JP2011014649A - Method of manufacturing ferroelectric thin film - Google Patents
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- JP2011014649A JP2011014649A JP2009156064A JP2009156064A JP2011014649A JP 2011014649 A JP2011014649 A JP 2011014649A JP 2009156064 A JP2009156064 A JP 2009156064A JP 2009156064 A JP2009156064 A JP 2009156064A JP 2011014649 A JP2011014649 A JP 2011014649A
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- 239000010409 thin film Substances 0.000 title claims abstract description 57
- 238000004519 manufacturing process Methods 0.000 title claims description 12
- 239000010408 film Substances 0.000 claims abstract description 76
- 239000000758 substrate Substances 0.000 claims abstract description 57
- 238000000576 coating method Methods 0.000 claims abstract description 38
- 238000000034 method Methods 0.000 claims abstract description 38
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- 238000010304 firing Methods 0.000 description 9
- HFGPZNIAWCZYJU-UHFFFAOYSA-N lead zirconate titanate Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ti+4].[Zr+4].[Pb+2] HFGPZNIAWCZYJU-UHFFFAOYSA-N 0.000 description 9
- 229910052451 lead zirconate titanate Inorganic materials 0.000 description 9
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- TVMXDCGIABBOFY-UHFFFAOYSA-N octane Chemical compound CCCCCCCC TVMXDCGIABBOFY-UHFFFAOYSA-N 0.000 description 2
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- 229910052710 silicon Inorganic materials 0.000 description 2
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- 239000000126 substance Substances 0.000 description 2
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- 235000012431 wafers Nutrition 0.000 description 2
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- SHXHPUAKLCCLDV-UHFFFAOYSA-N 1,1,1-trifluoropentane-2,4-dione Chemical compound CC(=O)CC(=O)C(F)(F)F SHXHPUAKLCCLDV-UHFFFAOYSA-N 0.000 description 1
- CVBUKMMMRLOKQR-UHFFFAOYSA-N 1-phenylbutane-1,3-dione Chemical compound CC(=O)CC(=O)C1=CC=CC=C1 CVBUKMMMRLOKQR-UHFFFAOYSA-N 0.000 description 1
- YRAJNWYBUCUFBD-UHFFFAOYSA-N 2,2,6,6-tetramethylheptane-3,5-dione Chemical compound CC(C)(C)C(=O)CC(=O)C(C)(C)C YRAJNWYBUCUFBD-UHFFFAOYSA-N 0.000 description 1
- HXUIDZOMTRMIOE-UHFFFAOYSA-N 3-oxo-3-phenylpropionic acid Chemical compound OC(=O)CC(=O)C1=CC=CC=C1 HXUIDZOMTRMIOE-UHFFFAOYSA-N 0.000 description 1
- FHSUFDYFOHSYHI-UHFFFAOYSA-N 3-oxopentanoic acid Chemical compound CCC(=O)CC(O)=O FHSUFDYFOHSYHI-UHFFFAOYSA-N 0.000 description 1
- SQNZLBOJCWQLGQ-UHFFFAOYSA-N 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyloctane-3,5-dione Chemical compound CC(C)(C)C(=O)CC(=O)C(F)(F)C(F)(F)C(F)(F)F SQNZLBOJCWQLGQ-UHFFFAOYSA-N 0.000 description 1
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- WDJHALXBUFZDSR-UHFFFAOYSA-N Acetoacetic acid Natural products CC(=O)CC(O)=O WDJHALXBUFZDSR-UHFFFAOYSA-N 0.000 description 1
- FIPWRIJSWJWJAI-UHFFFAOYSA-N Butyl carbitol 6-propylpiperonyl ether Chemical compound C1=C(CCC)C(COCCOCCOCCCC)=CC2=C1OCO2 FIPWRIJSWJWJAI-UHFFFAOYSA-N 0.000 description 1
- ZBZXIGONWYKEMZ-UHFFFAOYSA-N CCO[Ti] Chemical compound CCO[Ti] ZBZXIGONWYKEMZ-UHFFFAOYSA-N 0.000 description 1
- ZCTPOERCNOQBED-UHFFFAOYSA-N CO[Ti](OC)(OC(C)C)OC(C)C Chemical compound CO[Ti](OC)(OC(C)C)OC(C)C ZCTPOERCNOQBED-UHFFFAOYSA-N 0.000 description 1
- WWZKQHOCKIZLMA-UHFFFAOYSA-N Caprylic acid Natural products CCCCCCCC(O)=O WWZKQHOCKIZLMA-UHFFFAOYSA-N 0.000 description 1
- 229910018921 CoO 3 Inorganic materials 0.000 description 1
- 229910004121 SrRuO Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
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- KQNKJJBFUFKYFX-UHFFFAOYSA-N acetic acid;trihydrate Chemical compound O.O.O.CC(O)=O KQNKJJBFUFKYFX-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- GONOPSZTUGRENK-UHFFFAOYSA-N benzyl(trichloro)silane Chemical compound Cl[Si](Cl)(Cl)CC1=CC=CC=C1 GONOPSZTUGRENK-UHFFFAOYSA-N 0.000 description 1
- NUMHJBONQMZPBW-UHFFFAOYSA-K bis(2-ethylhexanoyloxy)bismuthanyl 2-ethylhexanoate Chemical compound [Bi+3].CCCCC(CC)C([O-])=O.CCCCC(CC)C([O-])=O.CCCCC(CC)C([O-])=O NUMHJBONQMZPBW-UHFFFAOYSA-K 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 1
- BSDOQSMQCZQLDV-UHFFFAOYSA-N butan-1-olate;zirconium(4+) Chemical compound [Zr+4].CCCC[O-].CCCC[O-].CCCC[O-].CCCC[O-] BSDOQSMQCZQLDV-UHFFFAOYSA-N 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 150000007942 carboxylates Chemical class 0.000 description 1
- 150000001735 carboxylic acids Chemical class 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
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- VSFQMZYFJAOOOG-UHFFFAOYSA-N di(propan-2-yloxy)lead Chemical compound CC(C)O[Pb]OC(C)C VSFQMZYFJAOOOG-UHFFFAOYSA-N 0.000 description 1
- WOWBFOBYOAGEEA-UHFFFAOYSA-N diafenthiuron Chemical compound CC(C)C1=C(NC(=S)NC(C)(C)C)C(C(C)C)=CC(OC=2C=CC=CC=2)=C1 WOWBFOBYOAGEEA-UHFFFAOYSA-N 0.000 description 1
- HTXDPTMKBJXEOW-UHFFFAOYSA-N dioxoiridium Chemical compound O=[Ir]=O HTXDPTMKBJXEOW-UHFFFAOYSA-N 0.000 description 1
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- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 229910000457 iridium oxide Inorganic materials 0.000 description 1
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- 229910052746 lanthanum Inorganic materials 0.000 description 1
