WO2001093293A1

WO2001093293A1 - Plasma ion source and method

Info

Publication number: WO2001093293A1
Application number: PCT/RU2001/000060
Authority: WO
Inventors: Gleb Elmirovich Bugrov; Sergei Gennadievich Kondranin; Elena Alexandrovna Kralkina; Vladimir Borisovich Pavlov
Original assignee: Plasma Tech Co., Ltd.
Priority date: 2000-05-30
Filing date: 2001-02-14
Publication date: 2001-12-06
Also published as: RU2167466C1; AU2001237845A1

Abstract

A plasma ion source comprises a cathode chamber (1) with a gas input unit (2). A hollow cathode (3) forming an anode chamber (4) is connected with the cathode chamber (1) via the outlet made in the wall of the latter. The ion source structure includes an electrostatic system of ion extraction with an emission electrode (5) fixed in the anode chamber (4) outlet. With the help of a magnetic system, in the cathode (1) and anode (4) chambers the magnetic field is created with the induction vector of a preferably axial direction. An ignition electrode electrically connected with the hollow anode (3) is fixed in the cathode chamber (1). An additional electrode (10) is mounted in the outlet of the cathode chamber (1), which is insulated from the hollow anode (3) and the cathode chamber (1). The additional electrode (10) has an axial orifice with a diameter much smaller than the maximum internal cross section of the hollow anode (3). The electrical discharge between the cathode (1) and anode (4) chambers is ignited through the orifice. A particular ion source configuration and the oparation method correspond to the present invention and ensure increased energy and gas efficiency and high degree of uniformity of the generated ion current density.

Description

PLASMAIONSOURCEAND METHOD

FIELD OF THE INVENTION

The present invention is related to plasma technology, in particular, to plasma sources designed for generating intensive ion beams and their operation methods. The invention may be applied in technological processes using ion beams for coating, ion assistance, ion implantation and modification of material properties.

DESCRIPTION OF THE PRIOR ART Several different types of plasma ion sources are known.

For instance, the gas discharge device with a hollow cathode is known from Japanese Application JP 57011448A (HOI J 3/04, 27/08) published on 21.01.82. The mentioned device is used as a part of ion sources. The electrons generated in the cathode chamber are extracted into the expansion chamber along the magnetic field lines of a particular configuration. The magnetic field in this device is created by the magnetic system comprising several electromagnetic coils mounted round the hollow cathode. The structure of this device makes it possible to decrease the consumption of energy in generating both the basic discharge and, accordingly, a wide-aperture ion beam.

Another plasma ion source described in Application DE 3429591A1 (H01J 3/04, published on 21.03.85) comprises a hollow cathode, an expansion anode chamber and a magnetic system. The magnetic system is designed so that it has a magnetic core forming a magnetic gap between two circular poles, by which the ion extraction into the expansion chamber takes place. This design of the ion source is intended to increase its gas and energy efficiency and to enhance the extracted ion current. In recent years plasma ion sources with cold hollow cathodes have found wide application in different ion-beam technologies. For instance, there was information on the development ofthe ion source operating on both inert and chemically active gases.

