TWI771864B - Precursor compound for atomic layer deposition (ald) and chemical vapor deposition (cvd) and ald/cvd process using same - Google Patents

Abstract

The present invention relates to a compound and a precursor comprising the compound. More particularly, it relates to a precursor comprising a metal of Group 13 of the periodic table and suitable for deposition of thin films by atomic layer deposition (ALD) or chemical vapor deposition (CVD), and to a thin film and preparation of thin films. method. The present invention also provides an electronic device comprising the film.

Description

Compound, precursor, thin film and preparation method thereof, and electronic device

The present invention relates to a novel precursor. More particularly, it relates to a precursor capable of depositing thin films by atomic layer deposition (ALD) and chemical vapor deposition (CVD), and the aforementioned ALD/CVD process.

Al ₂ O ₃ films are mainly used in the semiconductor industry where chemical inertness and high thermal conductivity are required.

Al ₂ O ₃ is used in the manufacture of liquid crystal displays, electroluminescent displays, solar cells, bipolar devices and silicon-on-insulator (SOI) devices. In addition, Al ₂ O ₃ can be used as a wear and corrosion resistant coating material in the tool making industry.

In particular, from the viewpoint of solving the problems of organic electronic devices (such as preventing corrosion of metal materials due to moisture and forming a moisture barrier, due to application to intermediate insulators, passivation of solar cells, etc.), the ALD/CVD process is used to prepare Al ₂ O ₃ Thin-film methods have received attention.

The Al ₂ O ₃ thin film process requires low deposition temperature, and trimethylaluminum [TMA, Al(CH ₃ ) ₃ ] is mainly used as a precursor for the Al ₂ O ₃ thin film prepared using the existing ALD/CVD process.

Although TMA has an ideal deposition rate for ALD films, it will spontaneously ignite, which is an undesirable phenomenon. Therefore, research into safe precursors that can be used for large-scale production on an industrial scale is underway.

Regarding studies on non-pyrophoric precursors including aluminum (Al) as a Group 13 metal, the preparation of [Al(CH ₃ ) ₂ ( μ -O ⁱ Pr)] ₂ (DMAI, ⁱ Pr=isopropyl ) method has been disclosed in the literature {Plasma-enhanced and thermal atomic layer deposition of Al ₂ O using dimethyl aluminum isopropoxide Al( _{CH 3} ) ₂ ( μ -O ⁱ Pr) ) as an alternative aluminum precursor ₃ [ J.Vac.Sci.Technol.A , 2012 , 30(2) , 021505-1]}, but it has problems because the density of the Al ₂ O ₃ film after the ALD process is low.

Another non-pyrophoric precursor includes aluminum, amine-alane, which has disadvantages such as short shelf life, high viscosity, and low vapor pressure.

Therefore, there is a need to develop a new aluminum precursor suitable for ALD/CVD process, which is non-autoflammable and thermally stable, and has high reactivity with various oxidizing, nitriding or reducing agents.

In addition, there is a need for precursors that are liquid at room temperature, have sufficient vapor pressure, and are able to obtain uniform films.

Therefore, there is a need to develop precursors with the aforementioned properties.

[Citation] [Patent Literature]

(Patent Document 1) Korean Patent No. 10-1787204 (Registration date: October 11, 2017)

Therefore, the present invention has been made in consideration of the problems encountered in the related art, and aims to provide novel precursors suitable for ALD (Atomic Layer Deposition) and CVD (Chemical Vapor Deposition), and a method for preparing the same. A method of depositing a thin film of a precursor thereon.

The novel precursors of the present invention include Group 13 metals, which are not pyrophoric and enable high thermal stability and reactivity.

In addition, the precursor of the present invention can obtain a thin film with high quality by ALD or CVD using various reactive gases.

However, the problems to be solved by the present invention are not limited to the foregoing, and other problems not mentioned will be clearly understood from the following description by those having ordinary knowledge in the technical field to which the present invention pertains.

Therefore, the first object of the present invention is to provide a compound. Thus, the compound of the present invention is shown in the following chemical formula 1:

In Chemical Formula 1, M is a Group 13 metal in the periodic table; R ₁ , R ₂ , R ₄ and R ₅ are the same or different from each other and each is hydrogen, or a substituted or unsubstituted C ₁ -C ₄ direct a chain or branched hydrocarbon or an isomer thereof; and R ₃ is a substituted or unsubstituted C ₄ -C ₆ straight or branched hydrocarbon or an isomer thereof.

