JPH11284136A - Ferroelectric thin film and its manufacture - Google Patents
Ferroelectric thin film and its manufactureInfo
- Publication number
- JPH11284136A JPH11284136A JP10083232A JP8323298A JPH11284136A JP H11284136 A JPH11284136 A JP H11284136A JP 10083232 A JP10083232 A JP 10083232A JP 8323298 A JP8323298 A JP 8323298A JP H11284136 A JPH11284136 A JP H11284136A
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- JP
- Japan
- Prior art keywords
- thin film
- film
- oxygen concentration
- lead
- ferroelectric thin
- Prior art date
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は強誘電体薄膜、特に
鉛系ペロブスカイト型強誘電体薄膜およびその製造方法
に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferroelectric thin film, particularly to a lead-based perovskite ferroelectric thin film and a method for producing the same.
【０００２】[0002]
【従来の技術】近年、半導体装置の高集積化に伴い、個
々の素子は微細化の一途をたどっている。たとえば、３
年で４倍のペースで高集積化を実現してきているＤＲＡ
Ｍ（Dynamic Random Access Memory）では、既に６４メ
ガビットメモリの量産が始まっているが、素子の微細化
に伴う蓄積容量の減少のために信号対雑音（ＳＮ）比の
低下や、α線の入射による信号反転等の弊害が顕在化
し、信頼性の確保が大きな問題となっている。2. Description of the Related Art In recent years, with the high integration of semiconductor devices, individual elements have been steadily miniaturized. For example, 3
DRA is achieving high integration four times a year
In M (Dynamic Random Access Memory), mass production of 64-Mbit memory has already begun, but the signal-to-noise (SN) ratio decreases due to the decrease in storage capacity due to miniaturization of elements and the incidence of α rays The adverse effects such as signal inversion have become apparent, and securing reliability has become a major problem.
【０００３】この問題を解決するため、キャパシタ絶縁
膜の薄膜化を進めると共に、３次元化によって小さな平
面面積のなかに大きなキャパシタ面積を持ったメモリセ
ルが開発されているが、このような方法によっても、メ
モリセルの微細化と構造の複雑化が進行し製造技術が非
常に難しくなるとともに、開発・製造コストが著しく増
大するという経済性の問題がある。In order to solve this problem, a memory cell having a large capacitor area in a small plane area has been developed by making the capacitor insulating film thinner and three-dimensional, and such a method has been developed. However, there is a problem of economical efficiency that the manufacturing technology becomes extremely difficult due to the progress of miniaturization and the complication of the structure of the memory cell, and the development and manufacturing costs are significantly increased.
【０００４】このため、小さな面積に大きな電荷を蓄積
することが出来る誘電率の大きな材料を用いたキャパシ
タが必要とされている。チタン酸ジルコン酸鉛を代表と
する強誘電体は、従来のキャパシタ用の誘電体膜ＳｉＯ
2 やＳｉ3Ｎ4に比較し１００〜１０００倍の誘電率を持
つため、比較的簡単なキャパシタ構造と組み合わせるだ
けで静電容量の大きなキャパシタを実現できる可能性が
ある。例えば、強誘電体薄膜をキャパシタ絶縁膜に用い
たＤＲＡＭとしては特開平3−165557 号や、特開平3−2
56358号，特開平3−296262号に記載されているものがあ
る。[0004] Therefore, a capacitor using a material having a large dielectric constant capable of storing a large charge in a small area is required. A ferroelectric represented by lead zirconate titanate is a conventional dielectric film SiO for a capacitor.
Since it has a dielectric constant 100 to 1000 times that of 2 or Si 3 N 4 , there is a possibility that a capacitor having a large capacitance can be realized only by combining it with a relatively simple capacitor structure. For example, as a DRAM using a ferroelectric thin film as a capacitor insulating film, Japanese Patent Application Laid-Open No. 3-165557 and Japanese Patent Application Laid-Open
No. 56358 and JP-A-3-296262.
