JP7119265B2 - Method for manufacturing dielectric film - Google Patents
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本発明は、Ｐｂを含まず、Ｂｉ、Ｋ及びＴｉを少なくとも含む液組成物を用いてボイドのない緻密な誘電体膜を製造する方法に関するものである。 The present invention relates to a method for producing a void-free, dense dielectric film using a liquid composition containing at least Bi, K and Ti, but not containing Pb.
従来、(１－ｘ)Ｂｉ0.5Ｎａ0.5ＴｉＯ3－ｘＢｉ0.5Ｋ0.5ＴｉＯ3［ＢＮＴ－ＢＫＴ］薄膜を、ゾルゲル法及び急速アニールにより基板上に堆積する、鉛フリーの強誘電体薄膜の合成方法が開示されている（例えば、非特許文献１参照。）。この強誘電体薄膜を合成するために、(１－ｘ)Ｂｉ0.5Ｎａ0.5ＴｉＯ3－ｘＢｉ0.5Ｋ0.5ＴｉＯ3のｘが０から０．２まで変化する薄膜（ＢＮＴ－ＢＫＴ）を、ゾルゲル法及び急速アニールにより合成した。具体的には、先ず、空気中７０℃で、９９．５％の硝酸ビスマス［Ｂｉ(ＮＯ3)3・５Ｈ2Ｏ］と、９９．５％の硝酸ナトリウム［ＮａＮＯ3］と、９９％の硝酸カリウム［ＫＮＯ3］を酢酸に適量溶解することにより、前駆体溶液を準備した。次いで、空気中の水分による加水分解を防ぐために、アセチルアセトン（９９％）をチタンイソプロポキシド［Ｔｉ(ＯＣ3Ｈ7)4］（９８％、スチームケミカルズ）に添加して安定な溶液を形成した。次に、化学量論量のチタンイソプロポキシド溶液を硝酸塩の溶液に室温で添加した。そして、０．２５モル／ｄｍ3の極性濃度を有する透明で安定な黄色前駆体溶液が得られるまで、混合物を絶えず攪拌した。更に、上記前駆体溶液を、Ｓｉ基板上にＳｉＯ2膜及びＴｉ膜を介して形成されたＰｔ膜上に３０００ｒｐｍの回転速度で２０秒間スピンコートして塗膜を形成した後、塗膜を空気中のホットプレート上で２５０℃に５分間保持して乾燥させた後、酸素雰囲気の急速熱処理装置（ＲＴＰ）中で７００℃に５分間保持して急速アニールした。このプロセス、即ち上記スピンコート、乾燥及び急速アニールを６回繰り返して、厚さ約６００ｎｍの厚膜を得た。 Conventionally, (1-x)Bi 0.5 Na 0.5 TiO 3 -xBi 0.5 K 0.5 TiO 3 [BNT-BKT] thin film is deposited on a substrate by a sol-gel method and rapid annealing in a method for synthesizing a lead-free ferroelectric thin film. is disclosed (see, for example, Non-Patent Document 1). In order to synthesize this ferroelectric thin film, a thin film (BNT-BKT) in which x of (1-x)Bi 0.5 Na 0.5 TiO 3 -xBi 0.5 K 0.5 TiO 3 varies from 0 to 0.2 was prepared by a sol-gel method. and synthesized by rapid annealing. Specifically, first, at 70° C. in air, 99.5% bismuth nitrate [Bi(NO 3 ) 3.5H 2 O], 99.5% sodium nitrate [NaNO 3 ], 99% A precursor solution was prepared by dissolving an appropriate amount of potassium nitrate [KNO 3 ] in acetic acid. Acetylacetone (99%) was then added to titanium isopropoxide [Ti( OC3H7 ) 4 ] ( 98%, Steam Chemicals) to form a stable solution to prevent hydrolysis due to moisture in the air. . A stoichiometric amount of titanium isopropoxide solution was then added to the nitrate solution at room temperature. The mixture was then stirred constantly until a clear, stable yellow precursor solution with a polar concentration of 0.25 mol/dm 3 was obtained. Furthermore, the above precursor solution was spin-coated on a Pt film formed on a Si substrate via a SiO 2 film and a Ti film at a rotation speed of 3000 rpm for 20 seconds to form a coating film. After being dried on a hot plate at 250° C. for 5 minutes, it was rapidly annealed at 700° C. for 5 minutes in a rapid thermal processor (RTP) in an oxygen atmosphere. This process, ie spin coating, drying and rapid annealing, was repeated six times to obtain a thick film with a thickness of about 600 nm.
このように合成された強誘電体薄膜は、Ｐｔ電極上に良好に堆積され、Ｂｉ0.5Ｎａ0.5ＴｉＯ3とＢｉ0.5Ｋ0.5ＴｉＯ3との間のモルフォトロピック相境界（ＭＰＢ）がｘ＝約０．１５で決定され、更にＭＰＢの近くにおいて、薄膜の粒度が最大となり、薄膜の誘電率εが３６０と最大値を示し、薄膜の分極値Ｐｒが１３．８μＣ／ｃｍ2と最大値を示した。 The ferroelectric thin films thus synthesized are well deposited on Pt electrodes and the morphotropic phase boundary (MPB) between Bi 0.5 Na 0.5 TiO 3 and Bi 0.5 K 0.5 TiO 3 is x=˜0. .15, and further near the MPB, the grain size of the thin film is maximized, the dielectric constant ε of the thin film has a maximum value of 360, and the polarization value Pr of the thin film has a maximum value of 13.8 μC/cm 2 . .
しかし、上記従来の非特許文献１に示された強誘電体薄膜の合成方法では、Ｂｉ原料として硝酸ビスマスを用いているため、強誘電体薄膜は緻密であるけれども、前駆体溶液の濡れ性が悪く、強誘電体薄膜に欠陥が発生し易い不具合があった。このため、前駆体溶液の大面積基板へのスピンコーティングによる塗布は困難となる問題点があった。 However, in the ferroelectric thin film synthesis method disclosed in the conventional non-patent document 1, since bismuth nitrate is used as the Bi raw material, the ferroelectric thin film is dense, but the wettability of the precursor solution is poor. Unfortunately, the ferroelectric thin film is prone to defects. Therefore, there is a problem that it is difficult to apply the precursor solution to a large-sized substrate by spin coating.
本発明の目的は、液組成物の基板への濡れ性が良好であり、かつ緻密で欠陥のない誘電体膜が得られる、誘電体膜の製造方法を提供することにある。 SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a dielectric film, in which the wettability of the liquid composition to the substrate is excellent, and a dense and defect-free dielectric film can be obtained.
本発明者らは、２－エチルヘキサン酸ビスマスとカリウム原料を反応させると、熱分解性の悪い液組成物（ゾルゲル液）になる、即ち誘電体膜中にＫが含まれていると、５００℃前後に加熱したときに炭酸塩が生成し易く、炭素鎖も除去され難いことを赤外分光法により確認した。これらの現象は、速度論的に説明が可能であり、安定で熱分解し難い炭酸塩やその他の異相が、ペロブスカイト相の形成前に生成することが主要因であると推測し、昇温速度を変化させる試験を実施したところ、２－エチルヘキサン酸ビスマスを用いて調製した液組成物では、焼成時における５００℃から６００℃までの温度帯を３０℃／秒未満の速度で昇温すると、誘電体膜中に炭酸塩が形成され、ボイドの生成や結晶性の悪化につながることを見出した。換言すると、上記液組成物を用いて緻密で結晶性の良好な誘電体膜を得るには上記温度帯を３０℃／秒以上の速度で昇温することが必要であることを知見して、本発明をなすに至った。 The present inventors have found that when bismuth 2-ethylhexanoate is reacted with a potassium raw material, a liquid composition (sol-gel liquid) with poor thermal decomposition is formed. It was confirmed by infrared spectroscopy that carbonates are likely to form and carbon chains are difficult to remove when heated to around °C. These phenomena can be explained kinetically, and we presume that the main factor is the formation of carbonates and other heterogeneous phases that are stable and difficult to thermally decompose before the formation of the perovskite phase. When the liquid composition prepared using bismuth 2-ethylhexanoate was heated at a rate of less than 30 ° C./sec in the temperature range from 500 ° C. to 600 ° C. during firing, It was found that carbonate is formed in the dielectric film, leading to void formation and deterioration of crystallinity. In other words, having found that it is necessary to raise the temperature in the above temperature range at a rate of 30° C./second or more in order to obtain a dense dielectric film with good crystallinity using the above liquid composition, The inventors have completed the present invention.
