JPH04159679A - Ferroelectric body thin-film element - Google Patents
Ferroelectric body thin-film elementInfo
- Publication number
- JPH04159679A JPH04159679A JP2285634A JP28563490A JPH04159679A JP H04159679 A JPH04159679 A JP H04159679A JP 2285634 A JP2285634 A JP 2285634A JP 28563490 A JP28563490 A JP 28563490A JP H04159679 A JPH04159679 A JP H04159679A
- Authority
- JP
- Japan
- Prior art keywords
- thin film
- ferroelectric
- ferroelectric thin
- electrode
- lower electrode
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000010409 thin film Substances 0.000 title claims description 43
- 239000000758 substrate Substances 0.000 claims abstract description 8
- 230000000694 effects Effects 0.000 abstract description 5
- 229910021421 monocrystalline silicon Inorganic materials 0.000 abstract description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 abstract 2
- 238000009413 insulation Methods 0.000 abstract 2
- 229910052681 coesite Inorganic materials 0.000 abstract 1
- 229910052906 cristobalite Inorganic materials 0.000 abstract 1
- 239000000377 silicon dioxide Substances 0.000 abstract 1
- 235000012239 silicon dioxide Nutrition 0.000 abstract 1
- 229910052682 stishovite Inorganic materials 0.000 abstract 1
- 229910052905 tridymite Inorganic materials 0.000 abstract 1
- 239000010408 film Substances 0.000 description 18
- 239000000463 material Substances 0.000 description 7
- 238000000605 extraction Methods 0.000 description 5
- 230000010287 polarization Effects 0.000 description 5
- 238000000034 method Methods 0.000 description 4
- 238000005336 cracking Methods 0.000 description 3
- 229910002113 barium titanate Inorganic materials 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- 229910002115 bismuth titanate Inorganic materials 0.000 description 1
- 239000004917 carbon fiber Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- XKENYNILAAWPFQ-UHFFFAOYSA-N dioxido(oxo)germane;lead(2+) Chemical compound [Pb+2].[O-][Ge]([O-])=O XKENYNILAAWPFQ-UHFFFAOYSA-N 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 230000006870 function Effects 0.000 description 1
Landscapes
- Thermistors And Varistors (AREA)
- Semiconductor Memories (AREA)
Abstract
Description
【発明の詳細な説明】
産業上の利用分野
本発明は、強誘電体メモリー素子など強誘電体の分極反
転を利用する素子、デバイスに利用される強誘電薄膜素
子に関するものである。DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a ferroelectric thin film element used in elements and devices that utilize polarization inversion of ferroelectric materials, such as ferroelectric memory elements.
従来の技術
従来、第４図に示すように、基板ｌ上の強誘電体薄膜３
と上部電極４と下部電極２は、はぼ同一面積を有してお
り、さらに、強誘電体薄膜の端部面は下部電極２に対し
ほぼ垂直になるよう尤こ処理されている（例えば、エレ
クトロニクス（Ｅｌｅｃｔｒｏ旧ｃｓ）Ｆｅｂ、、 １
８． ＰＯ２−９５（１９８９））。2. Description of the Related Art Conventionally, as shown in FIG.
The upper electrode 4 and the lower electrode 2 have approximately the same area, and furthermore, the end surface of the ferroelectric thin film is treated to be approximately perpendicular to the lower electrode 2 (for example, Electronics (Electro former cs) Feb,, 1
8. PO2-95 (1989)).
発明が解決しようとする課題
しかしながら、強誘電体は分極反転にともない体積変化
を生じるが、これは実際の素子構成では膜厚変化となっ
て現れる。この時、従来の素子構成では以下のような課
題が生じる。Problems to be Solved by the Invention However, a ferroelectric material undergoes a volume change due to polarization reversal, and this appears as a change in film thickness in an actual device configuration. At this time, the following problems arise with the conventional element configuration.
