JP2022131821A - metal film - Google Patents

Abstract

To provide a material having high gas absorption capacity.SOLUTION: A metal film contains at least two types of metal elements selected from the group consisting of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Hf, Ta, Pt and Au, and has a first surface and a second surface facing each other. When, of the two types of metal elements, a metal element A represents an element with a relatively large atomic number and a metal element B represents an element with a relatively small atomic number, the molar fraction A (1) of the metal element A with respect to the total of the metal element A and the metal element B on the first surface is less than the molar fraction A (2) of the metal element A with respect to the total of the metal element A and the metal element B on the second surface.SELECTED DRAWING: Figure 1

Description

The present invention relates to metal films.

A non-evaporable getter (NEG) is a substance that can chemically adsorb and fix gas molecules such as moisture (water vapor), oxygen, hydrogen, carbon oxide, and nitrogen. Non-evaporable getters are, for example, in the vacuum sealing of electronic devices and MEMS (Micro Electro-Mechanical System) technology. It is used for the purpose of removing the gas of

A metal is used as the material of the non-evaporable getter. For example, Patent Document 1 describes a non-evaporable getter containing one or more components selected from zirconium, cobalt, yttrium, lanthanum, and rare earth elements.

Japanese Patent No. 2893528

In the recent vacuum sealing of electronic devices and MEMS technology, the use of various materials such as silicon, glass, metals, and ceramics has been studied. Sealing may be required. Further, in vacuum sealing, a vacuum space with a higher degree of vacuum is required, and in gas sealing, a space filled with a gas of higher purity is sometimes required. Therefore, a non-evaporable getter with a high gas adsorption capacity is desired.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a material having a high gas adsorption capacity.

In order to solve the above problems, the following means are provided.

[1] The metal film according to the first aspect includes at least two selected from the group consisting of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Hf, Ta, Pt and Au. It contains a metal element and has a first surface and a second surface facing each other, and the one with a relatively higher atomic number among the two types of metal elements is defined as a metal element A, and the one with a relatively lower atomic number. is the metal element B, and the molar fraction A(1) of the metal element A with respect to the total of the metal element A and the metal element B on the first surface is the metal element A on the second surface and the metal element It is smaller than the molar fraction A(2) of the metal element A with respect to the sum of B.

[2] In the metal film according to the above aspect, the molar fraction A(3) of the metal element A with respect to the total of the metal element A and the metal element B in the middle of the first surface and the second surface is The molar fraction A(1) of the metal element A on the first surface may be larger than the mole fraction A(2) of the metal element A on the second surface.

[3] In the metal film according to the above aspect, the molar fraction A(2) of the metal element A with respect to the sum of the metal element A and the metal element B on the second surface is converted to the metal element A on the second surface and the value obtained by subtracting the molar fraction B (2) of the metal element B with respect to the total of the metal element B (A (2) - B (2)), and the metal element A and the metal element on the first surface A value obtained by subtracting the molar fraction B(1) of the metallic element B relative to the total of the metallic element A and the metallic element B on the first surface from the molar fraction A(1) of the metallic element A relative to the total of B The difference from (A(1)-B(1)) may be 0.05 or more.

[4] In the metal film according to the aspect described above, the density on the first surface may be lower than the density on the second surface.

[5] In the metal film according to the aspect described above, the density on the first surface may be 95% or less of the density on the second surface.

[6] The metal film according to the above aspect may further include a rare earth element.

[7] In the metal film according to the above aspect, the molar content of the rare earth element on the first surface may be higher than the molar content of the rare earth element on the second surface.

[8] In the metal film according to the above aspect, the difference between the molar content of the rare earth element on the first surface and the molar content of the rare earth element on the second surface is 3 mol% or more. may be

[9] In the metal film according to the above aspect, the film thickness may be in the range of 0.5 μm or more and 5.0 μm or less.

[10] The metal film according to the above aspect may further include a nitride inside.

[11] The metal film according to the above aspect may further include a substrate, and the substrate and the second surface may be in contact with each other.

The metal film according to the above aspect has a high gas adsorption capacity over a long period of time.

3 is a cross-sectional view of a metal film according to the first embodiment; FIG. 1 is a cross-sectional view showing a schematic configuration of an electron beam vapor deposition apparatus that can be used for manufacturing a metal film according to the first embodiment; FIG. FIG. 5 is a cross-sectional view of a metal film according to a first modification of the first embodiment; 1 is a block diagram of a gas adsorption rate measuring device used in Examples. FIG.

Hereinafter, embodiments will be described in detail with appropriate reference to the drawings. In the drawings used in the following description, characteristic parts may be shown enlarged for convenience in order to make the characteristics easier to understand, and the dimensional ratio of each component may differ from the actual one. The materials, dimensions, etc. exemplified in the following description are examples, and the present invention is not limited to them, and can be implemented with appropriate changes within the scope of the present invention.

