JP6673571B2 - Schottky barrier diode - Google Patents

Description

  The present invention relates to a Schottky barrier diode.

  Conventionally, a Schottky barrier diode having a guard ring on the surface of a second semiconductor layer has been known (for example, see Patent Document 1).

As shown in FIG. 9, the conventional Schottky barrier diode 900 is formed on an n ⁺ -type first semiconductor layer 910 and an n ⁻ -type impurity layer having a lower impurity concentration than the first semiconductor layer 910. Second semiconductor layer 920, a barrier metal layer 930 formed in a predetermined surface area on second semiconductor layer 920, and a portion of barrier metal layer 930 in contact with the surface of second semiconductor layer 920 when viewed in plan And a p ⁺ -type guard ring 940 formed on the surface of the second semiconductor layer 920 so as to cover the end of the second semiconductor layer 920.

According to the conventional Schottky barrier diode 900, the barrier metal layer 930 is formed on the surface of the second semiconductor layer 920 so as to include the end of the portion in contact with the surface of the second semiconductor layer 920 in plan view. Since the p ⁺ -type guard ring 940 is provided, a depletion layer extending from the Schottky contact (contact between the barrier metal layer 930 and the second semiconductor layer 920) toward the first semiconductor layer 910 is formed around the second semiconductor layer 920. Can be extended to As a result, the electric field concentration at the end of the portion of the barrier metal layer 930 in contact with the surface of the second semiconductor layer 920 can be reduced.

JP 2000-58875 A

  However, in the conventional Schottky barrier diode 900, when a reverse surge is applied, the Schottky contact (the contact between the barrier metal layer 930 and the second semiconductor layer 920) and the pn junction (the guard ring 940 and the second semiconductor layer 920) ), The depletion layer extends toward the first semiconductor layer 910 and reaches the first semiconductor layer 910, that is, a reach-through state (see FIG. 7B). If a large reverse surge occurs in this state, the Schottky barrier diode is destroyed.

Therefore, it is conceivable to increase the thickness of the second semiconductor layer 920 to form a Schottky barrier diode that is less likely to be in a reach-through state. However, in such a case, since the resistance of the second semiconductor layer 920 is increased, the higher the forward voltage V _F, unfavorable (Sample 5 in FIG. 8 to be described later (Comparative Example 2) reference.).

The present invention has been made in view of such a background, and an object thereof is to provide a Schottky barrier diode can be forward voltage without increasing the V _F, to increase the reverse surge resistance .

[1] A Schottky barrier diode according to the present invention includes a first conductive type first semiconductor layer and a first conductive type first semiconductor layer formed on the first semiconductor layer and having a lower impurity concentration than the first semiconductor layer. A second semiconductor layer, a barrier metal layer formed in a predetermined region on a surface of the second semiconductor layer, and an end of a portion of the barrier metal layer in contact with the surface of the second semiconductor layer when viewed in plan. A guard ring of the second conductivity type formed on the surface of the second semiconductor layer so that the impurity concentration of the second semiconductor layer in a region where the guard ring is formed is lower than that of the active region. It is characterized by having a higher impurity concentration than the two semiconductor layers.

  In the present specification, the “predetermined surface region” is a region including the active region and a region near the active region (a region where the guard ring contacts the barrier metal layer). Further, in the present specification, the “active region” refers to a region in which a Schottky barrier is formed by the barrier metal layer and the second semiconductor layer, and substantially functions as a Schottky barrier diode.

[2] In the Schottky barrier diode of the present invention, it is preferable that an impurity concentration of the second semiconductor layer in a region where the guard ring is formed is lower than an impurity concentration of the first semiconductor layer.

[3] In the Schottky barrier diode of the present invention, the impurity concentration of the second semiconductor layer in a region where the guard ring is formed is in a range of 7 × 10 ¹⁴ cm ^{−3 to} 7 × 10 ¹⁶ cm ⁻³ . It is preferably within.

[4] In the Schottky barrier diode of the present invention, it is preferable that an impurity concentration of the second semiconductor layer in a region around the guard ring is higher than an impurity concentration of the second semiconductor layer in the active region.

[5] In the Schottky barrier diode according to the present invention, the impurity concentration of the second semiconductor layer in a region on the outer peripheral side of the region where the guard ring is formed may be higher than the impurity concentration of the second semiconductor layer in the active region. Preferably, it is higher than the concentration.

