A method for preparing vanadium oxide thin films by physical vapor deposition

Abstract

This invention provides a physical vapor deposition method for preparing vanadium oxide thin films, comprising the following steps: Step S1, pre-sputtering: selecting a target material, adjusting the distance between the target material and the wafer, setting the substrate temperature to a preset temperature, the cavity vacuum degree to a preset vacuum degree, and pre-sputtering the target material at a preset power; Step S2, sputtering the semi-finished film: transferring the wafer to a magnetron sputtering vacuum cavity, introducing argon and oxygen into the magnetron sputtering cavity, setting the cavity reaction pressure and the target material input power, and obtaining a sputtered semi-finished film after sputtering; Step S3, post-sputtering treatment: spraying an electron beam into the magnetron sputtering cavity through an electron gun, continuing to introduce argon and oxygen into the magnetron sputtering cavity, setting the cavity reaction pressure and the target material input power, and obtaining the sputtered film. The vanadium oxide thin film prepared in this embodiment of the invention has high surface flatness and an average temperature coefficient of resistance of over -2.652% at 22–30°C.

Description

Technical Field

[0001] This invention belongs to the field of magnetron sputtering technology, and particularly relates to a physical vapor deposition method for preparing vanadium oxide thin films. Background Technology

[0002] Vanadium oxide thin films possess advantages such as a large temperature coefficient of resistance, good resistivity, low 1 / f noise, and compatibility with silicon-based microfabrication processes, making them widely used in thermal sensing layers of uncooled infrared imaging systems. The V₂O₅ phase exhibits good TCR characteristics but displays a high resistivity, while the VO₂ phase exhibits a significant phase transition effect around 341 K, which is something to be avoided in thermal sensing layers of uncooled infrared imaging systems. Therefore, V₂O₅ thin films with less VO₂ second phase can exhibit good TCR values ​​and suitable resistivity for infrared sensor applications.

[0003] Uncooled microcalorimeters based on vanadium oxide thin films offer high performance, but the deposition and processing conditions are extremely demanding, often requiring medium- to high-temperature deposition and annealing processes. Compatibility with existing complementary metal-oxide-semiconductor (CMOS) technology is crucial for any thermal sensing layer used as an infrared sensing element in microcalorimeters and infrared imagers. The sensor must be mounted directly on the silicon wafer so that signal processing can be performed effectively at the infrared focal plane. Therefore, to ensure compatibility of the microcalorimeter's thermal sensing layer with CMOS technology, the processing temperature during vanadium oxide fabrication is always kept as low as possible.

[0004] In the prior art, in reactive magnetron sputtering, Chinese patent CN201510030113.0, entitled "A method for preparing vanadium oxide thin films with high resistance temperature coefficients", discloses a method for preparing vanadium oxide thin films with high resistance temperature coefficients. The method involves sputtering a silicon nitride thin film onto a single-crystal silicon surface, and then sequentially depositing a vanadium oxide thin film, a zinc sulfide thin film, and a vanadium oxide thin film. The deposited thin film samples are then annealed. This method requires high-temperature annealing, has poor compatibility with existing complementary metal-oxide-semiconductor (CMOS) technology, and involves many thin film processing steps with low efficiency. Summary of the Invention

[0005] To address at least one technical problem in the prior art, a physical vapor deposition method for preparing vanadium oxide thin films is provided, which is simple to operate and improves the performance of metal thin films. To achieve the above technical objectives, the technical solution adopted in this invention is as follows:

[0006] This invention provides a method for preparing vanadium oxide thin films by physical vapor deposition, comprising the following steps:

[0007] Step S1, pre-sputtering: Select a target material, adjust the distance between the target material and the wafer, set the substrate temperature to a preset temperature, the cavity vacuum degree to a preset vacuum degree, and pre-sputter the target material at a preset power.

[0008] Step S2, Sputtered thin film semi-finished product: Argon and oxygen are introduced into the magnetron sputtering cavity, the cavity reaction pressure and the input power of the target are set, and the sputtered thin film semi-finished product is obtained after sputtering;

[0009] Step S3, post-sputtering processing: Electron beams are injected into the magnetron sputtering cavity through an electron gun. At the same time, argon and oxygen are continued to be introduced into the magnetron sputtering cavity. The cavity reaction pressure and the input power of the target are set to obtain the sputtered thin film.

