Method for forming a molybdenum-containing film deposited on an elemental metal film

Abstract

A method of forming a molybdenum-containing film is provided. The method includes, for example, thermally depositing a first film on a substrate surface at a first temperature less than or equal to about 400 °C, and thermally depositing the molybdenum-containing film (second film) on at least a portion of the first film at a second temperature greater than about 400 °C. The first film can comprise an elemental metal such as tungsten, molybdenum, ruthenium, or cobalt. The second film comprises a reaction product of a molybdenum-containing precursor and a reducing agent.

Description

Technical Field

[0001] The present invention relates to a method for forming a molybdenum-containing film deposited on an elemental metal film. Background Art

[0002] A variety of precursors are used to form thin films, and a variety of deposition techniques have been employed. Such techniques include reactive sputtering, ion-assisted deposition, chemical vapor deposition (CVD) (also known as metalorganic CVD or MOCVD), and atomic layer deposition (also known as atomic layer epitaxy). CVD and ALD methods are increasingly being used because they offer the advantages of enhanced compositional control, high film uniformity, and effective doping control. In addition, CVD and ALD methods provide excellent conformal step coverage for the highly non-planar geometries associated with modern microelectronic devices.

[0003] CVD is a chemical method in which precursors are used to form a thin film on a substrate surface. In a typical CVD method, the precursors are passed over the surface of a substrate (e.g., a wafer) in a low-pressure or ambient pressure reaction chamber. The precursors react and / or decompose on the substrate surface, thereby producing a thin film of the deposited material. A plasma can be used to assist the precursor reaction or to improve the material properties. Volatile by-products are removed by passing a gas stream through the reaction chamber. It can be difficult to control the thickness of the deposited film because it depends on the coordination of many parameters (such as temperature, pressure, gas flow volume and uniformity, chemical consumption effects, and time).

[0004] ALD is a chemical method for thin film deposition. It is a self-limiting, sequential, and unique film growth technique based on surface reactions, which can provide precise thickness control and deposit conformal thin films of the material provided by the precursors onto surface substrates of different compositions. In ALD, the precursors are separated during the reaction. The first precursor is passed over the substrate surface, thereby creating a monolayer on the substrate surface. Any excess unreacted precursor is pumped out of the reaction chamber. Then a second precursor or co-reactant is passed over the substrate surface and reacts with the first precursor, thereby forming a second film monolayer on the first formed film monolayer on the substrate surface. A plasma can be used to assist the precursor or co-reactant reaction or to improve the material quality. This cycle is repeated to produce a film of the desired thickness.

[0005] Thin films and especially metal-containing thin films have a variety of important applications, such as in the manufacture of nanotechnology and semiconductor devices. Examples of such applications include capacitor electrodes, gate electrodes, adhesive diffusion barriers, and integrated circuits.

[0006] The continuous reduction in the size of microelectronic components has increased the need for improved thin film technologies. Further, in logic and memory semiconductor manufacturing, there is a need to deposit molybdenum as the next generation metal electrode and cap or liner. Although low resistivity molybdenum films can be deposited by ALD or CVD at elevated temperatures (e.g., greater than 400 °C) using H2 to reduce molybdenum halides (such as MoCl5) or oxohalides (such as MoO2Cl2), such molybdenum films may suffer from little or no growth or island growth on oxide and nitride surfaces due to long nucleation delays. Diborane can be used as a nucleation layer to deposit boron, but the use of diborane may result in boron contamination and non-uniform deposition. Accordingly, there is a need for methods for forming molybdenum-containing films on metal-containing liners that can achieve lower resistivity films with improved molybdenum nucleation. Summary of the Invention

[0007] Accordingly, provided herein are methods for forming molybdenum-containing films on a substrate. The method includes thermally depositing a first film comprising elemental metal on a substrate surface at a first temperature less than or equal to about 400 °C. The elemental metal can be tungsten, molybdenum, or a combination thereof. The method further includes thermally depositing a second film on at least a portion of the first film at a second temperature greater than about 400 °C. The second film comprises a reaction product of a molybdenum-containing precursor and a reducing agent.

[0008] In other embodiments, provided herein is another method for forming a molybdenum-containing film on a substrate. The method includes thermally depositing a first film comprising elemental metal on a substrate surface at a first temperature less than or equal to about 400 °C. The elemental metal can be selected from the group consisting of ruthenium, cobalt, and combinations thereof. The method further includes thermally depositing a second film on at least a portion of the first film at a second temperature greater than about 400 °C. The second film comprises a reaction product of a molybdenum-containing precursor and a reducing agent.

[0009] Other embodiments will be apparent from the following detailed description, including specific aspects of the embodiments outlined above. Brief Description of the Drawings

[0010] Figure 1 is a graph showing thermogravimetric analysis (TGA) data of the weight (%) of MoO2Cl2 versus temperature.

[0011] Figure 2A is the growth rate of molybdenum-containing films grown on SiO2 substrates, WCN substrates, a first molybdenum elemental film, and a first ruthenium elemental film according to Example 2 plotted against deposition temperature (°C).

[0012] Figure 2B is the resistivity (μΩ-cm) and molybdenum thickness of molybdenum-containing films grown on a first molybdenum elemental film according to Example 2 Illustration of the deposition temperature (°C).

[0013] Figure 3A Is the growth rate of the molybdenum-containing film grown on the Al2O3 substrate, SiO2 substrate, WCN substrate, TiN substrate, and the first ruthenium film according to Example 3 Illustration of the deposition pressure (Torr).

[0014] Figure 3B Is the illustration of the resistivity (μΩ-cm) of the molybdenum-containing film grown on the WCN substrate and the first ruthenium film according to Example 3 versus the deposition pressure (Torr).

