JP5696882B2 - Charged body, and field effect transistor and memory element using the same - Google Patents

Description

  The present invention relates to a material (hereinafter referred to as a charged body) in which electric charges are confined in a material for a long time, and further, a field effect transistor (hereinafter referred to as “FET”) and a memory capable of controlling the threshold voltage as its application. It relates to an element. More specifically, the charged body of the present invention has a structure in which two kinds of materials having superior and inferior insulating properties are laminated, and the two electrodes are sandwiched between the two kinds of insulating materials so as to be in contact with the two kinds of insulating materials. By applying an electric field, charges can be injected and accumulated at the interface between the two insulating materials from the side of the material that is inferior in insulation characteristics, and can be retained in the charged body even after the electric field is removed to exert a Coulomb force on the periphery. Further, by configuring the FET using the charged body as a gate insulating film, the threshold voltage can be controlled by the charge accumulated in the charged body as described above. Furthermore, in the FET, the charge is held in the charged body for a long time. That is, the present invention relates to a memory element that utilizes the fact that a controlled threshold voltage is maintained.

Conventionally, static electricity has been used in dust collectors and toner printers. However, since these static electricity can move charges, the charge density is low and dissipates in a short time, so the application field is limited.
On the other hand, in a structure in which a conductor typified by a floating gate is covered with an extremely thin insulator, after the charge is injected into the conductor through the insulator, the dissipation of the charge is suppressed by the insulating layer, and the charge is held for a long time. . Such a material containing a charge is called a charged body and has attracted attention in recent years.

  In addition to being put into practical use as a floating gate memory (non-patent document), such a charged body can be used for a motor or a generator using Coulomb attractive force or repulsive force.

Japanese Patent No. 3222404

S. M.M. SZE, “Floating-Gate Devices”. Physics of semiconductor devices. third edition, New Jersey, John Wiley, 2007, 352-357. S. M.M. SZE, “Charge-Trapping Devices”. Physics of semiconductor devices. third edition, New Jersey, John Wiley, 2007, 357-360. S. M.M. SZE, "Appendix I, Properties of SiO2 and Si3N4 at 300K". Physics of semiconductor devices. second edition, New Jersey, John Wiley, 1981, page 852.

In order to charge the charged body, in the floating gate structure, a very thin insulating film is injected into the inner conductor by thermoelectrons or tunnel current. However, since an extremely thin insulating film is required, the insulating property is limited and can be accumulated. There are restrictions on the amount of charge and the retention time. In addition, there are restrictions on the manufacturing method and material of the extremely thin insulating film. On the other hand, a method of implanting charged particles (ions) accelerated by an accelerator into an insulator or internal metal has also been proposed. However, a large charged particle acceleration device is required, and further, generation of radicals occurs when charged particles are implanted, resulting in insulation. There is concern about deterioration.
The present invention does not require an ultra-thin insulating layer such as a floating gate memory or a MNOS (Metal-Nitride-Oxide-Semiconductor) memory, and allows a memory element to be manufactured by printing and coating. Provided an easily controllable charged body, and an FET and a memory element that can control a threshold voltage and maintain a threshold voltage state controlled for a long time by fabricating an FET using the charged body as a gate insulating film. The purpose is to do.

The present invention relates to the following.
[1] the charge injection occurs field strength (hereinafter, charge injection tolerance) and dielectric breakdown voltage respectively E _CI, insulators are _H and E _BH (hereinafter, high charge injection withstand material) and their charge injection withstand E _{CI, L} is an insulator in which two types of insulators (hereinafter referred to as a low charge injection withstand voltage material) having a relationship of E _{CI, L} <E _{CI, H} are laminated, and a high charge injection withstand voltage material and a low charge injection withstand voltage material. A voltage is applied to the two electrodes that are in contact with and separated from each other at an electric field strength of E _{CI, L} <| E | < _EBH , and charges are injected into the insulator from the low charge injection withstand voltage material side to be charged. Characteristic charged body.
[2] said _{E CI, H} and _{E CI,} the ratio of _{L (E CI, H / E} CI, L) is a from 1.5 to _{1,000, E CI, L} is at 0.01 MV / cm or more The charged body according to [1].
[3] The dielectric breakdown voltage (E _BH ) of the high charge injection withstand voltage material is 0.1 MV / cm or more, and the volume resistivity at 10 MV / cm of the high charge injection withstand voltage material and the low charge injection withstand voltage material is 10 respectively. The charged body according to [1] or [2], which is ¹¹ Ω · m or more.
[4] The charged body according to any one of [1] to [3], wherein at least one of the high charge injection withstand voltage material and the low charge injection withstand voltage material is formed of an organic polymer.
[5] The charged body according to any one of [1] to [4], wherein the low charge injection pressure-resistant material and / or the high charge injection pressure-resistant material is a three-dimensional crosslinked polymer material.
[6] The charged body according to [5], wherein the three-dimensional crosslinked polymer material is formed by a wet process.
[7] Wet process from dip coating, spin coating, spray coating, roll coating, ink jet coating, offset coating, ink jet printing, transfer method, offset printing, screen printing, letterpress printing, intaglio printing, soft lithography, or dispenser printing The charged body according to [6], which is selected.
[8] The field effect transistor according to any one of [1] to [7], wherein the gate insulating film has a gate electrode and a semiconductor layer sandwiching the gate insulating film and has a source-drain electrode in contact with the semiconductor layer. And a threshold voltage of the field effect transistor controlled by an amount of charge injected into the charged body.
[9] In the field effect transistor according to [8], information is recorded by the amount of injected charge held in the charged body, and the difference in drain current amount under the gate electric field strength of E _{CI, L} > | E | The present invention relates to a memory element characterized by calling information.

