region 15, or may be smaller. The area of opening 92 may be less than half the area of contact region 15 .

25A and 25B are diagrams showing an example of a method for manufacturing the semiconductor device 100. FIG. Note that the semiconductor device 200 may also be manufactured by the same method. In step S250, the base region 14 is formed in the semiconductor substrate 10 provided with the gate trench portion 40 and the dummy trench portion 30. As shown in FIG. The base region 14 may be formed by implanting a P-type impurity such as boron from the upper surface side of the semiconductor substrate 10 .

In step S252, an accumulation region 16 is formed. The accumulation region 16 may be formed by implanting an N-type impurity such as phosphorus from the upper surface side of the semiconductor substrate 10 using a mask such as photoresist.

At step S254, the first well region 13 is formed. The first well region 13 may be formed by implanting a P-type impurity such as boron from the upper surface side of the semiconductor substrate 10 using a mask such as photoresist. The P-type impurity may be implanted to different depths in multiple steps by changing the acceleration voltage.

In step S256, contact regions 15 are formed. The contact region 15 may be formed by implanting a P-type impurity such as boron from the upper surface side of the semiconductor substrate 10 using a mask such as photoresist.

In step S258, structures on the bottom side of the semiconductor substrate 10 are formed. For example, a collector region 22 is formed.

In step S260, the semiconductor substrate 10 is annealed under predetermined conditions. As a result, each region is formed by converting the impurity implanted in steps S250 to S258 into a donor or acceptor.

In step S262, emitter region 12 is formed. The emitter region 12 may be formed by implanting an N-type impurity such as arsenic from the upper surface side of the semiconductor substrate 10 using a mask such as photoresist.

In step S264, the semiconductor substrate 10 is annealed under predetermined conditions. As a result, the impurity implanted in step S262 is converted into donors to form the emitter region 12. Next, as shown in FIG.

After step S264, an interlayer insulating film 26, a contact hole 54, an emitter electrode 52, and the like are formed. Thereby, the semiconductor device 100 can be manufactured.

Note that step S254 may be performed after step S264. In this case, an annealing step may be included after step S254. In this case, since the number of times of annealing after forming the first well region 13 can be reduced, the depth of the first well region 13 can be accurately controlled.

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

The execution order of each process in the method shown in the claims, specification, and drawings is not specified as "before", "before", etc., and the result of the previous process may be implemented in any order unless used in subsequent processing. Regarding the operation flow in the claims, the specification, and the drawings, even if the description is made using "first," "next," etc. for the sake of convenience, it means that it is essential to carry out in this order. not a thing

DESCRIPTION OF SYMBOLS 10... Semiconductor substrate 11... Second well region 12... Emitter region 13... First well region 14... Base region 15... Contact region 16... Accumulation region 17 region 18 drift region 20 buffer region 21 upper surface 22 collector region 23 lower surface 26 interlayer insulating film 28...lower surface side region 30...dummy trench portion 31...extending portion 32...dummy insulating film 33...tip portion 34...dummy conductive portion 35... bottom, 36... end, 37... second dummy side wall, 38... first dummy side wall, 40... gate trench part, 41... extending part, 42... gate insulating film, 43... tip portion, 44... gate conductive portion, 45... gate wiring, 46... gate electrode, 52... emitter electrode, 54, 55, 56... contact hole, 57... Connection portion 58 Collector electrode 71 Mesa portion 72 Dummy mesa portion 73 Recess portion 74 First gate side wall 75 Second gate side wall 92... opening, 100... semiconductor device, 200... semiconductor device

The present invention relates to semiconductor devices.

2. Description of the Related Art Conventionally, power semiconductor devices such as insulated gate bipolar transistors (IGBTs) are known (see Patent Document 1, for example). In a semiconductor element such as an IGBT, the ON voltage can be lowered by accumulating carriers such as holes in the drift region.
Patent Document 1: JP 2015-72950 A

Holes gather at the lower end of the gate trench portion and the lower end of the dummy trench portion. In particular, since the dummy conductive portion has the same potential as that of the emitter electrode, a hole inversion layer is likely to be formed on the side wall of the dummy trench portion.

In a first aspect of the present invention, a first conductivity type drift region provided inside a semiconductor substrate, a first trench portion provided on the upper surface of the semiconductor substrate, and a drift region provided on the upper surface of the semiconductor substrate. , a second trench portion formed deeper than the first trench portion, and a region of the semiconductor substrate adjacent to any one of the first trench portions, between the upper surface of the semiconductor substrate and the drift region; a base region of a second conductivity type provided in the base region of the second conductivity type; and a well region.
In the above semiconductor device, the length from the lower end of the first trench portion to the lower end of the second trench portion may be 20% or more of the depth of the first trench portion.
In any one of the above semiconductor devices, the first well region may have a higher doping concentration than the base region.
In any one of the semiconductor devices described above, the first well region may include at least four peaks in a doping concentration distribution diagram in the depth direction.

In a second aspect of the present invention, any one of a first conductivity type drift region provided inside a semiconductor substrate, and a first trench portion and a second trench portion provided on an upper surface of the semiconductor substrate, a base region of a second conductivity type provided between the upper surface of the semiconductor substrate and the drift region in a region of the semiconductor substrate adjacent to the first trench; a first well region of a second conductivity type provided to a position deeper than the lower end of the second trench portion in a region of the semiconductor substrate, wherein the first well region has a doping concentration distribution in the depth direction; In the figure, a semiconductor device is provided that includes at least four peaks.

In any one of the semiconductor devices described above, among the at least four peaks, the peak closest to the upper surface side of the semiconductor substrate may have the highest doping concentration.

In any one of the semiconductor devices described above, the first trench portion and the second trench portion may have different widths.

In any one of the above semiconductor devices, the well region may have a depth of 2.0 μm or more and 10 μm or less.

In any one of the above semiconductor devices, the base region may have a depth of 0.5 μm or more and 5.0 μm or less.

In any one of the semiconductor devices described above, a first conductivity type having a doping concentration higher than that of the drift region is provided in a first mesa portion which is a region of the semiconductor substrate sandwiched between the first trench portion and the second trench portion. of emitter regions.

In any one of the semiconductor devices described above, the well region may be formed in a second mesa portion that is a region of the semiconductor substrate sandwiched between the second trench portions.

In any one of the semiconductor devices described above, at least three of the second trench portions may include first regions that are continuously arranged, and the well region may connect at least two second mesa portions.

In any one of the semiconductor devices described above, the width of the first mesa portion and the second mesa portion may be 0.1 μm or more and 3.0 μm or less.

In any one of the semiconductor devices described above, a gate electrode provided above the upper surface of the semiconductor substrate and an upper surface electrode provided above the upper surface of the semiconductor substrate may be provided, and the first trench portion and a first conductive portion electrically connected to the gate electrode, and the second trench portion includes a second insulating film and a second conductive portion electrically connected to the top electrode. 2 conductive portions;

In any one of the above semiconductor devices, the film thickness of the second insulating film may be thicker than the film thickness of the first insulating film.

In any one of the semiconductor devices described above, the semiconductor substrate may be a silicon substrate, a silicon carbide substrate, or a nitride semiconductor substrate.

The above summary of the invention is not an exhaustive list of all features of the present invention. Subcombinations of these features can also be inventive.

1 is a diagram partially showing the top surface of a semiconductor device 100 according to an embodiment of the present invention; FIG. FIG. 2 is a diagram showing an example of a cross section taken along line aa in FIG. 1; FIG. 2 is a diagram showing an example of a cross section taken along line aa in FIG. 1; FIG. 2 is a diagram showing an example of a cross section taken along line aa in FIG. 1; FIG. 2B is an example of a doping concentration distribution diagram taken along the cc section and the dd section of FIG. 2A. FIG. 2B is another example of a doping concentration distribution diagram taken along the cc section and the dd section of FIG. 2A. FIG. 4 is a diagram showing another example of the top surface of the semiconductor device 100; FIG. 4 is a diagram showing an example of a cross section taken along line aa in FIG. 3; FIG. 4 is a diagram showing an example of a cross section taken along line aa in FIG. 3; FIG. 4C is an example of a doping concentration distribution diagram when the cc section and the dd section of FIG. 4B are cut. FIG. 4C is another example of a doping concentration distribution diagram taken along the cc section and the dd section of FIG. 4B. FIG. 4 is a diagram showing an example of a cross section taken along line aa in FIG. 3; FIG. 4 is a diagram showing another example of the top surface of the semiconductor device 100; FIG. 6 is a diagram showing an example of a cross section taken along line aa in FIG. 5; 6 is a diagram showing another example of the aa cross section in FIG. 5. FIG. 6 is a diagram showing another example of the aa cross section in FIG. 5. FIG. FIG. 4 is a diagram showing another example of the aa cross section in FIG. 3; FIG. 4 is a diagram showing another example of the aa cross section in FIG. 3; 3 is an enlarged cross-sectional view of the vicinity of a first well region 13; FIG. 12 is a cross-sectional view showing an example in which the position of the end portion 36 of the first well region 13 covering the bottom portion 35 is changed in the structure shown in FIG. 11; FIG. 12 is a cross-sectional view showing an example in which the position of the end portion 36 of the first well region 13 covering the bottom portion 35 is changed in the structure shown in FIG. 11; FIG. FIG. 4 is a diagram showing another example of the dummy trench portion 30 and the gate trench portion 40; FIG. 4 is a diagram showing another example of the first well region 13; 3 is a diagram showing another example of the aa cross section of the semiconductor device 100; FIG. 4 is a diagram showing an example of a bb cross section shown in FIG. 3; FIG. It is a figure which shows partially the upper surface of the semiconductor device 200 which concerns on other embodiment of this invention. FIG. 19 is a diagram showing an example of the aa cross section in FIG. 18; FIG. 19 is a diagram showing another example of the aa cross section in FIG. 18; FIG. 4 is a diagram showing an arrangement example of emitter regions 12 and contact regions 15 on the upper surfaces of a first mesa portion 71-1 and a second mesa portion 71-2; FIG. 10 is a diagram showing another arrangement example of emitter regions 12 and contact regions 15 on the upper surfaces of the first mesa portion 71-1 and the second mesa portion 71-2; FIG. 10 is a diagram showing another arrangement example of emitter regions 12 and contact regions 15 on the upper surfaces of the first mesa portion 71-1 and the second mesa portion 71-2; 4 is a diagram showing an arrangement example of an accumulation area 16; FIG. 4A to 4C are diagrams illustrating an example of a method for manufacturing the semiconductor device 100; FIG.

