JPH05275407A - Sulfuric acid composition - Google Patents

Abstract

PURPOSE:To stably retain a low surface tension at a high temperature by using a specific fluorine surfactant. CONSTITUTION:In the formula, R<1> represents a fluoroalkyl group having 3 or more carbon atoms and R<2>, a hydrogen atom or lower alkyl group having 1-4 carbon atoms. Respective R<3>, R<4> and R<5> independently represent a lower alkyl group having 1-4 carbon atoms or aryl group or aralkyl group having one benzene ring. X represents a halogen or acid radical and m, the integer from 1 through 10. The fluoroalkylsulfonamide is contained in sulfuric acid so as to be made into a sulfuric acid composition. Thus, the sulfuric acid composition is small in the contact angle to a silicon wafer because of its low surface tension and therefore excellent in wettability and can display a satisfactory cleaning effect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sulfuric acid composition, and more particularly to a sulfuric acid composition suitable for use as a cleaning agent in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art In recent years, microfabrication technology represented by integrated circuits has been increasingly improved in machining accuracy. Taking dynamic random access memory (DRAM) as an example, submicron processing technology is now mass-produced. Established as a level technology. In microfabrication technology, particles present on the wafer have a significant effect on the processing accuracy, so in each process such as photolithography,
It is customary to remove particles on the wafer using a cleaning agent such as sulfuric acid before use. As the degree of integration of the integrated circuit is improved, the performance of removing particles required for the cleaning process is becoming more severe due to the miniaturization of patterns and the complication of irregularities.

Sulfuric acid is used alone or in a mixture with other substances for cleaning a silicon substrate, removing a resist film, etc. in a semiconductor manufacturing process. When conventional high purity sulfuric acid is used, the surface tension is large, the contact angle to the wafer is large, and the wettability is poor, so it is difficult for the cleaning agent to penetrate into the fine pattern, resulting in insufficient cleaning. there were. In order to solve these problems, a method of lowering the surface tension of sulfuric acid by adding a specific surfactant has been proposed (JP-A-2-240285).
issue).

[0004]

Sulfuric acid is usually mixed with hydrogen peroxide solution and often used for cleaning silicon wafers, and surface tension and wettability in this system are particularly problematic. Further, since this washing is carried out at a temperature of 100 to 130 ° C., stability at high temperature is particularly important, but under such conditions, an interface that stably maintains a low surface tension and improves wettability is obtained. No active agent has been found yet.

In view of the above background, an object of the present invention is to maintain a stable low surface tension at high temperature and to have excellent wettability, and in particular, a sulfuric acid composition having such properties even when mixed with hydrogen peroxide. To provide.

[0006]

As a result of various studies conducted by the present inventors in order to solve such problems, it was found that the above object can be achieved by using a specific fluorine surfactant. And completed the present invention. That is, the gist of the present invention is that sulfuric acid has the general formula (I)

[0007]

[Chemical 2]

(Wherein R ¹ is a fluoroalkyl group having 3 or more carbon atoms, R ² is a hydrogen atom or a lower alkyl group having 1 to 4 carbon atoms, and R ³ , R ⁴ and R ⁵ are independently carbon atoms. A lower alkyl group of the formulas 1 to 4 or an aryl group or an aralkyl group having one benzene ring is represented, X represents a halogen or an acid radical, and m represents an integer of 1 to 10.)
In a sulfuric acid composition containing a fluoroalkylsulfonamide compound represented by

The present invention will be described in detail below. The above formula
(I) Medium, R¹As a fluoroalkyl group represented by
Is an alkyl group having 3 or more carbon atoms, preferably 5 to 20 carbon atoms.
Group, more preferably an alkyl group having 5 to 10 carbon atoms.
An example is a fluorine substitution product. The alkyl group is a straight chain or
It may be branched, but is usually a straight chain alkyl group.
It Fluorine substitution rate of fluoroalkyl group is usually 50%
Or more, preferably 80% or more. R²As water
Elementary atom or straight or branched chain alkyl having 1 to 4 carbon atoms
Group. R³, R ^FourAnd R^FiveAs the carbon number
1-4 linear or branched alkyl groups or benzene
Examples include an aryl group having one ring or an aralkyl group.
Be done. As the aryl group, for example, a lower alkyl group,
May be substituted with halogen atom, hydroxyl group, etc.
Examples of the aralkyl group include a phenyl group.
Examples thereof include a benzyl group and a phenethyl group. As X
Is halogen, carboxylic acid such as acetic acid, sulfuric acid,
Acid radicals such as inorganic acids such as nitric acid, carbonic acid, boric acid, phosphoric acid, etc.
Be done. m is an integer of 1 to 10, preferably 1 to 5.
And more preferably an integer of 3 to 5.

