Nonvolatile memory read with asymmetric read-pass voltages
AssigneeSanDisk Technologies LLC
InventorsYiwen Qian, Jiahui Yuan
Life of this patent
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Abstract
An apparatus includes control circuits configured to connect to a plurality of nonvolatile memory cells in NAND strings. The one or more control circuits are configured to apply read voltages on selected word lines to read selected memory cells while read-pass voltages are applied to unselected word lines. The read-pass voltages including a first Near Word Line (NWL) read-pass voltage applied to a first unselected word line adjacent to a selected word line, a second NWL read-pass voltage applied to a second unselected word line adjacent to the selected word line and a common read-pass voltage applied to additional unselected word lines.
Claims18
An apparatus comprising:
- one or more control circuits configured to connect to a plurality of nonvolatile memory cells in NAND strings, wherein the one or more control circuits are configured to:
- apply read voltages on selected word lines connected to the plurality of nonvolatile memory cells to read selected memory cells coupled to the selected word lines while read-pass voltages are applied to unselected word lines connected to unselected nonvolatile memory cells, the read-pass voltages including a first symmetric Near Word Line (NWL) read-pass voltage applied to unselected word lines on either side of a first selected word line, a first NWL read-pass voltage applied to a first unselected word line adjacent to a second selected word line, a second NWL read-pass voltage applied to a second unselected word line adjacent to the second selected word line and a common read-pass voltage applied to additional unselected word lines, the second NWL read-pass voltage is less than the first NWL read-pass voltage and the common read-pass voltage is less than the first and second NWL read-pass voltages.
A method of reading a plurality of nonvolatile memory cells in a memory structure that includes word lines coupled to nonvolatile memory cells that are connected in NAND strings, comprising:
- while applying a read voltage on a first selected word line, applying a first Near Word Line (NWL) read-pass voltage on a first unselected word line that neighbors the first selected word line on a first side;
- while applying the read voltage on the first selected word line, applying the first NWL read-pass voltage on a second unselected word line that neighbors the first selected word line on a second side that is opposite to the first side;
- while applying the read voltage on a second selected word line, applying the first NWL read-pass voltage on a third unselected word line that neighbors the second selected word line on the first side;
- and
- while applying the read voltage on the second selected word line, applying a second NWL read-pass voltage on a fourth unselected word line that neighbors the second selected word line on the second side.
A storage system comprising:
- a plurality of nonvolatile memory cells arranged in NAND strings connected by word lines;
- and
- means for applying read voltages on selected word lines to read selected memory cells coupled to the selected word lines while read-pass voltages are applied to unselected word lines connected to unselected nonvolatile memory cells of the NAND strings, the read-pass voltages including a first symmetric Near Word Line (NWL) read-pass voltage applied to unselected word lines adjacent to a first selected word line, a first NWL read-pass voltage applied to a first unselected word line adjacent to a second selected word line, a second NWL read-pass voltage applied to a second unselected word line adjacent to the second selected word line and a common read-pass voltage applied to additional unselected word lines, wherein the second NWL read-pass voltage is less than the first NWL read-pass voltage and the common read-pass voltage is less than the first and second NWL read-pass voltages.
Dependencies are inferred from the claim text.