A N element regulates Ta 0.5 W 0.5 Nx hard film method

Abstract

The invention discloses a method for regulating Ta by N element 0.5 W 0.5 N x The method for forming a hard film comprises the following steps: using a Ta target and a W target as target materials, using argon as sputtering gas and nitrogen as reaction gas, and obtaining a Ta film on a substrate by DC magnetron sputtering the target material. 0.5 W 0.5 N x Hard film. The present invention uses multi-target DC magnetron sputtering from W2N to Ta 0.5 W 0.5 N x Transition design of thin films, using nitrogen content to control Ta 0.5 W 0.5 N x The valence electron concentration of the film allows tungsten to replace tantalum to prepare a single-phase solid solution structure film with an x ​​value of 0.82~1.02. Its surface combines the advantages of ductile metal materials tungsten and nitride to form a property of high hardness and toughness, which can effectively improve the strength and toughness of the film, and also has better durability in terms of wear resistance, which is beneficial to extending the service life of the tool.

Description

Technical Field

[0001] The present invention relates to a high-hardness and high-toughness ternary nitride hard film, in particular to a method for regulating Ta by N element. 0.5 W 0.5 N x The invention discloses a method for preparing a hard film, and belongs to the field of material surface protection. Background Art

[0002] With the rapid development of various industries such as industrial technology manufacturing and the national call for energy conservation and emission reduction, a large number of new materials and processes have been introduced, among which high hardness, high toughness and friction-resistant thin film materials have become the best. However, high hardness usually leads to brittle fracture of cracks. In order to avoid film failure caused by cracking, the film must improve both hardness and ductility, but it is often difficult to have both. The non-stoichiometric method based on the principle of regulating the valence electron concentration has advantages in improving the hardness and toughness of transition metal nitride (TMNs) single-phase solid solution. Therefore, it is of great significance to study the non-stoichiometric method to prepare surface protection materials with excellent mechanical properties. For metastable ternary nitrides with a single-phase solid solution structure, the actual structure of the film during the preparation process will deviate from the stoichiometric ratio, resulting in a decrease in performance, and the formation of point defects regulated by the N content can improve the above problems to a certain extent. Summary of the invention

[0003] In order to avoid brittle fracture of the film due to high hardness, the non-stoichiometric ratio method has advantages in improving the hardness and toughness of the film. However, in the preparation process, the actual structure of the film will deviate from the stoichiometric ratio, resulting in performance degradation. The formation of point defects regulated by the N content can improve this problem to a certain extent. The purpose of the present invention is to provide a method for regulating the Ta content by the N element. 0.5 W 0.5 N x Hard film method to extend the service life of the tool.

[0004] The technical solution to achieve the purpose of the present invention is: a N element regulates Ta 0.5 W 0.5 N x Hard film method, the Ta 0.5 W 0.5 N x The value of x in the hard film ranges from 0.82 to 1.02, preferably 0.93, and comprises the following steps:

[0005] Using Ta target and W target as target materials, argon as sputtering gas and nitrogen as reaction gas, the target material is sputtered by DC magnetron to obtain Ta on the substrate. 0.5 W 0.5 N x Hard film.

[0006] Preferably, the total flow rate of nitrogen and argon gas is 40 sccm, wherein the volume proportion of nitrogen gas is 10-30%.

[0007] Preferably, the substrate is a single crystal Si (100) substrate or a 718 high temperature nickel-based alloy.

[0008] Preferably, the sputtering temperature is 300±20°C, the sputtering time is 35-40 min, the sputtering current of the Ta target is 271 mA, and the sputtering current of the W target is 180 mA.

[0009] Preferably, before sputtering, a 80-100 nm W2N transition layer is deposited on the substrate.

[0010] Compared with the prior art, the advantages of the present invention are:

[0011] 1. Delta-TaN with the highest hardness x It can form a miscible Ta with tungsten metal which has good ductility. 0.5 W 0.5 N x Composite system, the hardness of this composite film is better than that of binary δ-TaN x The film's higher mechanical properties and wear resistance make it more advantageous in the field of extending tool life.

[0012] 2. The present invention can optimize the combination of strength characteristic bond strength and extension characteristic bond strength by regulating the valence electron concentration through the N content to prepare Ta with excellent performance 0.5 W 0.5 N x Hard film.

[0013] 3. The film preparation method of the present invention is easy to operate, highly repeatable, and very suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The Ta prepared by the present invention 0.5 W 0.5 N x Schematic diagram of the film structure.

