Molybdenum precursor compounds, methods for preparing same, and methods for depositing molybdenum-containing films using same - Patents.com

Abstract

The present invention relates to a molybdenum precursor compound, a composition for forming a molybdenum-containing film comprising the same, a molybdenum-containing film formed using the same, and a method for forming a molybdenum-containing film. The molybdenum precursor compound has a single structure and high purity, and can therefore form a high-quality molybdenum-containing film, and has excellent thermal stability and low resistivity, and can therefore have various applications in the semiconductor field. In particular, the molybdenum precursor compound can form a film with excellent coating properties and uniformity even on a substrate with a pattern (groove) on the surface, a porous substrate, a plastic substrate, or a substrate with a complex shape, so that a high-quality molybdenum-containing film can be easily achieved.

Description

[Technical field]

[0001] The present invention relates to a molybdenum precursor compound, a method for preparing the same, a precursor composition for forming a molybdenum-containing film comprising the same, a molybdenum-containing film using the same, and a method for depositing the same. [Background technology]

[0002] Molybdenum-containing metal films, molybdenum-containing oxide films, molybdenum-containing carbide films, molybdenum-containing sulfide films, and molybdenum-containing nitride films can be used in semiconductor processes as diffusion barrier layers for metal wiring, gate metals, electrodes, etc. Such films are widely used in industry as hard coating materials, sensors, channel layers, and catalysts.

[0003] For example, for use as a capacitor electrode for next-generation electronic devices, particularly DRAM devices with high step heights, it is necessary to use chemical vapor deposition (CVD) or atomic layer deposition (ALD) that can achieve excellent step coverage on very rough surfaces. The use of CVD and / or ALD may require liquid zero-valent molybdenum precursor compounds. In particular, low-resistance liquid zero-valent molybdenum precursor compounds are required for use in 3D NAND gates.

[0004] On the other hand, an example of a molybdenum precursor compound currently in use is bis(toluene)molybdenum ((η 6 -MeC6H5)2Mo) and bis(ethylbenzene molybdenum ((η 6 -EtC6H5)2Mo).

[0005] However, bis(toluene molybdenum) ((η 6 Since -MeC6H5)2Mo) is a solid at normal pressure and temperature, it is difficult to provide a source of it in the process, and there may be difficulties in the process of removing and reinstalling the vessel containing the solid precursor. Furthermore, there may be issues in mass production of semiconductor devices using the compound in terms of significantly reducing productivity.

[0006] In addition, bis(ethylbenzenemolybdenum) ((η 6 The precursor compound, Mo-EtC6H5)2Mo, is liquid at room temperature, but is not a single compound but a mixed structure, which limits the purity and makes it difficult to maintain the same composition during synthesis. Therefore, in mass production of semiconductor devices, it may be difficult to supply uniform, high-quality molybdenum-containing films due to the non-uniformity in the composition.

[0007] Accordingly, there is a need to develop liquid molybdenum precursor compounds that are suitable for various applications, e.g., process temperatures for memory and non-memory applications, can be used for CVD and / or ALD, and have a uniform structure and excellent purity to form uniform, high-quality molybdenum-containing films. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Patent Publication No. 2020-0091469 DISCLOSURE OF THEINVENTION Technical issues

[0009] The present invention has been devised to solve the problems of the prior art.

[0010] An object of the present invention is to provide a novel molybdenum precursor compound that has a single structure, is in a liquid state at room temperature and thus is advantageous in manufacturing processes, and has excellent thermal stability so that a molybdenum-containing film having a uniform thickness and excellent quality can be formed by atomic layer deposition (ALD), and the resistivity value of the molybdenum-containing film can be reduced to an optimal range.

[0011] Another object of the present invention is to provide a method for preparing molybdenum precursor compounds in a safe and efficient manner.

[0012] It is yet another object of the present invention to provide a composition for forming a molybdenum-containing film that includes a molybdenum precursor compound.

[0013] It is yet another object of the present invention to provide molybdenum-containing films of uniform thickness and excellent quality on various substrates by using molybdenum precursor compounds.

[0014] It is yet another object of the present invention to provide a method of depositing a molybdenum-containing film, wherein the molybdenum-containing film is deposited using a molybdenum precursor compound.

[0015] However, the problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned above will be clearly understood by those skilled in the art from the following description.

[0016] The present invention provides a molybdenum precursor compound represented by the following Chemical Formula 1:

[0017] [ka]

[0018] In Chemical Formula 1, R1 to R6 are each independently selected from the group consisting of hydrogen and linear or branched C1 to C8 alkyl groups, provided that at least two of R1 to R6 are not hydrogen.

[0019] Additionally, the present invention provides a composition for forming a molybdenum-containing film, comprising a molybdenum precursor compound.

[0020] Additionally, the present invention provides molybdenum-containing films formed using the molybdenum precursor compounds.

[0021] Additionally, the present invention provides a method of depositing a molybdenum-containing film comprising depositing a molybdenum-containing film on a substrate using a molybdenum precursor compound.

[0022] The molybdenum precursor compound according to the embodiment of the present invention has a single structure and is excellent in purity, so that a molybdenum-containing film of excellent quality can be formed.Moreover, the molybdenum precursor compound is in a liquid state at room temperature, which is advantageous in the manufacturing process, and has excellent thermal stability, so that a molybdenum-containing film can be easily formed by chemical vapor deposition (CVD) or atomic layer deposition (ALD), and its resistivity can be reduced to an optimal range, so that it can be used in DRAM or NAND flash, upper and lower electrodes that require low resistivity, and the gate electrode of the capacitor used in logic devices.