[0010] The oxygen flow rate in step S3 is greater than the oxygen flow rate in step S2.

[0011] Furthermore, in step S2, the oxygen flow rate is 1.0–5 sccm;

[0012] And / or, in step S3, the oxygen flow rate is 10–50 sccm.

[0013] Furthermore, in step S3, the voltage of the electron gun is 0.5 to 1.5 kV and the current is 5 to 15 A.

[0014] Furthermore, the input power of the target material in step S2 is greater than the input power of the target material in step S3.

[0015] Furthermore, in step S2, the input power of the target material is 1000-3000W;

[0016] And / or, in step S3, the input power of the target material is 50 to 500 W.

[0017] In step S1, the target material includes metallic vanadium;

[0018] And / or, the target material has a diameter of 320–321 mm.

[0019] And / or, the wafer is selected from at least one of silicon, gallium arsenide, silicon carbide, quartz glass, alumina, indium phosphide, gallium nitride, gallium oxide, and aluminum nitride;

[0020] And / or, the distance between the target and the wafer is 50 to 150 mm.

[0021] Furthermore, in step S1, the preset temperature is 25–200°C;

[0022] And / or, the preset vacuum degree is 5.0 × 10⁻⁶. -8 Below Torr;

[0023] And / or, the preset power is 1000-3000W;

[0024] And / or, the pre-sputtering time is 1 to 5 minutes.

[0025] Furthermore, in step S2, the argon flow rate is 15–30 sccm;

[0026] And / or, the cavity reaction pressure is 1.0 to 2.1 mTorr.

[0027] Furthermore, in step S3, the argon flow rate is 1–10 sccm;

[0028] And / or, the cavity reaction pressure is 1.0 to 3.6 mTorr.

[0029] The beneficial effects of the technical solution provided by the embodiments of the present invention are as follows:

[0030] This invention, through the addition of an electron emission device, enhances plasma density, causing collisions with oxygen molecules and exciting a large number of oxygen anions. These anions are accelerated into the plasma by the electric field of the target sheath. Although they may lose electrons within the plasma, their kinetic energy still propels them toward the substrate. This bombardment effect produces a certain degree of etching, making the atomic arrangement of the thin film more even. The oxygen reaching the film surface can repair defects and alter the composition distribution of the film. The vanadium oxide thin film prepared in this invention exhibits high surface flatness and an average temperature coefficient of resistance exceeding -2.652% at 22–30°C. Attached Figure Description

[0031] Figure 1 This is a SEM image of the cross-section and surface of the vanadium oxide thin film in Example 1 of the present invention.

[0032] Figure 2 This is an AFM image of the cross-section and surface of the vanadium oxide thin film in Example 1 of the present invention.

[0033] Figure 3 This is the XRD pattern of the vanadium oxide thin film in Example 1 of the present invention.

[0034] Figure 4 This is the XPS full spectrum of the vanadium oxide thin film in Example 1 of the present invention.

[0035] Figure 5 This is a fine XPS spectrum of vanadium (V) in the vanadium oxide thin film of Example 1 of the present invention.

[0036] Figure 6 This is a thickness distribution diagram of the vanadium oxide thin film in Example 1 of the present invention.

[0037] Figure 7 This is a resistance-temperature curve of the vanadium oxide thin film in Example 1 of the present invention.

[0038] Figure 8 This is a resistance-temperature curve of the vanadium oxide thin film in Comparative Example 1 of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] Furthermore, it should be understood that after reading the contents disclosed in this invention, those skilled in the art can make various alterations or modifications to this invention, and these equivalent forms also fall within the protection scope defined by this invention.

[0041] This invention provides a method for preparing vanadium oxide thin films by physical vapor deposition, comprising the following steps:

[0042] Step S1, pre-sputtering: Select a target material, adjust the distance between the target material and the wafer, set the substrate temperature to a preset temperature, the cavity vacuum degree to a preset vacuum degree, and pre-sputter the target material at a preset power.

