WO2012008866A1

WO2012008866A1 - Multilayered nanocomposite for capacitors and method for manufacturing same

Info

Publication number: WO2012008866A1
Application number: PCT/RU2010/000400
Authority: WO
Inventors: Василий Александрович БАРГАН; Петр Александрович БАРГАН; Дмитрий Евгеньевич КАШИН; Александр Викторович ПЕЙСАХОВ; Борис Дмитриевич БОЛЬЩИКОВ; Алексей Борисович ХАЛЯВИН
Original assignee: Общество С Ограниченной Ответственностыо "Бapгah Texhoлoджи"
Priority date: 2010-07-14
Filing date: 2010-07-19
Publication date: 2012-01-19
Also published as: RU2432634C1

Abstract

The multilayered nanocomposite for capacitors comprises a substrate 1 consisting of a graphite film with a density of from 0.27 to 1.2 g/cm³, wherein a layer 2 of amorphous aluminium oxide, a layer 3 of titanium oxide of the rutile modification and a layer 4 of titanium nitride are arranged successively on the face of said substrate, with the layers being formed using the method of atomic layer deposition. Furthermore, the application of the layer of aluminium oxide is performed at a temperature of 270-330°C by means of the alternate pulsed supply of the following precursors to the reaction chamber: trimethylaluminium and ozone. The application of the layer of titanium dioxide is performed at a temperature of 450-500°C by means of the alternate pulsed supply of the following precursors to the reaction chamber: titanium tetrachloride and water, while the application of the layer of titanium nitride is performed at a temperature of 460-490°C by means of the alternate pulsed supply of precursors to the reaction chamber, with the precursors used being titanium tetrachloride and ammonia.

Description

Multilayer nanocomposite for capacitors and method for its manufacture.

The field of technology.

The invention relates to microelectronics, and more specifically, to nanolayer structures of the type metal-dielectric-metal (MDM) with a large specific electrical and energy intensity.

The prior art.

As follows from the achieved level of technology, the task of creating capacitors with a large specific capacitance is becoming increasingly important, while there are essentially two alternative approaches to solving the problem of increasing the capacitance of solid dielectric capacitors (Si0 ₂ , Ti0 ₂ , CaTi0 ₃ , Zr0 ₂ ) or a ferroelectric VaTyuz by increasing the area of their plates.

Thus, a multilayer nanocomposite for capacitors is known, including layers of metal (molybdenum) and dielectric (amorphous silicon oxide) arranged in alternating sequence on a flat front surface of a dielectric substrate, forming a periodic multilayer structure with a period of 13.5 nm, as well as with the upper and lower layers metal (see US-A-N5414588, 1995, FIG. 1). The multilayer nanocomposite for capacitors described above is manufactured by sequentially depositing metal and dielectric layers in a vacuum on a flat front surface of a dielectric substrate using one of the methods widely known in microelectronics, preferably by magnetron sputtering.

The maximum capacitance of such a periodic multilayer structure occurs with an external electrical connection between each other of its odd and even metal layers, which provides, in essence, an η-fold (where n is the number of dielectric layers) increase in the area of the capacitor plates (obtained as a result of the above metal connection layers) compared with the area in terms of a multilayer nanocomposite.

However, as follows from the above patent, the implementation of an external electrical connection to each other respectively, odd and even metal layers is a complex process, leading to a significant increase in the cost of finished capacitors. As for the embodiment of the above-mentioned compounds of metal layers directly in the process of manufacturing a multilayer nanocomposite, then, as follows from the aforementioned patent, this, on the one hand, leads to a complication of the process, and on the other hand, leads to a significant increase in the dimensions of the capacitor, and therefore , to a decrease in specific capacity. This is the main disadvantage of the multilayer nanocomposite for capacitors described above.

There is also an alternative to the approach described above for solving the problem of creating a capacitor with a large specific capacity, which consists in the fact that an increase of more than an order of magnitude of the real area of the capacitor plates with constant geometric dimensions in terms of the substrate of a multilayer nanocomposite is provided by using a substrate with a highly developed at least face surface.

Thus, a multilayer nanocomposite for capacitors is known, taken as a prototype and containing a first layer of titanium nitride (5.6 nm), a layer of aluminum oxide (6.5 nm) and a second layer of titanium nitride (12 , 6 nm), while the substrate is made in the form of ultrapure aluminum deposited on a glass plate, and the developed front surface of the substrate is formed by anodic oxidation of the aforementioned aluminum layer to a depth corresponding to the required pore sizes, e.g. an example, about 50 nm in cross section and a depth of 1.0 to 10.0 μm (see: Parag Banerjee and al. Nanotubular metal-insulator-metal capacitor arrays for energy storage Nature Nanotechnology, v. 4, pp. 292-296 (2009)).

