JP3261819B2 - Low surface tension sulfuric acid composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sulfuric acid composition. More specifically, the present invention relates to a low surface tension sulfuric acid composition containing a specific fluorine-based surfactant and suitable for being used as a cleaning agent in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art In recent years, the fine processing technology represented by an integrated circuit and the like has been increasingly improved in processing accuracy. For example, in the case of a dynamic random access memory (DRAM),
At present, submicron processing technology has been established as a mass production level technology. In particular, in microfabrication technology, contamination of organic substances, metals, particles, and the like existing on a wafer has an important effect on processing accuracy. Therefore, in each process such as photolithography, it is usual to use a cleaning agent such as sulfuric acid to remove contamination on the wafer.

As described above, as the degree of integration of integrated circuits increases, stricter requirements have also been placed on the removal of contamination required in the cleaning step, in conjunction with the miniaturization of patterns and the complexity of unevenness. Sulfuric acid is used alone or as a mixture with other substances in a semiconductor manufacturing process for cleaning a silicon substrate, removing a resist film, and the like. However, when conventional high-purity sulfuric acid is used, the surface tension is large and the wettability is poor, so that it is difficult for the cleaning agent to penetrate into the fine pattern, and special stains such as a resist film denatured in each step such as an etching process. On the other hand, since the decomposition efficiency is low, there have been disadvantages such as insufficient cleaning.

[0004] In order to solve these problems, there has been proposed a method of adding a specific surfactant to lower the surface tension and improve the wettability (Japanese Patent Laid-Open No. 2-240).
285). However, even though these materials can be used to lower the surface tension, the cleaning rate is slow due to insufficient decomposition rate, or after the surfactant is adsorbed and remains on the silicon substrate after cleaning. There are problems such as adverse effects on the process, and a satisfactory cleaning agent has not yet been obtained.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned background, an object of the present invention is to improve the characteristics of a sulfuric acid composition which has been already proposed, to have a low surface tension and a good wettability, and to decompose a resist film. And to provide a sulfuric acid composition that does not easily remain after washing.

[0006]

The present inventors have made various studies to solve such problems, and as a result, have found that the above objects can be achieved by using a specific fluorine-based surfactant. Completed the invention. That is, the gist of the present invention resides in a low surface tension sulfuric acid composition containing a fluorinated surfactant comprising a tertiary ammonium salt of a fluoroalkylsulfonic acid represented by the following general formula (I) in sulfuric acid.

[0007]

Embedded image R ¹ — (CX ₂ ) _n —SO ₃ —A (I) (wherein, R ¹ is an alicyclic fluoroalkyl group, X is a hydrogen atom or a fluorine atom, and n is 0 to 3) Integer, A is NH
It represents a R ² ₃ or NHR ³ ₃ N. Where R ² is the number of carbon atoms
An alkyl group having 1 to 4 and R ³ represent an alkylene chain having 1 to 4 carbon atoms . )

Hereinafter, the present invention will be described in detail. In the above formula, the alicyclic fluoroalkyl group for R ¹ is usually
A cycloalkyl group having 4 to 18 carbon atoms, preferably 6 to 12 carbon atoms, in which a hydrogen atom is substituted with a fluorine atom, may be mentioned. As such a cycloalkyl group, for example, a cycloalkyl group having a 6-membered ring or a 6-membered condensed ring, that is, a cyclohexyl group or a decahydronaphthyl group is typically exemplified. These may be further substituted with a lower alkyl group. Further, the fluorine substitution ratio, that is, the substitution ratio of a hydrogen atom in a cycloalkyl group constituting the alicyclic fluoroalkyl group represented by R ¹ with a fluorine atom is 50% or more, preferably 80% or more; Particularly, 100% is preferable.

In the above formula, X is a hydrogen atom or a fluorine atom, preferably a fluorine atom. n is 0-3, preferably 1-2, and particularly preferably 1. In the above formula,
While A represents NHR ² ₃ or NHR ³ ₃ N, the number of carbon atoms in R ² 1
Alkyl group and 4 is particularly preferably include an alkyl group having 2 carbon atoms (ethyl group), of 1 to 4 carbon atoms R ³ A
Alkylene chain, especially preferably be mentioned alkylene chain of 2 carbon atoms (ethylene chain).

The low surface tension sulfuric acid composition of the present invention is obtained by adding, mixing and dissolving an appropriate amount of a tertiary ammonium salt of a fluoroalkylsulfonic acid represented by the above general formula. Usually 0.1 to net sulfuric acid.
001 to 0.1% by weight, more preferably 0.005 to 0.05% by weight. If the amount is too small, the effect is not sufficient, and if it is too large, no further effect is obtained and it is meaningless.

