JPH0817245A - Ferro-electric thin film and manufacture thereof - Google Patents
Ferro-electric thin film and manufacture thereofInfo
- Publication number
- JPH0817245A JPH0817245A JP17202094A JP17202094A JPH0817245A JP H0817245 A JPH0817245 A JP H0817245A JP 17202094 A JP17202094 A JP 17202094A JP 17202094 A JP17202094 A JP 17202094A JP H0817245 A JPH0817245 A JP H0817245A
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- thin film
- ferroelectric thin
- ferroelectric
- heat treatment
- sputtering
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- Inorganic Insulating Materials (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、強誘電体薄膜とその製
造方法とに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferroelectric thin film and its manufacturing method.
【０００２】[0002]
【従来の技術】強誘電体薄膜は、圧電効果や焦電効果を
利用してセンサー、記憶素子、通信部品等に用いられ
る。このような強誘電体薄膜には、従来、ＰｂＺｒＯ3
−ＰｂＴｉＯ3 固溶体（ＰＺＴ）が主として用いられて
いる。ＰＺＴ薄膜は、例えばAppl.Phys.Lett.58(11),11
61(1991)に示されるように、残留分極値が約１０μＣ／
cm 2 であり、比誘電率が１０００弱である。ＰＺＴ薄膜
は残留分極値が大きく強誘電性に優れているが、誘電率
が高いため、センサーや記憶素子に用いた場合に高感度
や高Ｓ／Ｎが得られにくい。したがって、残留分極値が
大きく、かつ誘電率が低い強誘電体薄膜が望まれてい
る。2. Description of the Related Art Ferroelectric thin films have a piezoelectric effect and a pyroelectric effect.
Used for sensors, memory elements, communication parts, etc.
It Conventionally, PbZrO has been used for such a ferroelectric thin film.3
-PbTiO3 Solid solution (PZT) is mainly used
There is. The PZT thin film is, for example, Appl. Phys. Lett.58(11), 11
61 (1991), the remanent polarization value is about 10 μC /
cm 2 And the relative dielectric constant is less than 1000. PZT thin film
Has a large remanent polarization value and excellent ferroelectricity, but its dielectric constant is
Has high sensitivity, so it has high sensitivity when used as a sensor or memory element.
It is difficult to obtain high S / N. Therefore, the remanent polarization value is
Ferroelectric thin films that are large and have a low dielectric constant are desired.
It
【０００３】ＢｉＦｅＯ3 は、その結晶構造やキュリー
温度から、低い誘電率と大きい残留分極値をもつことが
理論的に予測されている。しかし、例えばSolid State
Commun.,vol.8,No.13,1073(1970)に示されるように、従
来、多結晶や単結晶のバルク材として合成されたＢｉＦ
ｅＯ3 は室温での抵抗が低く、室温では強誘電体として
利用することができなかった。BiFeO 3 is theoretically predicted to have a low dielectric constant and a large remanent polarization value from its crystal structure and Curie temperature. But for example Solid State
As shown in Commun., Vol.8, No.13,1073 (1970), BiF conventionally synthesized as a bulk material of polycrystal or single crystal.
eO 3 has a low resistance at room temperature and cannot be used as a ferroelectric at room temperature.
