Ion guide including electrode wire and ion beam deposition system

Abstract

An ion guide (36) for guiding an ion beam along an ion path is disclosed, the ion guide having a longitudinal axis (44) corresponding to the ion path, the ion guide comprising a plurality of elongated electrodes arranged about and extending along the longitudinal axis, wherein an inner envelope (120) of the plurality of electrodes defines an ion guide volume (128). The elongated electrodes are formed by electrode wires (42), wherein adjacent electrode wires (42) are arranged at an inter-wire distance (122). The ion guide (36) comprises a retaining structure for supporting and straightening the electrode wires (42) by applying tension or maintaining tension applied to the electrode wires (42). Any portion of the retaining structure that is spaced from the ion guide volume by less than the local inter-wire distance (122) is made of a resistivity less than 10 12 Ω‑cm, preferably less than 10 9 Ω‑cm material, or has a thickness of less than 10 Ω‑cm on the surface facing the ion guide volume. 14 Ω, preferably less than 10 10 Sheet resistivity of Ω.

Description

Technical Field

[0001] The present invention relates to an ion guide for guiding an ion beam along a path. In particular, the present invention relates to an ion guide for an ion beam deposition system, and to an ion beam deposition system including such an ion guide and a method for guiding ions using such an ion guide. Background Art

[0002] Ion beams have many uses in various fields of natural science and technology, including experimental physics, medical devices, electronic component manufacturing or life sciences, especially mass spectrometry, in which charged molecules (ions) are guided to a mass spectrometer or collision cell, derived from a mass spectrometer or collision cell, or guided within a mass spectrometer or collision cell. The general purpose of an ion guide is to limit the ion beam along its predetermined path, usually using a plurality of electrodes arranged around the ion path, which in combination generate a potential for guiding the ions. In the simplest case, the potential can be a static DC potential, which is usually implemented as an ion Einzel lens device. However, this requires that the radial momentum and axial momentum of the ions have a fixed correlation to keep them on track. For example, due to collisions with residual gas atoms, the breakdown of this correlation can cause the ions to suddenly turn and lose track. These conditions are very common in the first stage of a multi-stage ion guide system or at relatively high pressures in a collision cell or drift cell, but can also occur due to space charge effects in subsequent stages. To make the ion guide more resistant to such perturbations, an electrode system driven by a radio frequency (RF) voltage having a frequency of about 0.5 to 5 MHz, and some voltages having amplitudes of up to about 100 volts, may be employed. When the amplitude and frequency of the RF potential are appropriately chosen, ions are effectively repelled from the RF electrodes by means of an effective potential or "pseudo-potential" that reflects the average effect of the RF field on the ions over many AC cycles. The repulsive force derivable from this pseudo-potential (the so-called "field gradient force") is proportional to the gradient of the square of the RF field strength, proportional to the square of the charge of the ion and, therefore, independent of its polarity, and inversely proportional to the ion mass and the square of the RF frequency.

[0003] In most RF operated ion guide systems, adjacent electrodes are driven by anti-phase sinusoidal voltages, i.e., with a 180° phase shift between adjacent electrodes. For example, in known multipole ion guides, four, six, or eight rod electrodes may be arranged in a circle around the ion path and extend parallel to the ion path, forming a quadrupole, hexapole, or octopole structure, respectively.

[0004] Although there are many uses for ion guides in various fields of science and technology, and the present invention is not limited to use in a specific one of them, the ion guide of the present invention is particularly suitable for ion beam deposition (IBD), mass spectrometry (MS), for example, a triple quadruple orbital trap or a quadrupole time-of-flight (Q-TOF) mass spectrometer used as an injection module of a quadrupole mass spectrometer, a collision cell or an ion trap in an ion mobility spectrometry (IMS) system. In IBD, ions are guided along an ion path through a series of pump chambers with decreasing pressure before being deposited on a substrate or a target by so-called "soft landing". The purpose of the pump chamber is to remove unwanted neutral particles from the ion beam. Ion beam deposition has important advantages over traditional deposition techniques. For example, unlike sputtering, plasma spraying, physical vapor deposition (PVD) and atomic layer deposition (ALD), IBD is not limited to the deposition of thermally stable molecules. Chemical vapor deposition (CVD) requires chemical reactions between sometimes toxic eductants on a substrate, which can also be avoided using IBD. Finally, while spin coating is limited to large thicknesses (on an atomic scale), IBD allows the deposition of layers of defined atomic thickness.

[0005] In addition, since the ion beam can be deflected in the IBD using appropriate electric fields, structures can be "written" on the substrate in a manner similar to maskless ion beam lithography. Thus, molecules ranging from low-mass highly sensitive, thermolabile molecules (e.g., amino acids) to high-mass molecules (e.g., peptides, proteins, or even DNA molecules with atomically defined layer thicknesses) can be placed in a microarray for the manufacture of assays, sensors, or highly specific catalysts.

[0006] Currently, all these advantages of IBD come at the expense of rather slow deposition rates due to the limited throughput of IBD systems given the relatively low intensity of the ion beams in current IBD systems.

[0007] US2014 / 0374589 discloses an ion guide comprising at least one multipole having a plurality of elongated electrodes carrying an RF voltage. The electrodes may comprise wires or rods and may have a square or flat cross section rather than a circular cross section, or the electrodes may have a cross section that varies along an allotted length.

[0008] GB 2416913a discloses a centrifugal particle mass analyzer for removing particles other than those having a mass-to-charge ratio close to a desired value from an aerosol by holding the desired particles in a rotating flow between two electrodes between which an electric field is present, forming a classifier channel therebetween. Other particles strike the electrodes. The analyzer is constructed so that the electric field is not inversely proportional to the centripetal acceleration required of the particles, thereby providing a stable classification of the particles. The electrodes are supported on bases that serve as side walls of the classifier channel. These bases are made of a material that allows a strong electric field to be applied between the electrodes but prevents the accumulation of static charge on the side walls, for example, a material with a resistivity of 10 9 and 10 12 Static dissipative plastics between Ω-cm.

[0009] US2017 / 350860A1 discloses a trapped ion mobility spectrometer and proposes the use of a high-order (N>2 order) linear multipole RF system to accumulate and analyze ions at a DC electric field barrier, wherein the high-order (N>2 order) linear multipole RF system is a pure high-order RF multipole system or a multipole RF system with a transition from high order to low order, for example, from a linear octupole RF system (N=4) to a linear quadrupole RF system (N=2) before the apex of the DC electric field barrier. The RF ion guide of the TIMS device is constructed by rolling or folding a printed circuit board (PCB), wherein the printed circuit board (PCB) carries electrodes for generating a radial RF field and an axial DC field. The surface of the PCB is covered with a high-resistance coating to prevent ion charging, wherein the envisioned specific surface resistance is 10 9 Up to 10 12 Oh hm.

[0010] US 4,885,500 discloses a quartz quadrupole comprising a quartz substrate, a conductive strip and a low conductive strip. The substrate comprises a hyperbolic inner surface which provides a geometric structure for the conductive strip to conform to generate an appropriate electric field for large-scale filtering operations. Quartz is selected as the substrate material to provide the thermal and electrical properties required for high-performance large-scale construction operations. During such operation, the potential field distortion caused by the accumulated charge in the top portion of the substrate is minimized by the low conductive strip, which is arranged to overlap the longitudinal edge of the conductive strip. Summary of the invention

[0011] The problem underlying the present invention is to provide an ion guide allowing to increase the output of an IBD system, as well as an improved IBD system.

[0012] This problem is solved by an ion guide according to an aspect of the invention as well as an IBD system according to an aspect of the invention and a method according to an aspect of the invention. Advantageous embodiments are defined in the dependent claims.

