JP5274768B2 - Film forming apparatus and method for preventing abnormal discharge from occurring at cylindrical cathode used in film forming apparatus - Google Patents

Film forming apparatus and method for preventing abnormal discharge from occurring at cylindrical cathode used in film forming apparatus Download PDF

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JP5274768B2
JP5274768B2 JP2006335934A JP2006335934A JP5274768B2 JP 5274768 B2 JP5274768 B2 JP 5274768B2 JP 2006335934 A JP2006335934 A JP 2006335934A JP 2006335934 A JP2006335934 A JP 2006335934A JP 5274768 B2 JP5274768 B2 JP 5274768B2
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南 江
暉 張
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Pureron Japan Co Ltd
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本発明は、電界放射型冷陰極材料としての炭素膜を成膜する成膜装置および該成膜装置に用いる筒状陰極での異常放電発生防止方法に関するものである。   The present invention relates to a film forming apparatus for forming a carbon film as a field emission cold cathode material, and a method for preventing abnormal discharge from occurring in a cylindrical cathode used in the film forming apparatus.

電界放射は電界集中により電子が真空に放射される現象であり、この電界放射により電子放出を行う電界放射型冷陰極（以下、冷陰極）材料として例えばカーボンナノチューブ（ＣＮＴ）が近年注目を集めその開発が進められてきている。ＣＮＴは、極めて細長く高アスペクト比のために冷陰極材料とした場合、電界放射特性に優れた冷陰極を得ることができるとされている。   Field emission is a phenomenon in which electrons are radiated to a vacuum due to electric field concentration. For example, carbon nanotubes (CNT) have recently attracted attention as a field emission type cold cathode (hereinafter, cold cathode) material that emits electrons by this field emission. Development is ongoing. CNTs are extremely thin and have a high aspect ratio, and when used as a cold cathode material, it is said that a cold cathode having excellent field emission characteristics can be obtained.

電界放射特性（電流電圧（ＩＶ）特性）とは、陽極と冷陰極との間に電圧Ｖを印加して冷陰極から電界放射する際の、電圧Ｖと電界放射電流（エミッション電流）Ｉとの関係を示す曲線により示される特性であり、電界放射を開始する電圧（閾値）や、上記曲線の傾きや形状で特徴づけられる。   The field emission characteristic (current / voltage (IV) characteristic) is a voltage V and a field emission current (emission current) I when a voltage V is applied between the anode and the cold cathode and electric field is emitted from the cold cathode. It is a characteristic indicated by a curve indicating the relationship, and is characterized by a voltage (threshold value) at which field emission is started, and the slope and shape of the curve.

このような冷陰極を蛍光体付きの陽極に対向配置し、冷陰極と陽極との間に電圧を印加して冷陰極から電界放射により電子を放出させ、この放出した電子を蛍光体に加速衝突させて蛍光体を励起発光させる冷陰極蛍光ランプがある。   Such a cold cathode is placed opposite to the anode with the phosphor, a voltage is applied between the cold cathode and the anode, and electrons are emitted from the cold cathode by field emission, and the emitted electrons collide with the phosphor for acceleration. There is a cold-cathode fluorescent lamp that causes a phosphor to be excited to emit light.

この蛍光体の発光には所定量の電子放出が必要である。この電子放出量を示すエミッション電流を縦軸に、陽陰極間の電圧を横軸にして示す電流電圧（ＩＶ）特性曲線は冷陰極の電子放出性能を示している。ＣＮＴの場合、上記ＩＶ特性曲線の傾きが緩やかに立ち上がってくる。そのため、ＣＮＴでは蛍光体が発光を開始させるためのエミッション電流を得るのに必要な電圧Ｖは高くなる。   A predetermined amount of electron emission is required for light emission of the phosphor. A current-voltage (IV) characteristic curve showing the emission current indicating the electron emission amount on the vertical axis and the voltage between the positive and negative electrodes on the horizontal axis indicates the electron emission performance of the cold cathode. In the case of CNT, the slope of the IV characteristic curve rises gently. For this reason, in CNT, the voltage V required for obtaining an emission current for the phosphor to start light emission becomes high.

そこで、より低い印加電圧Ｖで蛍光体を発光開始させることができるＩＶ特性を提供する冷陰極用の炭素膜の実現が望まれている。   Therefore, it is desired to realize a carbon film for a cold cathode that provides an IV characteristic capable of starting emission of a phosphor with a lower applied voltage V.

本出願人は、ＣＮＴよりもＩＶ特性に優れた冷陰極用の炭素膜を導電性ワイヤ等の基板表面に成膜する技術を開発してきている。以下に説明する成膜装置は本出願人が開発したものである。   The present applicant has developed a technique for forming a carbon film for a cold cathode, which has better IV characteristics than CNTs, on a substrate surface such as a conductive wire. The film forming apparatus described below has been developed by the present applicant.

