JP2003224282A - High voltage semiconductor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high voltage semiconductor element which improves reverse recovery characteristics. <P>SOLUTION: The semiconductor element is provided with a first conductivity first semiconductor layer, a second conductivity second semiconductor layer which is selectively formed on a first principal plane of the first semiconductor layer, a first conductivity third semiconductor layer which is formed on a second principal plane of the first semiconductor layer, a first electrode arranged on the second conductivity second semiconductor layer, and a second electrode arranged on the first conductivity third semiconductor layer. The second semiconductor layer comprises a plurality of first regions whose impurity concentration is comparatively high, and a plurality of second regions enclosing the first regions, whose impurity concentration is comparatively low. The first electrode is arranged so as to face the first regions, at least being connected thereto. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high breakdown voltage semiconductor device such as a high breakdown voltage diode, an IGBT and a thyristor.

[0002]

2. Description of the Related Art FIG. 9 shows a cross-sectional structure of a main part of a high breakdown voltage diode (first conventional high breakdown voltage diode), which is one of conventional high breakdown voltage elements, and an impurity concentration distribution and an ON state in the element. The carrier concentration distribution is shown.

An anode electrode 4 is formed on one surface of a high resistance N ^- type base layer 1 made of N ^- type silicon via a P ⁺ type anode layer 2 and an N ⁺ type cathode layer on the other side. Cathode electrode 5 is formed via 3.

In the case of a high withstand voltage diode with a blocking voltage of 4500 V, the impurity concentration and size of each part are such that the impurity concentration of the N ^-- type base layer 1 is 1.0 × 10 ^{13 to} 1.8 × 10 ¹³ /.
cm ³ , thickness 450 to 900 μm, P ⁺ type anode layer 2
And N ⁺ type cathode layer 3 has a surface concentration of 1 × 10 ¹⁹ / cm
³ , the thickness is set to 14 to 70 μm.

In such a high breakdown voltage diode,
An on-voltage of about 2.6 V can be obtained with a current of about 100 A / cm ² . High withstand voltage characteristics are achieved by using a bevel structure at the junction termination.

In the high breakdown voltage diode of this type of structure, a large amount of carriers are accumulated in the N ^-- type base layer 1 in the high injection state. The carrier distribution is as shown in FIG. In particular, a high carrier concentration is shown in the vicinity of the N ⁺ type cathode layer 3 and the P ⁺ type anode layer 2 where electrons and holes are injected.

As a result of accumulating a large amount of carriers in this way, a large reverse recovery current flows at the time of OFF when a reverse bias is applied. For example, in the case of the element parameters described above,
Reverse direction applied voltage 1000V, current change rate di / dt =-
100 A / c when turned off at 200 A / μs · cm ^2.
A large reverse recovery current of about m ² flows. Therefore, this reverse recovery current consumes more power and generates heat. This becomes a cause of hindering high-speed switching.

As a method of improving the reverse recovery characteristic of the high breakdown voltage diode, it is effective to reduce the surface impurity concentration of the P ⁺ -type anode layer 2 and reduce its thickness (for example, see Non-Patent Document 1).

This is because by lowering the hole injection efficiency on the P ⁺ -type anode layer 2 side, carriers near the junction where the depletion layer spreads can be reduced in the on state in the initial stage of reverse recovery. Be seen.

However, lowering the surface concentration of the P ⁺ -type anode layer 2 makes it difficult to sufficiently lower the ohmic contact with the anode electrode 4 and deteriorates the ON characteristics. In order to obtain a good ohmic contact required for electric power, the P ⁺ type anode layer 2
It is necessary to make the surface concentration of 1 × 10 ¹⁹ / cm ³ approximately.

Further, if the concentration of the P ⁺ -type anode layer 2 is made low and the thickness thereof is made thin, the depletion layer extending into the P ⁺ -type anode layer 2 reaches the anode electrode 4 when a reverse bias is applied. Such a high withstand voltage characteristic cannot be obtained.

In order to solve the problem of the first conventional high breakdown voltage diode, another high breakdown voltage diode (second conventional high breakdown voltage diode) has been proposed. Figure 1
0 (a) and (b) are a plan view of the second conventional high breakdown voltage diode on the anode side and a sectional view taken along the line AA '.

A high-concentration P-type anode layer (emitter layer) is selectively formed on one surface of the high-resistance N ^-- type base layer 1 by diffusion. Anode layer, N ^- type base layer P ⁺ -type anode layer is formed by diffusion on 1 and P ⁺ -type layer 2 ₁ a (P ⁺ emitter layer) body, the higher concentration is formed by diffusion on the surface portion P ⁺ It is constituted by the ⁺ type layer 2 ₂ .

Further, in the P ⁺⁺ type layer 2 ₂ , FIG.
As shown in (a). A plurality of high-concentration N ⁺⁺ type layers 6 having a stripe pattern are diffused and formed. The anode electrode 4 is formed so as to contact at the same time P ⁺⁺ type layer 2 _2, and N ⁺⁺ type layer 6.

The P ⁺⁺ type layer 2 ₂ is a contact layer for the anode electrode 4 to make a low resistance ohmic contact with the anode layer. The N ⁺⁺ type layer 6 is a current blocking layer for reducing the area of hole injection from the anode layer 2 to the N ⁻ type base layer 1 and discharging electrons. Therefore, the P ⁺⁺ type layer 2 ₂ and the N ⁺⁺ type layer 6 are formed in a state of being dispersed with each other with a predetermined area ratio in consideration of the low resistance contact and the hole injection amount.

On the other hand, a high-concentration N ⁺ type cathode layer 3 is formed on the entire other surface of the N ⁻ type base layer 1, and a cathode electrode 5 is formed on this. The surface of the N ⁻ type base layer 1 exposed on the anode side is covered with an oxide film 7.

A more specific example of the impurity concentration and shape of each part will be described. FIG. 11 shows the P ⁺⁺ type layer 2 ₂ on the anode side of the diode of the second conventional example and the N ⁺⁺ adjacent to the P ⁺⁺ type layer 2 _2.
The cross-section of the basic component part which consists of the type | mold layer 6, and the impurity concentration distribution of the AA 'cross section and its BB' cross section are shown.

N⁻ The mold base layer 1 has a thickness of 450 μm
Pure substance concentration 1 × 10¹³/ Cm³ And P⁺ Mold layer 2₁ Is
Dispersion depth 1.5 μm, surface concentration 1 × 10¹⁷/ Cm³ And
R, P ⁺⁺Mold layer 2₂Has a diffusion depth of 0.3 μm and surface concentration of 1 ×
10¹⁹/ Cm³ And N⁺⁺The mold layer 6 has a diffusion depth of 0.4 μ.
m, surface density 1 × 10²⁰/ Cm³ And N⁺ Type caustic
The diffusion layer 3 has a diffusion depth of 15 μm and a surface concentration of 1 × 10¹⁹/ Cm
³ Is.

The sheet resistance ρ of the portion of the P ⁺ type layer 2 ₁ below the N ⁺⁺ type layer 6 is preferably set in the range of 500Ω / □ <ρ <20000Ω / □.

N arranged alternately in stripes⁺⁺Mold layer
Width of 6₁And P⁺⁺Mold layer 2₂ Width d ₂ And d₁ ≤d₂ 
However, in this conventional example, d is set.₁ = D₂ Is. Well
Also, considering the current concentration during reverse recovery, d₁ <15 μm
It is desirable to set. This improves the breakage resistance
Is planned.

FIG. 11 shows the carrier concentration distribution in the N ^-- type base layer 1 in the ON state (high injection state) of the high breakdown voltage diode having the above-mentioned impurity concentration distribution and shape dimension. It is shown together with that (dashed line) of the conventional high withstand voltage diode.

According to the second conventional high breakdown voltage diode, the anode layer has a lower concentration of the P ⁺ type layer 2 than the conventional one.
By providing the N ⁺⁺ type layer 6 mainly as ₁ and as a blocking layer for suppressing the hole injection from the anode layer, N ⁻ in the high injection state as shown in FIG.
The carrier concentration distribution in the mold base layer 1 is 1 × 10 ¹⁷ / cm ³ on the cathode side, while it is about 1 × 10 ¹⁵ / cm ³ on the anode side, which is one digit less than this. As described above, the carrier concentration on the anode side in the N ⁻ type base layer 1 is reduced, and as a result, the reverse recovery characteristic is improved.

FIG. 12 shows the second conventional high withstand voltage diode.
The reverse recovery characteristics of the diode compared to the first conventional high voltage diode.
It shows in comparison. This is a current density of 100 A / cm² 
(ON voltage 2.6V), applied voltage 1000V, di /
dt = -200 A / μs · cm ² Is the waveform at. Figure 1
According to the second conventional high breakdown voltage diode,
The recovery current can be kept small and the reverse recovery characteristics can be improved.
I understand that.

By forming the N ⁺⁺ type layer 6 as an injection blocking layer in the anode layer, a parasitic transistor effect may occur during reverse recovery. As shown in FIG. 13, this is because the reverse recovery current is P in the anode layer.
⁺ Flow type layer 2 ₁ in the transverse direction, generated by joining consisting P ⁺ -type layer 2 ₁ and N ⁺⁺ type layer 6 which is built-in voltage (0.5V) or more forward biased. Therefore, it is necessary to suppress this.