[0015] Figure 4 Is the illustration of the X-ray photoelectron spectroscopy (XPS) chemical composition of the molybdenum-containing film deposited on the first ruthenium film according to Example 4

[0016] Figure 5A and Figure 5B Is the scanning electron microscope (SEM) image of the molybdenum-containing film deposited on the first ruthenium film

[0017] Figure 5C Is the SEM image of the molybdenum-containing film deposited on the Al2O3 substrate

[0018] Figure 5D and Figure 5E Is the SEM image of the molybdenum-containing film deposited on the WCN substrate

[0019] Figure 6A - Figure 6C Are the cross-sectional SEM images of the via structure of the SiO2 substrate, the TiN liner in the via structure, and the first molybdenum film liner deposited in the via structure, respectively, with the molybdenum-containing film directly deposited in the via structure

[0020] Figure 7A and Figure 7B Is the cross-sectional SEM image of the TiN via structure with the molybdenum-containing film directly deposited in the TiN via structure

[0021] Figure 7C and Figure 7D Is the cross-sectional SEM image of the molybdenum-containing film deposited on the first molybdenum film liner deposited in the TiN via structure Detailed Description of the Invention

[0022] Before describing several exemplary embodiments of the present invention technology, it should be understood that the present technology is not limited to the details of the structures or method steps set forth in the following description. The present invention technology can have other embodiments and can be practiced or implemented in different ways.

[0023] The inventors have discovered a two-step method for improving molybdenum deposition and the films formed therefrom. These methods can include a first step that includes depositing a first film or liner, such as an elemental molybdenum film or an elemental ruthenium film, on a substrate using a first metal-containing precursor and a co-reactant. In a second step, a second film (i.e., a molybdenum-containing film) can be formed on the first film by delivering a molybdenum-containing precursor and a reducing agent. Advantageously, the methods described herein can be carried out at lower temperatures. For example, the first step can be carried out at a temperature less than or equal to 400 °C. Additionally, a conformal molybdenum-containing second film with low resistivity can be achieved.

[0024] Definitions

[0025] For the purposes of this invention and its claims, the numbering scheme for the groups of the Periodic Table is according to the IUPAC Periodic Table of the Elements.

[0026] The term “and / or” as used in a phrase such as “A and / or B” is intended herein to include “A and B,” “A or B,” “A,” and “B.”

[0027] The terms “substituent,” “radical,” “group,” and “moiety” may be used interchangeably.

[0028] As used herein, the terms “metal-containing complex” (or more simply, “complex”) and “precursor” are used interchangeably and refer to a metal-containing molecule or compound that can be used to prepare a metal-containing film by a deposition process (e.g., such as ALD or CVD). The metal-containing complex can be deposited on, adsorbed to, decomposed on, delivered to, and / or pass through a substrate or its surface to form a metal-containing film.

[0029] As used herein, the term “metal-containing film” includes not only elemental metal films as more fully defined below, but also films that contain a metal along with one or more elements, such as metal nitride films, metal silicide films, metal carbide films, etc.

[0030] As used herein, the terms "elemental metal", "elemental metal film", and "pure metal film" are used interchangeably and refer to a film composed of or consisting essentially of a pure metal. For example, an elemental metal film can comprise 100% pure metal, or an elemental metal film can comprise at least about 70%, at least about 80%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, at least about 99.9%, or at least about 99.99% pure metal along with one or more impurities. However, a film containing elemental metal is distinct from a binary film containing a metal and a non-metal (e.g., C, N) and a ternary film containing a metal and two non-metals (e.g., C, N), although a film containing elemental metal can contain a certain amount of impurities. Unless the context otherwise dictates, the term "metal film" shall be construed to mean an elemental metal film.

[0031] As used herein, the terms "deposition process" and "thermal deposition" are used to refer to any type of deposition technique, including but not limited to CVD and ALD. In various embodiments, CVD can take the form of conventional (i.e., continuous flow) CVD, liquid injection CVD, plasma enhanced CVD, or photo-assisted CVD. CVD can also take the form of a pulsed technique, i.e., pulsed CVD. ALD is used to form a metal-containing film by vaporizing and / or passing at least one metal complex disclosed herein over a substrate surface. For a conventional ALD process, see, e.g., George S.M. et al., J. Phys. Chem. [Journal of Physical Chemistry], 1996, 100, 13121 - 13131. In other embodiments, ALD can take the form of conventional (i.e., pulsed injection) ALD, liquid injection ALD, photo-assisted ALD, plasma-assisted ALD, or plasma enhanced ALD. The term "vapor deposition process" further includes the various vapor deposition techniques described in Chemical Vapour Deposition: Precursors, Processes, and Applications; Jones, A.C.; Hitchman, M.L. editors. The Royal Society of Chemistry: Cambridge [The Royal Society of Chemistry: Cambridge], 2009; Chapter 1, pp. 1 - 36.

[0032] Method for forming a molybdenum-containing film

[0033] As stated above, provided herein is a method of forming a molybdenum (Mo)-containing film. The method can include a first step and a second step. In any embodiment, the first step can include forming a first film (or liner) on a substrate surface. The first film can comprise an elemental metal. For example, the elemental metal can be selected from the group consisting of tungsten (W), molybdenum (Mo), ruthenium (Ru), cobalt (Co), and combinations thereof. In any embodiment, the elemental metal can be tungsten (W), molybdenum (Mo), or a combination thereof. In another embodiment, the elemental metal can be selected from the group consisting of ruthenium (Ru), cobalt (Co), and combinations thereof.

[0034] The first film comprising an elemental metal (e.g., Mo, Ru) can have a thickness measured by X-ray fluorescence (XRF) that is greater than or equal to about 1 nm, greater than or equal to about 2 nm, greater than or equal to about 4 nm, greater than or equal to about 6 nm, greater than or equal to about 8 nm, greater than or equal to about 10 nm, greater than or equal to about 12 nm, or about 15 nm; or from about 1 nm to about 15 nm, about 2 nm to about 12 nm, about 2 nm to about 10 nm, or about 6 nm to about 12 nm.

[0035] Additionally or alternatively, the first film comprising an elemental metal (e.g., Mo, Ru) can have a conductivity that is less than or equal to about 300 μΩ·cm, less than or equal to about 250 μΩ·cm, less than or equal to about 200 μΩ·cm, less than or equal to about 175 μΩ·cm, less than or equal to about 150 μΩ·cm, less than or equal to about 125 μΩ·cm, or 100 μΩ·cm; or from about 100 μΩ·cm to about 300 μΩ·cm, about 100 μΩ·cm to about 250 μΩ·cm, about 100 μΩ·cm to about 200 μΩ·cm, or about 100 μΩ·cm to about 150 μΩ·cm.