Therefore, the second object of the present invention is to provide a precursor. Thus, the precursor of the present invention includes the compound shown in Chemical Formula 1.

Therefore, the third object of the present invention is to provide a method for preparing a thin film. Thus, the method for preparing a thin film of the present invention includes the following steps: introducing a precursor comprising the compound shown in Chemical Formula 1 into a reactor.

Therefore, the fourth object of the present invention is to provide a thin film. Thus, the thin film of the present invention is prepared by the aforementioned method using the precursor comprising the compound shown in Chemical Formula 1, and has a surface roughness (Ra) of not more than 1.4 Å and a density of not less than 3 g/cm ³ .

Therefore, the fifth object of the present invention is to provide an electronic device. Thus, the electronic device of the present invention includes the aforementioned thin film.

The effect of the present invention is that according to the present invention, novel precursors including Group 13 metals (Al: aluminum, Ga: gallium, In: indium, etc.) can be prepared. The precursor is not pyrophoric in ambient air and has high thermal stability and reactivity.

In addition, the precursor of the present invention can obtain a thin film with high quality by ALD or CVD using various reactive gases.

Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, wherein: FIG. 1 is a diagram showing the analysis results of the differential scanning calorimetry (DSC) of the novel precursor of the present invention; FIG. 2A and 2B are respectively a graph showing the analysis results of the thermogravimetric analysis (TG) of the novel precursor of the present invention; FIGS. 3A and 3B are respectively a graph showing the evaporation rate measurement results of the novel precursor of the present invention; FIGS. 4A to 4C Figure 5 is a graph showing the change of element content in Al ₂ O ₃ films by X-ray photoelectron spectroscopy (XPS) analysis according to process temperature; Graphs of density variation of Al ₂ O ₃ films; FIGS. 6A to 6C are graphs respectively showing the surface roughness of Al ₂ O ₃ films measured by atomic force microscopy (AFM) as a function of process temperature; and FIGS. 7A to 7C are respectively An image showing step coverage changes using transmission electron microscopy (TEM) analysis according to process temperature in a trench structure with an aspect ratio (AR) of 40:1.

Hereinafter, the embodiments and examples of the present application will be described in detail so that those skilled in the art can easily implement them. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments and examples herein.

Before description, it should be noted that the terms used in this specification should not be interpreted as having typical or dictionary meanings in a limited sense, but should be interpreted as having the meanings and concepts of the present invention, so as to keep the scope of the present invention based on The inventors may define terms as appropriate to best describe the principles of the invention.

In this specification, the singular is intended to include the plural as well, unless the context clearly dictates otherwise. In this specification, the terms "comprising", "including" and the like do not exclude the presence or addition of one or more other features, integers, steps, elements, or combinations thereof.

When numerical ranges are given in this specification, it is to be understood that all ranges formed by any pair of any upper or preferred value of the range and any lower or preferred value of the range are specifically disclosed, whether or not such ranges are expressly disclosed.

The compound according to the present invention is represented by the following Chemical Formula 1.

In Chemical Formula 1, M is a Group 13 metal in the periodic table; R ₁ , R ₂ , R ₄ and R ₅ are the same or different from each other and each is hydrogen, or a substituted or unsubstituted C ₁ -C ₄ direct a chain or branched hydrocarbon or an isomer thereof; and R ₃ is a substituted or unsubstituted C ₄ -C ₆ straight or branched chain hydrocarbon or an isomer thereof.

M in Chemical Formula 1 may be selected from the group consisting of Al, In, and Ga.

R in Chemical Formula ₁ may be selected from the group consisting of n-butyl group, isobutyl group, sec-butyl group, tert-butyl group. butyl group) and its isomers. Preferably, R ₃ in Chemical Formula 1 is a tertiary butyl group or a tertiary butyl group.

R ₁ , R ₂ , R ₄ and R ₅ are the same or different from each other and each may be methyl or ethyl.