The known sources use a cold hollow cathode, inside of which a magnetic field is generated by permanent magnets for stabilizing the discharge. The ion source also comprises an anode chamber separated from a hollow cathode. The maximum value ofthe ion current in ion sources of this type is 150 mA and 300 mA for different diameters of the discharge chamber outlet: for 5 and 10 cm, respectively. A discharge voltage between the hollow cathode walls and the anode chamber is in the range of 350-÷550V. The lifetime of the ion source with the diameter operating on a chemically active gas exceeded 500 hours thereof (Gontc arov Leonid, Makounin Sergei. Cold Hollow Cathodes for Ion Sources Operating on Active and Inert Gases [on-line], [2000-04-24]. Internet address: , http://www.orc/ru/~ platar/7r.htm). The closest analog of the invention being patented is the plasma ion source whose structure was described by N.V. Gavrilov, D.P. Yemlin and S.P. Nikulin in "Uniform Plasma Generation in Glow Discharge with a Hollow Anode and a Wide-Aperture Hollow Cathode" (ZhTF Letters, Journal, 1999, Nol 12, pp.83-88). The invention prototype has a cathode chamber with a gas-input unit, a hollow anode forming an anode chamber, an electrostatic system of ion extraction with an insulated emission electrode mounted at the anode chamber outlet, and a magnetic system. The anode chamber is connected with the cathode chamber via the outlet made in the wall of the latter. By means of the magnetic system a magnetic field with the induction vector predominantly ofthe axial direction is generated in the cathode and anode cavities. The mentioned ion source makes it possible to produce a nearly uniform density distribution of the ion emission current at a low gas pressure and is used for ion beam generation in a wide range of energies. That ion source is not, however, intended for operation on chemically active gases under the given requirements for service life, reliability, gas and energy efficiency. That ion source has limited possibilities to generate intensive ion beams: the generated ion current density does not exceed 3 mA/cm². These limiting values of the beam current are achieved with a considerable increase of the ion energy and a decrease ofthe current density uniformity across the beam. It should be noted that these parameters are decisive for ensuring a possibility of applying ion sources in a number of technological processes used for modification of materials. In addition, non-uniformity of intensive beams generated by that ion source can exceed 10%.

The closest analog ofthe operation method ofthe plasma ion source being patented is the operation method described in Patent Application GB 2064856A (H01J 37/08, published on 17.06.81). That operation method of the plasma ion source is to first inject the working plasma-generating substance through a gas-input unit and to apply voltage to the gas inlet, electrically insulated from the cathode chamber, to the walls and to the hollow anode. The hollow anode forms the anode chamber that is connected with the cathode chamber via the outlet made in the latter. The above mentioned operation method of the plasma ion source provides a discharge energy increase between the hollow cathode and the hollow anode and, accordingly, high densities of the ion current. But application of that method is limited due to a low gas efficiency, a low energy efficiency and non-uniformity ofthe ion current density in generating beams of large cross-sections. Disadvantages of the mentioned operation method of the plasma ion source are similar to those described above that are inherent to an ion source structure chosen as a prototype.

SUMMARY OF THE INVENTION The present invention is based on the problem of developing a plasma ion source of sufficiently high reliability, long lifetime, and high energy and gas efficiency. In addition, the plasma ion source is intended to produce ion beams, including those of large cross-sections, with uniform current density distributions. The design characteristics of the ion source are to be achieved not only while operating on inert gases but also on chemically active substances. The above-listed technical results are ensured owing to the following design of the plasma ion source.

The plasma ion source comprises the cathode chamber with the gas-input unit, the hollow anode forming the anode chamber connected with the cathode chamber via the outlet made in the wall of the latter, the electrostatic ion extraction system with the insulated emission electrode mounted at the anode chamber outlet, and the magnetic system producing a magnetic field with an induction vector of predominantly axial direction in the cathode and anode chambers. In addition, according to the present invention, the source contains the ignition electrode mounted in the cathode chamber and electrically connected with the hollow anode. The additional electrode insulated from the hollow anode and the cathode chamber is mounted at the cathode chamber outlet. This additional electrode has the axial orifice, with the diameter d being not greater than 0.1 D, where D is the maximum internal cross section of the hollow anode.

If the value of D is greater than 50 mm, the orifice diameter d is preferably chosen to be smaller than 5 mm. The additional electrode with the axial orifice diameter d equal to 3 mm is preferable, under the condition that the relation d < 0.1 D is fulfilled.

In the preferable variant of the ion source design the cathode is made in such a way that it can be force cooled. The best parameters of the device, including gas and energy efficiency, are achieved in the case when the magnetic system is designed in such a way that it is possible to create a magnetic field with the induction decreasing from the walls of the anode and cathode chambers towards their longitudinal symmetry axis and in the direction of the chamber outlets.

Alternatively, the magnetic system may be designed in the form of permanent magnet assemblies mounted along the external surface of either the cathode chamber or the cathode and anode chambers. The additional electrode is made of a magnetically soft material and serves as a pole ofthe magnetic system. In another alternative design of the ion source the magnetic system is formed by electromagnetic coils.

