JPH0744180B2 - Method for forming wiring layer by vapor phase growth - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] By mixing hydrogen with organic aluminum, the growth rate of metal is increased and the vapor deposition (CVD) method of aluminum, which is rich in coverage, is used, and the film formation of aluminum is also performed. A refractory metal layer, for example, a tungsten layer is grown before and after,
A method for forming a wiring layer by sandwiching an aluminum layer with a tungsten layer is proposed, which prevents electromigration of the wiring layer and diffusion into an underlying layer, and enables deep contact holes to be filled.

[Industrial application field]

The present invention relates to a method for forming a wiring layer composed of a composite layer by vapor phase growth.

Multi-layered wiring due to integration and miniaturization of semiconductor devices,
Also, a thin wiring layer is required, and electromigration and diffusion of upper and lower aluminum wiring layers, which are generally widely used, have become important issues for device reliability.

However, these problems have not been solved by aluminum growth by the sputtering method which has been often used conventionally.

[Conventional technology]

In the conventional wiring layer including only the aluminum layer, electromigration of the aluminum layer and diffusion from upper and lower layers occur as described above.

When the sputtering method is used to form the aluminum layer, it is difficult to cover the step due to the directional growth.

Therefore, the CVD method may be used to form the aluminum layer.

The conventional CVD method for aluminum is TIBA (triisobutylaluminum), TMA (trimethylaluminum), TEA (triethylaluminum) as organic aluminum.
Bubbling alkylaluminum such as helium (He), argon (Ar), etc., onto the substrate to be grown, 260 ~ 3
It is thermally decomposed at 40 ° C and grows on this substrate.

In this case, the growth rate is as slow as about 500Å / min, and the vapor pressure of the source gas is low, so it is difficult to increase the growth rate further.

Therefore, it has been difficult to cover deep steps.

[Problems to be solved by the invention]

In the conventional wiring layer including only the aluminum layer, electromigration, thermal migration, and diffusion from the upper and lower layers occur in the aluminum layer.

Furthermore, the conventional CVD method for aluminum has a low growth rate.

[Means for solving problems]

To solve the above problems, a growth substrate is placed in a reaction vessel capable of introducing a source gas containing a refractory metal, organoaluminum and hydrogen, and first a source gas containing a refractory metal is introduced into the reaction vessel. , A refractory metal layer is grown on the substrate to be grown by a reduction reaction of a raw material gas containing a refractory metal, then the introduction of the raw material gas containing a refractory metal is stopped, and organoaluminum and hydrogen are introduced into the reaction vessel. And a step of growing an aluminum layer on the substrate to be grown by thermal decomposition or reduction reaction of organoaluminum, and finally, stopping the introduction of organoaluminum and hydrogen and reacting a raw material gas containing a refractory metal A method for forming a wiring layer by vapor phase growth, characterized by including the step of introducing into a container and growing a refractory metal layer on the substrate to be grown by a reduction reaction of a source gas containing a refractory metal. It is made.

[Action]

According to the present invention, by sandwiching the aluminum layer with the tungsten layer, protrusions generated in aluminum and electromigration of aluminum are prevented.

Further, the upper and lower tungsten layers act as barrier layers, and prevent diffusion of aluminum into the upper and lower layers and absorption of aluminum from the upper and lower layers into the aluminum layer.

Further, since the growth of the tungsten / aluminum / tungsten composite layer is a continuous growth in which only the source gas is switched, the interface between the layers is clean and there is little risk of taking in contaminants.

Furthermore, the CV of aluminum mixed with hydrogen according to the invention
The D method increases the growth rate for the following reasons and is effective for deep step coverage.

For example, TIBA as an organoaluminum _{[Al (i-C 4 H 9} ) 3, i-C 4 H 9 is isobutyl] will be described with.

The reaction according to the conventional example is Al (iC ₄ H ₉ ) ₃ → Al + (3/2) H ₂ + 3CH ₂ ═C (CH ₃ ) _2. , But the reaction according to the present invention is Al (iC _{4 H 9) 3 + nH 2} → Al + mH 2 + 3CH 3 CH (CH 3) 2, the n> m. here.

Here, the effect of mixing hydrogen with organoaluminum is considered as follows.