The sulfuric acid composition of the present invention has the above general formula (I).
It is essential that the fluoroalkylsulfonamide compound represented by is mixed and dissolved in sulfuric acid in an appropriate amount, and the content thereof is usually 0.00
1 to 0.1% by weight, more preferably 0.0
It is from 05 to 0.05% by weight. If the amount is less than the above amount, the effect is not sufficient, and if the amount is too large, no further effect is obtained and it is meaningless.

On the other hand, sulfuric acid containing the compound represented by the above formula (I) is usually used as an aqueous solution. However, if it is too thin, the cleaning effect is not sufficient, so that it is generally 6
A concentration of 0% by weight or more, preferably 70% by weight or more is used. The sulfuric acid composition is usually mixed with hydrogen peroxide to form a cleaning liquid, and the mixing ratio of hydrogen peroxide in this case is about 5 to 20% by weight with respect to sulfuric acid. The fluoroalkyl sulfonamide compound used in the present invention is stable even in such a strongly oxidizing atmosphere. Moreover, although the washing is usually performed at a high temperature of 100 to 130 ° C.,
The sulfuric acid composition of the present invention exerts its effect sufficiently even under such a high temperature and is excellent in stability for a long time.
Since the sulfuric acid composition of the present invention is intended for use in the semiconductor manufacturing process, the sulfuric acid and the surfactant used are of high purity.

[0012]

EXAMPLES Next, specific examples of the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless the gist thereof is exceeded. Examples 1 to 5 and Comparative Examples 1 to 5 A sulfuric acid composition prepared by adding 0.01% by weight of the fluorine-based surfactant shown in Table 1 to 89% by weight sulfuric acid and 30% by weight hydrogen peroxide aqueous solution were added in a ratio of 4: The surface tension at 22 ° C. of the composition mixed at 1 (volume ratio) was measured. The surface tension was measured by the Wilhelmi method. For comparison, a sulfuric acid composition to which a surfactant was not added and a sulfuric acid composition using another fluorosurfactant were also mixed with hydrogen peroxide solution and the surface tension at 22 ° C. was measured. The results are shown in Table-2.

[0013]

[Table 1]

[0014]

[Table 2]

Examples 6 to 7 and Comparative Examples 6 to 8 The mixed compositions prepared in the same manner as Examples 2 to 3, Comparative Example 2 and Comparative Examples 4 to 5, respectively, were heated and kept at 130 ° C., and after 1 hour. After 2 hours, sampling was performed to measure the surface tension at 22 ° C. The results are shown in Table-3.

[0016]

[Table 3]

Examples 8 to 9 and Comparative Examples 9 to 10 The mixed compositions prepared in the same manner as Examples 2 to 3, Comparative Example 1 and Comparative Example 5 were heat treated at a temperature of 130 ° C. for 2 hours, and then, Was cooled and the contact angle with bare silicon at 22 ° C. was measured. The results are shown in Table-4. The contact angle was measured by the droplet method shown below. (Contact angle measurement method) A droplet to be measured is made on a silicon wafer and read with a microscope equipped with a goniometer. It was considered that the contact angle was twice the angle connecting the contacts.

[0018]

[Table 4]

[0019]

The sulfuric acid composition of the present invention has a low surface tension,
The contact angle with a silicon wafer is small, the wettability is excellent, and a good cleaning effect is exhibited. In particular, the sulfuric acid composition of the present invention stably exhibits the above physical properties even under a high oxidizing atmosphere and at a high temperature, so that it can exhibit a good effect without deterioration even in an actual production line.

Claims (1)

[Claims] 1. Sulfuric acid has the following general formula (I): (In the formula, R ¹ is a fluoroalkyl group having 3 or more carbon atoms,
R ² represents a hydrogen atom or a lower alkyl group having 1 to 4 carbon atoms, and R ³ , R ⁴ and R ⁵ each independently have 1 to 4 carbon atoms.
Represents a lower alkyl group, an aryl group having one benzene ring or an aralkyl group, X represents a halogen or an acid radical, and m represents an integer of 1 to 10. ) A sulfuric acid composition containing a fluoroalkyl sulfonamide compound represented by the formula (1).