JPH01245555A - Semiconductor switching element - Google Patents

Abstract

PURPOSE:To prevent a breakdown of a transistor due to a conduction energy and a breakdown of the transistor due to a surge voltage by a method wherein the title element is formed into a constitution, wherein a constant-voltage diode to be broken down before the collector-base of the transistor is broken down by the surge voltage is provided in addition to a diode for a flywheel. CONSTITUTION:As a result that the electrical connections between part, constitutes a transistor 28, of a base region 23 and emitter regions 24 are short- circuited by a wiring film 30, a constant-voltage diode 34 is constituted at a P-N junction region part between an auxiliary region 29 and the base region 23. Accordingly, as an inductive energy, which is generated when a switching of an inductive load is performed by the transistor 28, is returned to a power supply through a diode 32, a breakdown of the transistor 28 is prevented. On the other hand, in case a surge voltage is applied between a collector-emitter of the transistor 28, the diode 34 is broken down before the collector-base is broken down. Thereby, a situation that the transistor 28 is broken by the surge voltage is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a semiconductor switching element using a bipolar transistor as a switching element, and particularly to a semiconductor switching element suitable for controlling switching of an inductive load.

(Prior Art) When controlling the conduction and disconnection of an inductive load by switching transistors, it is necessary to prevent the transistor from being destroyed due to the induced energy generated when the load current is interrupted. For this reason, conventionally, a semiconductor switching element has been used in which a transistor as a switching element and a flywheel diode for circulating the above-mentioned induced energy to the power supply side are formed on the same chip. An example of the configuration is shown in FIG.

That is, in FIG. 4, 1 is an n-type collector substrate, 2 is an n-type collector region formed on the substrate 1 by epitaxial growth, 3 is a p-type base region formed by diffusion on the surface side of the collector region 2, 4 is an n-type emitter region formed on the surface side of the base region 3 by diffusion. Further, 5 is a base electrode film, 6 is an emitter electrode film, and 7 is a collector electrode film, of which a part of the emitter electrode film 6 is
It is provided so as to short-circuit between a part of the base region 3 and the emitter region 4. Note that 8 is an oxide film used as a diffusion mask or the like.

The equivalent circuit of the semiconductor switching element shown in Fig. 4 above is shown in Fig. 5.
The result will be as shown in the figure. That is, collector area 2. The base region 3 and the emitter region 4 constitute a transistor 9, and the pn junction region corresponding to the emitter electrode film 6 in the center constitutes a diode 10, which is sandwiched between a base-emitter junction and a base-collector junction. A resistor 11 is formed by the base region 3 .

(Problems to be Solved by the Invention) In the conventional configuration described above, when the inductive load such as a motor is cut off by switching the transistor 9,
The flywheel action of diode 10 provides protection for transistor 9.

However, in the above configuration, the breakdown voltage between the collector and the base of the transistor 9 is the same as the breakdown voltage when a reverse voltage is applied to the diode 10. When a surge voltage is applied, the diode 10
Therefore, the protection function of transistor 9 cannot be expected.
There is a risk that it may be destroyed.

The present invention has been made in view of the above circumstances, and its purpose is to prevent the situation where a transistor, which is a switching element, is destroyed by inductive energy accompanying switching of an inductive load, and the surge voltage applied between the collector and emitter. It is an object of the present invention to provide a semiconductor switching element that can effectively prevent the destruction of both elements.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention forms a base region on the surface side of the collector region of the substrate, and also forms an emitter region on the surface side of the base region. A semiconductor switching element having a transistor formed as a switching element, wherein a wiring film formed to short-circuit between a part of the base region and the emitter region is provided on the substrate, and the collector region An auxiliary region having the same characteristics as the emitter region is formed on the surface side of the transistor at a predetermined distance from the base region, and the distance between the auxiliary region and the base region is set to a break between the collector and base of the transistor. The configuration is such that the distance is set to be less than or equal to the extension of the depletion layer in the collector region when a down voltage is applied.

Further, a wiring film formed to short-circuit between a part of the base region and the emitter region is provided on the substrate, and an auxiliary region having the same characteristics as the base region is provided on the surface side of the collector region. The auxiliary region and the collector region are formed at a predetermined distance from the base region, and the auxiliary region and the collector region are short-circuited via an auxiliary wiring film, and the distance between the auxiliary region and the base region is set to the collector region of the transistor. - The distance may be set to be less than or equal to the extension of the depletion layer in the collector region when a breakdown voltage is applied between the bases.