The value of the transverse voltage drop VR of the P ⁺ -type layer 2 in ₁ just below the N ⁺⁺ type layer 6, and the sheet resistance of the P ⁺ -type layer 2 ₁ just below the N ⁺⁺ type layer 6 [rho _{p +,} there and the current density i flowing, with a width d ₁ of the N ⁺⁺ type layer 6 can be expressed as _{VR = ρ p + (i /} 2) (d 1 2/4). If this voltage VR is smaller than the built-in voltage (0.5V), the N ⁺⁺ P ⁺ N ^- N ⁺ parasitic transistor does not operate and the switching loss is reduced.

The conditions for preventing the operation of the parasitic transistor will be more generalized and explained assuming all cases of the distributed arrangement of the N ⁺⁺ type layer 6 and the P ⁺⁺ type layer 2 _2. become.

The density of the current flowing through the device is i [A / cm
² ], sheet resistance ρ _{p +} of the P ⁺ type layer 2 ₁ immediately below the N ⁺⁺ type layer 6
(Ω / □), the set of points in the region of the N ⁺⁺ type layer 6 is A (a),
Let B (b) be the set of points on the boundary between the region of the N ⁺⁺ type layer 6 and the region of the P ⁺⁺ type layer 2 ₂ .

At this time, assuming that the distance from arbitrary point a to b is dab, D = max. Assuming that the distance D [cm] that satisfies (min dab) and the junction voltage Vj [V] between the N ⁺⁺ type layer 6 and the P ⁺ type layer 2 ₁ are Vj> ρ _{p +} (i / 2) D ² Should be satisfied.

FIG. 14 shows the conditions under which the above-mentioned parasitic transistor operates by the relationship between the sheet resistance ρ _{p +} and the width d ₁ of the N ⁺⁺ type layer 6. When the sheet resistance of the P ⁺ type layer 2 ₁ of the anode layer is 20000 Ω / □, the current density (the same as the maximum current value when current concentration occurs) is 100 A.
/ Cm ² , d ₁ = 15 μm, Vj = 0.5
It becomes V.

From this, it is necessary that d ₁ <15 μm in order to suppress the parasitic transistor effect.
When the current density is 200 A / cm ² , d ₁ <7.5 μ
m, and when the current density is 500 A / cm ² , d ₁
<3 μm.

Further, when the element area is small and the current concentration is small, d ₁ can be selected relatively large. On the other hand, when the element area is large and current is concentrated, d ₁
Is small, and it is desirable to select, for example, 3 μm or less.

In the second conventional high breakdown voltage diode thus improved, d ₁ had to be set to a very small value of 3 μm or less in order to suppress the parasitic transistor effect.

Therefore, the accumulated amount of carriers is P ⁺⁺ type layer 2
Even just below ₂ , there was a problem that the amount was slightly higher than immediately below the N ⁺⁺ type layer 6 and a large ON voltage was generated when the current density became high.

Therefore, in the second conventional high breakdown voltage diode, it is difficult to improve both the ON characteristics (for example, reduction of ON voltage) and the reverse recovery characteristics (for example, reduction of reverse recovery current).

Further, as shown in FIG. 12, when it is attempted to set the same ON voltage as that of the first conventional high breakdown voltage diode, the carrier lifetime must be increased, so that reverse recovery is performed at the time of reverse recovery. Although the current is small, there is a problem that the tail current flows for a long time to cause a large power loss.

FIG. 15 shows a cross section of a basic constituent portion of a third conventional high breakdown voltage diode which is an improvement of the first conventional high breakdown voltage diode, and an impurity concentration distribution in the AA 'cross section and the BB' cross section. Is shown.

In the third conventional high breakdown voltage diode,
The second conventional high voltage diode is N ⁺⁺Formed mold layer 6
In the part, the surface impurity concentration was lowered and the thickness was thinned.
⁻Type anode layer 2₃ Are diffused.

Specifically, the P ⁺ type anode layer 2 ₁ has a diffusion depth of 5 μm and a surface concentration of 4 × 10 ¹⁸ / cm ³ , and P ⁻
Type anode layer 2 ₃ has a diffusion depth of 1 μm and a surface concentration of 5 × 1
It is 0 ¹⁵ / cm ³ . Also, P ^- sheet resistance [rho -type anode layer _{2 3, 500Ω / □ <ρ} <20000Ω / □
It is desirable to set within the range.

[0039] P is arranged in stripes alternately ^- with the width d ₁ of the type anode layer 2 _3, but the width d ₂ of the P ⁺ -type anode layer 2 ₁ is set to d ₁ ≦ d _2, specifically This third
In the conventional high breakdown voltage diode of, d ₁ = d ₂ .

FIG. 15 shows the impurity concentration distribution as described above.
ON state of high breakdown voltage diode set to
Along the AA 'section and the BB' section in the (high injection state)
Was N ^- The carrier concentration distribution in the mold base layer 1 is also shown.
There is. Also in this third conventional high withstand voltage diode,
Since the carrier concentration on the anode side is low,
Reverse recovery characteristics are improved.

By the way, P⁻ Type anode layer 2₃ Width d₁
 If is increased, the first conventional high voltage diode,
P⁻ Same as when the surface concentration of the anode layer 2 is lowered
To P ⁻ Type anode layer 2₃ There is a large depletion layer inside
Therefore, the leak current increases when the reverse bias is applied.

FIG. 16 shows the relationship between the reverse applied voltage and the leakage current current with d ₁ as a parameter. When d ₁ is small, the depletion layer spreading from the P ⁺ -type anode layer 2 ₁ shields the P ⁻ -type anode layer 2 ₃ , so that the leak current becomes small. However, d ₁ =
When the thickness is 3 μm, the shield effect is weakened and the leak current increases.

As described above, also in the third conventional high breakdown voltage diode, in order to reduce the leak current when the reverse bias is applied, it is unavoidable to set d ₁ to a very small value of 3 μm or less.

However, if d ₁ is reduced, the first
The carrier profile is similar to that of the conventional example, and the problem that the reverse recovery characteristic is not improved occurs. Therefore,
Even in the third conventional high withstand voltage diode, it was difficult to achieve both improvement of the ON characteristic and improvement of the reverse recovery characteristic.

FIG. 17 shows a cross section of a basic constituent portion of a fourth conventional high withstand voltage diode which is an improvement of the first conventional high withstand voltage diode, and an impurity concentration distribution in the AA ', BB' cross section thereof. The carrier concentration distribution in the ON state is shown.

In the fourth conventional high breakdown voltage diode,
The second conventional high voltage diode is N ⁺⁺Formed mold layer 6
Schottky contact 8 without forming a diffusion layer
Are formed so that only the electron current flows.

In the fourth conventional high withstand voltage diode as well, the reverse recovery characteristic is improved because the carrier concentration on the anode side is small, but like the third conventional high withstand voltage diode, d ₁ There is a problem in that the leakage current increases when the reverse bias is applied when the value is increased.

However, if d ₁ is made small, in this case as well, as in the case of the second conventional high breakdown voltage diode, the carrier accumulation amount in the AA ′ section is slightly larger than that in the BB ′ section. Therefore, when the current density increases, a problem that a large ON voltage is generated occurs. Therefore, even with the fourth conventional high withstand voltage diode, it is difficult to achieve both improvement of the ON characteristic and improvement of the reverse recovery characteristic.

Also, in these third and fourth conventional high withstand voltage diodes, if it is attempted to set the same ON voltage as that of the first conventional high withstand voltage diode, the same as in the case of the second conventional high withstand voltage diode. In addition, since the carrier lifetime must be increased, the reverse recovery current is small at the time of reverse recovery, but there is a problem that the tail current flows for a long time and a large power loss occurs.

FIG. 68 is a sectional view showing the element structure of another conventional high breakdown voltage diode.

In the figure, reference numeral 41 indicates a high resistance N ⁻ type substrate, and the P type emitter layer 4 is formed on the surface of the N ⁻ type substrate 41.
2 is formed, and a P ⁺ -type contact layer 45 provided with an anode electrode 49 is formed on the surface of the P-type emitter layer 42. On the other hand, on the back surface of the N ⁻ type substrate 41, an N ⁺ type emitter layer 43 provided with a cathode electrode 50 is formed.

Further, in order to have a high breakdown voltage characteristic, N
^A P ^- type RESURF layer 46 is formed on the surface of the −-type substrate 41.
It is formed in contact with the mold emitter layer 42. Also, P
^The N ⁺ type stopper layer 4 is provided outside the --- type RESURF layer 46.
7 is provided, and a stopper electrode 51 is provided on the N ⁺ -type stopper layer 47. In the figure, reference numeral 48 indicates an insulating film.

However, such a conventional high breakdown voltage diode has the following problems. That is, when a reverse voltage is suddenly applied to restore the blocking state in the forward conduction state, the element is near the point D at the end of the P-type emitter layer 42 where the depletion layer has the highest electric field when the depletion layer expands. The residual carriers existing in the peripheral area are concentrated. As a result, there is a problem that an avalanche current locally flows and the element is destroyed.

[0054]

[Non-Patent Document 1] M. Naito et al., “High Current Cha.
racteristics of Asymmetrical PiN Diodes Having L
ow Forward Voltage Drops ”, IEEE TRANSACTIONS OF E
LECTRONDEVICES. VOL. 23, NO. 8 pp. 945-949, 1976.

