JP6102358B2 - Dielectric thin film forming composition - Google Patents

Description

The present invention relates to a suitable dielectric thin film-forming composition to form a PLZT dielectric thin film used in the dielectric layer such as a thin film capacitor.

Thin films used for dielectric layers of thin film capacitors include strontium titanate (SrTiO ₃ ), barium strontium titanate (hereinafter referred to as “BST”), lead titanate (hereinafter referred to as “PT”), zirconate titanate. Lead (hereinafter referred to as “PZT”), fourth component added lead zirconate titanate represented by lanthanum-added lead zirconate titanate (hereinafter referred to as “PLZT”), etc. Dielectric thin films formed from these perovskite oxides have attracted attention. Moreover, as a method for forming a dielectric thin film, in addition to a chemical vapor deposition method such as a physical vapor deposition method such as a vacuum deposition method, a sputtering method, a laser ablation method, or a CVD (Chemical Vapor Deposition) method, A chemical solution method (Chemical Solution Deposition, CSD method) such as a sol-gel method is used (for example, see Patent Document 1). In particular, the sol-gel method does not require a vacuum process as compared with the CVD method, the sputtering method, and the like, and thus has an advantage that the manufacturing cost is low and it can be easily formed on a substrate having a large area. Moreover, by changing the composition in the solution material used to form the dielectric thin film, it is easy to make the composition in the film a theoretical ratio, and an extremely thin dielectric thin film can be obtained. It is expected as a method of forming.

  Also, as a method of forming a PLZT dielectric thin film by the sol-gel method, in order to eliminate the adverse effect on the transistor of the device and its peripheral circuit due to the heat treatment, firing for crystallization after coating the composition on the substrate A method of forming a PLZT dielectric thin film that has been realized at a very low temperature is disclosed (for example, see Patent Document 2).

  In this formation method, in addition to the organometallic compound for forming the metal oxide A composed of Pb, La, Zr, Ti, and O in the dielectric thin film after the formation, other materials composed of Bi, Si, Pb, Ge, etc. By using a liquid composition to which an organometallic compound for forming the metal oxide B is added, the firing temperature is drastically reduced.

JP-A-60-236404 (page 6, upper right column, line 10 to lower left column, line 3) Japanese Patent No. 4329287 (Claim 1, Claim 12, Paragraph [0010] to Paragraph [0013])

  On the other hand, in the formation of the dielectric thin film by the CSD method, in addition to the problem of lowering the firing temperature described in Patent Document 2, the characteristics as a capacitor, that is, the capacitance, the dielectric strength characteristics, etc. are sufficiently obtained. Research and development for drawing out is still active. It is thought that the metal composition in the dielectric thin film is most responsible for these characteristics in the capacitor, and the difference in these compositions greatly changes the characteristics of the capacitor. There are a large number of documents that disclose the above.

  However, in the case of a PLZT dielectric thin film, it is very difficult to select an optimum composition because there are particularly four main constituent elements, Pb, La, Zr, and Ti. Therefore, even if the composition disclosed in the prior art is adopted, the characteristics required at that time cannot be sufficiently obtained, or the capacitor is required due to a slight difference in these compositions. There has been a problem that any one of the plurality of characteristics is greatly deteriorated. For this reason, in the film formation of the PLZT dielectric thin film by the CSD method, development of a material having a composition capable of simultaneously improving a plurality of characteristics as a capacitor, a film formation method, and the like has been required.

As a result of intensive studies, the present inventors have found a composition of a composition for forming a PLZT dielectric thin film having a composition in which any of a plurality of characteristics required as a capacitor is improved to a satisfactory value.
It is an object of the present invention to provide, among other characteristics as a thin film capacitor, when used for a dielectric layer of a thin film capacitor, in particular, a capacitance change rate, a withstand voltage, and a capacitance characteristic when a voltage is changed. It is to provide a composition for forming a PLZT dielectric thin film that can be improved.

A first aspect of the present invention is an organometallic compound-containing composition for forming a PLZT dielectric thin film , wherein the PLZT dielectric thin film is a thin film used for a dielectric layer of a thin film capacitor, and is included in the composition When the sum of Zr atoms and Ti atoms is 100, the atomic ratio Zr / Ti of Zr atoms and Ti atoms is 70/30 to 80/20, and the sum of Pb atoms and La atoms is 103 to 107 , and wherein the La atom is 9-12.