【０００５】また、強誘電体は永久双極子間の相互作用
が強く、外部電場を印加しない状態でも自発分極と呼ば
れる電気分極を生じており、この自発分極を外部電場に
より反転することができ、電場をかけるとヒステリシス
曲線を描く。一旦高い電圧を印加したあとには電場が零
になっても残留分極＋Ｐｒ、または−Ｐｒが保持されて
いる。これらの状態をそれぞれ“１”と“０”と定義す
れば、外部電場の方向によって“１”，“０”の情報を
書き込むことが出来る。スイッチ用トランジスタと強誘
電体キャパシタを組み合わせたメモリセルを用いた分極
反転型不揮発性メモリは低電圧で高速の書き込み，読み
出し動作が可能であるためＩＣカードなどの用途に適し
ている。また、高集積化することができれば読み出し書
き込みともに高速な不揮発性のＲＡＭという理想的なメ
モリとなる可能性がある。スイッチ用トランジスタと強
誘電体キャパシタを組み合わせたメモリセルを用いた分
極反転型不揮発性メモリとしては例えば特開平1−15869
1 号に記載されているものがある。Further, the ferroelectric has a strong interaction between the permanent dipoles and generates an electric polarization called spontaneous polarization even in a state where no external electric field is applied. The spontaneous polarization can be reversed by the external electric field. When an electric field is applied, a hysteresis curve is drawn. Once a high voltage is applied, the residual polarization + Pr or -Pr is maintained even when the electric field becomes zero. If these states are defined as "1" and "0", information "1" and "0" can be written depending on the direction of the external electric field. A domain-inverted nonvolatile memory using a memory cell in which a switching transistor and a ferroelectric capacitor are combined is suitable for applications such as an IC card because it can perform high-speed writing and reading operations at a low voltage. In addition, if high integration is possible, there is a possibility that an ideal memory such as a nonvolatile RAM, which is high-speed for both reading and writing, may be used. As a domain-inverted nonvolatile memory using a memory cell in which a switching transistor and a ferroelectric capacitor are combined, for example, Japanese Patent Application Laid-Open No.
Some are listed in No. 1.
【０００６】このように優れた特性をもつ強誘電体チタ
ン酸ジルコン酸鉛系薄膜は主としてスパッタ法，ゾルゲ
ル法，反応性蒸着法，化学気相蒸着法（ＣＶＤ法）など
により形成される。The ferroelectric lead zirconate titanate-based thin film having such excellent characteristics is formed mainly by a sputtering method, a sol-gel method, a reactive evaporation method, a chemical vapor deposition method (CVD method) or the like.
【０００７】[0007]
【発明が解決しようとする課題】従来の技術でも、膜厚
や組成のウェハ面内でのバラツキは±５％程度以下にま
で抑えることが可能であるが、にもかかわらず、電気特
性は±１０％以上のウェハ面内バラツキがあった。現
在、Ｓｉ−ＬＳＩの量産には６〜８インチウェハが使用
されており、次世代のラインでは１２インチウェハが主
流となると考えられている。このような大面積に均一な
特性の素子を形成するためには特性バラツキの原因を明
らかにし、その対策を確立することが必要不可欠であ
る。In the prior art, the variation in the film thickness and composition in the wafer surface can be suppressed to about ± 5% or less. There was a 10% or more in-wafer variation. At present, 6 to 8 inch wafers are used for mass production of Si-LSI, and it is considered that 12 inch wafers will be the mainstream in next generation lines. In order to form an element having uniform characteristics in such a large area, it is indispensable to clarify the cause of the characteristic variation and establish a countermeasure.
【０００８】発明者等の検討によると特性分布の主な原
因は結晶配向性の面内バラツキによることが明らかとな
った。強誘電体の自発分極は結晶格子の歪みに基づくも
のなので、結晶に対して電界を印加する方向によりその
誘電率や、残留分極などが異なる。強誘電体を薄膜とし
て用いる素子では、通常、膜厚方向に電界を印加するの
で下地に対して強誘電体がどのような結晶方位に結晶化
しているかによってその電気特性が異なることになる。According to the studies by the inventors, it has been found that the main cause of the characteristic distribution is the in-plane variation of the crystal orientation. Since spontaneous polarization of a ferroelectric is based on distortion of a crystal lattice, its dielectric constant, remanent polarization, and the like differ depending on the direction in which an electric field is applied to the crystal. In an element using a ferroelectric substance as a thin film, an electric field is usually applied in the thickness direction, so that its electrical characteristics differ depending on the crystal orientation of the ferroelectric substance with respect to the base.
【０００９】図７はチタン酸ジルコン酸鉛（以下、ＰＺ
Ｔ）薄膜について、〔１１１〕配向膜，〔１００〕配向
膜，無配向の膜のヒステリシス特性を比較したものであ
る。〔１１１〕配向膜では飽和特性のよい角型ループで
あるのに対して、〔１００〕配向膜ではヒステリシスが
スリムになり、残留分極が小さくなっている。無配向膜
ではさらにスリムループとなる。〔１１１〕配向膜の残
留分極Ｐｒは４５μＣ／cm2、抗電圧Ｖｃは０.６Ｖ で
あるのに対し、無配向膜ではＰｒ＝１６μＣ／cm2，Ｖ
ｃ＝１.３Ｖである。FIG. 7 shows lead zirconate titanate (hereinafter referred to as PZ).
