KR20020058663A - Precursor composition for forming PZT film and a reservoir of the same - Google Patents

Abstract

PURPOSE: A precursor compound for manufacturing PZT layer is provided to prevent changes of a chemical and a thermal characteristic by optimizing a precursor and a solvent species, and the composition rate. CONSTITUTION: A precursor compound for manufacturing PZT layer comprises Pb(C11H19O2)2, Pb(C11H19O2)2(C8H2ON3) or Pb(C14H25O4)2 as a Pb precursor having in the range of 0.03-0.3 mole, Ti(C11H19O2)2(C3H7O)2 as a Ti precursor having in the range of 0.03-0.2 mole, Zr(C11H19O2)2(C3H7O)2 as a Zr precursor having in the range of 0.03-0.2 mole, and a defined solvent made of a heptane(C7H16) or a mixed material of the heptane(C7H16) and an isopropanol(C3H8O). At this time, the mixing rate of the heptane(C7H16) and the isopropanol(C3H8O) is in the rate of 85-99 :15-1 as a volume rate.

Description

Precursor composition for forming PZT film and a reservoir of the same}

The present invention relates to a precursor composition for ferroelectric film production and a storage container thereof, and more particularly, to a precursor composition for manufacturing a PZT film (PZT) film which does not change even when stored for a long time by using a solvent as heptane and its storage It's about courage.

Ferroelectric materials have spontaneous polarization by means of an internal permanent dipole arrangement, and the direction of such spontaneous polarization is nonvolatile because the direction of the spontaneous polarization is changed by an externally applied electric field and is maintained even when the electric field is removed. Thus, most of the nonvolatile memory is manufactured using such ferroelectric materials. Representative of such ferroelectric materials are oxide forms having a perovskite structure, PbZr _x Ti _1-x O ₃ (PZT) and SrBi ₂ Ta ₂ O ₉ (SBT).

Such ferroelectric material deposition methods include sputtering, sol-gel, pulsed laser, and metal-organic chemical vapor deposition (MOCVD). Among the above methods, the MOCVD method is widely used in the manufacturing process of the highly integrated ferroelectric memory device because of excellent compliance.

The PZT thin film generally refers to a thin film in which La, Sr, Ca, Sc, Nb, Ta, Ni, Fe, Er, and the like are added to Pb (Zr _x Ti _1-x ) O 3.

PZT precursor used in the process of forming PZT film by MOCVD method, mainly metal alkoxide (ex, Ti (i-OPr) ₄ , Zr (t-OBu) ₄ ..), metal alkyl (ex. Pb (Et) ₄ ) Or metal β-diketonate (ex, Pb (THD) ₂ , Ti (THD) ₂ (i-OPr) ₂ , Zr (THD) ₄ ...). However, the precursors have been known to be difficult to form a reproducible and productive PZT film due to thermal instability (for metal alkoxide), toxicity (Pb (Et) ₄ ) and lack of volatility (metal β-diketonate).

In order to solve the above problem, recently, a liquid source delivery method has been developed. This method mainly uses metal β-diketonates, which had relatively high thermal stability but lacked volatility, as precursors. The weak point is solved by dissolving in solvent. In addition, this method is a conceptually good method in terms of stable supply of precursors, but it is stable and does not change in the actual process application such as solvent and precursor reactivity, precursor solubility, reactivity between precursors, change of precursor over time, etc. There are too many factors to consider for the precursor supply, which is not easy to apply the actual process.

Accordingly, an object of the present invention is to improve the problems of the prior art described above, and to provide a precursor composition for manufacturing a pithy film that does not change in chemical and thermal properties by optimizing the type and composition ratio of the precursor and the solvent. .

Another technical object of the present invention is to provide a storage container for such a precursor composition.

FIG. 1 is a graph showing the pressure change in the vaporizer of the MOCVD apparatus when the PZT film using the MOCVD apparatus is used in the process of manufacturing the PIG film according to the embodiment of the present invention.

2 and 3 are schematic diagrams showing step-by-step manufacturing method of the precursor composition for manufacturing a PZT film according to the first embodiment of the present invention.

4 is a schematic diagram showing some steps of the manufacturing method of the precursor composition for manufacturing a PZT film according to the second embodiment of the present invention.

5 is a schematic structural diagram of a MOCVD apparatus used for producing a PZT film using a precursor composition according to an embodiment of the present invention.

6 is a graph showing a hysteresis characteristic curve of a PZT film manufactured using the precursor composition for manufacturing a PZT film according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

10, 20, 30: first to third precursors V1, V2, V3, V4: first to fourth containers

S1, S2, S3: First to Third Solvents S: PZT Composition

40: solvent 50: container containing the PZT composition

60: flow regulator 70: vaporizer

80: shower head 90: chamber

100: substrate 110: susceptor

In order to achieve the above technical problem, the invention is a Pb precursor Pb (C ₁₁ H ₁₉ O ₂ ) ₂ , Pb (C ₁₁ H ₁₉ O ₂ ) ₂ (C ₈ H ₂ 0N ₃ ) and Pb (C ₁₄ H ₂₅ O ₄ ) at least one selected from the group consisting of ₂ , Ti (C ₁₁ H ₁₉ O ₂ ) ₂ (C ₃ H ₇ O) ₂ as Ti precursor and Zr (C ₁₁ H ₁₉ O ₂ ) ₂ (C ₃ H as Zr precursor; _It provides a precursor composition for manufacturing a PZT film, characterized in that a predetermined solvent is mixed with precursors composed of ₇ O) ₂ .

