JPH09260687A - Large-capacity low-loss high-speed diode having high-breakdown-voltage structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress influence to a main diode section, by setting a range for forming a cathode region on a semiconductor wafer in the vicinity of a first major surface under a specific condition, narrower than that for forming an anode region on the semiconductor wafer in the vicinity of a second major surface, and making the dimension of the spacing equal to or larger than the length of diffusion of electrons. SOLUTION: A Schottky junction 10 is formed in the cathode-side isolation band part (SAK) of a first principal surface. A buried isolation band part 14 composed of a p<+> buried layer is formed in the anode-side isolation band part (SAA) of a second principal surface. Besides, an insulating film 9 is formed on the anode-side isolation band part (SAA) of the second principal surface and a bevel part p<-> layer 5. A parasitic diode formed in the bevel part (EDGE) has a p<-> (5)n(23)p<-> (6)n<-> (4)n<+> (7) junction structure, but it becomes possible to suppress the influence on a main diode section (DIODE) by interposing a film 9 and making the relation of the dimensions of isolation of the anode-side and cathode-side isolation band parts (SAA, SAK) a+b>b (a, b are equal to or larger than the length of diffusion of electrons).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of diodes as power semiconductor devices, especially as two-terminal elements,
Particularly in a diode that utilizes the electrostatic induction effect, the current density at the wafer edge is reduced to suppress element destruction at the wafer edge, and element destruction at the time of reverse recovery is suppressed.
The present invention relates to a large-capacity low-loss high-speed diode having a high breakdown voltage structure that allows the performance of the main diode section to be sufficiently brought out.

[0002]

2. Description of the Related Art Regarding an electrostatic induction diode in which a structure utilizing an electrostatic induction effect is set on the anode side, the cathode side, or both sides, "Pn-junction diode" by Inada, Nishizawa, Tamamushi, JP-A-1-91475. It is disclosed in the official gazette.

Further, the lifetime distribution of carriers is provided in the high resistance layer, and the lifetime is set to be long in the vicinity of the anode region and the cathode region so that the electrostatic induction effect is remarkably exerted, and the distance from the anode region and the cathode region increases. It has a feature that the lifetime is gradually set shorter, and a planar structure utilizing the electrostatic induction effect is set in one or both of the anode region and the cathode region, and the structure is relatively simple, high speed and low loss. A static induction diode having a planar structure capable of achieving high performance and high breakdown voltage is disclosed in "Static induction diode having a planar structure" in Japanese Patent Laid-Open No. 6-29558 by Tamamushi and Muraoka.

Further, the lifetime distribution of carriers is provided in the high resistance layer, and the lifetime is set to be long in the vicinity of the anode region and the cathode region so that the electrostatic induction effect is remarkably exerted, and the distance from the anode region and the cathode region increases. It has the characteristic that the lifetime is gradually set to a U-shape or a V-shape, and an embedding structure or a notch structure using the electrostatic induction effect is set in one or both of the anode region and the cathode region. As for the electrostatic induction diode having a buried structure or a notch structure that can easily achieve a large capacity (large current, high withstand voltage) due to its structure, and can achieve high speed and low loss, "Built-in structure or notch structure" And an electrostatic induction diode having the above "are disclosed in Japanese Patent Laid-Open No. 6-337335.

Further, it has a structure utilizing a similar electrostatic induction effect, has a fast reverse recovery characteristic while suppressing the lifetime control of minority carriers as much as possible, and has a good reverse current with suppressed generation of leakage current. Regarding the high breakdown voltage diode having the voltage characteristic, the planar structure is disclosed by Yura in "High speed diode" Japanese Patent Application No. 7-53237, and the buried structure is disclosed by Nishizawa, Yura in "Diode" Japanese Patent Application No. 7-245201. ing.

10 to 12 are schematic sectional structural views of a conventional diode, FIG. 10 is a planar pin diode, FIG. 11 is an SI diode having a planar structure, and FIG. 12 is an SI diode having a buried structure. . FIG.
Regarding the structure of No. 2, especially the above-mentioned Japanese Patent Application No. 7-245201.
As disclosed in the issue. In FIG. 10 to FIG. 12, the same reference numerals are used for the same regions in the structure of each part. That is, in FIGS. 10 to 12, 1 is a surface p emitter layer, 2 is a buried p emitter layer, 3 is an n emitter layer, 4 is a high resistance semiconductor substrate, n ⁻ base layer, 11 is an anode electrode, 12 Is a cathode electrode, and 23 is an n epitaxial layer.

10 and 11, the thickness of the semiconductor region (3, 4, 1) between the cathode electrode 12 and the anode electrode 11 is l ₁ , but in the structure of FIG. 12, the buried p emitter layer 2 and the surface p are formed. The semiconductor regions (3, 4, 2, 23, 3) corresponding to the thickness of the n epitaxial layer 23 interposed between the emitter layers 1 are formed.
The thickness l ₂ of 1) is formed thick. 10 to 1
1 shows a schematic structure, but the structure having the buried p-emitter layer 2 shown in FIG. 12 shows a structure in which it is easier to achieve a higher breakdown voltage than the planar structure shown in FIG. .

However, the present inventor has proposed a conventional bevel structure in order to increase the capacity and the withstand voltage of an SI diode having a planar structure or an embedded structure utilizing the electrostatic induction effect on one or both of the anode side and the cathode side. Alternatively, it has been found that the structure in which the conventional field limiting structure is simply combined with the SI diode structure is likely to cause element breakdown at the wafer edge.

