Vacuum component and evacuation method

Abstract

To provide a high evacuation capacity using a getter effect.SOLUTION: An NEG layer 3 composed of a NEG material in thin film form is formed on a low degasification substrate 2 composed of a metal (low degasification metal) having a particularly low gas emission rate from a surface thereof. The low degasification substrate 2 contains Cu as a main component, and is composed of a low degasification metal containing at least 0.1 wt% or more of any one of Al, Fe, Mn, Ni, Be, Mg, Si, Ti and V. The NEG layer 3 is a metal material having a getter effect, and is a thin film containing the NEG material of any one of Ti, Zr, V, Hf, Nb, Yb, Pd, Au, and Pt which can form a thin film using the same. Here, the NEG material is not brought into an oxidized state but in a metal state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vacuum component and a vacuum evacuation method that evacuates a space by using a getter action. [Background technology]

[0002] Vacuum pumps utilizing gettering are used in various devices requiring ultra-high vacuum, such as electron microscopes (SEM, TEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), and other surface analysis devices, as well as accelerators for electrons, light ions, and heavy ions. In these devices and equipment, vacuum pumps utilizing gettering have the significant advantages of not requiring power while functioning as a pump and being vibration-free. Furthermore, because they have a high pumping speed for gases such as hydrogen (H), which have a low pumping speed when pumped by turbomolecular pumps and other devices, they are particularly effective when used in conjunction with other vacuum pumps (such as turbomolecular pumps) to achieve ultra-high vacuums that cannot be achieved by those pumps alone.

[0003] When using this gettering effect, the overall configuration of the device in which it is used can be significantly modified compared to other vacuum pumps (e.g., turbomolecular pumps). Patent Document 1 describes a technology for evacuation using a vacuum component whose inner surface is composed of a thick titanium (Ti) base layer with a gettering effect due to the Ti, and a thin film (NEG thin film layer) made of a non-evaporable getter (NEG) material such as Ti, zirconium (Zr), vanadium (V), hafnium (Hf), or niobium (Nb) coated on the Ti layer. Removal of Ti oxide films and other impediments to evacuation performance from the Ti layer and formation of the NEG thin film layer are achieved by controlling electrodes installed inside the vacuum component, thereby maintaining high evacuation performance. Furthermore, this vacuum component can also be used to construct a vacuum vessel that requires a high vacuum. Furthermore, since no power is required for evacuation, its versatility is extremely high.

[0004] In this case, the vacuum component performs evacuation by adsorbing and capturing the pumped gas molecules (hydrogen and other gas molecules) on the Ti base material and the NEG thin film layer on its surface. Therefore, when this adsorption becomes saturated, the evacuation capability decreases, but in this case, an activation process is performed by heating the entire vacuum chamber to, for example, 400°C or less, and the desorbed molecules are then pumped out with another vacuum pump, allowing evacuation to be performed again in the same way. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7195504 Summary of the Invention [Problem to be solved by the invention]

[0006] In the technology described in Patent Document 1, gas molecules are trapped in the Ti that constitutes the thick underlying Ti layer. These gas molecules can be desorbed by activation treatment, but in reality, even without activation treatment, these gas molecules are desorbed from the Ti with a certain probability and released back into the vacuum during evacuation.

[0007] The gas molecules desorbed from the Ti substrate in this way deteriorate the vacuum level of the vacuum vessel in which this vacuum component is used. In other words, when the vacuum component is used to evacuate, gas molecules desorb from the Ti layer of the base material. As a result, the NEG layer is saturated with these gas molecules, reducing the getter effect and impairing the vacuum pumping capability. Therefore, a technology that utilizes the getter effect to further improve the vacuum pumping capability is desired.