Monoenergy ion beam generation is ensured when the magnetic system is designed in such a way that it is possible to create a magnetic field supply in the anode chamber cavity with the induction vector of an opposite direction with respect to the vector of magnetic field induction in the cathode chamber cavity.

The highest values of extracted ion current can be achieved when the magnetic system is designed so as to enable creation of the magnetic field in the anode chamber with the induction vector of the same direction as that of the magnetic field induction in the cathode chamber cavity. In this case the non-uniformity of the ion density distribution in the anode chamber is reduced and loss of generated ions is decreased.

To achieve the uniform distribution of high-energy electrons in the anode chamber and, accordingly, to increase uniformity of the extracted ion current in the anode chamber cavity, the electron reflector can be installed opposite the axial orifice in the additional electrode. It is also desirable that the ion source should comprise an extra gas-input unit of the annular configuration placed in the anode cavity, thereby making it possible to improve gas efficiency of the source and to ensure insulation of the cathode chamber walls against chemically active substances.

It is most effective to use the additional electrode with a projection directed towards the cathode cavity, the axial orifice being made in the additional electrode projection. This additional electrode projection may be made in the form of a truncated cone. The cathode cavity gas input is preferably designed so that it is connected electrically with the hollow anode via the variable resistor, with which the discharge parameters in the anode cavity can be controlled.

It is also desirable to design the power-supply-generating system ofthe source in such a way that the cathode chamber walls are connected with the negative pole of he first voltage source. The hollow anode is connected with the positive pole of the first voltage source and the positive pole ofthe second voltage source, the negative pole ofthe latter being grounded.

The gas-input unit of the cathode chamber may be used as an ignition electrode, the former insulated against the chamber. To achieve the above mentioned technical results it is also necessary to apply the method of operating the plasma ion source, which consists in the following.

While applying this method in practice, the working plasma-generating substance is first injected through the gas-input unit located in the cathode chamber cavity of the plasma ion source, then the voltage is applied to the ignition electrode mounted in the cathode chamber cavity, to the cathode chamber walls and to the hollow anode forming the anode chamber, which is connected with the cathode chamber via the outlet of the latter. In addition, according to the present invention, in the cathode and anode chamber cavities a magnetic field is created with the induction vector of a preferably axial direction. The voltage of positive polarity is applied to the cathode chamber gas-input and to the hollow anode, the voltage of negative polarity is applied to the walls ofthe cathode chamber. The voltage values are chosen to be sufficient for preliminary ignition of an electric discharge in the cathode chamber cavity between its walls and the ignition electrode and for subsequent ignition of an electric discharge between the cathode and anode chambers through the orifice made in the additional electrode. This electrode is electrically insulated from the hollow anode and the cathode chamber and mounted at the outlet of the latter. The orifice diameter d in the additional electrode is chosen to be not greater than 0.1 D, where D is the maximum internal cross section ofthe hollow anode.

To reduce losses of charged particles on the chamber walls, the magnetic field is created in such a way that the value of its induction decreases from the walls ofthe anode and cathode chambers towards their longitudinal symmetry axes and their outlets.

Monoenergy ion beam generation is effected in the case when in the anode chamber cavity the magnetic field is created with the induction vector of an opposite direction with respect to the direction of the induction vector of the magnetic field in the cathode chamber cavity.

The highest values of the extracted ion current may be achieved, if in the anode chamber cavity the magnetic field is created with the induction vector of the same direction as that ofthe magnetic field induction vector in the cathode chamber cavity.

The value of the extracted ion current and/or the value of the power contribution to the discharge can be controlled by choosing a resistance parameter of the variable resistor inserted into the electrical circuit between the hollow anode and the cathode chamber gas- input unit. To create a magnetic field it is possible to use a magnetic system made in the form of permanent magnet assemblies arranged along the external surface of either the cathode chamber or the cathode and anode chambers.

The magnetic field can also be created by the magnetic system formed by electromagnetic coils. Ion extraction from the anode chamber is preferably effected by means of the electrostatic extraction system, including the emission electrode, which is at a floating potential, the accelerating electrode and the grounded decelerating electrode.

