Auxiliary vacuum pump combination system

Abstract

The present invention relates to an auxiliary pumping system (1000) for evacuating an equipment chamber (1), which comprises a primary pump (12), an intermediate vacuum chamber (10) connected to the primary pump (12) through a vacuum conduit (14), and a high-pressure non-evaporable getter (NEG) pump contained in the intermediate vacuum chamber (10), wherein the vacuum conduit (14) has a length comprised between 5 cm and 200 cm, and the ratio between the volume of the high-pressure NEG pump and the volume of the intermediate vacuum chamber (10) is comprised between 0.022 and 0.540.

Description

[Technical Field]

[0001] The present invention relates generally to vacuum pumping systems, and more particularly to auxiliary pumping systems that evacuate an equipment chamber due to a combination of pumps connected to the equipment chamber through vacuum-tight openings, such as vacuum flanges, etc. Although reference will be made below to vacuum flanges, the invention is not limited to this type of vacuum-tight opening. [Background technology]

[0002] The vacuum pumping system of the present invention is defined as auxiliary because it is not freestanding, but rather is designed to be coupled to at least one other high vacuum pump and at least one equipment chamber.

[0003] In equipment for many scientific and technical applications, there is a need to provide a vacuum chamber inside which high vacuum (HV) or ultra-high vacuum (UHV) conditions are provided, such conditions being obtained, in a manner known per se, by the combined use of at least two different types of pumps.

[0004] The first pump, usually of a mechanical type, is required to reduce the pressure inside the equipment chamber from atmospheric pressure to a first vacuum level, usually having a pressure value comprised between 10 Pa and 0.1 Pa. Reaching such a first vacuum level is necessary to enable the operation of a second type of pump, which cannot operate at pressures above the aforementioned first vacuum level.

[0005] The second type of pump is intended to further reduce the pressure inside the chamber from the pressure of the first vacuum level, and such a second pump can be, for example, a cryopump, and most commonly a turbomolecular pump (TMP).

[0006] As mentioned, turbomolecular pumps are commonly used as secondary pumps for UHV chambers / systems, but they have several drawbacks, typically related to their mechanical vibrations, which is particularly relevant in applications such as scanning electron microscopes (SEMs) and transmission electron microscopes (TEMs). Therefore, they must be installed far away from the vacuum chamber, which must be evacuated by a long conduit, resulting in reduced pumping performance, such as pumping speed. This drawback is particularly relevant in portable systems, such as the one presented in the paper "Optimized DLP Linear Ion Trap for a Portable Non-Scanning Mass Spectrometer," International Journal of Mass Spectrometry 369, (2014) pp. 30-35.

[0007] Known uses of multiple pump combinations to evacuate vacuum equipment chambers are described in WO2020240152 and US Pat. No. 5,161,955.

[0008] More specifically, the system described in WO2020240152, which represents one of the most recent developments, shows a vacuum pumping assembly including a high-pressure getter pump and a non-mechanical high-vacuum pump (ion getter pump, evaporable / non-evaporable getter pump, sublimation pump) mounted on the same flange, which is connected to the equipment chamber to be evacuated.

[0009] The system described in U.S. Pat. No. 5,161,955 uses a rough pump and a high-pressure getter pump, which are separately and alternately connected to the instrument vacuum chamber, to evacuate the vessel. Switching between the operation of these two pumps is handled by a pressure sensor and two valves. In the preferred embodiment shown in this patent, activation of the high-pressure getter pump requires an external heater device made from a series of annular coil segments powered through a power cord, which increases the overall volume and connection complexity of the system. Furthermore, the getter pump housing is almost entirely surrounded by insulating material, which limits the pumping performance of the getter material.