[0008] The present invention has been made in view of the above problems, and an object of the present invention is to provide an invention that solves the above problems. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention has the following configurations. The vacuum component of the present invention comprises a laminated structure having a low degassing base composed of a low degassing metal containing copper (Cu) as its main component and at least 0.1 weight % of any of aluminum (Al), iron (Fe), manganese (Mn), nickel (Ni), beryllium (Be), magnesium (Mg), silicon (Si), and titanium (Ti), and an NEG layer formed on the low degassing base in a thin film state thinner than the low degassing base, the NEG layer containing an NEG material in a metallic state which is any of Ti, zirconium (Zr), vanadium (V), hafnium (Hf), niobium (Nb), ytterbium (Yb), palladium (Pd), gold (Au), silver (Ag), and platinum (Pt), and the surface of the NEG layer is provided in a vacuum. In the vacuum component of the present invention, the NEG layer has a surface on which irregularities are formed. The vacuum component of the present invention is characterized in that it is a vacuum container having the above-described laminated structure on its inner surface. The vacuum component of the present invention comprises an electrode provided inside the vacuum container and having an electrode surface that faces the inner surface, and a gas inlet for introducing an inert gas into the vacuum container, and is switchable between a first state in which the inert gas is introduced into the vacuum container, causing the electrode surface to have a negative potential and the inner surface to have a positive potential, thereby generating a DC discharge, and a second state in which the inert gas is not introduced into the vacuum container, and the electrode surface is at the same potential as the inner surface or is floating from the inner surface, and the electrode surface is formed of the NEG material and is switched to the second state when exhausting. The vacuum component of the present invention is characterized in that the NEG layer is formed on the surface of the plate-shaped low outgassing substrate, and is placed in a vacuum atmosphere. The vacuum component of the present invention is characterized in that the laminated structure is fixed to the inner surface of a vacuum container via a fixing layer. The vacuum evacuation method of the present invention is characterized in that in a vacuum component having a laminated structure including a low outgassing substrate made of metal and an NEG layer containing an NEG material in a metallic state, which is any of Ti, zirconium (Zr), vanadium (V), hafnium (Hf), niobium (Nb), ytterbium (Yb), palladium (Pd), gold (Au), silver (Ag), and platinum (Pt), and which is formed on the low outgassing substrate in a thin film state thinner than the low outgassing substrate, vacuum evacuation is performed by placing the surface of the NEG layer in a space to be evacuated. In the vacuum evacuation method of the present invention, the low outgassing substrate is characterized in that it is made of a low outgassing metal containing copper (Cu) as its main component and at least 0.1 wt % of any of aluminum (Al), iron (Fe), manganese (Mn), nickel (Ni), beryllium (Be), magnesium (Mg), silicon (Si), and titanium (Ti). In the vacuum evacuation method of the present invention, the low outgassing substrate is a stainless steel that has been heat-treated in a vacuum at 800° C. or higher. The vacuum evacuation method of the present invention is characterized in that vacuum evacuation is performed using the vacuum component after heating in a vacuum. [Effects of the Invention]

[0010] Since the present invention is configured as described above, it is possible to obtain a high vacuum evacuation capability by utilizing the getter effect. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing a cross-sectional structure near the surface of a vacuum component according to an embodiment of the present invention; [Figure 2] This is an example of measuring the change in pressure over time at room temperature after vacuum sealing a vacuum vessel made of BeCu alloy and a vacuum vessel made of SUS304. [Figure 3] These are the results of thermal desorption measurements of each type of gas for BeCu, Ti, and SUS304. [Figure 4]1 shows the results of measuring the change in pressure over time after vacuum sealing in an example of the present invention using a BeCu layer and an NEG layer, and in a comparative example using only a BeCu layer. [Figure 5] This shows the temperature dependence of the energy spectrum obtained by hard X-ray photoelectron spectroscopy when the NEG layer is formed on a BeCu layer (a) and a Ti layer (b). [Figure 6] The following are the results of SIMS measurements of the element distribution in the depth direction for a structure in which an NEG layer is formed on a BeCu layer, before (a), immediately after (b), and after (c), hydrogen is adsorbed in a vacuum atmosphere after the activation process. [Figure 7] 1 is a cross-sectional view showing the configuration of a vacuum system when a vacuum component according to an embodiment of the present invention is used as the inner surface of a vacuum container. [Figure 8] 10 is a cross-sectional view taken along another direction showing the configuration of a vacuum system when the vacuum component according to the embodiment of the present invention is used as the inner surface of a vacuum container. FIG. [Figure 9] FIG. 2 is a diagram showing a cross-sectional structure of a first modified example of a vacuum component according to an embodiment of the present invention. [Figure 10] FIG. 2 is a diagram showing a state in which a first modified example of a vacuum component according to an embodiment of the present invention is used. [Figure 11] 10A and 10B are diagrams showing cross-sectional structures of second and third modified examples of the vacuum component according to the embodiment of the present invention. [Figure 12] This shows the temperature dependence of the energy spectrum obtained by soft X-ray photoelectron spectroscopy when an NEG layer is formed on stainless steel (a) that has not been subjected to high-temperature heat treatment, and on stainless steel (b) that has been subjected to high-temperature heat treatment in advance. DETAILED DESCRIPTION OF THE INVENTION

[0012] A vacuum component according to an embodiment of the present invention will be described below. This vacuum component is connected to a vacuum chamber in which a high vacuum is maintained, and functions as a vacuum pump that evacuates the vacuum chamber by the getter effect. This vacuum chamber is a part of a surface analysis device such as an electron microscope (SEM, TEM), an X-ray photoelectron spectroscopy device (XPS), a secondary ion mass spectrometry device (SIMS), an accelerator for electrons, light ions, heavy ions, etc., and is used to create an ultra-high vacuum (e.g., 5×10 -8 Alternatively, the inner surface of the vacuum chamber itself may be the vacuum part, or the vacuum chamber may be made up of the vacuum part.

