Metal gas enclosing unit

Abstract

A metal gas sealing unit (100) is provided with a unit main body (10), a glass plate (11), an optical chamber (14) provided in at least one of the unit main body (10) and the glass plate (11) and communicating with a gas generation unit (20), and a metal gas sealed in the optical chamber (14). The gas generation unit (20) communicates with the optical chamber (14), and has a plurality of columns (24), a plurality of bottomed grooves (22) provided between the plurality of columns (24) and opening in the first surface (10p), and an introduction port (26) for introducing a raw material solution (34a) of a metal gas into the plurality of bottomed grooves (22). The introduction port (26) includes at least one of a structure in which a part of at least one column (24) selected from the plurality of columns (24) is deleted and a structure in which all of the at least one column (24) selected from the plurality of columns (24) is deleted.

Description

Technical Field

[0001] The present invention relates to a metal gas sealing unit. Background Art

[0002] Research and development related to the miniaturization of various atomic sensor devices, such as atomic clocks that can achieve high-precision time synchronization and atomic magnetic sensors that measure biomagnetism with high sensitivity, are being promoted worldwide. For example, if the atomic clock is miniaturized using MEMS (Micro Electro Mechanical Systems) processing technology, the current crystal oscillator can be replaced with an atomic clock. It is also expected that atomic clocks will be used in various devices such as smartphones and microsatellites.

[0003] An atomic clock has a gas sealing unit as a main component, which is obtained by sealing an alkali metal gas and a buffer gas in a container. 133 In the case of Cs, by using the CPT (Coherent Population Trapping) resonance of Cs, which is an interference effect of quantum mechanics, it is possible to realize an atomic clock that is small and power-saving while having high precision. As one of the important indicators that represent the performance of an atomic clock, there is frequency stability. Frequency stability is evaluated by distinguishing short-term stability and long-term stability. Short-term stability is theoretically determined by the product of the Q value of the CPT resonance and the S / N ratio. Long-term stability is evaluated by the phenomenon of frequency variation under the time-dependent changes of both the light intensity of the excitation semiconductor laser and the partial pressure of the buffer gas inside the gas sealing unit, which are the measurement conditions of the CPT resonance. Therefore, in order to improve the performance of the atomic clock, the technology for making the gas sealing unit becomes important.

[0004] Patent Document 1 describes an example of a conventional gas sealing unit. The alkali metal unit described in Patent Document 1 includes: a Si component having a unit interior; a pair of glass plates attached to both sides of the Si component; and an alkali metal raw material disposed inside the unit. The alkali metal raw material is solid CsN3. Cs vapor and N2 are generated by irradiating CsN3 with UV light or laser.

[0005] The Cs vapor generation method using the decomposition reaction of CsN3 can generate Cs vapor with higher purity, so it has the advantage of being able to produce high-quality gas cells. However, it is not easy to efficiently generate Cs vapor from solid CsN3. For example, when CsN3 is heated in a high vacuum so that the temperature of CsN3 reaches 310°C or above the melting point, CsN3 produces a decomposition reaction accompanied by scattering. Therefore, even if solid CsN3 is heated at a high temperature of more than 600°C and less than 700°C, the amount of Cs generated required to obtain CPT resonance cannot be obtained. Therefore, it is usually necessary to generate Cs vapor slowly (for example, over 24 hours) using UV irradiation.

[0006] Patent document 2 describes a structure for efficiently generating Cs vapor in a short time. The metal gas sealing unit described in Patent document 2 has a basic structure in which a unit body made of Si is sandwiched between two glass plates, and has the characteristics of being able to generate a solid raw material of metal gas from a raw material solution of metal gas and being able to generate metal gas from the solid raw material by relatively low temperature treatment.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2013-38382

[0010] Patent Document 2: International Publication No. 2022 / 097557 Summary of the invention

[0011] Problems to be solved by the invention

[0012] The metal gas sealing unit described in Patent Document 2 has a dripping port for supplying a raw material solution of metal gas to the gas generating part of the unit body. The dripping port becomes an invalid space after the completion of the metal gas sealing unit, and thus becomes an obstacle to the miniaturization of the metal gas sealing unit. It is also considered to omit the dripping port and directly inject the raw material solution into the groove of the gas generating part, but in this case, there is a possibility that the surface of the unit body is contaminated and the bonding between the unit body and the glass plate is hindered. In the case where the bonding between the unit body and the glass plate is insufficient, the metal gas density in the optical chamber decreases and the time-dependent variation of the gas pressure becomes larger, so the stability of the performance of the metal gas sealing unit is impaired. In addition, if the raw material solution of the metal gas is attached to the inner surface of the glass plate that closes the optical chamber, it may become an obstacle to the laser, thereby affecting the performance of the metal gas sealing unit. In order to avoid such an undesirable situation, it was previously believed that a dedicated dripping port was necessary so as to separate the injection position of the raw material solution of the metal gas from the optical chamber and the gas generating part.

[0013] An object of the present invention is to provide a technology for achieving miniaturization of a metal gas sealing unit and improving the stability of its performance.

