High-hardness high-reflectivity hafnium carbide film and preparation method thereof

Abstract

The invention provides a high-hardness high-reflectivity hafnium carbide film and a preparation method thereof. The method comprises the following steps: 1) target material position: placing a graphite target, a hafnium target and a substrate; 2) substrate surface pretreatment: performing ultrasonic cleaning on the substrate and then drying the substrate; 3) vacuumizing the chamber and heating the substrate: vacuumizing the chamber to high vacuum and heating the substrate; (4) pre-cleaning the target material: introducing inert gas into the chamber, keeping the working air pressure, and carrying out pre-sputtering cleaning on the target material; and 5) depositing a hafnium carbide film: continuously introducing inert gas into the chamber, keeping the working air pressure, the substrate temperature and the substrate autorotation speed, modulating an intermediate-frequency pulse waveform by adopting a pulse generator, applying the intermediate-frequency pulse waveform to the graphite target and the hafnium target, keeping a current value, and carrying out coating treatment. The hafnium carbide film with the low carbon vacancy concentration and the single-phase rock salt structure can be prepared through the method, and the hafnium carbide film has high hardness and broadband high reflection performance.

Description

Technical Field

[0001] The invention relates to the field of multifunctional film preparation, and in particular to a high-hardness and high-reflectivity hafnium carbide film and a preparation method thereof. Background Art

[0002] Multifunctional films with high hardness, high melting point and broadband high reflectivity are essential for protecting optical systems from long-term stable service in extreme environments. Traditional broadband high-reflectivity films are mainly pure metals such as aluminum, silver, gold and copper. Although these metal films have excellent broadband high-reflectivity performance, their hardness and melting point are very low and cannot be used in extremely harsh environments with high heat, corrosion and wear. Hafnium carbide ceramics have ultra-high melting point, high hardness and good thermal and electrical conductivity, and are an excellent candidate material for high-hardness and high-reflectivity films.

[0003] However, amorphous carbon phase is easily precipitated in near-stoichiometric carbides, which significantly affects the film properties. A small amount of amorphous carbon phase can improve the hardness and wear resistance of the film, but it will enhance the shadow effect during the film deposition process, thereby significantly increasing the film roughness and reducing the reflectivity. More amorphous carbon will deteriorate both the hardness and reflectivity of the film. Although reducing the carbon content in the film can inhibit the precipitation of amorphous carbon, it will introduce a large number of carbon vacancies in the film, reduce the covalent bond density, and thus lead to low film hardness. Therefore, minimizing the carbon vacancies in hafnium carbide without precipitating amorphous carbon is crucial to the preparation of hafnium carbide films with both high hardness and broadband high reflectivity.

[0004] In addition, hafnium carbide films prepared by existing magnetron sputtering methods are prone to precipitating amorphous carbon phases. This is because: on the one hand, existing magnetron sputtering methods usually use gases such as acetylene and methane as carbon sources, and these gases will introduce hydrogen elements into the film after decomposition and ionization. The active hydrogen atoms will induce the carbon in the film to undergo sp 2 On the other hand, the existing magnetron sputtering method usually uses a constant DC power supply, which has a high deposition rate, but the working voltage is low, and the sputtered carbon particles have low energy and cannot fully diffuse into the hafnium carbide lattice, so it is easy to form carbon clusters and further develop into an amorphous carbon phase.

[0005] Therefore, how to optimize the existing magnetron sputtering technology to prepare hafnium carbide films with high hardness and broadband high reflectivity is a technical problem that technicians in this field need to solve urgently. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a hafnium carbide film and method for preparing hafnium carbide film with high hardness and broadband high reflectivity by magnetron co-sputtering. The method can prepare a single-phase rock salt structure hafnium carbide film with low carbon vacancy concentration, which has high hardness and broadband high reflectivity.

[0007] In a first aspect, the present invention provides a method for producing a hafnium carbide film with high hardness and high reflectivity, comprising the following steps.

[0008] 1) Target position: Place graphite target, hafnium target and substrate.

[0009] 2) Substrate surface pretreatment: ultrasonically clean the substrate and then dry it.