The sulfuric acid to which the surfactant is added is usually used in the form of an aqueous solution, but if it is too thin, the washing effect is not sufficient. Therefore, it is generally 60% by weight or more, preferably 70% by weight.
% Or more are used. The sulfuric acid composition is
Usually, it is used as a cleaning liquid by mixing with a hydrogen peroxide solution.
An aqueous solution of about 30% by weight is used as the hydrogen peroxide solution. The mixing ratio of the hydrogen peroxide solution to the aqueous sulfuric acid solution is about 5 to 30% by weight.

The tertiary ammonium salt of a fluoroalkylsulfonic acid used in the present invention is stable even in such a strongly oxidizing atmosphere. Normally, the cleaning of the wafer is 1
Although it is carried out at a high temperature of 00 to 130 ° C., the sulfuric acid composition of the present invention can sufficiently exert its effect even at such a high temperature. Since the sulfuric acid composition of the present invention is intended for use in a semiconductor manufacturing process, high-purity sulfuric acid and a surfactant are used.

[0013]

EXAMPLES Next, specific embodiments 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 it exceeds the gist thereof. (Examples 1-3 and Comparative Examples 1-3) To 89% by weight of sulfuric acid, a fluorine-based surfactant represented by the general formula shown in Table 1 was added at a ratio shown in Table 1, and this was mixed with 31% by weight of peroxide. Hydrogen water 4:
A sulfuric acid composition mixed at a ratio of 1 (volume ratio) was prepared. For these sulfuric acid compositions, the surface tension, the photoresist removal rate for evaluating the cleaning rate, and the amount of residual surfactant after cleaning the silicon wafer were measured. Table 2 shows the results. In addition, the surface tension, the photoresist peeling speed, and the residual surfactant amount were measured by the following measurement methods.

Measurement of Surface Tension The surface tension at 22 ° C. was measured by the Wilhelmy method. Photoresist stripping rate measuring method Photoresist MC manufactured by Mitsubishi Kasei Co., Ltd.
PRi-6600 is applied in a thickness of 1 μm,
After the treatment for 0 second, the silicon wafer was immersed in the sulfuric acid composition (30 ° C.) for several minutes. Next, this silicon wafer was immersed in pure water (22 ° C.) for 5 minutes,
Washing is repeated twice, and after drying in an oven at 60 ° C. for 30 minutes, the thickness of the photoresist is measured. did. Measurement method of residual surfactant A silicon wafer cut into a 6 mm square was immersed in the above sulfuric acid composition (22 ° C) for 5 minutes, and then this silicon wafer was immersed in pure water (22 ° C) for 5 minutes. Washing is performed by repeating three times.
After drying for 30 minutes, quantitative analysis by X-ray photoelectron spectroscopy is performed on F remaining on the surface and Si on the substrate,
The number of surfactant molecules per 1 cm ² was calculated from the value of F / Si, and was defined as the amount of residual surfactant. Note that the detection limit in the depth direction by X-ray photoelectron spectroscopy was 5 nm, and the distance between Si-Si atoms was 0.235 nm, assuming that the surface was a single crystal of Si.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

[0018]

According to the present invention, there is provided a sulfuric acid composition which has good surface washability at a low surface tension and has little adverse effect on subsequent steps due to residual surfactant on the silicon surface after cleaning. It can be provided, which is advantageous for industrial production of highly integrated circuits.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI C11D 7/34 C11D 7/34 C23G 1/00 C23G 1/00 H01L 21/304 647 H01L 21/304 647B (56) References Special JP-A-4-325599 (JP, A) JP-A-4-323300 (JP, A) JP-A-2-240285 (JP, A) JP-A-5-70798 (JP, A) Int.Cl. ⁷ , DB name) C11D 1/14 C11D 7/34 H01L 21/304 647 CA (STN)

Claims (1)

(57) [Claims] 1. A low surface tension sulfuric acid composition containing a fluorinated surfactant comprising a tertiary ammonium salt of a fluoroalkylsulfonic acid represented by the following general formula (I). Embedded image R ¹ — (CX ₂ ) _n —SO ₃ —A (I) (wherein, R ¹ represents an alicyclic fluoroalkyl group, X represents a hydrogen atom or a fluorine atom, and n represents 0 to 3) Integer, A is NH
It represents a R ² ₃ or NHR ³ ₃ N. Where R ² is the number of carbon atoms
An alkyl group having 1 to 4 and R ³ represent an alkylene chain having 1 to 4 carbon atoms . )