T) For the thin film, the hysteresis characteristics of the [111] -oriented film, the [100] -oriented film, and the non-oriented film are compared. The [111] orientation film has a square loop with good saturation characteristics, whereas the [100] orientation film has a slim hysteresis and a small residual polarization. In a non-oriented film, a slim loop is further formed. [111] the residual polarization Pr of the alignment film is 45μC / cm 2, whereas the coercive voltage Vc is 0.6V, the non-oriented film Pr = 16μC / cm 2, V
c = 1.3V.
【００１０】図８はダブルパルス測定による分極反転電
荷の電圧依存性を比較したものである。〔１１１〕配向
膜の飽和特性の良さがよくわかる。３Ｖパルス印加時の
分極反転電荷は約３８μＣ／cm2 であった。FIG. 8 compares the voltage dependence of the domain-inverted charges by double pulse measurement. [111] The good saturation characteristics of the alignment film can be clearly understood. The domain-inverted charge when a 3 V pulse was applied was about 38 μC / cm 2 .
【００１１】従来の技術、特に、スパッタ法，ゾルゲル
法で非晶質膜を形成し、熱処理によってこの非晶質膜を
結晶化させてペロブスカイト構造とする薄膜作製法によ
って作製されるＰｂ系強誘電体薄膜は、通常〔１００〕
／〔１１１〕混合配向となっている。結晶粒の大きさが
数十〜数百ナノメータであるのに対して、素子に用いら
れるキャパシタの大きさはミクロンサイズなので、キャ
パシタ中に含まれる〔１００〕結晶粒と〔１１１〕結晶
粒の割合の違いによってそのキャパシタの電気特性が異
なったものとなるわけである。A Pb-based ferroelectric film is formed by a conventional technique, in particular, a method of forming an amorphous film by a sputtering method or a sol-gel method, and crystallizing the amorphous film by heat treatment to form a thin film having a perovskite structure. Body thin film is usually [100]
/ [111] mixed orientation. Since the size of a crystal grain is several tens to several hundreds of nanometers, whereas the size of a capacitor used in an element is a micron size, the ratio of [100] crystal grains and [111] crystal grains contained in the capacitor Therefore, the electrical characteristics of the capacitor are different depending on the difference.
【００１２】本発明の目的は大面積の基板上に均一な特
性をもつ強誘電体薄膜の製造方法を提供することにあ
る。An object of the present invention is to provide a method for manufacturing a ferroelectric thin film having uniform characteristics on a large-area substrate.
【００１３】[0013]
【課題を解決するための手段】本発明においては、３０
０〜４００℃以下の温度領域では酸素濃度を低くして酸
化鉛の形成を抑制し、ペロブスカイト構造への結晶化が
起こる５００℃以上の温度領域では酸素濃度を高くして
酸素欠損の発生を抑えるという方法を用いる。According to the present invention, 30
In a temperature range of 0 to 400 ° C. or lower, the oxygen concentration is reduced to suppress the formation of lead oxide, and in a temperature range of 500 ° C. or higher where crystallization to a perovskite structure occurs, the oxygen concentration is increased to suppress the generation of oxygen vacancies. Is used.
【００１４】従来技術においては、鉛が十分に酸化され
ず、膜中に酸素欠損が存在したり、また、酸化されない
鉛が電極中に拡散したり再蒸発したりして組成ずれを起
こしてしまう。特に、スパッタ法，ゾルゲル法で非晶質
膜を形成し、熱処理によってこの非晶質膜を結晶化させ
てペロブスカイト構造とする薄膜作製法においては、結
晶化熱処理中の鉛の再蒸発を防止することは困難である
ため、あらかじめ非晶質膜中に化学量論比（Ｐｂ＝Ｚｒ
＋Ｔｉ）よりも過剰に鉛が含まれるようにする方法が用
いられる。In the prior art, lead is not sufficiently oxidized, oxygen deficiency is present in the film, and lead that is not oxidized diffuses into the electrode or re-evaporates to cause a composition deviation. . In particular, in a thin film forming method in which an amorphous film is formed by a sputtering method or a sol-gel method and the amorphous film is crystallized by a heat treatment to have a perovskite structure, re-evaporation of lead during the crystallization heat treatment is prevented. Is difficult, the stoichiometric ratio (Pb = Zr) is previously stored in the amorphous film.
+ Ti) is used so that lead is contained in excess.
