JPH0730074A - Capacitor for non-volatile memory - Google Patents
Capacitor for non-volatile memoryInfo
- Publication number
- JPH0730074A JPH0730074A JP5153605A JP15360593A JPH0730074A JP H0730074 A JPH0730074 A JP H0730074A JP 5153605 A JP5153605 A JP 5153605A JP 15360593 A JP15360593 A JP 15360593A JP H0730074 A JPH0730074 A JP H0730074A
- Authority
- JP
- Japan
- Prior art keywords
- thin film
- ferroelectric thin
- lower electrode
- oxide layer
- capacitor
- 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.)
- Pending
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- Semiconductor Memories (AREA)
- Semiconductor Integrated Circuits (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、強誘電体薄膜を用いた
不揮発性メモリ用キャパシタに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-volatile memory capacitor using a ferroelectric thin film.
【０００２】[0002]
【従来の技術】近年、コンピュータの高性能化、小形化
の進展にともない、メモリデバイスの小形化、不揮発性
メモリ化の要求が益々増大してきている。こうした中
で、メモリデバイスのキャパシタとして、その高い誘電
率を利用して大きなキャパシタ容量が得られ、かつ分極
反転ができ、ヒステリシスによる不揮発性を有する強誘
電体材料が大きく期待されている。2. Description of the Related Art In recent years, with the progress of high performance and miniaturization of computers, the demand for miniaturization of memory devices and non-volatile memory has been increasing more and more. Under these circumstances, as a capacitor of a memory device, a ferroelectric material having a large capacitance by utilizing its high dielectric constant, capable of polarization reversal, and having non-volatility due to hysteresis is greatly expected.
【０００３】従来の強誘電体薄膜を用いた不揮発性メモ
リ用キャパシタは、図５に示すように、表面酸化処理に
より表面に酸化絶縁膜５が形成された半導体基板上４
に、下部電極２を形成し、その下部電極２上に強誘電体
薄膜１を形成し、その強誘電体薄膜１上に上部電極３を
形成した構成となっている。そして、下部電極２は強誘
電体薄膜と格子定数の近い白金が主として使用され、上
部電極３は白金、金、アルミニウム等の金属が使用され
ている。このキャパシタを不揮発性メモリデバイスに応
用して、この強誘電体薄膜のヒステリシス性を利用し、
残留分極の反転による情報の書き込み・読み出しを行っ
ている。A conventional non-volatile memory capacitor using a ferroelectric thin film is formed on a semiconductor substrate 4 having an oxide insulating film 5 formed on its surface by surface oxidation treatment, as shown in FIG.
Then, the lower electrode 2 is formed, the ferroelectric thin film 1 is formed on the lower electrode 2, and the upper electrode 3 is formed on the ferroelectric thin film 1. The lower electrode 2 is mainly made of platinum having a lattice constant close to that of the ferroelectric thin film, and the upper electrode 3 is made of metal such as platinum, gold or aluminum. By applying this capacitor to a non-volatile memory device, and utilizing the hysteresis property of this ferroelectric thin film,
Information is written and read by reversing the remanent polarization.
【０００４】[0004]
【発明が解決しようとする課題】強誘電体薄膜を用いた
不揮発性メモリ用キャパシタでは、分極反転を利用して
情報を記憶するため、分極反転可能回数がデバイスの寿
命を決定する。In a non-volatile memory capacitor using a ferroelectric thin film, information is stored by utilizing polarization inversion, and therefore the number of times polarization inversion is possible determines the life of the device.
【０００５】ところが、上記従来例のような強誘電体薄
膜を用いた不揮発性メモリ用キャパシタにおいて、下部
電極に白金、上部電極に白金、金、アルミニウム等の金
属を使用した場合には、情報の書き込み・読み出しのた
めに強誘電体薄膜の残留分極の反転を繰り返し行うと、
強誘電体薄膜と電極金属の間に元素やイオンの相互拡散
がおこる。このため、キャパシタの残留分極値が減少す
るという問題点があり、メモリ用デバイスとしての寿命
に問題があった。However, in the non-volatile memory capacitor using the ferroelectric thin film as in the conventional example described above, when platinum is used for the lower electrode and platinum, gold, aluminum, or another metal is used for the upper electrode, information of When reversal of remanent polarization of ferroelectric thin film is repeated for writing and reading,
Mutual diffusion of elements and ions occurs between the ferroelectric thin film and the electrode metal. Therefore, there is a problem in that the remanent polarization value of the capacitor is reduced, and there is a problem in the life of the memory device.
