METHOD FOR CAPACITIVELY COUPLED PLASMA SEPARATION OF ATOMIC LAYERS

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of plasma-assisted atomic layer deposition processes. Its application is particularly advantageous in the field of thin film deposition, and more specifically of thin films of controlled thickness, for example in the fabrication of microelectronic devices. STATE OF THE ART

[0002] Atomic layer deposition (ALD) processes are commonly used to deposit thin films, for example, with thicknesses of 100 nm or less, onto 2D or 3D substrates. Generally, ALD is a cyclic process comprising two main steps: an injection of a precursor, typically a metallic precursor, an injection of another precursor, typically a reagent such as an oxygen- or nitrogen-based reagent.

[0003] These steps are self-limiting, allowing for the deposition of conformal and uniform layers on the substrate. The energy required for the precursor reaction can typically be supplied by temperature (this is known as thermal ALD). This energy can be provided using plasma assistance (commonly referred to as PEALD, from Plasma Enhanced ALD) to improve surface reactivity. This notably allows for a reduction in the operating temperature, typically to temperatures at or below 250°C.

[0004] Plasma-assisted ALD processes have been used to deposit many materials that remain difficult to deposit by thermal ALD. For some deposits, thermal ALD processes may be too unreactive and / or require complex organic precursors.

[0005] Typically, PEALD processes utilize capacitively coupled plasmas (CCP) or inductively coupled plasmas (ICP), respectively. These processes are carried out in reactors generally comprising a 10' reaction chamber, a 12' gaseous precursor inlet configured to deliver gaseous precursors into the 10' chamber, and a 13' pumping module for the 10' chamber. A conventional 1' CCP reactor, for example, is illustrated in... Figure 1AThe plasma is typically generated at pressures on the order of a few Torr between two electrodes 110' and 18' using a radio frequency (RF) power device 16'. The electrodes 110' and 18' are arranged parallel to each other, and the substrate is deposited between them. One electrode 110' acts as the platform, connected to the ground 110' which carries the substrate. In conventional CCP processes, however, ion bombardment of the platform is significant. Grids can be added in the inter-electrode space to limit this ion bombardment.

[0006] In a 1' ICP reactor, for example illustrated in figure 1B The plasma is generated 3, typically at pressures on the order of 100 mTorr and remotely, by an induction source 15' with an RF power device 16', then is brought into the reaction chamber 10' to the substrate 2 by diffusion. Ion bombardment is thus limited.

[0007] US document 11 087 959 B2 describes a method for producing PEALD and PECVD deposits, using a conventional ICP source.

[0008] Indeed, ion bombardment can generate localized or widespread defects, such as implantations, atom displacements, compressive stress in the growing layer, or even its pulverization.

[0009] However, ion bombardment can be beneficial for modulating surface reactivity and improving deposit properties such as density, morphology, stress, conformity, particularly on a 3D substrate, provided that the energy of this bombardment and its ionic density are controlled.

[0010] To this end, some recently developed processes use ICP plasmas to which additional RF polarization has been added at the substrate carrier, to allow the extraction of ions from the remote plasma with controlled incident energy at the time they arrive in the vicinity of the substrate.

[0011] In practice, the materials produced in these reactors are primarily oxides or nitrides, whose physicochemical properties can be modulated by additional polarization to extract ions from the plasma and thus assist growth mechanisms. The production of other materials remains limited.

[0012] Furthermore, poorly controlled ion bombardment can affect the intended properties of the deposited layer, and the substrate can be damaged by ion bombardment.

[0013] One object of the present invention is therefore to provide an improved plasma-assisted deposition solution. A non-limiting objective of the invention may be to provide an improved plasma-assisted atomic layer deposition process, particularly in terms of the nature of the deposited layer and / or the selectivity of the deposition.

[0014] The other objects, features, and advantages of the present invention will become apparent from an examination of the following description and accompanying drawings. It is understood that other advantages may be incorporated. SUMMARY OF THE INVENTION

[0015] To achieve this objective, one aspect of the plan involves a plasma-assisted atomic layer deposition process comprising: The provision of a substrate with an exposed surface in a plasma reactor, the plasma reactor comprising a reaction chamber delimited by walls and an electrically conductive platform. The electrically conductive platform has a top face on which the substrate is placed. A side wall of the reaction chamber is at least partially non-parallel to the top face of the platform and electrically conductive. A plurality of atomic layer deposition cycles on the exposed surface of the substrate, each cycle comprising: ∘ an injection into the reaction chamber of a precursor based on a first species, ∘ a plasma treatment of the exposed surface of the substrate by a plasma generated by capacitive coupling between the platform and the side wall, by applying radiofrequency power to the platform.

[0016] Thanks to the non-parallel configuration of the two electrodes, the capacitive coupling between the platform and the chamber walls allows for the creation of a localized plasma near the substrate, with low and finely adjustable energy and ion density, particularly compared to a conventional CCP reactor. These parameters can be adjusted according to RF power and pressure conditions. This significantly limits substrate damage caused by ion bombardment. Furthermore, this lower ion flux is more precisely controllable compared to an ICP reactor with substrate polarization, resulting in a better compromise between substrate damage and ion bombardment efficiency. This significantly reduces substrate damage compared to both CCP reactors and ICP reactors with substrate polarization.

[0017] In addition, this allows access to plasma parameters enabling deposits of varied chemistry and microstructure, as will become apparent from reading the description.

[0018] According to a second aspect, a plasma-assisted deposition reactor is planned, comprising: a reaction chamber delimited by walls and comprising an electrically conductive platform having a top face intended to receive a substrate, a gaseous precursor inlet configured to bring gaseous precursors into the reaction chamber, a reaction chamber pumping module, a power source configured to apply radio frequency power to the platform.

[0019] One side wall of the reaction chamber is at least partially non-parallel to the top face of the platform and is electrically conductive. The top face of the platform and the side wall are separated by a distance configured to generate a plasma by capacitive coupling between the platform and the side wall.

[0020] The radiofrequency power applied to the platform and the distance between the platform and the side wall allow for plasma generation through capacitive coupling between these two elements. The plasma is thus generated in a localized manner near the substrate, thanks to the non-parallel configuration of the two electrodes, which offers the advantages described above. Finally, this reactor allows for the deposition of more varied chemical layers and microstructures than a conventional ICP reactor, with or without substrate polarization. BRIEF DESCRIPTION OF THE FIGURES

[0021] The aims, objects, features and advantages of the invention will become clearer from the detailed description of an embodiment thereof, which is illustrated by the following accompanying drawings in which: There Figure 1A This represents a cross-sectional view of a CCP reactor based on a prior art example. figure 1B This represents a cross-sectional view of an ICP reactor based on a prior art example. figure 2 represents a diagram of the deposition process, based on an example implementation. figures 3A to 3E They represent a diagram of a metallic layer deposition cycle, according to several implementation examples. figures 4A to 4C They represent a diagram of a deposition cycle for a layer of oxide, nitride, and / or sulfide, according to several embodiment examples. figure 5 represents a cross-sectional view of the plasma reactor according to an example embodiment, in which the side wall has a conical geometry. figure 6 represents a cross-sectional view of the plasma reactor according to another embodiment, in which the side wall has a hemispherical geometry. figure 7 represents a cross-sectional view of the plasma reactor according to another embodiment, coupled to an ICP source. figure 8 represents a cross-sectional view of the plasma reactor illustrated in figure 5 , equipped with an ellipsometer. The figures 9A to 9D And 10A at 10C represent graphs of ion flux generated by the plasma according to the plasma parameters, respectively at constant power and pressure.

[0022] The drawings are provided by way of example and are not intended to limit the scope of the invention. They are schematic representations of the principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications. In particular, the relative dimensions of the substrate, the deposited layers, and the reactor are not representative of reality. DETAILED DESCRIPTION OF THE INVENTION

[0023] Before beginning a detailed review of embodiments of the invention, optional characteristics of the process and the plasma reactor which may possibly be used in combination or alternatively are stated below.

