• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
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    • 专利摘要:
    The invention relates to a device (100) for forming a quasi-neutral beam of ions and electrons, comprising: - a chamber (20), - a set of means (31, 30, 40, 58) for forming an ion - electron plasma in this chamber (20); means (50) for extracting and accelerating the charged plasma particles from the chamber (20) capable of forming said beam, said extraction and acceleration means (50) comprising a set of at least two grids (51, 54) at one end of the chamber; a radio frequency alternating voltage source (52) adapted to generate a signal whose radio frequency is between the plasma frequency of the ions and the plasma frequency of the electrons, said radio frequency voltage source (52) being arranged in series with a capacitor (53); ) and connected by one of its outputs and via this capacitor (53) to at least one of the grids of said set of at least two grids (51, 54), at least one other gate said set of at least two gates (51,54) being either set to a reference potential or connected to the other of the outputs of the radio frequency voltage source (52).
    公开号:FR3020235A1
    申请号:FR1453469
    申请日:2014-04-17
    公开日:2015-10-23
    发明作者:Dmytro Rafalskyi；Ane Aanesland
    申请人:Ecole Polytechnique；
    IPC主号:
    专利说明:

    [0001] The invention relates to a device for forming a quasi-neutral beam of particles of opposite charges. Such devices are in particular used for plasma thrusters (application to satellites for trajectory correction, space probes, etc.), particle deposition devices on a target (vapor phase deposition, for example; microelectronics), target etching devices, polymer treatment devices or target surface activation devices. Typically, such a device comprises a chamber, means for introducing an ionizable gas into the chamber, means for ionizing the gas in order to form the plasma, and means for extracting and accelerating charged particles from the plasma out of the chamber. . In the field of electric propulsion, there are different techniques to ensure the acceleration of the machine provided with the plasma beam generating device, which is then assimilated to a plasma propellant. Thus, for a plasma propellant whose plasma is formed of positive ions and electrons, it is possible to extract and accelerate only the positive ions out of the chamber and to ensure the electroneutrality of the positive ion beam after the exit of the chamber. injecting electrons downstream of the exit of the chamber. Ensuring the electroneutrality of the beam at the exit of the chamber is indeed essential to prevent the spacecraft load electrically, the current of the ion beam is not particularly limited by the space charge.
    [0002] This type of plasma thruster, however, has the disadvantage of implementing an ancillary source of electrons to ensure this electroneutrality, an ancillary source that is generally at the origin of a lack of reliability. To ensure this electroneutrality by increasing the reliability (thus to overcome the ancillary source of electrons), several routes have been considered. A first way is to produce a plasma comprising positive ions, negative ions and electrons and to filter the electrons, within the chamber, to obtain at the output of the chamber only or almost as positive ions and negatives. The particles of opposite charges of the beam are thus formed of positive ions and negative ions. A second way is to produce a plasma comprising positive ions and electrons and to provide means for extracting and accelerating the positive ions and the electrons at the outlet of the chamber to ensure this electroneutrality. The charged particles of the beam are thus formed of positive ions and electrons. Solutions corresponding to the first route described above are proposed in the documents WO 2007/065915, WO 2010/060887 or WO 2012/042143. All these solutions must implement an electronegative ionizable gas capable of generating positive ions, negative ions and electrons as well as an electron filtering means so as to obtain, at the level of the chamber outlet only or substantially only, positive and negative ions. In document WO 2007/065915, two grids 3, 4 in contact with the plasma which are situated at the outlet of the chamber in the same plane (one at the top) are used as extraction and acceleration means. the other at the bottom), one of which is negatively polarized and the other of which is positively polarized. Figure 1 is a representative diagram of the device proposed in WO 2007/065915. In this figure, the chamber 1 comprises a plasma with positive ions A +, negative ions A- and electrons e-. The electron filtering means carries the reference 2. A simultaneous extraction and acceleration of the positive and negative ions is thus obtained, ensuring the electroneutrality of the ion beam after the exit of the chamber. However, this solution is difficult to put into effect. because of the presence of grids with opposite polarizations. Indeed, the presence of these grids of opposite polarizations may involve significant curvatures of the beams from each grid. The document WO 2010/060887 proposes an improved solution compared to that of the document WO 2007/065915, for which two different gases are provided in place of a single one in WO 2007/065915. One of these gases is electronegative and the other can be either electropositive or electronegative.
