Ion beam deposition of ruthenium thin films

Abstract

A method of forming a low resistivity ruthenium (Ru) thin film includes depositing ruthenium onto a substrate by deposition with an auxiliary ion beam in a process chamber having a reactive gas species and an inert gas species. The temperature of the substrate is at least 250 DEG C. The thickness of the obtained ruthenium thin film does not exceed 30 nm, the resistivity is smaller than 12 [mu] omega.cm, and the crystal structure comprises (0001) oriented crystal grains. The electrical resistivity is different under different thicknesses, for example, the electrical resistivity of a film of 50 nm or more is less than 9 [mu] Omega * cm, the electrical resistivity of a film of 35 nm or more is less than 9.5 [mu] Omega * cm, the electrical resistivity of a film of 20 nm or more is less than 11 [mu] Omega * cm, the electrical resistivity of a film of 10 nm or more is less than 15 [mu] Omega * cm, and the electrical resistivity of a film of 2 nm or more is less than 20 [mu] Omega * cm. The average crystal size of the grains is at least three times the thickness of the film.

Description

[0001] Cross-reference

[0002] This application claims priority to U.S. Provisional Application No. 63 / 377,065, filed on September 26, 2022, entitled "Ion Beam Deposition of Ruthenium Thin Films", the entire disclosure of which is incorporated herein by reference for all purposes. Background Art

[0003] In the sub-micron era, the continuous shrinking of the size of electronic devices has posed challenges to the metal conductors used in wiring and interconnect networks. This is because as the physical dimensions such as the length, width, and height of metal wires approach or are less than the electron mean free path, the resistivity of the metal increases. The size-related increase in resistivity is mainly due to the increase in electron scattering at the metal surface and layer boundaries, which is exacerbated not only by the increased scattering due to surface roughness but also by the increased scattering at the grain boundaries of the polycrystalline structure of the metal (which typically become finer as the size shrinks). The increase in resistivity is a major challenge, especially for copper, as the size of the most critical and smallest interconnects in integrated circuits continues to shrink, severely limiting the use of copper in its wiring and prompting efforts to find alternative metals. Ruthenium is a candidate metal that is promising to replace copper in integrated device wiring because the volume mean free path of ruthenium is significantly lower than that of copper (almost one-fifth of copper), indicating a correspondingly smaller resistivity size effect.

[0004] The resistivity size effect is typically quantified using classical models that consider both surface scattering and grain boundary scattering. Both model predictions and experimental observations show that the increase in resistivity is proportional to the bulk resistivity and the volume mean free path, both of which are related to the material selection and inversely proportional to the distance between scattering interfaces, including film thickness, line width, line height, and average grain size, all of which are proportional to size, but the latter especially depends on the metal microstructure characteristics. In addition, ruthenium and other metals (e.g., tungsten) exhibit size-related anisotropic resistivity, while typically isotropic resistivity shows a relationship with grain texture, orientation, and epitaxy. Modeling and experimental work in the literature show that for Ru, the (0001) orientation that conducts along the c-axis of the hexagonal crystal system is most favorable for achieving low resistivity. Moreover, the resistivity of a metal depends to a large extent on its microstructure, which includes characteristics such as the crystal size distribution and orientation. The crystal size distribution includes grain boundaries with variable spacing and their frequency, and orientation affects the electron scattering mechanics. Therefore, while metals with a smaller mean free path are promising candidate materials, the resistivity of the actually observed nanoscale conductors depends to a large extent on the microstructure of the thin films used to fabricate them and thus on the capabilities of the thin film growth method.

[0005] Optimizing the microstructure of metal thin films to achieve the lowest resistivity can be very challenging. Even for metals with a low mean free path, poor microstructure, impurities, random grain orientations, and small grain sizes increase the resistivity. It is necessary to deposit high-purity metal thin films with a low-resistivity phase, favorable grain orientation, and large grain size to mitigate the size scaling effect. For example, it is well known in the literature that ruthenium thin films require annealing after deposition or a high temperature during deposition to achieve grain growth, and low resistivity and low resistivity size effects are actually achieved. It is also well known in the literature that the growth and properties of sputtered thin films are closely and complexly related to the material, substrate, substrate temperature, surface chemistry, background and process gas species, deposition ambient chemistry, energy and flux of sputtered atoms.

[0006] Ion beam deposition (IBD) is one of the various methods suitable 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 suitable for depositing layers at extremely low energies, which can produce pseudomorphic layers. PVD is suitable for depositing layers at higher energies, which can produce layers with, for example, good conductivity. IBD is suitable for depositing layers at higher energies and lower pressures and controlling the deposition geometry, which can produce layers with higher crystallinity and controllable microstructure.

[0007] Films of various thicknesses can be produced using all these methods. Below a certain thickness, as the thickness of the metal film decreases, the resistivity of the metal increases. Summary of the Invention

[0008] The present disclosure relates to a method for forming a thin layer of a metal (e.g., ruthenium (Ru)) with low resistivity by ion beam deposition. Adding an auxiliary ion beam and / or a heating process and / or a reactive gas further reduces the resistivity. The ruthenium thin film layer obtained by these methods (e.g., not more than 50 nm thick, and in some embodiments, not more than 35 nm or 30 nm thick) can be pure (e.g., at least 99% ruthenium) and dense (e.g., at least 12.2 g.cm 3 or at least 99% of the theoretical density, i.e., 12.37 g / cm 3 to 12.41 g / cm 3 ).

[0009] These methods include depositing ruthenium metal on a substrate in a process chamber at a temperature not higher than 600 °C (in other embodiments, the temperature is not higher than 450 °C) by means of assisted ion beam deposition (in some embodiments, by reactive ion beam deposition). To reduce the resistivity of the ruthenium thin film, the method can include using a reactive gas species and / or using a reactive gas species for in-situ assistance.

[0010] In some embodiments, reactive ion beam deposition includes introducing one or both of a reactive gas species and an inert gas species into a deposition sputtering ion beam. To reduce the resistivity of the thin film, the method can include using an auxiliary ion beam to introduce the same or different reactive gas species and / or inert gas species.

[0011] The obtained ruthenium thin film can have large and mostly (0001)-oriented grains, where at least 95% and even all of the deposited ruthenium thin film has a (0001) crystal orientation plane relative to the top surface of the substrate; in some embodiments, these grains can be parallel to the top surface of the substrate, while in other embodiments, they can be perpendicular to the top surface of the substrate. The crystal size distribution can result in an average crystal size that is at least three times and up to ten times the thickness of the as-deposited film without additional annealing. Additionally, the obtained ruthenium thin film can have a low resistivity at different thicknesses, for example, the resistivity is less than 9 μΩ·cm when the film thickness is 50 nm or more, less than 9.5 μΩ·cm when the film thickness is 35 nm or more, less than 11 μΩ·cm when the film thickness is 20 nm or more, less than 15 μΩ·cm when the film thickness is 10 nm or more, or less than 20 μΩ·cm when the film thickness is 2 nm or more.

[0012] In some embodiments, the obtained ruthenium thin film with low resistivity is in-situ deposited on a dielectric barrier film deposited on a substrate using a reactive ion beam deposition process. Using the reactive ion beam deposition process, a capping film can be in-situ deposited on the obtained ruthenium thin film with low resistivity. Thus, the obtained ruthenium thin film can be between the dielectric barrier film and the dielectric capping film. The same dielectric can be used as the barrier film and the capping film, or different dielectrics can be used as the barrier film and the capping film.

[0013] In a particular embodiment, the present disclosure provides a method of forming a ruthenium thin film, the method comprising: in a process chamber, depositing a ruthenium film from a ruthenium target onto a substrate by ion beam deposition in the presence of a reactive gas species, the temperature of the substrate being at least 250°C; and in the process chamber, using an auxiliary ion beam to simultaneously bombard at least a portion of the deposited ruthenium in the presence of an inert gas species.

[0014] In an alternative particular embodiment, the present disclosure provides a method of forming a ruthenium thin film, the method comprising: in a process chamber, depositing a ruthenium film from a ruthenium target onto a substrate by ion beam deposition in the presence of an inert gas species, the temperature of the substrate being at least 250°C; and in the process chamber, using an auxiliary ion beam to simultaneously bombard at least a portion of the deposited ruthenium in the presence of a reactive gas species.

[0015] Other arrangements of adding more than one reactive gas species and more than one inert gas species are also disclosed.