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 1
- 150000002604 lanthanum compounds Chemical class 0.000 description 1
- 150000002611 lead compounds Chemical class 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 231100000053 low toxicity Toxicity 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000015654 memory Effects 0.000 description 1
- FUZZWVXGSFPDMH-UHFFFAOYSA-N n-hexanoic acid Natural products CCCCCC(O)=O FUZZWVXGSFPDMH-UHFFFAOYSA-N 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- ZTILUDNICMILKJ-UHFFFAOYSA-N niobium(v) ethoxide Chemical compound CCO[Nb](OCC)(OCC)(OCC)OCC ZTILUDNICMILKJ-UHFFFAOYSA-N 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 125000002524 organometallic group Chemical group 0.000 description 1
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- 229920002120 photoresistant polymer Polymers 0.000 description 1
- 229960005235 piperonyl butoxide Drugs 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 238000006068 polycondensation reaction Methods 0.000 description 1
- OGHBATFHNDZKSO-UHFFFAOYSA-N propan-2-olate Chemical compound CC(C)[O-] OGHBATFHNDZKSO-UHFFFAOYSA-N 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 229910001925 ruthenium oxide Inorganic materials 0.000 description 1
- WOCIAKWEIIZHES-UHFFFAOYSA-N ruthenium(iv) oxide Chemical compound O=[Ru]=O WOCIAKWEIIZHES-UHFFFAOYSA-N 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- DLWBHRIWCMOQKI-UHFFFAOYSA-L strontium;2-ethylhexanoate Chemical compound [Sr+2].CCCCC(CC)C([O-])=O.CCCCC(CC)C([O-])=O DLWBHRIWCMOQKI-UHFFFAOYSA-L 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- HSXKFDGTKKAEHL-UHFFFAOYSA-N tantalum(v) ethoxide Chemical compound [Ta+5].CC[O-].CC[O-].CC[O-].CC[O-].CC[O-] HSXKFDGTKKAEHL-UHFFFAOYSA-N 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 150000003755 zirconium compounds Chemical class 0.000 description 1
Landscapes
- Weting (AREA)
- Formation Of Insulating Films (AREA)
- Semiconductor Memories (AREA)
Abstract
Description
本発明は、ゾルゲル法等により製作した原料溶液を塗布焼成して、PZT膜、SBT膜等の強誘電体薄膜を形成する方法に関する。 The present invention relates to a method for forming a ferroelectric thin film such as a PZT film or an SBT film by applying and firing a raw material solution manufactured by a sol-gel method or the like.
PZT(チタン酸ジルコン酸鉛)やSBT(タンタル酸ビスマスストロンチウム)等の強誘電体は、ペロブスカイト型結晶構造を有し、キャパシタや強誘電体メモリ(FeRAM)等のデバイスへの応用が期待されている。これら強誘電体からなる薄膜の成膜法としてゾルゲル法、MOD(Metal Organic Decomposition)法、あるいはこれらを併用した方法など、CSD(Chemical Solution Deposition)法と呼ばれる化学溶液堆積法がある(特許文献1,2参照)。
ゾルゲル法は、金属アルコキシドからなるゾルを加水分解・重縮合反応により、流動性を失ったゲルとし、このゲルを加熱焼成して酸化物とする方法であり、基板(ウエハー)上に膜を形成する技術としては、基板を原料溶液に浸漬するディップコート法、ロールコート法、基板を回転させながら原料溶液を供給して成膜するスピンコート法等がある。このうち、特にスピンコート法の場合、基板の外周端部で膜が厚くなり易く、基板の裏面にも回り込む現象が生じ易い。
Ferroelectric materials such as PZT (lead zirconate titanate) and SBT (bismuth strontium tantalate) have a perovskite crystal structure and are expected to be applied to devices such as capacitors and ferroelectric memories (FeRAM). Yes. There is a chemical solution deposition method called a CSD (Chemical Solution Deposition) method such as a sol-gel method, a MOD (Metal Organic Decomposition) method, or a method using a combination of these as a method for forming a thin film made of such a ferroelectric (Patent Document 1). , 2).
The sol-gel method is a method in which a sol made of metal alkoxide is converted into a gel that loses fluidity by hydrolysis and polycondensation reaction, and this gel is heated and fired to form an oxide. A film is formed on a substrate (wafer). Examples of the technique include a dip coating method in which the substrate is immersed in the raw material solution, a roll coating method, and a spin coating method in which the raw material solution is supplied while the substrate is rotated to form a film. Among these, particularly in the case of the spin coating method, the film tends to be thick at the outer peripheral end portion of the substrate, and the phenomenon of wrapping around the back surface of the substrate easily occurs.
このようなゾルゲル法等(以下ではCSD法と総称し、その溶液をCSD溶液と称す)による塗布方法の場合、一回で塗布する膜厚が厚すぎると、熱処理後の膜にクラックが入りやすいという問題がある。このクラックで剥がれた膜がパーティクルとなり、デバイスの歩留まりが低下する原因となり得るため、基板の外周端部の膜は熱処理する前に除去するという方法が取られる。また、PZT等の鉛系ペロブスカイト型酸化物を形成する場合には、PZTの下部層としてPt等が使われるが、基板端部ではSiO2が剥き出しの構造のものもよく使われており、PZTとSiO2とが接触する場合には、PZTは薄くてもクラックが発生し易く、この場合も基板の外周端部は熱処理する前に膜を除去するという方法が取られる。 In the case of a coating method by such a sol-gel method or the like (hereinafter collectively referred to as a CSD method, and the solution is referred to as a CSD solution), if the film thickness applied at one time is too thick, the film after heat treatment is likely to crack. There is a problem. Since the film peeled off by the cracks becomes particles, which may cause a decrease in device yield, a method of removing the film at the outer peripheral edge of the substrate before heat treatment is taken. In the case of forming a lead-based perovskite oxide such as PZT, Pt or the like is used as the lower layer of PZT. However, a structure having a bare SiO 2 structure at the end of the substrate is often used. When SiO 2 contacts SiO 2 , cracks are likely to occur even if PZT is thin, and in this case as well, a method is used in which the outer peripheral edge of the substrate is removed before heat treatment.
