JP4386473B2 - Film thickness control method and film thickness control apparatus in arc ion plating apparatus - Google Patents

Description

【００３０】
図３中に、表１における累積電流量Ｌとターゲットの平均重量Ｗとの関係をグラフ化して示している。図のように、ターゲットの平均重量Ｗの低下は累積電流量Ｌに対して直線状ではなく、その低下の度合いは、累積電流量Ｌの増加に伴って徐々に小さくなっている。
このことは、ターゲットからの時々刻々の蒸発量が、累積電流量Ｌの増加、すなわち、ターゲットの消耗に伴って次第に低下していることを意味する。そこで、表１の測定データに基づき、ターゲットからの蒸発量と累積電流量との関係をさらに求めれば、表２のようになる。
【００３１】
【表２】

【００３２】
同表から、例えばT０〜T１の期間での中間時点、すなわち、累積電流量Ｌが 975.5ＡHrの時点で、単位電流量当たりの蒸発量ｖは0.089gであり、これが、T１〜T２の期間における累積電流量Ｌ＝2859.5ＡHrの時点では、0.077g／ＡHrに低下することが示されている。これをグラフ化したものも図３中に示している。
なお、上記のように蒸発量が次第に低下する現象については、ターゲットに対する冷却効果や表面性状の変化が考えられる。すなわち、一般にターゲットは背面側で冷却されており、したがって、ターゲットが消耗すると冷却効果が次第に大きくなる。また、アーク放電の継続に伴ってターゲット表面は次第に荒れてくる。これらに起因して、蒸発量の低下が生じるものと考えられる。
【００３３】
このように、アーク電流が一定のままでコーティングを行うと、ターゲットからの蒸発量ｖが次第に低下することから、コーティング開始時に所望の厚さに合わせてアーク電流初期値Ｉ_isや基材走行速度初期値Ｖ_isを設定しても、基材表面に形成されるコーティング膜の膜厚は、上記のような蒸発量ｖの低下に比例して次第に低下する。
【００３４】
そこで、コーティング開始時の膜厚で均一に維持するためには、上記のような蒸発量の低下を補償する操作が必要となる。すなわち、コーティング開始時の初期蒸発量をｖ₀ 、累積電流量Ｌの時点での蒸発量をｖとしたときの両者の比Ｃ(=ｖ₀/ｖ）に応じて、基材走行速度を低下させる操作やアーク電流を増加させる操作を行うことで、膜厚を均一に維持することが可能になる。
【００３５】
前記表２中には、さらに、上記の比Ｃと累積電流量Ｌとの関係を求めるために、蒸発量ｖの逆数をそれぞれ算出して付記し、その算出結果を図３中にグラフ化して示している。同図のように、算出値はほぼ一直線上にプロットされており、したがって、１／ｖは累積電流量Ｌに対する一次式で近似することができる。したがって、上記の比Ｃも、
Ｃ＝ｖ₀ ／ｖ＝a₁＋a₂・Ｌ ……(1)
のように、累積電流量Ｌについて一次式で表される関係を有している。これにより、上記の比Ｃ、すなわち補正係数は、累積電流量Ｌの変化毎に逐一求めておく必要はなく、(1) 式での定数a₁,a₂ が定まれば、この(1) 式に基づき、逐次算出することができる。
【００３６】
そこで、本実施形態では、前記したように、アーク電流一定の試験で、累積電 流量Ｌが０のときの初期膜厚t₀と、ターゲット限界量Ｌ_xeのときの最終膜厚ｔ_xeとを予め求めている。すなわち、これらの膜厚比S'(=t₀／ｔ_xe）は、初期蒸発量ｖ₀と、ターゲット限界量Ｌ_xeのときの蒸発量ｖ_xeとの比に相当する。そして、これらの値に基づき、(1) 式での定数a₁,a₂ は、
a₁＝１ （∵Ｌ＝０のとき、Ｃ＝ｖ₀/ｖ₀ ＝１）
a₂＝（S'−１）／Ｌ_xe
となる。また、前記した操作盤で設定される％単位での補正率Ｓと上記の膜厚比S'との関係（Ｓ=100×S'）を加味して(1) 式を書き換えれば、
Ｃ＝｛(S-100) ×( Ｌ／Ｌ_xe) ＋100 ｝/100 ……(2)
となる。
【００３７】
この補正係数Ｃを、前記膜厚制御装置10ではターゲット消耗量Ｌの増加に応じて時々刻々算出し、基材４の走行速度を制御する場合には、補正速度ＶをＶ＝Ｖ_is／Ｃで演算し、初期時からの蒸発量の低下に合わせて基材４の走行速度を低下させる。また、アーク電流を制御する場合には、補正電流ＩをＩ＝Ｉ_is×Ｃで演算し、蒸発量が初期蒸発量と同等に維持されるように、アーク電流を増加させる制御を行う。
【００３８】
次に、前述したように複数のターゲット８…が設けられている場合での上記の膜厚制御装置10での具体的な制御手順について、（i）基材の走行速度制御をアーク電流制御よりも優先して行う場合（基材走行速度制御）と、（ii）アーク電流制御を基材の走行速度制御よりも優先して行う場合（アーク電流制御）とに分けて説明する。
【００３９】
（i）基材走行速度制御
この制御では、まず、前記(2) 式に基づいて、各ターゲット８毎の補正係数Ｃ(k) を次式(3) により求める。
Ｃ(k) ＝｛(S-100) ×( L(k)／Ｌ_xe) ＋100 ｝/100 ……(3)
ここでｋはターゲットNoで、ｋ＝1,2,3,…
そして、Ｃ(k) のうちの最大の値をＣ_MAX とし、この補正係数Ｃ_MAX によって 基材４の補正速度Ｖ_t を、
Ｖ_t ＝Ｖ_is／Ｃ_MAX ……(4)
で求め、これに応じた速度指令信号を前記モータコントローラ12に出力することにより、基材４の走行速度を上記Ｖ_t に低下させる。
【００４０】
このとき、基材走行駆動系における速度制御精度の信頼性が、例えば小数点１桁である場合には(4) 式で得られた補正速度Ｖ_tにおける２桁以下は切り捨てる。そして、この切り捨て分を補い、かつ各ターゲット８…の消耗量が異なった場合に全てのターゲットからの蒸発量を同一とするために、各アーク電流Ｉ(k) を下記演算式(5) にてさらに補正する。すなわち、このときに２桁以下を切り捨てた補正速度をＶ_tCとし、補正後のアーク電流をＩ(k) とするとき、
