Method for depositing tungsten film or molybdenum film

Abstract

The invention relates to a method for depositing a tungsten or molybdenum thin film. Described herein are vapor deposition methods for depositing a metal thin film or layer onto a substrate, wherein the metal is molybdenum or tungsten; the method involves an organometallic precursor compound containing the metal and one or more carbonaceous ligands, and comprises depositing a metal layer formed from the metal of the precursor onto a substrate, followed by introducing an oxidizing agent to the formed metal layer.

Description

[0001] This application is a divisional application of the invention patent application with the application date of September 24, 2019, application number "201980066362.1", and name "Method for depositing tungsten thin film or molybdenum thin film". Technical Field

[0002] The present invention relates to a vapor deposition method for depositing a metal film, metal layer, or other metal structure onto a substrate, wherein the metal is molybdenum or tungsten. The method involves a metal precursor compound (or "complex") comprising the metal and one or more carbon-containing ligands, and comprises depositing a metal layer formed from the precursor metal onto the substrate, and then introducing an oxidant into the formed metal layer under heating. Background Art

[0003] Molybdenum and tungsten, particularly in purified form, are low-resistivity refractory metals used in microelectronic devices such as memory, logic chips, and other devices that include polysilicon-metal gate electrode structures. These applications have used various vapor deposition techniques and a variety of initial material inputs to deposit thin metallic layers of molybdenum or tungsten. With vapor deposition techniques, a "precursor" compound containing the metal is processed within a deposition chamber containing a substrate, and the processing materials and conditions are sufficient to cause the metal from the precursor to be deposited as a metallic layer on the substrate.

[0004] Vapor deposition techniques include chemical vapor deposition (CVD) and atomic layer deposition (ALD) techniques, including many derivatives of each, such as UV laser photodissociation CVD, plasma-assisted CVD, and plasma-ALD, among others. To deposit high-purity metals on two-dimensional or three-dimensional microelectronic device substrates, CVD and ALD processes may be desirable because they provide high purity and, typically, good conformal step coverage on highly non-planar microelectronic device geometries. However, the cost and complexity of plasma-assisted deposition and high-temperature deposition systems can increase production and tooling costs. Processes such as these that require particularly high temperatures can also damage previously deposited or underlying structures, especially those in logic devices known to be temperature-sensitive.

[0005] In a typical CVD process, a vaporized (gaseous) precursor is brought into contact with an optionally heated substrate (e.g., a wafer) in a low-pressure or ambient-pressure deposition chamber. The precursor introduced to the substrate decomposes, leaving behind a metal-containing deposit on the substrate surface to form a thin layer (or "film") of highly pure deposited metal. Volatile byproducts are removed by gas flow through the deposition chamber.

[0006] In addition to gaseous precursors, vapor deposition processes typically involve supplying one or more other gases (sometimes referred to as "reactant gases" or "co-reactants") to the deposition chamber. The reactant gases may function to make the deposition process more efficient or to improve deposition results. Some reactant gases react with the precursor to release metal from the precursor molecules, which is deposited as elemental metal on the substrate. Other reactant gases may perform a variety of functions, such as improving the performance or lifespan of the deposition chamber or deposition chamber components.

[0007] With respect to precursors, tungsten and molybdenum thin films have been formed by vapor deposition methods using some well-known fluorine-containing precursors, such as tungsten fluorides (e.g., tungsten hexafluoride, tungsten pentafluoride). However, the use of fluorine-containing precursors can be disadvantageous due to the presence of fluorine, leading to device performance issues and requiring "special" processing measures. Non-fluorinated precursor alternatives have been developed, such as chlorine-containing precursors, such as molybdenum pentachloride, molybdenum oxychloride (e.g., MoO2Cl2 and MoOCl4), tungsten pentachloride, and tungsten hexachloride. The difficulty in using these chlorine-containing precursors in vapor deposition methods generally involves heating the substrate to temperatures of at least about 400°C, for example, up to 800°C. These high temperatures require complex processing equipment and can consume the thermal budget of temperature-sensitive equipment, meaning that temperature-sensitive substrates, such as logic devices, may be damaged. Precursors that allow metal layers to be deposited at lower temperatures by allowing lower operating temperatures and using less expensive and less complex equipment would be preferred and would be particularly beneficial for the manufacture of temperature-sensitive devices, such as logic devices.

[0008] Other non-fluorinated precursors include carbonyl-containing precursors (e.g., molybdenum hexacarbonyl (Mo(CO)6) and tungsten hexacarbonyl (W(CO)6)) and imide-amide precursors. These can be deposited at temperatures lower than those required for chloride and oxychloride precursors. However, the deposited metal structures can suffer from high resistivity because carbon, oxygen, or nitrogen from the precursors can be incorporated into the deposited metal as contaminants. Furthermore, step coverage may lack sufficient quality for commercial applications.

