JPS62172739A - Semiconductor integrated circuit - Google Patents

Abstract

PURPOSE:To prevent insulating film breakdown by a method wherein a polycrystalline silicon film and metal film are formed on a semiconductor substrate and a diffusion layer opposite in conductivity to the semiconductor substrate, through the intermediary of an insulating film, and the diffusion layer is large enough to cover a polycrystalline silicon wiring, metal wiring, and polycrystalline silicon resistor. CONSTITUTION:A P-well 5 is formed on an N-type substrate 6 and thereon a fuse element.polycrystalline silicon resistor 2 is built with the intermediary of a silicon oxide film 4. Further, an Al electrode 1 is built through the intermediary of a silicon of a silicon oxide film 3 and a contact 7. In a circuit designed as such, with a diffusion layer lying just under a polycrystalline silicon resistor or a metal film through the intermediary of an insulating film, no short- circuiting occurs involving a substrate even in the presence of an insulating film breakdown because a short-circuiting occurs between the fuse element.polycrystalline silicon resistor and the diffusion layer isolated from the substrate by a junction. This realizes a fail-safe mechanism withstanding an interlayer insulating film breakdown.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to the structure of semiconductor integrated circuits, and in particular to the structure of so-called fuse elements that play the role of switches by cutting polysilicon wiring or metal wiring due to excessive current. Regarding.

The present invention also relates to the structure of a polysilicon resistance element as an END protection element.

[Conventional technology]

Conventionally, a semiconductor integrated circuit uses a mask R as a switch element.
We have been using OM extensively, but in order to handle small quantities and a wide variety of products, we have developed fuse ROM, E, which can write data with electrical stress.
PROM etc. began to be used.

On the other hand, polysilicon resistors have also been conventionally used as ESD protection elements. These elements are formed on a semiconductor substrate via an insulating film (see Figure 3). [Problems to be solved by the invention] The conventional fuse element/polysilicon resistor described above is Since it is formed through an insulating film, the insulating film may be broken by an electrical pulse with a particularly short pulse width, such as a high voltage electrostatic pulse discharged from a small capacitor. This risk is particularly high when one terminal of a fuse element or polysilicon resistor is used as an external terminal. As a result, a short circuit failure occurs between the fuse element or the polysilicon resistor and the semiconductor substrate.

[Failure to solve the problem]

In the fuse element/polysilicon resistor of the present invention, a diffusion layer is provided directly under the polysilicon resistor or metal film with an insulating film interposed therebetween. (FIG. 1) Therefore, even if the above-described breakdown of the insulating film occurs, the fuse element/polysilicon resistor will short-circuit with the diffusion layer insulated by the junction with the substrate, and will not short-circuit with the substrate.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIGS. 1 and 2 are a longitudinal sectional view and a plan view, respectively, of an embodiment of the present invention. A pwell 15 is formed on an N-type substrate 6, and a fuse element or a polysilicon resistor 2 is formed thereon with a silicon oxide film 4 interposed therebetween. Furthermore, an At electrode 1 is provided via a contact 7 through the silicon oxide film 3.

Now, consider a case where a polysilicon resistor is used as the fuse element 2. By flowing an overcurrent into the polysilicon resistor 2, it is fused and a Q pen state is created during this time.

A short pulse (
When an ESD pulse (less than 0.01 μsec) is applied, the silicon oxide film 4 is dielectrically broken down and the diffusion layer 5 and the polysilicon resistor 2 are short-circuited. However, since the semiconductor substrate 6 and the diffusion layer 5 are insulated by the junction, there is no functional problem at all. In order to obtain this effect, it is necessary to form the diffusion layer 5 wider than the fuse element 2 in FIG.

〔Effect of the invention〕

As explained above, the present invention has the effect of providing a fail-safe mechanism against interlayer insulating film breakdown by providing a diffusion layer directly below the fuse element.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of the heating element/ESD protection element of the present invention, and FIG. 2 is a plan view thereof. Further, FIG. 3 is a longitudinal cross-sectional view of a conventional element. 1...M electrode, 2...Polysilicon or metal wiring, 3...Interlayer insulating film, 4...
...Interlayer insulating film, 5...Diffusion layer, 6...
- Semiconductor substrate, 7...Contact through hole. 1st VFI half 2I! f

Claims (1)

[Claims] In semiconductor integrated circuits that include elements that play the role of switches by melting polysilicon wiring or metal wiring due to overcurrent, polysilicon or metal wiring is 1. A semiconductor integrated circuit in which a film is formed, and the diffusion layer has a size that covers the polysilicon wiring, the metal wiring, and the polysilicon resistor.