KR960004963B1 - Plasma devices using ion induced sputtering - Google Patents

Abstract

In the generating apparatus for high density plasma using ion induced sputtering, a needle valve(7) is mounted at a vacuum chamber(6), which mounts a metal plasma generating device consisting of a filament(1), a filament electric power supplier(14), an anode(4) and a main discharge electric power supplier(15). A metal ion generating device installed on the inner wall of the vacuum chamber(6), consists of a target(5), a lead-out electrode(9), an accelerating electrode(10) and a decelerating electrode(11). The apparatus is suitable for generation of high current metal ion.

Description

High Density Plasma Generation Using Ion Induced Sputtering and Its Apparatus

1 is a principle diagram of a single discharge box type metal ion source using the ion induced sputtering of the present invention.

FIG. 2 is a cross-sectional view of the discharging compartment of FIG. 1 for explaining the principle of the generation of high density metal element plasma by ion induced sputtering.

3 is a principle diagram of a conventional external oven type metal ion source.

4 is a schematic diagram of a practical application device of a metal ion source having two discharge boxes and a sputtering electrode structure of the present invention.

* Explanation of symbols for main parts of the drawings

1: filament 2: power lead conductor

3: insulator 4: anode

4 ': middle electrode 4 ": large cathode

5: sputtering target 6: vacuum box

7: needle valve 8: electromagnet

9: withdrawal electrode 10: acceleration electrode

11: Reduction electrode 12, 13: Leading electrode insulator

14 filament power supply 15 main discharge power supply

16: sputtering power supply 17: electromagnet power supply

18: acceleration power supply 19: bias power supply

20 plasma 21 ion beam

22: metal weight 23: metal

24: oven 25: resistance heating wire

26: resistance heating power supply 27: delivery pipe.

The present invention utilizes ion induced sputtering to generate and ionize atoms of solid elements, including high melting point elements, to generate a high density plasma therefrom, and the device, i.e. The present invention relates to a metal ion source for realizing the extraction of high current metal ions having a shape.

Ion sources are widely used as ion generation sources in particle accelerators, ion implanters, mass spectrometers and the like. Among various ion sources, the plasma type ion source is injected into a discharge state of the element of the ion to be obtained in a base state, and then discharged by direct current, high frequency, or microwave to ionize a gas and generate a plasma, and then It is a device that extracts ions by applying an appropriate voltage. Among the elements on the periodic table, use a suitable pressure reducing device for gaseous elements and a vaporization or evaporator for liquid elements, and discharge easily while maintaining the pressure within the discharge vessel while keeping the pressure around 10 ^-2 -10 ^-3 mbar. The ion beam can be generated to obtain a plasma, thereby generating an ion beam. However, the solid element, which occupies most of the periodic table, is usually heated to 1000 ° C. or higher in order to achieve the medium pressure in order to cause discharge. In the case of the ion source, which is usually an external oven type, the heating temperature is limited to about 1000 ° C. due to resistance heating. In this case, only the alkali, alkaline earth, Pb, In, Sn, and Ag on the periodic table can be generated.

In the case of the oven type ion source embedded in the discharge box, the heating temperature is about 1500 ° C., so that Fe, Al, Cu, Au, and Pb are added as target elements. However, relatively high melting point elements such as Co, Ni, Ti, V, Pt, Zr, Nb and refractory elements Mo, Ta, Re, W and the like have a heating temperature of about 1500 ° -3000 ° C., which is impossible with the oven heating method.

Therefore, in order to obtain ions of the high melting point element, a compound of the element and a halogen group such as chlorine or fluorine may be used, and high increasing pressures of the compounds may be used. In this case, since active halogen atoms or ions are simultaneously generated during discharge, Corrosion of the electrodes and the like in the discharge box is very serious and the lifetime of the ion source is shortened. In addition, ion beam transport systems and vacuum systems also have serious disadvantages of being corroded. In addition, when ion beam is extracted, only the desired metal ions cannot be extracted, and other types of ions such as halogen ions and halogen compound ions are generated. Therefore, a mass separation process to filter only metal ions after ion extraction is essential. Since the ratio is low, efficiency is a problem.

In the present invention, by devising a high-density plasma generator using ion-induced sputtering instead of heating evaporation to solve these problems occurring in conventional metal ion sources, Ion generation of all solid elements is possible, and no corrosion problems are caused, and as a result of reliable operation and long operation, the embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an electrode structure, an ion beam drawing system, an associated power supply, and a magnetic field generating device for generating a high density plasma of a metal element in a single discharge box type ion source. Plasma generation is carried out by vacuuming the inside of the vacuum chamber (6), opening the needle valve (7) while maintaining an inert gas such as Ar, Xe, etc. at a pressure of about 10 ^-2 -10 ^-3 mbar that is easy to discharge, A filament (1) made of a material such as tungsten, toria tungsten, or LaB ₆ is heated from a filament power supply 14 to heat the electrons to be discharged, and then a plurality of holes or a net positive electrode 4 When a voltage is applied from the main discharge power supply 15 between the filament and the filament, the gas is ionized by the collision of accelerated electrons and inert gas atoms, which are emitted from the filament, thereby generating a plasma 20. Next, place the desired metal target on the inner wall of the vacuum box (6) 1-2mm away from the anode (4) and connect a DC power source between the two so that the target becomes the cathode. The voltage, usually hundreds to thousands of volts, is applied from the sputtering power supply 16 to release cations from the plasma, which are accelerated to this potential difference and hit the target 5 at high speed.

