A MOS target, a preparation method thereof, and a thin film transistor

Abstract

This application relates to the technical field of target material preparation, and provides a MOS target, a preparation method thereof, and a thin film transistor, including: performing a coprecipitation reaction on a mixed salt solution of In, Ga, and Sn ions, a precipitating agent, and a complexing agent, and obtaining a high-purity indium gallium tin hydroxide colloid after washing and concentration; performing a hydrothermal reaction on the indium gallium tin hydroxide colloid and an auxiliary agent, and obtaining a first indium gallium tin oxide powder after washing and drying; performing a calcination treatment on the first indium gallium tin oxide powder to obtain a second indium gallium tin oxide powder; ball-milling and mixing the second indium gallium tin oxide powder, a dispersant, an antifoaming agent, and pure water to obtain a slurry; injecting and molding the slurry to obtain a green body; and performing a sintering treatment on the green body under a high-oxygen condition to obtain a MOS target. This application combines coprecipitation reaction, hydrothermal reaction, and calcination, precisely controls the oxygen content of the powder and makes it slightly deoxidized, preventing In2O3 from deoxidizing to form In2O or InO during the sintering process of the green body and affecting the conductivity of the target.

Description

Technical Field

[0001] This application belongs to the technical field of target material preparation, and particularly relates to a MOS target, a preparation method thereof, and a thin film transistor. Background Art

[0002] MOS (Metal-Oxide-Semiconductor) thin films have the advantages of high mobility, low preparation temperature, transparency in the visible light band, and good electrical stability, and are ideal materials for the active layer of oxide thin film transistors (TFTs). With the rapid development of display technology towards large size, ultra-high definition, ultra-high refresh rate, low power consumption, etc., higher requirements are put forward for the mobility of TFTs. Currently, the mobility of commonly used IGZO (In-Ga-Zn-based oxide) TFTs is about 20 cm 2 ·V -1 ·s -1 , but it is still far lower than the application standards of the next-generation display technology. Moreover, since the IGZO thin film contains Zn element, it is easily etched during wet etching of the source and drain, and ZnO in the IGZO thin film is sensitive to temperature, water vapor, etc., which easily leads to unstable electrical properties during the continuous operation of IGZO TFTs. Therefore, it is necessary to develop a MOS target without ZnO to overcome the problem of poor stability of IGZO.

[0003] In addition, currently, the preparation method of IGZO targets usually adopts air atmospheric pressure sintering. However, In 2 O 3 is prone to oxygen loss and generate In 2 O or InO during high-temperature sintering under atmospheric air conditions, thereby affecting the conductivity, composition, tissue uniformity, and density of the IGZO target, and further affecting the film-forming quality of the target. Summary of the Invention

[0004] The purpose of this application is to provide a MOS target, a preparation method thereof, and a thin film transistor, aiming to solve the problems that the existing IGZO targets have poor electrical property stability and are prone to oxygen loss during sintering, which affects the conductivity, composition, tissue uniformity, and density of the target.

[0005] To achieve the above application purpose, the technical solution adopted in this application is as follows:

[0006] In the first aspect, this application provides a preparation method of a MOS target, including the following steps:

[0007] Performing a coprecipitation reaction on a mixed salt solution of In, Ga, and Sn ions, a precipitant, and a complexing agent, and obtaining a high-purity indium gallium tin hydroxide colloid after washing and concentration;

[0008] After hydrothermally reacting the high-purity indium gallium tin hydroxide colloid and the additive, washing and drying, the first indium gallium tin oxide powder is obtained;

[0009] Calcining the first indium gallium tin oxide powder to obtain the second indium gallium tin oxide powder;

[0010] Mixing the second indium gallium tin oxide powder, a dispersant, an antifoaming agent and pure water by ball milling to obtain a slurry;

[0011] Injecting and molding the slurry to obtain a green body;

[0012] Sintering the green body under high oxygen conditions to obtain a MOS target;

[0013] In a second aspect, the present application provides a MOS target, including the MOS target prepared by the preparation method of the MOS target provided by the present application.

[0014] In a third aspect, the present application provides a thin film transistor, including an active layer thin film, and the active layer thin film is obtained by sputtering and coating with the MOS target provided by the present application.