The gas-input unit located in the cathode chamber and insulated from its walls can be used as an ignition electrode. In this case the positive polarity voltage is applied to a gas-input unit.

Chemically active plasma-generating working gas is preferably supplied through an extra gas-input unit located in the anode cavity, the inert plasma-generating gas is supplied via the cathode chamber gas-input unit.

BRIEF DESCRIPTION OF THE DRA WINGS

For further details of the invention, reference may be made to a particular design illustrated in the accompanying drawings, wherein:

Fig.1 presents a schematic view of the longitudinal section of the plasma ion source manufactured according to the invention. Fig.2 presents a schematic view of the transverse section of the anode chamber of the plasma ion source shown in Fig.l (section A- A).

Fig.3 presents schematically the electrical supply circuit ofthe plasma ion source. DESCRIPTION OF THE PREFERRED EMBODIMENTS

The plasma ion source patented can be made according to different designs and used as a part of industrial installations, e.g., plasma-chemical reactors and ion-beam facilities as well as a structural element of electrical rocket engines. The description a preferred design of the plasma ion source to be used as a part of the ion-beam industrial installation is given below. In the design considered the internal diameter ofthe hollow ion source cathode is 50 mm.

The plasma ion source is a structural type ofthe cold cathode ion source. The structure of the plasma ion source (see Figs. 1 and 2) comprises the cathode chamber 1 with the gas- input unit 2, the hollow anode 3 forming the anode chamber 4. The cathode chamber 1 being a hollow steel cylinder is connected with the anode chamber 4 via the cathode chamber outlet made in the end wall ofthe cathode chamber. At the outlet ofthe anode chamber 4 there is an electrostatic system for ion extraction with the emission electrode 5 located directly on the end wall of the anode chamber. The accelerating electrode 6 and the grounded output decelerating electrode 7 are arranged in series behind the emission electrode 5. All the electrodes ofthe electrostatic system are insulated from each other by means of insulators 8.

The ignition electrode, whose functions in this structural design are performed by a metal gas-input unit 2 electrically insulated from the cathode chamber walls, is fixed in the cathode chamber 1. For the ion source to operate, the mentioned gas-input unit is electrically connected with the hollow anode 3 via the adjustable resistor (see Fig. 3). The gas-input unit

2 is fixed to the end wall ofthe cathode chamber 1 by means of insulators 9.

The additional electrode 10 is installed at the outlet of the cathode chamber 1, the additional electrode is electrically insulated from the hollow anode 3 and the walls of the cathode chamber by means of the insulators 1. The additional electrode 10 has an axial orifice, with the diameter not exceeding 0.1 D, where D is the maximum internal cross section of the hollow anode. In the design considered D = 50 mm. With D being greater than 50 mm, the orifice diameter d is preferably chosen to be smaller than 5 mm. In the design considered the axial orifice diameter d in the additional electrode 10 is 3 mm if the following relation is fulfilled: d = 3 mm < 0.1 D = 5 mm.

The additional electrode 10 has a projection in the shape of a truncated cone, which is directed towards the cavity of the cathode chamber 1. The axial orifice is made in the additional electrode projection. The cathode chamber 1 is designed in such a way that it can be force cooled. For this purpose it is equipped with tubes 12 in which a cooling liquid is circulating. The tubes 12 are made of heat-resistant stainless steel and electrically insulated from the other parts ofthe ion source.

The magnetic system consists of permanent magnet assemblies 13 and 14 arranged along the external surface of the anode chamber 1 and the cathode chamber 4, respectively.

The additional electrode 10 serves as a pole of the magnetic system. For this purpose it is made of magnetically soft material. In other designs it is possible to apply electromagnetic coils instead of permanent magnet assemblies for creation ofthe magnetic field.

In order to create the optimal magnetic field configuration the magnetic system in the ion source chambers is designed so that it is possible to create a magnetic field in the cavity ofthe anode chamber 4. The induction vector points in the opposite direction with respect to the magnetic induction vector ofthe magnetic field in the cavity ofthe cathode chamber 1.

