JPH0128455B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface analysis device, and more particularly, to a surface analysis device that analyzes substances scattered in a gas when a sample surface is subjected to ion bombardment (hereinafter referred to as sputtering).

In recent years, surface analysis devices have become widespread in factories, research institutions, etc., and there are many types, and these are selected and used depending on the purpose.

In nuclear fusion research, emphasis is placed on suppressing impurities in plasma, and a major challenge is research on the interaction between plasma and solid walls (hereinafter referred to as plasma-wall interaction), which also serves as the impurity supply mechanism. Surface analysis equipment is indispensable as a means to study this plasma-wall interaction, but the nuclear fusion currently being pursued uses hydrogen isotopes as fuel and generates energy by causing a fusion reaction in plasma confined in a magnetic field. Since it is intended to extract
A surface analysis device used for such applications must be capable of analyzing hydrogen in the fuel and helium in the ash produced in the nuclear fusion reaction.

A secondary ion mass spectrometer is one of the surface analysis devices that have been put into practical use and can be effectively used as a means for studying the above-mentioned plasma-wall interaction. This device irradiates a sample whose surface is to be analyzed with primary ions and performs mass spectrometry analysis of the ions in the secondary particles that were the surface material of the sputtered sample. If this is installed in a fusion device to study plasma-wall interactions, the secondary ion mass spectrometer itself and the equipment to attach it to the fusion device will be large and complex, so it must be installed inside the fusion device. The drawback was that I couldn't do it.

To explain this in more detail, the ion source that generates primary ions for sample irradiation produces a large amount of working gas (gas that is to become ions) in addition to ions.
Therefore, it is necessary to take measures to prevent this working gas from contaminating the fusion device.
As a countermeasure, the gas efficiency of the ion source should be increased, and the beam line of the ion beam should be lengthened to exhaust the working gas, or the secondary ion mass spectrometer and the nuclear fusion device should be Although it is possible to shut it off with a valve and to connect an exhaust device with a high exhaust speed to the secondary ion mass spectrometer, it is inevitable that the device will become large and complicated in either case.

On the other hand, when a secondary ion mass spectrometer has a problem with contamination of the sample and objects commonly stored with the sample due to the working gas, in addition to the same problem as contamination of a nuclear fusion device, secondary ion mass spectrometers also collect Since the ratio, ie, the number of secondary ions per primary ion, is very small, mass spectrometry of secondary ions requires very sensitive measuring equipment. Furthermore, the yield value of secondary ions is easily affected by the surface condition and atmosphere, which causes ambiguity when estimating the composition of the sample surface from the results of mass spectrometry of secondary ions. It was hot.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and is designed to simplify and downsize so that it can be installed inside a nuclear fusion device, and to prevent contamination of the sample and other items housed in a common container with the sample. In addition, the purpose is to provide a novel surface analysis device that does not require a highly sensitive measurement device.

In order to achieve the above purpose, two crossed field discharge devices are constructed to apply an electromagnetic field to a discharge space consisting of a cylindrical anode and two cathodes provided close to both ends of the anode. using
The first clothed field discharge device is used as a neutral particle ionization device, and the sample is held in the discharge space of the second clothed field discharge device and sputtered to generate a large yield of secondary neutral particles. Next, neutral particles are ionized in the first crossed field discharge device, ion mass selection is performed, and the surface of the sample is analyzed.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an outline drawing showing the configuration of a surface analysis device according to the present invention. In the figure, reference numeral 1 denotes an air-core coil that generates a magnetic field. Two crossed field discharge devices, an ion velocity selection device, an ion detection device, etc. are installed inside the coil, and it is excited by a power source (not shown) through terminal 2. Along with water inlet 3
It is cooled by water flowing in from the drain port 4 and flowing out from the drain port 4. Reference numeral 5 denotes a support body of the first crossed field discharge device, and terminals 5e for supplying power to each electrode are provided on the wall of the support body, and these terminals are respectively connected to a power source (not shown).

Next, 7 is a vacuum device, which removes the internal gas of the vacuum container containing two crossed field discharge devices, an ion velocity selection device, an ion detection device, etc.
The part to which the flange 7a is connected and the flange 7
The discharge operating gas is evacuated through exhaust ports provided at the portions connected to the flange 7c, and supplied into the vacuum vessel through the intake ports provided at the portions connected to the flange 7c.

