Molybdenum indium zinc oxide selective etching solution

Abstract

The invention provides a selective etching solution for metal molybdenum, which comprises the following components in percentage by mass: 21%-34% of electronic-grade phosphoric acid, 43%-58% of electronic-grade acetic acid, 0.05%-0.075% of ammonium persulfate, 2.8%-3.5% of electronic-grade nitric acid, 0.5%-3.0% of indium zinc oxide (IZO) etching inhibitor and the balance of deionized water. According to the etching solution, on the premise that the indium zinc oxide (IZO) etching rate is smaller than or equal to 0.03 nm / min, a metal molybdenum deposition layer can be rapidly removed, residues of metal molybdenum and oxides of the metal molybdenum are not generated, and etching of the metal molybdenum and the indium zinc oxide (IZO) has a high selection ratio.

Description

Technical Field

[0001] This invention belongs to the field of electronic chemicals, and specifically relates to a selective etching solution for molybdenum and zinc indium oxide. Background Technology

[0002] As semiconductor and display technologies advance towards higher integration and precision, the demand for selective etching of metals in wet etching processes is becoming increasingly prominent. Molybdenum, with its low resistivity, excellent thermal stability, and anti-electromigration properties, has become a preferred material for constructing electrical signal paths. Indium zinc oxide (IZO), as a fourth-generation semiconductor material, excels in channel layer fabrication due to its high electron mobility. In advanced process technologies, with the continuous increase in the number of 3D NAND stacked layers and the continuous narrowing of logic chip linewidths, the drawbacks of tungsten, the traditional main material, are becoming increasingly apparent at the nanoscale—high resistivity causes signal delay, and deposition uniformity and reliability are insufficient to meet the requirements of next-generation chips. In contrast, molybdenum has a resistivity more than 30% lower than tungsten and requires no additional barrier layer. This significantly improves signal transmission efficiency, simplifies the process flow, and reduces defect rates, demonstrating strong scalability in multi-layer stacking and fine interconnection of 3D NAND, DRAM, and logic chips.

[0003] However, current wet etching processes still face numerous technical bottlenecks when processing multilayer structures such as molybdenum and indium zinc oxide (IZO) stacks. Molybdenum is chemically stable and has an extremely high melting point, making it difficult to achieve efficient and precise etching with conventional etching solutions. This often results in slow etching rates, increased surface roughness, and uneven etching, severely limiting subsequent processes and device performance. IZO etching, on the other hand, is limited by the low selectivity of existing etching solutions, easily leading to excessive material loss, significantly increasing defect rates, and reducing device yield. Achieving efficient, precise, and highly selective etching of molybdenum and IZO in complex structures has become a critical challenge that the industry urgently needs to overcome.

[0004] Indium zinc oxide (IZO) etching inhibitor and ammonium persulfate were added to the phosphoric acid, acetic acid, and nitric acid system to reduce the etching rate of IZO while accelerating the etching rate of molybdenum metal, so as to achieve a high selectivity etching ratio between molybdenum metal and indium zinc oxide (IZO). Summary of the Invention

[0005] The technical solution of the present invention is a selective etching solution for indium zinc oxide (IZO) of molybdenum, which can rapidly remove the molybdenum deposited layer while ensuring that the etching rate of indium zinc oxide (IZO) is ≤0.03nm / min, without producing any residue of molybdenum and its oxides. The etching of molybdenum and indium zinc oxide (IZO) has a high selectivity ratio.

[0006] The technical solution of the present invention comprises, by mass percentage, 21%-34% electronic grade phosphoric acid, 43%-58% electronic grade acetic acid, 0.05%-0.075% ammonium persulfate, 2.8%-3.5% electronic grade nitric acid, 0.5%-3.0% indium zinc oxide (IZO) etching inhibitor, with the remainder being deionized water.

[0007] Furthermore, the phosphoric acid is electronic grade, with a raw material concentration ≥84.5% and a metal ion content ≤0.05ppb; the acetic acid is electronic grade, with a raw material concentration ≥99.85% and a metal ion content ≤0.05ppb; the nitric acid is electronic grade, with a raw material concentration ≥71% and a metal ion content ≤0.05ppb; and the ammonium persulfate raw material purity is ≥99.99%.

