The first type of flash memory was NOR flash, invented by Intel in 1988,
which allows random access to any memory location on the chip. The
innovation that distinguished flash memory from earlier types of EEPROM
(Electrically Erasable Programmable Read-Only Memory) was that it allowed
multiple locations to be accessed simultaneously, thereby speeding up
data transfer times.
One year later, in 1989, Toshiba and Samsung introduced NAND flash to the
market. Toshiba still holds key patents on this technology. NAND flash
uses a different kind of logic gate to store data, and uses different
processes -- tunnel injection and tunnel release -- to perform the reading
and erasing operations. Compared to NOR flash, NAND flash is faster
and cheaper to make. However, NAND flash does not allow random access to
memory locations, thereby restricting its use to applications where serial
writing and reading are appropriate, such as music players and digital
cameras. NAND flash is not useful for general computer applications.
Wikipedia: Flash memory
Although Toshiba holds the basic NAND flash patents, another important
player in the intellectual-property game is SanDisk. Acting in a
partnership with Toshiba, SanDisk developed MLC (multi-level cell)
technology, which allows each NAND flash cell to hold two bits of data
rather than one. This means that a chip with MLC technology has twice the
capacity as a similarly priced chip without MLC. Thus, MLC effectively
halves the cost of producing chips with a given capacity.
Because SanDisk holds the patents on MLC, any company that wishes to
be competitive in the NAND flash marketplace must buy licensing from
SanDisk in addition to a license from Toshiba for the fundamental NAND
technology. Neither company has been shy about enforcing its patents
against corporate rivals. Toshiba has recently filed suit against
Hynix, an important Korean semiconductor manufacturer, charging it with
infringement of the basic NAND flash patents. SanDisk has also been
active in litigation over its MLC patents.
Toshiba and Hynix entered into a patent cross-licensing agreement
in August 1996 that included semiconductor products. The companies
started negotiation of an extension of the agreement prior to
its December 31, 2002 expiration. At the time, Toshiba sought
to secure a reasonable fee for access to its patents.
Failure to reach a satisfactory conclusion left Toshiba with no
alternative other than to pursue legal recourse.
So, in Japan, Toshiba filed a suit against Hynix for alleged
infringement of its NAND flash memory patents. Toshiba's suit
in Tokyo seeks damages against Hynix's alleged infringement
of three NAND-related patents. It seeks an injunction against
In the U.S., Toshiba filed a similar suit against Hynix and its
U.S. subsidiaries for infringement of Toshiba's DRAM and NAND
flash memory patents [...].
eeTimes: Toshiba files ITC suit against Hynix
"We want to make sure NAND flash remains protected," Sanjay
Mehrotra, co-founder and COO of SanDisk, told Electronics Weekly.
The reasons why Mehrotra believes this is possible is because
SanDisk owns the fundamental patents on multi-level cell (MLC)
technology; because NAND is the subject of a process race which
SanDisk and its manufacturing partner Toshiba are winning; and
because of the technological difficulties inherent in NAND flash.
"We have sued STMicroelectronics in the ITC [US International
Trade Commission] fast-track procedure and we expect judgement
by the end of the year," said Mehrotra.
"We sued Samsung in the ITC and had the patents declared valid. We
have a controller chip to manage MLC which no one else can do,
they cant productionise MLC the same way we can," he said.
"Without the ability to do MLC (two or more bits-per-transistor
memory), rivals will remain uncompetitive. Using multiple die
in a package does not work because it is twice as expensive. MLC
halves the cost per megabyte," said Mehrotra.
That helps SanDisks cross-licensees: Samsung, Toshiba, Sharp,
Renesas and Matsushita, but is a potential barrier for NAND
players it has not licensed, which are Hynix, STMicroelectronics
and Micron Technology.
Electronics Weekly: Patents keep NAND flash healthy
In short, a company that wishes to manufacture NAND flash memory chips
must indeed pay licensing fees to two patent holders: to Toshiba for the
basic technology, and to SanDisk for the MLC capacity-doubling technology.