[0013] The ion guide of the present invention is suitable for guiding an ion beam along an ion path. The ion guide has a longitudinal axis corresponding to the ion path and comprises a plurality of elongated electrodes arranged around and extending along the longitudinal axis, wherein an inner envelope of the plurality of electrodes defines an ion guide volume.

[0014] According to the present invention, the elongated electrode is formed by electrode wires having a diameter of 1.0 mm or less, wherein adjacent electrode wires are arranged at an inter-wire distance. In addition, the ion guide comprises a holding structure for supporting and straightening the electrode wires by applying tension or maintaining tension applied to the electrode wires, wherein any portion of the holding structure which is spaced from the ion guide volume by less than the local inter-wire distance, preferably less than two times the local inter-wire distance, and most preferably less than three times the local inter-wire distance, is composed of a material having a resistivity of less than 10 12 Ω-cm, preferably less than 10 9 Ω-cm, or on the surface facing the ion guide volume, preferably on any surface facing the ion guide volume, having a thickness of less than 10 14 Ω, preferably less than 10 10 Sheet resistivity of Ω.

[0015] If the electrode wires are arranged on a circle around the longitudinal axis, the "inner envelope" at a given axial position will correspond to the largest circle that can be inscribed in the circular arrangement of the electrode wires. The radius of such a circle may be referred to as the "inscribed radius". Fig.12 This is illustrated with reference to a more general case, where a cross-sectional view of an ion guide is shown, where six electrode wires 42 are arranged on an ellipse about a longitudinal axis. Note that the term "wire" does not only represent wires with a circular cross section, any type of cross section such as square or elliptical is possible. Adjacent electrode wires 42 are separated by an inter-wire distance 122. Herein, the inner envelope is represented by a dashed line 120, and the ion guide volume 128 is defined by this dashed line 120. In FIG. Fig.12 , the first to third multiples of the "local" inter-wire distance 122 that can be used to measure the "charging distance", that is, the distance from the ion guide volume 128 are indicated. The term "charging distance" indicates that this distance is critical to the likelihood that an isolator arranged at this distance will be easily charged by stray ions. In the present case, the inter-wire distance 122 between the electrode wires 42 is consistent so that the local inter-wire distance 122 is the same as any one of them. However, in the case where the distance should not be consistent, then the "local inter-wire distance" will be related to the individual inter-wire distances, and the individual inter-wire distances are related to a given axial position. If the electrodes are further parallel to the longitudinal axis, the ion guide volume 128 will correspond to the largest elliptical cylinder that fits in the electrode arrangement.

[0016] According to the present invention, instead of using electrode rods, the ion guide of the present invention uses electrode wires that are thinner than conventional rods, and in fact, the electrode wires are so thin that they need to be straightened by applying tension to avoid bending. That is, in the absence of straightening by applying mechanical tension, the electrode wire will tend to bend due to the inherent bending of the electrode wire (the wire is usually obtained from being stored on a reel), due to temperature increases caused by RF current passing through the electrode wire, or ambient temperature changes, which may occur, for example, during bake-out of the vacuum system in which the ion guide may reside.

[0017] The inventors have found that, with this design, the output of an IBD system employing such an ion guide can be significantly improved. The output of an IBD system is determined by the ion current that can be directed through the ion guide or ion guide device, which is referred to herein as the "current capacity" of the ion guide (device). The obvious way to increase the current capacity is to increase the diameter of the ion guide as a whole. However, when the diameter of the ion guide increases, the diameter of the holes in the partition wall separating adjacent pump chambers also needs to be correspondingly larger. This makes it more difficult to reduce the number of neutral particles in the ion beam by pumping. The neutral particle flow that is the same as the ion beam is hereinafter referred to as "gas load". In other words, the inventors note that when the diameter of the holes in the partition wall is increased, more pumping stages are ultimately required to reduce the gas load to the desired extent. However, a large number of pump chambers increase manufacturing and operating costs and extend the ion path, resulting in an inherent increase in ion losses.

[0018] The inventors have therefore realised that it is not possible to optimise the current capacity in a straightforward manner by simply increasing the diameter of the ion guide. The inventors have found that, at a given ion guide diameter, the current capacity increases with an increasing number of elongated electrodes. In addition, the inventors have found that the best results can be obtained with an ion guide of moderate diameter, but with a relatively large number of elongated electrodes. Then, when also selecting the optimum inter-wire distance, the inventors have found that in an advantageous ion guide, the elongated electrodes should be thinner than conventional rod-shaped electrodes, and in fact be formed of electrode wires that are so thin (and therefore flexible) that they need to be tensioned to remain straight. To this end, the ion guide of the present invention comprises the aforementioned retaining structure for supporting and straightening the electrode wires by applying tension or maintaining tension applied to the electrode wires.

[0019] In addition, the holding structure of the ion guide of the present invention is specifically designed so that any portion of the holding structure that is spaced from the ion guide volume by less than the local inter-line distance, preferably less than two times the local inter-line distance, and most preferably less than three times the local inter-line distance, is composed of a lattice having a resistivity of less than 10 12 Ω-cm-preferably less than 10 9Ω-cm-. In this way, it is avoided that the holding structure is charged by stray ions from the ion beam, which would lead to a distortion of the electric field used to guide the ion beam and thus to a reduction in the current capacity. If any part of the holding structure that is spaced from the ion guide volume by less than the local line distance, preferably less than two times the local line distance, and most preferably less than three times the local line distance, has a surface facing the ion guide volume, preferably less than 10 14 Ω-preferably less than 10 10 A similar effect can be obtained if the sheet resistivity is Ω-.

[0020] In a preferred embodiment, the number of electrode wires is 6 or more, preferably 8 or more, more preferably 10 or more, and most preferably 16 or more. As the number of electrode wires increases, the current capacity of the ion guide can be increased for a given diameter of the ion guide volume.

[0021] In a preferred embodiment, a portion of the holding structure in contact with one of the electrode wires is made of a medium resistivity material having a resistivity of about 10 2 Ω-cm and 10 12 Ω-cm, preferably between 3·10 5 Ω-cm and 10 9 Those parts of the retaining structure that are in physical contact with one of the electrode wires will generally not be separated from the ion guiding volume by more than the local inter-wire distance, because the inner envelope of the electrode wires defines the ion guiding volume. Therefore, in the present invention, those parts of the retaining structure that are actually in physical contact with the electrode wires must have a sufficiently low resistivity when too close to the inner envelope. When selecting a structure having a resistivity between 10 2 Ω-cm and 10 12 Ω-cm - preferably between 3.10 5 Ω-cm and 10 9 Ω-cm-, which is low enough to avoid unintentional charging of stray ions, but high enough to allow only moderate current to flow between electrode wires of opposite polarity in contact with the same holding structure. However, if the sheet resistivity on the surface facing the ion guide volume - preferably any surface facing the ion guide volume - is between 10 4 Ω and 10 14 Ω - preferably between 3 and 10 7 Ω and 10 10 Ω, and proper discharge of stray ions can also be achieved. Such surface resistivity can be obtained using the aforementioned medium resistivity material, but can also be obtained by appropriately coating the carrier with a suitable conductive coating, wherein, for example, the carrier can be an electrical insulator.

[0022] In a preferred embodiment, the medium resistivity material is a plastic material or a ceramic material comprising or mixed with conductive particles, in particular metal particles or graphite particles. In this context, the term "particle" should have a broad meaning and does not imply any specific geometry. In particular, the term "particle" should include, for example, elongated particles with a high aspect ratio, such as nanowires, etc. In addition or alternatively, ferrite-based materials can be used. It is important that the resistivity of the medium resistivity material does not change significantly with temperature, or that during normal operation of the ion guide, the resistivity values ​​achievable by the individual components fall within the above-mentioned boundaries over the entire temperature range. Due to the heating of the wire electrodes caused by the RF current, temperature changes are expected to occur, and since the ion guide is usually employed in a vacuum, no cooling by convection is performed. For this reason, conventional semiconductor materials are not preferred as medium resistivity materials because the resistance tends to drop a lot during heating during operation of the ion guide.