すなわち、通常の強誘電体薄膜素子では、下部電極２、
強誘電体膜３、および上部電極４よりなる部分の１に、
絶縁膜５、取り出し電極６、バヴシヘーション膜等が積
層されているが、実際強誘電薄膜素子を駆動した場合、
分極反転に伴う膜厚変化によりそれら取り出し電極６、
絶ｉｔＦ！５などの特に強誘電体膜端部側においてに、
大きな歪が生じることになる。そして、その分極反転の
繰り返しによる疲労により、割れ、あるいは剥離が生じ
素子の寿命が著しく短くなるという課題がある。また、
分極反転を用いない場合でも、強誘電体に電圧を印加す
ることで圧電効果により、同様の変形が生じ、寿命が短
くなるという課題がある。That is, in a normal ferroelectric thin film element, the lower electrode 2,
In part 1 consisting of the ferroelectric film 3 and the upper electrode 4,
The insulating film 5, the extraction electrode 6, the turbulence film, etc. are laminated, but when actually driving a ferroelectric thin film element,
These extraction electrodes 6,
Absolutely! Especially on the end side of the ferroelectric film such as 5,
A large distortion will occur. There is a problem in that fatigue due to repeated polarization reversal causes cracking or peeling, which significantly shortens the life of the element. Also,
Even when polarization inversion is not used, applying a voltage to a ferroelectric material causes similar deformation due to the piezoelectric effect, resulting in a shortened lifetime.
本発明は、このような従来の強誘電薄膜索子の課題を考
ばし、剥離や割れが生じず、寿命が長い強誘電薄膜索子
を提供することを目的とする。The present invention has been made in consideration of the problems of conventional ferroelectric thin film cords, and an object of the present invention is to provide a ferroelectric thin film cord that does not peel or crack and has a long life.
課題を解決するための手段
本発明は、少なくとも下部Ｎ、極と、その下部電極上に
形成された強誘電体薄膜と、その強誘電体薄膜上に形成
された上部電極とを備えた強誘電体薄膜素子において、
上部電極と下部電極のどちらか一方の電極面積が他方の
電極の面積より小さい強誘電体薄膜素子である。Means for Solving the Problems The present invention provides a ferroelectric device comprising at least a lower electrode, a ferroelectric thin film formed on the lower electrode, and an upper electrode formed on the ferroelectric thin film. In body thin film elements,
This is a ferroelectric thin film element in which the area of either the upper electrode or the lower electrode is smaller than the area of the other electrode.
また、本発明は、少なくとも下部電極と、その下部電極
上に形成された強訴電体薄膜と、その強誘電体薄膜−Ｅ
に形成された上部電極とを備えた強誘電体薄膜素子にお
いて、強誘電体薄膜の端部面が、それら電極、強誘電体
薄膜が形成された基板に対して傾斜している強誘電体薄
膜素子である。The present invention also provides at least a lower electrode, a ferroelectric thin film formed on the lower electrode, and a ferroelectric thin film -E.
A ferroelectric thin film element having an upper electrode formed on the ferroelectric thin film, in which the end surface of the ferroelectric thin film is inclined with respect to the electrode and the substrate on which the ferroelectric thin film is formed. It is element.
作用
上記の従来の課題を解決するためには、最も歪の集中す
る強誘電体膜端部の体積変化が小さくなるような素子構
成を用いれはよい。Effect: In order to solve the above-mentioned conventional problems, it is best to use an element configuration that reduces the volume change at the end of the ferroelectric film where strain is most concentrated.
すなわち、上下の電極の面積が異なるので、素子として
機能するのは強誘電体膜の中央部分であり、最も歪の大
きくかかる強誘電体膜の端部においては実質的体積変化
は非常に小さくなり、その上に形成された絶縁層、電極
等への影響は殆ど無くなり、素子の寿命が大きく改善さ
れる。In other words, since the areas of the upper and lower electrodes are different, it is the central part of the ferroelectric film that functions as an element, and the actual volume change is very small at the edges of the ferroelectric film, where the greatest strain is applied. , there is almost no influence on the insulating layer, electrodes, etc. formed thereon, and the life of the element is greatly improved.