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. Also, not all combinations of features described in the embodiments are essential for the solution of the invention.

In this specification, one side in a direction parallel to the depth direction of the semiconductor substrate is called "upper", and the other side is called "lower". One of the two main surfaces of a substrate, layer or other member is called the upper surface and the other surface is called the lower surface. The directions of "up" and "down" are not limited to the direction of gravity or the mounting direction to a substrate or the like when the semiconductor device is mounted. In this specification, technical matters may be described using X-, Y-, and Z-axis orthogonal coordinate axes. Let the depth direction of the semiconductor substrate be the Z-axis. Also, the orthogonal coordinate system is a so-called right-handed system in this example.

Although the terms "emitter" and "collector" are used in this specification, semiconductor devices are not limited to IGBTs. "Sources" and "drains" in transistors such as MOSFETs may also be included within the scope of the terms "emitter" and "collector" herein.

In each embodiment, an example in which the first conductivity type is the N type and the second conductivity type is the P type is shown, but the first conductivity type may be the P type and the second conductivity type may be the N type. In this case, the conductivity types of the substrate, layers, regions, etc. in each embodiment have opposite polarities. When comparing doping concentrations between regions herein, the peak concentration in each region may be used.

In the present specification, the term "same" may include the case where there is an error due to manufacturing variations or the like. The error is, for example, within 10%.

FIG. 1 is a diagram partially showing the top surface of a semiconductor device 100 according to an embodiment of the present invention. The semiconductor device 100 of this example is a semiconductor chip including transistors such as IGBTs. FIG. 1 shows the top surface of the chip around the edge of the chip, omitting other regions.

Also, although FIG. 1 shows an active region of a semiconductor substrate in semiconductor device 100, semiconductor device 100 may have edge terminations surrounding the active region. The active region refers to a region through which current flows when the semiconductor device 100 is controlled to be on. The edge termination relieves electric field concentration on the upper surface side of the semiconductor substrate. Edge terminations may include, for example, guard rings, field plates, RESURF, and combinations thereof.

The semiconductor device 100 of this example includes a gate trench portion 40, a dummy trench portion 30, an emitter region 12, a base region 14, a contact region 15, a first well region 13 and a second well region 11 provided inside a semiconductor substrate. Prepare. The semiconductor device 100 of this example also includes an emitter electrode 52 and a gate electrode 46 provided above the upper surface of the semiconductor substrate. Emitter electrode 52 and gate electrode 46 are provided separately from each other.

An interlayer insulating film is provided between the emitter electrode 52 and the gate electrode 46 and the upper surface of the semiconductor substrate, but is omitted in FIG. A contact hole 54, a contact hole 55, and a contact hole 56 are provided through the interlayer insulating film of this example.

Emitter electrode 52 contacts emitter region 12 , contact region 15 , base region 14 and first well region 13 on the upper surface of the semiconductor substrate through contact hole 54 . The contact holes 54 of this example are provided between the respective trench portions. Also, the emitter electrode 52 is connected to the dummy conductive portion in the dummy trench portion 30 through the contact hole 56 . Between the emitter electrode 52 and the dummy conductive portion, a connection portion 57 made of a conductive material such as impurity-doped polysilicon may be provided. The connecting portion 57 is provided on the upper surface of the semiconductor substrate with an insulating film such as a thermal oxide film interposed therebetween. In this example, the contact hole 56 is arranged at the tip of the dummy trench portion 30 in the X-axis direction.

Gate electrode 46 is in contact with gate wiring 45 through contact hole 55 . The gate wiring 45 is formed of impurity-doped polysilicon or the like. An insulating film such as a thermal oxide film is provided between the gate wiring 45 and the semiconductor substrate. The gate wiring 45 is connected to the gate conductive portion in the gate trench portion 40 on the upper surface of the semiconductor substrate. Gate wiring 45 is not connected to the dummy conductive portion in dummy trench portion 30 . The gate wiring 45 of this example is provided from below the contact hole 55 to the tip portion 43 of the gate trench portion 40 . The gate conductive portion is exposed on the upper surface of the semiconductor substrate at the tip portion 43 of the gate trench portion 40 and is in contact with the gate wiring 45 .

Emitter electrode 52 and gate electrode 46 are formed of a material containing metal. For example, at least a partial region of each electrode is made of aluminum or an aluminum-silicon alloy. Each electrode may have a barrier metal made of titanium, a titanium compound, or the like under a region made of aluminum or the like. Further, the contact hole may have a plug formed by embedding tungsten or the like so as to be in contact with the barrier metal and the aluminum or the like.

One or more gate trench portions 40 and one or more dummy trench portions 30 are arranged at predetermined intervals along a predetermined arrangement direction (transverse direction) on the upper surface of the semiconductor substrate. The arrangement direction in FIG. 1 is the Y-axis direction.

The gate trench portion 40 of this example includes two extending portions 41 that extend linearly along the extending direction (longitudinal direction of the trenches, which is the X-axis direction in this example) perpendicular to the arrangement direction, and It may have a tip 43 connecting the two extensions 41 . At least a part of the tip portion 43 is preferably formed in a curved shape on the upper surface of the semiconductor substrate. By connecting the tips of the two extending portions 41 of the gate trench portion 40 with the tip portion 43, electric field concentration at the ends of the extending portions 41 can be alleviated. In this specification, the two extending portions 41 connected by the tip portion 43 may be treated as two gate trench portions 40 .

One or more dummy trench portions 30 are provided between each extension portion 41 of the gate trench portion 40 . Like the gate trench portion 40 , the dummy trench portion 30 may have a tip portion 33 that connects the tips of the two extending portions 31 . In this example, a dummy trench portion 30 having two extension portions 31 and a tip portion 33 is provided between each extension portion 41 of the gate trench portion 40 . Another example of the dummy trench portion 30 may have a linear shape without the tip portion 33 . The dummy trench portion 30 is provided at a position not overlapping the gate wiring 45 . In this specification, the two extending portions 31 connected by the tip portion 33 may be treated as two dummy trench portions 30 .

Emitter electrode 52 is provided above gate trench portion 40 , dummy trench portion 30 , first well region 13 , second well region 11 , emitter region 12 , base region 14 and contact region 15 . The second well region 11 is provided within a predetermined range away from the longitudinal end of the contact hole 54 in the direction toward the gate electrode 46 . The diffusion depth of second well region 11 may be deeper than the depths of gate trench portion 40 and dummy trench portion 30 . A partial region of gate trench portion 40 and dummy trench portion 30 on the gate electrode 46 side is provided in second well region 11 . The ends of the dummy trench portion 30 in the extending direction and the bottom of the tip portion may be covered with the second well region 11 .

In this example, a region of the semiconductor substrate sandwiched between trench portions is called a mesa portion 71 . However, a region of the semiconductor substrate sandwiched between two dummy trench portions 30 (or two extension portions 31) is called a dummy mesa portion 72. As shown in FIG. The mesa portion 71 and the dummy mesa portion 72 are regions on the upper surface side of the deepest bottom of the trench portions in the region of the semiconductor substrate sandwiched between the trench portions.

A base region 14 is provided in the mesa portion 71 . The second well region 11 is of the second conductivity type. The base region 14 is of P− type with a lower doping concentration than the second well region 11, which is of P+ type.