FIG. 1 is a cross-sectional view of a metal film according to the first embodiment.
As shown in FIG. 1 , the metal film 1 has a substrate 10 and a metal film portion 20 arranged on the substrate 10 . The metal film portion 20 has a first surface 21 and a second surface 22 facing each other. The second surface 22 of the metal film portion 20 is in contact with the substrate 10 . The first surface 21 of the metal film portion 20 is in contact with the vacuum space and the gas-filled space, and adsorbs a small amount of gas mixed in these spaces.

The substrate 10 has a function of supporting the metal film portion 20 . The material of the substrate 10 is not particularly limited, and semiconductors, insulators, metals, and the like can be used. Examples of semiconductors that can be used include silicon (Si), silicon carbide (SiC), gallium arsenide (GaAs), and gallium nitride (GaN). As the insulator, for example, ceramics such as alumina (Al ₂ O ₃ ), magnesium oxide (MgO), strontium titanate (SrTiO ₃ ) and barium titanate (BaTiO ₃ ), and resins such as polyimide and polyamide can be used. can. Examples of metals that can be used include Al, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Hf, Ta, Pt, Au, and rare earth elements. These materials may be used individually by 1 type, and may be used in combination of 2 or more type.

The metal film portion 20 contains at least two metal elements selected from the group consisting of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Hf, Ta, Pt and Au. The total content of the metal elements in the metal film portion 20 is, for example, 80 mol % or more, preferably 90 mol % or more. Moreover, the metal film portion 20 may be formed only from the above metal elements. However, the metal film portion 20 may contain unavoidable impurities. The unavoidable impurities are impurities that are unavoidably mixed from the raw material of the metal film portion 20 or from the manufacturing process. The content of unavoidable impurities is, for example, 1.0 mol % or less, preferably 0.1 mol % or less. The two metal elements contained in the metal film portion 20 may form a solid solution, a eutectic, or an intermetallic compound.

Among the metal elements contained in the metal film portion 20, the metal element A having a relatively large atomic number may be, for example, Zr, Cr, Pt, Ni, V, Hf, or Au. Also, the metal element B having a relatively small atomic number may be, for example, Co, Ti, Al, Fe, V, Ni, or Cr. Combinations of metal elements contained in the metal film portion 20 include, for example, Zr--Co, Zr--Ti, Zr--Al, Zr--Fe, Zr--V, Zr--Ni, Cr--Ti, Pt--Ti, Ni-- Ti, V--Ti, Hf--Ti, Au--Ti, Au--Cr, Zr--V--Ti and Zr--V--Fe can be mentioned.

The metal film portion 20 has a metal element A having a relatively larger atomic number among the above two metal elements, and a metal element B having a relatively smaller atomic number. The molar fraction A(1) of the element A is set to be smaller than the molar fraction A(2) of the metal element A on the second surface 22 . That is, the molar fraction B(1) of the metal element B on the first surface 21 is set to be larger than the molar fraction B(2) of the metal element B on the second surface 22 . The mole fraction of the metal element A is the ratio of the number of moles of the metal element A to the total number of moles of the metal element A and the metal element B. Also, the mole fraction of the metal element B is the ratio of the number of moles of the metal element B to the total number of moles of the metal element A and the metal element B. The content of the metal element in the metal film portion 20 can be measured using the Rutherford backscattering analysis method. The content of the metal element on the second surface 22 in contact with the substrate 10 is determined by polishing the surface of the metal film portion 20 from the first surface 21 side, and measuring the content at a position 100 nm from the interface between the substrate 10 and the second surface 22. The content of the metal element may be the content of the metal element of the second surface 22 .

The mole fraction of the metal element A in the metal film portion 20 may decrease stepwise or continuously from the second surface 22 toward the first surface 21 . Alternatively, the mole fraction of the metal element B in the metal film portion 20 may increase stepwise or continuously from the second surface 22 toward the first surface 21 . The molar fraction A(3) of the element A in the middle 23 between the first surface 21 and the second surface 22 of the metal film portion 20 is larger than the molar fraction A(1) of the metal element A in the first surface 21, It is preferably smaller than the molar fraction A(2) of the metal element A on the second surface 22 . Furthermore, the molar fraction B(3) of the metal element B in the middle 23 between the first surface 21 and the second surface 22 of the metal film portion 20 is higher than the molar fraction B(2) of the metal element B in the second surface 22. is large and smaller than the molar fraction B(2) of the metal element B on the first surface 21 .

The content of the metal element A in the metal film portion 20 is preferably higher than the content of the metal element B. The molar fraction A(1) of the metal element A on the first surface 21 is, for example, in the range of 0.70 or more and 0.90 or less, and preferably in the range of 0.75 or more and 0.85 or less. . The value obtained by subtracting the mole fraction B(1) of the metal element B from the mole fraction A(1) of the metal element A on the first surface 21 (A(1)-B(1)) is, for example, 0.40. It is in the range of 0.80 or less, and preferably in the range of 0.50 or more and 0.70 or less. Further, the molar fraction A(2) of the metal element A on the second surface 22 is, for example, within the range of 0.80 or more and 1.00 or less, and is within the range of 0.85 or more and 0.95 or less. is preferred. The value obtained by subtracting the mole fraction B(1) of the metal element B from the mole fraction A(2) of the metal element A on the second surface 22 (A(2)-B(2)) is, for example, 0.60. It is in the range of 1.00 or less, and preferably in the range of 0.70 or more and 0.90 or less. The difference between (A(1)-B(1)) and (A(2)-B(2)) is preferably 0.05 or more. The difference between (A (1) - B (1)) and (A (2) - B (2)) is preferably in the range of 0.10 or more and 0.40 or less, and 0.15 or more and 0 It is more preferably in the range of 0.35 or less.

