Systems and methods for continuously supplying negative ions using multi-pulsed plasma sources

Abstract

The present disclosure relates to a system and method for continuously supplying negative ions using multi-pulsed plasma sources. The system includes a plurality of plasma generators each to generate plasma by applying pulsed power to the electronegative gas from a gas source; a negative ion supply unit connected to the plasma generators to receive the plasmas transferred therefrom and to continuously supply ions; and a controller connected to the plurality of plasma generators and configured to control characteristics of the pulsed powers delivered to the respective plasma generators and to adjust phase shift associated with the pulsed power envelopes. By adjusting the phase shift, the controller enables a plasma in one of the plasma generators to be in an after-glow state when a plasma in another plasma generator is in an active-glow state.

Claims

1. A system for supplying negative ions using multi-pulsed plasma sources, the system comprising: a plurality of plasma generators each configured to generate plasma by applying pulsed power to electronegative gas; a negative ion supply unit connected to each of the plurality of plasma generators to receive the generated plasma therefrom; and a controller connected to the plurality of plasma generators and configured to control characteristics of the pulsed powers supplied to the respective plasma generators, and to adjust phase shift between signals associated with pulsed power envelopes such that when one of the plasma generators is in an active-glow state, another plasma generator is switched to an after-glow state, wherein the plurality of plasma generators generates the plasmas in an alternating manner depending on the phase shift between the signals associated with pulsed power envelopes in a manner that a decreased amount of negative ion supply from one of the plasma generators in the active-glow state to the negative ion supply unit is compensated for by an additional supply of negative ions supplied from another plasma generator in the after-glow state to the negative ion supply unit.

2. The system of claim 1, wherein the plurality of plasma generators is configured such that, when one of the plasma generators supplies negative ion precursors and electrons generated in the active-glow state to the negative ion supply unit, another plasma generator supplies negative ions generated in the after-glow state to the negative ion supply unit.

3. The system of claim 1, wherein the controller comprises a plurality of pulse controllers and a system controller, wherein: the plurality of pulse controllers connected to the plasma generators, respectively, and configured to control the characteristics of the pulsed powers for switching the state of the plasma in each of the plasma generators between the active-glow state and the after-glow state; and the system controller connected to the pulse controllers, and configured to adjust the phase shift between the signals associated with the pulsed power envelopes modulated by the pulse controllers, so as to delay a start time of the active-glow state of one of the plasma generators after an end time of the active-glow state of another plasma generator.

4. The system of claim 1, further comprising a magnetic filter placed between each of the plasma generators and the negative ion supply unit, wherein the magnetic filter restricts high-energy electrons, among the electrons generated from the plasma generators in the active-glow state, from entering the negative ion supply unit.

5. The system of claim 4, wherein the magnetic filter comprises at least one permanent magnet.

6. The system of claim 4, wherein the magnetic filter comprises at least one electromagnet, and the electromagnet generates a magnetic field depending on an operating state of the plasma generator.

7. The system of claim 6, wherein the electromagnet is interlinked with the signal associated with the pulsed power envelope so as to produce the magnetic field when the corresponding plasma generator is in the active-glow state.

8. The system of claim 1, further comprising a plasma particle filter provided between the plasma generators and the negative ion supply unit, wherein the plasma particle filter selectively transports particles generated in the plasma generators toward the negative ion supply unit depending on charge states thereof.

9. The system of claim 8, wherein the plasma particle filter is provided with either of an electrode and a grid that produce an electric field.

10. The system of claim 1, further comprising gas supply units connected to the plasma generators, respectively, and configured to supply the plasma generators with the electronegative gas.

11. The system of claim 10, wherein the gas supply units comprise gas supply controllers, respectively, configured to control an amount of gas supplied to the plasma generators over time.

12. The system of claim 1, further comprising a beam extraction system connected to the negative ion supply unit and configured to extract the negative ions.

13. A method for supplying negative ions using multi-pulsed plasma sources, the method comprising: a negative ion generation-and-supply step of generating plasmas by applying pulsed powers to a plurality of plasma generators, respectively, and supplying the generated plasmas to a negative ion supply unit; a continuous negative ion supply step of supplying the negative ions to the negative ion supply unit through an alternating operation of the plasma generators by adjusting phase shift between signals associated with pulsed power envelopes applied to the plurality of plasma generators, respectively; and a negative ion extraction step of extracting the negative ions from the negative ion supply unit.

14. The method of claim 13, wherein the negative ion generation-and-supply step comprises: generating plasma containing the negative ions, negative ion precursors, and electrons when the plasma generator is in the power-on state; supplying the negative ion precursors and the electrons to the negative ion supply unit; generating first negative ions by reactions of the negative ion precursors with the electrons in the negative ion supply unit; generating second negative ions in the plasma generator when power is turned off, by reactions between plasma species generated before the power is turned off; and supplying the second negative ions to the negative ion supply unit.

