JPS5950544A - Formation of multi-layer wiring - Google Patents

Abstract

PURPOSE:To enable the connection of stricture parts of the first and second layer wirings by a method wherein a tungsten film is adhered on an Al-Si alloy film of the first layer wiring. CONSTITUTION:After adhering an oxide film 2 on an Si substrate 1, an Al-Si alloy film 3 is formed by sputtering method. Thereafter, the tungsten film 4 is formed, and a first layer wiring and the tungsten film thereon are formed. Next, a phosphorus glass film 5 is formed by bias sputtering method, a through hole is formed by etching, and thereafter a tunsten film 6 is formed. Then, after forming an Al film by sputtering method, an Al wiring film 7 of a second layer is formed by etching.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming multilayer interconnects, and more particularly to a method for connecting second layer interconnects to interconnects in which the first layer is made of an aluminum-silicon alloy even in small areas. .

Current semiconductor devices are becoming more and more integrated, and as a result, their structures have become finer, and wiring techniques have also become finer and multilayer wiring structures. The conventional method for forming multilayer wiring is to form an insulating film on the first layer wiring, then open a through hole and sputter aluminum for the second layer wiring when connecting the first layer wiring and the second layer wiring. It is formed using a method or a vacuum evaporation method. This method is based on the phenomenon that when the through-hole diameter becomes narrower than 2 μmφ, the film thickness at the stepped portion becomes thinner.In other words, the step coverage deteriorates, and the connection between the first layer wiring and the second layer wiring becomes impossible. , which had the disadvantage of causing wire breakage.

In order to solve this cause, a method has been proposed and known in which the first layer wiring and the second layer wiring are connected using a chemical vapor deposition method in which metal is selectively deposited in the through hole portion. This method is applied to a device in which aluminum oxide is easily formed on the surface because an alloy of aluminum and silicon (2%) is used for the first layer wiring. This aluminum oxide becomes an obstacle that reduces selectivity in the chemical vapor deposition method that selectively deposits metal only on the through-hole area, so the aluminum oxide on the surface must be removed by sputter etching or the like immediately before performing the chemical vapor deposition method. It has the disadvantage that it cannot be used.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a multilayer interconnection, which eliminates the drawbacks of the prior art described above and enables connection of a first layer interconnection and a second layer interconnection at a narrow portion.

The feature of the method for forming a multilayer wiring according to the present invention for the above purpose is that in forming a multilayer wiring that connects a first layer wiring and a second layer wiring, a tungsten film or the like is formed on the metal film of the first layer wiring. A transition metal film such as a tungsten film is selectively formed only in the through hole portion connecting the first layer wiring and the second layer wiring using a chemical vapor deposition method. The purpose of this method is to perform a process of connecting a first layer wiring and a second layer wiring through a transition metal film such as a tungsten film. In the above, when an aluminum-silicon alloy is used for the first-layer wiring, the aluminum-silicon alloy film for the first-layer wiring is formed by sputtering and then continuously in the same equipment. Preferably, a transition metal film, such as a tungsten film, is deposited thereon.

Currently, aluminum-silicon (2%) alloy is generally used as the material for the first layer wiring.

This alloy has the property that aluminum oxide is easily formed on the surface. In the present invention, in order to prevent such aluminum oxide from forming on the surface, a transition metal film such as a tungsten film is coated on the metal film of the first layer wiring. After forming an aluminum-silicon alloy, which is a metal film for one-layer wiring, by sputtering, a transition metal film such as a tungsten film is continuously formed in the same equipment to cover the surface of the aluminum-silicon alloy. It is. By doing this, in the chemical vapor deposition method in which a transition metal such as tungsten is selectively deposited only in the through-hole portion connecting the first layer wiring and the $2 layer wiring, there is no aluminum oxide, so it is possible to eliminate the conventional technology. Transition metals such as tungsten can be selectively deposited easily without sputter etching as in the conventional method.

EMBODIMENT OF THE INVENTION Below, one Example of this invention is demonstrated in more detail with reference to drawings.

FIG. 1, FIG. 2, and FIG. 3 are cross-sectional views of wiring layers in the order of steps.

Referring to FIG. 1, an oxide film 2 with a thickness of 30 nm is deposited on a silicon substrate 1 on which a semiconductor element is formed, electrode contacts are made by photoetching, and an aluminum-silicon alloy film with a thickness of 1 μm is formed by sputtering. 3 was formed. Thereafter, a tungsten film 4 having a thickness of 2 Q nm was continuously formed in the same apparatus, and a first layer wiring and a tungsten film on the first layer wiring were formed by photoetching and dry etching. FIG. 1 shows this state.

Next, referring to FIG. 2, a phosphorus glass film 5 with a thickness of 600 nm is formed by bias sputtering method, through holes are formed by photoetching and dry etching, and then selective deposition is performed only in the through hole portions. A 600 nm thick tungsten film of 6 gold was formed by chemical vapor deposition. FIG. 2 shows this state.

Next, referring to FIG. 3, a 2 μm thick aluminum film was formed by sputtering, and then a second layer aluminum wiring film 7 was formed by photoetching and dry etching. FIG. 3 shows this state.

In the multilayer wiring formed by the above process, by depositing a tungsten film on the aluminum-silicon alloy film of the first layer wiring, it was possible to prevent the formation of aluminum oxide that would otherwise be formed on the surface. A chemical vapor deposition method that selectively deposits a tungsten film only on the through-hole portion connecting the first layer wiring and the second layer wiring can be easily and reliably performed. Furthermore, since no aluminum oxide is present, the contact resistance between the first-layer wiring and the second-layer wiring is low9, and multi-layer wiring with narrow portion connections without disconnection can be produced with high productivity.

In the above embodiments, a tungsten film was used as the metal film deposited on the first layer wiring, but it was confirmed that transition metal films such as molybdenum films and tantalum films also exhibit similar effects. Further, in this example, tungsten was used as the metal to be selectively deposited by chemical vapor deposition, but it was confirmed that transition metals such as molybdenum and tantalum could be similarly deposited satisfactorily.

As is clear from the above description, according to the present invention, it is possible to easily, safely and reliably connect the interlayer pincers in multilayer wiring, which has been a drawback of the prior art.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 3 are cross-sectional views of wiring layers shown in the order of steps of the present invention.

Claims (1)

[Claims] 1. In forming a multilayer interconnect that connects a first layer interconnect and a second layer interconnect, a transition metal film such as a tungsten film is deposited on the metal film of the first layer interconnect, and the first A transition metal film such as a tungsten film is selectively formed only in the through-hole portion connecting the layer wiring and the second layer wiring using a chemical vapor deposition method, and the transition metal film such as the chemical vapor deposited tungsten film is A method for forming multilayer wiring, the method comprising the step of connecting first-layer wiring and second-layer wiring. 2. In the case where the first layer wiring is made of an aluminum-silicon alloy, a transition metal film such as a tungsten film is deposited on the metal film of the first layer wiring. The multilayer structure according to claim 1, in which an alloy film is formed by sputtering, and then a transition metal film such as a tungsten film is continuously formed in the same apparatus to cover the aluminum-silicon alloy film. How to form the edges.