(Ｖ_is／Ｖ_tC) ×（Ｉ(k) ／Ｉ_is) ＝Ｃ(k)
となるように、
Ｉ(k) ＝Ｉ_is(k) ×(V_tC/V_is) ×｛(S-100) ×(L(k)/Ｌ_xe) ＋100 ｝…(5) の演算式で算出し、その結果に基づいて、各ターゲットでのアーク電流Ｉ(k) を初期電流Ｉ_isから増加させる。
【００４１】
このような制御を行うことにより、基材４の全長にわたって均一なコーティング膜を形成することができる。しかも、上記のように基材走行速度の制御を優先して行い、その速度制御精度に合わせてアーク電流制御を加味することで、基材４の走行速度駆動系の制御精度がそれほど高くない構成でも、コーティング膜の均一をより高めた膜形成を行わせることが可能となる。
【００４２】
（ii）アーク電流制御
この制御では、まず、前記同様に、各ターゲット毎の補正係数Ｃ(k) を、
Ｃ(k) ＝｛(S-100) ×( L(k)／Ｌ_xe) ＋100 ｝/100 ……(6)
によって算出し、この算出結果から、各ターゲット毎の補正電流Ｉ(k) を、
Ｉ(k) ＝Ｉ_is(k) ×Ｃ(k) ……(7)
で求める。この結果に応じたアーク電流指令信号を前記アーク電源14に出力することによって、各ターゲット８…に流れるアーク電流を各々のアーク電流初期値Ｉ_is(k) から次第に増加させる。
【００４３】
そして、このアーク電流制御では、上記(7) 式によって算出される補正電流Ｉ(k) を前記アーク電流上限値Ｉ_xeと比較し、補正電流Ｉ(k) の中で一つでも上限値Ｉ_xeを超えた場合には、前記アーク電源14への出力はアーク電流上限値Ｉ_xeに対応する指令信号とし、補正電流Ｉ(k) とアーク電流上限値Ｉ_xeとの差に相当する補償は基材の走行速度制御で行う。すなわち、このときの補正電流Ｉ(k) とアーク電流上限値Ｉ_xeとの比の最大値をＣ_MAX とするとき、さらに補正走行速度Ｖ_t を、
Ｖ_t ＝Ｖ_is／Ｃ_MAX ……(8)
で求め、これを前記モータコントローラ12に出力し、基材４の走行速度を低下させる。
【００４４】
なお、この場合に、基材４の走行速度制御精度の信頼性が例えば小数点１桁である場合には、前記と同様に、補正走行速度Ｖ_tにおける２桁以下は切り捨て、この切り捨て分を補うために、さらに補正アーク電流を前記同様に算出し直す。すなわち、２桁以下を切り捨てたときの補正走行速度をＶ_tCとするとき、
(Ｖ_is／Ｖ_tC) ×（Ｉ(k) ／Ｉ_is) ＝Ｃ(k)
となるように、
Ｉ(k) ＝Ｉ_is×(V_tC/V_is) ×Ｃ(k) ……(9)
を算出し、これをアーク電源14に出力して、アーク電流を増加させる制御を行う。これにより、アーク電流は、その上限値Ｉ_xeをわずかに超える値以下に抑えられた状態で維持される。
【００４５】
このような制御により、基材４の全長にわたって均一なコーティング膜を形成することができる。しかも、上記のようにアーク電流の制御を優先して行う場合に、その上限値を過度に超えないように、基材の走行速度制御が併用される。これにより、アーク電源14としてその可変範囲がそれほど広くなく、また、基材の 走行駆動系もそれほど高精度のものでない簡単な構成で、膜厚の均一性をより高 精度に維持することができる。
【００４６】
特に、上記のようにアーク電流の上昇を予め設定した上限値近傍で抑える構成では、コーティング製品の品質の低下をより確実に防止できる。すなわち、アーク電流値を増加させていくと、その電流値に応じてターゲット表面における温度上昇の度合いが大きくなり、その輻射熱が、ターゲットに対向する位置で走行する基材に作用する。このような輻射熱により、従来、基材が例えばフィルム状の金属箔などの場合に、基材の局部的な温度上昇に伴う熱膨張が生じて、これに起因するしわが基材に発生していた。
【００４７】
そこで、上記のように上限値を設定し、この上限値でアーク電流の増加を抑え、その後の補正は基材の走行速度を低下させる制御とすることで、上記したようなシワの発生のない良質の製品を製造することが可能となる。
【００４８】
【発明の効果】
以上の説明のように、本発明においては、ターゲットの消耗に合わせて基材の走行速度を低下させ、また、アーク電流値を次第に増加させるので、基材が長尺の場合でも全体にわたっての膜厚均一性が向上し、これによってコーティング製品の品質を向上することができる。
【図面の簡単な説明】
【図１】 本発明の一実施形態におけるアークイオンプレーティング装置の制御構成を示すブロック図である。
【図２】 上記装置の要部構成を示す模式図である。
【図３】 アーク電流の累積電流量の増加に対するターゲット重量および蒸発量、蒸発量の逆数の各変化を示すグラフである。
【符号の説明】
１ 真空槽
４ 基材
８ ターゲット
8a 蒸発物質
10 膜厚制御装置（設定値変更手段）
11 基材走行駆動モータ（走行駆動手段）
14 アーク電源
15 積算電流計（アーク電流積算手段）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a film thickness control method and a film thickness control apparatus in an arc ion plating apparatus.
[0002]
[Prior art]
The arc ion plating apparatus is used for forming a hard film on the surface of a tool, for example, and also used for thin film coating on the surface of a film-like substrate such as a metal foil or a resin film.
