JP2014236166A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device which is low loss and has a high withstand voltage.SOLUTION: A semiconductor device comprises: p type termination regions 11, 12 which are formed in an ntype drift layer 2 formed on a surface composed of a (0001) plane of an ntype substrate; a surface electrode 10 formed on the ntype drift layer 2; and a back electrode formed in contact with a rear face of the ntype substrate. A curvature radius Rof each corner part of the p type termination regions 11, 12 in a [-1-120] direction side from the center of a semiconductor chip SC is made larger than a curvature radius Rof each corner part of the p type termination regions 11, 12 in a [11-20] direction side from the center of the semiconductor chip SC.

Description

  The present invention relates to a semiconductor device.

  Silicon carbide (SiC) is a material that has a breakdown electric field about 10 times larger than silicon (Si), so that the drift layer that maintains the withstand voltage can be made thin and highly concentrated, and conduction loss can be reduced. . For this reason, it is expected to be applied to the next-generation power device with high breakdown voltage and low loss.

  In a power device, in a blocking state, a termination region such as a junction termination extension (JTE) or a field limiting ring (FLR) is used to alleviate electric field concentration at the device end. A structure (termination structure) is formed. In addition, the blocking state here refers to a state where a high potential difference is generated between the electrodes of the power device and no current flows between the electrodes.

  As background art in this technical field, there is JP-A-08-316480 (Patent Document 1). In this publication, the second conductivity type semiconductor layer formed on the main surface of the first conductivity type semiconductor layer includes a first region having a relatively high injection efficiency and a second region having a relatively low injection efficiency. An example of a JTE structure in which a first region is surrounded by a second region and a first electrode is connected to the first region is described.

Japanese Patent Laid-Open No. 08-316480

  In order to reduce the power device loss, it is necessary to make the active area as large as possible. At this time, there are various technical problems described below.

  That is, in order to increase the active area of the power device formed on the semiconductor chip, it is preferable to make the shape of the active region square. However, since the four corners (corner portions) of the active region have a higher electric field than the side, even if the termination structure is formed so as to surround the active region, if the shape is a quadrangle, the breakdown voltage will be reduced or the power device will be destroyed. End up. For this reason, the corner portion of the active region is usually arcuate to ease the electric field and to have a high withstand capability.

  FIG. 11 is a graph showing an example of the relationship between the radius of curvature of the corner portion of the active region and the electric field strength. The electric field intensity on the vertical axis is normalized by the electric field when the radius of curvature of the corner portion of the active region is infinite, that is, the electric field on the side. Since the electric field decreases as the radius of curvature of the corner portion of the active region increases, a highly durable power device can be obtained.

  On the other hand, however, if the radius of curvature of the corner portion of the active region is large, the active area becomes small as shown in FIG. For this reason, it is difficult to realize a power device with low loss and high resistance.

  Accordingly, the present invention provides a semiconductor device with low loss and high withstand capability.

In order to solve the above-described problem, the present invention forms a p-type termination region in an n ⁻ type drift layer formed on the (0001) plane of a substrate so as to surround the active region in plan view. The radius of curvature of the corner portion of the p-type termination region on the [1-1-120] direction side is made larger than the radius of curvature of the corner portion of the p-type termination region on the [11-20] direction side from the center of the substrate.

  According to the present invention, it is possible to provide a semiconductor device with low loss and high resistance.

  Problems, configurations, and effects other than those described above will become apparent from the following description of embodiments.

It is sectional drawing which shows an example of the termination area | region of a power device. It is a figure which shows the equipotential line inside the power device in a blocking state (termination area | region). It is a light emission analysis image figure which shows the leak location of a power device. It is the schematic diagram which looked at the electric field in a termination area | region when a power device was formed on the approximate (0001) plane from the (1-100) plane which is a power device cross section. 1 is a plan view of a power device according to a first embodiment. 6 is a plan view of a power device according to Embodiment 2. FIG. It is a graph which shows an example which calculated the breakdown electric field strength of a termination area | region. 6 is a plan view of a power device according to Embodiment 3. FIG. 6 is a plan view of a power device of Example 4. FIG. 10 is a plan view of a power device according to Embodiment 5. FIG. It is a graph which shows an example of the relationship between the curvature radius of the corner part of an active area | region, and electric field strength. It is a graph which shows an example of the relationship between the curvature radius of the corner part of an active region, and an active area.

  In the following embodiments, when necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not irrelevant to each other, and one is the other. There are some or all of the modifications, details, supplementary explanations, and the like.

