JPH0332157B2 - - Google Patents
Info
- Publication number
- JPH0332157B2 JPH0332157B2 JP56003549A JP354981A JPH0332157B2 JP H0332157 B2 JPH0332157 B2 JP H0332157B2 JP 56003549 A JP56003549 A JP 56003549A JP 354981 A JP354981 A JP 354981A JP H0332157 B2 JPH0332157 B2 JP H0332157B2
- Authority
- JP
- Japan
- Prior art keywords
- ferroelectric
- light
- electrode
- thin film
- transmitting 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.)
- Expired - Lifetime
Links
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/21—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements
- G11C11/22—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using ferroelectric elements
Landscapes
- Engineering & Computer Science (AREA)
- Computer Hardware Design (AREA)
- Semiconductor Memories (AREA)
- Inorganic Insulating Materials (AREA)
Description
【発明の詳細な説明】
本発明は、強誘電体メモリ及びその駆動方法に
関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ferroelectric memory and a method for driving the same.
デジタルコンピユータ、電話交換器等のデータ
記憶素子として、最近、強誘電体材料のＤ−Ｅヒ
ステリシス特性に着目した強誘電体メモリが注目
されている。すなわち、第１図に示すような角形
のＤ−Ｅヒステリシス曲線を持つ強誘電体がある
とき、残留分極（Pr）を真理値０に、残留分極
（−Pr）を真理値１に対応させる。いま、強誘電
体に正方向の読出し電界Ｅを印加した場合、もし
強誘電体の記憶が真理値１であつたなら、Ｄ−Ｅ
ヒステリ曲線上を状態Arから状態Brの方向に変
化する。この部分におけるヒステリシスループの
傾斜は急峻であり、キヤパシタンスが急激に変化
する。したがつてこのキヤパシタンスの変化を電
流変化として取り出すことにより、真理値１の記
憶を読出すことができる。 Ferroelectric memories, which are based on the DE hysteresis characteristics of ferroelectric materials, have recently attracted attention as data storage elements for digital computers, telephone exchanges, and the like. That is, when there is a ferroelectric material having a rectangular DE hysteresis curve as shown in FIG. 1, the residual polarization (Pr) is made to correspond to a truth value of 0, and the residual polarization (-Pr) to a truth value of 1. Now, if we apply a readout electric field E in the positive direction to the ferroelectric, if the memory of the ferroelectric has a truth value of 1, then D-E
The state changes from state A r to state B r on the hysteria curve. The slope of the hysteresis loop in this part is steep, and the capacitance changes rapidly. Therefore, by extracting this capacitance change as a current change, the memory of truth value 1 can be read out.
一方、強誘電体の記憶状態が真理値０であつた
場合、正方向の読出し電界Ｅに対して、ヒステリ
シス曲線上を状態Drから状態Erの方向に変化す
る。この部分におけるヒステリシスループの傾斜
は緩やかであり、キヤパシタンスは低いから、小
さな電流変化しか取り出せない。したがつて、真
理値１から区別して、真理値０を読取ることがで
きる。 On the other hand, when the storage state of the ferroelectric material has a truth value of 0, the state changes from the state D r to the state E r on the hysteresis curve in response to the read electric field E in the positive direction. Since the slope of the hysteresis loop in this part is gentle and the capacitance is low, only small current changes can be extracted. Therefore, the truth value 0 can be read as distinct from the truth value 1.
この強誘電体メモリの利点は、従来より知られ
ている磁気バブル素子と異なり、外界からの磁気
的影響を受けないこと、情報の記憶、読出しの際
の電力消費量が低いこと、メモリ・アクセスタイ
ムが1μs以下になること、ビツト当りのサイズが
小さいこと、単純で低コストな構造となること高
信頼性であること等々であり、磁気バブル素子で
は実現できない小型大容量かつ高信頼性のデータ
記憶装置が得られる可能性かあるものとして期待
されている。 The advantages of this ferroelectric memory, unlike conventionally known magnetic bubble devices, are that it is not subject to magnetic influence from the outside world, that it consumes little power when storing and reading information, and that it has low power consumption when accessing information. The time is less than 1 μs, the size per bit is small, the structure is simple and low cost, and the reliability is high, etc., and it is possible to create small, large capacity, and highly reliable data that cannot be achieved with magnetic bubble elements. It is expected that there is a possibility of obtaining a storage device.