【０００４】特開平２−１７０３０６号公報には、酸化
鉄（Ｆｅ2 Ｏ3 ）−酸化ビスマス（Ｂｉ2 Ｏ3 ）−ペロ
ブスカイト型強誘電体酸化物（ＡＢＯ3 ）を主成分とし
た三元酸化物からなる強磁性強誘電体酸化物が記載され
ている。同公報の表１および表２には、ＡＢＯ3 を含ま
ずＦｅ2 Ｏ3 ：Ｂｉ2 Ｏ3 ＝１：１の組成の薄膜が比較
例として記載されている。これら比較例の薄膜の組成比
はＢｉＦｅＯ3 であるが、結晶質であった旨の記載はな
く、また、自発分極Ｐｓは０であり、強誘電性を示して
いない。これら比較例の薄膜は、Ｂｉ2 Ｏ3 とα−Ｆｅ
2 Ｏ3 との混合粉末をターゲットに用いたスパッタ法に
より形成され、スパッタ後に６２０〜７００℃で熱処理
が施されている。Japanese Unexamined Patent Publication (Kokai) No. 2-170306 discloses ternary oxidation containing iron oxide (Fe 2 O 3 ) -bismuth oxide (Bi 2 O 3 ) -perovskite type ferroelectric oxide (ABO 3 ) as a main component. Ferroelectric ferroelectric oxides consisting of objects are described. In Tables 1 and 2 of the publication, a thin film having a composition of Fe 2 O 3 : Bi 2 O 3 = 1: 1 containing no ABO 3 is described as a comparative example. The composition ratio of the thin films of these comparative examples was BiFeO 3 , but there was no description that it was crystalline, and the spontaneous polarization Ps was 0, indicating no ferroelectricity. The thin films of these comparative examples are Bi 2 O 3 and α-Fe.
It is formed by a sputtering method using a mixed powder of 2 O 3 as a target, and heat treatment is performed at 620 to 700 ° C. after sputtering.
【０００５】[0005]
【発明が解決しようとする課題】本発明の目的は、残留
分極値が大きく、かつ誘電率が低い強誘電体薄膜を提供
することである。An object of the present invention is to provide a ferroelectric thin film having a large remanent polarization value and a low dielectric constant.
【０００６】[0006]
【課題を解決するための手段】このような目的は、下記
（１）〜（４）のいずれかの構成により達成される。 （１） 式 Ｂｉx Ｆｅy Ｏ3 （上記式において、 ｘ／ｙ＝０．９〜１．８、 ｘ＋ｙ＝２ である）で表わされる組成を有し、ペロブスカイト相を
含み、残留分極値が２μＣ／cm2以上であることを特徴
とする強誘電体薄膜。 （２）比誘電率が１００以下である上記（１）の強誘電
体薄膜。 （３）上記（１）または（２）の強誘電体薄膜を製造す
る方法であって、ＢｉおよびＦｅを含み、ペロブスカイ
ト相を有する複合酸化物の焼結体ターゲットを用い、ス
パッタ法により薄膜を形成した後、薄膜に熱処理を施し
て、強誘電性を示すペロブスカイト相を析出させること
を特徴とする強誘電体薄膜の製造方法。 （４）熱処理温度が５００〜７５０℃である上記（３）
の強誘電体薄膜の製造方法。Such an object is achieved by any of the following constitutions (1) to (4). (1) (In the above formula, x / y = 0.9 to 1.8, an x + y = 2) formula Bi x Fe y O 3 has a composition represented by, include perovskite phase, the residual polarization value A ferroelectric thin film having a concentration of 2 μC / cm 2 or more. (2) The ferroelectric thin film according to (1) above, which has a relative dielectric constant of 100 or less. (3) A method for producing a ferroelectric thin film according to (1) or (2) above, wherein a thin film is formed by sputtering using a sintered body target of a complex oxide containing Bi and Fe and having a perovskite phase. After the formation, a heat treatment is applied to the thin film to precipitate a perovskite phase exhibiting ferroelectricity, which is a method for producing a ferroelectric thin film. (4) The heat treatment temperature is 500 to 750 ° C. (3)
Method for manufacturing ferroelectric thin film of.
【０００７】[0007]
【作用および効果】本発明の強誘電体薄膜は、従来の強
誘電体薄膜では得られなかった特性、すなわち残留分極
値が大きくかつ誘電率が低いという特性を有する。この
ため本発明の強誘電体薄膜を赤外線センサー等の焦電セ
ンサーに適用したときには高感度が得られ、また、記憶
素子に適用したときには高Ｓ／Ｎが得られる。FUNCTION AND EFFECT The ferroelectric thin film of the present invention has characteristics that cannot be obtained by the conventional ferroelectric thin film, that is, the characteristics that the remanent polarization value is large and the dielectric constant is low. Therefore, when the ferroelectric thin film of the present invention is applied to a pyroelectric sensor such as an infrared sensor, high sensitivity is obtained, and when it is applied to a memory element, high S / N is obtained.
