JP4419528B2 - Cleaning liquid and cleaning method using the same - Google Patents

Description

  The present invention relates to a cleaning solution for copper, and more particularly to a cleaning solution that does not attack copper, which is extremely useful for cleaning a copper wiring semiconductor device. The cleaning agent of the present invention relates to a cleaning solution capable of removing organic substances such as benzotriazole used as a copper rust preventive.

  In recent years, along with the rapid development of information technology, there is a trend toward miniaturization, high density, and high speed of large scale integrated circuits (LSI, ULSI, VLSI). Development is underway. In order to achieve multi-layer wiring, it is necessary to reduce the wiring pitch width and reduce the inter-wiring capacitance. As a solution for reducing the wiring pitch width, the current metal wiring materials tungsten and aluminum are more resistant. Technology development to change to low copper (Cu) has been energetically studied.

  In copper wiring, a damascene process by embedding tends to become mainstream. The planarization of the wiring embedded by the damascene method is performed by a so-called CMP (Chemical Mechanical Polishing) method using a mechanical polishing action and a chemical polishing action, and the copper wiring material is also polished by the same method. Has been.

  In the CMP method, after metal polishing, many particles such as abrasives and metal impurities adhere to the wafer, so it is necessary to clean the wafer surface.

  Conventionally, ammonia has generally been used in the case of metals other than copper, since cleaning with an alkaline solution can suppress the reattachment of impurities. However, copper is easily corroded by ammonia, and ammonia cannot be used as a cleaning agent.

  Therefore, in order to reduce the corrosion rate of copper, a method of adding a copper anticorrosive to ammonia has been proposed. For example, Patent Document 1 discloses a cleaning liquid in which a compound containing a mercapto group is added as an anticorrosive.

  Further, as shown in Patent Document 2, a cleaning agent using a compound obtained by adding water and / or a water-soluble organic solvent to morpholines as an anticorrosive agent has been proposed.

  However, as described in the publication, a compound containing a mercapto group has a peculiar unpleasant odor, and there is a problem in using it as an anticorrosive agent both environmentally and industrially. Aromatic compounds such as benzotriazole are known as other anticorrosive agents, but there are problems such as high toxicity and difficulty in removing benzotriazole once attached to copper. Further, these anticorrosives cannot suppress copper corrosion in a small amount, and the conventionally proposed ammonia-based cleaning solutions are not sufficient in terms of corrosiveness to copper and environmental problems.

  In particular, it is known that benzotriazole once attached to copper is difficult to remove. For example, Non-Patent Document 1 describes that benzotriazole forms a chelate with copper.

  Residue of benzotriazole formed with a chelate with copper caused a decrease in the yield of the semiconductor for copper wiring and had an adverse effect. Thus, benzotriazole prevents copper from being oxidized, but cannot be easily removed due to its strong adsorption. Non-Patent Document 1 describes the removal of benzotriazole under acidic conditions, but there is no description regarding the removal of benzotriazole under basic conditions, and benzotriazole is efficiently removed from a copper film under basic conditions. No cleaning solution is known.

  On the other hand, as an anticorrosive agent for copper, one having urea (derivative) and hydroxyaromatic as essential components has been proposed (Patent Document 3), and a CMP polishing slurry and a resist stripper using the same are known. However, if these do not contain hydroxy aromatics, the anticorrosive effect cannot be obtained, and resist stripping agents and polishing slurries are shown, but there is no suggestion about their use as cleaning liquids.

  On the other hand, a method using washing with dilute aqueous ammonia, a carboxylic acid having chelating ability, and an ammonium salt thereof has been proposed (Patent Document 4). However, such a method of washing in two steps is complicated and industrially problematic.

  Further, a cleaning agent having a copolymer such as a sulfonic acid group has been proposed (Patent Document 5). In the cleaning liquid, those containing ammonia as a cationic species and oxalic acid, citric acid and the like as a known detergent component are disclosed. However, a copolymer is indispensable for exerting the performance as a cleaning agent, and there has been no suggestion of a technique for extracting a cleaning function without adding such a component.