基板の外周端部の膜を除去する方法として、原料溶液を塗布した後に、基板を回転させながら基板の外周端部に有機溶剤を接触させて膜を取り除くエッジビードリンス(EBR)と称する方法がある。
特許文献3及び特許文献4は、基板表面に形成したフォトレジスト層をEBRで除去する方法について示されており、その除去のためのリンス液としてシンナー組成物が用いられている。
As a method for removing the film at the outer peripheral edge of the substrate, there is a method called edge beadiness (EBR) in which the organic solvent is brought into contact with the outer peripheral edge of the substrate while rotating the substrate and then the film is removed after applying the raw material solution. is there.
Patent Document 3 and Patent Document 4 show a method of removing a photoresist layer formed on a substrate surface by EBR, and a thinner composition is used as a rinsing liquid for the removal.
ところで、CSD法で形成した膜に有機溶剤を噴射してEBRを施す場合、噴射領域近傍の膜断面形状の制御が非常に難しく、部分的に膜が厚くなった箇所では加熱処理後においてクラックが発生し、また前記クラックの発生に伴って局部的に膜剥がれが生じることがあり、パーティクルの原因となっていた。 By the way, when an EBR is performed by injecting an organic solvent onto a film formed by the CSD method, it is very difficult to control the cross-sectional shape of the film in the vicinity of the injection region, and cracks occur after the heat treatment in the part where the film is partially thickened. In some cases, the film is peeled off locally with the occurrence of the cracks, which causes particles.
本発明は、このような事情に鑑みてなされたもので、基板の外周端部の膜をクラックや局部剥がれを生じることなく除去して、パーティクルの発生を防止することを目的とする。 The present invention has been made in view of such circumstances, and an object of the present invention is to prevent the generation of particles by removing the film at the outer peripheral end of the substrate without causing cracks or local peeling.
本発明の強誘電体薄膜の製造方法は、強誘電体薄膜形成用の有機金属化合物を含有するCSD溶液を基板に塗布してゲル状塗膜を形成する工程と、基板を回転させながら外周端部に水を噴射又は滴下して、前記ゲル状塗膜の外周端部を除去する工程と、前記外周端部について除去された後の前記ゲル状塗膜を加熱処理して強誘電体薄膜を形成する工程とを有することを特徴とする。 The method for producing a ferroelectric thin film according to the present invention includes a step of applying a CSD solution containing an organometallic compound for forming a ferroelectric thin film to a substrate to form a gel-like coating film, and a peripheral edge while rotating the substrate. A process of removing the outer peripheral edge of the gel-like coating film by spraying or dropping water on the part, and heat-treating the gel-like coating film after being removed from the outer peripheral edge portion to form a ferroelectric thin film And a step of forming.
CSD溶液による塗布膜の一部を除去する場合、一般的には、そのCSD溶液に使用されている溶媒を用いるものと考えられる。このCSD溶液の溶媒としては、メタノール、エタノール、ブタノール等が使用されているが、CSD溶液を塗布した後に、基板の外周端部の塗布膜の除去のために、外周端部にメタノール、エタノール、ブタノール等の溶媒を噴射又は滴下すると、噴射又は滴下領域近傍において加熱処理後にクラックや局部剥がれが生じ易い。
その原因としては次のように考えられる。すなわち、これらメタノール、エタノール、ブタノール等の溶媒はCSD溶液によるゲル状塗膜に噴射又は滴下されると、ゲル状塗膜に浸透し、その浸透により溶けた膜の一部が遠心力で半径方向外方に向けて引き剥がされる。このとき、溶媒の半径方向内方への浸透と、溶けた膜の半径方向外方への伸びとが相互に影響し合い、両者の作用力のばらつき等により、噴射又は滴下領域近傍の膜厚が不均一になり、そのため加熱処理後に噴射又は滴下領域近傍にクラックや局部剥がれが生じるものと想定される。
これに対して、このゲル状塗膜を水によって除去すると、水は膜への浸透力が小さいため、噴射又は滴下した箇所から半径方向外方位置の膜が部分的に厚くなることがなく、クラックや局部剥がれを防止することができる。
When removing a part of the coating film by the CSD solution, it is generally considered that the solvent used in the CSD solution is used. As the solvent of this CSD solution, methanol, ethanol, butanol, etc. are used. After coating the CSD solution, methanol, ethanol, When a solvent such as butanol is jetted or dripped, cracks and local peeling are likely to occur after heat treatment in the vicinity of the jetted or dripped region.
The cause is considered as follows. That is, when these solvents such as methanol, ethanol, butanol and the like are sprayed or dripped onto the gel-like coating film by the CSD solution, they penetrate into the gel-like coating film, and a part of the film dissolved by the permeation is radial direction by centrifugal force. It is peeled away. At this time, the penetration of the solvent inward in the radial direction and the outward extension of the melted film in the radial direction interact with each other. Therefore, it is assumed that cracks and local peeling occur in the vicinity of the spraying or dropping region after the heat treatment.
On the other hand, when this gel-like coating film is removed with water, since water has a small permeability to the film, the film at the radially outward position from the sprayed or dripped part does not partially thicken, Cracks and local peeling can be prevented.
本発明の強誘電体薄膜の製造方法において、前記CSD溶液がPbを含有するペロブスカイト型酸化物薄膜を形成するためのものであるとすることができる。
本発明の強誘電体薄膜の製造方法において、前記CSD溶液がBiを含有する層状ペロブスカイト型酸化物薄膜を形成するためのものであるとすることができる。
本発明の強誘電体薄膜の製造方法において、前記CSD溶液が、プロピレングリコール、ジエチレングリコール、トリエチレングリコールから選ばれる1種または2種以上の溶媒Aと、メタノール、エタノール、1−プロパノール、2−プロパノール、1−ブタノールから選ばれる1種または2種以上の溶媒Bとを含有するものとすることができる。
In the method for producing a ferroelectric thin film of the present invention, the CSD solution can be used for forming a perovskite oxide thin film containing Pb.
In the method for producing a ferroelectric thin film of the present invention, the CSD solution may be for forming a layered perovskite oxide thin film containing Bi.
In the method for producing a ferroelectric thin film of the present invention, the CSD solution is one or more solvents A selected from propylene glycol, diethylene glycol, and triethylene glycol, methanol, ethanol, 1-propanol, and 2-propanol. 1 type or 2 types or more of solvent B chosen from 1-butanol can be contained.
