Writing multiple levels in a phase change memory using a write/read reference voltage ramping up over a write/read period

摘要

Structures and methods for a multi-bit phase change memory are disclosed herein. A method includes establishing a write-reference voltage that incrementally ramps over a write period. The increments of the write-reference voltage correspond to discrete resistance states of a storage cell of the multi-bit phase change memory.

主权项

1. A method for storing information in a multi-bit phase change memory, the method comprising:
writing an initial write value in a storage cell of the multi-bit phase change memory, wherein the storage cell has a predetermined range of discrete resistance states, and the initial write value is a predetermined value at the midpoint of the range; reading a value stored in the storage cell by the writing; comparing the value stored in the storage cell to a target value; and adjusting the value stored in the storage cell based on the comparing.