JP2003163357A - Semiconductor device and method of manufacturing the same - Google Patents

Abstract

(57) Abstract: A semiconductor device capable of improving the reverse recovery current characteristic as compared with a conventional MPS diode and a method of manufacturing the same are provided. An n layer is formed by epitaxial growth on a high-concentration substrate to be an n ⁺ cathode layer, and a p anode region is formed on a surface layer of the n layer. The n region where the p anode region 3 is not formed is the n drift region 2. An anode electrode 5 is formed on the p anode region 3 and the n drift layer 2. The anode electrode 5 and the p anode region 3 are in ohmic contact, and a Schottky junction 6 is formed between the anode electrode 5 and the n drift layer 2. A cathode electrode 4 is formed on the n cathode layer 1. The p anode region 3 is ion-implanted at a low dose of 3 × 10 ¹² cm ⁻² to 3 × 10 ¹³ cm ⁻² , and is annealed at a low temperature of 600 ° C. or less, so that holes from the p anode region 3 Improves reverse recovery characteristics by suppressing injection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device such as a power semiconductor rectifier (hereinafter, simply referred to as a diode).

[0002]

2. Description of the Related Art Diodes are used for various purposes.
However, in recent years it has come to be used in high frequency circuits, and
There is a strong demand for shortening the recovery operation time. Figure
6 is a disconnection of the main part of the conventional pin diode
It is a side view. n⁺On the high-concentration substrate that will become the cathode layer 1,
An n-layer is formed by epitaxial growth and the surface layer of this n-layer is formed.
The p anode layer 3a is formed. n⁺Cathode layer 1 and p
The n layer sandwiched between the node layers 3a becomes the n drift layer 2.
The p anode layer 3a is 7 × 10¹³cm ^-2The dose is
Ion implantation is performed once at a fast voltage of 100 keV and 1150
Formed by high temperature annealing (high temperature heat treatment) for 90 minutes at ℃
It n⁺On the cathode layer 1 and the p anode layer 3a
The cathode electrode 4 and the anode electrode 5 are formed.

In this pin diode, it is easy to secure the breakdown voltage, but the p anode layer 3a is formed with a high concentration in order to increase the hole injection efficiency and lower the ON voltage.
Therefore, in the reverse recovery characteristic, the peak value Irp of the reverse recovery current Irr becomes high, and hard recovery occurs.
Further, the pin diode causes a large electrical loss in the diode due to the product of the reverse recovery current and the reverse recovery voltage. In recent years, there has been a strong demand for reducing the reverse recovery loss and further increasing the switching speed.

At present, minority carrier lifetime control using heavy metal diffusion, electron beam irradiation or the like is widely used in order to improve the reverse recovery characteristics of a diode. That is, by reducing the lifetime, the carrier concentration in the steady state is reduced and the carrier concentration swept out by the expansion of the space charge region during reverse recovery is reduced, and the reverse recovery time, reverse recovery current and reverse recovery charge are reduced. Then, the reverse recovery loss can be reduced.

Further, as a means for softening the reverse recovery current, there is a structure for suppressing the injection efficiency of minority carriers from the anode. As its typical structure,
MPS with a Schottky junction and a pn junction (Mer
Ged pin / Schottky) SFD (So
ft and Fast Recovery Period
e) and the like.

FIG. 7 is a sectional view of a main part of a conventional MPS diode. An n layer is formed by epitaxial growth on a high-concentration substrate to be the n ⁺ cathode layer 1, and a p anode region 3b is formed in the surface layer of this n layer. The n region where the p anode region 3b is not formed is the n drift region 2.
An anode electrode 5 is formed on the p anode region 3b and the n drift layer 2. The anode electrode 5 and the p anode region 3b are in ohmic contact with each other, and the anode electrode 5 and n
A Schottky junction 6 is formed with the drift layer 2. n
A cathode electrode 4 is formed on the cathode layer 1.

The p anode region 3b has a size of 7 × 10 ¹³ cm ^-2.
Ion implantation is performed once at an accelerating voltage of 100 keV with a dose amount of, and a high temperature annealing (high temperature heat treatment) is performed at 1150 ° C. for 90 minutes to form a film. This MPS diode is a pin
The reverse leakage current is about twice as large as that of the diode because of the electric field concentration at the Schottky interface during reverse bias. However, the reverse recovery characteristics are such that holes are not injected from the Schottky junction, and the area of the p anode region 3b is smaller by the Schottky junction area than that of the pin diode. Since the concentration of holes, which are minority carriers injected into the device, is suppressed, the reverse recovery current Irr and the reverse recovery loss Err can be reduced as compared with the pin diode, and soft recovery can be achieved.