Furthermore, 8 is a manifold, and a flange 8a for supporting a part of the second crossed field discharge device is integrally joined to a flange 8b at the bottom of the manifold, and these flanges are fastened to a flange 9c of the vacuum vessel. be done. Further, the upper flange 8c of the manifold 8 has a flange 6a of the support body 6 of the second crossed field discharge device, the right flange 8d of the manifold 8 has a flange 7b of the vacuum device 7, and the manifold 8 Flanges 7c of the vacuum device 7 are hermetically connected to the flanges 8e provided through the flow rate control valve 8f on the left side, respectively, to form exhaust ports or vents.

Next, FIG. 2 is a longitudinal cross-sectional view showing the configuration of the main parts of the surface analysis device according to the present invention, in which the same reference numerals as in FIG. A connecting fitting 9d is attached to the lower end of the body 9a.
Similarly, a flange 9c is provided at the upper end via a connecting fitting 9e, and this flange 9b connects to the flange 5b of the support 5 of the first crossed field discharge device, and the flange 9c connects to the manifold. 8 flanges 8a, respectively, in an airtight manner. Therefore, the support 5 of the first crost field discharge device, the vacuum vessel 9, the manifold 8, and the support 6 of the second crost field discharge device form a larger vacuum container, and the inside thereof Gas is exhausted through an exhaust port connected by flange 5a and an exhaust port connected by flange 8d. Note that when the inside of the vacuum container 9 reaches a vacuum state, the working gas controlled by the flow rate control valve 8f is supplied.

Next, 10 is a first crossed field discharge device, 11 constituting this is a cylindrical anode (also referred to as a first anode) having a hollow part 12 passing through as a discharge space, and 13 is a cylindrical anode (also referred to as a first anode) having a hollow part 12 passing through as a discharge space. A cathode (also referred to as a first cathode) 14, which has a through hole 19 at a position where the axis is extended, and which is close to the first anode and covers one open end, also has an axis extending from the hollow part 12. a cathode (also referred to as a second cathode) that has a through hole 30 at a position and is close to the first anode and covers the other open end;
15 is disposed parallel to and near the axis of the hollow portion 12, and is connected to the first cathode 13 and the second cathode 14.
A linear electrode (also referred to as a fourth electrode) is shown, which is insulated from and parallel to the direction of the magnetic lines of force formed in the coil 1. Note that a thin tungsten wire is suitable as the linear electrode 15, and is supported while being given an appropriate tension by supports (not shown) fixed to the sides of the cathodes 13 and 14 that do not face the anode 11, respectively. . In addition, a cylindrical anode 1
Since the anode 1 and the coil 1 are arranged substantially coaxially, the axis of the anode 11 coincides with the direction of the lines of magnetic force.

The first crossed field discharge device 10 is supported by a support 5, and an insulating plate 5c forming a part of the support 5 has a through hole formed in its center to serve as an exhaust port. , is fixed inside the flange 5b via the connecting fitting 5d. A large number of conductor columns are fixed to the support 5, one end of each of these conductor columns is electrically connected to a terminal 5e, and the other end of each conductor column is connected to an anode 11 and a cathode 13 of the first crossed field discharge device 10. , 14 and are also electrically connected. That is, the anode 11 actually has three conductor columns 16.
Accordingly, the cathodes 13 and 14 are also mechanically fixed and simultaneously supplied with power by the three conductor columns 17 actually provided. Further, the linear electrode 15 is fixed to the insulating plate 5c in the same manner as described above, and is electrically connected to the conductor column 18 whose one end is connected to the terminal 5e. Although the cathodes 13 and 14 are here short-circuited by the conductor column 17, it is of course possible to insulate them and apply different voltages to each other.

Next, 20 is a second crossed field discharge device, and 21 constituting this is a cylindrical anode (second
), 23 has a through hole 31 at a position extending from the axis of the hollow part 22, and the second anode 21
A cathode (also referred to as a third cathode) 24 that is close to and covers one open end, and has a through hole at a position extending from the axis of the hollow portion 22, and a second anode that covers the other open end. A cathode (also referred to as a fourth cathode) 28 holds the surface of the sample 25 to be analyzed in a substantially central part of the discharge space formed by the anode 21 and the cathodes 23 and 24, facing the first discharge device. Each holder is shown below. Here, the holder 28 is fitted into the through hole of the cathode 24 and is disposed on the axis of the hollow portion 22 . Further, since the cylindrical anode 21 and the coil 1 are arranged substantially coaxially, the axis of the anode 21 coincides with the direction of the magnetic lines of force. Further, the axial center of the hollow portion of the cylindrical anode 21 and the axial center of the hollow portion of the cylindrical anode 11 of the first discharge device 10 described above coincide.