[0016] In another specific embodiment, the present disclosure provides a ruthenium film having a thickness not exceeding 30 nm, a resistivity less than 12 μΩ·cm, and a crystal structure including grains having a (0001) orientation. In some cases, the present disclosure provides ruthenium films with low resistivity at different thicknesses. For example, when the film thickness is above 50 nm, the resistivity is less than 9 μΩ·cm; when the film thickness is above 35 nm, the resistivity is less than 9.5 μΩ·cm; when the film thickness is above 20 nm, the resistivity is less than 11 μΩ·cm; when the film thickness is above 10 nm, the resistivity is less than 15 μΩ·cm; or when the film thickness is above 2 nm, the resistivity is less than 20 μΩ·cm, and the film has a crystal structure including grains having a (0001) orientation.

[0017] The present invention content is provided to introduce selected concepts in a simplified form, which will be further described in the following specific embodiments. The present invention content is not intended to identify the key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter. These features and advantages, as well as various other features and advantages, will be apparent by reading the following specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic side view of an ion beam deposition system with an assist ion beam.

[0019] Figure 2 is a schematic diagram of various angular combinations in an ion beam system.

[0020] Figure 3 is a step-by-step method for depositing a ruthenium thin film.

[0021] Figure 4A is a diagram of a grazing incidence geometry X-ray θ-2θ scan of a sample ruthenium thin film; Figure 4B is a diagram of a Bragg-Brentano geometry X-ray θ-2θ scan; Figure 4C is an electron backscatter diffraction (EBSD) micrograph; Figure 4D is an inverse pole figure of the hexagonal crystal system, and the inverse pole figure is used as a key to the grain orientation of crystal directions.

[0022] Figure 5A is a diagram showing the variation of the resistivity of a ruthenium thin film on a silicon underlayer with thickness; Figure 5B is a diagram showing the variation of the resistivity of a ruthenium thin film on a tantalum nitride underlayer with thickness.

[0023] Figure 6 is a schematic side view of a multi-layer ruthenium thin film structure.

[0024] Figure 7 It is a diagram showing the variation of the resistivity of a multi-layer ruthenium thin film structure with thickness.

[0025] Figure 8 It is a step-by-step method for depositing a multi-layer ruthenium thin film structure. Detailed implementation

[0026] As described above, the present disclosure relates to methods for forming thin layers or thin films of low-resistivity metals (e.g., ruthenium) by ion beam deposition. These methods include using reactive ion beam deposition in one or more of the following cases: raising the process temperature, using a reactive gas as a background process gas, as a primary ion, or as a secondary ion. A particular method includes using a heated substrate during reactive ion beam deposition with an auxiliary ion beam.

[0027] In the sub-micron era, the continuous reduction in the size of electronic devices has posed challenges to the metal conductors used in wiring and interconnect networks. This is because as the physical dimensions such as the length, width, and height of the metal wires approach or are less than the electron mean free path, the resistivity of the metal increases. The size-related increase in resistivity is mainly due to the increase in electron scattering at the metal surface and layer boundaries, which is exacerbated not only by the increased scattering due to surface roughness but also by the increased scattering at the grain boundaries of the polycrystalline structure of the metal (which typically become finer as the size is reduced). The increase in resistivity is a major challenge, especially for copper, as the size of the most critical and smallest interconnects in integrated circuits is continuously reduced, severely limiting the use of copper in its wiring and prompting efforts to find alternative metals. Ruthenium is a candidate metal that shows promise for replacing copper in integrated device wiring because the volume average free path of ruthenium is significantly lower than that of copper (e.g., almost one-fifth of copper), indicating a correspondingly smaller resistivity size effect.

[0028] The resistivity size effect is typically quantified using classical models that consider both surface scattering and grain boundary scattering. Both model predictions and experimental observations show that the increase in resistivity is proportional to the bulk resistivity and the volume average free path, both of which are related to the material selection and are also inversely proportional to the distance between the scattering interfaces, which include the film thickness, line width, line height, and average grain size, all of which are proportional to the size, but the latter especially depends on the metal microstructure characteristics. Ruthenium shows size-related anisotropic resistivity, while typically isotropic resistivity shows a relationship with grain texture, orientation, and epitaxy. Modeling and experimental work show that for Ru, the (0001) orientation conducting along the c-axis of the hexagonal crystal system is most favorable for achieving low resistivity. In addition, the resistivity of a metal is closely related to the microstructure, which includes, for example, characteristics of the crystal size distribution and grain orientation. The crystal size distribution characteristics include grain boundaries with variable spacing and their frequencies, and the grain orientation affects the electron scattering mechanics.

[0029] Although metals with a small mean free path are promising candidate materials, the resistivity of the nanoscale conductors actually observed depends to a large extent on the microstructure of the thin film used to fabricate it, and the thin film depends on the thin film growth method.

[0030] The growth of the thin film and the properties obtained have a close and complex relationship with the material, substrate, substrate temperature, surface chemistry, background and process gas types, deposition environment chemistry, energy and flux of sputtered atoms, and post-treatment. Optimizing the microstructure of the metal thin film to achieve the lowest resistivity can be very challenging. Even for metals with a low mean free path, poor microstructure, impurities, random grain orientation, and small grain size will increase the resistivity. For favorable results, the metal thin film is of high purity, having a low resistivity phase, favorable grain orientation, and large grain size to mitigate the size scaling effect. For example, it is well known that ruthenium thin films need to be annealed after deposition or exposed to high temperature during deposition to achieve low resistivity and low resistivity size effect.

[0031] Ion-assisted ion beam deposition is a thin film technology with unique functions, which can adjust the microstructure of the thin film by controlling the density, purity, phase, texture, and grain size growth, so as to achieve low resistivity of the metal. Fundamentally speaking, when ion beam deposition is carried out, the generation of the sputtering beam and the sputtering plume forming the film is spatially separated from the thin film growth using the auxiliary ion beam. In addition, both the deposition ion beam and the auxiliary ion beam are monoenergetic, and the energy and flux of the two ion beams can be independently controlled. The combination of these functions enables the deposition of high-purity films at relatively low pressures (e.g., less than 0.1 mtorr to 0.01 mtorr), with low thermalization, and the energy characteristics of film deposition and growth are finely controlled. Both the deposition ion beam and the auxiliary ion beam have high selectivity and repeatability, and the energy distribution of the monoenergetic is narrow. By appropriately changing the ion beam parameters of the two ion beams, the energy distribution of neutrons and atoms forming the film can be changed, thus significantly affecting the growth mode of the thin film and the evolution of the microstructure. Fine control of the energy characteristics and energy distribution during the deposition and growth of the metal thin film can generate a selective microstructure during ion beam deposition.

[0032] In addition, ion beam deposition enables fine control over the types of background gas and process gas. The types of reactive gas 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 a type of reactive gas (e.g., oxygen or nitrogen) can, when used in combination with a metal target, deposit and produce a composite dielectric film containing the type of reactive gas (e.g., metal oxide or metal nitride) and the metal from the target. Since metal films require high-purity components to achieve low resistivity, reactive sputter deposition of pure metals is not performed in the prior art.

[0033] However, the present disclosure describes, in particular, methods of forming ruthenium films for integrated circuit wiring using reactive ion beam deposition with one or both of a type of reactive gas and a type of inert gas, using a ruthenium target. The type of reactive gas and / or the type of inert gas can be in the primary ion beam and / or the secondary ion beam, and optionally, can be distributed as a background process gas in the chamber. The various methods and apparatuses and combinations thereof described in the present disclosure can produce a dense, high-purity ruthenium metal film having, in the grain size distribution, an average grain size that is at least three times the film thickness, more than ten times the film thickness, and having a near-ideal (0001) orientation and texture, and having an ultra-low resistivity (e.g., less than 11 μΩ·cm for films having a thickness less than 20 nm) in the as-deposited state without additional steps such as annealing and other heat treatments.

[0034] In cases where a reactive gas is used in the process, this ability to deposit pure, dense, low-resistivity ruthenium using reactive ion beam deposition enables the deposition of such ruthenium films on a dielectric film underlayer, a metal film underlayer, or other film underlayers, where the underlayers are deposited in situ by reactive ion beam deposition without using another process chamber, interrupting the process, or additional steps (e.g., purging the reactive gas from the chamber). In addition, such reactive ion beam deposition can also in situ deposit a dielectric film, a metal film, or other film as a capping layer on the deposited ruthenium film by reactive ion beam deposition without using another process chamber, interrupting the process, or additional steps. This is in contrast to existing thin film deposition methods (e.g., chemical vapor deposition, atomic layer deposition, plasma vapor deposition, and other sputter depositions and other methods), where in these existing methods, a pure metal film cannot be deposited in situ together with a dielectric film in the same chamber. Using these known methods, depositing multiple thin film layers of a dielectric layer and a metal layer or a metal layer between dielectric layers or other layers requires separate process chambers.

