JP3134357B2 - Semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a semiconductor device having an input protection circuit.

[0002]

2. Description of the Related Art In an LSI, ESD (electrostatic discharge) is used.
In some cases, an input protection circuit is provided as a countermeasure against excessive voltage input.

FIG. 3 shows a first conventional example of an input protection circuit.
The circuit of the type shown by the equivalent circuit shown in FIG. This circuit uses a MOS transistor M as shown in FIG.
It is also called a V _DS input protection circuit. Conventionally, a BV _DS type input protection circuit is manufactured with a configuration as shown in FIGS. 5A and 5B. This is a normal MOS transistor having N-type diffusion layers 2c and 2d selectively formed on the surface of a P ^- type silicon substrate 1c as source and drain regions. Are in ohmic contact with the source electrode wiring 4b and the drain electrode wiring 5b, respectively. Also, the source electrode wiring 4b is
b is connected at an appropriate place.

Next, as a second conventional example of the input protection circuit, there is a circuit of a type shown by an equivalent circuit as shown in FIG. This circuit uses a diode D as shown. Conventionally, this type of input protection circuit is manufactured with a configuration as shown in FIGS. 6 (a) and 6 (b). That is, it is a PN junction diode composed of an N type diffusion layer 9b selectively formed on the P ⁻ type silicon substrate 1d and a P type diffusion layer 10b formed on the N type diffusion layer 9b. The wirings 12b are P
And the N type diffusion layer 9b.

As a conventional method for improving the resistance of a MOS transistor or a diode of an input / output protection circuit to an excessive voltage input such as ESD, a method of arranging a resistor before and after the input protection circuit, a method of using a MOS transistor or a MOS transistor, has been proposed. There is a method in which the distance between the PN junction of the diode and the electrode in contact with the P-type diffusion layer or the N-type diffusion layer is increased, and the resistance value between the distances is increased.

[0006]

As a problem of the prior art described above, when heat is locally generated at a PN junction of a semiconductor element used in an input protection circuit, measures are taken to radiate the heat. That is not done.

It is said that the junction breakdown of a semiconductor element in an LSI due to ESD (electrostatic discharge) is caused by the melting of the junction due to the generation of Joule heat.

That is, in a conventional semiconductor device,
When excessive power is input by ESD, heat is generated at the PN junction of the semiconductor element used in the input protection circuit, and the heat is not sufficiently released, so that the part is melted and the element is destroyed. The problem is that there is a tendency for the phenomenon to occur.

[0009]

Means for Solving the Problems The present invention has a first conductivity type diffusion layer selectively formed on a surface portion of a semiconductor substrate, and a drain electrode in contact with the first conductivity type diffusion layer.
In a semiconductor device provided with an input protection circuit including a MOS transistor , the first conductivity type diffusion layer includes the MOS transistor.
Between the drain electrode and the channel of the transistor.
Thus, a radiator made of a metal film or an alloy film is provided.

[0010]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1A is a partial plan view of a first embodiment of the present invention. FIG. 1B is a cross-sectional view of FIG.
It is an X-ray sectional view.

A MOS transistor is provided with a radiator 7a made of a tungsten film. This radiator is
Although arranged between the drain electrode wiring 5a and the source electrode wiring 4a, there is no electrical contact except for the N-type diffusion layer 7a. I have.

This semiconductor element is used as the MOS transistor M of the above-mentioned BV _DS type input protection circuit.
A metal film having a high thermal conductivity is disposed as a radiator near the PN junction near the drain electrode wiring 5a, which is a place where the Joule heat is generated when an excessive voltage is input due to SD or the like and the melt breakdown is likely to occur. This promotes the dissipation of Joule heat generated at the PN junction and makes it less likely to cause melt fracture.

FIG. 7 is a characteristic diagram showing the effect of this embodiment. In the figure, "radiator arrangement" indicates a semiconductor device in which the radiator of the present embodiment is arranged in the input protection circuit, and "no radiator" indicates a conventional semiconductor device in which no radiator is used in the input protection circuit. In each case, the channel length of the input protection transistor is 2 μm, the channel width is 100 μm, and the dimensions of the radiator are 2 μm in length, 90 μm in width, and 4 μm in length. As described above, in the semiconductor device of the present embodiment in which the radiator is arranged in the input protection circuit, the ESD withstand voltage is lower than that of the conventional device.
It is improved by about 0 to 400V.

The material of the radiator is the same as the material of the electrode wiring (eg, aluminum or tungsten silicide).
The same effect can be obtained by using.

FIG. 2A is a partial plan view of the second embodiment. FIG. 2B is a cross-sectional view taken along line XX of FIG. 2A.

The radiator 7b is made of a tungsten film as in the first embodiment. Such a tungsten radiator also has no electrical contact except for the N-type diffusion layer 9a of the PN junction diode.
Only in contact. Further, it has a portion sandwiched between the anode wiring 11a and the cathode wiring 12a.

Such a PN junction diode is shown in FIG.
In a semiconductor device used as a radiator, a metal film such as tungsten having a high thermal conductivity is radiated near a PN junction, which is a place where a Joule heat is generated when an excessive voltage is input due to ESD or the like and melting breakdown is likely to occur. By arranging as, the dissipation of the Joule heat generated at the joint is promoted, and the melt fracture is less likely to occur.

The same effect can be obtained by using the same material for the radiator as the material for the electrode wiring.

[0020]

According to the present invention, a semiconductor device is provided with an ESD.
When an excessive voltage is input due to, for example, Joule heat generated at a PN junction or the like in a semiconductor element such as a transistor or a diode used in an input protection circuit, a heat radiator promotes heat dissipation in that part. Therefore, it is possible to prevent the occurrence of melt fracture.

Therefore, there is an effect that the resistance of the semiconductor device to excessive voltage input can be increased.

[Brief description of the drawings]

FIG. 1 is a plan view (FIG. 1) showing a first embodiment of the present invention;
(A)) and sectional drawing (FIG.1 (b)).

FIG. 2 is a plan view (FIG. 2) showing a second embodiment of the present invention;
(A)) and sectional drawing (FIG. 2 (b)).

FIG. 3 is a circuit diagram illustrating an example of an input protection circuit.

FIG. 4 is a circuit diagram showing another example of the input protection circuit.

FIG. 5 is a plan view (FIG. 5A) and a cross-sectional view (FIG. 5B) showing a first conventional example.

6A and 6B are a plan view (FIG. 6A) and a cross-sectional view (FIG. 6B) showing a second conventional example.

FIG. 7 is a characteristic diagram used for describing the effect of the first embodiment.

[Description of Signs] 1a, 1b, 1c, 1d P ^- type silicon substrate 2a, 2b, 2c, 2d N type diffusion layer 3a, 3b Gate electrode wiring 4a, 4b Source electrode wiring 5a, 5b Drain electrode wiring 6a, 6b Contact Holes 7a, 7b Heatsinks 8a to 8d Insulating film 9a, 9b N-type diffusion layer 10a, 10b P-type diffusion layer 11a, 11b Anode wiring 12a, 12b Cathode wiring 13a, 13b Contact hole 14a, 14b Contact hole

Claims (1)

(57) [Claims] 1. An input protection circuit including a MOS transistor having a first conductivity type diffusion layer selectively formed on a surface portion of a semiconductor substrate, and a drain electrode contacting the first conductivity type diffusion layer. In the semiconductor device, the first conductivity type diffusion layer is sandwiched between the drain electrode of the MOS transistor and a channel portion, and has a metal film and a metal film.
Or a radiator comprising an alloy film .