A P + -type contact region 15 having a higher doping concentration than the base region 14 is provided on the upper surface of the base region 14 of the mesa portion 71 . The second well region 11 is provided apart in the direction of the gate electrode 46 from the contact region 15 arranged at the end in the extending direction of the trench portion among the contact regions 15 in the active region. An N + -type emitter region 12 having a doping concentration higher than that of the semiconductor substrate is selectively formed on the upper surface of the base region 14 .

Each of contact region 15 and emitter region 12 is provided from one trench portion to the other adjacent trench portion in the Y-axis direction. The contact regions 15 and the emitter regions 12 are alternately exposed on the upper surface of the semiconductor substrate along the extending direction (X-axis direction) of the trench portion. The contact region 15 and the emitter region 12 may be provided on the upper surface of the mesa portion 71 in a region sandwiched between the base regions 14 exposed at both ends in the X-axis direction.

In another example of the mesa portion 71, the contact regions 15 and the emitter regions 12 may be provided in stripes along the extending direction (X-axis direction). For example, an emitter region 12 is provided in a region adjacent to the trench portion, and a contact region 15 is provided in a region sandwiched between the emitter regions 12 .

The dummy mesa portion 72 is provided with the first well region 13 of the second conductivity type having a higher doping concentration than the base region 14 . The first well region 13 in this example is of P+ type. The doping concentration of the first well region 13 may be the same as or different from the doping concentration of the second well region 11 . The doping concentration of the first well region 13 may be 5 times or more, or 10 times or more, the doping concentration of the base region 14 .

The first well region 13 is exposed on the top surface of the dummy mesa portion 72 . The first well region 13 of this example is provided in a range facing the emitter region 12 and the contact region 15 in the mesa portion 71 adjacent in the Y-axis direction. The first well region 13 is continuously provided in the Y-axis direction on the upper surface of the dummy mesa portion 72 from a position in contact with one dummy trench portion 30 to a position in contact with the other dummy trench portion 30 . The first well region 13 may be provided continuously on the upper surface of the dummy mesa portion 72 in a region sandwiched between the exposed base regions 14 at both ends in the X-axis direction.

Contact hole 54 provided in mesa portion 71 is provided above contact region 15 and emitter region 12 . The contact hole 54 provided in the dummy mesa portion 72 is provided above the first well region 13 . Contact hole 54 is not provided in a region corresponding to base region 14 and second well region 11 . An emitter region may not be provided on the upper surface of the dummy mesa portion 72 . A contact region 15 may be provided on the upper surface of the dummy mesa portion 72 at least in a region where the contact hole 54 is formed.

FIG. 2A is a diagram showing an example of the aa cross section in FIG. The aa section of this example is the YZ plane passing through the emitter region 12 . The semiconductor device 100 of this example has a semiconductor substrate 10, an interlayer insulating film 26, an emitter electrode 52 and a collector electrode 58 in the cross section. The interlayer insulating film 26 is, for example, silicate glass doped with impurities such as boron and phosphorus. The interlayer insulating film 26 is selectively formed on the upper surface 21 of the semiconductor substrate 10 . Emitter electrode 52 is provided on top surface 21 of semiconductor substrate 10 and interlayer insulating film 26 . A collector electrode 58 is provided on the lower surface 23 of the semiconductor substrate 10 . The collector electrode 58 may be provided over the entire bottom surface 23 of the semiconductor substrate 10 .

The semiconductor substrate 10 may be a silicon substrate, a silicon carbide substrate, a nitride semiconductor substrate such as gallium nitride, or the like. The semiconductor substrate 10 of this example is a silicon substrate.

An N− type drift region 18 is provided inside the semiconductor substrate 10 . The drift region 18 in the cross section is a region of the semiconductor substrate 10 where the emitter region 12, the base region 14, the first well region 13, the buffer region 20 and the collector region 22 are not formed.

A P− type base region is provided between the upper surface 21 of the semiconductor substrate 10 and the drift region 18 in the region of the semiconductor substrate 10 adjacent to any gate trench portion 40 . In this example, each mesa portion 71 is provided with a P− type base region. The base region 14 may be formed by implanting a P-type impurity such as boron from the upper surface of the semiconductor substrate 10 .

In the mesa portion 71 , an N + -type emitter region 12 is provided on the upper surface of the base region 14 . The emitter region 12 may be formed by implanting an N-type impurity such as phosphorus or arsenic from the upper surface of the semiconductor substrate 10 .

A first well region 13 is provided between the upper surface 21 of the semiconductor substrate 10 and the drift region 18 in a region of the semiconductor substrate 10 adjacent to any dummy trench portion 30 . The first well region 13 is provided from the upper surface 21 of the semiconductor substrate 10 to a position deeper than the lower ends of the dummy trench portions 30 . In the cross section shown in FIG. 2A, the first well region 13 is provided in the entire dummy mesa portion 72 and the region below the dummy mesa portion 72 .

The lower end of the first well region 13 may be determined based on the doping concentration distribution in the depth direction (Z-axis direction) of the first well region 13 and drift region 18 . As used herein, the doping concentration refers to the concentration of impurities (dopants) that have become donors or acceptors. The depth position at which the concentration difference (net doping concentration) distribution between donors and acceptors measured by the spreading resistance (SR) method or the like has a minimum value may be the lower end of the first well region 13 .

Gate trench portion 40 is formed from upper surface 21 of semiconductor substrate 10 to the inside of semiconductor substrate 10 and is in contact with emitter region 12 and base region 14 at sidewalls. The gate trench portion 40 of this example is not in contact with the first well region 13 . The gate trench portion 40 of this example is provided from the upper surface 21 of the semiconductor substrate 10 so as to penetrate through the emitter region 12 and the base region 14 .

The dummy trench portion 30 is formed from the upper surface 21 of the semiconductor substrate 10 to the inside of the semiconductor substrate 10 and is in contact with the first well region 13 at the sidewall. Of the sidewalls of dummy trench portion 30 , those sidewalls facing gate trench portion 40 may be in contact with emitter region 12 and base region 14 . The gate trench portion 40 and the dummy trench portion 30 may be provided up to the same depth position Z1 in the Z-axis direction.

The bottom of the gate trench portion 40 in this example is located within the drift region 18 . A bottom portion of the dummy trench portion 30 may be arranged in the drift region 18 and may be covered with the first well region 13 . It should be noted that the fact that the trench penetrates through each doping region is not limited to the order in which the doping region is formed and then the trench is formed. A structure in which a doping region is formed between the trench portions after the trench portions are formed is also included in the structure in which the trench portion penetrates the doping regions.

Buffer region 20 is formed on the lower surface side of drift region 18 . The doping concentration of buffer region 20 is higher than the doping concentration of drift region 18 . The buffer region 20 may function as a field stop layer that prevents the depletion layer spreading from the lower surface side of the base region 14 from reaching the P + -type collector region 22 . A P+ type collector region 22 is formed on the lower surface side of the buffer region 20 .

The gate trench portion 40 has a gate insulating film 42 and a gate conductive portion 44 . A gate insulating film 42 is formed to cover the inner wall of the gate trench. The gate insulating film 42 may be formed by oxidizing or nitriding the semiconductor on the inner wall of the gate trench. The gate conductive portion 44 is covered with the gate insulating film 42 inside the gate trench. That is, the gate insulating film 42 insulates the gate conductive portion 44 and the semiconductor substrate 10 from each other. The gate conductive portion 44 is formed of a conductive material such as polysilicon.

The gate conductive portion 44 includes a region facing at least the adjacent base region 14 with the gate insulating film 42 interposed therebetween in the depth direction. The gate trench portion 40 in the cross section is covered with the interlayer insulating film 26 on the upper surface of the semiconductor substrate 10 . When a predetermined voltage is applied to the gate conductive portion 44 , a channel is formed by an electron inversion layer in the surface layer of the interface of the base region 14 in contact with the gate trench portion 40 .

The dummy trench portion 30 of this example has a dummy insulating film 32 and a dummy conductive portion 34 . The dummy insulating film 32 is formed covering the inner wall of the dummy trench. The dummy conductive portion 34 is formed inside the dummy trench portion 30 and covered with the dummy insulating film 32 . The dummy insulating film 32 insulates the dummy conductive portion 34 from the semiconductor substrate 10 . The dummy conductive portion 34 may be made of the same material as the gate conductive portion 44 . For example, the dummy conductive portion 34 is made of a conductive material such as polysilicon. The dummy conductive portion 34 may have the same length as the gate conductive portion 44 in the depth direction. The dummy trench portion 30 in the cross section is covered with the interlayer insulating film 26 on the upper surface of the semiconductor substrate 10 . The bottoms of the dummy trench portion 30 and the gate trench portion 40 may be curved (curved in cross section) convex downward.

The width of the mesa portion 71 and the width of the dummy mesa portion 72 may be equal. The width of the mesa portion 71 is typically 1.0 μm, and may be 0.1 μm or more and 3.0 μm or less. The width _WGT of the gate trench portion and the width _WDT of the dummy trench portion 30 may be equal or different. In this example, they are equal. Also, the width C of the mesa portion 71 may be equal to the width D of the dummy mesa portion 72 .