[0010] 3) Chamber vacuuming and substrate heating: The chamber is evacuated to high vacuum and the substrate is heated.

[0011] 4) Target pre-cleaning: Introduce inert gas into the chamber and maintain the working gas pressure to perform pre-sputtering cleaning of the target.

[0012] 5) Deposition of hafnium carbide film: continuously introduce inert gas into the chamber and maintain the working gas pressure, substrate temperature and substrate rotation speed, use a pulse generator to modulate the intermediate frequency pulse waveform and apply it to the graphite target and the hafnium target, maintain the current value and perform the coating process.

[0013] The present invention provides a hafnium carbide film and method for preparing the film by magnetron co-sputtering with high hardness and broadband high reflectivity. The method adopts medium frequency pulsed DC magnetron co-sputtering of graphite target and hafnium target to prepare a single-phase rock salt structure hafnium carbide film with low carbon vacancy concentration, which has high hardness and broadband high reflectivity. The single-phase rock salt structure hafnium carbide film is prepared by adjusting the process parameters, and the stoichiometric ratio is: HfC 0.5 ~HfC 0.8 , hardness greater than 20 GPa, and average reflectivity in the 800~2000 nm band greater than 60%.

[0014] Preferably, in step 1), the purity of the graphite target and the hafnium target are both ≥99.95%, the substrate is Si (100), the graphite target is horizontally placed directly below the substrate, with a distance of 8 to 15 cm from the substrate, and the hafnium target is placed at an inclination of 30±2° relative to the graphite target.

[0015] Preferably, in step 2), ultrasonic cleaning is performed in acetone, anhydrous ethanol and deionized water for 5 to 10 min respectively.

[0016] Further preferably, in step 3), the high vacuum degree is a pressure lower than 4×10 -4 Pa, the substrate heating temperature is 400~600℃.

[0017] Preferably, the chamber is evacuated to a pressure below 10 Pa, and then evacuated to a high vacuum and the substrate is heated.

[0018] In the present invention, the chamber is first evacuated to a pressure below 10 Pa using a mechanical pump, and then further evacuated to a high vacuum using a turbomolecular pump. At the same time, the substrate is heated by a resistance wire to remove residual gas and volatile substances in the chamber and on the surface of the substrate to the greatest extent, so as to ensure the adhesion of the thin film and the quality of the film layer.

[0019] Preferably, in step 4), the flow rate of the introduced argon gas is 30-50 sccm, and the working gas pressure is stabilized at 0.8-1.2 Pa.

[0020] In the present invention, preferably, argon gas is continuously introduced into the chamber, the working gas pressure is kept constant by adjusting the molecular pump valve, and then the graphite target and the hafnium target are pre-sputtered and cleaned to better remove oxides and contaminants on the surface of the target material, which is beneficial to subsequent processing.

[0021] Further preferably, in step 4), constant bias voltages of -300 to -350 V and -150 to -200 V are applied to the graphite target and the hafnium target, respectively, and the pre-sputtering cleaning time is 5 to 10 min.

[0022] Preferably, in step 5), the argon gas flow rate is 30-50 sccm, the working gas pressure is stabilized at 0.5-1.0 Pa, the substrate temperature is stabilized at 400-600°C, the substrate rotation speed is maintained at 5-20 rpm, the intermediate frequency pulse frequency is 50-150 kHz, the intermediate frequency pulse width is 0.2-0.6 µs, the current applied to the graphite target is 0.3-0.6 A, the power is 80-180 W, and the current applied to the hafnium target is 0.3-0.6 A, the power is 50-125 W.

[0023] Further preferably, in step 5), the argon gas flow rate is 35-45 sccm, the working gas pressure is stabilized at 0.7-0.9 Pa, the substrate temperature is stabilized at 450-550°C, the substrate rotation speed is maintained at 8-12 rpm, the intermediate frequency pulse frequency is 80-120 kHz, the intermediate frequency pulse width is 0.3-0.5 µs, the current applied to the graphite target is 0.3-0.6 A, preferably 0.5 A, the power is 80-180 W, preferably 150-170 W, the current applied to the hafnium target is 0.4-0.6 A, the power is 50-125 W, preferably 50-120 W; preferably, the coating treatment is performed for 60-180 min.

