JPH04243150A - Polysilicon fuse - Google Patents

Abstract

PURPOSE:To facilitate cutting of a polysilicon fuse by reducing the capacitance between the polysilicon fuse and silicon substrate through separating the fuse from the silicon substrate, because the polysilicon fuse, which is used for changing the circuit of a semiconductor device by cutting the fuse when electric pulse is applied in the semiconductor device, is difficult to cut due to the capacitance between the fuse and silicon substrate. CONSTITUTION:A fuse part 1 and pad part 2 composed of polysilicon are formed on a thick silicon oxide film 3 formed by the selective oxidation of silicon, the fuse part and pad part are separated from a silicon substrate 14 and the capacitance between the fuse and pad parts and the silicon substrate is made small.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to polysilicon fuses, and more particularly to polysilicon fuses used in semiconductor devices.

0002

2. Description of the Related Art A conventional fuse circuit using polysilicon, as shown in FIG. A polysilicon pad part 2, which is wider than part 1, is placed on a silicon substrate 4 to a thickness of 100 mm.
It is formed with an angstrom insulating film 6 interposed therebetween. The polysilicon fuse used in this semiconductor device is cut by applying an electric pulse to the fuse part 1 to burn out the polysilicon in the fuse part 1.

0003

[Problems to be Solved by the Invention] In the structure of this conventional polysilicon fuse circuit, the pad portion 2 and the fuse portion 1
are formed on the insulating film 6 of about several hundred angstroms on the silicon substrate 4, so a parasitic capacitance occurs between the fuse circuit and the silicon substrate. Due to this capacitance, the fuse itself becomes like an integrating circuit, which causes the waveform of the electric pulse applied to the fuse to become dull, making it difficult to blow the fuse.

0004

[Means for Solving the Problems] According to the present invention, there is provided a polysilicon fuse section that is cut by applying an electric pulse, and a polysilicon fuse section that is wider than the fuse section and that becomes a section connected to an external circuit. The fuse part and the pad part are formed on a semiconductor substrate via an insulating film, and the fuse part and the pad part are formed by an n-layer insulating layer (n is 1 or more) including a thick silicon oxide film formed by selective oxidation of silicon or the like. obtain a polysilicon fuse formed on a polysilicon fuse (an integer number).

The thickness of this insulating layer is 10 times the thickness of the thin oxide film other than the thick oxide film formed by selective oxidation of silicon.
It is set to be more than twice as large, that is, several thousand angstroms or more. Therefore, the capacitance between the fuse section, pad section, and silicon substrate is 1/10 when the fuse section and pad section are provided on the n-layer insulating layer, compared to when they are provided on a thin oxide film.
It becomes below. Therefore, the waveform of the electric pulse applied to the fuse becomes less rounded, making it easier to blow the fuse.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. A polysilicon fuse part 1 has a pad part 2 wider than the fuse part 1 at both ends, and the fuse part 1 and the pad part 2 are thick silicon oxide films formed on a silicon substrate 4 by selective oxidation of silicon. 3. This thick silicon oxide film 3 provides a distance between the fuse section 1, the pad section 2, and the silicon substrate 4, thereby reducing parasitic capacitance.

FIG. 2 is a cross-sectional view of another embodiment of the invention. In this embodiment, a thick silicon substrate film 3 formed by selective oxidation of silicon is formed between a fuse part 1, a pad part 2, and a silicon substrate 4, and a silicon nitride film 5 is formed thereon.
have. Here, since the silicon nitride film 5 is provided on the thick silicon oxide film 3, the distance between the pad portion 2 and the silicon substrate 4 can be larger than that in the embodiment shown in FIG.

[0009]

As described above, the present invention provides an n-layer insulating film including a thick silicon oxide film formed by selective oxidation of silicon between a polysilicon fuse portion, a polysilicon pad portion, and a silicon substrate. It has layers. The thickness of the thick silicon oxide film formed by selective oxidation of silicon is ten times or more the thickness of other thin oxide films. Therefore, when the fuse section and the pad section are formed on an n-layer insulating layer, the capacitance between the polysilicon fuse and the silicon substrate is 1/10 or less of the capacitance when formed on a thin silicon oxide film. Therefore, the waveform of the electric pulse applied to the fuse is less rounded, which has the effect of making it easier to blow the fuse.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing another embodiment of the present invention.

FIG. 3 is a sectional view showing a conventional example.

[Explanation of symbols]

1 Polysilicon fuse part 2 Polysilicon pad part 3 Thick silicon oxide film 4 Silicon substrate 5 Silicon nitride film 6 Insulating layer

Claims (1)

[Claims] 1. A polysilicon fuse section that is cut by applying an electric pulse, and a polysilicon pad section that is wider than the fuse section and is connected to an external circuit at both ends of the fuse section. In the polysilicon fuse, the fuse part and the pad part are formed by an n-layer insulating layer (n is 1) including a thick silicon oxide film.
(an integer greater than or equal to)).