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From: raob@munnari.oz (Richard Oxbrow)
Newsgroups: comp.arch
Subject: non-volatile RAMS --> FRAMS
Keywords: RAM, no-volatile memory, ferro, FRAM
Message-ID: <1496@murtoa.cs.mu.oz.au>
Date: 16 May 89 00:45:40 GMT
Sender: news@cs.mu.oz.au
Lines: 97



	The is a very late article following up the discussion on 
	non-volatile RAMs/memory . It has been reproduced from an
	article in an Australian newspaper about a FRAM cell ,
	currently under developement by Ramtron Australia .

	Basically the FRAM cell is very similar to a RAM cell does,
	but retains its "memory" when the power is turned	.

Longish article follows


Stolen from  "The Australian" page 57	, (a newspaper from Australia)
Tuesday May 2 , 1989


		Ferroelectric RAM (FRAM)

	[/* the first 6 paragraphs have been omitted */]
		
	The "ferro" part of the word is misleading.Apparently the effect
	was thought to be related in some way to the ferromagnetic properties
	of iron compounds.
		It was instead a characteristic of the small electrically-
	asymmetical elements, or dipoles, within some crystals. The dipoles
	become polarised spontaneously under the influence of an externally-
	applied electric field and remain polarised after the field is
	removed.
		Reversal of the field causes spontaneous polarisation in
	the opposite direction.
		This means that ferroelectric material has two stable
	polarisation states, and can be modelled as a "bistable capacitor"
	with two distinct polarisation voltage thresholds.
		No electrical field or current is required for the material to
	remain polarised in either state, hence a true nonvolatile 
	ferroelectric digital memory capacitor can be built for storing
	1s and 0s.
		Ramtron's development is based on a complex thin-film ceramic
	comprising primarily ferroelectric PZT (lead-zirconate-titanate).
		This  is      related to material used in ceramic filters 
	and the Perovskite ceramics used in warm superconducting.
		This is also compatible with standard semiconductor 
	fabrication techniques.
		The ferroelectronic process uses the thin film of ceramic
	PZT compound sandwiched between two metal electrodes to form
	nonvolatile digital memory capacitors that lie directly above the
	existing semi-conductor circuitry.
		The PZT file is extremely rugged and remains ferroelectric
	from below -80 C to above 350 C. This is well beyond the operating
	temperature range of existing silicon circuits.
		This result is also highly dense, since the features and 
	electrical properties of the underlying circuit are preserved and no
	additional area is required.
		In this way Ramtron's technology integrates ferroelectric
	materials with conventional semiconductor devices without 
	altering their underlying characteristics, and builds non volatile
	components which offer performance, density and cost advantages over 
	existing semiconductor products.
		The technology is an add-on and complementary technology to
	existing semiconductor production techniques, including silicon-
	based CMOS and bipolar, as well as gallium arsenide processes.


	A Cross section of FRAM Device ..

TE     :: Top electrode
PZT TF :: PZT thin Filem
BE     :: Bottom electrode
P      :: Poly
So     :: Source
Dr     :: Drain

	           _________________         ____________
         __________|____  Metal   __|_______|___Metal   _|_____     
	            ____\_      _/___      _____\      /
	        ____|_TE__\____/_____\____/_____|\    /
                |_PZT TF__\____/_____\____/_____|_\__/____             
         -------|_____BE__\____/_____\____/_______________|____ 
                          \____/     \____/                        
         Glass
	__________________      _____        _________________
                          \____/__P__\______/                        
         SiO              _____     _____                         
	____2_____________/ So  \___/ Dr  \__________________
                    \ Well\_____/   \_____/     /
		     \_________________________/
	Si substrate
	----------------------------------------------------


______________________________________________________________________________
Richard Oxbrow			 	ACSnet   :  raob@mullian.mu.oz
SITEE - (Elec Eng)		 	uunet    :  uunet!munnari!mullian!raob
University of Melbourne 	 	internet : raob@mullian.mu.oz.au
Australia                                       raob%mullian.oz.au@uunet.uu.nn
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