JP2001168295A - Formation of new dielectric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric of which Fc can be lowered and which can be patterned by light irradiation. SOLUTION: An organic ferroelectric is dispersed to a sensitive resin. Accordingly, in the patterning, the organic ferroelectric-materials are not put in the harsh environment such as plasma ashing, which allows preventing degradation in the performance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel dielectric. More specifically, the present invention relates to improvement of a ferroelectric material. The present invention relates to a ferroelectric memory using an improved organic ferroelectric. The present invention relates to a method for manufacturing a ferroelectric memory using an improved organic ferroelectric. The present invention relates to a ferroelectric memory device using an improved organic ferroelectric material.

[0002]

2. Description of the Related Art Ferroelectrics are materials having remanent polarization.
The direction of the remanent polarization changes depending on the direction of the electric field applied to the ferroelectric substance. Therefore, a ferroelectric nonvolatile memory is provided using the direction of the remanent polarization as information.

In a ferroelectric memory, for example, PZT (Pb (Zr, Ti)) which is an inorganic ferroelectric material is used as a ferroelectric material.
It is known that O ₃ ) is used, and this is sandwiched between upper and lower electrodes to form a capacitor. Further, for example, Japanese Patent Laid-Open No. 10-22
As described in Japanese Patent No. 470, a ferroelectric memory using an organic ferroelectric instead of an inorganic ferroelectric is also known. As the organic ferroelectric, a copolymer of vinylidene fluoride and ethylene trifluoride (P (VDF / TrFE)) is known. Organic ferroelectrics are advantageous in realizing a simple matrix type ferroelectric memory because of their low impedance.

When these ferroelectric memories are constructed, a ferroelectric thin film is formed on a lower electrode, and is patterned by plasma ashing in the case of an organic ferroelectric, and is formed by plasma ashing in the case of an inorganic ferroelectric. Patterning is performed by RIE ion milling. Next, an upper electrode is laminated. Inorganic ferroelectrics need to be annealed at 700-800 degrees Celsius. Annealing may damage the CMOS structure.

[0005]

The organic ferroelectric material is excellent in that it does not require high-temperature annealing and can form a simple matrix type memory because of its low impedance. However, the coercive electric field of the organic ferroelectric has a large value of about several to several tens of MV / cm, and there is a problem that the driving voltage is increased. If the thickness is smaller, the coercive electric field can be reduced, but the leak current increases. Further, when an organic ferroelectric is patterned by plasma ashing, Pr (residual polarization / spontaneous polarization) decreases due to damage, and the reliability of elements such as fatigue, imprint, and retention decreases.

On the other hand, as described in the above-mentioned prior art, a ferroelectric made of an oxide material has poor compatibility with a CMOS process. That is, in general, in a heating state in a gas containing hydrogen, an oxide ferroelectric substance such as PZT is very weak to heating in a reducing atmosphere, and a residual polarization is lost, so that a signal cannot be obtained. The hydrogen heat treatment of about 400 degrees which is normally performed cannot be performed. For this reason, it is difficult to ensure the reliability of the wiring formed after the formation of the storage capacitor, and a special process for using a ferroelectric must be developed.

Further, annealing the oxide material in a high oxygen atmosphere may damage the CMOS. TEOS
A semiconductor process that generates hydrogen gas, such as CVD, damages the ferroelectric;

Accordingly, an object of the present invention is to provide an organic ferroelectric substance which is excellent in reliability, has a small leak current, and has a low coercive electric field. Another object of the present invention is to provide an organic ferroelectric which can be patterned without severe conditions such as plasma ashing and ion milling. Still another object of the present invention is to provide a ferroelectric memory using the organic ferroelectric. Still another object of the present invention is to provide a memory device including the ferroelectric memory. Still another object of the present invention is to provide a method for patterning this ferroelectric memory.
Still another object of the present invention is to provide a method for manufacturing a memory device including the dielectric memory.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a dielectric material capable of dispersing a dielectric material in a photo-functional resin to reduce a coercive electric field, and irradiating light with a patternable dielectric material. It is characterized by being a body. Therefore, since the organic ferroelectric substance is not placed under a severe environment such as plasma ashing during the patterning as in the related art, it is possible to avoid the performance degradation as described above. This dielectric can be used as a ferroelectric, piezoelectric, pyroelectric, or the like. Therefore, the dielectric according to the present invention can be used for a ferroelectric memory, an ink jet recording head using a piezoelectric effect, a memory using a pyroelectric effect as described in JP-A-7-84231, and the like.

