CN104201281A - Organic-inorganic composite resistive random access memory and preparation method for same - Google Patents

Abstract

The invention relates to the technical field of electronic devices, and more specifically, relates to an organic-inorganic composite resistive variable memory and a preparation method thereof. An organic-inorganic composite resistive variable memory, which includes a substrate, a bottom electrode sequentially deposited on the substrate, an organic-inorganic composite medium layer embedded with lithium ion compound particles, and a top electrode. The present invention 1) utilizes the lithium ion compound particles embedded in the organic medium to provide metal lithium ions that form resistive filaments; 2) metal lithium ions have the characteristics of strong redox reaction activity and small atomic radius, which reduces the filament formation energy, Improve the speed of resistive storage; 3) The concentration of the electric field formed by the nanoparticles reduces the randomness of the formation of resistive filaments and improves the uniformity and reliability of the storage device; 4) The device is flexible and printable.

Description

An organic-inorganic composite resistive variable memory and its preparation method

technical field

The present invention relates to the technical field of electronic devices, and more specifically, relates to an organic-inorganic composite resistive variable memory and a preparation method thereof.

Background technique

With the development of information technology, the requirements for integration are getting higher and higher. The traditional flash memory (flash memory) is getting closer and closer to its physical limit due to the reliability problems caused by the shrinking device size. Looking for another Non-volatile memory with high integration, low power consumption and low cost has become the focus of attention in academia and industry. Among them, resistive RAM (RRAM), as a new type of non-volatile memory, has attracted widespread attention. It has a simple structure, a metal-dielectric layer-metal (M-I-M) structure, and has the advantages of low reading and writing voltage, low power consumption, high storage density and high reliability. On the other hand, with the development of organic electronics, thin-film transistors based on organic semiconductors, organic light-emitting displays, organic solar cells, organic sensors and organic memories are constantly coming out, flexible and printable organic semiconductor devices will make printed flexible circuits become It is possible and wearable electronics has become a research hotspot. It can be predicted that integrated circuits based on organic materials will greatly enrich people's production and life in the future. Among them, the organic resistive non-volatile memory as an organic memory is expected to be applied to the embedded system of the flexible printed circuit and become a device unit of the wearable circuit.

However, compared with the widely studied inorganic resistive non-volatile memory such as transition metal oxides (ZnO, TiO, NiO, etc.), solid electrolytes (Ag or Cu sulfide), the current organic resistive non-volatile memory has unstable characteristics. , Slow switching speed and other shortcomings. In order to solve this problem, we must start from the analysis of the resistance switching mechanism and the structural design of the resistance switching material. In a large number of reports on the mechanism of resistive switching materials, the resistive switching mechanism can be roughly divided into two categories, namely, the conductive filament model and the interface control model. Among them, the metal filament model occupies the mainstream, and the principle lies in the generation and fracture of conductive filaments. In the initial situation, there is no conductive filament in the dielectric layer, and an initial filament formation process is generally required. According to literature reports, conductive filaments are mainly formed by the generation and migration of electrode metal ions or oxygen vacancies in the metal oxide dielectric layer under the action of an electric field, and such conductive filaments can be activated under the action of a reverse electric field or a large current. destroy. The size of the conductive filament is small and has nothing to do with the size of the device, so it is beneficial to the improvement of the integration degree. The formation and destruction of filaments significantly depend on the magnitude of the electric field in the dielectric layer. Generally, the device structure of the resistive non-volatile memory adopts a simple capacitive structure, that is, an electrode/dielectric layer/electrode structure. Obviously, for such a structure, the electric field distribution in the dielectric layer is generally uniform, so the appearance of the filaments has a certain randomness, which is not conducive to the repeatability and stability of the device. In addition, there are no metal ions in organic materials, and the formation of conductive filaments generally depends on the diffusion of metal ions in the electrodes, resulting in slow switching speed and poor device stability.

Contents of the invention

In order to overcome at least one defect described in the above-mentioned prior art, the present invention provides an organic-inorganic composite resistive variable memory and a preparation method thereof, which is conducive to improving the speed of the resistive variable memory, improving the uniformity of device characteristics, and realizing fast and reliable storage .

In order to solve the above-mentioned technical problems, the technical solution adopted in the present invention is: an organic-inorganic composite resistive variable memory, which includes a substrate, a bottom electrode deposited on the substrate in sequence, an organic-inorganic composite medium layer embedded with lithium ion compound particles, top electrode.

