Cleaning liquid for semiconductor devices

#The present invention relates to a cleaning liquid for semiconductor devices used in the process for producing semiconductor integrated circuits, and more particularly to a cleaning liquid for semiconductor devices used for removal of resist residues left remaining after dry etching. 2. Description of the Related Arts

#Semiconductor integrated circuits are produced in accordance with the following procedures: an inorganic substrate is coated with a photoresist; patterns are formed on the photoresist by exposure of light followed by development; the patterned photoresist is used as a mask, and portions of the inorganic substrate not masked by the photoresist are dry etched with a reactive gas and then ashed; and resist residues (protective deposit films) left remaining on the inorganic substrate are removed from the inorganic substrate. A gas containing chlorine is generally used to dry etch the photoresist coated on the inorganic substrate. Resist residues are formed by the reaction of the photoresist with the reactive gas containing chlorine during the dry etching. Protective deposit films left remaining on the inorganic substrate cause disconnection and abnormal wiring, and various troubles arise. Therefore, complete removal of the protective deposit films is desired.

#Alkaline cleaning liquids have heretofore been used as the liquid for removing resist residues. Examples of the alkaline cleaning liquid include a cleaning liquid comprising an additional product of ethylene oxide to an alkanolamine or a polyalkylenepolyamine, a sulfone compound, and a glycol monoalkyl ether (Japanese Patent Application Laid-Open No. Showa 62(1987)-49355) and a cleaning liquid comprising dimethylsulfoxide as the main component and a diethylene glycol monoalkyl ether and an organic hydroxy compound containing nitrogen as other components (Japanese Patent Application Laid-Open No. Showa 64(1989)-42653). However, the above cleaning liquids become alkaline during the use because of dissociation of the amine caused by absorbed water. When cleaning is conducted with water without using an organic solvent such as an alcohol after the removal of the resist residues, water used in the cleaning becomes alkaline. This accelerates corrosion of aluminum which is frequently used as the wiring material in the formation of fine circuits. Therefore, the above cleaning liquids are not preferable for use in the recent working of fine structures which require rigorous precision.

#FIG. 1 shows a sectional view of a semiconductor device which has been dry etched using a resist film as a mask to form a circuit of an aluminum alloy (Al--Si--Cu) and ashed with oxygen plasma.

#1 A silicon substrate

#2 An oxide film

#The fluorine compound is a compound represented by R.sub.4 NF, wherein R represents hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Examples of the fluorine compound include ammonium fluoride, hydrofluoric acid, acidic ammonium fluoride, hydrogen fluoride salt of methylamine, hydrogen fluoride salt of ethylamine, hydrogen fluoride salt of propylamine, tetramethylammonium fluoride, and tetraethylammonium fluoride. Among these compounds, ammonium fluoride and tetramethylammonium fluoride are preferable, and ammonium fluoride is more preferable. The fluorine compound can be used singly or as a combination of two or more compounds. The fluorine compound is used in such an amount that the concentration in the entire solution is in the range of 0.1 to 10% by weight, preferably in the range of 0.1 to 5% by weight, more preferably in the range of 0.5 to 1.5% by weight. When the amount of the fluorine compound exceeds the above range, corrosion of wiring materials such as aluminum takes place. When the amount of the fluorine compound is less than the above range, the ability of removing resist residues decreases. Therefore, such amounts are not preferable.

#Examples of the organic solvent soluble in water include amides, such as formamide, monomethylformamide, dimethylformamide, acetamide, methylacetamide, dimethylacetamide, and N-methylpyrrolidone; ethers, such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, and diethylene glycol diethyl ether; sulfones, such as sulfolane; sulfoxides, such as dimethylsulfoxide; and alcohols, such as methanol, ethanol, isopropanol, ethylene glycol, and glycerol. Among these organic solvents soluble in water, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and dimethylsulfoxide are preferable. The organic solvent soluble in water can be used singly or as a combination of two or more solvents. The organic solvent soluble in water is used in such an amount that the concentration in the entire solution is in the range of 72 to 80% by weight, preferably in the range of 72 to 75% by weight. When the amount of the organic solvent soluble in water is less than 72% by weight in the entire solution, corrosion of wiring materials increases. When the amount exceeds 80% by weight, the ability to remove resist residues is inferior.

#The amount of water used in the present invention is not particularly limited and can be selected in accordance with the amounts of the fluorine compound and the organic solvent soluble in water.