This application is based upon provisional application No. 60/024,194 filed on August 20, 1996.

FIELD OF THE INVENTION

The present invention relates to improved electronic circuits or transduction means which use an electret to realize a nearly permanent charge and potential source or state.

BACKGROUND OF THE INVENTION

A permanent magnet exhibits a permanent external magnetic field. An electret exhibits a permanent external electric field. In both cases, the external field is not permanent. However, the fields, either magnetic or electric persist for a very long time. A single material can exhibit both a permanent external electric field and a permanent external magnetic field.

The field associated with a physical condition or structure and the behavior of such field is a complex set. For the purposes of this application, the complex set will be called "Field Set" or "Field State" to allow all to keep in mind the complexity and interaction of the complex set.

Field set does not imply static condition. Field set or state may be time variant.

Any simple discussion of the De Forest Triode tube cannot cover all or the complex interactions within the vacuum tube, nor can a simple description or discussion cover all of the applications of the triode.

By the same token no simple description can cover all the effects of field set or field state of an electret.

The scope of this discussion does not attempt to engage in the theory and controversy of quantum mechanism. The results of experimental physics research are related or conveyed herein. The effects of a permanent external electric field from an electret on the charge transport mechanism and current or voltage modulation on a MOSFET have been reduced to practice.

For this discussion, analogies and approximate theory are used. The theory is not intended to be construed as 'cast in stone' but is rather to be taken in the manner and spirit which Einstein established when relating the special theory of relativity where Einstein instructed the scientific community that his theory was a starting point only and not an end or complete and immutable set.

The area of electret study is not mature by any means.

Much of the discussion in this background section of the application and in the following description, manner, and process of making and using invention section is based on the 6th edition of the McGraw-Hill Encyclopedia of Science and Technology (Copyright 1987) articles on "Semiconductor Memories", "Computer Storage Technology", and "Electretε", (vol. and pages) . These articles are expressly incorporated herein by reference.

The two primary kinds of read/write random access memory (RAM) in use today are dynamic RAM (DRAM) and static RAM (SRAM).

Dynamic RAM uses a storage cell based on a transistor and capacitor combination in which the digital information is represented by a charge stored on each of the capacitors in the memory array. The memory is stored on each of the capacitors in the memory array. The memory is "dynamic" in that capacitors are imperfect and will

lose their charge unless the charge is repeatedly refreshed every few microseconds. Computer circuits repeatedly poll each capacitor. If an individual capacitor is not charged, the circuit leaves it alone and moves on to the next capacitor. If a capacitor is charged, the circuit recharges it and moves on to the next capacitor. As long as the capacitors are continuously refreshed, the information in memory will remain until intentionally changed or the power to the memory is shut off.

The main advantage of present day RAM is maturity, acceptance and high density due to the need for only a few transistors to realize memory cell.

The disadvantages of RAM are that the RAM needs to be 'refreshed' for retention of memory and needs electricity for retention.

Static memories, in contrast, do not use a charge-storage technique. Instead, they use several transistors to form a flip-flop for each cell in the array. Once data are loaded into the flip-flop storage elements, the flip-flop will indefinitely remain in that state until the information is intentionally changed or the power to the memory circuit is shut off.

In SRAM, more transistors are needed but SRAM does not need the constant attention or refresh. SRAM needs electricity.

Non-volatile memories are semiconductor memories in which the information stays even if power is shut off. Unfortunately, most read/write non-volatile - ultraviolet- erasable programmable read-only memories (UV EPROMs) , and electrically alterable programmable read-only memories (EEPROMs) require extraordinary voltage levels or extra circuitry for read and write operations.

An improvement on these non-volatile memories has been the NV RAM, a memory that combines a static RAM with a non-volatile (NV) memory array, so that for every stored bit there are two memory cells, one of which is

volatile and the other non-volatile. During normal system operation, the NV RAM uses the volatile memory array, but when it receives a special signal information held in the RAM area is transferred into the non-volatile section.

Thus the RAM section provides unlimited read and write operations, while the non-volatile section provides backup when power is removed.

Unfortunately, the EAROM, EEPROM and NV RAM suffer one common failing they wear out. The electrical processes used to store information in the no-volatile array causes a steady deterioration in the ability of the memory to retain data for a guaranteed time period.

The above NV memories are slow to write, due to the need to fully charge the floating gate capacitor.

