High mobility igo target material, method of making and use thereof

Abstract

The present application belongs to the technical field of thin film transistor sputtering target material, and specifically discloses a high-mobility IGO target material and a preparation method and application thereof.The raw material components of the IGO target material of the present application include indium oxide, gallium oxide, high-valence metal oxide and doped nitride; wherein the high-valence metal oxide includes at least one of niobium oxide or tantalum oxide.The IGO target material provided by the present application has the characteristics of high density and low resistivity, and has small grain size, single phase, uniform composition and microstructure distribution, and has good strength performance.The IGO thin film device prepared by using the target material has high carrier mobility and low threshold voltage, and can achieve better electrical performance and stability.The present application further provides a preparation method and application of the IGO target material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thin film transistor sputtering target material, in particular to a high mobility IGO target material and a preparation method and application thereof. BACKGROUND

[0002] With the continuous development of social economy and technological progress, people have higher requirements for the quality of display screens. At present, display technology is developing towards ultra-large size and ultra-high definition technology. The performance of thin film transistor (TFT) devices, which are the core materials of display technology, directly determines the quality of display technology. Future ultra-high definition display requires pixel subdivision to be smaller and smaller. Therefore, it is required that the carrier mobility of TFT thin film devices be high enough.

[0003] At present, indium gallium zinc oxide (IGZO) thin film material has been successfully commercialized and applied. However, the electron mobility of IGZO thin film as a channel layer material is only about 10 cm 2 / V·s, which cannot meet the requirements of future display technology. Moreover, IGZO thin film is easily affected by the backlight source of the LCD panel device under the condition of long-time opening, generates photo-generated carriers, causes threshold voltage negative drift, and greatly challenges the stability of TFT devices. At present, thin film transistors still have electrical and optical instability under severe test application conditions, so it is necessary to develop new material systems to adapt to the iterative development of TFT technology. In addition, although the mobility of the high mobility thin film developed by current research institutions has reached the level of 20~30 cm 2 / V·s, the stability of the thin film device is still insufficient under the condition of long-time device opening, and the threshold voltage negative bias phenomenon is still serious. It is generally believed in the industry that the conduction mechanism of the channel layer thin film in TFT is oxygen vacancy defect conduction of electrons, so for the system material with weak metal-oxygen bond energy, the high oxygen vacancy concentration in the thin film under the condition of long-time opening of the TFT thin film will cause the carrier concentration to be too high, resulting in insufficient stability of the device during the opening process of the device. Both indium zinc oxide (IZO) thin film and IGZO thin film have this problem.

[0004] Oxide target material is the raw material for making device thin film, and the performance of the target material deeply affects the film quality after plating. Therefore, only by preparing a good target material can the plating quality be fundamentally improved. Indium gallium oxide (IGO) target material is a simpler and more ideal target material in technology. However, the IGO thin film after sputtering of the current IGO target material system has low stability, and the mobility of the thin film still cannot meet the demand of high mobility thin film. Moreover, the IGO sputtering target prepared by the current related technology still generally has problems such as insufficient densification of the target material, too many pores, and uneven composition and organization, and even some IGO target materials have the abnormal phenomenon of high resistivity and large target grain.

[0005] Therefore, it is urgent to develop a new IGO target material system to prepare high-mobility thin films to meet the requirements of high mobility and stability of practical devices. SUMMARY

[0006] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a multi-element doped IGO target material. The IGO target material of the present application has a very high density, with a relative density of more than 99%, and a resistivity as low as 2-10 mΩ·cm. The IGO target material has a small grain size, a single phase, and a more uniform composition distribution and microstructure distribution, thereby enabling the preparation of an IGO thin film device with more uniform composition. In addition, the target material also has good strength performance, which helps to meet the high power requirements of sputtering film deposition and improve the film quality. The IGO thin film prepared using the IGO target material of the present application achieves a significant improvement in carrier mobility and a significant reduction in threshold voltage under NBTIS testing, thereby improving the electrical performance and stability of the thin film device.

[0007] The present application also provides a preparation method of the above-mentioned IGO target material.

[0008] The present application also provides an IGO thin film device.

