JPH02270377A - Switching element - Google Patents

Abstract

PURPOSE:To obtain a switching element which is small in ON-voltage and operable even at a voltage of 0.7V or below between a drain and a source by a method wherein the switching element is composed of a MOSFET and an IGBT connected in parallel. CONSTITUTION:A MOSFET 2 and an IGBT 3 are connected together in parallel to constitute a switching element of this design. For instance, the MOSFET 2 and the IGBT 3 are built in an integral structure on a P-type silicon substrate, and a source electrode 7, a drain electrode 10, and a gate electrode 13 of the MOSFET 2 are commonly connected with a source electrode 17, a drain electrode 20, and a gate electrode 23 of the IGBT 3 respectively. In an element constituted as above, when the voltage between the drain and source is 0.7V or lower, the MOSFET 2 operates and a drain current flows conforming a voltage-current characteristic Z of the MOSFET 2. When the voltage between the drain and source is 0.7V or above, both the MOSFET 2 and the IGBT 3 operate and a drain current X flows conforming the sum of the voltage-current characteristic curves Z and Y of the MOSFET 2 and the IGBT 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a switching element suitable for use in swing power supplies and the like.

[Conventional technology]

Conventionally, as switching elements, insulated gate field effect transistors, so-called MOSFETs, and insulated gate bipolar transistors, so-called IGBTs are known.

Here, as shown in the third factor, the IGBT has voltage-current characteristics similar to the forward characteristics of a -PN diode. In other words, even if the gate is opened, the drain-source voltage is 0 due to the built-in potential of the PN junction.
．． At 7 (V) or less, no drain current flows, but when a voltage higher than the built-in potential is applied, conductivity modulation occurs and the current suddenly begins to flow.

On the other hand, as shown in Figure 4, in a MOS FET, when the gate is opened, the drain-source voltage decreases to 0.7 (
Although the drain current flows even if the voltage is below V), conductivity modulation does not occur even if the drain current starts flowing, so the on-voltage is small compared to that of an IGBT.

[Problem to be solved by the invention]

As mentioned above, although IGBTs have the advantage of having a small on-state voltage, the drain-source voltage is 0.7 (
V) has the disadvantage that it does not work below, and on the other hand, MO
For SFET, the voltage between drain and source 2 is 0.7 (V)
Although it has the advantage of being able to operate even below this level, it has the disadvantage of having a large on-state voltage.

For this reason, there was a problem in that the uses of each of them were limited.

In view of these points, the present invention has a small on-voltage, and
It is an object of the present invention to provide a switching element that can operate even at a drain-to-source voltage of 0.7 (V) or less.

[Means to solve the problem]

The switching element of the present invention includes a MOS FET,
IGBTs are connected in parallel.

[Effect]

When the drain-source voltage is 0.7 (V) or less, the MOSFET operates and a drain current flows according to the voltage-current characteristics of the MOSFET.

In addition, when the drain-source voltage is 0.7 (V) or more, both the MOSFET and IGBT operate, and in these MOSFET and IGBT, each MOSFET and IGBT operate.
A drain current flows according to the voltage-current characteristics of the SFET and IGBT. As a result, the on-voltage of the present invention is MO
It is smaller than the on-voltage of SFET and IGBT.

〔Example〕

Below, l! An embodiment of the present invention will be described with reference to FIG. 1 and FIG. 2.

FIG. 1 is a sectional view showing a main part of an embodiment of the present invention, in which the switching element of this embodiment is mounted on a P-board silicon substrate.
MOS FET 2 and IGBT 3 are built into the base, and these are connected in parallel.

Here, 4 is an N layer grown on the P-type silicon substrate 1;
5 is a P layer selectively formed on the surface side of 8 layer 4, 6 is 2
A source region 6 is made of an N layer formed on the surface side of layer 5, and a source electrode 7 made of aluminum is ohmically connected to this source region 6. In addition, 8
is a PSG film.

Further, 9 is a drain region made of an N layer, and a drain electrode 10 made of aluminum is ohmically connected to this drain region 9.

Further, 11 is a gate insulating film, 12 is a gate electrode made of polysilicon, and a gate electrode 13 made of aluminum is laminated on this gate electrode 12 made of polysilicon.

Further, 14 is a P layer forming an element isolation band, 15 is a P layer selectively formed on the surface side of 8 layers 4, and 16 is an N layer formed on the surface side of 8 layers 4. A source electrode 17 made of aluminum is ohmically connected to the layers 15 and 8 layers 16.

In addition, 18 is N selectively formed on the surface side of the 8 layer 4.
Layer 19 is a P layer selectively formed on the narrow side of eight layers 18, and a drain electrode head made of aluminum is ohmically connected to these two layers 19.

Further, 21 is a gate oxide film, n is a gate electrode made of polysilicon, and a gate electrode device made of aluminum is laminated on this gate electrode n.

Here, the source electrode 7, drain electrode 10, and gate electrode 13 of the MOSFET 2 are commonly connected to the source electrode 17, the drain electrode □□□, and the gate electrode device of the IGBT 3, respectively.

In this embodiment, voltage-current characteristics as shown by the broken line X in FIG. 2 can be obtained.

Incidentally, in this FIG. 2, the symbol 11Y is the voltage-current characteristic of the IGBT 3, and the symbol z is the voltage-current characteristic of the MOS FET 2.

That is, when the drain-source voltage is 0.7 (V) or less, MOSFET2 operates and the MOSFET
A drain current flows according to the voltage-current characteristics of No. 2.

In addition, when the drain-source voltage is 0.7 (V) or more, both MOS FET2 and IGBT3 operate, and the voltage-current characteristics of MOS FET2 and IGBT3 are changed in these MOS FET2 and IGBT3, respectively. A corresponding drain current flows. As a result,
The on-voltage of this example is MOS FET2 and IGBT
It is smaller than the on-voltage of No. 3.

〔Effect of the invention〕

In the present invention, since the MOSFET and IGBT are connected in parallel, the drain-source voltage is 0.7 (
MOS FET that operates even below V) and has an on-voltage of
and smaller than IGBT. Therefore, MOSF
Unlike ET and IGBT, the range of applications is not limited, and it can be used in a wide range of applications.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the main part of an embodiment of the present invention, Fig. 2 is a voltage-current characteristic diagram of the example shown in Fig. 1, Fig. 3 is a voltage-current characteristic diagram of IGBT, and fJ4 diagram is of a MOSFET. It is a voltage-current characteristic diagram. MOSFET IGBTl Silicon substrate 13 Gate electrode (aluminum) 2 MOSFET
14 P+ layer (element isolation band) 3 IGBT
15 P layer 4N layer
16N1 layer Fig. 1 Fig. 2 Q, 7 (V) Voltage Fig. 3 0.7 (V) Voltage Fig. 4

Claims (1)

[Claims] A switching element characterized by a MOSFET and an IGBT connected in parallel.