[6] In the Schottky barrier diode of the present invention, in the second semiconductor layer in a region where the guard ring is formed, the entire second region of the guard ring has a depth region deeper than a deepest position of the guard ring. It is preferable that the impurity concentration is higher than the impurity concentration of the second semiconductor layer in the active region.

[7] In the Schottky barrier diode of the present invention, in the second semiconductor layer in a region where the guard ring is formed, a part of a depth region deeper than a depth position of a deepest portion of the guard ring. It is preferable that only the active region has a higher impurity concentration than the second semiconductor layer in the active region.

[8] The Schottky barrier diode according to the present invention further includes an insulating layer formed on the second semiconductor layer so as to surround the active region. It is preferably included in the guard ring.

  According to the Schottky barrier diode of the present invention, since the impurity concentration of the second semiconductor layer in the region where the guard ring is formed is higher than the impurity concentration of the second semiconductor layer in the active region, when a reverse surge occurs. However, suppression of the extension of the depletion layer extending from the Schottky contact (the contact between the barrier metal layer and the second semiconductor layer) and the pn junction (the junction between the guard ring and the second semiconductor layer) toward the first semiconductor layer. Can be. Therefore, it becomes difficult for the depletion layer to reach the first semiconductor layer 110 (see FIG. 7A), and as a result, the reverse surge withstand capability can be increased as compared with the related art.

According to the Schottky barrier diode of the present invention, the impurity concentration of the second semiconductor layer in the region where the guard ring is formed is higher than the impurity concentration of the second semiconductor layer in the active region. for the purpose of increasing, it is not necessary to increase the thickness of the second semiconductor layer itself, sample 3 (example in Fig. 8 the forward voltage V _F is the absence of (to be described later higher than conventional) see .).

As a result, the Schottky barrier diode of the present invention, without increasing the forward voltage V _F, the conventionally can be increased reverse surge resistance even Schottky barrier diode.

FIG. 2 is a diagram shown for explaining the Schottky barrier diode 100 according to the first embodiment. FIG. 1A is a cross-sectional view of the Schottky barrier diode 100, and FIG. 1B is a plan view of the Schottky barrier diode 100. In FIG. 1B, the illustration of the insulating layer 150 is omitted for simplicity of description. FIG. 4 is an enlarged cross-sectional view of a main part for explaining the method of manufacturing the Schottky barrier diode according to the first embodiment. 2A to 2D are process diagrams. FIG. 4 is an enlarged cross-sectional view of a main part for explaining the method of manufacturing the Schottky barrier diode according to the first embodiment. FIGS. 3A to 3C are process diagrams. FIG. 7 is a cross-sectional view of a Schottky barrier diode 102 according to a second embodiment. FIG. 9 is a cross-sectional view of a Schottky barrier diode 104 according to a third embodiment. FIG. 9 is a cross-sectional view of a Schottky barrier diode 106 according to a fourth embodiment. FIG. 6 is a diagram for explaining the results of Test Example 1. FIG. 7A is a schematic diagram illustrating a simulation result when a reverse surge is applied to the Schottky barrier diode according to Sample 1 (Example), and FIG. 7B is a schematic diagram illustrating Sample 2 (Comparative Example). FIG. 6 is a schematic diagram for explaining a simulation result when a reverse surge is applied to the Schottky barrier diode according to (1). FIGS. 7A and 7B show a state where the same voltage is applied. In the Schottky barrier diode according to the sample 1 (Example) in FIG. However, the Schottky barrier diode according to Sample 2 (Comparative Example) in FIG. 7B is in a reach-through state. In FIG. 7, the illustration of the barrier metal layer and the back electrode is omitted for simplicity of description. 9 is a chart shown to explain the results of Test Example 2. FIG. 9 is a cross-sectional view of a conventional Schottky barrier diode 900. In FIG. 9, reference numeral 932 indicates a front electrode, reference numeral 950 indicates an insulating layer, and reference numeral 960 indicates a back electrode.

  Hereinafter, a semiconductor device and a method of manufacturing the semiconductor device according to the present invention will be described based on an embodiment shown in the drawings. Each drawing is a schematic diagram, and does not always strictly reflect actual dimensions.

