Ion source for generating ions of a gas or vapour

17-04-1998 дата публикации
Номер:
AU0007092396A
Принадлежит: DEZSOOE SZIGETHY
Контакты:
Номер заявки: 7092396
Дата заявки: 27-09-1996

[1]

Technical FIELD This invention is related to an ion source device can be used for the generation of steam or gas ions in the ion beam processing of solid sample. By this invention the ion source and the ion beam can be generated with a small diameter is larger at a relatively low voltage current density. Background art The ion beam milling, and reducing the thickness of the device utilizing an ion beam structural feature for analysis using a layered structure or autoanalyzer widely used in manufacturing technology. In accordance with the requirements of various ion source device have been developed. In the research field structure, using an ion beam such as an electron microscope sample in a thin-walled, tunnel to clean the surface of the electron microscope or the like, or secondary electronic pts.mass Auger electron spectroscopy analysis of a gas such as chemical analysis of a buried layer research in an ion source is used. In accordance with the requirements of a measuring or thin-walled 10-5 to 10-2 Pa below the target pressure in the vacuum chamber. Conventionally, a cold cathode gas using an ion source and the ion beam device utilizing thin-walled generally, hot cathode gas used in the ion source and analyzing device. The cold-cathode ion source device is the most simple form of the cavity type twin electrode. The advantage of this type of ion source device is simple in construction and small in size. However, some drawbacks. That is, ion plasma ion source for the generation of pressure of the gas in the interior of the device is required to be as high as 40-50Pa, also suitable for the generation of the ion beam 2-15KeV high pressure must be applied. The vacuum chamber of the thin-walled low background pressure device in order to ensure the required speed of the vacuum pump and the exhaust speed 2000-5000l/s. Furthermore, in the inside of the ion source and the ion source device for scattering is considerably larger in the ion beam at a diffusion angle of the discharging opening (10°-20°) becomes large. Another drawback of this type of ion source device, the major portion of the neutralization of the accelerated ion in the vicinity of the discharge opening of an ion source for ion collision due to secondary electrons. The etching of the sample gas can be used to neutralize the beam, the beam further deflection or magnetic field or a field shaping or can not be started. In the ion source Penning type gas, from the cold-cathode ion collision occurs by accelerated ions toward the auxiliary anode spiral path and is forced to pass. The process of ionizing collision induced for ion plasma generator and electronic snowslide capable of sufficiently increasing the mean free path even in a low pressure state. The value of the pressure of the gas in the ionization chamber 0 of the ion source. 1-1Pa range. The ions generated by the ionizing chamber accumulates until the required energy and accelerated by the electrode, the ion beam is scanned with the additional electrode. One of the disadvantages of this type of ion source device is complicated in the structure. The target is held at a ground potential, the ion energy ionizing chamber according to the required relatively high potential must be maintained. Therefore, particularly when the cooling problem of requiring insulation. Another drawback of this type of ion source device is large in size, and, arrangement is limited to the portion thereof which is limited in order within a vacuum chamber. The mean free path of the electrons, i.e., the probability of ionization, cold cathode electron is forcibly vibrated by applying an electrostatic field can be increased. The device of the kind described ion source of electrostatic ion sources of vibration called EP-B10 267 481. The cold-cathode ion source device, when the gas pressure required in the ion source and ion source device similar to the above-mentioned Penning type of about 0. At 1 Pa, which has a high current density ion one class, having a simple construction, which can be held at the ground potential of the cooling system, even without additional focused ion beam in an ion emitting opening diffusion angle 1° or less. The hot cathode sputtering and ion source device to clean the surface by removing the surface layer mainly used for analytical equipment. The ions generated in another chamber. In the ordinary hot cathode and anode grid-shaped auxiliary chamber. This chamber is connected to a suitable potential determined by the ion energy. The acceleration of the ion beam, the scanning and shaping of the electrode structure used in other Penning type ion beam source and substantially the same as the constitution of the device. The required pressure value inside the ion source 10-3 -10-2 Pa and, the differential exhaust at low pressure in the vacuum chamber. Μ A is the maximum number of ion current obtained from the ion source. Since the large dimension of the ion source device must be fixed to the vacuum vessel. A combination of gas and hot cathode ion source device and magnetic field. These duo plasmo tron type gas source and the gas pressure required for the maximum current density parameter is preferably provided, is complex in structure and maintenance is not easy to use. Furthermore, since the large dimension must be fixed to the vacuum vessel. The highest efficiency of ion 10KeV obtained by sputtering. The high energy impact damage occurs in the target material, normal to the surface of the sample causing damage of layer thickness 10-15nm. This damage layer thickness in the spectral analysis of the sample using ion beam investigation is difficult. The thickness of the layer of beam incidence angle damage or by reducing the energy can be reduced. However, by reducing the angle of incidence and lowering energy sputtering. In this case, residual gas from a hydrocarbon such as carbon deposits of solid chemical reaction is produced on the surface of the sample, measurement is hindered. Even in the utilization of a buried layer thickness of the beam in the investigation, the angle of the incident beam energy is increased by increasing the beam collision to start, etching reaches a certain depth to reduce its value is preferable. Since the surface of the target is determined by the position of the analyzer, to properly adjust the angle of the incident beam on the ion source device must be capable of being tilted, the ion source device must be made in a small size. In the case of low energy ion etching , in order to reduce the acceleration voltage of the ion source and ion current is reduced since a sputtering rate is remarkably lowered. In the case of a cold cathode electron gun acceleration voltage limit value, to obtain a sufficiently parallel beam at least 1. 