JPH08290902A - Thin film dielectric and method of manufacturing the same - Google Patents

Abstract

(57) [Summary] (Correction) [Structure] 1. A thin film dielectric having a composition represented by the general formula (1) and having a film thickness of 0.02 to 5 μm. Au Cv (Bx M1-x) w Oz (1) (wherein A is Ca, Sr, Ba, Pb, Cd, La, C
e, Pr, Nd, Pm, Sm, Eu, Gd, Tb, D
1 selected from y, Ho, Er, Tm, Yb, Lu and Y
Or 2 or more elements, C is Bi, Sc, Sb, Cr, T
1 or 2 or more elements selected from l, B is Ti, T
a, 1 or 2 or more elements selected from Hf, W, Nb and Zr, M is 1 or 2 selected from Fe, Co and Mo
These are the above elements. x is in the range 0 ≦ x <0.99, u,
v, w and z are determined so that the total charge is zero. ) 2. A method for producing a thin film dielectric by applying a dielectric forming solution onto a substrate to form a thin film of the solution, and then heating the thin film to produce a dielectric forming solution that is soluble in an organic solvent and an organic solvent. A solution containing the compound of the element A, the compound of the element C, the compound of the element B, and the compound of the element M as main components is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film dielectric having a large relative permittivity, a high Curie temperature, a large spontaneous polarization and a small switching fatigue, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, titanium oxide, barium titanate, lead titanate, PZT and the like have been used as porcelain capacitors because of their dielectric properties. Barium titanate is known as a ferroelectric substance having a high relative dielectric constant of 2000 to 3000 at room temperature. However, there are drawbacks such as a large temperature coefficient of the dielectric constant and a significant decrease in the dielectric constant when a DC bias voltage is applied, which makes it difficult to apply to a signal delay circuit or the like. On the other hand, although titanium oxide has a low dielectric constant of about 100, it has been used as a temperature compensation capacitor because of its flat temperature characteristics and small dielectric loss. However, the sintering temperature is high, it is difficult to singly sinter,
There was a defect that oxygen in the lattice was easily lost.

In recent years, PZT and Bi ₄ Ti
Studies have been conducted to apply the polarization of ferroelectrics such as ₃ O ₁₂ and SrBi ₂ Ta ₂ O ₉ to integrated circuit memory materials.
There are problems such as fatigue due to repeated switching, short memory retention time due to leak current, and reduction in yield due to poor insulation.

When applied to a capacitor or the like as a porcelain, it is generally used as a laminated type in order to increase the capacity. In the method of manufacturing a multilayer capacitor, 0.5 to 5 μm of dielectric powder obtained by solid phase reaction or solution reaction is mixed with a binder and a solvent to prepare a slurry, and the slurry is thinned by a doctor blade method or the like. Shaped into a sheet, and laminated 10 to several tens of layers of the thin plate, 1200 to 13
The process of firing at 00 ° C is adopted.

Another method of increasing the capacitance is to thin the dielectric layer. In case of multilayer capacitor 1
Although the layer has a thickness of about 20 to 40 μm, if the thickness can be reduced to about 1 μm, a capacitance equal to or higher than that of the laminated type can be obtained without laminating, and the size can be reduced.

As a thinning method, there are a vapor phase method such as a sputtering method, a vacuum vapor deposition method and a CVD method, and a method for producing a thin film dielectric by coating an organic metal compound and thermally decomposing. For example, a method of obtaining a transparent barium titanate by mixing a butanol solution of barium naphthenate and a Ti alkoxide in a ratio of Ba: Ti = 1: 1 on a glass substrate and then baking the mixture in an electric furnace to obtain transparent barium titanate is known. (Ceramic Bullet
in) Vol.55 No.12 (1976) p1064-1065.

However, when the thin film dielectric is formed by the doctor blade method using the dielectric powder obtained by the solid phase method or the liquid phase method, the thickness of the dielectric is 20 μm because the dielectric powder is large. It is difficult to do the following.

