Vacuum feedthrough, electrode assembly, and device for generating silent plasma discharge

Abstract

A vacuum feedthrough (10) composed of radial layers is composed of the following components from inside out: - a lens component (11), - a first ring (12) made of glass, - a first hollow cylinder (13) made of a first dielectric material, - a first electrically conductive layer (18), - a second hollow cylinder (14) made of glass, - a third hollow cylinder (15) made of ceramic, - a second ring (16) made of glass, and a frame (17) made of metal. Based on the vacuum feedthrough, the present invention further relates to an electrode assembly, a device for generating a DBD plasma discharge, a measuring device for determining pressure and / or gas composition, and a method for operating the measuring device.

Description

Technology Field

[0001] The present invention relates to a vacuum feedthrough, an electrode assembly, and an apparatus for generating a silent plasma discharge. Additionally, the present invention relates to a measuring device for determining pressure and / or gas composition and a method for operating the measuring device. Background Technology

[0002] The present invention belongs to the technical field of plasma generation, the ionization and excitation of molecules and ions to generate plasma light, and further, the measurement and evaluation of information regarding the gas composition of the generated plasma. One possible type of plasma discharge is the so-called DBD plasma discharge. DBD plasma discharge (also called silent electric discharge or dielectric barrier discharge, abbreviated as DBD) is an AC gas discharge in which at least one electrode is electrically insulated from the gas space by galvanic separation using a dielectric. It is also called a dielectrically inhibited discharge because the insulator prevents the occurrence of an arc discharge.

[0003] The measurement and evaluation of light generated in DBD plasmas present many challenges. Major challenges include lifetime, optionally vacuum compatibility of components, the size and complexity of setups, and achievable sensitivity. The problem to be solved

[0004] The object of the present invention is to reduce at least one of the problems of the prior art. That is, one object of the present invention is to enable a compact sensor for pressure and / or gas composition based on DBD plasma discharge and to provide components suitable for this purpose. means of solving the problem

[0005] According to the present invention, this objective is achieved by a vacuum feedthrough according to claim 1. Embodiments are derived from the features of dependent claims 2 through 4. The vacuum feedthrough comprises the following components radially from the inside out in the following order.

[0006] - Lens components,

[0007] - First ring made of glass,

[0008] - First hollow cylinder manufactured from first dielectric material,

[0009] - First electrically conductive layer,

[0010] - Second hollow cylinder made of glass,

[0011] - Third hollow cylinder made of ceramic,

[0012] - Second ring made of glass,

[0013] - Metal frame

[0014] The frame may be particularly annular. The frame may be manufactured particularly of stainless steel. Starting from a first point on the first side and passing through a lens component to a second point on the second side of the vacuum feedthrough, there exists at least one continuous radiation path for radiation from an optical wavelength range. The lens component is transparent for at least one wavelength range of the optical wavelength range and thus constitutes the optical part of the vacuum feedthrough. The components of the vacuum feedthrough are not transparent in the said wavelength range, so that the passage along the at least one continuous radiation path is not obstructed. The optical wavelength range consists of electromagnetic radiation with wavelengths of 100 nm to 1 mm, specifically the range of visible light, UV radiation, and infrared radiation. The lens component may have the shape of a plano-convex lens, for example, with a convex side facing the first side of the sealing plane. For example, the lens component may have a mushroom-head-like diameter expansion on the first side so as to overlap radially with the first ring. In this way, radiation arriving from the first side can be focused. For example, a lens component can be designed by a combination of lens radius and refractive index to focus a parallel radiation path arriving from the first side to the focal point of the second side, or at least to a focal volume. Specifically, the first side may be provided as a vacuum side, and the second side as an atmospheric side. In the present invention, the term vacuum feedthrough should be understood to mean that the feedthrough is suitable for use in situations where there is a significant pressure difference between the first side and the second side and gas does not pass through the sealing surface to the opposite side. While this requirement is common when using feedthroughs in vacuum technology, it may also be useful in other applications where there is no pressure in the vacuum ranges on both sides.Accordingly, the vacuum feedthrough according to the present invention is an electro-optical vacuum feedthrough. A first electrically conductive layer insulated from the frame forms an electric feedthrough. A lens component forms an optical feedthrough.