Some SRAM have been combined with some power control circuitry and a button-type long-life battery in a single package. When built into a system, this form of NV RAM operates with the characteristics of a static RAM when the system supplies power - fast access times and unlimited reads and writes. However, when the power supply line drops below a preset level, the control circuitry in the memory package detects the drop, disables the memory's ability to store new data and then switches over the built-in battery to keep the stored data alive until main power returns.

Unfortunately, even button-type batteries are relatively large and have a limited life.

Power sources in general can be thermal, chemical, radiation, such as solar cells, nuclear or run from prime movers. All have advantages and disadvantages. A small internal or small external source such as an electret has advantage of being long term and non polluting. No moving parts, reusable.

It is an object of this invention to provide an improved potential or charge source for various electrical circuits and transduction means.

It is further an object to provide a potential or charge source or improved backup source for memories including, e.g. non-volatile static RAM.

BRIEF DESCRIPTION OF THE INVENTION

The unique discovery of this invention is the use of an electret as the means for realizing a simple reusable non polluting nearly permanent charge state source, charge source or potential source or combination of same.

An electret can be used to operate many things electronic from displays to oscillators to light sources to amplifiers filters and other electronic circuits as well as used for standby potential or charge source for a non-volatile memory element that can perform equivalent function of static RAM.

An electret is a solid dielectric with a quasipermanent electric moment. Real-charge electrets, which similar to a battery hold a charge of one polarity at or near one side of the dielectric and charges of opposite polarity at or near the other side, can store practical charge densities for 20 or more years. While these charge densities are not as large as possible from batteries at the present time, they are more than sufficient to serve as the power source, or charge source, for ultralow-power-consumption static RAMs such as CMOs SRAMs and other low power circuits and can be used in any device which are charges state source, charge source or potential source can benefit.

Such a circuit can be used in non-volatile random access memory (RAM) device or non-random memory devices. This purpose is achieved by an improved standby charge source for a non-volatile semiconductor memory including but not limited to static random access memory device.

It should be clear many methods are available to those skilled in the art of electronics to exploit such a long term charge, potential charge state source.

To overcome the limited number of storage cycles possible with the true non-volatile memory technologies, ultralow-power-consu ption static RAMs with a standby current of just l microampere or less) or are easily supplied by electret. If electret is integral then as few as 2 transistors can form cell. It is of course possible some clever designed could do this with one transistor, or with some other type of element.

BRIEF DESCRIPTION OF THE FIGURE

FIG. 1 shows a simplified schematic view of an example electret powered RAM, memory location.

DETAILED DESCRIPTION OF THE INVENTION AND THE FIGURE

Circuit element 10 is a memory unit such as a CMOS STAM. Element 10 is set to either one of two possible states by SET input 12 and RESET input 14. Element 16 represents an electret power source which powers element 10 whenever its regular power source is shut off or removed.

An electret power source for an NV RAM can be made in a variety of different ways. For example, and perhaps the simplest configuration, a suitable electret material can be applied to one face of an NV RAM. Another example is to add the electret during manufacture of the integrated circuit (IC) memory. As an IC is built-up layer by layer, layers of a suitable electret material can be included as part of the conventional IC manufacturing process. Of course it should be recognized that those skilled realize that there are various configurations

possible to exploit the advantageous properties of field state.

An electret backup power source for an NV RAM IS both smaller and longer lasting than presently available alternatives. Because the electret power source can be easily made an integral part of the NV RAM, it will simplify the circuity needed for NV RAMs.

The use of electret power sources need not be limited to NV RAMs, but can be used in any IC device where long lasting power sources are used and where backup power sources are currently not used because of the deficiencies of the present art.

Besides ICs, electrets can be used to bias circuits and transduction devices such as Geiger Counters, proportional radiation counters, and other similar radiation counters, provide operation bias and power to night vision tubes and other micro channel plate devices, bias for x-ray film detectors and x-ray film enhancement, bias and operation for LCDs, electroluminescent, nearly all luminescent, charge center, non linear and other crystal and ceramic structures. The permanent external electric field can be used to control materials' formation and separation, and can and has run electrostatic motors. Large and small units in series and parallel can provide spark for ignition and other purposes, provide charge state for particle analysis, for mono atomic gas generation.

While the electret is useful in standard well known and mature semiconductor work it is also very useful in non standard semiconductor work. Some non standard semiconductors include the class of non silicon, non gallium arsenide and the various sensors types. It is important to realize the use of the permanent external electric field of the electret in the growing class of polymeric, mettalo organic and similar semiconductors.