5-2kV since when he must also determined by ion energy. Due to the cold-cathode ion source EP-B10 267 481 of the central opening of the device and with the anode and cathode in two symmetrical cooling. The cathodes of both these hollow anode to one of shrinkable part is provided, at one side thereof, a conical portion projecting toward the anode. The ion beam of the ion source device in order to generate a minimum 1. 5-2kV voltage is required. By setting these parameters, the required gas pressure becomes the value of ion current 4-6μA and about 0. 5 Pa. The disclosure of the invention, The purpose of this invention is the absence of gas is lower than the relatively high energy range wider than a gas ion source and the ion current. Arranged in mirror symmetrical optical electrostatic lens telephotographing obtained by cold-cathode ion source having snowslide process of plasma ions, and electrons from a hot cathode electron is applied so as to pass through them by forcibly correct path, and lower than the gas pressure generated in the anode voltage lower than can be maintained. In other words, this invention is particularly thin-walled solid sample of gas or vapor for ion generation of ions in the ion source, and a housing, the housing and the means for introducing the steam or gas, is disposed in the inside of the housing along the axis of the ion source is opened on both sides in the rotational direction and having a symmetrical cavity in the anode, the anode is disposed along the axis of the space for arranging the first 1 and second 2 for partitioning between the electro-optical mirror means which vibrates between mutual electrostatic field 1 and 2 forming a first and a second electro-optical mirror means includes, first from the first mirror means 1 and 2, at least one of the electro-optical device in the space to pass part of the ions generated by the ion source and provided with an opening to the o Electron generator means and arranged with the ion source device on one of the sides of the cavity on the outside of the cavity, and means including a leading feature and the electrons are generated within the cavity. In a preferred embodiment of this invention, the ion source device the electron generating means disposed in a plane crossing the axis of the cathode. The cathode is constituted by an annular body symmetrical with respect to the axis in the direction of rotation. Therefore, this invention is a hot cathode cold cathode coupled type ion source. 1 and 2 of the first and the second electro-optical mirror means each of which is surrounded by a cylindrical wehnelt rotational direction includes a symmetrical cold cathode, the anode of the means for introducing into the cavity of the cold cathode and the second electro-optical mirror 1 is arranged between the inside of the cylindrical wehnelt two symmetrical in the direction of rotation of the auxiliary electrode is therefore advantageous. Heat of the anode the electrons from the cathode cavity leading to the two auxiliary field hot-cathode electrodes of each of the auxiliary electrodes is arranged between them in the axial direction between the two electrodes arranged in a symmetrical prestate improvement. The device of this invention, an ion source, the ions of electro-optical mirror means 2 of the part of the first workpiece 1 to reach the opening is provided, the first mirror means 1 ion of the electro-optical part of the second ion current measuring device 2, i.e. preferably a Faraday cage is guided to the measuring device embodied in the form of another opening is provided. The device of this invention, an ion source, an electrostatic lens in which a shaft is disposed in the vicinity of the first electro-optical mirror means and align the axis 2 of the ion source, an electrostatic lens is preferably provided with three electrodes having an axially arranged apart from each other. In other words, this electrostatic lens 2 and second by the electro-optical mirror means is mounted on a housing of the variable unit and it forms a troublesomenss. Brief description of the drawings: This invention is described with reference to the attached drawing showing a schematic cross section of an embodiment of this invention in more detail an ion source device. Mode of invention In the figure, the ion source device comprises two cold cathode 1 and 5 28 and a metal housing, and between the anode 3 of these cold cathode 1 and 5, these cold cathode 1 and 5 and respectively surrounding the two wehnelt cylinder 2 and 4, cold cathode 1 and arranged between the two cylindrical wehnelt 2 of auxiliary electrodes 11 and 13 and, arranged between the two auxiliary electrodes 11 and 13 and is provided with a hot cathode 12. A housing 28 and a gas inlet port 31 and a cooling pipe (not shown). The gas is supplied, for example, hydrogen, argon, iodine vapor or the l Cold cathode 1 of rear support block attached to a cold cathode 1 of cavity 22 for measuring an ion current flowing through (not shown) using a Faraday cage. Housing 28 is kept at zero volt potential (ground), the opposed electrode arranged symmetrically in the rotating direction of the first 1 and second 2 based on the cold cathode 1 and 5 are electrically connected. In the direction of rotation-symmetrical surface defined by an inner cavity 21 having a common anode 3 disposed between the cold cathode 1 and 5. The anode 3 and an insulating support 29 which is insulated from the housing 28, on the other hand, the high voltage V1 