JP2002016265A - High withstand voltage diode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high withstand voltage diode in which a current change rate is relaxed, surge voltage is suppressed, the generation of an electromagnetic noise is prevented and the breakdown of the diode is prevented by a method where holes are accumulated inside an n+-type stopper layer (cathode layer). SOLUTION: The high dielectric strength diode is provided with a p+-type anode layer 12, which is formed on one face of an n--type semiconductor substrate 11 and the n+-type stopper layer (cathode layer) 13, which is formed on the other face of the substrate 11. The total amount of impurities per unit area of the stopper layer 13 is 2.5×1015 cm-2 or less, and the depth of the stopper layer 13 is 40 μm or larger.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high withstand voltage diode, and more particularly to a diode used as a switching element for power equipment.

[0002]

2. Description of the Related Art A conventional high breakdown voltage diode will be described below.

FIG. 6A is a sectional view showing the structure of a conventional high voltage diode. FIG. 6B is a diagram showing an impurity concentration distribution in the high breakdown voltage diode.

As shown in FIG. 6A, ap + type anode layer 102 is formed on one surface of an n − type semiconductor substrate 101. On the other hand, an n + -type cathode layer 103 is formed on the other surface of the n − -type semiconductor substrate 101. Further, an anode electrode 104 is formed on the surface of the p + -type anode layer 102, and a cathode electrode 105 is formed on the surface of the n + -type cathode layer 103.

Conventionally, by irradiating such a high breakdown voltage diode with charged particles, the lifetime distribution in the device is controlled to improve the characteristics.

As shown in FIG. 6 (c), JP-A-8-102545 and JP-A-10-74959 disclose a p + type anode layer and an n- A method for reducing the reverse recovery current and loss by forming a low lifetime layer due to crystal defects near the junction of the n-type semiconductor substrate and near the boundary between the n + type cathode layer and the n − type semiconductor substrate has been described. I have.

[0007]

However, in order to further improve the reverse recovery current and the loss, it is not sufficient to control only the lifetime, and it is necessary to make the n − type semiconductor substrate thinner. However, when the substrate is made thinner, when the reverse recovery operation is completed and the substrate is completely depleted, the accumulated electrons and holes accumulated in the substrate rapidly disappear, and the current change rate di / dt increases. In addition, a high surge voltage is generated by the parasitic inductance of the circuit.

The reason why the above-described high surge voltage occurs will be described with reference to FIG. FIG. 7A to FIG.
FIG. 9 is a diagram showing a carrier distribution inside a conventional diode.

When a forward voltage is applied to a conventional diode, as shown in FIG.
, A high concentration of electron-hole pairs accumulate, and the holes accumulated in the n − -type semiconductor substrate 101 flow into the n + -type cathode layer 103. However, since the n + -type cathode layer 103 has a high concentration and a shallow diffusion depth, holes flowing into the n + -type cathode layer 103 are instantaneously recombined, and almost n
It does not accumulate in the + type cathode layer 103.

Next, when a reverse voltage is applied to this diode to perform a reverse recovery operation, as shown in FIG.
The depletion layer spreads from the junction between the p + type anode layer 102 and the n − type semiconductor substrate 101.

Next, as shown in FIG. 7C, when this depletion layer reaches the n + -type cathode layer 103, since almost no holes are accumulated in the n + -type cathode layer 103,
At this point, the current is suddenly cut off, the rate of change of the current becomes very large, and a large surge voltage is generated.

In the conventional high breakdown voltage diode, there is a problem that the above-mentioned surge voltage generates electromagnetic noise or, in the worst case, destroys the diode.

Accordingly, the present invention has been made in view of the above problems, and accumulates holes in an n + -type stopper layer (cathode layer) to reduce a current change rate and suppress a surge voltage. It is another object of the present invention to provide a high voltage diode capable of preventing generation of electromagnetic noise and destruction of the diode.

