Cuprous oxide target for sputtering, and preparation method and application thereof

Abstract

The application belongs to the technical field of sputtering target material, and discloses a cuprous oxide target material for sputtering, a preparation method and application thereof. The target material preparation method is as follows: cuprous oxide powder is vacuum degassed at 120-150 DEG C, then loaded into a graphite mold, cold-pressed to 5-10 MPa, then heated to 780-820 DEG C under vacuum, pressure is increased to 30-50 MPa for heat preservation and pressure preservation, after the heat preservation and pressure preservation time, the furnace is cooled to room temperature, demoulding is performed, and a cuprous oxide target blank is obtained; the obtained cuprous oxide target blank is subjected to face milling treatment, and a cuprous oxide target material for sputtering is obtained. The preparation method adopts cuprous oxide powder which is vacuum degassed and then loaded into a mold for hot-pressing sintering, and has the advantages of simple operation and low cost. The cuprous oxide target material prepared by the method has high relative density and single crystal type, and meets the sputtering target requirements.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sputtering targets, and particularly relates to a cuprous oxide target for sputtering, a preparation method and application thereof. BACKGROUND

[0002] Cuprous oxide (Cu2O) is a p-type semiconductor material with a high absorption coefficient (10-4 / cm), abundant raw materials, no toxicity, low cost, a band gap width of 2.1 eV, and the ability to directly utilize visible light with a wavelength of 400-800 nm in sunlight to excite photo-generated electron-hole pairs and produce photo-electric conversion effects. The theoretical energy conversion efficiency of a Cu2O solar cell is about 20%, so cuprous oxide thin films have been studied for long-term use as P-type absorption layers in heterojunction solar cells and other applications. In recent years, the energy conversion efficiency of solar cells has been rapidly improved by optimizing the quality of Cu2O thin films and p-n junction structures. Therefore, it is extremely challenging to manufacture high-quality p-type Cu2O thin films for use in Cu2O-based solar cells and various applications such as thin-film transistors, resistive memories, smart windows, infrared detectors, and the like.

[0003] The main method for preparing Cu2O thin films is magnetron sputtering. Conventional magnetron sputtering methods use a copper target to deposit thin films in an oxygen atmosphere. For example, patents CN101058484A, CN105821379A, and CN104846335A all disclose a method for preparing cuprous oxide thin films by using a copper target as a sputtering target and oxygen as a reaction gas through magnetron sputtering. However, the thin films prepared by this method are prone to problems such as phase inhomogeneity and poor electrical conductivity, and the process control requirements are very strict.

[0004] The existing copper target material is generally obtained by hot pressing treatment of high-purity copper raw material. For example, patent CN115533447A discloses a preparation method of a magnetron sputtering copper target material, and the preparation steps include: 1) continuous casting, 2) blank cutting, 3) different-diameter asynchronous stacking, 4) same-diameter synchronous rolling, and 5) heat treatment of copper raw material with a purity of ≥4N. However, the grain size uniformity of the target material obtained by simple hot pressing treatment is difficult to control. Patent CN101509125A discloses a method for preparing a copper sputtering target material. The preparation process is as follows: the copper raw material is melted, and then the molten copper liquid is dropped onto a cold plate to cool and form copper grains under the protection of a protective atmosphere at 1100-1200°C for 10-40 min. The copper grains are then hot-pressed into a copper sputtering target material. The invention adopts a vacuum melting method to melt and refine 5N and above high-purity copper. The continuous feeding mode is adopted during the melting process to ensure the continuity of the melting process, thereby improving the production efficiency. The molten copper liquid is cooled by a rapid cooling method to obtain fine-grained copper, thereby avoiding the defects of difficult control of the grain size uniformity of the target material in the traditional target material preparation process. The grain size is uniform and easy to control, which can improve the efficiency and reduce the cost.

[0005] However, there are few methods for directly preparing cuprous oxide thin films using cuprous oxide target materials, and there are few published studies on the process of preparing cuprous oxide target materials. SUMMARY

[0006] In view of the shortcomings and deficiencies of the prior art, the primary purpose of the present application is to provide a preparation method of a cuprous oxide target material for sputtering. The preparation method of the present application adopts cuprous oxide powder which is vacuum degassed and then hot-pressed and sintered in a mold, which has the advantages of simple operation and low cost. Moreover, the cuprous oxide target material prepared by this method has high relative density and single crystal type, which meets the requirements of sputtering targets.

