JP5591484B2 - Composition for forming ferroelectric thin film, method for forming ferroelectric thin film, and ferroelectric thin film formed by the method - Google Patents
Composition for forming ferroelectric thin film, method for forming ferroelectric thin film, and ferroelectric thin film formed by the method Download PDFInfo
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Description
本発明は、高容量密度、かつ低リーク電流密度の薄膜キャパシタ用途に適した強誘電体薄膜形成用組成物、強誘電体薄膜の形成方法並びに該方法により形成された強誘電体薄膜に関するものである。 The present invention relates to a ferroelectric thin film forming composition suitable for high capacity density and low leakage current density thin film capacitor applications, a method for forming a ferroelectric thin film, and a ferroelectric thin film formed by the method. is there.
この種の強誘電体膜の製造方法として、各成分金属のアルコキシドや有機酸塩を極性溶媒に溶解してなる混合溶液を用い、金属基板に塗布、乾燥して、塗膜を形成し、結晶化温度以上の温度に加熱して焼成することにより、誘電体薄膜を成膜することが一般的に知られている（例えば、特許文献１，２参照。）。 As a method of manufacturing this type of ferroelectric film, a mixed solution in which each component metal alkoxide or organic acid salt is dissolved in a polar solvent is used. It is generally known to form a dielectric thin film by heating to a temperature equal to or higher than the crystallization temperature and firing (see, for example, Patent Documents 1 and 2).
しかしながら、代表的な強誘電体であるＰＺＴ膜では、薄膜化して電圧を印加した場合、リーク電流密度が高くなり、更には絶縁破壊に至ってしまうことが確認されている。 However, it has been confirmed that a PZT film, which is a typical ferroelectric substance, has a high leakage current density and a dielectric breakdown when a voltage is applied after being thinned.
そこで、ＰＺＴ膜などの強誘電体薄膜に微量元素を添加して、リーク特性を改善する試みが行われてきたが、未だ不十分であった。 Therefore, attempts have been made to improve the leak characteristics by adding trace elements to a ferroelectric thin film such as a PZT film, but it has not been sufficient.
また、厚膜にしてリーク電流密度を減少させる試みが行われているが、この場合、静電容量が低下してしまうという問題を抱えている。 Attempts have also been made to reduce the leakage current density by using a thick film, but in this case, there is a problem that the capacitance is lowered.
上記問題の対策として、膜厚１μｍ程度のＰＺＴ膜に硝酸セリウムを１ａｔ.％ドーピングすることで、ノンドープのＰＺＴ膜の比誘電率が４００程度であったものを７００程度に向上させることが可能であることが示されているが、その比誘電率は依然として低いものであり、実用上不充分な値である（例えば、非特許文献１参照。）。 As a countermeasure against the above-mentioned problem, it is possible to improve the non-doped PZT film having a relative dielectric constant of about 400 to about 700 by doping the PZT film having a thickness of about 1 μm with 1 at.% Cerium nitrate. Although it is shown that the relative dielectric constant is still low, it is an insufficient value for practical use (for example, see Non-Patent Document 1).
形成した強誘電体薄膜の膜厚が十分でないとリーク電流密度が高く、絶縁破壊する可能性もあることから、キャパシタとしての性能を十分に発揮することができなかった。 If the thickness of the formed ferroelectric thin film is not sufficient, the leakage current density is high and there is a possibility of dielectric breakdown. Therefore, the performance as a capacitor could not be sufficiently exhibited.
また、膜厚を厚くしすぎると、十分な静電容量、比誘電率が得られないという問題点も抱えていた。 Further, if the film thickness is too thick, there is a problem that sufficient electrostatic capacity and relative dielectric constant cannot be obtained.
本発明の目的は、簡便な手法で、従来の強誘電体薄膜と同程度の比誘電率を有し、かつ、低いリーク電流密度が得られる、高容量密度の薄膜キャパシタ用途に適した強誘電体薄膜形成用組成物、強誘電体薄膜の形成方法並びに該方法により形成された強誘電体薄膜を提供することにある。 An object of the present invention is a ferroelectric material suitable for high-capacity density thin film capacitor applications that has a relative dielectric constant comparable to that of a conventional ferroelectric thin film and a low leakage current density by a simple technique. An object of the present invention is to provide a composition for forming a thin body film, a method for forming a ferroelectric thin film, and a ferroelectric thin film formed by the method.
本発明の第１の観点は、ＰＬＺＴ及びＰＺＴからなる群より選ばれた１種の強誘電体薄膜を形成するための強誘電体薄膜形成用組成物において、一般式：（ＰｂxＬａy）（ＺｒzＴｉ(1-z)）Ｏ3（式中０．９＜ｘ＜１．３、０≦ｙ＜０．１、０＜ｚ＜０．９）で示される複合金属酸化物Ａに、Ｃｅを含む複合金属酸化物Ｂが混合した混合複合金属酸化物の形態をとる薄膜を形成するための液状組成物であり、複合金属酸化物Ａを構成するための原料並びに複合金属酸化物Ｂを構成するための原料が上記一般式で示される金属原子比を与えるような割合で有機溶媒中に溶解している有機金属化合物溶液からななり、有機金属化合物溶液中の粒径０．５μｍ以上のパーティクルの個数を５０個／ｍＬ以下であり、前記複合金属酸化物Ｂが２−エチルヘキサン酸セリウム、２−エチル酪酸酸セリウム、セリウムトリｎ−ブトキシド、セリウムトリエトキシド又はトリス（アセチルアセトネート）セリウムからなることを特徴とする。 According to a first aspect of the present invention, there is provided a ferroelectric thin film forming composition for forming one kind of ferroelectric thin film selected from the group consisting of PLZT and PZT, wherein the general formula: (Pb x La y ) (Zr z Ti (1-z) ) O 3 (wherein 0.9 <x <1.3, 0 ≦ y <0.1, 0 < z <0.9) , A liquid composition for forming a thin film in the form of a mixed composite metal oxide mixed with a composite metal oxide B containing Ce, and a raw material for forming the composite metal oxide A and the composite metal oxide B The organic metal compound solution is dissolved in an organic solvent at a ratio that gives the metal atomic ratio represented by the above general formula, and the particle size in the organic metal compound solution is 0.5 μm or more. of the number of particles 50 cells / mL or less, the composite metal oxide B is 2- Chiruhekisan acid cerium 2-ethyl butyric acid cerium Seriumutori n- butoxide, characterized by comprising the cerium triethoxide or tris (acetylacetonate) cerium.
本発明の第２の観点は、第１の観点に基づく発明であって、更に複合金属酸化物Ａ及び複合金属酸化物Ｂを構成するための原料が、有機基がその酸素又は窒素原子を介して金属元素と結合している化合物であることを特徴とする。 A second aspect of the present invention is an invention based on the first aspect, wherein the raw material for constituting the composite metal oxide A and the composite metal oxide B is an organic group via its oxygen or nitrogen atom. It is a compound that is bonded to a metal element.
本発明の第３の観点は、第２の観点に基づく発明であって、更に複合金属酸化物Ａ及び複合金属酸化物Ｂを構成するための原料が、金属アルコキシド、金属ジオール錯体、金属トリオール錯体、金属カルボン酸塩、金属β−ジケトネート錯体、金属β−ジケトエステル錯体、金属β−イミノケト錯体、及び金属アミノ錯体からなる群より選ばれた１種又は２種以上であることを特徴とする。 The third aspect of the present invention is the invention based on the second aspect, and the raw materials for constituting the composite metal oxide A and the composite metal oxide B are metal alkoxide, metal diol complex, metal triol complex. , A metal carboxylate, a metal β-diketonate complex, a metal β-diketoester complex, a metal β-iminoketo complex, and one or more selected from the group consisting of metal amino complexes.
