Electricity: electrical systems and devices – Electric charge generating or conducting means – Use of forces of electric charge or field
Patent
1995-11-06
1997-10-14
Fleming, Fritz
Electricity: electrical systems and devices
Electric charge generating or conducting means
Use of forces of electric charge or field
361233, 200181, H01H 5900
Patent
active
056778236
DESCRIPTION:
BRIEF SUMMARY
This invention relates to memory elements for use in digital logic circuits and, in particular, memory elements which can be produced by standard integrated circuit manufacturing techniques.
In recent years there have been large advances in the electronics industry related to the fabrication of semiconductor devices for use in micro-processors and as computer memory elements. Semiconductor micro-processors are now found in a vast array of products, both at home and in the work place, but there are still many problems involved in using such devices in hazardous environments, where the device may be exposed to high energy particles such as cosmic rays, X-rays or electron beams which can destroy the semiconductor structure and/or alter current flow. Furthermore, semiconductor devices will only work within a narrow range of temperatures. High temperatures are a particular problem, above about 800K, where the dopants which are positioned in precise areas begin to diffuse at a rate that is exponentially dependent upon the temperature. More importantly, many of the insulating barriers used in such devices are thin enough that conduction through the barrier increases with increasing temperature. There are many areas, such as the design of devices for use in satellites, or in industrial processes, where high reliability is required in very harsh environments.
The sensitivity of semiconductors to the substrate on which they are formed creates a problem in that stacking of elements is complex and costly, reducing the ability to form small I.C. components. Another problem is that subsequent thermal annealing and oxidising work on higher layers damages the devices on lower layers, making reliable manufacture difficult.
Many semiconductor memory devices have a further problem in that they are unable to store data once their power supply has been cut off, leading to unwanted data loss or the use of more expensive non-volatile memory chips.
The present invention is directed to overcoming the above problems and provides a bi-stable memory element comprising: dimensioned so as to have two stable positions, in one of which the bridging contact is in contact with the base contact, and in the other of which the bridging contact is spaced apart from the base contact; and position to the other.
Preferably, the contacts and deflection means are formed using the well know production techniques of photolithography, chemical deposition, sputtering, metal evaporation, or the like.
The deflection means may comprise a pair of electrodes, electrically insulated from the base contact and bridging contact, and operating in sequence to attract or deflect the bridging contact towards or away from the base contact by electrostatic forces. A device with faster switching can be provided by having deflection means both above and below the bridging contact.
Because the bridging contact is stable in both the contacted and uncontacted states, even if the power is disconnected from the device, its state is held and the data digit stored in it is not lost. Because the bridging and base contacts are not made from the usual semiconductor material, the device is not as easily affected by interfering radiation or high temperatures. Furthermore, as the device can be formed on any smooth substrate surface, stacking of devices is easily performed and element density can be increased.
Also, as this invention may be implemented using evaporation and sputtering of thin metal and insulating films, it can be much more simple to fabricate than devices based on semiconductor technologies. As the number of devices on a chip may be hundreds of millions, this technique will have considerable advantages in the yield of working devices per chip.
Examples of the present invention will now be described with reference to the accompanying drawings, in which:
FIGS. 1A, 1B, and 1C show a first example of a device according to the present invention with the bridging contact in contact with the base contact, in a partially deflected state, and in an uncontacted state;
FIG. 2
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Cavendish Kinetics Ltd.
Fleming Fritz
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