The metal film portion 20 may be configured to contain three or more of the above metal elements. When three or more metal elements are contained, among the top two metal elements with a large molar ratio, the metal element with a relatively large atomic number is defined as a metal element A, and the genus element with a relatively small atomic number is a metal. Let it be element B.

The metal film portion 20 may further contain a rare earth element. Examples of rare earth elements that can be used include Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. These rare earth elements may be used singly or in combination of two or more.

The molar content of the rare earth element in the metal film portion 20 is, for example, in the range of 1 mol% or more and 20 mol% or less, and 2 mol% or more and 10 mol% or less with respect to the total of the metal elements in the metal film portion 20. is preferably within the range of Moreover, it is preferable that the content of the rare earth element in the first surface 21 is higher than the content of the rare earth element in the second surface 22 . Also, the second surface 22 may not contain a rare earth element. The difference between the molar content of the rare earth element in the first surface 21 and the molar content of the rare earth element in the second surface 22 is preferably 3 mol % or more. The difference between the molar content of the rare earth element in the first surface 21 and the molar content of the rare earth element in the second surface 22 may be 10 mol % or less.

The density of the metal film portion 20 on the first surface 21 is preferably lower than the density on the second surface 22 . The density on the first surface 21 is preferably 95% or less, more preferably 85% or less, and particularly preferably 75% or less with respect to the density on the second surface. The density on the first surface 21 may be 50% or more or 60% or more of the density on the second surface.

The thickness of the metal film portion 20 is preferably in the range of 0.5 μm or more and 5.0 μm or less.

The metal film 1 of this embodiment can be manufactured, for example, by laminating the metal film part 20 on the substrate 10 . As a method for laminating the metal film portion 20, for example, an electron beam vapor deposition method, a vacuum vapor deposition method, an ion plating method, an ion beam vapor deposition method, a molecular beam vapor deposition method, a sputtering method, or the like can be used. Next, the method of manufacturing the metal film 1 will be described by taking the electron beam vapor deposition method as an example.

FIG. 2 is a cross-sectional view showing a schematic configuration of an electron beam vapor deposition apparatus that can be used for manufacturing a metal film according to the first embodiment.
As shown in FIG. 2, the electron beam vapor deposition apparatus 30 has a vacuum chamber 31 and an oil diffusion pump 40 for evacuating the interior of the vacuum chamber. The vacuum chamber 31 has therein a substrate holder 32 for fixing the substrate 10, three deposition sources (first deposition source 34a, second deposition source 34b, third deposition source 34c), RF coil 37, MFC (Mass flow controller) 38 and a gas introduction pipe 39 . The substrate holder 32 is rotatable in the circumferential direction by a motor 33 provided outside. The first deposition source 34a, the second deposition source 34b, and the third deposition source 34c each include a hearth 35 and an electron gun 36. As shown in FIG. The metal raw material filled in the hearth 35 is irradiated with an electron beam EB generated by an electron gun 36 to vaporize the metal raw material, and the vaporized metal element is deposited on the surface of the substrate 10 to form a metal film. . The first deposition source 34a, the second deposition source 34b, and the third deposition source 34c can increase or decrease the output of the electron beam EB by adjusting the emission current supplied to the electron gun 36, respectively. film formation rate can be changed. Further, the electron beam vapor deposition apparatus 30 can introduce a gas whose flow rate is adjusted by the MFC 38 into the vacuum chamber 31 through the gas introduction pipe 39 .

Manufacture of the metal film 1 using the electron beam vapor deposition apparatus 30 is performed as follows.
First, the substrate 10 is fixed to the substrate holder 32 . Further, the hearths 35 of the first deposition source 34 a , the second deposition source 34 b , and the third deposition source 34 c are filled with the metal raw material, which is the raw material of the metal film portion 20 . For example, the hearth 35 of the first deposition source 34a is filled with the metal element A, the hearth 35 of the second deposition source 34b is filled with the metal element B, and the hearth 35 of the third deposition source 34c is filled with the rare earth element. The hearth 35 of the first deposition source 34a may be filled with the metal element A and the rare earth element, and the hearth 35 of the second deposition source 34b may be filled with the metal element B and the rare earth element.

Next, the vacuum chamber 31 is sealed, the oil diffusion pump 40 is operated, and the inside of the vacuum chamber 31 is evacuated to reach a predetermined pressure (for example, 1×10 ⁻⁴ Pa).