[0036] In any embodiment, thermally depositing the first film includes delivering a first metal-containing precursor and a co-reactant to a substrate. The first metal-containing precursor can be any suitable tungsten-containing precursor, molybdenum-containing precursor, ruthenium-containing precursor, cobalt-containing precursor, or a combination thereof. Examples of molybdenum-containing precursors include, but are not limited to, molybdenum halides, molybdenum halides oxides, molybdenum hexacarbonyl, or a combination thereof. Suitable molybdenum halides include, but are not limited to, MoCl5 or MoF6. Suitable molybdenum halide oxides include, but are not limited to, MoOCl4 or MoO2Cl2. Examples of tungsten precursors include, but are not limited to, WCl5, WF6, and W(CO)6. Examples of ruthenium-containing precursors include, but are not limited to, zero-valent ruthenium (Ru(0)) precursors such as, but not limited to, η4-2,3-dimethylbutadiene tricarbonyl ruthenium ((DMBD)Ru(CO)3) and (ethylbenzyl)(1-ethyl-1,4-cyclohexadienyl)(EtBz)Ru(EtCHD). In some embodiments, the first film is formed by delivering a first metal-containing precursor (including molybdenum halides) as described herein and a co-reactant as further described below to the substrate. In other embodiments, the first film is formed by delivering a first metal-containing precursor (including zero-valent ruthenium precursors) as described herein and a co-reactant as further described below to the substrate.

[0037] In various aspects, the co-reactant can be selected from the group consisting of: nitrogen plasma, ammonia plasma, oxygen, air, water, H2O2, ozone, NH3, H2, i-PrOH, t-BuOH, N2O, ammonia gas, alkyl hydrazine, hydrazine, ozone, 1,4-di-trimethylsilyl-2-methyl-cyclohex-2,5-diene (CHD), 1-trimethylsilylcyclohex-2,5-diene, 1,4-bis-trimethylsilyl-1,4-dihydropyrazine (DHP), and any combination of two or more thereof. In various aspects, the alkyl hydrazine can be C1-C8-alkyl hydrazine, C1-C4-alkyl hydrazine, or C1-C2-alkyl hydrazine. For example, the alkyl hydrazine can be methyl hydrazine, ethyl hydrazine, propyl hydrazine, or butyl hydrazine (including tert-butyl hydrazine).

[0038] In any embodiment, the second step of the method can include thermally depositing a second film (also referred to as a "molybdenum-containing film") on at least a portion of the first film. Thermally depositing the second film includes delivering a molybdenum-containing precursor and a reducing agent to the substrate. The second film can contain a reaction product of the molybdenum-containing precursor and the reducing agent. The second film can also optionally contain a dissociated portion of the molybdenum-containing precursor, a dissociated portion of the reducing agent, or a combination thereof. The molybdenum-containing precursor can be, for example, a molybdenum halide, a molybdenum halide oxide, or a combination thereof. The molybdenum halide can be MoCl5 or MoF6, and the molybdenum halide oxide can be MoOCl4 or MoO2Cl2. The reducing agent can be any suitable reducing agent, including but not limited to hydrogen, hydrogen plasma, or a combination thereof. It is contemplated herein that the first film and the second film can each be a continuous or discontinuous layer.

[0039] Advantageously, the methods described herein can produce a second film having a lower resistivity. For example, the second film can have a resistivity of less than or equal to about 300 μΩ-cm, less than or equal to about 250 μΩ-cm, less than or equal to about 200 μΩ-cm, less than or equal to about 175 μΩ-cm, less than or equal to about 150 μΩ-cm, less than or equal to about 125 μΩ-cm, less than or equal to about 100 μΩ-cm, less than or equal to about 75 μΩ-cm, less than or equal to about 50 μΩ-cm; or about 30 μΩ-cm; or from about 30 μΩ-cm to about 300 μΩ-cm, about 30 μΩ-cm to about 200 μΩ-cm, about 30 μΩ-cm to about 175 μΩ-cm, about 30 μΩ-cm to about 150 μΩ-cm, about 30 μΩ-cm to about 100 μΩ-cm, or about 30 μΩ-cm to about 50 μΩ-cm.

[0040] In any embodiment, the first step, the second step, or a combination thereof can include using a plasma. Using a plasma can, for example, enhance the reaction of one or more of the first metal-containing precursor, the molybdenum-containing precursor, the co-reactant, and the reducing agent. Additionally or alternatively, using a plasma can improve film quality.

[0041] In some embodiments, the first metal-containing precursor, the molybdenum-containing precursor, or a combination thereof can be dissolved in a suitable solvent (such as a hydrocarbon or amine solvent) to facilitate the vapor deposition process. Suitable hydrocarbon solvents include, but are not limited to, aliphatic hydrocarbons such as hexane, heptane, and nonane; aromatic hydrocarbons such as toluene and xylene; and aliphatic ethers and cyclic ethers such as diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. Examples of suitable amine solvents include, but are not limited to, octylamine and N,N-dimethyldodecylamine. For example, the first metal-containing precursor, the molybdenum-containing precursor, or a combination thereof can be dissolved in toluene to produce a solution having a concentration from about 0.05 M to about 1 M.

[0042] In alternative embodiments, the first metal-containing precursor, the molybdenum-containing precursor, or a combination thereof can be delivered "neat" (undiluted by a carrier gas) to the substrate surface. Thus, the precursors disclosed herein and used in these methods can be liquid, solid, or gaseous. Typically, ruthenium precursors and molybdenum precursors are liquid or solid at ambient temperature and a vapor pressure sufficient to allow consistent vapor transport to the processing chamber (e.g., at elevated temperatures).