[0013] Figure 1 is a diagram showing the cross-sectional structure near the surface of this vacuum component. Here, the upper side in the figure is high vacuum (the space to be evacuated). This vacuum component can take various forms, as will be described later, but at least a part of them has the cross-sectional structure shown here. Here, a thin-film NEG layer 3 made of an NEG material similar to that described in Patent Document 1 is formed on a low-degassing substrate 2 made of a metal (low-degassing metal) with an especially low gas release rate from its surface, as will be described later.

[0014] The low outgassing substrate 2 is composed of a low outgassing metal, as described in Japanese Patent No. 4829485, primarily composed of copper (Cu) and containing at least 0.1 wt% of any of aluminum (Al), iron (Fe), manganese (Mn), nickel (Ni), beryllium (Be), magnesium (Mg), silicon (Si), and titanium (Ti). The Cu content is 90 wt% or more. As described below, Be is particularly preferred, with a mixing ratio of about 0.2 wt%. While the shape and thickness of the low outgassing substrate 2 are arbitrary, it is preferable to choose a shape that facilitates the formation of the NEG layer 3 or facilitates use during evacuation. The thickness of the low outgassing substrate 2 is, for example, 20 μm or more. The structure below the low outgassing substrate 2 is arbitrary as long as the upper side in FIG. 1 can be evacuated.

[0015] The NEG layer 3 is a metal material having a getter effect, similar to the technology described in Patent Document 1, and is a thin film containing a metallic NEG material, such as Ti, zirconium (Zr), vanadium (V), hafnium (Hf), niobium (Nb), ytterbium (Yb), palladium (Pd), gold (Au), silver (Ag), or platinum (Pt), which can be used to form a thin film. The surface of the NEG material is not oxidized but remains metallic. Its thickness is, for example, about 1 μm, and it is formed by a sputtering method, as described below. This is also similar to Patent Document 1. Forming the NEG layer 3 on both sides or the entire surface of the low-degassing substrate 2 and placing the formation portion in a vacuum can also improve the vacuum evacuation capability.

[0016] 1, the getter effect allows for particularly efficient evacuation. This point will be explained in comparison with the technology described in Patent Document 1.

[0017] In the technology described in Patent Document 1, a Ti layer having a thickness of 100 μm or more is used instead of the low-degassing substrate 2, and an NEG layer (coating layer) similar to the above is formed on this surface. In this case, the Ti oxide film that typically forms on the Ti surface is not present, or this Ti oxide film is configured to be easily removed, thereby maintaining a high getter effect of Ti. Here, although the NEG layer also has a getter effect, in this structure, vacuum evacuation (adsorption of gas molecules) is mainly due to this thick Ti layer. The NEG layer contributes to preventing oxidation of the Ti layer and functions to maintain a high getter effect of the Ti layer.

[0018] In contrast, the low outgassing substrate 2 used in the present invention has a small getter effect of evacuating to a vacuum by adsorbing gas molecules, as in NEG materials such as Ti. On the other hand, as described in Japanese Patent No. 4829485, the amount of gas desorbed from the surface is extremely small even when the temperature is increased.

[0019] Figure 2 shows an example of measuring the time-dependent change in pressure at room temperature after vacuum sealing in a vacuum vessel made of the above-mentioned BeCu alloy and a vacuum vessel made of stainless steel (SUS304), a material traditionally used to construct vacuum components. The pressure change is shown here after evacuation is stopped at time 0. It is clear that the rate of pressure increase in the case of BeCu is one order of magnitude smaller.

[0020] Since neither SUS304 nor BeCu has the same getter effect (vacuum pumping ability) as NEG materials, this result reflects the small amount of gas desorption (degassing) from BeCu. This point is also described in Patent No. 4829485.

[0021] Similarly, Figures 3(a)-(e) show the results of pressure measurements (thermal desorption measurements) for each type of gas (total pressure: a, H2: b, HO: c, CO: d, CO2: e) during temperature rise. Here, the vertical axis represents the total pressure (a) only, and the remaining values ​​represent the ion current (corresponding to the partial pressure of each gas) corresponding to each measured gas. As a comparative example, in addition to SUS304, Ti, the base material for the structure described in Patent Document 1, is also shown. It was observed that all gas components desorbed at temperatures above 200°C. This is true for Ti, which has a getter effect, and SUS304 and BeCu, which do not. However, the results show that, regardless of temperature, the amount of gas desorbed from BeCu was significantly smaller than that of SUS304 and Ti.