[0024] In one example, the plate is polarized to ground.

[0025] According to one example, the plurality of deposition cycles further includes an injection into the reaction chamber of a precursor based on a second species.

[0026] For example, plasma treatment is performed simultaneously with, or following, at least one injection of a precursor into its reaction chamber. This allows for modulation of surface reactions during or between injections. This modulation is made possible, in particular, by the low-density plasma generated.

[0027] As an example, the radiofrequency polarization power can be less than or equal to 80 W. The pressure in the reaction chamber can be less than or equal to 80 mTorr. The plasma treatment time during a deposition cycle can be less than or equal to 1 minute. During the development of the invention, it was demonstrated that these parameters allow for the activation and / or modification of surface reactivity between precursor injections. These plasma conditions can advantageously modify the properties of the deposited material.

[0028] As an example, the radiofrequency polarization power can be greater than or equal to 50 W. The pressure in the reaction chamber can be less than or equal to 20 mTorr. The plasma treatment time during a deposition cycle is greater than or equal to 1 minute. During the development of the invention, it was demonstrated that these parameters allow for the removal, or even the spraying, of the chemisorbed precursor from the surface. These plasma conditions can be useful for selective deposition on 3D substrates.

[0029] For example, when the plasma is generated, the plasma treatment involves injecting a noble gas, also known as an inert gas, preferably argon, possibly mixed with H₂, into the reaction chamber. An argon-based "inert" plasma has low energy compared to other gases. Synergistically, with the generated low-density capacitive plasma, this allows for modulation of surface reactions, minimizing the risk of damaging the exposed substrate surface.

[0030] For example, plasma treatment is performed simultaneously with and / or after the injection of the precursor based on the first species, the first species being metal-based. Plasma treatment thus allows the removal of the ligand from the metallic precursor and therefore metal-on-metal adsorption, through the creation of dangling bonds when the plasma is generated from an inert gas, for example argon, or a reducing gas, for example H₂.

[0031] According to one example, the plasma treatment being carried out between the injection of the precursor based on the first species and the injection of the precursor based on the second species and / or simultaneously with at least one of said injections, the first species is based on a metal and the second species is based on a metal.

[0032] For example, when plasma is generated, the plasma treatment is free of dihydrogen injection. During the development of the invention, it was indeed demonstrated that the process does not require the reduction of the growing layer by dihydrogen.

[0033] Preferably, when the first species is a metal, the radiofrequency polarization power can be less than or equal to 80 W. The pressure in the reaction chamber can be less than or equal to 80 mTorr. The plasma treatment time during a deposition cycle can be less than or equal to 1 minute. The dose delivered by ion bombardment allows for the removal and / or modification of the precursor ligands to promote the deposition of a metallic layer. The depositional dose is limited, which further improves ligand removal without risking the removal of the deposited metal.

[0034] According to one example, the metal has an electronegativity between 1.1 and 2.4.

[0035] Preferably, the metal is chosen from the group consisting of titanium, tantalum, aluminum, silver, zinc, ruthenium, platinum, copper.

[0036] According to one example, the first species includes the metal and alkyl, amine, oxygenated (e.g. carbonyls) or halogenated ligands.

[0037] In one example, with plasma treatment performed simultaneously with the injection of the precursor based on the first species, the plasma treatment and precursor injection are each carried out by simultaneous or sequential pulses. In situ reduction of the precursor is thus achieved either in the gas phase or at the level of the adsorbates. The resulting process can be described as a pulsed, self-limiting CVD mode, with the phase shift between the precursor pulse and the plasma treatment. Preferably, in this example, the first species comprises the metal and alkyl ligands.

[0038] For example, plasma treatment is performed after the injection of the precursor based on the first species, for instance, before and / or simultaneously with the injection of the precursor based on the second species, and / or after the injection of the precursor based on the second species. The first species is metal-based, and the second species comprises at least one of the elements oxygen, nitrogen, and sulfur. Depending on the dose of metallic precursor deposited, the quantity and reactivity of the oxygen, nitrogen, or sulfur-based precursor can be limited to modulate the surface reactivity before the injection of the metallic precursor in the next cycle.

[0039] According to one example, with plasma treatment being carried out simultaneously with the injection of the precursor based on the second species, the second species is chosen from the group consisting of O2, N2 (possibly mixed with H2), NH3, H2S.

[0040] According to one example, the plasma treatment being carried out after the injection of the precursor based on the second species, the second species is chosen from the group consisting of H2O, O2, NH3.

[0041] For example, when the first species is metal-based and the second species includes at least one of the elements oxygen, nitrogen, and sulfur, the radiofrequency polarization power can be less than or equal to 80 W. The pressure in the reaction chamber can be less than or equal to 80 mTorr. The duration of the plasma treatment during a deposition cycle is less than or equal to 1 minute. Thus, the surface reactivity between the precursor based on the first species, the precursor based on the second species (thermal reactant or plasma), and / or the radicals of the oxidation, nitriding, or sulfiding plasma can be activated and / or modified. These plasma conditions can advantageously modify the properties of the deposited material.

[0042] In an alternative example, when the first species is metal-based and the second species includes at least one of the elements oxygen, nitrogen, and sulfur, the radiofrequency polarization power can be greater than or equal to 50 W. The pressure in the reaction chamber can be less than or equal to 20 mTorr. The plasma treatment time during a deposition cycle is greater than or equal to 1 minute. The chemisorbed precursor on the surface can thus be removed or even sprayed off. These plasma conditions can be useful for selective deposition on 3D substrates.

[0043] In one example, with the platform configured for height adjustment within the reaction chamber, the process includes adjusting the platform height prior to plasma treatment, preferably before the deposition cycle. This allows the distance d to be adjusted by the platform height, for example, for different pressure or bias voltage values, as required. The reactor thus gains versatility. When the reactor also includes an inductively coupled plasma source located away from the reaction chamber, this further allows adjustment of the distance d between the platform and the side wall, which is particularly advantageous in synergy with an additional ICP source. This makes it possible to couple or decouple the CCP and ICP plasmas as needed.

[0044] According to one example, the plasma treatment is configured so that the plasma exhibits the following ionic flux characteristics: power density: 0.05 to 0.5 W / cm 2< , ion flux: 10 12< to 10 14< ions / (cm 2< .s ), ion energy: 0 to 300 eV.

[0045] To achieve this, the pressure in the chamber, the frequency of the radio frequency polarization and the power of the frequency polarization can be adapted, as described in more detail later.

[0046] As an example, the reactor is a plasma-assisted atomic layer deposition reactor.

[0047] As an example, the reactor is configured to generate a plasma with an ion density substantially less than or equal to 1014 ions.cm-2.s-1. This low-density plasma, located in the vicinity of the substrate, allows for more precise exploitation of ion bombardment.

[0048] As an example, the distance, and for instance the minimum distance, between the top of the plate and the side wall is between 5 cm and 15 cm, preferably between 5 cm and 12 cm. This distance range, which allows for self-sustaining discharge, is dictated by Paschen's law, a function of the pressure P in the reactor and the minimum average voltage Umin of the RF power: Umin = Pd. This makes it possible to obtain an ion density ≤ 1014 cm-2 .s-1 for a very low-density plasma, further facilitating the adjustment of the plasma characteristics. It also makes it possible to obtain the low-density plasma without significantly reducing the pressure in the reaction chamber, for pressures on the order of mTorr to a few hundred mTorr, for example, 200 mTorr.

[0049] According to one example, the distance d is proportional, and preferably equal, to the ratio of U / P, where P is the pressure in the reactor, and U is the average voltage of the radio frequency bias applied to the platform, U being greater than or equal to a minimum average voltage value U min of radio frequency self-bias.

[0050] In one example, the side wall is at least partially arranged perpendicularly to the main extension plane of the top face of the tray. The side wall is thus substantially vertical.

