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METHOD FOR PRODUCING FERROELECTRIC FILM, FERROELECTRIC FILM, AND USAGE THEREOF

Foreign code F210010277
File No. (S2019-0399-N0)
Posted date Jan 27, 2021
Country WIPO
International application number 2020JP018031
International publication number WO 2020218617
Date of international filing Apr 27, 2020
Date of international publication Oct 29, 2020
Priority data
  • P2019-086836 (Apr 26, 2019) JP
  • P2019-086840 (Apr 26, 2019) JP
Title METHOD FOR PRODUCING FERROELECTRIC FILM, FERROELECTRIC FILM, AND USAGE THEREOF
Abstract Provided are a method for forming a ferroelectric film of a metal oxide having a fluorite structure at a temperature lower than 300˚C and a ferroelectric film obtained at a low temperature. The present invention provides a method for producing a ferroelectric film containing a crystalline metal oxide having an orthorhombic phase fluorite structure by sputtering a target by a sputtering method while the temperature of a substrate is less than 300˚C so as to deposit a film of a metal oxide capable of forming an orthorhombic phase fluorite structure on the substrate, and ensuring that the thermal history of the resulting film is less than 300˚C or applying an electric field to the film after the deposition or after the thermal history. In addition, the present invention also provides the above ferroelectric film formed on an organic substrate, glass, or metal substrate intended only for low-temperature use, and a ferroelectric element, ferroelectric functional element, or device using the ferroelectric film.
Outline of related art and contending technology BACKGROUND ART
Conventionally, barium titanate BaTiO3 , lead zirconate Pb (Zr , Ti) O3 , (Pb , La) (Zr , Ti) O3 , BiFeO3 and the like have been known as ferroelectric materials. Ferroelectric substance is a kind of dielectric substance, in which electric dipoles are aligned and the direction of the dipoles can be changed by electric field even if there is no electric field outside. Since the ferroelectric substance is a dielectric substance having not only ferroelectricity but also pyroelectricity and piezoelectricity, it is also utilized as a capacitor, electro-optical element, memory element, transistor, pyroelectric element, piezoelectric element, etc. The ferroelectric piezoelectric material is a material in which polarization proportional to pressure appears when pressure is applied to the material, and on the other hand, the material is deformed when an electric field is applied. Piezoelectric bodies are widely used as piezoelectric elements in igniters, sonars, speakers, and the like.
(Non-Patent Document 1,2, etc.), in which ferroelectric properties have been reported in a film using a HfO2-based solid solution material which is a metal oxide having a fluorite type structure of a rectangular crystal phase. To solve the problem that a conventional ferroelectric material is a composite oxide having a perovskite group structure and has a large number of constituent elements of (4 or more and), a large fluctuation in composition and crystal structure, a toxic constituent element is included, a high vapor pressure is included, and composition control is difficult by volatilization is difficult, and the like, and ZrO2 , Since the HfO2-based solid solution material has a fluorite structure and is a simple oxide, the number of constituent elements is small, fluctuation of composition and crystal structure is small, reproducibility is excellent, it is not necessary to use a material toxic to constituent elements, and it is possible to form a film.
As a method for forming the inorganic ferroelectric film, a sputtering method, a sol-gel method, a CVD (Chemical Vapor Deposition) method, PLD (Pulsed Laser Deposition) Method, ALD (Atomic Layer Deposition) Method, hydrothermal synthesis, and the like are known (, for example, Patent Document 1 and Patent Document 2). Of these known methods, an inorganic ferroelectric film cannot be obtained unless deposition is performed at a high temperature of 300 °C. or higher, or annealing is performed at a high temperature of 300 °C. or higher after deposition. Therefore, in addition to the problems of productivity and cost, there is a drawback in that heat resistance is required for a substrate that can be used, and an organic substrate or the like cannot be used. On the other hand, the hydrothermal synthesis method can obtain an inorganic ferroelectric substance at a temperature of 300 °C. or lower, but has problems in that it cannot be used depending on applications because of wet process.
Scope of claims (In Japanese)[請求項1]
 スパッタ法で、基体温度を300℃未満とし、ターゲットをスパッタして、前記基体上に直方晶相の蛍石型構造を有することが可能な金属酸化物の膜を堆積し、その後の前記膜の熱履歴が300℃未満であるか、または、前記堆積後又は前記熱履歴後に前記膜に電界印加することにより、直方晶相の蛍石型構造を有する結晶性の金属酸化物を含む強誘電性膜を製造することを特徴とする強誘電性膜の製造方法。