本発明の第１の観点は、Ｂｉ、Ｋ及びＴｉを少なくとも含む液組成物を基板上に塗布した塗膜を仮焼成して仮焼成膜を作製しこの仮焼成膜を焼成することにより金属酸化物からなる誘電体膜を製造する方法であって、Ｓｒ及びＺｒを更に含み、Ｂｉの原料が２－エチルヘキサン酸ビスマスであり、前記仮焼成膜の焼成時に５００℃から６００℃までの昇温速度を３０℃／秒以上にすることを特徴とする。 A first aspect of the present invention is to prepare a calcined film by calcining a coating film obtained by applying a liquid composition containing at least Bi, K and Ti on a substrate, and calcining the calcined film to metal oxidation. Further containing Sr and Zr, Bi raw material is bismuth 2-ethylhexanoate, and the temperature is raised from 500° C. to 600° C. during firing of the calcined film. It is characterized by setting the speed to 30° C./second or more.
本発明の第２の観点は、第１の観点に基づく発明であって、更にＮａを更に含むことを特徴とする。 A second aspect of the present invention is an invention based on the first aspect, characterized in that it further contains Na.
本発明の第３の観点は、第１又は第２の観点に基づく発明であって、更に液組成物が一般式：ｙ（ＢｉtＫsＴｉＯ3）－（１－ｙ）（ＳｒmＺｒnＯ3）又はｙ（Ｂｉt（Ｎａ、Ｋ）sＴｉＯ3）－（１－ｙ）（ＳｒmＺｒnＯ3）（但し、０．９≦ｙ≦１、０．４≦ｔ≦０．６、０．４≦ｓ≦０．６、０．９≦ｍ≦１．１、０．９≦ｎ≦１．１）で示される化合物であることを特徴とする。 A third aspect of the present invention is an invention based on the first or second aspect, wherein the liquid composition has the general formula: y(Bit K s TiO 3 )-(1- y )(Sr m Zr n O 3 ) or y(Bit (Na, K) s TiO 3 )-(1- y ) (Sr m Zr n O 3 ) (where 0.9≤y≤1, 0.4≤t≤0 .6, 0.4≤s≤0.6, 0.9≤m≤1.1, 0.9≤n≤1.1).
本発明の第１の観点の誘電体膜の製造方法では、Ｂｉの原料として２－エチルヘキサン酸ビスマスを用いたので、液組成物の基板への濡れ性が良好である。また、仮焼成膜の焼成時に５００℃から６００℃までの昇温速度を３０℃／秒以上にしたので、安定で熱分解し難い炭酸塩やその他の異相が、ペロブスカイト相の形成前に生成しない。この結果、誘電体膜中に炭酸塩が形成されないので、誘電体膜中にボイドが生成されず、誘電体膜の結晶性が良好になり、緻密で欠陥のない誘電体膜が得られる。
また、本発明の第１の観点の誘電体膜の製造方法では、Ｓｒ及びＺｒを更に含むので、より高い圧電特性を得ることができるという特長がある。
In the method for producing a dielectric film according to the first aspect of the present invention, bismuth 2-ethylhexanoate is used as the Bi raw material, so that the wettability of the liquid composition to the substrate is excellent. In addition, since the rate of temperature increase from 500° C. to 600° C. is set to 30° C./second or more during firing of the calcined film, carbonates that are stable and difficult to thermally decompose and other heterophases do not form before the perovskite phase is formed. . As a result, since carbonate is not formed in the dielectric film, voids are not generated in the dielectric film, the crystallinity of the dielectric film is improved, and a dense and defect-free dielectric film is obtained.
In addition, the method for manufacturing a dielectric film according to the first aspect of the present invention further contains Sr and Zr, so that it is possible to obtain higher piezoelectric properties.
本発明の第２の観点の誘電体膜の製造方法では、Ｎａを更に含むので、より高い圧電特性を得ることができるという特長がある。 In the method of manufacturing a dielectric film according to the second aspect of the present invention, since Na is further included, there is a feature that higher piezoelectric properties can be obtained.
本発明の第３の観点の誘電体膜の製造方法では、液組成物が一般式：ｙ（ＢｉtＫsＴｉＯ3）－（１－ｙ）（ＳｒmＺｒnＯ3）又はｙ（Ｂｉt（Ｎａ、Ｋ）sＴｉＯ3）－（１－ｙ）（ＳｒmＺｒnＯ3）（但し、０．９≦ｙ≦１、０．４≦ｔ≦０．６、０．４≦ｓ≦０．６、０．９≦ｍ≦１．１、０．９≦ｎ≦１．１）で示される化合物であり、非鉛であるので、鉛系材料の誘電体膜と比較して環境負荷が小さいという特長がある。
In the method for producing a dielectric film according to the third aspect of the present invention, the liquid composition has the general formula: y(Bi t K s TiO 3 )-(1-y)(Sr m Zr n O 3 ) or y(Bi t (Na, K) s TiO 3 )-(1-y)(Sr m Zr n O 3 ) (where 0.9≦y≦1, 0.4≦t≦0.6, 0.4≦s ≤ 0.6, 0.9 ≤ m ≤ 1.1, 0.9 ≤ n ≤ 1.1). It has the advantage of light load.
