JPH0673069A - Organometallic compound for thermal decomposition and aluminum thin film using the same - Google Patents

Abstract

PURPOSE:To provide a novel compound easy in its handling because of being liquid at ordinary temperature, capable of being stably and constantly fed into a growth chamber, and giving an Al thin film little in a carbon content and excellent in conductivity. CONSTITUTION:A compound of formula: RAlN2.NR<1>R<2>R<3> (R is 1-2C alkyl; R<1>-R<3> are 1-2C alkyl, H), e.g. methylaluminum dihalide trimethylamine. The compound is obtained e.g. by dropping dimethylaluminum chloride to a lithium aluminum halide-suspended ether solution, further adding trimethylamine to the solution for their reaction, and subsequently subjecting the reaction mixture to a vacuum distillation separation at a bottom temperature of 28-30 deg.C.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a chemical vapor deposition method (MO).
The present invention relates to an organometallic compound applied to CVD, MONBE, etc., and further to an aluminum thin film obtained by using the organometallic compound as a raw material in a chemical vapor deposition method.

[0002]

2. Description of the Related Art Conventionally, as organometallic compounds for thermal decomposition, trimethyl aluminum (hereinafter referred to as TMA), triisobutyl aluminum (hereinafter referred to as TIBA), dimethyl aluminum hydride (hereinafter referred to as
DMAH), trimethylamine alane (hereinafter,
TMAA), dialkylaluminum hydride amine (hereinafter referred to as DAHA) and the like are used. By thermally decomposing these organoaluminums using a chemical vapor deposition method, aluminum thin films are formed into quartz, silicon carbide, aluminum nitride, silicon, and GaAs.
A thin film is deposited on a substrate such as.

[0003]

As is well known, the physical properties of an organometallic compound required as a raw material for a chemical vapor deposition method are as follows: (1) Incorporation of carbon into an aluminum thin film formed by thermal decomposition is small. (Good conductivity). (2) The decomposition temperature is low, and the vapor pressure is as high as 1 Torr or more at room temperature from the point of mass flow control. (3) It is a gas or liquid at room temperature and easy to handle. Etc. are considered to be important requirements.

However, the above-mentioned conventionally used organometallic compounds do not satisfy all of these requirements.

For example, in thermal CVD using TMA, CH ₃ is easily incorporated into a formed film to form an insulating film. Except for special plasma CVD, etc., a low resistivity aluminum film with low carbon contamination cannot be deposited. Have difficulty.

On the other hand, when other organoaluminum is used, an aluminum film having relatively good conductivity is obtained as compared with TMA, but TIBA has a low vapor pressure (1 mmHg / 47
℃), in order to compensate for this, if heating at 50 ℃ or more for a long time, one isobutyl group is removed and the reaction to decompose into diisobutylaluminum hydride proceeds, and the vapor pressure becomes extremely small (0.01 mmHg / 60 ℃) It is not possible to obtain a sufficient amount of raw material supply.

Further, since DMAH has a high viscosity, it is difficult to charge it in a bubbler container, and there is a difficulty in handling such as a large pressure loss at the time of bubbling. Further, most of DAHAs are solids having a melting point close to room temperature, so that a stable evaporation amount cannot be supplied.

On the other hand, since TMAA is a solid at room temperature, it is impossible to supply a stable evaporation amount, and the decomposition reaction proceeds even during storage at room temperature, resulting in poor stability.

In view of such circumstances, the present inventors have found that the aluminum film produced has a low carbon content, a high vapor pressure at room temperature, is easy to handle, and is stable in the growth chamber.
As a result of extensive studies to find an organometallic compound that can be supplied in a fixed amount, it was found that an adduct of a specific alkylamine can satisfy the above-mentioned characteristics to a high degree, and the present invention has been completed.

