Reducing hot electron injection type of read disturb during read recovery phase in 3D memory
First Claim
1. An apparatus, comprising:
- a plurality of strings extending vertically in a stack, each string comprising a source end, a source side select gate transistor at the source end, a drain end, a dummy memory cell adjacent to a source side data memory cell, and a plurality of non-source side data memory cells between the source side data memory cell and the drain end;
a dummy word line connected to the dummy memory cells;
a plurality of data word lines comprising a source side data word line connected to the source side data memory cell and non-source side data word lines connected to the non-source side data memory cells; and
a control circuit, the control circuit configured to apply a voltage at a control gate read level to a selected data word line among the plurality of data word lines while sensing memory cells connected to the selected data word line and while applying a voltage at a read pass level to unselected data word lines among the plurality of data word lines, followed by ramping down a voltage of the non-source side data word line to a steady state voltage, followed by, after the ramping down the voltage of the non-source side data word line to the steady state voltage, ramping down a voltage of the source side data word line and the voltage of the dummy word line to the steady state voltage.
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Abstract
A memory device and associated techniques for reducing read disturb of memory cells during the last phase of a sensing operation when all voltage signals are ramped down to a steady state voltage. In one aspect, the voltages of the source side word line, WL0, and an adjacent dummy word line, WLDS1, are ramped down after the voltages of remaining word lines are ramped down. This can occur regardless of whether WL0 is the selected word line which is programmed or read. The technique can be applied after the sensing which occurs in a read or program-verify operation. Another option involves elevating the voltage of the selected word line so that all word lines are ramped down from the same level, such as a read pass level. The techniques are particularly useful when the memory device includes an interface in the channel between epitaxial silicon and polysilicon.
29 Citations
20 Claims
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1. An apparatus, comprising:
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a plurality of strings extending vertically in a stack, each string comprising a source end, a source side select gate transistor at the source end, a drain end, a dummy memory cell adjacent to a source side data memory cell, and a plurality of non-source side data memory cells between the source side data memory cell and the drain end; a dummy word line connected to the dummy memory cells; a plurality of data word lines comprising a source side data word line connected to the source side data memory cell and non-source side data word lines connected to the non-source side data memory cells; and a control circuit, the control circuit configured to apply a voltage at a control gate read level to a selected data word line among the plurality of data word lines while sensing memory cells connected to the selected data word line and while applying a voltage at a read pass level to unselected data word lines among the plurality of data word lines, followed by ramping down a voltage of the non-source side data word line to a steady state voltage, followed by, after the ramping down the voltage of the non-source side data word line to the steady state voltage, ramping down a voltage of the source side data word line and the voltage of the dummy word line to the steady state voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 20)
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14. A method, comprising:
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applying a voltage to a selected data word line in a block while sensing memory cells connected to the selected data word line and while applying a voltage at a read pass level to unselected data word lines in the block and to a dummy word line in the block, wherein the dummy word line is at a source side of the block; subsequently ramping down a voltage applied to data word lines which are not adjacent to the dummy word line to a steady state voltage; and subsequently, after the ramping down the voltage applied to the data word lines which are not adjacent to the dummy word line to the steady state voltage, ramping down a voltage applied to the dummy word line and a voltage applied to a data word line which is adjacent to the dummy word line to the steady state voltage. - View Dependent Claims (15, 16)
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17. An apparatus, comprising:
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means for sensing data memory cells in a block; and means for ramping down a voltage of a source side data word line to a steady state voltage concurrent with a ramping down of a dummy word line adjacent to the source side data word line to the steady state voltage, after ramping down a voltage of other data word lines in a block to the steady state voltage, and after the sensing of the data memory cells, wherein the source side data word line is at a source side of the block. - View Dependent Claims (18, 19)
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Specification