Vacuum feedthrough, electrode assembly, device, measuring instrument, and method of operating the measuring instrument for generating silent plasma discharge.

Abstract

The present invention relates to a vacuum feedthrough 10 constructed in a radial position, comprising the following elements (from inside to outside): - a lens 11; - a first ring 12, made of glass; - a first hollow cylinder 13, made of a first dielectric material; - a first 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 comprises an electrode assembly, a device for generating DBD-plasma discharge, a measuring instrument for performing characteristic analysis of pressure and / or gas composition, and a method for operating the measuring instrument.

Description

[Technical Field]

[0001] This invention relates to a vacuum feedthrough, electrode assembly, and apparatus for generating silent plasma discharge. Further, this invention relates to a measuring instrument for pressure and / or gas composition characterization analysis, and a method for operating the measuring instrument.

[0002] This invention belongs to the technical field of plasma generation, relating to ionization and the excitation of molecules and ions to generate plasma light, and further relating to the measurement and analysis of the composition of the generated plasma gas. One possible plasma discharge is the so-called DBD-plasma discharge (also known as silent discharge or dielectric barrier discharge, abbreviated as DBD), which is an alternating voltage gas discharge in which at least one electrode is isolated from the gas chamber by a dielectric material using a current isolation method. It is also generally referred to as dielectric barrier discharge because the isolation prevents the generation of arc discharge. [Previous Technology]

[0003] Measuring and analyzing the light generated by DBD plasma presents many difficulties. The device lifespan and potential vacuum applicability, the size and complexity of the device structure, and the achievable sensitivity are all significant challenges. [Summary of the Invention]

[0004] The object of the present invention is to at least reduce some of these prior art problems. That is, one object of the present invention is to provide a simplified sensor for pressure and / or gas composition based on DBD plasma discharge, and to provide suitable components.

[0005] This object of the present invention is achieved by the vacuum feedthrough of claim 1. Description of features in claims 2 to 4 of each embodiment.

[0006] The vacuum feedthrough includes the following elements: - a lens element; - a first glass ring; - a first hollow cylinder made of a first dielectric material; - a first conductive layer; - a second glass hollow cylinder; - a third ceramic hollow cylinder; - a second glass ring; and - a metal frame, viewed radially from the inside out in the listed order.

[0007] The frame may be, in particular, ring-shaped. The frame may be, in particular, made of stainless steel.

[0008] Light within an optical wavelength range firstly has at least one continuous illumination path, from a first point on a first side, through a lens element, to a second point on a vacuum-feeded second side.

[0009] The lens element is transparent to at least one wavelength range within the optical wavelength range and thus represents the optical portion of the vacuum feedthrough element. As long as the vacuum feedthrough element is opaque within the wavelength range, passage along at least one continuous illumination path is unimpeded. The optical wavelength range includes electromagnetic illumination with wavelengths from 100 nm to 1 mm, specifically the range of visible light, ultraviolet light, and infrared light. The lens element may, for example, be plano-convex, with the convex side facing the first side of the sealing plane. The lens element may, for example, have a mushroom-shaped diameter expansion on the first side, radially overlapping with the first ring. In this way, illumination from the first side can be focused. For example, the lens element may be designed in combination with the lens radius and refractive index to concentrate the parallel illumination path from the first side onto a focal point on a second side, or at least into a focal volume.

[0010] The first side can be specifically used as a vacuum side, and the second side can be specifically used as an atmospheric pressure side. In the context of this invention, the concept of vacuum feedthrough is understood to mean that the feedthrough is suitable for use when the pressure difference between the first and second sides is very large, without the need for gas to reach the other side through a sealing surface. This requirement is typical for feedthrough applications in vacuum technology, but it is also useful for applications where there is no dominant pressure on either side within the vacuum range.

[0011] The vacuum feedthrough of this invention is an electro-optic vacuum feedthrough. The first conductive layer is insulated from the frame, forming an electrical feedthrough. The lens element forms an optical feedthrough.

[0012] Alternatively, a rod-shaped or wire-shaped electrode can be additionally guided through the lens element along its central axis. This additional electrode can be encapsulated in glass by another glass ring. This additional electrode allows the overall construction to remain compact when voltage needs to be supplied to additional components.

[0013] In another embodiment of the vacuum feedthrough of the present invention, adjacent elements (the elements being lens elements and other elements listed above) are connected to each other in a vacuum-sealed manner to form a sealing surface, which separates the first side of the vacuum feedthrough, particularly the vacuum side, and the second side, particularly the atmospheric side, from each other.

[0014] A first conductive layer is applied to the outer surface of the first hollow cylinder. This conductive layer may be made of a metal, particularly platinum.