    [0003] In the document WO 2012/042143, it is proposed to implement an extraction and acceleration gate 5 powered by an alternately positive and negative voltage source, via the voltage source 6. At this gate 5 Another grid 7 is associated with the mass 8. When a positive potential is applied to the gate 5, the plasma potential becomes positive and the positive ions A + are consequently accelerated toward the other gate 7 who is in the mass. Indeed, under these conditions, a positive sheath is formed at the grids 5, 7, which allows the acceleration of the positive ions. The sheath is a space that is formed between each grid 5, 7 and the plasma where the density of the positive ions differs from the density of the negative ions. Under these conditions, the extraction and acceleration of the negative ions is blocked. Then, when a negative potential is applied to the gate 5, the plasma potential becomes negative and the negative ions A- are accelerated towards the other gate 7. More precisely, after applying a positive potential on the gate 5, the positive sheath disappears rapidly (about 1 microsecond) and a negative sheath is formed under the effect of the negative bias of this grid 5. Under these conditions, the extraction and acceleration of the positive ions is blocked. Depending on the polarization of the grid 5, it is possible to accelerate and extract either the positive ions or the negative ions. A representative diagram of the device proposed in WO 2012/042143 is shown in FIG. 2 (a). The electronegative gas is denoted A2 and the electron filtering means 2. RF 'here means the means for generating the plasma from the electronegative gas A2 injected into the chamber 1. This is a field source sinusoidal alternating magnetic emitting in the field of radio frequencies. Here, one does not have the disadvantage of having two opposite polarization grids, as in WO 2007/065915 and WO 2010/060887. However, the positive ions A + and negative A- being extracted successively, it is proposed to optimize the shape of the voltage signal generated by the AC voltage source 6 connected to the gate 5 to best ensure the electroneutrality of the beam. ions out of the room. This alternative voltage source can take advantage of the measurements of a probe S in the output beam and / or the RF signal for generating the plasma. This optimized signal is shown in Figure 2 (b). With this optimized signal, a good electron beam of the beam is obtained at the outlet of chamber 1, but only on average. Indeed, the fact of successively extracting the positive ions, then the negative ions and vice versa does not always make it possible to obtain a constantly neutral beam. As a result, the thruster potential varies over time, depending on the shape of the signal shown in Fig. 2 (b). Furthermore, it should be noted that all the ion-ion extraction devices, the use of an electronegative gas, which is generally highly reactive (presence of fluorine, chlorine, etc.), limit the service life. of the device. In addition, the solutions proposed in WO 2007/065915 (FIG. 1), WO 2010/060887 and FIGS. 2 (a) and 2 (b) (WO 2012/042143) are limited to ion-extraction. ions, but can not be considered for ion-electron extraction. Another solution corresponding to the second way described above is proposed in the article by SV Dudin & DV Rafalskyi, "On the 20 simultaneous extraction of positive ions and electrons from single-grid ICP source", A letters Journal Exploring the Frontiers of Physics, EPL, 88 (2009) 55002, pl-p4. This solution consists in using an electrode 9 in the core of the chamber 1 (thus within the plasma), the electrode 9 being fed by a radiofrequency voltage source 10 (RF), a sinusoidal alternating voltage source at a frequency included in the range of radio frequencies) through a capacitor 11 and associate a gate 7 ", located at the outlet of the chamber 1, in contact with the plasma and connected to the ground 8. 30 We can refer to 3, RF 'represents a radiofrequency source (for example one or more coil (s)) for ionizing the gas and thus forming a plasma comprising positive ions and The means 12 is a vacuum chamber in which are installed means for characterizing the ion beam from the chamber 1, which are not involved in the extraction and acceleration of the ions. the device is as follows. By construction, the electrode 9 has a surface much greater than that of the gate 7 "situated at the outlet of the chamber 1 and connected to the ground 8. In general, the application of an RF voltage to an electrode having a larger than the grid 7 "has the effect of generating at the interface between the electrode 9 and the plasma on the one hand, and at the interface between the grid 7" and the plasma of other An additional potential difference is added to the potential difference RF.This total potential difference is distributed over a sheath.Here, the sheath is a space which is formed between the grid 7 "or the electrode 9d. on the one hand and plasma on the other hand where the density of positive ions is higher than the density of electrons. This sheath has a variable thickness due to the RF signal applied to the electrode. In practice, most of the effect of the application of an RF signal on the electrode 9 is however located in the sheath of the grid 7 "(we can see the electrode-grid system as a capacitor with two walls asymmetrical, in this case the potential difference is applied to the lower capacitance part, hence the smaller area.) In the presence of the capacitor 11 in series with the RF source, 10, the application of the RF signal has the effect of converting the RF voltage into DC constant voltage due to the charge of the capacitor 11, mainly at the sheath of the grid 7 ". This constant voltage DC in the sheath of the grid 7 "implies that the positive ions are constantly accelerated, because this potential difference DC has the effect of making the plasma potential positive, consequently the positive ions of the plasma are constantly accelerated. in the direction of the gate 7 "(to the ground) and extracted from the chamber 1 by this gate 7". The energy of the positive ions corresponds to this potential difference DC (mean energy). The variation of the RF voltage, 10 allows to vary the RF + DC potential difference between the plasma and the grid 7 ". At the level of the sheath of the grid 7 ", this results in a change in the thickness of this sheath When this thickness becomes less than a critical value, which happens for a period of time at regular intervals given by the frequency of the RF signal, the potential difference between the gate and the plasma approaches the zero value (therefore the plasma potential approaches the zero value, the gate being grounded), which makes it possible to extract electrons. plasma below which electrons can be accelerated and extracted (= critical potential) is given by Child's Law, which links this critical potential to the critical thickness of the sheath below which this sheath disappears ("sheath collapse As long as the plasma potential is below the critical potential, then there is simultaneous acceleration and extraction of electrons and ions.
    [0004] Although the extraction of electrons is only possible over a certain period of time during a period of the RF signal applied to the electrode 9, this article shows the possibility of a complete compensation of the positive charge of the ions and therefore a good electroneutrality of the beam at the output of the plasma chamber.
    [0005] Moreover, one obtains an almost simultaneous acceleration and extraction of the positive ions and the electrons during a period of the RF signal, unlike the solution proposed in WO 2012/042143, whether for ion-ion extraction. or ion-electron extraction. The technique proposed in this article is therefore very different from those proposed in WO 2007/065915, WO 2010/060887 and WO 2012/042143 (especially that of FIG. 3, for ion-electron extraction). by using a single gate (ground) in contact with the plasma and a capacitor 11, which brings a DC component to the potential difference in the sheath, in series with an RF voltage source. A disadvantage of this technique is that there are many accelerated positive ion losses, i.e. accelerated positive ions at high energy, but which do not pass through the orifices of the gate. This causes a faster wear of the grid and therefore limits the life of this grid. In the case of an application to a plasma thruster (satellite, space probe, ...), this disadvantage can become critical. In practice, to limit this disadvantage, it is therefore necessary to implement ions whose energy is less than 300eV.
