A method for preparing IGZO target material by three-step segmented sintering process

Abstract

The present invention discloses a method for preparing an IGZO target material by a three-step segmented sintering process, which is carried out in the following steps: placing an IGZO green body into a sintering furnace, and under negative pressure and air atmosphere, heating the temperature from room temperature to a first sintering temperature of 500-700°C at a rate I, and keeping the temperature for 2-6 hours to perform degreasing; heating the temperature in the furnace to 700-800°C at a rate I, and then starting to fill with oxygen, and controlling the gas pressure in the furnace; heating the temperature in the furnace to a second sintering temperature of 1350-1550°C at a rate II under an oxygen atmosphere, and The process is then continued for 1 to 4 hours. The temperature in the furnace is lowered at rate III to a third sintering temperature of 1300 to 1380°C, and maintained for 4 to 6 hours. At the midpoint of this holding period, argon is introduced and the oxygen flow rate is adjusted to adjust the oxygen volume concentration in the furnace. The oxygen to argon flow rate ratio is controlled at (0.2 to 0.8):1. The temperature in the furnace is lowered at rate IV to 800 to 1000°C, followed by cooling. The oxygen introduction is stopped, and the argon introduction is stopped when the temperature drops to 650 to 950°C. The target is then removed from the furnace at room temperature to obtain an IGZO target. The present invention is simple to operate, has a simple and controllable process, and can be implemented for large-scale industrial production. The resulting IGZO target can achieve a relative density of 99.70% and a resistivity of no more than 1.49 mΩ·cm.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of IGZO target materials, and in particular relates to a method for preparing IGZO target materials by a three-step segmented sintering process. Background Art

[0002] IGZO (Indium Gallium Zinc Oxide) target is made of In2O3, Ga2O3 and ZnO sintered in a certain proportion. Due to the advantages of IGZO semiconductor film such as large bandgap, high carrier mobility, good uniformity over a large area, high stability, good low-temperature growth, ability to be prepared on a flexible substrate and ability to realize fully transparent devices, it is widely used in electronic display industries such as flexible electronics, rollable optoelectronic devices, and fully transparent display touch screens.

[0003] The currently disclosed IGZO target sintering methods mainly include hot pressing sintering, hot isostatic pressing sintering, atmospheric pressure sintering, etc. When making large-sized IGZO targets, atmospheric pressure sintering is often used. We have found the following published patents on the preparation of IGZO targets:

[0004] Chinese patent CN103819178 A discloses a method for preparing an IGZO target material, wherein the sintering process is as follows: the green blank is placed in a sintering furnace for sintering, and the temperature is increased at a heating rate of no more than 1°C / min to 1300-1550°C and sintered for 4-10 hours. Thereafter, the temperature is lowered to 950-1050°C at a cooling rate of 0.5-1°C / min, and finally the temperature is naturally lowered to obtain an IGZO target material. The prepared IGZO target material has high density, a relative density of >98%, and high conductivity. However, the IGZO target material prepared by this sintering method cannot be fully densified, and its internal microstructure still has many holes and is prone to defects such as coarse grains and poor uniformity.

[0005] Chinese patent CN110002853 A discloses a two-step sintering process for preparing IGZO ceramic targets. After the slurry is prepared and formed, it is cast using gypsum slip casting. The IGZO ceramic green body is then degreased at 600-800°C. The degreased IGZO ceramic green body is heated to a first-step sintering temperature of 1400-1500°C, then cooled to a second-step sintering temperature of 1320-1360°C and held at this temperature for 8-14 hours. This method can produce high-density, low-resistivity, and fine-grained IGZO ceramic targets. IGZO targets can achieve relative densities of up to 99.5%, resistivities as low as 1.59 mΩ·cm, and grain sizes as low as 4.78 μm. However, the resistivity of this method still needs to be improved. Summary of the Invention

[0006] The purpose of the present invention is to solve the above technical problems and provide a method for preparing an IGZO target material by a three-step segmented sintering process. The IGZO target material obtained by this method is stable and uniform, has a high relative density and low resistivity.