[0022] As mentioned above, Ti has a gettering effect, so it adsorbs (absorbs) many gas molecules. Meanwhile, while the temperature required for desorption differs from that of SUS304, the amount of gas desorbed is not significantly different from that of SUS304. Therefore, although Ti has gettering capabilities, it desorbs gas from itself, thereby degrading the vacuum level. Alternatively, if a NEG layer is formed on Ti as a base material, the gas desorbed from the Ti is adsorbed by the NEG layer, thereby impairing the gettering effect of the NEG layer.

[0023] From this perspective, in Figure 1, when the getter effect is obtained only by the NEG layer 3, forming the NEG layer 3 on a BeCu layer (low outgassing substrate 2) provides a higher vacuum evacuation capability than the structure described in Patent Document 1, which uses a Ti layer, because the getter effect is not reduced due to adsorption saturation of the NEG layer with gas from the base material.

[0024] Similar to the results shown in Fig. 2, Fig. 4 shows the results of measuring the change in pressure over time after vacuum sealing in the structure shown in Fig. 1 (Example) using a BeCu layer and an NEG layer 3 containing Zr, V, and Ti as the low outgassing substrate 2, and in the case of using only BeCu without an NEG layer 3 (Comparative Example 1). In Comparative Example 1, although the amount of gas desorption is small as described above, the absence of an NEG layer means that there is no vacuum evacuation capability, and therefore the rate of pressure increase is large. In contrast, in the Example, the rate of pressure increase is 1 x 10 -7 A high vacuum of less than 100 Pa is maintained, and the pressure gradually decreases. This means that the structure in Figure 1 is effective in evacuation, and the NEG layer has a gettering effect.

[0025] Figure 5 shows the results of hard X-ray photoelectron spectroscopy using synchrotron radiation to examine the differences in the oxidation state of the NEG layer 3 during heating when (a) V, Ti, or Zr was used as the NEG layer 3 and the low-degassing substrate 2 was made of the aforementioned BeCu in the structure of Figure 1, and (b) a Ti layer was used instead of the low-degassing substrate 2. In this figure, the energy spectrum of the generated photoelectrons (horizontal axis: eV) is shown as a color (brightness) pattern along the horizontal axis. This energy spectrum reflects the electronic state (particularly either the metallic state or the oxidized state) of the elements that make up the NEG layer 3. Here, the vertical axis represents the amount corresponding to the temperature of the sample, with the upper side representing the low temperature side and the lower side representing the high temperature side, and the corresponding temperatures are indicated in the figure.

[0026] In all results, spectra with peaks on the left (lower energy side) were obtained at low temperatures, and spectra with peaks on the right (higher energy side) were obtained at high temperatures. The former indicates that the NEG materials (V, Ti, Zr) are in an oxidized state, while the latter indicates that the NEG materials have become metallic (not oxidized). To obtain the getter effect of the NEG materials, it is preferable that the NEG materials be in a metallic state. Therefore, to activate the structure shown in Figure 1, it is preferable to desorb the absorbed gas components and perform a heat treatment (activation treatment) at a temperature above the transition temperature from the former state to the latter state. At this time, the gas components adsorbed on the NEG material are also desorbed, as shown by Ti in Figure 3.

[0027] From this perspective, whether V, Ti, or Zr is used, when a Ti layer is used as the substrate (Figure 5(b)), the required temperature (activation temperature) is 250°C or higher. In contrast, when BeCu is used as the substrate (Figure 5(a)), the required temperature is 174°C or higher, resulting in a lower activation temperature. This result reflects the fact that when BeCu is used, the amount of gas components (especially oxygen) desorbed from the base material is low. In other words, the structure shown in Figure 1 not only has high evacuation capability, but also allows for a lower temperature for the activation process, which is performed when the evacuation capability decreases. Furthermore, to achieve a high gettering effect from the NEG layer, it is preferable that the NEG layer be amorphous. However, lowering the activation temperature can suppress the influence on the internal structure of the NEG layer (such as crystallization of the NEG layer), and the gettering performance of the NEG layer can be maintained even after repeated activation processes.

[0028] Figure 6 shows the results of elemental analysis of each layer measured by SIMS (Secondary Ion Mass Spectrometry) in the structure of Figure 1 before (a) this activation treatment, immediately after (b) the activation treatment (230°C), and after (c) hydrogen absorption in a vacuum atmosphere. Here, a NEG layer 3 containing Zr, V, and Ti and a low outgassing substrate 2 made of BeCu are used. In addition, this activation temperature (230°C) is considered to be an effective temperature based on the results of Figure 5. Therefore, on the surface side, 90 Zr, 51 V, 48 The region with a high Ti content corresponds to the NEG layer 3, and the deeper region with high Be and Cu content corresponds to the low outgassing substrate 2 (BeCu layer). The distributions of Zr, V, Ti, Be, and Cu are not affected at temperatures of around 230°C, so their distributions are similar in Figures 6(a) to 6(c).