    [0006] Moreover, this technique can not work for ion-ion extraction and acceleration. An object of the invention is to provide a device for forming a positive ion beam and electrons having good electroneutrality and extraction efficiency improved over known devices. The improvement in efficiency results in particular in a lifetime of the device that can be improved for a given extraction energy. Another object of the invention is to provide such a device capable, in addition, of extracting ions with increased energy compared to known devices. To achieve at least one of these objectives, the invention proposes a device for forming a quasi-neutral beam of ions and electrons, comprising: a chamber; a set of means for forming a plasma ions; - electrons in this room; a means for extracting and accelerating charged plasma particles from the chamber capable of forming said beam, said extraction and acceleration means comprising a set of at least two gates situated at one end of the chamber; ; a radio frequency alternating voltage source adapted to generate a signal whose radiofrequency is between the plasma frequency of the ions and the electron plasma frequency, said radiofrequency voltage source being arranged in series with a capacitor and connected by one of its outputs and through this capacitor, at least one of the grids of said set of at least two grids, at least one other grid of said set of at least two grids being set to a reference potential, is connected to the other of the outputs of the radio frequency voltage source.
    [0007] This device may furthermore comprise the following characteristics, taken alone or in combination: the set of means for forming the ion-electron plasma comprises one or more coil (s) powered by a radio frequency alternating voltage source ; the source of radiofrequency voltage supplying the or each coil is the same as the radio frequency voltage source in series with the capacitor which are connected to at least one of the two gates, the device further comprising means for managing the signal supplied; by said source towards one hand, the or each coil and secondly, said at least one gate; the set of means for forming the ion - electron plasma in the chamber comprises a reservoir comprising at least one electropositive gas; the grids have circular orifices whose diameter is between 0.5 mm and 10 mm, for example between 1 mm and 2 mm; the distance between the two grids is between 0.5 mm and 10 mm, for example between 1 mm and 2 mm; the grids have slots in the form of a slot; the electroneutrality of the ion and electron beam is obtained at least partially by adjusting the duration of application of the positive and / or negative potentials originating from the radio frequency alternating voltage source; - Electroneutrality of the ion and electron beam is obtained at least in part by adjusting the amplitude of the positive and / or negative potentials from the radio frequency alternating voltage source; The radiofrequency AC voltage source is arranged to produce a rectangular signal; the radio frequency alternating voltage source is arranged to produce a sinusoidal signal. A more complete object of the invention is to obtain a device 30 which also makes it possible to extract and accelerate negative ions and positive ions, while ensuring good electroneutrality of the beam. To achieve this objective, the invention also proposes a device for forming a quasi-neutral beam of particles of opposite charges, comprising: a device for forming a quasi-neutral beam of ions and electrons according to FIG. invention; a set of means for forming an ion-ion plasma in the chamber, said assembly comprising an electron filtering means; a low-frequency alternating voltage source which is adapted to generate a signal whose radiofrequency is less than or equal to the plasma frequency of the ions; a means capable of connecting one of the gates either to the low-frequency voltage source while activating the electron-filtering means to form an ion-ion beam or to the radiofrequency voltage source in series with the capacitor while deactivating the electron filtering means to form an ion-electron beam. The device for forming a quasi-neutral beam of oppositely charged particles may, in addition, comprise the following characteristics, taken alone or in combination: the electron-neutrality of the ion-ion beam is obtained at least in part by adjusting the the duration of application of the positive and / or negative potentials coming from the low-frequency alternating voltage source; the electroneutrality of the ion-ion beam is obtained at least in part by adjusting the amplitude of the positive and / or negative potentials coming from the low-frequency alternating voltage source; the low frequency AC voltage source is arranged to produce a rectangular signal; the set of means for forming an ion-ion plasma in the chamber comprises a reservoir comprising at least one electronegative gas. Finally, it should be noted that the usable gases can be chosen, according to their electropositivity or electronegativity, from argon (Ar), hydrazine (N21-14), xenon (Xe), carbon tetrafluoride ( CF4), sulfur hexafluoride (SF6), diiodine (12), dinitrogen (N2) or dihydrogen (H2). The invention will be better understood and other objects, advantages and characteristics thereof will appear more clearly on reading the description which follows and which is made with reference to the appended figures, in which: FIG. 4 is a representative diagram a first embodiment of the invention, with which it is possible to extract and accelerate positive ions and electrons; - Figure 5 is an equivalent electrical diagram of the device shown in Figure 4; FIG. 6 represents an RF voltage signal that it is conceivable to apply to a gate of the device of FIG. 4 by means of a capacitor in series with the RF source, this voltage signal corresponds substantially to the potential plasma; FIG. 7 is an alternative embodiment of the device proposed in FIG. 4; FIG. 8 represents another variant embodiment of the device proposed in FIG. 4; FIG. 9 is a representative diagram of a second embodiment of the invention, with which it is possible to extract and accelerate either positive ions and negative ions, or positive ions and electrons other than share; FIG. 10 is a diagram of a test installation for testing the device according to the invention which is in accordance with that of FIG. 4; FIGS. 10 (a) to 10 (c) show some measurement results obtained with the test facility of FIG. 10 in the case of an ion-electron regime; FIG. 11 gives measurement results obtained with the device according to that of FIG. 9, with the measuring means represented in FIG. 10. A first embodiment of the invention is described below in FIG. FIG. 4. The device 100 comprises a chamber 20 into which a gas, for example stored in a reservoir 31, 30 capable of forming a plasma comprising ions and electrons, can be introduced, this introduction being effected by means of FIG. intermediate means 30, such as a conduit, connected to the reservoir 31 for introducing the gas into the chamber 20. It also comprises means 40, 58 for ionizing the gas to form the plasma. For example, the means 40 may be formed of coils fed by a radiofrequency source 58. Instead, other means 40, 58 known to those skilled in the art could be provided, namely from non-limiting examples. , a microwave source 58 with a resonator 40 or a source of direct current 58 with electrodes.
