ADAPTIVE PROGRAMMING METHODS FOR NONVOLATILE MEMORY CELLS

摘要

Adaptive write operations for non-volatile memories select programming parameters according to monitored programming performance of individual memory cells. In one embodiment of the invention, programming voltage for a memory cell increases by an amount that depends on the time required to reach a predetermined voltage and then a jump in the programming voltage is added to the programming voltage required to reach the next predetermined voltage. The adaptive programming method is applied to the gate voltage of memory cells; alternatively, it can be applied to the drain voltage of memory cells along a common word line. A circuit combines the function of a program switch and drain voltage regulator, allowing independent control of drain voltage of selected memory cells for parallel and adaptive programming. Verify and adaptive read operations use variable word line voltages to provide optimal biasing of memory and reference cells during sensing.

主权项

1. A programming method for a non-volatile memory comprising:
(a) applying a first programming voltage to a plurality of selected memory cells during a write process that changes threshold voltages of the selected memory cells; and (b) repeating step (a) until the threshold voltages of the selected memory cells reach respective target threshold voltages that represent data values being written, wherein before each of these repetitions of the step (a), the programming voltage is increased by a voltage increment until the first programming voltage has reached a maximum allowable voltage.