  Further, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), especially when clearly indicated and when clearly limited to a specific number in principle, etc. Except, it is not limited to the specific number, and may be more or less than the specific number.

  Further, in the following embodiments, the constituent elements (including element steps) are not necessarily indispensable unless otherwise specified and clearly considered essential in principle. Needless to say.

  In addition, when referring to “consisting of A”, “consisting of A”, “having A”, and “including A”, other elements are excluded unless specifically indicated that only that element is included. It goes without saying that it is not what you do. Similarly, in the following embodiments, when referring to the shapes, positional relationships, etc. of the components, etc., the shapes are substantially the same unless otherwise specified, or otherwise apparent in principle. And the like are included. The same applies to the above numerical values and ranges.

  Further, in the drawings used in the following embodiments, hatching may be added to make the drawings easy to see even if they are plan views. In all the drawings for explaining the following embodiments, components having the same function are denoted by the same reference numerals in principle, and repeated description thereof is omitted. Hereinafter, the present embodiment will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an example of a termination region of a power device.

An n ⁻ type drift layer 2 is formed on the first surface ((0001) surface) of the n ⁺ type substrate 1. On the upper surface of the n ⁻ type drift layer 2, a p ⁺ type guard ring region 3, a p type JTE region 4, and an n ⁺ type channel stop so as to surround an active region formed in the center of the semiconductor chip in plan view. A region 5 is formed, and a passivation film 6 is formed on the n ⁻ -type drift layer 2.

Further, a surface electrode 8 connected to the p ⁺ -type guard ring region 3 and the channel stop electrode 9 connected to the n ⁺ -type channel stop region 5 are formed through the opening formed in the passivation film 6. n ⁺ -type first surface and a second side opposite the substrate 1 on ((000-1) plane), the back surface electrode 7 connected to the ^{n +} -type substrate 1 is formed.

  Note that the passivation film and the resin film formed above the surface electrode 8 and the channel stop electrode 9 are not shown. The illustration of the active region at the center of the semiconductor chip is also omitted.

FIG. 2 is a diagram showing equipotential lines inside the power device (termination region) in a blocking state in which a voltage is applied between the back electrode 7 and the front electrode 8 shown in FIG. Although the electric field tends to concentrate on the edge portion of the p ⁺ -type guard ring region 3, the presence of the p-type JTE region 4 can alleviate the electric field concentration. This makes it possible to increase the breakdown voltage of the power device.

  However, on the other hand, in order to reduce the loss of the power device, as described above, it is desirable to make the active area as large as possible by making the active area square. However, in order to suppress a decrease in breakdown voltage or power device breakdown due to a high electric field at the corner portion of the active region, it is necessary to make the corner portion an arc shape with a large curvature radius. I can't. As a result, even if the p-type JTE region 4 is arranged, it is difficult to realize a power device with low loss and high withstand capability.

  As a result of examining the SiC power device, the present inventors have revealed the following facts.

  FIG. 3 is a light emission analysis image diagram showing a leak portion of the power device. A bright spot indicated by an arrow in FIG. 3 is a portion where a leak current flows. [−1-120] direction side (hereinafter referred to as [-1-120] side) from the center of the semiconductor chip on which the power device is formed and [11-20] direction side (hereinafter referred to as [11] from the center of the semiconductor chip). (−20] side), the withstand capability on the [−1−120] side is low, and when the applied voltage is increased, the leakage current begins to flow first from the [−1−120] side. That is, the leakage current at the corner on the [-1-120] side is the largest.

  This is due to the following reason.

  The crystal type of SiC used as a power device is a hexagonal crystal, and due to this, the breakdown electric field strength parallel to the <0001> direction axis (c axis) and the breakdown electric field strength perpendicular to the c axis are different. For example, “Physical modeling and scaling properties of 4H-SiC power devices,” T. Hatakeyama, C. Ohta, J. Nishio, T. Shinohe, Proc. Of 2005 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD ) p.171 (2005).

  FIG. 4 is a schematic view of the electric field in the termination region when the power device is formed on the approximate (0001) plane, as viewed from the (1-100) plane which is a cross section of the power device. In general, to produce high-quality SiC, it is effective to form an epitaxial layer by step flow growth. For this reason, a power device is manufactured using a surface inclined several degrees in the [11-20] direction from the (0001) plane which is a plane perpendicular to the c-axis. At this time, when the electric fields in the termination regions on the [-1-120] side and the [11-20] side are viewed from the (1-100) plane (device cross section), they are as shown in FIG.