The compound of the present invention is prepared by a method for preparing a compound comprising the steps of: reacting an aluminum compound with an organic diamine compound as a ligand in the presence of a solvent, and The synthesized compound was isolated from the reaction mixture.

The aluminum compound starting materials used to prepare the compounds of the present invention can be selected from various compounds known in the art. Examples of the aluminum compound may include Al(CH ₃ ) ₃ , Al(CH ₃ ) ₂ H, Al(CH ₃ CH ₂ ) ₃ , Al(CH ₃ CH ₂ ) ₂ (CH ₃ ), Al(CH ₃ CH _{2 )} ) ₂ H, Al(CH ₃ CH ₂ CH ₂ ) ₃ , etc.

The organic diamine compound starting materials for preparing the compounds of the present invention include substituted or unsubstituted C ₄ -C ₆ straight or branched chain hydrocarbons corresponding to the R ₃ substituent of Chemical Formula 1 or its isomer substituent.

The solvents used to prepare the compounds of the present invention may include any saturated or unsaturated hydrocarbon, aromatic hydrocarbon, aromatic heterocycle, alkyl halide, silylated hydrocarbon, ether, polyether, thioether ( thioether), ester, thioester (thioester), lactone (lactone), amide (amide), amine, polyamine (polyamine), nitrile, silicone oil (silicone oil), other aprotic solvents or two or more of the foregoing mixture. Preferably, the solvent is diethyl ether, pentane or dimethoxyethane. More preferably, the solvent is to use hexane or toluene. any combination A suitable solvent can be used as long as it does not seriously interfere with the intended reaction. If desired, a mixture of one or more different solvents can be used.

The compounds of the present invention can be purified by recrystallization, preferably by extraction and chromatography of the reaction residue (eg, hexane), more preferably by sublimation and distillation.

The compounds of the present invention are preferably liquid at room temperature (20°C).

The precursors of the present invention comprise the aforementioned compounds.

The method for preparing a thin film of the present invention comprises the following steps: introducing the precursor into a reactor.

In addition, the step of depositing at a process temperature of 150°C or higher (or not less than 150°C) is also included. The process temperature is preferably 230°C or higher, more preferably 300°C or higher.

The method for preparing a thin film of the present invention includes the step of using an oxidizing agent, a nitriding agent or a reducing agent to prepare an oxide film, a nitride film or a metal thin film.

The method of making thin films can be carried out by deposition, or can be carried out in the presence of other gaseous components. Deposition of thin films can be carried out in the presence of one or more inert carrier gases. Examples of inert carrier gases include not only nitrogen, argon, and helium, but also other gases that do not react with the precursors of the present invention under process conditions.

Furthermore, the thin film deposition of the present invention can be carried out in the presence of one or more reactive gases. The reactive gas that can be used here may be an oxidizing agent, a nitriding agent, a reducing agent, and the like. Examples include, but are not limited to, hydrazine, air, oxygen, oxygen-rich air, ozone, hydrogen, nitrogen, nitric oxide, nitrogen dioxide, nitrous oxide, water Steam, organic vapor, ammonia, etc.

In particular, the use of oxidizable gases such as air, oxygen, oxygen-enriched air, ozone, water vapor, nitrous oxide, or oxidizable organic compound vapors, as known in the art, facilitates the formation of thin metal oxide films.

The deposition of the present invention can be performed to form thin films comprising a single metal or thin films comprising multiple metals.

In addition, the thin film prepared by the deposition of the present invention may have a surface roughness (Ra) of not more than 1.4 Å and a density of not less than 3 g/cm ³ .

The thin film of the present invention can be used in various electronic devices, in particular, can be used in semiconductors, displays, solar cells, and the like.

The precursors of the present invention can be formed into thin films by atomic layer deposition (ALD) in which the substrate is sequentially exposed to alternate pulses of precursor, reactive and inert gas flows.

Specifically, atomic layer deposition is a process of forming a thin film through a self-limiting reaction by alternately supplying elements required to form a thin film, And can deposit very thin films with precise control of thickness and composition as needed. Therefore, a film with a uniform thickness can be formed even on a large-area substrate, and excellent step coverage can be exhibited even at a high aspect ratio. In addition, it has the advantage that there are few impurities in the thin film.