15. The method of claim 14, wherein the supplying of the negative ion precursors and the electrons to the negative ion supply unit comprises producing a magnetic field by a magnetic filter installed between the negative ion supply unit and the plasma generator, in order to restrict high-energy electrons of the electrons from entering the negative ion supply unit.

16. The method of claim 13, wherein the continuous negative ion supply step comprises: adjusting the phase shift between the signals associated with the pulsed power envelopes applied to the plurality of plasma generators, respectively, so that the plasma generators are supplied with the pulsed powers with a predetermined phase lag to one another; and allowing a plasma in one of the plasma generators to be in an after-glow state while a plasma in another plasma generator is in an active-glow state due to the applied pulsed power, and alternating the state of the plasma in each of the plurality of plasma generators between the active-glow state and the after-glow state, with the phase shift.

17. The method of claim 13, wherein the negative ion extraction step comprises: configuring a polarity of a beam extraction electrode connected to the negative ion supply unit; and extracting the negative ions from the negative ion supply unit when the beam extraction electrode is positive, and extracting positive ions from the negative ion supply unit when the beam extraction electrode is negative.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a conceptual view of a system of continuously supplying negative ions using multi-pulsed plasma sources.

(2) FIG. 2 is a conceptual scheme illustrating plasma characteristics with respect to time when pulsed power is delivered to a single plasma generator.

(3) FIG. 3 is a conceptual scheme illustrating plasma characteristics with respect to time when pulsed powers are delivered, in an alternating manner, to a plurality of plasma generators illustrated in FIG. 1.

(4) FIG. 4 is a flowchart illustrating a method of continuously supplying negative ions using multi-pulsed plasma sources.

(5) FIG. 5 is a detailed flowchart related to a negative ion generation-and-supply step in the flowchart illustrated in FIG. 4.

(6) FIG. 6 is a detailed flowchart related to a continuous negative ion supply step in the flowchart illustrated in FIG. 4.

(7) FIG. 7 is a detailed flowchart related to a negative ion extraction step in the flowchart illustrated in FIG. 4.

(8) FIG. 8 is a conceptual illustration visualizing the flowchart represented in FIG. 4.

BEST MODE FOR CARRYING OUT EMBODIMENTS

(9) Systems and methods for continuously supplying negative ions using multi-pulsed plasma sources (hereinafter, referred to as continuous negative ion supply systems based on multi-pulsed plasma sources and continuous negative ion supply methods based on multi-pulsed plasma sources, respectively) in accordance with a few embodiments of the present disclosure will now be described in more detail, which can be understood by reference to the illustrative embodiments depicted in the appended drawings.

(10) As used herein, the singular forms may be intended to include the plural forms as well, unless the context definitely indicates otherwise.

(11) In the following description of exemplary embodiments, moreover, a detailed description of known technologies in the technical fields related to the disclosure will be omitted if it unnecessarily obscures the gist of the present invention.

(12) Reference is made to the accompanying drawings which form a part hereof. Like reference numerals designate like elements throughout the specification, and redundant explanation thereof will be omitted.

(13) The accompanying drawings are for the purpose of easy understanding of the embodiments, but it should be understood that the technical idea of the present disclosure is not limited thereto. It should also be construed that the present disclosure is intended to cover all modifications, equivalents, and alternatives included within the scope of the present disclosure.

(14) In this specification, for convenience of explanation, a description will be given under the assumption that two plasma generators are disposed. In order to indicate the plasma generator, either a reference numeral 110 or reference numerals 110a and 110b will be chosen as needed. Since this is only for convenience of description, the disclosure is not limited thereto.

(15) For reference, pulsed power to generate a pulsed plasma (hereinafter called pulsed power for brevity) generally includes both a power-on state in which power delivery to the plasma is active and a power-off state in which that to the plasma is inactive. However, in this specification, a state in which pulsed power is applied to the plasma generator is represented as the power-on state in which power delivery to the plasma is active.

(16) Hereinafter, the configuration of a system for continuously supplying negative ions using multi-pulsed plasma sources (or a continuous negative ion supply system based on multi-pulsed plasma sources) will be described first and subsequently a method for continuously supplying negative ions using multi-pulsed plasma sources (or a continuous negative ion supply method based on multi-pulsed plasma sources) will be described in detail.