次に本発明を実施するための形態を説明する。本実施の形態の誘電体膜を製造するための液組成物は、Ｂｉ、Ｋ及びＴｉを少なくとも含む。この液組成物は、一般式：ＢｉxＫ1-xＴｉＯ3（０．４≦ｘ≦０．６）で示される化合物であることが好ましい。ここで、上記一般式において、ｘを０．４≦ｘ≦０．６の範囲内に限定したのは、０．４未満では化学量論比からのずれが大き過ぎるため十分な電気特性が得られず、０．６を超えると十分な電気特性が得られないからである。また、上記金属元素の他にＮａを更に含んでもよい。更に、上記金属元素の他に、Ｎａとともに、Ｓｒ及びＺｒを更に含んでもよく、或いはＮａを含まずに、Ｓｒ及びＺｒを更に含んでもよい。ここで、Ｎａを更に含むと、より高い圧電特性が得られるという利点があり、Ｓｒ及びＺｒを更に含むと、より高い圧電特性が得られるという利点がある。Ｎａを更に含む液組成物は、一般式：Ｂｉx（ＮａyＫ1-y）1-xＴｉＯ3（０．４≦ｘ≦０．６、０．１≦ｙ≦０．９）で示される化合物であることが好ましい。ここで、ｘを０．４≦ｘ≦０．６の範囲内に限定したのは、０．４未満では化学量論比からのずれが大き過ぎるため十分な電気特性が得られず、０．６を超えると十分な電気特性が得られないからである。また、ｙを０．１≦ｙ≦０．９の範囲内に限定したのは、０．１未満又は０．９を超えると十分な圧電特性が得られないからである。一方、Ｎａとともに、Ｓｒ及びＺｒを更に含む液組成物は、一般式：ｙ（ＢｉtＫsＴｉＯ3）－（１－ｙ）（ＳｒmＺｒnＯ3）又はｙ（Ｂｉt（Ｎａ、Ｋ）sＴｉＯ3）－（１－ｙ）（ＳｒmＺｒnＯ3）（但し、０．９≦ｙ≦１、０．４≦ｔ≦０．６、０．４≦ｓ≦０．６、０．９≦ｍ≦１．１、０．９≦ｎ≦１．１）で示される化合物であることが好ましい。ここで、ｙ、ｔ、ｓ、ｍ、ｎを０．９≦ｙ≦１、０．４≦ｔ≦０．６、０．４≦ｓ≦０．６、０．９≦ｍ≦１．１、０．９≦ｎ≦１．１の範囲内に限定したのは、十分な圧電定数を得るにはこの範囲内の組成で膜を形成する必要があるからである。 Next, a mode for carrying out the present invention will be described. The liquid composition for manufacturing the dielectric film of this embodiment contains at least Bi, K and Ti. This liquid composition is preferably a compound represented by the general formula: Bi x K 1-x TiO 3 (0.4≦x≦0.6). Here, in the above general formula, x is limited to the range of 0.4 ≤ x ≤ 0.6. This is because if the value exceeds 0.6, sufficient electrical characteristics cannot be obtained. Further, Na may be further included in addition to the above metal elements. Furthermore, in addition to the above metal elements, it may further contain Sr and Zr together with Na, or may further contain Sr and Zr without containing Na. Further containing Na has the advantage of obtaining higher piezoelectric properties, and further containing Sr and Zr has the advantage of obtaining higher piezoelectric properties. The liquid composition further containing Na is represented by the general formula: Bix(NayK1 -y ) 1- xTiO3 ( 0.4≤x≤0.6 , 0.1≤y≤0.9). It is preferably a compound that can be Here, the reason why x is limited to the range of 0.4≦x≦0.6 is that if it is less than 0.4, the deviation from the stoichiometric ratio is too large, and sufficient electrical characteristics cannot be obtained. This is because if it exceeds 6, sufficient electrical characteristics cannot be obtained. The reason why y is limited to the range of 0.1≦y≦0.9 is that if it is less than 0.1 or exceeds 0.9, sufficient piezoelectric characteristics cannot be obtained. On the other hand, the liquid composition further containing Sr and Zr together with Na has the general formula: y(Bi t K s TiO 3 )-(1-y)(Sr m Zr n O 3 ) or y(Bi t (Na, K) s TiO 3 )-(1-y)(Sr m Zr n O 3 ) (where 0.9≦y≦1, 0.4≦t≦0.6, 0.4≦s≦0.6 , 0.9≦m≦1.1, 0.9≦n≦1.1). Here, y, t, s, m, and n are 0.9≤y≤1, 0.4≤t≤0.6, 0.4≤s≤0.6, 0.9≤m≤1.1. , 0.9≦n≦1.1 because the film must be formed with a composition within this range in order to obtain a sufficient piezoelectric constant.
Ｂｉの原料としては、２-エチルヘキサン酸ビスマスが用いられる。ここで、Ｂｉの原料として２－エチルヘキサン酸ビスマスを用いたのは、液組成物の基板への濡れ性を良好にするためである。Ｋの原料としては、酢酸カリウム、２－エチルヘキサン酸カリウム、カリウムエトキシド、カリウムターシャリーブトキシド等が挙げられる。また、Ｔｉ原料としては、チタンテトラエトキシド：Ｔｉ(ＯＥｔ）4、チタンテトライソプロポキシド：Ｔｉ(ＯｉＰｒ）4、チタンテトラｎ－ブトキシド：Ｔｉ(ＯｉＢｕ）4、チタンテトライソブトキシド：Ｔｉ(ＯｉＢｕ）4、チタンテトラｔ－ブトキシド：Ｔｉ(ＯｔＢｕ）4、チタンジメトキシジイソプロポキシド：Ｔｉ(ＯＭｅ）2(ＯｉＰｒ）2等が挙げられる。更に、Ｎａ原料としては、ナトリウムメトキシド：Ｎａ2(ＯＭｅ）、ナトリウムエトキシド：Ｎａ2(ＯＥｔ）、ナトリウムｔ－ブトキシド：Ｎａ2(ＯｔＢｕ）等が挙げられる。 As a raw material for Bi, bismuth 2-ethylhexanoate is used. Here, the reason why bismuth 2-ethylhexanoate was used as the raw material of Bi is to improve the wettability of the liquid composition to the substrate. Raw materials for K include potassium acetate, potassium 2-ethylhexanoate, potassium ethoxide, potassium tertiary butoxide and the like. Ti raw materials include titanium tetraethoxide: Ti(OEt) 4 , titanium tetraisopropoxide: Ti(OiPr) 4 , titanium tetra-n-butoxide: Ti(OiBu) 4 , titanium tetraisobutoxide: Ti(OiBu). ) 4 , titanium tetra-t-butoxide: Ti(OtBu) 4 , titanium dimethoxydiisopropoxide: Ti(OMe) 2 (OiPr) 2 and the like. Furthermore, Na raw materials include sodium methoxide: Na 2 (OMe), sodium ethoxide: Na 2 (OEt), sodium t-butoxide: Na 2 (OtBu), and the like.
このように構成された液組成物の調製方法を説明する。
（１） Ｂｉ、Ｋ及びＴｉを含む誘電体膜、又はＢｉ、Ｎａ、Ｋ及びＴｉを含む誘電体膜を作製する場合
Ｂｉ、Ｋ及びＴｉを含む誘電体膜、又はＢｉ、Ｎａ、Ｋ及びＴｉを含む誘電体膜を作製するために、液組成物の調製プロセス中の揮発分を補填して、即ちＢｉ及びＫ、又はＢｉ、Ｎａ及びＫをある程度過剰に添加して液組成物を合成する。先ず、Ｔｉ原料とアセチルアセトン、エタノール、１－ブタノール等の溶媒を所定の割合で混合し、８０℃～１６０℃で３０分間～１８０分間還流を行って第１混合液を調製する。次いで、この第１混合液に、エタノール、１－ブタノール、酢酸等の溶媒と、酢酸カリウム（Ｋ原料）と、ナトリウムエトキシド（Ｎａ原料）を混合し、８０℃～１６０℃で３０分間～１８０分間還流を行って第２混合液を調製する。次に、この第２混合液に２－エチルヘキサン酸ビスマス（Ｂｉ原料）を加え、８０℃～１６０℃で３０分間～１８０分間還流を行って第３混合液を調製した後、この第３混合液を８０℃～１６０℃で加熱しながら減圧を行い、第３混合液中の溶媒を半分程度除去する。更に、この第３混合液を１－プロパノール、エタノール、１－ブタノール等の溶媒で希釈し、酸化物濃度で５質量％～１０質量％まで希釈して液組成物を得る。ここで、酸化物濃度とは、液組成物に含まれている金属元素が全て安定な酸化物になったと仮定したときの濃度である。即ち、液組成物中に存在する金属元素Ｂｉ、Ｎａ、Ｋ及びＴｉが、それぞれＢｉ2Ｏ3、Ｎａ2Ｏ、Ｋ2Ｏ、ＴｉＯ2であると仮定したときの濃度である。
A method for preparing the liquid composition thus constituted will be described.
