Selective etching solution for molybdenum

Abstract

The invention provides a selective etching solution for metal molybdenum, which comprises the following components in percentage by mass: 51%-69% of electronic-grade phosphoric acid, 13%-28% of electronic-grade acetic acid, 2.2%-3.8% of electronic-grade nitric acid, 0.04%-0.065% of periodic acid, 0.03%-0.09% of an organic amine additive, 0.2%-3.5% of a hafnium oxide etching inhibitor and the balance of deionized water. The etching liquid can effectively etch a metal molybdenum deposition layer on the premise that the hafnium oxide etching rate (ER) is smaller than or equal to 0.05 nm / min, no residues exist on the surface of the metal molybdenum after etching, and the metal molybdenum and the hafnium oxide have the high selection ratio.

Description

Technical Field

[0001] The invention belongs to the field of electronic chemicals, and in particular relates to a selective etching solution for metal molybdenum and hafnium oxide. Background Art

[0002] With the rapid progress of emerging technologies such as big data, cloud computing, the Internet of Things and artificial intelligence, as well as the continuous iteration and upgrading of consumer electronic products, the demand for storage capacity of various devices faces unprecedented challenges. 3D NAND flash memory technology, as one of the most widely used storage solutions, provides larger storage capacity and better working performance in a limited physical space by realizing vertical stacking of storage cells. A direct and effective strategy to improve the storage capacity of 3D NAND is to increase the number of vertically stacked storage layers. However, as the number of layers increases, in order to control the overall height of the stack and meet the challenges of graphic accuracy and stress management, the thickness of each layer must be reduced accordingly. But this measure also brings new problems: the reduction in the size of the storage cell exacerbates the electron scattering effect, thereby further increasing the channel resistance, which will have an adverse effect on the performance of the unit transistor, specifically manifested in the decline of transistor performance and the extension of product programming / erase time. In view of these problems, the use of metal molybdenum (Mo) with low resistivity, high resistance to electromigration and better transistor performance to replace the metals commonly used in traditional processes (such as copper and tungsten) has become a solution worth considering.

[0003] Hafnium oxide (HfO2) is an oxide with a wide bandgap and high dielectric constant. It can be used as a gate insulator material for microelectronics, integrated circuits, and dielectric devices. It has relatively low leakage current and good thermal / electrical stability. Traditional phosphoric acid-based etching solutions have a series of problems in the process of etching molybdenum metal layers, including excessive metal surface residues, which significantly increases the surface roughness, and low selectivity for hafnium oxide, which easily damages the underlying hafnium oxide structure.

[0004] In response to the above problems, attempts were made to add additives and hafnium oxide etching inhibitors to the phosphoric acid, acetic acid, and nitric acid system to ensure a lower hafnium oxide etching rate and faster etching of metal molybdenum while satisfying the metal molybdenum to hafnium oxide selectivity and slowing down hafnium oxide etching. Summary of the invention

[0005] The technical solution of the present invention is a selective etching solution for molybdenum, which can effectively etch the metal molybdenum deposition layer under the premise of ensuring that the etching rate (ER) of hafnium oxide is ≤0.05nm / min, and there is no residue on the surface of the metal molybdenum after etching, and the metal molybdenum and hafnium oxide have a high selectivity.

[0006] The technical solution of the present invention comprises, by mass percentage, 51%-69% of electronic grade phosphoric acid, 13%-28% of electronic grade acetic acid, 2.2%-3.8% of electronic grade nitric acid, 0.04%-0.065% of periodic acid, 0.03%-0.09% of organic amine additives, 0.2%-3.5% of hafnium oxide etching inhibitor, and the remaining components are deionized water.

[0007] Furthermore, the phosphoric acid is electronic grade, with a raw material concentration of ≥85% and a metal ion content of ≤0.03ppb; the acetic acid is electronic grade, with a raw material concentration of ≥99.9% and a metal ion content of ≤0.03ppb; the nitric acid is electronic grade, with a raw material concentration of ≥70% and a metal ion content of ≤0.03ppb; and the raw material purity of periodic acid is ≥99.99%.