[0007] Another purpose of the present application is to provide a cuprous oxide target material prepared by the above method.

[0008] Still another purpose of the present application is to provide the application of the above cuprous oxide target material in the preparation of cuprous oxide thin films by magnetron sputtering.

[0009] The purposes of the present application are achieved by the following technical solutions.

[0010] A preparation method of a cuprous oxide target material for sputtering, comprising the following preparation steps:

[0011] (1) cuprous oxide powder is vacuum degassed at 120-150°C and then loaded into a graphite mold;

[0012] (2) The cuprous oxide powder of step (1) is cold-pressed to 5-10 MPa, then heated to 780-820°C under vacuum, and held for treatment, and then pressurized to 30-50 MPa for holding and pressure treatment, after which the holding and pressure treatment time ends, the furnace is cooled to room temperature, and the cuprous oxide target blank is demolded to obtain a cuprous oxide target blank;

[0013] (3) The cuprous oxide target blank obtained in step (2) is subjected to face milling treatment to obtain a cuprous oxide target material for sputtering.

[0014] Further, the cuprous oxide powder in step (1) is preferably cuprous oxide powder with a purity greater than 99.99%.

[0015] Further, the D90 particle size of the cuprous oxide powder in step (1) is required to be <20 μm.

[0016] Further, the vacuum degassing step in step (1) is as follows: the cuprous oxide powder is placed in a clean alumina crucible, then placed in a vacuum furnace, vacuumed to less than 10 Pa, heated to 120-150°C at a rate of 2-10°C / min, held for 1-5 h, and then cooled to room temperature with the furnace.

[0017] Through the above vacuum degassing treatment, the powder is fully dried and the gas adhered to the powder is removed, which can significantly improve the relative density, uniformity and conductivity of the finally obtained cuprous oxide target material.

[0018] Further, the cold-pressing to 5-10 MPa in step (2) means cold-pressing to 5-10 MPa at a rate of 0.1-0.6 MPa / min.

[0019] Further, the vacuum condition in step (2) means vacuuming to less than 10 Pa.

[0020] Further, the rate of heating in step (2) is 5-10°C / min.

[0021] Further, the holding time of the holding treatment in step (2) is 0.5-3 h, and the holding and pressure treatment time is 1-5 h.

[0022] Further, the pressurization to 30-50 MPa in step (2) means pressurization to 30-50 MPa at a pressurization rate of 0.1-0.6 MPa / min.

[0023] Further, the face milling treatment in step (3) is as follows: the obtained cuprous oxide target blank is fixed on a numerical control milling machine, a 100-300 mesh resin diamond grinding wheel is used for face milling at a speed of 700-900 r / min, and the upper and lower surfaces of the cuprous oxide target blank are removed by more than 1 mm in thickness, thereby obtaining a cuprous oxide target material for sputtering.

[0024] A cuprous oxide target for sputtering is prepared by the method.

[0025] Further, the cuprous oxide target has a single phase of isometric cubic crystal system Cu2O, a relative density of >99%, and a resistivity of ≤8kΩ·cm.

[0026] Application of the cuprous oxide target in the preparation of cuprous oxide film by magnetron sputtering.

[0027] Further, the application method is: using the cuprous oxide target as a sputtering target, using Ar gas as a sputtering gas, and depositing a cuprous oxide film on a substrate surface by magnetron sputtering. The magnetron sputtering condition is Ar atmosphere, avoiding O2 atmosphere to generate CuO and other phases.

[0028] Compared with the prior art, the cuprous oxide target has the following advantages:

[0029] (1) The cuprous oxide target prepared by the method has a relative density of >99%, a single crystal structure, and is of isometric cubic crystal system, has uniform color, and has good conductivity. The cuprous oxide target can be directly used to prepare a pure-phase Cu2O film with good crystallinity and high hole mobility by magnetron sputtering.

[0030] (2) The preparation method of the cuprous oxide target is simple in operation and low in cost.

[0031] (3) The preparation process conditions of the cuprous oxide target meeting the requirements of a sputtering target are determined. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 FIG. 1 is an X-ray diffraction (XRD) pattern of the cuprous oxide target obtained in Example 1. DETAILED DESCRIPTION

[0033] The application will be further described in detail below with reference to the examples and the accompanying drawings, but the embodiments of the application are not limited thereto.

[0034] Example 1

[0035] The preparation method of the cuprous oxide target for sputtering comprises the following preparation steps:

[0036] (1) Preparation of raw materials: prepare cuprous oxide powder with a purity of >99.99%, a powder D50 of 5μm, and a D90 of 15μm.

