JPH07324199A - Cleaning composition and method for cleaning semiconductor substrate using same - Google Patents

Abstract

PURPOSE:To obtain a safe cleaning compsn. which exerts a high cleaning power on stains, such as those due to a metal or particles, without degrading electrical characteristics by compounding an electrolytic ionic water with a complexing agent and, if necessary, a dispersant. CONSTITUTION:A cleaning compsn. contains an electrolytic ionic water obtd. by electrolyzing water [an acidic water having a strong oxidizing power and formed on the anode side or an alkaline water having a strong reducing power and formed on the cathode side, both being formed by installing a porous partition film at the center of a water vessel filled with water, immersing the electrodes in both sides of the partition, and applying a voltage (usually 2-10V) to conduct electrolysis], a complexing agent (one which forms a complex with a metal which degrades electrical characteristics, pref. a combination of at least two complexing agents including a first component which forms a highly water-sol. complex and a second component which forms a complex specifically with a metal with a high electronegativity), and, if necessary, a dispersant. The compsn. can completely remove stains on a substrate at low temps. without degrading electrical characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning composition comprising electrolytic ionized water and a complexing agent and / or a dispersant, and a method for cleaning a semiconductor substrate using the cleaning composition.

[0002]

2. Description of the Related Art In recent years, fine processing technology typified by integrated circuits has been improved more and more in precision. Taking dynamic random access memory (DRAM) as an example, the design rule is now submicron. Processing technology is established as a mass production level technology.

In such a fine pattern, the contamination existing on the substrate has a serious adverse effect on the processing accuracy and hence on the yield. It is customary to use such cleaning agents to remove such contaminants before use. As the degree of integration of integrated circuits and the like has improved, stricter requirements have been placed on the level of contamination removal required in the cleaning process, due to the miniaturization of patterns and the complication of irregularities.

[0004]

An acidic cleaning solution represented by sulfuric acid or hydrochloric acid or an alkaline cleaning solution represented by ammonia usually has a high cleaning effect because it is usually used at a high temperature, but the danger of chemicals and corrosion. The load on the cleaning device is large due to the nature and the like. In addition, there is a problem that the waste liquid treatment after cleaning requires a huge cost.

In order to solve these problems, a method of cleaning a semiconductor substrate using electrolytic ionized water obtained by electrolyzing water has been proposed (JP-A-6-260480). According to this method, contamination on the wafer is cleaned by properly using acidic water having strong oxidizing property on the anode side and alkaline water having strong reducing property on the cathode side. Also, the processing temperature is 5
Easy to handle at a relatively low temperature of 0 to 70 ° C.

However, even if these materials are used for cleaning, the cleaning power is not sufficient and a small amount of residue remains, so that the electrical characteristics of the semiconductor are deteriorated and the yield is lowered. There is. In view of the above background, the object of the present invention is to improve the properties of the electrolytically-ionized water that have already been proposed, to completely remove the contamination on the substrate at low temperatures without causing the deterioration of electrical properties, and to ensure safety. Therefore, it is an object of the present invention to provide a cleaning composition which is easy to treat waste liquid, and a semiconductor substrate cleaning method using the same.

[0007]

Means for Solving the Problems As a result of various studies to solve the above-mentioned problems, the present inventors have found that a specific additive is added to electrolytic ionic water obtained by electrolyzing water. The inventors have found that the contamination on the substrate is completely removed and the electrical characteristics are not deteriorated, and have reached the present invention.

That is, the gist of the present invention is to use a cleaning composition containing electrolytic ionic water obtained by electrolyzing water and a complexing agent and / or a dispersant, and the cleaning composition. A method of cleaning a semiconductor substrate is characterized in that the semiconductor substrate is cleaned by means of a cleaning method. Hereinafter, the present invention will be described in detail. The electrolyzed ion water in the present invention means that an electrolytic cell is filled with water (pure water), a porous membrane-like partition wall is installed in the center, electrodes are immersed on both sides to apply a voltage, and electrolysis is performed. The acidic water with strong oxidizing power generated on the anode side or the alkaline water with strong reducing power generated on the cathode side is extracted and used.

As the electrode, a noble metal electrode, such as platinum, which hardly elutes the metal is used, but other high purity carbon electrode may be used. During electrolysis, the voltage is usually 2-10
The decomposition time is V and the decomposition time is not particularly limited and may be an appropriate time, but is preferably 0.5 to 2 hours. If the time is shorter than the above time, the electrolysis is not sufficient, and if it is too long, the effect is not improved and it is meaningless.

