JP4122430B2 - Ferroelectric film - Google Patents
Ferroelectric film Download PDFInfo
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- JP4122430B2 JP4122430B2 JP2003085419A JP2003085419A JP4122430B2 JP 4122430 B2 JP4122430 B2 JP 4122430B2 JP 2003085419 A JP2003085419 A JP 2003085419A JP 2003085419 A JP2003085419 A JP 2003085419A JP 4122430 B2 JP4122430 B2 JP 4122430B2
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 46
- 239000000758 substrate Substances 0.000 claims description 22
- 229910052697 platinum Inorganic materials 0.000 claims description 21
- 239000010936 titanium Substances 0.000 claims description 19
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 14
- 238000004519 manufacturing process Methods 0.000 claims description 14
- 239000010703 silicon Substances 0.000 claims description 14
- 229910052710 silicon Inorganic materials 0.000 claims description 14
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 13
- 238000003980 solgel method Methods 0.000 claims description 12
- 238000004549 pulsed laser deposition Methods 0.000 claims description 11
- 238000005979 thermal decomposition reaction Methods 0.000 claims description 11
- 229910052719 titanium Inorganic materials 0.000 claims description 11
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 9
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 8
- 239000002243 precursor Substances 0.000 claims description 7
- 229910020684 PbZr Inorganic materials 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 6
- 238000002425 crystallisation Methods 0.000 claims description 4
- 230000008025 crystallization Effects 0.000 claims description 4
- 238000010304 firing Methods 0.000 claims description 4
- 239000010410 layer Substances 0.000 description 66
- 238000000034 method Methods 0.000 description 60
- 229910052451 lead zirconate titanate Inorganic materials 0.000 description 39
- 239000000463 material Substances 0.000 description 29
- 230000008569 process Effects 0.000 description 16
- 239000000243 solution Substances 0.000 description 14
- 230000003287 optical effect Effects 0.000 description 12
- 230000015572 biosynthetic process Effects 0.000 description 11
- 229910052751 metal Inorganic materials 0.000 description 10
- 239000002184 metal Substances 0.000 description 10
- 238000010438 heat treatment Methods 0.000 description 9
- 239000000203 mixture Substances 0.000 description 8
- 239000002994 raw material Substances 0.000 description 8
- 238000004544 sputter deposition Methods 0.000 description 8
- 238000010884 ion-beam technique Methods 0.000 description 6
- 229910044991 metal oxide Inorganic materials 0.000 description 6
- 150000004706 metal oxides Chemical class 0.000 description 6
- 238000001451 molecular beam epitaxy Methods 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 5
- 238000000151 deposition Methods 0.000 description 5
- 230000015654 memory Effects 0.000 description 5
- 239000003990 capacitor Substances 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 238000007733 ion plating Methods 0.000 description 4
- 239000000395 magnesium oxide Substances 0.000 description 4
- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 description 4
- 238000001771 vacuum deposition Methods 0.000 description 4
- 230000008901 benefit Effects 0.000 description 3
- 229910052797 bismuth Inorganic materials 0.000 description 3
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- 238000001182 laser chemical vapour deposition Methods 0.000 description 3
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 3
- 238000001755 magnetron sputter deposition Methods 0.000 description 3
- 238000006116 polymerization reaction Methods 0.000 description 3
- 238000002230 thermal chemical vapour deposition Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 2
- PQCCZSBUXOQGIU-UHFFFAOYSA-N [La].[Pb] Chemical compound [La].[Pb] PQCCZSBUXOQGIU-UHFFFAOYSA-N 0.000 description 2
- 239000012790 adhesive layer Substances 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- JRPBQTZRNDNNOP-UHFFFAOYSA-N barium titanate Chemical compound [Ba+2].[Ba+2].[O-][Ti]([O-])([O-])[O-] JRPBQTZRNDNNOP-UHFFFAOYSA-N 0.000 description 2