[0015] Compared with the prior art, the present application has the following beneficial effects:

[0016] (1) After obtaining a high-purity indium gallium tin hydroxide colloid by coprecipitation reaction of a mixed salt solution of In, Ga, and Sn ions, adding an additive for hydrothermal reaction, a first indium gallium tin oxide powder with uniform distribution of each component can be obtained, and it is slightly deoxidized. Then, by calcination, the particle size of the powder is increased to facilitate molding, improve the density and strength of the green body, thereby contributing to providing the density of the target. At the same time, by controlling the calcination conditions, the oxygen content of the generated second indium gallium tin oxide powder can be more precisely controlled and slight deoxidation can be maintained, preventing In from 2 O 3 deoxidizing to form indium oxides with low valence states (such as In 2 O or InO) during the sintering process of the green body, which affects the conductivity and oxygen content of the target. Therefore, compared with the conventional method of air atmospheric pressure sintering of a mixed powder of indium oxide, gallium oxide, and tin oxide, the sintering process of the present application has a simple reaction, good uniformity of the target composition and structure, no segregation, high density, and good conductivity.

[0017] (2) Compared with the IGZO target, the MOS target of the present application does not contain ZnO. On the one hand, it avoids the problem that ZnO is sensitive to temperature, water vapor, etc. and easily affects the electrical stability of the TFT during continuous operation. On the other hand, Sn can increase the carrier concentration and improve the conductive performance of the target, and the ionic radius of Sn 4+ is closer to that of In 3+ , and it is easier to form a high-mobility channel, thereby contributing to improving the mobility of the TFT. Brief Description of the Drawings

[0018] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0019] Figure 1 is the process flow chart of the preparation method of the MOS target provided by the embodiment of the present application;

[0020] Figure 2 is the SEM image of the MOS target prepared in Embodiment 1 of the present application. Detailed Embodiments

[0021] In order to make the technical problems to be solved, technical solutions and beneficial effects of the present application more clearly understood, the following further details the present application in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0022] In the embodiments of the present application, the MOS target refers to a metal oxide semiconductor target, specifically an IGTO target.

[0023] The first aspect of the embodiments of the present application provides a method for preparing a MOS target, as Figure 1 shown, including the following steps:

[0024] S01: Perform a coprecipitation reaction on a mixed salt solution of In, Ga, and Sn ions, a precipitant, and a complexing agent, and obtain a high-purity indium gallium tin hydroxide colloid after washing and concentration;

[0025] S02: Perform a hydrothermal reaction on the high-purity indium gallium tin hydroxide colloid and an auxiliary agent, and obtain a first indium gallium tin oxide powder after washing and drying;

[0026] S03: Calcinate the first indium gallium tin oxide powder to obtain a second indium gallium tin oxide powder;

[0027] S04: Ball-mill and mix the second indium gallium tin oxide powder, a dispersant, an antifoaming agent, and pure water to obtain a slurry;

[0028] S05: Inject and mold the slurry to obtain a green body;

[0029] S06: Sinter the green body under high-oxygen conditions to obtain a MOS target.

[0030] In the preparation method of the MOS target provided by the embodiment of the present application, after a co-precipitation reaction is carried out on a mixed salt solution of In, Ga, and Sn ions to obtain a high-purity indium gallium tin hydroxide colloid, an auxiliary agent is added for a hydrothermal reaction, and a first indium gallium tin oxide powder with uniform distribution of each component can be obtained, and it is slightly deoxidized. Then, the particle size of the powder is increased by calcination to facilitate forming, improve the density and strength of the green body, thereby contributing to providing the target density. At the same time, by controlling the calcination conditions, the oxygen content of the generated second indium gallium tin oxide powder can be more precisely controlled and slight deoxidation can be maintained to prevent In 2 O 3 from deoxidizing to form indium oxides with low valence states (such as In 2 O or InO) and affecting the conductivity and oxygen content of the target; therefore, compared with the conventional method of air atmospheric pressure sintering of a mixed powder of indium oxide, gallium oxide, and tin oxide, the sintering process of the present application has a simple reaction, good uniformity of the target composition and structure, no segregation, high density, and good conductivity. Compared with the IGZO target, the MOS target of the present application does not contain ZnO. On the one hand, it avoids the problem that ZnO is sensitive to temperature, water vapor, etc. and easily affects the electrical stability of the TFT during continuous operation. On the other hand, Sn can increase the carrier concentration and improve the conductive performance of the target, and the ionic radius of Sn 4+ is closer to that of In 3+ , and it is easier to form a high-mobility channel, thereby contributing to improving the mobility of the TFT.

