JPS6235649A - Wiring layer forming method - Google Patents

Abstract

PURPOSE:To form a wiring layer with high reliability at the contact part, by selectively forming a barrier-metal layer of W on the bottom part of a contact window by a vapor-phase growth method to make an Al layer by vapor-phase growth. CONSTITUTION:By selectively forming a barrier metal layer of W on the bottom part of a contact window 3, a W layer 4 is embedded as a thick barrier metal layer at the bottom of an opening part of the contact window 3, to reduce a step difference in the contact window. Then, a source gas in a growth chamber is exchanged for a mixed gas of triisobutyl.aluminum (TIBA) and H2.TIBA, which is liquid at ordinary temperature, is heated at about 40 deg.C to increase its supplied amount, with He or Ar gas used in a bubbling state. Besides, H2 gas is mixed to be introduced as source gas into the reaction chamber. Hence, while an Al layer 5 is brought into good contact with the W layer 4, an Al wiring layer having a smooth surface can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] Aluminum is widely used as a wiring layer of semiconductor devices, and its lamination method is usually a physical vapor deposition method. In the present invention, TIBA (
We will explain a method for forming a wiring layer with good step coverage even in contact windows with deep steps using lysobutyl aluminum).

[Industrial application field]

The present invention uses a chemical vapor deposition method (CVD) instead of the physical vapor deposition method that is normally widely used to form aluminum wiring layers.
This invention relates to a method for growing aluminum wiring layers containing deeper contact windows.

Aluminum is mostly used in the formation of wiring layers in semiconductor devices, and at this point the formation of the semiconductor element portion is almost complete, so it is desirable that the temperature of the substrate be as low as possible when forming the aluminum layer.

Therefore, the vacuum evaporation method, which allows growth on a substrate even at room temperature, is exclusively used for growing aluminum.

For this reason, a fundamental problem with vacuum deposition is that of poor coverage at the stepped portion of the contact window.

Using TIBA, it is now possible to grow an aluminum layer by the CVD method with a sufficiently low substrate temperature of 280 to 320 degrees Celsius, and this technology can be used to form highly reliable wiring layers on substrates with deep contact windows. There is a need for technology to emerge.

[Conventional technology]

As a method for growing aluminum by CVD, a method using triisobutyl aluminum (abbreviated as TIBA) is already known.

TIBA is represented by the molecular formula A (1(Ca Hq)
Precipitate j2.

A l (C4H9)3→A J +3/2H2+3C
4HeTIBA is a liquid at room temperature, but in order to increase the supply amount, it is heated to about 40°C, He or Ar gas is bubbled, and the substrate heated to about 300 to 350°C is placed in a reaction chamber. be introduced.

When growing an aluminum layer using the TIBA decomposition method described above, if aluminum is grown directly on a silicon substrate, there is a problem with its adhesion to the aluminum, and even if aluminum is laminated on the contact window, it will adhere in a state that is extremely easy to peel off. ing.

Also, the silicon of the substrate dissolves into the aluminum layer,
There is a problem in that bit defects occur.

To prevent this, before growing the aluminum layer,
It has already been proposed that it is effective to selectively form a barrier metal layer made of tungsten at the contact portion with silicon.

[Problem that the invention seeks to solve]

Although the basic problems of aluminum layers in vapor phase growth are being clarified by the conventional techniques mentioned above, there are still problems in applying them to highly integrated semiconductor devices with deeper contact windows. There is a need to establish a vapor phase growth method for forming highly reliable wiring layers, especially in contact areas.

[Means for solving problems]

The above problem is solved by selectively forming a barrier metal layer made of tungsten at the bottom of the contact window by vapor phase growth. This is done by vapor phase growth using a gas mixture of tungsten fluoride, nitrogen, and hydrogen.

Next, the problem is solved by the method for forming a wiring layer of the present invention, which involves vapor-phase growth of an aluminum layer using TIBA.

[Effect]

The problems of silicon-aluminum interfaces caused by growing an aluminum layer directly on the silicon surface of the contact window are solved by interposing the refractory metal tungsten.

Furthermore, since the tungsten layer also functions as a buried layer for the contact window, the severity of the step is reduced and the reliability of the aluminum wiring layer formation is improved.

〔Example〕

An embodiment according to the present invention will be described in detail with reference to the drawings.

In FIG. 1, elements have already been formed on a silicon substrate 1, an insulating film 2 such as a SiO□ film or a PSG film is laminated on the substrate to form a wiring layer, and a contact window 3 is opened.

A tungsten barrier metal layer is selectively formed to prevent problems with the silicon contact surface described in the prior art section.

The barrier metal layer is formed by a gas phase reaction using a mixed gas of WF, N2, and N2 at the following flow rate ratio and at a substrate temperature of 280 to 320°C.

WF6 2 Nz: Hz=3:
20-40: 20-40 N2 in the above process
The gas functions to selectively grow tungsten only on the contact surface, and the NZ gas is mixed in for dilution.

Through this selective growth process, a thick tungsten layer 4 serving as a barrier metal layer is buried at the bottom of the opening of the contact window 3, as shown in FIG. 1, and the height difference in the contact window is reduced.

Next, the source gas in the growth chamber is switched to a mixed gas of TIBA and N2. TIBA is a liquid at room temperature, so
Heating to about 40 °C to increase the feed rate, He %
Alternatively, bubbling Ar gas is used.

Furthermore, N2 gas is mixed with this and introduced into the reaction chamber as a source gas. The Ht gas mixed in at this time functions to promote the growth of aluminum. The temperature of the substrate during growth is maintained at 280-320°C.

The above process ensures good contact between the aluminum layer 5 and the tungsten layer 4 as a barrier metal layer.

In addition, the presence of the barrier metal layer significantly reduces the step difference in the contact window, making it possible to obtain a smooth aluminum wiring layer with less surface irregularities. This is the second
As shown in the figure.

〔Effect of the invention〕

As explained above, by applying the wiring layer forming method of the present invention, it is possible to form a wiring layer with good contact properties and a large step coverage effect in a highly integrated semiconductor device having a deep contact window. It has become possible.

[Brief explanation of drawings]

FIG. 1 shows a cross-sectional view in the first step of forming a wiring layer according to the present invention, and FIG. 2 shows a cross-sectional view after forming a wiring layer according to the present invention. In the drawings, 1 is a silicon substrate, 2 is an insulating film, 3 is a contact window, 4 is a tungsten layer (barrier metal N), and 5 is an aluminum layer.

Claims (1)

[Claims] The invention is characterized in that after a barrier metal layer (4) made of tungsten is selectively formed at the bottom of the contact window (3) by a vapor phase growth method, an aluminum layer (5) is grown in a vapor phase. A method for forming a wiring layer.