For example, in one ALD cycle, the substrate can be sequentially exposed to a) an inert carrier gas carrying the precursor, b) an inert gas, c) a reactive gas (eg, oxidizing agent, reducing agent, nitriding agent, etc.), or an inert gas with reactive gases, and d) inert gases.

Typically, the execution time of each step can be as long as the equipment allows (eg, milliseconds), and as long as the process requires (eg, seconds or minutes). The duration of a cycle can be as short as milliseconds or as short as minutes. This cycle is repeated over a period of time ranging from minutes to hours.

The precursors of the present invention can be used to prepare films comprising a single aluminum or thin films comprising a single aluminum oxide, a single aluminum nitride, and the like. In addition, mixed films such as mixed metal oxide/nitride films and the like can also be deposited.

Such films can be prepared using, for example, some organometallic precursors. Metal films can also be prepared without the use of, for example, a carrier gas, vapor, or other reactive gas source.

A better understanding of the present invention can be obtained through the following examples, test examples and preparation examples, which should not be construed as limiting the present invention.

[Example 1]

Synthetic ligand N ¹ -(tertiary butyl)-N ² ,N ² -Dimethylethane-1,2-diamine[N ¹ -(tert-butyl)-N ² ,N ² -dimethylethane-1,2-diamine]

The ligand is synthesized by the following reaction formula 1.

(In Equation 1, tBu is tertiary butyl)

More specifically, 2-chloro-N,N-dimethylethylamine hydrochloride was put into a flask containing H ₂ O and stirred to prepare a clear aqueous solution, after which tert-butylamine was added to In the aqueous solution prepared above and stirring, the flask was placed in a constant temperature water bath at 20°C for about 24 hours.

Subsequently, the flask was transferred to an ice bath, cooled, an aqueous NaOH solution was added, stirred for 10 minutes, extracted with hexane, and treated under reduced pressure to remove the solvent, thereby obtaining N ¹ -(tertiary butyl)-N ² , ^N2 -dimethylethane-1,2-diamine.

The ligand N ¹ -(tertiary butyl)-N ² ,N ² -dimethylethane-1,2-diamine was obtained in 17-32% yield and the ligand was at room temperature Colorless liquid.

[Example 2]

Synthesis precursor Al(CH ₃ ) ₂ [(CH ₃ ) ₂ NCH ₂ CH ₂ NtBu]

The precursor is synthesized by the following reaction formula 2.

(In Equation 2, tBu is tertiary butyl)

More specifically, 1 equivalent of the ligand N ¹ -(tertiary butyl)-N ² ,N ² -dimethylethane-1,2-diamine synthesized in Example 1 was added to 1 equivalent and Dissolve in 1 M Al(CH ₃ ) ₃ in hexane or heptane at -78°C, gradually warm to room temperature, and stir for about 24 hours. After the reaction was complete, the solvent was removed in vacuo.

The reaction yield was 90-97%, and the compound thus obtained was a pale yellow liquid at room temperature.

After purification by vacuum distillation (45-50°C@ _300mTorr ), the colorless liquid precursor Al( _CH3 ) ₂ [( _{CH3 ) 2NCH2CH2NtBu} ] was obtained. The purification yield was 71-80%.

The ¹ H NMR of the obtained precursor is as follows.

¹ H NMR (C ₆ D ₆ ): δ 2.77 Al(CH ₃ ) ₂ [(CH ₃ ) ₂ NCH ₂ CH ₂ NtBu],t, 2H)

δ 2.11 Al(CH ₃ ) ₂ [(CH ₃ ) ₂ NCH ₂ CH ₂ NtBu],t,2H)

δ 1.66 Al(CH ₃ ) ₂ [(CH ₃ ) ₂ NCH ₂ CH ₂ NtBu],s,6H)

δ 1.33 Al(CH ₃ ) ₂ [(CH ₃ ) ₂ NCH ₂ CH ₂ NtBu],s,9H)

δ -0.47 Al(CH ₃ ) ₂ [(CH ₃ ) ₂ NCH ₂ CH ₂ NtBu],s,6H)

For the aluminum precursor synthesized in Example 2, differential scanning calorimetry (DSC), viscosity measurement, thermogravimetric analysis (TG), and evaporation rate measurement were performed as follows to confirm its physical properties.

