Tokyo, March 13, 2000 --- Fujitsu Limited announced today that it has
succeeded in developing one-transistor, one-capacitor (1T1C *1) memory
cell technology, which will help significantly increase memory capacity
in FRAM chips (Ferroelectric Random Access Memory). The new cell
technology will make it possible to produce megabit-class FRAM products
using 0.5 micron process technology, thus responding to growing demand
for large-volume memory for multi-function IC cards.
Due to the use of ferroelectric film, FRAMs retain information in memory
even when the power is turned off. They are as fast as SRAMs and DRAMs
in retrieving and writing data, and they have a re-write ability over
ten thousand times that of flash memories. Although FRAMs are currently
available mainly at the 64 kbit level, anticipated growth in the IC card
market is expected to drive demand for megabit-class devices.
Compared to 2T2C cell structure, 1T1C technology reduces the cell space
by half. In the past, circuit technology and manufacturing process
technology have been the major roadblocks in developing 1T1C structure
with stable operation because the architecture could only detect less
than half the memory information signal level. Fujitsu successfully
addressed this issue by developing new reference circuit technology (*2)
and by improving crystallization process technology (*3) to ensure
stable ferroelectric film.
Fujitsu and Ramtron International Corp. have been jointly developing
FRAMs since 1996, and the two companies presented their research on
an experimental 1T1C-structure 1 megabit FRAM in June 1998 at the
International VLSI Symposium. Building on improvements in the
ferroelectric material PZT (*4), Fujitsu introduced a commercial 2T2C-
cell structure 256 kbit FRAM at the end of last year.
To meet the rapidly expanding demand for multi-function IC cards,
Fujitsu intends to introduce large-capacity FRAM products by
utilizing increasingly finer process technology.
Glossary
- 1T1C memory cell (one-transistor/one-capacitor memory cell)
Digital data of "1s" and "0s" is distinguished by the difference
in electric levels between the dummy cell and the memory cell. The
circuit realizes reduced noise generation because of the small
electric gap with the dummy cell. In the case of 2T2C structure,
digital "1s" and "0s" are distinguished by the electric level
difference between capacitors within the cell.
- New reference circuit technology
- In order to detect "1s" and "0s" stored in the cell, dummy cells
are used in reference (standard electric level) occurrence circuits.
In addition, movement control mode is used to control special
changes in the dummy cell.
- The circuit is designed to lower noise generation in order to
improve cell signal detection capability.
- Manufacturing process technology
- Stability is secured by improving capacitor electrons.
- Crystal density quality becomes stable through improvements in
crystallization process.
- PZT, Pb (Zr, Ti) 03
Electric polarization (external electric field shifts Zr/Ti atoms
in crystal to move away from electric neutrality) enables storage
of data memory. The polarization remains after applying and
removing external electric field, thus achieving nonvolatile
property.
About Fujitsu Limited
Fujitsu Limited (TSE: 6702) is a leading provider of comprehensive
information technology and network solutions for the global
marketplace. Comprising over 500 group companies and affiliates
worldwide -- including ICL, Amdahl and DMR Consulting Group -- the
Fujitsu Group had consolidated revenues of 5.24 trillion yen
($43.3 billion) in the fiscal year ended March 31, 1999. With world-
class hardware and software technology in computers,
telecommunications and microelectronics, and a corps of 55,000
systems and services experts around the world, Fujitsu is uniquely
positioned to harness the power of the network to help its customers
succeed. Altogether, the Fujitsu Group has 188,000 employees and
operations in over 100 countries.
Homepage: http://www.fujitsu.com/
* FRAM (R) is a registered trademark of Ramtron International Co. All
other company/product names mentioned may be trademarks or registered trademarks of their respective holders and are used for identification purpose only.