(1) When manufacturing a dielectric film containing Bi, K and Ti, or a dielectric film containing Bi, Na, K and Ti Dielectric film containing Bi, K and Ti, or Bi, Na, K and Ti In order to make a dielectric film containing . First, a Ti raw material and a solvent such as acetylacetone, ethanol, or 1-butanol are mixed at a predetermined ratio, and refluxed at 80° C. to 160° C. for 30 minutes to 180 minutes to prepare a first mixed solution. Next, a solvent such as ethanol, 1-butanol, or acetic acid, potassium acetate (K raw material), and sodium ethoxide (Na raw material) are mixed with this first mixed liquid, and the mixture is heated at 80° C. to 160° C. for 30 minutes to 180° C. Reflux for 1 minute to prepare a second mixture. Next, bismuth 2-ethylhexanoate (Bi raw material) is added to this second mixed liquid and refluxed at 80° C. to 160° C. for 30 minutes to 180 minutes to prepare a third mixed liquid. The pressure is reduced while heating the liquid at 80° C. to 160° C. to remove about half of the solvent in the third mixed liquid. Further, this third mixed solution is diluted with a solvent such as 1-propanol, ethanol, 1-butanol, etc. to obtain a liquid composition by diluting the oxide concentration to 5% by mass to 10% by mass. Here, the oxide concentration is the concentration when all metal elements contained in the liquid composition are assumed to be stable oxides. That is, it is the concentration when the metal elements Bi, Na, K and Ti present in the liquid composition are assumed to be Bi 2 O 3 , Na 2 O, K 2 O and TiO 2 , respectively.
（２） Ｂｉ、Ｎａ、Ｋ及びＴｉに、Ｓｒ及びＺｒを更に含む誘電体膜を作製する場合
先ず、ナトリウムエトキシド、ナトリウムターシャリーブトキシド等のＮａ原料と、カリウムエトキシド、カリウムターシャリーブトキシド等のＫ原料と、エタノール、メタノール等の溶媒とを所定の割合で混合して、室温で３０分間～６０分間撹拌することにより懸濁液を調製する。次いで、この懸濁液に、テトラチタンイソプロポキシド、テトラチタンブトキシド等のＴｉ原料と、ジルコニウムブトキシド等のＺｒ原料とを添加し、３０分間～６０分間還流を行って第１混合液を調製する。この第１混合液に、２－エチルヘキサン酸ビスマス等のＢｉ原料と、酢酸ストロンチウム０．５水和物、硝酸ストロンチウム等のＳｒ原料と、プロピレングリコール、エチレングリコール等のジオールを添加し、３０分間～６０分間還流を行って第２混合液を調製する。次に、この第２混合液にアセチルアセトン等の安定化剤を添加し、３０分間～６０分間還流を行って第３混合液を調製する。この第３混合液から溶媒を脱離して、エタノール等の溶媒及び反応副生成物を除去した後、プロピレングリコール、エチレングリコール等のジオールを添加し、酸化物換算で８質量％～１２質量％まで希釈する。更に、この希釈した液に、２－ジメチルアミノエタノール、１－エタノールアミン等の安定化剤を、Ｔｉ：安定化剤がモル比で１：１となるように添加し、続けて１－ブタノール、エタノール等で液を酸化物換算で４質量％～１０質量％まで希釈した後、得られた液をフィルタでろ過することによりゴミを取除いて、液組成物を得る。
(2) In the case of producing a dielectric film further containing Sr and Zr in addition to Bi, Na, K and Ti First, Na raw materials such as sodium ethoxide and sodium tertiary butoxide, potassium ethoxide, potassium tertiary butoxide and the like are prepared. and a solvent such as ethanol or methanol are mixed in a predetermined ratio and stirred at room temperature for 30 to 60 minutes to prepare a suspension. Next, a Ti raw material such as tetratitanium isopropoxide and tetratitanium butoxide and a Zr raw material such as zirconium butoxide are added to this suspension, and refluxed for 30 to 60 minutes to prepare a first mixed liquid. . A Bi raw material such as bismuth 2-ethylhexanoate, an Sr raw material such as strontium acetate pentahydrate and strontium nitrate, and a diol such as propylene glycol and ethylene glycol are added to the first mixed solution, and the mixture is stirred for 30 minutes. Reflux for ~60 minutes to prepare a second mixture. Next, a stabilizing agent such as acetylacetone is added to the second mixture, and the mixture is refluxed for 30 to 60 minutes to prepare a third mixture. After desorbing the solvent from this third mixture to remove the solvent such as ethanol and the reaction by-products, a diol such as propylene glycol or ethylene glycol is added, and the content is reduced to 8% by mass to 12% by mass in terms of oxide. Dilute. Furthermore, a stabilizer such as 2-dimethylaminoethanol or 1-ethanolamine is added to the diluted solution so that the molar ratio of Ti:stabilizer is 1:1, followed by 1-butanol, After diluting the liquid with ethanol or the like to 4% by mass to 10% by mass in terms of oxides, the resulting liquid is filtered to remove dust to obtain a liquid composition.
一方、上記液組成物を塗布するために、例えばＰｔ電極付きシリコンウェーハを用意する。具体的には、先ず、シリコンウェーハ表面に厚さ１００ｎｍ～５００ｎｍの熱酸化膜を形成する。次に、この熱酸化膜上にスパッタリング法により厚さ１０ｎｍ～３０ｎｍのＴｉ膜を形成した後、酸素雰囲気中で赤外線急速加熱装置（ＲＴＡ）により７００℃～８００℃の温度に１分間～３分間保持して焼成することによりＴｉＯｘ膜を形成する。更に、ＴｉＯｘ膜上に厚さ１００ｎｍ～２００ｎｍのＰｔ電極を形成して、Ｐｔ電極付きシリコンウェーハを得る。 On the other hand, for example, a silicon wafer with a Pt electrode is prepared in order to apply the liquid composition. Specifically, first, a thermal oxide film having a thickness of 100 nm to 500 nm is formed on the silicon wafer surface. Next, after forming a Ti film with a thickness of 10 nm to 30 nm on this thermal oxide film by a sputtering method, it is heated to a temperature of 700° C. to 800° C. for 1 minute to 3 minutes by an infrared rapid heating apparatus (RTA) in an oxygen atmosphere. A TiOx film is formed by holding and baking. Furthermore, a Pt electrode with a thickness of 100 nm to 200 nm is formed on the TiOx film to obtain a silicon wafer with a Pt electrode.