以下、図４を参照して説明すると、この成膜装置１は、ガス導入系２と真空排気系４とを備えた真空成膜室６と、真空成膜室６内部に配置された筒状陰極８とを有する。この筒状陰極８の周壁は螺旋状（コイル状）をなしている。筒状陰極８の内部空間には成膜対象である基板として導電性ワイヤ１０が配置される。筒状陰極８は、その内部空間にプラズマを閉じ込め状態で生成する。この意味で筒状陰極８は、プラズマ閉じ込め型陰極と称することができる。   Hereinafter, with reference to FIG. 4, the film forming apparatus 1 includes a vacuum film forming chamber 6 having a gas introduction system 2 and a vacuum exhaust system 4, and a cylindrical shape disposed inside the vacuum film forming chamber 6. And a cathode 8. The peripheral wall of the cylindrical cathode 8 has a spiral shape (coil shape). A conductive wire 10 is disposed in the internal space of the cylindrical cathode 8 as a substrate to be deposited. The cylindrical cathode 8 generates plasma in a confined state in its internal space. In this sense, the cylindrical cathode 8 can be referred to as a plasma confined cathode.

筒状陰極８は直流電源１２の負極に接続されている。この直流電源１２の正極は接地される。導電性ワイヤ１０は交流電源１４で通電加熱されかつ直流電源１６により直流バイアスが印加されるようになっている。   The cylindrical cathode 8 is connected to the negative electrode of the DC power source 12. The positive electrode of the DC power supply 12 is grounded. The conductive wire 10 is energized and heated by an AC power supply 14 and a DC bias is applied by a DC power supply 16.

以上の構成を備えた成膜装置１において、真空排気系４で真空成膜室６内を減圧しかつガス導入系２から炭素膜成膜用ガスを導入し、直流電源１２からの直流負電圧を筒状陰極８に印加すると、筒状陰極８の内部空間にプラズマ１８が閉じ込め状態で発生する。これにより、筒状陰極８内に導入した炭素膜成膜用ガスが分解され、その分解した炭素成分が筒状陰極８内に配置した導電性ワイヤ１０の表面に成膜されるようになっていた。   In the film forming apparatus 1 having the above-described configuration, the vacuum film forming chamber 6 is depressurized by the vacuum exhaust system 4 and the carbon film forming gas is introduced from the gas introducing system 2, and the direct current negative voltage from the direct current power source 12 is obtained. Is applied to the cylindrical cathode 8, plasma 18 is generated in a confined state in the internal space of the cylindrical cathode 8. Thereby, the carbon film forming gas introduced into the cylindrical cathode 8 is decomposed, and the decomposed carbon component is formed on the surface of the conductive wire 10 disposed in the cylindrical cathode 8. It was.

しかしながら、真空成膜室６内の真空圧は１０００〜２０００Ｐａの範囲に制限されていた。この制限は、真空圧が２０００Ｐａを超えると、筒状陰極８から異常放電が発生し、導電性ワイヤ１０表面に炭素膜が成膜されなかったり、成膜されてもその膜質が劣化する原因となるからであった。   However, the vacuum pressure in the vacuum film forming chamber 6 was limited to a range of 1000 to 2000 Pa. This limitation is that when the vacuum pressure exceeds 2000 Pa, abnormal discharge occurs from the cylindrical cathode 8, and the carbon film is not formed on the surface of the conductive wire 10, or the film quality is deteriorated even if it is formed. Because it was.

異常放電の発生について本出願人が研究したところ、プラズマ発生により分解された炭素物質は導電性ワイヤ１０だけでなく筒状陰極８表面にも付着しやすくなる。この筒状陰極８に付着した炭素物質はアモルファス状の炭素物質であるために、電荷がチャージアップしやすく、その電荷のチャージアップ量が一定値を超えたときに放電することが原因していたと考えられる。   When the present applicant researched about generation | occurrence | production of abnormal discharge, the carbon substance decomposed | disassembled by plasma generation becomes easy to adhere not only to the electroconductive wire 10 but the cylindrical cathode 8 surface. Since the carbon material adhering to the cylindrical cathode 8 is an amorphous carbon material, the charge is likely to be charged up, and the discharge is caused when the charge charge amount exceeds a certain value. Conceivable.

そのため、真空圧は本出願人が実験した所に拠れば上記異常放電発生を防止するには真空圧を２０００Ｐａ以下に制限する必要があった。真空圧を低くすると、導電性ワイヤ１０表面に成膜条件が制約されると共にＩＶ特性に優れた冷陰極材料に適した炭素膜を成膜することができなくなる。
特開平１０−２２３１２８号公報 Therefore, the vacuum pressure must be limited to 2000 Pa or less in order to prevent the occurrence of the abnormal discharge according to the place where the present applicant experimented. When the vacuum pressure is lowered, film formation conditions are restricted on the surface of the conductive wire 10 and a carbon film suitable for a cold cathode material having excellent IV characteristics cannot be formed.
JP-A-10-223128

したがって、本発明により解決すべき課題は、真空圧を高めても異常放電が発生しないようにして炭素膜の成膜条件の範囲を拡大しかつその炭素膜を冷陰極材料に用いた場合にＩＶ特性が改善された冷陰極を提供できる成膜装置および該成膜装置に用いる筒状陰極での異常放電発生防止方法を提供することである。   Therefore, the problem to be solved by the present invention is that when the range of carbon film formation conditions is expanded so that abnormal discharge does not occur even when the vacuum pressure is increased, and the carbon film is used as a cold cathode material, IV It is an object of the present invention to provide a film forming apparatus capable of providing a cold cathode having improved characteristics and a method for preventing an abnormal discharge from occurring in a cylindrical cathode used in the film forming apparatus.