As shown in Fig. 2, the ions hitting the anode interact with atoms on the surface of the target 5 to release secondary electrons, secondary ions, and neutral atoms of a number of target constituents. . At this time, the emitted neutral atoms freely pass through the anode 4 composed of a network or the like and enter the plasma 20 region without being affected by the electric field. Incoming neutral atoms collide with high-energy electrons in the plasma or are ionized through charge exchange with ions, usually becoming cations. The cations produced are likewise accelerated and blown into targets to play the role of generating neutral atoms. When the ion beam extraction is provided with the extraction electrode 9 having a hole in a part of the vacuum chamber, the ions released through the ion beam are finally applied from the acceleration power supply 18 through the acceleration electrode 10 and the deceleration electrode 11. It is accelerated by and released. At this time, the electromagnet 8 composed of the coil and the magnetic circuit serves to promote the ionization of the gas efficiently in the center of the vacuum chamber by restraining the movement of electrons by generating an axial magnetic field inside the discharge box. The acceleration electrode 10 of the ion beam extraction system is installed to improve the focusing characteristics of the ion beam and to prevent backflow of electrons.

The number of neutral atoms released is proportional to the sputtering yield, and the sputtering yields of various incident ions and target atoms are given experimentally. In particular, the yield is directly related to the energy of the particle ions, for example 1.5 when 1KeV Ar ⁺ ions collide with the Al target, 1.8 on the Ni target, about 2.8 on the Cu target and 0.9 neutral particles on the W target. Is generated. However, for the same ion-target system, that is, the yield when colliding Al ions with the target is 1.5, the Ni ion Ni target is 2.0, the Cu ion Cu target is 3.5, the W ion W target is 1.8, etc. It can be seen that the yield is improved than that of other ions. In principle, if the yield is greater than 1, self-discharge can be maintained without assistance of an external auxiliary gas, in which case a pure metal ion beam can be generated. Since the ion beam is incident perpendicularly to the target surface, the angular distribution of the emitted neutral particles is mainly distributed in the vertical direction, so that the neutral atoms are directed toward the center of the vacuum chamber, thereby generating a high density plasma.

3 is a conventional external oven-type metal ion source by attaching the oven 24 to the outside of the bin and inserting the metal 23 of the desired ions therein and heating it with an external resistance heating wire 25 to remove the metal heavy metal ( 22) is obtained and guided into the discharge chamber to cause discharge. The technical problem in this case is that the temperature that can be raised with the resistance heating wire is limited to about 1000 ° C. The higher the temperature is, the higher the radiation loss is, the more power is consumed, and the oven 24 and The temperature between the delivery pipes 27 must have an appropriate gradient so that the delivery pipes are not blocked by the dew of the heavy metal pipe. Therefore, the delivery tube must be maintained at a temperature above the melting point of the metal. There is also the disadvantage that additional heating is required to prevent condensation of the heavy metals in the discharge box, which consumes enormous power.

4 is a metal ion source having two discharge bins, namely, a pre-discharge bin, a main discharge bin, and a sputtering electrode structure, which are capable of reliable operation and are suitable for high-density ion-on-beam extraction and are suitable as practical ion sources. The preliminary discharge bin is located in the intermediate electrode 4 "made of ferromagnetic material, and the part connected to the main discharge bin is through a thin hole having a diameter of 3-5 mm. The method of operating the ion source is performed through the needle valve 7. After injecting an inert gas into the battleship to heat the filament 1, and then operating the main discharge power supply 15, a discharge occurs in the preliminary discharge box to generate a plasma 20, which is generated through the intermediate electrode hole. After being compressed, it is double-compressed by the magnetic field formed at the end of the hole to send a high-density plasma into the main discharge bin. The main discharge bin is the positive electrode 4 ', the large negative electrode 4' "and the target 5 In the plasma introduced through the intermediate electrode 4 ", the electrons are accelerated through the anode, and when they reach the large cathode 4 '", they are reflected back and accelerated toward the anode. Back half As a by making the axial vibration is achieved by the ionization efficiency. In addition, the magnetic field composed of the magnetic circuit of the electromagnet 8 and the intermediate electrode 4 'generates an axial magnetic field in the main discharge box so that the electrons are constrained while rotating around the magnetic field lines as in the case of a single discharge.

Thus, this method has a very high ionization rate and can be discharged at a pressure as low as 10 ⁻³ mbar. The generated plasma 20 is accelerated by the sputtering power source 16 applied between the targets 5 from the outside through the large cathode 4 '", and then collides to generate the neutral atoms. It enters the discharge compartment and is ionized again, partly out of the ion beam, and partly in the neutral particle generation.

The advantage of the double discharge box type is that the filament is isolated from the main discharge compartment, which can prevent the contamination of the filament by metal heavy and ions, which can greatly increase the life span of the filament. High density plasma can be obtained. In addition, in the discharging region, electrons generate reflection vibration discharges constrained by the axial electric field and the lateral magnetic field, so that the electrons become very long, which enables efficient ionization and can be operated at low pressure.

It is also possible to use multiple extraction holes, which makes it suitable for the generation of high-current metal ions of several tens of mA, and thus can be widely applied in the industrial fields such as ion implantation and ion beam processing.

Claims (2)

The target neutral atom generated by ion extraction sputtering of the metal plasma is discharged to generate the ion ion sputtering, and the metal ion extracted from the metal plasma again discharges by ion induction sputtering of the target. A method of generating high density metal plasma using ion-induced sputtering, characterized in that self discharge is possible by generating a high density metal plasma therein. The needle valve 7 is installed in the vacuum chamber 6, and the metal including the filament 1, the filament power supply 14, the positive electrode 4, and the main discharge power supply 15 in the vacuum box 6 described above. Plasma generating device is installed, and a metal ion generating device comprising a target (5), an extraction electrode (9), an acceleration electrode (10), and a deceleration electrode (11) to be formed on the inner wall of the vacuum box (6). Ion-induced sputtering high density plasma generating device, characterized in that.