[0014] Solutions to Solve Problems

[0015] The present invention provides a metal gas sealing unit, wherein:

[0016] The metal gas sealing unit comprises:

[0017] a unit body having a first surface and a gas generating portion;

[0018] a glass plate attached to the first surface of the unit body;

[0019] an optical chamber provided in at least one selected from the unit body and the glass plate and communicating with the gas generating unit; and

[0020] a metal gas, which is sealed in the optical chamber,

[0021] The gas generating unit includes: a plurality of columns, a plurality of bottomed grooves provided between the plurality of columns and opening on the first surface, and an inlet for introducing a raw material solution of the metal gas into the plurality of bottomed grooves.

[0022] The introduction port includes at least one of a structure in which a portion of at least one column selected from the plurality of columns is missing and a structure in which all of at least one column selected from the plurality of columns is missing.

[0023] Effects of the Invention

[0024] According to the present invention, it is possible to provide a technique for achieving miniaturization of a metal gas sealing unit and improving the stability of its performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a perspective view of a metal gas sealing unit according to one embodiment of the present invention.

[0026] Figure 2 yes Figure 1 A top view of a unit body of the metal gas sealing unit is shown.

[0027] Figure 3A It is along Figure 2 A cross-sectional view of the unit body taken along line IIIA-IIIA is shown.

[0028] Figure 3B It is along Figure 2 A cross-sectional view of the unit body taken along line IIIB-IIIB is shown.

[0029] Figure 4 It is a process diagram showing a method of manufacturing the metal gas encapsulating unit.

[0030] Figure 5A It is a diagram for explaining a method of forming an introduction port.

[0031] Figure 5B It is a diagram for explaining a method of forming an introduction port.

[0032] Figure 6 The diagram is a plan view and a cross-sectional view for explaining another method of forming the introduction port.

[0033] Figure 7 It is a top view of the gas generating unit of Modification Example 1.

[0034] Fig. 8A It is a cross-sectional view of a metal gas sealing unit using a unit body according to Modification Example 2.

[0035] Figure 8B It is a top view of the unit body of Modification Example 2.

[0036] Fig. 9 It is a top view of the gas generating unit of Modification 3. DETAILED DESCRIPTION

[0037] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments.

[0038] (Implementation Method)

[0039] Figure 1 It is a perspective view of a metal gas encapsulation unit 100 according to an embodiment of the present invention. Figure 2 yes Figure 1 The top view of the unit body 10 of the metal gas sealing unit 100 shown. The metal gas sealing unit 100 has a unit body 10, a first glass plate 11, and a second glass plate 12. The unit body 10 has a first surface 10p and a second surface 10q. The first surface 10p and the second surface 10q are surfaces opposite to each other. The first surface 10p and the second surface 10q can also be the main surface of the unit body 10. "Main surface" refers to the surface with the largest area. The first glass plate 11 is bonded to the first surface 10p. The second glass plate 12 is bonded to the second surface 10q.

[0040] In this embodiment, the first glass plate 11 and the second glass plate 12 cover the entire first surface 10p and the entire second surface 10q, respectively. However, this is not necessary. The first surface 10p may include a portion not covered by the first glass plate 11. The second surface 10q may also include a portion not covered by the second glass plate 12.

[0041] Metal gas and buffer gas are sealed inside the metal gas sealing unit 100. The metal gas typically includes alkali metal gases such as K, Rb, and Cs. When the alkali metal gas is sealed, the metal gas sealing unit 100 can function as an atomic oscillator by detecting CPT resonance. As the buffer gas, an inert gas can be cited. As the inert gas, H2 gas, N2 gas, a rare gas, and a mixed gas thereof can be cited. The buffer gas is not essential, and only the metal gas can be sealed.

[0042] The first glass plate 11 and the second glass plate 12 are thinner glass plates that allow light of a specified wavelength band to be fully transmitted. "Light of a specified wavelength band" refers to light irradiated when the metal gas sealing unit 100 is actually used. For example, when the metal gas is Cs gas, the light of the specified wavelength band is light in the absorption band of Cs (for example, 894.6nm in the case of the Cs-D1 line). "Fully transmitted" means, for example, that the transmittance of light of the specified wavelength band is 90% or more. Glass plates that can be anodically bonded to the unit body 10 can be used as the first glass plate 11 and the second glass plate 12. Examples of glass that can be anodically bonded to silicon include silicate glass, borosilicate glass, aluminosilicate glass, borosilicate aluminum glass, and the like.

[0043] The unit body 10 is made of silicon, for example. When the processing technology of MEMS is used, a plurality of metal gas sealing units 100 can be manufactured from a silicon wafer. Silicon is difficult to react with alkali metal gas and buffer gas, so when the unit body 10 is made of silicon, the internal atmosphere of the metal gas sealing unit 100 can be kept stable, and the vapor pressure of the alkali metal gas can be kept constant. By using high-quality silicon wafers, it is also possible to expect the performance of the metal gas sealing unit 100 to be improved. In addition, when the unit body 10 is made of silicon, the first glass plate 11 and the second glass plate 12 can be bonded to the unit body 10 by anodic bonding without using other bonding materials. This also helps to keep the internal atmosphere of the metal gas sealing unit 100 stable and the vapor pressure of the alkali metal gas constant. However, the material of the unit body 10 is not particularly limited. As long as it is a material that can be finely processed, the unit body 10 can also be made of metal such as stainless steel, or it can be made of glass. The shape of the unit body 10 is also not particularly limited. The unit body 10 may have a plate-like shape, a cylindrical shape, or a rectangular parallelepiped shape. The unit body 10 having a rectangular parallelepiped shape means that the smallest polyhedron surrounding the unit body 10 is a rectangular parallelepiped. There is no particular limitation on the method for joining the first glass plate 11 and the second glass plate 12 to the unit body 10. At least one of the first glass plate 11 and the second glass plate 12 may be bonded to the unit body 10 using a bonding material such as an adhesive, glass frit, or a metal material. The method for joining the unit body 10 to the first glass plate 11 may be different from the method for joining the unit body 10 to the second glass plate 12.