The problem in realizing the high breakdown voltage structure will be described below by taking the SI diode having the buried structure shown in FIG. 12 as an example. FIG. 13 is an example in which an SI diode having a buried structure is formed as a main diode portion and a high breakdown voltage is achieved by a positive bevel structure for a p-emitter at a wafer edge. That is, the bevel buried p ⁺ layer 6, the n epitaxial layer 23, the bevel portion p ⁺ layer 5 are formed by the simultaneous process with the SI emitter structure consisting of the buried p emitter layer 2 and the surface emitter layer 1, and the n emitter layer 3 is formed. to form an n ⁺ guard layer 7 in the wafer edge portion of the side, p ⁺ (5,6) by relatively thick diffusion layer in the vicinity of the bevel edge 8 n - ⁽⁴⁾ forming the n ⁺ (7) diode structures In this structure, the bevel end surface 8 is stabilized and the breakdown voltage is increased.

In FIG. 13, 1 is a surface p emitter layer,
2 is a buried p emitter layer, 3 is an n emitter layer, 4 is a high resistance semiconductor substrate, and n ⁻ base layer, 5 is a bevel portion p ⁺
Layer, 6 is a p ⁺ layer embedded in the bevel portion, 7 is an n ⁺ guard layer, 8
Is a bevel end surface, 11 is an anode electrode, 12 is a cathode electrode, 13 is an end protection resin, and 23 is an n epitaxial layer.

Particularly in the case of having a bevel structure, in order to reduce the electric field concentration on the p ⁺ (1,2) n (23) n ⁻ (4) junction of the main SI diode part, the bevel part p ⁺ layer 5 and the bevel part The partial buried p ⁺ layer 6 needs to be a layer having a gentle concentration gradient, a relatively thick thickness, and a flat surface. The n ⁺ guard layer 7 also needs to be a layer having a gentle concentration gradient and a relatively thick and flat layer.

However, due to the reverse recovery characteristics, the diode structure having a flat junction has a large amount of reverse recovery charge, a high reverse recovery peak current, a long reverse recovery time, and consequently a large reverse recovery loss. is there. That is, comparing the SI diode structure capable of absorbing minority carriers due to the electrostatic induction effect from the main electrode and the diode structure having a general planar type, the SI diode structure is compared in the same forward voltage drop. Even so, the amount of reverse recovery charge is small, which is soft recovery. Therefore, when the bevel structure is simply formed at the end of the semiconductor wafer of the SI diode as shown in FIG. 13, it is equivalent to the SI diode and a diode having a general planar junction being connected in parallel.

The present inventor prototyped a diode having the structure shown in FIG. 13 and conducted a reverse recovery switching operation test.
When the relationship between the reverse recovery energy loss Err (mJ / pulse) and the forward voltage drop V _F (V) is obtained, as shown in the relationship between the (O) curve and the (C1) curve in FIG. It was found that no improvement was made.

Here, FIG. 9 shows the forward current I _T = 100.
A, the voltage between the anode and the cathode V _D = 1500 V, and the junction temperature T _j = 125 ° C., the forward voltage drop V _F (V) and the reverse recovery energy loss Err (when the lifetime is changed by the lifetime control). mJ /
Pulse). The curve indicated by (O) corresponds to a general plane-junction diode structure, and (C
The curve indicated by 1) corresponds to the parallel structure in FIG.

Further, the present inventor has found that the structure of FIG. 13 not only does not improve the reverse recovery energy loss Err but also easily causes device breakdown. In particular, in the destroyed element, thermal destruction due to current concentration at the edge of the semiconductor wafer was often seen.

The forward conduction current density is high and the forward voltage drop is lower than that of the SI diode portion in the edge portion of the semiconductor wafer, particularly in the region where the substantially planar junction type diode is formed, but the anode electrode 11 at the time of reverse recovery. , Cathode electrode 12
Since the amount of minority carriers absorbed in the n ^- high resistance semiconductor substrate is smaller than that in the SI diode portion, the minority carriers are more likely to remain in the n ⁻ high resistance semiconductor substrate. Therefore, at the edge of the semiconductor wafer where the characteristics of the planar junction diode are likely to be effective, the accumulation time during reverse recovery is long, the amount of reverse recovery charge is large, the reverse recovery current is high, and the reverse recovery energy loss is consequently high. It tends to increase. Therefore, even if an SI diode, which is expected to have high performance reverse recovery characteristics, is formed in the main thyristor,
It has become clear that the conventional diode on the edge of the semiconductor wafer is easily affected and the improvement in the trade-off cannot be expected for the overall performance. Further, since there is a large amount of reverse recovery energy loss at the edge of the semiconductor wafer, when high-speed and large-capacity switching is performed, device breakdown due to application of high dv / dt during reverse recovery is concentrated at the edge of the semiconductor wafer. was there.

In the high breakdown voltage structure using such a bevel structure, a structure of the bevel portion which does not cancel the performance of the SI diode of the main thyristor is desirable. A structure in which the performance of the planar junction type diode in the bevel portion is suppressed as much as possible and the performance of the diode in the bevel portion does not substantially affect the performance of the SI diode in the main diode portion is desirable.

On the other hand, a field limiting ring (FLR) structure has been conventionally used as a structure for increasing the breakdown voltage of a power semiconductor device. Even in the SI diode using such a field limiting ring structure, it is desirable to introduce an end structure and a separation band structure that do not cancel the performance of the main diode part.