上記液組成物を用いてＰｔ電極付きシリコンウェーハ上に誘電体膜を作製する方法を説明する。先ず、液組成物をメンブレンフィルタでろ過した後、この液組成物を２０００ｒｐｍ～３０００ｒｐｍの速度でスピンコーティングを行って、Ｐｔ電極付きウェーハ上に塗膜を形成する。ここで、液組成物のＢｉの原料として２－エチルヘキサン酸ビスマスを用いたので、液組成物の基板への濡れ性が良好である。次に、この塗膜をホットプレート等の加熱装置により３００℃～４００℃の温度に３分間～１０分間保持して仮焼成することにより、厚さ約５０ｎｍ～１００ｎｍの仮焼成膜を作製する。この操作を複数回繰り返して厚さ１００ｎｍ～２００ｎｍの仮焼成膜を得る。ここで、塗膜の仮焼成温度を３００℃～４００℃の範囲内に限定したのは、３００℃未満では脱脂が不十分であり誘電体膜中に炭素が残り易く、４００℃を超えると精密な温度制御が難しく均質な誘電体膜を得ることが困難になるからである。塗膜の仮焼成時間を３分間～１０分間の範囲内に限定したのは、３分間未満では脱脂が不十分であり誘電体膜中に炭素が残り易く、１０分間を超えると生産性が悪いからである。また、１回の仮焼成により形成された仮焼成膜の厚さを５０ｎｍ～１００ｎｍの範囲内に限定したのは、５０ｎｍ未満では生産性が悪く、１００ｎｍを超えるとクラックが発生し易くなるからである。更に、複数回の仮焼成を繰り返した後の仮焼成膜の厚さを１００ｎｍ～２００ｎｍの範囲内に限定したのは、１００ｎｍ未満では生産性が悪いという不具合があり、２００ｎｍを超えるとクラックが発生し易いという不具合があるからである。 A method of forming a dielectric film on a silicon wafer with a Pt electrode using the liquid composition will be described. First, after the liquid composition is filtered through a membrane filter, the liquid composition is spin-coated at a speed of 2000 rpm to 3000 rpm to form a coating film on a wafer with a Pt electrode. Here, since bismuth 2-ethylhexanoate was used as a raw material of Bi in the liquid composition, the wettability of the liquid composition to the substrate is excellent. Next, this coating film is calcined by holding it at a temperature of 300° C. to 400° C. for 3 to 10 minutes using a heating device such as a hot plate to prepare a calcined film having a thickness of about 50 nm to 100 nm. This operation is repeated several times to obtain a calcined film with a thickness of 100 nm to 200 nm. Here, the reason why the calcination temperature of the coating film is limited to the range of 300° C. to 400° C. is that if it is less than 300° C., degreasing is insufficient and carbon tends to remain in the dielectric film, and if it exceeds 400° C. This is because it is difficult to obtain a homogeneous dielectric film due to the difficulty of proper temperature control. The reason why the temporary baking time of the coating film is limited to the range of 3 minutes to 10 minutes is that if it is less than 3 minutes, degreasing is insufficient and carbon tends to remain in the dielectric film, and if it exceeds 10 minutes, productivity is poor. It is from. The reason why the thickness of the calcined film formed by one calcination is limited to within the range of 50 nm to 100 nm is that if it is less than 50 nm, the productivity is poor, and if it exceeds 100 nm, cracks are likely to occur. be. Furthermore, the reason why the thickness of the calcined film after repeated calcinations is limited to within the range of 100 nm to 200 nm is that if it is less than 100 nm, the productivity is poor, and if it exceeds 200 nm, cracks occur. This is because there is a problem that it is easy to
更に、表面に仮焼成膜が形成されたウェーハを酸素雰囲気中でＲＴＡにより室温から６５０℃～８００℃の範囲内の所定温度まで昇温して、この温度に所定時間保持する。詳しくは、室温から５００℃まで１０℃／秒～１００℃／秒の速度で昇温し、本発明の特徴ある温度範囲である５００℃から６００℃まで３０℃／秒以上の速度で昇温した後、６００℃から６５０℃～８００℃の範囲内の所定温度まで１０℃／秒～１００℃／秒の速度で昇温し、６５０℃～８００℃の範囲内の所定温度に１分間～１０分間の範囲内の所定時間保持することにより、ウェーハ表面に誘電体膜を作製する。ここで、仮焼成膜の焼成時の昇温速度のうち５００℃から６００℃までの昇温速度を３０℃／秒以上に限定したのは、３０℃／秒未満では速度論的に炭酸塩の生成が優勢になり、誘電体膜がポーラスになってしまうからである。５００℃から６００℃までの昇温速度は、速ければ速いほど良いが、１００℃／秒以上の出力を有するＲＴＡでは、装置コストが高くなるため、１００℃／秒以下であることが好ましい。また、室温から５００℃までの昇温速度を１０℃／秒～１００℃／秒の範囲内に広く設定し、６００℃から６５０℃～８００℃の範囲内の所定温度までの昇温速度を１０℃／秒～１００℃／秒の範囲内に広く設定したのは、特に限定する必要がないためであり、昇温速度の制御性等を考慮すると、本発明の特徴ある温度範囲である５００℃から６００℃までの昇温速度と同一にした方が好ましい。また、仮焼成膜の焼成温度を６５０℃～８００℃の範囲内の所定温度に限定したのは、６５０℃未満では十分に結晶化が進行せず、８００℃を超えると下部電極が劣化してしまうからである。更に、仮焼成膜の焼成時間を３分間～１０分間の範囲内の所定時間に限定したのは、３分間未満では十分な脱脂を行うことができず誘電体膜中に炭素が残り易く、１０分間を超えると生産性が悪いからである。 Further, the wafer having the calcined film formed on its surface is heated to a predetermined temperature within the range of room temperature to 650° C. to 800° C. by RTA in an oxygen atmosphere, and held at this temperature for a predetermined period of time. Specifically, the temperature was raised from room temperature to 500° C. at a rate of 10° C./sec to 100° C./sec, and then from 500° C. to 600° C., which is the characteristic temperature range of the present invention, at a rate of 30° C./sec or more. After that, the temperature is raised from 600° C. to a predetermined temperature in the range of 650° C. to 800° C. at a rate of 10° C./second to 100° C./second, and the predetermined temperature in the range of 650° C. to 800° C. is reached for 1 minute to 10 minutes. A dielectric film is formed on the wafer surface by holding for a predetermined time within the range of . Here, the reason why the temperature increase rate from 500° C. to 600° C. is limited to 30° C./sec or more among the temperature increase rates during firing of the calcined film is that if the temperature is less than 30° C./sec, the kinetics of carbonate increases. This is because the generation becomes dominant and the dielectric film becomes porous. The faster the rate of temperature rise from 500° C. to 600° C., the better. However, RTA having an output of 100° C./second or more increases the equipment cost, so it is preferably 100° C./second or less. In addition, the rate of temperature increase from room temperature to 500°C is set widely within the range of 10°C/sec to 100°C/sec, and the rate of temperature increase from 600°C to a predetermined temperature within the range of 650°C to 800°C is set to 10°C. The reason why the temperature is set widely within the range of ° C./sec to 100 ° C./sec is that there is no need to limit it. to 600° C. is preferably the same. The firing temperature of the calcined film is limited to a predetermined temperature in the range of 650° C. to 800° C. The reason is that crystallization does not proceed sufficiently below 650° C., and the lower electrode deteriorates if it exceeds 800° C. Because it will be stored away. Furthermore, the reason why the firing time of the calcined film is limited to a predetermined time in the range of 3 minutes to 10 minutes is that if it is less than 3 minutes, sufficient degreasing cannot be performed and carbon tends to remain in the dielectric film. This is because if the time exceeds one minute, the productivity is poor.
このように作製された誘電体膜では、仮焼成膜の焼成時に５００℃から６００℃までの昇温速度を３０℃／秒以上にしたので、安定で熱分解し難い炭酸塩やその他の異相が、ペロブスカイト相の形成前に生成しない。この結果、誘電体膜中に炭酸塩が形成されないので、誘電体膜中にボイドが生成されず、誘電体膜の結晶性が良好になり、緻密で欠陥のない誘電体膜が得られる。 In the dielectric film thus produced, since the rate of temperature increase from 500° C. to 600° C. was set to 30° C./second or more during firing of the pre-fired film, stable and hard to thermally decompose carbonates and other different phases were generated. , does not form before the formation of the perovskite phase. As a result, since carbonate is not formed in the dielectric film, voids are not generated in the dielectric film, the crystallinity of the dielectric film is improved, and a dense and defect-free dielectric film is obtained.
次に本発明の実施例を比較例とともに詳しく説明する。 Next, examples of the present invention will be described in detail together with comparative examples.