  The charged body of the present invention is simple and provides a charged body with easy control of the injected charge amount. By manufacturing an FET using this charged body as a gate insulating film, a threshold voltage can be controlled, and an FET and a memory element capable of maintaining a threshold voltage state controlled for a long time can be obtained. In addition, an extremely thin insulating layer such as a floating gate memory or an MNOS memory is not required, and a memory element can be manufactured by printing and coating.

1 is a schematic diagram schematically showing a cross section of an FET and a memory element according to a preferred embodiment of the present invention. 1 is a schematic diagram schematically showing a cross section of an FET and a memory element according to a preferred embodiment of the present invention. 1 is a schematic diagram schematically showing a cross section of an FET and a memory element according to a preferred embodiment of the present invention. 1 is a schematic diagram schematically showing a cross section of an FET and a memory element according to a preferred embodiment of the present invention. 1 is a schematic diagram schematically showing a cross section of an FET and a memory element according to a preferred embodiment of the present invention. 1 is a schematic diagram schematically showing a cross section of an FET and a memory element according to a preferred embodiment of the present invention. 1 is a schematic diagram schematically showing a cross section of an FET and a memory element according to a preferred embodiment of the present invention. 1 is a schematic diagram schematically showing a cross section of an FET and a memory element according to a preferred embodiment of the present invention. 1 is a schematic diagram schematically showing a cross section of an FET and a memory element according to a preferred embodiment of the present invention. FIG. 3 is a diagram showing the relationship between electric field strength and current of the epoxy resin used in Example 1. (Current transfer characteristic curve when the gate electric field strength is swept from positive to negative with respect to the element obtained in Example 1. (Current transfer characteristic curve when the gate electric field strength is swept from negative to positive with respect to the element obtained in Example 1. (Current transfer characteristic curve when the gate electric field strength is swept three times for the same element obtained in Example 1. (Current transfer characteristic curves after 0, 1, 5, and 30 minutes after applying a gate electric field of −5 MV / cm to the device obtained in Example 1. FIG. (Current transfer characteristic curve of the element obtained in Example 2. (Current transfer characteristic curve when the gate electric field strength is swept from negative to positive with respect to the element obtained in Example 3. (Current transfer characteristic curve when the gate electric field strength is swept from positive to negative with respect to the element obtained in Example 3. (The current transfer characteristic curve after 0, 1, and 30 minutes after applying a gate electric field of −5.9 MV / cm to the device obtained in Example 3. 10 is a current transfer characteristic curve of an element obtained in Example 4. (Relationship between electric field strength and current of low charge injection withstand voltage resin used in Example 5. 10 is a current transfer characteristic curve of an element obtained in Example 5. (A current transfer characteristic curve of an element obtained in Comparative Example 1.

  Hereinafter, the present invention will be described in more detail.

  It is desirable if charge can be obtained by injecting charges into the insulator without using an accelerator. When an electric field is applied to the insulator (for example, FIG. 10), when the electric field strength is low (3.5 MV / cm or less in FIG. 10), almost no current flows, but a certain electric field strength (hereinafter referred to as charge injection withstand voltage). ) Higher (3.5 MV / cm in FIG. 10), charges are injected from the electrode into the material, and a minute current flows. In this way, charges can be injected into the material by applying a high electric field, but the injected charges move through the material by the electric field and escape from the counter electrode side, so that the charged body does not have a sufficient charge amount. In addition, the high electric field strength at which charge injection occurs is close to the dielectric strength of the material (6.3 MV / cm in FIG. 10), and if there is a defect, the electric field strength below the dielectric strength of the material does not cause dielectric breakdown. Has stability. Insulating materials that have undergone dielectric breakdown are greatly deteriorated in insulating properties due to decomposition and carbonization of the materials, and cannot be used.

The principle of the charged body in the present invention will be described.
The charged body in the present invention includes a material having a high charge injection withstand voltage ( _{ECI, H} ) (hereinafter referred to as a high charge injection withstand voltage material) and a material having a low charge injection withstand voltage ( _{ECI, L} ) (hereinafter referred to as a low charge injection withstand voltage material). Has a laminated structure. When an electrode is placed on each of the charged material and the low charge injection withstand voltage material and an electric field of _{ECI, L} or higher is applied to the low charge injection withstand voltage material, Charge is injected into the material from the electrode, and the injected charge moves toward the pair of electrodes. However, in a material having a high charge injection withstand voltage, charge injection does not occur or is slight even at the same electric field strength, so that the charge that has moved through the low charge injection withstand voltage material is the interface between the low charge injection withstand voltage material and the high charge injection withstand voltage material. The charge is accumulated at this interface.
The charges accumulated at the interface between the low charge injection withstand voltage material and the high charge injection withstand voltage material in this way are affected by the mobility due to the electric field after the removal of the high electric field (| E | <| E _{CI, L} |). Since it is not fixed to the interface and is surrounded by an insulator, it does not dissipate or neutralize with other counter charges, and it exists stably for a long time. For this reason, this charged body is charged by electric charges, and exerts a Coulomb force around it, and can be used as a charged body.