    [0008] The device 100 finally comprises means 50 for extracting and accelerating the positive ions and electrons out of the chamber 20. This extraction / acceleration makes it possible to form, at the outlet of the chamber, a beam 60. The means 50 of FIG. extraction and acceleration comprise a set of at least two grids 51, 54 disposed at the end of the chamber 20. A first gate 51 is connected to a source of AC voltage at a frequency in the range of radio frequencies, ci -after named RF radio source, 52, through a capacitor 53. The capacitor 53 is arranged in series with the radio frequency source RF, 52. A second gate 54 is set to a reference potential 55, for example the mass. In practice, for some applications, the reference potential may be the mass. However, for other applications, for example in the space domain, the reference potential may be that of the satellite or the probe concerned. In the remainder of the description relating to this first embodiment, the reference potential will, unless otherwise indicated, be considered to be the mass. The RF source, 52 is set to define a coRF pulse such that Copi-co RF 5- (Ope, OÙ (Ope = is the plasma pulsation of the electrons and horn e Npu Wpj = is the plasma pulsation of the ions positive, comi with: eo, the charge of the electron, E0, the permittivity of the vacuum, np, the density of the plasma, m 'the mass of the ion, and me, the mass of the electron. Note that (op; "(ope because mi >> me.) In general, the frequency of the signal provided by the RF source, 52 may be between a few MHz and a few hundred MHz, depending on the gas used for the forming the plasma in the chamber 20 and this, to be between the plasma frequency of the ions and the plasma frequency of the electrons The device according to the invention shown in Figure 4 can be associated, in a simplified way, with the equivalent circuit of Figure 5.
    [0009] In this diagram, the RF source 52, the capacitor 53 in series with this source and the mass 55 are recognized. The reference P represents the plasma. Cint represents the capacitance between the two gates 51, 54. The block B1 represents the effect of the sheath that forms between the plasma and the first gate 51, which can be represented by a diode Df in parallel with a capacitance Cf '. Block B2 represents the effect of the cladding which forms between the plasma and the second gate 54, which can be associated with a diode Df in parallel with a capacitor C2. The existence of a diode function for each of the blocks B1 or B2, is linked to the fact that the ions can not follow the instantaneous evolution of the electric field between the gates, imposed by the radiofrequency variation of the signal coming from the radiofrequency source 52, but only the average value of this field whereas the electrons can follow the instantaneous evolution of this electric field. This is because the mass of the electrons (me) is very small compared to the mass (mi) of the positive ions (me "ml) and the frequency of the signal imposed by the source 52 (radiofrequency, pulse coRF) is chosen. to be between the plasma frequency of the ions and the plasma frequency of the electrons, ie Wpi WRF 5- (Ope.) Therefore, when an RF voltage (VRF) is applied via the source 52, the capacitor This charge of the capacitor 53 then produces a DC voltage across the capacitor, finally obtaining a VRF + DC voltage at the terminals of the assembly formed by the RF source, 52 in series with the capacitor (FIG. The DC constant part of the voltage VRF + DC then makes it possible to define the electric field between the two gates 51, 54, the average value of the single signal VRF being zero, this DC value thus makes it possible to extract and accelerate. the positive ions through the two grids 51, 54, continuously Moreover, the capacities cf and Cf are very different because of the arrangement of the grids 51, 54 in the device. Indeed, from the point of view of positive ions or electrons present in the plasma, the second gate 54, downstream with respect to the first gate 51, relative to the direction of propagation of the beam 60, has an effective surface. less than the effective surface sf of the first gate 51 since the second gate 54 is visible, for the plasma, only through the orifices of the first gate 51, namely 5f "sf. This therefore results in the inequality C2 even for identical grids 51, 54. In practice, the set of two grids 51, 54 thus makes it possible to form a capacitor with asymmetrical surfaces. Therefore, when an RF voltage (VRF) is applied via the source 52, the voltage VRF + DC across the assembly 20 formed by the RF source 52 in series with the capacitor 53 is expressed VRF + DC =, because Cf »Cf, where Vil ° represents the potential difference in the sheath formed between the plasma and the first gate 51 and 1` represents the potential difference in the sheath formed between the plasma and the second gate 54 The first gate 51 to which the RF signal is applied, via the capacitor 53, is in contact with and interacts with the plasma. The plasma potential follows the potential printed on the first gate 51, namely VRF + DC. As for the second gate 54, at mass 55, it is also in contact with the plasma but only during the brief time intervals during which the electrons are extracted at the same time as the positive ions, namely when = VRF + DC is below a threshold value 0, below which the sheath disappears ("sheath collapse" according to the English terminology). This threshold value Ocr is defined by the law of Child. This law is expressed as follows: Where: S 3/2 (Eq. 1) 4 Ocr 2e0 - (3. CO Ji mi s, is the thickness of the sheath to which it becomes smaller than the dimension gate orifices, E0, the permittivity of the vacuum, eo, the charge of the electron, mi, the mass of an ion, and j, the current density of the ions. FIG. 6 represents an example of evolution of the plasma potential as a function of time, related to the application of an RF voltage, 52 via the capacitor 53 on the first gate 51. The dotted line represents the component DC constant, here 550V, which is related to the presence of the capacitor 53. This component defines the energy of the positive ions present in the plasma which are constantly extracted and accelerated by the two gates 51, 54. The plasma potential varies however between extreme values (+ 1050V, 50V) around the constant component (550V, here) e Due to the RF signal provided by the source 52. When the plasma potential reaches the critical potential from which the cladding disappears, the electrons are extracted and accelerated through the grids 51, 54 with the positive ions. Here, Ocr 200V. This can be obtained with identical grids 51, 54 whose orifices, circular, have a diameter of 1.5 mm (makes it possible to define the value of s in (Eq.1)), the distance between the two grids being comparable to diameter of a gate hole. The gas used is argon. The current density of the ions, associated with these orifices and with this gas, is 5 mA / cm 2. It is noted in this figure that the plasma frequency is 13.56 MHz, to ensure that (Op; -5. (ORF 5 (Op.