[0008] Furthermore, the organic amine additive includes one or a combination of N-(prop-2-yn-1-yl)-1H-imidazole-1-carboxamide, (1H-imidazole-1-yl)(morpholinyl)methanone, {[4-(1H-imidazole-1-ylmethyl)phenyl]methyl}(methyl)amine, N-benzyl-1H-imidazole-1-carboxamide, 3-(1H-1,3-benzodiazol-1-yl)-2-(propylamino)propionic acid, (1H-benzo[d]imidazol-1-yl)methyl)ethyl carbamate, and 3,3'-(methylazadiyl)dipropionic acid.

[0009] Further, the hafnium oxide etching inhibitor includes at least one of biotinyl-4-aminobutyric acid, diethylcarbamic acid, 4-methylpiperazine-1-carboxylic acid, N-(2-aminoethyl)-N-methylacetamide, and 2-amino-N-(2-(dimethylamino)ethyl)-N-ethylacetamide.

[0010] Furthermore, organic amine additives can regulate the etching rate of metallic molybdenum.

[0011] Furthermore, periodic acid can improve the roughness of the surface of metal molybdenum after etching.

[0012] Furthermore, the hafnium oxide etching inhibitor can inhibit the etching rate of hafnium oxide, and the hafnium oxide etching rate (ER) is ≤0.05 nm / min.

[0013] Furthermore, the etching solution is preferably used at a temperature ranging from 45°C to 65°C, more preferably from 50°C to 60°C, and most preferably at 55°C.

[0014] The present invention has the following beneficial effects: The etching solution of the present invention has a good selectivity for etching metal molybdenum.

[0015] The organic amine additive in the present invention has unbonded lone pairs of electrons, which can be combined with empty metal orbitals through coordination bonds to form a protective layer on the surface of metal molybdenum, thereby regulating the etching rate of metal molybdenum.

[0016] The strong oxidizing property of periodic acid in the present invention enables low-valent molybdenum metal to be oxidized into high-valent, dense metal oxides, thereby reducing anisotropic etching, and improving the roughness of the surface of the metal molybdenum after etching under the combined action of organic amine additives.

[0017] The hafnium oxide etching inhibitor added in the present invention can form a chelate with the hafnium oxide to generate a stable chelate compound, which has the effect of slowing down the etching rate of the hafnium oxide, thereby making the hafnium oxide etching rate (ER) ≤0.05nm / min. DETAILED DESCRIPTION

[0018] The implementation process related to the present invention will be specifically introduced below. The implementation process is only used to deepen the understanding of the invention but does not limit the scope of the invention.

[0019] Example 1 A molybdenum etching solution, the formula of which is: 56% electronic grade phosphoric acid (mass fraction is 89%), 19% electronic grade acetic acid (mass fraction is 99.9%), 3.5% electronic grade nitric acid (mass fraction is 70.5%), 0.045% periodic acid, 0.07% N-(prop-2-yn-1-yl)-1H-imidazole-1-carboxamide and 2.5% biotinyl-4-aminobutyric acid, and the rest is deionized water.

[0020] Example 2 A molybdenum etching solution, the formula of which is: 56% electronic grade phosphoric acid (mass fraction is 89%), 19% electronic grade acetic acid (mass fraction is 99.9%), 3.5% electronic grade nitric acid (mass fraction is 70.5%), 0.045% periodic acid, 0.07% N-(prop-2-yn-1-yl)-1H-imidazole-1-carboxamide and 2.5% diethylaminoformic acid, and the rest is deionized water.

[0021] Example 3 A molybdenum etching solution, the formula of which is: 56% electronic grade phosphoric acid (mass fraction is 89%), 19% electronic grade acetic acid (mass fraction is 99.9%), 3.5% electronic grade nitric acid (mass fraction is 70.5%), 0.045% periodic acid, 0.07% N-(prop-2-yn-1-yl)-1H-imidazole-1-carboxamide and 2.5% 4-methylpiperazine-1-carboxylic acid, and the rest is deionized water.