[Embodiment 1]
1. 1. Configuration of Schottky Barrier Diode 100 According to First Embodiment As shown in FIG. 1, the Schottky barrier diode 100 according to the first embodiment is formed on an n ⁺ -type first semiconductor layer 110 and on the first semiconductor layer 110. An n ⁻ -type second semiconductor layer 120 having a lower impurity concentration than the first semiconductor layer 110, a barrier metal layer 130 formed in a predetermined surface region on the second semiconductor layer 120, A p ⁺ -type guard ring 140 formed on the surface of the second semiconductor layer 120 so as to cover an end of a portion of the metal layer 130 that is in contact with the surface of the second semiconductor layer 120; The semiconductor device includes an insulating layer 150 formed so as to surround the active region, and a back electrode 160 formed on the back surface of the first semiconductor layer 110. In the first embodiment, the first conductivity type impurity is an n-type impurity, and the second conductivity type impurity is a p-type impurity.

The impurity concentration of the second semiconductor layer 120 in the region where the guard ring 140 is formed is higher than the impurity concentration of the second semiconductor layer 120 in the active region and lower than the impurity concentration of the first semiconductor layer 110, for example, It is in the range of 7 × 10 ¹⁴ cm ^{−3 to} 7 × 10 ¹⁶ cm ⁻³ . (Hereinafter, in the second semiconductor layer 120 in the region where the guard ring 140 is formed, a region having an impurity concentration higher than the impurity concentration of the second semiconductor layer 120 in the active region is referred to as a “high concentration region”.)

  In the second semiconductor layer 120 in the region where the guard ring 140 is formed, the impurity concentration of the second semiconductor layer 120 in the active region in the entire depth region that is deeper than the deepest position of the guard ring 140 is higher. high.

The first semiconductor layer 110 has an n-type impurity concentration of, for example, about 5 × 10 ¹⁷ cm ^{−3 to} 5 × 10 ¹⁹ cm ⁻³ , and a thickness of the first semiconductor layer 110 in the active region of, for example, about 30 μm to 700 μm. Can be used. The material of the first semiconductor layer 110 is, for example, silicon.

The second semiconductor layer 120 preferably has an n-type impurity concentration of, for example, about 5 × 10 ¹⁴ cm ^{−3 to} 5 × 10 ¹⁶ cm ^{−3 and a} thickness in the active region of, for example, about 2 μm to 30 μm, for example, about 4 μm. Can be used. The second semiconductor layer 120 is formed by an epitaxial growth method.

The guard ring 140 has a depth of, for example, about 0.3 μm to 10 μm, for example, preferably 1 μm, and a p-type impurity concentration of, for example, about 1 × 10 ¹⁶ cm ⁻³ to 1 × 10 ¹⁸ cm ⁻³ . The guard ring 140 is formed in a ring shape on the surface of the second semiconductor layer 120 (see FIG. 1B).

  As the barrier metal layer 130, a barrier metal layer made of a metal (for example, titanium) that forms a Schottky contact with the second semiconductor layer 120 can be used. The thickness of the barrier metal layer 130 is, for example, 2000 nm. The barrier metal layer 130 forms an anode electrode.

  The insulating layer 150 is composed of, for example, a thermal oxide film and a PSG film. The inner peripheral end of the insulating layer 150 is included in the guard ring 140 when viewed in plan.

  As the back electrode 160, for example, a back electrode made of a laminated film in which titanium, nickel, and gold are laminated can be used. The back surface electrode 160 may be formed as it is on the back surface of the first semiconductor layer 110, or may be formed on the back surface of the first semiconductor layer 110 via a silicide layer (for example, a nickel silicide layer). The back electrode 160 constitutes a cathode electrode.

2. Method of Manufacturing Schottky Barrier Diode According to First Embodiment The Schottky barrier diode 100 according to the first embodiment can be manufactured by a manufacturing method having the following manufacturing steps.

(1) Semiconductor Substrate Preparation Step First, an n ⁺ -type first semiconductor layer 110 (n ⁺ -type semiconductor substrate) is prepared (see FIG. 2A).