In the present invention, a scheme of introducing lithium ion compound particles into an organic material is proposed. Lithium ion compound particles can provide metal ions to form conductive filaments, and the lithium ion radius is small, the diffusion speed is fast, the activity is high, and the oxidation-reduction reaction is easy to occur. improve. On the other hand, inorganic nanoparticles embedded in organic materials will cause concentrated regions of electric field distribution in the dielectric layer, thereby reducing the randomness of filament formation, improving the uniformity of device characteristics, and realizing fast and reliable storage.

The organic-inorganic composite resistive variable memory has fast storage speed and uniform and reliable storage characteristics, and is suitable for the development needs of flexible printed circuits and wearable electronics.

Further, the organic-inorganic composite dielectric layer embedded with lithium ion compound particles is a resistive dielectric material; the size of the lithium ion compound particles is on the order of nanometers; the organic dielectric material is an organic semiconductor or insulator, including polymers, Fused Rings, Oligomers , Star-shaped Compound.

Further, the substrate is an inorganic material or an organic plastic substrate. Preferably, the inorganic material is a silicon wafer or a quartz wafer or a glass wafer or a sapphire wafer; the organic plastic is PET or PI.

Further, the bottom electrode and the top electrode are made of metal or transparent conductive material. Preferably, the metal is one or more of Au, Al, Pt, Pd, Ti, Cr, Ni, TiN, Ag; the transparent conductive material is one or more of ITO, FTO, NTO and AZO kind.

A preparation method of the organic-inorganic composite resistive variable memory, which includes the following steps:

1) Select the substrate, after cleaning and drying;

2) Use physical vapor deposition (PVD) or chemical vapor deposition (CVD) to deposit metal or transparent conductive materials on the substrate to form the bottom electrode;

3) In the air or in a vacuum glove box or in an inert gas atmosphere, a large-area organic-inorganic composite dielectric layer is coated on the bottom electrode by spin coating, spraying or pulling process, and then thermally annealed to form a stable organic-inorganic composite dielectric layer ;

4) Using physical vapor deposition technology or chemical vapor deposition technology, by depositing metal or conductive compound, and using a mask to form a discrete top electrode, and finally forming a non-volatile resistive memory with an organic-inorganic composite structure. In this step, a circular or strip-shaped discrete top electrode is deposited by physical vapor deposition or chemical vapor deposition by means of a mask.

Further, the size of the lithium ion compound particles in step 3) is on the nanometer scale and has good dispersion in the organic medium; the surface of the organic-inorganic composite medium layer is flat; the lithium ion compound particles are dispersed in the lower part of the organic medium layer. The bottom electrode in the step 2) is a large-area electrode or patterned.

Compared with the prior art, the beneficial effects are: 1) Lithium ion compound particles embedded in the organic medium are used to provide metal lithium ions forming resistive filaments; 2) Metal lithium ions have strong redox reaction activity and small atomic radius 3) The electric field formed by nanoparticles is concentrated, which reduces the randomness of the formation of resistive filaments and improves the uniformity and reliability of the storage device; 4) The device is flexible Printable features.

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of the present invention.

Fig. 2 is an X-ray diffraction pattern of lithium iron phosphate nanoparticles prepared in Example 1 of the present invention.

FIG. 3 is a scanning electron micrograph (SEM) of a section of a resistive variable memory according to Embodiment 1 of the present invention.

FIG. 4 is a working curve of the resistive variable memory prepared in Example 1 of the present invention.

Detailed ways

The accompanying drawings are for illustrative purposes only, and should not be construed as limitations on this patent; in order to better illustrate this embodiment, certain components in the accompanying drawings will be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art It is understandable that some well-known structures and descriptions thereof may be omitted in the drawings. The positional relationship described in the drawings is for illustrative purposes only, and should not be construed as a limitation on this patent.

Example 1

As shown in Figures 1-4, an organic-inorganic composite resistive variable memory includes a substrate 1, a bottom electrode 2 sequentially deposited on the substrate 1, an organic-inorganic composite dielectric layer 3 embedded with lithium ion compound particles 5, and a top electrode. Electrode 4.

Mix ferrous iron salt and phosphoric acid solution, pre-calcine at 250-400 °C for 3-15 hours under the protection of inert gas to decompose phosphate and oxalate, and then roast at 450-800 °C for 5-30 hours to obtain The single-phase lithium iron phosphate with olivine structure is milled at high speed by a nano-grinding machine to particles below 50 nanometers to obtain lithium iron phosphate nanoparticles. Fig. 2 is an X-ray diffraction pattern of lithium iron phosphate powder with a particle size of 50nm, and the obtained lithium iron phosphate powder has a pure olivine-type orthorhombic single-phase structure.