[0009] The present application also provides applications of the above-mentioned IGO target material and IGO thin film device.

[0010] In a first aspect of the present application, an IGO target material is provided, characterized in that the raw material components of the IGO target material include indium oxide, gallium oxide, high-valence metal oxide, and nitride.

[0011] The high-valence metal oxide includes at least one of niobium oxide or tantalum oxide.

[0012] After the current IGO target material system is sputtered to form a film, a large number of oxygen vacancies are generated due to the weak binding ability of In ions to oxygen ions. During negative bias electrical testing, a large number of oxygen vacancies can cause a significant increase in carrier concentration, resulting in a serious negative shift in threshold voltage when the device is turned on. In addition, due to the phase structure of the IGO thin film, carrier scattering occurs, and the mobility is insufficient, which cannot meet the requirements of high-mobility devices. In addition, the current IGO target material generally has the problems of excessively large grain structure, insufficient bending strength, uneven microstructure distribution, and abnormal grain growth, which seriously affect the development of high-mobility device thin films by downstream panel manufacturers.

[0013] According to the specific embodiments of the present application, the IGO target material provided by the present application has at least the following beneficial effects:

[0014] By doping high-valence metal oxides in the IGO target material, the high-valence metal provides additional electrons, which helps to improve the carrier concentration of the device formed by sputtering the target material, and the doped high-valence metal element has stronger metal bond energy, which has the effect of enhancing the electrical stability of the thin film. In addition, the present application uses niobium oxide or tantalum oxide as the high-valence metal oxide for doping, and the ionic radius of the element is smaller than that of the main body indium and gallium elements. When the target material is prepared by doping and sintering, the doped element can be well dissolved in the main body element, avoiding the generation of secondary phases, and the composition distribution and microstructure distribution of the target material are more uniform, and the composition distribution of the thin film after sputtering is more uniform.

[0015] The present application also introduces nitrogen elements in the target material by doping nitrides, and the stronger bond energy of the nitrogen elements can partially replace oxygen atoms in the thin film, reducing the probability of oxygen vacancy generation, thereby further enhancing the electrical stability of the device in the long-term open state. In addition, because the nitrogen element can better bind metal ions, the number of pores in the target material is less, which is beneficial to the improvement of the density of the target material.

[0016] The IGO target material provided by the present application has extremely high density, and the resistivity is as low as 2-10 mΩ·cm. The grain size of the IGO target material is small, the phase is single, the composition distribution and microstructure distribution of the target material are more uniform, and the IGO thin film device with more uniform composition can be prepared. In addition, the target material also has good strength performance, which helps to meet the high power requirement of sputtering and improve the film forming quality. The IGO thin film prepared by using the IGO target material of the present application realizes a substantial increase in carrier mobility and a significant reduction in threshold voltage under NBTIS test, and realizes the improvement of the electrical performance and stability of the thin film device.

[0017] According to some embodiments of the present application, the nitride includes gallium nitride, indium nitride, niobium nitride or tantalum nitride.

[0018] The present application can select to use gallium nitride, indium nitride, niobium nitride or tantalum nitride as the nitride for doping, which can introduce nitrogen elements in the target material, and the stronger bond energy of the nitrogen elements can partially replace oxygen atoms in the thin film, reducing the probability of oxygen vacancy generation.

[0019] According to some embodiments of the present application, the nitride includes gallium nitride.

[0020] According to some embodiments of the present application, the raw material components of the IGO target material include indium oxide 80-90 parts, gallium oxide 7-14 parts, high-valence metal oxide 1-6 parts and doped nitride 0.4-2 parts by mass fraction.

[0021] The application also explores the amount of doping high-valence metal oxide and nitride in the IGO target material, and obtains the optimal amount of each component, so that the density, resistivity, strength performance of the target material and the mobility and electrical temperature performance of the prepared thin film are balanced, and the IGO target material and IGO thin film device with the best comprehensive performance are obtained.

[0022] According to some embodiments of the application, the raw material components of the IGO target material include 82-88 parts of indium oxide, 8-13 parts of gallium oxide, 1.5-5.5 parts of high-valence metal oxide and 0.5-1.5 parts of doped nitride by mass fraction.