【００１５】ところが、過剰に含まれる酸化不十分な鉛
は３００〜４００℃の低温で酸化鉛となる。立方晶のＰ
ｂＯは〔１００〕配向の層状化合物である。図９に示し
たようにＰｂＯの（１００）面はＰＺＴの(１００)面と
格子の整合性もよく、ＰＺＴの〔１００〕配向を促進す
る。However, excessively insufficiently oxidized lead becomes lead oxide at a low temperature of 300 to 400 ° C. Cubic P
bO is a layered compound having a [100] orientation. As shown in FIG. 9, the (100) plane of PbO has good lattice matching with the (100) plane of PZT, and promotes the [100] orientation of PZT.
【００１６】発明者は非晶質膜中に含まれる鉛の酸化の
度合いを調整できる反応性蒸着法を用いて検討を行っ
た。図１０に示したように非晶質膜堆積時に十分にオゾ
ンを供給して非晶質膜中に含まれる鉛を十分に酸化した
場合、結晶化熱処理後には〔１１１〕配向膜が得られ
た。一方、オゾンの供給量が不十分な場合には〔１０
０〕配向が混じってくる。図１１に結晶化熱処理後の薄
膜の配向性の鉛組成依存性を示す。鉛が化学量論比より
も過剰になると１００ピークが強くなっている。The inventor studied using a reactive evaporation method capable of adjusting the degree of oxidation of lead contained in an amorphous film. As shown in FIG. 10, when the ozone was sufficiently supplied during the deposition of the amorphous film to sufficiently oxidize the lead contained in the amorphous film, a [111] oriented film was obtained after the crystallization heat treatment. . On the other hand, if the supply amount of ozone is insufficient, [10
0] The orientation is mixed. FIG. 11 shows the lead composition dependence of the orientation of the thin film after the crystallization heat treatment. When the lead content exceeds the stoichiometric ratio, the 100 peak becomes strong.
【００１７】また、ジャーナル オブ アメリカン セ
ラミックス ソサイエティ ７７巻２３３７ページ（J.
Am. Ceram. Soc. 77, p. 2337 (1994））に述べられて
いるように、ゾルゲル法によるＰＺＴ薄膜形成において
も同様な結果が得られている。すなわち、仮焼成４００
℃，３０分を行った後６５０℃，３０分の熱処理を行う
と、過剰なＰｂが３５０〜４００℃で立方晶のＰｂＯと
なり、これが核となってＰＺＴの（１００）が成長する
ため、熱処理後のＰＺＴ膜は〔１００〕配向となる。さ
らに、ＰｂＯを５０ｎｍ基板上に塗布し、４００℃，１
時間熱処理して立方晶ＰｂＯ〔１００〕を形成し、この
うえにＰＺＴを塗布して結晶化させると、〔１００〕配
向のＰＺＴが得られることからＰｂＯが〔１００〕配向
のＰＺＴの核となっていることが示されている。したが
って、〔１００〕結晶粒の発生を抑制するためには過剰
な鉛が酸化鉛として結晶化するのを抑制すればよい。The Journal of American Ceramics Society, Vol. 77, p. 2337 (J.
As described in Am. Ceram. Soc. 77, p. 2337 (1994)), similar results have been obtained in forming a PZT thin film by a sol-gel method. That is, the preliminary firing 400
When the heat treatment is performed at 650 ° C. for 30 minutes after performing the heat treatment at 650 ° C. for 30 minutes, excess Pb becomes cubic PbO at 350 to 400 ° C., which becomes a nucleus to grow (100) of PZT. The subsequent PZT film has the [100] orientation. Further, PbO is applied on a 50 nm substrate,
When cubic PbO [100] is formed by heat treatment for a period of time, and PZT is applied thereon and crystallized, PZT of [100] orientation is obtained, so that PbO becomes a core of PZT of [100] orientation. Is shown. Therefore, in order to suppress the generation of the [100] crystal grains, it is only necessary to suppress the crystallization of excess lead as lead oxide.
