JP2614261B2 - Semiconductor switching element - Google Patents

Description

Description: 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 more particularly to a semiconductor switching element suitable for switching control of an inductive load.

(Prior Art) In the case of controlling the switching of an inductive load by switching a transistor, it is necessary to prevent the destruction of the transistor due to the induced energy generated when the load current is cut off. For this reason, conventionally, a semiconductor switching element having a configuration in which a transistor as a switching element and a flywheel diode for returning the inductive energy to the power supply side are formed on the same chip has been used. FIG. 4 shows a configuration example.

That is, in FIG. 4, 1 is an n-type collector substrate, 2
Is an n-type collector region formed by epitaxial growth on the substrate 1, 3 is a p-type base region formed by diffusion on the surface side of the collector region 2, and 4 is an n-type base region formed by diffusion on the surface side of the base region 3. This is the emitter region. 5 is a base electrode film, 6 is an emitter electrode film, and 7 is a collector electrode film. Of these, a part of the emitter electrode film 6 short-circuits a part of the base region 3 and the emitter region 4. It is provided in. Reference numeral 8 denotes an oxide film used for a diffusion mask or the like.

The equivalent circuit of the semiconductor switching element shown in FIG. 4 is as shown in FIG. That is, the transistor 9 is constituted by the collector region 2, the base region 3 and the emitter region 4, and the diode 10 is constituted by the pn junction region corresponding to the emitter electrode film 6 at the center, and the base-emitter junction and the base-collector The resistor 11 is constituted by the base region 3 interposed between the junctions.

(Problem to be Solved by the Invention) In the above-described conventional configuration, when the inductive load such as a motor is cut off by switching of the transistor 9, the diode 9 is protected by the flywheel action of the diode 10. 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, so that the voltage between the collector and the emitter of the transistor 9 is reduced. When a surge voltage is applied, the protection function of the diode 10 cannot be expected, and the transistor 9 may be destroyed.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a case where a transistor as a switching element is destroyed by inductive energy accompanying switching of an inductive load and a surge voltage applied between a collector and an emitter. It is an object of the present invention to provide a semiconductor switching element that can effectively prevent both situations from being destroyed.

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

Further, a wiring film formed so as to short-circuit 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 each other, and the auxiliary region and the collector region are short-circuited via an auxiliary wiring film.・
The distance may be set to be equal to or less than 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 constituting the transistor and the emitter region by the wiring film, this is equivalent to a state in which a flywheel diode is connected in parallel between the emitter and the collector of the transistor. Become. This prevents a situation in which the transistor is destroyed by inductive energy accompanying the switching of the inductive load. If an auxiliary region having the same characteristics as the emitter region is formed at a predetermined distance from the base region on the surface side of the collector region, a pn junction functioning as a constant voltage diode is formed. The voltage diode is equivalent to a state where the voltage diode is connected between the collector and the emitter of the 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 is filled with a depletion layer. On the other hand, the distance between the auxiliary region and the base region is set to be 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 the base of the transistor. Therefore, when a surge voltage is applied between the collector and the emitter of a transistor, the constant voltage diode breaks down before a breakdown occurs between the collector and the base of the transistor. The situation of being destroyed by the voltage is also prevented.

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 the auxiliary region and the collector region are short-circuited via an auxiliary wiring film. In this configuration, a pn junction that functions as a constant-voltage diode is formed, and this constant-voltage diode is equivalent to a state in which it is connected between the collector and emitter. The situation of being destroyed by the voltage is prevented. In particular, in the case of this configuration, since the auxiliary region and the base region have the same characteristics and can be formed in the same process, the distance between them can be strictly controlled. As a result, the breakdown voltage of the constant voltage diode determined by the distance between the auxiliary region and the base region can be set as desired and strictly.

(Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to the drawings.

In FIG. 1 showing a cross-sectional model structure, reference numeral 21 denotes an n-type substrate, on which a collector region 22 is formed by epitaxial growth. Reference numeral 23 denotes a p-type base region, which is formed by diffusing an impurity (acceptor) into a portion other than the center of the collector region 22.
Reference numeral 24 denotes an n-type emitter region, which is formed by diffusing an impurity (donor) on the base region 23.
As described above, the collector region 22 and the base region 23 are formed on the substrate 21.
And an emitter region 24, and a collector electrode film 25, a base electrode film 26, and an emitter electrode film 27 as shown in the figure.
Forming npn as a switching element
This forms a bipolar transistor 28 (see FIG. 2).

An auxiliary region 29 having the same characteristics as that of the emitter region 24 is provided at the center of the collector region 22 on the front surface side.
The auxiliary region 29 is formed at the same time in a diffusion step for forming the emitter region 24. 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 the base of the transistor 28. Reference numeral 30 denotes a wiring film formed on the substrate 21 so as to short-circuit a part of the base region 23 and the emitter region 24. The wiring film 30 includes the base electrode film 26 and the emitter electrode film 27.
Are formed simultaneously with the formation of Reference numeral 31 denotes an oxide film used for a diffusion mask and for forming a contact hole.

