RU2841367C1 - Sputtered magnetron assembly for the v-nb-mo-ta medium-entropy four-component alloy films deposition - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: disclosed is sputtered magnetron assembly for deposition of films of medium-entropy four-component alloy V_0.25Nb_0.25Mo_0.25Ta_0.25. Said assembly contains parallel-arranged sprayed metal plates, designed with the possibility of installation on the same axis with the magnetron and rigidly attached to it, and an additional lower cooled copper plate. Spraying assembly consists of four sprayed metal plates. Inner plate is made from tantalum in form of solid disc. Other three plates are successively made from molybdenum, niobium and vanadium and are in form of rings whose inner radii provide equal streams of tantalum, molybdenum, niobium and vanadium. Magnetron has an annular sputtering zone.

EFFECT: design of the sputtered magnetron unit, which provides deposition of films of medium-entropy four-component alloy V_{0_25}Nb_{0_25}Mo_{0_25}Ta_{0_25}.

1 cl, 3 dwg, 2 tbl

Description

The magnetron unit is a device used for synthesizing films of four-component alloys in the nuclear industry, mechanical engineering, automotive industry, etc.

Traditional metal alloys most often contain one main element. Twenty years ago, it was proposed to form alloys containing several metals in equimolar or nearly equimolar concentrations [doi:10.1016/j.msea.2003.10.257]. Such alloys, containing 3-4 metals, were called "medium-entropy". Medium-entropy alloys, with a unique compositional configuration, acquire high strength, excellent corrosion resistance, strong resistance to hydrogen embrittlement, etc. Films of these alloys are potential candidates for modifying the surface of materials operating under conditions of extremely high temperatures, increased radiation, chemical and mechanical effects. Films of alloys containing, for example, transition metals such as V, Nb, Ta, etc., have an excellent combination of strength and ductility both at room and cryogenic temperatures and have outstanding corrosion resistance [doi:10.1016/j.msea.2021.141908].

A magnetron with a sandwich target is effectively used for deposition of alloy films. For example, a magnetron described in the patent for utility model of the Russian Federation No. 207556 is known. The sputtering unit in it contains a target and a cooling plate. The target is made of two metal plates parallel to each other, located on the same axis with the cooling plate and rigidly attached to it. The inner plate is made of iron, and the outer one is made of nickel. In the erosion zone of the outer plate, slots are made, located symmetrically relative to its center. The technical result achieved is the creation of a unit that allows increasing the range of films obtained with a uniform chemical composition over the entire area, allowing deposition of films from ferromagnetic binary alloys.

The closest to the proposed device in terms of the set of essential features is the sputtering unit described in the patent for invention of the Russian Federation No. 2808293 "Sputtering unit of a magnetron for deposition of composite multicomponent films of Ni _0.60 Co _0.3 Fe _0.1 ". This unit contains a target rigidly attached to the magnetron coaxially with it, and an additional lower cooled copper plate. The target contains three plates made of different metals (iron, cobalt and nickel). The four plates mentioned are located in parallel and mounted on the same axis. In the emission zones of the two upper plates, slits are made in the form of holes located symmetrically relative to their center. The achieved technical result is the creation of such a design of the sputtering unit of the magnetron, which will allow the formation of flows of components of the deposited Ni0.60Co0.3Fe0.1 film with identical energy spectrum and an increase in the total heat flow emitted by the target.

The disadvantage of the known device is that its design does not allow deposition of films of equimolar composition. To solve this problem, it is necessary to ensure identical sprayed metal flows generated by each plate. With any total area of the slits in the outer plate, the metal flow it generates will be greater than the flows from the underlying plates.

The problem, which the claimed invention is aimed at solving, is the creation of such a design of the sputtering unit of the magnetron, which will allow the deposition of films of the medium-entropy four-component alloy V _0.25 Nb _0.25 Mo _0.25 Ta _0.25 .

The stated problem is solved due to the fact that the sputtering unit of the magnetron for depositing films of the medium-entropy four-component alloy V-Nb-Mo-Ta, like the known unit, contains parallel-arranged sputtering metal plates installed on the same axis with the magnetron and rigidly attached to it, and an additional lower cooled copper plate, wherein the unit is placed in plasma-forming argon, characterized in that it consists of four sputtering metal plates, the inner one is made of tantalum in the form of a solid disk, the other three are made of Mo, Nb and V, for a magnetron having an annular sputtering zone, they are rings with internal radii R _Mo , R _Nb and R _V .

The achieved technical result is the creation of such a design of the sputtering unit of the magnetron that will allow the deposition of films of the medium-entropy four-component alloy V _0.25 Nb _0.25 Mo _0.25 Ta _0.25 .

Fig. 1 - design of the sputtering unit of the magnetron;

Fig. 2 - dependences on the discharge current of the flux density of metals J _i , i = Ta, Mo, Nb, V, which are generated by the target plates;

Fig. 3 - dependences on the discharge current of the metal flows Q _i , i = Ta, Mo, Nb, V and the total flow ΣQ _i .

Let us consider an example of the implementation of the sputtering unit of the magnetron (Fig. 1). The model of the proposed invention was implemented on the basis of a balanced cylindrical magnetron 1, on which the authors performed experiments. The sputtering unit contains on one axis an internal water-cooled plate 2 with a thickness of 4 mm, made of copper. Then the sputtering plates are installed: 3 - solid, 1 mm thick - made of tantalum, 4 - ring with an internal radius R _Mo 1 mm thick - made of molybdenum, 5 - ring with an internal radius R _Nb 1 mm thick - made of niobium, 6 - ring with an internal radius R _V 1 mm thick - made of vanadium. The entire structure is rigidly fastened with bolts 7 to the magnetron body and placed in a gaseous medium consisting of plasma-forming argon. Washers 8 1 mm thick are installed between the plates, providing a gap between them. The annular spray area is limited by radii R ₀₁ = 20 mm and R ₀₂ = 40 mm. The lower copper plate 2 functions as a cooler, removing excess heat from the sprayed unit, and is not subject to spraying. Plates 3-6 operate in a free thermal mode, i.e. they are cooled by radiation and thermal conductivity of the fastening elements.