＜実施例１＞
Ｂｉ、Ｎａ、Ｋ及びＴｉを含む誘電体膜を作製するために、プロセス中の揮発分を補填して、即ちＢｉを８質量％、Ｎａ及びＫを１６質量％過剰に添加して、Ｂｉ0.54(Ｎａ0.8Ｋ0.2)0.58ＴｉＯ3となるように液組成物を合成した。具体的には、先ず、チタンイソプロポキシド（Ｔｉ原料）とアセチルアセトンをモル比で１：２として混合し、１５０℃で３０分間還流を行って第１混合液を調製した。次いで、この第１混合液に、エタノール、酢酸カリウム（Ｋ原料）及びナトリウムエトキシド（Ｎａ原料）を混合し、１５０℃で３０分間還流を行って第２混合液を調製した。次に、この第２混合液に２－エチルヘキサン酸ビスマス（Ｂｉ原料）を加え、１５０℃で３０分間還流を行って第３混合液を調製した後、この第３混合液を１５０℃で加熱しながら減圧を行い、第３混合液中のエタノールを半分除去した。更に、この第３混合液を１－プロパノールで希釈し、酸化物濃度で８質量％まで希釈して液組成物を得た。ここで、酸化物濃度とは、液組成物に含まれている金属元素が全て安定な酸化物になったと仮定したときの濃度である。即ち、液組成物中に存在する金属元素Ｂｉ、Ｎａ、Ｋ及びＴｉが、それぞれＢｉ2Ｏ3、Ｎａ2Ｏ、Ｋ2Ｏ、ＴｉＯ2であると仮定したときの濃度である。
<Example 1>
In order to make a dielectric film containing Bi, Na, K and Ti, the volatiles in the process were compensated, i.e. 8% by weight of Bi and 16% by weight of Na and K were added in excess to obtain Bi 0.54 A liquid composition was synthesized so as to be (Na 0.8 K 0.2 ) 0.58 TiO 3 . Specifically, first, titanium isopropoxide (Ti raw material) and acetylacetone were mixed at a molar ratio of 1:2, and refluxed at 150° C. for 30 minutes to prepare a first mixed solution. Next, ethanol, potassium acetate (K raw material) and sodium ethoxide (Na raw material) were mixed with this first mixed liquid, and refluxed at 150° C. for 30 minutes to prepare a second mixed liquid. Next, bismuth 2-ethylhexanoate (Bi raw material) is added to this second mixed liquid and refluxed at 150° C. for 30 minutes to prepare a third mixed liquid, and then this third mixed liquid is heated at 150° C. While reducing the pressure, half of the ethanol in the third mixture was removed. Furthermore, this third mixture was diluted with 1-propanol to an oxide concentration of 8% by mass to obtain a liquid composition. Here, the oxide concentration is the concentration when all metal elements contained in the liquid composition are assumed to be stable oxides. That is, it is the concentration when the metal elements Bi, Na, K and Ti present in the liquid composition are assumed to be Bi 2 O 3 , Na 2 O, K 2 O and TiO 2 , respectively.
一方、上記液組成物を塗布するためのＰｔ電極付きシリコンウェーハを用意した。具体的には、先ず、直径４インチのシリコンウェーハ表面に厚さ５００ｎｍの熱酸化膜を形成した。次に、この熱酸化膜上にスパッタリング法により厚さ２０ｎｍのＴｉ膜を形成した後、酸素雰囲気中で赤外線急速加熱装置（ＲＴＡ）により７００℃の温度に１分間保持して焼成することによりＴｉＯ2膜を形成した。更に、ＴｉＯ2膜上に厚さ２００ｎｍのＰｔ電極を形成して、Ｐｔ電極付きシリコンウェーハを得た。 On the other hand, a silicon wafer with a Pt electrode was prepared for coating the liquid composition. Specifically, first, a thermal oxide film with a thickness of 500 nm was formed on the surface of a silicon wafer with a diameter of 4 inches. Next, after forming a Ti film with a thickness of 20 nm on this thermal oxide film by a sputtering method, the TiO film was fired by holding at a temperature of 700° C. for 1 minute in an oxygen atmosphere with an infrared rapid heating apparatus (RTA). 2 films were formed. Furthermore, a Pt electrode with a thickness of 200 nm was formed on the TiO 2 film to obtain a silicon wafer with a Pt electrode.
そして、上記液組成物をメンブレンフィルタでろ過した後、この液組成物を３０００ｒｐｍの速度でスピンコーティングを行って、Ｐｔ電極付きウェーハ上に塗膜を形成した。スピンコーティング時の滴下時間は３０秒とした。次に、この塗膜をホットプレートにより３５０℃の温度に５分間保持して仮焼成することにより、厚さ約６７ｎｍの仮焼成膜を作製した。この操作を３回繰り返して厚さ約２００ｎｍの仮焼成膜を得た。更に、表面に仮焼成膜が形成されたウェーハを酸素雰囲気中でＲＴＡにより室温から７００℃まで５０℃／秒の速度で昇温した後、７００℃に１分間保持することにより、ウェーハ表面に誘電体膜を作製した。この誘電体膜を実施例１とした。 After the liquid composition was filtered through a membrane filter, the liquid composition was spin-coated at a speed of 3000 rpm to form a coating film on the wafer with the Pt electrode. The dropping time during spin coating was 30 seconds. Next, this coating film was calcined by holding it at a temperature of 350° C. for 5 minutes on a hot plate to prepare a calcined film having a thickness of about 67 nm. This operation was repeated three times to obtain a calcined film having a thickness of about 200 nm. Further, the wafer having the calcined film formed on its surface was heated from room temperature to 700° C. at a rate of 50° C./sec by RTA in an oxygen atmosphere, and then held at 700° C. for 1 minute to obtain a dielectric film on the wafer surface. A body membrane was prepared. This dielectric film was designated as Example 1.
＜実施例２～７及び比較例１～５＞
実施例２～７及び比較例１～５は、Ｂｉ原料として表１に示す原料を用い、Ｂｉ、Ｎａ、Ｋ及びＴｉの金属原子比が表１に示す金属原子比になるように各原料を配合して、液組成物をそれぞれ調製し、仮焼成膜の焼成時の昇温速度を表１に示す値としたこと以外は、実施例１と同様にして誘電体膜を作製した。
<Examples 2 to 7 and Comparative Examples 1 to 5>
In Examples 2 to 7 and Comparative Examples 1 to 5, the raw materials shown in Table 1 were used as Bi raw materials, and each raw material was used so that the metal atomic ratios of Bi, Na, K, and Ti were the metal atomic ratios shown in Table 1. A dielectric film was produced in the same manner as in Example 1, except that the rate of temperature rise during firing of the calcined film was set to the value shown in Table 1.
