JPH05195211A - Sputtering method of al or al alloy - Google Patents

Abstract

PURPOSE:To prevent reduction of coverage of a metal film in a hole part. CONSTITUTION:Sputtering is performed in a chamber 2 equipped with a discharge port 8, Ar gas inlet, and He gas inlet, while controlling the ventilation performance and flow rates of Ar and He to adjust the sputtering pressure to several mTorr. The compsn. of the mixture gas used is, for example, Ar:He=50%:50%. Even when sputtered atoms from the target collide with He atoms till the sputtered atoms reach the substrate 6, sputtered atoms maintain the straight movement and reach the bottom part of a contact hole or through-hole. Thus, the obtd. Al film or Al alloy film 14a shows no reduction of coverage performance in steps.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering method for forming an Al (aluminum) or Al alloy film used for metal wiring in a process for manufacturing a semiconductor integrated circuit device.

[0002]

2. Description of the Related Art In the sputtering method, as shown in FIG. 2A, a target 4 and a substrate 6 on which a metal film is to be deposited are placed in a chamber 2 so as to face each other, and a sputtering gas is placed in the chamber 2. As Ar (argon)
Is introduced and exhausted from the exhaust port 8 to adjust the pressure in the chamber 2 to a predetermined pressure. With the target 4 on the cathode side and the substrate 6 on the anode side, a discharge is generated in the chamber 2, and the target 4 is sputtered with Ar ions to produce the target 4
The sputtered atoms are deposited on the substrate 6 to form an Al film or an Al alloy film.

According to the result of measuring the sputter rate of the ions incident on the target, the sputter rate tends to increase as the atomic weight increases, but the sputter rate increases especially with an inert gas. Therefore, Ne (neon), Ar, Kr (krypton), Xe (xenon), etc. can be used as the sputtering gas.
Predominantly Ar is used. Ar has a higher abundance than Kr and Xe, and is therefore inexpensive. He
The atomic weight of (helium) is too small and the sputtering rate is close to zero. Ne has a sputtering rate as small as about half that of Ar, and has a low ionization rate. Thus, Ar is mainly used as a sputtering gas because it is an inert gas, has a high sputtering rate, is inexpensive, and is easily ionized. Sputtering includes reactive sputtering, in which N ₂ (nitrogen) and O ₂ (oxygen) are added in addition to Ar as a sputtering gas. N ₂ and O ₂ do not directly sputter the target but react with the object to be sputtered (target material) to form an alloy film.

[0004]

The Al or Al alloy used as the metal wiring of the semiconductor integrated circuit device and containing a slight amount of silicon in Al is formed by the sputtering method using Ar as the sputtering gas. , Ar atoms have an atomic weight of 39.94, which is heavier than Al atoms having an atomic weight of 26.98, so that the sputtered Al atoms can be retained only once until they reach the substrate. When it collides with, the straightness of Al atoms is impaired. The Al atoms that have collided and scattered repeatedly collide with other Al atoms, Ar ions, and Ar atoms, and the number of Al atoms that go straight in the vicinity of the substrate is extremely small. The situation is
The state is as schematically shown in FIG. Figure 2
In (B), black circles are Al atoms and white circles are Ar ions or Ar.
Represents an atom. As a result, in the contact hole portion and the through hole portion, the number of sputtered atoms entering the bottom portion of the hole is reduced and the upper portion of the hole is overhanged. As a result, the penetration of sputtered atoms into the bottom of the hole is further reduced, the film formation rate at the bottom and the side of the hole is reduced, and the thin film 14 as shown in FIG. 2C is formed. It may cause a disconnection due to electromigration in the. 2 (B) and 2 (C),
Reference numeral 10 is a substrate on which metal wiring is to be formed, and 12 is an interlayer insulating film, showing a state in which a contact hole is formed. a represents an overhang-like portion of the metal film.

Attempts have been made to reduce the Ar gas pressure in order to reduce the probability of collision of sputtered atoms with Ar ions or Ar atoms, but if the pressure is less than 1 mTorr, the discharge will not be stable and sputtering will be difficult. The present invention is Al or A
By maintaining the straightness of the sputtered atoms of the 1-alloy,
An object of the present invention is to provide a sputtering method capable of preventing the step coverage of a metal film from decreasing in a contact hole or a through hole.

[0006]

In the sputtering method of the present invention, a mixed gas of Ar and an inert gas other than Ar is used as the inert gas introduced into the chamber for sputtering. The inert gas other than Ar is preferably an element having a smaller atomic weight than Al, specifically He or Ne.
Is. In order to perform film formation efficiently, the composition of the inert gas in the chamber may be adjusted according to one or both of the shape of the substrate arranged facing the target and the elapsed sputtering time. The method of the present invention can be applied to various types of sputtering methods such as a diode sputtering method, a multipolar sputtering method, and a magnetron sputtering method.

