METHOD OF FORMING FLOATING GATE OF FLASH MEMORY ELEMENT

摘要

PROBLEM TO BE SOLVED: To provide a method of preventing the thickness of a cushion oxide film from increasing by a primary polysilicon film in the case of a consecutive wall oxidation process by depositing the cushion oxide film, and of minimizing an attack given to the primary polysilicon film in the case of a pad nitride film strip process. SOLUTION: The method comprises the steps of: providing a semiconductor substrate on which a tunnel oxide film 12 and a primary polysilicon film 14 are formed; successively forming the cushion oxide film and the pad nitride film on the primary polysilicon film; forming a trench in the semiconductor substrate; performing a planarizing process using the pad nitride film as a barrier after depositing an oxide film 24 for an element isolation film so that the trench may be embedded; performing a strip process so that the pad nitride film may be removed and at the same time at least about 50 % of the cushion oxide film may be removed; removing the cushion oxide film by a pretreatment cleaning process; and carrying out patterning by a patterning process after depositing a secondary polysilicon film 26 on the whole structure to form a floating gate consisting of primary and secondary polysilicon films. COPYRIGHT: (C)2005,JPO&NCIPI