しかし、従来検討された強誘電体メモリは、一
素子当り、真理値０または１の１ビツト分を記憶
できるだけであり、データ記憶装置の小型大容量
化という観点からは、十分なものとは言えなかつ
た。 However, the ferroelectric memories that have been considered so far can only store one bit of truth value 0 or 1 per element, and are not sufficient from the perspective of making data storage devices smaller and larger in capacity. Nakatsuta.
本発明は、記憶容量を飛躍的に増大しえ、しか
も情報の記憶、読み出しの高速化が可能で、リー
クによる記憶消失等を起すことのない強誘電体メ
モリ及びその駆動方法を提供することを目的とす
る。 An object of the present invention is to provide a ferroelectric memory that can dramatically increase storage capacity, speed up information storage and readout, and prevent memory loss due to leakage, and a method for driving the same. purpose.
この目的を達成するため、本発明に係る強誘電
体メモリは、強誘電体薄膜の一面上に光透過電極
を有し、前記強誘電体薄膜の他面側に、間に電気
絶縁膜を挟んで、前記光透過電極と対となる電極
を有することを特徴とする。 In order to achieve this object, the ferroelectric memory according to the present invention has a light-transmitting electrode on one side of the ferroelectric thin film, and an electrically insulating film sandwiched between the light-transmitting electrode on the other side of the ferroelectric thin film. The device is characterized in that it has an electrode that is paired with the light-transmitting electrode.
また、本発明に係る強誘電体メモリの駆動方法
は、強誘電体薄膜の一面上に光透過電極を有し、
前記強誘電体薄膜の他面側に、間に電気絶縁膜を
挟んで、前記光透過電極と対となる電極を有する
強誘電体メモリを使用し、前記強誘電体メモリの
前記電極間に抗電界より絶対値の小さい電界を印
加した状態で、前記光透過電極にレーザビームを
照射することにより、情報書き込み及び読み出し
を行なうことを特徴とする。 Further, the method for driving a ferroelectric memory according to the present invention includes a light-transmitting electrode on one surface of the ferroelectric thin film,
A ferroelectric memory is used, which has an electrode on the other side of the ferroelectric thin film, which is paired with the light-transmitting electrode, with an electrical insulating film sandwiched therebetween, and a resistor is provided between the electrodes of the ferroelectric memory. Information is written and read by irradiating the light-transmitting electrode with a laser beam while applying an electric field with an absolute value smaller than the electric field.
以下実施例たる添付図面を参照し、本発明の内
容を具体的に説明する。第２図は本発明に係る強
誘電体メモリの構造を示す断面図である。図にお
いて、１は強誘電体薄膜である。この強誘電体薄
膜１は、Ｄ−Ｅヒステリシス特性が急峻な角形特
性を示す強誘電体材料によつて構成する。そのよ
うな強誘電体材料の代表的な例としては、
BaTio3単結晶体、本出願人が先に提案（たとえ
ば特開昭55−56621号）したBaTiO3系多結晶体
より成る強誘電体磁器等を挙げることができる。
特に、前記BaTiO3系多結晶体より成る強誘電体
磁器は、BaTiO3単結晶の場合のような製造上の
困難性がなく、BaTiO3単結晶体と遜色のない急
峻な角形のＤ−Ｅヒステリシス特性を有し、しか
も誘電率が高く、温度特性が良好で、誘電体損失
が小さい等の利点があり、前記強誘電体薄膜１を
構成する材料として、現状では最も適している。 DESCRIPTION OF THE PREFERRED EMBODIMENTS The content of the present invention will be specifically described below with reference to the accompanying drawings, which are examples. FIG. 2 is a sectional view showing the structure of a ferroelectric memory according to the present invention. In the figure, 1 is a ferroelectric thin film. The ferroelectric thin film 1 is made of a ferroelectric material exhibiting a square characteristic with a steep DE hysteresis characteristic. Typical examples of such ferroelectric materials include:
Examples include BaTiO 3 single crystal and ferroelectric ceramics made of BaTiO 3 polycrystal, which was previously proposed by the present applicant (for example, in Japanese Patent Laid-Open No. 55-56621).