【０００８】[0008]
【具体的構成】以下、本発明の具体的構成について詳細
に説明する。Specific Structure The specific structure of the present invention will be described in detail below.
【０００９】本発明の強誘電体薄膜は、 式 Ｂｉx Ｆｅy Ｏ3 で表わされる組成を有する。上記式において、 ｘ／ｙ＝０．９〜１．８、好ましくはｘ／ｙ＝１．０〜
１．４ であり、 ｘ＋ｙ＝２ である。ｘ／ｙが小さすぎると、すなわちＦｅ過剰であ
ると、常誘電体相であるＢｉ2 Ｆｅ4 Ｏ9 等の異相が生
成しやすく、また、その割合が高くなって、良好な強誘
電特性が得られなくなる。一方、ｘ／ｙが大きすぎる
と、すなわちＢｉ過剰であると、Ｂｉ2 Ｏ3 等の異相が
生成しやすく、また、その割合が高くなって、良好な強
誘電特性が得られなくなる。なお、Ｂｉ＋Ｆｅに対する
Ｏの比率は、上記式で表わされる化学量論組成から偏倚
していてもよい。The ferroelectric thin film of the present invention has a composition represented by the formula Bi x Fe y O 3 . In the above formula, x / y = 0.9 to 1.8, preferably x / y = 1.0 to
1.4 and x + y = 2. If x / y is too small, that is, if Fe is excessive, a heterophase such as Bi 2 Fe 4 O 9 which is a paraelectric phase is likely to be formed, and the ratio thereof becomes high, so that good ferroelectric properties are obtained. You won't get it. On the other hand, if x / y is too large, that is, if Bi is excessive, a different phase such as Bi 2 O 3 is likely to be generated, and the ratio thereof becomes high, so that good ferroelectric properties cannot be obtained. The ratio of O to Bi + Fe may be deviated from the stoichiometric composition represented by the above formula.
【００１０】なお、本発明の強誘電体薄膜には、Ｂｉ、
ＦｅおよびＯの他に、微量添加物または不可避的不純物
として他の元素が含まれていてもよい。前記他の元素と
しては、例えばＮａ、Ｋ、Ｃａ、Ｍｇ、Ｓｒ、Ｂａ、Ｃ
ｕ、Ｐｂ、Ｓｉ、Ｍｎ、Ｔｉ、Ｚｒ、Ｎｂ、Ｔａ、Ｌ
ａ、Ｙなどの少なくとも１種が挙げられるが、強誘電体
薄膜中におけるこれらの元素の合計含有率は、５重量％
以下であることが好ましい。The ferroelectric thin film of the present invention contains Bi,
In addition to Fe and O, other elements may be contained as a trace additive or an unavoidable impurity. Examples of the other elements include Na, K, Ca, Mg, Sr, Ba, C
u, Pb, Si, Mn, Ti, Zr, Nb, Ta, L
At least one of a, Y, etc. may be mentioned, but the total content of these elements in the ferroelectric thin film is 5% by weight.
The following is preferred.
【００１１】本発明の強誘電体薄膜はペロブスカイト相
を有するが、多結晶であっても単結晶であってもよい。
多結晶である場合、平均結晶粒径は、好ましくは４０nm
〜１．２μm 、より好ましくは８０〜５００nmである。
平均結晶粒径が小さすぎると良好な強誘電特性を得るこ
とが難しくなり、大きすぎると膜中にクラックが生じて
良好な強誘電特性を得ることが難しくなる。強誘電体薄
膜が単結晶である場合には、より良好な強誘電特性を得
ることができる。Although the ferroelectric thin film of the present invention has a perovskite phase, it may be polycrystalline or single crystal.
When it is polycrystal, the average crystal grain size is preferably 40 nm
.About.1.2 .mu.m, more preferably 80 to 500 nm.
