Compositions – Etching or brightening compositions – Inorganic acid containing
Patent
1990-11-15
1994-07-05
Hearn, Brian E.
Compositions
Etching or brightening compositions
Inorganic acid containing
252 793, C09K 1304, C09K 1308, H01L 2100, H01L 2102
Patent
active
053264908
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a low surface tension sulfuric acid composition adapted for use in semiconductor manufacturing processes. More particularly, this invention relates to a low surface tension sulfuric acid composition containing specific fluoroalkylsulfonamides.
BACKGROUND ART AND PROBLEMS ASSOCIATED THEREWITH
In semiconductor manufacturing processes, sulfuric acid is used, either alone or in combination with other substances, for different purposes, for example, for cleaning silicon substrates, removing resist films or formulating etching solutions.
The increased density of integrated circuits nowadays has inevitably led to micronization of patterns and complication of the (trench structure (i.e. fine deep grooves). Use of conventional sulfuric acid under these condition gives rise to inconveniences such as difficult permeation into trenches and insufficient cleaning, due to high surface tension and poor wettability. Accordingly it is now strongly desired to develop a sulfuric acid composition with low surface tension and good wettability.
Although use of surface-active agent is expected to lower the surface tension of sulfuric acid, only very limited types of surface-active agent are stable in hot sulfuric acid, in particular, in highly oxidizing sulfuric acid/hydrogen peroxide liquid mixtures, with the result that it is in fact extremely difficult to find such surface-active agents that can be put into practical use.
As a result of research on a variety of surfaceactive agents, the inventors have found that specific ones amongst many fluorine-type surface-active agents are stable in hot liquid mixtures of sulfuric acid and hydrogen peroxide and capable of lowering the surface tension. The present invention bases itself on these findings.
DISCLOSURE OF THE INVENTION
The object of the present invention is to provide a sulfuric acid composition which has low surface tension and good wettability as well as excellent thermo-stability and oxidation resistance.
The present invention is concerned in particular with such low surface tension sulfuric acid composition adapted for use in semiconductor manufacturing processes. The present invention thus provides a low surface tension sulfuric acid composition characterized in that the sulfuric acid contains a fluorine-type surface-active agent comprising a fluoroalkylsulfonamide compound of the general formula: or a lower alkyl group and A for H or SO.sub.3 H. The present invention will now be described below in more detail.
The fluoroalkylsulfonamide compounds used in the composition of the present invention are readily available in that they are described for example in U.S. Pat. No. 2,803,656 and also commercially available. These sulfonamide compounds, not containing any metal such as sodium, potassium or calcium, exert no adverse effects on semiconductors.
The low surface tension sulfuric acid composition of the present invention has an appropriate amount of a sulfonamide compound of formula (I) above added to and dissolved in the sulfuric acid.
The amount of the above-mentioned sulfonamides of formula (I) added is in the range of 0.001-0.1%, more preferably 0.005-0.05% by weight relative to the sulfuric acid. Addition of amounts lower than the lower limit mentioned above was found to give no advantageous effects. Use of amounts higher than the upper limit mentioned above is meaningless because it produces no better effects.
The low surface tension sulfuric acid composition of the present invention has a surface tension as low as about one fourth that of conventional sulfuric acid, and a smaller contact angle relative to the silicon substrate, and can easily permeate into fine grooves of the trench structure, thereby significantly enhancing its cleaning effect. Furthermore, it is stable and retains its properties even in the form of liquid mixture with hydrogen peroxide, i.e. even when exposed to highly oxidizing condition.
Examples of the present invention will now be shown below together with comparative examples.
EXAMPLES 1-4
Hara, deceased Hisao
Mori Kiyoto
Shihoya Takao
Everhart B.
Hearn Brian E.
Kanto Kagaku Kabushiki Kaisha
Nissan Chemical Industries Ltd.
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