(17) FIG. 1 is a conceptual view illustrating a continuous negative ion supply system 100 based on multi-pulsed plasma sources according to one embodiment. FIG. 2 is a conceptual scheme illustrating characteristics of a plasma in either of plasma generators 110a and 110b with respect to time when pulsed power is delivered to the plasma generator 110. FIG. 3 is a conceptual scheme illustrating a continuous negative ion supply step implemented by the continuous negative ion supply system based on multi-pulsed plasma sources 100 through an alternating operation of the plurality of plasma generators 110a and 110b shown in FIG. 1 with a preset phase shift (phase difference) between signals associated with the pulsed powers applied to the plasma generators, respectively.

(18) The continuous negative ion supply system based on multi-pulsed plasma sources 100 is configured to generate a plasma containing negative ions, highly vibrationally excited molecules as precursors of the negative ions and high- and low-energy electrons by applying pulsed power to input gases including electronegative gas, and to transfer the generated plasma to a negative ion supply unit 120. Here, the highly vibrationally excited molecule generally refers to a vibrationally excited molecule in a state of a vibrational quantum number v more than 5, but is not always limited thereto. The present disclosure may alternatively be applied to a vibrationally excited molecule in a state of the vibrational quantum number v equal to or less than 4.

(19) Each of the plasma generators 110 is configured to generate plasma by applying pulsed power to electronegative gas while adjusting a phase difference between the signals associated with the pulsed powers applied to each of the plasma generators, such that negative ion density in the negative ion supply unit 120 is continuously maintained at a specific value. For reference, a process of transferring the plasma created by the plasma generator 110 to the negative ion supply unit 120 and the transferred species will be described in detail later.

(20) The continuous negative ion supply system based on multi-pulsed plasma sources 100 includes a plasma generator 110, a negative ion supply unit 120 and a controller 130.

(21) The plasma generator 110 includes a plurality of plasma generators 110a and 110b to generate plasma containing negative ions, their precursors (negative ion precursors), and electrons, and to transfer the generated plasma to the negative ion supply unit 120 connected thereto.

(22) In the drawing, the plurality of plasma generators 110a and 110b are connected to the negative ion supply unit 120, respectively, and configured to generate plasmas by applying pulsed powers to input gases containing the electronegative gas supplied from gas supply units 140a and 140b to be described later.

(23) However, although the two plasma generators 110a and 110b are illustrated in the drawing, the present disclosure is not limited thereto, and the system may be configured without limitation of the number of plasma generators. For reference, the control of the pulsed powers supplied to the respective plasma generators 110a and 110b will be described later in detail.

(24) One problem which has arisen in the related art is that the negative ion density in a negative ion source using plasma pulsing is time-varying, and thus a continuous supply of negative ions is not achievable. By configuring the system with the plurality of plasma generators 110, the problem can be solved so that continuously supplying the negative ions is possible.

(25) On the other hand, hereinafter, a phenomenon occurring in each plasma generator 110 depending on pulsed power characteristics will be described in detail with reference to FIG. 2.

(26) First of all, for pulsed power, depending upon whether or not power delivery to the plasma generator 110 is active, a period (or state) of a fraction of the cycle for which power is deposited may be referred to as an active-glow, while that for which power is not deposited may be referred to as an after-glow. If occasion arises, the active-glow period and the after-glow period may also be referred to as a power-on state and a power-off state, respectively.

(27) Hereinafter, characteristics of a plasma generated in the plasma generator 110 in each of the active-glow and after-glow states will be described in detail with reference to FIG. 2.

(28) First, temporal variations (μs) of electron temperature (eV), electron density (cm.sup.−3), highly vibrationally excited molecule density (cm.sup.−3), and negative ion density (cm.sup.−3) in the single plasma generator 110 during the active-glow will be described in detail.

(29) In FIG. 2, it can be seen that the electron temperature initially surges and then attains to a steady-state. On the other hand, the electron density increases gradually with increasing power, reaching a constant (or steady-state) value.

(30) In the active-glow state, the highly vibrationally excited molecule density is highly correlated with the electron temperature and the electron density, and thus it tends to increase at the beginning of the active-glow state and subsequently to saturate and remain at a constant value. This is due to the fact that high-energy electrons are involved in generation of the highly vibrationally excited molecules such that the reaction rate for the highly vibrationally excited molecule generation is increased with rises in the electron temperature and the electron density.

(31) Meanwhile, plenty of high-energy electrons in the active-glow contribute to the formation of the highly vibrationally excited molecules at high density but enable the negative ion density in the active-glow to be lower than that in the after-glow to be described later since the high-energy electrons are involved in destruction of the negative ions. Therefore, there is a problem that few negative ions are transferred to the negative ion supply unit 120 in the active-glow state in which power delivery to the plasma is active.

(32) Second, hereinafter, temporal variations of the electron temperature, the electron density, the highly vibrationally excited molecule density, and the negative ion density in the single plasma generator 110 during the after-glow will be described.