[0007] To achieve the above-mentioned purpose, the technical solution of the present invention is:

[0008] A method for preparing an IGZO target by a three-step segmented sintering process is carried out in the following steps:

[0009] (1) Place the IGZO green body in a sintering furnace, and under negative pressure and air atmosphere, raise the temperature from room temperature to the first sintering temperature of 500-700°C at a rate of I, and keep it at this temperature for 2-6 hours for degreasing;

[0010] (2) The temperature in the furnace is raised to 700-800°C at rate I, and then oxygen is introduced to control the gas pressure in the furnace;

[0011] (3) In an oxygen atmosphere, raise the temperature in the furnace to the second sintering temperature of 1350-1550°C at rate II and keep it at that temperature for 1-4 hours;

[0012] (4) The temperature in the furnace is lowered to the third sintering temperature of 1300-1380°C at a rate of III and kept at this temperature for 4-6 hours. At the midpoint of this holding time, argon is introduced and the oxygen flow rate is adjusted to adjust the oxygen volume concentration in the furnace. The oxygen and argon flow rate ratio is controlled at (0.2-0.8):1;

[0013] (5) The temperature in the furnace is reduced to 800-1000°C at a rate IV and then cooled with the furnace. The introduction of oxygen is stopped. When the temperature drops to 650-950°C, the introduction of argon is stopped. Finally, the target is taken out of the furnace at room temperature to obtain the IGZO target.

[0014] As a further technical solution, the above-mentioned IGZO green body is prepared by mixing In2O3 powder, nano-Ga2O3 powder and nano-ZnO powder, and the molar ratio of In, Ga and Zn is (1-6): (1-6): (1-6).

[0015] As a further technical solution, the preparation of the above-mentioned IGZO green body is to mechanically mix In2O3 powder, nano-Ga2O3 powder and nano-ZnO powder according to a molar ratio to obtain uniform IGZO powder, and then add a binder of 2 to 10‰ of the mass of the IGZO powder for spray drying and granulation to obtain IGZO powder particles; then the IGZO powder particles are pre-pressed at 15 to 30 MPa in a hydraulic press, and finally put into a cold isostatic press at 240 to 300 MPa to press into a uniform IGZO green body.

[0016] As a further technical solution, the negative pressure in the furnace in the above step (1) is -0.01 to -0.06 MPa.

[0017] As a further technical solution, the above-mentioned rate I is 1 to 5°C / min.

[0018] As a further technical solution, in the above step (2), the oxygen volume concentration in the furnace is greater than 99.5%, and the gas pressure is 0.03-0.05 MPa.

[0019] As a further technical solution, the above-mentioned rate II is 1 to 6°C / min.

[0020] As a further technical solution, the above-mentioned rate III is 6 to 10°C / min.

[0021] As a further technical solution, the above-mentioned rate IV is 2 to 6°C / min.

[0022] The technical principles of the present invention are:

[0023] When sintering temperatures are below 1100°C, the metal composition of the IGZO green body and the quality of the sintered body do not change significantly. The main mass loss is the binder in the green body. The low-temperature initial stage is used for degreasing and heat preservation. Timely vacuuming maintains negative pressure in the furnace and removes exhaust gases, ensuring a relatively pure sintered body.

[0024] When the sintering temperature is higher than 1300℃, the decomposition reaction of In2O3, Ga2O3 and ZnO in the IGZO sintered body at high temperature is particularly intense:

[0025] ZnO→Zn+O2↑

[0026] Ga2O3→Ga2O+O2↑

[0027] In2O3→In2O+O2↑

[0028] At this time, in order to prevent metals such as indium oxide from being reduced to suboxides during the sintering process, oxygen must be introduced to control this series of reactions.

