JPH07324198A - Cleaning composition and method for cleaning semiconductor substrate using the same - Google Patents

Abstract

PURPOSE:To obtain a safe cleaning compsn. which exerts a high cleaning power due to the effects of a fluorine compd. on a metallic stain and does not cause any degradation in electrical characteristics by incorporating an electrolytic ionic water and a fluorine compd. into the compsn. CONSTITUTION:A cleaning compsn. contains an electrolytic ionic water obtd. by electrolyzing water [an acidic water having a strong oxidizing power and formed on an anode side or an alkaline water having a strong reducing power and formed on a cathode side, the acidic or alkaline water 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] and a fluorine compd. (e.g. a mixture contg. 0.00001-10wt.% hydrofluoric acid and 1--4wt.% ammonium fluoride). Pref. the amt. of the fluorine compd. added is about 0.1-50wt.% of the compsn. The electrolytic ionic water exerts a very strong cleaning power on a metallic stain in the presence of the fluorine compd., does not cause any degradation in electrical characteristics, is safe, and enables a remarkable cost reduction in waste water treatment.

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 ionic water and a fluorine compound, and a semiconductor substrate cleaning method using the same.

[0002]

2. Description of the Related Art In recent years, microfabrication technology typified by integrated circuits has been increasingly improved in machining accuracy. Taking dynamic random access memory (DRAM) as an example,
At present, submicron processing technology is established as a mass production level technology as a design rule.

In such a fine pattern, the contamination existing on the wafer has a serious adverse effect on the processing accuracy and hence the yield, so that sulfuric acid, hydrochloric acid, ammonia, hydrogen peroxide, etc. are used in each step such as etching and ion implantation. It is customary to use such cleaning agents to remove such contaminants before use. As the degree of integration of the integrated circuit is improved, finer patterns and more complicated irregularities are combined with more stringent requirements for the level of contamination removal required in the cleaning process.

Acids typified by sulfuric acid and hydrochloric acid, and alkaline cleaning solutions typified by ammonia are usually used at a high temperature, so that they have a high cleaning effect, but they affect the cleaning device due to the danger of chemicals and corrosiveness. The burden is heavy. 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. 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. Moreover, the treatment temperature is relatively low at 50 to 70 ° C., which is easy to handle.

However, even if these materials are used for cleaning, the cleaning power is still insufficient and contamination remains.
There is a problem that the electrical characteristics of the semiconductor are deteriorated, and eventually the yield is reduced.

[0007]

SUMMARY OF THE INVENTION In view of the above background, an object of the present invention is to improve the characteristics of the electrolytic ion water that has already been proposed, and to completely remove the contamination on the semiconductor substrate at a low temperature so that the electrical characteristics can be improved. It is an object of the present invention to provide a cleaning composition that does not cause deterioration of the above, is safe, and can be easily treated with a waste liquid, and a semiconductor substrate cleaning method using the same.

[0008]

As a result of various studies to solve the above problems, the present inventors have found that a cleaning composition comprising electrolytic ionic water obtained by electrolyzing water and a fluorine compound. The present invention has been completed by finding that the contamination is almost completely removed and the electrical characteristics are not deteriorated when the cleaning is performed by using.

The present invention will be described in detail below. The electrolyzed ion water in the present invention is filled with water in a water tank, a porous membrane-like partition wall is installed in the center thereof, electrodes are immersed on both sides to apply a voltage, electrolyze, and generate on the anode side. The acidic water having a strong oxidizing power or the alkaline water having a 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 2-1
It is carried out at 0 V, and the decomposition time is carried out for an appropriate time, but 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. As the supporting electrolyte, one having a high degree of ionization is selected. Further, an electrolyte containing metal ions is not preferable because the metal ions of the supporting electrolyte may become a contamination source. Specific examples of the supporting electrolyte include ammonium nitrate, ammonium chloride, ammonium acetate and the like, and ammonium chloride is particularly preferable. The addition amount of the supporting electrolyte is usually 1 to 5 mmol / l.

The fluorine compound used in the present invention can be an active species for decomposing silicon oxide usually used for semiconductor substrates. Examples of such a fluorine compound include hydrofluoric acid and ammonium fluoride. And it is preferable to use at least one of these. Most preferred is the combined use of hydrofluoric acid and ammonium fluoride.

The amount of the fluorine compound added is not particularly limited, but is preferably about 0.1 to 50% by weight based on the entire cleaning composition. When hydrofluoric acid is added as a fluorine compound, an appropriate amount of hydrofluoric acid is used, but it is preferably 0.00001 to 10% by weight, more preferably 0.0001 to 5% by weight. On the other hand, when ammonium fluoride is added, an appropriate amount is used as the ammonium fluoride concentration, but preferably 1 to
It is 40% by weight. In the cleaning process for removing the natural oxide film, a cleaning liquid having a hydrofluoric acid concentration of 0.1% by weight or more is usually preferably used. On the other hand, in the cleaning process after the oxide film pattern is formed, in order to prevent side etching, In the rinse process after removing the natural oxide film, a low concentration cleaning liquid having a hydrofluoric acid concentration of 0.1 wt% or less is preferably used as the minimum concentration for preventing the growth of the natural oxide film. Needless to say, it is preferable to use as low a concentration as possible from the viewpoint of waste liquid treatment and environmental protection.

In the present invention, electrolyzed ionic water, hydrofluoric acid, and ammonium fluoride are used in the semiconductor manufacturing process, and therefore high purity ones are used. The cleaning composition of the present invention can be obtained by adding a fluorine compound to the above-mentioned electrolytic ionic water. The fluorine compound may be added either before or after electrolysis,
Addition to ultrapure water before electrolysis and subsequent electrolysis are more preferable because the fluorine compound itself acts as an electrolyte.