(33) In this drawing, it can be seen that the electron temperature decreases dramatically at the beginning of the after-glow state. This is due to the fact that the electrons dissipate their energy in collisions with other particles and by escaping to walls while not being supplied with external energy.

(34) It seems that the decay rate of the electron density is slower than that of the electron temperature. A comparison between the temporal variations of the electron temperature and the electron density reveals that high-energy electrons rather than low-energy electrons are mainly destructed at the beginning of the after-glow.

(35) The highly vibrationally excited molecule density is also reduced due to a decrease in a production rate caused by the loss of the high-energy electrons as reactants and an increase in a destruction rate by collisions (or reactions) of the highly vibrationally excited molecule with other particles and the like. The decay rate of the highly vibrationally excited molecule density is slower than that of the electron temperature.

(36) As a result, for a specific time after the after-glow starts, the densities of the low-energy electrons and the highly vibrationally excited molecules that are reactants in the volume production reaction of the negative ions are high enough for the formation of the negative ions. On the other hand, the densities of the high-energy electrons involved in the destruction reaction of the negative ions becomes very low. Consequently, the negative ion density in the after-glow is higher than that in the active-glow, which is followed by a gradual decrease in the negative ion density by the consumption of the reactants (i.e., the low-energy electrons and the highly vibrationally excited molecules) in the volume production reaction of the negative ions and the like.

(37) Therefore, by taking advantage of the fact that the negative ion density in the after-glow is high and by using the plurality of plasma generators 110, a relatively large amount of negative ions supplied in the after-glow can compensate for a relatively small amount of negative ions supplied in the active-glow.

(38) In other words, the plurality of plasma generators 110 is connected to the negative ion supply unit 120. With the configuration, when one plasma generator 110 in the active-glow state supplies a relatively small amount of negative ions to the negative ion supply unit 120, a state of a plasma in another plasma generator 110 can be switched to the after-glow state in order to compensate for the amount of negative ions supplied. Accordingly, the total amount of negative ions supplied from the plurality of plasma generators 110 to the negative ion supply unit 120 can be kept constant. A detailed description of the configuration and control thereof will be given later.

(39) Meanwhile, the plasma generator 110 may include an Inductively Coupled Plasma (ICP) source, an Electron Cyclotron Resonance (ECR) plasma source, a microwave plasma source, a filament driven arc discharge plasma source, a radio frequency plasma source, a helicon plasma source, a Capacitively Coupled Plasma (CCP) source, and the like, and may be configured by various combinations of those sources.

(40) In one embodiment illustrated in the drawing, the plasma generator 110 is configured by two plasma generators including the ICP source as a first plasma generator 110a and the ECR plasma source as a second plasma generator 110b, and each of the plasma generators 110a and 110b is connected to the negative ion supply unit 120.

(41) The first plasma generator 110a, the ICP source, includes a plasma vessel 111a, an antenna 114a to supply pulsed power to electronegative gas, a continuous wave power supply 113a to apply power to the antenna 114a, and an impedance matching network 112a.

(42) The second plasma generator 110b, the ECR plasma source, includes a plasma vessel 111b, a magnet 112b for producing a magnetic field and also creating an Electron Cyclotron Resonance (ECR) zone, a power supply 113b for a microwave generator (e.g., a magnetron and a klystron), and a microwave generation system 114b.

(43) The magnet 112b may include an electromagnet 112b1 and an electromagnet power supply 112b2. The microwave generation system 114b may include a microwave generator 114b1 that generates microwaves, a stub tuner 114b2 for impedance matching, and a waveguide 114b3 for transmitting the microwaves.

(44) However, the plasma generators 110a and 110b are not limited to the above embodiment and may alternatively be configured in various combinations as mentioned above.

(45) The negative ion supply unit 120 is connected with each of the plasma generators 110 to receive and accommodate the negative ions generated in the plasma generator 110 or to provide a region in which negative ions are generated by reactions between negative ion precursors and low-energy electrons received from the plasma generator 110.

(46) For a specific method of transferring the plasma generated by the plasma generator 110 to the negative ion supply unit 120, a method employing diffusion or an electric field formed by applying a voltage to a grid (or an electrode) may be considered. This will be described in detail later.

(47) The negative ion supply unit 120 may be maintained to have a high negative ion density by receiving a large number of negative ions generated in one plasma generator 110 in the after-glow state, and also negative ion precursors and electrons generated in another plasma generator 110 in the active-glow state.

(48) In addition, the plurality of plasma generators 110 operates in an alternating manner with a phase shift (or phase difference) between pulses, so that the negative ion supply unit 120 can contain negative ions while keeping the negative ion density constant (time-independent) over time. This will be described in detail later.

