Plasma-assisted deposition reactor

Abstract

The invention relates to a plasma-assisted deposition reactor (1) comprising a reaction chamber (10) that comprises: a plate (110) having an upper face (110a) for receiving a substrate (2); a gaseous precursor inlet (12) to the chamber (10); a pumping module (13) for the chamber (10); and a power source (14) configured to apply a radio frequency bias to the plate (110), wherein a side wall (100) of the chamber (10) is, at least in part, non-parallel to the upper face (110a) of the plate (110), and the upper face (110a) of the plate (110) and the side wall (100) are separated by a distance d configured to generate a plasma by capacitive coupling between the plate (110) and the side wall (100); the plasma is thus generated in a localised manner in the vicinity of the substrate with a low ion flux.

Description

[0001] "Plasma-enhanced deposition reactor"

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates to the field of plasma deposition reactors. It finds particularly advantageous application in the field of thin film deposition, and more particularly of thin film of controlled thickness, for example for the manufacture of microelectronic devices.

[0004] STATE OF THE ART

[0005] Atomic Layer Deposition (ALD) processes are commonly used to deposit thin layers, for example at thicknesses less than or equal to 100 nm, on 2D or 3D substrates. Generally, ALD deposition is a cyclic process comprising two main steps:

[0006] - an injection of a precursor, typically a metallic precursor,

[0007] - an injection of another precursor, typically a reagent such as an oxygen or nitrogen-based reagent.

[0008] These steps are self-limiting, allowing for the deposition of conformal and uniform layers on the substrate. The energy required for the reaction of the precursors can typically be provided by temperature (this is referred to as thermal ALD). This energy can be provided using plasma assistance (commonly referred to as PEALD, from the English Plasma Enhanced ALD) to improve surface reactivity. This notably allows the working temperature to be reduced, typically to temperatures lower than or equal to 250°C.

[0009] Industrial PEALD reactors mainly use capacitively coupled or inductively coupled plasma sources (respectively commonly referred to as CCP, from the English Capacitively Coupled Plasma, and ICP, from the English Inductively Coupled Plasma). These reactors conventionally comprise a reaction chamber 10', a gaseous precursor inlet 12' configured to bring gaseous precursors into the chamber 10', and a pumping module 13' of the chamber 10'. In a CCP reactor, for example illustrated in FIG. 1A, the plasma is generated 3 typically at pressures of the order of a few Torr between two electrodes 110', 18' with a radiofrequency (RF) power device 16'. The electrodes 110', 18' are arranged parallel to each other and the substrate is deposited between them, an electrode 110' being the plate connected to the ground 110' carrying the substrate 2.In conventional CCP technologies, ion bombardment on the plate is, however, significant. Grids can be added in the inter-electrode space to limit this ion bombardment. In an ICP reactor T, for example illustrated in Figure 1 B, the plasma is generated 3, typically at pressures of the order of 100 mTorr and remotely by a source 15', comprising an RF power device 16', then is brought into the reaction chamber 10' to the substrate 2 by diffusion. The ion bombardment is thus limited.

[0010] Indeed, ion bombardment can generate point or extended defects, such as implantations, displacements of atoms, compressive stress in the growing layer, or even its sputtering.

[0011] However, ion bombardment can be beneficial to modulate surface reactivity and improve deposit properties such as density, morphology, stress, and conformity, particularly on a 3D substrate, provided that the bombardment energy and its ion density are controlled. To this end, some recently developed reactors use ICP plasmas to which additional RF power has been added at the substrate holder, to enable the extraction of ions from the deported plasma with controlled incident energy as they arrive in the vicinity of the substrate. In practice, the materials produced in these reactors are mainly oxides or nitrides, whose physicochemical properties can be optionally modulated by additional polarization to extract ions from the plasma to assist the growth mechanisms. Obtaining other materials remains limited.

[0012] An object of the present invention is therefore to provide an improved plasma-assisted deposition reactor.

[0013] Other objects, features, and advantages of the present invention will become apparent from the following description and accompanying drawings. It is understood that other advantages may be incorporated.

[0014] SUMMARY OF THE INVENTION

[0015] To achieve this objective, according to a first aspect, a plasma-assisted deposition reactor is provided comprising:

[0016] - a reaction chamber delimited by walls and comprising an electrically conductive plate having an upper face intended to receive a substrate,

[0017] - a gaseous precursor inlet configured to bring gaseous precursors into the reaction chamber,

[0018] - a reaction chamber pumping module,

[0019] - a power source configured to apply radiofrequency power to the plate and generate the plasma.

[0020] A side wall of the reaction chamber is at least partially non-parallel to the top face of the tray and is electrically conductive. The top face of the tray and the side wall are separated by a distance configured to generate a plasma by capacitive coupling between the tray and the side wall.

