High-mobility IGO target material and preparation method and application thereof

Abstract

The invention belongs to the technical field of target materials for thin film transistor sputtering, and particularly discloses a high-mobility IGO target material and a preparation method and application thereof. The IGO target material comprises the following raw material components: indium oxide, gallium oxide, high-valence metal oxide and doped nitride, wherein the high-valence metal oxide comprises at least one of niobium oxide or tantalum oxide. The IGO target material provided by the invention has the characteristics of high density and low resistivity, the grain size is smaller, the phase is single, the components and microstructure distribution are uniform, the target material also has better strength performance, and an IGO thin film device prepared by using the target material has high carrier mobility and low threshold bias voltage and can be applied to the field of thin film devices. And better electrical performance and stability can be realized. The invention also provides a preparation method and application of the IGO target material.

Description

Technical Field

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

[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 displays require smaller and smaller pixel points. Based on this, the carrier mobility of TFT thin film devices is required to be high enough.

[0003] At present, indium gallium zinc oxide (IGZO) thin film materials have been successfully commercialized, but as a channel layer material, the electron mobility of IGZO thin film is only 10cm 2 / V·s, which can no longer meet the requirements of future display technology. Moreover, when the LCD panel device is turned on for a long time, the IGZO film is easily affected by the panel backlight, generating photogenerated carriers, causing the threshold voltage to drift negatively, and the stability of the TFT device will also be greatly challenged. At present, thin-film transistors are still electrically and optically unstable under harsh test application conditions. Therefore, it is necessary to develop new material systems to adapt to the iterative development of TFT technology. In addition, although the high-mobility films currently developed by various research institutions have reached a mobility of 20~30cm 2 / V·s level, but when the device is turned on for a long time, the stability of the thin film device is still insufficient, and the threshold voltage negative bias phenomenon is still serious. The industry has generally believed that the conductive mechanism of the channel layer film in TFT is that the oxygen vacancy defect conducts electrons. Therefore, for system materials with weak metal and oxygen bond energy, when the TFT film is turned on for a long time, the oxygen vacancy concentration in the film will cause excessive carrier concentration, resulting in insufficient stability of the device during the device opening process. Both indium zinc oxide (IZO) film and IGZO film have this problem.

[0004] Oxide targets are the raw materials for making device thin films. The performance of the targets has a profound impact on the quality of the film after coating. Therefore, only by preparing good targets can the quality of coating be fundamentally improved. Indium gallium oxide (IGO) targets are targets with simpler composition and more ideal technology. However, the stability of IGO thin films after sputtering in the current IGO target system is relatively low, and the mobility of the films still cannot meet the needs of high-migration thin films. Moreover, the IGO sputtering targets prepared by the current relevant technologies generally have problems such as insufficient target densification, excessive pores, and uneven composition and organization. Some IGO targets even have abnormal phenomena such as high resistivity and excessively large target grains.

[0005] Therefore, it is urgent to develop a new IGO target system to prepare high-mobility films to meet the requirements of real devices for high mobility and stability. Summary of the invention

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

[0007] The present invention also provides a method for preparing the IGO target material.

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

[0009] The present invention also proposes the application of the IGO target material and IGO thin film device.

[0010] In a first aspect of the present invention, an IGO target material is provided, characterized in that the raw material components of the IGO target material include indium oxide, gallium oxide, high-valent metal oxide and nitride; Wherein, the high-valent metal oxide includes at least one of niobium oxide or tantalum oxide.

[0011] After sputtering, the current IGO target system produces a large number of oxygen vacancies due to the weak ability of In ions to bind oxygen ions. During negative bias electrical testing, the generation of a large number of oxygen vacancies will cause a significant increase in carrier concentration, causing the threshold voltage of the device to drift negatively when it is turned on. In addition, due to the physical structure of the IGO film, carrier scattering occurs and the mobility is insufficient, which cannot meet the needs of high-mobility devices. In addition, the current IGO target materials generally have problems such as excessively large grain structure, insufficient bending strength, uneven microstructure distribution, and abnormal grain growth, which seriously affects the development of high-mobility device films by downstream panel manufacturers.