If the average crystal grain size is too small, it becomes difficult to obtain good ferroelectric properties, and if it is too large, cracks occur in the film, making it difficult to obtain good ferroelectric properties. When the ferroelectric thin film is a single crystal, better ferroelectric characteristics can be obtained.
【００１２】強誘電体薄膜の厚さは、好ましくは０．１
〜３μm 、より好ましくは２００〜５００nmである。強
誘電体薄膜が薄すぎると、ピンホール等の欠陥により短
絡が生じやすくなって良好な電気的特性が得られにくく
なり、一方、厚すぎると、熱処理時に発生する応力によ
りクラックが生じやすくなり、膜の均一性が悪くなりや
すい。The thickness of the ferroelectric thin film is preferably 0.1.
-3 μm, more preferably 200-500 nm. If the ferroelectric thin film is too thin, short circuit easily occurs due to defects such as pinholes and it becomes difficult to obtain good electrical characteristics, while if it is too thick, cracks easily occur due to stress generated during heat treatment, The uniformity of the film tends to deteriorate.
【００１３】本発明の強誘電体薄膜は、残留分極値とし
て２μＣ／cm2 以上の値が得られ、１０μＣ／cm2 以上
の値を得ることもできる。そして、比誘電率を１００以
下にすることができ、７０以下にすることもできる。The ferroelectric thin film of the present invention can obtain a remanent polarization value of 2 μC / cm 2 or more, and can also obtain a value of 10 μC / cm 2 or more. The relative permittivity can be 100 or less, or 70 or less.
【００１４】本発明の強誘電体薄膜の製造方法は特に限
定されず、公知の各種薄膜形成法を利用することができ
るが、好ましくは以下に説明するスパッタ法を用いる。The method for producing the ferroelectric thin film of the present invention is not particularly limited, and various known thin film forming methods can be used, but the sputtering method described below is preferably used.
【００１５】スパッタ法では、ＢｉおよびＦｅを含み、
ペロブスカイト相を有する複合酸化物の焼結体ターゲッ
トを用いる。ターゲットの組成は、目的とする強誘電体
薄膜に対応するものとすればよいが、化学量論組成のタ
ーゲットを用いて、スパッタリングガス圧等の膜形成条
件を適宜選択することにより、目的とする組成の膜を得
ることもできる。高特性の強誘電体薄膜を得るために
は、以下に示す条件でターゲットを製造することが好ま
しい。The sputtering method contains Bi and Fe,
A complex oxide sintered body target having a perovskite phase is used. The composition of the target may correspond to the desired ferroelectric thin film, but the target can be obtained by appropriately selecting the film forming conditions such as sputtering gas pressure using a stoichiometric target. It is also possible to obtain a film having a composition. In order to obtain a ferroelectric thin film with high characteristics, it is preferable to manufacture the target under the following conditions.
【００１６】まず、原料粉末としてＢｉ2 Ｏ3 粉末とＦ
ｅ2 Ｏ3 粉末とを準備し、所定の比率で混合する。原料
粉末は、平均粒径１〜１０μm 、純度９９．９９％以上
であることが好ましい。原料粉末を混合する手段は特に
限定されないが、不純物の混入を防ぐために、好ましく
はＦｅポットとＦｅボールとを備えたボールミルを利用
し、湿式混合を行なう。この場合、ボールミルに由来す
るＦｅが原料中に混入するので、それを見込んで原料粉
末の混合比率を調整する。湿式混合の溶媒は水系であっ
ても非水系であってもよく、例えば、アセトン、エタノ
ール、水などを用いればよい。混合時間は、好ましくは
２０〜１００時間である。混合後、脱水乾燥し、必要に
応じて解砕・整粒する。整粒後の２次粒子の径は、０．
５μm 以下であることが好ましい。次いで、必要に応じ
てポリビニルアルコール等のバインダを添加して混合し
た後、成形する。成形圧力は１００〜２０００kgf/cm2
であることが好ましい。成形後、焼成する。焼成は空気
中で行なえばよい。焼成温度は、好ましくは７５０〜８
００℃である。焼成温度が低すぎると未反応部が多量に
残存し、一方、高すぎると焼結体表面にＢｉリッチ相が
生じ、いずれもターゲットとして不適となる。なお、酸
素雰囲気中においてホットプレスや熱間静水圧プレスに
より焼結する方法を用いてもよい。First, as raw material powders, Bi 2 O 3 powder and F
e 2 O 3 powder is prepared and mixed in a predetermined ratio. The raw material powder preferably has an average particle size of 1 to 10 μm and a purity of 99.99% or more. The means for mixing the raw material powders is not particularly limited, but in order to prevent contamination of impurities, preferably a ball mill equipped with Fe pots and Fe balls is used to perform wet mixing. In this case, since Fe derived from the ball mill is mixed in the raw material, the mixing ratio of the raw material powder is adjusted in consideration of it. The solvent for wet mixing may be aqueous or non-aqueous, and for example, acetone, ethanol, water or the like may be used. The mixing time is preferably 20 to 100 hours. After mixing, dehydration and drying, and if necessary, crushing and sizing. The diameter of the secondary particles after sizing is 0.
