JPH09195040A - Target material for forming high purity dielectric thin film - Google Patents
Target material for forming high purity dielectric thin filmInfo
- Publication number
- JPH09195040A JPH09195040A JP6860294A JP6860294A JPH09195040A JP H09195040 A JPH09195040 A JP H09195040A JP 6860294 A JP6860294 A JP 6860294A JP 6860294 A JP6860294 A JP 6860294A JP H09195040 A JPH09195040 A JP H09195040A
- Authority
- JP
- Japan
- Prior art keywords
- thin film
- target material
- dielectric thin
- alkali metal
- content
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 239000010409 thin film Substances 0.000 title claims abstract description 38
- 239000013077 target material Substances 0.000 title claims abstract description 34
- 239000012535 impurity Substances 0.000 claims abstract description 30
- 229910052783 alkali metal Inorganic materials 0.000 claims abstract description 25
- 150000001340 alkali metals Chemical class 0.000 claims abstract description 25
- 229910052751 metal Inorganic materials 0.000 claims abstract description 22
- 239000002184 metal Substances 0.000 claims abstract description 19
- 238000004544 sputter deposition Methods 0.000 claims abstract description 17
- 239000000203 mixture Substances 0.000 claims abstract description 16
- 229910052776 Thorium Inorganic materials 0.000 claims abstract description 15
- 229910052770 Uranium Inorganic materials 0.000 claims abstract description 15
- 239000000843 powder Substances 0.000 claims abstract description 14
- 150000001875 compounds Chemical class 0.000 claims abstract description 9
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 7
- 229910052788 barium Inorganic materials 0.000 claims abstract description 6
- 229910052793 cadmium Inorganic materials 0.000 claims abstract description 6
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 6
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 6
- 229910052712 strontium Inorganic materials 0.000 claims abstract description 6
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 6
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 6
- 229910052742 iron Inorganic materials 0.000 claims abstract description 5
- 150000002902 organometallic compounds Chemical class 0.000 claims description 10
- 150000004706 metal oxides Chemical class 0.000 claims description 6
- 229910052749 magnesium Inorganic materials 0.000 abstract description 4
- 230000001105 regulatory effect Effects 0.000 abstract 5
- 229910000765 intermetallic Inorganic materials 0.000 abstract 1
- 239000010408 film Substances 0.000 description 19
- 238000010438 heat treatment Methods 0.000 description 10
- 239000002994 raw material Substances 0.000 description 7
- 238000004821 distillation Methods 0.000 description 6
- 238000000034 method Methods 0.000 description 6
- 238000001953 recrystallisation Methods 0.000 description 6
- 238000005477 sputtering target Methods 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 5
- 238000000859 sublimation Methods 0.000 description 5
- 230000008022 sublimation Effects 0.000 description 5
- 239000000758 substrate Substances 0.000 description 5
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 229910052745 lead Inorganic materials 0.000 description 4
- 229910052700 potassium Inorganic materials 0.000 description 4
- 238000000746 purification Methods 0.000 description 4
- 238000001514 detection method Methods 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 229910052744 lithium Inorganic materials 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- 229910052708 sodium Inorganic materials 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 229910020565 PbCd Inorganic materials 0.000 description 2
- YRKCREAYFQTBPV-UHFFFAOYSA-N acetylacetone Chemical class CC(=O)CC(C)=O YRKCREAYFQTBPV-UHFFFAOYSA-N 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- HHFAWKCIHAUFRX-UHFFFAOYSA-N ethoxide Chemical compound CC[O-] HHFAWKCIHAUFRX-UHFFFAOYSA-N 0.000 description 2
- 238000007731 hot pressing Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 150000002736 metal compounds Chemical class 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910002659 PbMg1/3Nb2/3O3 Inorganic materials 0.000 description 1
- 150000001242 acetic acid derivatives Chemical class 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 150000001339 alkali metal compounds Chemical class 0.000 description 1
- 150000004703 alkoxides Chemical class 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 238000005219 brazing Methods 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 150000007942 carboxylates Chemical class 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- -1 distillation Chemical class 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 238000004528 spin coating Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006557 surface reaction Methods 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 239000012808 vapor phase Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Physical Vapour Deposition (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、高純度のペロブスカイ
ト型鉛含有化合物（鉛と他の１種もしくは２種以上の金
属との複合酸化物）からなる誘電体薄膜をスパッタリン
グ法によって形成するのに用いるターゲット材に関す
る。この誘電体薄膜は、赤外線センサー、圧電フィルタ
ー、振動子、レーザーの変調素子、光シャッター、キャ
パシタ膜、不揮発性のメモリー等に適用される。FIELD OF THE INVENTION The present invention forms a dielectric thin film composed of a high-purity perovskite-type lead-containing compound (a complex oxide of lead and one or more other metals) by a sputtering method. The target material used for. This dielectric thin film is applied to an infrared sensor, a piezoelectric filter, a vibrator, a laser modulator, an optical shutter, a capacitor film, a non-volatile memory and the like.
