Low sheet resistance and high light transmittance ITO coating and preparation method thereof

Abstract

The application relates to the technical field of ITO coating materials, and provides a low-sheet-resistance high-transmittance ITO coating and a preparation method thereof, the preparation method comprising the following steps: S1, preparing a yttrium-doped zirconium oxide substrate; S2, activating the surface of the yttrium-doped zirconium oxide substrate; S3, placing the yttrium-doped zirconium oxide substrate into a radio frequency magnetron sputtering chamber to perform magnetron sputtering, so as to form an ITO film on the surface of the yttrium-doped zirconium oxide substrate; and S4, performing annealing treatment and gradient cooling treatment. The prepared yttrium-doped zirconium oxide substrate optimizes the epitaxial growth of the ITO coating, the microstructure of the film is optimized by combining the magnetron sputtering, annealing and gradient cooling processes, the carrier mobility and the uniformity and stability of the film are improved, the grain boundary defects and carrier scattering loss in the ITO coating are reduced, the low sheet resistance and the high transmittance of the ITO coating are synergistically improved, and the obtained ITO coating has important application value in the fields of high-performance optoelectronic devices and transparent conductive films.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ITO coating materials, and particularly relates to a low sheet resistance and high light transmittance ITO coating and a preparation method thereof. BACKGROUND

[0002] In the development of modern optoelectronic devices, intelligent displays and high-efficiency photovoltaic technology, transparent conductive thin film (TCO) materials play a crucial role. ITO (indium tin oxide) is widely used in touch panels, OLED displays, solar cells and smart windows due to its excellent electrical conductivity and high light transmittance. In these applications, the transparent conductive film not only needs to have a low resistivity to ensure the efficiency of electronic transmission, but also needs to have a high light transmittance to maintain high-quality optical performance, reduce light loss and improve display brightness or photovoltaic conversion efficiency. In addition, with the rapid development of high-resolution display technology, new flexible electronic devices and high-efficiency solar cells, higher requirements are placed on the performance of ITO thin films, such as lower sheet resistance to reduce energy consumption and improve response speed, and higher light transmittance to optimize optical performance, especially in the near-ultraviolet and infrared wave bands. Therefore, in the field of transparent conductive thin films, how to further reduce the sheet resistance of ITO while maintaining or even improving the optical transmittance has become a key to the development of this technology and an important technical breakthrough for improving the performance and application range of new-generation optoelectronic devices.

[0003] Although ITO has been widely used as the preferred material for transparent conductive thin films, the existing ITO thin films still face the challenge of balancing low sheet resistance and high light transmittance. For example, Chinese Patent No. CN108109722A discloses a method for preparing ITO thin films by using liquid-phase indium tin oxide precursors combined with annealing, but the thin films usually have poor crystallinity or crystal type control, so the electrical conductivity and light transmittance of the thin films have certain deficiencies. In addition, the grain orientation and crystalline quality of existing ITO thin films have an important influence on electrical conductivity and optical performance, but existing processes are difficult to precisely control the texture growth of ITO, resulting in enhanced carrier scattering in the thin film, thereby increasing the resistance and reducing the light transmittance. At the same time, some studies attempt to improve the electrical conductivity and transparency of ITO by optimizing the doping concentration or changing the deposition atmosphere, but these methods often accompany a decrease in the stability of the thin film, or lead to the complication and cost increase of the preparation process. Therefore, a technical solution is needed that can optimize the crystal structure of ITO while balancing low sheet resistance and high light transmittance, in order to realize the more extensive application of transparent conductive thin films in the field of optoelectronics and display technology. SUMMARY

[0004] (1) Technical problems solved

[0005] The application aims to provide a low sheet resistance and high light transmittance ITO coating and a preparation method, and solve the problems of insufficient sheet resistance and light transmittance of the current ITO coating.

[0006] (2) Technical scheme

[0007] In order to achieve the above-mentioned purpose, the application provides the following technical scheme:

[0008] A preparation method of a low sheet resistance and high light transmittance ITO coating, comprising the following steps:

[0009] S1, preparing a yttrium-doped zirconium oxide substrate with a root mean square (RMS) roughness of 0.2-0.5 nm;

[0010] S2, activating the surface of the yttrium-doped zirconium oxide substrate;

[0011] S3, placing the yttrium-doped zirconium oxide substrate after surface activation into a radio frequency magnetron sputtering chamber for magnetron sputtering to form an ITO film on the surface of the yttrium-doped zirconium oxide substrate;

[0012] S4, then performing annealing treatment and gradient cooling treatment to obtain the low sheet resistance and high light transmittance ITO coating.

[0013] The yttrium-doped zirconium oxide substrate prepared by the application has high orientation and low defect density, provides a stable lattice matching environment for the epitaxial growth of the ITO film, enhances the crystalline quality and interface matching of the ITO film, effectively reduces the internal stress accumulation of the ITO film, thereby improving the structural stability and long-term use reliability of the ITO film, and optimizing the conductivity and light transmittance of the ITO film.

[0014] By selecting the yttrium-doped zirconium oxide substrate of the application and combining the optimization steps of magnetron sputtering, annealing treatment and gradient cooling treatment, the optical transmittance characteristics of the obtained ITO coating are further optimized while maintaining low sheet resistance, so that the ITO coating has more excellent performance in the application of optoelectronic devices, transparent electrodes and high-performance display panels.

[0015] Preferably, in the yttrium-doped zirconium oxide substrate, the (200) crystal direction of the yttrium-doped zirconium oxide is perpendicular to the surface of the yttrium-doped zirconium oxide substrate; and the doping amount of yttrium oxide in the yttrium-doped zirconium oxide substrate is 4-8 at. %.

[0016] Preferably, the preparation method of the yttrium-doped zirconium oxide substrate comprises the following steps:

[0017] The clean Si(100) substrate with surface roughness Ra≤0.2nm is placed in a multi-cathode sputtering deposition system, the multi-cathode sputtering deposition system comprises two direct current sputtering sources and one radio frequency sputtering source, the two direct current sputtering sources and the radio frequency sputtering source are arranged in a confocal manner and form an angle of 55-65 degrees with the substrate normal, wherein the two direct current sputtering sources are used for reactive sputtering of zirconium targets, and the radio frequency sputtering source is used for reactive sputtering of yttrium targets, yttrium-doped zirconium oxide substrates are deposited by reactive co-sputtering of the two zirconium targets and the yttrium target in an argon-oxygen mixed plasma, wherein the volume flow ratio of argon to oxygen is 1.5-2.0:1, the total working pressure is 8-12 mTorr, the power density of the zirconium target is 12-15 W / cm 2 , the power density of the yttrium target is 2.0-2.5 W / cm 2 , the substrate bias is -300 to -500 V, and the substrate temperature is 70-80 DEG C.

