JP2815101B2 - Non-volatile recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonvolatile recording device having a high-density, large-capacity recording capacity and capable of electrically writing and reading information, and more particularly to a computer, a memory card and a word processor. The present invention relates to a non-volatile recording device that can be widely used in various devices.

[0002]

2. Description of the Related Art There are the following four types of typical nonvolatile recording devices in which information can be rewritten.

[0003] Magnetic tape.

[0004] Magnetic disk.

An IC nonvolatile memory such as an EPROM or an EEPROM.

[0006] A magneto-optical disk.

[0007] Each feature will be described below.

[0008] Magnetic tape is the most typical rewritable nonvolatile recording device,
Because it is inexpensive, it is most widely used as audio tapes and video tapes. It is a very large-capacity recording device, and is also used as a backup memory for a computer.

However, since only continuous writing and reading of information can be performed, random access cannot be performed, and the access time required for reading and writing information is long.

A magnetic disk is generally used as an external recording device for a computer or word processor. An inexpensive floppy disk that is easy to handle and has a larger recording capacity than a floppy disk, but is difficult to handle and often uses an expensive hard disk.

The advantages of these magnetic disks are that high-speed random access is possible and that writing and rewriting of information can be performed relatively easily.

The recording capacity of a 3.5-inch floppy disk is about 1 megabyte, and that of a 3.5-inch hard disk is about 40 megabytes. is there.

EPROM and EEPROM IC non-volatile memories are rewritable recording devices, and are capable of high-density recording. Typical examples of the IC non-volatile memory include an EPROM for performing electrical writing and erasing by ultraviolet irradiation, and an EEPROM for electrically writing and erasing. These IC nonvolatile memories have advantages such as small size and light weight, short access time, and low power consumption.

In the following, E which can be electrically written and erased is
The details will be described using an EPROM as an example. FIG. 10 shows an example of a cross-sectional shape of a memory cell of an EEPROM.
The gate oxide film 5 is laminated on the surface of the silicon substrate 7, and the floating gate 4 and the control gate 2 are formed on the gate oxide film 5. The control gate 2 stores carriers,
The carrier injection into the floating gate 4 to be stored is controlled. The two gates 2 and 4 are separated by an insulating film 3 made of a silicon oxide film. A surface protection film 1 is formed on a silicon substrate 7 so as to cover the gates 2 and 4. As the surface protection film 1, a silicon oxide film or a silicon nitride film is usually used. Further, a source region 8 and a drain region 6 into which impurities are implanted are formed in a surface layer portion of the silicon substrate 7, and a channel region 9 is formed therebetween.

In the above configuration, when recording information, a voltage is applied between the drain region 6 and the control gate 2, and carriers are injected into the floating gate 4 as hot electrons through the gate oxide film 5. on the other hand,
The erasure of the recorded information is performed by the source region 8 and the control gate 2.
And a Fowler-Nordhei
Carriers are removed using the m (NF) Tunneling phenomenon. Reading of recorded information is performed by determining ON / OFF based on the threshold voltage of the inversion voltage of the channel region 9 between the source region 8 and the drain region 6.

Since the injection and removal of carriers are performed through the gate oxide film 5, the film quality and thickness of the gate oxide film are set to E.
This is very important in the structure of the EPROM. For example, in an EEPROM having a recording capacity of 1 megabit, the gate oxide film 5 is usually a thin film having a thickness of about 20 nm. Therefore, it is difficult to control the film quality and the film thickness. Also, the dimensions of the chip are usually
Both the short side and the long side are about 7 to 10 mm. If the chip area is increased in order to increase the recording capacity, there is a disadvantage that the yield decreases and the cost increases.

Due to these disadvantages, EEPROM
However, while having the above advantages, there is a limit in improving the storage capacity. Incidentally, the recording capacity of the current EEPROM is about 1 to 4 megabits, and is smaller than that of other non-volatile recording devices such as a magneto-optical disk and a magnetic disk.

Magneto-optical disk A type of optical disk, a rewritable recording device, and one of the typical large-capacity nonvolatile recording devices.

FIG. 11 shows an example of the structure of a magneto-optical disk. The magneto-optical disk uses magnetic thin films 15 and 16 having perpendicular magnetization characteristics as a recording medium. Information is recorded by condensing a laser beam 20 on a condensing area 21 on a disk in a weak magnetic field opposite to a direction in which the magnetic thin films 15 and 16 have been magnetized in advance, and heating the magnetic thin films 15 and 16 by local heating. 1
Record the information in 6. On the other hand, information reproduction is performed using the Kerr effect or the Faraday effect. That is, when the linearly polarized laser light 20 is irradiated onto the disk,
Since the transmitted light or the reflected light rotates the plane of polarization according to the magnetization state of the magnetic thin films 15 and 16, the rotation of the plane of polarization is converted into a signal of the intensity of light using an analyzer, and converted into an electric signal by a photodetector. By detecting, the information is reproduced. Such a magneto-optical disk has been put to practical use as a recording device capable of large-capacity recording for document files and image files.

A feature of the magneto-optical disk is that the recording is performed by the laser beam 20, so that the recording can be performed through the transparent glass substrate 12 without contact. That is, according to this recording method, dust on the recording surface 23 side does not matter. On the other hand, dust on the substrate surface 22 side has an effect.
Since the laser beam 20 is out of focus on the side, the beam diameter is as large as several hundred microns, and there is no adverse effect due to the presence of some dust.