(49) The controller 130 is configured to be connected to each plasma generator 110 and to control characteristics of pulsed power delivered to the plasma generator 110. Here, the characteristics of the pulsed power refer to parameters characterizing the pulse at which the pulsed power is provided from a power supply to the single plasma generator 110, and may include pulse repetition frequency, pulse width, duty cycle and like.

(50) The controller 130 is configured to adjust the phase difference between signals associated with the pulsed powers supplied to the plasma generators 110 so that it enables a plasma in one of the plasma generators 110 to be in the after-glow state when a plasma in another is in the active-glow state.

(51) The controller 130 may be configured to adjust the phase difference between signals associated with the pulsed power envelopes to an optimum value depending on a system configuration and an operating condition, so as to keep the negative ion density in the negative ion supply unit 120 constant over time, resulting in the continuous supply of the negative ions.

(52) The controller 130 includes a plurality of pulse controllers 131a and 131b and a system controller 132.

(53) According to this drawing, the pulse controllers 131a and 131b are configured to be connected to the plasma generators 110a and 110b, respectively, and to adjust the characteristics of the pulsed powers delivered to the respective plasma generators 110a and 110b.

(54) For reference, although this drawing illustrates the two pulse controllers 131a and 131b, the present disclosure is not limited thereto. Of course, the pulse controller may alternatively be employed as many as the plasma generators 110 installed or only one pulse controller may be employed to control the plurality of plasma generators 110.

(55) The pulse controllers 131a and 131b are configured to be connected to the power supplies 113a and 113b of the plasma generators 110a and 110b, respectively, to control the characteristics of the pulsed powers for switching a state of a plasma in each of the plasma generators 110a and 110b between the active-glow state and the after-glow state.

(56) The system controller 132 may be configured to keep the negative ion density constant in the negative ion supply unit 120. To this end, the system controller 132 is configured to be connected to the pulse controllers 131a and 131b to adjust the phase shift between the signals associated with the pulsed power modulated by the pulse controllers 131a and 131b.

(57) The system controller 132 may be configured to adjust the phase shift between the signals associated with the pulse controllers 131a and 131b, so as to delay a start time point of an active-glow of one plasma generator 110 after an end time point of an active-glow of another plasma generator 110.

(58) Referring to FIG. 1, the plasma generator 110a, the ICP source, is referred to as the first plasma generator 110a, and the plasma generator 110b, the ECR plasma source, is referred to as the second plasma generator 110b. However, the present disclosure is not limited to the specified sources, and different types of plasma sources may alternatively be used.

(59) In one embodiment as illustrated in FIG. 3, pulsed powers are applied to the first plasma generator 110a and the second plasma generator 110b with a predetermined phase shift (or phase lag) so that after the end of the active-glow of the first plasma generator 110a, the active-glow of the second plasma generator 110b starts at a specified time interval.

(60) Specifically, when the negative ions supplied from the first plasma generator 110a to the negative ion supply unit 120 are reduced since the first plasma generator 110a is in the active-glow in which the destruction of the negative ions due to the high-energy electrons occurs, the configuration may be intended to supply more negative ions generated from the second plasma generator 110b to the negative ion supply unit 120 by putting the second plasma generator 110b into the after-glow.

(61) In addition, the first plasma generator 110a and the second plasma generator 110b are configured to generate the plasmas in the alternating manner depending on the phase shift between the signals associated with the pulsed power envelopes in a manner that a decreased number of negative ions in one plasma generator 110 is compensated for by negative ions generated in another plasma generator 110. Hence, it is shown that the negative ion density in the negative ion supply unit 120 is kept constant over time.

(62) Such structure can provide a solution to the problem, which has arisen in the related art, in that the negative ion source utilizing the related art pulsing based on the volume production mechanism is not available for the continuous supply of the negative ions. Specifically, the negative ion density in the negative ion supply unit 120 can remain unchanged over time by adjusting the phase difference between the signals associated with the pulsed powers applied to the plurality of plasma generators 110. Accordingly, the present disclosure can be applied to a device that requires such a continuous supply of negative ions.

(63) However, the present disclosure is not limited thereto. In view of the entire system according to the present disclosure, the active-glow state can continue in a way that the active-glow of one plasma generator 110 starts as soon as the active-glow of another plasma generator 110 ends, by adjusting the phase difference between the signals associated with the pulsed power envelopes.

(64) The system 100 for continuously supplying the negative ions using the multi-pulsed plasma sources may include gas supply units 140a and 140b, a magnetic filter 150, a beam extraction system 160, and a vacuum pump system 180.

(65) The gas supply units 140a and 140b are connected to the plasma generators 110a and 110b, respectively, and serve the plasma generators 110a and 110b with background (or diluent) gases, electronegative gases, or their gaseous mixtures for the purpose of controlling plasma characteristics and processes.