【００１８】図１２は結晶化熱処理時の雰囲気依存性を
検討した結果である。雰囲気ガスに含まれる酸素の割合
を５％以下とすると、同じ非晶質膜でも〔１１１〕配向
となることがわかる。すなわち、酸素濃度を酸化鉛が結
晶化を開始するよりも低くすることで〔１１１〕に配向
の揃ったＰＺＴ膜が得られるわけである。しかしこのよ
うに低い酸素濃度で結晶化熱処理を行うと膜中に酸素欠
損が発生しリーク電流の増大や膜疲労耐性の低下などの
信頼性に対する問題を引き起こす。一旦、結晶化した
後、酸素雰囲気中で追酸化することによりある程度の特
性改善が可能であるが、すでに結晶化してしまった後な
ので、高温，長時間の追酸化が必要となり、集積回路の
他の部分の信頼性に及ぼす影響は無視できない。たとえ
ば、強誘電体キャパシタとスイッチ用トランジスタを接
続するコンタクト部での抵抗増大や、膜剥がれなどの問
題による歩留まりの低下がおこる。FIG. 12 shows the result of studying the atmosphere dependency during the crystallization heat treatment. When the proportion of oxygen contained in the atmosphere gas is set to 5% or less, it can be seen that even the same amorphous film has [111] orientation. That is, a PZT film having a uniform orientation of [111] can be obtained by setting the oxygen concentration lower than that at which lead oxide starts crystallization. However, when the crystallization heat treatment is performed at such a low oxygen concentration, oxygen vacancies are generated in the film, which causes reliability problems such as an increase in leak current and a decrease in film fatigue resistance. Once crystallization is performed, additional characteristics can be improved to some extent by additional oxidation in an oxygen atmosphere. However, since it has already been crystallized, additional oxidation at high temperature and for a long time is required. The effect on the reliability of the part cannot be ignored. For example, a decrease in yield due to a problem such as an increase in resistance at a contact portion connecting the ferroelectric capacitor and the switching transistor and a problem such as film peeling occurs.
【００１９】前述のように過剰な鉛が酸化鉛として結晶
化するのは３００〜４００℃と強誘電体膜が結晶化を開
始する温度（約５００℃）よりも低いので、４００℃以
下の低温領域では酸素濃度を酸化鉛が結晶化を開始する
よりも低くし、ペロブスカイト構造の結晶化が開始する
温度よりも高温では酸素濃度を低温領域よりも高くする
ことにより酸素欠損の発生を抑え、かつ、配向の揃った
Ｐｂ系強誘電体薄膜が得られる。As described above, the excess lead crystallizes as lead oxide at 300 to 400 ° C., which is lower than the temperature at which the ferroelectric film starts to crystallize (about 500 ° C.). In the region, the oxygen concentration is made lower than that at which lead oxide starts to crystallize, and at a temperature higher than the temperature at which crystallization of the perovskite structure starts, the oxygen concentration is made higher than that at the lower temperature region to suppress the generation of oxygen deficiency, and Thus, a Pb-based ferroelectric thin film having a uniform orientation can be obtained.
【００２０】[0020]
【発明の実施の形態】（実施例１）基板にはシリコン基
板上に密着層として窒化チタンを５０ｎｍ形成し、その
上に下部電極の白金をＤＣスパッタ法により形成した物
を用いた。オゾンを用いた反応性同時蒸着により非晶質
のチタン酸ジルコン酸鉛薄膜を形成した。DESCRIPTION OF THE PREFERRED EMBODIMENTS (Example 1) A substrate obtained by forming titanium nitride as an adhesion layer to a thickness of 50 nm on a silicon substrate and forming platinum of a lower electrode thereon by DC sputtering is used. An amorphous lead zirconate titanate thin film was formed by reactive co-evaporation using ozone.
【００２１】結晶化熱処理は図１に示したようなシーケ
ンスを用いて行った。まず、ウェハをチャンバー内に搬
送した後、十分にＮ2 パージを行い搬送時に巻き込んだ
大気をＮ2 で置換する。そのままＮ2 雰囲気下で５００
℃まで加熱し、５００℃になったところでＮ2／Ｏ2＝１
／１のガスに切り替えて７００℃，３０sec の熱処理を
行い、ガスを流したままランプを切って冷却し、２００
℃以下になったところでウェハをチャンバーから取り出
した。比較のために雰囲気を１気圧酸素とする従来の結
晶化熱処理を行った試料も作製した。The crystallization heat treatment was performed using a sequence as shown in FIG. First, after the wafer is transferred into the chamber, N 2 is sufficiently purged to replace the air entrained during the transfer with N 2 . As it is 500 under N 2 atmosphere
℃ and when the temperature reaches 500 ℃, N 2 / O 2 = 1
/ 1 gas and heat treatment at 700 ° C. for 30 sec.
When the temperature fell below the temperature, the wafer was taken out of the chamber. For comparison, a sample subjected to a conventional crystallization heat treatment in which the atmosphere was 1 atm oxygen was also prepared.