- 229910002113 barium titanate Inorganic materials 0.000 description 2
- 229910002115 bismuth titanate Inorganic materials 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- NKZSPGSOXYXWQA-UHFFFAOYSA-N dioxido(oxo)titanium;lead(2+) Chemical compound [Pb+2].[O-][Ti]([O-])=O NKZSPGSOXYXWQA-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 108010025899 gelatin film Proteins 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 229940046892 lead acetate Drugs 0.000 description 2
- 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 2
- 239000012528 membrane Substances 0.000 description 2
- 125000002524 organometallic group Chemical group 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 229910003446 platinum oxide Inorganic materials 0.000 description 2
- 238000005498 polishing Methods 0.000 description 2
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 2
- 238000000197 pyrolysis Methods 0.000 description 2
- 229910052709 silver Inorganic materials 0.000 description 2
- 239000004332 silver Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000013077 target material Substances 0.000 description 2
- 229910052845 zircon Inorganic materials 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- GFQYVLUOOAAOGM-UHFFFAOYSA-N zirconium(iv) silicate Chemical compound [Zr+4].[O-][Si]([O-])([O-])[O-] GFQYVLUOOAAOGM-UHFFFAOYSA-N 0.000 description 2
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 description 1
- PILOURHZNVHRME-UHFFFAOYSA-N [Na].[Ba] Chemical compound [Na].[Ba] PILOURHZNVHRME-UHFFFAOYSA-N 0.000 description 1
- VNSWULZVUKFJHK-UHFFFAOYSA-N [Sr].[Bi] Chemical compound [Sr].[Bi] VNSWULZVUKFJHK-UHFFFAOYSA-N 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 239000000443 aerosol Substances 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
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000001174 ascending effect Effects 0.000 description 1
- 239000013590 bulk material Substances 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 229910000423 chromium oxide Inorganic materials 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000013016 damping Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000003618 dip coating Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000005621 ferroelectricity Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 1
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- OGHBATFHNDZKSO-UHFFFAOYSA-N propan-2-olate Chemical compound CC(C)[O-] OGHBATFHNDZKSO-UHFFFAOYSA-N 0.000 description 1
- 230000005616 pyroelectricity Effects 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 238000001552 radio frequency sputter deposition Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000012798 spherical particle Substances 0.000 description 1
- 238000004528 spin coating Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L28/00—Passive two-terminal components without a potential-jump or surface barrier for integrated circuits; Details thereof; Multistep manufacturing processes therefor
- H01L28/40—Capacitors
- H01L28/55—Capacitors with a dielectric comprising a perovskite structure material
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/01—Manufacture or treatment
- H10N30/07—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base
- H10N30/074—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing
- H10N30/076—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing by vapour phase deposition
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/01—Manufacture or treatment
- H10N30/07—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base
- H10N30/074—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing
- H10N30/077—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing by liquid phase deposition
- H10N30/078—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing by liquid phase deposition by sol-gel deposition
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/85—Piezoelectric or electrostrictive active materials
- H10N30/853—Ceramic compositions
- H10N30/8548—Lead-based oxides