[0022] Example 4 A molybdenum etching solution, the formula of which is: 56% electronic grade phosphoric acid (mass fraction is 89%), 19% electronic grade acetic acid (mass fraction is 99.9%), 3.5% electronic grade nitric acid (mass fraction is 70.5%), 0.045% periodic acid, 0.07% N-(prop-2-yn-1-yl)-1H-imidazole-1-carboxamide and 2.5% N-(2-aminoethyl)-N-methylacetamide, and the rest is deionized water.

[0023] Example 5 A molybdenum etching solution has a formula of: 56% electronic grade phosphoric acid (mass fraction is 89%), 19% electronic grade acetic acid (mass fraction is 99.9%), 3.5% electronic grade nitric acid (mass fraction is 70.5%), 0.045% periodic acid, 0.07% N-(prop-2-yn-1-yl)-1H-imidazole-1-carboxamide and 2.5% 2-amino-N-(2-(dimethylamino)ethyl)-N-ethylacetamide, and the rest is deionized water.

[0024] Example 6 A molybdenum etching solution, the formula of which is: 56% electronic grade phosphoric acid (mass fraction is 89%), 19% electronic grade acetic acid (mass fraction is 99.9%), 3.5% electronic grade nitric acid (mass fraction is 70.5%), 0.045% periodic acid, 0.07% (1H-imidazole-1-yl) (morpholinyl) ketone and 2.5% N-(2-aminoethyl)-N-methylacetamide, and the rest is deionized water.

[0025] Example 7 A molybdenum etching solution, the formula of which is: 56% electronic grade phosphoric acid (mass fraction is 89%), 19% electronic grade acetic acid (mass fraction is 99.9%), 3.5% electronic grade nitric acid (mass fraction is 70.5%), 0.045% periodic acid, 0.07% {[4-(1H-imidazole-1-ylmethyl)phenyl]methyl}(methyl)amine and 2.5% N-(2-aminoethyl)-N-methylacetamide, and the rest is deionized water.

[0026] Example 8 A molybdenum etching solution has a formula of: 56% electronic grade phosphoric acid (mass fraction is 89%), 19% electronic grade acetic acid (mass fraction is 99.9%), 3.5% electronic grade nitric acid (mass fraction is 70.5%), 0.045% periodic acid, 0.07% N-benzyl-1H-imidazole-1-carboxamide and 2.5% N-(2-aminoethyl)-N-methylacetamide, and the rest is deionized water.

[0027] Example 9 A molybdenum etching solution, the formula of which is: 56% electronic grade phosphoric acid (mass fraction is 89%), 19% electronic grade acetic acid (mass fraction is 99.9%), 3.5% electronic grade nitric acid (mass fraction is 70.5%), 0.045% periodic acid, 0.07% 3-(1H-1,3-benzodiazol-1-yl)-2-(propylamino) propionic acid and 2.5% N-(2-aminoethyl)-N-methylacetamide, and the rest is deionized water.

[0028] Example 10 A molybdenum etching solution, the formula of which is: 56% electronic grade phosphoric acid (mass fraction is 89%), 19% electronic grade acetic acid (mass fraction is 99.9%), 3.5% electronic grade nitric acid (mass fraction is 70.5%), 0.045% periodic acid, 0.07% (1H-benzo [d] imidazole-1-yl) methyl) ethyl carbamate and 2.5% N-(2-aminoethyl)-N-methylacetamide, and the rest is deionized water.

[0029] Embodiment 11 A molybdenum etching solution, the formula of which is: 56% electronic grade phosphoric acid (mass fraction is 89%), 19% electronic grade acetic acid (mass fraction is 99.9%), 3.5% electronic grade nitric acid (mass fraction is 70.5%), 0.045% periodic acid, 0.07% 3,3'-(methylazadiyl)dipropionic acid and 2.5% N-(2-aminoethyl)-N-methylacetamide, and the rest is deionized water.