By the way, as is well known, the capacitance of a capacitor is C = (ε0 εr S / d) × n (where C is capacitance, S is area, d is the distance between electrodes, ε
0 is the vacuum permittivity, εr is the relative permittivity, and n is the number of layers.)
Therefore, it is generally necessary to increase the number of laminated layers in order to increase the capacity, but the above method having a large film thickness naturally causes a limit to increase the capacity. In addition, this method has a drawback that the production cost is high because firing is required to obtain powder and firing of a green sheet for molding.

In the case of an integrated circuit memory, due to extremely high integration, SiO ₂ (ε = 4), which is currently used as a capacitor material, cannot store a sufficient amount of accumulated charge, and the memory cannot be miniaturized. There is. In order to avoid this, a method of physically increasing the area with a structure such as a trench type capacitor has been adopted, but the method is extremely complicated and there is a limit even with this method.

Further, in the case of an integrated circuit memory, when an attempt is made to form a thin film dielectric by a vapor phase method such as a sputtering method, a vacuum evaporation method or a CVD method, the stoichiometry of a target dielectric material can be controlled. Since it is difficult, it is difficult to obtain the desired dielectric characteristics.

In the method of forming a dielectric by coating thermal decomposition of a metal compound, a BaTiO ₃ thin film is disclosed in JP-A-61-3.
The 9313 publication describes the dielectric property, and the dielectric constant of about 500 is obtained, but the polarization property is not described. As is well known, the larger the permittivity, the larger the capacity per unit area, and therefore the capacitor can be downsized.

[0012]

The object of the present invention is to have a high relative dielectric constant, a high Curie temperature, and a large spontaneous polarization.
It is an object of the present invention to provide a thin film dielectric having less switching fatigue and a method for manufacturing the same.

[0013]

The present invention comprises the following inventions. [1] having a composition represented by the general formula (1) and having a film thickness of 0.0
A thin film dielectric having a thickness of 2 to 5 μm.

Embedded image Au Cv (Bx M1-x) w Oz (1) (In the formula, A is Ca, Sr, Ba, Pb, Cd, La, C
e, Pr, Nd, Pm, Sm, Eu, Gd, Tb, D
1 selected from y, Ho, Er, Tm, Yb, Lu and Y
Or 2 or more elements, C is Bi, Sc, Sb, Cr, T
1 or 2 or more elements selected from l, B is Ti, T
a, 1 or 2 or more elements selected from Hf, W, Nb and Zr, M is 1 or 2 selected from Fe, Co and Mo
These are the above elements. x is in the range 0 ≦ x <0.99, and u, v, w, and z are determined so that the total charge is zero. )

[2] A method for producing a thin film dielectric by applying a dielectric forming solution on a substrate to form a thin film of the solution, and then subjecting the thin film to a heat treatment to produce a thin film dielectric. The organic solvent and a solution containing the compound of the element A, the compound of the element C, the compound of the element B and the compound of the element M, which are soluble in the organic solvent, as the main components are used. Method for manufacturing thin film dielectric.

In the method for producing a thin film dielectric of the present invention, as a film forming method for forming a dielectric thin film, a dipping method, a spray method, a spinner method, a brush coating method, a CVD method, a sputtering method, a laser abrasion method, etc. The known coating method can be used.

Particularly, a spray method and a spinner method using a compound soluble in an organic solvent are excellent in terms of easy control of chemical composition.

As the compound of the element A soluble in the organic solvent used in the present invention, the following compounds can be exemplified. Element A is Ca, Sr, Ba, Pb, C
d, La, Ce, Pr, Nd, Pm, Sm, Eu, G
It is selected from d, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y.

Examples of the calcium compound include dimethoxy calcium, diethoxy calcium, diisopropoxy calcium, dibutoxy calcium, calcium acetylacetonate, calcium acetate, calcium nitrate and the like.

As the strontium compound, for example,
Examples thereof include dimethoxystrontium, diethoxystrontium, diisopropoxystrontium, dibutoxystrontium, strontium acetylacetonate, strontium acetate, and strontium nitrate.

Examples of the barium compound include dimethoxybarium, diethoxybarium, diisopropoxybarium, dibutoxybarium, barium acetylacetonate, barium acetate and barium nitrate.

Examples of the lead compound include dimethoxy lead, diethoxy lead, diisopropoxy lead, dibutoxy lead, lead acetylacetonate, lead acetate and lead nitrate.