[0018] The present application effectively reduces the surface roughness of the substrate by depositing yttrium-doped zirconium oxide film on the clean Si(100) substrate, so that the surface roughness reaches the nanometer level. The optimized substrate surface can significantly improve the epitaxial growth conditions of ITO film, reduce the adverse effects of grain boundary scattering on conductivity, and improve the optical uniformity of the film.

[0019] In the deposition process of the yttrium-doped zirconium oxide film, a multi-cathode sputtering system is used, wherein two direct current sputtering sources are used for reactive sputtering of zirconium targets, and one radio frequency sputtering source is used for collaborative deposition of yttrium targets. Each sputtering source is arranged in a confocal manner and forms a specific angle with the substrate normal to accurately control the deposition uniformity and composition distribution of the film. By optimizing the volume flow ratio of argon to oxygen, and controlling the sputtering power density, substrate bias and substrate temperature, the stoichiometric ratio and crystal phase stability of the film during deposition are ensured, so that a high-quality yttrium-doped zirconium oxide substrate is obtained. The substrate not only provides an excellent lattice matching environment to promote the (400) preferred orientation growth of ITO film, but also effectively reduces the stress accumulation of the film, improves its mechanical stability and long-term reliability. In addition, the optimized deposition environment and parameter control can ensure the density and uniformity of the yttrium-doped zirconium oxide film, further reduce the grain boundary defects and carrier scattering loss in the ITO film, and thus enhance the electrical and optical properties of the entire transparent conductive film.

[0020] Preferably, the method for preparing the clean Si(100) substrate comprises the following steps: soaking the Si(100) substrate in a hydrofluoric acid solution with a mass fraction of 3.0-5.0% to remove the surface oxide layer, then transferring to a mixed cleaning solution composed of deionized water, hydrogen peroxide with a mass fraction of 25-30%, and ammonia water with a mass fraction of 25-30% at a volume ratio of 5:1:1, and ultrasonic treating at 75-85°C for 10-20 min at an ultrasonic frequency of 40-60 kHz, then rinsing the substrate with ultrapure water, blowing the surface residual liquid under a nitrogen atmosphere, and finally drying in a vacuum oven to obtain the clean Si(100) substrate.

[0021] In the process of preparing the clean substrate with a surface roughness Ra≤0.2 nm, a hydrofluoric acid solution is used to remove the surface oxide layer to ensure that the Si(100) surface is pure and free of contamination, and then a mixed cleaning solution containing hydrogen peroxide and ammonia water is used for ultrasonic treatment to further remove organic contaminants and particulate impurities. Thereafter, the substrate surface is rinsed with ultrapure water, blown with nitrogen, and dried in a vacuum oven to achieve an ultralow roughness, thereby providing ideal conditions for the subsequent deposition of the yttrium-doped zirconium oxide film.

[0022] Preferably, the surface activation of the yttrium-doped zirconium oxide substrate comprises the following steps: placing the yttrium-doped zirconium oxide substrate in a plasma cleaning chamber, introducing a mixed gas of argon and oxygen at a volume flow ratio of 1:1, and performing radio frequency plasma treatment at a power density of 0.5-1.0 W / cm 2 , a pressure of 5-10 mTorr, and for 10-15 min.

[0023] The surface activation of the yttrium-doped zirconium oxide substrate effectively removes adsorbed impurities and optimizes the surface energy state, thereby providing a stable substrate environment for the subsequent epitaxial growth of the ITO film layer.

[0024] Preferably, the process parameters of the magnetron sputtering include: using a mixed gas of argon and oxygen as the working gas, wherein the volume flow ratio of oxygen to argon is 20-40:40-60, the total working pressure is 3.0-5.0 mTorr, an ITO target material is used, the content of SnO2 in the ITO target material is 8.5-9.5 wt%, the power density of the target material is 8.5-11.5 W / cm 2 , the substrate bias is -100 to -150 V, the substrate temperature is 255-295°C, the substrate rotation rate is 5-10 rpm, the deposition rate is 3.0-5.0 nm / min, the deposition time is 35-55 min, the plasma density is 1×10 10 -5×10 10 cm -3 , and the film thickness uniformity deviation is ≤±3%.

[0025] In the radio frequency magnetron sputtering process, the microstructure of the ITO film is controlled by precisely controlling the volume flow ratio of argon and oxygen, the total working pressure and the substrate temperature, and the densification of the ITO film is promoted to reduce carrier scattering and improve conductivity. In addition, the adjustment of the substrate bias helps to enhance the adhesion of the ITO film and optimize the nucleation process, so that the ITO film layer maintains high-quality crystal orientation.

[0026] Preferably, the process parameters of the annealing treatment include: continuously passing the mixed gas of hydrogen and nitrogen, the volume flow rate of hydrogen accounts for 3.5-4.5% of the volume flow rate of the mixed gas, the pressure in the annealing furnace is 1-5 Torr, the heating rate is 6-9 ℃ / min, the constant temperature is 420-540 ℃, the constant temperature time is 40-50 min, and the temperature fluctuation during the constant temperature is ≤±2 ℃.

[0027] The present application adopts the annealing treatment in the hydrogen-nitrogen mixed gas atmosphere, and further optimizes the crystallinity of the ITO film, reduces the grain boundary defects, improves the electronic mobility, and improves the optical performance of the film, and reduces the free carrier absorption effect by suitable gas composition ratio and temperature control.

[0028] Preferably, the process parameters of the gradient cooling treatment include: in the first stage, cooling from the annealing temperature to 200-230 ℃ at a rate of 3-4 ℃ / min, in the second stage, cooling to room temperature at a rate of 1-2 ℃ / min, maintaining the nitrogen protective atmosphere and the oxygen content ≤1 ppm throughout the process, and finally obtaining the ITO film with low sheet resistance and high transmittance.