[0009] Based on these considerations, there is a need to fabricate molybdenum and tungsten metal films and coatings on various substrates (eg, logic devices) at relatively low deposition temperatures while obtaining extremely high purity deposited metal layers from various organometallic precursors. Summary of the Invention

[0010] In microelectronics manufacturing, when depositing metal layers onto heat-sensitive devices, relatively low temperature (<400°C) vapor deposition processes are required to deposit layers of molybdenum or tungsten. Lower temperature deposition methods allow for process compatibility with existing logic device structures on partially fabricated device substrates. In particular, there is a need for relatively low temperature processes for depositing molybdenum or tungsten onto microelectronic device substrates (e.g., logic devices) to produce metal layers with purity levels that result in extremely low resistance and the conformality / fill characteristics required for fabricating these devices.

[0011] According to the applicant's invention, a vapor deposition method can be used to deposit a layer of highly pure molybdenum or tungsten metal onto a substrate using a gaseous precursor comprising molybdenum or tungsten and one or more carbon-containing ligands. These vapor deposition methods can be performed at relatively low temperatures (meaning, for example, temperatures lower than the deposition temperatures required for vapor deposition methods using halogenated (e.g., fluorinated, chlorinated, brominated, iodinated) or oxyhalogenated precursors). The vapor deposition method of the present invention comprises flowing a gaseous organometallic precursor into a deposition chamber containing a substrate for deposition and an optional co-reactant. The combination of the conditions of the deposition chamber (e.g., elevated temperature) and the flow rates and pressures of the precursors and optional co-reactants results in a substantially pure deposited metal film of tungsten or molybdenum metal from the precursor being deposited onto the surface of the substrate.

[0012] The vapor deposition step can be performed by an atomic layer deposition method, by a chemical vapor deposition method, or by modifications or derivatives of these methods, in any suitable manner as variously described herein. The method is performed using process parameters and conditions that include a pulsed flow of an oxidant that reacts, for example, with carbon in the deposition system at the surface of the deposited metal layer to oxidize the carbon and remove it from the deposited metal layer or prevent carbon from being deposited on the metal layer. The resulting metal layer is highly pure and includes a low concentration of carbon, preferably a concentration of carbon that is lower than the concentration of carbon contained in a metal layer prepared by a similar vapor deposition method that does not include providing an oxidant to the deposition chamber as described herein.

[0013] The molybdenum or tungsten layer can be deposited onto any desired substrate and any specific material of the substrate, an example substrate being a microelectronic device substrate that is "in process" (meaning that the process is not yet complete). The microelectronic device may be one that provides memory functions or one that provides logic functions. Examples of functions of the deposited molybdenum or tungsten include: serving as a conductive layer for a microelectronic logic device (for example, as an interconnect, contact, or electrode). The deposited molybdenum can have a thickness that is effective to perform the desired function and can be continuous. The method is particularly suitable for depositing metal layers onto substrates that include logic functions, which are known to be temperature sensitive. The vapor deposition method as described herein can be performed at relatively low temperatures that do not damage these temperature sensitive substrates.

[0014] One aspect of the present invention is a vapor deposition method for forming a metal thin film on a substrate. The method includes flowing a gaseous precursor into a deposition chamber and exposing the gaseous precursor to a substrate to deposit a metal onto the substrate to form a deposited metal layer. The precursor includes a metal and one or more carbon-containing ligands, wherein the metal is molybdenum or tungsten. The method also includes flowing an oxidant into the deposition chamber to expose the deposited metal layer to the oxidant. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 An example of a system that can be used for the described vapor deposition method is described.

[0016] Figure 2 An example of input flows for the described vapor deposition method using a pulsed oxidant flow is illustrated. DETAILED DESCRIPTION

[0017] The following description relates to a vapor deposition method that utilizes relatively low temperatures for depositing a layer of highly pure molybdenum or tungsten metal onto a substrate using a gaseous precursor comprising molybdenum or tungsten and one or more carbon-containing ligands. The vapor deposition method includes flowing a gaseous metal-containing precursor into a deposition chamber containing a substrate for deposition and optional co-reactants. The combination of the deposition chamber conditions (e.g., high temperature) and the flow rates and pressures of the precursor and optional co-reactants results in the deposition of a substantially pure thin film of tungsten or molybdenum metal from the precursor onto the surface of the substrate.

[0018] A challenge with vapor deposition methods using these types of precursors is that the conditions in the deposition chamber can also allow or cause small amounts of carbon derived from the precursor ligands to be deposited as contaminants in the metal layer. When the precursor includes a carbon-containing ligand (e.g., a carbonyl, alkylamide, alkylamino, alkyl or aryl group (which may be substituted), or a cyclopentadienyl group), carbon from the ligand can be released into the deposition chamber during the deposition process. At temperatures commonly used in vapor deposition methods using these types of precursors, which can be lower than temperatures used to deposit metal layers on substrates from various other types of precursors, such as halogenated precursors (i.e., fluorinated or chlorinated precursors), the precursor carbon can be deposited along with the metal as part of the deposited metal film, for example, in the form of a metal carbide (e.g., molybdenum carbide (Mo2C) or tungsten carbide (WC)). Any such carbon included in the metal layer is an undesirable contaminant because it can adversely affect the performance of the metal film in microelectronic devices. Carbon may, for example, undesirably increase the resistivity of the film, change the morphology or identity of the film, or both.