(2) Step of Forming Second Semiconductor Layer and Guard Ring Next, an epitaxial layer 121 having a lower impurity concentration than the first semiconductor layer 110 is formed on the first semiconductor layer 110 by an epitaxial growth method (see FIG. 2B). .). Next, a mask M1 having an opening corresponding to the high-concentration region 122 (and the guard ring 140) is formed on the epitaxial layer 121, and an n-type impurity (for example, phosphorus) of the second semiconductor layer 120 is formed using the mask. Ions are implanted into a relatively deep region (for example, an intermediate portion of the thickness of the second semiconductor layer 120) (see FIG. 2C). Next, p-type impurities (for example, boron) are ion-implanted into a relatively deep region of the second semiconductor layer 120 using the mask (see FIG. 2D). Next, a second semiconductor layer 120 having a high concentration region 122 and a guard ring 140 are formed by thermally diffusing an n-type impurity and a p-type impurity (see FIG. 3A).

(3) Insulating Layer Forming Step Next, after removing the mask M1, a laminated film of a thermal oxide film and a PSG film is formed on the second semiconductor layer 120. Next, a mask (not illustrated) having an opening in a region other than the region where the insulating layer 150 is formed is formed over the stacked film, and the stacked film is etched using the mask. Thus, an insulating layer 150 is formed on the surface of the second semiconductor layer 120 so as to surround the active region (see FIG. 3B). At this time, the inner peripheral end of the insulating layer 150 is included in the guard ring 140 in plan view.

(4) Barrier Metal Layer Forming Step and Cathode Electrode Forming Step Next, a predetermined region on the second semiconductor layer 120 (a region surrounded by the insulating layer 150) and a partial region on the inner peripheral side of the insulating layer 150 are formed. While forming the barrier metal layer 130, the back surface electrode 160 is formed on the back surface of the first semiconductor layer 110 (see FIG. 3C).

  Thus, the Schottky barrier diode 100 according to the first embodiment can be manufactured.

3. Effect of Schottky Barrier Diode 100 According to First Embodiment According to the Schottky barrier diode 100 according to the first embodiment, the impurity concentration of the second semiconductor layer 120 in the region where the guard ring 140 is formed is the second concentration in the active region. Since the impurity concentration is higher than the impurity concentration of the semiconductor layer 120, a Schottky contact (a contact between the barrier metal layer 130 and the second semiconductor layer 120) and a pn junction (a guard ring 140 and the second semiconductor layer 120) when a reverse surge is applied. Of the depletion layer (hereinafter simply referred to as a depletion layer) extending from the junction with the first semiconductor layer 110 to the first semiconductor layer 110. Therefore, it becomes difficult for the depletion layer to reach the first semiconductor layer 110 (see FIG. 7A to be described later). As a result, the reverse surge withstand capability can be made higher than in the related art.

According to the Schottky barrier diode 100 according to the first embodiment, the impurity concentration of the second semiconductor layer 120 in the region where the guard ring 140 is formed is higher than the impurity concentration of the second semiconductor layer 120 in the active region. from the purpose of increasing the reverse surge resistance, in Figure 8 it is not necessary to increase the thickness of the second semiconductor layer 120 itself, the forward voltage V _F is the absence of (to be described later higher than conventional See Sample 3 (Example).)

As a result, the Schottky barrier diode 100 according to the first embodiment, without increasing the forward voltage V _F, the conventionally can be increased reverse surge resistance even Schottky barrier diode.

  In the Schottky barrier diode 100 according to the first embodiment, the impurity concentration of the second semiconductor layer 120 in the region where the guard ring 140 is formed is lower than the impurity concentration of the first semiconductor layer 110. Such a configuration is depleted when the impurity concentration of the second semiconductor layer 120 in the region where the guard ring 140 is formed is equal to or higher than the impurity concentration of the first semiconductor layer 110. Even if the layer does not reach the first semiconductor layer 110, the depletion layer only reaches the region (the high concentration region 122) where the impurity concentration of the second semiconductor layer 120 is high (electrically equivalent to the reach-through state). Therefore, it is difficult to increase the reverse surge resistance.

According to the Schottky barrier diode 100 according to the first embodiment, the impurity concentration of the second semiconductor layer 120 in the region where the guard ring 140 is formed (that is, the impurity concentration of the high concentration region 122) is 7 × 10 ^14. Since it is within the range of cm ^{−3 to} 7 × 10 ¹⁶ cm ⁻³ , the depletion layer is unlikely to reach the first semiconductor layer 110, the reverse surge withstand capability can be made higher than before, and the second semiconductor It can be prevented that the depletion layer merely reaches the region (the high concentration region 122) where the impurity concentration of the layer 120 is high and becomes electrically equivalent to the reach-through state. From such a viewpoint, the impurity concentration of the high concentration region 122 is preferably in the range of 1 × 10 ¹⁵ cm ⁻³ to 1 × 10 ¹⁶ cm ⁻³ .