[0015] Figure 2 Ta prepared by the present invention 0.5 W 0.5 N x Thin film: (a) XRD pattern, (b) grain size diagram.

[0016] Figure 3 The Ta prepared by the present invention 0.5 W 0.5 N xSEM cross-sectional morphology of the film.

[0017] Figure 4 The Ta prepared by the present invention 0.5 W 0.5 N x XPS spectra of the film: (a) Ta 4f; (b) W 4f;

[0018] (c) N 1s.

[0019] Figure 5 The Ta prepared by the present invention 0.5 W 0.5 N x XPS valence band spectrum of the film.

[0020] Figure 6 The Ta prepared by the present invention 0.5 W 0.5 N x Thin film mechanical testing: (a) hardness and elastic modulus diagram, (b) toughness index H / E and H 3 / E 2 .

[0021] Figure 7 The Ta prepared by the present invention 0.5 W 0.5 N x Fracture toughness values ​​of thin film mechanical properties tests.

[0022] Figure 8 The Ta prepared by the present invention 0.5 W 0.5 N x Thin film friction performance test: (a) friction curve, (b) average friction coefficient and wear rate diagram. DETAILED DESCRIPTION

[0023] In recent years, δ-TaN x The film has attracted wide attention due to its excellent performance. Based on the existing research results, scholars have summarized some cubic B1 NaCl structure δ-TaN x Unique effects, such as the highest hardness (30-33 GPa) in TMN binary compounds, valence electron concentration close to the optimal value of toughness, the highest metal bonding characteristics, good stability at high temperatures, and theoretically supports up to 20% vacancy density. At the same time, tungsten is a ductile metal material with good ductility, so the combination of tungsten and δ-TaN x Features 0.5 W 0.5 N x Hard film has become a new type of toughened and friction-resistant protective film with development potential.

[0024] The present invention uses multi-target DC magnetron sputtering to convert W2N into Ta 0.5 W 0.5 N x Transition design of thin films, using nitrogen content to control Ta 0.5 W 0.5 N x The valence electron concentration of the film allows tungsten to replace tantalum to prepare a single-phase solid solution structure film with an x ​​value of 0.82~1.02. Its surface combines the advantages of ductile metal materials tungsten and nitride to form a property of high hardness and toughness, which can effectively improve the strength and toughness of the film, and also has better durability in terms of wear resistance, which is beneficial to extending the service life of the tool.

[0025] The specific implementation of the present invention is further described in detail below in conjunction with the drawings and examples. Example 1

[0026] 1. Prepare the target: Select a Ta target with a size of Φ 60×4 mm and a purity of 99.99% and a W target with a size of Φ 60×5 mm and a purity of 99.95%.

[0027] 2. Prepare the substrate: This example uses a polished single crystal silicon (100) substrate and a 718 high temperature nickel-based alloy, where the single crystal Si substrate is used for thin film structure analysis and mechanical properties testing, and the 718 high temperature nickel-based alloy is used for friction performance testing. Specifically, the following steps are included:

[0028] (1) Use wire cutting equipment to cut 718 alloy into a disk substrate with a size of Φ 20×2 mm. Subsequently, use 180#, 400#, 600#, and 800# metallographic sandpaper to polish it in turn to eliminate the scratches caused by cutting. Then use W5 and W2.5 diamond polishing pastes of different types to polish the substrate to a mirror surface. Finally, place the substrate in anhydrous ethanol, clean it with ultrasonic waves for 10 minutes and dry it. Cut the single crystal silicon with a size of 4 cm×4 cm into a size of 1×4 cm.

[0029] (2) The target material and the substrate are placed on the sample stage and the evaporation source position in the vacuum chamber of the DC magnetron sputtering equipment respectively.

[0030] 3. Sputtering deposition thin film:

[0031] (1) Close the vacuum chamber and sample stage valves, turn on the cooling water and vacuum gauge, start the mechanical pump, and start the pre-vacuum state of the vacuum chamber. Wait until the air pressure reaches 6.0×10 -3 Pa, open the molecular pump and the gate valve to further evacuate the air to 4.0×10 -3 Pa.

[0032] (2) After the vacuum is completed, Ar is introduced, and the Ta target W target power is adjusted to 30 W for pre-sputtering for 5 minutes to remove oxides and contaminants on the target surface, while heating to 300 °C.