- H10N30/8554—Lead-zirconium titanate [PZT] based
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Power Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Ceramic Engineering (AREA)
- Dispersion Chemistry (AREA)
- Materials Engineering (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Semiconductor Memories (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Description
【0001】
【発明の属する技術分野】
本発明は、アクチュエ−タやセンサ等の微小電気機械システ(MicroElectroMechanical Systems, 以下、MEMSともいう)用機能素子、強誘電体メモリ等の情報記録媒体、コンデンサ等の電子電気素子の機能性材料、光シャッター、光導波路等の光デバイス等に用いられ新規な強誘電体膜に関する。
【0002】
【従来の技術】
チタン酸ジルコン酸鉛(PZT)、チタン酸ジルコン酸ランタン鉛(PLZT)等の強誘電性の固体固溶体は、その組成に応じて材料特性が変化し種々の応用が行われている。これらは、室温付近においても複数(5種)の結晶構造が可能であり、コンデンサやメモリ等の電気的な応用だけでなく、光シャッタ−等の光学分野やアクチュエ−タ等の機械分野の適用も行われている。
【0003】
このような強誘電体は高い電気機械結合定数が高く、また圧電特性自身が入出力特性の線形性により、消費電力が小さく、熱的な影響が小さいため小型化に適した駆動方式が実現可能であり、これらの材料をMEMSの構成要素として適用する利点は多いとされている。しかしながら、これまでメモリへの応用を除いては、センサやアクチュエ−タ等のMEMS素子への応用例は他分野に比べて少ないのが現状である。
【0004】
この理由としてはMEMS分野においては素子に必要な膜厚さが1μmから100μm程度であり、これらの寸法領域は従来の成膜技術ではきわめて製造が困難であることがある。
【0005】
このため、従来、MEMS分野の製品はPZT等のセラミクスバルク体を研磨加工し、薄くしたものを貼り付ける方法で生産されていたのが実状であった。しかし、この機械加工による研磨では厚さ数10μmにするのが限界であり、これ以下の膜製品を得るのが困難であった。またこのバルク材を利用する方法では基板に接合する手法として接着剤が用いられるが、厚さの均一性、接着層でのダンピング等の問題を有し、更には、製造工程の煩雑さとコスト低減、大面積化が困難であり、量産化には不向きであった。
【0006】
このようなバルク法の問題点を解消するために、最近、スパッタ法やCVD法、ゾル・ゲル法などによる膜形成法によって大面積なPZT膜を形成し、強誘電体膜を形成する方法が研究されているが、実質的に良好な膜特性を発揮する基板は高価なマグネシア単結晶に限定されるという難点があった。
【0007】
このため、基板として安価なシリコンをベースとする製膜法が強く要請されるに至っているが、圧電性は異方性をもつために配向性を制御することが極めて困難であり、シリコン基板を対象とする製膜法は未だ充分に確立されるに至っておらず、特許文献1や特許文献2などに見られるに過ぎない。
【0008】
特許文献1の方法による膜の形成過程は、シリコンウェハ−の上に熱酸化法により100nmの酸化シリコン膜を、その上に、マグネトロンスパッタ法により、約70nmの白金の膜を形成する。更にその上に、配向性制御層として化学的成膜法(CVD)により作成したチタン酸バリウム(BTO)層を作成する。このBTO膜上にチタン酸鉛(PTO)を形成することによって、PTOを(111)方向に単一配向させることができ、また、この結果から白金上に格子定数の近い酸化物膜を配向性制御層として用いればPZT等の材料において有効としている。
【0009】
特許文献2の方法は、(100)面のシリコンウェハ上に酸素雰囲気中で酸化シリコン(絶縁層)を形成し、この上にスパッタ法によりチタンと白金を下部電極として設け、その上に配向性制御層を、その上に誘電体膜を設け、最後に誘電体膜上へ上部電極を形成することにより強誘電体膜を得ている。ここで、配向性制御層は、チタン酸ランタン鉛(PLT)やチタン酸ストロンチウムビスマス(BST)等の比較的低温で白金上にペロブスカイト構造を形成する材料を用いるか、あるいはチタンやジルコニウム等を金属状態でスパッタした後に酸化し緻密な膜を形成することにより得られ、このような方法により、とくに(111)方向に配向させた強誘電体膜を600度程度の低温で安定に形成できるとしている。
【0010】
しかしながら、これらの方法は、系統が近いか類似であっても機能性材料の本体部であるPTOやPZTとは異なる物質を配向性制御層として構造中に取り込んでおり、高品質性や熱処理時の拡散による微小な組成ずれを発生させるおそれがあり、また、量産レベルにおいては、製膜材料として少なくとも2種以上の異種材料を用意する必要があり、原料の調達、管理がコスト高となる上、これらの2種以上の異種材料による複数の製膜プロセスを必要とするので、工程が煩雑となり量産化には不向きであるといった難点がある。
【0011】
【特許文献1】
特開平7-142600号公報
【特許文献2】
特開2001-223403号公報
【0012】
【発明が解決しようとする課題】
本発明は、上記のような従来技術の問題点を克服し、簡便な組成でありながら高品質で熱処理持による微少な組成ずれがなく、誘電性、焦電性、圧電性、強誘電性、電気光学性、光起電力性、電歪、光歪などの有効な特性を有し、しかも製膜材料として2種以上の異種材料を用意することなく、低コストで原料の調達、管理ができ、かつ工程が煩雑な製膜プロセスを経ることなく、高速かつ低コストで量産化が可能な新規な強誘電体膜を提供することを目的とする。
【0013】
【課題を解決するための手段】
本発明者等は、上記問題点を解決するための鋭意検討した結果、配向制御層として、強誘電体層と同一の成分から強誘電体材料を用いれば上記課題が解決できることを見いだし本発明を完成するに至った。
すなわち、この出願は、以下の発明を提供するものである。
〈1〉シリコン基板上に酸化シリコン層とチタン層と下部白金電極を順次設け、ついで、該下部白金電極上に、ゾルゲル法により(100)配向したPbZr x Ti 1-x O 3 (xは 0 〜1の整数)配向制御層を設け、更にその上にパルスレーザー蒸着により(100)配向したPbZr x Ti 1-x O 3 (xは 0 〜1の整数)強誘電体層を設け、更に、その上に上記白金電極を設けたことを特徴とする強誘電体膜の製造方法。
〈2〉PbZr x Ti 1-x O 3 (xは 0 〜1の整数)の前駆体溶液をゾルゲル法により白金電極上に塗布し、乾燥、熱分解、焼成・結晶化させることを特徴とする〈1〉に記載の強誘電体膜の製造方法。
〈3〉乾燥温度が120℃、熱分解温度が350℃、焼成・結晶化温度が350℃であることを特徴とする〈2〉記載の強誘電体膜の製造方法。
【0014】
【発明の実施の形態】
本発明の強誘電体膜は、配向制御層の上に強誘電体層を設けた強誘電体膜であって、該配向制御層と強誘電体層とが同一の成分の強誘電体材料から形成されていることを特徴としている。
したがって、本発明に係る強誘電体膜は、簡便な組成でありながら高品質で熱処理持による微少な組成ずれがなく、誘電性、焦電性、圧電性、強誘電性、電気光学性、光起電力性、電歪、光歪などの有効な特性を有し、しかも製膜材料として2種以上の異種材料を用意することなく、低コストで原料の調達、管理ができ、かつ工程が煩雑な製膜プロセスを経ることなく、高速かつ低コストで量産化が可能なものである。
【0015】
本発明の配向制御層及び強誘電体層の形成に用いられる強誘電体材料としては、従来公知のものたとえば、チタン酸バリウム、チタン酸鉛、チタン酸ジルコン酸鉛(PZT)、チタン酸ジルコン酸ランタン鉛等のペロブスカイト構造系;ニオブ酸リチウム、ニオブ酸タンタル等の擬イルメナイト構造系;ニオブ酸鉛、ニオブ酸ナトリウムバリウム等のタングステンブロンズ構造系またはPb2Nb2O7,Cd2Nb2O7等のパイロクロア構造系;またはタンタル酸ビスマスストロチウム、タンタル酸ビスマス等のビスマス層状構造系の何れがが使用できる。
本発明で好ましく使用される強誘電体材料はペロブスカイト構造を有するものであり、この中でもPbZrx Ti1-x O3 (xは0〜1の整数)(以下、PZTともいう)である。
【0016】
本発明の強誘電体膜を得るには、たとえばあらかじめ基板上に金属又は金属酸化物層を設けておき、その上に強誘電体層と同一の成分を有する強誘電体材料からなる配向制御層を設け、ついで該配向制御層の上に該配向制御層と同一の成分を有する強誘電体材料からなる強誘電体層を設け、必要に応じその上に上部電極を形成すればよい。
【0017】
基板としては、シリコン(シリコンウェハ)、酸化マグネシウム、ステンレス、アルミナ、ガラスなどを用いることができるが、シリコン(シリコンウェハ)が好ましく使用される。基板の膜厚に特に制限はないが、通常0.05〜2μm、好ましくは0.1〜0.5μmである。