[0023] According to some embodiments of the application, the high-valence metal oxide includes niobium oxide and tantalum oxide.

[0024] The application explores and finds that using niobium oxide and tantalum oxide as high-valence metal oxide for co-doping can achieve better target material performance, and two suitable amounts of doped metal oxide can be well solid-solved in the target sintering process, and the electrical performance and stability of the target material and the thin film are synergistically improved.

[0025] According to some embodiments of the application, the mass fraction of the niobium oxide is 0.5-2.5 parts by mass fraction.

[0026] According to some embodiments of the application, the mass fraction of the niobium oxide is 1-2 parts by mass fraction.

[0027] According to some embodiments of the application, the mass fraction of the niobium oxide is 1.5-2 parts by mass fraction.

[0028] According to some embodiments of the application, the mass fraction of the tantalum oxide is 0.5-3.5 parts by mass fraction.

[0029] According to some embodiments of the application, the mass fraction of the tantalum oxide is 1-3 parts by mass fraction.

[0030] According to some embodiments of the application, the mass fraction of the tantalum oxide is 1.5-3 parts by mass fraction.

[0031] In the second aspect of the application, a preparation method of the IGO target material according to the first aspect of the application is provided, including the following steps:

[0032] S1, the raw material components and the dispersant are pre-mixed and ground, and then a binder, a plasticizer and water are added and mixed to obtain a mixed slurry;

[0033] S2, the mixed slurry is spray granulated to obtain a powder, and the powder is pressed into a green body;

[0034] S3, sintering the green body, to obtain the IGO target material.

[0035] According to the specific embodiment of the present application, the process of the preparation method of the IGO target material is mature, and can be applied to large-scale industrial production; and the preparation method can prepare the IGO target material of the first aspect of the present application, so the preparation method also comprises the aforementioned advantages of the IGO target material of the present application.

[0036] According to some embodiments of the present application, the dispersant comprises at least one of polyvinylpyrrolidone, polycarboxylic acid compound or polyvinyl acetate.

[0037] According to some embodiments of the present application, the dispersant is used in an amount of 1% to 5% of the total mass of the target material raw material components.

[0038] According to some embodiments of the present application, the binder comprises at least one of polypropylene alcohol, polyvinyl alcohol, carboxymethyl cellulose, polyacrylamide or polyacrylic acid salt.

[0039] According to some embodiments of the present application, the binder is used in an amount of 0.5% to 3% of the total mass of the target material raw material components.

[0040] According to some embodiments of the present application, the plasticizer comprises at least one of polyvinyl alcohol or polyethylene glycol.

[0041] According to some embodiments of the present application, the plasticizer is used in an amount of 0.5% to 3% of the total mass of the target material raw material components.

[0042] According to some embodiments of the present application, the grinding is two-stage ball milling, which is divided into primary ball milling and secondary ball milling, the primary ball milling uses zirconium beads of Φ1.0mm to Φ1.4mm, the ball milling tank is set to rotate at a speed of 400 to 600 rpm, and the grinding is cycled 5 to 7 times, each time for 3 to 5 hours; the secondary ball milling uses zirconium beads of Φ0.8mm to Φ1.2mm, the ball milling tank is set to rotate at a speed of 700 to 900 rpm, and the grinding is cycled 3 to 5 times, each time for 5 to 7 hours.

[0043] According to some embodiments of the present application, the cold isostatic pressing is used for the pressing, and the pressure is set to 200 to 300 Mpa.

[0044] According to some embodiments of the present application, the heating rate of the sintering is 3 to 4 ℃ / min, and the highest sintering temperature is 1400 to 1600 ℃.

[0045] According to some embodiments of the present application, after the sintering is heated to the highest sintering temperature, the highest temperature is maintained for 8 to 12 hours for sintering.

[0046] In a third aspect, the present application provides an IGO thin film device, wherein a raw material for preparing the IGO thin film device comprises the IGO target according to the first aspect of the present application.

[0047] According to some embodiments of the present application, the IGO thin film device is obtained by sputtering the IGO target according to the first aspect of the present application.