[0033] (3) After the pre-sputtering, the sample stage valve was opened and kept rotating, N2 was introduced, and the Ar:N2 ratio was adjusted to 36:4 sccm, the total flow rate was 40 sccm, the working pressure was 0.45 Pa, the W target power was 135 mA, and a W2N transition layer was generated on the substrate surface for 8 min with a thickness of about 80-100 nm.

[0034] (4) The N2 flow rate was adjusted to 20 vol%, that is, Ar:N2 was 32:8 sccm. Based on the goal of preparing the nitride film of the present invention, the Ta target current was maintained at 271 mA, the W target current was maintained at 180 mA, the coating was carried out for 35 minutes, x was 0.93, the film grain size was 18.6 nm, and the total thickness was 803.5 nm.

[0035] 4. Turn off the target power supply, turn off the gas, wait for the temperature to drop to 160°C, then turn off the equipment power supply, and then take out the film after the vacuum chamber cools naturally to room temperature.

[0036] 5. Test the properties of the film samples: hardness is 44.1 GPa, elastic modulus is 254.2 GPa, toughness index H / E and H 3 / E 2 They are 0.17 and 1.32 GPa respectively, and the fracture toughness value is 2.0 MPa·m 1 / 2 , the friction coefficient is 0.37, and the volume wear rate is 0.73×10 -6 mm 3 / (m·N).

[0037] Figure 1 is the Ta of the thin film sample of this embodiment 0.5 W 0.5 N x The structure of the hard film is W2N transition layer and Ta from the inside to the outside of the substrate surface. 0.5 W 0.5 N x film.

[0038] Figure 2 (a) XRD spectrum and (b) grain size diagram of the film sample of Example 1. Jade analysis shows that the film is a single-phase FCC solid solution structure, and the calculated grain size is 18.6 nm.

[0039] Figure 3: is the SEM cross-sectional morphology of the film sample of Example 1. The film has a typical columnar crystal structure and a thickness of 803.5 nm.

[0040] Figure 4 XPS spectra of the film sample of this embodiment (a) Ta 4f; (b) W 4f; (c) N 1s. It can be analyzed from the figure that with the increase of N content, the metallic property of the film is enhanced and the ductility is slightly weakened.

[0041] Figure 5 The valence electron spectrum of the thin film sample of this embodiment shows that the A peak corresponds to the metallic characteristic. d - t 2g (Ta)- d - t 2g (W) state; the B peak corresponds to p (N) and metal de g The interaction between (Me) orbitals indicates that TMN has high-intensity characteristics; the C peak is due to s (N)- s (Me) σ Track, Case 1 The improvement of film hardness is due to the first neighbor covalent bond strength characteristic p (N)- d - e g (Me), the toughness enhancement is due to the secondary adjacent metal-metal bonds that contribute to ductility d - t 2g (Ta)- d - t 2g (W) Still very strong.

[0042] Figure 6 (a) hardness and elastic modulus diagram and (b) toughness index H / E and H of the film sample of this embodiment 3 / E 2 The hardness of the film of Example 1 reaches a maximum value of 44.02 GPa, which is an increase of 32%. At this time, the elastic modulus is 254.2 GPa, and the toughness indexes H / E and H 3 / E 2 The maximum values ​​are 0.17 and 1.32 GPa, respectively, and the film has the highest hardness and toughness.

[0043] Figure 7 is a graph of the toughness index fracture toughness value of the samples in this embodiment, and the film of Example 1 K IC The highest is 2.0MPa·m 1 / 2, indicating that the film has excellent resistance to crack growth.

[0044] Figure 8 The friction coefficient of the film of Example 1 is as low as 0.37. According to the friction and wear coefficient curve, the volume wear rate of the film is only 0.7×10 -6 mm 3 / (m·N), indicating that the film has good wear resistance.

[0045] Embodiment 2:

[0046] Step 1, step 2, (1), (2) and (3) in step 3 and step 4 are the same as those in Example 1;

[0047] Among them, in step 3 (4), keep other conditions unchanged, adjust the N2 flow rate to 10%, that is, Ar: N2 is 36: 4 sccm, the film composition x is 0.82, the film grain size is 25.8 nm, and the total thickness is 1.18 μm.