[0031] In the above step S01, in the embodiment, the step of preparing a mixed salt solution of In, Ga, and Sn ions includes: adding indium salt, gallium salt, and tin salt to pure water and stirring evenly to obtain a mixed salt solution of In, Ga, and Sn ions. Among them, the mass ratio of In, Ga, and Sn in the mixed salt solution is (34.7~67.4)∶(1.5~27.5)∶(13.0~16.5); the indium salt is selected from InCl 3 powder, the gallium salt is selected from GaCl 3 powder, and the tin salt is selected from SnCl 4 ·5H 2 O.

[0032] In the embodiment, the temperature of the co-precipitation reaction is 50~65°C, the time is 6~8h, and the pH value is 8.5~9.5.

[0033] In the embodiment, the precipitating agent is selected from ammonia water or sodium hydroxide; the complexing agent is selected from ammonium nitrate or ammonium chloride.

[0034] In the above step S02, in the embodiment, the temperature of the hydrothermal reaction is 150~250°C, and the time is 12~24h. Under hydrothermal conditions, the auxiliary agent has a reducing effect, so that the generated first indium gallium tin oxide powder is slightly deoxidized, which is beneficial to preventing In during subsequent sintering2 O 3 Loss of oxygen to form In 2 O or InO affects the conductivity of the target, and the phase change is simple, which is beneficial to improving the tissue uniformity of the target. In addition, through the hydrothermal reaction, it is possible to avoid the hard agglomeration of the powder that is easily caused by traditional mechanical ball milling, improve the uniformity and dispersibility of the powder, make the powder have higher sintering activity, and thus contribute to improving the purity, tissue uniformity and density of the MOS target.

[0035] In the embodiment, the mass ratio of the high-purity indium gallium tin hydroxide colloid to the additive is (1~2)∶(0.01~0.05). Among them, the additive is selected from sucrose, glucose, fructose, etc.

[0036] In the embodiment, the primary particle size of the first indium gallium tin oxide powder is 0.05~0.1μm.

[0037] In the above step S03, in the embodiment, the atmosphere for the calcination treatment is an argon-hydrogen mixed gas with an argon-hydrogen volume ratio of (95~99)∶(1~5), the temperature is 600~800°C, and the time is 4~10h. Such calcination conditions are beneficial for the growth and increase of the particle size of the first indium gallium tin oxide powder, facilitating subsequent forming, and can more precisely control the oxygen content of the generated second indium gallium tin oxide powder and maintain slight oxygen loss.

[0038] In the embodiment, in the second indium gallium tin oxide powder, the mass ratio of In, Ga, and Sn is (34.7~67.4)∶(1.5~27.5)∶(13.0~16.5).

[0039] In the embodiment, the oxygen content of the second indium gallium tin oxide powder is less than that of the MOS target, which is beneficial to preventing In 2 O 3 Loss of oxygen to form In 2 O or InO affects the conductivity and density of the target.

[0040] In the embodiment, the particle size of the second indium gallium tin oxide powder is 0.2~0.5μm, and this particle size range is beneficial for the slip casting of the powder and provides the density and strength of the green body.

[0041] In the above step S04, in the embodiment, the step of ball milling and mixing the second indium gallium tin oxide powder, the dispersant, the defoamer and pure water includes: adding the second indium gallium tin oxide powder, the dispersant, the defoamer and pure water into the ball milling tank, and ball milling at a speed of 200~1000rpm for 6~18h to obtain a slurry.

[0042] In the embodiment, the solid content of the slurry is 60~70%.

[0043] In the embodiment, the addition amount of the dispersant is 0.1-1% of the mass of the second indium gallium tin oxide powder. Specifically, the dispersant can be selected from one or more of polyethylene glycol, cetyl sulfonate, polycarboxylate, polyacrylate or triethanolamine.