[0048] According to some embodiments of the present application, the IGO thin film device has a carrier mobility of 40-60 cm 2 / V·s, and a threshold voltage of less than 0.3 V under NBTIS test.

[0049] In a fourth aspect, the present application provides use of the IGO target according to the first aspect of the present application and the IGO thin film device according to the third aspect of the present application in the field of display technology.

[0050] Other features and advantages of the present application will be illustrated in the following description, and some will become apparent from the description, or will be understood through implementation of the present application. DETAILED DESCRIPTION

[0051] The concept and the resulting technical effects of the present application will be described in detail below with reference to the embodiments, so as to fully understand the purposes, features and effects of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0052] Unless otherwise specified in the detailed description, the conventional conditions or the conditions recommended by the manufacturer are used. Unless otherwise specified, the reagents or instruments used are conventional products that can be purchased on the market.

[0053] The purity of indium oxide, gallium oxide, niobium oxide, tantalum oxide and gallium nitride used in the detailed description is 4N, the specific surface area of indium oxide powder is 12-18 m 2 / g, the specific surface area of gallium oxide powder is 12-18 m 2 / g, the specific surface area of niobium oxide powder is 14-20 m 2 / g, the specific surface area of tantalum oxide powder is 16-24 m 2 / g, and the specific surface area of gallium nitride powder is 8-12 m 2 / g.

[0054] Example 1

[0055] The present embodiment provides a multi-doped IGO target and a preparation method thereof.

[0056] The raw material composition of the doped IGO target material of the present embodiment is as follows in terms of mass fraction: indium oxide (In2O3) 85 parts, gallium oxide (Ga2O3) 12.5 parts, niobium oxide (Nb2O5) 1 part, tantalum oxide (Ta2O5) 1 part, and gallium nitride (GaN) 0.5 part.

[0057] The preparation steps of the doped IGO target material of the present embodiment are as follows:

[0058] 1) According to the above mass fraction, the indium oxide, gallium oxide, niobium oxide, tantalum oxide, and gallium oxide powders are sequentially put into a mixing tank, and 1.5 parts of polyvinylpyrrolidone dispersant and pure water in a powder-to-water mass ratio of 1:1 are further put into the mixing tank for premixing to obtain a slurry;

[0059] 2) The slurry is pumped into a ball mill tank for ball milling, which is divided into front and rear stages of grinding. The grinding zirconium beads in the front-stage ball mill tank are Φ1.20 mm, the rotating speed is set to 500 rpm, the front-stage grinding time is 4 h, and the cycle grinding is 6 times. After the front-stage grinding is completed, the rear-stage grinding is performed. The grinding zirconium beads in the rear-stage ball mill tank are Φ1.00 mm, the rotating speed is set to 800 rpm, the rear-stage grinding time is 6 h, and the cycle grinding is 4 times to obtain a mixed powder. Then, 0.9 parts of polyvinyl alcohol binder and 0.8 parts of polyvinyl alcohol plasticizer are added, and the mixture is stirred for 10 h to obtain a mixed slurry;

[0060] Among them, the mixed powder after two-stage grinding is detected to have a specific surface area of 20-28 m 2 / g, and a loose bulk density of 0.95-1.85 g / cm 3 ;

[0061] 3) Spray granulation: the mixed slurry is pumped to the top end of a cyclone drying tower, which is provided with a centrifugal atomizer. Hot gas flows into one end of the centrifugal atomizer, and the slurry flows into the other end of the centrifugal atomizer. The slurry is granulated into powder particles under the action of centrifugal force, and the doped IGO powder is obtained by spray drying;

[0062] The powder is detected to have a specific surface area of 12-24 m 2 / g, and a loose bulk density of 0.95-1.85 g / cm 3 ;

[0063] 4) Pressing: the doped IGO powder is pressed using a wet cold isostatic pressing, and the forming pressure is set to 250 MPa. The green compact is obtained by pressing, which has a height of 600 mm, an outer diameter of 168 mm, an inner diameter of 138 mm, and a relative density of the target green compact of more than 72% after pressing;

[0064] 5) Sintering: The green target was sintered at high temperature under normal pressure. During sintering, the temperature was raised from room temperature at a rate of 3.5°C / min in the sintering furnace, the maximum sintering temperature was 1520°C, and the maximum temperature section needed to be kept for 10 hours. The final sintered target had a length of 480 mm, an outer diameter of 157 mm, and an inner diameter of 129 mm.

