Reducing hot electron injection type of read disturb in 3D non-volatile memory for edge word lines
First Claim
1. A method, comprising:
- while a demarcation voltage is applied to a selected word line among a plurality of word lines, applying a read pass voltage to unselected word lines among the plurality of word lines and applying a respective turn on voltage to a select gate line; and
after the demarcation voltage is applied to the selected word line;
ramping down a voltage of the select gate line from the respective turn on voltage to a respective turn off voltage;
ramping down a voltage of the selected word line at a specified time before the ramping down the voltage of the select gate line if the selected word line is among a predefined subset of the plurality of word lines; and
ramping down the voltage of the selected word line at a time which is after the specified time and no later than a time of the ramping down of the voltage of the select gate line if the selected word line is among a remaining subset of the plurality of word lines.
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Accused Products
Abstract
Read disturb due to hot electron injection is reduced in a 3D memory device by controlling the magnitude and timing of word line and select gate ramp down voltages at the end of a sensing operation. In an example read operation, a predefined subset of word lines includes source-side and drain-side word lines. For the predefined subset of word lines, word line voltages are ramped down before the voltages of the select gates are ramped down. Subsequently, for a remaining subset of word lines, word line voltages are ramped down, but no later than the ramping down of the voltages of the select gates. The timing of the ramp down of the selected word line depends on whether it is among the predefined subset or the remaining subset. The predefined subset can include a number of adjacent or non-adjacent word lines.
47 Citations
22 Claims
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1. A method, comprising:
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while a demarcation voltage is applied to a selected word line among a plurality of word lines, applying a read pass voltage to unselected word lines among the plurality of word lines and applying a respective turn on voltage to a select gate line; and after the demarcation voltage is applied to the selected word line; ramping down a voltage of the select gate line from the respective turn on voltage to a respective turn off voltage; ramping down a voltage of the selected word line at a specified time before the ramping down the voltage of the select gate line if the selected word line is among a predefined subset of the plurality of word lines; and ramping down the voltage of the selected word line at a time which is after the specified time and no later than a time of the ramping down of the voltage of the select gate line if the selected word line is among a remaining subset of the plurality of word lines. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. An apparatus, comprising:
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means for applying a demarcation voltage to a selected word line among a plurality of word lines; means for applying a read pass voltage to unselected word lines among the plurality of word lines, a respective turn on voltage to a source-side select gate line at a source-side of the plurality of word lines and a respective turn on voltage to a drain-side select gate line at a drain-side of the plurality of word lines; means for ramping down voltages of a predefined subset of multiple word lines of the plurality of word lines, before ramping down voltages of a remaining subset of multiple word lines of the plurality of word lines, wherein the selected word line is among the predefined subset of multiple word lines; and means for ramping down a voltage of the drain-side select gate line from the respective turn on voltage to a respective urn off voltage no sooner than the ramping down of the voltages of the remaining subset of multiple word lines. - View Dependent Claims (18)
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19. An apparatus, comprising:
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a plurality of word lines connected to memory cells, wherein the plurality of word lines comprise a selected word line and a plurality of unselected word lines; a source-side select gate line at a source-side of the plurality of word lines; a drain-side select gate line at a drain-side of the plurality of word lines; and a control circuit, the control circuit is configured to; apply a demarcation voltage to the selected word line; apply a read pass voltage to the plurality of unselected word lines; apply a respective turn on voltage to the source-side select gate line and a respective turn on voltage is applied to the drain-side select gate line; concurrently ramp down the voltage of the selected word line and ramp down a voltage of at least one other word line of the plurality of unselected word lines from the read pass voltage; and subsequently ramp down voltages of remaining unselected word lines of the plurality of unselected word lines from the read pass voltage and ramp down a voltage of the drain-side select gate line from the respective turn on voltage to a respective turn off voltage. - View Dependent Claims (20, 21, 22)
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Specification