SCAS NEWS 2001-II, p7

JP 2000-273663 A (Claims) JP 2002-241895 A (Claims) JP 2001-207170 A JP-A-11-330023 JP 2001-64681 A

  As described above, until now, cleaning liquids containing alkali such as ammonia have had problems with copper corrosion, and conventional cleaning liquids that do not use alkali such as ammonia have had a problem of insufficient cleaning effect. It was. Accordingly, there has been a demand for a cleaning solution that has a high cleaning effect by using an alkali such as ammonia and that has no problem with copper corrosion resistance.

  An object of the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a cleaning liquid that does not attack copper, has excellent impurity removability, and has no precipitation of cleaning liquid components. An object of the present invention is to provide a cleaning liquid that removes organic substances such as benzotriazole without attacking copper under the condition of copper.

As a result of intensive studies on the cleaning liquid, the present inventors have found that a cleaning liquid containing water, a urea compound, an organic acid, and ammonia and / or quaternary ammonium hydroxide can be used as a cleaning liquid that does not attack the copper material. Furthermore, the present inventors have found that a cleaning liquid containing hydrogen peroxide is particularly excellent in the effect of removing benzotriazole without corroding copper, and has completed the present invention.

That is, the present invention is a cleaning liquid comprising water, urea and / or ethylene urea, an organic acid and / or salt thereof, and ammonia and / or quaternary ammonium hydroxide .

  The present invention is described in detail below.

The cleaning liquid of the present invention comprises water, urea and / or ethylene urea, an organic acid, ammonia and / or quaternary ammonium hydroxide .

  In the cleaning liquid of the present invention, only urea or ethylene urea is sufficient as an anticorrosive, and it is not necessary to add other anticorrosive ingredients as in the prior art. However, those containing other anticorrosive ingredients are not excluded as long as the functions of the present invention are not impaired.

  Urea and ethylene urea used in the cleaning liquid of the present invention may be used alone or in combination. These are generally commercially available and can be easily obtained. Urea and / or ethylene urea exhibits good anticorrosion performance and is also excellent in biodegradability.

  The organic acid used in the cleaning liquid of the present invention contains a carboxylic acid or a sulfonic acid, and salts of these organic acids can also be suitably used.

Specific examples of organic acids include carboxylic acids such as formic acid, acetic acid, oxalic acid, malonic acid, succinic acid, and phthalic acid, hydroxycarboxylic acids such as citric acid, malic acid, tartaric acid, lactic acid, glycolic acid, and salicylic acid, and methanesulfone. Acids, ethanesulfonic acid, p-toluenesulfonic acid, sulfonic acids such as 2,4-toluenedisulfonic acid, and salts thereof include metal salts such as sodium salts and potassium salts, ammonium salts, and the like. .
Of these, hydroxycarboxylic acids are preferred from the viewpoint of metal impurity removal ability and prevention of crystal precipitation of urea compounds, and citric acid, malic acid, and tartaric acid are particularly preferred. These organic acids have the function of removing metal impurities and preventing crystal precipitation of urea compounds on the metal surface. When the urea compound is used alone, it precipitates as a crystal on the metal surface and becomes difficult to remove only by washing with water, but it can prevent crystal precipitation by combining the organic acid of the present invention, and is particularly effective in ethylene urea. It is. These organic acids and / or salts thereof may be used alone or in combination of two or more. These are generally commercially available and can be easily obtained.

As ammonia and / or quaternary ammonium hydroxide used in the cleaning liquid of the present invention, those containing alkali metals such as Li, Na and K may not be preferable because they dislike metal impurities particularly in semiconductor applications. Includes quaternary ammonium hydroxides such as tetramethylammonium hydroxide, trimethyl (hydroxyethyl) ammonium hydroxide (commonly known as choline), and ammonia .

  In the present invention, hydrogen peroxide can be used for the purpose of removing a strong film such as benzotriazole used as an anticorrosive and an organic substance that is difficult to remove.

  As the hydrogen peroxide used in the cleaning liquid of the present invention, commercially available ones can be used. However, since high-purity products for semiconductors are also readily available, this high-purity hydrogen peroxide is used. Is preferred.

  The cleaning liquid of the present invention is generally made into an aqueous solution by adding water, but a water-soluble organic solvent may be added for the purpose of improving the cleaning power. As the water-soluble organic solvent, those generally used as a cleaning liquid can be used.