[0014]

To achieve the above object, a first high breakdown voltage diode according to the present invention comprises a first conductive type semiconductor substrate formed on one surface of a first conductive type semiconductor substrate. A type impurity layer, and a first first conductivity type impurity layer formed on the other surface of the first conductivity type semiconductor substrate,
When a reverse voltage is applied between the first second conductivity type impurity layer and the first first conductivity type impurity layer to perform a reverse recovery operation, the first conductivity type semiconductor substrate, When the spread of the depletion layer formed in the first second conductivity type impurity layer and the first first conductivity type impurity layer stops, holes accumulate in the first first conductivity type impurity layer. It is characterized by being.

A second high-breakdown-voltage diode according to the present invention includes a first second-conductivity-type impurity layer formed on one surface of a first-conductivity-type semiconductor substrate and the other of the first-conductivity-type semiconductor substrate. The first first conductivity type impurity layer formed on the surface of the first conductive type impurity layer, and the total amount of impurities per unit area of the first first conductivity type impurity layer is 2.5 × 10 ¹⁵ cm ⁻² or less. ,
The depth of the first first conductivity type impurity layer is 40 μm or more.

Further, the third high-voltage diode according to the present invention may further comprise, in addition to the configuration of the first or second high-voltage diode, the first conductive type impurity layer of the first conductive type impurity layer. The semiconductor device further includes a second first conductivity type impurity layer formed on the other surface opposite to the one surface on which the type semiconductor substrate exists.

Further, the second first conductivity type impurity layer comprises:
The total amount of impurities per unit area is 5 × 10 ¹³ cm ⁻² or less, and the thickness of the layer is 1 μm or less.

When a reverse voltage is applied between the first second conductivity type impurity layer and the first first conductivity type impurity layer, the center of the low carrier lifetime layer becomes Neutral region at or near the boundary between the depletion layer formed in the one conductivity type semiconductor substrate and the first first conductivity type impurity layer and the neutral region formed in the first first conductivity type impurity layer It is characterized by being formed on the side.

Further, the low carrier lifetime layer includes:
It is a region formed by either particle beam irradiation or radiation irradiation.

According to the high breakdown voltage diode configured as above, when the reverse recovery operation is completed, the first first voltage is applied.
The recombination current continues to flow until holes accumulated in the conductivity type impurity layer disappear by recombination with electrons, so that the current change rate is reduced. Thereby, surge voltage can be suppressed, and generation of electromagnetic noise and destruction of the diode can be prevented.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1A is a sectional view showing the structure of a high breakdown voltage diode according to a first embodiment of the present invention. FIG. 1B is a diagram showing an impurity concentration distribution of the high breakdown voltage diode.

As shown in FIG. 1A, a shallow p + -type anode layer 12 of about 10 μm or less is formed on one surface of a high-resistance n − -type semiconductor substrate 11. The thickness of the n − type semiconductor substrate 11 is about 500 μm. On the other hand, on the other surface of the n − type semiconductor substrate 11, a thickness of 40
An n + type stopper layer (cathode layer) 13 of about μm is formed. The total amount of impurities per unit area of the n + type stopper layer is 2.5 × 10 ¹⁵ cm ⁻² or less.

Further, an anode electrode 14 is formed on the surface of the p + type anode layer 12, and a cathode electrode 15 is formed on the surface of the n + type stopper layer 13. FIG. 1 shows the impurity concentration distribution of the high breakdown voltage diode thus configured.
(B).

When a reverse voltage is applied to the diodes shown in FIGS. 1A and 1B, the n − type semiconductor substrate 11 is depleted, and the formed depletion layer is formed in the middle of the n + type stopper layer 13. Stop at the position. The diode is irradiated with a particle beam such as proton or helium in order to partially shorten the carrier lifetime. As shown in FIG. It is located on the neutral region side of the n + -type stopper layer 13 that is not depleted from the line.

