Abstract: A surface treatment agent containing a solution of hydrogen fluoride, ammonium fluoride and water, the solution containing less than 8 weight % of hydrogen fluoride (HF) and less than 15 weight % of ammonium fluoride (NH.sub.4 F).

Abstract: Dry etching apparatus composed of any of metal, silica, ceramic or combination thereof with a processing chamber in which substrates are placed and a diluted anhydrous hydrogen fluoride gas generator, the processing chamber being connected to the diluted anhydrous hydrogen fluoride gas generator through a pipe line of stainless steel or nickel. There is also disclosed a dry-etching method with the dry-etching apparatus, and a diluted anhydrous hydrogen gas generator used in the dry-etching apparatus and dry-etching method.

Abstract: Disclosed is a dry-etching apparatus composed of any of metal, silica, ceramic or combination thereof including a processing chamber in which substrates are placed and a diluted anhydrous hydrogen fluoride gas generator, the processing chamber being connected to the diluted anhydrous hydrogen fluoride gas generator through a pipe line of such metal as stainless steel or nickel. There is also provided according to the invention a dry-etching method with the dry-etching apparatus, a cooled anhydrous hydrogen fluoride gas source and a diluted anhydrous hydrogen gas generator used in the dry-etching apparatus and dry-etching method.

Abstract: A method for preventing anhydrous potassium fluoride from solidification by causing the anhydrous potassium fluoride to absorb carbon dioxide gas.

Abstract: A surface treating composition for micro processing which comprises a mixture of hydrofluoric acid, ammonium fluoride solution and water, and at least one compound selected from the group of surfactants consisting of aliphatic carboxylic acids, salts of aliphatic carboxylic acids, aliphatic amines and aliphatic alcohols.

Abstract: A process for purifying hydrogen fluroide characterized by adding fluorine to hydrogen fluoride containing at least one element selected from the group consisting of boron, silicon, phosphorus, sulfur, chlorine and arsenic, and/or at least one compound of these elements, reacting the fluorine with said element and/or said compound and distilling the resulting mixture.