[0037] (2) Degassing: Put the qualified cuprous oxide powder into a clean alumina crucible, cover it with a cover with a gas outlet, and place it in a vacuum furnace. Vacuumize to a vacuum degree less than 10 Pa, heat to 120℃ at a rate of 5℃ / min, and keep the temperature for 2 h to fully dry the powder and remove the gas adhered to the powder. Cool to room temperature with the furnace.

[0038] (3) Loading: Quickly load the powder after degassing into a graphite mold.

[0039] (4) Hot-press sintering: After loading into the furnace, cold-press to 6 MPa at a rate of 0.6 MPa / min, vacuumize to less than 10 Pa, start to increase the temperature to 800℃ at a rate of 10℃ / min, keep the temperature for 1 h, pressurize to 40 MPa at a rate of 0.5 MPa / min, and keep the temperature and pressure for 2 h. After the temperature and pressure keeping time ends, cool to room temperature with the furnace, open the furnace door, and take out the target blank from the mold to obtain a processable cuprous oxide target blank.

[0040] (5) Target blank processing: Fix the obtained cuprous oxide target blank on a numerical control milling machine, mill the surface with a 200-mesh resin diamond grinding wheel at a speed of 800 r / min, remove more than 1 mm thickness from the top and bottom surfaces of the cuprous oxide target blank, clean and dry to obtain a cuprous oxide target material for sputtering.

[0041] Test the relative density, electrical conductivity, appearance uniformity, and phase of the obtained cuprous oxide target material. The relative density is directly tested by the traditional Archimedes method, the electrical conductivity is tested by the four-probe method, the appearance uniformity is observed to see if there are color differences and pores and other defects on the surface of the target material, and the phase is analyzed by X-ray diffraction pattern.

[0042] The test results show that the relative density of the cuprous oxide target material obtained in this embodiment is 99.8%; the four-probe detection resistivity is 9 kΩ·cm; the appearance color is uniform, and there are no pores and other defects. The X-ray diffraction pattern of the obtained cuprous oxide target material is shown in Figure 1 Figure 1 It can be seen from the results that only the isometric cubic crystal system Cu2O phase exists in the obtained cuprous oxide target material, which meets the requirements of the sputtering target.

[0043] For crystalline photovoltaic and photoelectric conversion devices, crystallinity and pure crystal composition are important factors for limiting defect-related charge recombination. The cuprous oxide film prepared by sputtering the target material obtained in this embodiment in an Ar atmosphere has good crystallinity and is pure Cu2O, with a high hole mobility of 7.7 cm 2 ·V -1 ·s -1 , a low resistivity of 146 Ω·cm, and a hole concentration of 5.5×10 15 cm -3 ​On the contrary, other phases of CuO or Cu 2+ The crystallinity of Cu2O will be reduced, and the hole mobility of Cu2O will sharply decrease due to the scattering of impurities (grain boundaries and defects).

[0044] Example 2

[0045] The method for preparing the cuprous oxide target material for sputtering comprises the following preparation steps:

[0046] (1) Preparation of raw materials: prepare cuprous oxide powder with a purity greater than 99.99%, a powder D50 of 5 μm, and a powder D90 of 15 μm.

[0047] (2) Degassing: place the qualified cuprous oxide powder into a clean alumina crucible, cover it with a cover with a gas outlet hole, and place it in a vacuum furnace. Vacuumize it to a vacuum degree less than 10 Pa, heat it to 150 °C at a rate of 5 °C / min, and keep it for 2 h to fully dry the powder and remove the gas adhered to the powder. Cool it to room temperature with the furnace.

[0048] (3) Loading: quickly load the powder after degassing into a graphite mold.

[0049] (4) Hot-pressing sintering: after loading into the furnace, cold-press it to 6 MPa at a rate of 0.1 MPa / min, vacuumize it to less than 10 Pa, start to increase the temperature to 820 °C at a rate of 10 °C / min, keep it for 1 h, pressurize it to 40 MPa at a rate of 0.3 MPa / min, and keep it for 2 h. After the pressure-keeping time ends, cool it to room temperature with the furnace, open the furnace door, and take out the target blank from the mold to obtain a processable cuprous oxide target blank.

