US 8,897,062 B2 · Memory programming for a phase change memory cell

Abstract

Systems, methods, and devices for iteratively writing contents to memory locations are provided. A statistical model is used to determine a sequence of pulses to write desired contents to a memory location. The contents can be expressed as a resistance value in a range to store one or more bits in a memory cell. For phase change memory, an adaptive reset pulse and one or more annealing pulses are selected based on a desired resistance range. Reading the resistance value of the memory cell can provide feedback to determine adjustments in an overall pulse application strategy. The statistical model and a look up table can be used to select and modify pulses. Adaptively updating the statistical model and look up table may reduce the number of looping iterations to shift the resistance value of the memory cell into the desired resistance range.

Claims12

Dependent claims

A method for programming a phase change memory (PCM) cell, comprising:

receiving a desired resistance range for the PCM cell, the PCM cell having a state with a resistance value;
and
looping to determine adjustments to the resistance value of the PCM cell, the looping comprising:
reading the resistance value of the PCM cell;
applying an annealing pulse in response to determining that the resistance value of the PCM cell is greater than the desired resistance range, the annealing pulse shaped responsive to the resistance value of the PCM cell and the desired resistance range;
applying an adjustable reset pulse to reset the state of the PCM cell in response to determining that the resistance value of the PCM cell is less than the desired resistance range, the adjustable reset pulse shaped responsive to the desired resistance range by determining an index associated with the desired resistance range and using the index to lookup one or more adjustable reset pulse shape characteristics in a table;
and
repeating the looping until one or more termination criteria are met.

5 more elements

A method for programming a phase change memory (PCM) cell, comprising:

receiving a desired resistance range for the PCM cell, the PCM cell having a state with a resistance value;
and
looping to determine adjustments to the resistance value of the PCM cell, the looping comprising;
reading the resistance value of the PCM cell;
applying an annealing pulse in response to determining that the resistance value of the PCM cell is greater than the desired resistance range, the annealing pulse shaped responsive to the resistance value of the PCM cell and the desired resistance range;
applying an adjustable reset pulse to reset the state of the PCM cell in response to determining that the resistance value of the PCM cell is less than the desired resistance range, the adjustable reset pulse shaped responsive to the desired resistance range;
assigning a cost to each pulse;
determining a statistical model for a probable outcome of applying each pulse as a function of an initial state of the PCM cell;
selecting a pulse application sequence for the PCM cell that minimizes a total expected cost until one or more termination criteria are met;
and
repeating the looping until one or more of the termination criteria are met.

8 more elements

Dependencies are inferred from the claim text.

Memory programming for a phase change memory cell

Life of this patent

Memory programming for a phase change memory cell

Life of this patent

Abstract

Claims12