[0029] Here, other elements in this structure include hydrogen ( 1 H), carbon ( 12 C), oxygen ( 16 O), and in particular, the case where the target to be evacuated was hydrogen was investigated. Before the activation process (a), hydrogen and oxygen were mainly released from the NEG layer 3 ( 90 Zr, 51 V, 48 However, immediately after the activation treatment (b), the abundance ratios of hydrogen and oxygen in the NEG layer 3 are reduced. This means that hydrogen and oxygen are desorbed from the NEG layer 3 by the heat treatment at 230°C. Also, near the NEG layer of the BeCu layer, there is a region where the abundance ratio of oxygen is locally high, and this region corresponds to the oxide layer of Be and Cu.

[0030] After that, the vacuum chamber having this structure was evacuated as described above, and hydrogen was introduced to adsorb the hydrogen. In the result shown in (c), the increase in hydrogen is particularly noticeable in the region about 200 nm deep near the surface of the NEG layer 3, which means that hydrogen has been adsorbed by the NEG layer 3. At this time, the amount of hydrogen in the BeCu layer remains the same as in the state shown in (b). In other words, hydrogen is absorbed only by the NEG layer 3.

[0031] The oxide layer on the surface of the BeCu layer is thought to be effective in preventing hydrogen, oxygen, water, etc. from penetrating into the BeCu layer and in preventing gases (especially oxygen and hydrogen) from diffusing from the BeCu layer into the NEG layer, thereby realizing activation at low temperatures as shown in Figure 5.

[0032] From the above results, when the structure of FIG. 1 is used for evacuation, unlike the technology described in Patent Document 1, which uses a thick Ti layer as the substrate for the NEG layer, there is no getter effect in the BeCu layer that serves as the substrate, and gas desorption is negligibly small. From the above results, in this case, a sufficiently high evacuation capacity can be obtained solely through the getter effect of the NEG layer 3, and as a result, a higher evacuation capacity can be obtained. In this case, because there is little gas (particularly oxygen) desorption from the substrate side, the temperature required to activate the NEG layer 3 is lower. In other words, the evacuation capacity can be restored at a low activation temperature, and the activation process is also easy.

[0033] The following describes a specific form for actually performing evacuation using the structure shown in Fig. 1. Fig. 7 is a partial cross-sectional view of a vacuum system when the structure shown in Fig. 1 is used as the inner surface of a vacuum vessel 10, and Fig. 8 is a cross-sectional view taken along the line XX. Figs. 7 and 8 are similar to Figs. 1 and 2 of Patent Document 1, except that the material constituting the vacuum vessel 10 is the low outgassing substrate 2 described above.

[0034] In Figure 7, the object to be evacuated is a vacuum chamber 100. The vacuum chamber 100 is evacuated by a TMP (turbomolecular pump) 101, and the back pressure side of the TMP 101 is evacuated by a DP (dry pump) 102. The vacuum chamber 100 is also evacuated by a vacuum component 1 via an orifice O. When activating the vacuum component 1 (the structure in Figure 1), gas components mainly discharged from the NEG layer can be evacuated from the TMP 101. Thereafter, by closing a gate valve (not shown) between the TMP 101 and the vacuum chamber 100, the vacuum chamber 100 is evacuated only by the vacuum device 1.

[0035] The vacuum vessel 10 constituting the vacuum component 1 has a cylindrical inner surface 10A. A coil-shaped heater (heating means) 12 is wound around the vacuum vessel 10 to heat the vacuum vessel 10 to a temperature of 300°C or less for activation. Temperature sensors and the like are also installed as appropriate to measure and control this temperature, but their illustration is omitted.

[0036] In the structure described in Patent Document 1, the inner surface 10A of the vacuum vessel 10 is made of Ti, whereas in this case, the material that makes up the low outgassing substrate 2 is used instead of Ti.

[0037] In Figure 8, a hollow cylindrical electrode 20 is provided along the central axis and has an outer surface (electrode surface 20A) that is sufficiently smaller than the inner surface 10A of the vacuum vessel 10. The potential of the vacuum vessel 10 is grounded, while the potential of the electrode 20 is switched by a changeover switch S among three states: positive potential, negative potential (first state), and grounded state (second state). Note that the electrode 20 may be in a floating state instead of being grounded. The electrode surface 20A (the outer surface of the electrode 20 as viewed from the central axis), which is the surface of the electrode, is made of the NEG material that constitutes the NEG layer 3.

[0038] The vacuum vessel 10 is also provided with a gas inlet 11 through which an inert gas (Ar) can be introduced from outside, and the pressure of Ar inside the vacuum vessel 10 can be adjusted by a flow control valve (not shown) near the gas inlet 11. In the first state, the pressure of Ar and the absolute value of the potential when the electrode 20 is set to a negative potential are set to a level at which a DC discharge can occur between the electrode surface 20A and the inner surface 10A of the vacuum vessel 10, causing sputtering. In the second state, Ar is not introduced.

