JPH05127136A - Non-volatile recorder - Google Patents

Abstract

PURPOSE:To prevent the generation of thermal crosstalks and to enable recording with good accuracy. CONSTITUTION:A field insulating film 57 is formed over the entire surface of a silicon substrate 55 and plural pieces of band-shaped lower electrodes 42 extending in a line direction are wired thereon. Rugged parts are formed on the lower electrodes 42. Upper electrodes 41 are laminated and formed to hold the recessed parts of heating elements 44 having a planar shape. The upper electrodes 41 have the band shape similar to the shape of the lower electrodes 42. Oriented films 56 are formed on the surfaces of the upper electrodes 41 and the surfaces of the protruding parts of the heating elements 44. On the other hand, plural pieces of counter electrodes 51 extending in a row direction are formed on the opposite surface of a glass substrate 52 disposed to face the surface of a silicon substrate 55. The oriented film 56 is formed on the surface thereof. A liquid crystal 53 as a recording medium is sealed between the upper and lower substrates 55 and 52. A voltage is impressed between the lower and upper electrodes 41, 42 to allow the heating elements 44 to generate heat and to heat up the liquid crystal 53. In addition, a writing voltage is impressed between the counter electrodes 51 and the upper electrodes 41 to execute writing of information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-volatile recording device having a high-density and large-capacity recording capacity and capable of electrically writing and reading information, and 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 non-volatile recording devices in which information can be rewritten.

Magnetic tape.

A magnetic disk.

IC non-volatile memory such as EPROM and EEPROM.

Magneto-optical disk.

The respective features will be described below.

Magnetic tape This is the most typical rewritable non-volatile recording device,
Since it is cheap, it is most popular as an audio tape or a video tape. Further, it is a very large-capacity recording device and is also used as a backup memory for a computer.

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

Magnetic disk Generally used as an external recording device for computers and word processors. A floppy disk which is easy to handle and inexpensive, and a hard disk which has a larger recording capacity than the floppy disk but is difficult to handle and is expensive are often used.

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

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

The 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 that electrically writes and erases by irradiation of ultraviolet rays, and an EEPROM that can electrically write and erase. These IC non-volatile memories have advantages such as small size and light weight, short access time, and low power consumption.

The following is an electrically erasable / erasable E
The details will be described by taking an EPROM as an example. Figure 4 is E
An example of a cross-sectional shape of a memory cell of an EPROM is shown. 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 controls injection of carriers into the floating gate 4 where carriers are accumulated and stored. The 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 the silicon substrate 7 so as to cover the gates 2 and 4. A silicon oxide film or a silicon nitride film is usually used as the surface protective film 1. Further, a source region 8 and an drain region 6 in which impurities are implanted are formed in the surface layer portion of the silicon substrate 7, and a channel region 9 is further formed between them.

In the above structure, 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 recorded information can be erased by using the source region 8 and the control gate 2.
And a voltage is applied between the Fowler-Nordhei
Carriers are removed using the m (NF) tunneling phenomenon. Further, the recording information is read out by judging ON / OFF by the threshold voltage of the inversion voltage of the channel region 9 between the source region 8 and the drain region 6.

Since carrier injection and removal are performed through the gate oxide film 5, the quality and thickness of the gate oxide film are E.
It is very important for the EPROM structure. For example, in an EEPROM having a recording capacity of 1 megabit, the film thickness of the gate oxide film 5 is usually a thin film of about 20 nm, so that it is difficult to control the film quality and film thickness, and the increase in cost due to a decrease in yield is a serious problem. Also, the chip size is usually
Both the short side and the long side are about 7 to 10 mm, and when the chip area is increased to increase the recording capacity, the yield is reduced and the cost is further increased.

Since it has such drawbacks, the EEPROM is
However, although it has the above advantages, there is a limit in improving the storage capacity. Incidentally, the current EEPROM has a recording capacity of about 1 to 4 Mbits, which is smaller than that of other nonvolatile recording devices such as magneto-optical disks and magnetic disks.