[0008] Further, the indium zinc oxide (IZO) etching inhibitor comprises one or more of the following: 4,6-dichloro-3-methyl-1H-pyrazolo[3,4-d]pyrimidine, 2-(4-fluoro-1H-pyrazol-1-yl)pyrimidine-5-carboxylic acid, 5-oxo-4,5-dihydropyrazolo[1,5-a]pyrimidine-3-carboxylonitrile, 6,7-dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylic acid, 5-chloro-[1,2,4]triazolo[1,5-a]pyrimidine, 5-chloromethyl-2,4-dihydro[1,2,4]triazol-3-one, and 1H-1,2,4-triazol-1-acetic acid.

[0009] Furthermore, ammonium persulfate can regulate the etching rate of metallic molybdenum and improve the surface roughness of metallic molybdenum after etching.

[0010] Another technical solution of the present invention is a method for etching molybdenum indium zinc oxide (IGNOW) using the aforementioned selective etching solution. The etching solution is prepared according to the formula of the aforementioned IGNOW selective etching solution, and the IGNOW is immersed in the etching solution for etching. During the etching process, equivalent experiments are performed using IGNOW thin films and molybdenum thin films.

[0011] The preferred operating temperature range for the etching solution is 0℃-35℃, more preferably 5℃-17℃, and most preferably 12℃.

[0012] Another technical solution of the present invention is the application of the molybdenum indium zinc oxide selective etching solution in etching semiconductor materials containing molybdenum indium zinc oxide.

[0013] The etching rate of indium zinc oxide is ≤0.03nm / min, and no residue of metallic molybdenum and its oxide is produced after etching. The selectivity ratio of metallic molybdenum to indium zinc oxide is greater than 3000, more preferably greater than 4000, and even more preferably greater than 5000.

[0014] The present invention has the following beneficial effects: The etching solution of this invention has excellent selectivity for etching metallic molybdenum.

[0015] In this invention, ammonium persulfate, with its strong oxidizing properties, facilitates the oxidation of metallic molybdenum into a high-valence, highly dense metal oxide. This process effectively reduces the degree of anisotropic etching, thereby significantly improving the surface roughness of metallic molybdenum after etching.

[0016] The present invention incorporates an indium zinc oxide (IZO) etching inhibitor that can form a stable chelate compound with indium zinc oxide (IZO), forming a protective layer on the surface of indium zinc oxide (IZO), slowing down the etching rate of indium zinc oxide (IZO), and making the etching rate of indium zinc oxide (IZO) ≤0.03nm / min. Detailed Implementation

[0017] The following will describe in detail the implementation process of this invention. The implementation process is only used to deepen the understanding of the invention and does not limit the scope of the invention.

[0018] Example 1 A molybdenum etching solution has the following formulation: 57% electronic-grade acetic acid (99.89% by mass), 32% electronic-grade phosphoric acid (84.5% by mass), 3.3% electronic-grade nitric acid (71% by mass), 0.072% ammonium persulfate, 2.8% 4,6-dichloro-3-methyl-1H-pyrazolo[3,4-d]pyrimidine, with the remainder being deionized water.

[0019] Example 2 A molybdenum etching solution has the following formulation: 57% electronic-grade acetic acid (99.89% by mass), 32% electronic-grade phosphoric acid (84.5% by mass), 3.3% electronic-grade nitric acid (71% by mass), 0.072% ammonium persulfate, 2.8% 2-(4-fluoro-1H-pyrazol-1-yl)pyrimidine-5-carboxylic acid, with the remainder being deionized water.

[0020] Example 3 A molybdenum etching solution has the following formulation: 57% electronic-grade acetic acid (99.89% by mass), 32% electronic-grade phosphoric acid (84.5% by mass), 3.3% electronic-grade nitric acid (71% by mass), 0.072% ammonium persulfate, 2.8% 5-oxo-4,5-dihydropyrazolo[1,5-a]pyrimidine-3-carboxynitrile, with the remainder being deionized water.

[0021] Example 4 A molybdenum etching solution has the following formulation: 57% electronic-grade acetic acid (99.89% by mass), 32% electronic-grade phosphoric acid (84.5% by mass), 3.3% electronic-grade nitric acid (71% by mass), 0.072% ammonium persulfate, 2.8% 6,7-dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylic acid, with the remainder being deionized water.

[0022] Example 5 A molybdenum etching solution has the following formulation: 57% electronic-grade acetic acid (99.89% by mass), 32% electronic-grade phosphoric acid (84.5% by mass), 3.3% electronic-grade nitric acid (71% by mass), 0.072% ammonium persulfate, 2.8% 5-chloro-[1,2,4]triazolo[1,5-a]pyrimidine, with the remainder being deionized water.