Here, the solvent is heptane (C ₇ H ₁₆ ), preferably consisting of a mixture of the heptane and isopropanol (Isopropanol: C ₃ H ₈ O).

In order to achieve the above another technical problem, the present invention is to provide a precursor composition storage container for manufacturing a pithy membrane, characterized in that the inside is coated with Teflon.

Hereinafter, with reference to the accompanying drawings, a precursor composition and a storage container for manufacturing a PZT film according to an embodiment of the present invention will be described in detail. In this process, the thicknesses of layers or regions illustrated in the drawings are exaggerated for clarity.

Precursor composition for producing a film (hereinafter, referred to as 'PZT composition') is composed of a Pb precursor, a Ti precursor, and a solvent for dissolving them together with a Zr precursor. The present invention provides the Pb precursor as Pb (C ₁₁ H ₁₉ O ₂ ) ₂ , Pb (C ₁₁ H ₁₉ O ₂ ) ₂ (C ₈ H ₂ 0N ₃ ) and Pb (C ₁₄ H ₂₅ O ₄ ) ₂ , using at least one selected from a crowd, and using Ti (C ₁₁₎ as the Ti precursor. H ₁₉ O ₂ ) ₂ (C ₃ H ₇ O) ₂ is used, and Zr (C ₁₁ H ₁₉ O ₂ ) ₂ (C ₃ H ₇ O) ₂ is used as the Zr precursor. In addition, a predetermined amount of heptane is used as the solvent.

On the other hand, the concentration of each precursor is as follows.

Pb precursor: 0.03 to 0.3 mole

Ti precursor: 0.03-0.2 mole

Zr precursor: 0.03-0.2 mole

Isopropyl alcohol (IPA) may be added to heptane, the main solvent, to inhibit decomposition of each precursor. At this time, the mixing ratio of heptane and isopropyl alcohol is preferably 85 to 99: 1 to 15 in volume ratio.

1 is a graph showing the pressure change in the vaporizer according to the solvent used in the PZT composition, reference G1 is the first graph showing the pressure change when using only pure heptane without isopropanol added, G2 is 5 to heptane A second graph showing the pressure change that appears when% vol isopropanol is added.

Referring to the first graph G1 of FIG. 1, when only heptane is used, it can be seen that the pressure increases as time passes. Referring to the second graph G2, the pressure in the vaporizer may elapse even if time passes. It can be seen that there is no change. This means that the addition of isopropane alcohol to heptane does not change the chemical or thermal properties of the composition even after prolonged storage. Therefore, it can be seen that the pressure of the vaporizer does not change even when the PZT composition is passed in the vaporizer for a long time (for example, 20 hours).

In general, an electro-polished interior is used as a storage container for the precursor composition. In this case, the characteristics of the precursor may be changed by the iron (Fe) component therein. That is, the iron component acts as a catalyst to accelerate the decomposition of the precursor to reduce the reproducibility.

Accordingly, the inventor stored the PZT composition in a storage container coated with Teflon to prevent deterioration of the properties of the PZT composition.

Next, the manufacturing method of said PZT composition is demonstrated.

<First Embodiment>

Referring to FIG. 2, first, first to third containers V1, V2, and V3 filled with predetermined amounts of the first to third solvents S1, S2, and S3 are prepared. The first to third solvents S1, S2 and S3 are all the same solvent, for example heptane. Next, the first precursor 10 in the solid state is added to the first solvent S1, the second precursor 20 to the second solvent S2, and the third precursor 30 to the third solvent S3, respectively. Add independently and mix. The first to third precursors 10, 20, and 30 are Pb precursors, Ti precursors, and Zr precursors described in the description of the PZT composition, respectively, when mixed with a solvent, 0.03 to 0.3 mole, 0.03 to 0.2 mole, and Add about 0.03 to 0.2 mole.

Next, as shown in FIG. 3, the fourth container V4 is prepared and the solution contained in the first to third containers V1, V2, and V3 in which each precursor is dissolved is mixed into the fourth container V4. . In this way, the PZT composition (S) which consists of 1st thru | or 3rd precursor 10, 20, 30 and a solvent (S1 + S2 + S3) is manufactured.

Second Embodiment

As shown in FIG. 4, first, the fourth container V4 is prepared, and then the first to third precursors 10, 20, and 30 are mixed therein. Subsequently, the solvent 40 is added to the fourth vessel V4 in which the first to third precursors 10, 20, and 30 are mixed to dissolve the mixed precursors, thereby dissolving the PZT composition as shown in FIG. S) is manufactured.