    [0010] The electroneutrality of the beam 60 at the outlet of the chamber 20 is obtained by extracting the electrons through the two grids 51, 54 when the sheath present at the level of the first gate 51 disappears. Beyond the example associated with FIG. 6, it should be noted that the sizing of the grids 51, 54 will therefore depend on the gas used, on the ion current density that it is desired to obtain, in accordance with the law of Child. Generally, identical grids 51, 54 will be used. Each grid 51, 54 may have circular orifices whose diameter is between 1mm and 2mm. The distance between the two grids 51, 54 is then in the same range of values as the diameter of the orifices. Alternatively, each grid 51, 54 to present slot-shaped orifices. There are several differences between the embodiment according to the invention (FIGS. 4 and 5) with respect to the above-mentioned article 20 (FIG. 3), both in terms of structure and operation. Contrary to the aforementioned article (FIG. 3), it is not at the gate 54 that is connected to the mass 55 that there is, most of the time, an interaction with the plasma and the formation of a sheath of varying thickness. In terms of structure, the device 100 according to the invention differs from the device proposed in the article SV Dudin & DV Rafalskyi, in that it implements positive ion extraction and acceleration means. and electrons based on two gates 51, 54 located at the outlet of the chamber and not on one, cooperating with an electrode in the heart of the plasma. Operationally, using two grids 51, 54 at the outlet of the chamber changes the operation of the extraction and acceleration, relative to the aforementioned article (Figure 3). Indeed, if a sheath is formed at the first gate 51, whose thickness varies as a function of the plasma potential, the potential difference with the plasma in the sheath is low because the plasma potential follows the potential applied to the first gate 51. The constant potential difference DC therefore applies between the two gates 51, 54 and not, as is the case for the aforementioned article at the gate connected to ground. The acceleration of the positive ions comes from this potential difference DC taking place between the two gates 51, 54. As a result, the trajectory of the positive ions is better controlled and many fewer positive ions strike the first gate 51. These ions positive not more hit the wall of the second gate 54, which is visible from the point of view of these ions, only through the orifices of the first gate 51. Moreover, when the sheath disappears (lower plasma potential or equal to the critical potential), the electrons are directed through the orifices of the first gate 51 and also have little tendency to strike the wall of the second gate 54, which is visible from the point of view of electrons only to through the orifices of the first gate 51. The path of the electrons is well controlled. It is therefore possible to envisage a device having a significantly improved lifetime or using positive ions with a higher energy than in the aforementioned article (FIG. 3). The operation of the extraction and acceleration means formed of a set of at least two grids 51, 54 according to the invention also differs from the two grid means 5 ', 7' proposed in the document WO 2012/042143 ( Figure 3: positive ion extractions - electrons).
    [0011] Indeed, the alternating signal printed at the gate 5 'is centered on the zero value (absence of capacitor). No constant DC component therefore takes place in this device between the two gates 5 ', 7' whose potential difference is related only to the variation of the variable signal printed at the gate 5 '. No constant extraction of positive ions is possible in WO 2012/042143, but only a successive extraction of positive ions and electrons. FIG. 7 represents an alternative embodiment of the device 100 represented in FIG. 4, in which the radiofrequency source 52 is not implemented. In this case, a radiofrequency source 58 'used to activate the means 40, coils for example, is also used to power the gate 51. It is then necessary to provide a means 59 for managing the signal provided by said source in the direction of the one hand, the means 40, for example one or more coil (s) and secondly, of the grid 51. This design can be of interest for space applications because it reduces the risk of defect of the whole device 100. In FIGS. 4, 5 and 7, there is shown the case where the gate 51 is connected to the source RF, 52 (FIGS. 4 and 5), 58 '(FIG. 7) in series with the capacitor 53 and the other gate 54, set to a reference potential, for example ground. In this case, one of the outputs of the RF source, 52 (or 58 ', in Figure 7) is set to a reference potential, for example ground. To ensure the operation of the device, however, it is of little importance to know which output of the RF source, 52 is connected to which gate 51, 54. In other words, the gate 51 could be set to a reference potential and the another gate 54 connected to the RF source, 52 (FIGS. 4 and 5) or 58 '(FIG. 7) in series with the capacitor 53. FIG. 8 represents another variant embodiment of the device 100 represented in FIG.