It is preferably 5 μm or less. Then, if necessary, a binder such as polyvinyl alcohol is added and mixed, and then molded. Molding pressure is 100 ~ 2000kgf / cm 2
It is preferred that After molding, it is fired. The firing may be performed in the air. The firing temperature is preferably 750-8
It is 00 ° C. If the firing temperature is too low, a large amount of unreacted parts remain, while if it is too high, a Bi-rich phase is generated on the surface of the sintered body, and both are unsuitable as targets. A method of sintering by hot pressing or hot isostatic pressing in an oxygen atmosphere may be used.
【００１７】強誘電体薄膜を形成する基板は特に限定さ
れず、例えば、単結晶Ｓｉ、単結晶ＭｇＯ、単結晶また
は多結晶のＳｒＴｉＯ3 など、通常の酸化物薄膜形成に
使用可能な各種基板を用いることができ、また、これら
の表面にＰｔ等からなる電極を形成したものも基板とし
て用いることができる。The substrate on which the ferroelectric thin film is formed is not particularly limited. For example, various substrates such as single crystal Si, single crystal MgO, single crystal or polycrystal SrTiO 3 which can be used for forming a normal oxide thin film are used. It can be used, and those having an electrode made of Pt or the like formed on the surface thereof can also be used as the substrate.
【００１８】スパッタ時の雰囲気は特に限定されない
が、ターゲットの還元を防ぐためには酸素を含む不活性
ガス雰囲気中でスパッタを行なうことが好ましい。これ
により、繰り返しスパッタを行なう場合の組成ずれを抑
えることができる。The atmosphere at the time of sputtering is not particularly limited, but it is preferable to perform sputtering in an atmosphere of an inert gas containing oxygen in order to prevent reduction of the target. As a result, it is possible to suppress the composition deviation when the sputtering is repeatedly performed.
【００１９】スパッタ法により形成した薄膜は非晶質状
態であるので、薄膜形成後に熱処理を施して結晶化さ
せ、ペロブスカイト相を析出させる。熱処理温度は、好
ましくは５００〜７５０℃、より好ましくは５５０〜６
５０℃である。熱処理温度が低すぎると、ペロブスカイ
ト相が生成しなくなって強誘電性を示さなくなる。一
方、熱処理温度が高すぎると、Ｂｉx Ｆｅy Ｏ3 が分解
してＢｉが蒸発し、高特性が得られなくなる。熱処理
は、薄膜の還元を防ぐために酸化性雰囲気中、例えば空
気中で行なうことが好ましい。熱処理時間は、好ましく
は０．１〜１２０分間、より好ましくは１〜２０分間で
ある。熱処理時間が短すぎるとそれによる効果が不十分
となりやすく、長すぎるとＢｉの蒸発や薄膜と基板との
反応などが生じやすくなるため、好ましくない。Since the thin film formed by the sputtering method is in an amorphous state, a heat treatment is applied after the thin film is formed to crystallize the thin film to precipitate a perovskite phase. The heat treatment temperature is preferably 500 to 750 ° C, more preferably 550 to 6
50 ° C. If the heat treatment temperature is too low, the perovskite phase will not be formed and the ferroelectricity will not be exhibited. On the other hand, if the heat treatment temperature is too high, Bi x Fe y O 3 is decomposed and Bi is evaporated, so that high characteristics cannot be obtained. The heat treatment is preferably performed in an oxidizing atmosphere, for example, air, in order to prevent reduction of the thin film. The heat treatment time is preferably 0.1 to 120 minutes, more preferably 1 to 20 minutes. If the heat treatment time is too short, the effect thereof tends to be insufficient, and if it is too long, evaporation of Bi or reaction between the thin film and the substrate is likely to occur, which is not preferable.