[0015] Optionally, additional rod-shaped or wire-shaped electrodes may pass through the lens component at the central axis of the lens component, and these additional electrodes may be glazed by an additional glass ring. These additional electrodes allow the entire structure to remain compact when a power supply for the additional components is required. In one embodiment of the vacuum feedthrough according to the present invention, adjacent components (the components are lens components and additional components of the list above) are connected to each other in a vacuum-sealed manner to form a sealing surface that separates a first side, particularly the vacuum side, of the vacuum feedthrough from a second side, particularly the atmospheric side. A first electrically conductive layer is applied to the outer surface of a first hollow cylinder. This electrically conductive layer may be made of a metal, particularly platinum.

[0016] The first hollow cylinder and the first electrically conductive layer protrude beyond the second hollow cylinder on the atmospheric side to form an electrically conductive contact surface. At the contact surface, the first electrode is connected, for example, to a high voltage source so that the first electrically conductive layer can serve as an electrode for DBD plasma discharge. The first electrically conductive layer may be in the form of a hollow cylinder. The first electrically conductive layer may be divided, for example, into an area serving as an electrode for DBD discharge and / or a feedthrough area under the glass ring, and may be formed into longitudinal strips placed next to each other. The first, second, and third hollow cylinders and the first electrically conductive layer also extend beyond the lens component on the first side.

[0017] Each component forms a substantially annular region of the sealing surface. A first ring made of glass is adjacent to the radially outer side of the lens component and is connected to the lens component in a vacuum-sealed manner. A first hollow cylinder is adjacent to the radially outer side of the first ring and is vacuum-sealed. In this arrangement, each layer has at least one adjacent glass layer. The first and second glass rings and the second hollow cylinder may be made of fused glass in particular. In particular, the fused glass may be so-called soldered glass, which is particularly suitable for making vacuum-sealed connections to metal or ceramic. The metal frame may be in the form of a ring. The metal frame may have a flange designed to facilitate, for example, welding the frame to additional components. The metal frame may be made of, for example, stainless austenitic steel such as steel 1.4435 or steel 1.4404, which is characterized by high corrosion resistance. The components may each have the shape of a rotating body having an axis of rotation. The components may be arranged coaxially with respect to the axis of rotation.

[0018] In the first side, that is, in the vacuum side, the electrically conductive layer can be completely enclosed between the first hollow cylinder and the second hollow cylinder. In this case, only capacitive coupling to the electrode is possible in the vacuum side. Completely sealing the electrically conductive layer with an insulating material has the advantage of preventing arc discharge.

[0019] A third hollow cylinder made of ceramic has the effect of suppressing electrical breakdown through a second hollow cylinder made of glass when the glass is not sufficiently broken. For example, the third hollow cylinder made of ceramic can successfully prevent discharge between the metal housing tubes of the measuring device to be described later. In particular, the third hollow cylinder can be made of Al2O3 ceramic. In one embodiment of the vacuum feedthrough, the lens component is made of sapphire.

[0020] Sapphire has high transmittance in the wavelength range of 200 nm to 5000 nm, making it particularly suitable for inducing electromagnetic radiation outside the optical range with almost no loss in a vacuum. In particular, it has high transmittance in the ultraviolet range above 200 nm. In addition, sapphire is mechanically very robust.

[0021] In one embodiment of the vacuum feedthrough, the first hollow cylinder is made of sapphire.

[0022] The present invention also relates to an electrode assembly according to claim 5. An embodiment of the electrode assembly is derived from the features of claim 6.

[0023] The electrode assembly according to the present invention is an electrode assembly for generating a DBD plasma discharge. The electrode assembly includes a vacuum feedthrough according to the present invention as described above. It further includes a fourth hollow cylinder made of ceramic that carries a second electrically conductive layer on its outer surface. The second electrically conductive layer may be made of molybdenum in particular.

