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Technology Stocks : WDC/Sandisk Corporation -- Ignore unavailable to you. Want to Upgrade?

To: Craig Freeman who wrote (17020)	12/13/2000 2:56:53 PM
From: Binx Bolling	Read Replies (1) \| Respond to of 60323

United States Patent 6,160,739 Wong Dec. 12, 2000 -------------------------------------------------------------------------------- Non-volatile memories with improved endurance and extended lifetime Abstract Non-volatile memory cells in a sector of a memory array are selectively erased only when it is determined that the selected memory cells require erasing. A memory cell is selectively erased by applying two non-zero erase voltages to the cell, where the combination of the two erase voltages generates an electric field sufficient to induce Fowler-Nordheim tunneling and erase the cell. Memory cells not selected for erasing, either in the same sector or other sectors, have only one or none of the two erase voltages applied, which is insufficient to erase the unselected memory cells is a result, endurance of the non-volatile memory cells is improved because the memory cells are not subjected to repeated unnecessary erasing and programming operations. -------------------------------------------------------------------------------- Inventors: Wong; Sau C. (Hillsborough, CA). Assignee: SanDisk Corporation (Sunnyvale, CA). Appl. No.: 293,133 Filed: Apr. 16, 1999 Intl. Cl. : G11C 16/04 Current U.S. Cl.: 365/185.29; 365/185.33 Field of Search: 365/185.29, 185.33, 185.27, 185.18 -------------------------------------------------------------------------------- References Cited \| [Referenced By] -------------------------------------------------------------------------------- U.S. Patent Documents 5,047,981 Sept., 1991 Gill et al. 365/185.18 5,341,342 Aug., 1994 Brahmbhatt 365/185.3 5,777,923 Jul., 1998 Lee et al. 365/185.11 Foreign Patent Documents 226054A Jul., 1994 TW WO9749086 Dec., 1997 WO Primary Examiner: Le; Vu A. Attorney, Agent or Firm: Majestic, Parsons, Siebert & Hsue 10 Claims, 6 Drawing Figures