The recording capacity of the magneto-optical disk allows information to be recorded / reproduced by the condensed laser beam 20, so that high-density recording becomes possible. By the way, one for 3.5 inch disk
A large-capacity memory of about 20 megabytes can be realized.

However, a magneto-optical disk requires a laser, a magnet, and a rotating mechanism (a rotating mechanism of the disk) to write and read information.
There is a disadvantage that the price is high.

[0023]

A conventional nonvolatile recording device in which information is rewritable has the above-mentioned advantages and disadvantages. However, as a nonvolatile recording device desired in the future, the following ( 1), (2), (3),
It is required to satisfy item (4). Re-evaluation of the above-mentioned conventional non-volatile recording device for each item is as follows.

(1) Large-capacity, high-density recording is possible.

In the case of a floppy disk, a 3.5-inch disk has a recording capacity of about 1 megabyte and cannot cope with a large capacity and a high density.

Although high density can be realized with IC non-volatile memories such as EPROM and EEPROM, it is difficult to increase the capacity because the chip area cannot be increased due to the yield limit.

(2) It is resistant to shock and vibration.

In a hard disk, a large capacity can be realized by integrating a plurality of disks. However, in order to cope with high density, the distance between the head and the disk is reduced to 1 micron or less, and the disk is easily damaged by shock or vibration. In addition, there is a disadvantage that even if minute dust adheres to the head or the disk, the recording device is damaged.

(3) Small, simple and inexpensive peripheral devices for writing and reading.

A floppy disk, a hard disk, and a magneto-optical disk need to have a rotating mechanism such as a motor for rotating and writing / reading information by rotating the disk, which makes the peripheral device larger and more complicated.

In addition, the hard disk has a problem that the distance between the disk and the head must be made precise and a buffer material is required to secure impact resistance, so that the whole device becomes large and heavy.

In the case of a magneto-optical disk, since a laser and a magnet are used for writing and reading, the size of the apparatus becomes large,
There is a disadvantage that it becomes heavy and expensive.

(4) Writing and reading can be performed at a high speed.

In a floppy disk, a hard disk, and a magneto-optical disk, since the position of information to be accessed is searched for while rotating the disk, there is a limit in increasing the reading speed. Further, the magnetic tape has a disadvantage that both the reading and writing speeds are slow.

As described above, in the current non-volatile recording apparatus, none of the above items (1), (2), (3) and (4) are all satisfied, and a completely new type which satisfies all these items is not available. This is because the realization of the non-volatile recording device is required.

The present invention has been made to respond to such a demand, and can achieve high density and large capacity, can perform writing / reading at a high speed, and can reduce the size, simplicity, and power of peripheral devices. It is an object of the present invention to provide a completely new type of nonvolatile recording device that can be priced.

Another object of the present invention is to turn on the read signal.
It is an object of the present invention to provide a nonvolatile recording device capable of obtaining a large / OFF ratio and reading out information with high accuracy.

[0038]

According to the present invention, there is provided a non-volatile recording apparatus comprising: a pair of opposing substrates having opposing electrodes;
Paste the heating element side substrate with the upper and lower electrodes
Liquid crystal compound or molecules in the molecules between the substrates.
Non-volatile storage of a recording medium consisting of a compound containing
A recording device, wherein the upper electrode and the lower electrode are
Between the upper electrodes adjacent to each other in the column direction.
And an insulating film interposed between the lower electrodes adjacent in the row direction.
A memory cell at each intersection of the upper electrode and the lower electrode.
And thereby the above object is achieved.

Further , the nonvolatile recording apparatus of the present invention
The opposing substrate with electrodes and the upper electrode sandwiching the heating element
Affixing the heating element side substrate having the pole and the lower electrode,
A recording medium made of conductive polymer liquid crystal is sealed between both substrates.
A non-volatile recording device, comprising: the upper electrode and the lower electrode.
The poles are arranged in a matrix and are adjacent in the column direction
Insulated between the upper electrodes and between the lower electrodes adjacent in the row direction
Each intersection of the upper electrode and the lower electrode with a film interposed
The memory cell is configured in the
Is achieved.

Preferably, before the side in contact with the recording medium.
A conductive material is provided on the surface of the opposite side substrate and the heating element side substrate.
To form an alignment film made of a material.

Preferably, the insulating film is capable of generating the heat.
It is configured to be in contact with the body.

[0042]

According to the present invention, a heating element is sandwiched between a counter substrate having a counter electrode and a heating element.
The upper electrode and the lower electrode are arranged in a matrix.
Attach the heating element side substrate, and apply a liquid crystal compound between both substrates.
Or a recording medium composed of a compound containing a liquid crystal component in the molecule.
Enclose the memory cell at each intersection of the upper and lower electrodes.
The operation will be described below with reference to a nonvolatile recording device having a configuration as an example.

When a voltage is applied to the upper and lower electric wires arranged in a matrix and a current flows through the heating element, Joule heat is generated in the heating element. By controlling the current, voltage and application time, the liquid crystal constituting the recording medium is heated to a temperature at which a state change such as phase transition occurs, and then information is written between the counter electrode and the upper electrode (upper wiring). When the liquid crystal is rapidly cooled while applying a voltage, the liquid crystal undergoes a state change such as a phase transition and is brought into a written state. Since this state is maintained for a long time, the written information can be stored as recording information.

