New erase scheme for DINOR flash memory enhancing erase/write cycling endurance characteristics
Naoki Tsuji, N. Ajika, K. Yuzuriha, Yuichi Kunori, M. Hatanaka, Hirokazu Miyoshi · 2002
New erase scheme for DINOR (Divided Bit Line NOR) flash memory is proposed and investigated, which utilizes substrate hot electron(SHE) injection instead of FN tunnel injection for erasure. Additional process or alteration of the cell structure is not needed to realize SHE erasure. The cell is formed in a triple well structure. The bottom n-well layer, which surrounds the p-well, is used as electron supply source in the SHE. By adopting SHE for erasure, the electric field required across the tunnel oxide was reduced to 1/4, compared with FN erasure. It needs less than 1 second for erasure, which is sufficient for DINOR operation. It is shown that V th window narrowing during erase/write cycling was significantly reduced by using SHE for erasure, as compared with using FN tunneling. The mechanism of enhanced erase/write cycling endurance is also examined.>