[0051] In one example, the side wall is at least partially angled relative to the main extension plane of the top surface of the tray. This avoids edge effects and attenuates field lines on the substrate compared to a vertical wall.

[0052] In one example, the side wall is positioned relative to the main extension plane of the top surface of the tray so as to form an angle between 15° and 85°, preferably between 30° and 80°. In another example, and particularly when the side wall is domed, the tangent to the side wall defines an angle between 15° and 85°, preferably between 30° and 80°. The tangent to the side wall can be the tangent to a point on the side wall located in the main extension plane of the top surface of the tray.

[0053] According to one example, the electrically conductive side wall is at least partly positioned above the platform, projecting along a vertical plane, or substantially perpendicular to the top face of the platform.

[0054] As an example, the side wall exhibits rotational symmetry around a perpendicular direction and is approximately centered with respect to the top surface of the platform. This symmetry allows the plasma to be initiated across the entire surface of the top face. The plasma is therefore more homogeneous.

[0055] As an example, the side wall does not exhibit rotational symmetry about a direction perpendicular and substantially centered with respect to the top face of the platform. For instance, the conductive side wall can be designed to only partially surround the platform, projecting onto a plane parallel to the principal plane of extension of the platform's top face.

[0056] According to one example, the side wall forms at least partly a cone above the platform, preferably the side wall has a conical geometry with an axis of revolution substantially centered with respect to the platform.

[0057] According to one example, the side wall forms at least partly a dome over the platform, preferably the side wall has at least partly a hemispherical geometry, preferably substantially centered with respect to the platform.

[0058] In one example, the reactor is configured so that the plasma is generated solely in the reaction chamber by the power applied to the substrate holder. Thus, the reactor has a simplified configuration, and is therefore less expensive than that of a conventional PEALD ICP reactor.

[0059] In one example, the reactor is configured so that plasma is generated only between two electrodes, and the reactor is configured so that the platform constitutes one of the two electrodes. By comparison, in an ICP reactor, the ICP plasma is generated only by a coil powered by RF energy.

[0060] According to one example, the reactor is free of an additional ICP plasma type source.

[0061] In one example, the platform is not configured to be height-adjustable within the reaction chamber. This further simplifies the reactor configuration.

[0062] In one example, the reactor also includes an inductively coupled plasma source located away from the reaction chamber. The reactor is thus a multimode reactor enabling plasma-assisted deposition using ICP and / or plasma generated between the platform and the side wall, depending on the requirements. The reactor therefore allows for different deposition processes to be performed according to the specific needs.

[0063] When the reactor also includes an inductively coupled plasma source located away from the reaction chamber, the reactor may include two independent plasma sources that can be used interchangeably: the power source for CCP coupling and the inductively coupled plasma source for ICP coupling. The biasing powers applied by these two sources can be set independently.

[0064] In one example, the platform is not configured to be height-adjustable in the reaction chamber.

[0065] In one example, the platform is configured to be height-adjustable within the reaction chamber. This allows the distance d to be adjusted by the platform height, for instance, to suit different pressure or bias voltage values, as required. The reactor thus gains versatility. When the reactor also includes an inductively coupled plasma source located away from the reaction chamber, the distance d between the platform and the side wall can be adjusted, which is particularly advantageous for modulating the plasma properties in the vicinity of the substrate. This makes it possible to decouple or couple the two plasmas, CCP and ICP, as needed.

[0066] As an example, the gaseous precursor inlet and pumping module are configured to maintain, at least when plasma is generated, a pressure substantially between 5 and 200 mTorr, preferably between 5 and 100 mTorr in the reaction chamber, and preferably between 5 and 80 mTorr in the reaction chamber, at least when plasma is generated. These pressures correspond to a high secondary vacuum.

[0067] According to one example, the arrival of gaseous precursors and the pumping module are configured to maintain a pressure substantially less than or equal to 200 mTorr, preferably 100 mTorr in the reaction chamber, at least when plasma is generated.

[0068] According to one example, the arrival of gaseous precursors and the pumping module are configured to maintain a pressure substantially greater than or equal to 10 mTorr in the reaction chamber, at least when the plasma is generated, preferably greater than or equal to 15 mTorr.

[0069] According to one example, the power source is configured to apply radio frequency power with a frequency between 2 and 100 MHz, when plasma is generated by capacitive coupling between the tray and the side wall, or equivalently to generate plasma by capacitive coupling between the tray and the side wall.

[0070] In one example, the power source (for CCP coupling) is configured to apply radio frequency power with a value less than or equal to 100 W when plasma is generated by capacitive coupling between the platen and the side wall. In another example, a non-zero radio frequency power of 100 W or less is applied to the platen.

[0071] The remote inductively coupled plasma source from the reaction chamber can be configured to apply radio frequency power with a non-zero absolute power value between 0 and 300 W.

[0072] According to one example, the process further includes an adjustment of at least two plasma parameters, these parameters including the distance d, the pressure P in the reactor, and the average voltage U of the radiofrequency polarization applied to the platform, such that: d is proportional to, and preferably equal to, the U / P ratio, where U is greater than or equal to a minimum mean self-polarization voltage value (Umin). Preferably, this adjustment is performed before plasma treatment of the exposed surface. This allows the parameters to be adjusted without affecting the deposition on the substrate.

[0073] In one example, given that the reactor platform is configured to be height-adjustable within the reaction chamber, the process involves adjusting the distance d by moving the platform vertically to achieve a distance d that allows plasma generation. It is thus possible to position the platform at a distance that does not permit plasma generation and then move it until a plasma is observed. Preferably, this adjustment is performed before the plasma treatment of the exposed surface.

[0074] As an example, during plasma processing, the pressure in the reaction chamber is typically between 5 and 200 mTorr, preferably between 5 and 100 mTorr. For instance, the precursor supply can be configured to reach this pressure prior to plasma generation. The gaseous precursor supply and the pumping module can be configured to maintain this pressure.

[0075] As an example, during the adjustment of the plasma parameters, the process also includes the application of radio frequency power. The above parameters allow for obtaining the following ionic flux characteristics of the plasma at the plateau level: power density: 0.05 to 0.5 W / cm 2< , ion flux: 10 12< to 10 14< ions / (cm 2< .s ), ion energy: 0 to 300 eV.

[0076] In one example, the power source includes an attenuator configured to limit the power of the radio frequency polarization of the plasma generated by capacitive coupling.

[0077] In the following description, the term "on" does not necessarily mean "directly on." Thus, when it is stated that a part or component A rests "on" a part or component B, this does not mean that parts or components A and B are necessarily in direct contact with each other. These parts or components A and B may be either in direct contact or supported by one or more other parts. The same applies to other expressions such as, for example, "A acts on B," which can mean "A acts directly on B" or "A acts on B through one or more other parts."

[0078] In this patent application, the term mobile corresponds to a rotational movement or a translational movement or a combination of movements, for example the combination of a rotation and a translation.

[0079] In the detailed description that follows, terms such as "horizontal," "vertical," "longitudinal," "transverse," "upper," "lower," "top," "bottom," "front," "rear," "inside," and "outside" may be used. These terms should be interpreted relatively in relation to the reactor's normal operating position. For example, "horizontal" and "longitudinal" refer to the principal direction of extension of the upper surface of the platform.

[0080] We will also use a coordinate system whose longitudinal or right / left direction corresponds to the x-axis, the transverse or back / front direction corresponds to the y-axis and the vertical or bottom / up direction corresponds to the z-axis.

[0081] A microelectronic device is defined as any type of device made using microelectronics. These devices include, in addition to purely electronic devices, micromechanical or electromechanical devices (MEMS, NEMS, etc.) as well as optical or optoelectronic devices (MOEMS, LEDs, etc.).

[0082] It may be a device intended to perform an electronic, optical, mechanical, etc. function. It may also be an intermediate product solely intended for the production of another microelectronic device.