In addition, a high charge injection withstand voltage material generally has a higher withstand voltage (E _BH ) than an insulation withstand voltage (E _BL ) of a low charge injection withstand voltage material, and an electric field strength (| E _BH | Even when | E | ≈ | E _BL |) is applied, the amount of charge movement is limited by the high withstand voltage and the low charge injection amount of the high charge injection withstand voltage material, and the dielectric breakdown can be suppressed. As a result, in the operation near the withstand voltage of the low charge injection withstand voltage material, it is possible to suppress the dielectric breakdown and the insulation deterioration and to enable the stable operation.

Next, the operation principle of the field effect transistor (FET) and the memory element in the present invention will be described.
The FET and the memory element in the present invention have a FET structure using the charged body as a gate insulating film. When this FET is driven with a gate electric field strength (E _G ) lower than E _{CI, L} of the low charge injection withstand voltage material of the charged body, the same operation as a normal FET is performed. However, under the condition of E _BH > | E _G |> E _{CI, L} , charges are injected into the low charge injection withstand voltage material in the same manner as the charged body, and the interface between the low charge injection withstand voltage material and the high charge injection withstand voltage material. Charge is accumulated and stored in Thereafter, when the charge is accumulated in the charged body and the characteristics are measured with the gate electric field intensity in the range of | E _G | <E _{CI, L, the} threshold voltage is largely shifted by the electric field due to the charge held in the charged body. .
When positive charge is accumulated in the charged body, the threshold voltage is negative, and conversely, when negative charge is accumulated, the threshold voltage is shifted to positive, and the shift amount is the charge in the charged body. Depends on the amount.

  The structure of this transistor is similar to that of a MNOS (metal-nitride-oxide-silicon) transistor (Non-patent Document 1). However, in the MNOS transistor, an extremely thin oxide of 20 nm or less (Non-patent Document 1) from the silicon layer. Charges are injected and held at the interface between the nitride layer and the oxide film beyond the film due to the tunnel effect.

  On the other hand, in the present invention, two types of insulating films having different insulating characteristics are laminated in the same manner. However, charge from the material side having a low charge injection withstand voltage is not provided to the interface between the two types of insulating films by the tunnel effect. Charges are accumulated at the interface by injection and movement. Therefore, it is not necessary to form one insulating film into a thin layer of 20 nm or less so that the tunnel effect works like the MNOS transistor (Example 2), and there are few restrictions on the method and material for forming the insulating film.

  The thickness of the charged body is preferably 10,000 nm or less in total for the low charge injection withstand voltage material layer and the high charge injection withstand voltage material layer. This depends on the charge injection characteristics of the low charge injection withstand voltage material. However, when an electric field strength of 0.01 MV / cm or more is applied to the charge injection, if this electric field strength is applied at 100 V, this is less than 100,000 nm. There must be. Therefore, it is 10,000 nm or less in order to operate at a realistic voltage of 10 V or less. The minimum film thickness is 20 nm due to the restrictions described later.

  The thickness of the low charge injection withstand voltage material layer needs to be a thickness that can hold the charges accumulated at the interface without being dissipated, that is, 10 nm or more, more preferably 20 nm or more, and further preferably 25 nm or more. If the thickness is less than this thickness, charges are lost due to tunneling current or diffusion of charges in the insulator. Further, even for a material having a high charge injection withstand voltage, the same film thickness is required for the same reason, that is, 10 nm or more is required, more preferably 20 nm or more, and further preferably 25 nm or more.

In the charged body of the present invention, the ratio of the withstand voltage E _{CI, H} of the high charge injection withstand voltage material to the withstand voltage E _{CI, L} of the low charge injection withstand voltage material (E _{CI, H} / E _{CI, L} ) is 1.5. It is preferably a charged body having an ECI _{, L} of 0.1 MV / cm or more. When (E _{CI, H} / E _{CI, L} ) is less than 1.5, the electric field strength for injecting charges into the charged body is close to the insulation withstand voltage of the high charge injection withstand voltage material. The possibility of waking up is increased. On the other hand, if it exceeds 1000, the withstand voltage ECI _{, L of} the low charge injection withstand voltage material becomes too low (less than 0.01 MV / cm), and the amount of charge that can be held in the charged body is expected to be limited. .
Further, the dielectric breakdown voltage (E _BH ) of the high charge injection withstand voltage material is 0.1 MV / cm or more, and the volume resistivity at 0.5 MV / cm of the high charge injection withstand voltage material and the low charge injection withstand voltage material is 10 ¹¹ Ω, respectively. -It is preferable that it is a charged body which is m or more. If the dielectric breakdown voltage (E _BH ) of the high charge injection withstand voltage material is less than 0.1 MV / cm, it tends to be undesirable in that dielectric breakdown of the charged body occurs. In a charged body in which the volume resistivity at 0.5 MV / cm of the high charge injection withstand voltage material and the low charge injection withstand voltage material is less than 10 ¹¹ Ω · m, the charge injected into the charged body gradually flows out of the charged body. However, it tends to be undesirable in that it cannot be held for a long time.

  As the material of the above-mentioned charged body, a material having a low charge injection withstand voltage and a material having a higher charge injection withstand voltage may be selected and used, and the material is not particularly limited. Insulating material can be applied.

  Specific examples of suitable organic insulating materials include thermosetting resin, polyester, polycarbonate, polyvinyl alcohol, polyvinyl phenol, polyvinyl butyral, polyacetal, polyarylate, polyamide, polyamideimide, polyphenylene ether, polyphenylene sulfide, polyether sulfone, Polyether ketone, polyphthalamide, polyether nitrile, polybenzimidazole, polycarbodiimide, polysiloxane, polymethyl methacrylate, polymethacrylamide, nitrile rubber, acrylic rubber, polyethylene tetrafluoride, polybutene, polypentene, ethylene-propylene copolymer Including, but not limited to, coalesced, polybutadiene, polystyrene, and mixtures thereof.