In particular, the ferroelectric ceramic made of the BaTiO 3 polycrystal has no manufacturing difficulties unlike BaTiO 3 single crystal, and has a steep square D-E that is comparable to BaTiO 3 single crystal. It has advantages such as hysteresis characteristics, high dielectric constant, good temperature characteristics, and small dielectric loss, and is currently the most suitable material for forming the ferroelectric thin film 1.
強誘電体薄膜１は、その面に垂直方向にのみ強
誘電体として働くことが望ましい。たとえば
BaTiO3系の場合は、Ti原子の変位方向が垂直方
向のみであるように設定するものである。また膜
厚ｔは、レーザビームの太さ以下とすることが望
ましい。 It is desirable that the ferroelectric thin film 1 acts as a ferroelectric only in the direction perpendicular to its surface. for example
In the case of BaTiO 3 system, the displacement direction of Ti atoms is set to be only in the vertical direction. Further, it is desirable that the film thickness t be less than or equal to the thickness of the laser beam.
強誘電体薄膜１の表面上には、レーザビームを
透過させ得る光透過電極２を設けてある。この光
透過電極２は一般には透明電極として形成され
る。また、強誘電体薄膜１の裏面側には、リーク
電流を阻止するための電気絶縁層３を間に挟ん
で、電極４を積層してある。この電極４は基板と
してそのまま利用することもできるが、電極４の
裏面側に絶縁物でなる基板を別に貼り付けてもよ
い。 A light-transmitting electrode 2 is provided on the surface of the ferroelectric thin film 1 and is capable of transmitting a laser beam. This light-transmitting electrode 2 is generally formed as a transparent electrode. Further, on the back side of the ferroelectric thin film 1, an electrode 4 is laminated with an electrical insulating layer 3 therebetween for blocking leakage current. This electrode 4 can be used as it is as a substrate, but a separate substrate made of an insulating material may be attached to the back side of the electrode 4.
次に上記構成の強誘電体メモリにおける情報の
書込みおよび読出し動作について説明する。 Next, information writing and reading operations in the ferroelectric memory having the above configuration will be explained.
まず、情報の書込みについて説明する。光透過
電極２から電極４に向う電界の方向を順方向とし
この方向が第１図のヒステリシス曲線のグラフ軸
に一致しているものとする。光透過電極２と電極
４との間に順方向の電界を印加し、分極を同一方
向に揃えて飽和させた後、印加電界を除去すると
第１図のヒステリシスループは状態Drとなり、
真理値０が残留分極Prとして書込まれる。 First, writing of information will be explained. It is assumed that the direction of the electric field from the light-transmitting electrode 2 toward the electrode 4 is a forward direction, and this direction corresponds to the graph axis of the hysteresis curve in FIG. After applying a forward electric field between the light-transmitting electrode 2 and the electrode 4 to align the polarization in the same direction and saturating it, when the applied electric field is removed, the hysteresis loop in Fig. 1 becomes the state D r ,
A truth value of 0 is written as the residual polarization P r .
真理値１を書込むには、分極が反転する電解強
度をEcとしたとき、絶対値がEc以下で反対方向の
電界−Emを印加し、レーザビームを光透過電極
２の一点に照射する。すると、レーザビームの照
射された一点の分極が、レーザビーム・アニール
作用により印加電界の方向を向き、ヒステリシス
ループが状態Dr′（電界−Emに対応する）から
状態Erに変化する。ここで電界−Em、レーザビ
ームがなくなると、ヒステリシスループが状態Er
から状態Arに変化するから、真理値１が残留分
極（−Pr）として書込まれる。 To write a truth value of 1, when the electric field strength at which the polarization is reversed is E c , an electric field -Em in the opposite direction with an absolute value of E c or less is applied, and a laser beam is irradiated to one point on the light-transmitting electrode 2. do. Then, the polarization at one point irradiated by the laser beam turns in the direction of the applied electric field due to the laser beam annealing effect, and the hysteresis loop changes from the state D r ′ (corresponding to the electric field −Em) to the state E r . Here, when the electric field −Em and the laser beam disappear, the hysteresis loop changes to the state E r
Since the state changes from A to A r , the truth value 1 is written as residual polarization (-Pr).