  Specifically, methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, benzyl alcohol, ethylene glycol, propylene glycol, polyethylene Alcohols such as glycol and 1-butoxy-2-propanol, amides such as N, N-dimethylformamide, N-methylpyrrolidone and dimethylimidazolidinone, sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane and diglyme And the like.

In the cleaning liquid of the present invention, in order to lower the surface tension and improve the hydrophilicity, further ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene Glycol propyl ether, propylene glycol butyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol propyl ether, diethylene glycol butyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether Alcohols, in particular, propylene glycol butyl ether, may contain any of diethylene glycol butyl ether. When these compounds are contained, the contact between the organic substance such as hydrophobic benzotriazole and the cleaning agent of the present invention is improved, the benzotriazole removability is improved, and the particle contamination removal ability in fine wiring such as a semiconductor device is improved. Can be increased.

  The pH of the cleaning liquid of the present invention is preferably 7.1 to 12, more preferably 7.5 to 11.5, particularly preferably 8.0, in that copper corrosion is suppressed and an excellent cleaning effect is obtained. 11.0.

The composition of the cleaning liquid of the present invention is urea and / or ethylene urea, organic acid and / or salt thereof, ammonia and / or quaternary ammonium hydroxide , hydrogen peroxide, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl. Ether, ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, propylene glycol butyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol propyl ether, diethylene glycol butyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl Ether, dipropylene glycol Pills ether, alcohols such as dipropylene glycol butyl ether, especially, propylene glycol butyl ether, can be adjusted to a predetermined pH with any combination of diethylene glycol butyl ether, the mixing ratio of these compounds, the compounds used The content of urea and / or ethylene urea is 0.001 to 60% by weight, the content of organic acid and / or its salt is 0.0001 to 10% by weight, and ammonia and / or quaternary ammonium hydroxide, depending on as the concentration of 0.0001 wt%, the content of hydrogen peroxide is preferably 30 wt% or less, and from 0.01 to 30 wt% as a preferable content when using hydrogen peroxide, ethylene Glycol methyl ether, ethylene glycol ethyl Ether, ethylene glycol propyl ether, ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, propylene glycol butyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol propyl ether, diethylene glycol butyl ether, dipropylene glycol methyl ether In the case of adding ether alcohols such as dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, especially propylene glycol butyl ether or diethylene glycol butyl ether , the content is 0 0.0001 to 10% by weight is preferable (the balance is water and the total amount is 100% by weight).

  Even if it is out of this range, it cannot be used if it has a predetermined pH, but there is a possibility that the particle removal performance is lowered, copper is corroded, and urea or ethylene urea crystals are precipitated.

  In the cleaning liquid of the present invention, each component may be added at the time of cleaning, or may be used after mixing each component in advance.

  The cleaning liquid of the present invention can be used for cleaning copper wiring semiconductor devices. When the cleaning liquid of the present invention is used, the corrosiveness to the copper wiring is small, and it is particularly effective for cleaning after CMP.

  The cleaning means that can be used in the present invention is not particularly limited, and known means such as running water cleaning, immersion cleaning, rocking cleaning, spinner cleaning, paddle cleaning, spray cleaning, ultrasonic cleaning, brush cleaning, and the like can be used. Can be used. Although the temperature at the time of washing is not particularly limited, it is preferably 10 ° C. to 100 ° C. from the viewpoints of corrosion inhibition, particle removability, and operability.

  The cleaning liquid of the present invention exhibits an excellent cleaning ability with respect to impurity removal properties, has no precipitation component of the cleaning liquid, can be used as a cleaning liquid that does not corrode copper, and further adheres to the copper surface by adding hydrogen peroxide. Since organic substances such as benzotriazole can also be removed, it can be used very effectively for cleaning semiconductor devices.

Hereinafter, the method of the present invention will be described with reference to examples, but the present invention is not limited thereto.
Examples 1-8, Comparative Examples 1-4
(Particle removability)
The copper-plated wafer was immersed in ultrapure water in which colloidal silica having an average particle diameter of 120 nm was dispersed, and then washed with ultrapure water adjusted to pH 6 with sulfuric acid. This was dried to obtain particles contaminated with silica particles. This wafer was immersed and washed in the cleaning liquid shown in Table 1 at 50 ° C. for 30 minutes, then washed with water and dried. The surface was observed with SEM (scanning electron microscope), and the number of silica particles per unit area was examined. The SEM used was JSM T220A manufactured by JEOL.