  Further, according to the Schottky barrier diode 100 according to the first embodiment, in the second semiconductor layer 120 in the region where the guard ring 140 is formed, the depth region is deeper than the deepest position of the guard ring 140. Is higher than the impurity concentration of the second semiconductor layer 120 in the active region, the depletion layer is more difficult to extend when a reverse surge is applied, and the depletion layer is more difficult to reach the first semiconductor layer 110. As a result, the reverse surge withstand capability can be further increased as compared with the related art.

[Embodiment 2]
The Schottky barrier diode 102 according to the second embodiment has basically the same configuration as the Schottky barrier diode 100 according to the first embodiment, but the region where the high concentration region is formed in the second semiconductor layer is implemented. This is different from the case of the Schottky barrier diode 100 according to the first embodiment. That is, in the Schottky barrier diode 102 according to the second embodiment, as shown in FIG. 4, the impurity concentration of the second semiconductor layer 120 in the region around the guard ring 140 is changed to the impurity concentration of the second semiconductor layer 120 in the active region. It is higher than the concentration (that is, the high concentration region 122a is also formed around the guard ring 140).

  In the second embodiment, the high-concentration region 122a is formed in a region around the guard ring 140 in a plan view, and has a columnar shape (annular shape in plan view) in cross section.

As described above, the Schottky barrier diode 102 according to the second embodiment differs from the Schottky barrier diode 100 according to the first embodiment in the region where the high-concentration region is formed in the second semiconductor layer. As in the case of the Schottky barrier diode 100 according to No. 1, since the impurity concentration of the second semiconductor layer 120 in the region where the guard ring 140 is formed is higher than the impurity concentration of the second semiconductor layer 120 in the active region, forward voltage without increasing the V _F, the conventionally can be increased reverse surge resistance even Schottky barrier diode.

  Further, according to the Schottky barrier diode 102 according to the second embodiment, since the impurity concentration of the second semiconductor layer 120 around the guard ring 140 is higher than the impurity concentration of the second semiconductor layer 120 in the active region, a reverse surge is generated. When it enters, the depletion layer hardly extends around the guard ring 140, and the depletion layer hardly reaches the first semiconductor layer 110. As a result, the reverse surge withstand capability can be further increased as compared with the related art.

  Note that the Schottky barrier diode 102 according to the second embodiment has the same configuration as the Schottky barrier diode 100 according to the first embodiment except for a region where a high concentration region is formed in the second semiconductor layer. The second embodiment has a corresponding effect among the effects of the Schottky barrier diode 100 according to the first embodiment.

[Embodiment 3]
The Schottky barrier diode 104 according to the third embodiment has basically the same configuration as the Schottky barrier diode 100 according to the first embodiment, except that the region where the high concentration region is formed in the second semiconductor layer is implemented. This is different from the case of the Schottky barrier diode 100 according to the first embodiment. That is, in the Schottky barrier diode 104 according to the third embodiment, as shown in FIG. 5, the impurity concentration of the second semiconductor layer 120 in the region on the outer peripheral side of the region where the guard ring 140 is formed is lower than that in the active region. It is higher than the impurity concentration of the second semiconductor layer 120.

As described above, the Schottky barrier diode 104 according to the third embodiment differs from the Schottky barrier diode 100 according to the first embodiment in the region where the high-concentration region is formed in the second semiconductor layer. As in the case of the Schottky barrier diode 100 according to No. 1, since the impurity concentration of the second semiconductor layer 120 in the region where the guard ring 140 is formed is higher than the impurity concentration of the second semiconductor layer 120 in the active region, forward voltage without increasing the V _F, the conventionally can be increased reverse surge resistance even Schottky barrier diode.

  Further, according to the Schottky barrier diode 104 according to the third embodiment, the impurity concentration of the second semiconductor layer 120 in the region on the outer peripheral side of the region where the guard ring 140 is formed is lower than that in the active region. Since the impurity concentration is higher than the impurity concentration, the depletion layer hardly extends in a region on the outer peripheral side of the region where the guard ring 140 is formed, and the depletion layer hardly reaches the first semiconductor layer 110. As a result, the reverse surge withstand capability can be further increased as compared with the related art.