Meanwhile, in the PZT composition preparation method according to the first or second embodiment, predetermined isopropyl alcohol is added to the solvent (S1, S2, S3 or 40) to suppress decomposition of each precursor included in the PZT composition (S). Add. Isopropyl alcohol may be added after preparing the PZT composition (S) as shown in FIG. In this process, the isopropyl alcohol is preferably added so that the mixing ratio of the solvent and isopropyl alcohol is 85 to 99: 1 to 15 in volume ratio.

Wherein the concentration of the Pb precursor, Ti precursor and Zr precursor is preferably 0.03 to 0.3 mole, 0.03 to 0.2 mole and 0.03 to 0.2 mole, respectively. In addition, isopropyl alcohol may be added to heptane, the main solvent, to inhibit decomposition of each precursor. In this case, the mixing ratio of heptane and isopropyl alcohol may be 85 to 99: 1 to 15 by volume ratio.

The PZT thin film manufacturing process using the PZT composition thus prepared will be briefly described.

FIG. 2 is a schematic configuration diagram of a MOCVD apparatus used in this regard. Referring to this, first, a vessel 50 containing the PZT composition is connected to a vaporizer 70 (each precursor dissolved independently of a solvent is contained in an independent vessel). The substrate 100 may be mounted on a susceptor 110 in the chamber 90 of the MOCVD apparatus. Thereafter, an appropriate amount of the composition is passed through the liquid flow controller 60 to the vaporizer 70. The vaporizer 70 is vaporized by heating the composition is introduced to a temperature in the range of 180 ℃ to 220 ℃ to make a gaseous state. The gas thus formed is transported to the shower head 80 along with argon (Ar) gas, which is a carrier gas, and sprayed onto the substrate 100. As a result, a PZT film is formed on the substrate 100. . In the meantime, the board | substrate 100 is heated to 450 to 550 degreeC which becomes a film-forming condition of a PZT film | membrane.

6 is a graph showing the hysteresis curve of the PZT film thus formed, in which the horizontal axis represents applied voltage (V) and the vertical axis represents polarization. The dotted line indicates when the applied voltage is 5V and the solid line indicates when 3V.

Referring to FIG. 6, it can be seen that the PZT film formed of the PZT composition according to the present invention exhibits an ideal hysteresis loop.

While many details are set forth in the foregoing description, they should be construed as illustrative of preferred embodiments, rather than to limit the scope of the invention. For example, one of ordinary skill in the art to which the present invention pertains may use other solvents or additives than the above-described solvents, and thus may present a storage container having a different structure or internal coating material. In addition, the present invention composition may be used in a thin film forming apparatus other than MOCVD. In addition, the first and second precursors are dissolved in the same container, and the third precursor is dissolved in a solvent by first mixing only the first and second precursors or a method of preparing PZT, which is dissolved in another container. There may be a way to mix the melted one. Because of this diversity of the present invention, the scope of the present invention should not be defined by the embodiments described, but by the technical spirit described in the claims.

The present invention provides a PZT composition and a storage container thereof in which a Pb precursor, a Ti precursor, a Zr precursor, and a solvent are mixed as described above. At this time, the solvent is heptone, and a predetermined amount of isopropyl alcohol is added to suppress decomposition of each precursor. Therefore, when using such a PZT composition, it is possible to eliminate the problem of the conventional self-decomposition of the composition over time, the problem of delivery, and clogging of the vaporizer in the thin film manufacturing apparatus. As shown in Fig. 6, a PZT film having a stable hysteretic characteristic curve can be obtained.

Claims (6)

At least one selected from the group consisting of Pb (C ₁₁ H ₁₉ O ₂ ) ₂ , Pb (C ₁₁ H ₁₉ O ₂ ) ₂ (C ₈ H ₂ 0N ₃ ) and Pb (C ₁₄ H ₂₅ O ₄ ) ₂ as Pb precursors and _{Ti (C 11 H 19 O 2} ) as a Ti precursor _{2 (C 3 H 7 O)} Zr (C 11 H 19 O 2) as ₂ and Zr precursor ₂ (C ₃ H ₇ O) with the precursors consisting of ₂ Precursor composition for manufacturing a film for the manufacture of fiji, characterized in that a predetermined solvent is mixed. The method of claim 1, The solvent is heptane (C ₇ H ₁₆ ), the precursor composition for the manufacture of FIJI film. The method of claim 1, The solvent is a precursor composition for the manufacture of the FIGF film, characterized in that consisting of a mixture of heptane and isopropanol (Isopropanol: C ₃ H ₈ O). The method of claim 3, wherein The mixing ratio of the heptane and isopropanol is 85 ~ 99: 15 ~ 1 in the volume ratio precursor composition for manufacturing a pithytima film. The method of claim 1, The concentration of the Pb precursor is 0.03 to 0.3 mole, the concentration of the Ti precursor is 0.03 to 0.2 mole and the concentration of the Zr precursor is 0.03 to 0.2 mole precursor composition for the manufacture of the film. A container for storage of a precursor composition for manufacturing a FITITI film, which is used for storage of the precursor composition for producing a FITITI film according to claim 1, wherein the inner surface is coated with Teflon.