【００２２】図２に、結晶化熱処理後のＸＲＤ図形を、
従来法による結果と比較して示す。従来法では〔１０
０〕配向となる同じ非晶質膜でも、本発明の熱処理法を
用いれば加熱速度によらず〔１１１〕配向となっている
のがわかる。本発明の熱処理法により結晶化したＰＺＴ
膜は図３，図４に示すように残留分極の大きな角型ルー
プをもち飽和特性も優れている。また、リーク電流も酸
素１００％で結晶化した膜と比べて遜色のないものが得
られた。FIG. 2 shows an XRD pattern after the crystallization heat treatment.
The results are shown in comparison with the results of the conventional method. In the conventional method, [10
It can be seen that the same amorphous film having the [0] orientation has the [111] orientation regardless of the heating rate when the heat treatment method of the present invention is used. PZT crystallized by the heat treatment method of the present invention
As shown in FIGS. 3 and 4, the film has a square loop with large remanent polarization and excellent saturation characteristics. Also, a leak current comparable to that of a film crystallized with 100% oxygen was obtained.
【００２３】（実施例２）図５は、本実施例のキャパシ
タの断面を模式的に表したものである。シリコン基板５
１上に窒化チタン膜５２を５０ｎｍをスパッタ法により
形成し、次に、厚さ２００ｎｍの白金の下部電極５３を
スパッタ法により形成した。次に、厚さ１５０ｎｍの非
晶質膜チタン酸ジルコン酸鉛薄膜５４を反応性蒸着法に
より形成した。(Embodiment 2) FIG. 5 schematically shows a cross section of a capacitor of this embodiment. Silicon substrate 5
A 50 nm thick titanium nitride film 52 was formed on 1 by a sputtering method, and then a 200 nm-thick platinum lower electrode 53 was formed by a sputtering method. Next, an amorphous film of lead zirconate titanate thin film 54 having a thickness of 150 nm was formed by a reactive evaporation method.
【００２４】次に、図１に示した結晶化熱処理を行っ
た。次にＤＣスパッタ法により厚さ約５０ｎｍの白金膜
５５，２５０ｎｍタングステン膜５６を順次被着する。
フォトレジスト５７をマスクに最上層のタングステン膜
５６をドライエッチング法によりパターンニングする。
フォトレジスト５７を除去した後、タングステン５６を
マスクに用いたスパッタエッチング法により白金膜５
５，チタン酸ジルコン酸鉛薄膜５４，下地白金膜５３を
パターンニングする。次にドライエッチング法により最
下層の窒化チタン膜５２とマスクに用いたタングステン
膜５６を同時に除去しキャパシタを完成する。本実施例
ではドライエッチングのマスクにタングステンを用いた
が、窒化チタン膜を用いてもよい。また、目的の用途に
応じてチタン酸ジルコン酸鉛薄膜中の鉛の一部をＬａや
Ｂａなどの元素で置換してもよい。Next, the crystallization heat treatment shown in FIG. 1 was performed. Next, a platinum film 55 having a thickness of about 50 nm and a tungsten film 56 having a thickness of 250 nm are sequentially deposited by DC sputtering.
Using the photoresist 57 as a mask, the uppermost tungsten film 56 is patterned by dry etching.
After removing the photoresist 57, the platinum film 5 is formed by sputter etching using tungsten 56 as a mask.
5. Pattern the lead titanate zirconate thin film 54 and the underlying platinum film 53. Next, the lowermost titanium nitride film 52 and the tungsten film 56 used as the mask are simultaneously removed by dry etching to complete the capacitor. In this embodiment, tungsten is used as a mask for dry etching, but a titanium nitride film may be used. Further, depending on the intended use, part of the lead in the lead zirconate titanate thin film may be replaced with an element such as La or Ba.
【００２５】また、本実施例では非晶質膜の形成に反応
性蒸着法を用いたが、スパッタリング法やゾルゲル法に
よっても同様の効果が得られることは言うまでもない。In this embodiment, the reactive evaporation method is used for forming the amorphous film. However, it goes without saying that the same effect can be obtained by the sputtering method or the sol-gel method.
【００２６】図６には分極反転電荷の面内分布を示し
た。他のプロセスは同じで、結晶化熱処理のみ従来のプ
ロセスを用いたキャパシタの面内分布を比較して示す。
従来、±１０％以上あった面内分布が±１％程度に改善
された。FIG. 6 shows the in-plane distribution of the domain-inverted charges. The other processes are the same, and the in-plane distribution of the capacitor using the conventional process only for the crystallization heat treatment is shown for comparison.
The in-plane distribution, which was conventionally ± 10% or more, has been improved to about ± 1%.