(Operation) As a result of short-circuiting between a part of the base region and the emitter region that constitute the transistor by the wiring film, this is equivalent to a state in which a flywheel diode is connected in parallel between the emitter and collector of the transistor. Become. This prevents the transistor from being destroyed by the induced energy associated with switching the inductive load. If an auxiliary region with the same characteristics as the emitter region is formed on the surface side of the collector region at a predetermined distance from the base region, a pn junction that functions as a constant voltage diode is formed, and this constant The voltage diode is equivalent to being connected between the collector and emitter of a transistor with the same polarity as the diode. At this time, the constant voltage diode breaks down when the collector region located between the auxiliary region and the base region becomes filled with a depletion layer. On the other hand, the distance between the auxiliary region and the base region is set to be less than or equal to the extension of the depletion layer in the collector region when a breakdown voltage is applied between the collector and base of the transistor. Therefore, if a surge voltage is applied between the collector and emitter of a transistor, the voltage regulator diode will break down before the voltage between the collector and base of that transistor breaks down, and the transistor will respond to the surge voltage. It also prevents damage caused by voltage.

On the other hand, an auxiliary region having the same characteristics as the base region is formed on the surface side of the collector region at a predetermined distance from the base region, and an auxiliary wiring film is provided between the auxiliary region and the collector region. Even in the case of a short-circuit configuration, a pn junction is formed that functions as a constant voltage diode, and this is equivalent to a condition in which the constant voltage diode is connected between the collector and emitter. This prevents the situation from being destroyed.

Particularly in this configuration, the auxiliary region and the base region have the same characteristics and can be formed in the same process, making it possible to strictly control the distance between them. As a result, the breakdown voltage of the voltage regulator diode determined by the distance between the auxiliary region and the base region can be set as desired and precisely.

(Example) Hereinafter, a first example of the present invention will be described with reference to FIGS. 1 and 2.

In FIG. 1 showing the cross-sectional model structure, 21 is an n-type substrate, and a collector region 22 is formed on the upper surface of this by epitaxial growth. Reference numeral 23 denotes a p-type base region, which is formed by diffusing impurities (acceptors) into a portion of the collector region 22 other than the central portion. Reference numeral 24 denotes an n-type emitter region, which is formed by diffusing impurities (donors) onto the base region 23. In this way, the collector region 22 is placed on the substrate 21.
, a base region 23 and an emitter region 24 are formed, and a collector electrode film 25° and a base electrode film 2 are formed as shown in the figure.
6 and an emitter electrode film 27, an npn type bipolar transistor 28 (see FIG. 2) as a switching element is constructed.

Now, an auxiliary region 29 having the same characteristics as the emitter region 24 is provided at the center of the surface side of the collector region 22 at a predetermined distance from the base region 23. , are formed simultaneously in the diffusion process for forming the emitter region 24. In this case, the distance between the auxiliary region 29 and the base region 23 is set to be less than or equal to the extension of the depletion layer in the collector region 22 when a breakdown voltage is applied between the collector and base of the transistor 28. Further, 30 is a substrate 21
A wiring film is formed on the base electrode film 23 to short-circuit between a part of the base region 23 and the emitter region 24, and is formed at the same time as the base electrode film 26 and the emitter electrode film 27 are formed. Note that 31 is an oxide film used for a diffusion mask and for forming contact holes.

An equivalent circuit of the semiconductor switching element configured as described above is shown in FIG. That is, transistor 2
A part of the base region 23 and the emitter region 24 constituting the
As a result, as shown by the broken line in FIG. 32 is configured, and the base-emitter junction and the base-emitter junction are connected to each other.
Base region 23 sandwiched between collector and collector junctions
A resistor 33 is configured, and a constant voltage diode 34 is configured in the pn junction region between the auxiliary region 29 and the base region 22. Therefore, when the inductive load is switched by the transistor 28, the inductive energy generated by the switching is circulated back to the power supply through the diode 32, so that destruction of the transistor 28 is effectively prevented. On the other hand, the constant voltage diode 34 breaks down when the collector region 22 located between the auxiliary region 29 and the base region 23 becomes filled with a depletion layer. In this case, the distance between the auxiliary region 29 and the base region 23 is set to a distance equal to or less than the extension of the depletion layer in the collector region 22 when a breakdown voltage is applied between the collector and base of the transistor 28. Therefore, when a surge voltage is applied between the collector and emitter of the transistor 28, the voltage regulator diode 34 breaks down before the voltage between the collector and the base breaks down, and as a result, the voltage regulator diode 34 breaks down before the voltage between the collector and the base breaks down. This will prevent the damage caused by the surge voltage.