本発明の第４の観点は、第１ないし第３の観点に基づく発明であって、更にβ−ジケトン、β−ケトン酸、β−ケトエステル、オキシ酸、ジオール、トリオール、高級カルボン酸、アルカノールアミン及び多価アミンからなる群より選ばれた１種又は２種以上の安定化剤を、組成物中の金属合計量１モルに対して、０．２〜３モルの割合で更に含有することを特徴とする。 A fourth aspect of the present invention is an invention based on the first to third aspects, further comprising a β-diketone, β-ketone acid, β-ketoester, oxyacid, diol, triol, higher carboxylic acid, alkanolamine And further containing one or more stabilizers selected from the group consisting of polyamines in a proportion of 0.2 to 3 moles relative to 1 mole of the total amount of metals in the composition. Features.
本発明の第５の観点は、第１ないし第４の観点に基づく発明であって、更にＢとＡとのモル比Ｂ／Ａが０＜Ｂ／Ａ＜０．０５であることを特徴とする。 A fifth aspect of the present invention is the invention based on the first to fourth aspects, wherein the molar ratio B / A between B and A is 0 <B / A <0.05. To do.
本発明の第６の観点は、第５の観点に基づく発明であって、更にＢとＡとのモル比Ｂ／Ａが０．００５≦Ｂ／Ａ≦０．０３であることを特徴とする。 A sixth aspect of the present invention is the invention based on the fifth aspect, further characterized in that the molar ratio B / A between B and A is 0.005 ≦ B / A ≦ 0.03. .
本発明の第７の観点は、第１ないし第６の観点に基づく強誘電体薄膜形成用組成物を耐熱性基板に塗布し、空気中、酸化雰囲気中又は含水蒸気雰囲気中で加熱する工程を１回又は所望の厚さの膜が得られるまで繰返し、少なくとも最終工程における加熱中或いは加熱後に該膜を結晶化温度以上で焼成することを特徴とする強誘電体薄膜の形成方法である。 According to a seventh aspect of the present invention, there is provided a step of applying a ferroelectric thin film forming composition based on the first to sixth aspects to a heat resistant substrate and heating in air, an oxidizing atmosphere or a water-containing atmosphere. It is a method for forming a ferroelectric thin film characterized in that it is repeated once or until a film having a desired thickness is obtained, and the film is fired at a temperature equal to or higher than the crystallization temperature at least after heating in the final step.
本発明の第８の観点は、第７の観点に基づく方法により形成された強誘電体薄膜である。 An eighth aspect of the present invention is a ferroelectric thin film formed by a method based on the seventh aspect.
本発明の第９の観点は、第８の観点に基づく強誘電体薄膜を有する薄膜コンデンサ、キャパシタ、ＩＰＤ（Ｉｎｔｅｇｒａｔｅｄ Ｐａｓｓｉｖｅ Ｄｅｖｉｃｅ）、ＤＲＡＭメモリ用コンデンサ、積層コンデンサ、トランジスタのゲート絶縁体、不揮発性メモリ、焦電型赤外線検出素子、圧電素子、電気光学素子、アクチュエータ、共振子、超音波モータ、又はＬＣノイズフィルタ素子の複合電子部品である。 A ninth aspect of the present invention is a thin film capacitor having a ferroelectric thin film based on the eighth aspect, a capacitor, an IPD (Integrated Passive Device), a DRAM memory capacitor, a multilayer capacitor, a gate insulator of a transistor, and a nonvolatile memory , A pyroelectric infrared detecting element, a piezoelectric element, an electro-optical element, an actuator, a resonator, an ultrasonic motor, or an LC noise filter element.
本発明の第１０の観点は、第９の観点に基づく１００ＭＨｚ以上の周波数帯域に対応した、強誘電体薄膜を有する薄膜コンデンサ、キャパシタ、ＩＰＤ、ＤＲＡＭメモリ用コンデンサ、積層コンデンサ、トランジスタのゲート絶縁体、不揮発性メモリ、焦電型赤外線検出素子、圧電素子、電気光学素子、アクチュエータ、共振子、超音波モータ、又はＬＣノイズフィルタ素子の複合電子部品である。 A tenth aspect of the present invention is a thin film capacitor having a ferroelectric thin film, a capacitor, an IPD, a DRAM memory capacitor, a multilayer capacitor, and a gate insulator of a transistor corresponding to a frequency band of 100 MHz or more based on the ninth aspect. , A composite electronic component of a nonvolatile memory, a pyroelectric infrared detection element, a piezoelectric element, an electro-optical element, an actuator, a resonator, an ultrasonic motor, or an LC noise filter element.
本発明の強誘電体薄膜形成用組成物は、一般式：（ＰｂxＬａy）（ＺｒzＴｉ(1-z)）Ｏ3（式中０．９＜ｘ＜１．３、０≦ｙ＜０．１、０＜ｚ＜０．９）で示される複合金属酸化物Ａに、Ｃｅを含む複合金属酸化物Ｂが混合した混合複合金属酸化物の形態をとるように、有機金属化合物溶液に複合金属酸化物Ａを構成するための原料並びに複合金属酸化物Ｂを構成するための原料を所定の割合となるように、有機溶媒中に溶解させている。この組成物を用いて強誘電体薄膜を形成することにより、従来の強誘電体薄膜と同程度の比誘電率を有し、かつ、低いリーク電流密度が得られる、高容量密度の薄膜キャパシタ用途に適した強誘電体薄膜を簡便な手法で得ることができる、という利点がある。従って、従来と同程度のリーク電流密度とする場合には、更なる薄膜化が可能となり、より高い比誘電率が得られる。 The composition for forming a ferroelectric thin film of the present invention has a general formula: (Pb x La y ) (Zr z Ti (1-z) ) O 3 (where 0.9 <x <1.3, 0 ≦ y <0.1, 0 < z <0.9) Organometallic compound solution so as to take the form of mixed composite metal oxide in which composite metal oxide A containing Ce is mixed with composite metal oxide A represented by Ce The raw material for constituting the composite metal oxide A and the raw material for constituting the composite metal oxide B are dissolved in an organic solvent so as to have a predetermined ratio. By using this composition to form a ferroelectric thin film, it has the same dielectric constant as that of a conventional ferroelectric thin film, and a low leakage current density can be obtained. There is an advantage that a ferroelectric thin film suitable for the above can be obtained by a simple method. Therefore, when the leakage current density is about the same as that of the prior art, further thinning is possible, and a higher dielectric constant can be obtained.
次に本発明を実施するための形態を説明する。 Next, the form for implementing this invention is demonstrated.
本発明の強誘電体薄膜形成用組成物は、ＰＬＺＴ及びＰＺＴからなる群より選ばれた１種の強誘電体薄膜を形成するための組成物である。この組成物を用いて形成される強誘電体薄膜は、一般式：（ＰｂxＬａy）（ＺｒzＴｉ(1-z)）Ｏ3（式中０．９＜ｘ＜１．３、０≦ｙ＜０．１、０＜ｚ＜０．９）で示される複合金属酸化物Ａに、Ｃｅを含む複合金属酸化物Ｂが混合した混合複合金属酸化物の形態をとる。なお、上記式のｙ≠０かつｚ≠０の場合はＰＬＺＴであり、ｙ＝０かつｚ≠０の場合はＰＺＴであり、ｙ＝０かつｚ＝０の場合はＰＴである。この組成物は、複合金属酸化物Ａを構成するための原料と、複合金属酸化物Ｂを構成するための原料が上記一般式で示される金属原子比を与えるような割合となるように、有機溶媒中に溶解している有機金属化合物溶液からなる。 The composition for forming a ferroelectric thin film of the present invention is a composition for forming one kind of ferroelectric thin film selected from the group consisting of PLZT and PZT. A ferroelectric thin film formed using this composition has a general formula: (Pb x La y ) (Zr z Ti (1-z) ) O 3 (where 0.9 <x <1.3, 0 It takes the form of the mixed composite metal oxide in which the composite metal oxide A represented by ≦ y <0.1, 0 < z <0.9) is mixed with the composite metal oxide B containing Ce. In the above equation, when y ≠ 0 and z ≠ 0, it is PLZT, when y = 0 and z ≠ 0, it is PZT, and when y = 0 and z = 0, it is PT. This composition is organic so that the raw material for constituting the composite metal oxide A and the raw material for constituting the composite metal oxide B have a ratio that gives the metal atomic ratio represented by the above general formula. It consists of an organometallic compound solution dissolved in a solvent.