[0043] Step S2, Sputtered thin film semi-finished product: Argon and oxygen are introduced into the magnetron sputtering cavity, the cavity reaction pressure and the input power of the target are set, and the sputtered thin film semi-finished product is obtained after sputtering;

[0044] Step S3, post-sputtering processing: an electron beam is injected into the magnetron sputtering cavity through an electron gun, while argon and oxygen are continuously introduced into the magnetron sputtering cavity. The cavity reaction pressure and the input power of the target are set to obtain the sputtered thin film.

[0045] The oxygen flow rate in step S3 is greater than the oxygen flow rate in step S2.

[0046] It should be noted that by adding step S3 to perform post-processing on the sputtered thin film semi-finished product, specifically, an electron beam is added to the sputtering device to enhance the plasma density during sputtering, and the oxygen flow rate is increased. The electron beam excites a large number of oxygen negative ions, which are acted upon by the cathode target, move towards the substrate, and interact with the sputtered thin film semi-finished product, causing the atomic arrangement of the sputtered thin film semi-finished product to tend to be flat. The oxygen negative ions can repair defects, change the component distribution of the sputtered thin film semi-finished product, and thus improve the performance of the sputtered thin film.

[0047] Furthermore, in step S2, the oxygen flow rate is 1.0 to 5 sccm, for example, it can be 1.0 sccm, 2.0 sccm, 3.0 sccm, 4.0 sccm, 5.0 sccm, etc.;

[0048] And / or, in step S3, the oxygen flow rate is 10 to 50 sccm, for example, it can be 10 sccm, 20 sccm, 30 sccm, 40 sccm, 50 sccm, etc.

[0049] Furthermore, in step S3, the voltage of the electron gun is 0.5 to 1.5KV and the current is 5 to 15A. For example, the voltage can be 0.5KV, 0.8KV, 1.0KV, 1.2KV, 1.5KV, etc., and the current can be 5A, 7A, 9A, 10A, 12A, 15A, etc.

[0050] Furthermore, the input power of the target material in step S2 is greater than the input power of the target material in step S3.

[0051] Furthermore, in step S2, the input power of the target material is 1000-3000W, for example, it can be 1000W, 1500W, 2000W, 2500W, 3000W, etc.

[0052] And / or, in step S3, the input power of the target material is 50 to 500W, for example, it can be 50W, 100W, 200W, 300W, 400W, 500W, etc.

[0053] In step S1, the target material includes metallic vanadium;

[0054] And / or, the target material has a diameter of 320–321 mm.

[0055] And / or, the wafer is selected from at least one of silicon, gallium arsenide, silicon carbide, quartz glass, alumina, indium phosphide, gallium nitride, gallium oxide, and aluminum nitride;

[0056] And / or, the distance between the target and the wafer is 50 to 150 mm, for example, it can be 50 mm, 80 mm, 100 mm, 120 mm, 150 mm, etc.

[0057] Furthermore, in step S1, the preset temperature is 25 to 200°C, for example, it can be 25°C, 50°C, 80°C, 100°C, 120°C, 150°C, 180°C, 200°C, etc.

[0058] And / or, the preset vacuum degree is 5.0 × 10⁻⁶. -8 Below Torr, for example, it can be 1.0×10 -8 Torr, 2.0×10 -8 Torr, 3.0×10 -8 Torr, 4.0×10 -8 Torr, etc.

[0059] And / or, the preset power is 1000 to 3000W, for example, it can be 1000W, 1500W, 2000W, 2500W, 3000W, etc.

[0060] And / or, the pre-sputtering time is 1 to 5 minutes.

[0061] Furthermore, in step S2, the argon flow rate is 15-30 sccm, for example, it can be 15 sccm, 18 sccm, 20 sccm, 22 sccm, 25 sccm, 28 sccm, 30 sccm, etc.

[0062] And / or, the cavity reaction pressure is 1.0 to 2.1 mTorr, for example, it can be 1.0 mTorr, 1.2 mTorr, 1.5 mTorr, 1.8 mTorr, 2.0 mTorr, 2.1 mTorr, etc.

