Vierra Magen Marcus LLP
Reducing read disturb in two-tier memory device by modifying duration of channel discharge based on selected word line
Techniques for reducing read disturb of memory cells in a two-tier stack having a lower tier and an upper tier separated by an interface. In a read operation, the channels of NAND strings are discharged before reading the selected memory cells. A discharge period is set based on a position of the selected word line in a stack or block of memory cells. The discharge period is longer when the selected word line is in the lower tier than in the upper tier. Additionally, the discharge period is longer when the selected word line is at a top of the lower tier than at a bottom of the lower tier. Other options to increase the discharge include increasing a ramp up rate and a peak level of the word line voltages during the discharge period as a function of the position of the selected word line.
SanDisk Technologies LLC
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Hong-Yan Wei Yingda
Chen Zhao Dong