Ion beam deposition of ruthenium thin films.

Abstract

A method for forming low-resistivity ruthenium (Ru) thin films includes depositing ruthenium on a substrate by ion beam deposition assisted by reactive and noble gas species in a process chamber. The substrate is at least 250°C. The resulting ruthenium thin film has a thickness of 30 nm or less, a resistivity of less than 12 μΩ·cm, and a crystalline structure including grains with a (0001) orientation. The resistivity varies with thickness, e.g., less than 9 μΩ·cm for films 50 nm or thicker, less than 9.5 μΩ·cm for films 35 nm or thicker, less than 11 μΩ·cm for films 20 nm or thicker, less than 15 μΩ·cm for films 10 nm or thicker, or less than 20 μΩ·cm for films 2 nm or thicker. The grains have an average grain size at least three times the film thickness.

Description

[Background technology]

[0001] The continued miniaturization of electronic devices in the submicron era poses challenges for metal conductors used in wiring and interconnect networks due to the phenomenon of increasing resistivity of metals as physical dimensions such as the length, width, and height of interconnects approach or become smaller than the electron mean free path. The size-dependent increase in resistivity is primarily due to increased electron scattering at metal surfaces and layer boundaries, exacerbated not only by surface roughness but also by increased scattering at grain boundaries in the metal's polycrystalline structure, which typically becomes finer with downscaling. This increase in resistivity, particularly for copper, is a major challenge for the continued miniaturization of the most critical and smallest interconnects in integrated circuits, severely limiting their use for wiring and spurring efforts to identify alternative metals. Ruthenium is a promising candidate to replace copper in integrated device wiring, as its significantly smaller bulk mean free path—almost one-fifth that of copper—is predicted to correspondingly reduce the size effect on resistivity.

[0002] The size effect on resistivity is typically quantified using classical models that account for both surface and grain boundary scattering. Both model predictions and experimental observations reveal that the increase in resistivity is directly proportional to the bulk resistivity and bulk mean free path, which depend on the material choice, and inversely proportional to the distance between scattering interfaces, including film thickness, interconnect width and height, and average grain size. All of these scale with size, with the latter particularly depending on the metal's microstructural features. Furthermore, other metals, such as ruthenium and tungsten, exhibit size-dependent anisotropic electrical resistivity, while typically isotropic resistivity depends on grain texture, orientation, and epitaxy. In the case of Ru, modeling and experimental studies in the literature have shown that the (0001) orientation of conduction along the hexagonal c-axis is most favorable for low resistivity. Furthermore, the resistivity of a metal strongly depends on its microstructure, consisting of grain size distribution characteristics, which consist of varying spacing of grain boundaries and their frequency, as well as features such as orientation that affect electron scattering mechanisms. Therefore, metals with small mean free paths are promising candidates, but in practice the observed resistivity of nanometer-scale conductors depends heavily on the microstructure of the thin films from which they are fabricated and therefore on the capabilities of the thin film growth method.

[0003] Optimizing the microstructure of metal thin films to achieve the lowest resistivity can be extremely challenging. Unfavorable microstructure, impurities, random grain orientation, and small grain size can increase resistivity even for metals with small mean free paths. It is necessary to deposit high-purity metal thin films with low-resistivity phases, favorable grain orientation, and large grain sizes to mitigate scaling size effects. For example, it is well known in the literature that ruthenium thin films require post-deposition annealing or high temperatures during deposition to grow the grains and practically achieve low resistivity and low-resistivity size effects. It is also well known in the literature that sputtered thin film growth and its resulting properties have a strong and complex dependence on the material, substrate, substrate temperature, surface chemistry, background and process gas species, deposition environment chemistry, and the energy and flux of the sputtered atoms.

[0004] Ion beam deposition (IBD) is one of many suitable methods for forming metal films; other methods include (but are not limited to) plasma vapor deposition (PVD), chemical vapor deposition (CVD), and molecular beam epitaxy (MBE). MBE is useful for depositing layers at very low energies and can produce pseudo-epitaxial layers. PVD is useful for depositing layers at higher energies and can produce layers with good electrical conductivity, for example. IBD is useful for depositing layers at even higher energies and lower pressures while controlling the deposition shape and can produce layers with higher crystallinity and controlled microstructure.

[0005] All of these methods allow for the production of films of various thicknesses, below which the resistivity of the metal increases as the thickness of the metal film decreases. Summary of the Invention

[0006] The present disclosure relates to a method for forming thin layers of metals, such as ruthenium (Ru), having low resistivity by ion beam deposition. The addition of an assist ion beam and / or heating of the process gas and / or reactive gas further reduces the resistivity. The thin layers of ruthenium obtained by this method (e.g., 50 nm or less, in some embodiments, 35 nm or 30 nm or less in thickness) are pure (e.g., at least 99% ruthenium) and dense (e.g., at least 12.2 g cm 3 , or theoretical density 12.37~12.41g / cm 3 may be at least 99% of the total.

[0007] The method includes depositing ruthenium metal on a substrate by assisted ion beam deposition, and in some embodiments by reactive ion beam deposition, in a process chamber at a temperature of not greater than 600° C., and in other embodiments at a temperature of not greater than 450° C. The method can include in-situ use and / or assistance by reactive gas species to reduce the resistivity of the ruthenium thin film.

[0008] In some embodiments, the reactive ion beam deposition includes introducing one or both of a reactive gas species and a noble gas species into the deposition sputter ion beam. To reduce the resistivity of the thin film, the method can include introducing the same or different reactive gas species and / or noble gas species with the assist ion beam.

[0009] The resulting ruthenium thin film can have large, highly oriented (0001) grains with at least 95% and up to the entirety of the deposited ruthenium thin film having a (0001) crystallographic orientation relative to the top surface of the substrate. These grains can be parallel to the top surface of the substrate in some embodiments and perpendicular in other embodiments. The grain size distribution can be such that the average grain size is at least three times, and up to ten times, the as-deposited film thickness without additional annealing. Additionally, the resulting ruthenium thin film can have low resistivity at different thicknesses, such as less than 9 μΩ·cm for thicknesses of 50 nm or greater, less than 9.5 μΩ·cm for thicknesses of 35 nm or greater, less than 11 μΩ·cm for thicknesses of 20 nm or greater, less than 15 μΩ·cm for thicknesses of 10 nm or greater, or less than 20 μΩ·cm for thicknesses of 2 nm or greater.

[0010] In some embodiments, the resulting low-resistivity ruthenium thin film is deposited on a dielectric barrier film that has been deposited in-situ on a substrate using a reactive ion beam deposition process. A dielectric cap film can be deposited in-situ on the resulting low-resistivity ruthenium thin film using a reactive ion beam deposition process. Thus, the resulting ruthenium thin film can be sandwiched between the dielectric barrier film and the dielectric cap film. The same dielectric can be used as the barrier film and the cap film, or different dielectrics can be used for the barrier film and the cap film.

[0011] In one particular implementation, the present disclosure provides a method for forming a ruthenium thin film, the method including depositing a ruthenium film on a substrate from a ruthenium target by ion beam deposition in a process chamber in the presence of reactive gas species, wherein the substrate is at a temperature of at least 250°C; and simultaneously bombarding at least a portion of the deposited ruthenium in the process chamber with an assist ion beam in the presence of a noble gas species.

[0012] In an alternative specific implementation, the present disclosure provides a method of forming a ruthenium thin film, the method including depositing a ruthenium film on a substrate from a ruthenium target by ion beam deposition in a process chamber in the presence of a noble gas species, wherein the substrate is at a temperature of at least 250°C; and simultaneously bombarding at least a portion of the deposited ruthenium in the process chamber with an assist ion beam in the presence of a reactive gas species.

[0013] Other configurations for adding one or more reactive gas species and one or more noble gas species are also disclosed. In another specific implementation, the present disclosure provides a ruthenium film having a thickness of 30 nm or less with a resistivity of less than 12 μΩ·cm, the film having a crystalline structure with grains having a (0001) orientation. In some examples, the present disclosure provides low resistivity ruthenium films of different thicknesses, such as less than 9 μΩ·cm for a film thickness of 50 nm or more, less than 9.5 μΩ·cm for a film thickness of 35 nm or more, less than 11 μΩ·cm for a film thickness of 20 nm or more, less than 15 μΩ·cm for a film thickness of 10 nm or more, or less than 20 μΩ·cm for a film thickness of 2 nm or more, the film having a crystalline structure with grains having a (0001) orientation.