As the photofunctional resin, those applicable to the present invention such as acrylate derivatives such as PMMA, methacrylate derivatives, and styrene derivatives such as polystyrene and polyhydroxystyrene can be used. It is possible to use a photoresist which can be crosslinked with the photofunctional resin by irradiation of light to make a difference in etching property.

Examples of the dielectric material include the above-mentioned copolymer of vinylidene fluoride and ethylene trifluoride, polyvinylidene cyanide, odd-numbered nylon, etc.
(Kodansha Scientific, page 160, published on April 20, 1989) can be used.

In order to obtain the dielectric of the present invention, a dielectric material is dispersed in a photofunctional resin. Dispersion is performed as follows. That is, it is dispersed with a solvent in which the photofunctional resin and the dielectric are soluble. Examples of the solvent include the following. In addition to hydrocarbon solvents such as n-heptane, n-octane, dodecylbenzene, diethylbenzene, mesitylene, tetralin, decalin, toluene, xylene, cymene, durene, indene, dibenten, tetrahydronaphthalene, decahydronaphthalene, cyclohexylbenzene, ethylene Ether solvents such as glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, 1,2-dimethoxyethane, bis (2-methoxyethyl) ether, p-dioxysan and the like , Propylene carbonate, γ-butrolactone, N-methyl-2-pyrrolidone, dimethyl Formamide, 1,3-dimethyl-2-Imidazorujinon, 1,3 di-n-propyl-2-Imidazorujinon, dimethyl sulfoxide, can be mentioned polar solvents such as cyclohexanone. Among these, hydrocarbon solvents and ether solvents are preferred in view of the solubility of the cyclic silicon compound and the stability of the solution, and more preferred solvents are hydrocarbon solvents. These solvents can be used alone or in combination of two or more.

The ratio of the dielectric material (B) to the photofunctional resin (A) is, for example, A: B =
1: 4 to 1: 1.

The organic ferroelectric memory according to the present invention
Since it can be driven at 5 V, it is possible to achieve consistency with the CMOS circuit and achieve low power consumption. Further, since the organic ferroelectric can achieve a low temperature process of 170 to 200 degrees Celsius, it does not damage the CMOS side. Moreover,
Since patterning is possible by light irradiation, cost reduction can be achieved without lowering Pr of the battery body to be tied.

According to the present invention, the reliability of fating, imprinting, retention, etc. is compared with that of the conventional one, and the number of cycles of fating (3v) from 10 ⁶ to 10 ¹⁰
Imprint fluctuation can be increased from 30% to 10% or less, retention (65 degrees Celsius) from 5 to 10 years

Next, an embodiment of the present invention will be described. In this embodiment, a memory device including an FRAM (ferroelectric memory) using the above-described ferroelectric material as a capacitor will be described as an example. FIG. 1 illustrates a manufacturing process of a simple matrix type memory element.
As shown in FIG. 1A, the peripheral circuits 21 and 22 peeled off from the base are transferred to the substrate 1 by a known transfer method. In this transfer method, a part of an element component is formed on another substrate, the element component is separated therefrom, and the element component is transferred to a substrate to be transferred.

The substrate 1 is made of a flattening film, an organic thin film, X
In the step of forming the stripe electrode and the Y stripe electrode, the material is not particularly limited as long as the material has heat resistance, erosion resistance, and the like and has a desired mechanical strength, and a plastic substrate, a quartz substrate, or the like is used. be able to.