[0023] Example 6 A molybdenum etching solution has the following formulation: 57% electronic-grade acetic acid (99.89% by mass), 32% electronic-grade phosphoric acid (84.5% by mass), 3.3% electronic-grade nitric acid (71% by mass), 0.072% ammonium persulfate, 2.8% 5-chloromethyl-2,4-dihydro[1,2,4]triazol-3-one, with the remainder being deionized water.

[0024] Example 7 A molybdenum etching solution has the following formulation: 57% electronic-grade acetic acid (99.89% by mass), 32% electronic-grade phosphoric acid (84.5% by mass), 3.3% electronic-grade nitric acid (71% by mass), 0.072% ammonium persulfate, 2.8% 1H-1,2,4-triazole-1-acetic acid, and the remainder being deionized water.

[0025] Comparative Example 1 A molybdenum etching solution, with the same formulation as in Example 2, except that electronic-grade acetic acid is not added.

[0026] Comparative Example 2 A molybdenum etching solution, with the same formulation as in Example 2, except that electronic-grade phosphoric acid is not added.

[0027] Comparative Example 3 A molybdenum etching solution, with the same formulation as in Example 2, except that electronic-grade nitric acid is not added.

[0028] Comparative Example 4 A molybdenum etching solution, with the same formulation as in Example 2, except that ammonium persulfate is not added.

[0029] Comparative Example 5 A molybdenum etching solution with the same formulation as in Example 2, except that 2-(4-fluoro-1H-pyrazol-1-yl)pyrimidine-5-carboxylic acid is not added.

[0030] Comparative Example 6 A molybdenum etching solution, with the same formulation as in Example 2, but unlike Example 6, does not contain electronic-grade nitric acid and ammonium persulfate.

[0031] The etching method and result testing are as follows: 100g of etching solution was prepared using a 250ml beaker equipped with a stirrer according to the above formula. After preparation, the solution was placed in a low-temperature constant temperature device for temperature control. The stirring speed was 400 rpm / min, and the temperature was set at 12℃. When the solution temperature stabilized at 12±0.1℃, the corresponding structural sheet was etched. Before etching, a thin sheet with deposited molybdenum (1000nm thickness) was cut into 2*2cm pieces and etched using an immersion etching method, with the etching time recorded. After etching, the thin sheet was cleaned with deionized water and dried with nitrogen gas, and the thickness was measured using a four-point probe. Indium zinc oxide (IZO) thin sheets were etched in the same manner, and the thickness of the test pieces was measured using an ellipsometry. The etching rates of molybdenum and indium zinc oxide (IZO) were calculated based on the thickness difference before and after etching and the etching time, thereby calculating the corresponding selectivity ratio. In addition, the etching effect of the etching solution was verified by scanning electron microscopy and atomic force microscopy, and the presence of residues and increased roughness on the metal surface after etching were observed. This invention regulates the etching rate of molybdenum and indium zinc oxide (IZO) by adjusting the proportions of each component in the etching solution. The experimental results of the examples and comparative examples are shown in the table below: Table 1:

[0032] The etching solutions prepared in Examples 1-7 exhibited different etching rates for molybdenum and indium zinc oxide (IZO) due to differences in their components. The molybdenum deposit was rapidly removed without leaving any residue of molybdenum or its oxides. The selectivity of molybdenum for IZO reached a maximum of 5769.4.

[0033] Compared with the etching solution prepared in Comparative Example 1, the etching effect of the etching solution prepared in Example 2 shows that the presence of acetic acid has a certain inhibitory effect on both metallic molybdenum and indium zinc oxide (IZO). The inhibitory effect on indium zinc oxide (IZO) is stronger, while the inhibitory effect on metallic molybdenum is not obvious. However, acetic acid reduces the residue after etching metallic molybdenum to a certain extent.

[0034] Compared with the etching solution prepared in Comparative Example 2, the etching effect of the etching solution prepared in Example 2 shows that the presence of phosphoric acid in both cases helps dissolve molybdenum and indium zinc oxide (IZO) during the etching process and increases the etching rate. However, the oxide of molybdenum is more soluble in phosphoric acid and is more sensitive to the phosphoric acid content. A lack of phosphoric acid can easily lead to the residue of molybdenum and its oxide.

