JP3235596B2 - Ferroelectric element and semiconductor device - Google Patents
Ferroelectric element and semiconductor deviceInfo
- Publication number
- JP3235596B2 JP3235596B2 JP16268199A JP16268199A JP3235596B2 JP 3235596 B2 JP3235596 B2 JP 3235596B2 JP 16268199 A JP16268199 A JP 16268199A JP 16268199 A JP16268199 A JP 16268199A JP 3235596 B2 JP3235596 B2 JP 3235596B2
- Authority
- JP
- Japan
- Prior art keywords
- ferroelectric
- electrode
- ferroelectric element
- film
- denotes
- 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.)
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- Semiconductor Memories (AREA)
- Non-Volatile Memory (AREA)
- Semiconductor Integrated Circuits (AREA)
Description
【0001】[0001]
【産業上の利用分野】本発明は強誘電体を基質とする薄
膜を用いた強誘電体素子あるいは強誘電体素子の構造に
関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferroelectric element or a structure of a ferroelectric element using a thin film having a ferroelectric substrate.
【0002】[0002]
【従来の技術】強誘電体が2つの電極によって挟まれた
構造を有する誘電体素子において、小面積の大容量誘電
素子、あるいは強誘電性容量素子を得るために、従来は
例えばジャーナル・オブ・アプライド・フィジックス
(J.Appl.Phys)、1991年、第70巻、
第1号、382頁〜388頁に記載されていたように、
前記電極材料として白金(Pt)、強誘電体材料としては
PZT(Pb(ZrxTi1-x)O3)を用いていた。2. Description of the Related Art In a dielectric element having a structure in which a ferroelectric substance is sandwiched between two electrodes, in order to obtain a large-capacity dielectric element having a small area or a ferroelectric capacitive element, conventionally, for example, the journal of Applied Physics (J. Appl. Phys), 1991, Vol. 70,
No. 1, pages 382 to 388,
Platinum (Pt) was used as the electrode material and PZT (Pb (Zr x Ti 1 -x ) O 3 ) was used as the ferroelectric material.
【0003】図3にシリコン基板上に強誘電体を積層し
た構造の、強誘電体素子の一例を示す。図3において、
301はシリコン基板であり、302は二酸化シリコン
(SiO2)の絶縁層である。304がPZTを用いた強誘
電体膜であり、下部電極303と上部電極305により
挟まれ、容量素子を構成している。306は素子保護膜
である。FIG. 3 shows an example of a ferroelectric element having a structure in which a ferroelectric is laminated on a silicon substrate. In FIG.
Reference numeral 301 denotes a silicon substrate, and 302 denotes an insulating layer of silicon dioxide (SiO 2 ). Reference numeral 304 denotes a ferroelectric film using PZT, which is sandwiched between a lower electrode 303 and an upper electrode 305 to constitute a capacitive element. 306 is an element protection film.
【0004】[0004]
【発明が解決しようとする課題】このように下部電極3
03、強誘電体膜304、上部電極305を積層した構
造においては、電極に電圧を印加した場合、特に小さい
方の電極、この場合は上部電極305の周辺部に電界が
集中する。したがって、正負の電圧を交互に繰り返しか
けた場合、特に電界の集中した部分で強誘電体膜305
の膜疲労(fatigue)が進み、自発分極などの素子特性
が劣化する。また、高い電圧が印加されると上部電極3
05の周辺部の電界の集中した領域で強誘電体膜304
の絶縁破壊を起こす。As described above, the lower electrode 3
03, in the structure in which the ferroelectric film 304 and the upper electrode 305 are stacked, when a voltage is applied to the electrodes, the electric field concentrates on the smaller electrode, in this case, the periphery of the upper electrode 305. Therefore, when the positive and negative voltages are alternately applied, the ferroelectric film 305 particularly in the portion where the electric field is concentrated.
The film fatigue (fatigue) progresses, and the device characteristics such as spontaneous polarization deteriorate. When a high voltage is applied, the upper electrode 3
05 in the region where the electric field is concentrated around the periphery of the ferroelectric film 304
Causes dielectric breakdown.
【0005】本発明は、このような課題を解決するもの
で、電極周辺部の電界集中を防ぎ、強誘電体素子の疲労
特性や絶縁耐圧を向上させるものである。The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to prevent an electric field from being concentrated around an electrode and to improve the fatigue characteristics and dielectric strength of a ferroelectric element.
