Phosphoric acid group etching solution of molybdenum

Abstract

The invention provides a phosphate-based etching solution for metal molybdenum, which comprises the following components in percentage by mass: 48%-68% of electronic-grade phosphoric acid, 2.0%-5.5% of electronic-grade nitric acid, 12%-20% of electronic-grade acetic acid, 0.02%-0.07% of an organic phosphonate additive, 0.1%-2.0% of a molybdenum etching inhibitor and the balance of deionized water. The etching solution can effectively etch a metal molybdenum deposition layer on the premise that the molybdenum etching rate (ER) is larger than or equal to 0.05 nm / min and smaller than or equal to 20 nm / min, no residues exist on the surface after etching, and the roughness is further reduced.

Description

Technical Field

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

[0002] As the process feature size in integrated circuits continues to shrink, the resistance-capacitance (RC) delay in interconnect lines is rising rapidly. In technology nodes after 10 nm, the RC delay of the interconnect layer is the main factor in chip signal delay, which has become a technical bottleneck for high-performance chips. Metals (copper, tungsten) in traditional processes are difficult to maintain nanoscale performance. In contrast, molybdenum (Mo) has the advantages of low resistivity, high melting point, acid corrosion resistance, and high resistance to electromigration. It can effectively reduce the RC delay of interconnect line widths less than 10nm, and has greater potential in forming barrier-free layer filling. It is a strong candidate for the next generation of metal interconnect materials. Therefore, the development of a nanoscale controlled etching process for metal molybdenum has become a key prerequisite for its practical application.

[0003] Conventional metal molybdenum etching solutions include hydrogen peroxide systems, phosphoric acid systems, etc., and the phosphoric acid system has better stability and higher tolerance to various additives. Phosphoric acid-based etching solutions are often used for etching of panel-level metal molybdenum such as thin-film field effect transistor liquid crystal displays and light-emitting diodes. Due to the activity of metal molybdenum itself, the existing etching solution has too fast an etching rate for it, generally greater than 100nm / min. Under the existing system, it is difficult to etch metal molybdenum at a low rate while reducing the roughness, and if the etching rate is too fast, it will lead to excessive residues in the molybdenum layer after etching, and even damage the underlying structure. It is difficult to cope with the nano-level precision processing requirements of interconnect materials in integrated circuits. At the same time, different semiconductor customers have different manufacturing processes and have their own requirements for the etching of metal molybdenum, which requires the liquid formula to have an adjustable range, that is, the molybdenum etching rate can be adjusted as needed within 0.05 nm / min≤(ER)≤20 nm / min. In addition, the etching solution used in high-performance chip manufacturing processes has strict requirements on the metal content, particle size, and color of the etching solution. This makes it impossible to use chemical reagents such as sodium dodecyl sulfate, potassium permanganate, and sodium molybdate that introduce other metals and colors into the solution, which further increases the difficulty of developing etching solutions. Summary of the invention

[0004] In view of the above problems, the present invention attempts to add organic phosphonate additives and corresponding molybdenum etching inhibitors to the phosphoric acid, nitric acid and acetic acid system. The present invention effectively etches the metal molybdenum deposit layer while ensuring the molybdenum etching rate of 0.05 nm / min≤(ER)≤20 nm / min, and there is no residue on the metal molybdenum surface after etching, and the roughness is further reduced.

[0005] A phosphoric acid-based etching solution for molybdenum comprises phosphoric acid, nitric acid, acetic acid, an organic phosphonate additive and a molybdenum etching inhibitor.

[0006] The etching solution comprises, by mass percentage, 48%-68% phosphoric acid, 2.0%-5.5% nitric acid, 12%-20% acetic acid, 0.02%-0.07% organic phosphonate additives, 0.1%-2.0% molybdenum etching inhibitors and the balance deionized water.