  Although the electric field distribution is expanded outward by the termination structure, the front surface electrode is smaller than the back surface electrode, so the electric field faces inward. When this electric field is decomposed in the c-axis parallel direction and the c-axis vertical direction, the components are different between the [-1-120] side and the [11-20] side. This is because the electric field is symmetric with respect to the wafer surface, but the main surface of the power device is inclined from the c-axis. As described above, since the breakdown electric field strength in the c-axis parallel direction and the breakdown electric field strength in the c-axis vertical direction are different, the breakdown electric field strength is different between the [−1-120] side and the [11-20] side. The breakdown electric field strength on the −120] side is lower. Therefore, increasing the breakdown electric field strength on the [-1-120] side is effective for obtaining a power device with high resistance.

  When a power device is fabricated using a plane inclined several degrees in the [-1-120] direction from the (000-1) plane as a main surface, the breakdown electric field strength on the [11-20] side is [-1- 120] side breakdown electric field strength.

  In FIG. 5, the top view of the power device of Example 1 is shown. The power device of Example 1 is a power device such as a high breakdown voltage transistor formed on a semiconductor substrate made of SiC, and FIG. 5 shows a semiconductor chip formed by dicing the semiconductor substrate into individual pieces. Yes. Note that the structure shown in FIG. 5 illustrates a diode as an example; however, the structure can also be applied to a transistor. FIG. 5 is a perspective view of a protective film such as a passivation film.

As shown in FIG. 5, a surface electrode 10, p-type termination regions 11 and 12, and a channel stop electrode 9 are formed on the upper surface of the n ⁻ -type drift layer 2. Although not shown in FIG. 5, there is an active region under the surface electrode 10 disposed in the center of the semiconductor chip SC, and the p-type termination regions 11 and 12 and the channel stop electrode 9 are seen in a plan view. The semiconductor chip SC is arranged so as to surround the active area at the center. Here, JTE is described as the termination structure, but FLR may be used. Further, the termination region is formed of two regions including the p-type termination region 11 and the p-type termination region 12, but may be formed of a single region or a plurality of regions.

The p-type termination regions 11 and 12 are formed by providing an n ⁻ -type SiC epitaxial layer on a SiC n ⁺ -type substrate and introducing a p-type impurity (for example, Al (aluminum)) on the upper surface thereof. The SiC epitaxial layer becomes the n ⁻ type drift layer 2. The n ⁻ type drift layer 2 is formed on a surface inclined several degrees (for example, 4 degrees) in the [11-20] direction from the (0001) plane. Channel stop is a region for preventing the electric field applied to the device extends to an end portion of the semiconductor chip SC, the lower channel stop electrode 9 n ^- -type drift layer 2, n ⁺ -type regions of the n-type impurity (For example, N (nitrogen)) is introduced. Although not shown in FIG. 5, a back electrode is formed on the back surface of the n ⁺ type substrate. The back electrode, the front electrode 10, and the channel stop electrode 9 are made of, for example, Al (aluminum).

  The curvature radius of the corner portion on the [−1-120] side from the center of the semiconductor chip SC in the p-type termination regions 11 and 12 is larger than the curvature radius of the corner portion on the [11-20] side from the center of the semiconductor chip SC. It is formed.

That is, in FIG. 5, in the p-type termination regions 11 and 12, on the [−1−120] side and the [1-100] side, the [−1−120] side and the [−1100] side. The radius of curvature R ₀ of a certain corner portion is the radius of curvature R of the corner portion on the [11-20] side and on the [1-100] side and the corner portion on the [11-20] side and on the [−1100] side. Greater than ₁ . In Examples 2 to 5 described later, the termination region is described as a single region, but a plurality of regions may be used.

  The first embodiment relates to the planar structure of the p-type termination regions 11 and 12, and the planar shapes of the channel stop electrode 9 and the surface electrode 10 do not have to be as shown in FIG. Further, in FIG. 5, the semiconductor chip SC is described as a square, but it is not necessary to be a square.

  The effects of the power device of Example 1 are as follows. Since the electric field strength of the curved portion is stronger than that of the straight portion, the radius of curvature of the corner portion of the p-type termination regions 11 and 12 on the [-1-120] side is increased. On the other hand, when a power device is fabricated on the approximate (0001) plane, the breakdown electric field on the [11-20] side is larger than the breakdown electric field on the [-1-120] side, and thus the [11-20] side is not impaired. The radius of curvature of the corner portions of the p-type termination regions 11 and 12 can be reduced. As a result, the active area can be increased compared with the case where the radius of curvature of the corner portions of the p-type termination regions 11 and 12 is made uniform in the semiconductor chip surface, and a low-loss power device can be provided.