本発明の強誘電体薄膜の製造方法によれば、基板にCSD溶液を塗布した後、回転する基板に水を噴射又は滴下して外周端部のゲル状塗膜を除去することにより、噴射又は滴下した箇所から半径方向外方位置の膜が部分的に厚くなることがなく、クラックや局部剥がれを防止することができる。 According to the method for producing a ferroelectric thin film of the present invention, after applying the CSD solution to the substrate, water is sprayed or dropped on the rotating substrate to remove the gel-like coating film on the outer peripheral edge, thereby spraying or The film at the radially outward position from the dropped portion is not partially thickened, and cracks and local peeling can be prevented.
以下、本発明の実施形態を図面を参照しながら説明する。
この強誘電体薄膜の製造方法は、PZT、PLZTなどのPbを含有するペロブスカイト型酸化物薄膜、SBT、SBTNなどのBiを含有する層状ペロブスカイト形酸化物薄膜を製造する場合に好適であり、有機金属化合物を含有するCSD溶液を基板に塗布してゲル状塗膜を形成する工程(CSD溶液塗布工程)と、この基板を回転させながら外周端部に水を噴射又は滴下して、この外周端部のゲル状塗膜を除去する工程(EBR工程)と、この外周端部について除去された後のゲル状塗膜を加熱処理して強誘電体薄膜を形成する工程(加熱処理工程)とを有する。
Embodiments of the present invention will be described below with reference to the drawings.
This method of manufacturing a ferroelectric thin film is suitable for manufacturing a perovskite oxide thin film containing Pb such as PZT and PLZT, and a layered perovskite oxide thin film containing Bi such as SBT and SBTN. A step of applying a CSD solution containing a metal compound to a substrate to form a gel-like coating film (CSD solution application step), and spraying or dropping water on the outer peripheral edge while rotating the substrate, The step of removing the gel-like coating film (EBR step) and the step of heat-treating the gel-like coating film after the outer peripheral edge portion is removed to form a ferroelectric thin film (heating treatment step) Have.
<CSD溶液>
使用されるCSD溶液について説明しておくと、このCSD溶液は、金属化合物を溶媒により溶解し、安定化剤等を添加したものであり、例えば、PLZT用、SBTN用として以下のものがある。
PLZT用CSD溶液としては、その原料金属化合物には、鉛化合物及びランタン化合物としては酢酸塩(酢酸鉛、酢酸ランタン)などの有機酸塩並びにジイソプロポキシ鉛などのアルコキシド、チタン化合物としては、テトラエトキシチタン、テトライソプロポキシチタン、テトラn−ブトキシチタン、テトラi−ブトキシチタン、テトラt−ブトキシチタン、ジメトキシジイソプロポキシチタンなどのアルコキシドが好ましいが、有機酸塩又は有機金属錯体も使用できる。ジルコニウム化合物はチタン化合物と同様である。2種類以上の成分金属を含有する複合化した金属化合物であってもよい。微量のドープ元素を含有させてもよい。
<CSD solution>
The CSD solution to be used will be described. This CSD solution is obtained by dissolving a metal compound with a solvent and adding a stabilizer or the like. Examples thereof include the following for PLZT and SBTN.
As a CSD solution for PLZT, the starting metal compound includes an organic acid salt such as acetate (lead acetate, lanthanum acetate), an alkoxide such as diisopropoxylead as a lead compound and a lanthanum compound, and a tetra compound as a titanium compound. Alkoxides such as ethoxytitanium, tetraisopropoxytitanium, tetran-butoxytitanium, tetrai-butoxytitanium, tetrat-butoxytitanium and dimethoxydiisopropoxytitanium are preferred, but organic acid salts or organometallic complexes can also be used. The zirconium compound is the same as the titanium compound. It may be a compounded metal compound containing two or more kinds of component metals. A small amount of a doping element may be contained.
一方、SBTN用のCSD溶液の原料金属化合物には、Sr有機金属化合物としてSrイソプロポキシド、Srブトキシド等のアルコキシド、2−エチルヘキサン酸Sr等のカルボン酸塩等が挙げられる。Sr有機金属化合物はSrジエチレングリコラート又はSrトリエチレングリコラートであっても良く、従ってこの場合には、溶媒としてのジエチレングリコール又はトリエチレングリコールに金属Srを添加して加熱下反応させることにより、Srジエチレングリコラート又はSrトリエチレングリコラートを生成させても良い。Bi有機金属化合物としては2−エチルヘキサン酸Bi、Ta有機金属化合物としてはTaジエチレングリコラート又はTaトリエチレングリコラート、Nb有機金属化合物としてはNbジエチレングリコラート又はNbトリエチレングリコラートが用いられる。 On the other hand, the raw material metal compound of the CSD solution for SBTN includes Sr organometallic compounds such as Sr isopropoxide and alkoxides such as Sr butoxide, and carboxylates such as 2-ethylhexanoic acid Sr. The Sr organometallic compound may be Sr diethylene glycolate or Sr triethylene glycolate. Therefore, in this case, by adding metal Sr to diethylene glycol or triethylene glycol as a solvent and reacting with heating, Sr diethylene glycol is used. Lat or Sr triethylene glycolate may be produced. As the Bi organometallic compound, 2-ethylhexanoic acid Bi is used. As the Ta organometallic compound, Ta diethylene glycolate or Ta triethylene glycolate is used. As the Nb organometallic compound, Nb diethylene glycolate or Nb triethylene glycolate is used.
有機溶媒(溶媒A)としては、プロピレングリコール及び/又はトリエチレングリコールを用いるが、プロピレングリコールの単独溶媒、トリエチレングリコールの単独溶媒、プロピレングリコールとトリエチレングリコールとの混合溶媒、プロピレングリコールと他の有機溶媒との混合溶媒、トリエチレングリコールと他の有機溶媒との混合溶媒、プロピレングリコールとトリエチレングリコールと他の有機溶媒との混合溶媒等のいずれでも良い。
この有機溶媒と各有機金属化合物を、所望の金属成分濃度となるように、適当な比率で混合する。また、溶液の均質化のために加熱還流することが行われる。
As the organic solvent (solvent A), propylene glycol and / or triethylene glycol is used, but propylene glycol single solvent, triethylene glycol single solvent, mixed solvent of propylene glycol and triethylene glycol, propylene glycol and other solvents Any of a mixed solvent with an organic solvent, a mixed solvent of triethylene glycol and another organic solvent, a mixed solvent of propylene glycol, triethylene glycol and another organic solvent, or the like may be used.
The organic solvent and each organometallic compound are mixed at an appropriate ratio so as to obtain a desired metal component concentration. Moreover, heating and refluxing are performed for homogenization of the solution.