[0024] The fourth hollow cylinder is arranged coaxially with the first hollow cylinder on the first side (vacuum side) of the vacuum feedthrough. It is placed at least partially inside the first hollow cylinder. The first and second electrically conductive layers partially overlap in the axial direction.

[0025] A gap having a radial extension is kept open between the second electrically conductive layer and the inner surface of the first hollow cylinder.

[0026] The first and second electrically conductive layers form two electrodes of the electrode assembly. During operation, a plasma discharge zone is formed within the gap, that is, in the axial direction of the area where the two electrodes overlap.

[0027] The fourth hollow cylinder has a sputtering prevention effect. The lifespan of the electrode assembly is extended. The fourth hollow cylinder can be manufactured, for example, from Al2O3 ceramic. Another measure for sputtering prevention is selecting the feedthrough size. If the distance between the lens component and the plasma discharge region is large, the sputtering effect on the lens component is reduced. In particular, a large distance relative to the diameter of the lens component is effective for this purpose.

[0028] In one embodiment of the electrode assembly, the radial expansion of the gap is less than 1 mm. In particular, the radial expansion of the gap may be between 0.05 mm and 0.5 mm. The inventors recognized that due to this expansion of the gap, the DBD plasma discharge can be ignited with high-frequency voltages in the kilovolt range (1-10 kV, 1-10 kHz) over a wide pressure range. It is possible to operate in a pressure range of approximately 0.35-1500 Torr.

[0029] In addition, the present invention relates to an apparatus according to claim 7.

[0030] The device according to the present invention is a device for generating DBD plasma discharge. The device includes an electrode assembly according to the present invention as described above. The gap between the second electrically conductive layer and the inner surface of the first hollow cylinder is hydrodynamically connected with the interior of the vacuum chamber.

[0031] The first electrically conductive layer is electrically connected to an AC high voltage source at an electrically conductive contact surface, and the second electrically conductive layer is electrically connected to ground.

[0032] The electrode assembly may be installed, for example, on the metal wall of a vacuum chamber, and the frame is vacuum-sealed welded around its periphery to the wall of the vacuum chamber. Due to the large pressure range over which DBD discharge is made possible by the device according to the present invention, operation of the device may occur, for example, at atmospheric pressure, that is, without a chamber hydrodynamically separating the first side from the second side.

[0033] In addition, the present invention relates to a measuring device according to claim 8.

[0034] The measuring device according to the present invention is a measuring device for characterizing pressure and / or gas composition. The measuring device includes the apparatus according to the present invention described above for generating a DBD plasma discharge. Additionally, an optical sensor is disposed on the atmospheric side of the lens component.

[0035] Optical sensors are sensitive to the range of wavelengths that can be transmitted through lens components. Optical sensors can be simple radiation sensors (e.g., optical sensors), but they can also be more complex optical sensors, such as spectrometers. For example, a photodiode with a wavelength-selective filter can function as an optical sensor.

[0036] The measuring device according to the present invention is suitable for, for example, determining the pressure and / or gas composition within a vacuum chamber. Since the optimal use of the present invention is in a pressure range of 0.35–1500 Torr (~2000 mbar), i.e., a pressure range above atmospheric pressure, it is widely applicable. The specific selection of materials used can be specifically adjusted to meet vacuum requirements according to the above examples. In particular, using sapphire as a dielectric, platinum and molybdenum as electrode materials, and stainless steel as a frame contributes to the vacuum suitability of the measuring device.

[0037] In addition, the mentioned materials are compatible with the general requirements of vacuum process plants in the semiconductor industry.

[0038] Furthermore, the present invention relates to a method according to claim 9. This relates to a method for operating a measuring device according to the present invention. In the method according to the present invention, an alternating voltage having a voltage amplitude of 1 to 10 kilovolts and a frequency in the range of 1 to 10 kilohertz is applied between a first electrically conductive layer and a second electrically conductive layer. For example, the voltage waveform can vary from -5 kV to +5 kV over one cycle of the AC voltage, i.e., a voltage of 10 kV pp can be applied. For example, the voltage waveform can correspond to a sine wave. A square wave voltage is also possible. It is advantageous to change the voltage from positive to negative relative to the ground potential. In this way, a much more stable plasma is obtained than, for example, changing between zero and a positive voltage or between zero and a negative voltage. When the voltage is applied, plasma is ignited in the gap between the second conductive layer and the dielectric in the axial overlap region of the two electrically conductive layers, which has a short lifespan due to the accumulation of charge in the dielectric. By changing the sign of the applied AC voltage, the accumulated charge carriers move away from the dielectric again, so that a continuously appearing plasma can be maintained. Radiation emitted by the plasma is detected by an optical sensor. Brief explanation of the drawing