[0065] 6) Target polishing: The sintered target was polished using a numerical control processing machine to perform outer circle rough grinding, inner circle rough grinding, and outer circle fine grinding, so that the surface roughness Ra of the target was below 1.0 μm, and a multi-doped IGO target was obtained.

[0066] Examples 2-10

[0067] Examples 2-10 provide a series of multi-doped IGO targets, which differ from Example 1 only in the amount of the raw material used. The amount of the raw material components is shown in Table 1, and the preparation method is the same as that of Example 1.

[0068] Comparative Examples 1-10

[0069] Comparative Examples 1-10 provide a series of IGO targets, which differ from Example 1 only in the type or amount of the raw material used. The amount of the raw material components is shown in Table 1, and the preparation method is the same as that of Example 1.

[0070] Table 1

[0071]

[0072] Sputtering film deposition:

[0073] The targets prepared in Examples 1-10 and Comparative Examples 1-10 were used to perform PVD sputtering film deposition, and after annealing at 350°C, a TFT device channel layer film with a thickness of 20 nm was prepared, and the channel layer width-length ratio was 16:9.

[0074] Performance test:

[0075] The relative density of the targets prepared in each example and comparative example was determined using the Archimedes drainage method; the resistivity of the targets prepared in each example and comparative example was detected using a four-probe resistivity tester; the bending strength of the targets was tested using a universal testing machine; the microcrystalline grain size and grain distribution of the targets were analyzed using a metallographic analysis method; the carrier mobility and threshold voltage under NBTIS of the films obtained by sputtering film deposition of each target were tested; and the test results are shown in Table 2.

[0076] Table 2

[0077]

[0078] Performance test result analysis:

[0079] From the performance test results of Table 2, it can be seen that the multi-doped IGO target material prepared by using the embodiments 1-10 of the present application has a very high relative density (the relative density is all above 99%), a relatively low resistivity, and a grain size less than 10 μm, and further has a high bending strength performance of above 120 MPa. The target material prepared by using the present application has a high mobility and a very small threshold voltage under NBTIS test, and the TFT device channel layer film has excellent electrical performance.

[0080] From the comparative examples 1-3, it is found that the mobility of the final prepared thin film device is continuously improved with the increase of the doping amount of the niobium oxide. From the comparative examples 4-6, it is found that the mobility of the final prepared thin film device is continuously improved with the increase of the doping amount of the tantalum oxide. Therefore, in the present application, the appropriate doping of the niobium oxide and the tantalum oxide helps to improve the mobility of the thin film.

[0081] From the comparative examples 6-8, it is found that the threshold voltage under NBTIS test of the final prepared thin film device is reduced with the increase of the gallium nitride doping amount, which can further improve the electrical performance, the stability and the reliability of the device. It is analyzed that the doping of the gallium nitride helps to enhance the binding capacity to the oxygen vacancy. In addition, it is unexpectedly found that the density of the prepared target material is also improved with the increase of the gallium nitride doping amount.

[0082] In the embodiments 9 and 10, only one kind of high-valence metal oxide of the niobium oxide and the tantalum oxide is doped, respectively, and the prepared target material is difficult to achieve the best comprehensive performance, and the resistivity of the target material is slightly high.

[0083] In the IGO target material of the comparative example 1, only 1.5 parts of the niobium oxide is doped, and the tantalum oxide and the gallium nitride are not doped. The prepared target material has a high resistivity and a low density, and the threshold voltage under NBTIS test of the prepared thin film device is increased, so the performance of the target material is poor.

[0084] In the IGO target material of the comparative example 2, 1 part of the niobium oxide and 1 part of the tantalum oxide are doped, but the gallium nitride is not doped. The threshold voltage under NBTIS test of the thin film device prepared by the target material is high, and the electrical stability is poor.