このようにして得られた溶液を塗布に適した濃度及び濡れ性とするために、適当な溶媒(溶媒B)を使用して濃度調整する。その有機溶媒としては、一般的には、アルコール類(例えばエタノール、イソプロピルアルコール、ブタノール)、ケトン類(例えばアセトン、メチルエチルケトン)、エーテル類(ジエチルエーテル、テトラヒドロフラン)、カルボン酸(例えば酢酸、2−エチルヘキサン酸)、炭化水素(n−ヘキサン、n−オクタン)等が挙げられるが、好ましくは毒性が低いエタノール、イソプロピルアルコール、ブタノールが望ましい。
なお、溶液中の有機金属化合物の合計濃度は、金属酸化物換算量で0.1〜20重量%程度とするのが好ましい。
In order to make the solution thus obtained have a concentration and wettability suitable for coating, the concentration is adjusted using an appropriate solvent (solvent B). As the organic solvent, alcohols (eg, ethanol, isopropyl alcohol, butanol), ketones (eg, acetone, methyl ethyl ketone), ethers (diethyl ether, tetrahydrofuran), carboxylic acids (eg, acetic acid, 2-ethyl) are generally used. Hexanoic acid) and hydrocarbons (n-hexane, n-octane) and the like, and ethanol, isopropyl alcohol, and butanol having low toxicity are preferable.
The total concentration of organometallic compounds in the solution is preferably about 0.1 to 20% by weight in terms of metal oxide.
また、原料溶液中に必要に応じて安定化剤としてβ−ジケトン類(例えば、アセチルアセトン、ヘプタフルオロブタノイルピバロイルメタン、ジピバロイルメタン、トリフルオロアセチルアセトン、ベンゾイルアセトン等)、ケトン酸類(例えば、アセト酢酸、プロピオニル酢酸、ベンゾイル酢酸等)などを、金属に対するモル比で0.2〜3倍程度配合してもよい。 In addition, β-diketones (for example, acetylacetone, heptafluorobutanoylpivaloylmethane, dipivaloylmethane, trifluoroacetylacetone, benzoylacetone, etc.), ketone acids ( For example, acetoacetic acid, propionylacetic acid, benzoylacetic acid, etc.) may be blended in a molar ratio to the metal of about 0.2 to 3 times.
<CSD溶液塗布工程>
基板にCSD溶液を塗布することにより、基板の全面にゲル状塗膜を形成する。
基板材料としては、シリコンウエハ(単結晶)、および白金、ニッケルなどの金属類、酸化ルテニウム、酸化イリジウム、ルテニウム酸ストロンチウム(SrRuO3)又はコバルト酸ランタンストロンチウム((LaxSr1-x)CoO3)などのぺロブスカイト型導電性酸化物などの被膜を有した、シリコン、ガラス、アルミナ、石英などの基板が挙げられる。
CSD溶液を基板上に塗布する場合、スピンコート法が一般的であるが、噴霧塗布、浸漬塗布など他の塗布法も適用可能である。
<CSD solution application process>
A gel-like coating film is formed on the entire surface of the substrate by applying the CSD solution to the substrate.
Substrate materials include silicon wafers (single crystal), metals such as platinum and nickel, ruthenium oxide, iridium oxide, strontium ruthenate (SrRuO 3 ), or lanthanum strontium cobaltate ((La x Sr 1-x ) CoO 3. And a substrate made of silicon, glass, alumina, quartz or the like having a coating of a perovskite type conductive oxide or the like.
When the CSD solution is applied on the substrate, a spin coating method is generally used, but other application methods such as spray coating and dip coating are also applicable.
<EBR工程>
図1(a)に示すように、CSD溶液を塗布した後のゲル状塗膜1が形成された基板2を回転させながら、その外周端部に上方のノズル3から水Wを噴射又は滴下することにより、図1(b)に示すようにゲル状塗膜1の外周端部を除去する。この場合、基板の回転速度としては、例えば、1000〜3000rpmである。噴射又は滴下の位置は、除去対象の位置に対応して適宜設定すればよい。例えば、基板の外周縁5mmから半径方向外側を除去する場合、その基板の外周縁から半径方向内方に5mmの位置に水を噴射又は滴下し、その噴射又は滴下位置の外側の5mmの範囲の膜を除去する。噴射又は滴下量としては、塗膜の厚さ等から適宜に設定すればよく、除去対象の範囲に存在するゲル状塗膜を洗い流すのに十分な量であればよい。上記の回転速度であれば2〜5秒間水を噴射又は滴下し続ければ十分である。
また、このEBR工程においては、外周端部のゲル状塗膜1が流れ易いように、基板2を回転させながら、必要に応じて、ノズル3を半径方向外方に移動させるようにしてもよい。
<EBR process>
As shown in FIG. 1 (a), water W is sprayed or dropped from an upper nozzle 3 on the outer peripheral edge of the substrate 2 on which the gel-like coating film 1 after the CSD solution is applied is rotated. Thereby, as shown in FIG.1 (b), the outer peripheral edge part of the gel-like coating film 1 is removed. In this case, the rotation speed of the substrate is, for example, 1000 to 3000 rpm. What is necessary is just to set suitably the position of injection or dripping corresponding to the position of removal object. For example, when removing the outer side in the radial direction from the outer peripheral edge 5 mm of the substrate, water is sprayed or dropped at a position 5 mm inward in the radial direction from the outer peripheral edge of the substrate. Remove the membrane. What is necessary is just to set suitably as the amount of spraying or dripping from the thickness of a coating film, etc., and should just be sufficient quantity to wash away the gel-like coating film which exists in the range of removal object. If it is said rotation speed, it will be enough if it continues spraying or dripping water for 2 to 5 seconds.
Further, in this EBR process, the nozzle 3 may be moved outward in the radial direction as necessary while rotating the substrate 2 so that the gel-like coating film 1 at the outer peripheral end portion flows easily. .
<加熱処理工程>
加熱処理工程は、さらに乾燥工程、仮焼工程、結晶化アニール工程から構成される。
(乾燥工程)
外周端部を除去した後のゲル状塗膜を乾燥させ、溶媒を除去する。この乾燥温度は溶媒の種類によっても異なるが、通常は80〜200℃程度であり、好ましくは100〜180℃の範囲でよい。但し、原料溶液中の金属化合物を金属酸化物に転化させるための次工程の加熱の際の昇温中に、溶媒は除去されるので、塗膜の乾燥工程は必ずしも必要とされない。
(仮焼工程)
その後、仮焼工程として、塗布した基板を加熱し、有機金属化合物を完全に加水分解又は熱分解させて金属酸化物に転化させ、金属酸化物からなる膜を形成する。この加熱は、一般に加水分解の必要なゾルゲル法では水蒸気を含んでいる雰囲気、例えば、空気又は含水蒸気雰囲気(例えば、水蒸気を含有する窒素雰囲気)中で行われ、熱分解させるMOD法では含酸素雰囲気中で行われる。加熱温度は、金属酸化物の種類によっても異なるが、通常は150〜550℃の範囲であり、好ましくは、300〜450℃である。加熱時間は、加水分解及び熱分解が完全に進行するように選択するが、通常は1分ないし1時間程度である。
<Heat treatment process>
The heat treatment process further includes a drying process, a calcination process, and a crystallization annealing process.