[0019]

SUMMARY OF THE INVENTION It is an object of the present invention to fully utilize the large capacity, low loss and high speed switching performance of a SI diode utilizing the electrostatic induction effect in one or both of the anode side and cathode side structures. An object of the present invention is to provide a large-capacity low-loss high-speed diode having a high breakdown voltage structure characterized in that the influence of the wafer edge is suppressed as much as possible.

[0020]

In order to achieve the above-mentioned object of the present invention, the present invention employs the following configurations. That is, the present invention provides a cathode region formed in the vicinity of the first main surface of a semiconductor wafer made of a high resistance semiconductor substrate having a first main surface and a second main surface, and the second region.
In a diode including an anode region formed in the vicinity of the main surface, a cathode electrode in contact with the cathode region, and an anode electrode in contact with the anode region, in one or both of the cathode region and the anode region. The structure using the electrostatic induction effect is set, the distance between the end of the semiconductor wafer and the end of the cathode region is a + b, and the distance between the end of the semiconductor wafer and the end of the anode region is b. And a + b
> B, the formation range of the cathode region in the vicinity of the first main surface on the semiconductor wafer is compared with the formation range of the anode region in the vicinity of the second main surface on the semiconductor wafer. It has a structure as a large capacity low loss high speed diode having a high breakdown voltage structure characterized in that the dimensions a and b are set to be narrower than the diffusion length of electrons.

Alternatively, the structure utilizing the electrostatic induction effect may be a planar structure, a buried structure, a cut structure, or a combination thereof, as a large capacity low loss high speed diode having a high breakdown voltage structure. It has the configuration of.

Alternatively, the end portion of the semiconductor wafer has a structure as a large capacity low loss high speed diode having a high breakdown voltage structure characterized by having a bevel structure.

Alternatively, the end portion of the semiconductor wafer has a structure as a large capacity low loss high speed diode having a high breakdown voltage structure characterized by having a field limiting ring structure.

Alternatively, the anode region formed in the vicinity of the second main surface is composed of a surface p emitter layer having a planar structure and a buried p emitter layer having a buried structure. A large capacity and low capacitance structure having a high breakdown voltage structure, characterized in that the cathode region is provided with an emitter structure, and the cathode region formed near the first main surface is provided with an n emitter layer having a planar structure utilizing an electrostatic induction effect. It has a structure as a lossy high speed diode.

Alternatively, a diode portion formed at the center of a semiconductor wafer made of a high resistance semiconductor substrate having the first main surface and the second main surface and a bevel formed at the end of the semiconductor wafer. A cathode region formed in the vicinity of the first main surface of the diode portion, and a separation band portion formed between the diode portion and the bevel portion. Two
An anode region formed in the vicinity of the main surface, a cathode electrode in contact with the cathode region, and an anode electrode in contact with the anode region, the anode region being a surface p emitter layer of a planar structure and a buried structure of a buried structure. p
Utilizing the electrostatic induction effect composed of the emitter layer and 2
An n ⁺ guard formed on the first main surface of the semiconductor wafer in the bevel portion has a stepped emitter structure, the cathode region has a planar n emitter layer utilizing an electrostatic induction effect. Layer, a bevel portion p ⁺ layer formed on the second main surface of the semiconductor wafer, and a bevel portion embedded p ⁺ layer formed adjacent to the bevel portion p ⁺ layer at the same time as the embedded p emitter layer. And an end portion protection resin that substantially protects the bevel end surface of the bevel portion, wherein the separation portion on the first main surface is the end portion of the n emitter layer. Has a distance a + b from the n ⁺ guard layer, and the cathode electrode has the width a +
a high resistance semiconductor substrate having b and the n ⁺ guard layer are extended and contacted to form a Schottky junction having a width a + b substantially equal to the width a + b of the separation band portion between the high resistance semiconductor substrate and the n ⁺ guard layer; The separation band portion near the second main surface is the distance b between the end of the surface p emitter layer and the bevel p ⁺ layer.
An insulating film is formed between the anode electrode and the separator band portion at a distance b on the second main surface and on the bevel portion p ⁺ layer, and the second main surface is further formed. The width of the separation band portion on the side of the first main surface is formed in the separation band portion near the surface and has a width of substantially the distance b and is formed simultaneously with the buried p emitter layer. In a + b and the width b of the separation band portion on the side of the second main surface, a + b> b is satisfied, and a and b are both large in withstand voltage structure and have a high breakdown voltage structure. It has a configuration as a low-capacity low-speed diode.

Alternatively, a p ⁺ stopper layer having a width b is further formed adjacent to the n ⁺ guard layer 7 in the separation band portion on the side of the first main surface to provide a high breakdown voltage structure. It has a structure as a large capacity low loss high speed diode.

Alternatively, a surface p emitter layer sandwiching an n ⁺ stopper layer is formed to extend in the separation band portion on the second main surface side, and the n ⁺ stopper layer and the surface p emitter layer are insulated. It has a structure as a large capacity low loss high speed diode having a high breakdown voltage structure characterized by being insulated from the anode electrode through a film 9.

Alternatively, in the vicinity of the first main surface,
It has a structure as a large capacity low loss high speed diode having a high breakdown voltage structure characterized in that an n buffer layer is further formed.

Alternatively, a high breakdown voltage structure is characterized in that a dug end portion having a width b is formed at a depth substantially equal to the n epitaxial layer in the separation zone portion on the second main surface side. It has a structure as a large capacity low loss high speed diode.

