Electrically erasable phase change memory
AssigneeEnergy Conversion Devices, Inc.
InventorsStanford R. Ovshinsky, Stephen J. Hudgens, Wolodymyr Czubatyj, David A. Strand, Guy C. Wicker
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Abstract
An electrically erasable phase change memory utilizing a stoichiometrically and volumetrically balanced phase change material in which both the switching times and the switching energies required for the transitions between the amorphous and the crystalline states are substantially reduced below those attainable with prior art electrically erasable phase change memories. One embodiment of the invention comprises an integrated circuit implementation of the memory in a high bit density configuration in which manufacturing costs are correspondingly reduced and performance parameters are further improved.
Claims28
An electrically erasable phase change memory comprising:
- (a) at least one pore of phase change material which is capable of being reversibly electrically switched between at least two electrically detectable states, the first of said at least two detectable stages having a local atomic order which is detectably less ordered than the local atomic order of the second of said at least two detectable states;
- (b) electrical contact means making electrical contact with at least two portions of said pore to establish an electrical path through said pore between the points of contact with said at least two portions;
- and
- (c) means for applying electrical signals to said electrical contact means to cause reversible switching of at least a volume portion of said phase change material in said electrical path in said pore between said at least two detectable states, said first detectable state being characterized by an electrical conductivity which is lower than that of said second detectable state;
- (d) said phase change material being comprised of a plurality of elements which are distributed within said phase change material in said first detectable state and are converted into said second detectable state in said volume portion with substantially the same average local density of distribution of the constituent elements within said volume portion as present in said first detectable state.
An integrated circuit electrically erasable phase change memory comprising:
- (a) a single crystal semiconductor substrate;
- (b) a plurality of electrically erasable phase change memory elements formed on said substrate;
- (c) each of said memory elements comprising a pore of phase change material and an integrated circuit means for electrically isolating said memory element, said electrical isolating means and said pore of phase change material being electrically connected in series with each other;
- (d) said phase change material being comprised of a plurality of elements which are distributed within said phase change material in a first substantially amorphous state and are converted into a second substantially crystalline state in at least a volume portion of said pore with substantially the same average local density of distribution of the constituent elements within said volume portion as present in said substantially amorphous state;
- and
- (e) integrated electrical contact means extending across said substrate over the upper and lower portions respectively of said memory elements and making electrical contact on one side of each of said memory elements with said pore of phase change material and on the other side of each of said memory elements with said electrical isolating means and thereby providing means for selectively and individually electrically setting, erasing and reading said memory elements.
Dependencies are inferred from the claim text.