Next, the motor 33 is operated to rotate the substrate holder 32 in the circumferential direction. Further, while applying a voltage to the hearths 35 of the first deposition source 34a, the second deposition source 34b, and the third deposition source 34c, an emission current is supplied to the electron gun 36, and the electron beam EB is applied to the metal filled in the hearth 35. The deposition of the metal film is initiated by irradiating the raw material. After starting the deposition of the metal film, for example, the emission current value supplied to the electron gun 36 of the second deposition source 34b is adjusted so that the deposition rate of the metal element B increases continuously. As a result, the molar fraction of the metal element B continuously increases from the surface (second surface 22) on the side of the substrate 10 toward the surface (first surface 21) opposite to the substrate 10, and the molar fraction of the metal element A increases. It is possible to form the metal film portion 20 in which the molar fraction is continuously decreased from the second surface 22 toward the first surface 21 .

According to the metal film 1 of the first embodiment configured as described above, the metal film portion 20 contains at least two of the above metal elements, and the atomic numbers of these two metal elements are relatively large. The metal element A is the one with the relatively smaller atomic number, and the metal element B is the one with the relatively smaller atomic number. Since it is smaller than the fraction A(2), compared with the second surface 22, the first surface 21 is more likely to have pores, is porous, and has a larger specific surface area. As a result, the first surface 21 of the metal film portion 20 has an improved gas adsorption amount and a gas diffusion speed, thereby increasing the gas adsorption capacity.

In the metal film 1 of the first embodiment, the molar fraction A(3) of the metal element A in the middle 23 between the first surface 21 and the second surface 22 of the metal film part 20 is When it is larger than the molar fraction A(1) and smaller than the molar fraction A(2) of the metal element A on the second surface 22, the composition change in the film thickness direction of the metal film portion 20 becomes moderate. Therefore, the first surface 21 is likely to have more pores, is porous, and has a large specific surface area.

In the metal film 1 of the first embodiment, the mole fraction B(2) of the metal element B on the second surface 22 is subtracted from the mole fraction A(2) of the metal element A on the second surface 22 of the metal film portion 20 Subtract the molar fraction B(1) of the metal element B on the first surface 21 from the value (A(2)-B(2)) and the mole fraction A(1) of the metal element A on the first surface 21 When the difference from the obtained value (A(1)-B(1)) is 0.05 or more, the difference in the composition of the metal elements between the first surface 21 and the second surface 22 increases. Therefore, the first surface 21 is likely to have more pores, is porous, and has a large specific surface area.

In the metal film 1 of the first embodiment, when the density on the first surface 21 of the metal film part 20 is lower than the density on the second surface 22, the first surface 21 is porous. , the specific surface area increases. As a result, the first surface 21 of the metal film portion 20 has an improved gas adsorption amount and a gas diffusion speed, thereby increasing the gas adsorption capacity.

In the metal film 1 of the first embodiment, when the density on the first surface 21 of the metal film part 20 is 95% or less of the density on the second surface 22, more holes are formed on the first surface 21. It is porous and has a large specific surface area.

In the metal film 1 of the first embodiment, when the metal film portion 20 further contains a rare earth element, the gas adsorption amount of the metal film portion 20 increases due to the gas adsorption by the rare earth element.

In the metal film 1 of the first embodiment, when the molar content of the rare earth element on the first surface 21 of the metal film portion 20 is higher than the molar content of the rare earth element on the second surface 22 of the metal film portion 20, the The amount of gas adsorbed on the first surface 21 increases.

In the metal film 1 of the first embodiment, the difference between the molar content of the rare earth element on the first surface 21 of the metal film portion 20 and the molar content of the rare earth element on the second surface 22 is 3 mol% or more. In this case, the amount of gas adsorbed on the first surface 21 of the metal film portion 20 is further increased.

In the metal film 1 of the first embodiment, when the film thickness of the metal film portion 20 is thin in the range of 0.5 μm or more and 5.0 μm or less, it can be used as a non-evaporable getter for vacuum sealing of various electronic devices. and MEMS technology.

As described above, the first embodiment has been described in detail with reference to the drawings, but the first embodiment is not limited to this example. For example, in the first embodiment, the metal film 1 has the substrate 10, but instead of the substrate 10, the metal film portion 20 may be formed directly on the surface of a member used for vacuum sealing of electronic devices or MEMS technology. good.
Moreover, the metal film part 20 may further have a nitride inside.

(First modification)
FIG. 3 is a cross-sectional view of a metal film according to a first modification of the first embodiment; The metal film 2 differs from the first embodiment in that a nitride layer 24 is formed inside the metal film portion 20 . In the first modified example, configurations similar to those of the first embodiment are denoted by similar reference numerals, and descriptions thereof are omitted.

In the first modification, the nitride layer 24 is formed in an island shape. Two layers of the nitride layer 24 are formed with an interval therebetween. Nitride layer 24 preferably comprises a metal nitride. The nitride layer 24 preferably contains 80 mol % or more of metal nitride. Nitride layer 24 may be formed only of a metal nitride. The metal nitride may be a nitride of a metal element contained in the metal film portion 20 .