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

FIG. 5 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. The record of information is
The laser light 20 is focused on the disk in a weak magnetic field in the direction opposite to the direction in which the magnetic thin films 15 and 16 are pre-magnetized.
The information is recorded on the magnetic thin films 15 and 16 by focusing on 1 and locally heating. On the other hand, the reproduction of information is performed using the Kerr effect or the Faraday effect. That is, when the linearly polarized laser light 20 is irradiated onto the disk, the transmitted light or the reflected light has its polarization plane rotated according to the magnetization state of the magnetic thin films 15 and 16, and therefore the rotation of this polarization plane is analyzed by the analyzer. The information is reproduced by converting the signal into a light intensity signal by using, and detecting it as an electric signal by a photodetector. Such a magneto-optical disk has been put into practical use as a recording device capable of large-capacity recording for document files and image files.

The advantage of the magneto-optical disk is that the recording is performed by the laser beam 20, and therefore the recording can be performed without contact through the transparent glass substrate 12. That is, according to this recording method, dust on the recording surface 23 side does not pose a problem. On the other hand, although dust on the substrate surface 22 side has an effect,
Since the laser beam 20 is not focused on the side, the beam diameter is as large as several hundreds of microns, and some dust is not present and is not adversely affected.

With respect to the recording capacity of the magneto-optical disk, since information is recorded / reproduced by the condensed laser beam 20, high density recording becomes possible. By the way, one with a 3.5 inch disc
A large-capacity memory of about 20 megabytes can be realized.

However, since the magneto-optical disk requires a laser, a magnet, and a rotating mechanism (a rotating mechanism of the disk) for writing and reading information, a large peripheral device is required,
There is a drawback that the price becomes high.

[0023]

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

(1) Large capacity and high density recording is possible.

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

Although high density can be achieved with IC nonvolatile memories such as EPROM and EEPROM, it is difficult to increase the capacity because the chip area cannot be increased due to the limitation of yield.

(2) Strong against shock and vibration.

The capacity of a hard disk can be increased by accumulating a plurality of disks, but the distance between the head and the disk is narrowed to 1 micron or less in order to cope with high density, and it is easily damaged by shock or vibration. Further, even if minute dust is attached to the head or the disk, the recording device may be damaged.

(3) The peripheral devices for writing / reading are small, simple and inexpensive.

Since floppy disks, hard disks, and magneto-optical disks all rotate and read / write information, a rotating mechanism such as a motor is required, and the peripheral device becomes large and complicated.

In addition, in the hard disk, the distance between the disk and the head must be precise, and a shock-absorbing material is required to secure the shock resistance, so that there is a problem that the entire apparatus becomes large and heavy.

Further, in the magneto-optical disk, since the laser and the magnet are used for writing and reading, the device becomes large,
It has the drawback of becoming heavy and expensive.

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

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

As described above, none of the current non-volatile recording devices satisfy all of the above items (1), (2), (3) and (4), and a completely new type that satisfies all of these items. There has been a demand for realization of the non-volatile recording device.

Therefore, the applicant of the present application has proposed the above (1),
Japanese Patent Application No. 3-138027 has proposed a non-volatile recording apparatus that satisfies all the items (2), (3) and (4). 6 to 8 show a schematic configuration of this nonvolatile memory device. In the figure, a plurality of upper electrodes 41 are arranged at equal intervals in the column direction and are in contact with the liquid crystal 53 via the alignment film 56. 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 electrodes 41 and 42.

As shown in FIGS. 7 and 8, the memory cell 43 is composed of the following components arranged and enclosed between the silicon substrate 55 and the glass substrate 52. Silicon substrate 5
5, a counter electrode 51 is arranged on the surface of the glass substrate 52 opposed to the glass substrate 52, and an alignment film 56 is formed on the surface of the counter electrode 51.
Is formed.

On the other hand, the field oxide film 57 is formed on the surface of the silicon substrate 55, and the lower electrode 42 is formed thereon. An inter-electrode insulating film 54 made of a silicon nitride film is formed between the lower electrode 42 and the upper electrode 41 in order to maintain insulation between them. The inter-electrode insulating film 54 has an opening 54a in the memory cell 54 portion, and the heating element 44 is directly sandwiched between the upper electrode 41 and the lower electrode 42 in that portion. The heating element 44 has a flat plate shape as shown in FIG. An alignment film 56 is formed on the upper electrode 41 and the heating element 44 so as to contact the liquid crystal 53.

