JPH0665231B2 - Reverse conduction type gate turn-off thyristor - Google Patents

Description

Description: FIELD OF THE INVENTION This invention relates to reverse conducting gate turn-off (GTO) thyristors.

2. Description of the Related Art Generally, a GTO thyristor often employs a circuit configuration in which a diode 2 is connected in antiparallel between an anode and a cathode of a GTO thyristor 1 as shown in FIG. In this circuit, it is desirable that the inductance of the connecting line of the diode 2 be as small as possible, and the GTO thyristor part and the diode part are integrated on the same silicon substrate in the reverse conduction type.
Commercialization of GTO thyristors is required.

The GTO thyristor requires reverse breakdown voltage of the cathode junction (P ₂ N ₂ junction) in order to shift the main current (load current) to the off state by reverse biasing between the cathode and gate. The higher this breakdown voltage, the higher the GTO thyristor. The turn-off function of the thyristor is improved. However, in the conventional reverse conducting thyristor structure, the cathode junction is short-circuited, and there is a problem in the configuration of the reverse conducting GTO thyristor.

Therefore, conventionally, a thyristor section and a diode section are formed on the same silicon substrate, but a gate embedded structure is used to form a layer for separating the thyristor section and the diode section (for example, Japanese Utility Model Laid-Open No. 57-108354). ) Or a structure as shown in FIG. 6 (for example, Japanese Patent Laid-Open No. 58-128766).

In FIG. 6, the P ₁ N ₁ P ₂ N ₂ part is the GTO thyristor part, the P ₃ N ₁ N ₃ part formed via the isolation region is the diode part, and the divided N ₂ layer and P ₃ layer Are connected by the same electrode to form a cathode electrode K, the P ₁ layer and the N ₃ layer are connected by the same electrode to form an anode electrode A, and the divided P ₂ layer electrode forms a gate electrode G. Japanese Patent Application Laid-Open No. 58-73159 has the same structure as this.
JP-A-59-21063 and JP-A-59-21063.

Problems to be Solved by the Invention A conventional structure having a layer for separating the thyristor part and the diode part and having a gate-embedded structure separates a short circuit due to the diode part with the separation layer while increasing the reverse breakdown voltage of the cathode junction. However, there is a problem that the element manufacturing becomes difficult.

On the other hand, all of the structures shown in FIG. 6 are easy to manufacture in that they can be formed by the diffusion method, but the forward blocking voltage as a reverse conducting GTO thyristor element depends on the junction surface 3 of the N ₁ P ₂ junction. It is necessary to lower the surface concentration of the P ₂ layer. For this reason, increasing the lateral resistance of the gate layer P ₂ makes it difficult for the gate current to flow, making it difficult to select the highest concentration, and it is still in the state of laboratory level development and is not commercialized. is there.

In addition, as another problem of the structure shown in FIG. 6, N ₂ and P ₃ should be used to increase the heat dissipation efficiency in constructing an element having a large current capacity.
A structure in which a common electrode is pressed against the surface of each layer is adopted, but since the N ₁ P ₂ bonding surface 3 is on the same surface as N ₂ and P ₃ , there is a problem in protecting the bonding surface during electrode pressing. In the small-current element, aluminum bonding wires are used to connect N ₂ and P ₃ layers.

Means and Actions for Solving Problems According to the present invention, the thyristor portion and the diode portion are formed as independent epitaxial growth layers and formed into a structure having a planar junction state, and further, an amplification gate portion is formed in the diode portion. The structure is used to ensure and facilitate the separation of the junction between the thyristor part and the diode part.

Embodiment FIG. 1 is a half sectional structural view showing an embodiment of the present invention.
The GTO thyristor part 1A is formed in the central part of the substrate, and the diode part 2A is formed in an annular shape in the peripheral part of the substrate. Both parts have the N ₁ layer as a common base layer, and the thyristor part 1A has the buried gate layer P ₂ ⁺⁺ in the P ₁ ⁺ , N ₁ , P ₂ , N ₂ layers and the P ₂ layer, and the gate electrode G is It is formed on the P ₅ layer formed in the epitaxially grown layer P ₂ ⁻ at the center of the substrate, and the cathode electrode K is formed on the N ₂ layer in a ring shape around the gate electrode G, at the boundary between the electrodes G and K. The oxide film SiO ₂ at the time of forming both the electrodes and the N ₂ layer and the P ₅ layer region is left. In the buried gate layer P ₂ ⁺⁺ , the main current path is secured in a radial or lattice pattern in the portion facing the cathode N ₂ layer, and the portion for the gate P ₅ layer is formed over the entire surface to form the main current path. Refuse.