The second crossed field discharge device 20 is supported by a support 6 whose details are not shown, and each electrode is supported by a large number of conductor pillars that are constructed almost in the same way as the support 5. ing. That is, the anode 21 is actually mechanically supported and electrically connected by the three conductor columns 26, and the three conductor columns 27 are actually provided.
At the same time, the cathodes 23 and 24 are mechanically fixed and electrically connected, and the ends (not shown) of each conductor column are connected to an external power source via terminals that hermetically penetrate the wall of the vacuum chamber. connected to. Here, the cathode 23 is fitted into one open end of a cylinder 29 made of a good conductor by a leaf spring (not shown), and this cylinder
The other open end of 9 is fitted onto the inner diameter of flange 8a, and these are kept at ground potential. On the other hand, the first
The cathode 14 of the first crossed field discharge device and the cathode 23 of the second crossed field discharge device are arranged in close proximity.

Next, numeral 32 installed in parallel with the first crossed field discharge device in the vacuum vessel 9 is an ion velocity selection device, and a box body housing two mutually insulated parallel plate electrodes is shown. . An ion entrance hole is bored in the upper part of this box. This ion entrance hole is provided at a position such that ions emitted through the through hole 19 of the cathode 13 pass through the parallel plate electrode as they are. In addition, such a box body has a frame body 3.
5 and supported by two pillars 34, and different potentials are applied to each parallel plate electrode through conductive wires passed inside these pillars, so that an electric field perpendicular to the electrode plate surface is formed. . Since the flat plate electrode is also arranged parallel to the direction of the magnetic field lines of the magnetic field formed by the coil 1, the electric field and the magnetic field intersect perpendicularly inside the flat plate electrode. On the other hand, the ion incidence hole is provided on the box surface opposite to the surface of the box where the ion incidence hole is perforated, that is, on the box surface perpendicular to the magnetic field on the side farthest from the first crossed field discharge device 10. The ion emission hole is drilled in an eccentric position.

33 is an ion detection device, for example, a Faraday cup is used. This ion detecting device is placed close to the ion emitting hole so as to be able to detect ions passing through the ion emitting hole, and is also fixed to the frame 35, and at the same time, necessary conductive wires are passed through the inside of the support 34. be done.

The operation of the surface analysis device according to the present invention configured as described above will be explained below.

First, to replace the sample, untie the flanges 6a and 8c and insert the second crossed field discharge device 20.
is pulled out together with its support 6, and the holder 28 is removed from the cathode 24. After replacing the sample, reassembly is performed, and when the pressure inside the manifold 8 reaches a predetermined degree of vacuum after evacuation including rough vacuum evacuation, the working gas is supplied through the flow rate control valve 8f while continuing the evacuation operation. After the pressure inside the manifold 8 is adjusted to maintain a dynamic equilibrium state, discharge cleaning of the two crossed field discharge devices is started. Immediately after starting this discharge cleaning, it is necessary to set the voltage between the anode and cathode so that it does not become too high, and ultimately create discharge conditions that allow surface analysis. Such discharge cleaning typically takes a few minutes to complete.

By the way, if the pressure in the manifold is in a dynamic equilibrium state, the gas in the vacuum container containing the working gas is discharged through the exhaust port fastened by the flange 8d of the manifold 8, while the flange 5a of the support 5 It is also discharged through an exhaust port connected by. That is, part of the gas in the discharge space of the second crossed field discharge device 20 is exhausted through the through hole 31 of the cathode 23. Here, the flange 8a of the manifold, the cylindrical body 29 fixed thereto, and the cathode 23 are, except for the through hole 31, a partition wall that separates the discharge space of the first crost field discharge device and the second crost field discharge device. and furthermore, the first
Since the discharge space of the second crossed field discharge device is connected to the vacuum device 7 with high vacuum conductance, the gas in the discharge space of the second crossed field discharge device 20 flows through the through hole 31 of the cathode 23 with low conductance. is exhausted through.
As a result, the gas pressure in the discharge space of the first cross-field discharge device can be kept at a very low value compared to the gas pressure in the discharge space of the second cross-field discharge device. As will be described later, such a pressure difference is essential for reducing the amount of working gas that reaches the first crossed field discharge device during surface analysis. Although a method such as separately providing an exhaust device connected to the support body 5 of the first crossed field discharge device and an exhaust device connected to the support body 5 of the first crossfield discharge device may also be used, in this embodiment, a bellows is connected to the exhaust port connected to the manifold 8. It is sufficient to close the valve 7d provided via. That is, after discharge cleaning is completed, the valve is closed while keeping the magnetic field strength in the discharge space and the anode-cathode voltage constant, and the flow rate is adjusted so that the anode current of the second crossed field discharge device is equal to the anode current at the end of discharge cleaning. A required pressure difference can be obtained by adjusting the control valve 8f.