[0008]

However, as shown in FIG. 6, when the junction depth of the p anode region 3b is Xj, it diffuses in the lateral direction by about 0.75Xj2. Therefore, the p anode region 3b is the sum of the vertical diffusion region 7a and the horizontal diffusion region 8a. When the junction depth Xj2 is increased, the lateral diffusion region 8a (0.75Xj2) is increased and the injection of holes is increased. Therefore, the reverse recovery current Irr increases,
Reverse recovery loss Err increases and hard recovery is achieved.
That is, the reverse recovery characteristics (the above three characteristics) are deteriorated.

An object of the present invention is to solve the above problems and to provide a semiconductor device capable of achieving a reduction in reverse recovery current, a reduction in reverse recovery loss and further soft recovery as compared with a conventional MPS diode. It is to provide the manufacturing method.

[0010]

To achieve the above object, a semiconductor substrate of a first conductivity type and a second conductivity type anode selectively formed on one surface layer of the semiconductor substrate. A region, an anode electrode formed on one surface of the semiconductor substrate and an anode region surface, a first conductivity type cathode layer formed on the other surface, and a cathode electrode formed on the cathode layer surface. In the semiconductor device, comprising: a semiconductor substrate sandwiched between the anode regions and a junction surface between the anode electrode and the anode electrode is a Schottky junction, and a junction surface between the anode region and the anode electrode is an ohmic junction, Anode area is 3 × 10 ¹² c
It is configured to be formed at a dose amount of m ⁻² or more and 3 × 10 ¹³ cm ⁻² or less.

Further, a first semiconductor substrate of the first conductivity type, and a second semiconductor substrate of the first conductivity type epitaxially grown on the surface of the first semiconductor substrate with a concentration lower than that of the first semiconductor substrate. A second conductive type anode region selectively formed on one surface layer of the second semiconductor substrate, and an anode formed on one surface of the first semiconductor substrate and the anode region surface. The semiconductor substrate, which includes an electrode, a cathode layer of the first conductivity type formed on the surface of the first semiconductor substrate, and a cathode electrode formed on the surface of the cathode layer, and which is sandwiched between the anode regions. In a semiconductor device in which the junction surface with the anode electrode is a Schottky junction and the junction surface between the anode region and the anode electrode is an ohmic junction, the anode region is 3 × 10 ¹² cm ^-2.
With the above, the structure is formed with a dose amount of 3 × 10 ¹³ cm ⁻² or less.

The maximum concentration of the semiconductor substrate of the first conductivity type and one of the surface layers of the semiconductor substrate, which overlap each other in the surface layer, is 1 to 10 times the concentration of the semiconductor substrate. Second conductivity type anode layer thus formed, an anode electrode formed on the surface of the anode layer, a first conductivity type cathode layer formed on the other surface, and a cathode formed on the surface of the cathode layer In a semiconductor device including an electrode, the anode region is 3 ×
The dose is set to 10 ¹² cm ^-2 or more and 3 × 10 ¹³ cm ^-2 or less.

Further, a semiconductor substrate of the first conductivity type and a plurality of second semiconductor layers selectively formed on one surface layer of the semiconductor substrate.
A conductive type anode region, an anode electrode formed on one surface of the semiconductor substrate and the surface of the anode region, a first conductive type cathode layer formed on the other surface, and formed on the cathode layer surface. And a cathode electrode
In the method for manufacturing a semiconductor device, the junction surface between the semiconductor substrate sandwiched in the anode region and the anode electrode is a Schottky junction, and the junction surface between the anode region and the anode electrode is an ohmic junction. Area manufacturing process is 3 × 10 ¹² cm ^-2 or more, 3 ×
A step of implanting ions with a dose amount of 10 ¹³ cm ^-2 or less;
The process includes a process of performing low temperature heat treatment at a temperature of 600 ° C. or lower.