[0007]

[Function] He and Ne have a lower sputtering rate than Ar,
For sputtering, Ar mainly acts, and He and N
e acts to regulate the pressure of the gas. He or N for Ar
By mixing e, the pressure in the chamber can be increased to several mTorr.
The discharge can be performed in a certain degree, and the discharge becomes stable. When discharge starts and sputtering starts, sputtered atoms fly toward the substrate facing the target. Even if the sputtered atoms collide with He atoms or Ne atoms before reaching the substrate, the atomic weight of He or Ne is smaller than Al, so that the sputtered atoms can reach the substrate without impairing the straightness. Sputtered atoms that have not lost their straightness can easily reach the bottoms of contact holes and through holes.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1A schematically shows a sputtering apparatus to which the present invention is applied. The same reference numerals are used for the same parts as in FIG. Target 2 in chamber 2
The substrate 6 is disposed so as to face the
The substrate 6 is connected to the anode side. Exhaust port 8 in chamber 2
An argon gas inlet and a He gas inlet are provided. By adjusting the exhaust capacity and Ar flow rate and He flow rate,
Adjust the sputtering pressure to about a few mTorr. The composition of the mixed gas in the chamber is, for example, Ar: He = 50%:
It is 50% (mol%).

A discharge is caused to start sputtering. Even if the sputtered atoms collide with He atoms before reaching the substrate 4 from the target 4, the sputtered atoms maintain their straightness and reach the bottoms of the contact holes and through holes. This state is schematically shown in FIG. In FIG. 1B, black circles represent Al atoms, large white circles represent Ar ions or Ar atoms, and small white circles represent He ions or He atoms. As a result,
As shown in (C), an Al film or Al alloy film 14a is formed in which the step coverage is not lowered. Figure 1
Then, even if the gas mixed with the Ar gas is Ne gas, the same effect can be obtained.

By changing the composition of the mixed gas in the chamber, the sputtering rate and the characteristics of the deposited thin film are changed. If the ratio of He and Ne mixed with Ar is increased,
The step coverage of the thin film on the contact hole or through hole is improved, but the sputter rate is reduced. On the contrary, when He or Ne is decreased, the step coverage is deteriorated, but the sputter rate is increased. Therefore, in the initial stage of sputtering, the proportion of He or Ne can be increased to improve the film quality, and the proportion of He or Ne can be decreased halfway to increase the sputtering rate.

The composition of the inert gas can be changed depending on the shape of the substrate on which the metal film is to be formed. For example, in a substrate having vertical side wall contact holes and through holes, a metal film with good step coverage is deposited by increasing the ratio of He and Ne, and a mortar-shaped contact hole and the like is decreased in the ratio of He and Ne. However, since the step coverage is not deteriorated, the sputtering speed can be increased by reducing the He / Ne ratio in the substrate having the mortar-shaped contact holes and performing the sputtering. In this way, by adjusting the mixing ratio of the inert gas in the chamber according to the shape of the substrate and the elapsed time of sputtering, it is possible to efficiently perform film formation while preventing a decrease in step coverage.

[0012]

According to the present invention, when forming an Al film or an Al alloy film, Ar is mixed with an inert gas having a smaller atomic weight than Al such as He or Ne as a gas in the chamber.
It is possible to maintain the straightness of sputtered atoms and form a metal film having excellent step coverage. In addition, by adjusting the composition of the inert gas according to the shape of the substrate and the elapsed sputtering time, it is possible to efficiently form the metal film while preventing the step coverage from decreasing.

[Brief description of drawings]

1A and 1B are views showing the present invention, FIG. 1A is a view schematically showing an example of a sputtering apparatus, and FIG. 1B is a cross-sectional view showing a state where sputtered atoms come into a contact hole;
(C) is a cross-sectional view showing the obtained metal film.

FIG. 2 is a diagram showing a conventional sputtering method,
(A) is a diagram schematically showing an example of a sputtering apparatus,
(B) is a cross-sectional view showing a state in which sputtered atoms fly into the contact hole, and (C) is a cross-sectional view showing the obtained metal film.

[Explanation of symbols]

 2 chamber 4 target 6 substrate 8 exhaust port 10 silicon substrate 12 interlayer insulating film 14a aluminum film

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[Procedure amendment]

[Submission date] December 18, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

Claims (3)

[Claims] 1. A method of forming an Al film or an Al alloy film by injecting an inert gas ion into a target of Al or Al alloy and depositing sputtered atoms from the target on a substrate arranged facing the target. 2. The sputtering method, wherein a mixed gas of Ar and an inert gas other than Ar is used as the inert gas. 2. The sputtering method according to claim 1, wherein the inert gas other than Ar is an element having a smaller atomic weight than Al. 3. The sputtering method according to claim 1, wherein the composition of the mixed gas is adjusted according to one or both of the shape of the substrate arranged facing the target and the elapsed sputtering time.