Zinc oxide-based target material for magnetron sputtering plating of transparent conductive film and preparation method of zinc oxide-based target material

Abstract

The invention relates to a zinc oxide-based target material for magnetron sputtering plating of a transparent conductive film and a preparation method of the zinc oxide-based target material. The zinc oxide-based target material comprises the following raw materials: ZnO, In2O3, Ga2O3, Sc2O3, a SnO2-WO3 solid solution, and sintering aids Li2CO3 and ZrO2, the preparation method comprises the following steps: weighing the nano powder of the raw materials according to the molar percentage, grinding and mixing by a wet process, granulating, carrying out die forming and isostatic cool pressing, and sintering at high temperature in an oxygen atmosphere to obtain the target material. According to the target material, ZnO serves as a base body, the performance of the target material is optimized through collaborative doping and composite phase design, the optimized target material can be used for preparing a transparent conductive film with the photoelectric property superior to that of ITO through magnetron sputtering, the cost is lower, the stability is better, and the defects that in the prior art, a ZnO-based target material is insufficient in photoelectric property and poor in stability are overcome.

Description

Technical Field

[0001] This invention belongs to the field of transparent conductive thin film materials technology, specifically relating to a method for preparing a zinc oxide-based target for magnetron sputtering of transparent conductive thin films. Background Technology

[0002] Transparent conductive films are widely used in touchscreens, solar cells, flat panel displays, and other fields. Their core performance requirements are high visible light transmittance and low resistivity. Currently, indium tin oxide (ITO) is the most widely used transparent conductive material, but it has significant drawbacks: indium is a scarce element, resulting in high cost and price fluctuations; ITO films have poor chemical stability and are prone to oxidation and failure under high temperature and humidity conditions, leading to a significant increase in resistivity; furthermore, the low utilization rate of indium during ITO target preparation further increases application costs.

[0003] Zinc oxide (ZnO)-based materials are considered ideal alternatives to ITO due to their wide bandgap (3.37 eV), high exciton binding energy (60 meV), abundant raw materials, and environmental friendliness. Existing ZnO-based targets often employ single-element doping with Al or Ga (such as AZO and GZO), but this presents a challenge in balancing carrier concentration and mobility: while single-element doping can increase carrier concentration, it easily leads to increased lattice distortion, enhanced scattering, and decreased carrier mobility, ultimately making it difficult to achieve a film resistivity exceeding 10 Ω·cm. -4 The transmittance is also mostly below 85% (Ω·cm), which cannot meet the performance requirements of high-end fields for ITO alternative materials.

[0004] Therefore, developing a novel ZnO-based target material that combines high transmittance, low resistivity, high stability, and low cost is of great significance for promoting the industrial application of transparent conductive films. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a zinc oxide-based target material and its preparation method for magnetron sputtering of transparent conductive films. The target material uses ZnO as the substrate and optimizes the performance of the target material through synergistic doping and composite phase design. After optimization, the target material can be used to prepare transparent conductive films with photoelectric properties superior to ITO by magnetron sputtering, and the cost is lower and the stability is better.

[0006] The technical solution to the above-mentioned technical problems is: a zinc oxide-based target for magnetron sputtering of transparent conductive thin films, wherein the raw material composition of the target, by molar percentage, includes: ZnO 92.7-94.7 mol%; In2O3 2.0-2.5 mol%; Ga2O3 1.0-1.5 mol%; Sc2O3 0.5-0.8 mol%; SnO2-WO3 solid solution 1.5-2.0 mol%, wherein the molar ratio of SnO2 to WO3 is (2.9-3.1):1; sintering aids: Li2CO3 0.2-0.3 mol% and ZrO2 0.1-0.2 mol%.

[0007] Furthermore, the SnO2-WO3 solid solution is prepared by ball milling SnO2 and WO3 at a molar ratio until uniform, and then calcining at 700-850℃ for 3-8 hours.

[0008] Furthermore, the target material has a relative density of ≥98.5%.

[0009] Furthermore, the target material is used for magnetron sputtering, and the resulting thin film has an average transmittance of ≥88% in the visible light region (400–800 nm) and a resistivity of 5 × 10⁻⁶. -5 ~8×10 -5 Ω·cm, resistivity change rate ≤5% after 1000 h at 85℃ / 85% humidity.

[0010] Another technical solution of the present invention is: the preparation method of the zinc oxide-based target material for magnetron sputtering of transparent conductive thin films is as follows: the above raw material nanopowders are weighed by molar percentage, mixed by wet grinding, granulated, molded, cold isostatically pressed, and then sintered at a high temperature of 1300-1480°C for 4-10 hours in an oxygen atmosphere to obtain the target material.