Alternatively, a diode portion formed in the central portion of a semiconductor wafer made of a high resistance semiconductor substrate having a first main surface and a second main surface, an end portion of the semiconductor wafer, and the diode portion. A diode having a separation band portion formed between the semiconductor wafer and an end portion of the semiconductor wafer, wherein a cathode region formed in the diode portion in the vicinity of the first main surface and the second main surface. An anode region formed in the vicinity, a cathode electrode in contact with the cathode region, and an anode electrode in contact with the anode region are provided, and the anode region is a surface p emitter layer having a planar structure utilizing an electrostatic induction effect. The cathode region has an n-type planar structure utilizing an electrostatic induction effect.
With an emitter layer, at the edge of the semiconductor wafer,
N ⁺ formed on the second main surface of the semiconductor wafer
A channel stop ring layer, wherein in the separator, the separator on the first major surface has a distance a + c between an end of the n-emitter layer and an end of the semiconductor wafer, The cathode electrode extends over and contacts the end of the semiconductor wafer on the high resistance semiconductor substrate having the width a + c, and is substantially equal to the width a + c of the separation band portion between the cathode electrode and the high resistance semiconductor substrate. A Schottky junction is formed, the separation band portion on the side of the second main surface has a distance c between the end of the surface p emitter layer and the end of the semiconductor wafer, and the separation band on the second main surface is formed. Separation strip at distance c and n
^{+ An} insulating film is formed on the channel stop ring layer,
Further, the distance c is substantially equal to the separation band portion on the second main surface side.
A plurality of field limiting ring layers are formed simultaneously with the buried p emitter layer and have a width a + c of the separation band portion on the side of the first main surface and a width of the second main surface on the side of the second main surface. In the width c of the separation band portion, a + c> c is satisfied, and a and c are both equal to or more than the diffusion length of electrons, and have a structure as a large capacity low loss high speed diode having a high breakdown voltage structure. .

Alternatively, in the vicinity of the first main surface,
It has a structure as a large capacity low loss high speed diode having a high breakdown voltage structure characterized in that an n buffer layer is further formed.

Alternatively, with respect to the plurality of field limiting layers and the n ⁺ channel stop ring layer, metal electrodes are brought into contact with each other through contact holes formed by patterning the insulating film, so that the breakdown voltage is increased. It has a structure as a large capacity low loss high speed diode having a structure.

[0033]

According to the present invention, the current density at the end of the semiconductor wafer can be set lower than that of the main diode in the present invention, so that the influence of the parasitic diode at the end of the semiconductor wafer can be suppressed. it can.

Further, by setting the distance between the semiconductor wafer edge and the n emitter layer 3 as a + b, and the distance between the semiconductor wafer edge and the surface p emitter layer 1 as b, the injected carriers at the edge of the semiconductor wafer are set. The operation does not substantially affect the main diode portion. Here, b is set to be equal to or larger than the diffusion length of electrons.

Particularly, by arranging the arrangement range of the n-emitter layer 3 narrower than the arrangement range of the surface p-emitter layer 1 by the dimension a in the center direction of the semiconductor wafer, electrons having a small effective mass cause the semiconductor substrate to move from the cathode to the cathode. The extra hole injection from the anode region due to the lateral diffusion during the traveling time traveling to the anode is suppressed, and the low loss and high-speed switching performance in the main diode section are guaranteed. Here, the dimension a is set to be equal to or larger than the diffusion length of electrons.

In terms of increasing the capacity, it is sufficient to form a channel structure which causes an electrostatic induction effect by a multi-channel structure on the anode side and the cathode side of the semiconductor wafer,
The structure is relatively simple and easily realized.

As described above, the diode of the present invention can bring out the large capacity, low loss, and high-speed switching performance of the main diode without being affected by the parasitic diode at the end of the semiconductor wafer in the structure for increasing the withstand voltage.

A bevel structure and a field limiting ring (FLR) structure can be used as the structure having a high breakdown voltage.

[0039]

【Example】

(Embodiment 1) FIG. 1 is a schematic sectional structural view of a large capacity low loss high speed diode having a high breakdown voltage structure as a first embodiment of the present invention.

In FIG. 1, 1 is a surface p emitter layer, 2
Is a buried p emitter layer, 3 is an n emitter layer, 4 is an n ⁻ base layer made of a high resistance semiconductor substrate, and 5 is a bevel portion p.
⁺ Layer, 6 is a p ⁺ layer embedded in the bevel portion, 7 is an n ⁺ guard layer,
Reference numeral 8 is a bevel end surface, 9 is an insulating film such as a SiO ₂ film, 10 is a Schottky junction portion, 11 is an anode electrode, 12 is a cathode electrode, 13 is an end protection resin, and 14 is a buried separation band portion. The structural features of the first embodiment will be described below.

FIG. 1 has a patterned n-emitter layer 3 on a first main surface of a semiconductor wafer composed of a high-resistance semiconductor substrate 4, and an n-epitaxial layer 2 near the second main surface.
3 has a two-stage emitter structure including a front surface p emitter layer 1 and a buried p emitter layer 2. In the main diode part, a cathode region having a planar structure utilizing the electrostatic induction effect is formed on the first main surface, and on the second main surface, a combination of a buried structure and a planar structure utilizing the electrostatic induction effect is formed. (2-stage SI emitter structure) is formed. The edge of the semiconductor wafer has a positive bevel structure. The bevel angle is about 60 ° to 70 °, and the bevel angle increases as the resistivity of the high resistance semiconductor substrate 4 increases.