【０００２】[0002]
【従来の技術】薄膜の気相形成法の１つとしてスパッタ
リング法は従来よりよく知られ、工業的な薄膜製造にも
利用されてきた。スパッタリング法では、成膜物質と同
成分のターゲット材を用意し、通常は、このターゲット
材にグロー放電で発生させたアルゴンガスイオンを衝突
させてターゲット材の構成原子を叩き出し、基板上に原
子を堆積させることにより成膜が行われる。2. Description of the Related Art A sputtering method has been well known as one of the methods for forming a vapor phase of a thin film, and has been utilized for industrial thin film production. In the sputtering method, a target material having the same composition as that of the film-forming substance is prepared, and normally, argon gas ions generated by glow discharge are made to collide with the target material to knock out the constituent atoms of the target material, and the atoms on the substrate are atomized. Is deposited to form a film.
【０００３】[0003]
【発明が解決しようとする課題】一般に、誘電体薄膜を
形成する際、良好な特性を得るためには、どのような成
膜法でも最終的に熱処理を行い結晶性を上げることが必
要であり、スパッタリング法による成膜後もこの熱処理
が行われる。しかし結晶性を上げるために熱処理を行う
と、同時に結晶粒の成長が起こり、粒界に析出する不純
物を通じてリーク電流が増加する問題がある。そこで、
高純度化することによってリーク電流を減少させること
が考えられるが、原料成分を高純度化するのに手間がか
かるため、高純度化とリーク電流との関係については従
来はほとんど検討されておらず、どの程度高純度化すれ
ばリーク電流を抑制できるかは全く知られていなかっ
た。Generally, in forming a dielectric thin film, in order to obtain good characteristics, it is necessary to perform a final heat treatment by any film forming method to improve the crystallinity. The heat treatment is performed even after the film formation by the sputtering method. However, when heat treatment is performed to improve crystallinity, crystal grains grow at the same time, and there is a problem that leak current increases due to impurities precipitated at grain boundaries. Therefore,
Although it is possible to reduce the leakage current by purifying it, it takes time to purify the raw material components, so the relationship between the purification and the leakage current has hardly been studied so far. However, it has not been known at all about how highly purified the leakage current can be suppressed.
【０００４】本発明は、リーク電流の少ないペロブスカ
イト型鉛含有化合物からなる誘電体薄膜をスパッタリン
グ法により形成することができるターゲット材を提供す
ることを目的とする。An object of the present invention is to provide a target material capable of forming a dielectric thin film composed of a perovskite type lead-containing compound with a small leak current by a sputtering method.
【０００５】[0005]
【課題を解決するための手段】本発明者らは、一般式：
ＰｂＡＯ3 （式中、Ａは、Ｍｇ，Ｂａ，Ｓｒ，Ｃａ，Ｔ
ａ，Ｎｂ，Ｃｏ，Ｆｅ，Ｎｉ，Ｗ，Ｚｎ，Ｃｄから選ば
れる１種または２種以上の金属元素であって、Ａ全体で
４価である) で表されるペロブスカイト型鉛含有化合物
からなる誘電体薄膜の高純度化を試み、成分原料を有機
金属化合物の形で蒸留、昇華、再結晶を繰り返し、ある
いはこれらを組み合わせて繰り返すことによって高純度
化し、不純物濃度とリーク電流の関係を追及したとこ
ろ、アルカリ金属不純物の合計量が１ppm 以下、好まし
くは0.1 ppm 以下のときにリーク電流が大幅に減少する
ことを見出した。従って、スパッタリング法により上記
の誘電体薄膜を形成する場合、ターゲット材のアルカリ
金属不純物濃度が１ppm 以下であれば、得られる薄膜の
アルカリ金属不純物の合計量も１ppm 以下となって、リ
ーク電流が著しく低くなることが判明した。We have defined the general formula:
PbAO 3 (In the formula, A is Mg, Ba, Sr, Ca, T
a, Nb, Co, Fe, Ni, W, Zn, Cd, which is one or more kinds of metal elements and is tetravalent in total A). We tried to make the dielectric thin film highly purified, and made it highly purified by repeating distillation, sublimation, and recrystallization of the component raw materials in the form of an organometallic compound, or by repeating these in combination, and pursued the relationship between the impurity concentration and the leak current. However, it has been found that the leak current is significantly reduced when the total amount of alkali metal impurities is 1 ppm or less, preferably 0.1 ppm or less. Therefore, when the above-mentioned dielectric thin film is formed by the sputtering method, if the alkali metal impurity concentration of the target material is 1 ppm or less, the total amount of the alkali metal impurities of the obtained thin film is 1 ppm or less, and the leak current is significantly It turned out to be low.
