JPH03214546A - Ion source - Google Patents

Abstract

PURPOSE:To providing practicability of resuming ion emission in a short working time without exposing the ion source to the atmosphere even though the ion material is once exhausted, by forming ampoule rupturing part in such a structure that the ampule can rupture independently. CONSTITUTION:An ampoule 7 is installed level and supported at its two ends, and a load is applied to the neck of the ampoule 7 to cause rupture by a push rod 60 which is capable of moving in the direction perpendicular to the ampoule. This push rod 60 is installed with bellows 62 interposed for the purpose of vacuum sealing, and when the ampoule 7 is not needed ruptured, fixation is made in a position not touching the ampoule 7 so that no movement is generated by the atmospheric pressure. One push rod 60 is used as one unit for each ampoule 7, and placing a plurality of such units permits releasing the fixation part of the push rod 60 according to necessity and rupturing of the ampoule 7 independently. Thus ion emission can be made in a short time without exposing the ion source 1 to the atmosphere.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an ion beam device for manufacturing semiconductor devices in the semiconductor field, an ion source installed in a secondary ion mass spectrometer in the material analysis field, or an ion beam device equipped with the present ion source, a secondary ion mass spectrometer, etc. Regarding analysis devices and surface modification devices.

[Conventional technology]

Many types of ion sources have been developed for the purpose of analyzing solid surfaces and minute regions, fabricating microstructures, or modifying the surface of parts. Among them, focused ion beam equipment for manufacturing semiconductor devices in the semiconductor field is used. When focusing on the ion sources installed in secondary ion mass spectrometers in the field of materials analysis, liquid metal ion sources and surface ionization type ion sources are considered to be important ion sources. Here, first, an outline of a liquid metal ion source and a surface ionization type ion source will be explained. The liquid metal ion source has high brightness and emits ions from a point-like region, so it is possible to focus the ions into a beam with a diameter of 1 μm or less. By scanning and deflecting this focused ion beam, semiconductor process It becomes possible to perform lithography, doping, etching, deposition, etc. locally. Also,
The ion beam is irradiated onto the sample surface and the secondary ions ejected from the sample surface by the sputtering phenomenon are analyzed.
When a focused ion beam obtained from this liquid metal ion source is used in so-called secondary ion mass spectrometry, it becomes possible to analyze the components of an extremely small submicron region on the sample surface. Liquid metal ion sources are described, for example, in the academic journal “Applied Physics” No. 5.
Volume 4, No. 9 (1985), pages 935-9
As shown by Noda et al. in their paper entitled "Electron impact type micro ion source" (known example 1) on page 39, it has a schematic configuration as shown in FIG. 2. That is, in the figure, there is shown a reservoir 3 for holding the material to be ionized (ionized substance) 4 in a molten state, and a reservoir 3 for ejecting ions 9 of the molten ionic material 4 supplied from the reservoir 3 from its tip. It consists of an emitter 2 disposed at the emitter 2, and an extraction electrode 5 for extracting ions 9 from the emitter tip by concentrating a high electric field on the emitter 2 tip. ionic material 4
The heating method for bringing the emitter into a molten state is by electron bombardment from a filament 23 placed around the emitter 1. In other words, the filament 23 in the shield electrode 22 is heated red-hot, and the voltage between it and the emitter 2 is from several 100 V to several kV.
The emitter 2 and the reservoir 3 are heated by electron impact with the hot electrons from the filament 23, and the ionic material 4 is melted by heat conduction from the heated emitter 2 and reservoir 3. The ionic material 4 in a molten state oozes out from the reservoir 3,
Wet the tip of the emitter 2, and then apply a high voltage of several kilovolts to the emitter 2 to the extraction electrode 5. At a certain threshold voltage, the molten ion material 4 at the tip of the emitter
has a conical shape called a Taylor cone, and ions 9 are emitted from the tip of the cone through a field ionization process or a field evaporation process. In addition to the above-mentioned method of heating the vicinity of the tip of the emitter 2 by electron bombardment, methods for maintaining the ionized material 4 in a molten state include a method of heating the vicinity of the tip of the emitter 2 using a portion for storing the ionized material (also called a reservoir section or a reservoir). There are various methods, such as a method in which a heater also serves as a resistive heating method by applying electricity, and a method in which a heater is wrapped around a reservoir of ionic material and the ionic material is melted by the heat of the heater. However, there is no major difference in the basic configuration of the liquid metal ion source. The ions emitted in this way are transferred to an ion optical system (such as a lens, deflector, and aligner) installed downstream of the ion source.