また、強誘電体薄膜の端部面が基板に対して傾斜してい
る場合も同様に、端部において実質的体積変化は非常に
小さくなり、その上に形成された絶縁層、電極等への影
響は殆ど無くなり、素子の寿命が大きく改善される。Similarly, when the end surface of the ferroelectric thin film is inclined with respect to the substrate, the actual volume change at the end becomes very small, and the change in the volume at the end becomes very small, and the change in the volume of the ferroelectric thin film becomes very small. The influence is almost eliminated, and the life of the element is greatly improved.
実施例
以下、本発明の実施例について図面を参照して説明する
。Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.
第１図、及び第２図は本発明による強誘電体薄膜素子の
断面図である。基板ｌとして表面に３０Ｏｎ＋＋＋の５
１０２を成長させた単結晶Ｓｉを用い、その上に、通常
のＦｉｉ膜形成法、エツチング法等の素子形成法を用い
て、強誘電体薄膜素子を作製した。なお本実施例では強
誘電体膜３として、ＰｂＺｒ５．ｑＴｉ＠、２０３を、
また下部電極２、および上部電極４としてｐｔを用いた
。絶縁膜５は５ｉ３Ｎａを、また取り出し電極６として
はＡ１を用いた。1 and 2 are cross-sectional views of a ferroelectric thin film element according to the present invention. 5 of 30On+++ on the surface as a substrate l
A ferroelectric thin film element was fabricated on single crystal Si grown with 102 using a conventional element forming method such as a Fii film forming method or an etching method. In this example, the ferroelectric film 3 is made of PbZr5. qTi@, 203,
Further, PT was used as the lower electrode 2 and the upper electrode 4. The insulating film 5 was made of 5i3Na, and the extraction electrode 6 was made of A1.
第１図の強誘電体Ｆｉｔ ＩＩ素子は、上部電極４の方
が下部電極２より小さいものである。また、第２図の強
誘電体薄膜素子は、上部電極４は、下方に折れ曲がって
おり、その面積は、下部電極２の面積より大きくなって
いる。In the ferroelectric Fit II element shown in FIG. 1, the upper electrode 4 is smaller than the lower electrode 2. Further, in the ferroelectric thin film element shown in FIG. 2, the upper electrode 4 is bent downward, and its area is larger than the area of the lower electrode 2.
第４図は比較のために作製した従来例の素子構成よりな
る強誘電体薄膜素子で、下部ＩＩｉ極２と強誘電体膜３
と上部電極４がほぼ同面積で構成されている。FIG. 4 shows a ferroelectric thin film element with a conventional element configuration fabricated for comparison, with a lower IIi pole 2 and a ferroelectric film 3.
and the upper electrode 4 have approximately the same area.
ここで、第１図、第２図、および第３図の強誘電体薄膜
素子の構成をそれぞれ、構成！、構成２、および構成３
と呼ぶこととする。Here, the configurations of the ferroelectric thin film elements shown in FIGS. 1, 2, and 3 are respectively configured! , Configuration 2, and Configuration 3
I will call it.
それぞれの構成の強誘電体薄膜素子の１０５個の素子に
ついて、交流電圧を印加して分極反転を行うことで、こ
れらの素子を駆動し、各素子の寿命について検討した。The 105 ferroelectric thin film elements of each configuration were driven by applying an alternating current voltage to perform polarization inversion, and the lifespan of each element was examined.
このような繰り返し駆動による素子の劣化について調べ
た結果を表１に示す。Table 1 shows the results of investigating the deterioration of the element due to such repeated driving.
表１
表１の結果より明らかなように、従来の構成を用いた素
子では１０１２回の繰り返しにより、１／３以上の素子
が割れ、剥離により機能しなくなった。Table 1 As is clear from the results in Table 1, after 1012 repetitions of the elements using the conventional structure, more than 1/3 of the elements broke and stopped functioning due to peeling.