[0007] The phosphoric acid is electronic grade, with a raw material concentration of ≥85% and a metal ion content of ≤0.02ppb; the acetic acid is electronic grade, with a raw material concentration of ≥99.9% and a metal ion content of ≤0.02ppb; the nitric acid is electronic grade, with a raw material concentration of ≥70% and a metal ion content of ≤0.02ppb.

[0008] The organic phosphonate additive includes one or a combination of ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2-((6-oxidized-6H-dibenzo[c,e][1,2]phosphinothrein-6-yl)methyl)succinic acid, ethyl (2-(diethylamino)-2-oxyethyl)(phenyl)phosphinate, ethyl 1-(ethoxy(phenyl)phosphinoyl)butyrate, ethyl (4-fluorophenyl)(hydroxy(pyridin-3-yl)methyl)phosphinate, methyl (ethoxy(phenyl)phosphinoyl)(phenyl)butyrate or isopentyl(4-(dimethylamino)phenyl)(hydroxy(pyridin-3-yl)methyl)phosphinate.

[0009] The platinum etching inhibitor includes at least one of 4-(4-cyclohexylphenyl)-2-(decylamino)-4-oxobutanoic acid, (1,1,1-trifluoro-4-oxo-4-phenylbutan-2-yl)glycine, 2-(cyclohexylamino)-4-(4-cyclohexylphenyl)-4-oxobutanoic acid, (5R)-5-benzyl-1-piperidinic acid or 1-(4-methylphenyl)-3-(1H-1,2,4-triazol-1-yl)propan-1-one.

[0010] The etching solution is used at a temperature of 25°C-45°C, preferably 30°C-40°C, and more preferably 35°C.

[0011] The etching rate of the etching solution on molybdenum is 0.05 nm / min≤ER≤20 nm / min.

[0012] The phosphoric acid-based etching solution of molybdenum is used in etching semiconductor materials of metallic molybdenum.

[0013] The present invention has the following beneficial effects: (1) The etching solution of the present invention has extremely low metal impurities (<2 ppb), is homogeneous and colorless and transparent, has a stable and controllable etching rate, has good solution stability, and has a long service life.

[0014] (2) The organic phosphonate additive in the etching solution of the present invention forms a chelate with the molybdenum ions generated during the etching process to generate a stable chelate compound; and the molybdenum etching inhibitor has unbonded free electrons, which can combine with the empty orbits of metal molybdenum through coordination bonds, thereby forming a protective layer on the surface of metal molybdenum. The two can control the etching rate under the synergistic effect. The solution can adjust the metal molybdenum etching rate as needed within the range of 0.05 nm / min≤(ER)≤20nm / min while ensuring that there is no residue after etching and further reducing the roughness.

[0015] (3) The components of the etching solution of the present invention are simple and easy to obtain, and the etching effect is uniform, and it is also suitable for etching multi-layer metal film layers such as molybdenum alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the AFM image of a thin film deposited with metal molybdenum before etching; Figure 2 This is the AFM image of the etching solution prepared in Comparative Example 6 after etching; Figure 3 This is the AFM image of the etching solution prepared in Example 10 after etching; Figure 4 This is the SEM image of the thin slice deposited with metal molybdenum before etching; Figure 5 This is a SEM image of the etching solution prepared in Comparative Example 6 after etching; Figure 6 This is the SEM image of the etching solution prepared in Example 10 after etching. DETAILED DESCRIPTION