次に読出す場合は、光透過電極２と電極４との
間に、抗電界Ecよりは小さい順方向の電界Emを
印加し、読み出したい部分にレーザビームを照射
する。この場合、レーザビーム照射点の記憶が真
理値０であつたなら、Ｄ−Ｅヒステリシス曲線は
状態Drから状態Crに変化する。この部分におけ
るヒステリシスループの傾斜は緩やかであり、キ
ヤパシタンスの変化は非常に小さいから、小さな
電流変化しか取り出せない。 For next reading, a forward electric field Em smaller than the coercive electric field E c is applied between the light-transmitting electrode 2 and the electrode 4, and a laser beam is irradiated to the part to be read. In this case, if the memory of the laser beam irradiation point has a truth value of 0, the DE hysteresis curve changes from the state Dr to the state C r . Since the slope of the hysteresis loop in this part is gentle and the change in capacitance is very small, only a small change in current can be extracted.
一方、レーザビーム照射点の記憶が真理値１で
あつたなら、Ｄ−Ｅヒステリシス曲線は状態Ar
から状態Brを経て状態Crに変化する。この状態
変化は分極の反転をもたらすもので、キヤパシタ
ンスが急激に変化するから、光透過電極２−電極
４から大きな電流変化が取り出される。したがつ
て、この電流変化を検出することにより、真理値
１を真理値０から区別して読取ることができる。 On the other hand, if the memory of the laser beam irradiation point has a truth value of 1, the D-E hysteresis curve is in the state A r
It changes from state B r to state C r . This state change brings about a reversal of polarization, and since the capacitance changes rapidly, a large current change is taken out from the light-transmitting electrode 2 to the electrode 4. Therefore, by detecting this current change, truth value 1 can be distinguished from truth value 0 and read.
この場合、光透過電極２上でレーザビームをた
とえばＸ、Ｙ軸方向に動かすことにより、一個の
強誘電体メモリで非常に高密度の情報の書込み、
読出しを行なうことができる。したがつて、小型
かつ薄型で、記憶容量の非常に大きい強誘電体メ
モリが実現できる。また、光透過電極２と電極４
との間に印加される電界Em、−Emは、抗電界Ec
より小さいから、高周波電界とすることが可能で
あり、動作速度の高速化が可能である。たとえ
ば、電界Em、−Emを1MHzの高周波電界とした
場合は、1μsの動作時間となる。 In this case, by moving the laser beam on the light-transmitting electrode 2 in, for example, the X and Y axis directions, extremely high-density information can be written in one ferroelectric memory.
Reading can be performed. Therefore, it is possible to realize a ferroelectric memory that is small, thin, and has a very large storage capacity. In addition, the light-transmitting electrode 2 and the electrode 4
The electric field Em, −Em applied between is the coercive electric field Ec
Since it is smaller, it is possible to use a high frequency electric field, and the operation speed can be increased. For example, if the electric fields Em and -Em are high-frequency electric fields of 1 MHz, the operating time is 1 μs.
しかも、強誘電体薄膜１の他面側に、間に電気
絶縁膜３を挟んで、光透過電極２と対となる電極
４を有するので、電極２−４間にリーク電流が流
れるのを阻止し、記憶状態を長期間にわたつて安
定に保持することができる。 Moreover, since the other surface of the ferroelectric thin film 1 has an electrode 4 that pairs with the light-transmitting electrode 2 with an electric insulating film 3 in between, leakage current can be prevented from flowing between the electrodes 2 and 4. However, the memory state can be stably maintained over a long period of time.