Examples of the cadmium compound include dimethoxycadmium, diethoxycadmium, diisopropoxycadmium, dibutoxycadmium, cadmium acetylacetonate, cadmium acetate, and cadmium nitrate.

Examples of the lanthanum compound include triethoxylanthanum, triisopropoxylanthanum, tributoxylanthanum, lanthanum acetylacetonate, lanthanum acetate and lanthanum nitrate.

Examples of the cerium compound include triethoxycerium, triisopropoxycerium, tributoxycerium, cerium acetylacetonate, cerium acetate, and cerium nitrate.

Examples of the praseodymium compound include triethoxy praseodymium, triisopropoxy praseodymium, tributoxy praseodymium, praseodymium acetylacetonate, praseodymium acetate, praseodymium nitrate and the like.

Examples of the neodymium compound include triethoxyneodymium, triisopropoxyneodymium, tributoxyneodymium, neodymium acetylacetonate, neodymium acetate and neodymium nitrate.

Examples of the promethium compound include triethoxypromethium, triisopropoxypromethium, tributoxypromethium, promethium acetylacetonate, promethium acetate and promethium nitrate.

Examples of the samarium compound include triethoxysamarium, triisopropoxysamarium,
Tributoxy samarium, samarium acetylacetonate, samarium acetate, samarium nitrate and the like can be mentioned.

Examples of the europium compound include triethoxy europium, triisopropoxy europium, tributoxy europium, europium acetylacetonate, europium acetate, europium nitrate and the like.

Examples of the gadolinium compound include triethoxy gadolinium, triisopropoxy gadolinium, tributoxy gadolinium, gadolinium acetylacetonate, gadolinium acetate, gadolinium nitrate and the like.

Examples of the terbium compound include triethoxyterbium, triisopropoxyterbium,
Tributoxy terbium, terbium acetylacetonate, terbium acetate, terbium nitrate and the like can be mentioned.

Examples of the dysprosium compound include triethoxy dysprosium, triisopropoxy dysprosium, tributoxy dysprosium,
Examples include dysprosium acetylacetonate, dysprosium acetate, and dysprosium nitrate.

Examples of the holmium compound include triethoxyholmium, triisopropoxyholmium,
Tributoxy holmium, holmium acetylacetonate, holmium acetate, holmium nitrate and the like can be mentioned.

Examples of the erbium compound include triisopropoxy erbium, erbium nitrate, erbium chloride and the like.

Examples of the thulium compound include triethoxythulium, triisopropoxythulium, tributoxythulium, thulium acetylacetonate, thulium acetate, and thulium nitrate.

Examples of the ytterbium compound include:
Examples thereof include triethoxy ytterbium, triisopropoxy ytterbium, tributoxy ytterbium, ytterbium acetylacetonate, ytterbium acetate, and ytterbium nitrate.

Examples of the lutetium compound include triethoxy lutetium, triisopropoxy lutetium,
Tributoxyltethenium, lutetium acetylacetonate, lutetium acetate, lutetium nitrate and the like can be mentioned.

Examples of the yttrium compound include triethoxy yttrium, triisopropoxy yttrium, tributoxy yttrium, yttrium acetylacetonate, yttrium acetate, and yttrium nitrate.

As the compound of the element C soluble in the organic solvent used in the present invention, the following compounds can be exemplified. The element C is selected from Bi, Sc, Sb, Cr and Tl.

Examples of the bismuth compound include triethoxybismuth, triisopropoxybismuth, tributoxybismuth, bismuth acetylacetonate, bismuth acetate and bismuth nitrate.

Examples of scandium compounds include triethoxy scandium, triisopropoxy scandium, tributoxy scandium, scandium acetylacetonate, scandium acetate, scandium nitrate and the like.

Examples of the antimony compound include triethoxy antimony, triisopropoxy antimony, tributoxy antimony, antimony acetylacetonate, antimony acetate and antimony nitrate.

Examples of the chromium compound include triethoxy chromium, triisopropoxy chromium, tributoxy chromium, chromium acetylacetonate, chromium acetate, chromium nitrate and the like.