[0017] The embodiments of the present invention will be described in detail below with reference to examples. The following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0018] The Chinese and English names of the raw materials selected in the present invention are as follows: Ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate: ethyl 2,4,6-trimethylbenzoylphenylphosphinate; (6H-Dibenz[c,e][1,2]oxaphosphorin-6-ylmethyl)-p-oxide-butanediolicacid: 2-((6-oxido-6H-dibenzo[c,e][1,2]oxaphosphorin-6-ylmethyl)-p-oxide-butanediolicacid); (diethylamino) -2-oxoethyl) (phenyl) phosphonic acid ethyl ester: (2-(diethylamino)-2-oxoethyl) (phenyl) phosphonic acid ethyl ester; 1- (Ethoxy (phenyl) phosphoryl) butyric acid ethyl ester: 1-(Ethoxy (phenyl) phosphoryl) butyric acid ethyl ester; Ethyl (4-fluorophenyl)(hydroxy(pyridin-3-yl)methyl)phosphinate: Ethyl (4-fluorophenyl)(hydroxy(pyridin-3-yl)methyl)phosphinate; (Ethoxy(phenyl)phosphoryl)(phenyl)methyl butyrate: (Ethoxy(phenyl)phosphoryl)(phenyl)methyl butyrate; Isopentyl(4-(dimethylamino)phenyl)(hydroxy(pyridin-3-yl)methyl)phosphinate: Isopentyl(4-(dimethylamino)phenyl)(hydroxy(pyridin-3-yl)methyl)phosphinate; (4-Cyclohexylphenyl)-2-(decylamino)-4-oxobutanoic acid: 4-(4-cyclohexylphenyl)-2-(decylamino)-4-oxobutanoic acid; (1,1,1-trifluoro-4-oxo-4-phenylbut-2-yl) glycine: (1,1,1-trifluoro-4-oxo-4-phenylbut-2-yl) glycine; (Cyclohexylamino)-4-(4-cyclohexylphenyl)-4-oxobutanoic acid: 2-(Cyclohexylamino)-4-(4-cyclohexylphenyl)-4-oxobutanoic acid; (5R)-5-benzyl-l-pipecolinic acid: (5R)-5-benzyl-1-pipecolinic acid; 1-(4-Methylphenyl)-3-(1H-1,2,4-triazol-1-yl)propan-1-one: 1-(4-Methylphenyl)-3-(1H-1,2,4-triazol-1-yl)propan-1-one.

[0019] Example 1 A molybdenum etching solution, the formula of which is: 52% electronic grade phosphoric acid (mass fraction is 89%), 15% electronic grade acetic acid (mass fraction is 99.9%), 3.8% electronic grade nitric acid (mass fraction is 70.5%), 0.04% ethyl 2,4,6-trimethylbenzoylphenylphosphonate and 1.5% 4-(4-cyclohexylphenyl)-2-(decylamino)-4-oxobutanoic acid, and the rest is deionized water.

[0020] Example 2 A molybdenum etching solution, the formula of which is: 52% electronic grade phosphoric acid (mass fraction is 89%), 15% electronic grade acetic acid (mass fraction is 99.9%), 3.8% electronic grade nitric acid (mass fraction is 70.5%), 0.04% ethyl 2,4,6-trimethylbenzoylphenylphosphonate and 1.5% (1,1,1-trifluoro-4-oxo-4-phenylbutan-2-yl) glycine, and the rest is deionized water.

[0021] Example 3 A molybdenum etching solution, the formula of which is: 52% electronic grade phosphoric acid (mass fraction is 89%), 15% electronic grade acetic acid (mass fraction is 99.9%), 3.8% electronic grade nitric acid (mass fraction is 70.5%), 0.04% ethyl 2,4,6-trimethylbenzoylphenylphosphonate and 1.5% 2-(cyclohexylamino)-4-(4-cyclohexylphenyl)-4-oxobutanoic acid, and the rest is deionized water.

[0022] Example 4 A molybdenum etching solution has a formula of: 52% electronic grade phosphoric acid (mass fraction is 89%), 15% electronic grade acetic acid (mass fraction is 99.9%), 3.8% electronic grade nitric acid (mass fraction is 70.5%), 0.04% ethyl 2,4,6-trimethylbenzoylphenylphosphonate and 1.5% (5R)-5-benzyl-1-piperidinic acid, and the rest is deionized water.