    [0012] In this variant, the radiofrequency source RF, 52 is connected to the two gates 51, 54. More specifically, the radio frequency source RF, 52 is arranged in series with the capacitor 53 and connected, by one of its outputs and by the intermediate of this capacitor 53, to one 51 of the two gates 51, 54. In other words, one of the outputs of the RF source, 52 is connected to the capacitor 53, the latter being itself connected to the one 51 of the two grids 51, 54. As for the other output of the RF source, 52 it is then connected to the other 54 of the two grids 51, 54. In Figure 8, it is the gate 51 which is connected to the capacitor 53, but one could just as well connect the capacitor 53 to the gate 54 and the gate 51 to the output of the radiofrequency source RF, 52 which is not connected to the capacitor 53. In addition, it should be noted that such a variant could be provided for the device 100 shown in FIG. 7. In this case, it is the radio frequency source RF, 58 'which is connected to the two gates 51, 54, as described in the previous paragraph.
    [0013] This variant therefore does not imply a reference potential. In the spatial field, such a connection ensures an absence of parasitic currents flowing between, on the one hand, the external conductive parts of the satellite or of the space probe and, on the other hand, the device for extracting the particles of opposite charges proper. . Finally, the signal applied to the grid concerned may be a signal obtained at least in part by adjusting the duration of application of the positive and / or negative potentials from the RF radio frequency source, 52, 58 'and this, to improve the electroneutrality of the ion-electron beam. Alternatively or in addition, the signal applied to the grid concerned may be a signal obtained at least in part by adjusting the amplitude of the positive and / or negative potentials from the RF radio frequency source, 52, 58 'and , to improve the electroneutrality of the ion-electron beam.
    [0014] It may be a signal of arbitrary shape, for example rectangular. In particular, it may be a rectangular signal such as that shown in Figure 2 (b), namely a rectangular signal is formed by a sequence of positive (b '+) and negative (b) rectangular slots. '-) of variable amplitude (a') and duration (d '). The adjustment is thus performed both on the duration of application of the positive and negative potentials and on the amplitude of these potentials. Alternatively, it may be a sinusoidal signal. A second embodiment is described below in support of FIG. 9. This second embodiment can implement two modes of operation, one of which makes it possible to form a quasi-neutral beam of ions and ions. electrons as oppositely charged particles, the other forming a quasi-neutral beam of positive ions and negative ions or ion-ions, as particles of opposite charges. The device 100 'comprises all the means implemented in the device 100 according to the first embodiment. However, the device 100 'further comprises a set of means 32, 30, 40, 58, 80 for forming an ion-ion plasma in the chamber 20.
    [0015] With respect to the means provided in the device 100 for forming an ion-electron plasma, the means 32, 30, 40, 58, 80 comprise in particular a reservoir 32 comprising at least one electronegative ionizable gas, capable of generating positive and negative ions as well as than electrons, and a means 80 for filtering the electrons produced by this electronegative gas. The means 80 preferably produces a constant magnetic field H, oriented transversely with respect to the direction of movement of the ions and electrons in the chamber 20. The device 100 'also comprises a low-frequency alternating voltage source LF 56 capable of to be connected to the first gate 51 via a controllable means 57 to position itself either on the radio frequency source RF, 52, or on the low frequency source LF, 56. By LF source, 56 low frequency means a source emitting in a frequency less than or equal to the plasma frequency of the ions. It should be noted that the means 57 also makes it possible to activate or deactivate the filtering means 80. The signal coming from this low-frequency AC voltage source LF 56 can be obtained at least in part by adjusting the duration of the current. application of the positive and / or negative potentials from this source and to control the electroneutrality of the ion-ion beam. Alternatively or in addition, the signal from this source of low-frequency alternating voltage LF, 56 can be obtained at least in part by adjusting the amplitude of the positive and / or negative potentials from this source and this, to improve the electroneutrality of the ion-ion beam. It may in particular be a rectangular signal such as that shown in FIG. 2 (b), namely a rectangular signal formed by a series of positive rectangular slots b '+ and negative b'- of amplitude a 'and duration of variables. The adjustment is thus performed both on the duration of application of the positive and negative potentials and on the amplitude of these potentials. More generally, a rectangular signal form can be envisaged. The device 100 'thus has two modes of operation.
    [0016] In the first mode of operation, the means 57 is positioned on the RF source, 52, in series with the capacitor 53. A gas capable of generating a plasma comprising positive ions and electrons is introduced into the chamber 20, by the intermediate means of the reservoir 31 and the conduit 30. The means 80 for magnetic filtering electrons is rendered inactive, with the means 57 which also controls the activation or deactivation of the means 80 for filtering. The operation of the device 100 'is identical to that described for the first embodiment (device 100) for the extraction of positive ions and electrons.
    [0017] In the second mode of operation, the means 57 is positioned on the source LF, 56 and also makes it possible to activate the filtering means 80. The source LF, 56 emits a signal whose value is successively positive and negative at a frequency less than or equal to the plasma frequency of the ions, to successively extract the positive ions and the negative ions. An electronegative gas must be introduced into the chamber 20. The means 80 for filtering electrons must be activated in order to eliminate or almost eliminate the electrons and to obtain, at the output of this means 80, only or almost as much as positive ions and ions. negative. The electroneutrality of the beam obtained at the output is ensured.
    [0018] No plasma generating device proposes, to the knowledge of the applicant, such an all-in-one device. In particular, when the device 100 'is used in ion-ion mode, its use can be limited in time, by switching to positive-electron ion mode, to avoid problems of early aging of the equipment.