[0021] The radiofrequency power applied to the plate and the distance between the plate and the side wall allow the plasma to be generated by capacitive coupling between these two elements. The plasma thus generated locally in the vicinity of the substrate leads, thanks to the non-parallel configuration of the two electrodes, to a lower energy and ion density than for a conventional CCP reactor, and finely adjustable, in particular according to the RF power and pressure conditions. This greatly limits the damage to the substrate caused by ion bombardment. This lower ion flux is also more finely controllable compared to an ICP reactor with substrate polarization, which allows for a better compromise between induced damage to the substrate and ion bombardment efficiency.Finally, this reactor allows for the deposition of layers of more varied chemistry and microstructures than a conventional ICP reactor with or without substrate polarization.

[0022] According to a second aspect, a method is provided for generating a plasma by capacitive coupling in a reactor comprising:

[0023] - The supply of a reactor according to the first aspect,

[0024] - A supply of gas for the formation of plasma, in the reaction chamber of the reactor,

[0025] - The generation of a plasma by capacitive coupling between the plate and the side wall, the plate and the side wall being separated by a distance d capable of generating a plasma by capacitive coupling between the plate and the side wall, d being the shortest distance between the plate and the side wall, the generation of the plasma comprising the application of radiofrequency power to the plate.

[0026] BRIEF DESCRIPTION OF THE FIGURES

[0027] The aims, objects, as well as the characteristics and advantages of the invention will become more apparent from the detailed description of one embodiment thereof which is illustrated by the following accompanying drawings, in which:

[0028] Figure 1A shows a sectional view of a CCP reactor according to an example of the state of the art.

[0029] Figure 1B shows a sectional view of an ICP reactor according to an example of the state of the art.

[0030] Figure 2 represents a sectional view of the plasma reactor according to an exemplary embodiment, in which the side wall is of conical geometry.

[0031] Figure 3 represents a sectional view of the plasma reactor according to another exemplary embodiment, in which the side wall is of hemispherical geometry.

[0032] Figure 4 represents a sectional view of the plasma reactor according to another exemplary embodiment, coupled to an ICP source.

[0033] Figure 5 represents a sectional view of the plasma reactor illustrated in Figure 2, equipped with an ellipsometer.

[0034] Figures 6A to 6D and 7A to 7C represent graphs of ion fluxes generated by the plasma according to the plasma parameters, respectively at constant power and pressure. The drawings are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily on the scale of practical applications. In particular, the relative dimensions of the substrate and the reactor are not representative of reality.

[0035] DETAILED DESCRIPTION OF THE INVENTION

[0036] Before commencing a detailed review of embodiments of the invention, optional features are set forth below which may optionally be used in combination or alternatively for each aspect of the invention.

[0037] In one example, the reactor is a plasma-assisted atomic layer deposition reactor.

[0038] In one example, the board is polarized to ground.

[0039] According to one example, the reactor is configured to generate a plasma having an ion density substantially less than or equal to 10 14 ions. cm -2 . s -1 This low density plasma, located near the substrate, allows for more precise benefit from ion bombardment.

[0040] According to one example, the distance, and for example the minimum distance, between the upper face of the plate and the side wall is between 5 cm and 15 cm, preferably between 5 cm and 12 cm. This distance range allowing self-sustaining of the 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 polarization: Umin = Pd This makes it possible to obtain an ion density < 10 14 ions. cm -2 . s -1 for very low density plasma, further facilitating the adjustment of plasma characteristics. This also makes it possible to obtain low density plasma without excessively reducing the pressure in the reaction chamber, for pressures in the order of mTorr to a few hundred mTorr, for example 200 mTorr.

[0041] According to one example, the distance d is proportional, and preferably equal, to the ratio of ll / P, P being the pressure in the reactor, and U the average voltage of the radiofrequency polarization applied to the plate, U being greater than or equal to a value Umin of minimum average voltage of radiofrequency self-polarization.

[0042] According to one example, the side wall is at least partly arranged perpendicular to the main extension plane of the upper face of the tray. The side wall is thus substantially vertical.

[0043] According to one example, the side wall is at least partly arranged obliquely relative to the main extension plane of the upper face of the plate. Edge effects are thus avoided and the field lines on the substrate are attenuated compared to a vertical wall.

[0044] According to one example, the side wall is arranged relative to the main extension plane of the upper face of the tray, so as to form an angle of between 15° and 85°, preferably between 30° and 80°. According to one example, and in particular when the side wall has a dome shape, the tangent of the side wall defines an angle, relative to the main extension plane of the upper face of the tray, of between 15° and 85°, preferably between 30° and 80°. The tangent of the side wall may be the tangent at a point on the side wall located in the main extension plane of the upper face of the tray.

[0045] According to one example, the electrically conductive side wall is at least partly arranged above the plate, projecting along a vertical plane, or substantially perpendicular to the upper face of the plate.

