Plasma Enhanced Deposition Reactor

Abstract

The present invention relates to a plasma enhanced deposition reactor (1), comprising a reaction chamber (10) including a plate (110) having a top surface (110a) for receiving a substrate (2), a gas precursor inlet (12) in the chamber (10), a pumping module (13) of the chamber (10), and a power supply (14) configured to apply a radio frequency bias to the plate (110), wherein a sidewall (100) of the chamber (10) is at least partially non-parallel to the top surface (110a) of the plate (110), and the top surface (110a) of the plate (110) and the sidewall (100) are separated by a distance d configured to generate a plasma by capacitive coupling between the plate (110) and the sidewall (100), such that the plasma is generated locally in the vicinity of the substrate with low ion flux.

Description

[Technical field]

[0001] The present invention relates to the field of plasma deposition reactors. The present invention finds particularly advantageous applications in the field of thin layer deposition, more particularly in the field of thin layers having controlled thicknesses, for example for the manufacture of microelectronic devices. [Background technology]

[0002] Atomic layer deposition (commonly referred to as ALD) is a widely used method for depositing thin layers, e.g. with thicknesses below 100 nm, on 2D or 3D substrates. In general, ALD deposition is a cyclical method that includes two main steps: - injection of a precursor, typically a metal precursor, - Injection of another precursor, typically a reagent such as an oxygen or nitrogen based reagent.

[0003] These steps are self-limiting, making it possible to deposit conformal and uniform layers on the substrate. The energy required for the reaction of the precursors can typically be provided by temperature (this is called Thermal ALD). This energy can be provided by using plasma enhancement (commonly called PEALD, Plasma Enhanced ALD) to improve the surface reactivity. This allows, among other things, to reduce the operating temperature, typically to temperatures below 250°C.

[0004] Industrial PEALD reactors mainly use capacitively or inductively coupled plasma sources (commonly called CCP for Capacitively Coupled Plasma and ICP for Inductively Coupled Plasma, respectively). These reactors conventionally comprise a reaction chamber 10', a gas precursor inlet 12' configured to supply gas precursors to the chamber 10', and a pumping module 13' for the chamber 10'. For example, in a CCP reactor 1' shown in FIG. 1A, a plasma is generated by a radio frequency (RF) power unit 16' between two electrodes 110', 18', typically at a pressure in the range of several Torr. The electrodes 110', 18' are arranged parallel to each other facing each other, between which the substrate is deposited, and the electrode 110' is a plate connected to ground 110' carrying the substrate 2. However, in conventional CCP techniques, ion bombardment on the plate is significant. A grid can be added to the interelectrode space to limit this ion bombardment. For example, in the ICP reactor 1' shown in Figure 1B, the plasma 3 is generated remotely by a source 15' including an RF power unit 16', typically at a pressure in the range of 100 mTorr, and then brought to the substrate 2 in the reaction chamber 10' by diffusion. Thus, ion bombardment is limited.

[0005] Indeed, ion bombardment can generate point or extended defects such as implantation, atomic displacement, compressive stress in the grown layer, and even sputtering.

[0006] However, ion bombardment can be beneficial to modulate the surface reactivity and improve deposition properties such as density, morphology, stress, conformity, especially on 3D substrates, if the energy of this bombardment and its ion density are controlled. For this purpose, some recently developed reactors use ICP plasmas to which an additional RF power is applied at the substrate holder, making it possible to extract ions from a remote plasma with a controlled incident energy when 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 arbitrarily modulated by an additional bias that makes it possible to extract ions from the plasma, so that they support the growth mechanism. The availability of other materials is still limited. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] C. Torres, PG Reyes, F. Castillo, H. Martinez, Journal of Physics: Conference Series; Bristol Vol. 370, No. 1, (Jun 2012) Summary of the Invention [Problem to be solved by the invention]

[0008] SUMMARY OF THEINVENTION It is therefore an object of the present invention to propose an improved plasma-enhanced deposition reactor.

[0009] Other objects, features and advantages of the present invention will become apparent from a consideration of the following description and the accompanying drawings, and it should be understood that other advantages may be incorporated. [Means for solving the problem]

[0010] To this end, according to a first aspect, there is provided a plasma enhanced deposition reactor comprising: - a reaction chamber bounded by a wall and including a conductive plate having a top surface intended to receive a substrate; - a gas precursor inlet configured to supply a gas precursor to the reaction chamber; - a pump module for the reaction chamber; - a power supply configured to apply radio frequency power to the plate to generate a plasma.

[0011] The sidewall of the reaction chamber is at least partially non-parallel to the top surface of the plate and is electrically conductive, the top surface of the plate and the sidewall being separated by a distance configured to generate a plasma by capacitive coupling between the plate and the sidewall.