[0010]

That is, according to the present invention, the general formula RAlH ₂ · NR ¹ R ² R ³ (wherein R is a carbon number 1
~ 2 alkyl group, R ¹ , R ² and R ³ each represent an alkyl group having 1 to 2 carbon atoms or hydrogen)
Another object of the present invention is to provide an organometallic compound for thermal decomposition comprising an alkylaluminum dihydride amine represented by

Another aspect of the present invention is the chemical vapor deposition method, wherein the general formula RAlH ₂ · NR ¹ R ² R is used.
³ (In the formula, R is an alkyl group having 1 to 2 carbon atoms,
R ¹ , R ² and R ³ each represent an alkyl group having 1 to 2 carbon atoms or hydrogen), which is an alkylaluminum dihydride amine.

The organometallic compound used in the present invention is represented by the general formula RAlH ₂ .NR ¹ R ² R ³ (wherein R is an alkyl group having 1 to 2 carbon atoms, R ¹ , R ² and R ³
Each represents an alkyl group consisting of 1 or 2 or hydrogen)
Alkylaluminum dihydride amine represented by, more specifically methylaluminum dihydride trimethylamine (hereinafter referred to as MAD), methylaluminum dihydride dimethylamine, methylaluminum dihydride monomethylamine, ethylaluminum dihydride trimethylamine (hereinafter referred to as EAD).
H)), ethylaluminium dihydride dimethylamine, ethylaluminium dihydride monomethylamine, ethylaluminum dihydride methyldimethylamine, ethylaluminium dihydride methyldiethylamine, methylaluminum dihydride triethylamine, methylaluminium dihydride diethylamine and methylaluminum dihydride. Examples thereof include monoethylamine, ethylaluminum dihydride triethylamine, ethylaluminum dihydride diethylamine, ethylaluminum dihydride monoethylamine, methylaluminum dihydride methyldimethylamine, methylaluminum dihydride methyldiethylamine and the like.

Among the alkylaluminum dihydride amines represented by these general formulas, especially MAD and EAD
H is a liquid at room temperature, has a low viscosity, a relatively high vapor pressure, is excellent in thermal decomposability as compared with conventionally used organometallic compounds, and also has a low uptake of carbon into the produced film, It has advantages that an aluminum film having excellent conductivity can be obtained without taking in impurities due to nitrogen, and that a metallic bubbler container which has been conventionally used can be used.

Such an alkyl aluminum dihydride amine is synthesized by an existing method, for example, lithium aluminum hydride, dimethyl aluminum chloride and trimethyl amine. The alkylaluminum dihydride amine, which is a raw material for these chemical vapor deposition methods, may be mixed with some dialkylaluminum hydride amine or TMAA during its thermal decomposition. Usually, if these by-products are up to 30% by weight, preferably up to 20% by weight, the effect as a raw material of the present invention is not impaired, but the solvent used in the synthesis of alkylaluminum dihydride amine is excluded as much as possible. It is better to have Further, it is of course possible to purify the raw material alkylaluminum dihydride amine to remove trace metal impurities and oxygen compounds before use.

The organometallic compound for thermal decomposition of the present invention may be applied to a chemical vapor deposition method by the same method as that for a generally known organometallic compound. For example, FIG. 1 shows one embodiment of a CVD apparatus used for forming an aluminum thin film.
In this device structure, the pyrolysis organometallic compound filled in the bubbler container 3 is adjusted to a predetermined temperature by the temperature controller 4, and the carrier gas whose flow rate is adjusted from the carrier gas cylinder 1 through the flow rate controller 2 is bubbled. The carrier gas is entrained with the organometallic compound for thermal decomposition by bubbling by blowing into the container 3. Next, the carrier gas accompanied by the thermally decomposed organometallic compound is introduced into the growth chamber 5 from the bubbler container and heated by the heater 7, whereby the organometallic compound introduced on the substrate 6 is thermally decomposed to form an aluminum thin film.