[0023] Instead of using a medium resistivity material, in some embodiments, any material may be used which is coated with a coating suitable for discharging stray ions at least on the surface facing the ion guide volume - preferably on any surface facing the ion guide volume - to avoid electrostatic charging of the sealing element by stray ions. In this context, the coating may be a metal film with a thickness of 30 to 1000 nm, or a wet clay containing glass and a metal oxide such as ruthenium oxide, wherein the wet clay preferably has a thickness of 5 to 1000 μm. Such "wet clay" is also known in the art as a "cermet". The metal coating may be provided by evaporating or sputtering the metal on a support such as made of a ceramic material.

[0024] In an alternative embodiment, a portion of the holding structure in contact with one of the electrode wires is made of a conductive material, in particular of a metal, wherein the portion of the holding structure is further attached to an insulating carrier or a carrier made of the aforementioned medium resistivity material. In this way, unintentional charging of the portion of the holding structure close to the electrode wire by stray ions can be reliably prevented, while short circuits between portions of the holding structure in contact with electrode wires of different polarity can be avoided, since these portions of the holding structure are attached to the insulating or medium resistivity material carrier. The insulating (or medium resistivity) carrier can be common to a plurality of portions of the holding structure in contact with electrode wires of different polarity.

[0025] In a preferred embodiment, the holding structure comprises at least one electrode wire fixing structure in which the ends of the electrode wires are fixed, wherein in the electrode wire fixing structure the electrode wires are bent by at least 90°, preferably at least 120°, and most preferably at least 150°. This bending of the electrode wires allows a secure fixation even when space is limited. By bending the electrode wires by more than 90°, for example 120° or more, or 150° or more, a tip structure of the ion guide can be obtained, which will be further explained and illustrated with reference to the specific embodiments below. The tip structure is particularly suitable for guiding ions into an adjacent component, for example, another ion guide or a mass separator.

[0026] The electrode wire may be fixed to the electrode wire fixing structure by one or more of hard or soft soldering, spot welding, gluing, casting, clamping and fixing by fasteners, in particular screws. Although soft soldering provides a particularly simple way to fix the electrode wire to the electrode wire fixing structure, this may not match very high vacuum requirements, for example, since zinc is usually contained in the soldering material and has a relatively high vapor pressure. In this case, fixing by clamping or by fasteners such as screws is preferred.

[0027] In a preferred embodiment, the retaining structure comprises a tensioning structure, which is suitable for establishing and / or maintaining the tension of the electrode wire. In this article, the tensioning structure may include one or more elastic elements, in particular one or more springs suitable for establishing and / or maintaining the tension of the electrode wire. The elastic element can absorb thermal expansion of the electrode wire so that the wire can be kept tensioned despite this thermal expansion. Examples of elastic elements may be a coil spring, a clasp or an additional elastic element. Although in a preferred embodiment, the elastic element is incorporated into the retaining structure or the tensioning structure, it can also be incorporated into the electrode wire itself.

[0028] In various embodiments, the retention structure includes at least one electrode wire securing structure that is movable along the longitudinal axis to apply tension to the electrode wire.

[0029] In a preferred embodiment, the holding structure comprises at least one electrode wire guiding structure, wherein the electrode wire passes through the electrode wire guiding structure. In particular, the electrode wire can be bent while passing through the electrode wire guiding structure, thereby allowing the ion guiding structure to be bent or curved as a whole or have a varying diameter along its length.

[0030] In a preferred embodiment, the electrode wires diverge conically from the longitudinal axis, at least in a cross section of the ion guide, wherein the opening angle of the conical structure is greater than 0.1°, preferably greater than 0.2°, and most preferably greater than 0.5°, and is 90° or less, preferably 10° or less, and more preferably 2° or less. In this article, the "opening angle" of the cone or frustum is the maximum angle between two parent lines. For example, the wide end of the conical ion guide structure can help feed the ion beam into the ion guide and is less sensitive to slight misalignment of the ion guide relative to upstream components. At the same time, the opening angle of the conical structure is kept below 10°, and preferably below 2°, which allows the repulsive forces caused by the converging electrode wires in the direction of travel to be kept within acceptable limits. Even conical structures with very small opening angles below 1° are useful, in particular for guiding the electrode wires by radially constricting the electrode wire guiding structure to thereby obtain an hourglass-shaped double-conical structure with an electrode wire guiding structure defining the narrowest part. This double cone or hourglass structure ensures close contact of the electrode wire with the electrode wire guiding structure.As a result, for this purpose, a very small opening angle of the cone structure of less than 1° may be sufficient.

[0031] In a preferred embodiment, the electrode wire is made of copper, molybdenum, tungsten, nickel, alloys or combinations thereof, or stainless steel. Particularly preferred electrode wires are made of copper with a silver coating.

[0032] In a preferred embodiment, the electrode wire has a diameter of 0.6 mm or less, preferably 0.2 mm or less.Such a low electrode wire diameter allows for a relatively large number of electrode wires at a relatively small diameter of the ion guiding volume.

[0033] Preferably, the ratio of the electrode wire diameter to the local inter-wire distance is between 0.5 and 10.0, preferably between 0.8 and 6.0, and more preferably between 1.0 and 4.0. These ratios of electrode wire diameter and inter-wire distance have been found to be beneficial for high current capabilities of ion guides. The higher number of said ratios corresponding to lower local inter-wire distances simplifies the construction of the retaining structure as the charging distance decreases. These ratios can be achieved using electrode wires, in particular electrode wires having a diameter of less than 1.0 mm, or even less than 0.6 mm or 0.2 mm, despite a relatively large number of elongated electrodes in combination with a medium ion guide diameter. In a preferred embodiment, the above-mentioned and referenced Fig.12 The explained "inscribed radius" may be 5 mm or less, preferably 2 mm or less, and most preferably 1 mm or less, so as to reduce gas loading.

[0034] In a preferred embodiment, at least some of the electrode wires are made of a material having a strength of less than 0.06 Ω mm 2The electrode wire material is made of a material with a DC resistance of 0.9 Ω mm / m. The low resistance of the electrode wire material is important because it allows for the reduction of unwanted heating of the electrode wire caused by the RF current. This becomes particularly important for small electrode wire diameters. With overheating of the electrode wire, it becomes more difficult to keep the electrode wire taut in view of the thermal expansion of the electrode wire. However, while such a relatively low DC resistance is generally preferred, in alternative embodiments a high electrode wire resistance is employed so that at least some of the electrode wire is made of a material with a DC resistance of greater than 0.9 Ω mm / m. 2 The electrode wires are made of a material with a DC resistance of 1 / m. When a DC current flows, the high resistance allows an electric field to be generated along the length of the electrode wire, which can be used to accelerate ions in the longitudinal direction of the ion guide.

[0035] In a particularly preferred embodiment, the material of the electrode wire has a skin depth at 1 MHz higher than 10 μm, more preferably higher than 20 μm, and most preferably higher than 50 μm.

[0036] In a preferred embodiment, the electrode wires are connected to an RF drive source configured to drive every two adjacent electrode wires with voltages of opposite polarity and a freely adjustable radio frequency. The freely adjustable drive frequency allows the selection of an optimal frequency for each type of ions to be guided in the ion guide. Preferably, the RF drive source is configured to drive the electrode wires with an RF square wave signal or a superposition of RF square wave signals. A non-limiting example of a "superposition of square wave signals" is a so-called "digital signal", which corresponds to a superposition of square waves with different amplitudes and different duty cycles, but at the same fundamental frequency.