【００２０】このようにして得られる強誘電体薄膜は多
結晶であるが、例えば、基板として単結晶ＭｇＯや単結
晶ＳｒＴｉＯ3 等を用いて、スパッタ時の基板温度を制
御、例えば４００〜５５０℃程度とすることにより、基
板上に単結晶薄膜をエピタキシャル成長させることがで
きる。単結晶薄膜とした場合にも、強誘電性を得るため
必要に応じてスパッタ後に熱処理を施すことが好まし
い。この熱処理の条件は特に限定されないが、処理温度
は好ましくは４５０〜７００℃であり、処理時間は好ま
しくは０．１〜１２０分間、より好ましくは１〜２０分
間である。The ferroelectric thin film thus obtained is polycrystalline. For example, by using single crystal MgO or single crystal SrTiO 3 as the substrate, the substrate temperature during sputtering is controlled, for example, 400 to 550 ° C. Depending on the degree, a single crystal thin film can be epitaxially grown on the substrate. Even in the case of a single crystal thin film, it is preferable to perform a heat treatment after sputtering if necessary to obtain ferroelectricity. The conditions of this heat treatment are not particularly limited, but the treatment temperature is preferably 450 to 700 ° C., and the treatment time is preferably 0.1 to 120 minutes, more preferably 1 to 20 minutes.
【００２１】本発明の強誘電体薄膜は、このようなスパ
ッタ法以外でも形成することができる。例えば、Ｂｉお
よびＦｅをターゲットとして、酸素を含む雰囲気中で反
応性多元スパッタを行なってもよい。また、レーザーア
ブレージョンやＣＶＤ法を用いてもよい。レーザーアブ
レージョンを用いる場合には、上記した焼結体ターゲッ
トを利用することが好ましい。The ferroelectric thin film of the present invention can be formed by a method other than the sputtering method. For example, reactive multi-source sputtering may be performed in an atmosphere containing oxygen by using Bi and Fe as targets. Alternatively, laser abrasion or a CVD method may be used. When using laser abrasion, it is preferable to utilize the above-mentioned sintered compact target.
【００２２】[0022]
【実施例】以下、本発明の具体的実施例を示し、本発明
をさらに詳細に説明する。EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.
【００２３】表１に示される薄膜サンプルを、以下に示
す方法で作製した。The thin film samples shown in Table 1 were prepared by the following method.
【００２４】以下に示す方法でスパッタターゲットを作
製した。原料粉末としてＢｉ2 Ｏ3粉末とＦｅ2 Ｏ3 粉
末とを準備した。原料粉末の平均粒径は、１〜５μm で
あり、その純度は９９．９９％以上であった。これらの
原料粉末を、ＦｅポットとＦｅボールとを備えたボール
ミルにより湿式混合した。湿式混合の溶媒にはアセトン
を用いた。混合時間は４０時間とした。混合後、脱水乾
燥し、開きが４２５μm のふるいにより整粒した。次い
で、圧力１０００kgf/cm2 で成形した後、空気中におい
て７８０℃で１０時間焼成してターゲットとした。この
ようにして、原料粉末の混合比率の異なる複数のターゲ
ットを作製した。A sputter target was manufactured by the following method. Bi 2 O 3 powder and Fe 2 O 3 powder were prepared as raw material powders. The raw material powder had an average particle size of 1 to 5 μm and a purity of 99.99% or more. These raw material powders were wet-mixed by a ball mill equipped with an Fe pot and Fe balls. Acetone was used as the solvent for the wet mixing. The mixing time was 40 hours. After mixing, the mixture was dehydrated and dried, and sized by a sieve having an opening of 425 μm. Then, after molding at a pressure of 1000 kgf / cm 2 , the target was fired in air at 780 ° C. for 10 hours. In this way, a plurality of targets with different raw material powder mixing ratios were produced.