A separation band portion is formed between the diode portion (DIODE) and the bevel portion (EDGE). In Example 1 of FIG. 1, the cathode side separation band portion (SA
At K), a Schottky junction 10 is formed. The reason for this is to suppress the effect of the parasitic diode in the separation band portion (SAK) on the cathode side and suppress the injection of extra electrons. Separator zone (SAA) on the anode side of the second main surface
As shown in FIG. 1, a buried separation band portion 14 made of a p ⁺ buried layer is formed in the. Further, S is formed on the anode side separation band (SAA) and the bevel p ⁺ layer 5 on the second main surface.
An insulating film 9 such as an iO ₂ film is formed and is not in direct contact with the anode electrode 11. The reason for this is to suppress the influence of the parasitic diode in the separation band portion (SAA) on the anode side and the bevel portion p ⁺ layer 5 and suppress the injection of extra holes.

In the first embodiment shown in FIG. 1, the bevel portion (EDGE) is used.
The parasitic diode formed in p ⁺ (5) n (23) p
^{+ (6) n - (4} ) n + (7) has a junction structure, S
The relationship between the interposition of the iO ₂ film 9 and the separation dimension in the anode-side and cathode-side separation bands (SAA, SAK): a + b> b (where a and b are equal to or greater than the diffusion length of electrons) The effect on (DIODE) was substantially suppressed. This structure is complicated at first glance, but it is a characteristic structure discovered for the first time by repeated trial manufacture of the SI diode by the present inventor.

The arrow in FIG. 1 schematically shows the current density j in the forward conduction, and the current density j is almost uniform in the central direction of the semiconductor wafer in which the main diode is formed. At the edge of the semiconductor wafer, the cathode side and anode side separation zones (SA
K, SAA), the current density is significantly reduced.

Next, a method of determining the separation dimensions a and b will be described. The dimensions a and b are both set to about the diffusion length of electrons or more. The dimension b is the lateral dimension of the semiconductor wafer between the end of the n ⁺ guard layer 7 and the end of the front surface p emitter layer 1, and corresponds to the width of the anode side separation band (SAA). . ^{p + (1,2) n - (} 4) n + (7)
In order to suppress the influence of the parasitic diode formed of the junction, the dimension b needs to be equal to or larger than the diffusion length of electrons. That is, n ⁺
This is because it is necessary to set the diffusion length of the electrons injected from the guard layer 7 to the extent of the diffusion length in the lateral direction during the traveling time to the anode side or more. The dimension a corresponds to the lateral dimension difference between the occupied area of the n emitter layer 3 and the occupied area of the surface p emitter layer 1 on the semiconductor wafer. That is, for example, when considered on a circular semiconductor wafer, it means that the formation region of the n emitter layer 3 is formed within a circular range narrower in the center direction than the formation region of the surface p emitter layer 1. . In SI diodes facing each other, the dimension a is equal to or larger than the diffusion length in which electrons diffuse laterally during the transit time of electrons between the cathode and anode.
Means to set. If the dimension a is set within the diffusion length of the electrons, the electrons are separated from the anode side separation band (SA
This is because it penetrates into A) and causes the injection of extra holes from the anode side, and is easily affected by the parasitic diode from the separation band portion.

Next, the buried separation band portion 14 which is characteristic of the structure of the separation band portion of FIG. 1 will be described. Embedded separation zone 14
Has a structure in which p ⁺ buried layers are coupled to each other by a depletion layer. ^{That, p + (14) n -} (4) or p
⁺ (14) The depletion layer spreading around the p ⁺ (14) region due to the contact potential difference of the n (23) junction is p ⁺ (1
4) are in contact with each other and are capacitively coupled to each other. Since the separation resistance value is capacitive coupling, it shows a very high value. Due to the structure of FIG. 1, it can be manufactured at the same time as the buried p-emitter layer 2. Although three p ⁺ (14) regions are shown in the example of FIG. 1, any number may be set as long as the dimension b is equal to or larger than the diffusion length of electrons. In essence, it is sufficient that the separator structure is capacitive rather than resistive.

(Embodiment 2) FIG. 2 is a schematic sectional structural view of a large capacity loss high speed diode having a high breakdown voltage structure as a second embodiment of the present invention. The structure of FIG. 2 is different from the structure of FIG.
K, SAA) have different structures. The main components are the same and are designated with the same reference numbers. The same applies to the method of determining the dimensions a and b.

In FIG. 2, the separator on the cathode side (SAK)
In the Schottky junction portion 10 of 1., the p ⁺ stopper layer 15 was formed by short-circuiting with the n ⁺ guard layer 7. by this,
It is possible to reliably separate the n ⁺ guard layer 7 and the n emitter layer 3 and absorb excess holes in the vicinity of the separation band portion (SAK). Furthermore, in the structure of FIG. 2, in the separation band portion (SAA) on the anode side, the surface separation band portion 25 and the n ⁺ stopper layer 16 are formed in accordance with the width of the embedded separation band portion 14.
Is provided. Since the surface separation band portion 25 has capacitive coupling coupled to each other by a depletion layer, the buried separation band portion 14 is
It has the same capacitive isolation resistance as. n ⁺ stopper layer 16
Is a region for absorbing electrons in the n-epitaxial layer near the anode side separation band part (SAA) and ensuring separation between the surface separation band parts 25.