[0012] According to a specific embodiment of the present invention, the IGO target provided by the present invention has at least the following beneficial effects: By doping high-valent metal oxides in the IGO target material, the high-valent metal is used to provide additional electrons, which helps to increase the carrier concentration of the device for sputtering the target material into a film, and the doped high-valent metal element also has a stronger metal bond energy, which has the effect of enhancing the electrical stability of the film. In addition, the present invention uses niobium oxide or tantalum oxide as the high-valent metal oxide for doping, and the element ion radius is smaller than the ion radius of the main indium and gallium elements. When the target material is prepared by doping and sintering, the doped element can be well dissolved in the main element to avoid the generation of secondary phases. The component distribution and microstructure distribution of the target material are more uniform, and the film component is more evenly distributed after sputtering.

[0013] The present invention also introduces nitrogen into the target material by doping nitrides, and utilizes the stronger bonding energy of nitrogen to partially replace oxygen atoms in the film, reducing the probability of oxygen vacancies, thereby further enhancing the electrical stability of the device in a long-term open state. In addition, because nitrogen can better bind metal ions, the number of pores in the target material is reduced, which is conducive to improving the density of the target material.

[0014] The IGO target material provided by the present invention has extremely high density, and the resistivity is as low as the order of 2-10 mΩ·cm. In addition, the grain size of the IGO target material is small, the physical phase is single, and the component distribution and microstructure distribution of the target material are more uniform, so that an IGO thin film device with more uniform composition can be prepared. In addition, the target material also has good strength performance, which helps the target material meet the high power requirements of sputtering coating and improves the film quality. The IGO thin film prepared by using the IGO target material of the present invention achieves a significant improvement in carrier mobility and a significant reduction in threshold bias voltage under NBTIS test, thereby achieving an improvement in the electrical performance and stability of the thin film device.

[0015] According to some embodiments of the present invention, the nitride includes gallium nitride, indium nitride, niobium nitride or tantalum nitride.

[0016] The present invention can select gallium nitride, indium nitride, niobium nitride or tantalum nitride as nitride for doping, all of which can introduce nitrogen into the target material. By utilizing the stronger bonding energy of nitrogen, it can partially replace oxygen atoms in the film and reduce the probability of generating oxygen vacancies.

[0017] According to some embodiments of the invention, the nitride comprises gallium nitride.

[0018] According to some embodiments of the present invention, the raw material components of the IGO target include, by mass, 80-90 parts of indium oxide, 7-14 parts of gallium oxide, 1-6 parts of high-valent metal oxide and 0.4-2 parts of doped nitride.

[0019] The present invention also explores the dosage of doping high-valent metal oxides and nitrides in the IGO target material, obtains the optimal dosage ratio of each component, achieves a balance among the target material density, resistivity, strength performance, and the mobility and electrical temperature performance of the prepared film, and obtains an IGO target material and IGO thin film device with the best comprehensive performance.

[0020] According to some embodiments of the present invention, the raw material components of the IGO target include, by mass, 82-88 parts of indium oxide, 8-13 parts of gallium oxide, 1.5-5.5 parts of high-valent metal oxide and 0.5-1.5 parts of doped nitride.

[0021] According to some embodiments of the present invention, the high-valent metal oxide includes niobium oxide and tantalum oxide.

[0022] The present invention explores and finds that using niobium oxide and tantalum oxide as high-valent metal oxides for co-doping can achieve better target performance. The two appropriately doped metal oxides can be well dissolved during the target sintering process, synergistically improving the electrical properties and stability of the target and the film.

[0023] According to some embodiments of the present invention, the mass fraction of niobium oxide is 0.5-2.5 parts by mass.