[0019] According to the present invention, applicants have determined that an oxidant (e.g., gaseous oxygen (O), ozone (O), or a combination of water (H2O) and hydrogen (H2)) can be introduced into the deposition chamber during this type of deposition process, for example, to improve the composition of the deposited metal layer. The oxidant is introduced in an amount and in a manner such that the oxidant reduces the amount of carbon deposited in the finished metal layer; for example, the oxidant can react with carbon on the surface of the metal layer during the deposition process and remove carbon from the metal layer.

[0020] The presently described methods of depositing a metal layer onto a substrate using an organometallic precursor can be any type of vapor deposition method, including those generally referred to as atomic layer deposition, those generally referred to as chemical vapor deposition, or modifications of either of these methods.

[0021] Chemical vapor deposition (CVD) and atomic layer deposition (ALD) are chemical processes by which chemical precursors (optionally and typically, in combination with one or more other materials (e.g., co-reactants)) are introduced to a substrate within a deposition chamber, and the result is the formation of a thin "layer" or "film" of material derived from the precursor on the surface of the substrate. In chemical vapor deposition steps, the thickness of the deposited material can be controlled by deposition parameters (e.g., the length of time the substrate is exposed to the precursor). In atomic layer deposition steps, the thickness of the deposited layer can be "self-limiting" based on process conditions (e.g., the selected deposition temperature and pressure).

[0022] According to the present invention, a gaseous organometallic precursor containing molybdenum or tungsten as the metal and one or more optional co-reactant gases are introduced into a deposition chamber containing a substrate (also referred to as a "reaction chamber"). The gaseous metal precursor is a chemical compound comprising metal atoms chemically associated with one or more carbon-containing chemical groups (i.e., "ligands") attached to the metal atoms. The pressure and flow rate of the precursor and optional co-reactant gas streams, as well as the deposition chamber conditions (e.g., temperature, pressure, substrate temperature, and other conditions) are selected to release the metal atoms of the precursor from the precursor's ligands within the deposition chamber and cause the metal to be deposited onto the surface of the substrate. Volatile byproducts of the deposition process can be removed by the gas flow through the deposition chamber.

[0023] If needed or desired, the gaseous organometallic precursor can be carried to the deposition chamber using a carrier gas, which can be an inert gas such as helium, argon, nitrogen, or a combination thereof. The carrier gas can be mixed with the gaseous organometallic precursor so that the carrier gas carries the desired concentration and total amount of the gaseous precursor to the reaction chamber containing the substrate. The concentration of the gaseous precursor in the carrier gas and the flow rate of the gaseous carrier gas-precursor mixture to the deposition chamber can be selected to effectively produce the desired deposited metal layer as needed and in a particular deposition process, wherein the specific values of these parameters are selected in combination with other parameters of the deposition process, such as the size (volume) of the deposition chamber, the flow rate of the co-reactant gas, the substrate temperature, the deposition chamber pressure, etc.

[0024] Additionally, if necessary or desired, a co-reactant, such as a reducing gas (referred to herein as a "co-reactant gas," such as hydrogen (H2), is typically introduced into the deposition chamber to facilitate deposition of elemental metal from the precursor onto the substrate surface. The relative amounts (e.g., relative flow rates, pressures, etc.) of the co-reactant gas introduced into the deposition chamber can be selected as needed and effective to produce the desired deposited metal layer in a particular process, with the specific values of these parameters being selected in combination with other parameters of the deposition process (e.g., flow rates of the precursors, substrate temperature, and chamber pressure). Furthermore, various other steps may be performed and parameters controlled in accordance with the described vapor deposition methods, such as heating the substrate, selectively purging the deposition chamber by introducing a gaseous atmosphere or by a vacuum step, among other optional or desired steps.

[0025] The precursor used in the vapor deposition step is an organometallic precursor comprising tungsten or molybdenum and one or more organic ligands chemically bonded to the metal center. The organic ligand comprises carbon and may comprise hydrogen and oxygen, and may be in the form of an oxygen or hydrogen atom bonded to one of its carbon atoms or a chain of carbon atoms and one or more functional groups bonded to the carbon (e.g., amino, carbonyl, etc.). The ligand may be or may include, for example, an alkyl group, a substituted alkyl group, an optionally substituted cyclic or aromatic group, a carbonyl group (-C(O)), an alkylamide group, an alkylimide group, or a combination of these. Examples of these types of gaseous metal precursors (sometimes referred to as "organometallic" precursors) are known in the vapor deposition art and include compounds known as organometallic carbonyl precursors, and organometallic amide-imide precursors. Specific examples include bis(ethylphenyl)molybdenum, bis(ethylphenyl)tungsten, molybdenum hexacarbonyl (Mo(CO)6), tungsten hexacarbonyl (W(CO)6), as well as cyclopentadienyl (Cp) complexes of molybdenum and tungsten, alkylcyclopentadienyl and hydride complexes of molybdenum and tungsten.

[0026] A feature of the vapor deposition process of the present invention is that the deposition temperature is relatively lower than the deposition temperature required for depositing a metal layer from some other types of precursors. Compared with the temperature required for the deposition using halogenated (fluorinated, chlorinated, brominated, iodinated) or oxyhalogenated precursors, the deposition temperature of the vapor deposition process using an organometallic precursor comprising a carbon-containing ligand is relatively low. The vapor deposition of the metal layer using various organometallic precursors can be completed at a temperature lower than about 400 degrees Celsius, for example, lower than about 300 degrees Celsius. Advantageously, these lower temperatures allow the currently described method to be used for heat-sensitive substrates, such as microelectronic devices (e.g., microprocessors) designed for performing logic functions. However, another feature of these relatively low temperature vapor deposition steps using organometallic precursors can be the presence of carbon contaminants in the layer of deposited metal.