[0063] Furthermore, in step S3, the argon flow rate is 1 to 10 sccm, for example, it can be 1 sccm, 3 sccm, 5 sccm, 7 sccm, 9 sccm, 10 sccm, etc.

[0064] And / or, the cavity reaction pressure is 1.0 to 3.6 mTorr, for example, it can be 1.0 mTorr, 1.5 mTorr, 2.0 mTorr, 2.5 mTorr, 3.0 mTorr, 3.6 mTorr, etc.

[0065] In the following specific embodiments, operations not specified under certain conditions are performed under standard conditions or conditions recommended by the manufacturer. All raw materials without specified manufacturers and specifications are commercially available products.

[0066] Example 1

[0067] A method for preparing vanadium oxide thin films by physical vapor deposition includes the following steps:

[0068] Step S1, Pretreatment: A vanadium metal target with a diameter of 320 mm is selected. The distance between the target and the wafer stage is set to 90 mm. The substrate temperature is set to 150℃, and the vacuum level of the cavity is maintained at 4.0 × 10⁻⁶. -8 Torr, set the sputtering power to 3000W, pre-sputter the target for 1 minute;

[0069] Step S2, sputtering thin film semi-finished product: Argon gas with a flow rate of 15 sccm and oxygen gas with a flow rate of 1.5 sccm are introduced into the magnetron sputtering vacuum chamber. The reaction pressure of the chamber is set to 1.1 mTorr and the input power of the target material is 1500 W. After sputtering for 3 min, vanadium oxide thin film semi-finished product is obtained.

[0070] Step S3, post-sputtering treatment: An electron beam is injected into the magnetron sputtering chamber through an electron gun with a voltage of 1KV and a current of 10A. At the same time, argon gas with a flow rate of 5sccm and oxygen gas with a flow rate of 15sccm are continuously introduced into the magnetron sputtering chamber. The chamber reaction pressure is set to 1.2mTorr and the input power is 100W. After sputtering for 3 minutes, a vanadium oxide thin film is obtained.

[0071] Example 2

[0072] A method for preparing vanadium oxide thin films by physical vapor deposition includes the following steps:

[0073] Step S1, Pretreatment: A vanadium metal target with a diameter of 320 mm is selected. The distance between the target and the wafer stage is set to 50 mm. The substrate temperature is set to 25°C, and the vacuum level of the cavity is maintained at 3.0 × 10⁻⁶. -8 Torr, set the sputtering power to 1000W, pre-sputter the target for 1 minute;

[0074] Step S2, Sputtered thin film semi-finished product: Argon gas with a flow rate of 15 sccm and oxygen gas with a flow rate of 1.0 sccm are introduced into the magnetron sputtering vacuum chamber. The reaction pressure of the chamber is set to 1.0 mTorr and the input power of the target material is 1000 W. After sputtering for 3 min, vanadium oxide thin film semi-finished product is obtained.

[0075] Step S3, post-sputtering treatment: An electron beam is injected into the magnetron sputtering cavity through an electron gun with a voltage of 0.5 kV and a current of 5 A. At the same time, argon gas with a flow rate of 1 sccm and oxygen gas with a flow rate of 10 sccm are continuously introduced into the magnetron sputtering cavity. The cavity reaction pressure is set to 1.0 mTorr and the input power is 50 W. After sputtering for 3 min, a vanadium oxide thin film is obtained.

[0076] Example 3

[0077] A method for preparing vanadium oxide thin films by physical vapor deposition includes the following steps:

[0078] Step S1, Pretreatment: A vanadium metal target with a diameter of 320 mm is selected. The distance between the target and the wafer stage is set to 150 mm. The substrate temperature is set to 200℃, and the vacuum level of the cavity is maintained at 2.0 × 10⁻⁶. -8 Torr, set the sputtering power to 3000W, pre-sputter the target for 1 minute;

[0079] Step S2, sputtered thin film semi-finished product: Argon gas with a flow rate of 30 sccm and oxygen gas with a flow rate of 5 sccm are introduced into the magnetron sputtering vacuum chamber. The reaction pressure of the chamber is set to 2.1 mTorr and the input power of the target material is 3000 W. After sputtering for 3 min, vanadium oxide thin film semi-finished product is obtained.