[0014] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. These and various other features and advantages will become apparent from the following Detailed Description. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic side view of an ion beam deposition system with an assist ion beam. [Figure 2] FIG. 2 is a schematic diagram showing various angle combinations in an ion beam system. [Figure 3] FIG. 3 is a step-by-step method for depositing ruthenium thin films. [Figure 4A] FIG. 4A is a graphical representation of a grazing incidence geometry X-ray theta-2theta scan for a sample ruthenium thin film. [Figure 4B] FIG. 4B is a graphical representation of a Bragg-Brentano geometry X-ray theta-2theta scan. [Figure 4C] FIG. 4C is an electron backscatter diffraction (EBSD) micrograph. [Figure 4D] FIG. 4D is an inverse pole figure for the hexagonal crystal system, which serves as an orientation key for the grains relative to the crystallographic direction. [Figure 5A] FIG. 5A is a graphical representation of resistivity as a function of thickness for a ruthenium thin film on a silicon underlayer. [Figure 5B] FIG. 5B is a graphical representation of resistivity as a function of thickness for a ruthenium thin film on a tantalum nitride underlayer. [Figure 6] FIG. 6 is a schematic side view of a multilayer ruthenium thin film structure. [Figure 7] FIG. 7 is a graphical representation of resistivity as a function of thickness for a multilayer ruthenium thin film structure. [Figure 8] FIG. 8 is a step-by-step method for depositing a multi-layer ruthenium thin film structure. DETAILED DESCRIPTION OF THE INVENTION

[0016] As noted above, the present disclosure relates to methods for forming low resistivity thin or film layers of metals (e.g., ruthenium) by ion beam deposition. The methods include using reactive ion beam deposition with one or more of a high process temperature, a reactive gas as a background process gas, a reactive gas as primary ions, or a reactive gas as secondary ions. Particular methods include utilizing a heated substrate during reactive ion beam deposition with an assist ion beam.

[0017] The continued miniaturization of electronic devices in the submicron era poses challenges for metal conductors used in wiring and interconnect networks due to the phenomenon of increasing resistivity of metals as the physical dimensions of the interconnects, such as their length, width, and height, decrease and approach or become smaller than the electron mean free path. The size-dependent increase in resistivity is primarily due to increased electron scattering at metal surfaces and layer boundaries, exacerbated not only by surface roughness but also by increased scattering at grain boundaries in the metal's polycrystalline structure, which typically becomes finer with downscaling. This increase in resistivity, particularly for copper, poses a challenge for the continued miniaturization of the most critical and smallest interconnects in integrated circuits, severely limiting the use of certain metals, such as copper, for their wiring and prompting efforts to identify alternative metals. Ruthenium, with its significantly smaller bulk mean free path (e.g., nearly one-fifth that of copper) and correspondingly smaller size effect on resistivity, is a promising candidate to replace copper in integrated device wiring.

[0018] The size effect on resistivity is typically quantified using classical models that account for both surface and grain boundary scattering. Both model predictions and experimental observations reveal that the increase in resistivity is directly proportional to the bulk resistivity and bulk mean free path, which depend on the material choice, and inversely proportional to the distance between scattering interfaces, including film thickness, interconnect width and height, and average grain size, all of which scale with size, the latter particularly depending on the metal's microstructural features. Ruthenium exhibits size-dependent anisotropic electrical resistivity, with typically isotropic resistivity depending on grain texture, orientation, and epitaxy. In the case of Ru, modeling and experimental studies have shown that the (0001) orientation of conduction along the hexagonal c-axis is most favorable for low resistivity. Furthermore, the resistivity of a metal strongly depends on the microstructure, including grain size distribution characteristics, including the varying spacing of grain boundaries and their frequency, as well as features such as grain orientation, which affect electron scattering mechanics.

[0019] Metals with small mean free paths are promising candidates, but in practice the observed resistivity of nanometer-scale conductors depends heavily on the microstructure of the thin films from which they are fabricated, which in turn depends on the thin film growth method.

[0020] Thin film growth and resulting properties depend strongly and intricately on the material, substrate, substrate temperature, surface chemistry, background and process gas species, deposition environment chemistry, energy and flux of sputtered atoms, and post-treatment. Optimizing the microstructure of metal thin films to achieve the lowest resistivity can be extremely challenging. Unfavorable microstructure, impurities, random grain orientation, and small grain size can increase resistivity even for metals with small mean free paths. For favorable results, metal thin films must be highly pure, contain low-resistivity phases, favorable grain orientation, and have large grain sizes to mitigate scaling size effects. For example, ruthenium thin films are known to require post-deposition annealing or exposure to high temperatures during deposition to achieve low resistivity and low-resistivity size effects.

[0021] Ion-assisted ion beam deposition is a unique thin-film technology with the ability to tailor the microstructure of thin films through density, purity, phase, texture control, and grain size growth, achieving low resistivity in metals. Fundamentally, in ion beam deposition, the sputter beam and the film-forming sputter plume generation and thin-film growth by the assisting ion beam are spatially separated. In addition, both the deposition ion beam and the assisting ion beam are monoenergetic, allowing for independent control of the energy and flux of both beams. This combination of features allows for fine control of film deposition and growth energies with low thermal treatment, enabling the deposition of high-purity films at relatively low pressures, e.g., 0.1 mTorr to less than 0.01 mTorr (approximately 13.3322 mPa to less than 1.33322 mPa). Both the deposition ion beam and the assisting ion beam have high selectivity and reproducibility with narrow monoenergetic energy distributions. By appropriately varying the ion beam parameters of both beams, the energy distribution of film-forming neutrals and atoms can be modified, significantly affecting the thin film growth mode and microstructure evolution. Fine control of the energy profile and distribution during metal thin film deposition and growth allows for the creation of selective microstructures in ion beam deposition.

[0022] Additionally, ion beam deposition allows precise control of background and process gas species, and reactive gas species can be used as ions in the background gas or as primary ions in reactive ion beam deposition. For example, reactive ion beam deposition using reactive gas species such as oxygen or nitrogen, when used with a metal target, results in the deposition and production of composite dielectric thin films containing the reactive gas species, e.g., metal oxide or metal nitride, respectively, and the metal from the target. Because metal thin films require high-purity compositions to achieve low resistivity, reactive sputter deposition of pure metals has not been performed previously.

[0023] However, specific methods are described herein for forming ruthenium thin films for integrated circuit wiring using a ruthenium target utilizing reactive ion beam deposition with one or both of reactive and noble gas species. The reactive and / or noble gas species can be present in the primary and / or secondary ion beams, and optionally as background process gas supplied to the chamber. The various methods and apparatus described herein, and combinations thereof, can produce dense, high-purity ruthenium metal films in the as-deposited state without the need for additional steps such as annealing and other heat treatments, with a grain size distribution having an average grain size of at least 3 to more than 10 times the film thickness, near-ideal 0001 orientation and texture, and associated ultra-low resistivity (e.g., less than 11 μΩ·cm for films less than 20 nm thick).

[0024] This ability to deposit pure, high-density, low-resistivity ruthenium using reactive ion beam deposition with the reactive gases used in the process allows for the deposition of such ruthenium thin films on dielectric, metal, or other thin film underlayers, which are deposited in situ by reactive ion beam deposition without the need for a separate process chamber, process interruptions, or additional steps, such as purging the chamber of reactive gases. In addition, this reactive ion beam deposition allows for the deposition of a dielectric, metal, or other thin film as a cap layer on the deposited ruthenium thin film by in situ reactive ion beam deposition without the need for a separate process chamber, process interruptions, or additional steps. This contrasts with existing methods used for thin film deposition, such as chemical vapor deposition, atomic layer deposition, plasma vapor deposition, and other sputter depositions, as well as other methods that do not allow for the in-situ deposition of pure metal thin films with dielectric thin films in the same chamber. These known methods require separate process chambers for the deposition of multiple thin film layers, such as dielectric and metal layers, or metal layers sandwiched between dielectric or other layers.

[0025] The methods described herein can form films of predominantly 0001 ruthenium that have a highly oriented grain texture with a preferred orientation of the grains having a low resistivity basal 0001 plane and a 0001 hexagonal axis direction, and a grain size distribution with an average grain size greater than 3 to 10 times the film thickness.

[0026] One particular method includes depositing ruthenium from a target onto a substrate by ion beam deposition in a process chamber, the substrate being at a temperature of at least 300°C, or at least 350°C, or at least 400°C, or at least 450°C, and in some embodiments, the substrate temperature does not exceed 600°C.

[0027] In some examples, ion beam deposition is performed using reactive ion beam deposition techniques, using a variety of gases including background process gases such as inert noble gases, for example, argon, krypton, xenon, and reactive process gases, for example, but not limited to, gases containing oxygen, nitrogen, fluorine, hydrogen, and other reactive gases.

