JP3129175B2 - Method for manufacturing (Ba, Sr) TiO3 thin film capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to (Ba, Sr) Ti
O ₃ relates to a method of manufacturing a thin film capacitor, in particular, useful for a semiconductor integrated circuit or the like, a high dielectric constant high insulation (Ba, S
r) it relates to a method for producing TiO ₃ thin film capacitor.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of capacitor elements and the high integration of semiconductor integrated circuits, a material having a high dielectric constant is required for a capacitor insulating film.

Conventionally, materials such as SiO ₂ , Si ₃ N ₄ and Al ₂ O ₃ have been used for thin film capacitors used for integrated circuits and the like. While these substances have high insulating properties, their relative dielectric constants are as small as about 10.

The capacitance of a capacitor is proportional to the relative permittivity and the surface area (electrode area), and is inversely proportional to the film thickness.
Accordingly, there is a limit to the reduction of the film thickness in order to reduce the size of the thin film capacitor, and a dielectric material having a large relative dielectric constant is required.

As a substance having a large relative dielectric constant, conventionally, BaTiO ₃ , SrT having a perovskite type crystal structure is used.
_{iO 3, (Ba 1-x} Sr x) and barium titanate-based dielectric material such as TiO ₃ is focused, as its thin film forming method, a sputtering method, a sol-gel method, and a CVD method. Specifically, the following has been proposed.

(I) A composition for forming a barium titanate thin film by dissolving a barium lower carboxylate (preferably barium acetate) and titanium isopropoxide in an organic solvent containing ethylene glycol monomethyl ether, and contacting water with the dissolved solution. (JP-A-1-1000024).

(Ii) BaCO ₃ , SrCO ₃ and TiO
A method of calcining the mixed powder of No. ₂ at 800 to 1000 ° C. and using it as a target, and forming a (Ba _1-x Sr _x ) TiO ₃ thin film by a sputtering method at a substrate temperature of 400 to 600 ° C.

[0008] JP-A-7-17713 discloses that
As a dielectric thin film having a high dielectric constant and good insulation properties, (B
a, Sr) Mn in TiO ₃ based dielectric, Pb, those obtained by adding a rare earth element has been proposed.

[0009]

In a substance having a perovskite structure having a high dielectric constant, carriers due to defects are easily generated. In particular, a (Ba _1-x Sr _x ) TiO ₃ -based material has a high relative dielectric constant. Since there is a tendency that the larger the leakage current is, the countermeasures are required.

In the sol-gel method using a lower carboxylate as a raw material as in the method described in Japanese Patent Application Laid-Open No. 1-1000024, high-temperature sintering of 800 ° C. or more is required during crystallization, and the insulation property is deteriorated due to this high temperature However, it has not been practically used due to the large leakage current. It is considered that the deterioration of the insulating property is caused by generation of minute cracks and voids in the thin film due to abrupt shrinkage of the film due to high-temperature baking and deterioration of the lower electrode. In this sol-gel method, there is a method of forming a thin film using a raw material having a relatively low thermal decomposition temperature while keeping the heat treatment temperature as low as possible. However, this does not solve the problem of a decrease in the relative dielectric constant.

Even when a BST thin film is formed by a sputtering method, a film forming temperature of 700 ° C. or more is required to obtain a high relative dielectric constant. However, when the substrate temperature is 600 ° C. or more, the leak characteristics deteriorate. This is disclosed in Japanese Unexamined Patent Publication No. 3-257020.

As described above, in a substance having a perovskite structure having a high dielectric constant, carriers due to defects are particularly likely to occur, and the higher the relative dielectric constant, the larger the leak current tends to be. It is considered difficult to achieve both dielectric constant and high insulation.

In the dielectric thin film described in JP-A-7-17713 to which Mn, Pb and rare earth elements are added, when these elements are added, an integrated circuit may cause a malfunction of a semiconductor (transistor). There is.

The present invention solves the above-mentioned conventional problems, improves the dielectric constant without lowering the relative dielectric constant, ie, the capacitance of the capacitor, and is effective for various uses in electronic devices (Ba, Sr) TiO _3. and to provide a method of manufacturing a thin film capacitor.

[0015]

According to the first aspect of the present invention, (Ba, S
r) The manufacturing method of the TiO ₃ thin film capacitor is
Part electrode, dielectric thin film and upper electrode
A method for manufacturing a membrane capacitor, comprising:
Upon formation, (Ba _1-x Sr _x ) TiO ₃ (where
0 ≦ x ≦ 1.0) and a main component represented by
Containing 0.1 to 10 mol% of Si component as Si
Machine metal compound solution, applied on the lower electrode, dried
After calcining, by calcining at 450 to 800 ° C,
(Ba _1-x Sr _x ) TiO ₃ (where 0 ≦ x ≦ 1.
0) and the main component represented by Si
Perovskite comprising 0.1 to 10 mol% of Si component
A dielectric thin film having a gate structure .

The (Ba, Sr) TiO ₃ thin film of claim 2
The method of manufacturing capacitors consists of a lower electrode and a dielectric thin film on a substrate.
And a top electrode are sequentially laminated to manufacture a thin film capacitor
In forming the dielectric thin film, (Ba)
_1−x Sr _x ) TiO ₃ (where 0 ≦ x ≦ 1.0)
A main component represented by 0.1% as Si with respect to the main component.
Using a target containing 10 to 10 mol% of a Si component,
Sputtering on the lower electrode at a substrate temperature of 400 to 800 ° C
It is characterized by performing a ring.

(Ba _1-x Sr _x ) TiO ₃ (where,
0 ≦ x ≦ 1. By adding 0.1 to 10 mol% of Si component as Si to the main component of the perovskite structure represented by 0) , sinterability at the time of heat treatment is improved, and as a result, relatively At a low processing temperature, it is possible to form a (Ba, Sr) TiO ₃ thin film capacitor having a high dielectric constant (high capacity), a high insulating property (low leakage current density), and an excellent pressure resistance .

By the calcination of claim 1 , the Si component becomes a Si oxide.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

(Ba, Sr) TiO manufactured by the present invention
_{The three} thin-film capacitors are made of (Ba _1-x Sr _x ) TiO
₃ A dielectric thin film having a perovskite structure comprising a main component represented by 0 (x ≦ 1.0) and a Si component of 0.1 to 10 mol% as Si with respect to the main component. Things.

In this dielectric thin film, if the ratio of the Si component to the above main component is less than 0.1 mol% as Si, the effect of improving the sinterability due to the incorporation of Si is not sufficient, and the insulating property is low and the leakage is low. The current becomes large. When the Si component exceeds 10 mol% as Si with respect to the above-mentioned main component, the insulating property is excellent, but the capacitance becomes small.
Therefore, Si is 0.1 to 10 mol% based on the above main component.
And

Such a dielectric thin film can be formed by the following method according to the method of the present invention.

Sol-gel method: (Ba _1-x Sr _x ) T
An organometallic compound solution containing a main component represented by iO ₃ (where 0 ≦ x ≦ 1.0) and a Si component of 0.1 to 10 mol% as Si with respect to the main component was added to the lower part. After coating on the electrode, drying and calcining, baking is performed at 450 to 800 ° C.

Sputtering method: (Ba _1-x Sr
_x ) using a target containing a main component represented by TiO ₃ (where 0 ≦ x ≦ 1.0) and a Si component of 0.1 to 10 mol% as Si with respect to the main component, Temperature 4
Sputtering is performed on the lower electrode at 00 to 800 ° C.

In the sol-gel method described above, first, barium carboxylate is used as a Ba raw material,
Using strontium carboxylate as a raw material, titanium alkoxide as a Ti raw material, and silicon alkoxide as a Si raw material, so that these have a predetermined composition,
A solution of an organometallic compound prepared by mixing and dissolving in an organic solvent is applied to a lower electrode formed on a substrate by a spin coating method or the like.

Barium carboxylate and / or thin film raw material
Alternatively, as an acyloxy group forming strontium carboxylate, a general formula C _n H _{2n + 1} COO ⁻ (however,
n is an integer of 3 to 7), specifically, n-
Butyric acid, α-methylbutyric acid, i-valeric acid, 2-ethylbutyric acid,
2,2-dimethylbutyric acid, 3,3-dimethylbutyric acid, 2,3
-Dimethylbutyric acid, 3-methylpentanoic acid, 4-methylpentanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid, 2,2-dimethylpentanoic acid, 3,3-dimethylpentanoic acid, 2,3-dimethylpentane It is preferable to use an acyloxy group derived from an acid, 2-ethylhexanoic acid, or 3-ethylhexanoic acid.

In the above general formula, when n is 2 or less, a carbonate is easily formed at the time of thermal decomposition. Conversely, when n is 8 or more,
The change in weight due to evaporation of the organic components is large, and a homogeneous film without cracks cannot be formed.