[0037] Note that the RF square wave drive signal or superposition thereof is unusual for conventional ion guides, in which the electrodes are typically driven resonantly using an LC circuit established by adding an inductive element and using the inherent capacitance of the electrode to adjust the resonant frequency. The inventors have noted that the particular waveform (i.e., square wave digital waveform versus sine wave) has little to do with the current capacity of the ion guide, but that the square wave drive signal can be more easily generated at a freely adjustable frequency than a sine wave drive signal. In fact, the square wave signal can be generated simply by using a switching circuit without providing any resonant LC elements. Since the switching frequency, duty cycle, and superposition of square waves can be freely adjusted, the digital waveform or any other superposition of square waves can be equally freely adjusted to provide optimal ion guiding performance.

[0038] In a preferred embodiment, the electrode wire is connected to an RF drive source that supplies an RF voltage with a freely adjustable frequency between about 0.05 and 20 MHz. In a preferred embodiment, the RF drive source is connected to the electrode wire by a lead wire as short as possible to keep the electrode wire low capacitance.

[0039] In order to exert a driving force on the ions in the longitudinal direction of the ion guide, a DC electric field may be established along the longitudinal axis of the ion guide. In one embodiment, at least some of the electrode wires are segmented, having conductive portions separated by lower conductive intermediate portions (particularly insulating portions), and different DC voltages are applied to different conductive portions, thereby generating an electric field along the length of the electrode wire and thus along the overall longitudinal axis of the ion guide. Such a longitudinal DC field is particularly useful for overcoming the repulsive forces generated by the tapered structure of the ion guide.

[0040] Additionally or alternatively, a DC potential gradient is established along the length of the electrode wire by a DC current flowing through the respective electrode wire.This variant is particularly suitable for ion guides with a very small inscribed radius and a high length.

[0041] As mentioned above, the ion guide of the present invention may find practical use in many applications and is not limited to any one particular use. However, in a particularly preferred embodiment, the ion guide according to one of the foregoing embodiments is part of an apparatus in which an ion beam is guided through at least two, but typically a plurality of, decompression pump chambers, wherein adjacent pump chambers are separated by a dividing wall having an aperture for passage of the ion beam. An example of such an apparatus is an ion beam deposition system.

[0042] Herein, the ion guide preferably extends through at least one partition wall separating two adjacent pump chambers. That is, the ion guide according to one of the above-mentioned embodiments is particularly suitable for being accommodated in a hole in a partition wall separating two adjacent pump chambers, even if the hole has smaller dimensions compared to prior art designs, which is advantageous for reducing the gas load. In this way, the ion beam can pass smoothly and with no or only minimal losses from one pump chamber into the other.

[0043] In a particularly preferred embodiment, at least a portion of the ion guide (or its electrode wire) is contained in an airtight tube, wherein each end of the airtight tube is connected to a corresponding one of the adjacent pump chambers. Compared with a common hole with the same diameter, such an airtight tube allows a reduction in gas conductivity, which in turn allows a significant reduction in gas load. The inventors have found that if such an airtight tube is used to communicate with two adjacent pump chambers, the total pressure drop in the second downstream chamber is higher than the total pressure drop when there is no airtight tube. In fact, when using an airtight tube, a reduction in gas load by a factor of far more than 1000 has been achieved using a standard turbo pump in a downstream vacuum chamber.

[0044] In a particularly preferred embodiment, the gas-tight tube forms part of the holding structure.

[0045] In a preferred embodiment, the diameter of the hole in the partition wall through which the ion guide extends is 4.0 mm or less, preferably 3.0 mm or less, more preferably 2.0 mm or less.

[0046] Another aspect of the present invention relates to an ion beam deposition system, wherein an ion beam is guided through a plurality of pressure-reducing pump chambers, wherein adjacent pump chambers are separated by partition walls having holes for the ion beam to pass through, wherein the ion beam deposition system comprises an ion guide according to one of the above-described embodiments.

[0047] Another aspect of the invention relates to a method for guiding an ion beam along an ion path using an ion guide, wherein the ion guide has a longitudinal axis corresponding to the ion path, the ion guide includes a plurality of elongated electrodes arranged about and extending along the longitudinal axis, wherein an inner envelope of the plurality of electrodes defines an ion guide volume, wherein the elongated electrodes are formed of electrode wires having a diameter of 1.0 mm or less, and adjacent electrode wires are arranged at an inter-wire distance, wherein the ion guide includes a retaining structure for supporting and straightening the electrode wires by applying tension or maintaining tension applied to the electrode wires, wherein any portion of the retaining structure that is spaced from the ion guide volume by less than a local inter-wire distance, preferably less than two times the local inter-wire distance, and most preferably less than three times the local inter-wire distance, is composed of a resistivity of less than 10 12 Ω-cm-preferably less than 10 9 Ω-cm-, or having a surface facing the ion guide volume - preferably any surface facing the ion guide volume - with a resistance of less than 10 14 Ω-preferably less than 10 10 Ω-sheet resistivity.

[0048] In a preferred embodiment, the method further comprises the step of driving every two adjacent electrode lines with RF voltages of opposite polarity, in particular with RF square wave signals, wherein the method further comprises the step of adjusting the RF frequency and voltage amplitude of the driving signal depending on the type of ions to be guided by the ion guide.

[0049] In the method, the ion guide may be an ion guide according to one of the above-described embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 is a schematic diagram of an ion beam deposition system employing two wire-based ion guides (WIGs) in accordance with an embodiment of the present invention.

[0051] Figure 2 is a perspective view of a portion of a WIG according to a first embodiment.

[0052] Figure 3 is a perspective view of a WIG according to a second embodiment.

[0053] Figure 3a yes Figure 3 A stereogram of a slightly modified variant of the WIG.

[0054] Figure 3b It is used as an Figure 3 A three-dimensional diagram of the electrode guide structure of the special airtight tube.

[0055] Figure 4 is a perspective view of a WIG according to a third embodiment.

[0056] Figure 5 yes Figure 4 Cross-sectional view of WIG.

[0057] Figure 6 yes Figure 4 Stereoscopic image of WIG.

[0058] Figure 7 is a perspective view of a WIG according to a fourth embodiment.

[0059] Figure 8 yes Figure 7 Further stereogram of WIG.

[0060] Fig. 9 yes Figure 7 Side view of the WIG.

[0061] Fig.10 yes Figure 7 A magnified view of the tip portion of the WIG.

[0062] Fig.11 is a circuit diagram illustrating a driving circuit for driving electrode lines of a WIG according to various embodiments of the present invention.

[0063] Fig.12 is a schematic diagram of the inner envelope of the electrodes defining the ion guide volume. DETAILED DESCRIPTION

[0064] To promote an understanding of the principles of the invention, reference will now be made to the preferred embodiments shown in the drawings and specific language will be used to describe these embodiments. It should be understood, however, that the scope of the invention is not intended to be limited thereby and that such changes and further modifications in the illustrated apparatus as are generally believed to occur now or in the future and such further applications of the principles of the invention shown herein will be conceivable to those skilled in the art to which the invention relates.

