JPS605588Y2 - Protection device for insulated gate type semiconductor devices - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a protection device for an insulated gate type semiconductor device.

FIG. 1 shows a top view of a conventional protection device for an insulated gate type semiconductor device, and FIG. 2 shows a cross-sectional view taken along the line ■--■ in FIG.

This protection device is an insulated gate type semiconductor device (
The oxide film 5 on the PN junction formed by the tongue 4 and the substrate 1 is connected to the field oxide film 6 by forming the tongue 4 which is connected to the gate electrode (not shown) and protruding into the resistance region 2. The oxide film 5 is made thinner, the oxide film 5 is covered with an electrode 7 made of vapor-deposited aluminum, and the electrode 7 is grounded to make the PN junction breakdown voltage below the electrode 7 lower than the gate oxide film breakdown voltage of an insulated gate type semiconductor device to form an insulated gate. This protects type semiconductor devices from electrostatic damage.

FIG. 3 shows this equivalent circuit diagram.

In FIG. 3, D□ is a diode formed by the diffused resistance region 2 and the substrate 1, and R is the approximately water Ω of the diffused resistance region 2.
D2 is a diode with a low breakdown voltage formed by the tongue piece 4 and the substrate 1.

In such a protection device, a diode D□ is connected to the input terminal electrode 3.
For example, +100
When about V is applied, the substrate 1 is also lifted to about +100V, and the substrate 1 under the thin oxide film 5 forming the diode D2 also becomes about +100V, and about +100V is applied to the thin oxide film 5, causing dielectric breakdown. There was a drawback to it.

The present invention has been devised in view of these drawbacks and provides a protection device for an insulated gate type semiconductor device that completely eliminates the conventional drawbacks.

An embodiment of the present invention will be described in detail below with reference to FIGS. 4 to 6.

As shown in FIGS. 4 and 5, the protection device according to the present invention is provided with a P-type diffused resistance region 12 on an N-type silicon semiconductor substrate 11, an input terminal electrode 13 is connected to one end of the region, and the substrate is connected to the other end of the P-type diffused resistance region 12. Insulated gate semiconductor device (
A gate electrode (not shown) is connected to the gate electrode, a tongue piece 14 protruding from the diffusion resistance region 12 is formed, and a P-type protective diffusion region 15 is provided close to this tongue piece 14 so as to surround the tongue piece 14. ,
The oxide film 16 is formed to be thinner than the field oxide film 17 on the substrate 11 sandwiched between the tongue piece 14 and the protective diffusion region 15 and on the PN junction between the tongue piece 14 and the protective diffusion region 15 facing each other. The electrode 18 is coated with the electrode 18 to lower the PN junction breakdown voltage between the opposing tongue piece 14 and the protective diffusion region 15, and the electrode 18 and the protective diffusion region 15 are connected.

FIG. 6 shows an equivalent circuit of the protection device constructed by the applicant.

D□ is a diode formed by the diffused resistance region 12 and the substrate 11, and is the same as D□ in FIG.

Similarly to FIG. 3, R is a resistance of about 2 Ω of the diffused resistance region 12.

T represents the substrate 11 tongue 14 protective diffusion region 15 and electrode 18
This is a protection MOS transistor formed by.

In the protection device according to the present invention proposed by the applicant, when high static electricity of, for example, about +100V is applied to the input terminal electrode 13, the substrate 11 is also lifted to about +100V as described above. The junction breakdown voltage is, for example, 40V below the dielectric breakdown voltage of the thin oxide film 16 due to the electrode 18, and static electricity of about +100V on the substrate 11 is transferred from the protection diffusion region 15 through the low breakdown voltage PN junction of the protection diffusion region 15 mentioned above. Since the voltage is applied to the electrode 18, the electrode 18 and the substrate 11 have the same potential, and the thin oxide film 1
6 is protected from dielectric breakdown.

As detailed above, according to the present invention, a voltage higher than that of the conventional method is applied in order to guide the high static electricity applied to the substrate from the protective diffusion region with a low junction breakdown voltage to the electrode and make it equal potential with both ends of the thin oxide film. Provides protection against static electricity, etc.
A more complete protection device can be realized.

[Brief explanation of the drawing]

Figure 1 is a top view explaining the conventional example, and Figure 2 is the same as in Figure 1.
-■ line sectional view, Figure 3 is an equivalent circuit diagram of the conventional example, Figure 4 is a top view explaining the present invention, Figure 5 is a ■-■ line sectional view of Figure 4, and Figure 6 is the present invention. FIG. 11 is a semiconductor substrate, 12 is a diffused resistance region, 13 is an input terminal electrode, 14 is a tongue piece, 15 is a diffusion protection region, 16 is a thin oxide film, 17 is a field oxide film, and 18 is an electrode.

Claims (1)

[Scope of utility model registration request] A diffused resistance region of one conductivity type is provided, one end of which is connected to an input terminal electrode and the other end of which is connected to a gate electrode of an insulated gate semiconductor device, a tongue piece is formed in the resistance region, and a tongue piece is formed adjacent to the tongue piece. an insulated gate formed by forming a conductive type protective diffusion region, thinning an oxide film between the tongue and the protective diffusion region, covering the oxide film with an electrode, and connecting the electrode to the protective diffusion region; protection device for type semiconductor devices.