[0044] The unit body 10 has an optical chamber 14 and at least one gas generating unit 20. The optical chamber 14 may also be provided in the first glass plate 11 and / or the second glass plate 12. The optical chamber 14 is provided in at least one selected from the unit body 10, the first glass plate 11, and the second glass plate 12, and may be a portion communicating with the gas generating unit 20.

[0045] The optical chamber 14 is a portion where the metal gas is sealed and is a passage for light used to detect CPT resonance. Figure 1 As shown in FIG. 1 , when the optical chamber 14 is provided in the unit body 10, the optical chamber 14 is open at least on the first surface 10p and the second surface 10q. In this embodiment, the optical chamber 14 includes a through hole extending from the first surface 10p to the second surface 10q of the unit body 10. The cross-sectional area of ​​the through hole may be constant or variable in the thickness direction of the unit body 10. Figure 1In the example, the through hole serving as the optical chamber 14 is located at the center of the unit body 10. However, a bottomed hole that is open only on the first surface 10p or the second surface 10q can also be used as an optical chamber. The shape of the optical chamber 14 is not particularly limited. The shape of the optical chamber 14 can be circular, elliptical, or polygonal when viewed from above. The position of the optical chamber 14 is also not particularly limited, and the optical chamber can be provided at a position offset from the center of the unit body 10. As a method for forming an optical chamber in the first glass plate 11, a method of forming a recess in the first glass plate 11 by ion etching or the like, a method of molding the first glass plate 11 itself into a dome shape, and the like can be adopted.

[0046] In this embodiment, there is no through hole other than the through hole serving as the optical chamber 14 in the unit body 10. According to such a structure, the second glass plate 12 can be more firmly bonded to the second surface 10q of the unit body 10. As a result, the stability of the performance of the metal gas sealing unit 100 is improved. However, the optical chamber 14 may also be a bottomed hole. In this case, the second glass plate 12 can be omitted.

[0047] The gas generating section 20 is a section for generating a solid raw material of metal gas from a raw material solution of metal gas and generating metal gas from the solid raw material. The gas generating section 20 has a plurality of grooves 22, a plurality of columns 24, and an inlet 26. The plurality of grooves 22 are disposed between the plurality of columns 24 and open on the first surface 10p. The plurality of grooves 22 are bottomed grooves. The plurality of grooves 22 extend in a lattice shape when viewed from above in such a manner that the gas generating section 20 has a plurality of columns 24. Figure 1 In the example of , a plurality of grooves 22 are formed in a manner that a plurality of columns 24 are arranged in a staggered pattern. According to such a fine structure, the surface area for precipitating the solid raw material of the metal gas can be sufficiently ensured. The column 24 has a rectangular (typically square) shape in a plan view. However, the shape of the column 24 is not particularly limited. The shape of the column 24 can be a prism or a cylinder.

[0048] When the unit body 10 is square, the length D of one side thereof is, for example, not less than 2 mm and not more than 8 mm. When the shape of the optical chamber 14 is circular in a plan view, the diameter Φ thereof is, for example, not less than 1 mm and not more than 6 mm.

[0049] A microchannel 18 is provided between the optical chamber 14 and the gas generating section 20 to connect the two. In the present embodiment, the plurality of grooves opened on the first surface 10p respectively serve as the microchannel 18. The width of the groove as the microchannel 18 is, for example, narrower than the width of the groove 22 in the gas generating section 20. Such a structure is used to prevent the solid raw material or raw material solution of the metal gas from being introduced into the optical chamber 14. The width of the groove as the microchannel 18 is, for example, not less than 1 μm and not more than 30 μm. The microchannel 18 may also be composed of only one groove.

[0050] Figure 3A It is along Figure 2 The cross-sectional view of the unit body 10 taken along line IIIA-IIIA shown in the figure shows the gas generating section 20 in an enlarged manner from the lateral direction. Figure 3B It is along Figure 2 1 is a cross-sectional view of the unit body 10 along line IIIB-IIIB. Figure 3A As shown, the width of each of the plurality of grooves 22 changes periodically along the thickness direction DR of the unit body 10. The thickness direction DR of the unit body 10 is the direction from the first surface 10p toward the second surface 10q. Each of the plurality of grooves 22 has a portion wider than the opening width W of each of the plurality of grooves 22 in the first surface 10p. Specifically, each of the plurality of grooves 22 includes a plurality of first portions 22a and a plurality of second portions 22b. The first portion 22a is a portion where the gap distance between adjacent pillars 24 and pillars 24 is longer. The second portion 22b is a portion where the gap distance between adjacent pillars 24 and pillars 24 is shorter. The first portion 22a and the second portion 22b are alternately arranged from the first surface 10p toward the second surface 10q. The width W2 of the second portion 22b of the groove 22 is, for example, equal to the opening width W of the groove 22 in the first surface 10p. In the present embodiment, three levels of the first portion 22a are arranged along the thickness direction DR. However, the number of the first portion 22a and the second portion 22b is not particularly limited.