  Note that the Schottky barrier diode 104 according to the third embodiment has the same configuration as the Schottky barrier diode 100 according to the first embodiment in a configuration other than a region where a high concentration region is formed in the second semiconductor layer. The second embodiment has a corresponding effect among the effects of the Schottky barrier diode 100 according to the first embodiment.

[Embodiment 4]
The Schottky barrier diode 106 according to the fourth embodiment has basically the same configuration as the Schottky barrier diode 100 according to the first embodiment, but the region where the high concentration region is formed in the second semiconductor layer is implemented. This is different from the case of the Schottky barrier diode 100 according to the first embodiment. That is, in the Schottky barrier diode 106 according to the fourth embodiment, as shown in FIG. 6, in the second semiconductor layer 120 in the region where the guard ring 140 is formed, the depth position of the deepest part of the guard ring 140 Only a part of the deeper region has a higher impurity concentration than the second semiconductor layer 120 in the active region.

  In the fourth embodiment, the deepest part of the guard ring 140 and the high concentration region 122c are separated from each other.

  As described above, the Schottky barrier diode 106 according to the fourth embodiment differs from the Schottky barrier diode 100 according to the first embodiment in the region where the high-concentration region is formed in the second semiconductor layer. As in the case of the Schottky barrier diode 100 according to No. 1, since the impurity concentration of the second semiconductor layer 120 in the region where the guard ring 140 is formed is higher than the impurity concentration of the second semiconductor layer 120 in the active region, Even when a reverse surge is applied, the expansion of the depletion layer extending from the Schottky contact and the pn junction toward the first semiconductor layer 110 can be suppressed. Therefore, the depletion layer hardly reaches the first semiconductor layer 110, and as a result, the reverse surge withstand capability can be increased as compared with the related art.

  Further, according to the Schottky barrier diode 106 according to the fourth embodiment, in the second semiconductor layer 120 in the region where the guard ring 140 is formed, the depth region is deeper than the deepest position of the guard ring 140. Is higher than the impurity concentration of the second semiconductor layer 120 in the active region, the high concentration region does not need to be formed in the entire depth region deeper than the deepest position of the guard ring 140. Since the depletion layer does not easily extend and the depletion layer does not easily reach the first semiconductor layer 110, even in this case, the reverse surge withstand capability can be higher than in the related art.

  Note that the Schottky barrier diode 106 according to the fourth embodiment has the same configuration as the Schottky barrier diode 100 according to the first embodiment in a configuration other than a region where a high concentration region is formed in the second semiconductor layer. The second embodiment has a corresponding effect among the effects of the Schottky barrier diode 100 according to the first embodiment.

[Test example]
<Test Example 1>
Test Example 1 is a test example to show that the Schottky barrier diode of the present invention is a Schottky barrier diode having a higher reverse surge withstand capability than a conventional Schottky barrier diode.

1. Explanation of each sample (1) Sample 1 (Example)
A Schottky barrier diode basically having the same configuration as the Schottky barrier diode 100 according to the first embodiment was used as Sample 1. However, the impurity concentration of the second semiconductor layer 120 (high-concentration region 122) in the region where the guard ring 140 is formed is set to 1.5 times the impurity concentration of the second semiconductor layer 120 in the active region, and the guard ring The width of 140 was 20 μm, and the depth of guard ring 140 was 1 μm.

(2) Sample 2 (Comparative example)
A sample 2 was a Schottky barrier diode having the same configuration as that of the sample 1 except that the high-concentration region 122 was not formed.

2. Test Method In each sample, when a negative potential (for example, 60 V) is applied to the barrier metal layer 130, a Schottky contact (contact between the barrier metal layer 130 and the second semiconductor layer 120) and a pn junction (with the guard ring 140) The state of the depletion layer extending from the junction with the second semiconductor layer 120 to the first semiconductor layer 110 was simulated, and it was determined whether or not the depletion layer reached the first semiconductor layer 110 as illustrated. .

3. Test Results As can be seen from FIG. 7, in sample 2 (comparative example), when a reverse surge is applied, a depletion layer extends from the Schottky contact and the pn junction toward the first semiconductor layer 110, and the first semiconductor layer 110 , That is, a reach-through state (see FIG. 7B). On the other hand, in the sample 1 (Example), even when a reverse surge is applied, even if the depletion layer extends from the Schottky contact and the pn junction toward the first semiconductor layer 110, the depletion layer remains in the first state. It was found that the state did not reach the semiconductor layer 110, that is, the reach-through state (see FIG. 7A). From this, it was found that the Schottky barrier diode of the present invention is a Schottky barrier diode having higher reverse surge withstand capability than the conventional Schottky barrier diode.