In Example 1, the n ⁻ type drift layer 2 was formed on a surface inclined several degrees (for example, 4 degrees) in the [11-20] direction from the (0001) plane, but from the (000-1) plane, [ It may be formed on a surface inclined several degrees (for example, 4 degrees) in the (1-120) direction. In this case, the radius of curvature of the corner portion on the [11-20] side from the center of the semiconductor chip SC in the p-type termination region is larger than the radius of curvature of the corner portion on the [-1-120] side from the center of the semiconductor chip SC. Form large. Thereby, the effect similar to the effect of Example 1 mentioned above can be acquired.

  In FIG. 6, the top view of the power device of Example 2 is shown.

As shown in FIG. 6, a surface electrode 13, a p-type termination region 14, and a channel stop electrode 9 are formed on the upper surface of the n ⁻ type drift layer 2. Although not shown in FIG. 6, an active region exists under the surface electrode 13 disposed in the central portion of the semiconductor chip SC, and the p-type termination region 14 and the channel stop electrode 9 are in the semiconductor chip in plan view. It is arranged so as to surround the active area at the center of the SC. Here, JTE is described as the termination structure, but FLR may be used. The p-type termination region 14 is formed of a single region, but may be formed of a plurality of regions.

The p-type termination region 14 is formed by providing an n ⁻ -type SiC epitaxial layer on an SiC n ⁺ -type substrate and introducing a p-type impurity (for example, Al (aluminum)) on the upper surface thereof. The epitaxial layer becomes the n ⁻ type drift layer 2. The n ⁻ type drift layer 2 is formed on a surface inclined several degrees (for example, 4 degrees) in the [11-20] direction from the (0001) plane. Channel stop is a region for preventing the electric field applied to the device extends to an end portion of the semiconductor chip SC, the lower channel stop electrode 9 n ^- -type drift layer 2, n ⁺ -type regions of the n-type impurity (For example, N (nitrogen)) is introduced. Although not shown in FIG. 6, a back electrode is formed on the back surface of the n ⁺ type substrate. The back electrode, the front electrode 13, and the channel stop electrode 9 are made of, for example, Al (aluminum).

  The radius of curvature of the corner portion on the [−1-120] side from the center of the semiconductor chip SC in the p-type termination region 14 is formed larger than the radius of curvature of the corner portion on the [11-20] side from the center of the semiconductor chip SC. The

That is, in FIG. 6, in the p-type termination region 14, the corner on the [−1−120] side and on the [1-100] side and the corner on the [−1−120] side and on the [−1100] side. the radius of curvature _{R 2} of the parts are from the radius of curvature _{R 3} of the corner portion in the [11-20] side a and [1-100] side corner portions and in and a [11-20] side [-1100] side Is also big. When the p-type termination region 14 is formed of a plurality of regions having different impurity concentrations and depths, the curvature radius of the corner portion on the [-1-120] side is [11] in at least one p-type termination region. It is sufficient that it is larger than the radius of curvature of the corner portion on the −20] side.

  Further, in the p-type termination region 14, between the corner portion on the [−1−120] side and on the [1-100] side and the corner portion on the [−1−120] side and on the [−1100] side. And has a side along the <1-100> direction.

  Example 2 relates to the planar structure of the p-type termination region 14, and the planar shapes of the channel stop electrode 9 and the surface electrode 13 do not have to be as shown in FIG. 6. Further, in FIG. 6, the semiconductor chip SC is described as a square, but it is not necessary to be a square.

  The effects of the power device of Example 2 are as follows. Since the electric field strength of the curved portion is higher than that of the straight portion, the radius of curvature of the corner portion of the p-type termination region 14 on the [-1-120] side is increased. On the other hand, when a power device is fabricated on the approximate (0001) plane, the breakdown electric field on the [11-20] side is larger than the breakdown electric field on the [-1-120] side, and thus the [11-20] side is not impaired. The radius of curvature of the corner of the p-type termination region 14 can be reduced. As a result, the active area can be increased as compared with the case where the radius of curvature of the corner portion of the p-type termination region 14 is made uniform in the semiconductor chip surface, and a low-loss power device can be provided.