[0024] Preferably, after step 5), the method further includes lowering the substrate temperature to below 100° C. and removing the substrate.

[0025] In the present invention, after step 5) is completed, the power is turned off, and when the substrate temperature drops below 100° C., the chamber is opened and the substrate is taken out. The thin film on the surface of the substrate is a hafnium carbide thin film with high hardness, broadband and high reflectivity.

[0026] In a second aspect, the present invention provides a hafnium carbide film obtained by the above preparation method, wherein the hafnium carbide film has a single-phase rock salt structure and a stoichiometric ratio of HfC 0.5 ~HfC 0.8 , film hardness ≥ 20 GPa, average reflectivity in the 800~2000 nm band ≥ 60%.

[0027] The beneficial effects of the present invention are at least as follows: 1) The present invention uses a graphite target as a carbon source to prepare a hafnium carbide film, which can avoid the introduction of active hydrogen atoms into the film. Compared with the existing technology using acetylene or methane as a carbon source, the present invention can reduce the tendency of amorphous carbon phase precipitation in the film. 2) The present invention modulates a pulsed DC waveform through a pulse generator, which has significantly higher sputtering particle energy than constant DC magnetron sputtering technology, and has significantly higher deposition efficiency than high-power pulsed magnetron sputtering technology. The present invention can take into account both film quality and deposition efficiency. 3) The present invention can prepare a single-phase rock salt structure hafnium carbide film with a low carbon vacancy concentration and no amorphous carbon precipitation, which has high hardness and broadband high reflectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 The XRD spectrum of the single-phase hafnium carbide film obtained in Example 1-3.

[0030] Figure 2 This is the XPS spectrum of the single-phase hafnium carbide film obtained in Example 1-3.

[0031] Figure 3 This is a SEM photograph of the single-phase hafnium carbide film obtained in Example 1-3.

[0032] Figure 4 TEM photograph of the single-phase hafnium carbide film obtained in Example 1-3. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods. If no specific techniques or conditions are specified in the examples, they are all conventional methods or the techniques or conditions described in the literature in this field, or according to the product instructions. If the manufacturers of the reagents and instruments are not specified, they are all conventional products that can be purchased through regular channels.

[0035] Example 1

[0036] This embodiment provides a method for preparing a hafnium carbide film having high hardness and broadband high reflectivity by magnetron co-sputtering, which comprises the following steps.

[0037] (1) The purity of the selected graphite target and hafnium target is 99.95%. The substrate is Si (100). The graphite target is placed horizontally directly below the substrate at a distance of 11 cm from the substrate. The hafnium target is placed at an angle of 30° relative to the graphite target.

[0038] (2) The substrate was ultrasonically cleaned in acetone, anhydrous ethanol and deionized water for 10 min respectively.

[0039] (3) The chamber is first evacuated to a pressure below 10 Pa using a mechanical pump, and then further evacuated to a pressure of 4×10 -4 Pa, and at the same time the substrate is heated to 500°C by a resistance wire.

[0040] (4) 40 sccm of argon gas was continuously introduced into the chamber, and the working gas pressure was kept constant at 0.8 Pa by adjusting the molecular pump valve. Constant bias voltages of -325 V and -170 V were applied to the graphite target and hafnium target, respectively, for pre-sputtering and cleaning for 10 min to remove oxides and contaminants on the target surface.

[0041] (5) 40 sccm of argon gas was continuously introduced into the chamber, while the working gas pressure was kept constant at 0.8 Pa, the substrate temperature was kept constant at 500°C, and the substrate rotation speed was kept constant at 10 rpm. The power parameters applied to the graphite target were set as follows: pulse frequency of 100 kHz, pulse width of 0.4 µs, target current of 0.5 A, and target power of 162 W; the power parameters applied to the hafnium target were set as follows: pulse frequency of 100 kHz, pulse width of 0.4 µs, target current of 0.4 A, and target power of 69 W. The coating time was 120 min.