(1) Consideration from the viewpoint of concentration equilibrium Unsaturated hydrocarbons on the right-hand side of the above two equations [isobutylene 3CH ₂ = C
(CH ₃ ) ₂ ], saturated hydrocarbon [isobutane 3CH ₃ CH (C
H ₃ ) ₂ ] has a higher vapor pressure, and therefore the higher the vapor pressure at the reaction interface on the substrate, the easier it is to diffuse, so the concentration decreases.
Therefore, the reaction of the present invention proceeds in the direction of the right side.

(2) Consideration from the viewpoint of temperature equilibrium All the above reactions are exothermic reactions, and the reaction tends to proceed toward the left side due to heat generation. In the case of the present invention, however, the reaction is caused by hydrogen having a large thermal conductivity. By removing the heat, the reaction can be continued in the direction of the right side.

Due to the above actions, an increase in growth rate can be expected.

〔Example〕

 FIG. 1 is a side sectional view of a CVD apparatus for carrying out the present invention.

In the figure, 1 is a reaction vessel, which is exhausted from an exhaust port 2 by an ordinary exhaust system.

3 is a gas mixing container and a shower. TIBA bubbling with He from the organoaluminum inlet 4 and H ₂ from the H ₂ inlet 5
But, WF ₆ is introduced respectively from the WF ₆ introducing port 6.

The growth substrate 8 is placed on the stage 7 in the reaction container 1 and heated by the heater 9.

2 (1) to (3) are sectional views for explaining the manufacturing process of the present invention.

In FIG. 2 (1), a first Al layer 22 is formed on a silicon (Si) substrate 21, and a silicon nitride (Si ₃ N ₄ ) layer 23 of an insulating layer deposited on the first Al layer 22 is formed. The contact hole 24 is opened to expose the Al layer 22.

A wiring layer is formed by covering the contact hole 24 by the method of the present invention.

First, 3SCCM of WF ₆ was introduced into the reaction vessel 1, and the pressure was 1 to 5T.
A W layer 25 having a thickness of 1000Å is grown with orr of 300 to 340.

In Fig. 2 (2), the introduction of WF ₆ was stopped, TIBA was bubbled with He to introduce 10 SCCM, and H ₂ was introduced to 0 to 10 SCCM, and the pressure was 1 to 5 Torr, 300 to 340 ° C, and the thickness of the Al layer was 8,000 Å. Grow 26.

In Fig. 2 (3), the introduction of TIBA and H ₂ was stopped, and WF ₆ was changed to 3
Introducing SCCM, pressure 1-5 Torr, 300-340 ℃, thickness 1000
Å W layer 27 is grown.

The above three layers are continuously grown on the entire surface of the substrate, and then a wiring pattern is formed by using ordinary lithography.

Although TIBA was used as the organic aluminum in the examples, the effect of the present invention is the same when TMA or TEA is used instead of TIBA.

〔The invention's effect〕

As described in detail above, in the W / Al / W composite wiring layer according to the present invention, electromigration of aluminum and diffusion into upper and lower layers can be prevented, and device reliability is improved.

Furthermore, the growth rate of aluminum was high, and it became easy to cover deep steps.

[Brief description of drawings]

FIG. 1 is a side sectional view of a CVD apparatus for carrying out the present invention, and FIGS. 2 (1) to (3) are sectional views for explaining the manufacturing process of the present invention. In the figure, 1 is a reaction container, 2 is an exhaust port, 3 is a gas mixing container and shower, 4 is an organic aluminum introducing port, 5 is an H ₂ introducing port, 6 is a WF ₆ introducing port, 7 is a stage, and 8 is a growth target. A substrate and 9 are heaters.

Claims (1)

[Claims] 1. A substrate to be grown is placed in a reaction vessel capable of introducing a source gas containing a refractory metal, organoaluminum and hydrogen, and first, a source gas containing a refractory metal is introduced into the reaction vessel to increase the temperature. A high-melting-point metal layer is grown on the substrate to be grown by a reduction reaction of the raw-material gas containing the melting-point metal, then the introduction of the raw-material gas containing the high-melting-point metal is stopped, and organoaluminum and hydrogen are introduced into the reaction vessel. Then, a step of growing an aluminum layer on the substrate to be grown by thermal decomposition or reduction reaction of organoaluminum, and finally, stopping the introduction of organoaluminum and hydrogen, and feeding a source gas containing a refractory metal into the reaction vessel. And forming a refractory metal layer on the substrate to be grown by a reduction reaction of a source gas containing a refractory metal, the method for forming a wiring layer by vapor phase growth.