The recorded information written as the change in the dielectric constant or the change in the electric conductivity can be obtained by applying an AC or DC voltage between the counter electrode and the upper electric wiring and measuring the dielectric constant or the electric conductivity of the recording medium. Recorded information can be electrically read.

From this state, the temperature of the liquid crystal is raised again by the same procedure until a state change such as phase transition occurs, and then the current and voltage applied to the heating element are controlled to gradually cool or quench the liquid crystal. Even if a relatively high AC or DC voltage is applied during cooling, the liquid crystal undergoes a state change again,
Information once written can be rewritten.

As described above, according to the above configuration, it is possible to write / read information on / from the recording medium by static electric control.

The operation of writing and reading information by utilizing the change in the dielectric constant caused by the phase transition of the liquid crystal will be briefly described. The temperature of the liquid crystal is raised to, for example, a temperature at which the liquid crystal becomes an isotropic phase. A voltage for information writing is applied between the counter electrode and the counter electrode, and the application of a current for heating is stopped to rapidly cool down, or the voltage for information writing is not applied,
By controlling the heating current and voltage and gradually cooling the liquid crystal, the liquid crystal is in an alignment state and is in a monodomain state.

On the other hand, when the current for heating is stopped without rapid application of the voltage without applying the voltage for writing information, the liquid crystal enters a polydomain state. Thereafter, when cooled to room temperature, the liquid crystal becomes a glassy state, and that state is maintained.

This mono domain state and poly domain 2
Since the information written as one state is maintained for a long time at room temperature, the written information can be stored as record information. Since the liquid crystals in these different states have different dielectric constants, the recorded information can be electrically converted by applying an AC voltage between the counter electrode and the upper electrode and measuring the capacitance of the recording medium which is a dielectric. Can be read.

From this state, the temperature of the liquid crystal is raised again in the same procedure until a state change such as phase transition occurs, and then the current and voltage applied to the heating element are controlled to gradually cool or quench the liquid crystal. If an information writing voltage is applied during cooling, the liquid crystal enters a monodomain state. Alternatively, rapid cooling without applying an information writing voltage results in a polydomain state. Thereby, the information once written can be erased.

As described above, according to the above configuration, it is possible to write / read information on / from the recording medium by static electric control.

Further, when the conductive polymer liquid crystal is used as the recording medium, the ON / O of the read signal is controlled for the reason described later.
Since the FF ratio can be increased, information can be read with higher accuracy.

When a conductive polymer liquid crystal is used as a recording medium and a conductive alignment film is used as an alignment film, the S / N ratio of a read signal is further improved, so that more accurate information can be read.

[0054]

Embodiments of the present invention will be described below. FIG. 1 schematically shows the surface configuration of a nonvolatile recording apparatus according to the present invention, in which peripheral circuits are divided into blocks for each function. The input / output signal control unit 31 has a function of processing an input signal from another device and transmitting a signal (write information) to a memory cell, and a process of processing a signal read from the memory cell and transmitting the signal to another device. It has a sending function. The logic control unit 32 controls the signal processing of the entire nonvolatile recording device.
The drive circuit unit 33 controls and drives a current for supplying an electric signal to the memory cell of the recording unit 34 according to a command from the logical system control unit 32. The recording unit 34 is an input / output signal control unit 3
The signal given from 1 is accumulated and stored as record information.

As shown in FIGS. 2 to 4, the recording section 34 includes a heating element 44 for heating / writing the recorded information and a silicon substrate having a wiring for supplying a current to the heating element 44. The semiconductor device has a schematic configuration including a glass substrate 52 having a counter electrode 55 and a counter electrode 51 and disposed opposite to the silicon substrate 55, and a liquid crystal (liquid crystal layer) 53 sealed between the two substrates 55 and 52. The details will be described below.

FIG. 2 shows the surface configuration of the silicon substrate 52 of the recording unit 34 from which the glass substrate 52 and the liquid crystal layer 53 have been removed. In the figure, a plurality of upper electrodes 41 are arranged at substantially equal intervals in the column direction, and as shown in FIG.
Is in contact with the liquid crystal 53. Below the upper electrode 41, a plurality of lower electrodes 42 are arranged in a row direction orthogonal to the upper electrode 41. A memory cell 43 is formed between the upper electrode 41 and the lower electrode 42, more specifically, at the intersection of the two electrodes 41 and 42. In this embodiment, tungsten having excellent heat resistance was used as the material of the electrodes 41 and 42. Both the upper electrode 41 and the lower electrode 42 use a part of the wiring as a heating electrode for the heating element 44.

FIGS. 3 and 4 show a specific configuration of the memory cell 43. FIG. The memory cell 43 is formed at the intersection of the upper and lower electrodes 41 and 42 as described above, and includes the following components disposed and sealed between the silicon substrate 55 and the glass substrate 52. The configuration will be described below in order.

An opposing electrode 51 is provided on the opposing surface of a glass substrate 52 opposing a silicon substrate 55. On the surface of the counter electrode 51, an alignment film 56 in contact with the liquid crystal 53 is formed. The liquid crystal 53 has a function of recording a signal by the phase transition phenomenon.

