HfO2 / IGZO high-selection-ratio etching solution as well as preparation method and application thereof

Abstract

The invention provides an HfO2 / IGZO etching solution with a high selection ratio. The HfO2 / IGZO etching solution with the high selection ratio is prepared from 1%-10% of hydrofluoric acid, 10%-50% of organic acid, 0.5%-5% of a chelating agent, 0.01%-0.5% of a cationic surface active agent and the balance water. Wherein the organic acid can effectively reduce the F <-> content in a system and inhibit the etching rate of IGZO, so that the selective etching of the etching solution to HfO2 is improved. The chelating agent and organic acid can serve as a synergistic acid system, and the dissolving capacity of Hf < 4 + > is further improved. The HfO2 / IGZO selection ratio of the high-selection-ratio etching solution disclosed by the invention is higher than or equal to 4.1, and the HfO2 etching rate can reach 11 / s.

Description

Technical Field

[0001] The invention belongs to the technical field of etching solutions, and in particular relates to a HfO2 / IGZO high selectivity etching solution and a preparation method and application thereof. Background Art

[0002] Oxide semiconductor thin film transistors (TFTs) have high mobility, high conductivity and high visible light transmittance, providing a direction for replacing silicon-based or organic TFTs. Due to the abundance of Zn-based minerals and the lower cost compared to In-based materials, Zn oxide materials are more favored by researchers. Currently, ZnO, IGZO, or In-Ga-ZnO-IGZO are used as active channel materials. The corresponding Zn oxide materials require high dielectric constant materials as the corresponding gate dielectrics. Hafnium oxide has a high dielectric constant compared to traditional gate dielectrics SiO2 and SiO x N y The equivalent physical gate oxide layer thickness can significantly reduce gate leakage, and it also has a higher barrier height, which makes its dielectric constant higher and leakage current lower, making it an ideal alternative to SiO2 and SiO x N y As one of the most promising materials for gate dielectrics. In order to achieve a display screen transmittance of more than 85% and to observe light emission from both sides when turned on, transparent electrodes and transparent TFTs with high transmittance are required. Various transparent oxides of such devices require low etching damage and reliable pattern transfer, and the thickness of the channel layer is less than tens of nanometers, which puts higher requirements on the etching process. In addition, traditional wet etching chemistry used for etching oxide semiconductors and dielectric materials can no longer provide the necessary selectivity and etching rate. Therefore, highly selective etching technology for oxide semiconductors and dielectric materials is necessary for the preparation of transparent electrode TFTs. Summary of the invention

[0003] In view of the above technical problems, the present invention provides a HfO2 / IGZO high selectivity etching solution and a preparation method and application thereof. The HfO2 / IGZO high selectivity etching solution has the advantages of high selectivity and fast etching rate.

[0004] In order to achieve the above object, the present invention provides a HfO2 / IGZO high selectivity etching solution, which is composed of hydrofluoric acid, a chelating agent, an organic acid, water or a water-miscible organic solvent and a surfactant, wherein the hydrofluoric acid is 1-10%, the organic acid is 10-50%, the chelating agent is 0.5-5%, the cationic surfactant is 0.01-0.5%, and the balance is water.

[0005] Preferably, the organic acid is one of dioctyl phosphate, di(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301) and bis(2,4,4-trimethylpentyl)phosphonic acid (Cyanex 272).

[0006] More preferably, the chelating agent is one of L-aspartic acid, malic acid and diglycolic acid.

[0007] Further preferably, the cationic surfactant is one of octaalkyltrimethylammonium chloride, dodecyltrimethylammonium chloride and dodecyltrimethylammonium chloride.

[0008] Further preferably, the preparation method of the HfO2 / IGZO high selectivity etching solution is to sequentially add an organic acid, a chelating agent, a cationic surfactant and hydrofluoric acid into water and stir evenly.

[0009] The present invention also provides an application of a HfO2 / IGZO high selectivity etching solution, which is used for etching a silicon wafer containing HfO2 or IGZO; wherein the thickness of HfO2 in the silicon wafer is 100 nm, and the thickness of IGZO is 100 nm.

[0010] Preferably, the method for etching a silicon wafer containing HfO2 or IGZO is as follows: (1) Heat the HfO2 / IGZO high selectivity etching solution in a water bath to 25-50°C; (2) Soaking the HfO2 silicon wafer and the IGZO silicon wafer in a HfO2 / IGZO high selectivity etching solution for 1 minute to obtain an etched silicon wafer; (3) Rinse the etched silicon wafer with ultrapure water, and then use nitrogen to blow away the water stains on the surface of the silicon wafer to complete the etching.

[0011] The selective etching ratio of the HfO2 or IGZO silicon wafer is greater than 2, more preferably greater than 3, and further preferably greater than 4.

[0012] The beneficial effects of the present invention are: 1. The organic acids in the present invention can all be used as Hf 4+ It is a good solvent and has good solubility. At the same time, organic acids will ionize a small amount of H + , which has an inhibitory effect on the ionization of HF and can effectively reduce the F - content, inhibiting the etching rate of IGZO, thereby improving the selective etching of HfO2 by the etching solution.

[0013] 2. The chelating agent selected in the present invention can be used as a synergistic acid system with an organic acid to further increase Hf 4+ The solubility of hafnium is to prevent it from existing as a complex cation in the aqueous solution and adhering to the surface of the HfO2 silicon wafer, thus affecting the etching performance of the etching solution on HfO2. In addition, the chelating agent will still provide some H + , further suppressing the ionization of HF and improving the etching selectivity for HfO2.

[0014] 3. The above cationic surfactant can stably exist in the etching solution, which can reduce the surface tension of the liquid-solid interface, allowing the etching solution to enter the narrow line width of HfO2 or IGZO, and realize etching of transparent electrode TFTs. At the same time, the quaternary ammonium salt cationic surfactant has no metal elements, avoiding the introduction of other metal impurities and ensuring the stability of the chelating agent.

[0015] 4. The HfO2 / IGZO high selectivity etching solution prepared by the present invention has the advantages of high selectivity and fast HfO2 etching rate, and can be widely applied and promoted. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is further explained below in conjunction with specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The protection scope of the present invention shall be subject to the contents recorded in the claims. Any modification or replacement made by a person skilled in the art to the technical solution of the present invention without creative work shall fall within the protection scope of the present invention.

[0017] In the following examples and comparative examples, the concentration of hydrofluoric acid is 49%, L-aspartic acid, malic acid and diglycolic acid are all analytically pure, and the mass percentage of hydrofluoric acid is calculated based on the solute of the corresponding solution, for example, the mass percentage of hydrofluoric acid is calculated based on the mass of the solute HF.

[0018] Example 1 A HfO2 / IGZO high selectivity etching solution E1, which includes, by mass percentage, 1% hydrofluoric acid, 10% Cyanex301, 0.5% L-aspartic acid, 0.01% octaalkyltrimethylammonium chloride and the remainder water, accounting for the total mass percentage of the etching solution.

[0019] Preparation and etching method: (1) Etching solution E1 was prepared according to the formula, Cyanex301, L-aspartic acid, octaalkyltrimethylammonium chloride and hydrofluoric acid were added to water in sequence, and the mixture was stirred evenly to obtain HfO2 / IGZO high selectivity etching solution E1; (2) Use an ellipsometer to measure and record the thickness of HfO2 or IGZO silicon wafer (abbreviated as H1 or I1) before etching.

[0020] (3) The etching solution E1 is heated to 50°C in a water bath, and then the silicon wafer containing HfO2 or IGZO is immersed in the etching solution for 1 min to obtain an etched silicon wafer; (4) Rinse the etched silicon wafer with ultrapure water, and then use nitrogen to blow away the water stains on the surface of the silicon wafer to complete the etching; (5) Use an ellipsometer to measure and record the thickness of HfO2 or IGZO after H1 or I1 etching. The results are shown in Table 1.

[0021] Example 2 A HfO2 / IGZO high selectivity etching solution E2 includes, by mass percentage, 10% hydrofluoric acid, 50% Cyanex301, 5% L-aspartic acid, 0.5% octaalkyltrimethylammonium chloride and the remainder water, accounting for the total mass percentage of the etching solution.

[0022] The preparation and etching methods are the same as those in Example 1, except that the temperature of the HfO2 / IGZO high selectivity etching solution E2 is adjusted to 25°C, and the thickness change of HfO2 or IGZO before and after H2 or I2 etching is recorded.

[0023] Example 3 A HfO2 / IGZO high selectivity etching solution E3 includes, by mass percentage, 5% hydrofluoric acid, 25% Cyanex301, 3% L-aspartic acid, 0.3% octaalkyltrimethylammonium chloride and the remainder water, accounting for the total mass percentage of the etching solution.

[0024] The preparation and etching methods are the same as those in Example 1, except that the temperature of the HfO2 / IGZO high selectivity etching solution E3 is adjusted to 35°C, and the thickness change of HfO2 or IGZO before and after etching is recorded.

[0025] Example 4 A HfO2 / IGZO high selectivity etching solution E4 includes, by mass percentage, 1% hydrofluoric acid, 30% Cyanex301, 1% L-aspartic acid, 0.1% octaalkyltrimethylammonium chloride and the remainder water, accounting for the total mass percentage of the etching solution.

[0026] The preparation and etching methods are the same as those in Example 1, except that the temperature of the HfO2 / IGZO high selectivity etching solution E4 is adjusted to 25°C, and the thickness change of HfO2 or IGZO before and after etching of H4 or I4 is recorded.

[0027] Example 5 A HfO2 / IGZO high selectivity etching solution E5 includes, by mass percentage, 1% hydrofluoric acid, 20% Cyanex301, 1% L-aspartic acid, 0.1% octaalkyltrimethylammonium chloride and the remainder water, accounting for the total mass percentage of the etching solution.

[0028] The preparation and etching methods are the same as those in Example 1, except that the temperature of the HfO2 / IGZO high selectivity etching solution E5 is adjusted to 25°C, and the thickness change of HfO2 or IGZO before and after etching of H5 or I5 is recorded.

[0029] Example 6 A HfO2 / IGZO high selectivity etching solution E6 includes, by mass percentage, 1% hydrofluoric acid, 20% Cyanex272, 1% L-aspartic acid, 0.1% octaalkyltrimethylammonium chloride and the remainder water, accounting for the total mass percentage of the etching solution.

[0030] The preparation and etching methods are the same as those in Example 1, except that the temperature of the HfO2 / IGZO high selectivity etching solution E6 is adjusted to 25°C, and the thickness change of HfO2 or IGZO before and after etching H6 or I6 is recorded.

[0031] Example 7 A HfO2 / IGZO high selectivity etching solution E7 comprises, by mass percentage, 1% hydrofluoric acid, 40% dioctyl phosphate, 1% aspartic acid, 0.1% octaalkyltrimethylammonium chloride and the remainder water, accounting for the total mass percentage of the etching solution.

[0032] The preparation and etching methods are the same as those in Example 1, except that the temperature of the HfO2 / IGZO high selectivity etching solution E7 is adjusted to 25°C, and the thickness change of HfO2 or IGZO before and after etching of H7 or I7 is recorded.

[0033] Example 8 A HfO2 / IGZO high selectivity etching solution E8 comprises, by mass percentage, 3% hydrofluoric acid, 20% Cyanex301, 1% malic acid, 0.1% dodecyltrimethylammonium chloride and the remainder water, accounting for the total mass percentage of the etching solution.

[0034] The preparation and etching methods are the same as those in Example 1, except that the temperature of the HfO2 / IGZO high selectivity etching solution E8 is adjusted to 25°C, and the thickness change of HfO2 or IGZO before and after etching H8 or I8 is recorded.

[0035] Example 9 A HfO2 / IGZO high selectivity etching solution E9 comprises, by mass percentage, 3% hydrofluoric acid, 20% Cyanex301, 1% malic acid, 0.1% dodecyltrimethylammonium chloride and the remainder water, accounting for the total mass percentage of the etching solution.

[0036] The preparation and etching methods are the same as those in Example 1, except that the temperature of the HfO2 / IGZO high selectivity etching solution E9 is adjusted to 25°C, and the thickness change of HfO2 or IGZO before and after etching of H9 or I9 is ​​recorded.

[0037] Example 10 A HfO2 / IGZO high selectivity etching solution E10 comprises, by mass percentage, 3% hydrofluoric acid, 20% Cyanex301, 1% diglycolic acid, 0.2% dodecyltrimethylammonium chloride and the remainder water, accounting for the total mass percentage of the etching solution.

[0038] The preparation and etching methods are the same as those in Example 1, except that the temperature of the HfO2 / IGZO high selectivity etching solution E10 is adjusted to 25°C, and the thickness change of HfO2 or IGZO before and after etching of H10 or I10 is recorded.

[0039] Comparative Example 1 A HfO2 / IGZO high selectivity etching solution E11 has the same formula as Example 4, except that 0.1% of octaalkyltrimethylammonium chloride in the component is replaced by an equal amount of water. The preparation and etching methods are the same as Example 1, and the thickness change of HfO2 or IGZO before and after etching of H11 or I11 is recorded.

[0040] Comparative Example 2 A HfO2 / IGZO high selectivity etching solution E12, the formula of which is the same as that of Example 4, except that 30% of Cyanex301 in the component is replaced by an equal amount of water, the preparation and etching methods are the same as those of Example 1, and the thickness change of HfO2 or IGZO before and after etching of H12 or I12 is recorded.

[0041] Comparative Example 3 A HfO2 / IGZO high selectivity etching solution E13, the formula is the same as that of Example 4, except that 1% L-aspartic acid in the component is replaced by an equal amount of water, the preparation and etching methods are the same as those of Example 1, and the thickness change of HfO2 or IGZO before and after etching of H13 or I13 is recorded.

[0042] Comparative Example 4 A HfO2 / IGZO high selectivity etching solution E14 has the same formula as Example 4, except that 1% L-aspartic acid and 0.1% octaalkyltrimethylammonium chloride in the components are replaced with an equal amount of water. The preparation and etching methods are the same as Example 1, and the thickness change of HfO2 or IGZO before and after etching of H14 or I14 is recorded.

[0043] Comparative Example 5 A HfO2 / IGZO high selectivity etching solution E15 has the same formula as Example 4, except that 1% L-aspartic acid and 30% Cyanex301 in the components are replaced by an equal amount of water. The preparation and etching methods are the same as Example 1, and the thickness change of HfO2 or IGZO before and after etching of H15 or I15 is recorded.

[0044] Comparative Example 6 A HfO2 / IGZO high selectivity etching solution E16 has the same formula as Example 4, except that 1% L-aspartic acid and 0.1% octaalkyltrimethylammonium chloride in the components are replaced with an equal amount of water. The preparation and etching methods are the same as Example 1, and the thickness change of HfO2 or IGZO before and after etching of H16 or I16 is recorded.

[0045] Comparative Example 7 A HfO2 / IGZO high selectivity etching solution E17, the formula is the same as that in Example 4, except that 30% Cyanex301 in the component is replaced by 30% ethylenediaminetetramethylenephosphonic acid, the preparation and etching methods are the same as in Example 1, and the thickness change of HfO2 or IGZO before and after etching of H17 or I17 is recorded.

[0046] Comparative Example 8 A HfO2 / IGZO high selectivity etching solution E18, the formula is the same as that of Example 4, except that 30% of Cyanex301 in the component is replaced with aminodimethylenephosphoric acid, the preparation and etching methods are the same as those of Example 1, and the thickness change of HfO2 or IGZO before and after etching of H18 or I18 is recorded.

[0047] Comparative Example 9 A HfO2 / IGZO high selectivity etching solution E19, the formula is the same as that in Example 4, except that the Cyanex301 in the component is changed from 30% to 60%, the preparation and etching methods are the same as in Example 1, and the thickness change of HfO2 or IGZO before and after etching of H19 or I19 is recorded.

[0048] Comparative Example 10 A HfO2 / IGZO high selectivity etching solution E19, the formula is the same as that of Example 4, except that Cyanex301 in the component is changed from 30% to 1%, the preparation and etching methods are the same as those of Example 1, and the thickness change of HfO2 or IGZO before and after etching with H20 or I20 is recorded.

[0049] Comparative Example 11 A HfO2 / IGZO high selectivity etching solution E21, with the same formula as Example 4, and the same preparation and etching methods as Example 1, wherein the etching solution temperature is changed to 20°C, and the thickness change of HfO2 or IGZO before and after etching with H21 or I21 is recorded.

[0050] Comparative Example 12 A HfO2 / IGZO high selectivity etching solution E22, with the same formula as Example 4, and the same preparation and etching methods as Example 1, wherein the etching solution temperature is changed to 55°C, and the thickness change of HfO2 or IGZO before and after H22 or I22 etching is recorded.