[0028] To modify or etch at least a portion of the deposited material, an assisted ion beam can be used for bombardment. In some examples, this bombardment is performed in a reactive assisted ion beam mode using a background process gas, such as an inert gas, e.g., the noble gases argon, krypton, and xenon, and a reactive process gas, e.g., nitric oxide (NO), nitrogen dioxide (NO), ammonia (NH), and a gas containing oxygen, nitrogen, fluorine, or hydrogen, including fluorides. In some examples, ion beam deposition and ion beam assist are performed while simultaneously introducing a reactive process gas, e.g., a gas containing oxygen, nitrogen, fluorine, or hydrogen, through a gas distribution system designed to controllably supply the gas during deposition.

[0029] The methods described herein can be used to form ruthenium films having thicknesses of at least 1 nanometer, in some embodiments about 10 to about 30 nanometers, and having resistivities of about 8 to about 12 μΩ·cm; in some embodiments, the films have resistivities of about 8 to about 10 μΩ·cm. As an example, the methods described herein can be used to form ruthenium films having thicknesses of about 10 to about 20 nanometers and resistivities of about 8 to about 10 μΩ·cm. In some examples, the methods can be used to form ruthenium films having low resistivities at different thicknesses, such as less than 9 μΩ·cm for thicknesses of 50 nm or greater, less than 9.5 μΩ·cm for thicknesses of 35 nm or greater, less than 11 μΩ·cm for thicknesses of 20 nm or greater, less than 15 μΩ·cm for thicknesses of 10 nm or greater, or less than 20 μΩ·cm for thicknesses of 2 nm or greater.

[0030] Ruthenium films produced by the described methods can have a highly oriented microstructure with a predominant 0001 orientation, defined as a majority of grains (e.g., greater than 60%, 70%, 80%, 90%, 95%, and up to 99% of the grains) oriented in the low-resistivity 0001 hexagonal basal plane, in some embodiments along the film plane and in other embodiments along the film growth direction (i.e., perpendicular to the film plane). Ruthenium films produced by these methods can be highly pure and have little or no impurities of reactive or noble gas species included in the thin film. Ruthenium films produced by these methods can have a low-resistivity hexagonal 0001 fibrous texture. Ruthenium films can have a hexagonal 0001 crystallographic orientation, as evidenced by X-ray diffraction showing high intensity of the 0001 plane.

[0031] Ruthenium films produced by these methods can have highly controlled microstructures with grain size and orientation distributions that can be tailored by the method used to form the film. The film microstructure can be tailored to grains that grow to specific sizes and along specific planes and directions. The films may also be highly oriented and contain large grains. For example, the methods described herein can be used to form ruthenium films with a grain orientation distribution characterized by a majority of grains having orientation along specific crystallographic planes and directions, e.g., most or up to all grains having orientation along the hexagonal basal 0001 plane or along the 0001 direction of the crystal hexagonal axis. Ruthenium films produced by these methods can have a grain size distribution characterized by a large average grain size, e.g., at least three times, or even more than ten times, the film thickness. That is, the ruthenium films have grain sizes that are larger than the film thickness, and the grain sizes (e.g., diameters) are measured in the plane of the film. As an example, the methods described herein can be used to form ruthenium films having a thickness of about 2 to about 50 nanometers with a grain size distribution in which the average grain size is greater than 50 nanometers in equivalent circular diameter, in some instances greater than 100 nanometers, in other instances greater than 200 nanometers, or even greater than 300 nanometers, and in some instances greater than 500 nanometers.

[0032] Additionally, the present disclosure describes methods for controlling the microstructure, texture and grain orientation of ruthenium films using reactive and / or noble gas species, assisted ion etching sources, ion beam deposition sources, thermal and reactive ion beam deposition and etching, in combination or individually.

[0033] The present disclosure also provides, in certain implementations, a method for forming a ruthenium thin film, the method including depositing ruthenium from a target onto a substrate by ion beam deposition in a process chamber, wherein the substrate is at a temperature of at least 400° C., and in some embodiments up to 600° C., and simultaneously bombarding at least a portion of the deposited material from the substrate in the process chamber with a depositing, assist ion beam, or the like. In another specific implementation, the present disclosure provides a method for forming a ruthenium film by ion beam deposition using a movable target in a turret indexed to a position relative to the deposition ion beam and substrate assembly to exhibit a specific geometric angle.

[0034] For any of these methods, a process gas can be used with the ion deposition beam and assist ion beam to form primary ions. For example, the primary ions in the deposition ion beam and assist ion beam can be from an inert gas used as a process gas, such as argon, krypton, xenon, and other noble gases. Additionally or alternatively, the primary ions in the deposition ion beam and assist ion beam can be from a reactive gas used as a process gas, such as a gas containing oxygen, nitrogen, fluorine, hydrogen, and other reactive gases.

[0035] In another specific implementation, the present disclosure provides a method for forming a ruthenium thin film, the method including depositing ruthenium from a target onto a substrate by ion beam deposition in a process chamber, and simultaneously bombarding at least a portion of the material deposited from the substrate with an assist ion beam or the like in the process chamber, wherein one or both of a reactive gas and an inert gas are used, alone or in combination, for the primary ions of the ion deposition beam and / or the ions of the assist ion beam.

[0036] The present disclosure provides a method for forming ruthenium thin films using ion-assisted reactive ion beam deposition using an apparatus that controllably supplies both an inert gas and a reactive gas to both the ion deposition source and the assist ion source to controllably produce both inert ions and reactive ions in the ion beam. Alternatively, the reactive gas is controllably supplied into the process chamber independently from both the ion deposition source and the assist ion source.

[0037] Ruthenium can be deposited from a target onto a substrate by ion beam deposition utilizing an ion beam having a voltage of at least 400 V to at least 2000 V and a current of at least 100 mA to 2500 mA. Ruthenium can be bombarded with or etched from a substrate using an assist ion beam having a voltage of at least 100 V to at least 1500 V. In some embodiments, the assist ion beam has a current of at least 100 mA to as much as 1500 mA.

[0038] The independent ion beam energy characteristics, fine control of energy and flux distribution, combined with independent control of reactive and process gases, and therefore fine control of process chamber background pressure, along with independent control of substrate temperature, enable a high degree of control over the reactions between reactive and / or process gases and the ruthenium target and sputter plume in reactive ion beam deposition, as well as the energy characteristics of thin film ruthenium deposition, and therefore reactive ion beam deposition is capable of depositing pure, densified, low resistivity ruthenium thin films.

[0039] Under certain appropriate conditions, when a monoenergetic deposition ion beam is directed at a ruthenium target, a sputter plume of ruthenium atoms is generated, which is sputtered and directed at a heated, rotating substrate, which is also simultaneously bombarded by a monoenergetic assist ion beam, all in the presence of reactive gas species, such as oxygen-, nitrogen-, fluorine-, or hydrogen-containing gases. Under these conditions, a reaction between the reactive gas species and ruthenium occurs to form ruthenium compounds, which then undergo energetically induced spontaneous dissociation to form a pure, high-density ruthenium metal film on the substrate and release the reactive gas species. The reactive gas species can be present in the process chamber under these conditions in a variety of ways, such as through introduction into the deposition ion source with or without other process gases, into the assist ion source with or without other process gases, into the deposition ion source and / or assist ion source neutralizer with or without other process gases, or through a device for gas distribution within the chamber remote from and / or proximate to the substrate, located on the same plane as the substrate or above or below the substrate. Under such suitable conditions, pure and dense ruthenium films are deposited with a microstructure characterized by grains all having a fibrous orientation with the 0001 grains oriented with their basal planes parallel to the film surface, and a grain size distribution in which the average grain size is at least three times and at most ten times the film thickness. Under other suitable conditions, pure and dense ruthenium films are deposited with a microstructure characterized by grains all having a fibrous orientation with the 0001 grains oriented with their hexagonal 0001 axis parallel to the film surface, and a grain size distribution in which the average grain size is at least three times and at most ten times the film thickness.

[0040] As a generalization for metal thin film deposition, properties such as microstructure, grain size, grain distribution, grain orientation, grain boundaries, purity, morphology, and topography all depend on the energetics of film deposition on the substrate and are complex functions of the material, target, substrate, substrate temperature, surface chemistry, energy and flux of sputtered atoms, process gas species, process reactions at the target, process reactions in the process chamber, background pressure, and sputtered atom energy distribution during film formation.

[0041] Using the methods described herein, it is possible to control the ruthenium crystal orientation, particularly increasing the relative amount of (0001) and controlling the orientation of the (0001) basal plane relative to the film surface, thus affecting resistivity, and also increasing the texture of the metal film, forming a fibrous texture. As a result, randomly oriented grains are reduced and 0001-oriented grains are increased. The amount and percentage of (0001)-oriented grains in the ruthenium thin film is higher, with the percentage of (0001)-oriented grains exceeding 80%, in some implementations exceeding 90%, in other implementations exceeding 95%, and in some other implementations exceeding 99%.

