Method for forming a square oxide structure or a square floating gate structure without rounding effect

Abstract

Abstract A method for forming a square oxide structure or a square floating gate without a rounding effect at its corners. A first dielectric layer is formed on a pad layer for a square oxide structure or a polysilicon layer overlying a gate oxide layer for a floating gate, and a second dielectric layer is formed on the first dielectric layer. The second dielectric layer is patterned to form parallel openings in a first direction using a first photosensitive mask. A second photosensitive mask, having a plurality of parallel openings in a second direction perpendicular to the first direction is formed over the second dielectric layer and the first dielectric layer. The first dielectric layer is etched through square openings where the openings in the second photosensitive mask and the openings in the second dielectric layer intersect, thereby forming square openings in the first dielectric layer. The second photosensitive mask and the second dielectric layer are removed. The square oxide structure is completed by etching a trench in the semiconductor structure and forming an STI or LOCOS. The square floating gate is completed by growing polysilicon oxide structures in the square openings in the first dielectric layer and removing the first dielectric layer to form a pattern of openings therebetween, and etching the polysilicon layer through the pattern of openings between the polysilicon oxide structures forming square floating gate polysilicon regions under the polysilicon oxide hard masks.

Inventors

• 👤 Hung-Cheng Sung
• 👤 Di-Son Kuo
• 👤 Chia-Ta Hsieh

Bibliographic Details