  FIG. 7 is a graph showing an example of calculating the breakdown electric field strength in the termination region. (1) [1-120] side along <1-100> direction, (2) [-1-120] side corner, (3) [1-100] side <11-20> The breakdown electric field strength at the side along the direction, (4) the corner portion on the [11-20] side, and (5) the side along the <1-100> direction on the [11-20] side was determined.

  The power device can have a high withstand capability when only one corner portion does not reach a breakdown electric field when a voltage is applied. However, as shown in FIG. 11 described above, since the breakdown electric field at the corner portion of the termination region depends on the curvature radius of the termination region, the curvature radius of the corner portion on the [11-20] side is, for example, 170 μm or more, [ For example, the radius of curvature of the corner portion on the (1-120) side is preferably 350 μm or more.

In Example 2, the n ⁻ type drift layer 2 was formed on a surface inclined several degrees (for example, 4 degrees) in the [11-20] direction from the (0001) plane, but from the (000-1) plane, [ It may be formed on a surface inclined several degrees (for example, 4 degrees) in the (1-120) direction. In this case, the radius of curvature of the corner portion on the [11-20] side from the center of the semiconductor chip SC in the p-type termination region is larger than the radius of curvature of the corner portion on the [-1-120] side from the center of the semiconductor chip SC. Form large. Thereby, the effect similar to the effect of Example 2 mentioned above can be acquired.

  In FIG. 8, the top view of the power device of Example 3 is shown.

As shown in FIG. 8, a surface electrode 15, a p-type termination region 16, and a channel stop electrode 9 are formed on the upper surface of the n ⁻ type drift layer 2. Although not shown in FIG. 8, an active region exists under the surface electrode 15 disposed in the center of the semiconductor chip SC, and the p-type termination region 16 and the channel stop electrode 9 are in the semiconductor chip in plan view. It is arranged so as to surround the active area at the center of the SC. Here, JTE is described as the termination structure, but FLR may be used. The p-type termination region 16 is formed of a single region, but may be formed of a plurality of regions.

The p-type termination region 16 is formed by providing an n ⁻ -type SiC epitaxial layer on an SiC n ⁺ -type substrate and introducing a p-type impurity (for example, Al (aluminum)) on the upper surface thereof. The epitaxial layer becomes the n ⁻ type drift layer 2. The n ⁻ type drift layer 2 is formed on a surface inclined several degrees (for example, 4 degrees) in the [11-20] direction from the (0001) plane. Channel stop is a region for preventing the electric field applied to the device extends to an end portion of the semiconductor chip SC, the lower channel stop electrode 9 n ^- -type drift layer 2, n ⁺ -type regions of the n-type impurity (For example, N (nitrogen)) is introduced. Although not shown in FIG. 8, a back electrode is formed on the back surface of the n ⁺ type substrate. The back electrode, the front electrode 15, and the channel stop electrode 9 are made of, for example, Al (aluminum).

  The radius of curvature of the corner portion on the [−1-120] side from the center of the semiconductor chip SC in the p-type termination region 16 is formed larger than the radius of curvature of the corner portion on the [11-20] side from the center of the semiconductor chip SC. The

Here, the radius of curvature of the corner portion on the [-1-120] side is the radius of curvature of the corner portion connected to the side extending in the <1-100> direction on the [-1-120] side. As shown in FIG. 8, in the case of a part of an ellipse defined by a radius of curvature R ₄ (half the minor axis) and a radius of curvature R ₅ (half the major axis), the radius of curvature is R ₅ × R _5. / _R is _4. Similarly, the radius of curvature of the corner portion on the [11-20] side is the radius of curvature of the corner portion connected to the side extending in the <1-100> direction on the [11-20] side. is there. In FIG. 8, the corner portion on the [11-20] side is described as a part of a perfect circle, but may be a part of an ellipse. When the p-type termination region 16 is formed of a plurality of regions having different impurity concentrations and depths, the radius of curvature of the corner portion on the [-1-120] side is [11] in at least one p-type termination region. It is sufficient that it is larger than the curvature radius of the corner portion on the −20] side.

  Example 3 relates to the planar structure of the p-type termination region 16, and the planar shapes of the channel stop electrode 9 and the surface electrode 15 do not have to be as shown in FIG. In FIG. 8, the semiconductor chip SC is shown as a square, but it is not necessary to be a square.