[0029] The present application adopts the gradient cooling process to reduce the accumulation of thermal stress in a staged cooling manner, and inhibits the oxidation and phase change of the film in a nitrogen protective environment, so as to ensure that the final ITO film has excellent conductivity and high transmittance. The synergistic effect of the optimization of the process parameters in each link makes the ITO film further improve the optical uniformity and long-term environmental stability while maintaining low sheet resistance, so as to meet the demand of high-performance optoelectronic devices for high-quality transparent conductive film.

[0030] As a general inventive concept, the present application provides a preparation method of low sheet resistance and high transmittance ITO film, and the low sheet resistance and high transmittance ITO film prepared by the method is located on a yttrium-doped zirconium oxide substrate; the low sheet resistance and high transmittance ITO film is an ITO(400) strong texture; the (400) crystal direction of the ITO(400) strong texture is perpendicular to the surface of the yttrium-doped zirconium oxide substrate; and the ITO(400) strong texture has a columnar crystal morphology, and the average lateral size of the columnar crystal grains is 100-150 nm.

[0031] By growing ITO coating on the yttrium-doped zirconia substrate of the application, high-quality epitaxial growth is realized, the formation of ITO(400) strong texture in the ITO coating makes the grain orientation in the film more uniform, optimizes the microstructure of the film, and improves the carrier mobility, reduces the scattering loss of carriers by grain boundaries, and the introduction of columnar crystal morphology also helps to reduce the scattering of transverse carriers. Therefore, the application adopts yttrium-doped zirconia substrate to cooperate with ITO(400) strong texture epitaxial growth, which effectively enhances the conductivity and light transmittance of the ITO coating.

[0032] Preferably, a coherent interface is formed between the yttrium-doped zirconia substrate and the low sheet resistance and high light transmittance ITO coating.

[0033] The low sheet resistance and high light transmittance ITO coating has a 2-5° small angle grain boundary proportion of 72.0-85.0%, and a twin density of 10 5 ~4.5*10 6 cm-2.

[0034] The application optimizes the grain boundary structure, so that the proportion of 2-5° small angle grain boundaries in the ITO coating reaches a high level, and the twin density is controlled within a certain range to suppress the adverse effects of grain boundary state on electron transport.

[0035] (3) Beneficial technical effects

[0036] The application optimizes the epitaxial growth of the ITO coating by using a yttrium-doped zirconia substrate, and combines with precisely controlled magnetron sputtering, annealing and gradient cooling process, optimizes the microstructure of the film, and improves the carrier mobility and film uniformity and stability, reduces the grain boundary defects and carrier scattering loss in the ITO coating, realizes the synergistic improvement of low sheet resistance and high light transmittance of the ITO coating, and the obtained ITO coating has important application value in the field of high-performance optoelectronic devices and transparent conductive films, thereby promoting the upgrading of industry technology. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The XRD phase analysis diagram of the low sheet resistance and high light transmittance ITO coating prepared in Example 1 of the application.

[0038] Figure 2 The cross-sectional microstructure morphology diagram of the low sheet resistance and high light transmittance ITO coating prepared in Example 1 of the application.

[0039] Figure 3 The interface diagram between ITO(400) and yttrium-doped zirconia substrate in the low sheet resistance and high light transmittance ITO coating prepared in Example 1 of the application.

[0040] Figure 4 The surface roughness diagram of the yttrium-doped zirconia substrate prepared in Example 1 of the application.

[0041] Figure 5 XRD phase analysis diagram of ITO coating prepared for the present application comparative example 1.

[0042] Figure 6 Surface roughness diagram of yttrium-doped zirconium oxide substrate prepared for the present application comparative example 3. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application.

[0044] Embodiment 1:

[0045] A preparation method of a low sheet resistance and high light transmittance ITO coating, comprising the following steps:

[0046] S1, preparing a yttrium-doped zirconium oxide substrate:

[0047] A clean Si(100) substrate with a surface roughness Ra≤0.2 nm is placed in a multi-cathode sputtering deposition system, which includes two direct current sputtering sources and one radio frequency sputtering source. The two direct current sputtering sources and the radio frequency sputtering source are arranged in a confocal manner and form an angle of 55 degrees with the normal line of the substrate. The two direct current sputtering sources are used for reactive sputtering of zirconium targets, and the radio frequency sputtering source is used for reactive sputtering of yttrium targets. A yttrium-doped zirconium oxide substrate is deposited by reactive co-sputtering of two zirconium targets and one yttrium target in an argon-oxygen mixed plasma. The volume flow ratio of argon to oxygen is 1.5:1, the total working pressure is 8 mTorr, the power density of the zirconium target is 12 W / cm 2 , the power density of the yttrium target is 2.0 W / cm 2 , the substrate bias is -300 V, and the substrate temperature is 70℃.

[0048] In the above yttrium-doped zirconium oxide substrate, the (200) crystal direction of the yttrium-doped zirconium oxide is perpendicular to the surface of the yttrium-doped zirconium oxide substrate; the root mean square roughness of the yttrium-doped zirconium oxide substrate is 0.2 nm; and the incorporation amount of yttrium oxide in the yttrium-doped zirconium oxide substrate is 4 at. %.

[0049] The preparation method of the clean Si (100) substrate is as follows: a commercial Si (100) substrate is immersed in a 3.0% by mass fraction hydrofluoric acid solution for 5 min to remove the surface oxide layer, then transferred to a mixed cleaning solution composed of deionized water, 25% by mass fraction hydrogen peroxide and 25% by mass fraction ammonia water in a volume ratio of 5:1:1, ultrasonic treated at 75℃ for 10 min at an ultrasonic frequency of 40 kHz, then washed with ultrapure water for 3 times, then the surface residual liquid is blown off under a nitrogen atmosphere at a flow rate of 10 L / min, and finally dried in a vacuum oven at 120℃ and -0.08 MPa for 30 min, to obtain a clean Si (100) substrate with a surface roughness Ra≤0.2 nm.

[0050] S2, surface activation of the yttrium-doped zirconium oxide substrate:

[0051] The yttrium-doped zirconium oxide substrate is placed in a plasma cleaning chamber, a mixed gas of argon and oxygen in a volume flow ratio of 1:1 is introduced, and radio frequency plasma treatment is carried out at a power density of 0.5 W / cm 2 , a pressure of 5 mTorr for 10 min.