[0046] In one example, the side wall has a symmetry of revolution around a direction perpendicular and substantially centered relative to the upper face of the plate. This symmetry allows the plasma to be initiated over the entire surface of the upper face. The plasma is therefore more homogeneous.

[0047] According to one example, the side wall does not have a symmetry of revolution around a direction perpendicular and substantially centered relative to the upper face of the plate. For example, it is possible to provide that the conductive side wall only partially surrounds the plate, in projection in a plane parallel to the main extension plane of the upper face of the plate.

[0048] According to one example, the side wall at least partly forms a cone above the plate, preferably the side wall has a conical geometry with an axis of revolution substantially centered relative to the plate.

[0049] According to one example, the side wall at least partly forms a dome above the tray, preferably the side wall has at least partly a hemispherical geometry, preferably substantially centered relative to the tray.

[0050] In one example, the reactor is configured so that plasma is generated only in the reaction chamber by the power applied to the substrate holder by the power source. Thus, the reactor is of a simplified configuration, and therefore less expensive than that of a conventional PEALD ICP reactor.

[0051] In one example, the reactor is configured so that plasma is generated between only two electrodes and the reactor is configured so that the plate is one of the two electrodes. For comparison, in an ICP reactor, plasma is generated only by one coil supplied with RF power.

[0052] In one example, the reactor is free from an additional ICP plasma type source.

[0053] In one example, the tray is not configured to be height-adjustable in the reaction chamber. This further simplifies the reactor configuration.

[0054] According to one example, the reactor further comprises an inductively coupled plasma source remote from the reaction chamber. The reactor is thus a multi-mode reactor allowing deposition assisted by ICP plasma and / or by the plasma generated between the plate and the side wall, as required. The reactor thus makes it possible to carry out different deposition processes as required.

[0055] When the reactor also includes an inductively coupled plasma source remote from the reaction chamber, the reactor can thus include two independent plasma sources that can be used as desired: the power source for CCP coupling and the inductively coupled plasma source for ICP coupling. The polarization powers applied by these two sources can be adjusted independently.

[0056] In one example, the tray is not configured to be height-adjustable in the reaction chamber.

[0057] According to one example, the tray is configured to be height-adjustable in the reaction chamber. Thus, the distance d can be adjusted by the height of the tray, for example for different pressure or bias voltage values, as required. The reactor therefore gains in versatility. When the reactor also comprises an inductively coupled plasma source remote from the reaction chamber, the height adjustment of the tray also makes it possible to adjust the distance d between the tray and the side wall, which is particularly advantageous for modulating the plasma properties in the vicinity of the substrate. It is thus possible to decouple or couple the two CCP and ICP type plasmas as required.

[0058] According to one example, the gaseous precursor inlet and the pumping module are configured to maintain a pressure substantially between 5 and 200 mTorr, preferably between 5 mTorr and 100 mTorr, preferably between 5 mTorr and 80 mTorr in the reaction chamber, at least when the plasma is generated. These pressures correspond to a high secondary vacuum.

[0059] According to one example, the gaseous precursor inlet 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 the plasma is generated.

[0060] 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.

[0061] According to one example, the power source is configured to apply radio frequency power with a frequency between 2 and 100 MHz, when the plasma is generated by capacitive coupling between the platen and the sidewall.

[0062] According to one example, the power source (for CCP coupling) is configured to apply radiofrequency power with a strictly positive power and less than or equal to 100 W, when the plasma is generated by capacitive coupling between the plate and the side wall. The inductively coupled plasma source remote from the reaction chamber can be configured to apply radiofrequency power with a non-zero power in absolute value between 0 and 300 W.

[0063] The above parameters allow to obtain the following characteristics of plasma ion flux at the plateau by capacitive coupling:

[0064] - power density: 0.05 to 0.5 W / cm2 ,

[0065] - ionic flux: 10 12 at 10 14 ions / (cm 2 .s)

[0066] - ion energy: 0 to 300 eV.

[0067] 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.

[0068] According to one example, the supply of gas for the formation of the plasma, in the reaction chamber of the reactor, is carried out at least in part before the generation of a plasma by capacitive coupling, and preferably continues during the generation of the plasma.

[0069] According to one example, the generation of the plasma further comprises an adjustment of at least two plasma parameters, these parameters comprising the distance d, the pressure P in the reactor, the average voltage U of the radiofrequency polarization applied to the plate, so that:

[0070] - d is proportional, and preferably equal, to the ratio of U / P,

[0071] - U is greater than or equal to a value Umin of minimum average self-polarization voltage.

[0072] According to one example, the reactor tray being configured to be adjusted in height in the reaction chamber, the generation of the plasma comprises an adjustment of the distance d by a height displacement of the tray, so as to reach a distance d allowing the generation of the plasma. It is thus possible to position oneself at a distance not allowing the generation of the plasma, and to move the tray until a plasma is observed.