The width of the contact hole 54 in the Y-axis direction may be the same between the mesa portion 71 and the dummy mesa portion 72 . The width of the contact hole 54 is typically 0.6 μm, and may be 0.05 μm or more and 2.0 μm or less within a range not exceeding the mesa width or the dummy mesa width.

By providing the dummy trench portion 30, the effect of accumulating carriers can be enhanced, the conductivity modulation can be promoted, and the ON voltage can be lowered. Further, by adjusting the ratio of the dummy trench portion 30 to the gate trench portion 40, the switching speed of the semiconductor device 100 can be adjusted.

When the semiconductor device 100 is turned off, carriers accumulated near the bottom of the trench in the drift region 18 are extracted to the emitter electrode 52 through the region of the second conductivity type. If the withdrawal speed of carriers at the time of turn-off is slower than the concentration of accumulated carriers, the withstand capability of the semiconductor device 100 is lowered. The carrier extraction speed refers to the amount of carriers such as holes that are extracted per unit time from the drift region 18 to the emitter electrode 52 or the like when the semiconductor device 100 is turned off.

In the semiconductor device 100, by providing the first well region 13 formed deeper than the dummy trench portion 30, carriers such as holes accumulated in the vicinity of the trench bottom portion can be efficiently extracted. Therefore, it is possible to easily achieve both reduction of the ON voltage of the semiconductor device 100 and maintenance of the withstand voltage of the semiconductor device 100 .

FIG. 2B is a diagram showing an example of the aa cross section in FIG. In the semiconductor device 100 of this example, the contact width of the contact for connecting with the semiconductor substrate 10 is different from that in FIG. 2A. In this example, the contact width B of the contact formed on the first well region 13 is different from the contact width A of the contact formed on the emitter region 12 . The contact width B in this example may be larger or smaller than the contact width A. The contact width B is larger than the contact width A in this example. That is, by making the contact width B between the dummy trench portions 30 larger than the contact width A between the dummy trench portion 30 and the gate trench portion 40, the turn-off resistance of the semiconductor device 100 can be improved.

A ratio (A/B) between the contact width A and the contact width B may be 0.2 or more and 2.0 or less. When the contact width B is larger than the contact width A, the ratio (A/B) is 0.2 or more and less than 1.0, and may be 0.4 or more and 0.7 or less. On the other hand, when the contact width B is smaller than the contact width A, the ratio (A/B) is greater than 1.0 and 2.0 or less, and may be 1.3 or more and 1.7 or less.

FIG. 2C is a diagram showing an example of the aa cross section in FIG. The semiconductor device 100 of this example differs from the case of FIG. 2A in that the width of the dummy mesa portion 72 in the Y-axis direction is different from the width of the mesa portion 71 in the Y-axis direction. In this example, the width D of the dummy mesa portion 72 is different from the width C of the mesa portion 71 between the dummy trench portion 30 and the gate trench portion 40 . The width D of the dummy mesa portion 72 in this example may be larger than the width C of the mesa portion 71 . By making the width D of the dummy mesa portion 72 larger than the width C of the other mesa portions 71, the turn-off resistance of the semiconductor device 100 can be improved.

A ratio (D/C) between the width C of the mesa portion 71 and the width D of the dummy mesa portion 72 may be greater than 0.2 and less than or equal to 5.0. When the width D of the dummy mesa portion 72 is smaller than the width C of the mesa portion 71, the ratio (D/C) is 0.2 or more and less than 1.0, and may be 0.4 or more and 0.7 or less. On the other hand, when the width D of the dummy mesa portion 72 is greater than the width C of the mesa portion 71, the ratio (D/C) is greater than 1.0 and less than or equal to 5.0, and moreover, more than or equal to 2.0 and less than or equal to 4.0. good.

FIG. 2D is an example of a distribution map of doping concentration when the cc section and the dd section of FIG. 2A are cut. In the cc cross section, the emitter region 12, the base region 14, and the drift region 18 are arranged in this order from the upper surface side of the semiconductor substrate 10. As shown in FIG. In the dd cross section, the doping concentration distribution of the first well region 13 may have a Gaussian distribution from the top surface of the semiconductor substrate 10 . A Gaussian distribution is a profile when a dopant introduced into the upper surface of the semiconductor substrate 10 is diffused by thermal diffusion.

The depth from the upper surface of the pn junction between the base region 14 and the drift region 18, that is, the depth of the base region 14 is deeper than the lower end position Z1 of the trench portion. On the other hand, the depth of the pn junction between the first well region 13 and the drift region 18, that is, the depth of the first well region 13 may be deeper than the lower end position Z1 of the trench portion. The depth of the base region 14 is typically 3.0 μm, and may be between 0.5 μm and 5.0 μm. The depth of the first well region 13 is typically 7.0 μm, and may be 2.0 μm or more and 10 μm or less.

FIG. 2E is another example of a doping concentration distribution diagram taken along the cc section and the dd section of FIG. 2A. The doping concentration distribution along the cc section in this example is the same as the doping concentration distribution along the cc section in FIG. 2D. In this example, the doping concentration distribution in the dd cross section is different from that in FIG. 2D. The first well region 13 of this example has four peaks of first well region 13-1 to first well region 13-4. For example, in the dd cross section, the doping concentration distribution of the first well region 13 has a concentration peak at a position deeper than the base region 14 in the first step of lowering the contact resistance, the second step of the doping concentration distribution which is almost the same as that of the base region 14, and the base region 14. It consists of a third stage provided and a fourth stage provided with a concentration peak at a deeper position than the third stage.

The number and depth of peak positions of the first well region 13 are not limited to this example. The fourth stage of the first well region 13 is in contact with the drift region 18 and has a pn junction. The local minimum concentration in the valley between each concentration peak may be higher than the doping concentration of the drift region 18 . The third and fourth peak concentrations of the first well region 13 in FIG. 2E may be higher than the peak concentration of the base region 14 and may be lower than that of the base region 14 .

Also, the third stage peak position may be deeper than the position of the pn junction between the base region 14 and the drift region 18 . Also, the peak position of the fourth stage may be shallower than the lower end position Z1 of the trench portion.

FIG. 3 is a diagram showing another example of the top surface of the semiconductor device 100. As shown in FIG. The semiconductor device 100 of this example further includes an accumulation region 16 in addition to the configuration of the semiconductor device 100 described with reference to FIGS. 1 and 2A. The accumulation region 16 is a region of first conductivity type that is more heavily doped than the drift region 18 . The accumulation region 16 in this example is of the N+ type.

The accumulation region 16 is not exposed on the top surface of the semiconductor substrate 10 . Accumulation region 16 may be formed between drift region 18 and base region 14 . In FIG. 3, the region where the accumulation region 16 is provided in the XY plane parallel to the upper surface 21 of the semiconductor substrate 10 is indicated by broken lines. In this example, a plurality of accumulation regions 16 separated from each other are provided within the plane.

An accumulation region 16 is provided in at least a partial region of the mesa portion 71 sandwiched between two trench portions, at least one of which is the gate trench portion 40 . The accumulation region 16 in this example is provided below at least the emitter region 12 . The accumulation region 16 may also be provided below the contact region 15 . The accumulation region 16 of this example is provided over the entire mesa portion 71 in the width direction (Y-axis direction). The accumulation region 16 may not be provided below the base region 14 exposed on the upper surface of the mesa portion 71 . On the other hand, the dummy mesa portion 72 is not provided with the accumulation region 16 having a higher doping concentration than the base region 14 .

FIG. 4A is a diagram showing an example of the aa cross section in FIG. The aa section of this example is the YZ plane passing through the emitter region 12 . The semiconductor device 100 of this example further includes an accumulation region 16 in addition to the configuration of the semiconductor device 100 shown in FIG. 2A. The accumulation region 16 is provided between the base region 14 and the drift region 18 in each mesa portion 71 . The accumulation region 16 of this example is provided in each mesa portion 71 from a region adjacent to one trench portion to a region adjacent to the other trench portion.

The accumulation region 16 is an N+ type region with a higher doping concentration than the drift region 18 . For example, the accumulation region 16 may be a region between the drift region 18 and the base region 14 that has a doping concentration ten times or more higher than the average doping concentration of the drift region 18 . The doping concentration of accumulation region 16 may be 50 times or more, and may be 100 times or more, that of drift region 18 . The accumulation region 16 may be formed by implanting N-type impurities such as phosphorus or protons from the top surface 21 of the semiconductor substrate 10 .

By providing the accumulation region 16, the concentration of carriers accumulated below the accumulation region 16 can be further increased. Therefore, the ON voltage of the semiconductor device 100 can be reduced. Further, by providing the first well region 13, carriers accumulated in the accumulation region 16 can be efficiently extracted. Therefore, even if the accumulation region 16 is provided, the tolerance of the semiconductor device 100 can be maintained.