[0015] The first hollow cylinder and the first conductive layer protrude from the second cylinder on the atmospheric side, forming a conductive contact surface. On the contact surface, the first electrode can be connected, for example, to a high-voltage power supply, so that the first conductive layer can serve as an electrode for DBD-plasma discharge. The first conductive layer can be hollow cylindrical. The first conductive layer can be segmented, that is, segmented, for example, within its function as a DBD-discharge electrode and / or within the area fed through which parallel longitudinal strips are formed below the glass ring.

[0016] The first, second and third hollow cylinders, and the first conductive layer protrude beyond the lens element on the first side.

[0017] Each element constitutes a basically annular sealing surface area. A first glass ring is radially adjacent to the lens element from the outside, and is vacuum-sealed to the lens element. A first hollow cylinder is radially adjacent to the first ring from the outside, and is vacuum-sealed to it, and so on. In this configuration, each layer has at least one adjacent glass layer. The first and second glass rings, as well as the second hollow cylinder, may be made of molten glass, in particular. The molten glass may be, in particular, a so-called cryogenic softening glass, which is suitable for making vacuum-sealed connections to metals or ceramics. The metal frame may be annular. The metal frame may, for example, have a flange, the design of which facilitates welding the frame to other elements. The metal frame may be made of, for example, stainless steel, such as 1.4435 steel or 1.4404 steel, both of which are characterized by high corrosion resistance.

[0018] Each component can be a rotating body with a rotation axis. The components can be arranged coaxially with respect to their rotation axes.

[0019] On the first side, i.e., the vacuum side, the conductive layer can be completely contained between the first and second hollow cylinders. In this case, the vacuum side has only one possibility of capacitive coupling to the electrode. The advantage of completely containing the conductive layer in the insulating material is that it avoids arcing.

[0020] The function of the ceramic third hollow cylinder is to suppress electrical breakdown that may occur through the glass second hollow cylinder if the glass's breakdown resistance is insufficient. For example, it successfully prevents discharge between the metal housing and tube of the measuring instrument (described later) from passing through the ceramic third hollow cylinder. The third hollow cylinder may be made, in particular, of an Al2O3 ceramic.

[0021] In one embodiment of vacuum feedthrough, the lens element is made of sapphire. Sapphire has high transmittance in the wavelength range of 200 nm to 5000 nm, and is therefore particularly suitable for guiding electromagnetic irradiation from the optical range out of the vacuum range with minimal loss. In particular, it has very high transmittance in the ultraviolet range above 200 nm. Furthermore, sapphire has very robust mechanical properties.

[0022] In one embodiment of vacuum feedthrough, the first hollow cylinder is made of sapphire.

[0023] The present invention further relates to an electrode assembly as claimed in claim 5. One embodiment of the electrode assembly is described by the features of claim 6.

[0024] The electrode assembly of the present invention is an electrode assembly for generating DBD-plasma discharge. This electrode assembly includes the vacuum feedthrough of the present invention described above. It further includes a fourth ceramic hollow cylinder, on the outside of which a second conductive layer is supported. The second conductive layer may be made of molybdenum.

[0025] A fourth hollow cylinder is coaxially disposed with respect to the first hollow cylinder on the first vacuum feed side (vacuum side). It is at least partially located inside the first hollow cylinder. The first and second conductive layers overlap axially.

[0026] There is a gap between the second conductive layer and the inner surface of the first hollow cylinder, which expands radially.

[0027] The first and second conductive layers constitute the two electrodes of the electrode assembly. During operation, a plasma discharge region is formed in the gap between the two electrodes, and the discharge region is in the axially overlapping area of ​​the two electrodes.

[0028] The fourth hollow cylinder provides splash protection, thus extending the lifespan of the electrode assembly. The fourth hollow cylinder can be made, for example, from Al2O3 ceramic. Another measure to provide splash protection is the selection of the feedthrough size. A larger distance between the lens element and the plasma discharge region results in lower splashing effects on the lens element. In particular, a larger distance relative to the lens element helps reduce splashing effects.

[0029] In one embodiment of the electrode assembly, the radial expansion of the gap is less than 1 mm. The radial expansion of the gap can be particularly between 0.05 mm and 0.5 mm. The inventors have discovered that with this gap expansion range, DBD-plasma discharge can be induced over a wide pressure range with a high-frequency voltage in the kilovolt range (1-10 kV, 1-10 kHz). Operation is possible within a pressure range of approximately 0.35-1500 Torr.

[0030] Furthermore, the present invention relates to an apparatus as claimed in claim 7.