The acyloxy groups of barium carboxylate and strontium carboxylate may be the same or different.

On the other hand, examples of the titanium alkoxide include titanium alkoxides of linear or branched alcohols having 2 to 5 carbon atoms, for example, titanium ethoxide, titanium isopropoxide, titanium butoxide, and titanium amiloxide. It is preferable to use titanium isopropoxide since the reaction rate is appropriate.

Examples of the silicon alkoxide include silicon alkoxides of linear or branched alcohols having 1 to 5 carbon atoms, for example, silicon tetramethoxide, silicon tetraethoxide, silicon tetrabutoxide, and silicon tetraamyloxide. However, it is particularly preferable to use silicon tetraethoxide because of its moderate reaction rate.

As the organic solvent for dissolving these thin film materials, an ester and / or an alcohol, or a mixed solvent obtained by further mixing a carboxylic acid with the ester and / or an alcohol can be used.

Examples of the ester of the organic solvent include ethyl acetate, propyl acetate, n-butyl acetate, sec-butyl acetate, tert-butyl acetate, isobutyl acetate and n-acetate.
Amyl, sec-amyl acetate, tert-amyl acetate,
It is preferable to use isoamyl acetate, and as the alcohol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, iso-butyl alcohol,
-Pentanol, 2-pentanol, 2-methyl-2-
Pentanol and iso-amyl alcohol are preferably used. Further, as the carboxylic acid, it is preferable to use a carboxylic acid containing an acyloxy group constituting the barium carboxylate and / or strontium carboxylate.

In the present invention, barium carboxylate, strontium carboxylate and titanium alkoxide as thin film raw materials are added to such an organic solvent at a predetermined compositional ratio so that the total concentration in terms of oxide is 4 to 10% by weight. And a predetermined amount of silicon alkoxide is added and mixed.

The solution of the organometallic compound prepared as described above is applied on the lower electrode of the substrate, and dried, pre-baked, and main-baked. If the desired film thickness cannot be obtained by one application, the steps of application, drying, and preliminary firing are repeated a plurality of times, and then main firing is performed. Here, the preliminary firing is performed at 150 to 400 ° C., and the final firing is performed at 450 to 80 ° C.
This is performed at 0 ° C. for about 30 minutes to 2 hours.

On the other hand, in the sputtering method,
Specifically, first, barium carbonate (BaCO ₃ ), strontium carbonate (SrCO ₃ ), titanium dioxide (TiO 2)
₂ ) and silicon dioxide (SiO ₂ ) are mixed so as to have a predetermined composition, and calcined at 800 to 1000 ° C. to produce a powder target. Then, using this target, a dielectric thin film having a desired thickness is formed on the lower electrode formed on the substrate by a sputtering method. The sputtering conditions were such that the substrate temperature was 400 to 800 ° C., and the sputtering gas was Ar: 1 × 10 ⁻² to 1 × 10 ⁻⁵ Torr, O ₂ :
It is preferably performed at 1 × 10 ⁻² to 1 × 10 ⁻⁵ Torr.

In the present invention, the dielectric thin film preferably has a thickness of about 500 to 3000 °.

In the present invention, silicon, sapphire, quartz glass, zirconia or the like can be used as the substrate. The lower electrode and the upper electrode formed on the substrate include platinum, gold, silver, copper, chromium, aluminum, tantalum, iridium, ruthenium, platinum-
Titanium, platinum-tantalum, platinum-iridium and the like are generally used, and these electrodes are usually formed by a sputtering method.

[0038]

The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Examples 1 to 5 On a silicon substrate, a platinum film was formed as a lower electrode by a sputtering method, and a dielectric thin film was formed thereon by the following procedure.

That is, first, barium 2-ethylhexanoate, strontium 2-ethylhexanoate and titanium isopropoxide were used and their composition ratio (Ba _1−x S
r _x ) In TiO ₃ , x was dissolved in an organic solvent of isoamyl acetate so that x had a value shown in Table 1 and a total concentration in terms of oxide of the composition was 7% by weight. .

Further, silicon tetraethoxide was further added to this solution at a ratio of 5 mol% as Si with respect to the main component of (Ba _1-x Sr _x ) TiO ₃ , and then refluxed for 1 hour. The composition for thin film formation was prepared by homogenization.

The composition for forming a thin film is applied on the lower electrode by spin coating, dried, and temporarily baked at 300 ° C. for 10 minutes. The coating, drying and calcination steps are repeated, and finally at 600 ° C. for 0.5 hour. By firing, a (Ba _1-x Sr _x ) TiO ₃ dielectric thin film having a thickness of 2000 ° was formed.

