Method of forming sharp beak of poly to improve erase speed in split-gate flash EEPROM

A method of forming a beak of poly to improve erase speed in a split-gate flash memory cell comprising the steps of:

• providing a silicon substrate having a plurality of active and field regions defined;
• forming a tunnel oxide layer over said substrate;
• forming a first polysilicon layer over said tunnel oxide layer;
• forming a layer of nitride over said tunnel oxide layer;
• forming and patterning a first photoresist layer to form a photoresist mask with a pattern corresponding to the floating gate of said split-gate flash memory cell;
• etching said layer of nitride through said photoresist mask to form openings in said layer of nitride and to expose portions of said first polysilicon layer corresponding to said floating gate pattern;
• removing said first photoresist layer;
• oxidizing portions of said first polysilicon layer exposed in said openings in said layer of nitride to form a polyoxide;
• removing said layer of nitride;
• using said polyoxide as a hard mask to etch portions of said first polysilicon layer not covered by said polyoxide hard mask to form floating gate underlying said polyoxide;
• removing exposed peripheral portions of said polyoxide until said polyoxide is recessed into said floating gate forming a beak of poly;
• forming interpoly oxide over said polyoxide;
• depositing a second polysilicon layer over said interpoly oxide;
• and
• patterning said second polysilicon layer with a second photoresist mask having control gate pattern to form a control gate to complete the forming of said split-gate flash memory cell with said sharp beak of poly to improve erase speed of said memory.