In an apparatus used for coating on such a film-like substrate, for example, as shown in FIG. 2 which is an explanatory view of the present invention, a target 8 is installed in a vacuum chamber 1 and arc discharge is generated on the surface of the target 8. The can roll 7 is provided in the scattering direction of the evaporating substance 8a generated by generating the above. A thin film coating is applied to the surface of the base material 4 by causing the film-like base material 4 to wrap around the can roll 7 and running and attaching an evaporating substance 8a to the surface of the base material 4 where the can roll 7 is wound. Is supposed to do.
[0003]
In the above apparatus, conventionally, the arc current value of arc discharge generated on the target surface and the traveling speed of the substrate are set in advance according to the film thickness of the coating film, and then the arc current value and the substrate traveling speed are set. The coating is performed while maintaining at each set value.
[0004]
[Problems to be solved by the invention]
However, when the arc current value and the traveling speed of the base material are set according to the desired film thickness in advance as described above and coating is continued in this state, the coating film actually formed on the surface of the base material When the thickness gradually decreases and the base material is a long metal foil or the like, the difference in thickness between the first part and the last part of the foil becomes large, resulting in a problem that product defects occur. .
[0005]
The present invention has been made in view of the above-described conventional problems, and the object thereof is to improve the film thickness uniformity of the coating film formed on the surface of the base material and to simplify the apparatus configuration therefor. It is also possible to provide a film thickness control method and a film thickness control apparatus in an arc ion plating apparatus that can further improve the quality of a coated product.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the inventors of the present application have studied various factors of film thickness variation in the arc ion plating apparatus, and as a result, a film with a large target consumption that increases as the coating progresses. The inventors have newly found that this is a factor of thickness variation, and have made the present invention.
