Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!mailrus!csd4.milw.wisc.edu!leah!albanycs!crdgw1!uunet!murtoa.cs.mu.oz.au!munnari.oz.au!basser!steve
From: steve@basser.oz (Stephen Russell)
Newsgroups: comp.arch
Subject: Re: FRAM
Summary: FRAM not dead yet
Message-ID: <2244@basser.oz>
Date: 15 Jun 89 13:22:58 GMT
References: <1012@aber-cs.UUCP>
Organization: Dept of Comp Sci, Uni of Sydney, Australia
Lines: 57

In article <1012@aber-cs.UUCP> pcg@cs.aber.ac.uk (Piercarlo Grandi) writes:
>[...] It is the invention apparently of a single person (an old style
>inventor?), and was developed in coolaboration between him and some West
>Coast govnt. lab.

From article in June 1989 "Elcectronics Australia": the "technique for
applying ferro-electric materials to semiconductor devices [was]
invented by George Rohrer [from] Michigan".  Rights to this technology
was purchased in 1983 for $7.5M by (what is now) Ramtron Australia, a
wholly Aus company.

>Ferroelectric is a misnomer; from what I remeber a certain *potassium*
>compound has a rombohedrical crystalline structure;

It is the titanium atom in a PZT ceramic which can be in one of two
stable positions within the lattice.

>The advantages are: high noise immunity, very low power dissipation (none on
>standby), which means that multilayer (i.e. 3D) memories are possible, and
>almost infite scalability (down to the single crystal cell), the limit being
>the resolution of the electric grid.

Disadvantage of current technology is a "half-life" of around 10**10 state
reversals. Current implementations team the FRAM with CMOS SRAM which is
initialised/saved at power on/off to reduce FRAM cycling.

>It is therefore an old technology, and I haave been hoping for the last ten
>years that it comes of age.

It may happen yet. Here's some other snippets from the article:

o Ramtron International Corp, a subsiduary of Ramtron Aus, is developing
  chips at their plant in Colorado (no way it could happen in Aus, sigh...)
  Research was also done with U of Colorado, Colorado Springs, at cost to
  Ramtron of $13M.

o Ramtron has signed licensing agreements with ITT Semis, NMB Semis of Japan,
  TRW and Seiko Epson.

o R&D team at Colorado includes Fred Gnadinger, Sheffield Eaton and
  Doug Butler, ex Inmos. Richard Horton, ex Honeywell and TI, is President.

o Ramtech showed first device, FMx801, at ISSCC Feb 88. This was 256x1.
  Current production is 4K and 16K devices, with 256K due "early in 1990".
  Early device used 3 micron rules and a 6 transistor cell, current stuff
  is 4t, new design is 1t DRAM style cell.

o Charge storage density is around 100 times that of SiO2.

o Current goal is 10**15 cycle "half-life" for DRAM-style cell, giving
  "conservative 500,000 hour lifetime for 1T/1C [the C is FRAM `capacitor']
  operating at 20MHz".

So, should be worth watching. Ramtron seem confident they can scale up
to 1M+ chips in next copule of years. If the 1T/1C cell works, it
should make a dent in the DRAM market. Also, it appears the PZT will
work with other semiconductor materials such as gallium-arsenide.