[0042] (6) Turn off the power, wait until the substrate temperature drops below 100°C, open the chamber and take out the sample.

[0043] Example 2

[0044] This embodiment provides a method for preparing a hafnium carbide film having high hardness and broadband high reflectivity by magnetron co-sputtering, which comprises the following steps.

[0045] (1) The purity of the selected graphite target and hafnium target is 99.95%. The substrate is Si (100). The graphite target is placed horizontally directly below the substrate at a distance of 11 cm from the substrate. The hafnium target is placed at an angle of 30° relative to the graphite target.

[0046] (2) The substrate was ultrasonically cleaned in acetone, anhydrous ethanol and deionized water for 10 min respectively.

[0047] (3) The chamber is first evacuated to a pressure below 10 Pa using a mechanical pump, and then further evacuated to a pressure of 4×10 -4 Pa, and at the same time the substrate is heated to 500°C by a resistance wire.

[0048] (4) 40 sccm of argon gas was continuously introduced into the chamber, and the working gas pressure was kept constant at 0.8 Pa by adjusting the molecular pump valve. Constant bias voltages of -325 V and -170 V were applied to the graphite target and hafnium target, respectively, for pre-sputtering and cleaning for 10 min to remove oxides and contaminants on the target surface.

[0049] (5) 40 sccm of argon gas was continuously introduced into the chamber, while the working gas pressure was kept constant at 0.8 Pa, the substrate temperature was kept constant at 500°C, and the substrate rotation speed was kept constant at 10 rpm. The power parameters applied to the graphite target were set as follows: pulse frequency of 100 kHz, pulse width of 0.4 µs, target current of 0.5 A, and target power of 165 W; the power parameters applied to the hafnium target were set as follows: pulse frequency of 100 kHz, pulse width of 0.4 µs, target current of 0.5 A, and target power of 94 W. The coating time was 100 min.

[0050] (6) Turn off the power, wait until the substrate temperature drops below 100°C, open the chamber and take out the sample.

[0051] Example 3

[0052] This embodiment provides a method for preparing a hafnium carbide film having high hardness and broadband high reflectivity by magnetron co-sputtering, which comprises the following steps.

[0053] (1) The purity of the selected graphite target and hafnium target is 99.95%. The substrate is Si (100). The graphite target is placed horizontally directly below the substrate at a distance of 11 cm from the substrate. The hafnium target is placed at an angle of 30° relative to the graphite target.

[0054] (2) The substrate was ultrasonically cleaned in acetone, anhydrous ethanol and deionized water for 10 min respectively.

[0055] (3) The chamber is first evacuated to a pressure below 10 Pa using a mechanical pump, and then further evacuated to a pressure of 4×10 -4 Pa, and at the same time the substrate is heated to 500°C by a resistance wire.

[0056] (4) 40 sccm of argon gas was continuously introduced into the chamber, and the working gas pressure was kept constant at 0.8 Pa by adjusting the molecular pump valve. Constant bias voltages of -325 V and -170 V were applied to the graphite target and hafnium target, respectively, for pre-sputtering and cleaning for 10 min to remove oxides and contaminants on the target surface.

[0057] (5) 40 sccm of argon gas was continuously introduced into the chamber, while the working gas pressure was kept constant at 0.8 Pa, the substrate temperature was kept constant at 500°C, and the substrate rotation speed was kept constant at 10 rpm. The power parameters applied to the graphite target were set as follows: pulse frequency of 100 kHz, pulse width of 0.4 µs, target current of 0.5 A, and target power of 167 W; the power parameters applied to the hafnium target were set as follows: pulse frequency of 100 kHz, pulse width of 0.4 µs, target current of 0.6 A, and target power of 120 W. The coating time was 90 min.

[0058] (6) Turn off the power, wait until the substrate temperature drops below 100°C, open the chamber and take out the sample.

[0059] Figure 1-4 The XRD patterns, XPS patterns, SEM images and TEM images of the single-phase hafnium carbide films obtained in Examples 1-3 are shown respectively. Figure 1-4 It can be seen that the HfC prepared in Examples 1-3 x The films are all single-phase FCC structures, the films are well bonded to the substrate, and the surface is smooth and dense.