[0023] Furthermore, it is possible to form a uniform film with excellent coverage even on a substrate having unevenness or patterns (grooves) on its surface, a porous substrate, a plastic substrate, or a substrate having a complex shape with a three-dimensional structure, thereby making it possible to obtain a high-quality molybdenum-containing film. [Brief description of the drawings]

[0024] [Figure 1] 1 shows 1H-NMR spectra of the molybdenum precursor compounds prepared according to Examples 1 and 3 and Comparative Example 2 of the present application. [Diagram 2] 1 is a graph showing the results of thermogravimetric analysis (TGA) measurement of the molybdenum precursor compounds of Examples 1 and 3 and Comparative Example 1 of the present application. [Diagram 3] 4 is a transmission electron microscope (TEM) photograph of a molybdenum-containing nitride film formed by an ALD method using a molybdenum precursor compound prepared in Example 1 of the present application and ammonia (NH3) versus temperature; [Figure 4] 2 is a graph showing the resistivity versus temperature of a molybdenum-containing nitride film formed by an ALD method using the molybdenum precursor compound prepared in Example 1 of the present application and ammonia (NH3); [Diagram 5]3 is a TEM photograph of a molybdenum-containing nitride film formed by the PEALD method using the molybdenum precursor compound prepared in Example 1 of the present application and ammonia (NH3) plasma versus temperature. [Figure 6] 2 is a graph showing the deposition rate and resistivity of a molybdenum-containing nitride film formed by a PEALD method using the molybdenum precursor compound prepared in Example 1 of the present application and ammonia (NH3) plasma versus temperature; [Figure 7] FIG. 2 is a graph showing the elemental content (%) of a molybdenum-containing nitride film formed by the PEALD method using a molybdenum precursor compound prepared in Example 1 of the present application and ammonia (NH3) plasma at 350° C., as measured by Auger electron spectroscopy (AES). [Figure 8] 1 is a graph showing the elemental content (%) of a molybdenum-containing nitride film formed by the PEALD method using a molybdenum precursor compound prepared in Example 1 of the present application and ammonia (NH3) plasma at 400° C., as measured by AES. [Figure 9] 1 is a graph showing the elemental content (%) of a molybdenum-containing nitride film formed by the PEALD method using a molybdenum precursor compound prepared in Example 1 of the present application and ammonia (NH3) plasma at 450° C., as measured by AES. [Figure 10] 4 is a TEM photograph of a molybdenum-containing nitride film formed by the PEALD method using the molybdenum precursor compound prepared in Comparative Example 2 and ammonia (NH3) plasma versus temperature. [Figure 11] FIG. 1 is a graph showing the elemental content (%) of a molybdenum-containing nitride film formed by the PEALD method using the molybdenum precursor compound prepared in Comparative Example 2 and ammonia (NH3) plasma at 350° C., as measured by AES. [Figure 12] FIG. 1 is a graph showing the elemental content (%) of a molybdenum-containing nitride film formed by the PEALD method using the molybdenum precursor compound prepared in Comparative Example 2 and ammonia (NH3) plasma at 400° C., as measured by AES. [Figure 13] FIG. 1 is a graph showing the elemental content (%) of a molybdenum-containing nitride film formed by the PEALD method using the molybdenum precursor compound prepared in Comparative Example 2 and ammonia (NH3) plasma at 450° C., as measured by AES. BEST MODE FOR CARRYING OUT THEINVENTION

[0025] The present application is described in more detail below.

[0026] The advantages and features of the present invention, as well as the manner of obtaining them, will become apparent with reference to the embodiments described below. However, the present invention is not limited to the embodiments described below, but can be embodied in many different forms. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The present invention is defined solely by the claims.

[0027] Furthermore, when this specification describes an element as being formed "on" another element, it means not only that the element is formed directly "on" the other element, but also that there is another element(s) interposed therebetween.

[0028] In this specification, when an element is used to refer to "comprising" other elements, it will be understood that the element does not exclude other elements, but may include other elements unless otherwise specified.

[0029] All numbers and expressions expressing amounts of ingredients, reaction conditions, and the like used in this specification should be understood to be modified by the term "about," unless otherwise indicated.

[0030] As used herein, the terms "film" and "thin film," respectively, refer to both "membrane" and "thin film," unless otherwise specified.

[0031] As used herein, the term "alkyl" or "alkyl group" includes linear or branched alkyl groups and all possible isomers thereof. For example, alkyl groups include methyl (Me), ethyl (Et), n-propyl (N-propyl) and aryl groups. n Pr), isopropyl group ( i Pr), n-butyl group ( n Bu) group, tert-butyl group ( t Bu), isobutyl group ( i Bu), sec-butyl group ( s Bu), pentyl, hexyl, isohexyl, heptyl, 4,4-dimethylpentyl, octyl, 2,2,4-trimethylpentyl, nonyl, decyl, and isomers thereof.

[0032] [Molybdenum precursor compounds] According to an embodiment of the present invention, there is provided a molybdenum precursor compound represented by the following Formula 1:

[0033] [ka]

[0034] In Chemical Formula 1, R1 to R6 are each independently selected from the group consisting of hydrogen and linear or branched C1 to C8 alkyl groups, provided that at least two of R1 to R6 are not hydrogen.

[0035] The molybdenum precursor compound is 1 When analyzed by H-NMR, it has a single structure with one composition, is highly pure, and is in a liquid state at room temperature, which is advantageous for manufacturing processes. It also has excellent thermal stability, so molybdenum-containing films can be easily formed by not only chemical vapor deposition (CVD) but also atomic layer deposition (ALD).

[0036] In particular, the molybdenum-containing films, when formed using molybdenum precursor compounds, can provide low resistivity (μΩ·cm) values, for example, below 1,200 μΩ·cm, and therefore can be widely used as gate electrodes, diffusion barrier layers, and capacitor electrodes used in DRAM or NAND flash and logic devices that require low resistivity.

[0037] Moreover, the molybdenum-containing film can be formed as a uniform film with excellent coverage even on a substrate having an uneven surface or a pattern (groove), a porous substrate, a plastic substrate, or a substrate having a complex shape with a three-dimensional structure, thereby making it possible to provide a high-quality molybdenum-containing film. The molybdenum precursor compound is not only advantageously usable in various applications in the electronic device field, but also has technical significance in that it can exhibit excellent properties.

[0038] According to an embodiment of the present invention, in Chemical Formula 1, R1 to R6 are each independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and pentyl, provided that at least two of R1 to R6 are not hydrogen.

[0039] Furthermore, R1-R6 may be unsubstituted or substituted C1-C6 alkyl groups, and the substituents may each independently include a C1-C6 alkyl group, a C2-C6 alkenyl group, a C2-C6 alkynyl group, and a C1-C6 alkoxy group. For example, the substituents may each independently include a C1-C6 alkyl group, a C1-C4 alkyl group, or a C1-C2 alkyl group.

[0040] Specifically, the molybdenum precursor compound may be a compound represented by any one of the following chemical formulas 1-1 to 1-3.