[0043] In various aspects, the substrate surface can include a metal, a dielectric material, a metal oxide material, or a combination thereof. The dielectric material can be a low-k dielectric or a high-k dielectric. Examples of suitable dielectric materials include, but are not limited to, SiO2, SiON, Si3N4, and combinations thereof. Examples of suitable metal oxide materials include, but are not limited to, HfO2, ZrO2, SiO2, Al2O3, TiO2, and combinations thereof. Other suitable substrate materials include, but are not limited to, crystalline silicon, Si(100), Si(111), glass, strained silicon, silicon-on-insulator (SOI), one or more doped silicon or silicon oxides (e.g., carbon-doped silicon oxide), germanium, gallium arsenide, tantalum, tantalum nitride, aluminum, copper, ruthenium, titanium, titanium nitride, tungsten, tungsten nitride, tungsten carbonitride (WCN), and any number of other substrates commonly encountered in nanoscale device fabrication processes (e.g., semiconductor fabrication processes). In some embodiments, the substrate can include one or more of silicon dioxide, aluminum oxide, titanium nitride, tungsten nitride, tungsten carbonitride, and tantalum nitride. As will be understood by those skilled in the art, the substrate can be exposed to a pretreatment process to polish, etch, reduce, oxidize, hydroxylate, anneal, and / or bake the substrate surface. In one or more embodiments, the substrate surface includes a hydrogen-terminated surface.

[0044] The methods provided herein, particularly the thermal deposition of the first and second films, encompass various types of ALD and CVD processes, such as, but not limited to, continuous or pulsed injection processes, liquid injection processes, photo-assisted processes, plasma-assisted and plasma-enhanced processes. For clarity, the methods of the present invention particularly include direct liquid injection processes. For example, in direct liquid injection CVD ("DLI-CVD"), a solid or liquid metal complex can be dissolved in a suitable solvent and the resulting solution is injected into a vaporization chamber that serves as a means for vaporizing the metal complex. The vaporized metal complex is then transported / delivered to the substrate surface. Generally, DLI-CVD can be particularly useful in those cases where the metal complex exhibits relatively low volatility or is otherwise difficult to vaporize. For example, the first and second steps can independently be ALD or CVD processes.

[0045] In some embodiments, conventional or pulsed CVD is used to form the first film as described herein and / or the second film as described herein by vaporizing and / or passing all of the first metal-containing precursors and / or molybdenum-containing precursors disclosed herein over the substrate surface. For conventional CVD processes, see, e.g., Smith, Donald (1995). Thin-Film Deposition: Principles and Practice. McGraw-Hill.

[0046] In other embodiments, photo-assisted CVD is used to form the first film as described herein and / or the second film as described herein by vaporizing all of the first metal-containing precursors and / or molybdenum-containing precursors disclosed herein on the surface of the substrate and / or passing through the surface of the substrate.

[0047] In one embodiment, the CVD growth conditions for the first metal-containing precursors and / or molybdenum-containing precursors disclosed herein include, but are not limited to:

[0048] (1) Substrate temperature: 50 °C - 600 °C

[0049] (2) Evaporator temperature (metal precursor temperature): 0 - 120 °C

[0050] (3) Reactor pressure: 0 - 200 Torr

[0051] (4) Argon or nitrogen carrier gas flow rate: 0 - 100 sccm

[0052] (5) Oxygen flow rate: 0 - 100 sccm

[0053] (6) Hydrogen flow rate: 0 - 50 sccm

[0054] (7) Metal precursor pulse time: 0.01 - 5 seconds

[0055] (8) Purge gas pulse time: 1 - 30 seconds

[0056] (9) Run time: Will vary according to the desired film thickness

[0057] In another embodiment, photo-assisted CVD is used to form a metal-containing film by vaporizing all of the first metal-containing precursors and / or molybdenum-containing precursors disclosed herein on the surface of the substrate and / or passing through the surface of the substrate.

[0058] In some embodiments, conventional (i.e., pulsed injection) ALD is used to form the first film as described herein and / or the second film as described herein by vaporizing all of the first metal-containing precursors and / or molybdenum-containing precursors disclosed herein on the surface of the substrate and / or passing through the surface of the substrate. For conventional ALD processes, see, e.g., George S.M. et al., J. Phys. Chem. [Journal of Physical Chemistry], 1996, 100, 13121 - 13131.

[0059] In other embodiments, liquid injection ALD is used to form the first film as described herein and / or the second film as described herein by vaporizing all of the first metal-containing precursors and / or molybdenum-containing precursors disclosed herein on the surface of the substrate and / or passing through the surface of the substrate, wherein the foregoing precursors are delivered to the reaction chamber by direct liquid injection rather than by bubbler aspiration of the vapor. For liquid injection ALD processes, see, for example, Potter R. J. et al., Chem. Vap. Deposition, 2005, 11(3), 159-169.

[0060] In other embodiments, photo-assisted ALD is used to form the first film as described herein and / or the second film as described herein by vaporizing all of the first metal-containing precursors and / or molybdenum-containing precursors disclosed herein on the surface of the substrate and / or passing through the surface of the substrate. For photo-assisted ALD processes, see, for example, U.S. Patent No. 4,581,249.

[0061] In other embodiments, plasma-assisted or plasma-enhanced ALD is used to form the first film as described herein and / or the second film as described herein by vaporizing all of the first metal-containing precursors and / or molybdenum-containing precursors disclosed herein on the surface of the substrate and / or passing through the surface of the substrate.

[0062] Examples of ALD growth conditions for the first metal-containing precursors and / or molybdenum-containing precursors disclosed herein include, but are not limited to:

[0063] (1) Substrate temperature: 200 °C - 700 °C

[0064] (2) Evaporator temperature (metal precursor temperature): 20 °C - 150 °C

[0065] (3) Reactor pressure: 0.01 - 200 Torr

[0066] (4) Argon or nitrogen carrier gas flow rate: 0 - 100 sccm

[0067] (5) Reactive gas (co-reactant or reducing agent) pulse time: 0.01 - 30 seconds

[0068] (6) Metal precursor pulse time: 0.01 - 10 seconds

[0069] (7) Purge gas pulse time: 1 - 10 seconds

[0070] (8) Pulse sequence (metal complex / purge / reactive gas / purge): Will vary according to chamber size.

[0071] (9) Number of cycles: Will vary according to the desired film thickness, e.g., 1 - 100 cycles.