[0016]

INDUSTRIAL APPLICABILITY According to the present invention, in the chemical vapor deposition method, the alkylaluminum dihydride amine represented by the above-mentioned general formula as the organometallic compound for thermal decomposition is replaced with a conventionally known organometallic compound. Since it is a liquid at room temperature just by using it, it is easy to handle, stable and quantitative supply to the growth chamber is possible, and in addition, it is possible to obtain an aluminum thin film with extremely low carbon content and excellent conductivity. Therefore, it can be widely used as an aluminum wiring film material for semiconductors and LSIs, and its industrial value is enormous.

[0017]

EXAMPLES The present invention will now be described in more detail with reference to examples.

Example 1 62 g of dimethyl aluminum chloride was added dropwise to a solution of 22 g of lithium aluminum hydride suspended in 1 liter of ether, 106 g of trimethylamine was added to the solution, and this was distilled under reduced pressure at a kettle temperature of 28 ° C to 30 ° C. Separated to obtain a compound containing methylaluminum dihydride trimethylamine as a main component. This compound was hydrolyzed, and the amount of generated gas and its composition (gas chromatographic analysis), the Al content in water and the titration of trimethylamine were used to identify the contained substance and analyze the purity. As a result MAD
The content of H was 85% by weight and the content of dimethylaluminum hydride trimethylamine was 15% by weight.

The compound containing MADH as the main component thus obtained is converted into ARC [accelerating rate].
Accelerating Rate Calorimeter, Columbia Scientific Industries (CO
LUMBIA SCIENTIFIC INDUSTRIES), USA] was used to charge MADH in an amount shown in Table 1 into a container, and after thermally decomposing at a temperature shown in Table 1 in an argon-sealed atmosphere,
After returning to room temperature and releasing the evolved gas, the solid residue amount was measured, and the decomposition rate was determined by (substantial reduction amount / theoretical reduction amount) × 100. The results are shown in Table 1. For comparison, the decomposition rates of commercially available DMAH and TMA were determined by the same method as that for MAD. The results are shown in Table 1.

[0020]

[Table 1]

Example 2 Using the CVD apparatus having the structure shown in FIG. 1, quartz was used as a substrate and an Al thin film was formed on the substrate. In the implementation, argon was used as a carrier gas, and the mass flow controller (flow rate controller) controlled the pressure to 300-500 SCCM, continuously introducing it into a bubbler container, and after bubbling in an organometallic compound, from the bubbler container It was led out, introduced into a growth chamber, the organometallic compound was thermally decomposed in the growth chamber, and aluminum was deposited on the substrate. The bubbler container was adjusted to 40 ° C. by a temperature controller, and the growth chamber was maintained at 450 ° C. by an infrared heating furnace. In the above method,
When MADH obtained by the method of Example 1 was used as a raw material, it was confirmed by a tester that the film obtained on the substrate had conductivity, and X-ray diffraction confirmed that it was aluminum. On the other hand, the same DMA as used in Example 1 as a raw material
When H was used, the film obtained on the substrate was insulative as confirmed by a tester, and the presence of aluminum carbide was confirmed by X-ray diffraction in addition to aluminum. In addition, elemental analysis detected 3% (average value of samples collected at 4 points) of carbon.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a CVD apparatus using an organometallic compound.

[Explanation of symbols]

In the figure, 1 is a carrier gas cylinder, 2 is a flow rate controller, 3 is a bubbler container, 4 is a temperature controller, 5 is a growth chamber, 6 is a substrate, and 7
Indicates a heater.

Claims (2)

[Claims] 1. The general formula RAlH ₂ .NR ¹ R ² R
³ (In the formula, R is an alkyl group having 1 to 2 carbon atoms,
R ¹ , R ² and R ³ each represent an alkyl group having 1 to 2 carbon atoms or hydrogen), and an organometallic compound for thermal decomposition comprising an alkylaluminum dihydride amine. 2. In the chemical vapor deposition method, the general formula R
AlH₂・ NR¹R ²R³(In the formula, is R 1 to 2 carbon atoms?
An alkyl group consisting of R¹, R²And R³Are each carbon
Indicate an alkyl group consisting of the numbers 1 to 2 or hydrogen)
Alkyl aluminum dihydride amine
Aluminum thin film used as.