[0041] [ka]

[0042] The molybdenum precursor compound according to the embodiment of the present invention has excellent thermal stability, for example, can be applied at 300° C. to 550° C., and exists in a liquid state at room temperature, so that a molybdenum-containing film can be formed not only by ALD but also by CVD. In particular, the molybdenum precursor compound has a great advantage in that a molybdenum-containing metal film, a molybdenum-containing oxide film, a molybdenum-containing carbide film, a molybdenum-containing sulfide film, and a molybdenum-containing nitride film, which are uniform in atomic layer units and have excellent film properties, can be easily formed by ALD.

[0043] The molybdenum precursor compound is, for example, TG at 180°C to 350°C, for example, 180°C to 300°C, for example, 180°C to 250°C, for example, 190°C to 300°C, for example, 200°C to 300°C, for example, 200°C to 280°C, or for example, 200°C to 250°C. 50 (℃), but TG 50 is the temperature at which the weight of the molybdenum precursor compound decreases by 50% while being heated from room temperature to 500° C. at a heating rate of 10° C. / min in a thermogravimetric analysis (TGA).

[0044] According to an embodiment of the invention, the molybdenum precursor compound has a residual weight (W) at 500° C. of, for example, 36 wt % or less, such as 35 wt % or less, for example, 30 wt % or less, such as 20 wt % or less, for example, 15 wt % or less, such as 10 wt % or less, for example, 8 wt % or less, such as 7 wt % or less, for example, 5 wt % or less, such as 4.5 wt % or less, for example, 3 wt % or less, such as 2 wt % or less, for example, 1.5 wt % or less, such as 1.2 wt % or less, for example, 1 wt % or less, such as 0.7 wt % or less, or for example 0.6 wt % or less, as measured by thermogravimetric analysis (TGA). 500 ).

[0045] In particular, the molybdenum precursor compound has a residual weight (W) of 1.5% or less at 500° C. as measured by thermogravimetric analysis (TGA). 500 ).

[0046] According to an embodiment of the present invention, the molybdenum precursor compound has a readiness (WR) of 70% or greater according to Equation 1 below: 500 ) may be present.

[0047]

number

[0048] In Equation 1, W 25 is the initial weight (wt%) of the molybdenum precursor compound at 25° C., and W 500 is the weight (wt%) of the molybdenum precursor compound at 500°C when the temperature is increased from 25°C to 500°C at a heating rate of 10°C / min.

[0049] In detail, the molybdenum precursor compound has a residual ratio (WR) of, for example, 72 wt % or more, for example, 75 wt % or more, for example, 80 wt % or more, for example, 85 wt % or more, for example, 87 wt % or more, for example, 88 wt % or more, for example, 89 wt % or more, for example, 90 wt % or more, for example, 92 wt % or more, for example, 93 wt % or more, for example, 95 wt % or more, for example, 97 wt % or more, for example, 98 wt % or more, or for example, 99 wt % or more. 500 The molybdenum precursor compound may have a residual ratio (WR) that satisfies the above range. 500 ), it has excellent variability, and thus may be more advantageous for forming at least one selected from the group consisting of a molybdenum-containing metal film, a molybdenum-containing oxide film, a molybdenum-containing carbide film, a molybdenum-containing sulfide film, and a molybdenum-containing nitride film, for example, at a temperature range of 300° C. or higher, specifically, 300 to 550° C., for example, 350 to 550° C. In particular, the molybdenum precursor compound has a great advantage in that it is possible to obtain uniform and excellent film properties at the atomic layer level by ALD.

[0050] [Method of preparing molybdenum precursor compounds] According to an embodiment of the present invention, there is provided a method for preparing a molybdenum precursor compound represented by Formula 1 below:

[0051] The molybdenum precursor compounds of formula 1 can be prepared by a variety of methods.

[0052] A method for preparing a molybdenum precursor compound represented by formula 1 according to an embodiment of the present invention includes reacting a compound represented by the following formula A with a compound represented by the following formula B:

[0053] [ka]

[0054] In Chemical Formula B and Chemical Formula 1, R1 to R6 are each independently selected from the group consisting of hydrogen and linear or branched C1 to C8 alkyl groups, provided that at least two of R1 to R6 are not hydrogen.

[0055] In particular, the molybdenum precursor compound represented by Formula 1 may be prepared by the reaction as shown in Reaction Scheme 1 below.

[0056] [ka]

[0057] In Reaction Scheme 1, R1 to R6 are each as defined above.

[0058] As shown in Reaction Scheme 1, the molybdenum precursor compound of formula 1 can be easily obtained by reacting a compound represented by formula A with a compound represented by formula B, and then purifying the resultant. In particular, the compound represented by formula 1 prepared according to Reaction Scheme 1 can have a single structure and can be a liquid compound with high purity.

[0059] The molar ratio of the compound represented by chemical formula A to the compound represented by chemical formula B may be 1:2-50, 1:2-40, 1:2-30, or 1:2-20.

[0060] The reaction may be carried out at 150° C. or higher for 5 hours or more.

[0061] Specifically, the compound represented by chemical formula A and the compound represented by chemical formula B are placed in a flask and maintained at room temperature. A condenser is connected to the flask, and the mixture in the flask is heated to, for example, about 150° C. or higher, specifically, about 160° C. to 300° C., and then reacted for, for example, 5 hours or more, specifically, 8 to 20 hours, to obtain the compound represented by chemical formula 1. Furthermore, upon completion of the reaction, salts formed during the reaction may be removed by filtration or the like, and the solvent and volatile side reactants may be distilled under reduced pressure.

[0062] [Composition for forming a molybdenum-containing film] According to an embodiment of the present invention, there is provided a composition for forming a molybdenum-containing film, comprising a molybdenum precursor compound represented by Chemical Formula 1.

[0063] The composition may further comprise an oxygen source comprising at least one selected from the group consisting of water vapor (H2O), oxygen (O2), oxygen plasma (O2 plasma), nitric oxide (NO, N2O), nitric oxide plasma (N2O plasma), oxygen nitrate (N2O2), hydrogen peroxide (H2O2), and ozone (O3), and a nitrogen source comprising at least one selected from the group consisting of nitrogen (N2), ammonia (NH3), ammonia plasma (NH3 plasma), hydrazine (N2H4), and nitrogen plasma (N2 plasma). Additionally, the composition may further comprise hydrogen (H2).