[0039] As described in Patent Document 1, in this vacuum component 1, Ar is introduced into the interior, and the electrode surface 20A is set to a negative potential to generate a DC discharge. In this first state, the NEG layer 3 is formed on the inner surface 10A (low outgassing substrate 2) of the vacuum vessel 10, thereby forming the structure shown in FIG. 1. Then, by switching to a second state that does not require power, the vacuum chamber 100 can be evacuated from the vacuum component 1 side. The characteristics shown in FIG. 4 show the change in the degree of vacuum over time at this time.

[0040] It is also possible to remove the oxide film on the outermost surface of the inner surface 10A by generating a DC discharge with the electrode 20 at a positive potential, as with the technology described in Patent Document 1. However, as mentioned above, since the oxide film on the low-degassing substrate 2 is effective for the NEG layer 3, it is not preferable to perform this step before forming the NEG layer 3. Alternatively, if the surface of the NEG layer 3 is oxidized after the NEG layer 3 is formed on the inner surface 10A, this oxide layer can be removed by this method. It is also possible to form the NEG layer 3 by magnetron sputtering, by appropriately installing a magnet in the vacuum chamber 10, as shown in Figures 7 and 8.

[0041] Furthermore, compared to Ti, the BeCu and other materials constituting the low outgassing substrate 2 have a high thermal conductivity because they are mainly composed of Cu, which has a high thermal conductivity. Therefore, in addition to requiring a low temperature for activation, heating (activation) using the heater 12 in the configuration of FIG. 7 is particularly easy.

[0042] The above is an embodiment when the structure of Fig. 1 is formed and used in the same manner as the technology described in Patent Document 1. However, unlike the Ti layer described in Patent Document 1, the low outgassing substrate 2 used here has properties such as easy mechanical processing and easy elastic deformation. Therefore, vacuum evacuation can be performed without supplying power even in the configurations other than those shown in Figs. 7 and 8.

[0043] FIG. 9 is a cross-sectional view showing the structure of a vacuum component 4 as such an example (first modified example). While the inner surface 10A of the vacuum vessel 1 (vacuum vessel 10) in FIGS. 7 and 8 is flat (more precisely, cylindrical, without any irregularities), this vacuum component 4 uses a low-degassing substrate 2A with many irregularities, and a NEG layer 3A is formed on this surface. Unlike Ti used in the technology described in Patent Document 1, BeCu and other materials can be machined, making it easy to manufacture a low-degassing substrate 2A with such a shape. Furthermore, when the NEG layer 3A is deposited using a film deposition system using sputtering, the NEG layer 3A can be easily formed on such irregularities. In this case, the effective surface area of ​​the NEG layer 3A can be increased, thereby improving the evacuation efficiency, or, if the evacuation efficiency is the same, the vacuum vessel can be made smaller. Furthermore, after activation (heating), evacuation is possible after cooling. This structure also improves heat dissipation efficiency, shortening the cooling time.

[0044] Note that a low outgassing substrate with an uneven surface is not necessarily required to obtain the NEG layer 3 having the uneven surface as described above. Even if the low outgassing substrate 2A in Fig. 9 has a planar shape, it is possible to manufacture an NEG layer 3A having an uneven surface by forming and processing an NEG layer 3A on this surface.

[0045] The inner surface 10A of the vacuum vessel 10 in FIG. 7 can be made to have the shape of the low outgassing substrate 2A in FIG. 9, and in this case, the structure of FIG.

[0046] In the configurations shown in Figures 7 and 8, the vacuum component 1 has the structure shown in Figure 1 and also functions as a manufacturing device for manufacturing the structure shown in Figure 1. Alternatively, the vacuum component 4 may be manufactured in advance in the form shown in Figure 9 and installed (placed) in the vacuum chamber 100, allowing evacuation to be performed using the configuration shown in Figure 9 as is. Figure 10 shows the overall configuration of the vacuum system in this case, corresponding to Figure 7. Here, the vacuum component 4 is installed inside the vacuum chamber 100 to be evacuated. The TMP 101 and other components are the same as those in Figure 7, and evacuation can be performed using the TMP 101 when activating the vacuum component 4.

