JPH077753B2 - Method for forming aluminum alloy wiring - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for forming an aluminum alloy wiring, and more particularly to a method for forming a wiring with an Al alloy obtained by adding impurities to aluminum (Al).

[Conventional technology]

In the conventional method for forming an Al alloy wiring, when forming an Al alloy film on a semiconductor substrate, the semiconductor substrate is heated to 200 ° C to 400 ° C, and after forming the Al alloy film, it is naturally cooled without being particularly cooled. Was there. Even if it is cooled, the substrate holder is cooled with water to cool the semiconductor substrate, or the cooled inert gas is wiped onto the semiconductor substrate to cool it, but it takes several tens of seconds to return to room temperature. Was needed. Further, after the Al alloy film is formed, no special heat treatment is performed, and the Al alloy film is directly etched away by a lithographic technique, leaving a necessary portion, to form an Al alloy wiring.

[Problems to be solved by the invention]

In the conventional Al alloy wiring forming method described above, when forming an Al alloy film on a semiconductor substrate, if an additive having a solid solution limit or higher at room temperature is contained in Al, the additive having a solid solution limit or higher is added. As the semiconductor substrate cools, the
It precipitates at the interface of the alloy film.

After that, when the Al alloy film on which this additive is deposited is removed by etching while leaving a necessary portion by the lithography technique,
Precipitation of this additive remains as a residue, which makes it difficult to form an Al alloy wiring.

For example, when forming an Al alloy wiring with an Al-Cu alloy in which 1% of copper (Cu) is added to Al, the semiconductor substrate on which the element is formed is heated to 350 ° C. An Al-Cu alloy film is formed on a semiconductor substrate. 350 ° C
Then, Cu can be dissolved in Al up to 1%,
Immediately after the Al-Cu alloy film is formed, Cu is distributed almost uniformly in Al, but as the temperature of the semiconductor substrate approaches room temperature, Cu above the solid solution limit precipitates along the Al grain boundaries. Come on.

When this Al-Cu alloy is etched by the plasma etching technique, the Cu deposited at the grain boundaries is not etched and remains as a residue on the semiconductor substrate, and this residue causes a short between the Al wirings, resulting in Al-Cu alloy wiring. Has the drawback that it is difficult to form.

An object of the present invention is to provide a method for forming an aluminum alloy wiring, which solves the above-mentioned drawbacks and allows uniform Al alloy wiring to be easily formed on a semiconductor substrate.

[Means for solving problems]

The structure of the method for forming an aluminum alloy film of the present invention comprises the steps of heating a semiconductor substrate to form an aluminum alloy film on its main surface, rapidly cooling the substrate from a high temperature state, and rapidly cooling the alloy by the above-mentioned alloy. And a step of forming a predetermined wiring by etching the film.

〔Example〕

 The present invention will now be described in detail with reference to the drawings.

1 (a) to 1 (c) are cross-sectional views sequentially showing main steps of forming an Al--Cu alloy wiring according to the first embodiment of the present invention. In these drawings, as a first embodiment, a case of forming a wiring with an Al-Cu alloy in which 1% Cu is added to Al will be described. First, in FIG. 1A, a silicon substrate 1 on which a desired element is formed and covered with a silicon oxide film 2 is heated to 400 ° C. and Al is formed by a sputtering method.
-Cu alloy film 3 is formed. At this time, Cu is almost uniformly distributed in the Al—Cu alloy film 3. The method of heating the substrate is not limited to heating with a heater, a lamp, or the like, and a negative voltage may be applied to the substrate to heat it with plasma. Immediately after the Al—Cu alloy film 3 having a desired film thickness is formed, the heating is immediately stopped, liquid nitrogen is flown into the substrate holder, the entire silicon substrate 1 is rapidly cooled, and the temperature is returned to room temperature. At this time, as shown in FIG. 1 (b), the Cu in the Al—Cu alloy film 3 is cooled rapidly, so that it does not change from the distribution at 400 ° C. and is almost evenly distributed in the Al—Cu alloy film 3. It is distributed. After that, as shown in FIG. 1 (c), using a normal lithography technique,
The Al—Cu alloy film 3 is removed by etching, leaving a necessary portion, to form an Al—Cu alloy wiring 4.

2 (a) to 2 (c) are sectional views showing a method of forming an aluminum alloy wiring according to the second embodiment of the present invention in the order of main steps. First, referring to FIG. 2A, a silicon substrate on which a desired element is formed and which is covered with a silicon oxide film 12 is formed.
11 is heated to 200 ° C., the Al—Cu alloy film 13 is formed into a desired film thickness by the sputtering method, and the temperature is returned to room temperature. At this time, at room temperature, Cu precipitates 14 that are above the solid solution limit are precipitated at the Al grain boundaries and at the interface between the silicon substrate 11 and the Al—Cu alloy film 13. After that, the silicon substrate 11 is newly heated to 400 ° C. by a furnace tube, an electric oven or the like, and the substrate is rapidly cooled by water cooling as shown in FIG. 2 (b). At this time, Cu is Al-
It is evenly distributed in the Cu alloy film 15. After that, the Al—Cu alloy is removed by etching by the usual lithography technique leaving the necessary portion, and the Al—Cu alloy wiring 16 is formed as shown in FIG. 2C.

Although the Al alloy film is formed by the sputtering method in the first and second embodiments, the method for forming the Al alloy film is not limited to the sputtering method, and the vacuum evaporation method or
A CVD method or the like may be used, and as the heating method and the rapid cooling method of the semiconductor substrate, methods other than those used in these two embodiments may be used.

Further, the substance added to Al is not limited to Cu, and may be any substance that does not easily form a solid solution in Al at room temperature.
The substance to be added may be of one type or a double number.

Further, the above-described embodiment is not limited to the single-layer wiring, but is also applied to the formation of the second or more layers of the Al multi-layer wiring. Further, it is more preferable that the semiconductor substrate is preheated to a high temperature before or after the step of forming the aluminum alloy film.

〔The invention's effect〕

As described above, the present invention includes a step of rapidly cooling the semiconductor substrate from a high temperature after forming the Al alloy film on the semiconductor substrate and before removing the Al alloy film by a photolithography technique to remove a necessary portion by etching. As a result, the additives in the Al alloy are almost evenly distributed in Al, and there is no place where they are deposited.Therefore, the additives are simultaneously removed by etching using normal Al etching technology, and Al alloy wiring can be easily formed. The effect is that you can do it.

[Brief description of drawings]

1 (a) to 1 (c) are sectional views sequentially showing the main steps of the method for forming an aluminum alloy wiring according to the first embodiment of the present invention, and FIGS. 2 (a) to 2 (c). 8A to 8C are cross-sectional views sequentially showing main steps of the method for forming an aluminum alloy wiring according to the second embodiment of the present invention. 1,11 …… Silicon substrate, 2,12 …… Silicon oxide film, 3,1
3,15 ... Al-Cu alloy film, 4,16 ... Al-Cu alloy wiring, 14 ...
… Cu deposits.

Claims (1)

[Claims] 1. A step of heating a semiconductor substrate to form an aluminum alloy film on the main surface thereof, a step of rapidly cooling the substrate from a high temperature state, and a step of rapidly cooling the alloy film to etch a predetermined wiring. And a step of forming an aluminum alloy film.