構成３の素子のＴＥＭ観察を行ったところ、強誘電体膜
端部においてその上部の絶縁膜の割れ、読みだし電極の
断線、強誘電体膜と電極の剥離が観察された。When the device of Configuration 3 was observed by TEM, cracks in the insulating film above the ferroelectric film, disconnection of the readout electrode, and peeling between the ferroelectric film and the electrode were observed at the end of the ferroelectric film.
一方、本発明の構成を用いた強誘電体薄膜素子では上部
絶縁膜の割れ、剥離は観察されずきわめて良好な結果を
得た。構成２て１０１２の繰り返しにより欠陥素子が１
個観測されたが、これは取り出し電極６のＡ１の不良に
よるもので、本質的なものでは無かった。On the other hand, in the ferroelectric thin film element using the structure of the present invention, no cracking or peeling of the upper insulating film was observed, and very good results were obtained. By repeating 1012 steps in configuration 2, the number of defective elements is reduced to 1.
However, this was due to a defect in A1 of the extraction electrode 6 and was not essential.
ついで、強誘電体層の材料としてＰ ｈＺ ｒＴ ｉｏ
３、Ｂ ｉａ Ｔ ｉ３０１２、ＢａＴｉＯ３、ＬｉＴ
ａｏ３及びＰｂＣ；ｅｓＯ日を用い、構成ｌの素子を前
記の方法で同様に作製し、索子の繰り返し寿命について
検討を行った。いずれの材料を用いた場合でも１０１２
回の繰り返しでは素子の劣化は認められなかった。Next, P hZ rT io is used as the material for the ferroelectric layer.
3, B ia T i3012, BaTiO3, LiT
Using ao3 and PbC; esO, a device of configuration 1 was similarly fabricated by the method described above, and the repeated life of the cord was investigated. 1012 when using any material
No deterioration of the device was observed after repeated testing.
また、蓄えられる電荷量は狭い方の電極で制限されるた
めに（２ケの電極を精度良く合わせる必要がなく）、従
来に比べて１．５倍の精度の向上が観察された。Furthermore, since the amount of charge that can be stored is limited by the narrower electrode (there is no need to precisely match the two electrodes), an improvement in accuracy of 1.5 times compared to the conventional method was observed.
第３図は、他の本発明の一実施例を示すもので、その強
誘電体薄膜３の端部面は、基板ｌに対してテーパー状巳
こ傾斜している。このような傾斜によっても、割れや剥
離の無い寿命の長い強誘電体薄膜素子を製造できる。FIG. 3 shows another embodiment of the present invention, in which the end surface of the ferroelectric thin film 3 is inclined in a tapered shape with respect to the substrate l. Even with such an inclination, a ferroelectric thin film element with a long life without cracking or peeling can be manufactured.
上記実施例では、ＰＺＴ系材料、ＢａＴｉＯ３、ゲルマ
ン酸鉛、チタン酸ビスマスなどを用いたが、本発明はこ
れ以外の強誘電体を用いた場合でももちろん同様の効果
が得られらる。In the above embodiments, PZT-based materials, BaTiO3, lead germanate, bismuth titanate, etc. are used, but the present invention can of course obtain similar effects even when other ferroelectric materials are used.
発明の効果
以上の説明から明らかなように、本発明による強誘電体
薄膜素子では、４Ｌ下の電極面積に差をもたせ、あるい
は強誘電体膜端部面を傾斜するという簡単な構成で、素
子の寿命を飛躍的に向上させるもので、工業的応用の価
値は極めて高い。Effects of the Invention As is clear from the above explanation, the ferroelectric thin film device according to the present invention can be easily fabricated by providing a difference in the electrode area under 4L or by slanting the end surface of the ferroelectric film. This dramatically improves the lifespan of carbon fibers, and has extremely high value for industrial applications.
