| 摘要 |
PROBLEM TO BE SOLVED: To produce buffered hydrofluoric acid having a predetermined etching rate easily by diluting with wafer high etching rate buffered hydrofluoric acid in which the weight of hydrogen fluoride is specified. SOLUTION: The concentration of hydrofluoric acid in high etching rate buffered hydrofluoric acid supplied to a diluting step is 2.5 wt.% or higher, or usually in the range of about 3-15 wt.%. The pH of the high etching rate buffered hydrofluoric acid is usually 3 or higher, or more preferably 3.5 or higher. The content of a surface active agent is in the range of about 0.00001-5 wt.%, or more preferably about 0.001-0.1 wt.%. Any of a cationic surface active agent, an anionic surface active agent, a nonionic surface active agent may be used as the surface active agent. With this arrangement, buffered hydrofluoric acid having a desired etching rate can be obtained easily.
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