Further, a first semiconductor substrate of the first conductivity type, and a second semiconductor substrate of the first conductivity type epitaxially grown on the surface of the first semiconductor substrate in a concentration lower than that of the first semiconductor substrate. A second conductive type anode region selectively formed on one surface layer of the second semiconductor substrate, and an anode formed on one surface of the first semiconductor substrate and the anode region surface. The semiconductor substrate, which includes an electrode, a cathode layer of the first conductivity type formed on the surface of the first semiconductor substrate, and a cathode electrode formed on the surface of the cathode layer, and which is sandwiched between the anode regions. bonding surface between the anode electrode is a Schottky junction, in the manufacturing method of the junction surface between the anode electrode and the anode region is a semiconductor device comprising an ohmic junction, the manufacturing process of the anode region, 3 × 10 ¹² c In ^-2, a step of ion implantation 3 × 10 ¹³ cm ^-2 or less of the dose, the process comprising the step of low-temperature heat treatment at 600 ° C. or lower.

The maximum concentration of the semiconductor substrate of the first conductivity type and one of the surface layers of the semiconductor substrate, which overlap each other in the surface layer, is 1 to 10 times the concentration of the semiconductor substrate. Thus formed second conductive type anode layer, an anode electrode formed on the surface of the anode layer, a first conductive type cathode layer formed on the other surface, and a cathode formed on the surface of the cathode layer In a method of manufacturing a semiconductor device including an electrode, a step of implanting ions in the anode region with a dose amount of 3 × 10 ¹² cm ^-2 or more and 3 × 10 ¹³ cm ^-2 or less, and a temperature of 600 ° C. or less. It is formed in a process of heat treatment at low temperature.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description, the first conductivity type is n.
And the second conductivity type is p-type. Of course, the reverse is also possible. The same parts as those in FIG. 6 are designated by the same reference numerals. FIG. 1 is a sectional view of an essential part of an MPS diode according to an embodiment of the present invention. The difference from the conventional MPS diode shown in FIG. 6 is that the concentration of the p anode region 3 is low and the junction depth is shallow, and therefore the lateral diffusion region 8 is small. The area of the surface of the vertical diffusion region 7 is the same as that of the conventional structure (because the same ion implantation mask is used).

This MPS diode has the same basic structure as the conventional MPS diode. An n layer is formed by epitaxial growth on a high-concentration substrate serving as the n ⁺ cathode layer 1, and a p anode region 3 is formed in the surface layer of this n layer.
The n region where the p anode region 3 is not formed is the n drift region 2. On the p anode region 3 and the n drift layer 2
The anode electrode 5 is formed on top. The anode electrode 5 and the p anode region 3 are in ohmic contact with each other, and a Schottky junction 6 is formed between the anode electrode 5 and the n drift layer 2. A cathode electrode 4 is formed on the n cathode layer 1. The n cathode layer 1 is the n drift layer 2
It may be formed by diffusion on one surface layer of the n-type semiconductor substrate.

The p anode region 3 is formed by performing ion implantation once at an acceleration voltage of 200 keV with a dose amount of 1 × 10 ¹³ cm ^-2 and performing low temperature annealing (low temperature heat treatment) at 550 ° C./60 minutes. It is effective to perform laser annealing for activation. The dose amount is 3 × 10 ¹³
When it exceeds cm ⁻² , the hole injection efficiency becomes as large as that of the conventional MPS diode, and therefore, the reverse recovery characteristic becomes the same as that of the conventional MPS diode, and as a result, dv / dt (reverse recovery shown in FIG. (Generated by current and circuit inductance) increases rapidly. On the other hand, if it is less than 3 × 10 ¹² cm ⁻² , the concentration of the p-anode region 3 is too low, and the depletion layer in the p-anode region 3 is likely to expand, and the breakdown voltage sharply decreases as shown in FIG. 4 described later. . Therefore, the dose amount is preferably 3 × 10 ¹² cm ⁻² or more and 3 × 10 ¹³ cm ⁻² or less. More preferably, 7 × 10 ¹² cm ⁻² or more and 2 ×
A dose of 10 ¹³ cm ^-2 is good.

If the annealing temperature exceeds 600 ° C., the lateral diffusion region 8 increases and the hole injection efficiency increases, so that the reverse recovery characteristic cannot be improved. Also, 350 ℃
When it is less than the value, the junction depth Xj1 becomes shallow and the radius of curvature of the A portion becomes large. Then, the electric field strength at the portion A at the time of reverse bias increases, and the breakdown voltage decreases. Therefore, the annealing temperature is preferably 350 ° C. or higher and 600 ° C. or lower. The temperature is preferably 420 ° C. or higher and 550 ° C. or lower.