[0030] Comparative Example 1 A molybdenum etching solution, having the same formula as that of Example 6, except that electronic grade phosphoric acid is not added.

[0031] Comparative Example 2 A molybdenum etching solution, having the same formula as that of Example 6, except that electronic grade acetic acid is not added.

[0032] Comparative Example 3 A molybdenum etching solution, having the same formula as that of Example 6, except that electronic grade nitric acid is not added.

[0033] Comparative Example 4 A molybdenum etching solution, having the same formula as that of Example 6, except that periodic acid is not added.

[0034] Comparative Example 5 A molybdenum etching solution, having the same formula as that of Example 6, except that (1H-imidazole-1-yl)(morpholinyl)ketone is not added.

[0035] Comparative Example 6 A molybdenum etching solution, having the same formula as that of Example 6, except that N-(2-aminoethyl)-N-methylacetamide is not added.

[0036] Comparative Example 7 A molybdenum etching solution, whose formula is the same as that of Example 6, but different from Example 6 in that electronic grade nitric acid and periodic acid are not added.

[0037] Comparative Example 8 A molybdenum etching solution, having the same formula as that of Example 6, except that (1H-imidazole-1-yl)(morpholinyl)ketone and N-(2-aminoethyl)-N-methylacetamide are not added.

[0038] The etching method and test results are as follows: According to the above formula, 100g etching solution was prepared in a 250ml beaker with a stirrer, heated in a water bath, stirred at 350 rpm / min, and set at 55°C. When the solution temperature was stable at 55±0.2°C, the corresponding structure was etched. Before etching, the thin slices deposited with metal molybdenum (thickness of 500nm) were cut into 2*2cm in size, etched by immersion etching, and the etching time was recorded. After etching, the thin slices were washed with deionized water and dried with nitrogen, and the thickness was measured by a four-point probe. The hafnium oxide thin slices were etched in the same way, and the thickness of the test slices was measured using an ellipsometry spectropolarimeter. The etching rates of molybdenum and hafnium oxide were calculated based on the thickness difference before and after film etching and the etching time, so as to calculate the selectivity. In addition, scanning electron microscopy and atomic force microscopy were used to verify the etching effect of the etching solution, and to observe whether there was any residue on the metal surface after etching and whether the roughness increased. The present invention adjusts the etching rate of metal molybdenum and hafnium oxide by adjusting the proportion of each component in the etching solution. The experimental results of the embodiment and the comparative example are shown in the following table: Table 1:

[0039] The etching solutions prepared in Examples 1-11 have different etching rates for metal molybdenum and hafnium oxide due to differences in components. No residue is left after etching of metal molybdenum, and the selectivity of metal molybdenum to hafnium oxide can reach 3313.

[0040] Compared with the etching effect of the etching solution prepared in Example 6 and the etching effect of the etching solution prepared in Comparative Example 1, the presence of phosphoric acid helps to dissolve metal molybdenum during the etching process and increases its etching rate, while the solubility of hafnium oxide in phosphoric acid is limited, the etching rate is slightly reduced, and the selectivity is improved. At the same time, the presence of phosphoric acid reduces the residue after etching of metal molybdenum to a certain extent.

[0041] Compared with the etching effect of the etching solution prepared in Example 6 and the etching effect of the etching solution prepared in Comparative Example 2, the presence of acetic acid has a certain corrosion inhibition effect on hafnium oxide, but the corrosion inhibition effect on metal molybdenum is not obvious. However, acetic acid reduces the residue of metal molybdenum after etching to a certain extent.

[0042] Compared with the etching effects of the etching solutions prepared in Example 6 and Comparative Examples 3, 4 and 7, the oxidizing agents nitric acid and periodic acid are necessary for the etching solution, and the etching of metal molybdenum is difficult to carry out in the absence of an oxidizing agent. Among them, nitric acid mainly plays an oxidizing role, oxidizing metal molybdenum to a higher valence state, which is easier to be dissolved by the components in the etching solution. Periodic acid has a stronger oxidizing property, which oxidizes the low-valence molybdenum metal into a denser metal oxide, thereby reducing anisotropic etching, thereby reducing the residue after metal molybdenum etching.