[0007]
That is, the film thickness control method in the arc ion plating apparatus according to the present invention generates an arc discharge on the target surface while the substrate is running in a vacuum chamber, and deposits the evaporated substance from the target on the substrate surface. In the film thickness control method in the arc ion plating apparatus that performs the formation, an upper limit value of the arc current that flows through the target is determined in advance, and the amount of consumption of the target until the current value of the arc current that flows through the target reaches the upper limit value The current value of the arc current is increased in accordance with the current value, and after the current value of the arc current reaches the upper limit value, the current value of the arc current is maintained at the upper limit value to match the consumption amount of the target. The traveling speed of the base material is reduced.
[0008]
In the arc ion plating apparatus, as described above, coating is performed while generating an arc discharge on the target surface, generating an arc spot where a large current is concentrated, and locally evaporating the target surface. Therefore, the target is gradually consumed as the coating continues. When the arc current is constant, the evaporation amount per unit time gradually decreases as the target consumption increases. As a result, when the transport speed of the base material is constant, the film thickness of the coating film formed on the surface of the base material becomes gradually thinner.
[0009]
Therefore, in the present invention, the traveling speed of the base material is reduced in accordance with the consumption of the target. Thereby, the adhesion amount of the evaporated substance per unit area on the substrate surface can be maintained more uniformly, and as a result, the film thickness uniformity can be improved. Further, by increasing the arc current value in accordance with the consumption of the target and compensating for the evaporation amount that decreases in accordance with the consumption of the target, it is possible to improve the film thickness uniformity as described above.
[0010]
As a film thickness control device for suitably carrying out the above method, as described in claim 2, the driving means for driving the substrate in accordance with the set speed in the vacuum chamber, and the target according to the set current value A film in an arc ion plating apparatus, which has an arc power supply for supplying electric power so that a flowing arc current flows, and forms a film by attaching an evaporating substance generated by arc discharge on a target surface to the surface of a traveling substrate In the thickness control device, the set current value is increased in accordance with the consumption amount of the target until the set current value reaches a predetermined upper limit value, and after the set current value reaches the upper limit value, the arc is increased. configured to provide a set value changing means for performing control to reduce the set speed to match the current value of the current to the consumption of the target while maintaining in said upper limit value
[0011]
In this case, as described in claim 3, there is provided an arc current integrating means for successively obtaining a time integral of the arc current during arc discharge, and the above change is performed in accordance with an increase in the time integral value of the arc current. It is desirable to do. That is, the time integral value of the arc current and the amount of consumption of the target are substantially proportional to each other. Therefore, by adding an arc current integrating means that can be configured with an integrating ammeter, etc., and having a control configuration based on the measured value, a device having an automatic correction function according to the consumption amount of the target can be made simpler. can do.
[0012]
That is, in the control in which the arc current value is increased in accordance with the amount of consumption of the target, the degree of temperature rise on the target surface increases according to the current value, and the radiant heat travels at a position facing the target. Acts on the substrate. As a result, when the base material is, for example, a film-like metal foil, thermal expansion accompanying a local temperature rise of the base material occurs, which may cause wrinkles on the base material and cause a product defect.
[0013]
Therefore, an upper limit value for the arc current is determined, and an increase in the arc current is suppressed in the vicinity of the upper limit value, and then the control of lowering the traveling speed of the base material is performed, thereby preventing overheating of the base material. A coating excellent in film thickness uniformity can be formed, and a high-quality product without the occurrence of wrinkles can be produced.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 2 schematically shows a configuration of a main part in the vacuum chamber 1 in the arc ion plating apparatus. The vacuum chamber 1 is divided into a substrate transport driving chamber 2 and a vapor deposition chamber 3 by a partition wall 1a. ing. In the base material conveyance drive chamber 2, an unwinding roll 5 around which a film-like base material 4 is wound, a winding roll 6 for winding up the base material 4, and a canister disposed between these two rolls 5, 6. A roll 7 is provided.
[0015]
The can roll 7 is arranged so that a part of the outer peripheral surface protrudes toward the vapor deposition chamber 3 through an opening formed in the partition wall 1a. The substrate 4 supplied from the unwinding roll 5 is wound around the can roll 7 and traveled, and then wound up by the winding roll 6. An automatic tension adjusting device (not shown) is further provided on the travel path of the base material 4 so that the tension acting on the base material 4 in the travel state is maintained in a predetermined range.
[0016]
On the other hand, in the vapor deposition chamber 3, a target 8 made of a material corresponding to a film to be coated on the surface of the base material 4 and a discharge generated for generating a vacuum arc discharge on the surface of the target 8 (not shown). Mechanism.