[0035] The method described in this disclosure can form a ruthenium film mainly oriented in the (0001) direction, which has a highly oriented grain texture as follows: the grains are preferably oriented in the low-resistivity basal plane (0001) and the hexagonal (0001) axis direction; in the crystal size distribution, the average crystal size is 3 times larger than the film thickness, and even more than 10 times larger than the film thickness.

[0036] A specific method includes: depositing ruthenium from a target onto a substrate by ion beam deposition in a process chamber, where the temperature of the substrate is at least 300 °C, or at least 350 °C, or at least 400 °C, or at least 450 °C; in some embodiments, the temperature of the substrate does not exceed 600 °C.

[0037] In some cases, ion beam deposition is carried out in a reactive ion beam deposition manner using various gases, including: for example, background process gases, such as inert gases like argon, krypton, and xenon; and for example, reactive process gases, such as but not limited to gases containing oxygen, nitrogen, fluorine, hydrogen, and other reactive gases.

[0038] An auxiliary ion beam can be used for bombardment to change or etch at least a part of the deposited material. In some cases, this bombardment is carried out in a reactive auxiliary ion beam manner using a background process gas and, for example, a reactive gas. The background process gas is, for example, an inert gas such as argon, krypton, and xenon, and the reactive process gas is, for example, a gas containing oxygen, nitrogen, fluorine, or hydrogen, including nitric oxide (NO), nitrogen dioxide (NO2), ammonia (NH3), and fluorides. In some cases, ion beam deposition and ion beam assistance are carried out while simultaneously introducing a reactive process gas (for example, a gas containing oxygen, nitrogen, fluorine, or hydrogen), and these reactive process gases are introduced through a gas distribution device designed to supply the gas in a controllable manner during deposition.

[0039] The methods described in this disclosure can be used to form ruthenium films that are at least 1 nanometer thick, about 10 nanometers to about 30 nanometers thick in some embodiments, with a resistivity of about 8 μΩ·cm to about 12 μΩ·cm; in some embodiments, the resistivity of the film is about 8 μΩ·cm to about 10 μΩ·cm. As an example, the methods described in this disclosure can be used to form a ruthenium film that is about 10 nanometers to about 20 nanometers thick and has a resistivity of about 8 μΩ·cm to about 10 μΩ·cm. In some cases, these methods can be used to form ruthenium films with low resistivity at different thicknesses, for example, the resistivity is less than 9 μΩ·cm when the film thickness is above 50 nm, less than 9.5 μΩ·cm when the film thickness is above 35 nm, less than 11 μΩ·cm when the film thickness is above 20 nm, less than 15 μΩ·cm when the film thickness is above 10 nm, or less than 20 μΩ·cm when the film thickness is above 2 nm.

[0040] The ruthenium films made by the described methods can have a highly oriented microstructure, with the main orientation being the (0001) orientation. In some embodiments, this orientation is defined as most of the grains (e.g., greater than 60%, 70%, 80%, 90%, 95%, and even up to >99% of the grains) being oriented along the film plane with the low-resistivity hexagonal basal plane (0001) orientation, and in other embodiments, along the film growth direction (i.e., perpendicular to the film plane). The ruthenium films made by these methods can be of high purity, with few or no impurities of reactive gas species or inert gas species in the thin film. The ruthenium films made by these methods can have a low-resistivity hexagonal (0001) fiber texture. The ruthenium film can have a hexagonal (0001) crystal orientation, as shown by the high-intensity (0001) plane shown by X-ray diffraction.

[0041] The ruthenium films made by these methods can have a highly controllable microstructure, and their crystal size distribution and grain orientation distribution can be adjusted by the methods used to form the films. The microstructure of the film can be adjusted according to the growth of grains to a specific size and along a specific plane and direction. The film can be a highly textured large-grain film. For example, the methods described in the present disclosure can be used to form a ruthenium film having a grain orientation distribution characterized in that most grains are oriented along a specific crystallographic plane and direction. For example, most or even all grains are oriented along the basal plane (0001) of the hexagonal crystal system or along the direction of the hexagonal crystal axis (0001). The ruthenium films made by these methods can have the following grain size distribution: the grain size distribution is characterized by a large average grain size, for example, at least three times larger than the film thickness, and even more than ten times larger. That is, the grain size of the ruthenium film is larger than the film thickness, and the crystal size (e.g., diameter) is measured in the film plane. As an example, the methods described in the present disclosure can be used to form a ruthenium film having a thickness of about 2 nm to about 50 nm, and the ruthenium film has the following crystal size distribution: the average crystal size is larger than the diameter of a 50 nm equivalent circle. In some cases, the crystal size is larger than 100 nm. In other cases, the crystal size is larger than 200 nm, and even larger than 300 nm. In some cases, it is even larger than 500 nm.

[0042] Furthermore, the present disclosure describes methods for controlling the microstructure, texture, and grain orientation of ruthenium films by combining or separately using reactive gas species and / or inert gas species, an auxiliary ion etching source, an ion beam deposition source, heat, and reactive ion beam deposition and etching.

[0043] In a specific embodiment, the present disclosure also provides a method for forming a ruthenium thin film, the method comprising: depositing ruthenium from a target onto a substrate by ion beam deposition in a process chamber, the temperature of the substrate being 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, for example, with an auxiliary ion beam. In another specific embodiment, the present disclosure provides a method for forming a ruthenium film by ion beam deposition, wherein the target can be moved in a turret, and the turret is indexed to a position relative to the deposition ion beam and the substrate assembly to present a specific geometric angle.

[0044] For any one or more of these methods, a process gas can be used in conjunction with an ion deposition beam and an assist ion beam to form primary ions. For example, the primary ions in the deposition ion beam and the assist ion beam can be from an inert gas used as the process gas, such as argon, krypton, xenon, and other inert gases. Additionally or alternatively, the primary ions in the deposition ion beam and the assist ion beam can be from a reactive gas used as the process gas, such as a gas containing oxygen, nitrogen, fluorine, hydrogen, and other reactive gases.

[0045] In another specific embodiment, the present disclosure provides a method for forming a ruthenium thin film, the method comprising: 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 deposited material from the substrate in the process chamber, for example using an assist ion beam, wherein one or both of a reactive gas and an inert gas are used alone or in combination of multiple gases for the primary ions in the ion deposition beam and / or the ions in the assist ion beam.

[0046] The present disclosure provides a method for forming a ruthenium thin film using ion-assisted reactive ion beam deposition, wherein the apparatus distributes both the inert gas and the reactive gas in both the ion deposition source and the assist ion source in a controllable manner to generate both inert ions and reactive ions in a controllable manner in the ion beam. Alternatively, the reactive gas is distributed in a process chamber independently of both the ion deposition source and the assist ion source in a controllable manner.

[0047] Ruthenium can be deposited from a target onto a substrate by ion beam deposition using an ion beam having a voltage of at least 400 V and at most at least 2000 V and a current of at least 100 mA and at most at least 2500 mA. An assist ion beam can be used to bombard ruthenium or etch ruthenium from the substrate, the assist ion beam having a voltage of at least 100 V and at most 1500 V. In some embodiments, the current of the assist ion beam is not less than 100 mA and at most 1500 mA.

[0048] The fine control of the energy characteristics, energy, and flux distribution of the independent ion beam, combined with the independent control of the reactive gas and the process gas, enables fine control of the process chamber background pressure while independently controlling the temperature of the substrate, such that during reactive ion beam deposition, the reaction between the reactive gas and / or the process gas and the ruthenium target and the sputtering plume can be highly controlled, as well as the energy characteristics of the ruthenium thin film deposition. Thus, reactive ion beam deposition can deposit a pure, dense, and low-resistivity ruthenium thin film.

[0049] Under certain suitable conditions, when a mono-energetic deposited ion beam is directed towards a ruthenium target, a sputtering plume of ruthenium atoms is generated. The sputtering plume is sputtered and directed towards a heated and rotating substrate, which is also simultaneously bombarded by a mono-energetic assist ion beam, all of which occur in the presence of a reactive gas species (e.g., a gas containing oxygen, nitrogen, fluorine, or hydrogen). Under these conditions, a reaction occurs between the reactive gas species and ruthenium to form a ruthenium compound, which then spontaneously dissociates under energy induction to form a pure and dense ruthenium metal film on the substrate and release the reactive gas. The reactive gas species can be present in the process chamber in various ways under these conditions: for example, by introducing or not introducing other process gases in the deposition ion source, introducing or not introducing other process gases in the assist ion source, introducing or not introducing other process gases in the deposition and / or assist ion source neutralizer, or by introducing through a gas distribution device in the process chamber that is away from and / or close to the substrate, where the gas distribution device is in the same plane as the substrate or above or below the substrate. Under these suitable conditions, a pure and dense ruthenium film is deposited, and its microstructure is characterized in that all the grains have a fibrous orientation: the (0001) grain orientation has the basal plane parallel to the film surface, and in the crystal size distribution, the average crystal size is at least three times the film thickness and up to more than ten times. Under other suitable conditions, a pure and dense ruthenium film is deposited, and its microstructure is characterized in that all the grains have a fibrous orientation, where the (0001) grain orientation has the hexagonal (0001) axis parallel to the film surface, and in the crystal size distribution, the average crystal size is at least three times the film thickness and up to more than ten times.