[0060]

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for producing a high-hardness and high-reflectivity hafnium carbide film, characterized in that: The following steps are involved: 1) Target position: Place graphite target, hafnium target and substrate; 2) Substrate surface pretreatment: ultrasonically clean the substrate and then dry it; 3) Chamber vacuuming and substrate heating: evacuate the chamber to high vacuum and heat the substrate; 4) Target pre-cleaning: Introduce inert gas into the chamber and maintain the working gas pressure to perform pre-sputtering cleaning of the target; 5) Deposition of hafnium carbide film: continuously introduce inert gas into the chamber and maintain the working gas pressure, substrate temperature and substrate rotation speed, use a pulse generator to modulate the intermediate frequency pulse waveform and apply it to the graphite target and the hafnium target, maintain the current value and perform the coating process.

2. The method for preparing the hafnium carbide thin film according to claim 1, characterized in that: In step 1), the purity of the graphite target and the hafnium target are both ≥99.95%, the substrate is Si (100), the graphite target is horizontally placed directly below the substrate, with a distance of 8 to 15 cm from the substrate, and the hafnium target is placed at an inclination of 30±2° relative to the graphite target.

3. The method for preparing the hafnium carbide thin film according to claim 1 or 2, characterized in that: In step 2), ultrasonic cleaning is performed in acetone, anhydrous ethanol and deionized water for 5 to 10 min respectively.

4. The method for preparing a hafnium carbide thin film according to any one of claims 1 to 3, characterized in that: In step 3), the high vacuum degree is a pressure lower than 4×10 -4 Pa, the substrate heating temperature is 400~600℃.

5. The method for preparing a hafnium carbide thin film according to any one of claims 1 to 4, characterized in that: In step 4), the flow rate of the introduced argon gas is 30-50 sccm, and the working gas pressure is stabilized at 0.8-1.2 Pa.

6. The method for preparing the hafnium carbide thin film according to claim 5, characterized in that: In step 4), constant bias voltages of -300 to -350 V and -150 to -200 V are applied to the graphite target and the hafnium target, respectively, and the pre-sputtering cleaning time is 5 to 10 min.

7. The method for preparing a hafnium carbide thin film according to any one of claims 1 to 6, characterized in that: In step 5), the argon gas flow rate is 30-50 sccm, the working gas pressure is stabilized at 0.5-1.0 Pa, the substrate temperature is stabilized at 400-600°C, the substrate rotation speed is maintained at 5-20 rpm, the intermediate frequency pulse frequency is 50-150 kHz, the intermediate frequency pulse width is 0.2-0.6 µs, the current applied to the graphite target is 0.3-0.6 A, the power is 80-180 W, and the current applied to the hafnium target is 0.3-0.6 A, the power is 50-125 W.

8. The method for preparing the hafnium carbide thin film according to claim 7, characterized in that: In step 5), the argon gas flow rate is 35-45 sccm, the working gas pressure is stabilized at 0.7-0.9 Pa, the substrate temperature is stabilized at 450-550°C, the substrate rotation speed is maintained at 8-12 rpm, the intermediate frequency pulse frequency is 80-120 kHz, the intermediate frequency pulse width is 0.3-0.5 µs, the current applied to the graphite target is 0.3-0.6 A, the power is 80-180 W, and the current applied to the hafnium target is 0.4-0.6 A, the power is 50-125 W; preferably, the coating treatment is performed for 60-180 min.

9. The method for preparing a hafnium carbide thin film according to any one of claims 1 to 8, characterized in that: After step 5), the substrate temperature is lowered to below 100° C. and the substrate is removed.

10. The hafnium carbide film obtained by the preparation method according to any one of claims 1 to 9, characterized in that: The hafnium carbide film has a single-phase rock salt structure and a stoichiometric ratio of HfC 0.5 ~HfC 0.8 , film hardness ≥ 20 GPa, average reflectivity in the 800~2000 nm band ≥ 60%.

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