Examples of the thallium compound include triethoxythallium, triisopropoxytalium, tributoxythallium, thallium acetylacetonate, thallium acetate, thallium nitrate and the like.

As the compound of the element B soluble in the organic solvent used in the present invention, the following compounds can be exemplified. Element B is Ti, Ta, Hf, W, Nb, Z
It is selected from r.

Examples of the titanium compound include tetraethoxytitanium, tetraisopropoxytitanium, tetrabutoxytitanium, titanium tetrachloride and the like.

Examples of the zirconium compound include tetraethoxyzirconium, tetraisopropoxyzirconium, tetrabutoxyzirconium, zirconium tetrachloride and the like.

Examples of the hafnium compound include tetraethoxy hafnium, tetraisopropoxy hafnium, tetrabutoxy hafnium, hafnium tetrachloride and the like.

Examples of the tantalum compound include pentaethoxy tantalum, pentaisopropoxy tantalum, pentabtox tantalum, tantalum pentachloride and the like.

Examples of the niobium compound include pentaethoxy niobium, pentaisopropoxy niobium, pentabtox niobium, niobium pentachloride and the like.

Examples of the tungsten compound include pentaethoxytungsten, tungsten pentachloride, tungsten hexachloride and the like.

As the compound of the element M soluble in the organic solvent used in the present invention, the following compounds can be exemplified. The element M is selected from Fe, Co and Mo.

Examples of the iron compound include ferrous chloride,
Examples include ferric chloride, ferric nitrate, and iron acetylacetonate.

Examples of the cobalt compound include cobalt chloride, cobalt nitrate, cobalt acetylacetonate, cobalt naphthenate and the like.

Examples of molybdenum compounds include molybdenum chloride, pentaethoxy molybdenum, bisbenzene molybdenum and the like.

As the organic solvent used in the present invention, any solvent may be used as long as it dissolves the compound of the element A, the compound of the element B, the compound of the element C and the compound of the element M. , Preferably alcohols such as methanol, ethanol, propanol, butanol, pentanol, etc., aromatic hydrocarbons such as benzene, toluene, xylene, etc.,

Aliphatic hydrocarbons such as pentane, hexane, heptane and octane, ethers such as dioxane and tetrahydrofuran, ketones such as acetone, methyl ethyl ketone and diethyl ketone, methyl acetate and ethyl acetate,
Carboxylic esters such as ethyl formate, β such as acetylacetone, benzoylacetone and dibenzoylacetone
Examples thereof include amides such as diketones, dimethylformamide, and dimethylacetamide, and these solvents can be used alone or in combination of two or more kinds.

In the manufacturing method of the present invention, first, a dielectric forming solution (coating solution) is prepared. As the preparation method, the compound of the element A, the compound of the element B, the compound of the element C and the compound of the element M are mixed, mixed in an organic solvent at room temperature, or reacted in an organic solvent under heating. Is mentioned. Further, it may be necessary to polymerize the dielectric forming solution in order to improve the film quality of the coating film.

At this time, an appropriate amount of water or a solution prepared by diluting water in an organic solvent at an appropriate ratio may be added during the mixing or the heating reaction.

In the present invention, x in Formula 1 is 0 ≦ x
A real number satisfying <0.99, preferably 0 ≦ x <
0.90, and more preferably 0 ≦ x <0.80. If x is 0.99 or more, desired characteristics cannot be exhibited.

In the present invention, u in the general formula (1),
v, w and z are integers and are determined so that the total charge is zero. That is, for example,

In the case of Au Cv (Bx M1-x) w Oz (1) where A is divalent, C is trivalent, B is tetravalent and M is tetravalent, 2z = 2u + 3v + 4w should be satisfied. To be chosen. Also, A is trivalent, C is trivalent, B is pentavalent, and M is 3.
In case of valence, 2z = 3u + 3v + 5xw + 3 (1-
x) chosen to satisfy w. Usually, 1 ≦ u ≦ 3,
Although 2 ≦ v ≦ 6 and 1 ≦ w ≦ 8, they are not necessarily limited to this range.

