Preparation method of gallium oxide ceramic target material

Abstract

The invention provides a preparation method of a gallium oxide ceramic target material, and relates to the technical field of preparation of oxide target materials and preparation of semiconductor target materials. The method comprises the following steps: weighing a pure-phase gallium oxide target material by using an electronic scale, pouring powder into an alumina crucible, adding a proper amount of a binder, stirring, granulating, screening by using a proper screen, pouring into a mold, vibrating, and uniformly paving; and then preparing the pure gallium oxide target material by adopting a hydraulic machine for tabletting, sintering and other processes. The steps of mixing, drying and the like are added before granulation of the doped tin oxide target material. The target material prepared by the method is not easy to fall off powder, damage and the like in the transfer process. The ceramic target material sintered at 1200-1800 DEG C for 16-32 hours after low-temperature baking and degumming is smooth in surface and compact in structure, and the phenomena of damage, splashing and the like cannot occur in the use process of the subsequent laser technology.

Description

Technical Field

[0001] The invention belongs to the field of preparation of semiconductor material gallium oxide target material, and in particular relates to a preparation method of gallium oxide ceramic target material. Background Art

[0002] Gallium oxide materials are wide bandgap semiconductor materials with a bandgap width of 4.7-5.2eV. They have good chemical and thermal stability, sensitive resistivity to environmental changes at high temperatures, and most notably good light responsiveness, signal-to-noise ratio, stability, and response speed in the deep ultraviolet band. Compared with silicon carbide and gallium nitride materials, the Baliga figure of merit of gallium oxide is 3214, which is three times that of SiC materials, indicating that the on-resistance of gallium oxide materials is smaller; the breakdown electric field strength is 8MV / cm, so that under the same withstand voltage, the device can be made thinner, the single-item area on-resistance is smaller, the prepared power chip area is smaller, the junction capacitance is small, and the switching speed is fast, so that it can serve in high-power electronic devices. Therefore, in order to prepare gallium oxide thin film materials, physical vapor deposition methods such as pulsed laser deposition and molecular beam epitaxial growth are often used for growth. Compared with other physical vapor deposition methods, pulsed laser deposition can strictly control its stoichiometric ratio and has low requirements for target materials. Compared with chemical vapor deposition, it has the advantages of high film resolution, low pollution, and a wide range of process adjustment parameters. The pulsed laser deposition system needs to use solid ceramic targets with high density and smooth surface, but it does not want the ceramic targets to have high hardness and no breakage or powdering during laser bombardment.

[0003] At present, gallium oxide targets have not been industrialized for mass production, and some scientific research has not summarized the sintering process of targets in detail. This has led to the discovery in previous studies that ceramic targets prepared by directly using gallium oxide powder for tableting often have problems such as demolding and fragmentation during the preparation process, and too high hardness after sintering, which leads to brittle cracks of the target after laser bombardment. To solve the above problems, other oxide ceramic target materials are usually sintered by adding binders, doping, and setting appropriate sintering processes to obtain target materials with the required performance. Summary of the invention

[0004] Purpose of the invention: In view of the shortcomings of the prior art, the present invention proposes a method for preparing a gallium oxide ceramic target, which solves the problem that the gallium oxide ceramic target does not break during the preparation process and is dense and does not break during subsequent use.

[0005] Technical solution: In order to achieve the above-mentioned invention object, the present invention proposes a method for preparing a gallium oxide ceramic target, which comprises the following steps:

[0006] (1) Gallium oxide and tin oxide powders are weighed using an electronic balance according to the required ratio, the powders are poured into a crucible, and a solvent is added to prepare a slurry; the particle size of the gallium oxide is 2-5um, the purity is 5N, and the mass percentage is 90%-100%, the particle size of the tin oxide is 20-100nm, the purity is 5N, and the mass percentage is 0%-10%, and the solvent is anhydrous ethanol, and the amount of anhydrous ethanol added is 3-10 times the mass of the powder;

[0007] (2) heating and stirring the slurry in step (1) to volatilize the anhydrous ethanol;

[0008] (3) removing the crucible after the slurry in step (2) is heated to a molten state;

[0009] (4) taking a binder and adding it to the crucible in step (3), stirring and using the residual temperature to completely dry the powder;

[0010] (5) filtering the powder obtained in step (4) through a filter;

[0011] (6) Add the powder after granulation and filtration in step (5) into a mold of the required size.