[0043] Compared with the etching effects of the etching solutions prepared in Example 6 and Comparative Examples 5 and 6, the organic amine additives have a certain etching inhibition effect on both metal molybdenum and hafnium oxide. At the same time, the organic amine additives have unbonded lone pairs of electrons, which can be combined with metal empty orbitals through coordination bonds to form a protective layer on the surface of metal molybdenum, making the etching of metal molybdenum more uniform and reducing the residue after etching of metal molybdenum to a certain extent. The hafnium oxide etching inhibitor can form a chelate with hafnium oxide to generate a stable chelate compound, which has the effect of significantly slowing down the etching rate of hafnium oxide, so that the hafnium oxide etching rate (ER) is ≤0.05nm / min.

[0044] Compared with the etching effect of the etching solution prepared in Example 6 and the etching effect of the etching solution prepared in Comparative Example 8, the organic amine additive and the hafnium oxide etching inhibitor cooperate with each other for a better effect. Under the combined action of the two, the selectivity of metal molybdenum to hafnium oxide can reach 3313.

[0045] Obviously, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the above embodiments have many variations or combinations, and the present invention cannot cite all the embodiments. Therefore, the variations or changes made based on the above embodiments are still within the protection scope of the present invention.

Claims

1. A selective etching solution for metal molybdenum, characterized in that: Calculated by mass percentage, it includes 51%-69% electronic grade phosphoric acid, 13%-28% electronic grade acetic acid, 2.2%-3.8% electronic grade nitric acid, 0.04%-0.065% periodic acid, 0.03%-0.09% organic amine additives, 0.2%-3.5% hafnium oxide etching inhibitor, and the remaining components are deionized water.

2. The selective etching solution for molybdenum according to claim 1, characterized in that: Phosphoric acid is electronic grade, with raw material concentration ≥85% and metal ion content ≤0.03ppb; acetic acid is electronic grade, with raw material concentration ≥99.9% and metal ion content ≤0.03ppb; nitric acid is electronic grade, with raw material concentration ≥70% and metal ion content ≤0.03ppb; periodic acid raw material purity ≥99.99%.

3. The selective etching solution for molybdenum according to claim 1, characterized in that The organic amine additives include one or a combination of N-(prop-2-yn-1-yl)-1H-imidazole-1-carboxamide, (1H-imidazole-1-yl)(morpholinyl)methanone, {[4-(1H-imidazole-1-ylmethyl)phenyl]methyl}(methyl)amine, N-benzyl-1H-imidazole-1-carboxamide, 3-(1H-1,3-benzodiazol-1-yl)-2-(propylamino)propionic acid, (1H-benzo[d]imidazol-1-yl)methyl)ethyl carbamate, and 3,3'-(methylazadiyl)dipropionic acid.

4. The selective etching solution for molybdenum according to claim 1, characterized in that The hafnium oxide etching inhibitor includes at least one of biotinyl-4-aminobutyric acid, diethylcarbamic acid, 4-methylpiperazine-1-carboxylic acid, N-(2-aminoethyl)-N-methylacetamide, and 2-amino-N-(2-(dimethylamino)ethyl)-N-ethylacetamide.

5. The selective etching solution for molybdenum according to claim 1-4, characterized in that: The etching rate (ER) of hafnium oxide is ≤0.05nm / min, there is no residue on the surface of metal molybdenum after etching, and metal molybdenum and hafnium oxide have a high selectivity.

6. The selective etching solution for molybdenum according to claim 1-5, characterized in that: The etching solution is preferably used at a temperature ranging from 45°C to 65°C, more preferably from 50°C to 60°C, and most preferably at 55°C.

7. The selective etching solution for molybdenum according to any one of claims 1 to 6 is used in etching semiconductor materials for metallic molybdenum.

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