【０００６】本発明によれば、一般式：ＰｂＡＯ3 （式
中、Ａは上記に同じ) で表されるペロブスカイト型鉛含
有化合物からなる誘電体薄膜をスパッタリング法により
形成するためのターゲット材であって、このターゲット
材は各成分金属の精製された有機金属化合物から得た金
属酸化物粉末を前記一般式で表される所定組成比となる
ように混合した混合物の焼結体からなり、この焼結体の
アルカリ金属不純物の含有量が１ppm 以下であり、それ
によりアルカリ金属不純物の含有量が１ppm 以下の誘電
体薄膜を形成することができるターゲット材が提供され
る。According to the present invention, a target material for forming a dielectric thin film of a perovskite-type lead-containing compound represented by the general formula: PbAO 3 (where A is the same as above) by a sputtering method. The target material is composed of a sintered body of a mixture obtained by mixing metal oxide powders obtained from refined organometallic compounds of each component metal so as to have a predetermined composition ratio represented by the above general formula. A target material capable of forming a dielectric thin film having an alkali metal impurity content of 1 ppm or less in a bond and thereby an alkali metal impurity content of 1 ppm or less is provided.
【０００７】本発明の好適態様によれば、ターゲット材
は、上記のアルカリ金属含有量に加えて、ＵとＴｈの合
計含有量が10 ppb以下という特徴も有し、それによりア
ルカリ金属不純物の含有量が１ppm 以下、かつＵ，Ｔｈ
の合計含有量が10 ppb以下の誘電体薄膜を形成すること
ができる。According to a preferred embodiment of the present invention, the target material is characterized in that, in addition to the above-mentioned alkali metal content, the total content of U and Th is 10 ppb or less, whereby the content of alkali metal impurities is contained. Amount less than 1ppm, and U, Th
It is possible to form a dielectric thin film having a total content of 10 ppb or less.
【０００８】本発明のスパッタリング用ターゲット材か
ら形成される誘電体薄膜は、一般式：ＰｂＡＯ3 で表さ
れるペロブスカイト型鉛含有化合物からなる。式中、Ａ
は４価の金属元素または全体で４価の金属元素群であ
り、Ｍｇ、Ｂａ、Ｓｒ、Ｃａ、Ｔａ、Ｎｂ、Ｃｏ、Ｆ
ｅ、Ｎｉ，Ｗ，Ｚｎ，Ｃｄから選ばれる。この誘電体薄
膜の代表的な組成を以下に示す。 PbMg1/3Ta2/3Ｏ3, PbMg1/3Nb2/3Ｏ3, PbFe1/2Ta1/2Ｏ3, PbCo1/3Nb2/3Ｏ3, PbFe1/2Nb1/2Ｏ3, PbNi1/3Nb2/3Ｏ3, PbNi1/3Ta2/3Ｏ3, PbCd1/3Nb2/3Ｏ3, PbCo1/3Ta2/3Ｏ3, PbZn1/3Nb2/3Ｏ3, PbCa1/2W1/2 Ｏ3, PbCo1/2W1/2 Ｏ3, PbMg1/2W1/2 Ｏ3, PbFe1/3W2/3 Ｏ3, PbCd1/2W1/2 Ｏ3 。The dielectric thin film formed from the sputtering target material of the present invention comprises a perovskite-type lead-containing compound represented by the general formula: PbAO 3 . Where A
Is a tetravalent metal element or a group of tetravalent metal elements in total, and Mg, Ba, Sr, Ca, Ta, Nb, Co, F
e, Ni, W, Zn, Cd. A typical composition of this dielectric thin film is shown below. PbMg 1/3 Ta 2/3 O 3 , PbMg 1/3 Nb 2/3 O 3 , PbFe 1/2 Ta 1/2 O 3 , PbCo 1/3 Nb 2/3 O 3 , PbFe 1/2 Nb 1 / 2 O 3 , PbNi 1/3 Nb 2/3 O 3 , PbNi 1/3 Ta 2/3 O 3 , PbCd 1/3 Nb 2/3 O 3 , PbCo 1/3 Ta 2/3 O 3 , PbZn 1/3 Nb 2/3 O 3 , PbCa 1/2 W 1/2 O 3 , PbCo 1/2 W 1/2 O 3 , PbMg 1/2 W 1/2 O 3 , PbFe 1/3 W 2 / 3 O 3 , PbCd 1/2 W 1/2 O 3 .