The erosion zones 9, 10, 11 and 12 of the solid tantalum plate 3, the ring molybdenum 4, niobium 5 and vanadium ring plates 6, respectively, have the shape of rings with an area of:

(1) (2) (3) (4)

The device operates as follows (see Fig. 1). The process is carried out in an argon environment. At an argon pressure of 4-8 mTorr, a direct current gas discharge is initiated in a vacuum chamber using a magnetron, maintaining it in the range of 1.0 to 5.0 A. The magnetron used is balanced. This means that the magnetic field configuration in it provides an annular zone of intense target sputtering with internal and external radii R ₀₁ and R ₀₂ , respectively. Further, we will assume that the current density is distributed uniformly in this area. Along with the discharge current and argon pressure, the internal radii of the annular plates are independent variables of the device.

Each plate, due to the effect of the argon ion flow, becomes a generator of the flow of the corresponding metal: Q _Ta , Q _Mo , Q _Nb and Q _V , the densities of which are equal to

(5) (6) (7) (8)

where S _Ta , S _Nb , S _Mo and S _V are the metal sputtering coefficients; j is the discharge current density; e = 1.6⋅10- ¹⁹ C is the electron charge; γ _Ta , γ _Nb , γ _Mo and γ _V are the ion-electron emission coefficients of metals. Expressions (5)-(8) take into account only the flows that arise due to sputtering with argon ions. The flows possible due to evaporation of the plates are neglected. In (5)-(8), the notations a _i , i = Ta, Mo, Nb, V are introduced to shorten the notation. The formulas for these quantities can be presented in the general form

(9)

To solve the problem of depositing a film of a medium-entropy four-component alloy, it is necessary to determine the internal radii of the ring-shaped plates of the target. If we take into account that each of the plates generates a metal flow:

(10)

then the condition for the formation of an equimolar film is the equality of flows (10):

(11)

It is more convenient to express the system of equations (11) in relative form:

(12)

In expanded form, the system of equations (12) takes the form:

(13)

The solution to system (13) is the values of the radii of the ring-shaped plates R _V , R _Nb and R _Mo , which provide the solution to the problem. In general, we write the solution to system (13) in a form convenient for interpretation:

(14)

Solution (14) is obtained using the values of the physical parameters of the plate materials given in Table 1.

Table 1 Parameter Metal (i) Ta Mo Nb V S _i 0.40 0.60 0.45 0.65 γ _i 0.057 0.036 0.044 0,050 a _i 2.37⋅10 ¹⁸ 3.62⋅10 ¹⁸ 2.69⋅10 ¹⁸ 3.78⋅10 ¹⁸

Based on (14), we write the formulas for calculating the internal radii of the plates in the form

(15)

From (15) it is evident that the radii of the ring-shaped target plates are uniquely related to the parameters of the ring-shaped sputtering region. They are the hypotenuses of right triangles whose legs are proportional to the inner and outer radii of this region.

We use solution (15) to analyze the particular case of the magnetron used in our experiments. The design of the magnetic system of this device provides a ring-shaped sputtering region with inner and outer radii of 2.0 and 4.0 cm, respectively. The area of this region is , Then the discharge current density in the accepted current range of 1-5 A changes from 0.03 to 0.13 A/cm ² .

Table 2 Parameter Metal (i) Ta Mo Nb V R _i , cm - 2.8 3.2 3.7 s _i , cm ² 12.0 7.8 10.5 7.3

The values of the target plate radii calculated using formulas (15) and the corresponding areas of the sputtered regions (1)-(4) are shown in Table 2. Fig. 2 shows the dependences of the metal flux density calculated using formulas (5)-(8). The difference in values observed in Fig. 2 is due to the obvious difference in the physical parameters of the materials indicated in Table 1.

Fig. 3 shows the dependences of the metal flows that generate different plates, calculated from the curves in Fig. 2 taking into account (10), and the dependence of the total flow that forms the alloy film.

Fig. 3 shows that the set goal has been achieved. The proposed magnetron unit with the given parameters allows depositing films of medium-entropy alloys containing four components, since the metal flows generated by different target plates are equal to each other in the entire observed range of discharge currents. Experimental studies with a sputtering unit, the plates of which were manufactured in accordance with formulas (15), confirmed the results of the analysis performed.

Claims (2)

A sputtering unit of a magnetron for depositing films of the medium-entropy four-component alloy V _0.25 Nb _0.25 Mo _0.25 Ta _0.25 , comprising parallel sputtering metal plates made with the possibility of being installed on the same axis with the magnetron and rigidly attached to it, and an additional lower cooled copper plate, wherein the unit is placed in plasma-forming argon, characterized in that it consists of four sputtering metal plates, the inner one is made of tantalum in the form of a solid disk, the other three, sequentially made of molybdenum, niobium and vanadium for a magnetron having an annular sputtering zone with inner and outer radii R ₀₁ and R ₀₂ , respectively, represent rings, the inner radii of which, providing equal flows of tantalum, molybdenum, niobium and vanadium, are determined by the relations: