Selective etching solution of aluminum oxide and igzo

Abstract

The application provides a selective etching solution for aluminum oxide and IGZO, which comprises 3-5% of lye, 1-2% of halogen salt, 1-3% of indium gallium zinc salt compound, 0.1-1.0% of anthraquinone compound, 10-20% of alcohol organic solvent, and the rest is deionized water in percentage by mass. The etching solution can ensure that the selectivity ratio of aluminum oxide and IGZO is greater than 1000, and the wafer after etching has good roughness.

Description

[0001] This invention belongs to the field of electronic chemicals, and specifically relates to a selective etching solution of alumina and IGZO. Background Technology

[0002] As process dimensions continue to shrink, the capacitance limitation of 1T1C dynamic random access memory (DRAM) becomes increasingly significant, leading to a miniaturization bottleneck for traditional 1T1C-DRAM. Wide-bandgap oxide semiconductors, such as indium gallium zinc oxide (IGZO), can effectively suppress off-state leakage current and have significant application potential in 3D DRAM, overcoming the miniaturization bottleneck of 1T1C-DRAM. Furthermore, with decreasing process dimensions, traditional silicon dioxide materials are no longer sufficient. Various high-k materials, such as Al2O3, HfO2, and Ta2O5, have been used in the research of 3D DRAM memory cells with good results. By adjusting the equivalent oxide thickness (EOT) to control the threshold voltage (Vt), data retention performance under short gate lengths can be further optimized. Although Al₂O₃'s dielectric constant (8-10) is not the highest among high-κ materials, its large bandgap (8.9 eV), high breakdown field strength (5-10 MV / cm), low oxygen diffusion coefficient, good thermal stability, deep trap energy levels, and significant conduction band difference compared to silicon make it suitable for use as a barrier layer and tunneling layer. However, there is no dedicated selective etchant for Al₂O₃ / IGZO structures. Therefore, developing a selective etchant for Al₂O₃ and IGZO to etch specific Al₂O₃ / IGZO structures would further promote the development of 3D 1T1C DRAM technology.

[0003] The alkaline metal carbonate added to the alkaline etching solution in the JP2014011209A patent is potassium carbonate or sodium carbonate. In the actual etching process, it is easy to cause the residue of monovalent potassium ions and sodium ions, which are difficult to remove. This will directly affect the electrical performance of the device and thus affect the yield.

[0004] The alkaline etching solution described in US patent 20140193945A1, at a specific temperature of 30°C, etches aluminum oxide... The final selection ratio will be less than 200, which cannot meet the customer's etching requirements. Summary of the Invention

[0005] The present invention aims to provide a selective etching solution composition of alumina and IGZO and its application method, which has good etching morphology, high etching precision, and an alumina to IGZO selectivity ratio of over 1000. The etched wafer has good roughness, which can effectively meet customer requirements, while not damaging the electrical properties of the substrate.

[0006] The technical solution of this invention comprises, by mass percentage, 3%-5% alkaline solution, 1%-2% halogen salt, 1%-3% indium gallium zinc salt compound, 0.1%-1.0% anthraquinone compound, 10%-20% alcohol organic solvent, and the remainder being deionized water. The mass percentages refer to the percentage of each component of the etching solution relative to the total mass of the raw materials.

[0007] Furthermore, the alkaline solution may be derived from one or more combinations of ammonium hydroxide, tetramethylammonium hydroxide, and tetraethylammonium hydroxide.

[0008] Furthermore, the concentration of the alkaline solution is 3%-5%, and its main function is to provide the OH- required for the reaction. - Etching is performed on aluminum oxide.

[0009] Furthermore, the halogen salt is one or a combination of several of the following: ammonium bromide, ammonium chloride, and ammonium iodide.

[0010] Furthermore, the indium gallium zinc salt compound can be one or a combination of several soluble indium gallium zinc salt compounds such as indium nitrate, indium sulfate, indium chloride, indium acetate, gallium nitrate, gallium sulfate, gallium chloride, gallium acetate, zinc nitrate, zinc sulfate, zinc chloride, and zinc acetate, with zinc acetate being preferred.

[0011] Furthermore, the addition of indium gallium zinc salt compounds can introduce indium gallium zinc ions, thereby suppressing the etching of IGZO and improving the selectivity.

[0012] Furthermore, the anthraquinone compound may be one or a combination of several of the following: 5-hydroxy-1,4-naphthoquinone, 1,5-aminoanthraquinone, and 9,10-anthraquinone.

[0013] Furthermore, the alcoholic organic solvent can be one or a combination of methanol, ethanol, isopropanol, etc., and isopropanol is preferred considering factors such as stability.

[0014] Furthermore, the alcohol-based organic solvent has the function of cleaning surface residues and particles, as well as improving the surface roughness of the wafer after etching.

[0015] Furthermore, the etching solution is used in a temperature range of 25°C to 35°C, preferably 30°C.

[0016] Furthermore, the etching rate ratio of the etchant to alumina and IGZO is greater than 1000.

[0017] Furthermore, the surface of the wafer etched by this etching solution has a better surface roughness.

[0018] The present invention has the following beneficial effects:

[0019] The addition of halogen salts in this invention promotes the etching rate of alumina, thereby improving the selectivity of the alumina to IGZO ratio. Indium gallium zinc salt compounds reduce the IGZO etching rate, thus improving the selectivity of the alumina to IGZO ratio. Anthraquinone compounds synergistically work with indium gallium zinc salt compounds to reduce the IGZO etching rate, thereby improving the selectivity of the alumina to IGZO ratio. Alcoholic organic solvents effectively clean surface residues and particles, and impart a better surface roughness to the etched wafer. Specific Implementation

[0020] The abbreviations used in the embodiments and thereafter are as follows:

[0021] ALO - Alumina; IGZO - Indium gallium zinc oxide; TEAH - Tetraethylammonium hydroxide; TMAH - Tetramethylammonium hydroxide; HYDRO - 5-hydroxy-1,4-naphthoquinone, AMINO - 1,5-aminoanthraquinone, ANTH - 9,10-anthraquinone; IPA - Isopropanol; DHF - Low concentration hydrofluoric acid; AFM - Atomic force microscope; ER - Etching rate.

[0022] The specific implementation is as follows:

[0023] A selective etching solution for alumina and IGZO, by mass percentage, comprises 3%-5% alkaline solution, 1%-2% halide salt, 1%-3% indium gallium zinc salt compound, 0.1%-1.0% anthraquinone compound, 10%-20% alcohol organic solvent, and the remainder being deionized water. The component ratios of Examples 1-16 and Comparative Examples 1-6 are shown in Table 1.

[0024] A 100mL plastic measuring cup was selected as the reaction vessel. 70mL of etching solution was added to the measuring cup according to the above formula, and a stir bar was added. The water bath temperature was set to 30℃, and the stirring speed to 300r / min. The measuring cup containing the etching solution was placed in the water bath. When the etching solution temperature reached 30℃ and stabilized at 30±0.5℃, the alumina and IGZO sheets were etched.

[0025] Alumina sheets were cut into 1cm x 1cm pieces and held at both ends with tweezers. To avoid the influence of surface residues and particles on the experimental results, the alumina sheets were pretreated before etching. The sheets were immersed in 200:1 DHF for 30 seconds, rinsed thoroughly with water, then immersed in IPA for 20 seconds, rinsed with water, and dried with nitrogen. The pretreated alumina sheets were then immersed in heated etching solution for 1 minute, rinsed thoroughly with water, and dried with nitrogen. The wafer thickness was measured using an ellipsometry before and after etching, and the average value was taken after multiple measurements. The surface roughness of the etched wafer was determined by photographing it with an AFM camera.

[0026] IGZO wafers were cut into 1cm x 1cm pieces and held at both ends of the alumina using tweezers. To avoid the influence of surface residues and particles on the experimental results, the IGZO wafers underwent pretreatment before etching. They were immersed in 200:1 DHF for 30 seconds, rinsed thoroughly with water, then immersed in IPA for 20 seconds, rinsed with water, and dried with nitrogen. The pretreated IGZO wafers were then immersed in heated etching solution for 1 minute, rinsed thoroughly with water, and dried with nitrogen. The wafer thickness was measured using an ellipsometry before and after etching, and multiple measurements were taken, with the average value recorded. The surface roughness of the etched wafer was determined by photographing it using an AFM camera.

[0027] Table 1. Component content of examples and comparative examples

[0028]

[0029]

[0030] Table 2 shows the etching rate, selectivity, and surface roughness of the examples and comparative examples.

[0031]

[0032]

[0033] Note: The surface roughness in the table was measured by an AFM instrument. Excellent indicates that the etched surface is smooth with no residue; Good indicates that the etched surface is smooth with no residue but has slight undulations; Poor indicates that the etched surface is smooth with no residue but has more obvious undulations.

[0034] The experimental results in Table 2 show that the etching solution formulations of all the above embodiments have a significant effect on alumina. The etching rate ratio of the etching solution, alumina, to IGZO is greater than 1000, and it also has good surface roughness.

[0035] By comparing and analyzing the experimental results in Table 2, it can be seen from Examples 1, 4, and 5 that the etching solution has a high selectivity ratio for alumina and IGZO. With increasing NH3·H2O concentration, the etching rates of both alumina and IGZO increase, but their selectivity ratio decreases with increasing alkaline solution concentration.

[0036] As can be seen from the examples and comparative examples, the addition of halogen compounds can significantly increase the etching rate of alumina, thereby improving the selectivity. As can be seen from the examples and comparative examples, the addition of indium, gallium, zinc salts, and anthraquinone compounds has little effect on the etching rate of alumina, which remains essentially unchanged, but it can reduce the etching rate of IGZO, thereby improving the selectivity. Both compounds individually reduce the etching rate of IGZO, but their synergistic effect is more significant.

[0037] As can be seen from Examples 15-17, the type and content of alcohol-based organic solvents have little effect on the etching rate and selectivity.

[0038] Analysis of the comparative examples and embodiments shows that, compared with Embodiment 1, Comparative Example 1, using only 4% ammonia water by mass, cannot inhibit the etching of IGZO and has the disadvantage of poor surface roughness. Compared with Embodiment 1, Comparative Example 6, without the addition of the organic solvent IPA, results in poor surface roughness of the etched wafer, with more uneven surfaces.

[0039] Table 3 shows the etching rate and selectivity at different temperatures for the comparative example.

[0040]

[0041]

[0042] As shown in the comparative examples in Table 3, the selectivity of alumina and IGZO first increases and then decreases with increasing temperature, reaching its maximum of 25.7 at 30℃. Therefore, selecting an appropriate etching temperature will also improve the selectivity of the etching solution.

[0043] In summary, the OH groups generated by the ionization of the alkaline solution in the etching solution - Ions can etch alumina, halide salts can promote alumina etching, and the presence of indium gallium zinc salts and anthraquinones can significantly inhibit the etching rate of IGZO (etching rates of IGZO in Comparative Examples 3-5 and Examples). The presence of IPA significantly improves the surface roughness of the etched wafer, significantly reducing the unevenness without IPA, and the etching solution can achieve a high selectivity at specific operating temperatures. The etching solution, under the above combination, can achieve both high selectivity and good surface roughness.

[0044] Based on the features described above, any changes in proportions and equivalent substitutions or recombinations of raw materials are within the scope of protection of this invention.

[0045] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The embodiments and features described in these embodiments can be arbitrarily combined without conflict. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A selective etching solution for alumina and IGZO, characterized in that: By mass percentage, it includes 3%-5% alkaline solution, 1%-2% halide salts, 1%-3% indium gallium zinc salt compounds, 0.1%-1.0% anthraquinone compounds, 10%-20% alcohol organic solvents, and the remainder is deionized water; The alkaline solution is one or a combination of several of ammonium hydroxide, tetramethylammonium hydroxide, and tetraethylammonium hydroxide; The halogen salt is one or a combination of ammonium bromide, ammonium chloride, and ammonium iodide; The indium gallium zinc salt compound is one or a combination of several of the following: indium nitrate, indium sulfate, indium chloride, indium acetate, gallium nitrate, gallium sulfate, gallium chloride, gallium acetate, zinc nitrate, zinc sulfate, zinc chloride, and zinc acetate. The anthraquinone compounds are one or a combination of several of 5-hydroxy-1,4-naphthoquinone, 1,5-aminoanthraquinone, and 9,10-anthraquinone; The alcoholic organic solvent is one or a combination of methanol, ethanol, and isopropanol.

2. The selective etching solution of alumina and IGZO according to claim 1, characterized in that: The indium gallium zinc salt compound is zinc acetate.

3. The selective etching solution of alumina and IGZO according to claim 1, characterized in that: The alcohol-based organic solvent is isopropanol.

4. The selective etching solution of alumina and IGZO according to claim 1, characterized in that: The etching solution can be used in a temperature range of 25℃-35℃.

5. The selective etching solution of alumina and IGZO according to claim 4, characterized in that: The etching solution is designed for use at a temperature of 30°C.

6. The selective etching solution of alumina and IGZO according to any one of claims 1-5, characterized in that: The etching rate ratio of the etchant to alumina and IGZO is greater than 1000.

7. The selective etching solution of alumina and IGZO according to any one of claims 1-5 is used in etching semiconductor materials containing alumina and IGZO.

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