[0012] The RF power applied to the plate and the distance between the plate and the sidewall make it possible to generate a plasma by capacitive coupling between these two elements. The plasma thus generated locally in the vicinity of the substrate, thanks to the non-parallel configuration of the two electrodes, has a higher energy and ion density than conventional CCP reactors and is finely adjustable, especially according to the RF power and pressure conditions. This therefore significantly limits the damage to the substrate caused by ion bombardment. This lower ion flux is furthermore more controllable compared to ICP reactors with substrate bias, which allows a better compromise to be achieved between the damage induced in the substrate and the efficiency of the ion bombardment. Finally, the reactor allows the deposition of a wider variety of chemical and microstructural layers than conventional ICP reactors, with or without substrate polarization.

[0013] According to a second aspect, there is provided a method for generating a plasma by capacitive coupling in a reactor, comprising the steps of: - providing a reactor according to a first aspect; - providing a gas for forming a plasma in a reaction chamber of the reactor; generating a plasma by capacitive coupling between a plate and a sidewall, the plate and the sidewall being separated by a distance d that allows plasma to be generated by capacitive coupling between the plate and the sidewall, d being the shortest distance between the plate and the sidewall, and the generating of the plasma including applying high frequency power to the plate. [Brief description of the drawings]

[0014] [Figure 1A] FIG. 1 is a cross-sectional view of a CCP reactor according to an example of the prior art. [Figure 1B] FIG. 1 is a cross-sectional view of an ICP reactor according to an example of the prior art. [Diagram 2] 1 illustrates a cross-sectional view of a plasma reactor according to an exemplary embodiment, where the sidewall is cone-shaped. [Diagram 3] 2 shows a cross-sectional view of a plasma reactor according to another exemplary embodiment, where the sidewall is hemispherically shaped. [Figure 4] FIG. 2 is a cross-sectional view of a plasma reactor according to another exemplary embodiment coupled to an ICP source. [Diagram 5] FIG. 3 is a cross-sectional view of the plasma reactor shown in FIG. 2 with an ellipsometer attached. [Figure 6A] 1 shows a graph of ion flux generated by a plasma according to plasma parameters at constant power and pressure. [Figure 6B] 1 shows a graph of ion flux generated by a plasma according to plasma parameters at constant power and pressure. [Figure 6C] 1 shows a graph of ion flux generated by a plasma according to plasma parameters at constant power and pressure. [Figure 6D] 1 shows a graph of ion flux generated by a plasma according to plasma parameters at constant power and pressure. [Figure 7A] 1 shows a graph of ion flux generated by a plasma according to plasma parameters at constant power and pressure. [Figure 7B]1 shows a graph of ion flux generated by a plasma according to plasma parameters at constant power and pressure. [Figure 7C] 1 shows a graph of ion flux generated by a plasma according to plasma parameters at constant power and pressure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The objects, aims, features and advantages of the present invention will become better apparent from the following detailed description of the latter embodiment, illustrated by the accompanying drawings, in which:

[0016] The drawings are illustrative and not limiting of the invention. They form a schematic representation of the principles intended to facilitate understanding of the invention and are not necessarily plotted to scale in actual applications. In particular, the relative dimensions of the substrate and the reactor do not reflect reality.

[0017] Before commencing a detailed discussion of the embodiments of the present invention, optional features that can be used in any combination or alternatively for each aspect of the invention are described below.

[0018] According to one example, the reactor is a plasma enhanced atomic layer deposition reactor.

[0019] According to one example, the plate is biased to ground.

[0020] According to one example, the reactor is substantially 14 Ions cm -2 ·s -1 It is configured to generate a plasma having an ion density of: This low density plasma located close to the substrate allows for finer utilization of ion bombardment.

[0021] According to one example, the distance between the top surface of the plate and the side wall, e.g. the minimum distance, is between 5 cm and 15 cm, preferably between 5 cm and 12 cm. This distance range that allows self-maintenance of the discharge is determined by Paschen's law, a function of the pressure P in the reactor, and the minimum average voltage U of the RF bias. min Determined by U min = P × d. This gives a 10 14 Ions cm -2 ·s -1 This makes it possible to obtain an ion density of less than 100 mTorr, making it easier to adjust the plasma characteristics. This makes it possible to obtain a low-density plasma without excessively lowering the pressure in the reaction chamber for pressures ranging from mTorr to several hundred mTorr, for example 200 mTorr.

[0022] According to one example, the distance d is proportional to, and preferably equal to, the ratio U / P, where P is the pressure in the reactor, U is the average voltage of the high frequency bias applied to the plate, and U is the value U of the minimum average voltage of the high frequency self-bias. min That's all.

[0023] According to one example, the side walls are at least partially arranged perpendicular to the main extension plane of the upper surface of the plate, so that the side walls are substantially vertical.

[0024] According to one example, the side walls are at least partially arranged obliquely with respect to the main extension of the upper surface of the plate, so that edge effects are avoided and the magnetic field lines on the substrate are attenuated with respect to vertical walls.

[0025] According to one embodiment, the side wall is arranged relative to the main extension of the upper surface of the plate so as to form an angle between 15° and 85°, preferably between 30° and 80°. According to one embodiment, in particular when the side wall has a dome shape, the tangent of the side wall defines an angle between 15° and 85°, preferably between 30° and 80°, relative to the main extension of the upper surface of the plate. The tangent of the side wall may be a tangent to a point of the side wall located in the main extension of the upper surface of the plate.