[0023] Example 5 A molybdenum etching solution, the formula of which is: 52% electronic grade phosphoric acid (mass fraction is 89%), 15% electronic grade acetic acid (mass fraction is 99.9%), 3.8% electronic grade nitric acid (mass fraction is 70.5%), 0.04% ethyl 2,4,6-trimethylbenzoylphenylphosphonate and 1.5% 1-(4-methylphenyl)-3-(1H-1,2,4-triazol-1-yl)propan-1-one, and the rest is deionized water.

[0024] Example 6 A molybdenum etching solution, the formula of which is: 52% electronic grade phosphoric acid (mass fraction is 89%), 15% electronic grade acetic acid (mass fraction is 99.9%), 3.8% electronic grade nitric acid (mass fraction is 70.5%), 0.04% 2-((6-oxido-6H-dibenzo[c,e][1,2]phosphinothrein-6-yl)methyl)succinic acid and 1.5% 2-(cyclohexylamino)-4-(4-cyclohexylphenyl)-4-oxobutanoic acid, and the rest is deionized water.

[0025] Example 7 A molybdenum etching solution, the formula of which is: 52% electronic grade phosphoric acid (mass fraction is 89%), 15% electronic grade acetic acid (mass fraction is 99.9%), 3.8% electronic grade nitric acid (mass fraction is 70.5%), 0.04% (2-(diethylamino)-2-oxyethyl)(phenyl) ethyl phosphinate and 1.5% 2-(cyclohexylamino)-4-(4-cyclohexylphenyl)-4-oxobutanoic acid, and the rest is deionized water.

[0026] Example 8 A molybdenum etching solution, the formula of which is: 52% electronic grade phosphoric acid (mass fraction is 89%), 15% electronic grade acetic acid (mass fraction is 99.9%), 3.8% electronic grade nitric acid (mass fraction is 70.5%), 0.04% 1-(ethoxy(phenyl)phosphoryl)butyric acid ethyl ester and 1.5% 2-(cyclohexylamino)-4-(4-cyclohexylphenyl)-4-oxobutyric acid, and the rest is deionized water.

[0027] Example 9 A molybdenum etching solution, the formula of which is: 52% electronic grade phosphoric acid (mass fraction is 89%), 15% electronic grade acetic acid (mass fraction is 99.9%), 3.8% electronic grade nitric acid (mass fraction is 70.5%), 0.04% (4-fluorophenyl) (hydroxy (pyridin-3-yl) methyl) ethyl phosphinate and 1.5% 2- (cyclohexylamino) -4- (4-cyclohexylphenyl) -4-oxobutanoic acid, and the rest is deionized water.

[0028] Example 10 A molybdenum etching solution, the formula of which is: 52% electronic grade phosphoric acid (mass fraction is 89%), 15% electronic grade acetic acid (mass fraction is 99.9%), 3.8% electronic grade nitric acid (mass fraction is 70.5%), 0.04% (ethoxy (phenyl) phosphoryl) (phenyl) butyric acid methyl ester and 1.5% 2-(cyclohexylamino)-4-(4-cyclohexylphenyl)-4-oxobutyric acid, and the rest is deionized water.

[0029] Embodiment 11 A molybdenum etching solution, the formula of which is: 52% electronic grade phosphoric acid (mass fraction is 89%), 15% electronic grade acetic acid (mass fraction is 99.9%), 3.8% electronic grade nitric acid (mass fraction is 70.5%), 0.04% isopentyl (4- (dimethylamino) phenyl) (hydroxy (pyridin-3-yl) methyl) phosphinate and 1.5% 2- (cyclohexylamino) -4- (4-cyclohexylphenyl) -4-oxobutanoic acid, and the rest is deionized water.

[0030] Example 12 A molybdenum etching solution has a formula of: 52% electronic grade phosphoric acid (mass fraction is 89%), 15% electronic grade acetic acid (mass fraction is 99.9%), 3.8% electronic grade nitric acid (mass fraction is 70.5%), 0.04% (ethoxy (phenyl) phosphoryl) (phenyl) butyric acid methyl ester and 1.5% (5R)-5-benzyl-1-piperidinic acid, and the rest is deionized water.