[Test Example 1] Differential Scanning Calorimetry (DSC)

Differential scanning calorimetry analysis was performed on the aluminum precursor. Here, about 7.8 mg of each sample was placed in an alumina crucible, after which measurement was performed at a heating rate of 10° C./min in a temperature range of 35° C. to 500° C., and the results are shown in FIG. 1 .

Referring to FIG. 1 , the thermal decomposition temperature of the aluminum precursor was determined to be about 245°C.

[Test example 2] Viscosity measurement

The viscosity of the aluminum precursor (measured at 25°C) was measured in a glove box.

The average viscosity of the measured aluminum precursor was 5 times in total, and the average value was 4.78 cP.

[Test Example 3] Thermogravimetric analysis (Thermogravimetric, TG)

Thermogravimetric analysis of aluminum precursors.

The instrument used for thermogravimetric analysis was a 50 μL alumina crucible, a TGA/DSC 1 STAR system from METTLER TOLEDO. The amount of all samples was set to 10 mg, the measurement was performed in the temperature range of 30°C to 400°C, and the temperature was increased at a rate of 10°C/min.

As shown in FIG. 2A , the half-life [T _1/2 (°C)] of the aluminum precursor measured by thermogravimetric analysis was 161.9°C.

In addition, the residual amount was 0.8 wt% at 200°C and 0.2 wt% at 300°C.

In addition, isothermal analysis was performed on the aluminum precursor, and the results are shown in FIG. 2B.

The temperature was increased at a rate of 20°C/min, and isobaric analysis was performed while maintaining the temperature at 80°C, 100°C, 120°C, and 150°C for 2 hours, respectively.

Based on the results of the isothermal analysis, when the temperature was kept at 80°C for 2 hours, the residual amount was about 80%, and when the temperature was kept at 100°C for 2 hours, the residual amount was about 40%.

When the temperature was further increased and kept at 100°C for 2 hours, hardly any residual amount was observed after about 85 minutes, and when the temperature was kept at 150°C for 2 hours, almost no residue was observed after about 30 minutes .

[Test Example 4] Evaporation rate measurement

The evaporation rate of the aluminum precursor was measured.

As shown in Figure 3A, the evaporation rate increases with increasing temperature.

More specifically, the evaporation rate measured at 80°C was about 0.02 mg/min·cm ² , the evaporation rate measured at 120°C was about 0.06 mg/min·cm ² , and further, the evaporation rate at 150°C Significantly increased, and thus measured to be approximately 0.26 mg/min·cm ² .

In addition, by measuring the rate constant k at the temperature T (T: absolute temperature), the evaporation rate was expressed by a linear function ln(k) of 1/T, and the results are shown in Fig. 3B.

For the evaporation rate of the aluminum precursor, ln(k) was about -4.0 mg/min·cm ² measured at 353K and about -2.5 mg/min·cm ² measured at 423K.

[Preparation Example 1] Film formation by atomic layer deposition (ALD) process

Films were formed by atomic layer deposition (ALD) using the aluminum precursor synthesized as in Example 2. Purification was performed using ozone as the oxidant and argon as the inert gas. The implantation of precursors (20 s), argon (10 s), ozone (5 s) and argon (10 s) was considered as one cycle, and deposition was performed on Si (silicon) wafers at a deposition temperature of 200°C . Adjusted in the range of 150°C to 340°C to form an Al ₂ O ₃ thin film.

The thin films prepared in Preparation Example 1 were evaluated in the following items: X-ray photoelectron spectroscopy (X-ray photoelectron spectroscopy (X-ray) of Al ₂ O ₃ thin films deposited at different deposition temperatures using ozone as an oxidant in an ALD process using an aluminum precursor. Photoelectron spectroscopy, XPS) observed the respective contents of aluminum (Al), oxygen (O), carbon (C) and nitrogen (N) and the O/Al ratio in the deposited films, and the X-ray reflectivity (XRR) ) observed density, surface roughness observed using atomic force microscope (AFM), and step coverage observed by transmission electron microscopy (TEM).

[Preparation Example 2] X-ray Photoelectron Spectroscopy (XPS) Analysis

As in Preparation Example 1, in the ALD process using aluminum precursor and ozone as the oxidant, the changes of element content (atomic %) and element ratio (atomic ratio, O/Al ratio) depend on the change of alloy. The process temperature was measured by XPS (X-ray Photoelectron Spectroscopy) analysis.