[請求項2]
 前記金属酸化物の金属が、ハフニウム(Hf)、ジルコニウム(Zr)、セリウム(Ce)又はこれらの2つ以上を含むか、又は、ハフニウム(Hf)、ジルコニウム(Zr)、セリウム(Ce)又はこれらの2つ以上と、アルミニウム(Al),ケイ素(Si)、ストロンチウム(Sr)、バリウム(Ba)及び希土類元素(Sc,Y,La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm.Yb,Lu)から選ばれた少なくとも1種の金属元素とを含むことを特徴とする請求項1に記載の強誘電性膜の製造方法。

[請求項3]
 前記スパッタを、酸素分圧が1%未満の不活性雰囲気中で行うことを特徴とする請求項1又は2に記載の強誘電性膜の製造方法。

[請求項4]
 前記基体が、300℃未満のガラス転移点を有するガラスを含む基体、高分子有機物層を含む基体、300℃未満の軟化温度を有する金属層を含む基体、半導体デバイスの内部のいずれかであることを特徴とする請求項1~3のいずれか一項に記載の強誘電性膜の製造方法。

[請求項5]
 請求項1~4のいずれか一項に記載の製造方法で得られる強誘電性膜。

[請求項6]
 300℃未満のガラス転移点を有するガラスを含む基体、高分子有機物層を含む基体、300℃未満の軟化温度を有する金属層を含む基体のいずれかの基体上に設けられた、直方晶相の蛍石型構造を有する結晶性の金属酸化物を含む強誘電性膜。

[請求項7]
 前記金属酸化物の金属が、ハフニウム(Hf)、ジルコニウム(Zr)、セリウム(Ce)又はこれらの2つ以上を含むか、又は、ハフニウム(Hf)、ジルコニウム(Zr)、セリウム(Ce)又はこれらの2つ以上と、アルミニウム(Al),ケイ素(Si)、ストロンチウム(Sr)、バリウム(Ba)及び希土類元素(Sc,Y,La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm.Yb,Lu)から選ばれた少なくとも1種の金属元素とを含むことを特徴とする請求項5又は6に記載の強誘電性膜。

[請求項8]
 前記基体と前記強誘電性膜の間に導電性の膜層を有することを特徴とする請求項5~7のいずれか一項に記載の強誘電性膜。

[請求項9]
 請求項5~8のいずれか一項に記載の強誘電性膜と、一対の電極を含むことを特徴とする強誘電性機能素子。

[請求項10]
 前記強誘電性機能素子が、キャパシタ、電気光学素子、メモリ素子、トランジスタ、強誘電体データストレージ、圧電素子、焦電素子から選ばれるものであることを特徴とする請求項9に記載の強誘電性機能素子。

[請求項11]
 前記強誘電性機能素子が、アクチュエータ、インクジェットヘッド、ジャオロセンサー、振動発電素子、弾性表面波共振器、膜バルク波共振器、圧電ミラー、圧電センサーのいずれかであることを特徴とする請求項9に記載の圧電性機能性素子。
  • Applicant
  • ※All designated countries except for US in the data before July 2012
  • TOKYO INSTITUTE OF TECHNOLOGY
  • Inventor
  • FUNAKUBO, Hiroshi
  • SHIMIZU, Takao
  • MIMURA, Takanori
  • NAKAMURA, Yoshiko
  • SHIMURA, Reijiro
  • TASHIRO, Yu-ki
IPC(International Patent Classification)
Specified countries National States: AE AG AL AM AO AT AU AZ BA BB BG BH BN BR BW BY BZ CA CH CL CN CO CR CU CZ DE DJ DK DM DO DZ EC EE EG ES FI GB GD GE GH GM GT HN HR HU ID IL IN IR IS JO JP KE KG KH KN KP KR KW KZ LA LC LK LR LS LU LY MA MD ME MG MK MN MW MX MY MZ NA NG NI NO NZ OM PA PE PG PH PL PT QA RO RS RU RW SA SC SD SE SG SK SL ST SV SY TH TJ TM TN TR TT TZ UA UG US UZ VC VN WS ZA ZM ZW
ARIPO: BW GH GM KE LR LS MW MZ NA RW SD SL SZ TZ UG ZM ZW
EAPO: AM AZ BY KG KZ RU TJ TM
EPO: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR
OAPI: BF BJ CF CG CI CM GA GN GQ GW KM ML MR NE SN ST TD TG
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