[0050] (5) Processing of the target blank: fix the obtained cuprous oxide target blank on a numerical control milling machine, mill the surface with a 200-mesh resin diamond grinding wheel at a speed of 800 r / min, remove more than 1 mm in thickness from the upper and lower surfaces of the cuprous oxide target blank, clean and dry it, and obtain a cuprous oxide target material for sputtering.

[0051] The relative density of the cuprous oxide target material obtained in this example is 99.9%, the four-probe detected resistivity is 8 kΩ·cm, the appearance color is uniform, there are no defects such as pores, the phase is a single equiaxed cubic crystal system Cu2O, and it meets the requirements of a sputtering target.

[0052] Example 3

[0053] The method for preparing the cuprous oxide target material for sputtering comprises the following preparation steps:

[0054] (1) Preparation of raw materials: prepare cuprous oxide powder with a purity greater than 99.99%, a powder D50 of 5 μm, and a powder D90 of 15 μm.

[0055] (2) Degassing: Put the qualified cuprous oxide powder into a clean alumina crucible, cover it with a cover with a gas outlet, and place it in a vacuum furnace. Vacuumize it to a vacuum degree less than 10 Pa, heat it to 120 ℃ at a rate of 5 ℃ / min, and keep it for 2 h to fully dry the powder and remove the gas adhered to the powder. Cool it to room temperature with the furnace.

[0056] (3) Loading: Quickly load the powder after degassing into a graphite mold.

[0057] (4) Hot-pressing sintering: After loading into the furnace, cold-press it to 10 MPa at a rate of 0.1 MPa / min, vacuumize it to less than 10 Pa, start heating it to 780 ℃ at a rate of 10 ℃ / min, keep it for 1 h, pressurize it to 40 MPa at a rate of 0.5 MPa / min, and keep it for 2 h. After the pressure-keeping time is over, cool it to room temperature with the furnace, open the furnace door, and take out the target blank from the mold to obtain a processable cuprous oxide target blank.

[0058] (5) Target blank processing: Fix the obtained cuprous oxide target blank on a numerical control milling machine, mill the surface with a 200-mesh resin diamond grinding wheel at a speed of 800 r / min, remove more than 1 mm thickness from the top and bottom surfaces of the cuprous oxide target blank, clean and dry it, and obtain a cuprous oxide target material for sputtering.

[0059] The relative density of the cuprous oxide target material obtained in this example is 99.1%; the four-probe detected resistivity is 9.5 kΩ·cm; the appearance is uniform in color and free of defects such as pores; the phase is a single equiaxed cubic crystal system Cu2O, which meets the requirements of a sputtering target.

[0060] Comparative Example 1

[0061] The preparation method of a cuprous oxide target material for sputtering in this comparative example is compared with Example 1, and the D50 of the raw material cuprous oxide powder is 10 μm and the D90 is 20 μm. The rest of the process conditions are exactly the same.

[0062] The relative density of the cuprous oxide target material obtained in this comparative example is 98.0%; the four-probe detected resistivity is 12 kΩ·cm; the appearance is uniform in color and free of defects such as pores. It shows that the preparation of the cuprous oxide target material of the present application has requirements for the particle size of the raw material powder, and the excessive particle size of the powder will lead to the decrease of the relative density and the conductivity.

[0063] Comparative Example 2

[0064] The preparation method of a cuprous oxide target material for sputtering in this comparative example is compared with Example 1, and the sintering temperature in step (4) is reduced from 800 ℃ to 750 ℃, and the rest of the process conditions are exactly the same.

[0065] The relative density of the cuprous oxide target obtained by the present comparative example is 89.1%; the resistance cannot be measured by the four-probe in some places, indicating that the resistance is not conductive in some places; the appearance has color difference and porosity defects. It does not meet the requirements of sputtering target.

[0066] The comparison between the present comparative example and Example 1 shows that, in the preparation process of the cuprous oxide target of the present application, too low sintering temperature will result in the decrease of the relative density and uniformity of the cuprous oxide target.

[0067] Comparative Example 3

[0068] The preparation method of the cuprous oxide target for sputtering of the present comparative example is compared with Example 1, and the sintering temperature in step (4) is increased from 800℃ to 900℃, and the rest of the process conditions are exactly the same.

[0069] The cuprous oxide target obtained by the present comparative example has visible metallic luster spots on the surface, and the appearance has color difference; the reason is that the sintering temperature is too high, and the cuprous oxide is reduced to metal Cu by graphite. The relative density of the target is 105.6%, the resistance is 0.01-8KΩ·cm, and the resistance is not uniform.