Subsequently, as shown in FIG.
A flattening film 3 is formed in the upper memory cell region and the region including the peripheral circuits 21 and 22. Further, n flattening films 3 are formed in accordance with the positions of connection terminals between the peripheral circuit 21 and n X stripe electrodes formed later. , 4n are formed. At the same time, the peripheral circuit 22 and m formed later
M contact holes 51, 52,..., 5m are formed in accordance with the positions of the connection terminals with the Y stripe electrodes.

The flattening film 3 absorbs a step between the peripheral circuits 21 and 22 transferred and formed on the substrate 1 and the substrate 1, and enables connection between the peripheral circuits 21 and 22 and the X stripe electrode and the Y stripe electrode. It is a thin film provided for the purpose of the present invention, and is not particularly limited as long as it is a thin film having an insulating property.

For forming a polyimide film, for example, as the flattening film 3, an arbitrary method such as a lithography method or a printing method can be selected. When a lithography method is used, an organic material may be applied by a predetermined method such as spin coating, spray code, roll coating, die coating, and dip coating. When a silicon oxide film is formed as the planarizing film 3, for example, a silicon nitride film can be formed by a plasma CVD method using organic silane (TEOS) and oxygen as a reaction gas. If
The film can be formed by a plasma CVD method using a silane-based gas and nitrogen as a reaction gas.

Then, as shown in FIG. 2C, n X stripe electrodes 61, 62,..., 6n connected to the contact holes 41, 42,. To form an X stripe electrode, for example, Al, RuO ₂ , Pt, IrO ₂ , YBa ₂ Cu ₃
O ₇ , OsO ₂ , MoO ₂ , ReO ₂ , WO ₂ , Au,
A conductive material liquid (electrode material liquid) is prepared by dissolving fine particles of a conductive material such as Ag, In, an In-Ga alloy, and Ga in an appropriate solvent, and the liquid is discharged using an ink jet recording head (fluid ejection head). What is necessary is just to pattern-coat in stripe form.

As the solvent, butyl carbitol acetate, 3-dimethyl-2-imitazolidine, BMA and the like can be used. Ink jet recording heads use the piezo jet method, which discharges a desired fluid by changing the volume of the piezoelectric element, or the bubble jet method, which discharges the fluid by suddenly generating steam by applying heat. There may be. Subsequently, the applied electrode material liquid is subjected to a heat treatment to evaporate the solvent component.
A stripe electrode is formed.

Next, as shown in (D), an organic thin film 7 is formed in the memory cell region. The characteristic (voltage-current characteristic) of the organic thin film 7 changes when the electric field intensity applied between the X stripe electrode and the Y stripe electrode exceeds a certain threshold value, and the impedance does not change even when the applied electric field is zero. And a material having
Therefore, “0” or “1” respectively corresponds to the high impedance state and the low impedance state of the organic thin film 7.
, A non-volatile memory can be realized. When such an organic thin film 7 is used, one memory cell (unit memory cell) is formed at each intersection of the X stripe electrode and the Y stripe electrode which are orthogonal to each other.

As described above, this organic film is formed by dispersing an organic strong conductive material in a photo-functional resin and discharging it by an ink jet or bubble jet method, a spin coating method, or a spray coating method. That is, a photofunctional resin and the above-mentioned organic ferroelectric or Cu-TCNQ disclosed in International Publication WO98 / 58383 are dissolved in an organic solvent such as methanol, and this is formed on an electrode by the above-mentioned forming method. Is formed. Next, the solvent component in the film is evaporated by a heat treatment at about 170 degrees Celsius to solidify the film.

The thickness of the organic film based on one specific example of the production method was 100 nm, and the coercive electric field of this film was 150 kv / cm when measured. Further, the measured leakage current was 10 ⁻⁷ A / cm ² . When the leak current is 10 ⁻⁴ / cm ² or more, the hysteresis property is adversely affected. Subsequently, the organic film is irradiated with light from a mercury lamp having a wavelength of 254 nm and etched to pattern the organic film into an array.