第１図、第２図はそれぞれ本発明の実施例にかかる強誘
電体薄膜素子の断面図、第３図は別の本発明の一実施例
にかかる強誘電体薄膜素子の断面図、第４図は比較のた
めに作製された従来例の構成に基づく強誘電体薄膜素子
の断面図である。
ｌ・・・基板、２・・・下部電極、３・・・強誘電体層
、４・・・上部電極、５・・・絶縁層、６・・・取り出
し電極。
代理人 弁理士 松 １）正 道
第１図
１・・・基板 ２・・・下部電極３・・・強
誘電体層 ４・・・上部電極５・・・絶縁層
６・・・取り出しｔＳ第２図
第３図1 and 2 are cross-sectional views of a ferroelectric thin film element according to an embodiment of the present invention, FIG. 3 is a cross-sectional view of a ferroelectric thin film element according to another embodiment of the present invention, and FIG. The figure is a cross-sectional view of a ferroelectric thin film element based on the configuration of a conventional example prepared for comparison. 1... Substrate, 2... Lower electrode, 3... Ferroelectric layer, 4... Upper electrode, 5... Insulating layer, 6... Extraction electrode. Agent Patent Attorney Matsu 1) Tadashi Michi Figure 1 1... Substrate 2... Lower electrode 3... Ferroelectric layer 4... Upper electrode 5... Insulating layer
6...Removal tS Fig. 2 Fig. 3
Claims (2)
れた強誘電体薄膜と、その強誘電体薄膜上に形成された
上部電極とを備えた強誘電体薄膜素子において、前記上
部電極と前記下部電極のどちらか一方の電極面積が他方
の電極の面積より小さいことを特徴とする強誘電体薄膜
素子。(1) In a ferroelectric thin film element comprising at least a lower electrode, a ferroelectric thin film formed on the lower electrode, and an upper electrode formed on the ferroelectric thin film, the upper electrode and the A ferroelectric thin film element characterized in that the area of one of the lower electrodes is smaller than the area of the other electrode.
れた強誘電体薄膜と、その強誘電体薄膜上に形成された
上部電極とを備えた強誘電体薄膜素子において、前記強
誘電体薄膜の端部面が、それら電極、強誘電体薄膜が形
成された基板に対して傾斜していることを特徴とする強
誘電体薄膜素子。(2) In a ferroelectric thin film element comprising at least a lower electrode, a ferroelectric thin film formed on the lower electrode, and an upper electrode formed on the ferroelectric thin film, the ferroelectric thin film A ferroelectric thin film element characterized in that an end surface of the ferroelectric thin film element is inclined with respect to a substrate on which the electrodes and the ferroelectric thin film are formed.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2285634A JP3070087B2 (en) | 1990-10-22 | 1990-10-22 | Ferroelectric thin film element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2285634A JP3070087B2 (en) | 1990-10-22 | 1990-10-22 | Ferroelectric thin film element |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04159679A true JPH04159679A (en) | 1992-06-02 |
| JP3070087B2 JP3070087B2 (en) | 2000-07-24 |
Family
ID=17694072
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2285634A Expired - Lifetime JP3070087B2 (en) | 1990-10-22 | 1990-10-22 | Ferroelectric thin film element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3070087B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5384729A (en) * | 1991-10-28 | 1995-01-24 | Rohm Co., Ltd. | Semiconductor storage device having ferroelectric film |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6148983A (en) * | 1984-08-16 | 1986-03-10 | Toray Ind Inc | Ferrodielectric high polymer thin film |
| JPS63138808A (en) * | 1986-11-29 | 1988-06-10 | Toshiba Corp | Integrated type piezoelectric thin film function element |
-
1990
- 1990-10-22 JP JP2285634A patent/JP3070087B2/en not_active Expired - Lifetime
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6148983A (en) * | 1984-08-16 | 1986-03-10 | Toray Ind Inc | Ferrodielectric high polymer thin film |
| JPS63138808A (en) * | 1986-11-29 | 1988-06-10 | Toshiba Corp | Integrated type piezoelectric thin film function element |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5384729A (en) * | 1991-10-28 | 1995-01-24 | Rohm Co., Ltd. | Semiconductor storage device having ferroelectric film |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3070087B2 (en) | 2000-07-24 |
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