本発明による成膜装置は、真空成膜室内に配置した筒状陰極に直流負電圧を印加しその内部にプラズマを閉じ込め状態で生成して真空成膜室に導入した炭素膜成膜用のガスを分解することにより当該筒状陰極内部に配置した基板表面に炭素膜を成膜する成膜装置であって、上記直流負電圧を印加して生成したプラズマにより上記ガスが分解して上記成膜が行われる過程で、パルス状正電圧を筒状陰極に繰り返し印加して該筒状陰極に付着した炭素物質に帯電する電荷を中和することにより、上記電荷のチャージアップによる異常放電の発生を防止可能としたことを特徴とするものである。   A film forming apparatus according to the present invention is a carbon film forming gas introduced into a vacuum film forming chamber by applying a DC negative voltage to a cylindrical cathode disposed in a vacuum film forming chamber and generating plasma in a confined state inside the tube. Is a film forming apparatus for forming a carbon film on the surface of the substrate disposed inside the cylindrical cathode by decomposing the gas, and the gas is decomposed by the plasma generated by applying the DC negative voltage. In the process, the pulsed positive voltage is repeatedly applied to the cylindrical cathode to neutralize the charge charged on the carbon material adhering to the cylindrical cathode, thereby preventing the occurrence of abnormal discharge due to the charge charging up. It is possible to prevent it.

上記筒状陰極の形状は、特に限定しないが、両端のいずれか一方が開口していれば周壁は閉鎖していてもよいが、好ましくは周壁の一部に開口を有する。周壁の形状（パターン）には周壁に多数の開口を有する形状として、螺旋状、メッシュ状、柵状、格子状、等を含む。これら形状は筒状陰極内部に配置した基板表面に均等に炭素膜を成膜するうえで好ましい。   Although the shape of the said cylindrical cathode is not specifically limited, If either one of both ends is opening, a surrounding wall may be closed, Preferably it has an opening in a part of surrounding wall. The shape (pattern) of the peripheral wall includes a spiral shape, a mesh shape, a fence shape, a lattice shape, and the like as a shape having a large number of openings in the peripheral wall. These shapes are preferable for uniformly forming a carbon film on the surface of the substrate disposed inside the cylindrical cathode.

上記炭素物質は抵抗値が高く導電性が低い炭素物質である。  The carbon material is a carbon material having a high resistance value and low conductivity.

筒状陰極は両端開口、一端開口他端側閉鎖の筒体を含む。筒状陰極の断面形状は特に限定しないが、基板形状がワイヤ状の場合、円形が好ましい。   The cylindrical cathode includes a cylindrical body having both ends opened and one end opened and the other end closed. The cross-sectional shape of the cylindrical cathode is not particularly limited, but when the substrate shape is a wire shape, a circular shape is preferable.

基板の形状は特に限定しないが、平面状やワイヤ状を例示することができる。例えばワイヤ状基板に炭素膜を成膜してワイヤ状冷陰極を形成する場合、内面に蛍光体付き陽極を形成したガラス管内部にこのワイヤ状冷陰極を配置した冷陰極蛍光ランプを構成することができる。   Although the shape of a board | substrate is not specifically limited, A planar shape or wire shape can be illustrated. For example, when a wire-like cold cathode is formed by forming a carbon film on a wire-like substrate, a cold-cathode fluorescent lamp in which this wire-like cold cathode is arranged inside a glass tube having an anode with a phosphor on the inner surface is constructed. Can do.

パルス状正電圧を筒状陰極に繰り返し印加する趣旨には、周期的な繰り返しに限定するものではなく、不定期な繰り返しも含むものである。   The purpose of repeatedly applying the pulsed positive voltage to the cylindrical cathode is not limited to periodic repetition, but also includes irregular repetition.

上記の場合、１周期内における上記パルス状正電圧の印加期間が上記直流負電圧の印加期間より短い期間として該パルス状正電圧を周期的に繰り返し印加することが好ましい。この印加により、電荷のチャージアップによる異常放電の発生を、基板表面に対する炭素膜成膜に影響を及ぼさずに、効果的に防止できるようになる。   In the above case, it is preferable that the pulsed positive voltage is periodically and repeatedly applied so that the application period of the pulsed positive voltage within one period is shorter than the application period of the DC negative voltage. By this application, the occurrence of abnormal discharge due to charge up can be effectively prevented without affecting the carbon film formation on the substrate surface.

上記の場合、所定周波数における各周期内で上記直流負電圧の印加期間に対して上記パルス状正電圧の印加期間を上記帯電した電荷をパルス状正電圧の印加で中和できる期間にデューティ制御することが好ましい。   In the above case, the duty period of the pulsed positive voltage application period is controlled to the period during which the charged charge can be neutralized by the application of the pulsed positive voltage with respect to the DC negative voltage application period within each cycle at a predetermined frequency. It is preferable.

上記デューティ制御は周波数を制御することにより行ってもよいし、あるいは、周波数同一の場合ではパルス状正電圧の印加期間を変更することにより行ってもよい。この場合、パルス状正電圧の形状をデューティ制御に含むことができる。   The duty control may be performed by controlling the frequency, or may be performed by changing the application period of the pulsed positive voltage when the frequency is the same. In this case, the shape of the pulsed positive voltage can be included in the duty control.