FIG. 4B is a diagram showing an example of the aa cross section in FIG. The semiconductor device 100 of this example differs from the case of FIG. 4A in that the dummy mesa portion 72 has the accumulation region 16 . The accumulation region 16 of this example includes an accumulation region 16-1 formed in the mesa portion 71 and an accumulation region 16-2 formed in the dummy mesa portion 72. FIG. Storage region 16-1 and storage region 16-2 may be formed simultaneously in the same process. Also, accumulation region 16-1 and accumulation region 16-2 may be formed with different dopant concentrations by different processes.

The accumulation region 16 - 2 is formed sandwiched between the dummy trench portions 30 in the dummy mesa portion 72 . That is, the upper and lower ends of the accumulation region 16-2 are provided in contact with the first well region 13. As shown in FIG. The accumulation region 16-2 is a region of the first conductivity type with a higher doping concentration than the drift region 18. FIG. In the semiconductor device 100 of the present example, by providing the accumulation region 16-2 in the dummy mesa portion 72, extraction of carriers via the P-type inversion layer at the bottom of the dummy trench portion 30 is suppressed during turn-on, thereby reducing turn-on loss. can.

FIG. 4C is an example of a doping concentration distribution diagram when the cc section and the dd section of FIG. 4B are cut. In the cc cross section, the emitter region 12, the base region 14, and the drift region 18 are arranged in this order from the upper surface side of the semiconductor substrate 10. As shown in FIG. In the dd cross section, the doping concentration distribution of the first well region 13 may have a Gaussian distribution from the top surface of the semiconductor substrate 10 . A Gaussian distribution is a profile when a dopant introduced into the upper surface of the semiconductor substrate 10 is diffused by thermal diffusion.

The depth from the upper surface of the semiconductor substrate 10 to the peak position of the doping concentration of the accumulation region 16 may be deeper than the depth from the peak position to the lower end position Z1 of the trench portion. The peak position of the accumulation region 16 is typically 4.0 μm, and may be 1.0 μm or more and 6.0 μm or less.

FIG. 4D is another example of a doping concentration distribution diagram taken along the cc section and the dd section of FIG. 4B. The doping concentration distribution in the dd section is different from that in FIG. 2D. The first well region 13 of this example has three peaks of first well regions 13-1 to 13-3. For example, in the dd cross section, the doping concentration distribution is as follows: the first stage of the first well region 13 that lowers the contact resistance; It consists of the third stage of the first well region 13 having a concentration peak at a position deeper than the accumulation region 16-2. The third stage peak concentration of the first well region 13 in FIG. 4D may be higher than the peak concentration of the accumulation region 16-2 or lower than the accumulation region 16-2. In this example, the third stage peak concentration of the first well region 13 is higher than the peak concentration of the accumulation region 16-2.

FIG. 4E is a diagram showing an example of the aa cross section in FIG. The semiconductor device 100 of this example differs from the case of FIG. 4A in that the film thickness d1 of the dummy insulating film 32 and the film thickness d2 of the gate insulating film 42 are different. The film thickness d1 of the dummy insulating film 32 in this example is thicker than the film thickness d2 of the gate insulating film 42 . This suppresses extraction of carriers via the P-type inversion layer at the bottom of the dummy trench portion 30 during turn-on, thereby reducing turn-on loss. The film thickness d2 is typically 0.1 μm, and may be 0.05 μm or more and 0.3 μm or less. The film thickness d1 is typically 0.2 μm, and may be 0.1 μm or more and 1.0 μm or less within a range thicker than the film thickness d2. This suppresses extraction of carriers via the P-type inversion layer at the bottom of the dummy trench portion 30 during turn-on, thereby reducing turn-on loss.

In this example, the dummy trench portion 30 and the gate trench portion 40 have the same width in the Y-axis direction, and the film thickness d1 of the dummy insulating film 32 is increased. 44 in the Y-axis direction. By making the width of the dummy trench portion 30 in the Y-axis direction larger than the width of the gate trench portion 40 in the Y-axis direction, the film thickness d1 of the dummy insulating film 32 is made larger than the film thickness d2 of the gate insulating film 42. You may

FIG. 5 is a diagram showing another example of the top surface of the semiconductor device 100. FIG. The semiconductor device 100 of this example differs in arrangement of the accumulation region 16 from the configuration of the semiconductor device 100 shown in FIGS. 3 and 4A. Other configurations are the same as those of the semiconductor device 100 shown in FIGS. 3 and 4A.

The accumulation region 16 of this example is not provided in a region adjacent to at least one trench portion in at least a portion of the mesa portion 71 . In the example of FIG. 5, the accumulation region 16 is in contact with the gate trench portion 40 and not in contact with the dummy trench portion 30 at each mesa portion 71 . Also, the accumulation region 16 is not provided in the dummy mesa portion 72 .

FIG. 6 is a diagram showing an example of the aa cross section in FIG. The aa section of this example is the YZ plane passing through the emitter region 12 . The semiconductor device 100 of this example differs in arrangement of the accumulation region 16 from the configuration of the semiconductor device 100 shown in FIG. 4A. Other configurations are the same as those of the semiconductor device 100 shown in FIG. 4A.

The accumulation region 16 of this example is provided in a region adjacent to the gate trench portion 40 inside the semiconductor substrate 10 . The accumulation region 16 may be provided in contact with the base region 14 or may be provided apart from the base region 14 . However, the accumulation region 16 is preferably provided inside the mesa portion 71 (that is, the region from the upper surface 21 of the semiconductor substrate 10 to the lower end of the trench portion).

In each mesa portion 71 , the N-type doping concentration of the region 17 adjacent to the dummy trench portion 30 inside the semiconductor substrate 10 and at the same depth as the accumulation region 16 is lower than that of the accumulation region 16 . Region 17 in this example has the same doping concentration as drift region 18 . The accumulation region 16 may be provided in a region that is less than or equal to half the width of the mesa portion 71 in the Y-axis direction, or may be provided in a region that is more than or equal to half the width.

With such a structure, carriers can be accumulated in the vicinity of the lower end of the gate trench portion 40, and carriers such as holes can be extracted also from the mesa portion 71 at the time of turn-off. For example, carriers that have passed near the dummy trench portion 30 are extracted to the emitter electrode 52 through the base region 14 and the contact region 15 .

FIG. 7 is a diagram showing another example of the aa cross section in FIG. The semiconductor device 100 of this example differs from the configuration of the semiconductor device 100 shown in FIG. 6 in the arrangement of the accumulation regions 16 in the Z-axis direction. Other configurations are the same as those of the semiconductor device 100 shown in FIG.

The accumulation region 16 in this example is arranged apart from the base region 14 . A drift region 18 may be provided between the accumulation region 16 and the base region 14 . Note that the accumulation region 16 is in contact with the gate trench portion 40 and is not in contact with the dummy trench portion 30 . A partial region of the accumulation region 16 may be provided below the lower end of the gate trench portion 40 .

The bottom portion of the gate trench portion 40 of this example has a curved shape that protrudes downward. The accumulation region 16 may cover part of the curved surface at the bottom of the gate trench portion 40 . With such a structure as well, carriers can be accumulated in the vicinity of the lower end of the gate trench portion 40, and carriers such as holes can be extracted also from the mesa portion 71 at the time of turn-off.

FIG. 8 is a diagram showing another example of the aa cross section in FIG. The semiconductor device 100 of this example differs from the configuration of the semiconductor device 100 shown in FIG. 6 in the arrangement of the accumulation regions 16 . Other configurations are the same as those of the semiconductor device 100 shown in FIG.

The semiconductor device 100 of this example has a first accumulation region 16-1 and a second accumulation region 16-2 in each mesa portion 71. FIG. The first accumulation area 16-1 is identical to the accumulation area 16 shown in FIG. 6, and the second accumulation area 16-2 is identical to the accumulation area 16 shown in FIG.

The first accumulation region 16-1 and the second accumulation region 16-2 may have the same doping concentration or different doping concentrations. When viewed in the Z-axis direction, at least a portion of the first accumulation region 16-1 and at least a portion of the second accumulation region 16-2 overlap each other.

The first accumulation area 16-1 and the second accumulation area 16-2 may be provided apart in the Z-axis direction. In this case, a drift region 18 may be provided between the first accumulation region 16-1 and the second accumulation region 16-2. The first accumulation region 16-1 and the second accumulation region 16-2 may be provided continuously in the Z-axis direction. In this case, the doping concentration distribution in the depth direction of the first accumulation region 16-1 and the second accumulation region 16-2 is It may have a peak within the region. The doping concentration between the peaks is greater than the doping concentration of drift region 18 .

With such a structure as well, carriers can be accumulated in the vicinity of the lower end of the gate trench portion 40, and carriers such as holes can be extracted also from the mesa portion 71 at the time of turn-off.

FIG. 9 is a diagram showing another example of the aa cross section in FIG. The semiconductor device 100 of this example differs in arrangement of the accumulation region 16 from the configuration of the semiconductor device 100 shown in FIG. 4A. Other configurations are the same as those of the semiconductor device 100 shown in FIG. 4A.