また、この基板上には、基板と上部構造体の緩衝層を形成あるいはシリコンのエッチング時の下地材料とするために、酸化物シリコン膜などの絶縁層を設けておくことが望ましく、更には該絶縁層と配向制御層との密着性を向上させるためにチタンなどの密着向上層を設けておくことが好ましい。
【0018】
基板上(基板に絶縁層又は密着向上層を設けてある場合にはその上に)に金属又は金属酸化物を設けるには、従来公知の方法、たとえば、真空蒸着、スパッタリング、イオンプレ-ティングなどの方法を採ればよい。
金属又は金属酸化物層の膜厚は特に制限はないが、通常は0.05〜1μm、好ましくは0.1〜0.5μmである。
金属としては、白金、金、銀、アルミニウム、クロムなどの金属、酸化マグネシウム、酸化アルミニウム、酸化クロムなどの金属酸化物を用いることができる。この中でも白金、酸化マグネシウムが好ましく使用される。
【0019】
金属又は金属酸化物層の上に配向制御層を設けるには、強誘電体層と同一の成分を有する強誘電体材料を金属又は金属酸化物層に製膜すればよい。製膜法としてはゾルゲル法や有機金属分解塗布(MOD)法などの化学溶液法、MBE(分子線エピタキシー)イオンプレーティング、ICB(クラスタイオンビーム)などの真空蒸着法、スパッタ法、イオンビーム法、パルスレーザー蒸着法、熱CVD法(ACVD、LCVD)、プラズマ重合法などの従来公知の製膜法が適用できる。
【0020】
本発明においては、好ましく採用される配向制御層の製膜法は、ゾルゲル法や有機金属分解塗布(MOD)法などの化学溶液法である。これは、化学溶液法による膜では製膜時にその熱分解を行う温度を適宜調整することによりその配向性を容易に制御することが可能となること、その製膜工程が低温下で行うことができ、かつ一段階のプロセスで配向制御層を形成できるなどの利点を有するからである。
配向制御層の厚みに特に制限はないが、通常0.25〜0.5μm、好ましくは0.05〜0.2μmである。
【0021】
以下、ゾルゲル法によりPZTを成分とする配向制御層を形成する方法について具体的に説明する。PZTの各種原料溶液(例えば酢酸鉛、チタンイソプロポキシド、ジルコンイソプロポキシド)を用意し、エタノール、プロパノールなどの溶媒に溶解させPZT前駆体溶液を調製する。この場合、PZTの原料成分の中で鉛等の揮発成分はその製膜過程で一部揮発する場合が生じるので、これらの揮発成分は化学量論的にやや過剰に添加しておくことが望ましい。
次に、PZT前駆体溶液を該前記金属又は酸化物層にスピンコート、ディップコートなどにより塗布し、ゲル膜を形成させる、ついでこのゲル膜を乾燥、熱分解、焼成・結晶化させることによりPZTからなる配向制御層を得ることができる。
乾燥、熱分解、焼成・結晶化の温度は、夫々通常100〜150℃、250〜450℃、600℃〜700℃である。
【0022】
本発明においては、この熱分解温度を調整することにより、配向性の異なるPZT配向制御層を選択的に得ることが可能となる。たとえば後記するように熱分解温度を250度にすると(111)配向したPZT配向制御層が、350度にすると(100)配向したPZT配向制御層が得られる。
【0023】
本発明においては、上記配向制御層を形成させた後、その上に強誘電体層を設ける。強誘電体層を形成するには、前記配向制御層と同一の成分を有する強誘電体材料を配向制御層上に製膜すればよい。製膜法としてはパルスレーザー蒸着法(PLAD)、熱CVD法(ACVD、LCVD)、プラズマ重合法、MBE(分子線エピタキシー)イオンプレーティング、ICB(クラスタイオンビーム)などの真空蒸着法、スパッタ法、イオンビーム法、ゾルゲル法や有機金属分解塗布(MOD)法などの化学溶液法などの従来公知の製膜法が適用できる。
【0024】
本発明においては、好ましく採用される強誘電体層の製膜法は、パルスレ−ザ蒸着、熱CVD法(ACVD、LCVD)、プラズマ重合法、MBE(分子線エピタキシー)イオンプレーティング、ICB(クラスタイオンビーム)などの真空蒸着法、スパッタ法、イオンビーム法、ガスデポジション法、エアロゾルガスデポジション法である。これは、MEMSに適したセンサやアクチュエータ等の厚膜(1μm以上)を高速で製膜できること、量産が可能なこと、などの利点を有するからである。
強誘電体層の厚みに特に制限はないが、通常0.1〜1000μm好ましくは0.5〜10μmである。
【0025】
この誘電体膜層には、電力、電圧、電流の入出力を行うために必要に応じ上部電極を設けることができる。
このような上部電極としては、たとえば、白金、金、銀、アルミニウム、クロムなどを挙げることができる。上部電極はたとえば従来公知のマグネトロンスッパタ法により形成することができる。
【0026】
つぎに、上記のような方法で得られる本発明の代表的な強誘電体膜の模式断面図を図1に示す。
図1において、1は基板であり、(100)面のシリコンウェハである。膜厚は400μmである。3は絶縁層であり、1.5ミクロンの酸化シリコンである。5は密着層である50nmのチタン、7は150nmの下部電極である白金である。9は配向性制御層であるゾルゲル法により作製したPZT膜であり、厚さは100nmである。11はPLAD法により作製したPZTであり膜厚は4ミクロンである。13は100nmの上部電極である白金である。
【0027】
本発明に係る強誘電体膜は、簡便な組成でありながら高品質で熱処理持による微少な組成ずれがなく、誘電性、焦電性、圧電性、強誘電性、電気光学性、光起電力性、電歪、光歪などの有効な特性を有し、しかも製膜材料として2種以上の異種材料を用意することなく、低コストで原料の調達、管理ができ、かつ工程が煩雑な製膜プロセスを経ることなく、高速かつ低コストで量産化が可能なものである。また、本発明の強誘電体膜は配向制御層の熱分解温度を調整することにより、配向性の異なるPZT配向制御層を選択的に得ることが可能であることから、アクチュエ−タ,センサ,メモリ,コントロ−ラ、トランスデュ−サ、コンデンサ,光シャッター、光導波路等として有用なものである。また、1μm以上の厚膜とすることもできるのでMEMSに適したセンサやアクチュエータ等の機能素子として有効に利用することができる。
【0028】
【実施例】
以下、本発明を実施例により更に詳細に説明する。
実施例
【0029】
[本発明の代表的なPZT強誘電体膜]
まず、後記方法で得られるPZT強誘電体膜の模式断面図を図1に示す。図1において、1は基板であり、(100)面のシリコンウェハである。膜厚は400μmである。3は絶縁層であり、1.5ミクロンの酸化シリコンである。5は密着層である50nmのチタン、7は150nmの下部電極(白金)である。9は配向性制御層であるPZT膜であり、ゾルゲル法により形成されている。厚さは100nmである。11はPLAD法により作製したPZTであり膜厚は4ミクロンである。13は上部電極(白金)である。
【0030】
[本発明のPZT強誘電体膜の作製]
以上の構造を持つ誘電体膜を下記の要領により作製した。
基板材料であるシリコンを熱酸化炉中で20時間1200度で酸化させ表面に約1.5ミクロンの酸化シリコンを形成し絶縁層3とした。この基板をRFスパッタリング方法により、まずチタンを50nmついで白金を150nmスパッタする。チタンは白金と酸化シリコンの密着層の役割をしている、チタンの成膜条件はアルゴンガス圧2*10-1Pa、0.12kWの電源出力で20分の成膜時間であり、白金はチタンと同じガス圧及び出力で5分の成膜時間であった。また、スパッタリング時の基板温度は200度とした。
【0031】
引き続き、白金電極上へゾルゲル法により配向性制御層であるPZT膜を形成した。まず、原料となるゾルゲル溶液の合成方法を説明する。PZT前駆体の出発原料として、酢酸鉛(5.855g)、チタンイソプロボキシド(2.004g)、ジルコンイソボキシド(3.719g)を使用した。溶媒としてはプロパノ−ルを用いた。チタンとジルコニウムの成分をPb(Zr0.53Ti0.47)O3の組成になるように添加したが、プロセス中で蒸発する鉛分を補償するために鉛分は20%多く添加した。各組成の溶液を混合・攪拌し、37.5mlの0.4モル濃度の溶液(PZT前駆体溶液)を調製した。
【0032】
この前駆体溶液をスピンコーター上の真空チャックに固定した基板へ滴下し、スピンコーターの回転により均一に塗布を行った。回転数は700rpmで10秒、2700rpmで10秒、4000rpmで40秒行った。その後、溶液を塗布した基板を焼成炉中で熱処理した。この際の熱処理温度は3段階とし、低い順に乾燥、熱分解、焼成・結晶化の役割を果す。乾燥温度は120度で10分、焼成温度は600度で30分である。熱分解の温度は配向性と関連しており、250度にしたときには、(111)配向であり、350度にすると(100)配向となる。また時間は30分とした。熱処理の工程を図2に示す。
【0033】
続いて配向性制御用PZT膜上に図3のPLAD装置を用いPLAD法により、PZT膜を形成した。この装置はエキシマレーザ(248nmのKrF)と製膜装置からなる。
図3において、11はレーザ、13は成膜チャンバ、15は入射窓、17はPZTターゲット材料、21は基板、22は基板加熱ヒ−タ、23は原子源、25は高速酸素ビ−ムである。