The silicon substrate 55 is single crystal silicon for a semiconductor generally used for an IC, and is doped with impurities for controlling a resistance value. When the lower electrode 42 is formed on the silicon substrate 55 as it is, a driving current flowing between the lower electrode 42 and the upper electrode 41 leaks to the silicon substrate 55.
Therefore, in this embodiment, in order to prevent current leakage, the surface of the silicon substrate 55 is covered with the field insulating film 57, and the lower electrode 42 is formed thereon.

An inter-electrode insulating film 54 is formed between the lower electrode 42 and the upper electrode 41 in order to maintain insulation between them. In some cases, a voltage of 10 V or more is applied between the lower electrode 42 and the upper electrode 41, so that a uniform film quality without pinholes and a uniform film thickness are required. Therefore, in this embodiment, a silicon nitride film formed by a plasma CVD method is used as the inter-electrode insulating film 54.

The inter-electrode insulating film 54 has a structure in which an opening 54 a is formed at the memory cell 43, and the heating element 44 is directly interposed between the upper electrode 41 and the lower electrode 42 at that portion.
When writing / erasing recorded information, the heat generated by the heating element 44 causes a temperature rise in both the upper electrode 41 and the lower electrode 42, so that the electrode material is required to have heat resistance. Therefore,
In this embodiment, tungsten formed by a low pressure CVD method is used. On the other hand, it is necessary to use a material that has heat resistance and an appropriate resistance value and can be finely processed at the same time as the heating element 44.
Formed by the method.

On the upper electrode 41 and the heating element 44, an alignment film 56 in contact with the liquid crystal 42 is formed. The alignment film 56
And an alignment film 56 formed on the surface of the counter electrode 51.
Are formed by applying rubbing treatment after applying and heating polyimide. The alignment film 56 is not limited to polyimide, and another alignment film material may be used. If the liquid crystal material and the writing / rewriting conditions are selected, the alignment film 56 can be omitted.

In this embodiment, tungsten formed by low-pressure CVD is used as an electrode material, that is, a wiring material. However, the present invention is not limited to this, and has heat resistance and chemical resistance. Other materials that are easy and have low resistance may be used. Further, the forming method is not limited to the low pressure CVD method, and any method can be used as long as the film thickness can be made uniform. The heating element 44 is made of polycrystalline silicon formed by a low pressure CVD method. However, if the heating element 44 has a suitable resistance value, heat resistance, and chemical resistance and is easy to form and process, it may be formed of another material. A method may be used.

Next, a process for manufacturing the memory cells 43 formed in the recording section 34 in a matrix will be described. In this embodiment, a step of forming the peripheral MOS IC and a step of forming the recording unit 34 are necessary.
Without mentioning the IC process, the memory cell 43
Only the step will be described.

The silicon substrate 55 is a 6-inch P-type (10
The single crystal silicon wafer of 0) was used. First, an 800 nm field oxide film 57 is formed on a silicon substrate 55 by thermal oxidation. Next, a 1.2 μm-thick tungsten film is formed on the field oxide film 57 by a low pressure CVD method. Then, unnecessary portions of the film are removed by photolithography and dry etching, and the lower electrode 42 is patterned. Next, a silicon nitride film having a thickness of 1.0 μm is formed on the lower electrode 42 by a plasma CVD method to form an inter-electrode insulating film 54. Next, an opening 54a reaching the lower electrode 42 is formed in the inter-electrode insulating film 54 by photolithography and dry etching.

Next, the specific resistance is reduced to about
A heating element 44 is formed of polycrystalline silicon having a thickness of about 1000 Ω · cm and a thickness of about 1.0 μm. When impurities such as boron, phosphorus, and metal are mixed into the film of polycrystalline silicon, the resistance value decreases, and heat may not reach a predetermined temperature. Therefore, it is necessary to pay particular attention to the purity of the material used for the low pressure CVD method and the cleanliness of the apparatus. In this embodiment, the heating element 44 is formed by a low-pressure CVD method using a high-purity monosilane gas as a material for forming polycrystalline silicon. However, if a necessary resistance value can be secured, another silicon compound or another forming method may be used. You may use it.

Then, about 1.0 μm
An unnecessary portion is removed by photolithography and dry etching to form an upper electrode 4.
1 is patterned. Next, after a polyimide material was spin-coated and heated and polymerized, unnecessary portions were removed, and a rubbing treatment was performed to form an alignment film 56.

On the other hand, the glass substrate 52 on the side of the counter electrode is cut into a suitable size, and thereafter, the surface thereof is made of ITO (Indium Tin Oxide) by a sputtering method.
A transparent conductive film composed of a film is laminated, and the
Is formed. Next, unnecessary portions of the ITO film are removed by photolithography and etching, and the counter electrode 51 is arranged in the row direction. The arrangement pitch of the counter electrode 51 and the thickness of the electrode were selected so as to be optimal conditions for writing and reading information. After that, a polyimide material is spin-coated on the surface of the counter electrode 51, and after heat polymerization, unnecessary portions are removed and rubbed to form an alignment film 56.

