JP2608975B2 - Semiconductor device and igniter device using the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device that can be used as an igniter power element required to have a high withstand voltage, and an igniter device using the same.

2. Description of the Related Art Conventionally, when a MOSFET is used as an igniter as a switching element, a switching unit is configured as shown in FIG.
It was necessary to adopt a configuration in which a high withstand diode 14 for surge protection was connected between the drain and source of the MOSFET 13. In FIG. 3, 12 is a transformer and 15 is a firing point. Here, the reason why the dio 14 is necessary will be described with reference to FIG. Fig. 4 shows the operation of the MOSFET of Fig. 3.
Drain voltages at 16, 17 and at 18, 19 were shown. 4th
FIG. 4A shows the case without an external diode and FIG. 4B does not. Dashed lines 22 and 23 indicate the breakdown voltage between the drain and the source of the MOSFET. MOSFET because the load is an inductance load
At the moment when the motor stops, surges 20 and 21 of positive voltage occur.

Without an external surge protection diode, the surge voltage becomes higher than the drain-source breakdown voltage of the MOSFET, so the MOSFET breaks down between the drain and source, and as shown in Fig. 5, breaks down from the drain 28 to the source 31. When a current flows, a voltage difference occurs due to the resistance component 34 of the semiconductor substrate 35, and the parasitic bipolar transistor 33 operates to cause a temperature rise, leading to thermal destruction. Therefore, it is necessary to greatly enhance the avalanche withstand voltage at the time of the breakdown voltage of the MOSFET, or to insert a high withstand voltage diode having a breakdown voltage lower than the breakdown voltage of the MOSFET between the drain and the source of the MOSFET.

In FIG. 5, 24 is a drain electrode, 25 is a source electrode, 26 is a silicon oxide film, 27 is a gate electrode, 29 is a first conductivity type region, 30 is an extended drain-in region, and 32 is a substrate contact region.

Problems to be Solved by the Invention As described above, the conventional structure has a problem that a high withstand diode for surge protection is required.

Means for Solving the Problems In order to solve the above problems, the present invention employs the following lateral MOSFET structure.

That is, it was formed on a semiconductor substrate of the first conductivity type. Between the source region and the drain contact region of the second conductivity type,
An extended drain region of the second conductivity type in contact with the drain contact region is provided, and a first conductivity type region reverse-biased to the drain is provided on a surface in the extended drain region. In between, a separated first conductivity type region is provided, a second conductivity type region is provided in the separated first conductivity type region, and the separated first conductivity type region is electrically connected to the gate electrode, and separated. The second conductivity type region in the first conductivity type region is electrically connected to the drain electrode to form a diode between the gate and the drain, and the diode has a breakdown voltage lower than the breakdown voltage between the drain and the source. It is a structure that is made to happen.

According to the present invention, the breakdown of the diode occurs at a voltage lower than the breakdown voltage of the MOSFET, so that the current flows through the diode between the gate and the drain and the resistance between the gate and the source, so that the gate potential increases and the MOSFET operates. Therefore, the surge is absorbed by the operation of the MOSFET, and the surge can be absorbed even if the avalanche resistance of the diode between the drain and the source of the MOSFET is low.

Embodiment FIG. 1 shows a cross section of a lateral MOSFET according to an embodiment of the present invention. On the surface in the extended drain region 6 provided on the semiconductor substrate 10 of the first conductivity type, a first conductivity type region 7 reversely biased to the drain is provided. Drain 6
When a reverse voltage is applied between the source 8, the depletion layer expands from both the region 7 and the drain 6 and between the drain 6 and the substrate 10. Therefore, the concentration of the extended drain-in region is made higher than that of the structure without the region 7. In addition, since a high withstand voltage can be realized, the on-resistance between the drain 6 and the source 8 can be greatly reduced. In FIG. 1, 1 is a drain electrode, 2 is a source electrode, 3
Is a silicon oxide film, 4 is a gate electrode, 5 is a drain contact region, 9 is a substrate contact region, and 11 is a second conductivity type region.

In order to use the characteristics of the element for the igniter, the semiconductor substrate 10
a The concentration was set to 3 × E14 cm−3. The contact region 9 of the substrate 10 is formed in contact with the source region 8 and at the same time, the source electrode 2
Contact was made. Polycrystalline silicon is used as the gate electrode 4, the depth of the extended drain region 6 is 5 μm, and the depth of the first conductivity type region 7 on the extended drain region 6 is 2 μm.
m, and the depth of the second conductivity type region 11 in the separated first conductivity type region 7 ′ was 1 μm.

As a result, a breakdown voltage of the diode of 30 V was obtained. By connecting 13 of these diodes in series,
The breakdown voltage of the diode becomes 390V,
A voltage lower than the drain-to-drain breakdown voltage of 450 V was obtained. Second
The figure shows an igniter device using the transistor of FIG. 1, 12 is a transformer, 13 is the MOSFET shown in FIG. 1, 14 is a diode, and 15 is a firing point. D indicates a diode component formed between the drain and the gate of the MOSFET 13, and R indicates a resistance component formed between the gate and the source. The surge is absorbed by these diodes and the resistance components D and R, and the surge can be absorbed even if the avalanche resistance of the diode 14 between the drain and source of the MOSFET 13 is low.

As described above, by using the present invention, a diode having a breakdown voltage lower than the breakdown voltage of a MOSFET can be formed between a drain and a gate in one chip.

[Brief description of the drawings]

FIG. 1 is a sectional view of a semiconductor device according to one embodiment of the present invention, FIG. 2 is a circuit diagram of an igniter device using the same,
FIG. 3 is a circuit diagram of a conventional igniter device, and FIG.
FIG. 5 is a cross-sectional view of a parasitic bipolar transistor that operates when the breakdown occurs between the drain and source of the MOSFET, showing a waveform diagram illustrating a change in drain voltage during switching of the ET. DESCRIPTION OF SYMBOLS 1 ... Drain electrode, 2 ... Source electrode, 3 ... Silicon oxide film, 4 ... Gate electrode, 5 ... Drain contact region, 6 ... Extended drain region, 7 ... First conductivity type region, 8 ... ... source region, 9 ... substrate contact region, 10
... Semiconductor substrate, 11... Second conductivity type region.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Seiki Yamaguchi 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Denshi Kogyo Co., Ltd. In-company (72) Inventor Toshihiko Uno 1006 Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electronics Corporation

Claims (2)

(57) [Claims] 1. A method according to claim 1, wherein a second conductivity type source region and a drain contact region are formed on a first conductivity type semiconductor substrate.
An extended drain region of the second conductivity type is provided in contact with the drain contact region, a first conductivity type region reversely biased to the extended drain region is provided on a surface of the extended drain region, and the drain contact region is reverse biased to the drain contact region. Between the first conductivity type regions, a separated first conductivity type region is provided, a second conductivity type region is provided inside the separated first conductivity type region, and the separated first conductivity type region is provided with a gate electrode. A semiconductor device in which a second conductivity type region in a first conductivity type region which is electrically connected and separated is electrically connected to a drain electrode and a diode is provided between a gate and a drain. 2. An igniter device using the semiconductor device according to claim 1.