[0044] In the embodiment, the addition amount of the defoamer is 0.1-0.5% of the mass of the second indium gallium tin oxide powder. Specifically, the defoamer can be selected from polyether defoamers and / or higher alcohols.

[0045] In the above step S05, in the embodiment, the step of slip casting the slurry includes: loading the slurry into a vacuum tank, after vacuum degassing, injecting the slurry into a sealed resin or graphite mold cavity at a pressure of 0.2-1.5 MPa until no more water droplets drip out of the mold, opening the mold, taking out the cured green body, and standing it at room temperature for 24 h to obtain a green compact.

[0046] In the above step S06, in the embodiment, the step of sintering the green compact under high oxygen conditions includes: loading the green compact into an alumina sleeve and then placing it in a sintering furnace, then evacuating the alumina sleeve, starting to introduce oxygen when the vacuum degree is 10 -2 ~10 - 3 Pa, and making the oxygen pressure in the alumina sleeve be 0.05-0.1 MPa, and then heating up to 1400-1600 °C for heat preservation sintering for 12-48 h. In this embodiment, by placing the green compact in an alumina sleeve and then in a sintering furnace, the green compact is sintered in a narrow space, which is beneficial to accurately control the uniformity of the gas flow and temperature. It can not only slow down the heat exchange between the green compact and the furnace chamber, reduce the temperature fluctuation, make the green compact heat more uniformly, reduce the deformation or cracking caused by thermal stress, and improve the uniformity of the target tissue, but also ensure that the sintering gas flow field and temperature field are the same for different production batches, so that the performance of the produced target is stable and the repeatability is good. And, by controlling the oxygen pressure in the alumina sleeve, the green compact is sintered under high oxygen conditions, which helps the second indium gallium tin oxide powder with slight oxygen loss to be fully oxidized to form a target with uniform composition and good conductivity, preventing In 2 O 3 from losing oxygen to generate In 2 O or InO and affecting the conductivity and density of the target. In addition, through the alumina sleeve, the oxygen consumption can also be reduced and the cost can be lowered.

[0047] In the embodiment, the relative density of the MOS target is ≥98.5%, and the resistivity is ≤10 mΩ·cm.

[0048] The second aspect of the embodiments of the present application provides a MOS target, including the MOS target prepared by the preparation method of the MOS target provided by the present application.

[0049] The MOS target provided by the embodiment of the present application is prepared by the preparation method of the MOS target provided by the embodiment of the present application. Therefore, the target has the advantages of high density, good uniformity of composition and structure, low resistivity, and good stability.

[0050] The third aspect of the embodiment of the present application provides a thin film transistor, including an active layer thin film, which is obtained by sputtering and coating with the MOS target provided by the present application.

[0051] The thin film transistor provided by the embodiment of the present application, since its active layer thin film is obtained by sputtering and coating with the metal oxide semiconductor target provided by the embodiment of the present application, has the advantages of low resistivity, high carrier concentration, high mobility, and good stability against water, oxygen, light and heat. Therefore, it can improve performance indexes such as the mobility, threshold voltage and current on-off ratio of the TFT, and improve the reliability problem that is likely to occur during the long-term operation of the TFT, and extend the life of the TFT, thereby contributing to the realization of high resolution, high refresh rate, low power consumption and high definition of the display screen, as well as improving the stability of the display screen.

[0052] The following is illustrated with specific embodiments.

[0053] Embodiment 1

[0054] The present embodiment provides a preparation method of a MOS target, including the following steps:

[0055] S11: Weigh appropriate amounts of InCl 3 powder, GaCl 3 powder and SnCl 4 ·5H 2 O and add them to pure water and stir evenly to obtain a mixed salt solution of In, Ga and Sn ions; add the mixed salt solution of In, Ga and Sn ions, sodium hydroxide solution and ammonia water to a reaction kettle for mixing, control the temperature of the reaction kettle at 60°C, and the pH value of the reaction system at 9, carry out a co-precipitation reaction for 7 h, and obtain a high-purity indium gallium tin hydroxide colloid after washing and concentration;

[0056] S12: Weigh appropriate amounts of the high-purity indium gallium tin hydroxide colloid and glucose according to a mass ratio of 1.5:0.03, add them to pure water and stir evenly to obtain a suspension (concentration: 0.5 mol / L);