[0050] Generally speaking, as characteristics of metal thin film deposition, such as microstructure, grain size, grain distribution, grain orientation, grain boundary, purity, morphology, and topography, all depend on the energy characteristics during film deposition on the substrate and have complex relationships with materials, targets, substrates, 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 energy distribution of sputtered atoms during film formation.

[0051] Using the method described in the present disclosure, the orientation of ruthenium crystals can be controlled. In particular, the relative amount of (0001) is increased and the orientation of the (0001) basal plane relative to the film surface is controlled, thereby affecting the resistivity and also increasing the texture of the metal film to form a fibrous texture. Therefore, randomly oriented grains are reduced while (0001)-oriented grains are increased. The number and proportion of (0001)-oriented grains in the ruthenium thin film are relatively high, where the proportion of (0001)-oriented grains is greater than 80%, greater than 90% in some embodiments, greater than 95% in other embodiments, and greater than 99% in still other embodiments.

[0052] As described above, the methods described in the present disclosure provide thin, low-resistivity ruthenium films. For example, these methods provide ruthenium thin films having a resistivity of no more than 12 μΩ·cm, in some embodiments no more than 11 μΩ·cm, in some embodiments no more than 10 μΩ·cm, and even no more than 9 μΩ·cm (i.e., less than 9 μΩ·cm). The methods described in the present disclosure provide ruthenium films having a thickness in the range of 10 nanometers to 30 nanometers and a resistivity in the range of 8 μΩ·cm to 12 μΩ·cm. In some ruthenium films, the resistivity ranges from 8 μΩ·cm to 10 μΩ·cm, and in other films, the resistivity ranges from 9 μΩ·cm to 10 μΩ·cm. The methods described in the present disclosure can also provide ruthenium films having a thickness in the range of 15 nanometers to 25 nanometers and a resistivity in the range of 8 μΩ·cm to 10 μΩ·cm, and can provide ruthenium films having a thickness in the range of 15 nanometers to 20 nanometers and a resistivity in the range of 9 μΩ·cm to 10 μΩ·cm. In some cases, the ruthenium thin films provided by these methods have low resistivity at different thicknesses. For example, the resistivity is less than 9 μΩ·cm when the film thickness is more than 50 nm, less than 9.5 μΩ·cm when the film thickness is more than 35 nm, less than 11 μΩ·cm when the film thickness is more than 20 nm, less than 15 μΩ·cm when the film thickness is more than 10 nm, or less than 20 μΩ·cm when the film thickness is more than 2 nm.

[0053] The present disclosure also describes an ion beam deposition system having: an ion beam deposition source; a target mounted on a turret assembly that is capable of moving along a circular path and indexing relative to the position of the ion beam from the ion beam deposition source; an auxiliary ion beam source; a substrate assembly for holding a substrate; and a heater configured to heat the substrate to a temperature of at least 300 °C, at least up to 400 °C in some embodiments. The movement of the target in the turret assembly is referenced by indexing such that the target face of the target is geometrically at an angle relative to the ion deposition source and the substrate assembly, and the reference position of the target is changed by movement in the turret such that the angle of the target relative to the ion beam from the ion beam deposition source, the ion beam from the auxiliary ion beam source, and the substrate assembly is from about 0 degrees to about 70 degrees (e.g., 20 degrees to 35 degrees, e.g., 50 degrees to 60 degrees). The substrate assembly is arranged to receive the sputtering plume from the target and receive the ion beam from the auxiliary ion beam source. In some embodiments, the substrate assembly can be fixed, or in other embodiments, the substrate assembly can be rotatable relative to the target and the auxiliary ion beam source.

[0054] In the following description, reference will be made to the accompanying drawings, which form a part of this disclosure and in which at least one specific embodiment is shown illustratively. The following description provides additional specific embodiments. It should be understood that other embodiments can be contemplated and made without departing from the scope or spirit of this disclosure. Accordingly, the following detailed description is not limiting. Although this disclosure is not so limited, various aspects of this disclosure will be understood by discussing the examples provided below, including the drawings. In some cases, reference numerals may have associated sub-labels that include lower case letters to denote one of a plurality of similar components. When a reference numeral is mentioned without specifying a sub-label, the mention is intended to refer to all such plural similar components.

[0055] Turning to the drawings, Figure 1 shown is a system 100 in accordance with the present disclosure, the system 100 including an ion beam deposition (IBD) system and an assist ion or assist ion beam system. The system 100 also has one or more ion beam neutralizers and their associated gas distribution systems. The system 100 can have means for introducing reactive gas species into the process chamber.

[0056] System 100 includes various elements of a conventional IBD system, such as a chamber 102 having an ion beam source 104, a target assembly 106, and a substrate assembly 108 for supporting a substrate 118. For example, the substrate 118 can be formed of one or more layers of silicide, nitride, oxide, metal (including alloys), or ceramic.

[0057] The ion beam source 104 generates an ion beam 110, the ion beam 110 can include a plurality of ion beamlets directed at or towards the target assembly 106, the target assembly 106 including at least one target 116, in the illustrated system including a first target 116a, a second target 116b, and a third target ( Figure 1 not shown in the figure), if the metal to be deposited is ruthenium, all targets can be ruthenium (Ru)-containing; alternatively, the targets 116 include metals from Groups 6 to 11 of the periodic table, such as but not limited to: W, Mo, Ru, Co, Cu, Rh, Ta. For example, if titanium (Ti) is to be deposited in addition to ruthenium, one or more of the targets 116 contain a certain amount of titanium, or one or more of the targets 116 contain dielectric materials and semiconductor materials, such as but not limited to: nitrides of metals and semiconductors, such as titanium nitride, tantalum nitride, silicon nitride, molybdenum nitride, tungsten nitride; oxides of metals and semiconductors, such as silicon oxide, titanium oxide, aluminum oxide; silicides of metals and semiconductors, such as tungsten silicide, molybdenum silicide, titanium silicide; and other types of metal, dielectric, and semiconductor targets.

[0058] System 100 may include one or more grids 114 proximate to ion beam source 104 to direct ion beam 110 from ion beam source 104 to target 116.

[0059] The substrate 118 may have different films, layers, patterns, and / or structures on the surface on which ruthenium is deposited. The film / layer may include: nitrides of metals and semiconductors, such as titanium nitride, tantalum nitride, silicon nitride, molybdenum nitride, tungsten nitride; oxides of metals and semiconductors, such as silicon oxide, titanium oxide, aluminum oxide; and other types of metal, dielectric, and semiconductor films, structures, and patterns. These films may be deposited in-situ in the same process chamber or may be fabricated and deposited in other process chambers by other methods. Reactive ion beam deposition can deposit ruthenium with low resistivity in-situ or ex-situ on various types of metal, dielectric, and semiconductor films, structures, and patterns.

[0060] The source gas used in ion beam source 104 is typically an inert 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 the inert gas may be used alone or may be used in any combination, such as a pure reactive gas, a pure inert gas, or any combination of a reactive gas and an inert gas. For example, the volume ratio of the reactive gas to the inert gas may be as low as 0.1:1, the volume ratio of the reactive gas to the inert gas may be equal, such as 1:1, or the volume ratio of the reactive gas may be greater than the volume of the inert gas, such as 10:1. In some embodiments, the volume ratio of the reactive gas to the inert gas may be less than 0.1:1 or greater than 10:1.

[0061] The total volume of gas used in the system (including the inert gas and / or reactive gas in the ion source, the neutralizer, and the equipment for introducing the reactive gas into the chamber) may be as low as 1 sccm and as high as 100 sccm.

[0062] There are also heat sources in system 100. For example, there is a heating element (not shown) in chamber 102. For example, the heating element can be 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 substrate assembly 108. For example, the heating element can be a conductive coil, another conductive heat source, a radiative heat source (e.g., a lamp), or an inductive heat source. The heating element can directly or indirectly (e.g., by heating the air in chamber 102) heat substrate 118. The heating element is configured to heat substrate 118 to a temperature of at least 200°C. In some embodiments, the heating element is configured to heat substrate 118 to a temperature of at least 250°C; in some additional embodiments, the heating element is configured to heat substrate 118 to a temperature of at least 300°C, at least 400°C, or at least 450°C. Substrate 118 can be heated by the environment (e.g., the temperature of chamber 102), or can be heated by heating substrate assembly 108. If substrate 118 is heated by substrate assembly 108, such heating can also include flowing a gas (e.g., He, Ar, etc.) behind substrate 118 to more effectively transfer heat.

