Patent Application
20250207228
The present invention relates to an alloy for semiconductor production apparatuses, an alloy member for semiconductor production apparatuses, and a product using the same, in which the alloy is used for chambers or the like of the semiconductor production apparatuses.
Semiconductor chips are obtained by thinning a semiconductor wafer to a predetermined thickness through processes such as a back grind process and an etching process, followed by a dicing process to be divided into individual chips. At this time, processes of adding layers and etching for removing some parts of the semiconductor wafer are repeated inside a chamber.
In such the layering process and etching process, reactive gas is utilized. For example, reactive gas including chlorine and bromine may be used. Such the reactive gas affects not only the semiconductor wafer but also inner surfaces of the chamber or the like, and may make the inner surfaces of the chamber corrode.
To prevent such corrosion in a semiconductor production apparatus, a method for coating surfaces of parts inside a chamber with ceramics such as Al2O3, AlN, and TiN has been proposed (Patent Document 1, for example).
On the other hand, instead of improving corrosion resistance by conventional ceramics coating and the like, there has also been a demand for an improvement on corrosion resistance of an alloy itself that is used as a metal member. Thus, a purpose of the present invention is to provide an alloy for semiconductor production apparatuses, an alloy member for semiconductor production apparatuses, and a product using the same, in which the alloy can be used suitably in the semiconductor production apparatuses.
Non-Patent Documents 1 to 6 disclose technical documents that are necessary to provide supplementary descriptions of embodiments of the present invention. For example, Non-Patent Document 1 describes a method for simulating a process of atomic movements based on a basic equation of quantum mechanics, i.e. the calculation principle of the first principle molecular dynamics method. Since electrons and nuclei forming atoms of a material follow the rules of quantum mechanics, such the simulation can evaluate properties of the material. Non-Patent Document 2 mentions a method for calculating a diffusion coefficient by molecular dynamics simulation. Also, Non-Patent Document 3 mentions a method for calculating adsorption energy by molecular dynamics simulation. Remaining Non-Patent Documents 4 to 6 will be mentioned below in sections describing the embodiments of the present invention.
To achieve the above object, a first aspect of the present invention is an alloy for semiconductor production apparatuses. The alloy includes Ta and Mo as a first element group, at least one type of element selected from a group consisting of Nb, Hf, Zr, Ti, and Was a second element group, and unavoidable impurity elements. The alloy includes 10 at % or more and 35 at % or less of Ta, 5 at % or more and 25 at % or less of Mo, and 10 at % or more and 35 at % or less each of the elements of the second element group. A total of the first element group and the second element group together with the unavoidable elements is 100 at %, and adsorption energy of the alloy with Cl ions and Br radicals is 0.2 eV or less.
The alloy may further include, as a third element group, at least one type of element selected from a group consisting of Au, Pt, and Ag, in which 10 at % or more and 25 at % or less each of the second element group is included, and the total of the first element group, the second element group, the third element group, and the unavoidable elements may be 100 at %.
According to the first aspect of the present invention, since the adsorption energy with chlorine ions and bromine radicals is low and diffusion coefficients for chlorine ions and bromine radicals are small, reactiveness of the alloy to chlorine ions and bromine radicals is low, and thus corrosion resistance can be obtained when the alloy is used in semiconductor production apparatuses.
By further adding the third element group, higher corrosion resistance can be obtained.
A second aspect of the present invention is an alloy member for semiconductor production apparatuses including at least partly an alloy that includes Ta and Mo as a first element group, at least one type of element selected from a group consisting of Nb, Hf, Zr and W as a second element group, and unavoidable impurity elements. The alloy includes 10 at % or more and 35 at % or less of Ta, 5 at % or more and 25 at % or less of Mo, and 10 at % or more and 35 at % or less each of the elements of the second element group. A total of the first element group and the second element group together with the unavoidable elements is 100 at %, and adsorption energy of the alloy with Cl ions and Br radicals is 0.2 eV or less.