The concentration of the compound of various elements in the dielectric forming solution used in the present invention varies depending on the kind of the compound, but is preferably 2 to 80% by weight, more preferably 5 to 50% by weight in terms of oxide. %. If it is excessively diluted, such as less than 2% by weight, it is not preferable because it must be applied many times to obtain a predetermined film thickness, and if it exceeds 80% by weight, workability deteriorates. Usually, it is selected from the above range depending on the intended thickness of the thin film dielectric.

The dielectric forming solution used in the present invention includes
Carboxylic acid (C ₆ -C ₂₀ ), glycol, amine or the like for stabilizing the film thickness can be added. Specifically, caproic acid, caprylic acid, capric acid, lauric acid, palmitic acid, stearic acid: monovalent carboxylic acids such as isostearic acid, adipic acid, pimelic acid, divalent carboxylic acids such as sebacic acid phthalate, ethylene. Glycol,
Glycols such as propylene glycol diethylene glycol, monoethanolamine, diethanolamine,
Examples include amines such as triethanolamine.

These substances are preferably 0.1-3.
It can be added in an amount of 0 mol, more preferably 0.1 to 2.0 mol. If the addition amount is 0.1 mol or less, the effect of stabilizing the film thickness is poor, and if the addition amount is 3.0 mol or more, it is difficult to obtain a dense and smooth film after firing, which is not preferable. Further, a compound of an element such as Mn or Al as a reduction inhibitor for improving the insulation resistance can be added.

In order to make the thickness of the coating film uniform, for example, a polymer substance such as polyol or ethyl cellulose, a high boiling point compound such as methyl cellosolve, ethyl cellosolve, acetylacetone, glycerin, or nonion is added to the dielectric forming solution. A systemic or anionic surfactant or the like can be added.

The dielectric-forming solution thus synthesized is then applied onto the substrate. The substrate used for coating the dielectric forming solution may be any substrate that can withstand a temperature of 400 ° C. or higher, depending on the application. Examples of the substrate include a glass substrate, a ceramic substrate, a semiconductor substrate, a glass or ceramic substrate coated with a metal thin film or a conductive oxide, a semiconductor substrate, and a metal substrate.

Specifically, a quartz glass substrate, alumina,
Substrate such as zirconia, mica, silicon substrate, gold, platinum, palladium, silver, copper, chromium, titanium, aluminum, tantalum, gold-chromium, palladium-silver, platinum-tantalum, platinum-titanium, tin or antimony doped Substrates such as quartz glass, alumina, zirconia, mica, and silicon coated with a thin film such as indium oxide can be used. When used as a memory material for an integrated circuit, it is preferably formed on a gate portion or an electrode of a transistor formed on a Si substrate.

The heat treatment temperature of the thin film obtained by applying the dielectric forming solution varies depending on the concentration of the compound in the solution, the kind of the solvent, the kind of the substrate, etc., but is higher than the crystallization temperature of the target dielectric. Should preferably be about 400 to 1
The temperature is 200 ° C, more preferably about 500 to 1000 ° C. Organic substances do not decompose below 400 ° C, and 1200
When the temperature exceeds ℃, vacancies are generated at the grain boundaries along with remarkable grain growth, and it is difficult to obtain a thin film having good insulating properties. The heat treatment can be performed in air, but if the dielectric is easily reduced, firing in an oxygen atmosphere is preferable.

The thickness of the thin film dielectric of the present invention is 0.02.
˜5 μm, preferably 0.03 to 1 μm. 0.0
If the thickness is less than 2 μm, the withstand voltage is low and dielectric breakdown is likely to occur.
On the other hand, when it exceeds 5 μm, the electrostatic capacity per layer becomes small, which makes it difficult to increase the capacity, which is not preferable.

[0070]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 Titanium tetraisopropoxide 85.2 g (0.3
Mol), bismuth ethoxide 137.6 g (0.4 mol), lanthanum isopropoxide 31.6 g (0.1 mol) and iron acetylacetonate 35.32 g (0.1 mol).
Mol) and mixed with isopropanol / toluene 1: 1
(Weight ratio) Dissolve in mixed solvent and add isostearic acid to T
0.05 mol added to i, concentration of 1 as oxide
A 0 wt% dielectric forming solution was prepared.