[0042] As described above, the methods described herein provide low-resistivity ruthenium thin films. For example, the methods provide ruthenium thin films having resistivities of 12 μΩ·cm or less, in some implementations 11 μΩ·cm or less, and in some implementations 10 μΩ·cm or less, or even no more than 9 μΩ·cm (i.e., 9 μΩ·cm or less). The methods described herein provide ruthenium films having thicknesses in the range of 10 to 30 nanometers and resistivities of 8 μΩ·cm to 12 μΩ·cm. In some ruthenium films, the resistivity is in the range of 8 μΩ·cm to 10 μΩ·cm, and in other films, the resistivity is in the range of 9 μΩ·cm to 10 μΩ·cm. The methods described herein can provide ruthenium films having thicknesses in the range of 15 to 25 nanometers with resistivities in the range of 8 μΩ·cm to 10 μΩ·cm, as well as ruthenium films having thicknesses in the range of 15 to 20 nanometers with resistivities of 9 μΩ·cm to 10 μΩ·cm. In some examples, the method provides ruthenium thin films having low resistivities at different thicknesses, such as less than 9 μΩ·cm for film thicknesses of 50 nm or more, less than 9.5 μΩ·cm for film thicknesses of 35 nm or more, less than 11 μΩ·cm for film thicknesses of 20 nm or more, less than 15 μΩ·cm for film thicknesses of 10 nm or more, or less than 20 μΩ·cm for film thicknesses of 2 nm or more.

[0043] The present disclosure also describes an ion beam deposition system having an ion beam deposition source, a target mounted on a turret assembly capable of moving in a circular path and indexing its position relative to an ion beam from the ion beam deposition source, an assist ion beam source, a substrate assembly for holding the substrate, and a heater configured to heat the substrate to a temperature of at least 300°C, and in some embodiments, at least 400°C. Movement of the target within the turret assembly is referenced via indexing, whereby the target surface assumes an angle geometrically relative to the ion deposition source and the substrate assembly, and varying the index position of the target via movement within the turret causes the target to assume an angle of about 0 to about 70 degrees (e.g., 20 to 35 degrees, e.g., 50 to 60 degrees) relative to the ion beam from the ion beam deposition source, the assist ion beam source, and the substrate assembly. The substrate assembly is positioned to receive a sputter plume from the target and an ion beam from the assist ion beam source, and the substrate assembly may be fixed in some embodiments or pivotable in other embodiments relative to the target and the assist ion beam source.

[0044] In the following description, reference is made to the accompanying drawings, which form a part of this specification, and in which at least one specific implementation is shown by way of example. The following description provides additional specific implementations. It is to be understood that other implementations are contemplated and may be made without departing from the scope or spirit of the present disclosure. Therefore, the following detailed description should not be taken in a limiting sense. The disclosure is not so limited, but an understanding of various aspects of the disclosure will be gained through the description of examples, including the drawings, provided below. In some instances, a reference number may have an associated sub-label consisting of a lower case letter to indicate one of multiple similar components. When a reference number is made without specifying a sub-label, the reference is intended to refer to all such multiple similar components.

[0045] 1 illustrates a system 100 according to the present disclosure, which includes an ion beam deposition (IBD) system and an assisted ion or ion beam system. The system 100 also includes one or more ion beam neutralizers and their associated gas distribution systems. The system 100 may include an apparatus for introducing reactive gas species into the process chamber.

[0046] System 100 includes various elements from a conventional IBD system, such as an ion beam source 104, a target assembly 106, and a chamber 102 having a substrate assembly 108 therein for supporting a substrate 118. Substrate 118 may be formed from one or more layers of, for example, a silicide, a nitride, an oxide, a metal including an alloy, or a ceramic.

[0047] The ion beam source 104 generates an ion beam 110, which may include multiple ion beamlets directed toward the target assembly 106, which includes at least one target 116, which in this illustrated system includes a first target 116a, a second target 116b, and a third target (not shown in FIG. 1), which may all be ruthenium (Ru) if ruthenium is the metal to be deposited; alternatively, the target 116 includes a metal from groups 6 to 11 of the periodic table of the elements, such as, but not limited to, W, Mo, Ru, Co, Cu, Rh, Ta, etc. For example, if titanium (Ti) is to be deposited in addition to ruthenium, one or more of the targets 116 will contain an amount of titanium, or one or more of the targets 116 will comprise dielectric and semiconductor materials, including, but not limited to, metal and semiconductor nitrides such as titanium nitride, tantalum nitride, silicon nitride, molybdenum nitride, tungsten nitride, metal and semiconductor oxides such as silicon oxide, titanium oxide, aluminum oxide, metal and semiconductor silicides such as tungsten silicide, molybdenum silicide, titanium silicide, and other types of metal, dielectric, and semiconductor targets.

[0048] The system 100 may include one or more grids 114 proximate the ion beam source 104 to direct the ion beam 110 from the ion beam source 104 to a target 116 .

[0049] The substrate 118 may have different films, layers, patterns, and / or structures on its surface onto which ruthenium is deposited. The films / layers may include metal and semiconductor nitrides such as titanium nitride, tantalum nitride, silicon nitride, molybdenum nitride, and tungsten nitride; metal and semiconductor oxides such as silicon oxide, titanium oxide, and aluminum oxide; and other types of metal, dielectric, and semiconductor films, structures, and patterns. The films may be deposited in situ in the same process chamber or may be generated and deposited by other methods in other process chambers. Reactive ion beam deposition can deposit low-resistivity ruthenium in situ or ex situ on various such types of metal, dielectric, and semiconductor films, structures, and patterns.

[0050] The source gas used in the ion source 104 is typically a noble gas, such as helium, neon, xenon, argon, or krypton, but may also be a reactive gas, including, for example, oxygen, nitrogen, fluorine, or hydrogen. The reactive gas and noble gas may be used alone or in any combination, such as pure reactive gas, pure noble gas, or any combination of reactive gas(es) and noble gas(es). For example, the volume ratio of reactive gas to noble gas may be as low as 0.1:1, the volume ratio of reactive gas to noble gas may be equal, such as 1:1, or the reactive gas may have a larger volume than the noble gas, such as 10:1. In some embodiments, the volume ratio of reactive gas to noble gas may be lower than 0.1:1 or higher than 10:1.

[0051] The total volume of gas used in the system, including the noble and / or reactive gases in the ion source, neutralizer, and the device for introducing reactive gases into the chamber, is 1 sccm (approximately 1.69 x 10 -3 Pa·m 3 / s) to 100 sccm (approx. 0.169 Pa m 3 / s).

[0052] The system 100 also includes a heat source (not shown), such as a heating element(s) present within the chamber 102. The heating element may be, for example, a heating element disposed on the chamber wall, a heating element disposed within the chamber, or a heating element that is part of or connected to the substrate assembly 108. The heating element may be, for example, a conductive coil, another conductive heat source, a radiant heat source (e.g., a lamp), or an inductive heat source. The heating element may heat the substrate 118 directly or indirectly (e.g., by heating the atmosphere within the chamber 102). The heating element is configured to heat the substrate 118 to a temperature of at least 200°C. In some embodiments, the heating element is configured to heat the substrate 118 to a temperature of at least 250°C, and in some additional embodiments, the heating element is configured to heat the substrate 118 to a temperature of at least 300°C, at least 400°C, or at least 450°C. The substrate 118 may be heated by the environment (e.g., the temperature of the chamber 102) or by heating the substrate assembly 108. When the substrate 118 is heated by the substrate assembly 108, such heating may include flowing a gas, such as He, Ar, etc., behind the substrate 118 to transfer heat more effectively.

[0053] When the ion beam 110 strikes one of the targets 116, it generates a sputter plume 112 of material from the target 116. The ion beam 110 strikes the target 116 at an angle such that the sputter plume 112 generated from the target 116 travels toward the substrate assembly 108. The sputter plume 112 can be made more or less focused so that the resulting deposition of material on the substrate 118 is more effectively distributed over a particular area of ​​the substrate 118.

[0054] In some implementations, the deposition ion beam 110 induces a reaction between the gas species forming the ion beam 110 and the target 116 and / or between the gas species forming the ion beam 110 and the material being deposited by the sputter plume 112. In some implementations, the sputter plume 112 includes ruthenium atoms and / or ruthenium-reactive gas compounds.