Examples of methods for forming the nitride layer 24 include electron beam deposition, vacuum deposition, ion plating, ion beam deposition, molecular beam deposition, and sputtering. For example, in the case of the electron beam evaporation method, the nitride layer 24 is formed by irradiating the metal source with an electron beam EB in a state where nitrogen gas is introduced into the vacuum chamber 31 of the electron beam deposition device 30 to vaporize the metal source. can be formed.

Nitride layer 24 is preferably adjacent to first surface 21 . The nitride layer 24 is preferably arranged within 100 nm from the surface of the first surface 21 . The nitride layer 24 may have a monomolecular structure in which nitride molecules are arranged two-dimensionally in one layer, or may have a multi-molecular structure in which nitride molecules are arranged in multiple layers in a two-dimensional direction. When the nitride layer 24 has a polymolecular structure, the film thickness is preferably 5 nm or less.

The metal film 2 of the first modified example configured as described above has the same effects as the metal film 1, and since the nitride layer 24 is formed inside the metal film portion 20, the metal film portion Arrangement of the metal elements in the metal film portion 20 can be non-uniform, and holes are likely to be formed in the metal film portion 20 .

[Example 1]
The electron beam vapor deposition apparatus 30 shown in FIG. 2 was used as a film forming apparatus. A silicon substrate (diameter: 6 inches) was fixed to the substrate holder 32 . The hearth 35 of the first deposition source 34a was filled with Zr, and the hearth 35 of the second deposition source 34b was filled with Co.

Next, the vacuum chamber 31 was sealed, the oil diffusion pump 40 was operated, and the inside of the vacuum chamber 31 was evacuated until the internal pressure became 1×10 ⁻⁴ Pa or less.

Next, the motor 33 was operated to rotate the substrate holder 32 in the circumferential direction. After that, while applying a voltage of 7 kV to the hearth 35 of the first evaporation source 34a and the hearth 35 of the second evaporation source 34b, the electron gun 36 of the first evaporation source 34a is operated at a Zr film formation rate of 6 nm/. An emission current is supplied to the electron gun 36 of the second deposition source 34b so that the deposition rate of Co is 0.5 nm/minute, and the Zr--Co metal film is deposited. started. The Zr—Co metal film was formed until the film thickness reached 2 μm. The emission current supplied to the electron gun 36 of the second evaporation source 34b was adjusted so that the Co film formation rate increased at a constant rate immediately after the film formation started, and the Co film formation rate at the end of the film formation was adjusted. was set to 1 nm/min. Further, when the film thickness of the Zr--Co metal film reached 2/3 μm, introduction of argon gas into the vacuum chamber 31 was started, and the internal pressure of the vacuum chamber 31 was increased at a constant rate to form a film. The internal pressure of the vacuum chamber 31 at the end was set to 1×10 ⁻³ Pa.

[Comparative Example 1]
The emission current of the electron gun 36 of the second vapor deposition source 34b at the start of film formation is set to a value at which the film formation rate of Co is 0.5 nm/min. A Zr--Co metal film was formed in the same manner as in Example 1, except that the conditions at the start of film formation were maintained without performing the .

[Comparative Example 2]
The emission current of the electron gun 36 of the second vapor deposition source 34b at the start of film formation is set to a value at which the film formation rate of Co is 1.0 nm/min. A Zr--Co metal film was formed in the same manner as in Example 1, except that the conditions at the start of film formation were maintained without performing the .

[evaluation]
For the Zr--Co metal films obtained in Example 1 and Comparative Examples 1 and 2, the composition, density, and hydrogen gas adsorption capacity were measured by the following methods. The results are shown in Tables 1A and 1B. The composition and density were measured on the first surface of the metal film (position 2 μm from the silicon substrate), then the surface was polished, and the intermediate portion (position 1 μm from the silicon substrate) was measured. After polishing, the second surface (position of 100 nm from the interface between the silicon substrate and the second surface) was measured. The results are shown in Tables 1A and 1B. In Table 1A, the composition formulas of the first surface, the intermediate portion, and the second surface, the Zr mole fraction, the Co mole fraction, and the difference between the Zr mole fraction and the Co mole fraction are described, and Table 1B shows describes the difference in composition between the first and second surfaces, the density of the compositions of the first, intermediate and second surfaces, and the hydrogen gas adsorption capacity.

(composition)
It was measured by Rutherford Back-Scattering Spectroscopy (RBS).

(density)
It was calculated from the value of the total reflection critical angle measured by X-Ray-Reflectivity (XRR) and the composition of the metal film.

(Hydrogen gas adsorption capacity)
The gas adsorption capacity was evaluated by measuring the hydrogen gas adsorption rate of the Zr--Co metal film using the gas adsorption rate measuring device shown in FIG. The gas adsorption rate measuring device 50 includes a vacuum chamber 51 , an exhaust pump 56 , and a pipe 57 connecting the vacuum chamber 51 and the exhaust pump 56 . The vacuum chamber 51 has a sample mounting table 52 . The sample mounting table 52 has a heating system 55 with a thermocouple 53 and a heater 54 . The pipe 57 has a conductance valve 58, a first vacuum gauge 59a is arranged between the exhaust pump 56 and the conductance valve 58, and a second vacuum gauge 59b is arranged between the vacuum chamber 51 and the conductance valve 58. are placed. A gas supply pipe 60 is connected via an MFC 61 between the exhaust pump 56 of the pipe 57 and the first vacuum gauge 59a. The hydrogen gas adsorption rate of the Zr--Co metal film was measured as follows.

