JPH0653323A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor device of multilayer interconnection structure having a fuse wherein the fuse is readily fused and no damage is caused to wiring layers. CONSTITUTION:A polycrystalline silicon fuse 13 is formed, by a low temperature CVD method, in an upper layer of a multilayer interconnection structure, composed of a first wiring layer 4 through a fourth wiring layer. This reduces the number of films through which laser beam passes in fusing of the fuse 13, and facilitates the fusing. In addition no damage due to heat is caused to lower wiring layers during the formation of the fuse 13.

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 the structure of a fuse in a memory circuit.

[0002]

2. Description of the Related Art Conventionally, a semiconductor device is provided with a fuse as a redundant circuit. For example, when a part of some memory cells in one semiconductor device in a memory circuit becomes defective, this fuse is used by a laser beam from the outside when the part is not used. Used to blow out and switch connections. Figure 3
As shown in a cross-sectional view of an example thereof, polycrystalline silicon is grown on the entire surface of the substrate 1 by the CVD method, and the fuse 2 is formed by photolithography by wet etching leaving only the fuse portion. After that, a first interlayer insulating film 3 such as a nitride film is formed, through holes are formed in the portions corresponding to both ends of the fuse, and the first wiring layer 4 formed further thereon.
Connect with. A second interlayer film 5 and a third interlayer film 7, which are inorganic or organic insulating films, are laminated on top of this, and a fuse window is opened in the third interlayer film 7. When the fuse 2 is blown, a laser beam is irradiated through the window of the third interlayer film 7 to heat and fuse the fuse 2.

[0003]

In this conventional fuse, since the polycrystalline silicon used is also used as the extraction electrode of the element, it must be formed in a layer below the wiring layer. In the case of such a structure, if the wiring layers are one or two layers, the laser light for blowing the fuse can reach the fuse sufficiently, so that the blowing can be easily performed. Also,
Even if there are about three wiring layers, the fuse can be blown by opening a window in the upper interlayer film.

However, in recent years, the number of wiring layers has increased,
In the case of 5 to 7 layers, the interlayer film becomes very thick, so that the laser beam is attenuated by the time it reaches the fuse, and there is a possibility that the fuse cannot be blown. Moreover, even if an attempt is made to open windows in many interlayer films on the fuse,
In the layer, the thickness of the interlayer film becomes several μm, which makes it difficult to open a window. Furthermore, even if a fuse is to be formed on the upper layer of the wiring layer, since the growth temperature of polycrystalline silicon is as high as 650 ° C. in the normal low pressure CVD method, the wiring layer formed on the lower layer is damaged, so the fuse should be formed. Becomes difficult. An object of the present invention is to provide a semiconductor device having a fuse structure suitable for multilayer wiring.

[0005]

According to the present invention, a polycrystalline silicon fuse provided in a multi-layer wiring structure is formed by low temperature CVD.
Formed by the method and formed in the upper layer portion of the multilayer wiring structure.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of an embodiment of the present invention. After forming a base insulating film 3 such as a nitride film on the substrate 1 and opening a contact for connecting to an element, a first wiring layer 4 of aluminum or gold is formed. A first interlayer film 5 which is an organic or inorganic insulating film is formed thereon. Such a layered structure is repeated four layers, and the second wiring layer 6, the second interlayer film 7, the third wiring layer 8, the third interlayer film 9, the fourth wiring layer 10, and the fourth interlayer film 1 are repeated.
A multi-layer wiring including the first and fifth wiring layers 12 is formed.

Next, the fifth wiring layer 12 made of aluminum or gold is patterned so that the wiring is cut only in the fuse portion. After this, a tungsten film is selectively grown to a thickness of 2000 Å on the portion of the fifth wiring layer 12 corresponding to the fuse by the low temperature CVD method using FIB (Focus Ion Beam).
To form. Further, this fuse 13 can also selectively grow polycrystalline silicon using SiH ₄ , N ₂ , and AsH ₃ as source gases by using a photo-CVD method using a laser beam as a light source. Then, a cover insulating film 14 is formed on the entire surface to cover the fifth wiring layer 12 and the fuse 13.

According to this structure, the fuse 13 is formed in the uppermost layer of the wiring structure formed of five layers, and only the cover insulating film 14 is present thereon, so that the fuse 13 is blown. When the laser light is applied to the fuse 1, the laser light only passes through the cover insulating film 14.
3 can be reached and the fusing can be done easily. On the other hand, the fuse 13 is formed after the wiring layers up to the fifth layer are formed.
Since it can be formed by a low temperature process such as a photo CVD method, it does not damage other wiring layers.

FIG. 2 is a sectional view of the second embodiment of the present invention. Similar to the first embodiment, the fourth interlayer film 11 is formed.
Then, by the optical CVD method using a mercury lamp as a light source,
Polycrystalline silicon is grown on the entire surface with the same source gas as described above, and patterned by photolithography to form the fuse 13. A fifth interlayer film 15 is formed thereon, through holes are formed in both ends of the fuse 13, a fifth wiring layer 12 is formed, and the fuse 13 and the fifth wiring layer 12 are connected. Further, the cover insulating film 14 is formed thereon. Also in this configuration, since the fuse is formed in the layer immediately below the uppermost wiring layer, the fusing with the laser can be easily performed. Further, since the fuse 13 is formed by the low temperature process after forming the first to fourth wiring layers, these wirings are not damaged.

[0010]

As described above, according to the present invention, since the fuse is formed in the upper layer portion of the wiring layer by using the FIB method and the photo-CVD method which can be formed in the low temperature process, the number of layers is 5 to 7 layers. Even in the case of thick multilayer wiring, the laser light for blowing the fuse can reach the fuse sufficiently, the fuse can be easily blown, and the lower wiring layer is damaged when the fuse is formed. Never give.

[Brief description of drawings]

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

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

FIG. 3 is a cross-sectional view of a conventional fuse structure.

[Explanation of symbols]

 1 Substrate 3 Base Insulating Film 4, 6, 8, 10 First, Second, Third, Fourth Wiring Layer 5, 7, 9, 11 First, Second, Third, Fourth Interlayer Film 12 Fifth Wiring Layer 13 Fuse 14 Cover insulating film 15 Fifth interlayer film

Claims (1)

[Claims] 1. A semiconductor device having a multi-layer wiring structure including a wiring layer and an interlayer film, and having a fuse formed of polycrystalline silicon in a part of the wiring layer, wherein the fuse is formed by a low temperature CVD method, A semiconductor device formed on the upper layer of a multi-layer wiring structure.