[0031] Comparative Example 1 A molybdenum etching solution, whose formula is the same as that of Example 10, and the difference from Example 10 is that only electronic grade phosphoric acid is not added.

[0032] Comparative Example 2 A molybdenum etching solution, having the same formula as that of Example 10, differing from Example 10 in that only electronic grade acetic acid is not added.

[0033] Comparative Example 3 A molybdenum etching solution, having the same formula as that of Example 10, and differing from Example 10 in that only electronic grade nitric acid is not added.

[0034] Comparative Example 4 A molybdenum etching solution, having the same formula as that of Example 10, except that methyl (ethoxy(phenyl)phosphoryl)(phenyl)butyrate is not added.

[0035] Comparative Example 5 A molybdenum etching solution, whose formula is the same as that of Example 10, and the difference from Example 10 is that only 2-(cyclohexylamino)-4-(4-cyclohexylphenyl)-4-oxobutanoic acid is not added.

[0036] Comparative Example 6 A molybdenum etching solution, having the same formula as Example 10, except that (ethoxy(phenyl)phosphoryl)(phenyl)butyric acid methyl ester is replaced by triethyl phosphate.

[0037] Comparative Example 7 A molybdenum etching solution, having the same formula as Example 10, except that 2-(cyclohexylamino)-4-(4-cyclohexylphenyl)-4-oxobutanoic acid is replaced by 1,3-dimethyl-2-imidazolidinone.

[0038] The etching method and test results are as follows: According to the above formula, 100g of etching solution is prepared in a 250ml beaker, and a stirring bar is placed in the beaker. The stirring speed is 300 rpm / min, and a water bath is used for heating. The corresponding temperature is set to 35°C. When the solution temperature reaches and stabilizes at ±0.25°C, the structural sheet is etched. Before etching, the thin slices deposited with metal molybdenum (thickness of 300nm) are cut into 2*2cm in size, placed in the etching solution and immersion etching is performed, and the etching time is recorded. After etching, the thin slices deposited with metal molybdenum are cleaned with deionized water and blown dry with nitrogen, and the thickness is measured by a four-point probe instrument. According to the difference in thickness before and after etching of the metal film layer, the etching rate is calculated compared with the etching time. In addition, the etching effect of the etching solution is verified by scanning electron microscopy and atomic force microscopy, and it is observed whether there is any residue on the metal surface after etching and whether the roughness increases. The present invention adjusts the etching rate of metal molybdenum by regulating the proportion of each component in the etching solution. The experimental results of the embodiments and comparative examples are as follows: Table 1:

[0039] The etching solutions prepared in Examples 1-12 had different etching rates due to differences in components, and no residue was found after etching of the metal molybdenum, and the surface roughness of the metal did not increase compared to before etching.

[0040] Compared with the etching effect of the etching solution prepared in Examples 1 to 12 and the etching solution prepared in Comparative Example 1, the presence of phosphoric acid helps dissolve the metal molybdenum during the etching process and plays a certain corrosion inhibition role, and reduces the post-etching residue to a certain extent.

[0041] Compared with the etching effects of the etching solutions prepared in Examples 1 to 12 and the etching solutions prepared in Comparative Example 2, the presence of acetic acid helps dissolve metal molybdenum during the etching process and plays a certain corrosion inhibition role, and reduces the post-etching residue to a certain extent.

[0042] Compared with the etching effect of the etching solution prepared in Examples 1 to 12 and the etching solution prepared in Comparative Example 3, nitric acid is indispensable, and the etching of metal molybdenum is difficult to carry out in the absence of an oxidant. The presence of the oxidant oxidizes the metal molybdenum into a high-valent state, making it easier to be dissolved by the components in the etching solution.