An electron reflector 15 is fixed in the cavity of the anode chamber 4 just opposite the axial orifice in the additional electrode 10. This electron reflector provides the uniform distribution of the charged particle density in the radial direction in the cavity of chamber 4. The ion source also comprises a gas-input unit 16 of the annular shape, which ensures the uniform distribution of the working medium in the cavity of the anode chamber 4 and, accordingly, the uniform distribution ofthe extracted ion current.

The structural elements of the ion source are fixed on the flanges 17 and 18, which, in their turn, are fixed on the mounting flange 19. The assemblies of permanent magnets 13 and 14 are mounted on the flanges 17 and 18 by fasteners. The mentioned flanges are electrically insulated from the mounting flange 19 by means of rod insulators 20 arranged in series along the perimeter of the flange 18. In this particular design of the magnetic system the value of the magnetic field induction decreases from the anode 1 and the walls ofthe cathode chamber 4 towards their longitudinal symmetry axes and in the direction of their outlets.

The mounting flange 19 is intended to fix the plasma ion source in the vacuum chamber and made in such a way that it can be vacuum-tight attached to its body. The flange 19 has the vacuum ( hermetically sealed ) connectors 21 of the electrical input 22 of the power supply system for the ion source discharge electrodes and the electrostatic ion extraction system electrodes. In addition, the flange 19 has the vacuum connector 23 of the gas-input unit 2 and the vacuum connectors 24 of the tubes 12, through which the cooling liquid is pumped. The common mounting flange 19 is used to fix the ion source and makes it possible to remove quickly the ion source together with the vacuum connectors of the power supply system and the gas and liquid supply systems.

The plasma ion source is fitted with a power supply system (see Fig. 3). The walls of the cathode chamber 1 are connected with the negative pole of the power supply 25. The cathode 1 and anode 4 chambers are electrically insulated from each other by means of the insulators 11. The hollow anode 3 is electrically insulated from the walls of the anode chamber body by means of the insulators 26 and connected with the positive pole of the power supply 25 and the positive pole of the power supply 27, whose negative pole is grounded. The emission electrode 5 of the electrostatic ion extraction system is at a floating plasma potential. The accelerating electrode 6 is connected with the negative pole of the accelerating voltage source 28, whose positive pole is grounded. The outlet (decelerating) electrode 7 ofthe electrostatic system is grounded.

The operation of the plasma ion source, made according the design described above, and hence the operation method of the plasma ion source as given in the present invention, proceeds in the following manner.

The working plasma-generating inert gas, e.g., argon is supplied to the cathode chamber 1 through the gas-input unit 2. The plasma-generating gas, chemically active gases (for example, gases containing chlorine and fluorine gases, may be used) is supplied to an anode chamber 4 through the additional gas-input unit 16. With this arrangement of gas-input units the density of a chemically active gas decreases in the cathode chamber 1 and, consequently, the ion source reliability and lifetime increases. In addition, application of an additional gas- input unit 16 having the annular shape ensures a uniform distribution of a plasma-generating gas in the discharge volume of the anode chamber 4. By means of the permanent magnet assemblies 13 and 14, magnetically soft flanges and the additional magnetically soft electrode 10 a magnetic field is established with an induction vector of preferably axial direction. The value of magnetic field induction decreases from the walls of the anode and cathode chambers to their longitudinal symmetry axes and in the direction of the axial orifice of the additional electrode 10 and the emission electrode 5 ofthe electrostatic ion extraction system. The magnetic field induction vector in the anode chamber 4 cavity has an opposite direction with respect to that in the cavity ofthe cathode chamber 1.

Voltage from the power supplies 25 and 27 is applied between the walls of the cathode chamber 1 , the-gas input unit 2 insulated from the cathode chamber and the hollow anode. Voltage of the positive polarity from 25 and 27 is applied to the gas-input unit 2 of the cathode chamber 1 and the hollow anode. Voltage of the negative polarity from the power supply 25 is applied to the walls ofthe cathode chamber 1.

