JPH0347966A - Formation of thin al-cu alloy film - Google Patents

Abstract

PURPOSE:To allow a thin Al-Cu alloy film to simultaneously satisfy step covering property and migration resistance by alternately forming thin films of Al and Cu by CVD with an organoaluminum compd. and hexafluoroacetylacetonatocopper as starting materials and carrying out heating to form the alloy thin film. CONSTITUTION:An organoaluminum compd. is used as starting material for Al and hexafluoroacetylacetonatocopper as starting material for Cu. When a film is formed by CVD, gases of both the starting materials are intermittently and alternately fed without mixing and thin films of Al and Cu are alternately formed. The resulting multilayered film is heated to form a thin Al-Cu alloy film by counter diffusion of Al and Cu. The thickness of the Al-Cu alloy film and the ratio between Al and Cu in the film are controlled by regulating the flow rates of the gases. Small contact holes are embedded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for forming a Cu alloy thin film for wiring constituting an integrated circuit device or the like.

[Prior Art] Aluminum-based thin films for forming interconnections in integrated circuit devices must be deposited with good coverage at stepped portions, and bias sputtering (J, El) is a method for this purpose.
ect, rochem, soc, magazine, 1985 no.
Volume 32, page 1466) and chemical vapor deposition (J,
Electrochem, Soc, 1984, Vol. 131, p. 2175) (hereinafter abbreviated as CVD method) is being considered.

In addition, in the CVD method, which provides good step coverage, there is a report on adding 81 to Al (35th Applied Physics Association Lecture Proceedings, Volume 2, p605, Lecture No. 28a-v-6).

[Problem to be solved by the invention]

However, with the miniaturization of LSIs, it is necessary to miniaturize the width of the wiring used and the contact holes of the electrodes, and as a result, electric I/ROM migration and stress migration caused by increased current density have become problems. There is. In general, Al has a small atomic weight and is mobile, which causes the above-mentioned problems.

In the sputtering method, it is known that adding Cu to Al is effective against migration, but in the normal sputtering method, 1. , cannot cope with miniaturization of sI. Similar dosing is possible using the bias sputtering method, but since the bias is applied, the sample is exposed to the bombardment of charged particles such as ions and electrons, which causes characteristic changes in elements and wiring, and especially in wiring, migration resistance is reduced. known to deteriorate.

In addition, it has been reported that Al-3i film can be formed by CVD with good step coverage, but at the normally required process temperature, Si precipitates in the contact area, increasing contact resistance and causing contact failure. It has been reported that (Digest of Technical
Papers, 1986 Symposium on
VLSI Technology paper number V-4, p
p, 55-56. May 1986).

For these reasons, a technique that satisfies step coverage and migration resistance at the same time has not been realized to date.

An object of the present invention is to provide a method for forming an Al--Cu alloy thin film that satisfies step coverage and migration resistance at the same time.

[Means to solve the problem]

In order to achieve the above object, in the method for forming an Al-Cu alloy thin film of the present invention, organic aluminum is used as a raw material for aluminum, copper hexafluoroacetylacetonate (C
U(hfa) is used as a raw material for copper, and after forming Al and Cu thin films alternately from these raw materials into a multilayer thin film using a chemical vapor deposition method without mixing the respective raw material gases, the multilayer thin film is It is heated to generate an Al-Cu alloy thin film.

[Function] In the present invention, the decomposition temperature of the Al raw material is 250°C or higher, and copper hexafluoroacetylacetonate (Cu(hfa)
), the decomposition temperature is 250℃ or higher, and the substrate temperature is 25℃ or higher.
It takes advantage of the fact that Al and copper are deposited by thermal decomposition if the temperature is kept above 0°C. However, when the raw material gases are mixed, the oxidation reaction of Al progresses, and there is a possibility that Al oxide may be deposited in the film. Therefore, kQ and copper thin films are alternately formed by intermittently and alternately flowing each raw material gas so as not to mix these raw material gases in the gas phase. Next, by heating, Al and copper are mutually diffused to form an Aft-Cu alloy. In addition, by controlling the flow rate of each source gas, the film thickness can be controlled.
The component ratio of Al and copper in the deposited film after heating can be controlled.

It has been reported that an Al-Cu alloy film formed by sputtering is effective for stress migration (Proce
eding of 5th century International
onal IEEE VLSIMulilevel I
Interconnection Conference
pp, l73179, June 1985).

