JPH0638416B2 - Semiconductor device - Google Patents

Description

The present invention relates to a semiconductor device having highly reliable metal wiring.

[Conventional technology]

Conventionally, aluminum has been mainly used for metal wiring used in semiconductor devices, and is often composed of aluminum alone or a single composition film of an alloy of aluminum and silicon. Further, as another metal wiring, wiring having a multi-layer structure of refractory metal or metal and silicon has been proposed.

[Problems to be solved by the invention]

In the above-mentioned conventional aluminum wiring structure, since the aluminum or aluminum alloy layer is continuously formed over the entire wiring area, a migration phenomenon in which wiring constituent atoms of aluminum or aluminum alloy move in the wiring direction easily occurs at high temperature or when electricity is applied. . When this phenomenon occurs, the width of the wiring is reduced, and when the phenomenon is further advanced, the wiring is broken in an extreme case, and there is a serious problem that the reliability of the device is significantly impaired.

An object of the present invention is to provide a semiconductor device in which migration is prevented and the reliability of aluminum wiring is improved.

[Means for solving problems]

The semiconductor device of the present invention is a semiconductor device having a wiring formed mainly of aluminum, in which the wiring is divided into a plurality of parts by a refractory metal layer, and the refractory metal layer suppresses the movement of aluminum constituent atoms to prevent It is designed to prevent width reduction and disconnection.

〔Example〕

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

1 (a) to 1 (d) are views showing a first embodiment of the present invention in accordance with its manufacturing process.

First, as shown in FIG. 1A, a silicon oxide film 12 is formed on a silicon substrate 11, and an aluminum layer is formed thereon. Then, this aluminum layer is photoetched to form a mesh-shaped aluminum layer 13 having a width of 2 μm and a pitch interval of 10 μm.

Next, as shown in FIG. 1B, a tungsten layer 14 is selectively vapor-deposited to a thickness of 1000 Å on the upper surface and the side surface of the aluminum layer 13 in a mixed atmosphere of WF ₆ gas and hydrogen gas. At this time, the tungsten layer 14 is not grown on the silicon oxide film 12. Next, the aluminum layer 15
Is formed on the entire surface by sputtering. The thickness of the aluminum layer 15 is preferably about the same as the thickness of the aluminum layer 13, and both are set to 1 μm here.

Then, a photoresist 16 is applied to the entire surface to planarize the surface, and then the entire surface of the wafer is uniformly etched and removed by using oxygen plasma or CC ₄ gas, and the aluminum layer 13 as shown in FIG. 15 and the tungsten layer 14 are arranged in a plane direction to obtain a flat metal surface. In the case of this embodiment, the tungsten layer on the upper surface of the aluminum layer 13 is also removed.

Next, the obtained mesh metal layer of aluminum and tungsten is dry-etched using CC ₄ and CF ₄ to form a metal wiring layer as shown in FIG. 1 (d).
In this case, it is important to form the metal wiring layer so as to cross the tungsten layer 14, so that the aluminum wiring is divided by the tungsten layer 14.
The aluminum layers 13 and 15 and the tungsten layer 14 are connected in series in the length direction of the wiring.

In the wiring of this embodiment, the aluminum layer 15 is subdivided by the tungsten layer 14 into lengths of about 10 μm, which is the initial pitch interval of the aluminum layer 13. Further, although the electric resistance of tungsten is one digit higher than that of aluminum, since the film thickness of the tungsten layer 14 is extremely thin, 1000 Å, the electric resistance of the entire wiring hardly increases.

In the aluminum wiring thus formed, since the length of the aluminum layer 15 is as short as about 10 μm, the movement or densification due to heat or electric conduction of aluminum or aluminum alloy constituent atoms is extremely limited. . Therefore, microscopically, even if atoms such as aluminum move, the effective reduction of the width of the aluminum wiring is very slight, and the local disappearance and disconnection of the aluminum wiring substantially do not occur.

FIG. 2 is a perspective view for explaining the second embodiment of the present invention.

First, as shown in FIG. 2A, an aluminum layer 23 having a required pattern is appropriately arranged in advance in a region on the silicon oxide film 22 provided on the silicon substrate 21 where wiring is planned. Next, a tungsten layer 24 and an aluminum layer 25 are sequentially formed by using the same method as in the first embodiment,
After planarization, this is etched back to obtain a metal film in which aluminum and tungsten are arranged, and further processed into a desired shape to form wiring, thereby obtaining the aluminum wiring shown in FIG. 2 (b). .

This embodiment is characterized in that the aluminum layer 23 is arbitrarily formed in advance in a necessary area for wiring. For this reason, although the design is somewhat complicated as compared with the first embodiment, the tungsten layer 2 is made easier by the final processing step of the aluminum wiring or by the current density flowing in the wiring.
There are advantages such as that the density of 4 can be changed and the degree of freedom in design and the reliability of the finished product can be improved.

Here, in each of the above-described embodiments, only the method of forming the wiring is mentioned, but it goes without saying that the present invention can be applied to the general semiconductor device as a whole including circuit elements such as active elements such as transistors and contact holes.

Further, in order to make the present invention function more effectively, a process of applying a flattening technique such as a bias sputtering method to the formation of the aluminum layer, or making the side walls of the aluminum layers 13 and 23 have a gentle inclination beforehand The above device is especially effective.

Further, although the vapor phase growth method of tungsten is used as the method of forming the refractory metal in the present embodiment, other methods such as the sputtering method may be used. Needless to say, other materials such as titanium and molybdenum may be used.

〔The invention's effect〕

As described above, the present invention has a structure in which the wiring formed mainly of aluminum is divided into a plurality of parts by the refractory metal layer. Therefore, the refractory metal layer suppresses the movement of aluminum constituent atoms and It is possible to prevent width reduction and disconnection, and thereby improve the reliability of the entire device. In addition, since the current density per unit cross-sectional area can be increased in order to improve the reliability of the wiring, the function of the device can be achieved with a narrower wiring width than in the past, and the device can be highly dense and highly integrated.
There is an effect that the circuit function can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention in process order.
FIG. 1 (a) is a perspective view, FIG. 1 (b) and FIG. 1 (c) are sectional views, FIG. 1 (d) is a perspective view, and FIG. 2 (a) and FIG. It is a perspective view which shows the 2nd Example of invention in order of a process. 11, 21 ... Silicon substrate, 12, 22 ... Silicon oxide film, 13, 23 ... Aluminum layer, 14, 24 ...
… Tungsten layer, 15, 25 …… Aluminum layer, 1
6 ... Photoresist.

Claims (1)

[Claims] 1. A semiconductor device having a wiring mainly made of aluminum, wherein the wiring is divided into a plurality of portions by a refractory metal layer.