複合金属酸化物Ａ用原料並びに複合金属酸化物Ｂ用原料は、Ｐｂ、Ｌａ、Ｚｒ、Ｔｉ及びＣｅの各金属元素に、有機基がその酸素又は窒素原子を介して結合している化合物が好適である。例えば、金属アルコキシド、金属ジオール錯体、金属トリオール錯体、金属カルボン酸塩、金属β−ジケトネート錯体、金属β−ジケトエステル錯体、金属β−イミノケト錯体、及び金属アミノ錯体からなる群より選ばれた１種又は２種以上が例示される。特に好適な化合物は、金属アルコキシド、その部分加水分解物、有機酸塩である。このうち、Ｐｂ化合物、Ｌａ化合物、Ｃｅ化合物としては、酢酸塩（酢酸鉛、酢酸ランタン）、２−エチルヘキサン酸セリウム、２−エチル酪酸セリウム等の有機酸塩、鉛ジイソプロポキシド、セリウムトリｎ−ブトキシド、セリウムトリエトキシドなどのアルコキシド、トリス（アセチルアセトネート）セリウムなどの金属β−ジケトネート錯体が挙げられる。Ｔｉ化合物としては、チタニウムテトラエトキシド、チタニウムテトライソプロポキシド、チタニウムテトラブトキシド、チタニウムジメトキシジイソプロポキシドなどのアルコキシドが挙げられる。Ｚｒ化合物としては、上記Ｔｉ化合物と同様なアルコキシド類が好ましい。金属アルコキシドはそのまま使用しても良いが、分解を促進させるためにその部分加水分解物を使用しても良い。 The raw material for composite metal oxide A and the raw material for composite metal oxide B are preferably compounds in which an organic group is bonded to each metal element of Pb, La, Zr, Ti, and Ce via the oxygen or nitrogen atom. It is. For example, one kind selected from the group consisting of metal alkoxide, metal diol complex, metal triol complex, metal carboxylate, metal β-diketonate complex, metal β-diketoester complex, metal β-iminoketo complex, and metal amino complex Or 2 or more types are illustrated. Particularly suitable compounds are metal alkoxides, partial hydrolysates thereof, and organic acid salts. Among these, as Pb compound, La compound, and Ce compound, organic acid salts such as acetate (lead acetate, lanthanum acetate), cerium 2-ethylhexanoate, cerium 2-ethylbutyrate, lead diisopropoxide, cerium tri-n -Alkoxides such as butoxide and cerium triethoxide, and metal β-diketonate complexes such as tris (acetylacetonate) cerium. Examples of the Ti compound include alkoxides such as titanium tetraethoxide, titanium tetraisopropoxide, titanium tetrabutoxide, and 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.
本発明の強誘電体薄膜形成用組成物を調製するには、これらの原料を所望の強誘電体薄膜組成に相当する比率で適当な溶媒に溶解して、塗布に適した濃度に調製する。 In order to prepare the composition for forming a ferroelectric thin film of the present invention, these raw materials are dissolved in an appropriate solvent at a ratio corresponding to the desired ferroelectric thin film composition, and prepared to a concentration suitable for coating.
ＢとＡとのモル比Ｂ／Ａは、０＜Ｂ／Ａ＜０．０５の範囲内となるように調整される。上記範囲内であれば、本発明の効果である従来の強誘電体薄膜と同程度の比誘電率を有し、かつ、低いリーク電流密度を得ることができる。なお、上限値を越えると比誘電率の劣化の不具合を生じる。このうち、０．００５≦Ｂ／Ａ≦０．０３が特に好ましい。 The molar ratio B / A between B and A is adjusted to be in the range of 0 <B / A <0.05. If it is in the above-mentioned range, it has a relative dielectric constant comparable to that of the conventional ferroelectric thin film that is the effect of the present invention, and a low leakage current density can be obtained. If the upper limit value is exceeded, there will be a problem of deterioration of the relative dielectric constant. Among these, 0.005 ≦ B / A ≦ 0.03 is particularly preferable.
ここで用いる強誘電体薄膜形成用組成物の溶媒は、使用する原料に応じて適宜決定されるが、一般的には、カルボン酸、アルコール、エステル、ケトン類（例えば、アセトン、メチルエチルケトン）、エーテル類（例えば、ジメチルエーテル、ジエチルエーテル）、シクロアルカン類（例えば、シクロヘキサン、シクロヘキサノール）、芳香族系（例えば、ベンゼン、トルエン、キシレン）、その他テトラヒドロフランなど、或いはこれらの２種以上の混合溶媒を用いることができる。 The solvent for the composition for forming a ferroelectric thin film used here is appropriately determined according to the raw material to be used. Generally, carboxylic acid, alcohol, ester, ketones (for example, acetone, methyl ethyl ketone), ether (E.g., dimethyl ether, diethyl ether), cycloalkanes (e.g., cyclohexane, cyclohexanol), aromatics (e.g., benzene, toluene, xylene), other tetrahydrofuran, or a mixture of two or more of these be able to.
カルボン酸としては、具体的には、ｎ−酪酸、α−メチル酪酸、ｉ−吉草酸、２−エチル酪酸、２，２−ジメチル酪酸、３，３−ジメチル酪酸、２，３−ジメチル酪酸、３−メチルペンタン酸、４−メチルペンタン酸、２−エチルペンタン酸、３−エチルペンタン酸、２，２−ジメチルペンタン酸、３，３−ジメチルペンタン酸、２，３−ジメチルペンタン酸、２−エチルヘキサン酸、３−エチルヘキサン酸を用いるのが好ましい。 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.
また、エステルとしては、酢酸エチル、酢酸プロピル、酢酸ｎ−ブチル、酢酸ｓｅｃ−ブチル、酢酸ｔｅｒｔ−ブチル、酢酸イソブチル、酢酸ｎ−アミル、酢酸ｓｅｃ−アミル、酢酸ｔｅｒｔ−アミル、酢酸イソアミルを用いるのが好ましく、アルコールとしては、１−プロパノール、２−プロパノール、１−ブタノール、２−ブタノール、イソ−ブチルアルコール、１−ペンタノール、２−ペンタノール、２−メチル−２−ペンタノール、２−メトキシエタノールを用いるのが好適である。 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.
なお、強誘電体薄膜形成用組成物の有機金属化合物溶液中の有機金属化合物の合計濃度は、金属酸化物換算量で０．１〜２０質量％程度とすることが好ましい。 The total concentration of the organometallic compound in the organometallic compound solution of the ferroelectric thin film forming composition is preferably about 0.1 to 20% by mass in terms of metal oxide.
この有機金属化合物溶液中には、必要に応じて安定化剤として、β−ジケトン類（例えば、アセチルアセトン、ヘプタフルオロブタノイルピバロイルメタン、ジピバロイルメタン、トリフルオロアセチルアセトン、ベンゾイルアセトン等）、β−ケトン酸類（例えば、アセト酢酸、プロピオニル酢酸、ベンゾイル酢酸等）、β−ケトエステル類（例えば、上記ケトン酸のメチル、プロピル、ブチル等の低級アルキルエステル類）、オキシ酸類（例えば、乳酸、グリコール酸、α−オキシ酪酸、サリチル酸等）、上記オキシ酸の低級アルキルエステル類、オキシケトン類（例えば、ジアセトンアルコール、アセトイン等）、ジオール、トリオール、高級カルボン酸、アルカノールアミン類（例えば、ジエタノールアミン、トリエタノールアミン、モノエタノールアミン）、多価アミン等を、（安定化剤分子数）／（金属原子数）で０．２〜３程度添加しても良い。 In this organometallic compound solution, β-diketones (for example, acetylacetone, heptafluorobutanoylpivaloylmethane, dipivaloylmethane, trifluoroacetylacetone, benzoylacetone, etc.) are used as stabilizers as necessary. , Β-ketone acids (for example, acetoacetic acid, propionylacetic acid, benzoylacetic acid, etc.), β-ketoesters (for example, lower alkyl esters such as methyl, propyl, and butyl of the above ketone acids), 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, Roh ethanolamine), a polyvalent amine or the like, may be added from 0.2 to 3 approximately at (stabilizer number of molecules) / (number of metal atoms).