The planar area of the sample (Zr--Co metal film) 3 was measured. Next, the sample 3 was placed on the sample placement table 52 . Next, the sample 3 is heated to 300° C. using the heating system 55 of the sample mounting table 52, and the vacuum chamber 51 is evacuated to 1×10 ⁻⁷ Pa or less by the evacuation pump 56 while baking and heating the inside of the vacuum chamber 51. did. The conductance was adjusted to 70 mL·s ⁻¹ using the conductance valve 58 . Next, hydrogen gas was introduced into the pipe 57 from the gas supply pipe 60 . The supply amount of hydrogen gas was adjusted using the MFC 61 so that the pressure of the second vacuum gauge 59b was 4×10 ⁻⁴ Pa.
The pressure of the first vacuum gauge 59a and the pressure of the second vacuum gauge 59b were measured. The hydrogen gas adsorption speed S was calculated using the following formula.
S=C×(P ₁ −P ₂ )/(P ₂ ×A)
However, in the formula, S is the adsorption speed (mL s ^-1 cm ^-2 ), P ₁ is the pressure (Pa) of the first vacuum gauge 59a, P ₂ is the pressure of the second vacuum gauge 59b ( Pa), A is the planar area of the sample 3 (cm ² ), and C is the conductance (mL·s ⁻¹ ).

From the results of Tables 1A and 1B, the Zr--Co metal film of Example 1 has a higher density on the first surface than the Zr--Co metal films of Comparative Examples 1 and 2. is small, and it can be seen that the gas adsorption capacity is improved. In the Zr—Co metal film of Example 1, the Zr mole fraction Zr(1) on the first surface is smaller than the Zr mole fraction Zr(2) on the second surface, and the Co mole fraction on the first surface Since Co(1) is greater than the mole fraction Co(2) on the second surface, Zr and Co are deposited in random directions (various lattice directions) from the second surface toward the first surface. For this reason, the first surface of the Zr--Co metal film is more likely to have pores than the second surface, is porous, and has a large specific surface area. Therefore, the first surface has a lower density than the second surface. In addition, since the specific surface area of the first surface is increased, the contact area of the first surface with the gas (gas adsorption) is increased, the gas is easily adsorbed on the first surface, and the adsorbed gas is further removed. Since it becomes easier to diffuse into the Zr--Co metal film, the gas adsorption capacity is improved.
On the other hand, the Zr—Co metal films of Comparative Examples 1 and 2 had the same molar fraction of Zr and Co from the second surface to the first surface. are stacked in regular directions, and holes are less likely to be formed in the Zr--Co metal film.

[Example 2]
Zr to which Y is added (Zr:Y=93.5:6.5 (molar ratio)) is added to the hearth 35 of the first deposition source 34a, and Ti to which La is added to the hearth 35 of the second deposition source 34b (Ti: Y=93.5:6.5 (molar ratio)) was filled in the hearth 35 of the third vapor deposition source 34c. The emission current supplied to the electron gun 36 of the first deposition source 34a is set to a value that makes the deposition rate of Zr-Y 6 nm/min, and the emission current supplied to the electron gun 36 of the second deposition source 34b is set to Ti- The deposition of the Zr--Ti--Y--La metal film was started with the value of the La deposition rate of 0.5 nm/min. The Zr--Ti--Y--La metal film was formed until the film thickness reached 3 μm.

The emission current supplied to the electron gun 36 of the second vapor deposition source 34b is adjusted so that the Ti--La film formation rate rises at a constant rate immediately after the start of film formation, and the Ti--La growth rate at the end of the film formation is controlled. The film rate was set to 1 nm/min. After the start of film formation, when the film thickness of the Zr--Ti--Y--La metal film reached 1 μm, the introduction of argon gas into the vacuum chamber 31 was started, and the internal pressure of the vacuum chamber 31 was increased to a constant rate. to make the internal pressure of the vacuum chamber 31 1×10 ⁻³ Pa at the end of the film formation. Furthermore, at the same time as the introduction of the argon gas was started, the supply of the emission current to the electron gun 36 of the third deposition source 34c was started so that the deposition rate of Y was 0.3 nm/min. The emission current supplied to the electron gun 36 of the third evaporation source 34c is adjusted so that the film formation rate of Y rises at a constant rate immediately after the start of film formation, and the film formation rate of Y at the end of film formation is set to zero. 0.5 nm/min.

