JP2022052909A - Etchant - Google Patents

Abstract

To provide an etchant that allows an increased etching rate of molybdenum and prevents the occurrence of residual molybdenum.SOLUTION: The present invention discloses an etchant for etching bilayer membrane of copper and molybdenum, the etchant comprising hydrogen peroxide, an acidic substance, an amine compound, a hydrogen peroxide degradation inhibitor, and molybdenum erosion promoting ions. The etchant makes it possible to selectively control the etching rate of molybdenum in the bilayer membrane of copper/molybdenum, enabling etching without residual molybdenum.SELECTED DRAWING: None

Description

The present invention relates to an etching solution for etching a multilayer film of molybdenum / copper, and particularly provides an etching solution suitable for eliminating molybdenum residues.

In the liquid crystal display device, pixels are turned on and off by a TFT (thin film transistor). That is, the TFTs are arranged over the entire screen. These power supplies are supplied from the edge of the screen. Therefore, as the screen becomes larger, the wiring length to the pixel in the center of the screen becomes longer. Therefore, the wiring resistance cannot be ignored, and it is inevitable to use a low resistance material for the wiring.

Conventionally, aluminum or the like has been used for wiring of display devices, but in recent years, copper having a lower resistivity than that has been used. Then, in order to secure the adhesiveness with the substrate, a metal such as molybdenum is laid as a base, and wiring having a double structure is used.

Wet etching is indispensable for forming a large number of pixels on a large screen at once. Therefore, many etching solutions for etching copper / molybdenum two-layer wiring have been proposed.

In Patent Document 1, an etching solution for a copper / molybdenum-based multilayer thin film that reduces damage to an oxide semiconductor layer such as IGZO, and a selective copper / molybdenum-based multilayer thin film for an oxide semiconductor layer using the same. For the purpose of providing an etching method, (A) hydrogen peroxide, (B) an inorganic acid containing no fluorine atom, (C) an organic acid, (D) an amino group having 2 to 10 carbon atoms, and the like. It contains an amine compound having at least one group selected from an amino group and a hydroxyl group, (E) azoles, and (F) hydrogen peroxide stabilizer, and is characterized by having a pH of 2.5 to 5. The etching solution is disclosed.

International Publication No. 2013/015322

When the copper / molybdenum double film is etched, there is a problem that a molybdenum residue remains. Molybdenum is about 5 to 8% thicker than copper, but its etching rate is lower than that of copper. Further, although some means for adjusting the etching rate of copper have been found, no means for selectively adjusting the etching rate of molybdenum has been found.

The present invention was conceived in view of the above problems, and uses metal ions having strong oxidizing power (ability to take electrons from the molybdenum film) as molybdenum erosion promoting ions to increase the etching rate of molybdenum. An etching solution for preventing the generation of molybdenum residue is provided.

More specifically, the etching solution according to the present invention is
An etching solution that etches a two-layer film of copper and molybdenum.
With hydrogen peroxide,
With acidic substances
Amine compounds and
Hydrogen peroxide decomposition inhibitor and
It is characterized by having molybdenum erosion promoting ions.

The etching solution according to the present invention can increase the etching rate of molybdenum by containing molybdenum erosion promoting ions, which are specific metal ions. Therefore, the copper / molybdenum bilayer film can be etched so as not to generate molybdenum residue.

The image was taken on the Si substrate of the double-layer film sample after the treatment, (a) is the case of the sample basic composition liquid 2, and (b) is the case of the comparative sample liquid.

Examples of the etching solution according to the present invention will be described below. The following description exemplifies one embodiment and one embodiment of the present invention, and the present invention is not limited to the following description. The following description can be modified without departing from the spirit of the present invention. In the following description, the atomic weight of silver is 108 and the atomic weight of iron is 56.

<Etching target>
The etching solution according to the present invention is used for a two-layer film of molybdenum and copper. In particular, molybdenum having a thickness of 10 nm to 50 nm and a copper film having a thickness of 450 nm to 900 nm can be preferably used.

<Composition of etching solution>
The etching solution according to the present invention is characterized by having hydrogen peroxide, an acidic substance, amines, a hydrogen peroxide decomposition inhibitor, molybdenum erosion promoting ions, and water. In addition, other micro additives may be contained. The molybdenum erosion promoting ion is a specific metal ion derived from a molybdenum erosion promoting agent having a specific metal ion.

