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There are essentially two competing memory-storage solutions for
mobile consumer electronics--NAND flash and NOR flash. NAND flash is
capable of higher density, with 8-Gbit single-die and higher levels in
the multidie stacked packages available today. The increased density is
vitally important, given the additional functionality being integrated
into consumer products. NOR flash, for its part, offers Execute In
Place, which allows applications to run from the memory rather than from
Compared with NAND flash, the Mbit/millimeter-square rating for the
latest generations of NOR flash falls between 2- and 4-Gbit single-level
cell NAND flash devices and 1- and 2-Gbit multilevel-cell NAND flash.
This rating gives NOR flash a competitive edge against the encroachment
of NAND and OneNAND solutions.
The NOR flash market has seen some changes recently, according to
iSuppli. Spansion displaced Intel as the leader in the NOR flash market
by growing 25.6 percent in the past year. Intel and STMicroelectronics
were ranked second and third, respectively, followed by Samsung, Silicon
Storage Technology and others. Total NOR flash revenue rose from $7.86
million in 2005 to $8.49 million in 2006.
NOR flash is most commonly used in wireless and embedded
applications, specifically in cell phones and automobiles. Typical
designs are dual-die solutions with NOR flash and DRAM packaged
New, potentially lucrative revenue streams in consumer electronics
applications are possible, however, as the density of NOR flash
increases. With higher density, NOR flash can prolong the design
traction in these applications. New uses also can be found in areas such
as publishing and capturing content for music, video, games, e-books and
Smaller process lithographies must be reached if NOR flash is to
continue to provide increased density to meet growing storage
requirements. The implementation of smaller processes allows more die
per wafer to be generated, reducing the overall cost. In addition, die
sizes can be maintained while the density doubles.
Intel was the first vendor to introduce 65-nanometer NOR flash
solutions with its Strataflash Cellular Memory last year (M18, part
number PF48F6000 M0Y0BE). The device was built using Intel's ETOX X
65-nm process. Intel's 90-nm product was significantly redesigned and
featured a new sensing architecture, which is more robust and allowed
Intel to scale its designs faster. The 65-nm release is proof that the
redesign at 90 nm--specifically the work on the sensing scheme--is
yielding benefits already. Because Intel was able to maintain the same
architecture moving from 90 to 65 nm, the devices are drop-in
compatible, which will make the transition easier for cellular OEMs.
The next release was the Spansion 90-nm 1-Gbit MirrorBit (part number
S29GL01GP12FAI01). While Spansion has not yet migrated to a 65-nm
lithography, it was still able to reach a 1-Gbit density using 90-nm
technology. Spansion is also coming out with its QuadBit solution. While
MirrorBit can store 2 bits per cell, Quad-Bit can store 4 bits per cell.
Spansion said the 90-nm 1-Gbit device will have a die size of 47 mm2.
The company also has plans for a 2-Gbit device with a die size of 76 mm2.
The latest entrant is from STMicroelectronics (part number
M39P0R1080E4ZAD). A second company entering the 65-nm node gives OEMs
more options when choosing a NOR flash memory solution. Compared with
other devices analyzed, the ST part has the smallest die size, resulting
in the highest Mbit/mm square rating.
(Click on image to enlarge)
NOR flash technology is generating a lot of interest, and is still
considered the dominant flash technology for the handset and mobile
market. Considering the ongoing growth of the cellular industry, it's
clear why manufacturers continue to make process improvements to NOR
flash. Spansion, in announcing its soon-to-be-released 65-nm MirrorBit,
said it has already begun development of a 45-nm NOR flash.
Gregory A. Quirk is technical marketing manager at Semiconductor
Insights (Ottawa), a leading technical analyst company focusing