The composition for forming a dielectric thin film according to the first aspect of the present invention is an organometallic compound-containing composition for forming a PLZT dielectric thin film used for a dielectric layer of a thin film capacitor , and is contained in the composition. When the sum of atoms and Ti atoms is 100, the atomic ratio Zr / Ti of Zr atoms and Ti atoms is 70/30 to 80/20, the sum of Pb atoms and La atoms is 103 to 107 , and La atom is 9-12. Thus, the dielectric thin film-forming composition, the use in the formation of the dielectric layer of the thin-film capacitor, of the characteristics of the thin film capacitor, in particular, the capacity change rate when varying voltage, withstand voltage In addition, the capacitance characteristics can be improved at the same time.

It is a cross-sectional block diagram which shows the laminated structure of a general thin film capacitor.

  Next, the form for implementing this invention is demonstrated.

The composition for forming a dielectric thin film of the present invention is an improvement of a composition containing an organometallic compound for forming a PLZT dielectric thin film, that is, a dielectric thin film composed of lanthanum-doped lead zirconate titanate. The characteristic configuration is that the PLZT dielectric thin film is a thin film used for a dielectric layer of a thin film capacitor, and when the sum of Zr atoms and Ti atoms contained in the composition is 100, atoms of Zr atoms and Ti atoms The ratio Zr / Ti is 70/30 to 80/20, the sum of Pb atoms and La atoms is 103 to 107 , and La atoms are 9 to 12. Thereby, if this composition is used, the capacity | capacitance change rate when a voltage is changed is small, and the thin film capacitor etc. which have a high withstand voltage and an electrostatic capacitance can be manufactured.

Here, when the sum of Zr atoms and Ti atoms contained in the composition is taken as 100, the atomic ratio Zr / Ti of Zr atoms and Ti atoms is set in the above range because the capacity change occurs when the atomic ratio is less than the lower limit. This is because there is a problem that the rate increases, and on the other hand, if the upper limit value is exceeded, a problem that the withstand voltage decreases is caused. In addition, when the sum of Zr atoms and Ti atoms contained in the composition is 100, the sum of Pb atoms and La atoms is in the above range, and the La atom is in the above range is the sum of Pb atoms and La atoms. If the value is less than the lower limit, for example, a problem such as a significant decrease in the capacitance C _0V when the applied voltage is 0V occurs, and if the value exceeds the upper limit, a problem such as a decrease in dielectric strength occurs. Further, if the La atom is less than the lower limit value, there is a problem that the capacity change rate increases. On the other hand, if the La atom exceeds the upper limit value, the capacitance itself is small and insufficient .

  The organometallic compound contained in the composition for forming a dielectric thin film of the present invention is an organometallic compound of lead, lanthanum, titanium and zirconium, and each of the metal elements of Pb, La, Zr and Ti has an organic group whose oxygen. Or the compound couple | bonded through a nitrogen atom is suitable. Specifically, selected from the group consisting of these metal alkoxides, metal diol complexes, metal triol complexes, metal carboxylates, metal β-diketonate complexes, metal β-diketoester complexes, metal β-iminoketo complexes or metal amino complexes. 1 type or 2 types or more were mentioned. Particularly preferred compounds are metal alkoxides, partial hydrolysates or organic acid salts thereof. Among these, as the Pb compound and La compound, acetates such as lead acetate and lanthanum acetate, and alkoxides such as lead diisopropoxide and lanthanum triisopropoxide are particularly preferable. On the other hand, the Ti compound is particularly preferably an alkoxide such as titanium tetraethoxide, titanium tetraisopropoxide, titanium tetrabutoxide, titanium dimethoxydiisopropoxide. The Zr compound is preferably an alkoxide similar to the Ti compound. Although the metal alkoxide may be used as it is, a partially hydrolyzed product thereof may be used in order to promote decomposition.

  These lead compounds, lanthanum compounds, titanium compounds and zirconia compounds are dissolved in an organic solvent so that the Pb atom, La atom, Zr atom and Ti atom in the composition satisfy the above range. Examples of the organic solvent include carboxylic acids, alcohols (eg, propylene glycol which is a polyhydric alcohol), esters, ketones (eg, acetone, methyl ethyl ketone), ethers (eg, dimethyl ether, diethyl ether), cycloalkanes (eg, , Cyclohexane, cyclohexanol), aromatic (for example, benzene, toluene, xylene), other tetrahydrofuran, or a mixed solvent of two or more of these.