In such a structure, when a voltage is applied between the upper electrode 41 and the lower electrode 42 to heat the portion of the heating element 44 corresponding to the intersection of both electrodes 41, 42,
The corresponding liquid crystal 53, that is, the memory cell 43 undergoes a phase change, which allows information to be written. To explain a little, the liquid crystal 53 is composed of a liquid crystal compound such as an acrylic-type polymer nematic liquid crystal having p-cyanobiphenyl as a mesogen group or a polysiloxane-based polymer smectic liquid crystal, or a compound containing a liquid crystal component in its molecule.

By controlling the voltage applied between the upper electrode 41 and the lower electrode 42 and the time, the liquid crystal forming the recording medium is heated to a temperature such as a phase transition or other state change, for example, an isotropic phase. , And then the upper electrode 41 and the counter electrode 5
Applying a voltage for writing information during 1 and stopping the heating current for rapid cooling, or gradually cooling by controlling the heating current and voltage without applying the information writing voltage. Thereby, the liquid crystal is in an alignment state and in a monodomain state.

On the other hand, when the heating current is stopped and the liquid crystal is rapidly cooled without applying the voltage for writing information, the liquid crystal becomes a polydomain state. After that, when cooled to room temperature, the liquid crystal becomes a glass state, and that state is maintained.

Since the information written as the two states of the mono domain and the poly domain is retained at room temperature for a long period of time, the written information can be stored as recorded information. Since liquid crystals having different states have different dielectric constants, the recorded information can be electrically read.

By the way, the nonvolatile memory device has the following improvements. It's a matter of crosstalk. The details will be described below with reference to FIG. For convenience of description, the upper electrodes in the column direction are now U1, U2, U3, U
4, U5, the lower electrodes in the row direction are D1, D2, and D3, and the memory cells formed at the intersections of the upper electrodes and the lower electrodes are Mij (i is the number of rows, j is the number of columns, i =
1, 2, 3, j = 1, 2, 3, 4, 5). Assuming a case where a voltage of + V1 is applied to the lower electrode D1, a voltage of −V1 is applied to the upper electrodes U1 and U3, and a voltage of + V1 is applied to the upper electrodes U2, U4, and U5 to write information, memory cells M11 and M13 are assumed. Is applied with a voltage of 2V1, while no voltage is applied to the memory cells M12, M14, M15. Therefore, in this case, the memory cells M11 and M13 generate heat and the liquid crystal 5 corresponding to the memory cells M11 and M13.
3 causes a phase change, and information is written.

At the time of writing this information, the lower electrode D
Since no voltage is applied to the lower electrode D2 adjacent to 1, the memory cell adjacent to the heat generating portion, for example, the memory cell M.
A voltage of V1 is applied to 21 between the upper electrode U1 and the lower electrode D2. Therefore, at this time, if a material having a proportional relationship between the applied voltage and the calorific value is used, the memory cell M2
Since 1 generates heat with half the heat generation amount of the memory cell M11 to be written, there is a drawback that heat generation crosstalk occurs and the writing accuracy deteriorates.

Furthermore, the spread of heat may adversely affect crosstalk on the peripheral memory cells.
That is, for example, when the memory cell M11 generates heat, this heat is transmitted to the peripheral portion through the upper electrode, the lower electrode and the liquid crystal 53, and due to this heat transfer, for example, the memory cell M2.
This is because the temperatures of 1, M22 and M12 rise. Such a defect can be solved by increasing the distance between adjacent memory cells. However, this causes a new defect that the pitch of the memory cells becomes large and the recording density is lowered.

The present invention solves the above-mentioned drawbacks of the prior art, and realizes high density and large capacity, high speed writing / reading, and miniaturization, simplification and low cost of peripheral devices. It is an object of the present invention to provide a non-volatile recording device that can be priced, can reliably eliminate crosstalk due to heat generation, and can accurately write and read information.