[0064] In particular, the composition may include, for example, at least one selected from the group consisting of hydrogen (H2), nitrogen (N2), and ammonia (NH3).

[0065] The composition may include, for example, at least one selected from the group consisting of water vapor (H2O), oxygen (O2), oxygen plasma (O2 plasma), nitric oxide (NO, N2O), nitric oxide plasma (N2O plasma), oxygen nitrate (N2O2), hydrogen peroxide (H2O2), and ozone (O3).

[0066] The composition may include, for example, at least one selected from the group consisting of ammonia (NH3), ammonia plasma (NH3 plasma), hydrazine (N2H4), and nitrogen plasma (N2 plasma).

[0067] More specifically, the composition may include at least one selected from the group consisting of hydrogen (H2), ozone (O3), and ammonia (NH3).

[0068] [Molybdenum-containing film] According to an embodiment of the present invention, a molybdenum-containing film formed using a molybdenum precursor compound represented by Chemical Formula 1 can be provided.

[0069] The molybdenum-containing film may have a thickness of from a few nanometers (nm) to a few micrometers (μm) and may be applied in a variety of ways depending on the intended application.

[0070] For example, the thickness of the molybdenum-containing film may be about 1 nm or more, about 5 nm or more, about 10 nm or more, about 15 nm or more, about 20 nm or more, about 25 nm or more, about 30 nm or more, about 35 nm or more, about 40 nm or more, about 45 nm or more, or about 50 nm or more. Furthermore, the thickness of the molybdenum-containing film may be about 500 nm or less, about 450 nm or less, about 400 nm or less, about 350 nm or less, about 300 nm or less, about 250 nm or less, about 200 nm or less, about 150 nm or less, or about 100 nm or less. In particular, the thickness of the molybdenum-containing film may be variously selected from about 1 nm to about 500 nm.

[0071] The molybdenum-containing film may be formed on a substrate (or board).

[0072] The substrate may be, but is not limited to, a molybdenum semiconductor wafer, a compound semiconductor wafer, and a plastic plate (PI, PET, and PES). Substrates with holes or grooves may be used, and porous substrates with large surface areas may be used.

[0073] Since the molybdenum precursor compound according to the embodiment of the present invention has a specific structure of Chemical Formula 1, the molybdenum precursor compound has low density and high thermal stability, which enables a molybdenum-containing film to be efficiently formed in various temperature ranges by CVD and ALD. In particular, in the temperature range of 300° C. to 550° C., a molybdenum-containing film can be uniformly formed even on a substrate having a pattern (groove) or fine irregularities on its surface, a porous substrate, or a plastic substrate having a thickness of several micrometers to several tens of nanometers.

[0074] In accordance with an embodiment of the present invention, a molybdenum-containing film may be formed on a substrate that includes projections, recesses, or patterns (grooves) having an aspect ratio of 1-50 and a width of 1 μm to 10 nm or less.

[0075] In particular, the aspect ratio may be about 1 or more, about 2 or more, about 3 or more, about 5 or more, about 7 or more, about 10 or more, or about 15 or more. Additionally, the aspect ratio may be about 50 or less, about 45 or less, about 40 or less, about 35 or less, about 30 or less, about 25 or less, or about 20 or less.

[0076] Additionally, the width may be about 10 nm or more, about 15 nm or more, about 20 nm or more, about 25 nm or more, about 30 nm or more, about 35 nm or more, or about 40 nm or more. Additionally, the width may be about 1 μm or less, about 900 nm or less, about 800 nm or less, about 700 nm or less, about 600 nm or less, about 500 nm or less, or about 450 nm or less.

[0077] The molybdenum-containing film may be at least one selected from the group consisting of a molybdenum-containing metal film, a molybdenum-containing oxide film, a molybdenum-containing carbide film, a molybdenum-containing sulfide film, and a molybdenum-containing nitride film.

[0078] Moreover, the molybdenum-containing films according to embodiments of the present invention may have a low resistivity (μΩ·cm) of 1,200 μΩ·cm or less.

[0079] The molybdenum-containing film may have different resistivities depending on the temperature.

[0080] In detail, the resistivity of the molybdenum-containing film at about 350° C. may be, for example, 400 to 1,200 μΩ·cm, for example, 450 to 1,200 μΩ·cm, for example, 500 to 1,200 μΩ·cm, for example, 600 to 1,200 μΩ·cm, or for example, 700 to 1,200 μΩ·cm.

[0081] As another example, the resistivity of the molybdenum-containing film at about 400° C. may be, for example, 400 to 1,200 μΩ·cm, for example, 400 to 1,000 μΩ·cm, for example, 400 to 900 μΩ·cm, for example, 400 to 800 μΩ·cm, or for example, 500 to 800 μΩ·cm.

[0082] As yet another example, the resistivity of the molybdenum-containing film at about 450° C. may be, for example, 400 to 1,200 μΩ·cm, for example, 400 to 900 μΩ·cm, for example, 300 to 800 μΩ·cm, for example, 300 to 700 μΩ·cm, for example, 300 to 600 μΩ·cm, or for example, 300 to 500 μΩ·cm.

[0083] As yet another example, the resistivity of the molybdenum-containing film at about 500° C. may be, for example, 300 to 1,200 μΩ·cm, for example, 300 to 1,000 μΩ·cm, for example, 300 to 900 μΩ·cm, for example, 300 to 800 μΩ·cm, or for example, 300 to 700 μΩ·cm.

[0084] Therefore, the molybdenum-containing film can be used as a gate electrode, a diffusion barrier layer, and a capacitor electrode used in DRAM or NAND flash and logic devices that require low resistivity, and can be applied in a variety of ways depending on the application purpose.

[0085] [Method of forming a molybdenum-containing film] According to an embodiment of the present invention, there is provided a method of depositing a molybdenum-containing film, comprising depositing a molybdenum-containing film on a substrate (board) using a molybdenum precursor compound represented by Chemical Formula 1.

[0086] In detail, the method for forming a film may include, but is not limited to, the step of supplying a molybdenum precursor compound represented by Chemical Formula 1 or a composition for forming a molybdenum-containing film in a gaseous state and forming a molybdenum-containing film on a substrate.

[0087] The substrate is as described above.

[0088] The method of depositing the film may use any method and / or apparatus known in the art, and may, if desired, include one or more additional reactant gases, etc. In a method of depositing a molybdenum-containing film according to an embodiment of the present invention, a substrate is placed in a reaction chamber, and then a molybdenum precursor compound is delivered onto the substrate using a carrier gas or a diluent gas to deposit a molybdenum-containing film.