Taken as a prototype, a multilayer nanocomposite for capacitors is manufactured (parameters are not given) by 0 000400

- 3 - sequential deposition on the developed surface of the substrate and conductor and dielectric layers conformal to this surface by atomic layer deposition (Atomic Layer Deposition, hereinafter ALD method, see, for example, El. Dev / Lett, 29 (7), 740- 742, 2008).

However, the presence of open pores on the front surface of the substrate not only leads to an increase (mainly depending on the pore depth) of the real surface area of the substrate, and therefore to an increase in the area of the layers of the multilayer nanocomposite (or, in other words, to an increase in the area of the capacitor plates), but also imposes a strict upper restriction on the thickness of the multilayer nanocomposite, namely, the doubled maximum thickness of the multilayer nanocomposite is comparable (in particular, equal) with the minimum transverse dimensions then. Taking into account that, for a given dielectric strength, the energy of a charged capacitor is proportional to the thickness of the dielectric layer, we can conclude that multilayer nanocomposites formed on the front surface of an open-pore substrate with small transverse dimensions cannot be used to create capacitors with high specific electric and energy intensity. In addition, since the value of the relative non-uniformity of the thickness of the layers deposited by the ALD method on the front surface of the substrate and due to the unevenness of the surface of the micropores located on it increases with decreasing thickness of the applied layers, therefore, with a decrease in the thickness of the layers, not only does the scatter of electrophysical parameters over the area of the multilayer nanocomposite increase, but and decreases the reproducibility of the parameters of capacitors made on its basis.

Based on the foregoing, we can conclude that the prototype has the following disadvantages.

• The well-known multilayer nanocomposite cannot be used to create capacitors with simultaneously high specific electric and energy intensity, since the thickness of the dielectric layer is small (less than 10 nm), and it is not possible to increase it, on the one hand, due to the fact that the maximum transverse pore size (and therefore the doubled thickness of the multilayer nanocomposite for capacitors) obtained the anodizing method of ultrapure (99.99%) aluminum known from the prior art is about 50 nm (see the journal Doklady of the Belarusian State University of Informatics and Radioelectronics, 2 (14), pp. 127-183, 2006), and, on the other hand, due to the fact that with a multilayer thickness th nanocomposite not exceeding 25 nm, it should include not only the dielectric layer, but also two (upper and lower) layers of electrically conductive material (titanium nitride) as a known substrate may be used as one of the capacitor plates.

• The need to form two layers of electrically conductive material (in other words, the impossibility of using the known substrate as one of the capacitor plates) leads to an unjustified increase in the proportion of the electrically conductive part in the known multilayer nanocomposite for capacitors.

• In the multi-layer nanocomposite for capacitors known from the prototype, the lower layer of titanium nitride and the dielectric layer have a thickness of less than Yunm (respectively: 5.6 nm and 6, 5 nm), which negatively affects the reproducibility of the parameters of capacitors made on its basis.

In addition, the disadvantages of the prototype include the need to use substrates that are not manufactured by industry. The consequence of this is an increase in the cost of the known multilayer nanocomposite for capacitors.

It should be noted that in the description of the prototype there is no information regarding the operating parameters of the deposition of layers of a multilayer nanocomposite ALD method. This circumstance does not allow any analysis regarding the method of manufacturing a multilayer nanocomposite for capacitors.

Disclosure of the invention.

The present invention is directed to solving the technical problem of creating a multilayer nanocomposite for capacitors with a large specific electric and energy intensity on a substrate from an industrially produced electrically conductive material with a high specific surface while providing high adhesion to both the substrate and the layers to each other.

From the point of view of the device, the problem is solved in that a multilayer nanocomposite for capacitors containing a substrate with a front developed surface, as well as an amorphous alumina layer and a titanium nitride layer, according to the invention, it further comprises a rutile modification titanium dioxide layer, while the substrate is electrically conductive graphite foil density of from 0.27 to 1.2 g / cm ³ obtained by uniaxial compression of expanded graphite, while on the front surface of the substrate layer are sequentially disposed aux and aluminum, a titanium dioxide layer and a layer of titanium nitride formed by atomic layer deposition and having a thickness of 10 to 20 nm.