The semiconductor device 100 of this example has a first accumulation region 16-1 and a second accumulation region 16-2 in each mesa portion 71. FIG. The first storage area 16-1 is identical to the storage area 16 shown in FIG. 4A. The second accumulation region 16-2 is provided inside the mesa portion 71 below the first accumulation region 16-1. The second accumulation region 16-2 may have the same doping concentration as the first accumulation region 16-1, or may have a different doping concentration. The semiconductor device 100 may include an accumulation region 16 provided in three or more stages in the depth direction inside the mesa portion 71 .

Like the first accumulation region 16-1, the second accumulation region 16-2 is provided in the Y-axis direction from a region in contact with one trench to a region in contact with the other trench. The first accumulation region 16-1 and the second accumulation region 16-2 may be provided separately in the Z-axis direction, or may be provided continuously. Such a structure can further enhance the carrier accumulation effect.

By providing the accumulation region 16 in multiple stages in the depth direction, the electron current passing through the channel formed in the vicinity of the interface between the base region 14 and the gate trench portion 40 at the time of turn-on is transferred to the Y axis of the mesa portion 71. It becomes easier to flow near the center in the direction.

At the beginning of turn-on, the main current is electron current, not hole current. The initial stage is a period from just before the gate voltage Vge reaches the threshold voltage to before entering the mirror period in which Vge is almost constant at the value of the threshold voltage. As Vge approaches the threshold voltage, the channel begins to open and electrons begin to be injected into the drift region 18 .

Electrons traveling downward from the channel may once flow in the arrangement direction (the Y-axis direction or the direction from the vicinity of the gate trench portion 40 toward the center of the mesa portion 71) in the first accumulation region 16-1. If the second accumulation region 16-2 is not provided, an electron accumulation layer is already formed in the vicinity of the gate trench portion 40 in the drift region 18 below the first accumulation region 16-1. Therefore, it has a lower impedance than the drift region 18 (the threshold voltage at which an accumulation layer of electrons in the N-type region forms is much lower than the threshold voltage of the inversion layer in the P-type region). Therefore, the electron current mainly flows in the vicinity of the gate trench portion 40 .

When the electrons reach the backside collector region 22 , hole injection begins from collector region 22 to buffer region 20 and drift region 18 . As a result, holes are accumulated in the vicinity of the lower end of the trench portion. As an example, holes exist on the order of 1.0×10 ¹⁶ [cm ⁻³ ] from the vicinity of the lower end of the gate trench portion 40 to the side portion of the dummy trench portion 30 below the first accumulation region 16 . .

Holes gather at the lower end of the gate trench portion 40 and the lower end of the dummy trench portion 30 . In particular, since the dummy conductive portion 34 has the same potential as the emitter electrode 52 , a hole inversion layer is likely to be formed on the side wall of the dummy trench portion 30 . Holes injected from the collector region 22 collect in the vicinity of this hole inversion layer. Holes are continuously distributed from the dummy trench portion 30 to the lower end of the gate trench portion 40 . Due to this hole distribution, a large displacement current may flow near the lower end of the gate trench portion 40 at turn-on.

The semiconductor device 100 of this example further includes a second accumulation region 16-2. In this case, the impedance for the electron current is higher in the first accumulation region 16 than in the path flowing from the vicinity of the center of the first accumulation region 16-1 back to the vicinity of the gate trench portion 40 to the second accumulation region 16-2. The path that flows directly from -1 to the second storage region 16-2 is lower.

Holes tend to be accumulated in the high-hole-concentration region adjacent to the gate trench portion 40 below each accumulation region. Further, the electron current flows in the vicinity of the center of the mesa portion 71 instead of in the vicinity of the gate trench portion 40, thereby promoting the accumulation of holes in the high hole concentration region. Therefore, it is promoted that the electron current flows in the vicinity of the center of the mesa portion 71 .

By providing the accumulation regions 16 in multiple stages in the depth direction, it becomes easier for the electron current to travel downward in the vicinity of the center of the mesa portion 71 . When the electron current flows near the center of the mesa portion 71 , the hole distribution near the bottom of the mesa portion 71 is divided by the electron current near the center of the mesa portion 71 . Therefore, holes on the dummy trench portion 30 side of the electron current path do not flow to the gate trench portion 40 side. The division of the hole distribution at the central portion of the mesa portion 71 suppresses accumulation of holes at the lower end of the gate trench portion 40 . Therefore, the displacement current can be reduced. Since the displacement current can be reduced, the charging of the gate conductive portion 44 is also reduced, and the momentary increase in the gate electrode Vge is suppressed. As a result, the voltage reduction rate (dV/dt) of the collector-emitter voltage can also be suppressed.

FIG. 10 is a diagram showing another example of the aa cross section in FIG. The semiconductor device 100 of this example differs in the shape of the first well region 13 from the semiconductor device 100 of any one of the modes described with reference to FIGS. Other configurations are the same as any of the semiconductor devices 100 described with reference to FIGS. FIG. 10 shows an example in which the shape of the first well region 13 is changed in the semiconductor device 100 shown in FIG.

The first well region 13 of this example has a recessed portion 73 with a minimal width in the Y-axis direction on the YZ plane. Also, the first well region 13 may have a plurality of depressions 73 at different positions in the Z-axis direction. At least one recessed portion 73 may be provided below the lower end of the dummy trench portion 30 . The first well region 13 has doping concentration peaks above and below the recess 73 .

The first well region 13 of this example can be formed by implanting P-type impurities a plurality of times with different implantation depths. By changing the impurity implantation depth, the first well region 13 can be formed to a deeper position. That is, the first well region 13 having a relatively small width in the Y-axis direction and a large depth in the Z-axis direction can be easily formed. By forming the first well region 13 deep, carriers such as holes can be easily extracted.

As an example, the first well region 13 may be formed 20% or more, or 50% or more, deeper than the dummy trench portion 30 . Also, the difference in depth between the first well region 13 and the dummy trench portion 30 may be larger than the width of the dummy mesa portion 72 in the Y-axis direction. The first well region 13 may be formed deeper than the second well region 11 .

FIG. 11 is an enlarged sectional view of the vicinity of the first well region 13. As shown in FIG. The dummy trench portion 30 of this example has a first dummy sidewall 38, a second dummy sidewall 37 and a bottom portion 35 on the YZ plane. The first dummy sidewall 38 contacts the first well region 13 . The second dummy sidewall 37 is a sidewall opposite to the first dummy sidewall 38 in the YZ plane.

The first well region 13 of this example covers at least part of the bottom 35 of the dummy trench portion 30 . The bottom portion 35 of this example has a curved surface shape protruding downward from the lower ends of the first dummy side wall 38 and the second dummy side wall 37 . The lower end position Z2 of the first well region 13 is arranged below the lower end position Z1 of the dummy trench portion 30 .

Of the side walls of the dummy trench portion 30 , a region having the same inclination as that of the portion in contact with the base region 14 may be used as the second dummy side wall 37 . The first dummy sidewall 38 is a sidewall opposite to the second dummy sidewall 37 and has the same depth range as the second dummy sidewall 37 . The bottom portion 35 may refer to a region having a smaller inclination with respect to the upper surface 21 of the semiconductor substrate 10 than the first dummy sidewalls 38 and the second dummy sidewalls 37 . By covering at least a portion of the bottom portion 35 of the dummy trench portion 30 with the first well region 13, the carrier extraction speed can be further improved.

The first well region 13 covers at least part of the region between the center Y1 in the width direction (Y-axis direction) and the first dummy sidewall 38 in the bottom portion 35 of the dummy trench portion 30 . That is, the position Y2 of the Y-axis direction end portion 36 of the first well region 13 covering the bottom portion 35 is located between the center position Y1 of the bottom portion 35 and the first dummy side wall 38 . With such a structure, the carrier withdrawal speed can be further improved.

FIG. 12 is a cross-sectional view showing an example in which the position of the end portion 36 of the first well region 13 covering the bottom portion 35 is changed in the structure shown in FIG. The first well region 13 of this example covers the bottom portion 35 from the center Y1 of the bottom portion 35 to the second dummy side wall 37 side. That is, the position Y2 of the end portion 36 of the first well region 13 is arranged between the central position Y1 of the bottom portion 35 and the second dummy sidewall 37 . With such a structure, the carrier withdrawal speed can be further improved.

FIG. 13 is a cross-sectional view showing an example in which the position of the end portion 36 of the first well region 13 covering the bottom portion 35 is changed in the structure shown in FIG. The first well region 13 in this example covers the entire bottom portion 35 . In other words, the position Y2 of the end portion 36 of the first well region 13 is located closer to the center of the mesa portion 71 than the second dummy side wall 37 is. In this case, the first well region 13 extends below the mesa portion 71 . With such a structure, the carrier withdrawal speed can be further improved.

In the trench portion in contact with the mesa portion 71, the length from the trench portion side wall on the mesa portion 71 side to Y2 may be shorter or longer than the length from the trench portion side wall to Y1. In this example, in the trench portion in contact with the mesa portion 71, the length from the trench portion side wall on the side of the mesa portion 71 to Y2 is shorter than the length from the trench portion side wall to Y1.

