Computer-aided design and analysis of circuits and semiconductor – Nanotechnology related integrated circuit design
Reexamination Certificate
1999-03-29
2001-07-03
Smith, Matthew (Department: 2825)
Computer-aided design and analysis of circuits and semiconductor
Nanotechnology related integrated circuit design
C326S041000, C700S121000, C257S023000, C365S151000
Reexamination Certificate
active
06256767
ABSTRACT:
TECHNICAL FIELD
The present application relates generally to making connections to integrated circuits of electronic devices whose functional length scales are measured in nanometers, and, more particularly, to demultiplexers based on nanometer-scale wires crossed by larger wires and joined by bi-stable molecular scale switches at the intersecting junctions.
BACKGROUND ART
The silicon (Si) integrated circuit (IC) has dominated electronics and has helped it grow to become one of the world's largest and most critical industries over the past thirty-five years. However, because of a combination of physical and economic reasons, the miniaturization that has accompanied the growth of Si ICs is reaching its limit. The present scale of devices is on the order of tenths of micrometers. New solutions are being proposed to take electronics to ever smaller levels; such current solutions are directed to constructing nanometer scale devices.
Prior proposed solutions to the problem of constructing nanometer scale devices have involved (1) the utilization of extremely fine scale lithography using X-rays, electron, ions, scanning probes, or stamping to define the device components; (2) direct writing of the device components by electrons, ions, or scanning probes; or (3) the direct chemical synthesis and linking of components with covalent bonds. The major problem with (1) is that the wafer on which the devices are built must be aligned to within a fraction of a nanometer in at least two dimensions for several successive stages of lithography, followed by etching or deposition to build the devices. This level of control will be extremely expensive to implement. The major problem with (2) is that it is a serial process, and direct writing a wafer full of complex devices, each containing trillions of components, could well require many years. Finally, the problem with (3) is that the only known chemical analogues of high information content circuits are proteins and DNA, which both have extremely complex and, to date, unpredictable secondary and tertiary structures that causes them to twist into helices, fold into sheets, and form other complex 3D structures that will have a significant and usually deleterious effect on their desired electrical properties as well as make interfacing them to the outside world impossible.
The present inventors have developed new approaches to nanometer-scale devices, comprising crossed nano-scale wires that are joined at their intersecting junctions with bi-stable molecules, as disclosed and in application Ser. No. 09/282,767, filed on even date herewith. Wires, such as silicon, carbon and/or metal, are formed in two dimensional arrays. A bi-stable molecule, such as rotaxane, pseudo-rotaxane, or catenane, is formed at each intersection of a pair of wires. The bi-stable molecule is switchable between two states upon application of a voltage along a selected pair of wires.
There is at present no known or published solution for addressing molecular scale devices and getting information into or out of a molecular system such that it can be read or accessed by a much larger system, for instance, CMOS. All present solutions for connection end up making the molecular scale devices spread out on a scale comparable with available lithography or direct writing capability. A “wagon wheel” strategy, for example, does this, where nano-scale wires are formed, fanning out from a central “spoke”. The overlap of two such adjacent “wagon wheels” forms intersecting junctions where each pair of wires cross to form a molecular wire crossbar. When all of the wires in the molecular wire crossbar must spread out, however, the total size of the system, including input/output (I/O), becomes comparable with the area of a lithographically formed system, and thus much of the size advantage of a molecular scale system is lost.
Thus, there remains a need for getting information into and out of a nanometer-scale molecular wire crossbar, also known as a chemically assembled electronic nanocomputer.
DISCLOSURE OF INVENTION
In accordance with the present invention, a demultiplexer for a two-dimensional array of a plurality of nanometer-scale switches is disclosed. Each switch comprises a junction formed by a pair of crossed wires where one wire crosses another and at least one connector species connecting said pair of crossed wires in said junction. The connector species comprises a bi-stable molecule. The demultiplexer is assembled in parallel and comprises a plurality of microscopic address lines accessed by a first set of wires in the two-dimensional array by randomly forming contacts between each nanoscopic wire in the first set of wires to at least one of the address lines. The first set of wires crosses a second set of wires to form the junctions. Alternatively, the demultiplexer is serially assembled, which involves sequentially forming the contacts rather than randomly forming the contacts, as in the parallel assembly.
The present invention solves both the problems of data input and output to a molecular electronic system and also bridges the size gap between CMOS and molecules with an architecture that can scale up to extraordinarily large numbers of molecular devices. It is important that the architecture be able to scale to a very large number of components. If all of the nanometer sized wires must be spread out to the same pitch as the lithographically-formed components with which they communicate, then the size advantages of the molecular wire nano-architecture are going to be lost. If, however, the wires are assembled at the full density that the nanometer spacing would allow, then in the space accessible to a single lithographically-formed wire, close to a hundred distinct molecular wires must be connected. This invention solves this problem, by allowing selective connection to all of the molecular wires.
The present invention creates a partially random circuit using a random or pseudo-random physical or chemical process. Measurements of the output of that random circuit as the inputs are varied enable conclusions to be drawn as to which random connections have, in fact, been made. The resulting list of random connections lets the circuit be used as a demultiplexer.
It is desirable that when the demultiplexer is in use, the current drawn must not scale with the number of signal wires in the array when only one wire is addressed. The transistor version of the present invention draws current which does not increase with the total number of signal wires.
Having found the unique addresses of each of the demultiplexer outputs (nanowires), the present invention provides a method to determine the exact linear order of the nanoscopic wires, that is, which nanowire is next to which other nanowire. This information is necessary to configure a circuit using transistors or wire cutting.
The proposals for using cellular automata as shift registers to make nanometer scale structures cannot realistically solve the problem of connecting to larger structures, because the cellular automata lack defect tolerance. If cellular automata could be built, then in principle only one cell in one corner of the automata needs to be connected, and a raster scan shift register could be used to load states into the entire machine. The problem is that this cellular automata structure is easily destroyed by defects. That is to say, there is no effective defect tolerance in such a structure. The demultiplexer for a molecular wire crossbar network that is disclosed and claimed herein is very defect tolerant, and can work despite a large number of defects in the system.
The molecular wire demultiplexer addresses the fundamental problems of bridging length scales to connect lithographically-formed microscopic circuits that have to communicate with the nanoscopic arrays of wires which make up logic, memory, and interconnect of the molecular wire system, and of transferring data into and out of a system with an enormous number of elements by using an input/output circuit with a much smaller number of elements.
REF
Kuekes Philip J.
Williams R. Stanley
Hewlett--Packard Company
Smith Matthew
Speight Jibreel
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