[0012] (7) Pre-pressing the powder obtained in step (6) using a hydraulic press, and performing a demolding process after static pressing for a period of time to obtain a target blank;

[0013] (8) The green blank obtained in step (7) is sintered by a debonding-gradient sintering technology, firstly slowly heating from room temperature to 300-400° C., with a heating rate of 1.5-2.5° C. / min, and keeping the temperature for 2-4 hours; after 400° C., the heating rate is increased to 2-6° C. / min, and the temperature is raised to 1200-1600° C. and kept for 16-32 hours; the temperature is lowered to 900-1200° C. and kept for 10 hours, with a cooling rate of 0.5-1° C. / min; the temperature is further cooled to 250-300° C. at a cooling rate of 1.5-2.5° C.; heating is stopped and the temperature is cooled to room temperature, to obtain a doped gallium oxide target with a relative density of more than 98-99.5%.

[0014] Furthermore, in step (2), the heating temperature range is 70°C-110°C.

[0015] Furthermore, the binder added in step (3) is a 4-5wt% polyvinyl alcohol (PVA) solution with a mass of 0.1-0.2g; further, the binder is prepared by mixing 2.5-4g polyvinyl alcohol particles with 60-70ml deionized water; sealing the mouth of the beaker with tin foil to prevent water evaporation; placing the beaker in an oven and keeping it warm at 95-105°C for 4h to 5h, taking it out and stirring it once every half an hour during the process, and the single stirring time is not less than 3 minutes to avoid stratification.

[0016] Furthermore, the mesh size of the sieve selected in step (5) is 100 or 120 meshes.

[0017] Furthermore, the mold in step (6) can be one or two inches in size, but the inner wall of the mold is required to be smooth for easy demoulding.

[0018] Furthermore, in the step (7), the hydraulic press pressure in the pre-pressing molding is 10-15 MPa, and the isostatic pressing holding time is 3-10 min.

[0019] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0020] In order to achieve the required specific target material, the gallium oxide powder is re-granulated to solve the problem that when the powder is too fine, the particle specific surface area is too large, the powder fluidity is poor, and the formability is poor. The addition of the binder is to make the powder agglomerate into small particles, and at the same time strengthen the bonding force between the powders, so that the powder will have better formability, avoiding the problems of voids, cracks, and incomplete filling caused by uneven mold pressure that may occur during tableting or sintering. Therefore, this patent effectively prepares a highly dense and uniformly distributed gallium oxide ceramic target by mixing appropriate binders and powder ratios and setting appropriate sintering processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a process flow chart of the preparation process of gallium oxide target during implementation;

[0022] Figure 2 is a sintering temperature curve during the sintering of gallium oxide target material in the implementation process;

[0023] Figure 3 This is the XRD spectrum of the gallium oxide target after sintering. DETAILED DESCRIPTION

[0024] The following is a clear and complete description of the technical solution of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0025] Example 1: Preparation of 1at% Sn-doped Gallium Oxide Ceramic Target

[0026] Step 1: High-density gallium oxide ceramics, raw materials are prepared according to atomic percentage, and the required weight of powder is calculated, which is composed of the following components: From the periodic table, the unit molar mass of gallium is 69.72g, the unit molar mass of tin is 118.7g, and the unit molar mass of oxygen is 16. When the total target material weighs 5g of powder, the mass ratio is obtained according to the atomic percentage of tin: gallium = 1:99, that is, 0.0805g of tin oxide powder and 4.9195g of gallium oxide powder. In addition, a rubber-tipped dropper is used to absorb the polyvinyl alcohol solution, and the added amount is 0.15-0.3g.

[0027] Step 2: Pour the above powder into an alumina crucible, add 50 ml of anhydrous ethanol, and stir with a spatula or a glass rod to evenly disperse the powder.

[0028] Step 3: Heat the crucible in step 2 on a heating table at 90°C, stirring continuously during the heating process to accelerate the volatilization of anhydrous ethanol and disperse it evenly. When the slurry in the crucible is molten, remove the crucible from the heating table.

[0029] Step 4: Take a medicine spoon, peel the balance, use a rubber-tipped dropper to absorb the polyvinyl alcohol solution, and drop it on the medicine spoon. The weight is 0.1 g. Mix it with the molten powder for 10 minutes. During the process, the residual temperature is used to evaporate all the anhydrous ethanol solvent, completing the granulation work.

[0030] Step 5: Screen the granulated powder through a 120-mesh sieve.

[0031] Step 6: Place the granulated powder in a one-inch alloy steel mold and use a medicine spoon to vibrate and flatten it.