[0026] According to one example, the conductive sidewall is at least partially disposed above the plate and projects along a vertical plane or substantially perpendicular to the upper surface of the plate.

[0027] According to one example, the sidewall has rotational symmetry about a direction perpendicular to and substantially central to the top surface of the plate, which allows the plasma to be ignited over the entire surface of the top surface, which is therefore more uniform.

[0028] According to one example, the side wall does not have rotational symmetry with respect to a direction perpendicular to and substantially central to the top surface of the plate, for example the conductive side wall may be provided so as to project in a plane parallel to the main extension of the top surface of the plate and to only partially surround the plate.

[0029] According to one example, the side wall at least partially forms a cone above the plate, and preferably the side wall has a conical shape with an axis of rotation substantially centered relative to the plate.

[0030] According to one example, the sidewall at least partially forms a dome over the plate, and preferably the sidewall has an at least partially hemispherical shape and is preferably substantially centrally located with respect to the plate.

[0031] According to one example, the reactor is configured such that plasma is generated only within the reaction chamber by power applied to the substrate holder by the power supply, and thus the reactor is of simplified configuration and less expensive than conventional PEALD ICP reactors.

[0032] According to one example, the reactor is configured such that the plasma is generated only between two electrodes, and the reactor is configured such that the plate serves as one of the two electrodes. By way of comparison, in an ICP reactor, the plasma is generated only by an RF powered coil.

[0033] According to one example, the reactor does not have an additional source of the ICP plasma type.

[0034] According to one example, the plates are not configured to be height adjustable within the reaction chamber, which further simplifies the construction of the reactor.

[0035] According to one example, the reactor further comprises an inductively coupled plasma source remote from the reaction chamber, so that the reactor is a multi-mode reactor allowing deposition enhanced by ICP plasma and / or plasma generated between the plate and the sidewall, as required, so that the reactor allows different deposition methods to be carried out as required.

[0036] If the reactor further comprises an inductively coupled plasma source separate from the reaction chamber, the reactor may comprise two independent plasma sources that can be used as needed: a power supply for CCP coupling and an inductively coupled plasma source for ICP coupling. The bias power applied by these two plasma sources can be adjusted independently.

[0037] According to one example, the plate is not configured to be height adjustable within the reaction chamber.

[0038] According to one example, the plate is configured to be height-adjusted in the reaction chamber. Thus, the distance d can be adjusted by the height of the plate, for example, for different values ​​of bias pressure or voltage, as required. Thus, the versatility of the reactor is improved. If the reactor further comprises an inductively coupled plasma source remote from the reaction chamber, the height adjustment of the plate allows the distance d between the plate and the sidewall to be further adjusted, which is particularly advantageous for adjusting the characteristics of the plasma in the vicinity of the substrate. Thus, it is possible to separate or combine two plasmas of CCP and ICP type, as required.

[0039] According to one example, the gas precursor inlet and pumping module is configured to maintain a pressure in the reaction chamber of substantially 5-200 mTorr, preferably 5-100 mTorr, preferably 5-80 mTorr, at least when the plasma is generated, which pressure corresponds to a high secondary vacuum.

[0040] According to one example, the gas precursor inlet and pumping module is configured to maintain a pressure in the reaction chamber substantially below 200 mTorr, preferably below 100 mTorr, at least when the plasma is generated.

[0041] According to one example, the gas precursor inlet and pumping module is configured to maintain a pressure substantially equal to or greater than 10 mTorr, preferably equal to or greater than 15 mTorr, within the reaction chamber, at least when the plasma is generated.

[0042] According to one example, the power supply is configured to apply radio frequency power having a frequency between 2 and 100 MHz when the plasma is generated by capacitive coupling between the plate and the sidewall.

[0043] According to one example, the power supply (for CCP coupling) is configured to apply a radio frequency power having a strictly positive power of less than or equal to 100 W when the plasma is generated by capacitive coupling between the plate and the sidewall. An inductively coupled plasma source remote from the reaction chamber may be configured to apply a radio frequency power having a non-zero power in absolute value comprised between 0 and 300 W.

[0044] With the above parameters, the following characteristics of the ion flux of the plasma at the plate due to capacitive coupling can be obtained: - Power density: 0.05~0.5W / cm 2 , - Ion flux: 10 12 ~10 14 ions / (cm 2 s), - Ion energy: 0~300eV

[0045] According to one example, the power supply includes an attenuator configured to limit the power of the RF bias of the plasma generated by capacitive coupling.

[0046] According to one example, the supply of gas for the formation of plasma in the reaction chamber of the reactor is at least partially performed prior to the generation of the plasma by capacitive coupling and preferably continues during the generation of the plasma.

[0047] According to one example, generating the plasma further includes adjusting at least two plasma parameters, including the distance d, the pressure P in the reactor, and the average voltage U of the radio frequency bias applied to the plate, such that: - d is proportional to and preferably equal to the ratio U / P, - U is the value of the minimum average self-bias voltage U min That's all.