(Drying process)
The gel-like coating film after removing the outer peripheral edge is dried to remove the solvent. The drying temperature varies depending on the type of solvent, but is usually about 80 to 200 ° C, preferably 100 to 180 ° C. However, since the solvent is removed during the heating in the next step for converting the metal compound in the raw material solution into the metal oxide, the coating film drying step is not necessarily required.
(Calcination process)
Thereafter, as the calcination step, the coated substrate is heated to completely hydrolyze or thermally decompose the organometallic compound to convert it into a metal oxide, thereby forming a film made of the metal oxide. This heating is generally performed in an atmosphere containing water vapor in the sol-gel method that requires hydrolysis, for example, air or a water-containing atmosphere (for example, nitrogen atmosphere containing water vapor), and in the MOD method in which pyrolysis is performed, oxygen-containing. Performed in an atmosphere. Although heating temperature changes also with kinds of metal oxide, it is the range of 150-550 degreeC normally, Preferably, it is 300-450 degreeC. The heating time is selected so that hydrolysis and thermal decomposition proceed completely, but it is usually about 1 minute to 1 hour.
ゾルゲル法等の場合は、1回の塗布で、ペロブスカイト型酸化物薄膜に必要な膜厚とすることは難しい場合が多いので、必要に応じて、上記のCSD溶液塗布から仮焼までの工程を繰返すことによりCSD溶液を重ね塗りし、その塗布の都度、外周端部についてゲル状塗膜を除去しながら、所望の膜厚の金属酸化物の膜を得る。 In the case of the sol-gel method or the like, it is often difficult to obtain a film thickness required for the perovskite oxide thin film by a single application. Therefore, if necessary, the steps from the above CSD solution application to calcination are performed. By repeating the coating, the CSD solution is repeatedly applied, and each time the coating is applied, the gel-like coating film is removed from the outer peripheral edge, and a metal oxide film having a desired film thickness is obtained.
(結晶化アニール工程)
このようして得られた塗布膜は、非晶質であるか、結晶質であっても結晶性が不十分であるので、分極性が低く、強誘電体薄膜として利用できない。そのため、最後に結晶化アニール工程として、その金属酸化物の結晶化温度以上の温度で焼成して、ペロブスカイト型の結晶構造を持つ結晶質の金属酸化物薄膜とする。なお、結晶化のための焼成は、最後に一度で行うのではなく、各塗布した塗膜ごとに、上記の仮焼に続けて行ってもよいが、高温での焼成を何回も繰返す必要があるので、最後にまとめて行う方が経済的には有利である。
この結晶化のための焼成温度は通常は500〜800℃の比較的低い温度で良く、例えば550〜700℃である。従って、基板としては、この焼成温度に耐える程度の耐熱性を有するものを使用する。結晶化のための焼成(アニール)時間は、通常は1分から1時間程度であり、焼成雰囲気は特に制限されないが、通常は空気又は酸素である。
(Crystal annealing process)
Even if the coating film thus obtained is amorphous or crystalline, the crystallinity is insufficient, so the polarizability is low and it cannot be used as a ferroelectric thin film. Therefore, finally, as a crystallization annealing step, baking is performed at a temperature equal to or higher than the crystallization temperature of the metal oxide to form a crystalline metal oxide thin film having a perovskite crystal structure. The firing for crystallization is not performed once at the end, but may be performed after the above calcination for each applied coating film, but it is necessary to repeat the firing at a high temperature many times. Therefore, it is economically advantageous to carry out the process collectively at the end.
The firing temperature for this crystallization is usually a relatively low temperature of 500 to 800 ° C., for example, 550 to 700 ° C. Therefore, a substrate having heat resistance enough to withstand this firing temperature is used as the substrate. The firing (annealing) time for crystallization is usually about 1 minute to 1 hour, and the firing atmosphere is not particularly limited, but is usually air or oxygen.
このようにして形成されたペロブスカイト型酸化物薄膜は、基板の上に均一に形成され、その外周端部においてもクラックや局部剥がれがなく、したがって、パーティクルの付着のない強誘電体薄膜を得ることができる。
前述したようにPZT等の鉛系ペロブスカイト型酸化物のように、基板表面のPt層に対して外周端部にSiO2が剥き出しの構造のものの場合、このSiO2の上に塗布されたPZTにクラックが発生し易いため、このSiO2の範囲の膜を除去する方法として有効である。この場合、SiO2の範囲の内周縁よりわずかに内側に水を噴射又は滴下すればよい。
The perovskite oxide thin film formed in this way is uniformly formed on the substrate, and there is no crack or local peeling at the outer peripheral edge portion. Therefore, a ferroelectric thin film free from particle adhesion can be obtained. Can do.
As described above, in the case of a structure in which SiO 2 is exposed at the outer peripheral edge with respect to the Pt layer on the substrate surface, such as lead-based perovskite oxide such as PZT, the PZT coated on this SiO 2 Since cracks are likely to occur, this method is effective as a method for removing the film in the SiO 2 range. In this case, water may be sprayed or dropped slightly inward from the inner peripheral edge of the SiO 2 range.
次に、Pb含有ペロブスカイト型酸化物としてPLZT、Bi含有層状ペロブスカイト型酸化物としてSBTNの薄膜をそれぞれ形成して、基板の外周端部の膜を除去し、その表面を観察した。
Pb含有ペロブスカイト型酸化物薄膜(PLZT)用のCSD溶液としては以下の組成のものを用いた。
鉛原料として酢酸鉛3水和物、ランタン原料として酢酸ランタン1.5水和物、ジルコニウム原料としてジルコニウムn−ブトキシド、チタン原料としてチタンテトライソプロポキシドを用い、溶媒Aと、ZrとTiの合計モル数の2倍量のアセチルアセトンを安定化剤として混合し、150℃で1時間、窒素雰囲気の中で還流した。その後150℃で減圧蒸留し、副生成物をはじめとした低沸点有機物を除去し、溶媒Bで酸化物換算で10wt%となるように希釈し、各種Pb含有ペロブスカイト型酸化物薄膜用CSD溶液を得た。表1にPLZT組成、溶媒A、溶媒Bを記す。
Next, a thin film of PLZT as a Pb-containing perovskite oxide and a thin film of SBTN as a Bi-containing layered perovskite oxide were formed, the film at the outer peripheral edge of the substrate was removed, and the surface was observed.