Next, the silicon substrate 55 and the glass substrate 52 manufactured in the above steps are opposed to each other with the respective electrode forming surfaces inside, and the counter electrode 51 is positioned on the memory cell 43 on the silicon substrate 55 side. Position. Then, a portion of the glass substrate 55 corresponding to the periphery of the recording section 34 is sealed. Thereafter, an acrylic polymer nematic liquid crystal (Ti = 106 ° C., degree of polymerization: 150) having p-cyanobiphenyl as a mesogen group is filled between the silicon substrate 55 and the glass substrate 52. Then, the polymer nematic liquid crystal is gradually cooled from an isotropic phase while applying an AC voltage of 100 V and 500 Hz to be in a homeotropic alignment state. Finally, the completed silicon substrate 55 is diced and bonded, and then housed in a package.

As the liquid crystal material, a conductive polymer liquid crystal can be used. When such a conductive polymer liquid crystal is used, a charge transfer complex using phenanthrene as an electron donor and iodine as an electron acceptor is used as a conductivity-imparting group B, a mesogen group A is used as an ester-based liquid crystal, and an acrylic type liquid crystal is used. A conductive polymer liquid crystal having a main chain is filled between the silicon substrate 55 and the glass substrate 52. Then, the liquid crystal polymer was gradually cooled from the isotropic phase while applying an alternating current of 100 V and 500 Hz to obtain a homogeneous alignment. Finally, the completed silicon substrate 55 is diced and bonded, and then housed in a package.

Note that the liquid crystal material is not limited to the above-mentioned ones, and a state change such as a phase transition is caused by heat, and the information written by the state change can be electrically read out. Any other liquid crystal material may be used as long as the liquid crystal material can be maintained.

Next, the operation principle of writing and reading information to and from the memory cell 43 manufactured as described above will be described.

When an acrylic polymer nematic liquid crystal having a mesogen group of p-cyanobiphenyl or a polysiloxane-based polymer smectic liquid crystal as described above is used as the liquid crystal material, these liquid crystals 53 become isotropic by heating. The structure changes from a mono-domain state to a poly-domain state upon rapid cooling. This state of structural change can be maintained at room temperature for a long period of time, so that recording can be maintained.

On the other hand, when the liquid crystal material after heating is gradually cooled, it returns to the mono-domain state again. Since the dielectric constant of the liquid crystal 53 is different between the mono-domain state and the poly-domain state, recorded information can be electrically read. With the above operation principle, writing and reading of information becomes possible.

In the mono-domain state, the liquid crystal 53 is in a transparent state, whereas in the poly-domain state, it becomes opaque due to light scattering. Therefore, the memory cell 43
By irradiating the laser light or the like with the laser beam and detecting the reflected light from the liquid crystal 53, the information can be read also by this method. Although this method includes an optical detection unit, it includes a signal processing unit and can be said to be an electrical readout method as a whole.

On the other hand, when the above-mentioned conductive polymer liquid crystal is used as the liquid crystal material, the following operation principle is used. That is, a state change such as a phase transition of the conductive polymer liquid crystal due to heat is used as information recording, and a change in conductivity of the conductive polymer liquid crystal accompanying the state change is used as information reading.

As shown in FIG. 5, the structure of the conductive polymer liquid crystal is composed of a polymer main chain P, a mesogen group (liquid crystal portion) A, a conductivity imparting group B, and a spacer S. The mesogen group A, which is a liquid crystal component, is bonded to the polymer main chain P via a spacer S. Further, the conductivity-imparting group B is bonded to the mesogen group A via the spacer S.

Here, the main chain portion is an acrylic polymer,
It is a polymer such as a compound such as a silicone polymer and a methacrylic polymer. At the same time as fixing the ends of the mesogen group A and the conductivity imparting group B, it affects the phase transition temperature and the response speed. The mesogen group A is a liquid crystal compound such as azomethine, azooxy, and biphenyl. The mesogen group A is oriented according to the applied voltage during cooling from the isotropic phase, and the conductivity imparting group B is forcibly aligned. The conductivity-imparting group B is a charge-transfer complex, and is a medium for recording information by generating conductivity in the direction of alignment only when aligned. The spacer S is a part that determines the degree of freedom of the mesogen part, such as a methylene chain, and its molecular length affects important characteristics such as a response speed as a recording device. Therefore, the mesogen group A
The molecular design must be made while paying attention to the fact that is easy to align and the conductivity imparting group B is easily arranged. Further, these spacers S can be omitted.

FIG. 6A is a schematic view of a conductive polymer liquid crystal in which mesogen groups A are oriented and conductivity-providing groups B are arranged. The mesogen groups A are oriented, and the conductivity imparting groups B are arranged in an aligned state by the forcing force. For this reason, a current flows in the direction of the arrow (or the opposite direction) through the adjacent charge transfer complex, so that the state becomes conductive.

FIG. 6B shows a state where the mesogen group A is not oriented, and the conductivity imparting group B is not arranged. Therefore, no conductivity occurs and the state is high. A conductive polymer liquid crystal having such characteristics is formed on a silicon substrate 55.
Between the upper electrode 41 and the lower electrode 42, and the information writing voltage between the upper electrode 41 and the counter electrode 51 to switch between these two states. In addition, information can be written and rewritten.