    [0019] In Figure 9, it is noted that two separate RF sources 58, 52 are implemented. However, one could also provide an installation diagram according to that shown in Figure 8 for the device 100 ', namely a single RF source. Finally, and in general, the gases that can be used in the devices 100 or 100 'can be chosen, according to their electropositivity or electronegativity, from argon (Ar), hydrazine (N2H4), xenon (Xe), carbon tetrafluoride (CF4), sulfur hexafluoride (SF6), diiodine (12), dinitrogen (N2) or dihydrogen (H2).
    [0020] Tests have been carried out to show the advantage of the solution proposed in the context of the invention. Figure 10 is a representative diagram of a test facility used with the device 100 according to the invention. On the left part of this FIG. 10, the device 100 shown in FIG. 4 is recognized. The characteristics of the beam 60 are determined in a vacuum chamber 200, via a pump 205. The measurement is carried out at means of a target 201 with which is associated a power analyzer 203 disposed on the target 201, this analyzer being connected to a processing means 204. This analyzer is known by the acronym RFEA ("Retarding Field Energy Analyzers" according to the Anglo-Saxon terminology). Target 201 is connected to means for determining its potential 202. Some results are provided in Figs. 10 (a) through 10 (c), relating to ion-electron operation.
    [0021] The gas used is argon (25 sccm). The frequency of the RF source, 52 is 4MHz. The potential applied to the gate 51 by this source may have an amplitude between 0 and 300V (namely up to 600V peak-to-peak). The magnetic filter is inactive.
    [0022] Figure 10 (a) shows the energy distribution functions (EDF, ordinate, arbitrary unit ua) for Argon ions (IEDF) and electrons (EEDF) as a function of the energy of these ions / electrons (abscissa) . The presence of a peak for both electrons and ions shows that extraction and acceleration of both types of charged particles is achieved. This figure shows that the ions are extracted and accelerated at an average energy of 150eV, and the electrons at an average energy of 10eV. These measurements are obtained with an RF potential of amplitude 150 V (300V peak-to-peak). Figure 10 (b) shows the evolution of the potential of the target 201 y float, 1 (ordinate; d) as a function of the average energy of the argon ions. It is noted that on the energy range of argon ions considered for this measurement (0 to 300eV), the potential of the target is less than 15V, which is low compared to the energy of the ions. In other words, it shows that the beam is well compensated for the load (electroneutrality ensured).
    [0023] Figure 10 (c) shows a potential-current curve (Upr / Ipr) of the target 201; for an energy of argon ions of 300eV. The argon ion and electron currents are identical (Ipr = 0) when the potential of the target is 15V. It should be noted that (I) float is Upr when lp, = 0. Fig. 11 shows results relating to the ion-ion mode of operation. These results were obtained with a test installation using the device 100 'shown in FIG. 9, with the measuring means for characterizing the beam 60 coming from this device 100' which have been previously described in support of FIG. the 10.
    [0024] The gas used is sulfur hexafluoride (SF6). The LF frequency of the voltage source 56 is 20 kHz. The potential applied to the gate connected to the voltage source 56 is between -350V and + 350V. The magnetic filter 80 is active in order to eliminate or virtually eliminate the electrons produced by the ionization of the gas. Figure 11 shows more precisely the energy distribution functions (IEDF, ordinate, arbitrary unit ua) for the positive ions (solid line) and the negative ions (dashed lines) as a function of the energy of these ions (abscissa). . The presence of a peak for both electrons and ions shows that extraction and acceleration of both types of charged particles is achieved. This figure 11 shows that the positive and negative ions are extracted and accelerated at an average energy higher than 300eV. The devices 100, 100 'according to the invention can notably be used for: plasma thrusters (application to satellites for trajectory correction, space probes, etc.), particle deposition devices on a target (vapor deposition, for example in the field of microelectronics), - target etching devices, - polymer treatment devices or activation devices of the target surface.
    权利要求:
    Claims (17)
    [0001]
    REVENDICATIONS1. Apparatus (100) for forming a quasi-neutral beam of ions and electrons, characterized in that it comprises: - a chamber (20), - a set of means (31, 30, 40, 58 ) to form an electron ion plasma in this chamber (20); means (50) for extracting and accelerating the charged plasma particles from the chamber (20) capable of forming said beam, said means (50) for extracting and accelerating comprising a set of at least two grids (51, 54) at one end of the chamber; a radio frequency alternating voltage source (52, 58 ') adapted to generate a signal whose radio frequency is between the plasma frequency of the ions and the plasma frequency of the electrons, said radiofrequency voltage source (52, 58') being arranged in series with a capacitor (53) and connected, via one of its outputs and via this capacitor (53), to at least one of the grids of said set of at least two grids (51,54 ), at least one other gate of said set of at least two gates (51,54) being either set to a reference potential or connected to the other of the outputs of the radio frequency voltage source (52,58 ') .
    [0002]
    2. Device (100) according to claim 1, wherein the set of means (31, 30, 40, 58) for forming the ion-electron plasma comprises one or more coil (s) supplied (s) by a source of radio frequency alternating voltage (58 '; 52).
    [0003]
    3. Device (100) according to the preceding claim, wherein the radiofrequency voltage source (58 ') supplying the or each coil (40) is the same as the radiofrequency voltage source (52) in series with the capacitor which are connected to at least one of the two grids (51, 54), the device further comprising means (59) for managing the signal supplied by said source (58 ') towards, on the one hand, of the or each coil and secondly, of said at least one gate.
    [0004]
    4. Device (100) according to one of the preceding claims, wherein the set of means (31, 30, 40, 58) for forming the electron ion plasma in the chamber (20) comprises a reservoir (31) comprising at least one less an electropositive gas.