＜実施例８＞
先ず、フラスコに、エタノール（溶媒）と、ナトリウムエトキシド（Ｎａ原料）と、カリウムエトキシド（Ｋ原料）とを入れ、室温で３０分間撹拌することにより赤褐色の懸濁液を得た。次いで、この懸濁液にテトラチタンイソプロポキシド（Ｔｉ原料）と、ジルコニウムブトキシド（Ｚｒ原料）とを添加し、３０分間還流を行って第１混合液を調製した。この第１混合液に、２－エチルヘキサン酸ビスマス（Ｂｉ原料）と、酢酸ストロンチウム０．５水和物（Ｓｒ原料）と、プロピレングリコール（ジオール）とを添加し、３０分間還流を行って第２混合液を調製した。次に、この第２混合液にアセチルアセトン（安定化剤）を添加し、３０分間還流を行って第３混合液を調製した。この第３混合液から溶媒を脱離して、エタノール（溶媒）及び反応副生成物を除去した後、プロピレングリコール（ジオール）を添加し、酸化物換算で１５質量％まで希釈した。更に、この希釈した液に安定化剤として２－ジメチルアミノエタノールを、Ｔｉ：安定化剤がモル比で１：１となるように添加し、続けて１－ブタノールで液を酸化物換算で８質量％まで希釈した後、得られた液をフィルタでろ過することによりゴミを取除いて、液組成物を得た。そして、この液組成物を用いて、実施例１と同様の方法で誘電体膜を作製した。この誘電体膜を実施例８とした。
<Example 8>
First, ethanol (solvent), sodium ethoxide (Na raw material), and potassium ethoxide (K raw material) were placed in a flask and stirred at room temperature for 30 minutes to obtain a reddish brown suspension. Next, tetratitanium isopropoxide (Ti raw material) and zirconium butoxide (Zr raw material) were added to this suspension, and the mixture was refluxed for 30 minutes to prepare a first mixed liquid. Bismuth 2-ethylhexanoate (Bi raw material), strontium acetate 0.5 hydrate (Sr raw material), and propylene glycol (diol) were added to the first mixed solution, and refluxed for 30 minutes. 2 mixtures were prepared. Next, acetylacetone (stabilizer) was added to this second mixed liquid and refluxed for 30 minutes to prepare a third mixed liquid. After desorbing the solvent from this third mixture to remove ethanol (solvent) and reaction by-products, propylene glycol (diol) was added to dilute to 15 mass % in terms of oxide. Furthermore, 2-dimethylaminoethanol as a stabilizer was added to this diluted solution so that the molar ratio of Ti: stabilizer was 1:1, and then the solution was diluted with 1-butanol to 8 in terms of oxide. After diluting to % by mass, the resulting liquid was filtered to remove dust, thereby obtaining a liquid composition. Then, a dielectric film was produced in the same manner as in Example 1 using this liquid composition. This dielectric film was designated as Example 8.
＜実施例９～１２、比較例６及び比較例７＞
実施例９～１２、比較例６及び比較例７は、金属原子比を表１に示す金属原子比になるように原料を配合して、液組成物を調製するか（実施例１１及び実施例１２）、仮焼成膜の焼成時の昇温速度を表１に示す値に変更した（実施例９～１２、比較例６及び比較例７）こと以外は、実施例１と同様にして誘電体膜を作製した。
<Examples 9 to 12, Comparative Examples 6 and 7>
In Examples 9 to 12, Comparative Examples 6 and 7, raw materials were blended so that the metal atomic ratios shown in Table 1 were obtained to prepare liquid compositions (Examples 11 and 7). 12) Dielectrics were prepared in the same manner as in Example 1, except that the rate of temperature increase during firing of the calcined film was changed to the value shown in Table 1 (Examples 9 to 12, Comparative Examples 6 and 7). A membrane was prepared.
＜比較試験１及び評価＞
実施例１～１２及び比較例１～７の誘電体膜のボイド率及びピンホールの有無を調べた。上記ボイド率は、誘電体膜の断面をＳＥＭ（走査型電子顕微鏡：Scanning Electron Microscope）により観察し、その断面像を画像解析することにより膜部分の画像面積及び膜中のボイド部分の画像面積を算出し、［（ボイド部分の画像面積）／（膜部分の画像面積）］×１００という計算を行うことにより、ボイド率（％）を算出した。また、ピンホールの有無は、誘電体膜の表面を目視により観察し、ピンホールが全く無いものを『無し』とし、ピンホールが１個以上あるものを『有り』とした。その結果を表１に示す。なお、表１のＢｉ原料の欄において、『Ａ』は２－エチルヘキサン酸ビスマスを示し、『Ｂ』は硝酸ビスマス五水和物を示す。また、誘電体膜のＢｉ、Ｎａ、Ｋ、Ｔｉ、Ｓｒ及びＺｒの金属原子比を、液組成物のＢｉ、Ｎａ、Ｋ、Ｔｉ、Ｓｒ及びＺｒの金属原子比とともに、表２に示した。更に、誘電体膜の金属原子比は蛍光Ｘ線装置（リガク社製、型式名：Primus III+）によって測定した。
<Comparative test 1 and evaluation>
The dielectric films of Examples 1 to 12 and Comparative Examples 1 to 7 were examined for void ratio and presence or absence of pinholes. The above void ratio is obtained by observing the cross section of the dielectric film with a scanning electron microscope (SEM) and analyzing the image of the cross section to obtain the image area of the film portion and the image area of the void portion in the film. Then, the void ratio (%) was calculated by calculating [(image area of void portion)/(image area of film portion)]×100. In addition, the presence or absence of pinholes was determined by visually observing the surface of the dielectric film. If there were no pinholes, it was rated as "absent", and if there were one or more pinholes, it was rated as "yes". Table 1 shows the results. In the Bi raw material column of Table 1, "A" indicates bismuth 2-ethylhexanoate and "B" indicates bismuth nitrate pentahydrate. Table 2 shows the metal atomic ratios of Bi, Na, K, Ti, Sr and Zr in the dielectric film together with the metal atomic ratios of Bi, Na, K, Ti, Sr and Zr in the liquid composition. Furthermore, the metal atomic ratio of the dielectric film was measured with a fluorescent X-ray device (manufactured by Rigaku, model name: Primus III+).
表１から明らかなように、焼成時の昇温速度が１０～２５℃／秒と適切な範囲（３０℃／秒以上）より小さい比較例１～３、６及び７の誘電体膜では、ピンホールは無かったけれども、ボイド率が１９～３２％と大きくなったのに対し、焼成時の昇温速度が３０～１００℃／秒と適切な範囲（３０℃／秒以上）内である実施例１～１２では、ピンホールは無く、かつボイド率も２～１２％と小さくなった。また、液組成物のＢｉ、Ｎａ、Ｋ、Ｔｉ、Ｓｒ及びＺｒの金属原子比が０．５４：０．４６４：０．１１６：１：０：０であり、かつ液組成物のＢｉ原料として硝酸ビスマス五水和物を用いた比較例４及び５の誘電体膜では、焼成時の昇温速度の大きさに拘らず、ボイド率が８％及び９％と小さくなったけれども、ピンホールが発生した。これらに対し、液組成物のＢｉ、Ｎａ、Ｋ、Ｔｉ、Ｓｒ及びＺｒの金属原子比が０．５４：０．４６４：０．１１６：１：０：０であり、かつ液組成物のＢｉ原料として２－エチルヘキサン酸ビスマスを用いた実施例１～３の誘電体膜では、焼成時の昇温速度が３０～１００℃／秒と適切な範囲（３０℃／秒以上）内であるときに、ピンホールが無く、かつボイド率も４～１２％と小さくなった。これらのことから、Ｂｉ原料が２エチルヘキサン酸ビスマスであるときのみ、誘電体膜の緻密化に３０℃／秒以上の昇温速度が必要であることを確認できた。 As is clear from Table 1, the dielectric films of Comparative Examples 1 to 3, 6, and 7, which had a heating rate during firing of 10 to 25° C./sec, which was smaller than the appropriate range (30° C./sec or more), were not pinned. Although there were no holes, the void ratio increased to 19 to 32%, while the heating rate during firing was 30 to 100°C/sec, which was within an appropriate range (30°C/sec or more). In 1 to 12, there were no pinholes, and the void ratio was as small as 2 to 12%. Further, the metal atomic ratio of Bi, Na, K, Ti, Sr and Zr in the liquid composition is 0.54:0.464:0.116:1:0:0, and as the Bi raw material of the liquid composition In the dielectric films of Comparative Examples 4 and 5 using bismuth nitrate pentahydrate, the void ratio was as small as 8% and 9% regardless of the rate of temperature rise during firing, but pinholes were formed. Occurred. In contrast, the liquid composition has a metal atomic ratio of Bi, Na, K, Ti, Sr, and Zr of 0.54:0.464:0.116:1:0:0, and the liquid composition has a Bi In the dielectric films of Examples 1 to 3 using bismuth 2-ethylhexanoate as a raw material, when the temperature increase rate during firing is within an appropriate range of 30 to 100 ° C./sec (30 ° C./sec or more) Furthermore, there were no pinholes and the void ratio was as small as 4 to 12%. From these results, it was confirmed that a heating rate of 30° C./second or more is necessary for densification of the dielectric film only when the Bi raw material is bismuth diethylhexanoate.