[0051] When a solid raw material is generated from a raw material solution of a metal gas, the solid raw material easily adheres to the fine structure constituting the gas generating unit 20 and stays in the gas generating unit 20. In addition, the fine structure of the gas generating unit 20 makes the chemical reaction of the solid raw material such as CsN3 more efficient due to heating. Due to the combined effect of increasing the specific surface area and preventing the solid raw material from scattering during thermal decomposition, alkali metal gas can be efficiently generated by the chemical reaction of the solid raw material even at a relatively low temperature.

[0052] The width W of the groove 22 in the first surface 10p is, for example, not less than 1 μm and not more than 100 μm. The width W1 of the first portion 22a of the groove 22 is, for example, not less than 5 μm and not more than 200 μm. The width W2 of the second portion 22b of the groove 22 is substantially equal to the width W of the groove 22 in the first surface 10p. The width W1 of the first portion 22a and the width W2 of the second portion 22b may gradually narrow from the first surface 10p to the second surface 10q. The length of one side L of the column 24 in the first surface 10p is, for example, not less than 50 μm and not more than 500 μm.

[0053] The inlet 26 is an opening for introducing a raw material solution of a metal gas into the plurality of grooves 22. The inlet 26 is an opening with a bottom, and is connected to the plurality of grooves 22. The inlet 26 includes at least one of a structure in which a portion of at least one column 24 selected from the plurality of columns 24 is missing and a structure in which all of at least one column 24 selected from the plurality of columns 24 is missing. In the present embodiment, the inlet 26 includes both structures. According to such a structure, the inlet 26 is unlikely to become an invalid space, and is therefore advantageous for miniaturization of the metal gas encapsulation unit 100. Even when the droplets of the raw material solution are large relative to the width of the groove 22 and it is difficult to directly inject the droplets into the groove 22, the droplets can be injected into the inlet 26. Therefore, the possibility that the first surface 10p of the unit body 10 is contaminated by the raw material solution or the solid raw material can be reduced. When the first surface 10p can be kept clean, the first glass plate 11 can be reliably bonded to the first surface 10p. For these reasons, the stability of the performance of the metal gas encapsulation unit 100 can be improved while miniaturization is achieved.

[0054] The structure in which a part of the column 24 is missing can be formed by providing the introduction port 26 in the form of cutting off a part of the column 24. In this case, the plurality of columns 24 include a first column 24a and a second column 24b. The first column 24a is a column having the largest area among the plurality of columns 24 when the unit body 10 is viewed from above. In the present embodiment, the column 24 having a square shape when viewed from above is the first column 24a. The second column 24b is a column having a smaller area than the first column 24a. In the present embodiment, the second column 24b is a column adjacent to the introduction port 26. A part of the first column 24a is missing to form the second column 24b.

[0055] The structure in which all the pillars 24 are missing can be formed by providing the introduction port 26 in a manner of scraping away all the pillars 24. Alternatively, this structure can be formed by ensuring a region in the gas generating unit 20 where no pillars 24 exist.

[0056] The structure of the second column 24b is not particularly limited. The second column 24b may be a short-sized column formed by cutting or breaking the upper surface of the first column 24a, a notched column formed by cutting the side surface of the first column 24a, a thinner column formed by cutting the peripheral edge of the first column 24a, or a deformed column having all these features. They are collectively referred to as missing columns. In addition, in the case where all of the columns 24 are missing, the portion where the columns 24 exist is identified as a relatively large space between the column groups in the gas generating unit 20. Such a space is referred to as a column missing region. That is, the gas generating unit 20 includes a missing column and / or a column missing region.

[0057] The inlet 26 may also be surrounded by a plurality of columns 24. According to such a structure, the raw material solution can be delivered to each corner of the plurality of grooves 22, so that the solid raw material can be efficiently generated from the raw material solution. In this case, the amount of raw material solution used can be reduced, and the possibility of the first surface 10p of the unit body 10 being contaminated by the raw material solution or the solid raw material can be further reduced.

[0058] The entirety of the introduction port 26 may be contained within the region provided with the plurality of grooves 22 and the plurality of pillars 24. With such a structure, an ineffective space is less likely to be generated.

[0059] In the present embodiment, the unit body 10 has a rectangular shape, more specifically, a square shape, when viewed from above. A gas generating unit 20 is provided at at least one corner selected from the four corners of the unit body 10. According to such a structure, the amount of raw material solution introduced into the gas generating unit 20 is reduced. As a result, the possibility of the first surface 10p of the unit body 10 being contaminated by the raw material solution or the solid raw material can be reduced. In addition, the four corners are essentially prone to become invalid spaces. By providing the gas generating unit 20 at at least one corner selected from the four corners, the invalid space of the unit body 10 can be fully reduced. This is beneficial to the miniaturization of the metal gas sealing unit 100. In the present embodiment, the gas generating unit 20 is provided at each of the four corners of the unit body 10. According to such a structure, the above-mentioned effect is further improved. In addition, when the gas generating unit 20 is provided at each of the four corners, the metal gas sealing unit 100 has a highly symmetrical structure. This is beneficial to suppressing the deviation of the center of the optical axis, and can achieve stable installation of the metal gas sealing unit 100 (for example, installation to an atomic clock).