上記所定周波数が、１ｋＨｚ〜２０ｋＨｚであり、上記所定周波数における１周期内でパルス状正電圧の１回の印加期間が、５μｓ〜２００μｓであることが好ましい。   It is preferable that the predetermined frequency is 1 kHz to 20 kHz, and one application period of the pulsed positive voltage within one cycle at the predetermined frequency is 5 μs to 200 μs.

ただし、このパルス状正電圧の大きさは上記帯電した電荷を中和できる大きさであれば、特に限定しないが、好ましくは、＋１００Ｖ〜＋３００Ｖであり、より好ましくは＋１００Ｖ〜＋２５０Ｖであり、最適には約２００Ｖである。勿論、パルス状正電圧の大きさが＋１００Ｖ以下、＋２５０Ｖ以上であっても、上記帯電した電荷を中和できる大きさであれば本発明に含む。   However, the magnitude of the pulsed positive voltage is not particularly limited as long as it can neutralize the charged electric charge, but is preferably +100 V to +300 V, more preferably +100 V to +250 V, and optimally. Is about 200V. Of course, even if the magnitude of the pulsed positive voltage is +100 V or less and +250 V or more, the present invention includes the present invention as long as it has a magnitude capable of neutralizing the charged charge.

この場合、パルス状正電圧の形状は特に限定しないが、矩形波形ではなく頂点角度が例えば形状表現として数度程度の鋭角三角形状であれば、電圧ゼロＶから正方向に立ち上がり、最大値に達してから負方向に立ち下がるので、その印加期間は例えばゼロＶ近傍では５μｓ程度であり、例えば上記最適な最大高さ２００Ｖ近傍では１〜２μｓ程度になっている。   In this case, the shape of the pulsed positive voltage is not particularly limited. However, if the apex angle is not a rectangular waveform but an acute triangular shape of, for example, several degrees as a shape expression, the voltage rises from zero V in the positive direction and reaches the maximum value. Since the voltage falls in the negative direction after that, the application period is, for example, about 5 μs in the vicinity of zero V, and is, for example, about 1 to 2 μs in the vicinity of the optimum maximum height of 200 V.

したがって、上記パルス状正電圧の形状が上記鋭角三角形状であれば、パルス状正電圧の印加期間は５μｓ〜２００μｓにおいて最短の印加期間である５μｓは電圧ゼロＶ近傍の印加期間である。   Therefore, if the shape of the pulsed positive voltage is the acute triangular shape, the application period of the pulsed positive voltage is 5 μs to 200 μs, and 5 μs, which is the shortest application period, is an application period in the vicinity of a voltage of zero V.

パルス状正電圧の形状がほぼ完全な矩形形状であれば、上記印加期間はその立ち上がりから立ち下りまでのパルス幅相当期間となる。   If the shape of the pulsed positive voltage is a substantially perfect rectangular shape, the application period is a period corresponding to the pulse width from the rising edge to the falling edge.

パルス状正電圧の印加期間はこのパルス状正電圧により上記帯電した電荷を中和できればよいので、直流負電圧の印加期間と比較して極めて短く設定することができ、実質、直流負電圧を連続印加して直流プラズマ成膜を行うことができるようになっている。   Since the pulsed positive voltage need only be neutralized by the pulsed positive voltage, the pulsed positive voltage can be set very short compared to the DC negative voltage application period. The direct current plasma film formation can be performed by applying.

以上から、本発明の成膜装置によると、直流プラズマにより上記ガスが分解して上記成膜が行われる過程で所定周波数における各周期内で上記直流負電圧の印加期間に対して当該筒状陰極にパルス状正電圧を短い印加期間で印加するので、基板への成膜に影響を及ぼさずに、プラズマにより成膜する過程で抵抗が高く導電性が低い炭素物質が筒状陰極に付着しこの付着した炭素物質に電荷がチャージアップしてもパルス状正電圧で電荷中和し、結果として電荷チャージアップによる異常放電が発生しないように制御することができる。そのため、本発明の成膜装置では真空成膜室内を高真空圧に制御して基板表面に炭素膜の成膜を実施することができるようになり、成膜された炭素膜を冷陰極材料とする冷陰極のＩＶ特性を向上することができる。   As described above, according to the film forming apparatus of the present invention, the cylindrical cathode is applied to the DC negative voltage application period within each cycle at a predetermined frequency in the process in which the gas is decomposed by DC plasma and the film is formed. Since a pulsed positive voltage is applied in a short application period, a carbon material with high resistance and low conductivity adheres to the cylindrical cathode during the film formation process by plasma without affecting the film formation on the substrate. Even if the attached carbon substance is charged up, the charge can be neutralized with a pulsed positive voltage, and as a result, control can be performed so that abnormal discharge due to charge charge up does not occur. Therefore, in the film forming apparatus of the present invention, it becomes possible to form a carbon film on the substrate surface by controlling the vacuum film forming chamber to a high vacuum pressure, and the formed carbon film is used as a cold cathode material. It is possible to improve the IV characteristics of the cold cathode.