[0089] In particular, the film formation may be performed by chemical vapor deposition (CVD), in particular metal-organic chemical vapor deposition (MOCVD), or atomic layer deposition (ALD), at a temperature of 300°C to 550°C, 350°C to 550°C, 350°C to 500°C, or 350°C to 450°C.

[0090] Additionally, atomic layer deposition may include plasma enhanced atomic layer deposition (PEALD).

[0091] In particular, it is possible to uniformly form a molybdenum-containing film even on a substrate having a pattern (groove) on its surface, a porous substrate, or a plastic substrate in a temperature range of 300° C. to 550° C. It is possible to form a uniform film on the substrate, and the film covers the deepest surface of a fine pattern (groove) having an aspect ratio of about 1 to 50 or more and a width of 1 μm to 10 nm or less, as well as the upper surface of the fine pattern (groove).

[0092] Here, deposition performed at the above temperatures allows the film to be applied to memory devices, logic devices, and display devices. Since the process temperature is in a wide range, it is desirable to perform deposition at the above deposition temperatures in order to make the film applicable to various fields.

[0093] Moreover, it is more preferable to use a mixed gas of at least one selected from the group consisting of argon (Ar), nitrogen (N2), helium (He), and hydrogen (H2) as a carrier gas or diluent gas.

[0094] Furthermore, the method of delivering the molybdenum precursor compound onto the substrate may be at least one method selected from the group consisting of a bubble method, in which the molybdenum precursor compound is forced to evaporate using a carrier gas or a dilution gas; a liquid delivery system (LDS) method for delivering the molybdenum precursor compound in liquid phase at room temperature for evaporation by an evaporator; a vapor flow control (VFC) method for directly delivering the precursor using its vapor pressure; and a bypass method.

[0095] For example, when the vapor pressure is high, a vapor flow control method (VFC) may be used, and when the vapor pressure is low, at least one supply method selected from the group consisting of a bypass method of evaporation by heating the container and a bubbling method using argon (Ar) or nitrogen (N2) gas may be used.

[0096] More specifically, the transportation method includes a bubble method or a thermal evaporation bypass method, in which the bubble method may be performed using a carrier gas at a temperature range of 100°C to 150°C and a pressure of 0.1 to 10 Torr, and the thermal evaporation bypass method may be performed using a vapor pressure of 0.1 to 1.5 Torr at a temperature range of room temperature to 100°C.

[0097] Additionally, for example, argon (Ar) or nitrogen (N2) gas may be used for transport to evaporate the molybdenum precursor compound, thermal energy or plasma may be used during deposition, or a bias may be applied to the substrate.

[0098] On the other hand, to deposit a molybdenum-containing metal film, at least one selected from the group consisting of hydrogen (H2), neutral nitrogen (N2), and ammonia (NH3) may be used as a reactive gas during deposition.

[0099] In addition, during the deposition, at least one selected from the group consisting of water vapor (HO), oxygen (O), oxygen plasma (O plasma), nitric oxide (NO, NO), nitric oxide plasma (NO plasma), oxygen nitrate (NO), hydrogen peroxide (HO), and ozone (O) may be used as a reactive gas to deposit the molybdenum-containing oxide film.

[0100] In addition, for example, during deposition, at least one selected from the group consisting of ammonia (NH), ammonia plasma (NH plasma), hydrazine (N2H4), and nitrogen plasma (N2 plasma) may be used as a reactive gas to deposit a molybdenum-containing nitride film. EXAMPLES

[0101] The present invention will be described in detail below with reference to examples. The following examples are merely for the purpose of illustrating the present invention, and the scope of the present invention is not limited thereto.

[0102] <Example 1> Bis-4-isopropyltoluene-molybdenum: (η 6 -4- i Preparation of Pr-MeC6H4)2Mo [ka]

[0103] Into a heated and dried 2-liter Schlenk flask, about 88 g (0.31 mol) of bis(toluene molybdenum) ((η 6 -MeC6H5)2Mo), and about 1,000 ml of 4-isopropyltoluene (C 10 H 14 ) was added and maintained at room temperature. A condenser was connected to the flask, and the mixture in the flask was heated to 180°C and then stirred for 12 hours. Upon completion of the reaction, the salt formed during the reaction was removed by filtration, and the solvent and volatile side reactants were distilled off under reduced pressure to obtain about 120 g of a green liquid represented by formula 1-1 (yield: about 60%, based on MoCl5).

[0104] Density: 1.28 g / mol (25°C) Boiling point (bp): 105°C (0.4 Torr) (308.6°C at 760 mmHg) 1 H-NMR (400MHz, C6D6, 25℃): δ4.56(s,8H,Mo((CH3)2CH-C6H * 4-CH3)), δ2.46, 2.28, 2.26(m,2H,Mo((CH3)2CH * -C6H4-CH3)), δ1.96(s,6H,Mo((CH3)2CH-C6H4-CH * 3)), δ1.17, 1.15(d,12H,Mo((CH * 3)2CH-C6H4-CH3)

[0105] <Example 2> Bis-1,4-di-tert-butylbenzene-molybdenum: (η 6 -1,4-( t Preparation of Bu)C6H4)2Mo [ka]

[0106] Into a heated and dried 2-liter Schlenk flask, about 29 g (0.1 mole) of bis(toluene molybdenum) ((η 6 -MeC6H5)2Mo), and about 250 g of 1,4-di-tert-butylbenzene (C 14 H 22 ) was added and kept at room temperature. A condenser was connected to the flask, and the mixture in the flask was heated to 180°C and then stirred for 12 hours. Upon completion of the reaction, the salt formed during the reaction was removed by filtration, and the solvent and volatile side reactants were distilled off under reduced pressure to obtain about 30 g of a green solid represented by formula 1-2 (yield: about 60%, based on MoCl5).