【０００９】本発明のターゲット材の原料は、一般式：
ＰｂＡＯ3 で表される目的とする誘電体薄膜の各成分金
属 (即ち、ＰｂとＡ金属）の有機金属化合物であり、こ
れらは市販の有機金属化合物（例、アルコキシド、カル
ボン酸塩、アセチルアセトン錯体）を使用することがで
きる。原料の有機金属化合物は、蒸留、昇華、再結晶の
いずれかを繰返すか、或いはこれらを組合せて繰り返す
ことにより精製して高純度化したものを用いる。有機金
属化合物を原料とすることにより、蒸留、昇華、再結晶
といった有機化合物に適した精製法を採用して、アルカ
リ金属化合物やＵ、Ｔｈを実質的に完全に除去すること
ができ、従来に比べて著しい高純度化が可能となる。こ
の精製された有機金属化合物を大気中で焼成して熱分解
させることにより、各成分金属の酸化物粉末を得る。こ
うして、アルカリ金属やＵ、Ｔｈの含有量が著しく少な
い高純度の金属酸化物粉末を得ることができる。The raw material of the target material of the present invention has the general formula:
PbAO 3 is an organometallic compound of each component metal (ie, Pb and A metal) of the target dielectric thin film represented by PbAO 3 , and these are commercially available organometallic compounds (eg, alkoxides, carboxylates, acetylacetone complexes). Can be used. The organometallic compound used as a raw material is purified to be highly purified by repeating any one of distillation, sublimation, and recrystallization, or by repeating a combination thereof. By using an organic metal compound as a raw material, a purification method suitable for the organic compound such as distillation, sublimation, or recrystallization can be adopted to substantially completely remove the alkali metal compound, U, and Th. Compared with this, it is possible to achieve extremely high purification. The purified organometallic compound is fired in the atmosphere to be thermally decomposed to obtain an oxide powder of each component metal. In this way, it is possible to obtain a high-purity metal oxide powder having a remarkably low content of alkali metal, U, and Th.
【００１０】この高純度の酸化物粉末を使用して、常法
によりスパッタリング用ターゲット材を作製する。即
ち、各構成金属の酸化物粉末を、金属の存在比が目的と
する誘電体薄膜と同一になる所定組成比で混合し、得ら
れた混合物をホットプレスなどの適当な方法で焼結し
て、焼結体とし、これをターゲット材として使用する。
スパッタリング技術において周知のように、この焼結体
に、ターゲット作製のための後処理（例、歪取りのため
の熱処理、表面反応層を除去するための砥石研削、銅板
へのロウ付け）を行うと、スパッタリング用ターゲット
が作製される。Using this high-purity oxide powder, a sputtering target material is prepared by a conventional method. That is, the oxide powder of each constituent metal is mixed in a predetermined composition ratio such that the abundance ratio of the metal is the same as the desired dielectric thin film, and the obtained mixture is sintered by an appropriate method such as hot pressing. , A sintered body, which is used as a target material.
As is well known in the sputtering technology, this sintered body is subjected to post-treatment for target production (eg, heat treatment for strain relief, grinding wheel removal for removing surface reaction layer, brazing to copper plate). Then, a sputtering target is produced.