[0051] Table 1 Performance of HfO2 / IGZO high selectivity etching solution

[0052] The results show that the HfO2 / IGZO selectivity ratios of Examples 1 to 10 are all over 2, among which the selectivity ratio of Example 4 is the highest at 4.1, and the HfO2 etching rate in Example 2 is the fastest, exceeding 11Å / s. This is because after the hydrofluoric acid content increases, the fluoride ion content in the etching solution reaches the maximum. In Examples 1-5, the combination of Cyanex301 and L-aspartic acid with different contents can achieve a selectivity ratio of more than 3.5, and the selective etching of HfO2 is good. The content and different combinations of organic acids, chelating agents, and cationic surfactants in the etching solution will have a significant effect on the etching rate of HfO2 or IGZO, and thus affect the HfO2 / IGZO selectivity ratio. In Examples 6 and 7, the type of organic acid was changed, and the HfO2 / IGZO selectivity ratio decreased. In Example 6, the IGZO etching rate increased, resulting in a decrease in the selectivity, which may be due to the good solubility of Cyanex272 in the metal ions produced by the dissolved IGZO; in Example 7, the HfO2 etching rate decreased, which may be due to the effect of dioctyl phosphate on Hf 4+ The solubility of Hf is relatively poor. In Examples 8-9, the combination of organic acid and chelating agent is different, and the etching solution has a relatively poor solubility in Hf 4+ The solubility of hafnium is different, which reduces the complex cations adhering to the surface of HfO2 silicon wafer and improves the etching performance of HfO2. In Example 10, the type of cationic surfactant is changed. As the hydrophobic carbon chain increases, the surfactant molecules are easy to bend, which is not conducive to vertical close arrangement, resulting in an increase in the area occupied by a single molecule, affecting the saturated adsorption amount, and then causing the HfO2 etching rate and HfO2 / IGZO selectivity to decrease.

[0053] In Comparative Examples 1 to 6, the lack of any one or two of the cationic surfactant, organic acid, and chelating agent will lead to a decrease in the HfO2 etching rate. At the same time, the IGZO etching rate is greatly increased after the hydrofluoric acid ionization increases, resulting in a HfO2 / IGZO selectivity ratio of less than 0.7. In Comparative Examples 7 to 8, an organic acid other than that claimed is used, which has a significant effect on the HfO2 / IGZO selectivity ratio. 4+ The solubility of HfO2 is reduced, and the selectivity and HfO2 etching rate are reduced. The amount of organic acid used in Examples 9-10 is not within the range, resulting in a significantly lower HfO2 / IGZO selectivity. In Examples 11-12, the IGZO etching rate is more sensitive to temperature changes than HfO2, resulting in a more obvious change in the IGZO etching rate.

Claims

1. A HfO2 / IGZO high selectivity etching solution, characterized in that: The high selectivity etching solution is composed of 1-10% hydrofluoric acid, 10-50% organic acid, 0.5-5% chelating agent, 0.01-0.5% cationic surfactant, and the balance is water.

2. A HfO2 / IGZO high selectivity etching solution according to claim 1, characterized in that: The organic acid is any one of dioctyl phosphate, di(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301) and bis(2,4,4-trimethylpentyl)phosphonic acid (Cyanex 272).

3. The HfO2 / IGZO high selectivity etching solution according to claim 1, characterized in that: The chelating agent is any one of L-aspartic acid, malic acid and diglycolic acid.

4. The HfO2 / IGZO high selectivity etching solution according to claim 1, characterized in that: The cationic surfactant is one of octaalkyltrimethylammonium chloride, dodecyltrimethylammonium chloride and dodecyltrimethylammonium chloride.

5. A method for preparing a HfO2 / IGZO high selectivity etching solution as claimed in any one of claims 1 to 4, characterized in that: The preparation process is to add organic acid, chelating agent, cationic surfactant and hydrofluoric acid into water in sequence and stir evenly to obtain the product.

6. An application of the HfO2 / IGZO high selectivity etching solution as claimed in any one of claims 1 to 4, characterized in that: The application is the selective etching of silicon wafers containing HfO2 or IGZO.

7. The use according to claim 6, characterized in that: The method for etching a silicon wafer containing HfO2 or IGZO is as follows: (1) Heat the HfO2 / IGZO high selectivity etching solution in a water bath to 25-50°C; (2) Soaking the HfO2 silicon wafer and the IGZO silicon wafer in a HfO2 / IGZO high selectivity etching solution for 1 minute to obtain an etched silicon wafer; (3) Rinse the etched silicon wafer with ultrapure water, and then use nitrogen to blow away the water stains on the surface of the silicon wafer to complete the etching.

8. The use according to claim 7, characterized in that: The selective etching ratio of the HfO2 or IGZO silicon wafer is greater than 2, more preferably greater than 3, and further preferably greater than 4.

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