[0107] Boiling point (bp): 130°C (0.4 torr) (343.6°C at 760 mmHg) 1 H-NMR (400MHz, C6D6, 25℃): δ4.69(s,8H,Mo(C6H * 4(C(CH3)3)2)), 1.17(s,36H,Mo(C6H4(C(CH * 3)3)2))

[0108] <Example 3> Bis-1-isopropyl-3,5-dimethylbenzene-molybdenum: (η 6 -1- i Preparation of Pr-3,5-Me2C6H3)2Mo [ka]

[0109] Into a heat-dried 2-liter Schlenk flask, about 55 g (0.19 moles) of bis(toluene)molybdenum ((η 6 -MeC6H5)2Mo), and about 300 g of 1-isopropyl-3,5-dimethylbenzene (C 11 H 16) was added and maintained at room temperature. A condenser was connected to the flask, and the mixture in the flask was heated to 180°C and then stirred for 12 hours. Upon completion of the reaction, the salt formed during the reaction was removed by filtration, and the solvent and volatile side reactants were distilled off under reduced pressure to obtain about 47 g of a green liquid represented by formula 1-3 (yield: about 63%, based on MoCl5).

[0110] Density: 1.32 g / mol (at 25°C) Boiling point (bp) 132°C (0.5 torr) (338°C at 760 mmHg) 1 H-NMR (400MHz, C6D6, 25℃): δ4.51(s,4H,Mo((CH3)2CH-C6H * 3-(CH3)2)), δ4.40(s,2H,Mo((CH3)2CH-C6H * 3-(CH3)2)), δ2.31, 2.29, 2.27(m,2H,Mo((CH3)2CH * -C6H3-(CH3)2)), δ1.96(s,12H,Mo((CH3)2CH-C6H3-(CH * 3)2)), δ1.17, 1.15(d,12H,Mo((CH * 3) 2CH-C6H3-(CH3)2)

[0111] Comparative Example 1 Bistoluene molybdenum: (η 6 -MeC6H5)2Mo [ka]

[0112] Bis(toluene)molybdenum ((η 6 -MeC6H5)2Mo) (SPCI Co., Ltd.) was purchased and used.

[0113] Comparative Example 2: Bisethylbenzenemolybdenum: (η 6 -EtC6H5)2Mo [ka]

[0114] Bisethylbenzenemolybdenum ((η 6 -EtC6H5)2Mo) (Strem Chemicals, Inc.) was purchased and used.

[0115] Test Example <Test Example 1> Structural analysis of molybdenum precursor compound 1 H-NMR analysis was carried out to analyze the structures of the molybdenum precursor compounds prepared in Examples 1 and 3 and the molybdenum precursor compound prepared in Comparative Example 2. The results are shown in Table 1 below and FIG.

[0116] [Table 1]

[0117] As can be seen from FIG. 1 and Table 1, the molybdenum precursor compound of Comparative Example 2 had a composition of various structures (mixed structure) due to structural isomers, so the chemical shifts and the peak multiplicity of hydrogen (proton) were as follows: 1 On the other hand, the molybdenum precursor compound prepared in Example 1 of the present invention was 1 H-NMR analysis confirmed that it had one composition, and the chemical shifts and peak multiplicity were clearly evident.

[0118] The results of structural analysis of the molybdenum precursor compounds confirm that the molybdenum precursor compounds of Examples 1 and 3 are precursors of sufficiently high purity to be applied to the ALD method. The molybdenum precursor compounds of the examples can be used for the purpose of forming various films, such as a molybdenum-containing metal film, a molybdenum-containing oxide film, a molybdenum-containing carbide film, a molybdenum-containing sulfide film, and a molybdenum-containing nitride film.

[0119] <Test Example 2> Thermal property analysis of molybdenum precursor compound Thermogravimetric analysis (TGA) was performed to analyze the thermal properties of the molybdenum precursor compounds prepared in Examples 1 and 3, as well as the molybdenum precursor compound of Comparative Example 1. The results are shown in Table 2 below and in FIG.

[0120] For thermogravimetric analysis (TGA), the change in weight of the molybdenum precursor compound was measured while increasing the temperature from room temperature to about 500° C. at a rate of about 10° C. / min in a nitrogen (N2) atmosphere.

[0121] In detail, the evaporation start temperature (°C) of the molybdenum precursor compound, which is the temperature at which the weight loss of the molybdenum precursor compound is 50%, TG 50 (℃) and the remaining weight at 500℃, W 500 (wt%) and the remaining WR at 500°C 500 (%) was measured.

[0122] Here, the remaining ratio of WR at 500℃ is 500 (%) can be calculated from Equation 1 below:

[0123]

number

[0124] In Equation 1, W 25 is the initial weight (wt%) of the molybdenum precursor compound at 25° C., and W 500 is the weight (wt%) of the molybdenum precursor compound at 500°C when the temperature is increased from 25°C to 500°C at a heating rate of 10°C / min.

[0125] [Table 2]

[0126] 2, the molybdenum precursor compound of Comparative Example 1 had poor thermal stability, leaving a large amount of residue and was not suitable for use in a CVD or ALD process. On the other hand, the residue of the molybdenum precursor compounds prepared in Examples 1 and 3 volatilized without being altered, making the molybdenum precursor compounds suitable as precursors for use in a CVD or ALD process.

[0127] Moreover, as can be seen in Table 2, most of the molybdenum precursor compounds of Examples 1 and 3 of the present invention were evaporated at about 209°C to 213°C, and the temperature TG at which the weight loss of the molybdenum precursor compounds was 50% was 50 (℃) was approximately 226.88℃.

[0128] Moreover, in the molybdenum precursor compounds prepared in Examples 1 and 3, the remaining weight W 500 In the molybdenum precursor compound of Comparative Example 1, the remaining weight W 500 % by weight was about 36.9% by weight, a significant increase over the molybdenum precursor compounds of Examples 1 and 3.

[0129] On the other hand, in the molybdenum precursor compounds prepared in Examples 1 and 3, the remaining ratio (WR) at 500°C was 500 In the molybdenum precursor compound of Comparative Example 1, the remaining ratio (WR 500 ) dropped significantly to approximately 63.1%.

[0130] Accordingly, it has been confirmed that the molybdenum precursor compounds of the present invention exhibit excellent variability and, in particular, that the molybdenum precursor compounds of the present invention are excellent precursors for forming various molybdenum-containing films, such as molybdenum-containing metal films, molybdenum-containing oxide films, molybdenum-containing carbide films, molybdenum-containing sulfide films, and molybdenum-containing nitride films, in the temperature range of 300° C. to 500° C.