[0080] Step S3, post-sputtering treatment: An electron beam is injected into the magnetron sputtering chamber through an electron gun with a voltage of 1.5KV and a current of 15A. At the same time, argon gas with a flow rate of 10sccm and oxygen gas with a flow rate of 50sccm are continuously introduced into the magnetron sputtering chamber. The chamber reaction pressure is set to 3.6mTorr and the input power is 500W. After sputtering for 3 minutes, a vanadium oxide thin film is obtained.

[0081] Comparative Example 1

[0082] A method for preparing vanadium oxide thin films by physical vapor deposition includes the following steps:

[0083] Step S1, Pre-sputtering: A vanadium metal target with a diameter of 320 mm is selected, and the distance between the target and the wafer stage is 90 mm. The substrate temperature is set to 150℃, and the cavity vacuum is maintained at 4.0 × 10⁻⁶. -8 Torr, set the sputtering power to 3000W, pre-sputter the target for 1 minute;

[0084] Step S2, Sputtering thin film: The wafer is transferred to a DC magnetron sputtering vacuum chamber, and argon gas with a flow rate of 15 sccm and oxygen gas with a flow rate of 1.5 sccm are introduced. The chamber reaction pressure is set to 1.1 mTorr and the target input power is set to 1500 W. After sputtering for 3 minutes, a vanadium oxide thin film is obtained.

[0085] Application Examples

[0086] This application example tests the surface morphology, roughness, crystallinity, film thickness uniformity, stress, and elemental distribution ratio of the vanadium oxide thin film prepared in Example 1, and also tests the temperature coefficient of resistance (TCR) of the vanadium oxide thin films prepared in Example 1 and Comparative Example 1. Specifically, the surface morphology and roughness of the vanadium oxide thin film were observed by scanning electron microscopy (SEM) using a Hitachi S-4800 instrument; the surface roughness of the vanadium oxide thin film was tested by atomic force microscopy (AFM) using a Bruker Dimension® Icon™ instrument; the crystallinity of the vanadium oxide thin film was tested by X-ray diffraction (XRD) using a Brukersmart Apex II instrument; the elemental distribution ratio of vanadium oxide was calculated by X-ray photoelectron spectroscopy (XPS) using a Thermo Scientific K-Alpha instrument; and the temperature coefficient of resistance (TCR) of the vanadium oxide thin film was measured using a four-probe measurement method using a Changzhou Xinyang CXT2665 four-probe sheet resistance meter.

[0087] The fine XPS spectra of vanadium (V) in the vanadium oxide thin film of Example 1 are shown in Table 1 below, and the full XPS spectra of the vanadium oxide thin film are shown in Table 2 below.

[0088] Table 1 shows the fine XPS spectra of vanadium (V) in the vanadium oxide thin film in Example 1 of this invention.

[0089]

[0090] Table 2 shows the XPS full spectrum results of the vanadium oxide thin film in Example 1 of the present invention:

[0091]

[0092] Depend on Figure 1 , Figure 2 As shown in Table 1, the vanadium oxide thin film prepared in Example 1 of the present invention has a small surface roughness and a smooth surface, with a roughness Ra of only 0.463 nm.

[0093] Depend on Figure 3 It can be seen that the XRD pattern of the substrate is similar to that of the vanadium oxide thin film SiO2 / VO prepared in Example 1 of this invention. x The spectral peaks are almost identical; comparing the two, no VO was found. x The characteristic peaks were observed only at 2θ≈33° for Si, and the peak position at 50-60° was a characteristic peak for SiO2. These results indicate that the VO deposited in Example 1 of this invention... x The thin film is amorphous.

[0094] Depend on Figure 4As shown in Table 1, the vanadium oxide thin film prepared in Example 1 of this invention mainly has four peaks: O1s, V2p, C1s, and N1s. Among them, the O2s peak and V2p peak are relatively close and require fine spectral analysis. The C1s peak and N1s peak indicate that the C and N on the surface are caused by unavoidable surface contamination during the thin film characterization test.