[0055]

As described above, in the conventional high breakdown voltage diode, a large reverse recovery current flows at the time of off due to carrier accumulation in the high resistance N ^-- type base layer,
There is a problem that the reverse recovery characteristic is deteriorated. Therefore, in order to solve such a problem, various high breakdown voltage diodes have been proposed, and some effects could be expected, but it is difficult for any of the high breakdown voltage diodes to improve the reverse recovery characteristics and the ON characteristics at the same time. There was a problem.

Further, in the conventional high breakdown voltage diode, residual carriers existing in the peripheral portion of the element at the time of reverse recovery are concentrated near the end portion of the P-type emitter layer, and an avalanche current locally flows to destroy the element. There was a problem of being done.

The present invention has been made in consideration of the above circumstances, and an object thereof is to provide a high breakdown voltage semiconductor element capable of avoiding destruction due to residual carriers in the peripheral portion of the element when it is off.

[0058]

In order to achieve the above object, the first of the high withstand voltage elements according to the present invention is a first conductivity type first semiconductor layer having first and second main surfaces. A second conductive type second semiconductor layer selectively formed on the first main surface of the first semiconductor layer, and formed on the second main surface of the first semiconductor layer. A third semiconductor layer of a first conductivity type;
A first electrode provided on the second semiconductor layer of the second conductivity type and a second electrode provided on the third semiconductor layer of the first conductivity type; The semiconductor layer includes a plurality of first regions having a relatively high impurity concentration and a plurality of second regions surrounding the first region and having a relatively low impurity concentration, and the first electrode is the first electrode. And is connected to at least the first region.

The second high withstand voltage element according to the present invention is:
A first semiconductor layer of a first conductivity type having first and second main surfaces, and a second semiconductor layer of a second conductivity type selectively formed on the first main surface of the first semiconductor layer. A semiconductor layer and a first conductivity type third formed on the second main surface of the first semiconductor layer.
Semiconductor layer, a first electrode provided on the second conductive type second semiconductor layer, and a second electrode provided on the first conductive type third semiconductor layer. And the second semiconductor layer includes a plurality of first regions having a relatively high impurity concentration,
A plurality of second regions each of which surrounds the first region and is spaced apart from each other and has a relatively low impurity concentration, wherein the first electrode is provided corresponding to the first region, and at least the first region is provided. It is connected to.

The third high withstand voltage element according to the present invention is:
A first semiconductor layer of a first conductivity type having first and second main surfaces, and a second semiconductor layer of a second conductivity type selectively formed on the first main surface of the first semiconductor layer. A semiconductor layer and a first conductivity type third formed on the second main surface of the first semiconductor layer.
Semiconductor layer, a second conductive type fourth semiconductor layer formed on the first main surface of the first semiconductor layer and separated from the second semiconductor layer, and a second conductive type A first electrode provided on a second semiconductor layer; and a second electrode provided on the third semiconductor layer of the first conductivity type, wherein the second semiconductor layer has an impurity concentration. Of a relatively high impurity concentration and a plurality of second regions of a relatively low impurity concentration that surround the first region and are spaced apart from each other, wherein the first electrode is the first region. And is connected to at least the first region.

The fourth of the high breakdown voltage elements according to the present invention is:
A first semiconductor layer of a first conductivity type having first and second main surfaces, and a second semiconductor layer of a second conductivity type selectively formed on the first main surface of the first semiconductor layer. A semiconductor layer and a first conductivity type third formed on the second main surface of the first semiconductor layer.
Semiconductor layer, a second semiconductor layer of the second conductivity type and a first semiconductor layer of the second conductivity type which are sequentially formed on the first main surface of the first semiconductor layer separately from the second semiconductor layer. A fifth semiconductor layer, a first electrode provided on the second conductive type second semiconductor layer, and a second electrode provided on the first conductive type third semiconductor layer A third electrode provided on the fifth semiconductor layer of the first conductivity type, the second semiconductor layer including a plurality of first regions having a relatively high impurity concentration; A plurality of second regions each of which surrounds the region and is spaced apart from each other and has a relatively low impurity concentration, and the first electrode is provided corresponding to the first region and is connected to at least the first region. It is characterized by being

[0062]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
3A and 3B are a plan view and a cross-sectional view showing the element structure of the high breakdown voltage diode according to the embodiment. FIG. 1A is a plan view of the anode side, and FIG. 1B is a sectional view taken along the line AA ′. Also,
FIG. 2 is a diagram showing a cross-sectional structure of a main part of the same high breakdown voltage diode and a carrier concentration distribution in an ON state.

The high breakdown voltage diode of this embodiment uses the second conventional high breakdown voltage diode as the basic element structure, and the portions corresponding to those in FIGS. 10 and 11 are designated by the same reference numerals. Yes, detailed description is omitted.

In this embodiment, as shown in FIG.
The first implantation region 9 (first emitter implantation region) having a high emitter implantation efficiency having the basic structure of (a) and the second implantation of low emitter implantation efficiency in which the basic structure of FIG. 2 (b) is repeated. Regions 10 (second emitter injection regions) are alternately arranged.

The N ⁺⁺ layer (current blocking layer) 6 is formed in the second region 10 so that the parasitic transistor does not operate.
The width d ₁ of each is set to, for example, 3 μm or less. The width W ₂ of the second region 10 is, for example, if the carrier diffusion length La in the N ⁻ type base layer 1 in the high injection state is 130 μm,
If the thickness is selected to be smaller than 390 μm, which is three times that, it is possible to effectively suppress the increase of the on-voltage.

According to this embodiment, the widths of the first region 9 and the second region 10 can be set to a considerable size, so that the first region 9 and the second region 10 are accumulated. There is a large difference in the carrier concentration distribution as shown in FIG. 2 (c).

That is, in the first region 9, as in the first conventional high breakdown voltage diode (FIG. 9), a large amount of carriers are accumulated in the N ^-- type base layer 1, and in the second region 10, Similar to the second conventional high breakdown voltage diode (FIG. 11), the carrier concentration on the anode side in the N ⁻ type base layer 1 is reduced. As a result, even if the current density becomes high,
A sufficiently low on-voltage can be realized by the carriers accumulated in the first region 9.

FIG. 3 shows the reverse recovery characteristics of the high withstand voltage diode according to the present embodiment as a first conventional high withstand voltage diode (first conventional example) and a second conventional high withstand voltage diode (second conventional example). ) Is shown in comparison.

From FIG. 3, according to the present embodiment, the time until the reverse recovery current (anode current) becomes zero is shorter than that in the second conventional example, and the reverse recovery is greater than that in the first conventional example. It can be seen that the peak value of the current becomes smaller. This is because in the diode of the embodiment, a two-dimensional redistribution of current occurs between the first region 9 and the second region 10 during reverse recovery.

Further, since the ON voltage can be lowered even if the carrier lifetime is shortened, the time during which the tail current flows during reverse recovery can be shortened and the power loss can be reduced.

FIG. 4 is a diagram showing the relationship between the width W ₂ of the second region 10 of the high breakdown voltage diode of this embodiment, the carrier diffusion length La in the N ⁻ type base layer, and the ON voltage. Figure 4
As shown in FIG. 6, if the width W ₂ of the second region is within 3 times the carrier diffusion length La in the N ⁻ type base layer 1 in the high injection state, no increase in on-voltage can be seen. Therefore,
In order to suppress the increase of the ON voltage, it is desirable to set W ₂ / La ≦ 3.

FIG. 5 is a diagram showing an example of an anode side pattern in the second region 10 of the diode of this embodiment. When selecting any of these patterns, it is important to suppress the generation of the parasitic transistor in consideration of the conditions described in the description of the second conventional example.

In FIG. 1, the stripe-shaped first regions 9 and the second regions 10 are arranged alternately, but the shape and arrangement pattern of the regions can be variously modified. In FIG. 6, the rectangular first region 9 is arranged in the second region 10. In addition, the shape of these regions may be stripe-shaped, rectangular-shaped, or polka-dot-shaped as in FIG.

Further, in FIG. 1 and FIG. 6, the second region 10 having a low emitter injection efficiency is arranged at the end of the diode region in order to reduce the current density near the junction termination. Can also be variously changed. The size of the region, the interval when arranging the regions, and the like can be changed according to the requirements of the element characteristics.

Further, in these examples, the first area 9 is
Is a uniform P as shown in FIG. ⁺ Type anode layer 2
However, even in the first region 9, as shown in FIG.
With such a basic structure, the injection efficiency is higher than that of the second region 10.
Is higher, d₁ , D₂If you set the dimensions of
The same effect can be obtained.

At this time, in order to reduce the current density near the junction termination part, the injection efficiency of the second region 10 arranged at the end of the diode region is set to the second region 10 arranged at the center of the diode region. If it is set lower than that, it is possible to increase the breakdown resistance during reverse recovery of the diode.

In addition, the regions having the basic structure of the second region 10 are set, and the regions having the injection efficiencies of three or more are set by changing the dimensions of d _{1 and} d ₂ variously. The same effect can be obtained by arranging various shapes and arrangement patterns, and further delicate optimization can be achieved.

(Second Embodiment) FIG. 7 shows a second embodiment of the present invention.
FIG. 3 is a cross-sectional view showing the element structure of the high breakdown voltage diode according to the embodiment of FIG. The high breakdown voltage diode of the present embodiment is different from that of the first embodiment in that the first region and the second region are provided not only on the anode side but also on the cathode side.

That is, in the cathode layer, the N ⁺ type layer 3 ₁ as the first region having a high electron injection efficiency and the regions N ⁺⁺ type layer 3 ₂ and the N ⁺⁺ type layer 3 _{2 having a} higher concentration than this are formed. And a P ⁺⁺ type layer (current blocking layer) 11 as a second injection region having a low electron injection efficiency.