In this way, most of the working gas introduced into the manifold 8 is transferred to the discharge space (anode 21, cathode 23 and 2
4). Since a high density of electrons exists in this discharge space and their energy is sufficiently high, molecules of the working gas are efficiently ionized to form primary ions. Most of these primary ions are contained in the cathode 23, the sample 25 and the holder 2.
8 and become embedded under its surface, or are neutralized and returned to the discharge space as active particles. In addition, although the remaining few primary ions pass through the through hole 31 and head toward the discharge space of the first crossed field discharge device, these few primary ions are not necessary for surface analysis but rather become a nuisance. There are many cases. Therefore,
In this embodiment, between the potential V _a2 of the anode 21 of the second crossed field discharge device and the potential V _k2 of the cathode 14 of the first crossed field discharge device, V _k2 −V _a2 ≧−100 [v] . . . It has been found that this small amount of primary ions can be removed if a potential difference such as (1) is created.

However, if it is known in advance that there are no working gas molecules on the sample surface, or if there is no problem even if working gas ions are included in the surface analysis results, it is not necessary to apply the above-mentioned potential difference. By removing this small amount of ions, there is no need to consider at least the amount of ions in the working gas, and surface analysis can be performed quickly and with high precision.

At the same time, when the primary ions formed by the ionization of the working gas collide with the cathode 23, the sample 25, and the holder 28, sputtering occurs, but this effect is most remarkable on the cathode 2 of the sample 25.
3, neutral particles scattered from the sample surface are emitted into the discharge space of the first crossed field discharge device through the through hole 31 of the cathode 23. Of course, neutral particles are scattered on surfaces other than the sample surface, but neutral particles generated on a surface where the through hole 31 cannot be seen are difficult to pass through the through hole 31, and in reality, the particles passing through the through hole 31 are on the sample 25. Only from the sample surface facing the cathode 23.

This means that conventional equipment, which performs surface analysis by analyzing the mass of secondary ions, i.e., ions in particles generated by sputtering, cannot utilize neutral particles, which make up the majority of particles generated by sputtering. As a result of having to analyze a small amount of secondary ions, a particularly high-sensitivity measuring device was required, but since neutral particles are efficiently used in this example, such a highly sensitive measuring device is required. is no longer necessary.

In this way, most of the neutral particles (also referred to as secondary particles) that have passed through the through holes 31 of the cathode 23 are transferred to the discharge space of the first crossed field discharge device (the anode 1
1, a space surrounded by cathodes 13 and 14). In this case, the linear electrode 15 allows stable discharge even if the two cathodes have through holes 19 and 30, respectively. A high density of electrons also exists in the discharge space where the secondary particles fly in this way, and the flight distance of the secondary particles is quite long, so the secondary particles are efficiently ionized. In this case, the part to be ionized is the hollow part 12
Since it is located near the axis of the cathode 13, most of the ions generated in this discharge space pass through the through hole 19 of the cathode 13. On the other hand, since the initial kinetic energy of the secondary particles is very low at several eV, the energy distribution of the ions passing through the through-hole 19 is limited to a narrow width, and moreover, their paths are parallel to the lines of magnetic force. .

Therefore, these ions will fly through the ion entrance hole of the ion velocity selector 32. In addition to the above-mentioned magnetic field, an electric field perpendicular to the magnetic field is formed inside this ion velocity selection device. Can be separated. In other words, since the ion drift velocity E〓×B〓/1B〓1 ² is independent of mass, ions whose incident energy is approximately constant draw a unique trajectory depending on their mass. However, here, since the ion entrance hole and the ion ejection hole are drilled at fixed positions, only ions of a certain mass determined by the electric field strength will pass through the ion ejection hole. By comparing the mass of such ions with the potential difference between the parallel plate electrodes, it becomes possible to analyze particles scattered from the sample 25. In other words, surface analysis of the sample 25 becomes possible.