【0006】[0006]
【課題を解決するための手段】本発明の強誘電体素子
は、強誘電体膜が2つの電極によって挟まれた構造を有
する強誘電体素子であって、前記2つの電極間に強誘電
体薄膜が挟まれた第一の領域と、前記2つの電極間に強
誘電体薄膜及び常誘電体層が挟まれた第二の領域とを有
し、該第二の領域が、強誘電体薄膜の外周側に形成さ
れ、前記常誘電体層が、強誘電体薄膜の外周端面に延在
し、該端面を覆ってなることを特徴とする。また、本発
明の半導体装置は、上記の強誘電体素子を備えたことを
特徴とする。A ferroelectric element according to the present invention is a ferroelectric element having a structure in which a ferroelectric film is sandwiched between two electrodes, wherein a ferroelectric element is provided between the two electrodes. A first region in which a thin film is sandwiched, and a second region in which a ferroelectric thin film and a paraelectric layer are sandwiched between the two electrodes, wherein the second region is a ferroelectric thin film Wherein the paraelectric layer extends on the outer peripheral end face of the ferroelectric thin film and covers the end face . Further, a semiconductor device according to the present invention includes the above-described ferroelectric element.
【0007】[0007]
【実施例】図1は本発明の強誘電体素子の、第1の実施
例を示す主要断面図である。図2は本発明の強誘電体素
子の、第2の実施例を示す主要断面図である。FIG. 1 is a main sectional view showing a first embodiment of a ferroelectric element according to the present invention. FIG. 2 is a main sectional view showing a second embodiment of the ferroelectric element of the present invention.
【0008】以下、まず図1にしたがい、第1の実施例
として、上部電極の周辺部と強誘電体膜との間に、常誘
電体層をはさんだ構造について、本発明の強誘電体素子
を説明する。First, referring to FIG. 1, as a first embodiment, a structure in which a paraelectric layer is interposed between a peripheral portion of an upper electrode and a ferroelectric film according to the present invention will be described. Will be described.
【0009】図1において、101はシリコン基板であ
る。102は強誘電体素子の下地となる絶縁層であり、
例えば、シリコン基板101を熱酸化して1μmの二酸
化シリコン(SiO2)を形成する。103は強誘電体素子
の一方の電極(以下、下部電極とする)であり、例えば
白金を0.5μm、スパッタ法により形成する。104
は強誘電体膜であり、例えばPZT(Pb(Zr0.4Ti0.6)
O3)をゾル−ゲル法により0.5μm形成し、600℃
で焼結する。In FIG. 1, reference numeral 101 denotes a silicon substrate. Reference numeral 102 denotes an insulating layer serving as a base of the ferroelectric element,
For example, the silicon substrate 101 is thermally oxidized to form 1 μm silicon dioxide (SiO 2 ). Reference numeral 103 denotes one electrode (hereinafter, referred to as a lower electrode) of the ferroelectric element, which is formed, for example, of 0.5 μm of platinum by a sputtering method. 104
Is a ferroelectric film, for example, PZT (Pb (Zr 0.4 Ti 0.6 )
O 3 ) is formed to a thickness of 0.5 μm by a sol-gel method.
And sinter.
【0010】105は本発明の趣旨による常誘電体層で
あり、例えば二酸化シリコンを0.3μm、化学気相成
長法(以下、CVDとする)により形成し、所定の大き
さに開孔する。106は強誘電体素子のもう一方の電極
(以下、上部電極とする)であり、例えば白金を0.5
μm、スパッタ法により形成し、常誘電体層105の開
孔部より大きなパターンに形成する。Reference numeral 105 denotes a paraelectric layer according to the gist of the present invention. The paraelectric layer is made of, for example, 0.3 μm of silicon dioxide by chemical vapor deposition (hereinafter referred to as CVD) and has a predetermined size. Reference numeral 106 denotes another electrode (hereinafter, referred to as an upper electrode) of the ferroelectric element.
μm, formed by a sputtering method to form a pattern larger than the opening of the paraelectric layer 105.
【0011】以上をもって、本発明の第1の実施例とす
る。The above is a first embodiment of the present invention.
【0012】図3に示した従来の技術による構造の強誘
電体素子では、初期の自発分極が18μC/cm2であ
り、下部電極303と上部電極305との間に、±30
0kV/cm2の電界を交互に105回印加する電圧サイ
クルを行った後では、6μC/cm2となったが、本実
施例のように、上部電極106の周辺部と強誘電体膜1
04との間に、常誘電体層105をはさんだ構造にした
場合、初期の自発分極が18μC/cm2、同様な電界
サイクルを印加した後でも、13μC/cm2であっ
た。In the ferroelectric device having the structure according to the prior art shown in FIG. 3, the initial spontaneous polarization is 18 μC / cm 2 , and the distance between the lower electrode 303 and the upper electrode 305 is ± 30.