(Embodiment 3) FIG. 3 is a schematic sectional structural view of a large capacity low loss high speed diode having a high breakdown voltage structure as a third embodiment of the present invention. The structure is similar to that of the first embodiment shown in FIG. 1, except that an n buffer layer 17 is formed on the cathode side and a pin structure is provided between the anode and the cathode. Further, the high resistance semiconductor substrate 4 can be made to have a higher resistance than that of FIG. 1 by providing the n buffer layer 17. Therefore, the third embodiment has a structure suitable for higher breakdown voltage as compared with the first embodiment. It is clear that the bevel angle also changes as the breakdown voltage increases. The dimensions of a and b are set similarly.

(Embodiment 4) FIG. 4 is a schematic sectional structural view of a large-capacity low-loss high-speed diode having a high breakdown voltage structure according to a fourth embodiment of the present invention. The same regions as those shown in FIGS. 1 to 3 are indicated by the same reference numerals. The structure of FIG. 4 is a modification of the structure of FIG. That is, it is characterized in that an etching groove having a band width of about b and a thickness of about the same as the n epitaxial layer 13 is formed in the anode side separation band portion (SAA) by using an etching technique such as mesa etching. Although the buried separation zone portion 14 is exposed on the anode side surface by the dug end portion 18,
It is the same in that the separator structure is formed by capacitive coupling.

The dug end 18 in FIG. 4 has the same role as the insulating film (SiO ₂ film) 9 shown in FIGS. 1 to 3. That is, the bevel edge of the semiconductor wafer (ED
It has a function of suppressing the hole injection from the GE) and the separation band portion (SAA) on the anode side. In FIG. 4, the bevel portion p ⁺ layer 5 is not particularly formed on the outer end portion on the anode side, and the metal electrode 19 is contacted to keep the potential constant.

(Embodiment 5) FIG. 5 is a schematic sectional structural view of a large capacity low loss high speed diode having a high breakdown voltage structure as a fifth embodiment of the present invention. The structure of FIG. 5 is an example having a field limiting ring (FLR) structure as the high breakdown voltage structure instead of the bevel structure. Although the breakdown voltage is lower than that of the bevel structure, the structure is relatively simple and easy to manufacture because the main diode portion is suitable for the planar structure.

In FIG. 5, 1 is a surface p emitter layer, 3
Is an n emitter layer, 4 is an n ⁻ base layer made of a high resistance semiconductor substrate, 20 is an n ⁺ channel stop ring layer, 24 is a p ⁺ field limiting ring layer, and 9 is SiO _2.
An insulating film such as a film, 10 is a Schottky junction, 11 is an anode electrode, and 12 is a cathode electrode. In FIG.
The distance from the end of the front surface p emitter layer 1 to the n ⁺ channel stop ring layer 20 is defined as the dimension c. The dimension c corresponds to the width of the field limiting ring (FLR) portion where the field limiting ring layer 24 is formed.

The field limiting ring layer 24 is formed in a plural ring shape. Dimensions of each part l ₁ , l ₂ , l
The values of ₃ , l _4, etc. can be determined by adopting a conventionally known setting method of the field limiting ring.

The characteristic structure in FIG. 5 is that the diode portion (DI) on the anode side is the same as in Embodiments 1 to 4 of FIGS.
The diode part (DI that is on the cathode side of ODE (A))
The point is that the occupied area width of ODE (K) is narrowed by a dimension a. You.

For the same reason as described above, the value of the dimension a is
Set it to the same level as the diffusion length of electrons or more. On the cathode side of the structure of Example 5 in FIG. 5, a Schottky junction 10 is further formed on the outer end having a width of a + c between the end of the n-emitter layer 3 and the end of the semiconductor wafer. Thus, the influence of the parasitic diode on the FLR portion and the outer end portion is suppressed.

In the FLR portion on the anode side in FIG. 5, p ⁺
An insulating film 9 such as a SiO ₂ film is formed on the surfaces of the field limiting ring layer 24, the n ⁺ channel stop ring layer 20, and the n ⁻ base layer 4. Insulating film 9
The contact with the anode electrode 11 is prevented by the FLR
The extra hole injection from the part is suppressed.

(Embodiment 6) FIG. 6 is a schematic sectional structural view of a large capacity low loss high speed diode having a high breakdown voltage structure as a sixth embodiment of the present invention.

The structural features of FIG. 6 are that the n buffer layer 17 is formed on the cathode side and a pin structure is introduced to further increase the breakdown voltage, and a plurality of p ⁺ field limiting ring layers 24 are provided. To form the metal electrodes 211, 212, and 213, respectively, to stabilize the electric potential of each field limiting ring layer 24, and to contact the n ⁺ channel stop ring layer 20 in the same manner. This is the point where the metal electrode 22 for forming the potential is formed.

The method of selecting the dimensions a and c is the same as in the fifth embodiment.

The configuration of the sixth embodiment is also the same as that of the main diode portion (DIO
DE) is suitable for a planar structure SI diode.

FIG. 7 is a schematic diagram of switching waveforms.
The switching waveform at the time of reverse recovery is shown, the solid line corresponds to the diode of the conventional planar structure, and the dotted line is an example of the diode of the embodiment of the present invention shown in FIG.

When the forward current I _T = 100 A and the anode-cathode voltage V _D = 1500 V are kept constant, the peak value I _RP of the reverse recovery current is compared, and compared with the value I _RP ^(S) of the first embodiment, The value I _RP ^(O) of the mold structure is doubled. Moreover, the present invention is soft recovery.

Similarly, I _T = 100 A, V _D = 1500
FIG. 8 shows a graph in which the change in the energy loss Err of voltage × current at the time of reverse recovery under the condition of V, T _j = 125 ° C. is calculated with respect to the time axis.