[0039] Exemplary embodiments of the present invention are described in more detail below with reference to the drawings. FIG. 1 schematically and partially illustrates a cross-section of a vacuum feedthrough according to the present invention in relation to an example of an electrode assembly, an example of a device, and an example of a measuring device. FIG. 2 illustrates a cross-section of a vacuum feedthrough along a sealing surface according to one embodiment of the present invention. FIG. 3 illustrates a cross-section of a vacuum feedthrough along a sealing surface according to one embodiment of the present invention. FIG. 4 illustrates a cross-section of a vacuum feedthrough along a sealing surface according to another embodiment of the present invention. Specific details for implementing the invention

[0040] FIG. 1 illustrates a cross-sectional view of the central component of the present invention, namely, a vacuum feedthrough. The electro-optical vacuum feedthrough (10), composed of radial layers, comprises a lens component (11) arranged in the center and the following additional components arranged around the lens component, arranged radially from inside to outside:

[0041] - First ring (12) made of glass

[0042] - First hollow cylinder (13) made of first dielectric material,

[0043] - A second hollow cylinder (14) made of glass,

[0044] - A third hollow cylinder (15) made of ceramic,

[0045] - Second ring (16) made of glass,

[0046] - A frame made of metal (17).

[0047] In addition, a first electrically conductive layer (18) is applied to the outer surface of a first hollow cylinder shape, which can be made particularly of platinum.

[0048] The sealing surface (1) separates the first side (2) (in this case, the vacuum side) placed inside the vacuum chamber (31) from the second side (3) (in this case, the atmosphere side). In the illustrated cross-section, the sealing surface (1) intersects along the line illustrated by the dotted line. The optical sensor (41) and the high voltage source (32) are located on the atmosphere side of the vacuum chamber (31). The fourth hollow cylinder (21) and the second electrically conductive layer (22) attached to its outer surface complete the vacuum feedthrough to form the electrode assembly (20). In the illustrated embodiment, the components of the electrode assembly are all in the form of a rotating body having a common axis of rotation (4) (dotted line).

[0049] The first electrically conductive layer (18) is connected to a high-voltage source (32) at the contact surface (19). The second electrically conductive layer is connected to ground, so that the first and second electrically conductive layers form two electrodes of the electrode assembly. The two electrodes overlap in an axial overlap region (23). In this overlap region and radially between the second electrically conductive layer (22) and the hollow cylinder (13), a discharge region (25), which can be made of sapphire in particular, is formed during operation (indicated by a dashed line). For example, electromagnetic radiation in the visible range, UV range, or IR range is emitted from this discharge region. In particular, this radiation can be emitted in the direction of the lens component (indicated by a wavy arrow). This is radiation that passes through the lens component (11) and is transmitted to the optical sensor (41) to be detected.

[0050] The first electrically conductive layer (18) and the second electrically conductive layer (22) may overlap axially, for example, by 2 to 3 mm. The fourth hollow cylinder (21) may protrude about 5 mm toward the lens component, for example, beyond the second electrically conductive layer (22). The shortest distance from the second electrically conductive layer (22) to the lens component (11) may be, for example, about 10 mm. These figures correspond to a discharge area having a radial extension of 0.05 to 0.5 mm according to the above-described embodiment. Using the aforementioned spacing ratio creates the sputtering prevention effect already mentioned above. In this assembly, particles ejected from the electrode material by the discharge will, with high probability, remain attached to the protruding ceramic surface of the fourth hollow cylinder and will not contaminate the lens component. Radiation from the discharge area (25) can reach the lens component approximately parallel to the axial direction, even if the fourth hollow cylinder itself is not permeable to radiation or is already contaminated by the electrode material.

