METHOD FOR FABRICATING FLASH MEMORY DEVICE

摘要

PURPOSE: A method for fabricating a flash memory device is provided to form a layer of a uniform thickness on a wafer by using chemical mechanical polishing(CMP) slurry having excellent polishing selectivity regarding an oxide layer and polycrystalline silicon. CONSTITUTION: A pad oxide layer(13) and a pad nitride layer(15) are sequentially deposited on a substrate(11). The pad nitride layer, the pad oxide layer and the substrate in an isolation region are sequentially and selectively polished to form a trench. An isolating oxide layer(19) is deposited. An isolating oxide layer pattern includes a solvent, a polishing agent and an additive that includes at least one of polymers which are homo polymer or copolymer of a hydrocarbon compound including -COOH, -NO2 or -NH-CO-. A CMP process is performed on the resultant structure by using the first slurry composition with hydrogen ion concentration of 2-8 to form the isolating oxide layer pattern for separating an active region(100). The pad nitride layer and the pad oxide layer in the active region are removed to expose the substrate. A tunnel oxide layer is formed in the active region. A polycrystalline silicon layer is deposited. A floating gate includes a solvent, a polishing agent and an additive that is at least one of ammonium hydroxide or an amine compound. A CMP process is performed on a polycrystalline silicon layer to form the floating gate by using the second slurry compound with hydrogen ion concentration of 7-11 and using the isolating oxide layer as an etch stop layer.