[0072] Select the reaction time, temperature, and pressure of the methods described herein to produce a first film and a second film on a substrate surface. The reaction conditions will be selected based on the properties of the first metal-containing precursor and the molybdenum-containing precursor. The first and second steps can be carried out at atmospheric pressure, but are more typically carried out under reduced pressure. For example, during the first step, thermal deposition of the first film can be carried out at a pressure of greater than or equal to about 0.01 torr, greater than or equal to about 0.1 torr, greater than or equal to about 0.5 torr, greater than or equal to about 1 torr, greater than or equal to about 2 torr, greater than or equal to about 4 torr, greater than or equal to about 6 torr, greater than or equal to about 8 torr, or about 10 torr; or from about 0.01 torr to about 10 torr, about 0.1 torr to about 8 torr, about 0.1 torr to about 6 torr, or about 2 torr to about 6 torr. Additionally or alternatively, during the second step, thermal deposition of the second film can be carried out at a pressure of greater than or equal to about 1 torr, greater than or equal to about 5 torr, greater than or equal to about 10 torr, greater than or equal to about 25 torr, greater than or equal to about 50 torr, greater than or equal to about 75 torr, greater than or equal to about 100 torr, greater than or equal to about 150 torr, or about 200 torr; or from about 1 torr to about 200 torr, about 1 torr to about 100 torr, about 1 torr to about 50 torr, or about 5 torr to about 10 torr.

[0073] The vapor pressures of the first metal-containing precursor and the molybdenum-containing precursor should be high enough to be practical in such applications. The substrate temperature should be low enough to keep the bonds between metal atoms at the surface intact and prevent thermal decomposition of the gaseous reactants. However, the substrate temperature should also be high enough to keep the source materials (i.e., the reactants) in the gas phase and provide sufficient activation energy for surface reactions. The appropriate temperature depends on various parameters, including the specific first metal-containing precursor and molybdenum-containing precursor used and the pressure. In some embodiments, during the first step, the first film can be thermally deposited at a lower temperature, such as a first temperature of less than or equal to about 500 °C, less than or equal to about 450 °C, less than or equal to about 400 °C, less than or equal to about 350 °C, less than or equal to about 300 °C, less than or equal to about 290 °C, less than or equal to about 275 °C, less than or equal to about 250 °C, less than or equal to about 225 °C, or about 200 °C; or from about 200 °C to about 500 °C, about 200 °C to about 400 °C, about 200 °C to about 300 °C, or about 225 °C to about 290 °C. Additionally or alternatively, during the second step, the second film can be thermally deposited at a higher temperature, such as a second temperature of greater than or equal to about 300 °C, greater than or equal to about 350 °C, greater than or equal to about 400 °C, greater than or equal to about 450 °C, greater than or equal to about 500 °C, greater than or equal to about 550 °C, greater than or equal to about 600 °C, greater than or equal to about 650 °C, or about 700 °C; or from about 300 °C to about 700 °C, about 400 °C to about 600 °C, about 400 °C to about 500 °C, or about 400 °C to about 450 °C. The foregoing temperatures are to be understood as representing the substrate temperature. In any embodiment, the first step, the second step, or both can be carried out in an inert atmosphere (e.g., in an argon atmosphere).

[0074] The properties of the specific first metal-containing precursor and molybdenum-containing precursor used in the deposition methods disclosed herein can be evaluated using methods known in the art, allowing for the selection of appropriate temperatures and pressures for the reaction. Generally, lower molecular weights and the presence of functional groups that increase the rotational entropy of the ligand sphere result in melting points that produce liquids at typical delivery temperatures and increased vapor pressures.

[0075] The first metal-containing precursor and molybdenum-containing precursor used in the deposition method will meet all requirements for sufficient vapor pressure, sufficient thermal stability at the selected substrate temperature, and sufficient reactivity to produce a reaction on the substrate surface without unwanted impurities in the thin film. Sufficient vapor pressure ensures that source compound molecules are present at the substrate surface at a sufficient concentration to enable a complete self-saturating reaction. Sufficient thermal stability ensures that the source compound will not undergo thermal decomposition that produces impurities in the thin film.

[0076] In additional embodiments, the first step, e.g., during an ALD process, may include a first step cycle that includes delivering a first metal-containing precursor, a co-reactant, and a purge gas to a substrate. For example, the first metal-containing precursor may be pulsed for 0.01 - 1 second, followed by delivering the purge gas for 2 - 15 seconds, followed by pulsing the co-reactant for 0.001 - 3 seconds, and then delivering the purge gas for 2 - 15 seconds. The number of first step cycles may range from 1 to 100 cycles, 1 to 75 cycles, 1 to 50 cycles, 1 to 25 cycles, 1 to 10 cycles, or 1 to 5 cycles.

[0077] In various aspects, the second step, e.g., during a pulsed CVD process, may include a second step cycle that includes delivering a molybdenum-containing precursor, e.g., pulsing the molybdenum-containing precursor in a stream of a reducing agent and a purge gas to a substrate. For example, the molybdenum-containing precursor may be pulsed for about 0.01 - 2 seconds in a stream of a reducing agent and a purge gas, where the reducing agent and the purge gas flow for about 5 - 30 seconds. In some embodiments, the reducing agent may flow for a shorter period of time compared to the purge gas. Alternatively, after pulsing the molybdenum-containing precursor, the reducing agent, the purge gas, or both may be delivered to the substrate, e.g., for about 5 - 30 seconds. The number of pulses of the molybdenum-containing precursor is determined by the desired thickness of the molybdenum-containing film, e.g., the range of pulses may be from 1 to 500 pulses, 1 to 300 pulses, 1 to 200 pulses, 1 to 100 pulses, 1 to 50 pulses, or 1 to 25 pulses.

[0078] In alternative embodiments, the second step, e.g., during an ALD process, may include a second step cycle that includes delivering a molybdenum-containing precursor, a reducing agent, and a purge gas to a substrate. For example, the molybdenum-containing precursor may be pulsed for 0.01 - 2 seconds, followed by delivering the purge gas for 2 - 10 seconds, followed by pulsing the reducing agent for 2 - 15 seconds, and then delivering the purge gas for 2 - 10 seconds. The number of second step cycles may range from 1 to 1000 cycles, 1 to 750 cycles, 1 to 500 cycles, 1 to 250 cycles, 1 to 100 cycles, 1 to 75 cycles, 1 to 50 cycles, 1 to 25 cycles, 1 to 10 cycles, or 1 to 5 cycles.