When the film thickness of the Zr--Ti--Y--La metal film reaches 2.950 μm (50 nm remaining to 3 μm), the emission to the electron gun 36 of the first evaporation source 34a and the electron gun 36 of the third evaporation source 34c The current supply was stopped, the gas introduced into the vacuum chamber 31 was switched from argon gas to nitrogen gas, and a Ti—La nitride film was formed to a thickness of 2 nm. After that, the gas to be introduced into the vacuum chamber 31 is switched from nitrogen gas to argon gas, and the supply of the emission current to the electron gun 36 of the first deposition source 34a and the electron gun 36 of the third deposition source 34c is resumed, and Zr -Ti-Y-La metal film was formed.

Furthermore, when the film thickness of the Zr--Ti--Y--La metal film reaches 2.970 μm (30 nm remaining to 3 μm), the electron gun 36 of the first evaporation source 34a and the electron gun 36 of the third evaporation source 34c The supply of the emission current was stopped, the gas introduced into the vacuum chamber 31 was switched from argon gas to nitrogen gas, and a Ti—La nitride film was formed to a thickness of 2 nm. After that, the gas to be introduced into the vacuum chamber 31 is switched from nitrogen gas to argon gas, and the supply of the emission current to the electron gun 36 of the first deposition source 34a and the electron gun 36 of the third deposition source 34c is resumed, and Zr -Ti-Y-La metal film was formed.
A Zr--Ti--Y--La metal film was formed in the same manner as in Example 1 except for the above points.

[Comparative Example 3]
The emission current of the electron gun 36 of the second vapor deposition source 34b at the start of film formation is set to a value at which the film formation rate of Ti—La is 0.5 nm/min. A Zr--Ti--Y--La metal film was formed in the same manner as in Example 2, except that the deposition source 34c was not used and the conditions at the start of film formation were maintained.

[Comparative Example 4]
The emission current of the electron gun 36 of the second vapor deposition source 34b at the start of film formation is set to a value at which the film formation rate of Ti—La is 1.0 nm/min, and the electron gun 36 of the third vapor deposition source 34c is set at the start of film formation. Then, Zr- was formed in the same manner as in Example 2, except that the supply of the emission current was started so that the deposition rate of Y was 0.5 nm/min, and this condition was maintained at the end of the deposition. A Ti--Y--La metal film was prepared.

[evaluation]
The composition, density, and gas adsorption capacity of the Zr--Ti--Y--La metal films obtained in Example 2 and Comparative Examples 3 and 4 were measured by the methods described above. The results are shown in Tables 2A and 2B. The intermediate portion of the Zr--Ti--Y--La metal film was positioned 1.5 μm from the silicon substrate.

From the results in Tables 2A and 2B, the Zr--Ti--Y--La metal film of Example 2 has a higher It can be seen that the density is lower than that of the second surface and the gas adsorption capacity is improved. This is because the Zr--Ti--Y--La metal film of Example 2 has a Zr mole fraction Zr(1) on the first surface smaller than a Zr mole fraction Zr(2) on the second surface. Since the molar fraction Ti(1) of Ti on the surface is larger than the molar fraction Ti(2) of Ti on the second surface, the first surface is more susceptible to formation of pores than the second surface, and the porous structure is porous. This is because the specific surface area is increased in quality.

In addition, the Zr--Ti--Y--La metal film of Example 2 has significantly improved gas adsorption capability compared to the Zr--Co metal film of Example 1. The reason for this is believed to be the presence of the rare earth element and the nitride layer. In the Zr--Ti--Y--La metal film of Example 2, the content of the rare earth element is higher on the first surface than on the second surface. Since the rare earth elements have high reactivity and strong ionic bonding properties, filling the vacant positions of the alloy film with the rare earth elements has the effect of increasing gas adsorption. For this reason, it is considered that the Zr--Ti--Y--La metal film of Example 2 was more likely to adsorb gas on the first surface. In addition, the nitride layer has the effect of facilitating the formation of holes in the metal film by making the arrangement of the metal elements in the metal film non-uniform. Therefore, in the Zr--Ti--Y--La metal film of Example 2, more holes exist on the first surface, the specific surface area of the first surface increases, and gas is more adsorbed on the first surface. It is considered that the gas adsorbed on the first surface is easily diffused into the metal film, and the gas adsorption capacity is improved as compared with the Zr—Co metal film of Example 1.

[Example 3]
The hearth 35 of the first deposition source 34a was filled with Ni, and the hearth 35 of the second deposition source 34b was filled with Ti. The emission current supplied to the electron gun 36 of the first deposition source 34a is set to a value at which the Ni deposition rate is 6 nm/min, and the emission current supplied to the electron gun 36 of the second deposition source 34b is set to Deposition of the Ni—Ti metal film was started at a rate of 0.5 nm/min. The Ni—Ti metal film was formed until the film thickness reached 2 μm.

The emission current supplied to the electron gun 36 of the second deposition source 34b was adjusted so that the Ti film formation rate increased at a constant rate immediately after the start of film formation, and the Ti film formation rate at the end of the film formation was 1 nm. / minutes. After the start of film formation, when the film thickness of the Ni—Ti metal film reaches 2/3 μm, the introduction of argon gas into the vacuum chamber 31 is started to increase the internal pressure of the vacuum chamber 31 at a constant rate. The internal pressure of the vacuum chamber 31 was set to 1×10 ⁻³ Pa when the film formation was completed.
A Ni—Ti metal film was formed in the same manner as in Example 1 except for the above points.

