| 摘要 |
PROBLEM TO BE SOLVED: To provide an etchant which is capanble of etching a non-doped oxide film and a doped oxide film at the same speed by a method wherein the etchant has etching properties where the etching rates of a thermal oxide film and a boron phosphorus glass are set smaller than a specific rate, and an etching rate between these films is set smaller than a specific value. SOLUTION: The etching rates of a boron phosphorus silicate glass film (BPSG) and a thermal oxide film (THOX) are set equal to 100Å/min or below at a temperature of 25 deg.C. At the same time, an etching rate BPSG/THOX is set equal to about 1.5 or below. This etchant contains metal salt, ammonium salt, and quaternary ammonium salt as fluoride salt and bifluoride, and the dielectric constant of its solvent is set equal to about 35 or below. Furthermore, this etchant contains at least an element selected out of organic acid and organic solvent provided with hetero atoms. By this setup, a non-doped oxide film and a doped oxide film can be etched nearly at the same etching rate.
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