Write operations that simultaneously program multiple memory cells on the
same word line in an MBPC Flash memory employ word line voltage variation,
programming pulse width variation, and data-dependent bit line and/or
source line biasing to achieve uniform programming accuracy across a range
of target threshold voltages. A first type of write operations reaches
different target threshold voltages during different time intervals, but
uses word line signals that optimize threshold voltage resolution
regardless of the target threshold voltage. A second type uses bit line
and/or source line biases that depend on the multi-bit data values being
written so that different memory cells reach different target threshold
voltage at about the same time. Source line biasing can also reduce bit
line leakage current through unselected memory cells during read or verify
operations. A memory includes divided source lines that permit separate
data-dependent source biasing. During or at the end of write operations,
remedial programming sequences can adjust the threshold voltages of memory
cells that program slowly.