[0073] According to one example, during plasma generation, the pressure in the reaction chamber is substantially between 5 and 200 mTorr, preferably between 5 mTorr and 100 mTorr. For example, the precursor supply may be configured to reach this pressure prior to plasma generation. The gaseous precursor supply and the pumping module may be configured to maintain this pressure.

[0074] According to one example, a non-zero radio frequency power less than or equal to 100 W is applied to the plate. According to one example, the adjustment of the plasma parameters is carried out during and / or after application of the radio frequency power.

[0075] In one example, the method may include providing a substrate having an exposed surface in the plasma reactor and placing it on the top side of the tray. The method may include treating, for example, depositing, the exposed surface of the substrate during plasma generation.

[0076] In the remainder of the description, the term "on" does not necessarily mean "directly on". Thus, when it is indicated that a part or member A is supported "on" a part or member B, this does not mean that the parts or members A and B are necessarily in direct contact with each other. These parts or members A and B may be either in direct contact or be supported on each other by means of one or more other parts. The same applies to other expressions such as, for example, the expression "A acts on B", which may mean "A acts directly on B" or "A acts on B by means of one or more other parts".

[0077] In this patent application, the term mobile corresponds to a rotational movement or a translational movement or to a combination of movements, for example the combination of a rotation and a translation.

[0078] In the following detailed description, terms such as "horizontal", "vertical", "longitudinal", "transverse", "upper", "lower", "top", "bottom", "front", "rear", "inside", "outside" may be used. These terms must be interpreted relatively in relation to the normal operating position of the reactor. For example, the concepts "horizontal" and "longitudinal" correspond to the main direction of extension of the upper face of the plate.

[0079] We will also use a reference 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 down / up direction corresponds to the z axis.

[0080] A microelectronic device is any type of device made using microelectronics. These devices include, in addition to devices for purely electronic purposes, micromechanical or electromechanical devices (MEMS, NEMS, etc.) as well as optical or optoelectronic devices (MOEMS, LEDs, etc.).

[0081] It may be a device intended to perform an electronic, optical, mechanical, etc. function. It may also be an intermediate product intended solely for the production of another microelectronic device.

[0082] A parameter that is "substantially equal to / greater than / less than" a given value means that this parameter is equal to / greater than / less than the given value, within plus or minus 10% of this value. A parameter that is "substantially between" two given values ​​means that this parameter is at least equal to the smallest given value, within plus or minus 10% of this value, and at most equal to the largest given value, within plus or minus 10% of this value.

[0083] The plasma-assisted deposition reactor 1 is now described according to several exemplary embodiments with reference to figures 2 to 5. The reactor 1 is more particularly intended for plasma-assisted atomic layer deposition.

[0084] The reactor 1 comprises a reaction chamber 10 intended to accommodate a substrate 2 and in which the deposition is intended to be carried out. This chamber 10 is delimited by one or more side walls 100, an upper wall 101 and a lower wall 102.

[0085] To carry out the deposition of a layer on the substrate 2, the reactor 1 comprises means for supplying and removing gaseous precursor(s) and / or gaseous species for the formation of the plasma. The reactor 1 comprises a gaseous precursor inlet 12 configured to bring gaseous precursors into the chamber 10, as illustrated by the arrow at the top of the reactor in FIGS. 2 to 5. The gaseous precursor inlet 12 may further be configured to introduce gases into the chamber 10 for the formation of the plasma, for example rare gases such as helium or argon. The reactor 1 further comprises a pumping module 13 for the chamber 10. The pumping module 13 makes it possible to remove the gaseous species present in the chamber, as illustrated by the two arrows at the bottom of the reactor in FIGS. 2 to 5. These species may in particular be removed between different cycles of the ALD deposition.The pumping module 13 also makes it possible, with the inlet 12, to maintain a given pressure inside the chamber 10, typically lower than atmospheric pressure.

[0086] The substrate 2 is received in the reaction chamber 10 by a sample holder 11. The sample holder may comprise a tray 110 configured to receive the substrate 2, connected to an arm 111. The tray 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 tray 110 may have other inclined faces, for example on the edges or a rounded lower face.

[0087] The reactor 1 is configured so that a plasma is generated by capacitive coupling between the upper face 110a of the plate 110 and the side wall 100, polarized to ground as illustrated in FIGS. 2 to 5. For this, the plate 110 is electrically conductive. The plate 110 may be at least partly formed of an electrically conductive material. The side wall 100 is at least partly electrically conductive. The side wall 100 may be at least partly formed of an electrically conductive material. The reactor 1 further comprises a power source 14 configured to apply radiofrequency power to the plate 110. The power source 14 may for example comprise a radiofrequency power generator 142 connected to a member 140 for transmitting the radiofrequency to the plate 110.

