Three-dimensional NAND memory device and system and method for performing read operations thereof
The present disclosure provides a memory device that includes memory cells addressed by word lines and bit lines and a peripheral circuit for performing a read operation for the memory device. The peripheral circuit is configured to apply a read voltage to a selected word line and apply a pass voltage to an unselected word line adjacent to the selected word line, wherein a magnitude of the pass voltage is adjusted according to the read voltage applied to the selected word line.
1 . A memory device, comprising:
memory cells addressed by word lines and bit lines; and
a peripheral circuit for performing a read operation for the memory device, the peripheral circuit configured to:
apply a read voltage to a selected word line, wherein the selected word line is selected as one word line from among the word lines and a remainder of the word lines are unselected;
responsive to the read voltage having a first value, apply a second pass voltage to an unselected word line adjacent to the selected word line;
responsive to the read voltage subsequently having a second value, apply a first pass voltage to the unselected word line adjacent to the selected word line, the second value being less than the first value and the first pass voltage being greater in value than the second pass voltage; and
responsive to the read voltage subsequently having a third value, continue applying the first pass voltage to the unselected word line adjacent to the selected word line, the third value being less than the second value.
2 . The memory device of claim 1 , wherein:
the read voltage comprises a first read reference voltage and a second read reference voltage that is higher than the first read reference voltage; and
the first pass voltage and the second pass voltage are applied to the unselected word line when the first read reference voltage and the second read reference voltage are applied to the selected word line, respectively.
3 . The memory device of claim 2 , wherein:
the read voltage further comprises a first group of read reference voltages and a second group of read reference voltages that are higher than the first group of read reference voltages;
the first pass voltage is applied to the unselected word line when any read reference voltage in the first group is applied to the selected word line; and
the second pass voltage is applied to the unselected word line when any read reference voltage in the second group is applied to the selected word line.
4 . The memory device of claim 2 , wherein the peripheral circuit is further configured to:
apply a further pass voltage to a further unselected word line that is not adjacent to the selected word line, wherein the further pass voltage is lower than the first or second pass voltage applied to the unselected word line adjacent to the selected word line.
5 . The memory device of claim 4 , wherein the first or second pass voltage and the further pass voltage are configured to switch on the memory cells coupled to the pass voltage and the further pass voltage.
6 . The memory device of claim 4 , wherein the second pass voltage is higher than the further pass voltage by 0.5V to 1 V, and the first pass voltage is higher than the further pass voltage by 1 V to 2V.
7 . The memory device of claim 1 , wherein the read voltage comprises one or more read reference voltages, and each of the one or more read reference voltages distinguishes two logic states of the memory cells.
8 . A method for performing a read operation for a memory device, the memory device comprising memory cells addressable through word lines and bit lines, the method comprising:
applying a read voltage to a selected word line, wherein the selected word line is selected as one word line from among the word lines and a remainder of the word lines are unselected;
responsive to the read voltage having a first value, applying a second pass voltage to an unselected word line adjacent to the selected word line, wherein a magnitude of the pass voltage or the second pass voltage is adjusted according to the read voltage applied to the selected word line;
responsive to the read voltage subsequently having one of a second value, applying a first pass voltage to the unselected word line adjacent to the selected word line, the second value being less than the first value and the first pass voltage being greater in value than the second pass voltage;
responsive to the read voltage subsequently having a third value, continue applying the first pass voltage to the unselected word line adjacent to the selected word line, the third value being less than the second value.
9 . The method of claim 8 , further comprising:
applying a first read reference voltage to the selected word line at a first time;
applying a third pass voltage to the unselected word line at the first time;
applying a second read reference voltage to the selected word line at a second time, wherein the second read reference voltage is higher than the first read reference voltage; and
applying a fourth pass voltage to the unselected word line at the second time, wherein the fourth pass voltage is lower than the third pass voltage.
10 . The method of claim 9 , further comprising:
applying the third pass voltage to the unselected word line when the read voltage applied to the selected word line comprises a first group of read reference voltages; and
applying the fourth pass voltage to the unselected word line when the read voltage applied to the selected word line comprises a second group of read reference voltages, wherein the second group of read reference voltages comprise magnitudes higher than the first group of read reference voltages.
11 . The method of claim 9 , further comprising:
applying a further pass voltage to a further unselected word line that is not adjacent to the selected word line, wherein the further pass voltage is lower than the third or fourth pass voltages applied to the unselected word line adjacent to the selected word line.
12 . The method of claim 11 , wherein the third or fourth pass voltages and the further pass voltage are configured to switch on the memory cells coupled to the third or fourth pass voltages and the further pass voltage.
13 . The method of claim 11 , wherein the fourth pass voltage is higher than the further pass voltage by 0.5V to 1 V, and the third pass voltage is higher than the further pass voltage by 1 V to 2V.
14 . The method of claim 8 , wherein the applying of the read voltage comprises applying one or more read reference voltages, wherein each of the one or more read reference voltages distinguishes two logic states of the memory cells.
15 . A memory system, comprising:
a memory controller; and
a memory device configured to receive instructions from the memory controller to perform a read operation, the memory device comprising:
memory cells addressed by word lines and bit lines; and
a peripheral circuit configured to:
apply a read voltage to a selected word line, wherein the selected word line is selected as one word line from among the word lines and a remainder of the word lines are unselected;
responsive to the read voltage having a first value, apply a second pass voltage to an unselected word line adjacent to the selected word line, wherein a magnitude of the pass voltage or the second pass voltage is adjusted according to the read voltage applied to the selected word line;
responsive to the read voltage subsequently having one of a second value, apply a first pass voltage to the unselected word line adjacent to the selected word line, the second value being less than the first value and the first pass voltage being greater in value than the second pass voltage; and
responsive to the read voltage subsequently having a third value, continue applying the first pass voltage to the unselected word line adjacent to the selected word line, the third value being less than the second value.
16 . The memory system of claim 15 , wherein:
the read voltage comprises a first read reference voltage and a second read reference voltage that is higher than the first read reference voltage; and
the first pass voltage and the second pass voltage are applied to the unselected word line when the first read reference voltage and the second read reference voltage are applied to the selected word line, respectively.
17 . The memory system of claim 16 , wherein:
the read voltage further comprises a first group of read reference voltages and a second group of read reference voltages that are higher than the first group of read reference voltages;
the first pass voltage is applied to the unselected word line when any read reference voltage in the first group is applied to the selected word line; and
the second pass voltage is applied to the unselected word line when any read reference voltage in the second group is applied to the selected word line.
18 . The memory system of claim 16 , wherein the peripheral circuit is further configured to:
apply a further pass voltage to a further unselected word line that is not adjacent to the selected word line, wherein the further pass voltage is lower than the first or second pass voltage applied to the unselected word line adjacent to the selected word line.
19 . The memory system of claim 18 , wherein the pass voltage and the further pass voltage are configured to switch on the memory cells coupled to the first or second pass voltage and the further pass voltage.
20 . The memory system of claim 15 , wherein the read voltage comprises one or more read reference voltages, and each of the one or more read reference voltages distinguishes two logic states of the memory cells.