As described above, by performing low-temperature annealing at a predetermined temperature with a predetermined dose amount lower than that of the conventional MPS diode, the reverse recovery current, the reverse recovery loss, and the reverse recovery waveform are increased as compared with the conventional MPS diode. It is possible to improve reverse recovery characteristics such as (hard recovery or soft recovery). FIG. 2 is a reverse recovery waveform diagram of the conventional MPS diode and the MPS diode of the present invention. MP of the present invention
Since the S diode (invention product) has an extremely low concentration of the p anode layer 3 as compared with the conventional MPS diode (conventional product), the peak value Irp of the reverse recovery current Irr is significantly reduced. Further, since the injection of holes is low, a distribution with a large number of carriers is formed on the cathode side when a forward current is applied, resulting in a soft recovery waveform.

By using the present invention, it is difficult to realize soft recovery with the conventional MPS diode.
M with a high breakdown voltage of about 600V having a thin drift layer of m
It is possible to achieve soft recovery of the PS diode. That is, 6 having a drift layer as thin as several tens of μm
A high breakdown voltage MPS diode of about 00 V or higher can be used as a diode in which the voltage / current waveform does not oscillate in the reverse recovery process and the loss is small.

Further, since the lateral diffusion regions 8 of the p anode regions 3 can be made small, the lateral diffusion regions of the adjacent p anode regions 3 can be made even when the cell pitch (the repeating interval (cycle) of the p anode regions 3) is made small. 8 can be designed without contacting each other, and the pattern of the p anode region 3 and the Schottky junction 6 can be miniaturized. By making the pattern finer, the current-carrying region in the vicinity of immediately below the Schottky junction 6 is expanded, and the on-voltage can be lowered.

FIG. 5 is a cross-sectional view of an essential part showing another embodiment of the present invention. This is the structure described in Japanese Patent Application No. 2000-311442, and even with this structure, the same effect as that of the above embodiment can be obtained.

[0024]

According to the present invention, the p anode region of the MPS diode is formed by ion implantation with a dose lower than that of the conventional product and low-temperature annealing.
The reverse recovery current and the reverse recovery loss can be reduced, and further soft recovery can be achieved.

As a result, it is possible to improve the drapoff between the high speed / low loss and the soft recovery.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of an MPS diode according to an embodiment of the present invention.

FIG. 2 is a reverse recovery waveform diagram of a conventional MPS diode and the MPS diode of the present invention.

FIG. 3 is a diagram showing a relationship between a dose amount and dv / dt.

FIG. 4 is a diagram showing a relationship between a dose amount and a breakdown voltage.

FIG. 5 is a cross-sectional view of essential parts showing another embodiment of the present invention.

FIG. 6 is a cross-sectional view of a main part of a pin diode which is a conventional diode

FIG. 7 is a sectional view of a main part of a conventional MPS diode.

[Explanation of symbols]

1 n ⁺ Cathode layer 2 n Drift layer 3, 3b p Anode region 3a p Anode layer 4 Cathode electrode 5 Anode electrode 6, 6a Schottky junction 7, 7a Vertical diffusion region 8, 8a Horizontal diffusion region Xj1, Xj2 Junction depth

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masato Otsuki             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. F-term (reference) 4M104 CC01 DD26 DD78 DD81 GG03                       HH14 HH20

Claims (6)