[0088] This power source 14 may comprise a regulation device 141 and makes it possible to induce an RF voltage, also called self-polarization voltage, on the plate 110 to generate the CCP plasma. Preferably, this regulation device 141 comprises an automatic adaptation unit (qualified by its English term “auto match unit”) which adapts the impedance of the plasma in the chamber 10 to that of the radiofrequency power generator 142 so as to minimize the reflected power and allow the self-maintenance of the discharge. This power source 14 is configured to generate the plasma and allow the self-polarization of the plate 110. Indeed, the plasma is supplied with power, and the adaptation unit (or equivalently tuning box) adapts the impedance to minimize the reflected power and allow the self-maintenance of the discharge.Plasma is an electrical discharge having its own impedance depending on its degree of ionization and the chemistry of the gases, as well as the geometric parameters of the reactor and the electrical power supply. The self-polarization voltage can typically be from 50 V to 300 V for a power varying from 10 W to 100 W, in particular in a reactor receiving substrates with a maximum diameter of 200 mm. The regulation device 141 can in particular comprise an attenuator configured to limit the power of the generator 142.

[0089] The side wall 100 is at least partly non-parallel to the upper face 110a of the plate 110. The upper face 110a of the plate 110 and the side wall 100, at least on its part non-parallel to the upper face of the plate, are separated by a distance d configured so as to generate a plasma by capacitive coupling between the plate 110 and the side wall 100, each acting as an electrode for generating the plasma. During the development of the invention, it was in fact 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 a plasma generation zone 3.

[0090] The plasma is thus generated locally in the vicinity 3 of the substrate 2 with a much lower ion flux than for a conventional CCP reactor. This reactor 1 makes it possible to take advantage of low-energy ion bombardment to improve the material properties (density, purity, crystalline structure, internal stress). In addition, it opens new avenues for developing processes concerning metals, oxides, nitrides and sulfides on 2D and 3D substrates, as well as selective surface and topographic deposition processes. This reactor 1 therefore makes it possible to carry out deposits of various types, unlike existing reactors which are more limited. This mode of plasma generation makes it possible to make deposits of metallic layers, in particular of transition metals and / or rare earths. Depositions of oxide, nitride and / or sulfide layers are also possible, in particular of transition metals and / or rare earths.

[0091] The distance d allowing self-maintenance of the plasma discharge is dictated by Paschen's law, a function of the pressure P in the reactor, and the minimum average RF self-polarization voltage Umin: Umin = Pd We therefore understand that the distance d can vary depending on the pressure P in the chamber 10 and the minimum average voltage Umin imposed by the power source 14.

[0092] This distance d is the shortest distance between the two electrodes formed by the plate 110 and the side wall 100. This distance may for example be the distance between one or both end edges of the plate 110 and the side wall 100, preferably between an upper face of the plate 110 and the side wall 100, and more particularly between one or both end edges of the upper face 110a of the plate 110 and the side wall 100. During the generation of the plasma, the plate 110 and the side wall 100 are spaced apart from each other by the distance d.

[0093] According to one 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 and 8 cm. This distance range d is for example valid for a pressure P < 80 mTorr (with 1 mTorr = 10' 3Torr and 1 Torr ~ 133.322 Pa), and Umin (self-polarization voltage) whose absolute value is substantially 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, substantially less than or equal to 10 14 ions. cm -2 . s -1 , can thus be obtained.

[0094] For the deposition of a layer by capacitive coupling according to the invention, the pressures are of the order of mTorr to a few hundred mTorr, for example 200 mTorr. The radiofrequency 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 the generation of a plasma by capacitive coupling. As will be described in more detail later, it is possible in the reactor 1 for d to be fixed, and for the self-polarization voltage and the pressure to be adjusted in corresponding ranges above. Alternatively, the distance d can be adjustable for example with means for adjusting the height of the plate 110, as described later.

[0095] Note that the type of gas can have an influence on Paschen's law. These data are tabulated and known to those skilled in the art, as for example described for argon in C. Torres, R G. Reyes, F. Castillo, H. Martinez, Journal of Physics: Conference Series; Bristol Vol. 370, No. 1, (Jun 2012). Those skilled in the art will therefore know how 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.

[0096] In order to generate the plasma, the electrically conductive side wall 100 may be at least partly arranged above the plate 110, in projection of said wall onto a plane perpendicular to the upper face 110a of the plate 110. It is therefore understood that at least a part of the wall 100 is arranged opposite the upper face of the plate, so that the plasma by capacitive coupling can be generated between the side wall 100 and the upper face 110a of the plate 110, on which the substrate 2 is placed.

[0097] According to one example, the reaction chamber 10 and more particularly the side wall 100 has a symmetry of revolution around a direction parallel to the z axis and substantially centered relative to the upper face 110a of the plate 110. This symmetry allows the plasma to be ignited over the entire surface of the upper face 110a of the plate 110. As soon as the plasma is ignited, it spreads over the entire lower electrode (the upper face 110a of the plate 110). The plasma is therefore more homogeneous.