[0047] In this case, the vacuum component 4 is installed as shown in FIG. 10 . Fixing the vacuum component 4 to the vacuum chamber 100 can be achieved by various methods, as long as the NEG layer 3 is exposed. In FIG. 10 , a fixing layer 90 made of brazing material, adhesive, or the like is used between the underside of the vacuum component 4 (low-degassing substrate 2A) and the inner surface (bottom) of the vacuum chamber 100. Alternatively, a fixing layer equipped with a magnet for fixing the vacuum component to the vacuum chamber and a mounting member for holding the magnet may be provided on the underside of the vacuum component. Alternatively, the vacuum component may be fixed by screws, welding, or encased in a metal mesh separately attached to the vacuum chamber 100. When activation is performed in the vacuum chamber 100 while the vacuum component 4 is fixed, a heating means for heating the vacuum component 4 can be appropriately provided in the vacuum chamber 100. In this case, the activation temperature is low and the low-degassing substrate 2A has high thermal conductivity, making heating easy. The shape of the low-degassing substrate can be appropriately set depending on the fixing method.

[0048] Figure 11 shows two types of shapes (second and third modified examples) of the vacuum component that differ from the shape shown in Figure 9. As mentioned above, since BeCu and the like are elastic metal materials unlike Ti, the low outgassing substrate 2B can be made into a large-area thin plate, and an even thinner NEG layer 3B can be easily formed on top of this, as shown in the upper part of Figure 11(a). In this case, by appropriately rolling up the vacuum component 5 as shown in the lower part of Figure 11(a), the surface area of ​​the NEG layer 3B can be increased while the overall size can be reduced, making it easy to install this in the vacuum chamber 100 shown in Figure 10.

[0049] 11(b), the low outgassing substrate 2C is bellows-shaped, and an NEG layer 3C is formed on the surface thereof. In this case, the area of ​​the NEG layer 3C can be made large, as in the vacuum component 4, and the vacuum component 6 can be expanded and contracted as shown. This structure can be used in a tubular vacuum component in which the NEG layer 3C side is a vacuum (inner side).

[0050] As described above, the shape of the low-degassing substrate can be appropriately set, and accordingly, the above-mentioned vacuum component can be used in various configurations to evacuate a vacuum chamber. Furthermore, similar to the technology described in Patent Document 1, by forming part or the entire inner surface of a component (vacuum chamber 100 in FIG. 7) that requires a high vacuum inside, as shown in FIG. 1 or 9, a high degree of vacuum can be maintained inside the component. Examples of such applications include containers for transporting samples such as semiconductor wafers in a vacuum, and piping for carrying high-purity gases. In this case, too, using a machinable BeCu alloy or the like is advantageous when manufacturing such components. In addition to the above examples, the shape of the vacuum component can also be any shape depending on the intended use.

[0051] In the above example, Be was added to Cu in the low-degassing metal. However, as mentioned above, Al, Fe, Mn, Ni, Mg, Si, and Ti can be used instead of Be. As mentioned above, the oxide film on the surface of the low-degassing metal is effective for vacuum evacuation using the NEG layer on top of it. However, like Be, these materials can form a dense, thick oxide film on the base material surface, which suppresses gas desorption as mentioned above. Elements lighter than Be form unstable oxide films, making it difficult to achieve this effect. Furthermore, elements heavier than Ni have a large atomic radius, making it difficult for atoms to migrate to the surface, making it difficult for them to form a dense, thick oxide film like Be.

[0052] In the above example, the low outgassing substrate is made of a low outgassing metal (e.g., BeCu) containing Cu as the main component, as described in Japanese Patent No. 4829485. However, in addition to alloys with such metal compositions, other metals that have been subjected to heat treatment in a vacuum to sufficiently reduce the amount of gas absorbed therein can also be used as the low outgassing substrate.

[0053] As an example, we present the results when stainless steel (SUS304), whose internal gas components have been sufficiently reduced by heat treatment at 850°C in a vacuum, is used as the low-degassing substrate. Figure 12 shows (a) the temperature dependence of the photoelectron energy spectrum (horizontal axis: eV) measured by soft X-ray photoelectron spectroscopy when V, Ti, and Zr are used as the NEG layer without such high-temperature heat treatment, followed by subsequent heating. Figure 12 also shows (b) the same results when stainless steel with a similar structure is preheated to 850°C in a vacuum. Here, as in Figure 5, the pattern along the horizontal axis represents the photoelectron energy spectrum, and the vertical axis represents temperature.

[0054] In each of these results, two different types of spectra were obtained on the low-temperature side (above the vertical axis) and the high-temperature side (below the vertical axis). The spectrum on the low-temperature side corresponds to the oxidized state of each NEG material (V, Ti, Zr), and the spectrum on the high-temperature side corresponds to the metallic state.

[0055] For example, in the case of V (far left), without heat treatment (a), this state transition occurs at about 160°C, whereas with heat treatment (b), this transition occurs at about 130°C. Similar results were obtained for Ti (center) and Zr (far right). That is, by performing this degassing treatment (heat treatment at 850°C in a vacuum) on the substrate in advance, activation can be performed at a low temperature. In this case, although this substrate does not have the getter effect of NEG metals, it can be used in the same way as the low-degassing substrate because the amount of gas desorption is extremely small, just like the low-degassing substrate described above.