この装置においては、発振したレーザ光は石英フランジを透過して、チャンバ内のターゲットに照射される。ターゲットから発生したプルームが前記基板上に堆積して成膜が行われる。PLAD法のターゲット材料としては、化学量論組成のPZTに鉛を20%過剰に添加したものを用いた。これは成膜過程における鉛の蒸発を補償するためである。また、成膜時の条件は表1に示す。こうして30分の成膜により、約0.7ミクロンのPZT膜を形成することが出来た。
上部電極にはマグネトロンスパッタリングにより白金を形成した。膜厚は100nmである。
【0034】
【表1】
【0035】
上記方法で作製した膜の表面及び断面のSEM写真を図4(a)、(b)に示す。図4(a)から平滑な表面には球状で約100nm程度のグレインが成長していることが、また、図4(b)から緻密で均一な膜成長みられることが確認できる。
【0036】
作製した膜のX線回折法により測定した結果を図5に示す。図5において、(a)は熱分解温度が400度ものものであり、(b)は250度のものである。これから本発明の強誘電体膜は熱分解温度によって結晶の配向性が制御できることがわかる。
【0037】
また、各種強誘電体膜の強誘電性履歴曲線の測定結果を図6に示す。図6において、(A)は本発明のPZT強誘電体膜であり、(B)はPLAD法単独による単層のPZT強誘電体膜(比較例)である。図6から、本発明のPZT強誘電体膜は比較例1のものより約2倍の電気特性に優れていることがわかる。
【0038】
【発明の効果】
本発明に係る強誘電体膜は、簡便な組成でありながら高品質で熱処理持による微少な組成ずれがなく、誘電性、焦電性、圧電性、強誘電性、電気光学性、光起電力性、電歪、光歪などの有効な特性を有し、しかも製膜材料として2種以上の異種材料を用意することなく、低コストで原料の調達、管理ができ、かつ工程が煩雑な製膜プロセスを経ることなく、高速かつ低コストで量産化が可能なものである。また、本発明の強誘電体膜は配向制御層の熱分解温度を調整することにより、配向性の異なるPZT配向制御層を選択的に得ることが可能であることから、アクチュエ−タ,センサ,メモリ,コントロ−ラ、トランスデュ−サ、コンデンサ,光シャッター、光導波路等として有用なものである。また、厚膜とすることもできるのでMEMSに適したセンサやアクチュエータ等の素子として有効に利用することができる。
【図面の簡単な説明】
【図1】本発明のPZT強誘電体膜の模式断面図
【図2】本発明に係る配向制御層の熱処理による配向の変化図
【図3】本発明の強誘電体層を形成するために用いられる装置の説明図
【図4】本発明の強誘電体膜のSEM写真。
【図5】本発明の強誘電体膜結晶のX線回折法図
【図6】本発明と比較例の強誘電体膜の強誘電性履歴曲線[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a functional material for a microelectromechanical system (hereinafter also referred to as MEMS) such as an actuator or a sensor, an information recording medium such as a ferroelectric memory, a functional material of an electronic or electrical element such as a capacitor, The present invention relates to a novel ferroelectric film used for optical devices such as optical shutters and optical waveguides.
[0002]
[Prior art]
Ferroelectric solid solid solutions such as lead zirconate titanate (PZT) and lead lanthanum zirconate titanate (PLZT) vary in material properties according to their compositions and are used in various applications. These can have multiple (five types) crystal structures near room temperature, and not only in electrical applications such as capacitors and memories, but also in optical fields such as optical shutters and mechanical fields such as actuators. Has also been done.
[0003]
Such ferroelectrics have high electromechanical coupling constants, and the piezoelectric characteristics themselves are linear in the input / output characteristics, so the power consumption is small and the thermal effect is small, so a drive system suitable for miniaturization can be realized. Therefore, there are many advantages to applying these materials as components of MEMS. However, the present situation is that there are few application examples to MEMS elements, such as a sensor and an actuator, except the application to a memory until now compared with other fields.
[0004]
The reason for this is that in the MEMS field, the film thickness required for the element is about 1 μm to 100 μm, and these dimensional regions may be extremely difficult to manufacture with conventional film formation techniques.
[0005]
For this reason, in the past, products in the MEMS field were actually produced by polishing a ceramic bulk body such as PZT and pasting a thin one. However, the polishing by this machining is limited to a thickness of several tens of μm, and it has been difficult to obtain a film product having a thickness below this. In this method using bulk material, an adhesive is used as a method for bonding to the substrate, but there are problems such as uniformity of thickness, damping in the adhesive layer, and further, complexity of the manufacturing process and cost reduction. However, it is difficult to increase the area and is not suitable for mass production.
[0006]
In order to solve such problems of the bulk method, a method of forming a ferroelectric film by forming a large area PZT film by a film forming method such as a sputtering method, a CVD method, or a sol-gel method has recently been developed. Although being researched, there has been a problem that substrates that exhibit substantially good film properties are limited to expensive magnesia single crystals.