[0098] According to one example, the side wall 100 is arranged vertically relative to the main extension plane (x, y) of the upper face 110a of the plate 110. A vertical wall, however, generates very tight field lines on the edges of the substrate, and therefore a more localized (and therefore more energetic) plasma. A more localized plasma can generate breakdown phenomena at the edges of the substrate and therefore edge effects.

[0099] To limit this, as illustrated in Figures 2 and 3, the side wall 100 is preferably at least partly arranged obliquely relative to the main extension plane (x, y) of the upper face 110a of the plate 110. Equivalently, the side wall is arranged neither parallel nor perpendicular to the main extension plane (x, y) of the upper face 110a. This oblique arrangement makes it possible in particular to improve the plasma obtained by limiting the edge effects. The plasma generated is thus made more homogeneous for better layer deposition.

[0100] The side wall 100 may comprise several portions 100a, 100b. A first portion 100a may be arranged substantially perpendicular to the main extension plane (x, y) of the upper face 110a. A second portion 100b may be arranged obliquely relative to the main extension plane (x, y) of the upper face 110a of the plate 110. In the following, it is considered, without limitation, that the portion 100b of the side wall is arranged obliquely relative to the plane (x, y).

[0101] As for example illustrated by Figure 2, the second portion 100b of the side wall 100 may have a conical geometry above the plate 110. This geometry may more particularly be chosen as a function of 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 allows the side wall not to form a hollow in which the species generated by the plasma could accumulate. Preferably, the second portion 100b has a conical geometry with an axis of revolution substantially centered relative to the plate 110.

[0102] As for example illustrated by Figure 3, the second portion 100b of the side wall 100 can form a dome above the plate 110. The portion 100b can for example be in the form of a half-sphere above the plate 110. Again, this geometry can more particularly be chosen as a function of the distance d. A dome-shaped geometry, and more particularly a hemispherical geometry, makes it possible to have a smaller chamber volume (therefore fewer reagents consumed, a chamber that is easier to pump, and to limit the dead volume in the chamber. Preferably, the second portion 100b has a hemispherical geometry, preferably substantially centered relative to the plate 110. The dome can be truncated by the upper wall 101. Alternatively, the side wall 100 can form a non-truncated dome.

[0103] It is understood, for example with reference to the dome geometry described above, that the side wall 100 may extend so as to form all or part of the upper wall 101.

[0104] According to one example, the plate 110 may be non-adjustable in height in the chamber 10. Equivalently, the plate 110 may be non-movable at least in the vertical direction z in the chamber 10. However, it may be provided that the plate 110 is configured to be movable, for example in rotation, at the fixed height of the chamber 10, for example to improve the uniformity of the deposition. This rotation may be around the axis of its arm 111. The plate 110 may alternatively be completely fixed in the chamber 10. In particular when the plate 110 is non-adjustable in height, the geometry of the side wall 110 may be adapted relative to the sample holder to obtain the distance d allowing the generation of the plasma. The reactor 1 may thus be of simplified configuration, and therefore less expensive.

[0105] According to another example, the plate 110 may be adjustable in height in the chamber 10, as illustrated by the double vertical arrow in FIGS. 2 to 5. Equivalently, the plate 110 may be movable at least in the vertical direction z in the chamber 10. Thus, the distance d may be adjusted by the height of the plate 110, for example for different values ​​of minimum pressure or voltage Umin, as required. The properties of the plasma may further be modulated by adjusting the height of the plate 110 while ensuring that the plasma 3 is not extinguished. The height adjustment of the plate 110 may further be particularly advantageous when the reactor 1 comprises an additional plasma source, as described in more detail later. Provision may further be made for the plate 110 to be configured to be movable, for example in rotation, for example to improve the uniformity of the deposition. This rotation may here again be around the axis of its arm 111.

[0106] The movement(s) of the plate 110 may for example be actuated by a motor, not shown in the figures.

[0107] As for example described by figures 2 and 3, the reactor 1 can be configured to only form the plasma by capacitive coupling between the plate 110 and the side wall 100 in the reaction chamber. The plasma can in particular be generated between two electrodes only. The plate 110 can constitute one of the electrodes. The side wall 100 can constitute the other electrode. The reactor 1 can only comprise the generation by capacitive coupling between the plate 110 and the side wall 100 as a plasma source. The configuration of the reactor 1 is thus simplified, and therefore less expensive. Note that the adjustment or not in height of the plate 110 is possible according to this example.

[0108] As for example illustrated by Figure 4, the reactor 1 may comprise an inductively coupled plasma source 15 remote from the chamber 10. The reactor 1 may therefore be a multi-mode ICP and / or CCP reactor. Depending on requirements, the plasma may be generated in ICP mode and / or in CCP mode. For this, the reactor 1 may comprise a radiofrequency inductive source comprising a coil 15 powered by a radiofrequency power generation device 16. The power source 14 and the inductive source 15, 16 are configured so that the RF power applied to the plate 110 is independent of the RF power of the inductive source.

