【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION
【０００１】[0001]
【産業上の利用分野】本発明は、太陽電池、薄膜ディス
プレイ装置等に用いられる透明導電膜の成膜方法に関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a transparent conductive film used for a solar cell, a thin film display device and the like.
【０００２】[0002]
【従来の技術】太陽電池の光入射側の電極に用いられる
透明導電膜材料として、SnＯ2、ＩＴＯが実用化されて
いる。なかでもSnＯ2は安価であり、水素処理による低
抵抗化が可能である。膜製造条件により膜表面の凹凸を
制御する、いわゆるテキスチャ化により有効な光の閉じ
込めを期待できることから、薄膜太陽電池の集電電極と
して広く用いられている。ただＣＶＤによる成膜法が主
体となるため、基板温度を約400 ℃程度にしなければな
らず、たとえばアモルファスシリコン等の材料の上に後
付けで堆積することが不可能であった。2. Description of the Related Art SnO2 and ITO have been put into practical use as transparent conductive film materials used for electrodes on the light incident side of solar cells. Above all, SnO2 is inexpensive, and its resistance can be reduced by hydrogen treatment. It is widely used as a current-collecting electrode for thin-film solar cells because it is possible to expect effective light confinement by controlling unevenness on the film surface according to the film manufacturing conditions, that is, by so-called texturing. However, since the film formation method by CVD is mainly used, the substrate temperature must be set to about 400 ° C., and it has not been possible to deposit later on a material such as amorphous silicon.
【０００３】これに対し、ＩＴＯは150 ℃程度の低い基
板温度で、水分を含んだ雰囲気中でのスパッタ法によ
り、低抵抗で高透過率の膜特性が得られているが、高価
なInを使用するので電力用太陽電池等の面積の大きいも
のはコスト面での制約がある。このためZnＯ系材料が再
び見直されてきている。ZnＯは従来より圧電材料、ガス
センサ材料として実用化されてきており、弾性表面波デ
バイス、ガス漏れ警報器、バリスタ等の製品が市販され
ている。[0003] On the other hand, ITO has a film characteristic of low resistance and high transmittance obtained by sputtering at a substrate temperature as low as about 150 ° C. in an atmosphere containing moisture. A large area such as a solar cell for electric power is limited in terms of cost because it is used. For this reason, ZnO-based materials have been reviewed again. ZnO has been practically used as a piezoelectric material and a gas sensor material, and products such as surface acoustic wave devices, gas leak alarms, and varistors are commercially available.
【０００４】ZnＯ、SnＯ2は酸素欠損型の導電機構を持
っており、欠陥格子の電子との授受(酸化還元反応) に
よりその抵抗率が容易に変化する。すなわち、酸化反応
で抵抗率は増大し、還元反応で低下する。このため、A
l、Ｂ等の不純物を添加して低抵抗化、特性安定化を図
っている。Ｎ型半導体ZnＯの抵抗率は、移動度をμN、
キャリア密度をＮNとしたときに次式(1) で与えられ
る。[0004] ZnO and SnO2 have an oxygen-deficient conduction mechanism, and the resistivity thereof easily changes due to the exchange (oxidation-reduction reaction) with the electrons of the defective lattice. That is, the resistivity increases in the oxidation reaction and decreases in the reduction reaction. Therefore, A
Impurities such as l and B are added to reduce resistance and stabilize characteristics. The resistivity of the N-type semiconductor ZnO is represented by a mobility of μN ,
When the carrier density is NN , it is given by the following equation (1).
【０００５】 ρ＝１／ (μNＮN) ────── (1) 従って、高μN化、高ＮN化により抵抗率を下げること
ができる。高μN化は結晶性を改善することで、高ＮN
化は不純物の添加濃度を高めることで実現できる。一
方、もう一つの重要な特性である光透過率は、透過光強
度をＩ、入射光強度をＩO、吸収係数α、膜厚をｔ、電
子の電荷をｅ、波長をλ、屈折率をｎ、光速をＣ、電子
の有効質量をｍ*、緩和時間をτとしたとき、次の２式
(2)、(3) で表わされる。Ρ = 1 / (μN NN ) ────── (1) Accordingly, the resistivity can be reduced by increasing μN and increasing NN. High muN of the to improve the crystallinity, high NN
Can be realized by increasing the concentration of the impurity added. On the other hand, another important characteristic, light transmittance, is: transmitted light intensity I, incident light intensity IO , absorption coefficient α, film thickness t, electron charge e, wavelength λ, refractive index n, the speed of light C, and the effective mass of the electron m*, when the relaxation time was tau, the following two formulas
(2) and (3).
