Apparatuses and methods of reading memory cells

摘要

A method is provided for a reading memory even if there is a threshold voltage in an overlapped threshold voltage (VTH) region between a first state distribution and a second state distribution. The method includes ramping a bias on a memory cell a first time to determine a first threshold voltage (VTH1) of the memory cell and determining whether the VTH1 is within the overlapped VTH region. Upon determination that the memory cell is within the overlapped VTH region, the method further includes applying a write pulse to the memory cell; ramping a bias on the memory cell a second time to determine a second threshold voltage (VTH2); and determining the state of the memory cell prior to receiving the write pulse based on a comparison between the VTH1 and the VTH2.

主权项

1. A method of reading a memory cell in a memory array that can have an overlapped electrical response region between a first state distribution a second state distribution, comprising:
proving a plurality memory cells, wherein the first state distribution corresponds to a first memory state and has a mean electrical response lower than a mean electrical response of the second state distribution corresponding to a second memory state; ramping a bias on a memory cell a first time to determine a first electrical response of the memory cell; and determining whether the first electrical response is within the overlapped electrical response region, wherein upon determining that the first electrical response is within the overlapped electrical response region, the method further comprises applying a write pulse to the memory cell, ramping a bias on the memory cell a second time to determine a second electrical response, and determining a state of the memory cell prior to receiving the write pulse based on a comparison between the first electrical response and the second electrical response.