Note that the surface analysis device configured as described above is
For example, 1×10 ^-5 Pa (1
Since the cross-field discharge device is used, which is characterized by its ability to operate at pressures close to ultra-high vacuum (×10 ^-7 Torr), the pressure of the working gas can be extremely low. This means that sputtering can be performed at pressures close to ultra-high vacuum, yet a sufficient amount of ions needed for surface analysis can be obtained. As a result, contamination of the ion velocity selection device 32, ion detection device 33, etc. housed in the vacuum container 9 is prevented. In addition, here, we do not use secondary ions whose yield is affected by the atmosphere, but use neutral secondary particles that are hardly affected by the atmosphere, so when estimating the composition etc. ambiguity disappears.

On the other hand, since the amount of working gas introduced into the second crossfield discharge space is absolutely small, almost all of this working gas is ionized, and as a result, the first crossfield discharge device The amount of working gas flowing into the discharge space is small, and in this sense as well, contamination of the equipment housed in the vacuum container 9 can be kept to an extremely low level.

On the other hand, in the above embodiment, the main components such as the discharge electrode, ion velocity selection device, and ion detection device were housed in a vacuum container, and a magnetic field was applied from outside the vacuum container by a cylindrical coil. Since a strong magnetic field is originally formed in a plasma device, the cylindrical coil can be omitted when the above-mentioned surface analysis device is installed in this plasma device, and as a result, the configuration of the surface analysis device is extremely simplified. This also results in further miniaturization.

As is clear from the above description, according to the surface analysis device of the present invention, the overall shape is simplified and miniaturized, so that it can be easily installed inside a nuclear fusion device. Contamination of the sample and items housed in a common container with the sample can be prevented. Furthermore, reliable surface analysis is possible without the need for highly sensitive measurement equipment.

[Brief explanation of drawings]

FIG. 1 is an external view showing the structure of an embodiment of a surface analysis device according to the present invention, and FIG. 2 is a longitudinal sectional view showing the structure of the main part of the same embodiment. 1... Coil, 5, 6... Support, 7... Vacuum device, 8... Manifold, 9... Vacuum container, 1
0,20...Cross field discharge device, 1
1, 21... Anode, 12, 22... Hollow part, 1
3, 14, 23, 24... cathode, 15... linear electrode, 16, 17, 18, 26, 27... conductor column,
19, 30, 31...Through hole, 25...Sample, 2
8...Holder, 29...Cylinder, 32...Ion velocity selection device, 33...Ion detection device.

Claims (1)

[Scope of Claims] 1. A surface analysis device characterized by comprising the following components a to d. (a) a first anode having a hollow portion extending therethrough; and a through hole located at a position extending from the axis of the hollow portion;
A first discharge device comprising first and second cathodes that are close to the first anode and cover their respective open ends, and a linear electrode that is disposed parallel to and near the axis. (b) a second anode having a hollow portion extending through the second anode, the second anode being disposed such that the axis of the hollow portion coincides with the axis of the hollow portion of the first anode, and the second anode having an extended hollow portion; a third cathode having a through hole at a position and covering the open end of the second anode on the side facing the first discharge device; and a third cathode not facing the first discharge device. a fourth cathode close to and covering the open end of the second anode; A second discharge device including a holder facing the discharge device. (c) A vacuum container that houses the first discharge device and the second discharge device and has a terminal that can supply power to the electrodes. (d) A magnetic field generating device that generates a magnetic field from the outside of the vacuum container in the hollow portions of the first anode and the second anode, with lines of magnetic force parallel to the axis. 2. The surface analysis device according to claim 1, wherein the discharge working gas of the first discharge device is supplied to a hollow part of the second anode. 3 In the first discharge device, the potential difference between the potential V _k2 of the second cathode of the first discharge device and the potential V _a2 of the second anode of the second discharge device satisfies the following relational expression. A surface analysis device according to claim 1, characterized in that: V _k2 −V _a2 ≧−100 [v] 4. The surface analysis device according to claim 1, wherein the magnetic field generating device is a plasma device.