[0047]

A nonvolatile recording apparatus according to the present invention encloses a recording medium formed of a liquid crystal compound or a compound containing a liquid crystal component in a molecule between a pair of substrates arranged to face each other, and heats the recording medium. A non-volatile recording device in which the recording medium is heated by means to write information and the information written in the recording medium is read by reading means, wherein the heating means is entirely formed on one substrate. It is composed of a lower electrode wired in a strip shape on an insulating film, and a strip upper electrode laminated on the lower electrode with a heating element sandwiched therebetween. A voltage is applied between the upper and lower electrodes to remove the heating element. Information is written on the recording medium by generating heat and applying an information writing voltage between the upper electrode and a counter electrode arranged on the inner surface of the other substrate in a direction orthogonal to the upper and lower electrodes. To do It becomes Te, the objects can be achieved.

[0048]

First, the information writing / reading operation in the nonvolatile recording device having the above structure will be described. When a voltage is applied between the upper and lower electrodes and a current is passed through the heating element, Joule heat is generated in the heating element. By controlling the heating current and voltage and the application time thereof, the liquid crystal that constitutes the recording medium is heated to a temperature such as a phase change such as a phase transition, for example, an isotropic phase, and then the upper electrode and the counter electrode are heated. By applying a voltage for writing information between the two and stopping the current for heating to cool rapidly, or by not applying a voltage for writing information and controlling the current and voltage for heating to perform cooling. The liquid crystal is in an aligned state and in a monodomain state.

On the other hand, when the current for heating is stopped and the liquid crystal is rapidly cooled without applying the voltage for writing information, the liquid crystal becomes a polydomain state. After that, when cooled to room temperature, the liquid crystal becomes a glass state, and that state is maintained.

Since the information written as the two states of the mono domain and the poly domain is retained at room temperature for a long period of time, the written information can be stored as record information. Since liquid crystals in different states have different dielectric constants, the recorded information can be recorded electrically by applying an AC voltage between the counter electrode and the upper electrode and measuring the electric capacity of the recording medium as a dielectric. Can be read.

From this state, the liquid crystal is heated again by the same procedure until a state change such as a 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 there is, when the information writing voltage is applied during cooling, the liquid crystal becomes a monodomain state. Alternatively, when it is rapidly cooled without applying an information writing voltage, it becomes a polydomain shape. As a result, the information once written can be rewritten.

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

In addition, according to the structure in which the upper electrode and the lower electrode, which are laminated with the heating element sandwiched therebetween, are arranged in a strip shape as described above, when a voltage is applied between the upper electrode and the lower electrode, the heating element becomes a strip shape. Fever. At this time, in the present invention, unlike the conventional example shown in FIGS. 6 to 8, the upper electrode and the lower electrode are arranged in parallel with each other with the heating element interposed therebetween, and are electrically separated from the adjacent electrodes. ing. Therefore, in the structure of the present invention, among the crosstalks in the direction orthogonal to the electrode arrangement direction, the crosstalk between the adjacent electrodes does not occur.

On the other hand, the crosstalk in the direction horizontal to the electrodes and the arrangement direction is not a problem because the heating element sandwiched by the electrodes simultaneously heats when writing information.

[0055]

EXAMPLES Examples of the present invention will be described below. FIG. 1 schematically shows the surface structure of the nonvolatile recording device of the present invention, in which the peripheral circuits are divided into blocks according to their functions. The input / output signal control unit 31 has a function of processing an input signal from another device and transmitting a signal (writing information) to the memory cell, and a signal processing of a signal read from the memory cell to another device. It has the function of sending. The logic system controller 32 controls 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 logic system control unit 32. The recording unit 34 is the input / output signal control unit 3
The signal given from 1 is accumulated and saved as record information.

As shown in FIG. 2, the recording section 34 has a heating element 44 for heating for writing / rewriting recorded information.
And a glass substrate 52 and a silicon substrate 55 having wiring for supplying a current to the heating element 44.
A liquid crystal (liquid crystal layer) 53 as a recording medium is enclosed between 5 to form a schematic configuration.

The opposite electrode 51 is provided on the opposite surface of the glass substrate 52.
Are formed in the column direction (Y1, Y2, Y3 ...).
An alignment film 56 that contacts the liquid crystal 53 is formed on the surface of the counter electrode 51. The liquid crystal 53 has a function of recording a signal by its phase transition phenomenon.