The diode portion 2A has N ₁ and P ₃ ⁺ layers, and the cathode electrode K is formed on the P ₄ layer formed on the epitaxially grown layer P ₂ ⁻ on the P ₃ ⁺ layer.
_D is formed. Then, when the P ₃ ⁺ layer, P ₂ ⁺ layer is formed and the epitaxial layer P ₂ ^- is formed, the oxide film SiO ₂ is left on the N ₁ P ₃ ⁺ , N ₁ P ₂ ⁺ junction surface to form a planar junction state. To be done. Electrode K _D
A ring-shaped cathode electrode plate 4 which also serves as a heat sink is pressed against and K, and similarly, an anode electrode plate 5 is pressed against an anode electrode A common to the thyristor portion and the diode portion.

The characteristic of this structure is that N ₁ P ₂ ⁺
Bonding and N ₁ part P ₃ ⁺ suppressing surface impurity concentration at the time of bonding low and with the exception of the joining surface portion selectively epitaxial growth layer P ₂ on the other side ^- to form, the epitaxial growth layer To form the other joints needed. Further, when voltage is applied between the electrode plates 4 and 5, the junctions N ₁ P ₂ ⁺ and N ₁ P ₃ ⁺ each independently block the forward voltage in the planar junction state,
The breakdown voltage is influenced by the state of the silicon interface of the diode portion oxide film SiO ₂ , but is mechanically separated from the electrode plate 4 to eliminate the adverse effect of the pressure contact connection of the electrode plate 4.

A method of manufacturing a main part of the structure shown in FIG. 1 will be described with reference to FIG. Fig. 2
As shown in (a), an oxide film SiO ₂ is formed on the N-type silicon wafer.
After the formation of P, a window is opened in the P ₁ ⁺ , P ₂ ⁺ , P ₃ ⁺ layer pattern by photoetching, and boron is selectively diffused in this portion, for example, P ₁ ⁺
The layer, P ₂ ⁺ layer, and P ₃ ⁺ layer are collectively formed. Next, an oxide film SiO ₂ again entirely, as shown in FIG. 2 (b), oxide film SiO ₂
Then, a window is opened in the pattern of the buried gate layer P ₂ ⁺⁺ and, for example, boron is diffused at a high concentration to form a P ₂ ⁺⁺ layer. An oxide film is formed again, the window is opened, and the P ₃ ⁺ layer and P ₂ ⁺ layer are opened as shown in Fig. 2 (c).
The epitaxial layer P ₂ ⁻ is formed on the P ₂ ⁺⁺ layer. After that, phosphorus is selectively diffused again using the oxide film.
Form N ₃ layer and N ₂ layer, and similarly diffuse boron, for example.
Form P ₄ and P ₅ layers. Here, the P ₁ ⁺ layer and the P ₂ ⁺ layer are formed at substantially the same position. Further, P ₂ ^- layer P ₂ ^- N ₂ shall apply those to determine the reverse breakdown voltage of the configured thyristor cathode bonded by bonding is the resistance of about 1~5Ω-cm, P ₅ layers and P ₄ layers gate a diffusion layer for connecting the electrode G and K _D to a low resistance. Further, the bonding N ₁ P ₂ ⁺ surface and the N ₁ P ₃ ⁺ surface are each protected by an oxide film, and a protective film such as silicon rubber or glass is formed in this concave portion if necessary.

FIG. 3 shows another embodiment of the present invention. The difference between FIG. 1 and FIG. 1 is that a small area amplification gate section AG for amplifying a gate current is formed in the central portion of the thyristor section. In this case, the buried gate layer P ₂ ⁺⁺ is separated from the P ₂ ⁺⁺ layer facing the thyristor portion 1A, and P ₂₂ ⁺⁺ is N _{4 of the} amplification gate portion AG.
Formed opposite the layer. Further, the outer peripheral portion of the buried gate layer P ₂ ⁺⁺ thyristor unit 1A wide annular buried layer P ₂ ⁺⁺ is formed from the layer P ₂ ⁺⁺ through the wire 6 from the AG portion cathode K _AG An amplification gate current is supplied to the thyristor unit 1A.

The epitaxial growth layer P ₂ ⁻ is formed in the same manner as in FIG. 1 except that it is formed avoiding the buried gate layer around the thyristor portion.
Further, the electrode plate 4 is provided with holes necessary for passing the conducting wire 6.

In the present embodiment, the built-in amplification gate section AG reduces the sweep resistance at turn-off by causing the off-gate current of the thyristor section to flow from the peripheral section, and the reverse conducting diode section 2A has a large current capacity around the wafer. It can be taken big.