  The effects of the power device of Example 3 are as follows. Since the electric field strength of the curved portion is higher than that of the straight portion, the radius of curvature of the corner portion of the p-type termination region 16 on the [-1-120] side is increased. On the other hand, when a power device is fabricated on the approximate (0001) plane, the breakdown electric field on the [11-20] side is larger than the breakdown electric field on the [-1-120] side, and thus the [11-20] side is not impaired. The radius of curvature of the corner of the p-type termination region 16 can be reduced. As a result, the active area can be increased as compared with the case where the radius of curvature of the corner portion of the p-type termination region 16 is made uniform in the semiconductor chip surface, and a low-loss power device can be provided.

  The power device can have a high withstand capability when only one corner portion does not reach a breakdown electric field when a voltage is applied. However, as shown in FIG. 11 described above, since the breakdown electric field at the corner portion of the termination region depends on the curvature radius of the termination region, the curvature radius of the corner portion on the [11-20] side is, for example, 170 μm or more, [ For example, the radius of curvature of the corner portion on the (1-120) side is preferably 350 μm or more.

In Example 3, the n ⁻ -type drift layer 2 was formed on a surface inclined several degrees (for example, 4 degrees) in the [11-20] direction from the (0001) plane, but from the (000-1) plane, It may be formed on a surface inclined several degrees (for example, 4 degrees) in the (1-120) direction. In this case, the radius of curvature of the corner portion on the [11-20] side from the center of the semiconductor chip SC in the p-type termination region is larger than the radius of curvature of the corner portion on the [-1-120] side from the center of the semiconductor chip SC. Form large. Thereby, the effect similar to the effect of Example 3 mentioned above can be acquired.

  In FIG. 9, the top view of the power device of Example 4 is shown.

As shown in FIG. 9, the surface electrode 17, the p-type termination region 18, and the channel stop electrode 9 are formed on the upper surface of the n ⁻ type drift layer 2. Although not shown in FIG. 9, an active region exists under the surface electrode 17 disposed in the central portion of the semiconductor chip SC, and the p-type termination region 18 and the channel stop electrode 9 are in the semiconductor chip in plan view. It is arranged so as to surround the active area at the center of the SC. Here, JTE is described as the termination structure, but FLR may be used. The p-type termination region 18 is formed of a single region, but may be formed of a plurality of regions.

The p-type termination region 18 is formed by providing an n ⁻ -type SiC epitaxial layer on an SiC n ⁺ -type substrate and introducing a p-type impurity (for example, Al (aluminum)) on the upper surface thereof. The epitaxial layer becomes the n ⁻ type drift layer 2. The n ⁻ type drift layer 2 is formed on a surface inclined several degrees (for example, 4 degrees) in the [11-20] direction from the (0001) plane. Channel stop is a region for preventing the electric field applied to the device extends to an end portion of the semiconductor chip SC, the lower channel stop electrode 9 n ^- -type drift layer 2, n ⁺ -type regions of the n-type impurity (For example, N (nitrogen)) is introduced. Although not shown in FIG. 9, a back electrode is formed on the back surface of the n ⁺ type substrate. The back electrode, the front electrode 17, and the channel stop electrode 9 are made of, for example, Al (aluminum).

  The radius of curvature of the corner portion on the [−1-120] side from the center of the semiconductor chip SC in the p-type termination region 18 is formed larger than the radius of curvature of the corner portion on the [11-20] side from the center of the semiconductor chip SC. The

  Here, the radius of curvature of the corner portion on the [-1-120] side is the radius of curvature of the corner portion connected to the side extending in the <1-100> direction on the [-1-120] side. It is. Similarly, the radius of curvature of the corner portion on the [11-20] side is the radius of curvature of the corner portion connected to the side extending in the <1-100> direction on the [11-20] side. is there. When the p-type termination region 18 is formed of a plurality of regions having different impurity concentrations and depths, the curvature radius of the corner portion on the [-1-120] side in the at least one p-type termination region is [11 It is sufficient that it is larger than the radius of curvature of the corner portion on the −20] side.

Further, the length (L ₁ ) of the side of the semiconductor chip SC on the [1-100] side and the [−1100] side along the <11-20> direction is [−1-120] along the <1-100> direction. ] Side and [11-20] side semiconductor chip SC is longer than the side length (L ₂ ).

  The effects of the power device of Example 4 are as follows. Since the electric field strength of the curved portion is higher than that of the straight portion, the radius of curvature of the corner portion of the p-type termination region 18 on the [-1-120] side is increased. On the other hand, when a power device is fabricated on the approximate (0001) plane, the breakdown electric field on the [11-20] side is larger than the breakdown electric field on the [-1-120] side, and thus the [11-20] side is not impaired. The radius of curvature of the corner portion of the p-type termination region 18 can be reduced. As a result, the active area can be increased as compared with the case where the radius of curvature of the corner portion of the p-type termination region 18 is made uniform in the semiconductor chip surface, and a low-loss power device can be provided.