[0057] Transfer the suspension to the inner liner of the reactor, and add an appropriate amount of pure water so that the final volume of the suspension is 70% of the volume of the inner liner of the reactor. Place the reactor in an oven at 200 °C for hydrothermal reaction for 18 h. Then, repeatedly wash the precipitate obtained by centrifugation with pure water and absolute ethanol respectively, and dry it to obtain the first indium gallium tin oxide powder (D50 = 0.08 μm was detected);

[0058] S13: Place the first indium gallium tin oxide powder in an atmosphere sintering furnace, evacuate to 10 -2 Pa, then introduce an argon-hydrogen mixed gas (the volume ratio of argon to hydrogen is 98:2), start heating to 750 °C, and keep it calcined for 6 h to obtain the second indium gallium tin oxide powder (D50 = 0.35 μm was detected);

[0059] S14: Add the second indium gallium tin oxide powder, polyethylene glycol, polyoxypropylene glycerol ether and pure water into the ball milling tank, and ball mill at a speed of 500 rpm for 12 h to obtain a slurry (the solid content is 65%); the addition amount of polyethylene glycol is 0.5% of the mass of the second indium gallium tin oxide powder, and the addition amount of polyoxypropylene glycerol ether is 0.3% of the mass of the second indium gallium tin oxide powder;

[0060] S15: Load the slurry into a vacuum tank, after vacuum degassing, inject the slurry into the sealed graphite mold cavity at a pressure of 1 MPa until no more water drops out of the mold. Open the mold, take out the solidified green body, and let it stand at room temperature for 24 h to obtain a green compact.

[0061] S16: Load the green compact into an alumina sleeve and place it in a sintering furnace. Then evacuate the alumina sleeve. When the vacuum degree is 5×10 -2 Pa, start introducing oxygen and make the oxygen pressure in the alumina sleeve 0.08 MPa. Then heat up to 1500 °C and keep it sintered for 36 h to obtain the MOS target.

[0062] Comparative Example 1

[0063] This comparative example provides a method for preparing a MOS target, which is different from Example 1 in that:

[0064] Do not perform step S12;

[0065] In step S13, the high-purity indium gallium tin hydroxide colloid is placed in a sintering furnace, heated to 750 °C in an air atmosphere, and kept calcined for 6 h to obtain the second indium gallium tin oxide powder (D50 = 0.41 μm was detected).

[0066] Comparative Example 2

[0067] This comparative example provides a method for preparing a MOS target, which is different from Example 1 in that:

[0068] Step S13 is not performed;

[0069] In step S14, indium gallium tin oxide powder, polyethylene glycol, polyoxypropylene glycerol ether, and pure water are added to the ball milling tank.

[0070] Comparative Example 3

[0071] This embodiment provides a method for preparing a MOS target, which is different from that of Embodiment 1 in that:

[0072] In step S15, the green body is placed in a sintering furnace, and then the sintering furnace is evacuated. When the vacuum degree reaches 5×10 - Pa, oxygen is introduced, and then the temperature is raised to 1500 °C for heat preservation sintering for 36 h to obtain the MOS target.

[0073] Comparative Example 4

[0074] This comparative example provides a method for preparing a MOS target, including the following steps:

[0075] S1: Weigh appropriate amounts of indium oxide powder, gallium oxide powder, and tin oxide powder according to the mass ratio of indium, gallium, and tin of 37.6∶27.5∶14.3;

[0076] S2: Add indium oxide powder, gallium oxide powder, tin oxide powder, polyethylene glycol, polyoxypropylene glycerol ether, and pure water to the ball milling tank, and ball mill at a speed of 500 rpm for 12 h to obtain a slurry;

[0077] S3: Load the slurry into a vacuum tank. After vacuum degassing, inject the slurry into the sealed graphite mold cavity at a pressure of 1 MPa until no more water drops out of the mold. Open the mold, take out the solidified blank, and let it stand at room temperature for 24 h to obtain a green body;

[0078] S4: Place the green body in a sintering furnace, and then evacuate the sintering furnace. When the vacuum degree reaches 5×10 - Pa, oxygen is introduced, and then the temperature is raised to 1500 °C for heat preservation sintering for 36 h to obtain the MOS target.