14A and 14B are diagrams showing other examples of the dummy trench portion 30 and the gate trench portion 40. FIG. The dummy trench portion 30 of this example is formed deeper than the gate trench portion 40 when viewed from the upper surface 21 of the semiconductor substrate 10 . That is, the lower end position Z3 of the dummy trench portion 30 is arranged below the lower end position Z1 of the gate trench portion 40 . When viewed from the upper surface 21 of the semiconductor substrate 10, the dummy trench portion 30 may be formed 10% or more deeper than the gate trench portion 40, or may be formed 20% or more. With such a structure, the carrier withdrawal speed can be further improved.

FIG. 15 is a diagram showing another example of the first well region 13. As shown in FIG. In the semiconductor device 100 of this example, three or more dummy trench portions 30 are continuously arranged in the Y-axis direction. Three or more dummy trench portions 30 may be sandwiched between the gate trench portions 40 in the Y-axis direction. In this example, the first well regions 13 provided in two or more dummy mesa portions 72 are connected to each other.

In this example, among the plurality of continuously arranged dummy trench portions 30 , the entire bottom portion of the dummy trench portions 30 other than the dummy trench portions 30 arranged at both ends in the Y-axis direction is covered with the first well region 13 . can be broken The relationship between the dummy trench portions 30 arranged at both ends in the Y-axis direction and the first well regions 13 is the same as in any of the modes described with reference to FIGS. 1 to 14 . With such a structure, the carrier withdrawal speed can be further improved.

FIG. 16 is a diagram showing another example of the aa cross section of the semiconductor device 100. As shown in FIG. The semiconductor device 100 of this example differs from the semiconductor device 100 described with reference to FIGS. Other configurations are the same as those of the semiconductor device 100 of any aspect described in FIGS.

The lower surface side region 28 is provided at the same depth position as the collector region 22 in at least a partial region below the dummy mesa portion 72 . The lower surface side region 28 is an N-type region. Bottom side region 28 may be more heavily doped than drift region 18 . Bottom side region 28 may have a higher doping concentration than buffer region 20 .

The lower surface side region 28 may have the same width as the dummy mesa portion 72 in the Y-axis direction. The lower surface side region 28 may have a smaller width or a larger width than the dummy mesa portion 72 in the Y-axis direction. The lower surface side region 28 may also be formed below the dummy trench portion 30 and may also be formed in a partial region below the mesa portion 71 .

By providing the lower surface side region 28, accumulation of carriers of the second conductivity type below the dummy mesa portion 72 can be suppressed. The carrier concentration below the dummy mesa portion 72 has little effect on the ON voltage of the semiconductor device 100 . Therefore, it is possible to facilitate extraction of carriers at the time of turn-off or the like while reducing the on-voltage.

FIG. 17 is a diagram showing an example of the bb section shown in FIG. However, the structure shown in FIG. 17 can also be applied to the semiconductor device 100 shown in addition to FIG. The bb cross section is the XZ plane passing through the contact hole 54 in the dummy mesa portion 72 .

In the semiconductor device 100 of this example, the collector regions 22 and the lower surface side regions 28 are alternately arranged along the longitudinal direction of the dummy trench portion 30 below the dummy mesa portion 72 . With such a structure, the area ratio of the collector region 22 and the lower surface side region 28 can be easily adjusted. The width of one collector region 22 and the width of one lower surface side region 28 in the X-axis direction may be the same. In the X-axis direction, the width of one collector region 22 may be larger than the width of one lower surface side region 28 , and the width of one lower surface side region 28 may be larger than the width of one collector region 22 .

Further, the range in which the collector region 22 is provided in the X-axis direction may at least partially overlap the range in which the emitter region 12 is provided in the X-axis direction. The range in which the collector region 22 is provided in the X-axis direction may match the range in which the emitter region 12 is provided in the X-axis direction. The range in which the collector region 22 is provided in the X-axis direction may be included in the range in which the emitter region 12 is provided in the X-axis direction. may be included in the range provided.

The length _Lp in the X-axis direction of the collector region 22 sandwiched between the two bottom-side regions 28 in the X-axis direction may be longer or shorter than the length _Ln of the bottom-side regions 28 . In this example they are equal. The length _Lp of the collector region 22 in the X-axis direction is typically 10 μm, and may be 5 μm or more and 15 μm or less. The length _Ln of the lower surface side region 28 is typically 5 μm, and may be 5 μm or more and 15 μm or less.

FIG. 18 is a diagram partially showing the top surface of a semiconductor device 200 according to another embodiment of the present invention. Semiconductor device 200 differs from semiconductor device 100 described with reference to FIGS. Other configurations may be the same as any of the semiconductor devices 100 described with reference to FIGS.

In this example, the extended portion 41 of the gate trench portion 40 has a long side and a short side on the upper surface of the semiconductor substrate 10 . In the example of FIG. 18, the extended portion 41 has a long side in the X-axis direction and a short side in the Y-axis direction.

The gate trench portion 40 has first gate sidewalls 74 along the longitudinal direction and second gate sidewalls 75 opposite to the first gate sidewalls 74 . The first gate sidewall 74 and the second gate sidewall 75 are arranged inside the semiconductor substrate 10 so as to face each other.

In this example, of the mesa portion 71, the mesa portion 71 adjacent to the first gate sidewall 74 is designated as a first mesa portion 71-1, and the mesa portion 71 adjacent to the second gate sidewall 75 is designated as a second mesa portion 71-2. and That is, one mesa portion 71 arranged with the gate trench portion 40 interposed therebetween is referred to as a first mesa portion 71-1, and the other mesa portion 71 is referred to as a second mesa portion 71-2.

The emitter regions 12 and the contact regions 15 are alternately exposed along the X-axis direction on the upper surfaces of the first mesa portion 71-1 and the second mesa portion 71-2. In the semiconductor device 100 of this example, at least a partial region of at least one emitter region 12 in the first mesa portion 71-1 is arranged at a position facing the contact region 15 in the second mesa portion 71-2. there is That is, at least part of the range in the X-axis direction in which at least one emitter region 12 is provided in the first mesa portion 71-1 is the same as the range in the X-axis direction in which the contact region 15 is provided in the second mesa portion 71-2. overlapping.

In the example of FIG. 18, all the emitter regions 12 in the first mesa portion 71-1 are arranged at positions facing any one of the contact regions 15 in the second mesa portion 71-2. The width in the X-axis direction of the emitter region 12 in the first mesa portion 71-1 may be the same as the width in the X-axis direction of the contact region 15 in the second mesa portion 71-2.

At least a partial region of at least one contact region 15 in the first mesa portion 71-1 is arranged at a position facing the emitter region 12 in the second mesa portion 71-2. That is, at least part of the range in the X-axis direction in which at least one contact region 15 is provided in the first mesa portion 71-1 is the same as the range in the X-axis direction in which the emitter region 12 is provided in the second mesa portion 71-2. overlapping.

In the example of FIG. 18, the entirety of each contact region 15 in the first mesa portion 71-1 is arranged at a position facing any one of the emitter regions 12 in the second mesa portion 71-2. The width in the X-axis direction of the contact region 15 in the first mesa portion 71-1 may be the same as the width in the X-axis direction of the emitter region 12 in the second mesa portion 71-2. However, of the contact regions 15 in the first mesa portion 71-1, the contact regions 15 provided at both ends in the X-axis direction face both the emitter region 12 and the contact regions 15 of the second mesa portion 71-2. are placed. That is, in both the first mesa portion 71-1 and the second mesa portion 71-2, the contact regions 15 are arranged adjacent to the base regions 14 provided at both ends in the X-axis direction. As a result, the carriers below the base regions 14 provided at both ends in the X-axis direction can be efficiently pulled out. The width in the X-axis direction of the contact region 15 in the first mesa portion 71-1 may be the same as the sum of the widths in the X-axis direction of the emitter region 12 and the contact region 15 in the second mesa portion 71-2.

By displacing the emitter region 12 and the contact region 15 in the X-axis direction in the two mesa portions 71 adjacent to each other with the gate trench portion 40 interposed therebetween, the contact regions 15 contributing to extraction of holes are arranged in a dispersed manner. can do. For this reason, holes can be extracted evenly in the XY plane, and the withstand voltage when the semiconductor device 100 is turned off can be improved.

In addition, in the semiconductor device 200 of this example, the contact region 15 is exposed on the upper surface of the dummy mesa portion 72 . A base region 14 may be formed below the contact region 15 . Further, in the semiconductor device 200 of this example, the accumulation region 16 is formed in the mesa portion 71 and the dummy mesa portion 72 .