Finally, as shown in (E), m Y stripe electrodes 81, 82,..., 8m connected to the contact holes 51, 52,. The Y stripe electrode may be formed by patterning using an ink jet recording head in the same manner as the X stripe electrode. If the surface of the memory element is sealed with a resin or the like, a simple matrix type memory element is completed.

[0026]

As described above, the present invention can provide an organic ferroelectric substance which is excellent in reliability, has a small leakage current, and has a low coercive electric field. The present invention can also provide an organic ferroelectric that can be patterned without severe conditions such as plasma ashing and ion milling. Further, the present invention can provide a ferroelectric memory using the organic ferroelectric. The invention further provides
A memory device including the ferroelectric memory can be provided. The present invention can further provide a dielectric patterning method that can be patterned by light irradiation.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of a ferroelectric memory according to an embodiment of the present invention and a method of manufacturing the same.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 21 ... Peripheral circuit, 22 ... Peripheral circuit, 3 ... Planarization film, 41-4n ... Contact hole, 51-5m ... Contact hole, 61-6n ... X stripe electrode, 7 ...
Organic thin film, 81-8m ... Y stripe electrode

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission Date] January 26, 2000 (2000.1.2
6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

According to the present invention, the reliability of fating, imprinting, retention, etc. is compared with that of the conventional one, and the number of cycles of fating (3v) from 10 ⁶ to 10 ¹⁰
Imprint fluctuation can be increased from 30% to 10% or less, retention (65 degrees Celsius) from 5 to 10 years

Next, an embodiment of the present invention will be described. In this embodiment, a memory device including a ferroelectric memory using the above-described ferroelectric material as a capacitor will be described as an example. FIG. 1 illustrates a manufacturing process of a simple matrix type memory element. As shown in FIG. 1A, a peripheral circuit 2 peeled off from a base by a known transfer method.
The substrates 1 and 22 are transferred and formed on the substrate 1. This transfer method involves forming a part of an element component on another substrate, peeling the element component from the substrate, and transferring the element component to a substrate to be transferred.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Katsuyuki Morii 3-3-5 Yamato, Suwa-shi, Nagano F-term in Seiko Epson Corporation (reference) 4F071 AA22 AA26 AA33 AA34 AG28 AH12 BA03 BB02 BC02 BC12 4J002 BC03W BC12W BD12X BD14X BG06W BG09X GH00 GQ00 HA06 5F083 FR01 GA06 HA02 JA01 JA43 JA44 JA56 JA58 LA06 PR23 PR38 PR42 PR52

Claims (9)

[Claims] 1. A dielectric obtained by dispersing a dielectric material in a photofunctional resin. 2. The dielectric according to claim 1, wherein said dielectric material is an organic ferroelectric material. 3. The dielectric according to claim 1, wherein the photofunctional resin is one of an acrylate derivative, a methacrylate derivative, and a styrene derivative. 4. A ferroelectric memory in which a capacitor is formed between electrodes, and wherein the dielectric according to claim 1 is used for the capacitor. 5. A ferroelectric memory according to claim 4, wherein a plurality of ferroelectric memories are arranged in an array, and data is written to or read from a specific ferroelectric memory by specifying a row and column address. Ferroelectric memory device comprising a peripheral circuit to perform. 6. A method for patterning a dielectric, comprising: forming the dielectric according to claim 1 on an electrode; and irradiating the dielectric with a light to form a dielectric layer having a specific pattern. 7. A ferroelectric material according to claim 1, which is formed on an electrode, and irradiated with light to form a ferroelectric layer having a specific pattern as a capacitor between the electrodes. A step of arranging the ferroelectrics in an array and forming row and column electrodes, and writing data to or writing data from a specific ferroelectric by designating row and column addresses. Forming a peripheral circuit pattern for performing reading. 8. A ferroelectric material comprising an organic material having a thickness of 100 to 200 nm and a coercive electric field of 50 to 300 kv / cm. 9. The ferroelectric material according to claim 8, wherein a leak current is 10 ⁻⁴ cm ² or less.