[0063] When ion beam 110 impinges on one of targets 116, a sputter plume 112 of material is generated from target 116. Ion beam 110 impinges on target 116 at an angle such that sputter plume 112 generated from target 116 moves toward substrate assembly 108. Sputter plume 112 can be made more or less focused so that the material deposition obtained on substrate 118 is more effectively distributed over a specific area of substrate 118.

[0064] In some embodiments, depositing ion beam 110 causes a reaction to occur between the gas species forming ion beam 110 and target 116 and / or between the gas species forming ion beam 110 and the material being deposited by sputter plume 112. In some embodiments, sputter plume 112 includes ruthenium atoms and / or ruthenium reactive gas compounds.

[0065] System 100 also includes an auxiliary ion beam system 130 that provides an ion source for bombarding substrate 118 to remove or modify materials on substrate 118. The auxiliary ion beam system 130 may be referred to as an ion beam etching system or the like. The auxiliary ion beam system 130 includes an ion beam source 132 that generates an auxiliary ion beam 134, and the auxiliary ion beam 134 may include a plurality of ion beamlets that are directed or pointed at substrate assembly 108, particularly toward substrate 118. The auxiliary ion beam 134 controls the net amount of material being deposited on substrate 118 by sputter plume 112. In some embodiments, the auxiliary ion beam 134 modifies the material deposited by sputter plume 112. The auxiliary ion beam 134 may cause reactions between the gas species forming ion beam 110 and the material being deposited by sputter plume 112 and / or between the gas species forming ion beam 110 and the materials in sputter plume 112; the auxiliary ion beam 134 may also cause or alternately cause dissociation of the reacted components deposited on substrate 118. In some embodiments, the auxiliary ion beam 134 controls the reaction between the material deposited on substrate 118 by sputter plume 112 and the reactive gas components, as well as the dissociation reaction of the material deposited on substrate 118.

[0066] For example, the auxiliary ion beam system 130 may be a broad ion beam system, e.g., having a PBN for generating low energy electrons. The voltage range of the auxiliary ion beam energy is at least 100V to 2000V, but in some embodiments, does not exceed 1000V. Both the ion beam source 132 and the PBN (if present) may use the same gas as the ion beam source 104.

[0067] The target assembly 106 is arranged such that the sputter plume 112 impinges on the desired and selected target 116 at a predetermined desired angle. In one exemplary embodiment, the target assembly 106 is connected to a turret fixture 117 that is capable of rotating or moving the target 116 in a desired manner, such rotation or movement including rotation of the entire target assembly 106 about an axis 126, or rotation of the target 116 or target assembly 106 to change the angle of the target 116 relative to the axis 126. In another exemplary embodiment, the target assembly 106 is capable of moving the target 116 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 beam sources 104, 132. By indexing to position the movement of the target 116 caused by the turret fixture 117, the movement of the target 116 presents a relative angle geometrically between the surface of the target 116 and the ion deposition source and the substrate assembly 108, and changes the reference position of the target 116 by movement in the turret fixture 117 such that the target 116 has an angle of from about 0 degrees to about 70 degrees relative to the ion beam 110 from the ion beam source 104, the auxiliary ion beam source 132, and the substrate assembly 108. The movement of the target 116 on the turret fixture 117 can also select a desired target in a multi-target turret by indexing the position of each individual target.

[0068] The target assembly 106 is arranged such that the sputter plume 112 impinges on the desired and selected target 116 at a predetermined desired angle. In one exemplary embodiment, the target assembly 106 is connected to a turret fixture 117 that is capable of rotating or moving the target 116 in a desired manner, such as rotation of the entire target assembly 106 about an axis 126, or rotation of the target 116 or target assembly 106 to change the angle of the target 116 relative to the axis 126. In another exemplary embodiment, the target assembly 106 is capable of moving the target 116 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 beam sources 104, 132. By indexing to position the movement of the target 116 caused by the turret fixture 117, the movement of the target 116 presents a relative angle geometrically between the surface of the target 116 and the ion deposition source and the substrate assembly 108, and changes the reference position of the target 116 by movement in the turret fixture 117 such that the target 116 has an angle of from about 0 degrees to about 70 degrees relative to the ion beam 110 from the ion beam source 104, the auxiliary ion beam source 132, and the substrate assembly 108. The movement of the target 116 on the turret fixture 117 can also select a desired target in a multi-target turret by indexing the position of each individual target.

[0069] Additionally or alternatively, the substrate assembly 108 may be rotatable relative to the target 116 and the assist ion beam source 132. In another exemplary embodiment, the substrate assembly 108 may be fixed in position relative to the ion beam sources 104, 132 and the turret target assembly 106, and the substrate assembly 108, ion beam sources 104, 132 and turret target assembly 106 are positioned to form a fixed geometric relationship among all of these components. In different embodiments, the fixed geometric relationship among the ion beam sources 104, 132, turret target assembly 106 and substrate assembly 108 may be different.

[0070] Figure 2 A schematic illustration showing certain elements of an ion beam deposition system (e.g., system 100) and various angular combinations is shown. Figure 2 It includes a deposition ion source 204, an assist ion source 232, a target 216 and a substrate 218. The direction perpendicular to the surface of the target 216 is denoted as 226, and the direction perpendicular to the surface of the substrate 218 is denoted as 228.

[0071] The ion beam 210 from the deposition ion source 204 impinges on the target 216, forming a sputter plume 212 from the target 216. The sputter plume 212 travels towards the substrate 218 and is deposited on the substrate 218. At the same time, the assist ion beam 234 from the assist ion source 232 travels towards the substrate 218 and is deposited on the substrate 218.

[0072] The deposition ion beam 210 forms an angle α (alpha) relative to the direction 226. The sputter plume 212 forms an angle β (beta) relative to the direction 228, and this angle β is also referred to as the deposition angle. The assist ion beam 234 forms an angle δ (delta) relative to the direction 228, and this angle δ is also referred to as the etching angle, assist angle, etc.

[0073] For example, returning to Figure 1 , in one embodiment, the substrate assembly 108 may be fixed such that the surface of the substrate 118 extends parallel to the bottom of the chamber 102 and / or the horizontal ground, and the deposition ion beam source 104 is positioned relative to the turret target assembly 106 and the target 116 to form a geometric angular relationship (e.g., Figure 2 the angle β in Figure 2 ), with the angle ranging from 20 degrees to 25 degrees (e.g., 22 degrees). At the same time, the assist ion source 132 is positioned relative to the substrate assembly 108 to form a geometric angular relationship (e.g., Figure 2The angle α) therein, which is 30 degrees in one embodiment, 25 degrees in another embodiment, and 35 degrees in yet another embodiment, where the range of 25 to 35 is selected by the rotation of the target 116 in the turret target assembly 106. It can be understood from the geometric correlation that by positioning the various parts of the system in this way, various embodiments can be achieved including various angular relative combinations from 0 degrees to 90 degrees and then to -90 degrees.

[0074] Return to Figure 1 , for example, the deposition ion beam system 100 can be a wide ion beam system, for example, having a plasma bridge neutralizer (PBN) for generating low-energy electrons. The system 100, especially the IBD part of the system 100, can use a high-energy ion beam with a voltage range of 100V to 2000V or a voltage range of 1000V to 2000V. In some embodiments, the voltage of the ion beam is less than 1000V, while in other embodiments, the voltage of the ion beam is greater than 1500V. Both the ion beam source and the PBN (if present) can use the same inert gas, reactive gas, or a combination thereof as the ion beam source 104 of the system 100.

[0075] The system 100 further includes a device 140 for introducing a reactive gas into the chamber 102. The device 140 can introduce the reactive gas in a controllable manner in a plane flush with the substrate 118 (i.e., the same plane) or at a position above or below a plane close to the substrate 118. The system 100 typically operates at a process (chamber) pressure below 10 -3 Torr (e.g., 1x10 -4 Torr to 1x10 -5 Torr). The system 100 typically operates to introduce the reactive gas into the chamber 102 through one ion beam source 104 or 132 or two ion beam sources 104 and 132 and / or through the neutralizer of one ion beam source or two ion beam sources and / or through the device 140. Multiple gas sources can be present in the chamber 102 in the system 100.

[0076] Such a system 100 with an IBD system and an auxiliary ion beam can be referred to as an auxiliary ion beam deposition system. When a reactive gas (introduced in different ways) is used in the process chamber 102, the system 100 can be referred to as a reactive ion beam deposition system.