[0027] To remove carbon, an oxidant is introduced into the deposition chamber in such a manner that the oxidant reacts with carbon present in the deposited metal film. The oxidant, by reacting with carbon, inhibits or prevents carbon from being deposited on the metal layer during deposition, or removes carbon from the deposited metal layer. The oxidant can be any gaseous chemical material that reacts with carbon present in the deposited film (e.g., present in the metal layer) to form a volatile compound that separates from the metal layer and inhibits or prevents carbon from being incorporated into the metal layer.

[0028] Examples of useful oxidants include gaseous oxygen (O ), ozone (O ), and a combination of water vapor and gaseous hydrogen. The oxidant (e.g., gaseous oxygen) can react with carbon present in the deposited film (e.g., as a contaminant in the metal layer) and produce carbon dioxide, which is not incorporated into the metal layer or separated from the metal during the deposition step. The oxidant can be introduced into the deposition chamber in an amount, manner, flow rate, time, and pressure effective to react with the carbon during deposition of the metal layer. In a preferred method, the metal film prepared by using oxygen during deposition can contain a reduced amount of carbon compared to the amount of carbon present in a comparable metal film prepared by the same method and from the same material (but without introducing the oxidant into the deposition chamber). In a preferred method, the resistivity of the metal film prepared by using oxygen during deposition can be lower than the resistivity of a comparable metal film prepared by the same method and from the same material (but without introducing the oxidant into the deposition chamber and process). In certain currently preferred example methods, the oxidant can effectively remove carbon from the deposited metal layer, or prevent carbon from being incorporated into the metal layer, when the oxidant is introduced into the deposition process in an "interrupted" or "pulsed" manner, meaning that the flow rate of the gaseous oxidant is not stable and the timing of the pulse introduction can be controlled.

[0029] Deposition of elemental molybdenum or tungsten using a gaseous organometallic precursor (comprising molybdenum or tungsten and one or more carbon-containing ligands) as described can be performed using available vapor deposition equipment and generally understood techniques suitable for depositing layers of elemental molybdenum or tungsten from the precursors, with the addition of oxygen introduced into the deposition chamber to remove carbon from the deposited metal layer.

[0030] As an example of a useful system for the method of the present invention, Figure 1 Shown schematically (not to scale) is a system that can be used to perform the described vapor deposition process, which can be chemical vapor deposition, atomic layer deposition, or a modified version or derivative of any of these methods. Figure 1 Vapor deposition system 2 is shown including a deposition chamber 10 having an interior 12 containing a platen 14 that supports a substrate 16. As shown, interior 12 is sized to accommodate only a single substrate 16, but may alternatively have any dimensions necessary for accommodating multiple substrates for vapor deposition processing.

[0031] Still refer to Figure 1 , cylinders 40, 42, 44 and 46 are connected to the interior 12 to allow gaseous fluid to selectively flow from each cylinder into the interior 12. Each of the cylinders may contain a liquid or gaseous starting material that is supplied to the interior 12 in gaseous form for a vapor deposition step. For example, cylinder 46 may contain a liquid, solid or gaseous organometallic precursor. Cylinder 44 may contain an inert gas that is used as a carrier gas to carry a certain concentration of the organometallic precursor to the interior 12. In use, the carrier gas from the cylinder 44 containing the carrier gas may flow through a conduit that may also be connected to the cylinder 46 containing the precursor by an open valve. The combination of carrier gas and precursor may be controlled to flow into the chamber 12.

[0032] Gas cylinder 42 is optional and may contain a co-reactant (e.g., hydrogen), another reducing gas, or a different co-reactant. One or more additional optional gas cylinders (not shown) may also be present to contain and supply any other various useful or co-reactants or other gaseous fluids (e.g., another inert gas (e.g., for a purge step)) to interior 12.

[0033] The cylinder 40 contains an oxidant, such as oxygen (O 2 ).

[0034] Although not explicitly shown, any of a variety of known measurement or flow control devices may also be present in the system 2 to monitor and adjust the flow and relative flow of each gaseous fluid from the cylinder, as well as conditions such as the temperature or pressure of the gaseous stream, the temperature of the interior 12, or the temperature of the platen 14 or substrate 16; these may include pressure regulators, flow regulators (e.g., mass flow regulators), sensors (pressure sensors, temperature sensors), and the like. A control system 50 (which may be or may include a computer, central processing unit (CPU), programmable logic controller (PLC), or the like) includes wiring 52 or other (e.g., wireless) communication means to electrically connect the control system 50 to selected valves, sensors, or other flow control devices of the vapor deposition system 2. By controlling the valves and, optionally, other flow control mechanisms, and by monitoring the pressure and temperature sensors, the control system 50 may effectively control the flow of each fluid to the cylinder to provide the desired combination of gaseous fluid flows from the cylinder into the chamber 12.