[0010] Also, WO2020079396 and EP3945210 disclose vacuum pumping systems that include a combination of a primary pump and a non-mechanical NEG high vacuum pump. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] WO2020240152 [Patent Document 2] U.S. Patent No. 5,161,955 [Patent Document 3] WO2020079396 [Patent Document 4] EP3945210 [Patent Document 5] WO2013175340 [Patent Document 6] WO2015075648 [Patent Document 7] WO2017203015 [Patent Document 8] U.S. Patent No. 8,961,816 [Patent Document 9] U.S. Patent No. 9,416,435 [Patent Document 10] U.S. Patent No. 6,521,014 [Non-patent literature]

[0012] [Non-Patent Document 1] "Optimized DLP linear ion trap for a portable non-scanning mass spectrometer", International Journal of Mass Spectrometry 369, (2014) pp. 30-35 Summary of the Invention [Problem to be solved by the invention]

[0013] The object of the present invention is to provide a new vacuum pumping system, which has been found to be superior in terms of ease of installation, reduced size and energy consumption, and which is adaptable to a greater number of possible devices and applications, which is a great advantage, especially when the space for installing the system is limited, for example in complex vacuum equipment such as SEM, TEM, surface science tools. [Means for solving the problem]

[0014] In a first aspect, the present invention provides an auxiliary pumping system including a primary pump, an intermediate vacuum chamber connected to the primary pump through a first flange, and a high-pressure non-evaporable getter (NEG) pump contained within the intermediate vacuum chamber, wherein the primary pump operates from atmospheric pressure to a first vacuum level, and the NEG pump operates from the first vacuum level to a second vacuum level; ● The primary pump is flanged onto a vacuum conduit that distances the intermediate vacuum chamber from the primary pump, the length of said conduit being comprised between 5 cm and 200 cm; - in the auxiliary pumping system, characterized in that the ratio between the volume of the getter pump and the volume of the intermediate vacuum chamber is comprised between 0.022 and 0.540;

[0015] The definition of "volume of the getter pump" here should be considered as the total volume of its elements and components that are physically located inside the intermediate vacuum chamber; therefore, elements or components (e.g. flanges, connectors, etc.) whose installation is outside the intermediate vacuum chamber should not be included in this definition.

[0016] The term "vacuum conduit" also encompasses the equivalent concept and realization of more vacuum conduits connected in series with one or more vacuum components (such as a valve block as further described below) interposed therebetween, and the overall length of the vacuum conduit is considered to be the sum of the length contributions of each vacuum conduit interposed between the primary pump and the intermediate vacuum chamber.

[0017] As regards the primary pump, it can preferably be selected from so-called "dry pumps" (such as roots pumps, scroll pumps, membrane pumps or diaphragm pumps) and oil-lubricated pumps (such as rotary vane pumps), which operate from atmospheric pressure down to a first vacuum level between 10 Pa and 0.1 Pa.

[0018] Getter pumps have been known for a long time and are becoming more widely used and appreciated, in part due to continuous improvements (e.g., regarding the properties of the getter alloys used in getter pumps), as described in WO2013175340, WO2015075648, WO2017203015.

[0019] The high-pressure non-evaporable getter (NEG) pump operates from said first vacuum level to a second vacuum level between 0.01 Pa and 0.001 Pa, such operating vacuum range identifying this element in the context of the present invention. Some examples of such pumps are given in the already mentioned WO2020240152. It should also be emphasized that due to the specific design of the auxiliary pumping system of the present invention, "standard" high-vacuum getter pumps (such as those described in WO2013175340, WO2015075648, and WO2017203015) can also be operated at higher starting pressures and therefore fall within the definition of a high-pressure getter pump according to the present invention.

[0020] The invention will be further illustrated with the help of the accompanying non-limiting figures. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic perspective view of an equipment vacuum chamber fitted with an auxiliary pumping system according to a first embodiment of the present invention; FIG. [Figure 2] FIG. 1 is a schematic perspective view of an auxiliary pumping system according to a second embodiment of the present invention coupled to an HV pump. [Figure 3] FIG. 10 is a schematic perspective view of an intermediate vacuum chamber according to a third embodiment of the present invention, coupled with an HV pump. [Figure 4] FIG. 10 is a schematic perspective view of an auxiliary pumping system according to a fourth embodiment of the present invention coupled to a first HV pump and a second HV pump. [Figure 5] FIG. 10 is a top view of an intermediate vacuum chamber according to a fourth embodiment of the present invention. [Figure 6] FIG. 6 is a cross-sectional view taken along line AA in FIG. 5. DETAILED DESCRIPTION OF THE INVENTION

[0022] With regard to the above figures, it should be emphasized that the dimensions and dimensional ratios of certain elements may in some cases be modified to improve their understanding, and that reference is made in particular and non-exclusively to the distance between the respective getter disks constituting the NEG pump in FIG. 6 or the volume of the instrument vacuum chamber in FIG. 1.