Voltage from the power supply 25 is applied between the walls ofthe cathode chamber 1 and the gas-input unit 2 serving as an ignition electrode, the voltage is sufficient for discharge gap break-down and discharge ignition in the cathode chamber 1. Applying voltage application to the anode 3 and the gas-input unit 2 supplied from 25 and 27 results in ion extraction from the cathode chamber 1 to the anode chamber 4. Voltage of these sources is chosen to be sufficient for ignition of electrical discharge between the cathode and anode chambers through the orifice made in the additional electrode 10 which is insulated from the hollow anode 3 and the cathode chamber 1. As a result a discharge is ignited in the anode chamber 4. An essential condition for discharge ignition between the anode and the cathode chambers is to choose the orifice diameter d in the additional electrode fixed at the cathode chamber outlet. The diameter d must not exceed 0.1 D, where D is the maximum internal cross section of the hollow anode 3. In the design under consideration a discharge is ignited through the orifice made in the additional electrode, whose diameter is 3 mm.

The voltage applied is controlled by means of the variable resistor included in the electrical circuit. The magnetic field created in the chambers 1 and 4 promotes ignition and increases the ion source operation efficiency. The optimal values of the magnetic field induction are in the range from 0,001 to 0,05 T .. Improving of plasma density uniformity in the anode chamber as a whole and in the vicinity of the emission electrode 5 is effected by means of the electron reflector 15 connected with the additional electrode 10. The reflector 15 is insulated from the hollow anode 3. Application ofthe electron reflector is most effective, if the internal diameter of the anode chamber exceeds 5 cm. As a result of the studies conducted on the ion source prototype it was found that the basic discharge ignition is effected as the value ofthe discharge voltage applied between the walls of the cathode chamber 1 and the hollow anode 3 increases up to 350 V. Then there arises a discharge current between the cathode chamber 1 and the anode chamber 4. The ignition ofthe discharge is accompanied by decrease of the discharge voltage down to 300 V. The appearance ofthe discharge current in the anode chamber 4 is accompanied by extraction of the ion beam, with the current being stabilised within 3 ÷ 5 min. The discharge voltage variation in the range from 350 to 450 V results in discharge current variation in the range from 150 to 700 mA. Accordingly, the current ofthe extracted ion beam varies from 20 to 55 mA.

Under particular conditions, with the orifice diameter in the additional electrode 10 being equal to 3 mm, the value of the extracted ion current was 70 mA. The discharge between the cathode and anode chambers was ignited through this axial orifice. The value of the discharge voltage was 510 V. The measured value of the ion current corresponded to the emission outlet area of the anode chamber- 17 cm². In the case of an increased diameter of the orifice in the additional electrode 10, i.e. with a deviation from the condition d ≤ O.l D, the ion energy cost and gas efficiency increased considerably while the extracted ion current was decreased. Thus, for example, if the following dimensions ofthe ion source were chosen: d = 5 mm and D = 50 mm, the discharge voltage was increased up to 560 V with a simultaneous decrease of ion beam current down to 60 mA.

In addition, it was established that on achieving a steady operation mode of the ion source the value of the extracted ion current can be controlled by adjusting the variable resistor (see Fig. 3 ) included in the circuit between the ignition electrode (gas-input unit 2) and the hollow anode 3. At the value ofthe discharge current 500 mA, the resistor resistance increases from 660 Ohm to 1800 Ohm the ion beam current increases nonlinearly from 33 mA to 37 mA. Further growth of the resistance of the variable resistor up to 2680 Ohm did not affect the ion current. Thus, by choosing the value of resistance of the variable resistor included in the electrical circuit between the hollow anode 3 and the gas-input unit 2 of the cathode chamber it is possible to control the extracted ion current and/or the amount of energy contribution into the discharge.

The extraction and formation of the ion beam in the described design of the invention are realized by means of the three-electrode electrostatic ion extraction system operating on the "acceleration-deceleration" principle. A difference of potentials is established between the gas discharge plasma generated in the cavity of the anode chamber 4, whose potential is given by the hollow anode 3, the emission electrode 5 (that is at a floating potential), the accelerating electrode 6, at which the voltage of negative polarity is supplied from source 28 and the decelerating electrode 7. As a result the electric field extracts the ions from the chamber 4. With the help of the electrostatic extraction system an ion beam with a specified ion current density and specified cross-section is formed.