[0024] According to some embodiments of the present invention, the mass fraction of niobium oxide is 1 to 2 parts by mass.

[0025] According to some embodiments of the present invention, the mass fraction of niobium oxide is 1.5 to 2 parts by mass.

[0026] According to some embodiments of the present invention, the mass fraction of the tantalum oxide is 0.5-3.5 parts by mass.

[0027] According to some embodiments of the present invention, the mass fraction of the tantalum oxide is 1 to 3 parts by mass.

[0028] According to some embodiments of the present invention, the mass fraction of the tantalum oxide is 1.5 to 3 parts by mass.

[0029] The second aspect of the present invention provides a method for preparing the IGO target material as described in the first aspect of the present invention, comprising the following steps: S1, premixing the raw material components and the dispersant, grinding them, adding a binder, a plasticizer and water, and mixing to obtain a mixed slurry; S2, spray granulating the mixed slurry to obtain a powder, and pressing the powder to obtain a green blank; S3, sintering the green blank to obtain the IGO target material.

[0030] According to a specific embodiment of the present invention, the preparation method of the IGO target material provided by the present invention has a mature process and can be applied in large-scale industrial production; and the preparation method can prepare the IGO target material described in the first aspect of the present invention, so the preparation method also includes the aforementioned advantages of the IGO target material of the present invention.

[0031] According to some embodiments of the present invention, the dispersant includes at least one of polyvinyl pyrrolidone, a polycarboxylic acid compound or a polyvinyl salt.

[0032] According to some embodiments of the present invention, the amount of the dispersant used is 1% to 5% of the total mass of the target material raw material components.

[0033] According to some embodiments of the present invention, the binder includes at least one of polypropylene alcohol, polyvinyl alcohol, carboxymethyl cellulose, polyacrylamide or polyacrylic acid salt.

[0034] According to some embodiments of the present invention, the amount of the binder is 0.5% to 3% of the total mass of the target material raw material components.

[0035] According to some embodiments of the invention, the plasticizer comprises at least one of polyvinyl alcohol or polyethylene glycol.

[0036] According to some embodiments of the present invention, the amount of the plasticizer used is 0.5% to 3% of the total mass of the target material raw material components.

[0037] According to some embodiments of the present invention, the grinding is two-stage ball milling, and the two-stage ball milling is divided into primary ball milling and secondary ball milling. The primary ball milling uses zirconium beads of Φ1.0mm~Φ1.4mm, the ball mill jar is set to a speed of 400~600rpm, and the cycle grinding is 5~7 times, each time for 3~5h; the secondary ball milling uses zirconium beads of Φ0.8mm~Φ1.2mm, the ball mill jar is set to a speed of 700~900rpm, and the cycle grinding is 3~5 times, each time for 5~7h.

[0038] According to some embodiments of the present invention, the press molding is performed by cold isostatic pressing, and the pressure is set to 200-300 MPa.

[0039] According to some embodiments of the present invention, the heating rate of the sintering is 3-4°C / min, and the maximum sintering temperature is 1400-1600°C.

[0040] According to some embodiments of the present invention, after the sintering temperature is raised to the maximum sintering temperature, the maximum sintering temperature is maintained for 8 to 12 hours.

[0041] According to a third aspect of the present invention, an IGO thin film device is provided. The raw materials for preparing the IGO thin film device include the IGO target material according to the first aspect of the present invention.

[0042] According to some embodiments of the present invention, the IGO thin film device is obtained by sputtering the IGO target material described in the first aspect of the present invention.

[0043] According to some embodiments of the present invention, the carrier mobility of the IGO thin film device is 40-60 cm 2 / V·s, the threshold bias voltage of the IGO thin film device is less than 0.3V under NBTIS test.

[0044] The fourth aspect of the present invention provides applications of the IGO target material described in the first aspect of the present invention and the IGO thin film device described in the third aspect of the present invention in the field of display technology.