【００１１】こうして得ることができる本発明のターゲ
ット材は、アルカリ金属不純物含有量が１ppm 以下であ
り、好ましくはＵ，Ｔｈの合計含有量が10 ppb以下であ
る。原料の有機金属化合物が高度に精製されているた
め、このような高純度のターゲット材を得ることが可能
となる。このターゲット材を使用して、常法によりスパ
ッタリングを行うと、基板上に一般式：ＰｂＡＯ3 で表
され、アルカリ金属不純物含有量が１ppm 以下であっ
て、好ましくはＵ，Ｔｈの合計含有量が10 ppb以下の高
純度のペロブスカイト型鉛含有化合物からなる誘電体薄
膜を形成することができる。The target material of the present invention thus obtained has an alkali metal impurity content of 1 ppm or less, preferably a total content of U and Th of 10 ppb or less. Since the raw material organometallic compound is highly purified, it is possible to obtain such a highly pure target material. When this target material is used to perform sputtering in a conventional manner, it is represented by the general formula: PbAO 3 on the substrate, the content of alkali metal impurities is 1 ppm or less, and the total content of U and Th is preferably. It is possible to form a dielectric thin film made of a high-purity perovskite-type lead-containing compound of 10 ppb or less.
【００１２】なお、前述したように、膜の結晶性を確保
するために、スパッタリングによる成膜後に熱処理して
結晶性を高めることが必要である。次に説明するよう
に、本発明のターゲット材から得られた誘電体薄膜は非
常に高純度であるため、熱処理中に起こりうる粒界への
不純物の析出が少なく、熱処理によるリーク電流の増大
が抑制される。そのため、誘電特性に優れた誘電体薄膜
が得られる。As described above, in order to secure the crystallinity of the film, it is necessary to heat the film after forming it by sputtering to enhance the crystallinity. As will be described below, since the dielectric thin film obtained from the target material of the present invention has a very high purity, the precipitation of impurities at the grain boundaries that may occur during heat treatment is small, and the increase in leak current due to heat treatment is increased. Suppressed. Therefore, a dielectric thin film having excellent dielectric properties can be obtained.
【００１３】図１に、ゾル−ゲル法の成膜例であるが、
組成 PbMg1/3Ta2/3O3 の誘電体薄膜中の金属不純物量と
成膜・熱処理後の薄膜のリーク電流密度との関係を示
す。この実験での成膜は、各成分金属 (Pb、Mg、Ta) の
有機金属化合物原料として市販品をそのまま有機溶媒に
溶解した低純度の塗布液と、市販品を蒸留、昇華、再結
晶等を繰返して精製してから有機溶媒に溶解した高純度
の塗布液とを用意し、この２種類の塗布液を割合を変え
て混合することにより不純物含有量が異なる塗布液を調
製し、この塗布液を用いてPt基板上にスピンコート法で
膜厚約3000Åに塗布し、空気中、700 ℃で２時間熱処理
(焼成) することにより行った。リーク電流密度の測定
値は膜上の20箇所の測定点の平均値である。FIG. 1 shows an example of film formation by the sol-gel method.
The relation between the amount of metal impurities in the dielectric thin film of composition PbMg 1/3 Ta 2/3 O 3 and the leakage current density of the thin film after film formation and heat treatment is shown. The film formation in this experiment consisted of a low-purity coating solution prepared by directly dissolving a commercially available product as an organic metal compound raw material for each component metal (Pb, Mg, Ta) in an organic solvent, and distilling, sublimating, recrystallizing, etc. the commercially available product. To prepare a high-purity coating liquid dissolved in an organic solvent, and mix these two types of coating liquids at different ratios to prepare coating liquids having different impurity contents. The solution is applied to a Pt substrate by spin coating to a film thickness of about 3000Å and heat-treated in air at 700 ° C for 2 hours.
(Baking) was performed. The measured leakage current density is the average value of 20 measurement points on the film.
【００１４】図から明らかなように、金属不純物の合計
量が１ppm を超えると、リーク電流が急激に増大し、１
ppm 付近がリーク電流密度変化の変曲点になっている。
即ち、金属不純物が１ppm 以下ではリーク電流密度が抑
制される。金属不純物量がさらに減少して0.1 ppm 以下
になるとリーク電流がまた更に減少する。このような不
純物による影響は成膜法には依存しないので、スパッタ
リング法で成膜しても同様の結果になる。As is clear from the figure, when the total amount of metal impurities exceeds 1 ppm, the leak current increases sharply,
The inflection point of leakage current density change is around ppm.