[0052] S3, the surface-activated yttrium-doped zirconium oxide substrate is placed in a radio frequency magnetron sputtering chamber for magnetron sputtering to form an ITO film on the surface of the yttrium-doped zirconium oxide substrate;

[0053] The process parameters of magnetron sputtering include: a mixed gas of argon and oxygen is used as working gas, the volume flow ratio of oxygen to argon is 20:40, the total working pressure is 3.0 mTorr, an ITO target material is used, the content of SnO2 in the ITO target material is 8.5 wt%, the target power density is 8.5 W / cm 2 , the substrate bias is -100 V, the substrate temperature is 255℃, the substrate rotation rate is 5 rpm, the deposition rate is 3.0 nm / min, the deposition time is 35 min, the plasma density is 1×10 10 cm -3 , and the film thickness uniformity deviation is ≤±3%.

[0054] S4, then annealing treatment and gradient cooling treatment are carried out to obtain the low sheet resistance and high light transmittance ITO film.

[0055] The process parameters of the annealing treatment include: continuously introducing a mixed gas of hydrogen and nitrogen, the volume flow ratio of hydrogen to the mixed gas is 3.5%, the total flow rate of the mixed gas is 500 sccm, the furnace pressure is 1 Torr, the heating rate is 6℃ / min, the constant temperature is 420℃, the constant temperature time is 40 min, and the temperature fluctuation during the constant temperature is ≤±2℃.

[0056] The process parameters of the gradient cooling treatment include: the first stage is cooling from the annealing temperature to 200℃ at a rate of 3℃ / min, the second stage is cooling to room temperature at a rate of 1℃ / min, the nitrogen protective atmosphere is maintained throughout the process, and the oxygen content is ≤1ppm, and finally the low sheet resistance and high transmittance ITO coating film is obtained.

[0057] The low sheet resistance and high transmittance ITO coating film of the embodiment is located on a yttrium-doped zirconia substrate; the ITO coating film is ITO(400) strong texture; the (400) direction of the ITO(400) strong texture is perpendicular to the surface of the yttrium-doped zirconia substrate; the ITO(400) strong texture has a columnar crystal morphology, and the average lateral size of the columnar crystal grains is 100nm. A coherent interface is formed between the yttrium-doped zirconia substrate and the low sheet resistance and high transmittance ITO coating film; the proportion of 2° small-angle grain boundaries of the ITO coating film is 72.0%, and the twin density is 4.5×10 5 cm-2.

[0058] Figure 1 The XRD phase analysis results of the low sheet resistance and high transmittance ITO coating film prepared in Example 1 of the application are shown, wherein the existence of Si(100), ITO(400) and YSZ(200) diffraction peaks proves that the crystalline quality of the ITO thin film is good, and the ITO thin film is successfully grown on the preferentially oriented YSZ substrate. Figure 2 The cross-sectional microstructure morphology further proves that the ITO thin film presents obvious columnar crystal structure, which helps to improve its electrical and optical properties, and at the same time, a good coherent interface is formed between the ITO(400) and the yttrium zirconia substrate in Figure 3 , which indicates that the ITO thin film has good lattice matching and epitaxial relationship with the YSZ substrate. Figure 4 The surface roughness measurement results of the yttrium-doped zirconia substrate prepared in Example 1 are shown, and the surface root mean square roughness (RMS) is only 0.2nm, which indicates that the substrate surface is relatively flat, which helps the uniform growth of the ITO thin film.

[0059] Example 2:

[0060] A preparation method of a low sheet resistance and high transmittance ITO coating film, comprising the following steps:

[0061] S1, preparing a yttrium-doped zirconia substrate:

[0062] A clean Si(100) substrate with surface roughness Ra≤0.2 nm is placed in a multi-cathode sputtering deposition system, which includes two direct current sputtering sources and one radio frequency sputtering source, the two direct current sputtering sources and the one radio frequency sputtering source are arranged in a confocal manner and form an angle of 58 degrees with the normal line of the substrate, wherein the two direct current sputtering sources are used for reactive sputtering of zirconium targets, and the radio frequency sputtering source is used for reactive sputtering of a yttrium target, a yttrium-doped zirconia substrate is deposited by reactive co-sputtering of the two zirconium targets and the one yttrium target in an argon-oxygen mixed plasma, wherein the volume flow ratio of argon to oxygen is 1.7:1, the total working pressure is 9 mTorr, the power density of the zirconium target is 13 W / cm 2 , the power density of the yttrium target is 2.2 W / cm 2 , the substrate bias is -360 V, and the substrate temperature is 73℃.

[0063] In the yttrium-doped zirconia substrate, the (200) crystal direction of the yttrium-doped zirconia is perpendicular to the surface of the yttrium-doped zirconia substrate; the root mean square roughness of the yttrium-doped zirconia substrate is 0.3 nm; and the incorporation amount of yttria in the yttrium-doped zirconia substrate is 5 at. %.

[0064] The clean Si(100) substrate is prepared by the following method: a commercial Si(100) substrate is immersed in a 3.6% by mass hydrofluoric acid solution for 7 min to remove the surface oxide layer, then transferred to a mixed cleaning solution composed of deionized water, 26% by mass hydrogen peroxide and 26% by mass ammonia water in a volume ratio of 5:1:1, ultrasonic treated at 78℃ for 13 min at an ultrasonic frequency of 46 kHz, then rinsed with ultrapure water for 4 times, and finally dried in a vacuum oven at 129℃ and -0.09 MPa for 39 min after blowing the surface residual liquid at a flow rate of 12 L / min in a nitrogen atmosphere, to obtain a clean Si(100) substrate with a surface roughness Ra≤0.2 nm.

[0065] S2, surface activation of the yttrium-doped zirconia substrate:

[0066] The yttrium-doped zirconia substrate is placed in a plasma cleaning chamber, and a mixed gas of argon and oxygen with a volume flow ratio of 1:1 is introduced, and radio frequency plasma treatment is carried out at a power density of 0.7 W / cm 2 and a pressure of 7 mTorr for 12 min.