[0083] Furthermore, a species-based plasma can be based on, or equivalently formed from, a chemistry comprising only that species and possibly one or more other species, for example a noble gas such as argon or helium.

[0084] The term "step" refers to the execution of a part of the process and can designate a set of substeps. The term "step" does not necessarily imply that the actions carried out during a step are simultaneous or immediately successive. For example, some actions in a first step may be followed by actions related to a different step, and other actions from the first step may be repeated later. Thus, the term "step" does not necessarily imply unitary actions that are inseparable in time and in the sequence of process phases.

[0085] In this patent application, when a gas mixture is expressed as a percentage, these percentages correspond to fractions of the total flow rate of the gases injected into the reactor. Thus, if a gas mixture, for example intended to form a plasma, comprises x% of gas A, this means that the injection flow rate of gas A corresponds to x% of the total flow rate of the gases injected into the reactor to form the plasma.

[0086] A parameter that is "approximately equal to / greater than / less than" a given value means that the parameter is equal to / greater than / less than the given value, within ±10% of that value. A parameter that is "approximately between" two given values ​​means that the parameter is at least equal to the smaller of the two given values, within ±10% of that value, and at most equal to the larger of the two given values, within ±10% of that value.

[0087] Plasma-assisted atomic layer deposition process 4 and reactor 1 are now described in more detail with examples of implementation.

[0088] There figure 2 Figure 4 illustrates process 1 according to an example embodiment. Optional steps are indicated by dashed lines. Process 4 first involves supplying 40 with a substrate 2 having an exposed surface 20. This substrate 2 is supplied to a plasma reactor 1 comprising a reaction chamber 10. The reactor 1 is configured to generate a plasma by capacitive coupling between a tray 110 and a side wall 100 of the reaction chamber 10 of the reactor 1. Examples of plasma reactors 1 will be described in more detail later.

[0089] Following the supply 40 of substrate 2, the process 4 comprises a plurality of cycles 41 for depositing atomic layers onto the exposed surface 20 of substrate 2. A deposition cycle 41 includes an injection into the reaction chamber 10 of a precursor based on a first species 410. The cycle 41 further comprises a plasma treatment 412 of the exposed surface 20 of substrate 2 by the plasma generated by capacitive coupling between the tray 110 and the side wall 100 of the reaction chamber 10. As will be seen later, any relative order between the precursor injection(s) and the plasma treatment is conceivable, including a plasma treatment followed by the precursor injection(s).

[0090] The plasma is generated by applying radiofrequency power to the platform 110. The plasma is thus generated in a localized manner in the vicinity of substrate 2 with a much lower ion flux than in a conventional CCP reactor. This reactor 1 allows the exploitation of low-energy ion bombardment to improve material properties (density, purity, crystalline structure, internal stress). Furthermore, it opens new avenues for process development concerning metals, oxides, nitrides, and sulfides on 2D and 3D substrates, as well as selective surface and topographic deposition processes.

[0091] As illustrated by the figure 2The cycle 41 may further include the injection of a precursor based on a second species 413. The cycle 41 may be repeated a number of times n to achieve the desired layer thickness. Depending on the relative order of the precursor injections 410 and 413 and the plasma treatment 412, as well as the parameters of the plasma treatment 412, the surface reactions and thus the properties of the growing layer can be modified. Several examples of deposition cycle 41 are described below by way of non-limiting example. It is understood that these features may be combined to produce other embodiments, unless explicitly stated otherwise.

[0092] For example, plasma treatment 412 is performed simultaneously with, or following, at least one injection 410, 413 into the reaction chamber 10. Simultaneously, it is understood that plasma treatment 412 is carried out at least partially at the same time as the injection(s) 410, 413 in question. A delay between plasma treatment 412 and the injection(s) 410, 413 may be anticipated.

[0093] During the development of the invention, several plasma treatment regimes were identified, depending on the intended deposition. As a first example, the polarization power can be less than or equal to 80 W, the pressure in the reaction chamber 10 can be less than or equal to 80 mTorr, and the duration of the plasma treatment 412 during a cycle 41 can be less than or equal to one minute. These parameters allow the surface reactivity to be activated and / or modified between precursor injections within the same cycle 41 or between cycles of successor. In particular, these parameters allow the reactivity of the precursor ligands to be manipulated to influence the growing layer.In a second example, alternatively, the radiofrequency polarization power can be greater than or equal to 50 W, the reaction chamber pressure 10 can be less than or equal to 20 mTorr, and the plasma treatment duration 412 during a cycle 41 can be greater than or equal to one minute. These parameters allow the chemisorbed precursor to be removed from the surface. The deposited material can thus grow on localized portions of layers. These conditions therefore allow for selective deposition, for example, on a 3D substrate.

[0094] Each injection 410, 413 and / or each plasma treatment 412 can be followed by a purge phase 414. This purge 414 allows the species that have not been deposited on the exposed surface 20 of the substrate 2 to be eliminated, as well as the reaction products.

[0095] During plasma generation, plasma treatment 412 may include the injection of a noble gas, also known as an inert gas, such as helium or argon, into the reaction chamber 10. This gas may also be mixed with dihydrogen (H2). An argon-based plasma is indeed low in energy compared to other gases. Surface reactions can be further modulated, in synergy with the generated low-density capacitive plasma, while limiting the risk of damaging the exposed surface 20.

[0096] Plasma treatment 412 using a capacitive plasma generated between the platform 110 and the side wall 100, and therefore a low density plasma, process 4 allows the deposition of layers of various nature and in particular of layers whose deposition by conventional plasma-assisted deposition processes remains limited.

[0097] For example, process 4 allows a metallic layer to be deposited on the exposed surface 20 of the substrate 2. Examples of metallic layer deposition are now described.

[0098] Cycle 41 may include the injection of a precursor based on a metal 410. A cycle 41 may consist solely of the injection of a precursor based on a first metal. Alternatively, cycle 41 may include the injection of a second precursor based on a metal 413a, and in particular, a precursor based on a metal distinct from the first metal. When several precursors based on different metals are used, the process allows the deposition of a metallic alloy layer.

[0099] To deposit a metallic layer, the precursors injected during a cycle are preferably all metal-based. A precursor is distinguished from a gas injected into chamber 10 during plasma treatment 412, intended to form the reactive atmosphere of the plasma, such as a neutral gas or hydrogen (H2), this gas potentially not containing any metal in this example.

[0100] To deposit a metallic layer, plasma treatment 412 can be performed simultaneously with and / or after the injection of the first metal-based precursor 410. Alternatively or in addition, plasma treatment 412 can be performed simultaneously with and / or after the injection of the second precursor 413a. Plasma treatment 412 thus eliminates the ligand from the metallic precursor. This promotes metal-on-metal absorption during layer growth by creating dangling bonds.

[0101] As illustrated, for example, by the figure 3ACycle 41 may include an injection 410 of a metal-based precursor. Simultaneously with this injection, plasma treatment 412 may take place.

[0102] As an example, plasma injection and / or treatment can be continuous. As another example, injection 410 and / or plasma treatment 412 can be intermittent within a cycle 41. The use of pulses, and in particular precursor pulses, can modulate growth mechanisms. These pulses are particularly advantageous for metal layer deposition, especially for the creation of dangling bonds, using H₂ / Ar or Ar-only plasma. It is indeed more difficult to form this type of layer compared to oxides / nitrides / sulfides, which are much easier to form by ligand reactivation (chemical substitution).

[0103] As illustrated by the figure 3BThe plasma treatment 412 can comprise several plasma pulses. In a cycle 41, the application of radio frequency power to the platform 110 can be intermittent so as to generate the plasma only intermittently; that is, the plasma treatment 412 can comprise phases of RF power application separated by phases of non-application of RF power to the platform 110. Similarly, the injection 410 can be intermittent; that is, the injection 410 can comprise phases of injecting the metal-based precursor into the chamber 10 separated by phases of non-injection of the precursor into the chamber 10. The RF power application and injection phases, respectively, constitute the pulses. As illustrated by the figure 3B These pulses can be simultaneous between injection 410 and plasma treatment 412. Alternatively, as illustrated by the dotted line in figure 3B, these impulses can be shifted in time.