According to this embodiment, N ⁻ in the high injection state
Since the carrier concentration in the mold base layer 1 becomes lower than the conventional one on both the anode side and the cathode side, the reverse recovery characteristic is further improved. Further, in the present embodiment, as shown in FIG. 7, the cathode-side (lower side of the figure) surface of the junction termination region does not have the first region with high emitter injection efficiency, but only the second region with low emitter injection efficiency. Are arranged to reduce the current density in the junction termination region and enhance the breakdown withstanding capacity during reverse recovery of the diode.

In this embodiment, the second region with low emitter injection efficiency on the anode side (the second region with low hole injection efficiency) is the second region with high emitter injection efficiency on the cathode side.
Is formed so as to face the region (the second region where the electron injection efficiency is low), but this positional relationship can be variously changed. Further, only the second region may be formed on one surface, or the injection efficiency of the second region 10 arranged at the end of the diode region may be the same as that of the second region 10 arranged at the center of the diode basin. It is also possible to set it lower than the above to increase the breakdown withstand capability during reverse recovery of the diode.

(Third Embodiment) FIG. 8 shows a third embodiment of the present invention.
FIG. 3 is a cross-sectional view of an element structure of a reverse conduction type IGBT according to the embodiment of FIG. The reverse conducting type IGBT of the present embodiment is roughly divided into an IGBT region and a reverse conducting diode region.

First, the IGBT region will be described. N
^A P type layer (P base layer) 12 is selectively formed on the surface of the ⁻ type base layer 1, and an N ⁺⁺ type layer (source layer) 13 is formed on the surface portion thereof.

The P type layer (P base layer) 12 in the region sandwiched between the N ⁺⁺ type layer (source layer) 13 and the N ⁻ type base layer 1
A gate electrode 15 is formed on the gate insulating film 14. P on the N ⁺⁺ type layer (source layer) 13
The high-concentration portion of the mold layer (P base layer) 12 is diffused and formed,
The latch-up operation of the IGBT is prevented. A P ⁺⁺ type layer 2 ₂ is formed on the surface of the P type layer (P base layer) 12,
It is ohmic-connected to the source electrode 17 together with the N ⁺⁺ type layer (source layer) 13.

On the other hand, on the back surface of the N ⁻ type base layer 1,
A type buffer layer 22 is formed, and a P ⁺ type layer (drain layer) 16 is selectively formed therein. The N-type buffer layer 22 is in ohmic contact with the drain electrode 18.

In this embodiment, the P ⁺ type layer (drain layer)
A structure similar to that formed on the anode side surface of the high breakdown voltage diode of the first embodiment is adopted inside 16.
That is, inside the P ⁺ type layer (drain layer) 16, the second region 10 in which the injection efficiency is lowered by the ^{N ++} type layer (current blocking layer) 6 on the surface portion thereof and the first region having high injection efficiency are formed. 9 is formed.

In this embodiment, the first region 9 having a high injection efficiency is arranged under the gate electrode 15 which is the main current path in the ON state, and the second region having a low injection efficiency is provided in the other portions. By arranging 10, unnecessary carrier accumulation is avoided.

Next, the reverse conducting diode region will be described below. A P-type layer 2 ₁ is selectively formed on the surface of the N ⁻ -type base layer 1, and a first region and a second region for controlling the injection efficiency are arranged on the surface portion, and
The anode electrode 4 of the reverse conducting diode is ohmic-connected to the first and second regions.

On the surface of the N-type buffer layer 22 formed on the back surface of the N ^-- type base layer 1, a P ⁺⁺ -type layer (current blocking layer) 11 is used to reduce the emitter injection efficiency.
Region and a first region having high emitter injection efficiency are formed. The drain electrode 18 of the IGBT is ohmic-connected to these first and second regions. This IGBT
Drain electrode 18 functions as the cathode electrode of the reverse conducting diode.

Further, an isolation region sufficiently longer than the carrier diffusion length is provided between the IGBT region and the reverse conducting diode region so that residual carriers in the reverse conducting diode region do not diffuse into the IGBT region. .

As a result, even if the polarity of the voltage applied between the source electrode 17 and the drain electrode 18 is reversed immediately after the reverse conducting diode current flows, the leakage current discharged from the source electrode 17 of the IGBT is reduced. Can be low enough.

In order to prevent the breakdown voltage from decreasing in the isolation region,
A P ⁻ type layer (resurf layer) 20 is formed to relax the electric field. Further, a P ⁻ type layer (resurf) 20 is formed in the junction termination region for the same reason to realize a high breakdown voltage. The N ⁺⁺ type layer 21 is a channel stopper layer for stopping the expansion of the depletion layer.

According to this embodiment, the injection of holes from the drain layer is suppressed in the IGBT region, so that the carrier accumulation in the vicinity of the drain electrode 18 is reduced and the turn-off characteristic is improved.

Further, in the reverse conducting diode region, the injection efficiency on the anode side and the cathode side can be freely determined by the first region and the second region.
It can be set independently of the BT characteristic.

In general, it is difficult to separately control the carrier lifetimes of the IGBT region and the reverse conducting diode region by a method such as electron beam irradiation for controlling the carrier lifetime of the semiconductor element, so that the injection efficiency can be determined by a pattern. The method of the present invention is a very effective method in that the characteristics of each element of the composite element can be optimized independently.

In the first to third embodiments, the structure shown in FIG. 2B has been used as the basic structure constituting the second region, but instead of this, the structures shown in FIGS. The same effect can be obtained by using a modified structure.

By combining heavy metal diffusion, electron beam irradiation, proton or helium irradiation, etc. with the structures of these embodiments, the carrier lifetime inside the device is changed,
It is also possible to further improve the characteristics.

Further, as shown in the embodiment in which the present invention is applied to the reverse conducting IGBT, if the emitter structure (anode structure of the diode) of the present invention is applied to the emitters of various semiconductor elements, turn-off loss (reverse recovery). It is possible to improve the trade-off between the characteristics) and the on-voltage.

(Fourth Embodiment) FIG. 18 is a sectional view showing an element structure of a high breakdown voltage diode according to a fourth embodiment of the present invention. The parts corresponding to the high breakdown voltage diode in FIG. 68 are denoted by the same reference numerals as those in FIG. 68, and detailed description thereof will be omitted.

The feature of this embodiment is that the P-type emitter layer 42 is used.
The end portion of the N ⁺ type emitter layer 43 is formed inside the end portion (broken line). Further, the N-type buffer layer 4 formed outside the end of the N ⁺ -type emitter layer 43
The number 4 prevents the depletion layer from reaching the cathode electrode 50 (punch through) when a reverse voltage is applied.

With such an element structure, electrons are mainly injected from the cathode side only from the N ⁺ -type emitter layer 43 during forward conduction with a high current density. The carrier density near the point D becomes low.

Therefore, even when the point near D is the highest electric field point during reverse recovery, the problem that the element is destroyed by the local avalanche current due to carrier concentration does not occur. The end of the N ⁺ type emitter layer 43 and the P type emitter layer 42
The ends of may match.

(Fifth Embodiment) FIG. 19 is a sectional view showing an element structure of a high breakdown voltage diode according to a fifth embodiment of the present invention. The high withstand voltage diode of the present embodiment is different from that of the fourth embodiment in that the P ^-- type RESURF layer 46 is
In place of the above, the P-type guard ring layer 52 is used to provide high breakdown voltage characteristics. Also in the present embodiment, the carrier density near the point D at the end of the P-type emitter layer 42 becomes low, so that the same effect as in the previous embodiment can be obtained.

(Sixth Embodiment) FIG. 20 shows the sixth embodiment of the present invention.
6 shows a device structure of a high breakdown voltage diode according to the sixth embodiment.
FIG. The high breakdown voltage diode of the present embodiment is the fourth
The difference from the embodiment is that the N-type buffer layer 44 is not provided.
There is a problem. Thick N without worry of punch through ⁻ Type
If the layer (substrate) 41 is used, the high breakdown voltage of such a structure can be obtained.
Iod can be realized without problems.

(Seventh Embodiment) FIG. 21 is a sectional view showing an element structure of a high breakdown voltage diode according to a seventh embodiment of the present invention. The high withstand voltage diode of the present embodiment is different from that of the sixth embodiment in that the P ^-- type RESURF layer 46 is
In place of the above, the P-type guard ring layer 52 is used to provide high breakdown voltage characteristics. Also in this embodiment, the carrier density in the vicinity of the point D of the end of the P-type emitter layer 42 becomes low, so that the same effect as the previous embodiment can be obtained.

(Eighth Embodiment) FIG. 22 is a sectional view showing an element structure of a high breakdown voltage diode according to an eighth embodiment of the present invention. The high withstand voltage diode of this embodiment is different from that of the fourth embodiment in that an insulating film 48 is used instead of the N-type buffer layer 44 to prevent punch-through. Also in this embodiment, the carrier density near the point D at the end of the P-type emitter layer 42 becomes low, so that the same effect as that of the previous embodiment can be obtained.

(Ninth Embodiment) FIG. 23 is a sectional view showing an element structure of a high breakdown voltage diode according to a ninth embodiment of the present invention. The high breakdown voltage diode of the present embodiment is different from that of the fifth embodiment in that the P ^-- type RESURF layer 46 is
In place of, the P-type guard ring layer 52 is used to provide high withstand voltage characteristics. Also in this embodiment, the P-type emitter layer 4
Since the carrier density near the point D at the end of No. 2 becomes low, the same effect as in the previous embodiment can be obtained.