From the point of view of the method, the problem is solved in that in the method of manufacturing a multilayer nanocomposite for capacitors, comprising sequentially applying layers to a substrate with a developed front surface by atomic layer deposition, according to the invention, on the front surface of a graphite foil substrate with a density of 0.27 to 1.2 g / cm ³ obtained by uniaxial pressing of thermally expanded graphite, an alumina layer, a titanium dioxide layer and a titanium nitride layer are successively applied, while applying an oxide layer and aluminum is conducted at a temperature of 270-330 ° C by alternating pulsed feed into the reaction chamber of precursors which use trimethylaluminum and ozone, the deposition of a layer of titanium dioxide is conducted at a temperature of 450-500 ° C 2010/000400

- 6 - by alternating pulsed feed into the reaction chamber of precursors, which are used as titanium tetrachloride and water, applying a layer of titanium nitride is carried out at a temperature of 460-490 ° C by alternating pulsed feed into the reaction chamber of precursors, which are used as titanium tetrachloride and ammonia and alternately removing the precursors mentioned above by purging the reaction chamber with nitrogen.

The advantage of the patented multilayer nanocomposite for capacitors compared to the prototype is that due to the implementation of the substrate from an industrially produced electrically conductive material (graphite foil with a density of 0.27 to 1.2 g / cm ³ obtained by uniaxial pressing of thermally expanded graphite):

• there is no need to use special equipment for the manufacture of the substrate, and therefore, the process of manufacturing a multilayer nanocomposite for capacitors is simplified, and its cost is also reduced;

• there is no need to form a lower electrically conductive layer of titanium nitride, since the substrate itself performs the function of the lower lining of the capacitor;

• it is ensured (due to the pore parameters of the substrate and the absence of the lower layer of titanium nitride) not only a five-fold increase in the thickness of the dielectric part of the multilayer nanocomposite, but also its double-layer construction of dielectric materials with different dielectric constants and electric strength (in other words, providing an increase in only the capacitance of the capacitor, but also its breakdown voltage);

The high specific surface of the substrate material, as well as the structure and dimensions of its pores, allow the ALD method to form a multilayer nanocomposite for it on capacitors with two layers of dielectric material and one layer (top) of an electrically conductive material with a total thickness, twice the thickness of the prototype, as well as providing a higher specific electric capacity (2-3) · 10 ^{~ 2} F / g and high specific energy consumption (7-8) J / g

As for the patented method of manufacturing a multilayer nanocomposite for capacitors, the features related to the operating parameters of the deposition of layers provide high adhesion between the layers located in the patented sequence, as well as the layer of aluminum oxide with the substrate. In addition, patentable regime parameters of the deposition of layers provide the required modifications of alumina and titanium dioxide.

Other technical results achieved using the patented invention will become apparent from the following.

The invention is further illustrated by a specific example, which, however, is not the only possible, but clearly demonstrates the possibility of achieving the above technical results with a patentable combination of essential features.

A brief description of the drawings.

In FIG. 1 schematically depicts a fragment of a cross section of a graphite foil substrate; in FIG. 2 - a multilayer nanocomposite for capacitors (section in the region of the substrate fragment shown in Fig. 1).

The best embodiment of the invention.

The multilayer nanocomposite for capacitors contains an electrically conductive substrate 1 with a developed front surface, on which the first dielectric layer 2 of amorphous alumina (ΑΙ ₂ Ο ₃ ), the second dielectric layer 3 of titanium dioxide (Ti0 ₂ ) rutile modification and conductive are sequentially arranged layer 4 of titanium nitride (TiN), (Fig. 1 and 2).

The substrate 1 is made of an electrically conductive material, namely, industrially produced graphite foil with a density of 0.27 to 1.2 g / cm ³ obtained by uniaxial pressing of thermally expanded graphite, which is obtained by heat treatment in the heat shock mode of oxidized graphites synthesized, preferably, by anodic polarization of natural graphite in aqueous acid solutions (for example, 60% nitric acid), since this foil has a higher strength, thermal and electrical conductivity, and also a specific surface compared to graphite foil obtained from graphites synthesized by chemical methods, including the production of nitrate, chlorate a, graphite hydrosulfate, followed by its hydrolysis. It was found that the magnitude of the thermal and electrical conductivity, the angle of disorientation of graphite crystallites, and the specific surface measured by low-temperature nitrogen adsorption practically do not change in the density range from 0.27 to 1.2 g / cm ³ .