本発明による成膜装置用筒状陰極での異常放電発生防止方法は、真空成膜室内に配置した筒状陰極に直流負電圧を印加し、その内部にプラズマを閉じ込め状態で生成して、真空成膜室に導入した炭素膜成膜用のガスを分解することにより、当該筒状陰極内部に配置した基板表面に炭素膜を成膜する過程で、パルス状正電圧を筒状陰極に繰り返し、好ましくは周期的に印加して該筒状陰極に付着した上記炭素膜より導電性が低く抵抗が高い炭素物質に帯電する電荷を中和することにより、上記電荷のチャージアップによる異常放電の発生を防止する、ことを特徴とするものである。   According to the present invention, a method for preventing abnormal discharge from occurring in a cylindrical cathode for a film-forming apparatus applies a negative DC voltage to a cylindrical cathode disposed in a vacuum film-forming chamber, generates plasma in a confined state therein, and creates a vacuum. In the process of forming the carbon film on the surface of the substrate disposed inside the cylindrical cathode by decomposing the gas for forming the carbon film introduced into the deposition chamber, a pulsed positive voltage is repeatedly applied to the cylindrical cathode, Preferably, by applying a periodic charge to neutralize the electric charge charged to the carbon material having a lower conductivity and a higher resistance than the carbon film attached to the cylindrical cathode, the occurrence of abnormal discharge due to the charge up of the electric charge is prevented. It is characterized by preventing.

本発明によれば、成膜圧力範囲を高くしても筒状陰極から異常放電が発生することなく炭素膜を成膜することができる。その結果、本発明では、成膜圧力範囲を高くして炭素膜を成膜し、その成膜した炭素膜を冷陰極材料に用いた場合にＩＶ特性が改善された冷陰極を提供することができるようになる。   According to the present invention, a carbon film can be formed without causing abnormal discharge from the cylindrical cathode even if the film forming pressure range is increased. As a result, the present invention can provide a cold cathode having improved IV characteristics when the carbon film is formed at a higher deposition pressure range and the formed carbon film is used as a cold cathode material. become able to.

以下、添付した図面を参照して、本発明の実施の形態に係る成膜装置を説明する。図１に実施の形態の成膜装置を示す。図１において図４と同一の部分には同一の符号を付し、同一の符号に係る部分の説明は簡略する。   Hereinafter, a film forming apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a film forming apparatus according to an embodiment. In FIG. 1, the same parts as those in FIG. 4 are denoted by the same reference numerals, and description of the parts related to the same reference numerals will be simplified.

実施の形態では、直流電源１２に代えて、パルス電圧生成部２０を備える。パルス電圧生成部２０は、図２で示すように、所定の周波数範囲における各周期Ｔ内で筒状陰極８に直流負電圧Ｖ１を第１印加期間Ｔ１印加すると共にパルス状正電圧Ｖ２を第２印加期間Ｔ２印加するようになっている。   In the embodiment, a pulse voltage generation unit 20 is provided instead of the DC power supply 12. As shown in FIG. 2, the pulse voltage generator 20 applies the DC negative voltage V1 to the cylindrical cathode 8 in the first application period T1 and the pulsed positive voltage V2 to the second within each period T in a predetermined frequency range. Application period T2 is applied.

パルス電圧生成部２０は、パルス電源で構成することができるが、これに限定するものではない。上記直流負電圧Ｖ１、パルス状正電圧Ｖ２を出力制御することができればよい。また、パルス電圧生成部２０は、上記周波数における周期Ｔ、上記印加期間Ｔ１，Ｔ２を可変制御することができようになっている。   The pulse voltage generation unit 20 can be configured by a pulse power supply, but is not limited thereto. It is only necessary to be able to control the output of the DC negative voltage V1 and the pulsed positive voltage V2. Further, the pulse voltage generator 20 can variably control the period T at the frequency and the application periods T1 and T2.

筒状陰極８はその周壁の形状が一例として螺旋状になっているものを用いる。筒状陰極８はその両端が一例として開口したものを用いている。   As the cylindrical cathode 8, a cylindrical cathode having a spiral shape as an example is used. The cylindrical cathode 8 is one having both ends opened as an example.

図２中にはＴ，Ｔ１，Ｔ２は説明の都合で電圧ゼロＶを基準に示している。   In FIG. 2, T, T1, and T2 are shown based on a voltage of zero V for convenience of explanation.

パルス状正電圧Ｖ２は、直流負電圧Ｖ１に対して上記周波数における各周期Ｔごとにデューティ制御して周期的に繰り返して筒状陰極８に印加されるようになっている。この周期Ｔ内でパルス状正電圧Ｖ２のパルス幅をμｓオーダーに設定することにより、導電性ワイヤ１０表面には直流負電圧Ｖ１が実質、導電性の炭素膜が連続成膜するよう印加される。   The pulsed positive voltage V2 is applied to the cylindrical cathode 8 by repeating the duty with respect to the DC negative voltage V1 at each period T at the above frequency and periodically repeating. By setting the pulse width of the pulsed positive voltage V2 within this period T to the order of μs, the DC negative voltage V1 is applied to the surface of the conductive wire 10 so that a substantially conductive carbon film is continuously formed. .