[0065] Figure 1The schematic diagram of ion beam deposition (IBD) system 10 is shown. IBD system 10 comprises the first pump chamber 12 to the fourth pump chamber 18 separated by a partition wall 20. Each of the pump chambers 12 to 18 is connected to a corresponding vacuum pump 22. Although all vacuum pumps are indicated by the same reference numeral 22, they can be different types. At the left end of IBD system 10, an electrospray ionization (ESI) device 24 is provided, in which molecules are ionized to produce molecular ions for final deposition on a substrate 26 in the fourth chamber 18 located at the far right of the figure. The ESI method is first described in Malcolm Dole, LLMack, RLMhines, RCMobley, D.Furgeson, MAlice, Molecular Beams of Macroions, JChemPhys49p.2240 (1968). John B.Feen has been awarded the Nobel Prize because of this method, referring to John B.Fenn, Electrospray Wings for Molecular Elephants (Nobel Lecture), Angew Chem Int Ed 42p.3871 (2003). In ESI device 24, the charged droplet of electrolyte is attracted by the very high voltage of the pin 28 operated at atmospheric pressure. Except the charged molecule to be deposited, each droplet also comprises a large amount of unwanted solvent / carrier gas, and these unwanted solvent / carrier gas need to be removed by the pump 22 that is connected to continuous pump chamber 12 to pump chamber 18. Ions and solvent / carrier gas are imported in the first pump chamber 12 by the capillary 30 of heating.

[0066] The pressure of the first pump chamber 12 is between 0.1 mbar and 10 mbar. To form the ion beam, a combined ion funnel and tunnel device 32 is used, which extends from the first pump chamber 12 through the hole in the partition wall 20 into the second pump chamber 14. The combined ion funnel and tunnel device 32 is referred to herein as a TWIN guide 32 and is described in more detail in the co-pending patent application "Partially Sealed Ion Guide and Ion Beam Deposition System".

[0067] The figure schematically shows a first electrode wire based ion guide 36 according to an embodiment of the present invention, which extends from the second pump chamber 14 through an opening in the partition wall 20 into the third pump chamber 16. The wire based ion guide is referred to herein as a "wire ion guide" (WIG). Herein, a portion of the WIG forms an aperture 34 through which neutral gas molecules can inadvertently pass from one chamber to another and thus have an impact on the gas load as described above.

[0068] In the third pump chamber 16, a quadrupole mass separator 38 is provided which comprises four rod-shaped electrodes 40. Finally, another WIG 36 is provided which extends from the third pump chamber 16 into the fourth pump chamber 18 through an opening in the partition wall 20 and also defines an aperture 34. Note that the first WIGs 36 and the second WIGs 36 are only Figure 1 Schematically shown in FIG, wherein the wire electrode and the corresponding holding structure can be discerned, and the following will refer to Figures 2 to 10 Describe the structure in more detail.

[0069] Figure 2 FIG. 4 shows a portion of an ion guide 36 according to a first embodiment, the ion guide 36 comprising a total of 16 electrode wires 42 extending parallel to one another and arranged on a circle around a longitudinal axis 44. The inner envelope of the electrode wires 42 is 16. Fig.12 The ion guide volume is formed in the manner shown. The purpose of the ion guide 36 is to guide the ions along the longitudinal axis 44 as they pass through the ion guide. Figure 2 The electrode wire fixing structure 46 is further schematically shown in FIG. 4 , which is a specific embodiment of the electrode wire holding structure described above. The electrode wire fixing structure 46 is composed of a material with a resistivity of 2·10 6 The electrode wire fixing structure 46 is made of a medium resistivity material of Ω-cm and is made of ferrite. This resistivity is low enough to avoid unintentional charging due to scattered ions, but at the same time high enough to keep the leakage current between adjacent electrode wires sufficiently low, and the adjacent electrode wires are driven in opposite phases and therefore have opposite polarities. In the electrode wire fixing structure 46, a hole 34 is formed. In this context, Figure 1 The holes 34 in the partition wall 20 of the same embodiment use the same reference numeral 34 because in various embodiments, the fixing structure may be part of the partition wall 20, or attached to the partition wall 20, in which case the size of the fixing structure will determine the gas conductivity and thus the gas loading. In other words, in order to reduce the gas loading, it is advantageous if the holes 34 are as small as possible. Since the medium conductivity material can be in direct contact with the electrode wires 42, the holes 34 can be made very small while avoiding excessive leakage current between adjacent electrode wires 42 and the risk of unintentional charging of stray ions.

[0070] like Figure 2 As further shown, the electrode wire 42 is bent 90° in the electrode wire fixing structure 46. Then, the electrode wire 42 is fixed by welding, spot welding, bonding, casting, clamping and / or by screws ( Figure 2 The bent end of the electrode wire 42 can be fixed to the electrode wire fixing structure 46 by fixing a fastener (not shown).

[0071] Figure 3 A second embodiment of the WIG 36 is schematically shown in FIG. Figure 3The WIG 36 includes a tensioning structure 48, which includes two electrode wire fixing structures 46 connected by an extendable rod 50, which can be extended by operating a corresponding control element 52. In the example shown, the control element 52 is a hexagonal screw drive element, which allows the length of each rod 50 to be adjusted when turned, thereby moving the electrode wire fixing structures 46 away from each other and applying an appropriate tension to the electrode wire 42. Between the electrode wire fixing structures 46, an electrode wire guiding structure 54 is provided, which electrode wire guiding structure 54 again includes a hole 34. In various embodiments, the wire guiding structure 54 can be part of the dividing wall 20 between adjacent pump chambers, or attached to the dividing wall 20 between adjacent pump chambers. In the embodiment shown, the electrode wire guiding structure 54 is made of a medium resistivity material, thereby allowing it to be in direct contact with the electrode wire 42, facilitating the guidance of the electrode wire 42 and keeping the hole 34 to a minimum size.

[0072] Figure 3a Shows Figure 3 A closely related variation of the WIG includes a spring 53 arranged between a hexagonal screw drive element 52 and one of the fixing structures 46, which forces the two fixing structures 46 to separate from each other, thereby maintaining tension between the electrode wires 42. The spring 53 is an example of an elastic member or element mentioned in the overview of the invention, and although the spring 53 has a certain degree of expansion, the spring 53 allows the mechanical tension of the electrode wires 42 to be maintained. In this embodiment, the partition wall 20 and the electrode wire guide structure 54 are different elements as described above. In addition, the annular retaining elements 56 and 58 are inserted into the fixing structure 46. Therefore, the fixing structure 46 and the partition wall 20 themselves can be made of simple metal, while the electrode wire guide structure 54 and the annular retaining elements 56 and 58 have medium resistivity. In the present embodiment, the electrode wire guide structure 54 also serves as an airtight tube to be described later. In Figure 3b A partial cross-sectional view of the wire guiding structure 54 is shown in FIG.

[0073] Figures 4 to 6 A third embodiment of the WIG 36 is shown. Figure 4 and Figure 6 Two perspective views of a third embodiment are shown, and Figure 5 The WIG 36 of the third embodiment comprises 16 electrode wires 42 arranged parallel to the longitudinal axis 44 and arranged on a circumference around the longitudinal axis 44 (see Figure 5 ).exist Figures 4 to 6In the drawings, for the sake of clarity, the diameter of the electrode wire 42 is not shown to scale. In an actual embodiment, the thickness of the electrode wire 42 will be greater than the thickness shown, and in practice the thickness is made approximately the same as the distance between the wires or the thickness is made higher. The WIG 36 of the third embodiment includes a first annular retaining element 56 and a second annular retaining element 58 at their respective ends. Each of the first annular retaining element 56, the second annular retaining element 58 and the electrode wire guiding structure 54 is in direct contact with the electrode wire 42 and is made of a medium resistivity material of the type described above. Among the multiple electrode wires 42, only exemplary electrode wires are indicated in the drawings by reference numerals for the purpose of clarity. The first annular retaining element 56 is attached to a metal plate 60, which in turn is connected to the metal plate 60 by an extendable rod 50 to contact the metal plate 60. Figure 3 The electrode wire 42 is connected to the partition wall portion 20 that separates the two pump chambers in a similar manner as shown. By operating the screw drive element 52, the distance between the metal plate 60 and the partition wall 20 can be changed, and the tension of the electrode wire 42 can be adjusted. In an alternative embodiment (not shown), a Figure 3a Spring-loaded variant of the type shown. Thus, the metal plate 60, the partition wall 20 and the extendable rod 50 form an embodiment of a tensioning structure.