When a forward voltage is applied to the diode, holes are injected from the p + -type anode diffusion layer 12 and electrons are injected from the n + -type stopper layer 13 into the n − -type semiconductor substrate 11. A high concentration of electron-hole pairs accumulates on the semiconductor substrate 11. Then, the holes accumulated in the n − type semiconductor substrate 11 flow into the n + type stopper layer 13. FIG. 2 (a)
FIG. 4 is a diagram showing a carrier distribution inside the diode at this time.

At this time, as the impurity concentration of the n + stopper layer 13 is lower and the diffusion depth is deeper, the total amount of holes accumulated in the n + stopper layer 13 increases, and this embodiment will be described later. The effect increases.

Next, when a reverse voltage is applied to the diode to perform a reverse recovery operation, electrons accumulated in the n − type semiconductor substrate 11 are transferred to the n + type stopper layer 13 and holes are stored in the p + type As shown in FIG. 2B, the depletion layer spreads from the junction between the p + -type anode layer 12 and the n − -type semiconductor substrate 11 as it moves to the anode layer 12.

Next, as shown in FIG. 2C, when the depletion layer reaches the n + type stopper layer 13, the expansion of the depletion layer stops, and holes remain in the n + type stopper layer 13. Will remain. Therefore, the recombination current continues to flow until the holes remaining in the n + type stopper layer 13 disappear by recombination with the electrons in the stopper layer 13.

FIG. 3 shows the current and voltage waveforms during the reverse recovery operation.
Shown in The solid line shows the case of the embodiment shown in FIG. 1A, and the broken line shows the case of the conventional diode shown in FIG. 6A. As shown in FIG. 3, at the time point B, in the case of the related art, the current is suddenly cut off, the current change rate becomes extremely large, and a large surge voltage is generated. However, in this embodiment, the current is not suddenly interrupted,
The recombination current continues to flow until the holes remaining in the n + type stopper layer 13 disappear by recombination with electrons.

Therefore, in the first embodiment,
Due to the recombination current, the current change rate is reduced, and the surge voltage is suppressed. As a result, generation of electromagnetic noise and destruction of the diode due to the surge voltage can be prevented.

FIG. 4 is a diagram showing the relationship between the layer thickness of the n + type stopper layer 13 and the current density at which vibration occurs in the high breakdown voltage diode according to the first embodiment. If the thickness of the n + type stopper layer 13 is 40 μm or more, a diode having no practical problem can be formed. Further, when the thickness of the n + type stopper layer 13 is set in the range of 60 μm to 100 μm, the current density at which vibration occurs can be minimized, and more preferable characteristics are obtained in order to prevent generation of surge voltage. Can be formed.

As described above, according to the first embodiment, when the reverse recovery operation is completed, the current change rate is reduced by the holes accumulated in the n + type stopper layer. Surge voltage can be suppressed, and generation of electromagnetic noise and destruction of the diode can be prevented.

[Second Embodiment] FIG. 5A is a sectional view showing the structure of a high voltage diode according to a second embodiment of the present invention. FIG. 5B is a diagram showing an impurity concentration distribution of the high breakdown voltage diode.

The difference between the second embodiment and the first embodiment is that an n + type stopper layer (cathode layer) 13
N ++ type contact layer 1 between
6 is formed. Thereby, the contact resistance between n + type stopper layer 13 and cathode electrode 15 can be reduced. Other configurations are the same as those of the first embodiment. The n ++ type contact layer 16
Means that the total amount of impurities per unit area is 5 × 10 ¹³ cm
⁻² or less, and the thickness of the layer is 1 μm or less.

N + type stopper layer 13 and cathode electrode 15
By forming the n ++ contact layer 16 between these two, the total amount of impurities in the n + type stopper layer 13 can be further reduced without increasing the contact resistance between the n + type stopper layer 13 and the cathode electrode 15, or n + The depth of the mold stopper layer 13 can be further increased.