[0035] In e.g. Figure 1 In a system, or an alternative system described herein that is also effective for vapor deposition of molybdenum or tungsten, deposition process parameters can be controlled to perform vapor deposition as presently described, including: depositing a substantially pure metal layer onto a surface of a substrate having a metal layer containing carbon contaminants; and dispensing an oxidant into the interior to oxidize the carbon contaminants and remove carbon from the deposition chamber or from the metal layer (if already deposited). With the carbon removed, the deposited metal layer will have higher purity and improved properties, such as improved (reduced) resistivity, of the deposited metal layer of a microelectronic device, relative to a comparable deposited metal layer prepared by a similar deposition method (using the same materials and methods) that has not had carbon removed by exposure to and reaction with the oxidant as described herein.

[0036] The method of depositing elemental tungsten or molybdenum as a substantially pure metal layer on a substrate surface can be performed by a deposition step or a series of deposition steps that can provide a substantially pure metal layer having a desired purity level (especially with respect to relatively low levels of carbon contaminants). Various options are available regarding how the gaseous organometallic precursor is supplied to the interior of the deposition chamber and how the metal of the precursor is deposited onto the substrate. Variables (parameters) of the vapor deposition process include: the pressure and flow rate of the gaseous organometallic precursor; the relative amount of the gaseous precursor to the inert carrier gas (if used); the presence and type of any co-reactant (e.g., a reducing gas); the relative amount of the gaseous precursor to the co-reactant; the use of an inert gas purge in the method; and whether the flow of the gaseous precursor, co-reactant, oxidant, or inert purge gas is continuous (i.e., steady or uniform) or pulsed (e.g., interrupted).

[0037] The flow of gaseous materials (e.g., organometallic precursors (e.g., as part of a carrier gas-precursor mixture), co-reactants, oxidants, etc.) can be continuous (i.e., steady or uniform) or pulsed (e.g., "interrupted" or "non-uniform"), as desired and for various reasons. If pulsed, the flow of the gaseous fluid is discontinuous, but is caused to intermittently (e.g., periodically) flow into the deposition chamber and then not flow into the deposition chamber, with the cycle comprising an inflow period and an outflow period during the deposition process. During the same deposition process, other gaseous materials (e.g., precursors, co-reactants, inert purge gases, etc.) can be supplied to the deposition chamber in a continuous or pulsed manner. Purge periods or vacuum periods can be used in the process as desired. One reason for using a pulsed process is to improve the conformality or step coverage of thin films deposited on non-planar structures.

[0038] In certain embodiments of the method, the flow of the gaseous organometallic precursor (e.g., as part of a carrier gas-precursor mixture) may be steady, the flow of one or more co-reactants may be steady, and the flow of the oxidant may be pulsed (i.e., interrupted), with the inflow period of the oxidant and the outflow period of the oxidant constituting one pulsed "cycle" of the oxidant. Figure 2 The oxidant flow is not continuous, but is intermittently (e.g., periodically) pulsed onto the deposition chamber (during an "inflow period") and then pulsed off the deposition chamber in a cyclical manner (during an "outflow period") throughout the film deposition step.

[0039] According to other example methods (sometimes referred to as "continuous" vapor deposition methods), multiple different gaseous fluids (e.g., precursors, oxidants, co-reactants, and inert purge gases) can be supplied to a deposition chamber in an alternating and continuous pulsed manner during the deposition method, for example: the precursor flow is turned on for a first period while the flow of the co-reactant gas and oxidant is turned off; then the co-reactant flow is turned on for a second period while the precursor and oxidant flows are turned off; then the precursor and co-reactant flow are turned off for a third period while the oxidant flow is turned on; the precursor, oxidant, or co-reactant flow is discontinuous, and each flow is interrupted or "pulsed." In another example: for a first period, both the precursor flow and the co-reactant flow are turned on while the oxidant flow is turned off; then the oxidant flow is turned on for a certain period; followed by another period, such as the first period, in which both the precursor flow and the co-reactant flow are turned on while the oxidant flow is turned off; an inert purge gas may be flowed through the deposition chamber after the first precursor and co-reactant flow but before the oxidant flow, and then an inert purge gas is again flowed through the deposition chamber after the oxidant flow but before the continuous precursor and co-reactant flow.

[0040] Each inflow period and each outflow period of any pulsed flow of a gaseous fluid may be the same or different than the inflow period and outflow period of another gaseous fluid. Furthermore, the inflow period of a particular gaseous fluid may be the same as or different from its outflow period. As desired, for example, one or more purge or vacuum periods may be included in the method between any inflow or outflow periods.

[0041] According to certain embodiments of the present invention, a metal layer is deposited onto a substrate by a deposition step comprising a continuous gaseous organometallic precursor flow, a continuous co-reactant flow, and a pulsed (discontinuous) oxidant flow, and carbon is removed from the deposited metal layer or carbon deposition is inhibited on the metal layer. Figure 2 and Example 1, showing a CVD method. A combination of a continuous flow of an organometallic precursor and a reducing gas and a pulsed flow of an oxidant can be used to deposit a desired amount of metal layer (e.g., based on thickness) onto a substrate, wherein the oxidant is intermittently introduced during deposition of the metal layer. The deposition method includes periods of continuous precursor and co-reactant streams co-flowing with multiple pulse cycles of the oxidant, each cycle of the oxidant including an inflow period and an outflow period. The total number of pulse cycles, and the length of each cycle and its inflow and outflow periods can be selected to achieve the desired effect of removing carbon from the metal layer or preventing carbon from being deposited in the metal layer, consistent with not including the presence of an oxidant (e.g., Figure 2 The method provides a deposited metal layer containing reduced amounts of carbon contaminants compared to a comparable method using a method of producing a metal having a carbon-containing matrix and a carbon-containing matrix.