<Hydrogen peroxide>
In the etching of copper, copper is oxidized to copper oxide (CuO), which is dissolved by an acid (organic acid). In the etching of molybdenum, molybdenum is oxidized to molybdenum oxide (MoO ₃ ) and dissolved. Hydrogen peroxide is used as an oxidant to oxidize copper and molybdenum. Hydrogen peroxide and overwater are synonyms. Hydrogen peroxide is preferably 3.0% by mass to 8.0% by mass, more preferably 3.5% by mass to 6.0% by mass, based on the total amount of the etching solution.

<Acid substance>
Acidic substances include organic and inorganic acids. Organic acids are used to control the cross-sectional shape of the etched wiring.

The inorganic acid is used together with the amine compound described later for adjusting the pH of the etching solution, and mainly contributes to dissolving oxidized copper and molybdenum. It is also to keep the metal ions in the state of ions. When an inorganic acid is used, it is preferable not to use a phosphoric acid compound, a hydrofluoric acid compound and hydrochloric acid in order to reduce the environmental load when the etching solution is discarded. Nitric acid and sulfuric acid can be preferably used. If it is an inorganic acid, it is contained in the range of 0.01% by mass or more and 2.00% by mass or less, preferably 0.02% by mass or more and 1.50% by mass or less of the total amount of the etching solution.

Preferred examples of the organic acid include an aliphatic carboxylic acid having 1 to 18 carbon atoms, an aromatic carboxylic acid having 6 to 10 carbon atoms, and an amino acid having 1 to 10 carbon atoms.

Examples of the aliphatic carboxylic acids having 1 to 18 carbon atoms include formic acid, acetic acid, propionic acid, lactic acid, glycolic acid, diglycolic acid, pyruvate, malonic acid, butyric acid, hydroxybutyric acid, tartrate acid, succinic acid, malic acid and maleic acid. , Fumaric acid, valeric acid, glutaric acid, itaconic acid, adipic acid, caproic acid, adipic acid, citric acid, propanthricarboxylic acid, trans-aconytic acid, enanthic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearer Acids, oleic acids, linoleic acids, linolenic acids and the like are preferred.

Preferred examples of the aromatic carboxylic acid having 6 to 10 carbon atoms include benzoic acid, salicylic acid, mandelic acid, phthalic acid, isophthalic acid, and terephthalic acid.

Examples of amino acids having 1 to 10 carbon atoms include carbamic acid, alanine, glycine, aspartic acid, aspartic acid, sarcosine, serine, glutamine, glutamic acid, 4-aminobutyric acid, iminodibutyric acid, arginine, leucine, isoleucine, and nitrilotriacetic acid. Is preferably mentioned.

A plurality of kinds of the above organic acids may be mixed and used. The acidic organic acid is preferably contained in an amount of 1% by mass or more and 10% by mass or less with respect to the total amount of the etching solution.

<Amine compound>
The amine compound is responsible for adjusting the pH of the etching solution. The etching solution according to the present invention improves the etching rate of molybdenum not only by oxidizing the copper film or molybdenum film by hydrogen peroxide but also by strong oxidation by metal ions (capturing electrons from molybdenum). Therefore, the metal ion needs to exist in the ionic state. Therefore, it is necessary to control the pH of the etching solution to 1 to 5. The amine compound regulates the pH for this.

Examples of the amine compound include the following substances.
As the amine compound, a compound having 2 to 10 carbon atoms can be preferably used. More specifically, ethylenediamine, trimethylenediamine, tetramethylenediamine, N, N, N, N-tetramethylethylenediamine, 1,2-propanediamine, 1,3-propanediamine, N, N, N, N- Tetramethyl-1,3-propanediamine, N, N-dimethyl-1,3-propanediamine, N, N-diethyl-1,3-propanediamine, 1,3-diaminobutane, 2,3-diaminobutane, Pentamethylenediamine, 2,4-diaminopentane, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, N-methylethylenediamine, N, N-dimethylethylenediamine, trimethylethylenediamine, N-ethylethylenediamine, N, N -Diethylethylenediamine, triethylethylenediamine, 1,2,3-triaminopropane, hydrazine, tris (2-aminoethyl) amine, tetra (aminomethyl) methane, diethylenetriamine, triethylenetetramine, tetraethylpentamine, heptaethyleneoctamine, Polyamines such as nonaethylenedecamine, diazabicycloundecene; ethanolamine, N-methylethanolamine, N-methyldiethanolamine, N-ethylethanolamine, N-aminoethylethanolamine, N-propylethanolamine, N-butyl Ethanolamine, diethanolamine, triethanolamine, 1-amino-2-propanol, N-methylisopropanolamine, N-ethylisopropanolamine, N-propylisopropanolamine, 2-aminopropane-1-ol, N-methyl-2- Amino-Propane-1-ol, N-Ethyl-2-amino-Propane-1-ol, 1-Aminopropane-3-ol, N-Methyl-1-Aminopropane-3-ol, N-Ethyl-1- Aminopropane-3-ol, 1-aminobutane-2-ol, N-methyl-1-aminobutane-2-ol, N-ethyl-1-aminobutane-2ol, 2-aminobutane-1-ol, N-methyl- 2-Aminobutane-1-ol, N-ethyl-2-aminobutane-1-ol, 3-aminobutane-1-ol, N-methyl-3-aminobutane-1-ol, N-ethyl-3-aminobutane-1- All, 1-aminobutane-4-ol, N-methyl 1-aminobutane-4-ol, N-ethyl- 1-Aminobutane-4-ol, 1-amino-2-methylpropane-2-ol, 2-amino-2-methylpropane-1-ol, 1-aminopentane-4-ol, 2-amino-4-methyl Pentan-1-ol, 2-aminohexane-1-ol, 3-aminoheptane-4-ol, 1-aminooctane-2-ol, 5-aminooctane-4-ol, 1-aminopupan-2,3- Diol, 2-aminopropane-1,3-diol, tris (oxymethyl) aminomethane, 1,2-diaminopropane-3-ol, 1,3-diaminopropane-2-ol, 2- (2-aminoethoxy) ) Ethanol, 2- (2-aminoethylamino) ethanol, alkanolamines such as diglycolamine are preferably mentioned, and these can be used alone or in combination of two or more.