The energy loss Err ^(O) of the conventional structure is about twice as large as the energy loss Err ^(S) of the first embodiment of the present invention.

Energy loss Err and forward voltage drop V
_In FIG. 9 showing a group of _F trade-off curves, the curve (O) is the conventional structure, and the curve (C1) is the same as in FIG.
The curve (C2) corresponds to the structure of Example 1 (FIG. 1) of the present invention, and the curve (S) corresponds to the structure of Example 5 (FIG. 5) of the present invention.

FIG. 13 shows that the edge of the bevel is easily affected.
In the curve (C1) corresponding to the structure (1), the effect of improving the trade-off is small, but the buried structure (two-stage emitter structure) of the first embodiment (FIG. 1) of the present invention and the planar structure of the fifth embodiment (FIG. 5) of the present invention. Then, the trade-off relationship has been greatly improved.

[0068]

According to the large-capacity low-loss high-speed diode having the high breakdown voltage structure of the present invention, the high breakdown voltage structure is introduced, and the influence of the parasitic diode at the edge of the semiconductor wafer is suppressed to reduce the influence of the main diode portion. A diode that utilizes the electrostatic induction effect can be fully brought out, has excellent reverse recovery performance, has soft recovery, low loss, and high-speed switching performance. realizable.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional structure diagram of a large-capacity low-loss high-speed diode having a high breakdown voltage structure as a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional structure diagram of a large-capacity low-loss high-speed diode having a high breakdown voltage structure as a second embodiment of the present invention.

FIG. 3 is a schematic sectional structural view of a large capacity low loss high speed diode having a high breakdown voltage structure as a third embodiment of the present invention.

FIG. 4 is a schematic cross-sectional structure diagram of a large capacity low loss high speed diode having a high breakdown voltage structure as a fourth embodiment of the present invention.

FIG. 5 is a schematic cross-sectional structure diagram of a large capacity low loss high speed diode having a high breakdown voltage structure as a fifth embodiment of the present invention.

FIG. 6 is a schematic cross-sectional structure diagram of a large capacity low loss high speed diode having a high breakdown voltage structure as a sixth embodiment of the present invention.

FIG. 7 is a comparative example of switching waveforms during reverse recovery.

FIG. 8: Comparative example of reverse recovery energy loss

FIG. 9 is a comparative example of the relationship between reverse recovery energy loss and forward voltage drop.

FIG. 10 is a schematic cross-sectional structure diagram of a conventional pin diode having a planar structure.

FIG. 11 is a schematic sectional structural view of a conventional electrostatic induction emitter diode.

FIG. 12 is a schematic cross-sectional structure diagram of a conventional electrostatic induction emitter diode having a buried structure.

FIG. 13 is a schematic cross-sectional structure diagram of a diode manufactured by using a conventional bevel structure as a high breakdown voltage structure of a static induction emitter diode having a conventional buried structure (comparative example).

[Explanation of symbols]

1 surface p emitter layer 2 buried p emitter layer 3 n emitter layer 4 n ^- base layer (high resistance semiconductor substrate) 5 bevel part p ⁺ layer 6 bevel part buried p ⁺ layer 7 n ⁺ guard layer 8 bevel end face 9 SiO ₂ film (Insulating film) 10 Schottky junction part 11 Anode electrode 12 Cathode electrode 13 End protection resin 14 Embedded separation band part 15 p ⁺ Stopper layer 16 n ⁺ Stopper layer 17 n Buffer layer 18 Excavated end part 19, 22, 211, 212, 213 metal electrode 20 n ⁺ channel stop ring layer 23 n epitaxial layer 24 p ⁺ field limiting ring layer 25 surface separation band portion

Claims (13)