[0074] like Figure 5 and Figure 6 As shown, the electrode wire 42 is guided through an annular orifice plate 58, which is attached to a larger opening in the dividing wall 20, the annular orifice plate 58 being very close to the electrode wire 42 and therefore made of a medium resistivity material. Therefore, the orifice plate 58 and the electrode wire guiding structure 54 define the hole 34 of the dividing wall 20 and actually keep the hole 34 to a minimum, thereby reducing the gas load. Since the opening in the dividing wall 20 itself is large, its edge is far enough away from the electrode wire 42, so the dividing wall 20 can be made of metal, as is the case in the embodiment shown. It should be understood that Figures 4 to 6 The dividing wall indicated by reference numeral 20 in the figure may be only a part of the dividing wall separating adjacent pump chambers. However, in an improved variant, the hole 34 and the electrode wire guide structure 54 may be narrower than shown so that it radially restricts the electrode wire 42 and guides it into a double-conical, hourglass-like shape (not shown).

[0075] To the right of the partition wall 20, a gas-tight tube 62 is shown, which extends between the partition wall 20 and the second annular retaining element 58. The tube 62 is sufficiently far from the internal volume of the WIG 36 so that it is not easily struck and charged by stray ions, and it is also not in direct physical contact with the electrode wire 42. For this reason, there are no particular requirements for the resistivity of the material of the gas-tight tube 62. In the embodiment shown, it is made of metal because the gas-tight tube 62 can be manufactured easily and with high precision. The gas-tight tube 62 reduces the conductivity of the gas through the hole 34 and the orifice plate 58, thereby helping to reduce the gas load. In the embodiment showing the second embodiment, Figure 3 and Figure 3a In the embodiment, the task of the gas-tight tube 62 is taken over by the electrode guide structure 54 . Figure 3b Shown is a cross-sectional view of an electrode guide structure 54 that acts as a special gas-tight tube 62. The recess in the electrode guide structure 54 interrupts the smooth flow of neutral gas, resulting in reduced disturbance of the gas flow between two adjacent pump chambers and thus reducing the gas load.

[0076] Finally, a first annular fixing element 64 and a second annular fixing element 66 are provided for fixing respective ends of the electrode wire 42 .

[0077] The second annular retaining element 58 may be considered part of a fixing structure that also includes a second annular fixing element 66. The annular retaining element 58 has a tapered end about which the electrode wire 42 is bent before being fixed by the annular fixing element 66, thereby providing an elongated tip of the ion guide 36. This tip facilitates the attachment of the electrode wire 42 to the ion guide 36. Figures 4 to 6 The ions exiting at the right end of the WIG 36 of the third embodiment are shown to be fed to a downstream component, for example, another WIG 36 or a WIG such as Figure 1 The third embodiment WIG 36 is therefore ideal for directing ions through Figure 1 The separator wall 20 between the second pump chamber 14 and the third pump chamber 16 is shown and enters a quadrupole mass separator 38 .

[0078] From the overview of the present invention and Figures 2 to 6 As is apparent from the description of FIG. 1 , the term “holding structure” generally refers to a structure for supporting and straightening the electrode wire 42 by applying tension or maintaining tension applied to the electrode wire 42. Such a “holding structure” may include various substructures, such as a fixing structure (e.g., a fixing structure) specifically used to fix the electrode wire 42 to a portion of the holding structure. Figure 2 or Figure 3 ), a tensioning structure for applying tension to the electrode wire 42 (e.g., Figures 3 to 6 ), or an electrode wire guiding structure for guiding the electrode wire and reducing the gas load (e.g., Figures 3 to 6 Since the fixing structure, the tensioning structure or the electrode wire guiding structure are basically functional subunits of the holding structure, there may be overlap between the subunits, or in other words, some components may be part of several of the functional subunits. For example, Figure 3 The fixing structure 46 is part of the tensioning structure 48 and so on.

[0079] Finally, refer to Figures 7 to 10 , shows a WIG 36 according to a fourth embodiment. The fourth embodiment differs from the first to third embodiments in that no medium resistivity material is used. Instead, those parts of the holding structure that are in direct contact with the electrode wire 42 are made of metal and are further attached to a carrier with medium resistivity or a common insulating carrier 68.

[0080] More specifically, the WIG 36 according to the fourth embodiment includes two annular insulating carriers 68 separated by three extendable rods 50, the length of which can be adjusted again by operation of a hexagonal screw driving element 52 for adjusting the tension of the electrode wire 42. Although not shown, the extendable rods 50 can also be adjusted by similar Figure 3a The spring 53 shown in FIG. 5 is biased in an extended configuration. The electrode wire 42 extends through a relatively large opening 70 (see FIG. 5 ) within the annular insulating carrier 68. Figure 7 ), the edge of the insulating carrier 68 is far enough away from the internal volume of the WIG 36 so that there is no risk of the insulating carrier 68 being struck and charged by stray ions.

[0081] For each of the electrode wires 42, a metal element for fixing the respective end of the electrode wire 42 is provided, the metal element directly contacts the respective electrode wire 42, and is fixed to the corresponding insulating carrier 68. The respective metal elements do not contact each other, thereby avoiding short circuits between the electrode wires 42 of different polarities.

[0082] More specifically, in Figure 8 and Fig. 9 The left end of the WIG 36 shown, which is preferably the upstream end, is provided with eight first metal elements 72 having flat surfaces 74 to which respective ends of the corresponding electrode wires 42 are attached. The first metal elements 72 are fixed to the same annular insulating carrier 68 by screws 76. Thus, the insulating carrier 68, the first metal elements 72 and the screws 76 in combination form a fixed structure.

[0083] In such Figure 8 and Fig. 9At the right end, i.e., the downstream end, of the WIG 36 shown, eight second metal elements 78 are attached to the corresponding annular insulating carrier 68 by screws 76. The second metal elements 78 have a right-angled pyramid shape with a triangular base, which is attached to the insulating annular carrier 68 by screws 76 (see Figure 8 ). The electrode wire 42 is guided along the vertical edge of the pyramid and bent around its vertex, as shown in FIG. Fig.10 Although not shown in the figure, a notch or the like is provided in the vertex region to facilitate the guidance of the electrode wire 42. The electrode wire 42 is then attached to the outwardly directed face of the second metal element 78 by means of a further screw 76. Using the pyramid-shaped second metal element 78, a sharp end of the WIG 36 is obtained again, which facilitates the insertion of the electrode wire 42 in the apex region. Figure 8 and Fig. 9 The right end - preferably the downstream end - injects the exiting ions into a downstream structure or receives ions into a downstream structure, for example, Figure 1 For clarity, a mass separator of the type shown under reference numeral 38 in FIG. Figure 7 , only a single first metal element 72 and a single second metal element 78 with a corresponding electrode line 42 are shown. Likewise, the annular insulating carrier 68, the second metal element 78 and the screw 76 are combined to form a fixing structure.