【０００６】文献（Japanese Journal of Applied Phys
ics Vol.30,No.9B,September,1991pp.2159-2162) によ
れば分極反転が１０9 回程度から残留分極値の減少が観
測されており、残留分極の反転に伴う反転電荷量ＱSWが
半減している。この１０9 回の分極反転サイクルで劣化
するキャパシタでは、例えば１００μＳの周期で情報の
書き込み・読み出しを行う不揮発性メモリデバイスに応
用した場合、約１日の寿命となり実用性はない。Literature (Japanese Journal of Applied Phys
ics Vol.30, No.9B, September, 1991 pp.2159-2162), the decrease of the remanent polarization value is observed from about 10 9 times of the polarization reversal, and the inversion charge amount Q SW accompanying the reversal of the remanent polarization is observed. Is halved. A capacitor that deteriorates after 10 9 polarization inversion cycles has a practical life of about 1 day and is not practical when it is applied to a nonvolatile memory device that writes / reads information at a cycle of 100 μS, for example.
【０００７】そこで、本発明の目的は、不揮発性メモリ
に必要とされる１０13回以上の分極反転、すなわち情報
の書き込み・読み出しを行っても、残留分極、あるいは
残留分極の反転に伴う反転電荷量の減少がほとんどない
強誘電体薄膜を用いた不揮発性メモリ用キャパシタを提
供することにある。Therefore, an object of the present invention is to provide remanent polarization or reversal charge accompanying reversal of remanent polarization even when polarization inversion is performed 10 13 times or more, which is required for a non-volatile memory, that is, information writing / reading is performed. An object of the present invention is to provide a capacitor for a non-volatile memory using a ferroelectric thin film that hardly decreases in quantity.
【０００８】[0008]
【課題を解決するための手段】上記目的を達成するため
に、本発明に係る強誘電体薄膜を用いた不揮発性メモリ
用キャパシタは、表面酸化処理により表面に酸化絶縁膜
が形成された半導体基板上に、下部電極を形成し、その
下部電極上に強誘電体薄膜を形成し、その強誘電体薄膜
上に上部電極を形成した不揮発性メモリ用キャパシタに
おいて、下部電極はアルミニウムを含む合金からなり、
下部電極と強誘電体薄膜の界面にアルミニウムの酸化層
を形成し、上部電極と強誘電体薄膜の界面に金属の酸化
層を形成したことを特徴とするものである。To achieve the above object, a nonvolatile memory capacitor using a ferroelectric thin film according to the present invention is a semiconductor substrate having an oxide insulating film formed on its surface by surface oxidation treatment. In a non-volatile memory capacitor in which a lower electrode is formed on top, a ferroelectric thin film is formed on the lower electrode, and an upper electrode is formed on the ferroelectric thin film, the lower electrode is made of an alloy containing aluminum. ,
An aluminum oxide layer is formed at the interface between the lower electrode and the ferroelectric thin film, and a metal oxide layer is formed at the interface between the upper electrode and the ferroelectric thin film.
【０００９】[0009]
【作用】上記の構成によれば、下部電極と強誘電体薄膜
の界面に形成されたアルミニウムの酸化層、及び上部電
極と強誘電体薄膜の界面に形成された金属の酸化層は、
分極反転に伴う強誘電体薄膜と電極金属の間での元素や
イオンの相互拡散を防止するので、残留分極、あるいは
残留分極の反転に伴う反転電荷量の減少がほとんど起こ
らない。According to the above structure, the aluminum oxide layer formed at the interface between the lower electrode and the ferroelectric thin film and the metal oxide layer formed at the interface between the upper electrode and the ferroelectric thin film are
Since mutual diffusion of elements and ions between the ferroelectric thin film and the electrode metal due to the polarization reversal is prevented, the remanent polarization or the inversion charge amount accompanying the reversal of the remanent polarization hardly occurs.
【００１０】[0010]
【実施例】以下、本発明の一実施例を図面を用いて説明
する。図１に示すように、本発明による不揮発性メモリ
用キャパシタは、表面に酸化絶縁膜５が形成された半導
体基板４上に、下部電極２及び上部電極３が形成された
強誘電体薄膜１を形成し、強誘電体薄膜１と下部電極２
の界面、及び強誘電体薄膜１と上部電極３の界面には、
各電極金属の酸化層２ａ，３ａを形成した構成となって
いる。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a nonvolatile memory capacitor according to the present invention comprises a ferroelectric thin film 1 having a lower electrode 2 and an upper electrode 3 formed on a semiconductor substrate 4 having an oxide insulating film 5 formed on the surface thereof. Formed, ferroelectric thin film 1 and lower electrode 2
, And the interface between the ferroelectric thin film 1 and the upper electrode 3,
The structure is such that oxide layers 2a and 3a of each electrode metal are formed.