[0079] Any suitable purge gas may be used in the first and second steps, e.g., nitrogen, hydrogen, and inert gases such as helium, neon, argon, krypton, xenon, etc.

[0080] In additional embodiments, the methods described herein can be carried out under conditions that provide conformal growth, for example, for the first film, the second film, or a combination thereof. As used herein, the term "conformal growth" refers to a deposition process in which a film is deposited with a substantially uniform thickness along one or more of the bottom surface, sidewalls, upper corners, and exterior of a feature. "Conformal growth" is also intended to encompass some variation in the film thickness, e.g., the film can be thicker at the exterior of the feature and / or near the top or upper portion of the feature compared to the bottom or lower portion of the feature.

[0081] The first step (e.g., the first step cycle) and / or the second step can be carried out under conformal conditions such that conformal growth occurs. Conformal conditions include, but are not limited to, temperature (e.g., the temperature of the substrate, the first metal-containing precursor, the molybdenum-containing precursor, the purge gas, the co-reactant, the reducing agent, etc.), pressure (e.g., during the delivery of the first metal-containing precursor, the molybdenum-containing precursor, the purge gas, the co-reactant, the reducing agent, etc.), the amount of the first metal-containing precursor, the molybdenum-containing precursor, the purge gas, the co-reactant, and / or the reducing agent delivered, the purge duration, and / or the amount of the purge gas delivered.

[0082] In various aspects, the substrate can include one or more features on which conformal growth can occur. In various aspects, the features can be vias, trenches, contacts, dual damascenes, etc. The features can have a non-uniform width, also referred to as "re-entrant features", or the features can have a substantially uniform width.

[0083] In any embodiment, the first film, the second film, or both grown according to the methods described herein can be substantially continuous and conformal. In one or more embodiments, the first film, the second film, or both grown according to the methods described herein can be substantially void-free and / or free of hollow seams.

[0084] In various aspects, the method can include delivering a first metal-containing precursor, a purge gas, and at least one co-reactant to the surface of the substrate under conditions sufficient for the first metal-containing precursor to: (i) deposit elemental metal and etch a portion of the first film; (ii) deposit elemental metal, etch a portion of the first film, and allow desorption of the etched portion of the first film; or (iii) deposit elemental metal and allow desorption of a portion of the first film; such that the first film grows conformally on at least a portion of the substrate. Under such conditions, the first metal-containing precursor can undergo one or more of the following: (i) deposit elemental metal and etch a portion of the first film; (ii) deposit elemental metal, etch a portion of the first film, and allow desorption of the etched portion of the first film; or (iii) deposit elemental metal and allow desorption of a portion of the first film. Additionally or alternatively, the co-reactant can deposit elemental metal.

[0085] In some embodiments, the first film and the second film can be deposited in the same reaction vessel. Alternatively, the first film and the second film can be deposited in different reaction vessels. For example, the first film can be deposited on a substrate in a first reaction vessel, and then the substrate having the first film deposited thereon can be moved to a second reaction vessel where the second film can be deposited on at least a portion of the first film.

[0086] In any embodiment, the methods described herein can further include annealing the as-deposited first film, the as-deposited second film, or both at a higher temperature. In other words, annealing can be performed after the last cycle for forming the first film and / or the last cycle for forming the second film.

[0087] Thus, in some embodiments, the as-deposited first film, the as-deposited second film, or both can be annealed under vacuum, or in the presence of an inert gas (such as Ar or N2), or a reducing agent (such as H2), or a combination thereof (e.g., 5% H2 in Ar). Without being bound by theory, the annealing step can remove the incorporated carbon, oxygen, and / or nitrogen by densification at high temperature to reduce the resistivity and further improve the film quality. Annealing can be performed at a temperature of greater than or equal to about 400 °C, greater than or equal to about 700 °C, or about 800 °C; from about 300 °C to about 800 °C or about 500 °C to about 800 °C.

[0088] Applications

[0089] The films formed by the methods described herein can be used in memory and / or logic applications such as dynamic random access memory (DRAM), complementary metal oxide semiconductor (CMOS), and 3D NAND, 3D cross-point, and ReRAM.

[0090] References throughout this specification to "one embodiment", "certain embodiments", "one or more embodiments", or "an embodiment" mean that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the present inventive technique. Thus, appearances of the phrases such as "in one or more embodiments", "in certain embodiments", "in one embodiment", or "in an embodiment" in various places throughout this specification are not necessarily referring to the same embodiment of the present inventive technique. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

[0091] Although the present invention has been described with reference to specific embodiments, it should be understood that these embodiments merely illustrate the principles and applications of the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the methods and apparatuses of the present invention without departing from the spirit and scope of the present invention. Accordingly, the present invention is intended to cover modifications and variations within the scope of the appended claims and their equivalents. The present invention as generally described above will be more readily understood by reference to the following examples, which are provided by way of illustration and are not intended to be limiting.

[0092] Example

[0093] General conditions

[0094] In the following examples, MoCl5 (obtained from Strem Chemicals Inc.), MoO2Cl2 (obtained from MilliporeSigma), and (DMBD)Ru(CO)3 (also known as RuDMBD) were used as precursors. Methods for preparing (DMBD)Ru(CO)3 are known in the art. See, for example, U.S. 2011 / 0165780, which is incorporated herein by reference in its entirety. Unless otherwise specified, the film thickness was measured via XRF and the resistivity of the film was based on ellipsometer thickness.

[0095] I. First step

[0096] Unless otherwise specified, the first ruthenium element film was deposited on a substrate using (DMBD)Ru(CO)3 and O2 in an ALD process in a CN1 ALD / CVD reactor under the following conditions:

[0097] i. Substrate temperature: 250 °C

[0098] ii. At 40 °C, (DMBD)Ru(CO)3 was delivered to the substrate as follows: 1-second pulse of (DMBD)Ru(CO)3 (bubbler), purged with argon for 10 seconds, 3-second pulse of O2 co-reactant (20 sccm), and purged with argon for 10 seconds.

