JP2007031367A - Organic aluminum compound and method for producing aluminum-containing film using the compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic aluminum compound which can stably form aluminum-containing films at high film-forming rates, and to provide a method for producing an aluminum-containing film using the compound. <P>SOLUTION: This organic aluminum compound is represented by formula: Al(R<SP>1</SP>NH)<SB>n</SB>(R<SP>2</SP>R<SP>3</SP>N)<SB>3-n</SB>, wherein R<SP>1</SP>is a 1 to 5C alkyl; R<SP>2</SP>and R<SP>3</SP>are each identically or differently a 1 to 5C alkyl; (n) is an integer of 1 or 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to semiconductor insulating films formed by metal organic chemical vapor deposition (hereinafter referred to as MOCVD method) and aluminum such as AlN and Al ₂ O ₃ used for LCD applications. The present invention relates to an organic aluminum compound suitable as a raw material for producing a containing film and a method for producing an aluminum-containing film using the compound.

Conventionally, AlN thin films used as semiconductor insulating films have been produced by MOCVD using alkylaluminum such as trimethylaluminum (TMA) or triethylaluminum (TEA) as a raw material. However, these compounds are ignitable and water-inhibiting substances, and are highly pyrophoric. They are easily hydrolyzed by moisture contained in the air to form Al ₂ O ₃ , and heat is generated in the decomposed by-product methane and ethane. There was a problem that ignited and explosive ignition occurred. Although the amount of water that causes such hydrolysis can be confirmed as a spontaneously ignited spark even at a level of 30 ppm, it has been experimented to prevent the influence of moisture beyond this, but such compounds are strictly controlled at the factory. In normal use, it is difficult to completely suppress the mixing of moisture from the environment. For these reasons, it has been expected to propose a compound that is stable to moisture from the environment and can obtain a high film formation rate.

  A material for chemical vapor deposition containing an aluminum compound represented by the following formula (2) is disclosed as a new material in place of a conventionally known organoaluminum compound (see, for example, Patent Document 1). .).

In the formula, _one of R ₁ and R ₂ represents an alkyl group having 1 to 4 carbon atoms, the other represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and A represents an alkylene group having 1 to 4 carbon atoms. R ₃ represents an alkyl group having 1 to 8 carbon atoms which may have an oxygen atom in the chain.

By using the compound shown by this patent document 1, it has sufficient stability suitable for various CVD methods compared with the conventionally known organoaluminum compound.
Japanese Patent Laying-Open No. 2003-34868 (Claim 1)

  However, since the compound shown in Patent Document 1 is easily polymerized between the compounds via the alkyl group in the compound in the gas phase and the stability of the vapor pressure is poor, the material is not necessarily sufficient as a CVD raw material. I could not say.

  An object of the present invention is to provide an organoaluminum compound capable of stably forming an aluminum-containing film at a high film formation rate and a method for producing an aluminum-containing film using the compound.

The invention according to claim 1 is an organoaluminum compound represented by the following formula (1).
Al (R ¹ NH) _n (R ² R ³ N) _3-n (1)
In the formula, R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² and R ³ are each an alkyl group having 1 to 5 carbon atoms, and R ² and R ³ are the same or different from each other. N may represent an integer of 1 or 2.

  In the invention which concerns on Claim 1, an aluminum containing film can be stably formed at a high film-forming speed | rate by producing an aluminum containing film by MOCVD method using the compound shown by said Formula (1).

  The invention according to claim 2 is a method for producing an aluminum-containing film by organometallic chemical vapor deposition using the organoaluminum compound according to claim 1.

  The organoaluminum compound of the present invention is represented by the above-described formula (1), and has an excellent advantage that an aluminum-containing film can be stably formed at a high film formation rate.

Next, the best mode for carrying out the present invention will be described.
The organoaluminum compound of the present invention is a compound represented by the following formula (1).

Al (R ¹ NH) _n (R ² R ³ N) _3-n (1)
In the formula, R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² and R ³ are each an alkyl group having 1 to 5 carbon atoms, and R ² and R ³ are the same or different from each other. N may represent an integer of 1 or 2.

  The compound represented by the above formula (1) has a structure in which an alkylamino group having a linear or branched alkyl is bonded to an Al atom by a σ bond, and therefore has higher stability and excellent handling than conventional organoaluminum compounds. . When an aluminum-containing film is formed using this compound, the aluminum-containing film can be formed at a higher film formation rate and with higher stability than when a conventional organoaluminum compound is used.

The alkyl group having 1 to 5 carbon atoms of R ¹ , R ² and R ³ of the organoaluminum compound represented by the above formula (1) of the present invention includes a methyl group (Me), an ethyl group (Et), and a normal propyl group. (N-Pr), isopropyl group (i-Pr), normal butyl group (n-Bu), isobutyl group (i-Bu), secondary butyl group (s-Bu), tertiary butyl group (t-Bu), Examples thereof include a normal pentyl group (n-Pent), an isopentyl group (i-Pent), and a neopentyl group (neo-Pent).