The manufacturing procedure will be described with reference to an example in which an aluminum metal foil having a thickness of 50 μm and a width of 500 mm is used as the base material 4 and coated with, for example, a titanium film.
[0017]
First, the front end portion of the base material 4 wound around the unwinding roll 5 is wound around the can roll 7 and then locked to the take-up roll 6, and is placed in the base material transport driving chamber 2 of the vacuum chamber 1. , Set to the state shown in FIG. A titanium target 8 is mounted in the vapor deposition chamber 3. Thereafter, a vacuum pump (not shown) is driven to evacuate the vacuum chamber 1, and after reaching a predetermined degree of vacuum, the operation of the discharge generation mechanism is started, and the target 8 as a cathode electrode and the discharge generation mechanism A predetermined voltage is applied between the anode electrode and an arc discharge on the surface of the target 8.
[0018]
At the same time, the unwinding roll 5, the can roll 7 and the winding roll 6 are rotated in synchronization with each other, thereby starting the running of the substrate 4.
As described above, by causing arc discharge on the surface of the target 8 in a vacuum, a minute region on the surface of the target 8 is vaporized by the arc spot where the discharge current is concentrated. This vapor is further ionized to form a plasma flow, from which positive ions are extracted as an evaporating substance 8a in the direction of the can roll 7 to which a negative bias voltage is applied. This adheres to the surface of the base material 4 that runs around the can roll 7, and the base material 4 is coated with the same material as the target 8, that is, a film made of titanium. The coating is continued while the running speed and arc current value of the base material 4 are controlled by a film thickness control device 10 described later so that the film thickness becomes a desired value.
[0019]
As shown in FIG. 1, the film thickness control device 10 includes a base material travel drive motor (travel drive means) 11 that rotationally drives the unwinding roll 5, the winding roll 6, and the can roll 7. Connected through twelve. The film thickness controller 10 is further connected to an arc power source 14 that supplies discharge power of arc discharge generated between the discharge generation mechanism and the target 8.
[0020]
A speed command signal corresponding to the set speed is output from the film thickness control device 10 to the motor controller 12, whereby the base material travel drive motor 11 is driven at a rotational speed in accordance with the speed command signal. Also, an arc current command signal corresponding to the set current value is output to the arc power source 14, and the power supplied from the arc power source 14 is controlled so that arc discharge is maintained at the current value corresponding to the command signal. The Then, as described later, the set speed and the set current value are sequentially changed and output in the film thickness control apparatus 10 as the coating progresses. Therefore, the film thickness control apparatus 10 has a function as setting value changing means.
[0021]
The base material travel drive motor 11 is provided with a speed detector 13. A detection signal from the speed detector 13 is input to the film thickness control device 10, and the detection signal is compared with a set speed, and a correction signal for acceleration or deceleration according to the comparison result is further sent to the motor controller 12. Output. Thereby, the base material 4 travels from the unwinding roll 5 to the winding roll 6 through the can roll 7 while being maintained at a speed according to the set speed.
[0022]
On the other hand, the arc power source 14 is provided with an integrating ammeter 15 as an arc current integrating means for sequentially integrating the arc current value being output, and the measured value is sequentially input to the film thickness controller 10. Has been. Depending on the measured value, the film thickness control device 10 changes the set speed and the set current value, details of which will be described later.
When the substrate 4 is wide, a plurality of targets 8 are installed in the vapor deposition chamber 3 along the width direction of the substrate 4 to coat the substrate 4. In this case, an appropriate arc current value is determined for each of the targets 8... And individually controlled so that the film thickness formed on the surface of the substrate 4 is uniform in the width direction. Therefore, the integrated ammeter 15 is configured to measure an integrated current value for each target 8... And output them to the film thickness controller 10.
[0023]
Prior to operation, the following items a to e are input to the film thickness control apparatus 10 having the above configuration from an operation panel (not shown).
a. Base material traveling speed initial value V _is (unit: m / min)
b. Initial value of arc current I _is (k) (Unit: A)
Where k is the target number and k = 1,2,3, ...
c. Arc current upper limit I _xe (unit: A)
d. Target limit L _xe (Unit: A · Hr)
e. Correction factor S (Unit:%)
The base material traveling speed initial value V _is and the arc current initial value I _is (k) for each target 8... Are obtained in advance according to the desired film thickness. Operation starts.
[0024]
As will be described later, the arc current upper limit value I _xe is set as the upper limit value when control is performed to gradually increase the arc current from the arc current initial value I _is as the operation continues.