[0131] <Test Example 3> Film formation characteristics of molybdenum precursor compound mixed with ammonia The molybdenum precursor compound prepared in Example 1 was used in the ALD process. Ammonia gas (NH3) was used as the reactant gas to deposit a molybdenum-containing nitride film.

[0132] First, a silicon oxide substrate (board) (1,000 Å) was used as a substrate to prepare a molybdenum-containing nitride film. The silicon oxide substrate was a silicon oxide substrate in which the surface of the silicon oxide substrate was washed with running distilled water (ultrapure water) to remove organic matter from the surface of the silicon oxide substrate.

[0133] To form the molybdenum-containing nitride film, the ALD cycle was fixed at 100, the substrate temperature was set at 350° C., 400° C., and 500° C., and the characteristics of the molybdenum-containing nitride film versus the substrate temperature were investigated.

[0134] The molybdenum precursor compounds were each placed in a stainless steel vessel and heated for use to a temperature of about 120° C. In the above-mentioned conditions, the process pressure of the reactor was set to 1.8 Torr, and argon (Ar) gas was flowed as a carrier gas at a flow rate of about 200 sccm, and ammonia (NH3) was flowed at a flow rate of 400 sccm.

[0135] In order to investigate the optimized resistivity characteristics of each molybdenum-containing nitride film, a cycle of supplying ALD gas was repeated 100 times to form a molybdenum-containing nitride film, during which a molybdenum precursor compound was supplied for about 5 seconds (a precursor compound supplying step), argon (Ar) gas was supplied for about 10 seconds to remove the molybdenum precursor compound (gas) remaining in the reactor (precursor compound purging step), NH3 was supplied as a reaction gas for about 20 seconds (NH3 supplying step), and argon (Ar) gas was supplied for about 10 seconds to remove the NH3 remaining in the reactor (NH3 purging step).

[0136] The sheet resistance (μΩ / sq) of the molybdenum-containing nitride film formed on the silicon oxide thin film substrate was measured using a 4PPS (four-point probe system), and the thickness of the molybdenum-containing nitride film was measured using a transmission electron microscope (TEM). The resistivity (μΩ·cm) was calculated from the thickness and sheet resistance of the molybdenum-containing nitride film.

[0137] In the above mentioned situation, the resistivity (μΩ·cm) can be expressed as follows in Equation 2:

[0138] [Equation 2] Resistivity (μΩ cm) = sheet resistance (Ω / sq) × film thickness (×10 -8 ,cm)

[0139] The thicknesses of the molybdenum-containing nitride films formed by the ALD method using the molybdenum precursor compound prepared in Example 1 and ammonia (NH3) were measured to be 74.3 Å, 76.3 Å, and 91.5 Å at substrate temperatures of, for example, 350° C., 400° C., and 500° C., respectively. The results of the TEM analysis are shown in FIG. 3.

[0140] In addition, the resistivity (μΩ·cm) of the molybdenum-containing nitride film formed by the ALD method using the molybdenum precursor compound prepared in Example 1 and ammonia (NH3) was calculated. The results are shown in Table 3 and Figure 4.

[0141] [Table 3]

[0142] As seen in Table 3 and Figure 4, the resistivity values ​​of the molybdenum-containing nitride films formed at substrate temperatures of 350°C, 400°C, and 500°C were about 1,162.6 μΩ·cm, about 793.0 μΩ·cm, and about 653.4 μΩ·cm, respectively, which are very low resistivity values. The low resistivity values ​​are advantageous for use as gate electrodes, diffusion barrier layers, and capacitor electrodes in DRAM or NAND flash and logic devices that require low resistivity.

[0143] <Test Example 4> Film formation characteristics of molybdenum precursor compound mixed with ammonia (NH3) plasma The molybdenum precursor compounds of Example 1 and Comparative Example 2 were used in a plasma-enhanced atomic layer deposition (PEALD) process.

[0144] To deposit the molybdenum-containing nitride film, 500 W of RF power was applied to NH3 as the nitrogen source used as the reactive gas.

[0145] First, a molybdenum-containing nitride film was prepared using a silicon oxide substrate (board) (1,000 Å) as the substrate. The silicon oxide substrate was a silicon oxide substrate that had been washed with running distilled water (ultrapure water) to remove organic matter from the surface of the silicon oxide substrate.

[0146] In order to form a molybdenum-containing nitride film, the PEALD cycle was fixed at 100 times, the substrate temperature was set at 350° C., 400° C., and 450° C., and the characteristics of the molybdenum-containing nitride film relative to the substrate temperature were investigated.

[0147] The molybdenum precursor compound prepared in Example 1 was placed in a stainless steel container and heated to a temperature of about 140° C. for use. In the above-mentioned situation, the process pressure of the reactor was set to 1.8 Torr, argon (Ar) gas was flowed as a carrier gas at a flow rate of about 200 sccm, and ammonia (NH3) was flowed at a flow rate of about 500 sccm. RF power of 500 W was used for the plasma at 13.56 MHz.

[0148] In order to confirm the optimized resistivity characteristics of each molybdenum-containing nitride film, the PEALD gas supply cycle was repeated 100 times to form a molybdenum-containing nitride film, during which a molybdenum precursor compound was supplied for about 3 seconds (a precursor compound supplying step), argon (Ar) gas was supplied for about 10 seconds to remove the molybdenum precursor compound (gas) remaining in the reactor (precursor compound purging step), NH3 was supplied as a reaction gas for about 20 seconds (NH3 supplying step), and argon (Ar) gas was supplied for about 10 seconds to remove the NH3 remaining in the reactor (NH3 purging step).

[0149] The molybdenum precursor compound of Comparative Example 2 was tested under the same conditions, but the conditions for forming a molybdenum-containing nitride film by repeating the ALD gas supply cycle 100 times were different, and during the cycle, the molybdenum precursor compound was supplied for about 15 seconds (precursor compound supplying step), argon (Ar) gas was supplied for about 10 seconds to remove the molybdenum precursor compound (gas) remaining in the reactor (precursor compound purging step), NH3 was supplied as a reaction gas for about 20 seconds (NH3 supplying step), and argon (Ar) gas was supplied for about 15 seconds to remove the NH3 remaining in the reactor (NH3 purging step).

[0150] The sheet resistance (μΩ / sq) of the molybdenum-containing nitride film formed on the silicon oxide thin film substrate was measured using a 4PPS (four-point probe system), and the thickness was measured using a TEM.

