STATE DETERMINATION IN RESISTANCE VARIABLE MEMORY

摘要

An evaluation signal is applied to a memory cell in an array of resistance variable memory cells. The evaluation signal is configured to cause the memory cell to switch from a first state to a second state. Responses from the memory cell are sensed at three or more sample points. Differences between the responses are determined. For example, with three sample points, a first delta is determined between the first two responses and a second delta is determined between the last two responses. A difference of deltas is determined as a difference between the first and second delta, or vice versa. It is determined that the memory cell changes from the first to the second state if the difference of deltas is above a threshold. It is determined that the memory cell remains in the second state if the difference of deltas is below the threshold.

主权项

1. A method for sensing a resistance variable memory cell, comprising:
applying an evaluation signal to a resistance variable memory cell, the evaluation signal configured to cause the resistance variable memory cell to switch from a first data state to a second data state at a threshold current; sensing three or more responses of the resistance variable memory cell at three or more different sample points in time during application of the evaluation signal to the resistance variable memory cell; and analyzing the three or more responses to determine whether the resistance variable memory cell changes from the first data state to the second data state during the application of the evaluation signal to the resistance variable memory cell.