This dielectric forming solution was mixed with Pt / Ta / Si.
It was applied on a Si substrate coated with an O ₂ (0.5 / 0.05 / 0.3 μm) film by a spinner under the condition of 2000 rotations. Then, heat treatment was performed in oxygen at 500 ° C. for 30 minutes. This coating and firing operation is repeated twice,
Finally, heat treatment was performed at 900 ° C. for 10 minutes in the atmosphere to obtain a dense and transparent thin film dielectric having a film thickness of 0.2 μm. The composition of the obtained thin film dielectric was LaBi ₄ Ti ₃ FeO.
It was ₁₅ .

After forming an Au electrode (2 mm square) on this dielectric film by sputtering, the relative permittivity and the dielectric loss at 100 KHz and 25 ° C. were measured by Yokogawa Hewlett Packard LCR meter 4284A. Also,
Using a super insulation resistance meter YHP4329A, the insulation resistance when DC 10V was applied was measured. As a result, the relative permittivity is 10
0, the spontaneous polarization was 4 μC / cm ² . Moreover, the insulation resistance was large and the leak current was small, and it was a good insulating material.

Example 2 Bismuth ethoxide 68.8 g (0.2 mol), tantalum ethoxide 40.6 g (0.1 mol), molybdenum pentaethoxide 32.14 g (0.1 mol) and strontium ethoxide 1 0.78 g (0.1 mol) was dissolved in a hexane / methyl cellosolve mixed solvent to prepare a dielectric-forming solution having a concentration of 10% by weight in terms of oxide.

This dielectric forming solution was added to Pt / Ti / SiO 2.
S coated with ₂ (0.5 / 0.06 / 0.3 μm) film
The number of rotations of the spinner and the number of coatings were adjusted so that the film thickness was 0.1 μm on the i substrate. Then, heat treatment was performed in air at 950 ° C. for 10 minutes to obtain a transparent thin film dielectric. The composition of the obtained thin film dielectric is SrBi ₂ T
It was aMoO ₉ .

After forming an Au electrode (2 mm square) on this dielectric film by sputtering, the relative permittivity and the dielectric loss at 100 KHz and 25 ° C. were measured by Yokogawa Hewlett Packard LCR meter 4284A. Moreover, the insulation resistance when a direct current of 10 V was applied was measured using a super insulation resistance meter YHP4329A. As a result, the relative dielectric constant was 90 and the spontaneous polarization was 4 μC / cm ² . Moreover, the insulation resistance was large and the leak current was small, and it was a good insulating material.

[0077]

EFFECTS OF THE INVENTION The thin film dielectric of the present invention is superior in dielectric properties such as relative permittivity, temperature coefficient of relative permittivity, memory retention, switching fatigue property and leak current property to the conventional dielectrics. And its industrial value is enormous.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H01B 3/12 H01B 3/12 H01G 4/33 7924-5E H01G 4/06 102

Claims (2)

[Claims] 1. A thin-film dielectric having a composition represented by the general formula (1) and having a film thickness of 0.02 to 5 μm. Embedded image Au Cv (Bx M1-x) w Oz (1) (In the formula, A is Ca, Sr, Ba, Pb, Cd, La, C
e, Pr, Nd, Pm, Sm, Eu, Gd, Tb, D
1 selected from y, Ho, Er, Tm, Yb, Lu and Y
Or 2 or more elements, C is Bi, Sc, Sb, Cr, T
1 or 2 or more elements selected from l, B is Ti, T
a, 1 or 2 or more elements selected from Hf, W, Nb and Zr, M is 1 or 2 selected from Fe, Co and Mo
These are the above elements. x is in the range 0 ≦ x <0.99, and u, v, w, and z are determined so that the total charge is zero. ) 2. A method for producing a thin film dielectric by applying a dielectric forming solution on a substrate to form a thin film of the solution, and then subjecting the thin film to a heat treatment to produce a thin film dielectric, wherein the dielectric forming solution is an organic material. 2. The thin film dielectric according to claim 1, wherein a solution containing a compound of the element A, a compound of the element C, a compound of the element B and a compound of the element M as a main component, which is soluble in the solvent and the organic solvent, is used. Body manufacturing method.