[0029] The phases generated in the later stage of high temperature reaction are as follows:

[0030] Ga2O3+ZnO→ZnGa2O4

[0031] ZnGa2O4+ In2O3+ZnO→2InGaZnO4

[0032] At low temperatures, the sintered body forms ZnGa2O4. When the temperature exceeds 1200°C, the sintered body becomes primarily composed of the InGaZnO4 phase. In the later stages of the reaction, the oxygen vacancies in the In2O3 itself provide two charge carriers. If oxygen is continuously introduced during the later stages of sintering, the oxygen vacancies in the In2O3 decrease, reducing conductivity and increasing resistivity. Therefore, the present invention controls the oxygen volume concentration within the sintering furnace and adjusts the sintering atmosphere at appropriate times to reduce the resistivity of the IGZO target.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention adopts a three-step segmented sintering process. In the first step, the sintering temperature of 500-700°C is mainly for degreasing and heat preservation, while maintaining the negative pressure of the furnace body and removing the exhaust gas in the furnace to ensure that the sintered body is in a relatively pure sintering state; this step serves as the preheating stage of sintering, and the green body gradually enters the high-temperature sintering environment, and the internal microstructure and structure are gradually uniformly refined, which can avoid cracking of the target material; in the second step, the sintering temperature is controlled to be greater than 1350°C, and a high-concentration oxygen atmosphere can promote the densification of the target material; in the third step, the maximum sintering temperature is controlled to be less than 1380°C, and the sintering heat preservation time is shortened, which can reduce energy consumption while avoiding problems such as overburning of grain boundaries, coarse grains and poor uniformity.

[0035] The present invention precisely controls the time of introducing argon gas and utilizes the flow rates of oxygen and argon gas to control the oxygen volume concentration in the furnace, causing the IGZO target to partially lose oxygen and form oxygen vacancies. These oxygen vacancies act as carriers, improving the conductivity of the target material. While ensuring the high density of the target material, a low-resistivity IGZO target material is obtained.

[0036] The present invention is easy to operate, has a simple and controllable process, can realize large-scale industrial production, and the relative density of the obtained IGZO target material can reach 99.70%, and the resistivity is not higher than 1.49 mΩ·cm. DETAILED DESCRIPTION

[0037] The present invention will be further described in detail below with reference to examples, but the embodiments of the present invention are not limited to the scope of the examples.

[0038] To prepare IGZO green bodies, In2O3 powder, nano-Ga2O3 powder, and nano-ZnO powder were mechanically mixed in a molar ratio of 1:2:3 to obtain a uniform IGZO powder. A binder, PVA (polyvinyl alcohol), was then added at a concentration of 5‰ (based on the IGZO powder's mass) for spray drying and granulation to obtain IGZO granules. The spray-dried and granulated IGZO granules were pre-pressed in a hydraulic press at 30 MPa and then pressed in a cold isostatic press at 250 MPa to form uniform IGZO green bodies. This method is a conventional IGZO green body production process; where not explained in detail, the conventional process applies. The resulting IGZO green bodies were used for sintering in the Examples and Comparative Examples. Example 1:

[0039] A method for preparing IGZO target material by a three-step segmented sintering process is to take the IGZO green body and put it into a degreasing sintering furnace for sintering, heat it at a heating rate of 2.5℃ / min, evacuate the furnace body on time to keep the pressure at -0.04MPa, heat it to the first sintering temperature of 600℃ and keep it for 4h for degreasing, heat it to 700℃ at a heating rate of 2.5℃ / min, start to fill with oxygen, adjust the oxygen flow until the furnace pressure is stable at 0.04MPa and the oxygen volume concentration is >99.5%, and then heat it to the second sintering temperature at a heating rate of 2.5℃ / min. 1380℃, keep warm for 2h, then cool to the third sintering temperature 1320℃ at a cooling rate of 8℃ / min, keep warm for 2.5h, lower the oxygen flow rate, introduce argon, make the oxygen flow rate and argon flow rate 0.3:1, keep warm for another 2.5h, cool to 900℃ at a cooling rate of 3℃ / min, stop introducing oxygen, stop introducing argon when the temperature drops to 700℃, wait for the target material to reach room temperature and take out of the furnace. After post-processing, an IGZO target material with a size of 600×400×8mm, a relative density of 99.61% and a resistivity of 1.42mΩ·cm is obtained. Example 2:

[0040] A method for preparing IGZO target material by a three-step segmented sintering process is to take the IGZO green body and put it into a debinding sintering furnace for sintering, heat it at a heating rate of 1.5℃ / min, evacuate the furnace body on time to keep the pressure of -0.02MPa, heat it to the first sintering temperature of 650℃ and then keep it for 3h for debinding, heat it to 750℃ at a heating rate of 1.5℃ / min, start to fill with oxygen, adjust the oxygen flow until the furnace pressure is stable at 0.02MPa and the oxygen volume concentration is >99.5%, and then heat it to the second sintering temperature at a heating rate of 1.5℃ / min. The temperature was 1400°C, kept warm for 3 hours, then cooled to the third sintering temperature of 1340°C at a cooling rate of 6°C / min, kept warm for 3 hours, the oxygen flow rate was reduced, argon was introduced, and the oxygen flow rate and argon flow rate were 0.4:1, and then kept warm for 3 hours, cooled to 850°C at a cooling rate of 4°C / min, and the oxygen flow was stopped. When the temperature dropped to 700°C, the argon flow was stopped, and the target material was taken out of the furnace at room temperature. After post-processing, an IGZO target material with a size of 680×400×8mm, a relative density of 99.54%, and a resistivity of 1.36mΩ·cm was obtained. Example 3:

[0041] A method for preparing an IGZO target material by a three-step segmented sintering process is to take an IGZO green body and put it into a degreasing sintering furnace for sintering, heat it at a heating rate of 2.0℃ / min, evacuate the furnace body on time to keep the pressure at -0.03MPa, heat it to the first sintering temperature of 600℃ and keep it for 4h for degreasing, heat it to 700℃ at a heating rate of 2.0℃ / min, start to fill with oxygen, adjust the oxygen flow rate until the furnace pressure is stable at 0.03MPa and the oxygen volume concentration is >99.5%, and then heat it to the second sintering temperature at a heating rate of 2.0℃ / min. The temperature was set to 1420℃, kept at this temperature for 1.5h, then cooled to the third sintering temperature of 1320℃ at a cooling rate of 7℃ / min, kept at this temperature for 2h, the oxygen flow rate was lowered, argon was introduced, and the oxygen flow rate and argon flow rate were 0.5:1, and kept at this temperature for another 2h, cooled to 800℃ at a cooling rate of 5℃ / min, and the oxygen flow rate was stopped. When the temperature dropped to 700℃, the argon flow was stopped, and the target was taken out of the furnace at room temperature. After post-processing, an IGZO target with a size of 650×400×8mm, a relative density of 99.70%, and a resistivity of 1.49mΩ·cm was obtained.

[0042] Comparative experiment:

[0043] Comparative Example 1: Only oxygen was introduced during the entire sintering process, and the remaining process parameters were the same as those in Example 1, specifically:

[0044] The IGZO green body was loaded into a debinding sintering furnace for sintering, and the temperature was increased at a heating rate of 2.5°C / min. The furnace pressure was kept at -0.04MPa in time, and after the temperature was increased to the first sintering temperature of 600°C, it was kept warm for 4h for debinding. The temperature was increased to 700°C at a heating rate of 2.5°C / min, and oxygen was introduced. The oxygen flow rate was adjusted until the furnace pressure was stable at 0.04MPa and the oxygen volume concentration was >99.5%. The temperature was then increased to the second sintering temperature of 1380°C at a heating rate of 2.5°C / min, and kept warm for 2h. The temperature was then decreased to the third sintering temperature of 1320°C at a cooling rate of 8°C / min, and kept warm for 5h. The temperature was decreased to 900°C at a cooling rate of 3°C / min, and the oxygen was stopped. The target was taken out of the furnace at room temperature. After post-processing, an IGZO target with a size of 600×400×8mm, a relative density of 97.54%, and a resistivity of 3.79mΩ·cm was obtained.