supplied electrically connected to the plug. Cold cathode 1 is surrounded by a cylindrical wehnelt 2, on the other hand, cold cathode 5 is surrounded by a cylindrical wehnelt 4, these wehnelt cylinder 2 and 4 is electrically connected to the housing 28. Cold cathode 1 and 1 and second cylindrical wehnelt 2 of electro-optical mirror, cold cathode 5 and the electron and wehnelt cylinder 4 between them for a second electro-optical mirror 2. The auxiliary electrodes 11 and 13 mounted in the insulating body (not shown), a hot cathode 12 to the anode 3 of the smaller diameter of the conical end of a second relatively cold cathode 1 1 arranged to surround. The voltage V3 and V4 for supplying auxiliary electrodes 11 and 13 of the plug is connected to an auxiliary voltage, the voltage of the voltage V5 for heating a hot cathode 12 which is connected to the plug. The voltage value and the following relationships. In other words, V1 =+ 50-10000V, V3 =V4 =+ 40-250V, and V5 =+ 4-15V. The ion source and the common axis 30 of electrostatic lens for focusing an open, cold cathode 5 2 that is electrically connected to the first electrode 6 1 1 of the second electrode 6 and the insulating void 26 separated from the electrode 7 2 2 from the first electrode 7 and separated by an insulating gap 27 3 consisting of a first and a second electrode 8 of an electrostatic lens 2 for connection to the outside of the cold cathode 5. First and second electrodes 8 1 3 of the electrode 6 is connected to the housing 28, intermediate the first electrode 7 2 0 mounted on the insulating body 10. 6V1 2 for supplying a voltage V2 of the second plug is electrically connected to a high voltage. The hot cathode 12 high energy ions produced in the anode cavity 21 so as not to be affected by sputtering effect. This is extremely short life. In this configuration the hot cathode 12 does not receive the impact caused by the high energy ions is also confirmed by an experiment by computer simulation. Annular emitted from the hot cathode 12, electronic vibration anode 3 in order to efficiently enter the inside of the cavity 21 in the vicinity of the axis of symmetry 30 until forcibly needs to be passed through the passage. The meridian plane over a wide angle direction is emitted from the hot cathode 12 with the anode 3 and auxiliary electrodes 11 and 13 and wehnelt cylinder 2 by the electric field generated between the anode 3 of cavity 21. These hot electrons, the anode 3 of two opposite to each other are arranged respectively in the end part is reflected by a cold cathode 1 and 5, its anode vibrates along the axis, in which the space between the cathode 1 and 5 efficiently ionizing the gas molecules. The operation of the ion source is described n In the ion source, the ions generated by the collision of electrons, the anode 3 and between the cold cathode 1, 5 by high voltage cold cathode 1, 5 in the direction of acceleration. These cold cathode 1, 5 by ions collide with the secondary electrons generated by the voltage between the anode and cathode and anode 3 is accelerated in the direction of, the collision of gas molecules in the anode cavity 21 by ionization. The ions generated by either one of a cold cathode 1, 5 and the collision, a new secondary electrons are generated. The above-mentioned anode 21 snowslide ion plasma is generated in the process is maintained. 1 and 2 of the first anode 3 and between the second cold cathode 1, 5 a high voltage ion plasma ions are accelerated to inside, these ions through a part of the cathode cavity 22 is emitted from the ion source, (not shown) reaches the Faraday cage, these ions through another part of the cathode cavity 23 is released as the ion beam from the ion source, through the electro-optical focusing lens is focused into a workpiece. This invention hot cathode cold cathode combination type in the ion source, the low degree of 50V snowslide process generated at a voltage between the anode and cathode. Electrons emitted from the hot cathode 12, auxiliary electrodes 11 and 13, cold cathode 1 and 5, the anode 3, and wehnelt cylinder 2 and 4 of the accelerating, decelerating field, and mirror-like vibration in an electric field. The internal space of the ion source, in other words the anode cavity 21 inside the internal space 24 and 25 or if there is a gas molecule, heating the cathode 12 and anode voltage V1 generated by them is accelerated electrons ionize the collision of gas molecules by causing snowslide process described a In the above-mentioned ion plasma inside the anode cavity 21 are formed by the process of snowslide, the potential difference between the anode 3 and cold cathode 1 and 5 is accelerated by means of the ions from the anode cavity 21 through the discharge opening 14 and 16, an electro-optical lens is focused by this ion source via the discharge port 15 is discharged from the device. The ion beam energy and the anode voltage V1 and the focusing point focused voltage V2 and determined by the value of the ratio. The ion source and scanning, discharge port 15 is arranged on the outside of a deflection electrode (not shown) by a technique known per se can be realized. In a preferred embodiment, the anode 3 is composed of a stainless steel or copper, cold cathode 1 and 5 are made from aluminum, tungsten heat cathode 12. The ion source device of this invention in comparison with the conventional ones, the following advantages are provided. -The ion source device is at a low voltage of about 50V ignition. -The energy of ions can be set in a wide range of 50eV to 10KeV. Other hot cathode commercially-electrostatic ion source and the ion energy equivalent to that of equivalent as compared with the use of anode voltage, one step higher ion current is obtained from the ion source. -Ion beam from the ion beam of the ion source device 5-100mm wide range of distance of the discharge port. The auxiliary electrode and the cathode-to-heat to a value near ground potential, a high voltage and power requirements of the ion source device is viewed from both viewpoints of gentle. -Diameter 30-50mm, smaller dimension about the length 60-90mm. This cooling is maintained at ground potential and the metal housing of the ion source.