本発明では、上記調製された有機金属化合物溶液を濾過処理等によって、パーティクルを除去して、粒径０．５μｍ以上（特に０．３μｍ以上とりわけ０．２μｍ以上）のパーティクルの個数が溶液１ｍＬ当り５０個／ｍＬ以下とするのが好ましい。 In the present invention, particles are removed from the prepared organometallic compound solution by filtration or the like, 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) per 1 mL of the solution. It is preferable to be 50 / mL or less.
なお、当該有機金属化合物溶液中のパーティクルの個数の測定には、光散乱式パーティクルカウンターを用いる。 A light scattering particle counter is used for measuring the number of particles in the organometallic compound solution.
有機金属化合物溶液中の粒径０．５μｍ以上のパーティクルの個数が５０個／ｍＬを越えると、長期保存安定性が劣るものとなる。この有機金属化合物溶液中の粒径０．５μｍ以上のパーティクルの個数は少ない程好ましく、特に３０個／ｍＬ以下であることが好ましい。 If the number of particles having a particle size of 0.5 μm or more in the organometallic compound solution exceeds 50 particles / mL, the long-term storage stability becomes poor. The smaller the number of particles having a particle size of 0.5 μm or more in this organometallic compound solution, the more preferable, and particularly preferably 30 particles / mL or less.
上記パーティクル個数となるように、調製後の有機金属化合物溶液を処理する方法は特に限定されるものではないが、例えば、次のような方法が挙げられる。第１の方法としては、市販の０．２μｍ孔径のメンブランフィルターを使用し、シリンジで圧送する濾過法である。第２の方法としては、市販の０．０５μｍ孔径のメンブランフィルターと加圧タンクを組み合せた加圧濾過法である。第３の方法としては、上記第２の方法で使用したフィルターと溶液循環槽を組み合せた循環濾過法である。 The method for treating the organometallic compound solution after preparation so as to achieve the number of particles is not particularly limited, and examples thereof include the following method. 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.
いずれの方法においても、溶液圧送圧力によって、フィルターによるパーティクル捕捉率が異なる。圧力が低いほど捕捉率が高くなることは一般的に知られており、特に、第１の方法、第２の方法について、粒径０．５μｍ以上のパーティクルの個数を５０個以下とする条件を実現するためには、溶液を低圧で非常にゆっくりとフィルターに通すのが好ましい。 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.
本発明の強誘電体薄膜形成用組成物を用いることで、ＰＬＺＴ、ＰＺＴ及びＰＴからなる群より選ばれた１種の複合金属酸化物Ａに、Ｃｅを含む複合金属酸化物Ｂが混合した混合複合金属酸化物の形態をとる強誘電体薄膜を簡便に形成することができる。 By using the composition for forming a ferroelectric thin film of the present invention, a mixed metal oxide B containing Ce is mixed with one kind of mixed metal oxide A selected from the group consisting of PLZT, PZT, and PT. A ferroelectric thin film in the form of a composite metal oxide can be easily formed.
本発明の強誘電体薄膜形成用組成物を用いて、強誘電体薄膜を形成するには、上記組成物をスピンコート、ディップコート、ＬＳＭＣＤ（Ｌｉｑｕｉｄ Ｓｏｕｒｃｅ ＭｉｓｔｅｄＣｈｅｍｉｃａｌ Ｄｅｐｏｓｉｔｉｏｎ）法等の塗布法により耐熱性基板上に塗布し、乾燥（仮焼成）及び本焼成を行う。 In order to form a ferroelectric thin film by using the composition for forming a ferroelectric thin film of the present invention, the composition is heat-resistant by a coating method such as spin coating, dip coating, or LSMCD (Liquid Source Misted Chemical Deposition). It apply | coats on a board | substrate and performs drying (temporary baking) and main baking.
使用される耐熱性基板の具体例としては、基板表層部に、単結晶Ｓｉ、多結晶Ｓｉ，Ｐｔ，Ｐｔ（最上層）／Ｔｉ，Ｐｔ（最上層）／Ｔａ，Ｒｕ，ＲｕＯ2，Ｒｕ（最上層）／ＲｕＯ2，ＲｕＯ2（最上層）／Ｒｕ，Ｉｒ，ＩｒＯ2，Ｉｒ（最上層）／ＩｒＯ2，Ｐｔ（最上層）／Ｉｒ，Ｐｔ（最上層）／ＩｒＯ2，ＳｒＲｕＯ3又は（ＬａxＳｒ(1-x)）ＣｏＯ3等のペロブスカイト型導電性酸化物等を用いた基板が挙げられるが、これらに限定されるものではない。 As a specific example of the heat-resistant substrate to be used, a single crystal Si, polycrystalline Si, Pt, Pt (uppermost layer) / Ti, Pt (uppermost layer) / Ta, Ru, RuO 2 , Ru ( Top layer) / RuO 2 , RuO 2 (top layer) / Ru, Ir, IrO 2 , Ir (top layer) / IrO 2 , Pt (top layer) / Ir, Pt (top layer) / IrO 2 , SrRuO 3 or (La x Sr (1-x )) is a substrate with CoO 3 perovskite-type conductive oxide such like, but not limited thereto.
なお、１回の塗布では、所望の膜厚が得られない場合には、塗布、乾燥の工程を複数回繰返し行った後、本焼成を行う。ここで、所望の膜厚とは、本焼成後に得られる強誘電体薄膜の厚さをいい、高容量密度の薄膜キャパシタ用途の場合、本焼成後の強誘電体薄膜の膜厚が５０〜５００ｎｍの範囲である。 In addition, when a desired film thickness cannot be obtained by one application, the application and drying steps are repeated a plurality of times, followed by firing. Here, the desired film thickness refers to the thickness of the ferroelectric thin film obtained after the main firing, and in the case of a high capacity density thin film capacitor, the film thickness of the ferroelectric thin film after the main firing is 50 to 500 nm. Range.
また、仮焼成は、溶媒を除去するとともに有機金属化合物を熱分解又は加水分解して複合酸化物に転化させるために行うことから、空気中、酸化雰囲気中、又は含水蒸気雰囲気中で行う。空気中での加熱でも、加水分解に必要な水分は空気中の湿気により十分に確保される。この加熱は、溶媒の除去のための低温加熱と、有機金属化合物の分解のための高温加熱の２段階で実施しても良い。 In addition, the preliminary calcination is performed in order to remove the solvent and thermally decompose or hydrolyze the organometallic compound to convert it into a composite oxide. Therefore, the calcination is performed in air, in an oxidizing atmosphere, or in a steam-containing atmosphere. Even in heating in the air, the moisture required for hydrolysis is sufficiently secured by the humidity in the air. This heating may be performed in two stages: low temperature heating for removing the solvent and high temperature heating for decomposing the organometallic compound.
本焼成は、仮焼成で得られた薄膜を結晶化温度以上の温度で焼成して結晶化させるための工程であり、これにより強誘電体薄膜が得られる。この結晶化工程の焼成雰囲気はＯ2、Ｎ2、Ａｒ、Ｎ2Ｏ又はＨ2等或いはこれらの混合ガス等が好適である。 The main firing is a step for firing and crystallizing the thin film obtained by the pre-firing at a temperature equal to or higher than the crystallization temperature, whereby a ferroelectric 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.
仮焼成は、１５０〜５５０℃で５〜１０分間程度行われ、本焼成は４５０〜８００℃で１〜６０分間程度行われる。本焼成は、急速加熱処理（ＲＴＡ処理）で行っても良い。ＲＴＡ処理で本焼成する場合、その昇温速度は１０〜１００℃／秒が好ましい。 The pre-baking is performed at 150 to 550 ° C. for about 5 to 10 minutes, and the main baking is performed at 450 to 800 ° C. for about 1 to 60 minutes. The main baking may be performed by rapid heating treatment (RTA treatment). When the main baking is performed by the RTA treatment, the heating rate is preferably 10 to 100 ° C./second.