[0007]
For this reason, there has been a strong demand for an inexpensive silicon-based film forming method as a substrate. However, since piezoelectricity has anisotropy, it is extremely difficult to control the orientation, The target film-forming method has not yet been sufficiently established, and is only found in
[0008]
In the film formation process by the method of
[0009]
In the method of Patent Document 2, silicon oxide (insulating layer) is formed in an oxygen atmosphere on a (100) -plane silicon wafer, and titanium and platinum are provided thereon as a lower electrode by sputtering, and orientation is formed thereon. A ferroelectric film is obtained by providing a control layer, a dielectric film thereon, and finally forming an upper electrode on the dielectric film. Here, the orientation control layer uses a material that forms a perovskite structure on platinum at a relatively low temperature, such as lanthanum lead titanate (PLT) or strontium bismuth titanate (BST), or a metal such as titanium or zirconium. It is obtained by oxidizing after sputtering in the state and forming a dense film. By such a method, a ferroelectric film oriented in the (111) direction can be formed stably at a low temperature of about 600 degrees. .
[0010]
However, these methods incorporate a substance different from PTO or PZT, which is the main body part of the functional material, into the structure as an orientation control layer even if the system is close or similar, so that high quality and heat treatment can be achieved. In addition, at the mass production level, it is necessary to prepare at least two kinds of different materials as film forming materials, which increases the cost of procurement and management of raw materials. Since a plurality of film forming processes using two or more kinds of these different materials are required, the process is complicated and unsuitable for mass production.
[0011]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-22600 [Patent Document 2]
JP 2001-223403 A [0012]
[Problems to be solved by the invention]
The present invention overcomes the problems of the prior art as described above, has a simple composition, has high quality, and has no slight compositional deviation due to heat treatment, and has dielectricity, pyroelectricity, piezoelectricity, ferroelectricity, It has effective characteristics such as electro-optical properties, photovoltaic properties, electrostriction, and photostriction, and can procure and manage raw materials at low cost without preparing two or more different materials as film forming materials. Another object of the present invention is to provide a novel ferroelectric film that can be mass-produced at high speed and low cost without going through a complicated film forming process.
[0013]
[Means for Solving the Problems]
As a result of diligent studies to solve the above problems, the present inventors have found that the above problems can be solved by using a ferroelectric material from the same component as the ferroelectric layer as the orientation control layer. It came to be completed.
That is, this application provides the following invention.
<1> A silicon oxide layer, a titanium layer, and a lower platinum electrode are sequentially provided on a silicon substrate, and then PbZr x Ti 1-x O 3 (x is 0 ) oriented on the lower platinum electrode by a sol-gel method. the ~ 1 integer) the orientation control layer is provided, thereon by a pulsed laser deposition (100) is PbZr x Ti 1-x O 3 (x oriented provided 0-1 integer) ferroelectric layer further additionally, A method for producing a ferroelectric film, comprising the platinum electrode provided thereon.
<2> A precursor solution of PbZr x Ti 1-x O 3 (x is an integer of 0 to 1) is applied on a platinum electrode by a sol-gel method, dried, pyrolyzed, fired and crystallized. The method for producing a ferroelectric film according to <1>.
<3> The method for producing a ferroelectric film according to <2>, wherein the drying temperature is 120 ° C., the thermal decomposition temperature is 350 ° C., and the firing and crystallization temperature is 350 ° C.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The ferroelectric film of the present invention is a ferroelectric film in which a ferroelectric layer is provided on an orientation control layer, and the orientation control layer and the ferroelectric layer are made of a ferroelectric material having the same component. It is characterized by being formed.
Therefore, the ferroelectric film according to the present invention has a simple composition but high quality without a slight compositional deviation due to heat treatment, and is dielectric, pyroelectric, piezoelectric, ferroelectric, electro-optical, optical It has effective characteristics such as electromotive force, electrostriction, and photostriction, and can procure and manage raw materials at low cost without preparing two or more different materials as film forming materials, and the process is complicated. It can be mass-produced at a high speed and at a low cost without going through a film forming process.
[0015]
As the ferroelectric material used for forming the orientation control layer and the ferroelectric layer of the present invention, conventionally known ferroelectric materials such as barium titanate, lead titanate, lead zirconate titanate (PZT), zirconate titanate Perovskite structure systems such as lanthanum lead; pseudo-ilmenite structure systems such as lithium niobate and tantalum niobate; tungsten bronze structures such as lead niobate and sodium barium niobate, or Pb 2 Nb 2 O 7 and Cd 2 Nb 2 O 7 Or a bismuth layered structure system such as bismuth strotium tantalate or bismuth tantalate can be used.
Ferroelectric material is preferably used in the present invention are those having a perovskite structure, is PbZr x Ti 1-x O 3 Among (x is an integer from 0 to 1) (hereinafter also referred to as PZT).
[0016]
In order to obtain the ferroelectric film of the present invention, for example, a metal or metal oxide layer is previously provided on a substrate, and an orientation control layer made of a ferroelectric material having the same component as the ferroelectric layer is provided thereon. Then, a ferroelectric layer made of a ferroelectric material having the same component as that of the orientation control layer is provided on the orientation control layer, and an upper electrode is formed thereon if necessary.
[0017]
As the substrate, silicon (silicon wafer), magnesium oxide, stainless steel, alumina, glass, or the like can be used, but silicon (silicon wafer) is preferably used. Although there is no restriction | limiting in particular in the film thickness of a board | substrate, it is 0.05-2 micrometers normally, Preferably it is 0.1-0.5 micrometer.
In addition, an insulating layer such as an oxide silicon film is preferably provided on the substrate in order to form a buffer layer for the substrate and the upper structure or as a base material for etching silicon. In order to improve the adhesion between the insulating layer and the orientation control layer, it is preferable to provide an adhesion improving layer such as titanium.
[0018]
In order to provide a metal or a metal oxide on a substrate (if an insulating layer or an adhesion improving layer is provided on the substrate), a conventionally known method such as vacuum deposition, sputtering, ion plating, etc. The method should be taken.