(not shown), it is possible to irradiate a sample with a focused ion beam with a submicron diameter. On the other hand, in the case of positive ion generation with a surface ionization type ion source, when atoms with low ionization energy adsorb and desorb from a high-temperature metal surface with a high work function, the electrons of the adatom are transferred to the metal and the adatom is ionized on the surface. This is an ion source that utilizes the ions that are released as positive ions, and alkali metals such as sodium and cesium are often used as the ion species. In particular, cesium is an essential element as a primary ion species in a secondary ion mass spectrometer. Specifically, by using cesium (Cs) as the next ion species, C, O
, S (light elements), Au, Ag (heavy metals), etc., are very effective in increasing the ionization rate of elements with high ionization potential. Regarding this matter, please refer to the collection of papers "Analytical Chemistry" Volume 49, No. 13 (197
7th year) on pages 2023 to 2030 of H.A.
H.A. Storms et al.
Analytical Chemistry, vol.
．． 49, No. 13 (1977) 2023~
2030) is ``Evaluation of Cesium Positive Ion Source Four Secondary Ion Mass Spectrometry (Evaluation
of a CesiumPositive Ion
Source for Secondary Io
nMassSpectrometry) j (Public Known Example 2). Today, cesium is an indispensable element for secondary ion mass spectrometry, and it is extremely powerful in analyzing contaminants from the manufacturing of highly integrated semiconductor devices, and it is also suitable for long-term analysis. A cesium ion source that can also be used is desired. The ionic materials used in liquid metal ion sources may be solid at room temperature, or they may be solid at room temperature, such as mercury, gallium, cesium, etc.
Those that are liquid at a temperature of about 0°C are also used. Among materials that are liquid at room temperature, those that are particularly reactive, toxic, or resistant to oxidation are usually sealed in ampoules. In a conventional ion source that uses a material sealed in a glass ampoule as the ion material, the ampoule inside the vacuum container is broken by a force from outside the vacuum, and the sealed material flows out and enters the ion material reservoir. It was introduced and ionized. Conventional ion sources of this kind that use an ionic material sealed in an ampoule include, for example, cesium sealed in a glass ampoule as an ion source. ．D
．． Prewett et al.
acum), 1984, Volume 34, No. 1
``Aliquid Metal Source Obesium Ions for Secondary Ion Mass Spectrometry'' (A
liquidmetal source of cae
sium ions for secondaryio
n mass spectrometry) paper (
As explained in Publication Example 3), an ampoule 7 in a vacuum container is broken by compressive force using an ampoule breaking means 6 made of bellows or the like, and the ampoule 7 is sealed. The cesium 4 contained therein was flowed out, passed through a flow path 8, introduced into the ion material reservoir 3, and ionized. However, although there is a difference in the orientation of the emitter 1 between horizontal and vertical in FIG. 3 and FIG. 2, the configuration for emitting ions is essentially the same. As is clear from FIG. 3, the number of ampules loaded into the ion source was one.