The alloy may further include, as a third element group, 10 at % or more and 25 at % or less each of at least one type of element selected from a group consisting of Au, Pt, and Ag, and the total of the first element group, the second element group, the third element group, and the unavoidable elements may be 100 at %.
According to the second aspect of the present invention, since the adsorption energy with chlorine ions and bromine radicals is low, reactiveness of the alloy member to chlorine ions and bromine radicals is low, and thus corrosion resistance can be obtained when the alloy member is used in semiconductor production apparatuses.
By further adding the third element group, higher corrosion resistance can be obtained.
A third aspect of the present invention is a product including at least partly the alloy member for semiconductor production apparatuses according to the second aspect of the present invention.
The product may be a semiconductor production apparatus.
According to the third aspect of the present invention, the product using the alloy member for semiconductor production apparatuses with high corrosion resistance can be obtained. More particularly, a semiconductor production apparatus with high corrosion resistance can be obtained.
The present invention can provide an alloy for semiconductor production apparatuses, an alloy member for semiconductor production apparatuses, and a product using the alloy member, in which the alloy is suitable to be used in the semiconductor production apparatuses.
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. For example, for a semiconductor production apparatus to obtain corrosion resistance to halogen ions and radicals included in corrosive gas (may be referred to as “corrosive gas resistance”), it is required not to react easily with chlorine ions, chlorine radicals, bromine ions, bromine radicals, and the like (hereinafter, simply referred to as “chlorine ions and the like”). Thus, for the non-reactiveness to chlorine ions and the like, which is regarded highly in the present invention, it is important to make sure that adsorption with chlorine ions and the like is difficult (chlorine ions and the like can hardly approach) and intrusion by chlorine ions and the like is difficult (chlorine ions and the like can hardly spread from surfaces).
Difficulty of adsorption with chlorine ions and the like is expressed as how low adsorption energy (may also be referred to as detachment energy), such as the one disclosed in Non-Patent Document 5, is: the lower the adsorption energy is, the harder the adsorption becomes. The adsorption energy is found by calculation, and a method for the calculation will be described below.
Dominant factors of the adsorption energy are lattice constants and a lattice mismatch, which is a relative difference between the lattice constants, as shown in Non-Patent Document 6, for example. That is, the lattice constants and the lattice mismatch, which is the relative difference between the lattice constants, are more dominant factors than other factors such as surface energy, cohesive energy, and electronegativity. Thus, the inventor of the present invention has paid attention to the lattice mismatch, which is the relative difference between the lattice constants, and then has found out that, by using a material having the large lattice mismatch with chlorine ions and the like, it is possible to obtain corrosive gas resistance. The lattice mismatch is sometimes referred to as lattice inconsistency and can be found by calculation. A method of the calculation will be described below.
As an example in which the lattice mismatch is paid attention to in the conventional field of metal materials, Non-Patent Document 5 describes bonding strength such as interface strength between a wiring film and a barrier film of an electron component, in which an attempt to reduce the lattice mismatch as much as possible, ideally to zero, has been made. Contrary to the above, the present invention aims to obtain resistance to chlorine ions and the like, i.e. non-reactiveness to chlorine ions and the like, by increasing the lattice mismatch, which is an idea opposite to the conventional one.
It is also important, to enhance the corrosive gas resistance, that the chlorine ions and the like do not intrude from surfaces and react with the alloy. Difficulty of intrusion by chlorine ions and the like is evaluated by a diffusion coefficient from the surface to the inside. Results of a study on relationships between the lattice mismatch and the diffusion coefficients for chlorine ions and the like of some alloys show that the larger the lattice mismatch is, the more the adsorption energy and the diffusion coefficients for chlorine ions and the like (hereafter, may be simply referred to as diffusion coefficients) can be suppressed. The diffusion coefficient for chlorine ions and the like can be found by calculation, and a method for the calculation will be described below.