【００２５】これらのターゲットを用いて、高周波マグ
ネトロンスパッタにより基板上に薄膜を形成した。基板
には、Ｓｉ（１００）上に、ＳｉＯ2 膜（厚さ５０nm）
と、下部電極のＰｔ膜（厚さ１００nm）とを順次設けた
ものを用いた。スパッタは、Ａｒ雰囲気またはＡｒ＋Ｏ
2 雰囲気（サンプルNo. ６）中において室温で約１０分
間行なった。スパッタ時の圧力は０．３〜１０Paとし、
投入パワーはＲＦ１００W とした。得られた薄膜は非晶
質状態であり、厚さは約４００nmであった。次いで、空
気中において各薄膜に５５０℃で１０分間の熱処理を施
し、多結晶薄膜サンプルとした。平均結晶粒径は、サン
プルNo. ５が０．３μm であった他は０．１μm であっ
た。サンプルNo. １表面の走査型電子顕微鏡写真を、図
１に示す。Using these targets, a thin film was formed on the substrate by high frequency magnetron sputtering. For the substrate, a SiO 2 film (thickness: 50 nm) on Si (100)
And a Pt film (thickness: 100 nm) for the lower electrode were sequentially provided. Sputtering is performed in Ar atmosphere or Ar + O
It was performed for about 10 minutes at room temperature in 2 atmospheres (Sample No. 6). The pressure during sputtering is 0.3 to 10 Pa,
The input power was RF100W. The obtained thin film was in an amorphous state and had a thickness of about 400 nm. Then, each thin film was heat-treated in air at 550 ° C. for 10 minutes to obtain a polycrystalline thin film sample. The average crystal grain size was 0.1 μm except that Sample No. 5 had a grain size of 0.3 μm. A scanning electron micrograph of the surface of Sample No. 1 is shown in FIG.
【００２６】各サンプルの組成（Ｂｉ／Ｆｅ）、比誘電
率（εｒ）、残留分極値（Ｐｒ）を、表１に示す。誘電
特性の測定に際しては、サンプル上にＰｔ膜（厚さ１０
０nm）を形成して、上部電極とした。サンプルNo. ２に
ついての電圧Ｖと分極値Ｐとの関係を示すグラフを、図
２に示す。Table 1 shows the composition (Bi / Fe), relative permittivity (εr), and residual polarization value (Pr) of each sample. When measuring the dielectric properties, a Pt film (thickness 10
0 nm) to form an upper electrode. A graph showing the relationship between the voltage V and the polarization value P for sample No. 2 is shown in FIG.
【００２７】[0027]
【表１】 [Table 1]
【００２８】表１に示されるように、Ｂｉ／Ｆｅが本発
明範囲にあるサンプルでは、高Ｐｒと低εｒとが得られ
ている。As shown in Table 1, the samples having Bi / Fe within the range of the present invention have high Pr and low εr.