[0079] Relevant performance test and analysis:

[0080] 1. After the MOS target is plastic-sealed, the density of the MOS targets prepared in Embodiment 1 and Comparative Examples 1 to 4 is measured respectively by the Archimedes density measurement method. Specifically, the MOS target is evenly cut into 5 segments along its cross-section, and then the actual density of each segment is measured. Based on the theoretical density, the relative density = actual density / theoretical density × 100%; the test results are shown in Table 1 below;

[0081] 2. Use a four-probe tester to measure the resistivity of the MOS targets prepared in Example 1 and Comparative Examples 1-4 respectively; specifically, measure the resistivity of 5 different regions of the MOS target; the test results are shown in Table 2 below;

[0082] 3. Use an oxygen-nitrogen analyzer to measure the O content of the MOS targets prepared in Example 1 and Comparative Examples 1-4 respectively; specifically, intercept 5 specimens from different regions of the MOS target, and then measure the O content of each specimen; the test results are shown in Table 3 below;

[0083] Among them, the median uniformity = [(max - min) ÷ (max + min)] × 100%.

[0084] Table 1

[0085]

[0086] Table 2

[0087]

[0088] Table 3

[0089]

[0090] As can be seen from Tables 1-2, the relative densities of the targets prepared in Example 1 are all greater than 99.0% and the resistivities are all less than 3 mΩ·cm, indicating that the preparation method of the embodiments of the present application can prepare MOS targets with high density and low resistance.

[0091] The relative density of the target prepared in Example 1 is significantly higher than that of Comparative Examples 3 and 4, and the median uniformity of the relative density of the target prepared in Example 1 is significantly less than that of Comparative Examples 3 and 4. This is mainly due to the fact that in the embodiments of the present application, the green body is placed in an alumina sleeve for high-oxygen sintering, which can accurately control the uniformity of the gas flow and temperature, make the green body heat evenly, and thus help to improve the density and tissue uniformity of the target, making its density distribution more uniform.

[0092] The relative density of Comparative Example 1 is less than that of Example 1. The main reason may be that in Comparative Example 1, the high-purity indium gallium tin hydroxide colloid generated by the coprecipitation reaction is directly calcined in air, and the oxygen content of the indium gallium tin oxide powder cannot be regulated, resulting in oxygen loss of In 2 O 3 and leaving voids, which is not conducive to the formation of a highly dense target. The relative density of Comparative Example 2 is less than that of Example 1. The main reason may be that the particle size of the powder prepared by the hydrothermal reaction in Comparative Example 2 is too fine, which is not conducive to slip casting and thus not conducive to the formation of a highly dense target.

[0093] The resistivity and the median resistivity uniformity of the target prepared in Example 1 are significantly lower than those in Comparative Examples 1-2 and Comparative Example 4. This is mainly due to the combination of coprecipitation reaction, hydrothermal reaction and calcination in the embodiments of the present application. By adding glucose and reacting with high-purity indium gallium tin hydroxide colloid through hydrothermal reaction, the generated first indium gallium tin oxide powder is slightly deoxidized. Then, the first indium gallium tin oxide powder is further calcined in an argon-hydrogen mixed atmosphere, which can more precisely control the oxygen content of the powder and maintain slight deoxidation, so that it can be fully oxidized into stable In 2 O 3 during subsequent high-oxygen sintering, avoiding the influence of doped low-valence indium oxides (such as InO or In 2 O) on the electrical conductivity. Therefore, the resistivity of the target is lower.

[0094] The resistivity and the median resistivity uniformity of the target prepared in Example 1 are lower than those in Comparative Example 3. The main reason may be that in the embodiments of the present application, the green body is placed in an alumina sleeve and then sintered in a sintering furnace, which can precisely control the temperature and gas flow, making the green body heated more uniformly. As a result, the target has good uniformity of composition and structure and small resistivity.

[0095] As can be seen from Table 3, the oxygen content in each region of the target prepared in Example 1 is 20.3-20.6, approaching the theoretical value (20.6), and the median oxygen content uniformity is small. However, the oxygen content in each region of the targets prepared in Comparative Examples 1-2 is significantly lower than the theoretical value, and the median oxygen content uniformity is large. This is mainly due to the combination of coprecipitation reaction, hydrothermal reaction and calcination in the embodiments of the present application to precisely control the oxygen content of the second indium gallium tin oxide powder and make it slightly deoxidized, which can reduce the deoxidation of In 2 O 3 during the high-oxygen sintering process of the green body and affect the oxygen content of the target.

