JPH0555219A - Semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the deterioration of reliability and yield due to a metallic film having inferior stepped-section coating properties and a roughened surface shape having irregularities. CONSTITUTION:A semiconductor device has a first metallic film 3, film thickness of which from the sidewall of a connecting hole is kept approximately constant in the connecting hole and formed in approximately the radius of the connecting hole, and a second metallic film 4 having approximately fixed film thickness on the first metallic film on a substrate 1 having the connecting hole bored to an insulating film in a surface layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a metal film filling a fine connection hole.

[0002]

2. Description of the Related Art Conventionally, as a semiconductor device of this type, a semiconductor device having only one metal film with poor step coverage (Yoichi Funaki, Nickel Micro Devices NIKK)
EI MICRODEVICES, page 85, December issue
1986), a semiconductor device having only a metal film having a non-uniform film thickness on an insulating film (Extended Abstracts of Eighteenth Conference on Solid State Devices and Materials Extended Abstracts of
he 18th (1986 Internationala
l) Conference on Solid Sta
te Devices and Materials, T
tokyo, 1986, pp. 495-498).

[0003]

In the conventional semiconductor device having only one metal film having poor step coverage as described above, when the metal film is used for wiring, disconnection occurs at a portion having low step coverage. Therefore, it has a drawback of low reliability.
In addition, the current density in the step portion increases, so that the electromigration resistance is low. A semiconductor device having only a metal film whose thickness on the insulating film is not uniform is
Due to the rough surface shape of the metal film having many irregularities, incident light is diffusely reflected in the subsequent lithography process and the resolution of the resist is deteriorated, so that the yield is lowered.

[0004]

The semiconductor device of the present invention comprises:
In a substrate having a connection hole opened in the insulating film on the surface layer,
A first metal film having a film thickness from the side wall of the connection hole that is substantially constant within the connection hole and is about the radius of the connection hole, and a second metal film having a substantially constant film thickness on the first metal film. It is characterized by having. Also, the second metal film is an alloy, for example, an aluminum alloy, and the first metal film is an aluminum film, or
It is an alloy film in which the elements in the second metal film are diffused.

[0005]

[Function] The metal film deposited on the insulating film by vapor phase chemical growth has a smooth surface shape when the film thickness is thin, and as the film thickness increases, the surface shape becomes rough with many irregularities. Known as Al, Cu, W and the like. Even if the film thickness is thin, the step coverage of the film formed by vapor phase chemical growth is good. On the other hand, although the film formed by sputtering has poor step coverage, the surface shape is smooth. Taking advantage of these features in combination, first open the insulating film, for example with a diameter of 0.5.
After forming a thin metal film having a thickness of 0.25 μm and relatively good flatness by vapor phase chemical growth so as to almost completely fill a microscopic connection hole of μm or less, further metal film is formed to a desired film thickness by sputtering. It has been newly found that the deposition can form a metal film having excellent step coverage and flatness.

Further, it is difficult to form a desired alloy film by vapor phase chemical growth, because the decomposition temperatures of different kinds of raw materials are generally different and some raw materials react with each other. On the other hand, after depositing the first metal by chemical vapor deposition,
When a second metal or alloy film different from the above metal is deposited by sputtering and subsequently annealed, the second metal or alloy is diffused and formed in the first metal film by an amount determined by the annealing temperature. It has been newly found that the entire metal thin film is easily alloyed.

[0007]

The present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a substrate formed by the main steps in one embodiment of the present invention. This embodiment illustrates a case where the present invention is applied to a semiconductor device having an aluminum film in a silicon integrated circuit.

Using standard integrated circuit fabrication methods, FIG.
The structure before forming the aluminum film shown in (a) is formed. In the figure, 1 is a silicon substrate and 2 is a silicon oxide film. Before the vapor phase chemical growth of the metal film, the substrate is pretreated by immersing the substrate in a hydrofluoric acid solution in which 0.1 mol% of Ti is dissolved and then drying the substrate. Next in FIG.
As shown in (b), the first metal film 3 is deposited by vapor phase chemical growth using an organic aluminum material to a film thickness equal to or larger than the radius of the connection hole opened in the silicon oxide film 2 on the substrate surface. Deposition was carried out by using dimethylaluminum hydride as a raw material for the aluminum film, and the carrier hydrogen flow rate was 60 scc.
m, growth chamber pressure 3 Torr, substrate temperature 250 ° C., and vapor phase chemical growth. The thickness of the deposited aluminum film is 0.2
When the thickness is 5 μm or less, the flatness of the aluminum film on the silicon oxide film 2 is sufficiently high. Further, the connection hole opened in the silicon oxide film 2 is almost completely filled in flat. Next in FIG.
As shown in (c), the second metal film 4 is deposited on the first metal film 3 by sputtering. Even when the film thickness of the metal film 4 is about 0.3 μm, the surface shape of the deposited film is smooth and the flatness is sufficiently high. When the substrate is exposed to the atmosphere or oxygen after the first metal film is formed and before the second metal film is formed and an oxide film is formed on the surface of the first metal film, the second metal film is formed. Before forming the film, it is necessary to remove the oxide film by reverse sputtering or the like so that the first metal film 3 and the second metal film 4 become conductive.

Needless to say, a similar thin film can be formed by using triisobutylaluminum, acetyl aluminum hydride, trimethylamine alane, triethylamine alane or the like as a raw material for vapor phase chemical growth of aluminum.

A thin film formed by sputtering is
An l-Si alloy, an Al-Cu alloy, an Al-Si-Cu alloy or the like may be used. In this case, the heat treatment after sputtering causes Si, Cu, etc. in the alloy to diffuse into the first aluminum film 3 formed by the vapor phase growth method to improve the resistance of the aluminum wiring to electromigration and stress migration. It also has an effect.

The same effect can be obtained by using boron-doped glass, phosphorus-doped glass, silicon nitride film or the like as the insulating film.

As a metal to be deposited by vapor phase growth, WF
₆ , W that can be deposited by using W (CO) ₆
Alternatively, Cu, Au or the like may be used. The metals and alloys deposited by vapor deposition or sputtering include T, in addition to W, Cu, etc.
It goes without saying that the same effect can be obtained with barrier metals such as iN and TiW.

[0014]

As described above, since the semiconductor device of the present invention has good step coverage and has a metal film having a flat surface shape, there is an effect that reliability and yield are significantly improved. In addition, when an alloy film is formed, it has high migration resistance and an effect of improving reliability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the main steps of one embodiment of the present invention.

[Explanation of symbols]

 1 Silicon Substrate 2 Silicon Oxide Film 3 First Metal Film 4 Second Metal Film

Claims (5)

[Claims] 1. In a substrate having a contact hole opened in an insulating film in a surface layer, a first metal film whose film thickness from the sidewall of the contact hole is substantially constant within the contact hole and about the radius of the contact hole; A semiconductor device having a second metal film having a substantially constant film thickness on the first metal film. 2. The semiconductor device according to claim 1, wherein the second metal film is an alloy. 3. The semiconductor device according to claim 1, wherein the first metal film is an aluminum film. 4. The semiconductor device according to claim 1, wherein the second metal film is an aluminum alloy film. 5. The semiconductor device according to claim 4, wherein the first metal film is an alloy film in which an element in the second metal film is diffused.