[0055] The system 100 also includes an assist ion beam system 130 that provides a source of ions that bombard the substrate 118 so that material on the substrate 118 is removed or modified. The assist ion beam system 130 may be referred to as an ion beam etching system or the like. The assist ion beam system 130 includes an ion beam source 132 that generates an assist ion beam 134, which may include multiple ion beamlets directed toward the substrate assembly 108, and particularly the substrate 118. The assist ion beam 134 controls the net amount of material deposited on the substrate 118 by the sputter plume 112. In some implementations, the assist ion beam 134 modifies the material being deposited by the sputter plume 112. The assist ion beam 134 can induce reactions between the gas species forming the ion beam 110 and the material being deposited by the sputter plume 112 and / or between the gas species forming the ion beam 110 and the material in the sputter plume 112, and the assist ion beam 134 can additionally or alternatively induce dissociation of reacted components being deposited on the substrate 118. In some implementations, the assist ion beam 134 controls reactions between the material being deposited on the substrate 118 by the sputter plume 112 and the reactive gas components, and also controls dissociation reactions of the material being deposited on the substrate 118.

[0056] The assist ion beam system 130 may be, for example, a broad ion beam system with a PBN for generating low-energy electrons. The voltage range of the assist ion beam energy is at least 100 V to 2000 V, but in some implementations is 1000 V or less. Both the ion beam source 132 and the PBN (if present) can use the same gases as the ion source 104.

[0057] The target assembly 106 is positioned so that the sputter plume 112 impacts the desired selected target 116 at a predetermined desired angle. In one exemplary implementation, the target assembly 106 is mounted to a turret fixture 117 that allows the target 116 to be rotated or moved in a desired manner, including rotating the entire target assembly 106 about an axis 126 or pivoting the target 116 or the target assembly 106 to change the angle of the target 116 relative to the axis 126. In another example, the target assembly 106 allows movement of the target 116, which is fixed to the turret fixture 117, in a manner that indexes the relative position of the target 116 with respect to the substrate 118 and the ion source 104, 132. Movement of target 116 through turret 117 is referenced via an index such that the face of target 116 assumes an angle geometrically relative to the ion deposition source and substrate assembly 108, and as the index position of target 116 is changed via movement within turret 117, target 116 assumes an angle of about 0 to about 70 degrees relative to ion beam source 104, assist ion beam source 132, and ion beam 110 from substrate assembly 108. Movement of target 116 on turret 117 also enables selection of a desired target in a multi-target turret by indexing the position of each individual target.

[0058] The target assembly 106 is positioned so that the sputter plume 112 impacts the desired selected target 116 at a predetermined desired angle. In one exemplary implementation, the target assembly 106 is mounted in a turret fixture 117 that allows the target 116 to be rotated or moved in a desired manner, such as by rotating the entire target assembly 106 about an axis 126 or by pivoting the target 116 or the target assembly 106 to change the angle of the target 116 relative to the axis 126. In another example, the target assembly 106 allows movement of the target 116, which is fixed to the turret fixture 117, in a manner that indexes the relative position of the target 116 with respect to the substrate 118 and the ion source 104, 132. Movement of target 116 through turret 117 is referenced via an index such that the face of target 116 assumes an angle geometrically relative to the ion deposition source and substrate assembly 108, and as the index position of target 116 is changed via movement within turret 117, target 116 assumes an angle of about 0 to about 70 degrees relative to ion beam source 104, assist ion beam source 132, and ion beam 110 from substrate assembly 108. Movement of target 116 on turret 117 also enables selection of a desired target in a multi-target turret by indexing the position of each individual target.

[0059] Additionally or alternatively, the substrate assembly 108 may be pivotable relative to the target 116 and the assist ion beam source 132. In one other exemplary implementation, the substrate assembly 108 may be fixed in position relative to the ion sources 104, 132 and the turret target assembly 106, which are arranged to create a fixed geometric relationship between all. The fixed geometric relationship between the ion sources 104, 132, the turret target assembly 106, and the substrate assembly 108 may vary in different implementations.

[0060] Figure 2 is a schematic diagram showing certain elements and various angular combinations from an ion beam deposition system such as system 100. Figure 2 includes a deposition ion source 204, an assist ion source 232, a target 216, and a substrate 218. The direction normal to the plane of the target 216 is shown as 226, and the direction normal to the plane of the substrate 218 is shown as 228.

[0061] From the deposition ion source 204, an ion beam 210 strikes a target 216, forming a sputter plume 212 from the target 216, which travels toward and deposits on the substrate 218. Simultaneously, from the assist ion source 232, an assist ion beam 234 travels toward and deposits on the substrate 218.

[0062] The deposition ion beam 210 forms an angle α (alpha) with respect to the direction 226. The sputter plume 212 forms an angle β (beta) with respect to the direction 228, which is also referred to as the deposition angle. The assist ion beam 234 forms an angle δ (delta) with respect to the direction 228, which is also referred to as the etch angle, assist angle, etc.

[0063] For example, returning to FIG. 1 , in one implementation, the substrate assembly 108 can be fixed so that the surface of the substrate 118 extends parallel to the bottom and / or horizontal plane of the chamber 102, and the deposition ion source 104 is positioned to form a geometric angular relationship (e.g., angle β in FIG. 2 ) with respect to the turret-attached target assembly 106 and the target 116 in the range of 20-25 degrees (e.g., 22 degrees), while the assist ion source 132 is positioned to form a geometric angular relationship (e.g., angle β in FIG. 2 ) with respect to the substrate assembly 108 in the range of 50-60 degrees (e.g., 22 degrees). 2 ) with respect to the deposition ion source 104 and the substrate assembly 108, the target 116 in the turret target assembly 106 being referenced with a plane of the target 116 that is in an angular relationship (e.g., angle α in FIG. 2 ) of 30 degrees in one implementation, 25 degrees in another implementation, and 35 degrees in another implementation, the range of 25 degrees to 35 degrees being selected by rotation of the target 116 in the turret assembly 106. As can be seen from the geometric dependencies, various implementations consisting of various relative combinations of angles from 0 degrees to 90 degrees to −90 degrees can be formed by so arranging various parts of the system.

[0064] Returning to FIG. 1 , the deposition ion beam system 100 may be, for example, a broad ion beam system with a plasma bridge neutralizer (PBN) for generating low-energy electrons. The system 100, particularly the IBD portion of the system 100, may utilize a high-energy ion beam having a voltage in the range of 100 V to 2000 V, or in the range of 1000 V to 2000 V. In some implementations, the ion beam has a voltage less than 1000 V, while in other implementations, the ion beam has a voltage greater than 1500 V. Both the ion beam source and the PBN (if present) may use the same noble gas, reactive gas, or combination thereof as the ion source 104 of the system 100.

[0065] The system 100 also includes an apparatus 140 for introducing a reactive gas into the chamber 102. The apparatus 140 can introduce the reactive gas in a controlled manner at the same plane as (i.e., on the same plane as) the substrate 118, or at a location just above or just below the plane of the substrate 118. The system 100 is typically -3 torr (approximately 133.322 x 10 -3 Pa), e.g., 1×10 -4 torr~1×10 -5 torr (approx. 133.322 × 10 -4 Pa~133.322×10 -5 The system 100 typically operates at a process (chamber) pressure of 100 psi (100 psi) or 100 psi (100 psi) (Pa). The system 100 typically operates with reactive gases introduced into the chamber 102 via either the ion source 104 or the ion source 132 or both the ion source 104 and the ion source 132, and / or via a neutralizer in either ion source or both, and / or via device 140. There may be multiple sources of gas to the chamber 102 in the system 100.

[0066] Such a system 100 with an IBD system and an assisted ion beam may be referred to as an assisted ion beam deposition system. When using reactive gases (introduced in various ways) in the process chamber 102, the system 100 may be referred to as a reactive ion beam deposition system.

[0067] System 100 with ion beam deposition using an assisted ion beam can be used to deposit, deposit and modify, and / or deposit and etch, with or without a reactive gas, simultaneously, sequentially, or intermittently. The reactive ion beam deposition process of ruthenium is summarized below with respect to FIG. 3. In one embodiment, use of system 100 allows for control of the net deposition rate of a target material (e.g., ruthenium) on a substrate 118. In another embodiment using system 100, the net reaction between the target material (e.g., ruthenium) and a reactive gas (e.g., an oxide) and the dissociation of the reaction product (e.g., ruthenium oxide) to form a pure metal (e.g., ruthenium) are controlled. In another embodiment using system 100, the microstructure of a target material (e.g., ruthenium) deposited on a substrate 118 can be modified as desired, for example, by controlling growth habits to obtain a desired orientation of the crystal grains, in some cases forming highly oriented textured films with fibrous texture along specific planes such as the low resistivity hexagonal base (0001).