(Tenth Embodiment) FIG. 24 is a sectional view showing an element structure of a high breakdown voltage diode according to a tenth embodiment of the present invention. The feature of this embodiment is that between the first P-type emitter layer 42 and the P ^-- type RESURF layer 46, that is,
The second P ⁻ -type emitter layer 53 of low concentration is provided around the first P ⁻ -type emitter layer 42.

Here, the second P ^-- type emitter layer 53 has a low concentration within a range in which it is not completely depleted when a reverse voltage is applied, and the injection efficiency is lowered. This is the P ^-- type RESURF layer 4
Fundamentally different from the 6th layer.

With such an element structure, the carrier injection into the P ^-- type emitter layer 53 becomes small, so that the carrier density near the point D becomes low during forward conduction. Therefore, even when the point near D is the highest electric field point during reverse recovery, there is no problem that the element is destroyed by the local avalanche current due to carrier concentration.

(Eleventh Embodiment) FIG. 25 is a sectional view showing an element structure of a high breakdown voltage diode according to an eleventh embodiment of the present invention. The high breakdown voltage diode of the present embodiment is different from that of the tenth embodiment in that a P-type guard ring layer 52 is used instead of the P ^{− −} type RESURF layer 46,
It is to have high withstand voltage characteristics. Also in the present embodiment, the carrier density near the point D at the end of the P-type emitter layer 42 becomes low, so that the same effect as in the previous embodiment can be obtained.

(Twelfth Embodiment) FIG. 26 is a sectional view showing the element structure of a high breakdown voltage diode according to the twelfth embodiment of the present invention. A feature of this embodiment is that the N ⁺ layer 54 for electron emission is formed in the vicinity of the end portion in the P-type emitter layer 42.

With such an element structure, electrons near the point D are discharged from the N ⁺ layer 54 to the outside of the element during forward conduction, so that the carrier density near this end portion becomes low. Therefore, even when the point near D is the highest electric field point during reverse recovery, there is no problem that the element is destroyed by the local avalanche current due to carrier concentration.

(Thirteenth Embodiment) FIG. 27 is a sectional view showing the element structure of a high breakdown voltage diode according to the thirteenth embodiment of the present invention. The high withstand voltage diode of the present embodiment is different from that of the twelfth embodiment in that a P-type guard ring layer 52 is used instead of the P ^-- type RESURF layer 46,
It is to have high withstand voltage characteristics. Also in this embodiment, since the carrier density near the point D near the end of the P-type emitter layer 42 is low, the same effect as that of the previous embodiment can be obtained.

(Fourteenth Embodiment) FIG. 28 is a sectional view showing an element structure of a high breakdown voltage diode according to a fourteenth embodiment of the present invention. This embodiment is the first embodiment and the first.
0 is an example of combination with the embodiment of FIG. That is, the high breakdown voltage diode of this embodiment has a configuration in which, in the high breakdown voltage diode of FIG. 1, another low concentration P-type emitter layer 53 is formed around the P-type emitter layer 2 ₁ so as to be in contact therewith. .

[0117] Here, similarly to the tenth embodiment, P ^-
The type emitter layer 53 has a low concentration within a range in which it is not completely depleted when a reverse voltage is applied, thereby lowering the injection efficiency. According to the present embodiment, in addition to the effect of the first embodiment, the effect of increasing the breakdown resistance is provided by providing the P ⁻ type emitter layer 53.

(Fifteenth Embodiment) FIG. 29 is a sectional view showing an element structure of a high breakdown voltage diode according to a fifteenth embodiment of the present invention. The present embodiment is the first embodiment and the fourth embodiment.
It is an example in which the above embodiment is combined. That is, the high breakdown voltage diode of the present embodiment is the high breakdown voltage diode of FIG. 1 in which the end of the N-type emitter layer 3 is located inside the end of the P-type emitter layer 2 ₁ .
The positions of the two ends may be the same.

According to this embodiment, the following effects can be obtained in addition to the effects of the first embodiment. That is, even if the vicinity of the end of the P-type emitter layer 21 becomes the highest electric field point, carrier concentration does not occur, and the effect of improving the breakdown resistance is obtained.

(Sixteenth Embodiment) FIG. 30 shows the structure of the present invention.
16 is a cross-sectional view of a high breakdown voltage diode according to a sixteenth embodiment.
is there. In this example, the reverse voltage
For electric field relaxation designed to be fully depleted when applied
P⁻⁻A mold resurf layer 46 is provided. Features of this structure
Is the P-type emitter layer 42 and P⁻⁻Between the RESURF layer 46
And low injection efficiency P ⁻ A type emitter layer 53 is provided, and
The anode electrode 49 is contacted only with the P-type emitter layer 42.
Let me P⁻ Contact to the emitter layer 53
Is not.

[0121] In this structure, P ^- with decreasing carrier injection due to the low concentration of the type emitter layer 53, the P ^- carrier injection in the vicinity of point D is limited for lateral resistance 57 of the type emitter layer 53 Due to the double effect, the carrier density near the point D is low during forward conduction. Therefore, even if point D becomes the highest electric field point during reverse recovery, carrier concentration does not occur and the structure is strong against destruction.

As described above, according to this embodiment,
It is possible to improve the breakdown resistance while maintaining good forward characteristics.

FIG. 31 is a sectional view of a high breakdown voltage diode according to a first modification of this embodiment. In this modification, P
^The present embodiment is the same as the above embodiment except that the P-type guard ring layer 52 for relaxing the electric field is provided instead of the --- RESURF layer 46.

FIG. 32 is a sectional view showing the element structure of the high breakdown voltage diode according to the second modification of this embodiment.
In this modification, the P ⁻ type emitter layer 53 is formed so as to surround the P type emitter layer 42. Even in this case, the same effect as that of FIG. 30 can be obtained.

FIG. 33 is a sectional view of a high breakdown voltage diode of the third modification example of this embodiment. In this modification, P
^{The second} type except that a P-type guard ring layer 52 for relaxing an electric field is provided instead of the --- type RESURF layer 46.
This is the same as the modified example of.

(Seventeenth Embodiment) FIG. 34 is a sectional view of a high breakdown voltage diode according to a seventeenth embodiment of the present invention. In this example, a P ⁻ -type RESURF layer 46 for electric field relaxation is provided in order to have a high breakdown voltage characteristic. The feature of this structure is that the N-type layer 56 for adjusting the injection efficiency is provided on the peripheral surface in the P-type emitter layer 42, and the anode electrode 49 is in contact with only the P-type emitter layer 42.

In this structure, the impurity amount of the P-type emitter layer 42 immediately below the N-type layer 56 can be adjusted by adjusting the diffusion depth of the N-type layer 56 for adjusting the injection efficiency.
The carrier injection efficiency can be reduced.

Also in this case, in addition to the above effect, the double effect that the carrier injection in the vicinity of the point D is restricted by the lateral resistance 57 of the P-type emitter layer 42 causes the carrier in the vicinity of the point D in the forward direction to flow. The density is low. Therefore, even if point D becomes the highest electric field point during reverse recovery, carrier concentration does not occur and the structure is strong against destruction. A plurality of N-type layers 56 may be arranged side by side.

FIG. 35 is a sectional view of a high breakdown voltage diode according to a modification of this embodiment. This modification is the same as the above embodiment except that a P-type guard ring layer 52 for electric field relaxation is provided in place of the P ^-- type RESURF layer 46.

(Eighteenth Embodiment) FIG. 36 is a sectional view of a high breakdown voltage diode according to an eighteenth embodiment of the present invention. In this example, a P ⁻ -type RESURF layer 46 for electric field relaxation is provided in order to have a high breakdown voltage characteristic. The feature of this structure is that the peripheral surface in the P-type emitter layer 42 is RIEed.
That is, the anode electrode 49 is brought into contact with only the P-type emitter layer 42 by removing a certain amount by the above process.

In this structure, by adjusting the depth of the surface removal portion, the P-type emitter layer 42 immediately below the removal portion is formed.
Since the amount of impurities can be adjusted, the carrier injection efficiency can be reduced. In this case as well, in addition to the above effect, the double effect that the lateral resistance 57 of the P-type emitter layer 42 limits the carrier injection in the vicinity of the point D, the carrier density in the vicinity of the point D becomes low during forward conduction. Has become. Therefore, even if point D becomes the highest electric field point during reverse recovery, carrier concentration does not occur and the structure is strong against destruction.

FIG. 37 is a sectional view of a high breakdown voltage diode of a modification of this embodiment. This modification is the same as the above embodiment except that a P-type guard ring layer 52 for electric field relaxation is provided in place of the P ^-- type RESURF layer 46.

(Nineteenth Embodiment) FIG. 38 is a sectional view of a high breakdown voltage diode according to a nineteenth embodiment of the present invention. In this example, a P ⁻ -type RESURF layer 46 for electric field relaxation is provided in order to have a high breakdown voltage characteristic. The feature of this structure is that the P-type emitter layer 42 ₁ in the peripheral portion of the element is separated and the anode electrode 49 is also separated to provide the field plate electrode 58. In this structure,
As a result of the separation, the P-type emitter layer 42 _{1 in the} peripheral portion of the device
Since carrier injection does not occur, the carrier density in the vicinity of point D in the forward direction can be suppressed. Therefore, even if the point D becomes the highest electric field point during reverse recovery, carrier concentration does not occur and the structure is strong against destruction. Although the electric field at the point E becomes stronger due to the separation, if the separation distance is short, it can be suppressed to a range that has no influence.