[0042] According to other examples of the method of the present invention, a metal layer is deposited onto a substrate by a deposition method that includes pulsed flows of an organometallic precursor and a reducing gas, a pulsed flow of an oxidant, and a pulsed flow of a purge gas. See Example 2, which shows an ALD method. The first inflow provides a precursor supplied in an inert carrier gas, with no other flows entering the deposition chamber (i.e., "alone"). The inflow that follows is an inert purge gas, with no other flows. The next subsequent inflow is an oxidant combined with a flow of H2; the oxidant can effectively remove carbon from the surface of the thin film of the growing, deposited metal layer and the reducing H2 gas can reduce other contaminants present on the surface, such as oxygen. The oxidant and reducing gas are followed by a second pulsed flow of an inert purge gas. After the second inflow of purge gas, the series is repeated starting with the precursor flow in the carrier gas. With the method, none of these flows are continuous and all of the flows are pulsed. The overall deposition method includes a metal layer deposition period, followed by a purge, followed by an oxidant flow period to remove carbon from the surface of the deposited metal layer and a reducing gas flow to reduce contaminants, followed by a second purge, after which the sequence is repeated. The total number of repetitions of the sequence produces a metal layer having a desired thickness and containing a reduced amount of carbon compared to a metal layer produced by a comparable method that does not include an oxidant flow.

[0043] Yet another example of a vapor deposition method includes a series of pulsed flows, including a pulsed flow of an organometallic precursor (alone), a pulsed flow of an inert purge gas, a pulsed flow of an oxidant (e.g., water and hydrogen), an optional pulsed flow of gaseous hydrogen, and a second pulsed flow of an inert purge gas. See Example 3, which illustrates an ALD method. The first inflow provides the precursor alone, optionally supplied with an inert carrier gas (no other flows enter the deposition chamber during the inflow). The inflow immediately following this is the inert purge gas, with no other flows (i.e., alone). The next subsequent inflow is the oxidant (e.g., water vapor and gaseous hydrogen), with no other flows; the oxidant can effectively remove carbon from the surface of the deposited metal layer. Following the oxidant step, a pulse of a reducing gas can optionally be flowed into the deposition chamber without other flows; the reducing gas can reduce other contaminants present on the surface, such as oxygen. Following the oxidant flow or the optional reducing gas flow, there is a second pulsed flow of the inert purge gas. After the second inflow of the purge gas, the series is repeated, starting with the precursor flow. By the method, these flows are not continuous, and each identified gaseous composition (combination comprising water and hydrogen) can be flowed separately to the deposition chamber. The overall deposition method comprises a metal layer deposition process, followed by a purge, followed by an oxidant flow period to remove carbon from the surface of the deposited metal layer, optionally followed by a reducing gas to reduce other contaminants (e.g., oxygen), followed by a second purge, after which the series is repeated. The total number of repetitions of the series produces a metal layer having a desired thickness and comprising a reduced amount of carbon compared to a metal layer produced by a comparable method that does not include an oxidant flow.

[0044] The method can be performed in a deposition chamber that, during use, comprises substantially only the gaseous precursor, optional carrier gas, co-reactant gas, optional inert purge gas, and oxidant as an atmosphere. For example, the deposition chamber atmosphere can comprise, consist of, or consist essentially of a combination of the gaseous precursor, optional carrier gas, optional purge gas, co-reactant gas, and oxidant. For purposes of this disclosure, a deposition chamber or associated gas stream or combination of gas streams consisting essentially of a specified combination of gaseous materials is considered to comprise the specified combination of gaseous materials and no more than a non-substantial amount of any other gaseous material (e.g., no more than 2, 1, 0.5, 0.1, 0.05, 0.01, or 0.005% (by mass) of any other gaseous material).

[0045] The amount of gaseous precursor (also referred to as precursor vapor), the amount of co-reactant gas, the amount of optional purge gas, and the amount of oxidant supplied to the deposition chamber can be an amount that can be used to produce the desired effect of each gaseous fluid to produce a metal layer of molybdenum or tungsten and the desired small amount of carbon as a result of the process. The amount of each gas supplied to the deposition chamber, with respect to its respective flow rate, can be based on factors including other process parameters, the desired amount (e.g., thickness) of the deposited metal layer, the desired deposition rate, the size (volume) of the deposition chamber, and the internal pressure of the deposition chamber. Furthermore, the example amounts and ranges described as being useful for supplying each gaseous fluid to the deposition chamber can be consistent relative to one another, but can be larger or smaller based on similar mathematical factors determined by the size of the deposition chamber used.

