US 8,264,890 B2 · Two pass erase for non-volatile storage

Abstract

Techniques are disclosed herein for erasing non-volatile memory cells. A subset of the memory cells are pre-conditioned prior to erase. The pre-conditioning alters the threshold voltage of the memory cells in a way that may help make later calculations more accurate. As an example, memory cells along a single word line might be pre-conditioned. After the pre-conditioning, the memory cells are erased using a trial erase pulse. A suitable magnitude for a second pulse is determined based on the magnitude of the trial erase pulse and data collected about the threshold voltage distribution after the trial erase. The second erase pulse is used to erase the memory cells. Determining an appropriate magnitude for the second erase pulse minimizes or eliminates over-erasing.

Claims25

Dependent claims

A method for operating a non-volatile storage device, the method comprising:

pre-conditioning a subset of a group of non-volatile storage elements such that the subset of non-volatile storage elements have at least a certain threshold voltage;
performing a first erase of the group of non-volatile storage elements using a first erase voltage, the subset of non-volatile storage elements have a threshold voltage distribution as a result of the first erase, the first erase is performed after the pre-conditioning while the subset of non-volatile storage elements have at least the certain threshold voltage;
determining a reference voltage within the threshold voltage distribution;
determining a second erase voltage based on the first erase voltage and the reference voltage;
and
performing a second erase of the group of non-volatile storage elements using the second erase voltage.

3 more elements

A non-volatile storage device comprising:

a group of non-volatile storage elements;
and
one or more managing circuits in communication with the group of non-volatile storage elements, the one or more managing circuits pre-condition a subset of the group of non-volatile storage elements such that the subset of non-volatile storage elements have at least a certain threshold voltage, the one or more managing circuits perform a first erase of the group of non-volatile storage elements using a first erase voltage, the subset of non-volatile storage elements have a threshold voltage distribution as a result of the first erase, the first erase is performed while the subset of non-volatile storage elements have at least the certain threshold voltage, the one or more managing circuits determine a reference voltage within the threshold voltage distribution, the one or more managing circuits determine a second erase voltage based on the first erase voltage and the reference voltage, the one or more managing circuits perform a second erase of the group of non-volatile storage elements using the second erase voltage.

Dependencies are inferred from the claim text.

Two pass erase for non-volatile storage

Life of this patent

Two pass erase for non-volatile storage

Life of this patent

Abstract

Claims25