The target limit amount L _xe is the use limit of the target 8. That is, the target 8 is evaporated and consumed by arc discharge. When the remaining amount is reduced, stable evaporation due to arc discharge is not maintained. Therefore, a use limit that can maintain this stable evaporation is obtained in advance. Note that the use limit, that is, the remaining amount can be expressed as a cumulative evaporation amount if the initial weight is constant. This accumulated evaporation amount is approximately proportional to the time integral of the arc current (hereinafter referred to as the accumulated current amount), so here the accumulated current amount (unit: A · Hr) up to the limit of use is the target limit. Set as quantity _Lxe .
[0025]
The correction factor S is set as follows. That is, with the arc current and the traveling speed of the base material 4 set to the initial values I _is (k) · _Vis as described above, the coating is experimentally performed until the target limit amount L _xe is reached, At this time, a ratio between the initial film thickness of the coating film formed on the surface of the substrate 4 and the film thickness at the end is obtained in advance, and this ratio is set as the correction factor S. For example, if the film thickness at the end is the same as the initial film thickness, the correction rate S is set to 100%, and if the film thickness is reduced to half the initial film thickness, the correction rate S is set to 200%.
[0026]
Here, the “film thickness” means “film thickness deposited within a certain time (unit time)”.
When the initial setting as described above is completed and the operation is started, the film thickness control device 10 determines the speed command signal and the arc current according to the base material traveling speed initial value V _is and the arc current initial value I _is. Command signals are output to the motor controller 12 and the arc power supply 14, respectively. Thereby, the running of the base material 4 and the arc discharge at the initial values V _is · I _is are started, and coating on the surface of the base material 4 is started.
[0027]
Thereafter, the measured value of each target 8... By the integrated ammeter 15 is sequentially input to the film thickness controller 10 as each target consumption amount L (k) (k = 1, 2, 3,...). It is, in response to the input signal, performs control and gradually decrease the running speed of the substrate 4 from its initial value V _iS, increasingly control for increasing the arc current from its initial value I _iS.
Next, the reason why the control according to the target consumption amount L (k) is performed as described above will be described.
[0028]
Table 1 shows an example of a result of actual coating with respect to a change in the weight of the target when the coating was experimentally performed with the arc current kept constant. That is, for each target Nos. 4-6, 10-12, which had a weight of 1770 g at the start of coating T0, the change in weight with the progress of subsequent coating was determined at appropriate times T1, ... T5. It is measured sequentially with the accumulated current amount L up to the time.
[0029]
[Table 1]

[0030]
In FIG. 3, the relationship between the accumulated current amount L and the average weight W of the target in Table 1 is shown in a graph. As shown in the figure, the decrease in the average weight W of the target is not linear with respect to the accumulated current amount L, and the degree of the decrease gradually decreases as the accumulated current amount L increases.
This means that the amount of evaporation from the target every moment gradually decreases as the accumulated current amount L increases, that is, the target is consumed. Therefore, if the relationship between the evaporation amount from the target and the accumulated current amount is further obtained based on the measurement data in Table 1, Table 2 is obtained.
[0031]
[Table 2]

[0032]
From the table, for example, at an intermediate point in the period from T0 to T1, that is, when the accumulated current amount L is 975.5 AHr, the evaporation amount v per unit current amount is 0.089 g, and this is the period from T1 to T2. It is shown that the cumulative current amount L decreases to 0.077 g / AHr at the time of L = 2859.5 AHr. A graph of this is also shown in FIG.
As for the phenomenon in which the evaporation amount gradually decreases as described above, a cooling effect on the target and a change in surface properties can be considered. That is, the target is generally cooled on the back side, and therefore the cooling effect gradually increases when the target is consumed. In addition, the target surface gradually becomes rough as arc discharge continues. It is considered that the evaporation amount is reduced due to these reasons.
[0033]
As described above, when coating is performed with the arc current kept constant, the evaporation amount v from the target gradually decreases. Therefore, the arc current initial value I _is and the substrate traveling speed are matched to the desired thickness at the start of coating. Even if the initial value Vis _is set, the film thickness of the coating film formed on the substrate surface gradually decreases in proportion to the decrease in the evaporation amount v as described above.
[0034]
Therefore, in order to maintain a uniform film thickness at the start of coating, an operation for compensating for the decrease in the evaporation amount as described above is required. That is, the base material traveling speed is decreased according to the ratio C (= v ₀ / v) between the initial evaporation amount at the start of coating v ₀ and the evaporation amount at the time of the accumulated current amount L as v. It is possible to maintain a uniform film thickness by performing an operation for increasing the arc current and an operation for increasing the arc current.