Furthermore, as shown in FIG. 7 described above, in the termination region, the breakdown electric field strength of the side extending in the <1-100> direction on the [-1-120] side is the smallest among the power devices. Therefore, by making the length (L ₁ ) of the side of the semiconductor chip SC along the <11-20> direction longer than the length (L ₂ ) of the side of the semiconductor chip SC along the <1-100> direction. The length (L ₃ ) of the side of the termination region extending in the <1-100> direction on the [-1-120] side is relatively shortened. Thereby, a high withstand power device can be provided.

In Example 4, the n ⁻ type drift layer 2 was formed on a surface inclined several degrees (for example, 4 degrees) in the [11-20] direction from the (0001) plane, but from the (000-1) plane, [ It may be formed on a surface inclined several degrees (for example, 4 degrees) in the (1-120) direction. In this case, the radius of curvature of the corner portion on the [11-20] side from the center of the semiconductor chip SC in the p-type termination region is larger than the radius of curvature of the corner portion on the [-1-120] side from the center of the semiconductor chip SC. Form large. Thereby, the effect similar to the effect of Example 4 mentioned above can be acquired.

  In FIG. 10, the top view of the power device of Example 5 is shown.

As shown in FIG. 10, a surface electrode 31, a p-type termination region 32, and a channel stop electrode 33 are formed on the upper surface of the n ⁻ type drift layer 30. Although not shown in FIG. 10, an active region exists under the surface electrode 31 disposed in the center of the semiconductor chip SC, and the p-type termination region 32 and the channel stop electrode 33 are formed in the semiconductor chip in plan view. It is arranged so as to surround the active area at the center of the SC. Here, JTE is described as the termination structure, but FLR may be used. Further, the p-type termination region 32 is formed of a single region, but may be formed of a plurality of regions.

The p-type termination region 32 is formed by providing an n ⁻ -type SiC epitaxial layer on an SiC n ⁺ -type substrate and introducing a p-type impurity (for example, Al (aluminum)) on the upper surface thereof. The epitaxial layer becomes the n ⁻ type drift layer 30. The channel stop is a region for preventing the electric field applied to the device from reaching the end of the semiconductor chip SC, and the n ⁺ -type region in the n ⁻ -type drift layer 30 below the channel stop electrode 33 is an n-type impurity. (For example, N (nitrogen)) is introduced. Although not shown in FIG. 10, a back electrode is formed on the back surface of the n ⁺ type substrate. The back electrode, the front electrode 31, and the channel stop electrode 33 are made of, for example, Al (aluminum).

  Further, a passivation film is formed on the surface electrode 31, and an opening region 35 is provided in the passivation film. A wire or the like is bonded to the surface electrode 31 exposed from the opening region 35 when the semiconductor chip SC is mounted and modularized.

  As described in the first to fourth embodiments, the radius of curvature of the corner portion of the p-type termination region 32 is the radius of curvature of the corner portion on the [-1-120] side from the center of the semiconductor chip SC. Since the radius of curvature is larger than the radius of curvature of the corner portion on the [11-20] side from the center, the asymmetrical shape is formed according to the magnitude of the breakdown electric field strength. On the other hand, the opening region 35 formed in the passivation film on the surface electrode 31 is formed symmetrically with respect to the semiconductor chip SC.

  The effects of the power device of Example 5 are as follows. When the semiconductor chip SC is mounted and modularized, it is necessary to bond a wire or the like to the surface electrode 31 exposed from the opening region 35 formed in the passivation film. If the opening region 35 is formed symmetrically with respect to the semiconductor chip SC, it is possible to avoid mounting defects even when the semiconductor chip SC is rotated and arranged.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

1 n ⁺ type substrate 2 n ⁻ type drift layer 3 p ⁺ type guard ring region 4 p type JTE region 5 n ⁺ type channel stop region 6 passivation film 7 back electrode 8 surface electrode 9 channel stop electrode 10 surface electrodes 11 and 12 p Type termination region 13 surface electrode 14 p type termination region 15 surface electrode 16 p type termination region 17 surface electrode 18 p type termination region 30 n ⁻ type drift layer 31 surface electrode 32 p type termination region 33 channel stop electrode 35 opening region SC semiconductor Chip