FIG. 39 is a sectional view of a high breakdown voltage diode according to a modification of this embodiment. This modification is the same as the above embodiment except that a P-type guard ring layer 52 for electric field relaxation is provided in place of the P ^-- type RESURF layer 46.

(Twentieth Embodiment) FIG. 40 is a sectional view of a high breakdown voltage diode according to a twentieth embodiment of the present invention. In this example, a P ⁻ -type RESURF layer 46 for electric field relaxation is provided in order to have a high breakdown voltage characteristic.

The feature of this structure is that the anode electrode 49 and the field plate electrode 58 separated in FIG. 38 are connected by a high resistance film (polysilicon film or the like) 59. In this structure, the electric potential of the field plate electrode 58 is fixed to the same electric potential as the anode electrode 49 by the high resistance film 59, so that the electric field strength at the point E is lowered. Further, since the high resistance film 59 is provided, carrier injection does not occur from the P-type emitter layer 42 _{1 in the} peripheral portion of the element, so that the carrier density near the point D in the forward direction is suppressed. Therefore, even if the point D becomes the highest electric field point during reverse recovery, carrier concentration does not occur and the structure is strong against destruction.

FIG. 41 is a sectional view of a high breakdown voltage diode according to a modification of this embodiment. This modification is the same as the above embodiment except that a P-type guard ring layer 52 for electric field relaxation is provided in place of the P ^-- type RESURF layer 46.

(Twenty-first Embodiment) FIG. 42 is a sectional view of a high breakdown voltage diode according to a twenty-first embodiment of the present invention. In this example, a P ⁻ -type RESURF layer 46 for electric field relaxation is provided in order to have a high breakdown voltage characteristic.

The feature of this structure is that the P-type emitter layer 42 is
N inside the edge (shown with wavy lines) ⁺ Type emitter layer 43
Is formed. Formed on its outside
In the N-type buffer layer 44, the depletion layer is formed when a reverse voltage is applied.
Prevent it from reaching (catching through) the cathode electrode 50
There is. Also N⁺ The type emitter layer 43 is an N type buffer layer 43.
Formed deeper than.

In this structure, the N ⁺ type emitter layer 4
The end portion 3 is set inside and deeper than the end portion of the P-type emitter layer 42. As a result, the distance and the current spread of the main current flowing across the N ⁻ type substrate 41 can be reduced, and the thickness of the N ⁻ type substrate 41 in the vicinity immediately below the point D can be increased. Therefore, in the vicinity of the point D, the depletion layer greatly expands during reverse recovery, and the electric field strength decreases, and a high breakdown resistance is realized by the double effect of reducing the carrier injection amount by the N-type buffer layer 44.

FIG. 43 is a sectional view of a high breakdown voltage diode according to a first modification of this embodiment. This modification is the same as the above embodiment except that a P-type guard ring layer 52 for electric field relaxation is provided in place of the P ^-- type RESURF layer 46.

FIG. 44 is a sectional view showing the structure of a high breakdown voltage diode according to the second modification of this embodiment. Figure 4
Although basically the same as No. 2, the N-type buffer layer 44 is omitted in this example. This structure is possible for thick substrates that do not suffer from punch-through.

FIG. 45 is a right half sectional view of a high breakdown voltage diode according to the third modification of the present embodiment. This modification is the same as the second modification except that a P-type guard ring layer 52 for electric field relaxation is provided in place of the P ^-- type RESURF layer 46 of the second modification.

The above-mentioned Embodiments 4 to 21 are to improve the device structure of the high breakdown voltage diode to prevent the breakdown during reverse recovery. In the embodiment described below, before the destruction due to the residual carriers occurs around the inside of the device,
The present invention relates to a high withstand voltage diode having a terminal capable of detecting a precursor of the destruction. The gist of the present invention is that the potential of the peripheral portion of the P-type emitter layer of the high breakdown voltage diode is detected to rise due to current concentration, and this is fed back to the gate circuit of the main element such as the IGBT to speed up reverse recovery. To control and prevent destruction. For this,
A detection terminal separated from the anode electrode is provided on the P-type emitter layer around the element.

(Twenty-second Embodiment) FIG. 46 is a sectional view of a high breakdown voltage diode according to a twenty-second embodiment of the present invention.
In this embodiment, an electric field relaxing P ^{− −} type RESURF layer 46 designed to be completely depleted when a reverse voltage is applied is provided in order to have a high breakdown voltage characteristic.

The feature of this structure is that the detection electrode 6 independent of the anode electrode 49 is provided at the end of the P-type emitter layer 42.
0 is provided. In this structure, when current concentration occurs near point D during reverse recovery, the voltage drop that occurs in the lateral resistance 57 of the P-type emitter layer 42 due to the concentrated current can be detected at the detection terminal 60, and the current can be detected. You can see that concentration has occurred. If this signal is used as in the usage described later, current concentration can be avoided and diode breakdown can be prevented.

[0147] It should be noted that usually, ^P in order to improve the electrostatic breakdown voltage ^-
An anode potential is applied to the electrode (field plate electrode) on the RESURF layer 46, but in this embodiment, it is considered that the potential difference between the detection electrode 60 and the anode electrode 49 is not significantly different. Is used instead.

FIG. 47 is a circuit diagram showing a usage example of the diode of this embodiment. Generally, the diode of the present invention is used in an inverter, but for simplification of explanation, the chopper circuit shown in the figure will be used for explanation. With the circulating current 74 flowing in the diode 71 and the load inductance 69, the main element 70 is turned on to turn on the diode 71.
Reverse recovery begins.

At this time, if current concentration occurs at the end of the P-type emitter layer 42 of the diode 71, the potential of the detection terminal rises due to the mechanism described above. If this potential is detected and fed back to the gate circuit 73 of the main element 70 via the isolation amplifier 72 to stop the turn-on of the main element, the breakdown of the diode 71 due to current concentration can be prevented.

Further, when current concentration occurs, a reverse recovery speed can be controlled by arranging a sequence so that the gate voltage of the main element 70 is continuously changed according to the level (detection electrode potential). The operation of the device can be stopped.

FIG. 48 is a sectional view of a high breakdown voltage diode according to a modification of this embodiment. In this example, except that the P-type guard ring layer 52 is provided to alleviate the electric field, FIG.
Same as 6.

(Twenty-third Embodiment) FIG. 49 is a sectional view of a high breakdown voltage diode according to a twenty-third embodiment of the present invention.
A characteristic of this structure is that a P ⁻ type emitter layer 53 designed so as not to be completely depleted when a reverse voltage is applied is provided between the P type emitter layer 42 and the P ⁻ type RESURF layer 46. Other than that is the same as FIG. 46. In this structure, the lateral resistance 57 of the P ⁻ type emitter layer 53 is large, so that current concentration can be easily detected.

(Twenty-fourth Embodiment) FIG. 50 is a sectional view of a high breakdown voltage diode according to a twenty-fourth embodiment of the present invention.
The feature of this structure is that an N-type layer 56 for adjusting the lateral resistance 57 is provided on the surface of the peripheral portion in the P-type emitter layer 42, and the other points are the same as in FIG. In this structure, the lateral resistance 57 of the P-type emitter layer 42 immediately below the removed portion can be adjusted by adjusting the diffusion depth of the N-type layer 56, so that the detection sensitivity of current concentration can be adjusted.

(Twenty-fifth Embodiment) FIG. 51 is a sectional view of a high breakdown voltage diode according to a twenty-fifth embodiment of the present invention.
The feature of this structure is that the peripheral surface in the P-type emitter layer 42 is removed by a certain amount by RIE or the like, and the other points are the same as those in FIG. In this structure, the lateral resistance 57 of the P-type emitter layer 42 immediately below the removed portion can be adjusted by adjusting the depth of the removed portion, so that the detection sensitivity of current concentration can be adjusted.

(Twenty-sixth Embodiment) FIG. 52 is a sectional view of a high withstand voltage diode according to a twenty-sixth embodiment of the present invention.
The feature of this structure is that the P ⁻ -type emitter layer 53 is provided between the P-type emitter layer 42 and the P-type layer 65, and the other points are the same as in FIG. 46. In this structure, since the lateral resistance 57 of the P ⁻ type emitter layer 53 is large, the current concentration can be easily detected.

(Twenty-seventh Embodiment) FIG. 53 is a sectional view of a high breakdown voltage diode according to a twenty-seventh embodiment of the present invention.
The feature of this structure is that the P-type emitter layer 42 and the P-type layer 65 are completely separated and electrically connected to each other through the resistive film 67, and the other points are the same as in FIG. In this structure, the resistance of the resistive film 67 facilitates detection of current concentration.

In Embodiments 22 to 27, the detection electrode 6 was used.
The case where 0 is used as the field plate electrode has been described, but hereinafter, the case where the anode electrode 49 is used as the field plate electrode will be described.

(Twenty-eighth Embodiment) FIG. 54 is a plan view of a high breakdown voltage diode according to a twenty-eighth embodiment of the present invention.
FIG. 55 is a sectional view taken along line AA ′ and line BB ′ in the figure.
And FIG. 56 respectively. This structure is characterized in that the anode electrode 49 is used as a field plate electrode by covering the detection electrode 60 with the second insulating film 63, and a part of the second anode electrode 61 is used to observe the potential of the detection electrode 60. It is opened, and other than that is the same as FIG. 46. The reference numeral 64 indicates the detection electrode 6
This is an extraction electrode for measuring the potential of 0.