  Specific examples of the carboxylic acid include 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-dimethylpentanoic acid, 2- It is preferable to use ethylhexanoic acid or 3-ethylhexanoic acid.

  As the ester, ethyl acetate, propyl acetate, n-butyl acetate, sec-butyl acetate, tert-butyl acetate, isobutyl acetate, n-amyl acetate, sec-amyl acetate, tert-amyl acetate, isoamyl acetate are used. As the alcohol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, iso-butyl alcohol, 1-pentanol, 2-pentanol, 2-methyl-2-pentanol, 2-methoxy It is preferred to use ethanol.

  The total concentration of the organometallic compound in the composition for forming a dielectric thin film is preferably a concentration at which the PLZT oxide equivalent concentration in 100% by mass of the solution is 5 to 20% by mass. If it is less than the lower limit, the film thickness per application becomes thin, so that it becomes difficult to form a dielectric thin film having a desired film thickness. On the other hand, if the upper limit is exceeded, the dielectric thin film after firing Since cracks may occur, it is not preferable.

  Further, β-diketones (for example, acetylacetone, heptafluorobutanoylpivaloylmethane, dipivaloylmethane, trifluoroacetylacetone, benzoylacetone, etc.), β-ketone acids (for example, , Acetoacetic acid, propionylacetic acid, benzoylacetic acid, etc.), β-ketoesters (for example, lower alkyl esters of the above ketone acids such as methyl, propyl, butyl, etc.), oxyacids (for example, lactic acid, glycolic acid, α-oxybutyric acid) , Salicylic acid, etc.), lower alkyl esters of the above oxyacids, oxyketones (eg, diacetone alcohol, acetoin, etc.), diols, triols, higher carboxylic acids, alkanolamines (eg, diethanolamine, triethanolamine, monoethanolamine) ), Valence amines, may be added from 0.2 to 3 approximately at (stabilizer number of molecules) / (number of metal atoms).

  The prepared composition is filtered to remove particles, and the number of particles having a particle size of 0.5 μm or more (especially 0.3 μm or more, especially 0.2 μm or more) is 50 per 1 mL of the composition. / ML or less is preferable. When the number of particles having a particle diameter of 0.5 μm or more in the composition exceeds 50 / mL, long-term storage stability is deteriorated. The smaller the number of particles having a particle size of 0.5 μm or more in the composition, the more preferable, and particularly preferably 30 particles / mL or less.

  Although the method of processing the composition after preparation is not specifically limited so that it may become the said particle number, For example, the following methods are mentioned. The first method is a filtration method in which a commercially available membrane filter having a pore size of 0.2 μm is used and pressure-fed with a syringe. The second method is a pressure filtration method in which a commercially available membrane filter having a pore size of 0.05 μm and a pressure tank are combined. The third method is a circulation filtration method in which the filter used in the second method and the solution circulation tank are combined.

  In any method, the particle capture rate by the filter varies depending on the solution pressure. It is generally known that the lower the pressure, the higher the capture rate. In particular, in the first method and the second method, the number of particles having a particle size of 0.5 μm or more is set to 50 or less. In order to achieve, it is preferable to pass the solution through the filter very slowly at low pressure.

  Next, a method for forming a PLZT dielectric thin film using the dielectric thin film forming composition of the present invention will be described. Here, a method for manufacturing a thin film capacitor will be described as an example, and the manufacturing process will be described.

First, the composition for forming a dielectric thin film prepared above is applied to the lower electrode 14. As shown in FIG. 1, the lower electrode 14 is generally an Si film on which an insulating film 12 such as a thermal oxide film (SiO ₂ ) and an adhesion layer 13 for improving adhesion between the lower electrode 14 and its lower layer are formed. It is formed on a substrate 11 such as a substrate via these layers or films. For the formation of the lower electrode 14, a noble metal material such as Pt, Ru, or Ir, which hardly causes an oxidation reaction by heat treatment, is preferably used, and a vapor phase growth method such as a sputtering method or a vacuum evaporation method, or an electrode paste is used. Various methods such as a screen printing method, a spray method, and a droplet discharge method can be used.

Specifically, the support 20 having the substrate 11, the insulator film 12 formed on the substrate 11, and the lower electrode 14 formed on the insulator film 12 via the adhesion layer 13 is made of Pt / Ti / SiO ₂ / Si, Pt / TiO ₂ / SiO ₂ / Si, Pt / IrO / Ir / SiO ₂ / Si, Pt / TiN / SiO ₂ / Si, Pt / Ta / SiO ₂ / Si, Pt / Ir / An example of a laminated structure of SiO ₂ / Si (lower electrode / adhesion layer / insulator film / substrate) is shown. For coating the dielectric thin film forming composition onto the lower electrode 14, a conventional coating method such as spin coating, dip coating, spray coating, or LSMCD (Liquid Source Misted Chemical Deposition) can be suitably used. However, the spin coating method is particularly preferable because the film thickness can be easily adjusted.

  After the composition for forming a dielectric thin film is applied on the lower electrode 14, temporary baking (including drying) is performed to form a coating film. And the dielectric thin film 16 is formed by carrying out the main baking of the board | substrate 11 with which the coating film was formed. The steps from coating to pre-baking may be performed once, but preferably may be formed to a desired thickness by repeating 4 to 12 times.

  The preliminary calcination is preferably performed in an oxidizing atmosphere or a steam-containing atmosphere because it is performed to remove the solvent and thermally decompose or hydrolyze the organometallic compound to convert it into an amorphous composite oxide. Even in heating in the inside, the water necessary for hydrolysis is sufficiently ensured by the humidity in the air, so it may be carried out in the atmosphere. Pre-baking is preferably performed at 150 to 550 ° C. for 1 to 10 minutes using a hot plate or the like.

The main baking is a process for baking and crystallizing the thin film obtained by the preliminary baking at a temperature equal to or higher than the crystallization temperature, whereby a dielectric thin film is obtained. The firing atmosphere in this crystallization step is preferably O ₂ , N ₂ , Ar, N ₂ O, H _2, or a mixed gas thereof. Moreover, it is preferable to perform this baking at 450-800 degreeC for 1 to 60 minutes using rapid heat processing (RTA process) etc. Further, the rate of temperature rise is preferably 10 to 100 ° C./second.

  Through the above steps, the PLZT dielectric thin film of the present invention can be formed. The thickness of the PLZT dielectric thin film 16 of the present invention obtained after the main firing is 200 to 500 nm. The reason for limiting the thickness of the dielectric thin film to this range is that if the thickness of the dielectric thin film is less than the lower limit value, the dielectric withstand voltage is essentially insufficient, while if the upper limit value is exceeded, cracks occur. This is because the insulation breakdown voltage is reduced.

  Subsequent to the formation of the dielectric thin film 16, the upper electrode 17 is formed on the dielectric thin film 16 to obtain the thin film capacitor 10. The upper electrode 17 is also preferably made of the noble metal material used to form the lower electrode 14 and can be formed by the various methods described above. It is preferable to form by the method. Through the above steps, the PLZT dielectric thin film of the present invention and a thin film capacitor including this dielectric thin film as a dielectric layer are obtained.

  In this embodiment, the method for forming the dielectric thin film of the present invention has been described by taking the method for forming the dielectric layer of the thin film capacitor as an example. However, the PLZT dielectric thin film of the present invention is a dielectric of the above-described thin film capacitor. In addition to applications as layers, IPD, DRAM memory capacitors, multilayer capacitors, transistor gate insulators, nonvolatile memories, pyroelectric infrared detection elements, piezoelectric elements, electro-optic elements, actuators, resonators, ultrasonic motors, It can be used as a constituent material when manufacturing a composite electronic component of an electric switch, an optical switch, or an LC noise filter element.

Next, examples of the present invention will be described in detail together with comparative examples. Examples 1 , 3 , 6, 7 and 9 to 12 shown below are not examples but are reference examples.

<Example 1>
First, 2-methoxyethanol which had been sufficiently dehydrated as an organic solvent was prepared, Pb compound and Pb and La acetates as La compound were dissolved therein, and crystal water was removed by azeotropic distillation. Then, Zr tetrabutoxide as a Zr compound and Ti isopropoxide as a Ti compound were added and dissolved in the obtained solution. Furthermore, in order to stabilize this solution, acetylacetone was added in an amount that doubled in molar ratio to the total organometallic compound dissolved in the solution. Thus, the dielectric composition having an atomic ratio of Pb atom, La atom, Zr atom and Ti atom in the composition of 105: 9: 57: 43 and a PLZT oxide equivalent concentration in 100% by mass of the solution of 10% by mass. A composition for forming a thin body film was prepared.