[0048] The properties of the tested film samples are as follows: hardness is 33.4 GPa, elastic modulus is 320.3 GPa, toughness index H / E and H 3 / E 2 They are 0.12 and 0.52 GPa respectively, and the fracture toughness value is 1.38 MPa·m 1 / 2 , the friction coefficient is 0.66, and the volume wear rate is 10.19×10 -6 mm 3 / (m·N). Example 3

[0049] Step 1, step 2, (1), (2) and (3) in step 3 and step 4 are the same as those in Example 1;

[0050] Among them, in step 3 (4), keep other conditions unchanged, adjust the N2 flow rate to 15%, that is, Ar: N2 is 34: 6 sccm, the film composition x is 0.89, the film grain size is 21.8 nm, and the total thickness is 880 nm.

[0051] The properties of the tested film samples are as follows: hardness is 37.7 GPa, elastic modulus is 239.0 GPa, toughness index H / E and H 3 / E 2 They are 0.14 and 0.65 GPa respectively, and the fracture toughness value is 2.51 MPa·m 1 / 2 , the friction coefficient is 0.51, and the volume wear rate is 10×10 -6 mm 3 / (m·N). Example 4

[0052] Step 1, step 2, (1), (2) and (3) in step 3 and step 4 are the same as those in Example 1;

[0053] Among them, in step 3 (4), keep other conditions unchanged, adjust the N2 flow rate to 25%, that is, Ar: N2 is 30: 10 sccm, the film composition x is 0.98, the film grain size is 16.6 nm, and the total thickness is 783.5 nm.

[0054] The properties of the tested film samples are as follows: hardness is 41.2 GPa, elastic modulus is 309.6 GPa, toughness index H / E and H 3 / E 2 They are 0.13 and 0.73 GPa respectively, and the fracture toughness value is 1.81 MPa·m 1 / 2 , the friction coefficient is 0.30, and the volume wear rate is 4.23×10 -6 mm 3 / (m·N). Example 5

[0055] Step 1, step 2, (1), (2) and (3) in step 3 and step 4 are the same as those in Example 1;

[0056] Among them, in step 3 (4), keep other conditions unchanged, adjust the N2 flow rate to 30%, that is, Ar: N2 is 28: 12 sccm, the film composition x is 1.02, the film grain size is 14.5 nm, and the total thickness is 702.3 nm.

[0057] The properties of the tested film samples are as follows: hardness is 33.6 GPa, elastic modulus is 298.8 GPa, toughness index H / E and H 3 / E 2 They are 0.11 and 0.42 GPa respectively, and the fracture toughness value is 1.63 MPa·m 1 / 2 , the friction coefficient is 0.39, and the volume wear rate is 7.72×10 -6 mm 3 / (m·N).

[0058] In summary, the present invention is to 0.5 W 0.5 N x The transition design of the film greatly improves the bonding strength of the film, providing a guarantee for the realization of a hard film; the film surface is combined with ductile metal materials tungsten and δ-TaN xThe advantages of the film are used to form a compound that is both hard and tough, which effectively improves the mechanical and friction properties of the film; multi-target magnetron sputtering is used to adjust the N content, and some traditional metal Ta elements are replaced by W elements to form a substitutional solid solution. The TM-N bonds formed have the properties of both metallic bonds and ionic bonds. By adjusting the N content, the valence electron concentration optimizes the combination of the strength characteristic bond strength and the extension characteristic bond strength, that is, the improvement in hardness is due to the first adjacent covalent bond of the strength characteristic. p (N)- d - e g (Me), the toughness enhancement is due to the secondary adjacent metal-metal bonds that contribute to ductility d - t 2g (Ta)- d - t 2g (W) is still very strong; thanks to the excellent mechanical properties, the wear resistance of the film is improved, which is beneficial to extend the service life of the tool.

Claims

1. A N element regulates Ta 0.5 W 0.5 N x A method for forming a hard film, characterized in that The Ta 0.5 W 0.5 N x In the hard film, the value of x is 0.93, and the following steps are included: Before sputtering, a 80-100 nm W2N transition layer was deposited on the substrate; Using Ta target and W target as target materials, argon as sputtering gas and nitrogen as reaction gas, the target material is sputtered by DC magnetron sputtering to obtain Ta 0.5 W 0.5 N x Hard film; The total flow rate of nitrogen and argon gas is 40 sccm, of which the volume proportion of nitrogen is 10-30%; The substrate is 718 high temperature nickel-based alloy; The sputtering temperature was 300±20 ℃, the sputtering time was 35~40 min, the sputtering current of Ta target was 271 mA, and the sputtering current of W target was 180 mA.

2. The method according to claim 1, characterized in that A W2N transition layer is obtained on a substrate by DC magnetron sputtering of the target material using a W target as a target material, argon as a sputtering gas, and nitrogen as a reaction gas.

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