【００２７】[0027]
【発明の効果】本発明によれば、大面積で均一な電気特
性をもち、かつ酸素欠陥の少ないペロブスカイト構造の
鉛系強誘電体薄膜が得られる。この強誘電体薄膜を用い
れば、たとえば、２５６メガビットレベル以上の高集積
ダイナミックランダムアクセスメモリに必要とされる、
構造が簡単で大きな蓄積電荷量をもった微細なキャパシ
タを高均質な特性で形成できる。また、分極反転型不揮
発性メモリに必要とされる、強誘電体キャパシタの電気
特性の面内分布を、６インチ以上の大面積基板を用いた
場合でも±２％以下とすることができる。According to the present invention, it is possible to obtain a lead-based ferroelectric thin film having a perovskite structure having a large area and uniform electric characteristics and having few oxygen defects. Using this ferroelectric thin film, for example, is required for a highly integrated dynamic random access memory of 256 megabit level or more.
A fine capacitor having a simple structure and a large amount of accumulated charge can be formed with high uniform characteristics. Further, the in-plane distribution of the electric characteristics of the ferroelectric capacitor required for the domain-inverted nonvolatile memory can be set to ± 2% or less even when a large area substrate of 6 inches or more is used.
【図１】本発明の一実施例における熱処理方法のシーケ
ンス図。FIG. 1 is a sequence diagram of a heat treatment method according to an embodiment of the present invention.
【図２】本発明と従来の方法によるチタン酸ジルコン酸
鉛膜のＸ線回折スペクトル図。FIG. 2 is an X-ray diffraction spectrum of a lead zirconate titanate film according to the present invention and a conventional method.
【図３】本発明の一実施例の強誘電体を用いたキャパシ
タのヒステリシス特性図。FIG. 3 is a diagram showing a hysteresis characteristic of a capacitor using a ferroelectric according to one embodiment of the present invention.
【図４】本発明の一実施例の強誘電体を用いたキャパシ
タの分極反転電荷の電圧依存特性図。FIG. 4 is a diagram showing a voltage-dependent characteristic of domain-inverted charges of a capacitor using a ferroelectric substance according to one embodiment of the present invention.
【図５】本発明の一実施例の強誘電体を用いたキャパシ
タの断面図。FIG. 5 is a sectional view of a capacitor using a ferroelectric substance according to one embodiment of the present invention.
【図６】本発明と従来法による強誘電体を用いたキャパ
シタの分極反転電荷の面内分布図。FIG. 6 is an in-plane distribution diagram of domain-inverted charges of a capacitor using a ferroelectric according to the present invention and a conventional method.
【図７】チタン酸ジルコン酸鉛薄膜のヒステリシス特性
の配向性による差を示す図面。FIG. 7 is a view showing a difference in hysteresis characteristic of a lead zirconate titanate thin film due to orientation.
【図８】チタン酸ジルコン酸鉛薄膜の分極反転電荷の電
圧依存性の特性図。FIG. 8 is a characteristic diagram of the voltage dependence of the domain-inverted charge of a lead zirconate titanate thin film.
【図９】ＰｂＯの（１００）面とＰＺＴの（１００）面
との格子整合の説明図。FIG. 9 is an explanatory diagram of lattice matching between the (100) plane of PbO and the (100) plane of PZT.
【図１０】結晶化熱処理後のチタン酸ジルコン酸鉛薄膜
の配向性のオゾン供給量依存性の測定図。FIG. 10 is a view showing a measurement of the dependence of the orientation of the lead zirconate titanate thin film on the amount of supplied ozone after the crystallization heat treatment.
【図１１】結晶化熱処理後のチタン酸ジルコン酸鉛薄膜
の配向性の鉛組成依存性の測定図。FIG. 11 is a measurement diagram of the lead composition dependence of the orientation of a lead zirconate titanate thin film after crystallization heat treatment.
【図１２】チタン酸ジルコン酸鉛結晶薄膜の熱処理雰囲
気依存性を示すＸ線回折スペクトル図。FIG. 12 is an X-ray diffraction spectrum showing the heat treatment atmosphere dependence of a lead zirconate titanate crystal thin film.
５１…半導体基板、５２…窒化チタン膜、５３…白金膜
（下部電極）、５４…チタン酸ジルコン酸鉛薄膜、５５
…白金膜（上部電極）、５６…タングステン膜、５７…
フォトレジスト。51: semiconductor substrate, 52: titanium nitride film, 53: platinum film (lower electrode), 54: lead zirconate titanate thin film, 55
... Platinum film (upper electrode), 56 ... Tungsten film, 57 ...
Photoresist.