After performing a voltage cycle of applying an electric field of 0 kV / cm 2 alternately 10 5 times, the voltage was 6 μC / cm 2. However, as in this embodiment, the peripheral portion of the upper electrode 106 and the ferroelectric film 1
In a case where the paraelectric layer 105 was sandwiched between the first and fourth layers, the initial spontaneous polarization was 18 μC / cm 2 , and 13 μC / cm 2 even after applying a similar electric field cycle.
【0013】また、図3に示した従来の技術による構造
の強誘電体素子では、下部電極303と上部電極305
との間の初期の絶縁耐圧は、約3MV/cmであった
が、本実施例の構造においては、上部電極106周辺部
の電界は緩和され、下部電極103と上部電極106と
の間の絶縁耐圧は、約3.5MV/cmであった。Further, in the ferroelectric element having the structure according to the prior art shown in FIG. 3, the lower electrode 303 and the upper electrode 305
Is about 3 MV / cm, but in the structure of this embodiment, the electric field around the upper electrode 106 is relaxed, and the insulation between the lower electrode 103 and the upper electrode 106 is reduced. The withstand voltage was about 3.5 MV / cm.
【0014】次に、図2にしたがい、第2の実施例とし
て、下部電極の周辺部と強誘電体膜との間に、下部電極
の周辺部から中心部に向かって、厚みの小さくなるよう
にした常誘電体層をはさんだ構造について、本発明の強
誘電体素子を説明する。Next, referring to FIG. 2, as a second embodiment, between the peripheral portion of the lower electrode and the ferroelectric film, the thickness is reduced from the peripheral portion of the lower electrode toward the center portion. The ferroelectric element of the present invention will be described with respect to a structure having a paraelectric layer interposed therebetween.
【0015】図2において、201はシリコン基板であ
る。202は強誘電体素子の下地となる絶縁層であり、
例えば、シリコン基板201を熱酸化して1μmの二酸
化シリコン(SiO2)を形成する。203は強誘電体素子
の一方の電極(以下、下部電極とする)であり、例えば
白金を0.5μm、スパッタ法により形成する。In FIG. 2, reference numeral 201 denotes a silicon substrate. Reference numeral 202 denotes an insulating layer serving as a base of the ferroelectric element,
For example, the silicon substrate 201 is thermally oxidized to form 1 μm silicon dioxide (SiO 2 ). Reference numeral 203 denotes one electrode (hereinafter, referred to as a lower electrode) of the ferroelectric element, which is formed, for example, of 0.5 μm of platinum by a sputtering method.
【0016】204は本発明の趣旨による常誘電体層で
あり、例えば二酸化シリコンを0.5μm、化学気相成
長法(以下、CVDとする)により形成し、所定の大き
さに開孔する。この時、等方性のエッチング、例えば純
水で1:10に希釈したふっ酸を用いてエッチングすれ
ば、前記開孔部中心に向かって、常誘電体層204の厚
みを連続的に小さくすることができる。Reference numeral 204 denotes a paraelectric layer according to the gist of the present invention, which is formed, for example, of 0.5 μm silicon dioxide by a chemical vapor deposition method (hereinafter, referred to as CVD), and is opened to a predetermined size. At this time, if the isotropic etching, for example, etching using hydrofluoric acid diluted 1:10 with pure water, the thickness of the paraelectric layer 204 is continuously reduced toward the center of the opening. be able to.
【0017】205は強誘電体膜であり、例えばPZT
(Pb(Zr0.4Ti0.6)O3)をゾル−ゲル法により0.5μm
形成し、600℃で焼結する。206は強誘電体素子の
もう一方の電極(以下、上部電極とする)であり、例え
ば白金を0.5μm、スパッタ法により形成する。Reference numeral 205 denotes a ferroelectric film, for example, PZT
(Pb (Zr 0.4 Ti 0.6 ) O 3 ) by a sol-gel method
Form and sinter at 600 ° C. Reference numeral 206 denotes another electrode (hereinafter, referred to as an upper electrode) of the ferroelectric element, which is formed, for example, of 0.5 μm of platinum by a sputtering method.
【0018】以上をもって、本発明の第2の実施例とす
る。The above is a second embodiment of the present invention.
【0019】このように、常誘電体層204の開孔部の
厚みを、開孔部中心に向かって小さくなるようにしたこ
とにより、開孔部周辺での電界も緩和され、初期の自発
分極が18μC/cm2であったものが、前記電圧サイ
クル印加後でも16μC/cm2にしか減少しなかっ
た。また、下部電極203と上部電極206との間の絶
縁耐圧は、約5MV/cmであった。As described above, by reducing the thickness of the opening of the paraelectric layer 204 toward the center of the opening, the electric field around the opening is also reduced, and the initial spontaneous polarization there shall was 18μC / cm 2 is not only reduced to 16μC / cm 2 even after the voltage cycles applied. The withstand voltage between the lower electrode 203 and the upper electrode 206 was about 5 MV / cm.