[Comparative Example 5]
The emission current of the electron gun 36 of the second vapor deposition source 34b at the start of film formation is set to a value at which the film formation rate of Ti is 0.5 nm/min. A Ni—Ti metal film was formed in the same manner as in Example 2, except that the conditions at the start of film formation were maintained without performing the

[Comparative Example 6]
The emission current of the electron gun 36 of the second vapor deposition source 34b at the start of film formation is set to a value at which the film formation rate of Ti is 1.0 nm/min. A Ni—Ti metal film was formed in the same manner as in Example 2, except that the conditions at the start of film formation were maintained without performing the

[evaluation]
The Ni—Ti metal films obtained in Example 3 and Comparative Examples 5 and 6 were measured for composition, density, and gas adsorption capacity by the methods described above. The results are shown in Tables 3A and 3B.

From the results in Tables 3A and 3B, the Ni—Ti metal film of Example 3 has a higher density on the first surface than the density on the second surface compared to the Ni—Ti metal films of Comparative Examples 5 and 6. is small, and it can be seen that the gas adsorption capacity is improved. This is because, in the Ni—Ti metal film of Example 3, the molar fraction Ni(1) of Ni on the first surface is smaller than the molar fraction Ni(2) of Ni on the second surface, and the molar fraction Ni(2) of Ni on the first surface is Since the molar fraction Ti(1) is larger than the molar fraction Ti(2) of Ti on the second surface, the first surface is more likely to form pores than the second surface, is porous, and has a specific surface area of This is because the

Since the metal film according to the first aspect has a high gas adsorption capacity, it can be used as a non-evaporable getter for removing a small amount of gas mixed in a vacuum sealed space or a gas filled space for vacuum sealing of various electronic devices. and MEMS technology.

DESCRIPTION OF SYMBOLS 1, 2... Metal film, 3... Sample, 10... Substrate, 20... Metal film portion, 21... First surface, 22... Second surface, 23... Intermediate, 24... Nitride layer, 30... Electron beam deposition apparatus, 31 Vacuum chamber 32 Substrate holder 33 Motor 34a First vapor deposition source 34b Second vapor deposition source 34c Third vapor deposition source 35 Hearth 36 Electron gun 37 RF coil 38 MFC, 39 Gas introduction tube 40 Oil diffusion pump 50 Gas adsorption rate measuring device 51 Vacuum chamber 52 Sample installation table 53 Thermocouple 54 Heater 55 Heating system 56 Exhaust pump 57 Piping 58 Conductance valve 59a First vacuum gauge 59b Second vacuum gauge 60 Gas supply pipe 61 MFC

Claims (11)

At least two metal elements selected from the group consisting of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Hf, Ta, Pt and Au,
having a first surface and a second surface facing each other;
Among the two kinds of metal elements, the one with a relatively larger atomic number is defined as a metal element A, and the one with a relatively smaller atomic number is defined as a metal element B, and the metal element A and the metal element B on the first surface A metal in which the molar fraction A(1) of the metallic element A with respect to the total of is smaller than the molar fraction A(2) of the metallic element A with respect to the total of the metallic element A and the metallic element B on the second surface film. The molar fraction A(3) of the metal element A with respect to the total of the metal element A and the metal element B between the first surface and the second surface is the mole fraction of the metal element A on the first surface. 2. The metal film according to claim 1, wherein the molar fraction A(2) of the metal element A on the second surface is greater than the fraction A(1). From the molar fraction A(2) of the metal element A to the sum of the metal element A and the metal element B on the second surface, the metal element to the sum of the metal element A and the metal element B on the second surface A value (A(2)-B(2)) obtained by subtracting the mole fraction B(2) of B, and the mole fraction of the metal element A with respect to the sum of the metal element A and the metal element B on the first surface A value obtained by subtracting the molar fraction B(1) of the metal element B with respect to the total of the metal element A and the metal element B on the first surface from the ratio A(1) (A(1)-B(1)) 3. The metal film according to claim 1, wherein the difference between is 0.05 or more. 4. The metal film according to any one of claims 1 to 3, wherein the density on the first surface is lower than the density on the second surface. 5. The metal film according to claim 4, wherein the density on the first surface is 95% or less of the density on the second surface. 6. The metal film according to any one of claims 1 to 5, further comprising a rare earth element. 7. The metal film according to claim 6, wherein the molar content of the rare earth element on the first surface is higher than the molar content of the rare earth element on the second surface. 8. The metal film according to claim 7, wherein the difference between the molar content of the rare earth element on the first surface and the molar content of the rare earth element on the second surface is 3 mol % or more. 9. The metal film according to any one of claims 1 to 8, wherein the film thickness is in the range of 0.5 µm or more and 5.0 µm or less. 10. The metal film according to any one of claims 1 to 9, further comprising a nitride therein. 11. The metal film according to any one of claims 1 to 10, further comprising a substrate, wherein said substrate and said second surface are in contact with each other.

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