  Next, a 6-inch silicon substrate having a Pt lower electrode formed on the surface by sputtering was prepared as the substrate. On the Pt lower electrode of this substrate, the above-prepared composition for forming a dielectric thin film was applied by spin coating at 500 rpm for 3 seconds and then at 3000 rpm for 15 seconds. Subsequently, pre-baking was performed by heating at 350 ° C. for 5 minutes in an air atmosphere using a hot plate. The process from application of the composition for forming a dielectric thin film to temporary firing was repeated a total of 6 times, followed by main firing in which heating was performed at a temperature of 700 ° C. for 1 minute in a 100% oxygen atmosphere for crystallization. A 270 nm PLZT dielectric thin film was deposited.

<Example 2>
The same as in Example 1, except that the blending ratio of the organometallic compound was adjusted so that the atomic ratio of Pb atom, La atom, Zr atom and Ti atom in the composition was 95: 9: 70: 30. Then, a dielectric thin film forming composition was prepared, and a PLZT dielectric thin film was formed.

<Example 3>
Similar to Example 1, except that the compounding ratio of the organometallic compound was adjusted so that the atomic ratio of Pb atoms, La atoms, Zr atoms and Ti atoms in the composition was 100: 9: 70: 30. Then, a dielectric thin film forming composition was prepared, and a PLZT dielectric thin film was formed.

<Example 4>
The same as in Example 1, except that the blending ratio of the organometallic compound was adjusted so that the atomic ratio of Pb atoms, La atoms, Zr atoms and Ti atoms in the composition was 95: 12: 70: 30. Then, a dielectric thin film forming composition was prepared, and a PLZT dielectric thin film was formed.

<Example 5>
The same as in Example 1, except that the blending ratio of the organometallic compound was adjusted so that the atomic ratio of Pb atom, La atom, Zr atom and Ti atom in the composition was 95: 9: 80: 20 Then, a dielectric thin film forming composition was prepared, and a PLZT dielectric thin film was formed.

<Example 6>
The same as in Example 1, except that the blending ratio of the organometallic compound was adjusted so that the atomic ratio of Pb atom, La atom, Zr atom and Ti atom in the composition was 105: 9: 55: 45 Then, a dielectric thin film forming composition was prepared, and a PLZT dielectric thin film was formed.

<Example 7>
The same as in Example 1, except that the blending ratio of the organometallic compound was adjusted so that the atomic ratio of Pb atom, La atom, Zr atom and Ti atom in the composition was 105: 10: 57: 43 Then, a dielectric thin film forming composition was prepared, and a PLZT dielectric thin film was formed.

<Example 8>
The same as in Example 1, except that the blending ratio of the organometallic compound was adjusted so that the atomic ratio of Pb atoms, La atoms, Zr atoms and Ti atoms in the composition was 94: 9: 70: 30. Then, a dielectric thin film forming composition was prepared, and a PLZT dielectric thin film was formed.

<Example 9>
The same as in Example 1, except that the blending ratio of the organometallic compound was adjusted so that the atomic ratio of Pb atom, La atom, Zr atom and Ti atom in the composition was 105: 8: 57: 43 Then, a dielectric thin film forming composition was prepared, and a PLZT dielectric thin film was formed.

<Example 10>
The dielectric thin film forming composition was prepared so that the PLZT oxide equivalent concentration in 100% by mass of the solution was 11% by mass, and the steps from application of the composition to pre-firing were repeated 4 times in total. A composition for forming a dielectric thin film was prepared and a PLZT dielectric thin film was formed in the same manner as in Example 1 except that the film was formed to have a thickness of 200 nm.

<Example 11>
The dielectric thin film forming composition was prepared so that the PLZT oxide equivalent concentration in 100% by mass of the solution was 11% by mass, and the steps from application of the composition to pre-baking were repeated a total of 8 times. A composition for forming a dielectric thin film was prepared and a PLZT dielectric thin film was formed in the same manner as in Example 1, except that the film was formed to have a thickness of 400 nm.

<Example 12>
The composition for forming a dielectric thin film was prepared so that the PLZT oxide equivalent concentration in 100% by mass of the solution was 11% by mass, and the steps from application of the composition to pre-firing were repeated 10 times in total. A composition for forming a dielectric thin film was prepared and a PLZT dielectric thin film was formed in the same manner as in Example 1, except that the film was formed to have a thickness of 500 nm.