  The thermosetting resin is not particularly limited as long as it is cured by heat and exhibits an adhesive action. For example, epoxy resin, bistriazine resin, polyimide resin, phenol resin, melamine resin, silicon resin, Saturated polyester resins, cyanate ester resins, isocyanate resins, polybenzoxazole resins, polybenzocyclobutene resins or various modified resins thereof are suitable.

  The epoxy resin is not particularly limited. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, salicylaldehyde novolac type epoxy resin, bisphenol F novolac type epoxy resin. Alicyclic epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, hydantoin type epoxy resins, isocyanurate type epoxy resins, aliphatic cyclic epoxy resins, and their halides, hydrogenated products, etc. These may be used alone or in combination of two or more.

  You may add a hardening | curing agent to the charged body of this invention as needed. The curing agent may be appropriately determined depending on the thermosetting resin (insulating organic polymer) to be used, and is not particularly limited. For example, when the insulating organic polymer is an epoxy resin, an acid anhydride compound, Primary or secondary amine, polyamine, polyamide, dicyandiamide, polycondensation type aryloxysilane compound, compound having two or more phenolic hydroxyl groups in one molecule, bisphenol A resin, bisphenol F resin, phenol novolac resin, bisphenol novolac Resins, cresol novolac resins, salicylaldehyde novolak resins, and halides, hydrides, triazine structure-containing materials, and the like of these phenol resins can be used. These curing agents may be used alone or in combination of two or more.

  Although the compounding quantity of a hardening | curing agent is not specifically limited, For example, when using an epoxy resin as an insulating organic polymer, a hydroxyl group equivalent is the range of 0.5-2.0 equivalent with respect to an epoxy equivalent, Preferably , 0.8 to 1.2 equivalents, and more preferably 0.9 to 1.1 equivalents.

  Moreover, you may add a hardening accelerator to the charged body of this invention as needed. The curing accelerator is not particularly limited. For example, when the insulating organic polymer is an epoxy resin, an imidazole compound, an organic phosphorus compound, a tertiary amine, a quaternary ammonium salt, a Lewis acid, a trialkyl Oxonium salts, carbonium salts, diazonium salts, alkylating agents, sulfonium salts and diallyl iodonium salts can be used.

Examples of the inorganic insulating material include SiO ₂ , SiON, SiN, SiOC, SiOF, Al ₂ O ₃ , Ta ₂ O ₅ , TiO ₃ , ZrO ₂ , BaTiO ₃ , Nb ₂ O ₅ , ceramics, glass, and mica. However, it is not limited to this.

  Since the MNOS transistor does not need to be formed into a thin layer of 20 nm or less, the insulating film can be formed not only by a highly accurate film formation method such as thermal oxide film, vapor deposition, CVD, and sputtering, but also by coating and printing. The film forming method by can also be used. As a coating and printing method, a method capable of applying and printing each material with a desired coating thickness can be applied. For example, as a coating method, dip coating, spin coating, spray coating, inkjet coating, offset Examples of the printing method include an inkjet printing method, a transfer method, an offset printing method, a screen printing method, a relief printing, an intaglio printing, a soft lithography, and a dispenser method.

In the present invention, it is preferable that either one or both of the low charge injection withstand voltage material and the high charge injection withstand voltage material are composed of an organic polymer. A three-dimensional cross-linked polymer material is preferable. As described above, a film forming technique by coating or printing can be used, and a charged body can be easily formed. The three-dimensional crosslinked polymer material is obtained by crosslinking the thermosetting resin with a curing agent, a curing accelerator or the like. Also, a method of introducing a crosslinkable functional group such as —OH, —COOH, —NH ₂ into a thermoplastic resin, a side chain or a main chain of rubber, and crosslinking, an organic peroxide, a photopolymerization initiator, etc. And a method of generating a radical by heat or light to cause crosslinking. It is preferable that the three-dimensional crosslinked polymer material is formed by a wet process because a charged body can be easily formed.

(FET and memory device)
The FET and the memory element of the present invention comprise a gate electrode, a source-drain electrode, a semiconductor layer constituting a channel layer on the substrate, and the charged body (gate insulating film) sandwiched between the gate electrode and the channel layer. In the FET having the above structure, the charged body has a structure in which a material with a high withstand voltage and a material with a low withstand voltage are stacked. Although the basic element structure is shown in FIGS. 1 to 9, the present invention is not limited to the element structure shown in these drawings.

  In the FET and the memory element according to the present invention, a semiconductor used as a semiconductor layer can be manufactured using all known materials used as an organic semiconductor or an inorganic semiconductor. Preferred semiconductor layers are silicon, silicon nitride, pentacene, tetracene, TIPS-pentacene (6,13-bis (triisopropylsilylethynyl) pentacene), polythiophene, thienylthiophene derivatives, copper phthalocyanine, polyaniline, polypyrrole, polyphenylene vinylene, porfluorene. , Carbon nanotubes, SnO particles, ZnO particles, silicon, SnO precursor solution, ZnO precursor solution, or derivatives thereof, but is not limited thereto.