Next, the operation principle of writing / reading will be described with reference to FIGS. 7 and 8 (a) and 8 (b). When the conductive polymer liquid crystal is heated to an isotropic state and rapidly cooled while applying an information writing voltage, the mesogen group A is in an oriented state. In addition, the conductivity-imparting groups B are aligned by the force of the mesogen groups A. At this time, the charge transfer complex exhibits conductivity because charges can move through the adjacent charge transfer complex. FIG. 7 shows a state of the conductive polymer liquid crystal in a conductive state. When a liquid crystal exhibiting negative dielectric anisotropy is used as the mesogen group A, the mesogen group A assumes a homogeneous alignment state with respect to the substrate as shown in the figure. At this time, the charge transfer complex serving as the conductivity imparting group B is similarly arranged in a homogeneous alignment state by the forcing force of the mesogen group A. When the charge transfer complexes overlap, conductivity occurs in that direction. In FIG. 7, the opposing electrode 51 and the upper electrode 41 are in a conductive state.

On the other hand, if the liquid crystal 53 is rapidly cooled from the isotropic state without applying the information writing voltage, the mesogen group A is not oriented, the charge transfer complex is not arranged, and the liquid crystal 53 does not show conductivity and is in a high resistance state. .

FIGS. 8A and 8B show a high resistance state. Here, FIG. 8 (a) shows a state in which the arrangement of the polymer main chain P, the mesogen group A and the charge transfer complex B are both disturbed, and FIG. 8 (b) shows that the polymer main chain P is aligned, The orientation of the mesogen group A is disturbed, so that the charge transfer complex B is not arranged and does not exhibit conductivity. In this example, the space between the upper electrode 41 and the counter electrode 51 is in a high resistance state. 8A or 8B depends on the heating conditions, the alignment treatment of the substrate, the conductive polymer liquid crystal material, and the like. However, for high-speed response, FIG. 8B is used. It is more desirable to control it.

The above conduction state and high resistance state are determined by the upper electrode 4
AC and DC are applied between the liquid crystal 5 and the counter electrode 51.
Measure the impedance or conductivity of No. 3 and read out the information.

Hereinafter, specific operations of writing / rewriting and reading of information when a conductive polymer liquid crystal is used as a liquid crystal material will be described.

(Write / Rewrite) Information input from an external device is recorded in the buffer memory by the input / output signal control unit 31, and is written in the recording unit 34 after data processing. For writing, a heating voltage is applied to the heating element 44 sandwiched between the upper electrode 41 and the lower electrode 42 on the silicon substrate 55,
This is performed by heating the liquid crystal 53. When the liquid crystal (liquid crystal compound) 53 becomes isotropic, the supply of the heating voltage is stopped while applying the information writing voltage between the upper electrode 41 and the counter electrode 51, and the liquid crystal 53 is rapidly cooled. As a result, the liquid crystal 53 becomes conductive. At this time, the specific resistance ρ of the liquid crystal 53 is ρ = 10
It became ⁶ to 10 ⁸ Ωcm.

On the other hand, after the liquid crystal 53 becomes isotropic, if the liquid crystal 53 is rapidly cooled without applying an information writing voltage between the upper electrode 41 and the counter electrode 51, the liquid crystal 53 enters a high resistance state. At this time, the specific resistance ρ of the liquid crystal 53 was ρ = 10 ¹² to 10 ¹³ Ωcm.

The conductive state and the high resistance state can be rewritten at any time. Also, the memory cell 43 of the recording unit 34
Can be freely selected and random access is possible.

(Reading Method) An AC or DC voltage is applied between the upper electrode 41 on the silicon substrate 55 and the counter electrode 51 on the glass substrate 52, and the conductivity or impedance of the liquid crystal 53 is measured. Specifically, the specific resistance of the liquid crystal 53 is significantly different between the state where the mesogen groups are not oriented and the conductivity-imparting groups B are not aligned and the state where the mesogen groups A are oriented and the conductivity-imparting groups B are not aligned. Data can be read using the difference in the conductivity of the liquid crystal 53 in the two states. Here, either the conduction state or the high resistance state is changed to O
It may be in the N state.

As described above, the nonvolatile recording apparatus of the present invention
Since the single crystal silicon substrate 55 is used as the recording unit 34, a peripheral circuit including an IC for controlling input / output of information can be easily mounted in the same device. Therefore, it is convenient for miniaturization, simplification, and cost reduction of the device configuration. Note that the peripheral circuit is not limited to an IC, and any other circuit or circuit element may be used as long as it can be mounted on the single crystal silicon substrate 55.

In this embodiment, a charge transfer complex was used as the conductivity imparting group B as a recording medium. As such a conductive polymer liquid crystal (conductive liquid crystal polymer), for example, the one disclosed in JP-A-59-59705 may be used. Further, the present invention is not limited to a polymer liquid crystal using a charge transfer complex as the conductivity-imparting group B, and any other liquid crystal compound that causes a change in conductivity along with a change in alignment or phase transition of the liquid crystal may be used. Compounds may be used. For example, a polymer using a conjugated system of a main chain such as polyacetylene, an organic conductive polymer using a composite of such a polymer and a metal, and the like can be used.

When such a conductive alignment film is used as the alignment film, the read signal O
Since the N / OFF ratio can be further increased, more accurate reading can be performed.

That is, according to the present embodiment, the ON / OFF ratio of the read signal can be increased, in other words, the S / N ratio of the read signal can be improved, so that accurate reading can be performed. Also, there is an advantage that the amplification factor of the sense amplifier provided in the input / output signal control unit 31 can be reduced.