<Comparative Example 1>
The same as in Example 1, except that the compounding ratio of the organometallic compound was adjusted so that the atomic ratio of Pb atom, La atom, Zr atom and Ti atom in the composition was 110: 0: 52: 48 A composition for forming a dielectric thin film was prepared, and a PZT dielectric thin film was formed.

<Comparative example 2>
The same as in Example 1, except that the blending ratio of the organometallic compound was adjusted so that the atomic ratio of Pb atoms, La atoms, Zr atoms and Ti atoms in the composition was 110: 7: 58: 42 Then, a dielectric thin film forming composition was prepared, and a PLZT dielectric thin film was formed.

<Comparative Example 3>
The same as in Example 1 except that the blending ratio of the organometallic compound was adjusted so that the atomic ratio of Pb atom, La atom, Zr atom and Ti atom in the composition was 100: 5: 52: 48 Then, a dielectric thin film forming composition was prepared, and a PLZT dielectric thin film was formed.

<Comparative example 4>
The same as in Example 1, except that the compounding ratio of the organometallic compound was adjusted so that the atomic ratio of Pb atom, La atom, Zr atom and Ti atom in the composition was 106: 10: 70: 30. Then, a dielectric thin film forming composition was prepared, and a PLZT dielectric thin film was formed.

<Comparative Example 5>
The same as in Example 1 except that the blending ratio of the organometallic compound was adjusted so that the atomic ratio of Pb atoms, La atoms, Zr atoms, and Ti atoms in the composition was 105: 12: 70: 30. Then, a dielectric thin film forming composition was prepared, and a PLZT dielectric thin film was formed.

<Comparative Example 6>
The same as in Example 1, except that the blending ratio of the organometallic compound was adjusted so that the atomic ratio of Pb atom, La atom, Zr atom and Ti atom in the composition was 90: 12: 70: 30. Then, a dielectric thin film forming composition was prepared, and a PLZT dielectric thin film was formed.

<Comparative Example 7>
The same as in Example 1, except that the blending ratio of the organometallic compound was adjusted so that the atomic ratio of Pb atom, La atom, Zr atom and Ti atom in the composition was 106: 10: 80: 20 Then, a dielectric thin film forming composition was prepared, and a PLZT dielectric thin film was formed.

<Comparative Example 8>
The same as in Example 1, except that the blending ratio of the organometallic compound was adjusted so that the atomic ratio of Pb atoms, La atoms, Zr atoms and Ti atoms in the composition was 106: 10: 82: 18 Then, a dielectric thin film forming composition was prepared, and a PLZT dielectric thin film was formed.

<Comparative Example 9>
A composition for forming a dielectric thin film was prepared in the same manner as in Example 1 except that the steps from application of the composition to pre-baking were repeated a total of 4 times, and the film was formed to a film thickness of 180 nm. A PLZT dielectric thin film was formed.

<Comparative Example 10>
The dielectric thin film forming composition was prepared so that the PLZT oxide equivalent concentration in 100% by mass of the solution was 12% by mass, and the steps from application of the composition to pre-baking were repeated 10 times in total. A composition for forming a dielectric thin film was prepared and a PLZT dielectric thin film was formed in the same manner as in Example 1 except that the film was formed to have a thickness of 520 nm.

<Comparison test and evaluation>
For the dielectric thin films formed in Examples 1 to 12 and Comparative Examples 1 to 10 and the test thin film capacitors manufactured by the method described later, the film thickness, capacity change rate, and withstand voltage of the dielectric thin film were evaluated. These results are shown in Table 1 below.

  (1) Film thickness: The thickness of the cross section of the formed thin film was measured with a scanning electron microscope (SEM) apparatus (manufactured by Hitachi High-Tech, model name: S-4300SE).

(2) Capacitance change rate and capacitance C _0V : First, a Pt upper electrode of about 250 μm × 250 μm square is formed on the surface of the formed dielectric thin film by using a metal mask by a sputtering method. A thin film capacitor was obtained. The CV characteristic (voltage dependence of capacitance) between the Pt lower electrode and the Pt upper electrode of this thin film capacitor was evaluated in the range of applied voltage -5V to 5V at a frequency of 1 kHz. Specifically, a precision LCR meter (manufactured by Hewlett-Packard, LCR meter 4284A) was used, and measurement was performed under conditions of a temperature of 23 ° C. and a humidity of 50 ± 10%.