When the specific resistance of water is large and a sufficient current does not flow, a supporting electrolyte is added to water. One of the preferred embodiments of the present invention is a method of adding a supporting electrolyte to ultrapure water. An electrolyte having a high degree of ionization is used as the supporting electrolyte. Further, an electrolyte containing metal ions is not preferable because the metal ions of the electrolyte may become a contamination source of the semiconductor substrate. Specific examples of the supporting electrolyte include ammonium nitrate, ammonium acetate, ammonium chloride and the like, and ammonium chloride is particularly preferable. The amount of the supporting electrolyte added is usually 5 mmol / l.
It is below, preferably 1 to 5 mmol / l.

The complexing agent used in the present invention is selected to form a complex with a metal that causes deterioration of electrical properties.
Examples of such a complexing agent include ethylenediamine-
N, N, N ′, N′-tetraacetic acid (EDTA) diammonium salt, diethylenetriamine-N, N, N ′, N ″,
N "-pentaacetic acid (DTPA), triethylenetetramine-
N, N, N ', N ", N'", N '"-hexaacetic acid (TTH
A), ethylenediamine-N, N'-diacetic acid (EDD
A), an aminopolycarboxylic acid type chelating agent such as ethylenediamine-N, N'-dipropionic acid dihydrochloride (EDDP), 3-phenyl-5-mercapto-1,3,4-thiadiazole-2-thione ammonium salt Chelating agents such as ethylenediamine-N, N, N ′, N′-tetrakis (methylenephosphonic acid) (EDTPO), nitrilotris (methylenephosphonic acid) triammonium salt (NTP
O) or the like, a phosphonic acid-based chelating agent, a condensed phosphoric acid-based compound such as tripolyphosphoric acid, or a complexing agent having an ion having a high complex-forming ability such as hydrochloric acid, or 3-phenyl-5-
Examples thereof include complexing agents that specifically form a complex with a metal having a high electronegativity such as mercapto-1,3,4-thiadiazole-2-thione ammonium salt.

The addition amount of the complexing agent is usually 0.01
~ 2 wt%, preferably 0.05-0.5 wt%
Is. If the amount added is too small, the complex-forming effect is poor, and if the amount is too large, no further effect can be obtained, rather,
This is not preferable because it may contaminate the object to be cleaned such as the surface of the semiconductor substrate.

Further, in the present invention, it is more preferable to add two or more kinds of complexing agents in combination. The first component produces a highly water-soluble complex, and the second component is an electrode. It is preferable to add a substance that specifically forms a complex with a metal having a high electronegativity as used in the material. That is, as the first component, an aminocarboxylic acid type chelating agent such as EDTA diammonium salt, DTPA, TTHA, EDDA, and EDDP, EDTPO, and NTPO.
And a complexing agent having an anion that forms a complex with a metal, such as phosphonic acid-based chelating agent such as tripolyphosphoric acid, condensed polyphosphoric acid such as tripolyphosphoric acid or a salt thereof, or hydrochloric acid, and the like. Examples thereof include those that specifically form a complex with a highly concentrated metal, that is, 3-phenyl-5-mercapto-1,3,4-thiadiazole-2-thione ammonium salt and the like.

The amounts of these added are the first component and the second component.
The content of each component is usually 0.01 to 1% by weight, preferably 0.05 to 0.5% by weight. If the amount is less than the above amount, the complex-forming effect is poor, and if the amount is too large, no further effect can be obtained. Rather, the surface of the semiconductor substrate may be contaminated, which is not convenient.

In the present invention, when a complexing agent that specifically forms a complex with a metal having a high electronegativity, such as that used in an electrode material, is used as the second component of the complexing agent,
Instead of adding this to electrolytic ionized water, electrolytic ionized water treated with the above complexing agent may be used. As such a treatment method, for example, a method of passing the electrolytic ionic water through a column filled with a complexing agent that specifically forms a complex with a metal having a high electronegativity is used.

As the dispersant in the present invention, well-known surfactants can be mentioned, and anionic surfactants are particularly preferable from the viewpoint of the effect of the present invention. Examples of such anionic surfactants include hydrocarbon-based surfactants such as ammonium lauryl sulfate ester and ammonium salts of alkylbenzene sulfonate, fluorine-based surfactants such as perfluoroalkyl sulfonic acid, and condensed phosphoric acid-based surfactants. Examples thereof include surfactants.

The reason why such a dispersant is preferably used has not been clarified yet, and each dispersant plays a role of imparting an excellent cleaning ability. Among them, a hydrocarbon surfactant is particularly preferable after cleaning. The residue has a small effect on the electrical characteristics, and the fluorine-based surfactant is excellent in long-term stability. In addition, condensed phosphoric acid is preferable because it has less residue after washing.