[Claims] 1. A cathode region formed in the vicinity of the first main surface of a semiconductor wafer made of a high resistance semiconductor substrate having a first main surface and a second main surface, and in the vicinity of the second main surface. In a diode including an formed anode region, a cathode electrode in contact with the cathode region, and an anode electrode in contact with the anode region, an electrostatic induction effect is provided in one or both of the cathode region and the anode region. A + b, where the distance between the edge of the semiconductor wafer and the edge of the cathode region is a + b and the distance between the edge of the semiconductor wafer and the edge of the anode region is b, > B, the formation range of the cathode region in the vicinity of the first main surface on the semiconductor wafer is defined by the second main table. A large capacity and low loss having a high breakdown voltage structure characterized in that the anode region in the vicinity is set narrower than the forming range on the semiconductor wafer, and the dimensions of a and b are equal to or larger than the diffusion length of electrons. Fast diode. 2. The large capacity and low capacity having a high breakdown voltage structure according to claim 1, wherein the structure utilizing the electrostatic induction effect is a planar structure, a buried structure, a cut structure or a combination of these structures. Loss fast diode. 3. The large-capacity low-loss high-speed diode having a high breakdown voltage structure according to claim 1, wherein an end portion of the semiconductor wafer has a bevel structure. 4. A large-capacity low-loss high-speed diode having a high breakdown voltage structure according to claim 1, wherein an edge of the semiconductor wafer has a field limiting ring structure. . 5. The two-stage emitter utilizing the electrostatic induction effect, wherein the anode region formed near the second main surface is composed of a surface p emitter layer having a planar structure and a buried p emitter layer having a buried structure. 3. The structure according to claim 1, wherein the cathode region formed in the vicinity of the first main surface comprises an n-emitter layer having a planar structure utilizing an electrostatic induction effect. A large-capacity low-loss high-speed diode having the high breakdown voltage structure according to item 1. 6. A diode portion formed in a central portion of a semiconductor wafer made of a high resistance semiconductor substrate having the first main surface and a second main surface, and a bevel portion formed at an end portion of the semiconductor wafer. And a separation band portion formed between the diode portion and the bevel portion, wherein the diode portion has a cathode region formed in the vicinity of the first main surface, and the second portion An anode region formed in the vicinity of the main surface of the cathode, a cathode electrode in contact with the cathode region, and an anode electrode in contact with the anode region, the anode region including a surface p emitter layer having a planar structure and a buried structure embedded therein. The cathode structure has a two-stage emitter structure using an electrostatic induction effect, and the cathode region has a planar structure using the electrostatic induction effect. Has the n emitter layer, in the bevel part, formed in said first major surface of the semiconductor wafer n ⁺
A guard layer, a bevel portion p ⁺ layer formed on the second main surface of the semiconductor wafer, and a bevel portion embedded p ⁺ formed adjacent to the bevel portion p ⁺ layer at the same time as the embedded p emitter layer. A layer and an edge protecting resin that substantially protects the beveled end surface of the bevel portion, wherein the separator on the first main surface is an edge of the n emitter layer. And a distance a + b between the n ⁺ guard layer and the high resistance semiconductor substrate having the width a + b and the cathode electrode extending to and contacting the n ⁺ guard layer to substantially contact the high resistance semiconductor. The width a of the separation band portion between the substrate and
A Schottky junction equal to + b is formed, the separation band portion near the second main surface has a distance b between the end of the surface p emitter layer and the beveled p ⁺ layer, and the second main surface Separator part of the distance b on the surface and the bevel part p
^An insulating film is formed on the ⁺ layer so as to be interposed between the anode electrode and the ⁺ layer, and further has a width of a distance b in the separation band portion in the vicinity of the second main surface. A buried separating band portion formed at the same time as the layer is formed, and a + b> b is established in the width a + b of the separating band portion on the first main surface side and the width b of the separating band portion on the second main surface side. In addition, a and b are large-capacity low-loss high-speed diodes having a high breakdown voltage structure, characterized in that both a and b are electron diffusion lengths or more. 7. The high-voltage isolation layer according to claim 6, further comprising a p ⁺ stopper layer having a width b, which is formed adjacent to the n ⁺ guard layer 7 in the separation band portion on the first main surface side. A large-capacity low-loss high-speed diode with a breakdown voltage structure. 8. The n ^{+ in} the separation band portion on the second main surface side.
The surface p emitter layer sandwiching the stopper layer is extended and formed,
The high breakdown voltage structure according to any one of claims 6 to 7, wherein the n ⁺ stopper layer and the surface p emitter layer are insulated from the anode electrode through an insulating film 9. Large-capacity low-loss high-speed diode having 9. A large capacity having a high breakdown voltage structure according to claim 6, further comprising an n buffer layer formed in the vicinity of the first main surface. Low loss high speed diode. 10. The height according to claim 6, wherein a dug end portion having a width b is formed in the separation zone portion on the second main surface side with a depth substantially equal to that of the n epitaxial layer. A large-capacity low-loss high-speed diode with a breakdown voltage structure. 11. A diode portion formed in a central portion of a semiconductor wafer made of a high resistance semiconductor substrate having a first main surface and a second main surface, and an end portion of the semiconductor wafer,
A diode having a separation band portion formed between the diode portion and an end portion of the semiconductor wafer, wherein the diode portion has a cathode region formed near the first main surface, and 2 has an anode region formed near the main surface, a cathode electrode in contact with the cathode region, and an anode electrode in contact with the anode region, the anode region having a planar structure surface utilizing an electrostatic induction effect. a p-emitter layer, the cathode region has an n-emitter layer having a planar structure utilizing an electrostatic induction effect, and is formed on the second main surface of the semiconductor wafer at an edge of the semiconductor wafer. n ⁺
A channel stop ring layer, wherein in the separation band portion, the separation band portion on the first main surface has a distance a + c between an end portion of the n emitter layer and an end portion of the semiconductor wafer, The cathode electrode extends over and contacts the end of the semiconductor wafer on the high resistance semiconductor substrate having the width a + c, and is substantially equal to the width a + c of the separation band portion between the cathode electrode and the high resistance semiconductor substrate. A Schottky junction is formed, the separation band portion on the side of the second main surface has a distance c between the end portion of the surface p emitter layer and the end portion of the semiconductor wafer, and is on the second main surface. An insulating film is formed on the separation band portion at the distance c and the n ⁺ channel stop ring layer, and the separation band portion on the second main surface side has a width of the distance c substantially, Multiple fields formed at the same time as the p-emitter layer A mitting ring layer is formed, and in the width a + c of the separation band portion on the first main surface side and the width c of the separation band portion on the second main surface side, a + c> c is satisfied and a and c are A large-capacity low-loss high-speed diode having a high breakdown voltage structure, which is characterized in that each has a diffusion length of electrons or more. 12. The large-capacity low-loss high-speed diode having a high breakdown voltage structure according to claim 11, wherein an n buffer layer is further formed near the first main surface. 13. The metal electrode is brought into contact with each of the plurality of field limiting layers and the n ⁺ channel stop ring layer through a contact hole formed by patterning the insulating film.
12. A large-capacity low-loss high-speed diode having the high breakdown voltage structure according to any one of items 1 to 12.