[0046] According to non-limiting examples of certain methods that have been identified as useful, a precursor-carrier gas mixture can contain a range of 0.01 to 5% precursor in an inert gas (e.g., Ar, H2, or a combination thereof) and can be flowed to a deposition chamber at a rate useful for coating 300 mm wafers, as desired for large-scale semiconductor manufacturing. An example flow rate for the precursor-carrier gas mixture for a chamber operating at an internal pressure in the range of 0.1 to 500 Torr supporting 300 mm wafers can be in the range of 25 to 5,000 standard cubic centimeters per minute (25-5,000 sccm). Based on the flow rate per chamber volume, an example flow rate can be in the range of 10 to 400 sccm / cubic inch of deposition chamber volume, such as 1 to 100 sccm / cubic inch of deposition chamber volume. Based on the amount of precursor flowed to the deposition chamber, an example flow rate can be in the range of 0.1 to 100 micromoles / minute, such as 1 to 50 or 2 to 20 micromoles of precursor / minute.

[0047] According to non-limiting examples of certain methods that have been determined to be useful, the flow rate of a co-reactant gas (e.g., hydrogen), which may be continuous during a pulse cycle, may be in the range of 10 or 20 to 1000 sccm, which is useful for a deposition chamber supporting a single 300 mm wafer and operating at internal pressures in the range of 0.1 to 500 Torr; larger chambers will require correspondingly larger flow rates.

[0048] The internal pressure of the deposition chamber can be an internal pressure that is effective for depositing the metal layer. Typically, deposition chambers used for chemical vapor deposition are operated at a pressure no greater than approximately ambient pressure (generally understood to be about 760 Torr). Typically, the deposition chamber will operate at a pressure substantially below atmospheric pressure, such as in the range of 0.1 to 300, 400, or 500 Torr, for example, in the range of 1, 5, or 10 Torr to 100 Torr.

[0049] During deposition, the substrate can be maintained at any temperature that is effective for depositing molybdenum or tungsten onto the substrate according to the present invention. The use of organometallic precursors for tungsten or molybdenum should be understood to allow for lower substrate temperatures during deposition than would be required for depositing tungsten or molybdenum onto the substrate using other halogenated precursors (e.g., fluorinated, chlorinated, brominated, iodinated precursors) and oxyhalogenated precursors. For the methods of the present invention, during the deposition step, the substrate can be maintained at an elevated temperature not exceeding 400° C., for example, the temperature can be in the range of 100° C. to 350° C., or in the range of 150° C. to 300° C.

[0050] The method may be performed by a deposition step that includes processing parameters, including the processing parameters described herein (alone or in combination), that result in one or a desired combination of various desired physical properties of the processed substrate. The desired physical properties include a desired degree of uniformity of the metal layer on a horizontal or non-planar surface of the substrate, or to create interconnects, contacts, electrodes, or the like; a desired degree of conformality of the metal layer on a three-dimensionally processed substrate; a desired composition of the deposited metal layer, such as a low impurity (e.g., carbon or other non-metallic material) content; a low resistivity of the deposited metal layer; or one or more of a combination of these properties.

[0051] The vapor deposition step can be carried out in any suitable manner as described herein, preferably using process parameters comprising a pulsed flow of the oxidant in combination with values of other process parameters (including optional pulsed flows of other gaseous fluids) that will result in a deposited layer of molybdenum or tungsten exhibiting desired physical properties, such as high purity and low resistivity. The molybdenum or tungsten can be deposited onto any desired substrate surface, such as a semiconductor or microelectronic device substrate, and can be adapted to perform any useful function as part of the device, or to facilitate processing of the device. Examples of functions of the deposited molybdenum or tungsten include serving as a conductive layer for a microelectronic logic or memory device (e.g., as a via, channel, or contact). The deposited molybdenum can have a thickness effective to perform the desired function and can be continuous.

[0052] The substrate and surface on which the molybdenum or tungsten is deposited may include any two-dimensional or three-dimensional structure, with specific examples of microelectronic device substrates being memory devices (e.g., DRAM devices or 3D NAND devices) or "logic" devices. The logic device may be a microelectronic device including a microprocessor. Examples include programmable logic devices (PLDs) having configurable logic and flip-flops connected together with programmable interconnects. The or another logic device may provide a microprocessor or other electronic functions, such as device-to-device interfacing, data communications, signal processing, data display, timing and control operations, and the like. Other specific examples include those referred to as: programmable logic arrays (PLAs); programmable array logic (PALs) (e.g., logic devices having fixed OR arrays and programmable AND arrays; and continuous programmable logic devices (including flip-flops and AND-OR arrays within IC chips).

[0053] The specific chemical composition of the surface of the memory or logic type substrate on which the metal layer is to be deposited can be any chemical composition that can be used in the device to provide a deposited molybdenum or tungsten layer. Generally speaking, the metal layer can be deposited on a dielectric layer or a nucleation layer. Non-limiting examples of materials on the substrate surface on which molybdenum or tungsten can be deposited include: silicon, silicon dioxide, silicon nitride, other silicon-based materials, titanium nitride (TiN), molybdenum (metal), molybdenum carbide (MoC), boron (B), tungsten (W), and tungsten carbon nitride (WCN).