[0037]

As described above, according to the present invention, n
By accumulating holes in the + type stopper layer (cathode layer), the current change rate is reduced and the surge voltage is suppressed,
It is possible to provide a high breakdown voltage diode capable of preventing generation of electromagnetic noise and destruction of the diode.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view illustrating a structure of a high-breakdown-voltage diode according to a first embodiment of the present invention; FIG. 1B is a diagram illustrating an impurity concentration distribution of the high-breakdown-voltage diode;
(C) is a diagram showing a carrier lifetime and a defect density distribution of the high breakdown voltage diode.

FIG. 2 is a diagram showing a carrier density distribution and an impurity concentration distribution of the high breakdown voltage diode according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a current waveform and a voltage waveform during a reverse recovery operation in the high breakdown voltage diode according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a layer thickness of an n + type stopper layer and a current density at which vibration occurs in the high breakdown voltage diode according to the first embodiment of the present invention.

FIG. 5A is a cross-sectional view illustrating a structure of a high voltage diode according to a second embodiment of the present invention, and FIG. 5B is a diagram illustrating an impurity concentration distribution of the high voltage diode.

6A is a cross-sectional view showing a structure of a conventional high breakdown voltage diode, FIG. 6B is a diagram showing an impurity concentration distribution of the high breakdown voltage diode, and FIG. 6C is a diagram showing a carrier of the high breakdown voltage diode. It is a figure which shows a lifetime and a defect density distribution.

FIG. 7 is a diagram showing a carrier density distribution and an impurity concentration distribution of a conventional high breakdown voltage diode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... n-type semiconductor substrate 12 ... p + type anode layer 13 ... n + type stopper layer (cathode layer) 14 ... anode electrode 15 ... cathode electrode 16 ... n ++ type contact layer

Claims (6)

[Claims] A first conductive type impurity layer formed on one surface of the first conductive type semiconductor substrate; and a first conductive type impurity layer formed on the other surface of the first conductive type semiconductor substrate. A first conductivity type impurity layer, wherein a reverse recovery operation is performed by applying a reverse voltage between the first second conductivity type impurity layer and the first first conductivity type impurity layer. When the spread of the first conductivity type semiconductor substrate, the first second conductivity type impurity layer, and the depletion layer formed in the first first conductivity type impurity layer stops, the first first conductivity type A high breakdown voltage diode wherein holes are accumulated in the impurity layer. 2. The method according to claim 1, wherein the first conductive type semiconductor substrate has a shape on one surface thereof.
A first second conductivity type impurity layer formed, and a first second conductivity type impurity layer formed on the other surface of the first conductivity type semiconductor substrate.
An impurity layer per unit area of the first first conductivity type impurity layer.
2.5 × 10 ^Fifteencm^-2In the following, the first
The depth of the first conductivity type impurity layer is 40 μm or more.
High-voltage diode featuring. 3. The method according to claim 1, wherein the second first conductivity type impurity layer formed on the other surface of the first first conductivity type impurity layer opposite to the one surface on which the first conductivity type semiconductor substrate exists is provided. The high breakdown voltage diode according to claim 1, further comprising: 4. The second first-conductivity-type impurity layer has a total impurity amount per unit area of 5 × 10 ¹³ cm ⁻² or less and a thickness of 1 μm or less. 4. The high breakdown voltage diode according to 3. 5. When a reverse voltage is applied between said first second conductivity type impurity layer and said first first conductivity type impurity layer, the center of said low carrier lifetime layer is said Neutral region at or near the boundary between the depletion layer formed in the one conductivity type semiconductor substrate and the first first conductivity type impurity layer and the neutral region formed in the first first conductivity type impurity layer The high breakdown voltage diode according to any one of claims 1 to 4, wherein the diode is formed on the side. 6. The high breakdown voltage diode according to claim 5, wherein said low carrier lifetime layer is a region formed by either particle beam irradiation or radiation irradiation.