(66) The background gas refers to gas capable of controlling plasma characteristics, reactions during processes or side reactions, and may contain argon or hydrogen.

(67) The electronegative gas refers to feedstock gas or gas capable of producing negative ions, and may contain hydrogen, fluorine or chlorine.

(68) The gas supply units 140a and 140b may further include gas supply controller 141a and 141b, respectively, configured to control an amount of gases supplied to each of the plasma generators 110 over time. The configuration can control the gas supply for that to be changed or unchanged over time, thereby facilitating the control of plasma and process characteristics.

(69) A portion where the gas supply units 140a and 140b are connected to the respective plasma generators 110 may be formed in various shapes, such as a single hole or a round showerhead having multi-apertures, depending on what a user needs.

(70) Each of the gas supply units 140a and 140b may be provided with an evaporator for turning a liquid or solid form of an input substance into a gaseous form, or a gas blender for mixing background gas and feedstock gas (or electronegative gas).

(71) The gas supply units 140a and 140b may further include valves 142a and 142b for isolating and regulating gas flows to the plasma generators 110 or for preventing a backflow of the gases, filters, and temperature controllers (not shown in FIG. 1) for preventing an occurrence of liquefaction of a specific gas.

(72) In this drawing, it is shown that the gas supply units 140a and 140b are configured to supply background gas and electronegative gas separately. However, the present disclosure is not limited thereto, and a single gas supply unit (not shown in the drawing) that can supply blended gas of background gas and electronegative gas may alternatively be provided.

(73) The magnetic filter 150 is placed between the plasma generator 110 and the negative ion supply unit 120 to produce a magnetic field.

(74) The magnetic filter 150 is placed in the vicinity of each of connection portions 151a and 151b linking each of the plasma generators 110 and the negative ion supply unit 120. The magnetic filter 150 may, of course, be positioned toward the plasma generator 110 or the negative ion supply unit 120.

(75) The magnetic filter 150 is configured to produce a magnetic field to restrict high-energy electrons generated in the plasma generator 110 in the active-glow state from entering the negative ion supply unit 120.

(76) The magnetic filter 150 may be configured as a magnetic filter using electromagnets 150a (hereinafter, referred to as an electromagnet magnetic filter 150a) or a magnetic filter using permanent magnets 150b (hereinafter, referred to as a permanent magnet magnetic filter 150b), or may alternatively be provided in various other combinations.

(77) The electromagnet magnetic filter 150a may include a power supply for an electromagnet 150a1 and an electromagnet 150a2.

(78) The electromagnet magnetic filter 150a may operate while being synchronized with a signal associated with a pulsed power envelope by the system controller 132, and may adjust a magnitude of a magnetic field depending on an operating state of the plasma generator 110. Specifically, the magnetic filter 150 generates a magnetic field when the corresponding plasma generator 110 is in the active-glow state, so as to prevent the high-energy electrons from transferring to the negative ion supply unit 120. Of course, the electromagnet magnetic filter 150a may produce a static magnetic field or a time-varying magnetic field, or may operate with a predetermined phase shift with respect to the signal associated with the pulsed power envelope.

(79) Referring to this drawing, the configuration offers two advantages. First, the high-energy electrons are restricted from entering the negative ion supply unit 120 so that only the low-energy electrons and the negative ion precursors generated in the first plasma generator 110a in the active-glow state can be supplied to the negative ion supply unit 120, leading to the generation of the negative ions in there. Second, simultaneously, the destruction of the negative ions, which are supplied from the second plasma generator 110b in the after-glow state to the negative ion supply unit 120, due to the high-energy electrons can be suppressed.

(80) Accordingly, the negative ion density in the negative ion supply unit 120 can remain high, and a fluctuation in the negative ion supply can be reduced.

(81) The permanent magnet magnetic filter 150b has advantages of being simple to be installed and being able to filter out the high-energy electrons at lower cost than the electromagnet magnetic filter 150a.

(82) The configuration allows the destruction of the negative ions caused by the high-energy electrons in the negative ion supply unit 120 to be suppressed, resulting in prevention of reduction in the overall negative ion supply efficiency of the system 100 for continuously supplying the negative ions using the multi-pulsed plasma sources.

(83) Meanwhile, instead of installing the magnetic filter 150, a volume or shape of a plasma vessel in the plasma generator 110 or the negative ion supply unit 120 may be changed so as to decrease the number of the high-energy electrons and diffuse (or transport) other species to the negative ion supply unit 120. For the same purpose, a size or shape of each of the connection portions 151a and 151b between the plasma generator 110 and the negative ion supply unit 120 may as well be changed.

