Design andSimulation ofNovelArchitectures for Nanodevices
György Csaba, Christoph Erlen · 2007
Thispapershowshowcircuit andarchitecture Automata, QCA)isanovelcomputing paradigm where levelsimulations canbeapplied innanoelectronics. The computation isperformed bynanostructures whichare methodology isillustrated withtwoexamples: passive crossbarcoupled toeachother bytheir stray fields. Information is memories (madefromZnO ormolecular rectifiers) and propagated andprocessed by field-interactions. This magnetic field-coupled devices. We willdemonstrate how architecture could bewellsuitable fornanoscale systems device-level physical tools canhelp inthemodelling ofsystem-whicharedifficult tocontact electrically (4).Itisrelatively level properties such aspowergain andscalability. straightforward toconstruct circuit modelsforsuchdevices I. INTRODUCTION whoseoperation isbasedoncurrent conduction. Inthe circuit modelofmagnetic field coupled devices, the Several nanostructures andnanodevices havebeen magnetic fields havetoberepresented bye.g.currents, realized inrecent years, hh nofler promisnguevice wherethedynamics ofthese currents iscontrolled bythe characteristics. Itisthoughnot clearhow such micromagnetic equations. Theresulting equivalent circuit is nanocomponents couldbeassembled intocircuits and quite unusual, butitserves asanexcellent tool toanalyze systems. Duetotheir dimensions, contacting themishighly'system properties' ofthenanomagnets. Inparticular, we problematic. Device todevice fluctuations innanoscalewill showthat field-coupled nanomagnets showsignificant devices arealso generally higher thenintheir micron-scale powergain andlowdissipation (7). counterparts. Fromanengineering perspective, a novel nanoelectronic device isworthexploring onlywitha II. PASSIVE CROSSBAR MEMORIES: STRUCTURE ANDDEVICE- corresponding architecture. Constructing equivalent circuit LEVELSIMULATIONS models andperforming SPICEcircuit simulations isagood Thelayout ofapassive crossbar memoryissketched in wayassessing thecapability ofananodevice asabuildingFigure 1.Eachstorage cell ismadefromareconfigurable block oflarger scale systems. layer (anantifuse whichcanbeswitched fromalowtoa Thispaperpresents twodistinct examples forthe highconductive state) andadiode inseries. Eachmemory construction ofcircuit models andmodeling oflarger-scale element canbepermanently programmed byasufficiently devices. highvoltage pulse onthecorresponding wordandbitlines, Thefirst example (presented inSection IIandSection III) which renders theantifuse layer conductive. Thestate canbe iscross bararchitectures, whichcouldbeusedfornon read-out bybiasing thecell anddetecting thecorresponding volatile memories beyond the32nmtechnological node, current. Therectification ofthediode enables theaddressing where Flash cells areexpected toreach their intrinsic limit in ofindividual bits inside thearray, asall theparasitic current termsofscalability (1). A bigadvantage ofa crossbarpaths include atleast onereverse biased diode. memorylies inits simplicity, asonly aswitchable (antifuse) layer andadiode arerequired percell (2). Bits stored onthe array nodescanbeindividually addressed aslong asthe m m diode's I(V) characteristics issufficiently close toanideal one.Ifthediode ishighly non-ideal, thenparasitic currents bitline overwhelm thesense current. Wewill analyze howthenon- Memory