[0099] Unless otherwise specified, the first molybdenum element film was deposited on a substrate using MoCl5 and CHD in an ALD process in an Ultratech Savannah S200 reactor under the following conditions:

[0100] i. Substrate temperature: 280 °C

[0101] ii. At 114 °C, MoCl5 was delivered to the substrate as follows: a 1-second pulse of MoCl5, purged with nitrogen for 2 seconds, a 3-second pulse of the CHD co-reactant at 50 °C, and purged with nitrogen for 2 seconds.

[0102] II Second step

[0103] Unless otherwise stated, the molybdenum-containing film was deposited using MoO2Cl2 and H2 in a pulsed CVD process in a CN1 ALD / CVD reactor under the following conditions:

[0104] i. Substrate temperature: 430 °C - 490 °C.

[0105] ii. At 85 °C, MoO2Cl2 was pulsed with a constant flow of H2 in Ar: a 1 - 2-second pulse of MoO2Cl2 and purged with H2 in Ar for 10 - 30 seconds.

[0106] Example 1 - Thermogravimetric Analysis of MoO2Cl2

[0107] Thermogravimetric analysis (TGA) of MoO2Cl2 was performed and the results are shown in Figure 1 Mo2O2Cl2 showed a clean evaporation at about 170 °C, where the residue (1.6%) was negligible. The vapor pressure of MoO2Cl2 is LogP (torr) = 11.747 - (3830 / T).

[0108] Example 2 - Influence of Deposition Temperature on Growth Rate and Resistivity

[0109] The first molybdenum film was grown on a SiO2 substrate via the above ALD conditions, and a molybdenum-containing film was deposited on the first molybdenum film (″on Mo″) at four different substrate temperatures of 430 °C, 450 °C, 470 °C, and 490 °C via the above CVD conditions using 60% H2, a pressure of 2.0 torr, and 300 pulses. The first ruthenium film was grown on a SiO2 substrate via the above ALD conditions, and a molybdenum-containing film was deposited on the first ruthenium film (″on Ru″) at four different substrate temperatures of 430 °C, 450 °C, 470 °C, and 490 °C via the above CVD conditions using 60% H2, a pressure of 2.0 torr, and 300 pulses. A molybdenum-containing film was also deposited on a SiO2 substrate (″on SiO2″) and a WCN substrate (″on WCN″) at four different substrate temperatures of 430 °C, 450 °C, 470 °C, and 490 °C via the above CVD conditions using 60% H2, a pressure of 2.0 torr, and 300 pulses. The growth rates of the molybdenum-containing films at four different temperatures were measured, as Figure 2AAs shown. A metal Mo film deposited on the first film of molybdenum element and the first film of ruthenium element is observed. Mo grows slowly on WCN and grows little on SiO2. The resistivity and thickness of the molybdenum-containing film on Mo were also measured at four different temperatures, as Figure 2B shown.

[0110] Example 3 - Influence of Deposition Pressure on Growth Rate and Resistivity

[0111] The first film of ruthenium element was grown on the SiO2 substrate via the above ALD conditions, and the molybdenum-containing film was deposited on the first film of ruthenium element (″Ru″) at a substrate temperature of 490 °C and at three different pressures of 3.6 Torr, 4.9 Torr, and 5.8 Torr via the above CVD conditions. The molybdenum-containing film was also deposited on each of the Al2O3 substrate (″Al2O3″), SiO2 substrate (″SiO2″), TiN substrate (″TiN″), and WCN substrate (″WCN″) at a substrate temperature of 490 °C and at three different pressures via the above CVD conditions. The growth rate of the molybdenum-containing film at three different pressures was measured, as Figure 3A shown. The growth rate does not seem to be affected by the deposition pressure. The resistivity of the molybdenum-containing film deposited at 490 °C at three different pressures was also measured, as Figure 3B shown. It was found that the resistivity decreases with an increase in the deposition pressure. The lowest resistivity of the molybdenum-containing film grown on the first film of ruthenium element was found to be about 37 μΩ-cm at 5.8 Torr.

[0112] Example 4 - XPS Analysis of Molybdenum - containing Film on Ruthenium First Film

[0113] XPS analysis was performed on the molybdenum-containing film deposited on the first film of ruthenium element at 490 °C and 5.8 Torr via the above CVD conditions. As Figure 4 shown, the results confirmed that there is no Cl or C in the molybdenum-containing film, and there is about 6 at% of O.

[0114] Example 5 - Comparison of Molybdenum - containing Films on Different Surfaces

[0115] The first film of ruthenium element (thickness 6 nm) was grown on the SiO2 substrate via the above ALD conditions, and the molybdenum-containing film was deposited on the first film of ruthenium element at a substrate temperature of 490 °C and a pressure of 5.8 Torr via the above CVD conditions. Figure 5A is a SEM image of a cross-sectional side view of the molybdenum-containing film on the first film of ruthenium element, which shows a continuous molybdenum film (about 20 nm thick). Figure 5B is Figure 5A A SEM image of the top view of the molybdenum-containing film in. The molybdenum-containing film was deposited on the Al2O3 substrate at a substrate temperature of 490 °C and a pressure of 5.8 Torr via the above CVD conditions. Figure 5CIt is an SEM image of the top view of a molybdenum-containing film on an Al2O3 substrate, which shows separated molybdenum islands. A molybdenum-containing film was also deposited on a WCN substrate at a substrate temperature of 490 °C and a pressure of 5.8 Torr via the above CVD conditions. Figure 5D It is an SEM image of the cross-sectional side view of a molybdenum-containing film on WCN, which shows dispersed molybdenum crystals. Figure 5E is Figure 5D the SEM image of the top view of the molybdenum-containing film in