[0051] An embodiment of a measuring instrument or device is shown in which an electrode assembly is installed on the metal wall of a vacuum chamber (31), and the frame is welded to the surrounding vacuum chamber wall in a vacuum-sealed manner.

[0052] In particular, the vacuum chamber (31) and walls, the high voltage source (32) and the optical sensor (41) are depicted very schematically and do not match the dimensions of the electrode assembly. In particular, the vacuum chamber may be several times larger than depicted in relation to the vacuum feedthrough. Also, the second electrically conductive layer, which is located further away from the end of the fourth hollow cylinder and the lens component, is depicted schematically and incompletely. The axial ends of these two components are depicted offset from each other so that the two layers can be clearly seen. However, the two components may extend further axially than depicted, and the second electrically conductive layer may be placed particularly over the entire length of the fourth hollow cylinder. A mechanical fixture not depicted holds the fourth hollow cylinder in place.

[0053] FIG. 2 illustrates a cross-sectional view of a vacuum feedthrough (10). In a preferred embodiment, the order of materials from inside to outside is sapphire (vertical cross-hatching), glass (diagonal cross-hatching), sapphire, platinum (black), glass, ceramic (horizontal cross-hatching), glass, and metal (diagonal cross-hatching). The first electrically conductive layer (18) is electrically insulated from the metal frame (17). The components of the feedthrough, structured in a shell shape, are each connected to adjacent components in a vacuum-sealed manner.

[0054] FIG. 3 illustrates a cross-sectional view of an embodiment of a vacuum feedthrough (10) having an additional central electrode (26) passing through a lens component. The additional electrode is glazed to the lens component by an additional ring (27). The additional electrode may be rod-shaped or wire-shaped and may protrude beyond the feedthrough on both sides, namely the vacuum side and the air side.

[0055] FIG. 4 illustrates a cross-section of a vacuum feedthrough (10) having additional electrodes (28, 29) radially arranged in a second ring (16) region made of glass according to one embodiment of the present invention. For example, two additional electrodes are illustrated herein, but such a plurality of electrodes may be arranged in the form of strips spaced apart at an azimuth angle having a longitudinal direction parallel to the axis of the hollow cylinder at this radius. For example, one of these additional electrodes may replace the central electrode (26) of the exemplary embodiment illustrated in FIG. 3. In a further embodiment, the central electrode of FIG. 3 may also be combined with additional electrodes arranged further apart radially as illustrated in FIG. 4. The additional electrodes (28, 29) may be applied as thin metal wiring to a hollow cylinder (15) made of ceramic, for example, and surrounded by a second ring (16) made of glass in a vacuum-sealed manner on the side away from the ceramic cylinder. Various metals, in particular platinum, molybdenum, and titanium may be used as materials for the additional electrodes. For example, through additional electrodes, additional plasma chambers and / or sensors, such as cold cathode vacuum pressure gauges or Pirani pressure sensors, can be electrically contacted from the vacuum side. To enable electrical contact with these additional electrodes on the outside, the ceramic cylinder (15) may protrude beyond the ring (16) on the side of the vacuum feedthrough, for example, unlike the example in FIG. 1, and may protrude away from the vacuum side, thus also forming a contact surface for additional electrodes on this side and enabling electrical contact on the radially outer side. These additional electrodes may be covered with an insulating layer along their entire length, for example. This has the advantage of avoiding undesirable open potentials that can affect charged particles in electron / ion optics.To this end, for example, the glass ring placed over the electrodes may be further extended in the axial direction, or individual conductor tracks may be implemented as a thin glass layer that overlaps each conductor track.