[0031] The apparatus of the present invention is an apparatus for generating DBD-plasma discharge. This apparatus includes the electrode assembly described above according to the present invention. The gap between the second conductive layer and the inner surface of the first hollow cylinder is hydrodynamically connected to the interior of the vacuum chamber.

[0032] The first conductive layer is connected to the conductive contact surface and is electrically connected to a high-voltage AC power supply, and the second conductive layer is electrically connected to the ground.

[0033] The electrode assembly can be, for example, installed inside the metal wall of the vacuum chamber, and the frame is welded to the vacuum chamber wall at its periphery in a vacuum-sealed manner. The device of the present invention can generate DBD-discharge over a wide pressure range, and through this wide pressure range, the operation of the device can also be carried out, for example, at ambient pressure, that is, without the need for a partition to hydrodynamically separate the first side and the second side.

[0034] The present invention further relates to a measuring device as claimed in claim 8.

[0035] The measuring instrument of the present invention is an apparatus for analyzing pressure and / or gas composition characteristics. The measuring instrument includes the aforementioned apparatus for generating a DBD-plasma discharge. An optical sensor is additionally provided on the atmospheric side of the lens element.

[0036] Optical sensors are sensitive to wavelengths that can pass through the lens element. An optical sensor can be a simple illumination sensor, such as a light sensor, or it can be a complex optical sensor, such as a spectrometer. A photodiode with a wavelength-selective filter can be used as an example of an optical sensor.

[0037] The measuring instrument of the present invention is suitable for pressure- and / or gas composition characterization analysis, for example, within a vacuum chamber. The invention is best suited for pressure ranges from 0.35 to 1500 Torr (~2000 mbar), and is also applicable at atmospheric pressure and above, thus having broad applicability. Specific selections of materials can be tailored to vacuum requirements based on the foregoing embodiments. In particular, the use of sapphire as the dielectric, platinum and molybdenum as electrode materials, and stainless steel as the frame contribute to the vacuum suitability of the measuring instrument. Furthermore, the materials are compatible with the typical requirements of vacuum processing equipment in the semiconductor industry.

[0038] The present invention further relates to the method as claimed in claim 9. It is a method for operating the measuring device of the present invention. In the method of the present invention, an alternating voltage with an amplitude of 1 to 10 kV and a frequency of 1 to 10 kHz is applied between a first conductive layer and a second conductive layer. For example, the alternating voltage cycles from -5 kV to +5 kV and then back to the original voltage, i.e., a voltage of 10 kVpp is applied. The voltage cycle can, for example, correspond to a sinusoidal trend. A square wave voltage is also acceptable. Advantageously, the positive and negative voltage changes are relative to the chassis ground potential. In this way, the plasma obtained is significantly more stable than, for example, plasma obtained by varying between 0 and positive voltage or 0 and negative voltage.

[0039] By applying a voltage, a plasma is excited in the axial overlap region of the two conductive layers in the gap between the second conductive layer and the dielectric. Because the charge accumulates in the dielectric, the plasma duration is short. By switching the positive and negative charges of the applied alternating current, the accumulated charge carriers are sent away by the dielectric, thus maintaining a continuously irradiated plasma. The irradiation emitted by the plasma is detected by an optical sensor.

Implementation Method

[0041] FIG1 shows the central element of the present invention, namely the vacuum feedthrough, in a longitudinal section. The electro-optic vacuum feedthrough 10 constructed in a radial position includes a centrally located lens element 11 and the following other elements surrounding the lens element, listed radially from the inside out: - a first ring 12, made of glass; - a first hollow cylinder 13, made of a first dielectric material; - 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.

[0042] In addition, a first conductive layer 18 is applied to the outer surface of the first hollow cylinder, which may be made of platinum.

[0043] A sealing surface 1 separates the first side 2 and the second side 3. In this embodiment, the first side is the vacuum side, in contact with the interior of the vacuum chamber 31, and the second side is the atmospheric side. In the longitudinal section shown, the sealing surface 1 is cut along a dashed line. An optical sensor 41 and a high-voltage power supply 32 are provided on the atmospheric side of the vacuum chamber 31. The fourth hollow cylinder 21 and the second conductive layer 22 disposed on its outer surface complete the vacuum feedthrough to form the electrode assembly 20. In the embodiment shown, all elements of the electrode assembly are rotating bodies with a common axis of rotation 4 (a single-point chain).