[0045] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. DETAILED DESCRIPTION

[0046] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0047] If the specific conditions are not specified in the specific implementation mode, the conventional conditions or the conditions recommended by the manufacturer are used. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased from the market.

[0048] The purity of indium oxide, gallium oxide, niobium oxide, tantalum oxide and gallium nitride used in the specific implementation manner is 4N, and the specific surface area of ​​indium oxide powder is 12-18 m 2 / g, the specific surface area of ​​gallium oxide powder is 12~18m 2 / g, the specific surface area of ​​niobium oxide powder is 14~20m 2 / g, the specific surface area of ​​tantalum oxide powder is 16~24m 2 / g, the specific surface area of ​​gallium nitride powder is 8~12m 2 / g.

[0049] Example 1 This embodiment provides a multi-doped IGO target material and a preparation method thereof.

[0050] The raw material composition of the doped IGO target material in this embodiment is as follows by weight: indium oxide (In 2 O 3 ) 85 parts, gallium oxide (Ga 2 O 3 ) 12.5 parts, niobium oxide (Nb 2 O 5 ) 1 part, tantalum oxide (Ta 2 O 5 ) 1 part and gallium nitride (GaN) 0.5 part.

[0051] The steps for preparing the doped IGO target material of this embodiment are as follows: 1) Indium oxide, gallium oxide, niobium oxide, tantalum oxide and gallium oxide powders are sequentially added into a mixing tank according to the above mass parts, and then 1.5 parts of polyvinylpyrrolidone dispersant and pure water with a mass ratio of 1:1 to the powder are added for premixing to obtain a slurry; 2) The slurry is pumped into a ball mill for ball milling. The ball milling is divided into front and back stage grinding. The grinding zirconium beads in the front stage ball mill are Φ1.20 mm, the rotation speed is set to 500 rpm, the front stage grinding time is 4 hours, and the cycle grinding is repeated 6 times. After the front stage grinding is completed, the back stage grinding is performed. The grinding zirconium beads in the back stage ball mill are Φ1.00 mm, the rotation speed is set to 800 rpm, the back stage grinding time is 6 hours, and the cycle grinding is repeated 4 times to obtain a mixed powder, and then 0.9 parts of polypropylene alcohol binder and 0.8 parts of polyvinyl alcohol plasticizer are added, and stirred for 10 hours to obtain a mixed slurry; Among them, the mixed powder after two-stage grinding has a specific surface area of ​​20~28m 2 / g, and the bulk density is between 0.95~1.85g / cm 3 between; 3) Spray granulation: The mixed slurry is pumped to the top of the cyclone drying tower. A centrifugal atomizer is set at the top of the cyclone drying tower. A hot air flow is passed through one end, and the slurry introduced at the other end meets the hot air flow. Under the action of centrifugal force, the slurry is granulated to form powder particles, and the doped IGO powder is obtained by spray drying; According to the test, the specific surface area of ​​the powder is between 12m2 and 24m2. 2 / g, and the bulk density is between 0.95~1.85g / cm 3 between; 4) Pressing: The doped IGO powder is pressed by wet cold isostatic pressing, the molding pressure is set to 250MPa, and a green blank is obtained by pressing. The green blank has a height of 600mm, an outer diameter of 168mm, and an inner diameter of 138mm. The relative density of the pressed target green blank reaches more than 72%; 5) Sintering: The target blank is sintered at normal pressure and high temperature. During sintering, the temperature is increased from room temperature in the sintering furnace at a heating rate of 3.5℃ / min. The highest sintering temperature is 1520℃, and the highest temperature section needs to be kept warm for 10 hours. The final fired target has a length of 480mm, an outer diameter of 157mm, and an inner diameter of 129mm. 6) Target grinding: Use a CNC machining machine to perform outer rough grinding, inner rough grinding and outer fine grinding on the fired target, so that the surface roughness Ra of the target is below 1.0μm, and obtain a multi-doped IGO target.