    [0005]
    5. Device (100) according to one of the preceding claims, wherein the grids (51, 54) have circular orifices, whose diameter is between 0.5mm and 1mm, for example between 1mm and 2mm.
    [0006]
    6. Device (100) according to one of the preceding claims, wherein the distance between the two grids (51, 54) is between 0.5mm and 10mm, for example between 1mm and 2mm.
    [0007]
    7. Device (100) according to one of claims 1 to 4, wherein the grids (51, 54) have slots in the form of slit.
    [0008]
    8. Device (100) according to one of the preceding claims, wherein the electroneutrality of the ion beam and electrons is obtained at least in part by adjusting the duration of application of the positive potentials and / or negative from the radio frequency alternating voltage source (RF, 52, 58 ').
    [0009]
    9. Device (100) according to one of claims 1 to 7, wherein the electroneutrality of the ion beam and electrons is obtained at least in part by adjusting the amplitude of the positive and / or negative potentials from of the radio frequency alternating voltage source (RF, 52, 58 ').
    [0010]
    10. Device (100) according to one of the preceding claims, wherein the radiofrequency AC voltage source (RF, 52, 58 ') is arranged to produce a rectangular signal. 30
    [0011]
    11. Device (100) according to one of claims 1 to 7, wherein the radiofrequency AC voltage source (RF, 52, 58 ') is arranged to produce a sinusoidal signal.
    [0012]
    12. Apparatus for forming a quasi-neutral beam of particles of opposite charges, characterized in that it comprises: a device (100) for forming a quasi-neutral beam of ions and electrons according to FIG. one of the preceding claims; A set of means (32, 30, 40, 58, 80) for forming an ion-ion plasma in the chamber (20), said assembly including an electron filter means (80); a low frequency AC voltage source (LF, 56) which is adapted to generate a signal whose radiofrequency is less than or equal to the plasma frequency of the ions; means (57) adapted to connect one of the grids (51, 54), ie to the low-frequency voltage source (LF; 56) while activating the means (80) for filtering electrons in order to form a beam ion-ions at the radiofrequency voltage source (52, 58) in series with the capacitor (53) while deactivating the electron filtering means (80) to form an ion-electron beam.
    [0013]
    13. Device (100 ') according to the preceding claim, wherein the electroneutrality of the ion-ion beam is obtained at least in part by adjusting the duration of application of the positive and / or negative potentials from the source of low frequency alternating voltage (LF, 56).
    [0014]
    14. Device (100 ') according to one of claims 12 or 13, wherein the electroneutrality of the ion-ion beam is obtained at least in part by adjusting the amplitude of the positive and / or negative potentials from the 25 Low frequency alternating voltage source (LF, 56).
    [0015]
    15. Device (100 ') according to the preceding claim, wherein the low frequency AC voltage source (LF, 56) is arranged to produce a rectangular signal. 30
    [0016]
    16. Device (100 ') according to one of claims 12 to 15, wherein the set of means (32, 30, 40, 58, 80) for forming an ion-ion plasma in the chamber (20) comprises a reservoir (32) comprising at least one electronegative gas.
    [0017]
    17. Device (100, 100 ') according to one of the preceding claims, wherein the usable gases are selected, according to their electropositivity or electronegativity, among argon (Ar), hydrazine (N2H4), xenon (Xe), carbon tetrafluoride (CF4), sulfur hexafluoride (SF6), diiodine (12), dinitrogen (N2) or dihydrogen (H2).
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    同族专利:
    公开号 | 公开日
    WO2015159208A1|2015-10-22|
    JP2017520076A|2017-07-20|
    FR3020235B1|2016-05-27|
    US9776742B2|2017-10-03|
    RU2676683C2|2019-01-10|
    EP3146204A1|2017-03-29|
    JP6461999B2|2019-01-30|
    RU2016144102A3|2018-11-27|
    RU2016144102A|2018-05-10|
    US20170036785A1|2017-02-09|
    SG11201704629SA|2017-07-28|
    EP3146204B1|2020-07-08|
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    法律状态:
    2015-01-29| PLFP| Fee payment|Year of fee payment: 2 |
    2016-04-28| PLFP| Fee payment|Year of fee payment: 3 |
    2016-05-27| TQ| Partial transmission of property|Owner name: ECOLE POLYTECHNIQUE, FR Effective date: 20160425 Owner name: CENTRE NATIONAL DELA RECHERCHE SCIENTIFIQUE (C, FR Effective date: 20160425 |
    2017-02-20| PLFP| Fee payment|Year of fee payment: 4 |
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    2019-02-22| PLFP| Fee payment|Year of fee payment: 6 |
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    2021-03-30| PLFP| Fee payment|Year of fee payment: 8 |
    优先权:
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    FR1453469A|FR3020235B1|2014-04-17|2014-04-17|DEVICE FOR FORMING A NEAR-NEUTRAL BEAM OF PARTICLES OF OPPOSED LOADS.|FR1453469A| FR3020235B1|2014-04-17|2014-04-17|DEVICE FOR FORMING A NEAR-NEUTRAL BEAM OF PARTICLES OF OPPOSED LOADS.|
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    US15/304,482| US9776742B2|2014-04-17|2015-04-14|Device for forming a quasi-neutral beam of oppositely charged particles|
    PCT/IB2015/052697| WO2015159208A1|2014-04-17|2015-04-14|Device for forming a quasi-neutral beam of oppositely charged particles|
    JP2016562932A| JP6461999B2|2014-04-17|2015-04-14|Apparatus for forming a quasi-neutral beam of charged particles of different signs.|
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