Further, the amine compound is preferably contained in an amount of 0.5% by mass or more and 4.5% by mass or less, more preferably 1.5% by mass or more and 3.5% by mass or less, based on the total amount of the etching solution. ..

<Hydrogen peroxide decomposition inhibitor>
The etching solution for a multilayer film according to the present invention uses hydrogen peroxide as an oxidizing agent. Since hydrogen peroxide self-decomposes, a decomposition inhibitor that suppresses the decomposition is added. The hydrogen peroxide decomposition inhibitor is also referred to as a hydrogen peroxide stabilizer (or "hyperhydrogen peroxide stabilizer").

Examples of the hydrogen peroxide decomposition inhibitor include 2-butoxyethanol (ethylene glycol monobutyl ether), phenylurea, allylurea, 1,3-dimethylurea, thiourea, phenylacetateamide, phenylethylene glycol, 1-propanol, and 2 -Propanol and the like can be preferably used.

In particular, ethylene glycol monobutyl ether (CAS No. 111-76-2: also referred to hereinafter as "BG"), phenylurea (CAS No. 64-10-8), and 1-propanol (CAS No. 71-23-8). Is preferably used. This is because there is a strong tendency to maintain the etching rate even if the Cu concentration in the etching solution is high.

The hydrogen peroxide decomposition inhibitor is preferably 0.1% by mass or more and 2.0% by mass or less, and more preferably 0.5% by mass or more and 1.2% by mass or less with respect to the total amount of the etching solution.

<Molybdenum erosion promoting ion>
In the etching solution according to the present invention, iron ions or silver ions are used as molybdenum erosion promoting ions that take electrons from molybdenum and oxidize them to promote etching. A compound that supplies molybdenum erosion promoting ions is called a molybdenum erosion promoting agent.

As the molybdenum erosion accelerator having iron ions, iron chloride, iron nitrate, iron sulfate and the like can be preferably used. Further, as the molybdenum erosion accelerator having silver ions, silver chloride, silver nitrate, silver sulfate and the like can be preferably used. In particular, iron nitrate and silver nitrate can be preferably used from the viewpoint of disposal of the etching solution.

The content of molybdenum erosion promoting ions is preferably 0.08% by mass (80 ppm) or more and less than 1.0% by mass (10000 ppm), and 0.1% by mass (100 ppm) or more and 0.5% by mass, based on the total amount of the etching solution. It is more preferable if it is (5000 ppm) or less. The molybdenum erosion promoter that supplies molybdenum erosion promoter ions is supplied in the form of a salt, but the ratio of the molybdenum erosion promoter to the total amount of the etching solution changes depending on the anion ions in the salt. The adjustment may be adjusted by the composition ratio of water.

For example, when the molybdenum erosion promoting ion is silver ion and 0.08 g of silver ion (7.41 × 10 ^-4 mol) is supplied by silver nitrate, silver nitrate must be supplied by a weight of 0.126 g. However, when supplied with silver sulfate, the amount is 0.116 g. Both have the same number and weight of silver ions, but different weights as a salt (molybdenum erosion accelerator). This difference can be adjusted by the amount of water. This is because the amount of molybdenum erosion promoting ions is very small.