[0043] Compared with the etching effects of the etching solutions prepared in Examples 1 to 12 and Comparative Examples 4 and 5, the presence of organic phosphonate additives and platinum etching inhibitors can inhibit the etching of metal platinum, and the organic phosphonate additives can synergistically act with the platinum etching inhibitor to reduce the residual after etching (reference Figure 3 , Figure 6 ), compared with before etching (Ref. Figure 1 , Figure 4 ) The metal surface becomes smoother and more uniform. This shows that the synergistic effect of organic phosphonate additives and molybdenum etching inhibitors can effectively inhibit the etching rate and reduce material residues, reduce the phenomenon of uneven etching, and achieve efficient and precise etching at the nanoscale.

[0044] The etching solutions prepared in Examples 1 to 12 and Comparative Example 6 (reference Figure 2 , Figure 5 ), compared with the etching effect of the etching solution prepared in Comparative Example 7, the organic phosphonate additive and the molybdenum etching inhibitor selected in the present invention cooperate with each other for a better effect.

[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 list 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 phosphoric acid-based etching solution for molybdenum, characterized in that: Includes phosphoric acid, nitric acid, acetic acid, organic phosphonate additives and molybdenum etch inhibitors.

2. The phosphoric acid-based etching solution of molybdenum according to claim 1, characterized in that Calculated by mass percentage, it includes: 48%-68% phosphoric acid, 2.0%-5.5% nitric acid, 12%-20% acetic acid, 0.02%-0.07% organic phosphonate additives, 0.1%-2.0% molybdenum etching inhibitor and the balance deionized water.

3. The phosphoric acid-based etching solution of molybdenum according to claim 1, characterized in that The phosphoric acid is electronic grade, with a raw material concentration of ≥85% and a metal ion content of ≤0.02ppb; the acetic acid is electronic grade, with a raw material concentration of ≥99.9% and a metal ion content of ≤0.02ppb; the nitric acid is electronic grade, with a raw material concentration of ≥70% and a metal ion content of ≤0.02ppb.

4. The phosphoric acid-based etching solution for molybdenum according to claim 1, characterized in that The organic phosphonate additive includes one or a combination of ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2-((6-oxidized-6H-dibenzo[c,e][1,2]phosphinothrein-6-yl)methyl)succinic acid, ethyl (2-(diethylamino)-2-oxyethyl)(phenyl)phosphinate, ethyl 1-(ethoxy(phenyl)phosphinoyl)butyrate, ethyl (4-fluorophenyl)(hydroxy(pyridin-3-yl)methyl)phosphinate, methyl (ethoxy(phenyl)phosphinoyl)(phenyl)butyrate or isopentyl(4-(dimethylamino)phenyl)(hydroxy(pyridin-3-yl)methyl)phosphinate.

5. The phosphoric acid-based etching solution of molybdenum according to claim 1, characterized in that The platinum etching inhibitor includes at least one of 4-(4-cyclohexylphenyl)-2-(decylamino)-4-oxobutanoic acid, (1,1,1-trifluoro-4-oxo-4-phenylbutan-2-yl)glycine, 2-(cyclohexylamino)-4-(4-cyclohexylphenyl)-4-oxobutanoic acid, (5R)-5-benzyl-1-piperidinic acid or 1-(4-methylphenyl)-3-(1H-1,2,4-triazol-1-yl)propan-1-one.

6. The phosphoric acid-based etching solution for molybdenum according to any one of claims 1 to 5, characterized in that The etching solution is used at a temperature of 25°C-45°C, preferably 30°C-40°C, more preferably 35°C.

7. The phosphoric acid-based etching solution for platinum according to any one of claims 1 to 5, characterized in that The etching rate of the etching solution on molybdenum is 0.05 nm / min≤ER≤20 nm / min.

8. Use of a phosphoric acid-based etching solution of molybdenum as described in any one of claims 1 to 5 in etching semiconductor materials of metallic molybdenum.

Images