Weigh 1 mg to 1 g of lithium iron phosphate nanoparticles, add 10 to 1000 ml of 3-hexylthiophene polymer (P3HT), stir well at 40 °C for 12 hours, and spin-coat on the ITO glass where the bottom electrode is deposited , the spin coating speed is 500-2000 rpm, and a dielectric layer with a thickness of 30-100 nm is obtained. On this basis, 10-50 nm of P3HT was deposited as a buffer layer, and then annealed in vacuum at 40 degrees for 6 hours to form a stable organic-inorganic composite dielectric layer. Figure 3 is a scanning electron microscope photo of the organic-inorganic composite dielectric layer. Finally, a mask plate is used to deposit metal aluminum to form a top electrode, and finally an organic-inorganic composite resistive memory embedded with lithium iron phosphate particles is formed.

At room temperature (25 °C), a DC voltage-current (IV) test was performed on the RRAM. Figure 4 shows the electrical test results of a typical resistive variable memory. It can be seen from the figure that the device has low-voltage erasing and writing characteristics. The bottom electrode is grounded, and the top electrode is biased at about 1V, and the device is in a low-resistance state. On the contrary, the reverse voltage When it is about -0.5V, the device reverses to a high-impedance state. Between the storage device units, the erasing and writing voltage distribution is uniform and concentrated, and the storage window reaches 10 ⁴ .

Apparently, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. All modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (10)

1. the compound resistance-variable storing device of organic-inorganic, is characterized in that comprising substrate (1) and the hearth electrode (2), the compound dielectric layer of organic-inorganic (3) of inlaying lithium ion compound particle (5), the top electrode (4) that at substrate (1), above deposit successively.

2. the compound resistance-variable storing device of a kind of organic-inorganic according to claim 1, is characterized in that: the described compound dielectric layer of organic-inorganic (3) of inlaying lithium ion compound particle (5) is resistive dielectric material; Lithium ion compound particle (5) is of a size of nanometer scale; Organic media material is organic substance semiconductor or insulator.

3. the compound resistance-variable storing device of a kind of organic-inorganic according to claim 1, is characterized in that: described substrate (1) is inorganic material or organic plastics substrate.

4. the compound resistance-variable storing device of a kind of organic-inorganic according to claim 3, is characterized in that: described inorganic material is silicon chip or quartz plate or sheet glass or sapphire sheet; Organic plastics is PET or PI.

5. the compound resistance-variable storing device of a kind of organic-inorganic according to claim 1, is characterized in that: described organic substance comprises polymers, Fused Rings, Oligomers, Star-shaped Compound.

6. the compound resistance-variable storing device of a kind of organic-inorganic according to claim 1, is characterized in that: described hearth electrode (2) and top electrode (4) are metal or transparent conductive material.

7. the compound resistance-variable storing device of a kind of organic-inorganic according to claim 6, is characterized in that: described metal is wherein one or more of Au, Al, Pt, Pd, Ti, Cr, Ni, TiN, Ag; Transparent conductive material is wherein one or more of ITO, FTO, NTO and AZO.

8. a preparation method for the compound resistance-variable storing device of organic-inorganic as described in as arbitrary in claim 1-7, is characterized in that, comprises the following steps:

1) select substrate (1), through cleaning, drying and processing;

2) on substrate (1), utilize physical gas phase deposition technology or chemical vapour deposition technique depositing metal or transparent conductive material to form hearth electrode (2);

3) utilize spin coating, spraying or czochralski process to apply organic inorganic compounding dielectric layer in the upper large area of hearth electrode (2), after through thermal anneal process, form the compound dielectric layer of stable organic-inorganic (3);

4) utilize physical gas phase deposition technology or chemical vapour deposition technique, by plated metal or conductive compound, and by mask plate, form discrete top electrode (4), thus the final non-volatile resistance-variable storing device with the compound structure of organic-inorganic that forms.

9. the preparation method of the compound resistance-variable storing device of organic-inorganic according to claim 8, it is characterized in that: in described step 3), in the prepared compound dielectric layer of organic-inorganic, lithium ion compound particle (5) is embedded in the bottom of the compound dielectric layer of organic-inorganic (3), the compound dielectric layer of organic-inorganic (3) surfacing.

10. the preparation method of the compound resistance-variable storing device of organic-inorganic according to claim 8, is characterized in that: hearth electrode described step 2) (2) is broad-area electrode or graphically processes.