[0068] Returning again to FIG. 1 , the direction normal to the substrate 118 is shown as 128. In the embodiment shown in FIG. 1 , this direction 128 is tilted toward the sputter plume 112 and the assist ion beam 134. Generally, the angle that the surface of the substrate 118 makes with the sputter plume 112 is referred to as the deposition angle, and the angle that the surface of the substrate 118 makes with the assist ion beam 134 is referred to as the etch angle. The angles are measured relative to the direction 128, which is normal to the surface of the substrate 118. The deposition angle and the etch angle can be adjusted simultaneously by tilting the substrate assembly 108 that holds the substrate 118, thereby tilting the direction 128. The angles can be adjusted periodically, in steps, or continuously during operation of the system.

[0069] The angle may be, for example, a fixed, predetermined angle relative to the fixed positions of the substrate 118, sputter plume 112, assist ion beam 134, and turret target assembly 106. Various different combinations of angles and angular relationships between the substrate 118, ion sources 104, 132, and turret target assembly 106 are possible. In certain implementations, the deposition angle may range from 0 to +75 degrees, and the etch angle may range from 0 to +75 degrees. In other implementations, the deposition angle may range from +10 to −70 degrees, and the etch angle may also range from +10 to −70 degrees. In one embodiment of the system 100 shown in FIG. 1, the etch angle is fixed at 55 degrees, and the deposition angle is 22 degrees.

[0070] Those skilled in the art will appreciate that the relative positions of the sputter plume 112 and the assist ion beam 134 can be such that the deposition and etch angles can be adjusted over a range of angles depending on the required or desired film properties. In another embodiment, the turreted target assembly 106 can be angled between 0 and 70 degrees relative to the ion beam from the ion beam deposition source 104 by movement of the turret 117 indexed to the relative position of the target 116. Additionally, those skilled in the art will appreciate that in one embodiment of the system 100, the substrate 118 can be positioned such that both the sputter plume 112 and the assist ion beam 134 reach the substrate by tilting the substrate assembly 108, thereby tilting the direction 128.

[0071] Adjusting the net deposition rate of metal onto the substrate 118 not only controls the thickness of the deposited material, but also the physical properties of the deposited material, including microstructure and grain growth. Net deposition can be adjusted, for example, by adjusting the deposition rate by IBD and the modification rate by the assisted ion beam, by adjusting the net deposition rate of pure metal onto the substrate 118, by adjusting the reaction rate between gas species introduced into the chamber and the metal in the target 116 and / or sputter plume 112, and by the dissociation rate of the reacted metal compound to form the pure metal. The net deposition rate is greater than 10 Å / min, possibly greater than 100 Å / min, and in some implementations, greater than 1 Å / sec, or even greater than 5 or 10 Å / sec. In some implementations, the net deposition rate is 500 Å / min or less, and often 10 Å / sec or less. One example of a suitable range for the net deposition rate is 6-8 angstroms / second, and another example is 100-500 angstroms / minute.

[0072] Additionally or alternatively, the temperature of the system, e.g., the temperature of the surface of the substrate 118, is a factor in obtaining a low resistivity metal thin film. Low resistivity ruthenium films can be obtained by subjecting the substrate 118 to a temperature of at least 200°C, in some implementations at least 250°C, in other implementations at least 300°C, in other implementations at least 350°C, and in other implementations at least 400°C, with the substrate temperature typically being 600°C or less. The increased temperature affects the phase and crystal orientation and grain size of the resulting deposited material.

[0073] In another embodiment, low-resistivity ruthenium films are deposited on the substrate 118 using single or multiple steps with different net deposition rates of the metal. The net deposition rate can be adjusted by adjusting one or both of the IBD deposition rate and the assist ion beam 134 modification rate, with or without heating the substrate 118 and with or without using different volume ratios of reactive gas to the noble gas introduced into the chamber 102. By adjusting the deposition ion beam energy, e.g., from 100 V to 2000 V, and the assist ion beam energy, e.g., from 100 V to 2000 V, different combinations of IBD deposition rates from the deposition ion beam 110 and the assist ion beam 134, with or without different volume ratios of reactive gas, can be selected. Additionally or alternatively, the ion beam flux of the deposition ion beam 110 and the flux of the assist ion beam 134 can be adjusted, e.g., simultaneously, to adjust the energy of the ion beams.

[0074] With or without reactive gases, a particular combination of IBD deposition rate (i.e., ion beam 110) and assist ion beam rate (i.e., assist ion beam 134) can be selected to selectively grow ruthenium thin films with desired grain orientation and thin film texture, e.g., a high proportion of (0001) grains.

[0075] In a similar manner, specific combinations of IBD deposition rates and assisted ion beam modification rates, with or without reactive gases, can be selected to selectively influence grain growth and deposit low resistivity thin films of ruthenium having large grain sizes, e.g., average grain sizes greater than three times and up to ten times the film thickness, e.g., average grain sizes greater than 100 nm for 10 nm films, and even greater than 100 nm for 10 nm thick films, and greater than 250 nm for films 10 nm and thicker.

[0076] Therefore, by using different combinations of IBD deposition rate and assisted ion beam modification rate, low-resistivity ruthenium thin films can be deposited in single or multiple (different) steps, with or without reactive gases. By using specific combinations of IBD deposition rate and assisted ion beam modification rate, with or without reactive gases, desired textures can be deposited, such as ruthenium (0001) with hexagonal basal planes parallel to the film surface, or ruthenium (0001) with hexagonal c-axes parallel to the film surface. The growth of (0001) ruthenium crystal grains can be influenced by using the same or different combinations of IBD deposition rate and assisted ion beam modification rate, with or without reactive gases.

[0077] The system 100 and methods described herein can also be used to deposit low-resistivity ruthenium films with high smoothness (e.g., as measured by a surface roughness of less than 10 angstroms or less than 5 angstroms). Surface roughness is a measure of the irregularity or non-uniformity of the surface of a thin film, and the surface roughness referred to herein refers to the rms roughness of the metal thin film. The surface roughness of metal thin films can be measured using transmission electron microscopy (TEM) and atomic force microscopy (AFM). For metal thin films, surface roughness plays an important role in resistivity because a rough surface can create surface states, traps, and scattering sites for charge carriers, all of which affect the resistivity of the film. In addition, a rough thin film surface can have a detrimental effect on the integration and further processing of the metal thin film. Therefore, there is great interest in depositing smooth thin films or reducing the roughness of thin films.

[0078] Smooth ruthenium films can be formed on substrate 118 using single or multiple steps of different net deposition rates of material by adjusting the combination of deposition rate and assisted ion beam modification rate, with or without heating of substrate 118 and with or without the use of reactive gases. Specific combinations of IBD deposition rate and assisted ion beam modification rate, with or without the use of reactive gases, can be selected to selectively grow ruthenium thin films with uniform size distributions, as represented by low standard deviations from the mean of the grain size distribution. Controlled, uniform grain growth and uniform grain size distribution and desired grain size orientation during thin film deposition enable smooth, low-resistivity ruthenium thin films when deposited by combining appropriate IBD deposition rate(s) and assisted ion beam modification rate(s), with or without heating and with or without reactive gases.

[0079] FIG. 3 provides a schematic method 300 for forming a smooth ruthenium film on a substrate. In step 310, a deposition ion beam is directed at a ruthenium-containing target to sputter ruthenium atoms from the target. In step 320, the sputtered ruthenium atoms are directed at a substrate at a heated temperature, rotating about a central axis. At least partially concurrently with step 320, in step 330, the substrate is bombarded with an assist ion beam. Also at least partially concurrently with steps 320 and / or 330, in step 340, a reactive gas is introduced into the process chamber, and in some embodiments, the reactive gas may be a noble gas species. The resulting product of step 350 is an at least essentially pure, dense, low-resistivity layer of ruthenium.

[0080] Figure 4A shows a graph of a grazing incidence X-ray theta-2theta scan of a 20 nm thick ruthenium thin film deposited on a titanium nitride substrate by reactive ion beam deposition (RBE). Figure 4B shows a graph of a Bragg-Brentano X-ray theta-2theta scan. In Figure 4A, the X-ray diffraction pattern examines the ruthenium film structure in a grazing incidence X-ray diffraction pattern, which probes a plane nonparallel to the film surface. In Figure 4B, the X-ray diffraction pattern examines a plane parallel to the film surface. The intense (0002) ruthenium peak in the Bragg-Brentano configuration (Figure 4B) and the accompanying lower intensity (0002) peak in the grazing incidence X-ray diffraction pattern (Figure 4A) indicate a (0001) orientation of the basal hexagonal crystal plane parallel to the film surface. In the Bragg-Brentano configuration (Figure 4B), a substrate peak is also visible.

[0081] Figure 4C shows an electron backscatter diffraction (EBSD) micrograph of the same ruthenium thin film, and Figure 4D shows a hexagonal inverse pole figure, which serves as a grain orientation key relative to the crystallographic direction. Each color / shade in these images indicates a crystallographic direction determined by inverse pole analysis. The color / shade in Figure 4C indicates a predominance of (0001) grain orientation, with a fibrous texture and >95% of the grains exhibiting a (0001) orientation with the basal hexagonal crystal planes oriented parallel to the film surface. Furthermore, the (0001)-oriented grains are substantially larger, with an average grain size at least three times the 20 nm film thickness.