Next, referring to FIG. 9, a specific ON / OFF ratio (more specifically, an OFF / ON ratio) of a read signal when the memory cell 43 is turned ON / OFF in the present embodiment.
Will be described. In the equivalent circuit shown in FIG.
0 is an AC power source for applying a reading voltage between the counter electrode 51 and the upper electrode 41, C ₁ is the capacitance of the common electrode 51 side orientation film 56, the static of C ₂ is the conductive polymer liquid crystal 53 C ₃ indicates the capacitance, and C ₃ indicates the capacitance of the alignment film 56 on the upper electrode 41 side. R ₁ indicates the resistance of the alignment film 56 on the counter electrode 51 side, R ₂ indicates the resistance of the conductive polymer liquid crystal 53, and R ₃ indicates the resistance of the alignment film 56 on the upper electrode 41 side.

Now, let the area S of the memory cell 43 be S = 2 μm
^{× 2μm = 4 × 10 -12 m} 2, constituting the alignment film 56, 56 polyimide (dielectric) of the thickness t of t = 0.02 [mu] m =
2 × 10 ⁻⁸ m, and the layer thickness L of the conductive polymer liquid crystal 53 is L =
1.0 μm = 1 × 10 ⁻⁶ m, relative dielectric constant ε _{s of} polyimide
Is ε _s = 3.3, the relative permittivity ε _s of the conductive polymer liquid crystal 53 is ε _s = 5.0, and the specific resistance ρ of the polyimide is ρ = 10 ¹⁶ Ω ·
cm, when conductive polymer liquid crystal 53 is OFF (non-conductive state)
Is ρ = 10 ¹² Ω · cm, and the specific resistance ρ when the conductive polymer liquid crystal 53 is ON (high conductivity state) is ρ
= 10 ⁶ Ω · cm, the capacitance C _i (i = 1, 2,
3) is represented by the following equation.

C _i = ε ₀ · ε _s · S / t where ε ₀ = 8.9 × 10 ⁻¹² is the relative dielectric constant in a vacuum.

By substituting the above various numerical values into this equation,
C ₁ = C ₃ = 5.9 × 10 ⁻¹⁵ [F], and C ₂ = 1.8
× 10 ^-16 [F].

Here, the capacitance reactances R _C1 , R _C2 , and R _C3 of the alignment films 56 and 56 and the conductive polymer liquid crystal 53, ie, C ₁ , C ₂ and C ₃ are represented by the following equations.

R _Ci = 1 / (2πfC _i ) where f is the frequency of the read voltage applied between the counter electrode 51 and the upper electrode 41 from the AC power supply 100.
In this embodiment, an AC voltage of 60 Hz was used as the read voltage.

By substituting the values of C ₁ , C ₂ , and C ₃ calculated as described above into the above equation, the capacitance reactance R
_{C 1} , R _C2 , and R _C3 are R _C1 = R _C3 = 4.50 × 10 ¹¹ Ω,
R _C2 = 1.5 × 10 ¹³ Ω.

The resistance R _i is represented by the following equation.

R _i = ρ · L / S... Therefore, if the above numerical values are substituted into this equation, R ₁ = R ₃
= 5.0 × 10 ¹⁷ Ω. The values of R ₂ when OFF and ON are R _OFF2 = 2.5 × 10 ¹⁵ Ω, respectively.
R _ON2 = 2.5 × 10 ⁹ Ω.

From the above results, the OF of memory cell 43
F, the resistance R _OFF when ON, R _ON the following formula, are calculated by the equation.

R _OFF = R ₁ · R _C1 / (R ₁ + R _C1 ) + R _OFF2 · R _C2 /
(R _OFF2 + R _C2 ) + R ₃ · R _C3 / (R ₃ + R _C3 ) = 1.5
5 × 10 ¹³ Ω ... R _ON = R ₁ · R _C1 / (R ₁ + R _C1 ) + R _ON2 · R _C2 / (R
_ON2 + R _C2 ) + R ₃ · R _C3 / (R ₃ + R _C3 ) = 0.9 × 1
0 ¹² Ω... Therefore, the resistance ratio (1 / conductivity ratio) R at the time of ON / OFF of the memory cell 43 is obtained from the above expression and expression.
_OFF / R _ON is given by the following equation.

R _OFF / R _ON = 17 As is apparent from the equation, according to the present embodiment, the memory cell 4
Since the resistance ratio at ON / OFF of No. 3 can be increased, the OFF / ON ratio of the read signal can be increased as a result. Therefore, according to the present embodiment, readout accuracy can be improved.

In this embodiment, when a material having conductivity is employed for the alignment film 56, the OFF state is obtained as described below.
Since the / ON ratio can be further increased, there is an advantage that more accurate reading can be performed.

That is, a conductive polyimide obtained by mixing a small amount of carbon into polyimide is used as the alignment film, and the specific resistance ρ is ρ
= 10 ³ Ω · cm , realizing R ₁ = R ₃ = 5 × 10 ⁴ Ω according to the above equation, R _OFF and R _ON are respectively R _OFF = 1. 5x1
0 ¹³ Ω and R _ON = 2.5 × 10 ⁹ Ω. Accordingly, the resistance ratio R _OFF / R _ON is R _OFF / R _ON = 6 × 10 ³ , which indicates that the OFF / ON ratio of the read signal can be further increased.