[0023] The simplest auxiliary pumping system configuration according to the present invention is shown in the schematic diagram of Figure 1, in which auxiliary pumping system 1000 is mounted above instrument vacuum chamber 1, which has high vacuum (HV) pump 2 mounted thereon. Intermediate vacuum chamber 10 has a first flange 11 for connection to primary pump 12 via vacuum conduit 14, optionally through valve block 13 and elbow 131, which vacuum conduit 14 is preferably flexible to favor damping of vibrations coming from primary pump 12.

[0024] The construction of the optional valve block 13 is generally known to those skilled in the art and typically involves a shut-off valve as well as an appropriate coupling flange.

[0025] The intermediate vacuum chamber 10 also has a second flange 15 for a high pressure NEG pump inserted into the intermediate vacuum chamber 10, and a third flange 16 for connection to the instrument vacuum chamber 1. As already outlined, the auxiliary pumping system of the present invention cannot achieve pressures below the second vacuum level, and therefore, properly evacuating the instrument chamber of a high vacuum device requires the presence of at least an additional HV pump, either mounted on the instrument vacuum chamber 1 itself, as shown in Figure 1, or mounted on an additional fourth flange present on the intermediate vacuum chamber, as shown in the preferred embodiment of Figure 2.

[0026] FIG. 2 shows an auxiliary pumping system 2000, the configuration of which includes an intermediate vacuum chamber 20 having a first flange 21 for connection to a primary pump 22 via a flexible conduit 24, optionally through a valve block 23 and an elbow 231, a second flange 25 for a high-pressure NEG pump inserted into the intermediate vacuum chamber 20, a third flange 26 positioned opposite the second flange 25 for connection to an instrument vacuum chamber (not shown), and a fourth flange 27 for mounting an HV pump 28 (this HV pump 28 is not part of the auxiliary pumping system of the present invention).

[0027] 3 shows another possible alternative configuration 300 with an intermediate vacuum chamber 30 coupled to an HV pump 38 having a first flange 31 for connecting to a primary pump (not shown), a second flange 35 for a high-pressure NEG pump inserted into the intermediate vacuum chamber 30, a third flange 36 for connecting to an instrument vacuum chamber (not shown), and a fourth flange 37 for mounting the HV pump 38 (which is not part of the auxiliary pumping system of the present invention). The third embodiment has the same number and types of flanges as the second embodiment, but it is arranged differently in that the HV pump flange 37 is positioned at the opposite end of the intermediate vacuum chamber 30 relative to the high-pressure NEG pump flange 35.

[0028] 4 and 5 show another possible alternative configuration of an auxiliary pumping system 4000 according to the present invention, coupled with a first HV pump 48, in which the intermediate vacuum chamber 40 has a first flange 41 for connection to the primary pump 42 via a flexible conduit 44, optionally through a valve block 43 and an elbow 431, a second flange 45 for a high-pressure NEG pump inserted into the intermediate vacuum chamber 40, a third flange 46 for connection to an instrument vacuum system chamber (not shown), a fourth flange 47 for mounting the first HV pump 48, and a fifth flange 49 for mounting a second HV pump (not shown in this figure) positioned at the opposite end of the intermediate vacuum chamber 40 relative to the high-pressure NEG pump flange 45 (the HV pump is not part of the auxiliary pumping system of the present invention).

[0029] Figure 5 shows the intermediate vacuum chamber 40 in a top view without the first HV pump 48, and Figure 6 is a cross-sectional view taken along line AA in Figure 5, with Figure 5 showing configuration 400 to illustrate the internal arrangement of the intermediate vacuum chamber 40. More specifically, the second flange 45 is used to mount a high-pressure NEG pump 451 inserted into the intermediate vacuum chamber 40, and the fifth flange 49 is used to mount a second HV pump 491 also inserted into the intermediate vacuum chamber 40 at the opposite end relative to the high-pressure NEG pump 451.