(Twenty-ninth Embodiment) FIGS. 57 and 58 are cross-sectional views of a high breakdown voltage diode according to a twenty-ninth embodiment of the present invention, which are taken along the lines AA ′ and BB ′ of FIG. The cross-sectional views correspond respectively. The feature of this structure is that the anode electrode 49 is used as a field plate electrode by covering the detection electrode 60 with the second insulating film 63, and the second anode electrode 61 is used to observe the potential of the detection electrode 60.
Is partially opened, and other than that is the same as FIG. 49.

(30th Embodiment) FIGS. 59 and 60 are cross-sectional views of a high breakdown voltage diode according to a 30th embodiment of the present invention, which are taken along the lines AA 'and BB' in FIG. The cross-sectional views correspond respectively. The feature of this structure is that the anode electrode 49 is used as a field plate electrode by covering the detection electrode 60 with the second insulating film 63, and the second anode electrode 61 is used to observe the potential of the detection electrode 60.
Is partially opened, and other than that is the same as FIG.

(Thirty-First Embodiment) FIGS. 61 and 62 are cross-sectional views of a high breakdown voltage diode according to a thirty-first embodiment of the present invention, taken along the lines AA 'and BB' in FIG. The cross-sectional views correspond respectively. The feature of this structure is that the anode electrode 49 is used as a field plate electrode by covering the detection electrode 60 with the second insulating film 63, and the second anode electrode 61 is used to observe the potential of the detection electrode 60.
Is partially opened, and other than that is the same as FIG.

(32nd Embodiment) FIGS. 63 and 64 are cross-sectional views of a high breakdown voltage diode according to a 32nd embodiment of the present invention, which are taken along the lines AA 'and BB' in FIG. The cross-sectional views correspond respectively. The feature of this structure is that the anode electrode 49 is used as a field plate electrode by covering the detection electrode 60 with the second insulating film 63, and the second anode electrode 61 is used to observe the potential of the detection electrode 60.
Is partially opened, and other than that is the same as FIG.

(Thirty-Third Embodiment) FIGS. 65 and 66 are cross-sectional views of a high breakdown voltage diode according to a thirty-third embodiment of the present invention, taken along the lines AA ′ and BB ′ of FIG. The cross-sectional views correspond respectively. The feature of this structure is that the anode electrode 49 is used as a field plate electrode by covering the detection electrode 60 with the second insulating film 63, and the second anode electrode 61 is used to observe the potential of the detection electrode 60.
Is partially opened, and other than that is the same as FIG.

(34th Embodiment) FIG. 67 is a plan view of a high breakdown voltage diode according to a 34th embodiment of the present invention.
The feature of this structure is that the detection electrode 60 is divided and each potential can be measured. This structure has an advantage that even if a local current concentration occurs, it can be detected with high sensitivity. In many cases, current concentration occurs at the corners, so the actual locations used for detection may be limited to four corners.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the case of a high breakdown voltage diode was mainly described, but the present invention can be applied to other high breakdown voltage semiconductor elements such as thyristors, bipolar power transistors, and IGBTs having the same diode structure as the element. .

In the above embodiment, the first conductivity type is N.
In this embodiment, the mold and the second conductivity type are P-type.
The first conductivity type may be P type and the second conductivity type may be N type.

Besides, various modifications can be made without departing from the scope of the present invention.

[0168]

As described in detail above, according to the present invention,
Since the second conductivity type emitter layer is separated, the second
No carrier injection occurs from the conductivity type emitter layer. Therefore, the carrier density in the vicinity of the excessive peripheral portion of the outer periphery of the emitter layer is suppressed in the forward direction, and even if the corner becomes the highest electric field point in the reverse recovery, the concentration of carriers does not occur and the structure is strong against destruction.

[Brief description of drawings]

FIG. 1 is a plan view of a high breakdown voltage diode according to a first embodiment of the present invention and its AA ′ cross-sectional view.

2 is a diagram showing a cross-sectional structure of a main part of the high breakdown voltage diode of FIG. 1 and a carrier concentration distribution in an ON state.

FIG. 3 is a diagram showing the reverse recovery characteristics of the high breakdown voltage diode of FIG. 1 in comparison with the first conventional high breakdown voltage diode and the second conventional high breakdown voltage diode.

4 is a width and N of a second region of the high breakdown voltage diode of FIG.
^- characteristic diagram showing the relationship between the carrier diffusion length and the on-voltage type base layer

5 is a plan view showing an example of an anode side pattern of a second region of the high breakdown voltage diode of FIG. 1. FIG.

6 is a plan view showing another arrangement pattern of the first region and the second region of the high breakdown voltage diode of FIG. 1. FIG.

FIG. 7 is a sectional view showing an element structure of a high breakdown voltage diode according to a second embodiment of the present invention.

FIG. 8 is a reverse conducting type IGBT according to a third embodiment of the present invention.
Sectional view of element structure of T

FIG. 9 is a diagram showing a main part structure of a first conventional high breakdown voltage diode, an impurity concentration distribution in the element, and a carrier concentration distribution in an ON state.

FIG. 10 is a plan view of a second conventional high breakdown voltage diode and its AA ′ sectional view.

FIG. 11 is a diagram showing a basic constituent part of the high breakdown voltage diode of FIG. 10, an impurity concentration distribution in the element, and a carrier concentration distribution in an ON state.

FIG. 12 is a diagram showing the reverse recovery characteristics of a second conventional high withstand voltage diode in comparison with the first conventional high withstand voltage diode.

13 is a diagram for explaining a parasitic transistor effect of the high breakdown voltage diode of FIG.

14 is a desirable sheet resistance and N ⁺⁺ for suppressing the parasitic transistor effect of the high breakdown voltage diode of FIG.
Figure for explaining the width range of the mold layer

FIG. 15 is a cross-sectional view of a main part of a third conventional high breakdown voltage diode and a diagram showing a carrier concentration distribution in the ON state in the same element.

16 is a diagram showing the relationship between the reverse applied voltage and the leakage current of the high breakdown voltage diode of FIG. 15 with d ₁ as a parameter.

FIG. 17 is a cross-sectional view of a main part of a fourth conventional high breakdown voltage diode and a diagram showing a carrier concentration distribution in the ON state in the same element.

FIG. 18 is a sectional view showing an element structure of a high breakdown voltage diode according to a fourth embodiment of the present invention.

FIG. 19 is a sectional view showing an element structure of a high breakdown voltage diode according to a fifth embodiment of the present invention.

FIG. 20 is a sectional view showing an element structure of a high breakdown voltage diode according to a sixth embodiment of the present invention.

FIG. 21 is a sectional view showing an element structure of a high breakdown voltage diode according to a seventh embodiment of the present invention.

FIG. 22 is a sectional view showing an element structure of a high breakdown voltage diode according to an eighth embodiment of the present invention.

FIG. 23 is a sectional view showing an element structure of a high breakdown voltage diode according to a ninth embodiment of the present invention.

FIG. 24 is a sectional view showing an element structure of a high breakdown voltage diode according to a tenth embodiment of the present invention.

FIG. 25 is a sectional view showing an element structure of a high breakdown voltage diode according to an eleventh embodiment of the present invention.

FIG. 26 is a sectional view showing an element structure of a high breakdown voltage diode according to a twelfth embodiment of the present invention.

FIG. 27 is a sectional view showing an element structure of a high breakdown voltage diode according to a thirteenth embodiment of the present invention.

FIG. 28 is a sectional view showing an element structure of a high breakdown voltage diode according to a fourteenth embodiment of the present invention.

FIG. 29 is a sectional view showing an element structure of a high breakdown voltage diode according to a fifteenth embodiment of the present invention.

FIG. 30 is a sectional view showing an element structure of a high breakdown voltage diode according to a sixteenth embodiment of the present invention.

FIG. 31 is a sectional view showing an element structure of a high breakdown voltage diode according to a first modification of the sixteenth embodiment of the present invention.

FIG. 32 is a sectional view showing the device structure of a high breakdown voltage diode according to a second modification of the sixteenth embodiment of the present invention.

FIG. 33 is a sectional view showing an element structure of a high breakdown voltage diode according to a third modification of the sixteenth embodiment of the present invention.

FIG. 34 is a sectional view showing an element structure of a high breakdown voltage diode according to a seventeenth embodiment of the present invention.

FIG. 35 is a sectional view showing the element structure of a high breakdown voltage diode according to a modification of the seventeenth embodiment of the present invention.

FIG. 36 is a sectional view showing an element structure of a high breakdown voltage diode according to an eighteenth embodiment of the present invention.

FIG. 37 is a sectional view showing the element structure of a high breakdown voltage diode according to a modification of the eighteenth embodiment of the present invention.

FIG. 38 is a sectional view showing an element structure of a high breakdown voltage diode according to a nineteenth embodiment of the present invention.

FIG. 39 is a sectional view showing an element structure of a high breakdown voltage diode according to a modification of the nineteenth embodiment of the present invention.

FIG. 40 is a sectional view showing an element structure of a high breakdown voltage diode according to a twentieth embodiment of the present invention.

FIG. 41 is a sectional view showing an element structure of a high breakdown voltage diode according to a modification of the twentieth embodiment of the present invention.

