JPH06283531A - Al thin film forming method - Google Patents

Abstract

PURPOSE:To enable an Al thin film to be formed in a specific region at sufficient film forming rate without deteriorating the selectivity thereof by a method wherein the temperature of a substrate and the partial pressure of dimethylaluminum hydride gas are respectively specified in specific ranges. CONSTITUTION:A material gas containing dimethyl aluminum hydride (DMAH) is fed to a reactor vessel to deposit Al or Al alloy on the specific region of a substrate 10 so that pure Al or Al alloy film may be formed. In order to form the Al thin film in such a procedure, the temperature of the substrate 10 is specified to be 180 deg.-220 deg.C while the partial pressure of the DMAH gas to be 1mTorr-100mTorr. For example, a via hole 50 is bored through an insulating film 40 covering a lower layer metallic wiring 30 comprising an Al alloy film. Finally, Al is to be selectively deposited inside the via hole 50 only by thermal CVD process using the DMAH gas and hydrogen as material gas so as to form a via plug 52.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a chemical vapor deposition method (CV).
The present invention relates to a method of forming a pure Al film or an Al alloy film by using the D method), and particularly to wiring used in a semiconductor device.

[0002]

2. Description of the Related Art In recent years, as a technique for forming a metal thin film on a substrate, a technique using a CVD method using an organic metal gas as a raw material has been proposed.

Particularly, in the field of manufacturing semiconductor devices, a technique using a conventional sputtering method is required because a multi-layer wiring technique and a technique relating to the miniaturization of metal wiring are required as the density and integration of semiconductor elements increase. However, the technology using the CVD method is drawing attention as an alternative to this.

Therefore, a proposal has been made of a CVD method for forming an Al thin film by using dimethyl aluminum hydride (DMAH) as a source gas (see, for example, Japanese Patent Laid-Open No. Hei 3
-291920). This CVD method is effective not only as a fine wiring, but also as a technique for sufficiently filling fine holes.

Here, the CVD disclosed in the prior art.
According to the method, the conditions for depositing Al using DMAH as a raw material are that the substrate temperature is between 230 ° C. and 300 ° C., and the partial pressure of the DMAH gas is between 100 mTorr and 500 mTorr.
between mTorr or 0.1mT
It was performed between orr and 1 mTorr. More specifically, the substrate temperature is set to 260 ° C. (JP-A-3-291920, JP-A-03-15513).
3 etc.) Further, the partial pressure of the gas of DMAH is also specifically set to 0.15 mTorr (Japanese Patent Laid-Open Nos. 03-37121 and 03-110838).
Etc.) and those performed at 500 mTorr (Japanese Patent Laid-Open No. 04-291920 etc.).

[0006]

However, when the substrate temperature is set between 230 ° C. and 300 ° C. when Al is deposited using the CVD method using DMAH as a raw material, the DMAH molecules attached on the substrate are immediately formed. It reacts and precipitates on the substrate, and as a result, nuclei are generated and the selectivity, which is an advantage of the CVD method, is impaired. Further, whether or not nuclei are generated when the selective growth occurs is determined by the gas concentration in the gas phase, so that the partial pressure of DMAH determines the selectivity. When the partial pressure of DMAH is low, that is, when the gas concentration is low, nucleation becomes insufficient or a sufficient film formation rate cannot be obtained, whereas when the gas concentration is high, nucleation occurs more than necessary. As a result, selectivity is hindered.

Therefore, an object of the present invention is to provide an Al thin film forming method which solves such a problem.

[0008]

In order to solve the above problems, an Al thin film forming method according to the present invention, a source gas containing dimethylaluminum hydride (Al (CH ₃ ) ₂ H) is supplied into a reaction vessel. In a method for forming an Al thin film in which a pure Al film or an Al alloy film is formed by depositing Al or an Al alloy in a desired region on a substrate by a chemical vapor deposition method, the temperature of the substrate is 180 ° C. to 220 ° C. The partial pressure of the dimethylaluminum hydride gas is 1 mTorr to 100 mTorr.

[0009]

According to the above method, C prepared from DMAH as a raw material is used.
The partial pressure of the gas of DMAH when depositing Al using the VD method is in the range of 1 mTorr to 100 mTorr, and the temperature range of the substrate is 180 ° C. to 220 ° C.
The Al film can be formed by nucleation without impairing the selectivity.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

The Al thin film according to the present invention is basically formed by the following steps. Each step will be described with reference to FIGS. 1 and 2.