On this dielectric thin film, a platinum film was formed as an upper electrode by a sputtering method to produce a thin film capacitor.

The capacitance, leak current density and dielectric loss of the obtained thin film capacitor were measured, and the results are shown in Table 1.

Examples 6 and 7, Comparative Examples 1 and 2 Thin film capacitors were produced in the same manner as in Example 3 except that the amount of Si added was set to the value shown in Table 1 (no Si was added in Comparative Example 1). And the obtained thin film capacitor's capacitance,
The leakage current density and the dielectric loss were measured, and the results are shown in Table 1.

[0046]

[Table 1]

Examples 8 to 12 On a silicon substrate, a platinum film was formed as a lower electrode by a sputtering method, and a dielectric thin film was formed thereon by the following procedure.

That is, first, BaCO ₃ , SrCO ₃ and TiO ₂ are weighed such that x becomes a value shown in Table 2 in a composition ratio (Ba _1−x Sr _x ) TiO ₃ .
(Ba _1-x Sr _x ) SiO ₂ was weighed so that the content of Si was 10 mol% with respect to the main component of TiO ₃ , and these were mixed and calcined at 900 ° C. to produce a powder target.
Using this target, a (Ba _1-x Sr _x ) Ti having a thickness of 2000 ° is formed on the lower electrode by a sputtering method.
An O ₃ dielectric thin film was formed. The substrate temperature was 600 ° C.
And the sputtering gas is Ar: 1.4 × 10 ⁻⁴ Torr
r, O ₂ : 8.0 × 10 ⁻⁵ Torr.

On this dielectric thin film, a platinum film was formed as an upper electrode by a sputtering method to produce a thin film capacitor.

The capacitance, leak current density and dielectric loss of the obtained thin film capacitor were measured, and the results are shown in Table 2.

Examples 13 and 14, Comparative Examples 3 and 4 Thin-film capacitors were produced in the same manner as in Example 10 except that the amount of Si added was set to the value shown in Table 2 (in Comparative Example 3, no Si was added). Then, the capacitance, leakage current density and dielectric loss of the obtained thin film capacitor were measured, and the results were shown in Table 2.
It was shown to.

[0052]

[Table 2]

As is apparent from Tables 1 and 2, according to the present invention, by forming a dielectric thin film in which a predetermined amount of Si is blended in the (Ba _1-x Sr _x ) TiO ₃ perovskite structure, the capacitance can be increased. It is possible to obtain a thin film capacitor which is large and has excellent insulation properties.

[0054]

As described in detail above, (Ba, S) of the present invention
According to the manufacturing method of r) TiO ₃ thin film capacitor, is useful as a capacitor material for various applications in electronic devices, high capacity and high insulating thin film capacitor is provided.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI H01L 21/822 H01L 27/04 C 21/8242 27/04 (56) References JP-A-5-217425 (JP, A) JP-A-3-11716 (JP, A) JP-A-5-47213 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 27/108 C01G 23/00 C04B 35/46 H01G 4/12 397 H01G 4/33 H01L 21/822 H01L 21/8242 H01L 27/04

Claims (2)

(57) [Claims] A method of manufacturing a thin film capacitor by sequentially forming a lower electrode, a dielectric thin film and an upper electrode on a substrate.
In forming the dielectric thin film, (Ba _1−x S
r _x ) an organometallic compound solution containing a main component represented by TiO ₃ (where 0 ≦ x ≦ 1.0) and a Si component of 0.1 to 10 mol% as Si with respect to the main component. After coating on the lower electrode, drying and calcining,
(Ba _1-x Sr _x ) TiO 2
₃ (where 0 ≦ x ≦ 1.0)
0.1 to 10 mol% of Si as a Si component
Dielectric thin film with perovskite structure
Forming a (Ba, Sr) TiO ₃ thin film capacitor. 2. A method of manufacturing a thin film capacitor by sequentially laminating a lower electrode, a dielectric thin film and an upper electrode on a substrate, wherein (Ba _1−x S
r _x ) Using a target containing a main component represented by TiO ₃ (where 0 ≦ x ≦ 1.0) and a Si component of 0.1 to 10 mol% as Si with respect to the main component, at a substrate temperature of 400 to 800 ° C. and performing sputtering on the lower electrode (Ba, Sr) TiO ₃ method of manufacturing a thin film capacitor.