Next, an alloy according to the embodiment will be described in detail. The inventor of the present invention has found out from results of earnest studies that a multiple element alloy including Ta and Mo as main constituents (a total of Ta and Mo is 15 at % or more, for example) has a relatively large lattice mismatch with chlorine ions and the like, and, as a result, has the small adsorption energy and diffusion coefficients, thereby showing excellent properties. Table 1 shows each composition range of the alloy according to the present embodiment.
The alloy according to the present embodiment includes, as a first element group, Ta and Mo. Also, the alloy may further include, as a second element group, at least one type selected from a group consisting of Nb, Hf, Zr, and W. When a total of the first element group and the second element group is 100 at %, Ta included is 10 at % or more and 35 at % or less (at %: element ratio; hereafter, written as 10−35 at %), Mo included is 5-25 at %, and each of the elements of the second element included is 10−35 at %. Furthermore, as a third element group, at least one type selected from a group consisting of Au, Pt, and Ag may also be included. If the third element group is included, an amount of each element of the third element group included is 10 at %-25 at %, provided that the total of the first element group, the second element group, and the third element group is 100 at %.
The ranges of the element ratios of the first, second, and third element groups are acknowledged as content amounts of elements constituting a high entropy alloy. The element ratios of all the elements constituting the alloy may be equal. For example, an amount of each constituting element included is less than 50 at % at most, and preferably 35 at % or less. Also, with the third element group being included, although mechanical properties may be deteriorated, higher corrosion gas resistance can be obtained. The alloy according to the present embodiment may include unavoidable impurities. For example, 500 ppm or less each of unavoidable elements such as C, N, and O may be included.
Also,
Next, each items to be evaluated for the alloy according to the present embodiment will be described in detail.
As mentioned above, it is preferable that the alloy according to the present embodiment has the small adsorption energy and the small diffusion coefficient to prevent chlorine ions and the like from reacting by approaching surfaces thereof or even intruding therein.
(Adsorption Energy with Chlorine Ions and the Like)
To enhance resistance to corrosive gas, that is, to be difficult to react with chlorine ions and the like when in contact with chlorine ions and the like, it is important to have a state in which it is hard for chlorine ions and the like to approach and adsorp. How easy it is for chlorine ions and the like to adsorp can be evaluated by the adsorption energy, which will be described below: the smaller the adsorption energy is, the more difficult it is to adsorp. Details will be described along with simulations described below.
As mentioned above, the alloy according to the present embodiment has the adsorption energy with chlorine ions and the like (adsorption energy at 800° C., for example) of 0.2 eV or less. The adsorption energy can be considered as one of indicators that show resistance to chlorine ions and the like. In the present embodiment, the adsorption energy is more preferably 0.15 eV or less at a room temperature, further preferably 0.1 eV or less, further preferably 0.05 eV or less, further preferably 0.035 eV or less, or furthermore preferably 0.031 eV.
To improve the resistance, it is important that chlorine ions and the like do not intrude from the surface and react. How easy it is for chlorine ions and the like to intrude can be evaluated by a coefficient of diffusion from the surface to the inside. The diffusion coefficient can be considered as one of indicators that show resistance to chlorine ions and the like. Details of the diffusion coefficient will be described below.
Crystal structures of the alloy according to the present embodiment are all in body-centered cubic structures (bcc). The crystal structures can be observed under an X-ray diffraction (XRD). The alloy may have a single type of the bcc structure or multiple types of the bcc structures. Also, it is most preferable that an entire system of the alloy according to the present embodiment includes the body-centered cubic structures. However, the system of the alloy may include, as a volume ratio (content ratio), 60% or more, or more preferably 80% or more, of the body-centered cubic structures.
Next, the calculation method for each item in the present embodiment will be described. Each item can be calculated by using molecular dynamics simulation as disclosed in Non-Patent Document 1, etc.