The heating element 44 is in the form of a flat plate partially having an uneven portion, and is directly sandwiched between the upper electrode 41 and the lower electrode 42 in the memory cell portion. The upper electrode 41 has a strip shape having a predetermined width, and a plurality of upper electrodes 41 are arranged at substantially equal intervals in the row direction and are in contact with the liquid crystal 53 via the alignment film 56. Below the upper electrode 41, a plurality of lower electrodes 42 are provided in the same direction.
Is provided. The lower electrode 42 has a strip shape having substantially the same width dimension as the upper electrode 41, but is not limited to the same width dimension, and may have different width dimensions as long as the strip-shaped heat generating portion can uniformly heat.

A portion where the upper electrode 41 and the counter electrode 51 intersect corresponds to a memory cell, and a plurality of them are formed in the arrangement direction of both electrodes 41 and 42. As the material of both electrodes 41 and 42, tungsten having excellent heat resistance was used in this embodiment.

The alignment film 56 and the alignment film 56 formed on the surface of the counter electrode 51 are both formed by applying polyimide and heating and then rubbing. The alignment film 56 is not limited to polyimide, and other alignment film materials may be used. In some cases, the alignment film can be omitted by selecting the liquid crystal material and the writing / rewriting conditions.

The silicon substrate 55 is single crystal silicon for semiconductors generally used in ICs, and has impurities added to it to control the resistance value. If the lower electrode 42 is formed on the silicon substrate 55 as it is, the drive current conducted 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.

In addition, an insulating film 58 is formed between the lower electrodes 42 and 42 adjacent in the column direction. The insulating film 58
Is for electrically separating the lower electrodes 42, but also has the purpose of reducing the influence of the spread of heat due to heat conduction from the heating element 44. That is, the width is determined in consideration of the spread of heat. The heat generated from the heating element 44 spreads to the memory cells adjacent in the row direction,
A space must be secured so as not to affect the information written therein, but the width of the insulating film 58 is determined in consideration of the spread of this heat. The memory cell is heated by a corresponding portion of the heating element 44 sandwiched between the upper and lower electrodes 41, 42, and the corresponding portion of the liquid crystal 53 that causes a state change such as phase transition and the silicon substrate in which this liquid crystal portion is sealed. 55 to the glass substrate 52.

After the insulating film 58 is formed on the field insulating film 57 so as to cover the lower electrode 42, a portion corresponding to the upper surface of the lower electrode 42 is opened 58a, and the opening 5 is formed.
The heating element 44 is directly laminated on the lower electrode 42 through 8a, and then the upper electrode 41 is formed thereon.

At the time of 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 example, tungsten formed by the low pressure CVD method as described above was used. On the other hand, the heating element 44 needs to be made of a material that has heat resistance and also has an appropriate resistance value and fine processing, and in this embodiment, high-purity polycrystalline silicon is formed by the low pressure CVD method.

The electrode material is not limited to tungsten formed by the low pressure CVD method, but any other material can be used as long as it has heat resistance and chemical resistance, is easy to form and process, and has low resistance. Materials may be used. Further, the forming method is not limited to the low pressure CVD method, and any method capable of making the film thickness uniform may be used. Further, as the heat resistance 44, polycrystalline silicon formed by the low pressure CVD method was used, but if it is a material having an appropriate resistance value, heat resistance and chemical resistance and easy to form and process, it is formed with other material. Any method may be used.

Next, a schematic manufacturing process of the nonvolatile recording device of the present invention will be described. In this embodiment, a peripheral MOS IC
The process of forming the memory cell and the process of forming the recording portion 34 are required. However, for the sake of simplicity of description, the process of the MOS IC will not be described here, and only the process of the memory cell will be described.

The silicon substrate 55 is a 6-inch P-type (10
The single crystal silicon wafer of 0) was used. First, a 800 nm field oxide film 57 is formed on the silicon substrate 55 by thermal oxidation. Then, a 1.2 μm thick tungsten film is formed on the field oxide film 57 by the 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 is formed on the field oxide film 57 so as to cover the lower electrode 42 by, for example, a plasma CVD method to form an insulating film 58.
Next, an opening 58a is formed in a portion of the insulating film 58 corresponding to the upper surface of the lower electrode 42 by photolithography and dry etching.