[0052] Embodiment 2 to Embodiment 10 Examples 2 to 10 provide a series of multi-element doped IGO targets, which differ from Example 1 only in the different amounts of raw materials used. The amounts of raw material components are shown in Table 1, and the preparation method is the same as that of Example 1.

[0053] Comparative Example 1 to Comparative Example 10 Comparative Examples 1 to 10 provide a series of IGO target materials, which differ from Example 1 only in the types of raw materials or the amounts used. The amounts of the raw material components are shown in Table 1, and the preparation method is the same as that of Example 1.

[0054] Table 1

[0055] Sputtering coating: The target materials prepared in Examples 1 to 10 and Comparative Examples 1 to 10 were respectively used for PVD sputtering coating, 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-to-length ratio was 16:9.

[0056] Performance Testing: The relative density of the target material prepared in each embodiment and comparative example was determined by the Archimedean drainage method; the resistivity of the target material prepared in each embodiment and comparative example was detected by a four-probe resistivity tester; the bending strength of the target material was tested by a universal testing machine; the microscopic grain size and grain distribution of the target material were analyzed by a metallographic analysis method; the carrier mobility of the thin film obtained by sputtering coating of each target material and the threshold bias voltage under NBTIS were tested; the test results are shown in Table 2.

[0057] Table 2

[0058] Performance test results analysis: From the performance test results in Table 2, it can be seen that the multi-doped IGO target materials prepared by Examples 1 to 10 of the scheme of the present invention have very high relative density (relative density reaches more than 99%), relatively low resistivity, and grain size is less than 10μm, and also have high bending strength performance, reaching more than 120MPa. The target material prepared by the scheme of the present invention is sputtered and coated to obtain a TFT device channel layer film with high mobility, very small threshold bias voltage under NBTIS test, and excellent electrical performance.

[0059] By comparing Examples 1 to 3, it is found that with the increase of the doping amount of niobium oxide, the mobility of the thin film device finally prepared is continuously improved; by comparing Examples 4 to 6, it is found that with the increase of the doping amount of tantalum oxide, the mobility of the thin film device finally prepared is also continuously improved; therefore, in the scheme of the present invention, the appropriate amount of doping of niobium oxide and tantalum oxide helps to improve the mobility of the thin film.

[0060] By comparing Examples 6 to 8, it was found that with the increase in the doping amount of gallium nitride, the threshold bias voltage of the finally prepared thin film device under the NBTIS test was reduced, which can further improve its electrical performance and the stability and reliability of the device. It was analyzed that the doping of gallium nitride helps to enhance the binding ability of oxygen vacancies; in addition, it was unexpectedly found that with the increase in the doping amount of gallium nitride, the density of the prepared target material was also improved.

[0061] In Example 9 and Example 10, only one high-valent metal oxide of niobium oxide and tantalum oxide was doped respectively, and the prepared target materials were difficult to achieve the best comprehensive performance, and the resistivity of the target materials was also slightly high.

[0062] The IGO target of Comparative Example 1 is doped with only 1.5 parts of niobium oxide, but not tantalum oxide and gallium nitride. The prepared target has a high resistivity and a low density, and the prepared thin film device has an increased threshold bias voltage under the NBTIS test, so the target performance is poor.

[0063] The IGO target of Comparative Example 2 is doped with 1 part of niobium oxide and 1 part of tantalum oxide, but not doped with gallium nitride. The thin film device prepared from the target has a high threshold bias voltage and poor electrical stability under the NBTIS test.

[0064] In Comparative Examples 3 and 4, too much niobium oxide and tantalum oxide were doped respectively. During the preparation process, it was found that the target material solid solution effect was poor and secondary phases appeared. In addition, excessive niobium oxide or tantalum oxide doping also caused severe negative drift of the threshold voltage, affecting the electrical stability of the thin film device.

