CHEMICALS FOR WET ETCH

PURPOSE: Chemicals for wet etch are to provide good repeatability of an etch process by preventing variation of a density caused by volatility of the chemicals, and to improve productivity of the etch process by increasing an etch rate while having good selectivity. CONSTITUTION: Etching liquid is used in a process for wet-etching a silicon nitride layer in a closed chamber by using an oxide layer as a mask, wherein the etching liquid is composed of 85 H3PO4, 0.01-0.1 HF and 1 hydrogen peroxide. In the etching liquid, an etch rate of the silicon nitride layer is from 60 to 74 angstrom/minute and an etch selectivity of a nitride layer and an oxide layer is not lower than 20, at a temperature of 120 deg.C.