[0116] Example 6 - Film Formation in Through - holes of SiO2 Substrate

[0117] A molybdenum-containing film was deposited in the through-holes present in the SiO2 substrate at a substrate temperature of 490 °C via the above CVD conditions. Figure 6A It is an SEM image of the cross-sectional side view of a SiO2 through-hole, which shows that there is no molybdenum growth except at the bottom due to the entrapment of the precursor. The TiN liner was deposited on the SiO2 through-hole by ALD at 225 °C using tetrakis(dimethylamido)titanium (TDMAT) and ammonia. A molybdenum-containing film was deposited on the TiN liner (thickness about 2 nm) in the through-holes present in the SiO2 substrate at a substrate temperature of 490 °C via the above CVD conditions. Figure 6B It is an SEM image of the cross-sectional side view of a SiO2 through-hole with a TiN liner, which shows that molybdenum grows as islands with large particles. A first molybdenum elemental film (thickness 2.5 nm) was grown in the through-holes present in the SiO2 substrate at a substrate temperature of 280 °C via the above ALD conditions, and a molybdenum-containing film was deposited on the first molybdenum elemental film at a substrate temperature of 490 °C via the above CVD conditions. Figure 6C It is an SEM image of the cross-sectional side view of a SiO2 through-hole lined with Mo, which shows a uniform, conformal, and smooth molybdenum-containing film (thickness about 20 nm).

[0118] Example 7 - Film Formation in Through - holes of TiN Substrate

[0119] A molybdenum-containing film was deposited in the through-holes at a substrate temperature of 490 °C on a TiN substrate via the above CVD conditions. Figure 7A and Figure 7B It is an SEM image of the cross-sectional side view of a TiN through-hole, which shows a molybdenum-containing film in the form of large particles. A first molybdenum elemental film (Mo liner, thickness 3.2 nm) was grown in the through-holes of the TiN substrate at a substrate temperature of 280 °C via the above ALD conditions, and a molybdenum-containing film was deposited on the first molybdenum elemental film via the above CVD conditions. Figure 7C and Figure 7D It is an SEM image of the cross-sectional side view of a TiN through-hole lined with Mo, which shows a uniform and conformal growth of a molybdenum-containing film as small particles.

[0120] All publications, patent applications, issued patents, and other documents mentioned in this specification are hereby incorporated by reference as if each individual publication, patent application, issued patent, or other document were specifically and individually indicated to be incorporated by reference in its entirety. Definitions contained in text incorporated by reference are excluded to the extent they are inconsistent with definitions in this disclosure.

[0121] The terms "comprise," "comprises," and "comprising" are to be construed inclusively rather than exclusively.

Claims

1. A method for forming a molybdenum-containing film, the method comprising: A. thermally depositing a first film comprising elemental metal on a substrate surface at a first temperature less than or equal to 400 °C, wherein the elemental metal is selected from the group consisting of ruthenium, cobalt, and combinations thereof; and B. thermally depositing a second film on at least a portion of the first film at a second temperature greater than 400 °C, wherein the second film comprises a reaction product of a molybdenum-containing precursor and a reducing agent, wherein, the thermal deposition of the first film comprises delivering a first metal-containing precursor and a co-reactant to the substrate, wherein the first metal-containing precursor is a ruthenium-containing precursor, a cobalt-containing precursor, or a combination thereof.

2. The method according to claim 1, wherein The first film comprises elemental ruthenium and the first film has a thickness greater than or equal to 2 nm.

3. The method according to claim 1, wherein, The ruthenium-containing precursor is η4-2,3-dimethylbutadiene tricarbonyl ruthenium ((DMBD)Ru(CO)3) or (ethylbenzyl)(1-ethyl-1,4-cyclohexadienyl)(EtBz)Ru(EtCHD).

4. The method according to any one of the preceding claims 1-3, wherein, The thermal deposition of the second film comprises delivering the molybdenum-containing precursor and the reducing agent to the substrate, wherein the molybdenum-containing precursor is a molybdenum halide or a molybdenum halide oxide.

5. The method according to claim 4, wherein, The molybdenum halide is MoCl5 or MoF6, and the molybdenum halide oxide is MoOCl4 or MoO2Cl2.

6. The method according to any one of the preceding claims 1-3, wherein, The reducing agent is hydrogen or a hydrogen plasma.

7. The method according to claim 1, wherein, The co-reactant is selected from the group consisting of 1,4-di-trimethylsilyl-2-methyl-cyclohex-2,5-diene (CHD), 1,4-bis-trimethylsilyl-1,4-dihydropyrazine (DHP), 1-trimethylsilylcyclohex-2,5-diene, nitrogen plasma, ammonia plasma, oxygen, air, water, ozone, NH3, H2, hydrazine, alkyl hydrazine, and combinations thereof.

8. The method according to any one of the preceding claims 1-3, wherein, The first temperature is less than or equal to 300 °C.

9. The method according to any one of the preceding claims 1-3, wherein, The first temperature is 225 °C to 290 °C.

10. The method according to any one of the preceding claims 1-3, wherein, The second temperature is 400 °C to 600 °C.

11. The method according to any one of the preceding claims 1-3, wherein, The second temperature is 450 °C to 500 °C.

12. The method according to any one of the preceding claims 1-3, wherein, The second film is continuous and conformal.

13. The method according to any one of the preceding claims 1 to 3, wherein, The second film has a resistivity less than or equal to 200 μΩ-cm.

14. The method according to any one of the preceding claims 1-3, wherein, The thermal deposition of the first film is carried out at a pressure of 0.1 Torr to 6 Torr.

15. The method according to any one of the preceding claims 1-3, wherein, The thermal deposition of the second film is carried out at a pressure of 1 Torr to 100 Torr.

16. The method according to any one of the preceding claims 1-3, wherein, The thermal deposition of the second film is carried out at a pressure of 5 Torr to 10 Torr.

17. The method according to any one of the preceding claims 1-3, wherein, The first film is thermally deposited by chemical vapor deposition or atomic layer deposition.

18. The method according to any one of the preceding claims 1-3, wherein, The second film is thermally deposited by chemical vapor deposition or atomic layer deposition.

19. The method according to any one of the preceding claims 1-3, wherein, The substrate comprises one or more of silicon dioxide, alumina, titanium nitride, tungsten nitride, tungsten carbonitride, and tantalum nitride.

20. The method according to any one of the preceding claims 1-3, wherein, The first film and the second film are deposited in the same reaction vessel.

21. The method according to any one of the preceding claims 1-3, wherein, The first film and the second film are deposited in different reaction vessels.

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