Compositions – Etching or brightening compositions – Inorganic acid containing
Patent
1995-08-02
1998-05-26
Breneman, R. Bruce
Compositions
Etching or brightening compositions
Inorganic acid containing
252 793, H01L 21306, H01L 21308
Patent
active
057559899
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to wet etchants which are suitable for use in the wet etching process for semiconductor devices having high integration densities and which are improved especially in wetting property for use in fine working.
BACKGROUND ART
Many wet etching compositions (wet etchants) are already known which have a surfactant incorporated therein. For example, JP-B-19509/1987 discloses such a composition. With an increase in the integration density of semiconductor devices, however, the conventional surfactant-containing buffered hydrofluoric acid has become no longer satisfactory in wetting property. A mere increase in the amount of surfactant to be used fails to solve the problems associated with the solubility and cleaning property of the surfactant itself and further needs consideration to the resulting demerit with respect to cost. Accordingly, there arises a need to investigate new surfactants, whereas extreme difficulties are encountered in exploring surfactants which can be given an enhanced wetting property without sacrificing the conventional features of surfactants such as solubility, stability, usefulness in a small amount, low foaming property and property to ensure ease of cleaning.
We have conducted intensive research in order to overcome these problems and consequently found that some kinds of surfactants exhibit an outstanding wetting property with the usual features thereof unimpaired when used in combination although failing to produce a noticeable effect if used singly.
An object of the present invention is to provide a wet etching composition having all the features conventionally possessed by surfactants and yet exhibiting an excellent wetting property.
DISCLOSURE OF THE INVENTION
The present invention provides a wet etching composition for semiconductors which is characterized in that a surfactant comprising the two components of an alkylsulfonic acid and an .omega.-hydrofluoroalkylcarboxylic acid is added to a buffered hydrofluoric acid composed of hydrogen fluoride, ammonium fluoride and water.
According to the invention, an alkylsulfonic acid and an .omega.-hydrofluoroalkylcarboxylic acid are added to buffered hydrofluoric acid in proportions in accordance with the composition of the acid. The resulting composition then exhibits such a wetting property that is not available when these components are added singly. Combinations of other surfactants failed to produce an expected effect since the compatibility involved a problem, or the wetting property remained unaltered or the combination led to a less satisfactory result than is the case with single use.
Examples of preferred alkylsulfonic acids for use in the present invention are compounds represented by C.sub.n H.sub.2n+1 SO.sub.3 H wherein n is an integer of 5 to 10, more preferably an integer of 6 to 9. More specific examples are C.sub.6 H.sub.13 SO.sub.3 H, C.sub.7 H.sub.15 SO.sub.3 H, C.sub.8 H.sub.17 SO.sub.3 H, C.sub.9 H.sub.19 SO.sub.3 H, etc. C.sub.7 H.sub.15 SO.sub.3 H and C.sub.8 H.sub.17 SO.sub.3 H are especially preferable.
Examples of preferred .omega.-hydrofluoroalkylcarboxylic acids are compounds represented by H(CF.sub.2)mCOOH wherein m is an integer of 1 to 10, more preferably an integer of 4 to 8. More specific examples are H(CF.sub.2).sub.4 COOH, H(CF.sub.2).sub.6 COOH, H(CF.sub.2).sub.8 COOH, etc. H(CF.sub.2).sub.6 COOH is especially preferable.
The surfactants to be used in the present invention contain none of potassium, sodium, calcium and like metals in the molecule and are therefore unlikely to produce any electrically adverse influence on semiconductor materials.
The etching composition of the invention can be prepared by mixing the components together. The order in which they are added is not limited. The composition can be prepared, for example, by dissolving a required amount of the surfactant in one of hydrogen fluoride or an aqueous solution of ammonium fluoride and thereafter mixing the other with the resulting solution, or by mixing together hydrogen fluoride a
REFERENCES:
patent: 4517106 (1985-05-01), Hopkins et al.
patent: 4582624 (1986-04-01), Enjo et al.
patent: 4620934 (1986-11-01), Hopkins et al.
patent: 4795582 (1989-01-01), Ohmi et al.
Hosomi Tomohiro
Ishii Masao
Itano Mitsushi
Maruyama Shigeru
Breneman R. Bruce
Daikin Industries Ltd.
Goudreau George
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