[0108]

According to the nonvolatile recording apparatus of the present invention, information can be written to and read from a recording medium by static electric control. Therefore, a rotating mechanism and a moving mechanism required for a magneto-optical disk or a magnetic disk are required. Becomes unnecessary. Therefore, the size, simplicity, and cost of the device configuration can be reduced. In addition, since complicated components such as a laser pickup and a head and a precise structure are not required, the apparatus is not damaged due to vibration, impact, or adhesion of dust. Therefore,
The stability of record retention can be significantly improved.

Further, since the structure of the memory cell can be simplified as compared with a nonvolatile recording device using an IC nonvolatile memory, a large area can be realized. In addition, a fine memory cell can be realized by applying the fine processing technology of the IC. Therefore, a large-capacity, high-density nonvolatile recording device can be realized.

As described above, according to the present invention, it is possible to realize a completely new type of nonvolatile recording device which satisfies the desired conditions as a nonvolatile recording device.

In particular, the nonvolatile memory device of the present invention
Upper and lower electrodes sandwiching the body in a matrix
Arranged and between upper electrodes adjacent in the column direction and where
An insulating film is interposed between lower electrodes that are
Structure that forms a memory cell at each intersection of a pole and a lower electrode
Therefore, each of the upper electrode and the lower electrode is
Can electrically insulate each other and generate heat from each memory cell
Since heat diffusion to the outside of the cell of the body can be suppressed,
Leaks between memory cells can be reliably prevented
You. In addition, if the insulation film is configured to be in contact with the heating element,
Further enhances the heat diffusion of the heating element of the memory cell to the outside of the cell
Can be suppressed. In addition, it has high conductivity as a recording medium.
When molecular liquid crystal is used, when the memory cell is turned ON / OFF
ON / OF of read signal
Since the F ratio can be increased, information reading accuracy can be reduced.
The layer can be improved. Furthermore, it comes into contact with the recording medium
Conductive material on the surface of the substrate on the opposite side and the substrate on the heating element side
When an alignment film is formed , ON / OF of a read signal is performed.
Since the F ratio can be further increased, the information reading accuracy can be improved .
It can be further improved.

[Brief description of the drawings]

FIG. 1 is a surface configuration diagram of a nonvolatile recording device of the present invention.

FIG. 2 is a surface configuration diagram of a recording unit.

FIG. 3 is a sectional view of a memory cell corresponding to line AA in FIG. 2;

FIG. 4 is a perspective view of a memory cell.

FIG. 5 is a drawing showing a chemical structure of a conductive polymer liquid crystal.

FIG. 6 is a drawing showing a state where a mesogen portion and a charge transfer complex of a conductive polymer liquid crystal are arranged and a state where they are not arranged.

FIG. 7 is a view showing a state in which a mesogen portion of a conductive polymer liquid crystal and a charge transfer complex are arranged in a nonvolatile recording device in which a conductive polymer liquid crystal is sealed as a recording medium.

FIG. 8 is a drawing showing, in a non-volatile recording device in which a conductive polymer liquid crystal is sealed as a recording medium, a state in which a mesogen portion and a charge transfer complex of the conductive polymer liquid crystal are not arranged and a state in which the charge transfer complex is arranged. .

FIG. 9 is an equivalent circuit diagram of a memory cell in a nonvolatile recording device in which a conductive polymer liquid crystal is sealed as a recording medium.

FIG. 10 is a structural diagram of an EEPROM.

FIG. 11 is a structural diagram of a magneto-optical disk.

[Explanation of symbols]

 Reference Signs List 31 input / output signal control unit 32 logic system control unit 33 drive circuit unit 34 recording unit 41 upper electrode 42 lower electrode 43 memory cell 44 heating element 51 counter electrode 52 glass substrate 53 liquid crystal (liquid crystal compound) 54 interelectrode insulating film 55 silicon substrate 56 alignment film 57 field insulating film 100 AC power source A mesogen part B charge transfer complex P polymer main chain

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 29/788 29/792

Claims (4)

(57) [Claims] An opposing substrate having an opposing electrode and a heating element
Heating element side base with upper and lower electrodes sandwiching
And a liquid crystal compound or molecule between the substrates.
In which a recording medium made of a compound containing a liquid crystal component is enclosed.
A volatile recording device, wherein the upper electrode and the lower electrode are arranged in a matrix.
Both are adjacent between the upper electrodes adjacent in the column direction and adjacent in the row direction.
An insulating film is interposed between the matching lower electrodes, and
And a memory cell at each intersection of the lower electrode . 2. A counter substrate having a counter electrode, and a heating element.
Heating element side base with upper and lower electrodes sandwiching
And a conductive polymer liquid crystal between both substrates.
A non-volatile recording device enclosing a recording medium, wherein the upper electrode and the lower electrode are arranged in a matrix.
Both are adjacent between the upper electrodes adjacent in the column direction and adjacent in the row direction.
An insulating film is interposed between the matching lower electrodes, and
And a memory cell at each intersection of the lower electrode . 3. The opposing side group on the side in contact with the recording medium.
The surface of the plate and the heating element side substrate is made of a conductive material.
3. The nonvolatile recording device according to claim 1, wherein an alignment film is formed . 4. A structure in which said insulating film is in contact with said heating element.
The nonvolatile memory according to any one of claims 1 to 3,
Recording device.