The ExcelBit¢â is a proprietary Flash memory cell technology
of Excel Semiconductor in a NOR architecture. It has
been developed jointly with Dongbu Electronics, a strategic
foundry partner. Its baseline is a 0.18§ stack-based,
triple-well CMOS technology with 1.8 Vcc (core) that
is easily scalable to 0.13§ technology. The ExcelBit¢â
Flash memory cell is especially engineered to deliver
its optimum performance when combined with multi-level-cell
(MLC) technology (storing 2 bits of data in one memory
cell: refer to Table 1).
The charge storage state of a Flash memory cell transistor
is a key to Flash memory cell technology. For single-bit,
stack-gate devices like the ExcelBit¢â, the memory cell
has either a lot of charges (data 1) or little charges
(data 0). Charge is placed on the floating gate through
a programming technique known as channel hot electron
(CHE), generating a "1" state. Charge is extracted
from the floating gate through an erase technique known
as the Fowler-Nordheim(FN) tunneling through the channel
of the transistor.
Depending on the amount of the charges stored in a
Flash memory cell transistor, threshold voltage of the
cell transistor changes. It is possible to place a precise
amount of charges on the floating gate by means of a
cell-by-cell programming technique or erased by the
FNtunneling technique.
Combined with the standard CMOS logic technology, the
ExcelBit¢â can also be applied to embedded Flash IPs
to produce very compact and cost-effective arrays in
a wide variety of densities.