[0011] Furthermore, the cold isostatic pressure is 200-250 MPa, and the pressure is maintained for 5-10 minutes.

[0012] Furthermore, the purity of ZnO powder is ≥99.99%, and the purity of other powders is ≥99.9%.

[0013] Furthermore, the specific surface area of ​​each raw material powder is 2–20 cm². 2 / g.

[0014] The target material formulation of the present invention has the following synergistic mechanism: Ternary doped system: In 3+ and Ga 3+ As a donor impurity, it can effectively replace Zn. 2+ Sites that provide high carrier concentrations; Sc3+ The ionic radius (0.745 Å) of Zn 2+ (0.74 Å) is close, and doping can suppress lattice distortion, reduce defect scattering, and significantly improve carrier mobility (more than 30% higher than single doping).

[0015] SnO2-WO3 composite phase: SnO2 (band gap 3.6 eV) and WO3 (band gap 2.8 eV) form a solid solution, which constructs a highly efficient conductive channel through interfacial energy level matching, while maintaining the high light transmittance of each phase.

[0016] Sintering aids: Li2CO3 can lower the sintering temperature and promote particle diffusion; ZrO2 can inhibit the excessive growth of ZnO grains, increase the relative density of the target material (≥98.5%), and ensure plasma stability and uniform film composition during magnetron sputtering.

[0017] The target material prepared according to the above formula and method, when used for magnetron sputtering deposition (process parameters: Ar / O2=95:5, substrate temperature 200±10℃, sputtering power 100~150W, vacuum degree 1~3Pa), yields the following thin film properties: 1. Average transmittance in the visible light region (400–800 nm) ≥ 88%; 2. Resistivity as low as 5×10 -5 ~8×10 -5 Ω·cm; When placed in an environment of 3.85℃ / 85% humidity for 1000 h, the resistivity change rate is ≤5%, which is far superior to ITO (change rate ≥15%).

[0018] Compared with the prior art, the present invention has the following significant advantages: 1. Performance breakthrough: Through synergistic regulation of ternary doping and composite phases, the transmittance and resistivity of the thin film are superior to those of ITO, and the stability is significantly improved; 2. Cost advantage: Less In is used, resulting in significantly lower raw material costs compared to ITO; 3. Process feasibility: The target material preparation process is simple, with high relative density, making it suitable for industrial production.

[0019] This invention provides a new solution for ITO alternative materials, which has broad application prospects in fields such as display and energy. Attached Figure Description

[0020] Figure 1 shows the visible light transmittance of Examples 1-3 and Comparative Examples 1-5 of the present invention. As can be seen from the figure, the visible light transmittance of the target coating samples in each embodiment of the present invention is higher than that of the target coating samples in the comparative examples. Detailed Implementation

[0021] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Example 1

[0022] A zinc oxide-based target material has the following raw material molar composition: ZnO 94.7 mol%, In2O3 2.0 mol%, Ga2O3 1.0 mol%, Sc2O3 0.5 mol%, SnO2-WO3 solid solution 1.5 mol% (SnO2:WO3=3:1), Li2CO3 0.2 mol%, and ZrO2 0.1 mol%.

[0023] The method for preparing SnO2-WO3 solid solution is as follows: SnO2 and WO3 are ball-milled and mixed evenly at a molar ratio, and then calcined at 800℃ for 6 hours.

[0024] The above-mentioned raw material nanoparticles were wet-milled and mixed, granulated, then molded and subjected to cold isostatic pressing at 230 MPa for 8 minutes. Finally, they were sintered at 1400℃ for 7 hours in an oxygen atmosphere to obtain the corresponding target material, which has a relative density of 98.5%. The purity of the zinc oxide powder is 99.995%, and the purity of the other powders is 99.95%. The specific surface area of ​​each powder is 12.3 cm². 2 / g.

[0025] Using this target material for magnetron sputtering (Ar / O2=95:5, substrate temperature 200℃, power 120W, vacuum degree 2Pa), the resulting thin film had a visible light transmittance of 89% and a resistivity of 6.2×10⁻⁶. -5 The resistivity change rate after 1000 h at 85℃ / 85% humidity is 3.8% (Ω·cm). Example 2

[0026] A zinc oxide-based target material has the following raw material molar composition: ZnO 92.7 mol%, In2O3 2.5 mol%, Ga2O3 1.5 mol%, Sc2O3 0.8 mol%, SnO2-WO3 solid solution 2.0 mol% (SnO2:WO3=3:1), Li2CO3 0.3 mol%, and ZrO2 0.2 mol%.