Next, among the organoaluminum compounds of the present invention, R ¹ in the above formula (1) is a t-Bu group, R ² and R ³ are Me groups, and n is an integer of 2 [(t-Bu) A method for producing NH] ₂ (Me ₂ N) will be described.
First, aluminum trichloride is added to anhydrous tetrahydrofuran and suspended by stirring at room temperature for about 30 minutes to prepare a suspension. Next, dimethylaminolithium is added to this suspension and the mixture is further stirred for about 1 hour to be reacted. Next, while maintaining the reaction solution under ice-cooling, while stirring well with a stirring motor, t-butylaminobromide is twice the molar equivalent of aluminum chloride, and dimethylaminobromide is 1 molar equivalent of aluminum chloride slowly. And add. Next, the added solution is stirred for about 24 hours under ice-cooling, and the solution is heated to 60 ° C., and further stirred for 30 minutes to be reacted. Next, the reaction solution is filtered, and the obtained filtrate is concentrated under reduced pressure under the conditions of 2 Torr (about 266 Pa) and 30 ° C., so that the target product, an orange liquid Al [(t-Bu) NH] ₂ (Me ₂ N) is obtained.

The addition ratio of t-butylaminobromide added to aluminum chloride is changed to the above formula (1) by changing the addition ratio of 1-fold molar equivalent of aluminum chloride and dimethylaminobromide to 2-fold molar equivalent of aluminum chloride. ) In which n is an integer of 1, Al [(t-Bu) NH] (Me ₂ N) ₂ is obtained. Further, when t-butylamino bromide added to aluminum chloride is replaced with, for example, i-propylamino bromide, Al [(i-Pr) NH] ₂ (Me ₂ N) is obtained and is replaced with n-pentylamino bromide. And Al [(n-Pent) NH] ₂ (Me ₂ N) are obtained. Similarly, Al [(t-Bu) NH] (Et ₂ N) ₂ is obtained by replacing dimethylaminobromide added to aluminum chloride with, for example, diethylaminobromide, and Al [(t -Bu) NH] (MeEtN) ₂ is obtained.

Next, an example of forming an AlN thin film by the solution vaporization CVD method using the organoaluminum compound of the present invention will be described. The solution vaporization CVD method is a method in which each solution is supplied to a heated vaporizer, where each solution raw material is instantaneously vaporized and sent to a film formation chamber to form a film on a substrate.
As shown in FIG. 1, the MOCVD apparatus includes a film formation chamber 10 and a vapor generator 11. A heater 12 is provided inside the film forming chamber 10, and a substrate 13 is held on the heater 12. The inside of the film forming chamber 10 is evacuated by a pipe 17 including a pressure sensor 14, a cold trap 15 and a needle valve 16. An NH ₃ gas introduction pipe 37 is connected to the film forming chamber 10 via a needle valve 36 and a gas flow rate adjusting device 34. When the thin film formed here is an Al ₂ O ₃ thin film, H ₂ O gas is introduced from the gas introduction pipe 37. The steam generator 11 includes a raw material container 18 that stores the organoaluminum compound of the present invention. A carrier gas introduction pipe 21 is connected to the raw material container 18 through a gas flow rate control device 19, and a supply pipe 22 is connected to the raw material container 18. The supply pipe 22 is provided with a needle valve 23 and a solution flow rate adjusting device 24, and the supply pipe 22 is connected to a vaporizer 26. A carrier gas introduction pipe 29 is connected to the vaporizer 26 via a needle valve 31 and a gas flow rate control device 28. The vaporizer 26 is further connected to the film forming chamber 10 by a pipe 27. A gas drain 32 and a drain 33 are connected to the vaporizer 26, respectively.
In this apparatus, a carrier gas composed of an inert gas such as N ₂ , He, Ar is introduced into the raw material container 18 from the carrier gas introduction pipe 21, and the solution raw material stored in the raw material container 18 is vaporized by the supply pipe 22. To the container 26. The organoaluminum compound vaporized by the vaporizer 26 to become vapor is further supplied into the film forming chamber 10 through the pipe 27 by the carrier gas introduced into the vaporizer 26 from the carrier gas introduction pipe 28. In the film forming chamber 10, the vapor of the organoaluminum compound is thermally decomposed and reacted with NH ₃ gas introduced into the film forming chamber 10 through the NH ₃ gas introduction pipe 37, thereby heating the generated AlN substrate. 13 is deposited to form an AlN thin film. Since the organoaluminum compound of the present invention is thermally decomposed at a lower temperature than conventional organoaluminum compounds, film growth at a low temperature is possible. The organoaluminum compound of the present invention is excellent in vaporization stability and has a high film formation rate.