[0095] Depend on Figure 5 As shown in Table 2, the peak position of the V(2p3 / 2) electron layer of the vanadium oxide thin film prepared in Example 1 of this invention is at 517.38 eV, and the range is mainly V16.8 eV to 517.7 eV. 5+ (Elemental proportion is 62.53%), there is a small peak at 516.04 eV, ranging from 515.64 eV to 516.04 eV, mainly V. 4+ (The element ratio is 37.47%).

[0096] Depend on Figure 6 It can be seen that the vanadium oxide film prepared in Example 1 has a thickness of 534 Å and a film thickness uniformity of 0.899%. Furthermore, calculations show that the vanadium oxide film with a thickness of 534 Å has a VO₂O₃ content of 534 Å. x The film stress is approximately 120.7 MPa.

[0097] Figure 7 It can be seen that, through linear fitting of the TCR, the vanadium oxide thin film prepared in Example 1 has an average temperature coefficient of resistance of over -2.652% at 22–30°C, while... Figure 8 It can be seen that the vanadium oxide thin film prepared in Comparative Example 1 has an average temperature coefficient of resistance of over -2.487% at 22-30℃. This shows that the sputtering post-treatment in step S3 can effectively improve the average temperature coefficient of resistance performance of the vanadium oxide thin film.

[0098] In summary, the vanadium oxide thin film prepared in Example 1 of this invention has high surface flatness and an average temperature coefficient of resistance of over -2.652% at 22–30°C, which meets the requirements for use.

[0099] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing vanadium oxide thin films by physical vapor deposition, characterized in that, Includes the following steps: Step S1, pre-sputtering: Select a target material, adjust the distance between the target material and the wafer, set the substrate temperature to a preset temperature, the cavity vacuum degree to a preset vacuum degree, and pre-sputter the target material at a preset power. Step S2, Sputtered thin film semi-finished product: Argon and oxygen are introduced into the magnetron sputtering cavity. The flow rate of oxygen is 1.0-5 sccm and the flow rate of argon is 15-30 sccm. The cavity reaction pressure and the input power of the target are set. After sputtering, a sputtered thin film semi-finished product is obtained. Step S3, post-sputtering processing: An electron beam is injected into the magnetron sputtering cavity through an electron gun. The voltage of the electron gun is 0.5-1.5KV and the current is 5-15A. At the same time, argon and oxygen are continuously introduced into the magnetron sputtering cavity. The flow rate of oxygen is 10-50sccm and the flow rate of argon is 1-10sccm. The cavity reaction pressure and the input power of the target material are set to obtain the sputtered thin film. The oxygen flow rate in step S3 is greater than the oxygen flow rate in step S2.

2. The physical vapor deposition method for preparing vanadium oxide thin films as described in claim 1, characterized in that, The input power of the target in step S2 is greater than the input power of the target in step S3.

3. The physical vapor deposition method for preparing vanadium oxide thin films as described in claim 1, characterized in that, In step S2, the input power of the target material is 1000-3000W; And / or, in step S3, the input power of the target material is 50 to 500 W.

4. The physical vapor deposition method for preparing vanadium oxide thin films as described in claim 1, characterized in that, In step S1, the target material includes metallic vanadium; And / or, the target material has a diameter of 320–321 mm. And / or, the wafer is selected from at least one of silicon, gallium arsenide, silicon carbide, quartz glass, alumina, indium phosphide, gallium nitride, gallium oxide, and aluminum nitride; And / or, the distance between the target and the wafer is 50 to 150 mm.

5. The physical vapor deposition method for preparing vanadium oxide thin films as described in claim 1, characterized in that, In step S1, the preset temperature is 25–200°C; And / or, the preset vacuum degree is 5.0 × 10⁻⁶. -8 Below Torr; And / or, the preset power is 1000-3000W; And / or, the pre-sputtering time is 1 to 5 minutes.

6. The physical vapor deposition method for preparing vanadium oxide thin films as described in claim 1, characterized in that, In step S2, the chamber reaction pressure is 1.0 to 2.1 mTorr.

7. The physical vapor deposition method for preparing vanadium oxide thin films as described in claim 1, characterized in that, In step S3, the chamber reaction pressure is 1.0–3.6 mTorr.

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