[Problem to be solved by the invention] In an ion source in which the material sealed in an ampoule is an ionic material, the ampoule is broken in a vacuum container, and the ionic material is introduced into the ion emitting part, the ampoule held in the ion source The number of ion sources was one at most, so if the ion material sealed in the ampoule was consumed or depleted due to long-term ion emission or evaporation, ion emission could no longer be continued, and the ion source should be closed once. It must be exposed to the atmosphere and loaded with a new ampoule filled with ionic material. In particular, when the ion material is a material that easily reacts with air, such as cesium, once the ion source, including the broken part of the ampoule, is exposed to the atmosphere, the cesium attached to the surface of the ion source material changes chemically into a compound such as cesium oxide. do. Even if you reload the ampoule in this state,
If the new ionic material after rupture reacts with the remaining oxide, or especially if a reactant such as cesium oxide is generated in the ion emitting part, it is almost impossible to expect ion ejection again. Further, there is a problem in that the vacuum inside the ampoule fracture cannot be brought to an ultra-high vacuum state due to the oxide adhering to the inner wall of the ampoule fracture. Therefore, once the ion source is exposed to the atmosphere, it is necessary to wash and dry the ion source components, load a new ampoule, and evacuate the ion source. exposure work, ion source cleaning work,
After loading the ampoule, time-consuming work is required, such as starting up the vacuum of the device, so once the ampoule has to be replaced, a long time is required before the next desired ion release. In view of the above-mentioned problems, the present invention makes it possible to reintroduce ionic materials without exposing the ion source to the atmosphere even if the ionic materials are once depleted, and ion emission can be restarted in a short working time. The purpose is to extend life. [Means for Solving the Problems 1] One possible solution to extend the life of the ion source is to increase the amount of ionic material sealed in one ampoule. However, if the ionic material is a dangerous substance that requires careful handling, such as sodium or cesium, if the ion source is unexpectedly forced to be removed from the device, the remaining ionic material may be destroyed. This exposes the person handling the ion source to great danger. Therefore, when using dangerous or toxic substances such as alkali metals such as sodium or cesium as ionic materials, it is necessary to load many ampoules containing small amounts of these substances and store them in vacuum as necessary without exposing them to the atmosphere. The best solution is to break the ion and introduce it into the ion emitting section. In order to achieve the above object, an ampoule in which the ionic material is sealed, a holding part and a breaking part of the ampoule, a reservoir part for holding the ionic material in a molten state, and a molten ionic material supplied from the reservoir part are required. An ion source consisting of an ion emitting section arranged to emit ions from its tip can hold multiple ampoules filled with ionic material, and the ampoule breaking section can break the ampoules independently. The above problem can be solved by creating a structure like this. [Operation] Ampules usually have a narrowed part in the center, and if both ends are fixed and a load is applied to the narrowed part, the ampoule will easily break. The ampoule breaking section utilizes this, with the ampoule placed horizontally, both ends supported, and a push rod movable perpendicularly to the ampoule applying a load to the narrowed part of the ampoule to cause it to break. The push rod is installed via a bellows for vacuum sealing. When there is no need to break the ampoule, the push rod is fixed in a position where it does not touch the ampoule and does not move due to atmospheric pressure. One push rod is one unit for one ampoule,
By arranging a plurality of these units, it is possible to open the fixing part of the push rod and break the ampoules independently, if necessary. Upon rupture, the ionic material within the ampoule flows out and reaches the reservoir through a flow path installed downstream of the ampoule rupture. [Example] Hereinafter, an example according to the present invention will be specifically described using figures. (Example 1) Fig. 1 shows the overall schematic configuration of an ion source according to an embodiment of the present invention, and Fig. 5 shows a partial cross-section for explaining in more detail the ampoule fracture part 6, which is the center of this embodiment. An enlarged view is shown. In Example 1, the ampoule is broken by bending stress, and the ion source is a liquid metal ion source that emits ions from the tip of a needle electrode. The ionic material used was cesium (melting point: about 29°C). In the ion source 1 shown in FIG. 1, 2 is a needle-like electrode (also called an emitter), 3 is a reservoir (also called a reservoir), 4- is an ion material, 5 is an extraction electrode, 6 is an ampoule breaking stage,