[0067] S3, the surface-activated yttrium-doped zirconia substrate is placed in a radio frequency magnetron sputtering chamber for magnetron sputtering to form an ITO film on the surface of the yttrium-doped zirconia substrate;

[0068] The process parameters of the magnetron sputtering include: using a mixed gas of argon and oxygen as the working gas, wherein the volume flow ratio of oxygen to argon is 26:46, the total working pressure is 3.6 mTorr, the ITO target material is used, the SnO2 doping amount of the ITO target material is 8.8 wt%, the target power density is 9.4 W / cm 2 , the substrate bias is -115 V, the substrate temperature is 267℃, the substrate rotation rate is 7 rpm, the deposition rate is 3.6 nm / min, the deposition time is 41 min, the plasma density is 2.2 x 10 10 cm -3 , and the film thickness uniformity deviation is less than or equal to ±3%.

[0069] S4, then annealing treatment and gradient cooling treatment are performed to obtain the low sheet resistance and high light transmittance ITO coating.

[0070] The process parameters of the annealing treatment include: continuously passing the mixed gas of hydrogen and nitrogen, the volume flow of hydrogen accounts for 3.8% of the total volume flow of the mixed gas, the total flow of the mixed gas is 590 sccm, the furnace pressure is 2 Torr, the heating rate is 7℃ / min, the constant temperature is 456℃, the constant temperature time is 43 min, and the temperature fluctuation during the constant temperature is less than or equal to ±2℃.

[0071] The process parameters of the gradient cooling treatment include: the first stage is cooled from the annealing temperature to 200℃ at a rate of 3.3℃ / min, the second stage is cooled to room temperature at a rate of 1.3℃ / min, the nitrogen protective atmosphere is maintained throughout the process, and the oxygen content is less than or equal to 1 ppm, and finally the low sheet resistance and high light transmittance ITO coating is obtained.

[0072] The low sheet resistance and high light transmittance ITO coating of the embodiment is located on a yttrium-doped zirconia substrate; the ITO coating is an ITO(400) strong texture; the (400) crystal direction of the ITO(400) strong texture is perpendicular to the surface of the yttrium-doped zirconia substrate; the ITO(400) strong texture has a columnar crystal morphology; the average lateral size of the columnar crystal grains is 115 nm; a coherent interface is formed between the yttrium-doped zirconia substrate and the low sheet resistance and high light transmittance ITO coating; the 3° small-angle grain boundary of the ITO coating accounts for 76.0%, and the twin density is 3 x 10 5 cm-2.

[0073] Example 3:

[0074] A preparation method of a low sheet resistance and high light transmittance ITO coating includes the following steps:

[0075] S1, preparing a yttrium-doped zirconia substrate:

[0076] A clean Si(100) substrate with surface roughness Ra≤0.2 nm is placed in a multi-cathode sputtering deposition system, which includes two direct current sputtering sources and one radio frequency sputtering source, the two direct current sputtering sources and the one radio frequency sputtering source are arranged in a confocal manner and form an angle of 61 degrees with the normal line of the substrate, wherein the two direct current sputtering sources are used for reactive sputtering of zirconium targets, and the radio frequency sputtering source is used for reactive sputtering of a yttrium target, a yttrium-doped zirconium oxide substrate is deposited by reactive co-sputtering of the two zirconium targets and the one yttrium target in an argon-oxygen mixed plasma, wherein the volume flow ratio of argon to oxygen is 1.8:1, the total working pressure is 10 mTorr, the power density of the zirconium target is 14 W / cm 2 , the power density of the yttrium target is 2.3 W / cm 2 , the substrate bias is -420 V, and the substrate temperature is 76℃.

[0077] In the yttrium-doped zirconium oxide substrate, the (200) crystal direction of the yttrium-doped zirconium oxide is perpendicular to the surface of the yttrium-doped zirconium oxide substrate; the root mean square roughness of the yttrium-doped zirconium oxide substrate is 0.5 nm; and the incorporation amount of yttrium oxide in the yttrium-doped zirconium oxide substrate is 6.5 at. %.

[0078] The preparation method of the clean Si(100) substrate is as follows: a commercial Si(100) substrate is immersed in a 4.2% by mass fraction hydrofluoric acid solution for 8 min to remove the surface oxide layer, then transferred to a mixed cleaning solution composed of deionized water, 28% by mass fraction hydrogen peroxide and 28% by mass fraction ammonia water in a volume ratio of 5:1:1, ultrasonic treated at 81℃ for 16 min, the ultrasonic frequency is 52 kHz, the substrate is rinsed with ultrapure water for 4 times, then the surface residual liquid is blown off under a nitrogen atmosphere at a flow rate of 13 L / min, and finally dried in a vacuum oven at 138℃ and -0.09 MPa for 48 min, to obtain a clean Si(100) substrate with surface roughness Ra≤0.2 nm.

[0079] S2, surface activation of the yttrium-doped zirconium oxide substrate:

[0080] The yttrium-doped zirconium oxide substrate is placed in a plasma cleaning chamber, a mixed gas of argon and oxygen with a volume flow ratio of 1:1 is introduced, and radio frequency plasma treatment is carried out at a power density of 0.8 W / cm 2 and a pressure of 8 mTorr for 13 min.

[0081] S3, the surface-activated yttrium-doped zirconium oxide substrate is placed in a radio frequency magnetron sputtering chamber for magnetron sputtering to form an ITO film on the surface of the yttrium-doped zirconium oxide substrate;

[0082] The process parameters of the magnetron sputtering include: using a mixed gas of argon and oxygen as the working gas, wherein the volume flow ratio of oxygen to argon is 32:52, the total working pressure is 4.2 mTorr, an ITO target material is used, the SnO2 doping amount of the ITO target material is 9.1 wt%, the target power density is 10.3 W / cm 2 , the substrate bias is -130 V, the temperature is 279℃, the substrate rotation rate is 8 rpm, the deposition rate is 4.2 nm / min, the deposition time is 47 min, the plasma density is 3.4 x 10 10 cm -3 , and the film thickness uniformity deviation is less than or equal to ±3%.

[0083] S4, then annealing treatment and gradient cooling treatment are performed to obtain the low sheet resistance and high light transmittance ITO coating.

[0084] The process parameters of the annealing treatment include: continuously passing the mixed gas of hydrogen and nitrogen, the volume flow of hydrogen accounts for 4.1% of the total volume flow of the mixed gas, the total flow of the mixed gas is 680 sccm, the furnace pressure is 3 Torr, the heating rate is 8℃ / min, the constant temperature is 492℃, the constant temperature time is 46 min, and the temperature fluctuation during the constant temperature is less than or equal to ±2℃.