上記所定の周波数は好ましくは１ｋＨｚ〜２０ｋＨｚ、より好ましくは１ｋＨｚ〜３ｋＨｚの周波数範囲であり、最適には約２ｋＨｚである。   The predetermined frequency is preferably in the frequency range of 1 kHz to 20 kHz, more preferably 1 kHz to 3 kHz, and optimally about 2 kHz.

また、好ましくは第２印加期間Ｔ２は５μｓ〜２００μｓであり、より好ましくは１０μｓ〜３０μｓであり、最適には約２０μｓである。   The second application period T2 is preferably 5 μs to 200 μs, more preferably 10 μs to 30 μs, and most preferably about 20 μs.

また、好ましくは直流負電圧は−５５０Ｖ〜−７００Ｖであり、より好ましくは−５５０Ｖ〜６５０Ｖであり、最適には約６００Ｖである。   The DC negative voltage is preferably −550 V to −700 V, more preferably −550 V to 650 V, and most preferably about 600 V.

また、好ましくはパルス状正電圧は、＋１００Ｖ〜＋３００Ｖであり、より好ましくは＋１００Ｖ〜＋２５０Ｖであり、最適には約２００Ｖである。   The pulsed positive voltage is preferably +100 V to +300 V, more preferably +100 V to +250 V, and most preferably about 200 V.

筒状陰極８に対する電圧の印加条件において導電性ワイヤ１０表面への炭素膜の成膜過程を説明する。まず、真空成膜室６内を減圧しかつガス導入系２から炭素膜成膜用ガスの一例としてＣＨ４（メタンガス）とＨ２（水素ガス）とを導入し、筒状陰極８にパルス電圧生成部２０の生成電圧を印加する。   A process of forming a carbon film on the surface of the conductive wire 10 under the condition of applying a voltage to the cylindrical cathode 8 will be described. First, the inside of the vacuum film forming chamber 6 is depressurized, and CH4 (methane gas) and H2 (hydrogen gas) are introduced from the gas introduction system 2 as an example of the carbon film forming gas, and a pulse voltage generator is applied to the cylindrical cathode 8. Twenty generation voltages are applied.

この生成電圧は図２で示す電圧である。図２で示す電圧のうち、第１印加期間Ｔ１に印加する直流負電圧Ｖ１により、筒状陰極８内部にプラズマ１８が発生する。このプラズマ１８により、導入ガスが分解されて、筒状陰極８内部に配置された導電性ワイヤ１０の表面に炭素膜が成膜される。   This generated voltage is the voltage shown in FIG. Among the voltages shown in FIG. 2, the plasma 18 is generated inside the cylindrical cathode 8 by the DC negative voltage V <b> 1 applied in the first application period T <b> 1. The introduced gas is decomposed by the plasma 18, and a carbon film is formed on the surface of the conductive wire 10 disposed inside the cylindrical cathode 8.

この炭素膜は、カーボンナノウォール、カーボンナノチューブ、カーボンナノファイバー、針状炭素膜等を含む。炭素膜の成膜条件には、炭素膜成膜用のガス、例えば炭素系のガスの流量、キャリアガスの流量、導電性ワイヤ１０の温度、真空成膜室６内の圧力、等があり、これらを種々に定めることにより、目的とする炭素膜を成膜することができる。   This carbon film includes carbon nanowalls, carbon nanotubes, carbon nanofibers, acicular carbon films, and the like. The carbon film deposition conditions include a carbon film deposition gas, for example, a flow rate of a carbon-based gas, a flow rate of a carrier gas, a temperature of the conductive wire 10, a pressure in the vacuum deposition chamber 6, and the like. By defining these variously, a target carbon film can be formed.

一方、この第１印加期間Ｔ１における成膜過程で筒状陰極８の外周面にプラズマで分解された導電性が低く抵抗が高い炭素物質が付着してくるようになると、この炭素物質には負電荷がチャージアップされてくる。   On the other hand, when a carbon material decomposed by plasma and having a high resistance is deposited on the outer peripheral surface of the cylindrical cathode 8 during the film formation process in the first application period T1, the carbon material is negatively affected. Charges are charged up.

そして、第１印加期間Ｔ１に続く第２印加期間Ｔ２では、パルス状正電圧Ｖ２が筒状陰極８に印加されるので、上記筒状陰極８の外周面に付着している炭素物質にチャージアップしている負電荷はこのパルス状正電圧Ｖ２により電荷中和される。その結果、筒状陰極８からは従来のようにチャージアップ電荷により異常放電が発生しなくなる。   In the second application period T2 subsequent to the first application period T1, the pulsed positive voltage V2 is applied to the cylindrical cathode 8, so that the carbon material adhering to the outer peripheral surface of the cylindrical cathode 8 is charged up. The negative charges are neutralized by the pulsed positive voltage V2. As a result, abnormal discharge does not occur from the cylindrical cathode 8 due to the charge-up charge as in the prior art.

以上説明したように、この実施の形態では、直流プラズマ１８により上記ガスが分解して導電性ワイヤ１０の表面に炭素膜の成膜が行われる過程で筒状陰極８に周期的にパルス状正電圧Ｖ２を印加するので、プラズマ１８により炭素膜が成膜される過程で高抵抗の炭素物質が筒状陰極８に付着しこの付着した炭素物質に電荷がチャージアップしてもパルス状正電圧Ｖ２で電荷中和され、チャージアップが解消される結果として電荷チャージアップによる異常放電が発生しなくなる。   As described above, in this embodiment, the gas is decomposed by the DC plasma 18 and the carbon film is formed on the surface of the conductive wire 10. Since the voltage V2 is applied, even if a high-resistance carbon material adheres to the cylindrical cathode 8 in the process of forming the carbon film by the plasma 18 and the charged carbon material is charged up, the pulsed positive voltage V2 As a result of neutralizing the charge and eliminating the charge-up, abnormal discharge due to the charge charge-up does not occur.

