Importance

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Abstract

A wafer etching and impurity analysis method is presented where a wafer is held in a vessel having gas introduction and exhaust ports, a solution including a mixture of hydrofluoric acid and nitric acid alone or together with sulfuric acid is bubbled with a carrier gas without being heated, which generates a gas containing vaporized hydrofluoric acid and nitric acid, and the inside of the vessel is purged so that the amount of gas supplied is kept constant at all times. The molar ratio of the hydrofluoric acid and nitric acid (and sulfuric acid if used) in the solution is set to a specific value. The amount of gas introduced is specified. All or a specific portion of the wafer is cooled to a specific temperature between 0 and 20.degree. C. Consequently, the gas is condensed on the surface of the wafer, which allows the required portion of the wafer to be etched and the amount of required in-plane etching to be uniform. The method produces a wafer surface with good smoothness after etching, reduces the amount of recovery liquid needed, and reduces the amount of admixed silicon during impurity analysis, the concentration time, and so forth.

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First Claim