[0048] According to one example, the reactor plate is configured to be height adjustable within the reaction chamber, and generating the plasma involves adjusting the distance d by displacing the height of the plate to reach a distance d that allows for plasma generation, thereby allowing it to be positioned at a distance where plasma does not generate and displacing the plate until plasma is observed.

[0049] According to one example, during the generation of the plasma, the pressure in the reaction chamber is substantially comprised between 5 and 200 mTorr, preferably between 5 and 100 mTorr. For example, the precursor supply can be configured to reach this pressure before the generation of the plasma. The gas precursor supply and pumping module can be configured to maintain this pressure.

[0050] According to one example, a non-zero radio frequency power of up to 100 W is applied to the plate.

[0051] According to one example, adjustments to the plasma parameters occur during and / or after application of RF power.

[0052] According to one example, the method can include providing a substrate having an exposed surface in a plasma reactor and placing it on top of a plate, The method can include processing, e.g., deposition, on the exposed surface of the substrate during the generation of the plasma.

[0053] In the following description, "over" does not necessarily mean directly above. Thus, when a part or member A is shown to be "over" a part or member B, this does not necessarily mean that the parts or members A and B are in direct contact with each other. These parts or members A and B can be in direct contact or can be in contact with each other through one or more other parts. The same applies to other expressions such as "A acts on B," which can mean "A acts directly on B" or "A acts on B through one or more other parts."

[0054] In this patent application, the term movable corresponds to a rotational or translational movement or a combination of movements, for example a combination of rotation and translation.

[0055] In the following detailed description, the terms "horizontal", "vertical", "longitudinal", "transverse", "upper", "lower", "up", "down", "front", "rear", "inner", "outer" etc. may be used. These terms must be interpreted relatively with reference to the normal operating position of the reactor. For example, the concepts "horizontal" and "vertical" correspond to the main direction of extension of the upper surface of the plates.

[0056] A standard is also used in which the longitudinal or left-right direction corresponds to the x-axis, the horizontal or front-to-back direction corresponds to the y-axis, and the vertical or up-down direction corresponds to the z-axis.

[0057] The term "microelectronic device" refers to any type of device made with microelectronic means. These devices include in particular micromechanical or electromechanical devices (MEMS, NEMS, etc.) as well as optical or optoelectronic devices (MOEMS, LEDs, etc.) in addition to devices for purely electronic purposes.

[0058] This may be an apparatus intended to ensure electronic, optical, mechanical functionality, etc. It may also be an intermediate product intended solely for the manufacture of another microelectronic device.

[0059] A parameter being "substantially equal to / greater than / less than" a given value means that this parameter is equal to / greater than / less than the given value close to this value by ±10%. A parameter being "substantially included between" two given values ​​means that this parameter is at least equal to, and close to, a given minimum value by plus or minus 10%, and at most equal to, and close to, a given maximum value by plus or minus 10%.

[0060] A plasma enhanced deposition reactor 1 will now be described according to some exemplary embodiments with reference to Figures 2 to 5. The reactor 1 is more specifically for plasma enhanced atomic layer deposition.

[0061] The reactor 1 comprises a reaction chamber 10 for receiving a substrate 2, in which deposition takes place. The chamber 10 is bounded by one or more side walls 100, a top wall 101 and a bottom wall 102.

[0062] To perform the deposition of a layer on the substrate 2, the reactor 1 comprises means for the inflow and evacuation of gas precursors and / or gaseous species for the formation of a plasma. The reactor 1 comprises a gas precursor inlet 12, as indicated by the arrows at the top of the reactor in Figs. 2 to 5, configured to supply gas precursors to the reaction chamber 10. The gas precursor inlet 12 can further be configured to introduce a gas, such as a noble gas, for example helium or argon, into the chamber 10 for the formation of the plasma. The reactor 1 further comprises a pumping module 13 of the chamber 10. The pumping module 13 makes it possible to release gaseous species present in the chamber, as indicated by the two arrows at the bottom of the reactor in Figs. 2 to 5. These species can in particular be evacuated between the different ALD deposition cycles. The pumping module 13 also makes it possible to maintain a certain pressure in the chamber 10, typically lower than atmospheric pressure, by means of the gas precursor inlet 12.

[0063] The substrate 2 is accommodated in the reaction chamber 10 by a sample holder 11. The sample holder may comprise a plate 110 configured to receive the substrate 2 connected to an arm 111. The plate 110 may in particular have a flat upper surface 110a supporting the substrate 2. The upper surface 110a is, for example, substantially horizontal. It should be noted that the plate 110 may have other inclined surfaces, for example edges or a rounded lower surface.

[0064] The reactor 1 is configured such that a plasma is generated by capacitive coupling between the top surface 110a of the plate 110 and the sidewall 100, and is biased to ground as shown in Figures 2 to 5. Thus, the plate 110 is conductive. The plate 110 may be at least partially formed of a conductive material. The sidewall 100 is at least partially conductive. The sidewall 100 may be at least partially formed of a conductive material. The reactor 1 further comprises a power supply 14 configured to apply radio frequency power to the plate 110. The power supply 14 may, for example, comprise a radio frequency power generator 142 connected to a member 140 for transmitting radio frequency power to the plate 110.