【０００６】 Ｉ＝ＩOexp(−αｔ) ──────(2) α＝ＮNｅ2λa／ (πｎＣ3ｍ*τ) ──────(3) (3) 式より、吸収係数αを低減し高透過率化を図るに
は、ＮNを低減することが重要であることがわかる。こ
のことは、(1) 式によりρを下げるためにＮNを高くす
ることと矛盾する。したがって、適当な量の不純物を添
加し、かつ結晶性を悪化させず、高μNを保ことが良く
光を透過させ抵抗率の低い薄膜形成の条件となる。[0006]I = I O exp (-αt) ────── (2) α = N N e 2 λ a / (πnC 3 m * τ) ────── (3) (3) formula From this, it is understood that it is important to reduce NN in order to reduce the absorption coefficient α and increase the transmittance. This is inconsistent with increasing the NN in order to reduce the ρ by (1). Therefore, adding a suitable amount of impurities, and without deteriorating the crystallinity, the condition of high muN low film formation resistivity by transmitting good light coercive a.
【０００７】[0007]
【発明が解決しようとする課題】たとえば、太陽電池へ
の適用を考えると電流収集効率より、ρ＜１×10-3Ω・
cmが必要である。また光出力電流は透過率に比例するた
め、SnＯ2なみの電流を得ようとすると、透過率を90％
程度まで高める必要がある。しかし、不純物としてAl2
Ｏ3を用い、これを２重量％程度添加したZnＯでは２×
10-4Ω・cmの抵抗率が得られており、熱的安定性も良い
ため透明導電膜として従来用いられていたが、透過率は
約70％と低かった。For example, considering application to a solar cell, ρ <1 × 10−3 Ω ·
cm is required. In addition, since the light output current is proportional to the transmittance, if a current as high as SnO2 is to be obtained, the transmittance becomes 90%.
It is necessary to raise to the extent. However, Al2 as an impurity
O3 is used, and ZnO to which about 2% by weight is added is 2 ×
A resistivity of 10−4 Ω · cm was obtained, and thermal stability was good, so that it was conventionally used as a transparent conductive film, but the transmittance was as low as about 70%.
【０００８】本発明の目的は、Al2Ｏ3を不純物として
添加したZnＯからなり、高透過率で低抵抗率の透明導電
膜の成膜方法を提供することにある。An object of the present invention is to provide a method for forming a transparent conductive film having high transmittance and low resistivity, which is made of ZnO to which Al2 O3 is added as an impurity.
【０００９】[0009]
【課題を解決するための手段】上記の目的を達成するた
めに、本発明のよれば、０．５重量パ−セント〜１重量
パ−セントの濃度の酸化アルミニウムを含む酸化亜鉛か
らなるタ−ゲットを用い、水素を含む不活性ガス雰囲気
中でスパッタリングする透明導電膜の成膜方法であっ
て、水素を含む不活性ガス雰囲気中でのスパッタリング
により薄膜を形成する工程と、形成された薄膜を水素を
含む不活性ガス雰囲気にさらす工程とを交互に繰り返す
こととする。ここで、不活性ガスがアルゴンガスである
と好ましい。また、スパッタリングをＲＦマグネトロン
スパッタリング装置を用いて行うと良い。According to the present invention, there is provided, according to the present invention, a zinc oxide containing aluminum oxide at a concentration of 0.5 to 1 weight percent. A method for forming a transparent conductive film by sputtering in an inert gas atmosphere containing hydrogen, using a get, a step of forming a thin film by sputtering in an inert gas atmosphere containing hydrogen, and forming the formed thin film. The step of exposing to an inert gas atmosphere containing hydrogen is alternately repeated. Here, it is preferable that the inert gas is an argon gas. In addition, sputtering is preferably performed using an RF magnetron sputtering device.
【００１０】[0010]
【作用】0.５重量％以上のAl2Ｏ3をZnＯに添加するこ
とにより高ＮN化がはかれるが、Al2Ｏ3濃度を１重量
％以下に抑えると共にスパッタリング雰囲気中へ水素を
添加することにより低μN化がはかれる。これで高透過
率が実現する。ただしAl2Ｏ3が１重量％より多い場合
に比べて抵抗率は高くなるが、膜堆積と水素を含む不活
性ガス雰囲気中にさらすことによる還元反応を交互に繰
り返すことで、膜中の酸素濃度を低下させることなく水
素を添加することができる。この水素が格子欠陥部の酸
素を補償して伝導に寄与するため膜の抵抗が低減する。[Action] 0.5% by weight or more of AlTwoOThreeCan be added to ZnO
And higher NNAl can be removedTwoOThree1 weight concentration
% And hydrogen into the sputtering atmosphere
Low μ by addingNIs being measured. High transparency with this
The rate is realized. Where AlTwoOThreeIs more than 1% by weight
Resistivity, but film deposition and inertness including hydrogen
Reduction reaction by exposure to an inert gas atmosphere.