<Others>
In addition to these components, water as a solvent and various additives usually used as long as the etching performance is not impaired may be added to the etching solution according to the present invention. Further, azoles may be contained as an etching adjusting agent for the Cu film. Since water is intended for precision processing, it is desirable that water is free of foreign matter. Pure water or ultrapure water is preferable. Needless to say, the range of the content ratio of each component described above is appropriately adjusted so that the total amount of the etching solution is 100% by mass.

Further, since the etching solution according to the present invention contains metal ions, it is desirable to adjust the pH of the etching solution to the range of 1 to 5.

<Changes in molybdenum etching rate due to metal ions>
As the object to be etched, a film of molybdenum (300 nm) formed on a Si substrate was used. This is called a "molybdenum film sample".

The composition of the etching solution varies depending on the purpose, but the composition is as follows as the basic composition of the copper / molybdenum two-layer film (hereinafter referred to as "sample basic composition solution 1").

(Sample basic composition liquid 1)
Hydrogen peroxide 5.8% by mass,
As an inorganic acidic substance
1.3% by mass of nitric acid,
As an organic acidic substance
1.7% by mass of malonic acid,
As an amine compound
NNDPA (N, N-diethyl-1,3-propanediamine) 2.5% by mass,
As a hydrogen peroxide stabilizer
BG 0.7% by mass,
The rest were water and molybdenum erosion promoting ions. The molybdenum erosion promoting ion is 80 ppm or more and does not exceed 1.0% by mass with respect to the total amount of the sample basic composition liquid 1. This is because if the amount of molybdenum erosion promoting ions is too large, the decomposition of hydrogen peroxide will proceed too much even if the hydrogen peroxide stabilizer is added.

(Example 1)
Nitrate of silver, iron, zinc, copper, manganese, nickel and aluminum was prepared as a metal ion supply source in the sample basic composition liquid 1 so that each metal ion was 1000 ppm (0.1% by mass). Each sample etching solution is a silver solution (meaning that silver nitrate is prepared as a metal ion supply source so that the silver ion content is 1000 ppm. The same applies hereinafter), iron solution, zinc solution, copper solution, manganese solution, nickel solution, It was made of aluminum liquid. The reference liquid was used without a metal ion supply source.

A molybdenum film (300 nm) sample was immersed while maintaining each sample etching solution at 30 ° C., and observation was performed until the molybdenum film was completely dissolved, and the etching rate of molybdenum was calculated. The results are shown in Table 1.

It was silver ion, iron ion and copper ion that were effective in improving the etching rate of molybdenum, and zinc ion, manganese ion, nickel ion and aluminum ion had almost the same etching rate as the reference solution. In particular, silver ions and iron ions have been found to be effective in increasing the etching rate of molybdenum.

From the above experiments, silver ions and copper ions were used as molybdenum erosion promoting ions, and a metal ion supply source capable of supplying molybdenum erosion promoting ions was used as a molybdenum erosion promoting agent. For reference, 1000 ppm (0.1% by mass) of silver ions and iron ions are 0.018 mol% and 0.035 mol%, respectively, in the sample basic composition solution 1, and the weight% described below is also the same. Can be converted to mol%.

(Example 2)
Next, the concentrations of silver ions and iron ions were changed, and how the etching rate of molybdenum was converted was confirmed. The same molybdenum film sample as in Example 1 was used for etching.

The results for silver ions are shown in Table 2, and the results for iron ions are shown in Table 3. A "copper film sample" in which Cu was deposited at 600 nm on a Si substrate was prepared and immersed in a sample solution containing 1000 ppm of silver ions in Table 2 and 1000 ppm of iron ions in Table 3. The etching rate of Cu was also measured. The temperature of each sample solution was maintained at 30 ° C.

With reference to Table 2, the silver ion was 10 ppm and had a rate of 71 [nm / min], and the etching rate of molybdenum was higher than 14 [nm / min] of the reference solution (see Example 1). In addition, the higher the silver ion concentration, the higher the etching rate of molybdenum. However, at 8000 ppm (0.8 mass%), silver was deposited. Therefore, silver ions are at least 10 ppm or more and less than 8000 ppm (9.26 × 10 ^-6 mol or more and less than 7.41 × 10 ^-3 mol per 100 g of etching solution), more preferably 80 ppm or more and 5000 ppm or less (7.41 per 100 g of etching solution). It was available in × 10 ^-5 mol or more and 4.63 × 10 ^-3 mol or less). Note that 80 ppm is a value at which the etching rate of molybdenum becomes 90 nm / min or more, which is a value practically required. That is, from the experimental results, no Mo residue was confirmed when the etching rate of molybdenum was 90 nm / min or more.