In accordance with the above features, characterizing the boundaries of the density range of graphite foil are included among the essential features. Thermally expanded graphite graphite foil is supplied to the consumer in rolls and has a thickness of 0.1 to 0.8 mm (TU 5728-003-12058737-2000).

The developed surface of graphite foil (Fig. 1) made of thermally expanded graphite is formed by pores, which are mainly gaps between the flakes of thermally expanded graphite, the contact area between which remains practically unchanged in the above density range of graphite foil, thereby causing (noted above) practically a constant value of its specific surface within the patented range of densities.

It was also found that the pore characteristics of graphite foil provide the possibility, using the ALD method, of applying to the developed front surface of a graphite foil substrate a multilayer coating with a thickness of up to 60 nm, with an area of 87-91% of the developed front surface area of the substrate (due to " smoothing "wall irregularities RU2010 / 000400

- 9 - pores and filling very small pores).

The first dielectric layer 2 of amorphous alumina is deposited onto the developed surface of the substrate 1 by the ALD method on the surface of layer 2 and has a thickness of 10 to 20 nm. Conformal layer 2 of the second dielectric layer 3 of titanium dioxide modification of rutile deposited by the ALD method on the surface of layer 2 has a thickness of 10 to 20 nm. The lower limit of the thickness of layers 2, 3 and 4 is due to a decrease of not less than 1.5 times relative to the unevenness of the thickness of the layers compared to the prototype, which allows to reduce the dispersion of electrophysical parameters over the area of the multilayer composite, and therefore, increase the operating voltage of the capacitors made on its basis to 20V. The upper limit of the thicknesses of layers 2, 3, and 4 is due to a violation of the conformity of layer 4 with respect to layers 2 and 3.

The patented sequence of arrangement of layers 2 and 3, as well as modifications of the dielectric materials used, provides, as will be shown below, high adhesion to both substrate 1 and layers 2, 3, and 4 to each other.

The implementation of the dielectric part of a multilayer nanocomposite for two-layer capacitors of dielectric materials with different dielectric constants and electric strength, as is known, provides not only an increase in the capacitance of the obtained capacitor, but also its breakdown voltage. In other words, an increase in both the specific electric intensity and the specific energy intensity is provided.

A multilayer nanocomposite for capacitors is manufactured by atomic layer deposition (ALD method) as follows.

A substrate 1 of graphite foil with a density of 0.27 to 1.2 g / cm ³ obtained by uniaxial pressing of thermally expanded graphite is placed in a reaction chamber, the density of which is pumped to a pressure of about 5 mbar. A trimethylaluminum (CH3) 3A1 precursor is pulsed into the chamber under a pressure of 7 mbar for 10 to 20 seconds. at a temperature in the chamber of 270-330 ° C. As a result, a trimethylaluminum monolayer is adsorbed and chemisorbed on the surface of the substrate.

The chamber is purged with nitrogen followed by the inlet of another precursor of ozone 0 ₃ into the chamber at a pressure of 7 mbar for 10 to 20 seconds. As a result of the occurrence of a chemical reaction on the surface of the substrate 1:

2 (CH ₃ ) ₃ A1 + 6 0 ₃ = A1 ₂ 0 ₃ + 3 C0 ₂ + 9H ₂ 0

an alumina monolayer is formed. It should be noted here that it was found that only ozone (as a strong oxidizing agent) ensures the functionalization of the surface of graphite foil. The above temperature range has been found to provide the best adhesion of amorphous alumina to graphite foil. Going beyond the temperature range indicated above leads to peeling of alumina, including due to the formation of a crystalline phase of alumina.

Next, the chamber is purged with nitrogen to eliminate unreacted ozone, as well as reaction products, and then the alternate pulse supply of the above-mentioned precursors to the reaction chamber is repeated as many times as necessary to obtain an alumina layer 2 of the required thickness from 10 to 20 nm.

Next, a layer 3 of titanium dioxide is applied to modify the rutile conformal to layer 2. For this, a precursor is pulsed into the reaction chamber at a temperature of 450-500 ° C, using titanium tetrachloride (TiCl ₄ ) under a pressure of 7 mbar for 10- 20 sec During this pulse, a monolayer of titanium tetrachloride is adsorbed on the surface of layer 2 of aluminum oxide. After purging the chamber with nitrogen, another precursor, water, is supplied to it for 10-20 seconds. at a pressure of 7 mbar. AT 0 000400

- 11 - as a result of a chemical reaction:

TiCl ₄ + 2 H ₂ 0 = Ti0 ₂ + 4 HC1

a conformal monolayer of titanium dioxide is formed on the surface of the alumina layer 2. The above temperature range has been found to provide the best adhesion of the crystalline modification of rutile titanium dioxide to amorphous alumina. Going beyond the above temperature range leads to the exfoliation of titanium dioxide.