By repeating the process, water can be reduced without lowering the oxygen concentration in the film.
Element can be added. This hydrogen is the acid at the lattice defect.
Since the element is compensated and contributes to conduction, the resistance of the film is reduced.
【００１１】[0011]
【実施例】ＲＦマグネトロンスパッタ装置を用いて、Zn
Ｏターゲツト中のAl2Ｏ3濃度を０〜２重量％、雰囲気
ガスであるArガス中のＨ2濃度を０〜10％迄の範囲で変
え、ガラス基板へのZnＯ薄膜を形成した。基板温度は15
0 ℃とし、シート抵抗率が10Ωになるように膜厚を調整
した。成膜された透明導電膜の抵抗率と白色光透過率を
タングステンランプを用いて測定した結果を図１、図２
に示す。[Embodiment] Using an RF magnetron sputtering apparatus, Zn
The ZnO thin film was formed on a glass substrate by changing the concentration of Al2 O3 in the O target within the range of 0 to 2% by weight and the concentration of H2 in the atmosphere gas, Ar gas, within the range of 0 to 10%. Substrate temperature is 15
The temperature was set to 0 ° C., and the film thickness was adjusted so that the sheet resistivity became 10Ω. FIGS. 1 and 2 show the results of measuring the resistivity and the white light transmittance of the formed transparent conductive film using a tungsten lamp.
Shown in
【００１２】図１は抵抗率のZnＯターゲツト中のAl2Ｏ
3濃度依存性をAr雰囲気中に含有されたＨ2濃度とパラ
メータとして示し、実線11はAr100 ％、鎖線12はＨ2２
％含有Ar、点線13はＨ210％含有Ar中でスパッタリング
した場合である。図２は白色光透過率のZnＯターゲツト
中のAl2Ｏ3濃度依存性をAr雰囲気中に含有されたＨ2
濃度とパラメータとして示し、各線に付した符号の示す
条件は図１の同一符号の場合に対応している。FIG. 1 shows Al2 O in a ZnO target of resistivity.
3 The concentration dependency is shown as a parameter and the concentration of H2 contained in the Ar atmosphere. The solid line 11 is 100% Ar and the chain line 12 is H2 2
% Containing Ar, dotted line 13 is the case where sputtering is performed in H2 containing 10% Ar. FIG. 2 shows the dependence of the white light transmittance on the Al2 O3 concentration in the ZnO target in the presence of H2 in the Ar atmosphere.
The conditions shown as the density and the parameters, and the symbols attached to each line correspond to the case of the same symbol in FIG.
【００１３】図１、図２に示すように、従来例のAl2Ｏ
3濃度２重量％のターゲツトを用い水素無添加の雰囲気
中でスパッタリングした場合は、抵抗率ρ＝２×10-4Ω
・cmが得られているが、透過率は73％と低い値を示して
いる。これに対し本発明の実施例のAl2Ｏ3濃度0.５重
量％あるいは0.８重量％で水素添加の雰囲気中でスパッ
タリングしたときには、透過率は90％になり、SnＯ2同
様の特性が得られた。さらに、数秒程度のスパッタリン
グで１分子程度の薄膜を堆積したのち、スパッタリング
チャンバ中の雰囲気にさらす操作を繰り返すことによ
り、抵抗率を２×10-4Ω・cmにまで下げることができ
た。As shown in FIGS. 1 and 2, the conventional Al2 O
(3) When sputtering is performed in a hydrogen-free atmosphere using a target having a concentration of 2% by weight, the resistivity ρ = 2 × 10−4 Ω
-Although cm was obtained, the transmittance showed a low value of 73%. On the other hand, when sputtering is performed in an atmosphere of hydrogen addition at an Al2 O3 concentration of 0.5% by weight or 0.8% by weight according to the embodiment of the present invention, the transmittance becomes 90%, and characteristics similar to SnO2 are obtained. Obtained. Furthermore, by repeating the operation of depositing a thin film of about one molecule by sputtering for about several seconds and exposing it to the atmosphere in the sputtering chamber, the resistivity could be reduced to 2 × 10−4 Ω · cm.
