SONOS-Type Flash Memory Cell With Metal /\hbox\hbox/ \hbox/\hbox\hbox/\hbox Structure for Low-Voltage High-Speed Program/Erase Operation

High-quality Al 2 O 3 and Si 3 N 4 dielectrics synthesized in a molecular/atomic deposition system were developed and adopted as blocking oxide and tunnel dielectric, respectively in a SONOS-type NAND flash memory cell. In particular, the use of trap-free Si 3 N 4 as tunnel dielectric enables low-voltage erase operation due to its low barrier height for holes, and the relatively high-k value of Al 2 O 3 enhances the low-voltage and high-speed program/erase (P/E) operations. We fabricated and investigated NAND flash memory cells with metal/Al 2 O 3 /SiN/Si 3 N 4 /Si structure. The fabricated cell shows 3.8-V memory window with P/E conditions of +15 V for 100 mus and -10 V for 10 ms. It also shows good endurance up to 10 000 cycles and more than 1.5-V memory window after ten years.