Improved Endurance of SONOS Flash Cells by Facile Lithography Processing Adjustment

A facile lithography regulation method is proposed to improve the endurance of SONOS flash cells in this paper. The physical structure of ONO layer and electrical read/write performance of SONOS cells before and after cycling are extensively investigated. It is founded that the thinner ONO layers under polysilicon edge bear larger electric field, and are more likely to be burnt out during cycling. This ONO weak point is brought in by the inevitable overlay shift of lithography mask, as well as the etch bias of dry etch and wet etch. Here through facile lithography energy regulation and lithography mask modulation, we increase the width of ONO, avoid the weak point under poly, and efficiently improve the endurance performance of SONOS cell from 5K to over 500K.