Next, the specific resistance is about 10 by the low pressure CVD method on the upper surface of the lower electrode 42 and the field oxide film 57.
Polycrystalline silicon having a film thickness of 00 Ω · cm and a thickness of about 1.0 μm is formed on the entire surface to form the heating element 44. When impurities such as boron, phosphorus, and metals are mixed in the film, the resistance value of polycrystalline silicon decreases, and the temperature may not reach a predetermined temperature when heat is generated. Therefore, it is necessary to pay particular attention to the purity of the material used in the low pressure CVD method and the cleanliness of the apparatus. In this embodiment, the heating element 44 is formed by the low pressure CVD method using high-purity monosilane gas as the material for forming polycrystalline silicon. However, another silicon compound or another forming method may be used if the necessary resistance value can be secured. You can use it.

Then, the pressure is reduced to about 1.0 μm by the low pressure CVD method.
Of the tungsten film is formed, and unnecessary portions of the tungsten film are removed by photolithography and dry etching to remove the upper electrode 4.
1 is patterned. Next, a polyimide material was spin-coated, heated and polymerized, then unnecessary portions were removed, and 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 51 is cut into an appropriate size, and thereafter, ITO (Indium Tin Oxid) is formed on the surface by a sputtering method.
e) A transparent conductive film made of a film is laminated, and then an unnecessary portion of the ITO film is removed by photolithography and etching. The arrangement pitch of the counter electrodes 51 and the thickness of the electrodes are
The optimum conditions for writing and reading information were selected. Then, after that, a polyimide material is spin-coated on the surface of the counter electrode 51, and after heating and polymerization, unnecessary portions are removed and rubbing is performed to form an alignment film 56.

Then, the silicon substrate 55 and the glass substrate 52 produced in the above steps are opposed to each other with their respective electrode formation surfaces facing inward, and the counter electrode 51 is positioned on the memory cell on the silicon substrate 55 side. Align. Then, the portion of the glass substrate 55 that contacts the periphery of the recording portion 34 is sealed. After that, an acrylic-type polymer nematic liquid crystal (T-type) containing p-cyanobiphenyl as a mesogenic group (T
i = 106 ° C., degree of polymerization: 150) is filled between the silicon substrate 55 and the glass substrate 52. Then, the polymer nematic crystal is cooled from the isotropic phase while applying an AC voltage of 100 V and 500 Hz, and brought into a homeotropic alignment state. Finally, the completed silicon substrate 55 is diced, bonded, and then housed in a package.

The liquid crystal material is not limited to the above, and other liquid crystal materials may be used as long as they can cause a state change such as phase transition due to heat and can maintain the changed state. Absent.

The nonvolatile recording device of the present invention manufactured as described above uses a state change such as a phase transition due to heat of the liquid crystal 53 as information writing, and a change in the dielectric constant accompanying the state change as information reading. To use. That is, writing and reading of information are performed by utilizing the structural change of the liquid crystal 53 (polydomain structure ← → monodomain structure) due to the phase transition.

An outline of the information writing operation and the information reading operation in the nonvolatile recording apparatus of the present invention will be described below with reference to FIG. In FIG. 3, U1, U2, and U3 denote strip-shaped upper electrodes 41 arranged in the row direction, and D1, D2, and D
Reference numeral 3 denotes a strip-shaped lower electrode 42 formed below the heating element with the heating element interposed therebetween. Further, Y1, Y2, and Y3 represent counter electrodes 51 arranged in the column direction, and Hij (i represents the number of rows, j represents the number of columns, i = 1, 2, 3, j = 1, 2, 3). ) Indicates the heating element 44, and LCij (i = 1, 2, 3, j = 1, 2,
3) shows the liquid crystal 53 at the position corresponding to the heating element Hij.

Assuming that information is to be written in LC12, in this case, a voltage is applied between the upper electrode U1 and the lower electrode D1 to heat the heating elements H11, H12, H13 at the same time, and LC11, LC12, LC13. Is an isotropic phase, and at the same time, a write voltage is applied between the upper electrode U1 and the counter electrode Y2. Then, the supply of the voltage between the upper electrode U1 and the lower electrode D1 is stopped, and the heating elements H11 and H1 are
2. Stop the heat generation of H13. Then, the liquid crystal LC1
When the temperature of liquid crystal 2 drops to the liquid crystal phase temperature, the liquid crystal LC12 follows the voltage applied between the upper electrode U1 and the counter electrode Y2.
Are oriented and then reach the temperature of the glass phase, and that state is maintained. That is, the information written in the liquid crystal LC12 is retained.