[2]

An ion source for generating ions of a gas or vapor, especially for thinning solid state samples, includes a housing, an arrangement for introducing the gas or vapor into the housing and an anode positioned within the housing. The anode has a rotationally symmetrical cavity which is open at both sides along the axis of the source. First and second electrooptical mirrors are disposed along the source axis and define therebetween a space in which the anode is positioned The mirrors produce an electrostatic field to cause electrons to oscillate between them. At least one of the mirrors is apertured for exit therethrough of a fraction of ions generated in the space. An electron generating arrangement is disposed at one side of the cavity externally of the space between the mirrors and further, an arrangement causes the electrons to move into the cavity.



Especially for thin-walled solid sample of the ion source of vapor or gas ions in the ion generating device, and a housing (28), the housing (28) and (31), a means for introducing the gas or vapor, its housing (28) is disposed in the inside of the ion source device (30) is opened at both sides along the axis of rotation (21) having a symmetrical in the direction of the cavity (3) and the anode, the anode is disposed along the axis of the space for arranging the first 1 and second 2 for partitioning between the electro-optical mirror means (1, 2 ; 5, 4) between which an electronic so as to vibrate the first 1 and second 2 forming an electrostatic field to the electro-optical mirror means (1, 2 ; 5, 4) and includes a, 1 and 2 of the first and the second electro-optical mirror means (1, 2 ; 5, 4) in at least one of a part of the space for passing the ions generated by the ion source and provided with an opening to the outside of the device, the sides of the cavity (21) arranged on the outside of one of the space (12) and the electronic generation means, electrons generated within the cavity (21) and a guiding means seen contg., the electronic means to generate a plane crossing the axis (30) and cathode (12) arranged in and, (30) of the shaft (12) to the hot cathode symmetrically with respect to the rotation direction in an annular body with the ion source, 1 and 2 of the first and the second electro-optical mirror means is surrounded by a cylindrical wehnelt (2, 4) in the rotation direction of the cold cathode (1, 5) a symmetrical includes an ion source device a

The guiding means in the cavity (21) of the second electro-optical mirror means 1 of the cold cathode (1) in the cylinder (2) and the wehnelt arranged between the two symmetrical in the direction of rotation of the auxiliary electrode (11, 13) and includes an ion source device described in claim 1.

The hot cathode (12) to the auxiliary electrode (11, 13) of two arranged between the ion source of claim 2 and described.

Each of the auxiliary electrodes (11, 13) further in the direction of rotation of the two symmetric electrodes (17, 18, 19, 20) is arranged between the ion source of claim 3 and described.

2 of the first electro-optical mirror means (5, 4) of the first part 1 of the ions toward a workpiece having an opening (16), the first 1 of electro-optical mirror means (1, 2) is the first part of the ion of an ion current measuring device 2 for discharging toward the other opening (22) of claim 1 and which comprises an ion source device.

The shaft 2 has an axis aligned with the first (30) and the electro-optical mirror means (5, 4) disposed in the vicinity of, being spaced apart from each other in the axial direction of three electrodes (6, 7, 8) having an electrostatic lens (6, 7, 8) as described in claim 1 further includes an ion source device.

The electrostatic lens (6, 7, 8) 2 and the second electro-optical mirror means (5, 4) attached to the housing (28) is a replaceable unit is characterized in that the ion source of claim 6 and described.