[0035] Compared to the etching solutions prepared in Comparative Examples 3, 4, and 6, the etching solution prepared in Example 2 exhibits superior etching performance. Nitric acid and ammonium persulfate are essential for the etching solution; without an oxidizing agent, etching of metallic molybdenum is difficult. Nitric acid primarily acts as an oxidant, oxidizing metallic molybdenum into molybdenum oxide, which is more readily dissolved by the components in the etching solution. However, this process inevitably produces intermediate-valence molybdenum compounds. Ammonium persulfate, with its stronger oxidizing properties, prevents the formation of intermediate-valence molybdenum compounds. Lower-valence molybdenum compounds are oxidized into denser higher-valence oxides, thereby reducing anisotropic etching and minimizing the residue of metallic molybdenum and its oxides.

[0036] Compared with the etching solution prepared in Comparative Example 5, the etching solution prepared in Example 2 showed better etching inhibition of indium zinc oxide (IZO), significantly reducing its etching rate. The indium zinc oxide (IZO) etching inhibitor can form stable chelate compounds with indium zinc oxide (IZO), forming a protective layer on the surface of indium zinc oxide (IZO), slowing down the etching rate and achieving an etching rate ≤0.03 nm / min. This results in a selectivity of molybdenum for indium zinc oxide (IZO) as high as 5769.4.

[0037] Obviously, the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, there are numerous variations or combinations of the above embodiments, and the present invention cannot list all embodiments. Therefore, any changes or modifications made based on the above embodiments are still within the protection scope of the present invention.

Claims

1. A selective etching solution for molybdenum indium zinc oxide, characterized in that, By mass percentage, it includes 21%-34% electronic-grade phosphoric acid, 43%-58% electronic-grade acetic acid, 0.05%-0.075% ammonium persulfate, 2.8%-3.5% electronic-grade nitric acid, 0.5%-3.0% zinc indium oxide etching inhibitor, and the remainder is deionized water.

2. The selective etching solution for indium zinc oxide of molybdenum according to claim 1, characterized in that, Phosphoric acid is electronic grade, with a raw material concentration of ≥84.5% and a metal ion content of ≤0.05ppb.

3. The selective etching solution for indium zinc oxide of molybdenum according to claim 1, characterized in that, Acetic acid is electronic grade, with a raw material concentration of ≥99.85% and a metal ion content of ≤0.05ppb.

4. The selective etching solution for indium zinc oxide of molybdenum according to claim 1, characterized in that, Nitric acid is electronic grade, with a raw material concentration of ≥71% and a metal ion content of ≤0.05ppb.

5. The selective etching solution for indium zinc oxide of molybdenum according to claim 1, characterized in that, The purity of ammonium persulfate raw material is ≥99.99%.

6. The selective etching solution for indium zinc oxide of molybdenum according to claim 1, characterized in that, The zinc indium oxide etching inhibitor comprises at least one of 4,6-dichloro-3-methyl-1H-pyrazolo[3,4-d]pyrimidine, 2-(4-fluoro-1H-pyrazol-1-yl)pyrimidine-5-carboxylic acid, 5-oxo-4,5-dihydropyrazolo[1,5-a]pyrimidine-3-carboxylonitrile, 6,7-dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylic acid, 5-chloro-[1,2,4]triazolo[1,5-a]pyrimidine, 5-chloromethyl-2,4-dihydro[1,2,4]triazol-3-one, and 1H-1,2,4-triazol-1-acetic acid.

7. The method for etching indium molybdenum oxide (IMO) with a selective etching solution according to any one of claims 1-6, characterized in that, The etching solution is prepared using the formulation of the selective etching solution for molybdenum indium zinc oxide as described in any one of claims 1-6. The molybdenum indium zinc oxide is then immersed in the etching solution for etching.

8. The method for etching indium molybdenum oxide (IMO) with a selective etching solution according to claim 7, characterized in that, The preferred operating temperature range for the etching solution is 0℃-35℃, more preferably 5℃-17℃, and most preferably 12℃.

9. The selective etching solution of indium zinc molybdenum oxide according to any one of claims 1-6 is used in etching semiconductor materials containing indium zinc molybdenum oxide.

10. The application according to claim 9, characterized in that, The etching rate of indium zinc oxide is ≤0.03nm / min, and no residue of metallic molybdenum and its oxides is produced after etching. The selectivity ratio of metallic molybdenum to indium zinc oxide is greater than 3000.

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