  The materials of the substrate, gate electrode, and source-drain electrode of the FET and memory device according to the present invention include all materials known in the field of FET. More preferably, the substrate is a plastic substrate, a resin sheet, a metal sheet, a glass substrate, a quartz substrate, or a silicon substrate, and the gate and source-drain electrodes are made of a conductive material, preferably Au, Ag, Cu, Al, Aluminum alloy, nickel, Cr, calcium, tantalum, platinum, palladium, titanium, doped Si, ITO, SnO transparent electrode or organic conductive material PEDOT-PSS (Poly (3,4-ethylenedioxythiophene) poly (styreneenesulfonate) )), Carbon nanotubes, graphene sheets, and TTF-TCNQ (tetrathiafulvalene-tetracyanoquinodimethane), but are not limited thereto.

The FET of the present invention has a gate electrode and a semiconductor layer sandwiching a gate insulating film, and in a field effect transistor having a source-drain electrode in contact with the semiconductor layer, the gate insulating film is the above charged body, The threshold voltage of the field effect transistor is controlled by the amount of charge injected. The memory element of the present invention using the same records information on the above-mentioned field effect transistor by the amount of injected charge held in the charged body, under the gate electric field strength of E _{CI, L} > | E | The information is called as a difference in drain current amount.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not restrict | limited to an Example below.

(Example 1)
(Production of diphenylsilylated bisphenol F)
In a separable flask, bisphenol F (manufactured by Honshu Chemical Industry Co., Ltd.) 160 g (0.80 mol), dimethoxydiphenylsilane (AZ-6183: manufactured by Toray Dow Corning Co., Ltd.) 95.3 g (0.8 mol), phosphorus catalyst ( PPQ: manufactured by Hokuko Chemical Co., Ltd.) 0.80 g (0.5% by mass) was charged, dissolved at 130 ° C., and stirred for 15 hours. Methanol generated at this time was removed out of the system. Then, 270 g of diphenylsilylated bisphenol F was obtained by further reaction for 20 hours under heating and reduced pressure.

(Preparation of low charge injection pressure resistant resin solution)
Next, 0.50 g of bisphenol A novolac epoxy resin (N-865: manufactured by Dainippon Ink and Chemicals, Inc.), 0.34 g of diphenylsilylated bisphenol F synthesized according to (production of diphenylsilylated bisphenol F) 1-cyanoethyl-2-phenylimidazole (2PZ-CN: manufactured by Shikoku Kasei Kogyo Co., Ltd.) A 1% by weight anisole solution 0.01 g was dissolved in 41.16 g of anisole (resin concentration 2% by weight) to reduce the charge. An injection pressure resistant resin solution was prepared.

(Insulation characteristics measurement)
On a silicon wafer (diameter 50 mm, thickness 280 μm, type N, resistivity 1 to 10 Ω · cm, single-sided mirror polished, manufactured by KN Platz Co., Ltd.), on which Cr treated by O ₂ plasma asher at 250 W for 5 minutes was deposited by 50 nm. A solution of a low charge injection pressure resistant resin prepared to have a resin concentration of 15% by mass prepared in the same manner as described above was dropped after passing through a membrane filter (Anotop 10, manufactured by Whatman), and was spin-coated at 500 rpm, 5 seconds, 2000 rpm. And spin-coated under the conditions of 60 seconds. Then, it dried for 10 minutes on a 100 degreeC hotplate, and also hardened | cured for 15 minutes on a 200 degreeC hotplate. A portion of the resin was scratched with a cutter knife, and the depth of the scratch was measured with a stylus type surface shape measuring device (DEKTAK, manufactured by ULVAC, Inc.). As a result, the resin film thickness was 310 nm. On this resin film, a circular Au electrode having a diameter of 100 μm was vapor-deposited at a thickness of 30 nm at a rate of 0.4 mm / second by a vapor deposition apparatus (Thermal deposition system, manufactured by Kurt J. Lesker) using a metal mask. Using a needle probe to which a source measure unit (SOURCE MEASURE UNIT (SOURCE MEASURE UNIT 237, manufactured by KEITHLEY Instruments)) is connected, a voltage of 0 to 300 V is stepped up in 1 V step between Cr and Au electrodes. (Fig. 10) As a result of taking the average of 5 points, the electric field strength at which charge injection started was 3.4 MV / cm, and the withstand voltage was 6.3 MV / cm.
Note that the withstand voltage of the thermal oxide film of the silicon wafer is 10 MV / cm (Non-Patent Document 3).

(Memory element formation)
A highly doped silicon wafer (diameter 50 mm, thickness 280 μm, type N, resistivity 0.002 to 0.004 Ω · cm, single-side mirror polished, manufactured by KN Platz Co., Ltd.) having a thermal oxide film of 100 nm thickness is O ₂ plasma asher After 250 minutes of treatment at 250 W, a solution of a low charge injection pressure resistant resin that passed through a membrane filter (Anotop 10, manufactured by Whatman) was spin-coated with a spin coater under conditions of 500 rpm, 5 seconds, 2000 rpm, and 60 seconds. Then, it dried for 10 minutes on a 100 degreeC hotplate, and also hardened | cured for 15 minutes on a 200 degreeC hotplate. The film thickness of the low charge injection pressure-resistant resin was measured by damaging the cured resin with a cutter knife and measuring the depth of the damage with an atomic force microscope (Scanning Probe Microscope Dimension 3100, manufactured by Digital Instruments). As a result, the film thickness of the low charge injection withstand voltage resin was 21 nm. In this case, the thermal oxide film corresponds to an insulator with a high charge injection breakdown voltage, and the epoxy resin corresponds to an insulator with a low charge injection breakdown voltage.