[0060] exist Figure 1In the embodiment, multiple (four in the present embodiment) gas generating units 20 are independent of each other. Direct movement of raw materials from the gas generating unit 20 to the gas generating unit 20 cannot be performed. Multiple gas generating units 20 are connected only via the microchannel 18 and the optical chamber 14. With such a structure, the amount of raw material solution to be introduced into the gas generating unit 20 is also reduced, thereby obtaining the above-mentioned effect. When the amount of raw material solution used is reduced, the cost of the metal gas sealing unit 100 is also reduced. In addition, the amount of solid raw material remaining in the unit body 10 can also be reduced. This is also advantageous from the perspective of the stability of the performance of the metal gas sealing unit 100. It should be noted that an embodiment in which multiple gas generating units 20 are connected to each other is also possible. In the case where the amount of raw material solution supplied to the gas generating unit 20 is uneven, the effect of making its amount uniform can be expected.

[0061] The gas generating unit 20 may be provided only at two or three corners selected from the four corners of the unit body 10. For example, when the structure other than the metal gas sealing unit 100 is made at one or two specific corners selected from the four corners, the gas generating unit 20 can be made at two or three corners other than the specific corners.

[0062] like Figure 3B As shown in FIG. 1 , the depth D1 of the introduction port 26 may be greater than the depth D2 of the groove 22. When the introduction port 26 is slightly deeper than the groove 22, the introduction port 26 is easily formed. However, the depth D1 of the introduction port 26 may be equal to the depth D2 of the groove 22. The depth D1 of the introduction port 26 may be lower than the depth D2 of the groove 22. According to these structures, the raw material solution introduced into the introduction port 26 can smoothly move to the plurality of grooves 22.

[0063] The shape of the inlet 26 is not particularly limited. The shape of the inlet 26 when viewed from above may be circular, elliptical, or polygonal such as a rectangle. The inlet 26 may also have the shape of a cylinder, an elliptical cylinder, or a polygonal column. In the first surface 10p, the opening area of ​​the inlet 26 is smaller than the opening area of ​​the optical chamber 14. Such a structure contributes to the miniaturization of the metal gas sealing unit 100. However, the size of the optical chamber 14 and the inlet 26 is not particularly limited.

[0064] When the metal gas sealing unit 100 is viewed from above, the opening area of ​​the inlet 26 is larger than the area of ​​the column 24, for example. When the shape of the inlet 26 is circular when viewed from above, and the shape of the column 24 is rectangular such as a square when viewed from above, the diameter of the inlet 26 may be larger than the length of one side of the column 24. According to such a structure, it is easy to inject the raw material solution into the groove 22. For the same reason, the diameter of the inlet 26 may be larger than the width W of the groove 22. In the case where the inlet 26 has a shape other than a circle when viewed from above, the "diameter of the inlet 26" refers to the diameter of a circle having an area equal to the area defined by the outline of the inlet 26 when viewed from above.

[0065] In this embodiment, the inlet 26 and the plurality of grooves 22 are opened only in the first surface 10p. That is, the gas generating unit 20 does not penetrate the second surface 10q. With such a structure, the raw material solution can be easily supplied from the first surface 10p to the grooves 22 through the inlet 26.

[0066] Next, a method for manufacturing the metal gas sealing unit 100 will be described. Figure 4 1 is a process diagram showing a method of manufacturing the metal gas encapsulating unit 100 .

[0067] As shown in step 1, a thin film 30 for masking is formed on one side of the substrate 10y. The thin film 30 may be a metal thin film such as Cr, Al, Ni, or a silicon oxide film. The thin film 30 may be formed by a vapor phase method such as evaporation or sputtering. The substrate 10y is, for example, a silicon wafer. A plurality of metal gas sealing units 100 may be manufactured from one substrate 10y, so the method of this embodiment is excellent in productivity. The silicon wafer used as the substrate 10y may be a polycrystalline wafer or a single crystal wafer. If a single crystal wafer is used, the internal atmosphere of the metal gas sealing unit 100 may be kept more stable, and the vapor pressure of the alkali metal gas may be kept more constant. There are no grain boundaries in a single crystal wafer, so it is easy to form the fine structure of the gas generating unit 20 with a higher dimensional accuracy. The larger the substrate 10y is, the more mass production of the miniaturized metal gas sealing unit 100 can be achieved.

[0068] Next, as shown in step 2, a resist 32 is applied on the surface of the thin film 30, and the resist 32 is patterned using a photolithography technique. The thin film 30 may be omitted and the resist 32 may be formed directly on the substrate 10y.

[0069] Next, as shown in step 3, a part of the thin film 30 is removed by an etching solution to expose the surface of the substrate 10y.

[0070] Next, as shown in step 4, the optical chamber 14 (not shown) and the gas generating unit 20 are formed by deep reactive ion etching. In this embodiment, when the unit body 10 is prepared, the optical chamber 14 and the gas generating unit 20 are formed together by deep reactive ion etching. Therefore, the unit body 10 can be manufactured with a small number of steps. When the optical chamber 14 is provided on the first glass plate 11 and / or the second glass plate 12, the gas generating unit 20 is formed in step 4. The microchannel 18 is also formed in step 4.

