JPH0736395B2 - Aluminum film growth method - Google Patents

Description

DETAILED DESCRIPTION [Outline] Aluminum is widely used as a wiring layer of a semiconductor device, and the stacking method is a physical vapor deposition method (PVD).
Law) is used exclusively. An object of the present invention is to improve a vapor phase growth method (CVD method) of aluminum and a growth method utilizing a photoexcitation reaction.

[Industrial application field]

The present invention relates to an improvement of an aluminum film growth method by a vapor phase growth method using TIBA as a reaction gas instead of the PVD method which is generally widely used for forming an aluminum wiring layer.

Since aluminum has a problem in its film quality when grown by a vapor phase growth method, it is generally grown by a vacuum deposition method.

Almost all aluminum thin films are used in integrated circuits for the formation of wiring layers, and at this point the formation of semiconductor element parts is almost complete. Therefore, in the aluminum film formation process, the substrate temperature should be kept as low as possible. Is desirable.

Therefore, the vacuum vapor deposition method, which enables growth even at room temperature, is exclusively used for growing aluminum. For this reason, there is a problem of poor coverage at the stepped portion of the electrode window, which is a fundamental problem of vacuum deposition.

Also, if it becomes possible to grow aluminum by vapor phase growth,
At the time of growth, it is possible to grow an alloy film with a metal other than aluminum, and its appearance is desired.

[Conventional technology]

As a vapor growth method for aluminum, a method using triisobutyryl aluminum, which is abbreviated as TIBA, is already known.

TIBA is represented by a molecular formula of Al (C ₄ H ₉ ) ₃ and thermally decomposes at 250 to 300 ° C. to precipitate Al as shown below.

Al (C ₄ H ₉ ) ₃ → Al + 3 / 2H ₂ ＋ 3C ₄ H ₈ TIBA is a liquid at room temperature, but about 50% to accelerate the reaction.
After heating to ℃, bubbling He or Ar gas, it is introduced into the reaction tank where the substrate heated to about 300 ℃ is installed.

The thermal decomposition of TIBA described above is a temperature that can be sufficiently endured as an ordinary semiconductor manufacturing process, and there is a vapor phase growth method utilizing the photoreaction of TIBA gas for the purpose of growth at a low temperature.

As a method of utilizing light, there are cases where an ultraviolet ray method and an infrared ray are used, but the ultraviolet ray method has a lower temperature,
Mainly the excitation reaction of molecules by light energy,
The infrared method considerably includes a decomposition reaction by heat energy.

The use of infrared light is much more popular in vapor phase growth because the light source is much cheaper and the device is simpler in structure.

[Problems to be solved by the invention]

In the above-described conventional method, the TIBA decomposition method by the infrared irradiation method causes a problem that the growth on the semiconductor substrate is not always uniform.

Depending on the structure of the reaction tank, the semiconductor substrate is installed in a horizontal position in the tank, TIBA gas is introduced into the reaction tank, and infrared light is irradiated from above.

However, the source gas inflow hole is usually at one location, the gas flow in the reaction vessel is not uniform, and the gas concentration is uneven.

For this reason, when an aluminum film is grown,
There is a problem that the thin film does not grow uniformly on the surface of the substrate, and the coverage particularly at the step portion deteriorates.

[Means for solving problems]

The above-mentioned problem is that the substrate is placed on the support table inside the reaction tank of the present invention, and the reaction gas is supplied from the separator having a large number of gas ejection holes installed so as to face the substrate to supply the aluminum film. In the method of growing a., The end faces of a large number of optical fibers are arranged on the surface of the separator facing the substrate so as to be mixed with the large number of gas ejection holes, and the reaction gas is supplied from the large number of gas ejection holes. In addition, the method for growing an aluminum film is characterized by irradiating infrared rays toward the substrate from the end faces of the plurality of optical fibers in parallel with the flow of the reaction gas.

[Action]

A gas supply chamber is provided separately from the reaction tank, and a separator having a large number of gas ejection holes is installed at the bottom of the gas supply chamber. A single core or a bundled optical fiber is installed between the gas ejection holes so that the end faces the direction of the substrate, and the reaction tank is evacuated so that the gas is supplied between the gas supply chamber and the reaction tank. Since a pressure difference is generated, the reaction gas introduced into the gas supply chamber is supplied onto the substrate in a uniform shower-like flow form a large number of gas ejection ports.

In addition, since infrared rays are also irradiated onto the substrate evenly in the direction of the substrate in parallel with the gas flow from the optical fibers provided between the gas ejection ports, photochemical reaction by infrared rays in the reaction chamber and on the substrate. The reaction and thermal decomposition reaction proceed, and an aluminum film can be formed with a uniform thickness even on a large-area substrate.

〔Example〕

The structure of an apparatus used in the method for growing an aluminum film of the present invention will be described with reference to FIG.

Inside the reaction tank 1, a substrate 3 mounted on a support base 2 is installed. An exhaust hole is provided in the lower part of the reaction tank and is connected to the exhaust device 4.

A gas supply chamber 5 is provided above the reaction tank, and a reaction gas is supplied from a gas introduction hole 6. The gas introduction hole is connected to the gas source 7.

In the gas supply chamber, as shown in FIG. 2, a large number of gas ejection holes 9 are opened in the separator plate 8 facing the reaction tank.

Infrared light from the infrared light source 10 is projected onto the optical fiber 11 through the lens, and the optical fiber is guided to the gas supply chamber. Where a lot of single-core fibers,
Alternatively, it is divided into a plurality of fiber groups.

The divided fiber 12 is a separator plate 8 of the gas supply chamber.
Then, the end face of the fiber is fixed toward the reaction tank.

In order to grow the aluminum film, the substrate 3 is placed on the support 2 and then the pressure in the reaction tank 1 is reduced by the exhaust device 4. Next, TIBA gas is introduced into the gas supply chamber 5.

Since there is a separating plate 8 between the reaction tank and the reaction tank, a pressure difference is generated in the gas supply chamber, and a uniform flow from the gas ejection holes 9 is obtained.
BA gas is ejected.

On the other hand, infrared rays pass through the optical fiber and irradiate the reaction tank from its end face, causing decomposition reaction of TIBA gas. Further, a part of the energy also heats the substrate and contributes to uniform growth of the aluminum film.

〔The invention's effect〕

As explained above, the introduction of the reaction gas is made uniform by the method of the present invention, and the irradiation of infrared rays is also made uniform, so that the reaction is uniform and the growth of the aluminum film is uniform and the growth rate is uniform. Can be promoted.

[Brief description of drawings]

FIG. 1 is a sectional view of an apparatus used in the growth method according to the present invention, and FIG. 2 is a plan view of a separator. In the drawings, 1 is a reaction tank, 2 is a support base, 3 is a substrate, 4 is an exhaust device, 5
Is a gas supply chamber, 6 is a gas introduction hole, 7 is a gas source, 8 is a separator, 9 is a gas ejection hole, 10 is an infrared light source, 11 is an optical multi-fiber, and 12 is a divided optical fiber.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/3205

Claims (1)

[Claims] 1. An aluminum film is grown by mounting a substrate on a support inside a reaction tank, and supplying a reaction gas from a separator having a large number of gas ejection holes installed so as to face the substrate. In the method, the surface of the separator facing the substrate is arranged so that the end faces of a large number of optical fibers are mixed with the large number of gas ejection holes, and a reaction gas is supplied from the large number of gas ejection holes, A method for growing an aluminum film, which comprises irradiating infrared rays toward the substrate from the end faces of the plurality of optical fibers in parallel with the flow of the reaction gas.