[0085] The process parameters of the gradient cooling treatment include: the first stage is cooled from the annealing temperature to 200℃ at a rate of 3.6℃ / min, the second stage is cooled to room temperature at a rate of 1.6℃ / min, the nitrogen protective atmosphere is maintained throughout the process, and the oxygen content is less than or equal to 1 ppm, and finally the low sheet resistance and high light transmittance ITO coating is obtained.

[0086] The low sheet resistance and high light transmittance ITO coating of the embodiment is located on a yttrium-doped zirconia substrate; the ITO coating is an ITO(400) strong texture; the (400) crystal direction of the ITO(400) strong texture is perpendicular to the surface of the yttrium-doped zirconia substrate; the ITO(400) strong texture has a columnar crystal morphology; the average lateral size of the columnar crystal grains is 150 nm; a coherent interface is formed between the yttrium-doped zirconia substrate and the low sheet resistance and high light transmittance ITO coating; the proportion of 5° small-angle grain boundaries of the ITO coating is 85.0%, and the twin density is 1 x 10 5 cm-2.

[0087] Example 4:

[0088] A preparation method of a low sheet resistance and high light transmittance ITO coating includes the following steps:

[0089] S1, preparing a yttrium-doped zirconia substrate:

[0090] A clean Si(100) substrate with surface roughness Ra≤0.2 nm is placed in a multi-cathode sputtering deposition system, which includes two direct current sputtering sources and one radio frequency sputtering source, the two direct current sputtering sources and the one radio frequency sputtering source are arranged in a confocal manner and form an angle of 65 degrees with the normal line of the substrate, wherein the two direct current sputtering sources are used for reactive sputtering of zirconium targets, and the radio frequency sputtering source is used for reactive sputtering of a yttrium target, a yttrium-doped zirconium oxide substrate is deposited by reactive co-sputtering of the two zirconium targets and the one yttrium target in an argon-oxygen mixed plasma, wherein the volume flow ratio of argon to oxygen is 2.0:1, the total working pressure is 12 mTorr, the power density of the zirconium target is 15 W / cm 2 , the power density of the yttrium target is 2.5 W / cm 2 , the substrate bias is -500 V, and the substrate temperature is 80℃.

[0091] In the yttrium-doped zirconium oxide substrate, the (200) crystal direction of the yttrium-doped zirconium oxide is perpendicular to the surface of the yttrium-doped zirconium oxide substrate; the root mean square roughness of the yttrium-doped zirconium oxide substrate is 0.4 nm; and the incorporation amount of yttrium oxide in the yttrium-doped zirconium oxide substrate is 8 at.%.

[0092] The preparation method of the clean Si(100) substrate is as follows: a commercial Si(100) substrate is immersed in a 5.0% by mass fraction hydrofluoric acid solution for 10 min to remove the surface oxide layer, then transferred to a mixed cleaning solution composed of deionized water, 30% by mass fraction hydrogen peroxide and 30% by mass fraction ammonia water in a volume ratio of 5:1:1, ultrasonic treated at 85℃ for 20 min, the ultrasonic frequency is 60 kHz, the substrate is rinsed with ultrapure water for 5 times, then the surface residual liquid is blown off under a nitrogen atmosphere at a flow rate of 15 L / min, and finally dried in a vacuum oven at 150℃ and -0.1 MPa for 60 min, to obtain a clean Si(100) substrate with surface roughness Ra≤0.2 nm.

[0093] S2, surface activation of the yttrium-doped zirconium oxide substrate:

[0094] The yttrium-doped zirconium oxide substrate is placed in a plasma cleaning chamber, a mixed gas of argon and oxygen in a volume ratio of 1:1 is introduced, and radio frequency plasma treatment is carried out at a power density of 1.0 W / cm 2 and a pressure of 10 mTorr for 15 min.

[0095] S3, the yttrium-doped zirconium oxide substrate after surface activation is placed in a radio frequency magnetron sputtering chamber for magnetron sputtering to form an ITO film on the surface of the yttrium-doped zirconium oxide substrate;

[0096] The process parameters of the magnetron sputtering include: using a mixed gas of argon and oxygen as the working gas, wherein the volume flow ratio of oxygen to argon is 40:60, the total working pressure is 5.0 mTorr, the SnO2 doping amount of the ITO target material is 9.5 wt%, the target power density is 11.5 W / cm 2 , the substrate bias is -150 V, the substrate temperature is 295℃, the substrate rotation rate is 10 rpm, the deposition rate is 5.0 nm / min, the deposition time is 55 min, the plasma density is 5×10 10 cm -3 , and the film thickness uniformity deviation is ≤±3%.

[0097] S4, then annealing treatment and gradient cooling treatment are performed to obtain the low sheet resistance and high light transmittance ITO coating.

[0098] The process parameters of the annealing treatment include: continuously passing the mixed gas of hydrogen and nitrogen, the volume flow of hydrogen accounts for 4.5% of the total volume flow of the mixed gas, the total flow of the mixed gas is 800 sccm, the furnace pressure is 5 Torr, the heating rate is 9℃ / min, the constant temperature is 540℃, the constant temperature time is 50 min, and the temperature fluctuation during the constant temperature is ≤±2℃.

[0099] The process parameters of the gradient cooling treatment include: cooling from the annealing temperature to 200℃ at a rate of 4℃ / min in the first stage, cooling to room temperature at a rate of 2℃ / min in the second stage, maintaining the nitrogen protective atmosphere and oxygen content ≤1 ppm throughout the process, and finally obtaining the low sheet resistance and high light transmittance ITO coating.

[0100] The low sheet resistance and high light transmittance ITO coating of the embodiment is located on a yttrium-doped zirconia substrate; the ITO coating is an ITO(400) strong texture; the (400) crystal direction of the ITO(400) strong texture is perpendicular to the surface of the yttrium-doped zirconia substrate; the ITO(400) strong texture has a columnar crystal morphology; the average lateral size of the columnar crystal grains is 130 nm; a coherent interface is formed between the yttrium-doped zirconia substrate and the low sheet resistance and high light transmittance ITO coating; the proportion of 4° small-angle grain boundaries of the ITO coating is 80.0%, and the twin density is 2.2×10 6 cm-2.