[0054] Advantageously, the relatively low deposition temperatures used to deposit tungsten or molybdenum using an organometallic precursor (e.g., a carbonyl-type precursor or an amide-imide precursor, an aryl or substituted aryl precursor) in combination with an oxidant to remove carbon from the deposited thin film or metal layer allows the deposition temperature to not degrade the temperature-sensitive characteristics of the logic device, and also provides a metal layer with a reduced carbon contaminant content relative to other precursors or methods.

[0055] Example vapor deposition trains according to the present invention include the following:

[0056] Example 1 (Pulsed CVD)

[0057] Continuous CVD with pulsed oxygen is used at low temperatures and other conditions that result in the deposition of Mo2C, but with good step coverage. Figure 2 and Tables 1 to 4.

[0058] series:

[0059] (EtBz)2Mo+H2(time limit thickness ) / (EtBz)2Mo+O2:H2<50%

[0060] Example 2 (ALD)

[0061] series:

[0062] (EtBz)2Mo+Inert / Inert Purge / (O2 / H2) / Inert Purge

[0063] Temperature and pressure are controlled to result in self-limiting deposition with respect to precursor dosage time.

[0064] The oxygen (O2) dosage is limited by the surface oxidation of Mo.

[0065] The hydrogen (H2) dosage is sufficient to remove substantially all of the oxygen from the surface.

[0066] Example 3 (ALD)

[0067] series:

[0068] Mo imide-amide / inert purge / (H2O+H2) / optional H2 / inert purge

[0069] Temperature and pressure are controlled to result in self-limiting deposition with respect to precursor dosage time.

[0070] Results of Example 1

[0071] Tables 1-4 contain evaluation data for various processing conditions and parameters of the method of the present invention performed using a pulsed CVD process generally as described in Example 1. In the tables, the thickness of the deposited film (e.g., XRF Mo) or the carbon content of the deposited film (XRF C) was measured by x-ray fluorescence (XRF).

[0072] Tables 1 to 4 show the results of Example 1 and Figure 2 The general procedure of the method, using a pulsed flow of an oxidant during the formation of the metal layer, can result in a reduction in the concentration of carbon in the metal layer.

[0073] Effect of O2 on carbon content

[0074] 200°C, 30 Torr, 10 μmol / min, 400 sccm H2, 3.5 sccm O2

[0075]

[0076] The addition of O2 reduces the carbon content of MoC film Table 1

[0077] Effect of O2 pulse on carbon content 200℃, 20 Torr, 10μmol / min, 400sccm H2, 3.5sccm O2 pulse

[0078]

[0079] Adding O2 reduces carbon content

[0080] Table 2

[0081] Effect of O2 co-reactant on Mo deposition

[0082] 200°C, 15 Torr, 10 μmol / min, 400 sccm H2, 3.5 sccm O2 pulses

[0083]

[0084] Adding O2 reduces carbon content

[0085] Table 3

[0086] Effect of O2 co-reactant on Mo deposition at 175°C, 30 Torr, 10 μmol / min, 400 sccm H2, 3.5 sccm O2 pulses

[0087]

[0088] The addition of O2 reduces the carbon content of the deposited MoC films Table 4.

Claims

1. A deposition method for forming a metal thin film on a substrate, wherein the method is a pulsed chemical vapor deposition method, the method comprising: The gaseous precursor generated from the organometallic precursor and the reducing gas co-reactant are continuously flowed into the deposition chamber. exposing the substrate to the gaseous precursor and the reducing gas co-reactant to form a deposited metal layer on the substrate, the organometallic precursor comprising a metal and one or more carbon-containing ligands, wherein the metal is molybdenum or tungsten, The oxidant is flowed into the deposition chamber by a pulsed flow, and The deposited metal layer is exposed to the oxidant to form the metal thin film.

2. The method according to claim 1, wherein the method forms a metal thin film having a thickness of not more than 50 angstroms.

3. The method of claim 1, further comprising flowing hydrogen gas into the deposition chamber after exposing the deposited metal and the carbon to the oxidant.

4. A deposition method for forming a metal thin film on a substrate, wherein the method is a pulsed chemical vapor deposition method, the method comprising: A gaseous precursor generated from an organometallic precursor is flowed into a deposition chamber, exposing the substrate to the gaseous precursor, optionally in the presence of an inert gas, the substrate having a temperature below 300 degrees Celsius, to form a deposited metal layer on the substrate, the organometallic precursor comprising a metal and one or more carbon-containing ligands, wherein the metal is molybdenum or tungsten, Flowing an oxidizing agent and a reducing gas into the deposition chamber, and The deposited metal layer is exposed to the oxidizing agent and the reducing gas to form the metal film, wherein the metal film is deposited as a substantially pure metal film. The method of claim 4 , wherein the substrate comprises a partially fabricated integrated circuit.

6. The method of claim 4, wherein the substrate comprises a dielectric layer or a nucleation layer, and wherein the gaseous precursor is deposited onto the dielectric layer or the nucleation layer. The method of claim 4 , wherein the deposited metal layer has a structure selected from the group consisting of an interconnect, a contact, and an electrode.

8. The method of claim 4, wherein the oxidant is oxygen and the reducing gas is hydrogen.

9. The method of claim 4, wherein the oxidant is selected from the group consisting of oxygen, ozone, water, and hydrogen, and mixtures thereof.

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