On the other hand, referring to Table 3, iron ions showed an etching rate of 90 [nm / min] at 100 ppm, and the higher the iron ion concentration, the higher the etching rate of molybdenum. However, at 10,000 ppm (1.0% by mass), abnormal decomposition of hydrogen peroxide occurred, and the etching solution could not be maintained. Therefore, iron ions are 100 ppm or more and less than 10,000 ppm (1.79 × 10 ^-4 mol or more and less than 1.79 × 10 ⁻² mol per 100 g of etching solution), more preferably 100 ppm or more and 9000 ppm or less (1.79 × per 100 g of etching solution). It was available in 10 ^-4 mol or more and 1.61 × 10 ^-2 mol or less). It has been confirmed that abnormal decomposition of hydrogen peroxide does not occur at 9000 ppm.

Further, in the etching solution containing 1000 ppm of silver ions, the etching rate of copper was 637 nm / min, and in the absence of silver ions, it was 542 nm / min. In the etching solution containing 1000 ppm of iron ions, the etching rate of copper was 610 nm / min, and in the absence of iron ions, it was 563 nm / min.

That is, the presence of silver ions increased the etching rate of copper by about 18%, and the presence of iron ions increased the etching rate of copper by about 8%. However, this difference in the etching rate of copper ions can be sufficiently adjusted by the type and amount of the amino compound and the organic acid substance.

(Example 3)
Next, the effect of molybdenum erosion promoting ions was confirmed by actual etching of the two-layer film.
As the object to be etched, molybdenum having a film thickness of 30 nm and copper having a film thickness of 450 nm were sequentially formed on a Si substrate, and a part of which was partially coated with a photoresist so as to form a step was used. This is called a "double layer film sample".

The etching solution has the following composition, and this etching solution is referred to as "sample basic composition solution 2".
(Sample basic composition liquid 2)
Hydrogen peroxide at 5.81% by mass,
As an inorganic acidic substance
1.84% by mass of nitric acid,
As an organic acidic substance
3.0% by mass of malonic acid,
As an amine compound
TMEDA (N, N, N, N-tetramethylethylenediamine) 3.0% by mass,
As a hydrogen peroxide stabilizer
BG 0.88% by mass,
650 ppm of iron ions as molybdenum erosion promoting ions,
The rest was water. As iron ions, iron (III) nitrate hydrate [Fe (NO ₃ ) _{3.9H 2} O] (molybdenum erosion accelerator) was added in an amount of 0.47% by mass. Therefore, water is 85.0% by mass.

In addition, an etching solution containing no molybdenum erosion promoting ions was prepared as a "comparative example sample solution".

(Comparative example sample liquid)
Hydrogen peroxide at 5.81% by mass,
As an inorganic acidic substance
1.84% by mass of nitric acid,
As an organic acidic substance
3.0% by mass of malonic acid,
As an amine compound
TMEDA (N, N, N, N-tetramethylethylenediamine) 3.0% by mass,
As a hydrogen peroxide stabilizer
BG 0.88% by mass,
The rest was water. Water is 85.47% by mass.

The sample basic composition liquid 2 and the comparative sample liquid were maintained at a temperature of 35 ° C., and the two-layer membrane sample was immersed in each for 110 seconds. The just etch was the time when the substrate (Si) in the portion without the photoresist was visually confirmed.

The results are shown in FIG. FIG. 1 is an image taken on the Si substrate of the treated double-layer film sample. With reference to FIG. 1, FIG. 1A is the case of the sample basic composition liquid 2, and FIG. 1B is the case of the comparative sample liquid. The scale line is 500 nm. The just etch times were 48 seconds and 53 seconds, respectively.

In the case of the sample basic composition liquid 2 of FIG. 1 (a), it was observed that almost molybdenum was removed with only a small amount of molybdenum residue observed on the Si substrate. On the other hand, in the comparative sample solution of FIG. 1 (b), it was observed that molybdenum of about 50 nm remained in an island shape on the Si substrate. As described above, it was possible to solve the problem that the etching rate of molybdenum is increased by the presence of molybdenum erosion promoting ions and the etching residue of molybdenum remaining on the substrate remains.

The present invention can be suitably used for etching a two-layer film of molybdenum and copper.

Claims (3)

An etching solution that etches a two-layer film of copper and molybdenum.
With hydrogen peroxide,
With acidic substances
Amine compounds and
Hydrogen peroxide decomposition inhibitor and
An etching solution characterized by having molybdenum erosion promoting ions. The etching solution according to claim 1, wherein the molybdenum erosion promoting ion is an iron ion. The etching solution according to claim 1, wherein the molybdenum erosion promoting ion is a silver ion.

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