First, as shown in FIG. 1A, a base insulating film 20 is formed on the surface of a Si substrate 10, and an Al alloy of 300 to 800 n is formed on the base insulating film 20 by a sputtering method.
Then, the Al alloy film 31 is formed by depositing the Al alloy film 31 with a thickness of m. Next, the Al alloy film 31 is processed into a predetermined wiring pattern to form the lower layer metal wiring 30. The wiring pattern is formed by RIE (reactive ion etching) using a chlorine-based gas after forming a resist pattern using an exposure device. Next, as shown in FIG. 1B, an insulating film 40 having a thickness of 8000 angstrom is formed on the base insulating film 20 on which the lower layer metal wiring 30 is formed. The insulating film 40 is formed of Si by plasma CVD.
O ₂ is deposited to form a SiO ₂ film, and SOG (Spi
non glass) to form an SOG film,
It is formed by performing heat treatment at a required temperature.
After that, SiO ₂ is deposited again by the plasma CVD method to form a SiO ₂ film.

Next, a photomask is set on the insulating film 40, a resist pattern is formed using an exposure apparatus, and then RIE using a fluorine-based gas is performed in an RIE chamber as shown in FIG. The insulating film 40 has an inner diameter of 0.5
A μm via hole 50 is formed. Next, the lower metal wiring 30 (Al alloy film) exposed at the bottom of the via hole 50 is cleaned by plasma etching using a chlorine-based gas. This cleaning process is performed because deposits, alumina films, and the like adhere to the surface of the lower-layer metal wiring 30 exposed at the bottom of the via hole 50 during RIE and when exposed to the atmosphere after RIE. This is because these deposits and alumina film must be removed because they interfere with Al deposition in the CVD method.

Next, a gas of DMAH, which is an Al raw material,
By selectively depositing Al from the bottom surface only in the via hole 50 by a thermal CVD method using hydrogen as a raw material, as shown in FIG.
As shown in (b), the via plug 5 is placed in the via hole 50.
Form 2.

At this time, the CVD is carried out at a hydrogen gas flow rate of 100 sccm and a bubbling temperature of 25 ° C. The total pressure in the CVD reaction container for performing this film formation is 2 Torr.
r. Then, the partial pressure of the DMAH and the substrate temperature at this time are changed as described later.

When the CVD conditions for forming the via plug 52 obtained by the above steps were changed as follows, the following results were obtained regarding the film forming rate and the selectivity after film forming. The deposition time cannot be specified because it depends on the respective CVD conditions, but the time volume was set to the extent that the via hole was just filled by the preliminary investigation performed in advance. Also,
The selectivity is evaluated by SEM (Scanning Electron Micro) after film formation.
By observing the deposits on the insulating film of 100 μm square by observation, it is judged that the deposits of Al having a diameter of 0.5 μm or more on any part of the insulating film other than the via holes are judged to be unacceptable. did.

First, when the partial pressure of DMAH was fixed at 33 mTorr and the substrate temperature was changed, the results shown in Table 1 were obtained.

[0018]

[Table 1]

Next, the substrate temperature is fixed at 220 ° C. and D
When the partial pressure of MAH was changed, the results shown in Table 2 were obtained.

[0020]

[Table 2]

Then, when the substrate temperature and the partial pressure of DMAH were changed to form a film by the CVD method, the results shown in Table 3 were obtained.

[0022]

[Table 3]

Therefore, when Al is deposited by the CVD method using DMAH as a raw material, the temperature range of the substrate is 180.
If the partial pressure of the gas of DMAH is in the range of 1 mTorr to 100 mTorr, the nucleation is performed without impairing the selectivity. This was discovered by the earnest efforts of the inventors of the present invention.

[0024]

As described above in detail, according to the present invention, the partial pressure of the gas of DMAH is 1 mTorr to 1 when Al is deposited by the CVD method using DMAH as a raw material.
Since the substrate temperature is in the range of 00 mTorr and the temperature range of the substrate is 180 ° C to 220 ° C, nucleation is performed without impairing the selectivity. Therefore, the Al film can be formed in a desired region without impeding the selectivity. The ranges of the substrate temperature and the DMAH gas partial pressure, which are the CVD conditions at this time, have been found out by the inventors of the present invention.

[Brief description of drawings]

FIG. 1 is a diagram showing each step of forming an Al thin film according to an example of the present invention.

FIG. 2 is a diagram showing each step of forming an Al thin film according to an example of the present invention.

[Explanation of symbols]

10 ... Si substrate, 20 ... Base insulating film, 30 ... Lower metal wiring, 40 ... Insulating film, 50 ... Via hole, 51 ... Al film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Yamamoto 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Pref., Technical Research Division, Kawasaki Steel Co., Ltd. (72) Yoyo Ota 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Address: Kawasaki Iron & Steel Co., Ltd.

Claims (1)

[Claims] 1. A dimethyl aluminum hydride (A
A source gas containing 1 (CH ₃ ) ₂ H) is supplied into the reaction vessel, and Al is deposited in a desired region on the substrate by chemical vapor deposition.
Alternatively, in the Al thin film forming method of depositing an Al alloy to form a pure Al film or an Al alloy film, the temperature of the substrate is 180 ° C. to 220 ° C., and
The method for forming an Al thin film, wherein the partial pressure of the dimethylaluminum hydride gas is 1 mTorr to 100 mTorr.