以上述べたように、本発明によれば、記憶容量
を飛躍的に増大しえ、しかも情報の記憶、読み出
しの高速化が可能で、リークによる記憶消失等を
起すことのない強誘電体メモリ及びその駆動方法
を提供することができる。 As described above, the present invention provides a ferroelectric memory and a ferroelectric memory that can dramatically increase storage capacity, can store and read information at high speed, and do not cause memory loss due to leakage. A driving method thereof can be provided.
第１図は強誘電体のＤ−Ｅヒステリシス特性図
第２図は本発明に係る強誘電体メモリとその駆動
方法を示す図である。
１……強誘電体薄膜、２……光透過電極、４…
…電極。
FIG. 1 is a diagram showing DE hysteresis characteristics of a ferroelectric material. FIG. 2 is a diagram showing a ferroelectric memory according to the present invention and a method for driving the same. 1... Ferroelectric thin film, 2... Light-transmitting electrode, 4...
…electrode.
Claims (1)
前記強誘電体薄膜の他面側に、間に電気絶縁膜を
挟んで、前記光透過電極と対となる電極を有する
ことを特徴とする強誘電体メモリ。 ２ 前記強誘電体薄膜は、BaTiO3系多結晶体を
主成分とする強誘電体磁器でなることを特徴とす
る特許請求の範囲第１項に記載の強誘電体メモ
リ。 ３ 強誘電体薄膜の一面上に光透過電極を有し、
前記強誘電体薄膜の他面側に、間に電気絶縁膜を
挟んで、前記光透過電極と対となる電極を有する
強誘電体メモリを使用し、前記強誘電体メモリの
前記電極間に抗電界より絶対値の小さい電界を印
加した状態で、前記光透過電極にレーザビームを
照射することにより、情報書き込み及び読み出し
を行なうことを特徴とする強誘電体メモリの駆動
方法。[Claims] 1. A light-transmitting electrode on one surface of a ferroelectric thin film,
A ferroelectric memory characterized in that it has an electrode on the other side of the ferroelectric thin film, which pairs with the light-transmitting electrode, with an electrical insulating film interposed therebetween. 2. The ferroelectric memory according to claim 1, wherein the ferroelectric thin film is made of ferroelectric ceramic whose main component is BaTiO 3 -based polycrystalline material. 3 having a light-transmitting electrode on one surface of the ferroelectric thin film,
A ferroelectric memory is used, which has an electrode on the other side of the ferroelectric thin film, which is paired with the light-transmitting electrode, with an electrical insulating film sandwiched therebetween, and a resistor is provided between the electrodes of the ferroelectric memory. A method for driving a ferroelectric memory, comprising writing and reading information by irradiating the light-transmitting electrode with a laser beam while applying an electric field having an absolute value smaller than an electric field.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP354981A JPS57117186A (en) | 1981-01-12 | 1981-01-12 | Ferrodielectric memory and its driving method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP354981A JPS57117186A (en) | 1981-01-12 | 1981-01-12 | Ferrodielectric memory and its driving method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS57117186A JPS57117186A (en) | 1982-07-21 |
| JPH0332157B2 true JPH0332157B2 (en) | 1991-05-10 |
Family
ID=11560494
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP354981A Granted JPS57117186A (en) | 1981-01-12 | 1981-01-12 | Ferrodielectric memory and its driving method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS57117186A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5856242A (en) * | 1981-09-30 | 1983-04-02 | Clarion Co Ltd | Video disk |
| JPH0750540B2 (en) * | 1986-02-06 | 1995-05-31 | ソニー株式会社 | Recording / playback device |
| JPH0750539B2 (en) * | 1986-02-06 | 1995-05-31 | ソニー株式会社 | Recording / playback device |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ZA757388B (en) * | 1974-12-16 | 1977-07-27 | Photovoltaic Ceramic Corp | Ferroelectric ceramic devices |
-
1981
- 1981-01-12 JP JP354981A patent/JPS57117186A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS57117186A (en) | 1982-07-21 |
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