【００１１】具体的には、シリコン（Ｓｉ）からなる半
導体基板４の表面に、表面酸化処理により酸化シリコン
（ＳｉＯ2 ）の酸化絶縁膜５を形成する。この酸化絶縁
膜５上に、ニッケル（Ｎｉ）・クロム（Ｃｒ）・アルミ
ニウム（Ａｌ）・鉄（Ｆｅ）からなるニッケル合金ター
ゲットを空気雰囲気中でスパッタして、０．１〜０．５
μｍ厚のニッケル合金薄膜からなる下部電極２を形成す
る。Specifically, an oxide insulating film 5 of silicon oxide (SiO 2 ) is formed on the surface of the semiconductor substrate 4 made of silicon (Si) by surface oxidation treatment. A nickel alloy target made of nickel (Ni) / chromium (Cr) / aluminum (Al) / iron (Fe) is sputtered on the oxide insulating film 5 in an air atmosphere to form a sputtering target of 0.1 to 0.5.
A lower electrode 2 made of a nickel alloy thin film having a thickness of μm is formed.
【００１２】その後、酸素ガスを導入し１〜２００パス
カルの酸素雰囲気中に温度４００〜６００℃で約１０分
間保持すると、下部電極２の上部表面に、図２に示すよ
うに、アルミニウムが析出する。このアルミニウムが酸
化されて酸化アルミニウム（ＡｌＯX ）の酸化層２ａが
形成される。図２は上記方法により形成された、図１に
示す半導体基板４・酸化絶縁膜５・アルミニウムの酸化
層２ａのオージェ電子分光測定による組成の深さ方向の
元素の組成比分布図である。After that, when oxygen gas is introduced and kept in an oxygen atmosphere of 1 to 200 Pascal at a temperature of 400 to 600 ° C. for about 10 minutes, aluminum is deposited on the upper surface of the lower electrode 2 as shown in FIG. . The oxide layer 2a of the aluminum is oxidized aluminum oxide (AlO X) is formed. FIG. 2 is a composition ratio distribution diagram of elements in the depth direction of the composition of the semiconductor substrate 4, the oxide insulating film 5, and the aluminum oxide layer 2a shown in FIG. 1 formed by the above method by Auger electron spectroscopy.
【００１３】次に、アルミニウム酸化層２ａ上にレーザ
アブレーションで、強誘電体材料であるチタン酸ジルコ
ン酸鉛（以下ＰＺＴと記す）薄膜１を形成（基板温度：
４００〜６００℃、酸素圧力：１〜２００パスカル、膜
厚：０．１〜１μｍ）する。次に、ＰＺＴ薄膜１上にレ
ーザアブレーションにより、１〜２００パスカルの酸素
雰囲気中で温度４００〜６００℃にて、上部電極３の下
の部分にあたる２０〜１００ｎｍ厚のニッケル合金薄膜
を形成する。このとき、酸素雰囲気のために、このニッ
ケル合金薄膜は酸化され、ＰＺＴ薄膜１と上部電極３の
界面に膜厚数ｎｍ〜２０ｎｍの酸化アルミニウム（Ａｌ
ＯX ）の酸化層３ａが形成される。その後、酸素ガスを
排気し、レーザアブレーションを継続して、０．１〜
０．５μｍ厚のニッケル合金薄膜からなる上部電極３を
形成する。Next, a lead zirconate titanate (hereinafter referred to as PZT) thin film 1 which is a ferroelectric material is formed on the aluminum oxide layer 2a by laser ablation (substrate temperature:
400 to 600 ° C., oxygen pressure: 1 to 200 pascals, film thickness: 0.1 to 1 μm). Next, a nickel alloy thin film having a thickness of 20 to 100 nm corresponding to a lower portion of the upper electrode 3 is formed on the PZT thin film 1 by laser ablation at a temperature of 400 to 600 ° C. in an oxygen atmosphere of 1 to 200 Pascal. At this time, the nickel alloy thin film is oxidized due to the oxygen atmosphere, and aluminum oxide (Al) having a thickness of several nm to 20 nm is formed at the interface between the PZT thin film 1 and the upper electrode 3.
Oxide layer 3a of O X) is formed. Then, the oxygen gas is exhausted, laser ablation is continued, and
The upper electrode 3 made of a nickel alloy thin film having a thickness of 0.5 μm is formed.