[Claims] 1. A semiconductor substrate of a first conductivity type, an anode region of a second conductivity type selectively formed in a plurality of surface layers on one surface of the semiconductor substrate, and a surface and an anode on one side of the semiconductor substrate. The semiconductor sandwiched between the anode region, the anode electrode formed on the surface of the region, the cathode layer of the first conductivity type formed on the other surface, and the cathode electrode formed on the surface of the cathode layer. In a semiconductor device in which the junction surface between the substrate and the anode electrode is a Schottky junction, and the junction surface between the anode region and the anode electrode is an ohmic junction, the anode region is 3 × 10 ¹² cm ⁻² or more. 3 x 1
A semiconductor device, which is formed with a dose amount of 0 ¹³ cm ^-2 or less. 2. A first semiconductor substrate of the first conductivity type, and a second semiconductor substrate of the first conductivity type epitaxially grown on the surface of the first semiconductor substrate in a concentration lower than that of the first semiconductor substrate. ,
A plurality of second conductivity type anode regions selectively formed on one surface layer of the second semiconductor substrate, and an anode electrode formed on one surface of the first semiconductor substrate and the anode region surface. A semiconductor substrate sandwiched between the anode region and a cathode layer of the first conductivity type formed on the surface of the first semiconductor substrate, and a cathode electrode formed on the surface of the cathode layer; In a semiconductor device in which the junction surface with the anode electrode is a Schottky junction and the junction surface between the anode region and the anode electrode is an ohmic junction, the anode region is 3 × 10 ¹² cm ⁻² or more and 3 × 1
A semiconductor device, which is formed with a dose amount of 0 ¹³ cm ^-2 or less. 3. The maximum concentration of the first conductivity type semiconductor substrate and one of the surface layers of the semiconductor substrate, which overlap each other in the surface layer, is not less than 1 times and not more than 10 times the concentration of the semiconductor substrate. A second conductivity type anode layer formed as described above, and an anode electrode formed on the surface of the anode layer,
In a semiconductor device comprising a cathode layer of the first conductivity type formed on the other surface and a cathode electrode formed on the surface of the cathode layer, the anode region is 3 × 10 ¹² cm ⁻² or more and 3 × 1
A semiconductor device, which is formed with a dose amount of 0 ¹³ cm ^-2 or less. 4. A semiconductor substrate of a first conductivity type, a second conductivity type anode region selectively formed in one surface layer of the semiconductor substrate, a surface of one side of the semiconductor substrate and an anode. An anode electrode formed on the surface of the region, a cathode layer of the first conductivity type formed on the other surface of the region, and a cathode electrode formed on the surface of the cathode layer, and sandwiched between the anode regions. In the method of manufacturing a semiconductor device, wherein the junction surface between the semiconductor substrate and the anode electrode is a Schottky junction, and the junction surface between the anode region and the anode electrode is an ohmic junction, the anode region is 3 × 10 ¹² cm 2. ^-2 or more, 3 x 1
A step of implanting ions with a dose amount of 0 ¹³ cm ^-2 or less;
A method of manufacturing a semiconductor device, which is characterized in that it is formed in a step of performing a low temperature heat treatment at a temperature of 00 ° C. or lower. 5. A first semiconductor substrate of a first conductivity type, and a second semiconductor substrate of a first conductivity type epitaxially grown on the surface of the first semiconductor substrate in a concentration lower than that of the first semiconductor substrate. ,
A plurality of second conductivity type anode regions selectively formed on one surface layer of the second semiconductor substrate, and an anode electrode formed on one surface of the first semiconductor substrate and the anode region surface. A semiconductor substrate sandwiched between the anode region and a cathode layer of the first conductivity type formed on the surface of the first semiconductor substrate, and a cathode electrode formed on the surface of the cathode layer; In the method of manufacturing a semiconductor device, wherein the junction surface of the anode electrode is a Schottky junction, and the junction surface of the anode region and the anode electrode is an ohmic junction, the anode region is 3 × 10 ¹² cm ⁻² or more. 3 x 1
A step of implanting ions with a dose amount of 0 ¹³ cm ^-2 or less;
A method of manufacturing a semiconductor device, which is characterized in that it is formed in a step of performing a low temperature heat treatment at a temperature of 00 ° C. or lower. 6. The maximum concentration of a semiconductor substrate of the first conductivity type and one of the surface layers of the semiconductor substrate that overlap each other in the surface layer and is 1 to 10 times the concentration of the semiconductor substrate. A second conductivity type anode layer formed as described above, and an anode electrode formed on the surface of the anode layer,
A method for manufacturing a semiconductor device comprising a first conductivity type cathode layer formed on the other surface and a cathode electrode formed on the cathode layer surface, wherein the anode region is 3 × 10 ¹² cm ^-2 or more. So 3 × 1
A step of implanting ions with a dose amount of 0 ¹³ cm ^-2 or less;
A method of manufacturing a semiconductor device, which is characterized in that it is formed in a step of performing a low temperature heat treatment at a temperature of 00 ° C. or lower.