このようにして形成された本発明の強誘電体薄膜は、従来の強誘電体薄膜と同程度の比誘電率を有し、かつ、低いリーク電流密度が得られるため、高容量密度の薄膜キャパシタ用途に好適である。従って、従来の強誘電体薄膜と同程度のリーク電流密度とする場合には、更なる薄膜化が可能となり、より高い容量密度が得られ、キャパシタとしての基本的特性に優れる。また、薄膜化することによって、原材料の使用を低減することができるという別の利点も有する。また、本発明の強誘電体薄膜は、ＩＰＤとしての基本的特性にも優れる。 The ferroelectric thin film of the present invention thus formed has a relative dielectric constant comparable to that of a conventional ferroelectric thin film, and a low leakage current density can be obtained. Suitable for use. Therefore, when the leakage current density is about the same as that of the conventional ferroelectric thin film, further thinning is possible, a higher capacity density is obtained, and the basic characteristics as a capacitor are excellent. In addition, by using a thin film, there is another advantage that the use of raw materials can be reduced. The ferroelectric thin film of the present invention is also excellent in basic characteristics as an IPD.
また、本発明の強誘電体薄膜は、薄膜コンデンサ、キャパシタ、ＩＰＤ、ＤＲＡＭメモリ用コンデンサ、積層コンデンサ、トランジスタのゲート絶縁体、不揮発性メモリ、焦電型赤外線検出素子、圧電素子、電気光学素子、アクチュエータ、共振子、超音波モータ、又はＬＣノイズフィルタ素子の複合電子部品における構成材料として使用することができる。このうち特に１００ＭＨｚ以上の周波数帯域に対応したものに使用することもできる。 The ferroelectric thin film of the present invention includes 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, It can be used as a constituent material in composite electronic parts of actuators, resonators, ultrasonic motors, or LC noise filter elements. Among these, it can also be used especially for the thing corresponding to the frequency band of 100 MHz or more.
次に本発明の実施例を比較例とともに詳しく説明する。 Next, examples of the present invention will be described in detail together with comparative examples.
＜実施例１〜５＞
先ず、反応容器にジルコニウムテトラｎ−ブトキシドと安定化剤としてアセチルアセトンを添加し、窒素雰囲気下、１５０℃の温度で還流した。これにチタンテトライソプロポキシドと安定化剤としてアセチルアセトンを添加し、窒素雰囲気下、１５０℃の温度で還流した。次いで、これに酢酸鉛３水和物と溶媒としてプロピレングリコールを添加し、窒素雰囲気下、１５０℃の温度で還流した。その後、１５０℃で減圧蒸留して副生成物を除去し、更にプロピレングリコールを添加し、濃度調整することで酸化物換算で３０質量％濃度の金属化合物を含有する液を得た。更に、希釈アルコールを添加することで酸化物換算で各金属比がＰｂ／Ｚｒ／Ｔｉ＝１１０／５２／４８の１０質量％濃度の金属化合物を含有するゾルゲル液を得た。
<Examples 1-5>
First, zirconium tetra-n-butoxide and acetylacetone as a stabilizer were added to a reaction vessel, and refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Titanium tetraisopropoxide and acetylacetone as a stabilizer were added thereto and refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Next, lead acetate trihydrate and propylene glycol as a solvent were added thereto and refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Thereafter, the by-product was removed by distillation under reduced pressure at 150 ° C., and further, propylene glycol was added and the concentration was adjusted to obtain a liquid containing a 30% by mass metal compound in terms of oxide. Furthermore, by adding diluted alcohol, a sol-gel solution containing a metal compound having a concentration of 10% by mass with a metal ratio of Pb / Zr / Ti = 110/52/48 in terms of oxide was obtained.
次に、ゾルゲル液を５等分し、これらのゾルゲル液に外割で０．５ｍｏｌ％の各種セリウム化合物（２−エチルヘキサン酸セリウム、２−エチル酪酸セリウム、セリウムトリエトキシド、セリウムトリｎ−ブトキシド、トリス（アセチルアセトネート）セリウム）をそれぞれ添加することにより、５種類の薄膜形成用溶液を得た。 Next, the sol-gel solution is divided into five equal parts, and 0.5 mol% of various cerium compounds (2-ethylhexanoic acid cerium, 2-ethylbutyric acid cerium, cerium triethoxide, cerium tri-n-butoxide are divided into these sol-gel liquids in an external ratio. , Tris (acetylacetonate) cerium) were added to obtain 5 types of thin film forming solutions.
これら５種類の薄膜形成用溶液を用いて、下記方法によりＣＳＤ法による薄膜の形成を行った。即ち、各々の溶液をスピンコート法により５００ｒｐｍで３秒間、その後３０００ｒｐｍで１５秒間の条件でＰｔ薄膜を表面にスパッタリング法にて形成した６インチシリコン基板（Ｐｔ／ＴｉＯ2／ＳｉＯ2／Ｓｉ（１００）基板）上に塗布した。続いて、ホットプレートを用い、３５０℃で５分間加熱して仮焼成を行った。この塗布、仮焼成の工程を６回繰返した後、１００％酸素雰囲気中で７００℃、１分間ＲＴＡ（急速加熱処理装置）で焼成して膜厚２７０ｎｍの強誘電体薄膜を形成した。 Using these five types of thin film forming solutions, thin films were formed by the CSD method by the following method. That is, a 6-inch silicon substrate (Pt / TiO 2 / SiO 2 / Si (100) on which a Pt thin film was formed on the surface by a spin coating method at 500 rpm for 3 seconds and then at 3000 rpm for 15 seconds. ) Substrate). Subsequently, using a hot plate, heating was performed at 350 ° C. for 5 minutes to perform temporary baking. This coating and pre-baking process was repeated 6 times, and then baked with an RTA (rapid heat treatment apparatus) at 700 ° C. for 1 minute in a 100% oxygen atmosphere to form a 270 nm thick ferroelectric thin film.
＜実施例６〜１０＞
ゾルゲル液に外割で１．０ｍｏｌ％の各種セリウム化合物を添加して薄膜形成用溶液とした以外は、実施例１〜５と同様にして基板上に強誘電体薄膜を形成した。
<Examples 6 to 10>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 1 to 5, except that 1.0 mol% of various cerium compounds were added to the sol-gel solution to obtain a thin film forming solution.
＜実施例１１〜１５＞
ゾルゲル液に外割で３．０ｍｏｌ％の各種セリウム化合物を添加して薄膜形成用溶液とした以外は、実施例１〜５と同様にして基板上に強誘電体薄膜を形成した。
<Examples 11 to 15>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 1 to 5 except that 3.0 mol% of various cerium compounds were added to the sol-gel solution to obtain a thin film forming solution.
＜実施例１６＞
ゾルゲル液に外割で１．０ｍｏｌ％のランタン化合物（酢酸ランタン１．５水和物）と１．０ｍｏｌ％のセリウム化合物（２−エチルヘキサン酸セリウム）を添加して薄膜形成用溶液とした以外は、実施例１〜５と同様にして基板上に強誘電体薄膜を形成した。
<Example 16>
Other than adding 1.0 mol% of lanthanum compound (lanthanum acetate hemihydrate) and 1.0 mol% of cerium compound (cerium 2-ethylhexanoate) to the sol-gel solution to make a thin film forming solution In the same manner as in Examples 1 to 5, a ferroelectric thin film was formed on the substrate.
＜実施例１７＞
ゾルゲル液に外割で１．０ｍｏｌ％のランタン化合物（酢酸ランタン１．５水和物）と１．０ｍｏｌ％のセリウム化合物（セリウムトリエトキシド）を添加して薄膜形成用溶液とした以外は、実施例１〜５と同様にして基板上に強誘電体薄膜を形成した。
<Example 17>
Except for adding 1.0 mol% lanthanum compound (lanthanum acetate hemihydrate) and 1.0 mol% cerium compound (cerium triethoxide) to the sol-gel solution, A ferroelectric thin film was formed on the substrate in the same manner as in Examples 1-5.