The particle removability was evaluated as follows.
○: Good removability △: Some remain ×: Most remain (copper corrosion)
The copper-plated wafer was immersed in a cleaning solution shown in Table 1 at 70 ° C. for 1 hour, then washed with water and dried. The film thickness of the Cu film before and after the immersion of the wafer was measured, and the dissolution rate was calculated from the amount of film thickness change to determine the corrosion prevention effect. Moreover, the surface before and behind immersion was observed with AFM (atomic force microscope), and the state of the Cu film | membrane surface was observed. For measuring the film thickness, a sheet resistance measuring device manufactured by Mitsubishi Chemical Corporation was used, and a method of converting the film thickness from the value of the sheet resistance value was used.

Copper corrosivity was evaluated as follows.
○: Thickness reduction less than 3 angstroms / minute Δ: Thickness reduction of 3-10 angstroms / minute ×: Thickness reduction of more than 10 angstroms / minute (urea compound precipitation)
The copper-plated wafer was immersed in a cleaning solution shown in Table 1 at 70 ° C. for 1 hour, then washed with water and dried. The surface of the wafer before and after immersion was observed with an AFM (atomic force microscope), and the state of the Cu film surface was observed. In addition, Seiko Instruments Inc. Nanopics was used for AFM. The results are shown in Table 1.

Examples 9-12, Comparative Examples 5-8
Particle removability, copper corrosivity, and urea compound precipitation were evaluated by the same method as in Example 1.
(Removability of organic substance (benzotriazole))
The copper-plated wafer was immersed in a 0.6 wt% 1,2,3-benzotriazole aqueous solution at room temperature for 1 hour and washed with water to obtain a copper wafer having 1,2,3-benzotriazole attached thereto. This wafer was subjected to ultrasonic cleaning for 10 minutes at room temperature in the cleaning liquid shown in Table 1 (the balance is water, and the total cleaning liquid is 100% by weight), and then washed with water and dried. The copper wafer was analyzed by XPS (X-ray photoelectron spectroscopy) to check for the presence of benzotriazole.

The 1,2,3-benzotriazole (BTA) removability was evaluated as follows in comparison with the BTA adhesion amount before cleaning. The results are shown in Table 1.
○: Remaining amount less than 5% Δ: Remaining amount less than 5-50% ×: Remaining amount 50%

Claims (8)

A cleaning solution comprising water, urea and / or ethylene urea, an organic acid and / or salt thereof, and ammonia and / or quaternary ammonium hydroxide . The organic acid and / or salt thereof is at least one selected from the group consisting of oxalic acid, malonic acid, citric acid, malic acid, succinic acid, phthalic acid, tartaric acid, lactic acid, glycolic acid and salts thereof. cleaning solution described in 1. The cleaning liquid according to claim 1 or 2, further comprising hydrogen peroxide. Ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, propylene glycol butyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol propyl ether, diethylene glycol butyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, any one of claims 1 to 3 further comprising at least one selected from the group consisting of dipropylene glycol butyl ether Cleaning solution described. The cleaning liquid according to any one of claims 1 to 4 , wherein the pH of the cleaning liquid is 7.1 to 12. The concentration of urea and / or ethylene urea is 0.001 to 60% by weight, the concentration of organic acid is 0.0001 to 10% by weight, the concentration of ammonia and / or quaternary ammonium hydroxide is 0.0001 to 10% by weight, Hydrogen peroxide concentration is 30% by weight or less, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, propylene glycol butyl ether, diethylene glycol Methyl ether, diethylene glycol ethyl ether, diethylene glycol propyl ether, diethylene glycol butyl ether, dipropylene glycol methyl Ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, washing liquid according to any one of claims 4 to 5 at least one selected from the group consisting of dipropylene glycol ether is 10 wt% or less. Cleaning method characterized by cleaning a semiconductor device using the cleaning solution according to any one of claims 1 to 6. The cleaning method according to claim 7 , wherein the semiconductor device has a copper wiring.