In the past 90 plus years nearly every electret studied and all of the commercially produced types employ

a single type of material with this material in an homogeneous form to realize the permanent external electric field.

The electrets useful in the present invention can be made from various inorganic, organic or metalloorganic materials. Any dielectric material including, for example, a thermoplastic polymer resin can be employed. Useful plastics include polyethylene, polypropylene, polytetrafluoroethylene (TEFLON) , etc. Non uniform surfaces can greatly enhance effects. An oriented material can greatly enhance electret effects. More than one oriented or non oriented material can be combined. A single type of material, in different layers of difference or same orientation can greatly enhance effects. Inorganic, organic or metalloorganic materials can be used individually or in admixture. Useful exemplary inorganic materials include barium titanate, lead zirconium titanate and pyroelectric crystals such as tourmaline. Various waxes are exemplary of organic materials.

The external electric field of an electret provides charge. The charge is used to turn on a semiconductor such as a CMOS FET of the type used in modern day circuitry. A very small charge is all that is required to cause a CMOS FET to conduct.

The charge from an electret, being continuous, can be exploited in lieu of the charge provided by a battery.

In some memory applications a charge is deposited on a floating capacitor and the dielectric can function as an electret. Substantial voltage or duration of voltage is required to establish the charge. By the same token if a memory site so written as a logical "1" is to be set to the other logical value, or "0", then substantial voltage or duration of voltage of the opposite polarity is required.

A more useful application of the electret is to provide a continuous charge or field which would in other methods be provided by a battery or primary power source.

In this more useful application the permanent charge can be shunted to be turned off for logical "0" and the shunting removed to return to logical "1".

In a battery supplied charge the battery must be used. In an electret supplied charge the charge is always there and is shunted to ground or itself if not needed. This is a significant improvement.

An improved electronic circuit method is realized because an electret provides charge all the time and is shunted or shorted if not needed. This differs from a battery which is depleted when used.

Many types of electronic circuits and other systems benefit from a virtually inexhaustible or very long term source of charge.

The electret source of charge is not depleted by shorting or shunting.

An electret of organic polymer is produced by well known methods. For a preferred embodiment an organic polymer electret is made with two types of polymer being hydrocarbon and fluorocarbon to take advantage or desirable and complementary properties of both.

The charge state is impressed on the hybrid electret by means of two different charging methods used at the same time, those being a corona method coupled with controlled breakdown method. Again this is to take advantage of the strengths of both methods.

By not restricting manufacture to a single system a far superior electret is produced.

The electret is provided with electrodes and is part of a circuit which employs a standard CMOS Fet technology. The long term external charge causes the gate to conduct and for the purposes of testing the gate is loaded with capacitance equivalent to the capacitance exhibited by the input nodes of a 4 megabit CMOS SRAM.

No battery is required to maintain state of the gate conduction.

An organic hydrocarbon electret is charged by the dual method used in the example above. The hydrocarbon electret is of one chemical type but the material is realized in multiple layer types of differing orientations. The different orientations provide a type of composite realized with a single chemical compound type.

A Liquid Crystal Display (LCD) is placed in proximity with the electret and the external charge causes the liquid crystal to actuate and the display segments become visible.

In both cases above no battery is used to effect the charge.

If a battery is used to effect the charges the battery becomes depleted. If the effect, whatever it may be is not desired, i.e., another logical state or change in segment the electret is simple shorted or shunted to ground with no significant impact on the longevity of the electret.

In both reductions to practice described above an improved electret is realized due to the structure and method of manufacture.

A further classical application the electret material is intentionally made smooth. Many electret applications benefit from an air or dielectric gap or displacement for space charge effects between one or more of the electrodes.

In the improved method of the invention, due to the surface modification, there are "hills and valleys" the tops of the hills tend to contact the electrode and or the inter layer, if any, and the valleys being voids, provide a physical displacement from the electroding.

The "hills and valleys" may be physical or a variable property of the material. Small feature effects

such as point discharge and field concentration and fringing effects can be exploited.

There are many ways this modification can be realized that are useful and particulate composite types and encapulated types have been reduced to practice.

It will be understood by those skilled in the art that various modifications and substitutions may be made to the invention as described above without departing from the spirit and scope of the invention. Accordingly, it is understood that the present invention has been described by way of illustration and not limitation.