そのため、本実施の形態では、真空成膜室６内を高真空圧に制御することができるようになり、成膜された炭素膜を冷陰極材料とする冷陰極のＩＶ特性を向上することができる。   Therefore, in this embodiment, the inside of the vacuum film formation chamber 6 can be controlled to a high vacuum pressure, and the IV characteristics of the cold cathode using the formed carbon film as a cold cathode material can be improved. it can.

図３に真空成膜室６内の圧力を１５００Ｐａ（図中×印）、２０００Ｐａ（図中△印）、８０００Ｐａ（図中□印）で制御して炭素膜を導電性ワイヤ１０表面に成膜し、この導電性ワイヤ１０を冷陰極としてこれを陽極と対向配置した場合のＩＶ特性曲線Ａ，Ｂ，Ｃを示す。   In FIG. 3, the carbon film is formed on the surface of the conductive wire 10 by controlling the pressure in the vacuum film forming chamber 6 at 1500 Pa (x in the figure), 2000 Pa (Δ in the figure), and 8000 Pa (□ in the figure). The IV characteristic curves A, B, and C when the conductive wire 10 is used as a cold cathode and opposed to the anode are shown.

ＩＶ特性曲線Ａ，Ｂは筒状陰極８に直流負電圧Ｖ１として−６００Ｖを印加し、パルス状正電圧Ｖ２は印加していない。  In the IV characteristic curves A and B, −600 V is applied to the cylindrical cathode 8 as the DC negative voltage V1, and the pulsed positive voltage V2 is not applied.

ＩＶ特性曲線Ｃは周波数２ｋＨｚ、第１印加期間Ｔ１に直流負電圧Ｖ１として−６００Ｖを印加し、第２印加期間Ｔ２は２０μｓとしパルス状正電圧Ｖ２として＋２００Ｖを印加したときの曲線である。  The IV characteristic curve C is a curve when the frequency is 2 kHz, −600 V is applied as the DC negative voltage V1 in the first application period T1, and the second application period T2 is 20 μs and +200 V is applied as the pulsed positive voltage V2.

これらのＩＶ特性曲線Ａ，Ｂ，Ｃが示すように、圧力１５００Ｐａ（図中×印）で成膜した炭素膜で冷陰極を構成した場合のＩＶ特性は電圧２．２ＶでＩＶ特性曲線Ａが立ち上がり、圧力２０００Ｐａ（図中△印）で成膜した炭素膜で冷陰極を構成した場合のＩＶ特性は電圧１．８ＶでＩＶ特性曲線Ｂが立ち上がり、圧力８０００Ｐａ（図中□印）で成膜した炭素膜で冷陰極を構成した場合のＩＶ特性は電圧１．４ＶでＩＶ特性曲線Ｃが立ち上がる。   As shown by these IV characteristic curves A, B, and C, the IV characteristic when the cold cathode is composed of a carbon film formed at a pressure of 1500 Pa (marked in the drawing) is a voltage of 2.2 V and the IV characteristic curve A is When the cold cathode is made up of a carbon film formed at a pressure of 2000 Pa (Δ in the figure), the IV characteristic curve B rises at a voltage of 1.8 V and the film is formed at a pressure of 8000 Pa (□ in the figure). When the cold cathode is formed of the carbon film, the IV characteristic curve C rises at a voltage of 1.4V.

すなわち、パルス状正電圧Ｖ２を周期的に印加することにより、真空成膜室６内の圧力を高く制御しても筒状陰極８から異常放電が発生しなくなるので、真空成膜室６内圧力を高く制御することによりＩＶ特性に優れた炭素膜を成膜することができるようになった。   That is, by applying the pulsed positive voltage V2 periodically, abnormal discharge does not occur from the cylindrical cathode 8 even if the pressure in the vacuum film forming chamber 6 is controlled to be high. It is possible to form a carbon film excellent in IV characteristics by controlling the temperature high.

以上、実施の形態では、筒状陰極８内に発生したプラズマにより真空成膜室６に導入したガスが分解して導電性ワイヤ１０の表面に炭素膜の成膜が行われる過程で、筒状陰極８に周期的にパルス状正電圧Ｖ２を印加することにより、筒状陰極８側から異常放電が発生することなく真空成膜室６内の圧力を高く制御することが可能となり、冷陰極材料としてＩＶ特性に優れた炭素膜を成膜することができる。   As described above, in the embodiment, in the process in which the gas introduced into the vacuum film forming chamber 6 is decomposed by the plasma generated in the cylindrical cathode 8 and the carbon film is formed on the surface of the conductive wire 10, By periodically applying a pulsed positive voltage V2 to the cathode 8, it becomes possible to control the pressure in the vacuum film forming chamber 6 to be high without causing abnormal discharge from the cylindrical cathode 8 side. As described above, a carbon film having excellent IV characteristics can be formed.