In the course of experiments it was found that at the discharge voltage in the range from 300 to 600 V the ion current density varied from 0.1 to 5 mA/cm², respectively. Non- uniformity of the ion current density across the beam with the diameter of 40 mm did not exceed 5% ( measurement was carried out at the target placed at the distance of 200 mm from the outlet electrode 7 ofthe electrostatic ion extraction system ).

The experimental data obtained are indicative of a high energy and gas efficiency and a high degree of uniformity of the ion current density of the plasma ion source devised. It is possible to generate intensive beams ion of both inert and chemically active gases. The ion source constructed according to the present invention is of a high operation reliability and a long service life due to the fact that chemically active substances practically do not come in contact with the heated parts of the cathode chamber serving as an emitter. Thus, by the technical results achieved both the plasma ion source patented and its operation method surpass the corresponding variants ofthe device chosen as prototypes.

INDUSTRIAL APPLICABILITY

The invention may find a wide application in plasma technology, including structures of plasma ion sources designed for generation of intense ion beams of large cross-sections and for practical realization of their operation methods.

The plasma ion source patented and constructed according to the invention may be used in plasma technology, as a structural unit of technological facilities with gas-discharge ion sources, e.g., implanters, as well is in accelerators of changed particles (ions). The invention may find an application in various technological processes using ion beams. Uniform beams of large cross-section generated by the plasma ion source may be used for processing semiconductor materials, making coatings, ion implantation, ion assistance, cleaning the surfaces and modifying the properties of materials.

Claims

CLAIMSWe claim:

1. A plasma ion source comprising a cathode chamber (1) with a gas-input unit (2), a hollow anode (3) forming an anode chamber (4) connected with the cathode chamber (1) via the outlet made in the wall of the latter, an electrostatic ion extraction system with an insulated emission electrode (5) mounted on the outlet of the anode chamber (4), and a magnetic system designed for creating a magnetic field in the cathode and anode chambers with the induction vector of preferably axial direction, characterized by the fact that it contains an ignition electrode fixed in the cathode chamber and electrically connected with the hollow anode (3); the outlet of the cathode chamber (1) has an installed additional electrode (10) insulated from the hollow anode (3) and the cathode chamber (4), with an axial orifice made in the additional electrode (10), whose diameter does not exceed 0.1 D, where D is the maximum internal cross section ofthe hollow anode (3).

2. The ion source of claim 1, characterized by the fact that when D is greater than 50 mm the outlet diameter d is chosen to be smaller than 5 mm.

3. The ion source of claim 1 or claim 2, characterized by the fact that the diameter d is equal to 3 mm, under the condition that the relation d < 0.1 D is fulfilled.

4. The ion source of claim 1, characterized by the fact that the cathode chamber (1) is designed so that it can be force cooled.

5. The ion source of any above claims, characterized by the fact that the magnetic system is made so that it can create a magnetic field, with the induction value decreasing from the walls ofthe anode (3) and cathode (4) chambers to their longitudinal symmetry axes and in the direction of their outlets.

6. The ion source of any above claims, characterized by the fact that the magnetic system is made in the form of permanent magnet (3 and 14) assemblies arranged along the external surface of the cathode chamber or the cathode (1) and anode (4) chambers, the additional electrode (10) made of magnetically soft material, which serves as a pole of the magnetic system.

7. The ion source of any above claims, characterized by the fact that the magnetic system is formed by electromagnetic coils.

8. The ion source of claim 1, characterized by the fact that the magnetic system is made so that it can create a magnetic field in the cavity (4) of the anode chamber with the induction vector of an opposite direction with respect to the magnetic field induction vector in the cavity (1) ofthe cathode chamber.

9. The ion source of claim 1, characterized by the fact that the magnetic system is made so that it can create a magnetic field in the cavity (4) ofthe anode chamber with the induction vector of the same direction as the magnetic field induction vector in the cavity (1) of the cathode chamber.

10. The ion source of any above claims, characterized by the fact that in the anode chamber (4) the electron reflector (15) is fixed opposite the axial orifice in the additional electrode.