[0027] The preparation method was the same as in Example 1, and the resulting target material had a relative density of 99.1%. The visible light transmittance of the magnetron sputtered thin film was 88.5%, and the resistivity was 5.8 × 10⁻⁶. -5The resistivity change rate after high temperature and high humidity stability test (1000h at 85℃ / 85% humidity) was 4.2% Ω·cm. Example 3

[0028] A zinc oxide-based target material has the following raw material molar composition: ZnO 93.9 mol%, In2O3 2.2 mol%, Ga2O3 1.2 mol%, Sc2O3 0.6 mol%, SnO2-WO3 solid solution 1.7 mol% (SnO2:WO3=3:1), Li2CO3 0.25 mol%, and ZrO2 0.15 mol%.

[0029] The preparation method was the same as in Example 1, and the resulting target material had a relative density of 98.8%. The visible light transmittance of the magnetron sputtered thin film was 88.7%, and the resistivity was 6.0 × 10⁻⁶. -5 The resistivity change rate after high temperature and high humidity stability test (1000h at 85℃ / 85% humidity) was 4.2% Ω·cm.

[0030] Comparative Example 1 (Sc2O3 missing) A zinc oxide-based target material has the following raw material molar composition: ZnO 94.36 mol%, In2O3 2.22 mol%, Ga2O3 1.21 mol%, SnO2-WO3 solid solution 1.81 mol% (SnO2:WO3=3:1), Li2CO3 0.25 mol%, and ZrO2 0.15 mol%.

[0031] The preparation method was completely consistent with that of Example 1. The resulting target material had a relative density of 98.4%. The visible light transmittance of the magnetron sputtered thin film was 87%, and the resistivity was 1.5 × 10⁻⁶. -4 The resistivity change rate after 1000 h at 85℃ / 85% humidity is 8.2% (Ω·cm).

[0032] Note: The absence of Sc2O3 prevents the suppression of In. 3+ Ga 3+ Doping leads to lattice distortion, enhanced defect scattering, and decreased carrier mobility, resulting in a significant increase in thin film resistivity and a marked deterioration in stability.

[0033] Comparative Example 2 (Sc2O3 replaced with Y2O3) A zinc oxide-based target material has the following raw material molar composition: ZnO 93.76 mol%, In2O3 2.22 mol%, Ga2O3 1.21 mol%, Y2O3 0.6 mol%, SnO2-WO3 solid solution 1.81 mol% (SnO2:WO3=3:1), Li2CO3 0.25 mol%, and ZrO2 0.15 mol%.

[0034] The preparation method was completely consistent with that of Example 1. The relative density of the obtained target material was 98.4%. The visible light transmittance of the magnetron sputtered film was 86.5%, and the resistivity was 1.8 × 10⁻⁶. -4 The resistivity change rate after 1000 h at 85℃ / 85% humidity is 9.5% (Ω·cm).

[0035] Note: Y in Y2O3 3+ The ionic radius (0.89 Å) of Zn is similar to that of Zn. 2+ The difference of (0.74 Å) is significant. Doping will exacerbate lattice distortion and prevent the synergistic regulation effect of Sc2O3 from being achieved, resulting in a comprehensive deterioration of performance. This proves that the selection of Sc2O3 is unique and cannot be replaced by ordinary rare earth dopants.

[0036] Comparative Example 3 (SnO2-WO3 ratio deviation) A zinc oxide-based target material has the following raw material molar composition: ZnO 93.76 mol%, In2O3 2.22 mol%, Ga2O3 1.21 mol%, Sc2O3 0.6 mol%, SnO2-WO3 solid solution 1.81 mol% (SnO2:WO3=2:1), Li2CO3 0.25 mol%, and ZrO2 0.15 mol%.

[0037] The preparation method was exactly the same as in Example 1. The relative density of the obtained target material was 98.8%. The visible light transmittance of the magnetron sputtered thin film was 87.5%, and the resistivity was 2.1 × 10⁻⁶. -5 The resistivity change rate after 1000 h at 85℃ / 85% humidity is 12.3% (Ω·cm).

[0038] Explanation: When the SnO2-WO3 ratio deviates from 3:1, a stable solid solution structure cannot be formed, and the interfacial energy level with the ZnO matrix is ​​mismatched. The efficient conductive channels are destroyed, resulting in a significant decrease in conductivity and stability. This proves that the 3:1 ratio is the key to realizing the function of the composite phase.