[0071] When the optical chamber 14 and the gas generating unit 20 are formed together, the inner circumference of the optical chamber 14 is provided with unevenness not only in the gas generating unit 20 but also in the inner circumference of the optical chamber 14. In contrast, according to the following method, although the number of steps increases, it is difficult to generate unevenness in the inner circumference of the optical chamber 14. That is, the gas generating unit 20 is formed by deep reactive ion etching from one surface (first surface) of the substrate 10y. The optical chamber 14 is formed by deep reactive ion etching from the other surface (second surface) of the substrate 10y. By simply digging the substrate 10y, a through hole having a flat inner circumference can be formed as the optical chamber 14.

[0072] Figure 5A as well as Figure 5B This is a diagram for explaining a method of forming the introduction port 26 . Figure 5A It is a top view of the substrate 10y. Figure 5B is a cross-sectional view of the substrate 10y. Figure 5A As shown in FIG. 1 , the resist 32 is patterned so that a plurality of relatively thin columns 24c are located in a predetermined area, and the groove 22 is formed by deep reactive ion etching. The predetermined area is a region for forming the inlet 26. The number of relatively thin columns 24c may be one. Next, as shown in FIG. Figure 5B As shown, the substrate 10y is etched greatly in the horizontal direction at the deepest position of the groove 22. As a result, the thin pillars 24c are removed, and the introduction ports 26 are formed in the predetermined regions.

[0073] Figure 6 2 is a plan view and a cross-sectional view for explaining another method of forming the introduction port 26. In this example, the pattern of the pillar 24 is not drawn in a predetermined region corresponding to the introduction port 26. The introduction port 26 can be formed by deep reactive ion etching.

[0074] Note that a method of forming the gas generating unit 20 by deep reactive ion etching is described in detail in Patent Document 2, and this description is also cited in the present application.

[0075] After completion of the deep reactive ion etching, the thin film 30 and the resist 32 are removed to obtain the cell body 10 .

[0076] Next, as shown in step 5, the second glass plate 12 is bonded to the second surface 10q of the unit body 10. As a result, the second surface 10q side of the optical chamber 14 is covered. The method of bonding the second glass plate 12 to the unit body 10 is anodic bonding. In anodic bonding, the second glass plate 12 and the unit body 10 are overlapped, and a DC voltage is applied between the two while both are heated. The heating temperature is, for example, above 150°C and below 600°C. The applied voltage is, for example, above 200V and below 1200V. It should be noted that in the case where the optical chamber 14 has a bottom hole, the second glass plate 12 is not required and step 5 is omitted.

[0077] Next, as shown in step 6, a raw material solution 34a of the metal gas is injected into the inlet 26, and the raw material solution 34a is introduced into the tank 22. The raw material solution 34a is supplied to the tank 22 by a capillary phenomenon.

[0078] The introduction port 26 opens at the first surface 10p, so the injection of the raw material solution 34a is also performed from the first surface 10p. The injection is performed by a device or apparatus suitable for injecting a liquid into a micro area. As such a device or apparatus, a micropipette, an inkjet, etc. can be cited. For example, at least one of the groove 22, the column 24, and the introduction port 26 can be identified by image processing, and the raw material solution 34a can be automatically injected using these devices or apparatuses. Alternatively, in the case where the silicon wafer used to make the unit body 10 is provided with an alignment mark, such an alignment mark can also be used to align the above-mentioned device or apparatus.

[0079] Next, in step 7, the solvent contained in the raw material solution 34a is evaporated, and the solid raw material 34b of the metal gas is precipitated on the surface of the column 24. Specifically, the solvent is evaporated by heating the unit body 10. The heating of the unit body 10 can be achieved by placing the unit body 10 on a hot plate or treating the unit body 10 in a heating furnace.

[0080] The raw material solution 34a is a solution containing a metal compound. As the metal compound, metal azides such as CsN3 and metal halides such as CsCl can be cited. The metal compound is typically an alkali metal compound. In this embodiment, an alkali metal gas is generated using a chemical reaction of an alkali metal compound. For example, when the alkali metal is Cs, a CsN3 solution is introduced into the gas generating unit 20 of the unit body 10 to precipitate solid CsN3. The solvent in the CsN3 solution can be an inorganic solvent such as water, or an organic solvent such as alcohols, acetone, or acetonitrile.

[0081] The heating temperature of the unit body 10 when the solid raw material 34b is precipitated on the surface of the column 24 is, for example, 25°C or more and 315°C or less. The "heating temperature" is the ambient temperature of the unit body 10. When a hot plate is used, the heating temperature is the surface temperature of the hot plate. When a heating furnace is used, the heating temperature is the temperature inside the heating furnace.

[0082] After the solid raw material 34b is precipitated, the solid raw material 34b and the unit body 10 may be degassed in a vacuum atmosphere. According to the present embodiment, since the gas generating unit 20 is opened in the first surface 10p, efficient degassing can be performed.

[0083] Next, in step 8, the first glass plate 11 is bonded to the first surface 10p of the unit body 10. The method of bonding the first glass plate 11 to the unit body 10 is also anodic bonding. In anodic bonding, the first glass plate 11 and the unit body 10 are overlapped, and a DC voltage is applied between the two while both are heated. The heating temperature is, for example, 150°C or more and 300°C or less. The applied voltage is, for example, 200V or more and 1200V or less. The process of step 8 is performed in a vacuum or in an inert gas atmosphere such as a rare gas or N2 gas. The vacuum degree is, for example, 1×10 -3 Pa or more and 1×10 -7 Pa or less. The atmosphere for carrying out the process of step 8 is determined based on the amount of the solid raw material 34 b existing in the cell body 10 and the amount of the buffer gas existing in the cell body 10 after the first glass plate 11 is bonded to the cell body 10 .