[0065] The power supply 14 may comprise a tuning device 141, which is capable of inducing an RF voltage, also called self-bias voltage, on the plate 110 to generate the CCP plasma. Preferably, the tuning device 141 comprises an auto-match unit (known as an auto match unit) that matches the impedance of the plasma in the chamber 10 to the impedance of the RF power generator 142 to minimize the reflected power and to allow the discharge to be self-sustaining. The power supply 14 is configured to generate the plasma and to allow the plate 110 to be self-biased. In fact, the plasma is powered and the matching unit (or equivalently the tuning box) adapts the impedance to minimize the reflected power and to allow the discharge to be self-sustaining. The plasma is a discharge with its own impedance that depends on its degree of ionization and the chemistry of the gases, as well as on the geometric parameters of the reactor and the power supply. The self-bias voltage may typically be between 50V and 300V for a power range of 10W to 100W, especially in reactors that accept substrates with a maximum diameter of 200mm. The regulator 141 may in particular comprise an attenuator configured to limit the power of the generator 142 .

[0066] The sidewall 100 is at least partially non-parallel to the top surface 110a of the plate 110. The top surface 110a of the plate 110 and the sidewall 100 are separated by a distance d configured to generate plasma by capacitive coupling between the plate 110 and the sidewall 100, at least in the portion non-parallel to the top surface of the plate, each acting as an electrode for generating plasma. During the development of the present invention, it was indeed emphasized that the non-parallel arrangement of the sidewall 100 and the top surface 110a coupled at a certain distance d allows for generating plasma by capacitive coupling in the plasma generation zone 3 near the substrate 2.

[0067] Thus, the plasma is generated locally in the vicinity 3 of the substrate 2 with a much lower ion flux than in conventional CCP reactors. This reactor 1 allows to improve the properties of materials (density, purity, crystal structure, internal stress) by taking advantage of low energy ion bombardment. Furthermore, it opens new avenues for developing methods of metals, oxides, nitrides and sulfides on 2D and 3D substrates as well as selective surface and topographic deposition methods. This reactor 1 is therefore capable of carrying out depositions of various natures, unlike the more limited existing reactors. In fact, this plasma generation mode allows the deposition of metal layers, in particular of transition metals and / or rare earths. The deposition of oxide, nitride and / or sulfide layers, in particular of transition metals and / or rare earths, is also possible.

[0068] The distance d that allows the plasma discharge to self-sustain is determined by Paschen's law, i.e., the pressure P in the reactor and the minimum average RF self-bias voltage U min is determined by a function of U min = P × d. Thus, the distance d is proportional to the pressure P in the chamber 10 and the minimum average voltage U imposed by the power supply 14. min It is understood that this may vary depending on the

[0069] The distance d is the shortest distance between the two electrodes formed by the plate 110 and the sidewall 100. This distance may be, for example, the distance between one or both edges of the plate 110 and the sidewall 100, preferably the distance between the upper surface of the plate 110 and the sidewall 100, more specifically, the distance between one or both edges of the upper surface 110a of the plate 110 and the sidewall 100. During plasma generation, the plate 110 and the sidewall 100 are separated from each other by the distance d.

[0070] According to one example, the distance d between the upper surface 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 more preferably between 5 cm and 8 cm. This distance range d is, for example, within the pressure P≦80 mTorr (1 mTorr=10 -3Torr and 1 Torr ≈ 133.322 Pa), and the absolute value of U is substantially between 0 V and 300 V [0 V; 300 V], preferably between 50 V and 300 V [50 V; 300 V], and more preferably between 100 V and 300 V. min (self-bias voltage). Therefore, it is effective for 14 Ions cm -2 ·s -1 A sufficiently low ion density can be obtained below:

[0071] In the deposition of layers by capacitive coupling according to the invention, the pressure is in the range of mTorr to several hundred mTorr, for example 200 mTorr. Typically, the applied RF power is less than 100 W, and this power is not zero. The parameters of pressure, self-bias voltage and distance are interdependent to obtain the generation of plasma by capacitive coupling. It is also possible to set d in the reactor 1 and adjust the self-bias voltage and pressure to the corresponding ranges mentioned above, as will be described in detail later. Alternatively, the distance d may be adjustable, for example, by means of adjusting the height of the plate 110, as will be described later.

[0072] It should be noted that the type of gas may affect Paschen's law. These data are tabulated and known to those skilled in the art, for example for argon, as described in "Plasma Physics, vol. 14, no. 1, pp. 1111-1115, 2003". Thus, those skilled in the art can adapt these parameters, for example by adjusting the set self-bias voltage and pressure P, or even by adjusting the distance d, especially in the ranges mentioned above.