[0082] Further testing and characterization of the ruthenium thin films for impurity content revealed that the films were pure ruthenium within the limits of detection without any reactive component contamination, and were found to be pure, densified ruthenium thin films (theoretical density of ruthenium is 12.2 g / cm). 3 The resistivity of the film is <11 μΩ cm.

[0083] From the deposited films shown in Figures 4A-4D, it is clear that the microstructure, grain size, and grain orientation of ruthenium metal films can be controlled by using reactive ion beam deposition. For example, by controlling the microstructure, it is possible to obtain the grain size and grain orientation of pure, dense ruthenium films (formed by using reactive ion beam deposition) with low resistivity over a range of thicknesses, examples of which are shown in Figures 5A and 5B.

[0084] Figures 5A and 5B show the resistivity of ruthenium film structures as a function of thickness on different underlayers. Figure 5A shows the resistivity of a ruthenium film as a function of thickness on a silicon oxide underlayer. Figure 5B shows the resistivity of a ruthenium film as a function of thickness on a tantalum nitride underlayer. The graphs show that for both structures, resistivity increases quadratically as the thickness decreases.

[0085] Deposition of low-resistivity ruthenium thin films using a reactive ion beam deposition system or process can be performed in conjunction with ion beam deposition and / or reactive ion beam deposition of other films or layers. One or more dielectric, metal, or semiconductor thin films can be formed in situ in the same process chamber as the ruthenium film, stacked with the ruthenium film, by a variety of different sequences and step combinations using a multi-target turret assembly and additional targets as needed to deposit other films or layers. A system (e.g., system 100 of FIG. 1) allows for the in-situ deposition of single and multiple thin films of dielectric, metal, and semiconductor materials, all in the same process chamber as the ruthenium film, without requiring any process interruptions.

[0086] 6 shows an exemplary multi-layer structure 600 having a substrate 602 with a ruthenium thin film 604 thereon. An underlayer 606 is disposed between the ruthenium thin film 604 and the substrate 602. The ruthenium thin film 604 is directly on, and may be in contact with, the underlayer 606. A cap layer 608 is disposed on, and may be in contact with, the ruthenium thin film 604.

[0087] Materials for the liner 606 and cap layer 608 can independently include dielectric and semiconductor materials such as silicides (e.g., tungsten silicide, titanium silicide, nickel silicide, cobalt silicide, molybdenum silicide), nitrides (e.g., titanium nitride, tantalum nitride, silicon nitride, molybdenum nitride, tungsten nitride, aluminum nitride, gallium nitride), and oxides (e.g., silicon oxide or silicon dioxide, hafnium oxide, titanium oxide, aluminum oxide), and can include metals (e.g., titanium, copper, molybdenum, tungsten, tantalum). The liner 606 and cap layer 608 can be the same material or different materials, including different stoichiometric concentrations of the same material.

[0088] The undercoat film 606 and the cap layer 608 may independently be thinner than, thicker than, or the same thickness as the ruthenium thin film 604. Typically, however, the ruthenium thin film 604 is thicker than any undercoat film 606 and any cap layer 608, for example, by at least 5 times, in some embodiments by at least 10 times, and in other embodiments by at least 15 times.

[0089] In one particular embodiment, the liner film 606 has a thickness of about 1.5 nm, the ruthenium film 604 has a thickness of about 20 nm, and the cap layer 608 has a thickness of about 4 nm. In another particular embodiment, the liner film 606 has a thickness of about 1.5 nm, the ruthenium film 604 has a thickness of about 20 nm, and the cap layer 608 has a thickness of about 2 nm.

[0090] Structure 600 and variations thereof can have applications as wiring and interconnect elements for integrated circuit devices used in logic and memory circuits. Figure 7 shows the resistivity as a function of thickness for a multilayer ruthenium film with a 1-10 nm thick TiN underlayer, a 5-50 nm thick central Ru layer, and a 4 nm thick TiN overlayer. The graph shows that the resistivity increases quadratically as the thickness decreases.

[0091] FIG. 8 shows a schematic method 800 for forming a multilayer film or structure like structure 600, in which a pure, dense, low resistivity ruthenium thin film is deposited by reactive ion beam deposition on an underlayer film, which is deposited by reactive ion beam deposition immediately prior to the reactive ion beam deposition of the ruthenium film, and another thin film, a cap film, is deposited by reactive ion beam deposition on top of the ruthenium thin film, all depositions occurring in-situ in the same process chamber.

[0092] In step 810, a suitable target is selected for the deposition of a thin underlayer film. In step 820, the underlayer film is deposited by reactive ion beam deposition. After deposition of the underlayer film, in step 830, a ruthenium-containing target is selected for the deposition of a ruthenium film, and in step 840, the ruthenium film is deposited on the underlayer film by reactive ion beam deposition. Next, in step 850, a suitable target is selected for the deposition of a cap film. In step 860, the cap film is deposited on the ruthenium film by reactive ion beam deposition. Such method 800 can be used to form multilayer films with ruthenium between two layers.

[0093] If the low resistivity ruthenium film is deposited on the underlayer without a cap on the ruthenium, the steps for depositing the cap thin film (steps 850, 860) are omitted, and similarly, if the low resistivity ruthenium film is deposited on the substrate with only a cap without an additional underlayer thin film, the steps for depositing the underlayer thin film (steps 810, 820) are omitted. If it is desired to deposit only a low resistivity ruthenium thin film on the substrate without an underlayer thin film or cap thin film, the steps for depositing the underlayer thin film and cap thin film (steps 810, 820, 850, 860) are omitted, leaving steps 830 and 840.

[0094] As an example, a titanium nitride underlayer thin film (e.g., 1-2 nm thick) is deposited on a substrate using reactive ion beam deposition (RBE) with nitrogen gas as the reactive gas species and argon as the noble gas species in an ion beam deposition source with a titanium target in a multi-target turret assembly. The nitrogen and argon are supplied in a 1:1 volume ratio, and the gas flow rate is up to about 20 sccm (about 33.8 x 10 -3 Pa·m 3 / s). Appropriate energy and flux values ​​are used for the ion beam.

[0095] After the titanium nitride underlayer film is deposited, a low-resistivity ruthenium thin film (e.g., 10-20 nm thick) is deposited in situ using reactive ion beam deposition directly on top of the titanium nitride underlayer film using a ruthenium target from a multi-target turret assembly. Ruthenium deposition can be performed in a single or multiple steps. Oxygen can be used as the reactive gas species and xenon as the noble gas species, with a volumetric ratio of reactive gas to noble gas ranging from at least 1:10 to 10:1. The gas flow rate should be at least 1 sccm (approximately 1.69 x 10 -3 Pa·m 3 / s) to 100 sccm (approx. 0.169 Pa m 3 / s). Alternatively, the oxygen to xenon volume ratio can be 1:10, with a total flow rate of 15 sccm (approximately 25.35 x 10 -3Pa·m 3 / s), where xenon is used in the deposition ion source and both xenon and oxygen are used in the assist ion source.

[0096] The combined use of the deposition ion beam and assist ion beam deposits pure, dense, low resistivity ruthenium by reacting oxygen with ruthenium atoms to form ruthenium oxide, which is subsequently induced to dissociate to form pure ruthenium, thus resulting in an oxide-free, pure ruthenium thin film (e.g., at least 99% ruthenium).

[0097] Reactive gases for any of the thin films can be introduced through any one or more of the deposition ion source, assist ion source, deposition ion source neutralizer, assist ion source neutralizer, and apparatus for introducing reactive gases into the chamber.

[0098] After a low-resistivity ruthenium thin film is deposited on the underlying thin film, a capping thin film of titanium nitride (e.g., 2-4 nm thick) is deposited in situ directly onto the ruthenium thin film using reactive ion beam deposition. Nitrogen gas can be used as the reactive gas species and argon as the noble gas species in an ion beam deposition source with a titanium target in a multi-target turret assembly. The argon gas flow rate can be up to 20 sccm (approximately 33.8 × 10 -3 Pa·m 3 / s), with a nitrogen to argon volume ratio of 1:1, although other gas volumes and volume ratios may be used in other implementations.