The thickness of the metal or metal oxide layer is not particularly limited, but is usually 0.05 to 1 μm, preferably 0.1 to 0.5 μm.
As the metal, metals such as platinum, gold, silver, aluminum, and chromium, and metal oxides such as magnesium oxide, aluminum oxide, and chromium oxide can be used. Of these, platinum and magnesium oxide are preferably used.
[0019]
In order to provide the orientation control layer on the metal or metal oxide layer, a ferroelectric material having the same component as the ferroelectric layer may be formed on the metal or metal oxide layer. Film forming methods include chemical solution methods such as sol-gel method and organometallic decomposition coating (MOD) method, vacuum deposition methods such as MBE (molecular beam epitaxy) ion plating, ICB (cluster ion beam), sputtering method, ion beam method Conventionally known film forming methods such as pulsed laser deposition, thermal CVD (ACVD, LCVD), and plasma polymerization can be applied.
[0020]
In the present invention, the film forming method of the orientation control layer preferably employed is a chemical solution method such as a sol-gel method or a metal organic decomposition coating (MOD) method. This is because, in a film formed by a chemical solution method, the orientation can be easily controlled by appropriately adjusting the temperature at which the thermal decomposition is performed during film formation, and the film formation process can be performed at a low temperature. This is because there is an advantage that the orientation control layer can be formed by a one-step process.
Although there is no restriction | limiting in particular in the thickness of an orientation control layer, Usually, 0.25-0.5 micrometer, Preferably it is 0.05-0.2 micrometer.
[0021]
Hereinafter, a method for forming an orientation control layer containing PZT as a component by a sol-gel method will be specifically described. Various raw material solutions of PZT (for example, lead acetate, titanium isopropoxide, zircon isopropoxide) are prepared, and dissolved in a solvent such as ethanol or propanol to prepare a PZT precursor solution. In this case, volatile components such as lead in the raw material components of PZT may partially volatilize during the film forming process, so it is desirable to add these volatile components in a slightly stoichiometric amount. .
Next, the PZT precursor solution is applied to the metal or oxide layer by spin coating, dip coating or the like to form a gel film, and then the gel film is dried, pyrolyzed, fired and crystallized to form PZT. An orientation control layer made of can be obtained.
The temperatures for drying, pyrolysis, calcination and crystallization are usually 100 to 150 ° C, 250 to 450 ° C, and 600 ° C to 700 ° C, respectively.
[0022]
In the present invention, it is possible to selectively obtain PZT orientation control layers having different orientations by adjusting the thermal decomposition temperature. For example, as described later, when the thermal decomposition temperature is 250 degrees, a (111) -oriented PZT orientation control layer is obtained, and when it is 350 degrees, a (100) -oriented PZT orientation control layer is obtained.
[0023]
In the present invention, after the orientation control layer is formed, a ferroelectric layer is provided thereon. In order to form the ferroelectric layer, a ferroelectric material having the same component as the orientation control layer may be formed on the orientation control layer. Film deposition methods include pulsed laser deposition (PLAD), thermal CVD (ACVD, LCVD), plasma polymerization, MBE (molecular beam epitaxy) ion plating, ICB (cluster ion beam) and other vacuum deposition methods, sputtering method Conventionally known film forming methods such as chemical solution methods such as ion beam method, sol-gel method and organometallic decomposition coating (MOD) method can be applied.
[0024]
In the present invention, the ferroelectric layer is preferably formed by pulse laser deposition, thermal CVD (ACVD, LCVD), plasma polymerization, MBE (molecular beam epitaxy) ion plating, ICB (cluster). A vacuum deposition method such as ion beam), a sputtering method, an ion beam method, a gas deposition method, and an aerosol gas deposition method. This is because there are advantages such that a thick film (1 μm or more) such as a sensor or an actuator suitable for MEMS can be formed at a high speed and mass production is possible.
Although there is no restriction | limiting in particular in the thickness of a ferroelectric layer, Usually, 0.1-1000 micrometers, Preferably it is 0.5-10 micrometers.
[0025]
This dielectric film layer can be provided with an upper electrode as necessary in order to input and output power, voltage and current.
Examples of such an upper electrode include platinum, gold, silver, aluminum, and chromium. The upper electrode can be formed, for example, by a conventionally known magnetron sputtering method.
[0026]
Next, a schematic cross-sectional view of a typical ferroelectric film of the present invention obtained by the above method is shown in FIG.
In FIG. 1,
[0027]
The ferroelectric film according to the present invention has a simple composition but high quality without any slight compositional deviation due to heat treatment, and is dielectric, pyroelectric, piezoelectric, ferroelectric, electro-optical, photovoltaic. Production, which has effective properties such as property, electrostriction, and optical strain, and can procure and manage raw materials at low cost without preparing two or more different materials as film forming materials, and has complicated processes It can be mass-produced at high speed and low cost without going through a membrane process. Further, since the ferroelectric film of the present invention can selectively obtain PZT orientation control layers having different orientations by adjusting the thermal decomposition temperature of the orientation control layer, an actuator, a sensor, It is useful as a memory, controller, transducer, capacitor, optical shutter, optical waveguide, and the like. Further, since it can be a thick film of 1 μm or more, it can be effectively used as a functional element such as a sensor or an actuator suitable for MEMS.
[0028]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples.
Example [0029]
[Representative PZT ferroelectric film of the present invention]
First, a schematic cross-sectional view of a PZT ferroelectric film obtained by the method described later is shown in FIG. In FIG. 1,
[0030]
[Preparation of PZT Ferroelectric Film of the Present Invention]
A dielectric film having the above structure was produced in the following manner.
Silicon, which is a substrate material, was oxidized at 1200 ° C. for 20 hours in a thermal oxidation furnace to form silicon oxide having a thickness of about 1.5 μm on the surface. This substrate is first sputtered with 50 nm of titanium and then with 150 nm of platinum by an RF sputtering method. Titanium serves as an adhesion layer between platinum and silicon oxide. Titanium film formation conditions are an argon gas pressure of 2 * 10-1 Pa, a power output of 0.12 kW, and a film formation time of 20 minutes. The film formation time was 5 minutes at the same gas pressure and output. The substrate temperature during sputtering was 200 degrees.