As shown in FIGS. 4A to 4C , when the process temperature is set in the range of 230° C. to 340° C., the element content of the Al ₂ O ₃ film depends on the quantitatively determined variation of the process temperature.

As shown in Table 1 below, when the process temperatures were 230°C, 300°C and 340°C, impurities such as C (carbon) and N (nitrogen) were not present, and the Al (aluminum) content, O (oxygen) content and O/ The Al ratio remains constant.

[Preparation Example 3] X-ray reflectance (XRR) analysis

As in Preparation Example 1, in the ALD process using the aluminum precursor and ozone as the oxidizing agent, the density change of the film as a function of process temperature was measured by XRR (X-ray reflectance) analysis.

As shown in Figure 5 and Table 2 below, the density of the films appears to increase with increasing process temperature.

Bulk density : 3.95g/cm ³

[Preparation Example 4] Atomic Force Microscopy (AFM) Analysis

In the ALD process using aluminum precursor and ozone as oxidant, as described in Preparation Example 1, atomic force microscopy (AFM) was used to measure the surface roughness of the film as a function of process temperature variation. As shown in Figures 6A to 6C and Table 3 below, the surface roughness (Ra) of the films generally decreased as the process temperature increased from 230°C to 340°C.

[Preparation Example 5] Transmission Electron Microscope (TEM) Analysis

As in Preparation Example 1, in the ALD process using the aluminum precursor and ozone as the oxidant, the step coverage of the trench structure depending on the process temperature change was confirmed by TEM (transmission electron microscope) analysis. The process temperature was set in the range of 230°C to 340°C, and the aspect ratio of the trench structure was 40:1.

As shown in Figures 7A to 7C and Table 4 below, when the process temperature is 230°C, the bottom step coverage is 84%, and when the process temperature is 300°C and 340°C, The bottom step coverage is over 95%. Therefore, the aluminum precursors show excellent step coverage over a wide range of process temperatures.

Although the embodiments of the present disclosure have been described, those skilled in the art will appreciate that the present disclosure may be embodied in other specific forms without changing its technical spirit or essential characteristics. Accordingly, the above-described embodiments should be understood in various ways as non-limiting and illustrative. The scope of the present disclosure is indicated by the appended claims rather than the detailed description, and it should be understood that the meaning and scope of the claims and all variations or modifications derived from their equivalents fall within the scope of the invention.

Claims (12)

A compound, shown in Chemical Formula 1 below:

In Chemical Formula 1, M is a Group 13 metal in the periodic table; R ₁ , R ₂ , R ₄ and R ₅ are the same or different from each other and each is a substituted or unsubstituted C ₁ -C ₄ straight or branched chain a chain hydrocarbon or an isomer thereof; and R ₃ is a substituted or unsubstituted C ₄ -C ₆ straight or branched chain hydrocarbon or an isomer thereof. The compound of claim 1, wherein M in Chemical Formula 1 is selected from the group consisting of Al, In, and Ga. The compound of claim 1, wherein R ₃ in Chemical Formula 1 is selected from the group consisting of n-butyl, isobutyl, tertiary butyl, tertiary butyl and isomers thereof. The compound of claim 3, wherein R ₁ , R ₂ , R ₄ and R ₅ are the same or different from each other and each is a methyl group or an ethyl group. A precursor comprising the compound of any one of claims 1 to 4. A method of preparing a thin film, comprising the following steps: A precursor comprising the compound of any one of claims 1 to 4 is introduced into a reactor and deposited at a process temperature above 230°C. The method of claim 6, further comprising the step of atomic layer deposition or chemical vapor deposition. The method of claim 6, further comprising the step of using an oxidizing agent, a nitriding agent or a reducing agent. The method of claim 6, wherein the thin film comprises an oxide thin film, a nitride thin film or a metal thin film. A thin film prepared by the method as claimed in claim 6, having a surface roughness of not more than 1.4 Å and a density of not less than 3 g/cm ³ . An electronic device comprising the film of claim 10. The electronic device of claim 11, wherein the electronic device is selected from the group consisting of semiconductors, displays and solar cells.

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