[0099] As a result of multiple reactive ion beam depositions, a multilayer structure is formed as shown in FIG. Therefore, the microstructure, grain size and orientation, purity, and density of ruthenium thin films can be controlled by using ion beam deposition with assisted ion beams. Low-resistivity ruthenium films can be deposited on a variety of substrates, including, but not limited to, silicides (e.g., tungsten silicide, titanium silicide, nickel silicide, cobalt silicide), nitrides (e.g., titanium nitride, aluminum nitride, tantalum nitride), oxides (e.g., silicon oxide or silicon dioxide, hafnium oxide), metals (e.g., titanium, copper, molybdenum, tungsten, tantalum, and alloys), and ceramics. Underlayer and / or cap layers can be deposited in situ within the same processing system as the ruthenium film.

[0100] From the foregoing, it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.

[0101] Although the present technology has been described in terms specific to particular structures and materials, it should be understood that the invention defined by the appended claims is not necessarily limited to the particular structures and materials described. Rather, particular aspects are described as forms of implementing the claimed invention. Because many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.

[0102] Various features and details are provided in the multiple designs described above. It should be understood that any feature or detail of one design may be utilized for or with any other design, provided that it is not contrary to the process, structure, or configuration. Any variations may be made. For example, processing times, pressures, temperatures, etc. may be varied.

[0103] The above specification and examples provide a complete description of the structure and use of exemplary implementations of the present invention. The above description provides a particular implementation. It is to be understood that other implementations are contemplated and may be made without departing from the scope or spirit of the present disclosure. Therefore, the above detailed description should not be construed in a limiting sense. The present disclosure is not so limited, but an understanding of various aspects of the present disclosure will be gained through the description of the provided examples.

[0104] Unless otherwise indicated, all numerical values ​​expressing size, quantities, and physical properties of features should be understood as modified by the term "about," whether or not the term "about" is immediately present. Accordingly, unless otherwise indicated, the numerical parameters described are approximations that may vary depending upon the desired properties sought to be obtained by those of ordinary skill in the art using the teachings disclosed herein.

[0105] As used herein, the singular forms "a," "an," and "the" include implementations having plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally used in its sense including "and / or" unless the content clearly dictates otherwise.

[0106] As used herein, spatially related terms, including but not limited to "bottom," "lower," "top," "upper," "beneath," "below," "above," "on top," "on," etc., are utilized for ease of description to describe the spatial relationship of an element to another element. Such spatially related terms encompass different orientations of the device in addition to the specific orientation shown in the figures and described herein. For example, if a structure shown in the figures were flipped or turned over, parts previously described as being below or below other elements would now be above or above those other elements.

Claims

1. A method for forming a ruthenium film, A ruthenium film is deposited from a ruthenium target onto a substrate in a process chamber via a deposition ion beam from a deposition ion source in the presence of one or both of a first reactive gas species and a first noble gas species, wherein the substrate is deposited at a temperature of at least 250°C. In the presence of one or both of a second reactive gas species and a second noble gas species, an assist ion beam from an assist ion source is simultaneously collided with at least a portion of the deposited ruthenium within the process chamber. Includes, A method wherein any of the first reactive gas species, the second reactive gas species, the first noble gas species, and the second noble gas species are introduced into the process chamber by one or more of the deposition ion source, the assist ion source, the deposition ion source neutralizer, and the assist ion source neutralizer.

2. The method according to claim 1, wherein the deposition is carried out in the presence of the first reactive gas species, and the collision is carried out in the presence of the second noble gas species.

3. The method according to claim 1, wherein the deposition is carried out in the presence of the first noble gas species, and the collision is carried out in the presence of the second reactive gas species.

4. The method according to claim 1, wherein the deposition is carried out in the presence of the first reactive gas species, and the collision is carried out in the presence of the second reactive gas species.

5. The method according to claim 1, wherein the deposition is carried out in the presence of the first noble gas species, and the collision is carried out in the presence of the second noble gas species.

6. The method according to claim 1, wherein the deposition is carried out in the presence of both the first reactive gas species and the first noble gas species.

7. The method according to claim 1, wherein the collision is carried out in the presence of both the second reactive gas species and the second noble gas species.

8. The method according to claim 1, wherein the first reactive gas species is different from the second reactive gas species.

9. The method according to claim 1, wherein the first noble gas species is different from the second noble gas species.

10. The method according to claim 1, wherein the substrate is at a temperature of at least 300°C.

11. The first reactive gas species and the second reactive gas species are oxygen, nitrogen, nitric oxide (NO), and nitrogen dioxide (NO). ２ ), ammonia (NH ３ The method according to claim 1, comprising at least one of fluorine, fluoride, and hydrogen.

12. The method according to claim 1, wherein the first noble gas species and the second noble gas species are at least one of helium, neon, xenon, argon, and krypton.

13. The method according to claim 1, wherein the deposition of the ruthenium film is performed using an ion beam having a voltage of at least 400 V and a beam current of at least 100 mA.

14. The method according to claim 1, wherein the deposition of the ruthenium film is performed using an ion beam having a voltage of 2000 V or less and a beam current of 2500 mA or less.

15. The method according to claim 1, wherein the assist ion beam for simultaneously colliding with at least a portion of the deposited ruthenium has a voltage of 100 V to 1500 V and a beam current of 100 mA to 1500 mA.

16. Before depositing the ruthenium film, the underlying film is deposited in situ on the substrate within the process chamber. The ruthenium film is deposited on the aforementioned lower layer film and in contact with the aforementioned lower layer film. The method according to claim 1, further comprising:

17. The method according to claim 1, further comprising, after depositing the ruthenium film, depositing a cap layer in situ on and in contact with the ruthenium film within the process chamber.

18. A method for forming a ruthenium film, A ruthenium film is deposited on a substrate from a first target using a deposition ion beam in a process chamber in the presence of at least one of a first reactive gas species and a first noble gas species, wherein the substrate is deposited at a temperature of at least 250°C. Simultaneously etching at least a portion of the deposited ruthenium in the process chamber using an assist ion beam in the presence of at least one of a second reactive gas species and a second noble gas species. Includes, A method wherein any of the first reactive gas species, the second reactive gas species, the first noble gas species, and the second noble gas species are independently introduced into the process chamber via one or more of the deposited ion beam, the assist ion beam, the deposited ion source neutralizer, and the assist ion source neutralizer.

19. Before depositing the ruthenium film, a lower layer film is deposited onto the substrate from a second target in the process chamber. After depositing the ruthenium film, a cap layer is deposited on the ruthenium film from a third target within the process chamber. It further includes, The method according to claim 18, wherein the first target, the second target, and the third target are all located within the process chamber at the same time.

20. It is an ion beam deposition system, An ion beam source configured to generate an ion beam, A turret target assembly configured to accept at least one target, wherein the target is configured to generate a sputter beam when the ion beam collides with it, A pivotable substrate assembly configured to receive a substrate, wherein the substrate assembly is positioned at a first location where the substrate extends parallel to the horizontal plane, An assist ion beam source configured to generate an assist ion beam and Equipped with, The ion beam source, the turret target assembly, and the substrate assembly are each arranged to form a deposition angle of 20 to 25 degrees. The assist ion beam source and the substrate assembly are arranged to form an angle between the assist ion beam and the normal of the substrate extending parallel to the horizontal plane, within the range of 50 to 60 degrees. An ion beam deposition system in which the turret target assembly is positioned to form an angle between the ion beam and the substrate extending parallel to the horizontal plane, within the range of 25 to 35 degrees.

21. The ion beam source, the turret target assembly, and the substrate assembly are arranged to form a deposition angle of 22 degrees. The ion beam deposition system according to claim 20, wherein the assist ion beam source and the substrate assembly are arranged to form a 55-degree angle between the assist ion beam and the normal of the substrate extending parallel to the horizontal plane.

22. A deposition ion source, an assist ion source, a deposition ion source neutralizer, and one or more assist ion source neutralizers for depositing at least one of a first reactive gas species and a first noble gas species, located in close proximity to the ion beam source, A deposition ion source, an assist ion source, a deposition ion source neutralizer, and one or more assist ion source neutralizers are located in close proximity to the assist ion beam source for depositing at least one of a second reactive gas species and a second noble gas species. The ion beam deposition system according to claim 20, further comprising:

23. At least 10 nm thick, Resistivity less than 15 μΩ·cm, (0001) A crystal structure comprising crystal grains having orientation A ruthenium film formed by the method of any one of claims 1 to 19, comprising:

24. The aforementioned thickness is at least 20 nm. The resistivity is less than 11 μΩ·cm. The ruthenium film according to claim 23, wherein the crystal structure has at least 95% of the crystal grains having the (0001) orientation.

25. The aforementioned thickness is at least 50 nm. The resistivity is less than 9 μΩ·cm. The ruthenium film according to claim 23, wherein the crystal structure has at least 95% of the crystal grains having the (0001) orientation.

26. The ruthenium film according to claim 23, wherein the crystal grains have an average crystal grain size at least three times the thickness of the ruthenium film.

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