<Test Example 2>
Test Example 2, the Schottky barrier diode of the present invention, high reverse surge resistance, high electrostatic breakdown resistance, and, in the test example to show that the forward voltage V _F is lower Schottky barrier diode is there.

1. Explanation of each sample (1) Sample 3 (Example)
Basically, a Schottky barrier diode having the same configuration as the Schottky barrier diode 100 according to the first embodiment was manufactured, and this was used as Sample 3. However, the impurity concentration of the second semiconductor layer 120 (high-concentration region 122) in the region where the guard ring 140 is formed is set to 1.15 times the impurity concentration of the second semiconductor layer 120 in the active region, and the guard ring The width of 140 was 20 μm, and the depth of guard ring 140 was 1 μm.

(2) Sample 4 (Comparative Example 1)
A Schottky barrier diode having the same configuration as that of the Schottky barrier diode according to Sample 3 except that the high-concentration region 122 was not formed was manufactured, and this was used as Sample 4.

(3) Sample 5 (Comparative Example 2)
Except that the high-concentration region 122 is not formed and that the thickness of the second semiconductor layer is 1.15 times the thickness of the second semiconductor layer of the sample 3, the configuration is the same as that of the Schottky barrier diode according to the sample 3. A Schottky barrier diode having the same configuration was manufactured, and this was used as Sample 5.

2. Test Method Each sample, reverse surge resistance, electrostatic breakdown resistance and forward voltage V _F was measured.
(1) Reverse surge withstand capability A current having a pulse width of 10 μsec was applied to each of the samples (samples 3 to 5) so that the power was in increments of 100 W, and the applied power immediately before the breakdown was evaluated as the reverse surge withstand. When the reverse surge withstand capability was 1000 W or more, a rating of “○” was given, and when the reverse surge withstand capability was less than 1000 W, a rating of “x” was given.
(2) Electrostatic breakdown resistance After charging a capacitor of 200 pF with a power supply capable of applying from 50 V to 200 V in increments of 50 V, the capacitors used to charge each sample (samples 3 to 5) three times each in the forward and reverse directions. The discharge was performed, and the power supply voltage at the time when the sample was broken was evaluated as the electrostatic breakdown strength. A rating of “耐” was given when the electrostatic breakdown strength was 1500 V or more, and a rating of “x” was given when the electrostatic breakdown strength was less than 1500 V.
(3) the forward voltage _{V F}
The voltage when a forward current was 2A applied to each sample (Sample 3-5) was evaluated as a forward voltage V _F. If the forward voltage V _F is less than 700mV a score of "○", the forward voltage V _F is a score of "×" when greater than 700mV.
(4) Comprehensive evaluation described above, a score of "○" when the reverse surge resistance, all evaluation of the electrostatic breakdown resistance and forward voltage V _F is "○", even one "× among the evaluation Was given a rating of "x".

3. Test Results As can be seen from FIG. 8, all of the Schottky barrier diodes according to Samples 4 and 5 (Comparative Example) were evaluated as “×” in any of the evaluation items, and an overall evaluation of “×” was obtained. Was done. That is, the Schottky barrier diode according to Sample 4 (Comparative Example 1) was evaluated as “×” in the items of the reverse surge withstand capability and the electrostatic breakdown withstand capability, and the Schottky barrier diode according to Sample 5 (Comparative Example 2) was in order. for an item of direction voltage V _F there is an evaluation of "×", the overall evaluation was obtained of each "×".

On the other hand, for the Schottky barrier diode according to Sample 3 (Example), the evaluation of “○” was obtained for all evaluation items, and the comprehensive evaluation of “○” was obtained. As a result, the Schottky barrier diode of the present invention, high reverse surge resistance, high electrostatic breakdown resistance, and it was found that the forward voltage V _F is lower Schottky barrier diode.

  As described above, the present invention has been described based on the above embodiments, but the present invention is not limited to the above embodiments. The present invention can be implemented in various modes without departing from the spirit thereof. For example, the following modifications are also possible.

(1) The number, material, shape, position, size, and the like of the components described in the above embodiment are mere examples, and can be changed without impairing the effects of the present invention.