【0020】[0020]
【発明の効果】以上述べたように、本発明の強誘電体素
子の構成によれば、少なくとも一個の電極の周辺部と強
誘電体膜との間に、常誘電体層をはさみ、また、前記常
誘電体層を前記電極の周辺部から中心部方向に向かって
連続的に薄くしたことにより、電極周辺部での電界集中
が緩和され、前記強誘電体素子の疲労特性や、前記強誘
電体素子の二つの電極間の絶縁耐圧を向上せしめること
ができる。As described above, according to the structure of the ferroelectric element of the present invention, the paraelectric layer is interposed between the peripheral portion of at least one electrode and the ferroelectric film. By continuously reducing the thickness of the paraelectric layer from the periphery of the electrode toward the center, electric field concentration in the periphery of the electrode is reduced, and the fatigue characteristics of the ferroelectric element and the ferroelectric The withstand voltage between the two electrodes of the body element can be improved.
【図1】 本発明の第1の実施例の主要断面図。FIG. 1 is a main cross-sectional view of a first embodiment of the present invention.
【図2】 本発明の第2の実施例の主要断面図。FIG. 2 is a main cross-sectional view of a second embodiment of the present invention.
【図3】 従来の技術による、強誘電体素子の主要断面
図。FIG. 3 is a main cross-sectional view of a ferroelectric element according to a conventional technique.
101 シリコン基板 102 絶縁層 103 下部電極 104 強誘電体膜 105 常誘電体層 106 上部電極 201 シリコン基板 202 絶縁層 203 下部電極 204 常誘電体層 205 強誘電体膜 206 上部電極 301 シリコン基板 302 絶縁層 303 下部電極 304 強誘電体膜 305 上部電極 306 素子保護膜 Reference Signs List 101 silicon substrate 102 insulating layer 103 lower electrode 104 ferroelectric film 105 paraelectric layer 106 upper electrode 201 silicon substrate 202 insulating layer 203 lower electrode 204 paraelectric layer 205 ferroelectric film 206 upper electrode 301 silicon substrate 302 insulating layer 303 Lower electrode 304 Ferroelectric film 305 Upper electrode 306 Device protection film
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.7 識別記号 FI H01L 27/108 29/788 29/792 (58)調査した分野(Int.Cl.7,DB名) H01L 27/10 451 H01L 21/822 H01L 21/8242 H01L 21/8247 H01L 27/04 H01L 27/108 H01L 29/788 H01L 29/792 ──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. 7 identification code FI H01L 27/108 29/788 29/792 (58) Investigated field (Int.Cl. 7 , DB name) H01L 27/10 451 H01L 21/822 H01L 21/8242 H01L 21/8247 H01L 27/04 H01L 27/108 H01L 29/788 H01L 29/792
Claims (2)
た構造を有する強誘電体素子であって、 前記2つの電極間に強誘電体薄膜が挟まれた第一の領域
と、 前記2つの電極間に強誘電体薄膜及び常誘電体層が挟ま
れた第二の領域とを有し、 該第二の領域が、強誘電体薄膜の外周側に形成され、 前記常誘電体層が、強誘電体薄膜の外周端面に延在し、
該端面を覆ってなることを特徴とする強誘電体素子。1. A ferroelectric element having a structure in which a ferroelectric film is sandwiched between two electrodes, wherein: a first region in which a ferroelectric thin film is sandwiched between the two electrodes; A second region in which the ferroelectric thin film and the paraelectric layer are interposed between the two electrodes, wherein the second region is formed on the outer peripheral side of the ferroelectric thin film; Extending to the outer peripheral end surface of the ferroelectric thin film ,
A ferroelectric element, wherein the ferroelectric element covers the end face .
とを特徴とする半導体装置。2. A semiconductor device comprising the ferroelectric element according to claim 1.
Priority Applications (1)
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JP16268199A JP3235596B2 (en) | 1999-06-09 | 1999-06-09 | Ferroelectric element and semiconductor device |
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JP16268199A JP3235596B2 (en) | 1999-06-09 | 1999-06-09 | Ferroelectric element and semiconductor device |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
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JP14952092A Division JP3203767B2 (en) | 1992-06-09 | 1992-06-09 | Ferroelectric element and semiconductor storage device |
Publications (2)
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JP2000004005A JP2000004005A (en) | 2000-01-07 |
JP3235596B2 true JP3235596B2 (en) | 2001-12-04 |
Family
ID=15759283
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JP (1) | JP3235596B2 (en) |
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1999
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