Thereafter, the device characteristics were measured in a nitrogen glove box. Using a metal mask on the epoxy resin, pentacene is deposited at a thickness of 60 nm at a rate of 0.4 nm / second with a vapor deposition apparatus (Thermal deposition system, manufactured by Kurt J. Resker) to form a semiconductor layer, and then Au is metalized. A source / drain electrode was formed by vapor deposition at a thickness of 60 nm at 0.4 Å / sec using a mask.
The gate electrode of this element is highly doped silicon, the source and drain electrodes are Au, the gate length is 1 mm, and the gate width is 5 mm.

(Element characteristic measurement)
The memory element characteristic is that after removing the charged body (gate insulating film) on the upper surface, a silver paste is applied to make a terminal to the gate electrode, and conduction is made using a needle probe in a nitrogen glove box, and Parameter Analyzer (4156A or 4156C Precision Semiconductor Parameter Analyzer, manufactured by Agilent Technologies).
The gate current intensity range and the sweep direction were applied to the device, and the drain current I _D was measured under a constant condition of the drain voltage V _D = −10 V.
A graph of current transfer characteristics with (I _D ) ^1/2 and the gate voltage V _G as variables is obtained, and the slope and intercept are substituted into the following equation (1) to determine the field effect mobility μ and the threshold voltage V _th . Asked.

式（１）中、C_ｉはゲート絶縁膜の静電容量、Wはチャネル幅、Lはチャネル長、V_Ｇはゲート電圧である。

In formula (1), C _i is the capacitance of the gate insulating film, W is the channel width, L is the channel length, and V _G is the gate voltage.

(Element characteristics)
The measurement results of device characteristics are summarized in Table 1. When the absolute value of the electric field strength was 2.7 MV / cm or less, the threshold voltage was approximately constant -3 V regardless of the sweep direction. On the other hand, when the absolute value of the electric field strength is 3.6 MV / cm or more, the threshold voltage shifts from −3V to negative when sweeping from negative to positive, and shifts more negative as starting from a stronger electric field strength. (FIG. 12). On the contrary, when sweeping from positive to negative, the threshold voltage shifted to positive, and shifted more positively as it started from stronger electric field strength (FIG. 11). The electric field strength of 3.6 MV / cm or more at which the threshold voltage starts to shift corresponds to the electric field strength of 3.4 MV / cm in which a minute current flows through the epoxy resin due to the charge injection. Charges accumulated at the interface between the film and the epoxy resin, and the threshold voltage shifted due to the electric field generated by the accumulated charges.

(Operation multiple times)
The gate electric field strength was repeatedly measured by increasing and decreasing the pressure three times between +5 MV / cm and -5 MV / cm (FIG. 13). In the current transfer characteristic curve (FIG. 13), for the reason described above, after a positive high electric field (+5 MV / cm) is applied as the gate electric field strength, negative charges accumulate at the interface in the charged body, and the threshold voltage is positive. In contrast, after a negative high electric field (-5 MV / cm) is applied as the gate electric field strength, positive charges accumulate at the interface in the charged body, and the threshold voltage shifts negatively, resulting in strong hysteresis. Draw a transfer curve. Even if the same device is measured three times, the current transfer characteristic curve with hysteresis draws almost the same curve as shown in FIG. 13, and this behavior is not an irreversible change such as dielectric breakdown but a reversible characteristic. It shows that there is.
For this reason, the memory element using the charged body of the present invention functions as a rewritable memory.

(Memory operation)
A gate electric field strength of −5 MV / cm was applied, and then the gate voltage was removed. After a predetermined time, device characteristics were measured at a gate electric field strength of 0 to −5 MV / cm and a drain voltage of −10 V to obtain a threshold voltage. The results are summarized in FIG. 14 and FIG.
As described above, the threshold voltage when the device characteristics were measured at a gate field strength of −3.4 MV / cm or less, which is the field strength at which charge injection starts, was −4.1V. On the other hand, the threshold voltage immediately after applying the gate electric field strength of −5 MV / cm was −23.5 V, and charges accumulated at the interface between the thermal oxide film and the epoxy resin.
After applying −5 MV / cm, the threshold voltages after 1 minute, 5 minutes, and 30 minutes passed are −20.6, −19.8, and −17.8 V, respectively, and there is a charge at the interface between the thermal oxide film and the epoxy resin. The threshold voltage, which was largely negatively shifted compared to −4.1 V in the case where the charge was not accumulated, was retained, and the charge accumulated at the interface between the thermal oxide film and the epoxy resin was retained even after 30 minutes.
Thus, for example, in FIG. 14, if the drain current is read with a gate electric field strength of −1.5 MV / cm and a drain voltage of −10 V, no charge is accumulated at the interface between the thermal oxide film and the epoxy resin. In this case, the storage state can be read as a current difference of 1.7 × 10 ⁻⁶ A and 2.3 × 10 ⁻¹⁰ A and 4 digits, respectively. At this time, the gate electric field strength of −1.5 MV / cm is significantly lower than the electric field strength at which charge injection starts, and this read operation does not affect the amount of charge accumulated at the interface between the thermal oxide film and the epoxy resin. .

(Example 2)
The process was performed up to (element characteristics) in the same manner as in Example 1 except that the concentration of the low charge injection pressure resistant resin solution was 15% by mass and the film thickness of the resulting low charge injection pressure resistant resin was 327 nm. As shown in FIG. 15, there was a large difference between the threshold voltage and the threshold voltage of −30 V after applying −6.1 MV / cm before applying the high gate electric field strength in the initial stage. In this device, a charged body in which a thermal oxide film having a thickness of 100 nm and an epoxy resin having a thickness of 327 nm are stacked is used as a gate insulating film, and the thickness is such that the tunnel effect can be ignored. Therefore, −3.4 MV / cm or more As a result of this electric field strength being applied, charge injection occurred from the epoxy resin side, charges accumulated at the interface inside the charged body, and the threshold voltage shifted.