[0030] It should be emphasized that all flanges mentioned in the above description for connection to either a vacuum pump or a vacuum conduit or an equipment vacuum chamber may be separate elements or may be components already integrated into the intermediate vacuum chamber or into an element connected to it. In other words, the intermediate vacuum chamber is provided with at least three vacuum-tight mounting openings, which, in operation, are used to hermetically connect it to the required elements through flanges or the like.

[0031] All of the above embodiments are characterized by having a primary pump connected to the intermediate vacuum chamber through a vacuum conduit, the length of said conduit being comprised between 5 cm and 200 cm, and the ratio between the volume of the non-evaporable getter (NEG) getter pump and the volume of the intermediate vacuum chamber being comprised between 0.022 and 0.540. It should be emphasized that the optional valve block is advantageously present for lengths greater than 19 cm.

[0032] Unlike what is described in WO2020240152, the present invention addresses the issue of the size of the high-pressure NEG pump relative to the intermediate vacuum chamber, which is not considered in the aforementioned international patent application.

[0033] In the present invention, the primary pump and the high-pressure getter pump are kept a minimum distance of 5 cm apart, as the inventors have found that this reduces the effects of vibrations during the primary pump start-up phase. At the same time, for distances greater than 200 cm, the conductivity of the system becomes a limiting factor in terms of the performance of the auxiliary pumping system according to the present invention.

[0034] Another important parameter defining the auxiliary pumping system of the present invention is the ratio between the volume of the getter pump and the volume of the intermediate vacuum chamber, which is comprised between 0.022 and 0.540. Such a ratio range ensures and realizes a careful performance balance for the high-pressure getter pump in terms of speed and pump lifetime. In particular, for values ​​higher than 0.540, there is a limiting factor associated with the vacuum conductivity, while for values ​​below 0.022, the gas load on the getter material is excessive, which will accelerate the pumping performance degradation of the high-pressure getter pump.

[0035] In some embodiments, the auxiliary pumping system of the present invention also includes one or more pressure sensors, such as, for example, a hot cathode gauge, a capacitance manometer, a Pirani gauge, or the like.

[0036] It will be clear to those skilled in the art that the detailed solutions shown in the previously described figures can be combined as appropriate to give rise to other configurations that are still encompassed by the invention.

[0037] It is also important to emphasize that using a NEG pump instead of a turbomolecular pump (TMP) that is equivalent to the NEG pump in terms of pumping speed dramatically reduces the weight and overall size of the system. For example, considering a N2 pumping speed of about 70 l / s, replacing a common commercially available TMP with the NEG pump of the present invention results in a weight reduction of up to 70% and a volume reduction of up to 90%.

[0038] Moreover, the use of a NEG pump allows for energy savings, since while the TMP must be powered constantly during its operation, it is only powered during the activation phase (approximately 60 minutes) without requiring an additional power supply.

[0039] The present invention is not limited to a specific type of non-evaporable getter (NEG) material, which is known to those skilled in the art, for example, as described in U.S. Pat. Nos. 8,961,816, 9,416,435, and 6,521,014, or more generally, Zr-based or Ti-based alloys (i.e., alloys in which this element is most abundant in the composition). The shape of the NEG material is not limited to a disk, but includes pills, cartridges, or powders layered on a metal surface. Also, the getter material in the high-pressure getter pump can be used in sintered or compressed form.