As the CSD solution for the Pb-containing perovskite oxide thin film (PLZT), the following composition was used.
Lead acetate trihydrate as lead raw material, lanthanum acetate hemihydrate as lanthanum raw material, zirconium n-butoxide as zirconium raw material, titanium tetraisopropoxide as titanium raw material, and total of solvent A, Zr and Ti Two times the number of moles of acetylacetone was mixed as a stabilizer and refluxed at 150 ° C. for 1 hour in a nitrogen atmosphere. Thereafter, it is distilled under reduced pressure at 150 ° C. to remove low-boiling organic substances such as by-products, diluted with solvent B to 10 wt% in terms of oxides, and various Pb-containing perovskite oxide thin film CSD solutions. Obtained. Table 1 shows the PLZT composition, solvent A, and solvent B.
Bi含有層状ペロブスカイト型酸化物(SBTN)用のCSD溶液としては以下の組成のものを用いた。
ビスマス原料として2−エチルヘキサン酸ビスマス、ストロンチウム原料として2−エチルヘキサン酸ストロンチウム、タンタル原料としてタンタルペンタエトキシド、ニオブ原料としてニオブペンタエトキシドを用い、溶媒Aと、TaとNbの合計モル数の2.5倍量の2―エチルヘキサン酸を安定化剤として混合し、150℃で1時間、窒素雰囲気の中で還流した。その後150℃で減圧蒸留し、副生成物をはじめとした低沸点有機物を除去し、溶媒Bで酸化物換算で10wt%となるように希釈し、各種Bi含有層状ペロブスカイト型酸化物薄膜用CSD溶液を得た。表2にSBTN組成、溶媒A、溶媒Bを記す。
As a CSD solution for Bi-containing layered perovskite oxide (SBTN), the following composition was used.
Bismuth 2-ethylhexanoate as the bismuth raw material, strontium 2-ethylhexanoate as the strontium raw material, tantalum pentaethoxide as the tantalum raw material, niobium pentaethoxide as the niobium raw material, and the total number of moles of solvent A, Ta and Nb 2.5 times the amount of 2-ethylhexanoic acid was mixed as a stabilizer and refluxed at 150 ° C. for 1 hour in a nitrogen atmosphere. Thereafter, it is distilled at 150 ° C. under reduced pressure to remove low-boiling organic substances including by-products, diluted with solvent B to 10 wt% in terms of oxide, and various Bi-containing layered perovskite oxide thin film CSD solutions. Got. Table 2 shows the SBTN composition, solvent A, and solvent B.
これらCSD溶液を用いて、Pb含有ペロブスカイト型酸化物薄膜(PLZT薄膜)、Bi含有層状ペロブスカイト型酸化物(SBTN)薄膜を形成した。基板としては直径が4インチのSi基板の表面にSiO2膜を熱酸化により厚さ500nm形成し、その上に外周端部から半径方向内側3mmまでの領域を除きスパッタ法にてPt膜を形成したPt(200nm)/SiO2(500nm)/Si基板とした。 Using these CSD solutions, Pb-containing perovskite oxide thin films (PLZT thin films) and Bi-containing layered perovskite oxide (SBTN) thin films were formed. As a substrate, a SiO 2 film is formed on the surface of a Si substrate having a diameter of 4 inches by thermal oxidation to a thickness of 500 nm, and a Pt film is formed thereon by a sputtering method except for a region from the outer peripheral edge to 3 mm in the radial direction. A Pt (200 nm) / SiO 2 (500 nm) / Si substrate was used.
(Pb含有ペロブスカイト型酸化物薄膜)
まず、予備実験として、表1の溶液A1〜A6を用い、4インチPt/SiO2/Si基板上に2ml噴射し、スピン条件として500rpm×3sec回転した後、3000rpm×15sec回転して基板の全面にコーティングした。その後350℃に加熱したホットプレート上に基板を載せて5分間加熱し、有機物の熱分解を行い、鉛含有酸化物膜を得た。この操作を繰り返し、計6回塗布を行った後、急速熱処理装置RTA(Rapid Thermal Annealing)により700℃で5分焼成を行いPb含有ペロブスカイト型酸化物薄膜を得た。
この実験に使用した基板の最外周部はPtがコーティングされておらず、いずれもPLZT薄膜がSiO2と直接接触している部分は焼成後にクラックが発生した。
(Pb-containing perovskite oxide thin film)
First, as a preliminary experiment, using the solutions A1 to A6 shown in Table 1, 2 ml is sprayed onto a 4-inch Pt / SiO 2 / Si substrate, and spin conditions are set to 500 rpm × 3 sec. Coated. Thereafter, the substrate was placed on a hot plate heated to 350 ° C. and heated for 5 minutes to thermally decompose the organic matter, thereby obtaining a lead-containing oxide film. This operation was repeated and applied six times in total, and then fired at 700 ° C. for 5 minutes with a rapid thermal annealing apparatus RTA (Rapid Thermal Annealing) to obtain a Pb-containing perovskite oxide thin film.
The outermost peripheral portion of the substrate used in this experiment was not coated with Pt, and any portion where the PLZT thin film was in direct contact with SiO 2 was cracked after firing.
次に、実施例1として、同じPt/SiO2/Si基板上に、上記予備実験の方法と同様にして、溶液A1〜A6をスピンコートした後、Pb含有膜とSiO2の焼成時の反応を避けるため、基板をスピンコーターで2500rpmで回転させながら、基板の外周端部から半径方向内側5mmの位置に水を噴射してゲル状塗膜を溶解するEBR処理を行った。この基板を上記予備実験と同様にホットプレートに載せて加熱し、外周端部がエッチングされて除去された状態の鉛含有酸化物膜を得た。予備実験と同様にこの操作を繰り返し、計6回CSD溶液の塗布を行って、都度EBR処理を行った後、RTAにより700℃で5分焼成を行いPb含有ペロブスカイト型酸化物薄膜を得た。
得られたサンプルは、Pb含有膜端部にはクラックや膜剥がれは全く発生していなかった。
Next, as Example 1, after spin-coating the solutions A1 to A6 on the same Pt / SiO 2 / Si substrate in the same manner as the preliminary experiment, reaction at the time of firing the Pb-containing film and SiO 2 In order to avoid this, EBR treatment was performed in which the gel-like coating film was dissolved by spraying water to a position 5 mm radially inward from the outer peripheral edge of the substrate while rotating the substrate at 2500 rpm with a spin coater. This substrate was placed on a hot plate and heated in the same manner as in the preliminary experiment to obtain a lead-containing oxide film in a state where the outer peripheral edge was removed by etching. This operation was repeated in the same manner as in the preliminary experiment, and the CSD solution was applied a total of 6 times. EBR treatment was performed each time, and then baking was performed at 700 ° C. for 5 minutes by RTA to obtain a Pb-containing perovskite oxide thin film.