[0077] The system 100 using an auxiliary ion beam for ion beam deposition can be used for deposition, deposition and alteration and / or deposition and etching, with or without a reactive gas, and whether simultaneously, sequentially, or interspersed. In the following, reference will be made to Figure 3To generally describe the reactive ion beam deposition of a ruthenium process. In one embodiment, the system 100 can be used to control the net deposition rate of a target material (e.g., ruthenium) on a substrate 118. In another embodiment of using the 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) can be controlled to form a pure metal (e.g., ruthenium). In another embodiment of using the system 100, the microstructure of the target material (e.g., ruthenium) deposited on the substrate 118 can be modified as needed, for example, to obtain a desired grain orientation by controlling the growth habit, thereby forming a highly oriented textured film, where in some cases, the fiber texture is along a specific plane (e.g., the basal plane (0001) of the low resistivity hexagonal crystal system).

[0078] Returning again to Figure 1 , the direction perpendicular to the substrate 118 is denoted as 128. In Figure 1 the illustrated embodiment, this direction 128 is inclined with respect to the sputter plume 112 and the assist ion beam 134. Generally, the angle formed between the surface of the substrate 118 and the sputter plume 112 is referred to as the deposition angle, and the angle formed between the surface of the substrate 118 and the assist ion beam 134 is referred to as the etch angle. These angles are measured based on the direction 128 perpendicular to the surface of the substrate 118. By tilting the substrate assembly 108 that holds the substrate 118, and thus tilting the direction 128, the deposition angle and the etch angle can be adjusted simultaneously. These angles can be adjusted periodically, incrementally, or continuously during system operation.

[0079] These angles can be pre-determined angles that are fixed relative to, for example, the fixed positions of the substrate 118, the sputter plume 112, the assist ion beam 134, and the turret target assembly 106. There can be various different combinations of the angles and angular relationships between the substrate 118, the ion beam sources 104, 132, and the turret target assembly 106. In some embodiments, the range of the deposition angle can be from 0 degrees to +75 degrees, and the range of the etch angle can be from 0 degrees to +75 degrees. In other embodiments, the range of the deposition angle can be from +10 degrees to -70 degrees, and the range of the etch angle can also be from +10 degrees to -70 degrees. In Figure 1 one embodiment of the illustrated system 100, the etch angle is fixed at 55 degrees and the deposition angle is fixed at 22 degrees.

[0080] Those skilled in the art will understand that the relative positions of the sputter plume 112 and the assist ion beam 134 can be such that the deposition angle and the etch angle can be adjusted within a certain angular range based on the desired or expected film properties. In another embodiment, the turret target assembly 106 can index the relative position of the target 116 by movement in the turret fixture 117 to form an angle in the range of 0 degrees to 70 degrees with the ion beam from the ion beam deposition source 104. Additionally, those skilled in the art will understand 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 and thus tilting the direction 128.

[0081] By adjusting the net deposition rate of the metal on the substrate 118, not only can the thickness of the deposited material be controlled, but also the physical properties of the deposited material, including microstructure and grain growth, can be controlled. For example, the net deposition can be adjusted in the following ways: adjusting the deposition rate by IBD and changing the rate by the assist ion beam; adjusting the net deposition rate of the pure metal on the substrate 118; adjusting the reaction rate between the gas species introduced into the chamber and the metal in the target 116 and / or the sputter plume 112; and adjusting the rate at which the reacted metal compound dissociates to form the pure metal. The net deposition rate is greater than 10 Å / min, in some cases greater than 100 Å / min, and in some embodiments, greater than 1 Å / sec, and even greater than 5 Å / sec or 10 Å / sec. In some embodiments, the net deposition rate does not exceed 500 Å / min, and typically does not exceed 10 Å / sec. Examples of suitable ranges of the net deposition rate are 6 Å / sec to 8 Å / sec, and another example is 100 Å / min to 500 Å / min.

[0082] In addition or alternatively, the temperature of the system (e.g., the surface temperature of the substrate 118) is a factor in obtaining a thin, low-resistivity metal film. By having the temperature of the substrate 118 be at least 200°C, in some embodiments at least 250°C, in other embodiments at least 300°C, in other embodiments at least 350°C, in other embodiments at least 400°C, a ruthenium film with low resistivity can be obtained; generally, the temperature of the substrate is not higher than 600°C. The increase in temperature affects the phase, crystal orientation, and crystal size of the deposited material obtained.

[0083] In another embodiment, a ruthenium film with low resistivity is deposited on substrate 118 using one or more steps with different net metal deposition rates. Whether the substrate 118 is heated or not, and whether a reactive gas with a different volume ratio from the inert gas introduced into chamber 102 is used or not, the net deposition rate can be adjusted by adjusting one or both of the deposition rate by IBD and the change rate by the assist ion beam 134. Whether there is a reactive gas with a different volume ratio or not, different combinations of the IBD deposition rates of the deposition ion beam 110 and the assist ion beam 134 can be selected by adjusting the deposition ion beam energy (e.g., in the range of 100V to 2000V) and the assist ion beam energy (e.g., in the range of 100V to 2000V). Additionally or alternatively, the energy of the ion beam can be adjusted, for example, by simultaneously adjusting the ion beam flux of the deposition ion beam 110 and the flux of the assist ion beam 134.

[0084] Whether there is a reactive gas or not, certain combinations of the IBD deposition rate (i.e., ion beam 110) and the assist ion beam rate (i.e., assist ion beam 134) can be selected to selectively grow a ruthenium thin film with a desired grain orientation and film texture (e.g., having a high proportion of (0001) grains).

[0085] In a similar manner, whether there is a reactive gas or not, certain combinations of the IBD deposition rate and the assist ion beam change rate can be selected to selectively affect the growth of grains and deposit a ruthenium thin film with low resistivity and large crystal size (e.g., the average crystal size is greater than three times the film thickness, up to ten times the film thickness. For example, the average crystal size of a 10nm-thick film is equal to or greater than 100nm, the average crystal size of a 10nm-thick film is even greater than 100nm, even greater than 250nm, and the average crystal size of a film thicker than 10nm is even greater than 250nm).

[0086] Therefore, whether in one step or multiple (different) steps, and whether there is a reactive gas or not, a ruthenium thin film with low resistivity can be deposited by using different combinations of the IBD deposition rate and the assist ion beam change rate. Whether there is a reactive gas or not, the desired texture can be deposited by using a specific combination of the IBD deposition rate and the assist ion beam change rate, such as ruthenium (0001) with the basal plane of the hexagonal crystal system parallel to the film surface, or alternatively, such as ruthenium (0001) with the c-axis of the hexagonal crystal system parallel to the film surface. Whether there is a reactive gas or not, the growth of (0001) ruthenium grains can be affected by using the same or different combinations of the IBD deposition rate and the assist ion beam change rate.

[0087] Using system 100 and the methods described in the present disclosure, a low-resistivity ruthenium film with high smoothness (e.g., surface roughness less than 10 angstroms or less than 5 angstroms as measured) can also be deposited. Surface roughness is a measure of the surface irregularity or unevenness of the surface plane of a thin film; the surface roughness mentioned here is the root mean square roughness of a metal thin film. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) can be used to measure the surface roughness of a metal thin film. For a metal thin film, surface roughness plays a key role in resistivity because a rough surface forms surface states, traps, and charge carrier scattering sites, all of which affect the resistivity of the film. In addition, a rough thin film surface also has an adverse 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.

[0088] By combining the adjustment of the deposition rate and the rate change of the assisting ion beam, a smooth ruthenium film can be formed on substrate 118 in one or more steps with different net deposition rates of the material, regardless of whether the substrate 118 is heated or not, and regardless of whether a reactive gas is used or not. Regardless of whether a reactive gas is used or not, a specific combination of the IBD deposition rate and the assisting ion beam rate change can be selected to selectively grow ruthenium thin films with a uniform size distribution, for example, typically with a low standard deviation of the crystal size distribution from the average value. When depositing by combining an appropriate IBD deposition rate and an assisting ion beam rate change, regardless of heating or not, and regardless of the presence or absence of a reactive gas, controlling uniform grain growth, uniform crystal size distribution, and desired crystal size orientation during thin film deposition can smooth the low-resistivity ruthenium thin film.

[0089] Figure 3 A general method 300 for forming a smooth ruthenium film on a substrate is provided.

[0090] In step 310, a deposition ion beam is directed towards a target containing ruthenium to sputter ruthenium atoms from the target. In step 320, the sputtered ruthenium atoms are directed towards a substrate that is at a heated temperature and rotating about a central axis. In step 330, at least partially simultaneously with step 320, the substrate is bombarded with an assisting ion beam. In step 340, also at least partially simultaneously with step 320 and / or step 330, a reactive gas is introduced into the process chamber; in some embodiments, the reactive gas can be an inert gas species. In step 350, the resulting product is a ruthenium layer that is at least substantially pure, dense, and has low resistivity.