(2) In each of the above embodiments, the material of the first semiconductor layer and the second semiconductor layer is silicon, but the present invention is not limited to this. The material of the first semiconductor layer and the second semiconductor layer may be silicon carbide, gallium nitride, or another appropriate material.

(3) In the above embodiments, the material of the barrier metal layer is titanium, but the present invention is not limited to this. The material of the barrier metal layer may be titanium nitride, molybdenum, palladium, platinum, aluminum-silicon, or any other suitable material.

(4) In each of the above embodiments, the barrier metal layer 130 was used as the anode electrode as it was, but the present invention is not limited to this. A surface electrode for connecting to the outside may be formed on the barrier metal layer 130, and the barrier metal layer 130 and the surface electrode may be used as an anode electrode. In this case, as a material of the surface electrode, for example, a laminated film of titanium and aluminum, a nickel film, or the like can be used.

(5) In the above embodiment, the high concentration region was formed by the ion implantation method, but the present invention is not limited to this. A high concentration region may be formed by an epitaxial growth method.

(6) In the above embodiment, the guard ring 140 is formed by the ion implantation method, but the present invention is not limited to this. The guard ring 140 may be formed by an epitaxial growth method.

  100, 102, 104, 106, 900: Schottky barrier diode, 110, 910: first semiconductor layer, 120, 920: second semiconductor layer, 121: epitaxial layer, 122, 122a, 122b, 122c: high concentration region, 130, 930: barrier metal layer, 140, 940: guard ring, 150, 950: insulating layer, 160, 960: back electrode (cathode electrode), M1: mask

Claims (6)

A first semiconductor layer of a first conductivity type;
A second semiconductor layer of a first conductivity type formed on the first semiconductor layer and having a lower impurity concentration than the first semiconductor layer;
A barrier metal layer formed in a predetermined surface area on the second semiconductor layer;
A second conductive type guard ring formed on the surface of the second semiconductor layer so as to include an end of a portion of the barrier metal layer in contact with the surface of the second semiconductor layer when viewed in a plan view. ,
In the second semiconductor layer in the region where the guard ring is formed, a high concentration region having an impurity concentration higher than the impurity concentration of the second semiconductor layer in the active region is formed.
The high concentration region is formed in a region including at least a region where the guard ring is formed in a plan view,
In the second semiconductor layer in the area where the guard ring is formed, the impurity concentration of the second semiconductor layer in the active area is reduced in the entire depth region deeper than the deepest position of the guard ring. Wherein the high concentration region having a high impurity concentration is formed. A first semiconductor layer of a first conductivity type;
A second semiconductor layer of a first conductivity type formed on the first semiconductor layer and having a lower impurity concentration than the first semiconductor layer;
A barrier metal layer formed in a predetermined surface area on the second semiconductor layer;
A second conductive type guard ring formed on the surface of the second semiconductor layer so as to include an end of a portion of the barrier metal layer in contact with the surface of the second semiconductor layer when viewed in a plan view. ,
In the second semiconductor layer in the region where the guard ring is formed, a high concentration region having an impurity concentration higher than the impurity concentration of the second semiconductor layer in the active region is formed.
The high concentration region is formed in a region including at least a region where the guard ring is formed in a plan view,
In the second semiconductor layer in a region where the guard ring is formed, only a part of a depth region deeper than a depth position of a deepest portion of the guard ring has an impurity of the second semiconductor layer in the active region. A Schottky barrier diode, wherein the high concentration region having an impurity concentration higher than the concentration is formed.   The Schottky barrier diode according to claim 1, wherein an impurity concentration of the high concentration region is lower than an impurity concentration of the first semiconductor layer. 4. The Schottky barrier diode according to claim 1, wherein an impurity concentration of the high-concentration region is in a range of 7 × 10 ¹⁴ cm ^{−3 to} 7 × 10 ¹⁶ cm ⁻³ . The impurity concentration of the second semiconductor layer in the outer peripheral side region than the region where the guard ring is formed, in claim 1, wherein the higher than the impurity concentration of the second semiconductor layer in the active region Schottky barrier diode as described. An insulating layer formed on the second semiconductor layer so as to surround the active region;
The Schottky barrier diode according to any one of claims 1 to 5, wherein an inner peripheral end of the insulating layer is included in the guard ring when viewed in a plan view.

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