[0104] Note that this example of plasma pulses and / or pulses during precursor injection can be applied to the injection of a precursor based on a second metal 413a. This can apply to only some of the 410, 413a injections or to each 410, 413a injection of a cycle 41.

[0105] Preferably, the plasma treatment 412 and the injection of a precursor 410, 413a are each performed by simultaneous or sequential pulses. By "sequential," we mean that the pulses are not completely simultaneous between the injection and the plasma treatment, and preferably, the pulses do not overlap temporally between the injection and the plasma treatment. This allows for in-situ reduction of the precursor either in the gas phase or at the level of the adsorbates on the exposed layer 20 of the substrate 2. The duration of the pulses can be substantially identical between the injection 410, 413a and the plasma treatment 412, or these durations can be independent. This mode is self-limiting with respect to the phase shift between the precursor pulse and the plasma treatment. Since the metallic precursor does not react with itself, once the substrate surface is saturated by the adsorbates, no further reaction can occur.Plasma treatment reduces the ligands of the adsorbates, and a new pulse of metallic precursor can generate new adsorbates by releasing anchoring sites. The pulse durations for precursor injection and plasma treatment can be adapted as needed, particularly depending on the expansion of the precursor upon entering the chamber. For example, the precursor injection time can be ≤1 s of opening, and the plasma duration can be ≤20 s.

[0106] Preferably, when a metal-based precursor is pulsed, the precursor comprises the metal and alkyl ligands. The ligand is preferably halogen-free, as a halogenated ligand can potentially damage the reactor walls by forming a corrosive chemical reaction. Furthermore, since halogens are highly electronegative, they strengthen the metal-halogen bond, making the formation of dangling bonds even more difficult.

[0107] For example, as illustrated by the figures 3C and 3D An injection of a precursor based on a metal 410,413a can be followed by plasma treatment 412. This can apply to the injection of the precursor based on the first metal 410, as illustrated by the figure 3C , and / or for the injection of the precursor based on a second metal 413a as illustrated by the 3D figure .

[0108] As illustrated by the figure 3E, when cycle 41 includes several injections of precursor based on a metal 410, 413a, each injection can be made simultaneously with a plasma treatment 412, an injection and the associated plasma treatment 412 being separated from the injection 413a and the subsequent plasma treatment 412 by a purge phase 414.

[0109] Note that combinations of these examples are possible, for example an injection of a precursor based on a first metal 410 simultaneously with a plasma treatment 412, followed by an injection of a precursor based on a second metal 413a itself followed by a plasma treatment 412.

[0110] According to one example, plasma treatment 412 may include an injection of argon mixed with dihydrogen into the reaction chamber 10, for example when plasma treatment 412 follows the injection of a precursor based on a first metal as illustrated in figure 3CWhen the plasma is generated, the plasma treatment 412 may not include the injection of hydrogen into the reaction chamber 10. Indeed, during the development of the invention, it was demonstrated that it was not necessary to inject a reducing gas such as hydrogen into the chamber to reduce the deposited metal. The properties of the plasma generated by capacitive coupling, combined with the injection of the metallic precursor(s), are sufficient to grow a metallic layer on the exposed surface 20 of the substrate 2. This is particularly the case when the injection 410, 413a and the plasma treatment 412 are simultaneous, and especially when the metallic precursor contains alkyl-type ligands. When the plasma treatment 412 and / or the injection of a precursor 410, 413a are performed by pulse, the plasma treatment preferably includes an injection of dihydrogen into the reaction chamber 10.In simultaneous injection, it is best to avoid a reactive plasma (e.g., H₂-based) as this risks destroying the precursor and resulting in CVD-type growth (i.e., non-layer-by-layer growth, because it is not self-limiting). In sequential injection, a reactive plasma can be used, as only the adsorbate ligands will be treated by this plasma.

[0111] Regarding the plasma generation parameters for metal layer growth, these parameters are preferably chosen to modify and / or eliminate precursor ligands to promote metal-on-metal adsorption deposition of the layer. To this end, the radiofrequency polarization power can be less than or equal to 80 W, the pressure in the reaction chamber 10 can be less than or equal to 80 mTorr, and the plasma treatment time during a cycle 41 can be less than or equal to one minute. The depositional dose is thus limited, which improves ligand removal without risking the removal of the deposited metal.

[0112] Regarding the nature of the metal, this process is particularly suitable for depositing titanium, tantalum, aluminum, silver, zinc, ruthenium, platinum, and copper.

[0113] The precursor based on the first metal and the precursor based on the second metal are preferably organometallic precursors specifically designed for ALD processes. The process can be adapted depending on the metallic precursor. For example, for a chlorinated metallic precursor, a N₂ / H₂ plasma is preferred. For an organometallic precursor, an inert plasma, particularly an Ar plasma, is preferred to remove the organic ligand.

[0114] Examples of deposits are now described, with reference to figures 4A to 4C .

[0115] To deposit a layer of oxide, nitride, and / or sulfide of a metal onto the exposed surface 20, the process includes injecting a metal-based precursor 410 and injecting a precursor comprising at least one of the elements oxygen, nitrogen, and sulfur 413b. Preferably, in a cycle 41, the injection of the oxygen, nitrogen, and / or sulfur-based precursor 413b follows the injection of the metal-based precursor 410. The plasma treatment 412 can be carried out before and / or simultaneously with and / or after the injection of the oxygen, nitrogen, and / or sulfur-based precursor 413b. Thus, the quantity and reactivity of the oxygen, nitrogen, and / or sulfur-based precursor are limited so as to modulate the surface reactivity before the injection of the metal-based precursor 410 in the subsequent cycle 41.Depending on the relative order between plasma treatment 412 and the injection of the oxygen, nitrogen and / or sulfur-based precursor 413b, this precursor may be designated by the term "thermal reactant" when plasma treatment 412 follows injection 413b, or "plasma reactant" when plasma treatment 412 is simultaneous with injection 413b.

[0116] As illustrated by the figure 4A For example, the injection of the metal-based precursor 410 can be followed by the injection of the oxygen-, nitrogen-, and / or sulfur-based precursor 413b, itself followed by plasma treatment 412. According to this example, the oxygen-, nitrogen-, and / or sulfur-based precursor can be selected from the group consisting of H₂O, O₂, NH₃, or O₃ with an ozonator. The metal precursor can be heat-treated with the second precursor before plasma treatment 412. The plasma treatment 412 can be argon-based.

[0117] According to a second example, for example illustrated by the figure 4B The injection of the metal-based precursor 410 can be followed by the injection of the oxygen-, nitrogen-, and / or sulfur-based precursor 413b, itself performed simultaneously with the plasma treatment 412. According to this example, the oxygen-, nitrogen-, and / or sulfur-based precursor can be chosen from the group consisting of O₂, N₂, NH₃, and H₂S. The H₂O and O₃ precursors are not used by non-plasmagen. In the case of H₂S, simultaneous plasma treatment is necessary to activate the reaction energy. A layer of metal oxide, nitride, or sulfide, respectively, is therefore preferably deposited when the injection of the second precursor 413b is simultaneous with the plasma treatment 412. The oxygen-, nitrogen-, and / or sulfur-based precursor 413b can be injected with argon.

[0118] According to a third example, illustrated by the figure 4C, the injection of the metal-based precursor 410 can be followed by the plasma treatment 412, the latter being followed by the injection of the oxygen- and / or nitrogen-based precursor, and / or sulfur-based precursor in the case where a plasma treatment is also done simultaneously with the sulfur injection 413b.