FIG. 42 is a sectional view showing the element structure of the high breakdown voltage diode according to the twenty-first embodiment of the present invention.

FIG. 43 is a sectional view showing the element structure of a high breakdown voltage diode according to a first modification of the twenty-first embodiment of the present invention.

FIG. 44 is a sectional view showing an element structure of a high breakdown voltage diode according to a second modification of the twenty first embodiment of the present invention.

FIG. 45 is a sectional view showing the element structure of a high breakdown voltage diode according to a third modification of the twenty first embodiment of the present invention.

FIG. 46 is a sectional view showing the element structure of a high breakdown voltage diode according to a twenty-second embodiment of the present invention.

FIG. 47 is a circuit diagram showing a usage example of the high breakdown voltage diode of the present invention.

FIG. 48 is a sectional view showing an element structure of a high breakdown voltage diode according to a modification of the twenty second embodiment of the present invention.

FIG. 49 is a sectional view showing the element structure of a high breakdown voltage diode according to a twenty-third embodiment of the present invention.

FIG. 50 is a sectional view showing the element structure of the high breakdown voltage diode according to the twenty-fourth embodiment of the present invention.

FIG. 51 is a sectional view showing an element structure of a high breakdown voltage diode according to a twenty-fifth embodiment of the present invention.

52 is a sectional view showing the element structure of the high breakdown voltage diode according to the twenty sixth embodiment of the present invention. FIG.

FIG. 53 is a sectional view showing the element structure of a high breakdown voltage diode according to a twenty-seventh embodiment of the present invention.

FIG. 54 is a plan view of the high breakdown voltage diode according to the 28th embodiment of the present invention.

55 is a cross-sectional view taken along the line A-A ′ of FIG. 54.

56 is a cross-sectional view taken along the line B-B ′ of FIG. 54.

57 is a view showing the element structure of the high breakdown voltage diode according to the twenty ninth embodiment of the present invention, which is a cross sectional view corresponding to the cross section along the line AA ′ of FIG. 54; FIG.

FIG. 58 is a diagram showing the element structure of the high breakdown voltage diode according to the twenty ninth embodiment of the present invention, which is a cross-sectional view corresponding to the cross section along the line BB ′ of FIG. 54;

FIG. 59 is a view showing the element structure of the high breakdown voltage diode according to the thirtieth embodiment of the invention, which is a cross sectional view corresponding to the cross section along the line AA ′ of FIG. 54;

FIG. 60 is a diagram showing the element structure of the high breakdown voltage diode according to the thirtieth embodiment of the invention, which is a cross-sectional view corresponding to the cross section along the line BB ′ of FIG. 54;

FIG. 61 is a view showing the element structure of the high breakdown voltage diode according to the thirty-first embodiment of the present invention, which is a cross-sectional view corresponding to the cross section along the line AA ′ of FIG. 54;

FIG. 62 is a view showing the element structure of the high breakdown voltage diode according to the thirty-first embodiment of the present invention, which is a cross sectional view corresponding to the cross section along the line BB ′ of FIG. 54;

FIG. 63 is a view showing the element structure of the high breakdown voltage diode according to the thirty-second embodiment of the present invention, which is a cross-sectional view corresponding to the cross section along the line AA ′ of FIG. 54;

FIG. 64 is a view showing the element structure of the high breakdown voltage diode according to the thirty-second embodiment of the present invention, which is a cross-sectional view corresponding to the cross section along the line BB ′ of FIG. 54;

FIG. 65 is a view showing the element structure of the high breakdown voltage diode according to the thirty-third embodiment of the present invention, which is a cross-sectional view corresponding to the cross section along the line AA ′ of FIG. 54;

FIG. 66 is a view showing the element structure of the high breakdown voltage diode according to the thirty-third embodiment of the present invention, which is a cross-sectional view corresponding to the cross section along the line BB ′ of FIG. 54;

FIG. 67 is a plan view of a high breakdown voltage diode according to a thirty-fourth embodiment of the present invention.

FIG. 68 is a sectional view showing the element structure of another conventional high breakdown voltage diode.

[Explanation of symbols]

1 ... N ^- type base layer 2 ... P ⁺ -type emitter layer (P ⁺ -type anode layer) 2 ₁ ... P ⁺ -type layer (P ⁺ -type emitter layer) ₂ 2 ... P ⁺⁺ layer (contact layer) 2 ₃ ... P ^- type emitter layer (P ^- -type anode layer) 3 ... N ⁺ -type cathode layer 3 ₁ ... N ⁺ -type layer 3 ₂ ... N ⁺⁺ type layer (contact layer) 4: anode electrode 5 ... cathode electrode 6 ... N ⁺⁺ Mold layer (current blocking layer) 7 ... Oxide film 8 ... Schottky contact 9 ... First region (first emitter injection region) 10 ... Second region (second emitter injection region) 11 ... P ⁺⁺ type Layer (current blocking layer) 12 ... P-type layer 13 ... N ⁺⁺ type layer (source layer) 14 ... Gate insulating film 15 ... Gate electrode 16 ... P ⁺ type layer (drain layer) 17 ... Source electrode 18 ... Drain electrode 19 ... Electrode 20 ... P ^- type layer (resurf layer) 21 ... N ⁺⁺ type layer (channel stopper layer) 22 ... N-type buffer layer 23 ... N ⁺⁺ type layer (contact layer) 41 ... N ^- -type substrate 42 ... P-type emitter layer 43 ... N ⁺ -type emitter layer 44 ... N-type buffer layer 45 ... P ⁺ -type contact layer 46 ... P ^- -type RESURF layer 47 ... N ⁺ -type stopper layer 48: insulating film 49: anode electrode 50 ... cathode electrode 51 ... stopper electrode 52 ... P-type guard ring layer 53 ... second P ^- type emitter layer 54 ... electronic discharge N ⁺ type layer 55 ... Carrier (electron) flow

Claims (7)

[Claims] 1. A first conductivity type first semiconductor layer having first and second main surfaces, and a second conductivity selectively formed on the first main surface of the first semiconductor layer. Type second semiconductor layer, and a first semiconductor layer formed on the second main surface of the first semiconductor layer.
A conductive third semiconductor layer, a first electrode provided on the second conductive second semiconductor layer, and a second electrode provided on the first conductive third semiconductor layer. The second semiconductor layer includes a plurality of first regions having a relatively high impurity concentration, and a plurality of second regions surrounding the first region and having a relatively low impurity concentration. , The first electrode is provided corresponding to the first region, and at least the first electrode is provided.
A high breakdown voltage semiconductor device characterized in that it is connected to the region of. 2. A first conductive type first semiconductor layer having first and second main surfaces, and a second conductive layer selectively formed on the first main surface of the first semiconductor layer. Type second semiconductor layer, and a first semiconductor layer formed on the second main surface of the first semiconductor layer.
A conductive third semiconductor layer, a first electrode provided on the second conductive second semiconductor layer, and a second electrode provided on the first conductive third semiconductor layer. The second semiconductor layer has a plurality of first regions having a relatively high impurity concentration, and a plurality of second regions having a relatively low impurity concentration which respectively surround the first regions and are spaced apart from each other. A high withstand voltage semiconductor element including a region, wherein the first electrode is provided corresponding to the first region and is connected to at least the first region. 3. A first conductive type first semiconductor layer having first and second main surfaces, and a second conductive layer selectively formed on the first main surface of the first semiconductor layer. Type second semiconductor layer, and a first semiconductor layer formed on the second main surface of the first semiconductor layer.
A conductive-type third semiconductor layer; a second conductive-type fourth semiconductor layer formed on the first main surface of the first semiconductor layer and separated from the second semiconductor layer; A second electrode provided on the second conductive type second semiconductor layer; and a second electrode provided on the first conductive type third semiconductor layer; The semiconductor layer includes a plurality of first regions having a relatively high impurity concentration, and a plurality of second regions surrounding the first region and spaced from each other and having a relatively low impurity concentration. A high breakdown voltage semiconductor element, which is provided corresponding to the first region and is connected to at least the first region. 4. A first conductive type first semiconductor layer having first and second main surfaces, and a second conductive layer selectively formed on the first main surface of the first semiconductor layer. Type second semiconductor layer, and a first semiconductor layer formed on the second main surface of the first semiconductor layer.
A third semiconductor layer of conductivity type and a fourth semiconductor layer of second conductivity type sequentially formed on the first main surface of the first semiconductor layer separately from the second semiconductor layer.
Semiconductor layer and a fifth semiconductor layer of the first conductivity type, a first electrode provided on the second semiconductor layer of the second conductivity type, and a third semiconductor layer of the first conductivity type And a third electrode provided on the fifth semiconductor layer of the first conductivity type, wherein the second semiconductor layer includes a plurality of first electrodes having a relatively high impurity concentration. A first region and a plurality of second regions that surround the first region and are spaced apart from each other and have a relatively low impurity concentration, and the first electrode is provided corresponding to at least the first region. A high breakdown voltage semiconductor element, which is connected to the first region. 5. The high breakdown voltage semiconductor device according to claim 3, wherein the fourth semiconductor layer is a guard ring layer. 6. The high breakdown voltage semiconductor device according to claim 4, wherein the fifth semiconductor layer is a stopper layer. 7. The first electrode is provided corresponding to each of a plurality of first regions provided in the second semiconductor layer,
7. The high breakdown voltage semiconductor element according to claim 1, wherein the peripheral side is a field plate electrode.