Further, when the cleaning composition of the present invention is used to clean a large amount of or a contaminant which is difficult to remove, it is more preferable to carry out electrolysis after adding a well-known supporting electrolyte. Examples of such electrolytes include ammonium chloride, ammonium nitrate, ammonium acetate and the like.

The reason why the cleaning composition of the present invention exerts a good effect is not yet clear, but the conventional electrolytic ionic water cleans the metal contamination adhering to the outermost surface, but the surface is oxidized. The internal contamination of Fe, Cu, etc. taken into the film could not be cleaned, whereas the cleaning composition of the present invention has the ability to decompose the oxide film on the silicon surface, and thus such internal pollution is caused. Since it can also be washed, it is presumed that it exhibits an excellent washing effect.

Further, in the present invention, a surfactant may be further added. As such a surfactant,
For example, anionic surfactant, nonionic surfactant,
Examples include cationic surfactants, and specific examples include:
Examples thereof include alkylbenzenesulphonic acid ammonium salt and polyoxyethylene nonylphenyl ether. As an added amount, an appropriate amount is used, but preferably,
It is 0.01 to 1% by weight. The addition of the surfactant has the effect of reducing the microroughness of the substrate surface while maintaining the ability to remove contaminants.

The cleaning composition of the present invention is suitable for cleaning a semiconductor substrate. As a method of cleaning a semiconductor substrate in the present invention, wet cleaning with a cleaning liquid is used, and a method of directly contacting the liquid with the semiconductor substrate is used. To be 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 solution is set to an appropriate temperature, but it is usually in the range of 10 to 80 ° C. When used as a warm cleaning solution, it is preferably 30 to 8
It is 0 degreeC, More preferably, it is 50-70 degreeC. If the temperature 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 also 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.

[0021]

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. (Examples-1 to 3 and Comparative Examples-1 to 4) Table for ultrapure water-
Hydrofluoric acid and ammonium fluoride were added in the proportions shown in 1 and electrolyzed using a platinum electrode at a voltage of 5 V for 2 hours, and then acidic water was extracted to prepare a cleaning composition.

[0022]

[Table 1]

Then, the cleaning composition is filled in a cleaning tank,
The semiconductor substrate contaminated by heating to 65 ° C.
After soaking for 5 minutes, rinsing with pure water for 5 minutes, and then drying, the surface metal was collected with a mixed solution of hydrofluoric acid and hydrogen peroxide, and the amount of metal was measured by the flameless atomic absorption method and converted into the surface concentration. . As the semiconductor substrate used for cleaning, a 5-inch wafer was used, and a metal contaminated with Fe and Cu was prepared.

Further, as a comparative example, the same cleaning is performed with a cleaning solution in which hydrofluoric acid and ammonium fluoride are simply added to ultrapure water and electrolysis is not performed, and electrolytic ion water to which hydrofluoric acid and ammonium fluoride are not added. I did.
Table 2 shows the experimental results and the amount of contamination before cleaning. In addition, about Example-3, even when it wash | cleaned at 20 degreeC, without heating a cleaning composition, the effect similar to Example-3 was exhibited.

[0025]

[Table 2]

(Examples 4 to 11 and Comparative Examples 5 to 8) Hydrofluoric acid, ammonium fluoride and ammonium chloride were added to ultrapure water at the ratios shown in Table 3, and platinum electrodes were used. After electrolysis at a voltage of 5 V for 2 hours, acidic water was extracted and a cleaning composition was prepared.

[0027]

[Table 3]

Then, the cleaning composition is filled in a cleaning tank, and the contaminated wafer is immersed in a place heated to 65 ° C. for 10 minutes, rinsed with pure water for 5 minutes, and then dried to convert the surface metal to hydrofluoric acid. It was recovered with a mixed solution of hydrogen peroxide, the amount of metal was measured by the flameless atomic absorption method, and converted into the surface concentration.
Further, the same cleaning evaluation was performed with the cleaning liquids used in Examples-1 to 3. The semiconductor substrate used for cleaning is 5
Inch wafers were used, and a larger amount of Fe,
What was contaminated with Cu was prepared.

As a comparative example, a cleaning solution in which hydrofluoric acid, ammonium fluoride and ammonium chloride were simply added to ultrapure water and electrolysis was not performed and electrolysis in which hydrofluoric acid, ammonium fluoride and ammonium chloride were not added The same washing was performed with ionized water. Table 4 shows the experimental results and the amount of contamination before cleaning. Regarding Example-6, even when the cleaning composition was washed at 20 ° C without heating, the same effect as that of Example-6 was exhibited.

[0030]

[Table 4]

(Example-12) The same cleaning was carried out by using the cleaning solution used in Example-2 with 0.1% by weight of ammonium alkylbenzene sulfonate added. This was exactly the same as in Example-2, and the microroughness of the wafer surface was reduced.

[0032]

The electrolyzed ionized water of the present invention exerts a very good detergency against metal contamination due to the effect of hydrofluoric acid or ammonium fluoride, and therefore does not cause deterioration of electrical characteristics. 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 (5)

[Claims] 1. A cleaning composition comprising electrolytic ionic water obtained by electrolyzing water and a fluorine compound. 2. The cleaning composition according to claim 1, wherein the fluorine compound is at least one selected from hydrofluoric acid and ammonium fluoride. 3. The cleaning composition according to claim 1, wherein the fluorine compound is a mixture of hydrofluoric acid and ammonium fluoride. 4. 0.00001 to 10% by weight of hydrofluoric acid,
The cleaning composition according to claim 3, which contains 1 to 40% of ammonium fluoride. 5. A method of cleaning a semiconductor substrate, which comprises cleaning with the cleaning composition according to claim 1.