7 is an ampoule, and 8 is a channel for ionic material. The roles of the emitter 2, the reservoir 3, and the extraction electrode 5 are the same as in the conventional example, so a detailed explanation will be omitted here. (Although the ampoule is shown in the state before it is broken in this figure, the ionic material 4 is also accumulated in the reservoir 3, and the ions 9 are released, so that it is clear how the ions are released in the ion source.) Although only one ampoule breaking means 6 is shown in FIG. 1, a plurality of ampoule breaking means 6 of the same shape are lined up and cannot be seen because they are parallel to the plane of the paper. ) ionic material 4
The ampoule 7 containing the ampoule 7 is supported at both ends at the ampoule breaking section 6, and is installed so that the ampoule breaking means 6 is approximately in the center thereof. Further, as shown in FIG. 5, this ampoule breaking means 6 uses a push rod 60 which is vacuum-blocked by a metal bellows 62 or the like and can convert an external force outside the vacuum into linear motion, and its tip 61 is connected to the ampoule 7. The positional relationship is such that it hits the constriction 51 of. The combination of one linear introduction device 60 (or pushpiece) for one ampoule is called an ampoule breaking unit 70, and in the first embodiment, ten ampoule breaking units 70 are arranged in parallel. (Only five sets of ampoule breaking units 70 are shown in FIG. 5.) Here, a portion where a plurality of ampoule breaking units 70 are lined up is referred to as ampoule breaking means 6. FIG. 6 shows a set of side cross-sections of the ampoule breaking unit 70 in FIG. 5. When there is no need to break the ampoule 7, the pushpiece 60 is fixed with a U-shaped fixing jig 63 to prevent it from being pushed in by atmospheric pressure, as shown in FIG. 6(a). , this fixing jig 63 is released at the time of breakage (Figure (b)
)). The pushpiece 60 is pushed in by atmospheric pressure and comes into contact with the constriction 51 at the center of the ampoule, thereby applying a load. if,
If the ampoule 7 does not break in this state, the ampoule 7 will easily break if the end portion 64 of the bar 60 on the atmospheric pressure side is manually pushed. At this time, the ampoule is broken at two points that support both ends of the ampoule 7 and at one point where the force of the constriction 51 is applied, so-called three-point bending failure. As shown in FIG. 6(b), this operation allows the ionic material 4 to be removed from the ampoule 7.
flows out. At this time, the ampoule 7, which is the object to be broken, is approximately 7', although some small glass fragments come out.
The ionic material that flows out passes through the channel 8 and reaches the reservoir 3, while the broken ampoule 7'
71 stops before the flow path 8 and does not reach the reservoir 3. In this way, the ionic material 4 encapsulated in the ampoule 7
can be introduced into the reservoir 3 with almost no large glass fragments. Ionic material 4 introduced into reservoir 3
Since it contains almost no glass fragments, the flow path 8, capillary 10, and reservoir 3 are not blocked, and the ions 9 can be extracted stably for a long time. As a concrete value, the height is 50 m. 0.5 g (about 260 mm') of cesium is sealed in one ampoule with a diameter of 10 mm at the bottom, and if the total emitted ion current is set to about 10 μA, ion release for about 1000 hours can be confirmed for one ampoule. Ta. According to the present invention, it is possible to operate the ion source for about 10,000 hours until all the ion material in the ampoule loaded at the ampoule breakage part is exhausted and the ion source has to be detached from the device. It is. (Example 2) This example is a surface ionization type ion source, and the overall configuration of the ion source is shown in FIG.
A side cross section of is shown in FIG. (In Fig. 7, a part of the ampoule fracture part 6 is shown three-dimensionally, and the rest is shown in cross section.)
This example is an example in which cesium is used as the ionic material and applied to a secondary ion mass spectrometer. Conventionally, most of the cesium ion sources installed in secondary ion mass spectrometers are surface ionization type ion sources. As shown in the figure, cesium is heated and vaporized in a member separate from the ion emitting part, and this cesium vapor is passed through the introduction pipe to reach the ion emitting part, where it is cooled and liquefied, and then sent to the tip of the ion emitting part. lead to. After this, when the ion emitting section is heated to a high temperature, cesium is surface ionized at the tip of the ion emitting section, but in such conventional methods, it is difficult to control the temperature when vaporizing the cesium and introducing it into the ion emitting section. The device had problems such as requiring a heating power source for vaporization. In this embodiment, the ionic material 4 extracted at the ampoule break section 6 is introduced into the reservoir 3 as a liquid. The structure of the ampoule breakage portion 6 is shown in FIG. After the ampoule 7 is installed horizontally in the ampoule breakage portion main body 101, it is vacuum-sealed with a lid 102 which also serves as a jig and is in contact with the ampoule tip and the constriction 51. The ampoule has a pushbutton 103 at the end, a bellows 104, and a fixing jig 105.