[0096] From Figure 2 the SEM, it can be seen that the MOS target prepared in Example 1 has uniform grains, tight bonding between grains, and no obvious grain boundaries and pores.

[0097] It can be seen that through the preparation method of the MOS target provided by the embodiments of the present application, a MOS target with good uniformity of composition and structure, high density, good conductivity and stable electrical properties can be successfully prepared. Therefore, the MOS film sputtered from the MOS target of the present application has the advantages of good uniformity, large carrier concentration, high mobility, and good stability against water, oxygen, light and heat without ZnO.

[0098] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a MOS target, characterized in that: The following steps are involved: A mixed salt solution of In, Ga and Sn ions, a precipitant and a complexing agent are subjected to a coprecipitation reaction, and a high-purity indium gallium tin hydroxide colloid is obtained after washing and concentration; Add the high-purity indium gallium tin hydroxide colloid and the auxiliary agent in a mass ratio of (1-2) : (0.01-0.05) into pure water and stir evenly to obtain a suspension; the auxiliary agent is selected from any one of sucrose, glucose or fructose; The suspension is transferred to the inner tank of the reactor, and a proper amount of pure water is added so that the final volume of the suspension is 70% of the volume of the inner tank of the reactor. The reactor is placed in a drying oven at 150-250° C. and subjected to a hydrothermal reaction for 12-24 hours. After washing and drying, the first indium gallium tin oxide powder with slight oxygen loss is obtained. The first indium gallium tin oxide powder is calcined to obtain a second indium gallium tin oxide powder that is slightly deoxygenated and has a larger particle size than the first indium gallium tin oxide powder; the calcination atmosphere is an argon-hydrogen mixed gas with a volume ratio of argon to hydrogen of (95-99): (1-5); The second indium gallium tin oxide powder, a dispersant, a defoamer and pure water are ball-milled to obtain a slurry; Slip-casting the slurry to obtain a green blank; The green blank is placed in an alumina sleeve and placed in a sintering furnace, and then the alumina sleeve is evacuated to a vacuum degree of 10 -2 ~10 -3 Pa, oxygen is introduced to make the oxygen pressure of the alumina sleeve 0.05-0.1 MPa, and then the temperature is raised to 1400-1600° C. for heat preservation and sintering for 12-48 hours to obtain a MOS target.

2. The preparation method according to claim 1, characterized in that At least one of the following conditions is met: The oxygen content of the second indium gallium tin oxide powder is less than the oxygen content of the MOS target; The primary particle size of the first indium gallium tin oxide powder is 0.05-0.1 μm; The particle size of the second indium gallium tin oxide powder is 0.2-0.5 μm.

3. The preparation method according to claim 1, characterized in that: At least one of the following conditions is met: The steps of preparing a mixed salt solution of three ions of In, Ga and Sn include: adding indium salt, gallium salt and tin salt into pure water and stirring evenly to obtain a mixed salt solution of three ions of In, Ga and Sn; The coprecipitation reaction temperature is 50-65°C, the reaction time is 6-8h, and the pH value is 8.5-9.5; The precipitant is selected from ammonia water or sodium hydroxide; The complexing agent is selected from ammonium nitrate or ammonium chloride.

4. The preparation method according to claim 1, characterized in that: The calcination treatment is carried out at a temperature of 600-800° C. and for a time of 4-10 hours.

5. The preparation method according to claim 1, characterized in that: In the second indium gallium tin oxide powder, the mass ratio of In, Ga and Sn is (34.7-67.4): (1.5-27.5): (13.0-16.5); And / or, the solid content of the slurry is 60-70%.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The relative density of the MOS target material is ≥98.5%, and the resistivity is ≤10 mΩ·cm.

7. A MOS target material, characterized in that: A MOS target material prepared by the method for preparing a MOS target material according to any one of claims 1 to 6.

8. A thin film transistor comprising an active layer thin film, characterized in that: The active layer thin film is obtained by sputtering and coating the MOS target material according to claim 7.

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