Next, purge the chamber with nitrogen to remove unreacted water and the reaction product - HC1. Then, the above-described alternate supply of titanium tetrachloride and water is repeated as many times as necessary to obtain a conformal layer of 2 layers of titanium dioxide of the required thickness: from 10 to 20 nm.

Next, a conformal layer 4 of titanium nitride is applied to the titanium dioxide layer 3 thereof. For this, a precursor is pulsed into the reaction chamber at a temperature of 460 - 490 ° С, which is used as titanium tetrachloride under a pressure of 7 mbar for 10-20 seconds. During this pulse, a monolayer of titanium tetrachloride is adsorbed on the surface of layer 3 of titanium dioxide. After purging the reaction chamber with nitrogen, another precursor, ammonia NH _3, is fed into it for (10-20) seconds. at a pressure of 7 mbar. As a result of the occurrence on the surface of layer 3 of a chemical reaction:

6 TiCl ₄ + 8 NH ₃ = b TiN + 24 НС1 + N ₂

a conformal titanium nitride monolayer is formed on the surface of the titanium dioxide layer 3.

It should be noted here that the adhesion between the layers of titanium dioxide and titanium nitride was found to be better than between the layers of aluminum oxide and titanium nitride. This circumstance allowed the features relating to the sequence of layers 2, 3 and 4 to be included among the essential features of the patented invention. The above temperature range provides the best adhesion between layer 3 and layer 4. Next, purge the reaction chamber with nitrogen to remove unreacted ammonia and reaction products. After this, the above-described alternate supply of titanium tetrachloride and ammonia is repeated as many times as necessary to obtain a conformal layer 3 of layer 4 of titanium nitride of the required thickness: from 10 to 20 nm.

Example. The multilayer nanocomposite for capacitors made by the patented method comprises a substrate of graphite foil 0.3 mm thick with a density of 1.0 g / cm ³ and with a specific surface area of 28 m ² / g on the front surface of which (with an area of 25 mm ² in plan) there is an amorphous layer alumina with a thickness of 20 nm, a rutile modification titanium dioxide layer with a thickness of 15 nm and a conformal alumina layer, and a titanium nitride layer conformal with a titanium oxide layer and having a thickness of 15 nm. The capacity of this multilayer nanocomposite is 8 · 10 ^{~ 3} F and the operating voltage is 20V. Thus, this multilayer nanocomposite can be used for the manufacture of capacitors for hybrid battery-condenser power plants for cars or for solar panels.

Industrial applicability.

The industrial use of the patented invention is also confirmed by the wide popularity of the materials used in its implementation.

Claims

Claim.

1. A multilayer nanocomposite for capacitors, containing a substrate with a front developed surface, as well as an amorphous alumina layer and a titanium nitride layer, characterized in that it further comprises a rutile modification titanium dioxide layer, the substrate being made of a conductive graphite foil with a density of 0, 27 to 1.2 g / cm ³ obtained by uniaxial pressing of thermally expanded graphite, and on the front surface of the substrate there are successively arranged an alumina layer, a titanium dioxide layer and a titanium nitride layer, spho Framed by atomic layer deposition and having a thickness of 10 to 20 nm.

2. A method of manufacturing a multilayer nanocomposite for capacitors, including the sequential deposition of layers on a substrate with a developed front surface by atomic layer deposition, characterized in that on the front surface of a substrate of graphite foil with a density of from 0.27 to 1.2 g / cm ³ , obtained by uniaxial pressing of thermally expanded graphite, an alumina layer, a titanium dioxide layer and a titanium nitride layer are successively applied, while the alumina layer is applied at a temperature of 270-330 ° C by alternating and pulse feeding precursors into the reaction chamber using trimethylaluminium and ozone; applying a layer of titanium dioxide is carried out at a temperature of 450-500 ° C by alternately pulsing feeding precursors into the reaction chamber, using titanium tetrachloride and water, applying a layer of titanium nitride is carried out at temperature 460-90 ° С by alternating pulsed feed of precursors into the reaction chamber, which use titanium tetrachloride and ammonia, and alternating removal of the precursors mentioned above carried out in the reaction chamber by purging with nitrogen.