[0101] Comparative Example 1:

[0102] The same as Example 1, except that a common non-oriented Si substrate is used instead of a commercial Si(100) substrate.

[0103] In comparison, Figure 5The XRD phase analysis diagram of the ITO film of Comparative Example 1 is shown in the figure, and the results show that the ITO and YSZ grown on the general non-oriented Si substrate do not form strong texture, indicating that the orientation of the substrate has an important influence on the crystallization of the ITO film.

[0104] Comparative Example 2:

[0105] The difference between Example 1 and Comparative Example 2 is that the root mean square roughness of the yttrium-doped zirconia substrate is 2.0 nm;

[0106] The preparation method of the yttrium-doped zirconia substrate of the present comparative example is as follows: a clean Si(100) substrate is placed in a multi-cathode sputtering deposition system, the system includes two direct current sputtering sources and one radio frequency sputtering source, the two direct current sputtering sources and the radio frequency sputtering source are arranged in a confocal manner and form an angle of 55 degrees with the normal line of the substrate, wherein the two direct current sputtering sources are used for reactive sputtering of zirconium targets, and the radio frequency sputtering source is used for reactive sputtering of yttrium targets, and the yttrium-doped zirconia substrate is deposited by reactive co-sputtering of two zirconium targets and one yttrium target in an argon-oxygen mixed plasma, wherein the volume flow ratio of argon to oxygen is 1.5:1, the total working pressure is 20 mTorr, the power density of the zirconium target is 12 W / cm 2 , the power density of the yttrium target is 2.0 W / cm 2 , the substrate bias is -100 V, and the substrate temperature is 50℃.

[0107] In addition, Figure 6 The surface roughness measurement results of the yttrium-doped zirconia substrate of Comparative Example 2 show that the roughness reaches 2 nm, which is much higher than that of Example 1, indicating that the surface quality of the substrate is poor, which may affect the uniformity of the ITO film growth and the electrical properties. The above results fully prove that the ITO film with low sheet resistance and high transmittance is successfully prepared by optimizing the substrate orientation, surface quality and deposition process, and is significantly better than the comparative example scheme.

[0108] Comparative Example 3:

[0109] The difference between Example 1 and Comparative Example 3 is that the yttrium-doped zirconia substrate is polycrystalline without obvious preferred orientation, and the preparation method of the yttrium-doped zirconia substrate of the present comparative example is as follows: a clean Si(100) substrate is placed in a multi-cathode sputtering deposition system, the system includes two direct current sputtering sources and one radio frequency sputtering source, the two direct current sputtering sources and the radio frequency sputtering source are arranged in a confocal manner and form an angle of 55 degrees with the normal line of the substrate, wherein the two direct current sputtering sources are used for reactive sputtering of zirconium targets, and the radio frequency sputtering source is used for reactive sputtering of yttrium targets, and the yttrium-doped zirconia substrate is deposited by reactive co-sputtering of two zirconium targets and one yttrium target in an argon-oxygen mixed plasma, wherein the volume flow ratio of argon to oxygen is 3.5:1, the total working pressure is 8 mTorr, the power density of the zirconium target is 12 W / cm 2 , the power density of the yttrium target is 2.0 W / cm2 The substrate bias was -50 V and the substrate temperature was 70 °C.

[0110] Comparative Example 4:

[0111] The process parameters of the magnetron sputtering were substantially the same as in Example 1, except that the surface of the yttrium-doped zirconia substrate was not activated.

[0112] Comparative Example 5:

[0113] The process parameters of the magnetron sputtering were substantially the same as in Example 1, except that the substrate bias was -50 V.

[0114] Comparative Example 6:

[0115] The process parameters of the annealing were substantially the same as in Example 1, except that the constant temperature was 350 °C.

[0116] Comparative Example 7:

[0117] The process parameters of the gradient cooling were substantially the same as in Example 1, except that the first stage was cooled to 200 °C at a rate of 6 °C / min.

[0118] Performance testing:

[0119] Sheet resistance testing: The sheet resistance values at different positions were measured using a four-probe tester (Keithley 2400 series). With a fixed probe spacing, a constant current was applied and the voltage drop was measured, and the sheet resistance was calculated according to the formula Rs = (V / I) x (π / ln2).

[0120] Transmittance testing: Transmittance testing was performed using a UV-Vis spectrophotometer (such as PerkinElmer Lambda950) to measure the transmission spectrum of the ITO film in an air background. To avoid the influence of the yttrium-doped zirconia substrate (YSZ substrate) on the test results, a chemical etching method was used to separate the ITO film. The YSZ substrate was etched using a BOE (HF:NH4F = 1:10) solution to release the ITO, which was then transferred to a quartz substrate; after peeling, the sample was fixed on an optical holder, the light beam was vertically irradiated on the ITO film, and air was used as the background correction. The test range was set to 300-800 nm, and the transmittance data was recorded with a step of 1 nm, focusing on the 550 nm transmittance and the average transmittance from 380 to 780 nm.

[0121] Adhesion testing: Progressive load scratch testing was performed using a scratch tester (such as Anton Paar Revetest), and the critical load at which the film peeled off was recorded.

[0122] The performance data of the ITO films of Examples 1-4 and Comparative Examples 1-7 are summarized in Table 1.

[0123] Table 1 Performance data of ITO coating of Examples 1-4 and Comparative Examples 1-7

[0124]

[0125]

[0126] As shown in Table 1, the ordinary non-oriented Si substrate can cause the ITO crystalline quality to decrease, resulting in an increase in sheet resistance, a decrease in light transmittance, and a decrease in adhesion. The increase in substrate roughness to 2.0 nm can affect the ITO crystalline quality, resulting in an increase in sheet resistance, a decrease in light transmittance, and a decrease in adhesion. The polycrystalline non-preferential YSZ substrate can affect the ITO crystalline quality, resulting in a significant increase in sheet resistance, a decrease in light transmittance, and a decrease in adhesion. The non-activation treatment of the substrate surface can reduce the ITO adhesion, resulting in a significant decrease in adhesion, and affect the ITO crystalline quality, resulting in an increase in sheet resistance. The decrease in substrate bias to -50 V can result in a decrease in ITO particle size, affecting the carrier transport, resulting in a slight increase in sheet resistance, a decrease in light transmittance, and a slight decrease in adhesion. The decrease in annealing temperature to 350℃ can result in incomplete ITO crystallization, affecting the conductivity, resulting in a slight increase in sheet resistance, a decrease in light transmittance, and a decrease in adhesion. The adjustment of the cooling rate to 6℃ / min can cause stress accumulation, affecting the ITO structure, resulting in a slight increase in sheet resistance, a decrease in light transmittance, and a slight decrease in adhesion.