＜比較例１＞
ゾルゲル液にセリウム化合物を添加せず、薄膜形成用溶液とした以外は、実施例１〜５と同様にして基板上に強誘電体薄膜を形成した。
<Comparative Example 1>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 1 to 5 except that the cerium compound was not added to the sol-gel solution and the solution was used for forming a thin film.
＜比較例２＞
ゾルゲル液にセリウム化合物を添加せず、その代わりに外割で１．０ｍｏｌ％のランタン化合物（酢酸ランタン１．５水和物）を添加して薄膜形成用溶液とした以外は、実施例１〜５と同様にして基板上に強誘電体薄膜を形成した。
<Comparative example 2>
Example 1 except that no cerium compound was added to the sol-gel solution, and instead 1.0 mol% of a lanthanum compound (lanthanum acetate hemihydrate) was added to form a thin film forming solution. In the same manner as in 5, a ferroelectric thin film was formed on the substrate.
＜実施例１８〜２２＞
先ず、反応容器にジルコニウムテトラｎ−ブトキシドと安定化剤としてジエタノールアミンを添加し、窒素雰囲気下、１５０℃の温度で還流した。これにチタンテトライソプロポキシドと安定化剤としてジエタノールアミンを添加し、窒素雰囲気下、１５０℃の温度で還流した。次いで、これに酢酸鉛３水和物と溶媒としてプロピレングリコールを添加し、窒素雰囲気下、１５０℃の温度で還流した。その後、１５０℃で減圧蒸留して副生成物を除去し、更にプロピレングリコールを添加し、濃度調整することで酸化物換算で３０質量％濃度の金属化合物を含有する液を得た。更に、希釈アルコールを添加することで酸化物換算で各金属比がＰｂ／Ｚｒ／Ｔｉ＝１１０／５２／４８の１０質量％濃度の金属化合物を含有するゾルゲル液を得た。
<Examples 18 to 22>
First, zirconium tetra n-butoxide and diethanolamine as a stabilizer were added to a reaction vessel, and the mixture was refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Titanium tetraisopropoxide and diethanolamine as a stabilizer were added thereto, and the mixture was refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Next, lead acetate trihydrate and propylene glycol as a solvent were added thereto and refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Thereafter, the by-product was removed by distillation under reduced pressure at 150 ° C., and further, propylene glycol was added and the concentration was adjusted to obtain a liquid containing a 30% by mass metal compound in terms of oxide. Furthermore, by adding diluted alcohol, a sol-gel solution containing a metal compound having a concentration of 10% by mass with a metal ratio of Pb / Zr / Ti = 110/52/48 in terms of oxide was obtained.
次に、ゾルゲル液を５等分し、これらのゾルゲル液に外割で０．５ｍｏｌ％の各種セリウム化合物（２−エチルヘキサン酸セリウム、２−エチル酪酸セリウム、セリウムトリエトキシド、セリウムトリｎ−ブトキシド、トリス（アセチルアセトネート）セリウム）をそれぞれ添加することにより、５種類の薄膜形成用溶液を得た。 Next, the sol-gel solution is divided into five equal parts, and 0.5 mol% of various cerium compounds (2-ethylhexanoic acid cerium, 2-ethylbutyric acid cerium, cerium triethoxide, cerium tri-n-butoxide are divided into these sol-gel liquids in an external ratio. , Tris (acetylacetonate) cerium) were added to obtain 5 types of thin film forming solutions.
これら５種類の薄膜形成用溶液を用いて、下記方法によりＣＳＤ法による薄膜の形成を行った。即ち、各々の溶液をスピンコート法により５００ｒｐｍで３秒間、その後３０００ｒｐｍで１５秒間の条件でＰｔ薄膜を表面にスパッタリング法にて形成した６インチシリコン基板（Ｐｔ／ＴｉＯ2／ＳｉＯ2／Ｓｉ（１００）基板）上に塗布した。続いて、ホットプレートを用い、３５０℃で５分間加熱して仮焼成を行った。この塗布、仮焼成の工程を６回繰返した後、１００％酸素雰囲気中で７００℃、１分間ＲＴＡ（急速加熱処理装置）で焼成して膜厚２７０ｎｍの強誘電体薄膜を形成した。 Using these five types of thin film forming solutions, thin films were formed by the CSD method by the following method. That is, a 6-inch silicon substrate (Pt / TiO 2 / SiO 2 / Si (100) on which a Pt thin film was formed on the surface by a spin coating method at 500 rpm for 3 seconds and then at 3000 rpm for 15 seconds. ) Substrate). Subsequently, using a hot plate, heating was performed at 350 ° C. for 5 minutes to perform temporary baking. This coating and pre-baking process was repeated 6 times, and then baked with an RTA (rapid heat treatment apparatus) at 700 ° C. for 1 minute in a 100% oxygen atmosphere to form a 270 nm thick ferroelectric thin film.
＜実施例２３〜２７＞
ゾルゲル液に外割で１．０ｍｏｌ％の各種セリウム化合物を添加して薄膜形成用溶液とした以外は、実施例１８〜２２と同様にして基板上に強誘電体薄膜を形成した。
<Examples 23 to 27>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 18 to 22 except that 1.0 mol% of various cerium compounds were added to the sol-gel solution to obtain a thin film forming solution.
＜実施例２８〜３２＞
ゾルゲル液に外割で３．０ｍｏｌ％の各種セリウム化合物を添加して薄膜形成用溶液とした以外は、実施例１８〜２２と同様にして基板上に強誘電体薄膜を形成した。
<Examples 28 to 32>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 18 to 22, except that 3.0 mol% of various cerium compounds were added to the sol-gel solution to obtain a thin film forming solution.
＜実施例３３＞
ゾルゲル液に外割で１．０ｍｏｌ％のランタン化合物（酢酸ランタン１．５水和物）と１．０ｍｏｌ％のセリウム化合物（２−エチルヘキサン酸セリウム）を添加して薄膜形成用溶液とした以外は、実施例１８〜２２と同様にして基板上に強誘電体薄膜を形成した。
<Example 33>
Other than adding 1.0 mol% of lanthanum compound (lanthanum acetate hemihydrate) and 1.0 mol% of cerium compound (cerium 2-ethylhexanoate) to the sol-gel solution to make a thin film forming solution In the same manner as in Examples 18-22, a ferroelectric thin film was formed on the substrate.
＜実施例３４＞
ゾルゲル液に外割で１．０ｍｏｌ％のランタン化合物（酢酸ランタン１．５水和物）と１．０ｍｏｌ％のセリウム化合物（セリウムトリエトキシド）を添加して薄膜形成用溶液とした以外は、実施例１８〜２２と同様にして基板上に強誘電体薄膜を形成した。
<Example 34>
Except for adding 1.0 mol% lanthanum compound (lanthanum acetate hemihydrate) and 1.0 mol% cerium compound (cerium triethoxide) to the sol-gel solution, A ferroelectric thin film was formed on the substrate in the same manner as in Examples 18-22.
＜比較例３＞
ゾルゲル液にセリウム化合物を添加せず、薄膜形成用溶液とした以外は、実施例１８〜２２と同様にして基板上に強誘電体薄膜を形成した。
<Comparative Example 3>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 18 to 22, except that the sol-gel solution was not added with a cerium compound and used as a thin film forming solution.
＜比較例４＞
ゾルゲル液にセリウム化合物を添加せず、その代わりに外割で１．０ｍｏｌ％のランタン化合物（酢酸ランタン１．５水和物）を添加して薄膜形成用溶液とした以外は、実施例１８〜２２と同様にして基板上に強誘電体薄膜を形成した。
<Comparative example 4>
Except that the cerium compound was not added to the sol-gel solution, and instead, 1.0 mol% of lanthanum compound (lanthanum acetate hemihydrate) was added to obtain a solution for forming a thin film. In the same manner as in No. 22, a ferroelectric thin film was formed on the substrate.