In the obtained sample, no cracks or film peeling occurred at the end of the Pb-containing film.
次に、比較例1として、EBR用溶剤として、水の代わりにn−ブタノールを使うこと以外は全て実施例1と同様にして、Pb含有ペロブスカイト型酸化物薄膜を得た。得られたサンプルのPb含有膜端部には、クラックや膜剥がれが発生した。 Next, as Comparative Example 1, a Pb-containing perovskite oxide thin film was obtained in the same manner as in Example 1 except that n-butanol was used in place of water as the EBR solvent. Cracks and film peeling occurred at the end of the Pb-containing film of the obtained sample.
(Bi含有層状ペロブスカイト型酸化物薄膜)
Bi含有層状ペロブスカイト型酸化物薄膜の場合も、実施例2として、Pb含有ペロブスカイト型酸化物薄膜の場合と同様にして、表2の溶液B1〜B6を4インチPt/SiO2/Si基板上にスピンコートした後、基板の外周端部での厚膜化によるクラックを避けるため、基板をスピンコーターで2500rpmで回転させながら、基板の外周端部から半径方向内側5mmの位置に水を噴射してゲル状塗膜を溶解し、EBR処理を行った。この基板をPb含有ペロブスカイト型酸化物薄膜の場合と同様にホットプレート上で加熱し、外周端部がエッチングされた状態のBi含有酸化物薄膜を得た。Pb含有ペロブスカイト型酸化物薄膜の場合と同様にこの操作を繰り返し、計6回CSD溶液の塗布を行って、都度EBR処理を行った後、RTAにより800℃で5分焼成を行いBi含有層状ペロブスカイト型酸化物薄膜を得た。
得られたサンプルは、Bi含有膜端部にはクラック、膜剥がれは全く発生していなかった。
(Bi-containing layered perovskite oxide thin film)
In the case of the Bi-containing layered perovskite oxide thin film, as in Example 2, the solutions B1 to B6 in Table 2 were applied on a 4-inch Pt / SiO 2 / Si substrate as in the case of the Pb-containing perovskite oxide thin film. After spin coating, in order to avoid cracks due to thick film at the outer peripheral edge of the substrate, water is sprayed to a position 5 mm radially inward from the outer peripheral edge of the substrate while rotating the substrate at 2500 rpm with a spin coater. The gel-like coating film was dissolved and EBR treatment was performed. This substrate was heated on a hot plate in the same manner as in the case of the Pb-containing perovskite oxide thin film to obtain a Bi-containing oxide thin film in which the outer peripheral edge was etched. This operation was repeated in the same manner as in the case of the Pb-containing perovskite type oxide thin film, the CSD solution was applied six times in total, and after each EBR treatment, baked at 800 ° C. for 5 minutes with RTA, and the Bi-containing layered perovskite A type oxide thin film was obtained.
In the obtained sample, no cracks or film peeling occurred at the end of the Bi-containing film.
また、比較例2として、EBR用溶剤として、水の代わりにn−ブタノールを使うこと以外は全て実施例2と同様にして、Bi含有層状ペロブスカイト型酸化物薄膜を得た。得られたサンプルのBi含有膜端部には、クラック、膜剥がれが発生した。 Further, as Comparative Example 2, a Bi-containing layered perovskite oxide thin film was obtained in the same manner as Example 2 except that n-butanol was used instead of water as the EBR solvent. Cracks and film peeling occurred at the end of the Bi-containing film of the obtained sample.
次に、このようにして得られたサンプルについて、米国Veeco Instruments社製の触針式表面形状測定器Dektakを使用して表面の段差を確認したところ、比較例1及び比較例2とも、強誘電体薄膜の外周縁部に1000〜1500μmの幅の範囲で数百nm程度の凹凸が確認されたが、実施例1及び実施例2のものは100nm以下の微細な段差が認められるだけで、極めて平滑な表面であった。図2に、実施例1の薄膜の表面顕微鏡写真と、表面形状測定器による測定結果とを示した。図3には比較例1の同様の結果を示した。これらの図の比較でも明らかな通り、比較例のものは、膜の界面付近(図3に2本の破線で示す間の領域)でクラック等による凹凸が目立っているが、実施例のものは極めて平滑な表面状態であることがわかる。 Next, with respect to the sample obtained in this manner, when a surface level difference was confirmed using a stylus type surface shape measuring device Dektak manufactured by Veeco Instruments, Inc. in the United States, both Comparative Example 1 and Comparative Example 2 were ferroelectric. Concavities and convexities of about several hundred nanometers were confirmed in the range of 1000 to 1500 μm in the outer peripheral edge of the body thin film, but the ones of Example 1 and Example 2 were found to have only a minute step of 100 nm or less. The surface was smooth. In FIG. 2, the surface micrograph of the thin film of Example 1 and the measurement result by a surface shape measuring device were shown. FIG. 3 shows a similar result of Comparative Example 1. As is apparent from the comparison of these figures, in the comparative example, unevenness due to cracks or the like is conspicuous in the vicinity of the interface of the film (the region indicated by two broken lines in FIG. 3). It can be seen that the surface state is extremely smooth.
なお、本発明は上記実施形態に限定されるものではなく、本発明の趣旨を逸脱しない範囲において種々の変更を加えることが可能である。
上記実施形態ではPLZT膜、SBTN膜を中心に説明したが、CSD法により成膜される他の強誘電体薄膜を形成する場合にも適用することができる。
In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
In the above embodiment, the PLZT film and the SBTN film have been mainly described. However, the present invention can also be applied to the case of forming other ferroelectric thin films formed by the CSD method.
1 ゲル状塗膜
2 基板
3 ノズル
W 水
1 Gel-like coating film 2 Substrate 3 Nozzle W Water
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