[0127] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it, although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that: any equivalent structural transformation made under the concept of the present application, using the contents of the present application specification and drawings, should be covered within the scope of protection of the claims of the present application.

Claims

1. A method for preparing a low sheet resistance and high transmittance ITO coating, characterized in that, The method comprises the following steps: S1, preparing a yttrium-doped zirconia substrate with a root mean square roughness of 0.2-0.5 nm; In the yttrium-doped zirconia substrate, the (200) crystal direction of the yttrium-doped zirconia is perpendicular to the surface of the yttrium-doped zirconia substrate; and the doping amount of yttria in the yttrium-doped zirconia substrate is 4-8 at.%; S2, activating the surface of the yttrium-doped zirconia substrate; S3, placing the activated yttrium-doped zirconia substrate into a radio frequency magnetron sputtering chamber to perform magnetron sputtering, and forming an ITO film on the surface of the yttrium-doped zirconia substrate; The process parameters of the magnetron sputtering include: using a mixed gas of argon and oxygen as a working gas, wherein the volume flow ratio of oxygen to argon is 20-40:40-60, the total working pressure is 3.0-5.0 mTorr, an ITO target material is used, the content of SnO2 in the ITO target material is 8.5-9.5 wt%, the power density of the target material is 8.5-11.5 W / cm2, the substrate bias is -100 to -150 V, the substrate temperature is 255-295℃, the substrate rotation rate is 5-10 rpm, the deposition rate is 3.0-5.0 nm / min, the deposition time is 35-55 min, the plasma density is 1×101 0 -5×101 0 cm -3 -3%; the film thickness uniformity deviation is ≤±3%. S4, then performing annealing treatment and gradient cooling treatment to obtain the low-resistance high-transmittance ITO film; The process parameters of the annealing treatment include: continuously introducing a mixed gas of hydrogen and nitrogen, the volume fraction of hydrogen in the mixed gas being 3.5-4.5%, the pressure in the annealing furnace being 1-5 Torr, the heating rate being 6-9 ℃ / min, the constant temperature being 420-540 ℃, the constant temperature time being 40-50 min, and the temperature fluctuation during the constant temperature being ≤±2 ℃; The process parameters of the gradient cooling treatment include: cooling from the annealing temperature to 200-230 ℃ at a rate of 3-4 ℃ / min in the first stage, cooling to room temperature at a rate of 1-2 ℃ / min in the second stage, maintaining a nitrogen protective atmosphere and an oxygen content of ≤1 ppm throughout the whole process.

2. The method for preparing ITO coating film with low sheet resistance and high light transmittance according to claim 1, characterized in that, The preparation method of the yttrium-doped zirconia substrate comprises the following steps: A clean Si(100) substrate with a surface roughness Ra≤0.2 nm is placed in a multi-cathode sputtering deposition system, two direct current sputtering sources and one radio frequency sputtering source of the multi-cathode sputtering deposition system are arranged in a confocal manner and form an angle of 55-65 degrees with the substrate normal, the two direct current sputtering sources are used for reactive sputtering of zirconium targets, and the radio frequency sputtering source is used for reactive sputtering of a yttrium target, a yttrium-doped zirconia substrate is deposited in an argon-oxygen mixed plasma by reactive co-sputtering of two zirconium targets and one yttrium target, the volume flow ratio of argon to oxygen is 1.5-2.0:1, the total working pressure is 8-12 mTorr, the power density of the zirconium target is 12-15 W / cm2, the power density of the yttrium target is 2.0-2.5 W / cm2, the substrate bias is -300 to -500 V, and the substrate temperature is 70-80 ℃.

3. The method for preparing ITO coating film with low sheet resistance and high light transmittance according to claim 2, characterized in that, The preparation method of the clean Si(100) substrate comprises the following steps: immersing a Si(100) substrate in a hydrofluoric acid solution with a mass fraction of 3.0-5.0% to remove the surface oxide layer, then transferring the substrate to a mixed cleaning solution composed of deionized water, hydrogen peroxide with a mass fraction of 25-30%, and ammonia water with a mass fraction of 25-30% at a volume ratio of 5:1:1, ultrasonic treating the substrate in the mixed cleaning solution at 75-85 ℃ for 10-20 min, the ultrasonic frequency being 40-60 kHz, rinsing the substrate with ultrapure water, blowing the surface of the substrate to remove residual liquid in a nitrogen atmosphere, and finally drying the substrate in a vacuum oven.

4. The method for preparing ITO coating film with low sheet resistance and high light transmittance according to claim 1, characterized in that, The surface activation of the yttrium-doped zirconia substrate comprises the following steps: placing the yttrium-doped zirconia substrate in a plasma cleaning chamber, introducing a mixed gas of argon and oxygen with a volume flow ratio of 1:1, and performing radio frequency plasma treatment under the conditions of a power density of 0.5-1.0 W / cm2 and a pressure of 5-10 mTorr for 10-15 min.

5. A low sheet resistance and high light transmittance ITO coating prepared by the method according to any one of claims 1-4, wherein the low sheet resistance and high light transmittance ITO coating is located on a yttrium-doped zirconia substrate; the low sheet resistance and high light transmittance ITO coating is an ITO(400) strong texture; the (400) crystal orientation of the ITO(400) strong texture is perpendicular to the surface of the yttrium-doped zirconia substrate; and the ITO(400) strong texture has a columnar crystal morphology, and the average lateral size of the columnar crystal grains is 100-150 nm.

6. The low-resistance and high-transmittance ITO coating according to claim 5, characterized in that: A coherent interface is formed between the yttrium-doped zirconia substrate and the low sheet resistance and high light transmittance ITO coating. The low sheet resistance and high light transmittance ITO coating 2-5° small angle grain boundary proportion is 72.0-85.0%, and the twin crystal density is 10 5 ~4.5*10 6 cm -2 .

Images