図１は本発明の実施の形態に係る成膜装置の概略構成を示す図である。FIG. 1 is a diagram showing a schematic configuration of a film forming apparatus according to an embodiment of the present invention. 図２は筒状陰極に印加する電圧の波形を示す図である。FIG. 2 is a diagram showing a waveform of a voltage applied to the cylindrical cathode. 図３は筒状陰極内の圧力を高低に制御して炭素膜を成膜した場合、その成膜した炭素膜を冷陰極材料とした冷陰極のＩＶ特性を比較して示す図である。FIG. 3 is a diagram showing a comparison of IV characteristics of cold cathodes using a carbon film formed as a cold cathode material when a carbon film is formed by controlling the pressure in the cylindrical cathode at a high or low level. 図４は従来の成膜装置の概略構成を示す図である。FIG. 4 is a diagram showing a schematic configuration of a conventional film forming apparatus.

符号の説明Explanation of symbols

２ ガス導入系
４ 真空排気系
６ 真空成膜室
８ 筒状陰極
１０ 導電性ワイヤ（基板、成膜対象）
２０ パルス電圧生成部 2 Gas introduction system 4 Vacuum exhaust system 6 Vacuum deposition chamber 8 Cylindrical cathode 10 Conductive wire (substrate, deposition target)
20 Pulse voltage generator

Claims (5)

真空成膜室内に配置した筒状陰極に直流負電圧を印加し、その内部にプラズマを閉じ込め状態で生成して、真空成膜室に導入した炭素膜成膜用のガスを分解することにより、当該筒状陰極内部に配置した基板表面に炭素膜を成膜する成膜装置であって、
上記直流負電圧を印加して生成したプラズマにより上記ガスが分解して上記成膜が行われる過程で、パルス状正電圧を筒状陰極に繰り返し印加して該筒状陰極に付着した炭素物質に帯電する電荷を中和することにより、上記電荷のチャージアップによる異常放電の発生を防止可能とした、ことを特徴とする成膜装置。 By applying a DC negative voltage to the cylindrical cathode disposed in the vacuum film forming chamber, generating plasma in a confined state therein, and decomposing the carbon film forming gas introduced into the vacuum film forming chamber, A film forming apparatus for forming a carbon film on a substrate surface disposed inside the cylindrical cathode,
In the process in which the gas is decomposed by the plasma generated by applying the DC negative voltage and the film formation is performed, a pulsed positive voltage is repeatedly applied to the cylindrical cathode to the carbon material attached to the cylindrical cathode. A film forming apparatus characterized by neutralizing a charge to be charged, thereby preventing occurrence of abnormal discharge due to charge-up of the charge. １周期内における上記パルス状正電圧の印加期間を上記直流負電圧の印加期間より短い期間として該パルス状正電圧を周期的に繰り返し印加する、ことを特徴とする請求項１に記載の成膜装置。   2. The film formation according to claim 1, wherein the pulsed positive voltage is periodically and repeatedly applied with the pulsed positive voltage application period within one cycle being shorter than the DC negative voltage application period. apparatus. 所定周波数における各周期内で上記直流負電圧の印加期間に対して上記パルス状正電圧の印加期間を、上記帯電した電荷をパルス状正電圧の印加で中和できる期間にデューティ制御する、ことを特徴とする請求項１に記載の成膜装置。  Duty control of the application period of the pulsed positive voltage with respect to the application period of the DC negative voltage within each cycle at a predetermined frequency to a period in which the charged charge can be neutralized by application of the pulsed positive voltage. The film forming apparatus according to claim 1, wherein: 上記所定周波数が、１ｋＨｚ〜２０ｋＨｚであり、上記所定周波数における１周期内でパルス状正電圧の１回の印加期間が、５μｓ〜２００μｓである、ことを特徴とする請求項３に記載の成膜装置。   4. The film formation according to claim 3, wherein the predetermined frequency is 1 kHz to 20 kHz, and one application period of the pulsed positive voltage is 5 μs to 200 μs within one period at the predetermined frequency. apparatus. 真空成膜室内に配置した筒状陰極に直流負電圧を印加し、その内部にプラズマを閉じ込め状態で生成して、真空成膜室に導入した炭素膜成膜用のガスを分解することにより、当該筒状陰極内部に配置した基板表面に炭素膜を成膜する過程で、パルス状正電圧を筒状陰極に繰り返し印加して該筒状陰極に付着した炭素物質に帯電する電荷を中和することにより、上記電荷のチャージアップによる異常放電の発生を防止する、ことを特徴とする成膜装置用筒状陰極での異常放電発生防止方法。  By applying a DC negative voltage to the cylindrical cathode disposed in the vacuum film forming chamber, generating plasma in a confined state therein, and decomposing the carbon film forming gas introduced into the vacuum film forming chamber, In the process of forming a carbon film on the surface of the substrate disposed inside the cylindrical cathode, a pulsed positive voltage is repeatedly applied to the cylindrical cathode to neutralize the charge charged on the carbon material attached to the cylindrical cathode. Thus, an abnormal discharge is prevented from occurring in the cylindrical cathode for a film forming apparatus, wherein the occurrence of abnormal discharge due to charge-up is prevented.
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