[0045] Comparative Example 2: Only oxygen was introduced during the entire sintering process. The temperature was raised to a maximum sintering temperature of 1380°C at a heating rate of 2.5°C / min and kept at that temperature for 6 hours. Specifically:

[0046] The IGZO green body was loaded into a degreasing sintering furnace for sintering, and the temperature was increased at a heating rate of 2.5°C / min. The furnace pressure was kept at -0.04MPa by vacuuming on time. When the temperature reached 700°C, oxygen was introduced and the oxygen flow rate was adjusted until the furnace pressure stabilized at 0.04MPa and the oxygen volume concentration was >99.5%. The temperature was then increased to 1380°C at a heating rate of 2.5°C / min and kept at that temperature for 6h. The temperature was then decreased to 900°C at a cooling rate of 3°C / min. The oxygen introduction was stopped and the target was taken out of the furnace at room temperature. After post-processing, an IGZO target with a size of 600×400×8mm, a relative density of 96.82% and a resistivity of 4.36mΩ·cm was obtained.

[0047] Comparative Example 3: Only compressed air was introduced into the entire sintering process, and the remaining process parameters were the same as those in Example 1. Specifically:

[0048] The IGZO green body was loaded into a degreasing sintering furnace for sintering, and the temperature was increased at a heating rate of 2.5°C / min. The furnace pressure was kept at -0.04MPa by vacuuming on time. After the temperature was increased to the first sintering temperature of 600°C, it was kept warm for 4 hours for degreasing. After the temperature was increased to 700°C, compressed air was introduced and the flow rate was adjusted until the furnace pressure was stabilized at 0.04MPa. The temperature was then increased to the second sintering temperature of 1380°C at a heating rate of 2.5°C / min and kept warm for 2 hours. The temperature was then decreased to the third sintering temperature of 1320°C at a cooling rate of 8°C / min and kept warm for 5 hours. The temperature was then decreased to 900°C at a cooling rate of 3°C / min. The air supply was stopped and the target was taken out of the furnace at room temperature. After post-processing, an IGZO target with a size of 600×400×8mm, a relative density of 91.2% and a resistivity of 7.42mΩ·cm was obtained.

[0049] Comparative Example 4: Only compressed air was introduced during the entire sintering process, specifically:

[0050] The IGZO green body was loaded into a degreasing sintering furnace for sintering. The temperature was increased at a heating rate of 2.5°C / min. The furnace pressure was kept at -0.04MPa after vacuum was drawn on time. After the temperature was increased to the first sintering temperature of 600°C, it was kept warm for 4h. The temperature was increased to 700°C at a heating rate of 2.5°C / min and compressed air was introduced. The flow rate was until the furnace pressure stabilized at 0.04MPa. The temperature was then increased to the maximum sintering temperature of 1380°C at a heating rate of 2.5°C / min and kept warm for 5h. The temperature was then decreased to 700°C at a cooling rate of 3°C / min and ventilation was stopped. The target material was taken out of the furnace at room temperature to obtain an IGZO target with a relative density of 90.63% and a resistivity of 6.89mΩ·cm.