[0084] In operation, a high frequency AC voltage is applied to the electrode wire 42 at a frequency of about 0.05-20 MHz and an amplitude of about 0.1-100 V. For clarity of explanation, Figures 1 to 10 The corresponding high frequency driving source is omitted. Fig.11 An example of a suitable driving source is shown in FIG. The driving source includes a DC voltage source 104, four switches 100 and a control unit 106 for controlling the switching state of the switches 100. Between the switches 100 and the control unit 106, a potential separation element 102 is provided. An RF output voltage is supplied at the terminal 108 and the terminal 110. The control unit 106 controls the switch 100 to alternate between two switching states, the first switching state being that the upper left switch 100 and the lower right switch 100 are closed while the remaining switches 100 are open, and the second opposite state being that the lower left switch 100 and the upper right switch 100 are closed while the remaining switches 100 are open. In the first switching state, the RF terminal 108 has a positive voltage and the RF terminal 110 has a negative voltage, while in the second switching state, the voltage is reversed. Therefore, by alternating between the first switching state and the second switching state, a square wave RF output voltage is provided at the terminal 108, the terminal 110 under the control of the control unit 106. In addition, under the control of the control unit 106, the output RF frequency can be freely adjusted.

[0085] Although in reference Figures 2 to 10In the first to fourth embodiments shown, the electrode wires 42 are arranged parallel to each other and to the longitudinal axis 44 of the WIG 36. In various embodiments, the electrode wires 42 may diverge from the longitudinal axis 44 in a tapered manner, such as Figure 1 36, although shown in an exaggerated manner for illustrative purposes. In a preferred embodiment, the opening angle of the tapered structure should be limited to 90° or less, preferably 10° or less, and most preferably 2° or less. WIG 36 may also have a conical and a cylindrical portion, or two conical portions with different orientations, in order to produce an hourglass shape, such as Figure 1 In the embodiment of the present invention, the WIG 36 extends through the third pump chamber 16 and the fourth pump chamber 18. In order to obtain such a structure, it is advantageous to adopt a guide structure 54 through which the electrode wire 42 passes, wherein the electrode wire 42 is bent while passing through the guide structure. In particular, it is advantageous to manufacture such a guide structure that is in direct contact with the electrode wire 42 and close to the inner volume of the WIG 36 from a medium resistivity material.

[0086] Although the primary purpose of the ion guide 36 is to confine ions to a region close to the longitudinal axis 44, in some embodiments it is also desirable to apply an electric field in the longitudinal direction in order to accelerate the ions or to overcome the repulsive potential caused by the electrode wires 42 converging conically in the downstream direction. In some embodiments, the electrode wires 42 are therefore segmented, having conductive portions separated by lower conductive middle portions - in particular insulating portions. Different DC voltages may then be applied to the different conductive portions in addition to the RF voltage, thereby generating an electric field along the length of the electrode wires 42 and, accordingly, along the entire length of the WIG 36. Instead of using segmented electrode wires, it is also possible that at least some of the electrode wires have a 0.9 Ω mm 2 / m or greater resistance of the electrode wire 42. Then, a DC current can be applied through the respective electrode wires 42 to establish a DC potential gradient along the length of the electrode wire 42.

[0087] According to the above-mentioned embodiment, the WIG 36 is Figure 1 The type shown finds particularly advantageous use in ion beam deposition (IBD) systems 10, since they allow an unprecedentedly advantageous compromise between high current capacity and low gas production. In fact, using a WIG device 36 according to an embodiment of the invention, an IBD system 10 can be provided that allows the pressure to be reduced by at least 11 orders of magnitude, or even up to 13 orders of magnitude (i.e., from atmospheric pressure to 10-11 bar, or even 10-13 bar), using only four pump chambers 12, 14, 16, and 18. Depending on the desired final pressure, even fewer pump chambers can be used.

[0088] Although preferred exemplary embodiments are shown and described in detail in the drawings and the foregoing description, these embodiments should be regarded as purely exemplary and not limiting of the present invention. In this regard, it should be noted that only preferred exemplary embodiments are shown and described, and all changes and modifications within the scope of protection of the present invention as defined in the claims, whether current or future, should be protected.

[0089] Description of Reference Numerals

[0090] 10. IBD System

[0091] 12. First Pump Room

[0092] 14 Second Pump Room

[0093] 16. Third Pump Room

[0094] 18. Fourth Pump Room

[0095] 20 Divider Wall

[0096] 22 Vacuum pump

[0097] 24 Electrospray ionization (ESI) device

[0098] 26 Substrate

[0099] 28 pins

[0100] 30 Heated capillary

[0101] 32 Combined ion funnel and tunnel

[0102] 34 holes

[0103] 36 Wire-based ion guide (WIG)

[0104] 38 Quadrupole mass separator

[0105] 40 Rod Electrode

[0106] 42 Electrode wire

[0107] 44 Vertical axis

[0108] 46 Electrode wire fixing structure

[0109] 48 tension structure

[0110] 50 Extendable rod

[0111] 52 Hexagonal screw drive element

[0112] 53 Spring

[0113] 54 Electrode wire guide structure

[0114] 56 first annular retaining element

[0115] 58 second annular retaining element

[0116] 60 Metal Plate

[0117] 62 Airtight tube

[0118] 64 first annular fixing element

[0119] 66 second annular fixing element

[0120] 68 Insulation carrier

[0121] 70 Opening in the insulating carrier 68

[0122] 72 First metal element

[0123] 74 The flat surface of the first metal element 72

[0124] 76 Screws

[0125] 78 Second metal element

[0126] 100 Switch

[0127] 102 Potential separation element

[0128] 104 DC voltage source

[0129] 106 Control Unit

[0130] 108 RF Terminal

[0131] 110 RF Terminal

Claims

1. An ion guide (36) for guiding an ion beam along an ion path, the ion guide (36) having a longitudinal axis (44) corresponding to the ion path, the ion guide (36) comprising a plurality of elongated electrodes arranged around the longitudinal axis (44) and extending along the longitudinal axis (44), in, The inner envelope (120) of the plurality of elongated electrodes defines an ion guide volume (128), wherein the elongated electrode is formed by electrode wires (42) having a diameter of 1.0 mm or less, wherein adjacent electrode wires (42) are arranged with an inter-wire distance (122), wherein the electrode wires are arranged on a circle or an ellipse around the longitudinal axis, The ion guide (36) includes a holding structure for supporting and straightening the electrode wire (42) by applying tension to the electrode wire (42) or maintaining the tension applied to the electrode wire (42). wherein the ratio of the diameter of the electrode wire (42) to the local inter-wire distance (122) is between 0.8 and 6.0, wherein any portion of the retaining structure that is spaced from the ion guide volume by less than the local line-to-line distance (122) is composed of a material having a resistivity of less than 10 12 Ω-cm material, or having a surface facing the ion guide volume (128) of less than 10 14 Sheet resistivity of Ω.

2. The ion guide (36) of claim 1, wherein: Any portion of the retaining structure that is spaced from the ion guide volume by less than two times the local inter-wire distance (122) is composed of a material having a resistivity of less than 10 9 Ω-cm material, or having a surface facing the ion guide volume (128) of less than 10 10 Sheet resistivity of Ω.

3. The ion guide (36) of claim 1, wherein: Any portion of the retaining structure that is spaced from the ion guide volume by less than three times the local inter-wire distance (122) is composed of a resistivity less than 10 9 Ω-cm material, or having a surface facing the ion guide volume (128) of less than 10 10 Sheet resistivity of Ω.

4. The ion guide (36) of claim 1, wherein: The portion of the retaining structure that contacts one of the electrode wires (42) is made of a medium resistivity material having a resistivity of 10 2 Ω-cm and 10 12 Ω-cm, or a resistivity of between 10 4 Ω and 10 14 The sheet resistivity is between Ω.

5. The ion guide (36) of claim 1, wherein: The portion of the retaining structure in contact with one of the electrode wires (42) is made of a medium resistivity material having a resistivity of 3.10 5 Ω-cm and 10 9 Ω-cm, or has a resistivity of between 3·10 7 Ω and 10 10 The sheet resistivity is between Ω.