[0091] Figure 4A A graph showing a grazing incidence geometry X-ray θ-2θ scan of a 20 nm thick ruthenium thin film deposited on a titanium nitride substrate by reactive ion beam deposition is shown, Figure 4BFigure showing a Bragg-Brentano geometry X-ray θ-2θ scan of a 20 nm thick ruthenium film deposited on a titanium nitride substrate by reactive ion beam deposition. For Figure 4A the X-ray diffraction pattern probes the ruthenium thin film structure, and its grazing angle geometry probes planes that are not parallel to the film surface; for Figure 4B the Bragg-Brentano geometry probes planes that are parallel to the film surface. Figure 4B The intensity of the ruthenium peaks in the Bragg-Brentano geometry of Figure 4A is higher, while the intensity of the (0002) peak in the grazing angle geometry of Figure 4B is lower, indicating that the (0001)-oriented hexagonal basal plane is oriented parallel to the film surface. In the (

[0092] Figure 4C Bragg-Brentano geometry, peaks of the substrate are also observed. Figure 4D Figure shows an electron backscatter diffraction (EBSD) micrograph of the same ruthenium thin film, Figure 4C showing an inverse pole figure of the hexagonal crystal system, which is used as a key to the grain orientation of crystal directions. Each color / shading in these images represents a crystal direction determined by inverse pole analysis.

[0093] Additional tests and characterizations of the impurity content of the ruthenium thin film show that the film is pure ruthenium within the detection limit, contains no identifiable reactive components, and is a pure and dense ruthenium thin film (at least 99% of the theoretical density of ruthenium, i.e., 12.2 g / cm 3 ). The resistivity of the film < 11 μΩ·cm.

[0094] From Figures 4A to 4D the film shown and deposited, it is clear that the microstructure, crystal size, and grain orientation of ruthenium metal films can be controlled by using reactive ion beam deposition. For example, such thin films can be obtained by controlling the microstructure, crystal size, and grain orientation of a pure, dense ruthenium film with a low resistivity within a certain thickness range (formed by using reactive ion beam deposition); examples are shown in Figure 5A and Figure 5B .

[0095] Figure 5A and Figure 5B show the variation of the resistivity of ruthenium film structures with thickness on different underlying films. Figure 5A ​​Shows the variation of the resistivity of a ruthenium film with thickness on a silicon oxide underlayer. Figure 5B Shows the variation of the resistivity of a ruthenium film with thickness on a tantalum nitride underlayer. These graphs show that for both of these structures, the resistivity increases quadratically as its thickness decreases.

[0096] Depositing a ruthenium thin film with low resistivity using a reactive ion beam deposition system or a reactive ion beam deposition process can be carried out together with the ion beam deposition and / or reactive ion beam deposition of other films or layers. In the same process chamber as the ruthenium film, one or more dielectric thin films, metal thin films, or semiconductor thin films laminated with the ruthenium film can be formed in-situ by using a multi-target turret assembly and additional targets required for depositing other films or layers, through various combinations of different sequences and steps. The system (e.g., Figure 1 system 100 in) is capable of depositing single and multiple thin films of dielectric materials, metal materials, and semiconductor materials entirely in-situ in the same process chamber as the ruthenium film without any process interruption.

[0097] Figure 6 Shows an example of a multilayer structure 600 having a substrate 602 with a ruthenium thin film 604 thereon. An underlayer film 606 is provided between the ruthenium thin film 604 and the substrate 602. The ruthenium thin film 604 can be directly on and in contact with the underlayer film 606. A cover layer 608 is provided above the ruthenium thin film 604. The cover layer 608 can be directly on and in contact with the ruthenium thin film 604.

[0098] The materials of the underlayer film 606 and the cover layer 608 can each include dielectric materials 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 contain metals (e.g., titanium, copper, molybdenum, tungsten, tantalum). The underlayer film 606 and the cover layer 608 can be the same material or different materials including the same material with different steric concentrations.

[0099] The underlayer film 606 and the cover layer 608 can each be thinner than the ruthenium thin film 604, can be thicker than the ruthenium thin film 604, or can have the same thickness as the ruthenium thin film 604. However, typically, the ruthenium thin film 604 is thicker than any underlayer film 606 and any cover layer 608, for example, at least about 5 times, at least 10 times in some embodiments, and at least 15 times in other embodiments.

[0100] In a specific embodiment, the thickness of the underlayer film 606 is about 1.5 nm, the thickness of the ruthenium thin film 604 is about 20 nm, and the thickness of the cover layer 608 is about 4 nm.

[0101] In another specific embodiment, the thickness of the underlying film 606 is about 1.5 nm, the thickness of the ruthenium thin film 604 is about 20 nm, and the thickness of the cover layer 608 is about 2 nm.

[0102] The structure 600 and its variants can be applied to the wiring and interconnect elements of integrated circuit devices used in logic and memory circuits.

[0103] Figure 7 The resistivity variation of the multi-layer ruthenium film with thickness is shown; the multi-layer film has a TiN underlying layer with a thickness of 1 nm to 10 nm, a central Ru layer with a thickness of 5 nm to 50 nm, and a TiN top layer with a thickness of 4 nm. The curve shows that the resistivity increases quadratically as its thickness decreases.

[0104] Figure 8 A general method 800 for forming a multi-film or multi-layer structure (e.g., structure 600) is shown, in which a pure, dense, low-resistivity ruthenium thin film is deposited on top of an underlying thin film by reactive ion beam deposition, the underlying thin film being deposited by reactive ion beam deposition prior to the reactive ion beam deposition of the ruthenium film, and another film, i.e., a cover layer film, is deposited on the ruthenium thin film by reactive ion beam deposition, all depositions being carried out in-situ in the same process chamber.

[0105] In step 810, a suitable target is selected to deposit the underlying thin film. In step 820, the underlying thin film is deposited by reactive ion beam deposition. After depositing the underlying film, in step 830, a ruthenium-containing target is selected to deposit the ruthenium film, and in step 840, the ruthenium film is deposited on the underlying film by reactive ion beam deposition. Next, in step 850, a suitable target is selected to deposit the cover film. In step 860, the cover film is deposited on the ruthenium film by reactive ion beam deposition. Using this method 800, a multi-layer film with ruthenium between two layers can be formed.

[0106] If a low-resistivity ruthenium film is to be deposited on the underlying layer and there is no need for a cover above the ruthenium, the steps of depositing the cover layer film (steps 850, 860) are omitted. Similarly, if a low-resistivity ruthenium film is to be deposited on the substrate and there is no need for an additional underlying thin film but only a cover, the steps of depositing the underlying thin film (steps 810, 820) are omitted. If only a low-resistivity ruthenium thin film is desired to be deposited on the substrate without an underlying thin film or a cover layer film, the steps of depositing the underlying thin film and the cover layer film (steps 810, 820, 850, 860) are omitted, and steps 830 and 840 are retained.

[0107] As an example, using reactive ion beam deposition, nitrogen gas in the ion beam deposition source is used as the reactive gas species, and argon gas in the ion beam deposition source is used as the inert gas species. In the case where there is a titanium target in the multi-target turret assembly, a bottom film of titanium nitride (e.g., 1 nm to 2 nm thick) is deposited on the substrate. The volume ratio of nitrogen gas to argon gas is set to 1:1; the gas flow rate can be as high as about 20 sccm. The ion beam uses appropriate energy and flux values.

[0108] After depositing the bottom film of titanium nitride, using the ruthenium target in the multi-target turret assembly, a ruthenium film with low resistivity (e.g., 10 nm to 20 nm thick) is in-situ deposited directly on the bottom film of titanium nitride using reactive ion beam deposition. The deposition of ruthenium can be carried out in one step or multiple steps. Oxygen can be used as the reactive gas species, and xenon can be used as the inert gas species. The volume ratio of the reactive gas to the inert gas is at least 1:10 and at most 10:1. The gas flow rate can be at least 1 sccm and at most 100 sccm. In an alternative example, in the case where the total flux is 15 sccm, oxygen and xenon with a volume ratio of 1:10 are used, where xenon is used for the deposition ion source, and both xenon and oxygen are used for the assist ion source.

[0109] By combining the deposition ion beam and the assist ion beam, pure, dense, and low-resistivity ruthenium is deposited by reacting oxygen with ruthenium atoms to form ruthenium oxide and then causing the dissociation of ruthenium oxide to form pure ruthenium, thus obtaining an oxide-free, pure ruthenium film (e.g., at least 99% ruthenium).