[0109] When the reactor 1 operates in CCP mode, the plasma generation occurs by capacitive coupling between the upper face 110a of the plate 110 and the side wall 100 as described previously. When the reactor 1 operates in ICP mode, the plasma generation is done by the inductively coupled plasma source 15. The power source 14 can then be used as a polarization device configured to induce a polarization voltage on the substrate 2 allowing the extraction of the ions from the remote plasma with a controlled incident energy at the moment when they arrive in the vicinity of the substrate 2.

[0110] The arrival of the gaseous precursors 12 can be arranged at the level of 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 for passing the plasma species from the source to the chamber 10, and a closed configuration for blocking these species. Note that it can be provided that another arrival of gaseous precursors is arranged directly at the level of the chamber 10, without passing through the inductive source.

[0111] Preferably, when the reactor 1 can comprise an inductively coupled plasma source 15 remote from the chamber 10, the plate 110 is adjustable in height. Thus, depending on the distance d obtained between the plate 110 and the side wall 100, a plasma can be generated by the inductive source 15, 16 only, or by both the inductive source 15, 16 and the capacitive coupling between the plate 110 and the side wall 100. Note that an adjustment or not in height of the plate 110 is possible according to this example.

[0112] As illustrated for example in Figure 5, the reactor 1 may further comprise a module 17 for determining the thickness of the deposited layer. This module 17 may for example comprise an ellipsometer coupled to the reactor 1, for example to its side wall 100. Figure 5 is a representation of principle. In practice, the two points of intersection of the emitted and reflected rays intersect on the surface of the substrate where the growth takes place.

[0113] Examples of operating parameters of reactor 1 are now described.

[0114] The RF power and pressure conditions in chamber 10 allow for fine tuning of the plasma ion flow characteristics.

[0115] The gaseous precursor inlet 12 and the pumping module 13 may be configured to maintain a pressure substantially between 5 and 200 mTorr, preferably between 5 mTorr and 100 mTorr, preferably between 5 mTorr and 80 mTorr in the reaction chamber 10.

[0116] The power source 14 may be configured to apply the radio frequency bias with a power less than or equal to 100 W.

[0117] The power source 14 may be configured to apply the radio frequency bias with a frequency between 2 and 100 MHz when the plasma is generated by capacitive coupling.

[0118] Note that when the reactor comprises an inductively coupled plasma source 15, and operates in ICP mode, the power source acting as a polarization device configured to induce a polarization voltage to the substrate 2 can operate at a higher power and / or at a frequency other than the range specified above.

[0119] These parameters in the ranges indicated above allow to obtain the following ionic flux characteristics of the plasma generated by capacitive coupling, suitable for PEALD deposition:

[0120] - power density: 0.05 to 0.5 W / cm 2

[0121] - ionic flux: 10 12 at 10 14 ions / (cm 2 .s)

[0122] - ion energy: 0 to 300 eV (with 1 eV ~ 1, 60218.10' 19 J).

[0123] 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.

[0124] Table 1

[0125] The Vdc probe and flexal parameters give the self-polarization voltage, corresponding to the impedance matching between the plasma and the reactor tuning box. Vdc probe is given by a probe measurement (which allows the ion flux to be determined) and Vdc flexal is given directly by the reactor tuning box. The reactor is supplied with applied RF power and the self-polarization voltage remains zero when the plasma does not ignite or self-sustain. In this case, all the power is stored in the tuning box.

[0126] Figures 6A to 6D describe, for the example parameters of Table 1, the effect of the WCCP RF power applied to the plate 110 on the generated ion flux 4 (in arbitrary unit), at constant pressure P, and as a function of the self-polarization voltage U.

[0127] Figures 7A to 7C describe, for the example parameters of Table 1, the effect of the pressure P on the generated ion flux 4 (in arbitrary unit), at constant RF power WCCP applied to the plate 110, and as a function of the self-polarization voltage U, and the ion energy E. In view of the preceding description, it appears clearly that the invention proposes an improved plasma-assisted deposition reactor, allowing in particular a gentler plasma assistance than existing solutions, and therefore which generates fewer induced defects.

[0128] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention. The present invention is not limited to the examples previously described. Many other variant embodiments are possible, for example by combining previously described characteristics, without departing from the scope of the invention. In the examples illustrated, the inlet 12 has been shown at the upper face 101 of the reactor 1. Another arrangement, for example at the side wall 100, is possible. The same applies to the pumping module 13.