[0073] To generate plasma, the conductive sidewall 100 can be at least partially arranged on the plate 110 and protrudes therefrom in a plane perpendicular to the upper surface 110a of the plate 110. It is therefore understood that at least a part of the sidewall 100 is arranged opposite the upper surface of the plate so that a plasma can be generated by capacitive coupling between the sidewall 100 and the upper surface 110a of the plate 110 on which the substrate 2 is placed.

[0074] According to one example, the reaction chamber 10, more particularly the side wall 100, has a rotational symmetry with respect to a direction parallel to the z-axis and is substantially centered with respect to the upper surface 110a of the plate 110. This symmetry allows the plasma to be generated over the entire upper surface 110a of the plate 110. As soon as the plasma is generated, it propagates over the entire lower electrode (upper surface 110a of the plate 110). Therefore, the plasma is more uniform.

[0075] According to one example, the side walls 100 are arranged perpendicular to the main extension plane (x,y) of the top surface 110a of the plate 110. However, the perpendicular walls generate very narrow magnetic field lines on the edge of the substrate, thus generating a more localized (and therefore more energetic) plasma. The more localized plasma may generate a breakdown phenomenon at the edge of the substrate, thus generating edge effects.

[0076] To limit this, as shown in figures 2 and 3, the side walls 100 are preferably arranged at least partially obliquely to the main extension plane (x,y) of the upper surface 110a of the plate 110. Likewise, the side walls are arranged neither parallel nor perpendicular to the main extension plane (x,y) of the upper surface 110a. This oblique arrangement makes it possible in particular to improve the plasma obtained by limiting edge effects. The generated plasma is therefore made more uniform for better layer deposition.

[0077] The side wall 100 may include several portions 100a and 100b. The first portion 100a may be arranged substantially perpendicular to the main extension plane (x, y) of the upper surface 110a. The second portion 100b may be arranged obliquely to the main extension plane (x, y) of the upper surface 110a of the plate 110. In the following, the portion 100b of the side wall is assumed to be arranged obliquely to the plane (x, y), but is not limited to this.

[0078] For example, as shown in Fig. 2, the second portion 100b of the side wall 100 can have a conical shape above the plate 110. This geometry can be more specifically selected depending on the distance d. The portion 100b can for example be in the form of a cone truncated by the top wall 101. The truncated cone shape allows the side wall not to form a cavity in which the species generated by the plasma can accumulate. Preferably, the second portion 100b has a conical shape with an axis of rotation substantially centered relative to the plate 110.

[0079] For example, as shown in FIG. 3, the second portion 100b of the side wall 100 can form a dome on the plate 110. The portion 100b can be, for example, in the form of a hemisphere on the plate 110. Again, this geometry can be more specifically selected depending on the distance d. The dome-shaped geometry, more specifically the hemispherical geometry, makes it possible to have a smaller chamber volume (and therefore a chamber with less consumed reagent and easier to pump) and to limit the dead volume in the chamber. Preferably, the second portion 100b has a hemispherical geometry and is preferably substantially centrally located with respect to the plate 110. The dome can be truncated by the top wall 101. Alternatively, the side wall 100 can form a non-truncated dome.

[0080] For example, with respect to the dome shape discussed above, it will be appreciated that the side wall 100 may extend to form all or a portion of the top wall 101 .

[0081] According to an example, the plate 110 is not height adjustable in the chamber 10. Likewise, the plate 110 may not be movable in the chamber 10 at least in the vertical direction z. However, the plate 110 may be arranged to be movable, for example in rotation, at a fixed height in the chamber 10, for example to improve the uniformity of the deposition. This rotation can be performed about the axis of its arm 111. The plate 110 may also be completely fixed in the chamber 10. In particular, if the height of the plate 110 is not adjustable, the geometry of the side wall 110 can be adapted with respect to the sample holder in order to obtain a distance d that allows the generation of a plasma. This allows a simpler construction of the reactor 1 and therefore a lower cost.

[0082] According to another example, the plate 110 may be height adjustable within the chamber 10, as indicated by the two vertical arrows in Figures 2 to 5. Similarly, the plate 110 is movable within the chamber 10 in at least a vertical direction z. Thus, the distance d may be adjusted, for example, to a pressure or a minimum voltage U, as required. min For different values ​​of , the height of the plate 110 can be adjusted. By adjusting the height of the plate 110, the plasma characteristics can be further adjusted while ensuring that the plasma 3 is not extinguished. Height adjustment of the plate 110 can also be particularly advantageous when the reactor 1 comprises an additional plasma source, as will be explained in more detail later. It is also possible that the plate 110 is configured to be movable, for example during rotation, for example to improve the uniformity of the deposition. This rotation can again be performed about the axis of its arm 111.

[0083] The movement of the plate 110 can be actuated, for example, by a motor, not shown.

[0084] For example, as illustrated in Figures 2 and 3, the reactor 1 may be configured to form plasma only by capacitive coupling between the plate 110 and the sidewall 100 in the reaction chamber. The plasma may be generated only between two electrodes in particular. The plate 110 may constitute one of the electrodes. The sidewall 100 may constitute the other electrode. The reactor 1 may include only the generation by capacitive coupling between the plate 110 and the sidewall 100 as a plasma source. This simplifies the configuration of the reactor 1 and reduces costs. It should be noted that, according to this embodiment, it is possible to select whether or not to adjust the height of the plate 110.