[0044] The first conductive layer 18 is connected to the high-voltage power supply 32 on the contact surface 19. The second conductive layer is connected to ground, such that the first and second conductive layers constitute two electrodes of the electrode assembly. The two electrodes overlap in an axial overlap region 23. During operation, a discharge region 25 (shown as a dot) is formed in this overlap region and radially between the second conductive layer 22 and the hollow cylinder 13, which may be made of sapphire. This discharge region emits electromagnetic radiation, for example, beyond the visible range, emitted from the ultraviolet or infrared region. This radiation may be directed specifically toward the lens element (shown by a wavy arrow). This radiation passes through the lens 11 and reaches the optical sensor 41, where it is detected.

[0045] The first 18 and the second 22 conductive layers may overlap axially, for example, by 2-3 mm. The fourth hollow cylinder 21 may protrude, for example, in the direction of the lens element, extending approximately 5 mm beyond the second conductive layer 22. The shortest distance from the second conductive layer 22 to the lens element 11 may be, for example, approximately 10 mm. This size is suitable for the discharge range of the above embodiment with a radial expansion of 0.05 to 0.5 mm. With this distance ratio, the aforementioned sputter protection effect has been achieved. Because particles stripped from the electrode material by the discharge have a very high probability of remaining on the ceramic surface protruding from the fourth hollow cylinder in this assembly, they will not contaminate the lens element. Even if the fourth hollow cylinder itself is not transparent to irradiation or has been contaminated by the electrode material, irradiation from the discharge range 25 can still reach the lens element substantially parallel to the axial direction.

[0046] Shown is one embodiment of a measuring instrument and device, wherein the electrode assembly is built inside the metal wall of a vacuum chamber 31, and the vacuum chamber frame is welded to the wall of the vacuum chamber at its periphery by a vacuum seal.

[0047] In particular, the vacuum chamber 31 and its walls, as well as the high-voltage power supply 32 and the optical sensor 41, are shown schematically and are not a true match for the dimensions of the electrode assembly. The vacuum chamber, in particular, can be several times larger than shown relative to the vacuum feedthrough. Also shown, but not fully, is the end of the fourth hollow cylinder further away from the lens element, and the second conductive layer. The axial ends of these two elements are shown offset from each other for easy identification of their positions. The two elements may extend further axially than shown, and the second conductive layer may, for example, be in contact with the fourth hollow cylinder along its entire length. A mechanical retaining device, not shown in the figure, holds the fourth hollow cylinder in its position.

[0048] Figure 2 shows a cross-sectional view through the vacuum feedthrough 10. In a preferred embodiment, the materials are arranged in the following order from the inside to the outside: sapphire (vertical section), glass (diagonal cross section), sapphire, platinum (black), glass, ceramic (horizontal section), glass, and metal (diagonal section). The first conductive layer 18 is insulated from the metal frame 17. The elements of the layered feedthrough and adjacent elements are all vacuum-sealed.

[0049] Figure 3 shows a cross-sectional view through an embodiment of the vacuum feedthrough 10, which additionally has a central electrode 26 passing through a lens element. This additional electrode is encapsulated within the lens element by an additional glass ring 27. This additional electrode can be constructed in a rod or wire shape, and its two sides, i.e., the vacuum side and the atmospheric side, protrude beyond the feedthrough.

[0050] Figure 4 shows a cross-sectional view through an embodiment of the vacuum feedthrough 10, which additionally has electrodes 28 and 29 arranged radially within the range of the glass second ring 16. Only two electrodes are shown here as an example, but multiple such electrodes can be arranged in a strip shape, azimuthally spaced, with their longitudinal axis parallel to the axis of the hollow cylinder, on the radius of the hollow cylinder. One of these additional electrodes can, for example, replace the central electrode 26 of the embodiment in Figure 3. In another embodiment, the central electrode of Figure 3 can also be combined with the electrode arranged radially further out in Figure 4. The additional electrodes 28 and 29 can, for example, be a thin layer of metal applied to the ceramic hollow cylinder 15 and vacuum-sealed by the glass second ring 16 on the side away from the ceramic cylinder. The material of the additional electrodes can be a variety of different materials, particularly platinum, molybdenum, and titanium. Through the additional electrodes, additional plasma chambers and / or sensors can, for example, contact the vacuum side, such as a cold cathode vacuum gauge or a Pirani gauge. To establish an external electrical connection to such an additional electrode, as shown in Figure 1, or with some variation, the ceramic cylinder 15 can also protrude beyond the ring 16 on the vacuum feedthrough side away from the vacuum side, forming a contact surface for the additional electrode on this side and establishing electrical contact radially outward. Such an additional electrode can, for example, be covered along its entire length by an insulating layer. The advantage is that it avoids the often undesirable exposure potential in electron- / ion optics, which can affect charged particles. For this purpose, for example, a glass ring located on the electrode may be further axially expanded, or individual wire paths can be implemented with a thin glass layer overlapping each wire path.