[0119] The two plasma treatment regimes 412 described above can be used for the deposition of an oxide, nitride, and / or sulfide layer. As a first example, the radiofrequency polarization power can be less than or equal to 80 W, the pressure in the reaction chamber can be less than or equal to 80 mTorr, and the plasma treatment duration during a deposition cycle can be less than or equal to 1 minute. These parameters allow for manipulation of the surface reactivity between the metal-based precursor, the oxygen, nitrogen, and / or sulfur-based precursor (thermal or plasma reactant), and the plasma radicals.

[0120] In a second example, the radiofrequency polarization power can be greater than or equal to 50 W, the pressure in the reaction chamber can be less than or equal to 20 mTorr, and the plasma treatment time during a deposition cycle can be greater than or equal to 1 minute. Thus, here again, the chemisorbed precursor on the surface can be removed. The deposited material can then grow on localized portions of the layers. These conditions therefore allow for selective deposition, for example, on 3D substrates.

[0121] As an example, a metal-based precursor comprises the metal and an amine group. In the case of an amine precursor, adjusting the dose (duration and energy of the ion flux) by adjusting the plasma parameters allows the ligand to be desorbed from the metal in order to deposit the metal atomic layer, and also breaks the ligand's NC bond to facilitate nitride deposition. For example, the precursor might have one of the chemical formulas below.

[0122] Examples of reactor 1 are now described with reference to figures 5 to 8 Plasma treatment parameters 412 are further described.

[0123] Reactor 1 is more specifically designed for plasma-assisted atomic layer deposition.

[0124] The reactor 1 comprises a reaction chamber 10 intended to hold a substrate 2 and in which the deposition is intended to take place. This chamber 10 is delimited by one or more side walls 100, a top wall 101 and a bottom wall 102.

[0125] To deposit a layer onto the substrate 2, reactor 1 includes means for supplying and discharging gaseous precursor(s) and / or gaseous species for plasma formation. Reactor 1 includes a gaseous precursor inlet 12 configured to deliver gaseous precursors into chamber 10, as illustrated by the arrow at the top of the reactor in the figures 5 to 8The inlet of the gaseous precursor 12 can also be configured to introduce gases into chamber 10 for plasma formation, for example, noble gases such as helium or argon. Reactor 1 further includes a pumping module 13 for chamber 10. The pumping module 13 allows the gaseous species present in the chamber to be evacuated, as illustrated by the two arrows at the bottom of the reactor in the figures 5 to 8 These species can be removed between different cycles of the ALD storage facility. The pumping module 13, in conjunction with the inlet 12, also allows a given pressure to be maintained inside the chamber 10, typically lower than atmospheric pressure.

[0126] The substrate 2 is received in the reaction chamber 10 by a sample holder 11. The sample holder may include a platform 110 configured to receive the substrate 2, connected to an arm 111. The platform 110 may, in particular, have a flat upper face 110a supporting the substrate 2. The upper face 110a is, for example, substantially horizontal. Note that the platform 110 may have other inclined faces, for example, at the edges or a rounded lower face.

[0127] Reactor 1 is configured so that a plasma is generated by capacitive coupling between the upper face 110a of the platform 110 and the side wall 100, which is polarized to ground as illustrated in the figures 5 to 8For this purpose, the platform 110 is electrically conductive. The platform 110 may be at least partially made of an electrically conductive material. The side wall 100 is at least partially electrically conductive. The side wall 100 may be at least partially made of an electrically conductive material. The reactor 1 further includes a power source 14 configured to apply radio frequency power to the platform 110. The power source 14 may, for example, include a radio frequency power generator 142 connected to a radio frequency transmission device 140 to the platform 110.

[0128] This power source 14 may include a regulating device 141 and induces an RF voltage, also called a self-biasing voltage, on the platform 110 to generate the CCP plasma. Preferably, this regulating device 141 includes an auto-matching unit that matches the impedance of the plasma in the chamber 10 to that of the radio frequency power generator 142 in order to minimize reflected power and allow self-sustaining discharge. This power source 14 is configured to generate the plasma and allow self-biasing of the platform 110. In effect, the plasma is powered, and the matching unit (or equivalently, a matching network) matches the impedance to minimize reflected power and allow self-sustaining discharge.Plasma is an electrical discharge with its own impedance, which depends on its degree of ionization and the gas chemistry, as well as the geometric parameters of the reactor and the power supply. The self-polarization voltage can typically range from 50 V to 300 V for a power output varying from 10 W to 100 W in a reactor accepting substrates with a maximum diameter of 200 mm. The control device 141 may include an attenuator configured to limit the power output of the generator 142.

[0129] The side wall 100 is at least partially non-parallel to the upper face 110a of the platform 110. The upper face 110a of the platform 110 and the side wall 100, at least in the portion not parallel to the upper face of the platform, are separated by a distance d configured to generate a plasma by capacitive coupling between the platform 110 and the side wall 100, each acting as an electrode for plasma generation. During the development of the invention, it was indeed demonstrated that a non-parallel arrangement of the side wall 100 and the upper face 110a, coupled at a certain distance d, made it possible to generate the plasma by capacitive coupling near the substrate 2, at the level of a plasma generation zone 3.

[0130] The plasma is thus generated in a localized manner in the vicinity of substrate 2 (3) with a much lower ion flux than in a conventional CCP reactor. This reactor 1 allows the exploitation of low-energy ion bombardment to improve the material's properties (density, purity, crystalline structure, internal stress). Furthermore, as previously discussed in reference to process 4, this opens new avenues for developing processes for metals, oxides, nitrides, and sulfides on 2D and 3D substrates, as well as for selective surface and topographic deposition processes. This reactor 1 therefore enables the deposition of a variety of materials, unlike existing reactors which are more limited. This plasma generation method allows for the deposition of metallic layers, particularly transition metals and / or rare earth elements.Deposits of oxide, nitride and / or sulfide layers are also possible, including transition metals and / or rare earth elements.

[0131] The distance d allowing the self-sustaining of the plasma discharge is dictated by Paschen's law, a function of the pressure P in the reactor, and the minimum average voltage U min of RF self-polarization: U min = Pd We understand therefore that the distance d can vary according to the pressure P in chamber 10 and the minimum average voltage U min imposed by the power source 14.

[0132] This distance d is the shortest distance between the two electrodes formed by the platform 110 and the side wall 100. This distance can, for example, be the distance between one or both end edges of the platform 110 and the side wall 100, and more particularly between one or both end edges of the upper face 110a of the platform 110 and the side wall 100, preferably between an upper face of the platform 110 and the side wall 100, and more particularly between one or both end edges of the upper face 110a of the platform 110 and the side wall 100. During plasma generation, the platform 110 and the side wall 100 are separated from each other by the distance d.

[0133] As an example, the distance d between the upper face 110a of the plate 110 and the side wall 100 is between 5 cm and 15 cm, preferably between 5 cm and 12 cm, and even more preferably between 5 cm and 8 cm. This range of distance d is, for example, valid for a pressure P ≤ 80 mTorr (with 1 mTorr = 10⁻³ Torr and 1 Torr ≈ 133.322 Pa), and Umin (self-polarization voltage) whose absolute value is approximately between 0 V excluded and 300 V [0 V; 300 V], preferably between 50 V and 300 V [50 V; 300 V], and even more preferably between 100 V and 300 V. A sufficiently low ion density, approximately less than or equal to 10¹⁴ cm⁻² .s⁻¹, can thus be obtained.

[0134] For the capacitive coupling ALD deposition according to the invention, the pressures are on the order of mTorr to a few hundred mTorr, for example, 200 mTorr. The radio frequency power typically applied is less than or equal to 100 W, this power being non-zero. The parameters of pressure, self-polarization voltage, and distance are interdependent to obtain plasma generation by capacitive coupling. As will be described in more detail later, it is possible in reactor 1 for d to be fixed, and for the self-polarization voltage and pressure to be adjusted within the corresponding ranges above. Alternatively, the distance d can be adjustable, for example, with means for adjusting the height of the platform 110, as described later.