The amount of the dispersant added is usually 0.01.
~ 1% by weight, preferably 0.05 to 0.5% by weight
Is. If it is less than the above-mentioned addition amount, the dispersing action is poor, and if it is too much, no further effect is obtained, and the surface of the semiconductor substrate may be contaminated, which is not preferable.

In the present invention, only one of the complexing agent and the dispersant may be added, but more preferably the complexing agent and the dispersant are used in combination. When used in combination, the complexing agent and the dispersant are added in an appropriate combination, but it is preferable to avoid a combination that reacts to form an insoluble matter.

As a method for preparing the cleaning composition of the present invention,
There is no particular limitation, and either a method of adding a complexing agent and a dispersant before electrolyzing water or a method of adding a complexing agent and a dispersant after electrolyzing water. The electrolyzed ionic water, complexing agent and dispersant used in the present invention are used in the semiconductor manufacturing process, and therefore high purity ones are used.

The reason why the cleaning composition of the present invention exerts a good effect is not yet clear, but in the case of conventional cleaning with electrolytic ionic water, the charge of the silicon wafer and the particles are different in positive and negative in acidic water. As a result, electrostatic force is generated and particles are likely to adhere, and for metals, active species in electrolyzed ionized water are smaller than in conventional acid cleaning methods, and when the contamination is severe, the particles cannot be sufficiently cleaned and remain. In addition, the cleaning is insufficient, and in the case of alkaline water, the cleaning is insufficient because the metal is likely to form a hydroxide and easily remain on the wafer surface.
It is presumed that the electrical characteristics were deteriorated by either cleaning. Further, it is considered that the elution of noble metal such as platinum used as an electrode material had a bad influence on the wafer.
That is, since the cleaning composition of the present invention solves all of these problems, it is presumed that it exhibits an excellent cleaning effect.

Since the cleaning method in the present invention is wet cleaning with a cleaning liquid, a method of directly contacting the liquid with the semiconductor substrate is used. Examples of such cleaning methods include dip-type cleaning in which a cleaning tank is filled with a cleaning solution to immerse the semiconductor substrate, spray-type cleaning in which the semiconductor substrate is sprayed with the cleaning solution, and cleaning solution is dropped onto the semiconductor substrate and rotated at high speed. Spin cleaning and the like can be mentioned. In the present invention, an appropriate one of the above-mentioned cleaning methods is used, but dip-type cleaning in which a cleaning tank is filled with a cleaning liquid and the semiconductor substrate is immersed is preferably used.

The temperature of the cleaning liquid is set to an appropriate temperature, but it is usually in the range of 10 to 80 ° C. When used as a warm cleaning liquid, it is preferably 30 to 8
It is 0 degreeC, More preferably, it is 50-70 degreeC. If it is lower than the above temperature, the cleaning effect is not sufficient, and if it is too high, the cleaning liquid is volatilized, which is not preferable.

The washing time is not particularly limited, and washing is performed for an appropriate time, but it is preferably 3 to 20 minutes, more preferably 5 to 15 minutes. If the time is shorter than the above time, the cleaning effect is not sufficient, and if it is too long, the throughput is deteriorated, and the cleaning effect is not improved and is meaningless. Further, at the time of washing, a washing method using physical force may be used in combination. Examples of the cleaning method using such physical force include ultrasonic cleaning and mechanical cleaning using a cleaning brush.

[0025]

EXAMPLES Specific examples of the present invention will be described below with reference to examples, but the present invention is not limited to the following examples without departing from the scope of the invention. Reference Example-1 Preparation of Cleaning Composition 0.015% by weight of ammonium acetate was added to ultrapure water, and this was electrolyzed with a platinum electrode at a voltage of 5 V for 2 hours, and then acid water or alkaline water was added. Was extracted and the complexing agent or dispersant shown in Table 1 was added in the same proportion as shown in Table 1. Thus, cleaning compositions A to P (wherein P is for comparative example) were obtained.
For comparison, Q, R and S were prepared.

[0026]

[Table 1]

<Examples 1 to 12> The cleaning composition obtained in Reference Example 1 was filled in a cleaning tank and heated to 65 ° C., and a semiconductor substrate contaminated with metal was immersed for 10 minutes,
Then, it was rinsed with pure water for 5 minutes and then dried. afterwards,
The metal on the surface of the semiconductor substrate was recovered with a mixed solution of 0.1% hydrofluoric acid and 1% hydrogen peroxide, and the amount of the metal was measured by a flameless atomic absorption method and converted into a surface concentration. Table 2 shows the experimental results and the amount of metal before cleaning.