(Example 3)
As a low-charge injection pressure-resistant resin solution, a mesitylene solution of divinyltetramethylsiloxane-bis (benzocyclobutene) (hereinafter BCB) (30% by mass, manufactured by Merck & Co., Inc.) was diluted to 2% by mass with mesitylene and used as a result. The process was performed up to (element characteristics) in the same manner as in Example 1 except that the film thickness of the formed low charge injection withstand voltage resin was 15 nm.

(Element characteristics)
The measurement results of the device characteristics are summarized in Table 3. When the absolute value of the electric field strength was 2.3 MV / cm or less, the threshold voltage was approximately constant -5 V regardless of the sweep direction. On the other hand, when the absolute value of the electric field strength is 3.2 MV / cm or more, the threshold voltage shifts from -5 V to negative when sweeping from negative to positive, and shifts more negative as starting from a stronger electric field strength. (FIG. 16). On the contrary, when the absolute value of the electric field strength is swept from a positive gate electric field strength of 3.2 MV / cm to negative, the threshold voltage is shifted to positive, and the threshold voltage is shifted more positive as starting from a stronger electric field strength. (FIG. 17). Charges were injected into the BCB from the BCB side where the electric field strength started from the thermal oxide film was low, and charges were accumulated at the interface between the thermal oxide film and the BCB, and the threshold voltage was shifted by the electric field due to the accumulated charges.

(Memory operation)
The gate electric field strength is -5.9 MV / cm, then the gate voltage is removed, and after a certain period of time, the drain voltage is -10 V (constant), and the gate electric field strength is swept from -0.5 to -5.9 MV / cm. Was measured to determine the threshold voltage. The results are summarized in FIG. 18 and Table 4.
After applying −5.9 MV / cm, the threshold voltages after 0 minutes, 1 minute, and 30 minutes passed are significantly negative compared to −30.2, −27.1, −19.2 V, and −5.5 V, respectively. Had shifted to. The charge accumulated at the interface between the thermal oxide film and BCB was retained even after 30 minutes.
In BCB, compared with the epoxy resin of Example 1, the change in the threshold voltage for 30 minutes was as large as 11 V. This is because the BCB film thickness is 15 nm, which is thinner than 21 nm of the epoxy resin, so that the accumulated charge is retained. This is because the ability has decreased.

Example 4
Except that 0.27 g of bisphenol A novolak (VH-4170: manufactured by Dainippon Ink & Chemicals, Inc.) was used in place of the diphenylsilylated product of bisphenol F in the preparation of the low charge injection pressure resistant resin solution of Example 1 Similarly, a solution of a low charge injection pressure-resistant resin was prepared, and the process up to (element characteristics) was performed in the same manner as in Example 1.
As a result, the electric field strength at which charge injection started was 2.8 MV / cm, and the withstand voltage was 5.9 MV / cm. The thickness of the low charge injection pressure resistant resin of the charged body was 20 nm.

(Element characteristics)
When the drain current was measured by sweeping the gate electric field strength between +0.9 and −2.6 MV / cm at a drain voltage of −10 V (constant), the current transfer characteristic curve was +0.9 to −2.6 MV. In the case of sweeping to / cm, the case of sweeping from -2.6 to +0.9 MV / cm was almost the same. On the other hand, when the gate electric field strength is measured between +1.7 and −5.0 MV / cm, when swept from +1.7 to −5.0 MV / cm, +0.9 to −2.6 MV / cm However, when the current transfer characteristic curve was swept from -5.0 to +1.7 MV / cm, the current transfer characteristic curve was greatly shifted to a negative value (FIG. 19). That is, when an electric field of 2.8 MV / cm or more at which charge injection starts is applied, positive charges are injected and held in the gate insulating film (charged body), and the threshold voltage is shifted in the negative direction.

(Example 5)
(Solution adjustment of high charge injection pressure resistant resin)
The solution of the low charge injection pressure resistant resin of Example 1 prepared at a solution concentration of 12% by mass was used as the solution of the high charge injection pressure resistant resin.
(Preparation of low charge injection pressure resistant resin solution)
2.4 g of epoxy-modified silicone (manufactured by Shin-Etsu Silicone Co., Ltd.) and 1.0 g of bisphenol A type novolak (CZ256A: Dainippon Ink and Chemicals Co., Ltd.) were added to 2-ethyl-4-methylimidazole (2E4MZ: Shikoku Kasei Kogyo Co., Ltd.) (Company) 0.34 g of 1% by mass anisole solution was dissolved in 16.3 g of anisole (resin concentration: 17% by mass) to prepare a low charge injection pressure-resistant resin solution. Insulation characteristics were measured in the same manner as in Example 1 (FIG. 20). As a result, the electric field strength at which charge injection started was 0.1 MV / cm, and the withstand voltage was 1.5 MV / cm.