＜実施例３５〜３９＞
先ず、反応容器にジルコニウムテトラｎ−ブトキシドと安定化剤としてアセチルアセトンを添加し、窒素雰囲気下、１５０℃の温度で還流した。これにチタンテトライソプロポキシドと安定化剤としてアセチルアセトンを添加し、窒素雰囲気下、１５０℃の温度で還流した。次いで、これに酢酸鉛３水和物と溶媒としてプロピレングリコールを添加し、窒素雰囲気下、１５０℃の温度で還流した。その後、１５０℃で減圧蒸留して副生成物を除去し、更にプロピレングリコールを添加し、濃度調整することで酸化物換算で３０質量％濃度の金属化合物を含有する液を得た。更に、希釈アルコールを添加することで酸化物換算で各金属比がＰｂ／Ｚｒ／Ｔｉ＝１１０／５２／４８の１０質量％濃度の金属化合物を含有するゾルゲル液を得た。
<Examples 35 to 39>
First, zirconium tetra-n-butoxide and acetylacetone as a stabilizer were added to a reaction vessel, and refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Titanium tetraisopropoxide and acetylacetone as a stabilizer were added thereto and refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Next, lead acetate trihydrate and propylene glycol as a solvent were added thereto and refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Thereafter, the by-product was removed by distillation under reduced pressure at 150 ° C., and further, propylene glycol was added and the concentration was adjusted to obtain a liquid containing a 30% by mass metal compound in terms of oxide. Furthermore, by adding diluted alcohol, a sol-gel solution containing a metal compound having a concentration of 10% by mass with a metal ratio of Pb / Zr / Ti = 110/52/48 in terms of oxide was obtained.
次に、ゾルゲル液を５等分し、これらのゾルゲル液に外割で０．５ｍｏｌ％の各種セリウム化合物（２−エチルヘキサン酸セリウム、２−エチル酪酸セリウム、セリウムトリエトキシド、セリウムトリｎ−ブトキシド、トリス（アセチルアセトネート）セリウム）をそれぞれ添加することにより、５種類の薄膜形成用溶液を得た。 Next, the sol-gel solution is divided into five equal parts, and 0.5 mol% of various cerium compounds (2-ethylhexanoic acid cerium, 2-ethylbutyric acid cerium, cerium triethoxide, cerium tri-n-butoxide are divided into these sol-gel liquids in an external ratio. , Tris (acetylacetonate) cerium) were added to obtain 5 types of thin film forming solutions.
これら５種類の薄膜形成用溶液を用いて、下記方法によりＣＳＤ法による薄膜の形成を行った。即ち、各々の溶液をスピンコート法により５００ｒｐｍで３秒間、その後３０００ｒｐｍで１５秒間の条件でＰｔ薄膜を表面にスパッタリング法にて形成した６インチシリコン基板（Ｐｔ／ＴｉＯ2／ＳｉＯ2／Ｓｉ（１００）基板）上に塗布した。続いて、ホットプレートを用い、３５０℃で５分間加熱して仮焼成を行った。この塗布、仮焼成の工程を６回繰返した後、乾燥空気雰囲気中で７００℃、１分間ＲＴＡ（急速加熱処理装置）で焼成して膜厚２７０ｎｍの強誘電体薄膜を形成した。 Using these five types of thin film forming solutions, thin films were formed by the CSD method by the following method. That is, a 6-inch silicon substrate (Pt / TiO 2 / SiO 2 / Si (100) on which a Pt thin film was formed on the surface by a spin coating method at 500 rpm for 3 seconds and then at 3000 rpm for 15 seconds. ) Substrate). Subsequently, using a hot plate, heating was performed at 350 ° C. for 5 minutes to perform temporary baking. This coating and pre-baking process was repeated 6 times, and then baked in a dry air atmosphere at 700 ° C. for 1 minute with an RTA (rapid heat treatment apparatus) to form a 270 nm thick ferroelectric thin film.
＜実施例４０〜４４＞
ゾルゲル液に外割で１．０ｍｏｌ％の各種セリウム化合物を添加して薄膜形成用溶液とした以外は、実施例３５〜３９と同様にして基板上に強誘電体薄膜を形成した。
<Examples 40 to 44>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 35 to 39 except that 1.0 mol% of various cerium compounds were added to the sol-gel solution to obtain a thin film forming solution.
＜実施例４５〜４９＞
ゾルゲル液に外割で３．０ｍｏｌ％の各種セリウム化合物を添加して薄膜形成用溶液とした以外は、実施例３５〜３９と同様にして基板上に強誘電体薄膜を形成した。
<Examples 45-49>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 35 to 39 except that 3.0 mol% of various cerium compounds were added to the sol-gel solution to obtain a thin film forming solution.
＜実施例５０＞
ゾルゲル液に外割で１．０ｍｏｌ％のランタン化合物（酢酸ランタン１．５水和物）と１．０ｍｏｌ％のセリウム化合物（２−エチルヘキサン酸セリウム）を添加して薄膜形成用溶液とした以外は、実施例３５〜３９と同様にして基板上に強誘電体薄膜を形成した。
<Example 50>
Other than adding 1.0 mol% of lanthanum compound (lanthanum acetate hemihydrate) and 1.0 mol% of cerium compound (cerium 2-ethylhexanoate) to the sol-gel solution to make a thin film forming solution A ferroelectric thin film was formed on the substrate in the same manner as in Examples 35-39.
＜実施例５１＞
ゾルゲル液に外割で１．０ｍｏｌ％のランタン化合物（酢酸ランタン１．５水和物）と１．０ｍｏｌ％のセリウム化合物（セリウムトリエトキシド）を添加して薄膜形成用溶液とした以外は、実施例３５〜３９と同様にして基板上に強誘電体薄膜を形成した。
<Example 51>
Except for adding 1.0 mol% lanthanum compound (lanthanum acetate hemihydrate) and 1.0 mol% cerium compound (cerium triethoxide) to the sol-gel solution, In the same manner as in Examples 35 to 39, a ferroelectric thin film was formed on the substrate.
＜比較例５＞
ゾルゲル液にセリウム化合物を添加せず、薄膜形成用溶液とした以外は、実施例３５〜３９と同様にして基板上に強誘電体薄膜を形成した。
<Comparative Example 5>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 35 to 39 except that a cerium compound was not added to the sol-gel solution and a thin film forming solution was used.
＜比較例６＞
ゾルゲル液にセリウム化合物を添加せず、その代わりに外割で１．０ｍｏｌ％のランタン化合物（酢酸ランタン１．５水和物）を添加して薄膜形成用溶液とした以外は、実施例３５〜３９と同様にして基板上に強誘電体薄膜を形成した。
<Comparative Example 6>
Except that the cerium compound was not added to the sol-gel solution, instead of adding 1.0 mol% of a lanthanum compound (lanthanum acetate hemihydrate) to obtain a solution for forming a thin film, Example 35 to Example 35 In the same manner as in 39, a ferroelectric thin film was formed on the substrate.