Further, the capacitance change rate T is calculated from the measured values of C _0V (capacitance when the applied voltage is 0V) and C _5V (capacitance when the applied voltage is 5V) and the following equation (1). did.
T = (C _0V −C _5V ) / C _0V × 100 (1)

(3) Dielectric withstand voltage: A DC voltage was applied between the lower electrode and the upper electrode of the thin film capacitor, and the IV characteristics (voltage dependence of the leakage current density and withstand voltage) were evaluated. Specifically, using a current / voltage measuring device (236 SMU manufactured by Keithley), leakage current density under the conditions of temperature 23 ° C., humidity 50 ± 10%, bias step 0.5 V, delay time 0.1 second. The value of the applied voltage just before the value exceeding 1 A / cm ² was taken as the dielectric strength of the thin film capacitor.

As is clear from Table 1, when Examples 1 to 9 and Comparative Examples 1 to 8 are compared, in Comparative Example 1 that does not contain La atoms, the capacity change rate is 67%, which is much higher than that of Examples 1 to 9. The insulation withstand voltage was also slightly lower than those of Examples 1-9. Further, in Comparative Example 3 in which the atomic ratio Zr / Ti of Zr atoms to Ti atoms is less than 55/45 and La atoms are less than 8, the capacity change rate is 50%, which is a large value compared to Examples 1-9. showed that. On the other hand, in Comparative Example 8 in which the atomic ratio Zr / Ti of Zr atoms to Ti atoms exceeds 80/20 and the sum of Pb atoms and La atoms exceeds 115, the withstand voltage is 10.0 or less, and Examples 1 to 9 The value was very low compared to.
Further, in Comparative Example 4, Comparative Example 5, and Comparative Example 7 in which the sum of Pb atoms and La atoms exceeds 115, the withstand voltage was 10.0 or less, which was a very low value compared to Examples 1-9. . On the other hand, in Comparative Example 6 in which the sum of Pb atoms and La atoms was less than 103, the capacitance C _0V when the applied voltage was 0V was as low as 0.81V. Further, in Comparative Example 2 in which the sum of Pb atoms and La atoms exceeds 115 and La atoms are less than 8, the capacity change rate is 55%, which is a large value compared with Examples 1 to 9, and further insulation. The breakdown voltage was 27 V, which was lower than those of Examples 1-9.

On the other hand, in Examples 1-9 where atomic ratio Zr / Ti is 55 / 45-80 / 20, the sum of Pb atoms and La atoms is 103-115, and La atoms are 8-12, The capacitance change rate was 45% or less, the capacitance was 1.2 μF / cm ² or more, and the withstand voltage was 70 V or more.

  Further, when Examples 10 to 12 and Comparative Examples 9 and 10 are compared, in Comparative Example 9 having a film thickness of less than 200 nm, the capacity change rate is 47%, which is slightly larger than Examples 10 to 12, and The withstand voltage was 65 V, which was slightly lower than that of Examples 10-12. On the other hand, in Comparative Example 10 in which the film thickness exceeded 500 nm, cracks occurred, and the withstand voltage was significantly lower than in Examples 10-12.

  On the other hand, in Examples 10-12 in which the film thickness is in the range of 200 to 500 nm, excellent values were shown in all evaluations of the capacity change rate, the capacitance, and the withstand voltage.

  The present invention relates to a thin film capacitor, a capacitor, an IPD, a DRAM memory capacitor, a multilayer capacitor, a transistor gate insulator, a nonvolatile memory, a pyroelectric infrared detection element, a piezoelectric element, an electro-optical element, an actuator, a resonator, and an ultrasonic wave. The present invention can be used for manufacturing a composite electronic component of a motor, an electric switch, an optical switch, or an LC noise filter element.

DESCRIPTION OF SYMBOLS 10 Thin film capacitor 11 Substrate 12 Insulator film 13 Adhesion layer 14 Lower electrode 16 Dielectric thin film 17 Upper electrode 20 Support body

Claims (1)

In an organometallic compound-containing composition for forming a PLZT dielectric thin film,
The PLZT dielectric thin film is a thin film used for a dielectric layer of a thin film capacitor,
When the sum of Zr atoms and Ti atoms contained in the composition is 100,
The atomic ratio Zr / Ti of Zr atoms to Ti atoms is 70/30 to 80/20,
The sum of Pb atoms and La atoms is 103 to 107 , and La atoms are 9 to 12. A composition for forming a dielectric thin film, wherein:

Images