[0110] The reactive gas for any thin film can be introduced through any one or more of the deposition ion source, the assist ion source, the deposition ion source neutralizer, the assist ion source neutralizer, and the device for introducing the reactive gas into the chamber.

[0111] After depositing the ruthenium film with low resistivity on the bottom film, a capping film of titanium nitride (e.g., 2 nm to 4 nm thick) is in-situ deposited directly on the ruthenium film using reactive ion beam deposition. Nitrogen gas in the ion beam deposition source can be used as the reactive gas species, and argon gas in the ion beam deposition source can be used as the inert gas species, and there is a titanium target in the multi-target turret assembly. The flux of argon gas can be as high as 20 sccm, and the volume ratio of nitrogen gas to argon gas is 1:1; in other embodiments, other gas volumes and other volume ratios can be used.

[0112] Due to multiple reactive ion beam depositions, a multi-film structure as shown in Figure 6 is formed.

[0113] Thus, the microstructure, crystal size, grain orientation, purity, and density of ruthenium thin films can be controlled by using ion beam deposition with an assist ion beam. Ruthenium films with low resistivity can be deposited on various types 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 silica, hafnium oxide), and metals (e.g., titanium, copper, molybdenum, tungsten, tantalum, and alloys), as well as ceramics. The underlying film and / or the capping layer can be deposited in situ in the same process system as the ruthenium film.

[0114] From the foregoing, it should be understood that the present disclosure has described specific embodiments of the invention for purposes of illustration, but that various modifications can be made without departing from the scope of the invention. Accordingly, the invention is not limited except as by the appended claims.

[0115] Although the technology has been described in language specific to certain structures and materials, it should be understood that the invention as defined in the appended claims is not necessarily limited to the specific structures and materials described. Rather, specific aspects are described in a form that enables the claimed invention to be achieved. Since many embodiments of the invention can be practiced without departing from the spirit and scope of the invention, the invention is encompassed by the following appended claims.

[0116] Various features and details are provided in the above-described various designs. It should be understood that any feature or detail of one design can be used in any other design or in combination with any other design, unless contrary to the process, structure, or configuration. Any changes can be made. For example, the process time, pressure, temperature, etc. can be changed.

[0117] The above specification and examples provide a complete description of the structure and use of exemplary embodiments of the invention. The above description provides specific embodiments. It should be understood that other embodiments are contemplated and can be made without departing from the scope or spirit of the present disclosure. Accordingly, the above detailed description is not limiting. Although the present disclosure is not limited thereto, an understanding of the various aspects of the present disclosure will be gained through discussion of the examples provided.

[0118] Unless otherwise specified, all numbers expressing feature sizes, amounts, and physical properties are to be understood as being modified by the term "about," whether or not the term "about" is directly present. Accordingly, unless otherwise specified, the numerical parameters set forth are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein.

[0119] As used in this disclosure, the singular forms "a", "an", and "the" include embodiments having plural referents unless the context clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally meant to include "and / or" unless the context clearly dictates otherwise.

[0120] If spatial relative terms are used in this disclosure (including but not limited to: "bottom", "lower", "top", "upper", "beneath", "below", "above", "on top", "on", etc.), they are used for convenience in description to describe the spatial relationship of one (or more) element(s) to another (or more) element(s). These spatial relative terms include different orientations of the device in addition to the specific orientation shown in the figures and described in this disclosure. For example, if the structure shown in the figures is flipped or inverted, the portions previously described as below or beneath other elements will then be above or on those other elements.

Claims

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

2. The method for forming a ruthenium film according to claim 1, wherein, Performing the deposition in the presence of the first reactive gas species and performing the bombardment in the presence of the second inert gas species.

3. The method for forming a ruthenium film according to claim 1, wherein, Performing the deposition in the presence of the first inert gas species and performing the bombardment in the presence of the second reactive gas species.

4. The method for forming a ruthenium film according to claim 1, wherein, Performing the deposition in the presence of the first reactive gas species and performing the bombardment in the presence of the second reactive gas species.

5. The method for forming a ruthenium film according to claim 1, wherein, Performing the deposition in the presence of the first inert gas species and performing the bombardment in the presence of the second inert gas species.

6. The method for forming a ruthenium film according to claim 1, wherein, Performing the deposition in the presence of both the first reactive gas species and the first inert gas species.

7. The method for forming a ruthenium film according to claim 1, wherein, Performing the bombardment in the presence of both the second reactive gas species and the second inert gas species.

8. The method for forming a ruthenium film according to claim 1, wherein, The first reactive gas species is different from the second reactive gas species.

9. The method for forming a ruthenium film according to claim 1, wherein, The first inert gas species is different from the second inert gas species.

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

11. The method for forming a ruthenium film according to claim 1, wherein, The first reactive gas species and the second reactive gas species include at least one of oxygen, nitrogen, nitric oxide (NO), nitrogen dioxide (NO2), ammonia (NH3), fluorine, fluoride, and hydrogen.

12. The method for forming a ruthenium film according to claim 1, wherein, The first inert gas species and the second inert gas species are at least one of helium, neon, xenon, argon, and krypton.

13. The method for forming a ruthenium film according to claim 1, wherein, The voltage of the ion beam used for depositing the ruthenium film is at least 400 V, and the ion beam current is at least 100 mA.

14. The method for forming a ruthenium film according to claim 1, wherein, The voltage of the ion beam used for depositing the ruthenium film is not greater than 2000 V, and the ion beam current is not greater than 2500 mA.

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

16. The method of forming a ruthenium film according to claim 1, further comprising: in-situ depositing an underlying film onto the substrate in the process chamber before depositing the ruthenium film; and depositing the ruthenium film on the underlying film, and the ruthenium film is in contact with the underlying film.

17. The method of forming a ruthenium film according to claim 1, further comprising: After depositing the ruthenium film, a capping layer is deposited in-situ onto the ruthenium film in the process chamber, and the capping layer is in contact with the ruthenium film.

18. A method of forming a ruthenium film, comprising: in a process chamber, depositing a ruthenium film from a first target onto a substrate using a deposition ion beam in the presence of at least one of a first reactive gas species and a first inert gas species, the temperature of the substrate being at least 250 °C; and in the process chamber, simultaneously etching at least a portion of the deposited ruthenium using an assist ion beam in the presence of at least one of a second reactive gas species and a second inert gas species, wherein any one or more of the first reactive gas species, the second reactive gas species, the first inert gas species, and the second inert gas species are independently introduced into the process chamber by any one or more of the deposition ion beam, the assist ion beam, a deposition ion source neutralizer, and an assist ion source neutralizer.

19. The method of forming a ruthenium film according to claim 18, further comprising: before depositing the ruthenium film, depositing an underlying film from a second target onto the substrate in the process chamber; and after depositing the ruthenium film, depositing a capping layer from a third target onto the ruthenium film in the process chamber, wherein the first target, the second target, and the third target are all located in the process chamber simultaneously.

20. An ion beam deposition system, comprising: an ion beam source configured to generate an ion beam; a turret target assembly configured to accommodate at least one target thereon, the target being configured to generate a sputter beam when struck by the ion beam; a rotatable substrate assembly configured to accommodate a substrate thereon, the substrate assembly being disposed at a first position, at which the substrate extends parallel to a horizontal ground plane; and an assist ion beam source configured to generate an assist ion beam; wherein the ion beam source, the turret target assembly, and the substrate assembly are each disposed to form a deposition angle of 20 degrees to 25 degrees, the assist ion beam source and the substrate assembly are disposed to form an angle in the range of 50 degrees to 60 degrees between the assist ion beam and the normal to the substrate extending parallel to the horizontal ground plane, and the turret target assembly is disposed to form an angle in the range of 25 degrees to 35 degrees between the ion beam and the substrate extending parallel to the horizontal ground plane.

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

22. The ion beam deposition system according to claim 20, further comprising: one or more of a deposition ion source, an assist ion source, a deposition ion source neutralizer, and an assist ion source neutralizer for depositing at least one of a first reactive gas species and a first inert gas species near the ion beam source; and One or more of a deposition ion source, an auxiliary ion source, a deposition ion source neutralizer, and an auxiliary ion source neutralizer are configured to deposit at least one of a second reactive gas species and a second inert gas species in the vicinity of the auxiliary ion beam source.

23. A ruthenium film formed by the method according to any one of claims 1 to 19, the ruthenium film comprising: a thickness of at least 10 nm; a resistivity of less than 15 μΩ·cm; and a crystal structure comprising grains having a (0001) orientation.

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

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

26. The ruthenium film according to any one of claims 23 to 25, wherein, The average crystal size of the grains is at least three times the thickness of the ruthenium film.

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