[0085] For example, as shown in Fig. 4, the reactor 1 can be equipped with an inductively coupled plasma source 15 remote from the chamber 10. The reactor 1 can thus be a multi-mode ICP and / or CCP reactor. Depending on the requirements, the plasma can be generated in ICP mode and / or CCP mode. For this, the reactor 1 can be equipped with a high frequency induction source 15 including a coil powered by a high frequency power generator 16. The power supply 14 and the inductive power sources 15, 16 are configured such that the RF power applied to the plate 110 is independent of the RF power of the inductive power source.

[0086] When the reactor 1 operates in CCP mode, the generation of plasma occurs by capacitive coupling between the top surface 110a of the plate 110 and the sidewall 100, as previously described. When the reactor 1 operates in ICP mode, the plasma is generated by the inductively coupled plasma source 15. The power supply 14 can be used as a bias device configured to induce a bias voltage on the substrate 2, allowing ions to be extracted from the remote plasma with a controlled incident energy the moment they arrive in the vicinity of the substrate 2.

[0087] The gas precursor inlet 12 may be located at the induction sources 15, 16. The induction sources 15, 16 may be isolated from the chamber 10 by a valve 120 having an open configuration for the passage of plasma species from the induction sources to the chamber 10 and a closed configuration for blocking these species. It should be noted that it is possible to have another gas precursor inlet located directly at the chamber 10 without passing through the induction sources.

[0088] Preferably, the plate 110 is height adjustable, if the reactor 1 can be equipped with an inductively coupled plasma source 15 remote from the chamber 10. Thus, depending on the distance d obtained between the plate 110 and the side wall 100, the plasma can be generated only by the inductive sources 15, 16 or by both the inductive sources 15, 16 and the capacitive coupling between the plate 110 and the side wall 100. Note that, according to this embodiment, it is possible to select whether or not to adjust the height of the plate 110.

[0089] For example, as shown 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 an illustration of the principle. In practice, the two intersection points of the emitted and reflected light rays intersect on the surface of the substrate where the growth occurs.

[0090] Next, examples of operating parameters of the reactor 1 will be described.

[0091] The RF power and pressure conditions within the chamber 10 allow the ion flux characteristics of the plasma to be finely tailored.

[0092] The gas precursor inlet 12 and pumping module 13 may be configured to maintain a pressure within the reaction chamber 10 substantially between 5 and 200 mTorr, preferably between 5 and 100 mTorr, preferably between 5 and 80 mTorr.

[0093] The power supply 14 may be configured to apply a radio frequency bias at a power of up to 100 W.

[0094] The power supply 14 may be configured to apply a radio frequency bias at a frequency comprised between 2 and 100 MHz when the plasma is generated by capacitive coupling.

[0095] It should be noted that if the reactor includes an inductively coupled plasma source 15 and is operated in ICP mode, the power supply acting as a bias device configured to induce a bias voltage on the substrate 2 may operate at a higher power and / or at a frequency other than the ranges mentioned above.

[0096] These parameters in the above ranges make it possible to obtain the following ion flux characteristics of a plasma generated by capacitive coupling adapted for PEALD deposition: - Power density: 0.05~0.5W / cm 2 , - Ion flux: 10 12 ~10 14 ions / (cm 2 s), - Ion energy: 0 to 300 eV (1 eV ≒ 1.60218 x 10 -19 J).

[0097] The following table illustrates an example 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 comprised between 5 cm and 6 cm.

[0098] [Table 1]

[0099] The Vdc probe and flexal parameters provide the self-bias voltages that correspond to the impedance match between the plasma and the tuning box of the reactor. The Vdc probe and Vdc flexal provided by the probe measurements (allowing the determination of the ion flux) are provided directly by the tuning box of the reactor. The self-bias voltages remain zero when the reactor is supplied with applied RF power and the plasma is not initiated or self-sustaining. In this case, all power is stored in the tuning box.

[0100] 6A-6D show the RF power W applied to plate 110 as a function of self-bias voltage U at constant pressure P for the example parameters in Table 1. CCP on the generated ion flux 4 (in arbitrary units).

[0101] 7A-7C show the W of a constant RF applied to plate 110 for the example parameters in Table 1. CCP It describes the effect of pressure P on the generated ion flux 4 (arbitrary units) and the effect of ion energy E in terms of power, depending on the self-bias voltage U. From the above description it is clear that the present invention proposes an improved plasma enhanced deposition reactor, in particular allowing a gentler plasma enhancement than existing solutions, thus generating fewer induced defects.

[0102] The invention is not limited to the above-mentioned embodiment, but includes all embodiments that are encompassed by the invention. The invention is not limited to the above-mentioned examples. Many other variations are possible, for example by combining the above-mentioned features, without departing from the scope of the invention. In the illustrated example, the gas precursor inlet 12 is shown on the top surface 101 of the reactor 1. Other arrangements are possible, for example on the side wall 100. The same applies to the pumping module 13.