[0056] In summary, the present invention enables pressure measurement or gas analysis in the range of 0.35 Torr to 1500 Torr, i.e., the maximum overpressure range, using, for example, a cylindrical sapphire high-voltage feedthrough equipped with an integrated lens system. The DBD plasma can be ignited by applying an AC voltage in the range of 1 to 10 kilovolts and a frequency in the range of 1 to 10 kilohertz. The present invention provides a highly sensitive, energy-efficient, and flexible compact gas analyzer for various applications. Explanation of the symbols

[0057] Reference sign list 1 Sealing surface 2 First side (vacuum side) 3 Second side (atmosphere side) 4 common axes 5 vacuum feedthrough 11 Lens Components 12 1st Ring (Glass) 13 First hollow cylinder (first dielectric material) 14 Second hollow cylinder (glass) 15 3rd hollow cylinder (ceramic) 16 2nd Ring (Glass) 17 Frame (Metal) 18 First electrically conductive layer 19 contact surface 20 electrode assemblies 21 4th hollow cylinder (ceramic) 22 Second electrically conductive layer 23-axis overlapping area 24 gap 25 gap discharge region 26 Additional (Central) Electrode 27 Additional Ring (Glass) 28, 29 other electrodes 30 devices 31 vacuum chamber 32 AC high voltage source 40 measuring devices 41 Optical Sensor

Claims

Claim 1 A vacuum feedthrough (10) comprising the following components, wherein the vacuum feedthrough (10) radially comprises, in the order described above, a lens component (11), a first ring (12) made of glass, a first hollow cylinder (13) made of a first dielectric material, a first electrically conductive layer (18), a second hollow cylinder (14) made of glass, a third hollow cylinder (15) made of ceramic, a second ring (16) made of glass, and a frame (17) made of metal, and wherein at least one continuous radiation path exists for radiation from an optical wavelength range, starting from a first point on the first side (2) of the vacuum feedthrough and extending through the lens component to a second point on the second side (3) of the vacuum feedthrough. Claim 2 In claim 1, adjacent components (11, 12, 13, 14, 15, 16, 17) are connected to each other in a vacuum-tight manner to form a sealing surface (1) that separates the first side (2) and the second side (3) of the vacuum feedthrough, a first electrically conductive layer (18) is applied to the outer surface of the first hollow cylinder, the first electrically conductive layer on the first hollow cylinder and the second side protrudes beyond the second hollow cylinder to form an electrically conductive contact surface (19), and the first electrically conductive layer on the first side of the first, second, and third hollow cylinders protrudes beyond the lens component, vacuum feedthrough (10). Claim 3 In claim 1 or 2, the lens component (11) is a vacuum feedthrough (10) made of sapphire. Claim 4 In paragraph 1 or 2, the first hollow cylinder (13) is a vacuum feedthrough (10) made of sapphire. Claim 5 An electrode assembly (20) for generating a DBD plasma discharge, comprising a vacuum feedthrough (10) according to claim 1 or 2, and further comprising a fourth hollow cylinder (21) made of ceramic having a second electrically conductive layer (22) on its outer surface, wherein the fourth hollow cylinder (21) is arranged on a first side (2) of the vacuum feedthrough coaxially with the first hollow cylinder (13) and is at least partially disposed inside the first hollow cylinder, the first and second electrically conductive layers partially overlap in the axial direction, and a gap (24) having a radial extension is kept open between the second electrically conductive layer and the inner surface of the first hollow cylinder. Claim 6 In claim 5, the electrode assembly (20) has a radial expansion of the gap (24) of less than 1 mm. Claim 7 A device (30) for generating a DBD plasma discharge, wherein the device comprises an electrode assembly (20) according to claim 5, the gap between the second electrically conductive layer and the inner surface of the first hollow cylinder is hydrodynamically connected to the interior of the vacuum chamber, the first electrically conductive layer is electrically connected to an AC high voltage source (32) at an electrically conductive contact surface, and the second electrically conductive layer is electrically connected to ground. Claim 8 A measuring device (40) for determining pressure and / or gas composition, wherein the measuring device comprises a device according to claim 7, and the measuring device (40) has an optical sensor (41) arranged on the atmospheric side (3) of the lens component (11). Claim 9 A method of operating a measuring device (40) according to claim 8, wherein an AC voltage having a voltage amplitude of 1 to 10 kilovolts and a frequency in the range of 1 to 10 kilohertz is applied between a first electrically conductive layer (18) and a second electrically conductive layer (22).

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