Claims

DEMANDS 1. A plasma-assisted deposition reactor (1) comprising: a reaction chamber (10) delimited by walls (100, 101, 102, 103) and comprising an electrically conductive tray (110) having an upper face (110a) for receiving a substrate (2), a gaseous precursor inlet (12) configured to deliver gaseous precursors into the reaction chamber (10), a pumping module (13) for the reaction chamber (10), a power source (14) configured to apply radio frequency power to the tray (110) and generate the plasma, wherein a side wall (100) of the reaction chamber (10) is at least partially non-parallel to the upper face (110a) of the tray (110) and is electrically conductive, the reactor being characterized in that said side wall (100) is at least partially disposed above the tray (110), projecting said wall onto a perpendicular plane on the upper surface of the tray,the platform (110) is polarized to ground, and in that the upper face (110a) of the platform (110) and said side wall (100) are separated by a distance d configured so as to generate a plasma by capacitive coupling between the platform (110) and said side wall (100), d being the shortest distance between the platform (110) and said side wall (100).

2. Reactor (1) according to the preceding claim, in which the distance d is proportional to the ratio of ll / P, P being the pressure in the reactor (1), and U the average voltage of the radio frequency polarization applied to the platform (110), U being greater than or equal to a value Umin of minimum average voltage of radio frequency self-polarization.

3. Reactor (1) according to any one of the preceding claims, wherein the distance d between the upper face (110a) of the platform (110) and the side wall (100) is between 5 cm and 15 cm.

4. Reactor (1) according to any one of the preceding claims, wherein said side wall (100) is at least partly disposed obliquely with respect to the main extension plane of the upper face (110a) of the platform (110).

5. Reactor (1) according to the preceding claim, in which said side wall (100) forms at least in part a cone above the plate (110), preferably said side wall (100) has a conical geometry with axis of revolution substantially centered with respect to the plate (110). Reactor (1) according to claim 4, wherein the side wall (100) forms at least partially a dome over the platform (110), preferably said side wall (100) having at least partially a hemispherical geometry, preferably substantially centered with respect to the platform (110). Reactor (1) according to any one of the preceding claims, configured such that the plasma is generated only in the reaction chamber (10). Reactor (1) according to the preceding claim, configured such that the plasma is generated only between two electrodes and the reactor is configured such that the platform (110) constitutes one of the two electrodes. Reactor (1) according to any one of claims 1 to 6, reactor (1) further comprising an inductively coupled plasma source (15) located away from the reaction chamber (10).A reactor according to any one of the preceding claims, wherein the tray (110) is not configured to be height-adjustable in the reaction chamber (10). A reactor (1) according to any one of claims 1 to 9, wherein the tray (110) is configured to be height-adjustable in the reaction chamber (10). A reactor (1) according to any one of the preceding claims, wherein the gaseous precursor inlet (12) and the pumping module (13) are configured to maintain a pressure substantially between 5 and 200 mTorr, preferably between 5 and 100 mTorr, preferably between 5 and 80 mTorr in the reaction chamber (10).A reactor (1) according to any one of the preceding claims, wherein the power source (14) is configured to apply radio frequency power with a frequency between 2 and 100 MHz when the plasma is generated by capacitive coupling between the tray (110) and the side wall (100). A reactor (1) according to any one of the preceding claims, wherein the power source (14) is configured to apply radio frequency power with a power less than or equal to 100 W, when the plasma is generated by capacitive coupling between the tray and the side wall. A reactor (1) according to any one of the preceding claims, wherein the power source (14) includes an attenuator configured to limit the power of the radio frequency polarization. A method for generating a plasma by capacitive coupling in a reactor comprising: The supply of a reactor (1) according to any one of the preceding claims, A supply of gas for the formation of plasma in the reaction chamber (10) of the reactor, The generation of a plasma by capacitive coupling between the platform (110) and the electrically conductive side wall (100), the platform (110) and said side wall (100) being separated by a distance d suitable for generating a plasma by capacitive coupling between the platform (110) and the side wall (100), d being the shortest distance between the platform (110) and said side wall (100), the generation of the plasma comprising the application of radiofrequency power to the platform. Method according to the preceding claim, wherein the generation of the plasma further comprises an adjustment of at least two plasma parameters, these parameters comprising the distance d, the pressure P in the reactor (1), the average voltage U of the radiofrequency polarization applied to the platform (110), such that: d is proportional to the ratio of U / P, U is greater than or equal to a minimum average radiofrequency self-polarization voltage value Umin. A method according to any one of the two preceding claims, wherein, the reactor (110) platform (1) being configured to be height-adjustable within the reaction chamber (10), plasma generation comprises adjusting the distance d by a height displacement of the platform, so as to achieve a distance d enabling plasma generation. A method according to any one of the three preceding claims, wherein, during plasma generation, the pressure in the reaction chamber (10) is substantially between 5 and 200 mTorr, preferably between 5 mTorr and 100 mTorr, preferably between 5 mTorr and 80 mTorr.

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