Lattice constants for calculating the lattice mismatch are defined as follows based on Non-Patent Document 5. That is, mismatches of a short side lattice constant ‘a’ and a long side lattice constant ‘b’ of a face-centered rectangular lattice, which represents a plane with the highest atomic density, i.e., the closest-packed crystal plane described below, are expressed in percentages, and the short side lattice mismatch is represented byΔa and the long side lattice mismatch is represented byΔb. SinceΔa having a shorter interatomic distance is more important, Aa is considered as the lattice mismatch in the present embodiment, unless otherwise specified. Note that it is known from Non-Patent Document 5 etc. that crystal planes other than the closest-packed crystal plane defined here contribute less to the adsorption energy and have fewer effects. Thus, the closest-packed crystal plane is taken as a basis for the decision.
To calculate the lattice mismatch defined above, the above-mentioned ‘a’ and ‘b’ can be calculated by performing relaxation calculations and finding a stable crystal structure using a molecular dynamics simulation such as the one described in Non-Patent Document 5, and the lattice mismatch can be calculated based thereon. The lattice constant and the lattice mismatch are calculated using self-made molecular dynamics software, and in parallel, calculations are performed using Dmol3 and Forcite of Dassault Systemes' Materials Studio, and it was confirmed that both the results are consistent with each other.
Adsorption energy represents energy required to change an adsorption state into a detached state, and the adsorption energy can be obtained by, as shown as an equation (3) in Non-Patent Document 3, subtracting energy of the adsorption state from energy of the detached state. The adsorption energy is calculated using self-made molecular dynamics software, and in parallel, calculations are performed using Dmol3 and Forcite of Dassault Systemes' Materials Studio, and it was confirmed that both the results are consistent with each other. The higher the adsorption energy is, the easier the adsorption is.
The diffusion coefficient can be found, as shown as an equation (2) in Non-Patent Document 2, from the following Einstein relation: Equations 1 (an equation (A) and an equation (B)).
In the equation (B), a mean-square displacement from a time to, which is a reference time set after sufficient relaxation, to a time t+t0 is divided by 6t, converging in limited time steps in reality. Thus, the diffusion coefficient can be calculated without calculating up to infinity. Note that ri(t+t0)−ri (t0) can be calculated from a motion equation. When calculating the diffusion coefficient for intrusion in a direction perpendicular to an interface, the diffusion coefficient can be calculated from the mean square displacement of the displacement in that direction. The larger the diffusion coefficient is, the easier the intrusion is. This means that chlorine ions and the like easily intrudes from the surface and reacts.
Next, each alloy according the present embodiment will be described. Table 2 shows results of the calculation of adsorption energy and diffusion coefficients of thirteen types of alloys according to the present embodiment. The total of each alloy is 100 at %, and the element ratios of the alloys are shown in Table 3, respectively. The calculation results of the lattice mismatch are omitted.
In all calculations, the results show that all the alloys according to working examples have sufficient properties in that the adsorption energy with chlorine ions and the like is 0.2 eV or less (0.05 eV or less), and the diffusion coefficients for chlorine ions and the like are 1.0×10−22 m2/s or less (1.0×10−24 m2/s or less for chlorine ions). In particular, excellent results are obtained for the alloys including Au, Pt, and Ag, in which the adsorption energy with chlorine ions and the like is 0.032 eV or less at a room temperature and the diffusion coefficients for chlorine ions and the like are 4.0×10−27 m2/s or less.
As above, the alloy according to the present embodiment can be applied to an alloy member that at least partly includes the alloy (e.g., as a surface of a base material), and to a product that at least partly includes the alloy member. More specifically, it is preferable that the alloy is applied to inner surfaces or the like of a chamber in a semiconductor production apparatus. For example, the alloy can be shaped into a product by emitting an electron beam or a laser beam onto alloy powder having a desired element ratio to be melted and solidified.
Although the embodiments of the present invention have been described referring to the attached drawings, the technical scope of the present invention is not limited to the embodiments described above. It is obvious that persons skilled in the art can think out various examples of changes or modifications within the scope of the technical idea disclosed in the claims, and it will be understood that they naturally belong to the technical scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-008439 | Jan 2022 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2023/002127 | 1/24/2023 | WO |