[0039] Comparative Example 4 (Single In Doping)

[0040] A zinc oxide-based target material has the following raw material molar composition: ZnO 94.02 mol%, In2O3 5.58 mol%, Li2CO3 0.25 mol%, ZrO2 0.15 mol%.

[0041] The preparation method was exactly the same as in Example 1. The resulting target material had a relative density of 98.2%. The visible light transmittance of the magnetron sputtered thin film was 85%, and the resistivity was 2.5 × 10⁻⁶. -4The resistivity change rate after 1000 h at 85℃ / 85% humidity is 16.7% Ω·cm.

[0042] Note: In the existing single In doped system, even if the amount of In2O3 is increased to ensure that the total doping amount is consistent with that of the present invention, it is still impossible to balance the carrier concentration and mobility. The performance is far inferior to the ternary doped + composite phase synergistic system of the present invention.

[0043] Comparative Example 5 (Ternary doping exceeds the limit) A zinc oxide-based target material has the following raw material molar composition: ZnO 91.81 mol%, In2O3 2.99 mol%, Ga2O3 2.0 mol%, Sc2O3 1.0 mol%, SnO2-WO3 solid solution 1.8 mol% (SnO2:WO3=3:1), Li2CO3 0.25 mol%, and ZrO2 0.15 mol%.

[0044] The preparation method was completely consistent with that of Example 1. The resulting target material had a relative density of 98.4%. The visible light transmittance of the magnetron sputtered thin film was 84%, and the resistivity was 3.2 × 10⁻⁶. -4 The resistivity change rate after 1000 h at 85℃ / 85% humidity is 21.5% (Ω·cm).

[0045] Note: When the ternary doping amount exceeds the range defined in this invention, lattice defects increase dramatically and the relative density of the target material decreases. This not only leads to the collapse of the thin film's photoelectric properties but also significantly deteriorates its stability, proving that the ratio range defined in this invention is an optimized synergistic window.

Claims

1. A zinc oxide-based target for magnetron sputtering of transparent conductive thin films, characterized in that: The raw material composition of the target material, by molar percentage, includes: ZnO 92.7-94.7 mol%; In2O3 2.0-2.5 mol%; Ga2O3 1.0-1.5 mol%; Sc2O3 0.5-0.8 mol%; SnO2-WO3 solid solution 1.5-2.0 mol%, wherein the molar ratio of SnO2 to WO3 is (2.9-3.1):1; sintering aids: Li2CO3 0.2-0.3 mol% and ZrO2 0.1-0.2 mol%.

2. The zinc oxide-based target for magnetron sputtering of transparent conductive thin films according to claim 1, characterized in that: The method for preparing SnO2-WO3 solid solution is as follows: SnO2 and WO3 are ball-milled and mixed evenly at a molar ratio, and then calcined at a temperature of 700-850℃ for 3-8 hours.

3. The zinc oxide-based target for magnetron sputtering of transparent conductive thin films according to claim 1 or 2, characterized in that: The target material has a relative density of ≥98.5%.

4. The zinc oxide-based target for magnetron sputtering of transparent conductive thin films according to claim 1 or 2, characterized in that: The target material is used for magnetron sputtering, and the resulting thin film has an average transmittance of ≥88% in the visible light region (400–800 nm) and a resistivity of 5 × 10⁻⁶. -5 ~8×10 -5 Ω·cm, resistivity change rate ≤5% after 1000 h at 85℃ / 85% humidity.

5. The method for preparing a zinc oxide-based target for magnetron sputtering of transparent conductive thin films as described in any one of claims 1-4, characterized in that: Weigh the above raw material nanopowders by molar percentage, mix them by wet grinding, granulate them, then mold them, cold isostatically press them, and then sinter them at a high temperature of 1300-1480℃ for 4-10 hours in an oxygen atmosphere to obtain the target material.

6. The method for preparing a zinc oxide-based target for magnetron sputtering of a transparent conductive thin film according to claim 5, characterized in that: Cold isostatic pressing pressure is 200-250 MPa, and pressure is maintained for 5-10 minutes.

7. The method for preparing a zinc oxide-based target for magnetron sputtering of a transparent conductive thin film according to claim 5 or 6, characterized in that: ZnO powder purity ≥ 99.99%, other powder purity ≥ 99.9%.

8. The method for preparing a zinc oxide-based target for magnetron sputtering of a transparent conductive thin film according to claim 5 or 6, characterized in that: The specific surface area of ​​each raw material powder is 2-20 cm². 2 / g.

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