That is, when the metal impurities are 1 ppm or less, the leak current density is suppressed. When the amount of metal impurities is further reduced to 0.1 ppm or less, the leak current is further reduced. Since the influence of such impurities does not depend on the film forming method, the same result can be obtained even if the film is formed by the sputtering method.
【００１５】この金属不純物は主にアルカリ金属である
ことが確認された。このように、アルカリ金属は電荷移
動への関与が大きく、粒界に析出するとリーク電流を発
生させ易くなるので、本発明においては、これらＬｉ、
Ｎａ、Ｋなどのアルカリ金属不純物の合計含有量を１pp
m 以下、好ましくは0.1 ppm 以下の誘電体薄膜が得られ
るように、スパッタリング用のターゲット材中のアルカ
リ金属不純物濃度を同じように１ppm 以下、好ましくは
0.1 ppm 以下に制限する。それにより、成膜後の熱処理
中に結晶粒界に析出する不純物量が減少し、また膜欠陥
が少なくなって、リーク電流が大幅に減少する。It has been confirmed that the metal impurities are mainly alkali metals. As described above, the alkali metal has a large contribution to the charge transfer, and when it is deposited on the grain boundary, a leak current is likely to occur. Therefore, in the present invention, these Li,
The total content of alkali metal impurities such as Na and K is 1 pp
In order to obtain a dielectric thin film of m or less, preferably 0.1 ppm or less, the concentration of alkali metal impurities in the target material for sputtering is also 1 ppm or less, preferably
Limit to 0.1 ppm or less. As a result, the amount of impurities precipitated at the crystal grain boundaries during the heat treatment after film formation is reduced, and film defects are reduced, so that the leak current is significantly reduced.
【００１６】また、誘電体薄膜中のＵ、Ｔｈはα放射線
源となり、誘電体薄膜をDRAMのキャパシター膜として用
いた場合にα線によるソフトエラーを生ずる原因となる
ので、その合計含有量を10 ppb以下に制限することが好
ましい。そのため、スパッタリング用ターゲット材中の
Ｕ、Ｔｈの合計含有量も同様に10 ppb以下に制限するこ
とが好ましい。Further, U and Th in the dielectric thin film serve as an α radiation source, which causes a soft error due to α rays when the dielectric thin film is used as a capacitor film of DRAM, so the total content thereof is 10 It is preferable to limit it to ppb or less. Therefore, the total content of U and Th in the sputtering target material is also preferably limited to 10 ppb or less.
【００１７】[0017]
【実施例】実施例１ 蒸留、昇華または再結晶を繰返して精製したPb、Mg、Ta
の各有機金属化合物をそれぞれ大気中で焼成して熱分解
させることにより、PbO, MgO, Ta2O5 の各金属酸化物粉
末を得た。これらの金属酸化物粉末はいずれも、Na、
Ｋ、Liのアルカリ金属含有量がそれぞれ10 ppb以下であ
り、Ｕ、Thは検出限界(10 ppb)以下であった。これらの
金属酸化物粉末をPb：Mg：Ta＝１：0.33：0.67の組成比
となるように混合し、ホットプレス法により焼結体を作
製した。ホットプレス条件は、温度：900 ℃、加圧力：
150 kg/cm2、雰囲気：10-4 torr 、時間：２時間であっ
た。この焼結体に常法により熱処理、表面研削加工を施
し、PbMg1/3Ta2/3Ｏ3 の組成を有するターゲット材を得
た。 Example 1 Pb, Mg, Ta purified by repeating distillation, sublimation or recrystallization
Each of the organometallic compounds was heated in the air to be pyrolyzed to obtain PbO, MgO, and Ta 2 O 5 metal oxide powders. Each of these metal oxide powders is Na,
The alkali metal contents of K and Li were each 10 ppb or less, and U and Th were below the detection limit (10 ppb). These metal oxide powders were mixed so as to have a composition ratio of Pb: Mg: Ta = 1: 0.33: 0.67, and a sintered body was produced by a hot pressing method. Hot press conditions are temperature: 900 ℃, pressure:
It was 150 kg / cm 2 , atmosphere: 10 −4 torr, time: 2 hours. This sintered body was heat-treated and surface-ground by a conventional method to obtain a target material having a composition of PbMg 1/3 Ta 2/3 O 3 .