[0051] Comparative Example 5: The degreasing at the first sintering temperature is not performed during the sintering process. The remaining process parameters are the same as those of Example 1, specifically:

[0052] Take the IGZO green body and put it into the debinding sintering furnace for sintering. Heat it up at a heating rate of 2.5℃ / min. Vacuum the furnace body to keep the pressure at -0.04MPa. When the temperature reaches 700℃, start to fill it with oxygen. Adjust the oxygen flow rate until the furnace pressure is stable at 0.04MPa and the oxygen volume concentration is >99.5%. Then heat it up to the second sintering temperature of 1380℃ at a heating rate of 2.5℃ / min, keep it warm for 2h, and then cool it down to the third sintering temperature at a cooling rate of 8℃ / min. The junction temperature is 1320℃, kept warm for 2.5h, the oxygen flow rate is reduced, and argon is introduced to make the oxygen flow rate and argon flow rate 0.3:1, and then kept warm for 2.5h, and the temperature is reduced to 900℃ at a cooling rate of 3℃ / min, and the oxygen is stopped. When the temperature drops to 700℃, the argon is stopped. The target material is taken out of the furnace at room temperature. After post-processing, an IGZO target material with a size of 600×400×8mm, a relative density of 96.33%, and a resistivity of 1.86mΩ·cm is obtained.

[0053] Comparative Example 6: The sintering process does not adopt the second sintering temperature, and adopts the same oxygen-argon ratio as Example 1, specifically:

[0054] Take the IGZO green body and put it into the debinding sintering furnace for sintering. Heat it up at a heating rate of 2.5℃ / min. Vacuum the furnace body to keep the pressure at -0.04MPa on time. After heating to the first sintering temperature of 600℃, keep it warm for 4h for debinding. Heat it up to 700℃ at a heating rate of 2.5℃ / min and start to fill it with oxygen. Adjust the oxygen flow until the furnace pressure is stable at 0.04MPa and the oxygen volume concentration is >99.5%. Then heat it up to the first sintering temperature of 600℃ at a heating rate of 2.5℃ / min. The third sintering temperature is 1320℃, kept warm for 2.5h, the oxygen flow rate is reduced, and argon is introduced to make the oxygen flow rate and argon flow rate 0.3:1, and then kept warm for 2.5h, and the temperature is reduced to 900℃ at a cooling rate of 3℃ / min, and the oxygen introduction is stopped. When the temperature drops to 700℃, the argon introduction is stopped, and the target material is taken out of the furnace at room temperature. After post-processing, an IGZO target material with a size of 600×400×8mm, a relative density of 97.12%, and a resistivity of 1.72mΩ•cm is obtained.

[0055] Comparative Example 7: The sintering process does not adopt the third sintering temperature, and adopts the same oxygen-argon ratio as Example 1, specifically:

[0056] Take the IGZO green body and put it into the debinding sintering furnace for sintering. Heat it up at a heating rate of 2.5℃ / min. Vacuum the furnace body to keep the pressure at -0.04MPa on time. After heating to the first sintering temperature of 600℃, keep it warm for 4h for debinding. Heat it up at a heating rate of 2.5℃ / min to 700℃ and start to fill it with oxygen. Adjust the oxygen flow until the furnace pressure is stable at 0.04MPa and the oxygen volume concentration is >99.5%. Then heat it up at a heating rate of 2.5℃ / min to The second sintering temperature is 1380℃, which is kept for 1 hour. Then the oxygen flow rate is lowered and argon is introduced to make the oxygen flow rate and argon flow rate 0.3:1. The temperature is then kept for another 1 hour. The temperature is lowered to 900℃ at a cooling rate of 3℃ / min, and the introduction of oxygen is stopped. When the temperature drops to 700℃, the introduction of argon is stopped. The target material is taken out of the furnace at room temperature. After post-processing, an IGZO target material with a size of 600×400×8mm, a relative density of 98.74%, and a resistivity of 1.89mΩ•cm is obtained.