【００１４】上記のようにして作成したＰＺＴ薄膜のキ
ャパシタ（電極面積５×１０-4ｃｍ2 ）に、図３に示す
ような電圧±１０ＶＤＣ、パルス幅５μＳのバイポーラ
パルスを印加して、ＰＺＴ薄膜の分極反転を繰り返し行
い、反転電荷量ＱSWを測定したところ、図４に示すよう
に、１０13回の分極反転サイクルに於いてもほとんど反
転電荷量ＱSWの減少が見られなかった。A PZT thin film capacitor (electrode area 5 × 10 -4 cm 2 ) produced as described above is applied with a bipolar pulse having a voltage of ± 10 VDC and a pulse width of 5 μS as shown in FIG. The polarization inversion was repeated and the amount of inversion charge Q SW was measured. As shown in FIG. 4, almost no decrease in the amount of inversion charge Q SW was observed even after 10 13 polarization inversion cycles.
【００１５】このキャパシタを、例えば１００μＳの周
期で情報の書き込み、読み出しを行う不揮発性メモリに
応用した場合、１０13回の分極反転サイクルは約３０年
に相当し、実用上問題のない不揮発性メモリが実現でき
る。When this capacitor is applied to a non-volatile memory for writing and reading information at a cycle of 100 μS, for example, 10 13 polarization inversion cycles correspond to about 30 years, and the non-volatile memory has no practical problem. Can be realized.
【００１６】なお、上記実施例では、強誘電体薄膜の材
料としてＰＺＴを用いたが、チタン酸バリウム等の他の
強誘電体材料を用いてもよい。また、下部電極はシリコ
ン酸化膜上に信頼性の高い強誘電体薄膜を効率よく形成
するためにアルミニウムを含む合金が好ましいが、上部
電極は酸化物を作りやすい金属を含んだものであればよ
い。Although PZT is used as the material of the ferroelectric thin film in the above embodiment, other ferroelectric materials such as barium titanate may be used. Further, the lower electrode is preferably an alloy containing aluminum in order to efficiently form a highly reliable ferroelectric thin film on the silicon oxide film, but the upper electrode may be any one containing a metal that easily forms an oxide. .
【００１７】さらに、本発明は、下部電極と強誘電体薄
膜の界面、及び上部電極と強誘電体薄膜の界面に金属の
酸化層を形成することを特徴とするものであり、電極薄
膜、及び強誘電体薄膜の形成法については、特に限定さ
れることはなく、従来から公知の種々の薄膜形成法によ
り各々の薄膜を形成してもよい。Furthermore, the present invention is characterized in that a metal oxide layer is formed at the interface between the lower electrode and the ferroelectric thin film and at the interface between the upper electrode and the ferroelectric thin film. The method of forming the ferroelectric thin film is not particularly limited, and each thin film may be formed by various conventionally known thin film forming methods.
【００１８】[0018]
【発明の効果】以上説明したように、本発明に係る強誘
電体薄膜を用いた不揮発性メモリ用キャパシタは、下部
電極と強誘電体薄膜の界面、及び上部電極と強誘電体薄
膜の界面に形成された金属の酸化層が、分極反転に伴う
強誘電体薄膜と電極金属の間での元素やイオンの相互拡
散を防止するので、残留分極、あるいは残留分極の反転
に伴う反転電荷量の減少はほとんど起こらない。したが
って、このキャパシタを不揮発性メモリデバイスに応用
した場合、長寿命の不揮発性メモリデバイスが実現でき
る。さらに、強誘電体材料の性質に起因する、データ書
き込み・消去の高速性、大きなキャパシタ容量による集
積密度の向上、放射線耐性が強い等の効果が得られ、信
頼性の高い、高集積度の不揮発性メモリデバイスを実現
できる。As described above, the non-volatile memory capacitor using the ferroelectric thin film according to the present invention has the interface between the lower electrode and the ferroelectric thin film and the interface between the upper electrode and the ferroelectric thin film. The formed metal oxide layer prevents mutual diffusion of elements and ions between the ferroelectric thin film and the electrode metal due to polarization reversal, so that the reversal polarization or the amount of reversal charge accompanying reversal of the remnant polarization is reduced. Rarely happens. Therefore, when this capacitor is applied to a non-volatile memory device, a long-life non-volatile memory device can be realized. Further, due to the properties of the ferroelectric material, high speed of data writing / erasing, improvement of integration density due to large capacitor capacity, strong radiation resistance, etc. are obtained, and highly reliable and highly integrated nonvolatile Memory device can be realized.