また、液組成物のＢｉ、Ｎａ、Ｋ、Ｔｉ、Ｓｒ及びＺｒの金属原子比が０．５４：０：０．５８：１：０：０であり、かつ焼成時の昇温速度が２５℃／秒と適切な範囲（３０℃／秒以上）より小さい比較例３の誘電体膜では、ピンホールは無かったけれども、ボイド率が１９％と大きくなったのに対し、液組成物のＢｉ、Ｎａ、Ｋ、Ｔｉ、Ｓｒ及びＺｒの金属原子比が０．５４：０：０．５８：１：０：０であり、かつ焼成時の昇温速度が５０℃／秒と適切な範囲（３０℃／秒以上）内である実施例７では、ピンホールは無く、かつボイド率も２％と極めて小さくなった。このことから、昇温速度を３０℃／秒以上にしなければ、誘電体膜の緻密化が進行しないことを確認できた。 In addition, the metal atomic ratio of Bi, Na, K, Ti, Sr, and Zr in the liquid composition was 0.54:0:0.58:1:0:0, and the heating rate during firing was 25°C. /sec, which is smaller than the appropriate range (30°C/sec or more), the dielectric film of Comparative Example 3 did not have pinholes, but had a high void ratio of 19%. The metal atomic ratio of Na, K, Ti, Sr, and Zr is 0.54:0:0.58:1:0:0, and the heating rate during firing is 50°C/sec, which is an appropriate range (30 °C/sec), there were no pinholes, and the void fraction was extremely small at 2%. From this, it was confirmed that the densification of the dielectric film did not proceed unless the temperature increase rate was 30° C./second or more.
更に、表１及び表２から明らかなように、液組成物がＳｒ及びＺｒを含み、液組成物のＢｉ、Ｎａ、Ｋ、Ｔｉ、Ｓｒ及びＺｒの金属原子比が０．５４：０．４６４：０．１１６：０．９７５：０．０２５：０．０２５であり、かつ焼成時の昇温速度が２５℃／秒と適切な範囲（３０℃／秒以上）より小さい比較例６及び７の誘電体膜では、誘電体膜のＢｉの金属原子比が０．４９０～０．４９９と液組成物のＢｉの金属原子比０．５４からの低下率が大きかったのに対し、液組成物がＳｒ及びＺｒを含み、液組成物のＢｉ、Ｎａ、Ｋ、Ｔｉ、Ｓｒ及びＺｒの金属原子比が０．５４：０．４６４：０．１１６：０．９７５：０．０２５：０．０２５であり、かつ焼成時の昇温速度が３０℃／秒～１００℃／秒と適切な範囲（３０℃／秒以上）内である実施例８～１２の誘電体膜では、これらの誘電体膜のＢｉの金属原子比が０．５０２～０．５０８と液組成物のＢｉの金属原子比０．５４からの低下率は小さくなった。これは、Ｓｒ及びＺｒを添加することにより結晶化速度が速くなったことが要因であると考えられる。 Furthermore, as is clear from Tables 1 and 2, the liquid composition contains Sr and Zr, and the metal atomic ratio of Bi, Na, K, Ti, Sr and Zr in the liquid composition is 0.54:0.464. : 0.116: 0.975: 0.025: 0.025, and the temperature increase rate during firing is 25 ° C./sec, which is smaller than the appropriate range (30 ° C./sec or more). In the dielectric film, the metal atomic ratio of Bi in the dielectric film was 0.490 to 0.499, and the decrease rate from the metal atomic ratio of Bi in the liquid composition was 0.54. Sr and Zr are included, and the metal atomic ratio of Bi, Na, K, Ti, Sr and Zr in the liquid composition is 0.54:0.464:0.116:0.975:0.025:0.025 In the dielectric films of Examples 8 to 12, in which the rate of temperature rise during firing is within the appropriate range of 30° C./sec to 100° C./sec (30° C./sec or more), these dielectric films The metal atomic ratio of Bi was 0.502 to 0.508, and the rate of decrease from the metal atomic ratio of Bi of the liquid composition of 0.54 was small. The reason for this is thought to be that the addition of Sr and Zr increased the crystallization rate.
なお、実施例１～１２の仮焼成膜の焼成時において、室温から５００℃までの昇温速度を１５℃／秒とし、５００℃から６００℃までの昇温速度を表１に記載された昇温速度とし、６００℃から７００℃までの昇温速度を１５℃／秒としたとき、誘電体膜のボイド率は、表１に記載された実施例１～１２の値とほぼ同一であり、ピンホールは無かった。 In addition, when firing the calcined films of Examples 1 to 12, the rate of temperature increase from room temperature to 500° C. was 15° C./sec, and the rate of temperature increase from 500° C. to 600° C. was set at the rate shown in Table 1. When the temperature rate is 15° C./sec from 600° C. to 700° C., the void fraction of the dielectric film is almost the same as the values of Examples 1 to 12 shown in Table 1. There were no pinholes.
本発明の誘電体膜の製造方法は、キャパシタ、インクジェットヘッド、ミラーデバイス、オートフォーカス、ジャイロセンサ、マイクロポンプなどのＭＥＭＳ（Microelectromechanical Systems）アプリケーション用の誘電体膜を製造するために利用できる。 The method for producing a dielectric film of the present invention can be used to produce dielectric films for MEMS (Microelectromechanical Systems) applications such as capacitors, inkjet heads, mirror devices, autofocus, gyro sensors, and micropumps.
Claims (3)
Ｓｒ及びＺｒを更に含み、
前記Ｂｉの原料が２－エチルヘキサン酸ビスマスであり、
前記仮焼成膜の焼成時に５００℃から６００℃までの昇温速度を３０℃／秒以上にする
ことを特徴とする誘電体膜の製造方法。 A coating film obtained by applying a liquid composition containing at least Bi, K and Ti on a substrate is calcined to prepare a calcined film, and the calcined film is calcined to manufacture a dielectric film made of a metal oxide. a method,
further comprising Sr and Zr;
The Bi raw material is bismuth 2-ethylhexanoate,
A method for producing a dielectric film, wherein a rate of temperature increase from 500° C. to 600° C. is set to 30° C./second or more during firing of the calcined film.
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| JP2011238710A (en) | 2010-05-07 | 2011-11-24 | Seiko Epson Corp | Manufacturing method of liquid injection head and liquid injection device using the same, and manufacturing method of piezo-electric element |
| JP2012136487A (en) | 2010-12-27 | 2012-07-19 | Seiko Epson Corp | Method for producing composition for forming ceramic film, piezoelectric ceramic film, and method for producing bismuth 2-ethylhexanoate |
| JP2016187019A (en) | 2015-03-27 | 2016-10-27 | セイコーエプソン株式会社 | Piezoelectric element, piezoelectric element application device, and method for manufacturing piezoelectric element |
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