11. The ion source of any above claims, characterized by the fact that it has an additional gas-input unit (16) of an annular configuration arranged in the anode cavity (4).

12. The ion source of any above claims, characterized by the fact that the additional electrode (10) is made with a projection directed towards the cavity (1) of the cathode chamber, the axial orifice is made in the projection ofthe additional electrode (10).

13. The ion source of claim 12, characterized by the fact that the projection of the additional electrode (10) is made in the form of a truncated cone.

14. The ion source of any above claims, characterized by the fact that the ignition electrode arranged in the cathode cavity is electrically connected with the hollow anode (3) via the variable resistor.

15. The ion source of any above claims, characterized by the fact that the walls of the cathode chamber (1) are connected to the negative pole ofthe first power supply (25), and the hollow anode (3) is connected to the positive pole of the first power supply and to the positive pole ofthe second power supply (27), the negative pole ofthe latter is grounded.

16. The ion source of any above claims, characterized by the fact that the gas-input unit (2) ofthe cathode chamber (1) insulated from the latter serves as an ignition electrode.

17. The ion source operation method, during realization of which the working plasma- generating matter is introduced through the gas-input unit (2) arranged in the cavity (1) ofthe cathode chamber of the plasma ion source and the voltage is applied to the ignition electrode fixed in the cavity (1) ofthe cathode chamber, to the walls ofthe cathode chamber (1), and to the hollow anode (3) forming the anode chamber (4), which is connected with the cathode chamber (1) via the outlet of the latter, characterized by the fact that in the cathode (1) and anode (4) chambers a magnetic field is created with the induction vector of a preferably axial direction, the voltage value is chosen to be sufficient for preliminary ignition of the electric discharge in the cathode chamber cavity (1) between its walls and the ignition electrode and for the following ignition of the electrical discharge between the cathode (1) and anode (4) chambers through the orifice made in the additional electrode (10), which is insulated from the hollow anode (3) and the cathode chamber (1) and it is fixed in the outlet ofthe latter, the diameter d of the orifice is chosen to be not greater than 0.1 D, where D is the maximum internal cross section ofthe hollow anode (3).

18. The method of claim 17, characterized by the fact that the induction value of the created magnetic field decreases from the walls of the anode (4) and cathode (1) chambers towards their longitudinal symmetry axes and in the direction of their outlets.

19. The method of claim 17, characterized by the fact that in the cavity (4) of the anode chamber a magnetic field is generated with the induction vector of an opposite direction with respect to the magnetic field induction vector in the cavity (1) ofthe cathode chamber.

20. The method of claim 17, characterized by the fact that in the anode chamber cavity (4) a magnetic field is generated with the induction vector of the same direction as the magnetic field induction vector in the cavity (1) ofthe cathode chamber.

21. The method of claim 17, characterized by the fact that the value ofthe extracted ion current and/or the value of energy contribution to the discharge are controlled by choosing a resistance parameter of the variable resistor included in the electrical circuit between the hollow anode (3) and the ignition electrode.

22. The method of claim 17, characterized by the fact that the magnetic system made in the form of permanent magnet (13 and 14) assemblies arranged along the external surface of the cathode chamber (1) or cathode (1) and anode (4) chambers is used for creation of the magnetic field.

23. The method of claim 17, characterized by the fact that the magnetic system formed by electromagnetic coils is used for generation ofthe magnetic field.

24. The method of claim 17, characterized by the fact that ion extraction from the anode chamber (4) is effected with the help of the electrostatic system comprising an emission electrode (5), which is at a floating potential, and the accelerating (6) and decelerating (7) electrodes.

25. The method of claim 17, characterized by the fact that the gas-input unit (2) of the cathode chamber (1) insulated from the walls of the cathode chamber (1) is used as an ignition electrode, positive polarity voltage applied to the gas-input unit (2).

26. The method of claim . 17, characterized by the fact that a chemically active plasma- generating gas is injected through the additional gas-input (16) unit arranged in the cavity (4) of the anode, the inert plasma-generating gas is injected through the gas-input unit (2) of the cathode chamber (1).