[0135] Note that the type of gas can influence Paschen's law. This data is tabulated and known to those skilled in the art, as described for argon in C. Torres, PG Reyes, F. Castillo, H. Martinez, Journal of Physics: Conference Series; Bristol Vol. 370, No. 1, (Jun 2012) ). The person skilled in the art will therefore be able to adapt these parameters, for example by adjusting the self-polarization voltage and the pressure, d being fixed, or even in addition by adjusting the distance d, particularly in the aforementioned ranges.

[0136] In order to generate the plasma, the electrically conductive side wall 100 can be at least partly disposed above the platform 110, in projection of said wall onto a plane perpendicular to the upper face 110a of the platform 110. It is therefore understood that at least a part of the wall 100 is disposed opposite the upper face of the platform, so that the plasma by capacitive coupling can be generated between the side wall 100 and the upper face 110a of the platform 110, on which the substrate 2 is placed.

[0137] As an example, the reaction chamber 10, and more specifically the lateral wall 100, exhibits rotational symmetry around a direction parallel to the z-axis and substantially centered with respect to the upper face 110a of the platform 110. This symmetry allows the plasma to be initiated over the entire surface of the upper face 110a of the platform 110. As soon as the plasma is ignited, it propagates over the entire lower electrode (the upper face 110a of the platform 110). The plasma is therefore more homogeneous.

[0138] As an example, the side wall 100 is oriented vertically with respect to the main extension plane (x, y) of the upper face 110a of the platform 110. However, a vertical wall results in very tight field lines at the edges of the substrate, and therefore a more localized (and thus more energetic) plasma. A more localized plasma can generate breakdown phenomena at the edges of the substrate and thus edge effects.

[0139] To limit this, as illustrated by the Figures 5 And 6 The side wall 100 is preferably at least partially angled with respect to the principal extension plane (x, y) of the upper face 110a of the platform 110. Alternatively, the side wall is angled neither parallel nor perpendicular to the principal extension plane (x, y) of the upper face 110a. This angled arrangement improves the plasma obtained by limiting edge effects. The generated plasma is thus made more homogeneous for better layer deposition.

[0140] The side wall 100 can comprise several portions 100a, 100b. A first portion 100a can be arranged substantially perpendicular to the principal extension plane (x, y) of the upper face 110a. A second portion 100b can be arranged obliquely with respect to the principal extension plane (x, y) of the upper face 110a of the plate 110. In the following, it is considered, for the sake of completeness, that portion 100b of the side wall is arranged obliquely with respect to the plane (x, y).

[0141] As illustrated, for example, by the figure 5The second portion 100b of the side wall 100 may have a conical geometry above the platform 110. This geometry can be specifically chosen based on the distance d. The portion 100b may, for example, be in the form of a cone truncated by the upper wall 101. A truncated cone geometry prevents the side wall from forming a depression in which plasma-generated species could accumulate. Preferably, the second portion 100b has a conical geometry with its axis of revolution substantially centered with respect to the platform 110.

[0142] As illustrated, for example, by the figure 6The second portion 100b of the side wall 100 can form a dome over the platform 110. For example, portion 100b can be in the shape of a hemisphere over the platform 110. Again, this geometry can be chosen more specifically based on the distance d. A dome-shaped geometry, and more particularly a hemispherical one, allows for a smaller chamber volume (therefore less reagent consumed, easier chamber pumping, and reduced dead volume in the chamber). Preferably, the second portion 100b has a hemispherical geometry, preferably centered approximately with respect to the platform 110. The dome can be truncated by the upper wall 101. Alternatively, the side wall 100 can form a non-truncated dome.

[0143] We understand, for example with reference to the dome geometry described above, that the side wall 100 can extend so as to form all or part of the upper wall 101.

[0144] As an example, the platform 110 may be fixed in height within chamber 10. Equivalently, the platform 110 may be fixed, at least in the vertical direction z, within chamber 10. However, the platform 110 may be configured to be mobile, for example, by rotating, at a fixed height within chamber 10, for example, to improve the uniformity of the deposition. This rotation may be around the axis of its arm 111. Alternatively, the platform 110 may be completely fixed within chamber 10. In particular, when the platform 110 is fixed in height, the geometry of the side wall 110 can be adapted relative to the sample holder to obtain the distance d required for plasma generation. The reactor 1 can thus have a simplified configuration, and therefore be less expensive.

[0145] According to another example, the 110 tray can be height-adjustable in chamber 10, as illustrated by the double vertical arrow in the figures 5 to 8 Equivalently, the platform 110 can be movable at least along the vertical z-direction within the chamber 10. Thus, the distance d can be adjusted by the height of the platform 110, for example, for different pressure or minimum voltage values ​​Umin, as required. Furthermore, the plasma properties can be modulated by adjusting the height of the platform 110 while ensuring that the plasma 3 is not extinguished. Height adjustment of the platform 110 can be particularly advantageous when the reactor 1 includes an additional plasma source, as described in more detail later. The platform 110 can also be configured to be movable, for example, by rotation, to improve the uniformity of the deposition. This rotation can again be around the axis of its arm 111.

[0146] The movement(s) of the plate 110 can, for example, be operated by a motor, not shown in the figures.

[0147] As described, for example, by the Figures 5 And 6 Reactor 1 can be configured to generate only plasma through capacitive coupling between plate 110 and side wall 100 in the reaction chamber. The plasma can be generated between only two electrodes. Plate 110 can be one of the electrodes, and side wall 100 can be the other. Reactor 1 can therefore consist solely of the capacitive coupling between plate 110 and side wall 100 as the plasma source. This simplifies the configuration of reactor 1 and makes it less expensive. Note that the height of plate 110 can be adjusted in this example.

[0148] As illustrated, for example, by the figure 7The reactor 1 may include an inductively coupled plasma source 15 located away from the chamber 10. Therefore, the reactor 1 can be a multimode ICP and / or CCP reactor. Depending on the requirements, the plasma can be generated in ICP mode and / or CCP mode. For this purpose, the reactor 1 may include a radio frequency inductive source comprising a coil 15 powered by a radio frequency power generation device 16. The power source 14 and the inductive source 15, 16 are configured so that the RF power applied to the platform 110 is independent of the RF power of the inductive source.

[0149] When reactor 1 operates in CCP mode, plasma generation occurs through capacitive coupling between the upper face 110a of the platform 110 and the side wall 100, as described previously. When reactor 1 operates in ICP mode, plasma generation is performed by the inductively coupled plasma source 15. The power source 14 can then be used as a biasing device configured to induce a bias voltage at the substrate 2, enabling the extraction of ions from the remote plasma with controlled incident energy as they arrive in the vicinity of the substrate 2.

[0150] The inlet for the gaseous precursors 12 can be located at the inductive source 15, 16. The inductive source 15, 16 can be isolated from the chamber 10 by a valve 120 having an open configuration allowing the passage of plasma species from the source to the chamber 10, and a closed configuration blocking these species. Note that another inlet for the gaseous precursors can be located directly at the chamber 10, without passing through the inductive source.

[0151] Preferably, when reactor 1 can include an inductively coupled plasma source 15 located away from chamber 10, the platform 110 is height-adjustable. Thus, depending on the distance d obtained between the platform 110 and the side wall 100, plasma can be generated by the inductive source 15, 16 alone, or by both the inductive source 15, 16 and the capacitive coupling between the platform 110 and the side wall 100. Note that height adjustment of the platform 110 is possible in this example.

[0152] As illustrated, for example, by figure 8 The reactor 1 may further include a module 17 for determining the thickness of the deposited layer. This module 17 may, for example, include an ellipsometer coupled to the reactor 1, for example to its lateral wall 100. figure 8is a representation in principle. In practice, the two points of intersection of the emitted and reflected rays intersect on the surface of the substrate where growth takes place.

[0153] Examples of operating parameters of reactor 1 are now described.

[0154] The RF power and pressure conditions in chamber 10 allow for fine-tuning of the plasma ion flux characteristics.