【００２９】次に、サンプルNo. １について、Ｘ線回折
を行なった。また、スパッタ後の熱処理での処理温度を
変えた他はサンプルNo. １と同様にして多結晶薄膜サン
プルを作製し、これらについてもＸ線回折を行なった。
サンプルNo. １のＸ線回折チャートを図３に示す。図３
において、○印を付したピークがペロブスカイト構造の
ピークである。２θ＝４０°付近のピークは、下部電極
のＰｔ膜に由来するピークである。なお、熱処理を８０
０℃で行なった場合には、ペロブスカイト構造のピーク
がほとんど認められず、Ｆｅ2 Ｏ3 のピークが認められ
た。これは、ＢｉＦｅＯ3 の分解によりＢｉが蒸発した
ためと考えられる。また、熱処理を４５０℃で行なった
場合には、ペロブスカイト構造のピークが認められず、
熱処理を５００℃で行なった場合には、ペロブスカイト
構造を再現性よく析出することが難しかった。Next, the sample No. 1 was subjected to X-ray diffraction. In addition, polycrystalline thin film samples were prepared in the same manner as Sample No. 1 except that the processing temperature in the heat treatment after sputtering was changed, and X-ray diffraction was also performed on these samples.
The X-ray diffraction chart of sample No. 1 is shown in FIG. FIG.
In, the peak marked with a circle is the peak of the perovskite structure. The peak near 2θ = 40 ° is a peak derived from the Pt film of the lower electrode. The heat treatment is 80
When carried out at 0 ° C., almost no peak of the perovskite structure was observed, and a peak of Fe 2 O 3 was observed. It is considered that this is because Bi was evaporated by the decomposition of BiFeO 3 . Further, when the heat treatment is carried out at 450 ° C., no peak of the perovskite structure is observed,
When the heat treatment was performed at 500 ° C., it was difficult to deposit the perovskite structure with good reproducibility.
【００３０】以上の結果から、本発明の効果が明らかで
ある。From the above results, the effect of the present invention is clear.
【図１】粒子構造を表わす図面代用写真であって、本発
明の強誘電体薄膜表面の走査型電子顕微鏡写真である。FIG. 1 is a drawing-substituting photograph showing a grain structure, which is a scanning electron microscope photograph of a surface of a ferroelectric thin film of the present invention.
【図２】電圧Ｖと分極値Ｐとの関係を示すグラフであ
る。FIG. 2 is a graph showing the relationship between voltage V and polarization value P.
【図３】強誘電体薄膜のＸ線回折チャートである。FIG. 3 is an X-ray diffraction chart of a ferroelectric thin film.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 川口 行雄 東京都中央区日本橋一丁目13番１号 ティ ーディーケイ株式会社内 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Kawaguchi 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Corporation
Claims (4)
含み、残留分極値が２μＣ／cm2以上であることを特徴
とする強誘電体薄膜。1. A composition represented by the formula Bi x Fe y O 3 (where x / y = 0.9 to 1.8 and x + y = 2 in the above formula), containing a perovskite phase, and having a remanent polarization. A ferroelectric thin film having a value of 2 μC / cm 2 or more.
強誘電体薄膜。2. The ferroelectric thin film according to claim 1, which has a relative dielectric constant of 100 or less.
する方法であって、 ＢｉおよびＦｅを含み、ペロブスカイト相を有する複合
酸化物の焼結体ターゲットを用い、スパッタ法により薄
膜を形成した後、薄膜に熱処理を施して、強誘電性を示
すペロブスカイト相を析出させることを特徴とする強誘
電体薄膜の製造方法。3. A method of manufacturing a ferroelectric thin film according to claim 1, wherein the thin film is formed by a sputtering method using a sintered body target of a complex oxide containing Bi and Fe and having a perovskite phase. After that, a heat treatment is applied to the thin film to precipitate a perovskite phase exhibiting ferroelectricity, a method for producing a ferroelectric thin film.
求項３の強誘電体薄膜の製造方法。4. The method for producing a ferroelectric thin film according to claim 3, wherein the heat treatment temperature is 500 to 750 ° C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17202094A JPH0817245A (en) | 1994-06-30 | 1994-06-30 | Ferro-electric thin film and manufacture thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17202094A JPH0817245A (en) | 1994-06-30 | 1994-06-30 | Ferro-electric thin film and manufacture thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0817245A true JPH0817245A (en) | 1996-01-19 |
Family
ID=15934039
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP17202094A Withdrawn JPH0817245A (en) | 1994-06-30 | 1994-06-30 | Ferro-electric thin film and manufacture thereof |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0817245A (en) |
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