Further, in the first mesa portion 71-1 and the second mesa portion 71-2, a region in which the emitter region 12 or the contact region 15 is formed has a region extending in the lateral direction (Y-axis direction) of the gate trench portion 40. No trench is formed. That is, in the region where the emitter regions 12 and the contact regions 15 are regularly arranged, the gate trench portion 40 does not have branches or branches extending inside the mesa portion 71 . Moreover, the dummy trench part 30 is not provided in the said area|region, either. With such a structure, carriers such as holes can be effectively extracted through the dispersed contact regions 15 without being obstructed by the trench portion.

FIG. 19 is a diagram showing an example of the aa cross section in FIG. The aa section of this example is the YZ plane passing through the contact region 15 of the first mesa portion 71-1 and the emitter region 12 of the second mesa portion 71-2.

As described above, the contact region 15 of the first mesa portion 71-1 and the contact region 15 of the second mesa portion 71-2 are arranged to be shifted in the X-axis direction. Therefore, in the cross section shown in FIG. 19, the contact region 15 is provided in the first mesa portion 71-1, and the emitter region 12 is provided in the second mesa portion 71-2. With such an arrangement, the holes can be extracted evenly.

In the dummy mesa portion 72 of this example, the contact region 15 , the base region 14 and the accumulation region 16 are provided in order from the upper surface 21 side of the semiconductor substrate 10 . In another example, the dummy mesa portion 72 may not be provided with the accumulation region 16 . Further, like the semiconductor device 100 shown in FIGS. 1 and 2A, the storage region 16 may not be provided in the mesa portion 71 either.

FIG. 20 is a diagram showing another example of the aa cross section in FIG. In the semiconductor device 200 of this example, the structure of the dummy mesa portion 72 is the same as that of the semiconductor device 100 described with reference to FIGS. That is, the semiconductor device 200 of this example has the first well region 13 in the dummy mesa portion 72 . Such a structure allows the carrier to be pulled out more easily. Also, the structure of the accumulation region 16 in the semiconductor device 200 may be the same as that of the accumulation region 16 in the semiconductor device 100 . Moreover, the semiconductor device 200 may include the lower surface side region 28 shown in FIGS. 16 and 17 .

FIG. 21 is a diagram showing an arrangement example of the emitter regions 12 and the contact regions 15 on the upper surfaces of the first mesa portion 71-1 and the second mesa portion 71-2. In this example, the emitter region 12 and the contact region 15 in each mesa portion 71 have the same length in the X-axis direction. The contact region 15 in the first mesa portion 71-1 is arranged at a position facing the emitter region 12 in the second mesa portion 71-2, and the emitter region 12 in the first mesa portion 71-1 is located in the second mesa portion. It is arranged at a position facing the contact region 15 of the portion 71-2.

FIG. 22 is a diagram showing another arrangement example of the emitter regions 12 and the contact regions 15 on the upper surfaces of the first mesa portion 71-1 and the second mesa portion 71-2. In this example, the contact region 15 is formed longer than the emitter region 12 in the X-axis direction in the first mesa portion 71-1 and the second mesa portion 71-2. The length of contact region 15 may be more than double the length of emitter region 12 .

The range in the X-axis direction in which the emitter region 12 of the first mesa portion 71-1 is provided is included in the range in the X-axis direction in which the contact region 15 of the second mesa portion 71-2 is provided. The range in the X-axis direction in which the emitter region 12 of the second mesa portion 71-2 is provided is included in the range in the X-axis direction in which the contact region 15 of the first mesa portion 71-1 is provided. With such a structure, it is possible to improve the drawing speed of the carrier.

FIG. 23 is a diagram showing another arrangement example of the emitter regions 12 and the contact regions 15 on the upper surfaces of the first mesa portion 71-1 and the second mesa portion 71-2. In this example, in the first mesa portion 71-1 and the second mesa portion 71-2, the emitter region 12 is formed longer than the contact region 15 in the X-axis direction. The length of emitter region 12 may be more than double the length of contact region 15 .

The range in the X-axis direction in which the contact region 15 of the first mesa portion 71-1 is provided is included in the range in the X-axis direction in which the emitter region 12 of the second mesa portion 71-2 is provided. The range in the X-axis direction in which the contact region 15 of the second mesa portion 71-2 is provided is included in the range in the X-axis direction in which the emitter region 12 of the first mesa portion 71-1 is provided. Such a structure can improve the channel density.

FIG. 24 is a diagram showing an arrangement example of the accumulation area 16. As shown in FIG. The accumulation region 16 of this example has an opening 92 in the XY plane. A drift region 18 may be provided inside the opening 92 . The opening 92 may be arranged so as to overlap the contact region 15 in the first mesa portion 71-1 and the second mesa portion 71-2. With such a structure, the carrier can be pulled out at the first mesa portion 71-1 and the second mesa portion 71-2. The area of the opening 92 on the XY plane may be the same as the area of the contact region 15, or may be smaller. The area of opening 92 may be less than half the area of contact region 15 .

25A and 25B are diagrams showing an example of a method for manufacturing the semiconductor device 100. FIG. Note that the semiconductor device 200 may also be manufactured by the same method. In step S250, the base region 14 is formed in the semiconductor substrate 10 provided with the gate trench portion 40 and the dummy trench portion 30. As shown in FIG. The base region 14 may be formed by implanting a P-type impurity such as boron from the upper surface side of the semiconductor substrate 10 .

In step S252, an accumulation region 16 is formed. The accumulation region 16 may be formed by implanting an N-type impurity such as phosphorus from the upper surface side of the semiconductor substrate 10 using a mask such as photoresist.

At step S254, the first well region 13 is formed. The first well region 13 may be formed by implanting a P-type impurity such as boron from the upper surface side of the semiconductor substrate 10 using a mask such as photoresist. The P-type impurity may be implanted to different depths in multiple steps by changing the acceleration voltage.

In step S256, contact regions 15 are formed. The contact region 15 may be formed by implanting a P-type impurity such as boron from the upper surface side of the semiconductor substrate 10 using a mask such as photoresist.

In step S258, structures on the bottom side of the semiconductor substrate 10 are formed. For example, a collector region 22 is formed.

In step S260, the semiconductor substrate 10 is annealed under predetermined conditions. As a result, each region is formed by converting the impurity implanted in steps S250 to S258 into a donor or acceptor.

In step S262, emitter region 12 is formed. The emitter region 12 may be formed by implanting an N-type impurity such as arsenic from the upper surface side of the semiconductor substrate 10 using a mask such as photoresist.

In step S264, the semiconductor substrate 10 is annealed under predetermined conditions. As a result, the impurity implanted in step S262 is converted into donors to form the emitter region 12. Next, as shown in FIG.

After step S264, an interlayer insulating film 26, a contact hole 54, an emitter electrode 52, and the like are formed. Thereby, the semiconductor device 100 can be manufactured.

Note that step S254 may be performed after step S264. In this case, an annealing step may be included after step S254. In this case, since the number of times of annealing after forming the first well region 13 can be reduced, the depth of the first well region 13 can be accurately controlled.

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

The execution order of each process in the method shown in the claims, specification, and drawings is not specified as "before", "before", etc., and the result of the previous process may be implemented in any order unless used in subsequent processing. Regarding the operation flow in the claims, the specification, and the drawings, even if the description is made using "first," "next," etc. for the sake of convenience, it means that it is essential to carry out in this order. not a thing

DESCRIPTION OF SYMBOLS 10... Semiconductor substrate 11... Second well region 12... Emitter region 13... First well region 14... Base region 15... Contact region 16... Accumulation region 17 region 18 drift region 20 buffer region 21 upper surface 22 collector region 23 lower surface 26 interlayer insulating film 28...lower surface side region 30...dummy trench portion 31...extending portion 32...dummy insulating film 33...tip portion 34...dummy conductive portion 35... bottom, 36... end, 37... second dummy side wall, 38... first dummy side wall, 40... gate trench part, 41... extending part, 42... gate insulating film, 43... tip portion, 44... gate conductive portion, 45... gate wiring, 46... gate electrode, 52... emitter electrode, 54, 55, 56... contact hole, 57... Connection portion 58 Collector electrode 71 Mesa portion 72 Dummy mesa portion 73 Recess portion 74 First gate side wall 75 Second gate side wall 92... opening, 100... semiconductor device, 200... semiconductor device

Claims (1)

a plurality of trench portions provided on the upper surface of the semiconductor substrate;
a first mesa portion, which is a region of the semiconductor substrate sandwiched between the trench portions and includes an emitter region of a first conductivity type and a base region of a second conductivity type;
a second mesa portion, which is a region of the semiconductor substrate sandwiched between the trench portions and includes a first well region of a second conductivity type deeper than a lower end of the trench portion;
a collector region of a second conductivity type provided on the lower surface of the semiconductor substrate;
a buffer region of a first conductivity type provided on the upper surface side of the collector region;
a first conductivity type drift region provided from the inside of the first mesa portion to the buffer region;
a gate electrode provided above the semiconductor substrate;
an emitter electrode provided above the semiconductor substrate;
with
The first well region has a higher doping concentration than the base region, and extends beyond the bottom of the trench to below the first mesa in the width direction of the trench.

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