[0070] The comparison between the present comparative example and Example 1 shows that, in the preparation process of the cuprous oxide target of the present application, too high sintering temperature will result in the reduction of the surface and uniformity of the cuprous oxide target.

[0071] Comparative Example 4

[0072] The preparation method of the cuprous oxide target for sputtering of the present comparative example is compared with Example 1, and there is no step (2) of vacuum heating and degassing, and the rest of the process conditions are exactly the same.

[0073] The relative density of the cuprous oxide target obtained by the present comparative example is 95.2%; the resistance cannot be measured by the four-probe, and it is not conductive; the appearance has color difference. It does not meet the requirements of sputtering target.

[0074] The comparison between the present comparative example and Example 1 shows that, in the preparation process of the cuprous oxide target of the present application, the relative density, uniformity and conductivity of the target can be improved by pre-vacuum heating and degassing before hot-pressing sintering.

[0075] Comparative Example 5

[0076] The preparation method of the cuprous oxide target for sputtering of the present comparative example is compared with Example 1, and the temperature of vacuum heating and degassing in step (2) is increased from 120℃ to 180℃, and the rest of the process conditions are exactly the same.

[0077] The powder after vacuum heating and degassing of the present comparative example has partial clumping, which affects the subsequent loading process. It shows that too high degassing temperature has adverse effects on the powder loading process.

[0078] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications, etc. made without departing from the spirit and principles of the present application should be equivalent replacement manners and should be included in the protection scope of the present application.

Claims

1. A method for preparing a cuprous oxide target for sputtering, characterized in that, The preparation steps include the following: (1) After vacuum degassing the cuprous oxide powder at 120~150℃, it is loaded into a graphite mold; (2) The cuprous oxide powder from step (1) is cold-pressed to 5~10MPa, then heated to 780~820℃ under vacuum and kept warm, then pressurized to 30~50MPa and kept warm and pressurized. After the warm and pressurized time is over, it is cooled to room temperature with the furnace and demolded to obtain the cuprous oxide target blank. (3) The cuprous oxide target blank obtained in step (2) is milled to obtain a cuprous oxide target for sputtering; The D90 particle size requirement for the cuprous oxide powder mentioned in step (1) is <20μm; The vacuum degassing step in step (1) is as follows: place cuprous oxide powder into a clean alumina crucible, then place it in a vacuum furnace, evacuate to less than 10 Pa, heat to 120-150 °C at a rate of 2-10 °C / min, hold for 1-5 h, and then cool to room temperature with the furnace. The heating rate in step (2) is 5~10℃ / min; the heat preservation time is 0.5~3h; the heat preservation and pressure preservation time is 1~5h; the pressurization to 30~50MPa refers to pressurizing to 30~50MPa at a pressurization rate of 0.1~0.6MPa / min.

2. The method for preparing a cuprous oxide sputtering target according to claim 1, characterized in that, The purity of the cuprous oxide powder mentioned in step (1) is greater than 99.99%.

3. The method for preparing a cuprous oxide sputtering target according to claim 1, characterized in that, The cold pressing to 5~10MPa mentioned in step (2) refers to cold pressing to 5~10MPa at 0.1~0.6MPa / min; the vacuum condition refers to evacuating to less than 10Pa.

4. The method for preparing a cuprous oxide sputtering target according to claim 1, characterized in that, The milling process described in step (3) is as follows: the obtained cuprous oxide target blank is fixed on a CNC milling machine, and a 100~300 mesh resin diamond grinding wheel is used for milling at a speed of 700~900 r / min. The thickness of the cuprous oxide target blank is removed by more than 1 mm from both the top and bottom surfaces, thus obtaining the cuprous oxide target material for sputtering.

5. A cuprous oxide target material, characterized in that, It is prepared by the method described in any one of claims 1 to 4.

6. The cuprous oxide target material according to claim 5, characterized in that, The cuprous oxide target material has a single isometric cubic Cu2O phase with a relative density >99% and a resistivity ≤8kΩ·cm.

7. The application of the cuprous oxide target as described in claim 5 or 6 in the preparation of cuprous oxide thin films by magnetron sputtering.

8. The application of the cuprous oxide target according to claim 7 in the preparation of cuprous oxide thin films by magnetron sputtering, characterized in that, The application method is as follows: using a cuprous oxide target as the sputtering target and Ar gas as the sputtering gas, a cuprous oxide thin film is deposited on the substrate surface by magnetron sputtering.

Images