[0057] Comparative Example 8: During the sintering process, oxygen: argon = 1:1, and the other process parameters are the same as those in Example 1, specifically:

[0058] Take the IGZO green body and put it into the debinding sintering furnace for sintering. Heat it at a heating rate of 2.5℃ / min. Vacuum the furnace body to keep the pressure at -0.04MPa on time. After heating to the first sintering temperature of 600℃, keep it warm for 4h for debinding. Heat it to 700℃ at a heating rate of 2.5℃ / min and start to fill it with oxygen. Adjust the oxygen flow rate until the furnace pressure is stable at 0.04MPa and the oxygen volume concentration is >99.5%. Then heat it to the second sintering temperature of 1380℃ at a heating rate of 2.5℃ / min and keep it warm for 2h. Then, the temperature was lowered to the third sintering temperature of 1320℃ at a cooling rate of 8℃ / min, kept warm for 2.5h, the oxygen flow rate was lowered, argon was introduced so that the oxygen flow rate and argon flow rate were 1:1, and then kept warm for 2.5h, and the temperature was lowered to 900℃ at a cooling rate of 3℃ / min, and the oxygen flow rate was stopped. When the temperature dropped to 700℃, the argon flow was stopped, and the target material was taken out of the furnace at room temperature. After post-processing, an IGZO target material with a size of 600×400×8mm, a relative density of 99.28%, and a resistivity of 2.14mΩ•cm was obtained.

[0059] Comparative Example 9: Argon gas was immediately introduced to adjust the oxygen volume concentration after reaching the third sintering temperature during the sintering process. The remaining process parameters were the same as those in Example 1, specifically:

[0060] Take the IGZO green body and put it into the debinding sintering furnace for sintering. Heat it up at a heating rate of 2.5℃ / min. Vacuum the furnace body and keep the pressure at -0.04MPa on time. After heating to the first sintering temperature of 600℃, keep it warm for 4h for debinding. Heat it up to 700℃ at a heating rate of 2.5℃ / min and start to fill with oxygen. Adjust the oxygen flow rate until the furnace pressure is stable at 0.04MPa and the oxygen volume concentration is >99.5%. Then heat it up to the second sintering temperature of 1380℃ at a heating rate of 2.5℃ / min and keep it warm for 4h. The target was heated for 2 hours, then cooled to the third sintering temperature of 1320°C at a cooling rate of 8°C / min, the oxygen flow rate was immediately lowered, and argon was introduced to make the oxygen flow rate and argon flow rate 0.3:1, and kept warm for 5 hours. The target was cooled to 900°C at a cooling rate of 3°C / min, and the oxygen flow rate was stopped. When the temperature dropped to 700°C, the argon flow was stopped. The target was taken out of the furnace at room temperature, and after post-processing, an IGZO target with a size of 600×400×8mm, a relative density of 99.03%, and a resistivity of 2.37mΩ•cm was obtained.

[0061] The different results of the IGZO target materials obtained in the embodiment of the present invention and the comparative example are shown in Table 1.

[0062] Table 1 Comparison of different results between the examples and the comparative examples

[0063] Relative density (%) Resistivity (mΩ.cm) Sintering conditions Example 1 99.61 1.42 Three-step method, oxygen: argon = 0.3:1 Example 2 99.54 1.36 Three-step method, oxygen: argon = 0.4:1 Example 3 99.70 1.49 Three-step method, oxygen: argon = 0.5:1 Comparative Example 1 97.54 3.79 Three-step method, oxygen Comparative Example 2 96.82 4.36 One-step method, oxygen Comparative Example 3 91.20 7.42 Three-step method, compressed air Comparative Example 4 90.63 6.89 Two-step method, compressed air Comparative Example 5 96.33 1.86 The first sintering temperature is not used, oxygen: argon = 0.3:1 Comparative Example 6 97.12 1.72 No second sintering temperature is used, oxygen: argon = 0.3:1 Comparative Example 7 98.74 1.89 The third sintering temperature is not used, oxygen: argon = 0.3:1 Comparative Example 8 99.28 2.14 Three-step method, oxygen: argon = 1:1 Comparative Example 9 99.03 2.37 Argon is introduced immediately after reaching the third sintering temperature to adjust the oxygen volume concentration, oxygen: argon = 0.3:1

[0064] From the comparison results in Table 1, it can be seen that, compared with the comparative example, the embodiments of the present invention adopt various oxygen atmosphere conditions to sinter the IGZO green body, and different sintering methods and sintering conditions such as oxygen depletion, oxygen enrichment, and oxygen concentration are compared. Examples 1, 2, and 3 use a three-step sintering method to accurately control the oxygen volume concentration and the introduction time in the sintering furnace by adjusting the oxygen and argon flow rates, so that the oxygen and argon flow rate ratio is controlled within a certain range, which can not only ensure the relative density of the IGZO target material, but also reduce its resistivity, thereby obtaining a stable IGZO target material.