As a semiconductor substrate used for cleaning, a 5-inch wafer was used, and a metal contaminated with Fe, Cu and Al was prepared. In addition, in the case of Example-8, even when the cleaning composition was performed at 20 ° C without heating,
The same effect as was obtained.

[0029]

[Table 2]

<Examples 13 to 23> When the cleaning composition obtained in Reference Example 1 was filled in a cleaning tank and heated to 65 ° C., 0.3 μm PSL (polystyrene latex) was obtained.
A semiconductor substrate having about 1000 spheres attached was immersed for 10 minutes, rinsed with pure water for 5 minutes, and then dried. After that, the number of particles remaining on the semiconductor substrate was measured by a particle counter using a laser scattering method. Table 3 shows the experimental results and the amount of particles before cleaning.

A 5-inch wafer was used as a semiconductor substrate used for cleaning. In addition, in the case of Example-20, the case where the cleaning composition was carried out at 20 ° C without heating was also carried out in Example-20.
The same effect as was obtained.

[0032]

[Table 3]

<Comparative Example-1> As a comparative example, the residual contamination amount was measured using the cleaning liquids of P, Q, R, and S in the same manner as in the Examples. The residual amount was large, and particularly for Q and S, the residual amount of particles was large, and the electrical characteristics were significantly deteriorated. In addition, Q, R,
For S, the temperature of the cleaning tank is 25 ° C (Q), 80
℃ (R) and 130 ℃ (S).

Reference Example 2 0.015% by weight of ammonium chloride was added to ultrapure water, and this was added to 5% by using a platinum electrode.
After electrolysis for 2 hours at a voltage of V, extract the acidic water,
The complexing agent or dispersant shown in Table 4 was added in the same proportion as shown in Table 4. In this way, the cleaning composition T ~
Y (in which Y is for a comparative example) was obtained.

[0035]

[Table 4]

<Examples 24 to 33 and Comparative Examples 2 to 2>
3> Of the cleaning compositions obtained in Reference Examples 1 and 2, when a cleaning tank was filled with acidic water and heated to 65 ° C.,
A large number (about 10) of 0.3 μm PSL spheres
A semiconductor substrate on which both ¹⁴ atoms / cm ² of metal (Fe, Cu, Al) are attached is immersed for 10 minutes, and then pure water is applied for 5 minutes.
After rinsing for a minute, it was dried. Then, the number of particles remaining on the semiconductor substrate is measured by a particle counter using a laser scattering method, and then the metal on the surface of the semiconductor substrate is recovered with a mixed solution of 0.1% hydrofluoric acid and 1% hydrogen peroxide, The amount of the metal was measured by the less atomic absorption method and converted into the surface concentration. Table 5 shows the experimental results and the amount of particles and the amount of metal before cleaning. Further, in the case of Example-30, the same effect as in Example-30 was obtained even when the cleaning composition was heated at 20 ° C without heating.

[0037]

[Table 5]

[0038]

EFFECTS OF THE INVENTION The cleaning composition of the present invention is very good against contamination of metals, particles and the like with both acidic water and alkaline water due to the effect of the electrolytic ionic water and the complexing agent and / or dispersant. Since it exhibits excellent detergency, it does not cause deterioration of the electrical characteristics of the semiconductor. In addition, since it is safe and the wastewater treatment cost can be greatly reduced, it is a great advantage in industrial production of highly integrated circuits.

Claims (8)

[Claims] 1. A cleaning composition comprising electrolytic ionic water obtained by electrolyzing water and a complexing agent. 2. A cleaning composition comprising electrolytic ionic water obtained by electrolyzing water, a complexing agent and a dispersant. 3. The cleaning composition according to claim 1, wherein the content of the complexing agent is 0.01 to 2% by weight. 4. The complexing agent comprises a complexing agent having a high water-solubility of the produced complex and a complexing agent which forms a complex with a metal having a high electronegativity. The cleaning composition according to any one of 3 to 3. 5. A cleaning composition comprising electrolytic ionic water obtained by electrolyzing water and a dispersant. 6. The cleaning composition according to claim 2, wherein the content of the dispersant is 0.01 to 1% by weight. 7. The cleaning according to claim 1, wherein the electrolytic ionized water is treated with a complexing agent that forms a complex with a metal having a high electronegativity. Composition. 8. A semiconductor substrate according to claim 1.
7. A method for cleaning a semiconductor substrate, which comprises cleaning with the cleaning composition described in 1.