【図１】本発明の不揮発性メモリ用キャパシタの断面模
式図である。FIG. 1 is a schematic sectional view of a nonvolatile memory capacitor of the present invention.
【図２】図１に示す半導体基板４・酸化絶縁膜５・アル
ミニウムの酸化層２ａの組成の深さ方向の元素の組成比
分布図である。2 is a composition ratio distribution diagram of elements in the depth direction of the composition of the semiconductor substrate 4, the oxide insulating film 5, and the aluminum oxide layer 2a shown in FIG.
【図３】本発明の実施例の不揮発性メモリ用キャパシタ
に印加したバイポーラパルスである。FIG. 3 is a bipolar pulse applied to a capacitor for nonvolatile memory according to an example of the present invention.
【図４】図３に示したバイポーラパルスを印加した時の
反転電荷量ＱSWの測定値をプロットした図である。FIG. 4 is a diagram plotting measured values of the inversion charge amount Q SW when the bipolar pulse shown in FIG. 3 is applied.
【図５】従来の強誘電体薄膜を用いた不揮発性メモリ用
キャパシタの断面模式図である。FIG. 5 is a schematic cross-sectional view of a conventional nonvolatile memory capacitor using a ferroelectric thin film.
１ 強誘電体薄膜 ２ 下部電極 ２ａ アルミニウムの酸化層 ３ 上部電極 ３ａ 金属の酸化層 ４ 半導体基板 ５ 酸化絶縁膜 1 Ferroelectric Thin Film 2 Lower Electrode 2a Aluminum Oxide Layer 3 Upper Electrode 3a Metal Oxide Layer 4 Semiconductor Substrate 5 Oxide Insulation Film
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｈ０１Ｌ 27/04 27/108 ─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 6 Identification code Internal reference number FI Technical indication H01L 27/04 27/108
Claims (1)
形成された半導体基板上に、下部電極を形成し、その下
部電極上に強誘電体薄膜を形成し、その強誘電体薄膜上
に上部電極を形成した不揮発性メモリ用キャパシタにお
いて、下部電極はアルミニウムを含む合金からなり、下
部電極と強誘電体薄膜の界面にアルミニウムの酸化層を
形成し、上部電極と強誘電体薄膜の界面に金属の酸化層
を形成したことを特徴とする不揮発性メモリ用キャパシ
タ。1. A lower electrode is formed on a semiconductor substrate on which an oxide insulating film is formed by surface oxidation treatment, a ferroelectric thin film is formed on the lower electrode, and an upper portion is formed on the ferroelectric thin film. In a non-volatile memory capacitor with electrodes formed, the lower electrode is made of an alloy containing aluminum, an aluminum oxide layer is formed at the interface between the lower electrode and the ferroelectric thin film, and a metal is formed at the interface between the upper electrode and the ferroelectric thin film. A capacitor for a non-volatile memory, characterized in that an oxide layer of is formed.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5153605A JPH0730074A (en) | 1993-06-24 | 1993-06-24 | Capacitor for non-volatile memory |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5153605A JPH0730074A (en) | 1993-06-24 | 1993-06-24 | Capacitor for non-volatile memory |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0730074A true JPH0730074A (en) | 1995-01-31 |
Family
ID=15566143
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP5153605A Pending JPH0730074A (en) | 1993-06-24 | 1993-06-24 | Capacitor for non-volatile memory |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0730074A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5923056A (en) * | 1996-10-10 | 1999-07-13 | Lucent Technologies Inc. | Electronic components with doped metal oxide dielectric materials and a process for making electronic components with doped metal oxide dielectric materials |
| US6740531B2 (en) * | 2000-08-11 | 2004-05-25 | Samsung Electronics Co., Ltd. | Method of fabricating integrated circuit devices having dielectric regions protected with multi-layer insulation structures |
-
1993
- 1993-06-24 JP JP5153605A patent/JPH0730074A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5923056A (en) * | 1996-10-10 | 1999-07-13 | Lucent Technologies Inc. | Electronic components with doped metal oxide dielectric materials and a process for making electronic components with doped metal oxide dielectric materials |
| US6740531B2 (en) * | 2000-08-11 | 2004-05-25 | Samsung Electronics Co., Ltd. | Method of fabricating integrated circuit devices having dielectric regions protected with multi-layer insulation structures |
| US7023037B2 (en) | 2000-08-11 | 2006-04-04 | Samsung Electronics Co., Ltd. | Integrated circuit devices having dielectric regions protected with multi-layer insulation structures |
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