[0056] However, the temperature required for the degassing treatment in this case is 800°C or higher (850°C), which is higher than the activation temperature (130°C) in Figure 12, for example. If such a low-degassing metal is used as the substrate, degassing treatment at such a high temperature before forming the NEG layer is not required. Conversely, if such high-temperature heat treatment before forming the NEG layer is acceptable, various metals, including stainless steel, can be used as the material for the low-degassing substrate. In this case, the material itself can be made cheaper, and various shapes can be realized more inexpensively.

[0057] In the above example, Ti, Zr, and V were used as NEG metals. However, Hf, Nb, Yb, Pd, Au, Ag, and Pt can be used instead. Hf, Yb, and Nb are in the same group as Ti, Zr, and V or are located close to them in the periodic table. Like Ti, Zr, and V, they have high oxygen solubility and diffusibility, making them similarly effective. Furthermore, Pd and Pt are hydrogen absorbers, Ag is a hydrogen and oxygen absorber, and Au is an adsorbent of various molecules, making them similarly effective. In other words, these can be used as NEG metals as appropriate, depending on the type of gas to be evacuated. These may also be mixed, or other elements may be mixed with them. [Explanation of symbols]

[0058] 1, 4, 5, 6 Vacuum parts 2, 2A, 2B, 2C Low degassing substrate 3, 3A, 3B, 3C NEG layer 10 Vacuum container 10A inner surface 11 Gas inlet 12 Heater (heating means) 20 electrodes 20A electrode surface 30 Power supply section 90 Fixed layer 100 Vacuum Chamber 101 Turbomolecular pump (TMP) 102 Dry Pump (DP) O Orifice S selector switch

Claims

1. a low outgassing substrate made of a low outgassing metal containing copper (Cu) as a main component and at least 0.1 wt % of any of aluminum (Al), iron (Fe), manganese (Mn), nickel (Ni), beryllium (Be), magnesium (Mg), silicon (Si), and titanium (Ti); an NEG layer formed on the low degassing substrate in a thin film state thinner than the low degassing substrate, the NEG layer containing an NEG material in a metallic state, which is any one of Ti, zirconium (Zr), vanadium (V), hafnium (Hf), niobium (Nb), ytterbium (Yb), palladium (Pd), gold (Au), silver (Ag), and platinum (Pt); A vacuum component comprising a laminated structure having the above structure, wherein the surface of the NEG layer is provided in a vacuum.

2. The vacuum component according to claim 1 , wherein the NEG layer has a surface on which irregularities are formed.

3. 3. The vacuum component according to claim 1, wherein the vacuum component is a vacuum container having the laminated structure on its inner surface.

4. an electrode provided inside the vacuum vessel, the electrode having an electrode surface facing the inner surface; a gas inlet for introducing an inert gas into the vacuum vessel; Equipped with a first state in which the inert gas is introduced into the vacuum vessel, causing a DC discharge with the electrode surface at a negative potential and the inner surface at a positive potential, and a second state in which the inert gas is not introduced into the vacuum vessel, causing the electrode surface to have the same potential as the inner surface or to be floating above the inner surface; the electrode surface is formed of the NEG material; 4. The vacuum component according to claim 3, wherein the vacuum component is set to the second state when exhausting.

5. 3. The vacuum component according to claim 1, wherein the NEG layer is formed on a surface of the plate-shaped low-degassing substrate, and the vacuum component is placed in a vacuum atmosphere.

6. 3. The vacuum component according to claim 1, wherein the laminated structure is fixed to the inner surface of the vacuum container via a fixing layer.

7. a low outgassing substrate made of metal; an NEG layer formed on the low degassing substrate in a thin film state thinner than the low degassing substrate, the NEG layer containing an NEG material in a metallic state, which is any one of Ti, zirconium (Zr), vanadium (V), hafnium (Hf), niobium (Nb), ytterbium (Yb), palladium (Pd), gold (Au), silver (Ag), and platinum (Pt); 10. A vacuum pumping method for a vacuum component having a laminated structure having the above structure, characterized in that the surface of the NEG layer is provided in a space to be evacuated, thereby performing vacuum pumping.

8. 8. The vacuum evacuation method according to claim 7, wherein the low outgassing substrate is made of a low outgassing metal containing copper (Cu) as its main component and at least 0.1 wt % of any of aluminum (Al), iron (Fe), manganese (Mn), nickel (Ni), beryllium (Be), magnesium (Mg), silicon (Si), and titanium (Ti).

9. 8. The vacuum evacuation method according to claim 7, wherein the low outgassing substrate is stainless steel that has been heat-treated in a vacuum at 800° C. or higher.

10. 10. The vacuum evacuation method according to claim 8, wherein the vacuum evacuation is performed using the vacuum component after heating in a vacuum.

Images