[0051] In summary, the present invention provides a pressure measurement or gas analysis range from 0.35 Torr to 1500 Torr, i.e., up to the overpressure range, for example, via a cylindrical sapphire high-voltage feedthrough with a lens system. A DBD plasma can be excited by applying an AC voltage in the range of 1-10 kV and a frequency range of 1-10 kHz. The present invention provides a small, energy-efficient, and readily deployable gas analysis instrument with high sensitivity and applicability to a very wide range of applications. [Simplified Explanation of the Diagram]

[0040] The embodiments of the present invention are further described below with reference to the drawings. The drawings show: FIG1 schematically and partially cross-sectionally showing a vacuum feedthrough of the present invention, together with an embodiment of an electrode assembly, an embodiment of a device, and an embodiment of a measuring instrument; FIG2 shows a cross-sectional view through the vacuum feedthrough of the present invention along the sealing surface; FIG3 shows a cross-sectional view through an embodiment of the vacuum feedthrough of the present invention along the sealing surface; FIG4 shows a cross-sectional view through another embodiment of the vacuum feedthrough of the present invention along the sealing surface.

Claims

1. A vacuum feedthrough (10) comprising the following elements: a lens (11); a first ring (12) made of glass; a first hollow cylinder (13) made of a first dielectric material; a first 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 metal frame (17) arranged radially from the inside out in the order described, wherein there is at least one continuous illumination path for illumination emitted from an optical wavelength range to originate from a first point on the first side (2) of the vacuum feedthrough, pass through the lens element, and reach a second point on the second side (3) of the vacuum feedthrough.

2. The vacuum feedthrough (10) of claim 1, wherein adjacent elements (11, 12, 13, 14, 15, 16, 17) are connected to each other in a vacuum-sealed manner to form a sealing surface (1), which separates the first side (2) and the second side (3) of the vacuum feedthrough from each other, wherein, A first conductive layer (18) is applied to the outer surface of the first hollow cylinder, wherein the first hollow cylinder and the first conductive layer protrude outward from the hollow cylinder on the second side to form a conductive contact surface (19), wherein the first, second and third hollow cylinders and the first conductive layer protrude outward from the lens element on the first side.

3. Vacuum feedthrough (10) as requested in item 1 or 2, wherein the lens element (11) is made of sapphire.

4. Vacuum feedthrough (10) as requested in item 1 or 2, wherein the first hollow cylinder (13) is made of sapphire.

5. Vacuum feedthrough (10) as claimed in claim 2, wherein the first conductive layer (18) is made of platinum.

6. An electrode assembly (20) for generating DBD-plasma discharge, wherein the electrode assembly includes a vacuum feedthrough (10) as claimed in any one of claims 1 to 4, and further includes a fourth hollow ceramic cylinder (21) on which a second conductive layer (22) is mounted on the outer surface of the fourth hollow cylinder, wherein the fourth hollow cylinder (21) is coaxially disposed with respect to a first hollow cylinder (13) on a first side (2) of the vacuum feedthrough and is at least partially located within the first hollow cylinder, wherein the first and second conductive layers overlap axially, and wherein there is a gap (24) between the second conductive layer and the inner surface of the first hollow cylinder having an open radial expansion.

7. The electrode assembly (20) of claim 6, wherein the second conductive layer (22) is made of molybdenum.

8. The electrode assembly (20) of claim 6, wherein the radial expansion of the gap (24) is less than 1 mm.

9. The electrode assembly (20) of claim 8, wherein the radial expansion of the gap is between 0.05 mm and 0.5 mm.

10. An apparatus (30) for generating DBD-plasma discharge, the apparatus comprising an electrode assembly (20) as claimed in any one of claims 6 to 9, wherein the gap between a second conductive layer and the inner surface of a first hollow cylinder is in hydrodynamic communication with the interior of a vacuum chamber, wherein the first conductive layer is electrically connected to an AC voltage-high voltage source (32) at a conductive contact surface, and the second conductive layer is electrically connected to ground.

11. A measuring device (40) for performing characteristic analysis on pressure and / or gas composition. The measuring device includes the means as claimed in claim 10, wherein an optical sensor (41) is disposed on the atmospheric side (3) of the lens element (11).

12. A method for operating a measuring device (40) as claimed in claim 11, wherein an alternating voltage is applied between a first conductive layer (18) and a second conductive layer (22), the voltage amplitude of the alternating voltage being from 1 to 10 kilovolts and the frequency being in the range of 1 to 10 kilohertz.

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