(84) Alternatively, a plasma particle filter (not shown in FIG. 1) including an electrode or a grid capable of producing an electric field may be provided between the plasma generator 110 and the negative ion supply unit 120, in order to control transport characteristics of charged particles that are generated in the plasma generator 110 and transferred to the negative ion supply unit 120. For each species, an amount of the charged particles supplied can be controlled depending on a charge state through the plasma particle filter (not shown in the drawing).

(85) This configuration may offer a similar effect to the magnetic filter 150. In addition, of course, the configuration can be employed together with the magnetic filter 150.

(86) The beam extraction system 160 is configured to be connected to the negative ion supply unit 120 so as to extract negative ions from the negative ion supply unit 120 and use the extracted negative ions in the form of a negative ion beam.

(87) As a modified embodiment of the beam extraction system 160, an apertureless plate type electrode or a single-/multi-aperture grid 162 may be configured to be installed in the beam extraction system 160. By applying a voltage to the electrode/grid 162, extraction/use of positive ions or negative ions from an ion-ion plasma can be achieved. When the beam extraction system 160 includes the single-/multi-aperture grid 162, the beam extraction system 160 may further include a reaction chamber 170 in which an ion beam can be used.

(88) The beam extraction system 160 may include a power supply 161 for applying a voltage to the electrode/grid, and a beam extraction system controller 133 connected to the power supply 161 for controlling voltage characteristics.

(89) Device properties of the power supply 161, such as whether to use a direct-current (DC) or an alternating current/radio frequency (AC/RF) power supply, a voltage amplitude, a polarity of the DC power supply, a grounding option (e.g. negative ground, positive ground, or floating ground), and the like, may be determined depending on user's application.

(90) The beam extraction system controller 133 is configured to be connected to the system controller 132, and to receive commands for the control of time-varying output voltages therefrom. Consequently, the beam extraction system controller 133 may control characteristics (e.g., current, other time-varying properties, etc.) of the negative ions or beams extracted from the beam extraction system 160.

(91) The vacuum pump system 180 may be configured to be connected to the reaction chamber 170, and to enable a time-varying control of gas pressure in conjunction with the gas supply units 140a and 140b. Of course, various configurations can be provided by changing number and connection positions of the vacuum pump system.

(92) By providing the configuration, the present disclosure can offer a system utilizing the volume production mechanism, so as to facilitate maintenance of the plasma generators 110 and the like, compared to the negative ion source based on the surface production mechanism.

(93) In another embodiment, a system (not shown) for continuously supplying negative ions using multi-pulsed plasma sources may be configured to use a specific material capable of generating a large number of highly vibrationally excited molecules at a specific temperature for inner surfaces of the plasma generator 110 and the like in order to improve the negative ion production efficiency. For the same purpose, the system may also be configured by coating the inner surfaces of the plasma generator 110 and the like with a low work function material.

(94) The configuration provides higher negative ion production efficiency and even easier maintenance of the system, compared to the related art plasma negative ion source utilizing only the surface production mechanism.

(95) Hereinafter, a method for continuously supplying negative ions using multi-pulsed plasma sources will be described in detail.

(96) FIG. 4 is a flowchart illustrating a method of continuously supplying negative ions using multi-pulsed plasma sources, in accordance with one embodiment.

(97) FIG. 5 is a detailed flowchart related to a negative ion generation-and-supply step among those steps included in the flowchart illustrated in FIG. 4. FIG. 6 is a detailed flowchart related to a continuous negative ion supply step among those steps included in the flowchart illustrated in FIG. 4. FIG. 7 is a detailed flowchart related to a negative ion extraction step as the last step of the flowchart illustrated in FIG. 4.

(98) FIG. 8 is a conceptual illustration visualizing the flowchart represented in FIG. 4. Specifically, (a) of FIG. 8 illustrates a state of the plasma and behaviors of plasma species in the case where one plasma generator 110a is in the active-glow state and another plasma generator 110b is in the after-glow state, and (b) of FIG. 8 illustrates those in the case where the one plasma generator 110a is in the after-glow state and the another plasma generator 110b is in the active-glow state.

(99) Referring to FIG. 4 and (a) and (b) of FIG. 8, a method of continuously supplying negative ions using multi-pulsed plasma sources may include a negative ion generation-and-supply step (S10) of supplying negative ions, negative ion precursors and electrons generated in each of the plurality of plasma generators 110a and 110b in the active-glow state to the negative ion supply unit 120, or supplying negative ions generated in that in the after-glow state to the negative ion supply unit 120; a continuous negative ion supply step (S20) of continuously supplying negative ions to the negative ion supply unit 120 through an alternating operation of the plasma generators 110a and 110b while adjusting a phase difference between signals associated with pulsed powers applied to the respective plasma generators 110a and 110b; and a negative ion extraction step (S30) of extracting the negative ions from the negative ion supply unit 120.