A second embodiment of the present invention is shown in FIG. 3, and only the differences from the first embodiment will be described below. That is, 35 is an auxiliary region formed at the center of the surface side of the collector region 22, which is formed simultaneously with the base region 23 at a predetermined distance in the diffusion process for forming the base region 23. , so base area 2
It is provided so that it has the same characteristics as 3. In this case as well, the distance between the auxiliary region 35 and the base region 23 is the distance between the collector region 22 and the base region 23 when a breakdown voltage is applied between the collector and base of the transistor 28.
The distance is set to be less than the extension of the depletion layer at . Reference numeral 36 denotes a conduction ensuring region which is also formed in the central part of the front surface side of the collector region 22 so as to be adjacent to the auxiliary region 35. The emitter region 24 is formed so as to have the same characteristics as the emitter region 24. Also,
Reference numeral 37 indicates an auxiliary region 35 and a conduction ensuring region 3 on the substrate 21.
This is an auxiliary wiring film formed to short-circuit between base electrode films 26 and 26. Emitter electrode film 27 and wiring film 29
is formed simultaneously with the formation of . In this way, the auxiliary wiring film 3
As a result of providing 7, the auxiliary area 35 and the collector area 22
A short circuit is created between the conduction ensuring region 36 and the conduction ensuring region 36.

Therefore, the equivalent circuit of the semiconductor switching element configured as described above is also shown in FIG. That is, the third
As shown by the broken line in the figure, the pn between the base region 23 and the collector region 22 in the central region of the base region 23 is
Diode 3 for the flywheel in the junction area
2 is formed, and the point where the resistor 33 is formed by the base region 23 sandwiched between the base-emitter junction and the base-collector junction is the first point.
Furthermore, a constant voltage diode 38 is configured in the pn junction region portion on the base region 22 side between the auxiliary region 36 and the base region 22. Therefore, this embodiment also provides the same effects as the first embodiment. In particular, according to this embodiment, the auxiliary region 35 and the base region 23 have the same characteristics and can be formed in the same process using the same diffusion mask, so the distance between them can be strictly controlled. becomes possible.

As a result, the breakdown voltage of the constant voltage diode 38, that is, the breakdown voltage determined by the distance between the auxiliary region 35 and the base region 23, can be set as desired and precisely.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, and various modifications may be made without departing from the gist, such as for example, a pnp transistor may be used instead of an npn transistor. It can be implemented by

[Effects of the Invention] As is clear from the above description, according to the invention of claim 1, in addition to the flywheel diode, the transistor's collector φ base breaks down before it breaks down due to surge voltage. Since the configuration includes a constant voltage diode, it is possible to prevent both the above transistor from being destroyed by inductive energy due to switching of an inductive load, and the transistor from being destroyed by surge voltage applied between the collector and emitter. This can be effectively prevented.

Further, according to the second aspect of the present invention, the breakdown voltage of the constant voltage diode can be set as desired and precisely, so there is no possibility that the effect of preventing destruction of the transistor will become unstable.

[Brief explanation of the drawing]

1 and 2 show a first embodiment of the present invention, in which FIG. 1 shows a cross-sectional model structure, and FIG. 2 shows an equivalent circuit diagram. 3 is a diagram corresponding to FIG. 1 showing a second embodiment of the present invention, and FIGS. 4 and 5 are diagrams corresponding to FIG. 1 and 2, respectively, for explaining a conventional example. In the figure, 21 is a substrate, 22 is a collector region, 23 is a base region, 24 is an emitter region, 28 is a transistor, 29
30 is an auxiliary region, 30 is a wiring film, 32 is a diode, 33 is a resistor, 34 is a constant voltage diode, 35 is an auxiliary region, 36
37 is an auxiliary wiring film, and 38 is a constant voltage diode.

Claims (1)

[Scope of Claims] 1. A semiconductor switching element in which a switching element is a transistor having a base region formed on the surface side of a collector region of a substrate and an emitter region formed on the surface side of the base region. A wiring film formed to short-circuit between a part of the base region and the emitter region is provided on the substrate, and an auxiliary region having the same characteristics as the emitter region is provided on the surface side of the collector region in the base region. and the distance between the auxiliary region and the base region is equal to or less than the extension of the depletion layer in the collector region when a breakdown voltage is applied between the collector and base of the transistor. A semiconductor switching element characterized by: 2. In a semiconductor switching element using a transistor as a switching element, a base region is formed on the surface side of a collector region of a substrate, and an emitter region is formed on the surface side of this base region, in which the base region is formed on the substrate. A wiring film formed to short-circuit between a part of the collector region and the emitter region is provided, and an auxiliary region having the same characteristics as the base region is provided at a predetermined distance from the base region on the surface side of the collector region. At the same time, the auxiliary region and the collector region are short-circuited via an auxiliary wiring film, and the distance between the auxiliary region and the base region is set such that when a breakdown voltage is applied between the collector and base of the transistor, A semiconductor switching element characterized in that the distance is set to be less than or equal to the extension of the depletion layer in the collector region.