[0084] By bonding the first glass plate 11 to the unit body 10, not only the first surface 10p of the unit body 10 in the portion other than the gas generating unit 20 but also the upper surfaces of the plurality of columns 24 of the gas generating unit 20 are bonded to the first glass plate 11. The size of the first glass plate 11 in a plan view may be consistent with the size of the first surface 10p of the unit body 10. The size of the second glass plate 12 in a plan view may be consistent with the size of the second surface 10q of the unit body 10.

[0085] After the first glass plate 11 is bonded to the unit body 10, metal gas is generated from the solid raw material 34b, and the metal gas is introduced into the optical chamber 14. Specifically, the metal gas is generated from the solid raw material 34b by heating the unit body 10. The heating of the unit body 10 can be achieved by placing the unit body 10 on a heating plate or treating the unit body 10 using a heating furnace. The heating temperature of the unit body 10 when generating the metal gas is, for example, 250°C or more and 400°C or less. It should be noted that, instead of heating the unit body 10, the solid raw material 34b may be decomposed by UV irradiation to generate the metal gas, or the solid raw material 34b may be decomposed by laser irradiation to generate the metal gas.

[0086] When solid CsN3 is heated in a vacuum, Cs and N2 are generated according to the following chemical reactions. The alkali metal generation method based on the thermal decomposition of metal azide does not produce products that affect the performance of the gas pressure inside the metal gas encapsulation unit 100, and has the advantage of being able to simultaneously generate alkali metal gas and N2 gas as a buffer gas and encapsulate them in the unit body 10. In addition, there is an advantage that by-products other than alkali metals and N2 are not produced, so that the by-products do not affect the gas pressure and its changes.

[0087] 2CsN3→2Cs+3N2 (1)

[0088] The alkali metal compound is not limited to a metal azide. For example, as shown in the following formula (2), Cs gas can be generated by reacting CsCl with BaN6.

[0089] BaN6+2CsCl → 2Cs+BaCl2+3N2 (2)

[0090] After the above steps, the metal gas sealing unit 100 of the present embodiment is obtained. A portion of the solid raw material 34b remains in an undecomposed state and remains in the gas generating unit 20. That is, the metal gas sealing unit 100 has a solid raw material 34b of metal gas attached to the gas generating unit 20. According to the present embodiment, components or materials other than the solid raw material 34b do not exist inside the metal gas sealing unit 100. Therefore, the internal atmosphere of the metal gas sealing unit 100 can be kept stable, and the vapor pressure of the alkali metal gas can be kept constant. Since the solid raw material 34b remains in the gas generating unit 20, even if the vapor pressure of the metal gas in the optical chamber 14 decreases due to time-dependent degradation, the metal gas can be replenished by reheating the metal gas sealing unit 100.

[0091] The metal gas sealing unit 100 of the present embodiment contains a metal gas of a predetermined concentration generated inside the optical chamber 14 in an operating environment (for example, about 80° C. in the case of Cs gas). Therefore, the sizes required for the optical chamber 14 and the gas generating unit 20 are related to each other. In addition, the required size varies depending on the type of metal gas. In addition, the strength and durability achieved by making the first glass plate 11 and the second glass plate 12 close to the unit body 10 are also related to the area of ​​the bonding surface between these glass plates 11 and 12 and the unit body 10. Considering these conditions, the size of the unit body 10 and the size of each part are designed.

[0092] Several modified examples are described below. Sometimes, the same reference numerals are used for common elements in the embodiment and the modified example, and their description is omitted. The descriptions related to the embodiment and the modified example can be applied to each other as long as they are not technically contradictory. The embodiment and the modified example can also be combined with each other as long as they are not technically contradictory.

[0093] (Variation)

[0094] Figure 7 2 is a top view of a gas generating unit 20a according to Modification 1. The gas generating unit 20a can be applied to Figure 1 as well as Figure 2 The metal gas sealing unit 100 shown. In this modification, when the metal gas sealing unit 100 is viewed from above, the opening area of ​​the inlet 26 is smaller than the area of ​​the column 24. When the shape of the inlet 26 is circular when viewed from above, and the shape of the column 24 is rectangular such as square when viewed from above, the diameter of the inlet 26 can also be smaller than the length of one side of the column 24. According to such a structure, the first surface 10p is difficult to be contaminated when the solid raw material is generated from the raw material solution.

[0095] In this modification, the plurality of columns 24 are arranged in a staggered manner. The introduction port 26 is formed across a plurality of (for example, two or three) columns 24. In one example, the plurality of grooves 22 have a T-shaped portion. The center of the introduction port 26 is arranged in the T-shaped portion of the groove 22. That is, the introduction port 26 is formed across three columns 24.

[0096] Fig. 8A 1 is a cross-sectional view of a metal gas sealing unit 200 using a unit body 10 b according to a second modification. Figure 8B 2 is a top view of the unit body 10b of Modification 2. The metal gas sealing unit 200 includes a unit body 10b having a step 28. The step 28 is provided on the first surface 10p so as to surround the gas generating unit 20. According to such a structure, the first surface 10p is not easily contaminated by the raw material solution and the solid raw material around the step 28. Therefore, the first glass plate 11 can be reliably bonded to the first surface 10p of the unit body 10b.