Next, examples of the present invention will be described in detail together with comparative examples.
<Example 1>
First, 10 g of commercially available aluminum trichloride was added to 500 ml of anhydrous tetrahydrofuran, and the suspension was stirred for 30 minutes at room temperature to prepare a suspension. Next, 30 g of dimethylaminolithium was added to this suspension, and the mixture was further reacted by stirring for 1 hour. Next, while maintaining the reaction solution under ice-cooling, while stirring well with a stirring motor, t-butylaminobromide is twice the molar equivalent of aluminum chloride, and dimethylaminobromide is 1 molar equivalent of aluminum chloride slowly. And added. Next, the added solution was stirred under ice-cooling for 24 hours, and the solution was heated to 60 ° C., and further stirred for 30 minutes to be reacted. Next, the reaction solution was filtered, and the obtained filtrate was concentrated under reduced pressure at 2 Torr (about 266 Pa) and 30 ° C. to obtain an orange liquid compound. As a result of measuring the obtained compound by ¹ H-NMR, the data shown in the following Table 1 were obtained. The liquid obtained from the above analysis results has the structure represented by the above-described formula (1), R ¹ is t-Bu, R ² and R ³ are Me, and n is an integer of 2 which is an integer [( t-Bu) NH] ₂ (Me ₂ N).
<Examples 2-35>
The organoaluminum compounds shown in the following Table 1 were synthesized in the same manner as in Example 1 except that the kind of the amine compound added to aluminum trichloride and the amount of added mole were changed. The ¹ H-NMR identification data of the synthesized organoaluminum compounds are shown in the following Table 1 and Table 2, respectively.

<Comparative Example 1>
AlMe ₃ was prepared as an organoaluminum compound.
<Comparative example 2>
AlEt ₃ was prepared as an organoaluminum compound.
<Comparative Example 3>
Al (H) (Me) ₂ was prepared as an organoaluminum compound.

<Comparison test 1>
Using the organoaluminum compounds of Examples 1 to 35 and Comparative Examples 1 to 3, a film thickness test per film formation time was performed.
First, five silicon substrates each having a SiO ₂ film (thickness: 5000 mm) formed on the surface were prepared as substrates, and these substrates were placed in a film formation chamber of an MOCVD apparatus using the solution vaporization CVD method shown in FIG. Next, the substrate temperature was set to 250 ° C., the vaporization temperature was set to 100 ° C., and the pressure was set to about 266 Pa (2 Torr). NH ₃ gas was used as a reaction gas, and its partial pressure was 500 ccm. Next, when He gas is used as the carrier gas and the solution raw material is supplied at a rate of 0.1 cc / min, respectively, and the film formation time becomes 1, 5, 10, 20, and 30 minutes Each one was taken out from the film forming chamber. The film thickness of the AlN thin film on the substrate after film formation was measured from a cross-sectional SEM (scanning electron microscope) image. Further, the step coverage of the AlN thin film on the substrate having a film formation time of 10 minutes was measured from a cross-sectional SEM (scanning electron microscope) image.

<Evaluation>
Tables 3 and 4 show the results of film thickness and step coverage obtained per film formation time, respectively.

  As is clear from Table 1, the AlN thin film formed using the organoaluminum compounds of Comparative Examples 1 to 3 did not increase in thickness over time, and was formed to an even thickness. As a result, the film formation stability and the step coverage were poor. On the other hand, the AlN thin film formed using the organoaluminum compounds of Examples 1 to 35 has a thick film thickness per film formation time and a uniform thickness from the results of film thickness per film formation time and step coverage. Thus, the organoaluminum compounds of Examples 1 to 35 were found to be compounds capable of stably forming an AlN thin film at a high film formation rate.

<Comparison test 2>
A film was formed in the same manner as in Comparative Test 1 except that water vapor was supplied at a rate of 1000 ccm every 5 seconds using the organoaluminum compound of Example 4 to form an Al ₂ O ₃ thin film on the substrate. A film was formed in the same manner as in Comparative Test 1 except that water vapor was supplied at a rate of 500 ccm using the compound of Example 14, and an Al ₂ O ₃ thin film was formed on the substrate. Further, an Al ₂ O ₃ thin film was formed on the substrate in the same manner as in Comparative Test 1 except that water vapor was supplied at a rate of 100 ccm using the compound of Example 21. The film thickness of the Al ₂ O ₃ thin film on the substrate after film formation was measured from a cross-sectional SEM (scanning electron microscope) image. Further, the step coverage of the Al ₂ O ₃ thin film on the substrate having a film formation time of 10 minutes was measured from a cross-sectional SEM (scanning electron microscope) image.

<Evaluation>
Table 5 shows the obtained film thickness and step coverage results per film formation time.

As is apparent from Table 5, the Al ₂ O ₃ thin film formed using the organoaluminum compounds of Examples 4, 14 and 21 has a film formation time based on the results of film thickness per film formation time and step coverage. It was found that the organoaluminum compound of the present invention is a compound that can stably form an Al ₂ O ₃ thin film at a high film formation rate.

Schematic of an MOCVD apparatus using a solution vaporization CVD method.

Claims (2)

An organoaluminum compound represented by the following formula (1).
Al (R ¹ NH) _n (R ² R ³ N) _3-n (1)
In the formula, R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² and R ³ are each an alkyl group having 1 to 5 carbon atoms, and R ² and R ³ are the same or different from each other. N may represent an integer of 1 or 2. A method for producing an aluminum-containing film by organometallic chemical vapor deposition using the organoaluminum compound according to claim 1.

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