[0035]
Further, in Table 2, in order to obtain the relationship between the ratio C and the accumulated current amount L, the reciprocal of the evaporation amount v is calculated and added, and the calculation result is graphed in FIG. Show. As shown in the figure, the calculated values are plotted on a substantially straight line, and therefore 1 / v can be approximated by a linear expression with respect to the accumulated current amount L. Therefore, the above ratio C is also
C = v ₀ / v = a ₁ + a ₂ · L (1)
As shown, the cumulative current amount L has a relationship represented by a linear expression. Thus, the ratio C, that is, the correction coefficient does not need to be obtained for each change of the accumulated current amount L. If the constants a ₁ and a ₂ in the equation (1) are determined, this (1) It can be calculated sequentially based on the formula.
[0036]
Therefore, in the present embodiment, as described above, in the test with a constant arc current, the initial film thickness t ₀ when the accumulated current L is ₀ and the final film thickness t _xe when the target limit amount L _xe are obtained. It has been determined in advance. That is, these film thickness ratios S ′ (= t ₀ / t _xe ) correspond to the ratio between the initial evaporation amount v ₀ and the evaporation amount v _xe at the target limit amount L _xe . Based on these values, the constants a ₁ and a _{2 in} equation (1) are
a ₁ = 1 (when ∵L = 0, C = v ₀ / v ₀ = 1)
a ₂ = (S′−1) / L _xe
It becomes. In addition, if formula (1) is rewritten in consideration of the relationship (S = 100 × S ′) between the correction rate S in% units set on the operation panel and the film thickness ratio S ′ described above,
C = {(S-100) * (L / _Lxe ) +100} / 100 (2)
It becomes.
[0037]
The correction coefficient C is calculated from time to time in accordance with the increase in the target consumption amount L in the film thickness control device 10, and when the traveling speed of the base material 4 is controlled, the correction speed V is set to V = V _is / C. And the traveling speed of the base material 4 is decreased in accordance with the decrease in the evaporation amount from the initial stage. When the arc current is controlled, the correction current I _is calculated by I = I _is × C, and the control is performed to increase the arc current so that the evaporation amount is maintained equal to the initial evaporation amount.
[0038]
Next, as described above, with respect to a specific control procedure in the film thickness control apparatus 10 in the case where a plurality of targets 8 are provided, (i) the substrate traveling speed control is controlled by the arc current control. Are also divided into the case where the control is performed with priority (base material travel speed control) and the case where (ii) the arc current control is performed with priority over the travel speed control of the base material (arc current control).
[0039]
(I) Substrate traveling speed control In this control, first, the correction coefficient C (k) for each target 8 is obtained by the following equation (3) based on the equation (2).
C (k) = {(S-100) × (L (k) / L _xe ) +100} / 100 (3)
Where k is the target number and k = 1, 2, 3, ...
The maximum value of C (k) is defined as C _MAX, and the correction speed V _t of the substrate 4 is determined by this correction coefficient C _MAX .
V _t = V _is / C _MAX (4)
In determined, by outputting a speed command signal corresponding thereto to the motor controller 12 decreases the traveling speed of the substrate 4 in the V _t.
[0040]
At this time, if the reliability of the speed control accuracy in the base material traveling drive system is, for example, one digit after the decimal point, two digits or less in the corrected speed V _t obtained by the equation (4) are discarded. Then, in order to compensate for this cut-off, and to make the evaporation amount from all the targets equal when the consumption amount of each target 8 is different, each arc current I (k) is expressed by the following equation (5). Then correct further. In other words, when the correction speed rounded down by 2 digits is V _tC and the corrected arc current is I (k),
(V _is / V _tC ) × (I (k) / I _is ) = C (k)
So that
I (k) = I _is (k) × (V _tC / V _is ) × {(S-100) × (L (k) / L _xe ) +100} (5) Based on the above, the arc current I (k) at each target _is increased from the initial current I _is .
[0041]
By performing such control, a uniform coating film can be formed over the entire length of the substrate 4. Moreover, the control of the running speed drive system of the base material 4 is not so high by giving priority to the control of the running speed of the base material as described above and adding the arc current control in accordance with the speed control accuracy. However, it is possible to perform film formation with higher uniformity of the coating film.
[0042]
(Ii) Arc current control In this control, first, as described above, the correction coefficient C (k) for each target is set as follows.
C (k) = {(S-100) × (L (k) / L _xe ) +100} / 100 (6)
From this calculation result, the correction current I (k) for each target is
I (k) = I _is (k) x C (k) (7)
Ask for. By outputting an arc current command signal corresponding to this result to the arc power source 14, the arc current flowing through each target 8 _is gradually increased from the respective arc current initial value I _is (k).