(Memory element formation)
A high charge injection pressure-resistant resin solution was dropped on a silicon wafer on which Cr was deposited to 50 nm after passing through a membrane filter, and spin-coated with a spin coater under conditions of 500 rpm, 5 seconds, 2000 rpm, and 60 seconds. Then, it dried for 10 minutes on a 100 degreeC hotplate, and also hardened | cured for 15 minutes on a 200 degreeC hotplate. The resin film thickness measured with a stylus type surface shape measuring apparatus was 226 nm. Next, the solution of the low charge injection pressure resistant resin is dropped on the Cr-deposited silicon wafer coated with the high charge injection pressure resistant resin after passing through the membrane filter, and spin coated with a spin coater under the conditions of 500 rpm, 5 seconds, 2000 rpm, and 60 seconds. did. The film thickness of the low charge injection pressure resistant resin obtained by subtracting the thickness of the high charge injection pressure resistant resin from the resin film thickness measured by the stylus type surface shape measuring apparatus was 252 nm.
Thereafter, a semiconductor layer and an electrode were formed in the same manner as in Example 1 to obtain a device.

(Element characteristics)
Device characteristics were measured in the same manner as in Example 1.
When the gate electric field strength was swept in the range of 0 to -1 MV / cm at a drain voltage of -10 V (constant), and the device characteristics were measured, the gate electric field strength was changed from 0 to -1.0 MV / cm as shown in FIG. The transfer characteristic curve in the case of sweeping from -1.0 to 0 MV / cm was greatly shifted to a negative value compared with the case of sweeping to. That is, electric charges accumulated in the charged body with an electric field strength of 0.1 MV / cm or more at which charge injection started.

(Comparative Example 1)
A highly doped silicon wafer (diameter 50 mm, thickness 280 μm, type N, resistivity 0.002 to 0.004 Ω · cm, single-side mirror polishing, manufactured by KN Platz Co., Ltd.) having a thermal oxide film of 100 nm thickness is O ₂ plasma asher After treatment at 250 W for 5 minutes, hexamethyldisilazane (manufactured by Sigma-Aldrich) was held for 15 minutes in a gas stream heated and gasified to methylate the surface. Then, after vapor deposition of pentacene, it implemented to (element characteristic) like Example 1. FIG.

(Element characteristics)
The device characteristics were measured at a gate electric field strength of +2 to −6 MV / cm and a drain voltage of −10 V (constant), and a threshold voltage was obtained. The current transfer characteristic curve is shown in FIG. The threshold voltages before and after −6 MV / cm imprinting were almost unchanged at +3.3 V and +3.5 V, and no operation as a charged body due to charge injection was observed.

DESCRIPTION OF SYMBOLS 1 ... Area | region where electric charge injection arises by a high electric field, and a minute electric current flows 2 ... Dielectric breakdown 11, 21, 31, 41, 51, 61, 71, 81, 91 ... Substrate 12, 22, 32, 42, 52, 62, 72, 82, 82 ′, 92, 92 ′... Gate electrodes 13, 23, 33, 43, 53, 63, 73, 83, 83 ′, 93, 93 ′... Low charge injection withstand voltage material or high charge injection withstand voltage material 14 24, 34, 44, 54, 64, 74, 84, 84 ′, 94, 94 ′... High charge injection withstand voltage material or low charge injection withstand voltage material 15, 25, 35, 45, 55, 65, 75, 85, 95. Semiconductor layer 16, 17, 26, 27, 36, 37, 46, 47, 56, 57, 66, 67, 76, 77, 86, 87, 96, 97 Source-drain electrode

Claims (8)

Charge injection occurs field strength (hereinafter, charge injection tolerance) and dielectric breakdown voltage respectively E _CI, insulators are _H and E _BH (hereinafter, high charge injection withstand material) and their charge injection withstand E _{CI, L} is E An insulator in which two types of insulators of _CI , _L < _ECl , _H (hereinafter referred to as a low charge injection withstand voltage material) are laminated, and each of the high charge injection withstand voltage material and the low charge injection withstand voltage material is provided. A charged body in which a voltage is applied to two electrodes in contact with each other at an electric field strength of E _CI , _L <| E | < _EBH , and charges are injected into the insulator from the low charge injection withstand voltage material side and charged. A charged body , wherein at least one of the high charge injection withstand voltage material and the low charge injection withstand voltage material is composed of an organic polymer . Said _{E CI, H} and _{E CI,} the ratio of _{L (E CI, H / E} CI, L) is a 1.5 to _1,000, according to claim 1 _{E CI, L} is 0.01 MV / cm or more The charged body described in 1. The dielectric breakdown voltage (E _BH ) of the high charge injection breakdown voltage material is 0.1 MV / cm or more, and the volume resistivity at 0.5 MV / cm of the high charge injection breakdown voltage material and the low charge injection breakdown voltage material is 10 ¹¹ Ω, respectively. The charged body according to claim 1, wherein the charged body is m or more. Charged body according to any one of said low charge injection withstand voltage materials and / or high charge injection withstand voltage materials, claims 1 to 3 is a three-dimensional crosslinked polymeric material. The charged body according to claim 4 , wherein the three-dimensional crosslinked polymer material is formed by a wet process. Claims wherein the wet process is selected from dip coating, spin coating, spray coating, roll coating, inkjet coating, offset coating, inkjet printing, transfer method, offset printing, screen printing, letterpress printing, intaglio printing, soft lithography, or dispenser printing Item 6. A charged body according to Item 5 . In the field effect transistor which has a gate electrode and a semiconductor layer on both sides of a gate insulating film and has a source-drain electrode in contact with the semiconductor layer, the gate insulating film is the charged body according to any one of claims 1 to 6 , A field effect transistor characterized in that a threshold voltage of a field effect transistor is controlled by an amount of charge injected into a charged body. 8. The field effect transistor according to claim 7 , wherein information is recorded by an injected charge amount held in the charged body, and the information is called as a difference in drain current amount under a gate field intensity of E _CI , _L > | E |. A memory element characterized by that.

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