On the other hand, at this time, since no write voltage is applied to the liquid crystals LC11 and LC13 between the upper electrode U1 and the counter electrodes Y1 and Y3, the liquid crystals LC11 and LC13 are not aligned and are in a polydomain state. That is, the liquid crystal LC
11. No information is written in LC13.

Similarly, the upper electrode U2 and the lower electrode D
Voltage is sequentially applied between the two electrodes and to the upper electrode U3 and the lower electrode D3 to write information in the corresponding liquid crystal. Here, the combination of the upper electrode U1 and the lower electrode D1, the combination of the upper electrode U2 and the lower electrode D2, and the combination of the upper electrode U3 and the lower electrode D3 are independently configured as described above. Therefore, according to this embodiment, electrical crosstalk does not occur between these adjacent electrodes.

Since these elements are heated at the same time in the arrangement direction, that is, in the line direction, crosstalk does not occur in that direction.

In reading information, when an alternating current is applied between the upper electrode 41 and the lower electrode 42, the capacitance of the liquid crystal LCij is read, and the reading operation is performed.

Information can also be read by the following method. That is, in the monodomain structure, the liquid crystal 53 is in a transparent state, whereas in the polydomain structure, the liquid crystal 53 is in an opaque state due to light scattering.
Therefore, by irradiating the memory cell with light such as laser light and detecting the reflected light from the liquid crystal 53, the information can be read by this method as well. Although this method includes an optical detection means, it can be said to be an electrical reading method as a whole because it includes a signal processing means.

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

[0082]

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

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

In addition, in the non-volatile recording apparatus of the present invention, the heating means for heating the recording medium is formed by the strip-shaped upper and lower electrodes directly sandwiching the heating element, and electrically independent from the adjacent electrodes. ing. Therefore, electrical crosstalk does not occur between adjacent electrodes. Also, crosstalk does not pose a problem in the direction parallel to the electrodes, and the pitch of the memory cells can be reduced, which has the advantages of improving the recording density and at the same time enabling accurate information recording.

[Brief description of drawings]

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

FIG. 2 is a perspective view showing a memory cell of the nonvolatile recording device of the present invention.

FIG. 3 is an equivalent circuit diagram of a memory cell.

FIG. 4 is a structural diagram of an EEPROM.

FIG. 5 is a structural diagram of a magneto-optical disk.

FIG. 6 is a surface configuration diagram of a recording unit of the nonvolatile recording device previously proposed by the applicant of the present application.

7 is a cross-sectional view of the memory cell corresponding to the line AA in FIG.

FIG. 8 is a perspective view showing a memory cell of a nonvolatile recording device previously proposed by the applicant of the present application.

[Explanation of symbols]

 31 Input / output signal control unit 32 Logic system control unit 33 Drive circuit unit 34 Recording unit 41 (U1, U2, U3) Upper electrode 42 (D1, D2, D3) Lower electrode 44 (Hij) Heating element 51 (Y1, Y2, Y3) Counter electrode 52 Glass substrate 53 Liquid crystal 55 Silicon substrate 56 Alignment film 57 Field insulating film 58 Insulating film

Claims (1)

[Claims] 1. A recording medium formed of a liquid crystal compound or a compound containing a liquid crystal component in a molecule is enclosed between a pair of substrates arranged facing each other, and the recording medium is heated by a heating means to write information. A non-volatile recording device configured to read information written in the recording medium by a reading means, wherein the heating means includes a lower electrode wired in a strip shape on an insulating film entirely formed on one substrate, It is formed of a strip-shaped upper electrode laminated on the lower electrode with the heating element interposed therebetween, and a voltage is applied between the upper and lower electrodes to heat the heating element, and the upper electrode and the other substrate A non-volatile recording device for writing information to a recording medium by applying an information writing voltage between the counter electrode and the counter electrode arranged in a direction orthogonal to the upper and lower electrodes on the inner surface side.