[0155] The gaseous precursor inlet 12 and the pumping module 13 can be configured to maintain, at least during plasma treatment 412, a pressure substantially between 5 and 200 mTorr, preferably between 5 and 100 mTorr, and preferably between 5 and 80 mTorr in the reaction chamber 10. Preferably, the pressure in the reaction chamber is substantially less than or equal to 100 mTorr at least during plasma treatment 412.

[0156] Power source 14 can be configured to apply radio frequency power with a power less than or equal to 100 W.

[0157] The power source 14 can be configured to apply radio frequency power with a frequency between 2 and 100 MHz when plasma is generated by capacitive coupling.

[0158] Note that when the reactor includes an inductively coupled plasma source 15, and operates in ICP mode, the power source acting as a biasing device configured to induce a bias voltage to the substrate 2 can operate at a higher power and / or at a frequency other than the range specified above.

[0159] These parameters within the ranges indicated above allow us to obtain the following ionic flux characteristics of the plasma generated between the side wall 100 and the platform 110, suitable for PEALD deposition: power density: 0.05 to 0.5 W / cm 2< ionic flux: 10 12< to 10 14< ions / (cm 2< .s) ion energy: 0 to 300 eV (with 1 eV ≈ 1.60218.10 -19< J).

[0160] The following table describes examples of plasma generation parameters according to the invention, for an Argon plasma, without a remote ICP source. The distance d corresponding to these measurements is between 5 and 6 cm. Table 1 Gas Ar Ar Ar Ar Ar Ar Ar Ar Ar Ar Flow (sccm) or cm³ (standard / min) 60 60 60 60 60 60 60 60 60 60 Pressure (mTorr) 7 7 7 7 7 7 7 7 7 7 Power applied RF (W) 1 2 3 5 7 8 9 10 70 80 Vdc sond (V) 0 0 0 0 0 56 61 67 222 253 Vdc flexal (V) 0 0 0 0 0 56 62 68 233 241

[0161] The parameters Vdc probe and flexal define the self-biasing voltage, corresponding to the impedance matching between the plasma and the reactor's matching network. Vdc probe is given by a probe measurement (which determines the ion flux), and Vdc flexal is given directly by the reactor's matching network. The reactor is powered by applied RF power, and the self-biasing voltage remains zero when the plasma is not ignited or self-sustaining. In this case, all the power is stored in the matching network.

[0162] THE figures 9A to 9D describe, for the example parameters in Table 1, the effect of the RF power W CCP applied to the plateau 110 on the ion flux generated 4 (in arbitrary units), at constant pressure P, and as a function of the self-bias voltage U.

[0163] THE Figures 10A to 10Cdescribe, for the example parameters in Table 1, the effect of the pressure P applied to the 110 plate on the flow of generated ions 4 (in arbitrary units), with constant RF power W CCP applied to the 110 plate, and as a function of the self-bias voltage U, and as a function of the ion energy E.

[0164] In light of the preceding description, it is clear that the invention offers an improved plasma-assisted deposition solution. The process is improved, in particular, in terms of the nature of the deposited layer and / or the selectivity of the deposition. The PEALD process allows for better control of ion bombardment, and specifically gentler plasma assistance than existing solutions, thus generating fewer induced defects. Furthermore, it is clear that the invention offers an improved plasma-assisted deposition reactor, which also provides gentler plasma assistance than existing solutions, and therefore generates fewer induced defects.

[0165] The invention is not limited to the embodiments described above and extends to all embodiments covered by the invention. The present invention is not limited to the examples described above. Many other embodiments are possible, for example, by combining features described above, without departing from the scope of the invention. Furthermore, the features described with respect to one aspect of the invention can be combined with another aspect of the invention. In particular, the process may include any step resulting from the implementation of a feature of the reactor, and the reactor may have any feature enabling, for example, a configured element, the implementation of a step of the process.

[0166] In the illustrated examples, the inlet 12 has been shown at the top face 101 of reactor 1. Another arrangement, for example at the side wall 100, is possible. The same applies to the pumping module 13.

Claims

1. Plasma-enhanced atomic layer deposition method (4) comprising: • a supply (40) of a substrate (2) having an exposed surface (20) in a plasma reactor (1), the plasma reactor comprising a reaction chamber (10) delimited by walls (100, 101) and an electrically conductive plate (110) having an upper face (110a) whereon the substrate (2) is disposed, • a plurality of atomic layer deposition cycles (41) on the exposed surface (20) of the substrate (2), each cycle comprising: ∘ an injection into the reaction chamber of a precursor based on a first species (410), ∘ a plasma treatment (412) of the exposed surface (20) of the substrate (2), the method being characterised in that a side wall (100) of the reaction chamber is at least in part non-parallel to the upper face (110a) of the plate (110) and being electrically conductive, and the plasma treatment of the exposed surface (20) of the substrate (2) is a plasma treatment by capacitive coupling between the plate (110) and said side wall (100), by applying a radiofrequency power to the plate (110).

2. Method (4) according to the preceding claim, wherein the plurality of deposition cycles (41) further comprises an injection into the reaction chamber of a precursor based on a second species (413).

3. Method (4) according to any one of the preceding claims, wherein the plasma treatment (412) is performed simultaneously with at least one injection into the reaction chamber of a precursor (410, 413) or following at least one injection into the reaction chamber of a precursor (410, 413).

4. Method (4) according to any one of the preceding claims, wherein the radiofrequency power is less than or equal to 80 W, the pressure at the reaction chamber (10) is less than or equal to 80 mTorr, and the duration of the plasma treatment (412) during a deposition cycle (41) is less than or equal to 1 minute.

5. Method (4) according to any one of the preceding claims, wherein the radiofrequency polarisation power is greater than or equal to 50 W, the pressure in the reaction chamber (10) is less than or equal to 20 mTorr, and the duration of the plasma treatment (412) during a deposition cycle (41) is greater than or equal to 1 minute.

6. Method (4) according to any one of the preceding claims, wherein when the plasma is generated, the plasma treatment (412) comprises the injection into the reaction chamber of a rare gas, preferably argon, optionally in a mixture with H2.

7. Method (4) according to any one of the preceding claims, wherein the plasma treatment (412) being performed simultaneously with and / or after the injection of the precursor based on the first species (410), the first species is based on a metal.

8. Method (4) according to the preceding claim, wherein when the plasma is generated, the plasma treatment (412) is free from dihydrogen injection.

9. Method (4) according to any one of the two preceding claims, wherein the metal has an electronegativity between 1.1 and 2.4.

10. Method (4) according to any one of the three preceding claims, wherein the first species comprises the metal and alkyl, amine, oxygenated or halogenated ligands.

11. Method (4) according to any one of claims 7, 9 and 10, wherein the plasma treatment (412) being performed simultaneously with the injection of the precursor based on the first species (410), the plasma treatment (412) and the injection of said precursor (410) are each performed by simultaneous or sequential pulses between the plasma treatment (412) and the injection of said precursor (410).

12. Method (4) according to any one of claims 2 to 6, wherein, the plasma treatment (412) being performed after the injection of the precursor based on the first species and / or after the injection of the precursor based on the second species, the first species is based on a metal and the second species comprises at least one among the elements oxygen, nitrogen and sulphur.

13. Method (4) according to the preceding claim, the plasma treatment (412) being performed simultaneously with the injection of the precursor based on the second species (413), the second species is chosen from the group consisting of O2, N2 (optionally in a mixture with H2), NH3, H2S.

14. Method (4) according to claim 12, the plasma treatment (412) being performed after the injection of the precursor based on the second species (413), the second species is chosen from the group consisting of H2O, O2, NH3.

15. Method (4) according to any one of the preceding claims, wherein the plate (110) being configured to be adjusted in height in the reaction chamber (10), the method comprises an adjustment of the height of the plate prior to the plasma treatment (412), preferably prior to the deposition cycle (41).