＜比較評価＞
実施例１〜５１及び比較例１〜６で得られた強誘電体薄膜を形成した基板について、メタルマスクを用い、表面に約２５０μｍ□のＰｔ上部電極をスパッタリング法にて作製し、強誘電体薄膜直下のＰｔ下部電極間にて直流電圧を印加し、Ｉ−Ｖ特性（リーク電流密度の電圧依存性）を評価した。また、強誘電体薄膜直下のＰｔ下部電極間にてＣ−Ｖ特性（静電容量の電圧依存性）を周波数１ｋＨｚにて−５〜５Ｖの範囲で評価し、静電容量の最大値より比誘電率εｒを算出した。その結果を次の表１〜表３にそれぞれ示す。なお、Ｉ−Ｖ特性の測定には、Ｋｅｉｔｈｌｅｙ社製 ２３６ ＳＭＵを用い、Ｂｉａｓ ｓｔｅｐ ０．５Ｖ、Ｄｅｌａｙ ｔｉｍｅ ０．１ｓｅｃ、Ｔｅｍｐｅｒａｔｕｒｅ ２３℃、Ｈｙｇｒｏｍｅｔｒｙ ５０±１０％の条件で測定した。また、Ｃ−Ｖ特性の測定には、ＨＰ社製４２８４Ａ ｐｒｅｃｉｓｉｏｎ ＬＣＲ ｍｅｔｅｒを用い、Ｂｉａｓ ｓｔｅｐ ０．１Ｖ、Ｆｒｅｑｕｅｎｃｙ １ｋＨｚ、Ｏｓｃｉｌｌａｔｉｏｎ ｌｅｖｅｌ ３０ｍＶ、Ｄｅｌａｙ ｔｉｍｅ ０．２ｓｅｃ、Ｔｅｍｐｅｒａｔｕｒｅ ２３℃、Ｈｙｇｒｏｍｅｔｒｙ ５０±１０％の条件で測定した。
<Comparison evaluation>
About the board | substrate which formed the ferroelectric thin film obtained in Examples 1-51 and Comparative Examples 1-6, about 250 micrometers square Pt upper electrode was produced with the sputtering method on the surface, and the ferroelectric A DC voltage was applied between the Pt lower electrodes immediately below the thin film, and the IV characteristics (voltage dependence of leakage current density) were evaluated. Also, CV characteristics (voltage dependence of capacitance) are evaluated in the range of -5 to 5 V at a frequency of 1 kHz between the Pt lower electrodes directly below the ferroelectric thin film, and the ratio is compared with the maximum value of capacitance. The dielectric constant εr was calculated. The results are shown in the following Tables 1 to 3, respectively. The IV characteristics were measured using a 236 SMU manufactured by Keithley under the conditions of bias step 0.5 V, delay time 0.1 sec, temperature 23 ° C., and hygrometry 50 ± 10%. In addition, for measurement of the CV characteristics, 4284A precision LCR meter manufactured by HP was used, Bias step 0.1V, Frequency 1 kHz, Oscillation level 30 mV, Delay time 0.2 sec, Temperature 23 ° C., Hygrometer 10 ° C. Measured under conditions.
また、Ｌａを含む比較例２，４，６のＰＬＺＴ強誘電体薄膜との比較では、５Ｖ印加時、２０Ｖ印加時、いずれもリーク電流密度の低減が確認された。 Further, in comparison with the PLZT ferroelectric thin films of Comparative Examples 2, 4, and 6 containing La, it was confirmed that the leakage current density was reduced when 5V was applied and when 20V was applied.
また、静電容量及び比誘電率については、実施例１〜５１の強誘電体薄膜は、比較例１〜６の強誘電体薄膜と比較すると、若干数値が低い例も見られたが、全体として、見劣りしない結果であり、従来より知られている強誘電体薄膜と遜色ない数値が得られたといえる。 In addition, regarding the capacitance and relative dielectric constant, the ferroelectric thin films of Examples 1 to 51 were slightly lower in numerical values than the ferroelectric thin films of Comparative Examples 1 to 6, but overall The result is not inferior, and it can be said that a numerical value comparable to the conventionally known ferroelectric thin film was obtained.
しかし、実施例１〜５１の強誘電体薄膜を、比較例１〜６の強誘電体薄膜と同程度のリーク電流密度の水準とする場合には、更なる薄膜化が可能となり、薄膜化することで、より高い比誘電率が得られるという利点を有する。 However, when the ferroelectric thin film of Examples 1 to 51 is set to a leak current density level comparable to that of the ferroelectric thin films of Comparative Examples 1 to 6, further thinning is possible and the thinning is achieved. Thus, there is an advantage that a higher relative dielectric constant can be obtained.
これらの結果から、実施例１〜５１の強誘電体薄膜は、比誘電率を減少させることなく、リーク電流密度低減に優れた効果を有しており、薄膜化が可能であることから、高容量密度が達成できる。 From these results, the ferroelectric thin films of Examples 1 to 51 have an excellent effect of reducing the leakage current density without reducing the relative dielectric constant, and can be made thin. Capacity density can be achieved.
本発明の強誘電体薄膜形成用組成物、強誘電体薄膜の形成方法並びに該方法により形成された強誘電体薄膜は、キャパシタとしての基本的特性に優れ、高密度、高絶縁破壊耐圧のキャパシタに利用可能である。その他、ＩＰＤとしての基本的特性にも優れ、ＩＰＤ、ＤＲＡＭメモリ用コンデンサ、積層コンデンサ、トランジスタのゲート絶縁体、不揮発性メモリ、焦電型赤外線検出素子、圧電素子、電気光学素子、アクチュエータ、共振子、超音波モータ、又はＬＣノイズフィルタ素子等の複合電子部品に利用が可能である。 Composition for forming a ferroelectric thin film of the present invention, method for forming a ferroelectric thin film, and a ferroelectric thin film formed by the method are excellent in basic characteristics as a capacitor, and have a high density and a high breakdown voltage. Is available. In addition, it has excellent basic characteristics as an IPD. IPD, DRAM memory capacitor, multilayer capacitor, transistor gate insulator, nonvolatile memory, pyroelectric infrared detector, piezoelectric element, electro-optical element, actuator, resonator It can be used for composite electronic parts such as ultrasonic motors or LC noise filter elements.
Claims (10)
一般式：（ＰｂxＬａy）（ＺｒzＴｉ(1-z)）Ｏ3（式中０．９＜ｘ＜１．３、０≦ｙ＜０．１、０＜ｚ＜０．９）で示される複合金属酸化物Ａに、Ｃｅを含む複合金属酸化物Ｂが混合した混合複合金属酸化物の形態をとる薄膜を形成するための液状組成物であり、
前記複合金属酸化物Ａを構成するための原料並びに前記複合金属酸化物Ｂを構成するための原料が上記一般式で示される金属原子比を与えるような割合で有機溶媒中に溶解している有機金属化合物溶液からなり、
有機金属化合物溶液中の粒径０．５μｍ以上のパーティクルの個数が５０個／ｍＬ以下であり、
前記複合金属酸化物Ｂが２−エチルヘキサン酸セリウム、２−エチル酪酸酸セリウム、セリウムトリｎ−ブトキシド、セリウムトリエトキシド又はトリス（アセチルアセトネート）セリウムからなる
ことを特徴とする強誘電体薄膜形成用組成物。 In the composition for forming a ferroelectric thin film for forming one kind of ferroelectric thin film selected from the group consisting of PLZT and PZT,
General formula: (Pb x La y ) (Zr z Ti (1-z) ) O 3 (where 0.9 <x <1.3, 0 ≦ y <0.1, 0 < z <0.9) A liquid composition for forming a thin film in the form of a mixed composite metal oxide in which a composite metal oxide B containing Ce is mixed with the composite metal oxide A represented by
The organic material dissolved in the organic solvent at such a ratio that the raw material for constituting the composite metal oxide A and the raw material for constituting the composite metal oxide B give the metal atomic ratio represented by the above general formula A metal compound solution,
The number of particles having a particle size of 0.5 μm or more in the organometallic compound solution is 50 / mL or less ,
Ferroelectric thin film formation characterized in that the composite metal oxide B comprises cerium 2-ethylhexanoate, cerium 2-ethylbutyrate, cerium tri-n-butoxide, cerium triethoxide or tris (acetylacetonate) cerium Composition.
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| EP11195995.3A EP2436661B1 (en) | 2008-05-28 | 2009-05-28 | Composition for ferroelectric thin film formation and method for forming ferroelectric thin film |
| CN201410553563.3A CN104446463B (en) | 2008-05-28 | 2009-05-28 | Composition for ferroelectric thin film formation, method for ferroelectric thin film formation, and ferroelectric thin film formed by the method |
| PCT/JP2009/059804 WO2009145272A1 (en) | 2008-05-28 | 2009-05-28 | Composition for ferroelectric thin film formation, method for ferroelectric thin film formation, and ferroelectric thin film formed by the method |
| KR1020107029565A KR101242840B1 (en) | 2008-05-28 | 2009-05-28 | Composition for ferroelectric thin film formation, method for ferroelectric thin film formation, and ferroelectric thin film formed by the method |
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| EP09754780.6A EP2298714B1 (en) | 2008-05-28 | 2009-05-28 | Composition for ferroelectric thin film formation, method for ferroelectric thin film formation, and ferroelectric thin film formed by the method |
| US12/736,944 US8859051B2 (en) | 2008-05-28 | 2009-05-28 | Composition for ferroelectric thin film formation, method for forming ferroelectric thin film and ferroelectric thin film formed by the method thereof |
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