[0065] In Comparative Example 5, too much GaN is doped. Although the doping of GaN can improve the electrical stability of the thin film device, the excessive GaN will also bind more oxygen vacancies, causing a significant decrease in the mobility of the film, making it difficult to prepare a high-performance thin film device.

[0066] Comparative Example 6 is a pure IGO target material. The threshold voltage of the thin film device prepared by the target material without other dopants has a serious negative drift and a significantly reduced stability, and is not suitable for use as a TFT channel layer material.

[0067] The IGO target of Comparative Example 7 is only doped with gallium nitride. Although the prepared thin film device has good electrical stability, it lacks the doping of high-valent metal oxides niobium oxide and tantalum oxide, and its film mobility is low, which cannot meet the requirements of high-mobility film.

[0068] The IGO targets of Comparative Examples 8 and 9 respectively replaced niobium oxide and tantalum oxide doping with zirconium oxide doping, but the mobility of the prepared thin film devices was not significantly improved, indicating that the doping effect of the high-valent metal oxide zirconium oxide is not as good as that of niobium oxide and tantalum oxide.

[0069] In the IGO target of Comparative Example 10, niobium oxide and tantalum oxide doping are replaced by titanium dioxide doping. As a result, the density of the prepared target is low, a secondary phase appears, and the mobility of the prepared thin film device is low. Therefore, the high-valent metal oxide titanium dioxide is not suitable for being doped into the IGO target as a dopant.

[0070] In summary, the present invention can solve the problem of insufficient mobility of ultra-high-definition display TFT thin film devices and meet the application of ultra-large size and ultra-high-definition display panels in the future. The present invention uses high-valent metal oxides and nitrides to dope IGO targets, so that the target prepared by sintering has high density, a small number of pores, uniform target composition distribution and microstructure distribution, lower target resistivity than pure IGO targets, smaller target grains, and further improved mechanical properties; after the prepared doped target is sputtered into a film, after analysis and testing, the mobility of the film is significantly improved, the electrical stability is better than that of pure IGO film, and no threshold voltage negative drift phenomenon occurs when the device is turned on for a long time.

[0071] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention 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, gallium oxide, high-valent metal oxides and nitrides; Wherein, the high-valent metal oxide includes at least one of niobium oxide or tantalum oxide.

2. The IGO target according to claim 1, characterized in that Calculated by weight, the raw material components include 80-90 parts of indium oxide, 7-14 parts of gallium oxide, 1-6 parts of high-valent metal oxide and 0.4-2 parts of doped nitride.

3. The IGO target according to claim 2, characterized in that: The high-valent metal oxides include niobium oxide and tantalum oxide.

4. The IGO target according to claim 3, characterized in that: The mass fraction of the niobium oxide is 0.5 to 2.5 parts; And / or, the mass fraction of the tantalum oxide is 0.5 to 3.5 parts.

5. A method for preparing an IGO target according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, premixing the raw material components and the dispersant, grinding them, adding a binder, a plasticizer and water, and mixing to obtain a mixed slurry; S2, spray granulating the mixed slurry to obtain a powder, and pressing the powder to obtain a green blank; S3, sintering the green blank to obtain the IGO target material.

6. The preparation method according to claim 5, characterized in that: The pressing molding is performed by cold isostatic pressing at a pressure of 200-300 MPa.

7. The preparation method according to claim 5, characterized in that: The maximum sintering temperature is 1400-1600°C.

8. An IGO thin film device, characterized in that: The raw material for preparing the IGO thin film device includes the IGO target material according to any one of claims 1 to 4.

9. The IGO thin film device according to claim 8, characterized in that: The carrier mobility of the IGO thin film device is 40~60cm 2 / V·s; And / or, the threshold bias voltage of the IGO thin film device is less than 0.3V under NBTIS test.

10. Application of the IGO target material according to any one of claims 1 to 4 or the IGO thin film device according to any one of claims 8 to 9 in the field of display technology.

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