FIG. 2 shows an equivalent circuit of the semiconductor switching element configured as described above. That is, the transistor
As a result of a short circuit between the part of the base region 23 forming the base region 23 and the emitter region 24 by the wiring film 30, as shown by the broken line in FIG. A diode 32 for a flywheel is formed in the pn junction region between the regions 22, and the base 32
A resistor 33 is formed by the base region 23 sandwiched between the junction between the emitter and the junction between the base and the collector, and a constant voltage diode 34 is formed in a 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 induced energy generated by the switching is returned to the power supply through the diode 32, so that the breakdown 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 is filled with a depletion layer.
In this case, the distance between the auxiliary region 29 and the base region 23 is set to be 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 the base of the transistor 28. Therefore, when a surge voltage is applied between the collector and the emitter of the transistor 28, the constant voltage diode 34 breaks down before a breakdown occurs between the collector and the base of the transistor 28. Is prevented from being destroyed by the surge voltage.

FIG. 3 shows a second embodiment of the present invention, and only the portions different from the first embodiment will be described below. That is, reference numeral 35 denotes an auxiliary region formed in the central portion on the front surface side of the collector region 22, which is formed simultaneously with a predetermined distance from the base region 23 in a diffusion step for forming the base region 23. Thus, they are provided to have the same characteristics as the base region 23. Also in this case, the distance between the auxiliary region 35 and the base region 23 is set to be 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 the base of the transistor 28. . 36 is also the collector area 22
A conduction securing region formed adjacent to the auxiliary region 35 in the central portion on the front surface side of the semiconductor device, and is formed simultaneously with the emitter region 24 in a diffusion process for forming the emitter region 24; It is provided to have the same characteristics as the region 24. Reference numeral 37 denotes an auxiliary wiring film formed on the substrate 21 so as to short-circuit the auxiliary region 35 and the conduction securing region 36. It is formed. As a result of the provision of the auxiliary wiring film 37, the auxiliary region 35 and the collector region 22 are short-circuited through the conduction securing region 36.

Thus, an equivalent circuit of the semiconductor switching element configured as described above is as shown in FIG. That is, as shown by the broken line in FIG. 3, a flywheel diode 32 is formed in a pn junction region between the base region 23 and the collector region 22 at a position near the center of the base region 23, and The point that the resistor 33 is constituted by the base region 23 sandwiched between the inter-junction and the junction between the base and the collector is the same as that of the first embodiment, and the base region 22 side between the auxiliary region 36 and the base region 22 The constant voltage diode 38 is formed in the pn junction region portion of FIG. Therefore, the present embodiment also provides the same effects as the first embodiment. In particular, according to the present embodiment, since the auxiliary region 35 and the base region 23 have the same characteristics and can be formed in the same step using the same diffusion mask, the distance between them is strictly controlled. It 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 strictly.

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 scope of the invention, for example, a pnp transistor may be used instead of an npn transistor. Can be implemented.

[Effects of the Invention] As is apparent from the above description, according to the first aspect of the present invention, in addition to the flywheel diode, breakdown occurs between the collector and the base of the transistor before the breakdown occurs due to the surge voltage. Because of the configuration having the constant voltage diode, both the case where the transistor is destroyed by the inductive energy accompanying the switching of the inductive load and the case where the transistor is destroyed by the surge voltage applied between the collector and the emitter are both caused. It can be effectively blocked.

According to the second aspect of the present invention, the breakdown voltage of the constant voltage diode can be set as desired and strictly, so that there is no possibility that the effect of preventing breakdown of the transistor becomes unstable.

[Brief description of the drawings]

1 and 2 show a first embodiment of the present invention. FIG. 1 is a diagram showing a cross-sectional model structure, and FIG. 2 is an equivalent circuit diagram. FIG. 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 FIGS. 1 and 2 for explaining a conventional example, respectively. In the figure, 21 is a substrate, 22 is a collector region, 23 is a base region,
24 is the emitter region, 28 is the transistor, 29 is the auxiliary region,
Reference numeral 30 denotes a wiring film, 32 denotes a diode, 33 denotes a resistor, 34 denotes a constant voltage diode, 35 denotes an auxiliary area, 36 denotes a conduction securing area, 37 denotes an auxiliary wiring film, and 38 denotes a constant voltage diode.

Claims (2)

(57) [Claims] 1. A semiconductor switching element comprising a transistor having a base region formed on a surface side of a collector region of a substrate and an emitter region formed on a surface side of the base region as a switching element. A wiring film formed so as to short-circuit a part of the base region and the emitter region is provided, and an auxiliary region having the same characteristics as the emitter region is provided on the surface side of the collector region at a predetermined distance from the base region. And the distance between the auxiliary region and the base region is set to a distance 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 the base of the transistor. A semiconductor switching element characterized by the above-mentioned. 2. A semiconductor switching element comprising 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 as a switching element. A wiring film formed so as to short-circuit a part of the base region and the emitter region is provided, and 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. 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 reduced by the breakdown voltage between the collector and the base of the transistor. A semiconductor switching element characterized in that the distance is set to be equal to or less than the extension of the depletion layer in the collector region when added.