(100) For reference, the term “alternating” does not just mean that the active-glow state of one plasma generator 110b starts as soon as the after-glow state of another plasma generator 110a ends at a phase difference of 180 degrees to each other (i.e., out-of-phase), and even includes meaning of that the pulsed powers are applied to the plasma generators 110a and 110b with any phase lag so that after the end of the active-glow of one plasma generator, the active-glow of another plasma generator starts at a specific time interval.

(101) Hereinafter, each step will be described in detail.

(102) Referring to FIGS. 5 and 8, the negative ion generation-and-supply step S10 may be divided into two steps (S12 and S16) depending on whether or not the power is applied to each of the plasma generators 110a and 110b (S11).

(103) In the active-glow state in which the power delivery to the plasma generator 110 is active, the negative ion generation-and-supply step S10 includes generating a plasma that contains large numbers of positive ions, negative ion precursors and electrons and a relatively small number of negative ions (S12), and generating negative ions by reactions between the negative ion precursors and the low-energy electrons transferred from the plasma generator 110 (S15).

(104) In this respect, when the magnetic filter 150 is placed between each of the plasma generators 110a and 110b and the negative ion supply unit 120, if necessary, and the operation of magnetic filter 150 is controlled by the system controller 132, the step of supplying electrons to the negative ion supply unit 120 prior to the step (S15) may further include configuring the magnetic filter 150 to restrict high-energy electrons from entering the negative ion supply unit 120 (S13) and producing the magnetic field by the magnetic filter 150 (S14).

(105) In the after-glow state in which the power delivery to the plasma generator 110 is inactive, the negative ion generation-and-supply step (S10) includes generating negative ions in the plasma generator 110 by reactions of the negative ion precursors with the low-energy electrons in a circumstance where a large number of high-energy electrons is destructed (S16), and supplying the generated negative ions to the negative ion supply unit 120 (S17).

(106) Referring to FIGS. 6 and 8, the continuous negative ion supply step (S20) includes adjusting phase differences between the signals associated with pulsed powers applied to the respective plasma generators 110 through the system controller 132 (S21), and supplying negative ions generated in the after-glow state to the negative ion supply unit 120 through the alternating operation of the plasma generators 110 with the phase differences (S22). Here, positive ions, negative ion precursors and electrons are generated in a plasma generator 110 in the power-on state (S10′1). On the other hand, negative ions are generated in the remainder of plasma generators 110 in the power-off state (S10′2 to S10′n).

(107) Referring to FIG. 6, at the step of generating and supplying negative ions (S22), by adjusting pulse phases ϕ1, ϕ2, . . . ϕn associated with the respective pulsed powers applied to the plurality of plasma generators 110, the corresponding start times of the active-glows which are favorable for generation of negative ions may be the same or different. Here, the pulse phases ϕ1, ϕ2, . . . ϕn may be different from one another, or some of the pulse phases may be the same. However, setting all of the phases to the same value is not allowed.

(108) The foregoing embodiment has illustrated that when one plasma generator 110 is in the active-glow state, another plasma generator 110 in the after-glow state generates negative ions, but the present disclosure is not limited to this. Alternatively, when one group having a plurality of plasma generators is in the active-glow state, another group may be in the after-glow state by adjusting the phase differences between the signals associated with the pulsed powers.

(109) For reference, in the foregoing description, n is a natural number and denotes the total number of plasma generators 110 installed in the system for continuously supplying negative ions using the multi-pulsed plasma sources.

(110) Referring to FIGS. 7 and 8, the negative ion extraction step (S30) may include setting the polarity of the beam extraction system 160 connected to the negative ion supply unit 120 (S31), extracting positive or negative ions (S32). Specifically, the positive ions are extracted in the case of a negative electrode in beam extraction system 160 (S32a), and the negative ions are extracted in the case of a positive electrode (S32b).

(111) At the negative ion extraction step (S30), the configuration can not only supply negative ions, but also provide positive ions from the negative ion supply unit 120, if necessary, depending on user's application. Therefore, even though the step of extracting ions is named the negative ion extraction step (S30) in this specification, the function of the configuration at the step is not limited to the name.

(112) The foregoing description is merely illustrative for the embodiments to implement the system or method of continuously supplying the negative ions using the multi-pulsed plasma sources according to the present disclosure, and thus the present disclosure is not limited to the foregoing embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention as defined by the appended claims.

INDUSTRIAL APPLICABILITY

(113) The present disclosure may be implemented and applied in various industrial fields including semiconductor equipment, a space propulsion system, and a fusion reactor system in which a continuous supply of negative ions is needed.