[0151] The thicknesses of the molybdenum-containing nitride films formed by the PEALD method using the molybdenum precursor compound prepared in Example 1 and ammonia (NH3) plasma were measured to be, for example, about 116.2 Å, about 127.2 Å, and about 127.3 Å at substrate temperatures of 350° C., 400° C., and 450° C., respectively. The results of the TEM analysis are shown in FIG.

[0152] Moreover, the deposition rates of the molybdenum-containing nitride films formed by the PEALD method using the molybdenum precursor compound prepared in Example 1 and ammonia (NH3) plasma were about 1.16 Å / cycle, about 1.27 Å / cycle, and about 1.27 Å / cycle, respectively. The resistivity (μΩ·cm) was calculated from the sheet resistance. The results are shown in Table 4 and Figure 6.

[0153] [Table 4]

[0154] In addition, the element contents (%) of the molybdenum-containing nitride film at each temperature were measured by AES (Auger electron spectroscopy). The results are shown in Table 5 and Figures 7 to 9.

[0155] [Table 5]

[0156] Meanwhile, the thickness of the molybdenum-containing nitride film formed by the PEALD method using the molybdenum precursor compound of Comparative Example 2 and ammonia (NH3) plasma was measured, and was about 240.3 Å, about 250.1 Å, and about 243.3 Å at substrate temperatures of 350°C, 400°C, and 450°C, respectively. The result of the TEM analysis is shown in Figure 10. Furthermore, the element content (%) of the molybdenum-containing nitride film was measured by AES at each temperature. The results are shown in Table 6 and Figures 11 to 13.

[0157] [Table 6]

[0158] As can be seen from the film component analysis results by AES in Tables 5 and 6, FIGS. 7 to 9, and FIGS. 11 to 13, the carbon content of the molybdenum-containing nitride film formed by the PEALD method using the molybdenum precursor compound prepared in Example 1 and ammonia (NH3) plasma was significantly lower than the carbon content of the molybdenum-containing nitride film formed by the PEALD method using the molybdenum precursor compound of Comparative Example 2 and ammonia (NH3) plasma.

[0159] Generally, when carbon content is high, it may cause problems such as deterioration of electrical properties and reduction of work function. The molybdenum-containing film formed by using the molybdenum precursor compound prepared in Example 1 can solve the above problems.

[0160] Furthermore, as can be seen from Table 4, the resistivity values ​​of the molybdenum-containing nitride films formed by the PEALD method using the molybdenum precursor compound prepared in Example 1 and ammonia (NH3) plasma at substrate temperatures of 350°C, 400°C, and 500°C were approximately 716.6 μΩ·cm, approximately 581.3 μΩ·cm, and approximately 357.1 μΩ·cm, respectively, which were very low resistivities.

[0161] In summary, the method for forming a molybdenum-containing film using a molybdenum precursor compound according to an embodiment of the present invention allows a molybdenum-containing film to be easily formed by ALD, and allows the formation of a molybdenum-containing film having a low carbon content and a low resistivity.

[0162] In particular, according to the method for forming a molybdenum-containing film using the molybdenum precursor compound according to the embodiment of the present invention, a film having a desired thickness and a low resistivity of 1,200 μΩ·cm or less could be obtained at a temperature of 350° C. to 450° C. As a result, the carbon content of the molybdenum-containing nitride film thus obtained was significantly improved compared to the molybdenum-containing nitride film obtained using the molybdenum precursor compound of Comparative Example 2.

[0163] Moreover, when the molybdenum precursor compound of the present invention is used to form a molybdenum-containing film, the molybdenum-containing film can have a low carbon content of 5% or less and a low resistivity of 1,200 μΩ cm or less, and therefore can be widely used as a gate electrode, a diffusion barrier layer, and a capacitor electrode used in DRAM or NAND flash and logic devices that require low resistivity.

Claims

1. A molybdenum precursor compound represented by the following chemical formula 1: [Formula 1] [In chemical formula 1, R １ ~R ６ is hydrogen and linear or branched C １ ~C ８ alkyl groups, each independently selected from the group consisting of R １ ~R ６ At least two of the are not hydrogen.

2. In chemical formula 1, R １ ~R ６ are each independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and pentyl, with R １ ~R ６ 2. The molybdenum precursor compound of claim 1 , wherein at least two of

3. The molybdenum precursor compound according to claim 1, which is a compound represented by any one of the following chemical formulas 1-1 to 1-3. [Case 2]

4. The molybdenum precursor compound has a TG of 180° C. to 350° C. ５０ (° C.), TG ５０ is the temperature at which the molybdenum precursor compound loses 50% weight while being heated from room temperature to 500° C. at a heating rate of 10° C. / min in a thermogravimetric analysis (TGA).

5. According to the following equation 1, the remaining capacity (WR) is 70% or more. ５００ 5. The molybdenum precursor compound of claim 4 having the formula: [0010] [In equation 1, W ２５ is the initial weight (wt%) of the molybdenum precursor compound at 25° C., and W ５００is the weight (wt%) of the molybdenum precursor compound at 500°C when the temperature is increased from 25°C to 500°C at a heating rate of 10°C / min.

6. 10. A composition for forming a molybdenum-containing film comprising the molybdenum precursor compound of claim 1.

7. The composition for forming a molybdenum-containing film of claim 6 , wherein the molybdenum precursor compound is a liquid.

8. 7. The composition for forming a molybdenum-containing film according to claim 6, which is deposited using a molybdenum precursor compound represented by one of the following chemical formulas 1-1 to 1-3. [C3]

9. 10. A molybdenum-containing film formed using the molybdenum precursor compound of claim 1.

10. 10. The molybdenum-containing film of claim 9, having a resistivity of 1,200 μΩ cm or less.

11. 10. The molybdenum-containing film according to claim 9, which is at least one selected from the group consisting of a molybdenum-containing metal film, a molybdenum-containing oxide film, a molybdenum-containing carbide film, a molybdenum-containing sulfide film, and a molybdenum-containing nitride film.

12. 13. A method of depositing a molybdenum-containing film comprising depositing a molybdenum-containing film on a substrate using the molybdenum precursor compound of claim 1.

13. 13. The method of depositing a molybdenum-containing film according to claim 12, wherein the deposition is carried out by chemical vapor deposition (CVD) or atomic layer deposition (ALD) at a temperature between 300° C. and 550° C.

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