Claims

1. A plasma enhanced deposition reactor (1), comprising: a reaction chamber (10) bounded by walls (100, 101, 102, 103) and comprising an electrically conductive plate (110) having a top surface (110a) intended to receive a substrate (2); a gas precursor inlet (12) configured to supply a gas precursor to said reaction chamber (10); a pumping module (13) of said reaction chamber (10); a power source (14) configured to apply high frequency power to said plate (110) to generate a plasma; Equipped with the sidewall (100) of the reaction chamber (10) is at least partially non-parallel to the upper surface (110a) of the plate (110) and is electrically conductive; the side wall (100) is at least partially disposed on the plate (110) and projects from the wall in a plane perpendicular to an upper surface of the plate (110); the plate (110) is biased to ground, and an upper surface (110a) of the plate (110) and the sidewall (100) are separated by a predetermined distance d configured to generate a plasma by capacitive coupling between the plate (110) and the sidewall (100), d being the shortest distance between the plate (110) and the sidewall (100); A reactor characterized in that

2. The distance d is proportional to the ratio U / P, where P is the pressure in the reactor (1), U is the average voltage of the high frequency bias applied to the plate (110), and U is the value of the minimum average voltage of the high frequency self-bias U ｍｉｎ The reactor of claim 1 .

3. The reactor of claim 1 or 2, wherein the distance d between the upper surface (110a) of the plate (110) and the side wall (100) is 5 cm to 15 cm.

4. The reactor according to any one of claims 1 to 3, wherein at least a part of the side wall (100) is arranged obliquely with respect to a main extension plane of the upper surface (110a) of the plate (110).

5. 5. The reactor of claim 4, wherein the side wall (100) at least partially forms a cone on the plate (110), and preferably the side wall (100) has a conical shape with an axis of rotation substantially centered with respect to the plate (110).

6. 5. The reactor of claim 4, wherein the side wall (100) at least partially forms a dome over the plate (110), preferably the side wall (100) has an at least partially hemispherical shape and is preferably substantially centrally located with respect to the plate (110).

7. The reactor of any one of claims 1 to 6, configured to generate the plasma only in the reaction chamber (10).

8. The reactor of claim 7, wherein the plasma is generated only between two electrodes, and the plate (110) is configured to carry one of the two electrodes.

9. The reactor of any one of claims 1 to 6, further comprising an inductively coupled plasma source (15) remote from the reaction chamber (10).

10. The reactor of any one of claims 1 to 9, wherein the plate (110) is not configured for height adjustment within the reaction chamber (10).

11. The reactor of any one of claims 1 to 9, wherein the plate (110) is configured to be height adjustable within the reaction chamber (10).

12. The reactor of any one of claims 1 to 11, wherein the gas precursor inlet (12) and the pumping module (13) are configured to maintain a pressure in the reaction chamber (10) substantially between 5 and 200 mTorr, preferably between 5 and 100 mTorr, preferably between 5 and 80 mTorr.

13. The reactor of any one of claims 1 to 12, wherein the power supply (14) is configured to apply the radio frequency power having a frequency between 2 and 100 MHz when the plasma is generated by capacitive coupling between the plate (110) and the side wall (100).

14. The reactor of any one of claims 1 to 13, wherein the power supply (14) is configured to apply the radio frequency power of up to 100 W of power when the plasma is generated by capacitive coupling between the plate and the sidewall.

15. The reactor of any one of claims 1 to 14, wherein the power supply (14) comprises an attenuator configured to limit the power of the radio frequency bias.

16. 1. A method for generating a plasma by capacitive coupling in a reactor, comprising: - providing a reactor (1) according to any one of claims 1 to 15; - supplying a gas to form a plasma in the reaction chamber (10) of said reactor; generating a plasma by capacitive coupling between a plate (110) and a conductive sidewall (100), said plate (110) and said sidewall (100) being separated by a distance d that allows plasma to be generated by capacitive coupling between said plate (110) and said sidewall (100), d being the shortest distance between said plate (110) and said sidewall (100), the generation of the plasma comprising applying high frequency power to said plate; The method includes:

17. The step of generating the plasma further comprises adjusting at least two plasma parameters, including a distance d, a pressure P in the reactor (1), and an average voltage U of the high frequency bias applied to the plate (110). - d is proportional to the ratio U / P, - U is the value of the minimum average voltage of the high frequency self-bias U ｍｉｎ The method according to claim 16 .

18. 18. The method according to claim 16 or 17, wherein the plate (110) of the reactor (1) is configured to be height-adjusted in the reaction chamber (10), and the step of generating the plasma comprises adjusting the distance d by a height displacement of the plate to reach a distance d that allows generation of the plasma.

19. The method according to any one of claims 16 to 18, wherein during generation of the plasma the pressure in the reaction chamber (10) is substantially between 5 and 200 mTorr, preferably between 5 and 100 mTorr, preferably between 5 and 80 mTorr.

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