JPS62293934A - Input protection circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an input protection circuit for a transistor device, and particularly relates to a circuit including a field effect transistor. In the figure, reference numeral 2 indicates a field effect transistor for emitting surge voltage, and a portion A surrounded by a broken line uses an A x metal wiring.

Next, the operation will be explained. Since the field effect transistor 2 in the figure has a very high threshold potential, the input signal is directly transmitted to the internal circuit B without turning on the transistor 2 in response to a normal input signal Itn. However, when a very large surge voltage is applied from the outside, transistor 2 turns on and the current flows to the substrate, causing the surge voltage to flow into the internal circuit B.
to prevent transmission.

[Problem that the invention seeks to solve]

As mentioned above, conventional input protection circuits use only Al metal wiring for the circuit wiring, so if a very high surge voltage is applied, there is a possibility that the A1 metal wiring will melt.How to prevent this? One way to do this is to make the wiring thicker. However, this method has the problem of increasing the area occupied by the wiring.

This invention was made to solve the above-mentioned problems, and without increasing the area occupied by the wiring part,
AI! The promise is to obtain a 3W input protection circuit that can prevent wiring from melting.

[Means for solving problems]

In the input protection circuit according to the present invention, an Al metal wiring between an input pad and an internal circuit is contacted with polycrystalline silicon or a diffusion region.

[Effect]

In this invention, AI! between the input pad and the internal circuit!
Since the metal wiring is configured to be in contact with the polycrystalline silicon or the diffusion region, the polycrystalline silicon or the diffusion region serves as a heat dissipation material, and the heat generated by the AN metal wiring can be radiated.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows an input protection circuit according to an embodiment of the present invention.
As shown in the figure, it is in contact with polycrystalline silicon or a diffusion region 3. Here, this contact 4 is made as large as possible.

Next, the operation will be explained. In FIG. 1, the field effect transistor 2 has a very high threshold potential, so when a normal input signal of 1 inch is applied, the transistor 2 is in an OFF state and the input signal remains as it is in the internal circuit B.
is transmitted to. However, when a very large surge voltage is applied, the transistor 2 turns on and prevents the surge current from being transmitted to the internal circuit B by discharging it to the substrate. At this time, if the broken line part A is the AAfIlAl metal wiring 1 as in the conventional circuit, there is a possibility that the Al'A group will melt due to extremely large heat generation, but as in this circuit, the Al metal wiring 1 The polycrystalline silicon or diffusion region 3 in contact with the metal wire 1 radiates heat generated by the wire, thereby making it possible to prevent the Al metal wire 1 from fusing.

〔Effect of the invention〕

As described above, according to the present invention, A7! between the input pad and the internal circuit! Since the metal wiring is contacted with polycrystalline silicon or a diffusion region as a heat dissipation material, A
This has the effect of preventing the Al metal wiring from fusing due to heat generation without making the ffi metal wiring thicker.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing the state of contacts in an embodiment of the invention, and Fig. 3
The figure is a circuit diagram showing a conventional input protection circuit. 1... Al metal wiring, 2... Field effect transistor, 3... Polycrystalline silicon or diffusion region, 4 is contact. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In an input protection circuit in which a field effect transistor for surge voltage release is provided between an input pad and an internal circuit, and an Al metal wiring is used between the input pad and the internal circuit, An input protection circuit characterized by connecting Al wiring to polycrystalline silicon or a diffusion region.