[0085] In the comparative example 3 and the comparative example 4, too much niobium oxide and tantalum oxide is doped, respectively. It is found that the target material has a poor solid solution effect in the preparation process, and a secondary phase appears. Too much doping of the niobium oxide or the tantalum oxide also causes a serious negative drift of the threshold voltage, which affects the electrical stability of the thin film device.

[0086] In the comparative example 5, too much gallium nitride is doped, and although the doping of gallium nitride can improve the electrical stability of the thin film device, too much gallium nitride will bind more oxygen vacancies, so that the mobility of the thin film will decrease obviously, and therefore it is difficult to prepare a high-performance thin film device.

[0087] In the comparative example 6, the IGO target material is pure, and the thin film device prepared by the target material without other dopants has a serious negative threshold voltage drift and a significantly decreased stability, and is not suitable for being used as a TFT channel layer material.

[0088] In the comparative example 7, the IGO target material is only doped with gallium nitride, and although the electrical stability of the thin film device prepared is good, the doping of the high-valence metal oxide niobium oxide and tantalum oxide is lacking, and the mobility of the thin film is low, which cannot meet the requirement of a high-mobility thin film.

[0089] In the comparative example 8 and the comparative example 9, the IGO target material respectively replaces the doping of niobium oxide and tantalum oxide with the doping of zirconium oxide, and the mobility of the thin film device prepared is not obviously improved, which indicates that the doping effect of the high-valence metal oxide zirconium oxide is not as good as that of niobium oxide and tantalum oxide.

[0090] In the comparative example 10, the IGO target material replaces the doping of niobium oxide and tantalum oxide with the doping of titanium dioxide, and the prepared target material has a low density, a secondary phase appears, and the mobility of the thin film device prepared is low, and therefore the high-valence metal oxide titanium dioxide is not suitable for being doped into the IGO target material.

[0091] In summary, the present application can solve the problem of insufficient mobility of the ultra-clear display TFT thin film device, and meet the application of the future ultra-large size and ultra-high definition display panel. The high-valence metal oxide and the nitride are doped into the IGO target material, so that the target material prepared by sintering has a high density, a small number of pores, a uniform target material composition distribution and microstructure distribution, a lower resistivity than the pure IGO target material, smaller target material grains, and further improved mechanical properties. After the prepared doped target material is sputtered into a film, it is analyzed and tested that the mobility of the thin film is obviously improved, the electrical stability is better than that of the pure IGO thin film, and the threshold voltage does not drift negatively in a long-time device opening state.

[0092] The embodiments of the present application are described in detail above, but the present application is not limited to the above-described embodiments, and various changes can be made within the knowledge range of ordinary skilled persons in the art without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. An IGO target material, characterized in that, The raw material components of the IGO target material include indium oxide 80-90 parts by mass, gallium oxide 7-14 parts by mass, high-valence metal oxide 1-6 parts by mass, and nitride 0.4-2 parts by mass; The high-valence metal oxide includes niobium oxide and tantalum oxide, the mass fraction of the niobium oxide is 0.5-2.5 parts, and the mass fraction of the tantalum oxide is 0.5-3.5 parts; the nitride is at least one of gallium nitride, indium nitride, niobium nitride, and tantalum nitride.

2. A method of producing an IGO target according to claim 1, characterized by, The method comprises the following steps: S1, the raw material components and dispersants are pre-mixed and then ground, and then a binder, a plasticizer, and water are added and mixed to obtain a mixed slurry; S2, the mixed slurry is spray granulated to obtain a powder, and the powder is pressed to form a green body; S3, the green body is sintered to obtain the IGO target material.

3. The preparation method according to claim 2, characterized in that, The pressing is performed by cold isostatic pressing, and the pressure is 200-300 MPa.

4. The preparation method according to claim 2, characterized in that, The highest temperature of the sintering is 1400-1600 ℃.

5. An IGO thin film device, characterized by, The raw material for preparing the IGO thin film device includes the IGO target material of claim 1.

6. The IGO thin film device of claim 5, wherein, The carrier mobility of the IGO thin film device is 40-60 cm 2 / V·s; And / or, the threshold voltage of the IGO thin film device under NBTIS test is less than 0.3 V.

7. The IGO target material of claim 1 or the IGO thin film device of any one of claims 5-6 is applied in the field of display technology.

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