[0065] The above embodiments are only specific examples to further illustrate the purpose, technical solutions and beneficial effects of the present invention, and the present invention is not limited thereto. Any modifications, equivalent replacements, improvements, etc. made within the scope of the present invention are included in the scope of protection of the present invention.

Claims

1. A method for preparing an IGZO target material by a three-step segmented sintering process, characterized in that: Follow these steps: (1) Place the IGZO green body in a sintering furnace, and under negative pressure and air atmosphere, raise the temperature from room temperature to the first sintering temperature of 500-700°C at a rate of I, and keep it at this temperature for 2-6 hours for degreasing; (2) The temperature in the furnace is raised to 700-800°C at rate I, and then oxygen is introduced to control the gas pressure in the furnace; (3) In an oxygen atmosphere, raise the temperature in the furnace to the second sintering temperature of 1350-1550°C at rate II and keep it at that temperature for 1-4 hours; (4) The temperature in the furnace is lowered to the third sintering temperature of 1300-1380°C at a rate of III and kept at this temperature for 4-6 hours. At the midpoint of this holding time, argon is introduced and the oxygen flow rate is adjusted to adjust the oxygen volume concentration in the furnace. The oxygen and argon flow rate ratio is controlled at (0.2-0.8):1; (5) The temperature in the furnace is reduced to 800-1000°C at a rate IV and then cooled with the furnace. The introduction of oxygen is stopped. When the temperature drops to 650-950°C, the introduction of argon is stopped. Finally, the target is taken out of the furnace at room temperature to obtain the IGZO target.

2. The method for preparing an IGZO target by a three-step segmented sintering process according to claim 1, characterized in that: The IGZO green body is prepared by mixing In2O3 powder, nano-Ga2O3 powder and nano-ZnO powder, and the molar ratio of In, Ga and Zn is (1-6): (1-6): (1-6).

3. The method for preparing an IGZO target by a three-step segmented sintering process according to claim 2, characterized in that: The preparation of the IGZO green body is to mechanically mix In2O3 powder, nano-Ga2O3 powder and nano-ZnO powder according to a molar ratio to obtain uniform IGZO powder, then add a binder of 2 to 10‰ of the mass of the IGZO powder to perform spray drying and granulation to obtain IGZO powder particles; then pre-press the IGZO powder particles in a hydraulic press at 15 to 30 MPa, and finally press them into a uniform IGZO green body in a cold isostatic press at 240 to 300 MPa.

4. The method for preparing an IGZO target by a three-step segmented sintering process according to claim 1, characterized in that: The negative pressure in the furnace of step (1) is -0.01 to -0.06 MPa.

5. The method for preparing an IGZO target by a three-step segmented sintering process according to claim 1, characterized in that: The rate I is 1-5°C / min.

6. The method for preparing an IGZO target by a three-step segmented sintering process according to claim 1, characterized in that: In step (2), the oxygen volume concentration in the furnace is >99.5%, and the gas pressure is 0.03-0.05 MPa.

7. The method for preparing an IGZO target by a three-step segmented sintering process according to claim 1, characterized in that: The rate II is 1-6°C / min.

8. The method for preparing an IGZO target by a three-step segmented sintering process according to claim 1, characterized in that: The rate III is 6-10°C / min.

9. The method for preparing an IGZO target by a three-step segmented sintering process according to claim 1, characterized in that: The rate IV is 2-6°C / min.