FIG. 4 shows still another embodiment of the present invention. The difference from FIG. 3 is that the amplification gate section AG and the diode section 2A are provided on the same P ₃ ⁺ layer. That, and the buried gate layer P ₃ ⁺⁺ for the gate portion AG and the diode portion 2A to P ₃ ⁺ layer on which is provided separately from the P ₂ ⁺ layer of the thyristor unit, the epitaxial layer P ₃ ^- on the N ₄ layers, P ₄ layer on the outside of the layer, P ₅ layer for the gate on the center layer, and P ₆ layer for low resistance connection on the buried gate layer P ₂ ⁺⁺ layer in the thyristor part 1A Electrode G _S and amplification gate section
The cathode electrode K _{AG of the AG} is connected by a conductive wire 6, and the cathode electrode plate 4 is arranged across the diode portion 2A. Also,
The oxide film SiO ₂ is left during the formation of the epitaxial layers P ₂ ⁻ , P ₃ ⁻ and during the formation of the P ₂ ⁺ , P ₃ ⁺ layers, and the bonding surface is in a planar bonding state.

In FIG. 3, in order to prevent the gate firing current injected from the gate electrode G from being shunted to the N ₂ phase side of the thyristor portion 1A and increasing the gate firing current, the thyristor portion is prevented.
P ₂ between the 1A and the amplifying gate section AG ^- whereas it is necessary to increase the width of the layer, than those of the present structure P ₂ ^{- -} The P ₂ in order to increase the sheet resistance through the layer diverted P ₂ layer and P of the gate current
It is completely separated into _three layers, and the diode section 2A is provided between the thyristor section 1A and the amplification gate section AG, resulting in a structure with good area efficiency.

EFFECTS OF THE INVENTION According to the present invention, the thyristor portion and the diode portion are selectively separated by the independent epitaxial growth layer, so that the conventional etching does not require digging, and the protective measure against the pressure electrode plate is sure and easy. Become. In addition, a planar junction can be formed and the surfaces of the N ₁ P ₂ junction and N ₁ P ₃ junction can be reliably protected, and the pressure contact of the cathode side electrode plate can be ensured and facilitated. It is possible to form a diode portion that has less influence on the thyristor portion such as a sweep resistance and facilitate the formation of the thyristor portion.

[Brief description of drawings]

FIG. 1 is a half sectional structural view showing an embodiment of the present invention, FIG. 2 is a view showing a manufacturing process of a main part of FIG. 1, and FIGS. 3 and 4 are other embodiments of the present invention. FIG. 5 is a circuit diagram of a reverse conducting GTO thyristor, and FIG. 6 is a conventional reverse conducting GTO thyristor structure diagram. 1 ... GTO thyristor, 2 ... reverse conduction diode, 4
...... Cathode electrode plate, 5 …… Anode electrode plate, 6 …… Lead wire, 1A …… GTO thyristor part, 2A …… Diode part, AG
...... Amplification gate part, G ・ ・ ・ Gate electrode, K ・ ・ ・ Cathode electrode, A ・ ・ ・ Anode electrode.

Claims (2)

[Claims] 1. A thyristor portion having a P ₁ N ₁ P ₂ N ₂ layer, and
In a reverse conduction type gate turn-off thyristor which forms a diode section having a P ₃ N ₁ layer with the N ₁ layer as a common base layer in antiparallel, the P ₂ layer of the thyristor section and the P ₃ layer of the diode section are P ₂ ⁺ and P ₃ ⁺ layers separated and formed on the surface of the N ₁ layer by a relatively high concentration impurity diffusion, and a buried gate layer formed by high-concentration impurity diffusion by opening a window on the P ₂ ⁺ layer surface in a pattern P ₂ ⁺⁺ and the P ₂ ⁺⁺ layer and P ₂ ⁺ a layer plane of the layer and the P ₃ ⁺ respectively to the layer plane and separated epitaxially growing low concentration P ₂ ^- layer and the N ₁ P ₃ ⁺ and N A reverse conduction type gate turn-off thyristor characterized by a structure having an oxide film for forming a ₁ P ₂ ⁺ junction surface in a planar junction state. 2. A first term claims, P ₂ separated formed by the epitaxial growth ^{_{- P 1 N 1 P 2 N}} 4 in one of the layers
A reverse conduction type gate turn-off thyristor having a structure in which an amplification gate part of a layer and the diode part are formed and a thyristor part having a main current of the amplification gate part as a gate current is formed on the other side.