[0040] Suitable HV pumps to be used with the auxiliary pumping system of the present invention are selected from sputter ion pumps (SIPs), HV NEG pumps, and combinations thereof. [Explanation of symbols]

[0041] 1. Equipment Vacuum Chamber 2 High Vacuum (HV) Pump 10 Intermediate Vacuum Chamber 11 First flange 12 Primary pump 13 Valve Block 131 Elbow 14 Vacuum conduit 15 Second flange 16 Third flange 20 Intermediate Vacuum Chamber 21 First flange 22 Primary pump 23 Valve Block 231 Elbow 24 Flexible conduit 25 Second flange 26 Third flange 27 Fourth flange 28 HV pump 30 Intermediate Vacuum Chamber 31 First flange 35 Second flange 36 Third flange 37 Fourth flange 38 HV pump 40 Intermediate Vacuum Chamber 41 First flange 42 Primary pump 43 Valve Block 431 Elbow 44 Flexible conduit 45 Second flange 451 High-pressure NEG pump 46 Third flange 47 Fourth flange 48 First HV Pump 49 Fifth flange 491 Second HV Pump 300 Alternative Configurations 1000 Auxiliary Pumping System 2000 Auxiliary Pumping System 4000 Auxiliary Pumping System

Claims

1. An auxiliary pumping system (1000; 2000; 4000), Primary pumps (12; 22; 42) and an intermediate vacuum chamber (10; 20; 30; 40) with at least three vacuum-tight openings connected to said primary pump (12; 22; 42) through first vacuum-tight openings (11; 21; 31; 41); a high-pressure NEG pump (451) contained within the intermediate vacuum chamber (10; 20; 30; 40) and attached to the intermediate vacuum chamber (10; 20; 30; 40) through a second vacuum-tight opening (15, 25; 35; 45); Including, In an auxiliary pumping system (1000; 2000; 4000), the primary pump (12; 22; 42) operates from atmospheric pressure to a first vacuum level, and the high-pressure NEG pump (451) operates from the first vacuum level to a second vacuum level, the primary pump (12; 22; 42) is connected to the intermediate vacuum chamber (10; 20; 30; 40) through a vacuum conduit (14; 24; 44), the overall length of the vacuum conduit (14; 24; 44) being comprised between 5 cm and 200 cm; An auxiliary pumping system (1000; 2000; 4000), characterized in that the ratio between the volume of the high-pressure NEG pump (451) and the volume of the intermediate vacuum chamber (10; 20; 30; 40) is comprised between 0.022 and 0.

540.

2. 2. An auxiliary pumping system (1000; 2000; 4000) as claimed in claim 1, wherein a valve block (13; 23; 43) is preferably interposed between the primary pump (12; 22; 42) and the intermediate vacuum chamber (10; 20; 40) when the overall length of the vacuum conduit (14; 24; 44) is greater than 19 cm.

3. 3. An auxiliary pumping system (1000; 2000; 4000) according to claim 1 or 2, wherein the primary pump (12; 22; 42) is a dry pump.

4. 4. An auxiliary pumping system (1000; 2000; 4000) according to any one of claims 1 to 3, wherein the high-pressure NEG pump (451) comprises a plurality of sintered and / or compressed disks or pills made from a Zr-based alloy or a Ti-based alloy, or powders layered on a metal substrate.

5. An auxiliary pumping system (2000; 4000) according to any one of claims 1 to 4, wherein the intermediate chamber (20; 30; 40) has more than three vacuum-tight openings, one or more of which (27; 37; 47, 49) are suitable for mounting HV pumps, said HV pumps being preferably selected from sputter ion pumps (28; 38; 48), NEG pumps (491) or combinations thereof.

6. 6. The auxiliary pumping system (1000; 2000; 4000) according to any one of claims 1 to 5, wherein the auxiliary pumping system (1000; 2000; 4000) further comprises at least one pressure sensor.

7. 7. An auxiliary pumping system (1000; 2000; 4000) according to any one of claims 1 to 6, wherein the first vacuum level has a pressure range between 10 Pa and 0.1 Pa and the second vacuum level has a pressure range between 0.01 Pa and 0.001 Pa.

8. 8. An auxiliary pumping system (1000; 2000; 4000) according to any one of claims 1 to 7, wherein the high pressure NEG pump (451) comprises a replaceable cartridge of getter material.

9. 9. The auxiliary pumping system (1000; 2000; 4000) according to any one of claims 1 to 8, wherein the high pressure NEG pump (451) includes a replaceable heater.

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