6. The ion guide (36) of claim 4, wherein: The medium resistivity material is a plastic material or a ceramic material, the plastic material or the ceramic material comprising or mixed with conductive particles, or a ferrite-based material, or wherein the thin film resistivity is obtained by coating the surface of the holding structure in contact with one of the electrode wires (42) with a metal film having a thickness of 30 to 1000 nm, or a wet clay containing glass and metal oxide.

7. The ion guide (36) of claim 6, wherein: The conductive particles are metal particles or graphite particles, or wherein the wet clay has a thickness of 5 to 1000 μm.

8. An ion guide (36) for guiding an ion beam along an ion path, the ion guide (36) having a longitudinal axis (44) corresponding to the ion path, the ion guide (36) comprising a plurality of elongated electrodes arranged about and extending along the longitudinal axis (44), in, The inner envelope (120) of the plurality of elongated electrodes defines an ion guide volume (128), wherein the elongated electrode is formed by electrode wires (42) having a diameter of 1.0 mm or less, wherein adjacent electrode wires (42) are arranged with an inter-wire distance (122), wherein the electrode wires are arranged on a circle or an ellipse around the longitudinal axis, The ion guide (36) includes a holding structure for supporting and straightening the electrode wire (42) by applying tension to the electrode wire (42) or maintaining the tension applied to the electrode wire (42). wherein the ratio of the diameter of the electrode wire (42) to the local inter-wire distance (122) is between 0.8 and 6.0, and wherein the portion of the retaining structure in contact with one of the electrode wires (42) is made of a conductive material, wherein the portion of the retaining structure is further attached to an insulating carrier or a carrier made of a medium resistivity material.

9. The ion guide (36) according to claim 1 or 8, wherein: The number of the electrode wires (42) is 6 or more.

10. The ion guide (36) of claim 9, wherein: The number of the electrode wires (42) is 8 or more.

11. The ion guide (36) of claim 9, wherein: The number of the electrode wires (42) is 10 or more.

12. The ion guide (36) of claim 9, wherein: The number of the electrode wires (42) is 16 or more.

13. The ion guide (36) of claim 1 or 8, wherein: The holding structure comprises at least one electrode wire fixing structure (46), in which the end of the electrode wire (42) is fixed, wherein in the electrode wire fixing structure (46), the electrode wire (42) is bent by at least 90 degrees.

14. The ion guide (36) of claim 13, wherein: In the electrode wire fixing structure (46), the electrode wire (42) is bent by at least 120 degrees.

15. The ion guide (36) of claim 13, wherein: In the electrode wire fixing structure (46), the electrode wire (42) is bent by at least 150°.

16. The ion guide (36) of claim 13, wherein: The electrode wire (42) is fixed to the electrode wire fixing structure (46) by one or more of hard welding or soft welding, spot welding, bonding, casting, clamping and fasteners.

17. The ion guide (36) of claim 1 or 8, wherein: The retaining structure comprises a tensioning structure (48) adapted to establish and / or maintain tension in the electrode wire (42), wherein the tensioning structure (48) comprises one or more elastic elements.

18. The ion guide (36) of claim 17, wherein: The tensioning structure (48) comprises one or more springs (53) adapted to establish and / or maintain tension in the electrode wire (42).

19. The ion guide (36) of claim 1 or 8, wherein: The retaining structure includes at least one electrode wire securing structure (46) that is movable along the longitudinal axis (44) to apply tension to the electrode wire (42).

20. The ion guide (36) of claim 1 or 8, wherein: The holding structure includes at least one electrode wire guiding structure (54) through which the electrode wire (42) passes, and wherein the electrode wire (42) is bent while passing through the electrode wire guiding structure (54).

21. The ion guide (36) of claim 1 or 8, wherein: The electrode wire (42) diverges conically from the longitudinal axis (44) at least in a portion of the ion guide (36), wherein an opening angle of the conical structure is greater than 0.1° and 90° or less.

22. The ion guide (36) of claim 21, wherein: The opening angle of the conical structure is greater than 0.2° and less than or equal to 10°.

23. The ion guide (36) of claim 21, wherein: The opening angle of the conical structure is greater than 0.5° and less than or equal to 2°.

24. The ion guide (36) of claim 1 or 8, wherein: The electrode wire (42) is made of copper, molybdenum, tungsten, nickel, alloys thereof or stainless steel.

25. The ion guide (36) of claim 1 or 8, wherein: The electrode wire (42) has a diameter of 0.6 mm or less.

26. The ion guide (36) of claim 25, wherein: The electrode wire (42) has a diameter of 0.2 mm or less.

27. The ion guide (36) of claim 1 or 8, wherein: The ratio of the diameter of the electrode wire (42) to the local inter-wire distance (122) is between 1.0 and 4.

0.

28. The ion guide (36) of claim 1 or 8, wherein: At least some of the electrode wires (42) have a resistance less than 0.06 Ω·mm 2 / m, or wherein at least some of the electrode wires (42) are made of a material having a DC resistance greater than 0.9Ω·mm 2 / m DC resistance of the material.

29. The ion guide (36) of claim 1 or 8, wherein: The material of the electrode wire (42) has a skin depth higher than 10 μm at 1 MHz.

30. The ion guide (36) of claim 1 or 8, wherein: The electrode wires (42) are connected to an RF driving source, which is configured to drive two adjacent electrode wires (42) with voltages of opposite polarities and a freely adjustable radio frequency.

31. The ion guide (36) of claim 30, wherein: The RF driving source is configured to drive the electrode wire using an RF square wave signal or a superposition of RF square wave signals.

32. The ion guide (36) of claim 1 or 8, wherein: At least some of the electrode wires (42) are segmented so that at least some of the electrode wires (42) have conductive portions separated by intermediate portions having lower conductivity, and wherein different DC voltages are applied to different conductive portions to generate an electric field along the length of the electrode wire (42).

33. The ion guide (36) of claim 1 or 8, wherein: By means of a DC current passing through the respective electrode wire (42), a DC potential gradient is established along the length of said electrode wire (42).

34. The ion guide (36) of claim 1 or 8, wherein: The ion guide (36) extends through at least one partition wall (20) which separates two adjacent pump chambers (12, 14, 16, 18).

35. The ion guide (36) of claim 34, wherein: At least a portion of the ion guide (36) is housed in a gas-tight tube (62), wherein each end of the gas-tight tube (62) is in communication with a corresponding one of the adjacent pump chambers (12, 14, 16, 18).

36. The ion guide (36) of claim 35, wherein: The airtight tube (62) forms part of the retaining structure.

37. The ion guide (36) of claim 34, wherein: The diameter of the hole in the partition wall through which the ion guide (36) extends is 3.0 mm or less.

38. The ion guide (36) of claim 1 or 8, wherein: The ion guide (36) is part of an ion beam deposition system (10) in which an ion beam is guided through a plurality of pump chambers (12, 14, 16, 18) having decreasing pressures, wherein adjacent pump chambers (12, 14, 16, 18) are separated by a partition wall (20) having an aperture (34) for the ion beam to pass through.

39. An ion beam deposition system (10) comprising at least one ion guide (36) as claimed in claim 1 or 8.

40. A method of directing an ion beam along an ion path using the ion guide (36) of claim 1 or 8.

41. The method according to claim 40, further comprising the steps of: Each two adjacent electrode wires (42) are driven with RF voltages of opposite polarity, wherein the method further comprises the step of adjusting the RF frequency and voltage amplitude of the driving signal according to the type of ions to be guided by the ion guide (36).

42. The method according to claim 41 further comprising the steps of: Each two adjacent electrode lines (42) are driven by an RF square wave signal, or a superposition of RF square wave signals.

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