[0097] The groove 22 and the introduction port 26 open at the bottom of the recess formed by the step 28. The first glass plate 11 is bonded to the first surface 10p around the step 28. A space having a height corresponding to the step 28 exists between the first glass plate 11 and the gas generating unit 20.

[0098] The step 28 may be provided only around the gas generating unit 20. The optical chamber 14 is not surrounded by the step 28. Specifically, when the unit body 10b is viewed from above, the step 28 exists 360° around the gas generating unit 20, and on the other hand, there may be a line segment that does not intersect the step 28 and connects the outer edge of the unit body 10b and the optical chamber 14. According to such a structure, the first glass plate 11 and the first surface 10p can be reliably bonded. As a result, the stability of the performance of the metal gas sealing unit 200 is improved.

[0099] Fig. 9 It is a top view of the gas generating section 20b of variant example 3. A plurality of columns 24 are arranged radially. No column 24 is provided in the central portion of the gas generating section 20b, but an inlet 26 is provided. Each column 24 is not rectangular when viewed from above, and the sizes are also different. According to the gas generating section 20, the structure in each direction when viewed from the inlet 26 is isotropic. Thus, the solid raw material can be uniformly supplied to each column 24. A plurality of columns 24 can also be arranged in a spiral shape. The spiral configuration is a configuration obtained by twisting the radial configuration. In variant example 3, there is an inlet 26 in the central portion of the radial configuration, so the position of introducing the solution is easy to know.

[0100] exist Fig. 9 In the embodiment, the plurality of columns 24 are symmetrically arranged within a range of 360 degrees around the inlet 26. However, the plurality of columns 24 may be arranged only within a range of 180 degrees around the inlet 26. A structure having a plurality of columns 24 arranged within a range of 60 degrees may also be provided around the inlet 26. The columns 24 can be appropriately arranged according to the purpose. Of course, these arrangements may also be used in combination with other arrangements.

[0101] In the present invention, the size of the column, the configuration of the column, the configuration of the inlet, and the size of the inlet are not limited by the contents shown in the embodiments and the modified examples. For example, although not shown in the figure, a large column can be arranged only around the inlet in a top view for the purpose of preventing the accidental outflow of the raw material solution or the purpose of preventing the scattering of the solvent during evaporation.

[0102] As long as the introduction port 26 is provided in the region where the plurality of grooves 22 and the plurality of pillars 24 are located in a plan view, the introduction port 26 is not necessarily opened only on the first surface 10p. The introduction port 26 may be a bottomed hole opened only on the second surface 10q.

[0103] It is not necessary for the optical chamber to be provided only in the unit body. For example, the optical chamber may be formed by a first glass plate having a recess provided at a predetermined position and the unit body. The optical chamber may also be formed only by the recess of the first glass plate. Furthermore, the optical chamber may be provided on the second glass plate on the second surface side opposite to the first surface side where the gas generating part is opened. In this case, the gas generating part and the optical chamber are connected by a microchannel (connecting hole) that passes through the unit body. In this way, a design suitable for the method of use of the metal gas sealing unit can be selected. The recess of the glass plate can be formed by a method such as etching.

[0104] Industrial Applicability

[0105] The metal gas sealing unit of the present invention is useful for atomic clocks, magnetic sensors, inertial sensors, and the like.

Claims

1. A metal gas sealing unit, wherein: The metal gas sealing unit comprises: a unit body having a first surface and a gas generating portion; a glass plate attached to the first surface of the unit body; an optical chamber provided in at least one selected from the unit body and the glass plate and communicating with the gas generating unit; and a metal gas, which is sealed in the optical chamber, The gas generating unit includes: a plurality of columns, a plurality of bottomed grooves provided between the plurality of columns and opening on the first surface, and an inlet for introducing a raw material solution of the metal gas into the plurality of bottomed grooves. The introduction port includes at least one of a structure in which a portion of at least one column selected from the plurality of columns is missing and a structure in which all of at least one column selected from the plurality of columns is missing.

2. The metal gas sealing unit according to claim 1, wherein: The introduction port is surrounded by the plurality of pillars.

3. The metal gas sealing unit according to claim 1, wherein: The unit body has a rectangular shape in a plan view. The gas generating portion is provided at at least two corners selected from four corners of the unit body.

4. The metal gas sealing unit according to claim 1, wherein: The optical chamber is arranged in the unit body.

5. The metal gas sealing unit according to claim 1, wherein: The unit body further includes a step provided on the first surface so as to surround the gas generating unit.

6. The metal gas sealing unit according to claim 1, wherein: When the metal gas sealing unit is viewed in plan, the opening area of ​​the introduction port is larger than the area of ​​the pillar.

7. The metal gas sealing unit according to claim 1, wherein: The introduction port and the plurality of bottomed grooves are open only on the first surface.

8. The metal gas sealing unit according to claim 1, wherein: The unit body also has a second surface, The optical chamber includes a through hole extending from the first face to the second face in the unit body, There is no through hole other than the through hole serving as the optical chamber.

9. The metal gas sealing unit according to claim 1, wherein: The unit body also has a second surface, A first glass plate is attached to the first surface. A second glass plate is attached to the second surface. The optical chamber is provided in at least one selected from the group consisting of the unit body, the first glass plate, and the second glass plate.

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