[0031]
Subsequently, a PZT film as an orientation control layer was formed on the platinum electrode by a sol-gel method. First, a method for synthesizing a sol-gel solution as a raw material will be described. As starting materials for the PZT precursor, lead acetate (5.855 g), titanium isopropoxide (2.004 g), and zircon isoboxoxide (3.719 g) were used. Propanol was used as the solvent. Titanium and zirconium components were added so as to have a composition of Pb (Zr 0.53 Ti 0.47 ) O 3 , but 20% more lead was added to compensate for the lead that evaporates during the process. The solution of each composition was mixed and stirred to prepare 37.5 ml of a 0.4 molar solution (PZT precursor solution).
[0032]
This precursor solution was dropped onto a substrate fixed to a vacuum chuck on a spin coater, and uniformly applied by rotating the spin coater. The number of rotations was 700 rpm for 10 seconds, 2700 rpm for 10 seconds, and 4000 rpm for 40 seconds. Thereafter, the substrate coated with the solution was heat-treated in a firing furnace. In this case, the heat treatment temperature is set in three stages, and plays the role of drying, pyrolysis, firing and crystallization in ascending order. The drying temperature is 120 degrees for 10 minutes, and the baking temperature is 600 degrees for 30 minutes. The thermal decomposition temperature is related to the orientation, and when it is 250 degrees, it is (111) orientation, and when it is 350 degrees, it is (100) orientation. The time was 30 minutes. The heat treatment process is shown in FIG.
[0033]
Subsequently, a PZT film was formed on the orientation control PZT film by the PLAD method using the PLAD apparatus shown in FIG. This apparatus comprises an excimer laser (248 nm KrF) and a film forming apparatus.
In FIG. 3, 11 is a laser, 13 is a deposition chamber, 15 is an entrance window, 17 is a PZT target material, 21 is a substrate, 22 is a substrate heating heater, 23 is an atomic source, and 25 is a fast oxygen beam. is there.
In this apparatus, the oscillated laser light passes through the quartz flange and is irradiated onto the target in the chamber. A plume generated from the target is deposited on the substrate to form a film. As a target material for the PLAD method, a PZT having a stoichiometric composition with 20% excess of lead was used. This is to compensate for lead evaporation in the film formation process. The conditions during film formation are shown in Table 1. Thus, a PZT film of about 0.7 microns could be formed by the film formation for 30 minutes.
Platinum was formed on the upper electrode by magnetron sputtering. The film thickness is 100 nm.
[0034]
[Table 1]
[0035]
The SEM photograph of the surface and the cross section of the film produced by the above method is shown in FIGS. From FIG. 4A, it can be confirmed that spherical particles of about 100 nm are grown on the smooth surface, and that dense and uniform film growth is observed from FIG. 4B.
[0036]
FIG. 5 shows the result of measuring the produced film by the X-ray diffraction method. In FIG. 5, (a) has a thermal decomposition temperature of 400 degrees, and (b) has a temperature of 250 degrees. From this, it can be seen that the ferroelectric film of the present invention can control the crystal orientation by the thermal decomposition temperature.
[0037]
Moreover, the measurement result of the ferroelectric hysteresis curve of various ferroelectric films is shown in FIG. 6A is a PZT ferroelectric film of the present invention, and FIG. 6B is a single-layer PZT ferroelectric film (comparative example) obtained by the PLAD method alone. From FIG. 6, it can be seen that the PZT ferroelectric film of the present invention is about twice as excellent as that of Comparative Example 1.
[0038]
【The invention's effect】
The ferroelectric film according to the present invention has a simple composition but high quality without any slight compositional deviation due to heat treatment, and is dielectric, pyroelectric, piezoelectric, ferroelectric, electro-optical, photovoltaic. Production, which has effective properties such as property, electrostriction, and optical strain, and can procure and manage raw materials at low cost without preparing two or more different materials as film forming materials, and has complicated processes It can be mass-produced at high speed and low cost without going through a membrane process. Further, since the ferroelectric film of the present invention can selectively obtain PZT orientation control layers having different orientations by adjusting the thermal decomposition temperature of the orientation control layer, an actuator, a sensor, It is useful as a memory, controller, transducer, capacitor, optical shutter, optical waveguide, and the like. Further, since it can be a thick film, it can be effectively used as an element such as a sensor or an actuator suitable for MEMS.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a PZT ferroelectric film of the present invention. FIG. 2 is a diagram showing a change in orientation due to heat treatment of an orientation control layer according to the present invention. FIG. 4 is an SEM photograph of the ferroelectric film of the present invention.
FIG. 5 is an X-ray diffraction pattern of the ferroelectric film crystal of the present invention.
Claims (3)
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KR20060072680A (en) * | 2004-12-23 | 2006-06-28 | 주식회사 하이닉스반도체 | Capacitor for semiconductor device and manufacturing method thereof |
JP4978114B2 (en) * | 2006-08-21 | 2012-07-18 | セイコーエプソン株式会社 | Method for manufacturing piezoelectric vibrating piece |
WO2012016374A1 (en) * | 2010-08-03 | 2012-02-09 | Empire Technology Development Llc | Method for identifying objects in video |
JP5736829B2 (en) * | 2011-02-21 | 2015-06-17 | 株式会社リコー | Method for producing electromechanical transducer, electromechanical transducer produced by this production method, ink jet head and ink jet recording apparatus using the same |
JP5644975B2 (en) * | 2011-05-17 | 2014-12-24 | 三菱マテリアル株式会社 | Method for manufacturing PZT ferroelectric thin film |
JP5613910B2 (en) * | 2011-05-17 | 2014-10-29 | 三菱マテリアル株式会社 | Method for manufacturing PZT ferroelectric thin film |
JP5828293B2 (en) * | 2011-05-17 | 2015-12-02 | 三菱マテリアル株式会社 | Method for manufacturing PZT ferroelectric thin film |
JP2013211329A (en) | 2012-03-30 | 2013-10-10 | Mitsubishi Materials Corp | Pzt ferroelectric thin film and method for manufacturing the same |
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