Claims (12)

A first conductivity type substrate having a first main surface made of a (0001) surface and a second main surface opposite to the first main surface;
The first conductivity type drift layer formed on the first main surface of the substrate;
An active region formed in the center of the drift layer in plan view;
A second conductivity type termination region different from the first conductivity type formed in the drift layer so as to surround the active region in plan view;
A surface electrode formed on the drift layer;
A back electrode formed in contact with the second main surface of the substrate;
With
The termination region on the [−1-120] direction side from the center of the substrate is a first corner portion on the [1-100] direction side from the center of the substrate, and on the [−1100] direction side from the center of the substrate. Has a second corner,
The termination region on the [11-20] direction side from the center of the substrate has a third corner portion on the [1-100] direction side from the center of the substrate, and on the [-1100] direction side from the center of the substrate. It has 4 corners,
A semiconductor device in which a radius of curvature of the first corner portion and the second corner portion is larger than a radius of curvature of the third corner portion and the fourth corner portion. The semiconductor device according to claim 1,
The termination region is a semiconductor device having a side along a <1-100> direction between the first corner portion and the second corner portion. The semiconductor device according to claim 1,
The first corner portion has a larger radius of curvature from the [1-100] direction side toward the [-1100] direction side,
The semiconductor device in which the second corner portion has a radius of curvature that increases from the [−1100] direction side toward the [1-100] direction side. The semiconductor device according to claim 1,
The termination region has a side along the <1-100> direction between the first corner portion and the second corner portion,
The curvature radius of the portion where the first corner portion and the side along the <1-100> direction are connected and the portion where the second corner portion and the side along the <1-100> direction are connected are A semiconductor device having a radius of curvature larger than that of a third corner portion and the fourth corner portion. The semiconductor device according to claim 1,
The length of the side of the substrate along the <11-20> direction is larger than the length of the side of the substrate along the <1-100> direction. The semiconductor device according to claim 1, further comprising:
A passivation film formed on the surface electrode;
An opening region formed in the passivation film for exposing the surface electrode;
With
In plan view, the shape of the opening region on the [−1-120] direction side from the center of the substrate is symmetrical to the shape of the opening region on the [11-20] direction side from the center of the substrate. . A first conductivity type substrate having a first main surface comprising a (000-1) plane and a second main surface opposite to the first main surface;
The first conductivity type drift layer formed on the first main surface of the substrate;
An active region formed in the center of the drift layer in plan view;
A second conductivity type termination region different from the first conductivity type formed in the drift layer so as to surround the active region in plan view;
A surface electrode formed on the drift layer;
A back electrode formed in contact with the second main surface of the substrate;
With
The termination region on the [11-20] direction side from the center of the substrate has a first corner portion on the [1-100] direction side from the center of the substrate and a first corner portion on the [-1100] direction side from the center of the substrate. Has two corners,
The termination region on the [−1-120] direction side from the center of the substrate is a third corner portion on the [1-100] direction side from the center of the substrate, and on the [−1100] direction side from the center of the substrate. Has a fourth corner,
A semiconductor device in which a radius of curvature of the first corner portion and the second corner portion is larger than a radius of curvature of the third corner portion and the fourth corner portion. The semiconductor device according to claim 7.
The termination region is a semiconductor device having a side along a <1-100> direction between the first corner portion and the second corner portion. The semiconductor device according to claim 7.
The first corner portion has a larger radius of curvature from the [1-100] direction side toward the [-1100] direction side,
The second corner portion is a semiconductor device in which the radius of curvature increases from the [−1100] direction side to the [1-100] direction side. The semiconductor device according to claim 7.
The termination region has a side along the <1-100> direction between the first corner portion and the second corner portion,
The curvature radius of the portion where the first corner portion and the side along the <1-100> direction are connected and the portion where the second corner portion and the side along the <1-100> direction are connected are A semiconductor device having a radius of curvature larger than that of a third corner portion and the fourth corner portion. The semiconductor device according to claim 7.
The length of the side of the substrate along the <11-20> direction is larger than the length of the side of the substrate along the <1-100> direction. 8. The semiconductor device according to claim 7, further comprising:
A passivation film formed on the surface electrode;
An opening region formed in the passivation film for exposing the surface electrode;
With
In plan view, the shape of the opening region on the [11-20] direction side from the center of the substrate is symmetrical to the shape of the opening region on the [-1-120] direction side from the center of the substrate. .