【００１４】別の実施例として、基板をプラスチックフ
ィルムに変え、Ｈ2濃度を２％にしてAl2Ｏ3含有ZnＯ
ターゲツトを用いて透明導電膜を成膜したところ、ガラ
ス基板上の同等の抵抗率、透過率の膜特性が得られた。
プラスチックフィルムのような熱ダメージに弱い基板上
へのZnＯ薄膜の形成は、従来はプラズマ収束性の良いＤ
Ｃマグネトロンスパッタ法によりのみ可能であったが、
水素添加による低プラズマ温度化により制御性のよいＲ
Ｆマグネトロンスパッタ法によるフィルム上への成膜が
可能になった。In another embodiment, the substrate is changed to a plastic film, the H2 concentration is set to 2%, and ZnO containing Al2 O3 is used.
When a transparent conductive film was formed using the target, film characteristics with the same resistivity and transmittance on a glass substrate were obtained.
Conventionally, formation of a ZnO thin film on a substrate that is vulnerable to thermal damage, such as a plastic film, has conventionally required a D
Although it was possible only by the C magnetron sputtering method,
R with good controllability by lowering plasma temperature by adding hydrogen
Film formation on a film by F magnetron sputtering has become possible.
【００１５】[0015]
【発明の効果】本発明によれば、低抵抗化のためのZnＯ
ターゲツト中へのAl添加濃度を抑えるスパッタリング雰
囲気中にＨ2を加えることにより、SnＯ2なみの透過率
をもつ透明導電膜を形成することが可能になった。そし
て、スパッタリング時の雰囲気への水素添加により、プ
ラズマ温度が下げるとともに、成膜と雰囲気中にさらす
ことを交互に繰り返すことにより、Al2Ｏ3濃度の低下
による抵抗率の上昇も補償することも可能になり、低コ
ストのZnＯ膜として、太陽電池用の透明導電膜としてば
かりでなく、表示ディスプレイ用の透明導電膜等にも応
用でき、また結露防止用薄膜等にも実用化できる。According to the present invention, ZnO for lowering the resistance is used.
By adding H2 to a sputtering atmosphere that suppresses the concentration of Al added to the target, a transparent conductive film having a transmittance similar to that of SnO2 can be formed. The addition of hydrogen to the atmosphere during sputtering lowers the plasma temperature, and alternately repeats film formation and exposure to the atmosphere, thereby compensating for the increase in resistivity due to the decrease in Al2 O3 concentration. It can be applied to a low-cost ZnO film not only as a transparent conductive film for a solar cell but also as a transparent conductive film for a display and the like, and can be put into practical use as a thin film for preventing dew condensation.
【図１】ZnＯ太陽電池中のAl2Ｏ3濃度とZnＯ薄膜の抵
抗率との関係をAr中のＨ2濃度をパラメータとして示す
線図FIG. 1 is a diagram showing the relationship between the Al2 O3 concentration in a ZnO solar cell and the resistivity of a ZnO thin film using the H2 concentration in Ar as a parameter.
【図２】ZnＯ太陽電池中のAl2Ｏ3濃度とZnＯ薄膜白色
光透過率との関係をAr中のＨ2濃度をパラメータとして
示す線図FIG. 2 is a diagram showing the relationship between the Al2 O3 concentration in a ZnO solar cell and the transmittance of white light from a ZnO thin film using the H2 concentration in Ar as a parameter.
１１ Ar 100％ １２ Ｈ2２％含有Ar １３ Ｈ210％含有Ar11 Ar 100% 12 H2 2% content Ar 13 H2 10% content Ar
───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.6，ＤＢ名) H01L 31/04 C23C 14/08 H01B 13/00 H01L 21/285──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl.6 , DB name) H01L 31/04 C23C 14/08 H01B 13/00 H01L 21/285
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4066465AJP2928016B2 (en) | 1992-03-25 | 1992-03-25 | Method for forming transparent conductive film |
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4066465AJP2928016B2 (en) | 1992-03-25 | 1992-03-25 | Method for forming transparent conductive film |
| Publication Number | Publication Date |
|---|---|
| JPH05275727A JPH05275727A (en) | 1993-10-22 |
| JP2928016B2true JP2928016B2 (en) | 1999-07-28 |
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP4066465AExpired - LifetimeJP2928016B2 (en) | 1992-03-25 | 1992-03-25 | Method for forming transparent conductive film |
| Country | Link |
|---|---|
| JP (1) | JP2928016B2 (en) |
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|---|---|---|---|---|
| CN102165559B (en) | 2008-09-30 | 2013-09-04 | Lg化学株式会社 | Transparent conductive layer and transparent electrode including the transparent conductive layer |
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