[0043]
In this arc current control, the correction current I (k) calculated by the above equation (7) is compared with the arc current upper limit value I _xe, and even one of the correction currents I (k) has an upper limit value I. if it exceeds _xe, the output of the arc power supply 14 is a command signal corresponding to the arc current limit I _xe, compensation and correction current I (k) corresponding to the difference between the arc current limit I _xe is This is done by controlling the running speed of the substrate. That is, when the maximum value of the ratio of the correction current I (k) and the arc current upper limit value I _{xe at} this time is C _MAX , the correction travel speed V _t is further set to
V _t = V _is / C _MAX (8)
This is output to the motor controller 12 to reduce the traveling speed of the base material 4.
[0044]
In this case, if the reliability of the traveling speed control accuracy of the base material 4 is, for example, one digit after the decimal point, the two digits or less in the corrected traveling speed V _t are rounded down to compensate for this rounding down as described above. Therefore, the corrected arc current is recalculated in the same manner as described above. That is, when V _tC is the corrected traveling speed when rounding off two digits or less,
(V _is / V _tC ) × (I (k) / I _is ) = C (k)
So that
I (k) = I _is × (V _tC / V _is ) × C (k) (9)
Is calculated and output to the arc power source 14 to control to increase the arc current. Thus, the arc current is maintained in a state where the arc current is suppressed to a value slightly exceeding the upper limit value I _xe .
[0045]
By such control, a uniform coating film can be formed over the entire length of the substrate 4. In addition, when the arc current control is given priority as described above, the running speed control of the base material is used in combination so as not to exceed the upper limit value excessively. As a result, the variable range of the arc power source 14 is not so wide, and the travel driving system of the base material can be maintained with higher accuracy with a simple configuration with less precision. .
[0046]
In particular, in the configuration in which the increase in arc current is suppressed in the vicinity of the preset upper limit as described above, it is possible to more reliably prevent the quality of the coated product from being deteriorated. That is, as the arc current value is increased, the degree of temperature rise on the target surface increases in accordance with the current value, and the radiant heat acts on the substrate that travels at a position facing the target. Conventionally, when the base material is, for example, a film-like metal foil, such radiant heat causes thermal expansion accompanying a local temperature rise of the base material, and wrinkles due to this have occurred in the base material. It was.
[0047]
Therefore, the upper limit is set as described above, and the increase in arc current is suppressed by this upper limit, and the subsequent correction is controlled to reduce the traveling speed of the base material, so that the above-described wrinkle does not occur. It becomes possible to produce a high-quality product.
[0048]
【The invention's effect】
As described above, in the present invention, the traveling speed of the base material is reduced in accordance with the consumption of the target, and the arc current value is gradually increased. Therefore, even when the base material is long, the entire film is formed. Thickness uniformity is improved, which can improve the quality of the coated product.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a control configuration of an arc ion plating apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing a main configuration of the apparatus.
FIG. 3 is a graph showing changes in target weight, evaporation amount, and inverse number of evaporation amount with respect to an increase in the accumulated current amount of arc current.
[Explanation of symbols]
1 Vacuum chamber 4 Base material 8 Target
8a Evaporating substance
10 Film thickness controller (setting value changing means)
11 Substrate travel drive motor (travel drive means)
14 Arc power supply
15 Integrating ammeter (Arc current integrating means)

Claims (3)

In a film thickness control method in an arc ion plating apparatus that generates an arc discharge on a target surface while running the substrate in a vacuum chamber, and forms a film by attaching an evaporation substance from the target to the substrate surface.
An upper limit value of the arc current flowing through the target is determined in advance,
Until the current value of the arc current flowing through the target reaches the upper limit value, the current value of the arc current is increased according to the consumption amount of the target,
After the current value of the arc current reaches the upper limit value, the traveling speed of the base material is decreased according to the consumption amount of the target while maintaining the current value of the arc current at the upper limit value. Film thickness control method for arc ion plating apparatus. A traveling drive means for traveling the base material at a set speed in a vacuum chamber, and an arc power source for supplying electric power so that an arc current corresponding to a set current value flows to the target, and by arc discharge on the target surface In the film thickness control device in the arc ion plating apparatus that forms the film by attaching the generated evaporating substance to the traveling substrate surface,
The set current value is increased in accordance with the consumption amount of the target until the set current value reaches a predetermined upper limit value, and after the set current value reaches the upper limit value, the current value of the arc current is increased. A film thickness control apparatus in an arc ion plating apparatus, characterized in that setting value changing means is provided for performing control to reduce the set speed in accordance with the consumption amount of the target while maintaining the upper limit value . Arc current integration means for sequentially obtaining the time integral value of arc current during arc discharge is further provided,
3. The film thickness control in an arc ion plating apparatus according to claim 2, wherein the set value changing means performs the change in accordance with an increase in the time integral value of the arc current obtained by the arc current integrating means. apparatus.

Images