Claims (8)
含む非晶質膜を、４００℃以下の低温領域では酸素濃度
が酸化鉛が結晶化を開始するよりも低く、ペロブスカイ
ト構造の結晶化が開始する温度よりも高温では酸素濃度
を低温領域よりも高い雰囲気中で熱処理をして得られた
〔１１１〕配向度８０％以上であることを特徴とする強
誘電体薄膜。An amorphous film containing a metal element and oxygen constituting a lead-based ferroelectric material has an oxygen concentration in a low temperature region of 400 ° C. or lower which is lower than that at which lead oxide starts crystallization, and has a perovskite structure. A ferroelectric thin film having a degree of [111] orientation of 80% or more obtained by performing a heat treatment in an atmosphere in which the oxygen concentration is higher than the temperature at which crystallization starts and the oxygen concentration is higher than in the low temperature region.
含む非晶質膜を熱処理してペロブスカイト構造に結晶化
した薄膜を得る鉛系強誘電体薄膜の製造方法において、
400℃以下の低温領域では酸素濃度を酸化鉛が結晶化を
開始するよりも低くし、ペロブスカイト構造の結晶化が
開始する温度よりも高温では酸素濃度を低温領域よりも
高くすることを特徴とする強誘電体薄膜の製造方法。2. A method for producing a lead-based ferroelectric thin film, wherein an amorphous film containing a metal element and oxygen constituting a lead-based ferroelectric is heat-treated to obtain a thin film crystallized into a perovskite structure.
It is characterized in that the oxygen concentration is lower than the temperature at which lead oxide starts to crystallize in the low temperature region of 400 ° C or lower, and the oxygen concentration is higher than the low temperature region at a temperature higher than the temperature at which the perovskite structure starts to crystallize. A method for manufacturing a ferroelectric thin film.
おいて、低温領域での酸素濃度を５％以下とすることを
特徴とする強誘電体薄膜の製造方法。3. The method for producing a ferroelectric thin film according to claim 2, wherein the oxygen concentration in the low temperature region is 5% or less.
おいて、高温領域での酸素濃度を１０％以上とすること
を特徴とする強誘電体薄膜の製造方法。4. The method for producing a ferroelectric thin film according to claim 2, wherein the oxygen concentration in a high temperature region is 10% or more.
おいて、非晶質膜を反応性蒸着法により作製することを
特徴とする強誘電体薄膜の製造方法。5. The method for producing a ferroelectric thin film according to claim 2, wherein the amorphous film is produced by a reactive vapor deposition method.
おいて、非晶質膜をゾルゲル法により作製することを特
徴とする強誘電体薄膜の製造方法。6. The method for producing a ferroelectric thin film according to claim 2, wherein the amorphous film is produced by a sol-gel method.
おいて、非晶質膜をスパッタリング法により作製するこ
とを特徴とする強誘電体薄膜の製造方法。7. The method for producing a ferroelectric thin film according to claim 2, wherein the amorphous film is produced by a sputtering method.
からなることを特徴とする請求項２ないし請求項７の何
れかに記載の強誘電体薄膜の製造方法。8. The method according to claim 2, wherein said ferroelectric thin film is made of lead zirconate titanate.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10083232A JPH11284136A (en) | 1998-03-30 | 1998-03-30 | Ferroelectric thin film and its manufacture |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10083232A JPH11284136A (en) | 1998-03-30 | 1998-03-30 | Ferroelectric thin film and its manufacture |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH11284136A true JPH11284136A (en) | 1999-10-15 |
Family
ID=13796589
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10083232A Pending JPH11284136A (en) | 1998-03-30 | 1998-03-30 | Ferroelectric thin film and its manufacture |
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| Country | Link |
|---|---|
| JP (1) | JPH11284136A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012046706A1 (en) * | 2010-10-06 | 2012-04-12 | 株式会社アルバック | Method for producing dielectric thin film |
| CN103189968B (en) * | 2010-10-06 | 2016-11-30 | 株式会社爱发科 | The film build method of thin dielectric film |
-
1998
- 1998-03-30 JP JP10083232A patent/JPH11284136A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012046706A1 (en) * | 2010-10-06 | 2012-04-12 | 株式会社アルバック | Method for producing dielectric thin film |
| CN103189968A (en) * | 2010-10-06 | 2013-07-03 | 株式会社爱发科 | Method for producing dielectric thin film |
| US9347128B2 (en) | 2010-10-06 | 2016-05-24 | Ulvac, Inc. | Method for forming dielectric thin film |
| CN103189968B (en) * | 2010-10-06 | 2016-11-30 | 株式会社爱发科 | The film build method of thin dielectric film |
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