【００１８】このターゲット材からサンプリングした粉
末のNa、Ｋ、Liのアルカリ金属含有量を測定したとこ
ろ、いずれも10 ppb以下であり、Ｕ、Thは検出限界以下
であった。このターゲット材を用いてスパッタリング法
によりPt基板上に膜厚約3000Åの薄膜を形成した後、結
晶性を高めるために、空気中、700 ℃で２時間の熱処理
(焼成) を行って、PbMg1/3Ta2/3Ｏ3 の組成を有する、
ペロブスカイト型結晶構造の薄膜を得た。この膜上にPt
電極を形成し、電気的特性を測定したところ、次の通り
であった。When the alkali metal contents of Na, K, and Li of the powder sampled from this target material were measured, all were 10 ppb or less, and U and Th were below the detection limit. After using this target material to form a thin film with a thickness of about 3000Å on a Pt substrate by sputtering, heat treatment in air at 700 ° C for 2 hours to improve crystallinity.
(Calcination) to obtain a composition of PbMg 1/3 Ta 2/3 O 3 ,
A thin film having a perovskite crystal structure was obtained. Pt on this film
When an electrode was formed and the electrical characteristics were measured, it was as follows.
【００１９】[0019]
【表１】 [Table 1]
【００２０】実施例２〜14 実施例１と同様に蒸留、昇華、再結晶を繰返して精製し
たPb、Ba、Ca、Sr、Ta、Nb、Co、Fe、Ni、Ｗ、Zn、Cdの
各有機金属化合物をそれぞれ大気中で焼成して熱分解さ
せることにより、PbO, BaO, CaO, MgO, SrO, Ta2O5, Nb
2O5, CoO, Fe2O3, NiO, WO3, ZnO, CdO の各粉末を得
た。これらの粉末を表２に示す金属組成比となるような
割合で混合し、実施例１と同様にしてスパッタリング用
ターゲット材を作製した。これらのターゲット材からサ
ンプリングした粉末のNa、Ｋ、Liのアルカリ金属含有量
を測定したところ、いずれも10 ppb以下であり、Ｕ、Th
は検出限界以下であった。このターゲット材を用いてス
パッタリング法によりPt基板上に膜厚約3000Åの薄膜を
形成した後、結晶性を高めるために空気中、700 ℃で２
時間の熱処理を行って、所定組成を有するペロブスカイ
ト型結晶構造の薄膜を得た。この薄膜の電気的特性も表
２に併せて示す。 Examples 2 to 14 Pb, Ba, Ca, Sr, Ta, Nb, Co, Fe, Ni, W, Zn and Cd purified by repeating distillation, sublimation and recrystallization in the same manner as in Example 1 PbO, BaO, CaO, MgO, SrO, Ta 2 O 5 , Nb
Powders of 2 O 5 , CoO, Fe 2 O 3 , NiO, WO 3 , ZnO and CdO were obtained. These powders were mixed in a ratio such that the metal composition ratio shown in Table 2 was obtained, and a sputtering target material was produced in the same manner as in Example 1. When the alkali metal contents of Na, K, and Li of the powder sampled from these target materials were measured, all were 10 ppb or less, and U and Th
Was below the detection limit. Using this target material, a thin film with a thickness of about 3000 Å was formed on a Pt substrate by the sputtering method, and then, in air at 700 ° C for 2 hours to improve crystallinity.
After heat treatment for a time, a thin film having a perovskite crystal structure having a predetermined composition was obtained. The electrical characteristics of this thin film are also shown in Table 2.
【００２１】[0021]
【表２】 [Table 2]
【００２２】なお、以上の実施例で用いた有機金属化合
物は、２価金属については酢酸塩、即ち、 [M(CH3CO
O)2, M＝Mg、Ba、Sr、Ca、Co、Fe、Ni、Zn、Cd、Pb]
、５価金属についてはエトキサイド [M(OC2H5)5, M＝T
a、Nb、Ｗ]2であった。精製は、酢酸塩については水か
らの再結晶の反復、エトキサイドについては蒸留の反復
により行った。The organometallic compounds used in the above examples are acetates for divalent metals, that is, [M (CH 3 CO
O) 2 , M ＝ Mg, Ba, Sr, Ca, Co, Fe, Ni, Zn, Cd, Pb]
For pentavalent metals, ethoxide [M (OC 2 H 5 ) 5 , M ＝ T
a, Nb, W] 2 . Purification was carried out by repeating recrystallization from water for acetate and repeating distillation for ethoxide.