This is thought to be due to the fact that the addition of Cu suppresses the movement of Afl atoms, thereby increasing the migration resistance of Al. Therefore, the An-Cu alloy film formed by CVD also has excellent migration resistance. Moreover, CVD
Since the film is formed using the above method, the step coverage of the film is also good.

〔Example] The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a configuration diagram of a gas supply system and a low pressure CVD apparatus for forming an Al--Cu alloy thin film.

1 is a hydrogen gas cylinder, 2 and 3 are bubbler containers filled with Al raw material and copper raw material, respectively, 4 and 5 are temperature regulators to keep the temperature of these bubbler containers constant, and 6.7 and 8 are hydrogen gas. 9. a mass flow controller that adjusts the flow rate of the flow rate; IO and 11 are air valves for introducing hydrogen, hydrogen containing an Al raw material, and hydrogen containing a copper raw material into the growth chamber, respectively; 12 is a valve opening/closing control device that controls opening and closing of these three valves; 13 is a growth chamber; 14 is a wafer, 15 is a heater that heats the wafer and keeps the temperature constant, 16
is the exhaust system.

In the figure, first, dimethylaluminum hydride is sealed in a bubbler container 2, and hydrogen gas is caused to flow while controlling the flow rate with a mass flow controller 6, and the vapor pressure components of the raw materials are mixed in the bubbler container 2 at a partial pressure ratio. Further, copper hexafluoroacetylacetonate is sealed in the container 3, and hydrogen gas is caused to flow while controlling the flow rate with a mass flow controller 8, and the vapor pressure components of the raw materials are mixed at a partial pressure ratio with a valve 9.

Next, the pressure in the growth chamber 13 is maintained at 3 Torr, and the flow rate of hydrogen gas containing dimethylaluminum hydride is controlled to 603 CCM by the mass flow controller 6.

During growth, the temperature of bubbler container 2 is kept at 25°C by temperature regulator 4.
Next, the temperature of the container 3 is maintained at 80° C. by a temperature regulator 5.

Also, at this time, the partial pressure of the Al source gas in the growth chamber 13 is 0.
．． The partial pressure of copper hexafluoroacetylacetonate in the growth chamber 13 was estimated to be 0.05 Torr. The wafer 14 placed in the growth chamber 13 is maintained at 250° C. by a heater 15. The introduced raw material is heated on a wafer 14'' and converted into Al or Cu by thermal decomposition.
deposit.

FIG. 2 shows a cross section of a multilayer wiring structure of a device produced according to the present invention. In the figure, 21 is an existing wiring, 22 is an interlayer insulating film, 23, 25 and 27 are Al thin films, and 24 and 26 are Cu thin films. In this example, Al
3 layers with 0.2p m per layer and 0.05p per Cu layer
A two-layer multilayer thin film structure of m was formed by the above procedure.

When this was heated at 300°C for 2 hours, alloying of Al and Cu progressed, and a uniform Cu-containing Al thin film was formed.

The film thus formed had excellent step coverage, contained about one layer of Cu in Al, and had excellent migration resistance.

Note that the present invention can be modified as follows.

Instead of dimethylaluminum hydride, other organic aluminums such as triisobutylaluminum, dimethylaluminum dichloride, and methylaluminum dichloride can be used as raw materials.

[Effect 1 of the Invention As described above, according to the present invention, an Al-Cu alloy thin film with high migration resistance can be formed by a CVD method that allows filling of minute contact holes.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an apparatus for carrying out the present invention, and FIG. 2 is a cross-sectional block diagram of a thin film produced by the present invention. 1. Hydrogen bottle 2.3 Bubbler container 4.5.
- Temperature regulator 6, 7.8 - Mass flow controller 9.10.11... Air valve 12 - Valve opening/closing control device 13 - Growth chamber 14 - Wafer 15 - Heater 16 - Exhaust system 21 Existing Al wiring
22...Insulating film 23.25.27-Al thin film 24.26...-Cu thin film

Claims (1)

[Claims] (1) Organic aluminum is used as a raw material for aluminum, and copper hexafluoroacetylacetonate (Cu(hfa)_
2 is used as a raw material for copper, Al and Cu thin films are alternately formed from these raw materials in the form of a multilayer thin film using chemical vapor deposition method without mixing the respective raw material gases, and then the multilayer thin film is heated to form an Al - A characterized by producing a Cu alloy thin film
Method for forming l-Cu alloy thin film.