[0032] Step seven, use a hydraulic press to perform pre-pressing molding, the molding pressure is 15MPa, the pressure is maintained for 3 minutes, and after the pressing is completed, demolding is performed to obtain a target blank.

[0033] Step eight, transfer the target blank to the alumina stage and place it in a muffle furnace. Use debonding-gradient sintering technology for sintering, first slowly heat up from room temperature to 350°C, with a heating rate of 1.5°C / min, and keep warm for 2h; after 400°C, increase the heating rate to 3°C / min, heat up to 1600°C and keep warm for 24h; cool down to 900°C at a cooling rate of 1°C and keep warm for 10h; then cool down to 300°C at a cooling rate of 2.5°C, finally stop heating and slowly cool down to room temperature to obtain a 1at% tin oxide-doped gallium oxide target.

[0034] The density obtained in this example is 98.2%. The target material is characterized by powder X-ray diffraction. The results are as follows: Figure 3 As shown, the characteristic X-ray diffraction peak of the target material is the black curve, among which the dark blue curve is the characteristic diffraction peak of pure β-phase gallium oxide, and the purple curve is the characteristic diffraction peak of pure SnO2. It can be seen that the characteristic diffraction peak measured by the target material completely corresponds to the characteristic diffraction peak of β-phase gallium oxide. The two characteristic peaks of 54.77° and 26.642° correspond to the (220) and (110) crystal planes of SnO2, and there are no other impurity peaks, which means that the components of the prepared ceramic target material are Ga2O3 and SnO2. The absence of other impurity peaks indicates that there are no other components and no other transition phases.

Claims

1. A method for preparing a gallium oxide ceramic target, characterized in that: The method comprises the following steps (1) Gallium oxide and tin oxide powders are weighed using an electronic balance according to the required ratio, the powders are poured into a crucible, and a solvent is added to prepare a slurry; the particle size of the gallium oxide is 2-5um, the purity is 5N, and the mass percentage is 90%-100%, the particle size of the tin oxide is 20-100nm, the purity is 5N, and the mass percentage is 0%-10%, and the solvent is anhydrous ethanol, and the amount of anhydrous ethanol added is 3-10 times the mass of the powder; (2) heating and stirring the slurry in step (1) to volatilize the anhydrous ethanol; (3) removing the crucible after the slurry in step (2) is heated to a molten state; (4) taking a binder and adding it to the crucible in step (3), stirring and using the residual temperature to completely dry the powder; (5) filtering the powder obtained in step (4) using a filter screen; (6) Add the powder after granulation and filtration in step (5) into a mold of the required size. (7) Pre-pressing the powder obtained in step (6) using a hydraulic press, and performing a demolding process after static pressing for a period of time to obtain a target blank; (8) The green blank obtained in step (7) is sintered by a debonding-gradient sintering technology, firstly slowly heating from room temperature to 300-400° C., with a heating rate of 1.5-2.5° C. / min, and keeping the temperature for 2-4 hours; after 400° C., the heating rate is increased to 2-6° C. / min, and the temperature is raised to 1200-1600° C. and kept for 16-32 hours; the temperature is lowered to 900-1200° C. and kept for 10 hours, with a cooling rate of 0.5-1° C. / min; the temperature is further cooled to 250-300° C. at a cooling rate of 1.5-2.5° C.; heating is stopped and the temperature is cooled to room temperature, to obtain a doped gallium oxide target with a relative density of more than 98-99.5%.

2. The method for preparing a gallium oxide ceramic target according to claim 1, characterized in that: In step (2), the heating temperature range is 70°C-110°C.

3. The method for preparing a gallium oxide ceramic target according to claim 1, characterized in that: The binder added in step (3) is a 4-5wt% polyvinyl alcohol (PVA) solution with a mass of 0.1-0.2g.

4. The method for preparing a gallium oxide ceramic target according to claim 3, characterized in that: The binder is prepared by mixing 2.5-4g of polyvinyl alcohol particles with 60-70ml of deionized water; sealing the mouth of a beaker with tin foil, placing the beaker in an oven, keeping it warm at 95-105°C for 4-5h, taking it out for stirring every half an hour, and the single stirring time is not less than 3 minutes.

5. The method for preparing a gallium oxide ceramic target according to claim 1, characterized in that: The mesh size of the sieve selected in step (5) is 100 or 120 meshes.

6. The method for preparing a gallium oxide ceramic target according to claim 1, characterized in that: In the step (7), the hydraulic press pressure in the pre-pressing molding is 10-15 MPa, and the static pressure holding time is 3-10 min.

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