Sandisk Technologies Inc.

Towhidur Razzak

Jiahui Yuan

Abu Naser Zainuddin

Deepanshu Dutta

Ravi J Kumar

Different ramp rates for different regions, or zones, of word lines are used for the pass voltage applied to unselected word lines during a program operation. The properties of the word lines, such as their resistance and capacitance (RC) values, vary across the NAND memory array. By determining the RC values of the word lines across the array, the word lines can be broken into multiple zones based on these properties. The zones can then be individually assigned different ramp rates for applying a pass voltage to the unselected word lines, where a parameter for the ramp rates can be stored as a register value on the memory die.

Word line dependent pass voltage ramp rate to improve performance of NAND memory

In order to lower the peak and average current through the channel (thereby lowering peak and average power consumption) during program-verify, which exhibits a word line dependency, the inventors propose to program dummy memory cells connected to a dummy word line before programming data memory cells connected to a data word line. The additional resistance in the NAND string introduced by the preprogrammed dummy memory cells will cause the peak current, and power consumption, to be lower. To address the word line dependency, the dummy memory cells connected to the dummy word line can be programmed to different threshold voltages based on which data word line is to be programmed. Thus, prior to programming data non-volatile memory cells connected to a particular data word line, the dummy memory cells are programmed to a threshold voltage that is chosen based on the position of the particular data word line.

Non-volatile memory with programmable resistance non-data word line

Technology is disclosed herein for a memory system that balances peak Icc with programming speed. A memory system applies voltages to respective word lines during a verify operation that balances peak Icc with programming speed. The voltages for which the ramp rate is controlled include a read pass voltage applied to unselected word lines and a spike voltage applied to the selected word line at the beginning of the verify. The ramp rate of the voltages is slow enough to keep the peak Icc during verify to a target peak Icc regardless of which word line is selected for verify. However, the ramp rate of the voltages to the word lines during verify is fast enough to make use of the target peak Icc in order achieve faster programming. Therefore, the impact on programming time is minimized while staying within the allowed peak Icc.

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Santa Clara, CA, United States of America

Towhidur Razzak