It is bent and broken as necessary by a breaking tool 106 consisting of. The breaking order is the same as in Example 1, and the pushpiece 103 is pushed into atmospheric pressure by opening the fixing jig 105.
A load is applied to the end of the ampoule. At this time, since the other end 52 of the ampoule and the constriction 51 are supported by the lid 102 from the side opposite to the installation side of the push rod, the ampoule bends and breaks due to the load from the push rod, as shown in FIG. As shown in b), the ampoule 7 is broken into fragments 7'. In this example, an ampoule filled with 1 g of cesium was used, and five ampoule breakage units were lined up. However, in FIG. 7, four ampules 7 are lined up. In the ion emitting part of the surface ionization type ion source used in this example, tungsten particles with a diameter of about 100 μm are sintered at the tip of a metal tube, and the liquid cesium is sintered with tungsten particles. The ion source seeps through the voids in the body 30, reaches the ion emitting part, and is ionized.The configuration of the ion source according to the present invention as described above greatly extends the life of the ion source, which is the original purpose of the present invention. It used to take a lot of time to take the ion source out into the atmosphere, dismantle it, and clean it every time the ion source was depleted, but with this ion source, the number of these operations has been significantly reduced.Specifically, the lifespan of the ion source The life of the ion source was approximately 100 hours, but in this example, the life of the ion source has been extended to approximately 5 times, and the secondary ion mass spectrometer equipped with this ion source has a life of approximately 5 hours.
It could be used for analysis of materials for more than 00 hours. (Example 3) This example is a surface ionization type ion source using an alloy of alkali metals as the ion material. The configuration and operating principle of the surface ionization type ion source have already been shown and will not be described in detail here. However, the ampoule breaking part 6 uses the bellows 12 shown in FIG. 4(b), and has five bellows 12 lined up, each of which can be broken independently. The method of breaking the ampoule 7 is as follows. That is, the ampoule 7 is inserted into the ampoule break section 6 provided with the bellows 12, and its tip and bottom are supported. When the inside of the vacuum container 11 is evacuated in this state, the inside of the ampoule breakage portion 6 is also brought into a vacuum state, the bellows 12 is compressed, and a compressive force in the axial direction is applied to the ampoule 7. (Figure 4 (
(See b)) When the end portion 13 of the ampoule breakage portion 6 is bent while the vacuum chamber 11 has a sufficiently low degree of vacuum, the ampoule 7 is approximately bisected at the constriction portion 51 in the center due to the moment. (See Figure (e)) In this way, the ionic material 4 in the ampoule 7 passes through the channel 8 and reaches the reservoir 3. Among the alkali metals, the melting point of sodium (N a ) alone is 97.8°C, and that of potassium (K) is 63.7°C.
However, when Na and K are mixed in a weight ratio of 23.3 to 76.7, a eutectic alloy with a melting point of -12.5°C is produced. Similarly, the alloy Cs-Na with cesium (Cs; melting point; 28.4°C) has a weight ratio of Cs:Na=9 4.5
: 5.5, it becomes a eutectic alloy with a melting point of -29°C. There are many other metals and metal compounds that are liquid at room temperature. In particular, the alkali metals listed above are often sealed in ampoules, both alone and as alloys, so when such materials are used as ion materials for ion sources, the ion source according to the present invention is This is optimal because it does not affect the degree of vacuum in the ion emitting section. By using the above-mentioned ionic materials in a surface ionization type ion source, for example, when Na-K is an ionic material, N
Release of ions such as a' and K1 was confirmed. In addition to the secondary ion mass spectrometer described above, the ion source according to the present invention focuses the ion beam diameter to about 0.1 μm,