【００２３】[0023]
【発明の効果】本発明のスパッタリング用ターゲット材
から形成されたペロブスカイト型鉛含有化合物からなる
誘電体薄膜は、アルカリ金属不純物含有量およびＵ、Ｔ
ｈ含有量が低く、従来問題であったリーク電流が大幅に
減少し、優れた誘電特性を示す。また膜の部位による特
性変化が極めて少ない安定な膜が得られ、エレクトロニ
クスの分野等において広く用いることができる。The dielectric thin film made of the perovskite-type lead-containing compound formed from the sputtering target material of the present invention has an alkali metal impurity content and U, T
The h content is low, the leak current, which has been a problem in the past, is greatly reduced, and excellent dielectric properties are exhibited. In addition, a stable film having very little change in characteristics depending on the portion of the film is obtained, and can be widely used in the field of electronics and the like.
【図１】薄膜のアルカリ不純物量とリーク電流密度の関
係を示すグラフ。FIG. 1 is a graph showing the relationship between the amount of alkali impurities in a thin film and the leak current density.
Claims (2)
Ｂａ，Ｓｒ，Ｃａ，Ｔａ，Ｎｂ，Ｃｏ，Ｆｅ，Ｎｉ，
Ｗ，Ｚｎ，Ｃｄから選ばれる１種または２種以上の金属
元素であって、Ａ全体で４価である）で表されるペロブ
スカイト型鉛含有化合物からなる誘電体薄膜をスパッタ
リング法により形成するためのターゲット材であって、
このターゲット材は各成分金属の精製された有機金属化
合物から得た金属酸化物粉末を前記一般式で表される所
定組成比となるように混合した混合物の焼結体からな
り、この焼結体のアルカリ金属不純物の含有量が１ppm
以下であり、それによりアルカリ金属不純物の含有量が
１ppm 以下の誘電体薄膜を形成することができるターゲ
ット材。1. A general formula: PbAO 3 (wherein A is Mg,
Ba, Sr, Ca, Ta, Nb, Co, Fe, Ni,
To form a dielectric thin film made of a perovskite-type lead-containing compound represented by one or more metal elements selected from W, Zn, and Cd and having a valence of 4 as a whole by sputtering. Target material of
This target material is composed of a sintered body of a mixture of metal oxide powders obtained from refined organometallic compounds of each component metal so as to have a predetermined composition ratio represented by the above general formula. Content of alkali metal impurities is 1ppm
The target material which can form a dielectric thin film having an alkali metal impurity content of 1 ppm or less.
有量が１ppm 以下、かつＵ，Ｔｈの合計含有量が10 ppb
以下であり、それによりアルカリ金属不純物の含有量が
１ppm 以下、かつＵ，Ｔｈの合計含有量が10 ppb以下の
誘電体薄膜を形成することができる、請求項１記載のタ
ーゲット材。2. The sintered body has an alkali metal impurity content of 1 ppm or less and a total content of U and Th of 10 ppb.
The target material according to claim 1, wherein a dielectric thin film having an alkali metal impurity content of 1 ppm or less and a total content of U and Th of 10 ppb or less can be formed.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6860294A JPH09195040A (en) | 1994-04-06 | 1994-04-06 | Target material for forming high purity dielectric thin film |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6860294A JPH09195040A (en) | 1994-04-06 | 1994-04-06 | Target material for forming high purity dielectric thin film |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP4024293A Division JP2546466B2 (en) | 1992-01-16 | 1992-01-16 | High-purity dielectric thin film |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH09195040A true JPH09195040A (en) | 1997-07-29 |
Family
ID=13378511
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6860294A Withdrawn JPH09195040A (en) | 1994-04-06 | 1994-04-06 | Target material for forming high purity dielectric thin film |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH09195040A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004002887A1 (en) * | 2002-06-28 | 2004-01-08 | Arizona Board Of Regents | Barium cadmium tantalum-based compound having high dielectric properties and method of making the same |
-
1994
- 1994-04-06 JP JP6860294A patent/JPH09195040A/en not_active Withdrawn
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004002887A1 (en) * | 2002-06-28 | 2004-01-08 | Arizona Board Of Regents | Barium cadmium tantalum-based compound having high dielectric properties and method of making the same |
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