Patent ID: 7052627

Claim:
An etching solution having a thermal oxide (THOX) film etch rate and boron phosphosilicate glass (BPSG) film etch rate at 25° C. of 100 Å/min or lower and a ratio of (BPSG etch rate)/(THOX etch rate) of 1.5 or lower, wherein the solution comprises (i) at least one member selected from the group consisting of a fluoride salt and a hydrogen fluoride salt; and (ii) (a) solvent being at least one member selected from organic solvents and organic acids, or (b) solvent being at least one member selected from organic solvents and organic acids, and optionally water, said solvent comprising molecules having a hetero atom, and wherein said organic acids are selected from the group consisting of acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, caprylic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monofluoroacetic acid, difluoroacetic acid, trifluoroacetic acid, a-chlorobutyric acid, β-chlorobutyric acid, γ-chlorobutyric acid, lactic acid, glycolic acid, pyruvic acid, glyoxalic acid, acrylic acid, and like monocarboxylic acids methanesulfonic acid and toluenesulfonic acid.