A focused ion beam device that can irradiate a localized area of a sample, and can be used as a primary ion beam source for surface modification devices and other devices that aim to change the properties of a sample surface through ion irradiation. . Furthermore, in addition to liquid metal ion sources and surface ionization type ion sources, the ion source can also be used to supply materials for cluster ion sources for generating macromolecular ions and plasma ion sources for extracting ions from plasma. [Effects of the Invention] According to the present invention, stable ion emission can be realized for a long time without exposing the ion source to the atmosphere. Further, by installing such an ion source in a secondary ion mass spectrometer, an ion beam device, or a surface modification device, these devices can operate stably for a long time.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing a schematic configuration of an ion source according to an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view showing the configuration of a reservoir and an emitter section of a liquid metal ion source, and FIGS. Figure (.) is a schematic vertical cross-sectional view showing an example of a conventional liquid metal ion source equipped with an ampoule, Figures 4 (b) and (c) are vertical cross-sectional views of the broken part of the ampoule, and Figure 5 is a schematic vertical cross-sectional view of an example of a conventional liquid metal ion source equipped with an ampoule. FIG. 6(a) is a partial cross-sectional perspective view of a broken ampoule according to an embodiment of the invention;
(b) is a longitudinal cross-sectional view of an ampoule breaking unit according to an embodiment of the present invention, and FIG. The longitudinal sectional views shown in FIGS. 8(a) and 8(b) are longitudinal sectional views of an ampoule breaking unit according to yet another embodiment of the present invention. Explanation of symbols 1... Ion source 3... Reservoir 5... Extracting electrode 7... Ampoule 8... Channel 10... Capillary 12... Bellows 2l... Lid 23... Filament 51... Constriction 2... Emitter 4... Ionic material 6... Ampoule broken part 7 j, 7 + 7... Ampoule 9... Ion 11... Vacuum vessel 13... End portion 22 of ampoule fracture portion... Shield electrode 30... Sintered body 52... Ampoule tip 60... Push-piece 61... Tip portion 62...
Bellows 63...Fixing jig 70...Ampoule breaking unit 101...Ampoule breaking part body 102...Lid 103...Press 104...Bellows depth 1' Figure 7ρ Alphabet F! Separate Unisoto Z Figure 3 National Collection 4 Figure (tl) Toku 4 Su No. 5 Figure 2 Figure 2 (National Collection 7 Figure X

Claims (1)

[Claims] 1. An ampoule in which an ionic material is sealed, a holding part of the ampoule, a broken part of the ampoule, a reservoir for holding the ionic material in a molten state, and the molten ions supplied from the reservoir. In an ion source composed of an ion emitting part arranged to emit ions of a material, the ampoule holding part can hold a plurality of ampoules, and the ampoule breaking part has a structure that can break the ampoules independently. Characteristic ion source. 2. In the above ion source, the ion emitting part is a needle-shaped electrode, and the reservoir part of the ion material is arranged so that the ion material adheres to the needle-shaped electrode in a molten state, 2. The ion source according to claim 1, further comprising an extraction electrode that extracts ions of the molten ion material from the tip of the needle-like electrode by forming a high electric field therebetween. 3. The ion emitting section is provided with an indirect heating means, and the ion material is arranged so that the ionic material is ionized by surface ionization at the end face of the ion emitting section by heating by the heating means. The ion source according to item 1. 4. The ion source according to claim 1, wherein the ion source is of a type that gasifies the ion material taken out by breaking the ampoule, turns it into plasma, and extracts ions from the plasma. 5. Claims 1 to 4 apply to a secondary ion mass spectrometer that irradiates a sample with ions and analyzes the composition of the sample by mass spectrometry of the secondary ions released from the irradiation part.
A secondary ion mass spectrometer characterized by being equipped with the ion source according to any one of the items. 6. Claims 1 to 4 as an ion source for an ion beam apparatus for manufacturing semiconductor devices that focuses, deflects, etc. ions emitted from an ion source and performs implantation, exposure, etching, etc. into a sample. An ion beam device characterized by being equipped with the ion source according to any one of the items. 7. Among the claims 1 to 4, as an ion source for a surface modification device that focuses, deflects, etc. ions emitted from an ion source and implants them into a sample to modify the mechanical properties of the sample surface. A surface modification device characterized by being equipped with the ion source according to any one of the above. 8. An ion source according to any one of claims 1 to 4, characterized in that the ionic material sealed in the ampoule is, in particular, cesium. 9. A secondary ion mass spectrometer according to claim 5, characterized in that the material to be ionized is, in particular, cesium. 10. Ion beam device according to claim 6, characterized in that the material to be ionized is in particular cesium. 11. A surface modification device according to claim 7, characterized in that the material to be ionized is, in particular, cesium.